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BACKGROUND 1. Technical Field The present disclosure relates to storage devices and, particularly, to a portable storage device and a method for indicating storage capacity of the portable storage device. 2. Description of Related Art Commonly, if a user wants to know available or used storage capacity of a portable storage device, he or she often connects the portable storage device to a computer to get the current storage capacity. However, after a period of time, the user may forget the storage capacity, and has to use a computer again to get the storage capacity, which is troublesome. Attaching a label on a portable storage device to indicate storage capacity may solve the problem. However, the labels may easily fall off from the storage device. BRIEF DESCRIPTION OF THE DRAWINGS The components of the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of a portable storage device and a method for indicating storage capacity. Moreover, in the drawings, like reference numerals designate corresponding parts throughout several views. FIG. 1 is a block diagram of a portable storage device in accordance with an exemplary embodiment. FIG. 2 is a schematic view of a driver and a capacity indicator of the portable storage device of FIG. 1 . FIG. 3 is a flowchart of a method for indicating storage capacity in accordance with an exemplary embodiment. DETAILED DESCRIPTION Referring to FIG. 1 , an embodiment of a portable storage device 100 is illustrated. The device 100 includes a main storage unit 10 and a communication unit 20 . The main storage unit 10 stores data, such as images, videos, and the like. The device 100 is connected to a computer 200 through the communication unit 20 . The communication unit 20 may be a universal serial bus (USB) port, a BLUETOOTH unit, an infrared unit, or the like. The device 100 further includes a capacity indicator 30 , a driver 40 , and a secondary storage unit 50 . The capacity indicator 30 is configured to indicate a current storage capacity value of the main storage unit 10 . In this embodiment, the current storage capacity value is the current available storage capacity value. In an alternative embodiment, the current storage capacity value is the current used storage capacity value. The driver 40 is configured to drive the capacity indicator 30 to indicate the current storage capacity value. The secondary storage unit 50 stores a preset storage capacity value and a drive table recording relationship between storage capacity difference ranges and rotation angles of the driver 40 . As described below, in the drive table, each storage capacity difference range corresponds to one rotation angle. In this embodiment, the preset storage capacity value is the current available storage capacity value of the main storage unit 10 . In an alternative embodiment, the preset storage capacity value is the current used storage capacity value of the main storage unit 10 . When the storage capacity of the main storage unit 10 is changed, the preset storage capacity value is correspondingly updated. Therefore, the preset storage capacity value always represents the current available or used storage capacity value of the main storage unit 10 . Drive Table Storage capacity difference range Rotation angle   0 G~0.2 G 1 degrees 0.2 G~0.4 G 2 degrees . . . . . . The device 100 further includes a processing unit 60 . The processing unit 60 includes a storage capacity obtaining module 62 , a determining module 64 , and a driver control module 66 . The storage capacity obtaining module 62 is configured to periodically obtain a current storage capacity value of the main storage unit 10 from the computer 200 when the device 100 is connected to the computer 200 . The determining module 64 is configured to determine a difference between the obtained storage capacity value and the preset storage capacity value. If the difference is greater than zero, the determining module 64 determines the storage capacity difference range the difference falls within and the rotation angle the determined storage capacity difference range corresponds to in the drive table, and replaces the preset storage capacity value with the obtained storage capacity value. In this embodiment, a difference falling within one storage capacity difference range includes that the difference is equal to the upper threshold of the storage capacity difference range. The driver control module 66 is configured to control the driver 40 to rotate the determined rotation angle in clockwise or counterclockwise direction to drive the capacity indicator 30 to indicate the obtained storage capacity value. Referring to FIG. 2 , in this embodiment, the capacity indicator 30 includes a transparent glass tube 32 , an elastic capsule 34 , and colored liquid 36 . The tube 32 and the capsule 34 cooperatively form an enclosed space to receive the liquid 36 . The tube 32 defines a storage capacity graduation on its surface. The driver 40 includes a motor 402 and a cam 404 connected to the motor 402 . The motor 402 may be a servo motor. The motor 402 can drive the cam 404 to rotate. The rotation of the cam 42 can contract the capsule 34 , which causes the liquid 36 to flow in the enclosed space. The graduation value aligned with the liquid 36 thus changes, that is, the storage capacity value indicated by the capacity indicator 30 changes. In this embodiment, the graduation values gradually increase from a top of the tube 32 to the capsule 34 , and the graduation values represent different available storage capacity values of the main storage unit 10 . Initially, the main storage unit 10 has the greatest available storage capacity, the capsule 34 is in a normal state, and the liquid 36 is aligned with the graduation value representing the greatest available storage capacity. If the device 100 is connected to the computer 200 , and some data is stored in the main storage unit 10 , the available storage capacity of the main storage unit 10 correspondingly decreases, and the obtained available storage capacity value is less than the preset storage capacity value. The determining module 64 then determines the rotation angle corresponding to the obtained available storage capacity value and replaces the preset storage capacity value with the obtained storage capacity value. The driver control module 66 controls the motor 402 to rotate the cam 404 the determined rotation angle clockwise. The rotation of the cam 404 contracts the capsule 34 , causing the liquid 36 to rise to a position aligned with the graduation value representing the obtained available storage capacity value. Correspondingly, if some data is deleted from the main storage unit 10 , the obtained available storage capacity value is greater than the preset storage capacity value. The driver control module 66 then controls the motor 402 to rotate the cam 404 the rotation angle corresponding to the obtained available storage capacity value counterclockwise, causing the liquid 36 to drop to a position aligned with the graduation value representing the obtained available storage capacity value. In an alternative embodiment, the graduation values gradually increase from a top of the tube 32 to the capsule 34 , and the graduation values represent different used storage capacity values of the main storage unit 10 . Initially, the main storage unit 10 has the least used storage capacity, the capsule 34 is in the normal state, and the liquid 36 is aligned with the graduation value representing the least used storage capacity. If the device 100 is connected to the computer 200 , and some data is stored in the main storage unit 10 , the used storage capacity of the main storage unit 10 increases, and the obtained used storage capacity value is greater than the preset storage capacity value. The determining module 64 then determines the rotation angle corresponding to the obtained used storage capacity value and replaces the preset storage capacity value with the obtained used storage capacity value. The driver control module 66 controls the motor 402 to rotate the cam 404 the determined rotation angle clockwise. The rotation of the cam 404 contracts the capsule 34 , causing the liquid 36 to rise to a position aligned with the graduation value representing the obtained used storage capacity value. Correspondingly, if some data is deleted from the main storage unit 10 , the used available storage capacity value is less than the preset storage capacity value, the driver control module 66 controls the motor 402 to rotate the cam 404 the rotation angle corresponding to the obtained used storage capacity value counterclockwise, causing the liquid 36 to drop to a position aligned with the graduation value representing the obtained used storage capacity value. In an another alternative embodiment, the graduation values gradually decrease from a top of the tube 32 to the capsule 34 , and the graduation values represent different available or used storage capacity values of the main storage unit 10 . Initially, the capsule 34 is in a contracted state, causing the liquid 36 to be aligned with the graduation value representing the greatest available or the least used storage capacity. When the device 100 is connected to the computer 200 , and some data is stored in the main storage unit 10 , the capsule 34 is less contracted, and the liquid 36 drops to a position aligned with the graduation value represent the current available or used storage capacity. In this embodiment, when the device 100 and the computer 200 are disconnected, the cam 404 keeps in a position where the cam 404 contracts the capsule 34 to cause the liquid 36 to stay in a position aligned with the graduation value representing the current storage capacity value. Therefore, a user can know storage capacity of the device 100 through viewing the liquid 36 being aligned with which of the graduation values. Referring to FIG. 3 , a flowchart of a method for indicating storage capacity in accordance with an exemplary embodiment is illustrated. In step S 301 , the storage capacity obtaining module 62 periodically obtains a current storage capacity value of the main storage unit 10 from the computer 200 when the device 100 is connected to the computer 200 . In this embodiment, the current storage capacity value is the current available storage capacity. In an alternative embodiment, the current storage capacity value is the current used available storage capacity. In step S 302 , the determining module 64 determines a difference between the obtained storage capacity value and the preset storage capacity value. If the difference is zero, the procedure returns to step S 301 , otherwise, the procedure goes to step S 303 . In step S 303 , the determining module 64 determines the storage capacity difference range the difference falls within and the rotation angle the determined storage capacity difference range corresponds to in the drive table, and replaces the preset storage capacity value with the obtained storage capacity value. In step S 304 , the driver control module 66 controls the driver 40 to rotate the determined rotation angle clockwise or counterclockwise to drive the capacity indicator 30 to indicate the obtained storage capacity value. Although the present disclosure has been specifically described on the basis of the exemplary embodiment thereof, the disclosure is not to be construed as being limited thereto. Various changes or modifications may be made to the embodiment without departing from the scope and spirit of the disclosure.

A method for indicating storage capacity is applied in a storage device. The storage device includes a main storage unit, a capacity indicator, a driver, and a secondary storage unit. The second storage unit stores a preset storage capacity value and a drive table recording relationship between storage capacity difference ranges and rotation angles of the driver. The method includes: periodically obtaining a storage capacity value from a computer connected to the storage device; computing a difference between the obtained storage capacity value and the preset storage capacity value; determining the storage capacity difference range the difference falls within and the rotation angle the determined storage capacity difference range corresponds to in the drive table; and controlling the driver to rotate the determined rotation angle to drive the capacity indicator to indicate the obtained storage capacity value. A related storage device is also provided.

CLAIM OF PRIORITY This application is a continuation application of U.S. patent application Ser. No. 09/629,027, filed Jul. 31, 2000, which issued as U.S. Pat. No. 6,299,434 on Oct. 9, 2001, which is a continuation application of U.S. patent application Ser. No. 09/454,225, filed Dec. 2, 1999, which issued as U.S. Pat. No. 6,095,796 on Aug. 1, 2000. BACKGROUND OF INVENTION 1. Field of Invention This invention relates generally to cigarette lighters having a child-resistant mechanism and more specifically to lighters employing a double-button child-resistant mechanism. 2. Related Art Cigarette lighters containing piezoelectric units are very useful and have become quite prevalent in modern times. Cigarette lighters of the type described herein generally contain a lighter housing that is small enough to be held in the palm of an adult hand. The operation of piezoelectric cigarette lighters is somewhat simpler than that of the traditional flint / spark-wheel lighter. Generally, the lighter is operated by depressing an actuator button, which both activates the piezoelectric unit and acts on a fuel-release lever to release fuel. As a result, a flame is produced at a location opposite the actuator button. As is evident, this process avoids the need for operation of a spark wheel simultaneously with operation of a fuel-release button in order to generate a flame. Obviously, there is an advantage to the simplicity that is offered by piezoelectric cigarette lighters. On the other hand, in the hands of children, or others who do not know how to safely and properly operate the lighter, such lighters are as dangerous as any other spark and/or flame-producing device. Therefore, a need has been realized to equip cigarette lighters with safety features that minimize accidental or improper use by inexperienced persons, especially young children. Many inventions have been created to address this safety-related concern. Generally, these inventions have sought to introduce safety mechanisms that disable operation of the actuator button of the lighter. As such, these lighters normally consist of a safety feature whereby the operational path of the actuator button is blocked by a latch, button, slide, or other blocking means. Proper operation of the lighter requires that the blocking means be moved out of the path of the actuator button, or other structure that might be integral with the actuator button, before a flame can be produced. Only then is the operator able to depress the actuator button and produce a flame. As such, the prior art requires additional structural members. as well as additional steps (e.g., lateral or longitudinal disengagement of a blocking means), to operate the lighter. In some of the aforementioned cigarette lighters, the safety mechanism is passive. That is, once the safety feature is deactivated by moving the blocking member from the “locked” to the “unlocked” position, the lighter remains in the “unlocked” position, and thus is operable as a cigarette lighter with no safety feature at all. In these devices, the lighter remains in the “unlocked” position until the safety feature is activated again by manually re-engaging the safety mechanism (e.g., by manually returning the blocking means to the “locked” position). In order to address this problem, some inventions have introduced safety mechanisms that are activated automatically after each use of the lighter. In general, this improvement has alleviated some of the fears associated with leaving the lighter in an “unlocked”, operable position after the operator has finished using the lighter. Nevertheless, a disadvantage that is common to the passive, as well as the active, cigarette lighters is that their operation is usually quite cumbersome. Frequently, in order to use such cigarette lighters, the operator must use more than one finger, and sometimes more than one hand, to perform several functions simultaneously. As such, loss of ease of use is the price that is paid for any additional amount of safety that might be achieved. Therefore, there is a need for a device that not only achieves the stated safety goals, but also is amenable to operation with relative ease. The invention described herein offers such a combination and consists of a safety button that is similar in size and physical location to the conventional activation button. The invention requires that an ignition button, located in a cavity within the safety button, be depressed simultaneously with the safety button before a flame can be produced. In this way, young children are coaxed into believing that they can operate the lighter in the usual way, i.e., by pressing only the safety button. However, such operation will produce neither a spark nor a flame. Moreover, given the relatively small size of the ignition button, operation of this button requires an amount of strength and pulp that are rarely found in the fingers of young children. At the same time, due to the placement of the ignition button, simultaneous operation of both the safety button and the ignition button requires use of only one finger, so that operation of the lighter by the intended adult user is no different from operation of a lighter with no safety mechanism at all. SUMMARY OF THE INVENTION The primary object of this invention is to provide a safety mechanism for cigarette lighters so that children, or inexperienced users, will be less likely to inadvertently activate the lighter. Such a safety feature is especially important because young children often play with lighters as toys and because lighters have mechanically moveable parts that make them attractive to children as toys. A second object of the present invention is to provide an improved device for maximizing safety in cigarette lighters without compromising ease of use. The invention meets its objectives by providing an ignition button that must be depressed in order for a spark and a flame to be produced. The ignition button is placed within a cavity in the lighter's safety button, parallel to the lighter's longitudinal axis, with only a small portion of the ignition button (i.e., the ignition button's operation section) extending outside of the safety button's contact surface. Typically, a young child will attempt to activate the lighter by depressing the safety button only. However, when this is done, neither a spark nor a flame will be generated as the safety button is stopped along its path by a stopper before the spark-producing mechanism can be activated. The stopper is permanently attached to the inner surface of the lighter housing, so that it cannot be removed out of the safety button's path. As such, repeated operation of the safety button by a child will yield the same unsuccessful results. The only way to activate the lighter is to depress the ignition button. When this is done, initially, the ignition button and the safety button will move towards the bottom end of the lighter in unison. However, when the stopper engages the safety button, the operator must continue to depress the ignition button until the spark-producing mechanism is activated. This is a simple, yet effective concept. Nevertheless, it is a concept that a young child operating the lighter must recognize and grasp before he/she can successfully operate the lighter. In most cases, the child will not recognize the usefulness of the ignition button and will abandon the lighter after several unsuccessful attempts. Moreover, even if a child does attain an appreciation for the interrelationship between the ignition button, the safety button, and the production of a flame, he/she will still have difficulty activating the lighter. The portion of the ignition button that is exposed (i.e., the ignition button operation section) is small relative to the size of the safety button. As such, it is more difficult to fully depress the ignition button than if the operator needed to depress only the larger, more easily reachable, safety button. Thus, the single finger of a young child will not be able to fully depress the ignition button. Moreover, because of the smaller size and location of the ignition button, a child cannot use a plurality of fingers to try and depress the ignition button. As such, the strength needed to depress the ignition button, and the lack thereof in young children, itself acts as a deterrent in the present invention. Furthermore, in order for the lighter to be successfully operated, the ignition button must be pressed in far enough so that the ignition button's operation section travels just past the safety button's contact surface. In order to achieve this task, the operator's finger must have enough pulp to depress the ignition button past the contact surface of the safety button. While an adult operator can easily perform this procedure, a child operator will have difficulty doing so. Hence, again, the structural configuration of the safety mechanism of the present invention acts as a deterrent to use by young children. Finally, as can be understood from the above description, the invention disclosed herein achieves its safety objectives without making operation of the lighter any more cumbersome than a conventional piezoelectric cigarette lighter with no safety feature. Specifically, the ignition button is shaped and positioned in such a way that operation of the lighter is very simple in experienced hands. An adult user familiar with the operation of cigarette lighters need use only one finger and activate the lighter as he/she would normally by placing the finger on the safety and ignition buttons. This allows the user to operate the lighter in a safe, yet non-complicated manner. This and other advantages of the present invention will become more apparent through the following description of the drawings and detailed description of the preferred embodiment. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the preferred embodiment; FIG. 2 a perspective view with a thumb operating the lighter; FIG. 3 a top view of the preferred embodiment with the outline of the safety button and without the windscreen; FIG. 4A is longitudinal cross-sectional view of the preferred embodiment. FIG. 4B is the same view in the first stage of operation; and FIG. 4C is the same view in the second stage of operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A general description of the piezoelectric cigarette lighter ( 1 ) will be provided before presenting a detailed description of the safety feature that constitutes the invention. The primary elements of the cigarette lighter ( 1 ) include a lighter housing ( 10 ), a fuel tank ( 20 ) which occupies the bottom portion of the lighter housing, a piezoelectric unit ( 30 ), an electric circuit connector ( 40 ), a safety button ( 50 ), an ignition button ( 60 ), a flange ( 100 ), a fuel-release lever ( 70 ) that translates the motion of the ignition button to open a fuel-discharge valve ( 21 ), a stopper ( 80 ) which acts to limit motion of the safety button, and a windscreen ( 90 ). The lighter housing ( 10 ) of the lighter ( 1 ) has a cylindrical shape with an elliptical cross section, a bottom portion, and a top portion. A fuel tank ( 20 ) occupies substantially the bottom portion of the lighter housing ( 10 ) and contains conventional fuel, such as butane. Protruding from the top side of the fuel tank ( 20 ) is a fuel-discharge valve ( 21 ) which is spring loaded so that it is normally urged to the closed position. The valve is opened via the operation of a fuel-release lever ( 70 ). The lighter ( 1 ) is also equipped with a flame-adjusting wheel ( 22 ), which can be turned to adjust the amount of fuel released and thus, the height of the resultant flame. The next element of the lighter ( 1 ) is a piezoelectric unit ( 30 ). This unit is fitted within the top portion of the fuel tank and protrudes from said top portion, opposite the fuel-discharge valve ( 21 ). The piezoelectric unit has a lower section, which constitutes the piezoelectric housing ( 31 ), and an upper section, which constitutes the sliding section ( 32 ). Operation of the piezoelectric unit ( 30 ) creates an electric discharge that is carried to the fuel-discharge valve ( 21 ) via an electric circuit connector ( 40 ). The electric circuit connector ( 40 ) is generally made of material able to conduct electrical charge. Another element of the lighter is the flange ( 100 ) that has an upper horizontal surface and two lower horizontal surfaces. The two lower horizontal surfaces ( 101 and 102 ) engage the fuel-release lever ( 70 ). The upper horizontal surface adjoins the ignition button and the safety button. The flange is located between the ignition button and the sliding section of the piezoelectric unit. One of the primary elements of the child-resistant mechanism is the safety button ( 50 ). The safety button ( 50 ) is slidably mounted within the top portion of the lighter housing ( 10 ). The safety button ( 50 ) has integral guide arms ( 54 ) that allow the safety button to slide up and down along the longitudinal axis of, and relative to, the lighter housing ( 10 ). The safety button ( 50 ) has a contact surface ( 53 ), which has a generally flat surface, however, it is amenable to different degrees of curvature. The next primary element is an ignition button ( 60 ). The ignition button ( 60 ) is slidably fitted within an aperture in the safety button ( 50 ) and has an operation section ( 61 ) that is exposed outside of the safety button contact surface ( 53 ). The ignition button ( 60 ) is of a generally round shape and is located above the sliding section of the piezoelectric unit. The last primary element is the stopper ( 80 ). This is a projection that extends from the inner surface of the lighter housing ( 10 ), extending inward in a direction that is perpendicular to the longitudinal axis of the lighter ( 1 ). The stopper ( 80 ) functions by engaging and limiting the is downward movement of the safety button ( 50 ). Finally, the lighter ( 1 ) is equipped with a windscreen ( 90 ), which provides wind protection so that a flame is more easily generated, and less easily extinguished by wind. Moreover, the windscreen ( 90 ) holds the top portion of lighter ( 1 ) together by engaging the safety button ( 50 ) and the top portion of the lighter housing ( 10 ). In the preferred embodiment, the primary elements of the safety-related invention described herein, as well as the interaction between these and the other, more conventional, elements of the cigarette lighter can be further defined as follows. In the preferred embodiment, the safety button ( 50 ) is slidably secured between the lighter housing ( 10 ) and the windscreen ( 90 ). The guide arms of the safety button allow the safety button to slide in a direction that is parallel to the longitudinal axis of the lighter ( 1 ). As shown in FIGS. 4A through 4C, the safety button ( 50 ) abuts the upper horizontal surface ( 103 ) of the flange ( 100 ). In this manner, whenever the safety button ( 50 ) is depressed, the flange and, thus, the sliding section ( 32 ) of the piezoelectric unit ( 30 ), also move in the same direction. Depressing the safety button results in activation of the fuel-discharge valve though the fuel-release lever. Downward motion of the safety button ( 50 ) is limited, however, by the stopper ( 80 ). As shown in FIGS. 4A through 4C, the stopper ( 80 ) is a projection that extends inwardly from the inner surface of the lighter housing ( 10 ) and in a direction that is perpendicular to the longitudinal axis of the lighter ( 1 ). In the preferred embodiment, the stopper ( 80 ) is positioned so that it engages the bottom edge ( 51 ) of the back side of the safety button ( 50 ) as the safety button is depressed. Activation of the piezoelectric unit ( 70 ) is achieved via operation of the ignition button ( 60 ). As shown in FIGS. 3 and 4, the ignition button ( 60 ) is slidably held within a space ( 52 ) defined parallel to the longitudinal axis of the safety button ( 50 ) and has an operation section ( 61 ) that protrudes through the contact surface ( 53 ) of the safety button ( 50 ). The ignition button ( 60 ) is fixedly attached to the top surface of the flange ( 100 ). Although, in the diagrams depicting the preferred embodiment, the relative surface area of the operation section ( 61 ) of the ignition button ( 60 ) is shown to be approximately between one-third and one-half of that of the contact surface ( 53 ) of the safety button ( 50 ), this is not a requirement of the present invention. The smaller the cross-sectional area of the ignition button ( 60 ), the more difficult the operation of the lighter ( 1 ) for young children. As such, the relative sizes of the contact surface ( 53 ) and operation section ( 61 ) can be changed as dictated by safety requirements. Also, in the preferred embodiment, the aperture ( 52 ) is located near the middle of the safety button ( 50 ). The invention described herein is not limited to this feature of the embodiment either. For example, the aperture ( 52 ) and the ignition button ( 60 ) can be located much closer to the windscreen ( 90 ). This would not diminish from the effectiveness of the safety feature or the ease of use of the lighter ( 1 ) for adult operators. FIGS. 4A through 4C show the step-by-step operation of the preferred embodiment. The user operates the lighter ( 1 ) by depressing the operation section ( 61 ) of the ignition button ( 60 ). Initially, the ignition button ( 60 ) will move down slightly, until the surface of the operation section ( 61 ) of the ignition button ( 60 ) becomes parallel with the surface of the contact surface ( 53 ) of the safety button ( 50 ). As the user continues to apply downward pressure, both the ignition button ( 60 ) and the safety button ( 50 ) move in unison, until the stopper ( 80 ) engages the edge ( 51 ) of the safety button ( 50 ). As explained before, while this range of motion may be sufficient to open the fuel-discharge valve ( 21 ) via engagement of the fuel-release lever ( 70 ) by the flange ( 100 ), it is not enough to activate the piezoelectric unit ( 30 ). To achieve such activation, the user continues to depress the ignition button ( 60 ) below the contact surface ( 53 ) of the safety button ( 50 ). This requires that the user have sufficient pulp on his/her finger to push the operation section ( 61 ) of the ignition button ( 60 ) past the edge of, and inside, the aperture ( 52 ). This is a requirement that is rarely met in young children. When the user releases the ignition button ( 60 ), the ignition button ( 60 ) returns to its original position by the urging force of a spring, which is located in the piezoelectric unit ( 30 ). Also, as the sliding section ( 32 ) of the piezoelectric unit ( 30 ) moves upwards, the upper horizontal section ( 103 ) of the flange pushes up on the safety button ( 50 ), thereby disengaging the edge ( 51 ) of the safety button ( 50 ) from the stopper ( 80 ) and returning the safety button ( 50 ) to its original position. With reference to FIGS. 1 through 4, it is noted that the invention disclosed herein is not to be limited by the embodiment shown in the figures and described in the description, which is provided by way of example and not of limitation, but only in accordance with the scope of the appended claims.

A safety mechanism in a cigarette lighter that utilizes a double-button actuator system. The safety button has an aperture through which is positioned an ignition button. The safety button and the ignition button are adjoined by a flange such that when the safety button is depressed the ignition button is also depressed. The safety mechanism also includes a stopper, which limits the downward movement of the safety button. Thus the safety button translates downward sufficiently to operate the fuel-release lever opening the fuel-discharge valve. However, in order to activate the piezoelectric unit the ignition button must be depressed below the level of the contact surface of the safety button.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to German Application No. DE 10 2013 216 290.1, filed Aug. 16, 2013, the contents of which are hereby incorporated herein in its entirety by reference. TECHNOLOGICAL FIELD [0002] The invention relates to a heating device and to a method for operating a heating device. BACKGROUND [0003] U.S. Pat. No. 7,053,340 B2 discloses, in the case of a heating device which has a plurality of independent and separate long heating elements, dividing the heating elements into three heating elements. A first and a second heating element are connected to an energy supply means by means of an overtemperature protection means in the form of a so-called rod-type thermostat. The overtemperature protection means switches off the two heating elements in the event of an overtemperature. An overtemperature of this kind may be approximately 500° C. to 600° C. and be considered a hazard to a hob plate which is composed of glass ceramic. A third heating element is connected to an energy supply means directly and without monitoring by the overtemperature protection means and without interconnection of the overtemperature protection means. In this case, the electrical power of the third heating element is considerably lower than that of the first and second heating elements. BRIEF SUMMARY [0004] The invention is based on the object of providing a heating device of the kind described in the introductory part and also providing a method for operating the heating device, with which heating device and method problems in the prior art can be solved and it is possible, in particular, to allow firstly an accelerated initial cooking mode and secondly a keep-warm mode in conjunction with a so-called energy controller. [0005] This object is achieved by a heating device and also by a method. Advantageous and preferred refinements of the invention are the subject matter of the further claims and will be explained in greater detail in the text which follows. In the process, some of the features will be described only for the heating device or only for the method. However, irrespective of this, they are intended to be independently applicable both to the heating device and also to the method. The wording of the claims is incorporated in the description by express reference. [0006] Provision is made for the heating device to be provided for a cooking point in a hob or for a cooking point of this kind to be formed by the heating device. The heating device has a plurality of independent and separate long or elongate heating elements, for example according to U.S. Pat. No. 5,498,853 A, which are arranged on a support of the heating device in loops and/or in a spiral manner and/or in a meandering manner and/or substantially along concentric circles. The support has at least one central region in the middle or around a centre point, and also an outer region which adjoins an outer edge. The width of the central region and the width of the outer region can be approximately equal, wherein the central region can preferably be somewhat wider, for example 10% to 30% or even up to 40% wider. The heating elements run on the support so as to engage one in the other and cover a significant area of the support. This is known from the abovementioned document U.S. Pat. No. 5,498,853 A. [0007] An overtemperature protection means engages over the heating device or the support or the overtemperature protection means is located above the heating device or support. The overtemperature protection means can detect the temperature above the heating device or at least that a specific temperature has been reached, specifically the so-called overtemperature at the heating device. The overtemperature protection means can then act on the heating device such that the heating power of the heating device is reduced and the temperature falls again. At least a first heating element is connected to an energy supply means by means of this overtemperature protection means in order to switch off the first heating element in the event of an overtemperature. A second heating element, preferably solely the second heating element, is connected to an energy supply means without interconnection of the overtemperature protection means or another overtemperature protection means. [0008] According to the invention, the second heating element is arranged on the support both in the central region and in the outer region, advantageously in a distributed manner in each case, wherein the heating element has at least one turn or circulates once in each of the two regions. Therefore, expressed in simple terms, the second heating element is provided in an outer region of the heating device and in an inner region of the heating device and not only on the outside or only on the inside. As a result, both an abovementioned keep-warm mode with a low power and also an additionally increased power in the initial cooking mode can be achieved more easily. [0009] In an advantageous refinement of the invention, provision is made for the support to be circular in the case of two regions in which the second heating element runs. In this case, the central region lies in an inner radius range of up to 50% or 60% of the radius. The outer region adjoins the outside of the central region and therefore lies in an outer radius range over 40% or 50% of the radius. In this case, the second heating element runs in two regions, that is to say as it were on the inside and on the outside. [0010] In an alternative refinement, an intermediate region is further provided between the central region and the outer region, the second heating element likewise running with at least one turn in the intermediate region. The width of the three regions can be approximately equal, wherein the width of the central region is advantageously larger. The support can be circular in this case too, wherein the central region lies in an inner radius range of up to 40% to 50% or even up to 60% of the radius. The intermediate region adjoins the outside of the central region in an intermediate radius range of 40% or 50% to 70% or 80% of the radius. The outer region again adjoins the outside of the intermediate region and lies in an outer radius range over 70% or 80% of the radius. [0011] In a modification of the invention, the supports may not be circular in the two abovementioned alternatives, but rather elongate and oval or approximately rectangular. The information relating to the widths or the radii of the two or three regions is equivalent in this case, wherein the percentages in that case do not relate to the radius of a circular shape, but rather relate to the narrowest half width of the entire heating device. [0012] In an advantageous refinement, the majority of the support is covered by heating elements. At least 10% or 20% of the radius up to 100% of the radius, in particular up to a maximum of 95%, of the support is advantageously covered by at least one heating element. A distance between the heating elements or between two turns of the heating elements which run next to one another can lie in the region of a few mm, for example 2 mm to 5 mm or even 8 mm. This distance is advantageously substantially equal for the entire heating device. [0013] Provision may be made for an outermost turn of the heating device to not be formed by the second heating element, but rather, for example, by the first heating element or a third heating element. Provision may further be made for a second-outermost turn of all of the heating elements or of the heating device to be formed by the second heating element. Therefore, it is also the outermost turn of the second heating element. [0014] Provision may be made for, at most, a third-innermost turn of the heating elements or of the heating device to be formed by the second heating element as the innermost turn of the heating element. It is initially advantageously a fourth-innermost turn, so that no turn of the second heating element, but rather advantageously only of the first heating element, is provided around a centre of the heating device. [0015] In an advantageous refinement of the invention, provision is made for the second heating element to be arranged on the support substantially in duplicate and parallel next to another in so-called double turns. At least one turn, preferably at least one double turn, of another heating element or of the first heating element is provided between two double turns of the second heating element, in particular between the two outermost double turns of the second heating element. This results in no two double turns of the second heating element running directly next to one another because otherwise too great an annular region of the heating device or on the support would be covered only by the second heating element and this could mean an undesirably high power concentration without overtemperature protection. The second heating element is advantageously arranged only in double turns on the support. This may also apply to further heating elements. Two or four turns of another heating element, which may be the first heating element but under certain circumstances may also be a third heating element, particularly advantageously always run between two double turns of the second heating element. [0016] The heating device can be in the form of a twin-ring heating device and have three heating elements, wherein the three abovementioned regions are then also advantageously provided as central region, intermediate region and outer region. A first heating element can be provided primarily in the central region and not in the outer region. A third heating element can be provided primarily in the outer region and advantageously not in the central region. A second heating element runs in all three regions just as described above. [0017] In an advantageous refinement of the invention, the overtemperature protection means is a so-called rod-type thermostat with an elongate thermomechanical expansion element. Rod-type thermostats of this kind are known, for example, from U.S. Pat. No. 4,633,238 A or U.S. Pat. No. 4,544,831 A. At a specific temperature, a switch is tripped by the thermomechanical expansion element and therefore the first heating element, under certain circumstances also the abovementioned third heating element, is switched off [0018] Provision can be made for the power of the second heating element to be at most 1200 watts, preferably 1000 watts, at a mains voltage of 230 volts. The power per unit area of the second heating element may advantageously lie below 2.5 W/cm2. [0019] Therefore, according to the invention, the second heating element is operated without interconnection of the overtemperature protection means and also without monitoring by the overtemperature protection means. In a keep-warm mode of the cooking point or of the heating device, the second heating element can be operated on its own, without the overtemperature protection means. In a normal cooking mode, the second heating element can be connected as required, but does not have to be. In an initial cooking mode, all of the heating elements of the heating device are operated, in particular in a twin-ring heater in the twin-ring mode. In this case, the second heating element has the advantage for a particularly high initial cooking power that, at an excessive temperature, the overtemperature protection means for protecting a glass-ceramic hob plate responds and switches off a first and possibly a third heating element for safety reasons. However, in order that the electrical power does not fall to zero directly after this, but at the same time a relatively low power cannot be generated by the switched-off heating elements without changing the power stage set by an operator, the second heating element can continue to be operated. The power per unit area of the second heating element is relatively low on account of the large distribution, wherein it is advantageously less than 2.5 W/cm2. If the temperature beneath the hob plate has then again fallen so far that the overtemperature protection means again enables or again switches on the first and the third heating element, the first and third heating elements can again operate additionally and at a very high total power. [0020] These and further features are apparent not only from the claims but also from the description and the drawings, where the individual features can in each case be realized on their own or jointly in the form of subcombinations in an embodiment of the invention and in other fields and can constitute advantageous and inherently protectable embodiments for which protection is claimed here. The subdivision of the application into subheadings and individual sections does not restrict the general validity of the statements made thereunder. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS [0021] Exemplary embodiments of the invention are schematically illustrated in the drawings and will be explained in greater detail in the text which follows. In the drawings: [0022] FIG. 1 is a schematic illustration of a support for a heating device according to the invention divided into three radius ranges, [0023] FIG. 2 shows a heating device with the support from FIG. 1 and covered by three heating elements, wherein only an innermost heating element is active, [0024] FIG. 3 shows the heating device from FIG. 2 in another operating state with all three heating elements activated, [0025] FIG. 4 shows a modification of the support from FIG. 1 divided into two radius ranges, [0026] FIG. 5 is an illustration of a circuit diagram for driving with a setting switch for the heating device from FIG. 3 , and [0027] FIG. 6 shows a schematically illustrated energy controller with description of its rotation angle regions. DETAILED DESCRIPTION [0028] FIG. 1 shows a support 10 for an electrical heating device 11 according to FIG. 2 , which support is of circular design and has a peripheral support edge 10 a and a central raised support portion 10 b which is illustrated centrally in FIG. 2 . The flat area of the support 10 within the support edge 10 a is divided into three radius ranges, specifically a central region I, an intermediate region II and an outer region III. The central region I has a radius r 1 and a width b 1 . The intermediate region II extends with a width b 2 between the radii r 1 and r 2 . The outer region III extends with a width of b 3 between the radii of r 2 and r 3 . It can be seen that the radius r 1 takes up almost 50% of the total radius of the support 10 or within the support edge 10 a. The radius r 2 takes up approximately 75% and the radius r 3 takes up almost 100% within the support edge 10 a. The width b 1 of the central region I is therefore somewhat greater than that of the other regions II and III, wherein the area requirement for the raised support portion 10 b is to be taken into consideration. [0029] FIG. 2 shows how a rod-type thermostat 13 with a switching housing 14 and a long sensor 15 is arranged on the support 10 or on the heating device 11 . In this case, the elongate straight sensor 15 extends as far as the raised support portion 10 b and there is fitted to the raised support portion in a manner which is known per se, and possibly fastened by means of a clip. A connection region 17 is provided next to the rod-type thermostat 13 or its switching housing 14 , the connection region having a plurality of connection lugs or plug connections as an electrical contact-making means to the heating elements. [0030] The heating elements of the heating device 11 run on the support 10 . A first heating element 20 , which runs in the inner of the two regions I and II and in particular also forms the three innermost turns in the central region I, is illustrated shaded black. The first heating element is connected to a connection lug 17 ′ which is connected to the rod-type thermostat 13 or the rod-type thermostat 13 is looped into the energy supply means of the connection lug. The first heating element is also switched on. [0031] A second heating element 22 runs in three double turns. The innermost double turn runs in the central region I, specifically as it were embedded centrally into the first heating element 20 . The middle double turn runs in the intermediate region II so as to radially adjoin the outside of the first heating element 20 . The third and outermost double turn of the second heating element 22 runs in the outer region III relatively far on the outside of the support 10 . Only an individual turn of a third heating element 24 is further provided radially outside the outer region, the third heating element running in the outer region III and in the transition to the intermediate region II. The third heating element 24 has only one double turn and the outermost individual turn in this case. As described above for the first heating element 20 , the third heating element 24 is also connected to an energy supply means by means of the connection lug 17 ′ with a looped-in rod-type thermostat 13 as the overtemperature protection means. [0032] In the connection region 17 , it can be seen that the three heating elements 20 , 22 and 24 can each be switched on or driven separately. The electrical connections to the second heating element 22 pass by the rod-type thermostat 13 or the corresponding connection lug 17 ′. [0033] The transition between the three regions I, II and III is once again illustrated along the profile of the sensor 15 by the encircled vertical bars. [0034] Only the first heating element 20 is in operation here in FIG. 2 . Since the entire heating device 11 is in the form of a so-called twin-ring heating means, the first heating element 20 forms the first ring or the small diameter in the single-ring mode, wherein the diameter can in this case be considered to be an approximately 140 mm cooking point. During operation as a single ring according to FIG. 2 , the heating power of the first heating element 20 is approximately 1200 watts at 230 volts. The second heating element 22 and the third heating element 24 are switched off in this case. [0035] The illustration of FIG. 2 is repeated in FIG. 3 . In FIG. 3 , the second heating element 22 is illustrated shaded with wavy lines and the third heating element 24 is not marked, in order to distinguish between them. All three heating elements 20 , 22 and 24 are in operation in FIG. 3 . The diameter is approximately 230 mm in this twin-ring mode. In this case, the total electrical power is 3200 watts at a supply voltage of 230 volts; therefore all three heating elements are connected in parallel. The second heating element 22 and the third heating element 24 have a heating power of in each case approximately 1000 watts. [0036] With the known function of the rod-type thermostat 13 , it is apparent that the first heating element 20 and the third heating element 24 are switched off by the rod-type thermostat 13 in the event of an overtemperature. However, the second heating element 22 can be operated at a relatively high power without an overtemperature protection means of this kind or permanently operated on account of the widely-spaced or separated distribution. Therefore, the generation of power can be increased overall in a desired mode with a very high power or high initial cooking power as initial cooking mode. Furthermore, a low permanent power, which may be available in the twin-ring mode with a large pot, could theoretically also be achieved per se on account of the relatively low power of the second heating element which, in relation to the area which is heated by it overall, is less than the abovementioned 2.5 W/cm 2 . The second heating element would advantageously have to be electronically driven for this purpose. [0037] Furthermore, as an alternative, the unprotected power of the second heating element 22 can be switched off, in particular when even the initial cooking mode is not in operation, and a power of at most 2200 watts remains. Given a minimum power release by means of a power actuator or energy controller, for example in accordance with DE 102008014805 A1 or US RE 31596 E, of 6%, 132 watts are produced as the total power. Although this is relatively low, it may be sufficient for a keep-warm mode on the cooking point in the twin-ring mode with the full area. [0038] FIG. 5 shows a circuit diagram for the heating device 11 according to the invention together with the conventional energy controller as power control device 25 , as is known and primarily can be realized with a power control device according to US RE 31596 E together with additional switches or setting switch 26 . The power control device uses the so-called relative switch-on period ED according to U.S. Pat. No. 6,064,045 A to control the on and off times of the heating elements or the timing ratio for the energy supply. A setting switch 26 is illustrated using dashed lines, the setting switch being additionally mounted on a power control device 25 which is illustrated using dashed-and-dotted lines and being co-rotated by the same rotary shaft. In addition to setting the power by means of the power control device 25 , the setting switch 26 can connect or disconnect the second heating element 22 , which is illustrated at the bottom, to or from the power control device. [0039] FIG. 6 shows the setting options for the heating device 11 according to the invention in line with the method according to the invention. From the zero position at 0° or at OFF, it is possible to turn anticlockwise to the left, this leading to the so-called single-ring mode. In this case, only the first heating element 20 is operated and therefore the single-ring mode is largely of no interest in terms of the invention. [0040] Turning from the zero position at 0° at OFF to the right in the clockwise direction leads to the twin-ring mode with the heating elements 20 and 24 . At 45°, latching is provided with a latching position which corresponds to a maximum power. In this case, a value for ED of 100% is provided for the heating elements 20 and 24 , and the second heating element 22 is also connected by means of the setting switch 26 . Accordingly, the heating elements 20 and 24 are actually permanently switched on as standard, and only the overtemperature protection means switches off the heating elements by means of the rod-type thermostat 13 when the switching point of the rod-type thermostat is reached. However, the second heating element 22 continues to operate in this case, as explained above. [0041] Further rotation to the right reduces the value for ED until it reaches the lowest value, specifically ED=6%, at an angle of approximately 167°, wherein this position can be defined by latching and/or a stop. Furthermore, the second heating element 22 is switched off by means of the setting switch 26 starting from an angle of greater than 45°, and therefore the heating element can be operated only at the maximum power. At the position of 167°, a low power of 132 watts, which is advantageous for an abovementioned keep-warm mode, is available at 6% of the power of the heating elements 20 and 24 which together produce 2200 watts. [0042] FIG. 4 shows, as a modification of the illustration from FIG. 1 , a heating device 111 according to the invention with a support 110 , wherein the area of the support 110 is divided only into a central region I′ and an outer region II′. The central region I′ extends up to a radius of r 1 and has a width of b 1 . The outer region II′ extends from the radius r 1 up to a radius r 2 and has a width of b 2 . In this case, the statements made at the outset correspondingly apply; the second heating element 22 of FIG. 2 and FIG. 3 could run in the central region I′ and in the outer region II′. A first heating element and, where possible, also a third heating element could be divided between the central region I′ and the outer region II′.

A heating device for a cooking point in a hob has three independent and separate long heating elements which are arranged on a support of the heating device along concentric circles. The support has a central region around the centre point, an outer region adjoining an outer edge, and an intermediate region between the central region and outer region. A rod-type thermostat engages over the heating device for the purpose of temperature detection. The first and the third heating element are connected to an energy supply over the rod-type thermostat. A second heating element is connected to an energy supply without interconnection of the rod-type thermostat, wherein the second heating element is arranged on the support in the central region, in the intermediate region and in the outer region.

This application claims benefit to Provisional Application No. 60/287,720 filed May 2, 2001; the disclosure of which is incorporated herein by reference. TECHNICAL FIELD The present invention relates to a novel use of a 15-keto-prostaglandin compound for treating drug-induced constipation. RELATED ART Constipation is classified into functional constipation such as an atonic constipation, spastic constipation, rectal constipation, organic constipation such as caused by bowel disease and by stenosis due to postoperative adhesion, drug-induced constipation and the like. Drug-induced constipation occurs as a side effect caused by using a drug. The drug may cause constipation not directly but indirectly. For example, constipation may be due to hard feces caused by fluid excretion outside the body with a diuretic. Further, it may be caused by an additive or synergistic effect of using plural drugs, each of which does not introduce constipation if administrated individually. It is known that drugs causing constipation include narcotics used for controlling cancer pain (opioid-narcotic such as morphine and codeine), anticholinergic (such as antiparkinsonism drug, tricyclic and tetracyclic antidepressant and antiincontinence drug), antacid (such as aluminium preparation), bone weight increasing agent (such as calcium preparation), diuretic, iron preparation, calcium antagonist, benzodiazepine compound, phenotiazine compound (such as chlorpromazine), H 2 -blocker, pill, tocopherol and the like. For example, opioid such as morphine, which is one kind of narcotics, has a depressant action on the central nervous system (such as analgesic, antitussive, sedative or hypnotic action) and, since its analgesic action is extremely strong, it is effective for almost all pains including surgical and cancer pains. On the other hand, it exhibits a constipating action by affecting gastrointestine as a peripheral effect. Accordingly, when morphine is used for treating pain, almost all the patients applied with morphine constipate, and failure to control it will cause intractable constipation. Constipation is caused by administering the dose of morphine necessary for effecting analgesic action and it is hard to become tolerant, so that constipation continues as long as the administration of morphine by any route continues. For example, if morphine is applied to a cancer patient for relieving pain without taking sufficient steps for controlling constipation, it will become unable to continue the administration of morphine, thus degrading the therapeutic result of cancer pain relief. For this reason, during repetitious administration of morphine, it is very important to control constipation. However, it has been reported that constipation induced by opioid such as morphine is not often sufficiently controlled by conventional cathartics (Twycross, R. G. et al.: Constipation. In: Control of alimentary symptoms in far advanced cancer. Edinburgh: Churchill Livingstone, 1986: 172-177, the cited references are herein incorporated by reference). Recently, opioid antagonist such as naloxone has been tried to relax opioid-induced constipation at the sacrifice of analgesic action of opioid. It has been reported that use of opioid antagonist against opioid-induced constipation causes side effects such as return of pain and opioid withdrawal, which is contradict to the original purpose of the opioid administration (Culpepper-Morgan, J. A. et al.: NIDA Res. Monoger. 95: 399-400, 1989. and Clin. Pharmacol. Ther. 52: 90-95, 1992: Sykes, N. P.: Palliat-Med.10:135-144, 1996, the cited references are herein incorporated by reference). Accordingly, it has been desired to develop a drug for relaxing drug-induced constipation without losing the main effect, for example, analgesic action of opioid such as morphine, of the drug. Prostaglandins (hereinafter, referred to as PG(s)) are members of class of organic carboxylic acids, which are contained in tissues or organs of human or other mammals, and exhibit a wide range of physiological activity. PGs found in nature (primary PGs) generally have a prostanoic acid skeleton as shown in the formula (A): On the other hand, some of synthetic analogues of primary PGs have modified skeletons. The primary PGs are classified to PGAs, PGBs, PGCs, PGDs, PGEs, PGFs, PGGs, PGHs, PGIs and PGJs according to the structure of the five-membered ring moiety, and further classified into the following three types by the number and position of the unsaturated bond at the carbon chain moiety: Subscript 1: 13,14-unsaturated-15-OH Subscript 2: 5,6- and 13,14-diunsaturated-15-OH Subscript 3: 5,6-, 13,14-, and 17,18-triunsaturated-15-OH. Further, the PGFs are classified, according to the configuration of the hydroxyl group at the 9-position, into α type (the hydroxyl group is of an α-configuration) and β type (the hydroxyl group is of a β-configuration). PGE 1 and PGE 2 and PGE 3 are known to have vasodilatation, hypotension, gastric secretion decreasing, intestinal tract movement enhancement, uterine contraction, diuretic, bronchodilation and anti ulcer activities. PGF 1α , PGF 2α and PGF 3α have been known to have hypertension, vasoconstriction, intestinal tract movement enhancement, uterine contraction, lutein body atrophy and bronchoconstriction activities. In addition, some 15-keto PGs (i.e. those having an oxo group at position 15 in place of the hydroxy group) and 13,14-dihydro-15-keto-PGs are known as substances naturally produced by enzymatic reactions during in vivo metabolism of primary PGs. 15-keto PG compound have been disclosed in the specification of U.S. Pat. Nos. 5,073,569, 5,166,174, 5,221,763, 5,212,324 and 5,739,161 (These cited references are herein incorporated by reference). The so-called primary PGs having hydroxy at the 15-position such as PGE 1 , PGE 2 and the derivatives or analogs thereof are known to antagonize the enterogastric action of morphine (Christmas A. J.: Prostaglandins 18, 279-284, 1979; B. J. Broughton: Prostaglaindins 22, 53-64, 1981, the cited references are herein incorporated by reference). However, PGE 1 and PGE 2 are well known pain enhancing substances, which augment the action of bradykinin, a strong pain producing substance, and other pain producing substances. Accordingly, the so-called primary PGs having hydroxy at the 15-position have a possibility of affecting the analgesic action of opioid. On the other hand, a 15-keto-16-halogen-PG compound is known to be useful as a cathartic (U.S. Pat. No. 5,317,032). However, it is not known at all how the 15-keto-PG compound affects the opioid-induced constipation or how it affects the main effect of a drug, e.g., the analgesic action of opioid. SUMMARY OF THE INVENTION The purpose of the present invention is to provide a composition for treating drug-induced constipation, which has a strong antagonistic action against drug-induced constipation without substantially losing the main effect of the drug. As a result of a diligent research for biological activity of 15-keto-prostaglaindin compounds, the present inventor has found that a 15-keto-prostaglaindin compound has a superior antagonistic action against drug-induced constipation. Especially, because of its superior antagonistic action against opioid-induced constipation without affecting the analgesic action of opioid such as morphine on central nervous system, the compound has been found to be very useful for controlling opioid-induced constipation. Thus, the present invention has been completed. Namely, the present invention relates to a composition for treating drug-induced constipation comprising a 15-keto-prostaglandin compound as an active ingredient. The present invention also relates to a method for treating drug-induced constipation comprising a step of administering an effective amount of 15-keto-prostaglaindin compound to a subject suffering from drug-induced constipation or a subject having a strong possibility of suffering from it. The present invention further relates to use of a 15-keto-prostaglaindin compound for manufacturing a pharmaceutical composition for treating drug-induced constipation. DETAILED DESCRIPTION OF THE INVENTION In the present invention, the “15-keto-prostaglandin compound” (hereinafter, referred to as “15-keto-PG compound”) may include any of derivatives or analogs (including substituted derivatives) of a compound having an oxo group at 15-position of the prostanoic acid skeleton instead of the hydroxy group, irrespective of the configuration of the five-membered ring, the number of double bonds, presence or absence of a substituent, or any other modification in the α or ω chain. The nomenclature of the 15-keto-PG compounds used herein is based on the numbering system of the prostanoic acid represented in the above formula (A). The formula (A) shows a basic skeleton of the C-20 carbon atoms, but the 15-keto-PG compounds in the present invention are not limited to those having the same number of carbon atoms. In the formula (A), the numbering of the carbon atoms which constitute the basic skeleton of the PG compounds starts at the carboxylic acid (numbered 1), and carbon atoms in the α-chain are numbered 2 to 7 towards the five-membered ring, those in the ring are 8 to 12, and those in the ω-chain are 13 to 20. When the number of carbon atoms is decreased in the α-chain, the number is deleted in the order starting from position 2; and when the number of carbon atoms is increased in the α-chain, compounds are named as substitution compounds having respective substituents at position 2 in place of the carboxy group (C-1). Similarly, when the number of carbon atoms is decreased in the ω-chain, the number is deleted in the order starting from position 20; and when the number of carbon atoms is increased in the ω-chain, the carbon atoms beyond position 20 are named as substituents. Stereochemistry of the compounds is the same as that of the above formula (A) unless otherwise specified. In general, each of the terms PGD, PGE and PGF represents a PG compound having hydroxy groups at positions 9 and/or 11, but in the present specification, these terms also include those having substituents other than the hydroxy group at positions 9 and/or 11. Such compounds are referred to as 9-dehydroxy-9-substituted-PG compounds or 11-dehydroxy-11-substituted-PG compounds. A PG compound having hydrogen in place of the hydroxy group is simply named as 9- or 11-dehydroxy compound. As stated above, the nomenclature of the 15-keto-PG compounds is based on the prostanoic acid skeleton. However, in case the compound has a similar partial construction as a prostaglandin, the abbreviation of “PG” may be used. Thus, a PG compound of which α-chain is extended by two carbon atoms, that is, having 9 carbon atoms in the α-chain is named as 2-decarboxy-2-(2-carboxyethyl)-15-keto-PG compound. Similarly, a PG compound having 11 carbon atoms in the α-chain is named as 2-decarboxy-2-(4-carboxybutyl)-15-keto-PG compound. Further, a PG compound of which ω-chain is extended by two carbon atoms, that is, having 10 carbon atoms in the ω-chain is named as 15-keto-20-ethyl-PG compound. These compounds, however, may also be named according to the IUPAC nomenclatures. The 15-keto-PGs used in the present invention may include any PG derivatives or analogs insofar as having an oxo group at position 15 in place of the hydroxy group. Accordingly, for example, a 15-keto-PG type 1 compound having a double bond at 13-14 position, a 15-keto-PG type 2 compound having two double bond at 13-14 and 5-6 position, a 15-keto-PG type 3 compound having three double bond at 5-6, 13-14 and 17-18 position, 13,14-dihydro-15-keto-PG compound wherein the double bond at 13-14 position is single bond. Typical examples of the compounds used in the present invention include 15-keto-PG type 1, 15-keto-PG type 2, 15-keto-PG type 3, 13,14-dihydro-15-keto-PG type 1, 13,14-dihydro-15-keto-PG type 2, 13,14-dihydro-15-keto-PG type 3 and the derivatives or analogs thereof. Examples of the analogs (including substituted derivatives) or derivatives include a 15-keto-PG compound of which carboxy group at the end of α-chain is esterified; a compound of which α-chain is extended; physiologically acceptable salt thereof; a compound having a double bond at 2-3 position or a triple bond at position 5-6, a compound having substituent(s) at position 3, 5, 6, 16, 17, 18, 19 and/or 20; and a compound having lower alkyl or a hydroxy (lower) alkyl group at position 9 and/or 11 in place of the hydroxy group. According to the present invention, preferred substituents at position 3, 17, 18 and/or 19 include alkyl having 1-4 carbon atoms, especially methyl and ethyl. Preferred substituents at position 16 include lower alkyl such as methyl and ethyl, hydroxy, halogen atoms such as chlorine and fluorine, and aryloxy such as trifluoromethylphenoxy. Preferred substituents at position 17 include lower alkyl such as methyl and ethyl, hydroxy, halogen atoms such as chlorine and fluorine, aryloxy such as trifluoromethylphenoxy. Preferred substituents at position 20 include saturated or unsaturated lower alkyl such as C1-4 alkyl, lower alkoxy such as C1-4 alkoxy, and lower alkoxy alkyl such as C1-4 alkoxy-C1-4 alkyl. Preferred substituents at position 5 include halogen atoms such as chlorine and fluorine. Preferred substituents at position 6 include an oxo group forming a carbonyl group. Stereochemistry of PGs having hydroxy, lower alkyl or hydroxy(lower)alkyl substituent at position 9 and/or 11 may be α, β or a mixture thereof. Further, the above analogs or derivatives may be compounds having an alkoxy, cycloalkyl, cycloalkyloxy, phenoxy or phenyl group at the end of the ω-chain where the chain is shorter than the primary PGs. Especially preferred compounds include a 13,14-dihydro-15-keto-PG compound which has a single bond at position 13-14; a 15-keto-16 mono or di-halogen PG compound which has one or two halogen atoms such as chlorine and fluorine at position 16; and a 15-keto-PGE compound which has an oxo group at position 9 and a hydroxyl group at position 11 of the five membered ring. A preferred compound used in the present invention is represented by the formula (I): wherein L, M and N are hydrogen, hydroxy, halogen, lower alkyl, hydroxy(lower)alkyl, or oxo, wherein at least one of L and M is a group other than hydrogen, and the five-membered ring may have at least one double bond; A is —CH 2 OH, —COCH 2 OH, —COOH or a functional derivative thereof; B is —CH 2 —CH 2 —, —CH═CH— or —C≡C—; R 1 is a saturated or unsaturated bivalent lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, alkyl, hydroxy, oxo, aryl or heterocyclic group and at least one of carbon atom in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur; and Ra is a saturated or unsaturated lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, oxo, hydroxy, lower alkoxy, lower alkanoyloxy, cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclic group or hetrocyclic-oxy group; cyclo(lower)alkyl; cyclo(lower)alkyloxy; aryl; aryloxy; heterocyclic group; heterocyclic-oxy group. A group of particularly preferable compounds among the above-described compounds is represented by the formula (II): wherein L and M are hydrogen, hydroxy, halogen, lower alkyl, hydroxy(lower)alkyl or oxo, wherein at least one of L and M is a group other than hydrogen, and the five-membered ring may have at least one double bond; A is —CH 2 OH, —COCH 2 OH, —COOH or a functional derivative thereof; B is —CH 2 —CH 2 —, —CH═CH—, —C≡C—; X 1 and X 2 are hydrogen, lower alkyl, or halogen; R 1 is a saturated or unsaturated bivalent lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, alkyl, hydroxy, oxo, aryl or heterocyclic group and at least one of carbon atom in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur; R 2 is a single bond or lower alkylene; and R 3 is lower alkyl, lower alkoxy, cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclic group or heterocyclic-oxy group. In the above formula, the term “unsaturated” in the definitions for R 1 and Ra is intended to include at least one or more double bonds and/or triple bonds that are isolatedly, separately or serially present between carbon atoms of the main and/or side chains. According to the usual nomenclature, an unsaturated bond between two serial positions is represented by denoting the lower number of the two positions, and an unsaturated bond between two distal positions is represented by denoting both of the positions. The term “lower or medium aliphatic hydrocarbon” refers to a straight or branched chain hydrocarbon group having 1 to 14 carbon atoms (for a side chain, 1 to 3 carbon atoms are preferable) and preferably 1 to 10, especially 6 to 10 carbon atoms for R 1 and 1 to 10, especially 1 to 8 carbon atoms for R a . The term “halogen” covers fluorine, chlorine, bromine and iodine. The term “lower” throughout the specification is intended to include a group having 1 to 6 carbon atoms unless otherwise specified. The term “lower alkyl” refers to a straight or branched chain saturated hydrocarbon group containing 1 to 6 carbon atoms and includes, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl and hexyl. The term “lower alkylene” refers to a straight or branched chain bivalent saturated hydrocarbon group containing 1 to 6 carbon atoms and includes, for example, methylene, ethylene, propylene, isopropylene, butylene, isobutylene, t-butylene, pentylene and hexylene. The term “lower alkoxy” refers to a group of lower alkyl-O-, wherein lower alkyl is as defined above. The term “hydroxy(lower)alkyl” refers to a lower alkyl as defined above which is substituted with at least one hydroxy group such as hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl and 1-methyl-l-hydroxyethyl. The term “lower alkanoyloxy” refers to a group represented by the formula RCO—O—, wherein RCO— is an acyl group formed by oxidation of a lower alkyl group as defined above, such as acetyl. The term “cyclo(lower)alkyl” refers to a cyclic group formed by cyclization of a lower alkyl group as defined above but contains three or more carbon atoms, and includes, for example, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. The term “cyclo(lower)alkyloxy” refers to the group of cyclo(lower)alkyl-O-, wherein cyclo(lower)alkyl is as defined above. The term “aryl” may include unsubstituted or substituted aromatic hydrocarbon rings (preferably monocyclic groups), for example, phenyl, tolyl, and xylyl. Examples of the substituents are halogen atom and halo(lower)alkyl, wherein halogen atom and lower alkyl are as defined above. The term “aryloxy” refers to a group represented by the formula ArO—, wherein Ar is aryl as defined above. The term “heterocyclic group” may include mono- to tri-cyclic, preferably monocyclic heterocyclic group which is 5 to 14, preferably 5 to 10 membered ring having optionally substituted carbon atom and 1 to 4, preferably 1 to 3 of 1 or 2 types of hetero atoms selected from nitrogen atom, oxygen atom and sulfur atom. Examples of the heterocyclic group include furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, imidazolyl, pyrazolyl, furazanyl, pyranyl, pyridyl, pyridazinyl, pyrimidyl, pyrazinyl, 2-pyrrolinyl, pyrrolidinyl, 2-imidazolinyl, imidazolidinyl, 2-pyrazolinyl, pyrazolidinyl, piperidino, piperazinyl, morpholino, indolyl, benzothienyl, quinolyl, isoquinolyl, purinyl, quinazolinyl, carbazolyl, acridinyl, phenanthridinyl, benzimidazolyl, benzimidazolonyl, benzothiazolyl, phenothiazinyl. Examples of the substituent in this case include halogen, and halogen substituted lower alkyl group, wherein halogen atom and lower alkyl group are as described above. The term “heterocyclic-oxy group” means a group represented by the formula HcO—, wherein Hc is a heterocyclic group as described above. The term “functional derivative” of A includes salts (preferably pharmaceutically acceptable salts), ethers, esters and amides. Suitable “pharmaceutically acceptable salts” include conventionally used non-toxic salts, for example a salt with an inorganic base such as an alkali metal salt (such as sodium salt and potassium salt), an alkaline earth metal salt (such as calcium salt and magnesium salt), an ammonium salt; or a salt with an organic base, for example, an amine salt (such as methylamine salt, dimethylamine salt, cyclohexylamine salt, benzylamine salt, piperidine salt, ethylenediamine salt, ethanolamine salt, diethanolamine salt, triethanolamine salt, tris(hydroxymethylamino) ethane salt, monomethyl-monoethanolamine salt, procaine salt and caffeine salt), a basic amino acid salt (such as arginine salt and lysine salt), tetraalkyl ammonium salt and the like. These salts may be prepared by a conventional process, for example from the corresponding acid and base, or by salt interchange. Examples of the ethers include alkyl ethers, for example, lower alkyl ethers such as methyl ether, ethyl ether, propyl ether, isopropyl ether, butyl ether, isobutyl ether, t-butyl ether, pentyl ether and 1-cyclopropyl ethyl ether; and medium or higher alkyl ethers such as octyl ether, diethylhexyl ether, lauryl ether and cetyl ether; unsaturated ethers such as oleyl ether and linolenyl ether; lower alkenyl ethers such as vinyl ether, allyl ether; lower alkynyl ethers such as ethynyl ether and propynyl ether; hydroxy(lower)alkyl ethers such as hydroxyethyl ether and hydroxyisopropyl ether; lower alkoxy (lower)alkyl ethers such as methoxymethyl ether and 1-methoxyethyl ether; optionally substituted aryl ethers such as phenyl ether, tosyl ether, t-butylphenyl ether, salicyl ether, 3,4-di-methoxyphenyl ether and benzamidophenyl ether; and aryl(lower)alkyl ethers such as benzyl ether, trityl ether and benzhydryl ether. Examples of the esters include aliphatic esters, for example, lower alkyl esters such as methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, isobutyl ester, t-butyl ester, pentyl ester and 1-cyclopropylethyl ester; lower alkenyl esters such as vinyl ester and allyl ester; lower alkynyl esters such as ethynyl ester and propynyl ester; hydroxy(lower)alkyl ester such as hydroxyethyl ester; lower alkoxy (lower) alkyl esters such as methoxymethyl ester and 1-methoxyethyl ester; and optionally substituted aryl esters such as, for example, phenyl ester, tolyl ester, t-butylphenyl ester, salicyl ester, 3,4-di-methoxyphenyl ester and benzamidophenyl ester; and aryl(lower)alkyl ester such as benzyl ester, trityl ester and benzhydryl ester. The amide of A means a group represented by the formula —CONR′R″, wherein each of R′ and R″ is hydrogen, lower alkyl, aryl, alkyl- or aryl-sulfonyl, lower alkenyl and lower alkynyl, and include for example lower alkyl amides such as methylamide, ethylamide, dimethylamide and diethylamide; arylamides such as anilide and toluidide; and alkyl- or aryl-sulfonylamides such as methylsulfonylamide, ethylsulfonyl-amide and tolylsulfonylamide. Preferred examples of L and M include hydroxy and oxo, and especially, M is hydroxy and L is oxo which has a 5-membered ring structure of, so called, PGE type. Preferred example of A is —COOH, its pharmaceutically acceptable salt, ester or amide thereof. Preferred example of B is —CH 2 —CH 2 —, which provide the structure of so-called, 13,14-dihydro type. Preferred example of X 1 and X 2 is that at least one of them is halogen, more preferably, both of them are halogen, especially, fluorine that provides a structure of, so called 16,16-difluoro type. Preferred R 1 is a hydrocarbon containing 1-10 carbon atoms, preferably, 6-10 carbon atoms. Further, at least one of carbon atom in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur. Examples of R 1 include, for example, the following groups: —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —, —CH 2 —CH═CH—CH 2 —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —CH 2 —CH═CH—, —CH 2 —C≡C—CH 2 —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —CH 2 —CH(CH 3 )—CH 2 — —CH 2 —CH 2 —CH 2 —CH 2 —O—CH 2 —, —CH 2 —CH═CH—CH 2 —O—CH 2 —, —CH 2 —C≡C—CH 2 —O—CH 2 —, —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —, —CH 2 —CH═CH—CH 2 —CH 2 —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH═CH—, —CH 2 —C≡C—CH 2 —CH 2 —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH(CH 3 )—CH 2 —, —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —, —CH 2 —CH═CH—CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH═CH—, —CH 2 —C≡C—CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH(CH 3 )—CH 2 — Preferred Ra is a hydrocarbon containing 1-10 carbon atoms, more preferably, 1-8 carbon atoms. Ra may have one or two side chains having one carbon atom. The configuration of the ring and the α- and/or ω chains in the above formula (I) and (II) may be the same as or different from that of the primary PGs. However, the present invention also includes a mixture of a compound having a primary type configuration and a compound of a non-primary type configuration. The Examples of the typical compound in the invention are 13,14-dihydro-15-keto-16-mono or difluoro-PGE compound, the derivatives or analogs thereof. The 15-keto-PG compound of the present invention may be in the keto-hemiacetal equilibrium by formation of a hemiacetal between hydroxy at position 11 and oxo at position 15. For example, it has been revealed that when both of X 1 and X 2 are halogen atoms, especially, fluorine atoms, the compound contains a tautomeric isomer, bicyclic compound. If such tautomeric isomers as above are present, the proportion of both tautomeric isomers varies with the structure of the rest of the molecule or the kind of the substituent present. Sometimes one isomer may predominantly be present in comparison with the other. However, it is to be appreciated that the 15-keto-PG compounds used in the invention include both isomers. Further, the 15-keto-PG compounds used in the invention include the bicyclic compound and analogs or derivatives thereof. The bicyclic compounds is represented by the formula (III) whererin, A is —CH 2 OH, —COCH 2 OH, —COOH or a functional derivative thereof; X 1 ′ and X 2 ′ are hydrogen, lower alkyl, or halogen; Y is R 4 ′ and R 5 ′ are hydrogen, hydroxy, halogen, lower alkyl, lower alkoxy or hydroxy(lower)alkyl, wherein R 4 ′ and R 5 ′ are not hydroxy and lower alkoxy at the same time. R 1 is a divalent saturated or unsaturated lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, alkyl, hydroxy, oxo, aryl or heterocyclic group and at least one of carbon atom in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur; and Ra′ is a saturated or unsaturated lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, oxo, hydroxy, lower alkoxy, lower alkanoyloxy, cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclic group or hetrocyclic-oxy group; cyclo(lower)alkyl; cyclo(lower)alkyloxy; aryl; aryloxy; heterocyclic group; heterocyclic-oxy group. R 3 ′ is hydrogen, lower alkyl, cyclo(lower)alkyl, aryl or heterocyclic group. Further more, while the compounds used in the invention may be represented by a structure formula or name based on keto-type regardless of the presence or absence of the isomers, it is to be noted that such structure or name does not intend to exlclude the hemiacetal type compound. In the present invention, any of isomers such as the individual tautomeric isomers, the mixture thereof, or optical isomers, the mixture thereof, a racemic mixture, and other steric isomers may be used in the same purpose. Some of the compounds used in the present invention may be prepared by the method disclosed in U.S. Pat. Nos. 5,073,569, 5,166,174, 5,221,763, 5,212,324 and 5,739,161 and 6,242,485. (these cited references are herein incorporated by reference) The subject to be treated by the present invention may be any mammalian subject including animals and human beings. According to the method of the present invention, a pharmaceutical composition comprising a 15-keto-prostaglandin composition as an active ingredient may be administrated either systemically or topically. Usually, the composition is administered by oral administration, intravenous injection (including infusion), subcutaneous injection, intra rectal administration, intra vaginal administration and the like. The dose of the active ingredient may vary depending on the strain i.e. particular animal or human, age, sex, body weight of the patient to be treated, symptom to be treated, desired therapeutic effect, administration route, term of treatment and the like. Typically, a satisfactory effect can be obtained by systemic administration 1-4 times per day or continuous administration of the 15-keto-prostaglandin compound at the amount of 0.00001-100 mg/kg per day. The composition of the present invention can be formulated as a composition for oral administration, for injection, for perfusion or for external administration, tablet, sublingual, suppository, and vaginal suppository. The composition of the present invention may further contain physiologically acceptable additives. Said additives may include the ingredients used with the 15-keto-PG compound such as excipient, diluent, filler, resolvent, lubricant, adjuvant, binder, disintegrator, coating agent, cupsulating agent, ointment base, suppository base, aerozoling agent, emulsifier, dispersing agent, suspending agent, thickener, tonicity agent, buffering agent, soothing agent, preservative, antioxidant, corrigent, flavor, colorant, a functional material such as cyclodextrin and biodegradable polymer, stabilizer. The additives may be selected from those described in general reference books of pharmaceutics. The amount of the 15-keto-prostaglandin compound contained in a composition may vary depending on the formulation of the composition, and may generally be 0.0001-10.0 wt %, more preferably 0.001-1.0 wt %. Examples of solid compositions for oral administration include tablets, troches, sublingual tablets, capsules, pills, powders, granules and the like. The solid composition may be prepared by mixing one or more active ingredients with at least one inactive diluents. The composition may further contain additives other than the inactive diluents, for example, a lubricant, a disintegrator and a stabilizer. Tablets and pills may be coated with an enteric or gastroenteric film, if necessary. They may be covered with two or more layers. They may also be adsorbed to a sustained release material, or microcapsulated. Additionally, the compositions may be capsulated by means of an easily degradable material such gelatin. They may be further dissolved in a appropriate solvent such as fatty acid or its mono, di or triglyceride to be a soft capsule. Sublingual tablet may be used in need of fast-acting property. Examples of liquid compositions for oral administration include emulsions, solutions, suspensions, syrups and elixirs and the like. Said composition may further contain a conventionally used inactive diluents e.g. purified water or ethyl alcohol. The composition may contain additives other than the inactive diluents such as adjuvant e.g. wetting agents and suspending agents, sweeteners, flavors, fragrance and preservatives. The composition of the present invention may be in the form of spraying composition which contains one or more active ingredients and may be prepared according to a known method. Example of the injectable compositions of the present invention for parenteral administration include sterile aqueous or nonaqueous solutions, suspensions and emulsions comprising one or more active ingredient. Diluents for the aqueous solution or suspension may include, for example, distilled water for injection, physiological saline and Ringer's solution. Non-aqueous diluents for solution and suspension may include, for example, propylene glycol, polyethylene glycol, vegetable oils such as olive oil, alcohols such as ethanol and polysorbate. The composition may further comprise additives such as preservatives, wetting agents, emulsifying agents, dispersing agents and the like. They may be sterilized by filtration through, e.g. a bacteria-retaining filter, compounding with a sterilizer, or by means of gas or radioisotope irradiation sterilization. The injectable composition may also be provided as a sterilized powder composition to be dissolved in a sterilized solvent for injection before use. Another formulation of the composition according to the present invention may be rectal or vaginal suppository. Said suppository may be prepared by mixing at least one active compound according to the present invention with a suppository base e.g. cacao butter and may optionally be admixed with a nonionic surfactant having a suitable softening temperature to improve absorption. The term “treatment” or “treating” used herein includes any means of control such as prevention, care, relief of the condition, attenuation of the condition and arrest of progression. The term “drug-induced constipation” used herein is not limited to a particular constipation condition so far as the condition is caused by using a drug as its side effect, which also includes secondary constipation due to the drug use. Further, constipation caused by an additive or synergistic effect due to combined drug administration is also included. Drugs which cause drug-induced constipation to be treated by the present invention may include, for example, opioids of narcotic drugs such as morphine (such as morphine hydrocholoride and MS contin) and codeine (such as codeine phosphate); anticholineric agents such as antiparkinsonism drugs (trihexyphenidyl and levodopa), antidepressants (tricyclic antidepressants such as amoxapine, trimipramine, aminotriptyline, imipramine, clomipramine, dosulepin, nortriptyline and lofepramine, tetracyclic antidepressants such as setiptiline, maprotiline and mianserin) and anti-incontinence agents (such as propanetheline and oxybutynin); antacids (such as alminium preparation), bone weight increasing agents (such as calcium preparations), diuretic, iron preparations, calcium antagonist, benzodiazepine drugs, phenothiazine drugs (such as chlorpromazine), H 2 -blockers, pill, tocopherol. Especially, constipation conditions induced by opioid such as morphine and codeine, and antidepressants such as tricyclic antidepressants including imipramine are effectively treated 0with the composition of the present invention. In the present invention, “a subject suffering from drug-induced constipation or a subject having a strong possibility of suffering from it” includes both a subject actually constipating due to the administration of a drug which causes constipation and a subject having a strong possibility of constipating due to the administration of a drug, for example, a subject being administered with a drug such as an opioid or an antidepressant, that is known to have a strong possibility of constipation as a side effect. In the present invention, a dosage form may include one active ingredient only or a combination of two or more active ingredients. When a combination of a plurality of active ingredients are used, their respective contents can be suitably increased or decreased in consideration of their effects and safety. The composition of, the present invention can further include other pharmacologically active ingredients as far as they do not contradict the purpose of the present invention. The further details of the present invention will follow with reference to test examples, which, however, are not intended to limit the present invention. EXAMPLE 1 Antagonism to Morphine-Induced Constipation Male ICR mice were fasted overnight in wire-bottomed cages to prevent coprophagia, and 15 mice were used for each group. Morphine hydrochloride (Takeda Chemical Industries, Ltd., Osaka Japan) was injected intraperitoneally to animals at 5 mg/kg. Immediately after the morphine-injection, 0.1 mL graphite marker (2:1 mixture of Pilot INK-30-B and 10% tragacanth mucilage) and 5 mL/Kg vehicle (physiological saline containing 0.01% polysorbate 80 and 0.5% ethanol) or 1, 10, or 100 μg/kg test substance (13,14-dihydro-15-keto-16,16-difluoro-PGE 1 ) in 5 mL/Kg of the vehicle were administered orally. A normal control group received graphite marker and vehicle orally in the above volumes without the morphine-injection. One hundred and fifty minutes after the administration of graphite marker, animals were sacrificed by cervical dislocation, and examined the caecum for the presence of graphite marker. It was judged as a positive response when graphite marker was found in the caecum (positive score). The number of animals in which graphite marker was found in the caecum (number of animals with positive scores) and its ratio in each group are shown in Table 1. TABLE 1 Number of animals with Ratio of positive animals scores a) / with Number of positive Group animals tested scores Normal (vehicle) 15/15** 100%  Morphine + vehicle 3/15  20% Morphine + test substance  1 μg/kg 9/15* 60%  10 μg/kg 13/15** 87% 100 μg/kg 14/15** 93% a) Positive score: Presence of graphite marker in the caecum *p < 0.05, **p < 0.01 compared with morphine + vehicle group (χ 2 test) In the normal group, graphite marker was found in the caecum in all the 15 animals (100%). In the morphine+vehicle group, graphite marker was found in the caecum in 3 out of 15 animals (20%). The number of positive animals in the morphine+vehicle group was significantly decreased as compared with that of the normal group, which indicated that constipation was induced by the morphine treatment. In the groups received test substance at 1, 10 or 100 μg/kg immediately after the morphine administration, graphite marker was found dose-dependently in the caecum in 9 (60%), 13 (87%) and 14 (93%) out of 15 animals, respectively. The test substance group significantly antagonized the morphine-induced constipation as compared with control (morphine+vehicle) group. Above results demonstrate that the substances of the present invention antagonize the opioid-induced constipation even at a low dose of 1 μg/kg. EXAMPLE 2 (COMPARATIVE EXAMPLE) Antagonism to Morphine-Induced Constipation The effects of conventional cathartics (sennoside and sodium picosulfate) clinically used for the treatment of constipation in the patients applied with morphine on morphine-induced constipation were evaluated. Sennoside (tablets: Novartis Pharma K.K., Tokyo, Japan) were crushed with mortar and ground into fine powder, and suspended in 0.5% tragacanth solution to yield proper concentration for the intended dose level of administration. Sodium picosulfate (liquid: Teijin K.K., Tokyo, Japan) was diluted with physiological saline solution. Dosage levels of each test substance were set at 1 and 10 times of clinical daily dosage (clinical daily dosage: sennoside 24 mg, sodium picosulfate 7.5 mg; assuming body weight is 50 kg, they are equivalent to 0.48 mg/kg and 0.15 mg/kg, respectively). Each diluent for test substance was used as a vehicle. The experimental procedure was the same as described in example 1. The number of animals in which graphite marker was found in the caecum (number of animals with positive scores) and its ratio in each group are shown in Table 2 (sennoside) and Table 3 (sodium picosulfate). TABLE 2 Number of animals with Ratio of positive animals scores a) / with Number of positive Group animals tested scores Normal (vehicle)  10/10** 100%  Morphine + vehicle 2/10 20% Morphine + sennoside 0.48 mg/kg 2/10 20%  4.8 mg/kg 2/10 20% a) Positive score: Presence of graphite marker in the caecum **p < 0.01 compared with morphine + vehicle group (χ 2 test) TABLE 3 Number of animals with Ratio of positive animals scores a) / with Number of positive Group animals tested scores Normal (vehicle)  8/10* 80% Morphine + vehicle 3/10 30% Morphine + sodium picosulfate 0.15 mg/kg 3/10 30%  1.5 mg/kg 4/10 40% a) Positive score: Presence of graphite marker in the caecum *p < 0.05 compared with morphine + vehicle group (χ 2 test) The cathartics (sennoside and sodium picosulfate) conventionally used for the treatment of constipation in patients applied with morphine had no effect on morphine-induced constipation at the clinical daily dosage and even at 10 times of the clinical daily dosage. Above results demonstrate that conventional cathartics, which have purgative action, does not necessarily antagonize opioid-induced constipation, and suggests that the conventional cathartics are hard to control constipation sufficiently. EXAMPLE 3 Effect on Analgesic Action Male ICR mice were fasted overnight in wire-bottomed cages to prevent coprophagia. The tail of the animal was pinched with clamp forceps, and the response time from the tail-pinch to fierce striking, biting or crying was measured. 18 mice whose response time of 2 second or shorter were used as test animals. Morphine hydrochloride (Takeda Chemical Industries, Ltd., Osaka, Japan) was injected intraperitoneally to the animals at 5 mg/kg. Immediately after the morphine-injection, vehicle (physiological saline containing 0.01% polysorbate 80 and 0.5% ethanol) or 1, 10, or 100 μg/kg test substance (13,14-dihydro-15-keto-16,16-difluoro-PGE 1 ) dissolved in the vehicle was administered orally in an administration volume of 5 mL/kg. The animals of normal control group received vehicle orally in the above volume without morphine-injection. The response time of each animal following tail-pinch was measured 30, 60, 90, 120 and 150 minutes after the administration. If a mouse took longer than 10 seconds to respond, measurement was stopped to avoid injuring the tail tissue, and the response time was recorded as 10 second. Results are shown in Table 4. TABLE 4 Number Response time, mean ± S.E., sec. of Before Time after administration Group animals administration 30 min 60 min 90 min 120 min 150 min Normal (vehicle) 18 0.9 ± 0.1 1.0 ± 0.1  1.1 ± 0.1  1.1 ± 0.1  1.1 ± 0.1 1.3 ± 0.1 Morphine + vehicle 18 1.0 ± 0.1 2.8 ± 0.6** 1.9 ± 0.3* 1.8 ± 0.4 + 1.4 ± 0.2 1.2 ± 0.1 Morphine + test substance  1 μg/kg 18 1.0 ± 0.1 3.2 ± 0.7** 2.3 ± 0.6 + 1.5 ± 0.2* 1.3 ± 0.1 1.3 ± 0.1  10 μg/kg 18 1.0 ± 0.1 3.4 ± 0.5**  1.8 ± 0.2** 1.4 ± 0.1* 1.3 ± 0.1 1.2 ± 0.1 100 μg/kg 18 1.0 ± 0.1 2.9 ± 0.6** 1.8 ± 0.3* 1.5 ± 0.1* 1.2 ± 0.1 1.3 ± 0.1 + p < 0.1, *p < 0.05, **p < 0.01 compared with normal group (Student's t-test) No significant difference between Morphine + vehicle group and each Morphine + test substance group (Student's t-test) The response times before the administration were about 1 second in all the groups, and no difference was found among the groups. In the normal group, the response time at every measurement time after the vehicle administration was not different from that of before the administration. In the morphine+vehicle group, a significant increase in the response time was found 30 and 60 minutes after the morphine-treatment as compared with that of the normal group. The tendency for the increase of the response time was still found 90 minutes after the morphine-treatment. The analgesic effect of morphine was almost completely disappeared 120 and 150 minutes after the morphine-treatment. In each morphine+test substance group, significant increase of response time was observed as compared with that of the normal group. In the morphine+test substance groups, the response times were similar to those observed in the morphine+vehicle group. No significant difference in the response time was found between the morphine+vehicle group and the morphine+test substance groups, which indicates that test substance did not affect the analgesic action of morphine. Above results demonstrates that the substances of the present invention does not affect the analgesic action of opioid even at a high dose of 100 μg/kg. EXAMPLE 4 Antagonism to Imipramine (A Tricyclic Antidepressant)-Induced Constipation Male ICR mice were fasted overnight in wire-bottomed cages to prevent coprophagia, and 10 mice were used for each group. Imipramine hydrochloride (Wako Pure Chemical Industries, Ltd., Osaka, Japan) at 60 mg/kg was injected intraperitoneally to the animals. Immediately after the imipramine-injection, 0.1 mL of carbon marker (10% carbon powder suspension in 5% gum Arabic) and vehicle (physiological saline solution containing 0.01% polysorbate 80 and 0.5% ethanol) or test substance (13,14-dihydro-15-keto-16,16-difluoro-PGE 1 ) in an administration volume of 5 mL/kg were orally administered. A normal control group received carbon marker and vehicle in the above volume orally without the imipramine-injection. One hundred and fifty minutes after the administration of carbon marker, animals were sacrificed by cervical dislocation, and examined the caecum for the presence of carbon marker. It was judged as a positive response when carbon marker was found in the caecum (positive scores). The number of animals in which carbon marker was found in the caecum (number of animals with positive scores) and its ratio in each group are shown in Table 5. These results demonstrate that the substance of the present invention antagonize the imipramine-induced constipation. TABLE 5 Number of animals with Ratio of positive animals scores a) / with Number of positive Group animals tested scores Normal (vehicle) 9/10** 90% Imipramine + vehicle 1/10  10% Imipramine + 3/10  30% test substance 10 μg/kg Imipramine + 7/10** 70% test substance 100 μg/kg a) Positive score: Presence of carbon marker in the caecum **P < 0.01 compared with imipramine + vehicle group (χ 2 test) EXAMPLE 5 (COMPARATIVE EXAMPLE) Antagonism to Imipramine (A Tricyclic Antidepressant)-Induced Constipation The effect to the imipramine-induced constipation was evaluated on the cathartic (sennoside) clinically used for the treatment of the constipation in patients. Preparation and dose levels of sennoside were the same as described in example 2. The experimental procedure was the same as described in example 4. The number of animals in which carbon marker was found in the caecum (number of animals with positive scores) and its ratio in each group are shown in Table 6. These results demonstrate that sennoside has no effect on the imipramine-induced constipation. TABLE 6 Number of animals with Ratio of positive animals scores a) / with Number of positive Group animals tested scores Normal (vehicle)  7/10** 70% Imipramine + vehicle 1/10 10% Imipramine + 2/10 20% sennoside 0.48 μg/kg Imipramine + 2/10 20% sennoside 4.8 μg/kg a) Positive score: Presence of carbon marker in the caecum **P < 0.01 compared with imipramine + vehicle group (χ 2 test)

Provided is a method for treating drug-induced constipation comprising a step of administering an effective amount of a 15-keto-prostaglaindin compound to a subject suffering from drug-induced constipation or a subject having a strong possibility of suffering from it. According to the present invention, a strong antagonistic action against drug-induced constipation can be obtained without substantially losing the main effect of the drug.

BACKGROUND [0001] The present invention relates generally to a method and systems for automatically controlling the intermittent flow of water, and more specifically to the automatic control of flow with respect to irrigation systems. [0002] In the field of crop irrigation, there is a natural need for automated software tools and applications that may assist an owner in site operation, proper irrigation of a site for proper delivery of nutrients or pesticides to plants, and accurate crop data collection. For example, it may be desirable to have access to an automated interactive system which could be used to optimize or update an irrigation schedule in real time based on data collected from a crop, metrological conditions, soil conditions, and type of crops being irrigated. Such an automated interactive system can prevent plants from entering into a stressed state by adjusting irrigation in response to plant physiological conditions. [0003] Irrigation systems supply water to soil. They are primarily used to assist in the growing of agricultural crops and maintenance of landscapes. Irrigation systems typically include valves, controllers, pipes, and emitters such as sprinklers or drip tapes. Irrigation systems are usually divided into zones based on the spatial resolution of the detection system, and irrigation is performed on that zone based on reflection from all the crop plants within that zone. Each zone may have a solenoid valve controlled via irrigation controller opening or closing irrigation zones. The irrigation controller may be a mechanical or electrical device signaling a zone to turn start irrigating a section of crop for a specific amount of time, or until it is turned off manually. It is desired that the number of control points in the system be individually addressable, however, all points that perform the same command may be connected in order to reduce communication over the power/signaling channels and optimize the cost of the technology. [0004] Branch pipes in each zone are fed by a main line or common supply pipe. In existing systems, controllers are typically wired to the solenoid valves and the energy/power to actuate them is provided through a hardwired connection. Water can be pumped into the main line from a well source or a city supply. [0005] More advanced irrigation systems may use smart controllers. A “smart controller” is typically a controller that is capable of adjusting the watering time by itself in response to current environmental conditions. Smart controllers determine current conditions using real time sensor data, historic and predicted weather data for the local area, soil moisture sensors (water potential or water content), size of the canopy, and greenness of the leaves, weather stations, or a combination of these. [0006] Weather based smart controllers may provide a one dimensional answer to issues faced by irrigation sites. Although they may adjust the irrigation schedule for weather changes, and irrigate based on the needs of the field and, or landscape, they cannot account for other variables in the field, such as crop health or growth cycles. A smart controller may automatically reduce the watering times or frequency as the weather gets cooler determining that less water is needed, it does not take into account the individual need of the plants. [0007] Systems utilizing individual plant health in a field under cultivation are known. For example, U.S. Pat. No. 5,220,876 discloses a variable rate fertilizer spreading apparatus that uses a soil map, (which may be acquired, for example, from an aerial infrared photograph), in order to determine the amount of fertilizer that is to be applied at each location within the field. For this purpose, a map is prepared (referred to as a “fertilizer map”), which shows a spatially distributed desired fertilizer level throughout the field, as well as a “status” map which shows corresponding existing fertilizer distribution throughout the field. The desired distribution of fertilizer as recorded in the “fertilizer map” is prepared in advance, based on determined physical characteristics of the field itself, including field topography, soil type, drainage, sun exposure, and the like. In order to provide for application of the proper amount of fertilizer to achieve the desired distribution, an “Expert System” utilizes artificial intelligence to perform the necessary calculations, based on the fertilizer map, the status map, the soil type and the types of chemicals that are being applied. [0008] In a prescription forming control system disclosed in U.S. Pat. No. 5,919,242, a navigation controller controls the delivery rate of agricultural products by an applicator vehicle, as a function of the global position of the vehicle, based on digital maps which divide a field into “zones”, according for example to soil types. Several different products are delivered at differing rates depending on the soil content and the types of crops that are being cultivated. Similarly, U.S. Pat. No. 5,913,915 also discloses a multi-variable dispensing rate applicator for agricultural products in which a computerized control system stores a digital soil map containing information concerning the location of types of soils, topographic features, nutrient levels, soil compaction, drainage and the like. A map coordinate system allows for variable input control from side to side relative to the movement of the applicator system. [0009] U.S. Pat. No. 6,199,000 B1 provides a precision farming method in which seeding, cultivating and/or harvesting operations are controlled using GPS technology in conjunction with a digital map of an agricultural field, which may be created using satellite, aircraft or other overhead imagery. High resolution photographs acquired in this manner are used to generate the digital map. According to this disclosure, relevant information can then be stored in the map (location of irrigation systems, previous planting locations of other crops and the like), and used to determine, for example, the location at which new crops/seeds should be planted. [0010] Similar systems, in which soil characteristic maps are used to control automated agricultural machines are disclosed in U.S. Pat. Nos. 6,236,907 B1; 6,336,066 B1 and 6,141,614. [0011] Each of the above prior art systems is based on the premise that the likely development of a crop planted in a particular field can be calculated based on physical soil and field conditions, such as the type of soil, topography, drainage, existing nutrient levels, compaction, etc. Accordingly, such information concerning soil and field conditions is stored in the form of a map or maps, which are then used to determine an optimum distribution of fertilizer or the like, based on complex, in some cases proprietary, algorithms. (See, for example, U.S. Pat. No. 5,220,876 at Column 8, lines 58 et seq.) [0012] Such systems share the common deficiency that maps may have inherent variability from the moment was are created and may rely on GPS localization that is accurate at the level on the order of tens of feet. If the variable dispensing system needs to rely on a similar GPS localization system, the accuracy of the water/nutrients may be impaired as water/nutrients may be delivered to the wrong location, due to errors introduced by the GPS systems. The variable rate system is assuming that a mobile platform will move through the field and adjust the delivery of water/nutrients based on the map. One shortcoming of the above mentioned techniques is the two dimensional imaging of the top of the canopy yielding little information about the three dimensional shape and size of the plants. For example, satellite observation of the canopy having a spatial resolution of 30 meters by 30 meters will have reflection data from multiple plants/crops, making individual plant management impractical to implement. For single plant management it is desirable to have local sensor that can assess the condition of independent plants and be able to control the nutrients are delivered to individual plants. Without an accurate estimation of the biomass (volume of plant), for example, the estimation based on top imagery, the wrong amount of nutrients may be delivered. Variability may also reflect only the soil and other physical field characteristics, and in some instances the type of crop being cultivated. While these may be reasonable prognosticators of likely crop development, they do not and cannot take into account or adjust for actual crop growth due, for example, to the effects of weather, diseases, insects and the like. Nor can they take into account the effects of weather on the materials themselves after they have been applied—such as for example due to heavy rains and attendant runoff. They are also generally incapable of generating time variable dynamic crop prescriptions based on actual crop development throughout the growing season. Delivery of nutrients, multiple times per day, using a mobile platform may not be feasible due to time constrains in the operational efficiency. [0013] Accordingly, it is an object of the present invention to provide a method and apparatus for controlling a spatially variable rate delivery apparatus for applying irrigation, fertilizer, and/or pesticides delivery through an irrigation infrastructure that may grow crops in a cultivated field which dynamically takes into account actual crop development throughout the growing season. [0014] Another object of the invention is to provide such a method and apparatus for controlling application rates for agricultural irrigation, which automatically takes into account the effects of weather, disease and insects on crop development. Control system may need to optimize the delivery of instructions across the communications channels to increase time efficiency. [0015] Another object of the invention is to provide a method and apparatus for the efficient delivery of variable rate scheduling across a large area, for example a farm, where multiple communication paths may be needed. The communication paths may be combined and may transfer information via wireless and wired pathways. Wireless and wired pathways may be combined to acquire sensor data and deliver the sensor data to a central computer that will communicate the data to control nodes. The information may be distributed from a central computer to a gateway based on the timeframe determined by an irrigation schedule that is delivered. The use of gateways may allow a partial or complete shut down of the system in case of a malfunction. Real time sensor data from the field may be integrated at the central computer such that the central computer will determine the required resource (water, fertilizer, and/or pesticide), optimize the delivery, and create priority list based on the availability of the resources. SUMMARY [0016] Embodiments of the present invention disclose a system and method for an automated irrigation control and communication between a central computer and multiple control nodes that are distribute over an irrigation area and can be activated from a distributed gateway system or from the central computer. A system comprising crop sensor physically attached to a crop and a light sensitive sensor having a photo-detector for monitoring reflection of a crop as an indicator of the greenness of the canopy or the temperature of the crop. The irrigation system includes irrigation conduit extending along the span of the irrigation zone and adapted to carry fluid, with one or more controllable valves and sensors. The system includes RFID enabled sensors placed in close proximity of the crop sensors and a computer control system. The irrigation conduit may be connected to the irrigation controller, and activates the one or more controllable valves, and receives data from sensors coupled to the irrigation controller. The irrigation system can deliver, based on the sensor data, water, fertilizer, or pesticides on certain location of the system for differential management down to a single plant level. The system enable efficient management of crops taking into account local conditions. The system also includes a communications link between the computer control system, the one or more crop sensor, the three or more growth sensors, and the irrigation controller. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS [0017] FIG. 1 is a schematic representation of an irrigation system, in accordance with an embodiment of the present invention. [0018] FIG. 2A is a flow chart of the crop sensor, in accordance with an embodiment of the invention. [0019] FIG. 2B is a view of a split photodiode filters in the crop sensor, in accordance with an embodiment of the invention. [0020] FIG. 2C is a view of a split photodiode filters in the crop sensor, in accordance with an embodiment of the invention. [0021] FIG. 3 is a schematic block diagram illustrating field data flow in an irrigation system environment, in accordance with an embodiment of the present invention. [0022] FIG. 4 is a schematic block diagram of the growth detection element in the crop sensor, in accordance with an embodiment of the present invention. [0023] FIG. 5 is a schematic block diagram of the irrigation control system, in accordance with an embodiment of the present invention. [0024] FIG. 6 is a block diagram of internal and external components within the computer control system of FIG. 1 , in accordance with an embodiment of the present invention. DETAILED DESCRIPTION [0025] The present invention may be an apparatus, a method, and/or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention. [0026] The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. [0027] Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device. [0028] Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention. [0029] Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions. [0030] These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. [0031] The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. [0032] The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions. [0033] FIG. 1 is a schematic representation of an irrigation system, in accordance with an embodiment of the present invention. Irrigation system 199 includes a crop sensor 125 that acquires digital spectral information, or a spectral image, and growth data, of a crop 120 . It may also contain irrigation piping 130 , an irrigation controller 140 , and growth sensors 135 located near the crop sensor 125 . The growth sensors 135 may utilize the position of the crop sensor 125 , rigidly attached to crop 120 to determine its growth over a temporal period. Crop sensors 125 and growth sensors 135 may assess the canopy and growth rate of crops 120 and determine the health off the plant through spectral information in order to determine different resource crops 120 may require. [0034] The irrigation piping 130 may include multiple delivery sections, a plurality of irrigation tubes, allowing the flow of resources, for example, water, to be controlled by solenoid valves that are disposed along each of the multiple water tubes, and a main water distribution line. Each of the multiple water delivery sections may be fluidly coupled to the water distribution line wherein the water distribution line provides a fluid, such as water, fertilizer, or pesticides dissolved in water, to each of the multiple water tubes to be deposited around the crop 120 . [0035] The irrigation controller 140 includes a processor coupled to a memory, at least one input and an output. In some embodiments, connections to computer control system 100 are coupled to the at least one input in order to provide signaling that corresponds to sensed or measured data image. Furthermore, in some embodiments, the input may also function as an output allowing for bi-directional communication between the computer control system 100 and the crop sensors 125 . The output may be any output to cause or interrupt irrigation or may be a control output to provide messages to cause or interrupt irrigation. [0036] According to several embodiments, the irrigation controller 140 comprises a programmable irrigation controller that controls water flow to one or more irrigation stations, where each irrigation station comprises a water flow control device such as a solenoid valve or pump (not shown in FIG. 1 ). In many embodiments, the irrigation controller 140 is adapted to automatically receive sensed data image and plant growth data from the crop sensor, transmit such information to computer control system 100 , and if irrigation is needed, receive commands from the computer control system 100 and automatically execute, adjust or interrupt watering schedules on a periodic basis. [0037] In some embodiments, the irrigation controller 140 may store historical values of one or more of the variables needed to calculate the plant water requirements. In several embodiments, for example, the irrigation controller 140 stores historical geo-location values associated with a data image or plant growth. [0038] A computer control system 100 may receive spectral image data of an individual crop 120 from crop sensors 125 and may store it in a sensor module 106 , where it is processed into a form which can be used by a vegetation index module 110 . The spectral image data may comprise a value of reflected solar radiation from canopy of crop 120 . The image to be analyzed is taken so that it comprises as much vegetation as possible. Preferably the image is provided perpendicularly to the ground, normally at a distance of 0.1-2 m. It is also possible to provide the image from aside of the vegetation, so called panorama image. Preferably the image to be analyzed is taken so that the area and vegetation to be imaged is protected from direct sunlight. The image received by the sensor module 106 , is further forwarded to the vegetation index module 110 comprising means for dividing the image into sub-areas comprising a number of image units, such as pixels; means for determining the amount of certain colors and their ratios in the sub-areas of the image; and means for calculating vegetation index or indices on basis of the determined color amounts and ratios. [0039] The image can be divided into sub-areas in a desired manner. The number of image units forming an image sub-area can be chosen, for example, on the basis of image units comprised in the original received image. If the original image has a high resolution, one sub-area can comprise 2, 3 or 4 image units. If the resolution of the original image is low, one sub-area may comprise one image unit. Preferably the image to be analyzed is dived into sub-areas, each of which comprises one image unit. [0040] According to an embodiment of the invention the amount of certain colors and their ratios are then determined in the sub-areas of the image. Preferably relative amounts of red, green and blue colors in the image and the ratios between red and green, red and blue and green and blue color bands are used for determining vegetation index or indices. A typical digital image contains three color bands, for example red, green and blue. Each image unit of an image typically comprises a value ranging from 0 to 255 for each band. The simple relative index can be calculated for red band as follows: [0000] Red   Band   Index = R ( R + G + B ) . Formula   1 [0000] where R refers to red, G for green and B for blue band value. The ratio for red and green can be calculated as follows: [0000] Red   to   Green   Ratio = R G . Formula   2 [0041] The vegetation index, VARI, may be calculated as follows: [0000] VARI = ( G - R ) ( R + G + B ) . Formula   3 [0042] These indices are preferably calculated for each image unit. An average value for each index is then calculated for the whole image sub-area under analysis. Optionally, other statistical parameters like most common and median of each index may be calculated. [0043] The color ratios may be used in calculations, instead of absolute color digits, in order to minimize the optical disruption effect varying amounts of incoming light may have on the image to be analyzed. The vegetation index module 110 may calculate indices for the received image on basis of the determined color amounts and ratios. Preferably, a Bayes model is used to classify whether the vegetation of the received image is sufficient or deficient in growth aid by using the calculated variables as independent variables. Other models, like common multiple regression models using vegetation indices as independent variables and growth aid sufficiency index as a dependent variable can also be used for classifying the vegetation. However, multiple classification models, such as Bayes model, usually perform better compared to single variable model commonly used in image analysis applications, for example, a method used by Hoffmann & Blomberg (2004). The effect of errors caused by varying imagining conditions can be generally minimized by using multiple data sets or points instead of one variable. [0044] According to one embodiment of the invention the image received by the vegetation index module may be filtered before determination of the vegetation index or indices. Such filtering may be performed by filtering means that is adapted to differentiate the image sub-areas comprising vegetation information from sub-areas with less information content. The contents of the sub-areas are evaluated so that only sub-areas mainly describing vegetation are accepted for determination of the vegetation indices. For example, only sub-areas of which over 50%, typically over 60%, more typically over 70%, preferably over 80%, more preferably 90%, sometimes 100% of the area describes the vegetation are accepted for vegetation indices determination. Sub-areas not fulfilling the criteria are removed from further determination. In this way parts of the image that could distort the final result can be filtered away. [0045] According to an embodiment of the invention the vegetation index module 110 located in the computer control system 100 may comprise a database for storing the obtained vegetation index or indices, together with the identification code, and optionally the image attribute, which was received with the image. The information relating to the imaging location may be acquired from the crop sensor 125 and saved as data defined by position coordinates and/or the field name (discussed in more detail in FIG. 2A ). [0046] The analyzed data can be stored for further use within computer control system 100 . For example, a data base may be formed to aid the farm owner in conducted image analysis. As such, database's accuracy will increase where the images are stored from the same site and location conducted at the same location every year and referenced. The information stored, covering a longer time period, for example a whole vegetation period, or two or more vegetation periods, can be obtained by sending a special command to the system. Vegetation index module 110 can then compile the required information, whereby it can be sent to the defined receiver by the communication module. Such a database may then help to adjust management actions for a future season. [0047] The vegetation index or indices may also be optionally compared with reference values in order to obtain vegetation status information for the vegetation to be analyzed. After the determination of the vegetation index or indices for the received image, the image analysis module instructs the database module to retrieve the reference data associated with that identification code. After receiving the reference index/indices, the image analysis module performs a comparison between the index/indices of the received image and reference index/indices. The comparison can be done by using statistical methods, such as naive Bayes classification model (Kontkanen et al., 1998). As a result of this comparison, vegetation status information is obtained for the received image. The vegetation status information is usually classified, for example in number of different classes, such as “high”, “above average”, “average”, “below average”, “low”. Each class comprises a certain range of vegetation index values. [0048] The analysis of the image performed by the vegetation index module 110 coupled with growth rates recorded by the growth sensors 135 may reveal accurate near real-time water, or fertilization needs of a crop 120 , wherein the irrigation module can coordinate irrigation by generating irrigation schedules or be programmed by a user with irrigation schedules for the respective location identified, based on the analyzed image. The irrigation schedules, in some instances, define run times and, or desired amounts of water to be supplied through the irrigation piping 130 . Further, the irrigation schedules often define start times or time periods when the irrigation scheduling can be implemented. Accordingly, this allows the computer control system 100 , irrigation module 104 , and zone control module 108 to manage start times and durations to specific crop locations. [0049] Zone control module 108 may contain specific divisions of the irrigation area and cooperate with the irrigation module 104 in determining the schedule and proper section to irrigate. Zone control module 108 may calculate the amount that will be delivered to the target area identified by vegetation index module 110 by utilizing a plurality of zone parameters. A component of the zone control module maintains a plurality of zone parameters associated with the divisions that comprise the target area. Such divisions may include sections distinguished by manually predetermined areas, type of crops, type of soil or problem areas identified by the vegetation index module 110 . [0050] For example, each zone may include information related to the size of the zone, nutrient requirements, pesticide and herbicide requirements, soil conditions, moisture levels, or prior watering needs. The user may enter the zone parameters manually or the zone parameters may be automatically set to nominal values by the vegetation index module 110 . [0051] When the irrigation module 104 activates watering for a specific zone, the zone control module 108 may access the zone parameters associated with the specific zone and tailor the amount that is delivered to the zone. [0052] The computer control system 100 can be located at the property being irrigated or be located remote from the property. For example, in some instances the computer control system 100 may be located within wireless transmission range of the irrigation system 199 . The irrigation module 104 combines and cooperates irrigation system devices that were not intended to be cooperated within an irrigation system 199 . For example, the present embodiments can combine the use of AC powered irrigation control systems with DC battery powered controllers. Further, the irrigation module 104 combines zone control module 108 to implement irrigation schedules over a relatively wide geographic area with controls that may be local to valves, run valve specific schedules. Accordingly, the present embodiments can provide enhanced irrigation control over areas that are typically hard or expensive to incorporate programmed irrigation control while coordinating the controlled irrigation over a wide geographic area or in cooperation with a wide variety of irrigation control devices or irrigation systems. [0053] FIG. 2A is a flow chart of the crop sensor, in accordance with an embodiment of the invention. The elements of the crop sensor 125 include a photo-detector element 200 , a radio frequency identification element 205 , and a crop sensor microprocessor element 210 in communication with irrigation controller 140 . [0054] The role of the crop sensor 125 in the irrigation system 199 is to measure the biomass, or biochemical properties of the crop being monitored. Data produced by the sensor is collected by the crop sensor microprocessor element 210 for storage. Each sensor point is geo-referenced using radio frequency identification included in the radio frequency identification element 205 of the crop sensor 125 body. [0055] There are two primary ways in which crop data can be taken in the system. First, the image collected by the system, can be all inclusive, where every data point measured by the sensor can be stored away in the crop sensor microprocessor's element 210 memory for later retrieval and analysis by the computer control system 100 through irrigation controller 140 . Second, the crop sensor 125 can be programmed with a defined set of rules so as to distinguish poor performing regions of the irrigation site from good or healthy regions and vice versa and store only the poor performing regions. This mode of operation saves storage space in the controller and reduces the amount of data processing that has to be performed. [0056] The crop sensor 125 may either emit light which is then reflected back to a receiver, referred to herein as an “active sensor” since the sensor actively produces its own light, or a sensor may take advantage of available light to measure reflectance properties which, for purposes of this invention, is referred to as a “passive sensor”. Either sensor is well suited for use as a photo-detector element 200 . Simply by way of example and not a limitation, the operation of the photo-detector element 200 is described in terms of a passive sensor. The crop sensor 125 is to be directly mounted and facing the canopy of the crop 120 (not shown in FIG. 2A ). Light reflected from plant 120 passes through an emitter lens (not shown) of the photo-detector element 200 . The phase of the scattered light impinging upon photo-detector element 200 is used to assess the spectral reflectance characteristic of the scattered light. The data recorded by each crop sensor 125 is then accessed by the crop sensor microprocessor element 210 . An analogue-to-digital converter located within crop sensor microprocessor element 210 of each crop sensor 125 , converts the radiance detected in the wavelength, into electrical signals, which are then sent to its local irrigation controller 140 . [0057] The crop sensor 125 may also be used for determining crop growth parameters and geo location through the radio frequency identification element 205 . The radio frequency identification element 205 may contain a radio frequency identification (RFID) tag which is operatively connected to irrigation controller 140 of particular crop sensor 125 . The crop sensor 125 integrates an RFID tag that are actuated as electrical switches at thresholds of conditions, such as acceleration (crop growth) or initiation of image transfer by the crop sensor microprocessor element 210 to the irrigation controller 140 . The onboard data collection and storage components are powered only when those thresholds are exceeded. For example, the irrigation controller 140 receives a recorded image along with the radio frequency of the RFID tag, the reflected radiation provides location information and growth history. Attaching the crop sensor 125 with a RFID tag allows for dimensionally characterizing a target structure of the crop 120 over a specified temporal period (discussed in more detail in FIG. 4 ). For example, a RFID tag included in the radio frequency identification element 205 facilitates can characterize the height for one target crop taken from ground level by continuously recording the strength of the signal from the RFID tag to the receiver at controller 140 and may assess the three dimensional distance from the RFID tag to controller 140 , where controller 140 is in a fixed position, over a period of time. [0058] FIG. 2B is a view of a split photodiode filter in the crop sensor, in accordance with an embodiment of the invention. A portion of natural light, or illumination light, which has been reflected by a crop passes through color filters A and B. The lens system, and filters are respectively formed in four quadrants as divided by orthogonal coordinate axes into quadrant 1 221 , quadrant 2 222 , quadrant 3 223 , and quadrant 4 224 . A portion of light passes through the lens systems of photo-detector element 200 , forming data images. Each of the lens systems may be preferably a combination of lenses which are arranged along an optical axis in such a manner as to achieve a desired optical performance. However, each lens system will be conveniently described as a single lens for simplicity. [0059] In various embodiments, the crop sensor may have a split detector where the orientation of the sensor can be adjusted to have the reflected light focused on the middle of the split detector. Focus on the middle of the split detector may be achieved by adjusting the orientation of the split detector until the difference between the signals received by each section of the split detector is equal. The position of the split detector may be adjusted by a small motor that orients the split detector in order to maximize the signal that is captured. [0060] The color filters A and B are respectively formed in two halves on the filter substrate plane, and have a substantially zero transmittance for light of wavelengths other than in the vicinity of red, and light of wavelengths other than in the vicinity of infrared, respectively. Although the color filters A and B of the present embodiment are illustrated to be on the same plane in FIG. 2B , the color filters A and B may alternatively be placed on different planes from one another. [0061] In an exemplary embodiment of the invention the split filter arrangement, near-infrared and red cut filters are formed only over one-half of a photosensitive element. In accordance with the present invention, structures and methods are provided for assessing plant status using the chlorophyll status changes and biomass properties of the plant remotely sensed, in the red-edge portion of the vegetative reflectance spectrum of 650 nm to 900 nm, thereby allowing selective monitoring or treatment of individual plants. Preferably, the photo-detector element 200 will contain two narrow filters covering the red and infrared spectrums, where filter A covering the red spectrum will have a bandwidth of 650 nm and filter B covering infrared spectrum will comprise a bandwidth of 880 nm. [0062] The positive relationship between leaf greenness and crop health status means it should be possible to determine crop health requirements based on reflectance data collected from the crop canopy (Walberg et al., 1982; Girardin et al., 1985; Hinzman et al., 1986; Dwyer et al., 1991) and leaves (McMurtrey et al., 1994). Healthier plants typically have more chlorophyll (Inada, 1965; Rodolfo and Peregrina, 1962; Al-Abbas et al., 1974; Wolfe et al., 1988) and greater rates of photosynthesis (Sinclair and Horie, 1989). Hence, plants that appear a darker green are perceived to be healthier than deficient plants and as such healthier plants reflectance less light in the visible portion of the spectrum (400 to 700 nm) and reflect more light in the near infrared (>700 nm). Chlorophyll in leaves absorb strongly in the blue and red regions of the spectrum (460 nm and 670 nm) and as the wavelengths increase past 670 nm the leaves begin to strongly reflect infrared light, (see FIG. 2C ). The transition region between the photosynthetic portion (400 nm to 670 nm) and the biomass portion (>780 nm) of a plant's reflectance spectrum is sometimes referred to as the red-edge region. It has been reported in literature that the wavelength where the maxima of the derivative 6 for the red-edge band occurs is strongly correlated to changes in the chlorophyll status of a plant. Guyot and Baret (1988) developed an algebraic relationship expressing the wavelength of the red-edge inflection point (REIP), sometimes referred to as the red edge position (REP), using four reflectance bands spanning from 670 nm to 780 nm. The usefulness of measuring red-edge reflectance spectra, and subsequently determining the inflection point's wavelength position, is that the chlorophyll status of the plant can be measured independently of soil background interference. That is, the chlorophyll status as denoted by shifts in the red-edge inflection point is independent of the slope of the vegetative reflectance curve and has reduced sensitivity to soil and biomass reflectance characteristics. Shifts in the value of the inflection point are directly related to the chlorophyll status (and water content) of the plant with chlorophyll content being closely related to nutrient status. [0063] Furthermore, to improve the quality of the image the crop sensor microprocessor element 210 of FIG. 2A may correct the image based on the quadrants of FIGS. 2B and 2C . If a photo-detector element 200 contains two filter apparatus mentioned in FIG. 2B , a clearer image can be achieved through a ratio of quadrant data values: [0000] Two   Filter   Correction = ( A + C - B - D ) ( A + B + C + D ) . Formula   4 [0000] where quadrant 1 221 represents A, quadrant 2 222 represents B, quadrant 3 223 represents C, and quadrant 4 224 represents D. [0064] FIG. 2C is a view of a split photodiode filters in the crop sensor, in accordance with an embodiment of the invention. Similarly to FIG. 2B , the lens systems and filters are respectively formed in four quadrants as divided by quadrant 1 221 , quadrant 2 222 , quadrant 3 223 , and quadrant 4 224 . [0065] The filters A, B, C, and D, discussed in detail above, are four split parts of an otherwise single photo-detector, respectively corresponding to four quadrants. The four quadrant split may compensate for light reflection differences during a growing season and/or minimize the impact of the background signal as the canopy changes during a growing season. [0066] The filters A, B, C, and D are for red detection, green detection, blue detection, and infrared detection, respectively. In the present embodiment, the filters A, B, C, and D share the same lateral magnification. [0067] FIG. 3 is a schematic block diagram illustrating field data flow in an irrigation system environment, in accordance with an embodiment of the present invention. [0068] The system 399 includes one or more lateral driplines 310 fluidly coupled to a main water supply line. Each of the one or more driplines 310 is divided into zones 301 and comprising an irrigation plot 300 that are separated from one another by a controllable valve, such as a pressure regulating or solenoid valve. The controllable valve can be actuated by a voltage pulse issued from the irrigation controller 140 , as described in FIG. 1 . [0069] Each of the one or more driplines 310 is equipped with a plurality of emitters such that each dripline 310 has a group of emitters in each zone 301 . Each emitter is activated when the controllable valve associated with the corresponding zone is actuated or turned on. The one or more driplines 310 are arranged such that groups of emitters for each one of the driplines 310 may be provided in each zone 301 of irrigation plot 300 . [0070] In accordance with embodiments, different or multiple driplines 310 can be grouped together and controlled by the zone control module 108 of computer control system 100 to thereby create “variable rate irrigation” zones. In such an approach, the “variable rate irrigation” zones can be created continuously based on information provided by crop sensors 125 pertaining to crop health. Image data may be used by the computer control system 100 to delineate the “variable rate irrigation” zones and specify the amount of fluid needed in each corresponding location. [0071] In another embodiment, computer control system 100 may utilize other feedback in addition to image data and plant growth provided by crop sensors 125 , such additional information can be provided by soil moisture sensors that would monitor the water content in the soil, satellite sensing to monitor the evapo-transpiration of the associated canopy or canopy sensors to measure local water content. Any of the sensing approaches will have a spatial and temporal resolution determined by the detection methods and the resolution will be matched by the length of drip lines segments and by updating the irrigation schedule determined by irrigation module 104 and zone control module 108 within computer control system 100 . [0072] The control station 140 , as discussed in FIG. 1 , is provided as a master unit that is responsible for execution of irrigation schedule as well as other functionalities such as transmitting and receiving data from crop sensors 125 . [0073] The irrigation controller 140 may receive and transmit data through wired or wireless connection to sensors, valves and computer control system 100 . The irrigation controller 140 configured to be positioned locally at a site where irrigation is to be controlled, wherein the irrigation controller is configured to couple with one or more valves at the site and the irrigation controller is configured to control activation and deactivation of the one or more valves in accordance with an irrigation schedule stored in the irrigation controller to implement irrigation at the site; a wireless adapter coupled with the computer control system 100 , such that the coupling allows communication with the computer control system 100 ; a local network at the site, wherein the wireless adapter is configured to communicate over the local network at the site providing access to a communication network with the computer system 100 , crop sensors 125 , different or multiple driplines 310 , wherein the wireless adapter is configured to receive information from the irrigation controller and wirelessly communicate that information to the computer control system 100 , and to wirelessly receive information from the computer system 100 . [0074] FIG. 4 is a schematic block diagram of the growth detection element, in accordance with an embodiment of the present invention. The growth detection element 499 includes a crop sensor 125 rigidly mounted onto a plant 120 , with an RFID tag (not shown) enclosed within and being the functional part of the crop sensor 125 . The RFID tag is used to carry the coded information, pertaining to growth and location. The growth detection element 499 also includes three or more growth sensors 135 communicating with crop sensor 125 through transmissions 405 . [0075] An RFID tag located within crop sensor 125 is a contactless automatic identification technology which automatically identifies an object by using a radio signal. Specifically, a RFID tag is embedded within crop sensor 125 and attached to crop 120 , it communicates with three or more growth sensors 135 through transmissions 405 , for example, via reception of the radio signals. The strength of the transmissions 405 in respect to two or more reference point allows to identify the locations of the sensor in space. Since multiple RFID tags may be within the reach of a single growth sensors 135 , the ID may be associated with a specific plant at a specific time in order to determine the growth of the canopy. Identifying the ID and locations of the RFID tag may allow the reconstruction of growth data in order to determine how the canopy grows over a period of time and much of the growth is associated with canopy development. [0076] In a preferred embodiment of the invention, the growth detection element 499 may be a wireless component of crop sensor 125 for determining the location of a fixed crop 120 . It can comprise of three or more growth sensors 135 disposed on or around the target crop 120 , an RFID tag for monitoring the change in the height of the crops canopy, and a wireless communication system operating on at least one Radio Frequency (RF) band configured to allow communication between the RFID tag and the three or more growth sensors 135 . The three or more growth sensors 135 may then transmit the data location to the irrigation controller 140 . [0077] In an exemplary embodiment of the invention, the irrigation controller 140 may include a processor configured to find the RFID tags vertical or horizontal change by triangulation. The change may be calculated based on values of position information received from the RFID tag as its position changes during a growth cycle of a crop 120 and compared to previous values. The vertical or horizontal change may be associate with the growth of crop 120 . [0078] The irrigation controller 140 may determine triangulation based on successive values of the position information using at least three points P 1 , P 2 and P 3 of the RFID tag respective of the three or more growth sensors 135 . Triangulation may include the Received Signal Strength Indication (RSSI) method, based on using RF expansion equations, comparing the relative signal intensity received by the three or more growth sensors 135 from a single RFID tag. The location (coordinates) of the three or more growth sensors 135 is recorded at their initial installation. The irrigation controller 140 may also use the Time Difference on Arrival (TDOA) method, utilizing a single RFID tag and the three or more growth sensors 135 , by measuring signals emitted from three or more synchronized transmitters at known locations. For exemplary purposes, the three or more growth sensors 135 may be regarded as each broadcasting pulses at exactly the same time on a separate frequencies (to avoid interference). The crop sensor 125 measures the TDOAs of the pulses, which are converted to range differences. The difference in the time of receiving the signals divided by the speed of light should be an indication of the difference in distances between the RFID tag and the three or more growth sensors 135 , thereby allowing to calculate the tag's position. The processor may also include a triangulation technique that may account for erroneous readings caused by external factors such as weather, or wind gusts by correcting the position of the crop 120 based on the average speed of the motion of the RFID tag respective of the three or more growth sensors 135 . [0079] The computer control system 100 may also receive the three points P 1 , P 2 and P 3 of the RFID tag attached to the crop 120 via the three or more growth sensors 135 , directly. [0080] The three or more growth sensors 135 may then provide the identifier read from the RFID tag to the computer control system 100 . The computer control system 100 may then associate the determined geographical location with the data image transmitted by the photo detector element of the crop sensor 125 . In response to the association, the sensor module 106 (see FIG. 1 ) may then reference the location notification to the zone control module 108 (see FIG. 1 ), thus associating the location of the crop 120 to the image data. [0081] Returning to FIG. 4 , showing the interaction of crop sensor 125 with crop 120 vegetation in the growth detection element 499 . In operation, a radio signal is directed along a horizontal plane of the crop 120 , it is then scattered or reflected by the crop 120 . The signal is then measured as it returns to the three or more growth sensors 135 . As stated above, the triangulation method may measure both the intensity of the returned signal and the time delay between transmission 405 of the pulse and its return. Since the speed of light is well-defined for a given atmosphere, the distance can be calculated from the three or more growth sensors 135 to the scattering target (crop 120 ). When a vegetation canopy is located above the ground, the light may be scattered from different elements of the canopy and from the ground beneath. By measuring the change in the intensity of the signal as a function of time, it is also possible to infer the vertical structure of the vegetation. [0082] Each of the three or more growth sensors 135 may include a RF transmitter, and a RF receiver that operate in accordance with a wireless local area network protocol, an area network protocol, a wireless telephony protocol, a wireless data protocol, or other protocol. The three or more growth sensors 135 may also contain a wireless interface (for example, a Wi-Fi® interface) as used to communicate with different elements of the system. [0083] FIG. 5 is a schematic block diagram of the irrigation communication system, in accordance with an embodiment of the present invention. The irrigation communication system 599 include irrigation plots 300 containing irrigation control boxes 500 , solenoid valves 520 , and control gateways 530 all connected wirelessly or by wired communications network 510 . Communication system 599 may be adapted to control the irrigation of crops over many irrigation plots 300 . The use of wired or wireless communications network 510 may allow information and instructions to pass from an irrigation controller 140 ( FIG. 1 ) to control gateways 520 , irrigation control boxes 500 , and solenoid valves 510 all within an irrigation plot 300 . [0084] In various embodiments, control gateways 520 may include a processor coupled to a memory, at least one input and an output. In some embodiments, connections between control gateways 520 and irrigation controllers 140 are coupled to the at least one input in order to provide signaling that corresponds to sensed or measured data. In some embodiments, the input may also function as an output allowing for bi-directional communication. Control gateways 520 may act generally to maintain irrigation schedules, store time synchronization values and match to irrigation controller 140 or computer control module 100 ( FIG. 1 ), or store irrigation control instructions in memory. Control gateways 520 may send, as output, computer instructions to irrigation control boxes 500 to open or close solenoid valves 520 . Instructions from control gateways 520 may be performed sequentially or simultaneously. [0085] Communications network 510 may be wired, for example an RS-485 differential power line communication with a OFDM modulation or a standard CENELEC. Communications network 510 may be wireless, for example, a wireless ISM band of 900 MHz or 2.4 GHz frequencies. In various embodiments, a combination of wired and wireless communications network 510 may be used. [0086] For example, an area of land containing multiple irrigation plots 300 may provide an area large enough for multiple data paths for communications network 510 to be implemented. Computer controller 100 may be connected wirelessly through communications network 510 to multiple zones controlled by a gateway(s) 520 . Data paths being bi-directional, wired communication may transmit schedule data control boxes 500 and information aggregated from solenoid valves may be wirelessly transmitted to gateways 520 . [0087] In various embodiments, communication system 599 may be powered via solar power and generators (not shown) coupled to control boxes 500 at the end of each row or irrigation plots 300 . Control boxes 500 may contain capacitors to hold a charge in order to power wired communication to solenoid valves 520 . [0088] In various embodiments, communication system 599 may employ an optimization algorithm in order choose the most optimal path to deliver the data from a central computing device, for example, computer control modules 100 or control gateways 530 to individual crop sites (not shown). The output of the optimization may assign various computer control modules 100 or control gateways 530 various irrigation schedules or implement resource distribution in various orders in order to achieve the more efficient resource distribution. [0089] FIG. 6 is a block diagram of internal and external components within the computer control module of FIG. 4 , in accordance with an embodiment of the present invention. It should be appreciated that FIG. 5 provides only an illustration of one implementation and does not imply any limitations with regard to the environments in which different embodiments may be implemented. [0090] Computer control module 100 can include one or more processors 602 , one or more computer-readable RAMs 604 , one or more computer-readable ROMs 606 , one or more tangible storage devices 608 , device drivers 612 , read/write drive or interface 614 , and network adapter or interface 616 , all interconnected over a communications fabric 618 . Communications fabric 618 can be implemented with any architecture designed for passing data and/or control information between processors (such as microprocessors, communications and network processors, etc.), system memory, peripheral devices, and any other hardware components within a system. [0091] One or more operating systems 610 , irrigation module 104 , sensor module 106 , zone control module 108 , and vegetation index module 110 are stored on one or more of the computer-readable tangible storage devices 608 for execution by one or more of the processors 602 via one or more of the respective RAMs 604 (which typically include cache memory). In the illustrated embodiment, each of the computer-readable tangible storage devices 608 can be a magnetic disk storage device of an internal hard drive, CD-ROM, DVD, memory stick, magnetic tape, magnetic disk, optical disk, a semiconductor storage device such as RAM, ROM, EPROM, flash memory or any other computer-readable tangible storage device that can store a computer program and digital information. [0092] Computer control module 100 may also include a R/W drive or interface 614 to read from and write to one or more portable computer-readable tangible storage devices 626 . The irrigation module 104 , sensor module 106 , zone control module 108 , and vegetation index module 110 can be stored on one or more of the portable computer-readable tangible storage devices 526 , read via the respective R/W drive or interface 614 and loaded into the respective computer-readable tangible storage device 608 . [0093] Computer control module 100 can also include a network adapter or interface 616 , such as a TCP/IP adapter card or wireless communication adapter (such as a 4G wireless communication adapter using OFDMA technology). Irrigation module 104 , sensor module 106 , zone control module 108 , and vegetation index module 110 on computer control module 100 can be downloaded to the computing device from an external computer or external storage device via a network (for example, the Internet, a local area network or other, wide area network or wireless network) and network adapter or interface 616 . From the network adapter or interface 616 , the programs are loaded into the computer-readable tangible storage device 608 . The network may comprise copper wires, optical fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. [0094] Computer control module 100 may be connected to and receive and transmit data between the irrigation controller 140 , crop sensors 125 , and growth sensors 135 and may also include 435 a display screen 620 , a keyboard or keypad 622 , a microphone 625 and a computer mouse or touchpad 624 . Device drivers 612 interface to display screen 620 for imaging, to keyboard or keypad 622 , to microphone 625 , to computer mouse or touchpad 624 , and/or to display screen 620 for pressure sensing of alphanumeric character entry and user selections. The device drivers 612 , R/W drive or interface 614 and network adapter or interface 616 can comprise hardware and software (stored in computer-readable tangible storage device 608 and/or ROM 606 ). [0095] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one more other features, integers, steps, operations, element components, and/or groups thereof. [0096] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. [0097] While the preferred embodiments to the invention have been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.

An automated irrigation control comprising crop sensor physically attached to a crop and a light sensitive sensor having a photo-detector for monitoring light intensity of a crop, an irrigation conduit extending along the span of the irrigation zone and adapted to carry fluid, with one or more controllable valves and sensors, growth sensors placed in close proximity of the crop sensors, a computer control system, an irrigation controller, and a communications link between the computer control system, the one or more crop sensor, the three or more growth sensors, and the irrigation controller.

BACKGROUND 1. Technical Field The present invention relates to a light emitting device and a projector. 2. Related Art A super luminescent diode (hereinafter, also referred to as “SLD”) is a semiconductor light emitting device that can output several hundreds of milliwatts similar to a semiconductor laser, while exhibiting a broadband spectrum and thus being incoherent similar to a typical light emitting diode. An SLD is sometimes used as a light source of a projector. To realize a light source having high power and small etendue, it is desirable that light beams output from plural gain regions travel in the same direction. In JP-A-2010-3833, by combining a gain region having a linear shape and a gain region having a flexed shape via a reflection surface, light beams output from light output parts (light emitting areas) of the two gain regions travel in the same direction. To reduce loss of an optical system and reduce the number of optical components, a projector that can perform light collimation and uniform illumination simultaneously by providing a light emitting device immediately below a light valve and using a lens array, has been proposed. In this type of projector, however, it is necessary to provide light output parts according to intervals of the lens array. In the technology described in JP-A-2010-3833, it is difficult to arrange plural light output parts at distances according to various lens arrays with different intervals, and the technology is not applicable to the projector of the above described type. SUMMARY An advantage of some aspects of the invention is to provide a light emitting device that may be applied to a projector in which distances between plural light output parts may be made larger and a light emitting device is provided immediately below a light valve. Another advantage of some aspects of the invention is to provide a projector having the light emitting device. A light emitting device according to an aspect of the invention includes a first layer that generates light by injection current and forms a waveguide for the light, a second layer and a third layer that sandwich the first layer and suppress leakage of the light, and an electrode that injects the current into the first layer, wherein the waveguide has a first region having a belt-like (elongated) linear shape, a belt-like second region, and a belt-like third region, the first region and the second region connect at a first reflection part provided at a first side surface of the first layer, the first region and the third region connect at a second reflection part provided at a second side surface of the first layer different from the side surface on which the first reflection part is provided, the second region and the third region connect at a third side surface of the first layer which is an output surface that is different from the first and second side surfaces, a longitudinal direction of the first region is parallel to the output surface, and a first light output from the second region at the output surface and a second light output from the third region at the output surface are output in parallel. According to the light emitting device, for example, as compared to the case where the first region is not parallel to the output surface, distances between the light output parts may be made larger without increasing the total length of the first region, the second region, and the third region. That is, the distances between the light output parts may be made larger while the device lengths in the direction perpendicular to the light output surfaces are downsized. As such, a great amount of current is not necessary and electrical power consumption may be suppressed. Further, resources are not wasted and the manufacturing cost may be suppressed. In the light emitting device according to the aspect of the invention, the output surface may have a reflectance lower than a reflectance of the first reflection part and the second reflection part in a wavelength range of the light generated in the first layer. According to the light emitting device, the distances between the plural light output parts may be made larger. In the light emitting device according to the aspect of the invention, the first region and the second region may be tilted at a first angle with respect to a perpendicular of the first side surface as seen from a stacking direction of the first layer, and the second layer, the first region and the third region may be tilted at a second angle with respect to a perpendicular of the second side surface as seen from the stacking direction of the first layer, and the second layer, and the first angle and the second angle are equal to or more than a critical angle. According to the light emitting device, the first reflection part and the second reflection part may totally reflect the light generated in the first region, the second region, and the third region. Therefore, light loss in the first reflection part and the second reflection part may be suppressed and light may efficiently be reflected. In the light emitting device according to the aspect of the invention, the second region and the third region may extend to the output surface in the same direction as seen from a stacking direction of the first layer, and the second layer. According to the light emitting device, the distances between the plural light output parts may be made larger. In the light emitting device according to the aspect of the invention, the second region and the third region may be tilted with respect to a perpendicular of the output surface and extend to the output surface as seen from the stacking direction of the first layer, and the second layer. According to the light emitting device, it may be possible to prevent multiple reflections of the light generated in the first region, the second region, and the third region. As a result, it may be possible to prevent the formation of a direct resonator, and laser oscillation of the light generated in the first region, the second region, and the third region may be suppressed. In the light emitting device according to the aspect of the invention, the second region and the third region may be parallel to a perpendicular of the output surface and extend to the output surface as seen from the stacking direction of the first layer, and the second layer. According to the light emitting device, the design of a downstream optical system may be made easier. In the light emitting device according to the aspect of the invention, the second region may have a linear first part and a linear second part, the third region may have a linear third part and a linear fourth part, the first part and the second part may connected at a third reflection part provided on a fourth side surface of the first layer that is different from the first side surface, the second side surface, and the output surface, and the third part and the fourth part may connected at a fourth reflection part provided on a fifth side surface of the first layer that is different from the first side surface, the second side surface, the fourth side surface, and the output surface. According to the light emitting device, the light generated in the first region, the second region, and the third region may be easier to totally reflect in the first reflection part, the second reflection part, the third reflection part, and the fourth reflection part. In the light emitting device according to the aspect of the invention, the output surface may have a reflectance lower than a reflectance of the third reflection part and the fourth reflection part in a wavelength range of the light generated in the first layer. According to the light emitting device, the distances between the light output parts may be made larger. In the light emitting device according to the aspect of the invention, the first part and the second part may be tilted at a third angle with respect to a perpendicular of the fourth side surface, as seen from the stacking direction of the first layer, and the second layer, the third part and the fourth part may be tilted at a fourth angle with respect to a perpendicular of the fifth side surface as seen from the stacking direction of the first layer, and the second layer, and the third angle and the fourth angle may be equal to or more than a critical angle. According to the light emitting device, the third reflection part and the fourth reflection part may totally reflect the light generated in the first region, the second region, and the third region. Therefore, light loss in the third reflection part and the fourth reflection part may be suppressed and light may efficiently be reflected. In the light emitting device according to the aspect of the invention, a length of the first region may be larger than a length of the second region and a length of the third region. According to the light emitting device, the distances between the light output parts may reliably be made larger. A light emitting device according to another aspect of the invention includes a multilayered structure having a first layer, and second and third layers that sandwich the first layer; the first layer has a first gain region, a second gain region, and a third gain region that generate and guide light; the second layer and the third layer are layers that suppress leakage of the light generated in the first gain region, the second gain region, and the third gain region; the first layer has a first surface, a second surface, and a third surface forming an outer perimeter shape of the multilayered structure; a reflectance of the first surface is lower than a reflectance of the second surface and a reflectance of the third surface in a wavelength range of the light generated in the first gain region, the second gain region and the third gain region; the first gain region is provided parallel to the first surface and extends from the second surface to the third surface as seen from a stacking direction of the multilayered structure, the second gain region overlaps the first gain region at the second surface and extends from the second surface to the first surface, the third gain region overlaps the first gain region at the third surface and extends from the third surface to the first surface, and the second gain region and the third gain region are separated from each other and tilted at the same angle and extend to the first surface as seen from the stacking direction of the multilayered structure. According to the light emitting device, the distances between the light output parts may be made larger while downsizing is realized. A projector according to still another aspect of the invention includes the light emitting device according to the aspect of the invention, a microlens that collimates light output from the light emitting device, a light modulation device that modulates the light collimated by the microlens in response to image information, and a projection device that projects an image formed by the light modulation device. According to the projector, alignment of the lens array may be simplified and the light modulation device may be irradiated with good uniformity. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. FIG. 1 is a plan view schematically showing a light emitting device according to an embodiment of the invention. FIG. 2 is a sectional view schematically showing the light emitting device according to the embodiment. FIG. 3 is a sectional view schematically showing a manufacturing process of the light emitting device according to the embodiment. FIG. 4 is a plan view schematically showing a manufacturing process of the light emitting device according to the embodiment. FIG. 5 is a sectional view schematically showing a manufacturing process of the light emitting device according to the embodiment. FIG. 6 is a plan view schematically showing a light emitting device according to a first modified example of the embodiment. FIG. 7 is a sectional view schematically showing a light emitting device according to a second modified example of the embodiment. FIG. 8 is a plan view schematically showing a light emitting device according to a third modified example of the embodiment. FIG. 9 schematically shows a projector according to the embodiment. FIG. 10 schematically shows the projector according to the embodiment. FIG. 11 schematically shows a light source of the projector according to the embodiment. FIG. 12 is a sectional view schematically showing the light source of the projector according to the embodiment. FIG. 13 is a sectional view schematically showing the light source of the projector according to the embodiment. FIG. 14 is a sectional view schematically showing the light source of the projector according to the embodiment. DESCRIPTION OF EXEMPLARY EMBODIMENTS Below, a preferred embodiment of the invention will be explained with reference to the drawings. 1. Light Emitting Device First, a light emitting device according to the embodiment will be explained with reference to the drawings. FIG. 1 is a plan view schematically showing a light emitting device 100 according to the embodiment. FIG. 2 is a sectional view along II-II line of FIG. 1 schematically showing the light emitting device 100 according to the embodiment. Note that, in FIG. 1 , for convenience, an illustration of a second electrode 114 is omitted. Below, the case where the light emitting device 100 is an SLD of an InGaAlP system (red) will be explained. Unlike a semiconductor laser, the SLD can prevent laser oscillation by suppressing the formation of a resonator due to edge reflection. Accordingly, speckle noise may be reduced. As shown in FIGS. 1 and 2 , the light emitting device 100 may include a multilayered structure 120 , a first electrode 112 , and the second electrode 114 . The multilayered structure 120 may have a substrate 102 , a second layer 104 (also referred to as “first cladding layer 104 ”), a first layer 106 (also referred to as “active layer 106 ”), a third layer 108 (also referred to as “second cladding layer 108 ”), a fourth layer 110 (also referred to as “contact layer 110 ”), and an insulating layer 116 . As the substrate 102 , for example, a first conductivity-type (for example, n-type) GaAs substrate or the like may be used. The first cladding layer 104 is formed on the substrate 102 . As the first cladding layer 104 , for example, an n-type InGaAlp layer or the like may be used. Note that, although not illustrated, a buffer layer may be formed between the substrate 102 and the first cladding layer 104 . As the buffer layer, for example, an n-type GaAs layer, AlGaAs layer, InGaP layer, or the like may be used. The buffer layer may improve the crystal quality of layers formed thereon. The active layer 106 is formed on the first cladding layer 104 . The active layer 106 is sandwiched between the first cladding layer 104 and the second cladding layer 108 . The active layer 106 has a multiple quantum well (MQW) structure in which three quantum well structures each including an InGaP well layer and an InGaAlP barrier layer, for example, are stacked. The planar shape of the active layer 106 is the same as the planar shape of the multilayered structure 120 , for example. In the example shown in FIG. 1 , the planar shape of the active layer 106 is a hexagonal shape and has a first surface 131 , a second surface 132 , a third surface 133 , a fourth surface 134 , a fifth surface 135 , and a sixth surface 136 . The surfaces 131 to 136 are the surfaces of the active layer 106 , do not have in plane contact with the first cladding layer 104 and the second cladding layer 108 , and form an outer shape of the multilayered structure 120 . The surfaces 131 to 136 are flat surfaces provided on the side surfaces (side walls) of the active layer 106 as seen from the stacking direction of the multilayered structure 120 , in other words, in side surface parts of the multilayered structure 120 . In the example shown in FIG. 1 , the surfaces 134 , 135 are orthogonal to the surface 131 . The surface 136 is opposed to the surface 131 . The surface 132 is connected to the surfaces 134 , 136 and tilted with respect to the surface 131 . The surface 133 is connected to the surfaces 135 , 136 and tilted with respect to the surface 131 . For example, the surfaces 131 , 134 , 135 , 136 are formed by cleavage and the surfaces 132 , 133 are formed by etching. Parts of the active layer 106 form a first gain region 150 , a second gain region 160 , and a third gain region 170 . The gain regions 150 , 160 , 170 may generate light and the light may be amplified while propagating through the gain regions 150 , 160 , 170 . That is, the gain regions 150 , 160 , 170 also serve as waveguides for the light generated in the active layer 106 . The first gain region 150 has a belt-like linear longitudinal shape having a predetermined width (a shape having a longitudinal direction and a shorter direction) in a plan view from the stacking direction of the multilayered structure 120 as shown in FIG. 1 . Further, as seen from the stacking direction of the multilayered structure 120 (in the plan view), the first gain region 150 is provided so that its longitudinal direction from the second surface 132 toward the third surface 133 may be parallel to the first surface 131 . The first gain region 150 has a first end surface 181 provided on the second surface 132 and a second end surface 182 provided on the third surface 133 . Note that the longitudinal direction of the first gain region 150 is an extension direction of a straight line passing through the center of the first end surface 181 and the center of the second end surface 182 in the plan view from the stacking direction of the multilayered structure 120 , for example. Further, the longitudinal direction may be an extension direction of a boundary line of the first gain region 150 (and the part except the first gain region 150 ). Note that “the first gain region 150 is parallel to the first surface 131 ” means that the tilt angle of the first gain region 150 with respect to the first surface 131 is within ±1° in the plan view in consideration of manufacturing variations. The first gain region 150 is connected to the second surface 132 tilted at a first angle α 1 with respect to a perpendicular line P 2 of the second surface 132 in the plan view from the stacking direction of the multilayered structure 120 . In other words, the longitudinal direction of the belt-like shape of the first gain region 150 has the angle α 1 with respect to the perpendicular line P 2 . Further, the first gain region 150 is connected to the third surface 133 tilted at a second angle α 2 with respect to a perpendicular line P 3 of the third surface 133 . In other words, the longitudinal direction of the belt-like shape of the first gain region 150 has the angle α 2 with respect to the perpendicular line P 3 . The length of the first gain region 150 is larger than the length of the second gain region 160 and the length of the third gain region 170 . The length of the first gain region 150 may be equal to or more than the sum of the lengths of the second gain region 160 and the third gain region 170 . Note that “the length of the first gain region 150 ” is also a distance between the center of the first end surface 181 and the center of the second end surface 182 . Regarding the other gain regions, similarly, the length is also a distance between the centers of two end surfaces. The second gain region 160 has, for example, a belt-like linear longitudinal shape having a predetermined width from the second surface 132 to the first surface 131 in the plan view from the stacking direction of the multilayered structure 120 . The second gain region 160 has a third end surface 183 provided on to the second surface 132 and a fourth end surface 184 provided on the first surface 131 . Note that “the longitudinal direction of the second gain region 160 ” is an extension direction of a straight line passing through the center of the third end surface 183 and the center of the fourth end surface 184 in the plan view from the stacking direction of the multilayered structure 120 , for example. Further, the longitudinal direction may be an extension direction of a boundary line of the second gain region 160 (and the part except the second gain region 160 ). The third end surface 183 of the second gain region 160 overlaps with the first end surface 181 of the first gain region 150 on the second surface 132 . In the illustrated example, the first end surface 181 and the third end surface 183 completely overlap. The second gain region 160 is connected to the second surface 132 tilted at the first angle α 1 with respect to the perpendicular line P 2 in the plan view from the stacking direction of the multilayered structure 120 . In other words, the longitudinal direction of the second gain region 160 has the angle α 1 with respect to the perpendicular line P 2 . That is, the angle of the first gain region 150 with respect to the perpendicular line P 2 and the angle of the second gain region 160 with respect to the perpendicular line P 2 are the same in the range of manufacturing variations. The first angle α 1 is an acute angle and equal to or more than the critical angle. As such, the second surface 132 may totally reflect the light generated in the gain regions 150 , 160 , 170 . Note that “the angle of the first gain region 150 with respect to the perpendicular line P 2 and the angle of the second gain region 160 with respect to the perpendicular line P 2 are the same” means that they have an angle difference within about ±2°, for example, in consideration of manufacturing variations of etching or the like. The second gain region 160 is connected to the first surface 131 tilted at an angle β with respect to a perpendicular line P 1 of the first surface 131 in the plan view from the stacking direction of the multilayered structure 120 . In other words, the longitudinal direction of the second gain region 160 has the angle β with respect to the perpendicular line P 1 . The angle β is an acute angle less than the critical angle. Note that the second gain region 160 may be parallel to the perpendicular line P 1 of the first surface 131 (β=0°). The third gain region 170 has, for example, a belt-like linear longitudinal shape having a predetermined width from the third surface 133 to the first surface 131 in the plan view from the stacking direction of the multilayered structure 120 . That is, the third gain region 170 has a fifth end surface 185 provided on to the third surface 133 and a sixth end surface 186 provided on the first surface 131 . Note that “the longitudinal direction of the third gain region 170 ” is an extension direction of a straight line passing through the center of the fifth end surface 185 and the center of the sixth end surface 186 in the plan view from the stacking direction of the multilayered structure 120 , for example. Further, the longitudinal direction may be an extension direction of a boundary line of the third gain region 170 (and the part except the third gain region 170 ). The fifth end surface 185 of the third gain region 170 overlaps with the second end surface 182 of the first gain region 150 on the third surface 133 . In the illustrated example, the second end surface 182 and the fifth end surface 185 completely overlap. The second gain region 160 and the third gain region 170 are separated from each other. In the example shown in FIG. 1 , the fourth end surface 184 of the second gain region 160 and the sixth end surface 186 of the third gain region 170 are separated at a distance D. The third gain region 170 is connected to the third surface 133 tilted at the second angle α 2 with respect to the perpendicular line P 3 in the plan view from the stacking direction of the multilayered structure 120 . In other words, the longitudinal direction of the third gain region 170 has the angle α 2 with respect to the perpendicular line P 3 . That is, the angle of the first gain region 150 with respect to the perpendicular line P 3 and the angle of the third gain region 170 with respect to the perpendicular line P 3 are the same in the range of manufacturing variations. The second angle α 2 is an acute angle and equal to or more than the critical angle. As such, the third surface 133 may totally reflect the light generated in the gain regions 150 , 160 , 170 . Note that “the angle of the first gain region 150 with respect to the perpendicular line P 3 and the angle of the third gain region 170 with respect to the perpendicular line P 3 are the same” means that they have an angle difference within about ±2°, for example, in consideration of manufacturing variations of etching or the like. The third gain region 170 is connected to the first surface 131 tilted at the angle β with respect to the perpendicular line P 1 in the plan view from the stacking direction of the multilayered structure 120 . In other words, the longitudinal direction of the third gain region 170 has the angle β with respect to the perpendicular line P 1 . That is, the second gain region 160 and the third gain region 170 are connected to the first surface 131 and tilted at the same angle so as to be parallel to each other in the plan view. More specifically, the longitudinal direction of the second gain region 160 and the longitudinal direction of the third gain region 170 are parallel to each other. As such, a light 20 output from the fourth end surface 184 and a light 22 output from the sixth end surface 186 may travel in the same direction. The end surfaces 184 , 186 may serve as light output parts (light emitting areas). Note that the third gain region 170 may be parallel to the perpendicular line P 1 of the first surface 131 (β=0°). As described above, by setting the angles α 1 , α 2 equal to or more than the critical angle and the angle β less than the critical angle, reflectance of the first surface 131 may be made lower than reflectance of the second surface 132 and reflectance of the third surface 133 . That is, the first surface 131 may serve as a light output surface and the fourth end surface 184 and the sixth end surface 186 provided on the output surface may serve as light output parts (light emitting areas) that output light generated in the gain regions 150 , 160 , 170 . The second surface 132 and the third surface 133 may serve as reflection surfaces and the first end surface 181 and the third end surface 183 provided on the reflection surface may serve as a first reflection part (a first reflection area) that reflects the light generated in the gain regions 150 , 160 , 170 . Similarly, the second end surface 182 and the fifth end surface 185 provided on the reflection surface may serve as a second reflection part (a second reflection area) that reflects the light generated in the gain regions 150 , 160 , 170 . Note that, although not illustrated, for example, the first surface 131 may be covered by an antireflection film and the second surface 132 and the third surface 133 may be covered by reflection films. As such, even when incident angles, refractive indices, and the like may not satisfy the total reflection condition, the reflectance of the first surface 131 in the wavelength band of the light generated in the gain regions 150 , 160 , 170 may be made lower than that of the second surface 132 and the third surface 133 . Further, since the first surface 131 is covered by the antireflection film, direct multiple reflections of the light generated in the gain regions 150 , 160 , 170 between the fourth end surface 184 and the sixth end surface 186 may considerably be reduced. As a result, it may be possible to prevent formation of a direct resonator, and laser oscillation of the light generated in the gain regions 150 , 160 , 170 may be suppressed. As the reflection film and the antireflection film, SiO 2 layers, Ta 2 O 5 layers, Al 2 O 3 layers, TiN layers, TiO 2 layers, SiON layers, SiN layers, multilayer films of them, or the like may be used. Further, higher reflectance may be obtained using DBR (Distributed Bragg Reflector) formed by etching the part of the multilayered structure 120 outside the surfaces 132 , 133 . Furthermore, the angle β may be set to an angle larger than 0°. As such, it may be possible to prevent direct multiple reflections of the light generated in the gain regions 150 , 160 , 170 between the fourth end surface 184 and the sixth end surface 186 . As a result, it may be possible to prevent formation of a direct resonator, and laser oscillation of the light generated in the gain regions 150 , 160 , 170 may be suppressed or prevented. The second cladding layer 108 is formed on the active layer 106 as shown in FIG. 2 . As the second cladding layer 108 , for example, a second conductivity-type (for example, p-type) InGaAlP layer or the like may be used. For example, the p-type second cladding layer 108 , the active layer 106 not doped with impurity, and the n-type first cladding layer 104 form a pin diode. Each of the first cladding layer 104 and the second cladding layer 108 is a layer having a larger forbidden band gap and a lower refractive index than those of the active layer 106 . The active layer 106 has a function of generating light and amplifying and guiding the light. The first cladding layer 104 and the second cladding layer 108 sandwich the active layer 106 and have a function of confining injected carriers (electrons and holes) and light (suppressing leakage of light). In the light emitting device 100 , when a forward bias voltage of the pin diode is applied between the first electrode 112 and the second electrode 114 (when a current is injected), the gain regions 150 , 160 , 170 are produced in the active layer 106 and recombination of electrons and holes occurs in the gain regions 150 , 160 , 170 . Light is generated by the recombination. Starting from the generated light, stimulated emission occurs and the intensity of the light is amplified within the gain regions 150 , 160 , 170 . For example, as shown in FIG. 1 , the light generated in the second gain region 160 and traveling toward the second surface 132 side is amplified within the second gain region 160 , and then reflected by the second surface 132 (end surfaces 181 , 183 ) and travels in the first gain region 150 toward the third surface 133 . Then, the light is further reflected by the third surface 133 (end surfaces 182 , 185 ), travels in the third gain region 170 , and is output from the sixth end surface 186 as the output light 22 . Concurrently, the intensity of the light is also amplified within the gain regions 150 , 170 . Similarly, the light generated in the third gain region 170 and traveling toward the third end surface 133 side is amplified within the third gain region 170 , and then reflected by the third surface 133 and travels in the first gain region 150 toward the second surface 132 . Then, the light is further reflected by the second surface 132 , travels in the second gain region 160 , and is output from the fourth end surface 184 as the output light 20 . Concurrently, the intensity of the light is also amplified within the gain regions 150 , 160 . Note that the light generated in the second gain region 160 includes light directly output from the fourth end surface 184 as the output light 20 . Similarly, the light generated in the third gain region 170 includes light directly output from the sixth end surface 186 as the output light 22 . This light is similarly amplified in the respective gain regions 160 , 170 . The contact layer 110 is formed on the second cladding layer 108 as shown in FIG. 2 . The contact layer 110 may have ohmic contact with the second electrode 114 . The upper surface 113 of the contact layer 110 may be a contact surface between the contact layer 110 and the second electrode 114 . As the contact layer 110 , for example, a p-type GaAs layer may be used. The contact layer 110 and part of the second cladding layer 108 may compose a columnar part 111 . The planar shape of the columnar part 111 is the same as the planar shapes of the gain regions 150 , 160 , 170 as seen from the stacking direction of the multilayered structure 120 . That is, the planar shape of the upper surface 113 of the contact layer 110 may be the same as the planar shapes of the gain regions 150 , 160 , 170 . For example, current channels between the electrodes 112 , 114 are determined by the planar shape of the columnar part 111 and, as a result, the planar shapes of the gain regions 150 , 160 , 170 are determined. Note that, although not illustrated, the side surface of the columnar part 111 may be inclined. The insulating layer 116 may be formed at sides of the columnar part 111 on the second cladding layer 108 . The insulating layer 116 may be in contact with the side surfaces of the columnar part 111 . The upper surface of the insulating layer 116 may be continuous with the upper surface 113 of the contact layer 110 , for example. As the insulating layer 116 , for example, a SiN layer, an SiO 2 layer, an SiON layer, an Al 2 O 3 layer, a polyimide layer, or the like may be used. When the above described material is used for the insulating layer 116 , the current between the electrodes 112 , 114 may flow in the columnar part 111 sandwiched between the insulating layers 116 . The insulating layer 116 may have a smaller refractive index than the refractive index of the second cladding layer 108 . In this case, the effective refractive index of the vertical section of the part in which the insulating layer 116 is formed is smaller than the effective refractive index of the vertical section of the part in which the insulating layer 116 is not formed, i.e., the part in which the columnar part 111 is formed. As such, in the planar direction, the light may efficiently be confined within the gain regions 150 , 160 , 170 . Note that, although not illustrated, the insulating layer 116 may not be provided. In this case, an air surrounding the columnar part 111 may function as the insulating layer 116 . The first electrode 112 is formed on the entire lower surface of the substrate 102 . The first electrode 112 may be in contact with a layer that has ohmic contact with the first electrode 112 (the substrate 102 in the illustrated example). The first electrode 112 is electrically connected to the first cladding layer 104 via the substrate 102 . The first electrode 112 is one electrode for driving the light emitting device 100 . As the first electrode 112 , for example, an electrode formed by stacking a Cr layer, an AuGe layer, a Ni layer, and an Au layer in this order from the substrate 102 side may be used. Note that a second contact layer (not shown) may be provided between the first cladding layer 104 and the substrate 102 , the second contact layer may be exposed by dry etching or the like from the opposite side to the substrate 102 , and the first electrode 112 may be provided on the second contact layer. As such, a single-sided electrode structure may be obtained. This configuration is especially advantageous when the substrate 102 is insulative. The second electrode 114 is formed in contact with the upper surface 113 of the contact layer 110 . Further, the second electrode 114 may be formed on the insulating layer 116 as shown in FIG. 2 . The second electrode 114 is electrically connected to the second cladding layer 108 via the contact layer 110 . The second electrode 114 is the other electrode for driving the light emitting device 100 . As the second electrode 114 , for example, an electrode formed by stacking a Cr layer, an AuZn layer, and an Au layer in this order from the contact layer 110 side may be used. So far, the case of the InGaAlP system has been explained as an example of the light emitting device 100 according to the embodiment, and any material system that can form a gain region may be used for the light emitting device 100 . For example, a semiconductor material of an AlGaN system, a GaN system, an InGaN system, a GaAs system, an AlGaAs system, an InGaAs system, an InP system, an InGaAsP system, a GaInNAs system, a ZnCdSe system, or the like may be used. The light emitting device 100 according to the embodiment may be applied to a light source of a projector, a display, an illumination device, a measurement device, or the like, for example. The light emitting device 100 according to the embodiment has the following characteristics, for example. According to the light emitting device 100 , the first gain region 150 is provided from the second surface 132 to the third surface 133 parallel to the first surface 131 on which the light output parts 184 , 186 are formed. Accordingly, for example, as compared to the case where the first gain region is not parallel to the first surface, distances between the light output parts may be made larger without increasing the total length of the gain region. That is, the distances between the plural light output parts may be made larger while the device length in the direction perpendicular to the light output surface is made smaller. As such, in the light emitting device 100 , a great amount of current is not necessary and electrical power consumption may be suppressed. Further, resources are not wasted and the manufacturing cost may be suppressed. More specifically, in the light emitting device 100 , the distance D between the light output parts 184 , 186 may be set equal to or more than 0.262 mm and less than 3 mm, the angle β may be set equal to or less than 5° (including 0°), and the entire lengths of the gain regions 150 , 160 , 170 may be set equal to or more than 1.5 mm and equal to or less than 3 mm. For example, when the entire length of the gain region becomes larger, generally, higher power may be realized, however, a great amount of current is necessary to obtain the so-called population inversion and, as a result, higher efficiency may not be realized unless the device is used unnecessarily higher light output. That is, with light output less than the predetermined light output, the efficiency is deteriorated. Further, when the entire length of the gain region becomes larger, the area of the entire device becomes larger, and problems of wasted resources, rising manufacturing costs, and the like arise. In the light emitting device 100 according to the embodiment, these problems may be avoided. According to the light emitting device 100 , the first gain region 150 and the second gain region 160 are connected to the second surface 132 and may be tilted at the first angle α 1 with respect to the perpendicular line P 2 of the second surface 132 , and the first gain region 150 and the third gain region 170 are connected to the third surface 133 and may be tilted at the second angle α 2 with respect to the perpendicular line P 3 of the third surface 133 . The angles α 1 , α 2 may be equal to or more than the critical angle. Accordingly, the surfaces 132 , 133 may totally reflect the light generated in the gain regions 150 , 160 , 170 . Therefore, in the light emitting device 100 , light loss on the surfaces 132 , 133 (the end surfaces 181 , 183 and the end surfaces 182 , 185 ) may be suppressed and the light may efficiently be reflected. Further, the process of forming the reflection films on the surfaces 132 , 133 is not necessary, and the manufacturing cost and the materials and resources used for manufacturing the films may be reduced. According to the light emitting device 100 , the length of the first gain region 150 may be made larger than the length of the second gain region 160 and the length of the third gain region 170 . As such, the distance D between the light output parts 184 , 186 may reliably be made larger. 2. Manufacturing Method of Light Emitting Device Next, a manufacturing method of the light emitting device according to the embodiment will be explained with reference to the drawings. FIG. 3 is a sectional view schematically showing a manufacturing process of the light emitting device 100 according to the embodiment corresponding to FIG. 2 . FIG. 4 is a plan view schematically showing a manufacturing process of the light emitting device 100 according to the embodiment corresponding to FIG. 1 . FIG. 5 is a sectional view schematically showing a manufacturing process of the light emitting device 100 according to the embodiment corresponding to FIG. 2 . As shown in FIG. 3 , on the substrate 102 , the first cladding layer 104 , the active layer 106 , the second cladding layer 108 , and the contact layer 110 are epitaxially grown in this order. As the growth method, for example, an MOCVD (Metal Organic Chemical Vapor Deposition) method, an MBE (Molecular Beam Epitaxy) method, or the like may be used. As shown in FIG. 4 , the contact layer 110 , the second cladding layer 108 , the active layer 106 , the first cladding layer 104 , and the substrate 102 are patterned, and the second surface 132 and the third surface 133 are formed. The patterning is performed using photolithography and etching, for example. Note that, although not illustrated, as long as the second surface 132 and the third surface 133 of the active layer 106 are exposed, parts of the cladding layer 104 and the substrate 102 are not necessarily patterned. Further, the surfaces 134 , 135 , 136 may be formed at the same time with the surfaces 132 , 133 using photolithography and etching, but they may also be formed by cleavage or the like after fabrication of the columnar part 111 and the electrodes 112 , 114 , which will be described later. As shown in FIG. 5 , the contact layer 110 and the second cladding layer 108 are patterned. Through the process, the columnar part 111 may be formed. As shown in FIG. 2 , the insulating layer 116 is formed to cover the side surfaces of the columnar part 111 . Specifically, first, an insulating member (not shown) is deposited on the second cladding layer 108 (including the contact layer 110 ) by a CVD (Chemical Vapor Deposition) method, a coating method, or the like, for example. Then, the upper surface 113 of the contact layer 110 is exposed using etching or the like, for example. Through the above described processes, the insulating layer 116 may be formed. Then, the second electrode 114 is formed on the contact layer 110 and on the insulating layer 116 . Then, the first electrode 112 is formed on the lower surface of the substrate 102 . The first electrode 112 and the second electrode 114 are formed by vacuum evaporation, for example. Note that the order of formation of the first electrode 112 and the second electrode 114 is not particularly limited. Through the above described processes, the light emitting device 100 according to the embodiment may be manufactured. According to the manufacturing method of the light emitting device 100 , the light emitting device 100 in which the distances of the light output parts may be made larger while downsizing is realized may be obtained. 3. Modified Examples of Light Emitting Device Next, light emitting devices according to modified examples of the embodiment will be explained with reference to the drawings. Below, in the light emitting devices according to modified examples of the embodiment, the same signs are assigned to the members having the same functions as those of the light emitting device 100 according to the embodiment, and a detailed explanation will be omitted. 3.1. Light Emitting Device According to the First Modified Example First, a light emitting device according to the first modified example of the embodiment will be explained with reference to the drawings. FIG. 6 is a plan view schematically showing a light emitting device 200 according to the first modified example of the embodiment. Note that, in FIG. 6 , for convenience, illustration of the second electrode 114 is omitted. In the example of the light emitting device 100 , as shown in FIG. 1 , the second gain region 160 has been the belt-like linear longitudinal shape provided from the second surface 132 to the first surface 131 . Similarly, the third gain region 170 has been the belt-like linear longitudinal shape provided from the third surface 133 to the first surface 131 . On the other hand, in the light emitting device 200 , as shown in FIG. 6 , the second gain region 160 is provided from the second surface 132 to the first surface 131 via the fourth surface 134 , and the third gain region 170 is provided from the third surface 133 to the first surface 131 via the fifth surface 135 . In the light emitting device 200 , the fourth surface 134 and the fifth surface 135 are tilted with respect to the first surface 131 in the plan view from the stacking direction of the multilayered structure 120 . The surfaces 134 , 135 are formed by etching, for example. More specifically, the second gain region 160 includes a first gain part 162 having a belt-like linear longitudinal shape with a predetermined width from the second surface 132 to the fourth surface 134 and a second gain part 164 having a belt-like linear longitudinal shape with a predetermined width from the fourth surface 134 to the first surface 131 . The first gain part 162 has a third end part 183 provided on the second surface 132 and a seventh end surface 187 provided on the fourth surface 134 . The second gain part 164 has an eighth end surface 188 provided on the fourth surface 134 and a fourth end surface 184 provided on the first surface 131 . The seventh end surface 187 and the eighth end surface 188 completely overlap on the fourth surface 134 , for example. In other words, the first gain part 162 and the second gain part 164 are connected on the fourth surface 134 (the end surfaces 187 , 188 ). The fourth surface 134 (the end surfaces 187 , 188 ) functions as a reflection surface (third reflection part:third reflection area). Note that “the longitudinal direction of the first gain part 162 ” is an extension direction of a straight line passing through the center of the third end surface 183 and the center of the seventh end surface 187 in the plan view from stacking direction of the multilayered structure 120 , for example. Further, the longitudinal direction may be an extension direction of a boundary line of the first gain part 162 (and the part except the first gain part 162 ). Similarly, the longitudinal direction of the second gain part 164 is an extension direction of a straight line passing through the center of the fourth end surface 184 and the center of the eighth end surface 188 in the plan view from the stacking direction of the multilayered structure 120 , for example. Further, the longitudinal direction may be an extension direction of a boundary line of the second gain part 164 (and the part except the second gain part 164 ). Each of the first gain part 162 and the second gain part 164 is connected to the fourth surface 134 and tilted at an a third angle α 3 with respect to a perpendicular line P 4 of the fourth surface 134 in the plan view from the stacking direction of the multilayered structure 120 . In other words, each of the longitudinal direction of the first gain part 162 and the longitudinal direction of the second gain part 164 has the angle α 3 with respect to the perpendicular line P 4 . The third angle α 3 is an acute angle and equal to or more than the critical angle. As such, the fourth surface 134 may totally reflect the light generated in the gain regions 150 , 160 , 170 . The third gain region 170 includes a third gain part 172 having a belt-like linear longitudinal shape with a predetermined width from the third surface 133 to the fifth surface 135 and a fourth gain part 174 having a belt-like linear longitudinal shape with a predetermined width from the fifth surface 135 to the first surface 131 . The third gain part 172 has a fifth end part 185 provided on the third surface 133 and a ninth end surface 189 provided on the fifth surface 135 . The fourth gain part 174 has a tenth end surface 190 provided on the fifth surface 135 and a sixth end surface 186 provided in the connection part to the first surface 131 . The ninth end surface 189 and the tenth end surface 190 completely overlap on the fifth surface 135 , for example. In other words, the third gain part 172 and the fourth gain part 174 are connected on the fifth surface 135 (the end surfaces 189 , 190 ). The fifth surface 135 (the end surfaces 189 , 190 ) functions as a reflection surface (fourth reflection part:fourth reflection area). Note that the longitudinal direction of the third gain part 172 is an extension direction of a straight line passing through the center of the fifth end surface 185 and the center of the ninth end surface 189 in the plan view of from the stacking direction the multilayered structure 120 , for example. Further, the longitudinal direction may be an extension direction of a boundary line of the third gain part 172 (and the part except the third gain part 172 ). Similarly, “the longitudinal direction of the fourth gain part 174 ” is an extension direction of a straight line passing through the center of the sixth end surface 186 and the center of the tenth end surface 190 in the plan view of from the stacking direction the multilayered structure 120 , for example. Further, the longitudinal direction may be an extension direction of a boundary line of the fourth gain part 174 (and the part except the fourth gain part 174 ). Each of the third gain part 172 and the fourth gain part 174 is connected to the fifth surface 135 and tilted at an a fourth angle α 4 with respect to a perpendicular line P 5 of the fifth surface 135 in the plan view from the stacking direction of the multilayered structure 120 . In other words, each of the longitudinal direction of the third gain part 172 and the longitudinal direction of the fourth gain part 174 has the angle α 4 with respect to the perpendicular line P 4 . The fourth angle α 4 is an acute angle and equal to or more than the critical angle. As such, the fifth surface 135 may totally reflect the light generated in the gain regions 150 , 160 , 170 . Each of the second gain part 164 and the fourth gain part 174 is tilted at the angle β with respect to the perpendicular line P 1 of the first surface 131 so as to be parallel to each other in the plan view from the stacking direction of the multilayered structure 120 . In other words, each of the longitudinal direction of the second gain part 164 and the longitudinal direction of the fourth gain part 174 has the angle β with respect to the perpendicular line P 1 . Note that the angle β may be 0°. According to the light emitting device 200 , as compared to the example of the light emitting device 100 , the first angle α 1 and the second angle α 2 may be set larger. Accordingly, in the light emitting device 200 , the light generated in the gain regions 150 , 160 , 170 may be easier to be totally reflected on the second surface 132 and the third surface 133 . 3.2. Light Emitting Device According to the Second Modified Example Next, a light emitting device according to the second modified example of the embodiment will be explained with reference to the drawings. FIG. 7 is a sectional view schematically showing a light emitting device 300 according to the second modified example of the embodiment corresponding to FIG. 2 . In the example of the light emitting device 100 , as shown in FIG. 2 , the waveguide of the index-guiding type in which light is confined by the refractive index difference provided between the region where the insulating layer 116 is formed and the region where the insulating layer 116 is not formed, i.e., the region where the columnar part 111 is formed and the light is confined has been explained. On the other hand, in the light emitting device 300 , a waveguide of the gain-guiding type in which the columnar part 111 is not formed, i.e., the refractive index difference is not provided and the gain regions 150 , 160 , 170 serve as waveguide regions as they are may be employed as shown in FIG. 7 . That is, in the light emitting device 300 , the contact layer 110 and the second cladding layer 108 do not compose the columnar part 111 , and the insulating layer 116 is not formed at the sides thereof. The insulating layer 116 may be formed on the contact layer 110 except the parts of the gain regions 150 , 160 , 170 . That is, the insulating layer 116 may have openings at the gain regions 150 , 160 , 170 and the upper surface 113 of the contact layer 110 may be exposed in the openings. The second electrode 114 may be formed on the exposed parts of the contact layer 110 and the insulating layer 116 . The upper surface 113 of the contact layer 110 being contact with the second electrode 114 has the same planar shape as those of the gain regions 150 , 160 , 170 . In the illustrated example, current channels between the electrodes 112 , 114 are determined by the planar shape of the contact surface between the second electrode 114 and the contact layer 110 and, as a result, the planar shapes of the gain regions 150 , 160 , 170 are determined. Note that, although not illustrated, the second electrode 114 may not be formed on the insulating layer 116 , and instead may be formed only on the contact layer 110 at the gain regions 150 , 160 , 170 . According to the light emitting device 300 , as in the light emitting device 100 , the distances between the light output parts may be made larger while downsizing is realized. 3.3. Light Emitting Device According to the Third Modified Example Next, a light emitting device according to the third modified example of the embodiment will be explained with reference to the drawings. FIG. 8 is a plan view schematically showing a light emitting device 400 according to the third modified example of the embodiment. Note that, in FIG. 8 , for convenience, an illustration of the second electrode 114 is omitted. In the example of the light emitting device 100 , as shown in FIG. 1 , one first gain region 150 , one second gain region 160 , and one third gain region 170 have been provided. On the other hand, in the light emitting device 400 , as shown in FIG. 8 , plural first gain regions 150 , plural second gain regions 160 , and plural third gain regions 170 are respectively provided. That is, the first gain region 150 , the second gain region 160 , and the third gain region 170 may form a group of gain regions 450 , and, in the light emitting device 400 , plural groups of gain regions 450 are provided. In the illustrated example, three groups of gain regions 450 are provided, however, the number of groups is not particularly limited. The plural groups of gain regions 450 are arranged in a direction orthogonal to the direction in which the perpendicular line P 1 of the first surface 131 extends. More specifically, they are arranged so that, in the adjacent groups of gain regions 450 , the distance between the sixth end surface 186 of one group of gain regions 450 and the fourth end surface 184 of the other group of gain regions 450 may be D (the distance between the light output parts). As such, the light 20 , 22 may easily enter a lens array, which will be described later. According to the light emitting device 400 , higher power may be realized as compared to the example of the light emitting device 100 . 4. Projector Next, a projector according to the embodiment will be explained with reference to the drawings. FIG. 9 schematically shows a projector 700 according to the embodiment. FIG. 10 schematically shows part of the projector 700 according to the embodiment. Note that, in FIG. 9 , for convenience, a casing forming the projector 700 is omitted, and further, a light source 600 is simplified for illustration. Further, in FIG. 10 , for convenience, the light source 600 , a lens array 702 , and a liquid crystal light valve 704 are illustrated, and further, the light source 600 is simplified for illustration. The projector 700 includes a red light source 600 R, a green light source 600 G, and a blue light source 600 B that output red light, green light, and blue light as shown in FIG. 9 . The light sources 600 R, 600 G, 600 B have the light emitting devices according to the invention. In the following example, the light sources 600 R, 600 G, 600 B having the light emitting devices 400 as the light emitting devices according to the invention will be explained. FIG. 11 schematically shows the light source 600 of the projector 700 according to the embodiment. FIG. 12 is a sectional view along XII-XII of FIG. 1 schematically showing the light source 600 of the projector 700 according to the embodiment. The light source 600 may have the light emitting devices 400 , a base 610 , and sub-mounts 620 as shown in FIGS. 11 and 12 . The two light emitting devices 400 and the sub-mount 620 may form a structure 630 . Plural structures 630 are provided and arranged in the direction (Y-axis direction) orthogonal to the arrangement direction (X-axis direction) of the end surfaces 184 , 186 which are the light output parts of the light emitting devices 400 as shown in FIG. 11 . The structures 630 may be arranged so that the distance between the light output parts in the X-axis direction and the distance between the light output parts in the Y-axis direction may be equal. As such, the light output from the light emitting devices 400 may easily enter the lens array 702 . The two light emitting devices 400 forming the structure 630 are provided with the sub-mount 620 sandwiched in between. In the example shown in FIGS. 11 and 12 , the two light emitting devices 400 are provided so that the second electrodes 114 may be opposed via the sub-mount 620 . On part of the surface of the sub-mount 620 being contact with the second electrode 114 , for example, wiring is formed. As such, voltages may individually be supplied to the respective plural second electrodes 114 . As the material of the sub-mount 620 , for example, aluminum nitride and aluminum oxide may be cited. The base 610 supports the structures 630 . In the example shown in FIG. 12 , the base 610 is connected to the first electrodes 112 of the plural light emitting devices 400 . As such, the base 610 may function as a common electrode of the plural first electrodes 112 . As the material of the base 610 , for example, copper and aluminum may be cited. Although not illustrated, the base 610 may be connected to a heat sink via a Peltier device. Note that the form of the structure 630 is not limited to the example shown in FIGS. 11 and 12 . For example, as shown in FIG. 13 , two light emitting devices 400 forming the structure 630 may be provided so that the first electrode 112 of one light emitting device 400 and the second electrode 114 of the other light emitting device 400 may be opposed via the sub-mount 620 . Alternatively, as shown in FIG. 14 , they may be provided so that the first electrodes 112 of the two light emitting devices 400 may be a common electrode. As shown in FIG. 9 , the projector 700 further includes lens arrays 702 R, 702 G, 702 B and transmissive liquid crystal light valves (light modulation devices) 704 R, 704 G, 704 B, and a projection lens (projection device) 708 . The light output from the respective light sources 600 R, 600 G, 600 B enter the respective lens arrays 702 R, 702 G, 702 B. As shown in FIG. 10 , the lens array 702 may have flat surfaces 701 that the light 20 , 22 output from the light output parts 184 , 186 enters. Plural flat surfaces 701 are provided in correspondence with the plural light output parts 184 , 186 and arranged at equal distances. Further, the normal lines of the flat surfaces 701 are tilted with respect to the optical axes of the light 20 , 22 . By the flat surfaces 701 , the optical axes of the light 20 , 22 may be made orthogonal to an irradiated surface 705 of the liquid crystal light valve 704 . Especially, when the angles β formed by the first surface 131 and the second and the third gain regions 160 , 170 are not 0°, the light 20 , 22 output from the respective light output parts 184 , 186 are tilted with respect to the perpendicular line P 1 of the first surface 131 , and thus, it is desirable that the flat surfaces 701 are provided. The lens array 702 may have convex curved surfaces 703 at the liquid crystal light valve 704 side. Plural convex curved surfaces 703 are provided in correspondence with the plural flat surfaces 701 and arranged at equal distances. The light 20 , 22 with optical axes converted on the flat surfaces 701 are collected (collimated) or traveling at diffusion angles reduced by the convex curved surfaces 703 , and may be superimposed (partially superimposed). As such, the liquid crystal light valve 704 may be irradiated with good uniformity. As described above, the lens array 702 may control the optical axes of the light 20 , 22 output from the light source 600 and integrate the light 20 , 22 . As shown in FIG. 9 , the light integrated by the respective lens arrays 702 R, 702 G, 702 B enters the respective liquid crystal light valves 704 R, 704 G, 704 B. The respective liquid crystal light valves 704 R, 704 G, 704 B respectively modulate the incident light in response to image information. Then, the projection lens 708 enlarges images formed by the liquid crystal light valves 704 R, 704 G, 704 B and projects them on a screen (display surface) 710 . Further, the projector 700 may include a cross dichroic prism (color combining unit) 706 that combines light output from the liquid crystal light valves 704 R, 704 G, 704 B and guides the light to the projection lens 708 . The three colors of light modulated by the respective liquid crystal light valves 704 R, 704 G, 704 B enter the cross dichroic prism 706 . The prism is formed by bonding four right angle prisms, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are provided crosswise on its inner surfaces. By the dielectric multilayer films, the three colors of light are combined and light representing a color image is formed. Then, the combined light is projected on the screen 710 by the projection lens 708 as a projection system, and the enlarged image is displayed thereon. According to the projector 700 , the light emitting devices 400 that may make distances between the plural light output parts larger while downsizing is realized is provided. Accordingly, in the projector 700 , alignment of the lens array 702 may be easy and the liquid crystal light valve 704 may be irradiated with good uniformity. Note that, in the above described example, transmissive liquid crystal light valves have been used as the light modulation devices, however, other light valves than liquid crystal, or reflective light valves may be used. As the light valves, for example, reflective liquid crystal light valves and digital micromirror devices may be used. Further, the configuration of the projection system may appropriately be changed depending on the type of the light valves employed. Further, the light source 600 and the lens array 702 may be modularized in alignment with each other. Furthermore, the light source 600 , the lens array 702 , and the light valve 704 may be modularized in alignment with one another. In addition, the light source 600 may also be applied to a light source device of a scanning type image display device (projector) having a means of scanning light for displaying an image in a desired size on a display surface. The above described embodiments and modified examples are just examples, and the invention is not limited to these. For example, the respective embodiments and the respective modified examples may be appropriately combined. The embodiments of the invention have been specifically explained above, and a person skilled in the art could easily understand that many modifications may be carried out without substantively departing from the spirit and effect of the invention. Therefore, these modified examples are included in the range of the invention. The entire disclosure of Japanese Patent Application No. 2011-051570 filed Mar. 9, 2011 is expressly incorporated by reference herein.

A light emitting device includes a first layer that generates light by injection current and forms a waveguide for the light, and an electrode that injects the current into the first layer, wherein the waveguide has a first region, a second region, and a third region, the first region and the second region connect at a first reflection part, the first region and the third region connect at a second reflection part, the second region and the third region extend to an output surface, a longitudinal direction of the first region is parallel to the output surface, and a first light output from the second region at the output surface and a second light output from the third region at the output surface are output in parallel to one another.

BACKGROUND OF THE INVENTION This invention relates generally to fluid filters and devices for mounting and holding such filter. In particular, this invention relates to oil filters mounted in automobiles and other motor vehicles. As space and size limitations become greater considerations in automotive design, car and truck manufacturers have attempted to fit more and more equipment in smaller and smaller hood areas. As a result, there is very little working space around modern automotive engines. This lack of maneuvering room has turned the simple job of changing an oil filter into a gymnastic feat requiring double-jointed fingers and wrists. The awkward positioning of many oil filters has spawned the development of specialized tools for operating in the cramped hood space of many cars. These new tools have added to the expense of maintaining motor vehicles. What is needed, therefore, is an oil filter design that meets the space limitations of modern automobiles while allowing for easy replacement without the use of specialized tools. SUMMARY OF THE INVENTION This invention meets these and other needs by providing an oil filter and bracket that allows the filter to be moved into an accessible position before changing the filter. In the preferred embodiment of my invention, the filter is a rolled paper filter mounted about a cardboard tube within a filter container. The filter is mounted on a filter base which has inlet and outlet connections. The base is mounted on a bracket having two sets of prongs extending upwardly from a pair of fingers. The filter base has extending ear portions which fit between the prongs to support the filter in either an upright or an inverted position. The filter inlet and outlet are connected to the fluid source and drain, respectively, by flexible hoses or tubes. The filter and base may be turned from an inverted position where they are suspended from the bracket to an upright position where they are seated on the bracket so that the filter may be more easily removed for replacing. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an exploded view of the filter unit and base according to the preferred embodiment; FIG. 2 shows the bracket of the preferred embodiment; FIG. 3 shows two alternative mounting positions of the filter unit and base of the preferred embodiment; FIGS. 4A, 4B, and 4C show side views of three alternative mounting positions of the preferred filter unit, base and bracket within an automobile; and FIGS. 5A, 5B, and 5C show front views of three alternative mounting positions of the preferred filter unit, base and bracket within an automobile. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a filter unit 8 and base 40. A sealed cylindrical filter container 10 encloses a filter element 12 formed from rolled tissue paper 14 surrounding a cardboard tube 16. Filter container 10 has an open end 18 and a closed end 20. Formed in closed end 20 are a series of channels 22. Channels 22 permit the flow of fluid through the filter as described below. In the preferred embodiment, a perforated plate 24 is mounted in open end 18 of filter container 10 below filter element 12. Plate 24 has a ring 26 formed on its outer perimeter extending in a direction away from the filter element. Ring 26 is attached to filter container 10 by crimping the outer edge of the filter container around ring 26. Ring 26 may also be attached by welding or any other suitable means to the open end of the filter container to hold filter element 12 in place. A radially outward extending lip 27 is formed in ring 26 and filter container 10. Plate 24 has multiple perforations 28 and a large center opening 30 to provide access to the rolled paper 14 and to the center 32 of cardboard tube 16, respectively. The diameter of center opening 30 is larger than the diameter of cardboard tube 16. Alternatively, perforated plate 24 and ring 26 may be replaced with a removable circular spring element (not shown) made from metal wire. The circular spring element exerts tension against the inside surface of container 10 and holds filter element 12 in place. The circular spring element may be removed to permit replacement of filter element 12 so that filter container 10 may be reused. In the preferred embodiment, base 40 is formed from die cast aluminum. At the lower end of base 40 is a cylinder 42. Ear portions 44 extend radially from end 46 of cylinder 42. Formed in end 46 of cylinder 42 is a threaded hole 48. Mounted in hole 48 is a screw 50. Screw 50 and ear portions 44 mate with a bracket as explained below. A plate 52 extends radially from end 54 of cylinder 42. Plate 52 is substantially coaxial with cylinder 42. An upwardly extending ring 56 is formed at the outer periphery of plate 52. A resilient sealing gasket 58 is disposed in a circular groove 60 formed in plate 52 radially inward from ring 56. Gasket 58 interacts with ring 26 and lip 27 of filter unit 8 to seal the filter when assembled. Another ring 62 is formed on plate 52 radially inward from groove 60 and extends upward from groove 60. The diameter of ring 62 diminishes with the distance from groove 60 such that face 64 of ring 62 forms on obtuse angle with face 66 of plate 52. Face 64 mates with ring 26 of filter unit 8 to seal the filter when assembled. Face 68 of plate 52 extends radially inward from ring 62. Another upwardly extending ring 70 is formed on face 68 radially inward from ring 62. Mounted on ring 70 is a support tube 72. In the preferred embodiment, support tube 72 is attached to ring 70 by force-fitting. Support tube 72 may also be attached to ring 70 by welding, with glue, or by any other suitable means. When the filter unit and base are assembled, cardboard tube 16 surrounds support tube 72, and face 68 is proximate perforated plate 24. A threaded fluid inlet 74 is formed in cylinder 42. Inlet 74 has a radial portion 76 and an axial portion 78 extending upward from radial portion 76 and through face 68 at a location radially inward from ring 70. A series of interconnecting channels 80 is formed in face 68. An orifice 82 is formed in one channel 80 and extends downwardly through plate 52. A threaded outlet 84 is formed in surface 66 to meet orifice 82. In the preferred embodiment, orifice 82 has a diameter of 1/16 inch. Two mesh or screen rings 90 and 92 are disposed on and substantially cover face 68. The purpose of mesh rings 90 and 92 is to allow fluid to flow from perforated plate 24 into channels 80 and orifice 82. A cup ring 94 is disposed about support tube 72 to hold mesh rings 90 and 92 against face 68. Cup ring 94 has a wall 96 extending upward from its outer periphery at a substantially 90 degree angle and a wall 98 extending upward from its inner periphery at an obtuse angle. Cup ring 94 is force-fit onto support tube 72 to hold mesh rings 90 and 92 in place. To assemble, filter unit 8 is mounted on base 40 so that cardboard tube 16 surrounds support tube 72, ring 26 surrounds ring 62, and lip 27 rests on gasket 58. Perforated plate 24 rests against mesh rings 90 and 92. Wall 98 of cup ring 94 extends into filter element 12 to prevent filtered fluid from mixing with unfiltered fluid. A clamp 86 surrounds lip 27, gasket 58 and ring 56 to hold filter unit 8 in place on base 40. In operation, unfiltered oil is introduced into inlet 74 and flows through radial and axial portions 76 and 78 into a space 88 within tube 72. The oil then flows through channels 22 into rolled paper 14 where it is filtered. The filtered oil flows through perforations 28 and mesh rings 90 and 92 into channels 80, then through orifice 82 and outlet 84. As shown in FIGS. 2 through 5, base 40 may be removably mounted to a bracket 100 which supports the filter in the automobile engine area. In the preferred embodiment, bracket 100 is formed from a strip of carbon steel. A five-sided geometrically shaped material is removed from one end 101 of the strip leaving two fingers 102 extending from end 101. Fingers 102 cooperate with bracket 100 to form a space 103. Two sets of notches 104 and 106 are formed in fingers 102 by bending rectangular pairs of prongs 108 and 110 upward from fingers 102 at a substantially 90 degree angle to the top surface 112 of the bracket. The distance between adjacent prongs is slightly greater than the width of ear portions 44 of filter base 40. As shown in FIG. 3, base 40 may be mounted on bracket 100 in two alternative positions. Base 40 may be mounted such that all of base 40 and filter unit 8 extend upward from surface 112. In this upright position, ear portions 44 rest between and are laterally supported by prongs 108 and 110. Alternatively, base 40 may be mounted such that a portion of base 40 and all of filter unit 8 extend downward from surface 112. In this inverted position, ear portions 44 rest between prongs 108 and 110. Filter unit 8 and base 40 are suspended between fingers 102, and a portion of base 40 extends through the space 103 between fingers 102. An optional clasp or securing device (not shown) may be added to keep ear portions 44 in place between prongs 108 and 110 in the inverted position. Alternatively, base 40 may be attached to bracket 100 by inserting screw 50 through a hole 114 formed in bracket 100 adjacent space 103 and into threaded hole 48 of base 40. Base 40 may be attached to bracket 100 in this manner in either the upright or the inverted positions. FIGS. 4 and 5 show two ways to mount the assembled filter, base and bracket in an automobile. For either mounting method, bracket 100 may be attached to the engine area of the vehicle by bolting, welding or any other suitable means. The bracket may be bent to fit the contour of the mounting surface. Also for either mounting method, the filter mounting area of the bracket should be bent to make surface 112 generally horizontal. Inlet 74 and outlet 84 are connected to the engine oil system by flexible hoses 120 and 122, respectively, with threaded connections. In the first mounting method, bracket 100 is placed so that filter unit 8 and base 40 may be suspended within the engine space with the automobile hood closed as shown in FIGS. 4A and 5A. To replace a used filter, filter unit 8 and base 40 are removed from their suspended position on bracket 100, rotated 180 degrees and placed on top of bracket 100 as shown in FIGS. 4B and 5B. Flexible hoses 120 and 122 must be long enough to permit this movement. Ear portions 44 are placed between bracket prongs 108 and 110 to support base 40 during the replacement operation. The used filter unit may be detached from base 40 by removing clamp ring 86. A new filter may then be mounted on the base. After tightening the clamp, the new filter unit 8 and base 40 is once again suspended from bracket 100 by rotating the base 180 degrees to the underside of bracket 100 and placing the ear portions 44 between bracket prongs 108 and 110 as shown. The alternative mounting means is shown in FIGS. 4C and 5C. Bracket 100 be mounted such that filter unit 8 and base 40 (1) are upright within the engine space and (2) do not prevent the automobile hood from closing. Base 40 is secured to bracket 100 by inserting screw 50 through hole 114 into threaded hole 48. The filter and bracket design of my invention permits the placement of the filter in a location in the engine area during operation of the vehicle which would be inaccessible for the purpose of changing the filter. The filter changing position, on the other hand, may be one in which the upright filter container prevents the engine hood from closing, as shown in FIGS. 4B and 5B. This design makes maximum use of the limited space in the engine area. In addition, since my design permits the filter to be moved away from other engine parts which might limit access to the filter, no special tools are required to remove the filter. Finally, the design permits two different mounting methods for maximum flexibility. While the bracket according to the preferred embodiment is formed from carbon steel, any suitable material may be used. In addition, many different filter designs may be used along with the bracket of my invention. The description of the preferred embodiment is not intended to limit the scope of the claims.

A filter and bracket apparatus includes a filter element (8) mounted in a filter container (10) on a base (40). The filter base is supported in one of two operating positions by a bracket (100) which has two extending fingers (102) each having a pair of prongs (108, 110) thereon. The filter base has a pair of extending ears (44) which interact with the bracket's prongs to support the filter alternatively in an upright or an inverted position. The invention also relates to a method for changing an oil filter without disconnecting the fluid conduits delivering fluid to and receiving fluid from the filter.

BACKGROUND OF THE INVENTION [0001] This invention relates in general to vehicle wheels and, in particular, to an improved vehicle wheel and wheel cover assembly and method for producing the same. [0002] Automotive wheels serve two main purposes: the wheels support the vehicle and associated tires and the wheels provide an aesthetically pleasing appearance. Current technology often involves tradeoffs between those two goals. Wheels are typically constructed of metal or metal alloys, although alternative materials, such as composites, are envisioned. The aesthetic appearance of such a wheel is limited by manufacturing methods to form a given styled surface. Additionally, such a wheel will often have excess material (and weight) added to form the styled surface. Wheel clads or covers are used to simulate a styled wheel surface while utilizing a structural wheel underneath to support any loads imparted on the wheel. The wheel cover is typically made of a plastic or thin metal material that is more easily formable into pleasing aesthetic shapes. The cover is then attached to the wheel by mechanical means, whether fasteners, adhesives or locking features formed into the cover or the wheel. The cover can also receive a special surface coating to enhance its appearance, such as a bright paint or chrome plating. It is also desirable that the cover is not easily discernible as separate from the wheel. It is desirable to eliminate evidence of a cover being used such as mating lines, a hollow sound when tapped, yielding to moderate pressure, preventing the entry of foreign matter between the parts and visible wheel surfaces behind the cover. To this end, a suitable adhesive foam material is often used to deaden the hollow sound when tapped, fill the space between the wheel and cover to prevent entry of foreign matter and support the cover when pressure is applied to the cover. [0003] It can be very difficult to use adhesives to join the cover and the wheel in a high volume manufacturing environment because the adhesive requires sufficient time for a chemical reaction to occur and expand (in the case of foam adhesives), attain handling strength and subsequently full strength. A fast curing adhesive will allow faster throughput but also cures quickly in the mixing equipment and requires more maintenance. Conversely, a slow curing adhesive possesses a longer open time before clogging inside the dispensing equipment but requires more work-in-process inventory and related resources, such as, floor space, cure ovens, material handling equipment and tooling. [0004] Furthermore, when using an expanding foam adhesive material, the cover and wheel assembly can be encapsulated inside a masking mold to contain the expanding foam adhesive material. However, there often exists a path internal to the cover and wheel assembly through which it is undesirable to allow the expanding foam adhesive material to enter. It is not feasible to mask off certain areas when the cover and wheel are assembled. SUMMARY OF THE INVENTION [0005] This invention relates to a vehicle wheel and wheel cover assembly and method for producing the same. [0006] According to one embodiment, the method for producing a vehicle wheel and wheel cover assembly comprises the steps of: (a) providing a wheel cover having an inner surface and an outer surface; (b) selectively applying at least one shot of a first adhesive material to a portion of the inner surface of the wheel cover to define a predetermined masked area; (c) providing a vehicle wheel having an outboard face; (d) positioning the wheel cover and the vehicle wheel relative to one another whereby at least one cavity is formed between the inner surface of the wheel cover, the outboard face of the vehicle wheel, and the masked area of the wheel cover defined by the first adhesive material; and (e) selectively applying a second adhesive material to the cavity to secure the wheel cover to the vehicle wheel. [0007] According to another embodiment, the vehicle wheel and wheel cover assembly comprises: a vehicle wheel having an outboard face; and a wheel cover secured to the vehicle wheel, the wheel cover having an inner surface and an outer surface; wherein at least one shot of a first adhesive material is selectively applied to a portion of the inner surface of the wheel cover to define a predetermined masked area prior to selectively applying a second adhesive material to at least one cavity formed between the inner surface of the wheel cover, the outboard face of the vehicle wheel, and the masked area of the wheel cover defined by the first adhesive material to secure the wheel cover to the vehicle wheel. [0008] Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the invention, when read in light of the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0009] FIG. 1 is a view of an embodiment of a vehicle wheel and wheel cover assembly. [0010] FIG. 2 is another view of the vehicle wheel and wheel cover assembly but showing only the first shot of the adhesive/foam material. [0011] FIG. 3 is a view of the wheel cover illustrated in FIGS. 1 and 2 , showing the first shot of the adhesive/foam material applied to a portion thereof. [0012] FIG. 4 is an example of an embodiment of a sequence for producing the vehicle wheel and wheel cover assembly illustrated in FIG. 1 . [0013] FIG. 5 is a schematic diagram illustrated an example of an embodiment of a first step of a process for producing a vehicle wheel and wheel cover assembly. [0014] FIG. 6 is a schematic diagram illustrating an example of an embodiment of a second step of a process for producing a vehicle wheel and wheel cover assembly. [0015] FIG. 7 is a view similar to FIG. 3 showing an alternate embodiment of a first shot of an adhesive/foam material applied to a portion of the wheel cover. DETAILED DESCRIPTION OF THE INVENTION [0016] Referring now to the drawings, there is illustrated in FIGS. 1 and 2 a view of a vehicle wheel and cover assembly, indicated generally at 10 , including a first embodiment of a wheel cover retention system, indicated generally at 12 . As shown therein, the vehicle wheel and cover assembly 10 defines an axis X and includes a vehicle wheel, indicated generally at 22 , and a wheel cover, indicated generally at 30 which as will be discussed below, are secured together. The vehicle wheel 22 may be of any suitable type of material or materials, such as for example, steel, aluminum and alloys thereof, and may be of any suitable type of wheel construction, such as for example, a “full face” type of wheel, such as shown in FIG. 5A of U.S. Pat. No. 5,533,261 to Kemmerer, a “bead seat attached” wheel such as shown in FIG. 4 of U.S. Pat. No. 5,188,429 to Heck et al., a “well attached” wheel such as shown in FIG. 3 of U.S. Pat. No. 5,188,429 to Heck et al., a “bimetal” wheel construction including an aluminum disc and a steel rim such as shown in U.S. Pat. No. 5,421,642 to Wei et al., a “modular wheel” construction such as shown in U.S. Pat. No. 5,360,261 to Archibald et al., a cast aluminum wheel such as shown in U.S. Pat. No. 5,340,418 to Wei, or a euroflange type of wheel such as shown in U.S. Pat. No. 5,564,792 to Archibald, the disclosures of all of these patents incorporated by reference in entirety herein. [0017] In the illustrated embodiment the vehicle wheel 22 of the vehicle wheel and cover assembly 10 is a one-piece full cast aluminum wheel and includes a wheel rim, indicated generally at 14 , and a wheel disc, indicated generally at 16 . The wheel rim 14 includes an inboard tire bead seat retaining flange 14 A, and inboard tire bead seat 14 B, a generally axially extending well 14 C, and outboard tire bead seat 14 D, and an outboard tire bead seat retaining flange 14 E. Alternatively, the construction, material and/or make-up of the wheel rim 14 may be other than illustrated if so desired. [0018] The wheel disc 16 includes a generally centrally located inner wheel mounting surface or portion 18 , an outer annular portion 20 , and defines an outer surface or outboard face 22 A. The inner mounting surface 18 of the wheel disc 16 is provided with a center hub hole 18 A and a plurality of lug bolt mounting holes 18 B spaced circumferentially around the center hub hole 18 A (one of such lug bolt mounting holes 18 B illustrated in FIG. 1 ). The lug bolt receiving holes 18 B are adapted to receive lug bolts (not shown) and nuts (not shown) for securing the vehicle wheel 22 on an axle (not shown) of a vehicle. Also, as shown in this embodiment, the wheel disc 16 further includes a plurality of windows or openings 24 formed therein between each pair of spokes 26 . In the illustrated embodiment, the wheel disc 16 includes five window 20 , only one of such windows 20 illustrated in FIG. 1 and two of such windows 20 illustrated in FIG. 2 and five spokes 26 , only one of such spokes 26 illustrated in FIG. 1 . Alternatively, the construction, material and/or make-up of the wheel disc 16 may be other than illustrated if so desired. [0019] In the illustrated embodiment, the wheel cover retention system 12 includes the wheel cover 30 which is secured to the vehicle wheel 22 . As will be discussed below, the wheel cover retention system 12 utilizes multiple “shots” of a suitable material, i.e., an adhesive/foam material, dispensed preferably prior to the assembly of the wheel cover 30 and the vehicle wheel 22 and/or after the assembly of the wheel cover 30 and the vehicle wheel 22 . This will allow masking tools to effectively “shut off” areas of the wheel cover 30 and vehicle wheel 22 prior to assembly that are not accessible otherwise. [0020] In the illustrated embodiment, the wheel cover 30 is preferably formed from plastic and is a one-piece wheel cover and may have at least an outer surface which is painted, chrome-plated or otherwise adorned or decorated as desired. Alternatively, the wheel cover 30 may be formed from other materials, such as metal and/or may be a multi-piece (two or more pieces) wheel cover formed of like or unlike materials if so desired. [0021] The wheel cover 30 may have an inner surface which closely conforms to the outboard face of the wheel; may have an inner surface which is spaced from the outboard face of the wheel to impart the styling to the wheel; or may have a combination of both an inner surface which conforms and an inner surface which is spaced apart from the outboard face of the wheel. In the illustrated embodiment, the wheel cover 30 includes an inner surface 30 A which has portions which generally conform to the outboard face 22 A of the wheel 22 and portions which are spaced apart from the outboard face 22 A of the wheel 22 . [0022] Also, as best shown in FIG. 3 , the wheel cover 30 includes a center hub hole 32 , a plurality of lug bolt openings 34 , a plurality of window 36 , and a spoke 38 provided between each pair of the windows 36 . The center hub hole 32 of the wheel cover 30 is preferably adapted to be coaxial with the axis X of the wheel 10 and the center hub hole 18 A. The lug bolt openings 34 of the wheel cover 30 are preferably adapted to be coaxial with lug bolt holes 18 B of the wheel 22 . The windows 36 of the wheel cover 30 generally correspond to or resemble the windows 20 provided in the wheel 22 . The spokes 38 of the wheel cover 30 preferably cover the spokes 26 of the wheel 22 and preferably impart a desired styling to the vehicle wheel 22 . Alternatively, the construction, material and/or make-up of the wheel cover 30 may be other than illustrated if so desired. [0023] Referring now to FIG. 4 , there is illustrated a block diagram illustrating a preferred sequence of steps for producing the first embodiment of the vehicle wheel and cover assembly 10 . As shown therein, in step 40 and as illustrated schematically in FIG. 5 , the wheel cover 30 is placed face-down onto a lower masking tool (the lower masking tool shown schematically in FIG. 5 by reference number 60 ), such that the lower masking tool 60 is preferably adjacent the outer surface 30 B of the wheel cover 30 . As will be discussed below, the lower masking tool 60 is operative to support and locate the wheel cover 30 and prevent a selected adhesive/foam material from contacting the outer “decorative” surface 30 B of the wheel cover 30 . Also, in step 40 , a pre-form tool (shown schematically in FIG. 5 and identified by reference number 62 ) for the first “shot” of a selected adhesive/foam material is located on the wheel cover 30 preferably adjacent the inner surface 30 A thereof and all three parts (the lower masking tool 60 , the wheel cover 30 , and the pre-form tool 62 ) are located and clamped together as an assembly as shown schematically in FIG. 5 in step 40 . [0024] Next, in step 42 , the assembly is preferably allowed to reach a desired controlled temperature (either by external or internal, heating or cooling) and then a suitable adhesive/foam material 54 is selectively dispensed into one or more cavities (one of such cavities shown in phantom in FIG. 5 by reference number 56 defined between the pre-form tool 62 and the wheel cover 30 , and the adhesive/foam material 54 is allowed to react. Depending upon the particular adhesive/foam material 54 which is used, step 42 may not require any heating or cooling but may take place at room temperature. [0025] After a desired period of time, next in step 44 , the pre-form tool 62 is unclamped and the wheel cover 10 is removed having the first shot of the adhesive/foam material 54 selectively adhered thereon in a desired “masking pattern”, such as shown for example in the masking pattern shown in the embodiment illustrated in FIGS. 2 and 3 . As shown in this embodiment, the adhesive/foam material 54 is preferably generally deposited about an inner circumferential portion of the inner surface 30 A of the wheel cover 30 . More preferably, the first shot of the adhesive/foam material 54 is selectively adhered around the center hub hole 32 and the lug bolt openings 34 of the wheel cover 30 . Alternatively, it is possible that the wheel cover 30 may receive more than one shot or dose of the same or different adhesive/foam materials involving the use of one or multiple pre-form tools depending on the desired masking effect which is to be achieved and/or that the particular areas of the wheel cover 30 which receive the adhesive/foam material may be other than illustrated if so desired. For example, as shown in FIG. 7 , step 42 may be operative to deposit an adhesive/foam material 70 on the inner surface of the wheel cover 30 around the lug bolt openings 34 . Thus, it can be seen that one or more desired area or areas of the wheel cover 30 may be operatively masked by the selective application of the adhesive/foam material(s) during step 42 . [0026] Following this, in step 46 , the lower masking tool 60 from the step 42 may be used if desired. In this case, in step 44 as illustrated schematically in FIG. 6 , the wheel cover 30 would remain on the lower masking tool 60 and the vehicle wheel 22 is assembled face-down on top of the wheel cover 10 , such that the outboard surface 22 A of the wheel 22 is preferably adjacent the inner surface 30 A of the wheel cover 30 . A brake or back side 22 B of the vehicle wheel 22 is masked using an upper masking tool (schematically shown in FIG. 6 and identified by reference character 64 ). The four parts (the lower masking tool 60 , the wheel cover 30 , the vehicle wheel 22 and the upper masking tool 64 ) are clamped together and preferably allowed to reach a desired controlled temperature (either by external or internal, heating or cooling). Depending upon the particular adhesive/foam material which is used in the next step, step 48 may not require any heating or cooling but may take place at room temperature. [0027] Next, in step 48 , a suitable adhesive/foam material (shown in FIG. 1 by reference number 58 ) is dispensed into one or more cavity areas defined between the cover 30 and the wheel 10 and allowed to react (for discussion purposes, one of such cavity areas indicated by reference number 66 in FIG. 2 and one of such cavity areas also shown in phantom in FIG. 6 by reference number 66 ). During step 48 , the areas between the wheel cover 10 and the vehicle wheel 22 that are not masked properly by the upper and lower mask tools 64 and 60 , respectively, are preferably already sealed and filled by the pre-foam shot(s) of material 54 in prior step 42 and thus simplify the upper and lower mask tools 64 and 60 , respectively, by eliminating areas of negative draft and removing core-out members and their respective actuators. [0028] Preferably, during step 48 , all the cavity areas between the wheel cover 30 and the vehicle wheel 22 are filled with the suitable adhesive/foam material 58 ; however, if desired, only some of the such cavity areas may be filled during step 48 if so desired. Following this, in step 50 , preferably after a desired period of time, the upper mask tool 64 is unclamped and removed and the wheel assembly 10 is removed and packaged for shipment. During storage and shipment the adhesive/foam material(s) 54 and/or 58 is (are) allowed to cure and attain full strength and excess inventory is reduced. Preferably, the adhesive/foam material 58 that fills the cavity areas during step 48 permanently secures the wheel cover 30 to the vehicle wheel 22 . Alternatively, other means, such as mechanical retention means, i.e., snap tabs, fasteners and the like (not shown), may be used to assist in positioning the wheel cover 30 relative to the vehicle wheel 22 and/or for permanently securing the wheel cover 30 to the vehicle wheel 2 if so desired. [0029] Alternatively, the method for producing the vehicle wheel and cover assembly 10 may be other than illustrated if so desired. For example, the shot or shots of the adhesive/foam material(s) may be of the same or differing products. Each shot may be and masking tools may be heated and/or cooled as necessary at any time during the process. The timing between shots can be varied depending on the desired performance of the assembly such as seam lines, cohesive bond strength, appearance and manufacturing considerations. Finally, while the embodiments are illustrated for use in producing a vehicle wheel and cover assembly, it is envisioned that this method may be used in connection with other automotive and non-automotive parts that are joined by an adhesive/foam material (whether expanding foam or other product) and is not easily masked as an assembly. Also, while the first shot of the adhesive/foam material 54 in step 42 is preferably formed directly on the inner surface of the wheel cover to be used, it may be separately formed and secured to the inner surface of the wheel cover by suitable means, such as an adhesive, prior to application of the adhesive/foam material 58 in step 48 or it may be separately formed and secured and/or maintained (i.e., if used as an “insert” masking member which may or may not be secured in place), by the application of the adhesive/foam material 58 in step 48 . [0030] In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been described and illustrated in its preferred embodiments. However, it must be understood that the invention may be practiced otherwise than as specifically explained and illustrated without departing from the scope or spirit of the attached claims.

A method for producing a vehicle wheel and wheel cover assembly comprising the steps of: (a) providing a wheel cover having an inner surface and an outer surface; (b) selectively applying at least one shot of a first adhesive material to a portion of the inner surface of the wheel cover to define a predetermined masked area; (c) providing a vehicle wheel having an outboard face; (d) positioning the wheel cover and the vehicle wheel relative to one another whereby at least one cavity is formed between the inner surface of the wheel cover, the outboard face of the vehicle wheel, and the masked area of the wheel cover defined by the first adhesive material; and (e) selectively applying a second adhesive material to the cavity to secure the wheel cover to the vehicle wheel.

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method and apparatus of MOSFET gate doping by having separate drain/source dopant implant and gate dopant implant. [0003] 2. Background of the Invention [0004] For conventional very-large scale integration (VLSI) complementary metal oxide semiconductor (CMOS) technology, the gate electrode is doped at the same time when the source and the drain are doped. For such conventional CMOS devices, the gate material is formed from either polysilicon (poly-Si), polysilicon germanium (poly-SiGe), or amorphous silicon (α-Si). [0005] One of the disadvantages of the conventional approach is that the gate implantation dopant species has to be the same as that of the source and the drain, since the doping for the gate, source and drain is performed at the same time. [0006] Another of the disadvantages of the conventional approach is caused due to the projections of the gate implantation and the source/drain implantation being close to each other. Because the source/drain junction depth is typically smaller than the gate stack thickness, the gate implantation may not be deep enough to suppress the gate depletion near the gate electrode/gate oxide interface. This gate depletion effect causes a degradation in the drive current of the transistor that is formed by the conventional approach. [0007] Still another of the disadvantages of the conventional approach is that the gate implant has the same rapid thermal annealing (RTA) process as that of the source and drain. Because the source/drain (S/D) RTA process is limited by the shallow junction requirement, insufficient annealing may occur to the gate dopant, thereby causing high gate sheet resistance and gate depletion effect. SUMMARY OF THE INVENTION [0008] An object of the present invention is to form a MOSFET in which the gate depletion effect is lessened or eliminated. [0009] Another object of the present invention is to form a MOSFET in which the gate dopant implant species is different from the source/drain dopant implant species. [0010] Yet another object of the present invention is to form a MOSFET in which sufficient annealing is provided to the gate dopant. [0011] These and other objects and advantages of the present invention are achieved by a method of forming a semiconductor device on a semiconductor substrate, the semiconductor device including a first MOSFET of a first conductivity type and a second MOSFET of a second conductivity type. The method includes a step of forming a gate oxide layer on the semiconductor substrate. The method also includes a step of forming a gate material on the gate oxide layer, where the gate material is one of poly-Si, poly-SiGe, and α-Si. The method further includes a step of providing a first photo-resist on the gate material, the first photo-resist having at least one window over a first portion of the gate material. The method still further includes a step of providing a photo-lithography with an n+ type dopant, to thereby expose and implant the first portion of the gate material with the n+ type dopant. [0012] The method also includes a step of striping the first photo-resist. The method further includes a step of providing a second photo-resist on the gate material, the second photo-resist having at least one window over a second portion of the gate material, the second portion being separate from the first portion. The method still further includes a step of providing a photo-lithography with a p+ type dopant, to thereby expose and implant the second portion of the gate material with the p+ type dopant. The method also includes a step of striping the second photo-resist, thereby exposing all portions of the gate material. [0013] The method still further includes a step of depositing tungsten silicide (WSi x ) onto the gate material. The method also includes a step of providing a third photo-resist above the first and second portions of the gate material. The method further includes a step of etching the semiconductor device down to the semiconductor substrate, thereby leaving a first gate stack corresponding to a location of the first portion of the gate material, and a second gate stack corresponding to a location of the second portion of the gate material. The method still further includes a step of striping the third photo-resist, wherein the first gate stack corresponds to a gate of the first MOSFET of the first conductivity type, and the second MOSFET corresponds to a gate of the second MOSFET of the second conductivity type. [0014] The above-mentioned objects and other advantages may also be achieved by a semiconductor device, which includes a first MOSFET of a first conductivity type and a second MOSFET of a second conductivity type. The first MOSFET includes a first gate stack having a first region of the first conductivity type having a gate material of a first concentration disposed therein. The second MOSFET includes a second gate stack having a second region of the second conductivity type having the gate material of a second concentration different from the first concentration. The gate material is one of poly-Si, poly-SiGe, and α-Si. BRIEF DESCRIPTION OF THE DRAWINGS [0015] The above-mentioned objects and advantages of the invention will become more fully apparent from the following detailed description when read in conjunction with the accompanying drawings, with like reference numerals indicating corresponding parts throughout, and wherein: [0016] FIGS. 1 A- 1 H show the various steps involved in making a MOSFET semiconductor device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0017] The present invention will be discussed in detail below with reference to the drawings. FIGS. 1 A- 1 H show process steps in creating a semiconductor device having a plurality of MOSFETs formed thereon, according to the present invention. Unlike the conventional processes discussed hereinabove, in the present invention the gate implantation is done before gate patterning, and is locally confined to the desired gate regions for either an n-channel or a p-channel MOSFET by using photo-resist as an implantation mask. [0018] In the present invention, the gate dopant implantation is decoupled from the source/drain implantation. One advantage of having this decoupling is that, for either an n-channel or a p-channel MOSFET, the gate dopant species can be different from that used for the source and drain. Therefore, a degree of freedom is provided for the process design or device design to meet various application requirements. [0019] Another advantage is that the projection of gate implantation can be made larger than that of the source/drain implantation. Therefore, gate depletion at the interface between the gate material layer and gate oxide layer can be suppressed. [0020] Still another advantage is that the gate dopant can be annealed first, without the limitation set by the shallow source/drain junction. Sufficient gate dopant annealing helps to reduce the gate sheet resistance, which improves the circuit speed and AC performance. Sufficient gate dopant annealing also helps to suppress the gate depletion near the interface between the gate material layer and the gate oxide layer, which improves the transistor drive current, and hence the circuit speed. [0021] Yet another advantage of the present invention is that, in the conventional silicidation process, the thickness of the gate silicide is the same as that of the source/drain silicide, which is limited by the source/drain junction depth. In the present invention, however, a WSi x layer is deposited separately from the source/drain silicide formation. Therefore, low gate sheet resistance can be achieved by using a reasonably thick WSi x layer on the gate. [0022] Still another advantage of the present invention is that, for a poly-SiGe gate, the silicide (e.g., TiSi 2 or CoSi x ) on top of the gate is relatively difficult to form because of the high concentration of germanium (Ge). The use of tungsten silicide (e.g., WSi x ) instead, disposed on top of the gate, overcomes this conventional process difficulty. [0023] The various steps of forming a semiconductor device according to the present invention will be explained in detail below. FIG. 1A shows a silicon substrate 10 , on which a thin layer of insulator 20 , which acts as a gate insulator, is formed. This thin oxide layer 20 may be formed utilizing standard thermal growth techniques in an oxidation ambient. By way of example and not by way of limitation, the oxide layer 20 has a thickness of from 2 to 5 nanometers (nm). Of course, other thicknesses are possible, depending upon particular design considerations. [0024] [0024]FIG. 1A also shows a gate material layer 30 formed on top of the oxide layer 20 . The gate material layer 30 preferably is formed by using one of the following materials: polysilicon, poly-SiGe, or amorphous silicon. In the present invention, the gate material layer 30 is formed by any one of a number of deposition techniques (e.g., low pressure chemical vapor deposition, or LPCVD) that are well known in the art. By way of example and not by way of limitation, the gate material layer 30 has a thickness of from 100 to 300 nm. [0025] The semiconductor structure is shown with a patterned photo-resist layer 40 formed on top of the gate material layer 30 . The photo-resist layer 40 has a thickness of from 500 to 800 nm. The resist pattern is made so as to protect the areas where active devices will be formed. This patterning may be accomplished by means of standard lithography and etching techniques, which are well known in the art. In FIG. 1A, by way of example, the patterning of the photo-resist layer 40 creates a window or hole 45 by which a particular portion of the gate material layer 30 may be implanted with ions of a particular type. [0026] After the photo-resist layer 40 has been patterned, an n+ type dopant, such as phosphorus, arsenic or aluminum, is then implanted onto the semiconductor structure. The region of the gate material layer 30 directly underneath the window or hole 45 is doped with the n+ type dopant, thereby forming an n+ region within the gate material layer 30 . For ease in explanation, the region of the gate material layer 30 directly underneath the window or hole 45 will be called a first region. [0027] [0027]FIG. 1B shows the semiconductor substrate after the photo-resist layer 40 has been removed, or striped, from the semiconductor substrate. The photo-resist layer 40 may be removed by any one of a variety of conventional techniques, such as by using an etch chemistry with an argon or oxygen plasma. After the photo-resist layer 40 has been removed, the entire gate material layer 30 is exposed. [0028] [0028]FIG. 1C shows the semiconductor substrate after a p+ dopant has been implanted onto a second region of the gate material layer 30 . The formation of the p+ dopant on the second region of the gate material layer 30 is similar to the formation of the n+ dopant onto the first region of the gate material layer 30 . That is, a photo-resist layer 40 ′ is formed on the gate material layer 30 . The photo-resist layer 40 ′ is patterned by means of standard lithography and etching techniques, so as to create a window or hole 45 ′ by which another particular portion of the gate material layer 30 may be implanted with ions of a particular type. [0029] After the photo-resist layer 40 has been patterned, an p+ type dopant, such as boron (B), BF 2 or IN, is then implanted onto the semiconductor structure. The region of the gate material layer 30 directly underneath the window or hole 45 is doped with the p+ type dopant, thereby forming a p+ region, within the gate material layer 30 . This p+ region corresponds to the second region discussed above. [0030] [0030]FIG. 1D shows the semiconductor substrate after the photo-resist layer 40 ′ has been removed, or striped, from the semiconductor substrate. The photo-resist layer 40 ′ may be removed by the variety of conventional techniques discussed above with respect to the removal of the photoresist layer 40 . After the photo-resist layer 40 ′ has been removed, the entire gate material layer 30 , having an n+ doped region and a p+ doped region, is exposed to the exterior. [0031] [0031]FIG. 1E shows the semiconductor substrate after a tungsten silicide layer (WSi x ) 50 has been deposited thereon. The WSi x layer 50 may be deposited onto the semiconductor structure by any one of a variety of conventional techniques for forming such a metal silicide layer, such as chemical vapor deposition (CVD). By way of example and not by way of limitation, the WSi x layer 50 has a thickness in the range of from 50 to 200 nm. [0032] [0032]FIG. 1F shows a patterned layer 75 formed above the first and second regions of the gate material layer 30 . The patterned layer 75 may be, for example, a conventional photo-resist, that is patterned by any one of a variety of patterning processes. [0033] [0033]FIG. 1G shows the semiconductor substrate after an etching step has been conducted, in which a first gate stack 80 and a second gate stack 90 are formed. In a preferred embodiment, these openings are formed by directionally etching the top surface of semiconductor substrate after masking, using an anisotropic dry etch. The directional etch is utilized to form the first and second gate stacks 80 , 90 with substantially vertical sidewalls down to the silicon substrate 10 . [0034] [0034]FIG. 1H shows the semiconductor substrate after the patterned layer 75 has been removed, or striped. The first gate stack 80 has an oxide layer 21 , an n+ doped gate material layer 31 , and a tungsten silicide layer 41 . The second gate stack 90 has an oxide layer 22 , a p+ doped gate material layer 32 , and a tungsten silicide layer 42 . The first gate stack 80 may be used as a gate region for a MOSFET of a first conductivity type, and the second gate stack 90 may be used as a gate region for a MOSFET of a second conductivity type. [0035] Though not shown in FIGS. 1 A- 1 H, n-well and/or p-well regions are formed in the semiconductor substrate, to thereby form source and drain regions for the MOSFETs created on the semiconductor device. These regions may be formed with any type of dopant as required, without affecting the gate stacks already formed on the substrate. The WSi x layer of the gate stacks 80 , 90 form a cap or barrier for any dopants used to form the source and drain regions. The formation of such source and drain regions is known to those of ordinary skill of the art, and is not discussed herein to provide a concise explanation of the present invention. [0036] After the first and second gate stacks 80 , 90 are formed on the silicon substrate 10 , conventional follow-up processes can then be performed to provide the necessary connections among the different regions formed on the semiconductor device. For example, S/D doping, contact formation, and other steps are performed, which are known to those of ordinary skill in the art, and which are not discussed herein in order to provide a concise explanation of the present invention. [0037] While a preferred embodiment has been described herein, modification of the described embodiment may become apparent to those of ordinary skill in the art, following the teachings of the invention, without departing from the scope of the invention as set forth in the appended claims. [0038] For example, instead of having an n+ implant and then a p+ implant to form two separate transistors on a substrate, other types of implants may be utilized, such as forming an n+ implant of a first dosage onto a first region of a gate material, and then an n+ implant of a second dosage onto a second region of the gate material. By that process, two FETs of the same conductivity type, but having different characteristics, may be formed. Similarly, n− and/or p− implants may be performed to create different types of FETs on a substrate.

A semiconductor device includes a first gate stack and a second gate stack, each gate stack corresponding to a gate of a FET formed on the semiconductor device. The first gate stack includes a gate material formed from one of poly-silicon, poly-SiGe, and amorphous silicon. The gate material is implanted with a dopant of a first conductivity type at a first concentration. A metal silicide layer is formed over the doped gate material. The second gate stack includes a gate material formed from one of poly-silicon, poly-Si—Ge, and amorphous silicon. The gate material of the second gate stack is implanted with a dopant of a second conductivity type at a second concentration.

FIELD OF THE INVENTION [0001] This invention relates to wireless telecommunications services, and, in particular, to international roaming of wireless terminals. BACKGROUND OF THE INVENTION [0002] The operation of obtaining service outside of a wireless subscriber's home service area is commonly referred to as roaming. The ability of a subscriber to roam outside of his or her home service area depends on the relationship between the subscriber's home service provider and the service provider in the area being visited. This relationship ideally includes the ability to exchange information between the two systems. In order to provide a consistent exchange of information, with minimal user intervention, the telecommunications industry has developed standard protocols for communications between mobile switching centers, making it possible for roaming subscribers to originate, receive, and maintain calls as they cross system boundaries. [0003] Reference in this regard can be had, by example, to Telecommunications Industry Association Interim Standard 41 (TIA IS-41), also referred to as ANSI/TIA/EIA 41-D-1997 (ANSI-41), entitled “Cellular Radiotelecommunications Intersystem Operations.” [0004] ANSI-41 specifies two types of databases to facilitate roaming, the home location register (HLR) and the visitor location register (VLR). The home location register resides with the subscriber's home service provider and contains pertinent information about the subscriber's equipment and the services the subscriber is entitled to. The HLR also contains the current location and status of the subscriber's terminal. Access to the HLR is controlled by the subscriber's mobile identification number (MIN), which is stored in the terminal. The visitor location register (VLR) resides with the system being visited, referred to as the serving system, and contains information, including the MIN and the electronic serial number (ESN), regarding the terminals currently in the serving system service area. [0005] When a terminal enters a serving system, it attempts to register in that system. As part of the registration process, the serving system's mobile switching center (MSC) records information about the terminal, including the terminal's MIN and ESN, in its VLR. The serving system's VLR then attempts to contact the subscriber's HLR for authentication that the subscriber is entitled to access the system. [0006] ANSI-41 wireless networks worldwide use the MIN, mentioned above, to identify their subscribers within their own country. In North America, the MIN is often used as the subscriber's mobile directory number (MDN). ANSI-41 wireless networks in the United States and Canada also use the subscriber's 10 digit MIN to direct messages from the serving system to the subscriber's HLR. While MIN-based routing is generally supported in the ANSI networks of North America, it is not recognized as a valid global address type, also referred to as a title, by the International Telecommunications Union (ITU). As a result, using a subscriber's MIN to locate the subscriber's HLR is not generally supported by networks outside of North America. Thus, a subscriber's MIN is not necessarily a valid global title. [0007] New protocol extensions to ANSI-41 are being developed to provide true global title formats, specifically E.212, however, since the ITU has not yet accepted E212 as an officially sanctioned translation type, the useful application of E.212 is not expected to be available globally for some time. [0008] The International Forum for AMPS Standards Technology (I FAST) has issued unique network codes to operators outside of North America for use as the most significant four digits of their subscribers' MINs. MINs using these special codes are called International Roaming MINs (IRMs). The use of IRMs ensures that a globally unique identification is available for mobile subscribers, and IRMs provide a generally accepted global title for directing a visited system to a subscriber's HLR. The IRM always begins with a “0” or a “1” to ensure that they never conflict with MINs used in North America, as North American MINs never start with a “0” or a “1.” While IRMs provide a generally accepted method for designating a subscriber's HLR, North American MINs, because they never begin with a “0” or “1”, remain unacceptable as global titles. [0009] These problems are compounded when using a global satellite communications system, such as one shown in U.S. Pat. No. 5,655,005, issued Aug. 5, 1997, entitled “Worldwide telecommunications System Using Satellites”, by Robert A. Wiedeman and Paul A. Monte and U.S. Pat. No. 5,715,297, issued Feb. 3, 1998, entitled “Wireless Telephone/Satellite Roaming System”, by Robert A. Wiedeman. In a global satellite communications system, a user's terminal is intended to have service anywhere within the coverage area of a satellite system, regardless of international boundaries. OBJECTS AND ADVANTAGES OF THE INVENTION [0010] It is an object and advantage of this invention to provide a method and apparatus to allow subscribers of ANSI-41 based networks to roam internationally. It is a second object and advantage of this invention to provide a method and apparatus to allow subscribers of ANSI-41 based networks to roam internationally by correctly routing wireless signaling messages from a visited system to a subscribers home network using the terminal's MIN as the initial addressing format. It is a further object and advantage of this invention to provide a method and apparatus to allow subscribers of ANSI-41 based networks to roam internationally in a global satellite communications system. SUMMARY OF THE INVENTION [0011] The foregoing and other problems are overcome and the objects of the invention are realized by methods and apparatus in accordance with embodiments of this invention. [0012] A method is provided for routing a message through a telecommunications network. The method includes receiving an identifying number (eg: a MIN or ESN) from a wireless terminal and prepending at least one character to the identifying number to form a pseudo-global title. The message is then routed through the telecommunications network to a destination determined by the pseudo-global title. Upon arrival at the destination, the method further includes converting the pseudo-global title to a home location register address. The message is then routed to a home location register having the home location register address. BRIEF DESCRIPTION OF THE DRAWINGS [0013] The above set forth and other features of the invention are made more apparent in the ensuing Detailed Description of the Invention when read in conjunction with the attached Drawings, wherein: [0014] [0014]FIG. 1 shows a diagram of a system in which the invention may be practiced. [0015] [0015]FIG. 2 shows a block diagram of a mobile switching center coupled to a pseudo-global title translator as part of this invention. [0016] [0016]FIG. 3 shows a block diagram of an originating international signaling node and an international point code suitable for practicing the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0017] [0017]FIG. 1 shows a network environment that is suitable for practicing this invention. A wireless terminal 10 is shown roaming in a foreign serving network 15 . The foreign serving network includes a communications satellite 17 , satellite system gateway 20 , a mobile switching center 25 , and a pseudo-global title translator 30 . The pseudo-global title translator 30 is shown for convenience as being a unit coupled between the mobile switching center 25 and an originating international signaling node 35 through a local network 40 . The originating international signaling node 35 communicates with an international point code 45 , also through the local network 40 . The international point code 45 contains a global title translation and routing process 47 . The international point code 45 communicates with a destination international signaling node 50 through an international network 55 . The destination international signaling node 50 then communicates with the wireless terminal's home subscriber network 60 and the wireless terminal subscriber's HLR 65 through a local network 70 . The various aspects of this embodiment are now described in further detail. [0018] Assume first that the wireless terminal 10 roaming on the foreign serving system 15 attempts to register. Upon detecting the presence of the visiting wireless terminal 10 , the gateway 20 of the foreign serving system informs the foreign serving system's MSC 25 that it has received a registration message. The MSC 25 then communicates with the pseudo-global title converter 30 as will be described. [0019] Referring first to FIG. 2, there is illustrated in greater detail the MSC 25 and pseudo-global title converter 30 . As shown in FIG. 2, the MSC 25 examines an internal database 75 to determine if the wireless terminal 10 is already registered in its service area. If the wireless terminal 10 is not registered, the serving MSC 25 updates the internal database 75 with the information that the wireless terminal 10 is present and sends an IS-41 message containing the MIN and ESN of the wireless terminal 10 to its VLR 80 , also referred to as the serving VLR. The serving VLR 80 then determines if the wireless terminal 10 is already registered in its database 85 . If not, the serving VLR 80 stores the information and then attempts to contact the wireless terminal's HLR 65 (FIG. 1) for authentication. In order to accomplish this, the serving VLR 80 creates an ANSI-41 roaming signaling message with a destination, or title, based on the wireless terminal's MIN. The title is used to route the message to the wireless terminal's HLR 65 . As stated above, MIN-based titles are generally accepted in North America, but not in the rest of the world. In order to accommodate global routing of the roaming signaling message, the pseudo-global title converter 30 is used. The pseudo-global title converter 30 is coupled to the serving VLR 80 from which it receives the ANSI-41 roaming signaling message with its MIN-based title 90 . The pseudo-global title converter 30 converts the MIN-based title to a generally accepted E.164 type title 95 by prepending it with a country code of “1.” The converted title 95 , as generated in accordance with an aspect of this invention, is referred to herein as a pseudo-global title. [0020] It is important to note that any country code or identifier may be prepended to the MIN-based title 90 to create the pseudo-global title 95 , as long as the resulting digit string is unique to all international nodes within the system. Based on the pseudo-global title 95 , the pseudo-global title converter 30 selects an appropriate originating international signaling node 35 . After selecting the appropriate originating international signaling node 35 , the pseudo-global title converter 30 functions as a message router, and sends the ANSI-41 roaming signaling message with the pseudo-global title 95 to the originating international signaling node 35 over the local network 40 . [0021] Referring now to FIG. 3, the originating international signaling node 35 contains a routing table 100 and, using the most significant digits of the pseudo-global title 95 as a key, functions as a message router, routing the message to the international point code 45 , as specified by the international point code address 105 in its routing table 100 . [0022] At the international point code 45 , the global title translation and routing process 47 receives the message. The global title translation and routing process 47 contains a translation table 110 which links pseudo-global titles with the corresponding true E. 164 destination addresses for a subscriber's home network elements, including a subscriber's HLR 65 (FIG. 1). The global title translation and routing process 105 looks up the pseudo-global title 95 in its translation tables 110 and substitutes the true E. 164 destination title 115 for the subscriber's HLR 65 as the new destination address. The global title translation and routing process 105 then determines the address of the next appropriate node 120 in accordance with its routing tables 125 , and functioning as a message router, routes the message to the next appropriate node 120 . [0023] It is important to note that the global translation process from a pseudo-global title 95 to a true E. 164 destination title 115 is not limited to using the translation table 110 . For example, an algorithm could also be used to determine the true E. 164 destination title 115 from the pseudo-global title 95 . [0024] It is also important to note that the global title translation and routing process 105 is not limited to substituting the true E. 164 destination title 115 for the pseudo-global title 95 . The global title translation and routing process 105 may substitute any other acceptable format for the true destination address for the home network element including, without limitation, E.212, MIN, SS7 point code, etc. types of addresses, or any other type of address suitable to permit routing to the terminal's HLR 65 . [0025] If required, other nodes in the system (not shown) then route the message in accordance with its intended destination through the international network 55 . As shown in FIG. 1, eventually the destination international signaling node 50 receives the message and routes it to the subscriber's HLR 65 based on the true E. 164 title 115 . [0026] Although described in the context of a satellite communications system, it should be understood that the teachings of this invention may also be practiced in a terrestrial based communications system. [0027] While, for convenience, the pseudo-global title translator 30 has been described as a separate unit, it should be understood that the pseudo-global title translator 30 may also be implemented as software running in the MSC 25 . [0028] Although the MIN, ESN, etc., have been described as being stored in the wireless terminal, they could as well be stored in a detachable storage module installed in the wireless terminal. [0029] Thus, while the invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that changes in form and details may be made therein without departing from the scope and spirit of the invention.

A method is provided for routing a message through a telecommunications network. The method includes receiving an identifying number (eg: a MIN or ESN) from a wireless terminal and prepending at least one character to the identifying number to form a pseudo-global title. The message is then routed through the telecommunications network to a destination determined by the pseudo-global title. Upon arrival at the destination, the method further includes converting the pseudo-global title to a home location register address. The message is then routed to a home location register having the home location register address.

BACKGROUND OF THE INVENTION The invention generally relates to an apparatus for introducing waste or refuse into a collecting container or the like arranged e.g. on a vehicle, through a load hopper adapted to receive the waste and comprising means for transferring the waste to the collecting container. Such apparatus of the prior art, as exemplified by the U.S. Pat. No. 2,837,230, comprise a packing plate, which moves in a plane arc backwards over a loading hopper and in so doing cuts off the flow of garbage from a bin or container to the hopper when feeding in a batch of refuse from the hopper into the collecting container during its forward stroke. A circumstance, which has to be taken into consideration when improving such refuse handling apparatus, is the composition of the waste that is to be handled. Thus, in addition to ordinary and coarser domestic and store waste there is nowadays an increasing rate of industrial waste. Bearing this in mind, the principal object of the invention is to provide a feeding-in apparatus of the kind in question, which makes possible a more rational and effective handling of such waste in conjunction with removing or transporting away thereof. A particular object of the invention is to provide a substantially continuously operating feeding-in apparatus, which carries out precompressing, crushing and compacting without cutting off the stream of waste, before the waste or refuse is finally compressed in the collecting container, whereby a rapid introduction in combination with a high degree of compression is made possible. SUMMARY OF THE INVENTION These and other objects are attained thanks to the fact that said means for transferring the waste to the collecting container according to the invention comprise a pair of gripping members, which are movable, preferably synchronously, substantially in a common plane, towards and away from the collecting container, as well as towards and away from each other, substantially perpendicularly to their first mentioned movement, said means being adapted to grip and to compress the portion of waste between themselves and in conjunction herewith forward it to the collecting container. BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages will become apparent from the following detailed description and the annexed drawings, which diagrammatically and as non-limiting example illustrate an embodiment of the invention, which is preferred at present. FIG. 1 of the drawings is a longitudinal section through the rear part of a refuse collecting van. FIG. 2 is a simplified end view of the load hopper as seen in the direction of the arrow II--II in FIG. 1. FIG. 3 is a side view corresponding to FIG. 1. FIG. 4 is an end view of half of the load hopper on a larger scale as seen in the direction of the arrow IV in FIG. 3, to which FIG. 4 corresponds. FIG. 5 is a plan view illustrating the two gripping members and their associated parts. FIGS. 6-10 are diagrammatic representations of the position of the gripping members during different phases of a cycle of operation. FIG. 11 is a simplified diagram of the pressure fluid system. DESCRIPTION OF THE PREFERRED EMBODIMENT In the Figures there is shown a collecting container 1, which is arranged on a refuse collecting van and is combined with an emptying hood 2 and a load hopper 3. The emptying hood has an inlet opening 41 (FIGS. 1 and 3), which may be provided with bin holders 42 for the emptying of larger bins or containers. The load hopper 3 comprises a bottom 4, side walls 5 (FIGS. 1 and 2), a rear wall 6 having an emptying ramp 7 and an upper part 8 having a breaking edge 9. The bottom 4 and the upper part 8 of the hopper 3 define a feed shaft 11 and are provided with catch projections or teeth 12, which are adapted to desintegrate the refuse and to prevent it from sliding back into the load hopper 3. In its lower portion the inner end of the shaft 11 has an outlet opening 10, which is defined by the botton 4 (FIGS. 1 and 5) and opens into the collecting container 1. Just opposite the opening 10 the upper portion of the shaft 11 is provided with a guiding cone 13 (FIGS. 1, 2, 3), which is adapted to compress and to guide the refuse on its way into the collecting container 1. For transferring the refuse from the load hopper 3 into the collecting container 1 there are provided two movable gripping members 14, which are shown in four different positions in FIG. 5. These gripping members 14 have the shape of one-armed bell cranks, whose lever portions form an obtuse angle 26 (FIG. 5) with each other. At their one outer lever end the gripping members 14 are rotatably journalled through stub shafts 17 (FIGS. 1 and 5) in a pair of sliding blocks 18, which are movable back and forth in individual guide members 19. Two hydraulic pressure fluid motors (piston cylinder + piston with piston rod) 24, which are pivotable on stub shafts 23 and 25, are provided for reciprocating the gripping members 14 and their appurtenant sliding blocks 18 in their guide members 19 (FIGS. 2 and 5). The gripping members 14 are provided with stub shafts 20, by means of which they are coupled to a second pair of pressure fluid motors 21 (piston cylinder + piston with piston rod), which are hydraulic in the illustrated embodiment and which are pivotally journalled on stub shafts 22 and provided for rotating the gripping members or bell cranks 14. Those surfaces 15 of the respective gripping members 14, which face each other and are located between the vertex and the free end of the bell cranks, are provided with teeth 27, which are intended to improve the refuse holding capability of the gripping members 14. The circuit diagram of the hydraulic system, by means of which the gripping members 14 are operated, is illustrated in FIG. 11. Therein, we find the hydraulic motors 21 and 24, which are connected to each other and to the other members of the hydraulic system, which are illustrated by conventional symbols, by means of non-referenced conduits. In FIG. 11 P is a pump, 28 an oil reservoir, 30 a control valve having three setting positions (left-hand, central and right-hand position in the symbolical Figure), 31 and 36 are flow dividers, 32 and 35 are sequential valves, 33 and 37 are limit switches and 34 and 38 are pressure governors or switches. As is diagrammatically illustrated in FIGS. 6-10 the apparatus described above operates in the following way, the direction of flow of the pressure fluid in FIG. 11 being designated by dash-dot arrows when the gripping members move from the position according to FIG. 6 to the position according to FIG. 7, by solid arrows at the movement from FIG. 7 to FIG. 8, by dash arrows at the movement from FIG. 8 to FIG. 9 and by dash-dot-dot arrows at the movement from FIG. 9 to FIG. 10. The cycle of operations is supposed to start, when the gripping members 14 are located substantially in the point C in FIG. 6, the control valve 30 then being shifted from its central or neutral position shown in FIG. 11 to its left-hand position. Then, the pressure fluid flows in the direction of the dash-dot arrows, the pistons in the hydraulic motors 21 in FIG. 11 consequently being separated to the position shown therein. Hereby, the gripping members 14 are pivoted clockwise and anti-clockwise, respectively, from each other into the position D illustrated in FIG. 7. At a predetermined pressure in the hydraulic system, the sequence valve 32 admits supply of pressure fluid to the upper end of the cylinders of the pressure fluid motors 24 in FIG. 1, so that the pistons move downwards therein. Hereby, the gripping members are transferred from the position D in FIG. 7 to the position A in FIG. 8. The oil pressure in the hydraulic motors 21 is maintained, so that their pistons have the possibility of moving in both directions under the influence of pressure, as is indicated by the solid double arrows in FIG. 11. When the position A in FIGS. 5 and 8 has been attained and triggers the limit switch 33, the control valve 30 is switched to its right-hand position for initiating the return movement of the pistons in the pressure fluid motors 21, so that the pressure fluid flows in the direction of the dash arrows and the gripping members 14 are displaced in the direction from A to B (FIGS. 5, 8, 9). Hereby, the gripping members 14 seize the refuse or waste with their teeth 27 and carry out the pre-crushing thereof during their movement towards each other. If the gripping members should not reach the position A on account of un-deformable, obstructing refuse objects, the pressure switch 34 initiates the movement from A to B instead of the limit switch 33. When the position B has been attained, the sequence valve 35 initiates, at a set maximum pressure, the flow of the pressure medium in the direction of the dash-dot-dot arrows and the rising movement of the pistons in the pressure fluid motors 24 in FIG. 11 through the flow divider 36 for bringing about the movement of the gripping members to the position in FIGS. 5 and 10. During this movement the refuse is held by the teeth 27 of the gripping members 14, which transfer the refuse through the shaft 11, while compressing the refuse, further compressing thereof being brought about by the projections 12 and the guide cone 13, before the refuse is introduced through the opening 10 (FIG. 5) into the collecting container 1, where it is finally compressed against a press wall 29 (FIGS. 1 and 2) or the like. During the movement from A to B and at the beginning of the movement from B to C the surfaces 15 are pressed towards each other and thereby a higher compression under an increased force past the breaking edge 9 is attained also by the increase in moment which takes place at the movement and the change of position of the point 22 in relation to G 1 and G 2 , respectively, and E 1 and E 3 , respectively. Thanks to the fact that the gripping members 14 are designed with the angle 26, the two opposing, vertical surfaces 16 form a transporting and compressing means for further transport and compression of such refuse as has been advanced in the shaft 11 during the preceding cycle of operations, at the movement of the gripping members towards the position shown in FIG. 10. During the movement of the gripping members from B to C oil pressure in the hydraulic motors 21 is maintained with possibility for their pistons to reciprocate or move back and forth under the influence of pressure, as is indicated by the dash-dot-dot double-arrows, until the limit switch 37 or -- if the position C should not be reached on account of an undeformable refuse object, which blocks the movement of the gripping members 14 -- the pressure switch 38 initiates a new start of the operation cycle described above. As is evident from the above, the operation cycle of the gripping members 14 is not bound to follow the said points C-D-A-B-C, in that the movement of the gripping members may be obstructed by the refuse, thanks to the fact that the hydraulic system is so designed that the operation cycle is completed even though the different end positions of the gripping members should not be reached. In this case the hydraulic motor 21 is subjected to a continued pressure by means of a sequence valve 35, which is arranged in such a manner that the piston of the hydraulic motor 21 and its fastening 20 can move outwards and inwards in dependence of the varying load upon the gripping members during their movement from B to C (compare the dash-dot-dot arrows in FIG. 11). By this system, where the gripping members can seize the "refuse flow" from the sides at the emptying of large containers, a better mode of operation is attained than by prior devices known up to the present, which comprise a pressing plate, which moves in a plane arc backwards and on account hereof has to "cut off" the flow of garbage from the bin or container before the feeding-in into the collecting container. The embodiment described above and illustrated in the drawings is, of course, to be regarded merely as non-limiting example and can as to its details be modified in several ways within the scope of the following claims. Thus, the shaft 11 with its upper part 8 and the gripping members 14 with their teeth 27, the latch blocks 12 and the guiding cone 13 may have another shape, and the governing of the gripping members may be accomplished in combination with link movements instead of by means of guides. Furthermore, the illustrated hydraulic equipment may be replaced by another movement system, e.g. by hydraulic or electric motors with pinions and racks or the like. In addition hereto, the feeding-in apparatus according to the invention may be utilized in connection with stationary compressing systems as well as for other material than waste or refuse, e.g. as a stationary crusher or a transport apparatus for industrial purposes.

An apparatus for introducing waste or the like into a collecting container is associated with a load hopper adapted to receive the waste, and comprises a pair of gripping members for transferring the waste from the load hopper to the collecting container. The gripping members, which are adapted to grip and to compress consecutive portions of waste between themselves and forward these portions to the collecting container, are movable, preferably synchronously and substantially in a common plane, towards and away from each other, as well as towards and away from the collecting container.

FIELD OF THE INVENTION This invention is generally concerned with digital-to-analogue converters and more particularly relates to techniques for reducing signal dependent loading of reference voltage sources used by these converters. BACKGROUND TO THE INVENTION Digital-analogue conversion based on converting a delta-sigma digital representation of a signal into an analogue waveform is now a commonplace technique. In a simple delta-sigma digital-to-analogue converter a string of pulses is generated, with a pulse density dependent upon the digital value to be converted, and low-pass filtered. The technique is prevalent in many high-volume application areas, for example digital audio, where several channels of high quality relatively low frequency (audio frequency) signals are required. High quality in this context typically implies −100 dB THD (Total Harmonic Distortion) and 100 dB SNR (Signal to Noise Ratio). However, in such high-volume markets manufacturing cost is also very important. In general, a digital-to-analogue converter requires positive and negative reference voltages to define the amplitude of the output signal. A digital-to-analogue converter draws some current from these reference voltage ports, and this current will generally be signal dependent. These reference voltages are typically generated from a source of low but non-zero output impedance, for example by a power supply or buffer with a decoupling capacitor. The source will have a finite ESR (Equivalent Series Resistance), and there will be additional resistance between the source, the decoupling and the device due to the effects of resistive PCB tracking, package lead resistance, and bond wire resistance. The result is that any signal-dependent current drawn by the DAC from the references causes a signal-dependent voltage ripple to appear on the reference voltages actually applied to the DAC. Since the DAC output signal is proportional to the reference voltage, this multiplies the ideal digital-to-analogue converter output by this ripple. The consequent modulation of the output signal is apparent as signal distortion, for example, generating harmonic distortion components with a sine wave signal. Furthermore in a stereo or multi-channel system it is often uneconomic to supply a digital-to-analogue converter for each channel with a separate voltage reference supply, or even separate decoupling, PCB traces, or integrated circuit pins. In these situations the reference ripple caused by one channel's DAC can appear on the reference voltage for other DACs, modulating the outputs of these other DACs as well as its own output. The invention described herein is directed to digital-to-analogue converter circuits intended to reduce or eliminate signal dependent reference currents. A digital-to-analogue converter design for which the reference currents are substantially independent of output signal should be capable of lower distortion for a given source impedance. Alternatively, for a given acceptable level of performance, the digital-to-analogue converter should be more tolerant of source impedance, so allowing a design engineer to reduce costs by specifying fewer or cheaper, lower quality external components. Many delta-sigma digital-to-analogue converters use switched-capacitor techniques. FIG. 1 a shows an example of a simple switched-capacitor DAC 100 suitable for use in a delta-sigma DAC system. An operational amplifier 102 has a non-inverting input connected to a constant voltage V mid 118 , typically ground. Operational amplifier 102 has an output 120 providing an output voltage V out and a feedback capacitor C f 104 is connected between the output and an inverting input of the operational amplifier. A second capacitor C 2 106 is switchably connected across feedback capacitor 104 by means of switches 108 and 110 . Switch 108 allows one plate of capacitor 106 to be connected either to C f 104 or to a positive reference voltage V P 112 or a negative reference voltage V N 114 . Switch 110 allows the other plate of capacitor 106 to be connected either to feedback capacitor 104 or to a second constant voltage, V mid2 116 . In operation switches 108 and 110 are controlled respective by two-phase, preferably non-overlapping clocks supplied by a clock generator (not shown in FIG. 1 ). As shown in FIG. 1 b , each of these clock signals comprises a charge phase Phi 1 during which switch 110 is connected to V mid2 and switch 108 is connected to either V P or V N , and capacitor C 2 106 is charged and a dump phase Phi 2 during which switch 110 is connected to C f and switch 108 is connected to C f , and the charge on capacitor C 2 106 is shared with or dumped to the feedback capacitor C f 104 . This clocking scheme can conveniently be represented by the table of FIG. 1 c , reproduced below as Table 1a. TABLE 1a Switch positions versus clock phase for the circuit of FIG. 1a Connected to: Switch During Phi1 (Charge) During Phi2 (Dump) 110 Vmid2 Cf 108 VP/VN Cf Henceforth clocking schemes for subsequent circuits will likewise be represented by tables along the lines of table 1a, these representing corresponding, preferably non-overlapping switch control clock signals. FIG. 1 d shows an example of a clock generator circuit 150 for the circuit of FIG. 1 a . The input data signal is DIN. An external clock CKIN generates non-overlapping clocks CK 1 and CK 2 . CK 1 is ON in clock phase Phi 1 , CK 2 is ON in clock phase Phi 2 . CK 2 can thus be used to drive the poles of switches 108 and 110 connecting to Cf during Phi 2 , and CK 1 is suitable to drive the pole of switch 110 connecting to V mid2 during Phi 1 . To drive the remaining poles of switch 108 during Phi 1 to VP when DIN is high and VN when DIN is low, clocks CK 1 A and CK 1 B are generated by the AND gates 152 a and 152 b . The operation of these clocks is summarised in the expanded version of Table 1a, in Table 1b below, where the clocks in the right-hand column correspond to the connections shown in the centre two columns. TABLE 1b Connected to: During Phi1 During Phi2 Switch (Charge) (Dump) By Clock: 110 Vmid2 CK1 Cf CK2 108 VP/ CK1A VN CK1B Cf CK2 FIG. 1 e shows a timing diagram the circuit of FIG. 1 d , in particular CKIN 160 , DIN 162 (11001 . . . ), CK 1 164 , CK 2 166 , CK 1 A 168 a , & CK 1 B 168 b ; note the underlap of clocks CK 1 , CK 2 , and CK 1 A, CK 1 B alternating according to DIN. In more detail, during the charging phase Phi 1 capacitor C 2 is charged, with V mid2 (generally the same voltage as V mid ) applied to one terminal via switch 110 and V P or V N applied to the other terminal via switch 108 . Typically values of V P 112 and V N 114 are +3V and −3V respectively, with respect to V mid 118 . The choice of V P or V N for any particular cycle is defined by a digital delta-sigma signal applied to switch 108 during this charging phase Phil 1 . During the dump phase, Phi 2 , C 2 is disconnected from V P , V N and V mid2 and connected in parallel with the op amp feedback capacitor C f 104 via switches 110 and 108 . Typically C 2 106 is much smaller than the op amp feedback capacitor C f 104 . The left-hand side of C 2 is switched between a voltage equal to V mid 118 (since the inverting terminal of op amp 102 is a virtual earth, that is it is at substantially the same voltage as the non-inverting terminal) and V mid2 . Assume for simplicity that as usual V mid2 =V mid . Then if V P rather than V N is applied to the other end of C 2 during Phi 1 for many consecutive clock cycles, the output V out 120 will converge to equal V P 112 , to achieve a steady state in which both the left-hand side and the right-hand side of C 2 106 are switched between equal voltages each cycle. Similarly if V N 114 is applied each cycle, V out will converge to V N 114 . If V P and V N are each applied half the time, the output 120 will be the average of V P and V N . In general for a V P :V N duty cycle of m:(1−m), the steady-state output will be given by: V out =m*V P +(1− m )* V N   (Equation 1) For example, if m=0.9, V out =0.9V P +0.1V N . In this context “duty cycle” should be understood as the fraction, proportion or ratio of the number of connections to V P to the number of connections to V N , for example measured in clock cycles. In general m will vary with time, corresponding to the varying value of the input audio signal, but the clock frequency is generally much higher than a typical audio frequency, so it is a good approximation to discuss operation in terms of an m value constant over many cycles. The duty cycle m is controlled by a digital delta-sigma signal to alternately connect C 2 106 to V P and V N to provide the required output voltage 120 . This output voltage 120 will vary from V P to V N according to the duty cycle applied. Thus, in effect, the DAC circuit may be considered as having a gain from the voltages ( 112 and 114 ) applied to the switched capacitor to the output 102 defined by (V out,max −V out,min )/(V P −V N ) of substantially unity. The skilled person will recognise that the gain of circuit 100 may be adjusted, for example, by connecting a voltage divider to output 120 and taking the voltage for capacitor C f 104 from a tap point on this divider, for example to provide a gain of 2. However typically the circuit will have a relatively low gain, for example less than 10 and more typically less than 3. This also applies to the DAC circuits which are described later. An earlier patent of one of the inventors, U.S. Pat. No. 6,573,850, recognised that the above-described prior art DAC circuit suffers from a problem associated with signal-dependent loading of reference voltage sources for voltages V P 112 and V N 114 . The way in which this problem arises and the solution provided by U.S. Pat. No. 6,573,850 is discussed further below. Other background prior art (also referenced in U.S. Pat. No. 6,573,850) can be found in U.S. Pat. No. 5,790,064 (a switched capacitor integrator which does not operate on the principle of charge sharing but instead dumps charge into an input of an operational amplifier which in turn drives an integration capacitor), U.S. Pat. No. 5,703,589 and FR 2,666,708 (other switched capacitor integrators), all for analogue-to-digital converter circuits and not intended or suitable for use as high quality digital-to-analogue converters; U.S. Pat. No. 4,896,156, U.S. Pat. No. 4,994,805, EP 0 450 951 (and U.S. Pat. No. 5,148,167), U.S. Pat. No. 6,081,218, U.S. Pat. No. 6,337,647, EP 1 130 784, and “A 120 dB Multi-bit SC Audio DAC with Second Order Noise Shaping”, J Rhode, Xue-Mei Gong et al., pages 344–5 in IEEE Solid State Circuit Conference Procs. (ISSCC) 2000. The manner in which signal-dependent reference source loading arises in the DAC circuit of FIG. 1 can be seen by considering the charge taken from V P and V N averaged over many cycles. For the above m:(1−m) duty cycle, and assuming for simplicity that C 2 <<C f , so that cycle-by-cycle ripple on V out is small, for V P this is given by: m*(V P −V out )*C 2 =m*(V P −(m*V P +(1−m)*V N ))*C 2 =m*(1−m)*(V P −V N )*C 2 This has a parabolic dependence on m, with zeros at m=0 and m=1, and a maximum of 0.25*(V P −V N )*C 2 at m=0.5. Loading of V N shows a similar dependence. FIG. 2 shows a digital-to-analogue converter 200 with a differential voltage output 120 a, b , based upon the circuit of FIG. 1 . As can be seen from inspection of FIG. 2 , the differential DAC 200 comprises two similar but mirrored circuits 100 a , 100 b , each corresponding to DAC 100 . The positive differential signal processing circuit portion 100 a generates a positive output V out + 120 a and the negative differential signal processing portion 100 b generates a negative voltage output V out − 120 b . Likewise the positive circuit portion 100 a is coupled to first reference voltage supplies V P + 112 a and V N + 114 a and the negative circuit portion 100 b is coupled to second reference voltage supplies V P − 112 b and V N − 114 b. Preferably V P + 112 a and V P − 112 b are supplied from a common positive reference voltage source and V N + 114 a and V N − 114 b are supplied from a common negative reference voltage source. Thus preferably V P + and V P − are at the same voltage and V N + and V N − are at the same voltage. As can be seen C 2 + 106 a is switched to references V P + 112 a and V N + 114 a and C 2 − 106 b is switched to references V P − 112 b and V N − 114 b . Voltages V mid2 + 116 a and V mid2 − 116 b preferably have the same value, preferably the value of V mid 118 , typically ground. Preferably feedback capacitors 104 a, b and switched capacitors 106 a, b have the same value and op amps 102 a and 102 b are matched. Op amps 102 a, b may comprise a single differential-input, differential-output op amp. These same comments also apply to the later described differential DAC circuits. A clocking scheme for the DAC of FIG. 2 is shown in Table 2 below: TABLE 2 Switch positions versus clock phase for the differential circuit of FIG. 2 Connected to: Switch During Phi1 (Charge) During Phi2 (Dump) 110a Vmid2+ Cf+ 110b Vmid2− Cf− 108a VP+/VN+ Cf+ 108b VN−/VP− Cf− Continuing to refer to FIG. 2 , in operation, whenever V P + is chosen to charge C 2 + , then V N − is selected to charge C 2 − . Thus by symmetry, from equation (1) above, one can write V out − =m*V N − +(1− m )* V P −   (Equation 2) When, for example, m=0.9, V out − =0.9 V N − +0.1 V P − ; when m=0.5, V out + =V out − =(V P +V N )/2. As m varies V out + and V out − will swing in equal amplitude but opposite polarities about this common-mode (m=0.5) voltage. The average charge taken from V P + will be as above: m*(V P + −V out + )*C 2 + =m*(V P +−(m*V P + (1−m)*V N ))*C 2 =m*(1−m)*(V P + −V N + )*C 2 + The average charge taken from V P − will be: (1−m)*(V P − −V out −)*C2 − =(1−m)*(V P −m*V N − −(1−m)*V P − )*C 2 − =(1−M)*m(V P − −V N − )*C 2 − Thus the average total charge taken from V P (that is V P + and V P − ) is 2*m*(1−m)*(V P −V N )*C 2 (where V P + =V P − =V P and C 2 + =C 2 − =C 2 ). This is just double the charge of the single-sided implementation, as might be surmised by the symmetries of the circuit. Again the function is parabolic, with a minimum of zero (for m=0 or 1) and a maximum of 0.5*(V P −V N )*C 2 . To take an example, consider a case where V P =+3V, V N =−3V, and C 2 =10 pF. Assuming the circuit is clocked at 10 MHz, this will give rise to a current varying from zero to 0.5*(+3V−(−3V))*10 pF*01 MHz=300 μA drawn from V P and V N depending on the low-frequency level of the output signal V out . If the equivalent source impedance of the sources of V P and V N are 1 ohm each, this will give a modulation of (V P −V N ) of 0.6 m Vpk−pk., that is 0.1% of (V P −V N ). This will modulate the output signal by a similar amount (as with a multiplying DAC) and is a gross effect in a system aimed at typically −100 dB (0.001%) THD. FIG. 3 shows a multibit differential switched capacitor DAC 300 , a common extension to the circuit of FIG. 2 . In this extension multiple independently switched capacitors are used in place of the capacitor C 2 + (and C 2 − ). Although FIG. 3 shows just two additional capacitors for each circuit 106 aa,bb (for simplicity) and four corresponding additional switches 108 aa,bb , 110 aa,bb , in practice a plurality of additional capacitors and switches may be provided for each differential signal processing circuit portion. A clocking scheme for this circuit is given in Table 3 below. TABLE 3 Switch positions versus clock phase for the multi-bit differential circuit of FIG. 3 Connected to: Switch During Phi1 (Charge) During Phi2 (Dump) 110a Vmid2+ Cf+ 110b Vmid2− Cf− 108a VP+/VN+ Cf+ 108b VN−/VP− Cf− 110aa Vmid2+ Cf+ 110ba Vmid2− Cf− 108aa VP+/VN+ Cf+ 108ba VN−/VP− Cf− . . . In effect, the switched capacitors C 2 of FIG. 3 may be replaced by an array of capacitors. The capacitors in such arrays may or may not be binary weighted. In one arrangement the LSB capacitors are binary weighted, but the MSB capacitors are equally weighted, and used in a random manner to decrease the effects of mismatch. Suitable methods for deriving the necessary multi-bit delta-sigma digital control waveforms, to define the cycle-by-cycle connections to V P or V N of each capacitor in these arrays, are well known to those skilled in the art and described, for example, in “Delta-sigma data converters—theory design and simulation” edited by Steven R Norsworthy, Richard Schreier, Gabor C Temes, IEEE Press, New York 1997, ISBN 0-7803-1045-4, hereby incorporated by reference. Analysis of this circuit gives a similar variation in reference loading with signal. There is therefore a need for charge-sharing, switched capacitor DAC circuits which exhibit reduced signal-dependent loading of reference sources. The circuit of U.S. Pat. No. 6,573,850 achieves this by briefly connecting the switched capacitor to a substantially signal-independent reference voltage prior to connection of this capacitor to one of the reference voltages. Connecting the switched capacitor to a substantially signal-independent reference before connecting it to one of the references allows signal-dependent charges to flow onto or off the switched capacitor before the capacitor is recharged. In other words the charge on the switched capacitor may be brought to a substantially signal-independent or predetermined state of charge prior to its connection to one of the references, so that there is little or no signal-dependent loading of these references. However the circuits of U.S. Pat. No. 6,573,850 require an additional clock phase to be generated and distributed, and generally also require the generation of a suitable signal-independent reference voltage. Two further issues arise with high performance switched-capacitor audio DACs, firstly problems of flicker noise (sometimes called 1/f noise) in the MOS devices typically used to implement the op amps, and secondly problems with crosstalk between amplifiers due to combinations of common supply impedances, poor audio-frequency supply decoupling, and finite op amp power-supply rejection. Flicker noise power is approximately inversely proportional to the area of the devices used, so to gain 6 dB in reduced flicker noise requires input devices of four times the area. For SNR of 100 dB or greater (120 dB is becoming a target for high-performance systems), it rapidly becomes impractical to achieve a flicker noise corner frequency below say 1 kHz, and even then with a significant impact on chip area and hence cost. The load regulation bandwidth of active power supplies is often inadequate to prevent millivolts of ripple at higher audio frequencies, especially as these supplies may also be supplying high-power outputs to drive speakers or headphones. Often several channels of DAC (e.g. six) are implemented on the same silicon chip but without the expense of extra supply pins it is difficult to distribute the supplies to all amplifiers (including power output stages) without several ohms of common supply impedance. The resulting modulation of the local supply voltage of each channel in conjunction with the finite supply rejection of the op amps, itself diminishing with high audio frequency, can be a significant source of crosstalk between channels relative to a typical target of 100 dB. Both the op amp flicker noise and op amp supply rejection (or rather lack of it) can be modelled as a modulation of the input offset voltage of the op amps in question. One known technique for mitigating these effects is the “chopper” technique. FIG. 4 shows this applied to a simple DAC circuit 400 . Table 4, below, shows a clocking scheme for the DAC of FIG. 4 . TABLE 4 Switch positions versus clock phase for the chopped differential DAC circuit of FIG. 4 Connected to: During Phi1 During Phi2 During Phi3 During Phi4 Switch (Charge) (Dump) (Charge) (Dump) 110a Vmid2+ Cf+ Vmid2+ Cf+ 110b Vmid2− Cf− Vmid2− Cf− 108a VP+/VN+ Cf+ VP+/VN+ Cf+ 108b VN−/VP− Cf− VN−/VP− Cf− 401a Cf+ Cf+ Cf− Cf− 401b Cf− Cf− Cf+ Cf+ 402a Cf+ Cf+ Cf− Cf− 402b Cf− Cf− Cf+ Cf+ In the differential circuit of FIG. 4 the difference in offsets between the two op amps is modelled as an effective offset V off to the first op amp 102 a . In one clock cycle, op amp 102 a is connected to one feedback capacitor, and its effective offset V off affects the output of the respective output, V out + by V off . In the next clock cycle, op amp 102 a is connected to the other symmetric half of the capacitor network, and has the same effect on the negative output V out − . The low-frequency offset of the op amp thus appears on the outputs as a common-mode average signal of V off/ 2, together with a differential output as a modulation of +/−V off/ 2 at f s/ 2 where f s is the sample rate of the input signal (ie. the charge-dump cycle frequency), but there is no corresponding low-frequency differential signal. In embodiments the high frequency components are filtered out by a subsequent post-filter preferably employed in any case to attenuate the ultrasonic high-frequency delta-sigma quantisation noise components. The differential DAC circuits of U.S. Pat. No. 6,573,850 are intended to provide a substantially constant load on a clock cycle-by-cycle basis, for example to give a constant charge load on V P each clock cycle. We will now describe alternative schemes, based on a different but related principle, providing a substantially constant charge load only when averaged over multiple clock cycles. This is nonetheless useful, since the clock frequency is normally much greater than the signal frequency and thus any artefacts at half the clock frequency can be easily post-filtered. In any case some post-filtering is generally required because of spikes of current on V P and V N at the clock frequency. SUMMARY OF THE INVENTION According to a first aspect of the present invention there is therefore provided a differential switched capacitor digital-to-analogue (DAC) circuit comprising first and second differential signal circuit portions for providing respective positive and negative signal outputs with respect to a reference level, and having at least one first reference voltage input and at least one second reference voltage input for receiving respective positive and negative references with respect to said reference level; each of said first and second circuit portions comprising an amplifier with a feedback capacitor, a second capacitor, and a switch to switchably couple said second capacitor to a selected one of said reference voltage inputs to charge the second capacitor and to said feedback capacitor to share charge with the feedback capacitor, and wherein said switch of said first circuit portion is further configured to connect said second capacitor of said first circuit portion to share charge with said feedback capacitor of said second circuit portion, and wherein said switch of said second circuit portion is further configured to connect said second capacitor of said second circuit portion to share charge with said feedback capacitor of said first circuit portion. The facility to connect the second capacitor of each (say the positive) circuit portion to share charge with the feedback capacitor of either circuit portion enables the second capacitor to in effect be alternately pre-charged to positive and negative (signal dependent) nodes so that, on average, signal dependent loading of a reference source supplying positive and negative (voltage) references to which the second capacitor is connected for charging is mitigated. More particularly, in embodiments each second capacitor is connected alternately to positive and negative signal-dependent nodes of the circuit (in effect to share charge with the feedback capacitors of the positive and negative circuit portions). Still more particularly each second capacitor is connected alternately to positive and negative feedback capacitor (signal) nodes firstly when being charged to the positive reference voltage, and secondly when being charged to the negative reference voltage. Charging each second capacitor to both the positive reference voltage (for two charge-dump cycles) and to the negative reference voltage (for two charge-dump cycles) enables the capacitor to be charged (positively, and negatively) in such a way that the charge can be dumped to positive and negative signal nodes (feedback capacitors), thus facilitating the above-mentioned positive/negative pre-charge. In embodiments this results in an eight phase charge-dump clocking scheme, comprising four successive charge-dump cycles, the second (switched) capacitors being connected to a positive signal node for a first pair of charge-dump cycles and to a negative signal node for a second pair of charge-dump cycles. According to a related aspect of the present invention there is therefore further provided a differential switched capacitor circuit comprising positive and negative circuit portions to provide respective positive and negative differential signal outputs based upon positive and negative references, each of said positive and negative circuit portions comprising an operational amplifier with a feedback capacitor and at least one switched capacitor connectable to one of said positive and negative references to store charge and to one of a positive and negative signal node to substantially dump said stored charge to a said feedback capacitor, and wherein said switched capacitors of said positive and negative circuit portions are switched according to an eight phase clocking scheme comprising four successive charge-dump cycles and in which said switched capacitors are connected to a said positive signal node for a first pair of said charge-dump cycles and to a said negative signal node for a second pair of said charge-dump cycles. Preferred embodiments of the above described aspects of the invention also chop or exchange the amplifiers for the first and second (positive and negative) circuit portions in alternate charge-dump cycles, preferably alternating every second charge-dump cycle. In embodiments this provides additional benefits, of firstly desensitising the output signal to flicker noise of the amplifiers employed, allowing smaller devices to be used therein, with a consequent chip area saving; and secondly improving the rejection of audio frequency supply ripple, giving potentially less crosstalk between DACs, especially when sharing supplies on one chip, or allowing relaxation of the requirements for audio frequency supply decoupling for a given performance, with potential external component cost savings. Preferred embodiments of the above described aspects of the invention further include a switch controller or clock generator to control switching of the second (switched) capacitors and, where implemented, of the amplifiers of the first and second circuit portions, in particular responsive to a digital input to the DAC. In embodiments the above described DACs may be implemented as multi-bit DACs by using a plurality or array of capacitors in place of each of the above mentioned second (switched) capacitors, providing corresponding switching to allow each capacitor of the array to be connected to a selected one of the feedback capacitors of the first and second (or positive and negative) circuit portions. In a further aspect the invention provides a method of operating a differential digital-to-analogue (DAC) circuit to reduce signal dependent loading of a reference source associated with the DAC circuit, the DAC circuit comprising positive and negative signal processing devices each with a feedback capacitor coupled to a respective positive and negative signal node and each having a second capacitor switchably couplable to said reference source for charging and to a said signal node for dumping charge to a said feedback capacitor, the method comprising repeatedly: coupling said second capacitors to said reference source for charging; and coupling said second capacitors to alternate ones of said positive and negative signal nodes for dumping stored charge to a said feedback capacitor; such that on average over a plurality of charge-dump cycles charge loading of said reference source by said DAC circuit is substantially constant. Preferably each of the second capacitors is coupled to one of said positive and negative signal nodes for two cycles and then to the other of said positive and negative signal nodes for two cycles, for each of these two cycles the capacitor being charged from the same (positive or negative) reference voltage level (which preferably also alternates every two charge-dump cycles). BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will now be further described, by way of example only, with reference to the accompanying figures in which: FIGS. 1 a to 1 e show, respectively a switched capacitor digital-to-analogue converter (DAC) according to the prior art, a clocking scheme for the DAC of FIG. 1 , and a tabular representation of the clocking scheme, a clock generator circuit for the clocking scheme, and a timing diagram for the clock generator circuit; FIG. 2 shows a differential switched capacitor DAC according to the prior art; FIG. 3 shows a multi-bit differential switched capacitor DAC according to the prior art; FIG. 4 shows a differential switched capacitor DAC with chopper switching of the operational amplifiers; FIGS. 5 a to 5 c show, respectively, a digital-to-analogue converter (DAC) with chopper connections to the switched capacitors to reduce signal-dependent reference source loading, on eight phase clock generator for the DAC of FIG. 5 a , and a timing diagram for the clock generator, according to an embodiment of the present invention; FIG. 6 shows a digital-to-analogue converter (DAC) circuit with means to reduce signal dependent reference loading by simplified chopping connections to the switched capacitors; FIG. 7 shows a digital-to-analogue converter (DAC) circuit with chopper connections to op amp and switched-capacitor; and FIG. 8 shows multi-bit extension to the circuit of FIG. 7 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 5 a , this shows a differential DAC circuit 500 including chopper switches 501 a,b , 502 a,b to reduce the signal-dependent reference loading. The DAC circuit of FIG. 5 is a development of that shown in FIG. 2 (like elements are indicated by like reference numerals) and comprises a pair of DAC circuits 500 a,b to provide a differential output 520 a, b. Capacitor 106 a is still charged to V P or V N via switches 110 a , 108 a . However, rather than discharging directly via switches 110 a , 108 a onto capacitor 104 a , it discharges onto either capacitor 104 a or 104 b , via additional connections 503 , 505 , and 504 , 506 , according to the polarity of additional series switches 501 a , 502 a . There is a similar arrangement for capacitor 106 b . The switches 501 a , 501 b , 502 a , 502 b may be switched to alternate every cycle giving a 4-phase clocking scheme as shown in Table 5a (below) or every second cycle giving an 8-phase clocking scheme as shown in Table 5c. Other possible clocking schemes are discussed later. By alternately discharging to either capacitor 106 a or 106 b , i.e. to nodes whose signal voltages are equal and opposite, the aim is to cancel the signal-dependent terms in time-average charge taken from references V P and V N . Table 5a, below, shows a 4-phase clocking scheme for the DAC 500 of FIG. 5 a . TABLE 5a Switch positions versus clock phase for a 4-phase clocking scheme for the DAC circuit of FIG. 5 Connected to: During Phi1 During Phi2 During Phi3 During Phi4 Switch (Charge) (Dump) (Charge) (Dump) 110a Vmid2+ 501a Vmid2+ 501a 110b Vmid2− 501b Vmid2− 501b 108a VP+/VN+ 502a VN+/VP+ 502a 108b VN−/VP− 502b VP−/VN− 502b 501a Cf+ Cf+ Cf− Cf− 501b Cf− Cf− Cf+ Cf+ 502a Cf+ Cf+ Cf− Cf− 502b Cf− Cf− Cf+ Cf+ This clocking scheme is implemented by a clock generator 508 , in response to a digital signal input 510 , the clock generator also performing delta-sigma digital signal preprocessing in a conventional manner. In later described DAC circuits the clock generator will not be shown in the figures, for simplicity. The switches of this and the later described DAC circuits may comprise FET (or MOSFET) switches controlled by clock generator 508 . Additional low pass filtering (not shown in the Figure) may be provided on outputs 520 a,b , starting to roll off, for example just above the audio band (say 0.1 dB at 20 kHz) to maximise attenuation of ultrasonic delta-sigma quantisation noise, and so providing substantial (say>40 dB) attenuation by fs/4, (typically 3 MHz). We next analyse the clocking scheme of Table 5a (it is helpful to read this in conjunction with Table 5b below). As before assume C f + 104 a is to receive positive increments of charge from V P for a fraction m of the clock cycles, and negative increments of charge from V N for the remaining fraction (1−m). Then C f − 104 b is to receive positive increments of charge from VP for a fraction (1−m) of the clock cycles, and negative increments of charge from V N for the remaining fraction m, giving V out + =m*V P + (1−m)*V N , V OUt − =(1−m)*V P + m*V N . In those (charge) cycles where C 2 + has just previously been disconnected from C f − (and hence V out − ), i.e. Phi 1 , it will be connected to C f + on the next (dump) phase Phi 2 , so for a fraction (m) of the cycles it will be charged to V P , taking a charge of C 2 + *(V P −V out − ) and for a fraction (1−m) of the cycles it will be charged to V N , taking a charge of C 2 + * (V N −V out − ). In those (charge) cycles where C 2 + has just been disconnected from C f + (and hence V out + ), i.e. Phi 3 , it will be connected to C f − on the next (dump) phase Phi 4 , so for a fraction (1−m) of the cycles it will be charged to V P , taking a charge of C 2 + *(V P −V out − ), and for a fraction (m) of the cycles it will be charged to V N , taking a charge of C 2 + *(V N −V out ). Thus the (average) charge taken from V P by C 2 + over each four clock phases will be: C 2 + *( V P −V out + )*(1−m)+C 2 + *( V P −V out − )* m Since C 2 + and C 2 − are indistinguishable in this circuit, C 2 − will take an equal charge, so the total charge taken from V P will be: 2*C 2 *( V P −V out + *(1 −m )−V out − *m ). Noting that V out +=m*V P +(1−m)*V N , V out − =(1−m)*V P +m*V N , the total charge from V P can be written as: 2*C 2 *(V P −(1−m)*(m.V P +(1−m).V N )−m*((1−m).V P +m*V N ) =2*C 2 *(V P (1−m+m 2 −m+m 2 )−V N (1−2 m+m 2 +m 2 )) =2*C 2 *(V P −V N )(1−2 m+2 m 2 ) However this is still not signal independent as desired (having a maximum at m=0.5), essentially because of the correlation of V out + and V out − with m. Table 5b below summarises the charging and dumping of one of the switched capacitors (C 2 + ) and the above analysis. TABLE 5b Clock Charge Φ 1 C2 + (for fraction m) to V P [C2 + was at V out − ] cycle 1 Dump Φ 2 C2 + to C f + [C2 + to V out + ] Charge Φ 3 C2 + (for fraction m) to V N [C2 + was at V out + ] cycle 2 Dump Φ 4 C2 + to C f − [C2 + to V out − ] During Φ 1 C2 + takes m C2 + (V P − V out − ) from V P During Φ 3 C2 + takes (1 − m) C2 + (V P − V out + ) from V P Total for C2 + C2 (V P − V N )(1 − 2m + 2m 2 ) (average) for C2 − C2 (V P − V N )(1 − 2m + 2m 2 ) charge over (same as C2 + ) several cycles Total 2(C2(V P − V N )(1 − 2m + 2m 2 ) The situation can be improved by using an alternate, 8-phase clocking scheme for the DAC 500 of FIG. 5 a , as shown in Table 5c below, where the new switches are clocked at half the clock rate. TABLE 5c Switch positions versus clock phase for an 8-phase clocking scheme for the DAC circuit of FIG. 5 Connected to: Phi1 Phi2 Phi3 Phi4 Phi5 Phi6 Phi7 Phi8 Switch (Charge) (Dump) (Charge) (Dump) (Charge) (Dump) (Charge) (Dump) 110a Vmid2+ 501a Vmid2+ 501a Vmid2+ 501a Vmid2+ 501a 110b Vmid2− 501b Vmid2− 501b Vmid2− 501b Vmid2− 501b 108a VP+/VN+ 502a VP+/VN+ 502a VN+/VP+ 502a VN+/VP+ 502a 108b VN−/VP− 502b VN−/VP− 502b VP−/VN− 502b VP−/VN− 502b 501a Cf+ Cf+ Cf+ Cf+ Cf− Cf− Cf− Cf− 501b Cf− Cf− Cf− Cf− Cf+ Cf+ Cf+ Cf+ 502a Cf+ Cf+ Cf+ Cf+ Cf− Cf− Cf− Cf− 502b Cf− Cf− Cf− Cf− Cf+ Cf+ Cf+ Cf+ To analyse this scheme again consider operation with a “duty cycle” of m (it is helpful to read this in conjunction with Table 5d below). We start with Phi 1 where C 2 + has just been disconnected from V out − and anticipates a connection with V out + in the second half of the cycle, dump phase Phi 2 . The probability of being charged to V P from V out − is m, giving an expected average charge taken from V P of m.C 2 + (V P −V out − ). The next Phi 3 , there is still a probability m of being charged to V P , giving an expected charge taken from V P of m.C 2 + (V P −V out + ). Thus the (average) charge taken from V P by C 2 + over these two clock cycles is 2m.C 2 + (V P −(V out + +V out − )/2). Similarly, the charge taken by C 2 − over these two clock periods is 2(1−m)C 2 + (V P −(V out −+V out + )/2). So the total charge over these two clock periods (which is the same for the next two clock periods) taken by the combination of C 2 + and C 2 − is 2.C 2 (V P −(V out + +V out − )/2). Since the signals on V out + and V out − are in antiphase, this is independent of the signal (and can be simplified to C 2 (V P −V N ) relying on (V out ++V out −)/2=(V P +V N )/2). Table 5d below summarises the 8-phase charging and dumping clocking scheme for one of the switched capacitors (C 2 + ) and the results of the above analysis. TABLE 5d Clock Charge Φ1 (for fraction m) to V P [C2 + was at V out − ] cycle 1 Dump Φ2 to C f + [C2 to V out + ] (V P C f + ) Charge Φ3 (for fraction m) to V P [C2 was at V out + ) cycle 2 Dump Φ4 to C f + [C2 to V out + ] (V P C f + ) Charge Φ5 (for fraction m) to V N [C2 was at V out + ] cycle 3 Dump Φ6 to C f − [C2 to V out − ] (V N C f − ) Charge Φ7 (for fraction m) to V N [C2 + was at V out − ] cycle 4 Dump Φ8 to C f − [C2 to V out − ] (V N C f − ) Charge taken from V P during charging phases: Φ ⁢ ⁢ 1 Φ ⁢ ⁢ 3 Sum: Total: ⁢ By ⁢ ⁢ C2 + By ⁢ ⁢ C2 - ⁢ : mC2 + ⁡ ( V P - V out - ) mC2 + ⁡ ( V P - V out + ) 2 ⁢ mC2 + ( V P - 1 / 2 ⁢ ( V out + + V out - ) 2 ⁢ ( 1 - m ) ⁢ C2 - ( V P - 1 / 2 ⁢ ( V out + + V out - ) C2 ⁡ ( V P - V N ) Φ ⁢ ⁢ 5 ⁢ Φ ⁢ ⁢ 7 Sum: Total: ⁢ ( 1 - m ) ⁢ C2 + ⁡ ( V P - V out - ) ( 1 - m ) ⁢ C2 + ⁡ ( V P - V out - ) 2 ⁢ ( 1 - m ) ⁢ C2 + ( V P - 1 / 2 ⁢ ( V out + + V out - ) 2 ⁢ m ⁢ ⁢ C2 - ( V P - 1 / 2 ⁢ ( V out + + V out - ) C2 ⁡ ( V P - V N ) FIG. 5 b shows an example of a clock generator circuit 550 for the DAC circuit 500 of FIG. 5 a . The operation of these clocks is summarised in the expanded version of Table 5d in Table 5e, where the clocks in the right-hand column correspond to the connections shown in the centre eight columns. As before, the input data signal is DIN. An external clock CKIN generates non-overlapping clocks CK 1 and CK 2 . CK 1 is ON in odd phases, CK 2 is ON in even clock phases. CK 2 can thus be used to drive the poles of switches 110 a , 110 b , 108 a , 108 b , connecting to 501 a , 501 b , 502 a , 502 b respectively during even phases, and CK 1 is suitable to drive the poles of switches 110 a , 110 b connecting to Vmid 2 +, Vmid 2 − respectively during odd phases. Clock CHCK is derived by dividing CKIN by 4 using the two D-types. From CHCK are generated non-overlapping clocks CHCK 1 and CHCK 2 , respectively driving switches 501 a , 501 b , 502 a , 502 b to Cf+ or Cf− in alternate sets of four clock phases. To drive the remaining poles of switch, clocks CK 1 A and CK 1 B are generated by the AND gates 552 a and 552 b , but instead of the gates being driven directly from DIN, DIN is inverted in phases Phi 5 to Phi 8 , to allow for the effective periodic inversion of gain by the chopper action. TABLE 5e Connected to: Phi1 Phi2 Phi3 Phi4 Phi5 Phi6 Phi7 Phi8 By Switch (Charge) (Dump) (Charge) (Dump) (Charge) (Dump) (Charge) (Dump) Clock: 110a Vmid2+ Vmid2+ Vmid2+ Vmid2+ CK1 501a 501a 501a 501a CK2 110b Vmid2− Vmid2− Vmid2− Vmid2− CK1 501b 501b 501b 501b CK2 108a VP+/ VP+/ VP+/ VP+/ CK1A VN+ VN+ VN+ VN+ CK1B 502a 502a 502a 502a CK2 108b VN−/ VN−/ VN−/ VN−/ CK1A VP− VP− VP− VP− CK1B 502b 502b 502b 502b CK2 501a Cf+ Cf+ Cf+ Cf+ CHCK1 Cf− Cf− Cf− Cf− CHCK2 501b Cf− Cf− Cf− Cf− CHCK1 Cf+ Cf+ Cf+ Cf+ CHCK2 502a Cf+ Cf+ Cf+ Cf+ CHCK1 Cf− Cf− Cf− Cf− CHCK2 502b Cf− Cf− Cf− Cf− CHCK1 Cf+ Cf+ Cf+ Cf+ CHCK2 FIG. 5 c shows a timing diagram for the circuit of FIG. 5 b , in particular CKIN 560 , DIN 562 (1110001110 . . . ), CK 1564 , CK 2566 , CK 1 A 568 a , CK 1 B 568 b , CHCK 570 , CHCK 1 572 , CHCK 2 574 . Note that the senses of CK 1 A, CK 1 B are flipped according to CHCK. The desired underlaps depend on logic speed and loading for a particular technology and circuit design. FIG. 6 shows a functionally equivalent circuit 600 , that operates in essentially the same way, but combines switches 110 a and 501 a into switch 601 a , 108 a and 502 a into 602 a , 110 b and 501 b into 601 b , and 108 b and 502 b into switch 602 b . This gives a circuit with fewer switches, albeit more complex ones. The circuit is designed for use with a modified clocking scheme as defined by Table 6 below. TABLE 6 Switch positions versus clock phase for an 8-phase clocking scheme for the simplified DAC circuit of FIG. 6 Connected to: Phi1 Phi2 Phi3 Phi4 Phi5 Phi6 Phi7 Phi8 Switch (Charge) (Dump) (Charge) (Dump) (Charge) (Dump) (Charge) (Dump) 601a Vmid2+ Cf+ Vmid2+ Cf+ Vmid2+ Cf− Vmid2+ Cf− 601b Vmid2− Cf− Vmid2− Cf− Vmid2− Cf+ Vmid2− Cf+ 602a VP+/VN+ Cf+ VP+/VN+ Cf+ VN+/VP+ Cf− VN+/VP+ Cf− 602b VN−/VP− Cf− VN−/VP− Cf− VP−/VN− Cf+ VP−/VN− Cf+ In the circuits of FIGS. 5 and 6 it is the switched capacitor which can be regarded as being “chopped” i.e. with connections alternately swapped with the rest of the circuit. FIG. 7 shows a circuit 700 where both the op amp and the switched capacitor are chopped. As regards the loading of the references, switches 701 a , 702 a , 701 b , and 702 b serve the function of switches 601 a , 602 a , 601 b and 602 b of FIG. 6 respectively. However chopping the op amp connections gives advantages (as previously discussed with reference to prior art FIG. 4 ) in terms of rejection of low-frequency modulation of effective input offset voltages, i.e. of flicker noise or power supply coupling, and accomplishes this with no extra switches as compared with the arrangement of FIG. 5 . Table 7, below, shows a clocking scheme for the DAC 700 of FIG. 7 . TABLE 7 Switch positions versus clock phase for an 8-phase clocking scheme for the choppered op amp circuit of FIG. 7 Connected to: Phi1 Phi2 Phi3 Phi4 Phi5 Phi6 Phi7 Phi8 Switch (Charge) (Dump) (Charge) (Dump) (Charge) (Dump) (Charge) (Dump) 110a Vmid2+ 701a Vmid2+ 701a Vmid2+ 701a Vmid2+ 701a 110b Vmid2− 701b Vmid2− 701b Vmid2− 701b Vmid2− 701b 108a VP+/VN+ 702a VP+/VN+ 702a VN+/VP+ 702a VN+/VP+ 702a 108b VN−/VP− 702b VN−/VP− 702b VP−/VN− 702b VP−/VN− 702b 701a Cf+ Cf+ Cf+ Cf+ Cf− Cf− Cf− Cf− 701b Cf− Cf− Cf− Cf− Cf+ Cf+ Cf+ Cf+ 702a Cf+ Cf+ Cf+ Cf+ Cf− Cf− Cf− Cf− 702b Cf− Cf− Cf− Cf− Cf+ Cf+ Cf+ Cf+ Each of the circuits of FIGS. 5 , 6 , 7 can be readily extended to multi-bit DACs, as shown by way of example in FIG. 8 . Broadly speaking DAC 800 of FIG. 8 represents a modification to the DAC 700 of FIG. 7 , in a similar manner to that in which DAC 300 of FIG. 3 represents a modification to DAC 200 of FIG. 2 . Table 8, below, shows a clocking scheme for the DAC 800 of FIG. 8 . TABLE 8 Switch positions versus clock phase for an 8-phase clocking scheme for the op amp choppered, multi-bit DAC circuit of FIG. 8 Connected to Phi1 Phi2 Phi3 Phi4 Phi5 Phi6 Phi7 Phi8 Switch (Charge) (Dump) (Charge) (Dump) (Charge) (Dump) (Charge) (Dump) 110a Vmid2+ 701a Vmid2+ 701a Vmid2+ 701a Vmid2+ 701a 110b Vmid2− 701b Vmid2− 701b Vmid2− 701b Vmid2− 701b 108a VP+/VN+ 702a VP+/VN+ 702a VN+/VP+ 702a VN+/VP+ 702a 108b VN−/VP− 702b VN−/VP− 702b VP−/VN− 702b VP−/VN− 702b 110aa Vmid2+ 701a Vmid2+ 701a Vmid2+ 701a Vmid2+ 701a 110ba Vmid2− 701b Vmid2− 701b Vmid2− 701b Vmid2− 701b 108aa VP+/VN+ 702a VP+/VN+ 702a VN+/VP+ 702a VN+/VP+ 702a 108ba VN−/VP− 702b VN−/VP− 702b VP−/VN− 702b VP−/VN− 702b . . . 801a Cf+ Cf+ Cf+ Cf+ Cf− Cf− Cf− Cf− 801b Cf− Cf− Cf− Cf− Cf+ Cf+ Cf+ Cf+ 802a Cf+ Cf+ Cf+ Cf+ Cf− Cf− Cf− Cf− 802b Cf− Cf− Cf− Cf− Cf+ Cf+ Cf+ Cf+ Although FIG. 8 shows just two additional capacitors 106 aa,bb and two corresponding additional pairs of switches 108 aa,bb , 110 aa,bb for each circuit 800 a,b (for simplicity), in practice a plurality of additional capacitors may be provided for each differential signal processing circuit portion. Thus, in effect, the switched capacitors C 2 of FIG. 6 may be replaced by an array of capacitors. The capacitors in such arrays may or may not be binary weighted. In one embodiment the LSB capacitors are binary weighted, but the MSB capacitors are equally weighted, and used in a random manner to decrease the effects of mismatch. Clock generators for the clocking schemes of Tables 6, 7 and 8 above may be constructed along similar lines to the example clock generator circuit described with reference to FIG. 5 b. As previously mentioned, there are often many capacitors in the banks for a multi-bit coder, for example configured as a binary-weighted array. In this case, the V P /V N switching control signals to the large capacitors in the array often change only slowly, following an approximation to the output signal, and only the “LSB” (least significant bit) capacitors show much high-frequency switching activity. In this case it is therefore reasonable to assume that the drive to the biggest capacitors in each bank will be constant over several clock cycles. In such a case the load on V P due to the largest capacitors should average out to be signal independent and should show little or no frequency-shifted quantisation noise tones. The smaller capacitors will have more high-frequency activity, so these may exhibit such tones but, since they are smaller, the resulting baseband components will also be small. This small amount of high-frequency energy on the V P and V N reference inputs is relatively easy to decouple. The above analysis only deals with the effect of averaged m, corresponding to the audio frequency components of the applied delta-sigma input. However, delta-sigma techniques do not remove quantisation noise, but only move it up to higher frequencies. The chopper techniques will frequency-shift any components of charging requirements near to f s /4 down to audio-frequency, giving rise to baseband noise, rather than distortion or cross-talk. An approximate analysis to show this is not a significant problem is as follows. The total quantisation noise for a one-bit modulator small signal is that of a square wave with amplitude equal to the peak audio signal, i.e. +3 dB above the largest sine wave possible (ignoring a small correction due to the practical maximum modulation index being sub-unity). For a well-designed high order modulator, the quantisation noise above the audio bandwidth will be almost flat. This means that the quantisation noise power within an audio bandwidth around say f s /4 will be of the order of that of a +3 dB signal divided by the oversampling ratio, say 64 or 18 dB. The chopper techniques will frequency-shift such f s /4 components of charging requirements down to audio-frequency. Thus the consequent Vref currents, instead of being those due to say a 0 dB sine wave, will be similar to those which would be caused by trying to output a baseband noise signal whose power is only 15 dB down from the 0 dB sine wave, reducing the benefits of the technique. However, for multibit operation, the spectral density of the noise is already suppressed by typically 2 N where N is the number of capacitors in the binary array, say 5, giving 30 dB less quantisation energy at f s /4. By comparison multibit operation does not make much difference to the signal-dependent load current in a conventional modulator. So overall (with this example) one could expect 45 dB improvement in audio-band V P load current variation relative to conventional multibit modulators. This supports the contention that this quantisation noise aliasing effect is not a significant limit on performance. Strictly speaking the best load averaging will only occur for “random” spectra of the V P delta-sigma control signals. For example, if the delta-sigma control signals were to have tones close to f s /4, these would appear in the V P load current, frequency shifted by f s /4 into the low-frequency baseband. For well-designed high-order delta-sigma modulators, such tones are not an issue, but were this to become an issue in future high-performance systems, to reduce the possibility of this effect the “chopping” may be randomised, for example by alternating the switching of each C 2 to the positive or negative halves of the differential circuit according to a pseudo-random sequence generated by a pseudo-random sequence generator. The skilled person will recognise that many variations of the above-described circuits are possible. For example the above-described differential DAC circuits are illustrated using a pair of operational amplifiers 102 a,b but the skilled person will recognise that this pair of operational amplifiers may be replaced by a single differential-input, differential-output amplifier. Although the DAC circuits have been described in the general context of delta-sigma digital control techniques, applications of the circuits are not limited to schemes in which the switching control waveforms are generated by such techniques. For example other digital filter-derived techniques or PWM (pulse width modulation) could be employed or appropriate pulse trains could be retrieved from storage, for example for digital voice or other synthesis. The skilled person will further recognise that the above-described DAC circuits may be incorporated into other systems. For example one or more of the above-described DAC circuits may be incorporated within a switched-capacitor delta-sigma analogue-to-digital converter, in one or more feedback elements. For example, the skilled person will understand that a delta-sigma analogue-to-digital converter may be constructed by adding, for example, an integrator and a digital filter to one of the above DAC circuits. No doubt many other effective alternatives will occur to the skilled person and it would be understood that the invention is not limited to the described embodiments and encompasses modifications apparent to those skilled in the art lying within the spirit and scope of the claims appended hereto.

This invention is generally concerned with digital-to-analogue converters and more particularly relates to techniques for reducing signal dependent loading of reference voltage sources used by these converters. A differential switched capacitor digital-to-analogue (DAC) circuit ( 500 ) comprises first and second differential signal circuit portions ( 500 a,b ) for providing respective positive and negative signal outputs with respect to a reference level, and has first and second reference voltage inputs ( 112,114 ) for receiving respective positive and negative references. Each of said first and second circuit portions comprises an amplifier ( 102 a,b ) with a feedback capacitor ( 104 a,b ), a second capacitor ( 106 a,b ), and a switch ( 108 a,b, 110 a,b ) to switchably couple said second capacitor to a selected one of said reference voltage inputs to charge the second capacitor and to said feedback capacitor to share charge with the feedback capacitor. The switch of said first circuit portion is further configured to connect said second capacitor ( 106 a ) of said first circuit portion to share charge with said feedback capacitor ( 104 b ) of said second circuit portion; and the switch of said second circuit portion is further configured to connect said second capacitor ( 106 b ) of said second circuit portion to share charge with said feedback capacitor ( 104 a ) of said first circuit portion. This enables the second capacitors to in effect be alternately pre-charged to positive and negative signal-dependent nodes so that, on average, signal dependent loading of the references is approximately constant.

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to U.S. Provisional Application No. 60/203,025 entitled “Systems and Methods Useful for Detecting Presence and/or Location of Various Materials” filed in the U.S. Patent and Trademark Office on May 9, 2000. SUMMARY OF THE INVENTION The present invention provides systems and methods which can be employed to locate or detect presence of various materials, including nonferrous metals. These systems include new and useful sensors, circuits, systems and devices which power and/or interoperate with the sensors, and methods of making, operating and using such systems. Any or all of the systems, devices or processes can be combined with other systems, devices or processes disclosed. 1. Devices for Detecting and Identifying Conductive or Magnetic Objects Introduction Devices according to the present invention are capable of performing sophisticated target location, classification, and recognition of conductive or magnetic objects independently without the use of other devices or systems and can be deployed by themselves in an area survey. This is accomplished by the simultaneous and accurate phase and magnitude measurement of the response of a target object to time varying magnetic fields of several frequencies. While several types of magnetic/electromagnetic methods have been employed by others, the ability to accurately measure phase and amplitude as a function of frequency has been lacking. This measurement is necessary for the classification of materials. Much of the most sophisticated magnetic target location research to date has been conducted by the United States Navy for the purpose of location and detection of mines and unexploded ordnance. This work has been carried out primarily by the Coastal Systems Station (CSS) of the Navy's Naval Surface Warfare Center. They have developed some of the most sophisticated passive magnetic field sensing instruments. These include both total field and vector magnetometers as well as gradient magnetometers. However, their work does not include active time varying magnetic field generation. BACKGROUND Classical electromagnetic theory provides the underlying relationships for the description of operation of devices according to the present invention. An electrical current produces a magnetic field throughout space. The magnetic induction at any point in space, dB, due to a current flowing in an infinitely small (differential) length element is proportional to the magnitude of the current, I, times the vector cross product of the element length, dl, and the distance vector from the element to the point in space, x, divided by the cube of the magnitude of the distance vector: dB=k c I ( dlGx )/| x| 3 .  (1) where k C is the proportionality constant. In Gaussian units k C =1/c, where c is the speed of light. In MKSA units k C =1/(4πε 0 ) 1/2 . Therefore, the total magnetic induction at any point in space can be calculated by integrating over the total current path for all currents of concern. B=fk C I ( dlGx )/| x| 3 .  (2) Furthermore, if the current is varying with time, then both I and dB become functions of time, I(t) and dB(t), and the relation becomes: B ( t )= fk C I ( t )( dlGx )/| x| 3 .  (3) In free space the magnetic field, H, is proportional to the magnetic induction, B. The proportionality constant, μ 0 , is the permeability of free space and its value depends on the choice of the system of units. Thus: H ( t )=μ 0 B ( t ).  (4) The second relationship states that a time varying magnetic induction will produce an electric field, E, over any closed path as follows: gE ( t )· dl=−k E ( d/dt ) ffB ( t )· nda.   (5) Equation 5 states that the line integral of E over the closed path whose elements are dl is proportional, k E , to the negative of the time derivative of the surface integral, over any continuous surface bounded by the closed path, of the vector dot product of the magnetic induction and the unit surface normal, n, to the surface enclosed by the path. da is a surface element of that surface. Any material has an associated conductivity, σ M , and magnetic permeability, μ M . Both the conductivity and permeability are material specific as signified by the subscript, M. These properties react with the local electric and magnetic fields, E and H. This interaction produces both currents and magnetic fields within the material. The magnetic induction in a material produced by the magnetic field is given by: B ( t )=μ M μ 0 H ( t ),  (6) where μ 0 is the permeability of free space and μ M is the material's relative permeability. There are three major classes of magnetic materials. They are differentiated by the size of μ M . The ferromagnetic materials have large, positive permeabilities. These materials include iron, nickel, cobalt and most of their alloys. The paramagnetic materials, which include most other metals, have permeabilities that are greater than one by only parts per million; their permeabilities are small when compared to those of ferromagnetic materials. The third class of magnetic materials is the diamagnetic materials. These materials have permeabilities that are slightly less than one by amounts equivalent in size to that of the paramagnetic materials. A few of the metals are diamagnetic. Ferromagnetic materials are referred to as ferrous materials and paramagnetic and diamagnetic materials are referred to as nonferrous materials. The current by produced the imposed electric field, commonly called an eddy current, is proportional to the product of the impedance, Z M , which includes the conductivity and the shape functions, and the magnitude of the electric field, E; thus: I ( t )= k 1 E ( t )/ Z M ,  (7) where k 1 is the proportionality constant. The impedance is in general a complex number and is a function of the shape of the material along with its conductivity. As with magnetic materials there are three major classes of materials based on their conductivities. The conductors, which include metals, have relatively large conductivities. The insulators have conductivities that are a million to a trillion times smaller. In between lie the semiconductors. Materials can also be classified by their permitivities. In general the permitivities are relatively unimportant at the frequencies of interest for the conductors; therefore the effects due to the displacement currents are extremely small and can be neglected in the following arguments. Furthermore the displacement current will add a small −jZ C term which will be overwhelmed by the much larger inductive term in the case of conductors. The aspect ratios of the targets are generally close to one. In this case for the materials of interest the impedance is strongly inductive and can be described by the relation: Z M =Z R +jZ L ,  (8) where, Z R is the real impedance, which is a function of the conductivity and the shape, and Z L is the imaginary part of the impedance, which is a function of the shape. The materials of interest have high permeabilities, high conductivities, or both. Equations 6 and 7 show that these materials will produce a secondary magnetic field either directly from the applied magnetic field due to μ M or indirectly through an induced current due to σ M . It is these secondary magnetic fields that are sensed in all types of magnetic/electromagnetic sensing systems. Equation 5 shows that an electric field is only produced if the magnetic field is time varying; therefore, nonferrous materials cannot be detected by a constant magnetic field. The passive magnetic field sensing methods used by the Navy and all others for large area surveys are thus only capable of sensing the ferrous materials. In these methods the residual magnetic field from the earth, approximately 0.00005 T (Tesla) provides the local magnetic field at the target material. A ferrous target then creates a secondary field that can be sensed as a variation in the constant background field of the earth. This field is generally dipole in nature and falls off as the cube of the distance from the target. The field falls off very rapidly as the distance to the target increases. The field due to appropriate sized objects can be thousands or millions of times smaller than the background field of the earth. In addition the earth's field varies with time. These variations although spatially uniform can be greater than the signal from the target material. In order to remove these variations, gradient techniques are used. The difference in the signal originating from two sensors physically separated will not contain any part of the uniform background, even if it is varying with time, if the sensors are perfectly matched. Only that portion of the signal originating from “local” objects will be detected, due to their change as a function of position. The field from far away objects is much more uniform and will not be detected. In this manner the gradient technique is much more sensitive than the full field or vector magnetometers used in surveys. There are drawbacks to using this gradient based system, however. The gradient decreases much more rapidly with distance than does the field. It decreases as the distance to the fourth power. The other concern is matching of the sensors. It is this matching that governs the degree to which the uniform (common mode) portion of the signal can be rejected. Systems can be built that are capable of achieving a factor of a million in common mode rejection. As good as these passive systems are they cannot detect nonferrous materials; however, in most situations, ferrous materials are associated with the nonferrous targets of interest and their detection can be used to map the debris pattern of an area. In order to detect nonferrous materials, systems according to the present invention generate an alternating current in a transmitter coil. This current is of the form: I ( t )= I ω sin(ω t ),  (9) where I ( is the current magnitude and ω is the angular frequency ω=2πf, where f is the frequency). Equations 3 and 4 thus state that there is a magnetic field at the target that is proportional to this current. Equation 6 shows that the secondary magnetic induction, B f , produced by the target is proportional to this field; thus: B f t )= k f sin(ω t ),  (10) where k f is the proportionality constant. Equation 5 shows that there is an electric field at the target that is proportional to the negative of the time derivative of I(t). The time derivative of I(t) is given by: dI ( t )/ dt=ωI ω cos(ω t );  (11) thus the electric field impressed onto the target, E T , is: E T ( t )=− k E ωI ω cos ω t ),  (12) where k E is the proportionality constant. If the material is highly conductive as are most materials of interest then the character of its impedance is mostly imaginary and appears as an inductance of the form: Z L ≈jωL,   (13) where L is the effective inductance of the sample. This imaginary impedance adds an effective time integration to the electric field to produce the induced current. Thus the induced current, I T , at the target is: I T ( t )=− k 1 sin(ω t ),  (14) where k 1 is a constant of proportionality. Equation 3 gives the secondary magnetic induction as proportional to the current. Thus the secondary induction due to the conductivity of the target, B n , is: B n ( t )=− k n sin(ω t ),  (15) where k n is the proportionality constant. Equations 10 and 15 show that the contributions to the secondary fields at the sensors due to the magnetic and electrical properties of the materials would be opposite in sign. It is therefore possible for an active AC system of this type to differentiate between ferrous materials which are dominated by the B f term and the nonferrous materials which are dominated by the B n term. The total field at the sensors is: B tot ( t )= B f ( t )+ B n ( t ).  (16) In the simplified case described above the total field is given by: B tot ( t )=( k f −k n )sin(ω t ).  (17) Thus the signal varies from positive to negative depending on the relative strengths of the magnetic and electrical properties of the materials. The active DC magnetic field sensing methods create a time varying magnetic field by moving a magnet across the field to be surveyed. This creates a time varying magnetic field at a given any given point in the field. In this manner the active DC magnetic field sensing technique can be used to differentiate between ferrous and nonferrous materials. The limitation of the moving magnet type of system is that if there is a mixture of ferrous and non ferrous material, the one with the stronger secondary field will dominate. Only that material will be detected, but at a weaker signal strength than if it were present alone. It would be possible to mask the nonferrous signal with ferrous material. The active system overcomes this limitation. A more detailed analysis of the material impedance shows a complex character that can be used to better differentiate between materials. Equation 8 shows the material impedance as composed of a real part, Z R , and an imaginary part, Z L . The above approximation assumed that because the conductivity of the material was large that the real part of the impedance was near zero and could be neglected. This is true only to a first order approximation. In a real material the real part of the impedance is a factor. Not only does the material exhibit a real impedance but its magnitude is dependent on the permeability, conductivity and frequency. The real part of the impedance is proportional to the conductivity. In addition for an AC magnetic field the penetration into an object is limited by an attenuation factor. To first order approximation there is a surface layer in which all conduction can be considered to take place. This layer restricts the current flow. Its thickness is referred to as the skin depth, δ, which has the form: δ=[2/ωμ 0 μ M σ)] 1/2 .  (18) The real part of the impedance can be expressed as: Z R =k R /{σ[2/ωμ 0 μ M σ)] 1/2 },  (19) which reduces to: Z R =k R (ωμ 0 μ M ) 1/2 /(2σ) 1/2 .  (20) The impedance has p phase, φ Z , that is given by: φ Z =tan −1 ( Z L /Z R ).  (21) Thus Equation 14 becomes: I T ( t )=− k 1 sin ω( t+φ Z ),  (22) and by substitution into Equation 16, the magnetic field, due to the material, as seen at the sensor is given by: B tot ( t )= k f sin(ω t )− k n sin(ω t +φ Z ).  (23) The phase of the sensor signal at the target due to the secondary field generated by the target material has a phase which is no longer merely positive or negative. A measure of this phase is material specific. This phase is a function of the material conductivity and permeability and of the applied magnetic field frequency. A measure of the relative phase between the applied magnetic field and the secondary field generated by the target as a function of frequency gives a material specific signature which can be used to differentiate one material from another. In order for a system to make use of this feature it must be capable of accurately measuring the relative phases. The active DC magnetic field techniques, as practiced by others, of passing a magnetic field over a target, cannot accomplish this since there is no phase reference for the applied field. The active AC magnetic field generated by this system is capable of precise phase measurement. Since the active system generates a precise AC magnetic field and has the waveform available for comparison, it can use synchronous detection to precisely determine the phase and amplitude at any frequency and to reject noise both out of band and in band uncorrelated noise. The system in fact can generate multiple frequencies simultaneously and can synchronously detect the secondary fields generated by the target materials simultaneously at each frequency. The use of multiple frequencies all of which are exactly correlated achieves an extremely low dynamic noise level. These multiple frequencies are also preferably digitally time encoded to further eliminate background noise. This time encoding involves periodically in time changing the phase of the transmitted frequencies. The encoding can be designed so that the temporal correlation of a non correlated signal will be very close to zero; whereas the correlation of the transmitted signal with the target signal will remain unchanged and large. This system can suffer background and noise limitations similar to those of the passive magnetic field techniques. For that reason the preferred active system employs multiple matched sensor sets, positioned symmetrically to the transmitter field, to simultaneously measure in multiple directions both the magnetic field components and its gradients. The use of gradients greatly increases the system's immunity to background noise from distant objects and from slowly varying backgrounds. In this way the far field electromagnetic noise from the earth is eliminated along with the broad conductivities of mineralization. In addition the relative structure of the field gradients can be used to determine distance and direction of the target from the sensor system, not only providing desired target information but also providing a means of eliminating any signals from the tow vehicle. The precision of the background field elimination in the active system is different from that of the passive systems. In the passive systems the background field of the earth must be eliminated from the sensor signals. In the active system the field due to the transmitter coil must be eliminated from the sensor signals as well. While the earth's background signal is approximately 0.00005 T the field due to the source can be as high as a few Tesla or ten thousand times greater than the earth's field. Because the output of the transmitter is known, synchronous system techniques can be used along with the shape of the magnetic field transmitter to eliminate this field from the sensors. BRIEF DESCRIPTION FIG. 1-1 is a block diagram of systems according to an embodiment of the invention. FIG. 1-2 is a functional block diagram of certain transmitter with known output function according to an embodiment of the invention. FIG. 1-3 is a functional block diagram of a certain transmitter with magnetic field monitor according to an embodiment of the invention. FIG. 1-4A is functional block diagram of residual magnetic field nullling using a nulling magnetic field in accordance with an embodiment of the invention. FIG. 1-4B is a functional block diagram of voltage nulling of residual field sensor output according to an embodiment of the invention. FIG. 1-5A is a schematic view of a transmitter coil cross section for single wire coil showing sensor position and residual field according to an embodiment of the invention. FIG. 1-5B is a schematic view of a transmitter coil cross section for normal rectangular coil showing sensor position and residual field according to an embodiment of the invention. FIG. 1-5C is a schematic view of a transmitter coil cross section for shaped coil showing sensor position and residual field according to an embodiment of the invention. FIG. 1-6 is a functional block diagram showing a certain gradient sensing using a matched sensor pair according to an embodiment of the invention. FIG. 1-7 is a schematic view of sensor pair calibration using two transmitter equal coils according to an embodiment of the invention. FIG. 1-8 is a schematic view of sensor pair calibration using a large solenoid coil according to an embodiment of the invention. FIG. 1-9 is a functional block diagram of a system with multiple sensor pairs and synchronous detection based on DSP processors according to an embodiment of the invention. FIG. 1-10 is a schematic view of a time encoded waveform according to an embodiment of the invention. FIG. 2-1 is a functional block diagram of a synchronous pulse width modulation amplifier according to an embodiment of the invention. FIG. 2-2 is a schematic view of certain typical pulse width modulation waveforms according to an embodiment of the invention. FIG. 3-1 is a schematic diagram of a tank circuit of the sort which can be used in embodiments of the invention. FIG. 3-2 is a schematic diagram of a tank circuit according to an embodiment of the invention. FIG. 3-3 is a schematic diagram of a tank circuit with series capacitor and inductor according to an embodiment of the invention. FIG. 3-4 is a schematic diagram of a tank circuit with two resonances according to an embodiment of the invention. FIG. 3-5 is a schematic diagram of a tank circuit with single frequency blocking circuit according to an embodiment of the invention. FIG. 3-6 is a schematic diagram of a tank circuit with a multiple frequency blocking circuit for N discrete frequencies according to an embodiment of the invention. FIG. 4-1 is a schematic diagram of certain oscillators according to embodiments of the invention. FIG. 4-2 is a schematic diagram of a switch network for connecting charge capacitors to load coils according to embodiments of the invention. FIG. 4-3 is a schematic view of certain switched capacitor circuit waveforms according to embodiments of the invention. FIG. 4-4 is a schematic diagram of pulse width modulated switched capacitor resonators according to an embodiment of the invention. FIG. 4-5 is a schematic diagram of certain switched capacitor resonator with integral switching power supplies according to embodiments of the invention. FIG. 5-1 is a schematic diagram of a sense coil equivalent circuit according to an embodiment of the invention. FIG. 5-2 is a schematic diagram of an operational amplifier based voltage to current conversion circuit according to an embodiment of the invention. FIG. 5-3 is a sensitivity diagram according to certain embodiments of the invention. FIG. 6-1 is a diagram showing a time encoded waveform according to certain embodiments of the invention. FIG. 6-2 is a diagram of a 4 segment encoded waveform according to certain embodiments of the invention. FIG. 6-3 is a diagram of a 19 segment encoded waveform according to certain embodiments of the invention. FIG. 6-4 is a diagram of a 20 segment encoded waveform according to certain embodiments of the invention. FIG. 6-5 is a diagram of a 22 segment encoded waveform in accordance with certain embodiments of the invention. FIG. 7-1 is a functional block diagram of local magnetic field generation for residual field cancellation according to certain embodiments of the invention. DESCRIPTION FIG. 1-1. shows the basic components of one system according to the present invention. The system consists of a transmitter that produces a time varying magnetic field, one or more magnetic field detection sensors, and a detection unit for analyzing the data and controlling the unit. The phases and magnitudes of the frequency components of the transmitted magnetic field should be known relative to some known point in time. These can be known because the method of their production is controlled or because the transmitted magnetic field is monitored by some method. One method by which the transmitted magnetic field can be precisely known is to produce it under very controlled conditions. In the preferred embodiment this is accomplished using a digitally synthesized signal that is used to drive a precision linear amplifier. The amplifier then drives a transmitter coil. It is important that the transmitter be linear so as not to introduce harmonic distortion into the transmitted signal and to maintain the transmitted signal purity. A voltage drive signal for the transmitter coil could be used; however, a current drive signal is preferred. This is due to the fact that the magnetic field is proportional to the current flowing in the coil and not to the voltage applied across it. When a voltage is applied to a coil the current through it and hence the magnetic field is a function of the voltage and the effective inductance of the coil. The inductance of the coil is in turn a function of its internal construction as well as its external environment. This means that the current through the coil as well as the magnetic field it produces as a function of the applied voltage varies with the external environment and is not fixed. When a current drive is used the output field is much more insensitive to the external environment; therefore, the current drive produces a better known output magnetic field. Regardless of the method by which the magnetic field is created, the transfer function of the source drive amplifier should be accurately measured. In addition the spatial distribution of the transmitted field must be measured and/or calculated. FIG. 1-2 shows the components of a transmitter with a known transfer function. Another method of knowing the magnitude of the output magnetic field is to measure it in real time as the system is in operation. The magnetic field could be monitored by a magnetic field sensor, such as a coil, Hall effect device, or a magnetometer. The output of this field monitor would be available to the signal detection unit (FIG. 1-3.). The preferred embodiment of this device uses all of these methods. It drives the transmitting coil with a linear current source. The current source is controlled by a precisely generated digital signal. This drive system is tuned to produce a very accurate representation of the desired signal with out feedback from the actual signal that is produced. In addition a magnetic field monitoring device is used to monitor the magnetic field output. The signal from the sensor is then fed back to the system and used to make fine adjustments to the output magnetic field to accommodate errors in the system. The time varying magnetic field could be produced by alternate methods using permanent magnets and/or dc coils (electromagnets). In one method several magnets would be spatially oriented so as to produce a time varying field when the device is moved over a target. An array of magnets could be used in this manner to create an arbitrary time varying magnetic field. If the velocity of the array of magnets over the target was known then the magnetic field versus time could be calculated and used to calculate the phase information from the field created by the target. In another implementation a single magnet or an array of magnets could be rotated about an axis at a constant or time varying angular velocity to create the time varying field at the target. If the relative movement of the magnet array with respect to the target object is known then the temporal properties of the magnetic field seen by the object could be calculated and used to obtain phase and magnitude information from the object signal. In another implementation a single magnet or an array of magnets could be vibrated or moved in a non constant motion with respect to the target to produce a time varying magnetic field of known properties. These methods have the advantage over the transmitter coil in that the energy used to produce the magnetic field is smaller; however, it is generally more difficult to obtain accurate phase information using these methods. In addition the mechanical control of these types of systems can be very complex. In any of the transmitter implementations, whether ac or dc magnetics are used, the time varying magnetic field produced by the transmitter causes a secondary magnetic field to be produced by a conductive or magnetic target object in its presence. It is this stimulated field that the field detection sensor measures. Because of physical size limitations, the magnetic field sensors are close to the transmitter. The field due to the transmitter is many times larger (often a billion or more) than the stimulated signal from the conductive or magnetic object. The magnetic field detection sensor, therefore, should be capable of detecting the stimulated magnetic field from an object in the presence of the large signal from the transmitter without clipping or saturating the detector. There are several methods both active and passive by which this can be accomplished. The preferred method is passive. The sensor is placed in a location relative to the transmitter so that the field quantity in the direction sensed by the sensor is as near zero as possible. Typical active methods are nulling methods. The residual magnetic field at the sensor due to the transmitter field could be canceled by the use of a nulling transmitter (FIG. 1-4A.), a voltage null circuit (FIG. 1-4B.) used with the sensor amplifier, or subtracting the known or measured residual in the detection unit. These active nulling techniques generally only work over a limited field magnitude range; therefore they are generally used only to null the residual field after the sensor has been placed in a location relative to the transmitter that it senses only a small field. The effectiveness of this residual field nulling often times sets the sensitivity of the device. The stability of the null is often the noise limit of the system. If the residual field sensed by the field sensors is high then slight movements of the sensors can cause large signal noise. This is often the case since near to the transmitter there are large spatial field gradients. This factor makes the shape of the transmitter highly important. The preferred embodiment of this device has the transmitter coil so shaped as to create a region of near zero field and near zero field gradient where the sensor may be placed. If the field gradient is near zero in the region of the magnetic field sensors then the residual signal they see is less sensitive to their position. FIGS. 1-5A, 1 - 5 B, and 1 - 5 C show various coil configurations of the transmitter coil. They are in order of decreasing field gradient in the vicinity of the sensor. The coil in FIG. 1-5C. has been designed so that the field lines are flat in the vicinity of the sensor so that side to side movement of the sensor will have little effect on its residual signal. The preferred embodiment of this system will have the transmitter coil designed to specifically desensitize the sensors to movement with respect to the transmitter coil. The field shapes and gradients can also be modified by the use of different currents in different windings of the transmitter. This method is also effective in reducing the sensitivity of the sensors to their position relative to the transmitter coil. The use of secondary transmitters which function as field shaping devices could be used to locally null the transmitted field and/or its gradients. These same transmitter field shaping techniques can also be used to modify the transmitted magnetic field in the vicinity of the target object to improve the system performance. This is done to improve signal strength, to improve target classification, or to improve target spatial location. The magnetic field sensor used in the system can be a total field sensor, a field vector sensor, or a field gradient sensor. The preferred method for looking for small objects at reasonably short ranges is a field gradient sensor. Gradient sensing reduces the effect on the detected signal of large volumes of conductive or magnetic material such as iron rich mineralization or sea water and of the earth's background field. It also reduces the effects of large objects that are away from the immediate search area but not very far away. Deployment platforms and operators are such objects. The preferred implementation uses matched sensor pairs for sensing the gradient of the stimulated magnetic field produced by a conductive or magnetic object and simultaneously sensing the direct field components. The better the match of the sensor pairs, the better the rejection of the constant portions of the fields due to the transmitter, the earth, and the large far away volumes. The performance of the matched pairs will be limited by their matching errors. For this reason the preferred method includes fine gain adjustment amplifiers in order to adjust the sensitivity of each sensor in the pair as close as possible to that of the other sensor in the pair, FIG. 1-6. The adjustment amplifiers can be if desired controlled by the detection unit. The fine gain adjustment amplifiers of each pair would be adjusted to give the zero difference in the presence of a strong uniform filed. The common method for this calibration would be to use two transmitter coils placed relatively far from the sensor pair on either side of them (FIG. 1 - 7 ). These transmitters could be used to produce a uniform field at the two sensors. The gain adjustment amplifiers could then be adjusted to zero the difference of the two sensors in the pair. Other coil configurations such as a large solenoid (FIG. 1-8) could be used to produce a relatively strong uniform field for use in zeroing the difference in matched sensor pairs. The detection unit monitors the frequency composition of the transmitted signal and that of the received signal. It can be shown using classical electromagnetic theory and the physical properties of materials that the magnitude and phase at a given frequency of the stimulated secondary magnetic field are determined by the physical properties of the material. The detection unit calculates the phase and magnitude relationship between the transmitted magnetic field and the secondary magnetic field. The preferred embodiment of this device uses synchronous detection to determine the magnitude and phase relationship between the output signal from the transmitter and the received field generated by the target object. The synchronous detection is made possible since the detection unit is also responsible for generating and/or has knowledge of the output signal. The magnitude and phase relationship is found for each transmitted frequency and is compared to stored or calculated relationships for different types of materials to determine the nature of the material of the object. The change in this relationship as the system is passed over or by an object is used to determine the range and size of the object. The preferred embodiment uses multiple sensors and sensor pairs to measure/calculate the field and field gradient vectors and therefore can more precisely locate the object in range and direction than can a single sensor or sensor pair. The use of both direct field and gradient sensors can be used to enhance the positional location of the object. The ratio of the each gradient to the direct field as well as the ratios of the gradients among themselves are functions only of the range, distance and direction, to the object and not of the amount of material in the object as long as the distance to the object is relatively large compared to the size of the object. That is the object appears as a point object. These relations can be measured and /or calculated for the system and subsequently used to determine the range to the target object. Analysis such as matched filtering, spatial Fourier analysis, etc. can be used to discern multiple objects with overlapping signals due to the multiple objects being within the systems area of coverage. The preferred system can generate multiple frequencies simultaneously and can synchronously detect the secondary fields generated by the target materials simultaneously at each frequency. The use of multiple frequencies all of which are preferably exactly correlated achieves an extremely low dynamic noise level. FIG. 1-9 shows one preferred implementation of the system with multiple sensor pairs and synchronous detection based on DSP processors. The multiple DSP processors in conjunction with the control and data analysis computer make up the detection unit. In this system a master coordination DSP passes a digital output signal to the transmitter for output and to the synchronous detection DSPs for detection of the target signals. These multiple frequencies can be as well digitally time encoded to further eliminate background noise. This time encoding involves periodically in time changing the phase of the transmitted frequencies. The encoding can be designed so that the temporal correlation of a non correlated signal will be very close to zero; whereas, the correlation of the transmitted signal with the target signal will remain unchanged and large. FIG. 1-10 shows a typical time encoding scheme that could be used with this system. It periodically reverses the phase of the signal so that the correlation between the signal and a return is high but a non correlated slowly changing signal of the same frequency is very low. 2. Methods for Eliminating the Frequency and Phase Errors Between the Input and Output Signal of a Pulse Width Modulated Amplifier, Synchronous Pulse Width Modulation Amplifier The efficiency of high power amplifiers is one of the limiting factors in their utility. The power losses are converted to heat. This heat must be eliminated or it will cause poor performance and do damage to the amplifier. The elimination of this heat can be costly in both complexity and reliability of the amplifier. Cooling systems are necessary. Both active systems (forced air and water cooled ) and passive system add expense to the amplifier system. In order to reduce size and costs of the cooling systems much effort has been spent on increasing the amplifier efficiency. One of the major advances in this effort was the development of pulse width modulation, PWM. PWM techniques use high frequency switching to approximate the desired output voltage or current. This method adjusts the on and off times of a square wave so that the integral over any period of time longer than a few cycles of the square wave is equal to that of the desired output signal. This high frequency switched waveform is then usually lowpass filtered to eliminate the high frequency components in the output waveform that are due to the switching, thus smoothing the waveform. In this manner a good approximation to the desired output signal can be obtained. PWM achieves its efficiency from the fact that there is no real power loss in a ideal switch. When the switch is opened there is no current flow, thus no power loss. Also when the switch is closed the resistance is zero, thus the resistive power loss is again zero. In many real PWM devices the switching is performed by solid state switching transistors. These devices have some switching losses, but they are usually small at reasonable switching frequencies; therefore, PWM devices can be very efficient (greater than 98%). The fidelity of PWM based amplifiers can be in many cases limited by switching inconsistencies. This is caused by the fact that the switching clock and the amplifier input signal are not synchronized. This means that for a repeating output signal the switch points for each cycle occur at different times. This causes each cycle of the output to be different. These differences give rise to time varying signals. In the case where a very stable output is desired, this time varying error can be a major concern. This problem will persist to some extent even if both the PWM clock and the input signal to the amplifier are very stable. Frequency and phase drifts between the two signals will lead to the type of errors described above. The problems caused by relative phase and frequency drifts can be eliminated in the case where the input signal is digitally derived. This can be done with a common system clock to generate the amplifier input signal and the PWM switching clock signals. This means that the frequencies of the signals are absolutely locked and that the relative phases are fixed. This type of PWM amplifier will be referred to as a Synchronous Pulse Width Modulation, SPWM, amplifier. FIG. 2-1. shows a typical system diagram for a SPWM amplifier. In this system the digital controller contains the clock which is used to generate all of the signals within the system. It generates both the PWM square wave and the desired amplifier input signal. The square wave is integrated to form a triangle wave. Another option is to generate the triangle wave directly. This second option is better suited for systems where the system clock is many times faster than the triangular wave and PWM frequency. This triangular wave is then compared to the desired waveform. If the desired waveform is greater than the triangular wave voltage then the voltage comparitor outputs a signal to turn on the switch and apply voltage to the load. If it is less than the triangular wave voltage then the voltage comparitor turns the switch off and power is not applied to the load. In this manner the voltage to the load modified by the switch network so as to apply a signal to the load that is a function of the input drive. The output drive to the load will appear as in FIG. 2-2. The output drive may be optionally filtered to remove high frequency switching noise and to smooth the output. The amplifier can be used open loop as described. It may also be used in a closed loop manner by including an optional feed back network in the system to provide an error signal to the voltage comparitor. In this method the feedback can be related to any desired quantity, i.e. voltage, current, light output, temperature, etc. 2a. Methods for Stabilizing Synchronous Detection Systems Using SPWM Amplifiers—Single Clock Synchronous System Synchronous detection systems are used very effectively in areas where the signal to noise is low, that is where there is significant noise relative to the signal. These systems can typically measure a signal level that is one hundred thousand times smaller than the total noise level. In general synchronous detection systems have very high phase fidelity. This feature is critical to the elimination of noise. Much effort is expended to make the reference signal stable in both frequency and phase. All signals, will have some amount of phase jitter, frequency noise, phase drift, and frequency drift. If the input and system added amplitude noise levels are sufficiently low then these timing errors can be the limiting factors affecting the signal measurement. The lower noise limit is in fact in most synchronous detection systems limited by the phase stability of the source signal that is transmitted and the phase stability of the reference used for the synchronous detection. In a digital system the sampling clock stability adds further to the phase uncertainty by adding imprecision to the analog-to-digital conversion process. In many synchronous detection systems the signal to be measured is derived from the reference signal itself or the reference signal and the signal to be measured are derived from the same signal. In other systems the signal to be measured is derived from or can be derived from a digitally generated signal. This signal will again need a stable, in both frequency and phase, generating clock. This signal clock will have phase and frequency errors of the same types as the reference signal generating clock. Therefore the clocks will not be correlated and signal measurement errors will exist. These errors can be greatly reduced if the same system clock is used to generate both the signal to be measured and the reference signal. If the same clock is used to generate both signals then the phases of the two signals will be more closely related and the frequencies will track. This will greatly reduce any errors in the system. In this way the effects of phase instability are reduced by more than an order of magnitude. In addition all of the timing patterns and signals used in the system are integer sub multiples of the system repeat cycle time. The system repeat cycle time is an integer multiple of the system master clock period. All other timing sequences are thus integer multiples of the system master clock period. This type of system is referred to as a single clock synchronous system. In the case of a system employing a SWPM amplifier the clock used in the SPWM amplifier should be the same as that used in the synchronous detection scheme. This type of system will provide the best possible frequency and phase stability between all signals involved in the measurement process. 3. Methods of Efficiently Generating Multiple Frequency Signals in a Circuit—Multiresonant Tank Circuit Many systems require high power output at multiple frequencies for their best operation. One of the most common ways of achieving high power high efficiency outputs is to use a resonant circuit or resonant tank circuit. This type of circuit consists of a capacitor in parallel with an inductor (FIG. 3 - 1 ). The values of these components are adjusted so that the circuit resonates at the desired frequency. These circuits are capable of efficiently producing high power, very pure single frequency outputs. More than one of these circuits could be used to simultaneously produce outputs at multiple frequencies. This method is not applicable in many circumstances such as in particular when the output drive signals must be colocated. One example is the production of an acoustic signal from a single point in space. The use of multiple sources would be prohibited. An alternative would be to use a switch array to time multiplex the signals from multiple tank circuits into the single circuit. This is inappropriate in many cases since the switching noise and timing uncertainties would be intolerable. A modification of this method is to use a switch network to switch in different capacitors into the circuit to change the circuits resonant frequency. This method suffers from the same switching noise and timing instabilities as noted for the previous method. This could be achieved using multiple coils with multiple tank circuits or by time multiplexing frequencies. The time multiplexing of frequencies would be implemented by switching various values of capacitors into and out of the circuit, thus changing its resonant frequency. This patent describes a multiresonant tank circuit capable of simultaneously resonating at several frequencies. The multiresonant tank circuit in its simplest form includes an inductive load (the inductor L T ) and capacitor in series with the usual parallel capacitor of the tank circuit (FIG. 3 - 3 ). The impedance of the series inductor and capacitor, Z F , is given by: Z F =iωL F +1/( iωC F ),  (3-1) where L F and C F are the series inductance and series capacitance respectively. If L F and C F are chosen such that at the frequency, ω 1 , the resonant frequency of the tank circuit: ω 1 2 L F C F =1,  (3-2) then Z F is zero at ω 1 . In that case the addition of these two components does not change the resonant behavior of the circuit; the current gain at ω 1 remains unchanged. As the frequency moves away from ω 1 , the impedance, Z F , gets very large; therefore, at frequencies far away from ω R the current through the parallel capacitor goes to zero. If this current is small the circuit behaves as if only the inductor were present. Therefore at frequencies away from ω 1 , L F and C F have no effect on the inductor. It may also be noted that C T and C F could be combined into a single capacitor, C 1 , whose value is equal to the series combined values of C T and C F . A similar circuit could be developed for driving a capacitive load with C F and L F in series with L T . Another parallel capacitor, C T2 , could be added tuned with L T to a frequency away from ω 1 and a second resonance, ω 2 would occur at this frequency. If a series inductor, L 2 , and a series capacitor, C F2 , were added then this second parallel capacitor would have little effect on the first resonance. C F2 and the second parallel capacitor C T2 could be combined into the capacitor C 2 . This circuit (FIG. 3-4) would thus have two resonances, one at ω 1 , and one at ω 2 , where the current gain would be high. This procedure could be performed for several frequencies; thus achieving multiple resonances each with high current gains. These resonances would have to be well separated in frequency to avoid interference. In the more general case, however, other components could be added to establish a low resistance, multi-pole impedance network in parallel with the coil. Whenever the imaginary part of the impedance of the multi-pole impedance network was equal in magnitude but opposite in sign to the imaginary part of the coil impedance at a particular frequency, the current gain would be large. In addition if suitable resistors were added to the multi-pole impedance network then the Q of the resonances could be controlled and the gains of each resonance could be set to some desired value. In many cases it is desirable for the total circuit impedance to be high at frequencies other than the desired drive frequencies. In these cases parallel blocking circuits consisting of a capacitor, C B and an inductor, L B in series with the tank circuit to block signals at undesirable frequencies. FIG. 3-5 shows the blocking circuit for a single resonance circuit. The blocking circuit is tuned so as only to pass frequency ω 1 . The total impedance is given by:   Z TOT =  (3-3) with: ω 1 2 L B C B =1,  (3-4) The circuit shows a high impedance at all frequencies. FIG. 3-6 shows a blocking configuration for a multiresonant tank circuit. Each blocking circuit allows only the desired frequency to pass. Using a suitable multi-pole impedance network the resonant frequencies could be positioned at the desired frequencies as well as setting the Qs for each resonant. The design of this network if not a straight forward task, can be done by a fitting technique. The first guess could be made by choosing the parallel capacitors and the respective series capacitors and inductors as if there were no interactions between the different resonances and then using an optimization program using these as a starting point. The optimization program would then modify the original values looking for a best fit to the desired resonances. A simplex method would be an appropriate tool for this optimization. 4. Methods of Efficiently Generating Multiple Frequency Signals in an Inductive Load—Switched Capacitor Resonator Many systems require high power output at multiple frequencies for their best operation. One of the most common ways of achieving high power high efficiency outputs is to use a resonant circuit or resonant tank circuit. This type of circuit consists of a capacitor in parallel with an inductor (FIG. 4 - 1 ). The values of these components are adjusted so that the circuit resonates at the desired frequency. These circuits are capable of efficiently producing high power, very pure single frequency outputs. More than one of these circuits could be used to simultaneously produce outputs at multiple frequencies. This method is not applicable in many circumstances. These include when the output drive signals must be colocated such as for the production of an acoustic signal from a single point in space. The use of multiple sources would be prohibited. An alternative would be to use a switch array to time multiplex the signals from multiple tank circuits into the single circuit. This is inappropriate in many cases as the switching noise and timing uncertainties would be intolerable. A modification of this method is to use a switch network to switch in different capacitors into the circuit to change the circuits resonant frequency. This method suffers from the same switching noise and timing instabilities as noted for the previous method. This could be achieved using multiple coils with multiple tank circuits or by time multiplexing frequencies. The time multiplexing of frequencies would be implemented by switching various values of capacitors into and out of the circuit, thus changing its resonant frequency. This invention includes a switched capacitor resonator circuit capable of simultaneously resonating at several frequencies. A switched capacitor resonator uses a capacitor as the power source for the resonator as well as the parallel capacitance for the coil. This is a important feature, since the impedances of an ideal capacitor and the ideal coil are both imaginary, no real power is used in the ideal circuit. Therefore, the effeciency can be theroetically very high. In practice, however, there are losses due to losses in real components. FIG. 4-2 shows the switched capacitor resonator circuit configuration. The capacitor is connected across the coil by a set of switches connected in the configuration of a full wave bridge. Each switch in the set preferably has an optional reverse voltage shunt diode so that if the current through the coil can pass around the switch network if it is flowing in the reverse direction of the capacitor's applied voltage. The switch network applies the capacitors voltage first in one direction across the coil and then in the other direction across the coil. This is done at a very high rate, a rate that is much higher than the highest desired resonant frequency of the coil. This switching frequency should preferably be at least greater by a factor of ten than the highest desired resonant drive frequency. For an ideal coil (a coil with no resistance or parasitic capacitance) the duty cycle of the switch is varied so that the integral of the capacitor applied voltage is equal to the product of the desired change in current through the coil and the coil inductance (i.e. the derivative of the current times the inductance). The coil acts as an integrator smoothing out the steps in the current caused by the switching. This makes the current through the coil appear to be fairly smooth. FIG. 4-3 shows typical signal waveforms in the circuit. In the real case there is some resistance in both the coil and the capacitor as well as switching losses; therefore, a current monitoring device is used to monitor the current in the load to insure the proper drive levels. This current information is used in feedback to control the switch duration of the switch network. This feedback can be performed in the same way it is done in a switching power supply or a PWM amplifier. In order to insure the greatest possible stability, a synchronous switching clock can be used so that the switch network clock is generated by the same system clock as all other information used within the system. As with the other timing signals the period of this clock is an integer multiple of the system master clock and an integer sub multiple of the system repeat cycle time. The switched capacitor resonator is theoretically very efficient. The losses in the capacitor and the coil can be held to a minimum by reducing their respective resistances. In the case of the coil the resistance can be reduced by increasing the wire size. For the capacitor a decrease in the effective series resistance of the capacitor will result in a reduction of losses. Today highly efficient switches are available in IGBTs (insulated gate bipolar transistors). The product of the current in the coil and the maximum coil voltage divided by these power losses gives the current gain for this circuit configuration. The losses are made up by the power supplied to the circuit. The power supply which only supplies power to compensate for the losses, must have a supply voltage greater than the maximum voltage applied to the coil. FIG. 4-4 shows a typical switched capacitor resonator. The switched capacitor provides an added advantage in that it can serve as an integral part of the power supply that replaces the power lost due to the non ideal nature of the components used in the system. The capacitor can itself replace the filter capacitor used in the power supply. This means that if an AC power source is used, only a rectification circuit (typically a diode bridge) is needed to provide power directly to the capacitor circuit. The switched capacitor resonator can, therefore, be directly integrated with its power supply. The coils in this system generally operate at high voltages and moderate currents rather than high currents and moderate voltages. The switched capacitor resonator can be matched to any coil voltage by placing a voltage multiplication transformer between the capacitor and the coil. In this way the switched capacitor resonator can be constructed such as to have an efficient step up or step down switching power supply as part of its implementation. The capacitor and power supply can operate at a moderate voltage while the coil can operate in the high voltage ranges. In addition because of the high switching frequency the transformer can be small, making the circuit implementation very cost effective. These factors make the use of more readily available, more efficient components feasible. FIG. 4-5 shows a typical switched capacitor resonator with its integral switching power supply. 5. Highly Sensitive Broad Band AC Magnetic Field Sensors Introduction There are several methods of detecting magnetic fields. These include flux gate magnetometors, ion magnetometers, Hall effect devices, magnetoresistive devices, pickup coils, and SQUIDs. SQUIDs are generally considered to have the greatest sensitivity of the magnetic field sensors, especially in the area of dc magnetic field measurement. For the measurement of ac magnetic fields, coils provide a simple inexpensive sensitive detection device. The open circuit voltage of a single turn coil is proportional to the area integral over the area of the coil of the product of each area element with the magnitude of the magnetic field perpendicular to the coil area at that point. The total voltage is increased by the number of turns in the coil. The total voltage also increases linearly with frequency. This means that as the frequency increases the coil becomes more sensitive. In fact at radio frequencies the coil techniques work very well. At low frequencies where the sensitivity diminishes because of the low frequency many turns in the coil are necessary to keep the sensitivity at a high level. This poses a problem for real coils which are not ideal inductors. As the number of turns in the coil increases so does the coil's inductance and parallel capacitance (self capacitance). This creates a resonance in the coil response. In order to reduce the thermal noise of the coil, the coil resistance is kept low. This makes the Q of the resonance high. This means that the coil must be used at frequencies below resonance. This factor greatly reduces the range of use and can lead to spurious oscillations. Sensors according to the present invention preferably use the coil as a current source in conjunction with a current measuring device (circuit) which effectively short circuits the coil. The short circuit current in the coil is proportional to the magnetic field amplitude. This configuration effectively short circuits the coil capacitance and eliminates the resonance. This type of ac magnetic field sensor can, therefore, be used over a very wide frequency band. In addition increasing the number of turns does not reduce the useful band of the device. BACKGROUND FIG. 5-1 shows the simplified equivalent circuit for a coil in the presence of an ac magnetic field. The magnetic field induces voltage of magnitude, V B , in the coil. The coil has an inductance, L C , a resistance, R C , and a capacitance, C C . For simplicity consider a coil of circular cross section in a uniform ac magnetic field parallel to its axis whose amplitude is given by Bsin(ωt). The coil resistance is given by: R C =2 πrρN   (5-1) Where r is the radius of the coil, N is the number of turns in the coil, r is the radius of the coil, and ρ is the wire resistance per unit length. The coil inductance is given by: L C =μ 0 N 2 πr 2 K /1  (5-2) Where μ 0 is the permeability of free space, 1 is the coil length, and K is an inductive shape constant. K is generally in the range of 0.1 to 1.0 for real coils. There is no simple formula for the coil capacitance but it generally proportional to N X , where x is between 1 and 2. The magnitude of the voltage induced in the coil is given by: V B =−Nπr 2 ωB   (5-3) The magnitude of the open circuit voltage across the coil, V C , is given by: V C =V B /[(1−ω 2 L C C C )+ jωR C C C ]  (5-4) As ω goes to zero V C goes to V B which goes to zero. Also as ω goes to infinity V C goes to zero. This limits the range of usefulness. In addition when ω is equal to (1/L C C C ) 1/2 , then V C is given by: V C =−Nπr 2 ωB /( jωR C C C )  (5-5) This represents a resonance. Since the coil resistance and capacitance is small the Q of this resonance is high. The useful range of operation is thus limited to well below the resonance. If the number of turns and or radius of the coil are increased to improve the sensitivity then the resonant frequency is moved lower further reducing the useful frequency band of the sensor. If the coil is used instead as a current source, the short circuit coil current, I S , is given by: I S =−Nπr 2 ωB /( R C +jωL C )  (5-6) This is a highpass response with a corner frequency, ω 0 , given by, R C /L C or: ω 0 =2ρ1(μ 0 NrK )  (5-7) As the frequency goes to zero the short circuit coil current goes to zero; however above the corner frequency, the current is independent of the frequency and proportional to the magnetic field magnitude. For the frequency above the corner frequency the short circuit coil current is given by: I S =jB 1/(μ 0 NK )  (5-8) The current mode provides a wide frequency band of operation above the corner frequency. In addition the corner of the band can be made as small as desired by decreasing the wire resistance, ρ, or by increasing the coil radius, r. This can be accomplished without changing the sensitivity of the coil's response, I S . It is also important to note that the coil capacitance, which was responsible for the resonance in the voltage mode case, has no affect on the current mode transfer function. DESCRIPTION In order for the coil to be used as a magnetic field sensor it is necessary to provide a method of monitoring the coil short circuit current. A current amplifier will serve this purpose. FIG. 5-2 shows a simple operational amplifier current to voltage conversion circuit which is very effective with commercially available components at providing a reasonable voltage signal with low noise. The output voltage of the circuit, V S , is given by: V S =R F I S   (5-9) or: V S =jR F B 1/(μ 0 NK )  (5-10) In this circuit's operation the voltage across the inputs of the operational amplifier is driven to zero by the feedback; therefore, the coil capacitance has no effect in the circuit. The sensitivity of the coil as a sensor is determined by the signal to noise ratio of the circuit's output. There are several noise sources in this circuit. The major noise sources are the thermal noise due to the coils resistance, the thermal noise due to the feedback resistor, the input voltage noise of the operational amplifier, and the input current noise of the operational amplifier. The noise voltage due to the coil's resistance over a frequency bandwidth of B W , V RC , is given by: V RC =R F k n R C 1/2 B W 1/2 /( jωL C )  (5-11) Where k n is the thermal noise constant which is a function of the temperature of the resistive material. The noise voltage due to the feedback resistance over a frequency bandwidth of B W , V RF , is given by: V RF =k n R F 1/2 B W 1/2   (5-12) The noise voltage due to the operational amplifiers input voltage noise over a frequency bandwidth of B W , V en , is given by: V en =( R F +jωL C ) e n B W 1/2 /( jωL C )  (5-13) Where e n is the operational amplifier input voltage noise. The noise voltage due to the operational amplifiers input current noise over a frequency bandwidth of B W , V in , is given by: V in =i n R F B W 1/2   (5-14) Where i n is the operational amplifier input current noise. Since these four noise sources are not correlated, the total noise voltage, V N , is given by:   V N =( V RC +V RF +V en +V in ) 1/2   (5-15) A good measure of the smallest magnetic field that can be measured by the sensor is the magnetic field magnitude, B S , that will produce a signal equivalent to the noise voltage of the system. B S is given by: B S =−jμ 0 NK ( V RC +V RF +V en +V in ) 1/2 /( R F 1)  (5-16) The field magnitude B S can be calculated for various coil and amplifier systems to establish the component coil tradeoffs. FIG. 5-3 shows the value of B S for a typical system. This system uses a Burr Brown OPA627 operational amplifier with a feedback resister of 10 Mohm. The amplifier is band limited to 2 kHz by using a single capacitor in parallel with the feedback resistor. The coil size is 0.15 m in radius and 0.05 m long. The thickness of the windings is 0.012 m. The whole winding volume is filled with magnet wire of various sizes with a single layer of polyurethane insulation. The sensitivity for #32 wire is better than 120 picoGauss (12 femtoTesla) above 300 Hertz and better than 40 picoGauss (4 femtoTesla) above 1 kiloHertz in frequency. This is as good or better than most SQUID magnetic field sensors in this frequency range. 6. Methods of Digital Signal Encoding in Synchronous Detection to Improve Noise Rejection Synchronous detection schemes are very good at eliminating the out of band signals that may interfere with the detection of a weak signal. The effective bandwidth of the signals passed by an ideal synchronous detector is related to the inverse of the integration time as long as it occurs over complete cycle of a sine wave. These methods cannot eliminate in band noise that is equal to the reference frequency in content. In many systems there exist man made backgrounds that are approximately continuous in frequency. These will at times drift in to the desired frequency band and cause erroneous signals that will mask the real signal. In addition natural backgrounds may have the same effect. The present invention provides an algorithm which describes a method of digital encoding of the reference signal and the signal to be measured to eliminate in band signal that are not digitally encoded with the same pattern. The process involves periodically changing the phase of the signals of interest. FIG. 6-1 shows a sine wave signal that reverses its phase after N (N=3) complete cycles. The phases of this signal are +, −, −, and +. The synchronous detection reference signal is made up by repeating this pattern. The integration of any product of an acquired signal with this reference will integrate to near zero over each section if it is not close to the reference frequency over that band. If it is equal to the reference frequency and at some arbitrary phase, then the integral over each segment of length N will result in the same magnitude; however the signs of the integral will be opposite over the + phase and − phase of the reference. The sum of the integrals over each section (e.g., the integral over the whole length of the reference waveform.) will be zero, due to the opposite signs on the individual sections. The continuous signal will therefore not affect the measurement of the encoded signal. This technique reduces the effect of non encoded noises. In addition it can also reduce the effect of time delayed encoded signals. For instance if the acquired signal is delayed in time by the length of one of the segments then the integral over the whole waveform length will be zero; however, if the acquired signal is delayed by the length of two segment periods then the integral will be −1 times the non delayed integral of the same signal. FIG. 6-2 shows the values for the integral over one whole waveform period for delays equal to an integer number of segment periods for the reference pattern shown in FIG. 6-1. FIGS. 6-3, 6 - 4 , and 6 - 5 show the integral values for more practical encoding patterns of 19 , 20 , and 22 segments in length. The waveforms in FIGS. 6-3 and 6 - 4 have non zero but greatly reduced continuous signal integral values of 0.0526 and −0.1 respectively. These patterns have better localization of the delayed encoded pattern integrals than the 4 segment pattern. The waveform in FIG. 6-5 has both a zero continuous integral and well localized delayed encoded pattern integrals. There are variations of this technique that can be applied. The phases between segments can be stepped in other than +or −180 degree steps, such as: 90 degree or 60 degree steps. The segment lengths need not be the same length. This technique can be applied to multiple frequencies, with each frequency having different encoding patterns and different segment periods to obtain the best elimination of unwanted signals at each particular frequency. 7. Methods of Increasing the Ability of Magnetic Field Sensors to Detect Small Signals in the Presence of Large Background Signals The detection of small fields is frequently limited by the saturation of the initial amplifier's stages. In order to detect a small signal the gain of the first amplifier stages must be high enough to bring the signal above the amplifier noise. If the background or system offset signals are large with respect to the small signal to be detected, then amplifier saturation will result. This is a problem in both direct field and gradient systems. If the direct signal saturates before the gradient calculation can be performed then the information is also lost, even if the gradient calculation would have removed the large background or system offset signals. This problem still exists in the case of the ac magnetic field system with magnetic field sensor placed in a position with respect to the transmitter. The signal seen by the sensor is not always in phase or 180 degrees out of phase with the transmitter signal and therefore cannot be completely zeroed by position adjustments of the sensor. This is due to capacitive coupling between the system and the sensor, capacitive coupling between the sensor and the external environment, material responses within the system, or material responses of the background in the external environment to site a few causes. These items can have major phase components at 90 degrees to the transmitter signal. Methods according to the present invention can help resolve these issues. Such methods consist of a local magnetic field generation system for nulling the signal at the sensor. This system should be capable of being phased locked to the transmitter signal with the arbitrary phase and magnitude necessary to produce a cancellation field to zero the sensor signal. The preferred method would be to measure the sensor response with a small transmitter signal and measure and/or to calculate the cancellation signal at this level. The cancellation signal would be based on the transmitted signal level and adjusted for the magnitude of the transmitted signal. FIG. 7-1 shows one type of system that could be used. In this system the signal used to drive the transmitter amplifier is also passed to a signal processor which uses this signal to generate the signal to be passed to the nulling amplifier which in turn generates a field to zero the sensor output. In this manner the correct phase and amplitude relationships can be maintained. It is also preferable to keep the cancellation field as local as possible so as not to generate responses in the other sensors within the system. The nulling signal need not be magnetic; it could be capacitively coupled or directly injected into the sensor as a voltage or current. In this method the effect of the background magnetic field seen by the field sensor could be eliminated and the gain increased to facilitate the detection of small signals. In the case of gradient systems, the preferred implementation would use individual nulling signals for each primary sensor to insure that they do not saturate before the gradient calculation is made.

The present invention provides systems and methods which can be employed to locate or detect presence of various materials, including nonferrous metals. These systems include new and useful sensors, circuits, systems and devices which power and/or interoperate with the sensors, and methods of making, operating and using such systems. Any or all of the systems, devices or processes can be combined with other systems, devices or processes disclosed.

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display (LCD) device and a forming method of the plate electrodes thereof, and more specifically, to an LCD device and a forming method of the plate electrodes, utilizing forming a corresponding couple capacitor in a sub-pixel unit to adjust the voltage on the electrode plates for correcting the voltage-transmittance characteristic curve (V-T curve) of the sub-pixel unit, resulting in the elimination of color tracking effects. [0003] 2. Description of the Prior Art [0004] In a liquid crystal display (LCD) device, the transmittance of the liquid crystal panel is determined in accordance with the polar vector of light that is controlled via an upper polarizer, a lower polarizer, and a liquid crystal layer. Because of physical characteristics of the liquid crystal, when light passes through the liquid crystal layer, the phase of the light is delayed, so the direction of polarization of the light is variant, and results in different transmittance. This means that when a fixed voltage is applied on two sides of the liquid crystal layer, light with different wavelengths corresponds to different transmittance after passing through the liquid crystal layer and the polarizers. [0005] For a vertical aligned LCD device, the voltage-transmittance characteristic curve (V-T curve) is different with different wavelengths of light; therefore, for trichromatic colors R, G, and B, the corresponding V-T curves are different. Consequently, when the voltage between two sides of the liquid crystal layer is adjusted to regulate the gray-level value of the LCD device, due to the V-T curves of trichromatic colors R, G, and B being different, the mixing ratio of the trichromatic colors R, G, and B is also different, resulting in the named color tracking effect. [0006] Please refer to FIG. 1 . FIG. 1 is a voltage-transmittance characteristic curve of trichromatic colors R, G, and B in a vertical aligned liquid crystal display device according to the prior art. The horizontal axis represents the voltage applied across the liquid crystal layer, the vertical axis represents normalized transmittance, and the V-T curves 10 , 15 , 20 correspond to blue light, green light, and red light respectively. As shown in FIG. 1 , when the voltage between two sides of the liquid crystal layer is from 2 volts to 6 volts, the transmittance of blue, green, and red light is different, causing the color tracking effect. For example, if the voltage applied across two sides of the liquid crystal layer is 5.5 volts, the ratio of transmittance for red, green, and red light is approximately 1:1:1, and a pure white light is obtained. However, if the voltage applied across two sides of the liquid crystal layer is reduced to 3 volts, the brightness is decreased, and the ratio of transmittance for red, green, and red light becomes 7:7:12 approximately, therefore the original pure white light turns a little blue. As described above, the color tracking effect reduces display performance of related, vertical aligned LCD devices. SUMMARY OF THE INVENTION [0007] The objective of the claimed invention is to provide a liquid crystal display (LCD) device and a forming method of the plate electrodes that utilizes electrode plates and a dielectric layer to form a proper couple capacitor in a sub-pixel unit to adjust the V-T curve of the sub-pixel unit to solve the above-mentioned problems. [0008] According to an embodiment of the claimed invention, a forming method of the electrode plates is disclosed. The method includes positioning one or more lower plate electrodes, one or more conductive layers, and a dielectric layer, floating the lower plate electrodes, electrically connecting the conductive layers to one port of a thin-film transistor (TFT), and positioning the dielectric layer between the conductive layers and the lower plate electrodes; utilizing the conductive layers, the dielectric layer, and the lower plate electrodes to form a couple capacitor, and adjusting the capacitance of the couple capacitor to control the voltage on the lower plate electrodes. [0009] According to an embodiment of the claimed invention, a forming method of an LCD device is disclosed. The method includes setting a plurality of sub-pixel units; setting one or more first liquid crystal layers, one or more first upper plate electrodes, one or more first lower plate electrodes, one or more first conductive layers, and a first dielectric layer in a first sub-pixel unit, positioning the first liquid crystal layer between the first upper plate electrodes and the first lower plate electrodes, floating the first lower plate electrodes, positioning the first conductive layers on one side of the first lower plate electrodes, electrically connecting the first conductive layers with one port of a first TFT, and positioning the first dielectric layer between the first conductive layers and the first lower plate electrodes; utilizing the first conductive layers, the first dielectric layer, and the first lower plate electrodes to form a first couple capacitor, and adjusting the capacitance of the first couple capacitor to control the voltage on the first lower plate electrodes, causing the first sub-pixel unit to possess a predetermined voltage-transmittance characteristic curve (V-T curve); setting a second liquid crystal layer, one or more second upper plate electrodes, one or more second lower plate electrodes, one or more second conductive layers, and a second dielectric layer in a second sub-pixel unit, positioning the second liquid crystal layer between the second upper plate electrodes and the second lower plate electrodes, floating the second lower plate electrodes, positioning the second conductive layers on one side of the second lower plate electrodes, electrically connecting the second conductive layers with one port of a second TFT, and positioning the second dielectric layer between the second conductive layers and the second lower plate electrodes; and utilizing the second conductive layers, the second dielectric layer, and the second lower plate electrodes to form a second couple capacitor, and adjusting the capacitance of the second couple capacitor to control the voltage on the second lower plate electrodes, causing the second sub-pixel unit to possess substantially the predetermined V-T curve. [0010] According to an embodiment of the claimed invention, an LCD device is disclosed. The device includes at least two sub-pixel units, the first sub-pixel unit including one or more first upper plate electrodes; one or more first lower plate electrodes, which are floating; a first liquid crystal layer, positioned between the first upper plate electrodes and the first lower plate electrodes; one or more first conductive layers, positioned at one side of the first lower plate electrodes and electrically connected with one port of a first TFT, the first conductive layers forming a first couple capacitor with the first lower plate electrodes to adjust the first sub-pixel unit to possess a predetermined V-T curve; and a first dielectric layer, positioned between the first conductive layers and the first lower plate electrodes; the second sub-pixel unit including one or more second upper plate electrodes; one or more second lower plate electrodes, which are floating; a second liquid crystal layer, positioned between the second upper plate electrodes and the second lower plate electrodes; one or more second conductive layers, positioned at one side of the second lower plate electrodes and electrically connected with one port of a second TFT, the second conductive layers forming a second couple capacitor with the second lower plate electrodes to adjust the second sub-pixel unit to possess the predetermined V-T curve substantially; and a second dielectric layer, positioned between the second conductive layers and the second lower plate electrodes; wherein the first and second couple capacitors correspond to different capacitances respectively. [0011] The claimed invention, a liquid crystal display (LCD) device and a forming method of the plate electrode thereof, adjusts the V-T curve of the sub-pixel unit via adjusting the capacitance of the couple capacitor. Therefore, by utilizing methods disclosed in the present invention to adjust the capacitance of the couple capacitor in the sub-pixel unit, voltages on the electrode plates in R, G, B, named trichromatic sub-pixel units are adjusted respectively. That is to say, when the voltage between two sides of the liquid crystal layer is adjusted to regulate the gray-level value of the LCD device, due to the voltage dividing effect of the couple capacitor, the actual voltage drop on the electrode plate is changed. Through proper adjustment, the transmittance of R, G, and B sub-pixel units remains 1:1:1, therefore the known color tracking effect is eliminated. [0012] These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 is a voltage-transmittance characteristic curve of trichromatic colors R, G, and B in a vertical aligned liquid crystal display device according to the prior art. [0014] FIG. 2 is a diagram of a liquid crystal display device according to the present invention. [0015] FIG. 3 is a structure diagram of the liquid crystal display device and the electrode plate thereof shown in FIG. 2 . [0016] FIG. 4 is a sectional drawing along a cut line 3 ′- 3 ′ of the liquid crystal display device and the electrode plate thereof shown in FIG. 3 . [0017] FIG. 5 is an effective circuitry of the sub-pixel unit shown in FIG. 2 . [0018] FIG. 6 is a voltage-transmittance characteristic curve of trichromatic colors R, G, and B according to the present invention. DETAILED DESCRIPTION [0019] Please refer to FIG. 2 . FIG. 2 is a diagram of a liquid crystal display (LCD) device 100 according to the present invention. The LCD device 100 (for example, a vertical aligned LCD device) includes a plurality of pixel units 102 a - 102 d aligned as a matrix, where every pixel unit 102 a , 102 b , 102 c , and 102 d respectively includes a plurality of sub-pixel units. For example, there are three sub-pixel units 105 a , 105 b , and 105 c positioned in pixel unit 102 a , corresponding to trichromatic colors R, G, and B respectively. The pixel unit 102 a corresponds to a desired color through controlling the brightness of red light, green light, and blue light outputted from the sub-pixel units 105 a , 105 b , and 105 c . Please refer to FIG. 3 . FIG. 3 is a structure diagram of the sub-pixel unit 105 a and the electrode plate thereof shown in FIG. 2 . In the following disclosure, only structural components of the sub-pixel unit 105 a that are relevant to the present invention are illustrated and described, for the purposes of clarity and simplicity. In the embodiment, the sub-pixel unit includes a gate line 110 connected to the gate port of a thin-film transistor (TFT) 115 , wherein the function of the TFT 115 is a switch, the drain port and the source port of the TFT 115 are two ends of the switch respectively, and the gate line 110 transmits a gate voltage to control the TFT 115 conducting the drain port and the source port to turn on the switch. The drain port of the TFT 115 is connected to a data line 120 for receiving a voltage signal for controlling a gray-level value of the sub-pixel unit 105 a . The source port of the TFT 115 is connected to a lower plate electrode 125 and a conductive layer 130 via a through hole, therefore, in the TFT 115 , when the drain port is conducting to the source port, the voltage signal for controlling the gray-level value is transmitted to the lower plate electrode 125 and the conductive layer 130 through the source port of the TFT 115 . [0020] The sub-pixel unit 105 a further includes a plurality of floating lower plate electrodes 135 , 136 that are not connected with other conductive layers, where lower plate electrodes 125 , 135 , and 136 form an electrode plate. Please note that there are three lower plate electrodes 125 , 135 , and 136 illustrated in FIG. 3 , however, in a practical condition, the number of lower plate electrodes in the sub-pixel unit 105 a is not limited, and is adjustable according to a real requirement. The operation principle is described as follows. Note that the conductive layer 130 is not at the same level as the electrode plates described above (i.e. lower plate electrodes 125 , 135 , and 136 ). Please refer to FIG. 4 . FIG. 4 is a sectional drawing along a cut line 3 ′- 3 ′ of the sub-pixel unit 105 a and the electrode plate thereof shown in FIG. 3 . As illustrated by FIG. 4 , there is a dielectric layer 205 positioned between the conductive layer 130 and the lower plate electrode 135 , additionally, a liquid crystal layer 215 and an upper plate electrode 216 are positioned on the lower plate electrodes 135 and 125 , wherein the liquid crystal layer 215 includes a plurality of liquid crystal molecules and the upper plate electrode 216 is used as a common electrode COM. It is well known that the sub-pixel unit 105 a further includes polarizers and color filters; as these components are not related to the technical features in the claimed invention, the structure and function of these components are not described in the specification. Please note that the liquid crystal layer 215 is the same as other liquid crystal layers installed in well-known LCD devices. The lower plate electrodes 125 , 135 and the upper plate electrode 216 can be transparent conductive layers by utilizing ITO or IZO as materials, and the conductive layer 130 is allowed to use opaque and conductive materials, such as metal. [0021] Please refer to FIG. 3 , FIG. 4 and FIG. 5 . FIG. 5 is an effective circuitry of the sub-pixel unit 105 a shown in FIG. 2 . The capacitor 315 is an effective capacitor formed by the lower plate electrode 125 and the electrode at the other side of the liquid crystal layer 215 (i.e. the upper plate electrode 216 ) when a voltage signal is transmitted from the source port of the TFT 115 to the lower plate electrode 125 , wherein the liquid crystal layer 215 is the dielectric layer of the capacitor 315 . The couple capacitor 320 is an effective capacitor formed by the conductive layer 130 and the floating lower plate electrodes 135 , 136 when a voltage signal is transmitted from the source port of the TFT 115 to the conductive layer 130 , wherein the dielectric layer 205 is the dielectric layer of the couple capacitor 320 . The capacitor 325 is an effective capacitor formed by the floating lower plate electrode 135 and the electrode at the other side of the liquid crystal layer 215 (i.e. the upper plate electrode 216 ), wherein the liquid crystal layer 215 is the dielectric layer of the capacitor 325 . Lastly, the storage capacitor 310 is an effective capacitor formed by other elements of the sub-pixel unit 105 a . According to the description above, the couple capacitor 320 is connected in series with the capacitor 325 and then connected in parallel with the capacitor 315 and the storage capacitor 310 . This is because the couple capacitor 320 formed by the conductive layer 130 and the floating lower plate electrodes 135 , 136 causes a voltage dividing effect, so the capacitance of the couple capacitor 320 influences the voltage actually dropping on two sides of the capacitor 325 , and therefore the status of the liquid crystal layer 215 will be changed. Consequently, the voltage-transmittance characteristic curve (V-T curve) of the sub-pixel unit 105 a is adjustable, and the operation principle is described below. [0022] Two extreme conditions are considered; the first condition is: if the floating lower plate electrodes 135 , 136 are all replaced by the lower plate electrode 125 (i.e. all the electrode plates are constructed by the lower plate electrode 125 ), the layer below the liquid crystal layer 215 is formed by the lower plate electrode 125 completely. This causes the couple capacitor 320 and the capacitor 325 shown in FIG. 5 to disappear, and the voltage applied on the upper plate electrode 216 and the conductive layer 130 is the voltage across two sides of the liquid crystal layer 215 . In this condition, the V-T curve of the sub-pixel unit 105 a is shown in FIG. 1 . The second condition is: if the floating lower plate electrodes 135 , 136 replaces the lower plate electrode 125 completely (i.e. all the electrode plates are constructed by the lower plate electrode 135 , 136 ), then the capacitor 315 shown in FIG. 5 disappears. In this condition, the voltage applied on the upper plate electrode 216 and the conductive layer 130 equals the sum of voltages that drop on the couple capacitor 320 and the capacitor 325 respectively. In other words, the voltage actually applied on two sides of the liquid crystal layer 215 (i.e. the voltage drop across two sides of the capacitor 325 ) is less than the voltage applied on the upper plate electrode 216 and the conductive layer 130 . When the capacitance of the couple capacitor 320 increases, the voltage drop across two sides of the capacitor 325 decreases, meaning that the voltage actually applied on the liquid crystal layer 215 decreases. Then, the V-T curve corresponding to the sub-pixel unit 105 a shown in FIG. 1 shifts to the right, and the amount of shift is adjustable by controlling the capacitance of the couple capacitor 320 . If the lower plate electrode 125 and the floating lower plate electrodes 135 , 136 all exist, that is to say that the capacitor 315 , the couple capacitor 320 , and the capacitor 325 all exist, then the V-T curve of the sub-pixel unit 105 a combines with the V-T curves of the two extreme conditions discussed above. Therefore, the area ratio of the lower plate electrode 125 and the floating lower plate electrodes 135 , 136 influences the ratio of the V-T curves of two extreme conditions in a combined final V-T curve. [0023] In the embodiment, the sub-pixel unit 105 a corresponds to red light, and there is no conductive layer 130 positioned to form the couple capacitor 320 with the floating lower plate electrodes 135 , 136 . For the sub-pixel units 105 b , 105 c corresponding to green light and blue light respectively, the original V-T curve is adjustable by adding a suitable couple capacitor 320 (for example, shifting the V-T curve 10 , 15 shown in FIG. 11 to the right). The result is shown in FIG. 6 . FIG. 6 is a voltage-transmittance characteristic curve of trichromatic colors R, G, and B according to the present invention. As illustrated in FIG. 6 , when the voltage drops from 2 volts to 6 volts, three V-T curves 10 , 15 , 20 corresponding to blue light, green light, and red light respectively will nearly overlap. In other words, regardless of what the voltage value is, the transmittance ratio of trichromatic colors R, G, and B approaches 1:1:1, and therefore the well-known color tracking effect is eliminated. According to experiments, the best area ratio of the floating lower plate electrode (i.e. area sum of lower plate electrodes 135 , 136 ) and the electrode plate (i.e. area sum of lower plate electrodes 125 , 135 , and 136 ) in the sub-pixel units 105 a , 105 b , and 105 c corresponding to trichromatic colors R, G, and B respectively is: 0 (red light), 0.2 (green light), and 0.5 (blue light). Please note that the embodiment mentioned above discloses how to adjust the V-T curves of the sub-pixel units 105 b and 105 c corresponding to green light and blue light respectively, however, all V-T curves of the sub-pixel units 105 a , 105 b , and 105 c corresponding to red light, green light, and blue light are adjustable according to practical requirements, by setting proper couple capacitors to correct the transmittance ratio of trichromatic colors R, G, and B in the pixel unit 102 a approaching 1:1:1, this is also covered by the claimed invention. [0024] As mentioned above, adjusting the capacitance of the couple capacitor 320 in the sub-pixel unit 105 a can vary the voltage on the lower plate electrodes 135 , 136 to adjust the V-T curve. Therefore, the voltage on the lower plate electrodes 135 , 136 is adjusted through changing parameters listed below: [0000] (a) changing the shape, or area of the conductive layer 130 to adjust the capacitance of the couple capacitor 320 for controlling the voltage on the lower plate electrodes 135 , 136 ; [0000] (b) changing the shape, or area of the floating lower plate electrodes 135 , 136 to adjust the capacitance of the couple capacitor 320 for controlling the voltage on the lower plate electrodes 135 , 136 ; [0000] (c) changing the numbers of lower plate electrodes 135 , 136 positioned in the sub-pixel unit 105 a to adjust the capacitance of the couple capacitor 320 for controlling the voltage on the lower plate electrodes 135 , 136 ; [0000] (d) changing the material, or thickness of the dielectric layer 215 to adjust the capacitance of the couple capacitor 320 for controlling the voltage on the lower plate electrodes 135 , 136 ; and [0025] (e) adjusting areas of the lower plate electrodes 135 , 136 such that the area ratio compared to the electrode plate area (i.e. area sum of lower plate electrodes 125 , 135 , and 136 ) achieves a predetermined area ratio value, and the voltage on the lower plate electrode 135 , 136 is controlled by adjusting the predetermined area ratio value. [0026] In general, a pixel unit includes a plurality of sub-pixel units, taking the pixel unit 102 a in the embodiment for example, it includes sub-pixel units 105 a , 105 b , and 105 c , corresponding to three colors—red, green, and blue. However, it is possible to replace these colors with other colors; for this condition, the capacitance of the couple capacitor in a first sub-pixel unit (for example, 105 a ) is adjusted first to control the first sub-pixel unit possessing a predetermined V-T curve. The adjusting method is described above. Next, in the same pixel unit 102 a , the capacitance of the couple capacitor in a second sub-pixel unit is adjusted (for example, 105 b ) to control the second sub-pixel unit possessing the same V-T curve as the first sub-pixel unit. The adjusting method of the capacitance of the couple capacitor is also described above, but is allowed to differ from the adjusting method applied in the first sub-pixel unit. Other sub-pixel units are adjusted in turn, until all sub-pixel units included in the pixel unit 102 a possess substantially the same V-T curve. [0027] In short, the present invention, the LCD device 100 , includes a plurality of sub-pixel units. Taking the sub-pixel unit 105 a for example, floating lower plate electrodes 135 , 136 are utilized and a conductive layer 130 (electrically connected to one port of the TFT 115 ) is positioned at one side of the lower plate electrodes 125 , 135 , and 136 to form a required couple capacitor 320 . Therefore, the V-T curve of the sub-pixel unit 105 a can be adjusted by adjusting the capacitance of the couple capacitor 320 . In other words, through assistance of the couple capacitor 320 , the LCD device 100 disclosed in the claimed invention substantially eliminates the well-known color tracking effect. [0028] Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

A liquid crystal display device and a forming method of the electrode plate are disclosed. The forming method of the electrode plate includes providing one or more bottom plane electrodes, one or more conductive layers and a dielectric layer, floating the bottom plane electrodes, electrically connecting the conductive layers and an electrode of a thin film transistor, positioning the dielectric layer between the bottom plane electrodes and the conductive layers, utilizing the conductive layers, the dielectric layer and the bottom plane electrodes to form a coupling capacitor, and adjusting the capacitance of the coupling capacitor to control the voltage on the bottom plane electrodes. Therefore, the liquid crystal display device makes every sub-pixel have a predetermined voltage-transmittance characteristic curve by controlling the voltage on the bottom plane electrodes.

BACKGROUND OF THE INVENTION The invention described below relates to the field of automatic control of fluid flow, and it finds particular application in watering devices of the type used in lawn watering, gardening, and irrigation. In the course of watering lawns and home gardens, the problem is often encountered that the soil is such that it cannot absorb enough water to properly support the desired plant life. That is, sandy soils retain very little water, allowing most of it to flow through, while clay soils cause much of the water to run off. The solution to this problem is to water in a very slow manner, thereby supplying only the amount of water that can be retained or absorbed by the soil. In order to supply the water in this manner without constant human attention, devices have been employed in the past that automatically turn the water supply on and off, thereby providing water on a long-term basis but avoiding overwatering. When such devices are intended for the home market, it is important that they be simple, inexpensive, and unlikely to cause damage to the lawn or garden with which they are used. An example of an attempt to fulfill these requirements is described in Jones, U.S. Pat. No. 3,865,138, in which a solenoid-actuated value is controlled by a timer. That arrangement is relatively simple, but certain improvements may be desired. For instance, the use of an ordinary timer of the type normally available to the consumer is geared to the twenty-four-hour day so that water can be turned off and on a very limited number of times in an entire day. If such a device is timed to stay on for the approximate amount of time required to supply as much water as the ground can take, it will typically be on for a very short time, will then be turned off, and for the rest of the day will permit the ground to dry out. What would be more desirable would be a provision of a large number of relatively short on times throughout a day. However, such an arrangement would not be feasible with the type of inexpensive timer normally available. In addition, the provision of a timer, even a relatively inexpensive one, does add significantly to the cost of what should be a low-priced item. Finally, if the timer used with the Jones arrangement should malfunction and permit continuous operation of the watering throughout the day, a good deal of irreversible damage could conceivably be done to the garden. SUMMARY OF THE INVENTION Accordingly, the present invention is an apparatus that can inexpensively control fluid flow, allow a large number of short periods of flow each day, and avoid the danger of overwatering. According to the present invention, an automatically operated control valve includes a valve body including an inlet, an outlet and a flow passage providing fluid communication between the inlet and the outlet. A valve operating member is movably supported in the flow passage on the valve body for movement between an open position in which fluid is permitted to flow from the inlet to the outlet and a closed position in which fluid is prevented from flowing from the inlet to the outlet. Solenoid means are mounted on the valve body and include armature means movable between a first position and a second position. The armature means are operatively connected to the valve operating member for movement of the valve operating member between its closed and open positions when the armature means is operated between its first and second positions, respectively. The armature means is biased to the first position. The solenoid means also include coil means adjacent the armature means and operable upon current flowing through it in response to a potential difference applied across it to produce a magnetic field. The armature means is maintained in its second position by the magnetic field when a rated current flows through the coil. Thus, the valve operating member is maintained in the open position when the rated current flows through the coil means, and it is maintained in the closed position when no current flows through the coil means. Electric-circuit means adapted for application of a potential difference thereacross are electrically connected to the coil means for application of the potential difference across the coil means. Finally, thermostat means are electrically interposed in the circuit means to permit the application to the coil of potential difference applied across the circuit means when the temperature of the thermostat means is less than a predetermined minimum "off" temperature. The thermostat means prevent the application across the coil means of potential difference applied across the circuit means when the temperature of the thermostat means exceeds a predetermined maximum "on" temperature. The coil means is arranged in thermal communication with the thermostat means, the flow of current through the coil generating heat that is transferred to the thermostat means until it reaches a temperature that exceeds the maximum "on" temperature and the thermostat opens to prevent the application of the potential difference across the coil means. The thermostat means, upon cooling below the minimum "on" temperature when no current is flowing through the coil, closes to permit application of the potential difference across the coil means. The valve body may include a valve seat in the flow passage that bounds an orifice through which fluid in the flow passage must flow to pass from the inlet to the outlet. The valve operating member would then include a valve disc having a seating surface shaped for seating on the valve seat and movable between a closed position in which it seats on the valve seat, thereby blocking the orifice and preventing flow of fluid therethrough, and an open position in which it is spaced from the valve seat, thereby permitting flow of fluid through the orifice. The armature means is operatively connected to the valve disc for positioning of the disc in its closed and open positions when the armature is in its first and second positions, respectively. The valve body preferably forms an opening that provides fluid communication between the passage means and the exterior of the valve body, and the valve operating member includes a flexible diaphragm secured at its outer perimeter to the valve body about the perimeter of the opening. The diaphragm thereby blocks the opening. The disc includes a part of the diaphragm located interior to the outer perimeter of the diaphragm and movable between the first and second positions of the disc while the outer perimeter of the diaphragm remains stationary at the perimeter of the opening. Conveniently, the solenoid means further includes housing means housing the armature means and mounted on the valve body, the armature means being movable in the housing means between the first and second positions, and spring means mounted in the housing means between the armature means and the housing means to bias the armature means to the first position. As a fail-safe feature, the coil can be arranged to burn out when the rated current has flowed through the coil for at most a prohibited "on" duration, thereby preventing flow of fluid through the flow passage for a length of time greater than the prohibited "on" duration. Additionally, the flow passage can include a passage extension downstream on the valve operating means, the valve body forming a second opening that provides fluid communication between the passage extension and the exterior of the valve body. A Venturi insert means removably mounted in the passage extension can be provided to reduce the cross-sectional area of the passage means upstream of the opening, thereby increasing the velocity of fluid flowing through the passage extension and causing suction at the second opening for drawing fluid from the exterior of the valve body through the second opening to the passage extension. The thermostat means includes a pair of contacts interposed in the circuit means. The pair of contacts is closed when the temperature of the thermostat means is less than the minimum "off" temperature, thereby permitting current to flow through the pair of contacts and the coil. The contacts are open when the temperature of the thermostat means is greater than the maximum "on" temperature, thereby preventing current flow through the pair of contacts and the coil. BRIEF DESCRIPTION OF THE DRAWINGS These and further features and advantages of the present invention are described in connection with the attached drawings, in which: FIG. 1 is a vertical elevation of the automatic control valve of the present invention and a Venturi insert that may be used with it; FIG. 2 is a somewhat simplified cross-sectional view of the automatic control valve of FIG. 1; FIG. 3 is a simplified view of the automatic control valve in its open position; and FIG. 4 is a simplified view similar to FIG. 3 showing a Venturi insert in place for use of the automatic control valve as an applicator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The automatic control valve of the present invention, indicated generally by reference numeral 10, includes a valve body 14 having a T section that includes a vertical section 22 and a horizontal section 16. Section 16 terminates in an outlet 17, while the vertical section 22 terminates in a cap 24 that is connected to it. The valve body 14 includes an inlet portion 12 shown to the left of FIG. 1. Fluid communication is provided between the inlet 12 and the outlet 17 by passage means described below. A solenoid including a solenoid housing 32 and a handle 30 is provided with a bracket 28 on its upper surface that is fastened to the valve body by means of a bolt 26 that extends through a fastening plate 52 and engages the valve body 14. At its lower end and to the right in FIG. 1, the solenoid housing 32 extends into a hollow tongue 34 that is penetrated by leads 36 and 38. The leads extend through the hollow interior of the tongue 34 to either end of a coil mounted inside the housing 32. One of the leads 36 is electrically connected to a thermostat assembly 44 that is mounted on the solenoid housing 32 fitting snugly in a seal 46. The thermostat assembly 44 includes a thermostat electrically interposed between leads 36 and 42. Lead 42 joins lead 38 in a cable 40, which is suitably terminated by means not shown for the application of voltage to the solenoid. Application of a potential difference across leads 38 and 42 causes current to flow through lead 38, the coil, lead 36, the thermostat, and back through lead 42 when the thermostat switch is closed. As can be seen most clearly in FIG. 2, an armature housing 48 is secured to the valve body 14 by plate 52, which has a hole in its center to receive the armature housing 48. The interior of the automatic control valve 10 is shown in FIG. 2, in which the inlet region 12 is shown as being internally threaded and communicating with a first portion 56 of the internal passage means of the automatic control valve. The passage portion 56 continues into a generally annular passage region 62 oriented vertically within the valve body 14. The vertical annular region 62 is also indicated by reference numeral 88, which indicates the right-hand portion of the cross section of the vertical annular region 62. The inner surface of the vertical annular region 62 is defined by a downwardly projecting flange 64 formed in the valve body 14. A vertical passage region 58 is located interior to the downwardly extending flange 64 and communicates with a horizontal continuation 60 of the passage means. In order to flow from the portion 56 to the portion 60 of the passage means, it is necessary for fluid to flow through the circular orifice that is bounded by the lower edge of the downwardly projecting flange 64. As shown in FIG. 2, this flow is prevented by a valve operating member that comprises a diaphragm 87 whose shoulders abut the lower edge of the downwardly projecting flange 64 to prevent the passage of fluid from the vertical annular space 62 to the vertical space 58. The circumferential rim 86 of the diaphragm 87 is secured in a counterbore of the valve body 14 by an annular flange that forms the upper edge of the armature housing 48. Thus, the outer perimeter of the diaphragm 87 is held stationary at the perimeter of the opening in which the housing 48 is mounted. The diaphragm is stiffened interiorly to form a valve disc by an inverted-funnel-shaped brass member 66 embedded in it, and the lower edge of the downwardly projecting flange provides a seating surface for the valve disc. The diaphragm 87 is provided with an upwardly projecting circular portion that is receivable in the vertical passage 58 when the diaphragm 87 occupies the closed position shown in FIG. 2. At the center of the diaphragm there is provided a passage penetrating the diaphragm 87 and having a relatively small diameter. On its lower side the diaphragm forms a cone-shaped recess. The apex of the cone-shaped recess is aligned with the axis of the passage formed through the diaphragm 87. The armature housing 48 is generally cylindrical in shape, having one end closed and the other, widened end open. The armature housing 48 serves as an enclosure for an armature 68 and a bias spring 82 that is mounted on the lower end of the armature housing 48 and presses against the lower end of the armature 68 to bias it in an upward position. The armature 68 has its upper end formed in a cone shape so as to substantially conform to the cone-shaped recess of the diaphragm 87 for reception in it. The armature 68 is supported within the armature housing 48 so as to be movable between the position shown in FIG. 2 and a second position, in which it is held against the bias force from bias spring 82 by the action of the magnetic field provided by a coil 84 surrounding the armature. In the first position, shown in FIG. 2, the armature 68 holds the diaphragm in the opening formed at the bottom of the downwardly projecting flange 64 so as to block the passage formed by portions 56, 62, 58, and 60. In its second position, shown in FIG. 3, the diaphragm 87 permits flow through the passage because it is spaced from the opening formed by the flange 64. As FIG. 2 shows, the solenoid housing 32 encloses a coil 84 that is shown schematically in FIG. 2. The coil surrounds the armature 68. Leads 78 and 80 that lead from the coil 84 correspond to leads 36 and 38 of FIG. 1. These are the two electrical ends of the coil 84. Lead 78 is attached to one of the thermostat contacts 74, while a third lead 76 leads from the other thermostat contact 72. Those familiar with thermostats will appreciate that the thermostat is a switch whose contacts are open in one range of temperatures and closed in another. According to the present invention, temperatures above a maximum "on" temperature will cause the contacts to remain open and prevent a flow of current through the coil 84 in response to a potential difference impressed across the ends of leads 76 and 80. Below a minimum "off" temperature the contacts will remain closed to allow current to flow through the coil. The design of the solenoid is such that application of "house current" (that is, standard domestic voltage) to the coil causes a rated current to flow through the coil. This rated current exceeds the amount needed to move the armature to its second position against the bias applied by bias spring 82. The diaphragm 87 is therefore shifted into the position shown in FIG. 3, in which the orifice formed by downwardly projecting flange 64 is not blocked. Fluid communication is therefore permitted between passage portions 62 and 58 to allow liquid to flow from the inlet 12 to the outlet 17. In operation, a suitable connector such as a male end of a garden hose is threadedly connected to the inlet 12 of the device, and another appropriate connector is applied to the outlet to lead to a water distributing device such as a sprinkler. A plug (not shown) in which cable 40 terminates is plugged into an electrical outlet, thereby applying voltage across the leads 42 and 38, which are represented in FIG. 2 by leads 76 and 80. Initially, the thermostat is in the closed position shown in FIG. 3, but the armature 68 is biased to the position shown in FIG. 2 before power is applied. When current begins to flow through coil 84, however, the resultant magnetic field attracts the armature 68, which is pulled against the force from bias spring 82 to its second position. When this happens, the water pressure in the annular space 62 causes the diaphragm to move away from the opening at the bottom of the vertical passage 58, the small-diameter opening in the center of the diaphragm permitting air to flow from the interior of the armature housing 48 for pressure equalization. With the diaphragm 87 no longer blocking the orifice, a flow of water is permitted from the inlet 12 of the valve means to the outlet 17. Due to the presence of the cap 24 on the vertical part of the T section, water cannot escape from the vertical passage 90 through its lower end, so the flow is from inlet 12 to outlet 17. The resistance of coil 84 is such that a substantial amount of heat is liberated when a current flows through coil 84 that is sufficient to hold the armature in its second position. The thermostat 44 is arranged in close proximity to the coil for thermal communication between the coil 84 and the thermostat 44. That is, heat is effectively transferred from the coil to the thermostat. The result is that the thermostat 44 heats up in a relatively short time to a temperature at which the thermostat opens and interrupts the flow of current to the solenoid. This deenergizes the solenoid and permits the bias spring 82 to move the armature 68 back to its first position, in which it blocks the orifice at the base of the downwardly extending flange 64. The flow of water through the passage means comprising portions 56, 62, 58, and 60 is thereby stopped. In addition to permitting the collapse of the magnetic field that holds the armature 68 against the bias spring 82, the interruption of current through the coil 84 stops the resistive dissipation in the coil, and this allows the coil to cool down. The cooling of the coil 84 ultimately also permits cooling of the thermostat to a temperature below the minimum at which the thermostat contacts close. When terminals 72 and 74 are reconnected, the solenoid is energized as before to again permit water to flow through the passage means that includes portions 56, 62, 58, and 60. Those skilled in the art will recognize that the cycle time and duty cycle of such a device can be selected through proper selection of the solenoid, the thermostat, and the thermal connection between them. For example, the cycle time could be 5 minutes with an on-time of one minute to result in a duty cycle of 20%. Of course, ambient temperatures would have an effect on the cycle time and duty cycle, but the device would normally be used in a rather limited range of ambient temperatures, so the desired watering conditions could be achieved to a reasonable approximation. In the preferred embodiment of the present invention, the coil 84 is so chosen that it will burn out if it is energized continuously for any extended period of time such as, say, fifteen minutes. There would typically be a prohibited "on" duration at which the coil would burn out at the lowest expected ambient temperature, the time required for burnout being somewhat less at higher ambient temperatures. This is a particularly advantageous feature since it is normally quite a bit less desirable to have one day's overwatering than it is to have one day's underwatering. If the thermostat should malfunction so as to stay closed, overwatering would not result because the coil would be continuously energized for a time period long enough to burn it out so as to return the armature to the first position in which it causes the diaphragm to block the opening at the base of the downwardly extending flange 64. As a result, harmful overwatering is avoided. In view of the foregoing discussion, it can be seen that the coil 84 is used to significant advantage by being provided in such a manner as to provide several functions in a single element. The first function, of course, is to provide the force for the unblocking of the fluid passage. The second function is to provide a time base for the cycle time and the duty cycle by heating up during its energized period. Its third function is to act as a failsafe mechanism, burning out if there is a defect that would otherwise cause overwatering. Among the advantages of the device described above is its simplicity and low cost, factors which are contributed to substantially by the use of the solenoid coil 84 for several functions. This multi-function characteristic of the device is carried further by the arrangement of the T section, which includes horizontal section 16 and vertical section 22. This T section is provided so as to permit it to receive a Venturi insert 18 (FIG. 1) that has an orifice 20. Orifice 20 registers with the upper opening of the vertical passage 90 (FIG. 2) when it is inserted in the horizontal passage 60. The purpose of the insert, as is seen in FIG. 4, is to provide a passage portion 92 of reduced diameter at the right end of passage portion 60. The Venturi insert 18 is meant for use when the cap 24 is removed and a vessel 94 is included. Vessel 94 is sealed with a top 96 that is adapted for sealing engagement with the vertical section 22. The top 96 has an opening 98 in its center aligned with the entrance to the vertical section 22 for communication between the interior of the vessel 94 and the interior portion 90 of the vertical section 22. A tube 100 is provided to lead from the opening 98 to a point near the bottom of the vessel. The tube 100 is sealed to the vessel top 96 so that fluid most pass through the tube 100 in order to flow from the vessel 94 interior to the interior 90 of the vertical section 22. When the device is arranged as shown in FIG. 4, flow of fluid through the main passage that includes portions 56, 62, 58, and 60 will also result in flow through the narrow portion 92 to the outlet 17. As is apparent, forcing the fluid to flow through the narrow portion 92 greatly increases its velocity, which reduces the pressure downstream of the portion 92 by well-known principles to provide suction to the interior 90 of the vertical section 22. This draws fluid from the interior of the vessel 94, causing the fluid to flow up through tube 100, opening 98, passage 90, and orifice 20 to join the main flow of fluid in the horizontal direction out the outlet 17. Thus, the area being watered or irrigated can, for instance, be fertilized at the same time if the vessel 94 contains liquid fertilizer. Operation of the device with the Venturi section can be performed substantially as described above, with the solenoid-thermostat combination providing an on-and-off sequence to afford the desired amount of watering. Alternately, the coil/thermostat assembly could be replaced by a permanent magnet having a shape similar to that of the coil housing 32 to keep the passage open for manual operation. Thus, the effective cost of the device is still further reduced because it is easily adapted for manual application of fertilizer or insecticide, thus avoiding the need to purchase other equipment.

A solenoid-operated flow-control valve includes a solenoid coil that burns out if energized continuously. The energized solenoid permits fluid to flow, while fluid flow is prevented when the coil is not energized. A thermostat is interposed in the coil circuit and arranged in thermal communication with the coil. While fluid is being allowed to flow, the thermostat heats up until it causes the flow to be interrupted. It then cools down until it again allows fluid flow. A cycling flow of fluid thereby results. A sticking thermostat fails safe because continuous energization of the coil causes it to burn out, thereby interrupting the flow of fluid.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of application Ser. No. 13/035,755, filed on Feb. 25, 2011, which claims priority to provisional application Ser. No. 61/309,389, filed on Mar. 1, 2010 and provisional application Ser. No. 61/385,637, filed on Sep. 23, 2010. The entire contents of the priority applications are hereby incorporated by reference and made a part of this disclosure. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to medical devices and methods. More particularly, the present invention relates to apparatus for accessing vascular lumens and methods for clearing vascular lumens of occlusive materials. [0004] Removing occlusive materials from the vasculature and other body lumens is the objective of many medical procedures. Obstructive materials in the vasculature include plaque, thrombus, embolus, clots, and fatty deposits. To remove such occlusive materials, catheters may be inserted into the occluded artery or vein for opening or removing the occlusive material. Of particular interest to the present invention, procedures commonly referred to as thrombectomy or embolectomy use a balloon-tipped catheter which is inserted into a blood vessel, either percutaneously or via a surgical cut down, where the balloon is advanced to a position distal to the obstructing material. After inflating the balloon, the catheter is drawn proximally to dislodge the material and remove it from the blood vessel. In some instances, a second sheath or catheter is introduced coaxially over the balloon-tipped catheter in order to apply suction and help remove the occlusive material before it is drawn out of the blood vessel. [0005] When performing such thrombectomy or embolectomy procedures, the balloon-tipped catheters and other auxiliary tools may be introduced through a sheath which is positioned through a percutaneous tissue tract to allow access to the blood vessel. In addition, other auxiliary sheaths and tubular catheters may be employed and other aspects of the thrombectomy, embolectomy, or other vascular procedures. [0006] While very effective, thrombectomy and embolectomy procedures sometimes have difficulty dislodging and removing certain occlusive materials from certain types of vessels. For example, the use of thrombectomy for removing plaque, clot and other occlusive buildups in arterio-venous grafts (AVG's) and arterio-venous fistulas (AVF's) can be particularly problematic. For example, a plug of occlusive materials frequently forms at the anastomosis site between the artery and vein, or artery and graft, and can be very difficult to remove. Moreover, the access sheaths and capture devices used in such procedures are not always optimal. [0007] For these reasons, it would be desirable to provide improved methods and apparatus for performing thrombectomy and embolectomy procedures. It would be particularly desirable if such catheters and devices could improve the capture of clot, plaque, and other occlusive materials from AVG's and AVF's. Improved sheaths and other auxiliary devices for performing those procedures and others would also be desirable. At least some of these objectives will be met by the inventions described below. [0008] 2. Description of the Background Art [0009] Thrombectomy devices employing aspiration are described in U.S. Pat. No. 6,292,633; U.S. 2002/0169436; U.S. Pat. No. 7,141,045; U.S. Pat. No. 7,033,344; U.S. Pat. No. 6,544,276; U.S. Pat. No. 7,578,830; U.S. Pat. No. 6,695,858; U.S. Pat. No. 6,210,370; U.S. Pat. No. 5,102,415; and U.S. Pat. No. 5,092,839. Catheters and sheaths having self-expanding regions are described in U.S. 2010/0131000; U.S. 2007/0135832; U.S. Pat. No. 7,799,046; U.S. Pat. No. 7,410,491; U.S. Pat. No. 6,511,492; U.S. Pat. No. 6,159,230; and U.S. Pat. No. 5,971,938. SUMMARY OF THE INVENTION [0010] One embodiment of the present radially collapsible and expandable sheath is configured for introducing an intravascular device into a patient's vasculature through a percutaneous access site. The sheath comprises an elongate, elastomeric, tubular casing including an inner layer and an outer layer defining an annular space therebetween. The casing has a distal end. The sheath further comprises an elongate wire. At least a portion of the wire occupies the annular space and forms a helix around the casing inner layer. The helix includes a plurality of coils. A distally directed force applied to the wire decreases a pitch between adjacent ones of the coils and radially expands the helix and the casing. A proximally directed force applied to the wire increases the pitch between adjacent ones of the coils and radially contracts the helix and the casing. [0011] One embodiment of the present radially collapsible and expandable intravascular device is configured for removing a thrombus from a patient's vasculature through a percutaneous access site. The device comprises an elongate tubular catheter having a distal end. The device further comprises an elongate, elastomeric, tubular casing surrounding at least a portion of the catheter. The casing is secured to the catheter at or near the catheter distal end. The device further comprises an elongate wire. At least a portion of the wire occupies a space between the catheter and the casing and forms a helix around the catheter. The helix includes a plurality of coils. A distally directed force applied to the wire decreases a pitch between adjacent ones of the coils and radially expands the helix and the casing. A proximally directed force applied to the wire increases the pitch between adjacent ones of the coils and radially contracts the helix and the casing. [0012] One embodiment comprises a system for removing a thrombus from a patient's vasculature through a percutaneous access site. The system includes the sheath described above in combination with the thrombus collection device described above. [0013] One embodiment of the present methods for emplacing a radially collapsible and expandable sheath into a patient's vasculature through a percutaneous access site comprises a sheath including an elongate, elastomeric, tubular casing including an inner layer and an outer layer defining an annular space therebetween. The sheath further comprises an elongate wire, at least a portion of the wire occupying the annular space and forming a helix around the casing inner layer, the helix including a plurality of coils. The method comprises puncturing the patient's skin and vasculature with a catheter delivery needle in order to dispose a catheter within the patient's vasculature with a proximal end of the catheter protruding from the percutaneous access site. The method further comprises withdrawing the delivery needle. The method further comprises introducing the sheath, in a collapsed state, into the vasculature through a hollow lumen of the catheter. The method further comprises applying a distally directed force to the wire to decrease a pitch between adjacent ones of the coils and radially expand the helix and the casing so that the casing contacts interior walls of the vasculature. In certain embodiments, the method may further comprise applying a proximally directed force to the wire to increase a pitch between adjacent ones of the coils and radially collapse the helix and the casing. [0014] One embodiment of the present methods for extracting a thrombus from a patient's vasculature through a percutaneous access site using a radially collapsible and expandable thrombus collection device comprises the device including an elongate tubular catheter having a distal end, an elongate, elastomeric, tubular casing surrounding at least a portion of the catheter. The device further comprises an elongate wire, at least a portion of the wire occupying a space between the catheter and the casing and forming a helix around the catheter, the helix including a plurality of coils. The method comprises emplacing a percutaneous introducer sheath into the patient's vasculature. The method further comprises introducing the thrombus collection device, in a collapsed state, by passing it through the sheath and into the patient's vasculature. The method further comprises advancing the device through the patient's vasculature toward a location of the thrombus by applying a distally directed force to a portion of the catheter that protrudes from the percutaneous access site. The method further comprises continuing to apply the distally directed force to push a distal end of the device through the thrombus. The method further comprises advancing the device through the thrombus until the casing has completely passed through the thrombus. The method further comprises expanding the wire and the casing by applying a distally directed force to the wire while holding the catheter stationary until at least a proximal end of the casing contacts an interior diameter of the vasculature. The method further comprises drawing the device back through the vasculature by applying a proximally directed force to the catheter while holding the wire stationary with respect to the catheter to maintain the casing in its expanded state. The method further comprises collecting the thrombus and trapping it within the space between the casing and the catheter as the device is drawn back. The method further comprises continuing to pull back on the catheter until the thrombus collection device reaches the distal end of the sheath. The method further comprises drawing the device through the sheath, together with the collected thrombus, until the device and the thrombus are completely extracted from the patient; and withdrawing the sheath from the percutaneous access site. [0015] Another embodiment of the present methods for extracting a thrombus from a patient's vasculature through a percutaneous access site using a radially collapsible and expandable sheath and a radially collapsible and expandable thrombus collection device comprises the sheath including an elongate, elastomeric, tubular casing including an inner layer and an outer layer defining an annular space therebetween. The sheath further comprises an elongate wire, at least a portion of the sheath wire occupying the annular space and forming a helix around the casing inner layer, the sheath helix including a plurality of coils. The thrombus collection device includes an elongate tubular catheter having a distal end, an elongate, elastomeric, tubular casing surrounding at least a portion of the catheter, and an elongate wire. At least a portion of the device wire occupies a space between the catheter and the device casing and forms a helix around the catheter, the device helix including a plurality of coils. The method comprises puncturing the patient's skin and vasculature with a catheter delivery needle in order to dispose a delivery catheter within the patient's vasculature with a proximal end of the delivery catheter protruding from the percutaneous access site. The method further comprises withdrawing the delivery needle. The method further comprises introducing the sheath, in a collapsed state, into the vasculature through a hollow lumen of the delivery catheter. The method further comprises applying a distally directed force to the sheath wire to decrease a pitch between adjacent ones of the sheath coils and radially expand the sheath helix and the sheath casing so that the sheath casing contacts interior walls of the vasculature. The method further comprises introducing the thrombus collection device, in a collapsed state, by passing it through the sheath and into the patient's vasculature. The method further comprises advancing the device through the patient's vasculature toward a location of the thrombus by applying a distally directed force to a portion of the device catheter that protrudes from the percutaneous access site. The method further comprises continuing to apply the distally directed force to push a distal end of the device through the thrombus. The method further comprises advancing the device through the thrombus until the device casing has completely passed through the thrombus. The method further comprises expanding the device wire and the device casing by applying a distally directed force to the device wire while holding the device catheter stationary until at least a proximal end of the device casing contacts an interior diameter of the vasculature. The method further comprises drawing the device back through the vasculature by applying a proximally directed force to the device catheter while holding the device wire stationary with respect to the device catheter to maintain the device casing in its expanded state. The method further comprises collecting the thrombus and trapping it within the space between the device casing and the device catheter as the device is drawn back. The method further comprises continuing to pull back on the device catheter until the thrombus collection device reaches the distal end of the sheath. The method further comprises drawing the device through the sheath, together with the collected thrombus, until the device and the thrombus are completely extracted from the patient. The method further comprises applying a proximally directed force to the sheath wire to increase a pitch between adjacent ones of the sheath coils and radially collapse the sheath helix and the sheath casing. The method further comprises withdrawing the sheath from the percutaneous access site. [0016] Another embodiment of the present introducer sheaths is configured for introducing an intravascular device into a patient's vasculature through a percutaneous access site. The sheath is elongate, tubular, and defines a sheath lumen. The sheath comprises a medial neck portion that flares outwardly to a wider bell portion at a distal end. The distal end of the bell portion is open. The neck portion and the bell portion comprise a compliant material. The bell portion of the sheath includes a wire that is encased within the compliant material. The wire supports the compliant material, maintaining the bell portion in its expanded shape when the sheath is unstressed. At a proximal end, the sheath includes a flush port that enables fluid to be injected and/or aspirated from the sheath lumen. Once deployed within the vasculature, a hemostasis valve at the proximal end of the sheath resists outflow of bodily fluids through the sheath. [0017] One of the present embodiments comprises a deployment apparatus for an introducer sheath. The deployment apparatus includes a tubular dilator that is a rigid or semi-rigid component configured to guide the deployment apparatus through a skin puncture and through the vasculature. The dilator includes a proximal handle, a conically shaped distal tip, and defines a lumen that extends between the proximal and distal ends. The lumen is configured to receive a guide wire to facilitate introduction of the dilator into a patient. The introducer sheath is disposed coaxially about the outside of the dilator. An outer sheath is disposed coaxially about the outside of the introducer sheath. The outer sheath radially compresses the bell portion, which facilitates introduction of the sheath into the patient. The outer sheath is a tearaway sheath that can be torn by hand. [0018] Another embodiment of the present methods comprises a method for deploying an introducer sheath in a patient's vasculature at a percutaneous access site using a deployment apparatus. The access site is prepared by puncturing the skin, any underlying tissue, and the vasculature with a needle. The operator then introduces a guide wire through the lumen of the needle, and withdraws the needle. The method further comprises the operator introducing the deployment apparatus into the vasculature through the puncture site using the guide wire. The operator advances the apparatus through the puncture site and the vasculature until a bell portion of the sheath is located entirely within the vasculature and a neck portion traverses the puncture site. The operator next removes a tearaway outer sheath from the deployment apparatus and pulls the outer sheath through the puncture site. The operator then removes a dilator of the apparatus. [0019] Another embodiment of the present intravascular devices is configured for removing a thrombus from a patient's vasculature through a percutaneous access site. The device comprises an aspiration catheter including an elongate body having a balloon at its distal end. The catheter body comprises a flexible material having sufficient rigidity to facilitate guiding the catheter through the vasculature from the proximal end. The body defines two radially spaced lumens that are not in fluid communication with one another. The first lumen is an aspiration lumen that extends from an aspiration connector at the proximal end of the catheter to a plurality of aspiration openings toward the distal end of the catheter. The second lumen is an inflation lumen that extends from an inflation connector at the proximal end of the catheter to the balloon toward the distal end of the catheter. The aspiration lumen has a larger diameter than the inflation lumen, and is configured for passage of thrombus. [0020] Another embodiment of the present methods comprises a method for percutaneously removing a thrombus from a patient's vasculature. The method comprises introducing an aspiration catheter into a patient's vasculature through an introducer sheath. The aspiration catheter is then advanced distally through the sheath, the vasculature, and the thrombus until a balloon of the catheter is disposed on the far side of the thrombus. A guide wire may be used to advance the catheter. The method further comprises connecting a syringe filled with inflation liquid to an inflation connector of the catheter. The operator depresses the syringe plunger to force the inflation liquid into the balloon through an inflation lumen. The operator inflates the balloon until it presses against the interior walls of the vasculature on the far side of the thrombus. The operator moves a stopcock to a position to prevent liquid flow through the inflation connector and disconnects the syringe from the stopcock. The operator removes the thrombus from the vasculature by using a combination of suction through the aspiration openings, and proximal movement of the inflated balloon across the thrombus. To do so, the operator connects a Luer stopcock to an aspiration connector and an empty syringe to the stopcock. To generate suction, the operator draws back on the syringe plunger with the stopcock in the closed position and then locks the plunger. The operator then draws the catheter out of the vasculature while simultaneously moving the stopcock to the open position, thereby exposing the vacuum in the syringe barrel to the aspiration lumen, generating suction that pulls pieces of the thrombus into the aspiration lumen through the aspiration openings. The operator continues to pull back on the aspiration catheter until all or substantially all of the thrombus has been pulled into the sheath. The operator then continues to pull back on the aspiration catheter to force the thrombus out of the vasculature through the sheath. [0021] Thus, in a first aspect of the present invention, a sheath comprises a tubular body having a proximal, a distal end, and an axial passage therethrough. The tubular body is formed at least partially from an elastomeric material so that it can be collapsed, be expanded to a fully open configuration where it has an open diameter, and be further expanded beyond the open diameter by applying a radially outward force to an internal surface of the tubular body. The sheath further comprises a self-expanding scaffold coupled to at least a portion of the tubular body. The self-expanding scaffold also has a collapsed configuration, an expanded diameter when free from external constraint, and a super-expanded diameter or width when subject to a radially outward inner force. The expanded diameter of the self-expanding scaffold will be at least as large as the open diameter of the tubular body, optionally being larger. In this way, the scaffold will be able to open the tubular body. For example, the scaffold could be present only at the distal end of the tubular body so that said distal end will remain open while the remainder of the tubular body could remain in a collapsed configuration. [0022] Optionally, the sheath will further comprise a shaft extending from the proximal end of the tubular body. In many instances, the shaft will comprise an extension of the scaffold. For example, the scaffold may be in the form of a helical coil where the shaft is an integral extension of the coil. That is, the shaft and coil may be formed from a single wire, filament, bundle or other structure where only a distal portion of the structure is formed into the coil to act as the scaffold while the remaining proximal portion of the structure can act as the shaft. [0023] In most instances, the scaffold will have a cylindrical geometry when expanded, but in other instances the scaffold may have a tapered geometry when expanded. For example, the scaffold may be configured so that it tapers to a more narrow configuration in the distal direction. In such instances, the scaffold can form the tubular body into a capturing element for withdrawing clot. [0024] In still other embodiments, the sheath may further comprise a catheter body where the sheath and scaffold are disposed over a distal end of the catheter body. Optionally, a shaft of the sheath may then extend through a lumen of the catheter body to allow selective opening and closing of the sheath over the catheter by translating the shaft forwardly or distally. [0025] In specific embodiments, the self-expanding scaffold may be embedded in a wall of the sheath. Alternatively, the self-expanding scaffold may be secured to an inner or outer surface of a wall of the sheath. In a still further alternative embodiment, the self-expanding scaffold may be disposed in an annular space formed or created in a wall of the sheath so that the scaffold can foreshorten as it expands without constricting or deforming the wall (other than any radial expansion that may occur). [0026] The sheath will have dimensions typical for medical sheaths. Typically, the tubular body will have an expanded diameter in the range from 3 Fr. to 24 Fr., the self-expanding scaffold will have a diameter in the range from 3 Fr. to 38 Fr. and the sheath will have a length in the range from 10 cm to 200 cm. [0027] In a further aspect of the present invention, methods for aspirating occlusive material from a patient's vasculature comprise providing a catheter including a shaft, an expandable member at a distal end of the shaft, and an aspiration port on the shaft proximal to the expandable member. The aspiration port is connected to an aspiration lumen extending to a proximal end of the shaft. The catheter is introduced to a blood vessel (including implanted grafts and created fistulas) so that the expandable member lies on a distal side of the occlusive material. The expandable member is then expanded, and the catheter is drawn proximal while aspirating through the lumen end port to remove the occlusive material from the vessel. The methods of the present invention may be used in any blood vessel, but will find particular use with peripheral blood vessels, arterio-venous grafts, arterio-venous fistulas, and the like. [0028] In the preferred embodiments, the catheter will consist of only a single balloon at a distal end of the catheter shaft and further preferably will consist of only a single aspiration port located proximally of the balloon, typically at a distance from 5 mm to 3 cm. Usually, the drawing and aspiration steps are performed simultaneously and are able together to remove substantially all the occlusive material. In other instances, however, some portion of the occlusive material will be drawn proximally without being aspirated through the port and lumen and will be removed from the vessel, graft, or fistula through an access sheath and/or a capturing catheter. BRIEF DESCRIPTION OF THE DRAWINGS [0029] FIG. 1 is a cross-sectional end view of one embodiment of the present radially collapsible and expandable introducer sheath, taken along the line 1 - 1 in FIG. 3 , and illustrating the sheath in a collapsed state; [0030] FIG. 2 is a cross-sectional side view of the sheath of FIG. 1 , taken along the line 2 - 2 in FIG. 3 ; [0031] FIG. 3 is an end/side perspective view of the sheath of FIG. 1 ; [0032] FIG. 4 is a cross-sectional side view of the sheath of FIG. 1 , taken along the line 4 - 4 in FIG. 5 , and illustrating the sheath in an expanded state; [0033] FIG. 5 is an end/side perspective view of the sheath of FIG. 4 ; [0034] FIG. 6 is a partial cross-sectional side view of the sheath of FIGS. 1-5 disposed in a patient's vasculature at a percutaneous access site; [0035] FIG. 7 is a side elevation view of one embodiment of the present collapsible and expandable thrombus collection device, illustrating the device in a collapsed state; [0036] FIG. 8 is an end/side perspective view of the device of FIG. 7 ; [0037] FIG. 9 is a side elevation view of the device of FIG. 7 , illustrating the device in an expanded state; [0038] FIG. 10 is an end/side perspective view of the device of FIG. 9 ; [0039] FIG. 11 is a partial cross-sectional side view of the sheath of FIGS. 1-6 in combination with the device of FIGS. 7-10 ; [0040] FIG. 12 is a partial cross-sectional side view of the device of FIGS. 7-10 disposed in a patient's vasculature during a thrombectomy procedure; [0041] FIG. 13 is a partial cross-sectional side view of the device of FIGS. 7-10 disposed in a patient's vasculature during a thrombectomy procedure; [0042] FIG. 14 is a partial cross-sectional side view of the device of FIGS. 7-10 disposed in a patient's vasculature during a thrombectomy procedure; [0043] FIG. 15 is a partial cross-sectional side view of the device of FIGS. 7-10 disposed in a patient's vasculature during a thrombectomy procedure; [0044] FIG. 16 is a cross-sectional side view of another embodiment of the present radially collapsible and expandable introducer sheath; [0045] FIG. 17 is a cross-sectional side view of another embodiment of the present radially collapsible and expandable thrombus collection device; [0046] FIG. 18 is a side elevation view of another embodiment of the present introducer sheath; [0047] FIG. 19 is a side elevation view of one embodiment of a deployment apparatus for the introducer sheath of FIG. 18 ; [0048] FIG. 20 is a side cross-sectional view of the deployment apparatus of FIG. 19 ; [0049] FIGS. 21-24 are side elevation views of one embodiment of steps for deploying the introducer sheath of FIG. 18 in a patient's vasculature at a percutaneous access site; [0050] FIG. 25 is a side elevation view of one embodiment of the present thrombus collection device having aspiration ports; [0051] FIG. 26 is a cross-sectional end view of the thrombus collection device of FIG. 25 , taken along the line 26 - 26 in FIG. 25 ; [0052] FIGS. 27 and 28 are side elevation views of the proximal portions and distal portions, respectively, of the introducer sheath of FIG. 18 and the thrombus collection device of FIG. 25 during one step of a percutaneous thrombus collection procedure; [0053] FIGS. 29 and 30 are side elevation views of the proximal portions and distal portions, respectively, of the introducer sheath of FIG. 18 and the thrombus collection device of FIG. 25 during another step of a percutaneous thrombus collection procedure; [0054] FIGS. 31 and 32 are side elevation views of the proximal portions and distal portions, respectively, of the introducer sheath of FIG. 18 and the thrombus collection device of FIG. 25 during another step of a percutaneous thrombus collection procedure; [0055] FIGS. 33 and 34 are side elevation views of the proximal portions and distal portions, respectively, of the introducer sheath of FIG. 18 and the thrombus collection device of FIG. 25 during another step of a percutaneous thrombus collection procedure; [0056] FIG. 35 is a side elevation view of the introducer sheath of FIG. 18 after withdrawal from a patient's vasculature during another step of a percutaneous thrombus collection procedure; [0057] FIG. 36 is a side elevation view of another embodiment of the present thrombus collection device having aspiration ports; [0058] FIG. 37 is a side elevation view of the introducer sheath of FIG. 18 and a Fogarty balloon catheter disposed in a patient's vasculature during a percutaneous thrombus collection procedure; [0059] FIG. 38 is a side elevation view of the introducer sheath of FIG. 18 and the thrombus collection device of FIGS. 7-10 disposed in a patient's vasculature during a percutaneous thrombus collection procedure; and [0060] FIG. 39 is a side elevation view of a standard balloon catheter introducer sheath and the aspiration catheter of FIG. 25 disposed in a patient's vasculature during a percutaneous thrombus collection procedure. DETAILED DESCRIPTION OF THE INVENTION [0061] The following detailed description describes the present embodiments with reference to the drawings. In the drawings, reference numbers label elements of the present embodiments. These reference numbers are reproduced below in connection with the discussion of the corresponding drawing features. The various embodiments of the present introducer sheaths, thrombus collection devices and associated methods now will be discussed in detail. These embodiments include the introducer sheaths and thrombus collection devices shown in the accompanying drawings, which are for illustrative purposes only. [0062] Some embodiments of the present introducer sheaths, thrombus collection devices and associated methods are described below with reference to the figures. These figures, and their written descriptions, indicate that certain components of the apparatus are formed integrally, and certain other components are formed as separate pieces. Components shown and described herein as being formed integrally may in alternative embodiments be formed as separate pieces. Components shown and described herein as being formed as separate pieces may in alternative embodiments be formed integrally. Further, as used herein the term integral describes a single unitary piece. [0063] FIGS. 1-6 illustrate one embodiment of the present radially collapsible and expandable sheath 20 . As shown in FIG. 6 , the sheath 20 is configured for passage into a patient's vasculature 22 (e.g. in a vein or artery, an arterio-venous fistula (AVF) or arterio-venous graft (AVG), or alternatively in a non-vascular location such as the peritoneal cavity or other bodily cavities or hollow anatomical structures) through an opening 24 at a percutaneous access site 26 . Once deployed as shown in FIG. 6 , the sheath 20 can be used as a conduit for introducing one or more intravascular devices into the patient's vasculature 22 . For example, and as discussed further below, in one embodiment the sheath 20 can be used to introduce a thrombectomy device. [0064] FIGS. 1-3 illustrate the sheath 20 in a collapsed or contracted state. FIGS. 4 and 5 illustrate the sheath 20 in an expanded state. An operator may readily expand and contract the sheath 20 in the radial direction to increase or decrease its internal diameter 28 , 28 ′, respectively. For example, the internal diameter 28 , 28 ′ may be increased for the passage of intravascular devices, and decreased to promote hemostasis at the percutaneous access site 26 , as discussed further below. [0065] With reference to FIGS. 1-3 , the sheath 20 comprises an elongate, elastomeric, tubular casing 30 . As shown in the cross-sectional views of FIGS. 1 and 2 , the tubular casing 30 includes an inner layer 32 and an outer layer 34 . The layers 32 , 34 define an annular space 36 between them. The annular space 36 receives a portion of an elongate wire 38 that an operator may manipulate to expand and contract the casing 30 , as described in detail below. [0066] With particular reference to FIG. 2 , a distal end 40 of the wire 38 is disposed within the annular space 36 at or near a distal end 42 of the casing 30 . In one embodiment, the distal end 40 of the wire 38 may be secured to the casing 30 . In an alternative embodiment, the distal end 40 of the wire 38 may be freely movable with respect to the inner layer 32 and the outer layer 34 . The distal end 40 of the wire 38 may include a blunt cap (not shown) to reduce the likelihood of the wire 38 puncturing the elastomeric casing 30 . [0067] Proximal of the wire 38 distal end 40 , the wire 38 forms a helix 44 . The helix 44 includes a plurality of coils 46 that wrap around the casing inner layer 32 beneath the casing outer layer 34 . The helix 44 extends to a proximal end 48 of the casing 30 where the wire 38 extends through an opening 50 in the casing 30 . As indicated by the break lines in FIGS. 2 and 3 , the wire 38 may have any desired length extending proximally of the casing 30 . As explained in further detail below, an operator may manipulate the proximal end of the wire 38 to force more of the wire 38 into the annular space 36 through the opening 50 , or to withdraw some of the wire 38 from the annular space 36 through the opening 50 . This manipulation expands and contracts the helix 44 and the casing 30 , as described below. [0068] As described above, the casing 30 may comprise a compliant material. As used herein, the term compliant should be understood to include at least the following properties: flexibility, elasticity, and collapsibility/expandability. Further, because the casing 30 is configured for use internally, the material is preferably biocompatible. Example materials for the casing 30 include silicone film, polyisoprene, TECOTHANE®, PELLETHANE®, and other materials having similar properties. [0069] The wire 38 preferably comprises a material that is flexible but incompressible. Further, because the wire 38 is configured for use internally, the material is preferably biocompatible. Example materials for the wire 38 include nickel-titanium (NiTi) alloys, stainless steel, polyether ether ketone (PEEK) and other materials having similar properties. [0070] Again, FIGS. 1-3 illustrate the sheath 20 in a collapsed or contracted state. In this state, a relatively small portion of the wire 38 is disposed within the annular space 36 . However, when the flexible but incompressible wire 38 is subjected to a compressive force applied proximally of the casing 30 , wire 38 is forced into the annular space 36 through the opening 50 where the wire 38 enters the casing 30 . As more wire 38 enters the annular space 36 , the wire 38 forms tighter and more closely-spaced coils 46 within the helix 44 , with the coils 46 having increasingly larger diameters, as shown in FIGS. 4 and 5 . The elastomeric nature of the casing 30 makes it readily expandable in the radial direction as the wire 38 forces it outward. Similarly, when the wire 38 is subjected to a tensile force applied proximally of the opening 50 , the coils 46 within the helix 44 relax and spread apart as wire 38 is drawn out of the opening 50 . Again, the elastomeric nature of the casing 30 makes it readily contractible in the radial direction as the radial support provided by the wire 38 diminishes. [0071] In the illustrated embodiment, the wire 38 is freely slidable within the annular space 36 with respect to the inner layer 32 and the outer layer 34 . Thus, as the wire 38 is forced into the annular space 36 through the opening 50 , the helix 44 slides against the inner and outer layers 32 , 34 to enable the casing 30 to expand without forming pleats between adjacent coils 46 . The expanded sheath 20 thus presents a relatively smooth inner diameter 28 ′ for easy passage of intravascular devices. However, in alternative embodiments the wire 38 may be secured to the casing 30 at one or more locations. [0072] As shown in FIGS. 2 and 4 , the inner and outer layers 32 , 34 of the casing 30 preferably converge at the proximal end 52 , and at the distal end 42 , thereby sealing the proximal and distal ends 42 , 52 of the annular space 36 . The inner and outer layers 32 , 34 may, for example, be formed integrally. The sealed proximal end 52 of the annular space 36 facilitates controlled insertion and withdrawal of the wire 38 through the opening 50 . The sealed distal end 42 of the annular space 36 resists movement of the wire 38 distally out of the annular space 36 . The sealed distal end 42 can also form a smooth, atraumatic leading edge of the casing 30 to facilitate transport of material into the distal opening of the sheath 20 while avoiding injury to blood vessel walls or other nearby anatomy. [0073] FIG. 6 illustrates the sheath 20 positioned in a patient's vasculature 22 through an opening 24 at a percutaneous access site 26 . The sheath 20 may be deployed in this configuration using, for example, a catheter (not shown). An operator may puncture the patient's skin 54 and vasculature 22 with a catheter delivery needle (not shown) in order to dispose the catheter within the patient's vasculature 22 with a proximal end of the catheter protruding from the percutaneous access site 26 , e.g. via the Seldinger technique or any other suitable access technique. The operator may then introduce the sheath 20 into the vasculature 22 through the catheter lumen and then withdraw the catheter over the sheath 20 , leaving the sheath 20 in the state shown in FIG. 6 . Alternatively, the operator can insert the sheath 20 over a guidewire emplaced via the Seldinger technique. For ease of insertion, the operator would typically introduce the sheath 20 in its collapsed state ( FIGS. 1-3 ). Upon emplacement, the operator may thereafter expand the sheath 20 to the configuration shown in FIG. 6 so that it achieves wall-to-wall apposition with the interior walls 56 of the vasculature 22 . The operator expands the sheath 20 by applying a distally directed force to the wire 38 as described above. Further expansion of the sheath 20 may facilitate removing thrombus from the vasculature 22 , as explained further below. [0074] Once the sheath 20 is emplaced as shown in FIG. 6 , it is configured to provide an access path to the vasculature 22 for various intravascular devices. In one procedure described below, the sheath 20 is used to introduce a device for removing a thrombus. The sheath 20 can be used as an introducer for any type of intravascular device. The example described below is not limiting. [0075] The expandable and contractible nature of the sheath 20 allows it to accommodate devices of various sizes. For example, the sheath 20 may be expanded to such an extent that it also radially expands the vasculature 22 , allowing for passage of a particularly large device or thrombus. Further, when another device is not disposed through the interior of the sheath 20 , the sheath 20 may be contracted to tighten the percutaneous access opening 24 . This contraction aids hemostasis, reducing the tendency of blood to flow outward from the percutaneous access opening 24 . The contraction can occur “automatically” without requiring action by the operator, resulting from the natural compliance and collapsibility of the sheath. The subcutaneous tissues surrounding the sheath 20 can exert sufficient pressure on the sheath 20 to contract the sheath and/or force it closed entirely, or otherwise force the sheath walls into close contact with any object(s) in the sheath lumen. When the intravascular procedure is complete, the operator may contract the sheath 20 and withdraw it from the percutaneous access opening 24 . The operator contracts the sheath 20 by applying a proximally directed force to the wire 38 as described above. [0076] FIGS. 7-10 illustrate one embodiment of the present radially collapsible and expandable thrombus collection device 60 . As described further below, the device 60 is configured to be inserted into a patient's vasculature through an introducer sheath that passes through an opening at a percutaneous access site. When inserted in a collapsed state, the device 60 can be advanced past the thrombus, expanded, and then drawn back to pull the thrombus away from the interior of the vasculature and trap the thrombus within the device 60 . As the expanded device 60 is withdrawn further, it pulls the thrombus proximally through the introducer sheath until it eventually exits the vasculature through the percutaneous opening. This procedure is described further below. [0077] FIGS. 7 and 8 illustrate the device 60 in a collapsed or contracted state. FIGS. 9 and 10 illustrate the device 60 in an expanded state. An operator may readily expand and contract the device 60 in the radial direction to increase or decrease its external diameter. For example, the external diameter may be decreased to enable the device 60 to pass freely through the introducer sheath. Once deployed in the vasculature, the external diameter may be increased to contact the interior diameter of the vasculature, thereby matching the diameter of a thrombus. [0078] With reference to FIGS. 7 and 8 , the thrombus collection device 60 comprises an elongate, elastomeric, tubular casing 62 . As shown in the side elevation view of FIG. 7 , the tubular casing 62 extends over a tubular catheter 64 from a distal end 66 of the catheter 64 to a point distal of an opening 68 in the sidewall of the catheter 64 . A space between the catheter 64 and the casing 62 receives a portion of an elongate wire 70 that an operator may manipulate to expand and contract the casing 62 , as described in detail below. While FIG. 7 is not a cross-sectional view, the catheter 64 and the wire 70 are shown beneath the casing 62 for clarity. [0079] With continued reference to FIG. 7 , a distal end 72 of the wire 70 is disposed at or near a distal end 66 of the catheter 64 . For clarity, a distal portion 74 of the wire 70 that is positioned on the far side of the catheter 64 is shown in hidden lines. In one embodiment, the distal end 72 of the wire 70 may be secured to the catheter 64 . In an alternative embodiment, the distal end 72 of the wire 70 may be freely movable with respect to the catheter 64 and the casing 62 . The distal end 72 of the wire 70 may include a blunt cap (not shown) to reduce the likelihood of the wire 70 puncturing the elastomeric casing 62 . [0080] Proximal of the wire distal end 72 , the wire 70 forms a helix 76 . The helix 76 includes a plurality of coils 78 that wrap around the catheter 64 beneath the casing 62 . The wire 70 extends past a proximal end 80 of the casing 62 and then through the opening 68 in the catheter 64 . The wire 70 extends through the interior of the catheter 64 proximal of the opening 68 , exiting through a proximal end of the catheter lumen. In an alternative embodiment, the catheter 64 may omit the opening 68 , so that the wire 70 is always disposed externally of the catheter 64 . Further, the wire 70 may have any desired length extending proximally of the casing 62 and/or catheter 64 . As explained in further detail below, an operator may manipulate the proximal end of the wire 70 to force the wire 70 to expand and contract radially in a fashion similar to that described above with respect to the sheath 20 . [0081] The casing 62 and the wire 70 preferably comprise material properties corresponding to those described above with respect to the casing 30 and the wire 38 of the sheath 20 . Further, the example materials described with respect to the sheath 20 can also be implemented in the present thrombus collection device 60 . [0082] The catheter 64 preferably comprises a material that is flexible but rigid enough to support the casing 62 and the wire 70 as the device 60 is inserted into a patient's vasculature through an introducer sheath, and also rigid enough to support the casing 62 and the wire 70 as those components radially expand and contract. Further, because the catheter 64 is configured for use internally, the material is preferably biocompatible. Example materials for the catheter 64 include various thermoplastics such as polyimide, fluorinated ethylene propylene (FEP), PEBAX, and other materials having similar properties. [0083] Again, FIGS. 7 and 8 illustrate the device 60 in a collapsed or contracted state. In this state, the wire 70 includes a relatively straight portion 82 extending between the opening in the catheter 64 , and a helical portion distal of the straight portion 82 . However, when the flexible but incompressible wire 70 is subjected to a compressive force applied proximally of the opening 68 , the wire 70 is forced distally in the space between the casing 62 and the catheter 64 . As the wire 70 moves distally, it forms tighter coils 78 within the helix 76 , with the coils 78 having increasingly larger diameters, as shown in FIGS. 9 and 10 . The elastomeric nature of the casing 62 makes it readily expandable in the radial direction as the wire 70 forces it outward. The expanded casing 62 presents a wide proximal opening 84 to the space between the casing 62 and the catheter 64 . Similarly, when the wire 70 is subjected to a tensile force applied proximally of the opening 68 , the coils 78 within the helix 76 relax as wire 70 is pulled proximally, collapsing the wire 70 and the casing 62 and narrowing the proximal opening 84 . Again, the elastomeric nature of the casing 62 makes it readily contractible in the radial direction as the radial support provided by the wire 70 diminishes. [0084] In one embodiment, the wire 70 is freely slidable within the space between the casing 62 and the catheter 64 . Thus, as the wire 70 is forced distally, additional wire 70 is forced into the space between the casing 62 and the catheter 64 . The helix 76 slides against the casing 62 and the catheter 64 as it expands radially to enable the casing 62 to expand without forming pleats between adjacent coils 78 . The expanded sheath thus presents a relatively smooth outer diameter for easy passage of the device 60 within the patient's vasculature. However, in alternative embodiments the wire 70 may be secured to the casing 62 at one or more locations, such as at the proximal end 80 of the casing 62 . [0085] As shown in FIGS. 9 and 10 , the illustrated embodiment of the thrombus collection device 60 expands to form a substantially conical shape, or any other suitable shape, including any tapering shape with a proximal open end and a smaller, closed distal end. To achieve this expanded shape, the casing 62 may, for example, be secured to the catheter 64 at one or more locations along a straight line that traces the outer surface of the catheter 64 . In the illustrated embodiment, this line is along the lower side 86 of the catheter 64 . Because the casing 62 is attached to the catheter 64 , as the wire 70 is forced distally under an applied force the wire 70 and the casing 62 are constrained against expansion on the side 86 of the catheter 64 where the casing 62 is attached, causing the casing 62 to assume a generally conical or elongate conical shape as it expands. The conical expanded shape achieves advantages for thrombus collection, as described in further detail below. [0086] FIGS. 11-15 illustrate one method of using the thrombus collection device 60 of FIGS. 7-10 to perform a thrombectomy. As shown in FIG. 11 , the thrombus collection device 60 may be combined with the sheath 20 of FIGS. 1-6 to form a system 88 for performing a thrombectomy. However, the present thrombus collection device 60 may be used with any introducer sheath. Thus, the present sheath 20 and thrombus collection device 60 are each usable separately, or in combination. [0087] With reference to FIG. 11 , a process for extracting a thrombus begins with the operator emplacing the sheath 20 as described above with respect to FIG. 6 . The operator can then expand the sheath 20 by applying a distally directed force to the sheath wire 38 . With the sheath 20 expanded, the operator introduces the thrombus collection device 60 by passing it through the expanded sheath 20 and into the patient's vasculature 22 , as shown in FIG. 11 . To aid introduction, the operator would typically introduce the thrombus collection device 60 in its collapsed state ( FIGS. 7 and 8 ). FIG. 11 , however, illustrates the device wire 70 and the device casing 62 in their expanded states for clarity. Once the device 60 has been introduced into the vasculature 22 , the operator may collapse the sheath 20 by applying a proximally directed force to its wire 38 . In the collapsed state, the sheath 20 advantageously promotes hemostasis at the percutaneous access site 26 by allowing the percutaneous puncture 24 to reduce in size. The collapsed sheath 20 , however, still provides an adequate inside diameter to enable the thrombus collection device 60 to be manipulated within the vasculature 22 . The step of collapsing the sheath 20 is optional. [0088] With reference to FIG. 12 , the operator advances the device 60 through the patient's vasculature 22 toward the location of the thrombus 90 . The operator may advance the device 60 by applying a distally directed force to the portion of the catheter 64 that protrudes from the percutaneous access site 26 . The operator may use a guide wire (not shown) and/or imaging, such as ultrasound, to assist in guiding the device 60 through the vasculature 22 to the thrombus 90 . [0089] When the thrombus collection device 60 reaches the thrombus 90 , as shown in FIG. 13 , the operator continues applying distally directed force to push the distal end 66 of the device 60 through the thrombus 90 . The present thrombus collection device 60 is configured to collect acute thrombi, which typically have a gelatin-like consistency. The operator may thus typically pass the device 60 through the thrombus 90 without substantial difficulty. The moderate rigidity of the catheter 64 and the low profile of the device 60 aid in penetrating the thrombus 90 . [0090] The operator continues advancing the device 60 through the thrombus 90 until the device casing 62 has completely passed through the thrombus 90 . The operator then expands the device wire 70 and the device casing 62 as shown in FIG. 14 . The operator expands the device wire 70 and the device casing 62 by applying a distally directed force to the device wire 70 while holding the catheter 64 stationary. The operator may expand the device wire 70 and the device casing 62 until achieving wall-to-wall apposition with the interior diameter 56 of the vasculature. The operator may use imaging and/or tactile feedback to determine when the device casing 62 is expanded to the desired amount. [0091] With the device casing 62 expanded and positioned distally of the thrombus 90 , the operator draws the device 60 back through the vasculature 22 by applying a proximally directed force to the catheter 64 while holding the device wire 70 stationary with respect to the catheter to maintain the device casing 62 in its expanded state. As the expanded device 60 is pulled proximally, the proximal opening 84 of the device casing 62 collects the thrombus 90 and traps it within the space between the device casing 62 and the catheter 64 , as shown in FIG. 15 . The operator continues to pull back on the catheter 64 until the thrombus collection device 60 reaches the distal end 42 of the sheath 20 , as shown in FIG. 11 . Again, the operator may use imaging to determine the location of the thrombus collection device 60 . As illustrated, in FIGS. 12-15 , the operator may advantageously advance the device 60 through the thrombus 90 such that the line 86 along which the device casing 62 is attached to the catheter 64 faces the interior wall 56 of the vasculature 22 . Thus, when the conical device casing 62 is expanded, its proximal opening 84 is positioned to completely engulf the thrombus 90 when pulled back. [0092] When the thrombus collection device 60 reaches the distal end 42 of the sheath 20 , as shown in FIG. 11 , the operator draws the device 60 through the sheath 20 , together with the collected thrombus 90 , until the device 60 and the thrombus 90 are completely extracted from the patient. To aid in extraction, the operator would typically expand the sheath 20 prior to withdrawing the device 60 so that the sheath 20 may better accommodate the expanded device 60 . The sheath 20 may advantageously be expanded over a wide range, so that it can for example be expanded to contact the interior diameter 56 of the vasculature 22 , and be expanded even farther to radially expand the vasculature 22 . This increased expansion is advantageous for withdrawing the thrombus collection device 60 , as the thrombus collection device 60 may sometimes be expanded during withdrawal to a diameter that is substantially equal to the interior diameter of the vasculature 22 . Optionally, the operator can rely upon the natural expandability of the sheath 20 , rather than or in addition to manual expansion of the sheath, to expand the sheath 20 in response to the introduction of a large-diameter object (e.g. the device 60 containing a relatively large portion of thrombus) into the sheath lumen. Upon withdrawing the thrombus collection device 60 , the operator may thereafter collapse the sheath 20 and also withdraw it from the percutaneous access site 26 . Just before or during withdrawal of the device 60 , the operator can pull the device wire 70 proximally so that the wire 70 serves as a clamp or drawstring that holds the collected thrombus in the casing 62 or wire coils more securely during withdrawal. [0093] In an alternative embodiment of the sheath 20 ′, the sheath wire 38 ′ may not be coiled around the inner layer 32 ′ when the sheath 20 ′ is in the collapsed state. For example, FIG. 16 shows an alternative sheath 20 ′ in which the sheath wire 38 ′ extends substantially straight from the opening 50 ′ to the distal end 42 ′ of the sheath casing 30 ′. Similarly, in an alternative embodiment of the thrombus collection device 60 ′, the device wire 70 ′ may not be coiled around the catheter 64 ′ when the device casing 62 ′ is in the collapsed state. For example, FIG. 17 shows an alternative thrombus collection device 60 ′ in which the device wire 70 ′ extends substantially straight along the catheter 64 ′ from the opening 68 ′ to the distal end 66 ′ of the catheter 64 ′. In both embodiments of FIGS. 16 and 17 , the wire 38 ′, 70 ′ coils around the inner layer 32 ′/catheter 64 ′ in response to a distally directed force applied to the wire 38 ′, 70 ′, substantially as described above with respect to the foregoing embodiments. [0094] As illustrated above, the present embodiments of the radially collapsible and expandable sheath 20 advantageously provide an introducer sheath that can be adjusted to accommodate intravascular devices of various sizes. The sheath 20 is simple in construction, including only two pieces (the casing 30 and the wire 38 ) in certain embodiments. The sheath 20 is easily adjustable in radial dimension through the application of pushing or pulling force to the wire 38 . The sheath 20 can expand radially on its own in response to movement of a large object into the sheath, such as a large intravascular device or a device carrying a relatively large amount of thrombus. In the latter case, this property of the sheath facilitates removal of large thrombi without need for macerating the thrombi or treating them with a thrombolytic agent before moving them through the sheath. The sheath 20 can be expanded within the vasculature to radially expand the vasculature. When collapsed, the portion of the sheath 20 extending through the percutaneous access opening promotes hemostasis by allowing the opening to partially or completely collapse. [0095] As also illustrated above, the present embodiments of the radially collapsible and expandable thrombus collection device 60 advantageously provide a collection device that can be collapsed to a low profile for easy introduction to the vasculature through a sheath, and easy penetration of the thrombus. When the collapsed device 60 is advanced past the thrombus, it can be expanded to match the interior diameter of the vasculature and pulled back to entrain the thrombus. It is optional to macerate the thrombus or to soften it with a thrombolytic prior to extraction. The proximal opening of the casing, supported by the wire, simply pulls the thrombus away from the vasculature wall and traps it within the casing. This embodiment is particularly useful for removing thrombi that repeatedly form in arterio-venous fistulas (AVF) of hemodialysis patients. The thrombus collection device 60 enables removal of the thrombi without the need for repeated surgical cut downs. Several devices 60 can be provided in a package or kit for use within a single procedure, e.g. when thrombus is to be removed in several stages each calling for a separate device 60 . [0096] As also illustrated above, the present embodiments of the radially collapsible and expandable sheath 20 can be combined with the present embodiments of the radially collapsible and expandable thrombus collection device 60 to form a system 88 ( FIG. 11 ) for performing a thrombectomy. The system 88 achieves the combined advantages of each component of the system 88 . Those of ordinary skill in the art will appreciate, however, that both the sheath 20 and the thrombus collection device 60 are usable separately. [0097] FIG. 18 illustrates another embodiment of the present introducer sheaths. The sheath 100 is tubular, and includes a medial neck portion 102 . At a distal end, the neck portion 102 flares outwardly to a wider bell portion 104 . The distal end 106 of the bell portion 104 is open. [0098] The neck portion 102 and the bell portion 104 may comprise a compliant material. As used herein, the term compliant should be understood to include at least the following properties: flexibility, elasticity, and collapsibility/expandability. Further, because the sheath 100 is configured for use internally, the material is preferably biocompatible. Example materials for the sheath 100 include silicone film, polyisoprene, TECOTHANE®, PELLETHANE®, and other materials having similar properties. The compliant sheath material is advantageously kink resistant and capable of folding upon itself. [0099] In one embodiment, the sheath 100 comprises HT-310 synthetic polyisoprene having a thickness of approximately 3-4.5 mils. A length of the bell portion 104 is approximately 26 mm, as measured from the distal end 106 to the transition point 108 between the bell portion 104 and the flared portion 110 . A diameter of the bell portion 104 is approximately 10 mm. A length of the neck portion 102 is approximately 34 mm, as measured from the proximal end 112 to the transition point 114 between the neck portion 102 and the flared portion 110 . A diameter of the neck portion 102 is approximately 7 mm. A length of the flared portion 110 is approximately 10 mm. The foregoing material and dimensions are merely one example, and are not limiting. [0100] The bell portion 104 of the sheath 100 includes a wire 116 that is encased within the compliant material. Unlike the sheath 20 described above and illustrated in FIGS. 1-6 , the wire 116 is not movable relative to the compliant sheath material. The sheath 100 may, for example, be made by overmolding the compliant sheath material over the wire 116 . The resulting structure keeps the wire 116 in the desired position along the length of the bell portion 104 . [0101] The wire 116 extends around the circumference of the bell portion 104 along a path that repeatedly doubles back and forth in the direction of the longitudinal axis A of the sheath 100 . As measured in the direction of the longitudinal axis A, the wire 116 extends over approximately half the length of the bell portion 104 from the distal end 106 thereof to approximately the center thereof. As illustrated, however, a narrow band 118 of the bell portion 104 extends beyond the wire 116 at the distal end 106 . A length of this band 118 , as measured in the direction of the longitudinal axis A, may be approximately 1 mm in one embodiment. [0102] The wire 116 supports the compliant material, maintaining the bell portion 104 in its expanded shape when the sheath 100 is unstressed. The wire 116 comprises a material that is flexible but incompressible. Further, because the wire 116 is configured for use internally, the material is preferably biocompatible. Example materials for the wire 116 include nickel-titanium (NiTi) alloys, stainless steel, polyether ether ketone (PEEK) and other materials having similar properties. [0103] At a proximal end 120 , the sheath 100 includes a flush port 122 . The flush port 122 includes a tubular portion 124 that is coaxial with the neck portion 102 and the bell portion 104 . Together, the tubular portion 124 , the neck portion 102 and the bell portion 104 define an interior lumen, or sheath lumen (not shown). A port 126 extends radially from the tubular portion 124 . The port 126 defines a port lumen (not shown) that is in fluid communication with the sheath lumen. The port 126 is conically shaped, tapering down to a smaller diameter with increasing distance from the tubular portion 124 . A medial portion of the port 126 includes an annular bulge 128 where the exterior diameter of the port 126 is increased. The port 126 is configured to receive standard medical tubing 130 in a liquid tight friction fit with the tubing 130 extending around the outside of the bulge 128 . An end of the tubing 130 spaced from the port 126 includes a connector 132 . In the illustrated embodiment, the illustrated connector 132 is a female Luer connector 132 . A conical distal end 134 of the connector 132 is received within the tubing 130 in a liquid tight friction fit. The connector 132 includes a stopcock 136 that enables flow through the connector 132 to be selectively blocked. The flush port 122 enables fluid to be injected and/or aspirated from the sheath lumen. For example, a syringe (not shown) may be connected to the connector 132 , and fluid may be injected or aspirated by depressing or drawing back on the syringe plunger. [0104] The introducer sheath 100 of FIG. 18 is configured for passage into a patient's vasculature (e.g. in a vein or artery, an arterio-venous fistula (AVF) or arterio-venous graft (AVG), or alternatively in a non-vascular location such as the peritoneal cavity or other bodily cavities or hollow anatomical structures) through an opening at a percutaneous access site. Once deployed, the sheath 100 can be used as a conduit for introducing one or more intravascular devices into the patient's vasculature. For example, and as discussed further below, in one embodiment the sheath 100 can be used to introduce a thrombectomy device. FIG. 18 illustrates the introducer sheath 100 in an unstressed, or expanded, configuration. The compliant portions of the introducer sheath 100 are configured to be radially compressed for ease of introduction into the vasculature, as described below. Once deployed within the vasculature, a hemostasis valve 138 at the proximal end of the sheath 100 ( FIG. 20 ) resists outflow of bodily fluids through the sheath 100 . The hemostasis valve 138 is shaped substantially as a disk, and is located within the tubular portion 124 at the proximal end 120 thereof. The valve 138 may, for example, comprise a foam material. The valve 138 forms a seal around the exterior of a tubular dilator 140 , which is described below. [0105] FIGS. 19 and 20 illustrate one embodiment of a deployment apparatus 142 for the introducer sheath 100 of FIG. 18 . With reference to the cross-sectional view of FIG. 20 , the deployment apparatus 142 includes a tubular dilator 140 , which may also be referred to as a hypotube 140 . The dilator 140 is a rigid or semi-rigid component configured to guide the deployment apparatus 142 through a skin puncture and through the vasculature, as described in further detail below. The dilator 140 includes a proximal handle 144 , a conically shaped distal tip 146 , and defines a lumen 148 that extends between the proximal and distal ends. The handle 144 is shaped as a round knob. The lumen 148 extends through the handle 144 and through the distal tip 146 . The lumen is configured to receive a guide wire (not shown) to facilitate introduction of the dilator 140 into a patient, as described in detail below. [0106] With continued reference to FIG. 20 , the introducer sheath 100 of FIG. 18 is disposed coaxially about the outside of the dilator 140 , and an outer sheath 150 is disposed coaxially about the outside of the introducer sheath 100 . The outer sheath 150 has an inner diameter that is approximately equal to an outer diameter of the neck portion 102 of the introducer sheath 100 , but less than the outer diameter of the bell portion 104 of the introducer sheath 100 . The outer sheath 150 thus radially compresses the bell portion 104 , which facilitates introduction of the sheath 100 into the patient. In certain embodiments, the outer sheath 150 comprises a non-elastic material so that the radially compressed bell portion 104 does not induce expansion of the outer sheath 150 . [0107] The outer sheath 150 , however, is a tearaway sheath. Thus, it comprises a material that can be torn by hand. Example materials include polytetrafluoroethylene (PTFE) and materials having similar properties. The outer sheath 150 includes a proximal handle 152 that extends radially away from the outer sheath 150 at a location just distal of the tubular portion 124 of the introducer sheath 100 . As discussed further below, the operator may remove the outer sheath 150 by grasping the handle 152 and pulling it proximally while holding the introducer sheath 100 and the dilator 140 steady. The outer sheath 150 material tears away from the deployment apparatus 142 as it is withdrawn from the percutaneous access site. Once the outer sheath 150 is removed, the bell portion 104 of the introducer sheath 100 expands to its unstressed condition, subject to any stresses applied by the patient's vasculature. [0108] FIGS. 21-24 illustrate one embodiment of a method for deploying the introducer sheath 100 of FIG. 18 in a patient's vasculature 154 at a percutaneous access site 156 using the deployment apparatus 142 of FIGS. 19 and 20 . The access site 156 may be prepared by puncturing the skin 158 , any underlying tissue 160 , and the vasculature 154 with a needle 162 , as shown in FIG. 21 . The operator then introduces a guide wire 164 through the lumen of the needle 162 , and withdraws the needle 162 . [0109] With reference to FIG. 22 , the operator introduces the deployment apparatus 142 into the vasculature 154 through the puncture site 156 using the guide wire 164 . The operator threads the guide wire 164 into the dilator lumen 148 ( FIG. 20 ) from the distal end 146 and advances the deployment apparatus 142 through the puncture site 156 . In some embodiments the dilator 140 is a rigid component that provides sufficient column strength to facilitate tissue puncturing and/or penetration. However, in alternative embodiments the dilator 140 includes sufficient flexibility to facilitate navigating tortuous vasculature 154 . The conically shaped distal tip 146 of the dilator 140 facilitates passage of the deployment apparatus 142 through the patient's tissue 160 ( FIG. 21 ) and into the vasculature 154 . [0110] With reference to FIGS. 22 and 23 , after penetrating the vasculature 154 the deployment apparatus 142 is advanced through the vasculature 154 until the handle portion 152 of the outer sheath 150 approaches the puncture site 156 . In this position, the introducer sheath 100 is located such that the bell portion 104 is located entirely within the vasculature 154 and the neck portion 102 traverses the puncture site 156 . The hemostasis valve 138 ( FIG. 20 ) within the introducer sheath 100 resists outflow of blood through the annular space defined by the interior of the sheath 100 and the exterior of the dilator 140 . The dilator 140 may also include a hemostasis valve (not shown) to resist outflow of blood through the dilator lumen 148 . [0111] With reference to FIG. 23 , the operator next removes the outer sheath 150 from the deployment apparatus 142 . As indicated above, the outer sheath 150 is a tearaway sheath. Thus, to remove the outer sheath 150 , the operator grasps the handle 152 and pulls it proximally while holding the introducer sheath 100 and the dilator 140 steady. The operator may, for example, grasp the outer sheath handle 152 with one hand and the dilator handle 144 with the other hand. The outer sheath 150 tears away from the remainder of the deployment apparatus 142 and pulls through the puncture site 156 . [0112] With reference to FIGS. 23 and 24 , the operator draws the entire outer sheath 150 out of the body through the puncture site 156 . Upon removal of the outer sheath 150 , the compressive force applied to the introducer sheath 100 by the outer sheath 150 is no longer present. The bell portion 104 of the introducer sheath 100 thus expands as the stored energy in the wire 116 is released. FIG. 24 illustrates the introducer sheath 100 in its expanded state within the vasculature 154 . Depending upon the relative dimensions of the introducer sheath 100 and the vasculature 154 , the vasculature 154 may constrain the expansion of the introducer sheath 100 somewhat so that it does not achieve the fully relaxed state that it would outside the body. Skin 158 and underlying tissue 160 further constrain expansion of the neck portion 102 where it traverses the puncture site 156 . [0113] With reference to FIGS. 23 and 24 , after removing the outer sheath 150 the operator next removes the dilator 140 . To remove the dilator 140 , the operator draws back on the proximal handle 144 . During withdrawal, the operator may optionally apply digital pressure at the puncture site 156 in order to prevent the introducer sheath 100 from being withdrawn together with the dilator 140 due to friction between those two components where they are squeezed by the elastic skin 158 at the puncture site 156 . With the dilator 140 completely removed, the introducer sheath 100 is disposed within the vasculature 154 through the puncture site 156 as shown in FIG. 24 . The tubular portion 124 is disposed exteriorly of the body, the bell portion 104 is disposed within the vasculature 154 , and the neck portion 102 traverses the skin 158 and tissue 160 therebetween. Advantageously, the compliant nature of the neck portion 102 promotes hemostasis at the puncture site 156 by allowing the elastic skin 158 to collapse around the puncture. The compliant neck 102 further speeds hemostasis at the end of a procedure, because the skin 158 and underlying tissue 160 do not remain stretched for an extended period. The hemostasis valve 138 within the proximal end 120 of the introducer sheath 100 ( FIG. 20 ) further promotes hemostasis at the puncture site 156 . When the dilator 140 is withdrawn, the hemostasis valve 138 may close to seal the opening formerly occupied by the dilator 140 . The valve 138 may reopen as additional apparatus is introduced into the vasculature 154 through the sheath 100 . However, the valve 138 preferably forms a seal around any such apparatus. [0114] The introducer sheath 100 described above may advantageously be used to introduce a wide variety of instruments into a patient's vasculature 154 . For example, the introducer sheath 100 may be used to introduce a thrombus collection device. Various examples of thrombus collection procedures using the present embodiments are described below. [0115] FIGS. 25 and 26 illustrate an aspiration catheter 166 , which is another embodiment of the present thrombus collection devices. With reference to FIG. 25 , the catheter 166 includes an elongate body 168 having a balloon 170 at its distal end 172 . The catheter body 168 comprises a flexible material that is configured for navigating tortuous vasculature. However, the catheter body 168 material includes sufficient rigidity to facilitate guiding the catheter 166 through the vasculature from the proximal end 174 . Example materials for the catheter body 168 include polyether block amide (PEBAX®) and materials having similar properties. [0116] FIG. 26 illustrates a cross-sectional view of the catheter body 168 . The body 168 defines two radially spaced lumens 176 , 178 that are not in fluid communication with one another. The first lumen 176 is an aspiration lumen 176 that extends from an aspiration connector 180 ( FIG. 25 ) at the proximal end 174 of the catheter 166 to a plurality of aspiration openings 182 toward the distal end 172 of the catheter 166 . The second lumen 178 is an inflation lumen 178 that extends from an inflation connector 184 at the proximal end 174 of the catheter 166 to the balloon 170 toward the distal end 172 of the catheter 166 . The aspiration lumen 176 has a larger diameter than the inflation lumen 178 , and is configured for passage of thrombus, as described below. In one embodiment, the catheter body 168 may have a diameter of 6 Fr, while the aspiration lumen 176 may have a diameter of 0.055″. [0117] In certain embodiments, the aspiration lumen 176 may further extend to the distal end 172 , which is open but sealed by a valve (not shown). The valve enables a guide wire (not shown) to pass to facilitate introduction of the catheter 166 into the vasculature. However, upon withdrawal of the guide wire the valve seals to resist flow into or out of the distal end 172 of the aspiration lumen 176 . [0118] With reference to FIG. 25 , the aspiration connector 180 and the inflation connector 184 extend proximally from a Y-shaped body 186 . The body 186 includes a main conduit 188 that extends inline with the catheter body 168 . The aspiration connector 180 extends proximally from the main conduit 188 , inline therewith. The body 186 further includes a branch conduit 190 that extends at an angle from the body 186 . The inflation connector 184 extends proximally from the branch conduit 190 , inline therewith. In the illustrated embodiment, both connectors 180 , 184 comprise a female Luer connector including an external thread 192 . In alternative embodiments different types of connectors could be substituted. In certain embodiments, either or both of the connectors 180 , 184 may include a stopcock (not shown) for selectively halting liquid flow through the connector(s) 180 , 184 . [0119] The Y-shaped body 186 and the connectors 180 , 184 may be formed as a single piece or as multiple pieces. These portions are preferably formed from a rigid medical grade plastic. For example, these portions may comprise polycarbonate, acrylic, polypropylene, styrene, or any other suitable plastic material. [0120] With continued reference to FIG. 25 , and as indicated above, the aspiration catheter 166 includes a plurality of aspiration openings 182 toward the distal end 172 . Three openings are shown, but other embodiments may include any number of openings 182 , including only a single opening 182 . The aspiration openings 182 are in fluid communication with the aspiration connector 180 through the aspiration lumen 176 . During a thrombus collection procedure, a syringe (not shown) may be connected to the aspiration connector 180 . Drawing back upon a plunger of the syringe creates suction at the aspiration openings 182 . The suction can be used to draw pieces of the thrombus into the aspiration lumen 176 for removal from the vasculature. This process is described more fully below. [0121] The aspiration catheter 166 further includes a balloon 170 toward the distal end 172 . The balloon 170 is shown in a partially inflated state for illustration. The balloon 170 is sealed at its proximal end 194 and distal end 196 to the catheter body 168 . An inflation port (not shown) passes through the wall of the catheter body 168 within the balloon 170 . The interior of the balloon 170 is in fluid communication with the inflation lumen 178 through the inflation port. During a thrombus collection procedure, a syringe (not shown) may be connected to the inflation connector 184 . The balloon 170 may be inflated by depressing the syringe plunger to force a fluid through the inflation lumen 178 and into the balloon 170 . The balloon 170 may be deflated by drawing the syringe plunger back to evacuate the fluid from the balloon 170 . For intravascular procedures, the inflation fluid is preferably a non-toxic liquid, such as saline. Thus, as used herein the terms inflate and deflate are to be construed broadly enough to include using a liquid as the inflation agent. [0122] As described above, the aspiration catheter 166 shown in FIGS. 25 and 26 is configured for percutaneously removing a thrombus from a patient's vasculature. FIGS. 27-35 illustrate one example of such a procedure. In FIGS. 27-34 , each drawing sheet illustrates the proximal portions (odd numbered figures) of the introducer sheath 100 and the aspiration catheter 166 and the distal portions (even numbered figures) as they appear during the same step of the procedure. In other words, FIGS. 27 and 28 illustrate different portions of the apparatus during the same step of the procedure, FIGS. 29 and 30 illustrate different portions of the apparatus during a subsequent step of the procedure, etc. [0123] With reference to FIGS. 27 and 28 , the aspiration catheter 166 is introduced into the vasculature 154 through the introducer sheath 100 described above with respect to FIGS. 18-24 . The introducer sheath 100 may be deployed according to the method described above with respect to FIGS. 21-24 . The aspiration catheter 166 is then advanced distally through the sheath 100 , the vasculature 154 , and the thrombus 198 until the balloon 170 is disposed on the far side of the thrombus 198 ( FIG. 28 ). A guide wire 164 extending through the aspiration lumen 176 may be used to advance the catheter 166 . As shown, the catheter 166 is advanced with the balloon 170 in the deflated state for ease of passage through the sheath 100 , the vasculature 154 and the thrombus 198 . The conically shaped distal tip 172 further facilitates passage of the catheter 166 , especially through the constricted portion of the sheath 100 that traverses the puncture site, and through the thrombus 198 . [0124] With reference to FIGS. 29 and 30 , when the catheter 166 has advanced sufficiently that the balloon 170 is disposed on the far side of the thrombus 198 , the operator connects a syringe 200 ( FIG. 29 ) filled with inflation liquid to the inflation connector 184 . As shown, a Luer stopcock 202 may be connected between the syringe 200 and the inflation connector 184 . The operator depresses the syringe plunger 204 to force the inflation liquid into the balloon 170 through the inflation lumen 178 . The operator inflates the balloon 170 until it presses against the interior walls of the vasculature 154 on the far side of the thrombus 198 ( FIG. 30 ). If the stopcock 202 is not provided, the operator maintains the syringe 200 connected to the inflation connector 184 in order to maintain the inflation pressure within the balloon 170 . However, if the stopcock 202 is provided, the operator moves the stopcock 202 to a position to prevent liquid flow through the inflation connector 184 . The operator may then disconnect the syringe 200 from the stopcock 202 , which may make it easier for the operator to perform subsequent steps of the procedure. [0125] With reference to FIGS. 31 and 32 , the operator removes the thrombus 198 from the vasculature 154 by using a combination of suction through the aspiration openings 182 , and proximal movement of the inflated balloon 170 across the thrombus 198 . These actions may occur simultaneously, or in succession, or alternatingly. The following discussion describes a method for applying suction simultaneously while drawing the inflated balloon 170 across the thrombus 198 . This illustrated method is only one of many possibilities for removing the thrombus 198 , and is not intended to be limiting. [0126] With reference to FIG. 31 , the operator connects a Luer stopcock 202 to the aspiration connector 180 and an empty syringe 206 to the stopcock 202 . If a guide wire 164 was used to advance the catheter 166 , it is removed prior to connection of the syringe 206 . The syringe 206 is configured so that the plunger 208 can be drawn back to create a vacuum within the barrel 210 and the plunger 208 locked to maintain the vacuum. One such syringe is sold under the trade name VACLOK®. To generate suction, the operator draws back on the syringe plunger 208 with the stopcock 202 in the closed position and then locks the plunger 208 . The operator then draws the catheter 166 out of the vasculature 154 while simultaneously moving the stopcock 202 to the open position. Moving the stopcock 202 to the open position exposes the vacuum in the syringe barrel 210 to the aspiration lumen 178 , generating suction that pulls pieces of the thrombus 198 into the aspiration lumen 176 through the aspiration openings 182 . The aspiration openings 182 thus advantageously assist in collecting the thrombus 198 both by tearing away pieces of thrombus 198 from the larger whole, and by vacuuming up any loose pieces of thrombus 198 . Some of these pieces of thrombus 198 may be sucked into the syringe 206 , as shown in FIG. 31 . [0127] Because the operator draws the catheter 166 out of the vasculature 154 simultaneously while generating suction at the aspiration openings 182 , the aspiration openings 182 are more likely to be exposed to all portions of the thrombus 198 as the openings 182 are drawn across the thrombus 198 , as shown in FIG. 32 . The suction is thus more likely to remove more of the thrombus 198 than if the catheter 166 remains stationary while the vacuum is applied. In certain embodiments, the aspiration openings 182 may be located within the thrombus 198 at the point in the procedure where the operator opens the stopcock 202 . In alternative embodiments, some or all of the openings 182 may be disposed proximally and/or distally of the thrombus 198 at this point in the procedure. [0128] In addition to the vacuum action, pulling back on the aspiration catheter 166 pulls the balloon 170 against the distal side of the thrombus 198 , as shown in FIG. 32 . The balloon 170 , which fills the circumference of the vasculature 154 , pulls the thrombus 198 away from the vasculature 154 . Portions of the thrombus 198 that are not sucked into the aspiration lumen 176 are drawn into the sheath 100 by the balloon 170 . [0129] With continued reference to FIG. 32 , the operator continues to pull back on the aspiration catheter 166 until all or substantially all of the thrombus 198 has been pulled into the sheath 100 . The operator then continues to pull back on the aspiration catheter 166 in order to force the thrombus 198 out of the vasculature 154 through the sheath 100 . The balloon 170 is withdrawn through the percutaneous access site and into the portion of the sheath 100 that is disposed outside the body. The compliant material of the sheath 100 is advantageously able to expand as the inflated balloon 170 passes so that the balloon 170 can push the pieces of thrombus 198 out of the body. The compliant sheath 100 then collapses as the elastic skin at the puncture site constricts, advantageously facilitating hemostasis. With reference to FIG. 33 , the thrombus 198 and balloon 170 are eventually pulled through the proximal end 120 of the introducer sheath 100 . The introducer sheath 100 may include a hinged proximal door 212 at the proximal end 120 that facilitates withdrawal of the inflated balloon 170 . [0130] After the thrombus 198 has been removed from the vasculature 154 the introducer sheath 100 remains in the vasculature 154 through the percutaneous access site. The sheath 100 advantageously maintains a path into the vasculature 154 so that a guide wire 164 ( FIG. 35 ) may be reinserted into the vasculature 154 as shown. It may be advantageous to reinsert a guide wire 164 so that the location of the removed thrombus 198 can be re-accessed. Repeat access may be desired so that the thrombus 198 removal procedure may be repeated or so that a stent may be placed, for example. After the guide wire 164 is reinserted, the introducer sheath 100 may be removed if desired, as shown in FIG. 35 . [0131] The aspiration catheter 166 illustrated in FIG. 25 includes three aspiration openings 182 . The present aspiration catheters may include any number of aspiration openings 182 . However, it has been found that three aspiration openings 182 achieve advantageous thrombus removal results. Further, providing more than one aspiration opening 182 advantageously maintains suction in the event that a first aspiration opening 182 becomes clogged. In the illustrated embodiments, each of the aspiration openings 182 on the catheter 166 has substantially the same diameter. However, in alternative embodiments the aspiration openings 182 could have varying diameters. For example, a diameter of the openings 182 may increase with increasing distance from the source of suction (the syringe 206 at the aspiration connector 180 ) in order to combat head losses across the openings 182 . [0132] FIG. 36 illustrates another embodiment of an aspiration catheter 214 . The catheter 214 of FIG. 36 is similar to the catheter 166 of FIG. 25 , except that it includes only two aspiration openings 182 , and the distal balloon 216 has a different shape. The balloon 216 of FIG. 36 is shaped substantially as an arrowhead in profile. It includes a cone-shaped distal surface 218 and a proximal surface 220 shaped as an inverted cone. The inverted cone shape urges fluid to flow toward the centerline of the catheter 214 as the balloon 216 is pulled proximally. The flow direction carries thrombus particles toward the aspiration openings 182 , where they are more likely to be sucked into the aspiration lumen 176 . The balloon 216 thus increases the efficiency with which thrombus particles can be collected in the aspiration lumen 176 . [0133] As shown in FIGS. 27-35 , the introducer sheath 100 of FIG. 18 may be used to introduce the aspiration catheter 166 of FIG. 25 into a patient's vasculature 154 . However, both the introducer sheath 100 and the aspiration catheter 166 can be used in a wide variety of procedures other than a percutaneous thrombus collection procedure. For example, the introducer sheath 100 and the aspiration catheter 166 can be used in non-vascular locations such as the peritoneal cavity or other bodily cavities or hollow anatomical structures. [0134] Further, both the introducer sheath 100 and the aspiration catheter 166 can be used with a wide variety of other apparatus. It should be understood that any of the apparatus described herein can be used separately, and/or in combination with any of the other apparatus described herein, and/or in combination with other apparatus not described herein. Several of these combinations are described below. It should be further understood that wherever the aspiration catheter 166 of FIG. 25 is described, the aspiration catheter 214 of FIG. 36 may be substituted therefore, wherever the sheath 100 of FIG. 18 is described, the sheath 20 of FIGS. 1-6 or the sheath 20 ′ of FIG. 16 may be substituted therefore, and wherever the thrombus collection device 60 of FIGS. 7-10 is described, the thrombus collection device 60 ′ of FIG. 17 may be substituted therefore. [0135] With reference to FIG. 37 , the introducer sheath 100 of FIG. 18 can be used to introduce a standard Fogarty balloon catheter 222 into the vasculature 154 . Fogarty balloon catheters are well known, and will not be described in detail herein. The procedure for introducing the sheath 100 is as described above with respect to FIGS. 21-24 , and the procedure for introducing the Fogarty catheter 222 is similar to the procedure described above with respect to FIGS. 27 and 28 . [0136] With reference to FIG. 38 , the introducer sheath 100 of FIG. 18 can also be used to introduce the thrombus collection device 60 of FIGS. 7-10 into the vasculature 154 . The procedure for introducing the sheath 100 is as described above with respect to FIGS. 21-24 . The procedure for introducing the thrombus collection device 60 is described above with respect to FIGS. 11-15 , except that the sheath 100 of FIG. 18 is substituted for the sheath 20 of FIGS. 1-6 . [0137] With reference to FIG. 39 , the aspiration catheter 166 of FIG. 25 can be introduced into the vasculature 154 through a standard balloon catheter introducer sheath 224 . Balloon catheter introducer sheaths are well known, and will not be described in detail herein. The procedure for introducing the sheath 224 is similar to the procedure described above with respect to FIGS. 21-24 . The procedure for introducing the aspiration catheter 166 is described above with respect to FIGS. 27 and 28 , except that the balloon catheter introducer sheath 224 is substituted for the sheath 100 of FIG. 18 . [0138] While not illustrated herein, the introducer sheath 100 of FIG. 18 and the aspiration catheter 166 of FIG. 25 can also be used with other apparatus. For example, the sheath 20 of FIGS. 1-6 can be used to introduce the aspiration catheter 166 of FIG. 25 or the Fogarty balloon catheter 222 of FIG. 37 . Further, the standard balloon catheter introducer sheath 224 of FIG. 39 can be used to introduce the thrombus collection device 60 of FIGS. 7-10 . [0139] As illustrated above, the present embodiments of the introducer sheath 100 and the aspiration catheter 166 offer numerous advantages. For example, with reference to the introducer sheath 100 of FIG. 18 , the bell portion 104 expands upon deployment so that it contacts the interior walls of the vasculature 154 proximally of the thrombus 198 ( FIGS. 24 and 28 ). When a balloon 170 is then placed distally of the thrombus 198 and inflated, the thrombus 198 is isolated between the bell portion 104 and the balloon 170 . Since the bell portion 104 is open at its distal end 106 , drawing back the balloon 170 sweeps the thrombus 198 into the open mouth of the bell portion 104 . The removal process thus tends to reduce migration of thrombus 198 , and to collect a greater amount of the thrombus 198 as opposed to procedures not including a sheath having a wide, open distal end. [0140] The introducer sheath 100 of FIG. 18 is also advantageously compliant. It is thus able to expand to allow the withdrawal of thrombus 198 and an inflated catheter balloon 170 . The sheath 100 thus enables a greater amount of thrombus 198 to be collected as compared to non-compliant sheaths 100 . For example, clot burdens in arterio-venous fistulas (AVF) tend to be large, making them hard to remove percutaneously. The expandable compliant sheath 100 is well suited for removing these types of thrombus 198 . Further, it is advantageous to remove the plug portion of a thrombus 198 . The plug (not shown) is a relatively hard portion of thrombus 198 at the anastomosis where the vein is sewn to the artery. The harder plug tends not to compress as it is withdrawn percutaneously. The expandable compliant sheath 100 is thus well suited for removing the plug. The compliant nature of the sheath 100 facilitates removal of large thrombi 198 and plugs without need for macerating the thrombi and plugs or treating them with a thrombolytic agent before moving them through the sheath 100 . [0141] The expandable sheath 100 further enables devices of varying sizes to pass through it, so that various devices can be used during a single procedure without having to exchange the sheath 100 for a differently sized one. The compliant sheath 100 is also able to contract to maintain hemostasis at the percutaneous access site 156 after the catheter 166 has been withdrawn. The compliant sheath 100 further speeds hemostasis at the end of a procedure, because the skin and underlying tissue do not remain stretched for an extended period. [0142] With reference to the aspiration catheter 166 of FIG. 25 , the configuration of the catheter 166 advantageously provides push/pull inflation and aspiration. To inflate the balloon 170 , the operator need only connect a syringe 200 filled with inflation liquid and push the plunger 204 . To provide the suction force for thrombus aspiration, the operator need only connect an empty syringe 206 , draw back and lock the plunger 208 , then release the stopcock 202 while pulling on the catheter 166 . This push/pull inflation and aspiration provides mechanical stability that contributes to lesser incidence of user error. [0143] Both the introducer sheath 100 and the aspiration catheter 166 are also advantageously compatible with existing apparatus. As illustrated above, the introducer sheath 100 can be used to introduce a standard Fogarty balloon catheter 222 , and the aspiration catheter 166 can be introduced with a standard balloon catheter introducer sheath 224 . The introducer sheath 100 and the aspiration catheter 166 are thus easily adaptable to existing procedures that involve apparatus already familiar to those in the field.

A sheath comprises an elastomeric tube having a self-expanding scaffold coupled to a wall. The scaffold can expand to a diameter larger than the tube diameter to provide an enlarged distal opening. An aspiration catheter has a balloon and an aspiration port so that occlusive material can be removed from a blood vessel by drawing the balloon through the vessel while simultaneously aspirating through the port.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 12/820,687, filed Jun. 22, 2010, which is a continuation of U.S. patent application Ser. No. 11/845,438, filed Aug. 27, 2007, which is a continuation of U.S. patent application Ser. No. 11/043,157, filed Jan. 27, 2005, issued as U.S. Pat. No. 7,280,177 on Oct. 9, 2007, which is a continuation of U.S. Ser. No. 10/602,710, filed on Jun. 25, 2003, issued as U.S. Pat. No. 6,850,302 on Feb. 1, 2005, which claims priority to Korean Patent Application No. 2002-0036979, filed Jun. 28, 2002. The disclosures of the above-cited applications are incorporated by reference herein in their entireties. BACKGROUND OF THE INVENTION [0002] (a) Field of the Invention [0003] The present invention relates to a liquid crystal display, and in particular, to a panel for the liquid crystal display. [0004] (b) Description of Related Art [0005] Generally, a liquid crystal display (LCD) includes a liquid crystal (LC) panel assembly including two panels provided with two kinds of field generating electrodes such as pixel electrodes and a common electrode and a LC layer with dielectric anisotropy interposed therebetween. The variation of the voltage difference between the field generating electrodes, i.e., the variation in the strength of an electric field generated by the electrodes changes the transmittance of the light passing through the LCD, and thus desired images are obtained by controlling the voltage difference between the electrodes. [0006] However, the LCD involves a critical shortcoming of the narrow viewing angle. In order to overcome such a problem, various techniques for widen the viewing angle have been developed, and among them, a technique of forming cutouts or protrusions at the pixel electrodes and the common electrode while aligning the LC molecules vertical to the upper and lower panels is the strongest candidate for the wide viewing angle technique. [0007] The cutouts provided at the respective pixel electrodes and the common electrode generate fringe fields, which control the tilt directions of the LC molecules are controlled to thereby widen the viewing angle. [0008] The protrusions provided on the respective pixel electrodes and the common electrode deform the electric field, and the tilt directions of the LC molecules are controlled due to the deformed electric field to thereby widen the viewing angle. [0009] Alternatively, the cutouts are provided at the pixel electrodes of a lower panel while protrusions are provided at the common electrode of an upper panel. Fringe fields generated by the cutouts and the protrusions controls the tilt directions of the LC molecules to thereby form multiple domains. [0010] The multi-domain LCD involves a very excellent contrast-based viewing angle or gray inversion-based viewing angle of up to 80° or more in all directions. The contrast-based viewing angle is defined as a viewing angle showing the contrast ratio of 1:10, and the gray inversion-based viewing angle is defined by the limit angle of the inter-gray luminance inversion. However, the multi-domain LCD shows a lateral gamma curve distortion that the front gamma curve and the lateral gamma curve do not agree to each other is made to exhibit deteriorated left and right visibility even compared with the twisted nematic (TN) mode LCD. For instance, the patterned vertically aligned (PVA) mode LCD having cutouts for partitioning domains becomes brighter and color-shifts to white as it goes to the lateral sides. In a serious case, the difference between the bright grays is eradicated, and hence, the images become conglomerated. However, it becomes a critical matter to improve the visibility more and more as the LCD has been recently used for the multimedia purpose to display still or moving picture images. SUMMARY OF THE INVENTION [0011] A liquid crystal display is provided, which includes: a first insulating substrate; first and second signal lines formed on the first insulating substrate; a third signal line formed on the first insulating substrate and crossing the first and the second signal lines; a first thin film transistor connected to the first and the third signal lines; a second thin film transistor connected to the second and the third signal lines; a first pixel electrode connected to the first thin film transistor; a second pixel electrode connected to the second thin film transistor; a second insulating substrate facing the first insulating substrate; a common electrode formed on the second insulating substrate; a liquid crystal layer interposed between the first and the second insulating substrates and including a first liquid crystal region on the first pixel electrode and a second liquid crystal region on the second pixel electrode; and a domain partitioning member formed on at least one of the first and the second insulating substrates for partitioning the first and the second liquid crystal regions into a plurality of domains, respectively, wherein the domains of each of the first and the second liquid crystal regions includes a first directional domain and a second directional domain, the average directors of liquid crystal molecules in the first and the second directional domains are angled with respect to the first or the second signal line by a predetermined degree of about 0-90°, and the first pixel electrode and the second pixel electrode are capacitively coupled. [0012] It is preferable that the first pixel electrode occupies about 50-80% of an entire area of the first and the second pixel electrodes, and the second thin film transistor is activated after the first thin film transistor is activated. [0013] The threshold voltage of the first pixel electrode is preferably lower than the threshold voltage of the second pixel electrode by about 0.4-1.0V. [0014] The liquid crystal display may further includes a storage electrode line formed on the first substrate and forming storage capacitors along with the first and the second pixel electrodes. [0015] The average director of the liquid crystal molecules in the first and the second directional domains are preferably angled with respect to the first or the second signal line by about 45°. [0016] Preferably, the liquid crystal display further includes a first polarizer placed on an outer surface of the first substrate and having a polarizing axis parallel to the first or the second signal line, and a second polarizer placed on an outer surface of the second substrate and having a polarizing axis crossing the polarizing axis of the first polarizing plate. [0017] A thin film transistor array panel is provided, which includes: an insulating substrate; first and second gate lines formed on the substrate; a gate insulating layer formed on the first and the second gate lines; a semiconductor layer formed on the gate insulating layer; a data line formed at least on the semiconductor layer and intersecting the gate lines; first and second drain electrodes formed at least on the semiconductor layer and located near the intersection between the first gate line and the data line; third and fourth drain electrodes formed at least on the semiconductor layer and located near the intersection between the second gate line and the data line; a coupling electrode formed on the gate insulating layer; a passivation layer formed on the data line, the first to the fourth drain electrodes, and the coupling electrode and having a plurality of contact holes exposing the first to the fourth drain electrodes and the coupling electrode; a first pixel electrode formed on the passivation layer and connected to the first drain electrode and the coupling electrode; a second pixel electrode formed on the passivation layer and connected to the second drain electrode; a third pixel electrode formed on the passivation layer and connected to the third drain electrode; and a fourth pixel electrode formed on the passivation layer and connected to the fourth drain electrode and partially overlapping the coupling electrode, wherein at least one of the first and the fourth pixel electrodes has an oblique cutout. [0018] A liquid crystal display is provided, which includes: a first insulating substrate; first and second gate lines formed on the first substrate; a gate insulating layer formed on the first and the second gate lines; a semiconductor layer formed on the gate insulating layer; a data line formed at least on the semiconductor layer and intersecting the gate lines; first and second drain electrodes formed at least on the semiconductor layer and located near the intersection between the first gate line and the data line; third and fourth drain electrodes formed at least on the semiconductor layer and located near the intersection between the second gate line and the data line; a coupling electrode formed on the gate insulating layer; a passivation layer formed on the data line, the first to the fourth drain electrodes, and the coupling electrode and having a plurality of contact holes exposing the first to the fourth drain electrodes and the coupling electrode; a first pixel electrode formed on the passivation layer and connected to the first drain electrode and the coupling electrode; a second pixel electrode formed on the passivation layer and connected to the second drain electrode; a third pixel electrode formed on the passivation layer and connected to the third drain electrode; a fourth pixel electrode formed on the passivation layer and connected to the fourth drain electrode and partially overlapping the coupling electrode; a second insulating substrate facing the first insulating substrate; a common electrode formed on the second insulating substrate; a liquid crystal layer interposed between the first and the second insulating substrates; and a domain partitioning member formed on at least one of the first and the second insulating substrates and partitioning the liquid crystal layer into a plurality of domains, wherein two long edges of the domains are angled with respect to the gate line or the data line substantially by about 45°. [0019] Preferably, the first pixel electrode occupies about 50-80% of an entire area of the first and the fourth pixel electrodes and the fourth pixel electrode is supplied with a voltage after the first pixel electrode is supplied with a voltage. [0000] The threshold voltage of the first pixel electrode is preferably lower than the threshold voltage of the fourth pixel electrode by about 0.4-1.0V. BRIEF DESCRIPTION OF THE DRAWINGS [0020] The above and other advantages of the present invention will become more apparent by describing preferred embodiments thereof in detail with reference to the accompanying drawings in which: [0021] FIG. 1 is a circuit diagram of an LCD according to an embodiment of the present invention; [0022] FIG. 2 is a layout view of an LCD according to an embodiment of the present invention; [0023] FIG. 3A is a sectional view of the LC panel assembly shown in FIG. 2 taken along the line IIIB-IIIB′; [0024] FIG. 3B is a sectional view of a TFT array panel shown in FIG. 3A , which is a portion of the LC panel assembly shown in FIG. 3A except for a color filter array panel and polarization films; [0025] FIG. 3C is a sectional view of a TFT array panel shown in FIG. 2 taken along the line IIIC-IIIC′; [0026] FIG. 4 is a graph illustrating the distortion in the visibility as a function of the voltage shift and the domain ratio; [0027] FIG. 5 is a graph illustrating gamma curves for a front view and a lateral view of a conventional patterned-vertically-aligned (PVA) LCD; [0028] FIG. 6 is a graph illustrating gamma curves for a front view and a lateral view of an LCD according to an embodiment of the present invention; [0029] FIG. 7 illustrates measured gamma curves of a conventional PVA mode LCD; and [0030] FIG. 8 illustrates measured gamma curves of an LCD according to an embodiment of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0031] The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. [0032] In the drawings, the thickness of layers, films and regions are exaggerated for clarity. Like numerals refer to like elements throughout. It will be understood that when an element such as a layer, film, region or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. [0033] Now, LCDs according to embodiments of this invention will be described in detail with reference to the accompanying drawings. [0034] FIG. 1 is an equivalent circuit diagram of a pixel of an LCD according to an embodiment of the present invention. [0035] Referring to FIG. 1 , an LCD according to an embodiment includes a plurality of display signal lines G i , D j and 131 and a plurality of pixels connected thereto and arranged substantially in a matrix. [0036] The display signal lines G i and D j include a plurality of gate lines G i transmitting gate signals (called scanning signals) and a plurality of data lines D j transmitting data signals. The gate lines G i extend substantially in a row direction and are substantially parallel to each other, and the data lines D j extend substantially in a column direction and are substantially parallel to each other. [0037] The display signal lines 131 further includes a plurality of storage electrode lines 131 located between the gate lines G i and between the pixels and supplied with a common voltage Vcom. [0038] Each pixel P ij (i=1, 2, . . . , n and j=1, 2, . . . , m) includes a pair of subpixels P i,j 1 and P i,j 2 , and each subpixel P i,j 1 or P i,j 2 includes a switching element Q 1 or Q 2 connected to a pair of one of the gate lines G i and one of the data lines D j , and an LC capacitor C LC1 or C LC2 and a storage capacitor C ST1 or C ST2 that are connected to the switching element Q 1 or Q 2 . [0039] Two adjacent pixels in the column direction are capacitively coupled by a coupling capacitor Cpp. For example, an upper subpixel P i,j 1 of a pixel P ij is capacitively coupled with a lower subpixel P i,j 2 of an upper pixel P i−1j , and a lower subpixel P i,j 2 of a pixel P ij is capacitively coupled with an upper subpixel P i+1,j 1 of a lower pixel P i+1,j . [0040] The switching element Q 1 or Q 2 has three terminals: a control terminal connected to one of the gate lines G 1 -G n ; an input terminal connected to one of the data lines D 0 -D m ; and an output terminal connected to the LC capacitor C LC1 or C LC2 , the storage capacitor C ST1 or C ST2 , and the coupling capacitor Cpp. [0041] The LC capacitor C LC1 or C LC2 is connected between the switching element Q 1 or Q 2 and a common voltage Vcom. The storage capacitor C ST1 or C ST2 is connected between the switching element Q 1 or Q 2 and the storage electrode line 131 . [0042] Now, an LC panel assembly for an LCD according to an embodiment of the present invention is described in detail with reference to FIGS. 2 to 3C . [0043] FIG. 2 is a layout view of an LC panel assembly according to an embodiment of the present invention, FIG. 3A is a sectional view of the LC panel assembly shown in FIG. 2 taken along the line IIIB-IIIB′, and FIG. 3B is a sectional view of a TFT array panel shown in FIG. 3A , which is a portion of the LC panel assembly shown in FIG. 3A except for a color filter array panel and polarization films. FIG. 3C is a sectional view of a TFT array panel shown in FIG. 2 taken along the line IIIC-IIIC′. [0044] Referring to FIG. 3A , an LC panel assembly according to this embodiment includes a TFT array panel 100 , a color filter array panel 200 facing the TFT array panel 100 , and an LC layer 3 interposed therebetween. [0045] Referring to FIGS. 2 to 3C , the TFT array panel 100 includes a plurality of gate lines 121 and a plurality of storage electrode lines 131 formed on an insulating substrate 110 preferable made of transparent glass. Each gate line 121 extends substantially in a row direction and includes a plurality of gate electrodes 124 . The storage electrode lines 131 extend substantially in the row direction and are partially curved. [0046] A gate insulating layer 140 is formed on the gate lines 121 and the storage electrode lines 131 , and a plurality of semiconductor islands 154 is formed on the gate insulating layer 140 opposite the gate electrodes 124 . Each semiconductor island 154 is preferably made of amorphous silicon (“a-Si”) and forms a channel of a TFT. A plurality of ohmic contacts 163 , 165 a and 165 b preferably made of a-Si heavily doped with N type impurity such as phosphorous (P) are formed on the semiconductor islands 154 . [0047] A plurality of data lines 171 , a plurality of pairs of drain electrodes 175 a and 175 b , and a plurality of coupling electrodes 177 are formed on the ohmic contacts 163 , 165 a and 165 b and the gate insulating layer 140 . [0048] Each data line 171 extends substantially in a column direction and includes a plurality of source electrodes 173 , and each source electrode 173 is located opposite a pair of drain electrodes 175 a and 175 b separated therefrom with respect to the gate electrode 124 . [0049] Each pair of drain electrodes 175 a and 175 b extends opposite directions with respect to the gate line 124 . [0050] Each coupling electrode 177 extends in the column direction across the storage electrode line 131 . [0051] The portions of the semiconductor islands 154 located between the source electrode 173 and the drain electrodes 175 a and 175 b are exposed, and the ohmic contacts 163 , 165 a and 165 b are disposed only between the semiconductor islands 154 and the data lines 171 and the drain electrodes 175 a and 175 b. [0052] A passivation layer 180 is formed on the data lines 171 , the drain electrodes 175 a and 175 b , and the coupling electrodes 177 . The passivation layer 180 has a plurality of contact holes 185 a and 185 b exposing end portions of the drain electrodes 175 a and 175 b and a plurality of contact holes 187 exposing end portions of the coupling electrodes 177 . The passivation layer 180 further has a plurality of contact holes 182 exposing end portions 179 of the data lines 171 , and the passivation layer 180 and the gate insulating layer 140 have a plurality of contact holes 181 exposing end portions 129 of the gate lines 121 . [0053] A plurality of pairs of pixel electrodes 190 a and 190 b and a plurality of contact assistants 81 and 92 are formed on the passivation layer 180 . The pixel electrodes 190 a and 190 b and the contact assistants 81 and 92 are preferably made of a transparent conductive material such as indium-tin-oxide (ITO) and indium-zinc-oxide (IZO) or a reflective material. [0054] Each pair of pixel electrodes 190 a and 190 b includes a lower pixel electrode 190 a and an upper pixel electrode 190 b connected to the drain electrodes 175 a and 175 b through the contact holes 185 a and 185 b , respectively. The upper electrode 190 b is connected to the coupling electrode 177 through the contact hole 187 and the lower electrode 190 a overlaps the coupling electrode 177 such that the lower pixel electrode 190 a of an upper pixel and the upper pixel electrode 190 b of a lower pixel are capacitively coupled. In addition, the lower pixel electrode 190 a of an upper pixel and the upper pixel electrode 190 b of a lower pixel are located opposite across the storage electrodes line 131 and overlap the storage electrode line 131 to form a plurality of storage capacitors. The edges of the pixel electrodes 190 a and 190 b opposite across the storage electrode line 131 are curved to form V shapes, and the V-shaped edge of the pixel electrode 190 a is convex, while that of the pixel electrode 190 b is concave. [0055] Each lower pixel electrode 190 a has upper, lower and central linear cutouts 91 - 93 . The central cutout 93 is located at the middle portion in the column direction and enters into the pixel electrode 190 a from the left to the right, thereby partitioning the pixel electrode 190 a into upper and lower partitions. The upper and the lower cutouts 91 and 92 obliquely extend in the upper and the lower partitions, respectively, and are located symmetrically with respect to the central cutout 93 . [0056] The contact assistants 81 and 82 are connected to the exposed end portions 129 and 179 of the gate lines 121 and the data lines 171 through the contact holes 181 and 182 , respectively, and provided for protecting the exposed end portions 129 and 179 but is optional. [0057] An alignment layer 11 is coated on the entire surface of the TFT array panel 100 except for the contact assistants 81 and 82 . [0058] One gate electrode 124 , one source electrode 173 , and a pair of drain electrodes 175 a and 175 b along with one semiconductor island 154 form a pair of TFTs respectively connected to the pixel electrodes 190 a and 190 b. [0059] Referring to FIGS. 2 and 3B , the color filter array panel 200 includes a black matrix 220 formed on an insulating substrate 210 preferably made of transparent glass. The black matrix 220 defines a plurality of windows where a plurality of red, green and blue color filters 230 are formed. An overcoat is formed on the color filters and a common electrode 270 is formed thereon. The common electrode 270 is preferably made of a transparent conductive material such as ITO and IZO, and has a plurality of sets of four linear cutouts 271 - 274 . Three 271 - 273 of the cutouts 271 - 274 overlap the lower pixel electrode 190 a to partition the pixel electrode 190 a along with the cutouts 91 - 93 into a plurality of subareas. The cutout 274 having a V shape overlap the upper electrode 190 b to bisect the upper pixel electrode 190 b into two subareas. An alignment layer 21 is coated on the entire surface of the color filter array panel 200 . [0060] Each subarea defined by the cutouts 91 - 93 and 271 - 273 has substantially a shape of a tetragon having two major edges making an angle of about 45 degrees with the gate lines 121 and the data lines 171 . The subareas defined by edges of the upper pixel electrode 190 b and the cutout 274 have V shapes, which are combinations of two tetragons. [0061] A pair of polarizers 12 and 22 are attached to outer surfaces of the panels 100 and 200 , respectively. The polarization, axes of the polarizers 12 and 22 are crossed and substantially parallel to the gate lines 121 or the data lines 171 . [0062] The molecules of the LC layer 3 are aligned such that their major axes are substantially perpendicular to the surfaces of the panels 100 and 200 in absence of electric field. [0063] Referring back to FIG. 1 , the difference between the data voltage and the common voltage Vcom applied to a pixel is expressed as a charged voltage of the LC capacitor C LC1 or C LC2 , i.e., a pixel voltage. The LC molecules have orientations depending on the magnitude of the pixel voltage and the orientations determine the polarization of light passing through the LC capacitor C LC1 or C LC2 . The polarizers 11 and 21 convert the light polarization into the light transmittance. [0064] In the meantime, it is assumed that the difference between a data voltage for a pixel Pup and the common voltage Vcom is d up , and pixel voltages charged in LC capacitors C LC1 and C LC2 of the upper and the lower subpixels P up 1 and P up 2 of the pixel Pup are V(P up 1 ) and V(P up 2 ), respectively. In addition, let us assume that the lower subpixel P up 2 of the pixel Pup and the upper subpixel P down 1 of the pixel Pdown are coupled with a coupling capacitor Cpp, and the difference between the data voltage for the pixel Pdown and the common voltage Vcom is d down . Furthermore, after the pixel Pup is supplied with the data voltage, the pixel Pdown is supplied with the data voltage. Then, the following relations are satisfied: [0000] V  ( P up 1 ) = d up ; and ( 1 ) V  ( P up 2 ) = d up + Cpp C LC   2 + C ST   2 + Cpp · ( d down - d down ′ ) . ( 2 ) [0065] In Equations 1 and 2, C LC2 and C ST2 are the capacitances of the LC capacitor and the storage capacitor of the lower subpixel P up 2 , Cpp is the capacitance of the coupling capacitor, and d′ down is the difference between the data voltage applied to subpixel P down 1 in a previous frame and the common voltage Vcom. For descriptive convenience, the wire resistance and the signal delay of the data lines D j are ignored. [0066] In Equation 2, if d down and d′ down have opposite polarity since d up and d down have the same polarity, the pixel Pdown displays the same gray as the pixel Pup, and the displayed images are still images, d up =d down =−d down and thus Equation 2 becomes: [0000] V  ( P up 2 ) = d up + 2  d up  Cpp C LC   2 + C ST   2 + Cpp = C LC   2 + C ST   2 + 3  Cpp C LC   2 + C ST   2 + Cpp  d up = T 1  d up ,   where   T   1 = C LC   2 + C ST   2 + Cpp C LC   2 + C ST   2 + Cpp > 1. ( 3 ) [0067] On the contrary, if d up and d down have opposite polarities, the pixel Pdown displays the same gray as the pixel Pup, and the displayed images are still images, Equation 2 becomes: [0000] V  ( P up 2 ) = d up - 2  d up  Cpp C LC   2 + C ST   2 + Cpp = C LC   2 + C ST   2 - Cpp C LC   2 + C ST   2 + Cpp  d up = T 2  d up ,   where   T   2 = C LC   2 + C ST   2 - Cpp C LC   2 + C ST   2 + Cpp < 1. ( 4 ) [0068] According to Equations 3 and 4, if a lower subpixel P up 2 of a pixel Pup is capacitively coupled with a upper subpixel P down 1 of a pixel Pdown, the lower subpixel P up 2 of the pixel Pup is charged with a voltage higher than that charged in the upper subpixel P up 1 of the pixel Pup when the polarity of the data voltages applied to the two subpixels P up 2 and P down 1 is the same, and vice versa when the polarity is opposite. [0069] This pixel structure that a pixel includes two switching elements and two LC capacitors and adjacent pixels are capacitively coupled by a coupling capacitor prevents gray inversion at a bottom view and improves visibility at all directions. [0070] FIG. 4 is a graph illustrating the distortion in the visibility as function of the voltage shift and the areal ratio of the pixel electrodes. [0071] The vertical axis shown in FIG. 4 indicates the value of quantifying the distortion in the visibility, and the horizontal axis indicates the areal ratio between lower and upper pixel electrodes 190 a and 190 b for the voltage shifts 0, 0.4V and 0.6V. [0072] The visibility distortion in a range of 0.1-0.2 means that the visibility is exceptionally excellent, which is equal to the level of the cathode ray tube (CRT), and the visibility distortion in a range of 0.2-0.25 means that the visibility is very excellent. The visibility distortion in a range of 0.25-0.3 means that the visibility is excellent, and the visibility distortion in a range of 0.3-0.35 means that the visibility is good. However, the visibility distortion less than about 0.35 means that the visibility is bad, which results in the poor display quality. [0073] It is known from FIG. 4 that an excellent visibility is obtained when the areal ratio of the lower pixel electrode to the upper pixel electrode is in a range of 50:50-80:20, and when the voltage shift is in a range of 0.4-1.0V close to a threshold voltage Vth. That is, the lower pixel electrode is preferably designed to be larger than the upper pixel electrode. However, when the lower pixel electrode is equal to or larger than 80%, various problems such as a flicker phenomenon may be made due to the kick-back voltage or other factors. Furthermore, when the threshold voltage Vth of the lower pixel electrode is lower than the threshold voltage Vth of the upper pixel electrode by 0.4-1.0V, the visibility is improved. The voltage difference between the lower and the upper pixel electrodes for the higher grays may be greater. [0074] Then, the reason why the visibility is improved with the LCD according to the present invention will be now described with reference to FIGS. 5 and 6 . [0075] FIG. 5 is a graph illustrating gamma curves C 1 and C 2 respectively for a front view and a lateral view of a conventional patterned-vertically-aligned (PVA) LCD, and FIG. 6 is a graph illustrating gamma curves C 3 and C 4 respectively for a front view and a lateral view of an LCD according to an embodiment of the present invention. [0076] As shown in FIG. 5 , the lateral gamma curve C 2 of a conventional PVA LCD having one pixel electrode for a pixel is largely deformed upward compared with the front gamma curve C 1 . [0077] However, according to an embodiment of the present invention, when the data voltage is established such that the pixel voltage applied to the lower subpixel is lower than the usual data voltage, the voltage of the lower subpixel may be kept to be lower than a threshold voltage Vth for some lower grays. Accordingly, the lower subpixel is kept to be in a black state, while the upper subpixel exhibits a transmitting state as indicated by reference character A in FIG. 6 . However, since the area of the upper pixel electrode is small, the total luminance is small than that of a conventional LCD. For the gray equal to or larger than a predetermined value (indicated by reference character B), the voltage of the lower subpixel exceeds the threshold voltage Vth, and hence, the lower subpixel also contributes to the total luminance. Therefore, the increase of the luminance depending on the gray increase is enlarged. Accordingly, as shown in FIG. 6 , the distortion in the gamma curve becomes decreased. [0078] FIG. 7 illustrates measured gamma curves of a conventional PVA mode LCD, and FIG. 8 illustrates measured gamma curves of an LCD according to an embodiment of the present invention. [0079] Comparing the gamma curves illustrated in FIGS. 7 and 8 , it can be known that the gamma curve distortion for all directions of the LCD according to the embodiment of the present invention be smaller than that of the conventional LCD for all directions. [0080] As described above, two pixel electrodes and two TFTs are assigned to one pixel, and the two pixel electrodes of adjacent two pixels are capacitively coupled, thereby improving the visibility in all directions. Furthermore, as the domain partitioning is made such that the average director of the liquid crystal molecules is angled with respect to the gate line or the data line by 45°, polarizers having polarizing axes parallel to the gate line or the data line can be used. Consequently, the production cost for the polarizing plate can be reduced. [0081] Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the spirit and scope of the present invention, as defined in the appended claims.

A liquid crystal display (LCD) is provided, which includes: first and second gate lines, a data line intersecting the gate lines, first to fourth drain electrodes located near the intersections between the first and second gate lines and the data line, and a coupling electrode. First to fourth pixel electrodes respectively connected to the first to fourth drain electrodes are also provided, and the first pixel electrode is connected to the coupling electrode while the fourth pixel electrode overlaps the coupling electrode. The LCD further includes a common electrode opposite the pixel electrodes, a liquid crystal layer interposed between the pixel electrodes and the common electrode, and a domain partitioning member formed on at least one of the pixel electrode and the common electrode. Two long edges of the domains are angled with respect to the first and the second gate lines or the data line substantially by about 45°.

BACKGROUND OF THE INVENTION 1. Field of the Invention. The invention generally relates to conductors and insulators. More specifically, the invention relates to boxes and housings, especially to covers or face plates for termainal housings. The invention also generally relates to receptacles, and more specifically to the outlet or junction box type, with closure. A termainal block cover is disclosed that is especially adapted for use with terminal blocks of the type employed with telephone systems. 2. Description of the Prior Art The terminal block is a widely used commodity in commercial telephone installation equipment. The block usually is an elongated rectangle that is formed from nonconductive plastic material and supports a plurality of conductive wire terminators. The longitudinally elongated sides of the block carry fanning strips that aid in separating and supporting the many individual wires that are routed into the block. In a typical installation, one or more terminal blocks are mounted on a wall in vertical position, and telephone cables from a trunk system are routed to the blocks, where the individual wires of a trunk cable are individually attached to the separate terminating clips that are carried in the block. The terminating clip, also a well known device, is a metallic conductor that is capable of receiving and holding two or more separate wires in electrical contact with each other. Each separate terminating clip typically includes a distinct clip portion corresponding to each wire, all such clip portions being in electrical contact with each other, such that all wires that are to be connected via the same clip can be individually installed or removed. Thus, in incoming trunk cable containing, for example, twenty five wire pairs, will have its wires fanned out and attached to first clip portions of fifty individual terminating clips, which may be contained in a single terminal block. Then, these trunk system wires are readily available for individual connection to local telephone equipment by attachment of wires from the local system to the second clip portions of the terminating clips. The block, therefore, is an interface between trunk cables and local equipment, enabling the installer to easily and quickly identify the wire pairs of the trunk cable and make appropriate attachment to local system wires. Terminal blocks are covered for protection of the terminating clips and wires and to prevent accidental short circuits or other damage to the internal connections. It is quite important that the covers be employed, as the terminal blocks often must be mounted in closets or storage rooms, where various types of mistreatment and contact with foreign matter is common. At the same time, the terminal block may be subject to frequent rewiring and must be available to telephone service technicians. Thus, the covers should be readily removable so that technicians can locate relevant wire pairs. Still another function of the cover is to provide a location for technicians to record informtion about the connections and equipment. Thus, the requirements of a good cover include firm, easy fastening to the block; rapid opening for inspection; and an ability to be written upon. Various types of terminal block covers are known. For example, U.S. Pat. No. 3,836,826 discloses a snap-on cover that includes a means for preventing longitudinal sliding. U.S. Pat. No. 3,966,074 discloses a terminal block cover that has fastening elements that are adapted to engage parts of the fanning strips on the edges of the terminal block. While these types of covers are excellent in their protective functions, it is often desirable to be able to open terminal block covers while retaining the cover on the block. This prevents mixing covers, which is especially important when information concerning the connections is written on the cover. Also, a semi-permanently attached cover is less subject to loss or theft and is more likely to be reinstalled after removal. Still another desirable feature is to have a cover that can be indexed to the terminal block by its position, so that information on the cover can be related to specific terminals within the block. Another type of cover in present use, but for which no patent is known, employs a face plate of molded plastic with a plastic "living hinge" at one edge. The hinge is connected to a side plate that carries spring hooks that engage a plurality of the fanning strips on the sides of the terminal block. The opposite edge of the face plate carries another side plate, which includes a friction latch that engages over the fanning strips. This type of cover can be opened on its hinge and may stay attached to its terminal block even when open. Also, it may be removed from the terminal block by lateral pulling. Removal may be difficult, however, depending upon the amount of lateral space that is present. Also, the life of a plastic living hinge is short due to the quantity of fire-retardant that is required in plastic materials used in electrical service. A further disadvantage is that the side plate carrying the spring hooks largely covers the fanning strips on the hinge side of the terminal block, preventing the technician from wiring through that side of the block without entirely removing the cover. Consequently, it would be desirable to have a hinged cover of improved hinge durability. Also, it would be desirable to have a cover that is capable of being removed even in close-mounting situations. In addition, after such a cover is removed, it would be desirable to have its position indexed to the terminal block, so that it will be reinstalled in an indentical location. Further, it would be desirable to have an attachment between the cover and terminal block such that substantially all of the fanning strips on the terminal block are accessible. In those instances when it is necessary to entirely remove the cover from the block, it would be desirable to have a cover that retains its indexing. To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the terminal block cover of this invention may comprise the following. SUMMARY OF THE INVENTION Against the described background, it is therefore a general object of the invention to provide an improved terminal block cover of the type that is semi-permanently installed. More specifically, an object is to create a terminal block cover of plastic construction, wherein the structure is such that the necessary or required amounts of fire retardant materials can be used in the plastic without degrading the structure or operational life of the cover. Another object is to create a termainal block cover that attaches to the fanning strip on one side of the block without substantially interfering with the ability of the fanning strip to be used for wiring purposes. Still another object is to create a terminal block cover that can be removed from the terminal block while retaining the original indexing of the cover to the block. An important object is to create a terminal block cover that can be separated from the terminal block only when in a preselected relative position to the block, with the result that the cover is positively retained on the terminal block in substantially all other positions, whether closed or open, and therefore is unlikely to be lost or inadvertently removed under normal handling. Additional objects, advantages and novel features of the invention shall be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by the practice of the invention. The object and the advantages of the invention may be realized and attained by means of the instrumentalities and in combinations particularly pointed out in the appended claims. According to the invention, a terminal block cover is provided for use with a terminal block of the type having a longitudinally extending face, bottom, and first and second opposite sides, with a fanning strip located along each of the first and second longitudinal sides and defining a laterally extending lip at the side margins of the terminal block face. A cover body, in use, covers the face of a terminal block, and a latch means depends from the cover body for releasably engaging the first lateral side of the terminal block. Further, a hinge means depends from the cover body, engages a fanning strip on the second lateral side of the terminal block, and permits the cover body to pivot thereon. The hinge means includes a clip means for engaging the fanning strip at a substantially fixed position; a separable pivot means connected between the clip means and cover body for permitting pivotal movement of the cover body with respect to the clip means and permitting removal of the cover body from connection with the clip means; and a positional locking means for preventing removal of the cover body from connection with the clip means only when the cover body and clip means are in first predetermined relative pivotal positions on said pivot means, and permitting removal of the cover body from connection with the clip means when the cover body and clip means are in second predetermined relative pivotal positions on the clip means. The accompanying drawings, which are incorporated in and form a part of the specification illustrate preferred embodiments of the present invention, and together with the description, serve to explain the principles of the invention. In the drawings: BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of the terminal block cover as installed on a terminal block, as viewed from the hinge side of the cover. FIG. 2 is a cross-sectional view taken along the plane of line 2--2 of FIG. 1, showing a detail of hinge construction. FIG. 3 is a fragmentary cross-sectional view taken along the plane of line 3--3 of FIG. 1, showing another detail of hinge construction. FIG. 4 is a fragmentary side elevational view of a hinge area of the cover taken from inside the terminal block, with the cover installed on a terminal block, with the face plate of the cover open to ninety degrees to the terminal block, showing the relationship of the main cover to a pin unit. FIG. 5 is a cross-sectional view taken along the plane of line 5--5 of FIG. 4, showing the relationship of main cover to a pin unit. FIG. 6 is view similar to FIG. 5, but with the cover open to 180 degrees from the terminal block. FIG. 7 is a fragmentary side view of a pin unit being installed on the fanning strip of a terminal block, showing an initial position of the pin unit. FIG. 8 is a view similar to FIG. 7, showing an intermediate position of the pin unit. DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings, the terminal block cover assembly 10 is a three sided lid that fits over the top of a conventional terminal block 12. The cover is formed from two components, the first being the cover body 14 and the second being the pin unit 16. Each cover body 14 is connected to two or more pin units 16 to form an entire cover assembly 10. When the lid has been installed and is closed over a terminal block, the lid covers the face of the block and latches on one side. The second side is mounted on hinges that protrude laterally from the side of the block and pivot on an axis that is parallel to the longitudinal dimension of the terminal block. The hinges may be separated when the lid is partially open, such as at ninety degrees, to allow removal of the lid. At other open positions, the hinges are locked against separation. The terminal block 12 is an existing and well known element of telephone installation equipment. As can be seen in the drawings, the terminal block is in the general shape of an elongated rectangle, which is formed from a suitable electrically nonconductive material such as a plastic. The longitudinal surfaces of the terminal block include a face, an opposed bottom, and first and second opposite sides, with a row of fanning strips located along each of the first and second longitudinal sides and defining the side margins of the terminal block face. FIG. 2 shows that the block also is a rectangle in transverse cross-section. Defined within the terminal block body in longitudinally spaced sequence are a plurality of cavities 18, FIG. 2, that receive and retain conductive metal terminating clips 20. As best shown in FIGS. 1 and 4, the upper portion of the longitudinally extending side walls of the block are defined by rows of fanning strips 22, which are upstanding between the bottom and face of the terminal block. Each fanning strip is T-shaped in side view and ends at the face of the terminal block with a widened cap 24. A wire passage 26 is thus formed between adjacent fanning strips and has a narrow entrance formed between the widened caps 24. Each fanning strip is laterally aligned with a transversely extending terminating clip, with the resultant structure permitting a wire to be passed to a separate terminating clip through substantially each passage 26. Further, FIG. 2 shows that the cap 24 of each T-shaped fanning strip 22 is lengthened not only longitudinally but also laterally, such that the caps 24 form a laterally outwardly extending flange along the top edge of the longitudinally extending side of the terminal block. The cover 10 fits over the top face of the terminal block and mates with the side walls of the block to provide a three-sided shield over the terminating clips and their connections to the telephone cable wires. The three sides of the cover body 14 include a face plate means or top wall 28 for covering the face of the terminal block. The second side of the cover body constitutes a hinge means, which may include a hinge side wall 30 depending from the face plate and pivotally engaging a pin unit 16. The pin unit, in turn, includes a clip means for engagement with a fanning strip on one of the lateral sides of the terminal block. A pivot means is connected between the clip means and cover body for permitting pivotal movement of the cover body with respect to the clip means. Also, the pivot means permits removal of the cover body from connection with the clip means and thereby allows the cover body to be removed from the terminal block. The third side is a latch means or latch side wall 32 depending from the face plate for releasably engaging the other lateral side of the terminal block. The two side walls 30 and 32 are longitudinally perpendicular to the face plate and depend from its lower surface in order to follow the shape of the terminal block. The latch side wall 32 includes two cooperating elements that constitute a latch means. First, a rib 34 is connected to the latch side wall and extends inwardly, toward the hinge side wall 30. Second, one or more stand-offs 36 are connected to the top wall 28 and latch side wall 32 and extend downwardly toward the rib 34, terminating at a predetermined height above the rib, for example 1/8 inch above the upper edge of the rib. The gap that is thus created between the top of the rib 34 and the bottom of the stand-off 36 provides a reception area for latching engagement of the laterally extending flange of the terminal block, formed by the T-shaped caps 24. The flexibility and resiliency of the plastic walls of the cover 10 permit latch side wall 32 to deflect over the cap flanges 24 during engagement and disengagement of the latch. The rib 34 may be shorter than the length of the cover and is preferred to be centrally located with respect to the length of the cover. For example, the rib may be one inch long on a cover having a ten inch length. The stand-offs 36 may be longitudinally offset from the position of the rib. For example, two such stand-offs may be employed, one on each longitudinal end of the rib, each being offset longitudinally about half way between the closest end of the rib and the nearest longitudinal end of the cover. The hinge side wall 30 and pin units 16 define a separable pivot means for allowing both the pivotal hinging motion of the cover body 14 with respect to the terminal block and removal of the cover body from the termainal block. The hinge side wall 30 of the cover may have a hinge pin housing 38 connected to its outside surface. A preferred housing is formed from three or more spring fingers 40 that are composed of the same flexible, resilient plastic material as the cover body. Each finger forms approximately a semi-circular ring around a central cylindrical, longitudinal cavity that is sized to receive a hinge pin 42 of the pin unit. The fingers are axially juxtaposed and offset on alternating radially opposite sides of the cavity axis. One end of each finger is attached to the cover body at the hinge wall, and the other end is free, which permits each finger to flex from its attached end. When three such fingers are employed, the finger in the center position is alone on one radial side of the hinge axis and is opposed by the remaining two fingers, each of which is at an opposite axial end of the axis and is opposed to the central finger by one-half revolution. Thus, each finger is unrestricted by the others in its ability to flex radially to the housing axis so that the fingers are free to clamp the pin 42. At the same time, the fingers define a substantially continuous cylinder wall around the cavity, which permits longitudinal reception and removal of the pin. The hinge pin 42 is a part of the pin unit 16 and is attached at one end to a generally cylindrical base portion 43 of the pin unit that is of larger diameter than the pin and thereby provides a supporting surface at the attached end for contact with the hinge pin housing. The diameter of the pin is slightly larger than the diameter of the cavity in the hinge pin housing, so that the pin will be held in the housing under pressure of the flexible fingers. The diameter of the pin base may be similar to the diameter of the cylinder defined by the hinge pin housing. In use, the cover assembly 10 is expected to be mounted in vertical position, so that the pins 42 extend upwardly from the pin bases 43. Thus, the cover body 14 is retained on the pins by gravity and is not required to rely on the gripping strength of the fingers to hold the cover in place. The pin base 43 therefore provides the expected resting surface that limits the engagement of the pin into the hinge pin housing. The pin unit includes a clip means for engaging the fanning strip at a substantially fixed position, with the result that the pin is held in a stationary longitudinal position on the terminal block. FIG. 2 shows part of the attachment between the clip means and terminal block to be by a pair of flexible clip fingers connected to the pin base 43, including an inside finger 44 and an outside finger 46, each of which fits a surface contour of a fanning strip. Inside finger 44 has an inside bevel on its leading end 47 that serves as a camming means for guiding the deflection of the leading end during installation of the pin base on the terminal block, which will be described below. Further, the inside finger is generally L-shaped, with the longer arm including a shank 48 that is connected to the pin base and fits over the top of the fanning strip cap 24. The shorter arm constitutes a flange or lip that depends perpendicularly from the shank and engages the inside surface of a fanning strip. The shank may establish a face plane 49, FIGS. 7 and 8, that extends through the pin base and results in the diameter of the pin base being reduced where truncated by the face plane. Thus, the supporting surface for the hinge pin housing may be small or absent on the side of the pin base that is cut by the face plane 49. This feature is employed in conjunction with the locking means described below. Another part of the clip means is central prong or tongue 50, as shown in FIG. 3. This tongue is connected to the pin base 43 near the junction of the outside finger and extends parallel to and spaced below the shank of the inside finger. A gap is formed between the tongue and shank, which is of appropriate height to permit reception of a fanning strip cap 24. The tongue fits through the side of a wire passage 26 and is retained under a pair of neighboring caps 24 to index the clip means in a fixed position along the longitudinal dimension of the terminal block. The tongue is limited in its maximum width to the maximum width of a wire passage, and thus may be approximately 1/8 inch wide. In contrast, the fingers and shank may be considerably wider and overlie two or more fanning strip caps 24, such that the shank and fingers cover one fanning strip cap on each side the wire passage engaged by the tongue. The cover body 14 also defines a positional locking means for preventing removal of the main cover from connection with the clip means, but only when the face plate and clip means are in preselected relative pivotal positions with respect to the pin base. The locking means may comprise a notch 52, FIGS. 1 and 5, in the free edge of the hinge side wall, longitudinally juxtaposed to each hinge pin housing. The notch is longitudinally sized to receive the length of the pin base. Also, the notch has a predetermined height in the hinge side wall, as viewed in FIG. 1, that is sufficient to receive and have clearance with the maximum diameter of the pin base as the cover is rotated on the hinge pin axis to orbit the pin base. The locking means operates by engaging the pin base in the notch, which prevents the pin and hinge housing from sliding longitudinally with respect to each other. FIG. 1, for example, shows how the notch and pin base are engaged when the cover is closed on the terminal block. The notch engages the pin base on the inside edge of the hinge pin in the closed position of FIG. 1. However, when the cover is opened by ninety degrees, as shown in FIGS. 4 and 5, the hinge pin housing has elevated the hinge side wall 30 above the face plane 49 of pin base 43, and the notch has been rotated into position parallel with the face plane 49. Thus, according to FIG. 4, the notch 52 is in position to clear the face plane and, consequently, the pin and hinge pin housing can be moved longitudinally with respect to each other. Upon further opening of the cover to 180 degrees, as shown in FIG. 6, the notch again engages the pin base, now on the outside edge of the hinge pin, and locks the hinge against separation. The locking means operates by having a cylindrical hinge pin housing that is attached to and supports the hinge side wall 30 in a tangential position to the core of the housing. Thus, the plane of the hinge side wall 30 is a chord to the hinge pin housing wall, with the plane intersecting the cylindrical side of the hinge pin housing 38. The pin 42 is engaged coaxially in the housing core, and the pin base is sized to a similar large diameter as the hinge pin housing. Accordingly, the hinge side wall 30 also is a chord to the pin base 43 and receives the pin base in a notch formed within the hinge side wall, which prevents actual physical interference between the plane of the chord defined by the hinge side wall 30 and the cylindrical surface of the pin base 43. The shape of the pin base 43 is modified by a flattening at face plane 49, which provides substantially a single position of relative rotation in which the plane the hinge side wall can traverse the wall of the cylindrical pin base without physical interference. Hence, at the single predetermined position of non-interference, the hinge side wall and its attached hinge pin housing can be moved longitudinally with respect to the pin base. At the same longitudinal position as each notch on the cover body 14, a pin unit stand-off 54, FIGS. 5 and 6, depends from the top wall 28 and also may be joined to the hinge side wall 30. This stand-off 54 terminates at a free end that overlies the position of the pin unit when the cover is closed on the terminal block. The stand-off 54 contacts the pin unit on the face plane 49 of the shank when the cover unit and pin unit are in closed position, as shown in FIGS. 2 and 3. Thus, one function of the stand-off 54 is to space and support the hinge side of the cover body away from the face of the terminal block, in cooperation with the stand-offs 36 on the latch side. A second function is to support the pin units with respect to the cover body in a position equivalent to the closed position of the cover body on the terminal block. The latter function is useful for assuring that the pin units remain in locked position with respect to the cover body, such as during shipping. The latter function also aids in installation of the cover assembly to a terminal block. FIGS. 7 and 8 show stages in the installation of the pin unit to a terminal block. It is possible to install the pin units by hand, when they are removed from the cover body. However, the preferred installation method starts with the the pin units attached to the cover body and in closed position. Thus, each pin unit is to be attached to the cover body by engagement of the hinge pin in the hinge pin housing, where the spring fingers grip the hinge pin and prevent loss of the pin unit. Each pin unit is to be supported by a stand-off 54 during combined installation of the entire cover assembly. In such condition, the pin units first are moved into the position of FIG. 7, wherein the tongue 50 approaches the underside of caps 24 and begins to enter a wire passage 26 between two fanning strips 22. At the same time, the bevel 47 on the tip of the inside finger 44 is applied to the top of caps 24, where the bevel assists in deflecting the inside finger and shank while the inside finger slides over the top of caps 24. As the installation progresses to the position of FIG. 8, the pin base 43 is raised with respect to the fanning stip, and the inside finger 44 and tongue 50 are deflected mutually apart and are placed in tension by their resiliency. The beveled leading edge of the inside finger slides forwardly, to the left in FIGS. 7 and 8, until it snaps over the caps 24. In final, installed position, the pin base appears as shown in FIGS. 2 and 3, wherein the fingers 44 and 46 and tongue 50 are engaging the caps of the fanning strips. The tongue 50 then aids in retaining the pin unit on the terminal block by being placed in tension when lifting forces are applied to the free end of the inside finger. Because of the support provided by the stand-offs 54, the entire installation may be accomplished by moving the cover body 14, with the stand-offs applying the necessary force to the pin units. Installation of the cover assembly as a whole in this manner has the advantage of automatically correctly positioning the multiple pin units to carry the cover body in the desired longitudinal position with respect to the terminal block. Once correctly installed, the pin units need not be removed and will maintain their correct longitudinal spacing and positioning without further support from the cover body. Therefore, the pin units will be correctly indexed and positioned for re-hanging of the cover body after it has been removed. Also, such removal and re-installation of the cover, coupled with the small longitudinal length of the pin units compared to the terminal block, allows the installer to wire the terminal block from the hinge side, if desired. In use, the block 12 is mounted on a wall with its longitudinal dimension positioned vertically. Telephone wire cable from outside the terminal block is separated into its individual wires, which are passed into the block through wire passages 26 between the fanning strips 20. Each wire is connected to a terminating clip. The cover assembly 10 is preassembled with pin units 16 held in the hinge pin housings 38 by the spring tension of the fingers 40 and the engagement of the pin bases in notches 52. The cover assembly 10 is installed on the block 12 by positioning the pin units to engage a fanning strip with the pins 42 extending upwardly from the pin bases. The tongues 50 are inserted into wire passages from the outside surface of a fanning strip at appropriate locations to index the cover in the desired longitudinal position with respect to the terminal block, and the free ends of the inside clip fingers 44 are placed on the top of the fanning strip caps 24 with the beveled end 47 against the caps. The cover body is thus held in a plane angled at about forty-five degrees to the plane of the terminal block face. Then the cover assembly is slid in the direction of the opposite row of fanning strips and rotated slightly to reduce the angle with the terminal block face. Such sliding and rotation tensions the inside clip finger and tongue in mutually opposite directions, as these are increasingly deflected. With further sliding, the inside finger 44 snaps over the engaged fanning strips, and the outside finger 46 rests against the bottom outside surface of the flange formed by the caps 24. The assembly then is complete. The cover body then is capable of being pivoted on the hinge pins 42, both to close and open the cover. Removal requires that the cover be opened to the predetermined position at which the hinge side wall is pivoted out of longitudinal interference with the pin bases, after which the cover body is lifted longitudinally to slide the hinge pin housings off the free ends of the pins 42. Reassembly requires reengaging the pin housings on the pins, with the cover body in an equivalent, noninterfering position with respect to the pin bases. When the pins are received in the housings, the cover body may be rotated to close or further open the cover, as desired. The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be regarded as falling within the scope of the invention as defined by the claims that follow.

A terminal block cover provides a cover body having a latch mechanism depending from a side edge of the cover and a hinge mechanism depending from the opposite side edge. The hinge mechanism includes a clip that engages the terminal block's fanning strip, a separable hinge connected between the clip and cover body for permitting removal of the cover body from the terminal block, and a locking device that prevents the cover body from being removed from the terminal block except when it is in a predetermined rotational position on the hinge. The clip provides a prong that engages the fanning strip to index the clip in a fixed position so that the cover body can be reinstalled at the original position. In addition, the clip is held to the hinge mechanism by spring fingers on the hinge pin housing, which cooperate with the locking device to hold the clips in attachment to the cover body even when not installed on a terminal block.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of International Application No. PCT/CN2008/072267, filed on Sep. 4, 2008. This application claims the benefit of Chinese Application No. 200710154146.1, filed on Sep. 19, 2007. The disclosure of the above applications is incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to communication technologies, and in particular, to an IP connectivity access network (IP-CAN) technology. BACKGROUND OF THE INVENTION [0003] In a Third Generation Partnership Project (3GPP) system, policy and charging functions are implemented by a policy and charging control (PCC) architecture. [0004] The PCC architecture mainly enforces policy and charging control. As shown in FIG. 1 , a PCC architecture in the prior art includes an application function (AF), a policy and charging rules function (PCRF), a subscription profile repository (SPR), a policy and charging enforcement function (PCEF), and an online charging system (OCS) or an offline charging system (OFCS). [0005] The AF is adapted to provide access points for service applications and is connected to the PCRF through an Rx interface. Dynamic policy control needs to be performed on the network resources used by these service applications. During parameter negotiation on the service plane, the AF transfers relevant service information to the PCRF. If the service information is consistent with the policy rules defined on the PCRF by operators, the PCRF accepts the service parameters. Otherwise, the PCRF refuses the service parameters and may also carry acceptable service parameters in a response message. Then the AF may return these parameters to users. [0006] The PCRF is adapted to generate policies and charging rules and is connected to the SPR through an Sp interface. As the core of the PCC system, the PCRF provides service data flow based network control rules, including data flow detection, gating, quality of service (QoS) control, and flow-based charging control. The PCRF sends the generated polices and charging rules to the PCEF through a Gx interface and the PCEF charges for service flows accordingly. The PCRF needs to generate policies and charging rules according to the relevant service information obtained from the AF, relevant user subscription data obtained from the SPR, and relevant bearer network information obtained from the PCEF. In addition, the PCRF needs to ensure that these rules are consistent with the user subscription data and to deliver trigger events to the PCEF so that the PCEF may actively request PCC rules from the PCRF when these trigger events occur. [0007] The PCEF is adapted to: enforce the policies and charging rules generated by the PCRF on the bearer plane, receive trigger events delivered by the PCRF so as to actively request PCC rules from the PCRF when these trigger events occur, detect service data flows according to the traffic filter in the rules sent from the PCRF, control these service data flows according to the polices and charging rules generated by the PCRF, and charge for the service data flows online or offline. In online charging mode, the PCEF is connected to the OCS through a Gy interface and works with the OCS to complete credit management. The OCS includes customized applications for mobile network enhanced logic service control point (CAMEL SCP) and a service data flow based credit control. In offline charging mode, the PCEF is connected to the OFCS through a Gz interface and exchanges relevant charging information with the OFCS. In general, the PCEF is located on a gateway (GW) in a network. [0008] The SPR is adapted to store PCC-related user subscription data, including service information that can be used by users, QoS information that can be used by user services, charging-related user subscription data, and group types of users. The PCRF reads the information stored in the SPR through the Sp interface and performs policy control and charging based on user subscription data. [0009] In the PCC architecture, IP-CAN session modification may be initiated by the PCEF. For example, the PCEF may initiate an IP-CAN session modification process when detecting an internal event of IP-CAN session modification caused by an operator's configuration or when detecting a bearer change during data transmission. IP-CAN session modification may also be initiated by the PCRF. For example, the PCRF may initiate an IP-CAN session modification process when the service information at the application layer on the AF changes, when the user subscription data stored in the SPR changes, or when an internal event occurs. [0010] To ensure the competitiveness of the 3GPP system in the coming ten or more years, the 3GPP organization internally proposes system architecture evolution (SAE). In an SAE system, a new PPC architecture including multiple S7 or PCEF interface entities is adopted. In this PCC architecture, multiple S7 or PCEF interface entities are connected to the same PCRF at the same time for any IP-CAN session, which is beyond the capabilities of the PCC architecture in the prior art. [0011] The new PCC architecture includes a roaming PCC architecture and a non-roaming PCC architecture. [0012] FIG. 2 shows a non-roaming PCC architecture in the prior art. The non-roaming PCC architecture includes an AF in a packet data network (PDN), a home PCRF (h-PCRF), a home OCS (h-OCS), a first PCEF (PCEF a), and a second PCEF, PCEF b. The PCEF b is connected to the PDN, h-PCRF, h-OCS, and PCEF a through an SGi interface, an S7b interface, a Gyb interface, and a client mobility IP/proxy mobility IP (CMIP/PMIP) interface respectively. The PCEF a is connected to the h-PCRF and the PCEF b through an S7a interface and a CMIP/PMIP interface respectively. The h-PCRF is connected to the AF through an RX+ interface. [0013] As shown in FIG. 2 , the PCEF in the new PCC architecture is divided into two parts: PCEF a and PCEF b. The PCEF a may be configured on an IP access GW such as a serving GW, a PDN GW, or a core network (CN) entity. The PCEF b may be configured on a PDN GW or a CN entity. The bearer concept is not defined on the CMIP/PMIP interface between the PCEF a and the PCEF b. Thus, the bearer-related functions such as bearer binding are configured on the PCEF a. In addition, the SGi interface between the PCEF b and the PDN is a data transmission interface between the CN and the PDN. Thus, the charging and gating functions are configured on the PCEF b. [0014] FIG. 3 shows a structure of a first roaming PCC architecture in the prior art. Different from the non-roaming PCC architecture shown in FIG. 2 , the roaming PCC architecture further includes a visited PCRF (v-PCRF) and a visited OCS (v-OCS). As shown in FIG. 3 , the PCEF b is connected to the IP Access Network (such as a PDN), h-PCRF, h-OCS, and PCEF a through an SGi interface, an S7b interface, a Gyb interface, and a CMIP/PMIP interface respectively. The PCEF a is connected to the v-PCRF and PCEF b through an S7a interface and a CMIP/PMIP interface respectively. The h-PCRF is connected to the AF and v-PCRF through an RX+ interface and an S9 interface respectively. [0015] In the roaming PCC architecture, the PCEF b may be further divided into a PCEF b 1 and a PCEF b 2 . [0016] FIG. 4 shows a structure of a second roaming PCC architecture in the prior art. Different from the PCEF b in the first roaming PCC architecture shown in FIG. 3 , the PCEF b in the second roaming PCC architecture further includes first and second PCEF sub-elements (PCEF b 1 and PCEF b 2 ). As shown in FIG. 4 , the PCEF b 2 is connected to the IP Access Network (such as a PDN), h-PCRF, h-OCS, and PCEF b 1 through an SGi interface, an S7b2 interface, a Gyb2 interface, and a CMIP/PMIP interface respectively. The PCEF a is connected to the v-PCRF and PCEF b 1 through an S7a interface and a CMIP/PMIP interface respectively. The h-PCRF is connected to the AF and v-PCRF through an RX+ interface and an S9 interface respectively. The PCEF b 1 is connected to the PCEF b 2 and PCEF a through CMIP/PMIP interfaces respectively. In actual applications, the PCEF b 1 may be also connected to the v-PCRF through an S7b1 interface. [0017] The inventor of the present invention discovers that the PCEF in the PCC architecture of the SAE system in the prior art is divided into two parts. That is, the new PCC architecture includes two PCEFs and the PCEF that may perceive a bearer event does not support service data flow based charging. In this case, in online charging mode, it is impossible to ensure that all the PCC rules received by the PCEF that may perceive bearer events pass credit authorization. SUMMARY OF THE INVENTION [0018] Embodiments of the present invention provide a method and system for session modification to modify a session in a PCC architecture of an SAE system. [0019] To realize the preceding objective, an embodiment of the present invention provides a method for session modification. The method includes: [0020] sending, by a home policy and charging rules function, h-PCRF, a first policy and charging control, PCC, rule providing message to a first policy and charging enforcement function, according to a received PCC rule request message, an application layer service message, or an h-PCRF self-trigger event; and [0021] sending, by the h-PCRF, a second PCC rule providing message to a second PCEF according to a PCC rule response message received from the first PCEF. [0022] An embodiment of the present invention provides a method for transferring information. The method includes: [0023] receiving, by a home policy and charging rules function, h-PCRF, a policy and charging control, PCC rule request message from a first policy and charging enforcement function; [0024] obtaining, by the h-PCRF, information of a trigger event that occurs on the first PCEF and information of affected PCC rules from the received PCC rule request message; and [0025] sending, by the h-PCRF, a PCC rule providing message to a second PCEF, where the PCC rule providing message comprises the information of the trigger event that occurs on the first PCEF. [0026] An embodiment of the present invention provides a system for session modification. The system includes a first PCEF, a second PCEF, an AF, an h-OCS, and an h-PCRF, where: [0027] the second PCEF is connected to the AF, h-PCRF, h-OCS, and first PCEF through an SGi interface, an S7b interface, a Gyb interface, and a CMIP/PMIP interface respectively; [0028] the first PCEF is connected to the h-PCRF through an S7a interface; [0029] the h-PCRF is connected to the AF through an RX+ interface; [0030] the h-PCRF sends a PCC rule providing message to the second PCEF according to a received PCC rule request message, an application layer service message, or a self-trigger message; and [0031] the h-PCRF sends a PCC rule providing message to the first PCEF according to a PCC rule response message sent from the second PCEF. [0032] In the technical solution of the present invention, when the PCC architecture of the SAE system includes two or more PCEFs, the h-PCRF sends a PCC rule providing message to the second PCEF according to the received PCC rule request message and determines whether to send a PCC rule providing message to the first PCEF according to a PCC rule response message sent from the second PCEF. This ensures that all the PCC rules received by the first PCEF pass credit authorization in online charging mode so that operators may easily perform PCC on service data flows. BRIEF DESCRIPTION OF THE DRAWINGS [0033] FIG. 1 shows a general PCC architecture in the prior art; [0034] FIG. 2 shows a non-roaming PCC architecture in the prior art; [0035] FIG. 3 shows a first roaming PCC architecture in the prior art; [0036] FIG. 4 shows a second roaming PCC architecture in the prior art; [0037] FIG. 5 a is a flowchart showing that a PCEF a initiates an IP-CAN session modification process when an h-PCRF directly delivers a trigger event to the PCEF a in a first embodiment of the present invention; [0038] FIG. 5 b is a flowchart showing that a PCEF b initiates an IP-CAN session modification process in the first embodiment of the present invention; [0039] FIG. 5 c is a flowchart showing that an h-PCRF initiates an IP-CAN session modification process in the first embodiment of the present invention; [0040] FIG. 6 a is a flowchart showing that a PCEF a initiates an IP-CAN session modification process when an h-PCRF delivers a trigger event to the PCEF a through a v-PCRF in a second embodiment of the present invention; [0041] FIG. 6 b is a flowchart showing that a PCEF b initiates an IP-CAN session modification process in the second embodiment of the present invention; [0042] FIG. 6 c is a flowchart showing that an h-PCRF initiates an IP-CAN session modification process in the second embodiment of the present invention; [0043] FIG. 7 is a flowchart showing that a PCEF a initiates an IP-CAN session modification process when an h-PCRF delivers a trigger event to the PCEF a through a v-PCRF in a third embodiment of the present invention; [0044] FIG. 8 is a flowchart showing that a PCEF b 2 initiates an IP-CAN session modification process in the third embodiment of the present invention; and [0045] FIG. 9 is a flowchart showing that an h-PCRF initiates an IP-CAN session modification process in the third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0046] For better understanding of the objective, technical solution and merits of the present invention, the present invention is hereinafter described in detail with reference to accompanying drawings and exemplary embodiments. [0047] The first embodiment implements IP-CAN session modification and credit re-authorization based on a non-roaming PCC architecture shown in FIG. 2 . [0048] In the PCC architecture shown in FIG. 2 , the PCEF a and PCEF b both receive a trigger event delivered from the h-PCRF. The PCEF a may receive a trigger event in one of the following modes: [0049] the h-PCRF directly delivers the trigger event to the PCEF a; and [0050] the h-PCRF delivers the trigger event to the PCEF b, and then the PCEF b sends the bearer-related trigger event information to the PCEF a. [0051] The h-OCS sends credit re-authorization events to only the PCEF b and no credit re-authorization event is available on the PCEF a. [0052] Thus, when an event that occurs matches a trigger event, the PCEF a and PCEF b may both initiate an IP-CAN session modification process. When an event that occurs matches a credit re-authorization event, however, only the PCEF b initiates a credit re-authorization process. [0053] The h-PCRF may send PCC rules to the PCEF a and PCEF b in one of the following modes: [0054] A. PCC rules to be enforced are pre-configured on the PCEF a and PCEF b respectively. The h-PCRF sends the same PCC rules to the PCEF a and PCEF b. Then the PCEF a and PCEF b obtain their own PCC rules to be enforced from the received PCC rules according to their pre-configured PCC rule information. [0055] B. The h-PCRF sends the same PCC rules to the PCEF a and PCEF b. The h-PCRF provides instructions for enforcing PCC rules for the PCEF a and PCEF b before or when providing PCC rules for the PCEF a and PCEF b. Then the PCEF a and PCEF b obtain their own PCC rules to be enforced according to the received enforcement instructions. [0056] C. The h-PCRF generates different PCC rules for the PCEF a and PCEF b according to the functions of the PCEF a and PCEF b and sends corresponding PCC rules to the PCEF a and PCEF b respectively. Then the PCEF a and PCEF b directly enforce the received PCC rules. [0057] The following describes the IP-CAN session modification process and the credit re-authorization process respectively. [0058] When the h-PCRF directly delivers trigger events to the PCEF a, the PCEF a may perceive bearer-related events but the PCEF b may not because the bearer concept is not defined on the interface between the PCEF a and the PCEF b. The PCEF b, however, needs to perform credit re-authorization according to the bearer-related event that occurs. Thus, for the IP-CAN session modification process initiated by the PCEF a, the h-PCRF receives a PCC rule request message including the information of the trigger event that occurs and affected PCC rules from the PCEF a, generates new PCC rules, and then delivers the new PCC rules and the obtained information of the trigger event that occurs and affected PCC rules to the PCEF b, while giving an instruction indicating that trigger event information is used to match a credit re-authorization event. To indicate that trigger event information is used to match a credit re-authorization event, the h-PCRF may: [0059] add a trigger event type that is only used to match a credit re-authorization event when delivering the trigger event to the PCEF b; [0060] add a mark to the existing trigger event information to identify that the trigger event is used to update the trigger event stored on the PCEF b or match a credit re-authorization event; or [0061] use other methods. Then the PCEF b matches the received trigger event information for matching a credit re-authorization event from the h-PCRF with the stored credit re-authorization event and determines whether to perform credit re-authorization according to the matching result. If credit re-authorization is required, the PCEF b performs credit re-authorization on all the affected PCC rules received from the h-PCRF. [0062] FIG. 5 a is a flowchart showing that a PCEF a initiates an IP-CAN session modification process when an h-PCRF directly delivers a trigger event to the PCEF a in the first embodiment of the present invention. The process includes the following steps: [0063] Step 5 a 1 : The PCEF a determines that an IP-CAN session modification process needs to be initiated to update PCC rules. [0064] In this step, the PCEF a may determine whether to initiate an IP-CAN session modification process according to whether an event that matches the trigger event stored on the PCEF a or an internal trigger event occurs. The trigger event includes but is not limited to dedicated bearer setup, modification, and deletion initiated by a UE. [0065] Step 5 a 2 : The PCEF a sends a PCC rule request message to the h-PCRF. [0066] In this step, the PCC rule request message carries update information required for the h-PCRF to make PCC decisions, information of a trigger event that occurs, and information of the PCC rules affected by the trigger event. [0067] Step 5 a 3 : The h-PCRF generates PCC rules. [0068] When generating PCC rules, the h-PCRF may interact with the AF or the SPR to obtain the required application layer service information or subscription data information. [0069] Step 5 a 4 : The h-PCRF sends a PCC rule providing message to the PCEF b. [0070] In this step, the PCC rule providing message may carry the obtained information of the trigger event and affected PCC rules from the PCEF a and an instruction indicating that trigger event information is used to match a credit re-authorization event. [0071] Step 5 a 5 and step 5 a 6 : In online charging mode, the PCEF b determines whether to initiate a credit re-authorization process according to stored credit re-authorization event information and trigger event information in the PCC rule providing message. [0072] In this step, the PCEF b matches stored credit re-authorization event information with trigger event information in the PCC rule providing message. If the matching is successful, the PCEF b initiates a credit re-authorization process and performs credit re-authorization on all the affected PCC rules received from the h-PCRF. [0073] Step 5 a 7 : The PCEF b returns a PCC rule response message to the h-PCRF. The response message may carry the enforcement result information of the PCC rules. In online charging mode, the response message may also carry credit availability information. [0074] Step 5 a 8 : The h-PCRF sends a PCC rule providing message to the PCEF a according to the PCC rule response message sent from the PCEF b. [0075] In online charging mode, the PCC rule response message sent from the PCEF b to the h-PCRF may also carry credit availability information. If the credit is available, the h-PCRF sends a PCC rule providing message to the PCEF a, carrying new PCC rules. If the credit is unavailable, the h-PCRF sends a PCC rule providing message to the PCEF a, without carrying the new PCC rules generated for the unavailable credit. [0076] If the h-PCRF delivers a trigger event to the PCEF b, and then the PCEF b sends the bearer-related trigger event to the PCEF a, the PCEF a may also initiate an IP-CAN session modification process. In this case, after detecting the trigger event, the PCEF a sends the information of the trigger event and the information of the affected PCC rules to the PCEF b; the PCEF b sends the received information to the h-PCRF to request new PCC rules; after receiving the new PCC rules from the h-PCRF, the PCEF b determines whether to initiate a credit re-authorization process according to the information received from the PCEF a and the new PCC rules received from the h-PCRF. [0077] FIG. 5 b is a flowchart showing that a PCEF b initiates an IP-CAN session modification process. The process is different from the IP-CAN session modification process shown in FIG. 5 a . Specific differences are as follows: [0078] In step 5 b 1 , the PCEF b may determine whether to initiate an IP-CAN session modification process according to whether an event that matches the trigger event stored on the PCEF b or an internal trigger event occurs. [0079] In step 5 b 2 , the PCC rule request message sent from the PCEF b to the h-PCRF carries the update information required for the h-PCRF to make PCC decisions. [0080] In step 5 b 4 , the h-PCRF sends a PCC rule providing message to the PCEF b. [0081] FIG. 5 c is a flowchart showing that an h-PCRF initiates an IP-CAN session modification process in the first embodiment of the present invention. The process includes the following steps: [0082] Step 5 c 1 : The AF sends an application layer service providing or modification message to the h-PCRF to trigger the h-PCRF to initiate an IP-CAN session modification process. The h-PCRF may also initiate an IP-CAN session modification process according to an internal trigger event. [0083] Step 5 c 2 : The h-PCRF returns an application layer service providing or modification acknowledgement message to the AF. [0084] Step 5 c 3 : The h-PCRF generates PCC rules. [0085] Step 5 c 4 : The h-PCRF sends a PCC rule providing message to the PCEF b. [0086] Step 5 c 5 and step 5 c 6 : In online charging mode, the PCEF b determines whether to initiate a credit re-authorization process according to credit re-authorization event information and trigger event information in the PCC rule providing message. [0087] In this step, according to stored credit re-authorization event information and the PCC rule providing message, the PCEF b needs to request a new credit from the h-OCS for a new charging key. For an unavailable charging key, the PCEF b returns a final report and remaining credits to the h-OCS. Other events meeting credit re-authorization conditions may also trigger the PCEF b to request new credits from the h-OCS. [0088] Step 5 c 7 : The PCEF b returns a PCC rule response message to the h-PCRF. The response message may carry the enforcement result information of the PCC rules. In online charging mode, the response message may also carry credit availability information. [0089] Step 5 c 8 : The h-PCRF sends a PCC rule providing message to the PCEF a according to the PCC rule response message sent from the PCEF b. [0090] In online charging mode, the PCC rule response message sent from the PCEF b to the h-PCRF may also carry credit availability information. If the credit is available, the h-PCRF sends a PCC rule providing message to the PCEF a, carrying new PCC rules. If the credit is unavailable, the h-PCRF sends a PCC rule providing message to the PCEF a, without carrying the new PCC rules generated for the unavailable credit. [0091] The second embodiment implements IP-CAN session modification and credit re-authorization based on a roaming PCC architecture shown in FIG. 3 . [0092] In the PCC architecture shown in FIG. 3 , the PCEF a and PCEF b both receive the trigger event delivered from the h-PCRF. The PCEF a may receive a trigger event in one of the following modes: [0093] the h-PCRF directly sends the trigger event to the PCEF a; and [0094] the h-PCRF sends the trigger event to the PCEF b, and then the PCEF b sends the bearer-related trigger event information to the PCEF a. [0095] The h-OCS sends credit re-authorization events to only the PCEF b and no credit re-authorization event is available on the PCEF a. [0096] Thus, when an event that occurs matches a trigger event, the PCEF a and PCEF b both may initiate an IP-CAN session modification process. When an event that occurs matches a credit re-authorization event, however, only the PCEF b initiates a credit re-authorization process. [0097] In this embodiment, the h-PCRF may send PCC rules to the PCEF a and PCEF b in three modes, which is similar to the first embodiment and is not further described. [0098] The following describes the IP-CAN session modification process and the credit re-authorization process respectively. [0099] If the h-PCRF sends a trigger event to the PCEF a through a v-PCRF, the PCEF a initiates an IP-CAN session modification process. In this case, the h-PCRF receives a PCC rule request message including the information of the trigger event that occurs and affected PCC rules from the PCEF a through the v-PCRF, generates new PCC rules, and then delivers the new PCC rules and the obtained information of the trigger event that occurs and affected PCC rules to the PCEF b, while giving an instruction indicating that trigger event information is used to match a credit re-authorization event. To indicate that trigger event information is used to match a credit re-authorization event, the h-PCRF may: [0100] add a trigger event type that is only used to match a credit re-authorization event when delivering the trigger event to the PCEF b; [0101] add a mark to the existing trigger event information to identify that the trigger event is used to update the trigger event stored on the PCEF b or match a credit re-authorization event; or [0102] use other methods. [0103] Then the PCEF b matches the received trigger event information for matching a credit re-authorization event from the h-PCRF with the stored credit re-authorization event and determines whether to perform credit re-authorization according to the matching result. If credit re-authorization is required, the PCEF b performs credit re-authorization on all the affected PCC rules received from the h-PCRF. [0104] FIG. 6 a is a flowchart showing that a PCEF a initiates an IP-CAN session modification process when an h-PCRF delivers a trigger event to the PCEF a through a v-PCRF in the second embodiment of the present invention. The process includes the following steps: [0105] Step 6 a 1 : The PCEF a determines that an IP-CAN session modification process needs to be initiated to update PCC rules. [0106] In this step, the PCEF a may determine whether to initiate an IP-CAN session modification process according to whether an event that matches the trigger event stored on the PCEF a or an internal trigger event occurs. The trigger event includes but is not limited to dedicated bearer setup, modification, and deletion initiated by a UE. [0107] Step 6 a 2 : The PCEF a sends a PCC rule request message to the v-PCRF, carrying the update information required for the h-PCRF to make PCC decisions. [0108] Step 6 a 3 : The v-PCRF forwards the PCC rule request message received from the PCEF a. [0109] Step 6 a 4 : The h-PCRF generates PCC rules. [0110] When generating PCC rules, the h-PCRF may interact with the AF or the SPR to obtain the required application layer service information or subscription data information. [0111] Step 6 a 5 : The h-PCRF sends a PCC rule providing message to the PCEF b. [0112] In this step, when sending the PCC rule providing message to the PCEF b, the h-PCRF may also provide the received trigger event information and the information of the affected PCC rules from the PCEF a for the PCEF b, while giving an instruction indicating that trigger event information is used to match a credit re-authorization event. [0113] Step 6 a 6 and step 6 a 7 : In online charging mode, the PCEF b determines whether to initiate a credit re-authorization process according to stored credit re-authorization event information and trigger event information in the PCC rule providing message. [0114] In this step, the PCEF b matches stored credit re-authorization event information with trigger event information in the PCC rule providing message. If the matching is successful, the PCEF b initiates a credit re-authorization process and performs credit re-authorization on all the affected PCC rules received from the h-PCRF. [0115] Step 6 a 8 : The PCEF b returns a PCC rule response message to the h-PCRF. The response message may carry the enforcement result information of the PCC rules. In online charging mode, the response message may also carry credit availability information. [0116] Step 6 a 9 : The h-PCRF sends a PCC rule providing message to the v-PCRF according to the PCC rule response message sent from the PCEF b. [0117] In online charging mode, the PCC rule response message sent from the PCEF b to the h-PCRF may also carry credit availability information. If the credit is available, the h-PCRF sends a PCC rule providing message to the PCEF a, carrying new PCC rules. If the credit is unavailable, the h-PCRF sends a PCC rule providing message to the PCEF a, without carrying the new PCC rules generated for the unavailable credit. [0118] Step 6 a 10 : The v-PCRF sends a PCC rule providing message to the PCEF a. [0119] In this step, the v-PCRF may or may not process the received PCC rule providing message according to local policies. [0120] If the h-PCRF delivers a trigger event to the PCEF b and then the PCEF b sends the bearer-related trigger event to the PCEF a, the PCEF a may also initiate an IP-CAN session modification process. In this case, after detecting the trigger event, the PCEF a sends the information of the trigger event and the information of the affected PCC rules to the PCEF b; the PCEF b sends the received information to the h-PCRF to request new PCC rules; after receiving the new PCC rules from the h-PCRF, the PCEF b determines whether to initiate a credit re-authorization process according to the information received from the PCEF a and the new PCC rules received from the h-PCRF. [0121] FIG. 6 b is a flowchart showing that a PCEF b initiates an IP-CAN session modification process in the second embodiment of the present invention. The process includes the following steps: [0122] Step 6 b 1 : The PCEF b determines that an IP-CAN session modification process needs to be initiated to update PCC rules. [0123] In this step, the PCEF b may determine whether to initiate an IP-CAN session modification process according to whether an event that matches the trigger event stored on the PCEF b or an internal trigger event occurs. [0124] Step 6 b 2 : The PCEF b sends a PCC rule request message to the h-PCRF, carrying the update information required for the h-PCRF to make PCC decisions. [0125] Step 6 b 3 : The h-PCRF generates PCC rules. [0126] When generating PCC rules, the h-PCRF may interact with the AF or the SPR to obtain the required application layer service information or subscription data information. [0127] Step 6 b 4 : The h-PCRF sends a PCC rule providing message to the PCEF b. [0128] Step 6 b 5 and step 6 b 6 : In online charging mode, the PCEF b determines whether to initiate a credit re-authorization process according to credit re-authorization event information and trigger event information in the PCC rule providing message. [0129] In this step, according to stored credit re-authorization event information and the PCC rule providing message, the PCEF b needs to request a new credit from the h-OCS for a new charging key. For an unavailable charging key, the PCEF b returns a final report and remaining credits to the h-OCS. Other events meeting credit re-authorization conditions may also trigger the PCEF b to request new credits from the h-OCS. [0130] Step 6 b 7 : The PCEF b returns a PCC rule response message to the h-PCRF. The response message may carry the enforcement result information of the PCC rules. In online charging mode, the response message may also carry credit availability information. [0131] Step 6 b 8 : The h-PCRF sends a PCC rule providing message to the v-PCRF according to the PCC rule response message sent from the PCEF b. [0132] In online charging mode, the PCC rule response message sent from the PCEF b to the h-PCRF may also carry credit availability information. If the credit is available, the h-PCRF sends a PCC rule providing message to the PCEF a, carrying new PCC rules. If the credit is unavailable, the h-PCRF sends a PCC rule providing message to the PCEF a, without carrying the new PCC rules generated for the unavailable credit. [0133] Step 6 b 9 : The v-PCRF sends a PCC rule providing message to the PCEF a. [0134] In this step, the v-PCRF may or may not process the received PCC rule providing message according to local policies. [0135] FIG. 6 c is a flowchart showing that an h-PCRF initiates an IP-CAN session modification process in the second embodiment of the present invention. The process includes the following steps: [0136] Step 6 c 1 : The AF sends an application layer service providing or modification message to the h-PCRF to trigger the h-PCRF to initiate an IP-CAN session modification process. The h-PCRF may also initiate an IP-CAN session modification process according to an internal trigger event. [0137] Step 6 c 2 : The h-PCRF returns an application layer service providing or modification acknowledgement message to the AF. [0138] Step 6 c 3 : The h-PCRF generates PCC rules. [0139] Step 6 c 4 : The h-PCRF sends a PCC rule providing message to the PCEF b. [0140] Step 6 c 5 and step 6 c 6 : In online charging mode, the PCEF b determines whether to initiate a credit re-authorization process according to credit re-authorization event information and trigger event information in the PCC rule providing message. [0141] In this step, according to stored credit re-authorization event information and the PCC rule providing message, the PCEF b needs to request a new credit from the h-OCS for a new charging key. For an unavailable charging key, the PCEF b returns a final report and remaining credits to the h-OCS. Other events meeting credit re-authorization conditions may also trigger the PCEF b to request new credits from the h-OCS. [0142] Step 6 c 7 : The PCEF b returns a PCC rule response message to the h-PCRF. The response message may carry the enforcement result information of the PCC rules. In online charging mode, the response message may also carry credit availability information. [0143] Step 6 c 8 : The h-PCRF sends a PCC rule providing message to the v-PCRF according to the PCC rule response message sent from the PCEF b. [0144] In online charging mode, the PCC rule response message sent from the PCEF b to the h-PCRF may also carry credit availability information. If the credit is available, the h-PCRF sends a PCC rule providing message to the PCEF a, carrying new PCC rules. If the credit is unavailable, the h-PCRF sends a PCC rule providing message to the PCEF a, without carrying the new PCC rules generated for the unavailable credit. [0145] Step 6 c 9 : The v-PCRF sends a PCC rule providing message to the PCEF a. [0146] In this step, the v-PCRF may or may not process the received PCC rule providing message according to local policies. [0147] The third embodiment implements IP-CAN session modification and credit re-authorization based on a roaming PCC architecture shown in FIG. 4 . [0148] As shown in FIG. 4 , the PCEF a, PCEF b 1 , and PCEF b 2 receive the trigger events delivered from the h-PCRF respectively. The h-PCRF may deliver the trigger events to the PCEF a through the v-PCRF. The h-PCRF may also deliver the trigger events to the PCEF b 2 , and then the PCEF b 2 sends the bearer-related trigger events to the PCEF a through the PCEF b 1 . The h-OCS sends credit re-authorization events only to the PCEF b 2 and no credit re-authorization events are available on the PCEF a and PCEF b 1 . Thus, when an event that occurs matches a trigger event, the PCEF a, PCEF b 1 , and PCEF b 2 may initiate an IP-CAN session modification process respectively. When an event that occurs matches a credit re-authorization event, however, only the PCEF b 2 initiates a credit re-authorization process. [0149] In this embodiment, the h-PCRF may send PCC rules to the PCEF a, PCEF b 1 , and PCEF b 2 in three modes, which is similar to the first embodiment and is not further described. [0150] The h-PCRF may also provide different PCC rule enforcement instructions for different PCEFs or provide different PCC rules according to the functions of different PCEFs. Multiple S9 interfaces may be available between the h-PCRF and the v-PCRF and correspond to different PCEFs such as a PCEF a or a PCEF b 1 . In addition, there may be only one S9 interface between the h-PCRF and the v-PCRF. The PCC rule message transmitted on the S9 interface carries the indication provided for the target PCEF. [0151] The following describes the IP-CAN session modification process and the credit re-authorization process respectively. [0152] If the h-PCRF sends a trigger event to the PCEF a through the v-PCRF, the PCEF a initiates an IP-CAN session modification process. In this case, the h-PCRF receives a PCC rule request message including the information of the trigger event that occurs and affected PCC rules from the PCEF a through the v-PCRF, generates new PCC rules, and then delivers the new PCC rules and the obtained information of the trigger event that occurs and affected PCC rules to the PCEF b 2 , while giving an instruction indicating that trigger event information is used to match a credit re-authorization event. To indicate that trigger event information is used to match a credit re-authorization event, the h-PCRF may: [0153] add a trigger event type that is only used to match a credit re-authorization event when delivering the trigger event to the PCEF b 2 ; [0154] add a mark to the existing trigger event information to identify that the trigger event is used to update the trigger event stored on the PCEF b 2 or match a credit re-authorization event; or [0155] use other methods. Then the PCEF b 2 matches trigger event information received from the h-PCRF with the stored credit re-authorization event and determines whether to perform credit re-authorization according to the matching result. If credit re-authorization is required, the PCEF b 2 performs credit re-authorization on all the affected PCC rules received from the h-PCRF. [0156] FIG. 7 is a flowchart showing that a PCEF a initiates an IP-CAN session modification process when an h-PCRF delivers a trigger event to the PCEF a through a v-PCRF in the third embodiment of the present invention. The process includes the following steps: [0157] Step 701 : The PCEF a determines that an IP-CAN session modification process needs to be initiated to update PCC rules. [0158] In this step, the PCEF a may determine whether to initiate an IP-CAN session modification process according to whether an event that matches the trigger event stored on the PCEF a or an internal trigger event occurs. The trigger event includes but is not limited to dedicated bearer setup, modification, and deletion initiated by a UE. [0159] Step 702 : The PCEF a sends a PCC rule request message to the v-PCRF, carrying the update information required for the h-PCRF to make PCC decisions. [0160] Step 703 : The v-PCRF forwards the received PCC rule request message, carrying the update information sent from the PCEF a or PCEF b 1 and required for the h-PCRF to make PCC decisions. [0161] Step 704 : The h-PCRF generates PCC rules. [0162] When generating PCC rules, the h-PCRF may interact with the AF or the SPR to obtain the required application layer service information or subscription data information. [0163] Step 705 : The h-PCRF sends a PCC rule providing message to the PCEF b 2 . [0164] In this step, when sending the PCC rule providing message to the PCEF b 2 , the h-PCRF may also provide the received trigger event information and the information of the affected PCC rules from the PCEF a for the PCEF b 2 , while giving an instruction indicating that trigger event information is used to match a credit re-authorization event. [0165] Step 706 and step 707 : In online charging mode, the PCEF b 2 determines whether to initiate a credit re-authorization process according to stored credit re-authorization event information and trigger event information in the PCC rule providing message. [0166] In this step, the PCEF b 2 matches stored credit re-authorization event information with trigger event information in the PCC rule providing message. If the matching is successful, the PCEF b 2 initiates a credit re-authorization process and performs credit re-authorization on all the affected PCC rules received from the h-PCRF. [0167] Step 708 : The PCEF b 2 returns a PCC rule response message to the h-PCRF. The response message may carry the enforcement result information of the PCC rules. In online charging mode, the response message may also carry credit availability information. [0168] Step 709 : The h-PCRF sends a PCC rule providing message to the v-PCRF according to the PCC rule response message sent from the PCEF b 2 . [0169] In online charging mode, the PCC rule response message sent from the PCEF b to the h-PCRF may also carry credit availability information. If the credit is available, the h-PCRF sends a PCC rule providing message to the PCEF a, carrying new PCC rules. If the credit is unavailable, the h-PCRF sends a PCC rule providing message to the PCEF a, without carrying the new PCC rules generated for the unavailable credit. [0170] Step 710 : The v-PCRF sends a PCC rule providing message to the PCEF b 1 . [0171] In this step, before sending the received PCC rule providing message to the PCEF b 1 , the v-PCRF may or may not process the message according to local policies. [0172] Step 711 : The v-PCRF sends a PCC rule providing message to the PCEF a. [0173] In this step, the v-PCRF may or may not process the received PCC rule providing message according to local policies. [0174] If the h-PCRF delivers a trigger event to the PCEF b 2 and then the PCEF b 2 sends the bearer-related trigger event to the PCEF a through the PCEF b 1 , the PCEF a may also initiate an IP-CAN session modification process. In this case, after detecting the trigger event, the PCEF a sends the information of the trigger event and affected PCC rules to the PCEF b 2 through the PCEF b 1 ; the PCEF b 2 sends the received information to the h-PCRF to request new PCC rules; after receiving the new PCC rules from the h-PCRF, the PCEF b 2 determines whether to initiate a credit re-authorization process according to the information received from the PCEF a and the new PCC rules received from the h-PCRF. [0175] FIG. 8 is a flowchart showing that a PCEF b 2 initiates an IP-CAN session modification process in the third embodiment of the present invention. The process includes the following steps: [0176] Step 801 : The PCEF b 2 determines that an IP-CAN session modification process needs to be initiated to update PCC rules. [0177] In this step, the PCEF b 2 may determine whether to initiate an IP-CAN session modification process according to whether an event that matches the trigger event stored on the PCEF b 2 or an internal trigger event occurs. [0178] Step 802 : The PCEF b 2 sends a PCC rule request message to the h-PCRF, carrying the update information required for the h-PCRF to make PCC decisions. [0179] Step 803 : The h-PCRF generates PCC rules. [0180] When generating PCC rules, the h-PCRF may interact with the AF or the SPR to obtain the required application layer service information or subscription data information. [0181] Step 804 : The h-PCRF sends a PCC rule providing message to the PCEF b 2 . [0182] Step 805 and step 806 : In online charging mode, the PCEF b 2 determines whether to initiate a credit re-authorization process according to credit re-authorization event information and trigger event information in the PCC rule providing message. [0183] In this step, according to stored credit re-authorization event information and the PCC rule providing message, the PCEF b 2 needs to request a new credit from the h-OCS for a new charging key. For an unavailable charging key, the PCEF b 2 returns a final report and remaining credits to the h-OCS. Other events meeting credit re-authorization conditions may also trigger the PCEF b 2 to request new credits from the h-OCS. [0184] Step 807 : The PCEF b 2 returns a PCC rule response message to the h-PCRF. The response message may carry the enforcement result information of the PCC rules. In online charging mode, the response message may also carry credit availability information. [0185] Step 808 : The h-PCRF sends a PCC rule providing message to the v-PCRF according to the PCC rule response message sent from the PCEF b 2 . [0186] In online charging mode, the PCC rule response message sent from the PCEF b to the h-PCRF may also carry credit availability information. If the credit is available, the h-PCRF sends a PCC rule providing message to the PCEF a, carrying new PCC rules. If the credit is unavailable, the h-PCRF sends a PCC rule providing message to the PCEF a, without carrying the new PCC rules generated for the unavailable credit. [0187] Step 809 : The v-PCRF sends a PCC rule providing message to the PCEF b 1 . [0188] In this step, before sending the received PCC rule providing message to the PCEF b 1 , the v-PCRF may or may not process the message according to local policies. [0189] Step 810 : The v-PCRF sends a PCC rule providing message to the PCEF a. [0190] In this step, the v-PCRF may or may not process the received PCC rule providing message according to local policies. [0191] FIG. 9 is a flowchart showing that an h-PCRF initiates an IP-CAN session modification process in the third embodiment of the present invention. The process includes the following steps: [0192] Step 901 : The AF sends an application layer service providing or modification message to the h-PCRF to trigger the h-PCRF to initiate an IP-CAN session modification process. The h-PCRF may also initiate an IP-CAN session modification process according to an internal trigger event. [0193] Step 902 : The h-PCRF returns an application layer service providing or modification acknowledgement message to the AF. [0194] Step 903 : The h-PCRF generates PCC rules. [0195] Step 904 : The h-PCRF sends a PCC rule providing message to the PCEF b 2 . [0196] Step 905 and step 906 : In online charging mode, the PCEF b 2 determines whether to initiate a credit re-authorization process according to credit re-authorization event information and trigger event information in the PCC rule providing message. [0197] In this step, according to stored credit re-authorization event information and the PCC rule providing message, the PCEF b 2 needs to request a new credit from the h-OCS for a new charging key. For an unavailable charging key, the PCEF b 2 returns a final report and remaining credits to the h-OCS. Other events meeting credit re-authorization conditions may also trigger the PCEF b 2 to request new credits from the h-OCS. [0198] Step 907 : The PCEF b 2 returns a PCC rule response message to the h-PCRF. The response message may carry the enforcement result information of the PCC rules. In online charging mode, the response message may also carry credit availability information. [0199] Step 908 : The h-PCRF sends a PCC rule providing message to the v-PCRF according to the PCC rule response message sent from the PCEF b 2 . [0200] In online charging mode, the PCC rule response message sent from the PCEF b to the h-PCRF may also carry credit availability information. If the credit is available, the h-PCRF sends a PCC rule providing message to the PCEF a, carrying new PCC rules. If the credit is unavailable, the h-PCRF sends a PCC rule providing message to the PCEF a, without carrying the new PCC rules generated for the unavailable credit. [0201] Step 909 : The v-PCRF sends a PCC rule providing message to the PCEF b 1 . [0202] In this step, before sending the received PCC rule providing message to the PCEF b 1 , the v-PCRF may or may not process the message according to local policies. [0203] Step 910 : The v-PCRF sends a PCC rule providing message to the PCEF a. [0204] In this step, the v-PCRF may or may not process the received PCC rule providing message according to local policies. [0205] Although the objective, technical solution, and merits of the present invention have been described in detail with reference to some exemplary embodiments, the invention is not limited to such embodiments. It is apparent that those skilled in the art may make various modifications and variations to the invention without departing from the spirit and scope of the invention. The invention is intended to cover the modifications and variations provided that they fall in the scope of protection defined by the following claims or their equivalents

A method and system for session modification are provided. The method includes these steps: A home policy and charging rules function (h-PCRF) sends a policy and charging control (PCC) rule providing message to a first policy and charging enforcement function (PCEF) according to a received PCC rule request message, an application layer service message, or an h-PCRF self-trigger event; and the h-PCRF sends a PCC rule providing message to a second PCEF according to a PCC rule response message received from the first PCEF. With this present disclosure, session modification may be implemented when two or more PCEFs are included in the PCC architecture of a system architecture evolution (SAE) system.

FIELD OF THE DISCLOSURE The present disclosure relates to sunscreen compositions comprising a synergistic combination of ultra violet (“UV”) filters, and to methods of using the combination of UV filters to protect keratinous substrates such as skin and hair from UV radiation. BACKGROUND The negative effects of exposure to ultraviolet (“UV”) light are well-known. Prolonged exposure to sunlight causes damage such as sunburn to the skin and dries out hair making it brittle. When skin is exposed to UV light having a wavelength of from about 290 nm to about 400 nm, long term damage can lead to serious conditions such as skin cancer. UV light also contributes to aging by causing free radicals to form in the skin. Free radicals include, for example, singlet oxygen, hydroxyl radical, the superoxide anion, nitric oxide and hydrogen radicals. Free radicals attack DNA, membrane lipids and proteins, generating carbon radicals. These in turn react with oxygen to produce a peroxyl radical that can attack adjacent fatty acids to generate new carbon radicals. This cascade leads to a chain reaction producing lipid peroxidation products. Damage to the cell membrane results in loss of cell permeability, increased intercellular ionic concentration, and decreased ability to excrete or detoxify waste products. The end result is a loss of skin elasticity and the appearance of wrinkles. This process is commonly referred to as photo-aging. Sunscreens can be used to protect against UV damage and delay the signs of aging. The degree of UV protection afforded by a sunscreen composition is directly related to the amount and type of UV filters contained therein. The higher the amount of UV filters, the greater the degree of UV protection. Nevertheless, it is desirable to achieve the best photo protection efficacy with the lowest amount of UV filters. The inventors of the instant disclosure discovered ways to attain SPFs that were not previously attainable with such low amounts of overall UV filters. SUMMARY OF THE INVENTION The present disclosure relates to sunscreen compositions that have low amounts of UV filters yet excellent Sun Protection Factors (SPF). Typically, the more UV filters included in a sunscreen composition the higher the SPF. The inventors discovered that when certain UV filters are combined in particular ratios, they interact synergistically to exhibit a surprisingly effective SPF. This allows for use of less UV filters while achieving sufficient SPF. The present disclosure relates to a sunscreen composition comprising a combination of the UV filters set forth in the table below: INCI NAME TECHNICAL NAME Octocrylene Octocrylene Butyl Methoxydibenzoylmethane Avobenzone Bis-EthylHexyloxyphenol Methoxyphenyl Tinsorb S Triazine Ethylhexyl Triazone Uvinul T150 Drometrizole Trisiloxane Mexoryl XL The ratio of each filter relative to avobenzone in the sunscreen compositions is typically as follows: the ratio of octocrylene to avobenzone is 0.8:1.0 to 1.3:1.0; the ratio of Tinsorb S to avobenzone is 0.1:1.0 to 0.6:1.0; the ratio of Uvinul T150 to avobenzone is 0.2:1.0 to 0.6:1.0; and the ratio of Mexoryl XL to avobenzone is 0.3:1.0 to 0.7:1.0. In particular, the ratio of each filter relative to avobenzone is about: 1.0:1.0:0.3:0.5:0.5 (octocrylene:avobenzone:Tinsorb S:Uvinul T150:Mexoryl XL). In one embodiment the UV filters are present in the following percentages by weight relative to the entire weight of the sunscreen composition: 2 to 7 wt. % octocrylene; 2 to 5 wt. % avobenzone; 0.1% to 2 wt. % Tinsorb S; 0.1% to 3 wt. % Uvinul T150; and 0.1% to 3 wt. % Mexoryl XL. In another embodiment the UV filters are present in the following percentages by weight relative to the entire weight of the sunscreen composition: about 5% octocrylene; about 5% Avobenzone; about 2% Tinsorb S; about 2% Uvinul T150; and about 2.5% MexorylXL. Octisalate is another UV filter than can optionally be included in the sunscreen compositions described herein. If included, octisalate is typically present in an amount greater than 0 to about 5 wt. %. The present disclosure is also directed to methods of protecting a keratinous substrate from ultraviolet radiation and to methods of absorbing ultraviolet light. Such methods encompass applying a sunscreen composition to a keratinous substrate and subjecting the keratinous substrate to ultraviolet radiation. DETAILED DESCRIPTION Where the following terms are used in this specification, they are used as defined below. The terms “comprising,” “having,” and “including” are used in their open, non-limiting sense. The terms “a” and “the” are understood to encompass the plural as well as the singular. As used herein, the expression “at least one” means one or more and thus includes individual components as well as mixtures/combinations. “Cosmetically acceptable” means that the item in question is compatible with any keratinous substrate. For example, “cosmetically acceptable carrier” means a carrier that is compatible with any keratinous substrate. A “physiologically acceptable medium” means a medium which is not toxic and can be applied to the skin, lips, hair, scalp, lashes, brows, nails or any other cutaneous region of the body. The composition of the instant disclosure may especially constitute a cosmetic or dermatological composition. The phrase “essentially free” refers to less than or equal to 0.5, 0.1, 0.05 or 0.01 wt. %. The phrase “stable emulsion” refers to a composition that does not undergo phase separation up to a temperature of 45 C.° for at least two weeks. As mentioned above, the present disclosure relates to a sunscreen composition having the following combination of UV filters: octocrylene, avobenzone, Tinosorb S, Tinsorb S, Uvinul T150, Mexoryl XL; wherein the ratio of each filter relative to avobenzone is as follows: the ratio of octocrylene to avobenzone is 0.8:1.0 to 1.3:1.0; the ratio of Tinsorb S to avobenzone is 0.1:1.0 to 0.6:1.0; the ratio of Uvinul T150 to avobenzone is 0.2:1.0 to 0.75:1.0; and the ratio of Mexoryl XL to avobenzone is 0.3:1.0 to 0.7:1.0. In particular, the ratio of each filter relative to avobenzone is about: 1.0:1.0:0.3:0.5:0.5 (octocrylene:avobenzone:Tinsorb S:Uvinul T150: Mexoryl XL). The total amount of the combination of UV filters can vary depending on the desired SPF and overall UV filterting strength of a final sunscreen composition. In one aspect, the total amount of the combination of UV filters in a sunscreen combination is about 50, 40, 30, 25, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 wt. % or less. In another aspect, the sunscreen formulation has an SPF value that is at least about 2, 3, 4, 5, 6, 7, or 8 times the total weight percent of the combination of UV filters of the sunscreen compositions. For example, it is possible for a composition comprising about 16.92 wt. % of a total combination of UV filters to exhibit an SPF of 137, as shown in Example 1 below (the SPF is about 8 times higher than the total amount of the combination of UV filters used in the composition). In one embodiment the UV filters are independently present in the following percentages by weight relative to the entire weight of the sunscreen composition: from about 2, 3, or 4, to about 6 or 7 wt. % octocrylene; from about 2, 3, 4, or 4.5 to about 5 wt. % avobenzone; from about 0.1, 0.5, 1, or 1.5 to about 2 wt. % Tinsorb S; from about 0.1, 0.5, 1, or 1.5 to about 2.5 or 3 wt. % Uvinul T150; and from about 0.1, 1, 1.5, 2, or 2.5 to about 3 wt. % Mexoryl XL. In another embodiment the UV filters are present in the following percentages by weight relative to the entire weight of the sunscreen composition: about 5% octocrylene; about 5% Avobenzone; about 2% Tinsorb S; about 2% Uvinul T150; and about 3% MexorylXL. Octisalate is another UV filter than can optionally be included in the sunscreen compositions described herein. If included, octisalate is typically present in an amount greater than 0 to about 5 wt. %. It may also be present in an amount of about 0.1, 0.5, 1, 1.5, or 2 wt. % to about 2.5, 3, 3.5, 4, 4.5, or 5 wt. %. The present disclosure makes it possible to achieve the described SPFs in sunscreen compositions without the use of boosters, or essentially free of boosters, e.g., sorbeth-2-hexaoleate. Although boosters may be included in the sunscreen compositions of the instant disclosure, they are not required. Sunscreen compositions according to the present disclosure can be formulated to achieve a variety of different SPFs. For example, the sunscreen formulations can have an SPF of at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 135, or higher. The present disclosure is also directed to methods for protecting a keratinous substrate from ultraviolet radiation and to methods of absorbing ultraviolet light. Such methods encompass applying a sunscreen composition to a keratinous substrate and subjecting the keratinous substrate to ultraviolet radiation. Oils/Emollients Examples of oils/emollients that may be included in the sunscreen compositions include: hydrocarbon-based oils of plant origin, such as liquid triglycerides of fatty acids containing from 4 to 10 carbon atoms, for instance heptanoic or octanoic acid triglycerides, or alternatively, for example, sunflower oil, corn oil, soybean oil, marrow oil, grapeseed oil, sesameseed oil, hazelnut oil, apricot oil, macadamia oil, arara oil, coriander oil, castor oil, avocado oil, caprylic/capric acid triglycerides, for instance those sold by the company Stearineries Dubois or those sold under the names Miglyol 810, 812 and 818 by the company Dynamit Nobel, jojoba oil, shea butter oil and caprylyl glycol; synthetic esters and ethers, especially of fatty acids, for instance Purcellin oil, 2-octyldodecyl stearate, 2-octyldodecyl erucate, isostearyl isostearate; hydroxylated esters, for instance isostearyl lactate, octyl hydroxystearate, octyldodecyl hydroxystearate, diisostearyl malate or triisocetyl citrate; fatty alcohol heptanoates, octanoates or decanoates; polyol esters, for instance propylene glycol dioctanoate, neopentyl glycol diheptanoate and diethylene glycol diisononanoate; and pentaerythritol esters, for instance pentaerythrityl tetraisostearate, or isopropyl lauroyl sarcosinate, sold especially under the trade name Eldew SL 205 by the company Ajinomoto; linear or branched hydrocarbons, of mineral or synthetic origin, such as volatile or non-volatile liquid paraffins, and derivatives thereof, petroleum jelly, polydecenes, isohexadecane, isododecane, hydrogenated polyisobutene such as Parleam oil, or the mixture of n-undecane (C 11 ) and of n-tridecane (C 13 ) sold under the reference Cetiol UT by the company Cognis; fluoro oils that are partially hydrocarbon-based and/or silicone-based, for instance those described in document JP-A-2 295 912; silicone oils, for instance volatile or non-volatile polymethylsiloxanes (PDMS) with a linear or cyclic silicone chain, which are liquid or pasty at room temperature, in particular volatile silicone oils, especially cyclopolydimethylsiloxanes (cyclomethicones) such as cyclohexadimethylsiloxane and cyclopentadimethylsiloxane; polydimethylsiloxanes comprising alkyl, alkoxy or phenyl groups, which are pendent or at the end of a silicone chain, these groups containing from 2 to 24 carbon atoms; phenyl silicones, for instance phenyl trimethicones, phenyl dimethicones, phenyltrimethylsiloxydiphenylsiloxanes, diphenyl dimethicones, diphenylmethyldiphenyltrisiloxanes or 2-phenylethyl trimethylsiloxy silicates, and polymethylphenylsiloxanes; mixtures thereof. Additional examples include benzoic acid esters of C 9 -C 15 alcohols, isononyl iso-nonanoate, C 12 -C 15 alkyl benzoate, or any combinations thereof. Specific examples of oils/emollients include cocoglyceride, cyclomethicone, dimethicone, dicapryl maleate, caprylic/capric triglyceride, isopropyl myristate, octyl stearate, isostearyl linoleate, lanolin oil, coconut oil, cocoa butter, olive oil, avocado oil, aloe extracts, jojoba oil, castor oil, fatty acid, oleic acid, stearic acid, fatty alcohol, cetyl alcohol, hexadecyl alcohol, diisopropyl adipate, hydroxybenzoate esters, benzoic acid esters of C 9 -C 15 alcohols, isononyl iso-nonanoate, alkanes, mineral oil, silicone, dimethyl polysiloxane, ether, polyoxypropylene butyl ether, polyoxypropylene cetyl ether, C 12 -C 15 alkyl benzoate, aryl alkyl benzoate, Isopropyl Lauroyl sarcosinate, and any combinations thereof. Examples of hydrophilic organic solvents that may be included in the sunscreen compositions include: monohydric C 1 -C 8 alcohols such as ethanol, propanol, butanol, isopropanol, isobutanol; Polyethylene glycols from 6 to 80 ethylene oxides such as propylene glycol, isoprene glycol, butylene glycol, glycerol, sorbitol; mono or di-alkyl isosorbides such as dimethyl isosorbide; Examples of amphiphilic organic solvents include: polypropylene glycol (PPG) like propylene glycol alkyl ester or alkyl ether of PPG like PPG-23 oleyl ether and PPG-36 oleate. The above lists are only examples and not limiting. The total amount of oils/emollient present in the compositions is typically about 0.1, 0.5, 1.0, or 2.5 wt. % to about 5.0, 7.5, 10.0, 15.0, 20.0, or 30 wt. % of the total weight of the composition. Film Formers Film-formers are often incorporated into sunscreen compositions to ensure even coverage of the UV filters and can be used to render the composition water resistant. The film former is typically a hydrophobic material that imparts film forming and/or waterproofing characteristics. One such agent is polyethylene, which is available from New Phase Technologies as Performalene® 400, a polyethylene having a molecular weight of 400. Another suitable film former is polyethylene 2000 (molecular weight of 2000), which is available from New Phase Technologies as Performalene®. Yet, another suitable film former is synthetic wax, also available from New Phase Technologies as Performa® V-825. Other typical film-formers include acrylates/acrylamide copolymer, acrylates copolymer, acrylates/C 12 -C 22 alkylmethacrylate copolymer, polyethylene, waxes, VP/dimethiconylacrylate/polycarbamylpolyglycol ester, butylated PVP, PVP/hexadecene copolymer, octadecene/MA copolymer, PVP/eicosene copolymer, tricontanyl PVP, Brassica Campestris/Aleuritis Fordi Oil copolymer, decamethyl cyclopentasiloxane (and) trimethylsiloxysilicate, and mixtures thereof. In some cases, the film former is acrylates/C 12 -C 22 alkylmethacrylate copolymer sold under the tradename Allianz OPT® by ISP. Many of the common film-forming polymers included in sunscreen compositions are not soluble in ethanol (such as PVP/Eicosene copolymer). A common film-former employed in ethanol based sunscreen products is Dermacryl LT or Dermacryl 79 marketed by Akzo Nobel (INCI Name: acrylates/octylacrylamide copolymer). Dermacryl LT (CAS Number: 80570-62-3) is a hydrophobic, high molecular weight carboxylated acrylic copolymer. It functions as a film-former in a broad range of cosmetic formulations, imparting waterproofing, increased occlusivity and decreased rub-off of actives. The above lists are only examples and not limiting. The total amount of film-formers present in the compositions is typically in an amount of about 0.1, 0.5, 1.0, or 5 wt. % to about 5, 10, 20, or 25 wt. %, based on the total weight of the composition. Emulsifiers The sunscreen compositions typically include at least one emulsifier such as an amphoteric, anionic, cationic or nonionic emulsifier, used alone or as a mixture, and optionally a co-emulsifier. The emulsifiers are chosen in an appropriate manner according to the emulsion to be obtained (W/O or O/W). The emulsifier and the co-emulsifier are generally present in the composition in a proportion ranging from 0.3% to 30% by weight and preferably from 0.5% to 20% by weight relative to the total weight of the composition. For W/O emulsions, examples of emulsifiers that may be mentioned include dimethicone copolyols, such as the mixture of cyclomethicone and dimethicone copolyol sold under the trade name DC 5225 C by the company Dow Corning, and alkyl dimethicone copolyols such as the lauryl dimethicone copolyol sold under the name Dow Corning 5200 Formulation Aid by the company Dow Corning, and the cetyl dimethicone copolyol sold under the name Abil EM 90™ by the company Goldschmidt. A crosslinked elastomeric solid organopolysiloxane comprising at least one oxyalkylene group, such as those obtained according to the procedure of Examples 3, 4 and 8 of U.S. Pat. No. 5,412,004 and of the examples of U.S. Pat. No. 5,811,487, especially the product of Example 3 (synthesis example) of U.S. Pat. No. 5,412,004, such as the product sold under the reference KSG 21 by the company Shin-Etsu, may also be used as surfactants for W/O emulsions. For O/W emulsions, examples of emulsifiers that may be mentioned include nonionic emulsifiers such as oxyalkylenated (more particularly polyoxyethylenated) fatty acid esters of glycerol; oxyalkylenated fatty acid esters of sorbitan; oxyalkylenated (oxyethylenated and/or oxypropylenated) fatty acid esters; oxyalkylenated (oxyethylenated and/or oxypropylenated) fatty alcohol ethers; sugar esters such as sucrose stearate; and mixtures thereof. The fatty acid esters of a sugar that can be used as nonionic amphiphilic lipids can be chosen in particular from the group comprising esters or mixtures of esters of a C 8 -C 22 fatty acid and of sucrose, of maltose, of glucose or of fructose, and esters or mixtures of esters of a C 14 -C 22 fatty acid and of methylglucose. The C 8 -C 22 or C 14 -C 22 fatty acids forming the fatty unit of the esters that can be used in the emulsion comprise a saturated or unsaturated linear alkyl chain having, respectively, from 8 to 22 or from 14 to 22 carbon atoms. The fatty unit of the esters can be chosen in particular from stearates, behenates, arachidonates, palmitates, myristates, laurates, caprates and mixtures thereof. By way of example of esters or of mixtures of esters of a fatty acid and of sucrose, of maltose, of glucose or of fructose, mention may be made of sucrose monostearte, sucrose distearate, sucrose tristearate and mixtures thereof, such as the products sold by the company Croda under the name Crodesta F50, F70, F110 and F160 having, respectively, an HLB (Hydrophilic Lipophilic Balance) of 5, 7, 11 and 16; and, by way of example of esters or of mixtures of esters of a fatty acid and of methylglucose, mention may be made of the disearate of methylglucose and of polyglycerol-3, sold by the company Goldschmidt under the name Tego-care 450. Mention may also be made of glucose monoesters or maltose monoesters, such as methyl O-hexadecanoyl-6-D-glucoside and O-hexadecanoyl-6-D-maltoside. The fatty alcohol ethers of a sugar that can be used as nonionic amphiphilic lipids can be chosen in particular form the group comprising ethers or mixtures of ethers of a C 8 -C 22 fatty alcohol and of glucose, of maltose, of sucrose or of fructose, and ethers or mixtures of ethers of a C 14 -C 22 fatty alcohol and of methylglucose. They are in particular alkylpolyglucosides. The C 8 -C 22 or C 14 -C 22 fatty alcohols forming the fatty unit of the ethers that can be used in the emulsion of the instant disclosure comprise a saturated or unsaturated linear alkyl chain having, respectively, from 8 to 22 or from 14 to 22 carbon atoms. The fatty unit of the ethers can be chosen in particular from decyl, cetyl, behenyl, arachidyl, stearyl, palmityl, myristyl, lauryl, capryl and hexadecanoyl units, and mixtures thereof such as cetearyl. By way of example of fatty alcohol ethers of a sugar, mention may be made of alkylpolyglucosides, such as decylglucoside and laurylglucoside sold, for example, by the company Henkel under the respective names Plantaren 2000 and Plantaren 1200, cetostearylglucoside, optionally as a mixture with cetostearyl alcohol, sold, for example, under the name Montanov 68 by the company Seppic, under the name Tego-care CG90 by the company Goldschmidt and under the name Emulgade KE3302 by the company Henkel, and also arachidylglucoside, for example in the form of the mixture of arachidyl and behenyl alcohols and of arachidylglucoside sold under the name Montanov 202 by the company Seppic. Use is more particularly made, as nonionic amphiphilic lipid of this type, of sucrose monostearate, sucrose distearate, sucrose tristearate and mixtures thereof, the distearate of methylglucose and of polyglycerol-3, and alkylpolyglucosides. The glycerol fatty esters that can be used as nonionic amphiphilic lipids can be chosen in particular from the group comprising the esters formed from at least one acid comprising a saturated linear alkyl chain having from 16 to 22 carbon atoms, and from 1 to 10 glycerol units. Use may be made of one or more of these glycerol fatty esters in the emulsion of the instant disclosure. These esters may be chosen in particular from stearates, behenates, arachidates, palmitates and mixtures thereof. Stearates and palmitates are preferably used. By way of example of a surfactant that can be used in the emulsion of the instant disclosure, mention may be made of decaglycerol monostearate, distearate, tristearate and pentastearate (10 glycerol units) (CTFA names: polyglyceryl-10 stearate, polyglyceryl-10 distearate, polyglyceryl-10 tristearate, polyglyceryl-10 pentastearate), such as the products sold under the respective names Nikkol Decaglyn 1-S, 2-S, 3-S and 5-S by the company Nikko, and diglyceryl monostearate (CTFA name: polyglyceryl-2 stearate) such as the product sold by the company Nikko under the name Nikkol DGMS. The sorbitan fatty esters that can be used as nonionic amphiphilic lipids chosen in particular from the group comprising esters of a C 16 -C 22 fatty acid and of sorbitan and oxyethylenated esters of a C 16 -C 22 fatty acid and of sorbitan. They are formed from at least one fatty acid comprising at least one saturated linear alkyl chain, having, respectively, from 16 to 22 carbon atoms, and from sorbitol or from ethoxylated sorbitol. The oxyethylenated esters generally comprise from 1 to 100 ethylene oxide units, and preferably from 2 to 40 ethylene oxide (EO) units. These esters can be chosen in particular from stearates, behenates, arachidates, palmitates and mixtures thereof. Stearates and palmitates are preferably used. By way of example of sorbitan fatty ester and of an oxyethylenated sorbitan fatty ester, mention may be made of sorbitan monostearate (CTFA name: sorbitan stearate) sold by the company ICI under the name Span 60, sorbitan monopalmitate (CTFA name: sorbitan palmitate) sold by the company ICI under the name Span 40, or sorbitan 20 EO tristearate (CTFA name: polysorbate 65) sold by the company ICI under the name Tween 65. The ethoxylated fatty ethers are typically ethers made up of 1 to 100 ethylene oxide units and of at least one fatty alcohol chain having from 16 to 22 carbon atoms. The fatty chain of the ethers can be chosen in particular from behenyl, arachidyl, stearyl and cetyl units, and mixtures thereof, such as cetearyl. By way of example of ethoxylated fatty ethers, mention may be made of ethers of behenyl alcohol comprising 5, 10, 20 and 30 ethylene oxide units (CTFA names: beheneth-5, beheneth-10, beheneth-20 and beheneth-30), such as the products sold under the names Nikkol BBS, BB10, BB20 and BB30 by the company Nikko, and the ether of stearyl alcohol comprising 2 ethylene oxide units (CTFA name: steareth-2), such as the product sold under the name Brij 72 by the company ICI. The ethoxylated fatty esters that can be used as nonionic amphiphilic lipids are esters made up of 1 to 100 ethylene oxide units and of at least one fatty acid chain comprising from 16 to 22 carbon atoms. The fatty chain of the esters can be chosen in particular from stearate, behenate, arachidate and palmitate units, and mixtures thereof. By way of example of ethoxylated fatty esters, mention may be made of the ester of stearic acid comprising 40 ethylene oxide units, such as the product sold under the name Myrj 52 (CTFA name: PEG-40 stearate) by the company ICI, and the ester of behenic acid comprising 8 ethylene oxide units (CTFA name: PEG-8 behenate), such as the product sold under the name Compritol HD5 ATO by the company Gattefosse. The block copolymers of ethylene oxide and of propylene oxide that can be used as nonionic amphiphilic can be chosen in particular from poloxamers and in particular from Poloxamer 231, such as the product sold by the company ICI under the name Pluronic L81 of formula (V) with x=z=6, y=39 (HLB 2); Poloxamer 282, such as the product sold by the company ICI under the name Pluronic L92 of formula (V) with x=z=10, y=47 (HLB 6); and Poloxamer 124, such as the product sold by the company ICI under the name Pluronic L44 of formula (V) with x=z=11, y=21 (HLB 16). As nonionic amphiphilic lipids, mention may also be made of the mixtures of nonionic surfactants described in document EP-A-705593, incorporated herein for reference. Suitable hydrophobically-modified emulsifiers include, for example, inulin lauryl carbamate, commercially available from Beneo Orafti under the tradename Inutec SP1. The above lists are only examples and not limiting. The total amount of emulsifier present in the compositions is typically in an amount of about 0.1, 0.2, or 0.5 wt. % to about 4.0, 5.0, 6.0, or 7.5 wt. %, based on the total weight of the composition. Gelling Agent Gelling agents may also be included in the sunscreen compositions. Examples of suitable hydrophilic gelling agents include carboxyvinyl polymers such as the Carbopol products (carbomers) and the Pemulen products (acrylate/C10-C30-alkylacrylate copolymer); polyacrylamides, for instance the crosslinked copolymers sold under the names Sepigel 305 (CTFA name: polyacrylamide/C13-14 isoparaffin/Laureth 7) or Simulgel 600 (CTFA name: acrylamide/sodium acryloyldimethyltaurate copolymer/isohexadecane/polysorbate 80) by the company SEPPIC; 2-acrylamido-2-methylpropanesulfonic acid polymers and copolymers, which are optionally crosslinked and/or neutralized, for instance the poly(2-acrylamido-2-methylpropanesulfonic acid) (CTFA name: ammonium polyacryldimethyltauramide); cellulose-based derivatives such as hydroxyethyl-cellulose; polysaccharides and especially gums such as xanthan gum; and mixtures thereof. Lipophilic gelling agents (thickeners) that may be mentioned include modified clays such as hectorite and its derivatives, for instance the products sold under the name bentone. In some instances, the gelling agent is ammonium acryloyldimethyltaurate/steareth-25 methacrylate crosspolymer, commercially available from Clariant under the tradename Aristoflex HMS. The above lists are only examples and not limiting. The gelling agent is typically used in an amount of about 0.05 to about 1.5% by weight, from about 0.08 to about 1.0% by weight, or about 0.1 to about 0.5% by weight, based on the total weight of the composition. Additional Sunscreen Filters (Protective Agents) The sunscreen compositions can include additional sunscreen filters such as, for example, mineral UV filters. Examples of mineral UV filters include pigments and nanopigments (mean size of the primary particles is generally is from 5 nm to 100 nm or from 10 nm to 50 nm) of treated or untreated metal oxides such as, for example, nanopigments of titanium oxide (amorphous or crystallized in rutile and/or anatase form), of iron oxide, of zinc oxide, of zirconium oxide or of cerium oxide. The treated nanopigments are pigments that have undergone one or more surface treatments of chemical, electronic, mechanochemical and/or mechanical nature with compounds as described, for example, in Cosmetics & Toiletries, February 1990, Vol. 105, pp. 53-64, such as amino acids, beeswax, fatty acids, fatty alcohols, anionic surfactants, lecithins, sodium, potassium, zinc, iron or aluminium salts of fatty acids, metal (titanium or aluminium) alkoxides, polyethylene, silicones, proteins (collagen or elastin), alkanolamines, silicon oxides, metal oxides, sodium hexametaphosphate, alumina or glycerol. The treated nanopigments may more particularly be titanium oxides treated with: silica and alumina, such as the products “Microtitanium Dioxide MT 500 SA” and “Microtitanium Dioxide MT 100 SA” from the company Tayca, and the products “Tioveil Fin”, “Tioveil OP”, “Tioveil MOTG” and “Tioveil IPM” from the company Tioxide; alumina and aluminium stearate, such as the product “Microtitanium Dioxide MT 100 T” from the company Tayca; alumina and aluminium laurate, such as the product “Microtitanium Dioxide MT 100 S” from the company Tayca; iron oxides and iron stearate, such as the product “Microtitanium Dioxide MT 100 F” from the company Tayca; silica, alumina and silicone, such as the products “Microtitanium Dioxide MT 100 SAS”, “Microtitanium Dioxide MT 600 SAS” and “Microtitanium Dioxide MT 500 SAS” from the company Tayca; sodium hexametaphosphate, such as the product “Microtitanium Dioxide MT 150 W” from the company Tayca; octyltrimethoxysilane, such as the product “T-805” from the company Degussa; alumina and stearic acid, such as the product “UVT-M160” from the company Kemira; alumina and glycerol, such as the product “UVT-M212” from the company Kemira; alumina and silicone, such as the product “UVT-M262” from the company Kemira. Other titanium oxide nanopigments treated with a silicone are TiO 2 treated with octyltrimethylsilane and for which the mean size of the elementary particles is between 25 and 40 nm, such as the product sold under the trade name “T805” by the company Degussa Silices, TiO 2 treated with a polydimethylsiloxane and for which the mean size of the elementary particles is 21 nm, such as the product sold under the trade name “70250 Cardre UF TiO2SI3” by the company Cardre, anatase/rutile TiO 2 treated with a polydimethylhydrogenosiloxane and for which the mean size of the elementary particles is 25 nm, such as the product sold under the trade name “Microtitanium Dioxide USP Grade Hydrophobic” by the company Color Techniques. Uncoated titanium oxide nanopigments are sold, for example, by the company Tayca under the trade names “Microtitanium Dioxide MT 500 B” or “Microtitanium Dioxide MT 600 B”, by the company Degussa under the name “P 25”, by the company Wackher under the name “Oxyde de titane transparent PW”, by the company Myoshi Kasei under the name “UFTR”, by the company Tomen under the name “ITS” and by the company Tioxide under the name “Tioveil AQ”. The uncoated zinc oxide nanopigments are, for example: those sold under the name “Z-Cote” by the company Sunsmart; those sold under the name “Nanox” by the company Elementis; and those sold under the name “Nanogard WCD 2025” by the company Nanophase Technologies. The coated zinc oxide nanopigments are, for example: those sold under the name “Zinc Oxide CS-5” by the company Toshibi (ZnO coated with polymethylhydrogenosiloxane); those sold under the name “Nanogard Zinc Oxide FN” by the company Nanophase Technologies (as a 40% dispersion in Finsolv TN, C 12 -C 15 alkyl benzoate); those sold under the name “Daitopersion ZN-30” and “Daitopersion ZN-50” by the company Daito (dispersions in cyclopolymethylsiloxane/oxyethylenated polydimethylsiloxane, containing 30% or 50% of nanozinc oxides coated with silica and polymethylhydrogenosiloxane); those sold under the name “NFD Ultrafine ZNO” by the company Daikin (ZnO coated with perfluoroalkyl phosphate and copolymer based on perfluoroalkylethyl as a dispersion in cyclopentasiloxane); those sold under the name “SPD-Z1” by the company Shin-Etsu (ZnO coated with silicone-grafted acrylic polymer, dispersed in cyclodimethylsiloxane); those sold under the name “Escalol Z100” by the company ISP (alumina-treated ZnO dispersed in an ethylhexyl methoxycinnamate/PVP-hexadecene/methicone copolymer mixture); those sold under the name “Fuji ZNO-SMS-10” by the company Fuji Pigment (ZnO coated with silica and polymethylsilsesquioxane); and those sold under the name “Nanox Gel TN” by the company Elementis (ZnO dispersed at a concentration of 55% in C 12 -C 15 alkyl benzoate with hydroxystearic acid polycondensate). The uncoated cerium oxide nanopigments are sold under the name “Colloidal Cerium Oxide” by the company Rhone-Poulenc. The uncoated iron oxide nanopigments are sold, for example, by the company Arnaud under the names “Nanogard WCD 2002 (FE 45B)”, “Nanogard Iron FE 45 BL AQ”, “Nanogard FE 45R AQ” and “Nanogard WCD 2006 (FE 45R)” or by the company Mitsubishi under the name “TY-220”. The coated iron oxide nanopigments are sold, for example, by the company Arnaud under the names “Nanogard WCD 2008 (FE 45B FN)”, “Nanogard WCD 2009 (FE 45B 556)”, “Nanogard FE 45 BL 345” and “Nanogard FE 45 BL” or by the company BASF under the name “Transparent Iron Oxide”. Mixtures of metal oxides may also be used, especially of titanium dioxide and of cerium dioxide, including the silica-coated equal-weight mixture of titanium dioxide and of cerium dioxide, sold by the company Ikeda under the name “Sunveil A”, and also the alumina, silica and silicone-coated mixture of titanium dioxide and of zinc dioxide, such as the product “M 261” sold by the company Kemira, or the alumina, silica and glycerol-coated mixture of titanium dioxide and of zinc dioxide, such as the product “M 211” sold by the company Kemira. The above lists are only examples and not limiting. The compositions according to the instant disclosure may be prepared according to techniques that are well known to those skilled in the art, in particular those intended for the preparation of emulsions of oil-in-water or water-in-oil type. They may be in particular in the form of a simple or complex emulsion (O/W, W/O, O/W/O or W/O/W emulsion) such as a cream or a milk, in the form of a gel or a cream-gel, or in the form of a lotion. The instant disclosure will be better understood from the examples that follow, all of which are intended for illustrative purposes only and are not meant to limit the scope of the instant disclosure in any way. Examples 1-12 Samples comprising different amounts of UV filters were prepared by dissolving the UV filters in ethanol and solvent as illustrated in the table below. TABLE 1 Ingredient Range Octocrylene 5.30-5.92% Avobenzone 4.40-4.97% (Butyl Methoxydibenzoylmethane) Tinsorb S 0.94-1.93% (Bis-EthylHexyloxyphenol Methoxyphenyl Triazine) Uvinul T150 0.39-2.75% (Ethylhexyl Triazone) Mexoryl XL 2.67-2.90% (Drometrizole Trisiloxane) TEA   0-1.05% (Triethanolamine) Polysorbate 20  5.50% Propylene Glycol    5% Eldew SL205 Solvent* 31.75% Dermacryl 79**  2.5% Ethanol Qs 100% *Eldew SL 205 (Ajinomoto) is Isopropyl Lauroyl Sarcosinate (emollient) **Dermacryl 79 (Akzo Nobel) is an acrylate/octylacrylamide Copolymner (film-former) Each sample was applied to a PMMA (polymethyl methacrylate) plate with a draw down bar to control the thickness and the homogeneity of the film. The in vitro SPF was measured using a Labsphere 2000. Each measurement was made 6 times (6 times on each plate) times on 3 plates for each composition. The amount of UV filters included in each sample and the resulting SPF is reported in the table below. TABLE 2 Tinsorb S Avobenzone Bis-EthylHexyloxy- Uvinul Butyl Methoxy phenol T150 Mexoryl XL dibenzoyl- Methoxyphenyl Ethylhexyl Drometrizole Total UV No. Octocrylene methane Triazine Trizaone Trisiloxane Filters SPF 1 5.30 4.92 1.69 2.33 2.68 16.92 137.00 Comparisons 2 5.5 4.12 1.87 2.93 2.96 17.38 132.33 3 5.96 4.31 1.67 2.52 2.63 17.09 123.75 4 5.79 4.26 1.77 2.75 2.43 17 115.43 5 5.85 4.43 1.64 2.7 2.61 17.23 112.8 6 4.98 4.37 1.58 2.97 2.94 16.84 103.66 7 5.85 4.72 1.91 1.56 2.84 16.88 102.76 8 5.89 4.63 1.39 2.53 2.71 17.15 98.35 9 5.4 4.87 1.28 2.4 2.79 16.74 96.93 10 5.53 4.46 1.43 2.75 2.90 17.07 94.43 11 5.47 5.00 1.28 2.81 2.79 17.35 89.99 12 5.83 4.97 1.09 2.03 2.79 16.71 86.77 13 5.92 4.45 0.94 2.57 2.67 16.55 79.05 14 5.88 4.34 1.38 2.99 2.56 17.15 76.29 15 5.79 4.40 1.80 0.61 2.89 15.49 52.49 16 5.71 4.97 1.93 0.39 2.88 15.88 40.59 The following table corresponds to the table above (TABLE 2) but lists each UV filter as a ratio relative to avobenzone. TABLE 3 Tinsorb S Bis- Avobenzone EthylHexyloxy- Uvinul Butyl Methoxy phenol T150 Mexoryl XL dibenzoyl- Methoxyphenyl Ethylhexyl Drometrizole Total UV No. Octocrylene methane Triazine Trizaone Trisiloxane Filters SPF 1 1.08 1.00 0.34 0.47 0.54 16.92 137.00 Comparisons 2 1.33 1.00 0.45 0.71 0.72 17.38 132.33 3 1.38 1.00 0.39 0.58 0.61 17.09 123.75 4 1.36 1.00 0.42 0.65 0.57 17 115.43 5 1.32 1.00 0.37 0.61 0.59 17.23 112.8 6 1.14 1.00 0.36 0.68 0.67 16.84 103.66 7 1.24 1.00 0.40 0.33 0.60 16.88 102.76 8 1.27 1.00 0.30 0.55 0.59 17.15 98.35 9 1.11 1.00 0.26 0.49 0.57 16.74 96.93 10 1.24 1.00 0.32 0.62 0.65 17.07 94.43 11 1.09 1.00 0.26 0.56 0.56 17.35 89.99 12 1.17 1.00 0.22 0.41 0.56 16.71 86.77 13 1.33 1.00 0.21 0.58 0.60 16.55 79.05 14 1.35 1.00 0.32 0.69 0.59 17.15 76.29 15 1.32 1.00 0.41 0.14 0.66 15.49 52.49 16 1.15 1.00 0.39 0.08 0.58 15.88 40.59 *Note: the bolded numbers fall outside the claimed range. As illustrated in the tables above, Example 1, having a ratio of about 1.0:1.0:0.3:0.5:0.5 (Octocylene:Avobenzone:Tinsorb S:Uvinul T150:Mexoryl XL) shows an dramatic jump in SPF. Example 13 Using the procedures described above for Examples 1-12, the following composition was prepared and the SPF measured. TABLE 4 Clear Spray-On Sunscreen SPF 137 (In Vitro) Ingredient Range Octocrylene  5.3% Avobenzone  4.92% Tinsorb S  1.69% Uvinul T150  2.33% Mexoryl XL  2.68% Polysorbate 20  5.50% Propylene Glycol    5% Eldew SL205 Solvent* 31.75% Dermacryl 79**  2.5% Ethanol Qs 100% *Eldew SL 205 (Ajinomoto) is Isopropyl Lauroyl Sarcosinate (emollient) **Dermacryl 79 (Akzo Nobel) is an acrylate/octylacrylamide Copolymner (film-former) Example 14 The following composition was prepared and the SPF measured. TABLE 5 Lotion Sunscreen Spray Phase Chemical Name % wt/wt A-1 Water Q.S. Preservative 0.1 to 2.00 Disodium EDTA 0.100 O/W emulsifier 0.1 to 2.00 A-2 Avobenzone 4.92 Octocrylene 5.3 B Uvinul T150 2.33 Mexoryl XL 2.68 Tinsorb S 1.69 Emollient 2.0-20.0 Silicone 1.0-3.0 W/O emulsifier 0.1-2.5 Co-emulsifier 0.1-2.0 Vit E 0.100 C Water 7.000 Silicone 1.0-5.0 D Booster 1.0-6.0 E Wetting Agent 0.1-1.5 The components of the Lotion Sunscreen were combined as outlined below. 1) Weigh Phase A and heat to 85° C. 2) Weigh Phase B ingredients in another beaker and heat to 85° C. 3) Add Phase B into Phase A and homogenized for 20 minutes. Maintain the temperature at 90° C. 4) Check emulsion quality. If emulsion quality is good then begin cooling to room temperature. 5) Add Phase C into Phase A/B and homogenize for 5 minutes. 6) Pass the emulsion through a high pressure homogenizer two times at 500 bar. 7) Add phase D at room temperature and mix for 5 minutes.

The disclosure relates to sunscreen compositions having a synergistic combination of ultraviolet light (UV) filtering agents that provide a high sun protection factor (SPF). Compositions according to the disclosure have high SPF values without requiring high overall amounts of UV filtering agents. Furthermore, the disclosure relates to methods of using the described compositions for protecting keratinous substances such as skin and hair from UV radiation.

BACKGROUND In most general purpose computers, an operating system is the primary software that manages access to resources within the computer. The primary resources are the central processing unit (CPU), which executes application programs designed to run on the computer, main memory and storage. In some computer architectures, additional processing units (such as multiple cores in a processor) and/or additional processors, called co-processors, may be present. Examples of such co-processors include a graphic processing unit (GPU) and a digital signal processor (DSP). The operating system also manages access to these resources by multiple processes. A field programmable gate array (FPGA) is a kind of logic device that is commonly used in specialized computing devices. An FPGA typically is used to perform a specific, dedicated function, for which a gate array is particularly well-suited. FPGAs typically are found in peripheral devices, or other specialized hardware, such as a printed circuit board connected to and accessed through a system bus such as a PCI bus. In general, such devices are programmed once, and used many times. Because these devices are programmable, they have an advantage over other specialized logic devices in that they can be updated in the field. SUMMARY This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. One or more field programmable gate arrays (FPGA) can be used as a shared programmable co-processor resource in a general purpose computing system. An FPGA can be programmed to perform functions, which in turn can be associated with one or more processes. With multiple processes, the FPGA can be shared, and a process is assigned to at least one portion of the FPGA during a time slot in which to access the FPGA. Programs written in a hardware description language for programming the FPGA are made available as a hardware library. The operating system manages allocating the FPGA resources to processes, programming the FPGA in accordance with the functions to be performed by the processes using the FPGA and scheduling use of the FPGA by these processes. Given a set of hardware libraries in a system, an update process can be provided to periodically (or, on request) update the libraries to add new libraries or change existing libraries to new versions. One or more update servers can provide information about libraries available for download, either in response to a request or by notifying systems using such libraries. New available libraries can be presented to a user for selection and download. Requests for updated libraries can arise in several ways, such as through polling for updates, exceptions from applications attempting to use libraries, and upon compilation of application code. In the following description, reference is made to the accompanying drawings which form a part hereof, and in which are shown, by way of illustration, specific example implementations of this technique. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the disclosure. DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an example computing system with FPGA resources for which an operating system can be implemented. FIG. 2 is a schematic diagram of an illustrative example of FPGA functional units. FIG. 3 is a schematic diagram of an example architecture of an application using hardware and software libraries on a computer system with FPGA resources. FIG. 4 is a diagram illustrating the use of FPGA resources over time. FIG. 5 is a data flow diagram illustrating an example implementation of a system for updating hardware libraries FIG. 6 is a flowchart illustrating an example implementation of requesting a hardware library based on code analysis. FIG. 7 is a flowchart illustrating an example implementation of requesting a hardware library based on user selection. FIG. 8 is a flowchart illustrating an example implementation of requesting a hardware library based on polling an update server. DETAILED DESCRIPTION The following section provides a brief, general description of an example computing environment in which an operating system for managing use of FPGA resources can be implemented. The system can be implemented with numerous general purpose or special purpose computing devices. Examples of well known computing devices that may be suitable include, but are not limited to, personal computers, server computers, hand-held or laptop devices (for example, media players, notebook computers, cellular phones, personal data assistants, voice recorders), multiprocessor systems, microprocessor-based systems, set top boxes, game consoles, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like. FIG. 1 illustrates merely an example computing environment, and is not intended to suggest any limitation as to the scope of use or functionality of a suitable computing environment. With reference to FIG. 1 , an example computing environment includes a computing device 100 . In a basic configuration, computing device 100 includes at least one processing unit 102 , such as a typical central processing unit (CPU) of a general purpose computer, and memory 104 . The computing device may include multiple processing units and/or additional co-processing units such as a graphics processing unit (GPU). The computing device also includes one or more field programmable gate arrays (FPGA), denoted as FPGA unit 120 which is available as a shared (among processes running on the computer) co-processing resource. An FPGA may reside in its own CPU socket or on a separate card plugged into an expansion slot, such as a Peripheral Component Interconnect Express (PCI-E) slot. By providing such an FPGA unit, a variety of functions that are well-suited for implementation by a gate array can be implemented with the resulting benefit of hardware acceleration. Depending on the configuration of the processing unit and the FPGA unit, the unit, or each functional unit within it, has an associated input/output channel for communication with host operating system processes. For example, a memory region dedicated to the functional unit and shared between it and a process using that functional unit can be provided. A sort of request queue and response queue also can be used to enable asynchronous invocation of operations implemented in the FPGA unit. Additionally, state of the functional units in the FPGA unit for a process can be saved to and restored from a memory region for the functional unit and that process. Alternatively other techniques can be used to ensure that the functional unit is in a known state before it is used by its process. Depending on the configuration and type of computing device, memory 104 may be volatile (such as RAM), non-volatile (such as ROM, flash memory, etc.) or some combination of the two. This configuration of a processing unit, co-processor and memory is illustrated in FIG. 1 by dashed line 106 . Computing device 100 may also have additional resources and devices. For example, computing device 100 may include additional storage (removable and/or non-removable) including, but not limited to, magnetic or optical disks or tape. Such additional storage is illustrated in FIG. 1 by removable storage 108 and non-removable storage 110 . Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer program instructions, data files, data structures, program modules or other data. Memory 104 , removable storage 108 and non-removable storage 110 are all examples of computer storage media. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by computing device 100 . Any such computer storage media may be part of computing device 100 . Computing device 100 also can include communications connection(s) 112 that allow the device to communicate with other devices over a communication medium. The implementation of the communications connection 112 is dependent on the kind of communication medium being accessed by the computing device, as it provides an interface to such a medium to permit transmission and/or reception of data over the communication medium. A communication medium typically carries computer program instructions, data files, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Computing device 100 may have various input device(s) 114 such as a keyboard, mouse, pen, camera, touch input device, and so on. Output device(s) 116 such as a display, speakers, a printer, and so on may also be included. All of these devices are well known in the art and need not be discussed at length here. Applications executed on a computing device are implemented using computer-executable instructions and/or computer-interpreted instructions, such as program modules, that are processed by the computing device. Generally, program modules include routines, programs, objects, components, data structures, and so on, that, when processed by a processing unit, instruct the processing unit to perform particular tasks or implement particular abstract data types. In a distributed computing environment, such tasks can be performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices. An operating system executed on a computing device manages access to the various resources of the computer device by processes. Typically, running an application on the computer system causes one or more processes to be created, with each process being allocated to different resources over time. If a resource is shared among processes, and if the processes cannot share the resource concurrently, then the operating system schedules access to the resource over time. One of such resources is the FPGA unit 120 of FIG. 1 , which can include one or more discrete FPGA's. Referring to FIG. 2 , one of the resources within the FPGA unit is one or more groups of programmable gates, herein called functional units. Each functional unit is defined by a set of gates and/or other resources in the gate array. In general, functional units are nonoverlapping, i.e., do not share programmable elements within the gate array. For example, as illustrated schematically in FIG. 2 , functional units 200 , 202 , 204 and 206 are non-overlapping. Most FPGAs have only one functional unit. The FPGA unit 120 in FIG. 1 , however, can have one or more FPGAs. With multiple FPGAs, each FPGA can be considered a functional unit. Referring to FIG. 3 , each functional unit is a resource that can be assigned to one or more processes, programmed by the operating system using a hardware library that implements an operation, and then used by the processes assigned to it to perform the operation. Referring to FIG. 3 as an example, an application 300 can use conventional software libraries 302 , and FPGA hardware libraries 304 , to perform various operations. If an application relies on a hardware library 304 , then the operating system 306 uses the hardware library to program the FPGA resources 310 to allow the application 300 to use the library. The FPGA can be programmed prior to the application beginning execution. If an FPGA can be reprogrammed quickly enough, the library can be loaded into the FPGA in a scheduling quantum of the operating system. The operating system 306 also executes software commands from the application 300 and software libraries 302 on the CPU 308 . When the application makes calls to functions performed by a software library, the operating system executes the function from the software library on the CPU 308 . When the application makes calls to functions performed by the FPGA, the operating system ensures that the FPGA is programmed using the hardware library and executes the function using the FPGA. To illustrate how different functional units can be used over time, reference is now made to FIG. 4 . In FIG. 4 , at time T1, functional units 400 and 402 are being used. At time T2, functional units 400 and 404 are being used. At time T3, functional units 400 and 402 are again being used. At time T1, functional unit 400 can be assigned to process P1, and functional unit 402 can be assigned to process P2. At time T2, process P2 may be inactive, and process P1 can use functional unit 400 and process P3 can use functional unit 404 . At time T3, another process can start using functional unit 400 , such as process P4; and process P2 can be active again at use functional unit 402 . With current FPGA implementations, the use of multiple functional units at the same time by different processes implies the use of multiple FPGAs. To the extent that an FPGA can support multiple functional units being used by different processes at the same time, these functional units can be on the same FPGA. Effectively, the operating system is statistically multiplexing the FPGA in both time and space. To allow such usage of the FPGA resources by different processes over time, the operating system has a scheduler that determines which process has access to the FPGA resources at each scheduling quantum, i.e., time period, and when an FPGA functional unit will be programmed with a hardware library so that the functional unit is available to be used by that process. Thus, an implementation of a scheduler for the FPGA unit is dependent in part on the nature of the FPGA unit and the one or more FPGAs it includes. Factors related to the FPGAs to be considered include, but are not limited to, the following. For example, in some cases an entire FPGA is refreshed to program a functional unit if one functional unit cannot be programmed independently of other functional units. Another consideration is the speed with which a functional unit can be programmed, and whether programming of a functional unit prevents other functional units from being used during that programming phase. Another factor to consider is whether processes can share a hardware library by sharing a functional unit. The scheduler also takes into account such factors as the number of concurrent processes, application performance guarantees, priority of applications, process context switching costs, access to memory and buses, and availability of software libraries if no functional unit is available within the FPGA unit. There may be other instances where the FPGA unit provides a general purpose facility to applications or the operating system, which therefore are scheduled for the length of an application instantiation. For example, custom network protocols or offloading can be offered as an accelerated service on the FPGA unit. System calls or standard library calls, normally executed in a general purpose CPU, can be accelerated using the FPGA unit instead. Further, the operating system can multiplex the CPU based on preferences for process priority. In another instance, the operating system can use a profile of an application, generated statically or dynamically, to predict the functionality best suited for running on an FPGA unit and then pre-load that functionality so that it is available for scheduling. By using the profile as a guide, the operating system can ensure there is both space and time available on the FPGA unit to accelerate the application. Finally, the operating system can use simple hints from the application to know when to schedule time on the FPGA unit. For example, certain calls into the operating system (system calls) can denote long delays (calls to disk or the network), which provides a hint that the FPGA unit can be free for some amount of time for other threads or processes to use. Therefore, the operating system uses a variety of hints and preferences to create a schedule to multiplex access to the FPGA unit. Because the operating system controls the scheduler, it has detailed knowledge of executing and pending work, available hardware libraries, and time it takes to program an FPGA. Therefore, it can use this knowledge to determine which processes leverage the FPGA during execution. Having now described a general overview of such computer architecture, an example implementation for updating the hardware libraries will now be described. Referring to FIG. 5 , an update process 500 has access to a hardware library 502 which stores the code for implementing functions on the FPGA coprocessor. The update process 500 communicates with an update server 510 to receive, in some cases, information 504 describing available libraries, and in other cases, updated hardware libraries 506 . The update server 510 can push information 504 and libraries 506 to the update process 500 , or can provide such information upon receiving a request 508 from update server. The update process 500 can reside in the operating system of a host computer or can be a user-level service operating on the host computer. The update server 510 can be a separate server computer connected to the host computer over a computer network. The update server also can be configured to be accessible not only by the update process, but also, or alternatively, through a conventional web browser or other user interface. The update server can provide one or more virtual storefronts as an interfaced through which hardware libraries can be made available for selection, sale and/or download to users. Such an interface can include information describing the library and pricing and other terms for downloading the library. After the update process receives the information about available libraries, a list 512 of available libraries can be presented to a user for selection through a user interface 514 . Through appropriate input devices in the user interface, the user can provide the update process an indication of a selection 516 of one or more libraries for download. The update process can trigger a request for hardware libraries based on a variety of conditions. For example, code analysis could identify functions that are known to have corresponding hardware libraries. An application can trigger an exception when executed if a hardware library is unavailable or if an error occurs using it. In such a case, the operating system can attempt to handle the exception by using a corresponding software library if available. Alternatively, the operating system or application loader can make the decision about whether to dynamically link to a hardware or software library when the application is loaded. System parameters could be used to indicate whether a hardware library should be updated. Accordingly, as shown in FIG. 5 , the update process can be triggered by application exceptions 518 and/or system parameters 520 . Tools provided in a development environment 524 also could initiate a request 522 when an application 526 under development specifies or can use a hardware library. Some example implementations for requesting a hardware library follow. The channel between the update process and the update server can be secured to ensure the update process is communicating with a legitimate update server. Similarly, libraries downloaded from the update server can be authenticated as being authored by a trusted source to improve security. FIG. 6 is a flowchart illustrating an example implementation of requesting a hardware library based on code analysis. Information about hardware libraries is received 600 into memory. Application code is received and analyzed 602 to identify references to one or more hardware libraries. In some instances, a reference to a library can permit implementation by a software or hardware library. Any libraries referenced in the application code that have a corresponding implementation, according to the received hardware library information, are identified 604 . The identified hardware libraries then can be downloaded 606 . FIG. 7 is a flowchart illustrating an example implementation of requesting a hardware library based on user selection. Information about hardware libraries is received 700 into memory. A list or other formatted view of this information is presented 702 to the user, from which the user is allowed to make a selection. If a selection from the user is received 704 , then the identified hardware library can be downloaded 706 . The hardware library also can be advertised to provide an improved user experience and therefore warrant an upgrade which can be purchased or licensed and downloaded, whether for a fee or for free of compensation FIG. 8 is a flowchart illustrating an example implementation of requesting a hardware library based on polling or receiving a notification from an update server. In particular, the update process first identifies 800 currently used hardware libraries, such as stored in 502 in FIG. 5 . The update server is then polled 802 , given identifiers of the hardware libraries. The update server determines whether there are any updates related to the hardware libraries identified to it. The update process then receives ( 804 ) information about any available updates to the hardware libraries. These updates then can be requested 806 for download. The terms “article of manufacture”, “process”, “machine” and “composition of matter” in the preambles of the appended claims are intended to limit the claims to subject matter deemed to fall within the scope of patentable subject matter defined by the use of these terms in 35 U.S.C. §101. Any or all of the aforementioned alternate embodiments described herein may be used in any combination desired to form additional hybrid embodiments. It should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific implementations described above. The specific implementations described above are disclosed as examples only.

A computer system includes one or more field programmable gate arrays as a coprocessor that can be shared among processes and programmed using hardware libraries. Given a set of hardware libraries, an update process periodically updates the libraries and/or adds new libraries. One or more update servers can provide information about libraries available for download, either in response to a request or by notifying systems using such libraries. New available libraries can be presented to a user for selection and download. Requests for updated libraries can arise in several ways, such as through polling for updates, exceptions from applications attempting to use libraries, and upon compilation of application code.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a wireless communication system using light wave, radio wave, or the like. 2. Description of the Prior Art In a wired LAN (local area network), terminal devices are connected to each other via wires. The terminal devices can communicate with each other via the wires. It is known to combine a wired LAN and a wireless communication network. For example, a wired LAN is additionally provided with an access point device (a gateway device) which can execute both wired communication and wireless communication. The access point device is connected via wires to normal terminal devices in the wired LAN. The access point device can communicate with the normal terminal devices in the wired LAN via the wires. Also, the access point device can execute wireless communication with terminal devices in a wireless communication network. In this case, the wired LAN and the wireless communication network are connected via the access point device (the gateway device). In addition, the access point device is a member of the wired LAN as well as a member of the wireless communication network. In a wireless communication network, if two terminal devices simultaneously transmit wireless signals toward another terminal device, the transmitted wireless signals collide with each other. In this case, both the transmission-side terminal devices fail to normally communicate with the reception-side terminal device. There is a wireless communication network of a CSMA (carrier sense multiple access) type. In the CSMA wireless communication network, when a terminal device is required to transmit a wireless signal, the terminal device executes a process of sensing a carrier to check whether a communication channel is occupied or unoccupied. When the communication channel is unoccupied, the terminal device executes the transmission of the wireless signal. When the communication channel is occupied, the terminal device falls into a stand-by state to avoid a signal collision. In a wired LAN, if two terminal devices simultaneously transmit signals toward another terminal device via a common bus wire, the transmitted signals collide with each other. In this case, both the transmission-side terminal devices fail to normally communicate with the reception-side terminal device. There is a wired LAN of a CD (collision detection) type. In such a wired LAN, every terminal device monitors the level of a voltage at a common bus wire to check whether the common bus wire is occupied or unoccupied. The information of whether the common bus wire is occupied or unoccupied is used in avoiding a signal collision. There is a wired LAN having a star connection between a hub device and terminal devices. The connection between the hub device and each terminal device includes a duplex line. Such a wired LAN intrinsically has a function of avoiding a signal collision. SUMMARY OF THE INVENTION It is an object of this invention to provide an improved wireless communication system. A first aspect of this invention provides a terminal device in a wireless communication system having a wireless communication channel which comprises first means for converting a first electric signal into a first wireless signal, and transmitting the first wireless signal along the wireless communication channel; second means for receiving a second wireless signal along the wireless communication channel, and converting the second wireless signal into a second electric signal; and third means for deciding whether or not the first electric signal and the second electric signal are equal to each other to detect whether or not a signal collision occurs on the wireless communication channel. A second aspect of this invention is based on the first aspect thereof, and provides a terminal device further comprising fourth means for generating a third electric signal representative of occurrence of a signal collision on the wireless communication channel when the third means decides that the first electric signal and the second electric signal are not equal to each other. A third aspect of this invention is based on the second aspect thereof, and provides a terminal device further comprising fifth means for generating the third electric signal from the first electric signal. A fourth aspect of this invention provides a wireless communication system comprising a repeater; and a terminal device connected to the repeater via a wireless communication channel; wherein the terminal device comprises a) first means for converting a first electric signal into a first wireless signal, and transmitting the first wireless signal toward the repeater along the wireless communication channel; b) second means for receiving a second wireless signal from the repeater via the wireless communication channel, and converting the second wireless signal into a second electric signal; and c) third means for deciding whether or not the first electric signal and the second electric signal are equal to each other to detect whether or not a signal collision occurs on the wireless communication channel. A fifth aspect of this invention is based on the fourth aspect thereof, and provides a wireless communication system wherein the terminal device further comprises d) fourth means for generating a third electric signal representative of occurrence of a signal collision on the wireless communication channel when the third means decides that the first electric signal and the second electric signal are not equal to each other. A sixth aspect of this invention is based on the fifth aspect thereof, and provides a wireless communication system wherein the terminal device further comprises e) fifth means for generating the third electric signal from the first electric signal. A seventh aspect of this invention provides a wireless communication system comprising a repeater; and a terminal device connected to the repeater via a wireless communication channel; wherein the repeater comprises a) first means for receiving a first wireless signal from the terminal device via the wireless communication channel; b) second means for converting an electric signal into a second wireless signal, and transmitting the second wireless signal toward the terminal device along the wireless communication channel; c) third means for detecting whether or not the electric signal is present; d) fourth means for disabling the second means, and repeating the first wireless signal and transmitting the first wireless signal toward the terminal device along the wireless communication channel when the third means detects that the electric signal is not present; and e) fifth means for enabling the second means and inhibiting the fourth means from repeating the first wireless signal when the third means detects that the electric signal is present. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram of a combination of wired LAN's and a wireless communication network. FIG. 2 is a block diagram of a repeater in FIG. 1. FIG. 3 is a diagram of an example of a part of a selector in FIG. 2. FIG. 4 is a block diagram of a terminal device in FIG. 1. FIG. 5 is a diagram of an example of a part of a selector in FIG. 4. DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, a wired LAN 10a includes a hub device 11a and repeaters 12a and 12b. The wired LAN 10a conforms to, for example, the 10BASE-T standards in "ISO8802-3". The repeaters 12a and 12b are connected to the hub device 11a via wires providing a star connection. The repeater 12a and the hub device 11a can bidirectionally communicate with each other via the related wire. The repeater 12b and the hub device 11a can bidirectionally communicate with each other via the related wire. A wireless communication network includes the repeaters 12a and 12b, and also terminal devices 13a, 13b, and 13c. The wireless communication network uses, for example, light wave. The terminal device 13a and the repeater 12a can bidirectionally communicate with each other by wireless. Thus, the terminal device 13a and the repeater 12a are connected via a wireless communication channel. The terminal device 13b and the repeater 12a can bidirectionally communicate with each other by wireless. Thus, the terminal device 13b and the repeater 12b are connected via a wireless communication channel. The terminal device 13c and the repeater 12b can bidirectionally communicate with each other by wireless. Thus, the terminal device 13c and the repeater 12b are connected via a wireless communication channel. A wired LAN 10b includes the terminal device 13a, a hub device 11b, and a terminal device 14a. The wired LAN 10b conforms to, for example, the 10BASE-T standards in "ISO8802-3". The terminal devices 13a and 14a are connected to the hub device 11b via wires providing a star connection. The terminal device 13a and the hub device 11b can bidirectionally communicate with each other via the related wire. The terminal devices 14a and the hub device 11b can bidirectionally communicate with each other via the related wire. The terminal device 14a includes, for example, a computer. The terminal device 13b is connected to a terminal device 14b via a wire. The terminal device 13b and the terminal device 14b can bidirectionally communicate with each other via the wire. The terminal device 14b includes, for example, a computer. A wired LAN 10c includes the terminal device 13c and a hub device 11c. The wired LAN 10c conforms to, for example, the 10BASE-T standards in "ISO8802-3". The terminal devices 13c is connected to the hub device 11c via a wire. The terminal device 13c and the hub device 11c can bidirectionally communicate with each other via the wire. The repeaters 12a and 12b have a relatively large half-power angle in the directivity of wireless signal transmission and reception. On the other hand, the terminal devices 13a, 13b, and 13c have a relatively small half-power angle in the directivity of wireless signal transmission and reception. The repeaters 12a and 12b, and the terminal devices 13a, 13b, and 13c are directed so that the terminal devices 13a and 13b can communicate with the repeater 12a by wireless, and that the terminal device 13c can communicate with the repeater 12b by wireless. The terminal device 13c can not access the repeater 12a by wireless. In addition, the repeaters 12a and 12b can not directly communicate with each other by wireless. Furthermore, the terminal devices 13a, 13b, and 13c can not communicate with each other by wireless. The repeaters 12a and 12b are similar in structure. Therefore, only the structure of the repeater 12a will be explained hereinafter. As shown in FIG. 2, the repeater 12a includes a photodiode (or a photodiode array) 21, an amplifier 22, a decoding circuit 23, a code sync circuit 24, a LAN interface 25, a code sync circuit 26, a selector 27, an encoding circuit 28, a driver circuit 29, a light emitting diode (or a light emitting diode array) 30, and a carrier sensing circuit 43. The photodiode 21 is followed by the amplifier 22. The amplifier 22 is followed by the decoding circuit 23 and the carrier sensing circuit 43. The decoding circuit 23 is followed by the code sync circuit 24. The output terminal of the code sync circuit 24 is connected to the LAN interface 25 and the selector 27. The output terminal of the carrier sensing circuit 43 is connected to the selector 27. The LAN interface 25 is connected to the wire which leads to the hub device 11a (see FIG. 1). The LAN interface 25 is connected to the input terminal of the code sync circuit 26. In addition, the LAN interface 25 is directly connected to the selector 27. The output terminal of the code sync circuit 26 is connected to the selector 27. The selector 27 is connected to the input terminal of the encoding circuit 28. The encoding circuit 28 is successively followed by the driver circuit 29 and the light emitting diode 30. The photodiode 21 receives an optical signal from the terminal device 13a or 13b (see FIG. 1), and converts the optical signal into a corresponding electric signal. The photodiode 21 outputs the electric signal to the amplifier 22. The amplifier 22 enlarges the output signal of the photodiode 21. The amplifier 22 outputs the enlargement-resultant signal to the decoding circuit 23 and the carrier sensing circuit 43. The output signal of the photodiode 21 or the output signal of the amplifier 22 is equal to a signal which results from modulating a carrier with transmitted information (data). The optical signal handled by the photodiode 21 uses, for example, infrared light or visible light. It should be noted that the optical signal may be replaced by a radio wave signal. The carrier sensing circuit 43 serves to detect the carrier in the output signal of the amplifier 22. When an optical signal is currently received by the photodiode 21, the carrier sensing circuit 43 detects the presence of the carrier in the output signal of the amplifier 22. When any optical signal is not currently received by the photodiode 21, the carrier sensing circuit 43 detects the absence of the carrier from the output signal of the amplifier 22. The carrier sensing circuit 43 generates a binary detection signal "a" representing whether the carrier is present in or absent from the output signal of the amplifier 22, that is, whether or not an optical signal is currently received by the photodiode 21. Specifically, the detection signal "a" being in a high level state indicates the presence of the carrier in the output signal of the amplifier 22. The detection signal "a" being in a low level state indicates the absence of the carrier from the output signal of the amplifier 22. The carrier sensing circuit 43 outputs the detection signal "a" to a selection terminal S2 of the selector 27. The decoding circuit 23 decodes the output signal of the amplifier 22 into an information signal (data). In other words, the decoding circuit 23 recovers an information signal (data) from the output signal of the amplifier 22. The decoding circuit 23 outputs the information signal to the code sync circuit 24. The code sync circuit 24 subjects the information signal to a code synchronization process. The code sync circuit 24 outputs the resultant information signal to the LAN interface 25. In addition, the code sync circuit 24 outputs the resultant information signal to an input terminal I2 of the selector 27. The LAN interface 25 can transmit the output information signal of the code sync circuit 24 to the hub device 11a (see FIG. 1) via the wire. The LAN interface 25 can receive an information signal (data) from the hub device 11a (see FIG. 1) via the wire. The LAN interface 25 includes a known signal sensing section. The signal sensing section in the LAN interface 25 detects whether or not the LAN interface 25 currently receives an information signal from the hub device 11a (see FIG. 1). The signal sensing section in the LAN interface 25 generates a detection signal "b" representing whether or not the LAN interface 25 currently receives an information signal from the hub device 11a (see FIG. 1). Specifically, the detection signal "b" being in a high level state indicates that the LAN interface 25 currently receives an information signal from the hub device 11a (see FIG. 1). The detection signal "b" being in a low level state indicates that the LAN interface 25 does not currently receive any information signal from the hub device 11a (see FIG. 1). The LAN interface 25 outputs the detection signal "b" to a selection terminal S1 of the selector 27. The LAN interface 25 feeds the output information signal of the hub device 11a (see FIG. 1) to the code sync circuit 26. The code sync circuit 26 subjects the information signal to a code synchronization process. The code sync circuit 26 outputs the resultant information signal to an input terminal I1 of the selector 27. The selector 27 selects one from among the output information signal of the code sync circuit 24 and the output information signal of the code sync circuit 26 in response to the detection signals "a" and "b". Specifically, as will be made clear later, this signal selection depends on a combination of the level states (the logic level states) of the detection signals "a" and "b". The selector 27 feeds the selection-resultant information signal to the encoding circuit 28 via its output terminal O. The encoding circuit 28 encodes the information signal into an electric signal corresponding to a result of modulating a carrier with the information signal. The encoding circuit 28 outputs the electric signal to the driver circuit 29. The driver circuit 29 converts the output electric signal of the encoding circuit 28 into an electric drive signal for the light emitting diode 30. The driver circuit 29 outputs the electric drive signal to the light emitting diode 30. The light emitting diode 30 converts the output electric signal of the driver circuit 29 into a corresponding optical signal. The light emitting diode 30 transmits the optical signal toward the terminal devices 13a and 13b (see FIG. 1). The optical signal radiated from the light emitting diode 30 uses, for example, infrared light or visible light. It should be noted that the optical signal may be replaced by a radio wave signal. In the case where the photodiode 21 currently receives an optical signal but the LAN interface 25 does not currently receive any information signal from the hub device 11a (see FIG. 1), the detection signals "a" and "b" are in the high level state and the low level state respectively. In this case, the selector 27 selects the output information signal of the code sync circuit 24 in response to the detection signals "a" and "b" being in the high level state and the low level state respectively. The output information signal of the code sync circuit 24 originates from the output electric signal of the photodiode 21 or the optical signal received by the photodiode 21. The output information signal of the code sync circuit 24 is thus transmitted via the selector 27 to the encoding circuit 28. The encoding circuit 28 encodes the information signal into an electric signal corresponding to a result of modulating a carrier with the information signal. The encoding circuit 28 outputs the electric signal to the driver circuit 29. The output electric signal of the encoding circuit 28 corresponds to the output electric signal of the photodiode 21 or the optical signal received by the photodiode 21. The driver circuit 29 converts the output electric signal of the encoding circuit 28 into an electric drive signal for the light emitting diode 30. The driver circuit 29 outputs the electric drive signal to the light emitting diode 30. The light emitting diode 30 converts the output electric signal of the driver circuit 29 into a corresponding optical signal. The light emitting diode 30 transmits the optical signal toward the terminal devices 13a and 13b (see FIG. 1). The optical signal transmitted from the light emitting diode 30 corresponds to the optical signal received by the photodiode 21. Accordingly, in this case, the repeater 12a implements a repeating process with respect to the optical signal received by the photodiode 21. In the case where the LAN interface 25 currently receives an information signal from the hub device 11a (see FIG. 1) but the photodiode 21 does not currently receives any optical signal, the detection signals "a" and "b" are in the low level state and the high level state respectively. In this case, the selector 27 selects the output information signal of the code sync circuit 26 in response to the detection signals "a" and "b" being in the low level state and the high level state respectively. The output information signal of the code sync circuit 26 originates from the output information signal of the hub device 11a (see FIG. 1). The output information signal of the code sync circuit 26 is thus transmitted via the selector 27 to the encoding circuit 28. The encoding circuit 28 encodes the information signal into an electric signal corresponding to a result of modulating a carrier with the information signal. The encoding circuit 28 outputs the electric signal to the driver circuit 29. The driver circuit 29 converts the output electric signal of the encoding circuit 28 into an electric drive signal for the light emitting diode 30. The driver circuit 29 outputs the electric drive signal to the light emitting diode 30. The light emitting diode 30 converts the output electric signal of the driver circuit 29 into a corresponding optical signal. The light emitting diode 30 transmits the optical signal toward the terminal devices 13a and 13b (see FIG. 1). Accordingly, in this case, the repeater 12a transmits the output information signal of the hub device 11a (see FIG. 1) as an optical signal. In the case where the photodiode 21 currently receives an optical signal and also the LAN interface 25 currently receives an information signal from the hub device 11a (see FIG. 1), both the detection signals "a" and "b" are in the high level states. In this case, the selector 27 selects the output information signal of the code sync circuit 26 in response to the detection signals "a" and "b" being in the high level states. The output information signal of the code sync circuit 26 originates from the output information signal of the hub device 11a (see FIG. 1). The output information signal of the code sync circuit 26 is thus transmitted via the selector 27 to the encoding circuit 28. The encoding circuit 28 encodes the information signal into an electric signal corresponding to a result of modulating a carrier with the information signal. The encoding circuit 28 outputs the electric signal to the driver circuit 29. The driver circuit 29 converts the output electric signal of the encoding circuit 28 into an electric drive signal for the light emitting diode 30. The driver circuit 29 outputs the electric drive signal to the light emitting diode 30. The light emitting diode 30 converts the output electric signal of the driver circuit 29, into a corresponding optical signal. The light emitting diode 30 transmits the optical signal toward the terminal devices 13a and 13b (see FIG. 1). Accordingly, in this case, the repeater 12a transmits the output information signal of the hub device 11a (see FIG. 1) as an optical signal. At the same time, the output information signal of the code sync circuit 24 is fed to both the selector 27 and the LAN interface 25. The output information signal of the code sync circuit 24 is rejected by the selector 27. The output information signal of the code sync circuit 24 originates from the output electric signal of the photodiode 21 or the optical signal received by the photodiode 21. Accordingly, in this case, the repeater 12a fails to implement a repeating process with respect to the optical signal received by the photodiode 21. FIG. 3 shows an example of a related part of the selector 27. The selector 27 in FIG. 3 includes a switch 27A having a movable contact 27B and two fixed contacts 27C and 27D. The movable contact 27B of the switch 27 selectively touches either the fixed contact 27C or the fixed contact 27D thereof. The fixed contact 27C of the switch 27A receives the output information signal of the code sync circuit 26 via the selector input terminal I1. The fixed contact 27D of the switch 27A receives the output information signal of the code sync circuit 24 via the selector input terminal 12. The movable contact 27B of the switch 27A leads to the encoding circuit 28 via the selector output terminal O. The switch 27A has a control terminal which receives the detection signal "b" from the LAN interface 25 via the selector selection terminal S1. The selector selection terminal S2 which receives the detection signal "a" from the carrier sensing circuit 43 has no connection. When the detection signal "b" assumes the low level state, the switch 27A touches the fixed contact 27D and thus selects the output information signal of the code sync circuit 24. When the detection signal "b" assumes the high level state, the switch 27A touches the fixed contact 27C and thus selects the output information signal of the code sync circuit 26 regardless of the state of the detection signal "a". The terminal devices 13a, 13b, and 13c are similar in structure. Therefore, only the structure of the terminal device 13a will be explained hereinafter. As shown in FIG. 4, the terminal device 13a includes a photodiode (or a photodiode array) 31, an amplifier 32, a decoding circuit 33, a code sync circuit 34, a selector 35, a LAN interface 36, a frame sync circuit 37, a comparator 38, a code sync circuit 39, an encoding circuit 40, a driver circuit 41, and a light emitting diode (or a light emitting diode array) 42. The photodiode 31 is successively followed by the amplifier 32, the decoding circuit 33, and the code sync circuit 34. The output terminal of the code sync circuit 34 is connected to the selector 35, the frame sync circuit 37, and the comparator 38. The selector 35 is connected to the LAN interface 36. The output terminal of the frame sync circuit 37 is connected to the comparator 38. The output terminal of the comparator 38 is connected to the selector 35. The LAN interface 36 is connected to the wire which leads to the hub device 11b (see FIG. 1). The LAN interface 36 is connected to the input terminal of the code sync circuit 39. The output terminal of the code sync circuit 39 is connected to the selector 35 and the frame sync circuit 37. In addition, the code sync circuit 39 is successively followed by the encoding circuit 40, the driver circuit 41, and the light emitting diode 42. The photodiode 31 receives an optical signal from the repeater 12a (see FIG. 1), and converts the optical signal into a corresponding electric signal. The photodiode 31 outputs the electric signal to the amplifier 32. The amplifier 32 enlarges the output signal of the photodiode 31. The amplifier 32 outputs the enlargement-resultant signal to the decoding circuit 33. The optical signal handled by the photodiode 31 uses, for example, infrared light or visible light. It should be noted that the optical signal may be replaced by a radio wave signal. The decoding circuit 33 decodes the output signal of the amplifier 32 into an information signal (data). In other words, the decoding circuit 33 recovers an information signal (data) from the output signal of the amplifier 32. The decoding circuit 33 outputs the information signal to the code sync circuit 34. The code sync circuit 34 subjects the information signal to a code synchronization process. The code sync circuit 34 outputs the resultant information signal to an input terminal 12 of the selector 35, a first input terminal of the frame sync circuit 37, and a first input terminal of the comparator 38. When predetermined conditions are satisfied, the selector 35 transmits the output information signal of the code sync circuit 34 to the LAN interface 36. The LAN interface 36 can transmit the output information signal of the code sync circuit 34 to the hub device 11b (see FIG. 1) via the wire. The LAN interface 36 can receive an information signal (data) from the hub device 11b (see FIG. 1) via the wire. The LAN interface 36 includes a known signal sensing section. The signal sensing section in the LAN interface 36 detects whether or not the LAN interface 36 currently receives an information signal from the hub device 11b (see FIG. 1). The signal sensing section in the LAN interface 36 generates a detection signal "c" representing whether or not the LAN interface 36 currently receives an information signal from the hub device 11b (see FIG. 1). Specifically, the detection signal "c" being in a high level state indicates that the LAN interface 36 currently receives an information signal from the hub device 11b (see FIG. 1). The detection signal "c" being in a low level state indicates that the LAN interface 36 does not currently receive any information signal from the hub device 11b (see FIG. 1). The LAN interface 36 outputs the detection signal "c" to a selection terminal S2 of the selector 35. The LAN interface 36 feeds the output information signal of the hub device 11b (see FIG. 1) to the code sync circuit 39. The code sync circuit 39 subjects the information signal to a code synchronization process. The code sync circuit 39 outputs the resultant information signal to an input terminal I1 of the selector 35. Also, the code sync circuit 39 outputs the resultant information signal to a second input terminal of the frame sync circuit 37. Furthermore, the code sync circuit 39 outputs the resultant information signal to the encoding circuit 40. The frame sync circuit 37 delays the output information signal of the code sync circuit 39 in response to the output information signal of the code sync circuit 34 to provide frame synchronization. In other words, the frame sync circuit 37 delays the output information signal of the code sync circuit 39 into an information signal frame-synchronized with the output information signal of the code sync circuit 34. The frame sync circuit 37 outputs the delay-resultant information signal to a second input terminal of the comparator 38. The comparator 38 decides whether or not the output information signal of the frame sync circuit 37 and the output information signal of the code sync circuit 34 are equal to each other. When the output information signal of the frame sync circuit 37 and the output information signal of the code sync circuit 34 are equal to each other, the comparator 38 outputs a high-level detection signal "d" to a selection terminal S1 of the selector 35 as an equality-indicating signal. Otherwise, the comparator 38 outputs a low-level detection signal "d" to the selection terminal S1 of the selector 35 as an inequality-indicating signal. The selector 35 can select one from among the output information signal of the code sync circuit 34 and the output information signal of the code sync circuit 39 in response to the detection signals "c" and "d". Specifically, as will be made clear later, this signal selection depends on a combination of the level states (the logic level states) of the detection signals "c" and "d". In addition, the selector 35 can select neither the output information signal of the code sync circuit 34 nor the output information signal of the code sync circuit 39 when the detection signals "c" and "d" assume predetermined states respectively. The selector 35 feeds the selection-resultant information signal to the LAN interface 36 via its output terminal O. The LAN interface 36 transmits the output information signal of the selector 35 to the hub device 11b (see FIG. 1) via the wire. As previously described, the code sync circuit 39 outputs the information signal to the encoding circuit 40. The encoding circuit 40 encodes the information signal into an electric signal corresponding to a result of modulating a carrier with the information signal. The encoding circuit 40 outputs the electric signal to the driver circuit 41. The driver circuit 41 converts the output electric signal of the encoding circuit 40 into an electric drive signal for the light emitting diode 42. The driver circuit 41 outputs the electric drive signal to the light emitting diode 42. The light emitting diode 42 converts the output electric signal of the driver circuit 41 into a corresponding optical signal. The light emitting diode 42 transmits the optical signal toward the repeater 12a (see FIG. 1). The optical signal radiated from the light emitting diode 42 uses, for example, infrared light or visible light. It should be noted that the optical signal may be replaced by a radio wave signal. It is now assumed that the photodiode 31 currently receives an optical signal but the LAN interface 36 does not currently receive any information signal from the hub device 11b (see FIG. 1). In this case, the detection signal "c" is in the low level state. The selector 35 selects the output information signal of the code sync circuit 34 in response to the detection signal "c" being in the low level state regardless of the state of the detection signal "d". The output information signal of the code sync circuit 34 originates from the output electric signal of the photodiode 31 or the optical signal received by the photodiode 31. The selector 35 feeds the selection-resultant information signal to the LAN interface 36. The LAN interface 36 transmits the output information signal of the selector 35 to the hub device 11b (see FIG. 1) via the wire. Accordingly, in this case, the terminal device 13a extracts information from the optical signal received by the photodiode 31, and transmits the extracted information to the hub device 11b (see FIG. 1) via the wire. It is now assumed that the photodiode 31 currently receives an optical signal and also the LAN interface 36 currently receive an information signal from the hub device 11b (see FIG. 1). In this case, the detection signal "c" is in the high level state. The LAN interface 36 transmits the output information signal of the hub device 11b (see FIG. 1) to the code sync circuit 39. The output information signal of the hub device 11b (see FIG. 1) undergoes the code synchronization process in the code sync circuit 39. The resultant information signal is fed from the code sync circuit 39 to the selector 35, the frame sync circuit 37, and the encoding circuit 40. The encoding circuit 40 encodes the information signal into an electric signal corresponding to a result of modulating a carrier with the information signal. The encoding circuit 40 outputs the electric signal to the driver circuit 41. The driver circuit 41 converts the output electric signal of the encoding circuit 40 into an electric drive signal for the light emitting diode 42. The driver circuit 41 outputs the electric drive signal to the light emitting diode 42. The light emitting diode 42 converts the output electric signal of the driver circuit 41 into a corresponding optical signal. The light emitting diode 42 transmits the optical signal toward the repeater 12a (see FIG. 1). Accordingly, in this case, the terminal device 13a transmits the output information signal of the hub device 11b (see FIG. 1) as an optical signal. On the other hand, the photodiode 31 converts the received optical signal into a corresponding electric signal. The photodiode 31 outputs the electric signal to the amplifier 32. The amplifier 32 enlarges the output signal of the photodiode 31. The amplifier 32 outputs the enlargement-resultant signal to the decoding circuit 33. The decoding circuit 33 decodes the output signal of the amplifier 32 into an information signal (data). The decoding circuit 33 outputs the information signal to the code sync circuit 34. The code sync circuit 34 subjects the information signal to a code synchronization process. The code sync circuit 34 outputs the resultant information signal to the selector 35, the frame sync circuit 37, and the comparator 38. As previously explained, the output information signal of the code sync circuit 39 is fed to the frame sync circuit 37. The frame sync circuit 37 delays the output information signal of the code sync circuit 39 into an information signal frame-synchronized with the output information signal of the code sync circuit 34. The frame sync circuit 37 outputs the delay-resultant information signal to the comparator 38. When the output information signal of the frame sync circuit 37 and the output information signal of the code sync circuit 34 are equal to each other, the comparator 38 outputs a high-level detection signal "d" to the selector 35 as an equality-indicating signal. Otherwise, the comparator 38 outputs a low-level detection signal "d" to the selector 35 as an inequality-indicating signal. When the optical signal transmitted by the terminal device 13a is normally returned thereto from the repeater 12a, the output information signal of the frame sync circuit 37 and the output information signal of the code sync circuit 34 are equal to each other so that the detection signal "d" is in the high level state. The selector 35 selects neither the output information signal of the code sync circuit 34 nor the output information signal of the code sync circuit 39 in response to the detection signals "c" and "d" both being in the high level states. As a result, the selector 35 does not output any effective signal to the LAN interface 36, and the LAN interface 36 does not transmit any effective signal to the hub device 11b (see FIG. 1). On the other hand, when the optical signal transmitted by the terminal device 13a is not returned thereto from the repeater 12a since the repeater 12a transmits another optical signal which originates from the output information signal of the hub device 11a (see FIG. 1) or which corresponds to the output optical signal of the terminal device 13b, the output information signal of the frame sync circuit 37 and the output information signal of the code sync circuit 34 are different from each other so that the detection signal "d" is in the low level state. The selector 35 selects the output information signal of the code sync circuit 39 in response to the detection signals "c" and "d" being in the high level state and the low level state respectively. As a result, the selector 35 transmits the output information signal of the code sync circuit 39 to the LAN interface 36. The LAN interface 36 transmits the output information signal of the selector 35 to the hub device 11b (see FIG. 1) via the wire. Since the output information signal of the code sync circuit 39 is equal to the output information signal of the hub device 11b (see FIG. 1), the output information signal of the hub device 11b (see FIG. 1) is returned thereto from the terminal device 13a. The signal return is used as an indication of occupancy of the repeater 12a or signal collisions on the related wireless communication channel. Another signal generated in the terminal device 13a may be transmitted to the hub device 11b (see FIG. 1) instead of the output information signal of the code sync circuit 39. It is preferable that the LAN interface 36 or the hub device 11b (see FIG. 1) takes a suitable step of interrupting the transmission of the output information signal of the hub device 11b as the optical signal in response to the information of signal collision. In the case where the terminal devices 13a and 13b simultaneously transmit different optical signals to the repeater 12a respectively, the repeater 12a returns a combination of the optical signals to the terminal devices 13a and 13b. In this case, the optical signal received by the terminal device 13a is different from the optical signal transmitted thereby. Also, the optical signal received by the terminal device 13b is different from the optical signal transmitted thereby. Accordingly, the terminal device 13a informs the hub device 11b of occupancy of the repeater 12a or signal collision on the related wireless communication channel. Also, the terminal device 13b informs the terminal device 14b of occupancy of the repeater 12a or signal collisions on the related wireless communication channel. FIG. 5 shows an example of a related part of the selector 35. The selector 35 in FIG. 3 includes switches 35A and 35E, and an AND gate 35F. The switch 35A has a movable contact 35B and two fixed contacts 35C and 35D. The movable contact 35B of the switch 35A selectively touches either the fixed contact 35C or the fixed contact 35D thereof. The fixed contact 35C of the switch 35A receives the output information signal of the code sync circuit 39 via the selector input terminal I1. The fixed contact 35D of the switch 35A receives the output information signal of the code sync circuit 34 via the selector input terminal I2. The movable contact 35B of the switch 35A is connected via the switch 35E to the selector output terminal O which leads to the LAN interface 36. The switch 35A has a control terminal which receives the detection signal "c" from the LAN interface 36 via the selector selection terminal S2. When the detection signal "c" assumes the low level state, the switch 35A touches the fixed contact 35D and thus selects the output information signal of the code sync circuit 34. When the detection signal "c" assumes the high level state, the switch 35A touches the fixed contact 35C and thus selects the output information signal of the code sync circuit 39. The switch 35E can change between a closed state and an open state. A first input terminal of the AND gate 35F receives the detection signal "c" from the LAN interface 36 via the selector selection terminal S2. A second input terminal of the AND gate 35F receives the detection signal "d" from the comparator 38 via the selector selection terminal S1. The AND gate 35F executes AND operation between the detection signals "c" and "d". The switch 35E has a control terminal connected to the output terminal of the AND gate 35F. When an output signal of the AND gate 35F assumes the low level state, the switch 35E is closed. Accordingly, in this case, the information signal selected by the switch 35A is transmitted through the switch 35E to the LAN interface 36. When the output signal of the AND gate 35F assumes the high level state, the switch 35E is opened. Accordingly, in this case, any effective signal is not transmitted through the selector 35 to the LAN interface 36.

A wireless communication system includes a repeater and a terminal device. The terminal device is connected to the repeater via a wireless communication channel. The terminal device includes a first section for converting a first electric signal into a first wireless signal, and transmitting the first wireless signal toward the repeater along the wireless communication channel. The terminal device includes a second section for receiving a second wireless signal from the repeater via the wireless communication channel, and converting the second wireless signal into a second electric signal. The terminal device includes a third section for deciding whether or not the first electric signal and the second electric signal are equal to each other to detect whether or not a signal collision occurs on the wireless communication channel.

This application is a continuation of application Ser. No. 09/759,124 filed on Jan. 12, 2001 now U.S. Pat. No. 6,370,302, which is a divisional of application Ser. No. 09/350,024 filed on Jul. 9, 1999 now U.S. Pat. No. 6,366,720. FIELD OF THE INVENTION The present invention relates to integrated optical devices generally and more particularly to packaging of integrated optical devices. BACKGROUND OF THE INVENTION Various types of integrated optical devices are known. It is well known to pigtail an optical fiber onto an integrated optical device. Difficulties arise, however, when it is sought to pigtail multiple optical fibers onto integrated optical devices. When the optical modes in waveguides and optical fibers are similar, it is conventional to pigtail them by suitable alignment and butt coupling in an integrated optical device. When there exists a substantial disparity in the respective optical modes of the optical fibers and the waveguides, optical elements must be employed to enable successful pigtailing. Particularly when the optical modes are relatively small, very high alignment accuracy is required in the alignment of three elements, the waveguide, the optical element and the fiber. The following patents are believed to representative of the present state of the art: 5,737,138; 5,732,181; 5,732,173; 5,721,797; 5,712,940; 5,712,937; 5,703,973; 5,703,980; 5,708,741; 5,706,378; 5,611,014; 5,600,745; 5,600,741; 5,579,424; 5,570,442; 5,559,915; 5,907,649; 5,898,806; 5,892,857; 5,881,190; 5,875,274; 5,867,619; 5,859,945; 5,854,868; 5,854,867; 5,828,800; 5,793,914; 5,784,509; 5,835,659; 5,656,120; 5,482,585; 5,482,585; 5,625,726; 5,210,800; and 5,195,154. SUMMARY OF THE INVENTION The present invention seeks to provide a cost-effective and reliable integrated optics packaging technique and optical devices constructed thereby. There is thus provided in accordance with a preferred embodiment of the present invention an optical device including at least one first substrate defining a multiplicity of optical fiber positioning grooves, a multiplicity of optical fibers fixed in each of the multiplicity of optical fiber positioning grooves on the at least one first substrate, whereby the multiplicity of optical fibers lie in an optical fiber plane and the ends of each of the multiplicity of optical fibers lie substantially in a first predetermined arrangement in the optical fiber plane, a second substrate fixed onto the at least one first substrate such that an edge of the second substrate extends beyond the ends of each of the multiplicity of optical fibers, a lens assembly including a third substrate, and a lens fixed onto the third substrate, the lens assembly being mounted onto the second substrate such that the lens lies in a second predetermined arrangement with respect to the ends of each of the multiplicity of optical fibers, whereby the separation between the lens and the ends of each of the multiplicity of optical fibers is defined in a plane perpendicular to the optical fiber plane to a first degree of accuracy and the separation between the lens and the ends of each of the multiplicity of optical fibers is defined in the optical fiber plane to a second degree of accuracy, less than the first degree of accuracy. Further in accordance with a preferred embodiment of the present invention the at least one first substrate comprises a pair of first substrates having the optical fiber positioning grooves thereon arranged in mutually facing relationship. Still further in accordance with a preferred embodiment of the present invention the lens comprises a cylindrical lens which extends along a cylindrical lens axis. Preferably the cylindrical lens axis lies parallel to the optical fiber plane. Additionally in accordance with a preferred embodiment of the present invention the third substrate is fixed in engagement with the edge of the second substrate by an adhesive. Preferably the third substrate is fixed in engagement with the edge of the second substrate by an adhesive. Additionally in accordance with a preferred embodiment of the present invention the multiplicity of optical fiber positioning grooves are mutually parallel. Preferably the multiplicity of optical fiber positioning grooves are arranged in a fan arrangement in order to compensate for optical aberrations. There is also provided. in accordance with a preferred embodiment of the present invention a method for producing an optical device including the steps of forming a multiplicity of optical fiber positioning grooves on at least one first substrate, placing each of a multiplicity of optical fibers in each of the multiplicity of optical fiber positioning grooves on the at least one first substrate, retaining each of the multiplicity of optical fibers in each of the multiplicity of optical fiber positioning grooves on the at least one first substrate, such that the multiplicity of optical fibers lie in an optical fiber plane, precisely defining the ends of each of the multiplicity of optical fibers so that they all lie substantially in a first predetermined arrangement, fixing a second substrate onto the at least one first substrate such that an edge of the second substrate extends beyond the ends of each of the multiplicity of optical fibers, fixing a lens onto a third substrate, precisely aligning the third substrate in engagement with the edge of the second substrate such that the lens lies in a second predetermined arrangement with respect to the ends of each of the multiplicity of optical fibers, and fixing the third substrate in engagement with said edge of the second substrate such that the lens lies in a second predetermined arrangement with respect to the ends of each of the multiplicity of optical fibers, whereby the separation between the lens and the ends of each of the multiplicity of optical fibers is defined in a plane perpendicular to the optical fiber plane to a first degree of accuracy and the separation between the lens and the ends of each of the multiplicity of optical fibers is defined in the optical fiber plane to a second degree of accuracy, less than the first degree of accuracy. Preferably the step of fixing the third substrate in engagement with the edge employs an adhesive and the step of precisely aligning the third substrate in engagement with the edge of the second substrate employs an external positioner. Further in accordance with a preferred embodiment of the present invention the at least one first substrate includes a pair of first substrates having the optical fiber positioning grooves thereon arranged in mutually facing relationship. Additionally or alternatively the lens includes a cylindrical lens which extends along a cylindrical lens axis. Preferably the precisely aligning step and the fixing step arrange the cylindrical lens such that the cylindrical lens axis lies parallel to the optical fiber plane. Preferably the multiplicity of optical fiber positioning grooves are mutually parallel. Alternatively accordance with a preferred embodiment of the present invention the multiplicity of optical fiber positioning grooves are arranged in a fan arrangement in order to compensate for optical aberrations. There is further provided in accordance with a preferred embodiment of the present invention an optical device including at least one optical substrate having formed thereon at least one waveguide, at least one base substrate onto which the at least one optical substrate is fixed, and at least one optical module, precisely positioned onto each at least one base substrate and fixed thereto by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one module and the at least one waveguide. Further in accordance with a preferred embodiment of the present invention the at least one optical module includes a lens or includes a cylindrical lens, and at least one optical fiber. Preferably the at least one optical module also includes a lens which is operative to couple light from the at least one fiber to the at least one waveguide and also including the step of positioning output optics including at least one output fiber on the at least one base substrate so as to receive light from the at least one waveguide. Additionally or alternatively the lens is operative to couple light from a first number of fibers to a greater number of waveguides. Additionally in accordance with a preferred embodiment of the present invention the at least one waveguide includes stacking a plurality of base substrates each having mounted thereon at least one optical substrate having formed thereon at least one waveguide and wherein the step of positioning the output optics includes arranging at least one lens to receive light from waveguides formed on multiple ones of the plurality of optical substrates. Preferably the step of positioning the output optics includes employing side mounting blocks thereby to preserve precise mutual alignment of said at least one lens and the at least one waveguide. Still further in accordance with a preferred embodiment of the present invention the step of positioning output optics includes employing side mounting blocks thereby to preserve precise mutual alignment of said at least one lens and said at least one waveguide, and the at least one waveguide includes a multiplicity of waveguides. The step of positioning the output optics includes positioning at least one lens so as to receive light from multiple ones of the multiplicity of waveguides. Still further in accordance with a preferred embodiment of the present invention the lens is operative to couple light from a first number of fibers to an identical number of waveguides. Preferably the first number of waveguides comprises at least one waveguide. Still further in accordance with a preferred embodiment of the present invention the at least one optical substrate is a light deflector. Additionally in accordance with a preferred embodiment of the present invention, the optical device includes output optics receiving light from the at least one waveguide and including at least one output fiber. Additionally or alternatively the output optics includes at least one lens fixed onto the base substrate by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one lens and the at least one waveguide. The at least one optical substrate may be a light deflector and preferably the at least one optical substrate is formed of gallium arsenide. Still further in accordance with a preferred embodiment of the present invention the at least one waveguide includes a multiplicity of waveguides and wherein the output optics includes at least one lens receiving light from multiple ones of the multiplicity of waveguides. Additionally or alternatively the output optics includes at least one lens receiving light from waveguides formed on multiple ones of the plurality of optical substrates. Furthermore the at least one optical substrate may be a light deflector. The output optics may also include at least one lens fixed onto the base substrate by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one lens and the at least one waveguide. Additionally or preferably the at least one optical substrate is formed of gallium arsenide. Still further in accordance with a preferred embodiment of the present invention the optical module includes at least one first substrate defining a multiplicity of optical fiber positioning grooves, a multiplicity of optical fibers fixed in each of the multiplicity of optical fiber positioning grooves on the at least one first substrate, whereby the multiplicity of optical fibers lie in an optical fiber plane. The ends of each of the multiplicity of optical fibers may lie substantially in a first predetermined arrangement in the optical fiber plane. A second substrate is preferably fixed on at least one first substrate such that an edge of the second substrate extends beyond the ends of each of the multiplicity of optical fibers, a lens assembly including a third substrate, and a lens fixed onto the third substrate, the lens assembly being mounted onto the second substrate such that the lens lies in a second predetermined arrangement with respect to the ends of each of the multiplicity of optical fibers. The separation between the lens and the ends of each of the multiplicity of optical fibers may be defined in a plane perpendicular to the optical fiber plane to a first degree of accuracy and the separation between the lens and the ends of each of the multiplicity of optical fibers may be defined in the optical fiber plane to a second degree of accuracy, less than the first degree of accuracy. Further in accordance with a preferred embodiment of the present invention the lens includes a cylindrical lens. Additionally in accordance with a preferred embodiment of the present invention also including output optics receiving light from the at least one waveguide and including at least one output fiber. Additionally or alternatively the output optics includes at least one lens fixed onto the base substrate by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one lens and the at least one waveguide. Preferably the at least one optical substrate is a light deflector and the at least one optical substrate is formed of gallium arsenide. Further in accordance with a preferred embodiment of the present invention the at least one waveguide includes a multiplicity of waveguides and wherein the output optics includes at least one lens receiving light from multiple ones of the multiplicity of waveguides. Additionally or alternatively the multiplicity of waveguides is formed on a plurality of optical substrates and the output optics includes at least one lens receiving light from waveguides formed on multiple ones of the plurality of optical substrates. Preferably the at least one optical substrate is a light deflector and the output optics includes at least one lens fixed onto the base substrate by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one lens and the at least one waveguide. The at least one optical substrate may be formed of gallium arsenide. There is also provided in accordance with a preferred embodiment of the present invention an optical device including at least one optical substrate having formed thereon at least one waveguide having a center which lies in a waveguide plane, a base substrate onto which the at least one optical substrate is fixed and defining at least one optical fiber positioning groove, and at least one optical fiber fixed in the at least one optical fiber positioning groove on the base substrate, whereby a center of the at least one optical fiber lies in a plane which is substantially coplanar with the waveguide plane. Preferably electrical connections are mounted on the base substrate. Additionally the at least one optical module is precisely positioned onto the base substrate and fixed thereto by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one module and the at least one waveguide. Additionally or alternatively the at least one optical substrate is a light deflector. There is further provided in accordance with a preferred embodiment of the present invention a method for producing an optical device including the steps of forming at least one waveguide onto at least one optical substrate, mounting the at least one optical substrate onto at least one base substrate, and precisely positioning at least one-optical module onto the base substrate, including employing side mounting blocks thereby to preserve precise mutual alignment of the at least one module and the at least one waveguide. Additionally or alternatively the at least one optical module comprises a lens which is preferably a cylindrical lens. Further in accordance with a preferred embodiment of the present invention the at least one optical module includes at least one optical fiber. Additionally or alternatively the at least one optical module also includes a lens which is operative to couple light from the at least one fiber to the at least one waveguide. Preferably the lens is operative to couple light from a first number of fibers to a greater number of waveguides. Alternatively the lens is operative to couple light from a first number of fibers to an identical number of waveguides. Additionally in accordance with a preferred embodiment of the present invention the first number of waveguides includes at least one waveguide. Still further in accordance with a preferred the at least one optical substrate is a light deflector. Additionally in accordance with a preferred embodiment of the present invention, the method for producing an optical device also includes the steps of providing output optics receiving light from the at least one waveguide and including at least one output fiber. Furthermore, the output optics may include at least one lens fixed onto the base substrate by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one lens and the at least one waveguide. Additionally or alternatively the at least one optical substrate is a light deflector. Preferably the at least one optical substrate is formed of gallium arsenide. Still further in accordance with a preferred embodiment of the present invention the at least one waveguide includes a multiplicity of waveguides and wherein the output optics includes at least one lens receiving light from multiple ones of the multiplicity of waveguides. Further in accordance with a preferred embodiment of the present invention the at least one waveguide includes a multiplicity of waveguides formed on a plurality of optical substrates and wherein the output optics includes at least one lens receiving light from waveguides formed on multiple ones of the plurality of optical substrates. Additionally or alternatively the at least one optical substrate is a light deflector. Preferably the output optics includes at least one lens fixed onto the base substrate by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one lens and the at least one waveguide. Preferably the at least one optical substrate is formed of gallium arsenide. Still further in accordance with a preferred embodiment of the present invention the optical module includes at least one first substrate defining a multiplicity of optical fiber positioning grooves, a multiplicity of optical fibers fixed in each of the multiplicity of optical fiber positioning grooves on the at least one first substrate, whereby the multiplicity of optical fibers lie in an optical fiber plane and the ends of each of the multiplicity of optical fibers lie substantially in a first predetermined arrangement in the optical fiber plane, a second substrate fixed onto the at least one first substrate such that an edge of the second substrate extends beyond the ends of each of the multiplicity of optical fibers, a lens assembly including a third substrate, and a lens fixed onto the third substrate, the lens assembly being mounted onto the second substrate such that the lens lies in a second predetermined arrangement with respect to the ends of each of the multiplicity of optical fibers, whereby the separation between the lens and the ends of each of the multiplicity of optical fibers is defined in a plane perpendicular to the optical fiber plane to a first degree of accuracy and the separation between the lens and the ends of each of the multiplicity of optical fibers is defined in the optical fiber plane to a second degree of accuracy, less than the first degree of accuracy. Additionally or alternatively the lens includes a cylindrical lens. Preferably the at least one optical substrate is a light deflector. Additionally in accordance with a preferred embodiment of the present invention and also including providing output optics receiving light from said at least one waveguide and including at least one output fiber. Additionally or alternatively the output optics includes at least one lens fixed onto the base substrate by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one lens and the at least one waveguide. The at least one optical substrate may be a light deflector and preferably the at least one optical substrate is formed of gallium arsenide. Still further according to a preferred embodiment of the present invention the at least one waveguide includes a multiplicity of waveguides and wherein the output optics includes at least one lens receiving light from multiple ones of the multiplicity of waveguides. Further in accordance with a preferred embodiment of the present invention the at least one waveguide includes a multiplicity of waveguides formed on a plurality of optical substrates and wherein the output optics includes at least one lens receiving light from waveguides formed on multiple ones of the plurality of optical substrates. Preferably the at least one optical substrate is a light deflector. Additionally in accordance with a preferred embodiment of the present invention the output optics includes at least one lens fixed onto the base substrate by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one lens and the at least one waveguide. Preferably the at least one optical substrate is formed of gallium arsenide. There is also provided in accordance with yet another preferred embodiment of the present invention a method including forming on at least one optical substrate at least one waveguide having a center which lies in a waveguide plane, fixing the at least one optical substrate onto a base substrate and defining on the base substrate at least one optical fiber positioning groove, and fixing at least one optical fiber in the at least one optical fiber positioning groove on the base substrate, whereby a center of the at least one optical fiber lies in a plane which is substantially coplanar with the waveguide plane. Preferably electrical connections are mounted on the base substrate. Additionally the at least one optical module is precisely positioned onto the base substrate and fixed thereto by means of side mounting blocks thereby to preserve precise mutual alignment of the at least one module and the at least one waveguide. Still further in accordance with a preferred embodiment of the present invention the at least one optical substrate is a light deflector. Preferably also including mounting electrical connections on said base substrate. There is further provided in accordance with another preferred embodiment of the present invention a method for producing an optical device including the steps of lithographically forming a multiplicity of waveguides onto an optical substrate, mounting the optical substrate onto a base substrate, and precisely positioning a fiber optic module, having a multiplicity of optical fiber ends and an optical mode modifying lens, onto the base substrate, including using at least one external positioner, manipulating at least one of the fiber optic module and the base substrate relative to the other such that the mode of each optical fiber matches the mode of at least one corresponding waveguide with relatively low light loss, and fixing the fiber optic module in a desired relative position on the base substrate independently of the external positioner, and disengaging the at least one external positioner from the modulated light source. Further in accordance with a preferred embodiment of the present invention the step of fixing includes employing side mounting blocks to fix the module in position on the base substrate upon precise-mutual alignment of the module and the multiplicity of waveguides. Still further in accordance with a preferred embodiment of the present invention also including the step of producing a fiber optic module which includes the steps of forming a multiplicity of optical fiber positioning grooves on at least one first substrate, placing each of a multiplicity of optical fibers in each of the multiplicity of optical fiber positioning grooves on the at least one first substrate, retaining each of the multiplicity of optical fibers in each of the multiplicity of optical fiber positioning grooves on the at least one first substrate, such that the multiplicity of optical fibers lie in an optical fiber plane, precisely defining the ends of each of the multiplicity of optical fibers so that they all lie substantially in a first predetermined arrangement, fixing a second substrate onto the first substrate such that an edge of the second substrate extends beyond the ends of each of the multiplicity of optical fibers, fixing a lens onto a third substrate, precisely aligning the third substrate in engagement with the edge of the second substrate such that the lens lies in a second predetermined arrangement with respect to the ends of each of the multiplicity of optical fibers, and fixing the third substrate in engagement with the edge of the second substrate such that the lens lies in a second predetermined arrangement with respect to the ends of each of the multiplicity of optical fibers, whereby the separation between the lens and the ends of each of the multiplicity of optical fibers is defined in a plane perpendicular to the optical fiber plane to a first degree of accuracy and the separation between the lens and the ends of each of the multiplicity of optical fibers is defined in the optical fiber plane to a second degree of accuracy, less than the first degree of accuracy. Preferably the optical substrate is gallium arsenide and the optical device functions as a switch. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: FIGS. 1A-1I are simplified pictorial illustrations of a method for producing an optical fiber module in accordance with a preferred embodiment of the present invention; FIGS. 2A-2C are simplified pictorial illustrations of three alternative embodiments of a method for mounting an active integrated optics waveguide assembly onto a base substrate which are useful in the present invention; FIGS. 3A-3F are simplified pictorial illustrations of a method for producing an optical device using an optical fiber module and an integrated optics waveguide assembly in accordance with a preferred embodiment of the present invention corresponding to FIGS. 2A and 2B; FIGS. 4A-4F are simplified pictorial illustrations of a method for producing an optical device using an optical fiber module and an integrated optics waveguide assembly in accordance with another preferred embodiment of the present invention corresponding to the embodiment of FIG. 2C; FIGS. 5A-5F are simplified pictorial illustrations of a method for producing an optical device using an optical fiber module and an integrated optics waveguide assembly in accordance with yet another preferred embodiment of the present invention corresponding to the embodiment of FIG. 2C; FIGS. 6A-6E are simplified pictorial illustrations of a method for associating output optics with the optical device of FIG. 3F in accordance with a preferred embodiment of the present invention; FIGS. 7A-7D are simplified pictorial illustrations of a method for constructing an integrated optics optical fiber switch using a plurality of base substrates bearing integrated optics waveguide assemblies and optical fiber modules as shown in FIG. 3F; FIGS. 8A-8D are simplified pictorial illustrations of a method for associating output optics with the optical device of FIG. 4F in accordance with a preferred embodiment of the present invention; FIGS. 9A-9D are simplified pictorial illustrations of a method for constructing an integrated optics optical fiber switch using a plurality of base substrates bearing integrated optics waveguide assemblies and optical fiber modules as shown in FIG. 4 F. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Reference is now made to FIGS. 1A-1I, which are simplified pictorial illustrations of a method for producing an optical fiber module in accordance with a preferred embodiment of the present invention. The method preferably begins with the provision of a V-grooved substrate, such as substrate 10 in FIG. 1A or substrate 12 in FIG. 1 B. The substrate is typically silicon, but may alternatively be silica, glass or any other suitable material. The V-grooves may be parallel as shown in FIG. 1A at reference numeral 14 or non-parallel as shown in FIG. 1B at reference numeral 16 . The description that follows refers to a parallel orientation, it being understood that a non-parallel orientation may be employed instead. Preferably, the V-grooves are formed by lithography or by grinding. The accuracy of the dimensions of the V-grooves is preferably to a fraction of a micron, such that when optical fibers 20 are secured in the V-grooves 22 formed in a substrate 24 , as shown in FIG. 1C, their relative alignment is within one-half micron in two dimensions. Following placement of the optical fibers 20 in V-grooves 22 , as shown in FIG. 1C, the fibers are secured in position by a cover element 26 , as shown in FIG. 1 D. The cover element 26 may be identical to the V-grooved substrate 24 in an upside down orientation. It is appreciated that the ends of the optical fibers 20 may all be suitably aligned at the time of their placement in the V-grooves. Preferably, however, this alignment is not required and following placement of the fibers and securing thereof in the V-grooves 22 , the fiber ends are cut and polished together with substrate 24 and cover element 26 such that the fiber ends lie in the same plane as the edge of the substrate 24 and cover 26 . In FIG. 1D, this plane is indicated by reference numeral 28 . Preferably, suitable adhesive is employed both at the stages shown in FIGS. 1C and 1D to retain the fibers in place and subsequently to hold the cover element 26 onto substrate 24 in secure engagement with fibers 20 . As seen in FIG. 1E, a sheet of glass 30 or any other suitable substrate, which is preferably transparent for ease of alignment, is aligned with cover element 26 such that at least one edge 32 thereof lies in highly accurate parallel alignment with plane 28 , and separately therefrom by a precisely determined distance. The substrate 30 is then fixed onto cover element 26 , as by means of a UV curable adhesive 27 and a UV light source 29 , as shown in FIG. 1 F. Referring now to FIG. 1G, a lens 40 , preferably a cylindrical lens, which is mounted onto a mounting substrate 42 , is aligned with respect to edge 32 of substrate 30 . This alignment is preferably provided to a high degree of accuracy, to the order of one-half micron, by means of a vacuum engagement assembly 44 connected to a suitable positioner, not shown, such as Melees Grist Nanoblock. This degree of accuracy is greater than that required in the parallelism and separation distance between edge 32 and plane 28 . As seen in FIG. 1H, the substrate 42 is then fixed onto edge 32 of substrate 30 , as by means of a UV curable adhesive 41 and the UV light source 29 . FIG. 1I illustrates the resulting optical relationship between the optical modes 50 of the fibers 20 , which are seen to be circular upstream of lens 40 and the optical modes 52 downstream of the lens 40 , which are seen to be highly elliptical. It is appreciated that it is a particular advantage of the present invention that the highly elliptical modes which are produced by lens 40 are very similar to whose in integrated optical waveguides, as is described in applicant's published PCT application WO 98/59276. Furthermore, the arrangement described hereinabove produces a mode from a single fiber which is sufficiently highly elliptical so that it may be coupled to a multiplicity of waveguides arranged side by side, as described in applicant's published PCT application WO 98/59276, the contents of which are hereby incorporated by reference. It is appreciated that in accordance with a preferred embodiment of the present invention, lens 40 may couple a single fiber to a single waveguide or to multiple waveguides. Reference is now made to FIGS. 2A-2C, which are simplified pictorial illustrations of three alternative embodiments of a method for mounting an active integrated optics waveguide assembly onto a base substrate which is useful in the present invention. FIG. 2A illustrates flip-chip type mounting of an integrated optics waveguide device 100 , such as a waveguide device described and claimed in applicant's published PCT application WO 98/59276, the disclosure of which is hereby incorporated by reference. Device 100 is preferably embodied in a flip-chip package, such as that described in FIG. 31 of applicant's published PCT application WO 98/59276. In this embodiment, device 100 is mounted onto an integrated electronic circuit 102 , such as an ASIC. FIG. 2B illustrates conventional wire bond type mounting of an integrated optics waveguide device 104 , such as a waveguide device described and claimed in applicant's published PCT application WO 98/59276, the disclosure of which is hereby incorporated by reference. Device 104 is preferably embodied in a wire bond package, such-as that described in FIG. 30 of applicant's published PCT application WO 98/59276. FIG. 2C illustrates conventional flip-chip type mounting of an integrated optics waveguide device 100 , such as a waveguide device described and claimed in applicant's published PCT application WO 98/59276, the disclosure of which is hereby incorporated by reference. Device 100 is preferably embodied in a flip-chip package, such as that described in FIG. 31 of applicant's published, PCT application WO 98/59276. The mountings of FIGS. 2A and 2B are both characterized in that the waveguides of the active integrated optics waveguide device are located in a plane which is spaced from the surface of a substrate by a distance of at least a few hundred microns. This may be contrasted from the mounting of FIG. 2C, wherein the waveguides of the active integrated optics waveguide device are located in a plane which is spaced from the surface of a substrate by a distance of less than one hundred microns. Reference is now made to FIGS. 3A-3F, which are simplified pictorial illustrations of a method for producing an optical device using an optical fiber module and an integrated optics waveguide assembly in accordance with a preferred embodiment of the present invention. The illustrations of FIGS. 3A-3F show a mounting of the type illustrated in FIGS. 2A & 2B. FIG. 3A shows a substrate 200 onto which is mounted an active integrated optics waveguide device 202 as well as various other integrated circuits 204 . As seen in FIG. 3B, an optical fiber module 206 , preferably of the type described hereinabove with reference to FIGS. 1A-1I, is brought into proximity with substrate 200 and active integrated optics waveguide device 202 , as by a vacuum engagement assembly 208 , connected to a suitable positioner (not shown), such as Melles Griot Nanoblock. As seen in FIG. 3C, the optical fiber module 206 is precisely positioned with respect to the active integrated optics waveguide device 202 with six degrees of freedom so as to achieve a high degree of accuracy in order to realize optimal optical coupling efficiency between the fibers in module 206 and the waveguides in device 202 . This degree of accuracy is greater than that required in the previously described alignment steps illustrated in FIGS. 1A-1I and preferably reaches one tenth of a micron. FIG. 3D illustrates precise mounting of the optical fiber module 206 with respect to the active integrated optics waveguide device 202 on substrate 200 . This precise mounting is preferably achieved by using the positioner (not shown) to manipulate the fiber optic module 206 relative to substrate 200 such that the mode of each optical fiber 209 in module 206 matches the mode of at least one corresponding waveguide of waveguide device 202 with relatively low light loss. The fiber optic module 206 is mounted in a desired relative position on the substrate 200 independently of the positioner by employing side mounting blocks 210 to fix the module 206 in position on substrate 200 upon precise mutual alignment of the module 206 and the waveguide device 202 . Preferably side mounting blocks 210 are carefully positioned alongside module 206 and are bonded thereto and to substrate 200 , preferably using a thin layer of UV curable adhesive 211 which does not involve significant shrinkage during curing, as by use of a UV light source 220 as shown in FIG. 3E, so that the relative position shown in FIG. 3D is preserved, as seen in FIG. 3 F. It is appreciated that in order to affix the mounting blocks 210 to the substrate 200 , a coating of the adhesive 211 is applied to the appropriate side surfaces and lower surfaces of the mounting blocks 210 . The use of side mounting blocks 210 enables accurate fixation with six degrees of freedom by virtue of the use of the thin layer of adhesive 211 , which does not involve significant shrinkage during curing, along two mutually orthogonal planes. Reference is now made to FIGS. 4A-4F, which are simplified pictorial illustrations of a method for producing an optical device using an optical fiber module and an integrated optics waveguide assembly in accordance with another preferred embodiment of the present invention corresponding to the embodiment of FIG. 2 C. As noted above, in the mounting arrangement of FIG. 2C, the waveguides of the active integrated optics waveguide device are located in a plane which is spaced from the surface of a substrate by a distance of less than one hundred microns. In order to accommodate this very small spacing a hole or a recess is formed in the substrate to receive the optical fiber module. FIG. 4A shows a substrate 300 onto which is mounted an active integrated optics waveguide device 302 as well as various other integrated circuits 304 . A hole or recess 305 is preferably formed in substrate 300 as shown. As seen in FIG. 4B, an optical fiber module 306 , preferably of the type described hereinabove with reference to FIGS. 1A-1I, is brought into proximity with substrate 300 and active integrated optics waveguide device 302 , as by a vacuum engagement assembly 308 , connected to a suitable positioner (not shown), such as Melles Griot Nanoblock. As seen in FIG. 4C, the optical fiber module 306 is precisely positioned with respect to the active integrated optics waveguide device 302 with six degrees of freedom so as to achieve a high degree of accuracy in order to realize optimal optical coupling efficiency between the fibers in module 306 and the waveguides in device 302 . This degree of accuracy is greater than that required in the previously described alignment steps illustrated in FIGS. 1A-1I and preferably reaches one tenth of a micron. FIG. 4D illustrates precise mounting of the optical fiber module 306 with respect to the active integrated optics waveguide device 302 on substrate 300 partially overlapping hole 305 , such that the cylindrical lens, such as lens 40 (FIG. 1H) and the ends of the optical fibers, such as fibers 20 (FIG. 1D) lie partially below the top surface of substrate 300 . This construction ensures that the images of the centers of the ends of fibers 20 lie in the same plane as the centers of the waveguides of waveguide device 302 . This precise mounting is preferably achieved by using the positioner (not shown) to manipulate the fiber optic module 306 relative to substrate 300 such that the mode of each optical fiber 20 in module 306 matches the mode of at least one corresponding waveguide of waveguide device 302 with relatively low light loss. The fiber optic module 306 is mounted in a desired relative position on the substrate 302 independently of the positioner by employing side mounting blocks 310 to fix the module 306 in position on substrate 300 upon precise mutual alignment of the module 306 and the waveguide device 302 . Preferably side mounting blocks 310 are carefully positioned alongside module 306 and are bonded thereto and to substrate 300 , preferably using a thin layer of UV curable adhesive 311 which does not involve significant shrinkage during curing, as by use of a UV light source 320 as shown in FIG. 4E, so that the relative position shown in FIG. 4D is preserved, as seen in FIG. 4 F. The use of side mounting blocks 310 enables accurate fixation with six degrees of freedom by virtue of the use of the thin layer of adhesive 311 , which does not involve significant shrinkage during curing, along two mutually orthogonal planes. Reference is now made to FIGS. 5A-5F, which are simplified pictorial illustrations yet another method for producing an optical device using an optical fiber module and an integrated optics waveguide assembly in accordance with yet another preferred embodiment of the present invention corresponding to the embodiment of FIG. 2 C. FIG. 5A shows a substrate 400 onto which is mounted an active integrated optics waveguide device 402 as well as various other integrated circuits 404 . A hole or recess 405 is preferably formed in substrate 400 as shown. In this embodiment a multiplicity of optical fibers 406 are mounted in V-grooves 407 formed in substrate 400 , such that the centers of the ends of fibers 406 all lie in the same plane as that of the centers of the waveguides of waveguide device 402 . It is appreciated that this type of structure may be adapted for use with the embodiment of FIGS. 2A and 2B by providing a raised platform portion of substrate 400 underlying V-grooves 407 . In such an arrangement, the centers of the ends of fibers 406 would all lie in the same plane as that of the centers of the waveguides of waveguide device 100 (FIG. 2A) or 104 (FIG. 2 B). As seen in FIG. 5B, a lens module 408 , preferably comprising a lens 409 fixedly mounted onto a mounting substrate 410 , is brought into proximity with substrate 400 and active integrated optics waveguide device 402 , as by a vacuum engagement assembly 411 , connected to a suitable positioner (not shown), such as Melles Griot Nanoblock. As seen in FIG. 5C, the lens module 408 is precisely positioned with respect to the active integrated optics waveguide device 402 with six degrees of freedom so as to achieve a high degree of accuracy in order to realize optimal optical coupling efficiency between the fibers 406 and the waveguides in device 402 . This degree of accuracy is greater than that required in the previously described alignment steps illustrated in FIGS. 1A-1I and preferably reaches one tenth of a micron. FIG. 5D illustrates precise mounting of the lens module 408 with respect to the active integrated optics waveguide device 402 on substrate 400 partially overlapping hole 405 , such that the lens 409 lies partially below the top surface of substrate 400 . This construction ensures that the images of the centers of the ends of fibers 406 lie in the same plane as the centers of the waveguides of waveguide device 402 . This precise mounting is preferably achieved by using the positioner (not shown) to manipulate the lens module 408 relative to substrate 400 such that the mode of each optical fiber 406 matches the mode of at least one corresponding waveguide of waveguide device 402 with relatively low light loss. The lens module 408 is mounted in a desired relative position on the substrate 400 independently of the positioner by employing side mounting blocks 412 to fix the module 408 in position on substrate 400 upon precise mutual alignment of the module 408 and the waveguide device 402 . Preferably side mounting blocks 412 are carefully positioned alongside module 408 and are bonded thereto and to substrate 400 , preferably using a thin layer of UV curable adhesive 413 which does not involve significant shrinkage during curing, as by use of a UV light source 420 as shown in FIG. 5E, so that the relative position shown in FIG. 5D is preserved, as seen in FIG. 5 F. The use of side mounting blocks 412 enables accurate fixation with six degrees of freedom by virtue of the use of the thin layer of adhesive 413 , which does not involve significant shrinkage during curing, along two mutually orthogonal planes. Reference is now made to FIGS. 6A-6E, which are simplified pictorial illustrations of a method for associating output optics with the optical device of FIG. 3F in accordance with a preferred embodiment of the present invention; FIG. 6A shows a chassis 500 onto which is mounted an optical device 501 , preferably the optical device described hereinabove and shown in FIG. 3 F. For the sake of conciseness and clarity, the reference numerals appearing in FIG. 3F are employed also in FIG. 6A as appropriate. Also mounted on chassis 500 is an optical fiber bundle 502 and a lens 504 arranged such that the center of the lens 504 lies in the same plane as the centers of the ends of the fibers in fiber bundle 502 within conventional mechanical tolerances, such as 10-50 microns. As seen in FIG. 6A, a lens module 508 , preferably comprising a lens 509 fixedly mounted onto a mounting substrate 510 , is brought into proximity with substrate 200 of device 501 and active integrated optics waveguide device 202 of device 501 , as by a vacuum engagement assembly 511 , connected to a suitable positioner (not shown), such as Melles Griot Nanoblock. As seen in FIG. 6B, the lens module 508 is precisely positioned with respect to the active integrated optics waveguide device 202 with six degrees of freedom so as to achieve a high degree of accuracy in order to realize optimal optical coupling efficiency between the fibers of fiber bundle 502 and the waveguides in device 202 . This degree of accuracy is greater than that required in the previously described alignment steps illustrated in FIGS. 1A-1I and preferably reaches one tenth of a micron. FIG. 6C illustrates precise mounting of the lens module 508 with respect to the active integrated optics waveguide device 202 of device 501 . This construction ensures that the images of the centers of the ends of fibers of fiber bundle 502 lie in the same plane as the centers of the waveguides of waveguide device 202 . This precise mounting is preferably achieved by using the positioner (not shown) to manipulate the lens module 508 relative to substrate 200 such that the mode of each optical fiber in bundle 502 matches the mode of at least one corresponding The lens module 508 is mounted in a desired relative position on the substrate 200 independently of the positioner by employing side mounting blocks 512 to fix the module 508 in position on substrate 200 upon precise mutual alignment of the module 508 and the waveguide device 202 . Preferably side mounting blocks 512 are carefully positioned alongside module 508 and are bonded thereto and to substrate 200 , preferably using a thin layer of UV curable adhesive 513 which does not involve significant shrinkage during curing, as by use of a UV light source 520 as shown in FIG. 6D, so that the relative position shown in FIG. 6C is preserved, as seen in FIG. 6 E. The use of side mounting blocks 512 enables accurate fixation with six degrees of freedom by virtue of the use of the thin layer of adhesive 513 , which does not involve significant shrinkage during curing, along two mutually orthogonal planes. Reference is now made to FIGS. 7A-7D, which are simplified pictorial illustrations of a method for constructing an integrated optics optical fiber switch using a plurality of base substrates bearing integrated optics waveguide assemblies and optical fiber modules as shown in FIG. 3 F. The switch is constructed on the basis of the apparatus shown in FIG. 6 E. For the sake of conciseness and clarity, the reference numerals appearing in FIG. 6E are also employed, as appropriate in FIGS. 7A-7D. As seen in FIG. 7A an optical device 601 , preferably identical to optical device 501 (FIG. 6 E), as shown in FIG. 3F, is stacked over optical device 501 and spaced therefrom by mounting spacers 602 . For the sake of conciseness and clarity, the reference numerals appearing in FIG. 3F are also employed, as appropriate in FIGS. 7A-7D. Spacers 602 may be mounted either on device 501 as shown or alternatively on device 601 or on chassis 500 . The alignment between devices 501 and 601 may be within conventional mechanical tolerances, such as 10 microns. The most important aspect of the alignment between devices 501 and 601 is the parallelism of the planes of the respective substrates 200 of devices 501 and 601 about the axes of the waveguides of respective optical devices 202 . As seen in FIG. 7B, a lens module 608 , preferably comprising a lens 609 fixedly mounted onto a mounting substrate 610 , is brought into proximity with substrate 200 of device 601 and active integrated optics waveguide device 202 of device 601 , as by a vacuum engagement assembly 611 , connected to a suitable positioner (not shown), such as Melles Griot Nanoblock. As seen in FIG. 7C, the lens module 608 is precisely positioned with respect to the active integrated optics waveguide device 202 of device 601 with six degrees of freedom so as to achieve a high degree of accuracy in order to realize optimal optical coupling efficiency between the fibers of fiber bundle 502 and the waveguides in device 202 of device 601 . This degree of accuracy is greater than that-required in the previously described alignment steps illustrated in FIGS. 1A-1I and preferably reaches one tenth of a micron. Precise mounting of the lens module 608 with respect to the active integrated optics waveguide device 202 of device 601 as described hereinabove with respect to device 501 ensures that the images of the centers of the ends of fibers of fiber bundle 502 lie in the same plane as the centers of the waveguides of waveguide device 202 of device 601 . This precise mounting is preferably achieved by using the positioner (not shown) to manipulate the lens module 608 relative to substrate 200 of device 601 such that the mode of each optical fiber in bundle 502 matches the mode of at least one corresponding waveguide of waveguide device 202 of device 601 with relatively low light loss. As seen in FIG. 7D, the lens module 608 is mounted in a desired relative position on the substrate 200 of device 601 independently of the-positioner by employing side mounting blocks 612 to fix the module 608 in position on substrate 200 of device 601 upon precise mutual alignment of the module 608 and the waveguide device 202 of device 601 . Preferably side mounting blocks 612 are carefully positioned alongside module 608 and are bonded thereto and to substrate 200 of device 601 , preferably using a thin layer of UV curable adhesive 613 which does not involve significant shrinkage during curing, as by use of a UV light source (not shown). Reference is now made to FIGS. 8A-8D, which are simplified pictorial illustrations of a method for associating output optics with the optical device of FIG. 4F in accordance with a preferred embodiment of the present invention; FIG. 8A shows a chassis 700 onto which is mounted an optical device 701 , preferably the optical device described hereinabove and shown in FIG. 4 F. For the sake of conciseness and clarity, the reference numerals appearing in FIG. 4F are employed also in FIG. 8A as appropriate. Also mounted on chassis 700 is an optical fiber bundle 702 and a lens 704 arranged such that the center of the lens 704 lies in the same plane as the centers of the ends of the fibers in fiber bundle 702 within conventional mechanical tolerances, such as 10-50 microns. As seen in FIG. 8A, a lens module 708 , preferably comprising a lens 709 fixedly mounted onto a mounting substrate 710 , is brought into proximity with substrate 300 of device 701 and active integrated optics waveguide device 302 of device 701 , as by a vacuum engagement assembly 711 , connected to a suitable positioner (not shown), such as Melles Griot Nanoblock. As seen in FIG. 8B, the lens module 708 is precisely positioned with respect to the active integrated optics waveguide device 302 with six degrees of freedom so as to achieve a high degree of accuracy in order to realize optimal optical coupling efficiency between the fibers of fiber bundle 702 and the waveguides in device 302 . This degree of accuracy is greater than that required in the previously described alignment steps illustrated in FIGS. 1A-1I and preferably reaches one tenth of a micron. FIG. 8C illustrates precise mounting of the lens module 708 with respect to the active integrated optics waveguide device 302 of device 701 . This construction ensures that the images of the centers of the ends of fibers of fiber bundle 702 lie in the same plane as the centers of the waveguides of waveguide device 302 . This precise mounting is preferably achieved by using the positioner (not shown) to manipulate the lens module 708 relative to substrate 300 such that the mode of each optical fiber in bundle 702 matches the mode of at least one corresponding waveguide of waveguide device 302 with relatively low light loss. The lens module 708 is mounted in a desired relative position on the substrate 300 independently of the positioner by employing side mounting blocks 712 to fix the module 708 in position on substrate 300 upon precise mutual alignment of the module 708 and the waveguide device 302 . Preferably side mounting blocks 712 are carefully positioned alongside module 708 and are bonded thereto and to substrate 300 , preferably using a thin layer of UV curable adhesive 713 which does not involve significant shrinkage during curing, as by use of a UV light source 720 as shown in FIG. 8C, so that the relative position shown in FIG. 8C is preserved, as seen in FIG. 8 D. The use of side mounting blocks 712 enables accurate fixation with six degrees of freedom by virtue of the use of the thin layer of adhesive 713 , which does not involve significant shrinkage during curing, along two mutually orthogonal planes. Reference is now made to FIGS. 9A-9D, which are simplified pictorial illustrations of a method for constructing an integrated optics optical fiber switch using a plurality of base substrates bearing integrated optics waveguide assemblies and optical fiber modules as shown in FIG. 4 F. The switch is constructed on the basis of the apparatus shown in FIG. 8 D. For the sake of conciseness and clarity, the reference numerals appearing in FIG. 8D are also employed, as appropriate in FIGS. 9A-9D. As seen in FIG. 9A an optical device 801 , preferably identical to optical device 701 (FIG. 8 D), as shown in FIG. 4F, is stacked over optical device 701 and spaced therefrom by mounting spacers 802 . For the sake of conciseness and clarity, the reference numerals appearing in FIG. 4F are also employed, as appropriate in FIGS. 9A-9D. Spacers 802 may be may mounted either on device 701 as shown or alternatively on device 801 or on chassis 700 . The alignment between devices 701 and 801 may be within conventional mechanical tolerances, such as 10 microns. The most important aspect of the alignment between devices 701 and 801 is the parallelism of the planes of the respective substrates 300 of devices 701 and 801 about the axes of the waveguides of respective optical devices 302 (FIG. 9 B). As seen in FIG. 9C, a lens module 808 , preferably comprising a lens 809 fixedly mounted onto a mounting substrate 810 , is brought into proximity with substrate 300 of device 801 and active integrated optics waveguide device 302 of device 801 , as by a vacuum engagement assembly 811 , connected to a suitable positioner (not shown), such as Melles Griot Nanoblock. Also seen in FIG. 9C, the lens module 808 is precisely positioned with respect to the active integrated optics waveguide device 302 of device 801 with six degrees of freedom so as to achieve a high degree of accuracy in order to realize optimal optical coupling efficiency between the fibers of fiber bundle 702 and the waveguides in device 302 of device 801 . This degree of accuracy is greater than that required in the previously described alignment steps illustrated in FIGS. 1A-1I and preferably reaches one tenth of a micron. Precise mounting of the lens module 808 with respect to the active integrated optics waveguide device 302 of device 801 as described hereinabove with respect to device 701 ensures that the images of the centers of the ends of fibers of fiber bundle 702 lie in the same plane as the centers of the waveguides of waveguide device 302 of device 801 . This precise mounting is preferably achieved by using the positioner (not shown) to manipulate the lens module 808 relative to substrate 300 of device 801 such that the mode of each optical fiber in bundle 702 matches the mode of at least one corresponding waveguide of waveguide device 302 of device 801 with relatively low light loss. As seen in FIG. 9D, the lens module 808 is mounted in a desired relative position on the substrate 300 of device 801 independently of the positioner by employing side mounting blocks 812 to fix the module 808 in position on substrate 300 of device 801 upon precise mutual alignment of the module 808 and the waveguide device 302 of device 801 . Preferably side mounting blocks 812 are carefully positioned alongside module 808 and are bonded thereto and to substrate 300 of device 801 , preferably using a thin layer of UV curable adhesive 813 which does not involve significant shrinkage during curing, as by use of a UV light source 820 . It will be appreciated by persons skilled in the art that the present invention is not limited by the claims which follow, rather the scope of the invention includes both combinations and subcombinations of the various features described hereinabove as well as variations and modifications thereof which would occur to a person of ordinary skill in the art upon reading the foregoing description and which are not in the prior art.

This invention discloses an optical device including at least one first substrate defining a multiplicity of optical fiber positioning grooves, a multiplicity of optical fibers fixed in each of said multiplicity of optical fiber positioning grooves on the at least one first substrate, whereby the multiplicity of optical fibers lie in an optical fiber plane and the ends of each of the multiplicity of optical fibers lie substantially in a first predetermined arrangement in the optical fiber plane, a second substrate fixed onto the at least one first substrate such that an edge of the second substrate extends beyond the ends of each of the multiplicity of optical fibers, a lens assembly including a third substrate, and a lens fixed onto the third substrate, the lens assembly being mounted onto the second substrate such that the lens lies in a second predetermined arrangement with respect to the ends of each of the multiplicity of optical fibers, whereby the separation between the lens and the ends of each of the multiplicity of optical fibers is defined in a plane perpendicular to the optical fiber plane to a first degree of accuracy and the separation between the lens and the ends of each of the multiplicity of optical fibers is defined in the optical fiber plane to a second degree of accuracy, less than the first degree of accuracy.

FIELD OF THE INVENTION The invention relates to a method and apparatus for detecting a watermark in a signal and in particular, but not exclusively, to detecting of a multiplicative watermark. BACKGROUND OF THE INVENTION The illicit distribution of copyright material deprives the holder of the copyright the legitimate royalties for this material, and could provide the supplier of this illicitly distributed material with gains that encourages continued illicit distributions. In light of the ease of transfer provided by e.g. the Internet, content material that is intended to be copyright protected, such as artistic renderings or other material having limited distribution rights are susceptible to wide-scale illicit distribution. In particular, content items such as music or video items are currently attracting a significant amount of unauthorised distribution and copying. This is partly due to the increasing practicality and feasibility of distribution and copying provided by new technologies. For example, the MP3 format for storing and transmitting compressed audio files has made a wide-scale distribution of audio recordings feasible. For instance, a 30 or 40 megabyte digital PCM (Pulse Code Modulation) audio recording of a song can be compressed into a 3 or 4 megabyte MP3 file. Using a typical 56 kbps dial-up connection to the Internet, this MP3 file can be downloaded to a user's computer in a few minutes. This may for example allow a malicious party could provide a direct dial-in service for downloading an MP3 encoded song. Moreover, the introduction of broadband internet connections stimulates the download of even bigger files such as MPEG video. The illicit copy of the MP3 encoded song can be subsequently rendered by software or hardware devices or can be decompressed and stored on a recordable CD for playback on a conventional CD player. A number of techniques have been proposed for limiting the reproduction of copy-protected content material. The Secure Digital Music Initiative (SDMI) and others advocate the use of “digital watermarks” to prevent unauthorised copying. Digital watermarks can be used for copy protection according to the scenarios mentioned above. However, the use of digital watermarks is not limited to copy prevention but can also be used for so-called forensic tracking, where watermarks are embedded in e.g. files distributed via an Electronic Content Delivery System, and used to track for instance illegally copied content on the Internet. Watermarks can furthermore be used for monitoring broadcast stations (e.g. commercials); or for authentication purposes etc. Techniques have been proposed for embedding watermarks directly in a coded bit stream. This technique is frequently referred to as bitstream watermarking. Further description of bitstream watermarking may be found in PCT Patent Application WO 01/49363 A1‘Method and System of Digital Watermarking for Compressed Audio’ or in ‘Audio Watermarking of MPEG-2 AAC Bitsteams’ by Christian Neubauer and Jurgen Herre, 108th AES Convention, Paris, Feb. 2000. Audio Engineering Society, preprint 5101. Techniques have further been proposed for embedding watermarks directly in uncompressed signals (also referred to as a base band signal), and there are several known techniques for embedding watermarks in a raw uncompressed signal. For example a watermark may be directly embedded in a PCM (Pulse Coded Modulation) signal which may subsequently be encoded. An example of a watermarking system for embedding a watermark in a base band signal may be found in “A temporal domain audio watermarking technique” by A. N. Lemma, J. Aprea, W. Oomen, and L. van de Kerkhof, IEEE Transactions on signal processing, Vol 51, No 4, Apr. 2003, page 1088-1097, Institute of Electrical and Electronic Engineers. Naturally the performance and characteristics of watermark detection processes is a major factor in the success of a watermark based system. A method for detecting watermarks embedded in accordance with the above described approach comprises a two stage approach wherein individual watermark symbols are estimated in the first stage, a plurality of estimated watermark symbols are correlated with a known watermark pattern in the second stage and a detection decision is made depending on the degree of correlation. Further details of this watermark detection method may be found in “A Temporal Domain Audio Watermarking Technique” by A. N. Lemma, J. Aprea, W. Oomen, and L. van de Kerkhof, IEEE Transactions on signal processing, Vol 51, No 4, April 2003, page 1088-1097, Institute of Electrical and Electronic Engineers. However, although such a detector is useful for watermark detection, it is sensitive to noise which may affect the performance. Noise may e.g. comprise distortions introduced by e.g. common signal processing (e.g. audio compression, dynamic amplitude compression etc) or noise introduced in a broadcast chain. Noise may cause the detector to indicate that a signal comprises a watermark although none is present or the detector may fail to detect a watermark embedded in a signal. Accordingly, it would be advantageous if improved performance and in particular improved detection accuracy could be achieved. Furthermore, in practical implementations it is important that complexity and computational requirements of the watermark detection is minimised. However, improved performance and reliability of detection is typically achieved at the cost of increased processing and complexity. Hence, an improved system for watermark detection would be advantageous and in particular a system allowing improved detection performance, reduced complexity and/or facilitated implementation. SUMMARY OF THE INVENTION Accordingly, the Invention preferably seeks to mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination. According to a feature of the invention, there is provided a method of detecting a watermark in a first signal, the method comprising the steps of: receiving the first signal potentially having a watermark embedded in an original signal; receiving a second signal corresponding to the original signal; segmenting the signal into a plurality of segments each corresponding to a watermark symbol; and for each of the segments performing the steps of: determining a first characteristic for a first section of the segment in response to a set of data values of the first signal in the first section and set of data values of the second signal in the first section, determining a second characteristic for a second section of the segment in response to a set of data values of the first signal in the second section and set of data values of the second signal in the second section, and determining a watermark symbol estimate for the segment in response to the first characteristic and the second characteristic; and determining if a watermark is embedded by comparison of the watermark symbol estimates with a reference watermark symbol pattern. The inventor's of the current invention have realised that improved performance may be achieved by using informed detection of watermarks and in particular by using information of the original signal in different sections of segments corresponding to watermark symbols. Specifically, the invention allows increased reliability of the watermark detection in the presence of noise. Furthermore, the use of information related to the original signal may be achieved without an unacceptable complexity or computational resource increase and the watermark detection is highly suitable for practical implementations. The second signal may be received from any suitable source and may be in any suitable format for providing information related to the original signal. Specifically, the second signal may be identical or similar to all or part of the original signal. The source of the second signal may furthermore be an external or an internal source. Furthermore, the first and second signals may be received together or separately. The comparison between the watermark symbol estimates and the reference watermark symbol pattern may specifically comprise a coffelation between the watermark symbol estimates and the reference watermark symbol pattern. According to a feature of the invention, the step of determining the first characteristic comprises determining an envelope characteristic of the first signal in the first section. The envelope characteristic may specifically be a sum and/or average and/or variation of the absolute amplitude values of the first signal. This may provide a particularly suitable parameter for estimating a watermark symbol. Additionally or alternatively, the second characteristic comprises determining an envelope characteristic of the first signal in the second section. According to another feature of the invention, the step of determining the first characteristic comprises determining an envelope characteristic of the second signal in the first section. The envelope characteristic may specifically be a sum and/or average and/or variation of the absolute amplitude values of the second signal. This may provide a particularly suitable parameter for estimating a watermark symbol. Additionally or alternatively, the second characteristic comprises determining an envelope characteristic of the first signal in the second section. According to another feature of the invention, the step of determining the first characteristic comprises determining the first characteristic as a first relationship between an envelope characteristic of the first signal in the first section and an envelope characteristic of the second signal in the first section. The relationship between envelope characteristics associated with the received signal and an original non-watermark embedded signal may provide a particularly advantageous indication of a watermark symbol. According to another feature of the invention, the first relationship is a ratio. This relationship may provide particularly advantageous performance as well as acceptable resource complexity. According to another feature of the invention, the step of determining the second characteristic comprises determining the second characteristic as a second ratio between an envelope characteristic of the first signal in the second section, and an envelope characteristic of the second signal in the second section, and the step of determining a watermark symbol estimate comprises determining the watermark symbol estimate as a mathematical function of the first ratio and the second ratio. The relationship between ratios of envelope characteristics in different sections may for appropriate watermark symbol shapes provide particularly suitable and accurate indications of the presence of a watermark. According to another feature of the invention, the mathematical relationship comprises a subtraction. This may provide a particularly suitable mathematical relationship for certain watermark symbol shapes, and in particular for a substantially bi-phase window symbol shape. According to another feature of the invention, the method further comprises the step of determining a property of the first characteristic in response to a symbol shape of the watermark symbols. Alternatively or additionally, the method comprises the step of determining a property of the second characteristic in response to a symbol shape of the watermark symbols. For example, depending on the symbol shape of the watermark symbols, it may be advantageous to alternatively or additionally consider amplitude characteristics or energy characteristics. Thus, the watermark detection may be particularly customised for a given symbol shape. According to another feature of the invention, the method further comprises the step of extracting a first portion of the first signal and performing the segmentation and watermark symbol estimation by processing of the first portion only. Preferably, the step of extracting the first portion comprises filtering the first signal. For example, the watermark detection may comprise band-bass filtering of the first signal. This may provide improved detection performance and in particular the extraction of the first portion may be compatible with a similar process performed in the watermark embedder. Preferably, the watermark is a multiplicative watermark. According to a second aspect of the invention, there is provided an apparatus for detecting a watermark in a first signal, the method comprising: means for receiving the first signal potentially having a watermark embedded in an original signal; means for receiving a second signal corresponding to the original signal; means for segmenting the signal into a plurality of segments each corresponding to a watermark symbol; and means for, for each of the segments, determining a first characteristic for a first section of the segment in response to a set of data values of the first signal in the first section and set of data values of the second signal in the first section, determining a second characteristic for a second section of the segment in response to a set of data values of the first signal in the second section and set of data values of the second signal in the second section, and determining a watermark symbol estimate for the segment in response to the first characteristic and the second characteristic; and means for determining if a watermark is embedded by comparison of the watermark symbol estimates with a reference watermark symbol pattern. These and other aspects, features and advantages of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will be described, by way of example only, with reference to the drawings, in which FIG. 1 illustrates a watermark embedder for embedding a multiplicative watermark in accordance with prior art; FIG. 2 illustrates a system for generating watermark samples from watermark symbols; FIG. 3 illustrates a raised cosine window symbol shape suitable for the watermark embedder of FIG. 1 ; FIG. 4 illustrates a bi-phase window symbol shape suitable for the watermark embedder of FIG. 1 ; FIG. 5 illustrates a block diagram of a watermark detector in accordance with an embodiment of the invention; and FIG. 6 illustrates a method of detecting a watermark in accordance with an embodiment of the invention. DESCRIPTION OF PREFERRED EMBODIMENTS The following description focuses on an embodiment of the invention applicable to a detection of a multiplicative watermark but it will be appreciated that the invention is not limited to this specific application. Initially, a system for embedding a multiplicative watermark will be described. The system is compatible with the system described in “A temporal domain audio watermarking technique” by A. N. Lemma, J. Aprea, W. Oomen, and L. van de Kerkhof, IEEE Transactions on signal processing, Vol 51, No 4, Apr. 2003, page 1088-1097, Institute of Electrical and Electronic Engineers, where further details may be found. FIG. 1 illustrates a watermark embedder for embedding a multiplicative watermark in accordance with prior art. The watermark embedder receives samples x[n] of a base band signal to be watermarked. The samples are fed to a base band filter 101 having an impulse response h[n]. Thus, the filtered signal x b [n]=x[n]*h[n] where * denotes the convolution operation is generated. The filtered signal x b [n] is fed to a multiplier 103 where it is multiplied by watermark samples w[n] to generate the samples x b [n]−w[n] which are fed to a scaling unit 105 which scales the samples by a value α. The resulting sample values are added to the original samples x[n] in an adder 107 . Thus the signal generated by the watermark embedder is: y[n]=x[n]+α·x b [n]−w[n] Specifically, α corresponds to the embedding strength of the watermark which may be controlled dynamically by a psycho-acoustic model. The watermark w[n] is chosen such that multiplying it with xb[n] predominantly modifies the short time envelope of xb[n]. FIG. 2 illustrates a system for generating watermark samples from watermark symbols. First, a finite length, zero mean, uniformly distributed random sequence w di [k] w di [k]ε[− 1,1] for k= 0,1 , L w −1, where L w is the number of symbols in a watermark. The watermark pattern is converted into a periodic, slowly varying narrow-band signal w i [n] of length L w ·T s , where T s is the symbol length in samples, by the system of FIG. 2 . The watermark symbols w di [k] are up-sampled by a factor T s in the upsampler 201 . w di [n]=w di [n/T s ] for n= 0, T s ,2 T s and 0 otherwise. The upsampled signal is then filtered by the window shaping function s[n] in a convolution element 203 : w i [n]=w di [n]*s[n] Thus the window shape corresponds to the symbol shape for the watermark symbol. w i [n] may then be used as the watermark samples w[n] of the watermark embedder of FIG. 1 . The performance of the watermark system has been found to be dependent on the window shaping function and thus the watermark symbol shape. FIG. 3 illustrates a raised cosine window symbol shape suitable for the watermark embedder of FIG. 1 and FIG. 4 illustrates a bi-phase window symbol shape suitable for the watermark embedder of FIG. 1 . The following description will focus on an embodiment employing the bi-phase window symbol shape but it will be appreciated that other embodiments may use other window symbol shapes. FIG. 5 illustrates a block diagram of a watermark detector 500 in accordance with an embodiment of the invention. The watermark detector 500 comprises a first receiver 501 which receives a first signal. The first signal may or may not comprise a watermark and the watermark detector 500 is arranged to detect if the first signal comprises a watermark. Specifically, the first signal may comprise a multiplicative watermark embedded into a signal as described above. The watermark detector 500 further comprises a second receiver 503 which is operable to receive a second signal which corresponds to the original signal of the first signal before a watermark was embedded. Specifically the second signal may consist in the signal samples x[n] of the original signal. The first receiver 501 is coupled to a first segmenter 505 . In some embodiments, the first segmenter 505 comprises means for processing the first signal in order to extract a specific portion of the first signal. Specifically, if the original signal x[n] was filtered by a filter h[n] in the watermark embedder, the first segmenter 505 comprises a similar filter for extracting the same frequency range as the filter of the watermark embedder. The first segmenter 505 is operable to divide the received signal into a plurality of segments wherein each segment corresponds to one watermark symbol. In the following, the current description will for clarity and brevity focus on an embodiment wherein the watermark embedder and the watermark detector 500 are synchronised. However, it will be appreciated that in other embodiments, the watermark detector 500 may comprise further functionality for synchronising the watermark detector 500 to the watermark embedder such that the first segmenter 505 may segment the first signal into appropriate symbol segments. Such functionality may for example be based on fingerprinting techniques as is well known in the art. The watermark detector 500 furthermore comprises a second segmenter 507 which is coupled to the second receiver 503 and which is operable to segment the second signal in segments corresponding to watermark symbols. Thus, the first and second segmenter 505 , 507 generate synchronised sample sets for each watermark symbol. The first and second segmenter 505 , 507 are coupled to a first section processor 509 which is operable to determine a first characteristic for a section or interval of each watermark symbol. In the described embodiment, the first section processor 509 processes one watermark symbol at a time. Initially, the first section processor 509 selects a set of samples for the current watermark symbols which corresponds to a particular section of the current watermark symbol. It then proceeds to determine a first characteristic for this section in response to the data values of the first signal in the given portion as well as the data values of the second signal in the given portion. Specifically, the first section processor 509 generates a first characteristic which indicates envelope characteristics of the two signals in the first section. Thus, the first characteristic is indicative of the relative envelope characteristics of the potentially watermarked signal and the original signal in a specific interval of the watermark symbol period. Similarly, the first and second segmenter 505 , 507 are coupled to a second section processor 511 which is operable to determine a second characteristic related to a different second section or interval of each watermark symbol. In the described embodiment, the second section processor 511 also processes one watermark symbol at a time. Similarly to the first section processor 509 , the second section processor 511 also selects a set of samples for the current watermark symbols which corresponds to a particular (but different) section of the current watermark symbol. It then proceeds to determine the second characteristic for this section in response to the data values of the first signal in the given portion as well as the data values of the second signal in the given portion. Specifically, the second section processor 511 generates a second characteristic which indicates envelope characteristics of the two signals in the second section. Thus, the second characteristic is indicative of the relative envelope characteristics of the potentially watermarked signal and the original signal in a specific interval of the watermark symbol period. Specifically, in the described embodiment, the first and second section processor 509 , 511 performs the same processing but on different sections of the watermark symbol. Thus, the first and second characteristics are indicative of how a given parameter (or combination of parameters) may vary in different sections of the watermark symbol. Thus, depending on the watermark symbol shape, the first and second characteristic may be assumed to vary in a certain way if a watermark is present but not if no watermark is present. By determining the first and second characteristic in response to known parameters of the original signal a more reliable and predictable variation may be expected. The first and second section processors 509 , 511 are coupled to a watermark symbol estimator 513 and feed the first and second characteristic to this. The watermark symbol estimator 513 estimates the current watermark symbol in response to the first and second characteristic. The process is repeated for a plurality of watermark symbols and these are fed to a decision unit 515 . The decision unit 515 is operable to compare the watermark symbol estimates to a reference watermark symbol pattern. Specifically, the watermark symbol estimates are correlated with the reference watermark symbol pattern and if the correlation is sufficiently high, the decision unit 515 determines that a watermark is embedded in the first signal and otherwise it is determined that a watermark is not embedded. FIG. 6 illustrates a method of detecting a watermark in accordance with an embodiment of the invention. The method is applicable to the watermark detector of FIG. 5 and will be described with reference to a specific embodiment using envelope characteristics. The method will further be described with reference to a signal potentially having a watermark embedded by the method described with reference to the watermark embedder of FIG. 1 . In step 601 the first signal potentially comprising a watermark is received. The first signal is filtered by a filter h b to generate the filtered signal y b [n]. The filter h b corresponds to the filter h of the watermark embedder 100 and is specifically a bandpass filter having the same frequency response as h. Thus, h b simply extracts the same frequency band as was used for watermark embedding. Thus y b [n]≅y[n]= (1 +α·w[n ])· x b [n] In step 603 , a second signal is received, possibly from an internal source, which corresponds to the original signal x[n] before watermarking. Step 603 is followed by step 605 wherein the (filtered) first and second signals are segmented into individual segments corresponding to a watermark symbol. Thus, after filtering, the first signal is segmented into frames of length T s . Denoting the frame number by k and letting w k [n]=w di [k]s[n] be the n-th sample of the watermark signal for watermark symbol w di [k], the watermarked signal in segment k is given by y b,k[n]= (1 +α·w di [k]s[n] )· x b,k [n] where s[n] is the bi-phase window shaping function of FIG. 4 and w di [k] is an estimate of the k-th watermark symbol of the embedded watermark sequence. In a further step it is tried to estimate w di [k] given the known signal y b,k [n]. The following envelope values may be determined from the first half and second half of the segment corresponding to watermark symbol k: ∑ n = 0 T s / 2 - 1 ⁢ ⁢  y b , k ⁡ [ n ]  = ∑ n = 0 T s / 2 - 1 ⁢ ⁢  ( 1 + α ⁢ ⁢ w dl ⁡ [ k ] ⁢ s ⁡ [ n ] ) ⁢ x b , k ⁡ [ n ]  ∑ n = T s / 2 T s - 1 ⁢ ⁢  y b , k ⁡ [ n ]  = ∑ n = T s / 2 T s - 1 ⁢ ⁢  ( 1 + α ⁢ ⁢ w dl ⁡ [ k ] ⁢ s ⁡ [ n ] ) ⁢ x b , k ⁡ [ n ]  A rough approximation of the bi-phase window of FIG. 4 may be given by 0 for 0 ≦n<T s /6 1 for T s /6 ≦n< 2 T s /6−1 s[n]= for 2 T s /6−1≦ n< 4 T s /6−1 −1 for 4 T s /6−1≦ n< 5 T s /6−1 0 for 5 T s /6−1≦ n<T s −1 Inserting this approximation yields the following approximation: ∑ n = T s / 6 2 ⁢ T s / 6 - 1 ⁢ ⁢  y b , k ⁡ [ n ]  = ( 1 + α ⁢ ⁢ w dl ⁡ [ k ] ) ⁢ ∑ n = T s / 6 2 ⁢ ⁢ T s / 6 - 1 ⁢  x b , k ⁡ [ n ]  ∑ n = 4 ⁢ ⁢ T s / 6 5 ⁢ ⁢ T s / 6 - 1 ⁢ ⁢  y b , k ⁡ [ n ]  = ( 1 - α ⁢ ⁢ w dl ⁡ [ k ] ) ⁢ ∑ n = 4 ⁢ ⁢ T s / 6 5 ⁢ ⁢ T s / 6 - 1 ⁢  x b , k ⁡ [ n ]  Note that if |α·w[k]|≦1 the only approximation is that of the approximation of s[n]. Since both y b,k [n] (i.e. band-pass filtered watermark signal) and x b,k [n] (i.e. band-pass filtered host signal) are known, the watermark signal w di [k] can be derived from: w dl ⁡ [ k ] = 1 2 ⁢ ⁢ α ⁢ ( ∑ n = T s / 6 2 ⁢ T s / 6 - 1 ⁢ ⁢  y b , k ⁡ [ n ]  ∑ n = T s / 6 2 ⁢ ⁢ T s / 6 - 1 ⁢  x b , k ⁡ [ n ]  - ∑ n = 4 ⁢ ⁢ T s / 6 5 ⁢ ⁢ T s / 6 - 1 ⁢ ⁢  y b , k ⁡ [ n ]  ∑ n = 4 ⁢ ⁢ T s / 6 5 ⁢ ⁢ T s / 6 - 1 ⁢  x b , k ⁡ [ n ]  ) In the described embodiment, the above approach is used for determining the watermark symbol estimates. Specifically step 605 is followed by step 607 wherein samples from T s /6≦n<2T s /6−1 are processed to determine a first characteristic given by: c 1 = ∑ n = T s / 6 2 ⁢ T s / 6 - 1 ⁢ ⁢  y b , k ⁡ [ n ]  ∑ n = T s / 6 2 ⁢ ⁢ T s / 6 - 1 ⁢  x b , k ⁡ [ n ]  Thus, step 607 comprises determining the first characteristic as an envelope characteristic of the first and second signal. Step 607 is followed by step 609 wherein samples from 4T s /6−1≦n<5T s /6−1 are processed to determine a second characteristic given by: c 2 = ∑ n = 4 ⁢ ⁢ T s / 6 5 ⁢ ⁢ T s / 6 - 1 ⁢ ⁢  y b , k ⁡ [ n ]  ∑ n = 4 ⁢ ⁢ T s / 6 5 ⁢ ⁢ T s / 6 - 1 ⁢  x b , k ⁡ [ n ]  Thus, step 609 comprises determining the second characteristic as an envelope characteristic of the first and second signal. Step 609 is followed by step 611 wherein the watermark symbol is estimated from the first and second characteristic as: w dl ⁡ [ k ] = 1 2 ⁢ ⁢ α ⁢ ( c 1 - c 2 ) Step 611 is followed by step 613 wherein it is determined if all watermark symbols of the watermark sequence have been estimated. If not, the method returns to step 607 . Otherwise, the method continues in step 615 where the estimated watermark symbol sequence is correlated with a reference watermark symbol pattern. If the correlation is above a threshold, it is decided that the first signal comprises a watermark, and if it is below the threshold it is decided that the first signal does not comprise a watermark. Thus, the described embodiment provides a system for detecting a watermark which has high performance and which in particular has high watermark detection reliability. Furthermore, the method is particularly suited for implementation in a firmware or software processing unit and may be implemented with relatively low complexity. The exact parameters and characteristics used for estimating the watermark symbols may depend on the exact symbol shape of the watermark symbols. Accordingly, a property of the first characteristic and/or second characteristic may be determined in response to the symbol shape of the watermark symbols. For example, different formulas and equations may be determined for different symbol shapes and depending on the specific symbol shape used, the operation may be modified. The invention can be implemented in any suitable form including hardware, software, firmware or any combination of these. However, preferably, the invention is implemented as computer software running on one or more data processors and/or digital signal processors. The elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the invention may be implemented in a single unit or may be physically and functionally distributed between different units and processors. Although the present invention has been described in connection with the preferred embodiment, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. In the claims, the term comprising does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is no feasible and/or advantageous. In addition, singular references do not exclude a plurality. Thus references to “a”, “an”, “first”, “second” etc do not preclude a plurality.

The invention relates to a system for detecting a watermark using informed detection. A first signal potentially having a watermark embedded is received ( 601 ) as is a second signal corresponding to the original signal. The signals are segmented ( 605 ) into symbol segments. For each symbol segment a first characteristic is determined ( 607 ) for a first section and a second characteristic is determined ( 609 ) for a second section in response to the first and second signals in those sections. Specifically, ratios between average envelopes are determined. Thus, the first and second characteristic is indicative of the variations of the envelope during a watermark symbol. A watermark symbol estimate is determined ( 611 ) from the first and second characteristic. A sequence of estimated watermark symbols is compared to reference watermark symbols and the presence of a watermark symbol is determined ( 615 ) depending on the comparison. The invention is particularly suitable for improved detection of a multiplicative watermark.

[0001] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 60/487,231, filed on Jul. 16, 2003, the entire content of which is hereby incorporated herein by reference. BACKGROUND [0002] 1. Field of the Invention [0003] The present invention relates to multimedia information communication systems. More particularly, the present invention relates to a system and method for compressing, transmitting and receiving multimedia information, including high-resolution video, audio and data, over an information transmission network. [0004] 2. Background Information [0005] Immersive visualization theaters provide environments for detailed inspection of intricate images, often in three dimensions and often in true “immersive” settings. Image content can be from various fields of scientific and industrial endeavor, such as from the earth sciences, the manufacturing industry (e.g., automobile, aircraft, earthmoving vehicles), the medical industry, military and government applications, and the like. Immersive visualization theaters can be multi-million dollar installations with sophisticated projection systems, high-end graphics servers and large, multi-terabyte data sets to be inspected. These data sets can contain critical information requiring inspection by a group of experts that are geographically distributed. Consequently, there is a need for a collaborative solution. A multimedia collaboration system is described in, for example, U.S. Pat. No. 5,617,539. [0006] The transmission networks supporting immersive visualization theaters can be SONET/SDH based with rates from, for example, OC-3 and higher. High bandwidth data transmission using rates below OC-48 requires sophisticated compression techniques. Existing compression techniques, such as, for example, JPEG and MPEG, are inadequate, because the rapid computations required for these techniques are not realizable with existing hardware. [0007] Conventional motion-estimation-based compression algorithms, such as, for example, MPEG-2 and MPEG-4, rely on complex computations to find the best prediction for each frame so that more frames can be sent at a particular bitrate at higher quality. However, as the required frame rates increase and as the frame resolution increases, it becomes difficult to perform the complex computations in real-time. Consequently, many conventional compression products are limited to rates such as, for example, 720×480 at 30 frames per second (fps). Such products are typically targeted towards DVD and HDTV applications and are, therefore, unable to process stereo video at rates of, for example, 1280×1024 or 1600×1200 at 96 fps or 120 fps. A stereoscopic video telecommunication system is described in, for example, U.S. Pat. No. 5,677,728. The left and right frames at any time in stereo video have data content similarities that can be exploited by compression algorithms. State-of-the-art stereo video compression can use disparity based coding. Such disparity based coding algorithms are highly computational intensive and are not realizable using existing hardware for high resolution, high frame rate images. [0008] Video can be variable bitrate (VBR) in nature, since different frames can have different content and hence can be compressed to different degrees. This variation in bitrates can present several design approaches and tradeoffs for a particular application. In conventional video streaming applications over IP, the VBR stream can be converted to a constant bitrate (CBR) stream by buffering the data after encoding, and similarly buffering up to a few seconds of video before decoding at the receiver. Buffering allows for the smoothing of out-of-bitrate variations to meet the CBR requirements of the network. However, the buffering can introduce many seconds of latency for the application. With more buffering capability prior to transmission, there is more flexibility in terms of adapting the VBR to a CBR bitstream, but with the penalty of increased delay. For applications such as immersive visualization over SONET, the buffer sizes required for buffering many seconds of video can be large. Moreover, immersive visualization applications require low latency. [0009] An immersive visualization system should be robust to errors in the bitstream introduced by the transmission network. Transmission errors can cause the video to be decoded incorrectly. Conventional compression algorithms encode P-frames (Predicted frames) based on references to the content in I-frames (Intra-frames). If each frame is coded as an I-frame, it is easier to recover from any transmission errors by synchronization to the next I-frame. Transmission errors occurring in a P-frame would cause the receiver to loose synchronization with the transmitter. Synchronization between the transmitter and the receiver can be regained to the next I-frame. In addition, any bit errors introduced in an I-frame would also require synchronization to the next I-frame. In conventional compression algorithms, the compression factor achieved is dependent on the number of P-frames introduced between I-frames. If more I-frames are inserted periodically, then the time delay required for resynchronization can be reduced at the expense of lower compression factors. [0010] The metric that is most commonly used for measuring decoded image quality is the Peak Signal-to-Noise Ratio (PSNR), which is expressed in dB. The PSNR is measured from the pixel-to-pixel errors between the original and decoded images, on a frame-by-frame basis. Though a particular PSNR number might translate to different visual qualities for different images, beyond a certain point for most classes of images, the quality becomes visually acceptable. For the applications discussed herein, a PSNR of 45 dB or more would be considered good quality, and that of 55-60 dB would be more or less visually lossless. Such image quality can be achievable at compression ratios that range from approximately 2:1 up to approximately 10:1 or 12:1, based on, for example, the image content, bandwidth availability and acceptable frame rate. Typically, chrominance sub-sampling in the horizontal and vertical directions can also be used to achieve compression, since the human visual system is less sensitive to chrominance than luminance. For natural images, chrominance sub-sampling can work well, but for images generated by computers, such as the ones produced by an immersive visualization system, chrominance sub-sampling may not work well. [0011] Some commercial systems can deploy target immersive visualization applications, but use very high bitrates to transmit the data, either uncompressed or using lossless compression that does not compress more than, for example, approximately 2:1 or 3:1. Other commercial systems are unable to compress full frames at high resolution at the frame rates that immersive visualization systems require, due to hardware limitations. Alternatively, other commercial systems can use temporal compression algorithms that use frame differencing methods to find redundant parts of successive images and minimize the transmission of such parts to achieve high video compression. However, due to noise introduced by interfacing electronics, such as analog-to-digital converters, such algorithms fail to effectively detect redundant portions of successive images and do not achieve optimal compression. SUMMARY OF THE INVENTION [0012] A system and method are disclosed for providing immersive visualization at low bandwidth rates. In accordance with exemplary embodiments, according to a first aspect of the present invention, a system for transmitting multimedia information via a network includes means for retrieving a frame of multimedia information for transmission over the network. The system includes means for converting the frame from a first color space to a second color space. Each component of the second color space can be formed as a weighted combination of components of the first color space. The system includes means for slicing the frame into a plurality of frame slices, and means for transforming each of the plurality of frame slices into a plurality of corresponding frequency domain components. The system includes means for quantizing the frequency domain components of each frame slice when it is determined that each frame slice is to be processed as one of an intra-slice and a refresh slice to generate quantized frequency domain components of each frame slice. The system includes means for variable-length encoding the quantized frequency domain components of each frame slice to generate compressed multimedia information associated with each frame slice. The system also includes means for constructing network packets of the compressed multimedia information associated with each frame slice, and means for transmitting the network packets via the network. [0013] According to the first aspect, the means for retrieving can include means for discarding a retrieved frame based on at least one of a size of a frame buffer for storing the retrieved frame and a rate at which frames are transmitted. The system can include means for discarding porches surrounding an active portion of the frame. The first color space can comprise a red, green, blue (RGB) color space, and the second color space comprises a luminance and chrominance (YUV) color space. The system can include means for sub-sampling chrominance of the frame in a horizontal direction. Each of the plurality of frame slices can be transformed into the plurality of corresponding frequency domain components using a discrete cosine transform. The system can include means for subtracting the frequency domain components of each frame slice from frequency domain components of a corresponding frame slice associated with a previous frame to generate a frame difference. The system can include means for comparing the generated frame difference against predetermined noise filter threshold parameters to determine whether noise is associated with each frame slice. The system can include means for canceling a noise contribution from the frame difference, to determine whether the frame slice is substantially identical to the corresponding frame slice associated with the previous frame. [0014] According to the first aspect, the system can include means for determining whether each frame slice is to be (i) discarded or (ii) transmitted as the intra-slice or the refresh slice. The means for determining can comprise means for characterizing a feature within the frame as static when (i) the feature within the frame is substantially identical to a feature associated with a previous frame or (ii) movement of the feature within the frame is below a predetermined threshold. The system can include means for detecting a change in status of the feature within the frame from static to moving. The system can include means for assigning all frame slices of the frame as refresh slices when the change in status is detected. The means for quantizing can comprise means for modifying an amount of quantization based on available bandwidth for transmitting. According to an exemplary embodiment of the first aspect, the network packets can comprise Ethernet packets. The means for transmitting can comprise means for receiving network statistic information associated with transmission of the network packets, and means for modifying a transmission rate of the network packets based on the received network statistic information. [0015] According to a second aspect of the present invention, a system for receiving multimedia information transmitted via a network includes means for extracting compressed multimedia information from network packets received via the network. The system includes means for inverse variable length coding the extracted compressed multimedia information to generate quantized frequency domain components of frame slices of a frame of multimedia information. The system includes means for inverse quantizing the quantized frequency domain components of the frame slices to generate frequency domain components of the frame slices. The system includes means for inverse transforming the frequency domain components of the frames slices to generate a plurality of frame slices. The system includes means for combining the plurality of frame slices to form the frame of multimedia information. The system includes means for converting the frame from a first color space to a second color space. Each component of the second color space is formed as a weighted combination of components of the first color space. The system includes means for displaying the converted frame. [0016] According to the second aspect, the means for combining can comprise means for replacing missing frame slices of the plurality of frame slices using corresponding frame slices from a previous frame. Frequency domain components of the frame slices can be inverse transformed into the plurality of frame slices using an inverse discrete cosine transform. The first color space can comprise a luminance and chrominance (YUV) color space, and the second color space can comprise a red, green, blue (RGB) color space. The system can include means for adding porches surrounding an active portion of the frame. [0017] According to a third aspect of the present invention, a method of transmitting multimedia information via a network includes the steps of: a.) retrieving a frame of multimedia information for transmission over the network; b.) converting the frame from a first color space to a second color space, wherein each component of the second color space is formed as a weighted combination of components of the first color space; c.) slicing the frame into a plurality of frame slices; d.) transforming each of the plurality of frame slices into a plurality of corresponding frequency domain components; e.) quantizing the frequency domain components of each frame slice when it is determined that each frame slice is to be processed as one of an intra-slice and a refresh slice to generate quantized frequency domain components of each frame slice; f.) variable-length encoding the quantized frequency domain components of each frame slice to generate compressed multimedia information associated with each frame slice; g.) constructing network packets of the compressed multimedia information associated with each frame slice; and h.) transmitting the network packets via the network. [0018] According to the third aspect, the step of retrieving can comprise the step of: i.) discarding a retrieved frame based on at least one of a size of a frame buffer for storing the retrieved frame and a rate at which frames are transmitted. The method can comprise the step of: j.) discarding porches surrounding an active portion of the frame. The first color space can comprise a red, green, blue (RGB) color space, and the second color space comprises a luminance and chrominance (YUV) color space. The method can comprise the step of: k.) sub-sampling chrominance of the frame in a horizontal direction. Each of the plurality of frame slices can be transformed into the plurality of corresponding frequency domain components using a discrete cosine transform. The method can comprise the steps of: l.) subtracting the frequency domain components of each frame slice from frequency domain components of a corresponding frame slice associated with a previous frame to generate a frame difference; m.) comparing the generated frame difference against predetermined noise filter threshold parameters to determine whether noise is associated with each frame slice; and n.) canceling a noise contribution from the frame difference, to determine whether the frame slice is substantially identical to the corresponding frame slice associated with the previous frame. [0019] According to the third aspect, the method can comprise the step of: o.) determining whether each frame slice is to be (1) discarded or (2) transmitted as either the intra-slice or the refresh slice. The step of determining can comprise the steps of: p.) characterizing a feature within the frame as static when (1) the feature within the frame is substantially identical to a feature associated with a previous frame and (2) movement of the feature within the frame is below a predetermined threshold; q.) detecting a change in status of the feature within the frame from static to moving; and r.) assigning all frame slices of the frame as refresh slices when the change in status is detected. The step of quantizing can comprise the step of: s.) modifying an amount of quantization based on available bandwidth for transmitting. According to an exemplary embodiment of the third aspect, the network packets can comprise Ethernet packets. The step of transmitting can comprise the steps of: t.) receiving network statistic information associated with transmission of the network packets; and u.) modifying a transmission rate of the network packets based on the received network statistic information. [0020] According to a fourth aspect of the present invention, a method of receiving multimedia information transmitted via a network includes the steps of: a.) extracting compressed multimedia information from network packets received via the network; b.) inverse variable length coding the extracted compressed multimedia information to generate quantized frequency domain components of frame slices of a frame of multimedia information; c.) inverse quantizing the quantized frequency domain components of the frame slices to generate frequency domain components of the frame slices; d.) inverse transforming the frequency domain components of the frames slices to generate a plurality of frame slices; e.) combining the plurality of frame slices to form the frame of multimedia information; f.) converting the frame from a first color space to a second color space, wherein each component of the second color space is formed as a weighted combination of components of the first color space; and g.) displaying the converted frame on a display device. [0021] According to the fourth aspect, the step of combining can comprise the step of: h.) replacing missing frame slices of the plurality of frame slices using corresponding frame slices from a previous frame. Frequency domain components of the frame slices can be inverse transformed into the plurality of frame slices using an inverse discrete cosine transform. The first color space can comprise a luminance and chrominance (YUV) color space, and the second color space can comprise a red, green, blue (RGB) color space. The method can include the step of: i.) adding porches surrounding an active portion of the frame. [0022] A system and method are disclosed for communicating multimedia information. Exemplary embodiments provide a Video-to-Data (V 2 D) element that can be used over private and/or public transmission networks. The V 2 D elements can transfer multimedia information in, for example, Ethernet, IP, ATM, SONET/SDH or DS3 frame formats over Gigabit Ethernet, Fast Ethernet, Ethernet, IP networks, as well as optical carrier networks and ATM networks. The V 2 D elements can use optimized video compression techniques to transmit high-resolution mono and stereoscopic images and other multimedia information through the network with high efficiency, high accuracy and low latency. The V 2 D elements can interface with a visualization graphics server on one side and a network on the other. A plurality of multimedia visualization centers can be coupled to the network. Each multimedia visualization center can include, for example: (i) a V 2 D element that transmits and/or receives compressed multimedia information; and (ii) multimedia presentation equipment suitable for displaying multimedia information, such as video and audio. BRIEF DESCRIPTION OF THE DRAWINGS [0023] Other objects and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments, in conjunction with the accompanying drawings, wherein like reference numerals have been used to designate like elements, and wherein: [0024] FIG. 1 is a diagram illustrating a multimedia immersive visualization system connected by Video-to-Data (V 2 D) elements, in accordance with an exemplary embodiment of the present invention. [0025] FIG. 2 is a flowchart illustrating steps for transmitting and receiving multimedia information through the network 125 , in accordance with an exemplary embodiment of the present invention. [0026] FIG. 3 is a diagram illustrating an external interface of a V 2 D transmitter, in accordance with an exemplary embodiment of the present invention. [0027] FIG. 4 is a diagram illustrating an external interface of a V 2 D Receiver, in accordance with an exemplary embodiment of the present invention. [0028] FIG. 5 is a data flow diagram and interface specification of a V 2 D transmitter, in accordance with an exemplary embodiment of the present invention. [0029] FIG. 6 is a data flow diagram and interface specification of a V 2 D receiver, in accordance with an exemplary embodiment of the present invention. [0030] FIG. 7 is a flowchart illustrating the steps performed by the V 2 D transmitter compression module, in accordance with an exemplary embodiment of the present invention. [0031] FIG. 8 is a flowchart illustrating the steps performed by the V 2 D receiver uncompression module, in accordance with an exemplary embodiment of the present invention. [0032] FIG. 9A is an illustration of a format of a video frame as constructed and transmitted using variable-length coding, in accordance with an exemplary embodiment of the present invention. [0033] FIG. 9B is an illustration of a format of a video slices within a video frame as constructed and transmitted using variable-length coding, in accordance with an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0034] A system and method are disclosed for compressing high bandwidth multimedia information for transmission over low bandwidth networks. As used herein, “multimedia information” can include any suitable type of audio, video and other data that can be transmitted over a network. Exemplary embodiments of the present invention provide Video-to-Data (V 2 D) elements that can be used over private and/or public networks and can transfer multimedia information in, for example, Ethernet, DS3, or SONET/SDH frame formats or the like. The V 2 D elements according to exemplary embodiments include a transmitter, referred to as a V 2 D transmitter. The V 2 D elements can also include a receiver, that can either be a hardware-based device, referred to as a V 2 D receiver, or a software-based device, referred to as a V 2 D client. The V 2 D elements can use algorithms to reduce the bandwidth of high-resolution mono and stereoscopic images and other multimedia information efficiently with minimal visual artifacts. The V 2 D elements can be placed in a public and/or private network that offers, for example, an end-to-end 10/100 Base-T Ethernet circuit or the like. [0035] The V 2 D elements can interface with a visualization graphics server on one side and an information transmission network (e.g., copper-based, optical, a combination of such, or the like) on the other. The V 2 D elements provide a means for transmitting and receiving high-quality multimedia information at sub-gigabit rates using optimized video compression techniques. The embodiments presented herein can be applied to any suitable network, such as, for example, SONET/SDH, Gigabit Ethernet, Fast Ethernet, Ethernet, ATM, (routed) IP networks and the like. As used herein, the term “network” applies to any such suitable network. [0036] According to exemplary embodiments, compressed multimedia information can be transferred between the V 2 D elements, such as between a V 2 D transmitter and a V 2 D receiver or between a V 2 D transmitter and a V 2 D client. The V 2 D transmitter can be located at one end of a network line and the V 2 D receiver or client can be located at the other end. Compressed multimedia information can be transferred between a V 2 D transmitter and multiple V 2 D receivers or clients (referred to as multicast or broadcast). For example, the V 2 D transmitter can located at one end of the network, while the V 2 D receivers or clients are located at different locations throughout the network. Because the software-based V 2 D client may not be able to process computations as fast as the hardware-based V 2 D receiver can, exemplary embodiments can have dual video streams out of the V 2 D transmitter, one a high-bandwidth video stream for the hardware-based V 2 D receiver and the other a low-bandwidth video stream for the software-based V 2 D client. [0037] According to the present invention, sub-gigabit transmission of high resolution, high frame-rate stereo multimedia information can be achieved using multiple optimized compression techniques. These compression techniques can include, for example, frame dropping, color space conversion with chrominance sub-sampling in the horizontal direction, discrete cosine transformation followed by intelligent frame differencing that can include slice dropping, followed by quantization, and variable length coding. [0038] Exemplary embodiments can slice each frame horizontally and/or vertically into smaller portions called “video slices.” These video slices from a left/right frame can then be compared with preceding video slices of the corresponding sections of the left/right frame. For example, if the difference between the compared video slices is within the configured system interface electronic noise levels, the video slice can be dropped and not transmitted. However, if the difference is large enough, the video slice can be further compressed and transmitted. [0039] Frame dropping should not create any visual distortions. According to an exemplary embodiment, when a left frame of a stereo video is dropped, the corresponding right frame can also be dropped. A rate-control algorithm can ensure that left and right frames of stereo video are dropped uniformly and that the concomitant compression parameters are altered to the same extent so that the frames are similarly compressed, so that there are no visual artifacts in a 3-D video. [0040] Exemplary embodiments of the present invention can employ slice dropping based on slice comparison, and can include an intelligent slice dropping technique referred to as “signature-based slice dropping.” In signature-based slice dropping, redundant video slices are dropped through the computation of feature vectors that describe the video slice. Examples of such feature vectors include the DCT coefficients of blocks in a video slice and the like. [0041] Exemplary embodiments can use a band-pass filter to filter out the contribution due to noise introduced by an analog-to-digital converter and other interface circuits for the purposes of intelligent frame differencing and intelligent slice dropping. Such filtering can be performed in the frequency domain of the pixel data after the DCT calculation has been performed in the compression algorithm. The filter parameters can be user-settable. According to exemplary embodiments, on applications that require lossless transmission of video, the compression logic in the V 2 D elements can be bypassed by the use of, for example, a selector multiplexer. Exemplary embodiments can handle transmission losses inherent to networks such as, for example, IP networks, through a periodic slice refresh (R-Slice) mechanism in which lost or corrupted I-slices can be replaced at set periodic intervals by R-Slices. [0042] Exemplary embodiments can perform chrominance sub-sampling in the horizontal direction. Such a methodology is referred to as 4:2:2 sub-sampling. However, some applications require that no chrominance information is lost. For such applications, exemplary embodiments can provide a 4:4:4 sampling mode whereby the color information not sent in the I-slices can be sent in R-Slices. The V 2 D receiver can receive color information for odd and even horizontal pixels in alternating R-Slices, and assimilate the information to reconstruct complete color information on the display side. The sub-sampling method can also be bypassed using a selector multiplexer and all the luminance and chrominance information can be preserved for further processing. [0043] According to an exemplary embodiment, a technique referred to as “dual compression” can be used, where moving parts and static parts of an image can be compressed using different compression parameters. The present invention can detect small movements and consider those small movements as static parts of the screen for the purposes of using static compression parameters in a dual compression environment. According to another exemplary embodiment, a software control algorithm can be used to keep track of moving parts of the image to detect a change in status from large movements to small or no movements. Such an algorithm can also force a burst of refresh slices (R-Slices) with better compression parameters for the purpose of replacing all of the highly compressed parts of the image previously sent with better quality slices. According to an exemplary embodiment, the output video frame buffer size can be optimized to hold approximately one video frame. Data can be extracted from this buffer to be sent over, for example, a 10/100 base-T IP network or the like at a configured average rate. Furthermore, the rate at which data is transmitted over the transmission network can be controlled. If the rate at which data is generated after compression exceeds the configured average rate, then a rate control algorithm can begin to drop input video frames. Exemplary embodiments can also allow for an occasional burst of data on top of the configured average rate on the network as configured by, for example, the system or network administrator. [0044] According to exemplary embodiments, network quality of service can be monitored on the V 2 D receiver end or on the V 2 D client end by means of counting dropped and/or corrupted video data due to network congestion. Statistical information can then be passed in the reverse channel back to the V 2 D transmitter. The V 2 D transmitter can use the statistical information to automatically rate control the amount of video data sent over the network. [0045] According to exemplary embodiments, the connection setup between the V 2 D transmitter and the V 2 D receiver or V 2 D client can be performed using a connection setup environment including a connection server, a connection client and a connection console to provide flexibility in controlling the connection set-ups and switching. A database of connection authorizations can be maintained, wherein a V 2 D receiver or a V 2 D client can be allowed to connect or prevented from connecting to a V 2 D transmitter based on, for example, permissions set by the system or network administrator. Alternatively, network and compression parameters can be pre-assigned for use by the V 2 D elements during a connection set-up. [0046] According to an exemplary embodiment, the audio that is associated with the video can be synchronized to the video data at the receiving end, such as by buffering the audio data at the V 2 D transmitter and transmitting the buffered audio data periodically at, for example, the end of every video frame. [0047] According to a further exemplary embodiment, the phase of the sampling pixel clock can be automatically adjusted to minimize the noise contribution due to an incorrect sampling phase of the pixel clock used by the analog-to-digital converter to digitize analog pixel data. Phase adjustment of the pixel clock can be performed by, for example, incrementing or decrementing the phase of the pixel clock within the bounds of the analog-to-digital converter and determining the phase at which the least number of I-Slices are transmitted for the static portions of the screen. [0048] These and other aspects of the present invention will now be described in greater detail. FIG. 1 is a diagram illustrating a multimedia immersive visualization system 100 connected by V 2 D elements, in accordance with an exemplary embodiment of the present invention. FIG. 1 illustrates an end-to-end system deployment scenario with multiple sites connected over an information transmission network. These sites can collaborate interactively in an immersive environment supported by the V 2 D elements, according to exemplary embodiments of the present invention. [0049] In FIG. 1 , the V 2 D elements can include a V 2 D transmitter 105 , a V 2 D receiver 110 , and a V 2 D client 115 . The V 2 D transmitter 105 can be connected to a network 125 for switching and transport of information signals between one or more V 2 D transmitters 105 , and one or more V 2 D receivers 110 and V 2 D clients 115 . Multimedia displays 101 can be connected to the V 2 D receiver 110 and the V 2 D client 115 , such that there can be one or more multimedia displays for each V 2 D receiver 110 and the V 2 D client 115 . Any number of sites can be configured for use in the system 100 , with each site using any type of data or optical networking elements. In the network 125 , appropriate transmission circuits (e.g., Ethernet, IP, ATM, DS3, OC-3, OC-12, OC-48, OC-192, and the like) can be provisioned to the destination sites. [0050] For purposes of illustration and not limitation, in a unicast configuration, site A can be in communication with site B using the network 125 . Site A can be in communication with site C or to site D, but not both site C and site D concurrently, using the network 125 . Additionally or alternatively, the network 125 can be bypassed, and site A can be in direct communication with site B, or site A can be in direct communication with site C, or site A can be in direct communication with site D using suitable network transmission elements (e.g., a cross over cable). Other configurations of the system 100 are possible. [0051] For purposes of illustration and not limitation, in a broadcast or multicast configuration, site A can be in communication with site B, site C and site D or other multiple sites concurrently by using suitable network multicast and/or broadcast methods and protocols. [0052] FIG. 2 is a flowchart illustrating steps for transmitting and receiving multimedia information through the network 125 , in accordance with an exemplary embodiment of the present invention. Thus, FIG. 2 illustrates the steps for transmission and reception of multimedia information in an end-to-end system, from when data is transmitted by a V 2 D transmitter 105 on the transmit side, to when it is decoded and displayed by the V 2 D receiver 110 or V 2 D client 115 on the receive side. In step 200 , a determination can be made as to whether the multimedia information to be transmitted is in digital format or analog format. If the multimedia information is in analog format, then in step 201 , the analog multimedia information can be converted to corresponding digital multimedia information using, for example, an analog-to-digital converter (ADC) or the like. In step 202 , the digital multimedia information can be compressed. In step 203 , the compressed multimedia information can be encoded into, for example, Ethernet frames or the like with appropriate destination addresses. In step 204 , the Ethernet frames can be transmitted over the network. [0053] In step 205 , the Ethernet frames can be received from the network. In step 206 , the compressed multimedia information that was encoded into the Ethernet frames can be decoded from the Ethernet frames. In step 207 , the decoded multimedia information can be uncompressed. In step 208 , the uncompressed multimedia information can be formatted into digital video interface (DVI) output and/or analog video format, using, for example, a digital-to-analog converter (DAC). In step 209 , the decoded and uncompressed multimedia information can be presented using any suitable type of multimedia presentation equipment. [0054] The V 2 D elements according to exemplary embodiments can support any suitable number of combinations of resolution and refresh rates. The V 2 D elements can be configurable to allow a user to select from a range of resolutions including, but not limited to, VGA, XGA (1024×768), SXGA (1280×1024) and UXGA (2048×1536) and the like. Similarly, the refresh rates can be selected from, for example, approximately 30 Hz to approximately 120 Hz or higher. In addition, the system 100 can be used to provide for RG S B (sync on green), RGBS (composite sync), RGBHV (separate sync) or the like. [0055] FIG. 3 is a diagram illustrating an external interface 300 of a V 2 D transmitter 105 , in accordance with an exemplary embodiment of the present invention. The V 2 D transmitter 105 can transmit, for example, Ethernet packets or the like containing multimedia information, using a bi-directional port 325 . As shown in FIG. 3 , the external interface 300 can include one channel of input analog video 305 with three input colors red 306 , green 307 and blue 308 , along with input video synchronization signals HSYNC 341 and VSYNC 342 . The external interface 300 can also include one channel of input Digital Video Interface (DVI) 360 . In addition, the external interface 300 can include an input left/right sync pulse 343 that can be used for stereo video. The external interface 300 can include one channel of input stereo audio 315 , including input left and right audio channels 316 and 317 , respectively. The external interface 300 can include one channel of output stereo audio 320 , including output left and right audio channels 321 and 322 , respectively. The external interface 300 can also include one bi-directional RS-232 serial port 335 . The external interface 300 can also include one channel of output keyboard data 386 and one channel of output mouse data 388 . The external interface 300 can include one input power supply 392 of 110V or 220V, auto-switchable. Other configurations of the external interface 300 are possible, according to exemplary embodiments. [0056] FIG. 4 is a diagram illustrating an external interface 400 of a V 2 D receiver 110 , in accordance with an exemplary embodiment of the present invention. The V 2 D receiver 110 can receive, for example, Ethernet packets containing multimedia information, using a bi-directional port 425 . As shown in FIG. 4 , the external interface 400 can include a output channel of analog video 410 with three output colors red 406 , green 407 and blue 408 along with horizontal 446 and vertical synchronization 447 pulses. The external interface 400 can include one channel of output DVI 460 . In addition, the external interface 400 can include an output for left/right synchronization pulse 449 that can be used to drive, for example, stereographic emitters for stereo video. The external interface 400 can include one channel of input stereo audio 415 , including left and right input audio channels 416 and 417 , respectively. The external interface 400 can include one channel of output stereo audio 420 , including left and right output audio channels 421 and 422 , respectively. The external interface 400 can include one bi-directional RS-232 serial port 435 . The external interface 400 can include a pair of input Genlock and output Genlock channels 450 and 451 , respectively. The external interface 400 can also include one channel of input keyboard data 482 and one channel of input mouse data 484 . The external interface 400 can include one input power supply 492 of 110V or 220V, auto-switchable. Other configurations of external interface 400 are possible, according to exemplary embodiments. [0057] FIG. 5 is a data flow diagram and interface specification of the V 2 D transmitter 500 , in accordance with an exemplary embodiment of the present invention. A high-definition analog video input 510 , with an option of, for example, stereoscopic video, can be sent to an Analog-to-Digital Converter (ADC) 530 . The ADC 530 converts analog video into digital format. For digital video input 505 , the ADC 530 can be bypassed. The digital video can be compressed using the video compression encoder 540 associated with the ASIC/FPGA 598 . The compressed video can be combined with an associated stereo audio input 515 , which can also be converted into digital format using ADC 530 , if the audio is in analog format. The combination of high-resolution video and audio can form the multimedia information. The control of keyboard data 520 and mouse data 525 for the local computer (i.e., on the V 2 D transmitter end) can be transferred from the remote V 2 D receiver end to enable remote users to control the local computer. The V 2 D transmitter 500 can act as, for example, a PS/2 device emulator 535 to the computer connected to it. The compressed video and audio can be multiplexed together in the ASIC/FPGA 598 to form the multimedia information stream. The multimedia information stream can be transferred to the single board computer (SBC) 550 over the Peripheral Control Interface (PCI) 545 . The SBC 550 can construct Ethernet frames and transfer those Ethernet frames to the remote receiver end via, for example, an Ethernet network. The SBC 550 can transmit Ethernet frames containing multimedia information based on the average and burst transmission rates configured by the system administrator and on rate limits on the data transfer between the ASIC/FPGA 598 and the SBC 550 over the PCI bus 545 . The rate limitation algorithm defines the number of frames processed and transmitted per second. [0058] FIG. 6 is a data flow diagram and interface specification of the V 2 D receiver 600 , in accordance with an exemplary embodiment of the present invention. The single board computer 650 can receive Ethernet frames transmitted by a V 2 D transmitter and can transfer those frames to the ASIC/FPGA 698 over the PCI interface 645 . The ASIC/FPGA 698 then de-multiplexes the multimedia information stream to form compressed video and audio outputs. The compressed video output is then uncompressed using the video decoder codec 640 associated with the ASIC/FPGA 698 . The uncompressed video and audio data are then converted back to the original analog format using a Digital-to-Analog Converter (DAC) 630 . The analog video and audio data are then sent out as analog video signal 610 and analog audio signal 615 . The uncompressed digital video can also be sent out in DVI format 605 . The V 2 D receiver 600 can act as a computer (e.g., PS/2 or the like) host emulator 635 to the keyboard 620 and mouse 625 connected to it, and can encode the keyboard strokes and mouse movements into packets. The keyboard and mouse movement packets can be communicated back to the V 2 D transmitter 500 to control the keyboard and mouse of the remote computer. [0059] Two parameters that can be used for configuring the V 2 D transmitter are the refresh rate and resolution. The refresh rate is the rate at which a new screen is projected on a monitor's CRT screen, expressed in Hertz, and is reflected in the frequency of the VSYNC (vertical synchronization) signal, that comes directly from any standard video card. [0060] The format of a screen is determined using HSYNC and VSYNC pulses. HSYNC denotes when a new line of pixels is to be projected onto a monitor's CRT screen. When a VSYNC pulse arrives, the monitor starts at the top of the screen, and when an HSYNC pulse arrives, the monitor starts at the beginning of a new line. Using a counter that runs off a known clock with fixed frequency (e.g., 38.88 MHz), the number of clock cycles between rising edges of VSYNC is measured to determine the refresh rate. The number of HSYNC pulses between VSYNC pulses is counted to determine the number of vertical lines in the video. In addition, the width of the VSYNC pulse is determined by counting the number of clock cycles between the rising and falling edges of the VSYNC pulse. Finally, a counter counts the time between HSYNC pulses to determine the frequency of the HSYNC pulses. [0061] Using information obtained from the refresh rate, the frequency of HSYNC pulses, the number of vertical lines in a video and the VSYNC pulse width, a matching entry can be found in a user-configured video look-up table that can be stored on, for example, the V 2 D transmitter. The look-up table can include other information needed to configure the V 2 D transmitter, such as, for example, pixel clock, number of pixels in a horizontal line of video, active horizontal pixels, active vertical pixels, horizontal front porch, horizontal back porch, vertical front porch, vertical back porch and the like. [0062] Various techniques can be used for reducing the required bandwidth for high resolution and high refresh rate multimedia information. Details of several of these techniques are described in, for example, “Video Demystified: A Handbook for the Digital Engineer,” by Keith Jack, pages 219, 311-312 and 519-556. Some of these techniques include, for example: RGB color depth reduction; RGB-to-YUV and YUV-to-RGB conversions; frame dropping, where the image is displayed at the same rate as the original, but transmission rate is reduced by not transmitting all the frames, motion estimation based on commercially available cores such as MPEG2, MPEG4, H.26× and the like; discrete cosine transformation; quantization; and variable length coding. However, other techniques can be used to reduce the required bandwidth for high resolution and high refresh rate multimedia information. [0063] FIG. 7 is a flowchart illustrating the steps performed by the V 2 D transmitter compression module, in accordance with an exemplary embodiment of the present invention. In sum, based on input from the rate control mechanism, a determination is made as to whether to process the current frame, or to discard the frame and wait for the next frame. Once a frame is taken up for encoding, it is converted to the YUV color space from the RGB color space. The frame is sliced into small parts and each color component is then converted into frequency domain through the discrete cosine transformation (DCT). The DCT components are then compared to the corresponding values of the previous frame to get a difference result. The difference result is then compared against user set thresholds to determine if the slice has to be further processed as an I-Slice. In addition, a decision is also made as to whether to force send the slice as a refresh slice (R-Slice). If the decision algorithm results in sending the slice as an I-Slice or an R-Slice, quantization is performed on the original DCT coefficients. If the decision algorithm results in not sending the slice as an I-Slice or an R-Slice, the slice is discarded and not processed any further. The choice of quantizer could be set either by the user, or through the automatic rate control mechanism. The outputs of the quantizer are variable length encoded and are transferred from the ASIC/FPGA memory into the processor memory by, for example, Direct Memory Access (DMA). The processor can then pack the compressed data into Ethernet frames and transmit those frames on the transmission network. [0064] More particularly, in step 701 , the start of a video frame is detected. In step 702 , a determination is made as to whether there is enough space to fit one video frame in the input frame buffer. If there is not enough space in the input frame buffer, then in step 703 , a determination is made as to whether the input video is in stereo format. If not in stereo format, then in step 704 , one complete frame is discarded for mono video, otherwise, in step 705 , two complete frames, both left and right eye pair, are discarded for the stereo video. If there is enough space in the input frame buffer, or after video frames have been discarded, then in step 706 , the porches surrounding the active area of the video are discarded. In step 707 , only active portions of the video are written into the input frame buffer, resulting in a compression factor of, for example, 40% or more depending on the format of the video. [0065] In step 708 , data in the input frame buffer is transformed into a color space in which the properties of the human visual system can be exploited. For example, the Red (R), Green (G) and Blue (B) components (RGB) of the video samples can be converted to Luminance (Y) and Chrominance (UV) samples (YUV). Such a conversion can be considered a linear transform. Each of the YUV components can be formed as a weighted combination of R, G and B values: The equations that can be used in the transform are, for example, given in Equations (1): Y =0.257 R+ 0.504 G+ 0.098 B+ 16 U =−0.148 R −0.291 G+ 0.439 B+ 128 V =0.439 R− 0.368 G− 0.071 B+ 128 For finite precision implementation, the coefficients used in Equations (1) can be approximated to rational fractions, with the denominator being the power of two that correspond to the required precision. For example, 0.257 can be approximated as 16843/65536 for a 16-bit implementation. However, other color transformation equations can be used, along with other coefficients, depending on the nature and type of video content being processed, the hardware specifications of the system, and the like. [0067] Based on the nature of the content of the video, the chrominance can be sub-sampled in the horizontal and vertical directions. For natural images, such sub-sampling can work well, since the color gradients are small. For images created by visualization systems, the color transitions are much more pronounced and the color information should be preserved as close to the original as possible. For this reason, the V 2 D transmitter according to exemplary embodiments can perform sub-sampling in step 708 of chrominance in the horizontal direction for the purpose of compression (4:2:2), or not at all (4:4:4). [0068] In step 709 , the video frame can be divided into smaller segments, known as “slices.” The size of the slice can be chosen based on, for example, the video resolution, so that the number of slices in a video frame is an integer and not a fraction. The size of a slice can be chosen to be between, for example, 8 and 128 blocks, inclusive, for optimal performance, where each block can be comprised of, for example, and 8×8 pixel data block. However, a slice can be any desired size, depending on the nature of the application and the like. [0069] In step 710 , using a discrete cosine transform (DCT), an 8×8 pixel data block of chrominance and luminance can be transformed into an 8×8 block of frequency coefficients using the following Equation (2): F ⁡ ( u , υ ) = C u 2 ⁢ C υ 2 ⁢ ∑ y = 0 7 ⁢ ∑ x = 0 7 ⁢ f ⁡ ( x , y ) ⁢ cos ⁡ [ ( 2 ⁢ x + 1 ) ⁢ u ⁢   ⁢ π 16 ] ⁢ cos ⁡ [ ( 2 ⁢ y + 1 ) ⁢ υπ 16 ] ⁢ ⁢ with ⁢ : ⁢ ⁢ C u = { 1 2 if ⁢   ⁢ u = 0 , 1 if ⁢   ⁢ u > 0 ;   ⁢ C υ = { 1 2 if ⁢   ⁢ v = 0 , 1 if ⁢   ⁢ v > 0 ( 2 ) In Equation (2), f(x,y) represent the samples of the Y, U or V block, and F(u,v) represents the DCT coefficient corresponding to each of those samples. [0071] After performing a DCT on a complete slice, in step 711 , frame differencing is performed. More particularly, the resulting values from the DCT are subtracted from the determined values from the DCT of the corresponding slice from the previous frame that are stored in a previous input frame buffer, with the previous frame being provided by step 712 . Additionally in step 712 , the results of the current DCT values of the slice are written into the corresponding slice location of the previous frame buffer for frame differencing operation on the next frame. In step 713 , the outputs of the differences (referred to as difference DCT values) between the slice of current frame and the corresponding slice of the previous frame are compared against user-defined noise filter parameters to eliminate the effects of any noise contribution due to cables or electronic components, such as, for example, ADCs and the like. Difference DCT values are used for the purpose of frame differencing. [0072] According to exemplary embodiments, DCT frequency components contributed by electronic and cable noise are filtered out for the purposes of frame differencing, as described previously. The filtering is performed by sending the difference DCT values through, for example, a band-pass filter. The low frequency components of an 8×8 pixel data block can reside in the upper left portion of the 64-value matrix, while the high frequency values can reside in the lower right portion of the 64-value matrix. By choosing the appropriate band-pass filter parameter values, the noise contributed to these 64 difference DCT values of the 8×8 pixel block can be zeroed by dividing the low frequency and high frequency difference DCT values with the corresponding low frequency and high frequency filter parameters and truncating the results to the nearest integer. If after this division, all the 64 values become zero, a decision can be made that the block that is being compared to the previous frame is the same as the previous frame. If all of the blocks in a slice are the same as the blocks in the slice of the previous frame, the slice is considered substantially identical to the previous frame. [0073] The ADC can sample the analog data using a clock that is substantially identical to the pixel clock frequency at which the video is generated by a video source, such as, for example, a graphics card inside a computer. The pixel clock can be generated by, for example, multiplying the HSYNC signal by a known integer value. The phase of the sampling pixel clock must be aligned to the data that is being sampled. According to exemplary embodiments, an automatic phase adjustment of the sampling pixel clock can be provided to the user through a user menu. The automatic phase adjustment can be performed by, for example, monitoring the number of slices transmitted as I-Slices, while incrementing or decrementing the phase of the sampling clock in small increments. An incorrect sampling phase may incorrectly generate more I-Slices in the static parts of the video frame, while a correct sampling phase would ideally generate zero I-Slices in the static parts of the video frame. The phase of the sampling pixel clock at which the least number of slices is sent is chosen as the “correct” sampling phase. The correct sampling phase can then be used to sample all of the incoming pixels by the ADC. [0074] In step 714 , if a determination is made to not send the slice as an I-Slice, because the slice is the same as the previous slice, a decision is made whether to send the slice as a periodic update refresh slice (R-Slice). R-Slices can be sent in a round robin method, where sets of slices are selected and marked as R-Slices. For example, a slice counter can keep track of which slices should be sent out as R-Slices. The slice counter can be incremented each time a new frame is sent, and can roll to zero when all slices in a frame are sent out as R-Slices, thereby beginning counting again. The amount of increment at which the counter updates determines the number of slices to be sent out as R-Slices in each frame. For example, if the counter increments by one every new frame, one R-Slice is sent out every frame. However, if the counter increments by five every new frame, five R-Slices are sent out each frame. The number by which the counter increments can be user programmable. Consequently, all the parts of the frame can be updated periodically and continuously. [0075] In step 714 , if a determination is made to not send the slice as either an I-Slice or an R-Slice, the slice can be discarded in step 726 and no further processing is performed. Since, in general, most portions of the video can be static between frames, discarding redundant static parts and updating those parts of video that are changing from one frame to the next can result in greater amounts of video compression. For example, small movements based on user-defined block thresholds supplied by step 716 can be considered static. In step 715 , when it is detected that the video content has changed status from moving to static, such information can be provided to step 714 to send, for example, all slices in one frame as R-Slices (e.g., using ASIC/FPGA 598 ). [0076] A slice difference counter can keep track of how many slices in a frame are sent out as I-Slices. These slices contain moving parts of the image and are different from the corresponding slices of the image in the preceding frame. The slice difference counter increments each time there is a new I-slice in the frame. The difference counter can be reset to zero at the start of a new frame. When the value of the difference counter transitions from a high value to a low value, as defined by user settable parameters, R-Slices can be forced for a complete frame. The difference counter does not increment when the number of changed blocks (e.g., 8×8 pixels) that are contained in a slice are less than a block threshold parameter defined by the user in, for example, the user-settable parameters. This ensures that small movements in a video, for example, mouse movements, do not trigger the “Force All Slices in One Frame” determination provided by step 715 . [0077] The original DCT values of I-Slices and R-Slices computed in step 710 can be further processed in step 717 through quantization. There are two components to quantization. First, the human visual system is more sensitive to low frequency DCT coefficients than high frequency DCT coefficients. Therefore, the higher frequency coefficients can be divided with larger numbers than the lower frequency coefficients, resulting in several values being truncated to zero. The table of, for example, 64 values that can be used for dividing the corresponding 64 DCT frequency components in an 8×8 block, according to an exemplary embodiment, can be referred to as quantizer table, although the quantizer table can be of any suitable size or dimension. The second component to quantization is the quantizer scale. The quantizer scale is used to divide all of the, for example, 64 DCT frequency components of an 8×8 pixel data block uniformly, resulting in control over the bit-rate. Based on the quantizer scale, the frame can consume more bits or fewer bits. [0078] According to exemplary embodiments, two different values for the quantizer scale can be used, one assigned to I-Slices and another assigned to R-Slices. In general the I-Slice quantizer scale value can be greater than or equal to the R-Slice quantizer scale value. In general, the human eye is less sensitive to changing parts of a video image compared to the static parts of the video image. The human eye sensitivity can be taken advantage of to reduce the transmission bitrate by compressing the changing parts of the video image (I-Slices) to a higher extent than the static parts of the video image (R-Slices). Compressing I-Slices to a higher extent than the R-Slices can result in better visual quality of R-Slices compared to the I-Slices. In addition, when the moving parts of the image become static, the static parts of the image can be quickly refreshed by better visual quality R-Slices, as defined by the methods described previously. According to exemplary embodiments, the same visual quality can be maintained for a reconstructed three-dimensional (3-D) image in case of stereo video. To achieve this, the quantization parameters used for I-Slices and R-Slices for both left and right frames of stereo video can be kept substantially identical. [0079] The V 2 D transmitter can utilize a quantizer table with values that are powers of, for example, two. Similarly, the quantizer scale that divides all of the 64 values in a block can use values that are power of, for example, two. By rounding the values of the quantizer table and the values of quantizer scale to powers of two, the need for dividers and multipliers in the quantizer module can be eliminated, thereby greatly speeding up the module and reducing hardware complexity. Consequently, divisions can be achieved by right shifting the DCT results, while multiplications can be achieved by left shifting the DCT results. [0080] In step 721 , a variable-length coding (VLC) scheme can be used to encode the multimedia information. Based on probability functions, VLC schemes use the shortest code for the most frequently occurring symbol, which can result in maximum data compression. Each video frame can be constructed and transmitted by the VLC scheme in step 721 in the format illustrated in FIG. 9A , in accordance with an exemplary embodiment of the present invention. In FIG. 9A , the “start of frame code” and “end of frame code” words uniquely identify the frame as left frame or right frame in the case of a stereo video. In the case of a mono video, all frames can be formatted as left frames. [0081] Video Slices within a video frame can be constructed by the VLC in step 721 in the format illustrated in FIG. 9B , in accordance with an exemplary embodiment of the present invention. The “start of slice code” can have, for example, the following information that uniquely identifies the slice properties: (a) Slice number: The sequential slice number that identifies the part of the video frame to which the slice belongs; (b) Stereo Properties: A bit that represents whether the slice belongs to a left frame or a right frame; (c) I-Slice/R-Slice: A bit that represents whether the slice is an I-Slice or an R-Slice; (d) Quantization Parameters: A byte that represents the quantization scale values used during the process of compression. The “end of slice code” signals to the V 2 D receiver an end of slice information. The “end of slice code” can also contain the slice number, which is used by the V 2 D receiver as one of the parameters for identifying slices that are corrupted due to transmission errors. [0087] According to exemplary embodiments, the “start of frame code,” “end of frame code,” “start of slice code” and “end of slice code” are unique and do not appear in any of the compressed data. Additionally, the aforementioned code words can be uniquely identified on a 32-bit boundary for synchronization purposes at the V 2 D receiver. [0088] Video compression is inherently variable bitrate (VBR). Different frames can have different amounts of information, and, based on the differing amounts of information, the compression ratios for those frames will be different. Buffer memory known as an output frame buffer is used between the encoder and the transmission channel so that compressed video of VBR can be read out at an average constant bitrate (CBR). Therefore, the buffer size can be optimized to accommodate at least one frame to be transmitted over time at the configured CBR. If the memory buffer becomes full, a decision to either drop a frame or reduce frame quality can then made. [0089] Continuing with the flowchart of FIG. 7 , in step 722 , the compressed multimedia information is written by the VLC into the optimized output buffer. The output frame buffer can be a circular memory. When the output data rate is slower than the input data rate coming into the output frame buffer, the buffer can start to become full. When the data in the output frame buffer crosses a substantially full threshold, a signal can be sent to the input frame buffer to stop sending further multimedia information for the purposes of compression. Such a signal stops further computations and flow into the output frame buffer. Multimedia information flow from the input frame buffer into the compression blocks resumes when the remaining data in the output frame buffer crosses a lower threshold boundary and the output frame buffer can accept further data. [0090] According to exemplary embodiments, the quantization scale values of both I-Slices and R-Slices can be automatically adjusted based on the frequency at which the output frame buffer crosses the substantially full threshold. In an ideal situation where there is enough network bandwidth available for transmission of compressed video, the data in the output frame buffer should never cross the substantially full threshold. However, if the available bandwidth for transmission is not large enough to accommodate the data after compression, further data compression can be achieved by increasing the quantizer scale values provided by the auto tune compression parameters in step 719 . In other circumstances, data produced after compression might under-utilize available bandwidth for transmission. In such cases, quantizer scale values can be reduced to produce more data after compression while improving visual quality of the image. According to an exemplary embodiment, the auto tune compression parameters provided in step 719 can be overridden and bypassed, and the quantizer scale values can be set to the user-defined compression parameters in step 718 . [0091] In step 723 , the data from the output frame buffer is then transferred to the processor memory through, for example, Direct Memory Access (DMA) using a PCI bus for further processing. DMA provides for fast transfers of large sets of data between memory elements with minimal processor cycles, thereby freeing up processor cycles for other tasks. According to exemplary embodiments, the rate at which the DMA transfers are performed can be controlled. The DMA transfer rate can be controlled by a rate control algorithm. The rate control algorithm ensures that the data flowing out of the V 2 D transmitter is always within the user-specified parameters. The user-specified parameters include, for example, maximum average rate over a period of time and maximum burst rate over a short time. The user-specified maximum average rate and maximum burst rate dictate the flow of Ethernet data out of the V 2 D transmitter and into the transmission network to which it is connected. [0092] According to an exemplary embodiment, feedback can be received from the V 2 D receiver about the network characteristics or statistics, such as, for example, the number of corrupted or dropped slices over the network due to network congestion. The statistics obtained from such a feedback mechanism can be used by the rate control algorithm to either decrease or increase the transmission rate. If there are many dropped or corrupted slices over a given period of time, the rate at which compressed multimedia information is extracted out of the output frame buffer using DMA is slowly reduced in small increments until the number of error or dropped slices is reduced close to zero. Network congestion is sometimes a temporary effect and can go away over time. In cases where the data flowing out of the V 2 D transmitter is less than the user-specified maximum average rate, the rate at which the data is extracted from the output frame buffer is slowly increased in small increments back to the user-specified maximum average rate, while the feedback statistics are monitored. Sometimes, the data rate generated after compression is less than the maximum average rate set by the user. In such cases, the rate at which the Ethernet packets are transmitted can be set to the rate at which compressed multimedia information is generated. [0093] In step 724 , information that is written from the ASIC/FPGA output frame buffer into the processor memory is formatted into valid Ethernet packets, or any suitable network packet, with a destination IP address(es). The destination IP address can be set by the user in a menu interface provided by the system supporting the V 2 D transmitter. In addition, if a multicast or a broadcast option is selected in the user menu, the Ethernet packets can be transmitted using the destination broadcast/multicast group IP address(es). [0094] FIG. 8 is a flowchart illustrating the steps performed by the V 2 D receiver uncompression module, in accordance with an exemplary embodiment of the present invention. In sum, the compressed bitstream is extracted from Ethernet payloads by the processor. The processor then performs a DMA into the compression FPGA/ASIC memory. After performing inverse variable length coding, a sanity check is made to see if the received slice is valid and not corrupted due to transmission errors. If no errors are detected, an inverse quantization (IQUANT) and inverse discrete cosine transformation (IDCT) is performed. If errors are detected, the slice is discarded and no further processing is performed. Missing slices are then replaced by slices from the previous frames stored in the previous frame buffer. The resulting IDCT bit stream is then converted from YUV to RGB and then sent to a display device from the output frame buffers. [0095] More particularly, in step 801 , Ethernet packets containing compressed multimedia information are received. The compressed multimedia information is then extracted from the received Ethernet packets and is stored in the processor memory in step 802 . In step 803 , depending on the fullness of the buffer of the input DMA memory of the ASIC/FPGA, the compressed data is transferred from the processor memory to the input DMA memory using PCI DMA. [0096] In step 804 , data is pulled from the input DMA memory by Inverse Variable Length Coding (IVLC) for further processing. The IVLC scans for valid frame headers and slice headers, in addition to decoding the code words generated by the VLC in the V 2 D transmitter. According to exemplary embodiments, the left frame data can be distinguished from the right frame data by the IVLC based on the frame headers. All of the compressed data that is contained between the start of the left frame and the end of the left frame can be decoded as left frame data, while all of the data contained between the start of the right frame and the end of the right frame can be decoded as right frame data. In step 805 , the IVLC checks for any corrupted slices due to transmission errors. For example, the detection of corrupted slices can be performed using the following checks during the decoding process: (a) The total numbers of blocks within a slice that are decoded match the blocks per slice configuration; (b) The number of pixels decoded in each block of a slice is equal to 64; and (c) The slice number in the start of slice header matches the slice number in the end of slice header after all of the blocks in a slice are decoded. If any one of the above three conditions are violated, the slice is considered to be an error or corrupted slice, then in step 806 , the corrupted slice is discarded and no further processing is performed on the slice. [0101] The quantization scale values of each slice are extracted from the slice headers and are then passed to the Inverse Quantization (IQUANT) in step 807 , along with IVLC decoded data of the corresponding slice. The order of the steps used in the quantization step 717 of FIG. 7 are reversed in the IQUANT of step 807 . In step 808 , the results of the IQUANT are passed to the inverse discrete cosine transformation. [0102] The inverse discrete cosine transform (IDCT) converts the pixels back to their original spatial domain through the following Equation (3): f ⁡ ( x , y ) = ∑ u = 0 7 ⁢ ∑ υ = 0 7 ⁢ F ⁡ ( u , υ ) ⁢ C u 2 ⁢ C υ 2 ⁢ cos ⁡ [ ( 2 ⁢ x + 1 ) ⁢ u ⁢   ⁢ π 16 ] ⁢ cos ⁡ [ ( 2 ⁢ y + 1 ) ⁢ υπ 16 ] ( 3 ) In step 809 , the IDCT values are passed to a slice number sequence check, where slice numbers are checked for missing or dropped slices. If a missing slice is detected in step 809 , then in step 810 a , the corresponding slice from the previous frame in the previous frame buffer is copied and used to replace the missing slice. The missing slice can be the result of, for example, slice dropping, intelligent frame differencing or due of a corrupted slice resulting from transmission errors. In steps 810 b and 810 c , the results of a successfully-decoded IDCT slice are copied into the previous frame buffer. The previous frame buffer can store a complete frame and can update corresponding slices of the complete frame as successfully decoded IDCT values of slices are received. The slice number sequence check of step 809 ensures that all of the slices that make up a complete frame are passed on to the color space conversion. [0104] In step 811 , the color space conversion block converts the pixel color information from YUV back to the RGB domain using known algorithms. In step 812 , the RGB values are transferred into an output video frame buffer. Data from the output video frame buffer is pulled out at a constant frequency. In step 813 , the original porches that were discarded during compression by the V2D transmitter in step 706 of FIG. 7 can be added back to the active video. In step 814 , the video image data can be displayed onto a display output, such as a monitor or other suitable type of multimedia display device. [0105] According to exemplary embodiments, the look-up-table values that define the video parameters can be received by the V 2 D receiver and can be used to reconstruct the original image before displaying it onto the display output. Some of the video parameters that can used are, for example: (a) The pixel clock that determines the rate at which the data is to be extracted from the video frame buffer; (b) The refresh rate that determines the rate at which the video is to be refreshed every second onto the display output; (c) Porches information that is used to reconstruct the original video before display onto the display output; and (d) Generation of video synchronization pulses for driving the display output. [0110] It will be appreciated by those of ordinary skill in the art that the present invention can be embodied in various specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, rather than the foregoing description, and all changes that come within the meaning and range of equivalence thereof are intended to be embraced. [0111] All United States patents and applications, foreign patents, and publications discussed above are hereby incorporated herein by reference in their entireties.

A system and method are disclosed for providing immersive visualization at low bandwidth rates. The system retrieves a frame of multimedia information for transmission over a network and converts the frame from a first color space to a second color space. The system slices the frame into a plurality of frame slices and transforms each of the plurality of frame slices into a plurality of corresponding frequency domain components. The system quantizes the frequency domain components of each frame slice, when the frame slice to be processed is an intra-slice or a refresh slice, to generate quantized frequency domain components of each frame slice. The system variable-length encodes the quantized frequency domain components of each frame slice to generate compressed multimedia information associated with each frame slice. The system constructs network packets of the compressed multimedia information associated with each frame slice, and transmits the network packets via the network.

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is based upon and claims priority under 35 U.S.C. § 119(e) from U.S. Provisional Application No. 60/929,518 filed Jun. 29, 2007, entitled High Sensitivity Radiation Detector and Radiation Imaging Device, the contents of which are hereby incorporated in their entirety by reference thereto. FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT [0002] None. BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] The present invention generally relates to a micromechanical device for use within infrared imaging devices. Specifically, the invention is a micromechanical pixel including improved sensing and bending elements which separately and in combination increase the sensitivity and decrease the response time of the pixel. [0005] 2. Description of the Related Art [0006] Infrared imaging devices enable a user to view an object via the infrared band of the spectrum, which is otherwise invisible to the human eye. Infrared imaging devices are applicable to security and surveillance, firefighting, automotive safety, and industrial monitoring because the peak thermal emission of objects in such applications is centered within the infrared region. However, the high cost of infrared imaging devices remains a challenge, thereby limiting their use. [0007] The radiation detectors employed within imaging devices are either photon detectors or thermal detectors. [0008] Photon detectors produce an image when incident radiation is absorbed within a sensing material via interactions with electrons bound to lattice or impurity atoms or with free electrons. An output signal, in the form of a voltage or current change, is produced by changes in the electronic energy distribution. The materials used in photon detectors, typically HgCdTe and InSb, exhibit very high quantum efficiency in the infrared band. However, photon detectors must be cryogenically cooled, thus increasing the weight, volume, and power consumption of presently known devices. Furthermore, materials which are highly quantum efficiency are notoriously difficult to process and costly. As such, imaging devices based on photon detector technologies are limited to specialized applications within the fields of national defense and astronomy. [0009] Thermal detectors produce an image when incident radiation is absorbed by a thermally-sensitive material that alters some physical property of the material, examples including resistance or capacitance. The alteration of the physical property is typically detected by a readout integrated circuit (ROIC), which generates an output signal. Thermal detectors operate at room temperature, thus avoiding the cooling required by and complexity of photon detector devices; however, the performance of thermal detectors, as measured by their noise equivalent temperature difference (NETD), is approximately ten times less sensitive than photon detectors. The thermal sensitivity of detector materials, examples including vanadium oxide or amorphous silicon, is characteristically in the range of 2%/K to 3%/K. The bias of an interrogation pulse from a ROIC, which controls detector responsivity, is restricted to prevent self-heating of a pixel. While less costly than photon detector devices, thermal detector devices are affordable within the fields of industrial monitoring and firefighting, yet too costly for most consumer and many industrial applications. [0010] Thermal imaging devices employing passive thermal bending, composed of bi-layer micro-cantilevers for temperature and radiation sensing and electrical, capacitive, or optical readout, are described within the related arts. For example, FIG. 1 a shows an exemplary bi-layer cantilever 50 including a first layer 1 contacting and attached to a second layer 2 which are thereafter attached to a stationary support 51 . The first layer 1 has a coefficient of thermal expansion different from that of the second layer 2 . FIG. 1 b shows the same bi-layer cantilever 50 after the first layer 1 and second layer 2 are heated by infrared radiation 52 causing the bi-layer cantilever 50 to bend. This approach to thermal imaging eliminates the monolithic integration of a pixel-level ROIC, further eliminating electronic noise and simplifying device fabrication. However, the sensitivity of presently known cantilevers is poor because of their low absorption efficiency and large mass. [0011] An improved micromechanical thermal imaging device is described by Ishizuya et al. in U.S. Pat. Nos. 6,080,988, 6,339,219, 6,469,301, and 6,835,932. Referring now to FIGS. 2-4 , a micromechanical pixel 3 is shown including a sensing element 4 disposed between and separated from a pair of bending elements 5 a , 5 b adjacent to a substrate 9 . The sensing element 4 includes an optical absorption cavity 7 bounded by an absorber layer 8 and a reflector 6 which are spaced apart by and attached to a support post 29 , as shown in FIG. 3 . Each u-shaped bending element 5 a , 5 b is composed of a pair of bi-layer cantilevers 10 a , 11 a and 10 b , 11 b . Each paired arrangement of bi-layer cantilevers 10 a , 11 a and 10 b , 11 b is separated by a thermal isolation region 12 a , 12 b having a low thermal conductance. Each bi-layer cantilever 10 a , 10 b , 11 a , 11 b is composed of a high expansion layer 33 which contacts and is attached to a portion of a low expansion layer 34 , as shown in FIG. 4 , opposite of the substrate 9 . The low expansion layer 34 of the innermost bi-layer cantilevers 11 a , 11 b is attached to the sides of the absorber layer 8 , as represented in FIG. 2 . Bending elements 5 a , 5 b are attached to the substrate 9 via a pair of anchor posts 13 a , 13 b so that a gap 49 is provided between the sensing element 4 and substrate 9 and between the bending elements 5 a , 5 b and substrate 9 . The height of the gap 49 may be adjusted by making the length of the innermost bi-layer cantilevers 11 a , 11 b shorter than the outermost bi-layer cantilevers 10 a , 10 b. [0012] In the absence of infrared illumination, the outermost bi-layer cantilevers 10 a , 10 b negate the deflection of the innermost bi-layer cantilevers 11 a , 11 b , thus producing a net bending of zero so as to maintain zero tilt along the sensing element 4 , regardless of the change in ambient temperature. When illuminated via an infrared source, the optical absorption cavity 7 receives and converts infrared radiation into heat which is conducted into the innermost bi-layer cantilevers 11 a , 11 b , resulting in additional bending with respect to the outermost bi-layer cantilevers 10 a , 10 b and causing the sensing element 4 to tilt with respect to the plane of the substrate 9 . Proper function of the device in FIG. 2 requires the micromechanical pixel 3 to be backside illuminated 32 , whereby infrared radiation is transmitted through the substrate 9 . High sensitivity is achieved via an efficient, yet lightweight, sensing element 4 and thin bi-layer cantilevers 10 a , 10 b , 11 a , 11 b . However, the micromechanical pixel 3 in FIG. 2 suffers from several deficiencies, which limit sensitivity and contribute to sensor noise, including a low fill factor, poor reflector flatness, and mechanical complexity. [0013] The micromechanical pixel 3 described in FIGS. 2-4 is applicable to a variety of detectors. For example, FIG. 5 shows an exemplary optical readout device 28 described by Ishizuya et al. in U.S. Pat. No. 6,339,219 which includes an infrared lens system 15 , an infrared detection array 16 , a first lens system 19 , an aperture plate 22 , a second lens system 24 , and an imager 25 arranged in the order described. Within the front end of the apparatus, rays from a source 14 pass through the infrared lens system 15 and are thereafter directed onto the infrared detection array 16 . The infrared detection array 16 includes a focal plane array 17 composed of micromechanical pixels 18 which are mechanically responsive to the thermal loading induced by the infrared rays. Within the back end of the apparatus, micromechanical pixels 18 reflect the incident light 20 from a visible light source 23 , one example being a light emitting diode (LED), so that the reflected light 21 passes through the first lens system 19 which compresses the reflected light 21 allowing it to pass through the pinhole 53 along the aperture plate 22 . The reflected light 21 then passes through the second lens system 24 which expands the reflected light 21 so as to impinge a focal plane array 27 composed of receptor pixels 26 within the imager 25 , examples being a complementary metal oxide semiconductor (CMOS) device or charged-coupled device (CCD). Thereafter, the resultant image is communicated to a video display device. [0014] The detector in FIG. 5 employs an optical system to simultaneously measure the deflections of all micromechanical pixels 18 so as to project a visible image of spatially-varying infrared radiation directly onto a commercial-off-the-shelf visible CMOS or CCD imager. The number of receptor pixels 26 within the CMOS or CCD array is generally chosen to be more than the number of micromechanical pixels 18 . In operation, an image produced by the detector in FIG. 5 is of uniform intensity over the entire array of receptor pixels 26 when no illumination is present because of the canceling effect of the paired arrangement of bi-layer cantilevers 10 a , 11 a and 10 b , 11 b , as described above for FIGS. 2-4 . When illuminated by an infrared source, a sensing element 4 tilts within each micromechanical pixel 18 and deflects light away from the pinhole 53 , thus projecting darker receptor pixels 26 with intensities which are proportional to the radiation level. The detector effectively converts infrared radiation into intensity change at a visible or near-infrared readout wavelength. [0015] The micromechanical pixel 3 in FIG. 2 produces design related noise including: (1) noise caused by the radiative heat exchange between each pixel and its environment, referred to as background fluctuations; (2) noise caused by the dynamic heat exchange between each pixel and the substrate, referred to as thermal fluctuations; (3) noise from mechanical energy stored in the cantilever continuously exchanged with thermal energy, referred to as thermomechanical noise; and (4) noise caused by the random arrival rate of photons at the CMOS/CCD imager, referred to as shot noise. Since all noise sources are probabilistic, the total NETD for a micromechanical IR imager is equal to the square root of the sum of the squares of the contributing noise sources and is given by [0000] NETD TOT =√ {square root over ( NETD BF 2 +NETD TF 2 +NETD TM 2 +NETD SN 2 )},  (1) [0000] where the subscripts BF, TF, TM, and SN refer to the NETD due to background fluctuations, thermal fluctuations, thermomechanical noise, and shot noise, respectively. The background fluctuation NETD is given by [0000] NETD BF = 2  ( 4  f 2 + 1 ) ɛτ 0  η   P /  T  2  k B  σ   B  ( T D 5 + T B 5 ) A , ( 2 ) [0000] where f is the f-number of the lens, ε is the pixel emissivity, τ 0 is the transmission of the optics, η is the pixel absorption efficiency, dP/dT is the differential irradiance, k B is Boltzmann's constant, σ is the Stefan-Boltzmann constant, B is the thermal bandwidth, T D is the detector temperature, T B is the background temperature, and A is the active pixel area. [0016] The NETD due to thermal fluctuations is given by [0000] NETD TF = 2  ( 4  f 2 + 1 )  T D  k B  BG τ 0  η   A   P /  T , ( 3 ) [0000] where G is the thermal conductivity. [0017] The NETD due to thermomechanical noise is equal to [0000] NETD TM = 2  ( 4  f 2 + 1 )  G ητ 0  A      P /  T   ℜ  k B  T D  B kQ   ω 0 , ( 4 ) [0000] where l is the length of the bimaterial cantilever, is the pixel responsivity (defined as the change in pixel deflection angle per degree Kelvin), k is the stiffness of the cantilever, Q is the cantilever Q-factor, and ω 0 is the cantilever resonant frequency. [0018] The NETD due to shot noise is given by the expression [0000] NETD SN = ( 4  f 2 + 1 )  G ητ 0  A   P /  T   Δ   P  2  qPB ℜ c , ( 5 ) [0000] where P is the visible light power received by a CMOS/CCD pixel, ΔP is the change in light power per degree Kelvin (where ΔP∝ ), q is the elementary charge, and c is the responsivity of the CMOS/CCD imager. [0019] The dominant source contributing to the NETD in a micromechanical pixel is typically the shot noise NETD. The shot noise NETD may be lowered by increasing the responsivity or lowering the absolute shot noise. It may be appreciated, therefore, that there remains a need for further advancements and improvements, thus facilitating a micromechanical pixel with improved thermal sensitivity and response time. [0020] Accordingly, what is required is a micromechanical pixel with enhanced responsivity without adversely affecting thermal properties of the pixel. [0021] What is also required is a micromechanical pixel with enhanced thermal response time without adversely affecting the responsivity of the pixel. SUMMARY OF THE INVENTION [0022] An object of the present invention is to provide a micromechanical pixel with enhanced responsivity without adversely affecting thermal properties of the pixel. [0023] Another object of the present invention is to provide a micromechanical pixel with enhanced thermal response time without adversely affecting responsivity of the pixel. [0024] The present invention is a micromechanical device for infrared sensing with improved thermal sensitivity and thermal response time. Performance of sensing element within the micromechanical device is improved by increasing its absorption efficiency and greater control of light reflected therefrom. Performance of the bending elements within the micromechanical device is improved by increasing their sensitivity to thermal loading and isolating the sensing element and innermost bi-layer cantilever from the outermost bi-layer cantilever and substrate. The design features described below may be implemented alone or combined within a pixel, as described in the Detailed Description of the Invention. [0025] The thermal sensitivity of a micromechanical pixel is directly related to the absorption efficiency of infrared radiation within the sensing element. The distance between the reflector and absorber layer within a sensing element is typically designed to serve as a quarter-wavelength resonant cavity to enhance absorption in a specific infrared band; however, absorption peaks in both the long-wavelength infrared band (λ=8-14 μm) and mid-wavelength infrared band (λ=3-5 μm) are possible due to harmonic effects. Long and mid wavelength bands are preferred for infrared imaging because atmospheric transmission is very high within these wavelengths. Broadband infrared anti-reflection coatings, which minimize reflections in the infrared band of interest, may be applied to both the top and bottom surfaces of the substrate to maximize absorption by the sensing element. [0026] The responsivity of a micromechanical pixel is related to the contrast in intensity of light that passes through a pinhole aperture, or the intensity changes from bright to dark during pixel deflection, after the light is reflected by a reflector within a sensing element. As such, the reflector, typically a highly reflective metal including, but not limited to, aluminum and gold, must tightly focus the reflected light, thus requiring strict tolerance on the flatness of the reflector to prevent stray reflections or scattering. To achieve acceptable contrast, the radius of curvature of the reflector should be larger than approximately 2 cm. When the optical absorption cavity is disposed between the absorber layer and reflector, the reflector is freely suspended via an attachment post at the center of the reflector, as described above. To satisfy the flatness criterion, the reflector thickness must be greater than ˜0.5 μm, thus creating a large thermal mass within the pixel which slows the thermal response time. Accordingly, the reflector thickness must be decreased to minimize the thermal response time of the pixel. [0027] The sensitivity of a micromechanical pixel is related to the bending of bi-layer cantilevers in response to heat transferred from the absorber layer. As such, any increase in the bending sensitivity of the bi-layer cantilevers causes a corresponding increase in the reflected intensity contrast over same temperature change. In general terms, the bending sensitivity of a bi-layer cantilever is proportional to the difference in thermal expansion coefficients of the two constituent materials and inversely proportional to the cantilever thickness. The constituent materials composing a bi-layer cantilever include a metal having a high thermal expansion coefficient, typically aluminum or gold, and a dielectric having a low thermal expansion coefficient, typically Si 3 N 4 or SiO 2 , although other materials are possible. Accordingly, a material having a higher thermal expansion coefficient and a smaller thickness enhances the thermal sensitivity of the bending elements. [0028] The sensitivity and response time of a micromechanical pixel is related to degree of isolation offered by the thermal isolation region between the innermost bi-layer cantilevers and the outermost bi-layer cantilevers. The ideal thermal resistance within the isolation region represents a trade-off between thermal sensitivity and thermal response time. A large thermal resistance allows heat to accumulate within the pixel, which enhances thermal sensitivity, but a small thermal resistance allows heat to be more quickly removed from the pixel so as to reduce the thermal response time. Accordingly, thermal resistance within the thermal isolation region must be tailored to optimize both sensitivity and response time. [0029] The micromechanical pixel from FIG. 2 facilitates designs variations within the pixel structure so as to enhance the responsivity of the pixel without affecting the thermal properties thereof. Likewise, the thermal response time of the micromechanical pixel from FIG. 2 is characterized by the thermal time constant τ, defined by [0000] τ = C G ( 6 ) [0000] where C is the heat capacitance of the pixel. For a micromechanical pixel, the heat capacitance is the sum of all components, especially the absorber and reflector since these have by far the largest volumes. The thermal response time of a pixel is minimized by reducing its heat capacitance, either by shrinking the pixel dimensions or choosing materials with lower specific heat capacities. [0030] It will be appreciated by those skilled in the art that the description herein, including the disclosure provided by the illustrative claims section, is illustrative and explanatory of this invention, but is not intended to be restrictive thereof or limiting of the advantages, applications, and uses which can be achieved by this invention. [0031] Several exemplary advantages are noteworthy. For example, the present invention is simpler to fabricate, more robust thus enabling tighter manufacturing tolerances and higher uniformity, more responsive to thermal inputs, and more optically flat than the related arts. Furthermore, the present invention achieves a higher fill factor, higher absorption efficiency, greater bending, and greater tilt than the related arts. BRIEF DESCRIPTION OF THE DRAWINGS [0032] The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which: [0033] FIG. 1 a is perspective view of an exemplary bi-layer cantilever element composed of a layer having a high thermal expansion coefficient and a layer having a low thermal expansion coefficient. [0034] FIG. 1 b is a perspective view of the bi-layer cantilever element from FIG. 1 a showing resultant bending after the cantilever is heated by infrared radiation. [0035] FIG. 2 is a perspective view of a micromechanical pixel including a sensing element, a pair of bi-layer micro-cantilevers, and a substrate. [0036] FIG. 3 is a front elevation view of the micromechanical pixel in FIG. 2 showing arrangement of sensing element and substrate. [0037] FIG. 4 is a side elevation view of a bi-layer micro-cantilever for the micromechanical pixel in FIG. 2 showing arrangement of layers with high and low thermal expansion coefficients. [0038] FIG. 5 is a schematic diagram showing an exemplary imaging device including an array of micro-cantilever pixels within an optical readout camera and an array of receptor pixels within an imager. [0039] FIG. 6 a is a front elevation view of an embodiment of the present invention including a multi-layer reflector. [0040] FIG. 6 b is a front elevation view of an alternate embodiment of the device in FIG. 6 a wherein the sensing element is front illuminated by inverting the order of the absorber and reflector and optical readout occurs through the substrate. [0041] FIG. 7 is a front elevation view of an embodiment of the present invention showing reflector, absorber, and partially absorbing layers contacting in a layered arrangement. [0042] FIG. 8 is a front elevation view of an alternate embodiment of the device in FIG. 7 wherein the sensing element is front illuminated and having a reflective coating applied to the top surface of the substrate opposite of the partially absorbing layer so that optical readout occurs through the substrate. [0043] FIG. 9 a is a front elevation view of an alternate embodiment of the present invention wherein a readout circuit with capacitive sensor contacts the substrate opposite of an absorbing layer so as to allow the capacitive sensor to measure the gap between substrate and sensing element. [0044] FIG. 9 b is a side elevation view of a bending element showing an electrically conductive layer with low thermal conductance applied to the low expansion layer. [0045] FIG. 10 is an exemplary absorption spectrum plot for one exemplary implementation of the device in FIG. 7 . [0046] FIG. 11 is a top elevation view of an embodiment of the present invention including bending elements arranged in an opposing fashion so that they deflect in opposed directions. [0047] FIG. 12 is a side elevation view of one bending element showing arrangement of the low and high expansion layers so that the high expansion layer is disposed opposite of the substrate. [0048] FIG. 13 is a top elevation view of an alternate embodiment of the device in FIG. 11 wherein the bending elements are joined to the sensing element at its center. [0049] FIG. 14 is a top elevation view of an alternate embodiment of the device from FIG. 11 wherein the bending elements are joined to the sensing element in an offset arrangement. [0050] FIG. 15 is a top elevation view of an alternate embodiment of the device in FIG. 11 wherein one bending element is a bi-layered element and the other bending element is a single layer element. [0051] FIG. 16 is side elevation view of a bending element wherein an ultra-high expansion polymer is attached to a low-expansion dielectric. [0052] FIG. 17 is a side elevation view of a bending element wherein an ultra-high expansion polymer is attached to a high-expansion metal which is thereafter attached to a low expansion dielectric. [0053] FIG. 18 is an exemplary deflection-temperature plot for a bi-layered cantilever without and with a polymer coating. [0054] FIG. 19 a is top elevation view of an alternate embodiment of the present invention including a pair of interlocking bending elements, wherein sensing element and substrate are not shown. [0055] FIG. 19 b is a front elevation view of a micromechanical device showing the interlocking elements in FIG. 19 a disposed between a sensing element and substrate. [0056] FIGS. 20 a - 20 d are sectional views from the device in FIG. 19 a showing arrangement of high and low thermal expansion layers. [0057] FIGS. 21 a - 21 d are sectional views of alternate embodiments of the bi-layer cantilever showing various non-planar structures. DETAILED DESCRIPTION OF THE INVENTION [0058] Embodiments of the present micromechanical device 65 are described with reference to the micromechanical pixel 3 shown in FIG. 2 . However, the present invention is applicable within a wide variety of micromechanical pixels that rely on mechanical deflection in response to infrared absorption to generate an optically readable signal. [0059] Accordingly, the description of and drawing for embodiments for the present invention provided below describe and show design features of the new micromechanical device 65 without further reference to features the embodiment may have with other micromechanical devices. The embodiments described below may be fabricated via micromechanical methods and processes understood in the art. [0060] Referring now to FIG. 6 a , the sensing element 4 of a micromechanical device 65 with backside illumination 32 includes a layered reflector 35 , an optical absorption cavity 7 , and an absorber layer 8 . The layered reflector 35 is constructed to have a multi-layered structure including a pair of outer layers 36 , 38 disposed about and contacting an inner layer 37 . Outer layers 36 , 38 are composed of a highly reflective metal, examples including, but not limited to, aluminum, gold, silver, copper, chromium, nickel, platinum, tantalum, titanium, and alloys thereof, to accommodate optical readout. The inner layer 37 is composed of a MEMS compatible dielectric, examples including, but not limited to, Al 2 O 3 , HfO 2 , MgO, SiC, Si 3 N 4 , SiO 2 , TiN, and ZrO 2 . In preferred embodiments, the layered reflector 35 should be planar in extent and have a radius of curvature greater than approximately 2 cm to ensure a flatness which minimizes stray reflections and scattering. In some embodiments, the layered reflector 35 is preferred to have a thickness not more than approximately 0.5 μm to ensure flatness and thermal response time required for most applications. [0061] Outer layers 36 , 38 and inner layer 37 are typically thin films of uniform thickness. Outer layers 36 , 38 may have the same thickness so as to form a layered reflector 35 of symmetric extent or different thicknesses so as to form a layered reflector 35 of asymmetric design. Both embodiments may offset the presence of stress gradients that develop within the layered reflector 35 during fabrication of the micromechanical device 65 . [0062] Outer layers 36 , 38 and inner layer 37 are layered to form a single structure via thin-film deposition methods understood in the art. The layered reflector 35 distributes stresses more evenly throughout the thickness of the structure than a single layer element, so as to prevent warp along the layered reflector 35 . [0063] The thin film outer layers 36 , 38 and inner layer 37 may develop an intrinsic stress on the order of −300 MPa to +300 MPa during fabrication of the layered reflector 35 and the micromechanical device 65 . This stress may be reduced via a low-temperature anneal cycle at a temperature less than 400° C. Thin films having a thickness of at least 0.5 μm were also found to mitigate stress related warp; however, it is desired to minimize film thickness to minimize the heat capacity of the micromechanical device 65 . [0064] In most embodiments, it is not possible to completely remove stress gradients within the layered reflector 35 . The layered reflector 35 may be used to balance and offset stresses across the median plane of the structure to avoid stress induced warp. A layered reflector 35 with balanced internal stresses further allows the thickness thereof to be less than that of a single layer structure composed of a metal, without compromising the flatness of the element. [0065] The layered reflector 35 shown in FIG. 6 a reduces the heat capacity of a micromechanical device 65 and the thermal response thereof because the layered reflector 35 is thinner than a single layer structure and the dielectric inner layer 37 has a lower specific heat capacity than metals which typically comprise a layered reflector 35 . [0066] A partially absorbing layer 41 may be applied to the absorber layer 8 so as to maintain a high absorption efficiency within the micromechanical device 65 . The partially absorbing layer 41 is a thin-film layer, which enhances absorption within the sensing element 4 . In preferred embodiments, the thickness of the partially absorbing layer 41 is approximately 10 nm. [0067] The absorption characteristics of the partially absorbing layer 41 are directly related to the sheet resistance of the composition comprising the layer. In preferred embodiments, the partially absorbing layer 41 should be an alloy with an adjustable sheet resistance, one example being NiCr, to facilitate the optimization of absorption within a specific infrared band or for a specific pixel design. [0068] Referring again to FIG. 6 a , the substrate 9 may in some embodiments include an anti-reflection coatings 30 , 31 , examples including, but not limited to, IRX/Ge/YF 3 , IRX/Ge/BaF 2 , and IRX/Ge/ZnS which are transmissive of the infrared regions of interest, applied to the surfaces 54 a , 54 b along the top and/or bottom of the substrate 9 . Anti-reflection coatings 30 , 31 are applied via deposition methods understood within the art. The substrate 9 is likewise transmissive of infrared wavelengths of interest. [0069] Referring now to FIG. 6 b , the micromechanical device 65 is shown so as to facilitate use with applications having frontside illumination 47 . In this embodiment, absorption and reflection losses caused by the transmission of infrared radiation through the substrate 9 are avoided, thus improving the absorption of infrared light by the micromechanical device 65 and facilitating a higher responsivity. Frontside illumination 47 heats the sensing element 4 via infrared radiation. Compared to the sensing element 4 in FIG. 6 a , the sensing element 4 in FIG. 6 b is inverted so that the infrared radiation reaches the absorber layer 8 first. The optical absorption cavity 7 is situated between the partially absorbing layer 41 and reflector 35 , which may consist of only a single highly reflective metal layer or, as shown in FIG. 6 b , a layered reflector 35 . [0070] Substrate 9 materials include, but are not limited to, silicon and glass. Optical readout now occurs through the substrate 9 , necessitating the substrate 9 to be transmissive in the visible or near-infrared region. To maximize infrared absorption in the sensing element 4 , thin film coatings 30 , 31 composed of materials that are transmissive in the visible or near infrared region and reflective in the MWIR and/or LWIR regions are applied to both surfaces 54 a , 54 b of the substrate 9 ; however, the thin film coatings 30 , 31 should allow for optical readout. One exemplary thin film coating 30 , 31 is indium tin oxide (ITO). Anti-reflection coatings designed for the visible or near-infrared regions may also be applied to both surfaces 54 a , 54 b to increase transmission of the readout light. [0071] Referring now to FIG. 7 , the sensing element 4 of a micromechanical device 65 includes a reflector 6 , an absorber layer 8 , and a partially absorbing layer 41 arranged and contacting in the order described. In this embodiment, the thickness of the reflector 6 may be reduced to decrease the thermal response time of the sensing element 4 without compromising the flatness thereof. The optical absorption cavity 7 is now situated between the partially absorbing layer 41 and substrate 9 . [0072] The reflector 6 is desired to have good reflectivity and low absorptivity in the visible or near-infrared regions to facilitate optical readout. Reflector 6 materials may include, but are not limited to, aluminum, gold, silver, copper, chromium, nickel, platinum, tantalum, titanium, and alloys thereof. The thickness of the reflector 6 may be approximately 0.2 μm because it is now supported by the absorber layer 8 . In preferred embodiments, the thickness of the reflector 6 should be less than that of the absorber layer 8 , so as to minimize thermally-induced bending within the sensing element 4 . [0073] Referring again to FIG. 7 , backside illumination 32 of the micromechanical device 65 may in some embodiments require an anti-reflection coating 31 along the surface 54 b of the substrate 9 closest to the infrared source to maximize transmission. The anti-reflection coating 31 should be transmissive of the infrared regions of interest. It is not necessary to apply an anti-reflection coating to the other surface 54 a along the substrate 9 , because higher reflectivity is desired within the optical absorption cavity 7 . [0074] Referring now to FIG. 10 , the absorption spectrum is shown for an exemplary micromechanical device 65 including the structure in FIG. 7 . The micromechanical device 65 is comprised of a sensing element 4 including a partially absorbing layer 41 composed of NiCr, an absorber layer 8 composed of SiN, a reflector 6 composed of NiCr/Au, a substrate 9 composed of silicon, and an anti-reflection coating 31 composed of IRX/Ge/ZnS. The optical absorption cavity 7 is a gap or space dimensioned to form a half-wavelength resonance cavity. FIG. 10 indicates that absorption is achievable within both MWIR and LWIR bands via a single pixel design. [0075] Referring now to FIG. 8 , the sensing element 4 of the micromechanical device 65 is shown where the absorber layer 8 is in contact with the reflector 6 . In this embodiment, the optical absorption cavity 7 is situated between the partially absorbing layer 41 and substrate 9 . Frontside illumination 47 heats the sensing element 4 via infrared radiation. The combination of absorber layer 8 and reflector 6 into a single stack facilitates the 2 cm flatness requirement via a lower total thickness than otherwise achievable when the layers are separated. The lower heat capacity resulting from the lower material volume within the combined stack facilitates a quicker response time. [0076] The reflector 6 must transmit medium-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) and reflect in the visible or near-infrared regions. Exemplary materials comprising the reflector 6 include Yb 2 O 3 , Y 2 O 3 , Zr 2 O 3 , and Hf 2 O 3 . The absorber layer 8 may be composed of Al 2 O 3 , HfO 2 , MgO, SiC, Si 3 N 4 , SiO 2 , TiN, and ZrO 2 . The partially absorbing layer 41 may be composed of NiCr to enhance absorption. In some embodiments, the reflector 6 may be eliminated through careful design of the absorber layer 8 and partially absorbing layer 41 . [0077] Referring now to FIG. 9 a , the micromechanical device 65 is shown so as to facilitate use with applications having capacitive readout to detect the tilt within a sensing element 4 , rather than the optical readout as described for embodiments in FIGS. 6 a , 6 b , 7 , and 8 . The sensing element 4 contains a conductive layer 56 which contacts and is attached to an absorber layer 8 . The absorber layer 8 may be composed of materials including, but not limited to, Al 2 O 3 , HfO 2 , MgO, SiC, Si 3 N 4 , SiO 2 , TiN, and ZrO 2 . The micromechanical device 65 also contains a capacitive sensor with readout circuit 48 which resides on along one surface 54 a of the substrate 9 . The conductive layer 56 and capacitive sensor with readout circuit 48 facilitate measurements of the gap 55 between the substrate 9 and sensing element 4 , which is dependent on the intensity of infrared radiation absorbed by the pixel. [0078] The conductive layer 56 serves as one plate of a parallel-plate capacitor. The conductive layer 56 may be composed of a metal or metal alloy which is electrically conductive or a partially-absorbing metal or alloy, examples including, but not limited to, NiCr, to enhance absorption. The second plate of the parallel-plate capacitor is located within the capacitive sensor with readout circuit 48 attached to the substrate 9 using thin-film deposition methods understood in the art. The second plate may be composed of a metal or metal alloy. In this embodiment, the bending elements 5 a , 5 b also contain an electrically conductive layer 56 along its length, as represented in FIG. 9 b , to electrically connect the sensing element 4 to the readout circuit disposed along the substrate 9 . Since the thermal isolation region 12 a , 12 b along a bending element 5 a , 5 b must have low thermal conductance, the conductive layer 56 must also have low thermal conductance. Exemplary compositions for the conductive layer 56 include indium tin oxide and titanium nitride. [0079] The sensing element 4 absorbs infrared radiation deflecting the sensing element 4 and decreasing the distance between the two parallel plates, thereby altering the capacitance in the parallel-plate capacitor. The capacitive sensor with readout circuit 48 measures the resultant gap 55 . In this embodiment, the bi-layer cantilevers 10 a , 10 b , 11 a , 11 b provide automatic compensation to changes in ambient temperature. The present embodiment eliminates shot noise which is common to optical readout devices. [0080] Referring now to FIG. 11 , a micromechanical device 65 is shown whereby the bending elements 5 a , 5 b are disposed so as to be separately responsive such that the left bending element 5 b deflects towards the substrate 9 and the right bending element 5 a deflects away from the substrate 9 . It is likewise possible for the order of deflection noted above to be reversed. Unlike the micromechanical pixel 3 shown in FIG. 2 , which has the sensing element 4 tilt in the direction parallel to the bi-layer cantilevers 10 a , 10 b , 11 a , 11 b , the present embodiment enables the sensing element 4 to twist in the direction perpendicular to the bi-layer cantilevers 10 a , 10 b , 11 a , 11 b . The resultant device enhances the overall tilt angle of the sensing element 4 , thus improving thermal sensitivity. The sensing elements 4 and substrate 9 described herein are applicable to this embodiment. [0081] Opposed functionality of the bending elements 5 a , 5 b is achieved by placing the high expansion layers 33 along the top surface 57 of the low expansion layers 34 along the left bending element 5 b , as represented in FIG. 4 , and the high expansion layers 33 along the bottom surface 58 of the low expansion layers 34 along the right bending element 5 a , as represented in FIG. 12 . The bending elements 5 a , 5 b contact and are attached to the sensing element 4 at one end thereof in a symmetric fashion. [0082] Opposed functionality of the bending elements 5 a , 5 b may also be achieved by placing the high expansion layer 33 along the top surface 57 of the low expansion layer 34 for half of its length and along the bottom surface 58 of the low expansion layer 34 for the other half of its length. The bending elements 5 a , 5 b deflect in an s-shape in this configuration. This configuration prevents the bending elements 5 a , 5 b from contacting the substrate that may occur if they were to deflect downward. [0083] The responsivity of a micromechanical device 65 is proportional to the tilt angle of the sensing element 4 , which is equal to the difference between the angles of tilt along the outer bi-layer cantilevers 10 a , 10 b at ambient temperature and the inner bi-layer cantilevers 11 a , 11 b heated by incident infrared radiation. The sensing element 4 tilts at the same angle as the inner bi-layer cantilevers 11 a , 11 b , or Δθ, when the bending elements 5 a , 5 b are mutually responsive so as to deflect in the same direction, as provided by the device in FIG. 2 . Assuming a small deflection angle, the change in angle, Δθ, of a bi-layer cantilever 10 a , 10 b , 11 a , 11 b in response to a change above ambient temperature ΔT is given by the expression [0000] Δ   θ = 3   b t 1 + t 2  [ ( 1 + t 1 t 2 ) 2 3  ( 1 + t 1 t 2 ) 2 + ( 1 + t 1 t 2  E 1 E 2 )  ( t 1 2 t 2 2 + t 2 t 1  E 2 E 1 ) ]  ( α 1 - α 2 )  Δ   T , ( 7 ) [0000] where l b is the length of the bi-layer cantilevers 10 a , 10 b , 11 a , 11 b and t 1 and t 2 are the thicknesses, E 1 and E 2 are the Young's modulus, and α 1 and α 2 are the thermal expansion coefficients of the two materials comprising the cantilevers. [0084] Referring again to FIG. 11 , the sensing element 4 twists at an angle determined by the out-of-plane deflection of the opposed bending elements 5 a , 5 b . Assuming a small angle, the out-of-plane deflection of the bending elements 5 a , 5 b is l b Δθ and the angle of twist is equal to 2l b Δθ/w, where w is the width between the bending elements 5 a , 5 b or the width of the sensing element 4 , and the factor of 2 results from the opposed deflections of the bending elements 5 a , 5 b . The degree of enhancement achievable by bending elements 5 a , 5 b with opposed functionality is approximately 2l b /w, corresponding to a 2 to 4 times increase in the responsivity of a typical micromechanical pixel 3 . [0085] Referring now to FIG. 13 , a micromechanical device 65 is shown wherein the bending elements 5 a , 5 b from FIG. 12 are arranged to contact and attach to the sensing element 4 at an offset 60 from an edge 59 a along the sensing element 4 . In preferred embodiments, the offset 60 should be approximately one-half of the total height (h) of the sensing element 4 , although other arrangements are possible. This embodiment increases the rigidity of the micromechanical device 65 , however, the bending moment between bending elements 5 a , 5 b and sensing element 4 is reduced. The sensing elements 4 and substrates 9 described herein are applicable to this embodiment. [0086] The twisting of the sensing element 4 , as described above, produces torsion within the bending elements 5 a , 5 b . The degree of responsivity enhancement may be limited by the torsional rigidity of the bending elements 5 a , 5 b . In some embodiments, it might be desirous to reduce the thickness of the contact structure between each bending element 5 a , 5 b and the sensing element 4 so as to further reduce the torsional rigidity. In other embodiments, it might be advantageous to include a spring-like or hinge-like connection between each bending element 5 a , 5 b and sensing element 4 . In yet other embodiments, it could be advantageous to have the contact be composed of a material having a low Young's modulus. [0087] Referring now to FIG. 14 , a micromechanical device 65 is shown wherein the bending elements 5 a , 5 b from FIG. 12 are arranged to contact and attach to the sensing element 4 in an asymmetric arrangement at an offset 42 along the sensing element 4 . While FIG. 14 shows the left bending element 5 b aligned with the top edge 59 a and the right bending element 5 a aligned with the bottom edge 59 b , other arrangements are possible whereby one or both bending elements 5 a , 5 b are located along the sensing element 4 at a distance from the respective edge 59 a , 59 b . The sensing elements 4 and substrates 9 described herein are applicable to this embodiment. [0088] In this embodiment, the degree of tilt is increased over the device shown in FIG. 2 by approximately 2l b /√{square root over (w 2 +l 2 p )}, where l p is the length of the sensing element 4 . Accordingly, the responsivity of the present embodiment is 1.5 to 3 times greater than that of a micromechanical pixel 3 shown in FIG. 2 . [0089] Referring now to FIG. 15 , a micromechanical device 65 is shown wherein the right bending element 5 b includes a pair of bi-layer cantilevers 10 b , 11 b and thermal isolation region 12 b , as described above, and the left bending element 5 a is comprised of a low expansion layer 43 composed of a single material or composition. In this embodiment, the bending element 5 b deflects towards or away from the substrate 9 enabling the sensing element 4 to tilt in the direction parallel to the bending elements 5 a , 5 b and to twist in the direction perpendicular to the bending elements 5 a , 5 b . It is likewise possible for the arrangement of deflecting and non-deflecting members to be reversed. The sensing elements 4 and substrate 9 described herein are applicable to this embodiment. [0090] In this embodiment, the degree of tilt is increased over the device shown in FIG. 2 by approximately l b /w, and approximately one-half that for the device in FIG. 11 . [0091] Referring now to FIG. 16 , the high expansion layer 33 within a bi-layer cantilever 45 may be replaced by an ultra-high expansion layer 44 comprised of a polymer, having a coefficient of thermal expansion greater than approximately 5×10 −5 K −1 . Exemplary ultra-high expansion polymers include, but are not limited to, styrene, acrylonitrile, pentafluorostyrene, methylmethacrylate, methacrylonitrile, benzonitrile, trimethylsilylacetylene, and trimethylsilylacetonitrile. The ultra-high expansion layer 44 contacts and is joined to a low expansion layer 34 composed of materials known within the art. [0092] Referring now to FIG. 17 , the ultra-high expansion layer 44 may be directly joined to the high expansion layer 33 opposite of the low expansion layer 34 to form a tri-layer cantilever 46 . FIG. 18 compares the deflection achieved by an exemplary bi-layer cantilever 10 a , 10 b , 11 a , 11 b and a tri-layer cantilever 46 . [0093] Referring now to FIGS. 19 a , 19 b , and 20 a - 20 d , a micromechanical device 65 is shown including a pair of u-shaped bending elements 5 a , 5 b which are oppositely disposed and interlocking. The first bending element 5 a includes a pair of bi-layer cantilevers 10 a , 11 a separated by a thermal isolation region 12 a . The right bi-layer cantilever 10 a includes a high expansion layer 33 disposed along the upper surface of a low expansion layer 34 and the left bi-layer cantilever 11 a includes a high expansion layer 33 disposed along the lower or opposing surface of the low expansion layer 34 . The second bending element 5 b includes a pair of bi-layer cantilevers 10 b , 11 b separated by a thermal isolation region 12 b . The left bi-layer cantilever 10 b includes a high expansion layer 33 disposed along the lower surface of a low expansion layer 34 and the left bi-layer cantilever 11 b includes a high expansion layer 33 disposed along the upper surface of the low expansion layer 34 . When interlocked in an opposing fashion, the high expansion layers 33 are disposed along the same surface of the bi-layer cantilevers 10 b and 11 a and bi-layer cantilevers 10 a and 11 b . In some embodiments, the paired arrangement of high expansion layers 33 may be oppositely disposed, as shown in FIG. 19 a , or on the same side as in FIG. 2 . [0094] The outermost bi-layer cantilevers 10 a , 10 b are attached at their outermost end 63 to the substrate 9 via anchor posts 13 d , 13 a , respectively. The inner most bi-layer cantilevers 11 a , 11 b are attached at their innermost end 62 to the planar surface 61 of the sensing element 4 via anchor posts 13 b , 13 c , respectively. While a variety of arrangements are possible for the sensing element 4 , bi-layer cantilevers 10 a , 10 b , 11 a , 11 b , and substrate 9 , it is preferred for the bi-layer cantilevers 10 a , 10 b , 11 a , 11 b to be disposed between the sensing element 4 and substrate 9 , as shown in FIG. 19 b . The responsivity of the present embodiment is 3 to 6 times greater than that of a typical micromechanical pixel 3 shown in FIG. 2 . The sensing elements 4 and substrates 9 described herein are applicable to this embodiment. [0095] Referring now to FIGS. 21 a - 21 d , a variety of non-planar cantilevers, referred to as folded bi-layer cantilevers 64 , are described. Profiles may include, but are not limited to, triangular, square, trapezoidal, and curved, as shown in FIGS. 21 a - 21 d , respectively. Folding is provided along the length (L) of the otherwise planar high expansion layer 33 and low expansion layer 34 comprising the bi-layer cantilevers 10 a , 10 b , 11 a , 11 b , 45 , 46 described in FIGS. 4 , 12 , and 16 . Folding increases the effective length of the bi-layer cantilever 10 a , 10 b , 11 a , 11 b , 45 , 46 without increasing the lateral length and pitch of a micromechanical device 65 . Folded bi-layer cantilevers 64 may be formed by three-dimensional patterning via standard micromechanical fabrication techniques. [0096] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. [0097] The description above indicates that a great degree of flexibility is offered in terms of the invention. Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.

A micromechanical device including an improved sensing element and improved bending elements is described. Sensing elements include multi-layered structures which are thinner, lighter, and flatter than structures presently known within the related arts. Bending elements include structures which separately respond to illumination by an infrared source so as to twist a sensing element. Micromechanical pixels may be arranged to form two-dimensional arrays of infrared sensitive pixels. Arrays of micromechanical pixels are applicable to imaging devices for use within the fields of security and surveillance, firefighting, automotive safety, and industrial monitoring.

This application is a continuation of U.S. application Ser. No. 09/672,738, filed on Sep. 28, 2000 now U.S. Pat. No. 6,885,366. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device. Specifically, the invention relates to a display device using an active matrix type display device such as liquid crystal display device. 2. Description of the Related Art Rapid development has been made in recent years in a technique for manufacturing a semiconductor device, for example, a thin film transistor (TFT), which has a semiconductor thin film formed on an inexpensive glass substrate. This is because there is an increasing demand for active matrix type liquid crystal display devices (hereinafter referred to as liquid crystal display devices). In the liquid crystal display device, several tens thousand to several million TFTs are arranged in matrix form in a pixel portion, and an electric charge going in and out of a pixel electrode connected to each TFT is controlled by a switching function of the TFT, so that an image is displayed. Conventionally, thin film transistors using amorphous silicon formed on a glass substrate are arranged in the pixel portion. A structure has come to be known in recent years in which quartz is utilized as a substrate and thin film transistors are fabricated from a polycrystalline silicon film. In this case, both of a peripheral driving circuit and the pixel portion are formed integrally on the quartz substrate. Also known recently is a technique in which thin film transistors using a crystalline silicon film are formed on a glass substrate by laser annealing or other technologies. FIG. 17 is a schematic structural view of a conventional active matrix type liquid crystal display device. In FIG. 17 , reference numeral 20000 designates a source driver; 21000 , a gate driver; and 22000 , a pixel portion. The pixel portion 22000 is a circuit in which a plurality of TFTs 22100 are arranged in matrix form. Gate signal lines (G 1 , G 2 , . . . , G 480 ) and source signal lines (S 1 , S 2 , . . . , S 640 ) are respectively connected to gate electrodes and source electrodes of the pixel TFTs 22100 . A pixel electrode is connected to a drain electrode of the TFT 22100 . Reference numeral 22400 designates a storage capacitor. Here, the pixel portion includes (480×640) pixels. For convenience of explanation, symbols of ( 1 , 1 ) to ( 480 , 640 ) are given to the respective pixels. In general, a substrate including a driving circuit and a pixel portion is called an active matrix substrate. A liquid crystal 22300 is held between the active matrix substrate and an opposite substrate (not shown) on one surface of which an opposite electrode is formed. In the conventional active matrix type liquid crystal display device shown in FIG. 17 , a clock signal (CK), a clock back signal (CLKB), a start pulse (SP), and a video signal (VIDEO) are inputted to the source driver, and a clock signal (CK), a clock back signal (CLKB), and a start pulse (SP) are inputted to the gate driver from the external. Next, reference will be made to FIG. 18 . FIG. 18 shows an operation timing chart of the conventional active matrix type liquid crystal display device shown in FIG. 17 . In the conventional active matrix type liquid crystal display device, the source driver 20000 sequentially generates timing signals in accordance with the clock signal (CLK), the clock back signal (CLKB), and the start pulse (SP), and outputs the timing signal to a sampling circuit in the source driver. The sampling circuit samples the externally inputted video signal (VIDEO) on the basis of the timing signal, and outputs to the corresponding source signal lines (S 1 , S 2 , . . . , S 640 ). Selection signals are sequentially supplied from the gate driver 21000 to the gate signal lines (G 1 , G 2 , . . . , G 480 ). All TFTs connected to the gate signal line to which the selection signal is supplied are turned ON, and the source driver sequentially supplies the video signals to the source signal lines, so that an image signal is written in the TFT (that is, the liquid crystal and storage capacitor). Note that after the input of the selection signal to the gate signal line G 1 is completed, the input of the selection signal of the gate signal line G 2 is started. Then, after the input of the selection signal to the gate signal line G 2 is completed, the input of the selection signal to the gate signal line G 3 is started. In this way, the selection signals are sequentially inputted to the gate signal lines G 1 to G 480 , and one frame period (TF) is completed. For example, when the selection signal is inputted to the gate signal line G 1 , video signals ( 1 , 1 ), ( 1 , 2 ), . . . , ( 1 , 640 ) are respectively inputted to the pixels ( 1 , 1 ), ( 1 , 2 ), . . . , ( 1 , 640 ) connected to the source signal lines (S 1 , S 2 , . . . , S 640 ). A period during which the video signals ( 1 , 1 ), ( 1 , 2 ), . . . , ( 1 , 640 ) are inputted is called one line period (T L ), and a period to a next one line period is called a horizontal retrace period (T H ). In such a conventional dot sequential active matrix type liquid crystal display device, since a load capacitor of the source signal line is large, it takes a time to write the video signal into the source signal line. Besides, since a time spent for writing the video signal into a storage capacitor of a pixel while the selection signal is inputted to the gate signal line varies for every pixel, especially in a pixel (for example, ( 1 , 639 ), ( 1 , 640 ), etc.) near the end of the selection signal, writing of the video signal into the storage capacitor of the pixel is made only in a part of the horizontal retrace period (T H ). Thus, writing of the video signal is not sufficiently made into the storage capacitor of such a pixel, and as a result, degradation of display quality is caused. As has just been described, there is fluctuation in a writing period of a video signal into a storage capacitor depending on in which pixel the signal is written, and hence some pixels are not allowed to have sufficient writing period. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an active matrix type liquid crystal display device in which every pixel can realize sufficient writing of a video signal into a storage capacitor and a high quality image can be displayed. The liquid crystal display device of the present invention includes left and right gate drivers. The left gate driver is connected to supply selection signals to TFTs of pixels of a left half of a pixel portion. The right gate driver is connected to supply selection signals to TFTs of pixels of a right half of the pixel portion. In the liquid crystal display device of the present invention, timing when the left gate driver outputs a selection signal to a gate signal line connected to a pixel of a column is different from timing when the right gate driver outputs a selection signal to a gate signal line connected to a pixel of the same row as the aforementioned pixel. A liquid crystal display device of the present invention will be described with reference to FIG. 1 . FIG. 1 is a schematic structural view of a liquid crystal display device 1000 of the present invention. In FIG. 1 , reference numeral 1100 designates a source driver; 1200 , a first gate driver L; 1300 , a second gate driver R; and 1400 , a pixel portion. The source driver 1100 generally includes a shift register circuit, a sampling circuit, a buffer circuit, a level shifter circuit, and the like (none of which is shown). The first gate driver L 1200 and the second gate driver R 1300 each include a shift register circuit, a buffer circuit, a level shifter circuit, and the like (none of which is shown). The pixel portion 1400 is a circuit in which a plurality of TFTs 1401 are arranged in matrix form. For convenience of explanation, symbols of ( 1 , 1 ) to ( 4 , 4 ) are given to the respective pixels. The first gate driver L 1200 supplies selection signals to first gate signal lines G 1 L, G 2 L, G 3 L and G 4 L. The gate signal line G 1 L is connected to the gate electrodes of the TFTs of the pixel ( 1 , 1 ) and the pixel ( 1 , 2 ). The gate signal line G 2 L is connected to the gate electrodes of the TFTs of the pixel ( 2 , 1 ) and the pixel ( 2 , 2 ). The gate signal line G 3 L is connected to the gate electrodes of the TFTs of the pixel ( 3 , 1 ) and the pixel ( 3 , 2 ). The gate signal line G 4 L is connected to the gate electrodes of the TFTs of the pixel ( 4 , 1 ) and the pixel ( 4 , 2 ). The second gate driver R 1300 supplies selection signals to second gate signal lines G 1 R, G 2 R, G 3 R and G 4 R. The gate signal line G 1 R is connected to the gate electrodes of the TFTs of the pixel ( 1 , 3 ) and the pixel ( 1 , 4 ). The gate signal line G 2 R is connected to the gate electrodes of the TFTs of the pixel ( 2 , 3 ) and the pixel ( 2 , 4 ). The gate signal line G 3 R is connected to the gate electrodes of the TFTs of the pixel ( 3 , 3 ) and the pixel ( 3 , 4 ). The gate signal line G 4 R is connected to the gate electrodes of the TFTs of the pixel ( 4 , 3 ) and the pixel ( 4 , 4 ). Note that the first gate signal line G 1 L of the first gate driver L 1200 is not connected to the second gate signal line G 1 R of the second gate driver R 1300 . Also, the first gate signal line G 2 L is not connected to the second gate signal line G 2 R. Also, the first gate signal line G 3 L is not connected to the second gate signal line G 3 R. Also, the first gate signal line G 4 L is not connected to the second gate signal line G 4 R. The source driver 1100 supplies video signals to source signal lines S 1 , S 2 , S 3 and S 4 . The source signal line S 1 is connected to source electrodes of TFTs of the pixel ( 1 , 1 ), pixel ( 2 , 1 ), pixel ( 3 , 1 ) and pixel ( 4 , 1 ). The source signal line S 2 is connected to source electrodes of TFTs of the pixel ( 1 , 2 ), pixel ( 2 , 2 ), pixel ( 3 , 2 ) and pixel ( 4 , 2 ). The source signal line S 3 is connected to source electrodes of TFTs of the pixel ( 1 , 3 ), pixel ( 2 , 3 ), pixel ( 3 , 3 ) and pixel ( 4 , 3 ). The source signal line S 4 is connected to source electrodes of TFTs of the pixel ( 1 , 4 ), pixel ( 2 , 4 ), pixel ( 3 , 4 ) and pixel ( 4 , 4 ). Note that here, for simplification of explanation, the description is made taking the liquid crystal display device including the pixel portion constituted of (4×4) pixels as an example. However, according to the present invention, it is possible to provide a liquid crystal display device including a pixel portion constituted of (m×2n) pixels (both m and n are natural numbers). A pixel electrode is connected to a drain electrode of a TFT 1401 of each pixel. Reference numeral 1403 designate a storage capacitor. In general, a substrate including a driving circuit and a pixel portion is called an active matrix substrate (or a TFT substrate). A liquid crystal 1404 is held between the active matrix substrate and an opposite substrate (not shown) on one surface of which an opposite electrode is formed. In the active matrix type liquid crystal display device of the present invention shown in FIG. 1 , a clock signal (CK), a clock back signal (CLKB) with a reverse phase to the clock signal, a start pulse (SP), a video signal (VIDEO), and the like are inputted to the source driver from the external, and a clock signal (CK), a clock back signal (CLKB), a start pulse (SP), and the like are inputted to the gate driver from the external. Next, reference will be made to FIG. 2 . FIG. 2 shows an operation timing chart of the liquid crystal display device of the present invention shown in FIG. 1 . In the liquid crystal display device of the present invention shown in FIG. 1 , the source driver 1100 sequentially generates timing signals in accordance with the clock signal (CLK), the clock back signal (CLKB), the start pulse (SP) and the like, and outputs the timing signal to a sampling circuit in the source driver. The sampling circuit samples the externally inputted video signal (VIDEO) on the basis of the timing signal, and sequentially outputs to the corresponding source signal lines (S 1 , S 2 , S 3 , S 4 ). In the present specification, a period during which the selection signal is inputted to each of the gate signal lines is called a line period (T L ) and a half period of the line period (T L ) is called a half line period (T HL ). Note that symbols corresponding to the image signals supplied to the respective pixels are given to the video signals (VIDEO) shown in FIG. 2 . That is, video signals ( 1 , 1 ), ( 1 , 2 ), ( 1 , 3 ), ( 1 , 4 ), ( 2 , 1 ), . . . , ( 4 , 3 ), and ( 4 , 4 ) are supplied to and written in the pixel ( 1 , 1 ), pixel ( 1 , 2 ), pixel ( 1 , 3 ), pixel ( 1 , 4 ), pixel ( 2 , 1 ), . . . , pixel ( 4 , 3 ), and pixel ( 4 , 4 ). The flow of the respective signals will be described below. First, a selection signal is inputted to the gate signal line G 1 L. When the selection signal is inputted to the gate signal line G 1 L, the selection signal is applied to the gate electrodes of the TFTs of the pixel ( 1 , 1 ) and the pixel ( 1 , 2 ) which are connected to the gate signal line G 1 L. The video signal ( 1 , 1 ) is inputted to the source signal line S 1 in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 L and the video signal ( 1 , 1 ) is written in the storage capacitor of the pixel ( 1 , 1 ). After the input of the video signal ( 1 , 1 ), the video signal ( 1 , 2 ) is inputted to the source signal line S 2 , and the video signal ( 1 , 2 ) is written in the storage capacitor of the pixel ( 1 , 2 ). Then, after completion of the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 L, a selection signal is inputted to the gate signal line G 1 R. When the selection signal is inputted to the gate signal line G 1 R, the selection signal is applied to the gate electrodes of the TFTs of the pixel ( 1 , 3 ) and the pixel ( 1 , 4 ) which are connected to the gate signal line G 1 R. The video signal ( 1 , 3 ) is inputted to the source signal line S 3 in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 R and the video signal ( 1 , 3 ) is written in the storage capacitor of the pixel ( 1 , 3 ). After the input of the video signal ( 1 , 3 ), the video signal ( 1 , 4 ) is inputted to the source signal line S 4 , and the video signal ( 1 , 4 ) is written in the storage capacitor of the pixel ( 1 , 4 ). Note that in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 R, the selection signal is kept inputted to the gate signal line G 1 L, and the selection signal is kept applied to the gate electrodes of the TFTs of the pixel ( 1 , 1 ) and the pixel ( 1 , 2 ). After completion of the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 R, a selection signal is inputted to the gate signal line G 2 L. When the selection signal is inputted to the gate signal line G 2 L, the selection signal is applied to the gate electrodes of the TFTs of the pixel ( 2 , 1 ) and the pixel ( 2 , 2 ) which are connected to the gate signal line G 2 L. The video signal ( 2 , 1 ) is inputted to the source signal line S 1 in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 2 L and the video signal ( 2 , 1 ) is written in the storage capacitor of the pixel ( 2 , 1 ). After the input of the video signal ( 2 , 1 ), the video signal ( 2 , 2 ) is inputted to the source signal line S 2 , and the video signal ( 2 , 2 ) is written in the storage capacitor of the pixel ( 2 , 2 ). Note that in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 2 L, the selection signal is kept inputted to the gate signal line G 1 R, and the selection signal is kept applied to the gate electrodes of the TFTs of the pixel ( 1 , 3 ) and the pixel ( 1 , 4 ). After completion of the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 2 L, a selection signal is inputted to the gate signal line G 2 R. When the selection signal is inputted to the gate signal line G 2 R, the selection signal is applied to the gate electrodes of the TFTs of the pixel ( 2 , 3 ) and the pixel ( 2 , 4 ) which are connected to the gate signal line G 2 R. The video signal ( 2 , 3 ) is inputted to the source signal line S 3 in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 2 R and the video signal ( 2 , 3 ) is written in the storage capacitor of the pixel ( 2 , 3 ). After the input of the video signal ( 2 , 3 ), the video signal ( 2 , 4 ) is inputted to the source signal line S 4 , and the video signal ( 2 , 4 ) is written in the storage capacitor of the pixel ( 2 , 4 ). Note that in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 2 R, the selection signal is kept inputted to the gate signal line G 2 L, and the selection signal is kept applied to the gate electrodes of the TFTs of the pixel ( 2 , 1 ) and the pixel ( 2 , 2 ). Generally speaking, in the liquid crystal display device, the load capacitor of a gate signal line and a source signal line is large, selection of the gate signal line in a short period is not sufficient to write a video signal in a liquid crystal and a storage capacitor which are connected to a TFT. However, in the liquid crystal display device of the present invention, since the selection signal is kept inputted to the gate signal line after the video signal is inputted to the source signal line, even in the case where the load capacitor of the gate signal line and the source signal line is very large, it is possible to gain a time sufficient to write the video signal in the liquid crystal and the storage capacitor. For example, FIG. 19 shows a timing chart in the case where load capacitor of a gate signal line is large, and it takes a considerable time for a potential to rise and fall by a selection signal of the gate signal line. As shown in FIG. 19 , it takes a rise time (Tr) until the gate signal line reaches a desired potential by the selection signal inputted to the gate signal line, and it takes a fall time (Ts) until the gate signal line reaches a desired potential after the selection signal is inputted to the gate signal line. However, by using the present invention, it is possible to input the selection signal in view of the rise time (Tr) and the fall time (Ts) of the gate signal line. That is, it is designed such that after the potential by the selection signal of the gate signal line G 1 L sufficiently falls, the potential by the selection signal of the gate signal line G 2 L sufficiently rises. Besides, even if the operation speed of the TFT of the pixel is slow, it is possible to gain a time sufficient to write the video signal in the liquid crystal and the storage capacitor. Further, since the ratio (holding period/writing period) in writing period to a storage capacitor of pixel-holding period can be made lower than the prior art, a demand to an ON-OFF ratio of a TFT of a pixel is moderated. Here, the structure of the present invention will be explained below. According to a first aspect of the present invention, there is provided a liquid crystal display device comprising: a pixel portion in which (m×2n) pixels, each including a TFT, are arranged in matrix form (both m and n are natural numbers); a source driver for supplying video signals to 2n source signal lines S 1 , S 2 , . . . , Sn, Sn+1, Sn+2, . . . , S2n; a first gate driver for supplying selection signals to m first gate signal lines G 1 L, G 2 L, . . . , GmL; and a second gate driver for supplying selection signals to m second gate signal lines G 1 R, G 2 R, . . . , GmR, characterized in that: the pixels connected to the source signal lines S 1 , S 2 , . . . , Sn are supplied with the selection signals from the first gate signal lines G 1 L, G 2 L, . . . , GmL; the pixels connected to the source signal lines Sn+1, SN+2, . . . , S2n are supplied with the selection signals from the second gate signal lines G 1 R, G 2 R, . . . , GmR; the selection signal starts to be supplied to the second gate signal line G 1 R while the selection signal is supplied to the first gate signal line G 1 L; and the selection signal starts to be supplied to the first gate signal line G 2 L while the selection signal is supplied to the second gate signal line G 1 R. According to a second aspect of the present invention, there is provided a liquid crystal display device comprising: a pixel portion in which (m×2n) pixels, each including a TFT, are arranged in matrix form (both m and n are natural numbers); a source driver for supplying video signals to 2n source signal lines S 1 , S 2 , . . . , Sn, Sn+1, Sn+2, . . . , S2n; a first gate driver for supplying selection signals to m first gate signal lines G 1 L, G 2 L, . . . , GmL; and a second gate driver for supplying selection signals to m second gate signal lines G 1 R, G 2 R, . . . , GmR, characterized in that: the pixels connected to the source signal lines S 1 , S 2 , . . . , Sn are supplied with the selection signals from the first gate signal lines G 1 L, G 2 L, . . . , GmL; the pixels connected to the source signal lines Sn+1, Sn+2, . . . , S2n are supplied with the selection signals from the second gate signal lines G 1 R, G 2 R, . . . , GmR; and the selection signals are sequentially supplied to the first gate signal line G 1 L, the second gate signal line G 1 R, the first gate signal line G 2 L, the second gate signal line G 2 R, . . . , the first gate signal line GmL, and the second gate signal line GmR in this order with a delay of a half period between the respective adjacent gate signal lines. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: FIG. 1 is a schematic structural view of a liquid crystal display device of the present invention; FIG. 2 is a driving timing chart of the liquid crystal display device of the present invention; FIG. 3 is a schematic structural view of a liquid crystal display device of the present invention; FIG. 4 is a block diagram showing a schematic structure of a liquid crystal display device of the present invention; FIG. 5 is a driving timing chart of a liquid crystal display device of the present invention; FIG. 6 is a block diagram showing a schematic structure of a liquid crystal display device of the present invention; FIG. 7 is a driving timing chart of a liquid crystal display device of the present invention; FIGS. 8A to 8D are views showing an example of a fabricating process of a liquid crystal display device using a driving circuit of the present invention; FIGS. 9A to 9D are views showing the fabricating process example of the liquid crystal display device of the present invention; FIGS. 10A to 10D are views showing the fabricating process example of the liquid crystal display device of the present invention; FIGS. 11A and 11B are views showing the fabricating process example of the liquid crystal display device of the present invention; FIG. 12 is a view showing the fabricating process example of the liquid crystal display device of the present invention; FIGS. 13A and 13B are sectional views each showing a liquid crystal display device of the present invention; FIG. 14 is a graph showing applied voltage-transmissivity characteristics of ferroelectric liquid crystal that exhibits Half-V-shaped electro-optical characteristics; FIGS. 15A and 15B are diagrams showing examples of electronic equipment having incorporated therein a liquid crystal display device of the present invention; FIGS. 16A to 16F are diagrams showing examples of electronic equipment having incorporated therein one or more liquid crystal display devices of the present invention; FIG. 17 is a schematic structural view of a conventional liquid crystal display device; FIG. 18 is a driving timing chart of the conventional liquid crystal display device; and FIG. 19 is a driving timing chart of a liquid crystal display device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment mode for carrying out the present invention will be described below. Reference will be made to FIG. 3 . FIG. 3 is a schematic structural view of a liquid crystal display device 2000 of the present invention. In FIG. 3 , reference numeral 2100 designates a source driver; 2200 , a gate driver L; 2300 , a gate driver R; and 2400 , a pixel portion. As shown in FIG. 4 , the source driver 2100 includes a shift register circuit 2110 , a level shifter circuit 2120 , a buffer circuit 2130 , and a sampling circuit 2140 . The gate driver L 2200 includes a shift register circuit 2210 , a level shifter circuit 2220 , and a buffer circuit 2230 . The gate driver R 2300 includes a shift register circuit 2310 , a level shifter circuit 2320 , and a buffer circuit 2330 . The pixel portion 2400 is a circuit in which a plurality of TFTs 2401 are arranged in matrix form. For convenience of explanation, symbols of ( 1 , 1 ) to ( 480 , 640 ) are given to the respective pixels. The gate driver L 2200 supplies selection signals to gate signal lines G 1 L, G 2 L, . . . , G 480 L. The gate signal line G 1 L is connected to gate electrodes of TFTs of the pixel ( 1 , 1 ), pixel ( 1 , 2 ), pixel ( 1 , 319 ), and pixel ( 1 , 320 ). The gate signal line G 2 L is connected to gate electrodes of TFTs of the pixel ( 2 , 1 ), pixel ( 2 , 2 ), . . . , pixel ( 2 , 319 ), and pixel ( 2 , 320 ). The gate signal line G 480 L is connected to gate electrodes of TFTs of the pixel ( 480 , 1 ), pixel ( 480 , 2 ), pixel ( 480 , 319 ), and pixel ( 480 , 320 ). The not-shown gate signal lines G 3 L to G 479 L are also connected to gate electrodes of TFTs in the same way. The gate driver R 2300 supplies selection signals to gate signal lines G 1 R, G 2 R, . . . , G 479 R, and G 480 R. The gate signal line G 1 R is connected to gate electrodes of TFTs of the pixel ( 1 , 321 ), pixel ( 1 , 322 ), . . . , pixel ( 1 , 639 ), and pixel ( 1 , 640 ). The gate signal line G 2 R is connected to gate electrodes of TFTs of the pixel ( 2 , 321 ), pixel ( 2 , 322 ), . . . , pixel ( 2 , 639 ), and pixel ( 2 , 640 ). The gate signal line G 480 R is connected to gate electrodes of TFTs of the pixel ( 480 , 321 ), pixel ( 480 , 322 ), . . . , pixel ( 480 , 639 ), and pixel ( 480 , 640 ). The not-shown gate signal lines G 3 R to G 479 R are also connected to gate electrodes of TFTs in the same way. Note that the gate signal line G 1 L of the gate driver L 2200 is not connected to the gate signal line G 1 R of the gate driver R 2300 . Also, the gate signal line G 2 L is not connected to the gate signal line G 2 R. Also, the gate signal line 480 L is not connected to the gate signal line G 480 R. The same is the case with the relation between the not-shown gate signal lines G 3 L to G 479 L and the gate signal lines G 3 R to G 479 R. The source driver 2100 supplies video signals to source signal lines S 1 , S 2 , . . . , S 639 and S 640 . The source signal line S 1 is connected to source electrodes of the TFTs of the pixel ( 1 , 1 ), pixel ( 2 , 1 ), pixel ( 3 , 1 ), . . . , pixel ( 479 , 1 ), and pixel ( 480 , 1 ). The source signal line S 2 is connected to source electrodes of the TFTs of the pixel ( 1 , 2 ), pixel ( 2 , 2 ), pixel ( 3 , 2 ), . . . , pixel ( 479 , 2 ), and pixel ( 480 , 2 ). The source signal line S 640 is connected to source electrodes of the TFTs of the pixel ( 1 , 640 ), pixel ( 2 , 640 ), . . . , pixel ( 3 , 640 ), pixel ( 479 , 640 ), and pixel ( 480 , 640 ). The not-shown source signal lines S 3 to S 639 also have the same connection structure. Note that here, for simplification of explanation, the description is made taking the liquid crystal display device including the pixel portion constituted of (480×640) pixels as an example. However, according to the present invention, it is possible to provide a liquid crystal display device including a pixel portion constituted of (m×2n) pixels (both m and n are positive integers). Note that FIGS. 6 and 7 show an example of a liquid crystal display device including a pixel portion constituted of (m×2n) pixels and an operation timing chart thereof, respectively. In the active matrix type liquid crystal display device of the present invention shown in FIG. 3 , a clock signal (CK), a clock back signal (CLKB) with a reverse phase to the clock signal, a start pulse (SP), a video signal (VIDEO), and the like are inputted to the source driver 2100 from the external, and a clock signal (CK), a clock back signal (CLKB), a start pulse (SP), and the like are inputted to the gate driver L 2200 and the gate driver R 2300 from the external. Next, reference will be made to FIG. 5 . FIG. 5 shows an operation timing chart of the liquid crystal display device of the present invention. Symbols corresponding to the image signals supplied to the respective pixels are given to the video signals (VIDEO) shown in FIG. 5 . The flow of the respective signals will be described below. First, a selection signal is inputted to the gate signal line G 1 L. When the selection signal is inputted to the gate signal line G 1 L, the selection signal is applied to the gate electrodes of the TFTs of the pixel ( 1 , 1 ), pixel ( 1 , 2 ), . . . , pixel ( 1 , 319 ) and pixel ( 1 , 320 ) which are connected to the gate signal line G 1 L. The video signals (VIDEO) are sequentially inputted to the source signal lines S 1 to S 320 in a half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 L. That is, in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 L, the video signal ( 1 , 1 ) is inputted to the source signal line S 1 , and the video signal ( 1 , 1 ) is written in the liquid crystal and the storage capacitor of the pixel ( 1 , 1 ), and then, the video signal ( 1 , 2 ) is inputted to the source signal line S 2 , and the video signal ( 1 , 2 ) is written in the liquid crystal and the storage capacitor of the pixel ( 1 , 2 ). The video signals are thus sequentially written in the source signal lines. Then, the video signal ( 1 , 320 ) is inputted to the source signal line S 320 , and the video signal ( 1 , 320 ) is written in the liquid crystal and the storage capacitor of the pixel ( 1 , 320 ), so that the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 L is completed. After completion of the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 L, a selection signal is inputted to the gate signal line G 1 R. In a half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 R, the video signals (VIDEO) are inputted to the source signal lines S 321 to S 640 . That is, in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 R, the video signal ( 1 , 321 ) is inputted to the source signal line S 321 , and the video signal ( 1 , 321 ) is written in the liquid crystal and the storage capacitor of the pixel ( 1 , 321 ), and then, the video signal ( 1 , 322 ) is inputted to the source signal line S 322 , and the video signal ( 1 , 322 ) is written in the liquid crystal and the storage capacitor of the pixel ( 1 , 322 ). The video signals are thus sequentially written in the source signal lines. Then, the video signal ( 1 , 640 ) is inputted to the source signal line S 640 , and the video signal ( 1 , 640 ) is written in the liquid crystal and the storage capacitor of the pixel ( 1 , 640 ), so that the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 R is completed. Note that in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 R, the selection signal is kept inputted to the gate signal line G 1 L, and the selection signal is kept applied to the gate electrodes of the TFTs of the pixel ( 1 , 1 ), pixel ( 1 , 2 ), . . . , pixel ( 1 , 319 ) and pixel ( 1 , 320 ). After completion of the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 1 R, a selection signal is inputted to the gate signal line G 2 L. In a half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 2 L, the video signals (VIDEO) are inputted to the source signal lines S 1 to S 320 . That is, in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 2 L, the video signal ( 2 , 1 ) is inputted to the source signal line S 1 , and the video signal ( 2 , 1 ) is written in the liquid crystal and the storage capacitor of the pixel ( 2 , 1 ), and then, the video signal ( 2 , 2 ) is inputted to the source signal line S 2 , and the video signal ( 2 , 2 ) is written in the liquid crystal and the storage capacitor of the pixel ( 2 , 2 ). The video signals are thus sequentially written in the source signal lines. Then, the video signal ( 2 , 320 ) is inputted to the source signal line S 320 , and the video signal ( 2 , 320 ) is written in the liquid crystal and the storage capacitor of the pixel ( 2 , 320 ), so that the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 2 L is completed. Note that in the half line period (T HL ) subsequent to the start of the selection signal input to the gate signal line G 2 L, the selection signal is kept inputted to the gate signal line G 1 R, and the selection signal is kept applied to the gate electrodes of the TFTs of the pixel ( 1 , 321 ), pixel ( 1 , 322 ), . . . , pixel ( 1 , 639 ) and pixel ( 1 , 640 ). Hereinafter, embodiments of the present invention will be described. Embodiment 1 In this embodiment, an example of a fabricating process of a liquid crystal display device including a driving circuit of the present invention will be described with reference to FIGS. 8A to 12 . In the liquid crystal display device of this embodiment, a pixel portion, a source driver, a gate driver, and the like are integrally formed on one substrate. Note that for convenience of explanation, shown here is a case in which a pixel TFT, an n-channel TFT constituting a part of the driving circuit, a p-channel TFT and an n-channel TFT constituting an inverter circuit are formed on the same substrate. In FIG. 8A , a low alkali glass substrate or a quartz substrate can be used as a substrate 6001 . In this embodiment, a low alkali glass substrate is used as the substrate 6001 . In this case, the glass substrate may be thermally treated in advance at a temperature lower than the glass distortion point by 10 to 20° C. On the surface of the substrate 6001 where the TFTs are to be formed, for the purpose of preventing impurity diffusion from the substrate 6001 , an base film 6002 of silicon oxide film, silicon nitride film, silicon nitride oxide film, or the like is formed. For example, a silicon nitride oxide film formed from SiH 4 , NH 3 , and N 2 O may be formed by plasma CVD to a thickness of 100 nm, and a silicon nitride oxide film formed from SiH 4 and N 2 O may be formed similarly to a thickness of 200 nm to form lamination. Next, a semiconductor film 6003 a having the amorphous structure is formed by a known method such as plasma CVD or sputtering to a thickness of from 20 to 150 nm (preferably 30 to 80 nm). In this embodiment, an amorphous silicon film is formed by plasma CVD to a thickness of 54 nm. Such semiconductor films having the amorphous structure include amorphous semiconductor films, microcrystalline semiconductor films, and the like, and a compound semiconductor film having the amorphous structure such as an amorphous silicon germanium film may also be used. Further, since the base film 6002 and an amorphous silicon film 6003 a can be formed using the same film forming method, the two may be continuously formed. By not exposing the substrate to the atmosphere after the base film is formed thereon, contamination of the surface can be prevented, and thus, variation in the characteristics of the TFTs to be formed thereon and variation in the threshold voltage can be decreased ( FIG. 8A ). Then, using known crystallization technique, a crystalline silicon film 6003 b is formed from the amorphous silicon film 6003 a . For example, laser crystallization or thermal crystallization (solid phase growth method) may be used. Here, according to the technique disclosed in Japanese Patent Application Laid-open No. Hei 7-130652, with the crystallization method using a catalytic element, the crystalline silicon film 6003 b is formed. Prior to the crystallization step, it is preferable to, though depending on the amount of hydrogen contained in the amorphous silicon film, carry out heat treatment at 400 to 500° C. for about an hour to make the amount of hydrogen contained to be 5 atomic % or less. Since the atoms are rearranged to be denser when the amorphous silicon film is crystallized, the thickness of the crystalline silicon film to be formed is reduced from that of the original amorphous silicon film (54 nm in this embodiment) by 1 to 15% ( FIG. 8B ). Then, the crystalline silicon film 6003 b is patterned to have an island shape to form island-like semiconductor layers 6004 to 6007 . After that, a mask layer 6008 is formed of silicon oxide film by plasma CVD or sputtering to a thickness of from 50 to 150 nm ( FIG. 8C ). In this embodiment, the thickness of the mask layer 6008 is 130 nm. Next, a resist mask 6009 is provided and boron (B) is doped all over the surfaces of island-like semiconductor layers 6005 to 6007 for forming n-channel TFTs as an impurity element imparting p-type conductivity at the concentration of from about 1×10 16 to 5×10 17 atoms/cm 3 . This boron (B) doping is made for the purpose of controlling the threshold voltage. Boron (B) may be doped by ion doping, or, alternatively, may be doped simultaneously with the formation of the amorphous silicon film. The boron (B) doping here is not always needed ( FIG. 8D ). For the purpose of forming the LDD regions of the n-channel TFTs of the driving circuit such as a driver, an impurity element imparting n-type conductivity is selectively doped in the island-like semiconductor layers 6010 to 6012 , which requires the formation of resist masks 6013 to 6016 in advance. As the impurity element imparting n-type conductivity, phosphorus (P) or arsenic (As) may be used. Here, ion doping with phosphine (PH 3 ) is used to dope phosphorus (P). The appropriate concentration of phosphorus (P) in formed impurity regions 6017 and 6018 is in the range of from 2×10 16 to 5×10 19 atoms/cm 3 . Herein, the concentration of the impurity element imparting n-type conductivity contained in impurity regions 6017 to 6019 formed here is referred to as (n − ). An impurity region 6019 is a semiconductor layer for forming the storage capacitor of the pixel portion. Phosphorus (P) at the same concentration is also doped in this region ( FIG. 9A ). After that, the resist masks 6013 to 6016 are removed. Next, the mask layer 6008 is removed with fluoric acid or the like and an activation step for the impurity elements doped in FIGS. 8D and 9A is carried out. The activation can be carried out by heat treatment in a nitrogen atmosphere at 500 to 600° C. for 1 to 4 hours or by laser activation. Alternatively, the two may be used jointly. In this embodiment, laser activation is adopted and KrF excimer laser light (wavelength: 248 nm) is used to form linear beams having the oscillating frequency of from 5 to 50 Hz and the energy density of from 100 to 500 mJ/cm 2 which scans with the overlapping ratio of from 80 to 98% to treat the whole surface of the substrate having the island-like semiconductor layers formed thereon. Note that there is no limitation on the conditions of the laser light irradiation, and the conditions may be appropriately decided. Then, a gate insulating film 6020 is formed from an insulating film containing silicon by plasma CVD or sputtering to a thickness of from 10 to 150 nm. For example, a silicon nitride oxide film with a thickness of 120 nm is formed. A single layer or lamination of other insulating films containing silicon may also be used as the gate insulating film ( FIG. 9B ). Next, a first conductive layer to be gate electrodes is formed. Though the conductive layer may be a single-layer conductive layer, it may have a lamination structure of, for example, two or three layers, if necessary. In this embodiment, a lamination layer consisting of a conductive layer (A) 6021 made of a conductive metallic nitride film and a conductive layer (B) 6022 made of a metal film is formed. The conductive layer (B) 6022 may be formed of an element selected from a group consisting of tantalum (Ta), titanium (Ti), molybdenum (Mo), and tungsten (W), or an alloy containing the foregoing elements as its main constituent, or an alloy film of a combination of the elements (typically Mo—W alloy film or Mo—Ta alloy film). The conductive layer (A) 6021 may be formed of tantalum nitride (TaN), tungsten nitride (WN), titanium nitride (TiN) or molybdenum nitride (MoN). Further, the conductive layer (A) 6021 also may be formed of tungsten silicide, titanium silicide or molybdenum silicide as a substitute material. As to the conductive layer (B) 6022 , it is preferable that the concentration of the impurity contained is reduced in order to lower the resistance. In particular, the concentration of oxygen is desirable to be 30 ppm or less. For example, if the concentration of oxygen is 30 ppm or less, resistance value of 20 μÙcm or less can be realized with respect to tungsten (W). The thickness of the conductive layer (A) 6021 is 10 to 50 nm (preferably 20 to 30 nm) while the thickness of the conductive layer (B) 6022 is 200 to 400 nm (preferably 250 to 350 nm). In this embodiment, a tantalum nitride film with a thickness of 50 nm is used as the conductive layer (A) 6021 while a Ta film with a thickness of 350 nm is used as the conductive layer (B) 6022 , both of which are formed by sputtering. When sputtering is used to form the films, by adding an appropriate amount of Xe or Kr to Ar as the sputtering gas, the internal stress of the film to be formed can be alleviated to prevent the film from peeling off. Note that, though not shown, it is effective to form a silicon film with a thickness of from 2 to 20 nm, doped with phosphorus (P), under the conductive layer (A) 6021 . This improves the adherence of the conductive layer to be formed thereon, and oxidation can be prevented. At the same time, a small amount of alkaline element contained in the conductive layer (A) or the conductive layer (B) can be prevented from diffusing into the gate insulating film 6020 ( FIG. 9C ). Then, resist masks 6023 to 6027 are formed and the conductive layers (A) 6021 and (B) 6022 are etched together to form gate electrodes 6028 to 6031 , and a capacitor wiring 6032 . The gate electrodes 6028 to 6031 and the a capacitor wiring 6032 are integrally formed from the conducive layer (A) including regions 6028 a to 6032 a and from the conductive layer (B) including regions 6028 b to 6032 b . Here, the gate electrodes 6029 and 6030 of TFTs constituting the driving circuit such as a driver are formed so as to partially overlap the impurity regions 6017 and 6018 through the gate insulating film 6020 ( FIG. 9D ). Then, for the purpose of forming the source and drain regions of the p-channel TFT of the driving circuit, a step of doping an impurity element imparting p-type conductivity is carried out. Here, with the gate electrode 6028 being as the mask, the impurity region is formed in a self-aligning manner. At this point, the regions where the n-channel TFTs are to be formed are covered with a resist mask 6033 . Impurity regions 6034 are formed by ion doping using diborane (B 2 H 6 ). The concentration of boron (B) in these regions is 3×10 20 to 3×10 21 atoms/cm 3 . Herein, the concentration of the impurity element imparting p-type conductivity contained in the impurity regions 6034 formed here is referred to as (p ++ ) ( FIG. 10A ). Next, in the n-channel TFTs, impurity regions to function as source regions or drain regions are formed. Resist masks 6035 to 6037 are formed and an impurity element imparting n-type conductivity is doped to form impurity regions 6038 to 6042 . This is done by ion doping using phosphine (PH 3 ) with the concentration of phosphorus (P) in these regions being 1×10 20 to 1×10 21 atoms/cm 3 . Herein, the concentration of the impurity element imparting n-type conductivity contained in the impurity regions 6038 to 6042 formed here is referred to as (n + ) ( FIG. 10B ). The impurity regions 6038 to 6042 already contain phosphorus (P) or boron (B) doped in previous steps, but since phosphorus (P) is doped at a sufficiently greater concentration as compared to the concentration of previous impurities, the influence of phosphorus (P) or boron (B) doped in the previous steps can be neglected. Further, since the concentration of phosphorus (P) doped in the impurity regions 6038 is ½ to ⅓ of that of boron (B) doped in FIG. 10A , the conductivity of p-type is secured without exerting influence on the TFT characteristics. Then, for the purpose of forming the LDD regions of the n-channel TFT of the pixel portion, a step of doping impurity element imparting n-type conductivity is carried out. Here, an impurity element imparting n-type conductivity is doped in a self-aligning manner by ion doping with the gate electrode 6031 as a mask. The concentration of the doped phosphorus (P) is 1×10 16 to 5×10 18 atoms/cm 3 . By carrying out the doping with the concentration lower than that of the impurity elements doped in FIGS. 9A , 10 A, and 10 B, only impurity regions 6043 and 6044 are formed actually. Herein, the concentration of the impurity element imparting n-type conductivity contained in the impurity regions 6043 and 6044 formed here is referred to as (n − ) ( FIG. 10C ). Here, an SiON film or the like may be formed to a thickness of 200 nm as an interlayer film in order to prevent the Ta film of the gate electrode from peeling off. After that, a heat treatment step is carried out to activate the impurity elements imparting n or p-type conductivity and doped at the respective concentrations. The step can be carried out by furnace annealing, laser annealing, or rapid thermal annealing (RTA). Here, the activation step is carried out by furnace annealing. Heat treatment is performed at the concentration of oxygen of 1 ppm or less, preferably 0.1 ppm or less, in a nitrogen atmosphere at 400 to 800° C., typically 500 to 600° C., 500° C., in this embodiment, for four hours. Further, in the case of using a quartz substrate or the like having heat resistance as the substrate 6001 , a heat treatment may be carried out at 800° C. for 1 hour. Then, the activation of the impurity element can be realized, and an impurity region doped with the impurity element and a channel forming region are satisfactory joined together. Note that this effect may not be obtained in the case where an interlayer film for preventing the Ta film of the gate electrode from peeling off has been formed. In the above heat treatment, conductive layers (C) 6028 c to 6032 c are formed to a thickness of 5 to 80 nm on the surface of metallic films 6028 b to 6032 c constituting the gate electrodes 6028 to 6031 and the capacitor wiring 6032 . For example, tungsten nitride (WN) and tantalum nitride (TaN) can be formed when the conductive layers (B) 6028 b to 6032 b are tungsten (W) and tantalum (Ta), respectively. The conductive layers (C) 6028 c to 6032 c can be formed similarly by exposing the gate electrodes 6028 to 6031 and the capacitor wiring 6032 to a plasma atmosphere containing nitrogen using nitrogen or ammonia. Then, heat treatment is carried out in an atmosphere containing 3 to 100% of hydrogen at 300 to 450° C. for 1 to 12 hours to hydrogenate the island-like semiconductor layers. This is a step where the dangling bonds in the semiconductor layers are terminated by thermally excited hydrogen. As other means for hydrogenation, plasma hydrogenation (hydrogen excited by plasma is used) may be carried out. In the case where the island-like semiconductor layers are formed from an amorphous silicon film by the crystallization method using a catalytic element, a small amount of catalytic element remains in the island-like semiconductor layers. Of course, it is still possible to complete a TFT in such a condition, but it is more desirable to remove the remaining catalytic element, at least from the channel forming region. To utilize the gettering action by phosphorus (P) is one of the means for removing the catalytic element. The concentration of phosphorus (P) necessary for the gettering is about the same as that in the impurity region (n + ) formed in FIG. 10B . By the heat treatment in the activation step carried out here, the catalytic element can be gettered from the channel forming regions of the n-channel TFTs and the p-channel TFTs ( FIG. 10D ). A first interlayer insulating film 6045 is formed from a silicon oxide film or a silicon nitride oxide film to a thickness of from 500 to 1500 nm. After that, contact holes reaching the source regions or the drain regions of the respective island-like semiconductor layers are formed, and source wirings 6046 to 6049 and drain wirings 6050 to 6053 are formed ( FIG. 11A ). Although not shown, in this embodiment, the electrode is a lamination film of three-layer structure obtained by forming a Ti film with a thickness of 100 nm, an aluminum film containing Ti and having a thickness of 500 nm, and another Ti film with a thickness of 150 nm, which are formed continuously by sputtering. Then, as a passivation film 6054 , a silicon nitride film, a silicon oxide film, or a silicon nitride oxide film is formed to a thickness of from 50 to 500 nm (typically 100 to 300 nm). In this embodiment, the passivation film 6054 is a lamination film of a silicon nitride film with a thickness of 50 nm and a silicon oxide film with a thickness of 24.5 nm. Hydrogenation treatment carried out in this condition results in improvement in the TFT characteristics. For example, heat treatment in an atmosphere containing 3 to 100% of hydrogen at 300 to 450° C. for 1 to 12 hours is preferable. The use of plasma hydrogenation instead brings about similar effects. Note that, here, an opening portion may be formed in the passivation film 6054 at a position where a contact hole for connecting a pixel electrode and the drain wirings is to be formed later ( FIG. 11A ). After that, a second interlayer insulating film 6055 of an organic resin is formed to a thickness of from 1.0 to 1.5 μm. As the organic resin, polyimide, acrylic resin, polyamide, polyimideamide, BCB (benzocyclobutene), or the like can be used. Here, acrylic resin of the type that is thermally polymerized type after being applied to the substrate is used, and the film is formed by carrying out baking at 250° C. ( FIG. 11B ). In this embodiment, a black matrix is formed to have a laminate structure in which a Ti film is formed to a thickness of 100 nm, and then, an alloy film of Al and Ti is formed to a thickness of 300 nm. After that, a third interlayer insulating film 6059 of an organic resin is formed to a thickness of from 1.0 to 1.5 μm m. As the organic resin, the same resin that forms the second interlayer insulating film can be used. Here, polyimide of the type that is thermally polymerized after being applied to the substrate is used, and the film is formed by carrying out baking at 300° C. A contact hole reaching the drain wirings 6053 is formed through the second interlayer insulating film 6055 and the third interlayer insulating film 6059 , and a pixel electrode 6060 is formed. In a transmission type liquid crystal display device according to the present invention, a transparent conductive film such as an indium tin oxide (ITO) film is used for the pixel electrode 6060 ( FIG. 11B ). In this way, a substrate having a driving circuit TFT and a pixel TFT in the pixel portion on the same substrate is completed. In the driving circuit, a p-channel TFT 6101 , a first n-channel TFT 6102 , and a second n-channel TFT 6103 are formed. In the pixel portion, a pixel TFT 6104 and a storage capacitor 6105 are formed ( FIG. 12 ). Such a substrate is herein referred to as an active matrix substrate for convenience. Described next is a process of manufacturing a transmission type liquid crystal display device on the basis of the active matrix substrate manufactured through the above steps. An orientation film 6061 is formed on the active matrix substrate in the state of FIG. 12 . In this embodiment, a polyimide is used for the orientation film 6061 . Next, an opposing substrate is prepared. The opposing substrate is formed of a glass substrate 6062 , an opposing electrode 6063 made from a transparent conductive film, and an orientation film 6064 . In this embodiment, a polyimide resin in which liquid crystal molecules are orientated parallel to the substrate is used for the orientation film. Note that, after forming the orientation films, a rubbing treatment is performed to give the liquid crystal molecules a certain fixed pre-tilt angle, bringing them into parallel orientation. The active matrix substrate and the opposing substrate which have undergone the above steps are then joined to each other by a known cell assembling process through a sealing material or a spacer (neither is shown). After that, a liquid crystal 6065 is injected between the substrates and an end sealing material (not shown) is used to completely seal the substrates. A transmission type liquid crystal display device as shown in FIG. 12 is thus completed. In this embodiment, the transmission type liquid crystal display device is designed so as to operate in a TN (Twisted Nematic) mode. Accordingly, a polarizing plate (not shown) is disposed on an upper part of the transmission type liquid crystal display device. The p-channel TFT 6101 of the driving circuit has a channel forming region 806 , source regions 807 a and 807 b , and drain regions 808 a and 808 b in the island-like semiconductor layer 6004 . The first n-channel TFT 6102 has a channel forming region 809 , an LDD region 810 that overlaps the gate electrode 6071 (hereafter referred to as L ov for such LDD regions), a source region 811 , and a drain region 812 in the island-like semiconductor layer 6005 . The length of the L ov region in the direction of the channel length is 0.5 to 3.0 μm, preferably 1.0 to 1.5 μm. The second n-channel TFT 6103 has a channel forming region 813 , LDD regions 814 and 815 , a source region 816 , and a drain region 817 in the island-like semiconductor layer 6006 . The LDD regions can be divided into the L ov region and an LDD region which does not overlap with the gate electrode 6072 (hereafter referred to as a L off region). The length of the L off region in the direction of the channel length is 0.3 to 2.0 μm, preferably 0.5 to 1.5 μm. The pixel TFT 6104 has channel forming regions 818 and 819 , L off regions 820 to 823 , and source or drain regions 824 to 826 in the island shape semiconductor layer 6007 . The length of the L off regions in the direction of the channel length is 0.5 to 3.0 μm, preferably 1.5 to 2.5 μm. An offset region (not shown) is formed between the channel forming regions 818 and 819 of the pixel TFT 6104 and the L off regions 820 to 823 that are (LDD regions of the pixel TFT). Further, a storage capacitor 805 is formed of the capacitor wirings 6074 , an insulating film formed of the gate insulating film 6020 , and a semiconductor layer 827 with an impurity element imparting n-type conductivity doped therein for connecting with the drain region 826 of the pixel TFT 6073 . In FIG. 12 , the pixel TFT 804 has the double gate structure, but it may have the single gate structure, or the multi gate structure provided with a plurality of gate electrodes. As described above, by selecting the optimal structure of TFTs that constitute in the respective circuits in accordance with specifications for the pixel TFT and the driver, the operating performance and the reliability of the liquid crystal display device can be improved in this embodiment. Note that the description has been made on the transmission type liquid crystal display device. However, the present invention is not limited to thereto, and it may also be applied to a reflection type liquid crystal display device. Embodiment 2 Shown in this embodiment is an example in which a liquid crystal display device according to the present invention is composed of a reverse stagger type TFT. Reference is made to FIGS. 13A and 13B which are sectional views showing reverse stagger type n-channel TFTs for forming the liquid crystal display device of this embodiment. Needless to say, both p-channel TFT and n-channel TFT may be used to form a CMOS circuit, although merely one n-channel TFT is shown in each of FIGS. 13A and 13B . Also it goes without saying that a pixel TFT may be formed with a similar structure. Referring to FIG. 13A , denoted by 4001 is a substrate, a material of which is chosen from ones mentioned in Embodiment 1. Reference symbol 4002 denotes a silicon oxide film, 4003 , a gate electrode, and 4004 , a gate insulating film. Denoted by 4005 , 4006 , 4007 , 4008 are active layers made of a polycrystalline silicon film. To form these active layers, the same method by which an amorphous silicon film is crystallized into a polycrystalline silicon film, described in Embodiment 1, is used. Alternatively, the amorphous silicon film may be crystallized by laser light (preferably, linear laser light or sheet-like laser light). Specifically, denoted by 4005 is a source region, 4006 , a drain region, 4007 , low concentration impurity regions (LDD regions), and 4008 , a channel forming region. Reference symbol 4009 denotes a channel protective film, 4010 , an interlayer insulating film, 4011 , a source electrode, and 4012 , a drain electrode. Referring next to FIG. 13B , a description will be given on a case where the liquid crystal display device is composed of a reverse stagger type TFT having a structure different from that of the TFT shown in FIG. 13A . Also in FIG. 13B , merely one n-channel TFT is shown in the drawing. However, as described above, a CMOS circuit may of course be composed of both the p-channel TFT and the n-channel TFT. Also it goes without saying that a pixel TFT may be formed with a similar structure. Reference symbol 4101 denotes a substrate, 4102 , a silicon oxide film, and 4103 , a gate electrode. Denoted by 4104 is a benzocyclobutene (BCB) film, of which top surface is planarized. A silicon nitride film is denoted by 4105 . The BCB film and the silicon nitride film together form a gate insulating film. Reference symbols 4106 , 4107 , 4108 , 4109 denote active layers made of a polycrystalline silicon film. To form these active layers, the same method by which an amorphous silicon film is crystallized into a polycrystalline silicon film, described in Embodiment 1, is used. Alternatively, the amorphous silicon film may be crystallized by laser light (preferably, linear laser light or sheet-like laser light). Specifically, denoted by 4106 is a source region, 4107 , a drain region, 4108 , low concentration impurity regions (LDD regions), and 4109 , a channel forming region. Reference symbol 4110 denotes a channel protective film, 4111 , an interlayer insulating film, 4112 , a source electrode, and 4113 , a drain electrode. According to this embodiment, the gate insulating film consisting of the BCB film and the silicon nitride film are leveled so that the amorphous silicon film to be formed thereon is also planar. Therefore in crystallizing the amorphous silicon film into a polycrystalline silicon film, more uniform polycrystalline silicon film can be obtained as compared to conventional reverse stagger type TFTs. Embodiment 3 In the above-described liquid crystal display devices of the present invention, various kinds of liquid crystal may be used other than the nematic liquid crystal. For example, usable liquid crystal materials include ones disclosed in: 1998, SID, “Characteristics and Driving Scheme of Polymer-Stabilized Monostable FLCD Exhibiting Fast Response Time and High Contrast Ratio with Gray-Scale Capability” by H. Furue et al.; 1997, SID DIGEST, 841, “A Full-Color Thresholdless Antiferroelectric LCD Exhibiting Wide Viewing Angle with Fast Response Time” by T. Yoshida et al.; 1996, J. Mater. Chem. 6(4), 671–673, “Thresholdless Antiferroelectricity in Liquid Crystals and its Application to Displays” by S. Inui et al.; and U.S. Pat. No. 5,594,569. FIG. 14 shows electro-optical characteristics of single stable ferroelectric liquid crystal (FLC) in which the ferroelectric liquid crystal (FLC) exhibiting a transition series of isometric phase-cholesteric phase-chiral smectic C phase is used, transition of cholesteric phase-chiral smectic C phase is caused while applying a DC voltage, and a cone edge is made to almost coincide with a rubbing direction. A display mode by the ferroelectric liquid crystal as shown in FIG. 14 is called a “Half-V-shaped switching mode”. The vertical axis of the graph shown in FIG. 14 indicates transmittance (in an arbitrary unit) and the horizontal axis indicates applied voltage. The details of the “Half-V-shaped switching mode” are described in “Half-V-shaped switching mode FLCD” by Terada et al., Collection of Preliminary Paper for 46th Applied Physics Concerned Joint Lecture Meeting, March 1993, p. 1316, and “Time-division full-color LCD with ferroelectric liquid crystal” by Yoshihara et al., Liquid Crystal, Vol. 3, No. 3, p. 190. As shown in FIG. 14 , it is understood that when such ferroelectric mixed liquid crystal is used, low voltage driving and gray-scale display become possible. For the liquid crystal display device of the present invention, it is also possible to use the ferroelectric liquid crystal exhibiting such electro-optical characteristics. In addition, a liquid crystal that exhibits an antiferroelectric phase in a certain temperature range is called an antiferroelectric liquid crystal (AFLC). There are mixed liquid crystals mixed therein, with an anti-ferroelectric liquid crystal, that show electro-optical response characteristics in which the transmittance continuously changes in response to the electric field, and are called thresholdless antiferroelectric mixed liquid crystals. There are thresholdless antiferroelectric mixed liquid crystals that show V-shaped electro-optical response characteristics, and some have been found to have a drive voltage of approximately ±2.5 V (when the cell thickness is between 1 μm and 2 μm). Further, in general the spontaneous polarization of a thresholdless antiferroelectric mixed liquid crystal is large, and the dielectric constant of the liquid crystal itself is high. Thus a relatively large storage capacitor for the pixel is necessary when a thresholdless antiferroelectric mixed liquid crystal is used for a liquid crystal display device. Therefore it is desirable to use a thresholdless antiferroelectric mixed liquid crystal that has a small spontaneous polarization. Note that by using this type of thresholdless antiferroelectric mixed liquid crystal in the liquid crystal display device of the present invention, a low voltage drive can be realized, so that low power consumption can also be realized. Embodiment 4 The present invention may be embodied in all the electronic equipments that incorporate those display devices into display units. As such electronic equipment, a video camera, a digital camera, a projector (rear-type or front-type projector), a head mount display (goggle-type display), a game machine, a navigation system for vehicles, a personal computer, and a portable information terminal (a mobile computer, a cellular phone, an electronic book, etc.) may be enumerated. Examples of those are shown in FIGS. 15A and 15B , and FIGS. 16A and 16F . FIG. 15A shows a front type projector which is constituted of a main body 10001 , a liquid crystal display device 10002 of the present invention, a light source 10003 , an optical system 10004 , and a screen 10005 . Although FIG. 15A shows a front projector including one liquid crystal display device, when three liquid crystal display devices (made to correspond to light of R, G and B, respectively) are incorporated, a front type projector with higher resolution and higher difinition can be realized. FIG. 15B shows a rear type projector which is constituted of a main body 10006 , a liquid crystal display device 10007 of the present invention, a light source 10008 , a reflector 10009 , and a screen 10010 . FIG. 15B shows a rear type projector including three liquid crystal display devices (made to correspond to light of R, G and B, respectively). It is also possible to provide a rear type projector including one liquid crystal display device of the present invention. FIG. 16A shows a personal computer comprising a main body 7001 , an image inputting unit 7002 , a liquid crystal display display device 7003 of the present invention, and a key board 7004 of the present invention. FIG. 16B shows a video camera comprising a main body 7101 , a liquid crystal display device 7102 , a voice input unit 7103 , operation switches 7104 , a battery 7105 , and an image receiving unit 7106 of the present invention. FIG. 16C shows a mobile computer comprising a main body 7201 , a camera unit 7202 , an image receiving unit 7203 , an operation switch 7204 , and a liquid crystal display device 7205 of the present invention. FIG. 16D shows a goggle-type display comprising a main body 7301 , a liquid crystal display device 7302 and arm portions 7303 of the present invention. FIG. 16E shows a player that employs a recoding medium in which programs are recorded (hereinafter referred to as recording medium), and comprises a main body 7401 , a liquid crystal display display device 7402 , a speaker unit 7403 , a recording medium 404 , and an operation switch 7405 of the present invention. Note that this player uses as the recoding medium a DVD (digital versatile disc), a CD of the present invention to serve as a tool for enjoying music or movies, for playing video games and for connecting to the Internet. FIG. 16F shows a display device using a liquid crystal display device of the present invention. Reference numeral 7501 designates a main body and 7502 , the liquid crystal display device of the present invention. As described above, the present invention has so wide application range that it is applicable to electronic equipments in any field. As described above, in the liquid crystal display device of the present invention, since the selection signal is kept inputted to the gate signal line after the video signal is inputted to the source signal line, even in the case where the load capacitor of the gate signal line and the source signal line is large, it is possible to gain a time sufficient to write the video signal into the liquid crystal and the storage capacitor. Besides, even if the operation speed of the TFT of the pixel is slow, it is possible to gain a time sufficient to write the video signal into the liquid crystal and the storage capacitor. Although a liquid crystal display devices have been described in the preferred embodiments, the present invention can be applied to other types of display devices such as an active matrix type electro-luminescence display device.

A device such as a liquid crystal display is provide, in which every pixel can sufficiently realize writing of a video signal into a storage capacitor. The liquid crystal display device of the present invention includes left and right gate drivers. The left gate driver is connected to supply selection signals to TFTs of pixels of a left half of a pixel portion. The right gate driver is connected to supply selection signals to TFTs of pixels of a right half of the pixel portion. In the liquid crystal display device of the present invention, timing when the left gate driver outputs a selection signal to a gate signal line connected to a pixel of a column is different from timing when the right gate driver outputs a selection signal to a gate signal line connected to a pixel of the same row as the pixel.

The invention relates to a drawer pull-out guide provided with an automatic retraction device and with a guide rail to be fixed on a carcass wall of a piece of furniture and a running rail which is movably mounted relative to the guide rail and to be fixed on the drawer—optionally with a central rail interposed—wherein a pawl component which is movable between two end positions which are spaced from one another in the direction of movement of the drawer is provided in a pawl housing disposed on one of the two aforementioned outer rails, the pawl component being biased by a spring arrangement into one end position and lockable in the other end position against retraction into the first end position and having a receptacle for a catch which is provided on the other rail and which moves into the receptacle as the rails move relative to each other when approaching the closed position, thereby disengaging the pretensioned movable pawl component from the associated end position so that the pawl component is moved under the effect of spring tension into the first end position and by way of the catch held in the receptacle entrains the rail associated therewith in the direction of retraction of the drawer, a damper which acts on the pawl component being provided on or in the pawl housing to damp and/or slow down the retraction movement of the pawl component. BACKGROUND OF THE INVENTION Drawer guides which are provided with an automatic retraction device and by which during the closing movement before the completely closed position is reached a drawer held so that it can be pulled out on a cupboard carcass is forcibly retained by the tensional force of a biased spring in the closed position of the drawer and secured against inadvertent outward movement—for example by the reaction of the impact of the front drawer panel on the cupboard carcass or by displacement of air within the cupboard carcass when adjacent drawers are pushed in or pulled out—have been introduced to an increasing extent in recent years (e.g. DE 4 020 277 C2). Because modem drawer guides have a very easy action due to the mounting of the rails by means of anti-friction bearing or rollers, the bias of the biasing springs used for retraction must be such that the appertaining drawers can be securely retracted even in the event of relatively heavy loading and on the other hand drawers which are less heavily loaded are not accidentally opened even in the event of air currents in the carcass. In this case it has been shown that it is difficult to design the bias of a spring which is optimal and takes account of all requirements. As a rule, therefore, the tensional force of the spring is designed with a safety margin, but the consequence of this is that at least lighter drawers are speeded up on the retraction path and strike the cupboard carcass if it is not intentionally slowed down by the a person operating the drawer. Many furniture purchasers object to this jerky slamming or snapping shut, so that in recent years furniture manufacturers have changed over to the provision of dampers which are additionally effective between the drawers and the cupboard carcass during the automatic retraction process and which prevent the possibility of the drawer also being speeded up excessively by the spring of the automatic retraction device with its relative bias. In order for the design expenditure which is increased by the use of such additional damping and also the production expenditure—increased due to the necessary installation work—it has already been proposed that the damper which becomes effective during the automatic retraction movement should be integrated into the retraction device (DE 202 04 860.8). On the other hand, however, due to the use of dampers it is also necessary to increase the spring force of the automatic retraction device further in order to ensure that the associated drawer is closed exactly. This also produces the disadvantage during opening of the drawer that due to the usual longer spring path the spring force increases significantly, which results in unpleasantly high pull-out forces. BRIEF SUMMARY OR THE INVENTION The object of the invention, therefore, is to improve the automatic retraction devices with dampers developed for drawer pull-out guides in such a way that on the one hand the spring forces necessary for secure closing of the drawers are achieved without excessively high pull-out forces being produced when the drawer is pulled out. Starting from a drawer pull-out guide of the type referred to in the introduction this object is achieved according to the invention in that an entraining rocker which is coupled to the pawl component and is movable during a final part of the retraction movement of the pawl component is additionally provided in the pawl housing and during the initial displacement path is decoupled therefrom and is retained so that it is secured against longitudinal displacement in the pawl housing, and that a separate spring which biases the entraining rocker in the direction of retraction engages on the entraining rocker. The arrangement of an entraining rocker which is coupled to the pawl component only over a part of the pull-out path and with which a separate spring is associated ensures that the pull-out force to be overcome during the first part of the pull-out movement is determined by the pull-out path of both springs, but that then because of the locking of the entraining rocker during the second part of the pull-out movement and decoupling of the pawl component only the force of the first spring to engage on the pawl component still has to be overcome. In a preferred embodiment of the invention the movable pawl component is longitudinally movable in the elongate pawl housing which is U-shaped in cross-section and is guided in the end which is at the front in the direction of retraction of the drawer for locking so as to be pivotable about an axis which extends at right angles to the direction of displacement, the entraining rocker being provided in the surface of the pawl component between the inner face of the web of the pawl housing facing the pawl component and the surface within the housing facing it. As a result the design can be such that in one of the side walls of the pawl housing forming the leg of the U-shaped cross-section in the pull-out direction to the entraining rocker a recess which extends in the direction of displacement of the pawl component can be provided in which a portion of the entraining rocker can be pivoted into a predetermined displacement position and can be locked against further displacement, wherein from the boundary surface of the pawl component facing the entraining rocker an entraining lug projects towards the entraining rocker and in the position of the entraining rocker in which it is not pivoted into the recess of the pawl housing engages in an associated receptacle in the entraining rocker and couples the latter to the pawl component in the position of the entraining rocker in which it is pivoted into the recess but freely comes out of the receptacle, as a result of which the pawl component is decoupled from the entraining rocker. In this case it is recommended to provide an elongate depression or through opening extending in the direction of displacement of the pawl component in the inner surface of the web of the pawl housing in which a lug projecting from the facing flat face of the entraining rocker engages, wherein in the end region opposite the lug in the pivoted-out position of the entraining rocker the elongate recess then has a laterally enlarged receiving portion for the lug into which the lug is moved in the pivoted-out position of the entraining rocker, i.e. the position in which it is locked in the pawl housing. In order to ensure the pivoting of the entraining rocker along the desired partial pull-out path, in a variant of the invention it is proposed that the end surfaces of the receptacle in the entraining rocker are constructed as oblique surfaces extending obliquely with respect to the direction of displacement of the pawl component in such a way that during displacement of the pawl component in the drawer pull-out direction the entraining lug projecting from the pawl component slides on the associated oblique surface and pivots the entraining rocker out into the associated recess but during displacement of the pawl component in the drawer retraction direction on entering the receptacle the entraining lug slides downwards on the associated oblique surface and pivots the entraining rocker back out of the recess. BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in greater detail in the following description with reference to the drawings of an embodiment, in which: FIG. 1 shows a vertical sectional view through an embodiment of a drawer pull-out guide according to the invention with an automatic retraction device; FIG. 2 shows a side view of the automatic retraction device of the pull-out guide shown in FIG. 1 ; FIG. 3 shows a plan view in the direction of the arrow 3 in FIG. 2 ; FIG. 4 shows a sectional view in the direction of the arrows 4 - 4 in FIG. 2 ; FIG. 5 shows a sectional view in the direction of the arrows 5 - 5 in FIG. 2 ; FIG. 6 shows a view of the pawl housing of the automatic retraction device of the pull-out guide according to the invention in the viewing direction corresponding to FIG. 2 with a liner damper shown lifted off from the pawl housing; FIG. 7 shows a view of the pawl housing in the direction of the arrow 7 in FIG. 6 ; FIG. 8 shows a side view of a pawl component guided so as to be longitudinally displaceable in the pawl housing according to FIGS. 6 and 7 ; FIG. 9 shows a view of the pawl component in the direction of the arrow 9 in FIG. 8 ; FIG. 10 shows a side view of an entraining rocker which is likewise guided so as to be longitudinally displaceable in the pawl housing; FIG. 11 shows a view of the entraining rocker in the direction of the arrow 11 in FIG. 10 ; FIGS. 12 a to 12 c each show a side view, a plan view and a sectional view of the automatic retraction device shown in FIGS. 2 to 5 without the linear damper in the completely retraction position of the pawl component; FIGS. 13 a to 13 c show views of the automatic retraction device which correspond to the representations in FIGS. 12 a to 12 c in an intermediate position of the pawl component in which the entraining rocker is locked in the pawl housing; FIGS. 14 a, 14 b show views of the automatic retraction device corresponding to FIGS. 12 a and 12 b in the fully pulled-out position of the pawl component in which it is locked against being pulled back by the spring force acting on it; and FIG. 15 shows a sectional view on an enlarged scale corresponding to FIG. 13 showing the entraining rocker in the position in which it is locked in the pawl housing. DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a sectional view taken at right angles to the pull-out direction through a pull-out guide denoted as a whole by 10 , the guide rail 12 of which can be fixed on the supporting wall (not shown) of a cupboard carcass by way of a vertical fixing leg 14 . On the other hand, the running rail 16 can be placed in the open underside of a side wall frame—likewise not shown—of a drawer as a closed metal hollow profile. In the special case the pull-out guide 10 is constructed as a full pull-out means, i.e. between the guide rail 12 end the running rail 16 a central rail 18 is also disposed which is formed by a metal profile of U-shaped cross-section, of which the legs which are bent horizontally at right angles from the connecting web part and are guided into the interior of the guide rail 12 or of the running rail 16 are guided and retained by anti-friction bearings constructed in the illustrated case as rollers mounted in cages so as to be longitudinally displaceable in each case relative to the associated rail. Since this design of drawer pull-out guides is known per se and the invention is not limited to the type of pull-out guides described in the special embodiment, the pull-out guide 10 is not described in detail below. The automatic retraction device 20 which is illustrated in section in the drawings and is explained in greater detail below in connection with FIGS. 2 to 11 is disposed in the intermediate space formed between the guide rail 12 and the fixing leg 14 intended for fixing the guide rail on a supporting wall. The automatic refraction device 20 has a pawl housing 22 which is of approximately U-shaped construction in cross-section and in which a pawl component 24 is guided so as to be longitudinally displaceable over a predetermined path, wherein in the upper edge region of the pawl component projecting out of the pawl housing 22 a receptacle 26 is provided in which the horizontal leg of an angled catch fixed on the running rail can engage. When the running rail 16 is displaced relative to the guide rail 12 in the pull-out direction, the catch 28 engaging in the receptacle 26 entrains the pawl component 24 , so that the pawl component 26 is entrained over the displacement path provided in the pawl housing. The automatic retraction device 20 corresponds in principle to the aforementioned automatic retraction device already known from DE 40 20 277 C2, i.e. the flat pawl component 24 which is shown separately in FIGS. 8 and 9 and is provided with the receptacle 26 has on each of its opposing flat sides a pair of guide lugs 30 which are spaced from one another and engage in elongate slot-like guides 32 provided in the facing inner faces of the pawl housing 22 . Over the greater part of their longitudinal extent the guides 32 extend in a straight line and are only curved in an arc in their left-hand end region shown in FIGS. 2 and 6 so that the appertaining guide lugs 30 are guided downwards into the left-hand end position in the curved end portions when the pawl component 24 is displaced and then pivot the pawl component 24 into the tilted end position shown in FIG. 14 in which the catch 28 provided on the running rail 16 can enter or leave the receptacle 26 depending upon the direction of displacement of the running rail relative to the guide rail 12 . In the tilted end position the pawl component 24 is locked by an elongate helical spring 34 . The locking takes place by displacement of the running rail 16 or of the drawer resting on the running rail in the direction into the interior of the carcass. The catch provided on the running rail 16 then exerts a force on the right-hand limit of the receptacle 26 in FIG. 8 , as a result of which the pawl component is tilted back out of the locked position and disengaged. Due to the bias of the spring 34 the pawl component is then drawn into the right-hand end position shown in FIGS. 12 a and 12 c and thereby entrains the running rail 16 and the drawer resting thereon into the completely retracted position. The retraction movement is slowed down by a damper constructed as an elongate piston damper 38 ( FIGS. 2 and 6 ) as a function of the speed, so that the drawer is guided into the end position without impact and without corresponding resulting vibrations. In the case of drawers with a high carrying capacity and also potentially high dead weight, the spring 34 must engage with a corresponding high biasing force on the locked pawl component 24 . The consequence of this is that during opening of a drawer a correspondingly high pull-out force must be generated until the pawl component 24 is locked in the pawl housing 22 . This means that as pulling out begins the drawer has a significant resistance to pulling out, which is already undesirable for reasons of comfort. In order to create a marked reduction in this resistance to pulling out and nevertheless to ensure smooth and complete retraction of a drawer mounted with the pull-out guide 10 according to the invention in a cupboard carcass, in a variant according to the invention it is proposed that the retraction forced exerted by the spring 34 on the pawl component is only so strong that the opening force to be exerted by a person opening the drawer is of a comfortable magnitude, i.e. not too high, even in the end region of the locking path. On the other hand, in order as the drawer approaches the closed position in which the biasing force of the spring 34 decreases markedly due to the largest possible displacement path the closing force is kept sufficiently high in order to close the drawer completely and reliably, in a variant according to the invention a second spring 36 ( FIG. 3 ) is disposed parallel to the spring 34 in the pawl housing 22 and the end of this second spring near the pawl component does not engage directly on the pawl component 24 but on an entraining rocker 40 which is displaceable together with the pawl component in the pawl housing 22 and is shown separately in FIGS. 10 and 11 . A crucial factor in ensuring that the total force necessary for pulling out the drawer does not rise again to an undesirable value due to the spring 36 additionally engaging on the entraining rocker 40 , the entraining coupling of the entraining rocker 40 with the pawl component 24 only occurs over a first part of the pull-out path during which the two springs 34 , 36 build up relatively low spring forces in spite of their parallel arrangement. After a first part of the pull-out path the entraining rocker 40 is decoupled from the pawl component 24 and locked in the pawl housing 22 , so that then over the rest of the pull-out path only the spring tension of the spring 34 exerts a restoring force on the pawl component 24 . Thus when the drawer is closed the automatic retraction device 20 first of all exerts the closing force built up in the spring 34 as the closed position is approached and retracts the drawer by way of the catch 28 and the running rail 16 . After a predetermined part of the retraction path the entraining coupling of the pawl component 24 to the entraining rocker 40 is restored, so that the latter is disengaged from the pawl housing 22 . As a result in addition to the force of the already partially relaxed spring 34 the biasing force of the additional spring 36 then becomes effective and the total retraction force is increased to a value necessary for reliable closing of the drawer. For the embodiment of the pull-out guide according to the invention which is described here, the actual release of the entraining coupling of the entraining rocker 40 to the pawl component 24 only during a part of the total retraction or pull-out path is produced by an arrangement whereby the entraining rocker 40 is disposed between the inner face of the web of the pawl housing 22 facing the pawl component and the underside of the pawl component 24 facing it, wherein an entraining lug 44 projects from the underside of the pawl component 24 towards the entraining rocker 40 and is for its part disposed below the pawl component 24 so as to be pivotable or tiltable in the transverse direction in the pawl housing 22 . Associated with the entraining lug 44 is a receptacle 46 in the entraining rocker 40 in which the entraining lug 44 engages during the entraining coupling of the pawl component 24 and entraining rocker 40 . In alignment with the entraining rocker 40 there is provided in the pawl housing 22 a recess 48 which extends in the direction of displacement of the pawl component and into which a portion of the entraining rocker 40 can be pivoted in a predetermined displacement position and can be locked against further displacement. This locked position is shown for example in FIG. 13 c and—on an enlarged scale—in FIG. 15 . In this position of the entraining rocker 40 in which it is pivoted into the recess 48 the entraining lug 44 can come out of the receptacle 46 and is then decoupled from the entraining rocker during the further tension of the pawl component 24 . Due to the oblique design of the limits of the receptacle 46 the entraining lug 44 forcibly tilts the entraining rocker 40 into the locked position or unlocks it again when each respective end of the partial displacement path of the entraining rocker 40 is reached. The locking itself takes place on a step 48 of the entraining rocker 40 or by means of a lug 50 which projects from the entraining rocker 40 to the base of the pawl housing 22 and engages in an elongate depression or through opening 52 which extends in the base of the pawl housing 22 and has on one end a laterally enlarged receiving portion 52 a for the lug 50 so that when the entraining rocker 40 is tilted the lug 50 goes over into this receiving portion. Three different positions of the pawl component 24 are illustrated in FIGS. 12 a to 14 b in different views or sections. In FIGS. 12 a to 12 c the position of the pawl component 24 and also of the entraining rocker 40 in locking engagement with the pawl component is shown in the completely retracted end position. In FIGS. 13 a to 13 c in a corresponding representation the position of the pawl component 24 is shown in the displacement position in which the entraining coupling of the entraining rocker 40 already locked in the pawl housing 22 is released, whilst in FIGS. 14 a and 14 b the outermost end position of the pawl component 24 is shown in which the pawl component 24 is locked in its tilted end position, so that the catch 28 provided on the running rail 16 can leave the receptacle 26 or enter the receptacle 26 .

A drawer pull-out guide including an automatic retraction device having a pawl component with a receptacle that receives a catch on a running rail as the rails move relative to the guide rail when approaching a closed position and an entraining rocker. During a final part of retraction movement of the pawl component, the entraining rocker being coupled to and movable with the pawl component; and during an initial displacement path of the pawl component the entraining rocker being decoupled from the pawl component and retained against longitudinal displacement in the pawl housing. A first spring biasing the pawl component into a first end position and locking the pawl component; and a second spring for biasing the entraining rocker in a direction of retraction engages on the entraining rocker.

The present patent application is a Continuation of application Ser. No. 11/084,388, filed Mar. 17, 2005 now U.S. Pat. No. 7,515,179. FIELD OF THE INVENTION The present invention relates to an image sensor; and more particularly, to a method for integrating an image sensor capable of removing a flicker noise. DESCRIPTION OF RELATED ARTS An image sensor is a device generating an image by using a characteristic that a semiconductor device reacts to a light. That is, the image sensor is a device that reads an electric value by sensing a brightness and a wavelength of each different light coming from a subject. The image sensor serves a role in changing the electric value into a level capable of a signal process. That is, an image sensor is a semiconductor device that converts an optical image into electrical signals. In the image sensors, a charge coupled device (CCD) is the semiconductor device that each of metal-oxide-silicon (MOS) capacitors are placed in close proximity and charge carriers are stored in or transferred between capacitors. CMOS image sensors are devices adopting a switching method for detecting output sequentially by making and using as many MOS transistors as the number of pixels based on CMOS technology that uses peripheral circuits such as control circuits and signal processing circuits. The CMOS image sensor has a great advantage of consuming a low voltage, thereby being very useful to a personal portable system such as a cellular phone. Applicable fields of the image sensor are various, including a still-camera, a personal computer (PC) camera and terminals for a medicine, a toy and carrying. Meanwhile, if a light source is different, a flicker noise appears. However, most cases applied to the applicable fields of the image sensor requires to be used regardless of the light source and thus, it is necessary to have a capability for automatically removing the flicker noise. The CMOS image sensor is supposed to obtain an image by controlling a time that the image sensor is exposed to a light, i.e., an integration time. If this exposed time has the integration time with an integer multiple compared with a frequency of the light source, then there is no problem. However, if this exposed time has a different integration time compared from the frequency of the light source, an amount of the light received by each line becomes different in case of the CMOS image sensor taking a data according to each line. Accordingly, a final image seems to have stripes on the image, thereby being called the flicker noise. FIG. 1 is a graph briefly illustrating a light energy distribution according to a time when an integration time accords with a frequency of a light source. Referring to FIG. 1 , the light source having the frequency of approximately 60 Hz is used and at this time, an energy distribution period of the light source is approximately 1/120 seconds. If the integration time is identical with the energy distribution period of the light source, i.e. approximately 1/120 seconds, the light energy of a section A where integration to a first line is performed at a point where a phase of the light source is approximately 0 appears identically with the light energy of a section B where integration to a first line is performed at a point where a phase of the light sources is maximum during integration, i.e., scanning, of the image sensor using a line scanning way. Accordingly, the flicker noise is not generated. FIG. 2 is a graph briefly illustrating a light energy distribution according to a time when an integration time does not accord with a frequency of a light source. Referring to FIG. 2 , the light source of approximately 60 Hz is used and at this time, the energy distribution period of the light source is approximately 1/120 seconds. If the integration time is approximately 1/100 seconds which is different from the energy distribution period of the light source, i.e. approximately 1/120 seconds, the light energy of a section C where integration to the first line is performed at a point where the phase of the light source is approximately 0 appears differently from the light energy of a section D where integration to the first line is performed at the point where the phase of the light sources is maximum during integration, i.e., scanning, of the image sensor using the line scanning way. Accordingly, the flicker noise is generated. Most CMOS image sensor controls the integration time in case of using only one frequency, thereby solving a problem generating the flicker noise. However, Japan and some countries of Europe use a frequency of approximately 50 Hz and the rest uses a frequency of approximately 60 Hz. An auto flicker cancellation (AFC) capability to these two frequencies is mostly operated by using logics. However, in case of using the logics, a number of logics are necessary, thereby causing a big burden on a digital circuit. SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a method for integrating an image sensor capable of removing a flicker noise without causing any burdens on a hardware due to setting up additional logics. In accordance with one aspect of the present invention, there is provided a method for integrating an exposure time of an image sensor employing a line scan method, including the steps of: performing an integration to a first line when an integer multiple of a light source frequency is different from an integration time; and performing an integration to a second line at a phase substantially equal to a phase in which the integration to the first line is started. In accordance with another aspect of the present invention, there is provided a method for integrating an image sensor using a line type scan, including the steps of: performing an integration to a first line; comparing an integration time with an integer multiple of a frequency of a light source; delaying an integration to a second line until a phase of the second line is substantially identical with a phase of the frequency of the light source started from the integration to the first line as the integer multiple of the frequency of the light source and the integration time are different from each other as a result of the comparison; and performing the integration to the second line in the phase which is substantially identical with the phase of the frequency of the light source started from the integration to the first line. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects and features of the present invention will become better understood with respect to the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which: FIG. 1 is a graph briefly illustrating a light energy distribution according to a time when an integration time accords with a frequency of a light source; FIG. 2 is a graph briefly illustrating a light energy distribution according to a time when an integration time does not accord with a frequency of a light source; FIG. 3 is a graph illustrating a time control when a frequency of a light source is an integer multiple of approximately 50 Hz and an integration time is 1/(an integer multiple of approximately 60 Hz) in accordance with the present invention; FIG. 4 is a graph illustrating a time control when a frequency of a light source is an integer multiple of approximately 60 Hz and an integration time is 1/(an integer multiple of approximately 50 Hz) in accordance with the present invention; and FIG. 5 is a flowchart schematizing an integration method of a line scanning way in accordance with a present invention for removing a flicker noise. DETAILED DESCRIPTION OF THE INVENTION Hereinafter, detailed descriptions on preferred embodiments of the present invention will be provided with reference to the accompanying drawings. A flicker noise phenomenon happens because a frequency of a light source and an integration time of an image sensor are different from each other. A light source is a light generator used in our daily life. Accordingly, the sun is an example of the light source and a fluorescent lamp is also an example of the light source. In case of the sun light, the frequency is fairly high and thus, the integration time is always several thousands times greater than a sun light period. Therefore, the flicker noise is not generated under the sun light. However, in case of the fluorescent lamp, the frequency is approximately 50 Hz or approximately 60 Hz, thereby causing the flicker noise as to an image sensor having an integration time of several tens ms. A reason why various methods are applied to a CMOS image sensor to remove the flicker noise is because a method for extracting a data from a pixel uses a method for reading one line by one line. Since an identical integration time is applied to each line, if the integration time is different from the frequency of the light source, an amount of energy formed by the light source every each line becomes different from the integration time. Accordingly, the same amount of energy is not inputted and a different amount of energy is inputted, thereby appearing the flicker noise. The present invention solves this problem of the flicker noise by only using a time control without setting up any additional logics to a hardware. That is, in accordance with the present invention, during applying the integration method to the image sensor using a line scanning way, in case of an integer multiple of the frequency of the light source is different from the integration time, the integration to a first line is first finished and then, the integration to a second line is performed at the same phase which is practically identical with the phase at which the integration to the first line started. FIG. 3 is a graph illustrating a time control in case of a frequency of a light source is an integer multiple of approximately 50 Hz and an integration time is 1/(an integer multiple of approximately 60 Hz) in accordance with the present invention. Referring to FIG. 3 , the frequency of the light source is approximately 50 Hz and thus, an energy distribution period of the light source becomes approximately 1/100 seconds. The integration time is approximately 1/120 seconds which is different from approximately 1/100 seconds, an energy distribution period of the light source. A section E representing the integration to the first line shows to perform the integration at a point at which a phase of the light source is approximately 0. After completing the integration to the first line, the integration to the second line is performed at a section G after waiting approximately 1/(an integer multiple of 50) to approximately 1/(an integer multiple of 60), i.e., approximately 1/100 seconds to approximately 1/120 seconds. By using the same way, the integration is employed at a point of approximately 0 where the phase of the light source in a section G is practically identical with the phase of the light source in a section E. Then, the integration is paused in a section H for approximately 1/100 seconds to approximately 1/120 seconds. Afterwards, the integration is performed again at a point of approximately 0 where the phase of the light source in a section I is practically identical with the phase of the light source in a section E. As described above, although the frequency of the light source is approximately 50 Hz and the integration time is approximately 60 Hz, it is possible to maintain the light energy almost identically every each line by controlling each phase point of the light source identically with the integration time of each line. FIG. 4 is a graph illustrating a time control when a frequency of a light source is an integer multiple of approximately 60 Hz and an integration time is 1/(an integer multiple of approximately 50 Hz). Referring to FIG. 4 , since the frequency of the light source is approximately 60 Hz, the energy distribution period of the light source is approximately 1/120 seconds. The integration time is approximately 1/100 seconds which is different from the energy distribution period of the light source which is approximately 1/120 seconds. A section J representing the integration to the first line shows to perform the integration at a point at which a phase of the light source is approximately 0. After completing the integration to the first line, the integration to the second line is performed at a section L after waiting approximately 2/(an integer multiple of 60) to approximately 1/(an integer multiple of 50), i.e., from approximately 2/120 seconds to approximately 1/100 seconds. By using the same way, the integration is employed at a point of approximately 0 where the phase of the light source in a section L is practically identical with the phase of the light source in a section G. Then, the integration is paused in a section M for approximately 1/100 seconds to approximately 1/120 seconds. Afterwards, the integration is performed again at a point of approximately 0 where the phase of the light source in a section J is practically identical with the phase of the light source in a section L. As shown above, although the frequency of the light source is approximately 50 Hz and the integration time is approximately 60 Hz, it is possible to maintain the light energy almost identically every each line by controlling each phase point of the light source identically with the integration time every each line. Accordingly, in all cases shown in FIGS. 3 and 4 , it is possible to remove the flicker noise. FIG. 5 is a flowchart schematizing an integration method of a line scanning way in accordance with a present invention for removing a flicker noise. Referring to FIG. 5 , an integration method of an image sensor using a line scanning way is examined. First, an integration is employed to a first line at step S 501 and then, an integer multiple of a frequency of a light source is compared with an integration time at step S 502 . As a result of comparing the integer multiple of the frequency of the light source with the integration time, as the integer multiple of the frequency of the light source is different from the integration time, the integration to a second line is delayed until a phase becomes substantially identical with the phase of the frequency of the light source started from the integration to the first line. That is, until the integration time of the first line and the integration time of the second line become the same phase, a feedback loop is continuously operated. Afterwards, when becoming the identical phase, the integration to the second line is performed at the substantially identical phase of the frequency of the light source started from the integration to the first line. Meanwhile, as a result of a step S 504 , if the integer multiple of the frequency of the light source is identical with the integration time, the integration to the second line is performed after a predetermined delaying time, i.e., approximately 808 clicks. It is a typical way for the line scanning method to perform the integration to a subsequent line after the predetermined delaying time. This delaying time can be variably controlled according to a property of each image sensor and an operating region. As described above, the present invention makes an auto flicker cancellation (AFC) possible simply by using a time control without causing any burdens on a hardware. The present invention can remove the flicker noise without causing any burdens on the hardware, thereby improving a price competitiveness. The present application contains subject matter related to the Korean patent application No. KR 2004-0029015, filed in the Korean Patent Office on Apr. 27, 2004, the entire contents of which being incorporated herein by reference. While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

Disclosed is a method for integrating an image sensor capable of removing a flicker noise without causing any burdens on a hardware due to setting up additional logics. The method for integrating an exposure time of an image sensor employing a line scan method, including the steps of: performing an integration to a first line when an integer multiple of a light source frequency is different from an integration time; and performing an integration to a second line at a phase substantially equal to a phase in which the integration to the first line is started.

CROSS REFERENCE TO RELATED APPLICATION [0001] This application is a continuation of U.S. application Ser. No. 14/493,893, filed Sep. 23, 2014, which is a continuation of U.S. application Ser. No. 14/167,477, filed Jan. 29, 2014, now U.S. Pat. No. 8,854,582, which is a divisional of U.S. application Ser. No. 13/028,311, filed Feb. 16, 2011, now U.S. Pat. No. 8,648,988, the contents of which are incorporated herein by reference. CLAIM OF PRIORITY [0002] The present application claims priority from Japanese Patent Application JP 2010-032443 filed on Feb. 17, 2010, the content of which is hereby incorporated by reference into this application. FIELD OF THE INVENTION [0003] The present invention relates to a liquid crystal display device and particularly to a liquid crystal display device including a liquid crystal display panel in which alignment films are provided with the capability of liquid crystal (LC) alignment control by light irradiation. BACKGROUND OF THE INVENTION [0004] In a liquid crystal display (LCD) device, a TFT substrate over which pixel electrodes and thin-film transistors, inter alia, are formed in a matrix and an opposing substrate over which color filters, inter alia, are formed in positions corresponding to the pixel electrodes in the TFT substrate are placed facing each other and liquid crystals are sandwiched between the TFT substrate and the opposing substrate. An image is produced by controlling light transmissibility through liquid crystal modules pixel by pixel. [0005] Owing to the fact that LCD devices are flat and light, they are used in an increasing wide range of applications in various fields including a large-screen display of TV and the like, mobile phones, Digital Still Camera (DSC), etc. Meanwhile, viewing angles are a problem specific to LCD devices. Viewing angles imply a phenomenon in which brightness and chromaticity change depending on when the screen is viewed squarely and when viewed from an oblique direction. An In Plane Switching (IPS) type LCD in which liquid crystal molecules are moved by applying an electric field in a horizontal direction offers superior viewing angle performance. [0006] As an LC alignment process applied for alignment films for use in an LCD device, that is, a method for providing the alignment films with the capability of LC alignment control, rubbing is a conventionally used method. The LC alignment process by this rubbing accomplishes alignment of liquid crystals by rubbing the alignment films with a cloth. An alternative method for providing the alignment films with the capability of LC alignment control without touching the alignment films is called a photo-alignment method. Because liquid crystals in the IPS type LCD do not need to have a pretilt angle, the photo-alignment method can be applied to the IPS type LCD. [0007] A photo-alignment process, namely, a photolytic LC alignment by irradiation of light such as, typically, ultraviolet light is disclosed in Japanese Published Unexamined Patent Application No. 2004-206091, in which the following are described about the photo-alignment process of photolytic LC alignment: (1) this process decreases the disturbance of LC alignment due to a complex level difference configuration in a pixel region; and (2) this process eliminates thin-film transistor breakdown caused by static electricity generated in the LC alignment process by rubbing and a poor-quality display caused by the disturbance of LC alignment due to pilling of the rubbing cloth or dust attached thereto and also eliminates process complexity because of frequent rubbing cloth replacement required to obtain the capability of uniform LC alignment control. [0008] In Japanese Published Unexamined Patent Application No. 2008-235900, a two-layer alignment film structure is described, wherein an alignment film capable of photo-alignment is formed in an upper layer and an alignment film having a lower volume resistance than the upper layer is formed in a lower layer, thereby shortening the time in which an afterimage disappears. In Japanese Published Unexamined Patent Application No. 2003-57147, a method for measuring azimuthal anchoring strength which becomes a problem in photo-alignment is described. SUMMARY OF THE INVENTION [0009] In terms of providing the alignment films with the capability of LC alignment control, it is known that the alignment stability of the photo-alignment process is generally lower than that of the rubbing process. Low alignment stability varies an initial LC alignment direction, resulting in a poor-quality display. Especially, in an LCD device using an IPS type LCD panel for which high alignment stability is required, low alignment stability tends to give rise to a power-quality display typified by afterimages. [0010] In the photo-alignment process, a step of stretching and straightening the main chains of polymeric molecules as in the rubbing process does not exist in the LCD process. Instead, in the photo-alignment process, an alignment film made of a synthetic polymer typified by polyimide, irradiated by polarized light, is provided with uniaxial anisotropy in a direction perpendicular to the polarization direction, resulting from that the main chains of the polymer are broken in a direction parallel to the polarization direction. Liquid crystal molecules are aligned along the orientation of long main chains that remained extending straight without being broken. If the length of the main chains is short, it results in a decrease in the uniaxial anisotropy, which in turn weakens the interaction with liquid crystals. As a result, the alignment stability decreases and the above-mentioned afterimages are liable to occur. [0011] Therefore, in order to improve the uniaxial anisotropy and the alignment stability of an alignment film, an increase in the molecular weight of the alignment film is needed. As a solution for this, it is possible to use a photo-alignment film material obtained by imidization of polyamide acid ester. According to this solution, such polyamide acid ester material is not accompanied by a reaction of decomposition into diamine and acid anhydride during an imidization reaction, which would take place in a conventionally used polyamide acid material. Thus, the alignment film can be maintained to have a large molecular weight after imidization and its alignment stability comparable to that provided by the rubbing process can be obtained. [0012] Because the polyamide acid ester material does not include a carboxylic acid in its chemical structure, it yields a higher voltage retention rate of LCD as compared with a polyamide acid material and can ensure an improvement in long-term reliability. [0013] For the meantime, as for LCD devices using photo-alignment, during long time operation, the direction of initial alignment of liquid crystals will offset from that direction initially determined when the LCD device was manufactured. Due to this, afterimages arise, which are called AC afterimages. It is found that these afterimages are generated because the azimuthal anchoring strength of alignment films is weak. Hence, the AC afterimages are irreversible and unrecoverable. The azimuthal anchoring strength means the strength that provides resistance against the offset of liquid crystals in an azimuthal direction from the initial alignment direction. [0014] Meanwhile, afterimages also arise from charge accumulation in alignment films. They are called DC afterimages. The DC afterimages are reversible and disappear over time. [0015] A problem of the present invention is to improve the azimuthal anchoring strength of alignment films in the photo-alignment method and prevent so-called AC afterimages from arising. An object of the present invention is to prevent so-called DC afterimages from arising or to make the DC afterimages disappear quickly even if they arise. [0016] The present invention overcomes the above-discussed problems and offers practical means as will be outlined below. Specifically, an alignment film for aligning liquid crystals is adapted to have a two-layer structure including a photo-alignment film in an upper layer adjoining liquid crystals and an alignment film with enhanced film strength in a lower layer adjoining a substrate. The upper layer photo-alignment film is formed of a precursor of polyamide acid ester containing 80% or more polyamide acid ester including cyclobutane. The lower layer alignment film with enhanced film strength is formed of a precursor of polyamide acid. [0017] After drying and firing the alignment film thus including the two layers, the film is irradiated with polarized ultraviolet light, so that photo-alignment of the photo-alignment film is performed. Thereafter, the alignment film is finished by heating the substrate irradiated with the ultraviolet light. [0018] The photo-alignment film is imidized at a rate of 50% or more. The photo-alignment film accounts for between 30% and 60% of the whole alignment film. The volume resistivity of the upper layer photo-alignment film is larger than that of the lower layer alignment film with enhanced film strength. [0019] An alternative structure of the present invention is as follows: the upper layer photo-alignment film is formed of a precursor of polyamide acid containing 80% or more polyamide acid including cyclobutane, and the lower layer alignment film with enhanced film strength is formed of a precursor of polyamide acid not including cyclobutane. The fabrication process is the same as described above. [0020] A further alternative structure of the present invention is as follows: the upper layer photo-alignment film is formed of a precursor of polyamide acid ester containing 80% or more polyamide acid ester including cyclobutane, and the lower layer alignment film with enhanced film strength is formed of a precursor of polyamide acid ester not including cyclobutane. The fabrication process is the same as described above. [0021] According to the present invention, the alignment film has the two-layer structure including the photo-alignment film adjoining liquid crystals and the alignment film with enhanced film strength adjoining the substrate. Therefore, by way of photo-alignment, it is possible realize a liquid crystal display device in which the azimuthal anchoring strength is strong and less afterimages appear after long time operation. [0022] According to the present invention, after photo-alignment by performed by ultraviolet light irradiation, the substrate is heated at a predetermined temperature. Therefore, it is possible to enhance the (LC) anchoring strength of the alignment film, as degrading the mechanical strength of the alignment film is avoided. BRIEF DESCRIPTION OF THE DRAWINGS [0023] FIG. 1 is a cross-sectional diagram of an IPS type liquid crystal display device; [0024] FIG. 2 is a plan view of a pixel electrode in FIG. 1 ; [0025] FIGS. 3A and 3B illustrate an alignment film structure according to the present invention; [0026] FIGS. 4A and 4B illustrate the principle of a photo-alignment film; [0027] FIGS. 5A and 5B are cross-sectional diagrams of an alignment film of the present invention; [0028] FIG. 6 is a chemical formula of polyamide acid ester including cyclobutane; [0029] FIG. 7 is a chemical formula of polyamide acid including cyclobutane; [0030] FIG. 8 is a process for forming the alignment film for photo-alignment; [0031] FIG. 9 is a graph showing a relationship between azimuthal anchoring strength and afterimage; [0032] FIG. 10 is a graph showing a relationship among alignment film structure, process for forming the alignment film, and azimuthal anchoring strength; [0033] FIG. 11 is a graph showing a relationship between process conditions for forming a photo-alignment film and azimuthal anchoring strength; [0034] FIG. 12 shows a pattern for evaluating DC afterimages; and [0035] FIG. 13 shows a result of DC afterimage evaluation. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0036] Subject matters of the present invention will be described in detail by means of the following exemplary embodiments. First Embodiment [0037] FIG. 1 is a cross-sectional diagram showing a structure in a display region of an IPS type liquid crystal display device. A variety of electrode structures for IPS type liquid crystal display devices are proposed and put in practical use. The structure shown in FIG. 1 is widely used now. In simple terms, over a common electrode 108 formed in a flat monolithic form, a comb-shaped pixel electrode 110 is formed with an insulation layer intervening therebetween. By rotating liquid crystals 301 depending on a voltage between the pixel electrode 110 and the common electrode 108 , light transmissibility through a liquid crystal layer 300 is controlled pixel by pixel and an image is thus produced. The structure in FIG. 1 will be described in detail below. While the present invention is described by taking the structure in FIG. 1 as an example, the invention can be applied to an IPS type liquid crystal display device having a structure other than that shown in FIG. 1 . [0038] In FIG. 1 , a gate electrode 101 is formed on the top of a TFT substrate 100 made of glass. The gate electrode 101 is formed in the same layer as for a scan line. The gate electrode 101 is formed of an AlNd alloy and a MoCr alloy layered over the AlNd alloy. [0039] A gate insulation film 102 covering the gate electrode 101 is formed of SiN. On the top of the gate insulation film 102 , a semiconductor layer 103 is formed of a-Si film in a position opposed to the gate electrode 101 . The a-Si film is formed by plasma CVD. The a-Si film defines a channel portion of a TFT, and a source electrode 104 and a drain electrode 105 are formed over the a-Si film, sandwiching the channel portion therebetween. In addition, an n+Si layer, not shown, is formed between the a-Si film and the source electrode 104 or the drain electrode 105 . The n+Si layer is formed for providing an ohmic contact between the semiconductor layer and the source electrode 104 or the drain electrode 105 . [0040] The source electrode 104 overlaps a part of an image signal line and the drain electrode 105 is connected to the pixel electrode 110 . Both the source electrode 104 and the drain electrode 105 are formed together in the same layer. In the present embodiment, the source electrode 104 or the drain electrode 105 is formed of a MoCr alloy. If it is desired to decrease the electrical resistance of the source electrode 104 or the drain electrode 105 , an electrode structure in which, for example, an AlNd alloy is sandwiched between MoCr alloys is used. [0041] An inorganic passivation film 106 covering the TFT is formed of SiN. The inorganic passivation film 106 protects the TFT, particularly, its channel portion against impurities 401 . Over the inorganic passivation film 106 , an organic passivation film 107 is formed. Since the organic passivation film 107 protects the TFT and also acts to planarize the surface, it is formed thick. Its thickness ranges from 1 μmm to 4 μm. [0042] As the material of the organic passivation film 107 , a photosensitive acryl resin, silicon resin, or polyimide resin, inter alia, is used. In the organic passivation film 107 , a through hole 111 needs to be formed in a location to connect the pixel electrode 110 and the drain electrode 105 . Because the organic passivation film 107 is photosensitive, the through hole 111 can be formed by exposing the organic passivation film 107 itself to light and through development without using a photoresist. [0043] On the top of the organic passivation film 107 , the common electrode 108 is formed. The common electrode 108 is formed by sputtering ITO (Indium Tin Oxide), which makes a transparent, electrically conductive film, over the display region. That is, the common electrode 108 is formed in a planar form. After forming the common electrode 108 over the surface by sputtering, the common electrode 108 is removed by etching only in the portion of the through hole 111 to provide electrical conduction between the pixel electrode 110 and the drain electrode 105 . [0044] An upper insulation film 109 covering the common electrode 108 is formed of SiN. After the upper insulation film 109 is formed, the through hole 111 is formed by etching. By etching the inorganic passivation film 106 , using the upper insulation film 109 as a resist, the through hole 111 is formed. Then, an ITO film, which becomes the pixel electrode 110 , covering the upper insulation film 109 and the through hole 111 , is formed by sputtering the ITO. The pixel electrode 110 is formed by patterning the ITO film deposited by sputtering. The ITO film which becomes the pixel electrode 110 is also deposited on the walls of the drain hole 111 . This makes electrical conduction between the drain electrode 105 extending from the TFT and the pixel electrode 110 in the through hole 111 and an image signal is thus supplied to the pixel electrode 110 . [0045] FIG. 2 shows one example of the pixel electrode 110 . The pixel electrode is a comb-shaped electrode. Slits 112 are defined between each comb teeth. The planar common electrode is formed under the pixel electrode 110 . When an image signal is applied to the pixel electrode 110 , liquid crystals 301 are rotated by lines of electric force generated between the pixel electrode 110 and the common electrode 108 and passing through the slits 112 . Thereby, light passing through the liquid crystal layer 300 is controlled to produce an image. [0046] FIG. 1 is also intended to explain this aspect. Gaps between each comb teeth of the comb-shaped electrode correspond to the slits 112 as shown in FIG. 1 . A constant voltage is applied to the common electrode 108 and a voltage of an image signal is applied to the pixel electrode 110 . When the voltage is applied to the pixel electrode 110 , as shown in FIG. 1 , lines of electric force are generated to rotate liquid crystals 301 in the direction of the lines of electric force and control the transmission of light from a backlight. Due to the fact that the transmission of light from the backlight is controlled pixel by pixel, an image is produced. [0047] In the example of FIG. 1 , the common electrode 108 formed in the planar form is placed on the top of the organic passivation film 107 and the comb-shaped electrode 110 is placed on the top of the upper insulation film 109 . Conversely to this, however, there may be a case where a pixel electrode 110 formed in a planar form is placed on the top of the organic passivation film 107 and a comb-shaped common electrode 018 is placed on the top of the upper insulation film 109 . [0048] Over the pixel electrode 110 , an alignment film 113 is formed to align the liquid crystals 301 . In the present invention, the alignment film 113 has a two-layer structure including a photo-alignment film 1131 adjoining the liquid crystal layer 300 and an alignment film with enhanced film strength 1132 formed underlying the photo-alignment film 1131 . The structure of the alignment film 113 will be described in detail later. [0049] In FIG. 1 , an opposing substrate 200 is placed across the liquid crystal layer 300 . Inside the opposing substrate 200 , color filters 201 are formed. Red, green, and blue color filters 201 are formed for each pixel to produce a color image. Between each color filter 201 , a black matrix 202 is formed to improve an image contrast. The black matrix 202 also acts as a light shielding film of the TFT and prevents a photo current being flowing in the TFT. [0050] An overcoat film 203 covering the color filters 201 and black matrixes 202 is formed. Because the surface of the color filters 201 and black matrixes 202 is uneven, the surface is planarized by the overcoat film 203 . [0051] Over the overcoat film 203 , an alignment film 113 is formed to determine an initial alignment of liquid crystals. The alignment film 113 of the opposing substrate also has a two-layer structure including a photo-alignment film 1131 adjoining the liquid crystal layer 300 and an alignment film with a lower resistance 1132 formed underlying the photo-alignment film 1131 . Because of IPS that is shown in FIG. 1 , the common electrode 108 is formed in the TFT substrate 100 , not in the opposing substrate 200 . [0052] As shown in FIG. 1 , in IPS, an electrically conductive film is not formed inside the opposing electrode 200 . This makes the potential of the opposing electrode 200 unstable. In addition, an external electromagnetic noise intrudes the liquid crystal layer 300 and has an influence on an image. To eliminate such a problem, a surface electrically conductive film 210 is formed over the outside of the opposing electrode 200 . The surface electrically conductive film 210 is formed by sputtering ITO, which makes a transparent, electrically conductive film. [0053] FIGS. 3A and 3B schematically illustrate an alignment film 113 according to the present invention. FIG. 3A is a transparent plane view of the alignment film 113 and FIG. 3B is a cross-sectional perspective view thereof. The alignment film 113 of the present invention has a two-layer structure including an upper photo-alignment film 1131 adjoining the liquid crystal layer and a lower alignment film with enhanced film strength 1132 . [0054] The molecular formula of polyamide acid ester is represented by chemical formula (1). [0000] [0055] In chemical formula (1), R1 is, individually, an alkyl group having a carbon number from 1 to 8, R2 is, individually, a hydrogen atom, fluorine atom, chlorine atom, bromine atom, phenyl group, alkyl group having a carbon number from 1 to 6, alkoxy group having a carbon number from 1 to 6, vinyl group (—(CH2) m-CH═CH2, m=0, 1, 2) or acetyl group (—(CH2) m-C≡CH, m=0, 1, 2), and Ar is an aromatic compound. [0056] Chemical formula (1) is polyamide acid ester including cyclobutane, but there is also polyamide acid ester not including cyclobutane. However, because what is capable of photo-alignment is polyamide acid ester including cyclobutane, polyamide acid ester including cyclobutane should account for 80% or more of the alignment film material. [0057] The molecular formula of polyamide acid in FIG. 3A is represented by chemical formula (2). Chemical formula (2) is an exemplary structure of polyamide acid not including cyclobutane. [0000] [0058] In chemical formula (2), R2 is, individually, a hydrogen atom, fluorine atom, chlorine atom, bromine atom, phenyl group, alkyl group having a carbon number from 1 to 6, alkoxy group having a carbon number from 1 to 6, vinyl group (—(CH2) m-CH═CH2, m=0, 1, 2) or acetyl group (—(CH2) m-C≡CH, m=0, 1, 2) and Ar is an aromatic compound. [0059] Unlike chemical formula (1), chemical formula (2) does not include cyclobutane. Because the alignment film with enhanced film strength does not need to perform photo-alignment, it is unnecessary for this film to include cyclobutane. Conversely, polyamide acid represented by chemical formula (2) is not susceptible to ultraviolet light, because no cyclobutane exists in it. In addition, a difference between chemical formula (1) and chemical formula (2) lies in that R1 existing in chemical formula (1) representing polyamide acid ester is replaced by H in chemical formula (2). [0060] Since FIG. 3A is a transparent view, a photolytic polymer 10 in the photo-alignment film and a non-photolytic polymer 11 in the alignment film with enhanced film strength are visible in a transparent fashion. In FIG. 3B , the alignment film 113 is formed over the pixel electrode 110 or organic passivation film 107 in FIG. 1 . In FIG. 3B , the alignment film 113 is formed over the pixel electrode 110 . The thickness t 1 of the upper photo-alignment film 1131 is about 50 nm and the thickness t 2 of the lower alignment film with enhanced film strength 1132 is about 50 nm. The boundary between the photo-alignment film 1131 and the alignment film with enhanced film strength 1132 is indefinite and, therefore, it is drawn by a dotted line. [0061] FIGS. 4A and 4B schematically illustrate the principle for aligning liquid crystals by the photo-alignment film 1131 . In FIGS. 4A and 4B , the alignment film with enhanced film strength 1132 is omitted. FIG. 4A shows a state in which the photo-alignment film 1131 has been deposited. The photo-alignment film 1131 is formed of the photolytic polymer 10 . [0062] The photo-alignment film 1131 shown in FIG. 4A is irradiated with ultraviolet light polarized in a horizontal direction, e.g., at an energy of 6 J/cm 2 . In the photo-alignment film 1131 , then, the photolytic polymer 10 in the polarization direction of the polarized ultraviolet light is broken by the ultraviolet light, as is shown in FIG. 4B . That is, breaks 15 are made by the ultraviolet light along the polarization direction of the ultraviolet light. In consequence, liquid crystal modules are aligned in a direction of arrow A in FIG. 4B . [0063] If the main chains of the photolytic polymer 10 are short, as shown in FIGS. 4A and 4B , it results in a decrease in the uniaxial anisotropy of the alignment film, which in turn weakens the interaction with liquid crystals. In consequence, the alignment performance decreases. Hence, it is desirable that the photolytic polymer 10 extends as long as possible in the direction of arrow A in FIG. 4B even after the photo-alignment. In other words, an increase in the molecular weight of the alignment film 113 is needed in order to improve the uniaxial anisotropy and the alignment stability of the alignment film 113 . [0064] The molecular weight of the alignment film 113 can be evaluated in terms of a number average molecular weight. Given that polymers with diverse molecular weights exist in the alignment film 113 , the number average molecular weight is an average molecular weight among the polymers. In the photo-alignment film 1131 , a number average molecular weight of 5000 or more is required to obtain sufficient alignment stability. [0065] In order to achieve the photo-alignment film 1131 with such a large number average molecular weight, imidized polyamide acid ester can be used. The structure of polyamide acid ester is as given previously in chemical formula (1). [0066] Polyamide acid ester is characterized by R1 in chemical formula (1). In the polyamide acid ester, R1 is CnH2n−1, where n is 1 or more. If the polyamide acid ester is used as a precursor of the photo-alignment film 1131 , it is not accompanied by a reaction of decomposition into diamine and acid anhydride during an imidization reaction, which would take place in a conventionally used polyamide acid material. Thus, the photo-alignment film can be maintained to have a large molecular weight after imidization and its alignment stability comparable to that provided by the rubbing process can be obtained. [0067] However, the photo-alignment film suffers from a decrease in the film strength, because the main chains are broken in a particular direction. Study efforts made by the present inventors have revealed that degradation in the azimuthal anchoring strength of an alignment film relates to the mechanical strength of the alignment film. Thus, by making the alignment film of the two-layer structure and by disposing the alignment film with enhanced film strength in the lower layer and the photo-alignment film in the upper layer, the film strength of the whole alignment film is increased, which is effective for improving the azimuthal anchoring strength of the alignment film. [0068] FIGS. 5A and 5B are cross-sectional diagrams to schematically illustrate a way of forming the two-layer alignment film. Forming the alignment film 113 of the two-layer structure can be accomplished without an additional process for forming the alignment film 113 . That is, as shown in FIG. 5A , a mixture material of the photolytic polymer 10 and the polymer 11 for forming the alignment film with enhanced film strength is deposited onto the substrate. Then, one substance that will more readily settle on the substrate is deposited in the lower layer and the other substance is deposited in the upper layer by a leveling effect, as shown in FIG. 5B ; so-called phase separation takes place. [0069] In this embodiment for depositing the two-layer alignment film, what is called the substrate is the ITO film from which the pixel electrode 110 is formed or the organic passivation film 107 . In comparison with polyamide acid ester, polyamide acid has a higher polarity (larger surface energy) and will more readily settle on the ITO film or the organic passivation film 107 . Hence, polyamide acid always makes the lower layer. In the present invention, since the number average molecular weight of the alignment film with enhanced film strength formed of polyamide acid is larger than that of the photo-alignment film formed of polyamide acid ester, phase separation can take place more easily in addition to the polarity or surface energy effect. Of the two layers of alignment film, the photo-alignment film 1131 accounts for between 30% and 60% of the whole alignment film. One reason for this is disposing the photo-alignment film with a sufficient thickness in the upper layer and another reason is that phase separation is easy to take place after depositing the two-layer alignment film. [0070] By heating the thus formed resin film at about 200° C., the alignment film is imidized. Imidization is performed for both polyamide acid 1132 in the lower layer and polyamide acid ester 1131 in the upper layer at the same time. Therefore, it is possible to form the two-layer alignment film 113 through the same process as for forming a one-layer alignment film 113 . [0071] In order to stabilize LC alignment performance, the photo-alignment film 1131 in the upper layer needs to be imidized at a high rate, as it is required to increase the photolysis efficiency of the photolytic polymer 10 . This is because a photolysis reaction is hard to take place, unless the photo-alignment film is well imidized. Since polyamide acid ester is generally hard to imidize, an imidization accelerator may be added as an additive for aiding the imidization. The photo-alignment film 1131 should be imidized at a rate of 50% or more, more preferably, 70% or more. The remaining is polyamide acid ester existing as a precursor in the photo-alignment film 1131 . [0072] On the other hand, because the alignment film with enhanced film strength 1132 in the lower layer has no relation to liquid crystal alignment performance, a rate at which it should be imidized does not need to be specified particularly. That is, a condition for imidization may be set with regard to the imidization of polyamide acid ester in the upper layer. [0073] The boundary between the upper and lower layers of the alignment film is indefinite. This boundary is denoted by a dotted line in FIG. 5B . In FIG. 5B , the photo-alignment film 1131 in the upper layer is composed of polyamide acid ester; particularly, polyamide acid ester including cyclobutane, as is shown in FIG. 6 , accounts for 80% or more of the whole. That is, in the polyamide acid ester, cyclobutane is decomposed by polarized ultraviolet light and this cyclobutane decomposition yields photo-alignment performance. Thus, it is requisite that the proportion of polyamide acid ester including cyclobutane is considerably large. [0074] On the other hand, the alignment film with enhanced film strength 1132 in the lower layer is formed of polyamide acid; it is desirable that polyamide acid including cyclobutane which is shown in FIG. 7 does not exist therein. Instead, polyamide acid not including cyclobutane, as represented by chemical formula (2), is used. That is, this is because it will be expedient that the alignment film with enhanced film strength in the lower layer is not decomposed by ultraviolet light in order to maintain the mechanical strength of the alignment film as the whole even after photo-alignment. [0075] As explained above, the two-layer alignment film is characterized in that it is formed such that the photo-alignment film 1131 in the upper layer includes a considerable amount of cyclobutane, whereas the alignment film with enhanced film strength 1132 in the lower layer does not include cyclobutane. In other words, the photo-alignment film 1131 adjoining liquid crystals includes a considerable amount of cyclobutane, whereas the alignment film with enhanced film strength 1132 adjoining the pixel electrode or organic passivation film, substantially, does not include cyclobutane. [0076] As above, even if the upper layer is formed of polyamide acid ester including a considerable amount of cyclobutane, as a precursor of the alignment film 113 , and the lower layer is formed of polyamide acid not including cyclobutane, as a precursor, the mechanical strength of the whole alignment film may degrade depending on post processing for carrying out photo-alignment. [0077] FIG. 8 is a flowchart illustrating a process for photo-alignment. In FIG. 8 , after depositing an alignment film, the film is dried. Until the film has been dried, the alignment film is phase-separated into two layers of the photo-alignment film 1131 and the alignment film with enhanced film strength 1132 . Then, the alignment film is imidized by firing (burning) it. After that, photo-alignment is performed. Conventionally, the substrate, while being heated at about 200° C., is irradiated with linearly polarized ultraviolet light for photo-alignment. However, during ultraviolet light irradiation that is performed, while the substrate is heated, photolysis takes place by the ultraviolet light also in the lower layer alignment film with enhanced film strength and results in a decrease in the film hardness. [0078] In contrast, the present invention adopts a process in which the substrate is irradiated with polarized ultraviolet light without being heated and, after that, the substrate is heated, as shown in a right-hand section surrounded by a dotted line in FIG. 8 . By carrying out this process, the lower layer alignment film with enhanced film strength can be prevented being subjected to photolysis by the ultraviolet light and the required film strength of the alignment film as the whole can be maintained. [0079] Owing to the structure as described above, the initial azimuthal anchoring strength of the alignment film can be improved. FIG. 9 shows a relationship between azimuthal anchoring strength and a rate of change of afterimage brightness. As for a method for measuring azimuthal anchoring strength, we used the method described in Japanese Published Unexamined Patent Application No. 2003-57147. In FIG. 9 , the abscissa indicates azimuthal anchoring strength in units of 10 −3 J/m 2 and the ordinate indicates a rate of change of afterimage brightness. A rate of change of afterimage brightness is determined as follows. For example, a checker flag pattern, as is shown in FIG. 12 , is displayed for 12 hours and, then, the display returns to a gray flat halftone. A gray level of the halftone is 64/256. At this time, a brightness ratio between a light cell and a dark cell in the checker flag is a rate of change of afterimage brightness. [0080] In FIG. 9 , if a rate of change of afterimage brightness is 1% or less, afterimage may be regarded to be invisible. In FIG. 9 , in order to make afterimage invisible, azimuthal anchoring strength is required to be 3.5×10 −3 J/m 2 or more. [0081] FIG. 10 is a table showing a result of comparison of azimuthal anchoring strengths depending on alignment film structure and process for photo-alignment. In FIG. 10 , the above comparison is made between the one-layer structure of alignment film, as used conventionally, and the two-layer structure of alignment film. With regard to the process for photo-alignment, the above comparison is made between the process in which substrate heating and ultraviolet light irradiation are performed at the same time and the process in which the substrate is heated after ultraviolet light irradiation. [0082] As can be seen in FIG. 10 , a condition satisfying a target value, i.e., azimuthal anchoring strength of 3.5×10 −3 J/m 2 or more, is only the case where the alignment film has the two-layer structure and the process in which the substrate is heated after ultraviolet light irradiation is used. That is, by using the present invention, it is possible to realize a liquid crystal display device that, substantially, solves an afterimage problem in the photo-alignment method. [0083] As explained above, it is possible to obtain an alignment film in which a countermeasure against afterimages was taken by the process condition for photo-alignment. FIG. 11 is a table showing a result of evaluating process tolerance to avoid afterimages. In FIG. 11 , azimuthal anchoring strengths are compared, based on the following parameters: ultraviolet light (UV) irradiance level, heating temperature after ultraviolet light irradiation, interval from ultraviolet light irradiation until substrate heating. [0084] In FIG. 11 , the parameter of ultraviolet light irradiance level is energy obtained by integrating the energies of all wavelengths from 230 to 330 nm. The ultraviolet light, particularly, polarized ultraviolet light is used. A ratio (extinction ratio) between the intensity of ultraviolet light in the polarization direction and that in the direction perpendicular to the polarization direction is not less than 15:1 in the range of the wavelengths from 230 to 330 nm. [0085] In FIG. 11 , condition A defines that the ultraviolet light irradiance level is from 2000 to 5000 mJ/cm 2 , the heating temperature after ultraviolet light irradiation is not less than 230° C., and the interval after ultraviolet light irradiation until substrate heating is within one hour. Condition B defines that the ultraviolet light irradiance level is from 1000 to 7000 mJ/cm 2 , the heating temperature after ultraviolet light irradiation is not less than 200° C., and the interval after ultraviolet light irradiation until substrate heating is within 24 hours. Condition C defines that the ultraviolet light irradiance level is from 500 to 8000 mJ/cm 2 , the heating temperature after ultraviolet light irradiation is not less than 150° C., and the interval after ultraviolet light irradiation until substrate heating is within 168 hours. [0086] In FIG. 11 , condition A can provide the largest azimuthal anchoring strength, i.e., an azimuthal anchoring strength of 4.2. Next, condition B provides an azimuthal anchoring strength of 4.0 and condition C provides an azimuthal anchoring strength of 3.5. It is desirable that photo-alignment is performed according to condition A. However, photo-alignment according to condition A may be impossible because of requirements of a fabrication line. It is required to ensure particular process conditions for photo-alignment complying with at least the level of condition C or more. [0087] In the foregoing description of the embodiment, the alignment film is discussed which uses polyamide acid ester, 80 percent or more of which is polyamide acid ester including cyclobutane, as the upper layer photo-alignment film and uses polyamide acid not including cyclobutane as the lower layer alignment film with enhanced film strength. However, the present invention is not so limited. Even with an alignment film which uses polyamide acid ester, 80 percent or more of which is polyamide acid ester including cyclobutane, in the upper layer and uses polyamide acid ester not including cyclobutane in the lower layer, it is possible to achieve the desired effect by heating the substrate after ultraviolet light irradiation as the process for photo-alignment. [0088] Moreover, even with an alignment film which uses polyamide acid, 80 percent or more of which is polyamide acid including cyclobutane, in the upper layer and uses polyamide acid not including cyclobutane in the lower layer, it is possible to achieve the desired effect by heating the substrate after ultraviolet light irradiation as the process for photo-alignment. Second Embodiment [0089] In the first embodiment, how the alignment film structure and the process for photo-alignment contribute to an advantageous effect against AC afterimages is mainly discussed. The structure of the present invention can achieve the effect against so-called DC afterimages, besides AC afterimages. [0090] DC afterimages are a phenomenon resulting from charge accumulation in certain portions of the alignment film. Hence, DC afterimages are a reversible phenomenon, because they disappear when charges dissipate. In order to avoid DC afterimages, it is conceivable that the alignment film is adapted to have a structure that facilitates fast dissipation of charges accumulated in the alignment film or a structure that primarily prevents charges from being accumulated in the alignment film. [0091] First, descriptions are provided for the structure that facilitates fast dissipation of accumulated charges. We evaluated DC afterimages as follows. That is, the checker flag pattern made up of 8×8 white and black cells, as shown in FIG. 12 , is displayed for 12 hours and, then, the display returns to a gray flat halftone. A gray level of the halftone is 64/256. At 10 minutes after the return to the halftone, if the checker flag pattern can be recognized, the test result is FAIL; if the pattern cannot be recognized, the test result is PASS. [0092] As described in the first embodiment, the alignment film of the present invention includes the upper layer photo-alignment film and the lower layer alignment film with enhanced film strength. In the second embodiment, the alignment film with enhanced film strength is adapted to have a volume resistance of 10 14 Ωcm or less, preferable, 10 13 Ωcm or less. That is, this volume resistance is made smaller by one digit than the volume resistance of the upper layer photo-alignment film. This volume resistance may be that obtained when the alignment film is irradiated with light from the backlight. Thereby, charges charged in the alignment film are discharged soon. [0093] FIG. 13 shows a evaluation result from comparing DC afterimages for the alignment film of the two-layer structure as above and for a conventional one-layer alignment film. In FIG. 13 , the abscissa indicates time elapsed after the return to the gray flat halftone and the ordinate indicates an afterimage level. On the ordinate, RR indicates a state that the checker flag pattern is visible well at the return to the halftone, which is FAIL. R indicates a state that the checker flag pattern is visible, but vaguely at the return to the halftone. [0094] In FIG. 13 , curve A is a DC afterimage characteristic when the alignment film according to the present invention is used. Curve B is an example of a DC afterimage characteristic when a single layer photo-alignment film is only used as the alignment film. [0095] Even though the afterimage level is R at the return to the halftone, if the afterimage disappears in a short time, it can be considered to be practically no program. In the case of the single layer photo-alignment film, the level R at the return to the halftone persists long and, practically, a problem remains. On the other hand, for the alignment film 113 of the two-layer structure according to the present invention, DC afterimage rapidly attenuates and completely disappears at about 17 minutes after the return to the halftone. [0096] As explained above, a large difference between the single layer photo-alignment film and the photo-alignment film of the present invention is that DC afterimage persists long in the case of the single layer photo-alignment film, whereas DC afterimage rapidly attenuates through the use of the alignment film of the present invention. In FIG. 13 , according to the present invention, DC afterimage becomes 25% or less at 10 minutes after the return to the halftone, whereas DC afterimage is 90% or more at the corresponding time in the case of the single layer photo-alignment film. [0097] An alternative method as a countermeasure against DC afterimages is to adapt the alignment film to have a structure that prevents charges from being accumulated in the alignment film, even if a certain pattern is displayed for a long time. This can be accomplished by increasing the volume resistance of the alignment film extremely. In order to accomplish this, in the present invention, the alignment film of the two-layer structure is used, wherein the photo-alignment film is formed in the upper layer and the alignment film with enhanced film strength is formed in the lower layer. In this structure, the volume resistivity of the lower layer is made larger than that of the upper layer. The upper layer photo-alignment film has a small degree of freedom in varying its volume resistance, restricted by its photo-alignment performance. On the other hand, the lower layer alignment film with enhanced film strength can have a large degree of freedom in varying its volume resistance. [0098] If the volume resistance of the alignment film with enhanced film strength is made larger than 10 15 Ωcm, the electrical resistance of the alignment film as the whole becomes larger, thereby impeding charges from being accumulated in the alignment film and the passivation film. Since the volume resistance of polyamide acid ester as the photo-alignment film is as large as about 10 15 Ωcm, by making the volume resistance of the lower layer alignment film with enhanced film strength larger than 10 15 Ωcm, charges are further impeded from being accumulated in the alignment film. [0099] The structure of the two-layer alignment film described in the first and second embodiments is digested as below. In the structure including the photo-alignment film in the upper layer and the alignment film with enhanced film strength in the lower layer, polyamide acid ester is used in the upper layer and polyamide acid is used in the lower layer, wherein the upper layer contains 80% or more polyamide acid ester including cyclobutane. The upper layer is imidized at a rate of 50% or more. In the structure as above, the volume resistivity of the lower layer is made smaller than that of the upper layer in order to reduce DC afterimages. [0100] As an example of another structure of the two-layer alignment film, polyamide acid is used in the upper layer and polyamide acid is used in the lower layer, wherein the upper layer contains 80% or more polyamide acid including cyclobutane. The upper layer is imidized at a rate of 50% or more. In the structure as above, the volume resistivity of the lower layer is made smaller than that of the upper layer in order to reduce DC afterimages. [0101] As an example of yet another structure of the two-layer alignment film, polyamide acid ester is used in the upper layer and polyamide acid ester is used in the lower layer, wherein the upper layer contains 80% or more polyamide acid including cyclobutane. The upper layer is imidized at a rate of 50% or more. In the structure as above, the volume resistivity of the lower layer is made larger than that of the upper layer in order to prevent DC afterimages. [0102] While the foregoing description concerns the alignment film 113 in the TFT substrate 100 , the same holds true for the alignment film 113 in the opposing substrate 200 . The alignment film 113 in the opposing substrate 200 is formed over the overcoat film 203 . In this case also, the non-photolytic polymer 11 from which the alignment film with enhanced film strength 1132 is formed will more readily settle on the overcoat film 203 . Consequently, the alignment film with enhanced film strength 1132 is formed contiguous to the overcoat film 203 and the photo-alignment film 1131 is formed on the top of the lower layer alignment film. Moreover, because the number average molecular weight of the alignment film with enhanced film strength is larger than that of the photo-alignment film, phase separation is easier to take place.

A liquid crystal display device includes a TFT substrate having a first alignment film and an opposing substrate having a second alignment film with liquid crystals sandwiched therebetween. One of the first and second alignment films, comprises a first polyimide produced via polyamide acid ester containing cyclobutane as a precursor and a second polyimide produced via polyamide acid as a precursor. The polyamide acid has a higher polarity than that of the polyamide acid ester. The one of the first and second alignment films is responsive to photo-alignment. A first side of the one of the first and second alignment films is adjacent to the liquid crystals, and a second side thereof is closer to one of the TFT substrate and the counter substrate than the first side. The first side contains more of the first polyimide and less of the second polyimide than the second side.

TECHNICAL FIELD OF THE INVENTION The invention relates to laser power supplies and, more specifically to low-noise power supplies for laser diodes. BACKGROUND OF THE INVENTION In semiconductor lasers, particularly CW-operated laser diodes (Continuous Wave, or continuous mode), power supply induced noise currents manifest themselves as corresponding instabilities in output level and wavelength. Accordingly, CW laser diodes typically require an accurate, low-noise current source to achieve high stability. Due to the high power levels often required of laser power supplies, it is common practice to use switch-mode power supplies to maximize efficiency. However, it is well-known that such switching power supplies generate considerable noise and high output ripple as compared to “quieter” but less efficient linear supplies. To overcome this problem, a linear pass element connected as a current driver is usually employed in series with “raw” power supply output and the laser diode load. An example of such an arrangement 100 is shown in FIG. 1. A voltage regulated “raw” or “bulk” power supply 102 provides power for a load comprising one or more laser diodes 104 (e.g., an array or diodes). Typically, the power supply 102 is a switching power supply. The output of the power supply 102 is smoothed by a capacitor 106 . A ground-referenced current source 108 comprising a linear pass element 110 , a current sensing element 112 and an error amplifier 114 controls the amount of current conducted through the diode load. The linear pass element 110 , typically a FET (field-effect transistor), conducts current from the power supply 102 through the laser diode(s) 104 into the grounded current sensing element 112 . A voltage develops across the current sensing element 112 in proportion to the amount of current being conducted through the laser diodes 104 . The error amplifier 114 compares the sensed current to a control voltage that indicates the desired laser diode current and adjusts the current conducted by the linear pass element 110 accordingly to maintain constant current at the desired level. The filtering effect of the capacitor 106 , in combination with the ripple and noise rejection of the linear current source 108 , improves overall stability and minimizes power supply induced noise. In operation, with the current source 108 conducting current through the laser diode(s) 104 , energy is drawn from the capacitor 106 through the diodes, as a result of which the voltage on the capacitor falls. Therefore, the current source has to have sufficient compliance to continue to maintain current regulation as the “raw” supply voltage falls. For good efficiency, a low voltage loss across the current source is desired, but this requires a large and bulky capacitor to minimize voltage “droop”. The disadvantages of such an implementation include: a) The power dissipated in the linear pass element 110 may be considerable, resulting in substantial heat generation and consequent inefficiency. Heat sinking and cooling may be required, resulting in a large, expensive, inefficient system. b) All of the laser diode current flows through the linear pass element 110 , requiring a high-current device with commensurate size and cost penalties. c) Laser diodes are presently very expensive. If the series pass element 110 were to fail to a short-circuit condition, then the voltage stored on the capacitor 106 would be applied directly across the laser diode(s) 104 , resulting in unregulated current flow, potentially producing excessive light output and possible diode damage. Another example of a series-connected linear pass element being used to regulate current conducted through laser diode load is disclosed in U.S. Pat. No. 5,287,372 (“ORTIZ”), incorporated in its entirety by reference herein. ORTIZ discloses a zero-current, switched, full wave quasi-resonant converter that provides a current to directly drive the laser diode. Referring to FIG. 2 of ORTIZ, a linear pass element 24 (Q 1 ) is connected in series with the laser diode load 31 and is used to regulate the current conducted therethrough. The laser diode driver circuit described in ORTIZ suffers from the disadvantages described hereinabove with respect to the current driver circuit arrangement of FIG. 1 . BRIEF DESCRIPTION (SUMMARY) OF THE INVENTION It therefore is a general object of the present invention to provide an improved technique for driving laser diodes. It is a further object of the present invention to create a smaller, less expensive, low-noise current driver for laser diodes without the efficiency loss of a series-connected linear pass element. It is a further object of the present invention to create a low-noise current driver for laser diodes that can employ less expensive, lower-current devices while maintaining good load regulation. According to the invention, a low-noise current source driver for a laser diode load comprises a current-regulated supply connected across the load, and a shunt regulator. The shunt regulator comprises a shunting element, a current sensing element for sensing current conducted through the load, and an error amplifier responsive to a difference between the current sensed by the current sensing element and a signal representative of a first reference current. The current regulator is designed to respond to a signal representative of a second reference current to produce an appropriate corresponding output current. The shunting element is connected across the power supply and load, and is controlled by the error amplifier to conduct all current from the current regulated supply in excess of the first reference current. The second reference current is greater than the first reference current. The shunting element may be a field-effect transistor (FET) or a bipolar transistor. The current sensing element may be a small-value resistor or a Hall-effect device. Generally speaking, the second reference current is always greater than the first reference current by an amount sufficient to ensure that ripple and noise currents cannot cause the current-regulated supply output to dip below the first reference current. This is accomplished in one of three ways: the second reference current is made greater than the first reference current by a fixed amount; the second reference current is made greater than the first reference current by a fixed proportion (e.g., percentage); or the second reference current is made greater than the first reference current by an amount equal to the sum of a fixed proportion of the first reference current and a fixed amount. Other objects, features and advantages of the invention will become apparent in light of the following description thereof. BRIEF DESCRIPTION OF THE DRAWINGS Reference will be made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. The drawings are intended to be illustrative, not limiting. Although the invention will be described in the context of these preferred embodiments, it should be understood that it is not intended to limit the spirit and scope of the invention to these particular embodiments. Often, similar elements throughout the drawings may be referred to by similar references numerals. For example, the element 199 in a figure (or embodiment) may be similar or analogous in many respects to an element 199 A in another figure (or embodiment). Such a relationship, if any, between similar elements in different figures or embodiments will become apparent throughout the specification, including, if applicable, in the claims and abstract. In some cases, similar elements may be referred to with similar numbers in a single drawing. For example, a plurality of elements 199 may be referred to as 199 A, 199 B, 199 B, etc. The structure, operation, and advantages of the present preferred embodiment of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings, wherein: FIG. 1 is a schematic diagram of a prior-art current driver for laser diodes; FIG. 2 is a schematic diagram of a current driver for laser diodes, according to the invention; FIGS. 3A and 3B are graphs illustrating one aspect of the current driver, according to the invention; FIG. 4A is a block diagram demonstrating a technique for generation of an offset demand signal, according to the invention; FIG. 4B is a schematic diagram of a circuit realization of the block diagram of FIG. 4A, according to the invention; FIG. 5A is a block diagram demonstrating another technique for generation of an offset demand signal, according to the invention; FIG. 5B is a schematic diagram of a circuit realization of the block diagram of FIG. 5A, according to the invention; FIG. 6A is a block diagram demonstrating another technique for generation of an offset demand signal, according to the invention; and FIG. 6B is a schematic diagram of a circuit realization of the block diagram of FIG. 6A, according to the invention. DETAILED DESCRIPTION OF THE INVENTION As a general proposition, the present inventive technique provides an efficient low-noise current source driver for laser diodes by “shunting” noise currents around the load rather than by attempting to “block” noise currents from passing through the load using a series-connected pass element. According to the invention generally, a current source laser diode driver comprises a “bulk” current supply set to provide slightly more current than is required by a laser diode load and a shunting element such as an FET connected across the laser diode load. An error amplifier measures the current in the laser diode load, and controls the shunting element to “shunt” any load current in excess of the required load current. FIG. 2 is a schematic diagram of a low-noise current source laser diode driver 200 , according to the invention. A current-regulated power supply 202 (contrast 102 ) supplies current to a load comprising one or more laser diodes 204 (compare 104 ). A shunt regulator 208 comprising a shunting element 210 (which may be an FET; compare 110 ), a current sensing element 212 (compare 112 ) and an error amplifier 214 (compare 114 ) is connected across (around) the laser diodes 204 , as shown. The error amplifier 214 measures the difference in current between a desired current (“Demand”) through the laser diodes 204 and the current passing through the laser diodes, as measured by the current sensing element 210 . The current sensing element 212 is suitably a small-value resistor or a Hall-effect sensing device. The current-regulated power supply 202 is set to provide slightly more current than what is required by the laser diode load 204 . This is accomplished by providing a reference signal (“Demand+Δ”) to power supply 202 that exceeds the desired load current (“Demand”) by a small amount “Δ”. The amount of current “Δ” in excess of the required current is determined such that it slightly exceeds the amount of ripple and current noise present in the output of the current-regulated power supply 202 . By shunting essentially any and all current in excess of the required load current (“Demand”), the laser diodes 204 are provided with clean, substantially noise-free current at the required level. The current-regulated power supply 202 may be implemented using any of a wide variety of different circuit topologies. Typically, however, it is implemented by controlling the duty cycle of one or more power switching elements according to an error signal derived from the difference between the desired output current (“Demand+Δ”, in this case) and actual output current. Typically, output current pulses from such a switching (switch-mode) current supply are smoothed by a low-pass filtering element such as a capacitor. The connections between of the elements in FIG. 2 are as illustrated. The power supply 202 has an output which supplies current to one of two terminals of the laser diode load 204 . The other terminal of the laser diode load 204 connects to ground via the current sensing element 212 , and to an input of the error amplifier 214 . The other input of the error amplifier 214 receives the signal indicative of desired current (“Demand”). The output of the error amplifier 214 is provided to the gate of the shunting element (FET) 210 . The source and drain of the FET 210 are connected between the output of the power supply 202 and ground. The power supply 202 has an input for receiving a signal indicative of the reference signal (“Demand+Δ”). The operation of current source driver 200 of the present invention is illustrated in FIGS. 3A and 3B. FIG. 3A is a graph 300 A showing the current output 302 of the current-regulated power supply 202 and the signal 304 at the output of the error amplifier 214 . The output current 302 includes noise and ripple currents that cause its actual current output to deviate from its desired output current (“Demand+Δ” indicated by a dashed line). Note that the amount “Δ” by which the current output 302 of the power supply 202 is set to exceed the desired load current (“Demand”) is selected such that the minimum excursions of the current output 302 , including noise, will not dip below the desired load current. That is, “Δ” is chosen to be at least as great as, preferably just greater than, the anticipated magnitude of the noise and ripple present in the current output 302 of the current-regulated power supply 202 . The signal 304 is generally representative of the “excess” load current (i.e., current in excess of the required current (“Demand”) as measured by the error amplifier 214 and is used to drive the shunting element 210 to conduct (divert) said “excess” load current around the laser diodes 204 . FIG. 3B is a graph 300 B showing the current 306 conducted (shunted) through the shunting element 210 under control of the error amplifier 214 and the load current 308 through the laser diodes 204 . By shunting all of the excess current through the shunting element 210 , the load current 308 through the laser diodes 204 is accurately controlled to the desired level (“Demand”) with minimal noise. Note that for proper operation, the regulated current output of the power supply must always be maintained (slightly) greater than the desired current in the diode load. The gain of the error amplifier 214 may be enhanced at high frequencies to cancel out any high frequency noise current in the diode load current. The advantages of this approach include: a) A high current series pass element is not required. b) The efficiency is high because the switching power supply drives the load directly. c) The ripple and noise is “skimmed” from the power supply output current and is bypassed around the laser diode load. Only “smooth” current flows into the diode load. Only noise and ripple currents (plus a small margin) are conducted by the shunting element. d) The diode driver is more reliable due to the elimination of the high power series element along with its related heat. e) The power supply can be designed to limit the maximum current (and therefore, the maximum power) into the diode load. In the worst case, if the shunting element were to fail to an open-circuit condition, power into the laser diode load would still be maintained at non-damaging levels by the current supply. If the shunting element were to fail to a short-circuit condition, this would not normally cause damage to the laser diodes. Optionally, when the required load current (Demand) is set to zero, the power supply can be commanded to zero as well, but the pass element can be turned on slightly to absorb any slight noise current output from the power supply and prevent it from being conducted through the load. Those of ordinary skill in the art will understand that this is readily accomplished by setting (Demand+Δ) equal to zero such that the reference input to the error amplifier (Demand) is slightly negative. In this condition, the error amplifier will cause the shunt element to absorb any and all noise and/or leakage current from the power supply output, preventing it from being conducted through the laser diode load. Those of ordinary skill in the art will also understand that there are alternative methods of accomplishing essentially the same result. Three general approaches to controlling the output of the current-regulated power supply are now described: 1) The power supply can be commanded (controlled) to provide an output current that is a fixed amount “Δ” greater than the desired load current. A benefit of this approach is its simplicity. This approach is shown and described hereinbelow with respect to FIGS. 4A and 4B. 2) The power supply can be commanded to provide an output current that is a greater than the desired load current by a fixed portion “α” of the desired load current. A benefit of this approach is its efficiency. Switching noise and ripple tend to increase roughly in proportion to the current output setting, so this technique tends to maintain the output current of the power supply at the lowest possible setting, thereby minimizing the amount of current that must be conducted by the shunting element. This approach is shown and described hereinbelow with respect to FIGS. 5A and 5B. 3) The power supply can be commanded to provide an output current that is the sum of a fixed amount “Δ” greater than the desired load current and a fixed portion “α” of the desired load current. A benefit of this approach is combined efficiency and reliability. This approach is shown and described hereinbelow with respect to FIGS. 6A and 6B. FIG. 4A is a block diagram 400 A of a circuit for generating a controlling signal for the power supply. A signal representative of the desired load current (“Demand”) is presented at a first input 422 of a summing element 420 . A signal representative of an offset amount “Δ” is presented at a second input 424 of the summing element 420 . The summing element 420 produces an output signal 426 representative of the sum of the two signals at its inputs 422 and 424 . FIG. 4B is a schematic diagram of a circuit realization 400 B generally equivalent to the block diagram of FIG. 4 A. An operational amplifier 440 has a first input resistor 442 and a second input resistor 444 connected to a positive input (“+”) thereof. A signal representative of the desired load current (“Demand”) is provided to the operational amplifier 440 via the first input resistor 442 and a signal representative of an offset amount “Δ” is provided via the second input resistor 444 . A first feedback network resistor 446 is connected between an output of the operational amplifier 440 and a negative input (“−”) thereof. A second feedback network resistor 448 is connected between the negative input (“−”) and ground. In this configuration, assuming all equal-valued resistors (“R”), a signal at the output of the operational amplifier is representative of the sum of the two input signals (“Demand+Δ”). FIG. 5A is a block diagram 500 A of another circuit for generating a controlling signal for the power supply. A signal representative of the desired load current (“Demand”) is presented at a first input 532 of a scaling element 530 . A scale factor (“1+α”) is applied via a second input 534 of the scaling element 530 . The scaling element 530 produces an output signal 536 representative of the desired load current multiplied by the scale factor (“Demand(1+α)”). FIG. 5B is a schematic diagram of a circuit realization 500 B generally equivalent to the block diagram of FIG. 5 A. An operational amplifier 540 has a signal representative of the desired load current (“Demand”) connected to a positive input (“+”) thereof. A first feedback network resistor 546 (“αR”) is connected between an output of the operational amplifier 440 and a negative input (“−”) thereof. A second feedback network resistor 548 (“R”) is connected between the negative input (“−”) and ground. In this configuration, with resistor values “R” and “αR” as shown, a signal at the output of the operational amplifier is representative of the desired load current multiplied by the scale factor (1+α), i.e., (“Demand(1+α)”). FIG. 6A is a block diagram 600 A of another circuit for generating a controlling signal for the power supply. A signal representative of the desired load current (“Demand”) is presented at a first input 632 of a scaling element 630 . A scale factor (“1+α”) is applied via a second input 634 of the scaling element 630 . The scaling element 630 produces an output signal representative of the desired load current multiplied by the scale factor (“Demand(1+α)”), which is in turn connected to a first input 622 of a summing element 620 . A signal representative of an offset amount “Δ” is presented at a second input 624 of the summing element 620 . The summing element 620 produces an output signal 626 representative of the sum of the two signals at its inputs 622 and 624 , or (“Demand(1+α)+Δ”). FIG. 6B is a schematic diagram of a circuit realization 600 B generally equivalent to the block diagram of FIG. 6 A. An operational amplifier 640 has a first input resistor 442 (“RA”) and a second input resistor 644 (“RB”) connected to a positive input (“+”) thereof. A signal representative of the desired load current (“Demand”) is provided to the operational amplifier 640 via the first input resistor 642 and a signal representative of an offset amount “Bias” is provided via the second input resistor 644 . A first feedback network resistor 646 (“RC”) is connected between an output of the operational amplifier 640 and a negative input (“−”) thereof. A second feedback network resistor 648 (“RD”) is connected between the negative input (“−”) and ground. In this configuration, assuming resistor values “RA”, “RB”, “RC” and “RD” as shown signal at the output of the operational amplifier is represented by the expression below: O     u     t     p     u     t = D     e     m     a     n     d · R     B + B     i     a     s · R     A R     A + R     B  ( 1 + R     C R     D ) Converting to the equivalent notation used in FIG. 6 A: α = R     B  ( R     C + R     D ) ( R     A + R     B )  R     D - 1 Δ = B     i     a     s · R     A  ( R     C + R     D ) ( R     A + R     B )  R     D Those of ordinary skill in the art will understand that there are many other ways to generate the signal (“Demand+Δ”) that controls the output of the current-regulated power supply, including the use of virtual ground summing stages. Those of ordinary skill in the art will also recognize that suitable current-regulated power supplies can be designed to be responsive to many different types of controlling signal, e.g., a control voltage or a controlling current. The present inventive technique provides a combination of good efficiency, low noise, lower-cost components, and high reliability. Although the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character—it being understood that only preferred embodiments have been shown and described, and that all changes and modifications that come within the spirit of the invention are desired to be protected. Undoubtedly, many other “variations” on the “themes” set forth hereinabove will occur to one having ordinary skill in the art to which the present invention most nearly pertains, and such variations are intended to be within the scope of the invention, as disclosed herein.

A low-noise current source driver for a laser diode load is achieved by means of a current-regulated supply connected across the load, and a shunt regulator. The shunt regulator comprises a shunting element, a current sensing element for sensing current conducted through the load, and an error amplifier responsive to a difference between the current sensed by the current sensing element and a first reference current. The current regulator is designed to respond to a signal a signal representative of a second reference current to produce an appropriate corresponding output current. The shunting element is connected across the power supply and load, and is controlled by the error amplifier to conduct all current from the current regulated supply in excess of the first reference current. The second reference current is greater than the first reference current by an amount sufficient to ensure that noise and ripple currents cannot cause the output of the current-regulated supply to drop below the first reference current.

FIELD OF THE INVENTION AND RELATED ART The present invention relates to a liquid container used as an ink container for an inkjet recording apparatus; or the like. It also relates to a liquid ejecting recording apparatus in which such a liquid container is removably mountable, and a method for disconnecting such a liquid container. There are various methods for supplying ink to a recording head which ejects ink as recording liquid. According to one of such methods, a liquid container (ink container) is rendered separable from a recording head, or a liquid supply line connected to a recording head, and such an ink container is replaced. There has been known an ink container structure such that a piece of porous material such as sponge, or a piece of fibrous material, is stored, preferably in a compressed state, in a manner to fill the entirety of an ink container to store ink. Also, there have been known various structural arrangements such that, from the standpoint of improvement in storage efficiency, ink is directly stored In an ink container, or is stored in such an ink pouch which deforms in response to ink consumption. For example, Japanese Laid-Open Patent Application 9-267483 (U.S. Pat. No. 6,145,970) proposes an ink container having such a structural arrangement. According to this structural arrangement, the ink container is a multi-layer ink container, the wall of which has multiple layers separable from each other, and in which ink is directly stored to improve ink storage efficiency. It is made with the use of a molding technology such as blow molding. There have been made various proposals to prevent the ink leakage which occurs as such as ink container as the one described above is repeatedly connected or disconnected. For example, Japanese Laid-Open Patent Application 10-278293 (U.S. Pat. No. 6,135,590) discloses an ink cartridge which is enabled to deliver ink by being penetrated by a hollow connecting needle. It comprises: a boxy case; an ink storage portion, or the internal space of the ink cartridge, partitioned by a plurality of partitioning walls; a connecting portion, which is provided as a part of one of the partitioning walls, and is penetrable by a connecting needle; a stray Ink catching portion, which is independent from the ink storage portion, is located within the case, away from the ink storage portion, and holds the ink which has leaked from the ink storage portion; and a connecting needle cleaning portion, which is formed of wafer repellent elastic substance, and is penetrable by the connecting needle. In the case of the structural arrangement in the above described ink cartridge, however, attention has been paid only to the stray ink which adheres to the connecting needle, and the stray ink is wiped and retained by the stray ink catching portion. Thus, it is necessary for the stray ink catching portion to be large enough to assure that even if the connecting and disconnecting of the ink cartridge is repeated substantial number of times, the stray ink which adheres to the connecting needle each time connection and disconnection of the ink cartridge occurs can be always completely wiped and retained by the stray ink catching portion. This need for a large stray ink catching portion has been a significant problem from the standpoint of storage efficiency improvement. Further, Japanese Laid-Open U.M. Application 59-131837 (U.S. Pat. No. 4,700,202) discloses an ink cartridge structure such that an ink cartridge which is enabled to deliver ink by being penetrated by a hollow connecting needle is provided with an ink absorbing member, which is positioned on the outward side of a sealing member. However, the studies made by the inventors of the present invention revealed that this structural arrangement suffered from the following problems. That is, in the case of an ink container having this structural arrangement, when the number of the repetitions of the connection and disconnection of the ink container was smaller, the stray ink could be thoroughly wiped away by the stray ink catching portion. However, as the number of the repetition of the connection and disconnection of the ink container became larger, the stray ink catching portion sometimes failed to thoroughly wipe the stray ink away, even when some regions of the stray ink catching portion were not retaining any ink. Further, any of the above described structural arrangements limits the means for connecting an ink container to a recording apparatus to a hollow needle capable of penetrating the elastic member of the ink container, making it necessary to provide the recording apparatus with a device or mechanism for eliminating the possibility that a user could be hurt by accidentally touching the hollow needle of the recording apparatus when the recording apparatus is not fitted with the ink container In other words, it increases the number of restraints regarding the recording apparatus. Thus, it has been desired to solve the above described problems without relying solely upon a hollow needle. SUMMARY OF THE INVENTION The primary object of the present invention is to solve the above described problems, and to provide a liquid container which Is high in ink storage efficiency, does not cause ink dripping or the like problem even when it is connected or disconnected substantial number of times, and is superior in terms of ease of handling, and also to provide a method for disconnecting such a liquid container. According to an aspect of the present invention, there is provided a liquid container comprising a liquid storing portion, which is enabled to be connected to, or disconnected from, a supply tube connected to a liquid ejecting recording head, and which is for storing the liquid to be supplied to the liquid ejecting recording head, and a liquid outlet, through which the liquid within the liquid storing portion is delivered to the recording head as it is connected to the supply tube, further comprises a capillary force generating member for generating the capillary force for causing the stray portions of the recording liquid, which have adhered to the surface of the supply tube and the internal surface of the ink outlet, to be absorbed into a space different from the liquid storing portion (space) within the liquid container, wherein the capillary force A of a region of the capillary force generating member, which is located next to the liquid outlet for absorbing the stray portion of the recording liquid left behind within the liquid outlet, and the capillary force B of another region of the capillary force generating member for storing the stray portion of the recording liquid having been absorbed into the absorbing region of the capillary force generating member, satisfy an inequity: A<B. According to another aspect of the present invention, there is provided a liquid container, which is enabled to be connected to, or disconnected from, a liquid ejecting recording apparatus provided with a means for drawing out the liquid from a liquid container, and comprises a liquid storing portion in which liquid is directly stored, and a liquid outlet into which the liquid drawing tube of the aforementioned means for drawing out the liquid from a liquid container, can be inserted, further comprises a first capillary force generating member in the form of a ring, and a second capillary force generating member, wherein the liquid outlet of the liquid container comprises a liquid delivery tube which constitutes the actual liquid outlet, and a cover for covering the outward opening of the liquid delivery tube; the first capillary force generating member is disposed between the cover and liquid delivery tube; the second capillary force generating member is disposed in contact with the first capillary force generating member, and is protected by the cover, and the capillary force A of the first capillary force generating member and the capillary force B of the second capillary force generating member satisfy an inequity: A<B. According to a further aspect of the present invention, a liquid container comprising a liquid storing portion in which liquid is directly stored, and a liquid outlet through which the liquid within the liquid storing portion is drawn out, further comprises a liquid absorbing member comprising first and second capillary force generating members for absorbing the stray portion of the liquid left behind within the ink outlet as the liquid container is disconnected, and the liquid absorbing member is extended outward of the liquid outlet from the inside of the liquid outlet. Therefore, even if the liquid from the liquid storing portion is left behind by a certain amount in the liquid outlet when disengaging the liquid drawing tube of the means for drawing the liquid out of the liquid container, which has been inserted into the liquid outlet, by disconnecting the liquid container from the means for drawing out the liquid from a liquid container, of the liquid ejecting recording apparatus, the stray portion of the liquid is absorbed and retained by the liquid absorbing member. Since the liquid absorbing member extends outward of the liquid outlet from the inside of the liquid outlet, it is possible for the liquid retained in the liquid absorbing member to evaporate from the second capillary generating portion, that is, the outwardly extending portion of the liquid absorbing member. Therefore, the absorbency of the liquid absorbing member remains virtually intact even after the liquid container has been connected and disconnected a substantial number of times. Thus, the problem that recording liquid drips and/or splashes from the liquid outlet of a liquid container when the liquid container is connected or disconnected does not occur, and therefore, the problem that the hands, clothing, and/or the like, of a user is soiled with the liquid does not occur. Further, even in the case of a liquid container, the wall of which is given multiple layers separable from each other, with the use of such technology as blow molding, and in which liquid is directly stored to improve ink storage efficiency, the employment of a liquid absorbing member such as the above described one comprising the first and second capillary force generating members, can prevent the problem that liquid drips and/or splashes from the liquid outlet when the liquid container is disconnected. As a result, the liquid absorbing member for absorbing a certain amount of liquid left behind as the liquid container is disconnected is enabled to remain virtually intact in terms of its absorbency. Therefore, it is possible to provide a liquid container for liquid to be ejected, which is high in ink storage efficiency, does not suffer from such a problem as ink dropping even when the liquid container is connected or disconnected, and is superior in terms of ease of handling. According to a further aspect of the present invention, there is provided a method for disconnecting a liquid container comprising: a liquid storing portion in which liquid is directly stored; a liquid outlet through which the liquid within the liquid storing portion is drawn out; and a liquid absorbing member extending outward of the liquid outlet from the inside of the liquid outlet, from a liquid drawing means which comprises a tube for drawing out the liquid within the liquid storing portion and draws the liquid out of the liquid storing portion, after connecting the liquid container to the liquid drawing means for drawing out the liquid within the liquid container, comprises: a liquid absorbing step in which the liquid adhering to the internal surface of the liquid outlet is absorbed with the use of the region of the liquid absorbing member exposed to the internal space of the liquid outlet; a liquid transferring step in which the absorbed liquid is transferred into the region of the liquid absorbing member on the outward side of the liquid outlet; and a liquid evaporating step in which the transferred liquid evaporates from the region of the liquid absorbing member on the outward side of the liquid outlet. According to the above described method for disconnecting a liquid container from a liquid drawing means for drawing out the liquid within the liquid container, when disconnecting a liquid container for containing liquid to be ejected, comprising a liquid storing portion, a liquid outlet, and a liquid absorbing member, from a liquid drawing means comprising a liquid drawing tube insertable into the liquid outlet of the liquid container, after the liquid container is connected to the liquid drawing means, the liquid adhering to the surface of the liquid delivery hole of the liquid outlet is absorbed by the liquid absorbing member, is transferred into the region of the liquid absorbing member on the outward side of the liquid outlet, and is evaporated from the region of the liquid absorbing member on the outward side of the liquid outlet. Therefore, as described above, the problem that when the liquid container is connected or disconnected, the liquid left behind in the liquid outlet drips and/splashes from the liquid outlet, does not occur, and therefore, the problem that when the liquid container is connected or disconnected, the hands, clothing, and/or the like, of a user are soiled with the liquid, does not occur. Further, even in the case of a liquid container, the wall of which is given multiple layers separable from each other, with the use of such technology as blow molding, and in which liquid is directly stored to improve ink storage efficiency, the employment of a liquid container disconnecting means such as the above described one can eliminate such a problem that when a liquid container is disconnected, the liquid left behind in the liquid outlet drips and/or splashes from the liquid outlet, eliminating therefore, the problem that the hands, clothing, or the like, of a user are soiled by the liquid, when disconnecting the liquid container. Further, even in the case of a liquid container, such as a conventional one, the wall of which is given multiple layers separable from each other, with the use of such technology as blow molding, and in which liquid is directly stored to improve ink storage efficiency, the employment of a liquid container disconnecting method such as the above described one can eliminate the problem that when the liquid container is disconnected, recording liquid drips and/splashes from the liquid outlet of the liquid container. As a result, even when a liquid container, the wall of which is given multiple layers separable from each other, in order to improve ink storage efficiency, is employed, the liquid container can be easily disconnected without causing such a problem as ink dripping and/or ink splashing. These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of the essential portion of the ink container unit in the first embodiment of the present invention. FIG. 2 is a perspective view of the ink re-absorbing member shown in FIG. 2, for showing the configuration thereof. FIG. 3 is a sectional view of the essential portions of the ink container unit shown in FIG. 1, and an inkjet head which can be connected to, or disconnected from, the ink container unit, for showing the process for disconnecting the two. FIG. 4 is an enlarged sectional view of the essential portions of the ink container unit in the state shown in FIG. 3 ( b ). FIG. 5 is an enlarged sectional view of the essential portions of the ink container in the state shown in FIG. 3 ( c ), for depicting the ink splash. FIG. 6 is an enlarged sectional view of the essential portions of the ink container in the state shown in FIG. 5, for depicting the effect of the ink re-absorbing member. FIG. 7 is a sectional view of the essential portion of the ink container unit in the second embodiment of the present invention. FIG. 8 is a perspective view of the ink container unit in the third embodiment of the present invention. FIG. 9 is an exploded perspective view of the ink container unit in the third embodiment of the present invention. FIG. 10 is a sectional view of the essential portions of the ink container unit in the third embodiment of the present invention. FIG. 11 is a sectional view of the essential portions of modified versions of the ink container in the third embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the preferred embodiments of the present invention will be described with reference to the appended drawings. (Embodiment 1) FIG. 1 is a sectional view of the essential portions of the ink container unit, as a liquid container, in the first embodiment of the present invention. As shown in FIG. 1, the ink container unit 200 in this embodiment comprises; an ink container 201 as a liquid storing portion; a valve mechanism inclusive of a first valve frame 260 a and a second valve frame 260 b ; and an ID member 250 as an identification member. The ink container unit 200 is removably mounted in an inkjet recording apparatus as a liquid ejecting recording apparatus. In this embodiment, the ink container unit 200 is removably mounted in a holder to which a liquid delivering means for drawing out the ink within the liquid container unit 200 is fixed; in other words, an ink cartridge comprising the holder with the ink delivering means, the ink container unit 200 , and the like, is mounted in an inkjet recording apparatus. The ink container 201 is enabled to generate negative pressure, and is a hollow container, approximately in the form of a polygonal pillar. It comprises an external shell 210 , and an internal pouch 220 as a liquid storing pouch. The internal pouch 220 is enclosed in the external shell 210 . They are separable from each other. The internal pouch 220 is flexible, being therefore enabled to deform as ink, as recording liquid therein, is drawn out of it. Further, the internal pouch 220 has a pinch-off portion 221 (welding seam portion), which contributes to the proper support of the internal pouch 220 by the external shell 210 . It also has an air vent (unshown), which is located adjacent to the pinch-off portion 221 , and through which ambient air is allowed to enter between the internal pouch 220 and external shell 210 . To the ink container 201 , a valve mechanism is welded. The valve mechanism has a joint hole 230 , which is connected to a joint pipe 180 , which will be described later with reference to FIG. 3, to deliver ink to the joint pipe 110 . The valve mechanism has a first valve frame 260 a , a second valve frame 260 b , a valve plug 261 , a valve cover 262 , and a pressure generating member 263 . The valve mechanism with the joint hole 230 is positioned so that it will be at the bottom of the ink container unit 200 when the ink container unit 200 is in use. The valve plug 261 is slidably fitted in the second valve plug 260 b , and is kept under the pressure generated in the direction of the first valve frame 260 a by the pressure generating member 263 . When the joint pipe 180 is not within the joint hole 230 , the first valve frame 260 a side edge of the valve plug 261 is kept pressed against the first valve frame 260 a , by the resiliency of the pressure generating member 263 , keeping the ink container unit 200 hermetically sealed. As the joint pipe 180 is inserted into the joint hole 230 , the joint pipe 180 is disengageably connected to the joint hole 230 , and opens the valve mechanism. The ID member 250 is for preventing the erroneous mounting of the ink container unit 200 . The ID member has a plurality of ID recesses 252 , located on the left and right sides of the ID member, in a manner to correspond to a plurality of ID members 170 (FIG. 3 ), which will be described later with reference to FIG. 3 . The ID member 250 is fixed to the external shell 210 of the ink container 201 . The ID member 250 makes it possible for an ink container to be mounted only to a position which corresponds in ink type to the ink container, in an inkjet recording apparatus. As for the fixing of the ID member 250 to the external shell 210 , a surface of the external shell 210 , which faces the sealing surface of the first valve frame 260 a , at which the first valve frame 260 a is connected to the ink container 201 , is engaged with the click portion of the ID member 250 , which is a part of the bottom portion of the ID member 250 , and the catch portion 210 a on the side surface of the external shell 210 is engaged with the corresponding click portion on the ID member 250 side. Therefore, the ID member 250 is securely fixed to the ink container 201 . As regards the mounting error prevention function which is realized by the ID member and ID recess 252 , the mounting error prevention mechanism is realized by providing the ID member 250 with the plurality of the ID recesses 252 , which correspond to the plurality of ID members 170 with which a negative pressure control chamber unit 100 , which will be described later with reference to FIG. 3, is provided. Thus, various ID functions can be realized by varying the configurations and positions of the ID members 170 and ID recesses 252 . The ink re-absorbing member 255 , which is a liquid absorbing member, that is, an absorbing means, is placed within the internal space of the ID member 250 , which is on the ink container 201 side and is different from any of the ID recesses 252 . It is securely held to the ID member 250 with the use of an ink re-absorbing member retainer 256 . The perspective view of the ink re-absorbing member 255 is FIG. 2 . Although the ink re-absorbing member 255 is formed in a single piece, it can be conceptually divided into two regions in terms of external appearance and function. One of the two regions of the ink re-absorbing member 255 is in the form of a thin ring, and has a hole 255 c , which is smaller in cross section than the hole of the first valve frame 260 a . It is an ink absorbing region 255 a confined in the space between the first valve frame 260 a and ID member 250 . It is located next to the joint hole 230 , with the hole 255 c connected to the joint hole 230 . The liquid outlet is constituted of the first valve frame 260 a , which is an ink delivery tube having the joint hole 230 , the portion of the ink re-absorbing member 255 adjacent to the joint hole 230 , and the portion of the ID member 250 adjacent to the joint hole 230 . The ink absorbing region 255 a of the ink re-absorbing member 255 is exposed at the inward surface of the ink outlet. Thus, after the valve mechanism is closed as the ink container unit 200 is dismounted from the inkjet recording apparatus, the ink remaining between the outward edge of the joint hole 230 and the valve mechanism is absorbed by the portion of the ink re-absorbing member 255 , which is exposed to the internal space of the ink outlet. Another region of the ink re-absorbing member 255 is thicker than the above described ring-shaped region, and is large enough to virtually fill up the space above the ID member 250 . It is an ink storing region designated by a referential code 255 b in FIG. 2 . The ink storage region 255 b is provided with a recess 255 d so that it matches in shape with the recess-less space of the ID member 250 . The ink storage region 255 b is positioned so that it will be above the ink absorbing region 255 a when the ink container unit 200 is in usage. In other words, the ink re-absorbing member 255 extends upward from the inward surface of the ink outlet into the internal space of the ID member 250 , that is, outward of the ink outlet. The ID member 250 also functions as a cover which covers the outward edge portion of the first valve frame 260 a , and the ink re-absorbing member 255 ; the ink re-absorbing member 255 is protected by the ID member 250 , eliminating the possibility that the ink having been absorbed by the ink re-absorbing member 255 might soil the hands of a user. The ink re-absorbing member 255 is a piece of capillary force generating material. In this embodiment, it is a piece of fibrous substance uniform in fiber direction. However, substances other than the fibrous substance, which generate capillary force, may be used as the material for the ink re-absorbing member 255 ; for example, foamed urethane, porous substances formed by molding, sintering, or the like, may be employed. Further, the ink re-absorbing member 255 may be such material that generates capillary force with the use of fine tubes. Next, the function of the ink re-absorbing member 255 will be described along with the mechanism of the ink dripping, which occurs as the ink container unit 200 is separated from the negative pressure control chamber unit 100 . FIG. 3 shows the steps through which the ink container unit 200 in this embodiment is dismounted from the inkjet cartridge in which the ink container unit 200 has been removably mounted. FIG. 3 ( a ) shows the ink container unit 200 and inkjet cartridge in the properly connected state; FIG. 3 ( b ), the ink container unit 200 and inkjet cartridge during their separation from each other; and FIG. 3 ( c ) shows the state in which ink container unit 200 and inkjet cartridge are perfectly in connection to each other. The inkjet cartridge comprises: an inkjet head unit 160 as a recording element; a holder 150 ; the negative pressure control chamber unit 100 as a liquid drawing means; the ink container unit 201 ; and the like. The negative pressure control chamber unit 100 is securely held with the holder 150 , and the inkjet head unit 160 is fixed to the bottom end of the negative pressure control chamber unit 100 , with the interposition of the holder 150 . Regarding the means for securing the holder and negative pressure control chamber unit 100 relative to each other, and the means for securing the holder 150 and inkjet head unit 160 relative to each other, such a means as using screws, providing the components with snap-fitting features, or the like, that allows the above described components to be easily disassembled from each other is preferable, since ease of disassembly is effective for cost reduction in recycling, structural modification for upgrading, or the like. Further, ease of disassembly is also preferable due to the fact that the various components are different in service life length; ease of disassembly makes it easier to replace the components which need to be replaced. However, under certain circumstances, such means as welding, thermal crimping, or the like, may be used to permanently fix the components to each other, which is obvious. The negative pressure control chamber unit 100 has a negative pressure control chamber container 110 which has a hole in the top wall; a negative pressure control chamber lid 120 attached to the top wall of the negative pressure control chamber container 110 ; and two absorbent members 130 and 140 , which fill the negative pressure control chamber container 110 to absorb and remain ink. The absorbent members 130 and 140 fill the negative pressure control chamber container 110 , remaining in contact with each other, in such a manner that when the inkjet head cartridge is in use, they will be vertically layered. The amount of the capillary force which the absorbent member 140 , or the bottom layer, generates is greater than that which the absorbent member 130 , or the top layer, generates. Therefore, the absorbent member 140 , the bottom layer, is greater in ink retaining capability. The ink within the negative pressure control chamber unit 100 is supplied to the inkjet head unit 160 through an ink supply tube 165 . On the other hand, the inkjet head unit 160 comprises: an ink path (unshown) in connection with the ink supply tube 165 ; a plurality of nozzles (unshown), each of which is equipped with an energy generating element (unshown) for generating ink election energy; and a common liquid chamber which temporarily holds the ink supplied through the ink path, and from which the ink is supplied to each nozzle. The energy generation element is connected to the terminal with which the holder 150 is provided. The terminal of the holder 150 becomes connected to the electrical control system of the recording apparatus as the holder 150 is mounted on the carriage of the inkjet recording apparatus. A recording signal from the recording apparatus is sent to the energy generation element of the inkjet head unit 160 through the terminal of the holder 150 to drive the energy generation element to give ejection energy to the ink within the nozzle. As a result, the ink is ejected from an ejection orifice, that is, the outward end of the nozzle. As the ejected ink adheres to a recording medium such as a piece of paper, an image in the form of a letter, a figure, or the like, is recorded on the recording medium. An ink delivery opening 131 , which is the end of the ink delivery tube 165 , on the absorbent member 140 side, is fitted with a filter 161 , with the filter 161 pressing on the absorbent member 140 . The ink container unit 200 is structured so that it can be removably mounted in the holder 150 . The joint pipe 180 , which is a part of the negative pressure control chamber container 110 , located on the ink container unit 200 side of the negative pressure control chamber container 110 , and to which the ink container unit 200 is connected, is such a pipe that will have been inserted into, being therefore connected to, the joint hole 230 of the ink container unit 200 when the ink container unit 200 is properly placed in the holder 150 . The negative pressure control chamber unit 100 and ink container unit 200 are structured so that as the joint pipe 180 and joint hole 230 are connected to each other, the ink within the ink container unit 200 is supplied into the negative pressure control chamber unit 100 . In other words, the joint pipe 180 is a liquid delivery pipe for drawing the ink within the ink container unit 200 into the negative pressure control chamber unit 100 ; it is a liquid drawing tube through which the ink within the ink container unit 200 is drawn into the negative pressure control chamber unit 100 . The negative pressure control chamber unit 100 is provided with the ID member 170 , which is for preventing the ink container unit 200 from being erroneously mounted, projects outward from a portion of the external surface of the negative pressure control chamber container 110 , and is on the ink container unit 200 side of the negative pressure control chamber container 110 and above the joint pipe 180 . The negative pressure control chamber lid 120 is provided with an air vent 115 for connecting the internal space of the negative pressure control chamber container 110 , more specifically, the absorbent member 130 stored in the negative pressure control chamber container 110 , to ambient air. Within the negative pressure control chamber container 110 , a buffer space 116 is provided, which is created by the provision of the ribs projecting inward from the absorbent member 130 side surface of the negative pressure control chamber lid 120 . The buffer space 116 is the portion of the internal space of the negative pressure control chamber container 110 , in which no ink (liquid) is present. It is located next to the air vent 115 . When the ink container unit 200 is connected to the negative pressure control chamber unit 100 , the joint pipe 180 is inserted into the joint hole 230 , pressing the valve plug 261 . As the valve plug 261 is pressed by the joint pipe 180 , it moves in the direction to separate from the first valve frame 260 a . As a result, the internal space of the joint pipe 180 becomes connected to the internal space of the ink container unit 200 through the hole made in the side wall of the second valve frame 260 b ; the hermetically sealed ink container unit 200 is opened to allow the ink within the ink container unit 200 to be drawn into the negative pressure control chamber unit 100 through the joint hole 230 and joint pipe 180 . In other words, the ink storage portion of the ink container unit 200 which has remained hermetically sealed becomes connected to the negative pressure control chamber unit 100 only through the above described hole. When the ink container unit 200 is in connection with the negative pressure control chamber unit 100 as shown in FIG. 3 ( a ), the joint pipe 180 remains filled with ink. However, as the ink container unit 200 is separated from the negative pressure control chamber unit 100 as shown in FIG. 3 ( b ), air is introduced into the joint pipe 180 from the bottom side of the outward end of the joint pipe 180 , allowing the ink within the joint pipe 180 and joint hole 230 to be absorbed into the negative pressure control chamber unit 100 due to the capillary force of the absorbent member 140 within the negative pressure control chamber unit 100 . In this situation, if the speed at which the ink container unit 200 is separated from the negative pressure control chamber unit 100 is greater than the speed at which the ink is absorbed into the negative pressure control chamber unit 100 , the separation ends with a certain amount of the ink left behind in the joint pipe 180 and joint hole 230 ; some of the ink is left in the joint pipe 180 , and the other is left in the joint hole 230 . The ink left in the joint pipe 180 is absorbed into the negative pressure control chamber unit 100 . As for the ink 301 left in the joint hole 230 , if the ink re-absorbing member is not present as shown in FIG. 4 the ink 301 in the joint hole 230 remains unabsorbed since the valve mechanism on the ink container unit 200 side has been closed. In this situation, the ink left in the joint hole 230 , or stray ink, fails, due to its inertia, to follow the ink container unit 200 which is moving away. As a result, some of the ink 301 left in the joint hole 230 is released into the air as shown in FIG. 5, turning into a stray ink droplet 302 , which leads out of the joint hole 230 , dripping or splashing. The ink re-absorbing member 255 is provided as a means for absorbing the aforementioned ink left behind in the joint hole 230 . Referring to FIG. 6, the ink left in the joint hole 230 , that is, the ink adhering to the surface of the joint hole 230 , comes into contact with the edge 255 c of the ink re-absorbing member 255 , and then is absorbed into the ink absorbing region 255 a from this edge 255 c . The absorbing ink 303 is retained within the ink re-absorbing member 255 , and the liquid components of the absorbed ink 303 evaporate with time. The diameter of the hole 255 c of the ink re-absorbing member 255 is made slightly smaller than the diameter of the joint hole 230 . Therefore, the ink left within the joint hole 230 is enabled to easily come into contact with the edge portion of the hole 255 c of the ink re-absorbing member 255 . In the above, the present invention was described with reference to an ink container in which ink is directly stored. However, an ink re-absorbing member in accordance with the present invention is also applicable to a liquid container of a conventional type in which ink is stored with the use of capillary force from an ink absorbing member. The effects of such an application will be similar to those described above regarding this embodiment. The ink absorbing capacity of the ink absorbing region 255 a is only twice the amount of the ink which might be left behind in the joint hole 230 each time the ink container unit 200 is disconnected. However, if the ink container unit 200 is disconnected after it has already been disconnected two or more times, the absorbed ink moves to the ink storage region 255 b from the top portion of the ink absorbing region 255 a . Since the ink storage region 255 b is kept compressed by being secured by the ink re-absorbing member holder 256 , the capillary force in this region is greater than that of the ink absorbing region 255 a . In other words, when A and B represent the capillary forces of the ink absorbing region 255 a and ink storage region 255 b , respectively, an inequity: A<B is satisfied. Therefore, the ink within the ink absorbing region 255 a swiftly moves into the ink storage region 255 b , always leaving the ink absorbing region 255 a in the condition under which the ink absorbing region 255 a is capable of absorbing ink. Thus, even if the ink container unit 200 is disconnected a large number of times with short intervals, the ink absorbing region 255 a is always capable of dealing with the ink left behind in the joint hole 230 . Further, even if the hands of a user happen to come into contact with the ink storing region 255 b , there is little possibility that the hands will be soiled with ink. As for the ink absorbing capacity of the ink storage region 255 b , it is eight times the amount of the ink which will be left behind in joint hole 230 each time the ink container unit 200 is disconnected. Thus, the overall ink absorbing capacity of the ink re-absorbing member 255 is ten times, that is, a combination of twice by the ink absorbing region 255 a and eight times by the ink storage region 255 b , the amount of the ink which will be left behind within the joint hole 230 and will have to be absorbed by the ink absorbing region 255 a each time the ink container unit 200 is disconnected. It is possible that in reality, there is a certain amount of interval between a given operation for disconnecting an ink container unit and the following operation for disconnecting the same ink container. Further, it is assured that the ID member 250 is not placed in contact with the ink container 201 without any gap between them. In other words, a gap is provided as a passage between the ID member 250 and ink container 201 . The space within the ID member 250 , that is, the space for holding the ink re-absorbing member 255 within the ink container unit 200 , is connected to the atmospheric air through this gap. Therefore, it can be expected that the ink evaporates from the ink re-absorbing member 255 through this gap between the ID member 250 and ink container 201 . It is mainly the liquid components of the ink retained by the ink storage region 255 b , that is, the liquid components retained in the outward portion of the ink delivery portion of the ink re-absorbing member 255 , that vaporate through the gap between the ID member 250 and ink container 201 . Because of the above described evaporation of the liquid components of the ink, the ink re-absorbing member 255 is capable of dealing with such an amount of the ink which will be left behind in the joint hole 230 , that is equivalent to approximately twenty times the amount of the ink which will be left behind in the joint hole 230 and will have to be absorbed by the ink absorbing region 255 a each time the ink container unit 200 is disconnected. In other words, in consideration of the number of times the ink container unit 200 is connected to, and disconnected from, the negative pressure control chamber unit 100 until the ink within the ink container unit 200 is completely used, the ink absorbing capacity of the ink re-absorbing member 255 is more than sufficient. Instead of providing the gap between the ID member 250 and ink container unit 201 in order to connect the space for storing the ink reabsorbing member 255 to the atmospheric air, an opening such as a hole, as an air passage, may be provided between the ID member 250 and ink container 201 , or the ID member 250 itself may be provided with such an opening. As described above, in the case of the ink container unit 200 in this embodiment, even when a certain amount of ink is left behind astray in the joint hole 230 as the ink container unit 200 is disconnected from the negative pressure control chamber unit 100 , the stray ink in the joint hole 230 is absorbed and retained by the ink re-absorbing member 255 . Therefore, the problem that when the ink container unit 200 is disconnected, ink drips and/or splashes from the joint hole 230 , does not occur, preventing the hands and/or clothing of a user from being soiled by liquid. The extension of the ink re-absorbing member 255 from the surface of the joint hole 230 outward of the joint hole 230 allows the liquid components of the ink retained by the ink re-absorbing member 255 to evaporate from the outwardly extending portion of the ink re-absorbing member 255 . Therefore, even when the ink container unit 200 is connected and disconnected a plural number of times with relatively short intervals, the ink re-absorbing member 255 remains sufficiently absorbent. Further, even in the case of a liquid container, such as a conventional liquid container, the wall of which is given a plurality of layers separable from each other; with the use of such a molding technology as blow molding, and in which liquid is directly stored to improve ink storage efficiency, the employment of a liquid absorbing member similar in function to the ink re-absorbing member 255 can prevent recording liquid from dripping and/or splashing from the ink delivery hole, when the ink container unit 200 is separated from the negative pressure control chamber unit 100 . Consequently, the liquid absorbing member for absorbing the liquid left behind in the liquid outlet is enabled to remain sufficiently absorbent, and it is possible to realize a liquid container which is high in ink storage efficiency, does not allow problems such as ink dripping even during its connection and disconnection, and is superior in terms of ease of handling. (Embodiment 2) FIG. 7 is a sectional view of the essential portion of the ink container unit, that is, a liquid container, in the second embodiment of the present invention. As depicted in FIG. 7, the ink container unit in this embodiment employs an ink re-absorbing member 257 in the place of the ink re-absorbing member 255 of the ink container unit 200 in the first embodiment. The ink re-absorbing member 257 comprises two members: an ink absorbing member 257 a as a capillary force generating first member, and an ink storage member 257 b as a capillary force generating second member. The two members are in contact with each other at an interface 270 . The ink storing member 257 b and ink absorbing member 257 a are positioned so that the top portion of the ink storing member 257 b will be above the ink absorbing member 257 a when the ink container unit is in use. The ink absorbing member 257 a is in the form of a thin ring as is the ink absorbing region 255 a of the ink re-absorbing member 255 in the first embodiment. It has a hole smaller in cross section than the first valve frame 260 a , and is disposed within the space between the first valve frame 260 a and ID member 250 in a manner of being sandwiched by the first valve frame 260 a and ID member 250 . The ink absorbing member 257 a and ink storing member 257 b are protected by the ID member 250 . Therefore, there is no possibility that the hands of a user will be soiled by the Ink having been absorbed in the ink absorbing member 257 a and ink storing member 257 b . The capillary force of the ink storing member 257 b is rendered greater than that of the ink absorbing member 257 a ; there is a substantial difference in capillary force between the two members. In other words, representing the capillary forces of the ink absorbing member 257 a and ink storing member 257 b with C and D, an inequity; C<D is satisfied. This setup increases the speed of the ink movement between the two members. In the case of a single piece ink re-absorbing member such as the ink re-absorbing member 255 in the first embodiment, its configuration is required to conform to the shape of the internal space of the ID member 250 . Therefore, a dedicated ink re-absorbing member is necessary for each of the plurality of the ink container units for an inkjet head, since each ink container unit is different in ink color from the others, and therefore, is different in ID member configuration from the others. In comparison, dividing an ink re-absorbing member into two pieces as in the case of the ink re-absorbing member 257 , that is, a two piece member, makes it possible to devise the two pieces in terms of the configuration of their front and/or back sides, and/or the direction in which the two pieces are mounted, so that the internal spaces of all the ID members can be properly filled with identical ink re-absorbing members. Therefore, it is possible to reduce component count. The ink re-absorbing member 257 in this embodiment comprises two members: ink absorbing member 257 a and ink storing member 257 b . The ink absorbing member 257 a may be replaced by a member with grooves, which is capable of generating capillary force, and is placed in a manner to occupy the same location as the ink absorbing member 257 a . In such a case, the member with grooves may be a part of the ID member 250 , or a member independent from the ID member 250 . (Embodiment 3) FIG. 8 is a perspective view of the ink container unit, that is, a liquid container, in the third embodiment of the present invention, and FIG. 9 is an exploded perspective view thereof. An ink container unit 50 has an ink container 6 and a lid 7 . The lid 7 is hermetically attached to the top side 6 a of the ink container 6 , creating an ink storing chamber (unshown), in which ink (liquid to be ejected) is stored. The ink container 6 is provided with a liquid outlet 6 c , which projects outward from a surface of the ink container 6 , on the side opposite to the side to which the lid 7 is attached, that is, the bottom wall 6 b of the ink container 6 . The ink container unit 50 also comprises a bottom cover 1 , which is attached to the ink container unit 50 in a manner to encase the liquid outlet 6 c . The bottom cover 1 is provided with a hole, the position of which corresponds with that of the liquid outlet 6 c. The liquid outlet 6 c has two through holes: liquid delivery first hole 11 and liquid delivery second hole 12 , both of which lead to the ink storing chamber. The liquid container unit 6 also comprises; a pair of elastic members 5 , which are inserted in the liquid delivery-first and second holes 11 and 12 , one for one, and holding members 4 and 9 , which have a pair of holes, the positions of which correspond to those of the liquid delivery holes 11 and 12 , one for one. The holding members 4 and 9 are fixed to the liquid outlet 6 c by ultrasonic welding, in a manner to keep the elastic members 5 compressed. In other words, the elastic members 5 are held compressed within the liquid delivery holes 11 and 12 , one for one, in a manner to virtually hermetically plug the liquid delivery holes 11 and 12 . Thus, until the hollow needle on the recording apparatus main assembly side is inserted into the liquid delivery holes 11 and 12 through the elastic members 5 , the ink storing chamber 523 is kept hermetically sealed by these elastic members 5 and lid 7 . Incidentally, a capillary force generating member 8 is placed between the holding members 4 and 9 . Referring to FIG. 10, at this time, the ink re-absorbing member, which characterizes the present invention, will be described. FIG. 10 is a sectional view of the essential portions of the ink container unit in this third embodiment of the present invention; FIGS. 10 ( a ) and 10 ( b ) showing the essential portions through which the hollow needle has not been, and has been, inserted into the elastic members 5 , respectively. In this embodiment, the capillary force generating member 8 is formed of felt or the like material, which is virtually uniform in thickness and fiber density. The position of the capillary force generating member 8 is fixed by being sandwiched by the two holding members 4 and 9 . Referring to FIG. 10 ( a ), as the capillary force generating member 8 is sandwiched by the two holding members 4 and 9 , the sandwiched portion of the capillary force generating member 8 is compressed, whereas the portion of the capillary force generating member 8 adjacent to its hole is caused to protrude inward of the ink delivery hole 11 (or 12 ). As a result, the capillary force generating member 8 is divided into a region 8 a , as an ink absorbing region, which is relatively small in capillary force, and a region 8 b , as an ink storing region, which is relatively large in capillary force. Next, referring to FIG. 10 ( b ), after the insertion of the hollow ink delivery needle 10 , the ink absorbing region 8 a of the capillary force generating member 8 is in contact with the hollow needle 10 , being therefore enabled to absorb the ink adhering to the needle, and also the ink left on the outward side of the ink delivery hole 11 (or 12 ) relative to the elastic member 5 , as the hollow needle 10 is inserted or pulled out. The ink having been absorbed into the ink absorbing region 8 a moves into the ink storing region 8 b due to the difference in capillary force between the two regions. Further, the ink retained in the ink absorbing region 8 a quickly evaporates because this region is exposed to the atmospheric air. Thus, it is assured that even if the insertion and extraction of the hollow needle are repeated, the ink on the hollow needle and the ink left behind on the outward side of the ink delivery hole 11 (or 12 ) with respect to the elastic member 5 are absorbed and retained. FIG. 11 shows modifications of the capillary force generating member 8 in this embodiment. In the case of the modification shown in FIG. 11 ( a ), the holding member 14 is provided with a tapered portion 14 a , so that the capillary force of the capillary force generating member gradually changes in terms of the radial direction of the ink delivery hole. In the case of the modification shown in FIG. 11 ( b ), the capillary force generating member comprises two portions: a portion 18 , which is formed of a piece of felt or a fiber bundle, and is relatively smaller in capillary force, and a groove 28 , which is formed as a part of the holding member 24 or 19 , and is relatively high in capillary force. These structural arrangements also provided effects similar to those provided by the preceding embodiments. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.

A liquid container which is in detachably connectable to a supply tube which is in fluid communication with a liquid ejection recording head, the liquid container including a liquid accommodating portion for accommodating liquid to be supplied to the liquid ejection recording head and a supply port for permitting supply of the liquid to the recording head from the liquid accommodating portion by connection of the liquid container to the liquid ejection recording head, the liquid container includes a capillary force generating member for generating a capillary force to absorb the recording liquid deposited on the surface of the supply tube and in the supply port into a space, other than the liquid accommodating portion, in the liquid container; wherein a capillary force A generated in an absorption region for absorbing the recording liquid remaining in the supply port adjacent the supply port of the capillary force generating member and a capillary force B in a storing region for storing the recording liquid absorbed in the absorption region, satisfy A<B.

This application is a continuation-in-part of application Ser. No. 07/339,311 filed Apr. 17, 1989, now abandoned. This invention relates to mechanically stacked, tandem photovoltaic solar cells which converts incident sunlight to electric power preferably with high energy conversion efficiencies, and more particularly to a novel III-V diffused booster cell, its method of fabrication and the tandem interconnection with an improved transparent upper photovoltaic cell. BACKGROUND Several different types and methods of producing solar cells are known in the industry. An ongoing objective of solar cell manufacturers is to improve the conversion efficiencies of the solar cells in a cost effective manner. More recently, higher energy conversion efficiencies have been obtained with mechanically stacked multijunction solar cells. This mechanical stacking generally consists of stacking a top cell that absorbs higher frequency light (i.e. a high bandgap cell) on a booster cell which will absorb the lower frequency light that passes through the top cell (i.e. a low bandgap cell). See Fraas, "Current Topics in Phtovoltaics", p. 169, Academic Press (1985) Partain et al., "26.1% Solar Cell Efficiency For Ge Mechanically Stacked Under GaAs", 62 J. Appl. Phys., p. 3010 (1987). One example of a lower band gap booster cell is germanium (Ge). See Partain, supra, Another example of a lower band gap booster is gallium antimonide (GaSb). See Fraas et al, "GaSb Film Grown by Vacuum Chemical Epitaxy Using Triethyl Antimony And Triethyl Gallium Source", 61 J. Appl. Phys., p. 2861 (1987). Theoretical projections of the performance of a GaAs on GaSb mechanical stack have been reported; see Fraas et al, "Near-Term Higher Efficiencies With Mechanically Stacked Two-Color Solar Batteries", 19 Solar Cells p. 73 (1986-87), but no high performance booster cells have previously been fabricated. Copper Indium Diselenide is another booster cell for GaAs. See U.S. Pat. Nos. 4,680,422 and 4,795,501. In Mc Leod et al U.S. Pat. No. 4,776,893 it was presumed that a passivation window of aluminum gallium antimonide (AlGaSb) would be required for the bottom cell. Forming such a passivation window would necessitate the use of a costly, low throughput epitaxial processing to produce the GaSb cells. GaSb photodiodes fabricated by zinc diffusion from a zinc-silica spin on film is described by W. Schmidt auf. Altenstadt and C. Heinz in Physica 129B, p. 497, 1985. The zinc concentration obtained by that process were too low for solar cells. SUMMARY OF THE INVENTION Accordingly, the present invention preferably provides a novel solar cell that overcomes the above deficiencies. When located at the focus of a sunlight concentrating lens, the best of the prior art GaAs satellite solar cells, where air mass effects are 0, i.e. AMO, convert about 22% (AMO) of the incident sunlight to electric power. By the invention disclosed herein, this conversion efficiency has been increased to about 31% (AMO, 100 suns D) which is a new world record conversion efficiency for a satellite photovoltaic device. The improved results come from a number of refinements constituting light conditioning means which include modifying the upper or front GaAs cell of the tandem unit to be transparent to energy having a longer wavelength than the wavelength to which GaAs is responsive, use of multiple layers of anti-reflective coatings, placing a novel infrared sensitive GaSb booster cell that has a band gap of about 0.72 eV behind the GaAs cell, and attaching a prism or prismatic coverglass that is aligned with cell grid lines of each cell or at least the GaAs cell, to deflect incident light rays into active cell area. The invention also provides a method for improving the energy conversion efficiency of a GaAs/GaSb tandem solar cell by using a diffused junction GaSb cell which does not have an upper, passivating, epitaxial overcoat in a tandem concentrator configuration. Still other features of the present invention are to provide a novel cell production method that is scaleable for efficient large volume production for GaSb cells, certain aspects of which are applicable to other III-V solar cells, and to provide cells produced by that method. Yet another feature of the invention is to provide a photovoltaic GaSb cell which does not require a passivation layer, but instead uses a p-dopant such as zinc, the thickness of the layer being reduced in active areas between grid lines to nearly double the short circuit current. It is another major object of the invention to provide a novel solar cell array composed of a solar collecting lens and multiple wafer type cells that are mechanically stacked with the upper cell being transparent to pass infrared energy to the lower cell. The mounting of the tandem cells and the current collecting and voltage matching arrangements provide a two-terminal device which may be used also in terrestrial applications where a world record conversion efficiency of about 34-37% has been measured AM 1.5D (100suns). The preferred embodiment of the present invention utilizes a III-V compound semiconductor material, such as gallium antimonide (GaSb), as a substrate for the booster cell. Into a windowed portion of the n-type substrate surface a p-type doping material, such as zinc, is diffused. A passivating layer for GaSb, previously through to be essential, is not used. A grid in the form of parallel lines of conductive material that are in direct contact with the p-type material in the diffused region of the semiconductor is connected to the front side metallization bus which is on an insulative mask of a suitable material such as silicon nitride. A metal contact is also formed on the back side of the substrate. Prior to coating with an anti-reflective material, the diffused area is etched back to reduce the emitter depth so that the short circuit current will be increased. According to a preferred method of fabricating the GaSb cell, the n-type semiconductor material receives a patterned layer of insulative material containing an opening through which a p-type dopant is diffused. A grid of conductive material is thereafter formed on the diffused area and a bus is placed on the layer of insulative material to contact said grid, but not the semiconductor material. A metallized surface is formed on the opposite side of the semiconductor material. Non-metallized areas of the diffused portions are etched to increase the short circuit current and anti-reflective layers are applied to said etched areas to further increase the short circuit current. These and other features of the invention will become more fully apparent from the claims and from the description as it proceeds in connection with the appended drawings. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a pictorial view of a multi-cell solar energy array embodying a preferred embodiment of the present invention; FIG. 2 is a diagrammatic view of a single cell of the array of FIG. 1; FIG. 3 is a view of a circuit ribbon that may be used for connecting the four terminals of a tandem cell unit to provide a two-terminal device; FIG. 4 is an elevation in cross section of the upper cell of a tandem cell unit; FIG. 5 is a curve showing the optical transparency properties of a gallium arsenide photovoltaic cell as shown in FIG. 4; FIG. 6 is a top view of the lower cell of a tandem cell unit; FIG. 7 is a elevation in cross section of the lower cell taken along lines 7--7 of FIG. 6; FIG. 8A-8E are process flow diagrams outlining the novel process for fabricating a III-V booster solar cell in accord with one feature of the present invention; FIG. 9 is an elevation to a large scale showing a prismatic lens which optically eliminates grid line obscuration losses for the solar cells; FIG. 10 is a curve showing current vs. voltage for an illuminated GaSb cell; and FIG. 11 is a curve showing current vs. voltage for an illuminated GaAs cell. DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, the sunlight concentrating photovoltaic array of the present invention is illustrated by an arrangement of nine solar cell units 10 in a housing 11 which includes also a concentrating lens 12 which has nine focal regions, one for each cell. Each of the solar cell units 10 is substantially equidistant from its respective concentrating lens 12. Each solar cell unit 10 may be of a type illustrated in FIG. 2, and positioned in optical alignment with its portion of the concentrating lens. The cell unit 10 is shown to be formed of two cells, one being an upper cell 14 and the other being a lower cell 16. The cells 14, 16 are mechanically separate so that during manufacture, an upper cell 14 may be selected for use with one of a group of lower cells 16. The cells 14,16 may have an active surface area of 0.049 cm 2 , although it should be understood that areas of other sizes are also useful. The upper cell 14 is ideally transparent to the radiation to which the lower cell has sensitivity. The cells 14, 16 may be separated by a space which allows separate electrical terminals to be provided for the lower surface of the upper cell 14 and the upper surface of the lower cell 16. The cells 14,16 may be mounted over holes in a ceramic-double sided printed wiring card 18 which is supported at an index position on the housing 11 thereby to serve as part of the array structure. The upper cells 14 are mounted on the front side of card 18 and the lower cells 16 of the tandem arrangement are mounted on the back side of the same card 18 to be an optical alignment with its associated upper cell. Other mounting arrangements for the cells may be used. As illustrated in FIG. 2, the upper cell may have two terminals 20, 22 and the lower cell may have two terminals 24, 26. The terminal 22 may be connected with printed circuit wiring on the front side of card 18 while the terminal 24 is connected with an electrically separate printed circuit wiring on the back side of card 18. Card 18 may be a sapphire layer that serves also as a heat sink or spreader. Al 2 O 3 and AlN materials are suitable as a support between the upper and lower cells, because they have electrical insulating and thermal conducting properties. An alternative interconnect between adjacent cells for terrestrial installations may be provided by a flex circuit ribbon 29 as shown in FIG. 3 which comprises electrical conductors on a suitable synthetic resin material. Three elongated flexible strips 30,31,32 of conductive material extend along the length of ribbon 29. The strip 30 is formed with a flap 34 that may engage the metallized surface that is on the upper surface of upper cell 14. The strip 32 is formed with a flap 40 that serves as an electrical connection to the lower surface of the upper cell 14. The strip 31 is connected electrically to the upper and lower surfaces of the lower cell 16 so that all three lower cells 16 are connected electrically in series. The upper cells are connected electrically in parallel. Where the upper cell open circuit voltage is approximately three times the open circuit voltage of the lower cell, this series and parallel connection system allows the cells to be connected together to give a two terminal device. It may be noted from FIGS. 10 and 11 that a GaAs cell has a maximum power voltage of 971 mV which is slightly less than the maximum power voltage for three series connected GaSb cells where each has a corresponding voltage of 380 mV. GaAs Cell Conventional GaAs cells must be made transparent to achieve the highest conversion efficiency in a tandem or stacked cell application. Several methods of forming GaAs photovoltaic cells are known in the art as explained in the Mc Leod et al U.S. Pat. No. 4,776,893. Further recent developments are reported in an article "Tertiary Butyl Arsine Grown GaAs Solar Cell" by Sundaram et al, Appl. Phys. Lett. 54 (7), Feb. 13, 1989, where growing p- and n-doped GaAs layers and p-AlGaAs layers for use as a concentrator solar cell structure is described. See also Fan et al, U.S. Pat. No. 4,547,622. Three modifications to such GaAs cells are made when used with GaSb lower cells to optimize the conversion efficiency. First, the conventional continuous back metallization should be replaced with a gridded metallization. The back grid should use fewer grid liens than the front grid because the thicker wafer conductivity is much higher than the thinner emitter conductivity. The shading from the back grid may be omitted entirely. Second, the water n-dopant density of the GaAs material should be reduced from 1×10 18 cm -3 to about 1×10 17 cm -3 to reduce free electron absorption. Third, the anti-reflective (AR) coatings on the front and back of the GaAs cell are modified in order to provide minimal reflection across a broader bandwidth to assure passage of longer wavelength energy to which the GaSb cells are responsive. The presently preferred transparent GaAs cell design incorporates a 450 micrometer (micron) thick n-type wafer doped to about 1×10 17 cm -3 with complete photovoltaic epitaxial structure grown on it including an AlGaAs window layer. A three layer AR coating on the front surface in addition to the AlGaAs window layer serves as the front side AR coating and a two layer AR coating has been applied to the back side in some embodiments. Important design parameters include the thickness and refractive index of each layer including the AlGaAs which functions not only as an electronic heteroface but also as one of the front AR layers. This multi-layer optical system produces a very broadband reflectance minimization through the visible energy range on out beyond the GaSb band edge at 1700 nm as illustrated in FIG. 5. The GaAs cells and the GaSb cells may be of the same size. The chip size may be 3 mm×5 mm and the cell active area diameter may be 2.5 mm. Nineteen grid lines traverse the front active area of each such cell. The grid density is similar to that used with a GaAs cell designed for 20× sunlight concentration. For an n-type GaAs wafer doping density of 1×10 17 cm -3 and for a 20× sunlight concentration, it appears that no grid lines are required on the back side of the GaAs cell. FIG. 4 shows a cross section of one preferred GaAs solar cell that is adapted for use as part of the present invention. The solar energy along line 42 is directed toward the GaAs cell with a part being reflected along line R and a part being transmitted along line T. With anti-reflective coating layers AR on both the front and back sides of the GaAs cell, the relative transmittance and reflectance can be made to have values indicated by FIG. 5. The upper AR layer includes the AlGaAs layer which may specifically be Al 0 .5 Ga 0 .5 As and about 0.05 microns thick to reflect free electrons toward the p-n junction in this cell. Three additional layers have been found effective to enhance the anti-reflective properties. Materials such as Ta 2 O 5 , MgO, MgF, Tio x and SiO 2 are materials that have been found effective. The thickness of each layer is but a fraction of the wavelength of the visible portion of the spectrum. For optimum anti-reflective properties, the AR layer on the back side may require two equally thin layers of TiO x and SiO 2 . Deposition by electron beam evaporation at room temperature may be used for applying these layers. The electrical conducting grid pattern on the upper surface of the cell of FIG. 4 may consist of the usual parallel conductors applied by conventional photolithographic techniques. Pt/Au and Au/Ge/Ni/Au layers that are electron beam evaporated and appropriately heat treated to make p and n ohmic contacts on the front and back sides, respectively, may be used. Because electrical conductivity of the n-type GaAs material is good, the back electrode may be made with fewer conductors and larger spacings between conductors. To provide maximum transparency properties to the upper GaAs cell, the electrical conductors on the base surface may be omitted in cases where cell areas are small. GaSb Cell FIGS. 6 and 7 diagrammatically illustrate the lower cell which is preferably made of GaSb. In the prior art Mc Leod U.S. Pat. No. 4,776,893, the GaSb solar cell included the use of an AlGaSb window layer. Fabrication was by a liquid-phase epitaxy method. The photovoltaic GaSb cell used in the tandem cell of the present invention does not employ the AlGaSb window layer in a preferred form, but instead advantageously may use an n-type GaSb wafer with a p-dopant, such as zinc, that is added by a less costly diffusion process. The cell shown in FIG. 7, has a metallized base 44 which may be connected to the terminal 26 of FIG. 2. The bus conductor layer 46 is an upper metallized surface which may be connected to the terminal 24 of FIG. 2. Two important aspects are that only the grid lines 48 are in contact with the semiconductor at the zinc diffused region designated P GaSb in FIG. 8 and the bus conductor layer 46 must be isolated from the GaSb semiconductor substrate. Because the process is essentially planar, the front side metallization is on an insulation mask 50 of an insulative material such as silicon nitride. The anti-reflective coating 52 is important in achieving efficient energy conversion but is not essential to operability of the solar cell. The process for fabrication of the GaSb booster cell is generally applicable to III-V diffused junction photovoltaic cells. The reference to the specific gallium antimonide material is therefore to be construed as illustrative and not limiting. The process will be described with reference to FIGS. 8A-8E. Preferably, substrate 61 is composed of a III-V compound semiconductor material single crystal. The use of an n-type substrate with a room temperature carrier concentration of approximately 10 17 atoms/cm 3 is preferred and results in good device performance without a surface passivation layer. At lower doping levels, the surface of the n-type GaSb converts to p-type to an extent that degrades device performance. At higher doping levels, excessive tunneling through a junction degrades device performance. In one embodiment, the GaSb wafer may be doped with Te to 4×10 17 /cm 3 . Zinc is a preferred p-type dopant material. An insulating layer 62 is then formed as a coating on the upper surface of substrate 61. Insulative layer 62 is preferably a two-layer coating of silicon nitride/silicon oxynitride. This two-layer system has been used in fabricating gallium arsenide lasers, and has been discovered here to be also effective for use in the method of the present invention. The first layer comprising silicon nitride is utilized to minimize any oxygen contact with substrate 61. The second layer comprising silicon oxynitride is much more stable and holds up to the high temperature excursion of a subsequent diffusion step. The two-layer insulating layer may be deposited using plasma chemical vapor deposition. The first layer of silicon nitride may be about 0.01 microns thick and the second layer of silicon oxynitride approximately 0.1 microns to perform effectively. Insulating layer 62 may also be applied by sputtering. Insulating layer 62 is next treated to form opening 63 exposing a portion of substrate 61 as by using standard photolithography techniques. Thus, a layer of photoresist may be deposited in a patterned form on the insulating layer 62. Thereafter the photoresist is developed to remove the insulating layer 62 at the opening 63. A p-type dopant material, such as zinc, is then diffused into the exposed surface of substrate 61 to serve as a conductivity type modifier and form a p/n junction and p-type emitter 64. The diffusion step may be accomplished using a quasi-closed graphite box, not shown, in a conventional manner. The box has an elemental zinc source and an elemental antimony source. The elemental Sb source is provided to build up the antimony pressure in the diffusion chamber to prevent portions of the antimony in substrate 61 from exiting substrate 61. The elemental Zn provides a source of p-type dopant atoms which diffuse through opening 63 into the lattice substrate 61. The concentration versus depth into substrate 61 of the Zn dopant atoms is a function of time and temperature. The diffusion step preferably creates an emitter doped in the mid-10 20 /cm 3 range to a depth of approximately 0.5 micrometers (microns). During the diffusion process, an unwanted zinc diffused region 65 forms on the back side of the substrate 61 as illustrated in FIG. 8A. Following the diffusion step, a protective photoresist layer 66 is deposited on the surface of substrate 61 to form a patterned insulating layer 62 as shown in FIG. 8B. The back side or lower surface of substrate 61 is thereafter non-selectively etched to remove unwanted zinc that has diffused into region 65. Protective photoresist layer 66 is removed and a back side metallization contact layer 67 is formed. Metallization contact layer 67 must have low electrical resistance, be adherent to the lower surface of substrate 61 and meet the qualifications for use in space or terrestial applications. A typical example may comprise three layers of metal: a layer of titanium (Ti) 68, a layer of palladium (Pd) 69, and a layer of gold (Au) 70. Platinum (Pt) would also be an acceptable alternative to palladium 69. Gold 70 is used because of its good electrical properties. Palladium 69 is used as a gold diffusion barrier to make contact between titanium 68 and gold 20 and to prevent gold 20 from diffusing into titanium 68 or substrate 61, FIG. 8B. The back side metal layers may be alloyed in a furnace. A second photolithographic step is used to form the grid pattern for a top metal 71. Top metal 71 consists of a grid portion of parallel lines 71A of conductive material and a bus portion 71B of conductive material as illustrated in FIG. 8C. Top metal 71 may comprise a layer of Pt and a layer of Au. Top metal 71 including grid lines 71A and bus portion 71B is formed using standard metal liftoff techniques. In actual processing, the thickness of metal layer 71 may be approximately 0.3 microns. Only the grid lines touch the junction region. The bus pad is deposited only on the patterned insulative material and is isolated from the n-type semiconductor substrate. A front side etch is then performed to reduce the emitter thickness. This is illustrated in FIG. 8D but the drawing is not to scale. It should be noted that while the front side etch is not necessary, it has been found that with removal of emitter material to provide a recess between grid lines 71A beneficial results are obtained. For example, if the depth of the recess is sufficient so that the emitter material thickness is reduced from about 0.5 micrometers to about 0.1 micrometers, the device short circuit current rises by a factor of about 2. It is apparent that the depth of the zinc diffusion is variable with the depth under the conductive strips 71A being greater than the depth between the strips. An anti-reflective coating 72 may be deposited as a coating over the emitter between the grid lines 71A as illustrated in FIG. 8E. FIG. 8E, like FIG. 8D, is diagrammatic and not to scale. Anti-reflective coating 22 may comprise a single layer or double layers and is often deposited using a vacuum deposition process as discussed in conjunction with the upper GaAs layer fabrication. It should be apparent to those skilled in the art that anti-reflective coating 22 should be tailored specifcally for a spectral region of interest for booster cell. One preferred embodiment of anti-reflective coating 22 is tantalum pentoxide (Ta 2 O 5 ) having a thickness of approximately 0.15 microns which was found to raise the short circuit current by another 1.5 times. A prismatic cover-glass 74 which optically eliminates grid line obscuration losses for concentrator cells is shown in FIG. 2, and on an enlarged scale in FIG. 9. Incoming light rays 76 that otherwise might hit parallel grid lines 78 are simply bent slightly toward active cell areas 80 as they enter the thin molded cover 74 which may have the form of a cylindrical lens and be made of a synthetic resin material. FIG. 9 shows the cover-glass 74 as it is applied by an adhesive 82 to both the GaAs and GaSb cells to boost the light generated currents and efficiencies of both cells 14,16. The observed gain in the GaAs cell current is near 10%. Since the GaSb cell in the FIG. 2 configuration is shaded by both the GaSb grid lines and the GaAs cell grid lines, the current increase for the GaSb cell is more than 10%. For assembled GaAs/GaSb tandem stacks the two cells are preferably mounted with their respective grid lines perpendicular to each other. The two sets of cylindrical lenses in the two prismatic covers are cross linear and such an arrangement contributes to the high energy conversion levels that have been obtained. FIG. 10 shows performance data for an individual GaSb cell with a cover 74 as described in connection with FIG. 9 and broadband anti-reflective coatings as described and tested behind a GaAs radiation filter. The cell has an illuminated current versus voltage as illustrated and fill factor of 71.3%. The open circuit voltage is 480 mV. The illuminated short circuit current density is 2702 mA/cm 2 . Boost efficiencies are 8.2% for space application where air mass effects are 0 (AMO) and 9.3% where air mass density is 1.5 directed (AM 1.5 D). Concentrated light intensities of near 100 suns equivalent were used. FIG. 11 shows similar data for an individual GaAs cell with a prismatic cover 74 as described in connection with FIG. 10 and anti-reflective coatings as described above. The curve shows illuminated current versus voltage. The open circuit voltage is 1100 mV and the fill factor is 0.85. The illuminated short circuit current density is 3472 mA/cm 2 . Energy conversion efficiencies are 24.1% (AMO) and 28.9% (AM 1.5 D) at a light concentration near 100 suns equivalent. Theoretical tandem cell stack efficiencies sum to 9.3%+28.9%=38.2 at AM 1.5 D. This conversion efficiency translates to 8.2%+24.1%=32.3% for space (AMO). Several tandem cell stacks actually have been fabricated with AMO energy conversion efficiencies of at least 31% and with AM 1.5 D energy conversion efficiencies of between 34% and 37%. The higher efficiencies are achieved with the best cells used. While preferred embodiments have been shown and described, those skilled in the art will readily recognize alterations, variations, or modifications that might be made to the particular embodiments that have described without departing from the inventive concept. This description and the drawings are intended to illustrate the invention (and its preferred embodiments), and are not meant to limit the invention.

A photovoltaic cell array involving rows and columns of tandem or stacked solar cell units composed of GaSa/GaSb associated with a radiation collector have produced measured energy conversion efficiencies of 31% AMO. The booster GaSb cell is manufactured by a process which produces a p-type diffusion region within an n-type substrate, has improved energy conversion efficiencies and can be mounted as part of a four terminal stacked solar cell unit.

BACKGROUND [0001] 1. Field of the Invention [0002] The present invention relates to computing systems, and more particularly to maintaining data integrity in PCI-Express devices. BACKGROUND OF THE INVENTION [0003] Conventional computing systems typically include several functional components. These components may include a central processing unit (CPU), main memory, input/output (“I/O”) devices, and streaming storage devices (for example, tape drives). In conventional systems, the main memory is coupled to the CPU via a system bus or a local memory bus. The main memory is used to provide the CPU access to data and/or program information that is stored in main memory at execution time. Typically, the main memory is composed of random access memory (RAM) circuits. A computer system with the CPU and main memory is often referred to as a host system. [0004] Host systems are used in various network applications, including storage area networks (“SANs”). In SANs, plural memory storage devices are made available to various host computing systems. Data in a SAN is typically moved between plural host systems and storage systems (or storage devices, used interchangeably throughout this specification) through various controllers/adapters. Host systems often communicate with storage systems via a host bus adapter (“HBA”, may also be referred to as a “controller” and/or “adapter”). [0005] Host systems often communicate with peripheral devices via an interface such as the Peripheral Component Interconnect (“PCI”) interface, a local bus standard that uses parallel data transfer, or the extension of PCI known as PCI-X. Both the PCI and PCI-X standard specifications are incorporated herein by reference in their entirety. [0006] More recently, PCI-Express, a standard interface incorporating PCI transaction protocols at the logical level, but using serial data transfer at the physical level has been developed to offer better performance than PCI or PCI-X. PCI-Express is an Input/Output (“I/O”) bus standard (incorporated herein by reference in its entirety) that is compatible with existing PCI cards using the PCI Express bus. [0007] HBAs (a PCI-Express device) that are placed in SANs, receive serial data streams (bit stream), align the serial data and then convert it into parallel data for processing. HBAs operate as a transmitting device as well as a receiving device. [0008] When data is moved from host system memory to storage systems and vice-versa, it needs to be protected. This is because memory in electronic devices has the potential to return incorrect information. There are two types of errors, “hard” and “soft”. A hard error may occur when a bit may be stuck so that it always returns “0”. A soft error occurs when a bit reads back wrong information once and then functions properly. Soft errors are more difficult to detect versus hard errors. [0009] Data can be protected using parity and error correction code (“ECC”). Parity checking is a rudimentary way of checking single bit errors. Parity adds a bit of data to every 8-bits (or other sizes) of data. When parity checking is enabled, a logic circuit called a parity generator/checker examines every byte of data and determines whether the data byte has an even or an odd number of ones. If it has odd number of ones, the ninth bit is set to one; otherwise it is set to zero. When data is read, the parity circuit operates as a checker and determines if there are odd or even number of ones to determine if there is a bit-error. Parity checking provides single-bit error detection, but does not handle multi-bit errors, and does not correct errors. [0010] ECC is used to detect single/multiple bit errors and corrects errors. A special algorithm (for example, SECDED (Single Error Correction with Double Error Detection) algorithm) is used to encode information in a block of bits that contains enough detail to permit recovery of a single bit error in the protected data. ECC typically uses 8 bits of code to protect 64 bits of data. [0011] HBAs operating in networks use ECC to protect data when data is moved from host system memory to HBA memory and then sent to a storage system (i.e. in the transmit path). ECC is also used to protect data when it is received from a storage system and sent to host system memory via the HBA (receive path). [0012] Often data has to be aligned, padded and/or shortened (by removing padding) at the HBA level when data is being moved through a data path in the HBA. ECC has to be generated/re-generated depending on how data is being aligned and handled. This requires ECC data to be checked and re-generated for each re-alignment option at each transition in transmit/receive data paths. As the number of re-alignments increase, the number of gates required to re-generate and check ECC increases. This increases cost and complexity and is hence undesirable. [0013] Therefore, there is a need for a method and system that can efficiently generate and verify ECC in an environment where data is aligned/re-aligned. SUMMARY OF THE INVENTION [0014] In one aspect of the present invention, a method for protecting data in a PCI-Express device is provided. The method includes adding error correction code (ECC) to every byte of data that enters a PCI-Express Transaction Handler (“PTH”) Module and is destined for a host system memory or destined to another device, before data is aligned within the PTH module; verifying ECC code for every byte of data before data leaves the PTH module; and generating ECC code for a data block size, wherein the data block size depends on the destination of the data. [0015] In another aspect of the present inventions, a PCI-Express device coupled to a host system via a PCI Express bus and to another device via a network connection is provided. The PCI-Express device includes a PCI-Express Transaction Handler (“PTH”) Module that (1) adds error correction code (ECC) to every byte of data that is destined for a host system memory or destined to another device, before data is aligned within the PTH module, (2) verifies the ECC code for every byte of the data, and (3) generates the ECC code for a data block size before the data leaves the PTH module, wherein the data block size depends on the destination of the data. [0016] This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiments thereof concerning the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0017] The foregoing features and other features of the present invention will now be described with reference to the drawings of a preferred embodiment. In the drawings, the same components have the same reference numerals. The illustrated embodiment is intended to illustrate, but not to limit the invention. The drawings include the following Figures: [0018] FIG. 1A is a block diagram showing various components of a SAN; [0019] FIG. 1B shows a block diagram of a HBA, as an example of a PCI-Express device; [0020] FIG. 2 shows a block diagram of a system for protecting data in the transmit path, according to one aspect of the present invention; [0021] FIG. 3 shows a block diagram of a system for protecting data in the receive path, according to one aspect of the present invention; [0022] FIG. 4 shows a schematic for protecting data in the transmit/receive paths, according to one aspect of the present invention; [0023] FIG. 5 shows a process flow diagram for protecting data in the receive path, according to one aspect of the present invention; and [0024] FIG. 6 shows process flow diagram for protecting data in the transmit path, according to one aspect of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0025] In one aspect of the present invention, data is protected at a byte level by a PCI Express device that has to align/re-align data received from another device and/or sent to another device. This means that every byte (8 bits) of data that is being received from a storage device for a host system or every byte of data that is to be transmitted to another device is protected/verified. [0026] Since ECC data is generated and verified for every byte of data, the complexities involved in generating/re-generating ECC after alignment/re-alignment is minimized. It is noteworthy that the byte level ECC protection is provided when data has to be modified, aligned or re-aligned, otherwise, to improve efficiency, data blocks (where a data block is greater than a byte) are protected by ECC (for example, ECC is used for every 64-bits of data). [0027] To facilitate an understanding of the preferred embodiment, the general architecture and operation of a SAN, and a HBA will be described. The specific architecture and operation of the preferred embodiment will then be described with reference to the general architecture of the host system and HBA. [0028] SAN Overview: [0029] FIG. 1A shows a SAN system 100 that uses a HBA 106 (referred to as “adapter 106 ”) for communication between a host system with host memory 101 to various storage systems (for example, storage subsystem 116 and 121 , tape library 118 and 120 ) using fibre channel storage area networks 114 and 115 . Host memory 101 includes a driver 102 that co-ordinates all data transfer via adapter 106 using input/output control blocks (“IOCBs”). Servers 117 and 119 can also access the storage sub-systems using SAN 115 and 114 , respectively. [0030] A request queue 103 and response queue 104 is maintained in host memory 101 for transferring information using adapter 106 . Host system communicates with adapter 106 via a PCI-Express bus 105 . [0031] HBA 106 : [0032] FIG. 1B shows a block diagram of adapter 106 . Adapter 106 includes processors (may also be referred to as “sequencers”) “RSEQ” 109 and “XSEQ” 112 for receive and transmit side, respectively, for processing data received from storage sub-systems and transmitting data to storage sub-systems. Transmit path in this context means data path from host memory 101 to the storage systems via adapter 106 . Receive path means data path from storage subsystem via adapter 106 . It is noteworthy, that only one processor is used for receive and transmit paths, and the present invention is not limited to any particular number/type of processors. Buffers 111 A and 111 B are used to store information in receive and transmit paths, respectively. [0033] Beside dedicated processors on the receive and transmit path, adapter 106 also includes processor 106 A, which may be a reduced instruction set computer (“RISC”) for performing various functions in adapter 106 . [0034] Adapter 106 also includes fibre channel interface (also referred to as fibre channel protocol manager “FPM”) 113 that includes modules 113 B and 113 A in receive and transmit paths, respectively (shown as “FC RCV” and “FC XMT”). Modules 113 B and 113 A allow data to move to/from storage systems. [0035] Adapter 106 is also coupled to external memory 108 and 110 via connection 116 A ( FIG. 1A ) (referred interchangeably, hereinafter) and local memory interface 122 . Memory interface 122 is provided for managing local memory 108 and 110 . Local DMA module 137 A is used for gaining access to move data from local memory ( 108 / 110 ). Adapter 106 also includes a serial/de-serializer 136 for converting data from 10-bit to 8-bit format and vice-versa. [0036] Adapter 106 also includes request queue DMA channel ( 0 ) 130 , response queue DMA channel 131 , request queue ( 1 ) DMA channel 132 that interface with request queue 103 and response queue 104 ; and a command DMA channel 133 for managing command information. DMA channels are coupled to arbiter 107 that receives requests and grants access to a certain channel. [0037] Both receive and transmit paths have DMA modules “RCV DATA DMA” 129 and “XMT DATA DMA” 135 that are used to gain access to a channel for data transfer in the receive/transmit paths. Transmit path also has a scheduler 134 that is coupled to processor 112 and schedules transmit operations. [0038] A host processor (not shown) sets up shared data structures in buffer memory 108 . A host command is stored in buffer 108 and the appropriate sequencer (i.e., 109 or 112 ) is initialized to execute the command. [0039] Various DMA units (or channels, used interchangeably throughout this specification) (for example, 129 , 130 , 131 , 132 , 133 and 135 ) send a request to arbiter 107 . When a request is granted, the DMA unit is informed of the grant and memory access is granted to a particular channel. [0040] Arbiter 107 is coupled to a PCI-Express Transaction Handler (PTH) 137 . PTH 137 is coupled to PCI-Express port logic 137 B that moves information to/from a host system. PTH 137 has also been referred to as PCI-Express interface and includes a receive side and transmit side link that allows communication between the host system and adapter 106 . The transmit side receives information from adapter 106 and destined for the host system and the receive side receives information from adapter 106 and destined for the host system. [0041] ECC Protection: In one aspect of the present invention, to simplify handling of plural data path transitions, ECC protection is provided for every individual byte of data in certain components of HBA 106 . After data is merged, split and aligned, the ECC protection is again converted to 64-bit blocks to improve the overall efficiency for data handling/integrity. ECC for each byte flows through byte splitting logic and re-alignment logic with each byte of data. Since data at the byte level does not change, there is no need to generate/regenerate ECC each time data is aligned/re-aligned. [0042] FIG. 2 shows a block diagram of a system 200 for protecting data along the transmit path. Data is received from host system memory based on a DMA request from a DMA module. Data 200 A is received from system memory by PCI-Express logic 201 that is a part of PCI-Express Transaction handler 137 . ECC module 202 includes ECC checker 202 B and ECC generator 202 A. ECC checker 202 B checks the 7 bits of ECC data for every 32 data bits ( FIG. 4 ), while ECC generator 202 A generates 5 bits of ECC data for every byte. Once 7-bit ECC is checked and 5-bit ECC is generated, it is sent to Data Inserter/Data Removal module 204 . [0043] Module 204 pads or removes certain segments from the data whose ECC has been verified. This data is then sent to a data handler 205 that receives the data, 5-bit ECC from ECC generator 202 A and CRC from CRC logic 203 . Data from data handler 205 is then sent to ECC module 206 , which includes ECC checker 206 B and ECC generator 206 A. ECC checker 206 B checks 5 bits of ECC data for every byte, while ECC Generator 206 A generates an 8-bit ECC for every 64 data bits. The ECC and data are then sent to a staging memory buffer 207 (shown as FIFO 207 ) that operates as a First-In and First-Out memory. Data 200 B with ECC and CRC is then sent to the DMA channel that had requested the data from host memory. [0044] FIG. 3 shows a block diagram of a system 300 for protecting data 301 that is received from the DMA channel and staged in FIFO 302 . ECC module 303 has an ECC checker 300 B and ECC generator 303 A. ECC checker 303 B checks the 8-bit ECC for incoming data and ECC generator 303 A generates 5-bit of ECC for every byte of data. The 5-bit ECC and data are then sent to Data inserter/remover module 305 (similar to module 204 in FIG. 2 ). CRC logic Module 304 is similar to CRC logic module 203 , while data handler module 306 is similar to data handler module 205 , except they operate in the receive path. [0045] ECC module 307 has a ECC checker 307 B that verifies 5-bit ECC for every byte of data and ECC generator generates 7-bit of ECC for every 32-bit of data. Logic 308 is similar to logic 201 and data 309 (with ECC and CRC) is sent to host system memory. [0046] FIG. 4 shows a schematic diagram for systems 200 , 300 shown in FIGS. 2 and 3 . All the logic is included in PTH 137 module. All incoming data comes with 8-bits of ECC per 64 bits of data (shown as 414 C), then a 5-bit ECC (shown as 414 B) protects every byte of data in PTH 137 so that ECC flows with data while data is being aligned/adjusted. 7-bit ECC for every 32 data bits (shown as 414 A) occurs while interfacing with the host system. [0047] Turning in detail to FIG. 4 , data 406 and header 407 A (also shown as 200 A, FIG. 2 ) is received from system memory. Header 407 A is protected by 7-bit ECC and is staged in FIFO (a first-in-first out memory module) 407 . Module 407 B checks the 7-bit ECC code for the header and sends it to control logic 401 . [0048] Incoming data 406 is received from host system memory. Data 406 has every 32 bits protected by 7-bit ECC. The 7-bit ECC is checked by ECC checker 202 B (module 202 B). A 5-bit ECC is generated by ECC generator 202 A (module 202 A) that is then sent with the data to logic (a multiplexer (“Mux”)) 408 . CRC generator 411 (in CRC module 410 ) generates the CRC and ECC generator 411 A (module 411 A) generates 5-bit ECC for the CRC. The CRC with 5-bit ECC is sent to Mux 408 . [0049] Data 406 , 5-bit ECC generated by ECC generator 202 A and by module 411 A is sent to a data read alignment module 205 . Module 205 in the transmit path (i.e. for a read request) aligns data 406 . Since ECC is for every byte of data, new ECC is not required after the alignment. ECC code from module 202 A/ 411 A simply moves with regular data. The 5-bit ECC from modules 202 A/ 202 B is checked by ECC checker 206 B. ECC generator 206 A generates 8 bit ECC for every 64-bits of data. The Data with 8-bit ECC is sent to the DMA channel that had requested the data. [0050] Data flow in the receive path (i.e. for a write request to host system memory) is shown as 301 . For clarity, incoming information 301 is shown to have three components. Address information is shown as 301 A, CRC is shown as 301 B and data is shown as 301 C. ECC checker 405 B checks 8-bit ECC that accompanies data 301 C, while module 405 verifies the 8-bit ECC for address 301 A. [0051] ECC generators 405 A and 405 C generate 5-bit ECC for data 301 B and for CRC 301 C, respectively. At this stage, every byte of data is protected by 5-bit ECC. The ECC flows with the data in the receive path. Module 405 receives the incoming data with the 5-bit ECC, after the 8-bit ECC has been verified. Module 405 also receives 5-bit ECC generated by ECC generator 404 B (module 404 B) in CRC module 304 . CRC module 304 also includes a CRC generator 404 and CRC aligner 403 for generating and aligning CRC. [0052] Data and 5-bit ECC (shown jointly as 402 ) with 5-bit ECC for the CRC is sent to module 400 . Module 400 includes ECC generator 307 A and ECC checker 307 B. ECC generator 307 A generates 7-bit ECC for every 32-bits of data after ECC checker 307 B has verified the 5-bit ECC for every byte of data/CRC. Data with the 7-bit ECC is then sent to a staging module 308 that stages data and ECC, before it is sent (shown as 309 ) to host system memory. [0053] FIG. 5 shows a process flow diagram for managing data flow in the receive path, according to one aspect of the present invention. When data is received from the network, a DMA channel provides data and address in step S 500 . The incoming data is typically protected by 8-bit ECC for every 64-bits. In step S 502 , the 8-bit CRC is verified (for example, by ECC checkers 405 B and 405 D). [0054] In step S 504 A, a 5-bit ECC is generated for every 8-bits of data. In step S 504 B, 5-bit ECC for every 8 bits of CRC is generated. It is noteworthy that steps S 504 A and S 504 B can occur simultaneously. [0055] In step S 506 , the data (with 5-Bit ECC) is aligned (for example, by module 205 ). In step S 508 , the 5-bit ECC is checked and in step S 510 , 7-bit ECC for every 32-bit of data is created. In step S 512 , data with 7-bit ECC is sent to host system memory. [0056] FIG. 6 shows a process flow diagram for processing data in the transmit path, according to one aspect of the present invention. The process starts in step S 600 , when data/address is received from host system memory. This data is protected by 7-bit ECC per 32 bits of data. In step S 602 , the 7-bit ECC is verified. [0057] In step S 602 A, 5-bit ECC is generated for data and in step S 602 B, 5-bit ECC is generated for every 8-bit of CRC. It is noteworthy that steps S 602 A and S 602 B may occur simultaneously. [0058] In step S 604 , data is aligned and 5-bit ECC is verified. In step S 606 , 8-bit ECC is generated for every 64-bits of data. Thereafter, in step S 608 , data with 8-bit ECC is sent to the DMA channel. [0059] It is noteworthy that the present invention is not limited to using 5-bit, 7-bit or 8-bit ECC. Any number of bits may be used depending on processing ability of the hardware components. The present invention protects every byte of data, which allows ECC to flow with data and even after alignment/re-alignment; the same ECC can be used. [0060] Although the present invention has been described with reference to specific embodiments, these embodiments are illustrative only and not limiting. Many other applications and embodiments of the present invention will be apparent in light of this disclosure and the following claims.

Method and system for protecting data in a PCI-Express device is provided. The method includes adding error correction code (ECC) to every byte of data that enters a PCI-Express Transaction Handler (“PTH”) Module and is destined for a host system memory or destined to another device, before the data is aligned within the PTH module; verifying the ECC code for every byte of the data before the data leaves the PTH module; and generating the ECC code for a data block size, wherein the data block size depends on the destination of the data.

CROSS-REFERENCE TO THE RELATED APPLICATION This application relates to an application U.S. Ser. No. 09/144,989 being filed based on Japanese Patent Application No. 9-238031 filed on Sept. 3, 1997 by the present assignee. The disclosure of that application is herein incorporated by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and system for embedding information such as a copyright notice in data, and more particularly to a digital watermark embedded in an image. 2. Description of the Related Art Digital watermarking is applied to various contents. A watermark embedded in an image will be described by way of example. Information of a digital watermark is embedded in an image by modifying pixel values such as luminance components, and frequency components so that a set of images represents particular information of “0” or “1”. In conventional techniques, for example, in “Still Image Data Hiding in Pixel Blocks”, Shimizu et al., Proc. of IPSJ 53rd Annual Conference, 1996, the values of two pixels are changed minutely to represent “0” or “1” based upon a difference of values between two pixels. However, the following two conditions are required to be satisfied, when a digital watermark is to be embedded. 1) It is necessary that an image embedded with watermark information hardly changes from an original image (that the watermark is invisible). 2) It is necessary that embedded information is hard to be erased during an image conversion process such as JPEG compression (“Digital Compression and Coding of Continuous-Tone Still Images”, ISO/IEC/0918-1). An error rate of each bit subjected to JPEG compression is 0.1 to 0.2. In order to lower the bit error rate of JPEG compression to a −8 power of 10, it is necessary to provide each bit of an embedded watermark with a redundancy of ten times or higher, so that the values of a number of pixels are necessary to be changed. Since the values of a number of pixels and frequencies are required to be changed in order to lower the bit error rate, there is a tradeoff between a reliability of watermark data detection and a quality of contents. An image compression process such as MPEG is necessary for an image having a large amount of data such as a moving image. In such a case, it is essential to detect watermark data under the condition of MPEG compression, i.e., under the condition of MPEG streams. It is also necessary to prepare a fundamental function of detecting a watermark under the image condition. In this case, a detector system is required to have a MPEG decoder, increasing its cost and process time. SUMMARY OF THE INVENTION It is an object of the present invention to provide digital watermark embedding/detecting techniques capable of minimizing the number of pixels to be changed in order to embed a digital watermark, while a reliability of detecting embedded data is maintained high. It is another object of the invention to provide a digital watermark embedding method and system capable of suppressing as much as possible the quality of contents from being degraded upon modification of pixels. It is still another object of the present invention to provide a digital watermark detecting method and system capable of detecting embedded data not only under the image condition but also under the condition of compression streams. In order to achieve the above objects, the invention provides the following four solution methods. According to a first aspect of the invention, a first data embedding and detecting approach is provided in which data is embedded in a two-dimensional image as a position pattern of blocks whose pixel values are changed. Accordingly, a reliability same as that obtained through conventional techniques can be retained irrespective of that the number of pixels whose values are changed is smaller. According to a second aspect of the invention, a second data embedding and detecting approach is provided in which a sum (or average) of pixel values of partial images is changed to a specific value. Accordingly, it becomes possible to optimize the change amount of pixel values of partial images. According to a third aspect of the invention, a data embedding system is provided which uses the first and second data embedding approaches. According to a fourth aspect of the invention, a data detecting system is provided which uses the first and second data detecting approaches. According to a fifth aspect of the invention, an approach is provided in which the first and second aspects are combined, namely, an image is divided into blocks of k×1 pixels and a sum or average of pixel values of each block is changed to a value satisfying particular conditions. According to a sixth aspect of the invention, an approach is provided in which the size of each block embedded with watermark information based upon the fifth aspect is set to the size (e.g., 8×8 pixels) of a block used as the processing unit of a compression process such as JPEG and MPEG. Accordingly, embedded data under the image condition and under the condition of compression streams has one-to-one correspondence so that the embedded data can be detected both under the image condition and under the condition of compression streams. Other objects, features and advantages of the present invention will become apparent from reading the following description of the invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a method of embedding data in an image, according to an embodiment of the invention. FIG. 2 is a flow chart illustrating a pixel value changing approach according to an embodiment of the invention. FIG. 3 is a diagram showing a data embedding system according to an embodiment of the invention. FIG. 4A is a diagram illustrating a method of detecting data from an image, according to an embodiment of the invention. FIG. 4B is a diagram showing a data detecting system according to an embodiment of the invention. FIGS. 5A to 5 C are diagrams illustrating an example of watermark embedding and detecting realized by software. FIG. 6 is a flow chart illustrating an application of the invention to image data to be recorded in a recording medium, according to an embodiment of the invention. FIG. 7 is a diagram illustrating a method of embedding data in an image according to an embodiment of the invention. FIG. 8 is a diagram showing a system of embedding data in an image according to an embodiment of the invention. FIG. 9 is a flow chart illustrating a method of embedding data in an image according to an embodiment of the invention. FIG. 10 is a flow chart illustrating a method of detecting data from an image according to an embodiment of the invention. FIG. 11 is a diagram illustrating a method of embedding data in an image according to an embodiment of the invention. FIG. 12 is a correspondence table illustrating a method of embedding data in an image according to an embodiment of the invention. FIG. 13 is a flow chart illustrating a method of embedding data in an image according to an embodiment of the invention. FIG. 14 is a flow chart illustrating a method of detecting data from an image according to an embodiment of the invention. FIG. 15 is a diagram illustrating a method of embedding data in an image according to an embodiment of the invention. FIG. 16 is a diagram illustrating a method of embedding data in an image according to an embodiment of the invention. FIG. 17 is a diagram illustrating a method of embedding data in an image according to an embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the invention will be described with reference to the accompanying drawings. First, an embodiment according to the first aspect of the invention will be described with reference to FIG. 1 which is a schematic diagram illustrating an approach to embedding data in an image. In the first embodiment shown in FIG. 1, each block 2 divided from an image 1 having m×n pixels represents a two-dimensional partial image of k×1 pixels where m, n, k and 1 are positive integers. A block 3 with hatched lines has pixel values changed through a pixel value changing approach so that the block 3 has a specific value, the pixel value representing image information such as a luminance, a color difference, R, G and B color data. Information to be embedded is not represented by respective blocks, but it is represented by a block interval d . In this embodiment, the two-dimensional partial images whose pixel values are changed are disposed at the block interval d which corresponds to a data value x of a copyright notice for example, to thereby embed the data x in the image. In embedding watermark information, the data x is converted into the block interval d and the pixel values are changed based upon this block interval d . In detecting a watermark, a block pattern converted from the image is detected to read the block interval and convert the block interval into the data. In this embodiment, although the block interval d corresponding to the data x is set constant, it may be changed. For example, three different block intervals d 1 , d 2 and d 3 corresponding to the data x may be cyclically used to irregularly dispose blocks whose pixel values are changed. Next, a pixel value changing approach according to a second embodiment of the second aspect of the invention will be described. In embedding a watermark, each pixel value in a block of a two-dimensional partial image shown in FIG. 1 is changed so that the sum of pixel values of the block takes a specific value near the sum. For example, each pixel value in the partial image is changed so that the sum of luminance values of pixels takes a multiple of a certain value. This embodiment will be described with reference to FIG. 2 which is a flow chart illustrating the pixel value changing approach. Consider now that the size of the two-dimensional partial image is 8×8 pixels, and that each pixel value is changed so that the sum of pixel values of the partial image takes a multiple of “512”, i.e., so that the sum of pixel values is smaller than a particular value (in this case “512”). It is assumed that pixels of each block are given pixel numbers from “1” to “64”. First at Step 201 , “1” is set to a pixel number I. At Step 202 , each of the pixel values of the pixel number “1” is incremented by “1”. At Step 203 the sum of pixel values of the two-dimensional partial image (block) having 8×8 pixels is incremented or decremented by “1” after the pixel value of the pixel number “1” is changed. It is checked at Step 204 whether the changed sum of the two-dimensional partial image is equal to the specific value of “512”. If equal, this approach is terminated, whereas if not, the approach advances to Step 205 whereat it is checked whether the pixel number I is “64”, i.e., whether all the pixels of the two-dimensional partial image have been changed. If changed, the approach is terminated, whereas if not, the pixel number I is incremented by “1” at Step 206 to change the pixel value of the next pixel. If this approach to simply changing each pixel value has a fear that a third party may steal the watermark information, then a change amount in each pixel value representative of a luminance, a color difference, R, G, B or the like may be changed, as disclosed in the U.S. application being filed based on Japanese Patent Application No. 9-238031 filed on Sep. 3, 1997 by the present assignee, et al. In detecting a watermark, the sum of pixel values of each two-dimensional partial image (block) is calculated to check whether the sum is the specific value or a value near the specific value and to detect the block whose pixel values were changed. In this case, a block is also detected, whose pixel values were not changed and its original sum was a value near the specific value. To deal with this issue, blocks can be detected at a higher precision if known pattern matching, majority decision, or the like is performed. Presumption of the specific value by a third party becomes difficult if a different specific value is used for each two-dimensional partial image (block) depending upon the position of each partial image. Next, an embodiment according to the third aspect of the invention will be described with reference to FIG. 3 which is a schematic diagram showing a data embedding system using the data embedding approach of the first and second embodiments. In the third embodiment shown in FIG. 3, data x to be embedded is converted into the block interval d through the pixel value changing approach of the first embodiment, and blocks whose pixel values are to be changed are determined. Next, the position information of the determined blocks is supplied to the image in which the data x is embedded, and the pixel values of each block is changed through the data embedding approach of the second embodiment. Next, a fourth embodiment according to the third aspect of the invention will be described with reference to FIG. 4A which is a schematic diagram showing a data detecting system using the data detecting approach. In the fourth embodiment shown in FIG. 4A, blocks whose pixel values were changed are detected from two-dimensional partial images (blocks) with the data x being embedded, by a changed block detecting means which checks the specific value of each block from the sum of pixel values thereof. Next, the block interval between the blocks whose pixel values were changed is converted into the data x by a pattern detecting means, so that the data x can be reproduced from the watermark embedded image. FIG. 4B illustrates a modification of the fourth embodiment shown in FIG. 4 A. In FIG. 4B, like elements to those shown in FIG. 4A are represented by identical reference numerals. Reference numeral 23 represents a storage means for storing position information of blocks to be supplied to a pattern detecting means 21 . In this fifth embodiment, after the position information detected with the changed block detecting means 20 is temporarily stored in storage mans 23 , a pattern is detected by the pattern detecting means 21 to reproduce the data x . FIGS. 5A to 5 C illustrate an example of a method of embodying watermark embedding and detecting of this invention by using software running on a computer. FIG. 5A is a diagram illustrating a functional structure of the inside of a computer. In embedding a watermark, an image and embedding data are input from an input/output unit 501 and stored in a storage device 503 . Next, an operation unit 502 executes a watermark embedding process, and a watermark embedded image is output from the input/output unit 501 . In detecting a watermark, a watermark embedded image is input from the input/output unit 501 and stored in the storage device 503 . Next, the operation unit 502 executes a watermark detecting process, and embedded data is output from the input/output unit 501 . FIG. 5B is a diagram illustrating a functional structure of embedding a watermark. Reference numerals 511 , 512 , and 513 represent processes to be executed by a CPU of the computer. Reference numerals 514 to 516 represent data stored in the storage device 503 of the computer. An input/output unit 511 stores image data 514 and embedding information (data x) 515 in the storage device 503 . In a watermark embedding process 513 , the embedding information is converted into watermarking information which is embedded in image data 514 . The watermark embedded image 516 is stored in the storage device. The watermark embedded image 516 stored in the storage device 503 is output from the input/output unit 501 . FIG. 5C is a diagram illustrating a functional structure of detecting a watermark. Reference numeral 521 represents a process to be executed by CPU of the computer. The input/output unit 511 stores a watermark embedded image 516 in the storage device 503 . In the watermark detecting process 521 , watermarking information is derived from the watermark embedded image 516 and converted into embedding information (data x ) which is stored in the storage device 503 . The embedding information stored in the storage device 503 is output from the input/output unit 501 . FIG. 6 is a flow chart illustrating an operation of storing an image embedded with data in a recording medium according to a fifth embodiment of the invention. Reference numeral 32 represents a data embedding means of this invention, reference numeral 33 represents an image compressing means, and reference numeral 34 represents a formatting means specific to a recording medium 35 . Digital watermark data 31 is embedded in a two-dimensional image 30 by the data embedding approach of this invention. The watermark embedded two-dimensional image is then compressed by the image compressing means 33 , formatted to have a format specific to the recording medium 35 , and stored in the recording medium 35 . It is therefore possible to form a recording medium such as an optical disk which stores data such as a digital watermark embedded two-dimensional image. Next, a sixth embodiment of the invention will be described. In this embodiment, watermark data can be detected both under the image condition and under the condition of compression streams. FIG. 7 is a diagram illustrating an example of a method of embedding data in an image, the method being suitable for an image compression process. In FIG. 7, reference numeral 171 represents a two-dimensional partial image (block) of 8×8 pixels. This size (8×8 pixels) of the two-dimensional partial image 71 to be subjected to the pixel changing approach is an image processing unit of an image compression process such as JPEG and MPEG. Therefore, embedded information becomes hard to be lost during the image processing process. It is also known that sum of values of 8×8 pixels is a DC component value of I-frame under the condition of MPEG compression, i.e., MPEG streams. Therefore, the information embedded in such a manner that the sum of pixel values of each two-dimensional partial image takes the specific value, can be detected by judging whether or not the DC component value of I-frame under the condition of MPEG streams takes the above-described specific value and by deriving the interval of blocks satisfying the specific value. With this embodiment method, it is possible to derive the embedded information both under the image condition and under the condition of compression streams. If detection from only under the condition of compression streams is used, it is not necessary for a detector system to have a MPEG decoder so that the cost of the system can be lowered. Next, a seventh embodiment of the invention will be described. FIG. 8 is a schematic diagram illustrating the format of data embedded in an image. In FIG. 8, an image 81 of 720×480 pixels is divided into two-dimensional partial images (blocks) 82 each being constituted of 8×8 pixels. A macro block 83 is constituted of 64 blocks. There are 84 macro blocks in the image. As shown, a y-th block in an x-th macro block is represented by Bxy, where x is an integer from 1 to 84 and y is an integer from 1 to 64. Blocks in a block pattern whose pixel values are changed are disposed at a constant block interval d (in this example, d=64). The embedding information is represented by a shift amount m (m=0 to 63) of a block whose pixel values are changed. In this example, watermark information of 64 types (6 bits) can be embedded, including block patterns of (B 11 , B 21 , . . . , B 84 1 ), (B 12 , B 22 , . . . , B 84 2 ), . . . , (B 1 m+1, B 2 m+1, . . . , B 84 m+1), . . . , (B 1 64 , B 2 64 , . . . , B 84 64 ). In the example shown in FIG. 8, the block pattern (B 11 , B 21 , . . . , B 84 1 ) 84 is embedded. FIG. 9 is a flow chart illustrating the data embedding method. At Step 901 a block pattern shift amount m is calculated from 6-bit data x . Step 902 and following Steps illustrate an operation of embedding watermark information in the block pattern (B 1 m+1, B 2 m+1, . . . , B 84 m+1) shifted by m blocks from the block pattern (B 1 , B 21 , . . . , B 84 1 ). At Step 902 the number n of the macro block in which watermark information was embedded is set to “1”. At Step 903 it is checked whether the watermark information has been embedded in all the macro blocks (84 blocks). If embedded, the flow is terminated, whereas if not, the flow advances to Step 904 . At Step 904 the (m+1)-th block in the n-th macro block is designated, and at Step 905 watermark information is embedded in the designated block by changing the pixel values thereof. At Step 906 the number n of the macro block embedded with the watermark information is incremented by FIG. 10 is a flow chart illustrating the data detecting approach. First, at Step 1002 the block pattern shift amount m is set to “0”. At Step 1003 it is checked whether detection number D temporarily stored in the system has been obtained for all the block patterns of 64 types. If obtained, the flow advances to Step 1012 , whereas if not the flow advances to Step 1004 . The detection number D indicates the number of blocks satisfying a particular rule. For example, the detection number D is the number of blocks each having a sum of luminance values equal to a multiple of “512”. At Step 1004 , the macro block number n is set to “1” and the detection number D is set to “0”. At Step 1005 it is checked whether detection for all the macro blocks with the shift amount m has been completed. If completed, at Step 1010 a detection number Dm at the shift amount m is stored as the detection number D, and at Step 1011 the shift amount m is incremented by “1” to continue the detecting process at the new shift amount. If not completed at Step 1005 , the flow advances to Step 1006 whereat the block Bn m+1 in the n-th macro block at the shift amount m is designated. At Step 1007 it is checked from the pixel values of the designated block whether the watermark information can be detected. If detected, at Step 1008 the detection number D is incremented by “1”, and thereafter at Step 1009 the macro block number n is incremented by “1” in order to designate the corresponding block in the next macro block. If not detected at Step 1007 , the flow advances directly to Step 1009 whereat only the macro block number n is incremented by “1”. After the detection numbers Dm for all the shift amounts m are obtained, i.e., after it is judged at Step 1003 as m=63, at Step 1012 the detection number Dm larger than a threshold value is searched from the detection numbers Dm at respective shift numbers m and the shift amount m at the searched detection number Dm is used as the shift amount m when the watermark information was embedded. At Step 1013 the shift amount m is converted into the data x to derive the watermark information. Next, an eighth embodiment of the invention will be described. FIG. 11 is a schematic diagram illustrating the format of data embedded in an-image. Hatched blocks 111 constitute a block pattern. A different point from the format shown in FIG. 8 resides in that the block intervals of the block pattern whose pixel values are changed, are not constant but random. If the block interval is constant as shown in FIG. 8, there is a fear that watermark information may be erroneously detected or easily removed illicitly, although depending on the type of an image. In accordance with a correspondence table between data x and a block pattern shown in FIG. 12, blocks in each block pattern are randomly allocated to each macro block, and data x of 6 bits can be embedded. The block pattern shown in FIG. 11 corresponds to the block pattern “1” shown in the table of FIG. 12 . FIG. 13 is a flow chart illustrating the data embedding approach according to the eight embodiment. At Step 1301 , data x is converted into a block pattern by referring to the correspondence table shown in FIG. 12 . At Step 1302 watermark information is embedded randomly in a block Bn An (An is a random number series from “0” to “64”) of the n-th macro block. Other Steps correspond to those described with FIG. 9 . FIG. 14 is a flow chart illustrating the data detecting approach. At Step 1401 the block pattern number p shown in FIG. 12 is set to “1”. At Step 1402 it is checked whether detection has been obtained for all the block patterns of 64 types. If obtained, the flow advances to Step 1406 , whereas if not, the flow advances to Step 1004 whereat the macro block number n and detection number D are initialized. If detection for all the 84 macro blocks in one block pattern has been completed at Step 1005 , a detection number Dp at the block pattern p is stored at Step 1404 as the detection number D, and at Step 1405 the block pattern p is incremented by “1”. If not completed at Step 1005 , the flow advances to Step 1403 whereat the An-th block Bn An in the n-th macro block is designated and watermark information is detected at Step 1007 . If detection has been obtained for all the block patterns at the judgement Step 1402 , then at Step 1402 the block pattern p detection number Dp larger than a threshold value is searched from the detection numbers Dp and the block pattern p at the searched detection number Dp is used as the block pattern p when the watermark information was embedded. At Step 1407 the block pattern p is converted into the data x by referring to the correspondence table shown in FIG. 12 to derive the watermark information. Next, a ninth embodiment of the invention will be described. In the seventh and eighth embodiments, 6-bit watermark information can be embedded because the block interval is set to “64” without permitting any duplication of blocks between block patterns. This ninth embodiment aims to allow watermark information of 6 bits or larger to be embedded, by permitting duplication of blocks between block patterns while the number of blocks of each block pattern is maintained “84”. FIG. 15 is a schematic diagram of an image embedded with a 7-bit watermark information by the embodiment data embedding method. There are 128 block patterns in total. In FIG. 15, hatched blocks embedded with watermark information are shown disposed in respective macro blocks of each block pattern. The data embedding method same as the seventh embodiment is used for the block patterns 1 to 64 . Namely, these block patterns 1 to 64 are represented by (B 11 , B 21 , . . . , B 84 1 ), (B 12 , B 22 , . . . , B 84 2 ), . . . , (B 1 64 , B 2 64 , . . . , B 84 64 ). The block patterns 65 to 128 are formed in accordance the following rules, as illustrated in FIG. 15 . The block pattern p is represented by (B 1 (p−1)mod 64 +1, B 2 (p−2)mod 64 +2, . . . , Bn (p−1)mod 64 +n , . . . , B 84 (p−1)mod 64 +84). A mod B is a remainder of A divided by B, and the second suffix of B takes “1” after “64”. For example, B 80 65 =B 80 1 , B 80 66 =B 80 2 , and so on. With this block pattern setting, the embedding position of a block in each macro block in one block pattern becomes essentially coincident with the embedding position of a corresponding macro block in another block pattern. The number of coincident embedding positions between arbitrary two block patterns is “2”. For example, in the block patterns shown in FIG. 15, the watermark embedding position of the macro block 2 of the block pattern 65 is B 2 2 which is the same as that of the macro block 2 of the block pattern 2 . In all the block patterns, the number of coincident watermark embedding positions of the block patterns 65 and 2 is “2” and this is true for any of other combinations of two block patterns. In the above manner, since blocks between block patterns are duplicated, information of larger bits can be embedded. In this embodiment data embedding method, blocks may be determined randomly by using the eighth embodiment described above. The data embedding method and detecting method of this embodiment are similar to those shown in FIGS. 13 and 14 except that An is set so as to match the ninth embodiment. The description of the methods is therefore omitted. A tenth embodiment of the invention will be described with reference to FIGS. 16 and 17. This embodiment aims to embed watermark information of 8 bits or larger, expanding the ninth embodiment. FIGS. 16 and 17 are schematic diagrams of an image embedded with an 8-bit watermark information by the embodiment data embedding method. There are 256 block patterns in total. The other layout of the blocks is the same as that shown in FIG. 15 . Block patterns in FIGS. 16 and 17 are represented as in the following. Block patterns p 1 to 64 are represented in the manner same as the ninth embodiment. Block patterns p 65 to 128 are represented by (B 1 (p−1)mod 64 +1, B 2 (p−2)mod 64 +1+7, . . . , Bn (p−1)mod 64 +1+7(n−1), . . . , B 84 (p−1)mod 64 +1+7*83). Block patterns p 129 to 192 are represented by (B 1 (p−1)mod 64 +1, B 2 (p−2)mod 64 +1+11, . . . , Bn (p−1)mod 64 +1+11(n−1), . . . , B 84 (p−1)mod 64 +1+11*83). Block patterns p 193 to 256 are represented by (B 1 (p−1)mod 64 +1, B 2 (p−2)mod 64 +1+13, . . . , Bn (p−1)mod 64 +1+13(n−1), . . . , B 84 (p−1)mod 64 +1+13*83). Similar to the ninth embodiment, A mod B is a remainder of A divided by B, and the second suffix of B takes “1” after “64”. For example, B 80 65 =B 80 1 , B 80 66 =B 80 2 , and so on. With this block pattern setting, watermark information can be embedded while duplication of block patterns is minimized. Namely, by making uniform the number of arbitrary duplication block patterns, the number of duplications can be minimized. According to the invention, it is possible to embed data such as digital watermark information in a two-dimensional image and to detect the embedded data from a data embedded two-dimensional image, while a change in the contents is minimized, the image quality is prevented from being degraded, and the data detection reliability is improved. Furthermore, by designating the size of a two-dimensional partial image, not only embedded information becomes hard to be lost during an image compression process, but also the embedded information can be derived and reproduced both under the image condition and under the condition of compression streams. If detection only under the condition of compression streams is performed, it is not necessary for a detector system to install a MPEG decoder and the system cost can be lowered.

A data embedding method and apparatus and a data reproducing method and apparatus are provided which can apply a digital watermark to various contents. Instead of embedding watermarking information in respective pixels or by using a relation between pixels, the watermarking information is embedded as a position pattern of changed pixels in the contents. Reliability comparable with conventional techniques can be obtained irrespective of a change in a smaller number of pixels for the contents.

TECHNICAL FIELD [0001] The present disclosure relates to a control system for a hybrid-electric powertrain, and more particularly to a control system for a hybrid-electric powertrain that controls initiation, battery testing, and de-initiation of the hybrid-electric powertrain. BACKGROUND [0002] Many vehicles now utilize hybrid-electric powertrains in order to increase the efficiency of the vehicle. Hybrid-electric powertrains typically improve overall vehicle fuel efficiency by allowing supplementing an internal combustion engine with electric motors, such that less power output is required of the internal combustion engine, as power from the electric motors may also be utilized in situations when maximum powertrain output is required, such as acceleration, or climbing a grade. Additionally, hybrid-electric powertrains may be utilized to power equipment mounted to a vehicle, such as, for example, a lift, an auger, a post hole digger, a crane, or other known equipment that may be utilized when a vehicle is not in motion. Such power equipment may be powered through a power take off (“PTO”) that may be driven by electric motors of the hybrid-electric powertrain to reduce the time an internal combustion engine is operated. [0003] The initiation and de-initiation, or startup and shutdown, of the electrical systems in a vehicle having a hybrid-electric powertrain presents issues not experienced previously. For instance, during initiation of electrical systems, simply transitioning high-voltage isolation contactors from an open state, which prevents the flow of electricity, to a closed state, which allows the flow of electricity, upon activation of a vehicle's key, may cause a rapid uncontrolled free flow of electrical energy that may damage system components. For example, design limits of system components may be exceeded by rapid loading of electrical energy, thereby damaging the system components. Similarly, when electrical systems are de-initiated, premature component failure or excessive battery discharge may occur if the flow of electrical energy is suddenly stopped. [0004] Further, in addition to initiation and de-initiation of the electrical systems, voltage of individual cells in batteries of the hybrid-electric powertrain needs to be balanced to allow the electrical system to function as intended and to allow the battery packs to offer performance and life cycle that is acceptable. If voltage of the individual battery cells is not kept within a certain range, battery pack life may be adversely affected, and electrical systems may not have sufficient voltage if one of the individual cells in a battery pack is not as charged as the rest of the cells. Previous efforts to provide battery management systems focused on either balancing voltage within the battery cells after the vehicle had been shut off, which can drain the battery packs to a level to prevent the vehicle from starting, or the battery management system is active during operation of the hybrid-electric powertrain, which makes it increasingly difficult to balance the battery packs as electric loads are constantly varying the voltage within the battery packs. [0005] Therefore, a need exists for a control system that controls the initiation, de-initiation, and battery management system for an electrical system of a vehicle having a hybrid-electric powertrain. SUMMARY [0006] According to one process, a method of operating a vehicle with hybrid-electric powertrain having an internal combustion engine, a generator, and a battery is provided. A vehicle start input signal is received from an operator interface. A master controller initiates after receiving the input from the operator interface. At least one secondary controller initiates after starting the initiation of the master controller. A high-voltage battery pack cell voltage balancing test is performed utilizing the master controller. Voltage within the high-voltage battery pack cells is balanced based upon results of the high-voltage battery pack cell voltage balancing test. A high-voltage isolation contactor closes after balancing the voltage within the high-voltage battery pack. A signal from the master controller to the at least one secondary controller to begin operation is generated after closing the high-voltage isolation contactor. The balancing of the high voltage batteries also occurs dynamically during normal vehicle operation. The high voltage battery cell voltage “test” occurs before the pre-charge contactors and main isolation contactors close. The “test” is a momentary look/glimpse by the BMS at the high voltage battery cells to determine their state of charge (SOC), which becomes a fixed point of reference in order to later direct more or less electrical potential to a given cell during dynamic vehicle operation. [0007] According to another process, a method of operating a vehicle with hybrid-electric powertrain having an internal combustion engine, a generator, and a battery, is provided. A shut-down signal input is provided from an operator interface. A master controller determines a current amount of electrical activity of the hybrid-electric powertrain. Electrical activity of the hybrid-electric powertrain is reduced by transmitting a control signal from the master controller to at least one secondary controller. A high-voltage isolation contactor opens once the electrical activity of the hybrid-electric powertrain reaches a predetermined threshold. A high-voltage battery pack cell voltage balancing test is performed utilizing the master controller. Voltage within the high-voltage battery pack is balanced based upon results of the high-voltage battery pack cell voltage balancing test. The at least one secondary controller is placed into a sleep mode. The master controller is placed into a sleep mode after the at least one secondary controller enters into the sleep mode. The hybrid-electric powertrain shuts-down once the master controller enters into the sleep mode. [0008] According to a further process, a method of balancing voltage within cells of a high-voltage battery pack of a vehicle having hybrid-electric powertrain is provided. It is determined if a high-voltage electrical system discharge rate is between a first limit and a second limit. It is determined if a low-voltage electrical system discharge rate is between a third limit and a fourth limit. A high-voltage isolation contactor transitions from a first state to a second state. An amount of voltage is determined in a plurality of cells of a high-voltage battery back. An amount of voltage in the plurality of cells of the high-voltage battery pack is balanced. [0009] As described above, the Supervisory Control System for Hybrid-Electric Powertrains and a vehicle made with this system provide a number of advantages, some of which have been described above and others of which are inherent in the invention. Also, modifications may be proposed to the Supervisory Control System for Hybrid-Electric Powertrains or a vehicle made with this system without departing from the teachings herein. BRIEF DESCRIPTION OF THE DRAWINGS [0010] FIG. 1 is a schematic diagram showing a vehicle having a hybrid-electric powertrain. [0011] FIG. 2 is a flow chart showing the initialization process of an electrical system of a vehicle having a hybrid-electric powertrain. [0012] FIG. 3 is a flow chart showing the de-initiation process of an electrical system of a vehicle having a hybrid-electric powertrain. [0013] FIG. 4 is a graph showing current flow before a battery management system is utilized during initiation of an electrical system of a vehicle having a hybrid-electric powertrain. [0014] FIG. 5 is a flow chart showing current flow before a battery management system is utilized during de-initiation of an electrical system of a vehicle having a hybrid-electric powertrain. DETAILED DESCRIPTION [0015] Referring now to the figures and in particular to FIG. 1 , a schematic diagram of a vehicle having a hybrid-electric powertrain 10 is depicted. The hybrid-electric powertrain 10 comprises an internal combustion engine 12 and a hybrid-electric system 14 that is coupled to the internal combustion engine 12 . The hybrid-electric system 14 may comprise an electric motor and generator adapted to function as a generator and generate electrical power when being driven by the internal combustion engine, and also is capable of functioning as an electric motor when being powered by first and second high-voltage battery packs 20 , 22 . A hybrid motor controller 16 is coupled to the hybrid-electric system 14 to control the function of the hybrid-electric system 14 as either a motor or a generator. [0016] The hybrid motor controller 16 is electrically coupled to a high-voltage distribution box 18 . The high-voltage distribution box 18 is adapted to control the distribution of electrical energy to and from the hybrid system 16 , the first high-voltage battery pack 20 , the second high-voltage battery pack 22 , and electrically powered components of the vehicle. The high-voltage distribution box 18 comprises a first isolation contactor 24 and a second isolation contactor 26 . The first isolation contactor 24 and the second isolation contactor 26 may be transitioned between an open position, preventing flow of electricity, and a closed position, allowing flow of electricity. [0017] The first high-voltage battery pack 20 includes at least one high-voltage battery cell 28 and battery management system (“BMS”) circuit 30 . The at least one high-voltage battery cell 28 stores electrical energy utilized by the hybrid-electrical system 14 . The BMS circuit 30 is utilized to test the state of the first battery pack 20 and to balance voltage within high-voltage battery cell 28 of the first high-voltage battery pack 20 and other high-voltage battery cells, both within the first high-voltage battery pack 20 , and in other high-voltage battery packs, such as the second high-voltage battery pack 22 . [0018] The second high-voltage battery pack 22 includes at least one high-voltage battery cell 32 and a BMS circuit 34 . The second high-voltage battery pack 22 is generally identical to the first high-voltage battery pack 20 . [0019] The BMS circuits 30 , 34 allow-voltage within the high-voltage battery cells 28 , 32 to be measured when there is no load on the electrical system, such as when the first and second isolation contactors 24 , 26 are in an open position. Once the voltage in the high-voltage battery cells 28 , 32 has been measured, the voltage within each cell 28 , 32 may be equalized, as a battery pack 20 , 22 may typically only output as much electrical power as that found in the least charged cell of the battery pack 20 , 22 . [0020] The high-voltage distribution box 18 additionally includes a pre-charge resistor circuit 36 . The pre-charge resistor circuit 36 may be utilized to determine an amount of electrical current flowing through the high-voltage distribution box 18 . The role of the pre-charge resistor circuit 36 is to reduce or prevent a free flow of electrical energy to all components of the vehicle's electrical architecture. Such rapid uncontrolled free flow of electrical energy places heavy, rapid loads on electrical components at rates possibly exceeding their design limits, contributing to undue or premature failure of these components. A DC to DC converter 38 is also provided within the high-voltage distribution box 18 . The DC to DC converter 38 is adapted to convert the high-voltage output from the first battery pack 20 and the second battery pack 22 to a lower voltage for use with low-voltage electrical system, such as those typically found to power electrical accessories in a vehicle. In addition to the DC to DC converter 38 found in the high-voltage distribution box 18 , a second DC to DC converter 40 may also be provided. [0021] An electronic system controller (“ESC”) 42 is also provided. The ESC 42 acts as a master controller for the electrical system of the hybrid-electric powertrain 10 . The ESC 42 is electrically coupled to an operator interface 44 , such as an ignition key. The operator interface 44 allows a user to indicate that the hybrid-electric powertrain 10 should initiate, or start-up, by placing the operator interface 44 into a start position. Similarly, the operator interface 44 also allows a user to indicate that the hybrid-electric powertrain should de-initiate, or shut-down, by placing the operator interface 44 into an off position. [0022] The ESC 42 is electrically coupled via control networks 46 , 48 , 50 to a number of secondary controllers, and electrical devices. For instance, a powertrain control network 48 may electrically couple the ESC 42 with an electronic control module (“ECM”), or electronic control unit (“ECU”), 52 , a hybrid control unit (“HCU”) 54 , and transmission control unit (“TCU”) 56 , an anti-lock brake system control unit (“ABS”) 58 , and a regenerative braking system 60 . The powertrain control network 48 may operate according to SAE standard J1939. [0023] The ESC 42 is also coupled to a dash control panel 62 via a dash control network 46 . The dash control network 46 may operate according to SAE standard J1708. [0024] Finally, the ESC 42 is coupled via hybrid control network 50 . The hybrid control network 50 may operate according to SAE standard J1939. The hybrid control network 50 comprises a pneumatic compressor controller 64 , a power steering controller 66 , and an HVAC controller 68 . The pneumatic compressor controller 64 , the power steering controller 66 , and the HVAC controller 68 are all also electrically coupled to the high-voltage distribution box 18 , to receive power. The hybrid control network 50 also comprises a first remote power module (“RPM”) 70 and a second RPM 72 . The first RPM 70 and the second RPM 72 are adapted to control various equipment of a vehicle having a hybrid-electric powertrain, such as a lift, or a hydraulically driven component like an auger. The hybrid control network 50 additional comprises the first high-voltage battery pack 20 and the second high-voltage battery pack 22 . Thus, the hybrid control network 50 allows the ESC 42 to be electrically connected to a number of controllable components of the hybrid-electric powertrain 10 . [0025] Turning now to FIG. 2 , a flow chart of the initialization process 100 of an electrical system of a vehicle having the hybrid-electric powertrain 10 is shown. The initialization process 100 begins when a user places an operator interface into an operating position as shown at block 102 . The operator interface generates a signal that is transmitted to an ESC, also referred to as a master controller at block 104 indicating that operator interface has been placed into an operating position. The master controller then initiates its operation at block 106 . Once the master controller begins its initiation, at least one secondary controller, such as a pneumatic compressor controller, also begins to initiate, as shown at block 108 . [0026] A high-voltage battery pack cell voltage balancing test is performed at block 110 . The high-voltage battery pack cell voltage balancing test includes the master controller broadcasting a signal to the secondary controllers to remain in a state of minimal power consumption, or no power consumption, until the high-voltage battery pack cell voltage balancing test is complete. The high-voltage battery pack cell voltage balancing test is conducted with the high-voltage isolation contactor in an open position, preventing the flow of electrical current from a high-voltage battery pack. Performing the high-voltage battery pack cell voltage balancing test with the high-voltage isolation contactor in the open position provides a more stable voltage environment. The voltage within the cells of the battery pack or packs is then balanced by either discharging cells with an excess voltage, or to charge any cells with a voltage lower than the desired voltage, or a combination of the two may be utilized. [0027] Next, current from the high-voltage battery pack may be provided to a DC to DC converter for use with the vehicle's low-voltage electrical system. The master controller further initiates a high-voltage pre-charge cycle, where the master controller monitors current flow in the both the high-voltage electrical system and the low-voltage electrical system. The current flow in both the high-voltage electrical system must be between an upper current limit and a lower current limit. Further, the current flow in the high-voltage electrical system must remain between the upper current limit and the lower current limit for a predetermined time. Similarly, the low-voltage electrical system must also have a current flow that is between an upper current limit and a lower current limit for a predetermined time. The upper and lower current limits and the predetermined time may vary based upon the application of the vehicle. [0028] Once the high-voltage battery pack cell voltage balancing test, and pre-charge cycle indicates that the high-voltage and low-voltage current flows are within the predefined current limits, a high-voltage isolation contactor may be transitioned from an open position to a closed position as seen in block 114 . Finally, the master controller broadcasts a signal to the secondary controllers that they may begin operating as shown at block 116 . [0029] Alternatively, once the high-voltage battery pack cell voltage balancing test performed at block 110 is complete, the balancing step may be skipped, and the master controller may proceed to initiate the pre-charge cycle of the high and low voltage systems. Once the high-voltage battery pack cell voltage balancing test and pre-charge cycle indicates that the high-voltage and low-voltage current flows are within the predefined current limits, the high-voltage isolation contactor may be transitioned from an open position to a closed position as seen in block 114 . Balancing of the voltage within the cells of the battery pack or packs is then balanced dynamically during operation of the vehicle by either discharging cells with an excess voltage or charging cells with deficient voltage, or by a combination of both. [0030] FIG. 3 depicts a flowchart of the shutdown process 200 of an electrical system of a vehicle having the hybrid-electric powertrain 10 . The shutdown process 200 begins when a user places an operator interface, or user interface, into a shutdown position as shown at block 202 . The operator interface generates a signal that is transmitted to an ESC, also referred to as a master controller at block 204 indicating that the operator interface has been placed into an operating position. The master controller then determines an amount of electrical activity in the hybrid-electric powertrain at block 206 . The master controller reduces the electrical activity within the hybrid-electric powertrain until the total level of electrical activity falls below a predetermined shutdown threshold, as shown at block 208 . Once the electrical activity is below the predetermine shutdown threshold, a high-voltage isolation contactor is transitioned from a closed state to an open state at block 210 . [0031] A high-voltage battery pack cell voltage balancing test is performed at block 212 . The high-voltage battery pack cell voltage balancing test includes the master controller broadcasting a signal to the secondary controllers to remain in a state of minimal or no power consumption until the high-voltage battery pack cell voltage balancing test is complete. The high-voltage battery pack cell voltage balancing test is conducted with the high-voltage isolation contactor in an open position, preventing the flow of electrical current from a high-voltage battery pack. Performing the high-voltage battery pack cell voltage balancing test with the high-voltage isolation contactor in the open position provides a more stable voltage environment. The voltage within the cells of the battery pack or packs is then balanced at block 214 by either discharging cells with an excess voltage, or by charging any cells with a voltage lower than the desired voltage, or a combination of the two may be utilized. Alternatively, the balancing of the high voltage batteries may occur dynamically during the next or subsequent vehicle operation cycle. In this scenario, the high-voltage battery pack cell voltage balancing test functions as a momentary look by the BMS at the high voltage battery cells to determine their state of charge (SOC). This SOC becomes a fixed point of reference in order to direct more or less electrical potential to a given cell during dynamic vehicle operation the next time the vehicle is operated. In other words, the BMS remembers the ending cell SOC for use during a subsequent re-initialization of the system. [0032] Finally, the master controller signals the secondary controllers to enter into a sleep mode at block 216 . The sleep mode stops activity on the control network between the secondary controllers and the master controller. The master controller enters into a sleep mode at block 21 , and the entire hybrid-electric powertrain is shutdown at block 220 . [0033] FIG. 4 shows a current chart 300 indicating an amount of current flowing from a high-voltage electrical system 302 as well as an amount of current flowing from a low-voltage electrical system 304 prior to initiation of the ESC and any additional controllers. An upper current limit b1 is shown as is a lower current limit b2. As shown in FIG. 4 , the upper current limit b1 and the lower current limit b2 are shown as being identical for both the current flow from the high-voltage electrical system 302 and the current flow from the low-voltage electrical system 304 , however, it is contemplated that different limits may be utilized. A preset time frame 306 is also shown in FIG. 4 . The preset time frame 306 provides assurance that the current flow from the high-voltage electrical system 302 and the current flow from the low-voltage electrical system 304 remain within the upper current limit b1 and the lower current limit b2 for a sufficient period of time to indicate that the operation of the hybrid-electric powertrain has stabilized and it is unlikely that damage will be caused by a transition of an isolation contactor to a closed position to allow current to flow from a high-voltage distribution box. [0034] Similarly, FIG. 5 shows a current chart 400 indicating an amount of current flowing from a high-voltage electrical system 402 as well as an amount of current flowing from a low-voltage electrical system 404 prior to shut-down of the ESC and any additional controllers. An upper current limit b3 is shown as is a lower current limit b4. As shown in FIG. 5 , the upper current limit b3 and the lower current limit b4 are shown as being identical for both the current flow from the high-voltage electrical system 402 and the current flow from the low-voltage electrical system 404 , however, it is contemplated that different limits may be utilized. In one embodiment, the high voltage current and low voltage current levels do not need to be identical, but both the high voltage current and low voltage current levels need to be within the “deadband” range created between b3 and b4. A preset time frame 406 is also shown in FIG. 5 . The preset time frame 406 provides assurance that the current flow from the high-voltage electrical system 402 and the current flow from the low-voltage electrical system 404 remain within the upper current limit b3 and the lower current limit b4 for a sufficient period of time to indicate that the operation of the hybrid-electric powertrain has stabilized and it is unlikely that damage will be caused by transitioning an isolation contactor to an open position to stop current flow from a high-voltage distribution box. [0035] It will be understood that a control system may be implemented in hardware to effectuate the method. The control system can be implemented with any or a combination of the following technologies, which are each well known in the art: a discrete logic circuit(s) having logic gates for implementing logic functions upon data signals, an application specific integrated circuit (ASIC) having appropriate combinational logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc. [0036] When the control system is implemented in software, it should be noted that the control system can be stored on any computer readable medium for use by or in connection with any computer related system or method. In the context of this document, a computer-readable medium can be any medium that can store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic) having one or more wires, a portable computer diskette (magnetic), a random access memory (RAM) (electronic), a read-only memory (ROM) (electronic), an erasable programmable read-only memory (EPROM, EEPROM, or Flash memory) (electronic), an optical fiber (optical), and a portable compact disc read-only memory (CDROM) (optical). The control system can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. [0037] While specific embodiments have been described in detail in the foregoing detailed description and illustrated in the accompanying drawings, those with ordinary skill in the art will appreciate that various permutations of the invention are possible without departing from the teachings disclosed herein. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof Other advantages to a Supervisory Control System for Hybrid-Electric Powertrains and a vehicle made with this system may also be inherent in the invention, without having been described above.

A method of operating a vehicle with hybrid-electric powertrain having an engine, a generator, and a battery is provided. A vehicle start input signal is received from an operator interface. A master controller initiates after receiving input from the operator interface. A secondary controller initiates after starting initiation of the master controller. A battery pack cell voltage balancing test is performed utilizing the master controller. Voltage within the battery pack cells is balanced based upon the balancing test. An isolation contactor closes after balancing the voltage within the battery pack. A signal from the master controller to the secondary controller to begin operation is generated after closing the isolation contactor. Alternately, voltage within the battery pack cells based upon results of the balancing test may take place dynamically during vehicle operation after closure of the isolation contactor.

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to provisional application No. 60/927,552, the contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] Wood and coal have been a principle source of fuel for hundreds of years. In modern times, petroleum has become a primary commodity for the generation of energy. Petroleum has had the advantages of relatively low cost and ease of transportation and storage because of its liquid consistency. Further, petroleum is readily amenable to fractionation and conversion into a variety of valuable industrial products such as fuels, building products, chemical intermediates and the like. [0003] International developments have led to increase in the price of this crude oil. The consumption of petroleum has been increasing exponentially and concomitantly the readily available world petroleum supply has diminished. Governments and industrial concerns are dedicating increased attention to alternatives to petroleum as sources for fuels and chemical intermediates. [0004] In recent years, the world has seen many innovations in “green” technologies, including methods for making synthetic fuels for transportation and heat utilizing the enzymatic and bacterial decomposition of cellulose and starch material to ethanol or similar alkanol products. Vegetable oils of many varied plant sources have been converted to alkyl esters. While these processes are clean and environmental friendly and can provide an alternative source of synthetic fuel, the use of edible plants inevitably leads to the increase of price for food supply. Moreover, many of these plants require high energy costs during the planting, harvesting and processing phases. [0005] New programs are being developed for the provision of carbonaceous fuel products which complement and enhance conventional petroleum or coal-derived energy sources. Processes for liquefying coal or the gasification and then condensation of other carbon-containing materials have been proposed. However, these processes have not been deemed to be fully satisfactory for various cost or environmental reasons. There remains a pressing need for new technology that can deliver high quality fuels at economically and environmentally favorable levels, while maintaining atmospheric carbon neutrality. [0006] Accordingly, it is desirable to provide a system and process of producing liquid synthetic fuels that overcomes drawbacks of conventional systems and methods of producing synthetic fuel. [0007] Other objects and advantages of the present invention shall become apparent from the accompanying description and examples. SUMMARY OF THE INVENTION [0008] Generally speaking, in accordance with the invention, a system and method for producing synthetic fuels, especially those that are essentially chemically identical to conventional vehicle fuels, is provided in which a feedstock containing polymers from a wide variety of sources is re-formed into a more satisfactory fuel source for producing heat, electricity, powering vehicles and the like. The feedstock can comprise scrap rubber, plastic and/or organic matter or other materials that are not particularly well suited for use as fuels in their existing state. The system and method can involve breaking relatively long polymer hydrocarbon and/or carbohydrate polymer molecules into shorter chain hydrocarbon radicals and then polymerizing the short chain hydrocarbons and forming a fuel comprising hydrocarbons of selected length. Reactors in accordance with preferred embodiments of the invention do not involve adding oxygen to the system and can be considered anaerobic. Reactions in accordance with preferred embodiments of the invention involve much less water than many conventional methods and can be considered relatively anhydrous. [0009] Processes in accordance with preferred embodiments of the invention can involve physical reduction of the size of the various components; drying or wetting components to controlled water levels; liquefying reactions where components are broken down into shorter molecules; removal of oxygen atoms from carbohydrates and/or unsaturated bonds from hydrocarbon monomers; and recombination of short chain hydrocarbon monomers to desired molecular lengths to make synthetic fuels. [0010] Feedstocks in accordance with the invention can include a wide variety of sources of cellulose. These can include various biomass sources, including wood chips, sawdust, brush, hay, straw, switch grass, corn stalks, kudzu and other sources of cellulose material. The sources of cellulose can be permitted to dry or actively dried to a selected moisture content. They can also be blended to result in desired moisture content. If necessary, water can be added to overly dry feedstocks. These sources of cellulose material can be blended with other polymer feedstocks, different types of cellulose or used as a single uniform type of cellulose. [0011] The process can also involve the use of hydrocarbon polymers as a feed source. For example, waste plastic and rubber, such as used automobile tires can be used as a feedstock source. Mixtures of waste polymers with cellulose material are also acceptable for use as the feedstock. Tires can include all of the polymers now used to manufacture tires, such as butadienes and fillers, such as carbon, silica, aluminum and zinc acetate. [0012] In one preferred embodiment of the invention, a feedstock is reduced in size, into particles that are preferably less than about 1,000 microns, more preferably less than about 500 microns and most preferably less than about 300 microns. This can be done in multiple stages with the final reductions in size preferably done with the feedstock in a slurry. The liquid for the slurry is preferably recycled hydrocarbon fuel product from the synthetic fuel process. [0013] In one preferred embodiment of the invention, the polymer feedstock is combined with metals, such as Group VIII, IB, IIB, IIIA, IVA metals or in particular, platinum, iron, aluminum, zinc, copper and so forth. The metals can be provided as metal powders with substantially all, but at least 80% of which have a diameter of less than about 1000 microns, preferably less than about 500 microns, more preferably about 300 microns or less. [0014] The feedstock should be subjected to the controlled application of high temperature and pressure to liquefy the feedstock. High temperature and pressure can be used to help break feedstock polymer molecules into short chain radicals, preferably 3, 6 and 9 carbon hydrocarbon radicals in accordance with the invention. Most, if not all of the original oxygen should be removed. The short chain hydrocarbons are advantageously combined into hydrocarbons of selected carbon chain length. [0015] Processes in accordance with the invention are preferably conducted in substantially airtight conditions. It is preferred to put the feedstock into a non-aqueous slurry, with the liquid phase comprising mostly a hydrocarbon solvent. This phase should, however, while mostly comprising organic solvent, contain controlled amounts of water. The water can act as a source of hydrogen for aiding the reduction of molecular size. Water content is preferably about 25% to 5%, more preferably about 15% to 20% and most preferably about 16%-17%. [0016] A preferred source of the metal powder comes from ground up automobile tires. Conventional automobile tires include steel belts. These belts are commonly formed from iron wire that is coated with copper, which in turn, may be coated with zinc. In a preferred embodiment of the invention, essentially all, but at least 80% of the tires are ground into smaller pieces, preferably in multiple stages, to a size less than about 1,000 microns, preferably less than about 500 microns and most preferably about 300 microns or less. This results in the production of metal particles in the above sizes. The final size reductions advantageously take place in a slurry. [0017] In a preferred embodiment of the invention, the chemical reactions take place in an organic liquid phase. The hydrocarbon output of reactions in accordance with the invention can be recycled and use as the organic liquid, such as that combined with the initial feedstock, to ensure a substantially air free system and to assist in the downsizing of the feedstock solids. The recycled hydrocarbon output is at elevated temperature. Thus, the recycled stream aids in the initial elevation of feedstock temperature and reduces instances of charring. Recycling the output can also lead to branched chain hydrocarbons, which tend to increase octane or cetane ratings. [0018] The invention can be run with multiple reactors, with three as a preferred number. In a first reactor, the feedstock can be substantially, at least about 80%, liquefied. This can involve breaking intermolecular bonds and reducing the size of the feedstock molecules and polymers. The output temperature is between about 250° F. to 450° F. In a second reactor, additional bonds are advantageously broken and the feedstock material can be transformed into shorter chain radicals. Dehydration takes place to replace hydroxyl groups with hydrogen. The output temperature is about 500° F. Finally, those radicals can be formed into polymerized hydrocarbons of selected length in the third reactor, the output temperature of which is about 700° F. to about 850° F. [0019] Preferred reactors are in the form of horizontal tubes. The tubes are preferably formed of steel. The tubes are capable of containing liquid at over 700° F. and 500 psig. An internal screw is used to move the reactants in plug-flow, through the reactor at controlled speeds. Electrical heating elements on the reactor surfaces advantageously control the temperature of the reactors. Measuring the temperature and viscosity at the output can provide valuable feedback for controlling the heating elements and screw speed. [0020] It is the believed that the metal powders in the slurry react with the water in the feed stream to yield metal oxides and hydrogen. At the temperatures involved, ranging from over about 250° F. to 450° F. and above, the free hydrogen is believed to attack bonds in the feed material and thereby reduce the size of the feedstock molecules and promote the liquefication of the feed stream. Increasing the temperature, either in the same or in a separate reactor, further breaks down the feed material into small chain hydrocarbon radicals, advantageously 3, 6, and 9 carbons in length. Molecular size can be adjusted by controlling the temperature, reactor time and the amount of metal added. As the reaction proceeds, the metal powder can be substantially converted into sufficient oxide powder to act as a surface catalyst for the polymerization of the short chain hydrocarbon radicals into hydrocarbons of selected lengths. By adjusting reaction temperatures, at least 80% if not substantially all of the output can be gasoline, diesel fuel or aircraft fuel. Alternatively, the output can be refined (or otherwise purified or separated) to one of these fuels. In another embodiment of the invention, the output can be blended as more than least 5% or 10% with one of these fuels. The resulting product can be used as is or further refined or purified. It can also be advisable to employ a mechanism, such as a shockwave producer, to break up any relatively long chain hydrocarbons, such as waxes, that might be in the final product. [0021] The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, the system embodying features of construction, combinations and arrangement of parts which are adapted to effect such steps, and the product which possesses the characteristics, properties, and relation of constituents (components), all as exemplified in the detailed disclosure hereinafter set forth, and the scope of the invention will be indicated in the claims. DESCRIPTION OF THE DRAWINGS [0022] For a fuller understanding of the invention, reference is had to the following description, taken in connection with the accompanying drawings, in which: [0023] FIG. 1 is a schematic diagram of a system for producing synthetic fuels, in accordance with preferred embodiments of the invention; [0024] FIG. 2 is a schematic diagram of a size reduction section of the system of FIG. 1 ; [0025] FIG. 3 is a schematic diagram of a reaction section of the system of FIG. 1 ; [0026] FIG. 4 is a schematic diagram of a finishing section of the system of FIG. 1 ; [0027] FIG. 5 is a chemical drawing of the chemical breakdown of cellulose to aldotriose and/or aldohexose; and [0028] FIG. 6 is a chemical drawing of bond cleavage when butadiene containing tires are used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0029] FIG. 1 is a schematic view of a fuel production plant 10 in accordance with a preferred embodiment of the invention. Plant 10 comprises three general process sections: a size reduction section 200 , a reaction section 300 and a finishing section 400 , each shown in greater detail in FIGS. 2 , 3 and 4 , respectively. [0030] A preferred embodiment of the invention comprises a size reduction step having multiple stages to gradually reduce the size of the feedstock to the desired particle size. Referring to FIG. 2 , size reduction section 200 preferably comprises a first stage size reduction grinder 210 , a second stage size reduction grinder 220 , a third stage size reduction grinder 230 , a fourth stage size reduction safety grinder 240 and a slurry storage tank 250 . Acceptable grinders in accordance with preferred embodiments of the invention include the MultiShear and Arde Barinco brand grinders, from MultiShear Corporation of Graniteville, S.C. and Arde Barinco, Inc. of Norwood, N.J. [0031] A size reduction process begins when a truck or other vehicle delivers a variety of feedstock to plant 10 or when the materials are reduced in size off site. A feedstock 201 is placed on a first conveyor belt 205 , which carries the feedstock upon unloading to first stage size reduction grinder 210 . The output of first stage size reduction grinder 210 is placed on a second conveyor belt 215 , which carries once-reduced feedstock 211 to second stage size reduction grinder 220 . Similarly, the twice-reduced output 221 of second stage size reduction grinder 220 is placed on a third conveyor belt 225 and transported to third stage size reduction grinder 230 . Optionally, a storage tank, such as tank 235 , can be added to store once-reduced output 211 of first stage size reduction grinder 210 or twice-reduced output 221 of second stage size reduction grinder 220 . The three times reduced output 231 from third stage size reduction grinder 230 can be fed into fourth stage size reduction safety grinder 240 to insure substantially complete size reduction before a slurry output 241 is being stored in slurry storage tank 250 . Alternatively, output 231 can be stored in slurry storage tank 250 without being fed into fourth stage size reduction safety grinder 240 . [0032] Safety grinder 240 is optionally attached to slurry storage tank 250 to ensure uniformity particles of less than about 300 microns before the slurry enters reaction section 300 . [0033] A wide variety of synthetic polymer or cellulosic materials, including rubber, plastic, trees, bushes, brush, bark, sawdust, wood chips, hay, straw, switch grass field stubble and the like can be used as feedstock in accordance with the invention. However, certain materials require additional attention. For instance, bark can be used. However, because bark is high in ash and absorbs water readily, when using bark as feedstock, special attention needs to be paid to insure moisture content. Similarly, while pine saw dust can be used, it is recommended to limit the weight of pine saw dust used at less than 25% of the total feedstock weight. [0034] An important purpose of the size reduction process of section 200 is to gradually decrease the size of the feedstock to desirable sizes, preferably less than 300 microns. In one embodiment, the feedstock is first ground to ½ inch to 1 inch pieces in first stage size reduction grinder 210 , then to ⅛ inch to ⅜ inch size particles in second stage size reduction grinder 220 before entering third stage size reduction grinder 230 . Both first and second stage grinders 210 , 220 can be operated while the feedstock remains dry. In contrast, twice-reduced feedstock 221 is preferably combined with liquid to form a slurry form when it enters third stage grinder 230 and fourth stage safety grinder 240 . [0035] One important aspect of the invention is the moisture content of the feedstock. The moisture content of the feedstock can be controlled and adjusted before or after the feedstock enters the first or second stage size reduction grinders 210 , 220 . Feedstock of various moisture contents can be blended to achieve desirable average moisture content. If necessary, additional water can be sprayed or otherwise added into the system. Feedstock such as grasses, brush and wood chips can be permitted to dry before entering a process in accordance with the invention. Regardless of when the feedstock is dried, the average water content is preferably about 5-25%, more preferably about 15-20% and most preferably about 16-17%. [0036] In accordance with embodiments of the invention shown in FIG. 2 , third stage grinder 230 can be constructed and arranged to receive output 221 from second stage grinder 220 and, in addition, two additional feeds, including a liquid feed 270 and an initiator feed 280 . All the inputs to third stage grinder 230 should be mixed to form a slurry 231 of the above-identified water content. [0037] The input from liquid feed 270 advantageously comprises a non-aqueous hydrocarbon solvent 271 . In one preferred embodiment of the invention, the hydrocarbon solvent can be final output 421 of plant 10 . However, it is not necessary to use a recycle of the final product, and other hydrocarbon solvents can be used. Liquid feed 270 advantageously changes the viscosity of slurry 231 . The addition of hydrocarbon solvent 271 fills out the available space in reactors discussed below to ensure an oxygen free environment. It also makes size reduction easier. [0038] Initiator feed 280 introduces initiator/catalyst particles 281 to the input of third stage grinder 230 . Initiators can include elements of Group IB, IIB, IIIB, IVA, VB, VIIB, VIIB and Group VIII. Preferred initiators include Group IB, IIB and VIII metals. Preferred examples include platinum, iron, aluminum, aluminum silica, zinc and copper. The initiator can be provided as pure metal powders. Alternatively, polymeric materials, such as used tires, can be used to provide the metal initiator. The steel belts in tires contain iron which can be coated with copper and/or zinc. The synthetic rubber itself includes aluminum and silica materials. All the metals in the tire can serve as initiators. [0039] Initiator 281 is added to third stage grinder 230 . Regardless of the source of initiator 281 , it should have a particle size less than about 1000 microns, preferably less than 400 microns and more preferably about 300 microns or less. The smaller size can lead to a more optimal reaction rate because of the increased surface area. Initiator 281 should comprise more than 1% by weight of feedstock 201 , preferably more than 3% and most preferably 5% or more. [0040] Once feedstock 201 has undergone reduction, the slurry output 231 is fed into slurry storage tank 250 awaiting to be utilized in a chemical reaction process in reaction section 300 . [0041] Preferred embodiments of the invention comprise a reaction section 300 . Preferred processes can involve multiple reaction stages in multiple reactors (2, 3, 4 or more) to break down feedstock into short chain carbon radicals. Those radicals, preferably 3, 6 or 9 carbon chains, repolymerize to form a burnable synthetic fuel as a final output 421 of plant 10 . Such fuels can be prepared to be identical to conventional vehicle fuels refined from crude oil. [0042] Referring to FIG. 3 , reaction section 300 preferably comprises a first reactor 310 , a second reactor 320 and a third reactor 330 linked in series. Optional systems and methods can involve fewer or more reactors. Each reactor is preferably in the form of a horizontal tube. Preferred sizes are about 30 feet in length with a 2 foot inside diameter. Lengths and diameters of the reactors will vary depending on plant production capacity. However, a length to diameter ratio of 5:20 to 9:12, is acceptable with about 8:15 preferred. An internal screw (auger) is used to move the reactants in plug-flow, through the reactor at controlled speeds. The screw is of a variable speed so that time of plug flow through the reactor can be adjusted despite changes in flow volume and reaction rates. Electrical heating elements on the reactor surfaces advantageously control the temperature inside the reactors, allowing a gradual and uniform rise in temperature across the length of the reactor. Viscosity is generally proportional to molecular size. Thus, viscosity measurements are advantageously taken at the output of each reactor and analyzed, in order to adjust the heating elements and screw speed, to provide the optimal reaction time, temperature and pressure. Temperature can be measured at the input, output and at intermediate points. The viscosity measurements can be used to affect the heating elements and screw speeds to adjust residence times and reactor temperature as needed. The reactants can spend between 10 to 15 minutes, preferably a residence time of about 11-13 minutes in each reactor. [0043] Each reactor should be sealed off from the atmosphere and pressurized to ensure an anaerobic reaction with no added atmospheric oxygen. However, the pressure in each reactor need not be specifically controlled. Rather, pressure can be the result of the increase in temperature. Because of the lack of oxygen and the ability to control surface temperature of the reactors, there is relatively negligible char build-up after reactions to require extensive and frequent cleaning. In addition, the auger tends to provide a constant cleaning function. [0044] The goal of first reactor 310 and second reactor 320 is to liquefy and break down the feedstock to short chain monomers and monomer radicals. In one embodiment of the invention, to begin reaction, slurry output 241 is heated to about 250° F. at a pressure of about 100 psig and fed into first reactor 310 . The temperature increase can be achieved in various ways, preferably by recycling hot liquid or slurry streams from other parts of plant 10 . While in first reactor 310 , the temperature of the reactants continues to rise, resulting in a liquefied output 311 with the temperature about 450-500° F. at a pressure about 500 psig. During the residence time in first reactor 310 , various solids of slurry output 241 are liquefied by the increasing temperature and pressure. Speed and temperature should be adjusted so that no more than a trace of non-liquid material leaves first reactor 310 . [0045] Second reactor 320 is constructed and set up in a similar fashion as first reactor 310 . Liquefied output 311 from first reactor 310 enters second reactor 320 at about 450° F. and a pressure at about 500 psig. Generally, unlike the endothermic reaction in first reactor 310 , because the reaction in second reactor 320 is typically exothermic, no additional heat is needed except for the purpose of maintaining constant temperature and controlling reaction rate. [0046] It is believed that while in first reactor 310 , as the temperature increases from about 250° F. to 450° F., initiator 281 begins to react with available water in the feedstock to become oxidized by freeing hydrogen in water, creating free hydrogen. The free hydrogen, along with high temperature and pressure, liquefy solids in slurry output 241 by attacking the double bonds in hydrocarbon polymers and weak covalent bonds in cellulosic materials to make shorter chain molecules and promote the liquefication of the feed stream. When carbon-carbon bonds are cleaved, more hydrogen is produced. About 50-70% of the breakdown of plastic and cellulosic materials to short chain molecules can occur in first reactor 310 . Reforming: [0047] [0048] Once liquefied output 311 enters second reactor 320 , components are believed to continue to be broken down into short molecular links and further into intermediates through the process of dehydration on the surface of initiator 281 . The length of carbon chains can be altered and controlled by changing the temperature, reactor residence time and amounts of initiator 281 added. The free hydrogen created in reactor 310 is believed to react with dehydration intermediates to replace hydroxyl groups with hydrogen to form alkyl hydrocarbon radicals. These hydrocarbon radicals, preferably 3, 6, 9 carbon in length are believed to be weakly bonded to the surface of initiator 281 with unsaturated double bonds, readily available for polymerization while the oxygen from the hydroxyl groups continue to oxidize initiator 281 . Some oxygen reacts with free hydrogen to form water. Some traces of alcohols such as ethanol and methanol are also formed. Dehydration: [0049] Hydrogenation: [0050] [0051] The series of reformation, dehydration and hydrogenation are self-activating because of the derivative intermediates formed. As long as the surface area of initiator 281 plus the temperature and pressure are maintained in an optimum balance, the cycle of reformation, dehydration and hydrogenation continue to replicate. Furthermore, dehydration and hydrogenation are both self-sustaining steps because they are exothermic reactions. [0052] An output 321 of second reactor 320 , typically comprising short chain hydrocarbon radicals as well as substantially oxidized initiator 281 , exits second reactor 320 at about 650° F. and about 700 psig after a residence time of about 10-12 minutes in second reactor 320 . The exothermic effect of dehydrogenation provides heat to be recycled to first reactor 310 to raise the temperature of slurry output 241 from storage take 250. [0053] Head-to-tail polymerization of short chain carbon radicals is understood to begin automatically in third reactor 330 as temperature is raised up to between 700°-800° F. At this point in the reaction, initiator 281 should be converted to a sufficiently high oxidation state or fully oxidized to become inactive as to attack bonds to create free hydrogen as experienced in first reactor 310 . However, oxidized initiator particles continue to provide surface sites for the polymerization of the short chain hydrocarbon radicals into hydrocarbons of selected lengths. The length of the carbon chain of the polymers can be controlled by adjusting the residence time and temperature of third reactor 330 . For example, to produce gasoline, shorter molecules of 6-12 carbon atoms are best. For diesel duel, 12-21 carbon molecules and for aircraft fuel, 15-19 carbon molecules are preferred. [0054] It would be within the skill of the art to adjust time, temperature and pressure in the three reactors to adjust the output as desired. In any event, for diesel fuel, polymerization in the 700-800° F. range; gasoline, 800-850° F. and kerosene, 750-850° F. should be acceptable. The polymerization takes place at a very high temperature. Dropping the temperature lowers and stops the rate of polymerization. Some co-polymerization and branched polymerization can also occur. This can be enhanced by recycling the output. This leads to enhanced octane ratings. [0055] When the desired polymerization has occurred, the content of third reactor 330 , a polymerized output 331 , is fed into a flash column 420 shown more clearly as part of final section 400 in FIG. 4 . Optionally, before polymerized output 331 enters flash column 410 , a shock wave device 410 can be employed to use shock waves to break up long chain polymers into shorter chain polymers. Shock wave device 410 operates at high temperatures and sends sonic waves to break up long molecular chains. Acceptable shock wave devices are available from Seepex, Inc. of Enon, Ohio. In the present invention, shock wave device 410 helps break up any wax and other 25-30 carbon chain alkynes into shorter chain molecules. [0056] As the pressurized polymerized output 331 enters flash column 420 , the pressure is reduced from 800 psig to 200 psig while the temperature is lowered to about 400° F. The decrease in temperature ends polymerization. Within flash column 420 , lighter carbon chains, such as those with fewer than 12 carbons, are understood to vaporize, can be collected through a vent and can be condensed through a condenser 430 as a fuel source such as gasoline. In the production of diesel fuel, 6 to 8% of polymerized output 331 is understood to vaporize in flash column 420 . Traces of carbon dioxide and carbon monoxide are also vented off at this time. They can be collected or processed, if it is desired, to reduce greenhouse emissions. Carbon chains with more than 12 carbons tend to stay in liquid phase and can be collected as a final output fuel 421 . Final output fuel 421 is advantageously recycled as input to liquid feed 270 to serve as the required non-aqueous hydrocarbon solvent. [0057] Typically, the weight of final output fuel 421 recycled and the weight of solid feedstock 201 input into size reduction section 200 of plant 10 should have about a 1 to 1 to a 1 to 2 ratio. Recycled final output fuel 421 acts a as heat source and provides initiators 281 to the feedstock stream. [0058] In a preferred embodiment, a ferrous metal separator 430 and a non-ferrous metal separator 440 are utilized to remove and recycle initiators 281 . Ferrous metal separator 430 can be assembled as a magnetic system that captures any iron or iron oxides in final output 421 . The collected iron particles can be reduced back to their metallic form to be reused in the invention again, or sold as scrap. Non-ferrous metal separator 440 is a pressure filter type separator. Once separated, these non-ferrous metal particles can be washed and sold to the fertilizer industry. [0059] Preferred embodiments of the invention will be illustrated with reference to the following examples, which are presented by way of illustration only and should not be construed as limiting. [0000] Example I Feedstock 75 g (30% wood, 30% hay, 15% switch grass, 25% styrene/butadiene polymeric plastic) Feedstock particle size <300 microns Moisture content 15% Initiator 25 g of iron (Fe) Initiator particle size <300 microns Solvent Mixture of organic liquids (alkanes of carbon number C 5 to C 21 ) Polymerization temperature 700-800° F. Polymerization duration 3-20 minutes Product 95% C 3 to C 21 molecules, 5% carbon number greater than 21 Example II Feedstock 100 g of pure wood cellulose Feedstock particle size 500 microns or less Moisture content 20% Imitator 10 g of copper (Cu) and 10 g of zinc (Zn) Initiator particle size <200 microns Solvent 100 g of diesel fuel Polymerization temperature 600° F. Polymerization duration 10 minutes Product 93% C 6 to C 12 alkanes and alkanols, 7% C 12 to C 21 alkanes and alkanols Example III Feedstock 100 g of hay Feedstock particle size <100 microns Moisture content 7% Imitator 5 g of platinum (Pt) Initiator particle size <100 microns Solvent 100 g of combined liquid products of Example I and Example II Polymerization temperature 850° F. Polymerization duration 15 minutes Product 94% C 6 to C 12 alkanes and alkanols, 6% C 12 to C 18 alkanes and alkanols [0060] The above examples show the variety of feedstocks that can be used in the system to produce different synthetic fuels in accordance with the invention. The type of synthetic fuel produced can be controlled by the type of initiator used as well as reaction conditions such as those within third reactor 330 . It is understood that in first and second reactors 310 , 320 , the feedstock is substantially liquefied by breaking intermolecular bonds using increased temperature and the reaction between the water and metal catalyst initiators. Feedstock is broken into short chain hydrocarbon radicals, ready to combine with others and polymerize. In third reactor 330 , the radicals automatically polymerize as the temperature and pressure are increased to optimize the reaction rate. At this point, initiators that played a significant role in creating hydrogen that attacks and breaks intermolecular bonds have transformed from highly active chemical initiators to highly oxidized and therefore active surface catalysts that provide surface sites for polymerization. The initiators serve different purposes in the reformation, dehydration, rehydrogenation and polymerization reactions in the various reactors as their oxidation state alters with the reaction. [0061] Below is a summary of product that can be produced using a blend of tire chips, wood chips and straws after running the entire system for 24 hours. Runs 1 to 7 use iron and initiator/catalysts from tires (copper, zinc, silica, aluminum) to initiate and further reactions. Instead of using tires as a source of initiators, runs 8, 9 and 10 use pure metal powder comprising 90% iron and 10% copper. Runs 11 to 13, also use metal powder at the ratio of 90% iron, 5% silica and 5% aluminum. The polymerization times are listed, as well as temperature and pressure during polymerization. [0000] Runs 1 2 3 4 5 6 7 8 9 10 11 12 13 Polymerization time 12 12 12 12 12 8 13 8 10 12 6 8 10 (min) Polymerization 500 600 700 750 800 800 600 500 750 850 500 700 850 temperature (° F.) Polymerization 20 25 30 40 50 50 30 40 45 50 30 40 50 pressure (atm) [0000] Product Analysis % 1 2 3 4 5 6 7 8 9 10 11 12 13 C1 — <.5 1 1 2 — — — — 1 — Trace 4 C2 — <.5 3 4 4 — — — — 1 — Trace 4 C3 — — 3 3 4 1 — — — 2 — 4 3 C4 2 3 3 3 3 3 — <1 1 2 — 4 4 C5 — <1 <1 1 3 1 3 <1 1 9 2 3 6 C6 2 3 5 5 8 — — 1 2 20 2 3 11 C8 2 2 2 26 20 2 9 1 2 23 1 13 26 C10 4 6 18 25 21 — — 3 1 31 1 11 23 C12 39 61 52 20 33 35 27 13 14 6 24 19 13 C14 10 17 9 6 — 5 11 21 21 2 12 17 3 C16 13 1 2 2 1 17 10 24 21 1 12 18 1 C18 18 1 — 1 1 19 26 14 14 1 32 9 <1 C20 5 <1 1 1 — 9 21 10 14 — 10 4 <1 C22 4 3 — 1 — 9 1 10 8 — 3 1 — C24 1 — — 1 — 4 — 1 1 1 1 4 — [0062] As discussed herein, a system and method are provided for converting cellulosic and plastic materials into synthetic form of gasoline, diesel, kerosene and home heating fuel. This can be achieved by using non-food related cellulosic and plastic material to generate transportation fuels. Polymeric raw material is depolymerized to a low molecular weight intermediate and then re-polymerized to a controlled molecular weight, which is similar to the molecular structures of gasoline or diesel. [0063] The invention involves a proprietary process that can convert tires, plastics and biomass materials into synthetic fuels by breaking down cellulose and hemicellulose into short chain monomer molecules and recombining these monomers into synthetic gasoline, diesel fuel and jet fuel, among other products. The process combines pressure, heat and chemical catalysts. Specifically, the process combines the following general steps: (i) size reduction process that reduces feedstock materials to a low-micron level particle; (ii) liquefication reactor system which reduces the feedstock to short chain monomers; (iii) second stage processing system which recombines the monomers into synthetic gasoline (based on a 6-12 carbon chain molecule), diesel fuel (based on a 12-21 carbon chain molecule), or jet fuel (based on a 12-18 carbon chain molecule); and (iv) transfer and storage tanks for final products. Processes and systems in accordance with the invention can be used to produce one gallon of synthetic fuel from about 12 to 15 pounds of dry cellulose or plastic polymer. [0064] The process may be highly environmentally friendly. The process can be anaerobic and anhydrous (non-aqueous carrier liquid) which crates negligible amounts of carbon dioxide, a major byproduct of many competing processes, and the anhydrous process generates no wastewater. [0065] Fuels produced can have boiling points of 300° to 700° F., room temperature viscosities of 1-200 cp and can be suitable for a variety of uses. [0066] It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above method in the constructions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in the limiting sense. [0067] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween. [0068] Particularly it is to be understood that in said claims, ingredients or compounds recited in the singular are intended to include compatible mixtures of such ingredients wherever the sense permits.

A method for producing synthetic fuels is provided in which a feedstock containing polymers from a wide variety of sources is re-formed into a more satisfactory fuel source for producing heat, electricity, powering vehicles and the like. The feedstock can comprise scrap rubber, plastic and/or plant matter or other materials that are not particularly well suited for use as fuels in their existing state. The system can involve breaking long polymer molecules and/or carbohydrate molecules into shorter chain hydrocarbon radicals and then forming a fuel of hydrocarbons of selected length via what can be anaerobic and anhydrous reactions. The process can be environmentally friendly, producing no net greenhouse gases.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Application No. 60/481,536, titled “Portable Mister for Adjusting Ambient Temperature,” filed Oct. 21, 2003. FIELD OF INVENTION [0002] The present invention relates to a portable mister for adjusting the ambient temperature of an environment. BACKGROUND OF INVENTION [0003] Recent years have seen an increase in worldwide global temperatures. The result of the increasing global temperatures is that many places and people around the world experience uncomfortably hot seasonal temperatures especially during the summer months. Finding respite from the uncomfortable temperatures often means staying indoors and being blanketed by the cooling affects of air-conditioned air. For those forced to venture outdoors, “air conditioning” is not typically available. Some relief from the uncomfortable outside temperatures can be obtained by finding a shaded area not in direct sunlight. However, in some cases, even shaded areas do not provide sufficient cooling, especially if, for example, the temperature in the shade is 100° F. or higher. As such, much effort and resources are being focused on developing techniques for cooling persons who are forced to endure uncomfortably hot seasonal temperatures when outdoors. [0004] One such technique provides cooling by exploring the cooling properties of evaporating mist. Cooling occurs when mist droplets impinge upon a target and are evaporated into the surrounding air. Additional cooling takes place if the liquid itself is very cold relative to the surrounding air. Further, an object or observer may be additionally cooled if an air stream transports the liquid to an observer, and the air stream blows on the user so as to accelerate the evaporation process. [0005] The evaporative temperature change results from the process whereby droplets of the liquid extract heat energy from the air and use the energy to change the phase of the droplet from liquid to vapor. Thus the temperature change is achieved without the introduction of external refrigeration power, unlike cooling systems which extract heat from the refrigeration system component(s). In contrast, when a droplet evaporates, the latent heat energy expended in vaporization is drawn from the warm air, which accounts for the temperature drop. [0006] It is well known that with a given mixture of the air and water, the temperature achieved by evaporative cooling varies with the initial dryness of the ambient air. For example, given dry warm air at 95° F. (35° C.) and 20 percent relative humidity, atomizing ambient temperature water therein can drop the temperature of the mixture to as low as 66° F. (19° C.). Similarly, if the same ambient air at 95° F. has a relative humidity of 50 percent, then atomizing the water reduces the temperature of the mixture to about 80° F. (27° C.). As should be easily understood, atomizing a cooled water source into ambient air reduces the temperature of the resulting air-water mixture even further. Where tap water from the domestic supply is used as a water source, the tap water will be relatively cool after flowing for a time. As such, many inventions, which use atomized water as a cooling source, make use of ordinary tap water as a cooling agent. The prior art systems, however, contain various deficiencies, in that the systems are often too inconvenient or not fully portable, as described below. [0007] With the above in mind, many prior art systems incorporate a fine mist or spray as the primary cooling agent. For example, one conventional method for providing a mist or spray for cooling is disclosed in U.S. Pat. No. 6,398,132, issued Jun. 4, 2002, to Junkel. The Junkel patent generally discloses a portable spray misting device, which is fully handheld when operated. The device includes an internally hollowed body capable of holding a volume of fluid to be dispensed. The liquid is dispensed when a user manually pulls a trigger disposed alongside the hollowed body, which causes the liquid to be drawn toward a spray dispensing head for projecting the liquid as a mist into fan blades of a fan unit. The fan unit, in turn, dispenses the mist into the atmosphere, and onto a user, thereby cooling the user through mist evaporative principles. [0008] The invention of the Junkel patent is suitable for users who wish to achieve personal cooling, since it ordinarily may be used by only one user at a time using one hand. However, the Junkel invention is deficient in that users must operate the invention manually, typically leaving only one hand to perform everyday tasks. That is, since the Junkel invention requires the use of at least one user hand to operate, the user of the Junkel invention will be limited in the activities the user may perform while staying cool. Thus, an invention is needed which cools a user without user assistance or user manipulation, thereby freeing the user to perform various other activities. [0009] A typical invention, which cools a user without user assistance, is disclosed, for example, in U.S. Pat. No. 5,613,371, issued Mar. 25, 1997, to Nelson. The Nelson patent generally discloses a method and apparatus for misting vehicle occupants by providing a fine spray of water into the air inside and surrounding the vehicle. In accordance with Nelson, a pumping system forces water from a water reservoir on board the vehicle through mister nozzles. When attached to a vehicle, the Nelson invention cools the vehicle occupants while permitting the occupants to perform other activities. For example, where the Nelson invention is affixed to a golf cart, the occupants are cooled when being transported from golf stroke to golf stroke. [0010] Similar systems are disclosed for example, in U.S. Pat. No. 5,373,703, issued Dec. 20, 1994, [0011] to Pal, and U.S. Pat. No. 6,151,907, issued Nov. 28, 2000, to Hale. The aforementioned Nelson, Pal, and Hale systems are sufficient for cooling a vehicle occupant while the occupant is seated therein. However, the systems are not suitable for cooling the occupant when the occupant exits the vehicle, such as, for example, when the user must leave the vehicle to engage in an outside activity. For example, where a user installs the aforementioned system on a golf cart while golfing, the user must typically exit the vehicle to advance the ball down the course. As such, the Nelson, Pal and Hale systems are not suitable for cooling persons situated on the outside of a vehicle. [0012] One method for cooling a user outside a vehicle is disclosed in U.S. Pat. No. 5,330,104, issued Jul. 19, 1994, to Marcus. The Marcus patent generally discloses a self-contained portable mister which may mist an outdoors environment without assistance or intervention from a user. The portable misting apparatus includes a self-priming pump disposed inside a soundproof housing. The housing may include an operable lid and pivotable carrying handle. The invention further includes a rechargeable battery for powering the pump and a solar cell array disposed in the operable lid for recharging the battery. Liquid is supplied to the invention by drawing the liquid from a reservoir, such as a lake, stream, pond, swimming pool, ice chest, bucket, or the like, which is remote to the location of the invention housing. Alternatively, the invention may be adapted to provide the liquid from a pressure source of water. The pump further provides the liquid to a misting wand, which conveys the liquid to a plurality of misting nozzles. The housing of the Marcus invention further includes a cavity suitable for storage of a misting wand, when the invention is not in use. [0013] One problem with the Marcus invention, however, is that a solar cell battery powers the invention. It is well known that solar cell batteries need the advent of light (e.g., sunlight or direct sunlight) for recharging and for continuous operation. Thus, the Marcus invention would necessarily have limited use when used in shaded environments or environments where light is limited. As such, a need exists for a mister system which can be used irrespective of whether the system is placed in direct light, or in a shaded area. [0014] In addition, as a source for providing the cooling liquid, the Marcus invention uses a reservoir, such as a lake, stream, pond, swimming pool, ice chest, bucket, or the like, located remote to, and in communication with, the invention housing. To operate the Marcus invention, a user must provide the cooling liquid to the invention by, for example, locating the invention near a source of water (e.g., lake, stream, etc.) or to bringing the water to the invention (e.g., ice chest, bucket, etc.). As such, for example, the Marcus invention is limited in its portability, in that the user must determine the location of the liquid supply when deciding the location of invention usage, and the user may ordinarily have to supply the liquid supply in the form of a reservoir positioned externally to the invention housing. Therefore, a need exists for a more portable misting system, such as, a misting system which permits usage without requiring the user to supply an externally positioned cooling liquid source. [0015] U.S. Pat. No. 6,257,502, issued Jul. 10, 2001, to Hanish, et al., is a conventional example of a system which cools a user without user assistance, and which does not require the user to transport a cooling source to the system. In accordance with Hanish, an integrated multi-head misting device is provided which is removably attached to a household faucet or garden hose for receiving a cooling liquid. A misting fan is provided which includes a fan shroud including a grille and fan blades for permitting an air stream therethrough, where the air stream results from fan blade operation. A misting device is secured to the fan hub, and a plurality of misting heads are secured to the fan housing for directing a spray of mist across a fan grille. When the mist is projected into the air stream, the blowing action of the fan blades directs the mist away from the device and into the direction of an invention user. [0016] Power is supplied to the Hanish fan via a typical outlet, and the mist is provided via a pressurized source. The mist is injected across the fan grille via a misting manifold which directs the liquid through the misting heads. That is, no pump, or electricity of powering the pump, is required for providing the cooling liquid to the misting heads. More particularly, no solar powered batter is required as with, for example, the Marcus patent noted above. In that regard, the Hanish invention provides advantages over the Marcus invention in that the Hanish invention is not dependent on direct light for operation, but instead may be operated in a relatively shaded area. [0017] The cooling liquid is supplied to the Hanish invention by connecting the invention to a pressurized water supply, such as, a faucet or garden hose. Consequently, the Hanish invention still includes a similar disadvantage as Marcus, in that the invention must be operated near, or connected to, a cooling liquid source. As such, the Hanish invention, like the Marcus invention, does not provide a totally portable mister device. [0018] The Hanish invention includes the additional disadvantage in that the area of airflow created by the Hanish fan blades limits the area of dispersion of the cooling mist. Thus, where the fan blades blow air to a maximum area in front of the fan, the cooling liquid, which is transported by the air stream, will only travel over that area. Further, unless the Hanish invention is positioned above a user, such that the mist droplets may settle on the user, the user would necessarily need to be directly in the air stream flow in order to be properly cooled. Further still, when used with conventional household fans, the Hanish invention is typically suitable for cooling only a limited number of people at any one time. [0019] Another conventional misting device of similar operation as Hanish, is disclosed in U.S. Pat. No. 5,497,633, issued Mar. 12, 1996, to Hensley. The Hensley patent generally discloses an indoor/outdoor evaporative cooling unit which is inflatable via flexible walls. The flexible walls form a partially sealed enclosure for making the invention more portable when deflated. The cooling unit includes an inner wall and an outer wall of thin flexible material. A fan forces ambient air from an inlet through a flow divider, which directs some of the flow into the enclosure and the remainder of the flow into a chamber to exhaust through a chamber outlet. Spray nozzles are attached to the enclosure and aimed to spray a coolant, such as water, into the air exhausting through the outlet. [0020] In essence, the Hensley invention operates by drawing in a steady flow of ambient air through an intake, and exhausting the drawn air through a ring of nozzles spraying a coolant into the exhaust stream. The coolant (e.g., water) is supplied to the invention via a pressurized water source or by suitable flexible flow connections and a pump. In one embodiment, the combination of the chamber design and the positioning of the spray nozzles permits the Hensley mister to spray a mist at the chambers outlet, which is modestly sized for permitting service of multiple users on, for example, a walk-by basis. That is, one embodiment of the Hensley invention is similar to the Hanish invention in that it is only suitable for cooling only a limited number of people at any one time. In an alternate embodiment, however, the Hensley invention may be adapted for use in simultaneously cooling multiple persons by including multiple outlet pairs in the chamber and arranging the spray nozzles such that the nozzles are mounted in a middle of an outlet pair. This, in turn, permits the Hensley invention to create a billowing stream or cloud with a greater effective cooling range than a typical mist or stream. [0021] Although the Hensley invention provides for the production of a cooling cloud for cooling multiple users, the users must typically walk through or under the point of discharge of the coolant to be cooled down. In that regard, the Hensley invention, while providing a means for cooling multiple users, does not cool the users simultaneously. [0022] Accordingly, a need exists for a mister for cooling multiple users simultaneously, which is completely portable, does not require user assistance for operation, and which may be used in any light. SUMMARY OF INVENTION [0023] The present application discloses a portable mister for use in lowering ambient temperature of an environment indoors or outdoors. In one aspect, the present invention lowers ambient temperature by providing a mist of droplet size moisture to the atmosphere, wherein the droplets include a temperature less than or equal to ambient temperature of the atmosphere. The droplets size, rate of distribution and distribution area maybe adjusted as desired. The droplets may be provided to the atmosphere such that the droplets may travel on air currents and descend toward the earth's surface due to the effects of air currents and gravity. The evaporative properties of the droplets cool the surface on which the droplets come to rest. [0024] In another aspect of the invention, the present invention operates to cool surrounding articles, people and other similar objects on which the droplets settle by providing added moisture to the surface of those objects. The moisture may then cool the article by lowering the article's temperature relative to the droplet temperature and via the droplet's evaporative properties. Moisture may be provided to the atmosphere at any location and over any desired area for cooling multiple users by proper placement of the droplet delivery means. [0025] In yet another aspect of the invention, the droplet size or rate of dispersion may be controlled either manually or automatically, to provide more or less of the droplets to the atmosphere. For example, the size of the individual droplets and the rate of dispersion may be increased when it is desired to disperse a greater quantity of droplets in a shorter period of time. Where increasing droplet size but conserving the overall quantity of droplets dispersed is a concern, then the droplet size may be increased, but the rate of dispersion may be decreased. Similarly, where it is desired to, for example, increase the quantity of individual droplets, but to decrease the overall quantity of droplets dispersed, the size and dispersion rates of the droplets may be decreased. [0026] In yet another aspect of the present invention, a portable mister is provided which is more convenient to use than the prior art. First, the mister of the present invention is fully portable in that the invention does not require the user to separately transport a cooling agent (e.g., water) for misting. That is, the cooling agent may be entirely contained within the invention housing, thereby eliminating the need to supply a hose, reservoir, bucket, or the like, including the agent. Second, the mister includes an irrigation system for providing a spray of thin mist to the atmosphere, which may be comprised of flexible, foldable and easily storable tubing. As such, the tubing may be arranged as desired for cooling multiple users simultaneously. Lastly, the invention is easily transportable and storable due to the unique design of the invention housing. The invention may use wheels, rollers, handles, or the like, for facilitating easy transport of the system. [0027] In still another aspect of the invention, the portable mister may include means for introducing a perfume, cologne or other aromatic fragrance, or the like, into the air to enhance the misting experience. The fragrance may be included in or with the droplets as the droplets are dispersed into the atmosphere. Alternatively, the fragrance may be mixed with the cooling agent prior to dispersion. The fragrance may then be perceived by a casual observer who detects the fragrance as a pleasant addition to the environment. [0028] The present invention provides advantages over the prior art in that the present invention provides a mister system for cooling ambient air, which is fully portable, provides means for including a fragrance in a cooling mist, and which is substantially totally contained in one conveniently usable unit. Thus, when taken in combination, the overall portable mister system of the present invention is improved above the prior art. [0029] These features and other advantages of the system and method, as well as the structure and operation of various exemplary embodiments of the system and method, are described below. BRIEF DESCRIPTION OF THE DRAWINGS [0030] The accompanying drawings, wherein like numerals depict like elements, illustrate exemplary embodiments of the present invention, and together with the description, serve to explain the principles of the invention. In the drawings: [0031] FIG. 1 depicts an exemplary embodiment of the portable mister system in accordance with the present invention; [0032] FIG. 2 is an illustration of an exemplary misting vane/irrigation tubing and nozzles in accordance with exemplary embodiments of the present invention; [0033] FIG. 3 is an illustration of an exemplary housing arrangement in accordance with an exemplary embodiment of the present invention; [0034] FIG. 4 is an illustration of another exemplary embodiment of a portable mister system in accordance with an exemplary embodiment of the present invention; [0035] FIG. 5 is an illustration of an exemplary embodiment of a housing control panel and system processor in accordance with various embodiments of the present invention; [0036] FIG. 6 is a depiction of an exemplary method of operating an exemplary embodiment of a portable mister in accordance with the present invention; [0037] FIG. 7 is another exemplary embodiment of an exemplary portable mister housing in accordance with exemplary embodiments of the present invention; and [0038] FIG. 8 is an illustration of a cross-sectional top view of an exemplary portable mister housing in accordance with exemplary embodiments of the present invention. DETAILED DESCRIPTION [0039] The subject matter of the invention is particularly suited for use in lowering the ambient temperature of atmosphere and cooling one or more system users when positioned outdoors. As a result, the preferred exemplary embodiment of the present invention is described in that context. It should be recognized, however, that such description is not intended as a limitation on the use or applicability of the present invention, but is instead provided merely to enable a full and complete description of a preferred embodiment. That is, the invention is suitable for use indoors or outdoors. [0040] The present invention may be described herein in terms of functional block components, optional selections and various processing steps. Such functional blocks may be realized by any number of hardware and/or software components configured to perform to specified functions. For example, the present invention may employ various integrated circuit components (e.g., memory elements, processing elements, logic elements, look-up tables, and the like), which may carry out a variety of functions under the control of one or more microprocessors or other control devices. Similarly, the software elements of the present invention, where included, may be implemented with any programming or scripting language such as C, C++, Java, COBOL, assembler, PERL, or the like, with the various algorithms being implemented with any combination of data structures, objects, processes, routines or other programming elements. Further, it should be noted that the present invention may employ any number of conventional techniques for data transmission, signaling, data processing, network control, and the like. [0041] Where required, the system user may interact with the system via any input device such as, a keypad, keyboard, control panel, mouse, personal digital assistant, handheld computer (e.g., Palm Pilot®, Blueberry®), cellular phone and/or the like). Similarly, the invention could be used in conjunction with any type of personal computer, network computer, work station, minicomputer, mainframe, or the like, running any operating system such as any version of Windows, Windows NT, Windows 2000, Windows 98, Windows 95, MacOS, OS/2, BeOS, Linux, UNIX, Solaris, or the like, by interfacing the control panel, described below, with, for example, a conventional user computer. One skilled in the art will understand the modifications necessary to include the aforementioned systems in the present invention. In that regard, the modifications are considered within the scope of the present invention. [0042] It should be noted that the terms used in this description have their ordinary meaning unless otherwise specified. For example, the terms “safe” and “unsafe” may be used herein in accordance with their ordinary meanings relative to each other. Further, no element of the invention is considered “critical” or “essential” unless so indicated. [0043] FIG. 1 illustrates an exemplary embodiment of the portable mister system 100 of the present invention. In the exemplary embodiment shown, portable mister system 100 includes a housing 102 having a removable cap 112 . A liquid dispersion system including tubing 116 (e.g., irrigation tubing 116 ) and dispersion nozzles 118 may be connected to housing 102 via connector 117 for providing a passageway for a coolant to travel from the housing 102 to the tubing 116 . Housing 102 may further include a compartment 104 including a pump 106 in communication with a second compartment 107 (called “coolant tank 107 ,” herein for brevity) via a conduit 108 . System 100 may further include a power chord 110 for powering, for example, pump 106 . [0044] Housing 102 may be constructed of any material capable of being compartmentalized for holding a cooling liquid (e.g., water). In that regard, housing 102 may be preferably rigid and waterproof. In one exemplary embodiment, housing 102 may include a coolant tank 107 for holding the cooling liquid during operation. Tank 107 may be waterproof and may be constructed of any suitable material capable of holding a liquid. For example, tank 107 may be comprised of a soft, semi-rigid or rigid plastic, rubber, vinyl, synthetic polymer or the like. It should be noted that housing 102 is described both as including a second compartment 107 and a cooling liquid tank 107 . It should be understood that where the second compartment 107 comprises a cooling liquid tank 107 , the compartment and tank are discussed interchangeably. However, it is contemplated that the inventor may include a second compartment distinct from the cooling liquid tank. [0045] As shown in FIG. 8 , tank 107 may be partially surrounded by a cavity 802 in housing 102 . Cavity 802 provides a space between the housing 102 and the tank 107 for providing, for example, a thermal agent for regulating the temperature of the coolant. Exemplary thermal agents may include, for example, thermal insulation for regulating the temperature of the cooling liquid in tank 107 . Alternatively, the thermal agent may include a cooling agent for reducing the temperature of the cooling liquid, such as, for example, ice, may also be included in cavity 107 for lowering the temperature of the cooling agent. Further, in one exemplary embodiment, housing 102 includes a combination of an insulation and a cooling agent positioned in cavity 802 . [0046] Tank 107 may additionally include a removable cap 112 and a filter 114 disposed adjacent thereto. Filter 114 may be any suitable filter for removing particulates from the liquid as the liquid is added. Further, instead of placing the filter 114 as shown, filter 114 may be an in-line filter included in the irrigation tubing 116 . Alternatively, filter 114 may be included in tubing coupling 117 between the tank 107 and the tubing 116 . Cap 112 may be any means for providing access to the tank 107 for adding, for example, a cooling liquid. Preferably, cap 112 forms a substantially airtight seal with tank 107 . In one exemplary embodiment, cap 112 is a screw cap including a threading around its inner perimeter which mates with a threading on tank 107 for permitting the cap 112 to be twisted on and off. When twisted off, a system user is provided access to the inside of tank 107 . When the cap 112 is twisted on, a relatively airtight seal may be created between the cap 112 and tank 107 . [0047] Housing 102 may further include a first compartment 104 which includes pump 106 . Compartment 104 may be such that it is sealed from tank 107 to prevent any cross-generation of chemicals or liquids between the tank 107 and compartment 104 . The compartment 104 may include a noise insulation for dampening any noise generated by the system pump 106 . The compartment 104 may additionally include a door (not shown) or passageway for providing access to the inside of the compartment 104 . Preferably the door is of sufficient size to permit replacement or repair of, for example, pump 106 . Further, housing 102 may include a pair of wheels 120 and a handle 121 for aiding in transporting the system 100 . Compartment 104 may additionally include one or more openings or grommets, etc. (not shown), for passing an electrical cord 110 therethrough or for the insertion of a conduit (e.g., conduit 108 , connector 117 , tubing 116 ). [0048] Electric cord 104 may be used to provide power to the pump 106 . For example, cord 110 may be plugged into a standard 120V socket. Alternatively, pump 106 may be powered by dc current using a battery (not shown) which may be positioned in compartment 104 in proximity to pump 106 . In which case, compartment 104 may be suitably sealed against, for example, leakage of the liquid in tank 107 into the compartment, or leakage of the electrolytic battery chemicals into tank 107 . [0049] In one exemplary embodiment, pump 106 may be any pump for forcing air into tank 107 via conduit 108 . Preferably, the air pumped by pump 106 is ambient air, and most preferably, the temperature of the air is cool relative to the temperature of the cooling liquid in tank 107 . In that regard, pump 106 may be any air pump which is capable of pumping air into tank 107 , thereby increasing the volume of free space in tank 107 and forcing the liquid into irrigation tubing 116 . The air for pumping may be drawn from outside housing 102 via an opening of port 136 . A suitable pump for use with the invention includes any bladder or diaphragm pump having cylinders, as are commonly found in the art. For example, a B series pump produced by SENSODYNE®, 16333 Bay Vista Drive, Clearwater, Fla. 33760, may be suitable for use with this invention. [0050] Tank 107 may be placed in communication with irrigation tubing 116 via a tubing connector 117 . Connector 117 may be any suitable connector for connecting irrigation tubing to tank 107 , thereby providing an airtight or watertight passageway through which a cooling liquid may travel. As such, connector 117 is suitably positioned in one side of tank 107 . Preferably, the connector 117 is disposed in proximity to the bottom portion of the tank 107 to ensure that the liquid will be provided to the tubing 116 , when the liquid is at its lowest fill level inside tank 107 . Additionally, it is preferred that the connector 117 and the tank 107 form a leak-proof seal. [0051] Connector 117 may be further coupled to irrigation tubing 116 having nozzles 118 for dispensing a mist of cooling liquid. Tubing 116 may be constructed of any suitable material for conveying a fluid. In that regard, tubing 116 may be made of a rubber, plastic, or the like, and preferably, the tubing is UV resistant to permit the tubing to withstand the damaging effects of direct sunlight. The tubing 116 may be treated with, or include, materials or compounds for retarding floral or bacterial growth. Tubing 116 may also be flexible, and may include portions which are rigid. As such, tubing 116 may be arranged in any suitable manner for misting a desired area. Tubing 116 may be affixed to any structure capable of holding the tubing for positioning the nozzles 118 to spray or mist. The tubing 116 may be affixed using any conventional method for holding an article affixed substantially stationary to another article. For example, the tubing 116 may be affixed using tape, nails, screws, Velcro®, or the like. Preferably, during operation, tubing 116 is placed at a height sufficient for permitting the mist to drop onto a system 100 user. For example, the tubing may be placed on a patio overhang, hung from a tree, or the like. In one exemplary embodiment, tubing 116 may include a tubing support apparatus which may be segmented into multiple pieces, and which may be assembled in any desired shape. U.S. Pat. No. 5,337,960, issued Aug. 16, 1994, to Allen, discloses a suitable irrigation tubing arrangement which may be used with the present invention. As shown in FIG. 2 , the Allen patent discloses a lightweight, portable and collapsible support apparatus for pressurized water conveyance and overhead mist spraying nozzles 88 . [0052] In one exemplary embodiment, the nozzles 118 may be any conventional nozzles which may be used for atomizing a liquid. Nozzles 118 may be comprised of a rust resistant metal, such as, for example, copper, or the nozzles 118 may be treated with a rust resistant compound. The nozzles 118 may include an entrance opening for accepting a liquid at a first velocity and an exit opening for emitting or ejecting the liquid of a higher velocity. The nozzles 118 may be adjustable in spray volume, pattern, direction and/or droplet size. For example, the nozzles 118 may be pivotable, such that the spray of cooling liquid emanating therefrom may be directed as desired. Further, the nozzles 118 may be configured to provide multiple spray patterns. For example, a user may adjust the nozzles 118 opening to spray in the shape of a cloud wherein the cooling liquid is substantially completely atomized. Alternatively, the nozzles 118 may be adjusted such that less atomization takes place and the cooling liquid droplets are of a larger size providing for a heavier mist. Further, a user may adjust the nozzles 118 to emit the cooling liquid in a cloud, cone, stream or other shape. [0053] It should be noted that to achieve proper dispersion of the cooling liquid from nozzles 118 , an appropriate level of liquid pressure must be ordinarily maintained inside of irrigation tubing 116 . As such, alternate embodiments of the invention described herein may include a pressure regulator. A pressure regulator suitable for the invention may ensure that the liquid pressure is maintained relatively constant in tank 107 , tubing 116 , and/or at the nozzles 118 , so as to ensure proper dispersing of the liquid cooling agent. [0054] FIG. 1 depicts a suitable pressure regulator 111 in communication with the tubing 116 . As shown, the pressure regulator 111 may be an in-line pressure regulator configured to ensure that the liquid pressure in tubing 116 is maintained at a sufficient level to promote dispersion of the liquid from nozzles 118 . Preferably, the pressure is maintained at a sufficient level to promote dispersion of the liquid in the desired dispersion pattern. A suitable in-line pressure regulator, which may be used in exemplary embodiments of this invention, is disclosed in U.S. Pat. No. 5,035,260, issued Jul. 30, 1991, to Davey. [0055] Although, FIG. 1 depicts an in-line pressure regulator, the invention is not so limited. For example, other suitable pressure regulators capable of regulating the liquid pressure in the portable system 100 , thereby promoting dispersion of the liquid from the tubing 116 and/or nozzles 118 , may be used. For example, system 100 may include a pressure regulator configured to regulate the pressure at an outlet of a tank 107 containing a liquid, such as a liquid coolant. The regulator (not shown) may be disposed or fitted in the housing of the tank, wherein the regulator is not in contact with the liquid, but instead regulates the pressure in the tank by, for example, comparing the pressure inside the tank with ambient pressure and adjusting the pressure in the tank accordingly to a predetermined target pressure. Alternatively, the regulator (not shown) for regulating the output pressure of the tank may be positioned in the housing 102 and in-line with the tubing 116 . In one particular example, the regulator may be positioned in proximity to the connector 117 . The regulator thusly positioned may regulate the output pressure by measuring the pressure in the tank relative to the pressure in the tubing. Suitable exemplary pressure regulators, which may be used in accordance with the above, are disclosed in U.S. Pat. No. 6,186,168 B1, issued Feb. 13, 2001, to Shultz et al., and U.S. Pat. No. 5,595,209, issued Jan. 21, 1997, to Atkinson et al., for example. [0056] One key advantage of the present invention over the prior art is the ability of the system 100 user to include a fragrance in the misting cooling liquid. The fragrance may be included in the cooling liquid prior to providing the liquid to tank 107 . Alternatively, the fragrance may be included in the liquid after the liquid is filled into tank 107 . Further still, the fragrance may be added when the cooling liquid traverses through, or is emitted from, irrigation tubing 116 . By adding a fragrance to the cooling liquid, a user is able to include in the cooling mist a pleasant experience enhancing smell. For example, a user could add a rose or springtime fragrance which may be included in the mist, and which may be perceived by the casual observer. [0057] Referring now to FIG. 4 , an alternate exemplary embodiment of the system 100 is depicted including a fragrance container 122 which may be connected to pump 106 via a conduit 124 , and to cooling tank 107 , in waterproof fashion. Container 122 may be any suitable container for holding a liquid, such as, a fragrance. The fragrance may be any suitable fragrance which may be readily mixed in a liquid. Preferably the fragrance may be mixed with the cooling liquid in tank 107 such that no “clumping” exists. That is, the liquid and the fragrance are mixed such that they may not be easily physically separated. In that regard, the fragrance is preferably a liquid. In addition, container 122 may be in communication with tank 107 via conduit 126 , such that the fragrance held in container 122 may be added to the cooling liquid contained therein. As such, container 122 may include means for providing the fragrance to the tank 107 , such as, a conventional fluid ejector nozzle as are known in the art. The ejector nozzle may be included in the conduit 126 disposed inside tank 107 . The ejector nozzle may be included, for example, in a pneumatically operated sprayer, as are found in the art. [0058] In one exemplary embodiment, container 122 includes a pump (not shown) for facilitating the providing of the fragrance to the tank 107 . The fragrance container 122 pump may be any suitable pump for pumping a liquid. The container 122 pump may preferably include an inlet in communication with the fragrance, preferably via a hose. The container 122 pump also preferably includes an outlet which is in communication with the tank 107 for providing the fragrance therein. In one exemplary embodiment, the container 122 pump is electrical and may be powered via alternating or direct current (e.g., battery). Alternatively, the container 122 pump may be pneumatic. Where the container 122 pump is pneumatic, it may be powered by air provided by pump 106 . For example, attached to pump 106 may be a conduit 124 for diverting some of the air generated by pump 106 to the container pneumatic pump. The container 122 pump may be such that the air from pump 106 causes the container 122 pump to pump fragrance into the tank 107 . Preferably the fragrance is pumped in a liquid or solid (powder-like) form, and most preferable, the fragrance is pumped into the tank 107 in a liquid solid mixture or the like. [0059] In an alternative embodiment, the fragrance container 122 may not include a pump, but instead may include a pneumatic sprayer in communication with pump 106 via conduit 124 . Conduit 124 may divert a portion of the air generated to the pneumatic sprayer for spraying the fragrance into the tank 107 . Suitable sprayer/mixer arrangements which may be used with this invention to include a fragrance in the liquid coolant are disclosed for example in U.S. Pat. No. 6,156,159, issued Dec. 5, 2000, to Ekholm et al.; U.S. Pat. No. 6,103,128, issued Aug. 15, 2000, to Koso et al., U.S. Pat. No. 5,902,042, issued May 11, 1999, to Imaizumi et al.; U.S. Pat. No. 6,305,580 B1, issued Oct. 23, 2001, to Chen; U.S. Pat. No. 6,296,151,B1, issued Oct. 2, 2001, to Chen; U.S. Pat. No. 5,676,283, issued Oct. 14, 1997, to Wang; U.S. Pat. No. 6,598,803 B1, issued Jul. 29, 2003, to Haas et al.; and U.S. Pat. No. 6,216,966 B1, issued Apr. 17, 2001, to Prendergast et al. Those skilled in the art will recognize that various modifications may be made to the above noted patents without departing from the scope of the invention. [0060] With continued reference to FIG. 4 , housing 102 may include a mixer 130 for ensuring substantially complete mixing of the fragrance and cooling liquid combination when the fragrance is added. Mixer 130 may be any suitable mixer capable of mixing two liquids, a solid and a liquid or any similar configuration capable of mixing a fragrance promoting composition with cooling agent. Mixer 130 may be electric and may include its own motor (not shown). Alternatively, mixer 130 may be pneumatic, and may be powered by air provided by pump 106 via conduit 132 , in similar manner as was discussed with respect to the container 122 pump. Suitable mixers which may be used with the invention include for example, any mixer operable to blend, mix, or aerate a liquid such as a cooling liquid. [0061] FIG. 7 depicts another exemplary embodiment of the present invention wherein system 100 includes a pump 706 . Pump 706 pumps the cooling liquid from tank 107 , and provides the liquid to tubing 116 . In this exemplary embodiment, the pump 706 may be an in-line diaphragm pump of sufficient pumping capacity to ensure that the cooling liquid may mist from nozzles 118 . The pump 706 may be a high-pressure self-priming pump, such as, for example, those manufactured by SHURflo®. [0062] It should be noted, that where an in-line pump 706 is used as described above, it may not be necessary for the cap 112 and the tank 107 to form an airtight seal. That is, it may be required that the pump 706 experience minimal pressure inside tank 107 during operation to enable the pump 706 to efficiently draw the liquid from the tank 107 . More particularly, when the liquid is removed from tank 107 , the volume of the free space in the tank must also increase to ensure proper liquid removal. As such, the housing 102 , tank 107 and/or cap 112 may be provided with air holes or openings (e.g., apertures) (not shown) in the housing 102 , tank 107 , or cap 112 top surface to permit air to be drawn into the tank 107 as the cooling liquid level decreases. Alternatively, the invention may be operated with the cap 112 removed or loosened to permit air to be drawn into the tank as the level of the coolant decreases. Further still, pump 706 may be configured such that the needed air is provided by the pump 706 , as described below. [0063] As shown in FIGS. 3 and 7 , housing 102 may further include a second compartment 138 . Compartment 138 may be of sufficient size to store flexible irrigation tubing 116 . In addition, compartment 138 may be of sufficient size to store any tubing supports such as those which are depicted in FIG. 2 . [0064] System 100 may further include sensors 132 shown in FIG. 3 , for reporting the operational status of various elements of the invention. In that regard, sensors 132 may be any micro or macrosensors capable of translating a physical occurrence in an environment to a perceptive analog or digital signal. The sensors 132 may include, for example, pressure, temperature, or positional sensors, transducers, or the like. For example, a sensor 132 may be any suitable sensor (i.e., pressure sensor or temperature sensor) for sensing and reporting the level of the cooling liquid in tank 107 . A sensor (not shown), such as a pressure sensor, may also be included adjacent to the nozzles 118 for detecting the emission of the cooling liquid from the nozzles 118 . In addition, a position sensor (not shown) may be included adjacent to cap 112 for detecting whether the cap 112 is tightly affixed to tank 107 . [0065] The aforementioned sensors may be in communication with a processor 134 which may be in further communication with a control panel 130 , as best shown in FIG. 5 . Processor 134 may be any suitable processor capable of receiving a signal from a sensor and providing a responsive signal to a control panel 130 . For example, processor 134 may be any conventional processor or microprocessor configured to provide a “safe operation” or “unsafe operation” signal to the control panel 130 . In addition, processor 134 may be any conventional processor or microprocessor for providing an “enable signal” or a “disable signal” for operation of the various system components as described below. Conventional sensors, such as these, are known in the art, and will not be discussed herein for brevity. [0066] Control panel 130 includes means for activating/deactivating system 100 operation. For example, control panel 130 may include a power switch 506 for turning the system 100 off and on. The control panel 130 may further include visual indicators 504 for indicating the status of the sensed components. The visual indicators 504 may be, for example, lights or a LED display. The indicators 504 may flash intermittently or not at all. Additionally, the indicators 504 may change colors. For example, where the indicator flashes the color red, the indicator may inform the user that a particular condition exists which is not preferred. For example, the cooling liquid level may too low for safe operation of the invention. Alternatively, the visual indicator may flash green to indicate that safe operation of the invention is permitted. [0067] In addition to the visual indicators 504 , control panel 130 may include means for providing an audible notification of operational status. For example, the control panel 130 may include a speaker 508 for audibly indicating that a status of the invention has changed. On the other hand, the speaker 508 may notify a user that safe operation of the invention is permitted. The audible indications may be, for example, one or more tones perceptible by the human ear. [0068] It should be noted, that the present invention may include alternate means for informing a user of system status. For example, the visual and audible indications may be used simultaneously. Alternatively, the system 100 may include means for providing tactile indications of system operational status, which may or may not be used in conjunction with one or more of the visual and audible indications. For example, the tactile indications may be perceived as a mild or moderate vibration of the system housing 102 . In that regard, system 100 may include means for facilitating a shaking of a portion of system 100 housing when, for example, the system 100 is to be placed in an inoperable state. [0069] The processor 134 may additionally be connected to at least one of the elements of system 100 for controlling the operational status of these elements. For example, processor 134 may be connected or in communication with pump 106 , 706 , container 122 pump, and/or mixer 130 . The processor 134 may be configured to enable or disable those elements as required. Processor 134 may enable or disable the operation of an element by providing an appropriate signal to the element. [0070] Control panel 130 may additionally include switches, buttons, or the like, for use in notifying the user that an element is to be disabled by processor 134 . For example, one button may give indication that a signal is provided to the processor, which disables operation of the mixer 130 . The signal may be received from an appropriate sensor (e.g., motion, positional) and provided to the processor 134 , which may then provide a signal to the mixer 130 causing the mixer 130 to cease operation. In similar manner, control panel 130 , may include indicators for notifying a user that a signal is provided by processor 134 for disabling/enabling the operation of the pump 106 , 706 . [0071] FIG. 6 is an illustration of an exemplary method 600 of operating the portable mister system 100 in accordance with the invention. The method may begin with a user filling the tank 107 with a cooling agent, such as, for example, water (step 602 ). However, it should be noted that the present invention is not so limited. That is, although the invention is described with respect to a water misting agent, any liquid or aqueous cooling agent capable of misting may be employed. Typical liquid or aqueous cooling agents for use with the invention may include additives for facilitating cooling. Such cooling agents are well known, and as such, will not be discussed herein for brevity. [0072] The user may then arrange the irrigation tubing 116 including the nozzles 118 such that a mist emitted from the nozzles 118 will blanket a predetermined area (step 604 ). For example, where a user wishes to cool the environment surrounding a back yard patio, the user may place the irrigation tubing 116 on a patio awning or overhang to ensure that those persons positioned on or around the patio experience the evaporative cooling affects of the misting cooling agent. Once the irrigation tubing 116 is properly arranged, the user may then turn on the mister by, for example, activating a power button 506 , or the like (step 606 ). [0073] Where the invention includes sensors 132 , the sensors 132 may be arranged to provide indication of the status of certain components of the system 100 . The sensors 132 may be configured to ensure safe operation of the invention by reporting the status of, for example, the level of coolant, whether the nozzles 118 are functional, and/or whether the cap 112 is securely fastened, etc. As such, more or less sensors may be included in the invention as needed. In the exemplary embodiment shown, the system 100 may include a sensor for sensing the level of cooling liquid (e.g., cooling agent) included in the tank 107 (step 608 ). [0074] Where the cooling agent falls below a predetermined level inside tank 107 , the motor 106 may overheat thereby increasing the risk that a fire safety hazard would result. As such, the tank sensor 132 is configured to provide an “unsafe operation” signal to the processor 134 when the liquid falls below the predetermined level inside tank 107 . The processor 134 may receive the “unsafe operation” signal and disable the pump 106 preventing the pump 106 from initiating or continuing operation (step 610 ). The processor 134 may further provide an “unsafe operation” signal to the control panel 130 . The control panel 130 may then provide a visual or audible (or tactile) indication to the user thereby informing the user that an unsafe condition exists which prevents safe operation of the system 100 (step 612 ). The unsafe operation indication may be provided to the user in the form of warning lights 504 or an audible tone or message emitted from a speaker 508 . The user is then permitted to correct the unsafe condition and the system processor 134 re-checks the sensor to determine if the unsafe condition remains (e.g., step 608 ). The processor 134 may check and/or the sensor 132 may provide the status signal at some predetermined period or continuously. If the unsafe condition remains, then the pump 106 remains disabled. Further, where the system 100 includes more than one pump, such as, for example, a fragrance pump 122 , the processor 134 may disable one or all of the pumps as desired. For example, if the operation of only one pump may cause an unsafe operation condition, then that one pump may be disabled while the other pumps included in system 100 remain in operation. Alternatively, processor 134 may disable all pumps until the identified unsafe condition is corrected. [0075] In similar manner as with tank 107 , the system 100 may include sensors for detecting whether the nozzles 118 are operational or open (step 614 ). In this context, the nozzles 118 may be considered “operational” or in “safe operation” when one ore more of the nozzles is arranged, positioned and/or configured to permit a cooling liquid to be emitted therefrom (e.g., nozzles are “open”). In contrast, the nozzles 118 may be considered “nonoperational” or in “unsafe operation” where one or more of the nozzles 118 is arranged, positioned and/or configured to prohibit the free flow of a cooling liquid therefrom (e.g., nozzles are “closed”). [0076] For example, one suitable sensor may detect a pressure or temperature change at the nozzle 118 opening due to the dispensing of the cooling agent into the atmosphere. That is, since the pressure and/or temperature at the opening of the nozzle 118 changes as the cooling agent is emitted therethrough, such change may be reported to the processor 134 in the form of a “safe operation” or “unsafe operation” signal. Where the safe operation signal is received by the processor 134 , the system 100 may continue with additional safety checks. Alternatively, if no change in pressure or temperature is detected/sensed at the nozzles 118 opening, then the sensor may provide the processor 134 with an unsafe operation (e.g., nozzles 118 are closed) signal and the processor 134 may disable the pump 106 accordingly (step 610 ). The processor 134 may then provide a warning signal to the user (step 612 ) and perform additional checks to see if the unsafe condition has been corrected (e.g., nozzles 118 are open) (step 614 ). [0077] As noted with respect to one exemplary embodiment of the invention, the pump 706 may be an in-line self-priming pump which provides the coolant directly to the irrigation tubing 116 . In this case, it may be required that there be provided means for increasing the volume of free space in the tank 107 , once the cooling liquid is pumped out (e.g., removed) from the tank. As noted, this particular embodiment may require there to be air holes (not shown) included in the top surface of the housing 102 , tank 107 , cap 112 , or the like, for permitting ambient air to be drawn into the tank 107 during system 100 operation. [0078] On the other hand, when pump 106 is configured to operate to remove the cooling liquid by forcing air into tank 107 , thereby forcing the cooling liquid into tubing 116 , there ordinarily needs to be an airtight seal created in tank 107 . More particularly, there may ordinarily need to be an airtight seal created between cap 112 and tank 107 . The airtight seal, for example, permits the air pressure in the tank be controlled so that the pressure in the tubing 116 for proper dispersion of the liquid at nozzles 118 may be maintained. As such, the system 100 may include a sensor (e.g., positional sensor) for detecting whether the cap 112 is tightly secured to tank 107 so as to create the needed airtight seal (step 616 ). [0079] If the cap 112 is not tightly secured, a cap sensor may provide an “unsafe operation” (e.g., cap 112 is open) signal to the processor 134 . The processor 134 may then provide a disable signal to the pump 106 for disabling pump 106 operation (step 610 ) and may also provide an indication signal to the appropriate control panel 130 indicator for notifying a user that the cap 112 is not tightly affixed to tank 107 (step 612 ). The system 100 processor 134 may then check and re-check the signal received from the cap sensor to determine if the unsafe condition still exists (step 610 ). If so, then the processor 134 continues disabling pump 106 and the system 100 is not operational. [0080] In some instances, the invention may include a pressure regulator, as noted above. In certain exemplary embodiments, the pressure regulator may be used to enhance the safe operation features of the invention. For example, the pressure regulator may be in communication with the processor 134 , such that when the processor receives an unsafe operation signal, the processor 134 , may provide a “disable pressure regulator signal” to the pressure regulator for disabling regulator operation. In this instance, “disabling operation” of the regulator may mean prohibiting normal regulator function, by for example, operating the regulator such that pressure build up in the tank 107 , tubing 116 , or at the nozzles 118 , is not achieved. More particularly, the disabled pressure regulator may be operated such that minimal pressure exists in system 100 , and even more particularly, the pressure in system 100 is such that dispersion of the liquid from nozzles 118 is interrupted. [0081] It should be noted that the present checks for unsafe conditions could include checking the status of any component of system 100 . Preferably, the system sensors check to determine if any of the components may be operated in an unsafe manner. As such, system 100 may include sensors for checking any number of the system 100 components and the sensors may be in communication with the processor 134 and control panel 130 in similar manner as discussed above. [0082] Further, the processor 134 may be configured to check one or more sensor components simultaneously or in a predetermined order. The processor 134 may check the sensors one or more times during system operation. For example, the processor 134 may check the sensors when the operation of the system 100 is initiated, and may additionally check periodically throughout the operation of the system 100 , such that if an unsafe condition results, the operation of one or more of the system components or the entire system 100 may be disabled. In any event, where the processor 134 detects that an unsafe condition does not exist or has been corrected, the processor 134 may provide an enable signal to the pump(s) or other system element, permitting the system 100 to operate (step 616 ). [0083] Once the pump 106 is initiated and permitted to operate, the pump 106 pumps air into the tank 107 , thereby forcing the cooling liquid contained therein into irrigation tube 116 . For example, pump 106 may provide ambient air from outside the housing 102 (via port 136 ), to the tank 107 via conduit 108 . The air may fill the tank causing pressure to rise in the free space therein. As the air is provided, the tank 107 may become pressurized, and the cooling liquid may escape through the tubing 116 , thereby creating additional free space for the pumped in air. [0084] In an alternative embodiment, pump 706 may be an in-line self-priming pump, which pumps the cooling liquid from the tank 107 into the tubing 116 . The cooling liquid may be pumped directly from the tank 107 into the tube 116 . During pumping, air may be provided to the tank 107 passively. That is, as the liquid moves into the tubing 116 from the tank 107 , free space may be created in the tank by the escape of the cooling liquid into the tube 116 . Air holes may be provided in the tank 107 , housing 102 or cap 112 , for example, for permitting the air to enter the tank 107 , thereby allowing the liquid to be provided to the tubing 116 . Alternatively, air may be provided to the system 100 via operation of the pump 706 . For example, the pump 706 may be affixed with a first opening for receiving the cooling liquid, a second opening for providing the liquid to the tubing 116 , and a third opening for drawing in additional air. Such pumps are well known and will not be discussed herein for brevity. [0085] Upon entering the tubing 116 , the cooling liquid becomes pressurized in part, because the liquid is forced into tubing 116 having a relatively small cross-sectional area as compared to the area of the tank 107 . Additionally, the pumping action of the pump 106 , 706 causes the liquid to assume a certain velocity when traveling through the irrigation tubing 116 . Thus, the velocity of the liquid and the forcing/pumping action of the pump 106 , 706 causes the cooling liquid to be delivered to the nozzles 118 in a pressurized state. Once the nozzles 118 are opened, the pressurized liquid may be provided from the dispensing end of the nozzles 118 into the ambient air at a higher velocity than when the liquid entered the tubing 116 . The cooling liquid may be emitted from any one of the nozzle 118 openings in, for example, the shape of a spray, which may assume any desired shape or spray pattern. Preferably, the nozzles 118 emit the cooling liquid in the shape of a cloud, and most preferably, the liquid is emitted in the shape of a mist. [0086] Having been emitted into the atmosphere, the cooling agent may begin descending and may begin evaporation. The cooling agent may evaporate when emitted into the atmosphere or when it settles on a surface waiting below. As noted, the evaporative quality of the mist is such that the surface receiving the mist may be readily cooled. [0087] In summary, the present invention provides a portable mister which has advantages over the prior art in that the invention is more portable and more convenient to use. For example, the invention is substantially self-contained, in that the cooling liquid is included in a part of the system housing, thereby eliminating the need to provide a source of cooling liquid to the system during operation. The invention additionally may include a means for providing in the mist, an experience enhancing fragrance. Further, the invention provides advantages over the prior art in that means for determining safe operation of the invention are included therein. [0088] The preceding detailed description of exemplary embodiments of the invention makes reference to the accompanying drawings, which show the exemplary embodiments of the invention by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that logical and mechanical changes may be made without departing from the spirit and scope of the invention. For example, the steps recited in any of the method or process claims may be executed in any order and are not limited to the order presented. Additionally, the present invention may include any construction or arrangement of a control panel and sensors for sensing unsafe operating conditions of the system and reporting unsafe operation indications to the user. Further, the invention may include any conventional nozzles, irrigation tubing, couplings, connectors, processors, pneumatic, electrical or mechanical sprayers as are found in the art. Further still, the housing of the present invention may assume any shape, and may include any form of irrigation tubing storage, wheels or handles as desired. For example, the housing may be oval, square, polygonal, oblong, or the like, and the tubing may be stored on the outside of the system housing. The housing may include disposed therein, means for eliminating any standing cooling agent remaining in the cooling liquid tank thereby prohibiting the growth of bacteria therein. The means may, for example, be a removable plug positioned in a bottommost portion of the system housing or tank for draining any cooing liquid remaining in the cooling liquid tank when the system is not in use. Even further, the cooling liquid tank 107 may take any shape or construction suitable for holding a liquid, and may take the shape of the system housing. Yet further, the components included herein may be mechanical, electrical, pneumatic, or any combination of the above as is dictated by the environment the portable misting system uses. [0089] The invention in its broadest aspects is therefore not limited to the specification details, preferred embodiment, and illustrative examples shown and described. The above aspects and embodiments of the present invention are understood with reference to the attached claims, specification and drawings included herewith.

A portable mister for cooling ambient air is disclosed comprising a housing for entirely containing a cooling agent, an irrigation system connected to the housing for receiving the cooling agent from the housing and dispersing the cooling agent in ambient air, and a pump for facilitating the transfer of the cooling agent to the irrigation system. The mister is portable in that the cooling agent is entirely enclosed in a portable housing. That is, the mister user need not connect the mister to a continuous cooling agent source for operation. Additionally, the irrigation system is configured for placement to cool the ambient air of a broad area. The housing may include a system for including a fragrance in the cooling agent. The fragrance including system facilitates added a pleasant aroma to the dispersed cooling agent.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of “Controlling Access By Code”, U.S. application Ser. No. 14/459,785, filed Aug. 14, 2014, now U.S. Pat. No. 9,507,920, which claims priority to the following applications: “Software Code Signing System And Method,” U.S. application Ser. No. 13/754,162, filed Jan. 30, 2013, now U.S. Pat. No. 8,984,278; “Software Code Signing System And Method,” U.S. application Ser. No. 10/381,219, filed Mar. 20, 2003, now U.S. Pat. No. 8,489,868; “Code Signing System And Method,” U.S. Provisional Application No. 60/270,663, filed Feb. 20, 2001; “Code Signing System And Method,” U.S. Provisional Application No. 60/235,354, filed Sep. 26, 2000; “Code Signing System And Method,” U.S. Provisional Application No. 60/234,152, filed Sep. 21, 2000; and “Code Signing System and Method,” International (PCT) Application No. CA/01/01344 filed Sep. 20, 2001. The entire disclosures of each of the above-referenced applications are hereby incorporated by reference hereinto in their entirety. BACKGROUND [0002] 1. Field of the Invention [0003] This invention relates generally to the field of security protocols for software applications. More particularly, the invention provides a code signing system and method that is particularly well suited for Java™ applications for mobile communication devices, such as Personal Digital Assistants, cellular telephones, and wireless two-way communication devices (collectively referred to hereinafter as “mobile devices” or simply “devices”). [0004] 2. Description of the Related Art [0005] Security protocols involving software code signing schemes are known. Typically, such security protocols are used to ensure the reliability of software applications that are downloaded from the Internet. In a typical software code signing scheme, a digital signature is attached to a software application that identifies the software developer. Once the software is downloaded by a user, the user typically must use his or her judgment to determine whether or not the software application is reliable, based solely on his or her knowledge of the software developer's reputation. This type of code signing scheme does not ensure that a software application written by a third party for a mobile device will properly interact with the device's native applications and other resources. Because typical code signing protocols are not secure and rely solely on the judgment of the user, there is a serious risk that destructive, “Trojan horse” type software applications may be downloaded and installed onto a mobile device. [0006] There also remains a need for network operators to have a system and method to maintain control over which software applications are activated on mobile devices. [0007] There remains a further need in 2.5G and 3G networks where corporate clients or network operators would like to control the types of software on the devices issued to its employees. SUMMARY [0008] A code signing system and method is provided. The code signing system operates in conjunction with a software application having a digital signature and includes an application platform, an application programming interface (API), and a virtual machine. The API is configured to link the software application with the application platform. The virtual machine verifies the authenticity of the digital signature in order to control access to the API by the software application. [0009] A code signing system for operation in conjunction with a software application having a digital signature, according to another embodiment of the invention comprises an application platform, a plurality of APIs, each configured to link the software application with a resource on the application platform, and a virtual machine that verifies the authenticity of the digital signature in order to control access to the API by the software application, wherein the virtual machine verifies the authenticity of the digital signature in order to control access to the plurality of APIs by the software application. [0010] According to a further embodiment of the invention, a method of controlling access to sensitive application programming interfaces on a mobile device comprises the steps of loading a software application on the mobile device that requires access to a sensitive API, determining whether or not the software application includes a digital signature associated with the sensitive API, and if the software application does not include a digital signature associated with the sensitive API, then denying the software application access to the sensitive API. [0011] In another embodiment of the invention, a method of controlling access to an application programming interface (API) on a mobile device by a software application created by a software developer comprises the steps of receiving the software application from the software developer, reviewing the software application to determine if it may access the API, if the software application may access the API, then appending a digital signature to the software application, verifying the authenticity of a digital signature appended to a software application, and providing access to the API to software applications for which the appended digital signature is authentic. [0012] A method of restricting access to a sensitive API on a mobile device, according to a further embodiment of the invention, comprises the steps of registering one or more software developers that are trusted to design software applications which access the sensitive API, receiving a hash of a software application, determining if the software application was designed by one of the registered software developers, and if the software application was designed by one of the registered software developers, then generating a digital signature using the hash of the software application, wherein the digital signature may be appended to the software application, and the mobile device verifies the authenticity of the digital signature in order to control access to the sensitive API by the software application. [0013] In a still further embodiment, a method of restricting access to application programming interfaces on a mobile device comprises the steps of loading a software application on the mobile device that requires access to one or more API, determining whether or not the software application includes a digital signature associated with the mobile device, and if the software application does not include a digital signature associated with the mobile device, then denying the software application access to the one or more APIs. BRIEF DESCRIPTION OF THE DRAWINGS [0014] FIG. 1 is a diagram illustrating a code signing protocol according to one embodiment of the invention; [0015] FIG. 2 is a flow diagram of the code signing protocol described above with reference to FIG. 1 ; [0016] FIG. 3 is a block diagram of a code signing system on a mobile device; [0017] FIG. 3A is a block diagram of a code signing system on a plurality of mobile devices; [0018] FIG. 4 is a flow diagram illustrating the operation of the code signing system described above with reference to FIG. 3 and FIG. 3A ; [0019] FIG. 5 is a flow diagram illustrating the management of the code signing authorities described with reference to FIG. 3A ; and [0020] FIG. 6 is a block diagram of a mobile communication device in which a code signing system and method may be implemented. DETAILED DESCRIPTION [0021] Referring now to the drawing figures, FIG. 1 is a diagram illustrating a code signing protocol according to one embodiment of the invention. An application developer 12 creates a software application 14 (application Y) for a mobile device that requires access to one or more sensitive APIs on the mobile device. The software application Y 14 may, for example, be a Java application that operates on a Java virtual machine installed on the mobile device. An API enables the software application Y to interface with an application platform that may include, for example, resources such as the device hardware, operating system and core software and data models. In order to make function calls to or otherwise interact with such device resources, a software application Y must access one or more APIs. APIs can thereby effectively “bridge” a software application and associated device resources. In this description and the appended claims, references to API access should be interpreted to include access of an API in such a way as to allow a software application Y to interact with one or more corresponding device resources. Providing access to any API therefore allows a software application Y to interact with associated device resources, whereas denying access to an API prevents the software application Y from interacting with the associated resources. For example, a database API may communicate with a device file or data storage system, and access to the database API would provide for interaction between a software application Y and the file or data storage system. A user interface (UI) API would communicate with controllers and/or control software for such device components as a screen, a keyboard, and any other device components that provide output to a user or accept input from a user. In a mobile device, a radio API may also be provided as an interface to wireless communication resources such as a transmitter and receiver. Similarly, a cryptographic API may be provided to interact with a crypto module which implements crypto algorithms on a device. These are merely illustrative examples of APIs that may be provided on a device. A device may include any of these example APIs, or different APIs instead of or in addition to those described above. [0022] Preferably, any API may be classified as sensitive by a mobile device manufacturer, or possibly by an API author, a wireless network operator, a device owner or operator, or some other entity that may be affected by a virus or malicious code in a device software application. For instance, a mobile device manufacturer may classify as sensitive those APIs that interface with cryptographic routines, wireless communication functions, or proprietary data models such as address book or calendar entries. To protect against unauthorized access to these sensitive APIs, the application developer 12 is required to obtain one or more digital signatures from the mobile device manufacturer or other entity that classified any APIs as sensitive, or from a code signing authority 16 acting on behalf of the manufacturer or other entity with an interest in protecting access to sensitive device APIs, and append the signature(s) to the software application Y 14 . [0023] In one embodiment, a digital signature is obtained for each sensitive API or library that includes a sensitive API to which the software application requires access. In some cases, multiple signatures are desirable. This would allow a service provider, company or network operator to restrict some or all software applications loaded or updated onto a particular set of mobile devices. In this multiple-signature scenario, all APIs are restricted and locked until a “global” signature is verified for a software application. For example, a company may wish to prevent its employees from executing any software applications onto their devices without first obtaining permission from a corporate information technology (IT) or computer services department. All such corporate mobile devices may then be configured to require verification of at least a global signature before a software application can be executed. Access to sensitive device APIs and libraries, if any, could then be further restricted, dependent upon verification of respective corresponding digital signatures. [0024] The binary executable representation of software application Y 14 may be independent of the particular type of mobile device or model of a mobile device. Software application Y 14 may for example be in a write-once-run-anywhere binary format such as is the case with Java software applications. However, it may be desirable to have a digital signature for each mobile device type or model, or alternatively for each mobile device platform or manufacturer. Therefore, software application Y 14 may be submitted to several code signing authorities if software application Y 14 targets several mobile devices. [0025] Software application Y 14 is sent from the application developer 12 to the code signing authority 16 . In the embodiment shown in FIG. 1 , the code signing authority 16 reviews the software application Y 14 , although as described in further detail below, it is contemplated that the code signing authority 16 may also or instead consider the identity of the application developer 12 to determine whether or not the software application Y 14 should be signed. The code signing authority 16 is preferably one or more representatives from the mobile device manufacturer, the authors of any sensitive APIs, or possibly others that have knowledge of the operation of the sensitive APIs to which the software application needs access. [0026] If the code signing authority 16 determines that software application Y 14 may access the sensitive API and therefore should be signed, then a signature (not shown) for the software application Y 14 is generated by the code signing authority 16 and appended to the software application Y 14 . The signed software application Y 22 , comprising the software application Y 14 and the digital signature, is then returned to the application developer 12 . The digital signature is preferably a tag that is generated using a private signature key 18 maintained solely by the code signing authority 16 . For example, according to one signature scheme, a hash of the software application Y 14 may be generated, using a hashing algorithm such as the Secure Hash Algorithm SHA1, and then used with the private signature key 18 to create the digital signature. In some signature schemes, the private signature key is used to encrypt a hash of information to be signed, such as software application Y 14 , whereas in other schemes, the private key may be used in other ways to generate a signature from the information to be signed or a transformed version of the information. [0027] The signed software application Y 22 may then be sent to a mobile device 28 or downloaded by the mobile device 28 over a wireless network 24 . It should be understood, however, that a code signing protocol according to the present invention is not limited to software applications that are downloaded over a wireless network. For instance, in alternative embodiments, the signed software application Y 22 may be downloaded to a personal computer via a computer network and loaded to the mobile device through a serial link, or may be acquired from the application developer 12 in any other manner and loaded onto the mobile device. Once the signed software application Y 22 is loaded on the mobile device 28 , each digital signature is preferably verified with a public signature key 20 before the software application Y 14 is granted access to a sensitive API library. Although the signed software application Y 22 is loaded onto a device, it should be appreciated that the software application that may eventually be executed on the device is the software application Y 14 . As described above, the signed software application Y 22 includes the software application Y 14 and one or more appended digital signatures (not shown). When the signatures are verified, the software application Y 14 can be executed on the device and access any APIs for which corresponding signatures have been verified. [0028] The public signature key 20 corresponds to the private signature key 18 maintained by the code signing authority 16 , and is preferably installed on the mobile device along with the sensitive API. However, the public key 10 may instead be obtained from a public key repository (not shown), using the device 28 or possibly a personal computer system, and installed on the device 28 as needed. According to one embodiment of a signature scheme, the mobile device 28 calculates a hash of the software application Y 14 in the signed software application Y 22 , using the same hashing algorithm as the code signing authority 16 , and uses the digital signature and the public signature key 20 to recover the hash calculated by the signing authority 16 . The resultant locally calculated hash and the hash recovered from the digital signature are then compared, and if the hashes are the same, the signature is verified. The software application Y 14 can then be executed on the device 28 and access any sensitive APIs for which the corresponding signature(s) have been verified. As described above, the invention is in no way limited to this particular illustrative example signature scheme. Other signature schemes, including further public key signature schemes, may also be used in conjunction with the code signing methods and systems described herein. [0029] FIG. 2 is a flow diagram 30 of the code signing protocol described above with reference to FIG. 1 . The protocol begins at step 32 . At step 34 , a software developer writes the software application Y for a mobile device that requires access to a sensitive API or library that exposes a sensitive API (API library A). As discussed above, some or all APIs on a mobile device may be classified as sensitive, thus requiring verification of a digital signature for access by any software application such as software application Y. In step 36 , application Y is tested by the software developer, preferably using a device simulator in which the digital signature verification function has been disabled. In this manner, the software developer may debug the software application Y before the digital signature is acquired from the code signing authority. Once the software application Y has been written and debugged, it is forwarded to the code signing authority in step 38 . [0030] In steps 40 and 42 , the code signing authority reviews the software application Y to determine whether or not it should be given access to the sensitive API, and either accepts or rejects the software application. The code signing authority may apply a number of criteria to determine whether or not to grant the software application access to the sensitive API including, for example, the size of the software application, the device resources accessed by the API, the perceived utility of the software application, the interaction with other software applications, the inclusion of a virus or other destructive code, and whether or not the developer has a contractual obligation or other business arrangement with the mobile device manufacturer. Further details of managing code signing authorities and developers are described below in reference to FIG. 5 . [0031] If the code signing authority accepts the software application Y, then a digital signature, and preferably a signature identification, are appended to the software application Y in step 46 . As described above, the digital signature may be generated by using a hash of the software application Y and a private signature key 18 . The signature identification is described below with reference to FIGS. 3 and 4 . Once the digital signature and signature identification are appended to the software application Y to generate a signed software application, the signed software application Y is returned to the software developer in step 48 . The software developer may then license the signed software application Y to be loaded onto a mobile device (step 50 ). If the code signing authority rejects the software application Y, however, then a rejection notification is preferably sent to the software developer (step 44 ), and the software application Y will be unable to access any API(s) associated with the signature. [0032] In an alternative embodiment, the software developer may provide the code signing authority with only a hash of the software application Y, or provide the software application Y in some type of abridged format. If the software application Y is a Java application, then the device independent binary *.class files may be used in the hashing operation, although device dependent files such as *.cod files used by the assignee of the present application may instead be used in hashing or other digital signature operations when software applications are intended for operation on particular devices or device types. By providing only a hash or abridged version of the software application Y, the software developer may have the software application Y signed without revealing proprietary code to the code signing authority. The hash of the software application Y, along with the private signature key 18 , may then be used by the code signing authority to generate the digital signature. If an otherwise abridged version of the software application Y is sent to the code signing authority, then the abridged version may similarly be used to generate the digital signature, provided that the abridging scheme or algorithm, like a hashing algorithm, generates different outputs for different inputs. This ensures that every software application will have a different abridged version and thus a different signature that can only be verified when appended to the particular corresponding software application from which the abridged version was generated. Because this embodiment does not enable the code signing authority to thoroughly review the software application for viruses or other destructive code, however, a registration process between the software developer and the code signing authority may also be required. For instance, the code signing authority may agree in advance to provide a trusted software developer access to a limited set of sensitive APIs. [0033] In still another alternative embodiment, a software application Y may be submitted to more than one signing authority. Each signing authority may for example be responsible for signing software applications for particular sensitive APIs or APIs on a particular model of mobile device or set of mobile devices that supports the sensitive APIs required by a software application. A manufacturer, mobile communication network operator, service provider, or corporate client for example may thereby have signing authority over the use of sensitive APIs for their particular mobile device model(s), or the mobile devices operating on a particular network, subscribing to one or more particular services, or distributed to corporate employees. A signed software application may then include a software application and at least one appended digital signature appended from each of the signing authorities. Even though these signing authorities in this example would be generating a signature for the same software application, different signing and signature verification schemes may be associated with the different signing authorities. [0034] FIG. 3 is a block diagram of a code signing system 60 on a mobile device 62 . The system 60 includes a virtual machine 64 , a plurality of software applications 66 - 70 , a plurality of API libraries 72 - 78 , and an application platform 80 . The application platform 80 preferably includes all of the resources on the mobile device 62 that may be accessed by the software applications 66 - 70 . For instance, the application platform may include device hardware 82 , the mobile device's operating system 84 , or core software and data models 86 . Each API library 72 - 78 preferably includes a plurality of APIs that interface with a resource available in the application platform. For instance, one API library might include all of the APIs that interface with a calendar program and calendar entry data models. Another API library might include all of the APIs that interface with the transmission circuitry and functions of the mobile device 62 . Yet another API library might include all of the APIs capable of interfacing with lower-level services performed by the mobile device's operating system 84 . In addition, the plurality of API libraries 72 - 78 may include both libraries that expose a sensitive API 74 and 78 , such as an interface to a cryptographic function, and libraries 72 and 76 , that may be accessed without exposing sensitive APIs. Similarly, the plurality of software applications 66 - 70 may include both signed software applications 66 and 70 that require access to one or more sensitive APIs, and unsigned software applications such as 68 . The virtual machine 64 is preferably an object oriented run-time environment such as Sun Micro System's J2ME™ (Java 2 Platform, Micro Edition), which manages the execution of all of the software applications 66 - 70 operating on the mobile device 62 , and links the software applications 66 - 70 to the various API libraries 72 - 78 . [0035] Software application Y 70 is an example of a signed software application. Each signed software application preferably includes an actual software application such as software application Y comprising for example software code that can be executed on the application platform 80 , one or more signature identifications 94 and one or more corresponding digital signatures 96 . Preferably each digital signature 96 and associated signature identification 94 in a signed software application 66 or 70 corresponds to a sensitive API library 74 or 78 to which the software application X or software application Y requires access. The sensitive API library 74 or 78 may include one or more sensitive APIs. In an alternative embodiment, the signed software applications 66 and 70 may include a digital signature 96 for each sensitive API within an API library 74 or 78 . The signature identifications 94 may be unique integers or some other means of relating a digital signature 96 to a specific API library 74 or 78 , API, application platform 80 , or model of mobile device 62 . [0036] API library A 78 is an example of an API library that exposes a sensitive API. Each API library 74 and 78 including a sensitive API should preferably include a description string 88 , a public signature key 20 , and a signature identifier 92 . The signature identifier 92 preferably corresponds to a signature identification 94 in a signed software application 66 or 70 , and enables the virtual machine 64 to quickly match a digital signature 96 with an API library 74 or 78 . The public signature key 20 corresponds to the private signature key 18 maintained by the code signing authority, and is used to verify the authenticity of a digital signature 96 . The description string 88 may for example be a textual message that is displayed on the mobile device when a signed software application 66 or 70 is loaded, or alternatively when a software application X or Y attempts to access a sensitive API. [0037] Operationally, when a signed software application 68 - 70 , respectively including a software application X, Z, or Y, that requires access to a sensitive API library 74 or 78 is loaded onto a mobile device, the virtual machine 64 searches the signed software application for an appended digital signature 96 associated with the API library 74 or 78 . Preferably, the appropriate digital signature 96 is located by the virtual machine 64 by matching the signature identifier 92 in the API library 74 or 78 with a signature identification 94 on the signed software application. If the signed software application includes the appropriate digital signature 96 , then the virtual machine 64 verifies its authenticity using the public signature key 20 . Then, once the appropriate digital signature 96 has been located and verified, the description string 88 is preferably displayed on the mobile device before the software application X or Y is executed and accesses the sensitive API. For instance, the description string 88 may display a message stating that “Application Y is attempting to access API Library A,” and thereby provide the mobile device user with the final control to grant or deny access to the sensitive API. [0038] FIG. 3A is a block diagram of a code signing system 61 on a plurality of mobile devices 62 E, 62 F and 62 G. The system 61 includes a plurality of mobile devices each of which only three are illustrated, mobile devices 62 E, 62 F and 62 G. Also shown is a signed software application 70 , including a software application Y to which two digital signatures 96 E and 96 F with corresponding signature identifications 94 E and 94 F have been appended. In the example system 61 , each pair composed of a digital signature and identification, 94 E/ 96 E and 94 F/ 96 F, corresponds to a model of mobile device 62 , API library 78 , or associated platform 80 . If signature identifications 94 E and 94 F correspond to different models of mobile device 62 , then when a signed software application 70 which includes a software application Y that requires access to a sensitive API library 78 is loaded onto mobile device 62 E, the virtual machine 64 searches the signed software application 70 for a digital signature 96 E associated with the API library 78 by matching identifier 94 E with signature identifier 92 . Similarly, when a signed software application 70 including a software application Y that requires access to a sensitive API library 78 is loaded onto a mobile device 62 F, the virtual machine 64 in device 62 F searches the signed software application 70 for a digital signature 96 F associated with the API library 78 . However, when a software application Y in a signed software application 70 that requires access to a sensitive API library 78 is loaded onto a mobile device model for which the application developer has not obtained a digital signature, device 62 G in the example of FIG. 3A , the virtual machine 64 in the device 64 G does not find a digital signature appended to the software application Y and consequently, access to the API library 78 is denied on device 62 G. It should be appreciated from the foregoing description that a software application such as software application Y may have multiple device-specific, library-specific, or API-specific signatures or some combination of such signatures appended thereto. Similarly, different signature verification requirements may be configured for the different devices. For example, device 62 E may require verification of both a global signature, as well as additional signatures for any sensitive APIs to which a software application, requires access in order for the software application to be executed, whereas device 62 F may require verification of only a global signature and device 62 G may require verification of signatures only for its sensitive APIs. It should also be apparent that a communication system may include devices (not shown) on which a software application Y received as part of a signed software application such as 70 may execute without any signature verification. Although a signed software application has one or more signatures appended thereto, the software application Y might possibly be executed on some devices without first having any of its signature(s) verified. Signing of a software application preferably does not interfere with its execution on devices in which digital signature verification is not implemented. [0039] FIG. 4 is a flow diagram 100 illustrating the operation of the code signing system described above with reference to FIGS. 3 and 3A . In step 102 , a software application is loaded onto a mobile device. Once the software application is loaded, the device, preferably using a virtual machine, determines whether or not the software application requires access to any API libraries that expose a sensitive API (step 104 ). If not, then the software application is linked with all of its required API libraries and executed (step 118 ). If the software application does require access to a sensitive API, however, then the virtual machine verifies that the software application includes a valid digital signature associated with any sensitive APIs to which access is required, in steps 106 - 116 . [0040] In step 106 , the virtual machine retrieves the public signature key 20 and signature identifier 92 from the sensitive API library. The signature identifier 92 is then used by the virtual machine in step 108 to determine whether or not the software application has an appended digital signature 96 with a corresponding signature identification 94 . If not, then the software application has not been approved for access to the sensitive API by a code signing authority, and the software application is preferably prevented from being executed in step 116 . In alternative embodiments, a software application without a proper digital signature 96 may be purged from the mobile device, or may be denied access to the API library exposing the sensitive API but executed to the extent possible without access to the API library. It is also contemplated that a user may be prompted for an input when signature verification fails, thereby providing for user control of such subsequent operations as purging of the software application from the device. [0041] If a digital signature 96 corresponding to the sensitive API library is appended to the software application and located by the virtual machine, then the virtual machine uses the public key 20 to verify the authenticity of the digital signature 96 in step 110 . This step may be performed, for example, by using the signature verification scheme described above or other alternative signature schemes. If the digital signature 96 is not authentic, then the software application is preferably either not executed, purged, or restricted from accessing the sensitive API as described above with reference to step 116 . If the digital signature is authentic, however, then the description string 88 is preferably displayed in step 112 , warning the mobile device user that the software application requires access to a sensitive API, and possibly prompting the user for authorization to execute or load the software application (step 114 ). When more than one signature is to be verified for a software application, then the steps 104 - 110 are preferably repeated for each signature before the user is prompted in step 112 . If the mobile device user in step 114 authorizes the software application, then it may be executed and linked to the sensitive API library in step 118 . [0042] FIG. 5 is a flow diagram 200 illustrating the management of the code signing authorities described with reference to FIG. 3A . At step 210 , an application developer has developed a new software application which is intended to be executable one or more target device models or types. The target devices may include sets of devices from different manufacturers, sets of device models or types from the same manufacturer, or generally any sets of devices having particular signature and verification requirements. The term “target device” refers to any such set of devices having a common signature requirement. For example, a set of devices requiring verification of a device-specific global signature for execution of all software applications may comprise a target device, and devices that require both a global signature and further signatures for sensitive APIs may be part of more than one target device set. The software application may be written in a device independent manner by using at least one known API, supported on at least one target device with an API library. Preferably, the developed software application is intended to be executable on several target devices, each of which has its own at least one API library. [0043] At step 220 , a code signing authority for one target device receives a target-signing request from the developer. The target signing request includes the software application or a hash of the software application, a developer identifier, as well as at least one target device identifier which identifies the target device for which a signature is being requested. At step 230 , the signing authority consults a developer database 235 or other records to determine whether or not to trust developer 220 . This determination can be made according to several criteria discussed above, such as whether or not the developer has a contractual obligation or has entered into some other type of business arrangement with a device manufacturer, network operator, service provider, or device manufacturer. If the developer is trusted, then the method proceeds at step 240 . However, if the developer is not trusted, then the software application is rejected ( 250 ) and not signed by the signing authority. Assuming the developer was trusted, at step 240 the signing authority determines if it has the target private key corresponding to the submitted target identifier by consulting a private key store such as a target private key database 245 . If the target private key is found, then a digital signature for the software application is generated at step 260 and the digital signature or a signed software application including the digital signature appended to the software application is returned to the developer at step 280 . However, if the target private key is not found at step 240 , then the software application is rejected at step 270 and no digital signature is generated for the software application. [0044] Advantageously, if target signing authorities follow compatible embodiments of the method outlined in FIG. 5 , a network of target signing authorities may be established in order to expediently manage code signing authorities and a developer community code signing process providing signed software applications for multiple targets with low likelihood of destructive code. [0045] Should any destructive or otherwise problematic code be found in a software application or suspected because of behavior exhibited when a software application is executed on a device, then the registration or privileges of the corresponding application developer with any or all signing authorities may also be suspended or revoked, since the digital signature provides an audit trail through which the developer of a problematic software application may be identified. In such an event, devices may be informed of the revocation by being configured to periodically download signature revocation lists, for example. If software applications for which the corresponding digital signatures have been revoked are running on a device, the device may then halt execution of any such software application and possibly purge the software application from its local storage. If preferred, devices may also be configured to re-execute digital signature verifications, for instance periodically or when a new revocation list is downloaded. [0046] Although a digital signature generated by a signing authority is dependent upon authentication of the application developer and confirmation that the application developer has been properly registered, the digital signature is preferably generated from a hash or otherwise transformed version of the software application and is therefore application-specific. This contrasts with known code signing schemes, in which API access is granted to any software applications arriving from trusted application developers or authors. In the code signing systems and methods described herein, API access is granted on an application-by-application basis and thus can be more strictly controlled or regulated. [0047] FIG. 6 is a block diagram of a mobile communication device in which a code signing system and method may be implemented. The mobile communication device 610 is preferably a two-way communication device having at least voice and data communication capabilities. The device preferably has the capability to communicate with other computer systems on the Internet. Depending on the functionality provided by the device, the device may be referred to as a data messaging device, a two-way pager, a cellular telephone with data messaging capabilities, a wireless Internet appliance or a data communication device (with or without telephony capabilities). [0048] Where the device 610 is enabled for two-way communications, the device will incorporate a communication subsystem 611 , including a receiver 612 , a transmitter 614 , and associated components such as one or more, preferably embedded or internal, antenna elements 616 and 618 , local oscillators (LOs) 613 , and a processing module such as a digital signal processor (DSP) 620 . As will be apparent to those skilled in the field of communications, the particular design of the communication subsystem 611 will be dependent upon the communication network in which the device is intended to operate. For example, a device 610 destined for a North American market may include a communication subsystem 611 designed to operate within the Mobitex™ mobile communication system or DataTAC™ mobile communication system, whereas a device 610 intended for use in Europe may incorporate a General Packet Radio Service (GPRS) communication subsystem 611 . [0049] Network access requirements will also vary depending upon the type of network 919 . For example, in the Mobitex and DataTAC networks, mobile devices such as 610 are registered on the network using a unique identification number associated with each device. In GPRS networks however, network access is associated with a subscriber or user of a device 610 . A GPRS device therefore requires a subscriber identity module (not shown), commonly referred to as a SIM card, in order to operate on a GPRS network. Without a SIM card, a GPRS device will not be fully functional. Local or non-network communication functions (if any) may be operable, but the device 610 will be unable to carry out any functions involving communications over network 619 , other than any legally required operations such as “911” emergency calling. [0050] When required network registration or activation procedures have been completed, a device 610 may send and receive communication signals over the network 619 . Signals received by the antenna 616 through a communication network 619 are input to the receiver 612 , which may perform such common receiver functions as signal amplification, frequency down conversion, filtering, channel selection and the like, and in the example system shown in FIG. 6 , analog to digital conversion. Analog to digital conversion of a received signal allows more complex communication functions such as demodulation and decoding to be performed in the DSP 620 . In a similar manner, signals to be transmitted are processed, including modulation and encoding for example, by the DSP 620 and input to the transmitter 614 for digital to analog conversion, frequency up conversion, filtering, amplification and transmission over the communication network 619 via the antenna 618 . [0051] The DSP 620 not only processes communication signals, but also provides for receiver and transmitter control. For example, the gains applied to communication signals in the receiver 612 and transmitter 614 may be adaptively controlled through automatic gain control algorithms implemented in the DSP 620 . [0052] The device 610 preferably includes a microprocessor 638 which controls the overall operation of the device. Communication functions, including at least data and voice communications, are performed through the communication subsystem 611 . The microprocessor 638 also interacts with further device subsystems or resources such as the display 622 , flash memory 624 , random access memory (RAM) 626 , auxiliary input/output (I/O) subsystems 628 , serial port 630 , keyboard 632 , speaker 634 , microphone 636 , a short-range communications subsystem 640 and any other device subsystems generally designated as 642 . APIs, including sensitive APIs requiring verification of one or more corresponding digital signatures before access is granted, may be provided on the device 610 to interface between software applications and any of the resources shown in FIG. 6 . [0053] Some of the subsystems shown in FIG. 6 perform communication-related functions, whereas other subsystems may provide “resident” or on-device functions. Notably, some subsystems, such as keyboard 632 and display 622 for example, may be used for both communication-related functions, such as entering a text message for transmission over a communication network, and device-resident functions such as a calculator or task list. [0054] Operating system software used by the microprocessor 638 , and possibly APIs to be accessed by software applications, is preferably stored in a persistent store such as flash memory 624 , which may instead be a read only memory (ROM) or similar storage element (not shown). Those skilled in the art will appreciate that the operating system, specific device software applications, or parts thereof, may be temporarily loaded into a volatile store such as RAM 626 . It is contemplated that received and transmitted communication signals may also be stored to RAM 626 . [0055] The microprocessor 638 , in addition to its operating system functions, preferably enables execution of software applications on the device. A predetermined set of applications which control basic device operations, including at least data and voice communication applications for example, will normally be installed on the device 610 during manufacture. A preferred application that may be loaded onto the device may be a personal information manager (PIM) application having the ability to organize and manage data items relating to the device user such as, but not limited to e-mail, calendar events, voice mails, appointments, and task items. Naturally, one or more memory stores would be available on the device to facilitate storage of PIM data items on the device. Such PIM application would preferably have the ability to send and receive data items, via the wireless network. In a preferred embodiment, the PIM data items are seamlessly integrated, synchronized and updated, via the wireless network, with the device user's corresponding data items stored or associated with a host computer system thereby creating a mirrored host computer on the mobile device with respect to the data items at least. This would be especially advantageous in the case where the host computer system is the mobile device user's office computer system. Further applications, including signed software applications as described above, may also be loaded onto the device 610 through the network 619 , an auxiliary I/O subsystem 62 S, serial port 630 , short-range communications subsystem 640 or any other suitable subsystem 642 . The device microprocessor 638 may then verify any digital signatures, possibly including both “global” device signatures and API-specific signatures, appended to such a software application before the software application can be executed by the microprocessor 638 and/or access any associated sensitive APIs. Such flexibility in application installation increases the functionality of the device and may provide enhanced on-device functions, communication-related functions, or both. For example, secure communication applications may enable electronic commerce functions and other such financial transactions to be performed using the device 610 , through a crypto API and a crypto module which implements crypto algorithms on the device (not shown). [0056] In a data communication mode, a received signal such as a text message or web page download will be processed by the communication subsystem 611 and input to the microprocessor 638 , which will preferably further process the received signal for output to the display 622 , or alternatively to an auxiliary I/O device 628 . A user of device 610 may also compose data items such as email messages for example, using the keyboard 632 , which is preferably a complete alphanumeric keyboard or telephone-type keypad, in conjunction with the display 622 and possibly an auxiliary I/O device 628 . Such composed items may then be transmitted over a communication network through the communication subsystem 611 . [0057] For voice communications, overall operation of the device 610 is substantially similar, except that received signals would preferably be output to a speaker 634 and signals for transmission would be generated by a microphone 636 . Alternative voice or audio I/O subsystems such as a voice message recording subsystem may also be implemented on the device 610 . Although voice or audio signal output is preferably accomplished primarily through the speaker 634 , the display 622 may also be used to provide an indication of the identity of a calling party, the duration of a voice call, or other voice call related information for example. [0058] The serial port 630 in FIG. 6 would normally be implemented in a personal digital assistant (PDA)-type communication device for which synchronization with a user's desktop computer (not shown) may be desirable, but is an optional device component. Such a port 630 would enable a user to set preferences through an external device or software application and would extend the capabilities of the device by providing for information or software downloads to the device 610 other than through a wireless communication network. The alternate download path may for example be used to load an encryption key onto the device through a direct and thus reliable and trusted connection to thereby enable secure device communication. [0059] A short-range communications subsystem 640 is a further optional component which may provide for communication between the device 624 and different systems or devices, which need not necessarily be similar devices. For example, the subsystem 640 may include an infrared device and associated circuits and components or a Bluetooth™ communication module to provide for communication with similarly-enabled systems and devices. [0060] The embodiments described herein are examples of structures, systems or methods having elements corresponding to the elements of the invention recited in the claims. This written description may enable those skilled in the art to make and use embodiments having alternative elements that likewise correspond to the elements of the invention recited in the claims. The intended scope of the invention thus includes other structures, systems or methods that do not differ from the literal language of the claims, and further includes other structures, systems or methods with insubstantial differences from the literal language of the claims. [0061] For example, when a software application is rejected at step 250 in the method shown in FIG. 5 , the signing authority may request that the developer sign a contract or enter into a business relationship with a device manufacturer or other entity on whose behalf the signing authority acts. Similarly, if a software application is rejected at step 270 , authority to sign the software application may be delegated to a different signing authority. The signing of a software application following delegation of signing of the software application to the different authority can proceed substantially as shown in FIG. 5 , wherein the target signing authority that received the original request from the trusted developer at step 220 requests that the software application be signed by the different signing authority on behalf of the trusted developer from the target signing authority. Once a trust relationship has been established between code signing authorities, target private code signing keys could be shared between code signing authorities to improve performance of the method at step 240 , or a device may be configured to validate digital signatures from either of the trusted signing authorities. [0062] In addition, although described primarily in the context of software applications, code signing systems and methods according to the present invention may also be applied to other device-related components, including but in no way limited to, commands and associated command arguments, and libraries configured to interface with device resources. Such commands and libraries may be sent to mobile devices by device manufacturers, device owners, network operators, service providers, software application developers and the like. It would be desirable to control the execution of any command that may affect device operation, such as a command to change a device identification code or wireless communication network address for example, by requiring verification of one or more digital signatures before a command can be executed on a device, in accordance with the code signing systems and methods described and claimed herein.

A novel code signing system, computer readable media, and method are provided. The code signing method includes receiving a code signing request from a requestor in order to gain access to one or more specific application programming interfaces (APIs). A digital signature is provided to the requestor. The digital signature indicates authorization by a code signing authority for code of the requestor to access the one or more specific APIs. In one example, the digital signature is provided by the code signing authority or a delegate thereof. In another example, the code signing request may include one or more of the following: code, an application, a hash of an application, an abridged version of the application, a transformed version of an application, a command, a command argument, and a library.

BACKGROUND OF THE INVENTION The present invention relates to fluid pressure controllers and particularly controllers of the type which provide a regulated output signal when connected to a source of variable fluid pressure and which are responsive to a mechanical input to alter the desired value of the regulated output signal. Devices of this type are employed in accessory controls for internal combustion engines in automotive applications where it is desired to provide a regulated and selectively changeable fluid pressure vacuum signal responsive to movement of the engine throttle and also to provide for the completing and the breaking of an electrical circuit at a predetermined position of the mechanical input such as the vehicle throttle position. An example of such an application is a vacuum controller which provides a regulated vacuum signal, upon connection to the vacuum pump source and receives an input from the vehicle throttle to provide changes in the regulated vacuum output signal in accordance with the predetermined scheduled throttle position for actuating an exhaust gas recirculation control valve. The electrical circuit which is completed and broken at predetermined throttle position may be employed to actuate and de-actuate an electrically operated transmission shift control mechanism. It is known to provide a rotary cam for adjusting the bias force on a pressure force-balance type vacuum modulator valve for adjusting the level of a regulated vacuum output signal. An example of such a device is that shown and described in U.S. patent application Ser. No. 88,806 filed Oct. 29, 1979, in the names of R. J. Franz, V. DeVera and J. Dahlstrom and assigned to the assignee of the present application. The aforesaid Franz et al. application employs a rotating cap which engages an annular helical cam disposed therewithin for effecting axial movement of the cam to vary the preload on a tension spring connected to provide a variable bias on a pressure responsive modulator valve for providing a regulated vacuum output signal. Such devices as that described in the Franz et al. application are employed for providing a regulated vacuum signal from varying source, such as a vacuum pump source, for use in controlling devices such as transmissions and exhaust gas recirculation valves. Another known vacuum signal controller is that described in U.S. patent application Ser. No. 897,604 filed Apr. 18, 1978, now U.S. Pat. No. 4,245,789 issued Jan. 20, 1981 in the name of R. J. Franz and assigned to the assignee of the present invention. The Franz device utilizes a rotating cam to vary the preload on a temperature sensitive element operated vacuum modulator valve. SUMMARY OF THE INVENTION The present invention provides a fluid pressure signal controller responsive to a mechanical input to vary the level of a regulated fluid pressure signal upon connection of the controller to the source of variable fluid pressure. The controller also contains an electrical switching mechanism responsive to the mechanical input to provide making and breaking of an electrical circuit at predetermined positions of the mechanical input. The novel controller of the present invention finds particularly useful application in controlling exhaust gas recirculation (EGR) valve for an internal combustion engine and particularly diesel engines having the throttle connected to the fuel supply feed to the combustion chambers for controlling engine speed at any given engine load. The controller of the present invention employs a diaphragm actuated pressure-operated force-balance modulator valve responsive to a mechanical preload to provide a regulated fluid pressure output signal of a desired level, irrespective of normal variations in the fluid pressure supply. The present controller when employed in the aforementioned diesel engine application, is connected to the vacuum pump for the fluid pressure source, and has a rotary cam adapted for attachment to a rotatable shaft connected directly to the engine fuel injection throttle mechanism. The rotatable cam causes linear movement of a slidable cam follower which is connected to a preload spring attached to the modulator valve diaphragm wherein movement of the cam follower varies the preload on the modulator valve diaphragm. The preload on the modulator valve diaphragm serves to alter the level of the regulated fluid pressure signal provided at the output of the modulator valve. An electrical switch is mounted such that the switch actuator also follows the rotary cam and the rotary cam is operative to effect actuation and deactuation of the switch. The rotary cam, cam follower, electrical switch mechanism and modulator valve are mounted to a common body portion. The present invention thus provides a solution to the above-described problems with heretofore known rotary cam adjustable vacuum regulator valve assemblies by employing unique structural arrangement wherein the modulator valve is slidably mounted on the base or body. A threaded ring is provided, rotation of which adjusts the position of the modulator valve with respect to the body for adjusting the initial preload on the diaphragm bias spring thereby permitting ease of calibration of the controller. The present invention thus provides a novel controller for providing a regulated fluid pressure signal from a variable source of fluid pressure and an electrical switching function, wherein the level of the regulated fluid pressure signal and the point of actuation of the switching function are determined by the position of a rotatable cam provided on the controller. The controller employs a diaphragm actuated pressure operated force-balance modulator valve, the bias of which is varied in service from the rotary cam connected to a preload spring attached to the diaphragm. The modulator valve is slidably adjusted with respect to the cam for readily adjusting the calibration by rotation of a ring threadedly engaging the modulator valve for slidably adjusting the valve position with respect to the controller body. Movement of the valve position on the controller body effects a change in the length of the bias spring which in turn changes the calibration of the modulator valve output signal for any given position of the input cam. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view of the controller of the present invention with portions of the body and rotary cam broken away to illustrate the assembly of the cam follower; FIG. 2 is a right-hand end view of the controller of FIG. 1; FIG. 3 is a top view of the controller of FIG. 1; FIG. 4 is a bottom view of the controller of FIG. 1; FIG. 5 is an enlarged section view through the longitudinal center-line of the modulator valve of the controller of FIG. 1; FIG. 6 is a section view taken along section-indicating lines 6--6 of FIG. 5; FIG. 7 is a section view taken along section-indicating lines 7--7 of FIG. 4; FIG. 8 is a section view taken along section-indicating lines 8--8 of FIG. 1 and shows the cam surfaces of the rotary cam. FIG. 9 is a section view taken along section-indicating lines 9--9 of FIG. 8; FIG. 10 is an enlarged section view taken along section-indicating lines 10--10 of FIG. 5; FIG. 11 is a graph of vacuum signal level plotted as a function of the rotary cam position. DETAILED DESCRIPTION Referring now to FIGS. 1-4, the controller 10 of the prsent invention is shown as having a body or base 12 with a rotary cam indicated generally at 14 mounted thereon on the upper face thereof and a modulator valve assembly indicated generally at 16 slidably mounted at the right-hand end thereof with respect to FIG. 1. An electrical switching mechanism indicated generally at 18 is provided on the under surface of the body and has electrical leads 20, 22 provided thereon for attachment to a circuit to be switched. The body 12 has a bore 24 formed therein with an annular shoulder 26 formed in the bore. The upper surface of a flange 28 provided on rotary cam 14 is slidably registered against shoulder 26. Cam 14 is retained in bore 24 by a cover 30 retained on the body 12 by suitable fastening expedients as, for example locking tabs 31 (see FIG. 4) and a self-tapping screw 32. Cover 30 has a bore 34 provided therein and the cam 14 has a pilot 36 journaled in bore 34 for guiding and locating the cam flange 28 on the annular shoulder 26. Referring to FIGS. 1, 8 and 9, the undersurface 38 of the cam flange 28 is shown as having a recess 40 formed therein with a variable radius wall portion forming a cam surface 42. A cam follower 44 is slidably received in a recess 46 provided in the undersuface of body 12 and is slidably guided therein and retained by the upper surface 48 of cover 30. The left end of cam follower 44 in FIG. 1 has an upwardly extending portion with a cam following surface 50 formed thereon which registers against the cam surface 42 of the rotary cam. The right-hand end of cam follower 44 also has an upwardly extending portion 52 which has an aperture provided therein with one end 54 of a tension spring received in the aperture and retained therein by deformation of the end of the spring. Referring to FIGS. 1 and 3, a torsion spring 56 is received over the cylindrical surface 58 of cam 14, with one end 60 of spring 56 registered in a notch 62 provided in the body 12 and the other end 64 of spring 56 bent at right angles to the coil of the spring and received in an aperture 66 formed in the cylindrical surface 58 of the cam. Referring particularly to FIG. 3, the upper portion of cam 14 has a pair of arcuately shaped recesses 67 provided therein, the ends of which are adapted to receive diametrically thereacross a torsional driving member therein as, for example, a flat blade member (not shown). In operation, with such a torsional driving member (not shown) engaging the arcuate recesses 67, and upon rotation of cam 14, cam follower 44 is moved in a horizontal direction to vary the position of spring end 54. The body 12 has, at the right end thereof, with respect to FIG. 1, a threaded portion 68 for receiving adjustably thereon the modulator valve 16 as will be hereinafter described in greater detail. In the presently preferred practice of the invention, the rotary cam 58, body 12, cam follower 44, and cover 30 are made of plastic material suitable for service in a vehicle engine compartment environment. Referring now to FIGS. 1, 5 and 6, the modulator valve 16 will now be described in greater detail as having a body 70 having provided thereon a vacuum source nipple 72 having therein a vacuum source port 74 and spaced therefrom a signal output nipple 76 having therein a signal port 78. The nipples 72 and 76 are adapted to have received over the ends thereof a suitable hose for connection to, respectively, a source of vacuum and a vacuum operated device to be controlled. Referring particularly to FIG. 5, the upper portion of body 70 has a cylindrical cavity 80 formed therein, which cavity has received and retained therein a diaphragm vent-valve subassembly indicated generally at 82 received and retained therein. The vent valve subassembly 82 includes a vent seat member 84 having the lower end 55 of the tension spring received therein through a transverse aperture. The vent seat member 84 is thus biased in an upward direction with respect to FIG. 5 by the end 55 of the spring. The vent valve subassembly 82 includes a movable valve member 86 having at its upper end a vent valve seating surface 86a and at its lower end a vacuum valve surface 86b. Valve body 70 has a signal chamber 88 formed therein below cavity 80 which chamber 88 has a central passage 90 provided therein communicating with vacuum supply ports 74. Passage 90 has at the upper end thereof a vacuum valve seating surface 92 against which valve surface 86b is moved to provide a valving action to control fluid flow between chamber 88 and supply port 74. Referring to FIG. 6 passage 94 is provided in valve body 70 which communicates signal chamber 88 with signal output port 76. The diaphragm vent-valve subassembly 82 includes a resilient annular diaphragm 96, preferably formed of a suitable elastomeric material, having its outer periphery sealed therearound against body 70, with its inner periphery sealed about vent seat member 84 to complete the upper wall of signal chamber 88. In the presently preferred practice, the body 70 is molded of a plastic material suitable for vehicle engine compartment service. In operation, diaphragm 96, responsive to the difference in pressure in cavity 80 thereabove, and signal chamber 88 therebelow, causes vent seat member 84 to move vertically to seek a force balance equilibrium as against the upward tension force of spring end 54a. The movement of vent seat member 84 causes seating and unseating of valve surfaces 86a and 86b which in turn alternately prevents and blocks fluid flow between chamber 88 and the vacuum port 74 to maintain a regulated pressure in chamber 88 and thus a regulated signal to port 78. The details of the operation of modulator valve 16 are well known in the art and a more detailed description thereof may be found in the published literature as, for example, U.S. Pat. Nos. 3,779,195 and 3,831,841 and accordingly, further description herein has been omitted for the sake of brevity. Referring to FIGS. 1, 4 and 5, the upper portion of body 70 (leftward portion in FIGS. 1 and 4) has an annular flange 98 extending outwardly therefrom with the lower face thereon 98a as shown in FIG. 5 (rightward face in FIGS. 1 and 4) extending preferably generally right angles to the outer periphery of the upper portion of body 70. An annular adjustment ring 100 is provided having the inner periphery thereof threadedly received over the threads 68 provided on the end of the body 12. The ring 100 has a plurality of axial tabs 101 extending downwardly therefrom with respect to FIG. 5 (rightwardly with respect to FIGS. 4 and 1) and circumferentially, preferably equally spaced, arrangement. Each of the tabs 101 has an inwardly extending lug 102 provided on the lower end thereof which lug 102 has a radial shoulder 104 provided thereon for engagement with the face 98a of the body flange 98. In the presently preferred practice of the invention, the ring 100 is made of a plastic material suitable for vehicle engine compartment service and the tabs 101 are dimensioned and configured so as to be slightly radially deformable to permit snap assembly of the lugs 102 over flange 98. The lower threaded portion of body 12 has a plurality of radially outwardly extending lugs 106 provided thereon which lugs are spaced in circumferentially equally spaced arrangement about the lower portion of the body 12 as shown in FIG. 5. Corresponding grooves 108 are provided in the wall of cavity 80 to permit sliding assembly of the lugs 106 into the cavity 80 in a manner preventing relative rotation of the valve body 70 with respect to the threaded portion of body 12. As the ring 100 is rotated the shoulder portion 104 of each of the tabs 101 rotates with respect to the shoulder portion 98a of body flange 98 such that the lugs 102 slide on the shoulder 982; and, the threads on the inner periphery of ring 100 rotate about the threads on body 12, thereby causing vertical movement of the body 12 with respect to the cavity 80 in the valve body 70. The vertical movement of the body 12 causes cam follower 44 to alter the tension on spring 54 and thus change the preload on the seat member 84. Therefore, by merely rotating ring 100 the calibration of the regulated output signal from modulator valve 16 may be changed selectively. It will be understood however that such calibration is valid only for a fixed position of cam 58; and, that once ring 100 has been set to the desired preload calibration, variations in the regulated value of the output signal are thereafter effected by rotation of cam 58 during engine operation. Referring now to FIGS. 5 and 10, the lower portion of body 12 is shown as having a spring-receiving cavity 105 formed centrally within the region of threads 68. Cavity 105 is configured to provide adequate clearance for axial or vertical movement of the coil 107 of the tension spring. The lower end of body 12 has provided thereon a plurality of radially outwardly extending guide lugs 106 which are each slidably received respectively in a corresponding groove 108 formed in the wall of chamber 80 of valve body 70. The lugs 106 function to guide axial movment of the valve body 70 on controller body 12, and to further prevent relative rotation therebetween upon rotation of annular calibration ring 100 about threads 68. Referring now to FIGS. 1, 4, 7 and 8, the electrical switching meachanism 18 is shown in detail in FIG. 7, which is inverted with respect to the orientation of FIG. 1. The switch 18 has a housing 110 with a stationary contact assembly, indicated generally at 112, secured to the housing 110 by suitable fastener, as for example, rivet 114, which retains a terminal 116 which has connected thereto electrical lead 120. A second terminal is provided by a fastener, such as rivet 118, which secures terminal 120 to the housing, which terminal has attached thereto the electrical lead 122. Rivet 118 also attaches to the housing a snap-acting switchblade mechanism, indicated generally at 122, which has attached thereto movable contact 124 for making and breaking an electrical circuit between contact 124 and stationary contact assembly 112. An actuator member 126 is provided and is pivotally mounted on housing 110, at the right end thereof with respect to FIG. 7, by portion 128 received in an aperture provided in the wall of housing 110. The actuator 126 has provided thereon a cam follower 130 shown on the left end thereof in FIG. 7, which cam follower is received against a cam surface provided on rotary cam face 38 as will be hereinafter described. Referring to FIGS. 8 and 9, an arcuate recess 132 is provided about a sector of the outer periphery of the lower face of cam flange 38, the recess 132, having ramps 134 provided at the ends thereof. The cam follower 130 of switch actuator 126 is received in the recess 132; and, so long as cam follower 130 is not engaged in either of the cam surfaces 134 or the surface 38, switch 18 is not actuated. Upon rotation of cam 58, such that either of the cam surfaces 134 contacts cam follower 130, the actuator arm 126 is moved to cause snap-over of the switch blade mechanism 122 and contact between switch contacts 124. Referring to FIG. 4, cover 30 is shown an having an arcuate slot 136 provided therein for receiving the fastener 32 in such a manner as to permit rotation of the cover 30 with respect to body 12 by loosening of fastener 32. With housing 110 of switch 18 secured to the cover 30, rotation of the cover 30 causes rotary movement of the cam follower 30 with respect to the recess 132 and thereby permits adjustment of the position of cam follower 30 with respect to cam surfaces 134 for an initial or at-rest position of cam surface 38. Referring now to FIG. 11, a signal output graph is shown for one presently used embodiment of the invention. FIG. 11 shows the signal output plotted as ordinates as a function of angle of rotation of cam 14 plotted as obscissae. It will be understood by those skilled in the art that the choice of diaphragm area, force constant of the tension spring and configuration angular position of cam surface 42 are suitably chosen to give the desired signal output which may differ, as desired, from the relationship shown in FIG. 11. The present invention thus provides a fluid pressure signal controller having a regulated fluid pressure output signal which may be selectively varied by a mechanical input as, for example, the position of a rotary shaft connected to an internal combustion engine throttle. A switch mechanism is also actuated by movement of a cam rotated by the mechanical input. The value of the regulated fluid pressure output signal is controlled by a force-balance type modulator valve having the preload or bias thereon varied during service operation by movement of the mechanical input. The modulator valve is attached to the controller body by a slidable mounting which is easily and conveniently adjusted by rotation of an annular ring threadedly connected to the body. The present invention thus provides an easily calibrated and adjusted fluid pressure signal controller having accompanied therewith an electrical switching function. Although the invention has been hereinabove described with respect to the presently preferred practice, it will be apparent to those having ordinary skill in the art that the invention is capable of modification and variation and is limited only by the scope of the following claims.

A fluid pressure and electrical signal controller for providing a predetermined regulated vacuum signal from a variable source in response to changes in position of a rotatable input shaft when attached thereto and an electrical signal at a predetermined position of the input shaft. A pressure force balance type vacuum modulator valve is preloaded and biased by a spring connected to a cam follower which tracks a rotary cam turned by the input shaft. The modulator valve is slidably attached to the controller body for adjusting the preload length of the spring and a rotatable adjustment ring engages the valve and is threadedly received on the controller body for effecting sliding adjustment of the valve position on the controller body.

RELATED APPLICATIONS This application is assigned to the same assignee as the following application which contains related subject matter: U.S. patent application Ser. No. 08/775,313, entitled "Statistical Multiplexed Video Encoding Using Pre-encoding a Priori Statistics and a Posteriori Statistics," filed on Dec. 31, 1996 for Elliot Linzer and Aaron Wells. The contents of the above-listed application are incorporated herein by reference. FIELD OF THE INVENTION The present invention pertains to real-time video encoding, such as is defined in the MPEG-2 standard. More particularly, the present invention pertains to encoding video signals so as to achieve a truly constant encoding to decoding delay. BACKGROUND OF THE INVENTION In a broadcast environment, it is some times desirable to encode (compress) video signals of multiple video programs in real time and then multiplex or combine the encoded video signals together. The combined encoded video signals are then broadcast to one or more receivers which are capable of demultiplexing out a desired one of the video programs, including the desired encoded video signal. The receiver then decodes the video signal (and possibly associated audio signal(s), an associated closed captioned text signal, a private data signal, etc.) and presents (displays) the decoded video signal. Video signals are preferably encoded using an encoding technique such as MPEG-1 or MPEG-2. Such encoding techniques produce a variable amount of encoded data for each picture (frame or field) of the video signal. The amount of encoded data produced for each picture depends on a number of factors including the amount of motion between the to-be-encoded picture and other pictures used as references for generating predictions therefor. For example, a video signal depicting a football game tends to have high motion pictures and a video signal depicting a talk show tends to have low motion pictures. Accordingly, the average amount of data produced for each picture of the football game video signal tends to be higher than the average amount of data produced for each picture of comparable quality of the talk show. The allocation of bits from picture to picture or even within a picture may also be controlled to generate a certain amount of data for that picture. Consider that the amount of data for each picture may vary. However, the buffer at the decoder has a finite storage capacity. When encoding a video signal, a dynamically adjusted bit budget may be set for each picture to prevent overflow and underflow at the decoder buffer given the transmission bit rate, the storage capacity of the decoder buffer and the fullness of the decoder buffer over time. Note that varying the number of bits that can be allocated to a picture impacts the quality of the pictures of the video signal upon decoding. In general, the transmission medium over which the multiplexed encoded video signals are transmitted has a finite transmission bit rate. It is desirable to share this transmission bit rate amongst the different video signals that are multiplexed together. One manner of doing so is to simply allocate fixed sized fractions of the total transmission capacity to each video signal. However, as noted above, the amount of data produced for each picture of each video signal tends to vary depending on the content thereof and from moment to moment. This would tend to produce low motion video signals with unnecessarily high quality and high motion video signals with poor quality. A preferred real-time video encoding system 10 is shown in FIG. 1. This video encoding system 10 is described in greater detail in U.S. patent application Ser. No. 08/775,313. As shown, digital video signals are produced from k>1 sources 12-1, 12-2, . . . , 12-k. The video sources 12-1 to 12-k can be video tape recorders, magnetic or optical discs, cameras or the like. Each digital video signal is received at a respective encoder 14-1, 14-2, . . . , 14-k. Each encoder 14-1 to 14-k encodes the video signal received thereat and outputs an encoded video signal to the multiplexer 16. The multiplexer 16 multiplexes the encoded video signals together to produce an output signal. In the encoding of the video signals, each encoder 14-1 to 14-k can generate statistical data regarding the complexity of encoding its respective video signal. Such complexity statistics can be a priori (pre-encoding) statistics and/or a posteriori (or post encoding) statistics. Examples of such statistics include measures of inter-pixel differences or the actual number of bits needed to encode a picture. These statistics are outputted from each encoder 14-1 to 14-k to a statistics computer 18. The statistics computer 18 uses the measure of encoding complexity of each encoder 14-1 to 14-k as a basis to allocate a fraction of the transmission bit rate of the transmission channel to each encoder 14-1 to 14-k, e.g., so as to equalize the picture quality over all of the encoders 14-1 to 14-k. Thus, an encoder 14-1 which encodes a video signal with a high encoding complexity can be allocated a higher bit rate than an encoder 14-2 which encodes a video signal with a low encoding complexity. This tends to equalize the quality of all of the encoded video signals that are multiplexed together. To allocate the bit rates, the statistics computer 18 can transfer an indication of a bit rate to each encoder 14-1 to 14-k. Each encoder 14-1 to 14-k responds to an indication of an allocated bit rate by accordingly adjusting the number of bits produced for each picture in an effort to meet the allocated bit rate. Preferably, statistics are provided periodically from the encoders 14-1 to 14-k to the statistics computer 18 and indications of periodically allocated bit rates are transferred periodically from the statistics computer 18 to the encoders 14-1 to 14-k. As noted above, each encoder 14-1 to 14-k encodes each picture in order to generate a certain number of bits for that picture according to a bit budget for that picture. Furthermore, the bit budget is set to prevent a decoder buffer underflow or overflow given a certain transmission channel bit rate. In order to prevent decoder buffer underflow and overflow, the encoder models the decoder buffer in order to determine the fullness of the decoder's buffer from time to time. The behavior of the decoder buffer is now considered in greater detail. FIG. 2 illustrates a model of a decoder buffer for a sequence of pictures. A sequence of pictures is assigned a picture type, namely, intracoded or I, predictively coded or P or bidirectionally predictively encoded or B. I pictures are spatially only encoded. P pictures are temporally encoded and spatially encoded wherein predictions for encoding P pictures originate from only previous P or I reference pictures. B pictures are temporally and spatially encoded wherein predictions for B pictures may originate from previous and/or subsequent I or P reference pictures. Predictions must be obtained from decoded, reconstructed versions of the reference I or P pictures according to the MPEG-2 standard. (This ensures that the encoder uses the same prediction as is available to the decoder.) As such, the encoding of each B picture, e.g., pictures B0 and B1, is delayed until the subsequent reference picture, namely, I2, is encoded, even though such a reference picture is presented (displayed) later. Pictures are decoded in the same order that they are encoded. In modeling the decoder buffer, the encoder determines the buffer fullness of the decoder buffer. The encoder can know how many bits are present in the decoder buffer given the allocated transmission channel bit rate at which such pictures are transmitted to the decoder buffer, the delay between encoding a picture at the encoder and decoding a picture at the decoder, and the knowledge that the decoder buffer is assumed to remove the next to be decoded picture instantaneously at prescribed picture intervals. For example, as depicted, at time interval A, the allocated bit rate is R1 bits/second, at time interval B, the bit rate is R2 bits/second and at time interval C, the allocated bit rate is R3 bits/second. The number of bits produced for each picture I2, B0, B1, P5, B3, B4, P8, B5, B6, P11, B9, B10 and I14, is b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12 or b13, respectively. The encoder attempts to determine each maxima and minima of the decoder buffer's fullness which correspond to the number of bits in the buffer immediately before the decoder removes a picture and the number of bits in the buffer immediately after the decoder removes a picture, respectively. Given such information, the encoder can determine the number of bits to allocate to successive pictures to prevent decoder buffer underflows (decoder buffer does not have all of the bits of a picture in time for the decoder to decode them at a predefined decode time) or overflows (decoder buffer fullness exceeds the maximum decoder buffer storage capacity of B max bits). As shown in FIG. 2, the encoder typically further restricts the number of bits produced during encoding to prevent the decoder buffer fullness from falling below a threshold b lo or exceeding a threshold b hi . The reasons for this pertains to inaccuracies in the encoder's model of the decoder's buffer fullness, for example, as caused by a variation in the delay between encoding each picture and decoding each picture. Such variations can occur when the original source video signal contains repeat fields, as occurs when the video signal is produced from film using the 3:2 pull-down technique. Specifically, to match the film rate of 24 frames per second to the NTSC video signal rate of 60 fields per second, some (approximately every other) film frame is converted to three fields instead of two, where the third field is a duplicate or repeat of the first field of that film frame. According to MPEG-2, repeated fields can be entirely eliminated from the encoded video signal and substituted with a flag (called the "repeat -- first -- field" flag) which causes the decoder to repeat a designated field of the decoded, reconstructed video signal. FIG. 3 illustrates an illustrative encoder 14 for encoding a video signal that can include repeat fields. A video signal outputted from a video source 12 is processed by a inverse teleciner 21 to detect and discard repeat fields. Next, a frame organizer and type selector 23 determines whether each frame is an I frame, P frame or B frame, aggregates adjacent non-repeated fields into frames, and reorders the frames according to the appropriate encoding order. Finally, a compressor 25 compresses the video signals according to the selected order. Illustratively, the inverse teleciner 21, frame organizer and type selector 23 and compressor 25 are implemented using one or more processors, such as the DV Expert™ encoder distributed by C-Cube Microsystems, Inc.™, a company located in Milpitas Calif. Such a processor actually includes multiple processing sections, such as a RISC processor, a motion estimator, and a video digital signal processor, on a single integrated circuit. A single such integrated circuit, or multiple integrated circuits of this type working in concert, may be used to perform such processing. FIG. 4 illustrates a sample timing relationship between capture (i.e., input) of the unencoded digital video signal at the encoder 14 (more specifically to the inverse teleciner 21), repeat field detection by the inverse teleciner 21 and encoding by the compressor 25. As shown, a sequence of 40 fields is outputted from the video source 12 labeled 0 to 39. Using one of a number of well known techniques, the captured fields are processed to identify repeat fields. As indicated by letters "N", fields 2, 4, 6, 8, 10, 15, 20, 25, 30, 35 and 40 are not detected as repeat fields. As indicated by letters "Y", fields 12, 17, 22, 27, 32 and 37 are detected as repeat fields. Adjacent pairs of fields are combined into frames as indicated, except in the case that a repeat field is detected. In such a case, the repeat field is discarded, i.e., not encoded. The discarding of repeat fields allows the encoder to increase the number of bits available for allocation to the remaining pictures (or allows reducing the bit rate allocated to the encoded video signal for a given quality). In place of the discarded repeat field, the encoder sets the repeat -- first -- field flag. The decoder decodes the encoded frames from the encoded video signal and, in response to detecting the set repeat -- first -- field flag, simply repeats display of an appropriate one of the fields of the previously decoded and reconstructed frames. The encoder must pause for one field time for every discarded repeat field so that the encoder does not run out of pictures to encode. MPEG-2 does not specify precisely when pausing should occur and conventional encoders tend to pause at different times. According to the technique shown in FIG. 4, as soon as the encoder detects that the next to-be-encoded frame precedes a repeat field, the encoder encodes the non-repeated fields of the frame and then pauses encoding for one field time. For example, as shown in FIG. 4, frame I2 is encoded, followed immediately by encoding frames B0, B1 and P5. However, because the field immediately following frame P5 is a repeat field (and therefore is discarded), the encoder pauses for one field time before resuming encoding of frame B3. Likewise, after encoding frame B3, the encoder immediately encodes frame B4. However, because a repeat field is detected immediately following frame B7 while encoding frame B4, the encoder pauses for one field time after encoding frame B4. As shown, encoding pauses after each of frames P5, B4, B6, P11, B10, and B12. This manner of pausing the encoding operation is referred to herein as the immediate stall technique. The encoder in FIG. 4 has a single frame pipeline because only a single frame time is needed for a frame to complete processing in the compressor 25. Thus, this encoder is more precisely referred to as an immediate stall/single stage pipeline encoder. FIG. 5 illustrates the timing associated with capture, repeat field detection and encoding for a three frame pipeline encoder. In this encoder, two successive motion estimation search stages or steps ME1 and ME2 are performed successively on each frame, followed by a final encoding stage. Each of the motion estimation search stages ME1 and ME2 (nominally) requires one frame time to complete for each frame, and the final encoding stage requires one frame time. As such, each frame requires three frame times to complete processing in the compressor 25 portion of the encoder. Each stage ME1, ME2 and the final encoding stage simultaneously pause encoding for one field time immediately upon detecting a repeat field. However, this corresponds to different frames at each stage. For example, upon detecting a repeat field following the frame P5, the stage ME1 immediately pauses for one field time. The stage ME2 also pauses at the same time. However, the frame ME2 pauses after processing the immediately preceding frame B1. Likewise, the final encoding stage also pauses at the same time as the stages ME1 and ME2. However, this corresponds to the time immediately following the processing of the frame B0 in the final encoding stage. As such, the one field pauses are shifted back in the encoded sequence of frames by one frame time for each additional stage (or a total of two frame times) in comparison to the encoding pauses shown in FIG. 4. Thus, using the same repeat field detection pattern, the encoding pauses after frames, B0, P5, B4, B6, P11 and B10 for the immediate stall/three frame pipeline encoder. FIG. 6 illustrates the capture, repeat field detection and encoding timing relationship for a single frame pipeline encoder employing a delayed stall manner of encoding. In this encoder, encoding does not pause immediately upon detecting a repeat field but rather is delayed. Specifically, upon detecting a repeat field, encoding of frames continues until the next to-be-encoded reference frame (P frame or I frame). As may be appreciated, this corresponds to the moment in time at which the encoder exhausts all to-be-encoded frames that have completed inverse telecine processing. The encoding then pauses one field time for each repeat field detected between reference frames. For example, using the same repeat field sequence as in FIGS. 4 and 5, a repeat field is detected following frame P5. However, encoding does not pause. Rather, previously inverse telecine processed, reordered B frames B3 and B4 are encoded. Note that while encoding frame B4, yet another repeat field is detected following frame B7. As such, immediately before encoding frame P8, encoding pauses for two field times, i.e., one field time for each of the two detected repeat fields following frame P5 and frame B7. Such a pausing is needed to complete inverse telecine processing of fields 18 and 19 of frame P8. Encoding then continues for frames P8, B6 and B7. Note that while encoding frame B6, another repeat field is detected following frame B9. Nevertheless, encoding continues and does not pause until immediately before encoding frame P11. Again, the pausing is furthermore needed to complete inverse telecine processing of field 26 of frame P11 so that frame P11 is available for encoding. The behavior of the delayed stall encoder can be analyzed as follows. Each frame is encoded as soon as possible. Any discarded repeat fields that delay capture of a reference frame delays encoding of such a reference frame. The encoding of B frames, on the other hand, is delayed only as is necessary to encode the subsequent reference frame. FIG. 7 illustrates the capture, repeat field detection and encoding timing of a delayed stall/three frame pipeline encoder. As in the delayed stall/single frame pipeline encoder (the behavior of which is described in FIG. 6), when a repeat field is detected, encoding does not pause immediately. Rather, any available frames are encoded. Pausing occurs only inasmuch as is needed to obtain the data of the next reference frame. This same behavior occurs at each stage. That is, upon detecting the first repeat field following frame P5, the ME1 stage continues to process available frames. Nor does detecting a repeat field after frame B7 pause processing at the ME1 stage. Rather, processing continues in the ME1 stage until after the frame B4 at which point the ME1 stage pauses until the fields 18 and 19 of the next to-be-encoded reference frame, namely, the reference frame P8, have completed inverse telecine processing. This requires two field times as shown. The same behavior is performed by the ME2 search stage. Specifically, processing does not pause immediately upon detecting repeat fields following frames P5 or B7 but rather continues until the stage ME2 must wait for data to be available, i.e., when the ME1 stage has completed processing the frame P8. As noted, the ME1 stage pauses (in this case, for two field times) prior to processing the frame P8 which in turn causes the ME2 stage to pause, albeit, at a different point in time than the ME1 stage, until the frame P8 is available for processing. The same is true for the final encoding stage. As such, encoding pauses at the same pictures and for the same durations in the delayed stall/three frame pipeline encoder as in the delayed stall/single frame pipeline encoder. FIG. 8 illustrates the timing associated with decoding and presentation of pictures at a decoder. As shown, the frames are decoded in the order I2, B0, B1, P5, B3, B4, . . . etc. A real-time decoder is capable of decoding each frame in one frame time. To reduce memory requirements, and to also enable separate display of each field of each frame, the decoder preferably begins display of a B frame about halfway through decoding of the B frame. On the other hand, reference frames, namely P and I frames, are not displayed until about half of the very next to-be-decoded reference frame is decoded. When displaying a repeat field, the decoder will pause decoding. This behavior is demonstrated in FIG. 8. First, frame I2 is decoded. Next, frames B0 and B1 are decoded using I2 as a reference picture. Presentation of frame B0 begins when about half of the frame B0 is decoded. Likewise presentation of frame B1 begins when about half of frame B1 is decoded. Next, frame P5 is decoded. At the time that presentation of frame B1 is complete, half of frame P5 is decoded. Thus, presentation of frame I2 can begin. After this, frames B3 and B4 are decoded using frames I2 and P5 as references. As above, presentation of the frame B3 begins when half of frame B3 is decoded and presentation of frame B4 begins when about half of frame B4 is decoded. Next frame P8 is decoded. At the completion of presentation of frame B4, about half of frame P8 has been decoded. As such, presentation of frame P5 begins. Frame P5 includes a set repeat -- first -- field flag for causing the repeated display of field 10 as field 12. When field 10 is displayed during the field time for field 12, decoding pauses until the display of field 10 in the field time of field 12 is complete. Decoding then resumes with frames B6 and B7 using frames P5 and P8 as references. Frames B6 and B7 are presented, wherein frame B7 has a set repeat -- first -- field flag causing field 15 of frame B7 to be displayed a second time during the field time for field 17. Again this causes the decoder to pause decoding for one field time, namely, during the field time for field 17. The net result is that seamless presentation of decoded, reconstructed video frames and fields are achieved. In this example, decoding pauses after each of frames P8, B7, B9, P14 and B13 for one field time. Compare now the encoding timing of the encoders shown in FIGS. 4-7 with the decoding timing shown in FIG. 8. None of the conventional encoders always pauses its encoding in between precisely the same frames as does the decoder. It is not a requirement of MPEG-2, but nevertheless desirable for sake of modeling the decoder buffer, for the delay between encoding and decoding to be constant. (Note that even when the transmission rate is constant, the number of bits in each picture will vary. As such, the number of pictures buffered at the encoder will vary over time as will the number of pictures buffered at the decoder.) However, since conventional encoders do not pause encoding when repeat fields are detected in between the same frames as the decoders pause decoding while repeating corresponding fields, the delay between encoding and decoding individual frames varies. Note that the delay between encoding and decoding will remain constant if repeat fields are never detected. For example, FIG. 9 shows the encoding and decoding timing relationship assuming that the video frames are encoded using the immediate stall/three frame pipeline encoder of FIG. 5. Suppose that the delay between encoding a picture and decoding that same picture will be n field times (n being a real number >0) if repeat fields are never detected. Because no repeat fields are detected through the encoding of picture I2, the delay between the encoding and decoding of frame I2 is n field times. The same is true for the frame B0. However, there is a one field delay between encoding frame B0 and encoding frame B1 but no delay between decoding these two frames. As such, the delay between encoding frame B1 and decoding frame B1 is n-1 fields. The encoding to decoding delay for frame P5 is also n-1 fields. The encoder pauses again for one field time between encoding frame P5 and encoding frame B3. However, the decoder does not pause at this same point in the sequence of frames. Thus, the encoding to decoding delay for the frame B3 is n-2 fields. The encoding to decoding delay for frame B4 is also n-2 fields. After encoding field B4, encoding pauses for another field time. Again, decoding does not pause between decoding frames B4 and P8 and thus the encoding to decoding delay for frame P8 is n-3 fields. Finally, the decoder pauses between decoding frame P8 and decoding frame B6. There are no pauses in encoding between these frames. Thus, the encoding to decoding delay for frame B6 is only n-2 fields. In short, the encoding to decoding delay using the aforementioned immediate stall/three frame pipeline encoder varies between n and n-3 fields. More generally stated, if the spacing between reference pictures is M pictures, and the number of stages in the encoder pipeline is S, then the encoding to decoding delay variation is n to n-r(M+S-1), where r(y) is the maximum number of times the encoder will set the repeat -- first -- field flag in y consecutively captured frame pictures. Although the MPEG-2 standard allows for the repeat -- first -- field flag to be set every frame (r(y)=y), a typical encoder will not set the repeat -- first -- field flag in any two consecutively captured frames. This is because the conventional 3:2 pull-down process adds one repeat field every other frame. In this latter case, the variation in delay will be between n and n-.left brkt-top.(M+S-1)/2.right brkt-top. fields (where ".left brkt-top.x.right brkt-top." denotes the "ceiling of x," i.e., x if x is an integer and the integer portion of x+1 otherwise). In the above example, M=3 and S=3 and thus the encoder to decoder delay is n to n-3 fields. However, in an encoder that can produce an arbitrary repeat -- first -- field pattern, the variation may be as many as M+S-1 fields, namely, 5 fields for M=S=3. FIG. 10 shows the timing relationship between the delayed stall/single frame pipeline encoder or delayed stall/three frame pipeline encoder shown in FIGS. 6-7. The derivation of the encode to decode delays is only briefly described here. Specifically, encoding pauses for two field times between frames B4 and P8 but decoding does not pause until after decoding frame P8 (and then pauses for only one field time). Thus, while the encoding to decoding delay of frames I2, B0, B1, P5, B3 and B4 are each n fields, the encoding to decoding delay for the frame P8 is n-2 fields. Decoding pauses before frame B6 for one field time but encoding does not pause until frame P11. Thus, the encoding to decoding delay for frames B6 and B7 is n-1 fields, and so on. In short, the encoding to decoding delay over the sequence of pictures previously described for the delayed stall pipeline encoder is between n and n-2 fields. More generally stated, the variation in encoding to decoding delay is n to n- the maximum number of repeat fields in a sequence of M pictures (where M is the picture spacing between reference frames). If the encoder does not set the repeat field flag in two consecutively captured frames, the variation in delay will be between n and n-.left brkt-top.M/2.right brkt-top. fields. However, for an encoder that can produce an arbitrary repeat -- first -- field pattern, the variation will be between n and n-M fields. Consider that encoded frame data is preferably transmitted as a frame-wise contiguous stream, irrespective of any encoding or decoding pauses. In the decoder buffer model, the decoder is envisioned as filling at a piece-wise constant bit rate (namely, the bit rate allocated to a respective portion of the encoded video signal). The decoding of a picture by the decoder is delayed from the encoding of the same picture by the above noted encoding-to-decoding delay time, which can vary depending on the detection of repeat fields and the encoding pausing policy of the encoder. However, prior to encoding a given picture, an encoder must be able to deduce (from its model of the decoder buffer) the fullness of the decoder buffer prior to decoding the same picture (in order to determine the bit budget for that picture). Therefore, the statistics computer 18 (FIG. 1) will allocate the bit rates r1, r2, . . . rk to the encoders 14-1 to 14-k, and the encoders 14-1 to 14-k will update their decoder buffer models with such allocated bit rates after a delay of d field times, where d is a non-negative real number. Relative to the encoder's model of the decoder buffer (which, in the absence of encoding and decoding pauses, is presumed in the conventional encoders to decode each picture n field times after the encoder encodes it), the encoder implements the bit rate after a delay of n+d field times. See M. Perkins & D. Arnstein, Statistical Multiplexing of Multiple MPEG-2 Video Programs in a Single Channel, SMPTE J., vol. 104, no. 9, p. 569-599, September, 1995. If an encoder behaves in such a manner but the actual encode to decode delay is not n, then the encoder's model of the decoder buffer will not be accurate. To illustrate this, consider as an example a case where d=0 and the statistic computer 18 allocates a new bit rate R1 to an encoder 14-2 representing a bit rate at which the decoder buffer fills just after frame B4 is decoded (the bit rate previously having been R0) and then allocates a new bit rate R2 to the encoder 14-2 representing a bit rate at which the decoder buffer fills just after frame B6 is decoded. Assume that the encoder 14-2 is a delayed stall type of encoder (the behavior of which is illustrated in FIGS. 6 and 7). FIG. 18 is a timing chart illustrating the curve C1 of the fullness of the encoder's model of the decoder's buffer superimposed on the curve C2 actual fullness of the decoder's buffer. The first bit rate change is received at the encoder approximately n field times before frame B4 is decoded, i.e., approximately when frame B4 is encoded. As shown, the encoder correctly changes its model of the decoder buffer to use the bit rate R1 after frame B4 is removed from the decoder buffer. The second bit rate change is received four field times later, i.e., n field times before frame B6 is decoded. As noted above, the encoder delays encoding the frame P8 until four field times later as a result of two repeat field triggered pauses. Accordingly, the encoder changes the bit rate at which its model of the decoder buffer fills to R2 after picture P8 is removed. In contrast, the decoder decodes the frame P8 only two field times after the frame B6 is decoded. As such, the decoder changes its bit rate to R2 after the frame B6 is removed. The net effect is that the fullness of the encoder's model of the decoder buffer diverges from the actual decoder buffer fullness after frame P8 is removed from the decoder buffer. Conventional encoders behave as depicted in one of the FIGS. 4-7, i.e., with variable encode to decode delay. As noted above, variations in encode to decode delay cause the encoder's model of the decoder buffer fullness to diverge from the actual buffer fullness. Left unchecked, this divergence will cause the decoder buffer to overflow or underflow. To keep the decoder buffer from underflowing, a conventional encoder will normally delay updating its model of the decoder buffer with each rate increase allocated by the statistics computer by an amount of time equal to at least the maximum possible variation in encode-to-decode delay. As can be appreciated, such an approach would have prevented an encoder from modeling the decoder buffer fullness higher than the actual buffer fullness in, for example, the illustration of FIG. 18. However, such an approach generally causes the encoder's model of the decoder's buffer to be less full than the actual decoder buffer fullness. For example, when a rate increase is allocated to the encoder and the encode to decode delay is not decreasing (i.e., the encode to decode delay is constant or is increasing), or when a rate decrease is allocated to the encoder and the encode to decode delay decreases, the encoder's model of the decoder's buffer will be less full than the actual fullness of the decoder buffer. This inaccuracy will lead the encoder to use fewer bits than possible--an underestimate of the decoder buffer fullness by x bits will cause x bits to be wasted. In a conventional encoder, decoder buffer underflows are avoided by monitoring the encoder buffer fullness (which in a sense mirrors the decoder buffer fullness) and by substituting transmission of null data instead of useful data (e.g., compressed picture data or header/control data) when the encoder buffer is too empty. (Null data is typically transmitted as null transport packets, which are discarded before entering the decoder's compressed video data buffer.) With these methods used by conventional encoders to insure buffer compliance with the variable bit rate (e.g., statistical multiplexing) situations, the encoder periodically encodes pictures using bit allocations that are calculated assuming a lower transmission bit rate than will actually be used, and a considerable fraction of the transmitted data will be null data. Because fewer bits are spent to represent the video signal, the quality of the video (after decoding) is reduced. Moreover, a conventional encoder may model the real-time behavior of the decoder buffer fullness in part by measuring the fullness of an output buffer at the encoder which temporarily stores encoded pictures pending transmission. (This may even be done in a constant bit rate system, e.g., where statistical multiplexing is not used, because of the drift between the synchronization of the video picture timing and the channel transmission. That is, a decoder buffer model based solely on the number of bits used in each picture, the number of fields produced per second and the number of bits transmitted per second will be inaccurate considering that the synchronization of the occurrence of the fields is drifting relative to the channel slots in which bits are transmitted.) However, the encoder buffer fullness only provides an accurate mirror image of the decoder buffer fullness when the encoding to decoding delay is constant. Specifically, in the encoder buffer model, the bits of each encoded picture are presumed to be inserted into the encoder buffer instantly upon completion of encoding and are removed gradually over time at the allocated fraction of the transmission channel bit rate allocated to the encoded video signal at that moment in time. However, as noted above, the decoder buffer removes pictures at different times for decoding. As a result, the times at which the encoder inserts a picture into the decoder buffer do not necessarily correspond to a fixed delay preceding the times at which the decoder removes such pictures from the decoder buffer. To prevent decoder buffer underflow and overflow given this lack of precise correlation, such encoders further constrain the allocation of bits to each picture to ensure that the encoder's model of the decoder's buffer fullness never exceeds some threshold b hi or falls below some threshold b lo where the high threshold b hi is somewhat below the maximum decoder buffer fullness B max and the low threshold b lo is somewhat above 0. Such headroom reduces the encoder's flexibility to use bits in pictures. Specifically, the encoder must use too many bits for low complexity pictures if the fullness of the encoder's model of the decoder's buffer is close to b hi (because a risk of a decoder buffer overflow is presumed) and too few bits for high complexity pictures if the fullness of the encoder's model of the decoder's buffer is too close to b lo (because a risk of a decoder buffer underflow is presumed). It is an object of the present invention to overcome these disadvantages. SUMMARY OF THE INVENTION This and other objects are achieved according to the present invention. According to one embodiment, an encoding process and encoding apparatus are provided. According to the process, fields of a digital signal are processed to detect repeat fields. Adjacent pairs of the non-repeated fields are organized into frames. A determination is made whether to encode each of the frames as an intraframe, a predicted frame or a bidirectionally predicted frame. The frames are encoded in a specific, predefined order relative to the order of capture of the frames and the type of frame (intraframe, predicted frame, bidirectionally predicted frame, etc.) After each bidirectionally predicted frame that immediately precedes one of the detected repeat fields, encoding of a frame is delayed for one field time. Additionally, after encoding each reference frame that is the very next reference frame to be encoded after a second reference frame, which second reference frame immediately precedes one of the detected repeat fields, encoding of a frame is delayed for one field time. According to this embodiment, encoding is paused for one field time at the same points in the encoded frame sequence that a decoder pauses the decoding of the encoded frame sequence. The apparatus for encoding includes an inverse teleciner, a picture organizer and type selector, a compressor and a repeat field delay matcher. The inverse teleciner is for processing fields of the digital signal to detect repeat fields. The picture organizer and type selector is for organizing adjacent pairs of the non-repeated fields into frames. The picture organizer and type selector is also for determining whether to encode each of the frames as an intraframe, a predicted frame or a bidirectionally predicted frame. The compressor is for encoding the frames in a specific, predefined order relative to the order of capture of the frames and the type of frame as determined by the picture organizer and type selector. The repeat field delay matcher is for, after each bidirectionally predicted frame that immediately precedes one of the detected repeat fields, and each reference frame that is the very next reference frame to be encoded after a second reference frame that immediately precedes a repeat field, delaying encoding of a frame for one field time. Illustratively, statistics may be gathered for multiple encoded video signals and used to allocate a bit rate for transmitting each encoded video signal. Such statistics gathering and bit rate allocation illustratively may be performed by a statistics computer. According to another embodiment, a process and apparatus for statistically multiplexing multiple encoded digital video signals are provided. According to the process, statistics are gathered for one or more of the encoded digital video signals. Based on the gathered statistics, bit rates are allocated for transmitting one or more of the digital video signals as encoded. One of the digital video signals is encoded to produce a certain number of bits for each encoded picture in accordance with a decoder buffer model having a predefined size and filling at a certain bit rate. This "certain bit rate" is updated with the bit rate allocated to the one digital video signal. However, the update is delayed by a number of field display times depending on the number of times encoding pauses, and a presumed number of times decoding pauses, as a result of detected repeat fields in the video signal. Illustratively, the bit rate update delay at the start of encoding a particular frame equals a constant plus the number of field times during which decoding is presumed to pause for each previously encoded frame minus the number of field times during which encoding pauses prior to the start of encoding the particular frame. The apparatus for encoding includes a statistics computer, encoder and delay calculator. The statistics computer is for gathering statistics on one or more of the encoded digital video signals. Based on the gathered statistics, the statistics computer allocates bit rates for transmitting one or more of the digital video signals as encoded. The encoder is for encoding one of the digital video signals to produce a certain number of bits for each encoded picture in accordance with a decoder buffer model having a predefined size and filling at a certain bit rate. The delay calculator updates the "certain bit rate" with the bit rate allocated to the one digital video signal. The delay calculator delays this update by a certain number of field display times depending on the number of times encoding pauses, and a presumed number of times decoding pauses, as a result of detected repeat fields. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a conventional statistical multiplexer. FIG. 2 shows a conventional decoder buffer model timing diagram. FIG. 3 shows a conventional encoder. FIGS. 4-7 are timing diagrams showing capture, inverse telecine processing and encoding timing for conventional encoders. FIG. 8 is a timing diagram showing decoding and presentation timing of a conventional decoder. FIGS. 9 and 10 are timing diagrams showing encoding to decoding delay fluctuations for the encoders of FIGS. 5-7 and the decoder of FIG. 8. FIG 11 shows a statistical multiplexer according to an embodiment of the present invention. FIG. 12 is a timing diagram showing the calculation of delays by the delay calculators of FIG. 11. FIG. 13 shows an encoder according to a second embodiment of the present invention. FIGS. 14 and 15 are timing diagrams showing encoding timing of the encoder of FIG. 13. FIG. 16 is a timing diagram showing encoding to decoding delay for the encoder of FIG. 13. FIG. 17 is a timing diagram showing capture to encoding delay in the encoder of FIG. 13. FIG. 18 is a timing diagram showing a divergence in the fullness of an encoder's model decoder buffer and the actual fullness in an actual decoder buffer that decodes the encoded video signal produced by the encoder. DETAILED DESCRIPTION OF THE INVENTION This invention is illustrated herein in the context of encoding a video signal which contains repeat fields. Encoding is performed using a compression technique, such as MPEG-2, which discards each repeat field and sets a "repeat -- first -- field" flag in its place. The repeat -- first -- field flag causes a decoder to automatically repeat the appropriate field in the reconstructed video signal. Of course, this invention applies for other types of encoded signals where it is desired to cause encoding pauses to track decoding pauses to reduce fluctuations in encoding to decoding delay. FIG. 11 shows a statistical multiplexing system 100 according to an embodiment of the present invention. Illustratively, the statistical multiplexing system 100 combines multiple encoded digital video signals for output in a transmission channel. Each of k>1 video sources 112-1, 112-2, . . . , 112-k outputs a digital video signal. The video sources 112-1, 112-2, . . . , 112-k may be video tape players, video file servers including magnetic or optical disc drives, cameras, editors, special effects generators or the like. The digital video signals are received at a respective encoder 114-1, 114-2, . . . , 114-k. Illustratively, the encoders 114-1, 114-2, . . . , 114-k may be implemented using one or more DV Expert™ encoders. Furthermore, the digital video signals outputted from video sources 112-1, 112-2, . . . , 112-k preferably include, or are later combined with, digital audio signals and other data signals that, in conjunction with each respective digital video signal, constitute a complete video program. Such audio signals are also preferably encoded. (The encoding of audio signals is typically much simpler as the number of bits per audio frame does not vary for certain audio encoding standards, such as Dolby AC-3. Audio encoding is therefore not described herein.) Multiple DV Expert™ encoders can be connected together to operate in concert in encoding a high resolution video signal or to perform other signal processing in conjunction with encoding. The encoded video signals outputted from each video encoder 114-1, 114-2, . . . , 114-k are received at the multiplexer 116 which multiplexes the received encoded video signals together. The multiplexer can be the System Remultiplexer™ distributed by Divicom, Inc.™, a company located in Milpitas Calif. Each encoder 114-1, 114-2, . . . , 114-k furthermore generates a priori and/or a posteriori statistics regarding the complexity of encoding pictures. The following is a non-exhaustive list of the types of statistics which may be generated: number of bits in a compressed picture, average quantization level, scene change locations, repeat field locations, picture types (i.e., I, B, P, field/frame, etc), and inter-pixel differences. Such statistics are dynamically generated by each encoder 114-1, 114-2, . . . , 114-k and are periodically outputted to a statistics computer 118. The statistics computer 118 gathers all of the statistics provided by each processor. Using the statistics provided by each processor, the statistics computer 118 periodically allocates, or reallocates, fractions of the transmission channel bit rate to each of the encoders 114-1, 114-2, . . . , 114-k. Illustratively, the statistics computer 118 uses the information indicating the complexity of encoding each digital video signal to equalize the quality of each video signal. In other words, the statistics computer allocates a fraction of the transmission channel bit rate to encoding a video signal which is proportional to the complexity of encoding that particular video signal relative to the complexity of encoding each other video signal, at that moment in time. The statistics computer 118 may be implemented with any suitably programmed processor. Also shown are multiple delay calculators 120-1, 120-2, . . . , 120-k, namely, one delay calculator 120-1, 120-2, . . . , 120-k for each encoder 114-1, 114-2, . . . , 114-k. Illustratively, each delay calculator 120-1 to 120-k is implemented as either part of each encoder 114-1 to 114-k or part of the statistics computer 118. Preferably, the delay calculators 120-1 to 120-k are implemented using processors in the encoders 114-1 to 114-k or the statistics computer 118. The delay calculators 120-1 to 120-k receive indications of when repeat fields are detected by the inverse teleciner of each encoder 114-1 to 114-k. The delay calculators 120-1 to 120-k also receive information from the statistics computer 118. Illustratively, communication of bit rates allocated to each encoder 114-1 to 114-k by the statistics computer 118 may be delayed by the delay calculators 120-1 to 120-k depending on the detection of repeat fields. The calculation by the delay calculators 120-1 to 120-k is now described. Each delay calculator determines (1) the maximum number of "uncleared stalls", (2) the actual number of "uncleared stalls" and the difference between these two values. Here an "uncleared stall" is a count of the number of fields times for which the encoder has paused encoding previously to this point in the sequence of encoded frames minus the presumed number of field times the decoder will pause while decoding each frame previously encoded to this point in the sequence of encoded frames. For example, consider the timing chart of FIG. 12 which illustrates the calculation of actual uncleared stalls for the immediate stall/three frame pipeline encoder using the aforementioned previously considered repeat field pattern shown in FIG. 5. As shown, the number of actual uncleared stalls during encoding of frames I2 and B0 is 0 because neither encoding nor decoding pauses for these frames. After frame B0, encoding pauses for one field time, but decoding does not pause at this frame. Thus, the number of uncleared stalls at the start of encoding each of frames B2 and P5 increases to 1. Next, after frame P5, encoding pauses again for one field time, but decoding does not pause after frame P5. This is a second uncleared stall, so the actual number of uncleared stalls increases to 2 at the start of encoding each of frames B3 and B4. Likewise, the actual number of uncleared stalls increases to 3 at the start of encoding frame P8. The decoder then pauses decoding after frame P8. This constitutes clearance of one of the stalls and thus decreases the actual number of uncleared stalls to 2 at the start of encoding frame B6, etc. In the immediate stall encoders, the maximum delay variation equals the maximum number of uncleared stalls. As noted above, the maximum delay variation is, in general, M+S-1 fields for an immediate stall decoder but only .left brkt-top.(M+S-1)/2.right brkt-top. fields if the encoder will not detect repeat fields in any two consecutive frames, where M is the picture spacing between reference frames and S is the number stages in the pipeline. In the case of a delayed stall encoder, the maximum delay variation is M fields but only .left brkt-top.M/2.right brkt-top. fields if the encoder will not detect repeat fields in any two consecutive frames. Assuming that the immediate stall encoder used is the type which does not detect repeat fields in any two consecutive frames, and using the appropriate formula .left brkt-top.(M+S-1)/2.right brkt-top. fields for FIG. 12, the maximum number of uncleared stalls is 3. The decoder model adjustment delay is thus 3 field times while encoding frame I2 and B0, 2 field times while encoding frames, B1 and P5, 1 field time while encoding the frames B3, B4, B6, P11, B10 and B12 and 0 field times while encoding the frames P8, B7, B9 and P14. The decoder model adjustment delay indicates the number of field times that an allocated bit rate is delayed (from the time it issues) until the time the encoder uses the bit rate to update the decoder buffer model (that is, update the bit rate at which the decoder buffer fills with encoded video signal data). For example, the encoder delays updating its decoder buffer model with a new bit rate for 3 field times, if the new bit rate is received at the encoder while the encoder encodes frame B0, but delays updating its decoder buffer model with a new received bit rate by only 0 fields times if the new bit rate is received while encoding frame P8. In the preferred embodiment, the delay between the allocation of the new bit rates by the statistics computer 118 and the update of the decoder buffer models with the bit rates by the respective encoders 114-1 to 114-k exactly equals the above-noted "decoder model adjust field times". However, in the general case, additional delays may be added, e.g., the transmission time for transferring the rates from the statistics computer 118 to the encoders 114-1 to 114-k, or a delay needed to synchronize a received bit rate to the field or frame boundaries of the video signal encoded by the respective encoder 114-1 to 114-k. By calculating the delay between allocating a bit rate and updating the decoder buffer model, it is possible to more precisely prevent decoder buffer overflows and underflows. Specifically, the allocation of bits to each picture is a function of the encoding to decoding delay, and the bit rate at which bits of each encoded picture are transferred. Conventional encoders assume that the encoding to decoding delay is constant. However, because of the different points in the sequence of encoded frames at which encoding and decoding pause in response to repeat fields, the delay between encoding and decoding of each picture tends to vary. Conventional encoders do not keep precise track of such variation and instead arbitrarily delay updating the decoder buffer model with the newly allocated bit rate, if the newly allocated bit rate is an increase over the previously allocated bit rate. The result is that null data is inserted to maintain the bit rate of the encoded video signal at times when such a delay is not needed. On the other hand, according to the present invention, the updating of the decoder buffer model with the newly allocated bit rate is delayed in exact correspondence to the variation in the encoding to decoding delay in effect at that moment. As such, the need to insert null data due to the variation in encode to decode delay is eliminated. Operationally, the delaying of the update to the decoder buffer models using the allocated bit rates differs from the conventional delaying of rates. Specifically, according to the invention, the delays in updating the decoder buffer model depend on the times that the encoder has paused encoding due to detected repeat fields, the picture types and a presumed pause in decoding by the decoder in response to repeat -- field -- flags set for such detected repeat fields. On the other hand, conventional decoder buffer model update delays do not depend in any way on encoding pauses, picture types encoded in the encoded video signal or repeat -- first -- field flags. Rather, conventional encoder delays depend solely on whether or not the newly allocated rate is a rate increase (in which case, the update of the decoder buffer model by the newly allocated bit rate is delayed) or a decrease (in which case no delay is imposed on updating the decoder buffer model). The advantage of the delaying technique according to the invention is that the encoder is allowed to maintain an accurate model of the decoder buffer fullness, whereas conventional techniques only allow the encoder to ensure that the fullness of its model of the decoder buffer is always less than or equal to the actual fullness of the actual decoder buffer. As can be appreciated, whenever the fullness of the conventional encoder's model of the decoder buffer is less than the actual fullness of the actual decoder buffer, the number of bits by which the actual fullness exceeds the fullness of the modeled decoder buffer are wasted. Referring to FIG. 13, an encoder 114' according to another embodiment is illustrated. Such an encoder 114' may be substituted for one of the encoders 14-1 to 14-k of FIG. 1. Furthermore, one or more encoders 114' and one or more encoders 114-1 to 114-k, and their corresponding delay calculators 120-1 to 120-k, can be connected together in the same statistical multiplexing system. Like the encoder 14 of FIG. 3, the encoder 114' has an inverse teleciner 121 and a compressor 125. The frame (picture) organizer and type selector 123 is modified to include a repeat field delay matcher 127. As with the counterpart devices of FIG. 3, each of the inverse teleciner 121, frame organizer and type selector 123, compressor 125 and repeat field delay matcher 127 can be implemented through appropriate programming of a processor such as the DV Expert™ encoder. As before, the inverse teleciner 121 processes the video signal produced by a video source 112 in order to detect repeat fields. The frame organizer and type selector 123 discards the repeat fields and organizes the remaining adjacent fields into frames. The frame organizer and type selector 123 also selects the picture type of each frame, i.e., determines whether to encode the frame as an I frame, a P frame or a B frame. The repeat field delay matcher 127 determines when to pause encoding so that encoding pauses at precisely the same pictures and for the same number of field times as decoding. This is described in greater detail below. The compressor 125 encodes each frame and pauses encoding frames at the times determined by the repeat field delay matcher 127. As noted above, the repeat field delay matcher 127 determines the precise frames of the encoded sequence of frames at which the decoder pauses and causes the compressor 125 to pause encoding at the same frames and for the same durations. A decoder pauses decoding in the following instances: (1) if a B frame precedes a repeat field (the repeat field is part of that B frame), decoding pauses immediately for one field time after decoding that B frame, and (2) if a reference frame (I or P frame) precedes a repeat field (the repeat field is part of that reference frame) then decoding pauses for one field time after decoding the very next subsequent reference frame. As illustrated in FIG. 14, which shows the timing relationship between capture, inverse telecine processing and encoding for a single frame pipeline encoder, the repeat field delay matcher 127 achieves this same delay behavior for encoding. The repeat field pattern used in FIG. 14 is the same pattern as was used in the description above in connection with FIGS. 4-10 and 12. First, the repeat field delay matcher 127 allows M+m fields to be captured and to complete inverse telecine processing before sending any frame data to the compressor 125, where M is the inter-frame spacing between reference frames and m is the maximum number of repeat fields that can be detected in a sequence of M frames. In this case M=3 and m is assumed to be 2. This assumption presumes that the inverse teleciner 121 operates in a manner such that repeat fields are never detected in any two consecutive frames. If the inverse teleciner 121 can detect repeat fields in consecutive frames, then m would equal 3. (Note that the compressor 125 also uses one frame time to encode each frame and thus the first encoded frame is encoded when fields 7 and 8 are being inverse telecine processed.) The first repeat field is detected at field 12. This field 12 is a repetition of field 10 which is part of the reference frame P5. Thus, the repeat field delay matcher 127 causes encoding to pause for one field time immediately following the very next to-be-encoded reference frame, namely, frame P8. As noted above, this is precisely the same point in the encoded frame sequence that the decoder pauses while presenting field 10 during field time 12. A similar encoding pause is achieved after encoding frame P14, which follows a previous reference frame P11 that precedes a repeat field detected at field time 27. The next repeat field is detected at field 17. Field 17 is a repetition of field 15 which is part of frame B7. As such, the repeat field delay matcher 127 causes encoding to pause for one field time immediately after encoding frame B7. Again, this is precisely the same point in the encoded frame sequence at which decoding pauses while presenting field 15 during field time 17. Similar encoding pauses are achieved after encoding each of frames B9 and B13 which both have repeat fields. FIG. 15 shows a similar timing relationship when a repeat filed delay matcher 127 is employed in a three stage pipeline encoder. Again, the same repeat field sequence is used to illustrate the invention and the same assumptions regarding inter-reference frame spacing (M=3) and maximum number of repeat fields (m=2) are made. Since the repeat filed delay matcher 127 regulates the flow of encoded pictures, each stage of the three stage pipeline encoder need only process frames when available from the previous stage. As noted, encoding pauses in the final stage match the encoding pauses in the single stage pipeline encoder illustrated in FIG. 14 and the decoder timing pauses in FIG. 8. Note that the encoded frames begin to be outputted when inverse telecine processing of field 11 begins. In the embodiment in FIG. 15, all stages (ME1, ME2 and encode) pause processing in between the same frames that a decoder is presumed to pause decoding. FIG. 16 illustrates the encode and decode timing and the amount of delay for each frame between encoding and decoding. As can be seen the delay does not fluctuate but rather is always constant at n field times. By causing encoding to pause at the same points in the sequence of encoded pictures that decoding is presumed to pause, the encoding to decoding delay is made constant in regard to repeat fields. As such, any newly allocated bit rate can be implemented immediately. Moreover, because encoding to decoding delay fluctuations as introduced by repeat fields are suppressed, the decoder buffer model in the encoder more accurately tracks the actual behavior (i.e., fullness) of the decoder buffer. This allows the encoder to relax or even eliminate the thresholds b lo and b hi in the decoder model. By relaxing or eliminating such thresholds, the encoder can allow its model of the decoder buffer fullness to more closely approach the maximum storage capacity of the decoder buffer, immediately before removing a picture, or to more closely approach the zero fullness, when a picture is removed. Such increases in the swing of the encoder model of the decoder buffer fullness allow the encoder more freedom in allocating bits from picture to picture. As such, the quality of the pictures, when decoded and reconstructed from the encoded video signal, is increased. A rule can be devised for delaying the input of frames to the compressor 125 by the frame organizer and type selector 123 and repeat field delay matcher 127 when a single frame encoding pipeline is used. A B frame is delayed 2M+m fields between the time that capture of the B frame begins and the time that encoding of the B frame begins. For example, FIG. 17 shows the delay between capture of frames and encoding of frames for the single frame pipeline encoder using the above noted sequence of pictures. In such a sequence of pictures, the inter-reference frame spacing M is equal to 3 and the maximum number of repeat fields in a sequence of M frames m is equal to 2. Thus, B frames are delayed 8 field times between the time they are captured and the time they are submitted for encoding. As shown, B frames B0 and B1, which precede all encoding and decoding pauses, are delayed 8 field times from the time at which capture of these frames beings to the time at which encoding of these frames begins. Likewise, frames B6 and B7, which are encoded after an encoding delay of one field and are decoded after a decoding delay of one field, are also delayed for 8 field times after capture before they are submitted for encoding. On the other hand, the delay between capturing a reference (I or P) frame is m-p fields, where p is the number of decoding pauses between the time this reference frame is decoded and the time the next reference frame is decoded. In FIG. 17, the delay between the beginning of capture of frame I2 and the beginning of encoding of frame I2 is 2 field times because p=0 (decoding does not pause between decoding frame I2 and the next reference frame P5). Likewise, the delay between the beginning of capture of frame P5 and the beginning of encoding of frame P5 is also 2 field times because p=0 (decoding does not pause between decoding frame P5 and the next reference frame P8). However, the delay between the beginning of capture of frame P8 and the encoding of frame P8 is 0 field times because p=2. In this latter example, decoding pauses twice between decoding frame P8 and decoding the next reference frame P11, namely, once after decoding frame P8 and once after decoding frame B7. The above rule can be generalized for a pipeline with S processing stages: A B frame will be delayed 2M+m+c field times, where the constant c=2(S-1) (and thus the delay is 2(M+S-1)+m) fields between the time at which capture of the B frame begins and the time at which encoding of the B frame begins. A reference frame will be delayed m-p+c field times (i.e., 2(S-1)+m-p fields) between the time at which capture of the reference frame begins and the time at which encoding of the reference frame begins. Moreover, if, as in the example of FIG. 15, each processing stage pauses processing in between the same frames at which a decoder would pause decoding, then processing for stage s (1≦s≦S) of a B frame will be delayed 2(M+s-1)+m field times between the time at which capture of the B frame begins and the time at which processing of the B frame in the stage s begins. A reference frame will be delayed 2(s-1)+m-p fields between the time at which capture of the reference frame begins and the time at which processing of the reference frame in the stage s begins. In FIG. 15, s=1 for ME1, s=2 for ME2 and s=3 for the final encode stage. Use of the encoder 114' with repeat field delay matcher 127 (FIG. 13) requires more memory than the encoders 114-1 to 114-k in the statistical multiplexer 100 with delay calculators 120-1 to 120-k (FIG. 11). This is because captured frames must be stored for a longer period of time (i.e, as much as 2·M+m field times) after inverse telecine processing pending encoding. In total, a single frame pipeline encoder 114' with repeat field delay matcher 127 requires enough memory for storing 10 fields (assuming M=3, m=2 and 2 fields must be stored for inverse telecine processing). On the other hand, a single frame pipeline encoder, e.g., encoder 114-2, in the statistical multiplexer 100 only requires enough memory for storing 8 fields (under the same assumptions). Nevertheless, the encoder 114' produces superior quality encoded pictures when used in a statistical multiplexer 10 or 100 versus an encoder 114-1 to 114-k with delay calculator 120-1 to 120-k. This is because the encoder 114' does not simply compensate for delay variations (as do the delay calculators 120-1 to 120-k). Rather, the encoding to decoding delay is the same for all frames encoded by the encoder 114'. As such the encoder 114' can use each newly allocated bit rate immediately. For instance, if the encoder 114' detects increased picture complexity, this is reflected in the statistics provided to the statistics computer 18 or 118. In response, the encoder 114' is allocated an increased bit rate. This allocated bit rate can be implemented by the encoder 114' as soon as it is received and without further delay. By using the increased bit rate immediately, the encoder 114' is able to allocate more bits per picture sooner which results in higher quality pictures reconstructed from the video signal for which the increased bit rate is used. In contrast, the delay calculators 120-1 to 120-k impose a variable delay time on newly allocated bit rates which can delay use of the newly allocated bit rate by the respective encoder 114-1 to 114-k for one or more field times. The above discussion is intended to be merely illustrative of the invention. Those having ordinary skill in the art may devise numerous alternative embodiments without departing from the spirit and scope of the following claims.

A process and apparatus for encoding are provided, wherein fields of a digital signal are processed to detect repeat fields. Adjacent pairs of the non-repeated fields are organized into frames. A determination is made whether to encode each of the frames as an intraframe, a predicted frame or a bidirectionally predicted frame. The frames are encoded in a specific, predefined order relative to the order of capture of the frames and the type of frame. After each bidirectionally predicted frame that immediately precedes one of the detected repeat fields, encoding of a frame is delayed for one field time. Encoding is paused after encoding each reference frame that is the very next reference frame to be encoded after a second reference frame, which second reference frame immediately precedes one of the detected repeat fields. A process and apparatus for statistically multiplexing multiple encoded digital video signals are also provided. Statistics are gathered for one or more of the encoded digital video signals and bit rates are allocated for transmitting one or more of the digital video signals as encoded. One of the digital video signals is encoded to produce a certain number of bits for each encoded picture in accordance with a decoder buffer model having a predefined size and filling at a certain bit rate, which is updated with the bit rate allocated to the one digital video signal. The update is delayed by a number of field display times depending on the number of times encoding pauses, and a presumed number of times decoding pauses, as a result of the detected repeat fields.

[0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 61/370,682, entitled “SYNTHESIS AND USE OF THERAPEUTIC METAL ION-CONTAINING POLYMERIC PARTICLES,” filed on Aug. 4, 2010, the entire content of which is hereby incorporated by reference. BACKGROUND [0002] This invention pertains to drug delivery mechanisms, namely, therapeutic particles containing metal ions that are capable of selective delivery of the metal ions to targeted cells. [0003] Targeted drug delivery is a type of drug delivery in which medication is delivered to a patient in a way that results in increased concentration of the medication in certain areas and not in others. This is particularly useful to treat diseased areas while avoiding excessive exposure of non-diseased areas to the medication, which may have harmful side effects. Targeted drug delivery is often used to treat cancer. The delivery of agents capable of inducing toxicity to cancerous cells only without exposure of non-cancerous cells is highly desirable. [0004] Current approaches in targeted drug delivery focus primarily on delivering organic or genetic cargos and have almost completely neglected the potential for delivering transition metal ions or complexes. The use of transition metals as potential therapeutics is worthy of increased attention. Transition metals can display a range of chemical behaviors inside a cell ranging from catalysis to facilitating oxidation/reduction chemistry to targeted binding of DNA. This diversity is unmatched by organic molecules in terms of reactivity and bonding and these unique characteristics make transition metals attractive candidates for use in therapeutic interventions. [0005] Even essential transition metal elements, such as copper, become toxic at elevated concentrations, and as a result their intracellular concentrations are tightly regulated. The mechanisms that have evolved for maintaining the requisite metal ion concentrations impose a delicate balance between expression and degradation of metal transport proteins. Elevated concentrations of copper, like all transition metals, are toxic and have been reported to lead to the generation of radical species, which result in oxidative stress inside the cell. [0006] There has been a resurgence of recent interest in metallopharmaceuticals with a number of transition metal complexes displaying promising activity in vitro only to fail in vivo. However, examples of delivery vectors for metal ions other than platinum are scarce (Treiber et al. 2009; Withey et al. 2009; Chen et al. 2009). SUMMARY [0007] The present invention relates generally to therapeutic micro- or nanoparticles containing metal ions, their synthesis, and their use particularly in targeted drug delivery applications. [0008] In general, engineered particles, including both nanoparticles and microparticles, intended for cellular uptake and delivery of therapeutic agents can contain a number of surface modifications. The various surface modifications are commonly pre-engineered and include those intended to promote cellular targeting, particle “stealthing.” and organelle targeting. Ligands to extend circulation half-life and to reduce immunogenicity (including polyethylene glycol chains) are typically linked to the surface of the particle together with other ligands that promote targeting, such as antibodies, aptamers or small molecules known to bind to surface proteins expressed on target cells or that are capable of guiding particle localization once inside the cell. Chemotherapeutics or other biologically relevant cargo can be encapsulated inside the particle. Release of the cargo at the intended site of action is typically achieved through the incorporation of a stimuli-responsive material that changes state on exposure to the targeted environment. [0009] The therapeutic metal ion-containing particles are characterized by the use of unique ligand sets capable of making metal ion complex soluble in biological media and inducing selective toxicity in diseased cells. One significant innovative aspect of the particles is the use of ligand-free metal ions to achieve desired responses. This is a fundamentally new way of delivering the metal with no predilection to its ligands. The metal is bound to a targeted particle via a stimuli-responsive linage. Thus, when the metal ion-containing particle enters a pre-defined environment, the ligands binding the metal to the particle are broken, triggering release of the free metal ion while the original ligands remain covalently bound to the particle. Simultaneous targeting of the particle to a cell surface receptor also mitigates issues related to off-target toxicity. [0010] Thus, the current therapeutic particles effectively bypass the mechanisms that have evolved for metal ion import, which allows for the concentration of substantial amounts of the metal ions inside particular cells. The metal ion bound to the particle is expected to be inert. Once inside, it is expected that the release of the metal ion contained in the particles should retain its full biological activity, which should be enough to overwhelm the export mechanisms resulting in oxidative damage and ultimately cell death. FIG. 1 shows a general representation of one example of how this process could be carried out in a cell using metal-ion loaded nanoparticles targeted using transferrin (Tf). In this representation, the peptide-based targeting ligand on the nanoparticle surface will bind T. The Tf-targeted nanoparticle will then be preferentially taken up by cells, such as lung cancer cells, via receptor mediated endocytosis. Once inside the cell, acidification will facilitate release of Cu 2+ from the nanoparticle. These particles are not likely to be specific to any particular cell type and thus should constitute a viable alternative for treating a number of diseases, including lung cancer, where the targeted eradication of diseased cells typically leads to a cure or at least an improved patient response. [0011] The therapeutic particles comprise a polymeric base particle, a pharmaceutically active metal ion, a ligand that is covalently attached to the polymeric base particle and attached to the metal ion via a stimuli-responsive bond, and a cell targeting component. The particles may also comprise a non-pharmaceutically active component and additional pharmaceutically active components. The particles preferably have a broadest dimension that is less than about 10 μm. [0012] A number of benefits are associated with the therapeutic particles. The use of the therapeutic particles in drug delivery would reduce off-target toxicity, such as that associated with cisplatin, thereby improving patient response to chemotherapy. The use of certain metal ions might also allow for image-guided drug delivery. Certain ions, such as 64 Cu, could be easily loaded into the nanoparticle to provide real time data on nanoparticle distribution as well as metallopharmaceutical delivery processes. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 shows an example of a mechanism for intracellular release of metal ions from a metal-ion loaded nanoparticle targeted using transferrin (T r ); [0014] FIG. 2 shows a general representation of how an example of the polymeric base particle material can be created; [0015] FIG. 3 shows a general representation of how an example of a carxoylate functionalized particle can be loaded with copper ions and how a subsequent drop in pH can release the copper ions; [0016] FIG. 4 shows an example mechanism for the proposed synthesis of a chelating dicarboxylate functionalized monomer; [0017] FIG. 5 shows a scanning electron micrograph image of copper-loaded, carboxylate-functionalized acrylate-based nanoparticles; [0018] FIG. 6 shows an X-ray photoelectron spectrum of copper holo (i.e. loaded) (A) and apo (i.e. control) (B) carboxylate-functionalized acrylate-based nanoparticles; [0019] FIG. 7 shows the cytotoxicity of copper holo vs apo carboxylate-functionalized acrylate-based nanoparticles; [0020] FIG. 8 shows dynamic light scattering data for phosphate-functionalized acrylate-based nanoparticles before purification via dialysis; [0021] FIG. 9 shows dynamic light scattering data for phosphate-functionalized acrylate-based nanoparticles after purification via dialysis; [0022] FIG. 10 shows the cytotoxicity of copper holo vs apo phosphate-functionalized acrylate-based nanoparticles; [0023] FIG. 11 shows the cytotoxicity of chromium holo vs apo phosphate-functionalized acrylate-based nanoparticles; [0024] FIG. 12 shows the cytotoxicity of iron holo vs apo phosphate-functionalized acrylate-based nanoparticles; [0025] FIG. 13 shows the cytotoxicity of manganese holo vs apo phosphate-functionalized acrylate-based nanoparticles; [0026] FIG. 14 shows the cytotoxicity of nickel holo vs apo phosphate-functionalized acrylate-based nanoparticles; [0027] FIG. 15 shows the cytotoxicity of an iron/copper mixture of holo vs apo phosphate-functionalized acrylate-based nanoparticles; [0028] FIG. 16 shows reaction condition data collected via an internal temperature/pressure sensor during the synthesis of phosphate-functionalized acrylate-based nanoparticles; [0029] FIG. 17 shows dynamic light scattering data for phosphate-functionalized acrylate-based nanoparticles; [0030] FIG. 18 shows the cytotoxicity of zinc holo vs apo phosphate-functional ized acrylate-based nanoparticles; [0031] FIG. 19 shows the cytotoxicity of silver holo vs apo phosphate-functionalized acrylate-based nanoparticles; and [0032] FIG. 20 shows one example proposed synthesis mechanism of a triazole-functionalized monomer. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0033] Generally, the present invention relates to metal ion-containing particles. The particles have particular therapeutic capabilities due to their ability to deliver metal ions to targeted cells. The particles may comprise a polymeric base particle, at least one pharmaceutically active metal ion, including metal ions from more than one metal element, a ligand that is covalently attached to the polymeric base particle and attached to the metal ion via a stimuli-responsive bond, and a cell targeting component. The particles may also comprise a non-pharmaceutically active component and additional pharmaceutically active components. [0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this presently described subject matter belongs. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. Throughout the specification and claims, a given chemical formula or name shall encompass all optical and stereoisomers, as well as racemic mixtures where such isomers and mixtures exist. [0035] The bulk material that can be used to create the polymeric base particle includes a range of modifiable degradable and non-degradable polymers. In some embodiments, a monomer is modified to have a desired metal binding ligand prior to polymerization, while in others functional groups on preformed particles are transformed to contain the desired metal binding ligand. Polymers include natural or synthetic ones. In some embodiments the particle matrix materials of the present invention can include synthetic polyelectrolytes and polar polymers, such as poly(acrylic acid), poly(styrene sulfonate), carboxymethylcellulose (“CMC”), poly(vinyl alcohol), poly(ethylene oxide) (“PEW), poly(vinyl pyrrolidone) (“PVP”), dextran, and the like. FIG. 2 shows a general representation of how an example of the polymeric base particle material can be created. [0036] In some embodiments, water insoluble polymers are made water soluble by ionization or protonation of a pendant group. As will be appreciated by one skilled in the art, water insoluble polymers containing pendent anhydride or ester groups can be solubilized when the anhydride or esters hydrolyze to form ionized acids on the polymer chain. In some embodiments, water soluble polymers are preferred polymers for the polymer component of the intracellular delivery particle because the polymers can be solublized in cellular and body fluids and excreted therefrom. In some embodiments, the polymers of the matrix are selected or tuned to degrade upon encountering a dissolution condition, which in some embodiments can be a condition selected from a cellular or biologic environment, such as for example pH. Further polymers, water soluble polymers, solubilization of polymers and the like are described in Park K., 1993, which is incorporated herein by reference in its entirety. According to some embodiments, the water soluble polymer useful as the polymer base in the particles can include poly(vinyl pyrrolidinone), reactive oligomeric poly(vinylpyrrolidinone), poly(ethylene glycol), protected polyvinyl alcohol, poly(DMAEMA), HEA, HEMA, branched PEGs, combinations thereof, and the like. In some embodiments, the polymer is a non-water soluble polymer such as, for example poly(beta-amino esters), PLGA, PLA, or poly(caprolactone). [0037] In some embodiments, the synthesis of well-defined polymers having controlled molecular structures can be essential to the preparation of the intracellular delivery particles. Depending on the polymer material of interest and the processing conditions and environment, the intracellular delivery nanoparticle can be fabricated from prepolymers having well-defined pre-determined molecular weight, low volatility, high volatility, narrow molecular weight distribution, combinations thereof, and the like. In certain embodiments polymers for forming the intracellular delivery particle can be prepolymerized from volatile or otherwise unstable monomers. [0038] In some embodiments, when a volatile monomer is a component of the matrix materials, a prepolymer or oligomer of the volatile monomer can be produced by, but is not limited to living polymerization reactions, anionic polymerization reactions, free radical living polymerization, catalytic chain transfer agent (CCT), iniferter mediated polymerization, stable free radical mediated polymerization (SFRP), atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization, step-growth polymerization, combinations thereof, and the like. [0039] In some embodiments, the monomer can be, but is not limited to, butadienes, styrenes, propene, acrylates, methacrylates, vinyl ketones, vinyl esters, vinyl acetates, vinyl chlorides, vinyl fluorides, vinyl ethers, vinyl pyrrolidone, acrylonitrile, methacrylnitrile, acrylamide, methacrylamide allyl acetates, fumarates, maleates, ethylenes, propylenes, tetrafluoroethylene, ethers, isobutylene, fumaronitrile, vinyl alcohols, acrylic acids, amides, carbohydrates, esters, urethanes, siloxanes, formaldehyde, phenol, urea, melamine, isoprene, isocyanates, expoxides, bisphenol A, chlorsianes, dihalides, dienes, alkyl olefins, ketones, aldehydes, vinylidene chloride, anhydrides, saccharide, acetylenes, naphthalenes, pyridines, lactams, lactones, acetals, thiiranes, episulf[iota]de, peptides, derivatives thereof, combinations thereof, and the like. [0040] In some embodiments, the prepolymer can include, but is not limited to polyamides, proteins, polyesters, polystyrene, polyethers, polyketones, polysulfones, polyurethanes, polysiloxanes, polysilanes, chitosan, cellulose, amylase, polyacetals, polyethylene, glycols, poly(acrylate)s, poly(methacrylate)s, poly(vinyl alcohol), poly(vinyl pyrrolidone), poly(vinylidene chloride), poly(vinyl acetate), poly(ethylene glycol), polystyrene, poly isoprene, polyisobutylenes, poly(vinyl chloride), poly(propylene), poly(lactic acid), polyisocyanates, polycarbonates, alkyds, phenolics, epoxy resins, polysulf[iota]des, polyimides, liquid crystal polymers, heterocyclic polymers, polypeptides, conducting polymers including polyacetylene, polyquinoline, polyaniline, polypyrrole, polythiophene, poly(p-phenylene), fluoropolymers, derivatives thereof, combinations thereof, and the like. [0041] In some embodiments, the reactive prepolymer is generally capable of undergoing further polymerization, post-prepolymerization, and in some embodiments can be made by living polymerization. Living polymerizations are chain polymerizations from which chain transfer and chain termination are absent. In many cases the rate of chain initiation is fast compared with the rate of chain propagation so that the number of kinetic-chain carriers is essentially constant throughout the polymerization, leading to controlled polymer architecture. In some embodiments, reactive prepolymers for particle compositions can be made by anionic living polymerizations. In other embodiments, reactive prepolymers for particle compositions can be made by free radical living polymerization. In some embodiments, the free radical living polymerization includes one or more of the following: catalytic chain transfer agent (CCT), the iniferter mediated polymerization, stable free radical mediated polymerization (SFRP), atom transfer radical polymerization (ATRP), and reversible addition-fragmentation chain transfer (RAFT) polymerization. Descriptions and examples of these and similar methods and techniques can be found in U.S. Pat. Nos. 4,680,352; 5,371,151; 5,763,548; 6,653,429; 6,677,413; and 7,132,491; each of which is incorporated herein by reference in its entirety. [0042] Reactive prepolymers, according to some embodiments, can also be made through a variety of other polymerization techniques that allow for controlled chain length. A brief list of techniques follows, although it should be appreciated by one skilled in the art that many additional techniques can be applied to the current therapeutic particles. Techniques include catalytic chain transfer polymerization, which is a very efficient and versatile free-radical polymerization technique for the synthesis of functional macromonomers. This process is based on the ability of certain transition metal complexes, most notably of low-spin Co complexes such as cobaloximes, to catalyze the chain transfer to monomer reaction, as described in Australian Journal of Chemistry 55(7) 381-398, which is incorporated herein by reference in its entirety. Stable free radical mediated polymerization, also called Nitroxide mediated polymerization (NMP) often uses a radical scavenger called TEMPO to control polymerization. In NMP, reactions and equilibrium exists between the dormant alkoxy amine and the nitroxide and carbon centered radical. This equilibrium lies greatly toward the alkoxyamine, resulting in a low concentration of radicals (dormant state) and, therefore, minimizes the termination rate of the polymerization. Atom transfer radical polymerization (ATRP) is similar to NMP. The ATRP technique includes an easy experimental setup, use of readily accessible and inexpensive catalysts (usually copper complexes formed with aliphatic amines or imines, or pyridines, many of which are commercially available), and simple initiators, such as alkyl halides. RAFT is a form of free radical polymerization that shows living characteristics the presence of RAFT agents by a reversible addition and fragmentation chain transfer process. Finally, polymers made by step growth methods increase in molecular weight at a very slow rate at lower conversions and only reach moderately high molecular weights at very high conversion. Step growth polymers are defined as polymers formed by the stepwise reaction between functional groups of monomers. Most step growth polymers are also classified as condensation polymers, but not all step growth polymers release condensates. Further related disclosure and compositions are found in the following: U.S. Pat. Nos. 3,215,506; 4,259,023; 5,489,654; 5,763,548; 5,789,487; 5,807937; 5,866,047; 6,169,147; International Patent Application Publication WO 2002/085957; and publications Lokaj et al, Journal of Applied Polymer science, 67 755-762 (1998); Kroeze et al., Macromolecules, 28, 6650-6656 (1995); Nair et al., J. Macromol. Sci.-Chem. A27 (6), 791-806 (1990); Nair et al., Polymer, 29, 1909-1979 (1988); Suw ier et al., Journal of Polymer Science: Part A: Poly mer Chemistry, 38, 3558-3568 (2000); Nair et al., Macromolecules, 23 1361-1369 (1990); Chen et al, European Polymer Journal, 36 1547-1554 (2000); Tharanikkarusa et al., Journal of Applied Polymer Science, 66 1551-1560 (1997); Tharanikkarusa et al., J. m. S.-Pure Appl. Chem., A33 (4), 417-437 (1996); Otsu et al., Polymer Bulletin. 16, 277-284 (1996); Qin et al., Macromolecules 33 6987-6992 (2000); Qin et al., Journal of Polymer Science: Part A: Polymer Chemistry, 38 2115-2120 (2000); Qin et al., Polymer. 41 7347-7353 (2000): Qin et al., Journal of Polymer Science: Part A: Polymer Chemistry, 37 4610-4615 (1999); Tharanikkarusa et al., European Polymer Journal, 33 1779-1789 9 (1997); Tazaki et al. Polymer Bulletin, 17 127-134 (1987); and Otsu et al, Polymer Bulleting 17 323-330 987); each of which is incorporated herein by reference in its entirety. [0043] The pharmaceutically active metal ion component includes any transition or main group metal element. More specifically, the metal ion can be, without limitation, an ion of Li, Na, K, Rb, Cs, Fr, Be, Mg, Co, Sr, Ba, Ra, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Gd, Al, Ga, In, TI, Sn, Pb, As, Sb, Bi. Metals can be bound in any of their common or uncommon oxidations such as, but not limited to Sc(3), Ti (3,4), V (2,3,4,5), Cr(2,3,4,6), Mn(2,3,4,6,7), Fe(2,3), Co(2,3), Ni(2), Cu(1,2), Zn(2). Y(3), Zr(4), Nb(3,4,5), Mo(2,3,4,5,6), Tc(2,3,4,5,6,7), Ru (2,3,4,5,6,7,8), Rh (1,3), Pd(2,4), Ag(1), Cd(2), La(3), Hf(4), Ta(3,4,5), W(2,3,4,5,6), Re (2,3,4,5,6,7), Os(3,4,5,6,7,8), Ir(1,3), Pt(2,4). Au(1,3), Hg(1,2). A single therapeutic particle can be loaded with metal ions from more than one transition or main group metal element. [0044] The therapeutic particles further comprise a ligand covalently bound to the base particle that is also bound to the metal ion. Such ligands include, but are not limited to carboxylates, phosphates, sulfates, oxylato, acetylacetonato, amine, bipyridine, carbanato, diamines, triamines, aceto, glycinato, maleonitriledithiolato, nitrilotriacetato. FIG. 3 shows a general representation of how an example of a carxoylate functionalized particle can be loaded with copper ions and how a subsequent drop in pH can release the copper ions. [0045] An almost infinite number of ligands having stimuli-responsive bonds can be proposed for use in the therapeutic particles. The ligands typically have heteroatoms such as oxygen, nitrogen, or sulfur, which are known to bind tightly to metals. In general, most of these ligands will show some degree of pH dependence because the metal ion will be competing with H + for the donor's electrons. The binding strength of the ligand is important. Use of a relatively weak binder has demonstrated that the particles were capable of releasing metal ions, but they were also unstable in PBS. It is desirable to select ligands that bind with a strength somewhere between the two extremes. The ligands can either be attached to pre-formed nanoparticles or can be incorporated into a monomer prior to particle formation. FIG. 4 shows an example mechanism for the proposed synthesis of a chelating dicarboxylate functionalized monomer. [0046] The therapeutic particles further comprise a cell targeting component, i.e., a cell targeting moiety able to bind to or otherwise associate with a biological entity, for example, a membrane component, a cell surface receptor, prostate specific membrane antigen, or the like. For example, a targeting portion may cause the particles to become localized to a tumor, a disease site, a tissue, an organ, a type of cell, etc. within the body of a subject, depending on the targeting moiety used. The term “bind” or “binding,” as used herein, refers to the interaction between a corresponding pair of molecules or portions thereof that exhibit mutual affinity or binding capacity, typically due to specific or non-specific binding or interaction, including, but not limited to, biochemical, physiological, and/or chemical interactions. “Biological binding” defines a type of interaction that occurs between pairs of molecules including proteins, nucleic acids, glycoproteins, carbohydrates, hormones, or the like. The term “binding partner” refers to a molecule that can undergo binding with a particular molecule. “Specific binding” refers to molecules, such as polynucleotides, that are able to bind to or recognize a binding partner (or a limited number of binding partners) to a substantially higher degree than to other, similar biological entities. In one set of embodiments, the targeting moiety has an affinity (as measured via a disassociation constant) of less than about 1 micromolar, at least about 10 micromolar, or at least about 100 micromolar. [0047] The cell targeting component or targeting moiety (also known as an aptamer) can be covalently bonded to the polymeric matrix and/or another component of the nanoparticle. In some embodiments, the targeting moiety can be covalently associated with the surface of a polymeric matrix (e.g., PEG). In some embodiments, covalent association is mediated by a linker. In some embodiments, the therapeutic agent can be associated with the surface of, encapsulated within, surrounded by, and/or dispersed throughout the polymeric matrix. [0048] A targeting moiety may be a nucleic acid, polypeptide, glycoprotein, carbohydrate, lipid, etc. For example, a targeting moiety can be a nucleic acid targeting moiety (e.g. an aptamer) that binds to a cell type specific marker. In general, an aptamer is an oligonucleotide (e.g., DNA, RNA, or an analog or derivative thereof) that binds to a particular target, such as a polypeptide. In some embodiments, a targeting moiety may be a naturally occurring or synthetic ligand for a cell surface receptor, e.g., a growth factor, hormone, LDL, transferrin, etc. A targeting moiety can be an antibody, which term is intended to include antibody fragments, characteristic portions of antibodies, single chain targeting moieties can be identified, e.g., using procedures such as phage display. This widely used technique has been used to identify cell specific ligands for a variety of different cell types. [0049] In some embodiments, targeting moieties bind to an organ, tissue, cell, extracellular matrix component, and/or intracellular compartment that is associated with a specific developmental stage or a specific disease state. In some embodiments, a target is an antigen on the surface of a cell, such as a cell surface receptor, an integrin, a transmembrane protein, an ion channel, and/or a membrane transport protein. In some embodiments, a target is an intracellular protein. In some embodiments, a target is a soluble protein, such as immunoglobulin. In certain specific embodiments, a target is a tumor marker. In some embodiments, a tumor marker is an antigen that is present in a tumor that is not present in normal tissue. In some embodiments, a tumor marker is an antigen that is more prevalent in a tumor than in normal tissue. In some embodiments, a tumor marker is an antigen that is more prevalent in malignant cancer cells than in normal cells. [0050] In some embodiments, a target is preferentially expressed in tumor tissues versus normal tissues. For example, when compared with expression in normal tissues, expression of prostate specific membrane antigen (PSMA) is at least 10-fold overexpressed in malignant prostate relative to normal tissue, and the level of PSMA expression is further up-regulated as the disease progresses into metastatic phases (Silver et [alpha]1, 1997, Clin. Cancer Res., 3:81). In some embodiments, inventive targeted particles comprise less than 50% by weight, less than 40% by weight, less than 30% by weight, less than 20% by weight, less than 15% by weight, less than 10% by weight, less than 5% by weight, less than 1% by weight, or less than 0.5% by weight of the targeting moiety. [0051] In some embodiments, the targeting moieties are covalently associated with the nanoparticle. In some embodiments, covalent association is mediated by a linker. Any suitable linker for attaching the targeting moieties to the nanoparticle can be used. [0052] As used herein, a “nucleic acid targeting moiety” is a nucleic acid that binds selectively to a target. In some embodiments, a nucleic acid targeting moiety is a nucleic acid that is associated with a particular organ, tissue, cell, extracellular matrix component, and/or intracellular compartment. In general, the targeting function of the aptamer is based on the three-dimensional structure of the aptamer. In some embodiments, binding of an aptamer to a target is typically mediated by the interaction between the two- and/or three-dimensional structures of both the aptamer and the target. In some embodiments, binding of an aptamer to a target is not solely based on the primary sequence of the aptamer, but depends on the three-dimensional structure(s) of the aptamer and/or target. In some embodiments, aptamers bind to their targets via complementary Watson-Crick base pairing which is interrupted by structures (e.g. hairpin loops) that disrupt base pairing. [0053] One of ordinary skill in the art will recognize that any aptamer that is capable of specifically binding to a target can be used in accordance with the present invention. In some embodiments, aptamers to be used in accordance with the present invention may target cancer-associated targets. In some embodiments, aptamers to be used in accordance with the present invention may target tumor markers. [0054] Nucleic acids of the present invention (including nucleic acid targeting moieties and/or functional RNAs to be delivered, e.g., RNAi agents, ribozymes, tRNAs, etc., described in further detail below) may be prepared according to any available technique including, but not limited to, chemical synthesis, enzymatic synthesis, enzymatic or chemical cleavage of a longer precursor, etc. Methods of synthesizing RNAs are known in the art (see, e.g., Gait, M J. (ed.) Oligonucleotide synthesis: a practical approach, Oxford [Oxfordshire], Washington, D.C.: IRL Press, 1984; and Herdewijn, P. (ed.) Oligonucleotide synthesis: methods and applications, Methods in molecular biology, v. 288 (Clifton, N.J.) Totowa, N.J.: Humana Press, 2005). [0055] The nucleic acid that forms the nucleic acid targeting moiety may comprise naturally occurring nucleosides, modified nucleosides, naturally occurring nucleosides with hydrocarbon linkers (e.g., an alkylene) or a polyether linker (e.g., a PEG linker) inserted between one or more nucleosides, modified nucleosides with hydrocarbon or PEG linkers inserted between one or more nucleosides, or a combination of thereof. In some embodiments, nucleotides or modified nucleotides of the nucleic acid targeting moiety can be replaced with a hydrocarbon linker or a polyether linker provided that the binding affinity and selectivity of the nucleic acid targeting moiety is not substantially reduced by the substitution (e.g., the dissociation constant of the nucleic acid targeting moiety for the target should not be greater than about 1×10 −3 M). [0056] It will be appreciated by those of ordinary skill in the art that nucleic acids in accordance with the present invention may comprise nucleotides entirely of the types found in naturally occurring nucleic acids, or may instead include one or more nucleotide analogs or have a structure that otherwise differs from that of a naturally occurring nucleic acid. U.S. Pat. Nos. 6,403,779; 6,399,754; 6,225,460; 6,127,533; 6,031,086; 6,005,087; 5,977,089; and references therein disclose a wide variety of specific nucleotide analogs and modifications that may be used. See Crooke, S. (ed.) Antisense Drug Technology: Principles, Strategies, and Applications (1st ed), Marcel Dekker; ISBN: 0824705661; 1st edition (2001) and references therein. For example, T-modifications include halo, alkoxy and allyloxy groups. In some embodiments, the T-OH group is replaced by a group selected from H, OR, R, halo, SH, NH 2 , NHR, NR 2 or CN, wherein R is C1-C6 alkyl, alkenyl, or alkynyl, and halo is F, Cl, Br or I. Examples of modified linkages include phosphorothioate and 5′-N-phosphoramidite linkages. Nucleic acids of the present invention may include natural nucleosides (i.e. adenosine, thymidine, guanosine, cytidine, uridine, deoxyadenosine, deoxythymidine, deoxyguanosine, and deoxycytidine) or modified nucleosides. Examples of modified nucleotides include base modified nucleoside (e.g., aracytidine, inosine, isoguanosine, nebularine, pseudouridine, 2,6-diaminopurine, 2-aminopurine, 2-thiothymidine, 3-deaza-5-azacytidine, 2′-deoxy uridine, 3-nitorpyrrole, 4-methylindole, 4-thiouridine, A-thiothymidine, 2-aminoadenosine, 2-thiothymidine, 2-thiouridine. 5-bromocytidine, 5-iodouridine, inosine., 6-azauridine, 6-chloropurine, 7-deazaadenosine, 7-deazaguanosine, 8-azaadenosine, 8-azidoadenosine, benzimidazole, Ml-methyladenosine, pyrrolo-pyrimidine, 2-amino-6-chloropurine, 3-methyl adenosine. 5-propynylcytidine, 5-propynyluridine, 5-bromouridine, 5-fluorouridine, 5-methylcytidine, 7-deazaadenosine, 7-deazaguanosine, 8-oxoadenosine, 8-oxoguanosine, O(6)-methylguanine, and 2-thiocytidine), chemically or biologically modified bases (e.g., methylated bases), modified sugars (e.g., 2′-fluororibose., 2′-aminoribose, 2′-azidoribose, 2′-O-methylribose, L-enantiomeric nucleosides arabinose, and hexose), modified phosphate groups (e.g., phosphorothioates and S′—N-phosphoramidite linkages), and combinations thereof. Natural and modified nucleotide monomers for the chemical synthesis of nucleic acids are readily available. In some cases, nucleic acids comprising such modifications display improved properties relative to nucleic acids consisting only of naturally occurring nucleotides. In some embodiments, nucleic acid modifications described herein are utilized to reduce and/or prevent digestion by nucleases (e.g. exonucleases, endonucleases, etc.). For example, the structure of a nucleic acid may be stabilized by including nucleotide analogs at the 3′ end of one or both strands order to reduce digestion. [0057] Modified nucleic acids need not be uniformly modified along the entire length of the molecule. Different nucleotide modifications and/or backbone structures may exist at various positions in the nucleic acid. One of ordinary skill in the art will appreciate that the nucleotide analogs or other modification(s) may be located at any position(s) of a nucleic acid such that the function of the nucleic acid is not substantially affected. To give but one example, modifications may be located at any position of an aptamer such that the ability of the aptamer to specifically bind to the aptamer target is not substantially affected. The modified region may be at the 5′-end and/or the 3′-end of one or both strands. For example, modified aptamers in which approximately 1-5 residues at the 5′ and/or 3′ end of either of employed. The modification may be a 5′ or 3′ terminal modification. One or both nucleic acid strands may comprise at least 50% unmodified nucleotides, at least 80% unmodified nucleotides, at least 90% unmodified nucleotides, or 100% unmodified nucleotides. [0058] Nucleic acids in accordance with the present invention may, for example, comprise a modification to a sugar, nucleoside, or internucleoside linkage such as those described in U.S. Patent Publications 2003/0175950, 2004/0192626, 2004/0092470, 2005/0020525, and 2005/0032733. The present invention encompasses the use of any nucleic acid having any one or more of the modification described therein. For example, a number of terminal conjugates, e.g., lipids such as cholesterol, lithocholic acid, aluric acid, or long alkyl branched chains have been reported to improve cellular uptake. Analogs and modifications may be tested using, e.g., using any appropriate assay known in the art, for example, to select those that result in improved delivery of a therapeutic agent, improved specific binding of an aptamer to an aptamer target, etc. In some embodiments, nucleic acids in accordance with the present invention may comprise one or more non-natural nucleoside linkages. In some embodiments, one or more internal nucleotides at the 3′-end, 5′- end, or both 3′- and 5′-ends of the aptamer are inverted to yield a such as a 3′-3′ linkage or a 5′-5′ linkage. [0059] In some embodiments, nucleic acids in accordance with the present invention are not synthetic, but are naturally-occurring entities that have been isolated from their natural inments. [0060] In some embodiments, a targeting moiety in accordance with the present invention may be a protein or peptide targeting moiety. In certain embodiments, peptides range from about 5 to 100, 10 to 75, 15 to 50, or 20 to 25 amino acids in size. In some embodiments, a peptide sequence is a random arrangement of amino acids. In a particular embodiment, the targeting peptide to be used with the nanoparticles of the invention is less than 8 amino acids in length. [0061] The terms “polypeptide” and “peptide” are used interchangeably herein, with “peptide” typically referring to a polypeptide has: ing a length of less than about 100 amino acids. Polypeptides may contain L-amino acids, D-amino acids, or both and may contain any of a variety of amino acid modifications or analogs known in the art. Useful modifications include, e.g., terminal acetylation, amidation, lipidation, phosphorylation, glycosylation, acylation, framesylation, sulfation, etc. [0062] In another embodiment, the targeting moiety can be a targeting peptide or targeting peptidomimetic has a length of at most 50 residues. In a further embodiment, a nanopaticle of the invention contains a targeting peptide or peptidomimetic that includes the amino acid sequence AKERC, CREKA, ARYLQKLN or AXYLZZLN, wherein X and Z are variable amino acids, or conservative variants or peptidomimetic s thereof. In particular embodiments, the targeting moiety is a peptide that includes the amino acid sequence AKERC, CREKA, ARYLQKLN or AXYLZZLN, wherein X and Z are variable amino acids, and has a length of less than 20, 50 or 100 residues. The CREKA peptide is known in the art, and is described in U.S. Patent Application No. 2005/0048063, which is incorporated herein by reference in its entirety. The octapeptide AXYLZZLN is described in Dinkla et al, The Journal of Biological Chemistry, Vol. 282, No. 26, pp. 18686-18693, which is incorporated herein by reference in its entirety. [0063] In one embodiment, the targeting moiety is an isolated peptide or peptidomimetic that has a length of less than 100 residues and includes the amino acid sequence CREKA (Cys Arg Glu Lys Ala) or a peptidomimetic thereof. Such an isolated peptide- or peptidomimetic can have, for example, a length of less than 50 residues or a length of less than 20 residues. In particular embodiments, the invention provides a peptide that includes the amino acid sequence CREKA and has a length of less than 20, 50 or 100 residues. Moreover, the authors of The Journal of Biological Chemistry, Vol. 282, No. 26, pp. 18686-18693 describe a binding motif in streptococci that forms an autoantigenic complex with human collagen IV. Accordingly, any peptide, or conservative variants or peptidomimetics thereof, that binds or forms a complex with collagen IV, or the targets tissue basement membrane (e.g., the basement membrane of a blood vessel), can be used as a targeting moiety for the nanoparticles of the invention. [0064] Exemplary proteins that may be used as targeting moieties in accordance with the present invention include, but are not limited to, antibodies, receptors, cytokines, peptide hormones, proteins derrived from combinatorial libraries (e.g. avimers, affibodies, etc.), and characteristic portions thereof. [0065] In some embodiments, any protein targeting moiety can be utilized in accordance with the present invention. To give but a few examples, IL-2, transferrin, GM-CSF, a-CD25, a-CD22, TGF-a, folic acid, a-CEA, a-EpCAM scFV, VEGF, LHRH, bombesin, somatostin, Gal, α-GD2, [ alpha]-EpCAM, α-CD20, M0v19, scFv, α-Her-2, and α-CD64 can be used to target a variety of cancers, such as lymphoma, glioma, leukemia, brain tumors, melanoma, ovarian cancer, neuroblastoma, folate receptor-expressing tumors. CEA-expressing tumors, EpCAM-expressing tumors, VEGF-expressing tumors, etc. (Eklund et al, 2005, Expert Rev. Anticancer Ther., 5:33; Kreitman et al, 2000,/. Clin. Oncol., 18:1622; Kreitman et al, 2001, N. Engl. J. Med, 345:241; Sampson et al, 2003, J. Neurooncol, 65:27; Weaver et al., 2003,/. Neurooncol, 65:3; Leamon et al., 1993,/. Biol. Chem., 268:24847; Leamon et al, 1994,/. Drug Target., 2:101; Atkinson et al, 2001,/. Biol. Chem., 276:27930; Frankel et al, 2002, Clin. Cancer Res., 8:1004; Francis et al, 2002, Br. J. Cancer, 87:600; de Graaf et al, 2002, Br. J. Cancer, 86:811; Spooner et al, 2003, Br. J. Cancer, 88:1622; Liu et al, 1999, J. Drug Target., 7:43; Robinson et al, 2004, Proc. Natl. Acad. ScL, USA, 101:14527; Sondel et al, 2003, Curr. Opin. Investig. Drugs, 4:696; Connor et al, 2004,/. Immunother., 27:211; Gillies et al, 2005, Blood, 105:3972; Melani et al, 1998, Cancer Res., 58:4146; Metelitsa et al, 2002, Blood, 99:4166; Lyu et al, 2005, Mol Cancer Ther., 4:1205; and Hotter et al, 2001, Blood, 97:3138). [0066] In some embodiments, protein targeting moieties can be peptides. One of ordinary skill in the art will appreciate that any peptide that specifically binds to a desired target can be used in accordance with the present invention. In some embodiments, peptides targeting tumor vasculature are antagonists or inhibitors of angiogenic proteins that include VEGFR (Binetruy-Tournaire et al, 2000, EMBO J., 19:1525), CD36 (Reiher et al, 2002, Int. J. Cancer, 98:682) and Kumar et al, 2001, Cancer Res., 61:2232) aminopeptidase N (Pasqualini et al, 2000, Cancer Res., 60:722), and matrix metalloproteinases (Koivunen et al., 1999, Nat. Biotechnol, 17:768). For instance, ATWLPPR peptide is a potent antagonist of VEGF (Binetruy-Tournaire et al, 2000, EMBO J., 19:1525); thrombospondin-1 (TSP-I) mimetics can induce apoptosis in endothelial cells (Reiher et al, 2002, Int. J. Cancer, 98:682); RGD-motif mimics (e.g. cyclic peptide ACDCRGDCFCG and ROD peptidomimetic SCH 221 153) block integrin receptors (Koivunen et al. 1995, Biotechnology (NY), 13:265; and Kumar et al, 2001, Cancer Res., 61:2232); NGR-containing peptides (e.g. cyclic CNGRC) inhibit aminopeptidase N (Pasqualini et al. 2000, Cancer Res., 60:722); and cyclic peptides containing the sequence of HWGF (e.g. CTTHWGFTLC) selectively inhibit MMP-2 and MMP-9 (Koivunen et al, 1999, Nat. Biotechnol, 17:768); and a LyP-I peptide has been identified (CGNKRTRGC) which specifically binds to tumor lymphatic vessels and induces apoptosis of endothelial cells (Laakkonen et al, 2004, Proc. Nail Acad. ScL, USA, 101:9381). [0067] In some embodiments, peptide targeting moieties include peptide analogs that block binding of peptide hormones to receptors expressed in human cancers (Bauer et al, 1982, Life ScL, 31:1133). Exemplary hormone receptors (Reubi et al, 2003, Endocr. Rev., 24:389) include (I) somatostatin receptors (e.g. octreotide, vapreotide, and lanretode) (Froidevaux et al, 2002, Biopolymers, 66:161); (2) bombesin/gastrin-releasing peptide (GRP) receptor (e.g. RC-3940 series) (Kanashiro et al, 2003, Proc. Natl. Acad. ScL, USA, 100:15836); and (3) LHRH receptor (e.g. Decapeptyf, Lupron(R), Zoladex(R), and Cetrorelix(R)) (Schally et al, 2000, Prostate, 45:158). [0068] In some embodiments, peptides that recognize IL-II receptor-a can be used to target cells associated with prostate cancer tumors (see, e.g., U.S. Patent Publication 2005/0191294). [0069] In some embodiments, a targeting moiety may be an antibody and/or characteristic portion thereof. The term “antibody” refers to any immunoglobulin, whether natural or wholly or partially synthetically produced and to derivatives thereof and characteristic portions thereof. An antibody may be monoclonal or polyclonal. An antibody may be a member of any immunoglobulin class, including any of the human classes: IgG, IgM, IgA, IgD, and IgE. One of ordinary skill in the art will appreciate that any antibody that specifically binds to a desired target can be used in accordance with the present invention. [0070] In some embodiments, antibodies that recognize PSMA can be used to target cells associated with prostate cancer tumors. Such antibodies include, but are not limited to, scFv antibodies A5, G0, G1, G2, and G4 and mAbs 3/B7, 3/F11, 3/A12, K1, K12, and D20 (Elsasser-Beile et al, 2006, Prostate, 66:1359): mAbs E99, J591, J533, and J415 (Liu et al, 1997, Cancer Res., 57:3629; Liu et al, 1998, Cancer Res. 58:4055; Fracasso et al, 2002, Prostate, 53:9; McDevitt et al, 2000, Cancer Res., 60:6095: McDevitt et al, 2001, Science, 294:1537; Smith-Jones et al, 2000, Cancer Res. 60:5237; VallabhajosulâL al, 2004. Prostate, 58:145; Bander er a/., 2003, J. C/ro/., 170:1717; Patri et al, 2004, Bioconj. Chem. 15:1174; and U.S. Pat. No. 7,163,680); mAb 7E11-05.3 (Horoszewicz et al, 1987, Anticancer Res., 7:927); antibody 7E11 (Horoszewicz et al, 1987, Anticancer Res., 7:927: and U.S. Pat. No. 5,162,504); and antibodies described in Chang et al, 1999, Cancer Res., 59:3192; Murphy et al, 1998,/. Urol, 160:2396: Grauer et al, 1998, Cancer Res., 58:4787; and Wang era/., 2001, M J. Cancer, 92:871. One of ordinary skill in the art will appreciate that any antibody that recognizes and/or specifically binds to PSMA may be used in accordance with the present invention. [0071] In some embodiments, antibodies which recognize other prostate tumor-associated antigens are known in the art and can be used in accordance with the present invention to target cells associated with prostate cancer tumors (see, e.g., Vihko et al, 1985, Biotechnology in Diagnostics, 131; Babaian et al, 1987,/. Urol, 137:439; Leroy et al, 1989, Cancer, 64:1; Meyers et al, 1989, Prostate, 14:209; and U.S. Pat. Nos. 4,970,299; 4,902,615; 4,446,122 and Re 33,405; 4,862,851; 5,055,404). To give but a few examples, antibodies have been identified which recognize transmembrane protein 24P4C12 (U.S. Patent Publication 2005/0019870); calveolin (U.S. Patent Publications 2003/0003103 and 2001/0012890); L6 (U.S. Patent Publication 2004/0156846); prostate specific reductase polypeptide (U.S. Pat. No. 5,786,204; and U.S. Patent Publication 2002/0150578); and prostate stem cell antigen (U.S. Patent Publication 2006/0269557). [0072] In some embodiments, protein targeting moieties that may be used to target cells associated with prostate cancer tumors include conformationally constricted dipeptide mimetics (Ding et al, 2004, Org. Lett, 6:1805). As used herein, an antibody fragment (i.e., characteristic portion of an antibody) refers to any derivative of an antibody which is less than full-length. In general, an antibody fragment retains at least a significant portion of the full-length antibody's specific binding ability. Examples of antibody fragments include, but are not limited to, Fab. Fab″, F(ab′)2, scFv. Fv, dsFy diabody, and Fd fragments. [0073] An antibody fragment can be produced by any means. For example, an antibody fragment may be enzymatically or chemically produced by fragmentation of an intact antibody and/or it may be recombinantly produced from a gene encoding the partial antibody sequence. Alternatively or additionally, an antibody fragment may be wholly or partially synthetically produced. An antibody fragment may optionally comprise a single chain antibody fragment. Alternatively or additionally, an antibody fragment may comprise multiple chains that are linked together, for example, by disulfide linkages. An antibody fragment may optionally comprise a multimolecular complex. A functional antibody fragment will typically comprise at least about 50 amino acids and more typically will comprise at least about 200 amino acids. In some embodiments, antibodies may include chimeric (e.g., “humanized”) and single chain (recombinant) antibodies. In some embodiments, antibodies may have reduced effector functions and/or bispecific molecules. In some embodiments, antibodies may include fragments produced by a Fab expression library. [0074] Single-chain Fvs (scFvs) are recombinant antibody fragments consisting of only the variable light chain (VL) and variable heavy chain (VH) covalently connected to one another by a polypeptide linker. Either VL or VH may comprise the NH2-terminal domain. The polypeptide linker may be of variable length and composition so long as the two variable domains are bridged without significant steric interference. Typically, linkers primarily comprise stretches of glycine and serine residues with some glutamic acid or lysine residues interspersed for solubility. [0075] Diabodies are dimeric scFvs. Diabodies typically have shorter peptide linkers than most scFvs, and they often show a preference for associating as dimers. [0076] An Fv fragment is an antibody fragment which consists of one VH and one VL domain held together by noncovalent interactions. The term “dsFv” as used herein refers to an Fv with an engineered intermolecular disulfide bond to stabilize the VH-VL pair. A Fab′ fragment is an antibody fragment essentially equivalent to that obtained by reduction of the disulfide bridge or bridges joining the two heavy chain pieces in the F(ab′)2 fragment. The Fab′ fragment may be recombinantly produced. [0077] A Fab fragment is an antibody fragment essentially equivalent to that obtained by digestion of immunoglobulins with an enzyme (e.g. papain). The Fab fragment may be recombinantly produced. The heavy chain segment of the Fab fragment is the Fd piece. [0078] In some embodiments, a targeting moiety in accordance with the present invention may comprise a carbohydrate targeting moiety. To give but one example, lactose and/or galactose can be used for targeting hepatocytes. [0079] In some embodiments, a carbohydrate may be a polysaccharide comprising simple sugars (or their derivatives) connected by glycosidic bonds, as known in the art. Such sugars may include, but are not limited to, glucose, fructose, galactose, ribose, lactose, sucrose, maltose, trehalose, cellbiose, mannose, xylose, arabinose, glucdronic acid, galactoronic acid, mannuronic acid, glucosamine, galatosatnine, and neuramic acid. In some embodiments, a carbohydrate may be one or more of pullulan, cellulose, microcrystalline cellulose, hydroxypropyl methylcellulose, hydroxycellulose, methylcellulose, dextran, cyclodextran, glycogen, starch, hydroxyethylstarch, carageenan, glycon, amylose, chitosan, algin and alginic acid, starch, chitin, heparin, konjac, glucommannan, pustulan, heparin, hyaluronic acid, curdlan, and xanthan. [0080] In some embodiments, the carbohydrate may be aminated, carboxyluted, and/or sulfated. In some embodiments, hydropbilic polysaccharides can be modified to become hydrophobic by introducing a large number of side-chain hydrophobic groups. In some embodiments, a hydrophobic carbohydrate may include cellulose acetate, pullulan acetate, konjac acetate, amylose acetate, and dextran acetate. [0081] In some embodiments, a targeting moiety in accordance with the present invention may be a lipid targeting moiety and may comprise one or more fatty acid groups or salts thereof. In some embodiments, a fatty acid group may comprise digestible, long chain (e.g., Cs-Cso), substituted or unsubstituted hydrocarbons. In some embodiments, a fatty acid group may be a C10-C20 fatty acid or salt thereof. In some embodiments, a fatty acid group may be a C15-C20 fatty acid or salt thereof. In some embodiments, a fatty acid group may be unsaturated. In some embodiments, a fatty acid group may be monounsaturated. In some embodiments, a fatty acid group may be polyunsaturated. In some embodiments, a double bond of an unsaturated fatty acid group may be in the cis conformation. In some embodiments, a double bond of an unsaturated fatty acid may be in the trans conformation. [0082] In some embodiments, a fatty acid group may be one or more of butyric, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, arachidic, behenic, or lignoceric acid. In some embodiments, a fatty acid group may be one or more of palmitoleic, oleic, vaccenic, linoleic, alpha-linoleic, gamma-linoleic, arachidonic, gadoleic, arachidonic, eicosapentaenoic, docosahexaenoic, or erucic acid. [0083] The targeting moiety can be conjugated to the polymeric matrix or amphiphilic component using any suitable conjugation technique. For instance, two polymers such as a targeting moiety and a biocompatible polymer, a biocompatible polymer and a poly(ethylene glycol), etc., may be conjugated together using techniques such as EDC-NHS chemistry (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide) or a reaction involving a maleimide or a carboxylic acid, which can be conjugated to one end of a thiol, an amine, or a similarly functionalized polyether. The conjugation of such polymers, for instance, the conjugation of a poly(ester) and a poly(ether) to form a poly(ester-ether), can be performed in an organic solvent, such as, but not limited to, dichloromethane, acetonitrile, chloroform, dimethylformamide, tetrahydrofuran, acetone, or the like. Specific reaction conditions can be determined by those of ordinary skill in the art using no more than routine experimentation. [0084] In another set of embodiments, a conjugation reaction may be performed by reacting a polymer that comprises a carboxylic acid functional group (e.g., a polyester-ether) compound) with a polymer or other moiety (such as a targeting moiety) comprising an amine. For instance, a targeting moiety, such as an aptamer or peptide, may be reacted with an amine to form an amine-containing moiety, which can then be conjugated to the carboxylic acid of the polymer. Such a reaction may occur as a single-step reaction, i.e., the conjugation is performed without using intermediates such as N— hydroxysuccinimide or a maleimide. The conjugation reaction between the amine-containing moiety and the carboxylic acid-terminated polymer (such as a polyester-ether) compound) may be achieved, in one set of embodiments, by adding the amine-containing moiety, solubilized in an organic solvent such as (but not limited to) dichloromethane, acetonitrile, chloroform, tetrahydrofuran, acetone, formamide, dimethylformamide, pyridines, dioxane, or dimethysulfoxide, to a solution containing the carboxylic acid-terminated polymer. The carboxylic acid-terminated polymer may be contained within an organic solvent such as, but not limited to, dichloromethane, acetonitrile, chloroform, dimethylformamide, tetrahydrofuran, or acetone. Reaction between the amine-containing moiety and the carboxylic acid-terminated polymer may occur spontaneously, in some cases. Unconjugated reactants may be washed away after such reactions, and the polymer may be precipitated in solvents such as, for instance, ethyl ether, hexane, methanol, or ethanol. [0085] The therapeutic particles can optionally include other agents, excipients or stabilizers. For example, to increase stability or decrease non-specific uptake by increasing the negative zeta potential of nanoparticles, certain negatively charged components may be added. Such negatively charged components include, but are not limited to bile salts of bile acids consisting of glycocholic acid, cholic acid, chenodeoxycholic acid, taurocholic acid, glycochenodeoxycholic acid, taurochenodeoxycholic acid, litocholic acid, ursodeoxycholic acid, dehydrocholic acid and others; phospholipids including lecithin (egg yolk) based phospholipids which include the following phosphatidylcholines: palmitoyloleoylphosphatidylcholine, palmitoyllinoleoylphosphatidylcholine, stearoyllinoleoylphosphatidylcholine stearoyloleoylphosphatidylcholine, stearoylarachidoylphosphatidylcholine, and dipalmitoylphosphatidylcholine. Other phospholipids including L-, alpha.-dimyristoylphosphatidylcholine (DMPC), dioleoylphosphatidylcholine (DOPC), distearoylphosphatidylcholine (DSPC), hydrogenated soy phosphatidylcholine (HSPC), and other related compounds. Negatively charged surfactants or emulsifiers are also suitable as additives, for example, sodium cholesteryl sulfate and the like. Similarly, the positive zeta potential of nanoparticles can be altered by adding positively charged components. [0086] Formulations suitable for oral administration can consist of (a) liquid solutions, such as an effective amount of the particles dissolved in diluents, such as water, saline, or orange juice, (b) capsules, sachets or tablets, each containing a predetermined amount of the particles, as solids or granules, (c) suspensions in an appropriate liquid, and (d) suitable emulsions. Tablet forms can include one or more of lactose, mannitol, corn starch, potato starch, microcrystalline cellulose, acacia, gelatin, colloidal silicon dioxide, croscarmellose sodium, talc, magnesium stearate, stearic acid, and other excipients, colorants, diluents, buffering agents, moistening agents, preservatives, flavoring agents, and pharmacologically compatible excipients. Lozenge forms can comprise the particles in a flavor, usually sucrose and acacia or tragacanth, as well as pastilles comprising the active ingredient in an inert base, such as gelatin and glycerin, or sucrose and acacia, emulsions, gels, and the like containing, in addition to the active ingredient, such excipients as are known in the art. [0087] Examples of suitable pharmaceutical carriers, excipients, and diluents include, but are not limited to, lactose, dextrose, sucrose, sorbitol, mannitol, starches, gum acacia, calcium phosphate, alginates, tragacanth, gelatin, calcium silicate, microcrystalline cellulose, polyvinylpyrrolidone, cellulose, water, saline solution, syrup, methylcellulose, methyl- and propylhydroxybenzoates, talc, magnesium stearate, and mineral oil. The formulations can additionally include lubricating agents, wetting agents, emulsifying and suspending agents, preserving agents, sweetening agents or flavoring agents. [0088] Pharmaceutical compositions or formulations can include a therapeutically effective amount of the therapeutic particles. These pharmaceutical compositions or formulations can also include one or more pharmaceutically acceptable excipients, adjuvants, carriers, buffers, stabilizers, or combinations thereof. Pharmaceutical formulations suitable for parenteral administration include aqueous and non-aqueous, isotonic sterile injection solutions, which can contain antioxidants, buffers, bacteriostats, and solutes that render the formulation compatible with the blood of the intended recipient, and aqueous and non-aqueous sterile suspensions that can include suspending agents, solubilizers, thickening agents, stabilizers, and preservatives. The formulations can be presented in unit-dose or multi-dose sealed containers, such as ampules and vials, and can be stored in a freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid excipient, for example, water, for injections, immediately prior to use. Extemporaneous injection solutions and suspensions can be prepared from sterile powders, granules, and tablets of the kind previously described. In some embodiments, the pharmaceutical composition is formulated to have a pH range of about 4.5 to about 9.0, including for example pH ranges of any of about 5.0 to about 8.0, about 6.5 to about 7.5, and about 6.5 to about 7.0. In some embodiments, the pH of the pharmaceutical composition is formulated to no less than about 6, including, for example, no less than about any of 6.5, 7 or 8 (such as about 8). The pharmaceutical composition can also be made to be isotonic with blood by the addition of a suitable tonicity modifier, such as glycerol. The pharmaceutical compositions comprising the immune cell-targeted micro and/or nanoparticles described herein can be administered to a subject (such as human) via various routes, such as parenterally, including intravenous, intra-arterial, intraperitoneal, intrapulmonary, oral, inhalation, intravesicular, intramuscular, intratracheal, subcutaneous, intraocular, intrathecal, or transdermal. For example, the nanoparticle composition can be administered by inhalation to target immune cells of the respiratory tract. In some embodiments, the nanoparticle composition is administrated intravenously, and in some embodiments, the nanoparticle composition is administered orally. [0089] The therapeutic particles can also contain additional pharmaceutically active components. Non-limiting examples of potentially suitable pharmaceutically active components include anti-cancer agents, including, for example, docetaxel, mitoxantrone, and mitoxantrone hydrochloride. In another embodiment, the additional pharmaceutically active component may be an anti-cancer drug such as 20-epi-1, 25 dihydroxy vitamin D3,4-ipomeanol, 5-ethynyluracil, 9-dihydrotaxol, abiraterone, acivicin, aclarubicin, acodazole hydrochloride, acronine, acylfiilvene, adecypenol, adozelesin, aldesleukin, all-tk antagonists, altretamine, ambamustine, ambomycin, ametantrone acetate, amidox, amifostine, aminogrutethimide, aminolevulinic acid, amrubicin, amsacrine, anagrelide, anastrozole, andrographolide, angiogenesis inhibitors, antagonist D, antagonist G, antarelix, anthramycin, anti-dorsalizdng morphogenetic protein-1, antiestrogen, antineoplaston, antisense oligonucleotides, aphidicolin glycinate, apoptosis gene modulators, apoptosis regulators, apurinic acid, ARA-CDP-DL-PTBA, arginine deaminase, asparaginase, asperlin, asulacrine, atamestane, atrimustine, axinastatin 1, axinastatin 2, axinastatin 3, azacitidine, azasetron, azatoxin, azatyrosine, azetepa, azotomycin, baccatin ID derivatives, balanol, batimastat, benzochlorins, benzodepa, benzoylstaurosporine, beta lactam derivatives, beta-alethine, betaclamycin B, betulinic acid, BFGF inhibitor, bicalutamide, bisantrene, bisantrene hydrochloride, bisazuidinylspermine, bisnafide, bisnafide dimesylate, bistratene A, bizelesin, bleomycin, bleomycin sulfate, BRC/ABL antagonists, breflate, brequinar sodium, bropirimine, budotitane, busulfan, buthionine sulfoximine, cactinomycin, calcipotriol, calphostin C, calusterone, camptothecin derivatives, canarypox IL-2, capecitabine, caraceraide, carbetimer, carboplatin, carboxamide-amino-triazole, carboxyamidotriazole, carest M3, carmustine, earn 700, cartilage derived inhibitor, carubicin hydrochloride, carzelesin, casein kinase inhibitors, castanosperrnine, cecropin B, cedefingol, cetrorelix, chlorambucil, chlorins, chloroquinoxaline sulfonamide, cicaprost, cirolemycin, cisplatin, cis-porphyrin, cladribine, clomifene analogs, clotrimazole, collismycin A, collismycin B, combretastatin A4, combretastatin analog, conagenin, crambescidin 816, crisnatol, crisnatol mesylate, cryptophycin 8, cryptophycin A derivatives, curacin A, cyclopentanthraquinones, cyclophosphamide, cycloplatam, cypemycin, cytarabine, cytarabine ocfosfate, cytolytic factor, cytostatin, dacarbazine, dacliximab, dactinomycin, daunorubicin hydrochloride, decitabine, dehydrodidemnin B, deslorelin, dexifosfamide, dexormaplatin, dexrazoxane, dexverapamil, dezaguanine, dezaguanine mesylate, diaziquone, didemnin B, didox, diethyhiorspermine, dihydro-5-azacytidine, dioxamycin, diphenyl spiromustine, docetaxel, docosanol, dolasetron, doxifluridine, doxorubicin, doxorubicin hydrochloride, droloxifene, droloxifene citrate, dromostanolone propionate, dronabinol, duazomycin, duocannycin SA, ebselen, ecomustine, edatrexate, edelfosine, edrecolomab, eflomithine, eflomithine hydrochloride, elemene, elsarnitrucin, emitefur, enloplatin, enpromate, epipropidine, epirubicin, epirubicin hydrochloride, epristeride, erbulozole, erythrocyte gene therapy vector system, esorubicin hydrochloride, estramustine, estramustine analog, estramustine phosphate sodium, estrogen agonists, estrogen antagonists, etanidazole, etoposide, etoposide phosphate, etoprine, exemestane, fadrozole, fadrozole hydrochloride, fazarabine, fenretinide, filgrastim, finasteride, flavopiridol, flezelastine, floxuridine, fruasterone, fludarabine, fludarabine phosphate, fluorodaunorunicin hydrochloride, fluorouracil, fluorocitabine, forfenimex, formestane, fosquidone, fostriecin, fostriecin sodium, fotemustine, gadolinium texaphyrin, gallium nitrate, galocitabine, ganirelix, gelatinase inhibitors, gemcitabine, gemcitabine hydrochloride, glutathione inhibitors, hepsulfam, heregulin, hexamethylene bisacetamide, hydroxyurea, hypericin, ibandronic acid, idarubicin, idarubicin hydrochloride, idoxifene, idramantone, ifosfamide, ihnofosine, ilomastat, imidazoacridones, imiquimod, immuno stimulant peptides, insulin-like growth factor-1 receptor inhibitor, interferon agonists, interferon alpha-2A, interferon alpha-2B, interferon alpha-N1, interferon alpha-N3, interferon beta-1A, interferon gamma-IB, interferons, interleukins, iobenguane, iododoxorubicin, iproplatm, irinotecan, irinotecan hydrochloride, iroplact, irsogladine, isobengazole, isohomohalicondrin B, itasetron, jasplakinolide, kahalalide F, lamellarin-N triacetate, lanreotide, lanreotide acetate, leinamycin, lenograstim, lentinan sulfate, leptolstatin, letrozole, leukemia inhibiting factor, leukocyte alpha interferon, leuprolide acetate, leuprolide/estrogen/progesterone, leuprorelin, levamisole, liarozole, liarozole hydrochloride, linear polyamine analog, lipophilic disaccharide peptide, lipophilic platinum compounds, lissoclinamide, lobaplatin, lombricine, lometrexol, lometrexol sodium, lomustine, lonidamine, losoxantrone, losoxantrone hydrochloride, lovastatin, loxoribine, lurtotecan, lutetium texaphyrin lysofylline, lytic peptides, maitansine, mannostatin A, marimastat, masoprocol, maspin, matrilysin inhibitors, matrix metalloproteinase inhibitors, maytansine, mechlorethamine hydrochloride, megestrol acetate, melengestrol acetate, melphalan, menogaril, merbarone, mercaptopurine, meterelin, methioninase, methotrexate, methotrexate sodium, metoclopramide, metoprine, meturedepa, microalgal protein kinase C uihibitors, MIF inhibitor, mifepristone, miltefosine, mirimostim, mismatched double stranded RNA, mitindomide, mitocarcin, mitocromin, mitogillin, mitoguazone, mitolactol, mitomalcin, mitomycin, mitomycin analogs, mitonafide, mitosper, mitotane, mitotoxin fibroblast growth factor-saporin, mitoxantrone, mitoxantrone hydrochloride, mofarotene, molgramostim, monoclonal antibody, human chorionic gonadotrophin, monophosphoryl lipid a/myobacterium cell wall SK, mopidamol, multiple drug resistance gene inhibitor, multiple tumor suppressor 1-based therapy, mustard anticancer agent, mycaperoxide B, mycobacterial cell wall extract, mycophenolic acid, myriaporone, n-acetyldinaline, nafarelin, nagrestip, naloxone/pentazocine, napavin, naphterpin, nartograstim, nedaplatin, nemorubicin, neridronic acid, neutral endopeptidase, nilutamide, nisamycin, nitric oxide modulators, nitroxide antioxidant, nitrullyn, nocodazole, nogalamycin, n-substituted benzamides, O6-benzylguanine, octreotide, okicenone, oligonucleotides, onapristone, ondansetron, oracin, oral cytokine inducer, ormaplatin, osaterone, oxaliplatin, oxaunomycin, oxisuran, paclitaxel, paclitaxel analogs, paclitaxel derivatives, palauamine, palmitoylrhizoxin, pamidronic acid, panaxytriol, panomifene, parabactin, pazelliptine, peaspargase, peldesine, peliomycin, pentamustine, pentosan poly/sulfate sodium, pentostatin, pentrozole, peplomycin sulfate, perflubron, perfosfamide, perillyl alcohol, phenazinomycin, phenylacetate, phosphatase inhibitors, picibanil, pilocarpine hydrochloride, pipobroman, piposulfan, pirarubicin, piritrexim, piroxantrone hydrochloride, placetin A, placetin B, plasminogen activator inhibitor, platinum complex, platinum compounds, platinum-triamine complex, plicamycin, plomestane, porfimer sodium, porfiromycin, prednimustine, procarbazine hydrochloride, propyl bis-acridone, prostaglandin J2, prostatic carcinoma antiandrogen, proteasome inhibitors, protein A-based immune modulator, protein kinase C inhibitor, protein tyrosine phosphatase inhibitors, purine nucleoside phosphorylase inhibitors, puromycin, puromycin drochloride, purpurins, pyrazorurin, pyrazoloacridine, pyridoxylated hemoglobin polyoxyethylene conjugate, RAF antagonists, raltitrexed, ramosetron, RAS farnesyl protein transferase inhibitors, RAS inhibitors, RAS-GAP inhibitor, retelliptine demethylated, rhenium RE 186 etidronate, rhizoxin, riboprine, ribozymes, RH retinamide, RNAi, rogletimide, rohitukine, romurtide, roquinimex, rubiginone B1, ruboxyl, safingol, safingol hydrochloride, saintopin, sarcnu, sarcophytol A, sargramostim, SDII mimetics, semustine, senescence derived inhibitor 1, sense oligonucleotides, signal transduction inhibitors, signal transduction modulators, simtrazene, single chain antigen binding protein, sizofuran, sobuzoxane, sodium borocaptate, sodium phenylacetate, solverol, somatomedin binding protein, sonermin, sparfosafe sodium, sparfosic acid, sparsomycin, spicamycin D, spirogermanium hydrochloride, spiromustine, spiroplatin, splenopentin, spongistatin 1, squalamine, stem cell inhibitor, stem-cell division inhibitors, stipiamide, streptonigrin, streptozocin, stromelysin inhibitors, sulfinosine, sulofenur, superactive vasoactive intestinal peptide antagonist, suradista, suramin, swainsonine, synthetic glycosaminoglycans, talisomycin, tallimustine, tamoxifen methiodide, tauromustine, tazarotene, tecogalan sodium, tegafur, tellurapyrylium, telomerase inhibitors, teloxantrone hydrochloride, temoporfin, temozolomide, teniposide, teroxirone, testolactone, tetrachlorodecaoxide, tetrazomine, thaliblastine, thalidomide, thiamiprine, thiocoraline, thioguanine, thiotepa, thrombopoietin, thrombopoietin mimetic, thymalfasin, thymopoietin receptor agonist, thymotrinan, thyroid stimulating hormone, tiazofurin, tin ethyl etiopurpurin, tirapazamine, titanocene dichloride, topotecan hydrochloride, topsentin, toremifene, toremifene citrate, totipotent stem cell factor, translation inhibitors, trestolone acetate, tretinoin, triacetyluridine, triciribine, triciribine phosphate, trimetrexate, trimetrexate glucuronate, triptorel in, tropisetron, tubulozole hydrochloride, turosteride, tyrosine kinase inhibitors, tyrphostins, UBC inhibitors, ubenimex, uracil mustard, uredepa, urogenital sinus-derived growth inhibitory factor, urokinase receptor antagonists, vapreotide, variolin B, velaresol, veramine, verdins, verteporfin, vinblastine sulfate, vincristine sulfate, vindesine, vindesine sulfate, vinepidine sulfate, vinglycinate sulfate, vinleurosine sulfate, vinorelbine, vinorelbine tartrate, vinrosidine sulfate, vinxaltine, vinzolidine sulfate, vitaxin, vorozole, zanoterone, zeniplatin, zilascorb, zinostatin, zino statin stimalamer, or zorubicin hydrochloride. [0090] The size and shape of the therapeutic particle should play a key role in its performance as a drug delivery vector. The therapeutic particles can have a size that ranges up to 10 μm. The selected size should be small enough so that it doesn't hinder uptake and at the same time large enough to be conveniently centrifuged. [0091] The therapeutic particles could be useful for targeted drug delivery where the metal ion is the pharmacologically active molecule, as well as for a variety of other applications. [0092] By way of example only, and without limitation, one procedure for nanoparticle synthesis is as follows: in an inert atmosphere glovebox, monoacryloxyethyl phosphate (80 wt %), methyl methacrylate (15 wt %), and a PEG-diacrylate cross linker (5 wt %) are dissolved in de-oxygenated ultra pure water (18 MΩ-cm, Barnstead, NANOpure) containing the photoinitiator potassium persulfate (1 mM) at a total monomer concentration of about 10 mM. The vessel is then microwave irradiated (Anton Paar, Synthos 3000) at a temperature of 80° C. for 30 minutes. Nanoparticles are purified by dialysis (4 hours) to remove excess photoinitiator and any unreacted starting materials and then lyophilized for storage. Nanoparticle size averages 50-200 nm in diameter (dynamic light scattering measured on a Nanotrac Ultra instrument) when the above method is employed. Metal loading is achieved by dispersing the lyophilized nanoparticle solid in ultrapure water and then adding two molar equivalents of 1M NaOH, followed by the immediate addition (less than 2 minutes reaction time as the phosphate ester bond is sensitive to hydrolysis at elevated pH) of an aqueous solution containing the desired metal salt. The metal-ion-loaded nanoparticles can then be dialyzed for 2 hours to remove unbound metal and lyophilized for storage. [0093] The presently disclosed subject matter will now be described more fully hereinafter with reference to the accompanying Examples, in which representative embodiments are shown. The presently disclosed subject matter can, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the embodiments to those skilled in the art. [0094] As set forth in the examples below, various different metal ions have been loaded onto phosphate-functionalized nanoparticles, including Cu, Co, Ni, Mn, Fe, Cr, and others, and two different metals (Fe and Cu) have been loaded onto the same nanoparticle. Loading metal solutions included CuSO 4 5H 2 O, CoCl 2 6H 2 O, NiSO 4 6H 2 O, MnSO 4 H 2 O, FeSO 4 7H 2 O, CrCl 3 6H 2 O, and FeSO 4 7H 2 O and CuSO 4 5H 2 O together for the Fe and Cu loaded in combination. Of these six metals tested initially, all were bound to the nanoparticle. Based on this, it is reasonable to expect that every transition metal can be sequestered on these types of particles. Initial cell studies to estimate toxicity, described below, also indicate that phosphate-functionalized nanoparticles themselves are not toxic at the dosages measured, while several phosphate-metal combinations are. Cu appears to be the most toxic. Toxicity was measured in HeLa Cells after 48 hours exposure to the nanoparticles via the MTT assay. Example 1 Preparation of Carboxylate-Functionalized Nanoparticles for Binding Copper [0095] Potassium sulfate (0.1 g, 37.0 μmol) was added to a vial followed by the addition of 3 mL of deionized water (Nanopure, 18 MΩcm) pre-purged with nitrogen for 20 minutes. Methyl methacrylate (28.4 mg), poly(ethylene glycol) (n) diacrylate (n=200 MW, CAS#26570-48-9, 3.2 mg), and acrylic acid (31.5 mg) were added to the vial and the mixture was agitated briefly. The tube was heated to 80° C. via microwave irradiation (CEM LabMate Microwave, max power 200 W) in closed vessel mode for 30 min. Dynamic light scattering (DLS) results showed a monomodal distribution of nanoparticles with an average diameter of 124 nm. Sodium hydroxide (0.145 mL, 1M in water) was added to 1 mL of the nanoparticle containing solution followed by the addition of copper sulfate pentahydrate (1.46 mL, 0.1M in water). The solution was then centrifuged (10 min at 12,000 rpm, Eppendorf model 5810 R) to form a pellet and the supernatant removed. The nanoparticle pellet was re-dispersed in 1 mL deionized water followed by centrifugation. The re-disperse, pellet procedure was conducted two additional times. The pellet was then re-dispersed in 0.955 mL of deionized water to give a 22 mg/mL nanoparticle solution. The solution was analyzed via scanning electron microscopy ( FIG. 5 ) and X-ray photoelectron spectroscopy ( FIG. 6 ). XPS confirmed the presence of ˜3.6 atomic % copper. Cytotoxicity of both the copper apo and holo nanoparticles was measured via an MTT assay in HeLa cells according to the following procedure. Briefly. 10,000 cells per well on 96-well plate were dosed with nanoparticles followed by incubation at 37° C. (5% CO 2 ) for 48 h. After incubation, cell viability was evaluated via an MTT assay. Light absorption was measured on a Synergy 2 plate reader (BioTek). As shown in FIG. 7 , the viability of the cells exposed to particles is expressed as a percentage of the viability of cells grown in the absence of particles. Example 2 Preparation of Phosphate-Functionalized Nanoparticles [0096] A total of two samples were prepared in the following manner. In an inert atmosphere glovebox, potassium persulfate (81 mg), monoacryloxyethyl phosphate (480 mg), methyl methacrylate (90 mg), and poly(ethylene glycol) (n)diacrylate (n=200 MW, CAS/426570-48-9, 30 mg) were added to 30 mL of deionized, degassed water (Nanopure, 18 MΩcm) in a 100 mL PTFE lined vessel (Rotor 16MF100, Anton Paar). The vessels were sealed, brought out of the inert atmosphere glovebox, and placed in the rotor. The rotor was placed in the microwave (Synthos Multiwave 3000, Anton Paar) and heated to 90° C. to initiate polymerization. Temperature inside the vessels was monitored via an external IR temperature sensor. The reaction temperature was allowed to rise to 52° C. by IR (2 min 58s) and then was maintained at 65° C. for a total reaction time of 30 min. The maximum temperature recorded by IR was 72° C. The temperature inside the vessels was expected to be slightly higher than that measured by IR as per Anton Paar's observations. An internal temperature/pressure accessory was purchased after this synthesis to eliminate ambiguity in nanoparticle synthesis reaction conditions. DLS data pre-dialysis indicated the presence of nanoparticles (120 nm average size, as shown in FIG. 8 ). The two samples were combined and dialyzed against 24 L of deionized water over 24 hours. DLS data post-dialysis indicated the presence of nanoparticles (139 nm average size, as shown in FIG. 9 ). The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System). The dry nanoparticle pellet was weighed (728 mg) and then used in the synthesis of metal-ion-loaded particles. Example 3 Synthesis of Copper-Loaded, Phosphate-Functionalized Nanoparticles [0097] Phosphate-functionalized nanoparticles (70 mg) synthesized according to Example 2 were dispersed in 2 mL of deionized water (Nanopure, 18 MΩcm) and the pH was measured (pH=1.44). Sodium hydroxide (0.3 mL, 1M in water) was added and the pH was measured (pH=11.49). Copper sulfate pentahydrate (0.6 mL, 1M in water) was added and the pH was measured (pH=3.7). The nanoparticle solution was then dialyzed against 3 L of deionized water over 24 h. The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System). Cytoxicity of both the copper apo and holo nanoparticles was measured via an MTT assay in HeLa cells as follows. Briefly, 10,000 cells per well on 96-well plate were dosed with nanoparticles followed by incubation at 37° C. (5° A) CO 2 ) for 48 h. After incubation, cell viability was evaluated via an MTT assay. Light absorption was measured on a Synergy 2 plate reader (BioTek). As shown in FIG. 10 , the viability of the cells exposed to particles is expressed as a percentage of the viability of cells grown in the absence of particles. Example 4 Synthesis of Chromium-Loaded, Phosphate-Functionalized Nanoparticles [0098] Phosphate-functionalized nanoparticles (70 mg) synthesized according to Example 2 were dispersed in 2 mL of deionized water (Nanopure, 18 MΩcm) and the pH vs. as measured (pH=1.44). Sodium hydroxide (0.3 mL, 1M in water) was added and the pH was measured (pH-11.49). Chromium (III) chloride hexahydrate (0.6 mL, 1M in water) was added and the pH was measured (pH=3.4). The nanoparticle solution was then dialyzed against 3 L of deionized water over 24 h. The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System). Cytoxicity of both the chromium apo and holo nanoparticles was measured via an MTT assay in HeLa cells as follows. Briefly, 10,000 cells per well on 96-well plate were dosed with nanoparticles followed by incubation at 37° C. (5% CO 2 ) for 48 h. After incubation, cell viability was evaluated via an MTT assay. Light absorption was measured on a Synergy 2 plate reader (BioTek). As shown in FIG. 11 , the viability of the cells exposed to particles is expressed as a percentage of the viability of cells grown in the absence of particles. Example 5 Synthesis of Iron-Loaded, Phosphate-Functionalized Nanoparticles [0099] Phosphate-functionalized nanoparticles (70 mg) synthesized according to Example 2 were dispersed in 2 mL of deionized water (Nanopure, 18 MΩcm) and the pH was measured (pH=1.44). Sodium hydroxide (0.3 mL, 1M in water) was added and the pH was measured (pH=11.49). Iron (II) sulfate heptahydrate (0.6 mL, 1M in water) was added and the pH was measured (pH=6.2). The nanoparticle solution was then dialyzed against 3 L of deionized water over 24 h. The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System). Cytoxicity of both the iron apo and holo nanoparticles was measured via an MTT assay in HeLa cells as follows. Briefly, 5,000 cells per well on 96-well plate were dosed with nanoparticles followed by incubation at 37° C. (5% CO 2 ) for 48 h. After incubation, cell viability was evaluated via an MTT assay. Light absorption was measured on a Synergy 2 plate reader (BioTek). As shown in FIG. 12 , the viability of the cells exposed to particles is expressed as a percentage of the viability of cells grown in the absence of particles. Example 6 Synthesis of Manganese-Loaded, Phosphate-Functionalized Nanoparticles [0100] Phosphate-functionalized nanoparticles (70 mg) synthesized according to Example 2 were dispersed in 2 mL of deionized water (Nanopure, 18 MΩcm) and the pH was measured (pH=1.44). Sodium hydroxide (0.3 mL. 1M in water) was added and the pH was measured (pH=11.49). Manganese (11) sulfate monohydrate (0.6 mL, 1M in water) was added. The nanoparticle solution was then dialyzed against 3 L of deionized water over 24 h. The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System). Cytoxicity of both the manganese apo and holo nanoparticles was measured via an MTT assay in HeLa cells as follows. Briefly, 10,000 cells per well on 96-well plate were dosed with nanoparticles followed by incubation at 37° C. (5% CO 2 ) for 48 h. After incubation, cell viability was evaluated via an MTT assay. Light absorption was measured on a Synergy 2 plate reader (BioTek). As shown in FIG. 13 , the viability of the cells exposed to particles is expressed as a percentage of the viability of cells grown in the absence of particles. Example 7 Synthesis of Nickel-Loaded, Phosphate-Functionalized Nanoparticles [0101] Phosphate-functionalized nanoparticles (70 mg) synthesized according to Example 2 were dispersed in 2 mL of deionized water (Nanopure, 18 MΩcm) and the pH was measured (pH=1.44). Sodium hydroxide (0.3 mL, 1M in water) was added and the pH was measured (pH=11.49). Nickel (II) sulfate hexahydrate (0.6 mL, 1M in water) was added and the pH was measured (pH=6.1). The nanoparticle solution was then dialyzed against 3 L of deionized water over 24 h. The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System). Cytoxicity of both the nickel apo and holo nanoparticles was measured via an MTT assay in HeLa cells as follows. Briefly, 10,000 cells per well on 96-well plate were dosed with nanoparticles followed by incubation at 37° C. (5% CO 2 ) for 48 h. After incubation, cell viability was evaluated via an MTT assay. Light absorption was measured on a Synergy 2 plate reader (BioTek). As shown in FIG. 14 , the viability of the cells exposed to particles is expressed as a percentage of the viability of cells grow n in the absence of particles. Example 8 Synthesis of Iron and Copper-Loaded, Phosphate-Functionalized Nanoparticles [0102] Phosphate-functionalized nanoparticles (70 mg) synthesized according to Example 2 were dispersed in 2 mL of deionized water (Nanopure, 18 MΩcm) and the pH was measured (pH=1.44). Sodium hydroxide (0.3 mL, 1M in water) was added and the pH was measured (pH=11.49). Copper (II) sulfate pentahydrate (0.3 mL, 1M in water) and iron (II) sulfate heptahydrate (0.3 mL, 1M in water) were added and the pH was measured (pH=3.4). The nanoparticle solution was then dialyzed against 3 L of deionized water over 24 h. The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System). Cytoxicity of both the iron/copper apo and holo nanoparticles was measured via an MTT assay in HeLa cells as follows. Briefly, 5,000 cells per well on 96-well plate were dosed with nanoparticles followed by incubation at 37° C. (5% CO 2 ) for 48 h. After incubation, cell viability was evaluated via an MTT assay. Light absorption was measured on a Synergy 2 plate reader (BioTek). As shown in FIG. 15 , the viability of the cells exposed to particles is expressed as a percentage of the viability of cells grown in the absence of particles. Example 9 Synthesis of Phosphate-Functionalized Nanoparticles for Binding Zinc, Zirconium, and Silver [0103] A total of eight samples were prepared in the following manner. In an inert atmosphere glovebox, potassium persulfate (81 mg), monoacryloxyethyl phosphate (480 mg), methyl methacrylate (90 mg), and poly(ethylene glycol) (n)diacrylate (n=200 MW, CAS#26570-48-9, 30 mg) were added to 30 mL of deionized, degassed water (Nanopure, 18 MΩcm) in a 100 mL PTFE lined vessel (Rotor 16MF100, Anton Paar). The vessels were sealed, brought out of the inert atmosphere glovebox, and placed in the rotor. The rotor was placed in the microwave (Synthos Multiwave 3000, Anton Paar) and heated to 100° C. to initiate polymerization. Temperature and pressure inside one of the eight vessels was monitored via an internal temperature/pressure sensor accessory. The reaction temperature was then allowed to cool to 80° C. where it was maintained for a total reaction time of 30 min, as shown in FIG. 16 . DLS data for each of the eight samples indicated the presence of nanoparticles (130 nm average size, as shown in FIG. 17 ) in all eight samples with similar particle distributions. The eight samples were then combined and dialyzed against 24 L of deionized water over 24 hours. The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System). The dry nanoparticle pellet was weighed (2.1 g) and then used in the synthesis of metal-ion loaded particles in Examples 10-12 below. The nanoparticles were titrated with dilute sodium hydroxide to determine the amount of phosphate ester contained in the nanoparticles. Phenolphthalein was used as the indicator. The amount of phosphate per mg of nanoparticles was calculated to be 1.8×10̂-5 mol P/mg. Example 10 Synthesis of Zinc-Loaded, Phosphate-Functionalized Nanoparticles [0104] Phosphate-functionalized nanoparticles (200 mg) synthesized according to Example 9 were dispersed in 5 mL of deionized water (Nanopure, 18 MΩcm) and the pH was measured (pH=1.9). Sodium hydroxide (0.69 mL, 1M in water) was added and the pH was measured (pH=12.3). Zinc (II) sulfate heptahydrate (1.38 mL, 1M in water) was added. The nanoparticle solution was then dialyzed against 8 L of deionized water over 24 h. The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System). Cytoxicity of both the zinc apo and holo nanoparticles was measured in LLC-PK1 cells as follows. Briefly, 5,000 cells per well on 96-well plate were dosed with nanoparticles followed by incubation at 37° C. (5% CO 2 )) for 48 h. After incubation, cell viability was evaluated via an MTT assay. Light absorption was measured on a Synergy 2 plate reader (BioTek). As shown in FIG. 18 , the viability of the cells exposed to particles is expressed as a percentage of the viability of cells grown in the absence of particles. Example 11 Synthesis of Zirconium-Loaded, Phosphate-Functionalized Nanoparticles [0105] Phosphate-functionalized nanoparticles (200 mg) synthesized according to Example 9 were dispersed in 5 mL of deionized water (Nanopure, 18 MΩcm) and the pH was measured (pH=1.9). Sodium hydroxide (0.69 mL, 1M in water) was added and the pH was measured (pH=12.3). Zirconium (IV)disulfate tetrahydrate (1.38 mL, 1M in water) was added. The nanoparticle solution was then dialyzed against 8 L of deionized water over 24 h. The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System Example 12 Synthesis of Silver-Loaded, Phosphate-Nanoparticles [0106] Phosphate-functionalized nanoparticles (200 mg) synthesized according to Example 9 were dispersed in 5 mL of deionized water (Nanopure. 18 MΩcm) and the pH was measured (pH=1.9). Sodium hydroxide (0.69 mL, 1M in water) was added and the pH was measured (pH=12.3). Silver nitrate (1.38 mL, 0.5 M in water) was added and the pH was measured (pH=8.1). The nanoparticle solution was then dialyzed against 8 L of deionized water over 24 h. The nanoparticle solution was then frozen in liquid nitrogen and lyophilized (Labconco FreeZone 2.5 Liter Benchtop Freeze Dry System). Cytoxicity of both the silver apo and holo nanoparticles was measured in LLC-PK1 cells as follows. Briefly, 5,000 cells per well on 96-well plate were dosed with nanoparticles followed by incubation at 37° C. (5% CO 2 ) for 48 h. After incubation, cell viability was evaluated via an MTT assay. Light absorption was measured on a Synergy 2 plate reader (BioTek). As shown in FIG. 19 , the viability of the cells exposed to particles is expressed as a percentage of the viability of cells grown in the absence of particles. Example 13 Synthesis of Triazole-Functionalized Nanoparticles [0107] The design of nanoparticles containing triazole groups is as follows. Propargyl alcohol (1 eq), sodium azide (1.5 eq) and cuprous chloride (1 eq) are refluxed in methanol; 1,4-dioxane (1:2) under nitrogen for two days. The (1H-1,2,3-triazol-4-yl)methanol formed is then reacted with methacrylic anhydride to form the triazol methacrylate monomer shown in FIG. 20 . This monomer is then polymerized under reaction conditions similar to those described in Examples 1, 2, and 9. REFERENCES CITED [0108] The following documents and publications are hereby incorporated by reference. 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Therapeutic particles contain metal ions and are characterized by the use of unique ligand sets capable of making the metal ion complex soluble in biological media to induce selective toxicity in diseased cells. The particles may comprise a polymeric base particle, at least one pharmaceutically active metal ion, including metal ions from more than one metal element, a ligand that is covalently attached to the polymeric base particle and attached to the metal ion via a stimuli-responsive bond, and a cell targeting component. When the metal ion-containing particle enters a pre-defined environment, the ligands binding the metal to the particle are broken, triggering release of the free metal ion while the original ligands remain covalently bound to the particle.

FIELD OF THE INVENTION This invention relates to a two-component type developer and an image forming process in which the two-component type developer is used. BACKGROUND OF THE INVENTION Heretofore, for a developer applicable to the image formation in an electrophotographic system, two kinds of roughly classified developers have been used, namely, a single-component type developer and a two-component type developer. Particularly among color developers, a two-component type developer has been advantageous from the point that a stable charging property can be secured. As the multicolor image forming processes in which the two-component type developer is used, there have been two known developing processes, namely, a contact developing process characterized in making use of an intermediate image transfer member and a non-contact developing process characterized in putting colors on a latent image carrier one over another without making use of any intermediate image transfer member. From the viewpoint that the process itself can be miniaturized, the non-contact developing process has been advantageous. However, in a simple non-contact developing process, a developability is usually deteriorated as compared to the contact developing process. JP OPI Publication No. 3-271753/1991 and so forth, therefore, overcome the above-mentioned problem in such a manner that a developer layer is made thinner to bring a distance between a latent image carrier member and a developer carrier member (developing roller) closer so that the electric field of a development can be intensified. As a means for achieving an extreme thin developer layer, there are the following known means; namely, Item 1. a means for pressing a developer layer regulating rod against the surface of a developing roller; Item 2. another means for regulating a developer layer by bringing an elastic blade into contact with the surface of a developing roller; and Item 3. a further means for regulating a developer layer by keeping a specific gap between a non-elastic blade and the surface of a developing roller. Among the means, the following means are effective to form a layer having a stable layer thickness, namely; a means for pressing a developer regulating rod against the surface of a developing roller, mentioned in item 1; and a thin layer forming process carried out by making use of a rigid rod-type magnetic member, that is proposed in JP OPI Publication No. 2-50184/1990. However, when making use of the above-given processes, there is such a disadvantage that a developer used therein is received by an excessive stress, though there is such an advantage that a stable layer can be formed. Particularly when miniaturizing an equipment, it is expected that the state of things may getting more serious. The increase of the above-mentioned stress in forming a thin layer may cause the destroy or peeling-off of a carrier-coated layer and may also seriously affect the durability of a developer used. With the advance of the miniaturization of an equipment and a developing apparatus, it becomes an important thema for a two-component type developer how to electrically charge rapidly and properly within a period between a time when a toner is supplied and a time when the toner is transferred to a development nip section. Heretofore, it has been usual to add a negatively chargeable charge-control agent to a toner so as to improve the charge-rising property of a negatively chargeable developer. However, when making use of such a miniaturized developing apparatus as mentioned above, only the addition of a charge-control agent is not enough, because a toner is scattered in the developing apparatus and an image is also seriously fogged by the increase of the amount of a weakly charged toner. As a means for improving an electric charge rising property on a carrier side, a positive charge control agent is added to a carrier, such as described in JP OPI Publication No. 2-8860/1990. The positive charge controlled agents include, for example, a quaternary ammonium compound such as those disclosed in JP OPI Publication No. 52-10141/1977, and an alkyl pyridinium compound and an alkyl picolinium compound (including, for example, nigrosine SO and nigrosine EX) such as those disclosed in JP OPI Publication Nos. 56-11461/1981 and 54-158932/1979. These charge control agents an organic compound having a high cohesive property and, accordingly, they have a poor dispersibility. It has, therefore, been liable to produce a charge failure with toner, because a charge control agent is maldistributed or extricated in the coated layer of a carrier. When a toner component is fused to a carrier, that is, when producing a so-called spent in making a multicopying, the charge rising property cannot be stabilized in making the multicopying, because a charge control agent component made present on the surface of the carrier is covered by the toner component. As described in JP OPI Publication Nos. 57-168256/1982, 59-228261/1984, 63-71860/1988 and 2-110577/1990, the attempts for improving the environmental differences of chargeability between developers have been tried to inhibit the variation of a water-absorption by covering a magnetic particle with a silicon resin or by adding an inorganic fine particle subjected to a hydrophobic treatment to a coated layer. However, even in the above-mentioned attempts, the hydrophobic treatment cannot be enough for allowing to stand under the conditions of a high temperature and a high humidity for a long time, but a variation of the charging function of a carrier is observed and, there still remains such a problem that a developability is varied by the variation of the amount of a developer transported, that is produced in a thin-layer forming section by the variation of the above-mentioned charging function of the carrier. As the means for preventing a chargeability variation produced by a toner-spent, it has been carried out the addition of silica with the purpose of abrading a spent toner, as described in JP OPI Publication Nos. 54-21730/1979, 58-117555/1983 and 59-232362/1984. However, silica applied thereto has a few abrading effect, because it is usually the spherical form. Further, in the case of such a system having a great stress as in a thin-layer forming process, silica has such a defect that it is split off. Therefore, the abrading effect of the silica cannot be kept on, though the spent production may be relatively retarded as compared to a carrier without adding silica thereto, and silica is completely split off after making a multicopying and, thereby, a lot of the spent are produced. Therefore, a charged amount is seriously varied so that a toner flying and a background fog are resultingly induced. SUMMARY OF THE INVENTION It is an object of the invention to provide each of such a developer and an image forming process as that a charge-rising property is excellent, that neither fog nor toner flying can be produced for a long time, particularly that a carrier coated layer cannot be destroyed even in a thin developer layer forming process that may give a great stress to a developer, and besides that any toner spent cannot be produced on a carrier. To try to improve a charge-rising, the positive chargeability of a carrier is robe improved. Further, to prevent a toner spent production, an abrading effect is to be provided to a carrier. The objects of the invention can be achieved thereby or by the following constitution. The above-mentioned problems can be solved in the following image forming process. In an image forming process comprising making a developer comprising a colored toner particle containing at least a binder resin and a colorant and a carrier to be a thin developer layer having a thickness within the range of 20 to 800 μm by making use of a developer regulating member and non-contact developing an electrostatic latent image on a latent image carrier member, wherein the above-mentioned carrier is a carrier for negatively chargeable developer use that is coated with a magnesium compound and a resin over a magnetic particle. A magnesium compound of to the present invention can be selected from the group consisting of magnesium oxide, magnesium hydroxide and a hydroxidized magnesium compound. And, in the course of preparing the above-mentioned carrier of the invention, magnesium oxide, magnesium hydroxide and a hydroxidized magnesium compound each applicable thereto are preferable to have a single crystal structure in which a crystal is grown up in a vapor-phase reaction. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a rod type development unit; FIG. 2 illustrates a soft blade type development unit; FIG. 3 illustrates a hard blade type development unit; and FIG. 4 is a schematic illustration of Konica 9028 (a modified model) used in the invention. DETAILED DESCRIPTION OF THE INVENTION The cause of varying a charged amount under the conditions of a high temperature and a high humidity is a charging property variation produced by that the component materials of a developer absorb the water content of the air in the course of aging the developer. Particularly about a carrier, it has been tried to prevent the carrier from the above-mentioned variation of a water-absorption, by adding an inorganic fine particle subjected to a hydrophobic treatment to a coated layer. However, the above-mentioned measure has still not been satisfactory. A magnesium hydroxide compound or a magnesium compound subjected to a hydroxidizing treatment used in the present invention is excellent in the aging stability of the charging property to a water-content in the air and capable of displaying an excellent positive chargeability. Therefore, a carrier containing the compound can give a stable negative-charge to a toner for a long time even under the conditions of a high temperature and a high humidity. Further, by adding magnesium oxide compound of the present invention to a carrier, the above-mentioned effect can be achieved. The reason thereof is that magnesium oxide compound has a very high positive chargeability, so that a toner can readily be negatively charged when adding it to a carrier. Therefore, a charge rising property can be excellent and neither fog nor toner flying may be produced even when a small amount of a developer is used. Besides the above, a stable charge rising property can be enjoyed for a long time, because it is a hard inorganic material and, when it is composed of single crystal structure, a toner spent produced when carrying out a multicopying operation can gradually be shaved off by the friction of the carriers each having a sharp edge. Carrier Applicable to the Present Invention Magnetic particle Magnetic particles include, for example, those made of iron, ferrite or magnetite, those made of a metal such as iron, nickel or cobalt and an alloy or a compound containing such a metal as given above. Among them, it is preferable when making use of a magnetic particle having (a density within the range of 3 to 7 g/cm 3 ), because they may readily be mixed up in a developing apparatus and also because a stress may be reduced when a developer receives the stress when they are stirred to be mixed up. Besides the above, when carrying out a non-contact development, a developer layer is to inevitably be thinned. It is, therefore, preferable that a saturated magnetization is to be within the range of 15 to 40 emu/g and a volume average particle-size is to be within the range of 10 to 60 μm. Resin for carrier coating As a coating resin for constituting the resin-coated layer of a carrier, there is no special limitation thereto, provided that a resin can give a negatively frictional charge to the subject toner, by the friction with the toner. The resins applicable thereto include, for example, a styrene type resin, an acrylic type resin, a styrene-acrylic resin, a vinyl type resin, an ethylene type resin, a rosin-denatured resin, a polyamide resin and a polyester resin. These resins may also be used in combination. Magnesium oxide Magnesium oxide can be prepared by heat-decomposing magnesium carbonate, magnesium hydroxycarbonate or magnesium hydroxide. Magnesium oxide prepared in a vapor-phase reaction can be prepared by oxidizing a metal magnesium at an oxygen atmosphere. Magnesium oxide prepared in this process is high in purity and capable of making the particle-size thereof smaller. Magnesium hydroxide Magnesium hydroxide may be prepared by adding an alkali to an aqueous solution of a magnesium salt of magnesium oxide and then by heating and pressurizing the resulting mixture. Magnesium hydroxide prepared in a vapor-phase reaction can be prepared by hydroxidizing a metal magnesium vapor in a steam atmosphere. Hydroxidized magnesium compound Hydroxidized magnesium compound can be prepared by hydroxidizing magnesium oxide, magnesium carbonate or the like. A hydroxidizing treatment is carried out by making aqueous vapor act on magnesium oxide or magnesium carbonate. To be more concrete, the above-mentioned treatment may be performed by allowing the particle of magnesium oxide or magnesium carbonate to stand for one hour under the atmosphere of 50° C. and 80% RH. In this case, they may be mixed up in a specific vessel or may also be treated by making use of a fluidized bed device. A process for preparing magnesium oxide or magnesium carbonate which is to serve as a core may be performed in the following manner. For example, a trihydrate crystal may be prepared in such a manner that, while putting carbon dioxide through an aqueous magnesium salt solution, sodium carbonate is added thereto. And, an anhydrous salt may be prepared by drying and dehydrating the trihydrate salt crystal in carbon dioxide flow. Further, with magnesium prepared in a vapor-phase reaction, a single crystal may be produced by reacting a metal magnesium vapor with and in the atmosphere of aqueous vapor containing carbon dioxide. In this patent specification, the expression, a "vapor-phase reaction", means a "vapor with vapor reaction", namely, a reaction of a metal magnesium vapor with a gas (such as oxygen gas, aqueous vapor and carbon dioxide gas) for forming a magnesium compound. Also in this patent specification, a magnesium compound produced in any other processes than the above-mentioned process of "vapor-phase reaction" shall be regarded as a "polycrystal magnesium compound". It is preferable that a magnesium compound particle applicable to the invention is to have a number average particle-size within the range of 1 to 200 nm and a BET specific surface area within the range of 500 to 10 m 2 /g. However, from the viewpoint of dispersibility, it is further preferable that such a particle as mentioned above is to have a number average particle-size within the range of 5 to 120 nm and a BET specific surface area within the range of 200 to 10 m 2 /g, respectively. If a particle has a particle-size of smaller than 1 nm or a specific surface area of not narrower than 500 m 2 /g, a spent prevention effect can hardly be realized. If a particle has a particle-size of exceeding 200 nm and a specific surface area of not wider than 10 m 2 /g, the dispersion thereof in a coated layer can hardly be made and the free components thereof are increased, so that the chargeability thereof to a toner is liable to be spoiled. The above-mentioned number average particle-size is to be obtained from an image magnified 10,000 times through a transmission type electron microscope. A magnesium compound may be added in a proportion within the range of, preferably, 0.5 to 70% by weight in a coated layer and, more preferably, 1 to 60% by weight therein. If a proportion to be added is less than 0.5% by weight, the effects would not be satisfactory and, if exceeding 70% by weight, a coated layer can hardly be formed, because there are too much inorganic substances, so that a durability deterioration such as a delamination of a layer may be induced. A layer thickness of a carrier-coated layer is to be within the range of, preferably, 0.5 to 4.5% by weight of an amount containing a resin particle and, more preferably, 1.0 to 3.0% by weight thereof. If a coated layer thickness is thinner than 0.5% by weight, the destroy of a core (or a magnetic particle) is liable to produce when preparing a carrier, so that there may be a danger of producing the unevenness of a coated layer. On the contrary, if exceeding 4.5% by weight, an adhesion force to a magnetic particle may be lowered, because a coated layer thickness is increased, so that a layer delamination and so forth may be induced. Toner Any common types of toner may be used. It is, however, preferable to use a toner externally added with an inorganic fine particle capable of improving a developability and cleanability through the improvement of a fluidity. As the above-mentioned inorganic fine particles, the following fine particles are preferably be used from the viewpoints of a capability of providing a negative chargeability and an effect of improving a fluidity; namely, a hydrophobic silica fine particle and a hydrophobic titania fine particle each treated on the surface thereof with a coupling agent containing an alkyl group. As for the binder resins, a polyester resin is preferably used from the viewpoint of the capacity of providing a negative chargeability. Besides, for more improving a charge rising property, it is further preferable to add a negatively chargeable charge control agent such as an azo type chrome complex. Process for Forming a Thin Layer Developer Layer Thickness A layer thickness is to be within the range of, preferably, 20 to 800 μm and, more preferably, 20 to 500 μm. If it is not thicker than 20 μm, the subject developer cannot be formed into a satisfactory and stable layer. If it is not thinner than 800 μm, the developer may be seriously scattered about by a centrifugal force produced by the rotation of a developing roller. The developer layer thickness of the present invention is defined as a developer layer thickness at the point on the surface of a developer carrier member (a developing roller) closest to a photoconductor. The developer layer thickness can be calculated by using an optical microscope with a scale. The means for achieving a thin layer having a developer layer thickness include the following means, for example, Item 1. a means for pressing a developer layer regulating member against the surface of a developing roller, (See FIG. 1); Item 2. another means for regulating a developer layer by bringing an elastic blade into contact with the surface of a developing roller, (See FIG. 2); and Item 3. a further means for regulating a developer layer by keeping a specific gap between a non-elastic blade and the surface of a developing roller, (See FIG. 3). This invention shall not be limited thereto, provided that a developer layer thickness can be specified within the scope mentioned above. For example, when making use of such a thin layer forming means as mentioned in the above paragraph 1; a diameter of the developer layer regulation member is preferable to be within the range of 1 mm.O slashed. to 10 mm.O slashed.; concerning a rigidity of the toner layer regulation bar member, it is allowed to use the following materials, namely; a variety of magnetic metals including iron having a rigidity of not lower than 10 4 kg/cm 2 and the alloys thereof; a hard resin containing a magnetic powder having a rigidity of the order of (1.0 to 10)×10 4 kg/cm 2 ; iron plated thereon with chrome or the like; and an iron alloy; and as a pressing force applied to a developing roller, it is reasonable to be within the range of 1 to 20 gf/mm and, particularly preferable to be within the range of 2 to 10 gf/mm. When making use of such a thin layer forming means as mentioned in the above paragraph 2, as a pressing force applied to a developing roller, it is reasonable to be within the range of 1 to 20 gf/mm and, particularly preferable to be within the range of 2 to 10 gf/mm. As such a non-elastic blade as mentioned above, it is allowed to use a polyurethane rubber sheet having a thickness of the order within the range of 1 to 5 mm, and a phosphor bronze plate, an SUS plate and an aluminum plate each having a thickness within the range of 50 μm to 500 μm. When making use of such a thin layer forming means as mentioned in the above paragraph 3, a gap between a non-elastic blade and the surface of a developing roller is preferable to be within the range of 20 μm to 800 μm. As such a non-elastic blade as mentioned above, it is allowed to use a phosphor bronze plate, an SUS plate and an aluminum plate each having a thickness within the range of 500 μm to 5,000 μm. Physical Property Measurement Apparatus In this invention, the following apparatuses and materials were used. Magnesium compounds (See Table 1) Particle-size: A number average particle-size obtained by observing the subject particles through a transmission type electron microscope Model JEM-2000FX (manufactured by Nihon Denshi Co.) and then by measuring them through an image analyzer Model SPICA (manufactured by Nihon Avionix Co.). BET specific surface area: obtained through a BET specific surface area measurement apparatus Model Flow Sorb 2300 (manufactured by Shimazu Mfg. Works) Carrier Volume average particle-size: Microtrack SRA Model MK-II (manufactured by Nitsukiso Co., Ltd.) Improvement of the durability of a layer coated on a carrier Magnesium oxide contained in a coated layer can serve as a filler suitable for the coated layer so as to improve the durability of the coated layer and, at the same time, to increase an adhesion strength on the interface between the coated layer and a core, because it has a high affinity to a core member (or a magnetic particle), so that the coated layer cannot be peeled off. EXAMPLES NOW, the invention will be detailed with reference to the following examples. However, the embodiments of the invention shall not be limited thereto. In the examples given hereinafter, the term, "a part or parts", means "a part or parts by weight". Example 1 Preparation of Toner ______________________________________Polyester resin 100 partsCarbon black 10 partsPolypropylene 5 partsAzo type chromium complex, (a negatively 3 partschargeable charge control agent)______________________________________ The above-given components were mixed up, kneaded, pulverized and then classified so as to obtain a powder having a volume average particle-size of 8 μm. Further, 100 parts of the resulting powder and 2.0 parts of hydrophobic silica fine particles (having a particle-size of 16 nm) were mixed up by making use of a Henschel mixer, so that toner A could be obtained. Preparation of Carrier When an external magnetic field of 1000 Oe was applied to a surface of a Cu--Zn ferrite particle having a specific gravity and a volume average particle size of 50 μm, a saturated magnetization of 25 emu/g was obtained on the surface of the ferrite particle. On the resulting surface of the ferrite, a copolymer having a composition of MMA/st=6/4 was added so as to have an average coated layer thickness of 2.0 μm and the additives shown in the following Table 1 were contained in the coated layer. TABLE 1______________________________________Additive Average BET specific AmountCarrier particle- surface area addedNo. Kind size (in nm) (in m.sup.2 /g) (in wt %)______________________________________C-1 MgO (single 12 152 10 crystal)C-2 MgO (single 15 155 10 crystal)C-3 MgO (single 50 31 30 crystal)C-4 MgO (single 111 14 30 crystal)C-5 MgO (poly- 45 78 30 crystal)C-6 MgO (single 12 152 60 crystal)HC-1 Nigrosine SO 302 5 3 (a positively chargeable charge control agent)HC-2 R-972 (hydro- 16 120 50 phobic silica)HC-3 -- -- -- --______________________________________ * An average particlesize indicates a number average particlesize Preparation of Developer The above-given carriers each in an amount of 460 g and 40 g of toner were mixed together by making use of a V-type mixer under the testing environment for 20 minutes, so that the developers for practical testing use were prepared, respectively. Development conditions 1 for evaluating a practical test (on a plate having a developer layer thickness of 50 μm) Evaluation on a Practical Test There used a Konica Modified Model 9028 (See FIG. 4), manufactured by Konica Corp. Konica Modified Model 9028, manufactured by Konica Corp., is a non-contact, reversal development type multicolored image forming apparatus that is comprised of an organic photoreceptor and a cleaning blade. The following development conditions were used therein. A developer adhering to the surface of a development sleeve was formed into a thin layer by making use of a magnetic stainless-steel made pressure regulation rod member (of the SUS 416 type having a curvature radius of 1.5 mm and a pressure regulation force of 5 gf/mm). The resulting thinned developer layer is transported to a development region in the state of non-contact with an organic photoreceptor. An electrostatic latent image resulted on the photoreceptor is then developed under the oscillating electric field obtained by applying an AC bias voltage to the development sleeve. ______________________________________Photoreceptor surface potential: -700 vDC bias: -500 vAC bias (Vp-p): 1.6 kvAC frequency: 1.6 kHzDevelopment sleeve revolutions: 400 rpm(Developing roller revolution)Development gap: 0.5 mmDeveloper layer thickness in the developer layer form- 50 μming sectionDevelopment conditions 2 for evaluating a practicaltest (on a plate having a developer layer thickness of500 μm)______________________________________ Evaluation on a Practical Test There used a Konica Modified Model 9028, manufactured by Konica Corp. Konica Modified Model 9028, manufactured by Konica Corp., is a non-contact, reversal development type multicolored image forming apparatus that is comprised of an organic photoreceptor and a cleaning blade. The following development conditions were used therein. A developer adhering to the surface of a development sleeve was formed into a thin layer by making use of a magnetic stainless-steel made pressure regulation blade member (of the SUS 416 type having a thickness of 1 mm and a gap of 500 μm between the sleeve and the blade. The resulting thinned developer layer is transported to a development region in the state of non-contact with an organic photoreceptor. An electrostatic latent image resulted on the photoreceptor is then developed under the oscillating electric field obtained by applying an AC bias voltage to the development sleeve. ______________________________________Photoreceptor surface potential: -700 vDC bias: -500 vAC bias (Vp-p): 2.2 kvAC frequency: 1.6 kHzDevelopment sleeve revolutions: 400 rpmDevelopment gap: 0.9 mmDeveloper layer thickness in the developer layer form- 500 μming section______________________________________ TABLE 2__________________________________________________________________________Development conditions for practical evaluation (1) Fog density Carrier after coverage Coated Toner fly- making Varied layerSample Carrier ing (in 50000 (in amount destroyedNo. evaluated number) copies wt %) (in %) (in number) Remarks__________________________________________________________________________1 C-1 2 0 1.98 -0.02 1 Invention2 C-1 3 0.004 1.98 -0.02 2 Invention3 C-2 1 0.003 1.97 -0.03 2 Invention4 C-2 4 0.003 1.95 -0.05 1 Invention5 C-3 3 0.006 1.98 -0.02 3 Invention6 C-3 3 0.008 1.96 -0.04 2 Invention7 C-4 4 0.005 1.99 -0.01 2 Invention8 C-5 1 0.006 1.99 -0.01 3 Invention9 C-6 1 0.002 1.98 -0.02 1 Invention10 HC-1 180 0.052 2.68 +0.68 62 Comparison11 HC-1 387 0.062 2.91 +0.91 52 Comparison12 HC-2 683 0.061 2.61 +0.61 59 Comparison13 HC-2 520 0.073 2.70 +0.70 69 Comparison14 HC-3 725 0.115 2.84 +0.84 94 Comparison__________________________________________________________________________ TABLE 3__________________________________________________________________________Development conditions for practical evaluation (2) Carrier coverage Coated Toner Fog Amount layerSample flying density in varied destroyedNo. (in number) at 50k c wt % (in %) (in number) Remarks__________________________________________________________________________15 C-1 3 0 1.98 -0.02 2 Invention16 C-1 2 0.001 1.97 -0.03 1 Invention17 C-2 1 0 1.96 -0.04 1 Invention18 C-2 2 0.003 1.98 -0.02 2 Invention19 C-3 2 0.003 1.95 -0.05 2 Invention20 C-3 4 0.002 1.95 -0.05 3 Invention21 C-4 3 0.002 1.98 -0.02 2 Invention22 C-5 2 0.003 1.95 -0.05 3 Invention23 C-6 1 0.002 1.98 -0.02 2 Invention24 HC-1 250 0.054 2.58 0.58 59 Comparison25 HC-1 281 0.041 2.92 0.92 86 Comparison26 HC-2 596 0.068 2.93 0.93 66 Comparison27 HC-2 832 0.054 2.65 0.65 72 Comparison28 HC-3 452 0.107 2.66 0.66 88 Comparison__________________________________________________________________________ (1) Fogginess After completing 50,000 copies, the relative density of the fog produced in the white background of each copied image was measured through an image density measurement apparatus (a densitometer Model RD918 manufactured by Macbeth Co.) (2) Toner flying inside the apparatus The probe of a particle-counter (Model KC-01B manufactured by Lion Co., Ltd.) was set inside to the position 1 cm lower than the top of a development device. After completing 50,000 copies, the numbers of toner flied were counted in the 10 μm-size channel section. (3) Destruction of coated layer After completing 50,000 copies, 100 pieces of carrier were observed through a scanning type electron microscope and the carriers having coated layer destroyed were then counted and judged. (4) Antispent property (coating rate) After completing 50,000 copies, the resulting developer was washed with water and the toner was separated. After drying the rest of them, the carrier was obtained. The coated layer of the resulted carrier was dissolved with methylethyl ketone. After that, the weight of the resulted magnetic material (or the magnetic particle) was measured and the coverage was calculated out in accordance with the following formula. Formula (A-B)/B=Carrier coating rate (by wt %) wherein A: the weight of a carrier obtained after dried; and B: the weight of a magnetic material obtained after dissolving a coated layer As is obvious from Tables 2 and 3, even in an image forming process applied with a thin layer forming means giving a great stress to a developer, the invention was proved that any carrier was not destroyed, that any toner spent was not produced, that a charge rising property was excellent, and that any fog and toner flying were not produced for a long time. Example 2 Developers were prepared in the same manner as in Example 1, except that the carriers were prepared in such a manner as shown in Table 4. TABLE 4______________________________________Additive Average BET specific AmountCarrier particle- surface area addedNo. Kind size (in nm) (in m.sup.2 /g) (in wt %)______________________________________C-1 Hydroxidized 13 152 10 MgOC-2 Hydroxidized 15 155 10 MgcO.sub.3C-3 Hydroxidized 47 33 35 MgOC-4 Hydroxidized 113 14 30 MgcO.sub.3C-5 Hydroxidized 13 152 60 MgOHC-1 Not added -- -- --HC-2 Nigrosine SO 302 5 3 (a charge control agent)HC-3 R-972 (hydro- 16 120 50 phobic silica)______________________________________ * An average particlesize was indicated by a number average particlesize. The results of the evaluation made under the above-mentioned development conditions (1) and (2) will be shown in Tables 5 and 6, respectively. TABLE 5__________________________________________________________________________ Developability Toner flying Fog density After After After Carrier Initial 50,000 Initial 50,000 Initial 50,000Sample evaluated stage copies stage copies stage copies Remarks__________________________________________________________________________1 C-1 1.21 1.20 2 1 0.001 0.002 Invention2 C-2 1.23 1.22 0 2 0.002 0.002 Invention3 C-3 1.19 1.19 1 2 0.002 0.001 Invention4 C-4 1.20 1.20 1 30 0.001 0.005 Invention5 HC-1 1.33 1.64 10 2089 0.009 0.031 Comparison6 HC-2 1.27 1.49 4 1789 0.009 0.027 Comparison7 HC-3 1.25 1.57 6 1799 0.007 0.024 Comparison__________________________________________________________________________ (1) Developability A 2.0 cm×5.0 cm-sized patch having an original density of 1.3 was developed, and the toner amount thereof per cm 2 was calculated out. (2) Toner flying and fog density The resulted toner flying and toner density were evaluated by the same methods described in Example 1. TABLE 6__________________________________________________________________________Evaluation Developability Toner flying (in mg/cm.sup.2) (in number) Fog densitySample Initial Initial InitialNo. stage 50k c stage 50k c stage 50k c Remarks__________________________________________________________________________ 9 C-1 1.23 1.22 1 1 0.001 0.003 Invention10 C-2 1.22 1.22 3 2 0.001 0.003 Invention11 C-3 1.19 1.19 2 2 0.001 0.002 Invention12 C-4 1.19 1.2 1 3 0.002 0.002 Invention13 C-5 1.22 1.22 2 1 0.001 0.02 Invention14 HC-1 1.35 1.67 21 2320 0.012 0.082 Comparison15 HC-2 1.28 1.55 32 3250 0.013 0.122 Comparison16 HC-3 1.25 1.66 12 4011 0.021 0.068 Comparison__________________________________________________________________________ As is obvious from Tables 5 and 6, the samples of the invention were proved to have all the excellent characteristics including the developability, toner flying and fog density. Example 3 The developers were prepared in the same manner as in Example 1, except that the carriers were prepared in such a manner as shown in Table 7. TABLE 7______________________________________Additive Average particle- BET specific AmountCarrier size surface area addedNo. Kind (in nm)* (in m.sup.2 /g) (in wt %)______________________________________C-1 Mg(OH).sub.2 12 152 10 (single crystal)C-2 Mg(OH).sub.2 15 155 10 (single crystal)C-3 Mg(OH).sub.2 50 31 30 (single crystal)C-4 Mg(OH).sub.2 111 14 30 (single crystal)C-5 Mg(OH).sub.2 (poly- 45 78 30 crystal)C-6 Mg(OH).sub.2 12 152 60 (single crystal)HC-1 R-972 (hydro- 16 120 50 phobic silica)HC-2 -- -- -- --______________________________________ *The average particlesize indicates a number average particlesize. Preparation of Developer The developers for practical testing use were prepared by mixing 460 g each of the above-mentioned carriers and 40 g of toner through a V type mixer for 20 minutes in the testing environment. (1) Charged amount The charged amount was measured by blowing for 60 minutes at a blow-off pressure of 1.0 kg/cm 2 , by making use of a charged amount distribution measurement apparatus Model TB-200 manufactured by Toshiba, that is used in a blow-off method. (2) Developability A 2.0 cm×5.0 cm-sized patch having an original density of 1.3 was developed and the developed toner amount per cm 2 was calculated out. TABLE 8__________________________________________________________________________(1) Charged amountSample Carrier Charged amount (in μc/g) AmountNo. evaluated 0 min 5 min 30 min 1 hr 3 hrs 6 hrs 12 hrs 24 hrs 1 wk. varied Remarks__________________________________________________________________________1 C-1 29.1 28.9 29.0 29.0 30.0 29.8 29.8 30.0 30.1 1.0 Invention2 C-2 29.0 29.3 29.6 29.6 29.6 29.7 29.7 30.0 30.2 1.2 Invention3 C-3 28.6 28.6 28.5 28.5 28.4 28.5 28.5 28.5 29.0 0.4 Invention4 C-4 29.2 29.0 29.1 30.2 30.1 30.2 30.3 30.1 29.6 0.4 Invention5 C-5 29.2 30.0 30.2 30.0 30.0 30.2 30.0 30.0 29.9 0.7 Invention6 C-6 29.1 29.2 29.1 29.2 29.2 29.2 29.3 29.4 29.5 0.4 Invention7 HC-1 28.5 24.2 21.2 18.6 16.2 13.6 12.9 11.0 8.4 20.1 Comparison8 HC-2 29.2 23.5 19.2 17.4 14.8 12.0 11.4 10.1 7.6 21.6 Comparison__________________________________________________________________________ The results of the evaluations made under the above-mentioned development conditions (1) and (2) will be shown in Table 9 and 10, respectively. TABLE 9__________________________________________________________________________Sample Carrier Developability (mg/cm.sup.2) AmountNo. evaluated 0 min 5 min 30 min 1 hr 3 hrs 6 hrs 12 hrs 24 hrs 1 wk. varied Remarks__________________________________________________________________________1 C-1 1.21 1.20 1.19 1.20 1.20 1.21 1.21 1.20 1.20 0.01 Invention2 C-2 1.27 1.24 1.22 1.20 1.20 1.25 1.25 1.25 1.23 0.05 Invention3 C-3 1.27 1.25 1.26 1.23 1.25 1.26 1.26 1.26 1.27 0 Invention4 C-4 1.21 1.22 1.22 1.20 1.21 1.22 1.21 1.21 1.21 0 Invention5 C-5 1.24 1.25 1.24 1.23 1.22 1.21 1.22 1.21 1.23 0.02 Invention6 C-6 1.24 1.24 1.24 1.24 1.24 1.23 1.23 1.23 1.23 0.01 Invention7 HC-1 1.20 1.23 1.24 1.26 1.32 1.39 1.50 1.52 1.54 0.34 Comparison8 HC-2 1.22 1.30 1.37 1.39 1.43 1.47 1.53 1.57 1.61 0.39 Comparison__________________________________________________________________________ TABLE 10__________________________________________________________________________Sample Carrier Developability (mg/cm.sup.2) AmountNo. evaluated 0 min 5 min 30 min 1 hr 3 hrs 6 hrs 12 hrs 24 hrs 1 wk. varied Remarks__________________________________________________________________________1 C-1 1.25 1.24 1.25 1.24 1.24 1.25 1.25 1.24 1.25 0.01 Invention2 C-2 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 0 Invention3 C-3 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 0 Invention4 C-4 1.27 1.27 1.27 1.27 1.27 1.27 1.27 1.27 1.27 0 Invention5 C-5 1.26 1.26 1.25 1.26 1.25 1.25 1.24 1.24 1.24 0.02 Invention6 C-6 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 0 Invention7 HC-1 1.21 1.23 1.24 1.25 1.28 1.32 1.34 1.41 1.41 0.2 Comparison8 HC-2 1.22 1.21 1.3 1.32 1.34 1.36 1.39 1.39 1.42 0.2 Comparison__________________________________________________________________________ As is obvious from Tables 9 and 10, the samples of the present invention show an excellent improved result in developability respectively.

Disclosed is a two component type developer for negatively chargeable developer use, comprising a carrier and a colored toner particle comprising a binder resin and a colorant, wherein said carrier comprises a magnetic particle having thereon a resin coated layer containing a resin and a magnesium compound.

This application is a divisional of U.S. application Ser. No. 09/669,051, filed Sep. 24, 2000, now U.S. Pat. No. 7,063,838 B1 issued on Jun. 20, 2006, which claims the benefit of U.S. Provisional Application Ser. No. 60/155,938, filed Sep. 24, 1999, each of which is incorporated by reference herein in its entirety. STATEMENT REGARDING GOVERNMENT RIGHTS This invention was made with government support under grant no. HL07712-07 awarded by the National Institutes of Health. The government has certain rights in the invention. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to methods of opening obstructed biological conduits. Preferred methods of the invention include methods and systems for opening obstructed biological conduits using local delivery of a therapeutic agent, particularly a protease, to lyse the extracellular matrix of the obstructing tissue. 2. Background Obstructions to biological conduits frequently result from trauma to the conduit which can result from transplant, graft or other surgical procedures wherein the extracellular matrix of the obstructing tissue largely comprises collagen. Balloon angioplasty is a common initial treatment for stenosis or stricture obstruction that yields excellent initial results (Pauletto, Clinical Science , (1994) 87:467-79). However, this dilation method does not remove the obstructing tissue. It only stretches open the lumen, the trauma of which has been associated with the release of several potent cytokines and growth factors that can cause an injury which induces another round of cell proliferation, cell migration toward the lumen and synthesis of more extracellular matrix. Consequently, balloon angioplasty is associated with restenosis in nearly all patients (Pauletto, Clinical Science , (1994) 87:467-79). There is currently no treatment that can sustain patency over the long term. The extracellular matrix, which holds a tissue together, is composed primarily of collagen, the major fibrous component of animal extracellular connective tissue (Krane, J. Investigative Dermatology (1982) 79:83s-86s; Shingleton, Biochem. Cell Biol., (1996) 74:759-75). The collagen molecule has a base unit of three stands of repeating amino acids coiled into a triple helix. These triple helix coils are then woven into a right-handed cable. As the collagen matures, cross-links form between the chains and the collagen becomes progressively more insoluble and resistant to lysis. When properly formed, collagen has a greater tensile strength than steel. Not surprisingly, when the body builds new tissue collagen provides the extracellular structural framework such that the deposition of hard collagen in the lesion can result in duct obstruction. Benign biliary stricture results in obstruction of the flow of bile from the liver and can result in jaundice and hepatic dysfunction. If untreated, biliary obstruction can result in hepatic failure and death. Biliary strictures can form after duct injury during cholecystectomy. They can also from at biliary anastomoses after liver transplantation and other biliary reconstructive surgeries (Vitale, Am. J. Surgery (1996) 171:553-7; Lilliemoe, Annals of Surgery (1997) 225). Historically, benign biliary stricture has been treated surgically by removing the diseased duct segment and reconnecting the duct end-to-end, or connecting the duct to the bowel via a hepaticojejunostomy loop (Lilliemoe, Annals of Surgery (1997) 225). These long and difficult surgeries have significant morbidity and mortality due to bleeding, infection, biliary leak, and recurrent biliary obstruction at the anastomosis. Post-operative recovery takes weeks to months. More recently, minimally invasive treatments such as percutaneous balloon dilation have been utilized, yielding good initial biliary patency results (Vitale, Am. J. Surgery (1996) 171:553-7, Lilliemoe, Annals of Surgery (1997) 2250). However, balloon dilation causes a localized injury, inducing a healing response that often results in restenosis (Pauletto, Clinical Science, (1994)87:467-79). Long-term stenting at the common bile duct with flexible biliary drainage catheters is another minimally invasive alternative to surgery (Vitale, Am. J. Surgery (1996) 171:553-7). However, these indwelling biliary drainage catheters often become infected, or clogged with debris, and must be changed frequently. At present, long-term treatment of biliary stricture remains a difficult clinical problem. Patients with chronic, end-stage renal failure may require replacement of their kidney function in order to survive. In the United States, long-term hemodialysis is the most common treatment method for end stage chronic renal failure. In 1993, more than 130,000 patients underwent long term hemodialysis (Gaylord, J. Vascular and Interventional Radiology (1993) 4:103-7); more than 80% of these patients implement hemodialysis through the use of a synthetic arteriovenous graft (Windus, Am. J. Kidney Diseases (1993) 21:457-71). In a majority of these patients, the graft consists of a 6 mm Gore-Tex tube that is surgically implanted between an artery and a vein, usually in the forearm or upper arm. This high flow conduit can then be accessed with needles for hemodialysis sessions. Nearly all hemodialysis grafts fail, usually within two years, and a new graft must be created surgically to maintain hemodialysis. These patients face repeated interruption of hemodialysis, and multiple hospitalizations for radiological and surgical procedures. Since each surgical graft revision consumes more available vein, eventually they are at risk for mortality from lack of sites for hemodialysis access. One estimate placed the cost of graft placement, hemodialysis, treatment of complications, placement of venous catheters, hospitalization costs, and time away from work at as much as $500 million, in 1990 alone (Windus, Am. J. Kidney Diseases (1993) 21:457-71). The most frequent cause of hemodialysis graft failure is thrombosis, which is often due to development of a stenosis in the veinjust downstream from the graft-vein anastomosis (Safa, Radiology (1996) 199:653-7. Histologic analysis of the stenosis reveals a firm, pale, relatively homogeneous lesion interposed between the intimal and medial layers of the vein which thickens the vessel wall and narrows the lumen (Swedberg, Circulation (1989) 80:1726-36). This lesion, which has been given the name intimal hyperplasia is composed of vascular smooth muscle cells surrounded by an extensive extracellular collagen matrix (Swedberg, Circulation (1989) 80:1726-36; Trerotola, J. Vascular and Interventional Radiology (1995) 6:387-96). Balloon angioplasty is the most common initial treatment for stenosis of hemodialysis grafts and yields excellent initial patency results (Safa, Radiology (1996) 199:653-7). However, this purely mechanical method of stretching open the stenosis causes an injury which induces another round of cell proliferation, cell migration toward the lumen and synthesis of more extracellular matrix. Consequently, balloon angioplasty is associated with restenosis in nearly all patients (Safa, Radiology (1996) 199:653-7). There is currently no treatment which can sustain the patency of synthetic arteriovenous hemodialysis grafts over the long term. Intimal hyperplasia research has focused largely on the cellular component of the lesion. The use of radiation and pharmaceutical agents to inhibit cell proliferation and migration are active areas of research (Hirai, ACTA Radiologica (1996) 37:229-33; Reimers, J. Invasive Cardiology (1998) 10:323-31; Choi, J. Vascular Surgery (1994) 19:125-34). To date, the results of these studies have been equivocal, and none of these new treatments has gained wide clinical acceptance. This matrix is composed predominantly of collagen and previous work in animals has demonstrated that systemic inhibition of collagen synthesis decreases the production of intimal hyperplasia (Choi, Archives of Surgery (1995) 130:257-261). During normal tissue growth and remodeling, existing collagen matrices must be removed or modified. This collagen remodeling is carried out by macrophages and fibroblasts, two cell types which secrete a distinct class of proteases called “collagenases” (Swedberg, Circulation (1989) 80:1726-36; Trerotola, J. Vascular and Interventional Radiology (1995) 6:387-96; Hirai, ACTA Radiologica (1996) 37:229-33). These collagenases rapidly degrade insoluble collagen fibrils to small, soluble peptide fragments, which are carried away from the site by the flow of blood and lymph. See also U.S. Pat. Nos. 5,981,568; 5,409,926; and 6,074,659. It thus would be desirable to provide new methods to relieve obstructions blocking flow through biological conduits. SUMMARY OF THE INVENTION I have now found new methods and systems for relieving an obstruction in a biological conduit, e.g. mammalian vasculature. Methods of the invention include administration to an obstruction site of a therapeutic agent that can preferably degrade (in vivo) the extracellular matrix of the obstructing tissue, particularly collagen and/or elastin. Preferred methods of the invention include administration to an obstruction of an enzyme or a mixture of enzymes that are capable of degrading key extracellular matrix components (including collagen and/or elastin) resulting in the solubilization or other removal of the obstructing tissue. Methods and systems of the invention can be applied to a variety of specific therapies. For example, methods of the invention include treatment of biliary stricture with the use of exogenous collagenase, elastase or other agent, whereby an enzyme composition comprising collagenase, elastase or other agent is directly administered to or into (such as by catheter injection) the wall of the lesion or other obstruction. The enzyme(s) dissolves the collagen and/or elastin in the extracellular matrix, resulting in the solubilization of fibrous tissue from the duct wall near the lumen, and a return of duct flow or opening. Methods of the invention also include pretreating an obstruction (e.g. in a mammalian duct) with collagenase, elastase or other agent to facilitate dilation such that if treatment under enzymatic degradation conditions alone is insufficient to reopen a conduit, then conventional treatment with e.g. balloon dilation is still an option. It has been found that enzymatic degradation pre-treatment in accordance with the invention can improve the outcome of balloon dilation since enzyme treatment partially digests the collagen fibrils. Therefore, the overall effect will be a softening of the remaining tissue. The softened tissue is more amenable to balloon dilation at lower pressures, resulting in less mechanical trauma to the duct during dilation. Preferably, the therapeutic agent is delivered proximately to a targeted site, e.g. by injection, catheter delivery or the like. A variety of therapeutic agents may be employed in the methods of the invention. Suitable therapeutic agents for use in the methods and systems of the invention can be readily identified, e.g. simply by testing a candidate agent to determine if it reduces an undesired vasculature obstruction in a mammal, particularly a coronary obstruction in a mammalian heart. Preferred therapeutic agents comprise one or more peptide bonds (i.e a peptidic agent), and typically contain at least 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more amino acids, preferably one or more of the natural amino acids. Preferred therapeutic agents include large molecules, e.g. compounds having a molecular weight of at least about 1,000, 2,000, 5,000 or 10,000 kD, or even at least about 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000 or 100,000 kD. Specifically preferred therapeutic agents for use in the methods and systems of the invention include proteases and other enzymes e.g. a collagenase such as Clostridial collagenase, a proteolytic enzyme that dissolves collagen, and/or an elastase such as a pancreatic elastase, a proteolytic enzyme that dissolves elastin. Preferred delivery of collagenase and other therapeutic agents of the invention include directly injecting the agent into the target lesion or other obstruction. Preferably, a homogeneous distribution of a therapeutic enzyme or enzyme mixture is administered to a target site with a drug delivery catheter. The therapeutic agent can then dissolve the key extracellular collagen components necessary to solubilize the obstructing tissue from the vessel wall near the lumen. Treatment methods of the invention provide significant advantages over prior treatment methodologies. For example, enzymatic degradation of one or more key components of the extracellular matrix gently removes the tissue obstructing the lumen. Additionally, collagenolysis or other therapeutic administration is relatively atraumatic. Moreover, collagenase also can liberate intact, viable cells from tissue. Therefore, treatment methods of the invention can remove both the source of mechanical obstruction and a source of cytokines and growth factors, which stimulate restenosis. A single or combination of more than one distinct therapeutic agents may be administered in a particular therapeutic application. In this regard, a particular treatment protocol can be optimized by selection of an optimal therapeutic agent, or optimal “cocktail” of multiple therapeutic agents. Such optimal agent(s) for a specific treatment method can be readily identified by routine procedures, e.g. testing selected therapeutic agents and combinations thereof in in vivo or in vitro assays. In another aspect of the invention, treatment compositions and treatment kits are provided. More particularly, treatment compositions of the invention preferably contain one or more enzymatic agents such as collagenase preferably admixed with a pharmaceutically acceptable carrier. Such compositions can be suitable packaged in conjunction with an appropriate delivery tool such as an injection syringe or a delivery catheter. The delivery device and/or treatment solution are preferably packaged in sterile condition. The delivery device and treatment composition can be packaged separately or in combination, more typically in combination. The delivery device preferably is adapted for in situ, preferably localized, delivery of the therapeutic agent directly into the targeted biological conduit obstruction. Typical subjects for treatment in accordance with the invention include mammals, particularly primates, especially humans. Other subjects may be treated in accordance with the invention such as domesticated animals, e.g. pets such as dogs, cats and the like, and horses and livestock animals such as cattle, pigs, sheep and the like. Subjects that may be treated in accordance with the invention include those mammals suffering from or susceptible to biliary stricture including benign biliary stricture, stenosis of hemodialysis graft, intimal hyperplasia, and/or coronary obstruction, and the like. As discussed above, methods of the invention may be administered as a pre-treatment protocol before another therapeutic regime such as a balloon angioplasty; during the course of another therapeutic regime, e.g. where a therapeutic composition of the invention is administered during the course of an angioplasty or other procedure; or after another treatment regime, e.g. where a therapeutic composition of the invention is administered after an angioplasty or administration of other therapeutic agents. Other aspects of the invention are disclosed infra. BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a common bile duct in a dog with a high grade stricture; FIG. 2 shows a common bile duct in a dog with a high grade stricture after treatment; FIG. 3 is a histology picture of a normal common bile duct from a dog; FIG. 4 is a histology picture of a common bile duct stricture from a dog with a high grade stricture before treatment; FIG. 5 is a histology picture of a common bile duct stricture from a dog after treatment with collagenase wherein the arrows denote the outer limit of collagen breakdown; and FIG. 6 shows a normal common bile duct in a dog. DETAILED DESCRIPTION OF THE INVENTION The present invention provides methods of introducing a therapeutic agent that is capable of degrading an extracellular matrix component to thereby facilitate the reopening of a constricted biological conduit. In particular, the invention provides for introduction to an obstructed biological conduit of a therapeutic agent that degrades collagen and/or elastin. The present invention further provides methods of dilating a biological conduit by introducing a therapeutic agent into a biological conduit, preferably an isolated segment of the conduit. In one embodiment of the present invention, the degradation of a stricture, lesion or other obstruction is accomplished by introducing one or more therapeutic agents that are capable of degrading one or more extracellular matrix components thereby facilitating the reopening of the constricted segment of the conduit. Major structural components of the extracellular matrix include collagen and elastin. Preferred therapeutic agents for use in accordance with the invention are able to interact with and degrade either one or both of collagen and elastin. As discussed above, a variety of compositions may be used in the methods and systems of the invention. Preferred therapeutic compositions comprise one or more agents that can solubilize or otherwise degrade collagen or elastin in vivo. Suitable therapeutic agents can be readily identified by simple testing, e.g. in vitro testing of a candidate therapeutic compound relative to a control for the ability to solubilize or otherwise degrade collagen or elastin, e.g. at least 10% more than a control. More particularly, a candidate therapeutic compound can be identified in the following in vitro assay that includes steps 1) and 2): 1) contacting comparable mammalian tissue samples with i) a candidate therapeutic agent and ii) a control (i.e. vehicle carrier without added candidate agent), suitably with a 0.1 mg of the candidate agent contacted to 0.5 ml of the tissue sample; and 2) detecting digestion of the tissue sample by the candidate agent relative to the control. Digestion can be suitably assessed e.g. by microscopic analysis. Tissue digestion is suitably carried out in a water bath at 37° C. Fresh pig tendon is suitably employed as a tissue sample. The tissue sample can be excised, trimmed, washed blotted dry and weighed, and individual tendon pieces suspended in 3.58 mg/ml HEPES buffer at neutral pH. See Example 1 which follows for a detailed discussion of this protocol. Such an in vitro protocol that contains steps 1) and 2) is referred to herein as a “standard in vitro tissue digestion assay” or other similar phrase. Preferred therapeutic agents for use in accordance with the invention include those that exhibit digestion activity in such a standard in vitro tissue digestion assay at least about 10 percent greater relative to a control, more preferably at least about 20% greater digestion activity relative to a control; still more preferably at least about 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100% greater digestion activity relative to a control. Appropriate therapeutic agents can comprise at least one and frequently several enzymes such that the therapeutic agent is capable of degrading both significant matrix components of tissue obstruction. Particularly preferable therapeutic agents will comprise either a collagenase or elastase or both. Specifically preferred are therapeutic agents comprising a highly purified, injectable collagenase preparation such as that produced from cultures of Clostridium histolyticum by BioSpecifics Technologies Corporation (Lynbrook, N.Y.). This enzyme preparation is composed of two similar but distinct collagenases. The Clostridial collagenases cleave all forms of collagen at multiple sites along the helix, rapidly converting insoluble collagen fibrils to small, soluble peptides. Also preferable are therapeutic agents comprising elastase, particularly pancreatic elastase, an enzyme capable of degrading elastin. Trypsin inhibitors also can be suitably employed as the therapeutic agent in the methods of the invention. In a further aspect of the present invention, the methods further include means to prevent damage to tissue that is not associated with conduit obstruction. Preferred enzymes incorporated in the therapeutic agents are large (>100,000 kD) and diffuse slowly in the extracellular compartment after injection. Further, collagenases comprise a domain (in addition to the active site) which binds tightly to tissue. Consequently, these enzymes remain largely contained within collagen-rich target tissues after injection. Also, the enzyme's activity is quickly extinguished in the blood pool by circulating inhibitors. Therefore, injected collagenase, which diffuses from the interstitial compartment into the blood pool, will be rapidly inhibited, preventing systemic side effects. Fragments of therapeutic agents also can be administered to a patient in accordance with the invention. For example, fragments of the above-mentioned collagenases and elastases can be administered to a patient provided such fragments provide the desired therapeutic effect, i.e. degradation of obstruction of a biological conduit. As referred to herein, a collagenase, elastase or other enzyme includes therapeutically effective fragments of such enzymes. In certain preferred aspects of the invention, the therapeutic agent(s) that are administered to a patient are other than a cytostatic agent; cytoskeletal inhibitor; an aminoquinazolinone, particularly a 6-aminoquinazolinone; a vascular smooth muscle protein such as antibodies, growth hormones or cytokines. In specific embodiments, the degradation of elastin, an extracellular matrix component that contributes to tissue elasticity, is not desirable. Therapeutic agents comprising only enzymes, which do not degrade elastin, such as collagenases, can be employed. Therefore, the elastic properties of the conduit wall will likely be preserved after treatment. In a preferred aspect of the invention, a therapeutic agent comprising at least one enzyme capable of degrading elastin, collagen or both is delivered to the targeted obstruction site with a catheter. Preferred catheters are capable of directly localizing a therapeutic agent directly into the extracellular matrix of the obstruction. Particularly preferable catheters are capable of delivering accurate doses of the therapeutic agent with an even distribution over the entire obstructed area of the conduct. One particularly preferred example of a catheter for use in the method of the present invention is the Infiltrator® catheter produced by InterVentional Technologies Corporation (IVT) (San Diego, Calif.), which delivers a precisely controlled dosage of a drug directly into a selected segment of vessel wall ( FIG. 1 ) (Reimers, J. Invasive Cardiology (1998) 10:323-331; Barath, Catheterization and Cardiovascular Diagnosis (1997) 41:333-41; Woessner, Biochem. Cell Biol . (1996) 74: 777-84). Using this preferred catheter a therapeutic agent can be delivered at low pressure via a series of miniaturized injector ports mounted on the balloon surface. When the positioning balloon is inflated, the injector ports extend and enter the vessel wall over the 360° surface of a 15 mm segment of vessel. Each injector port is les than 0.0035 inch in size. Drug delivery can be performed in less than 10 seconds, with microliter precision and minimal immediate drug washout. The injected drug is delivered homogeneously in the wall of the vessel or duct ( FIG. 2 ). The triple lumen design provides independent channels for guidewire advancement, balloon inflation and drug delivery. Trauma associated with injector port penetration is minimal and the long-term histologic effects are negligible (Woessner, Biochem. Cell Biol . (1996) 74: 777-84). In addition, the device has been engineered such that the injector ports are recessed while maneuvering in the vessel. Additionally, the Infiltrator® catheter is capable of balloon inflation with sufficient force for angioplasty applications. The excellent control of drug delivery observed with Infiltratorg can be significant since preferred therapeutic agents of the present invention potentially can degrade collagen and/or elastin in nearly all forms of tissue in a non-specific manner. In yet another embodiment of the present invention, a therapeutic dose is employed which will restore conduit flow while maintaining conduit wall integrity. Several parameters need to be defined to maximize method efficiency, including the amount of enzyme to be delivered, and the volume of enzyme solution to be injected so that the reopening of the conduit occurs with a single dose protocol. Ideally repeat or multiple dosing is reserved only for patients who have an incomplete response to the initial injection. In regards to the volume of therapeutic agent solution delivered, preferably the conduit wall is not saturated completely, as this can lead to transmural digestion and conduit rupture. Instead, the optimal dose is determined by targeting the thickness of the wall (from the outside in) which needs to be removed in order to restore adequate flow, while leaving the remaining wall intact. An overly dilute solution will be ineffective at collagen lysis while an overly concentrated solution will have a higher diffusion gradient into the surrounding tissues, thereby increasing the risk of transmural digestion and rupture. Collagenase doses are generally expressed as “units” of activity, instead of mass units. Individual lots of collagenase are evaluated for enzymatic activity using standardized assays and a specific activity (expressed in units/mg) of the lot is determined. BTC uses an assay that generates “ABC units” of activity. The specific activity of other collagenase preparations are sometimes expressed in the older “Mandel units”. One ABC unit is roughly equivalent to two Mandel units. Preferable doses and concentrations of enzyme solution are between 1000 and 20000 ABC units, more preferable are between 2500 and 10000 ABC units and enzyme doses of 5,000 ABC units in 0.5 ml of buffer are most preferred. It will be appreciated that actual preferred dosage amounts of other therapeutic agents in a given therapy will vary according to e.g. the specific compound being utilized, the particular composition formulated, the mode of administration and characteristics of the subject, e.g. the species, sex, weight, general health and age of the subject. Optimal administration doses for a given protocol of administration can be readily ascertained by those skilled in the art using dosage determination tests, including those described above and in the examples which follow. Therapeutic agents of the invention are suitably administered as a pharmaceutical composition with one or more suitable carriers. Therapeutic agents of the invention are typically formulated in injectable form, e.g. with the therapeutic agent dissolved in a suitable fluid carrier. See the examples which follow for preferred compositions. As discussed above, the methods and systems of the invention can be employed to treat (including prophylactic treatment) a variety of diseases and disorders. In particular, methods and systems of the invention can be employed to relieve or otherwise treat a variety of lesions and other obstructions found in common bile ducts or vascular systems. Methods of the invention are also useful to relieve lesions and other obstructions in other biological conduits including e.g. ureterer, pancreatic duct, bronchi, coronary and the like. The invention also includes prophylactic-type treatment, e.g. methods to dilate a biological conduit whereby the increased conduit diameter obviates the potential of obstruction formation with a conduit. Temporary and partial degradation of the elastin component of a conduit wall reduces the elasticity of the conduit, thereby facilitating modifications of the size and shape of the conduit. Introducing a dose of therapeutic agent in accordance with the invention into the lumen of an isolated conduit or some section thereof results in complete or partial diffusion of the therapeutic agent into the wall of the isolated conduit during a specified period of time. Subsequent pressurization of the treated region, either while the region is still isolated or after removing the means of isolation, increases the lumen diameter by dilation. Regeneration of the conduit elastin framework results in a conduit with a larger lumen diameter without compromising the structural integrity. Arteriovenous hemodialysis grafts are frequently placed in the arm of the patient such that blood can be withdrawn and purified blood returned through the graft. Frequently the lumenal diameter of the venous outflow is smaller than the graft lumenal diameter. Development of a stenosis due to intimal hyperplasia can further reduce the lumenal diameter of the venous outflow such that an insufficient volume of blood passes through the venous outflow. To prevent intimal hyperplasia and stenosis formation, dilating the venous outflow vein using the above described method of partially degrading the elastin component of the vascular wall downstream of the site of graft implantation such that the lumenal diameter of the venous outflow is similar to or larger than the diameter of the interposed loop graft reduces the likelihood of forming a stenosis due to intimal hyperplasia. Venous dilation can be performed either before or after interposing a graft between the artery and vein. All documents mentioned herein are incorporated herein by reference. The present invention is further illustrated by the following non-limiting examples. Example 1 Tissue Digestion Analysis The protocol of the following example is a detailed description of a “standard in vitro tissue digestion assay” as referred to herein. The rate of tissue digestion, which is composed mostly of collagen, by a mixture of collagenase and elastase, proteolytic enzymes with activity respectively against collagen and elastin, was determined. Trypsin inhibitor was added to negate the effect of any residual trypsin activity. Briefly, fresh pig tendon was excised, trimmed, washed, blotted dry and weighed. Individual tendon pieces were suspended in 3.58 mg/ml HEPES buffer at neutral pH and various concentrations of enzymes were added. lodinated radiographic contrast was added in various concentrations to some of the enzyme solutions. The tissue digestion was carried out in a water bath at 37° C. At various time points, the tendon pieces were removed from the enzyme solution, washed, blotted dry and weighed. Each time point was derived from the average of three samples. The effect of enzyme concentration on tissue digestion rates was studied. As expected, increasing the concentration of enzymes in vitro increased the rate of tissue digestion ( FIG. 3 ). Buffer alone had no effect on the tissue. Extrapolating digestion rates in vitro to an in vivo situation has proven difficult. For Dupuytren's contractures, the effective dose for transecting fibrous cords in vitro was 500 ABC units. However, the effective in vivo dose was 10,000 ABC units. The effect of iodinated radiographic contrast material on tissue digestion rates was also studied ( FIG. 4 ). This study was performed to monitor enzyme delivery by mixing it with contrast prior to injection. These results demonstrate that Omnipaque 350 iodinated contrast material inhibits enzyme activity at radiographically visible (35%) concentrations, but not at lower (1-5%) concentrations ( FIG. 4 ). Similar results were observed with Hypaque 60 contrast. Example 2 Determining Dose Dependent in vitro Activity of a Therapeutic Agent Including Collagenase, Elastase, and a Trypsin Inhibitor The effect of enzyme concentration on tissue digestion rates was studied ( FIG. 3 ). The “1×” tissue sample was treated with collagenase 156 Mandel units/ml+elastase 0.125 mg/ml+trypsin inhibitor 0.38 mg/ml. The “2×” sample was treated with collagenase 312 Mandel units/ml+elastase 0.25 mg/ml+trypsin inhibitor 0.76 mg/ml. The “5×” sample was treated with collagenase 780 Mandel units/ml+elastase 0.625 mg/ml+trypsin inhibitor 1.9 mg/ml. All digestion volumes were 0.5 ml. Increasing the concentration of enzymes in vitro increased the rate of tissue digestion ( FIG. 3 ). Buffer alone had no effect on the tissue. An effective in vivo dose was found to be 10,000 ABC units. Example 3 Determining the Effect of Iodinated Radiographic Contrast Material on Tissue Digestion Rates to Facilitate Monitoring Enzyme Delivery Prior to Injection of a Therapeutic Agent Comprising a Contrast Material into a Patient The “35% Omnipaque” tissue sample was treated with collagenase 156 Mandel units/ml+elastase 0.125 mg/ml+0.38 trypsin inhibitor with 35% Omnipaque 350 contrast (volume:volume). The “5% Omnipaque” sample was treated with collagenase 312 Mandel units/ml+elastase 0.25 mg/ml+0.76 trypsin inhibitor with 5% Omnipaque 350 (volume:volume). The “1% Omnipaque” sample was treated with collagenase 312 Mandel units/ml+elastase 0.25 mg/ml+0.76 trypsin inhibitor with 1% Omnipaque 350. All digestion volumes were 0.5 ml. These results demonstrate that Omnipaque 350 iodinated contrast material inhibits enzyme activity at radiographically visible (35%) concentrations, but not at lower (15%) concentrations ( FIG. 4 ). Similar results were observed with Hypaque 60 contrast. Example 4 Creating a Stricture in the Common Bile Duct of Dogs and Treatment of the Resulting Stricture with Transcatheter Intramural Collagenase Therapy Right subcostal laparotomy was performed in dogs to expose the gallbladder, which was then affixed to the anterior abdominal wall of 11 dogs (n=11). After 2 weeks, a single focal thermal injury was made in the common bile duct (CBD) using a catheter with an electrocoagulation tip placed through the gallbladder access. A 4.8 Fr biliary stent was placed to prevent complete duct occlusion in 7 animals. Stricture development was monitored with percutaneous cholangiography over five weeks. Collagenase was then directly infused into the wall of the strictured CBD using an Infiltrator drug delivery catheter (n=3). The Infiltrator has three arrays of microinjector needles mounted on a balloon which extend and enter the duct wall over the 360-degree surface. After treatment, internal plastic stents were placed in 2 animals. Explants of the CBD were obtained the following day. H&E, trichrome, and elastin staining were used for histopathologic analysis. CBD strictures were successfully created in 7/11 animals as determined by cholangiography ( FIG. 1 ). Failures were due to gallbladder leak (n=2) and perforation at the site of thermal injury (n=2). Histologic analysis of an untreated stricture demonstrated a thickened wall with a circumferential network of collagen bundles and associated lumenal narrowing ( FIG. 4 ). Strictures treated with collagenase demonstrated a circumferential lysis of collagen at the treatment site, with sparing of the normal duct, arteries and veins ( FIGS. 2 and 5 ). All three animals developed bile leaks after treatment, two from the gallbladder access site and one from the treatment site. There was vascular congestion and inflammation in portions of the small bowel mucosa and peritoneum after treatment in all animals, to varying degrees. Example 5 Relief of Strictures in the Common Bile Duct of a Patient A large dog was used as the patient such that under general anesthesia a cholecystostomy tract was created and the gallbladder was “tacked” to the abdominal wall with retention sutures. A cholangiogram was performed with Hypaque-60, using a marker catheter, in order to define the anatomy. Then, a flexible catheter with a bipolar electrode tip was constructed as previously described (Becker, Radiology (1988) 167:63-8). This catheter was inserted through the gallbladder ( FIG. 5 ) and positioned with its “hot” tip (arrow) in the distal common bile duct such that the catheter was pulled back and the treatment was repeated until a 1.0 cm length of duct was injured ( FIG. 6 ). Immediately after delivering the current there was a mild-moderate amount of smooth narrowing of the treated segment of duct (arrow), possibly due to spasm or edema. A pigtail nephrostomy drainage catheter was then inserted through the fresh cholecystotomy tract into the gallbladder. The distal end was closed with an IV cap and buried in the subcutaneous tissue. The surgical wounds were then closed in a two-layer fashion. After 7 days, a follow-up cholangiogram was performed to evaluate the thermally induced stenosis. A 20 gauge needle was used to percutaneously access the drainage catheter through the IV cap. A cholangiogram was performed demonstrating moderate-marked dilation of the biliary tree ( FIG. 1 ). There was a high-grade stricture of the mid common bile duct, where the thermal injury had been made. Strictures are created in five large dogs using the methods described above and in Example 4. In addition, an objective measurement of biliary patency (the Whitaker study) is made of the common bile duct, both before and after making a stricture. The Whitaker study is performed by injecting normal saline through a catheter positioned in the common bile duct. Flow rates are increased and pressure measurements are taken until a peak pressure of 40 mmHg is reached. The thermal lesions mature into fibrous strictures over a six week period. One animal is then sacrificed and a histologic assessment is made of the extrahepatic biliary tree. Samples are taken of the duct proximal to the lesion, the mid portion of the lesion ( FIG. 4 ), the lesion edge, and the duct distal to the lesion. Assessments of 1) duct morphology. 2) cell type and number, 3) the extent and appearance of the extracellular matrix, and 4) extent of epithelialization are made. A second animal is sacrificed after an additional 6 weeks after thermal injury and a similar analysis carried out. A cholangiogram is performed to visually assess the stricture ( FIG. 1 ) and a whitaker test is also performed on the remaining 3 dogs. Then, the Infiltrator catheter is then deployed within the lesion and 0.5 mL of collagenase preparation (10,000 Units/ml) is injected into the wall of the lesion. On post-treatment day 1, a follow-up cholangiogram and Whitaker test are performed. In cases where incomplete response is noted, a second treatment can be given and a second follow-up chlorangiogram and Whitaker test is performed the following day. Hepatic enzyme levels will be drawn to assess the effect of stricture and then treatment on hepatic function. Alternatively, incomplete response from collagenase can be followed up with subsequent angioplasty or a combined collagenase/angioplasty treatment. After treatment with collagenase, a final cholangiogram is taken after 1 week ( FIG. 2 ). At this time, the animal is sacrificed and the extrahepatic biliary tree harvested. Histologic assessments are made of the bile duct proximal to the treated lesion, the mid portion of the treated lesion ( FIG. 5 ), the treated lesion edge, and the duct distal to the lesion. Assessments of 1) duct morphology, 2) cell type and number, 3) the extent and appearance of the extracellular matrix, and 4) extent of epithelialization were made. FIG. 5 is a histology image of a common bile duct stricture after treatment. The arrows denote the outer limit of collagen breakdown. The histological examination of the treated common bile duct stricture demonstrates a circumferential lysis of collagen at the treatment site, while sparing damage to the normal duct, arteries and veins. Example 6 Relief of Stenosis Due to Intimal Hyperplasia of a Synthetic Hemodialysis Graft Standard, untapered 5 mm diameter polytetrafluoroethylene (PFTE) loop grafts were interposed between the femoral artery and the femoral vein in the hind limbs of 25-35 kg dogs, as described previously (Trerotola, J. Vascular and Interventional Radiology (1995) 6:387-96). An end-to-end configuration had been selected to facilitate optimal positioning of the catheter drug delivery balloon during treatment of a stenosis. Standard, cut-film angiography is performed one week after surgery to assess the arterial inflow, the artery-graft anastomosis, the vein-graft anastomosis, and the venous outflow. After this, routine physical examination of the grafts will be carried out to screen for patency. Twenty weeks after surgery, standard, cut-film angiography is performed to assess the lumenal diameter of the grafts and their venous outflow. At this time, a stenosis due to intimal hyperplasia is seen in the venous outflow with an associated pressure gradient (Trerotola, J. Vascular and Interventional Radiology (1995) 6:387-96). Then, using the first animal, the therapy delivery catheter is deployed within a graft and 5000 ABC units of collagenase in 0.5 ml is infiltrated into the wall of the lesion at the venous outflow. The catheter is flushed and the contralateral lesion receives 1 ml of saline, delivered in an identical manner. Nearly all collagenase activity is extinguished after 1-2 days such that the grafts are re-examined with angiography after 3 days. Repeat measurements of lumenal diameter and invasive pressure measurements across the lesion are also taken. The animals are sacrificed and the grafts excised, pressure-fixed, and examined histologically. Assessments are made of the distal graft, the venous anastomosis, the mid-portion of the treated lesion, the lesion edge, and the normal vein downstream from the graft. Additional assessments of 1) cell type, morphology and number, 2) extent of extracellular matrix, 3) overall adventitial, medial, and intimal thickness, 4) extent of intimal hyperplasia, and 5) extent of endothelialization are made. Example 7 Four dogs are used for a controlled study of collagenase treatment. Bilateral grafts are created as described previously and standard, cut-film angiography is performed one week after surgery to access the arterial inflow, the artery-graft anastomosis, the vein-graft anastomosis, and the venous outflow. After this, routine physical examination of the grafts is carried out to screen for patency. Then, twenty weeks after surgery, standard, cut-film angiography is performed to assess the lumenal diameter of the grafts and their venous outflow. An obvious stenosis due to intimal hyperplasia is usually seen in the venous outflow with an associated pressure gradient (Trerotola, J. Vascular and Interventional Radiology (1995) 6:387-96). The Infiltrator catheter is then deployed within the lesion and the selected dose of collagenase is infiltrated into the wall of the lesion. The contralateral, control graft is treated in an identical manner, except that saline is delivered instead of collagenase. Three days after treatment, the grafts are restudied with angiography and invasive pressure measurements to determine the acute effects of collagenase treatment. Changes in lumenal diameter and pressure gradients are calculated for both the collagenase-treated group and the saline-treated group and ten days after collagenase treatment, the grafts are studied a final time. The animals are sacrificed and the grafts are excised, pressure-fixed, and examined histologically, as described above. The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated that those skilled in the art, upon consideration of this disclosure, may make modifications and improvements within the spirit and scope of the invention as set forth in the following claims.

The invention provides methods for treating an obstructed biological conduit that include administering to the conduit an agent that can degrade extracellular matrix of obstructing tissue. Particular methods include delivery of an enzyme or a mixture of several enzymes to the area or region of obstruction wherein the enzyme(s) have the capability to degrade extracellular matrix components within the obstruction thereby restoring the normal flow of transported fluid through the conduit. The invention also includes prophylactically dilating a section of conduit to minimize the risk of obstruction formation.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Provisional Application No. 61/894,581; filed on 2013 Oct. 23 by present inventor. [0002] Provisional Application No. 61/900,632; filed on 2013 Nov. 6 by present inventor. [0003] Provisional Application No. 62/030,764; filed on 2014 Jul. 7 by present inventor. BACKGROUND [0004] Prior art that appears relevant: [0005] U.S. Pat. No. 7,610,661 B2; 2009 Nov. 3 by Sween, Kleeman, Nalwad. [0006] U.S. Pat. No. 8,147,270 B1; 2012 Apr. 3 by Wescott. [0007] U.S. Pat. No. 8,261,416 B2; 2012 Sep. 11 by Rothbaum, Conner, Curtis, Damon, Sanchez. [0008] This application relates to accessories used to manage a cord on earbuds or earphones. In today's market, there are various styles of earbuds and earphones available. The cords on many earbuds/earphones are thin and often become tangled making them difficult to manage. There are existing products that allow earbud/earphone cords to be wrapped around a separate object for storage and cord management. This type of system requires that the user spend time wrapping up the cord tightly after each use to prevent tangles. Furthermore, the separate storage object must be present and available for use when needed. These storage items are often small and can be easily lost or misplaced. [0009] Other storage solutions require that the cord must form a closed loop by fastening either end of the cord to a conical shaped object. However, when the cords are in use, the storage object remains thus awkwardly hanging on the cord. If the large closed loop gets caught on an object, an end of the cord may become detached from the fastener and fall freely. [0010] Storage management structures that involve straps and magnets add unwanted weight to the object to which they are attached. Also, this solution is bulky and visually unappealing. SUMMARY [0011] It is an object of the invention to produce a cover that surrounds the cord on earbuds and earphones and keeps the cord free of tangles during use and storage. An additional object of the invention is to provide a solution that is easy to use and visually appealing. Several advantages of one or more aspects are stated below. It is a lightweight covering that wraps around the majority of the length of the cord. The cover remains on the cord during use and is easily rolled up and placed in a pocket or bag for tangle-free storage. Since the cover can always remain on the cord, it will not become misplaced or lost. Considering that earbuds/earphone cords are often exposed during use, many users are concerned with visual appeal. The cover provides a fashion component in that the cover can be personalized given a variety of color choices and patterns. DRAWINGS Figures [0012] FIG. 1 is a perspective view of a first embodiment [0013] FIG. 2 is an exploded view of a threading device [0014] FIG. 3 is a view of the threading device placed around earbuds cords [0015] FIG. 4 shows first step in threading the cord [0016] FIG. 5 is a perspective view of a second embodiment [0017] FIG. 6 is an exploded view of stitching on FIG. 5 REFERENCE NUMBERS [0000] 1 —fabric of the covering 2 a —end hem 2 b —end hem 3 —vertical seam 4 —top stitching 5 —cord 6 —hook 7 —plastic threading device 8 —vertical slit 9 —earbud/earphone cord 10 —earbud connector 11 —opening of cover 12 —zipper slider 13 —zipper tape 14 —top seam 15 —horizontal tacking stitch 16 a —vertical stitching 16 b —vertical stitching DETAILED DESCRIPTION [0036] FIG. 1 illustrates one embodiment of a cover that will surround the cord on earbuds and earphones. The cover is made of a fabric 1 or any other soft material. The fabric 1 is made of nylon, spandex, polyester, rayon, cotton or any combination of various fabrics. The fabric 1 contains solid colors, printed patterns and other selected printed motifs. [0037] To make the cover in FIG. 1 , begin with a piece of fabric 1 with overall dimensions of roughly 32″ by 1 ½″. First hem each end 2 a and 2 b by turning each end by 1/4″ with wrong sides of the fabric facing and sew to create finished edge. Next, with right sides of the fabric facing, sew vertical seam 3 using 1/4″ seam allowance, from end with hem 2 a to opposite end and stop the stitching approximately 1″ from end with hem 2 b. Next the tube is turned so right side of fabric is facing out leaving opening at either end. Create a loop with cord 5 and place inside the cover at end near hem 2 b. The cord 5 is typically 1/16″ thick and 1 ½″ in length and is made of satin or any other such material. Finish with top stitching 4 to close the length. Add hook 6 to cord loop 5 . Hook 6 is typically ¾″ in length and is made of plastic, metal or some other material. [0038] FIG. 2 shows a threading device 7 that is roughly 3″ in length and is made of plastic or other such material. It has a vertical slit 8 that extends its full length. The threading device 7 is placed inside the end of the cover in FIG. 1 where hem 2 a resides to complete the production of this embodiment. The finished cover forms a tube that is approximately 31 ½″ long and ½″ wide on either side if pressed flat (or 1″ around). The cover surrounds the majority of the length of most earbud and earphone cords. [0039] The threading device 7 is used to place the cover in FIG. 1 on a set of earbud or earphone cords. In FIG. 3 , the vertical slit 8 on threading device 7 is opened and placed around earbud cord 9 at end of the cord near the earbud connector. Once the threading device 7 is in place surrounding the cord 9 , the earbud connector 10 ( FIG. 4 ) is placed into the opening at the top of cover 11 ( FIG. 4 ). The threading device 7 is then pushed through the length of cover until the connector exits through the other end. The threading device 7 can be stored inside the cover or removed for future use. [0040] FIG. 5 illustrates another embodiment of the cover. The cover is made of a fabric 1 or any other soft material. The fabric 1 is made of nylon, spandex, polyester, rayon, cotton or any combination of various fabrics. The fabric 1 contains solid colors, printed patterns and other selected printed motifs. [0041] To make the cover in FIG. 5 , begin with a piece of fabric 1 with overall dimensions of roughly 32″ by 1 ½″. First hem each of the ends 2 a and 2 b by turning each end by ¼″ with wrong sides of the fabric facing and sew to create finished edge. Next with wrong sides of fabric facing, sew vertical seam 14 with approximate length of stitching to be 1″ beginning at end of cover near hem 2 a using roughly ¼″ seam allowance. Next, zipper slider 12 is removed from zipper tape 13 . Zipper slider 12 is made of metal, plastic or any other material. Zipper tape 13 is approximately 30″ long. Zipper teeth on zipper tape 13 are made of metal, plastic or any other material. With the wrong side of fabric facing up, place zipper tape 13 right side down on fabric approximately ¼″ below seam 14 . Tack down zipper at top with ¼″ horizontal stitch. Next sew 2 lines of vertical stitching to secure the zipper tape 13 . Vertical stitching will stop roughly 1″ from end with hem 2 b. FIG. 6 shows an exploded view of placement of horizontal stitch 15 and vertical stitching 16 a and 16 b on zipper tape 13 . The tube is then turned so right side of fabric is facing out. The zipper slider 12 is placed on zipper tape 13 . Create a loop with cord 5 and place inside the cover at end near hem 2 b . The cord 5 is typically 1/16″ thick and 1 ½″ in length and is made of satin or any other such material. Finish with top stitching 4 to close the length. Add hook 6 to cord loop 5 . Hook 6 is typically ¾″ in length and is made of plastic, metal or some other material. The finished cover forms a tube that is approximately 31 ½″ long and ½″ wide on either side if pressed flat (or 1″ around). The cover surrounds the majority of the length of most earbud and earphone cords. [0042] To use the zipper cover, pull zipper down to unzipped position (near end with hem 2 b ). The threading device 7 is not used in this embodiment. Insert the earbud or earphone connector through opening at end of cover near hem 2 a and feed connector through cover for approximately 1″ under seam 14 . When connector appears through opening, pull on the connector so the length of the cord follows behind Take the connector and feed it through the opening at the bottom near stitching 4 until connector exits opening at bottom near hem 2 b. Zip up the zipper to complete placing the cover on the cords. [0043] The decorative cover is easy to use and keeps earbud and earphone cords protected and untangled. The hook on the end of the cover may be used to hold a key (to home, locker, desk, car, etc.) or to hold a student/employee badge or to secure cord to a jogging shirt or for any other use determined by the owner. When not in use, the cover remains on the earphone cord and is easily rolled up and placed in a pocket or bag for tangle-free storage. The cover is visually appealing and is made in variety of colors, patterns and motifs. The lightweight, sleek cover is easily removed and interchanged for a new fashion statement or personal preference.

A decorative cover that surrounds the cord on earbuds and earphones and keeps the cord free of tangles during use and storage. The tubular shape has openings at either end. A plastic threading device is used to push the connector end of the cord through the length of the cover. There is a hook at one end intended for a key, id badge or to hook the cover to a jogging shirt. The cover remains on the cord during use and is easily rolled up and placed in a pocket or bag for tangle-free storage.

BACKGROUND OF THE INVENTION The present invention relates to a method for the navigation of a vehicle, wherein the vehicle includes a course reference device which furnishes a course signal which represents the direction of the vehicle with reference to an earthbound coordinate system; a longitudinal movement sensor for detecting longitudinal movement of the vehicle and generating a longitudinal movement signal; a position computer for calculating vehicle position data, segregated into north and east position values, from signals generated by the course reference device and the longitudinal movement sensor; display means connected to the position computer for displaying vehicle position data calculated by the position computer; and input means including manual input means and signal receiving means for providing, respectively, additional position data and course, velocity and path data for navigation support. A navigation system of this type is described in German Pat. No. 3,033,279. Such a navigation system is used for determining the position of a vehicle in a grid coordinate system, namely the UTM (Universal Transverse Mercator) grid system. The vehicle position is determined from the course angle furnished by a course reference device with reference to the UTM grid coordinate system and from distance signals obtained by integration of the vehicle speed. Position errors occurring during travel, which have no linear relationship to the path traveled or the travel time, are eliminated in that, at the moment at which the vehicle is at a known point in the terrain, a comparison is made between the displayed location and the actual location of the vehicle, a path adaptation factor is determined and the course angle is corrected. However, it has been found to be desirable to correct the indicated positon not only when a known terrain point is reached, but also to make a correction of the displayed data continuously and in a discrete-time manner. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a navigation system which, with the use of simple sensors, furnishes all navigation data with the greatest accuracy, with such accuracy remaining constant over time. The above and other objects of the invention are accomplished by a method for navigation of a vehicle in the context of a vehicle which includes: a course reference means for furnishing a course angle signal θM which represents the direction of the vehicle with reference to an earthbound coordinate system; longitudinal movement sensor means for detecting longitudinal movement of the vehicle and generating a longitudinal movement signal VM corresponding to the longitudinal movement of the vehicle; position computer means for calculating vehicle position data, segregated into north and east position values, from signals generated by the course reference means and the longitudinal movement sensor means; display means connected to the position computer for displaying vehicle position data calculated by the position computer; and input means including at least one of manual input means and the signal receiving means for providing navigation support data including at least one of additional position, course, velocity and path data; said method comprising: checking the longitudinal movement signal VM and the course angle signal θM for plausibility; adding a known, empirically derived, deterministic velocity error component signal DF(V) to the VM signal and a known, emipirically derived, deterministic course angle error component value to the θM signal to produce, respectively, a corrected longitudinal movement signal CV and a corrected course angle signal Cθ; optimally estimating, with the use of a Kalman filter, the stochastic position and direction errors resulting from the VM and θM signals and using such errors to calculate direction and change-in-direction correction values C(θ) and C(ε), respectively, and north and east position correction values C(RN) and C(RE), respectively; adding the direction correction value C(θ) to the θM signal; feeding the position correction values C(RN) and C(RE) to the position computer means for use in correcting the position data; forming corrected north and east component signals CVN and CVE, respectively, from the corrected longitudinal vehicle movement signal CV and from the corrected course angle signal Cθ and feeding the CVN and CVE signals to the position computer means; calculating, with the use of the position computer means, corrected north and east position coordinate values CRN and CRE, respectively, in dependence of the C(RN) and C(RE) correction values and the CVN and the CVE corrected north and east component signals; obtaining north and east position bearing data RNS.sup.(jP) and RES.sup.(jP), respectively, from the input means; comparing the corrected north and east position coordinate values CRN and CRE with the position bearing data RNS.sup.(jP) and RES.sup.(jP), respectively, to form north and east position bearing signals CZN.sup.(jP) and CZE.sup.(jP), respectively; and feeding the CZN.sup.(jP) and CZE.sup.(jP) signals to the Kalman filter, with the Kalman filter developing the following error model of the vehicle course angle error: Δθ(t)=Δθ.sub.1 (t)+Δθ.sub.2 (t)+Δθ.sub.3 (t), wherein Δθ 1 (t) comprises a component of exponentially, time correlated, colored noise; Δθ 2 (t) comprises a time linearly variable component representing drift angle with an unknown starting value Δθ 2 (O) and an unknown pitch ε(t) representing a random ramp process; and Δθ 3 (t) comprises a component of Gaussian white, time uncorrelated, noise; and wherein the component Δθ 1 (t) is described by a form filter excited with white noise in a Gauss-Markov process of the first order, error which is contained in the position bearing data, RNS.sup.(jP) and RES.sup.(jP), is developed solely be stationary Gaussian white, time uncorrelated, noise and C(θ), C(ε), C(RN), C(RE), CVN, CVE, CRN, CRE, RNS.sup.(jP), RES.sup.((jP), CZN.sup.(jP), CZE.sup.(jP), Δθ(t), Δθ 2 (t), Δθ 3 (t) and ε(t) are defined in the detailed description below. A significant advantage of the invention lies in the provision of a navigation system which receives navigation signals from sensors in the vehicle, such as the course and velocity or path sensors, as well as from additional input means, and forms, by means of the use of a modified Kalman filter, optimized navigation data therefrom. Additional input means include, for example, manual input of the position, as well as receiving devices for radio and/or satellite navigation methods known, for example, by the names "Transit" or "GPS Navstar" (see in this connection German Offenlegungsschrift [laid-open patent application] No. 2,043,812). According to a further feature of the invention, course and/or longitudinal vehicle movement support data are derived from the signals of a satellite navigation system and compared with the corrected signals of the course reference device and/or the signals of the longitudinal vehicle movement sensor. The comparison data are then likewise fed to the error behavior model forming block and to the Kalman filter. According to yet another feature of the invention, a compensation of stochastic longitudinal vehicle movement error components is accomplished in addition to the compensation of deterministic course and velocity error and the stochastic course error components, for which purpose corresponding velocity correction values (C(V)) are formed by means of the Kalman filter longitudinal movement error estimation and these correction values are added to the longitudinal movement signals VM of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block circuit diagram of a navigation system employing a Kalman filter for implementing the method according to the invention. FIG. 2 is a time sequence diagram for the individual steps of the method according to the invention. FIG. 3 is a diagram showing a dead reckoning position. FIG. 4 is a block circuit diagram for a simple navigation system with Kalman filter employing only manual position input which can be used to implement the method according to the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there is shown a navigation system as it is used, for example, in a land vehicle. Longitudinal vehicle movement is sensed by a velocity sensor 1 which produces a measured speed value (VM), and course direction is detected by a direction sensor 2, for example a course gyro, which produces a measured course angle (θM) value. Velocity sensor 1 and direction sensor 2 are of known design, for example as described in the "Operation Manual, Vehicle Navigation System FNA 4-15", provided by Teldix GmbH of Heidelberg, Federal Republic of Germany. The measured values (VM) and (θM) furnished by sensors 1 and 2, respectively, are values which include errors and are thus checked for plausibility based upon changes in course and velocity, maximum value determinations and statistical diagnosis calculation concepts such as, mean value and variance estimates. Such errors are, in particular, due to seeming drift, random drift, wheel slip and the like. Therefore, known deterministic error component values (DF(V)) and (DF(θ)), which are empirically derived values, are added to the measured values at linkage points 3, 4. Moreover, direction (course angle) correction values (C(θ)) and velocity correction values (C(V)) furnished by a Kalman filter to be described in greater detail below are added at these linkage points, with (C(V)) being adapted to the actually measured velocity values from the velocity sensor via a proportionality device 5 which generates a proportionality factor. The thus corrected signals for velocity and course are fed to a base navigation unit 6 which segregates the velocity into component values for north and east and feeds these values to position computer 7 and an error behavior model forming block 8 to determine the error ratio. Position computer 7 also receives starting conditions (B A ), such as original location, starting orientation of the course gyro and of the vehicle, starting time and starting speed for determining the dead reckoning position in the north and east directions. If the vehicle reaches a terrain point for which the coordinates are known, for example a certain geodetic point, then the coordinates of that point are fed to the navigation system through an input unit 9 and are compared at linkage points 10 and 11, respectively, with respective ones of the north and east values of the dead reckoning position. Input unit 9 additionally serves as a display means for radio and/or satellite navigation devices which may be provided in the vehicle, and which are able to furnish the actual vehicle position information, which also must be checked for plausibility, and corresponding course and/or velocity data. In this case, not only are the position signals from the radio and/or satellite navigation systems compared with the dead reckoning position but additionally comparisons are made at linkage points 12 and 13, respectively, between the corresponding velocity and/or course signals and the corrected signals from the velocity sensor 1 and/or direction sensor 2. Any existing deviations in position in the two coordinate directions (CZN.sup.(jP)), (CZE.sup.(jP)), as well as the course and/or velocity differences (CZθ.sup.(jP)) and/or (CZV.sup.(jV)), respectively, are fed to the error behavior model forming block 8 as well as to Kalman filter 15. In addition to the already mentioned direction and velocity correction values (C(θ)) and (C(V)), the Kalman filter also furnishes direction change corrections C(ε) which are fed to the error behavior model forming block 8, as well as position correction values in the north and east directions (C(RN)) and (C(RE)), respectively, which are additionally fed to position computer 7 for a correction of the dead reckoning position data. Kalman filter 15 serves to estimate all of the modelled navigation errors. The thus extrapolated navigation errors are utilized to calculate the above-mentioned correction values which are returned to the navigation system for the compensation of errors. The thus designed system forms a closed control circuit which automatically furnishes the "optimally" corrected navigation values which can be displayed by a suitable display means 16. The starting point of the method of the invention is in the so-called base navigation system, which is composed of direction sensor 2 (course gyro) as well as the velocity sensor 1. For the case of "navigation in the plane", the physical base navigation equations, i.e. equations for dead reckoning navigation from vehicle speed V(t) and course angle θ(t) (see FIG. 3), are as follows: ##EQU1## where RN(t) and RE(t) are the vehicle positions in the north (N) and east (E) directions, respectively. VN(t) and VE(t) are the vehicle speeds in the north (N) and east (E) directions, respectively, and t is time As already mentioned above, the vehicle position values resulting from dead reckoning according to Equations (1) and (2) are wrong due to the errors made by the course and velocity sensors and such errors are corrected by navigation support data--it being assumed that these also contain errors. Below is a description of the formulation of the error behavior model forming and Kalman filter algorithms for the case in which position data are fed in from time to time exclusively by manual input means, such as that described in Teldix Operation Manual for the FNA 4-15 Vehicle Navigation System referred to above and as diagrammatically shown in FIG. 4. Input unit 9' in FIG. 1 also accepts position data which is fed in manually as well as additional navigation support data which it receives via radio and/or satellite receiving devices as previously noted. The following model assumptions are then made for the individual measured values: Measured vehicle velocity signal VM(t) from velocity sensor and checked for plausibility: VM(t)=V(t)+ΔV(t) (3) where ΔV(t) is the error-free vehicle speed, and V(t) is the velocity error Measured course angle signal θM(t) from direction sensor and checked for plausibility: θM(t)=θ(t)+Δθ(t) (4) where θ(t) is the error-free course angle and Δθ(t) is the course angle error Measured vehicle position (position fix) RNS(t), RES(t): RNS(t)=RN(t)+ΔRNS(t) (5) RES(t)=RE(t)+ΔRES(t) (6) where RN(t) and RE(t) are error-free vehicle positions in the north (N) and east (E) directions, respectively; and ΔRNS(t) and ΔRES(t) are the position measurement (bearing) errors in the north (N) and east (E) directions, respectively. For the "real" base navigation system, Equations (1), (2), (3) and (4) provide the following continuous-time system equations: RN.sup.FOA (t)=VNM(t)=VM(t)·cos θM(t) (7a) RE.sup.FOA (t)=VEM(t)=VM(t)·sin θM(t) (7b) where RN FOA (t) and RE FOA (t) are erroneous position coordinates of the vehicle navigation/orientation system (FOA) determined from the measured base navigation values by means of dead reckoning. The continuous-time measurement (bearing) equations are obtained by a comparison of the location resulting from dead reckoning (RN FOA (t), RE FOA (t)) with the measured (position fix) vehicle position (RNS(t), RES(t)), respectively. This means: ZN(t)=RNS(t)-RN.sup.FOA (t) (8a) NE(t)=RES(t)-RE.sup.FOA (t) (8b) where ZN(t) and ZE(t) are the differences between dead reckoning and bearing in the north (N) and east (E) directions, respectively. CONTINUOUS-TIME ERROR EQUATIONS The use of the error propagation theorem for Equations (7a/7b) as well as (8a/8b) furnishes the following error equations: Errors in the base navigation system→system errors: ΔRN(t)}=cos θM(t)·ΔV(t)-VEM(t)·Δθ(t) (9a) ΔRE(t)}=sin θM(t)·ΔV(t)+VNM(t)·Δθ(t) (9b) where ΔRN(t) and ΔRE(t) are position errors after dead reckoning. Errors due to position bearings (fixes)→measuring errors: ΔZN(t)=ΔRNS(t)=ΔRN(t)=ZN(ε) (10a) ΔZE(t)=ΔRES(t)=ΔRE(t)=ZE(ε) (10b) where ΔZN(t) and ΔZE(t) are position error differences in the north (N) and east (E) directions, respectively, with the individual errors being modelled as follows: Velocity error modelling With the assumption that the (stochastic) speed error can be modelled by a sum of (time) correlated, i.e. colored noise (describable by Guass-Markov processes of the first order) and Gaussian white, i.e. (time) uncorrelated, noise, the following results: ΔV(t)=ΔV.sub.1 (t)+ΔV.sub.2 (t) (11) where the following definitions apply: ΔV 1 (t)=-β V1 (t)·ΔV 1 (t)+W V1 (t)=form filter description for the error component in the Gauss-Markov process of the first order; β V1 =reciprocal autocorrelation time of the form filter; ΔV 1 (O)˜N[O;E(ΔV 1 2 (O))=σ V1 2 ]=abbreviated form for the starting value ΔV 1 (O) of the Gauss-Markov error component with normal (N) distribution, starting mean O and starting variance σ V1 2 (O)=σ V1 2 ; W V1 (t)=q V1 ·W(t)˜N[O;E(W V1 2 (t))=q V1 2 ]=abbreviated form for the stationary white noise which drives the form filter with normal (N) distribution, mean O and spectral power density q V1 2 ; ΔV 2 (t)˜N[O;E(ΔV 2 2 (t))=q V2 2 ]=abbreviated form for the error component of stationary white noise with normal (N) distribution, mean O and spectral power density q V2 2 ; ##EQU2## Course angle error modelling For forming the model of the (stochastic) course angle error, it is assumed that the latter is additively composed of a component of exponentially (time) correlated (colored) noise Δθ 1 (t), a component Δθ 2 (t) which is linearly variable in time (drift angle) having an unknown starting value Δθ 2 (O) and unknown pitch ε(t) (random ramp process) as well as a component of Gaussian white, i.e. (time) uncorrelated, noise Δθ 3 (t). The error component Δθ 1 (t) can here again be described by the form filter excited by white noise in the Gauss-Markov process of the first order. As a whole, the following course angle error model is then obtained: Δθ(t)=Δθ.sub.1 (t)+Δθ.sub.2 (t)+Δθ.sub.3 (t) (12) where Δθ 1 (t)=-β.sub.θ1 ·Δθ 1 (t)+W.sub.θ1 (t)=form filter description for the error component in the Gauss-Markov process of the first order; β.sub.θ1 =reciprocal autocorrelation time of the form filter; Δθ 1 (O)˜N[O;E(Δθ 1 2 (O))=σ.sub.θ1 2 ]=abbreviated form for the starting value Δθ 1 (O) of the Gauss-Markov error component with normal (N) distribution, starting mean O and starting variance ε.sub.θ1 2 (O)=ε.sub.θ1 2 ; W.sub.θ1 (t)=q.sub.θ1 ·W(t)˜N[O;E(W.sub.θ1 2 (t))=q.sub.θ1 2 ]=abbreviated form for the stationary white noise which drives the form filter with normal (N) distribution, mean O and spectral power density q.sub.θ1 2 ; ##EQU3## Δθ 3 (t)˜N[O;E(Δθ 3 2 (t))=q.sub.θ3 2 ]=abbreviated form for the error component of stationary white noise with normal (N) distribution, mean O and spectral power density q.sub.θ3 2 ; ##EQU4## Position error modelling The mathematical modelling of the errors occurring during position fixes (bearings) is effected under the assumption that they can be described by Gaussian white, i.e. normally distributed, uncorrelated, noise. In vector representation, this results in the following position error model; ##EQU5## with ΔRS.sup.WR (t)˜N[O;V(t)] and ##EQU6## By inserting Equations (11) through (13) into Equations (9) and (10), the following equation systems are obtained which describe the entire error behavior of the present navigation system: Continuous-time system error equations: ##EQU7## Continuous-time measurement (bearing) error equations: ΔZN(t)=-ΔRN(t)+ΔRNS.sup.WR (t) (15a) ΔZE(t)=-ΔRE(t)+ΔRES.sup.WR (t) (15b) The space state representation of the above equations suitable for design of a Kalman filter, after introduction of the following: State vector: ΔX(t)=(ΔRN(t), ΔRE(t); ΔV.sub.1 (t); Δθ.sub.1 (t), Δθ.sub.2 (t), ε(t))T (16) System noise vector: W(t)=(ΔV.sub.2 (t); Δθ.sub.3 (t); W.sub.V1 (t); W.sub.θ1 (t)).sup.T (17) Measurement (bearing) vector: ΔZ(t) =(ΔZN(t), ΔZE(t)).sup.T (18) Measurement (bearing) noise vector: V(t)=ΔRS.sup.WR (t)=(ΔRNS.sup.WR (t), ΔRES.sup.WR (t)).sup.T (19) provides: ##EQU8## ΔZ(t)=M(t)·ΔX(t)+V(t)=measurement (bearing) error equation (21) Equations (20) and (21) thus define the error values at the output of error behavior model forming block 8. System matrix A(t): ##EQU9## System noise input matrix D(t): ##EQU10## Measurement (bearing) matrix M(t): ##EQU11## System noise matrix Q(t): ##EQU12## where ##EQU13## E(W(t))=D(t)·E(W(t))=O Measurement (support) noise matrix V(t): V(t)=E(V(t)·V.sup.T (t)) where ##EQU14## and E(V(t))=O. Uncorrelated system and measurement noise: ##EQU15## Providing discrete time The present navigation system can be realized or simulated with the aid of a digital computer, particularly a microcomputer, for example, a fixed program system of two or three microprocessors, such as Motorola MC 68000 microprocessors integrated with GPS Navstar. The blocks within the dashed lines of FIGS. 1 and 4 can be realized by such a microprocessor system. For such a digital system, the continuous-time system and measurement error (differential) equations (14) and (15) and (16) through (27), respectively, must be converted to discrete-time differential equations--the position fixes (bearings) being taken at discrete instants in time in any case. The "time axis" shown in FIG. 2 is intended to explain the connections between continuous time t, the processing times required to implement the dead reckoning and Kalman filter calculations and the instants in time at which position fixes (bearings) are taken. The following then apply: T KO =duration of dead-reckoning cycle within which dead reckoning is performed once; T KA =duration of a Kalman cycle within which the Kalman filter calculation is performed once; T i =instants in time at which position fixes (bearings) are taken, i=1, 2, 3, . . . ; t=l·T.sub.KO =k·T.sub.KA =T.sub.i (28) where l=number of dead reckoning cycles, with l=0, 1, 2, 3, . . . ; and k=number of Kalman cycles, with k=0, 1, 2, 3, . . . DISCRETE-TIME SYSTEM EQUATIONS The transition from a continuous-time to a discrete-time system takes place in discrete-time conversion block 14 in FIG. 1 by way of a determination of the so-called transition matrix. For this purpose, the broken series set-up is proposed. With the assumption that the continuous-time system matrix A(t) is constant during one Kalman interval T KA =(t k -t k-1 ) and that T KA can be selected sufficiently small, the following results for the transition matrix within the time interval (t k =kT KA , t k-1 =(k-1)T KA ) ##EQU16## where k=1, 2, 3, . . . ; A(t K )=system matrix at time t k =(k)T KA ; and I=unit matrix Because the most suitable Kalman cycle duration T KA from a calculation point of view often becomes too large for the above assumption of A k ,k-1 =constant; k=1, 2, 3, . . . , T KA is subdivided into ##EQU17## where wnm is a whole number multiple; identical strips T KO =(t l -t l-1 ) (the dead reckoning cycle duration T KO can be used for this purpose) and the following can then be set up: ##EQU18## where ##EQU19## according to Equation (29) and A(t l ) is the system matrix at time t l =lT KO . In this way, continuous-time system error equation (20) changes to the discrete-time form ΔX.sub.k (33) ΔX O is given; with the discrete-time system noise vector ##EQU20## and D(τ), W(τ) according to Equations (23) and (17). Corresponding to the procedure in the determination of the discrete-time system noise vector according to Equation (34), the discrete-time system noise matrix is obtained as follows: ##EQU21## where E(W k-1 )=O k=1, 2, 3, . . . and Q=E(W(τ)WTtτ)) according to Equation (25) For an approximated calculation of Q k-1 , the trapezoidal integration method is recommended. Accordingly, the following results: ##EQU22## where D(t K ) is the system noise input matrix at time t K =kT KA . Since position bearings (fixes) are taken exclusively at discrete instances in time t=T i ; i=1, 2, 3, . . . , continuous-time measurement (bearing) error equation (21) changes to ΔZ(t=T.sub.i)=M(t=T.sub.i) ΔX(t=T.sub.i)+V(t=T.sub.i) (37) where M(t=T i ) according to Equation (24). In discrete-time form, this means: ##EQU23## Equations (33) and (38) are therefore the main equations for the discrete-time conversion performed in block 14. For the discrete-time measurement (bearing) noise matrix, the following results: E(V.sub.k ·V.sub.k T)=V.sub.k =V=constant (39) where E(V k )=O and V is used according to Equation (26) For discrete-time dead reckoning for a calculation of the dead reckoning position from the actual velocity and course informations, either of the following two methods can be employed: METHOD 1 In this method, differential equations (7a) and (7b) which describe the "real" base navigation system are put directly in discrete-time form, i.e. the rectangular integration method is used. The following then results as the dead reckoning position at time t l+1 =(l+1)T KO ##EQU24## METHOD 2 The use of the trapezoidal integration method with Equations (7a) and (7b) furnishes somewhat more accurate results. According to this method, the following results: ##EQU25## Discrete-time Kalman filter algorithms (simultaneous bearing data processing) Discrete-time Kalman filter algorithms suitable for realization by microcomputer are formulated as follows: Recursive prediction (extrapolation) algorithms for a priori system error estimation A priori estimation error ΔX k at time t k =kT KA : ΔX.sub.k =Φ.sub.k,k-1 ·ΔX.sub.k-1 where k=1, 2, 3, . . . ΔX.sub.o =starting estimation error (to be suitably given) (42) .sub.Φk,k-1 is according to Equation (31) A priori estimation covariance matrix P k * at time t k =kT KA : ##EQU26## where k=1, 2, 3, . . . ; D(t K ) is the system noise input matrix at time t k =kT KA ; and Q is according to Equation (25) Starting estimation error covariance matrix P o (to be suitably given). P.sub.o =Diag(σ.sub.N.sup.2 (O), σ.sub.E.sup.2 (O); σ.sub.V1.sup.2 ; σ.sub.θ1.sup.2, σ.sub.θ2.sup.2, σ.sub.ε.sup.2) (44) Algorithms for the correction of the a priori system error estimation by measurements (position fixes): Amplification matrix B k at time t k =kT KA : ##EQU27## where i=1, 2, 3, . . . ; k=1, 2, 3, . . . ; M is according to Equation (24); and V is according to Equation (39). A posteriori estimation error ΔX k at time t k =kT KA : ##EQU28## where i=1, 2, 3, . . . ; k=1, 2, 3, . . . ; and Z k =(ZN(t k ), ZE(t k )) T according to Equations (8a) and (8b); A posteriori estimation error covariance matrix P k at time t k =kT KA : P.sub.k =1/2·(P.sub.k +P.sub.k T) (47) where ##EQU29## and i=1, 2, 3, . . . k=1, 2, 3, . . . MODIFIED ALGORITHMS FOR THE CORRECTED NAVIGATION SYSTEM The discrete-time Kalman filter 15 thus furnishes quasi continuously, in addition to the a priori estimation errors and the a priori and a posteriori estimation error covariance matrices, also the a posteriori estimation errors. From these estimation errors with minimum error variance, "optimum" correction values can now be calculated directly and these are returned to the navigation system for error compensation. The thus resulting navigation system is a closed control circuit, corrected navigation system, which then automatically produces the "optimally" corrected navigation data, i.e. data with minimum errors. For the corrected navigation system, the modified algorithms as a result of returns are given below. DISCRETE-TIME MATHEMATICAL MODELS FOR THE CORRECTED MEASUREMENT (INPUT) VALUES (SIGNALS) Corrected vehicle speed CV k ,k-1 as provided by the proportionality unit 5 is as follows: CV.sub.k,k-1 =VM.sub.k,k-1 -χ.sub.k,k-1 ·C(V).sub.k-1 -DF(V).sub.k-1 (49) where ##EQU30## k=1, 2, 3, . . . The following here applies: CV k ,k -1 =corrected vehicle speeds during the Kalman interval (t k =kT KA , t k-1 =(k-1)T KA ), i.e. within a range of kqT KO >t 1 >(k-1)qT KO and l=(k-1)q+1, . . . , kq, respectively; VM k ,k-1 =measured plausible vehicle speeds during the Kalman interval (t k =kT KA , t k-1 =(k-1)T KA ), i.e. within a range of kqT KO >t l >(k-1)qT KO and l=(k-1)q+1, . . . , Kq, respectively; VM k-1 =measured plausible vehicle speed at time t k-1 =(k-1)T KA ; C(V) k-1 =correction value for the measured plausible vehicle speed at time t k-1 =(k-1)T KA ; DF(V) k-1 =deterministic speed error at time t k-1 =(k-1)T KA ; χk,k-1=proportionality factor for the vehicle speed correction value C(V) k-1 during the Kalman interval (t k =kT KA , t k-1 =(k-1)T KA ), i.e. within a range of kqT KO >t l >(k-1)qT KO and l=(k-1)q+1, . . . , kq, respectively; =constant speed value dependent upon the selected velocity sensor. Corrected course angle Cθ k ,k-1 : Cθ.sub.k,k-1 =θM.sub.k,k-1 -C(θ).sub.k-1 -DF(θ).sub.k-1 (51) k=1, 2, 3, . . . wherein Cθ k ,k-1 =corrected course angle during the Kalman interval (t k =kT KA , t k-1 =(k-1)T KA ), i.e. within a range of kqT KO >t l >(k-1)qT KO and l=(k-1)q+1, . . . , kq, respectively; θM k ,k-1 =measured plausible course angle during the Kalman interval (t k =kT KA , t k-1 =(k-1)T KA ), i.e. within a range of kqT KO >t l >(k-1)qT KO and l=(k-1)q+1, . . . , kq, respectively; C(θ) k-1 =correction value for the measured plausible course angle at time t k-1 =(k-1)T KA ; DF(θ) k-1 =deterministic course angle error at time t k-1 =(k-1)T KA . Vehicle position (position fix): Position fixes themselves are not corrected. Corrected, discrete-time base navigation system→corrected, discrete-time system equations: Corresponding to Equations (7a) and (7b), Equations (49) through (51) here yield CVN.sub.k,k-1 =CV.sub.k,k-1 ·cos Cθ.sub.k,k-1 (52a) CVE.sub.k,k-1 =CV.sub.k,k-1 ·cos Cθ.sub.k,k-1 (52b) where CVN k ,k-1 and CVE k ,k-1 are corrected vehicle speeds in the North (N) and East (E) directions, respectively, during the Kalman interval (t k =kT KA , t k-1 =(k-1)T KA ), i.e. within a range of kqT KO >t l >(k-1)qT KO and l=(k-1)q+1, . . . , kq, respectively. Corrected, discrete-time measurement (bearing) equations Analogously to Equations (8a) and (8b), a comparison of the position bearing data (RNS l ; RES l ) with the corrected vehicle position (CRN l ; CRE l ) to be calculated by means of the dead reckoning calculation shown below, here results in ##EQU31## i=1, 2, 3, . . . CZN l and CZE l are "corrected" position differences in the north (N) and east (E) directions, respectively, at time t l =lT KO . The dead reckoning calculation in the corrected navigation system can again be effected according to the above-described two methods. METHOD 1 Rectangular integration according to Equations (40) and (40b) The dead reckoning position at time t l+1 =(l+1)T KO , using Equations (52a) and (52b) is as follows: ##EQU32## i=1, 2, 3, . . . METHOD 2 Trapezoidal integration according to Equations (41a) and (41b) Here one obtains, at time t l+1 =(l+1)T KO , using Equations (52a) and (52b): ##EQU33## i=1, 2, 3, . . . For this, the following starting conditions must be suitably given: CRN.sub.O =RN.sub.O CRE.sub.O =RE.sub.O CV.sub.O =V.sub.O Cθ.sub.O =θ.sub.O The position correction values C(RN) l and C(RE) l , l=l i =Ti/T KO =k i q; i=1, 2, 3, . . . in Equations (54) and (55) are calculated in the same manner as correction values C(V) k and C(θ) k , (where k=1, 2, 3, . . . ) by means of the modified discrete-time Kalman filter as formulated below. Modified discrete-time Kalman filter algorithms (simultaneous bearings processing) for the corrected navigation system After setting up the error equations for the corrected navigation system by use of the error propagation theorem and subsequently setting up the error models, the space state representations of the discrete-time system and measurement (bearing) error equations are effected according to the procedures for the uncorrected case. These equations constitute the prerequisite for use of the modified discrete-time Kalman filter as formulated below for the corrected navigation system. Recursive prediction (extrapolation) algorithm for an a priori system error estimate Corrected a priori estimating error covariance matrix CP k * at time t k =kT KA : ##EQU34## where CP 0 =P 0 is suitably given according to Equation (44). ##EQU35## where ##EQU36## l=1, 2, 3, . . . ; I=unit matrix; CA(t l )=corrected system matrix at time t l =lT KO CD(t k )=corrected system noise input matrix at time t k =kT KA . with Cθ l according to Equation (51), CVN l according to Equation (52a), VCE l according to Equation (52b), and Q according to Equation (25). Recursive algorithms for the correction of the a priori system error estimate by way of measurements (position fixes): Corrected amplification matrix CB k at time t k =kT KA : ##EQU37## i=1, 2, 3, . . . k=1, 2, 3, . . . with M according to Equation (24) and V according to Equation (39). Correction value vector C k at time t k =kT KA : ##EQU38## i=1, 2, 3, . . . k=1, 2, 3, . . . where C k =O: starting conditions C.sub.k =(C(RN).sub.k, C(RE).sub.k ; C(V.sub.1).sub.k ; C(θ.sub.1)k, C(θ.sub.2).sub.k, C(ε).sub.k).sup.T (61) C.sub.k-1 =(O, O; χ.sub.k,k-1 ·C(V.sub.1).sub.k-1 ; C(θ.sub.1).sub.k-1, C(θ.sub.2).sub.k-1, C(ε).sub.k-1).sup.T (62) with the limit conditions: ##EQU39## and where ##EQU40## and CZ.sub.k =(CZN.sub.k, CZE.sub.k).sup.T (64) with CZN k according to Equation (53a) CZE k according to Equation (63b). The finally obtained "optimum" course and velocity correction values then are: C(V).sub.k ←C(V.sub.1).sub.k (65) C(θ).sub.k ←C(θ.sub.1).sub.k +C(θ.sub.2).sub.k (66) Corrected a posteriori estimation error covariance matrix CP k at time t k =kT KA : CP.sub.k =1/2·(CP.sub.k +CP.sub.k.sup.T) (67) with ##EQU41## i=1, 2, 3, . . . k=1, 2, 3, . . . For the more general use according to FIG. 1, where, quasi simultaneously, a plurality of vehicle navigation data for bearings, e.g. position and/or course angle and/or velocity values from radio and/or satellite navigation systems, are available, the changes or additions resulting therefrom will be given below in model forming and Kalman filter algorithms. The individual bearing values are now modelled as follows (instead of according to Equations (5), (6)): Position measurement data checked for plausibility for position bearings RNS.sup.(jP) (t), RES.sup.(jP) (t): RNS.sup.(jP) (t)=RN(t)+ΔRNS.sup.(jP) (t) (69a) RES.sup.(jP) (t)=RE(t)+ΔRES.sup.(jP) (t) (69b) where RN(t) and RE(t) are error-free vehicle positions in the north (N) and (E) directions, respectively; ΔRNS.sup.(jP) (t) and ΔES.sup.(jP) (t) are the jP th position measurement (bearing) errors in the north (N) and east (E) directions, respectively; and jP=1, . . . NP is the number of quasi simultaneously available position bearing data. Course angle measurement data checked for plausibility for course angle bearings θS.sup.(Jθ) (t): θS.sup.(jθ) (t)=θ(t)+ΔθS.sup.(jθ) (t) (70) where θS(t) is the error-free course angle; ΔθS.sup.(jθ) (t) is the jθ th course angle measurement (bearing) error; and jθ=1, . . . , Nθ is the number of quasi simultaneously available course angle bearing data. Velocity measurement data checked for plausibility for velocity bearings VS.sup.(jV) (t): VS.sup.(jV) (t)=V(t)+ΔVS.sup.(jV) (t) (71) where V(t) is the error-free vehicle velocity ΔVS.sup.(jV) (t) is the jV th velocity (bearing) measurement error; and jV=1, . . . , NV is the number of quasi simultaneously available velocity bearing data. In deviation from Equations (8a) and (8b), one now obtains the following continuous-time measurement (bearing) equations: The position bearing equations result from comparisons of the positions obtained as a result of dead reckoning (RN FOA (t), RE FOA (t)) with the position bearing data (RNS.sup.(jP) (t), RES.sup.(jP) (t): ZN.sup.(jP) (t)=RNS.sup.(jP) (t)-RN.sup.FOA (t) (72a) ZE.sup.(jP) (t)=RES.sup.(jP) (t)-RE.sup.FOA (t) (72b) jP=1, . . . , NP where ZN.sup.(jP) (t) and ZE.sup.(jP) (t) is the jP th deviation between the dead reckoning position and the jP th bearing position in the north (N) and east (E) directions, respectively. The course angle bearing equations are obtained by comparing the course angle measurement signals (θM(t)) with the course angle bearing data (θS.sup.(jθ) (t): Zθ.sup.(jθ) (t)=θS.sup.(jθ) (t)-θM(t) (73) jθ=1, . . . , Nθ where Zθ.sup.(jθ) (t) is the jθ th difference between the course angle measurement signal and the jθ th course angle bearing value. The velocity bearing equations are obtained correspondingly in that the velocity measurement signals (VM(t)) are compared with the velocity bearing data (VS.sup.(jV) (t)): ZV.sup.(jV) (t)=VS.sup.(jV) (t)-VM(t) (74) jV=1, . . . , NV where ZV.sup.(jV) (t) is the jV th deviation between velocity measurement signal and jV th velocity bearing value. Continuous-time Error Equations Instead of Equations (10a) and (10b), the use of the error propagation theorem for Equations (72a) to (74) will provide the following measurement bearing error equations: Error due to position bearings: ΔZN.sup.(jP) (t)=ΔRNS.sup.(jP) (t)-ΔRN(t)=ZN.sup.(jP) (t) (75a) ΔZE.sup.(jP) (t)=ΔRES.sup.(jP) (t)-ΔRE(t)=ZE.sup.(jP) (t) (75b) jP=1, . . . , NP where ΔZN.sup.(jP) (t) and ΔZE.sup.(jP) (t) are the jP th position error differences in the north (N) and east (E) directions, respectively. Error due to course angle bearings: ΔZθ.sup.(jθ) (t)=ΔθS.sup.(jθ) (t)-Δθ(t)=Zθ.sup.(jθ) (t) (76) jθ=1, . . . , Nθ where ΔZθ.sup.(jθ) (t) is the jθ th course angle error difference. Error due to velocity bearings: ΔZV.sup.(jV) (t)=ΔVS.sup.(jV) (t)-ΔV(t)=ZV.sup.(jV) (t) (77) jV=1, . . . , NV where ΔZV.sup.(jV) (t) is the jV th velocity error difference. The mathematical model formation for the individual bearing errors is now effected, in deviation from Equation (13), as follows: It is assumed that all errors occurring in the bearings can be described by Gaussian white, i.e. normally distributed, (time) uncorrelated, noise. The following error models then result: Position bearing error models (in vector representation): ##EQU42## This means that the vectors of the position error components (ΔRNSWR.sup.(jP) (t), ΔRESWR.sup.(jP) (t); jP=1, . . . , NP) are each developed by stationary white noise with normal (N) distributions, shown in the abbreviated form by mean vectors O and the covariance or spectral density matrices VP.sup.(jP) with individual variances in the north (N) and east (E) directions (σ N .sup.(jP)) 2 and (σ E .sup.(jP)) 2 . Course angle bearing error models: ΔθS.sup.(jθ) (t)=ΔθSWR.sup.(jθ) (t) (79) where ##EQU43## is the abbreviated form for the course angle bearing error simulation (ΔθSWR.sup.(jθ) (t); jθ=1, . . . , Nθ) as stationary white noise with normal (N) distributions, O mean values and spectral power densities or variances (σ.sub.θS.sup.(jθ)) 2 , respectively. Velocity bearing error models: ΔVS.sup.(jV) (t)=ΔVSWR.sup.(jV) (t) (80) where ##EQU44## is the abbreviated form for the velocity bearing error simulation (ΔVSWR.sup.(jV) (t); jV=1, . . . , NV) as stationary white noise with normal (N) distributions, O mean values and spectral power densities or variances (σ VS .sup.(jV)) 2 , respectively. Furthermore, in this connection, assumptions are being made that the errors Δθ 3 (t) and ΔθSWR.sup.(jθ) (t); jθ=1, . . . , Nθ, as well as the errors ΔV 2 (t) and ΔVSWR.sup.(jV) (t); jV=1, . . . , NV are uncorrelated with one another. By using Equations (78) to (80) in Equations (75) to (77), the following continuous-time measurement (bearing) error equation system is obtained instead of Equations (15a) and (15b): ##EQU45## For the space state representation of the continuous-time measurement (bearing) error equations (Equations (81) to (83)) according to Equation (21), the corresponding vectors and matrices (Equations (18), (19), (24) and (26)) must be newly defined. The following determinations are favorable for microcomputer realization: Measurement (bearing) vector (instead of Equation (18)): ΔZ(t)=(ΔZP.sup.(jP) (t)|ΔZθ.sup.(jθ) (t)|ΔZV.sup.(jV) (t)).sup.T (84) where ##EQU46## Measurement (bearing) matrix (instead of Equation (24)): M(t)=M=(MP.sup.(jP) |Mθ.sup.(jθ) |MV.sup.(jV)).sup.T (85) where ##EQU47## Measurement (bearing) noise vector (instead of Equation (19)): V(t)=(VP.sup.(jP) (t)|Vθ.sup.(jθ) (t)|VV.sup.(jV) (t)).sup.T (86) where ##EQU48## Measurement (bearing) noise input matrix (new): S(t)=S=(SP.sup.(jP) |Sθ.sup.(jθ) |SV.sup.(jV)).sup.T (87) where ##EQU49## Measurement (bearing) error equation (analogous to Equation (21)): Combination of Equations (84) to (87) and (16) provides: ΔZ(t)=M·ΔX(t)+V(t) (88) where V(t)=S·V(t) according to Equations (86) and (87). Measurement (bearing) noise matrix (instead of Equation (26)): By using Equations (78) to (80), (11) and (12) as well as (86) and (87), the following results: ##EQU50## with ##EQU51## where E{V(t)}=S·E{V(t)}=O and ##EQU52## The conversion of the continuous-time system and measurement (bearing) error (differential) equations according to Equations (20) and (88) to discrete-time difference equations is effected, even with the quasi simultaneous availability of a plurality of navigation data for bearings, by means of the formalisms of Equations (28) to (39). Here again it is assumed that all bearings are taken exclusively at discrete points in time t=T i ; 1, 2, 3, . . . In this way, the continuous-time measurement (bearing) error equation (88) changes to ##EQU53## where i=1, 2, 3, . . . k=1, 2, 3, . . . according to Equation (28) V k =S·V k according to Equation (88) M is according to Equation (85); and Equations (89) and (90) apply for the discrete-time measurement (bearing) noise matrix. The discrete-time dead reckoning calculation according to Equations (40) and (41), respectively, which employs the actual velocity and course informations from the velocity sensor and the direction sensor remains just as uninfluenced from the quasi simultaneous multiple bearings. DISCRETE-TIME KALMAN FILTER ALGORITHMS Instead of a discrete-time Kalman filter with simultaneous measurement (bearing) data processing employed heretofore, it is here possible to use (and thus save computer time) an algorithm with sequential measuring (bearing) data processing. Starting from the recursive prediction (extrapolation) equations for the a priori system error estimate according to Equations (42) to (44), one now obtains, in deviation from Equations (45) to (48), the following algorithms for correction of the a priori systmem error estimate by measurements (bearings): Amplification matrices B k .sup.(j) at time t k =kT KA : ##EQU54## where VA.sub.m.sup.(i) =M.sup.(i) ·P.sub.x.sup.(i) ·(M.sup.(i)).sup.T +V.sup.(i) (91a) A posteriori estimation error ΔX k .sup.(j+l) at time t k =kT KA : ##EQU55## A posteriori estimation error covariance matrices P k .sup.(j+l) at time t k =kT KA : ##EQU56## where BM.sub.k.sup.(j) =(I-B.sub.k.sup.(j) M.sup.(j)) (93a) V.sup.(j) =S.sup.(j) ·V.sup.(j) ·(S.sup.(j)) T according to Equation (89); i=1, 2, 3, . . . , k=1, 2, 3, . . . , according to Equation (23); j=(jP), (jθ), (jV)=1, . . . , p; jP=1, . . . , NP; jθ=1, . . . , Nθ jV=1, . . . , NV; P=(NP+Nθ+NV); M.sup.(j) is according to Equation (85); S.sup.(j) is according to Equation (87); V.sup.(j) is according to Equation (90); Z k .sup.(j=jP) =ZP k .sup.(jP) =(ZN k .sup.(jP), ZE k .sup.(jP)) T according to Equations (72a) and (72b); Z k .sup.(j=jθ) =Zθ k .sup.(jθ) =Zθ k .sup.(jθ) according to Equation (73); Z k .sup.(j=jV) =ZV k .sup.(jV) =ZV k .sup.(jV) according to Equation (74); and the Marginal conditions P k .sup.(j=1)=P k * according to Equation (43); ΔX k .sup.(j=1) =ΔX k * according to Equation (42); ΔX.sub.k =ΔX.sub.k.sup.(j=p+1) ; (94) P.sub.k =1/2·[P.sub.k.sup.(j=p+1) +(P.sub.k.sup.(j=p+1)).sup.T ](95) With the modified algorithms for the corrected navigation system, the following changes and additions, respectively, result, on the basis of the multiple bearings: In deviation from Equations (53a) and (53b), one here obtains, analogously to the procedure with Equations (72a) to (74), the corrected discrete-time measurement (bearing) equations. Corrected discrete-time position bearing equations: CZP.sub.1.sup.(jP) =(CZN.sub.1.sup.(jP), CZE.sub.1.sup.(jP)).sup.T (96) with ##EQU57## and ##EQU58## and jP=1, . . . , NP, P=1,2,3, . . . i=1,2,3, . . . CZN 1 .sup.(jP) =jp th deviation between corrected dead reckoning CZE 1 .sup.(jP) =position and jp th bearing position in the north (N) and east (E) directions at time t 1 =1T KO . CRN 1 FOA =are according to Equations (54a) and (54b) or CRE 1 FOA =(55a) and (55b), respectively. Corrected discrete-time course angle bearing equations: CZθ.sub.1.sup.(jθ) =CZθ.sub.1.sup.(jθ) (97) with ##EQU59## and ##EQU60## as well as CZθ 1 .sup.(jθ) is the jθ th difference between corrected course angle measurement signal and the jθ th course angle bearing value at time t 1 =lT KO ; and Cθ 1 is according to Equation (51). Corrected discrete-time velocity bearing equations: CZV.sub.1.sup.(jV) =CZV.sub.1.sup.(jV) (98) with ##EQU61## ps and as well as CZV 1 .sup.(jV), which is the jV th deviation between corrected velocity measurement signal and the jV th velocity bearing value at time t 1 =1T KO ; and CV 1 is according to Equation (49). Dead reckoning in the corrected navigation system is again performed according to Equations (54a) and (54b) or Equations (55a) and (55b), respectively. The modified discrete-time Kalman filter algorithms will be given below for the corrected naviagation system with the sequential measurement (bearing) data processing appropriate here. The basis for this is the recursive prediction (extrapolation) algorithm for the a priori system error estimate according to Equations (56) to (58). Instead of Equations (59) to (68), the following relationships are now obtained as recursive modified algorithms for correction of the a priori system error estimate by the various measurements (bearings). Corrected amplification matrices CB k .sup.(j) at time t k =kT KA : ##EQU62## where CVA.sub.k.sup.(j) =M.sup.(j) ·CP.sub.k.sup.(j) ·(M.sup.(j)).sup.T +V.sup.(j) (99a) Corrected a posteriori estimation errors y k .sup.(j+1) at time t k =kT KA : ##EQU63## Corrected a posteriori estimation error covariance matrices CP k .sup.(j+1) at time t=kT KA : ##EQU64## with CBM.sub.k.sup.(j) =(I-CB.sub.k.sup.(j) ·M.sup.(j)) (102) V.sup.(j) =S.sup.(j) ·V.sup.(j) ·S.sup.(j) according to Equation (89); i=1, 2, 3, . . . ) according to Equation (28); k=1, 2, 3, . . . j=(jP), (jθ), (jV)=1, . . . , p; jP=1, . . . , NP; jθ=1, . . . , Nθ; jV=1, . . . , NV; p=(NP+Nθ+NV); M.sup.(j) is according to Equation (85); S.sup.(j) is according to Equation (87); V.sup.(j) is according to Equation (90); CZ k .sup.(j=jP) is according to Equation (96); CZ k .sup.(j=jθ) is according to Equation (97); CZ k .sup.(j=jV) is according to Equation (98); and the Marginal conditions: CP k .sup.(j=1)=CP k * according to Equation (56) ##EQU65## Here, Equation (105) now defines the correction value vector at time t k =k·T KA with the definitions according to Equations (61) to (63) as well as Equations (65) and (66). It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

A navigation method for the navigation of a vehicle employing direction and longitudinal movement sensors. Signals from the sensors are fed to a position computer which determines the vehicle position relative to a coordinate grid system. When the vehicle reaches a position of known coordinates the position values which are determined from the sensor signals are corrected with reference to the known coordinates, and a Kalman filter is provided which effects an error estimate and subsequently a correction value determination from the error estimate which results in a significant increase in accuracy of the displayed navigation data. The particular advantage of the method is the use of uncomplicated sensors which are able, in connection with the Kalman filter, to obtain highly accurate vehicle position data.

FIELD OF THE INVENTION [0001] The present claimed invention relates generally to the field of wireless communication systems. More particularly, the present claimed invention relates to client aware file system management in a client independent wireless environment. BACKGROUND ART [0002] The Internet has become the dominant vehicle for data communications. And with the growth of Internet usage has come a corresponding growth in the usage of Internet devices, wireless devices and services. [0003] The growing base of Internet users has become accustomed to readily accessing Internet-based services such as e-mail, calendar or content at any time from any location. These services, however, have traditionally been accessible primarily through stationary PCs. However, demand is now building for easy access to these and other communication services for mobile devices. [0004] As the demand for mobile and wireless devices increases, enterprises must roll out new communication capabilities beyond the reach of traditional wired devices, by extending the enterprise with extra-net applications, etc., to effectively and efficiently connect mobile employees with their home base. As the number of digital subscribers grows, traditional wireless providers must find applications suitable to the needs of these new mobile users. [0005] However, service providers are not the only ones seeking applications to meet the growing service needs of wireless users. Traditional portal developers are also extending their traditional PC browser desktop services to these new wireless markets. [0006] With the growth of the wireless market comes a corresponding growth in wireless business opportunities which in today's ever-growing markets means, there is a plethora of services available to customers of the people that use these services. Many wireless service providers are now looking to add to basic core services by extending services such as e-mail, short messaging service notification, and other links to IP-based applications to drive additional business and revenues. [0007] As the wireless market grows and Internet access becomes more mainstream and begins to move to new devices, wireless service providers are looking to develop highly leveraged Internet Protocol based applications on top of existing network infrastructure. To meet the growing demand for wireless client devices, enterprises need to provide access to any type of service from any type of device from anywhere and to provide content suitable for these devices without incurring substantial cost overhead. [0008] The growth in wireless devices also means that traditional computer users who used to be tied to their desktop computers may now be mobile and would require remote access to network applications and services such as email. The mobility of wireless users presents a host of challenges to service providers who may have to provide traditional service to these new wireless devices. One such service is provided by Sun Microsystems, Inc., through its iPlanet™ platform to allow service providers to grow their services from basic traditional services such as voice to leading edge wireless applications with carrier-grade reliability and performance. [0009] In addition to the traditional network applications that these new wireless users seek, the growth of the Internet and the introduction of new Internet enabled wireless devices have led to the explosive use of community-based web sites or portals. The growth in portals has created a need for wireless environments to provide portal support to handle the collection of data related to different topics such as news, stock quotes, applications and services required by wireless device users. [0010] [0010]FIG. 1 depicts a prior art wireless client dependent based environment solution to handle similarly configured wireless clients running similar applications or portals. The environment depicted in FIG. 1 includes wireless devices such as a WAP phone 101 , a wireless PC 102 , a refrigerator 103 , etc. In general, the wireless environment depicted in FIG. 1 is categorized into the network (Internet 104 ), Clients (e.g. mobile phone 101 , PCs 102 and household appliances 103 ) and resources (e.g., web-sites 105 , portals 106 and other applications 107 ). [0011] For most of the wireless clients connected to the Internet 104 , portals 106 offer the client the starting point of experiencing the Internet 104 . Portals 106 are typically community based web-sites that securely hold a collection of data related to different topics, including such applications as news, stock quotes, etc. For example, a wireless client connecting to the Internet will first login to a web portal site (e.g., yahoo) and from there browse through various sites to search for a host of different services. [0012] The portals typically reside in a portal server which bundles an aggregation of services provided by an Internet service provider and provides these services to wireless clients. A wireless portal server such as that developed by Sun Microsystems, Inc. provides such portal access to wireless application resources residing on resource servers A 108 , B 109 and C 110 . [0013] The prior art wireless server depicted in FIG. 1 primarily supports the two major types of browsers known by most Internet users. These include the Microsoft Internet Explorer Browser and the Netscape Communicator Browser. These browsers are both Hyper Text Markup Language (HTML) based and suitable for some wireless devices, especially devices with large display screens. However, as wireless display screens get smaller in size, traditional HTML browsers are no longer suitable for transmitting content to these wireless devices. [0014] To ensure suitable content delivery, wireless device and wireless software providers have developed a myriad of micro-browsers which appropriately adapt to these wireless devices with different display screen requirements in order to take advantage of the numerous content on the Internet. The availability of these new micro-browsers means that service providers do not have to create different sets of content for different wireless devices even if the devices are dissimilar. [0015] The support of primarily only two major types of browsers is a drawback because it does not allow the wireless server to identify and recognize a myriad of today's micro browsers such as those used by a host of wireless phones and other handheld devices other than the two major types. This restricts the number of wireless client devices which may be connected to the server. [0016] In the prior art wireless environment depicted in FIG. 1, clients requesting services to the wireless environment are identified by the server by one of two ways. The first is by way of predefined, pre-configured device types which are stored in the server and enable the server to identify clients trying to connect to it The second method of detection is by way of a complex tool-kit which is typically sold with the wireless clients. In the case of the tool-kit approach, the end-user has the burden to program the client in order for the wireless server to identify the client during a connection session to the server. [0017] Either one of these prior art detection schemes have some drawback. In the first detection scheme, the wireless server is unable to identify device types which are not pre-defined and stored in the server. An entire software upgrade is required to recognize new client types. And in the second scheme, the end-user requires technical software programming expertise to be able to program the tool-kit to enable detection and use of the wireless server resources. [0018] Another drawback of the prior art system as shown in FIG. 1, is that most of the servers are designed to identify clients using the least common characteristics of known clients. For example, a server which is designed to recognize wireless phones will have as the least common identifier the phone characteristics common to all the identifiable phones which will be used to identify service request to the wireless environment. Thus, if two wireless phones exist of the same manufacturer, but with two dissimilar screen requirements (e.g., 4 line text display vs. 8 line text display), then the server will be designed to support wireless phones by that manufacturer as requiring only 4 line text display (least common characteristic). [0019] The discrepancies between display information on the two phones in this example becomes very pronounced if one considers the fact that the phone requiring an 8 line text display loses 50% of its display capabilities. Thus, the client is unable to take advantage of the full richness such as the look and feel features of the client interface with the end-user, the scripting behavior of the interface, etc. [0020] A further drawback of the wireless server of the prior art is that most of the servers are designed to identify wireless clients using HTML as the default identifier. Thus, a client running any other Internet language will not be identified and therefore denied services, or given incompatible content SUMMARY OF INVENTION [0021] Accordingly, to take advantage of the myriad of applications and the numerous wireless clients being developed, a wireless server with extensibility capabilities to allow wireless clients to be dynamically configured and identified by the wireless server is needed. A need exists for “out-of-the-box” wireless system solutions to allow technically inept end-users to connect to the wireless environment without unduly tasking the end-user's technical abilities. A need further exists for an improved and less costly device independent system which improves efficiency and identification of various wireless clients without losing the embedded features designed for these devices. [0022] The present invention is directed to a system and a method for identifying wireless clients in a client independent wireless system. The present invention is capable of handling both voice and data transmission over an Internet protocol local access network within wireless systems without the losing inherent characteristics of the client when it connects to a wireless server within the wireless system to request services. [0023] Embodiments of the invention include pluggable Client Detection Modules which provide automatic and extensible client identification using characteristics of the client as unique identifiers by the wireless server to provide services. The client characteristics may or may not be known to the wireless server at the time a client attempts to connect to the server. An Application Program Interface (API) is used which can assist newly created “out-of-the-box” detection modules to add detection support to the server. [0024] Embodiments of the present invention further include client extensible logic which allows the wireless client to dynamically add additional characteristics to any defaults that might be stored in the wireless server to enable the server to identify the client as the client attempts to connect to the server. In this way, the client detection logic of the invention is extensible to recognize new device classes without requiring software version updates or complex programming tasks. An API can be used to collect extensible data sets that include custom parameters for recognizing a particular client class, such as defined header information of the client's browser, the time of day the client requests are received and the client's bandwidth. [0025] Embodiments of the present invention further include a User Agent information decipher which is coupled to parse client request HTTP headers. The User Agent information is parsed to identify wireless client type information to enable the wireless server to provide the appropriate services to identified clients connected to the system. [0026] These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures. BRIEF DESCRIPTION OF THE DRAWINGS [0027] The accompanying drawings, which are incorporated in and form a part of this specification, illustrates embodiments of the invention and, together with the description, serve to explain the principles of the invention: [0028] Prior Art FIG. 1 is a block diagram of a conventional device dependent wireless system; [0029] [0029]FIG. 2 is a block diagram of an implementation of a device independent wireless system of the present invention; [0030] [0030]FIG. 3 is a block diagram of an exemplary internal architecture of the wireless server of FIG. 2; [0031] [0031]FIG. 4 is a block diagram of an embodiment of the client aware detection system of the present invention; and [0032] [0032]FIG. 5 is a flow diagram of an embodiment of the client detection logic of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0033] Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. [0034] On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended Claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention. [0035] The invention is directed to a system, an architecture, subsystem and method to manage wireless client detection in a client independent wireless environment in a way superior to the prior art In accordance with an aspect of the invention, a wireless server provides wireless client extensibility which enables non predefined devices to be identified by the wireless server. [0036] In the following detailed description of the present invention, a system and method for a wireless Internet protocol based communication system is described. Numerous specific details are not set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one skilled in the art that the present invention may be practiced without these specific details or with equivalents thereof. [0037] Generally, an aspect of the invention encompasses providing an integrated wireless Internet server which provides a wide range of voice, data, video and other services to wireless clients which may connect to the wireless environment to be serviced alongside predefined wireless clients. The invention can be more fully described with reference to FIGS. 2 through 5. [0038] [0038]FIG. 2 depicts an embodiment of the wireless device independent based environment of the present invention. The wireless environment depicted in FIG. 2 comprises a wireless application protocol (WAP) based phone, a WAP transmission infrastructure 203 , a WAP gateway 205 , the Internet 206 and a wireless server 210 . In a Global Switch Mobile network for instance, when the phone transmission is received by the mobile switching center, it realizes it is packet data and sends it to the proper channel to be processed. The WAP gateway 205 typically resides on the Local Area Network (LAN) within a telecom carriers premises. It is not generally a part of the wireless server. The WAP gateway 205 is responsible for connecting the Wireless Markup Language/HTTP content and protocol into a bundled compressed, encoded, encrypted version of WML over WAP. [0039] Conversely, the WAP gateway 205 also performs the translation of WAP commands into HTTP requests which can be sent over the public Internet. The WAP gateway 205 can also store user's bookmarks, two of which could point to the wireless server's messaging and other resource services. The wireless server 210 communicates WML over HTTP on the front -end and communicates in native protocol of the target server on the back-end. [0040] The wireless server 210 communicates to these back-end resource servers using the backend server's native protocol. For example, the wireless server may communicate to resource server A which may be a messaging server using Internet Message Access Protocol (IMAP). A Lightweight Directory Access Protocol (LDAP) is used for all communications to and from the resource server B. And an extensible markup language Q(ML) protocol may be used to communicate with resource server C. [0041] Although the wireless server depicted in FIG. 2 is capable of communicating in these native protocols shown in FIG. 2, the wireless server protocol's handling capability can be extended to support other protocols. The wireless server implements the Wireless Markup Language (WML) interface and generates the corresponding WML content based on what it receives from the back-end server. [0042] [0042]FIG. 3 is a block diagram illustration of one embodiment of the wireless system of the present invention. The wireless system shown in FIG. 3 includes a Wireless Server 210 (WS) and Wireless Clients 200 . The WS 210 includes Client Detection Module (CDM) 300 , Client Data (CD) module 310 which couples to CDM 300 , Profile Service (PS) module 320 which couples to CD 310 and Session Service (SS) module 340 . WS 210 may include other modules which have not been disclosed here in order not to confuse the teachings of the present invention. [0043] The wireless server 210 shown in FIG. 3 is flexible, scalable, extensible and capable of supporting a rich evolving range of networks such as Global system for mobile communication (GSM) Networks, Code Division Multiple Access (CDMA) Networks, Time Division Multiple Access (TDMA) Networks, Third Generation (3G) Networks and others. [0044] The architecture of the server is also capable of handling a variety of wireless environments and markup languages such as the wireless markup language (WML), the handheld device markup language (HDML) and the hypertext markup language (HTML). The server 210 is capable of providing support for multiple devices and is easily adaptable and extensible to additional devices and markup languages. [0045] CDM 300 receives client service request to WS 210 via a client detection software API CDM 300 determines the clients device characteristic such as content-type, template directory, etc. Unlike the prior art, CDM 300 does not assume a client request to only emanate from HTML based devices and is therefore capable of identifying a host of micro-browsers used by a number of wireless clients. [0046] The client type information gathered by the CDM 300 in the present invention may include the client's browser type, version number and underlying Operating System supporting the browser. The client type information may further include the client's bandwidth information, time of the day the client is allowed to receive certain services by the content provider (e.g., real time stock quotes, etc.), client's location, etc. All of this information can be used by the CDM 300 to automatically detect the client type. [0047] Client data extracted by CDM 300 is passed to CD 310 which stores client data objects of various properties of the client, such as user-agent matching pattern, acceptable response content-type, cookie support status, etc. Unlike the prior art, CD 310 relies on other characteristics of a client's request information for storage rather than assuming that any client request information represented a generic HTML device. Furthermore, in the present invention, CD 310 is readily extensible to enable additional attributes of a client connecting to WS 210 to be dynamically added as needed. [0048] SS module 340 stores transient information pertaining to a user's active session with the client device when the client initiates a service request to the server. A new session property is defined to store a clientType identifier after the client has been detected by the Wireless Server 210 . [0049] CDM 300 performs automatic client detection based on header information contained in the client's browser, (e.g., name of browser, version, operating system supported by the browser, hardware descriptions, etc.), the time of day the client request is received and the bandwidth of the client's communication. These and other factors are aggregated together and considered by the CDM 300 during its automatic detection processes. [0050] Importantly, the CDM 300 requires data modules for performing individual client type detection. These data modules are extensible so that new detection can be added for header type information, bandwidth information, time of day information, which all can be used to recognize a particular new client type. [0051] Referring to FIG. 4, a block diagram illustration of one embodiment of the Client Detection Module (CDM) 300 is shown. CDM 300 comprises a client request receiving logic (CRRL) unit 410 , a client request processing logic (CRP) 420 , Predefined Client Data Logic (PCD) 430 and Extensible Client Data (ECD) 440 . [0052] All client service requests made to the WS 210 from clients connected to the wireless network are passed to CRRL 410 . When a client initiates a service request, the request is forwarded to CRRL 410 . Each client service request includes header information from which CRRL 410 is able to extract the necessary client characteristics to process the request. When CRRL 410 receives the client's initial request, it parses the HTTP header to get the User Agent (UA) information. The parsed information is then passed on to the CRL 420 . CRRL 410 may also use other headers apart form the user-agent headers to extract the client-type information. [0053] CRL 420 couples to CRRL 410 to process the UA information received from the client request HTTP headers. Embedded in each UA is information which specifies the client device type. If the UA indicates a device type which matches known client types (predefined clients), CRD 420 executes a call to PCD 430 and attempts to find a match for user agents. If a match is determined by PCD 430 , the client is connected to an authenticating servers of the server 210 and provided with the service being requested. For example, if the UA indicates that the device is a WAP phone, the appropriate Client type identifier is stored in session for the client. [0054] Based on the stored Client type identifier, the server knows which method to invoke to provided the requested service. In addition to the UA, CRD 420 can look at other headers of the client request, such as the time of day (e.g., time of day the client can have access to certain services in the wireless environment as defined by the service provider), the user making the request and other information that may be gathered from the client's environment in determining what services to provide the client in response to the client's request. [0055] If no known device type is found by CRD 420 , a call is executed to ECD 440 to extend the current data objects stored in the server; thereby effectively creating a subclass and overriding certain predefined methods in the server. This functionality is extremely important since many wireless devices have unique interfaces and do not follow a common implementation standard, it is critical for a WML generation engine in WS 210 to be flexible and extensible to add these new devices. Extensibility in the present invention is achieved by implementing API level additions by the content server provider, who provide services to the wireless clients, to add environmental characteristics to uniquely identify and distinguish a class of clients from others. The extensible API could also be programmed by a system developer from run-time information gathered from the client. [0056] Since WS 210 knows about the differences between various wireless devices, e.g., differences between WAP phones or differences between phone and Palm browsers, etc. CRD 420 does not need to know the differences between devices. It only needs to present the client characteristics provided by the client to be processed in WS 210 . [0057] Referring now to FIG. 5, a logic flow diagram of one embodiment of the client detection scheme of the present invention is shown. A client initiates service request to initiate the detection scheme at step 510 . [0058] At step 520 , the client detection module examines the HTTP header from the client request using the client data API to access the client data objects to find a suitable match. [0059] At step 530 , if the client device type information included in the user agent information matches, CDM 300 returns a unique identifier (clientType) of the matching client data object and the client type information is presented to the session service logic at step 550 . In the present invention, clientType defines a logic group of clients uniquely identified by an extensible list of properties. Two devices that are of the same clientType can be treated as identical as far as how the server should respond to their requests. [0060] On the other hand, if the client type in the UA is not a match in the client data objects, the client type information is added to extend the current WMNL object class and processing ends at step 540 and the client type information is provided to the session service at step 550 . [0061] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.

A wireless portal system having a wireless server with an automatic client aware detection mechanism. The client aware detection mechanism includes logic for identifying client wireless devices connected to the wireless server by using particular characteristics of the client in detecting service connection requests from the client to the server. In one embodiment of the invention, the client aware detection mechanism is capable of being extended by the client to add-on client information characteristics which are not already pre-stored in the wireless server. In this way, the client detection logic of the invention is extensible to recognize new devices without requiring software version updates or complex programming tasks. An API can be used to collect extensible data sets that include custom parameters for recognizing a particular client class, such as defined header information of the client's browser, the time of day the client requests are received and the client's bandwidth.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is divisional application of U.S. application Ser. No. 13/133,096, filed on Jun. 6, 2011, which is a United States Application under 37 U.S.C. §371 claiming benefit of PCT application No. PCT/US2009/006443, filed on Dec. 7, 2009, which claims the benefit of U.S. Provisional Application No. 61/120,444, filed on Dec. 6, 2008, the contents of each of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to a compound of Formula I as described below, processes for their production, their use as pharmaceuticals and pharmaceutical compositions comprising them. Of particular interest are novel compounds useful as inhibitors of phosphodiesterase 1 (PDE1), e.g., in the treatment of diseases involving disorders of the dopamine D1 receptor intracellular pathway, such as Parkinson's disease, depression, narcolepsy, damage to cognitive function, e.g., in schizophrenia, or disorders that may be ameliorated through enhanced progesterone-signaling pathway, e.g., female sexual dysfunction. BACKGROUND OF THE INVENTION Eleven families of phosphodiesterases (PDEs) have been identified but only PDEs in Family I, the Ca 2+ -calmodulin-dependent phosphodiesterases (CaM-PDEs), have been shown to mediate both the calcium and cyclic nucleotide (e.g. cAMP and cGMP) signaling pathways. The three known CaM-PDE genes, PDE1A, PDE1B, and PDE1C, are all expressed in central nervous system tissue. PDE1A is expressed throughout the brain with higher levels of expression in the CA1 to CA3 layers of the hippocampus and cerebellum and at a low level in the striatum. PDE1A is also expressed in the lung and heart. PDE1B is predominately expressed in the striatum, dentate gyms, olfactory tract and cerebellum, and its expression correlates with brain regions having high levels of dopaminergic innervation. Although PDE1B is primarily expressed in the central nervous system, it may be detected in the heart. PDE1C is primarily expressed in olfactory epithelium, cerebellar granule cells, and striatum. PDE1C is also expressed in the heart and vascular smooth muscle. Cyclic nucleotide phosphodiesterases decrease intracellular cAMP and cGMP signaling by hydrolyzing these cyclic nucleotides to their respective inactive 5′-monophosphates (5′AMP and 5′GMP). CaM-PDEs play a critical role in mediating signal transduction in brain cells, particularly within an area of the brain known as the basal ganglia or striatum. For example, NMDA-type glutamate receptor activation and/or dopamine D2 receptor activation result in increased intracellular calcium concentrations, leading to activation of effectors such as calmodulin-dependent kinase II (CaMKII) and calcineurin and to activation of CaM-PDEs, resulting in reduced cAMP and cGMP. Dopamine D1 receptor activation, on the other hand, leads to activation of nucleotide cyclases, resulting in increased cAMP and cGMP. These cyclic nucleotides in turn activate protein kinase A (PKA; cAMP-dependent protein kinase) and/or protein kinase G (PKG; cGMP-dependent protein kinase) that phosphorylate downstream signal transduction pathway elements such as DARPP-32 (dopamine and cAMP-regulated phosphoprotein) and cAMP responsive element binding protein (CREB). Phosphorylated DARPP-32 in turn inhibits the activity of protein phosphates-1 (PP-1), thereby increasing the state of phosphorylation of substrate proteins such as progesterone receptor (PR), leading to induction of physiologic responses. Studies in rodents have suggested that inducing cAMP and cGMP synthesis through activation of dopamine D1 or progesterone receptor enhances progesterone signaling associated with various physiological responses, including the lordosis response associated with receptivity to mating in some rodents. See Mani, et al., Science (2000) 287: 1053, the contents of which are incorporated herein by reference. CaM-PDEs can therefore affect dopamine-regulated and other intracellular signaling pathways in the basal ganglia (striatum), including but not limited to nitric oxide, noradrenergic, neurotensin, CCK, VIP, serotonin, glutamate (e.g., NMDA receptor, AMPA receptor), GABA, acetylcholine, adenosine (e.g., A2A receptor), cannabinoid receptor, natriuretic peptide (e.g., ANP, BNP, CNP), DARPP-32, and endorphin intracellular signaling pathways. Phosphodiesterase (PDE) activity, in particular, phosphodiesterase 1 (PDE1) activity, functions in brain tissue as a regulator of locomotor activity and learning and memory. PDE1 is a therapeutic target for regulation of intracellular signaling pathways, preferably in the nervous system, including but not limited to a dopamine D1 receptor, dopamine D2 receptor, nitric oxide, noradrenergic, neurotensin, CCK, VIP, serotonin, glutamate (e.g., NMDA receptor, AMPA receptor), GABA, acetylcholine, adenosine (e.g., A2A receptor), cannabinoid receptor, natriuretic peptide (e.g., ANP, BNP, CNP), endorphin intracellular signaling pathway and progesterone signaling pathway. For example, inhibition of PDE1B should act to potentiate the effect of a dopamine D1 agonist by protecting cGMP and cAMP from degradation, and should similarly inhibit dopamine D2 receptor signaling pathways, by inhibiting PDE1 activity. Chronic elevation in intracellular calcium levels is linked to cell death in numerous disorders, particularly in neurodegerative diseases such as Alzheimer's, Parkinson's and Huntington's Diseases and in disorders of the circulatory system leading to stroke and myocardial infarction. PDE1 inhibitors are therefore potentially useful in diseases characterized by reduced dopamine D1 receptor signaling activity, such as Parkinson's disease, restless leg syndrome, depression, narcolepsy and cognitive impairment. PDE1 inhibitors are also useful in diseases that may be alleviated by the enhancement of progesterone-signaling such as female sexual dysfunction. There is thus a need for compounds that selectively inhibit PDE1 activity, especially PDE1A and/or PDE1B activity. SUMMARY OF THE INVENTION In the first embodiment, the invention provides a compound of Formula II wherein (i) L is S, SO or SO 2 ; (ii) R 1 is H or C 1-6 alkyl (e.g., methyl or ethyl); (iii) R 2 is H, C 1-6 alkyl (e.g., isopropyl, isobutyl, neopentyl, 2-methylbutyl, 2,2-dimethylpropyl) wherein said alkyl group is optionally substituted with halo (e.g., fluoro) or hydroxy (e.g., 1-hydroxypropan-2-yl, 3-hydroxy-2-methylpropyl), —C 0-4 alkyl-C 3-8 cycloalkyl (e.g., cyclopentyl, cyclohexyl) optionally substituted with one or more amino (e.g., —NH 2 ), for example, 2-aminocyclopentyl or 2-aminocyclohexyl), wherein said cycloalkyl optionally contains one or more heteroatom selected from N and O and is optionally substituted with C 1-6 alkyl (e.g., 1-methyl-pyrrolindin-2-yl, 1-methyl-pyrrolindin-3-yl, 1-methyl-pyrrolindin-2-yl-methyl or 1-methyl-pyrrolindin-3-yl-methyl), C 3-8 heterocycloalkyl (e.g., pyrrolidinyl, for example, pyrrolidin-3-yl) optionally substituted with C 1-6 alkyl (e.g., methyl), for example, 1-methylpyrrolidin-3-yl, C 3-8 cycloalkyl-C 1-6 alkyl (e.g.,cyclopropylmethyl), haloC 1-6 alkyl (e.g., trifluoromethyl, 2,2,2-trifluoroethyl), —N(R 14 )(R 15 )—C 1-6 alkyl (e.g., 2-(dimethylamino)ethyl,2-aminopropyl), hydroxyC 1-6 alkyl (e.g., (e.g., 3-hydroxy-2-methylpropyl, 1-hydroxyprop-2-yl), arylC 0-6 alkyl (e.g., benzyl), heteroarylC 1-6 alkyl (e.g., pyridinylmethyl), C 1-6 alkoxyarylC 1-6 alkyl (e.g., 4-methoxybenzyl); -G-J wherein: G is a single bond or, alkylene (e.g., methylene); J is cycloalkyl or heterocycloalkyl (e.g., oxetan-2-yl, pyrolyin-3-yl, pyrolyin-2-yl) optionally substituted with C 1-6 alkyl (e.g., (1-methylpyrolidin-2-yl)); (iv) R 3 is attached to one of the nitrogens on the pyrazolo portion of Formula I and is a moiety of Formula A wherein X, Y and Z are, independently, N or C, and R 8 , R 9 , R 11 and R 12 are independently H or halogen (e.g., Cl or F); and R 10 is halogen, C 1-6 alkyl, C 3-8 cycloalkyl, heteroC 3-8 cycloalkyl (e.g., pyrrolidinyl or piperidinyl) haloC 1-6 alkyl (e.g., trifluoromethyl), aryl (e.g., phenyl), heteroaryl (e.g., pyridyl, (for example, pyrid-2-yl) or e.g., thiadiazolyl (for example, 1,2,3-thiadiazol-4-yl), diazolyl, triazolyl (e.g., 1,2,4-triazol-1-yl), tetrazolyl (e.g., tetrazol-5-yl), alkoxadiazolyl (e.g., 5-methyl-1,2,4-oxadiazol), pyrazolyl (e.g., pyrazol-1-yl), alkyl sulfonyl (e.g., methyl sulfonyl), arylcarbonyl (e.g., benzoyl), or heteroarylcarbonyl, alkoxycarbonyl, (e.g., methoxycarbonyl), aminocarbonyl; preferably phenyl, pyridyl, e.g., 2-pyridyl, piperidinyl, or pyrrolidinyl; wherein the aryl, heteroaryl cycloalkyl or heterocycloalkyl is optionally substituted with one or more halo (e.g., F or Cl), C 1-4 alkyl, C 1-4 alkoxy, C 1-4 haloalkyl (e.g., trifluoromethyl), and/or —SH, provided that when X, Y or X is nitrogen, R 8 , R 9 or R 10 , respectively, is not present; (v) R 4 is H, C 1-6 alkyl (e.g., methyl, isopropyl), C 3-8 cycloalkyl (e.g., cyclopentyl), C 3-8 heterocycloalkyl (e.g., pyrrolidin-3-yl), aryl (e.g., phenyl) or heteroaryl (e.g., pyrid-4-yl, pyrid-2-yl or pyrazol-3-yl) wherein said aryl or heteroaryl is optionally substituted with halo (e.g., 4-fluorophenyl), hydroxy (e.g., 4-hydroxyphenyl), C 1-6 alkyl, C 1-6 alkoxy or another aryl group (e.g., biphenyl-4-ylmethyl); (vi) R 14 and R 15 are independently H or C 1-6 alkyl, in free or salt form. In still another embodiment, the invention provides a Compound of Formula II as described above, wherein R 4 is: C 1-6 alkyl (e.g., methyl, isopropyl), C 3-8 cycloalkyl (e.g., cyclopentyl), C 3-8 heterocycloalkyl (e.g., pyrrolidin-3-yl), aryl (e.g., phenyl) or heteroaryl (e.g., pyrid-4-yl, pyrid-2-yl or pyrazol-3-yl) wherein said aryl or heteroaryl is optionally substituted with halo (e.g., 4-fluorophenyl), hydroxy (e.g., 4-hydroxyphenyl), C 1-6 alkyl, C 1-6 alkoxy or another aryl group (e.g., biphenyl-4-ylmethyl); and R 3 is attached to one of the nitrogens on the pyrazolo portion of Formula I and is a moiety of Formula A wherein X, Y and Z are, independently, N or C, and R 8 , R 9 , R 11 and R 12 are independently H or halogen (e.g., Cl or F); and R 10 is C 3-8 cycloalkyl heteroC 3-8 cycloalkyl (e.g., pyrrolidinyl or piperidinyl) aryl (e.g., phenyl), or heteroaryl (e.g., pyridyl, (for example, pyrid-2-yl) or e.g., thiadiazolyl (for example, 1,2,3-thiadiazol-4-yl), diazolyl, triazolyl (e.g., 1,2,4-triazol-1-yl), tetrazolyl (e.g., tetrazol-5-yl), alkoxadiazolyl (e.g., 5-methyl-1,2,4-oxadiazol), pyrazolyl (e.g., pyrazol-1-yl), wherein the aryl or heteroaryl is optionally substituted with one or more halo (e.g., F or Cl), C 1-4 alkyl, C 1-4 alkoxy, C 1-4 haloalkyl (e.g., trifluoromethyl), and/or —SH, provided that when X, Y or X is nitrogen, R 8 , R 9 or R 10 , respectively, is not present; in free or salt form. The invention also provides a compound of formula I wherein (i) Lis S, SO or SO 2 ; (ii) R 1 is H or C 1-6 alkyl (e.g., methyl or ethyl); (iii) R 2 is H, C 1-6 alkyl (e.g., isopropyl, isobutyl, neopentyl, 2-methylbutyl, 2,2-dimethylpropyl) wherein said alkyl group is optionally substituted with halo (e.g., fluoro) or hydroxy (e.g., 1-hydroxypropan-2-yl, 3-hydroxy-2-methylpropyl), —C 0-4 alkyl-C 3-8 cycloalkyl (e.g., cyclopentyl, cyclohexyl) optionally substituted with one or more amino (e.g., —NH 2 ), for example, 2-aminocyclopentyl or 2-aminocyclohexyl), wherein said cycloalkyl optionally contains one or more heteroatom selected from N and O and is optionally substituted with C 1-6 alkyl (e.g., 1-methyl-pyrrolindin-2-yl, 1-methyl-pyrrolindin-3-yl, 1-methyl-pyrrolindin-2-yl-methyl or 1-methyl-pyrrolindin-3-yl-methyl), C 3-8 heterocycloalkyl (e.g., pyrrolidinyl, for example, pyrrolidin-3-yl) optionally substituted with C 1-6 alkyl (e.g., methyl), for example, 1-methylpyrrolidin-3-yl, C 3-8 cycloalkyl-C 1-6 alkyl (e.g.,cyclopropylmethyl), haloC 1-6 alkyl (e.g., trifluoromethyl, 2,2,2-trifluoroethyl), —N(R 14 )(R 15 )—C 1-6 alkyl (e.g., 2-(dimethylamino)ethyl,2-aminopropyl), hydroxyC 1-6 alkyl (e.g., (e.g., 3-hydroxy-2-methylpropyl, 1-hydroxyprop-2-yl), arylC 0-6 alkyl (e.g., benzyl), heteroarylC 1-6 alkyl (e.g., pyridinylmethyl), C 1-6 alkoxyarylC 1-6 alkyl (e.g., 4-methoxybenzyl); -G-J wherein: G is a single bond or, alkylene (e.g., methylene); J is cycloalkyl or heterocycloalkyl (e.g., oxetan-2-yl, pyrolyin-3-yl, pyrolyin-2-yl) optionally substituted with C 1-6 alkyl (e.g., (1-methylpyrolidin-2-yl)); (iv) R 3 is 1) -D-E-F wherein: D is a single bond, C 1-6 alkylene (e.g., methylene), or arylalkylene (e.g., pbenzylene or —CH 2 C 6 H 4 —); E is a single bond, C 1-4 alkylene (e.g., methylene, ethynylene, prop-2-yn-1-ylene), —C 0-4 alkylarylene (e.g., phenylene or —C 6 H 4 —, -benzylene- or —CH 2 C 6 H 4 —), wherein the arylene group is optionally substituted with halo (e.g., Cl or F), heteroarylene (e.g., pyridinylene or pyrimidinylene), aminoC 1-6 alkylene (e.g., —CH 2 N(H)—), amino (e.g., —N(H)—); C 3-8 cycloalkylene optionally containing one or more heteroatom selected from N or O (e.g., piperidinylene), F is H, halo (e.g., F, Br, Cl), C 1-6 alkyl (e.g., isopropyl or isobutyl), haloC 1-6 alkyl (e.g., trifluoromethyl), aryl (e.g., phenyl), C 3-8 cycloalkyl optionally containing at least one atom selected from a group consisting of N or O (e.g., cyclopentyl, cyclohexyl, piperidinyl, pyrrolidinyl, tetrahydro-2H-pyran-4-yl, or morpholinyl), and optionally substituted with C 1-6 alkyl (e.g., methyl or isopropyl), for example, 1-methylpyrrolidin-2-yl, pyrrolidin-1-yl, pyrrolidin-2-yl, piperidin-2-yl, 1-methylpiperidin-2-yl, 1-ethylpiperidin-2-yl, heteroaryl optionally substituted with C 1-6 alkyl, (e.g., pyridyl, (for example, pyrid-2-yl), pyrimidinyl (for example, pyrimidin-2-yl, pyrimidin-4-yl), thiadiazolyl (for example, 1,2,3-thiadiazol-4-yl), oxazolyl (e.g., oxazol-2-yl), diazolyl (e.g., pyrazolyl (for example, pyrazol-1-yl) or imidazolyl (for example, imidazol-1-yl, 4-methylimidazolyl, 1-methylimidazol-2-yl,), triazolyl (e.g., 1,2,4-triazol-1-yl), tetrazolyl (e.g., tetrazol-5-yl), alkoxadiazolyl (e.g., 5-methyl-1,2,4-oxadiazol), wherein said heteroaryl is optionally substituted with halo (e.g., fluoro) or haloC 1-6 alkyl; amino (e.g., —NH 2 ), C 1-6 alkoxy, —O-haloC 1-6 alkyl (e.g., —O—CF 3 ), C 1-6 alkylsulfonyl (for example, methylsulfonyl or —S(O) 2 CH 3 ), —C(O)—R 13 , —N(R 14 )(R 15 ); or 2) a substituted heteroarylaklyl, e.g., substituted with haloalkyl; or 3) attached to one of the nitrogens on the pyrazolo portion of Formula I and is a moiety of Formula A wherein X, Y and Z are, independently, N or C, and R 8 , R 9 , R 11 and R 12 are independently H or halogen (e.g., Cl or F); and R 10 is halogen, alkyl, cycloalkyl, haloalkyl (e.g., trifluoromethyl), aryl (e.g., phenyl), heteroaryl (e.g., pyridyl, (for example, pyrid-2-yl) or e.g., thiadiazolyl (for example, 1,2,3-thiadiazol-4-yl), diazolyl, triazolyl (e.g., 1,2,4-triazol-1-yl), tetrazolyl (e.g., tetrazol-5-yl), alkoxadiazolyl (e.g., 5-methyl-1,2,4-oxadiazol), pyrazolyl (e.g., pyrazol-1-yl), alkyl sulfonyl (e.g., methyl sulfonyl), arylcarbonyl (e.g., benzoyl), or heteroarylcarbonyl, alkoxycarbonyl, (e.g., methoxycarbonyl), aminocarbonyl; preferably phenyl or pyridyl, e.g., 2-pyridyl; provided that when X, Y or X is nitrogen, R 8 , R 9 or R 10 , respectively, is not present; (v) R 4 is selected from: H, C 1-6 alkyl (e.g., methyl, isopropyl), C 3-8 cycloalkyl (e.g., cyclopentyl), C 3-8 heterocycloalkyl (e.g., pyrrolidin-3-yl), aryl (e.g., phenyl) or heteroaryl (e.g., pyrid-4-yl, pyrid-2-yl or pyrazol-3-yl) wherein said aryl or heteroaryl is optionally substituted with halo (e.g., 4-fluorophenyl), hydroxy (e.g., 4-hydroxyphenyl), C 1-6 alkyl, C 1-6 alkoxy or another aryl group (e.g., biphenyl-4-ylmethyl); (vi) R 13 is —N(R 14 )(R 15 ), C 1-6 alkyl (e.g., methyl), —OC 1-6 alkyl (e.g., —OCH 3 ), haloC 1-6 alkyl (trifluoromethyl), aryl (e.g., phenyl), or heteroaryl; and (vii) R 14 and R 15 are independently H or C 1-6 alkyl, in free or salt form. The invention further provides compounds of Formula I as follows: 1.1 Formula I, wherein R 3 is -D-E-F; 1.2 Formula 1.1, D is a single bond, C 1-6 alkylene (e.g., methylene), or arylalkylene (e.g., benzylene or —CH 2 C 6 H 4 —); 1.3 Formula 1.1, wherein D is a single bond; 1.4 Formula 1.1, wherein D is C 1-6 alkylene (e.g., methylene); 1.5 Formula 1.1, wherein D is methylene; 1.6 Formula 1.1, wherein D is arylalkylene (e.g., benzylene or —CH 2 C 6 H 4 —); 1.7 Formula 1.1, wherein D is benzylene or —CH 2 C 6 H 4 —; 1.8 Any of formulae 1.1-1.7, wherein E is a single bond, C 2-4 alkylene (e.g., methylene, ethynylene, prop-2-yn-1-ylene), —C 0-4 alkylarylene (e.g., phenylene or —C 6 H 4 —, -benzylene- or —CH 2 C 6 H 4 —), wherein the arylene group is optionally substituted with halo (e.g., Cl or F), heteroarylene (e.g., pyridinylene or pyrimidinylene),aminoC 1-6 alkylene (e.g., —CH 2 N(H)—), amino (e.g., —N(H)—); C 3-8 cycloalkylene optionally containing one or more heteroatom selected from N or O (e.g., piperidinylene); 1.9 Any of formulae 1.1-1.7, wherein E is a single bond; 1.10 Any of formulae 1.1-1.7, wherein E is C 2 -4alkylene (e.g., methylene, ethynylene, prop-2-yn-1-ylene); 1.11 Any of formulae 1.1-1.7, wherein E is methylene; 1.12 Any of formulae 1.1-1.7, wherein E is ethynylene; 1.13 Any of formulae 1.1-1.7, wherein E is prop-2-yn-1-ylene; 1.14 Any of formulae 1.1-1.7, wherein E is —C 0-4 alkylarylene (e.g., phenylene or —C 6 H 4 —, -benzylene- or —CH 2 C 6 H 4 —), wherein the arylene group is optionally substituted with halo (e.g., Cl or F); 1.15 Any of formulae 1.1-1.7, wherein E is phenylene or —C 6 H 4 —; 1.16 Any of formulae 1.1-1.7, wherein E is heteroarylene (e.g., pyridinylene or pyrimidinylene); 1.17 Any of formulae 1.1-1.7, wherein E is pyridinylene; 1.18 Any of formulae 1.1-1.7, wherein E is pyrimidinylene; 1.19 Any of formulae 1.1-1.7, wherein E is aminoC 1-6 alkylene (e.g., —CH 2 N(H)—); 1.20 Any of formulae 1.1-1.7, wherein E is amino (e.g., —N(H)—); 1.21 Any of formulae 1.1-1.7, wherein E is C 3-8 cycloalkylene optionally containing one or more heteroatom selected from N or O (e.g., piperidinylene); 1.22 Any of formulae 1.1-1.21, wherein F is H, halo (e.g., F, Br, Cl), C 1-6 alkyl (e.g., isopropyl or isobutyl), haloC 1-6 alkyl (e.g., trifluoromethyl), aryl (e.g., phenyl), C 3-8 cycloalkyl optionally containing at least one atom selected from a group consisting of N or O (e.g., cyclopentyl, cyclohexyl, piperidinyl, pyrrolidinyl, tetrahydro-2H-pyran-4-yl, or morpholinyl), and optionally substituted with C 1-6 alkyl (e.g., methyl or isopropyl), for example, 1-methylpyrrolidin-2-yl, pyrrolidin-1-yl, pyrrolidin-2-yl, piperidin-2-yl, 1-methylpiperidin-2-yl, 1-ethylpiperidin-2-yl; heteroaryl optionally substituted with C 1-6 alkyl (e.g., pyridyl, (for example, pyrid-2-yl), pyrimidinyl (for example, pyrimidin-2-yl, pyrimidin-4-yl), thiadiazolyl (for example, 1,2,3-thiadiazol-4-yl), oxazolyl (e.g., oxazol-2-yl), diazolyl (e.g., pyrazolyl (for example, pyrazol-1-yl) or imidazolyl (for example, imidazol-1-yl, 4-methylimidazolyl, 1-methylimidazol-2-yl,), triazolyl (e.g., 1,2,4-triazol-1-yl), tetrazolyl (e.g., tetrazol-5-yl), alkoxadiazolyl (e.g., 5-methyl-1,2,4-oxadiazol), pyrazolyl (e.g., pyrazol-1-yl), amino (e.g., —NH 2 ), C 1-6 alkoxy, —O-haloC 1-6 alkyl (e.g., —O—CF 3 ), C 1-6 alkylsulfonyl (for example, methylsulfonyl or —S(O) 2 CH 3 ), C(O)—R 13 or —N(R 14 )(R 15 ); 1.23 Any of formulae 1.1-1.22, wherein F is H; 1.24 Any of formulae 1.1-1.22, wherein F is halo (e.g., F, Br, Cl); 1.25 Any of formulae 1.1-1.22, wherein F is fluoro; 1.26 Any of formulae 1.1-1.22, wherein F is C 1-6 alkyl (e.g., isopropyl or isobutyl); 1.27 Any of formulae 1.1-1.22, wherein F is isopropyl; 1.28 Any of formulae 1.1-1.22, wherein F is isobutyl; 1.29 Any of formulae 1.1-1.22, wherein F is haloC 1-6 alkyl (e.g., trifluoromethyl); 1.30 Any of formulae 1.1-1.22, wherein F is trifluoromethyl; 1.31 Any of formulae 1.1-1.22, wherein F is aryl (e.g., phenyl); 1.32 Any of formulae 1.1-1.22, wherein F is phenyl; 1.33 Any of formulae 1.1-1.22, wherein F is C 3-8 cycloalkyl optionally containing at least one atom selected from a group consisting of N or O (e.g., cyclopentyl, cyclohexyl, piperidinyl, pyrrolidinyl tetrahydro-2H-pyran-4-yl, morpholinyl); and optionally substituted with C 1-6 alkyl (e.g., methyl or isopropyl), for example, 1-methylpyrrolidin-2-yl,), for example, 1-methylpyrrolidin-2-yl, pyrrolidin-1-yl, pyrrolidin-2-yl, piperidin-2-yl, 1-methylpiperidin-2-yl, 1-ethylpiperidin-2-yl; 1.34 Any of formulae 1.1-1.22, wherein F is cyclopentyl or cyclohexyl; 1.35 Any of formulae 1.1-1.22, wherein F is 1-methylpyrrolidin-2-yl; 1.36 Any of formulae 1.1-1.22, wherein F is heteroaryl optionally substituted with C 1-6 alkyl (e.g., pyridyl, (for example, pyrid-2-yl), pyrimidinyl (for example, pyrimidin-2-yl, pyrimidin-4-yl), thiadiazolyl (for example, 1,2,3-thiadiazol-4-yl), oxazolyl (e.g., oxazol-2-yl), diazolyl (e.g., pyrazolyl (for example, pyrazol-1-yl) or imidazolyl (for example, imidazol-1-yl, 4-methylimidazolyl, 1-methylimidazol-2-yl,), triazolyl (e.g., 1,2,4-triazol-1-yl), tetrazolyl (e.g., tetrazol-5-yl), alkoxadiazolyl (e.g., 5-methyl-1,2,4-oxadiazol), pyrazolyl (e.g., pyrazol-1-yl), wherein said heteroaryl is optionally substituted with halo (e.g., fluoro) or haloC 1-6 alkyl; 1.37 Any of formulae 1.1-1.22, wherein F is pyrid-2-yl optionally substituted with halo (e.g., fluoro); 1.38 Any of formulae 1.1-1.22, wherein F is 6-fluoro-pyrid-2-yl; 1.39 Any of formulae 1.1-1.22, wherein F is pyrimidinyl (for example, pyrimidin-2-yl, pyrimidin-4-yl); 1.40 Any of formulae 1.1-1.22, wherein F is oxazolyl (e.g., oxazol-2-yl), 1.41 Any of formulae 1.1-1.22, wherein F is triazolyl (e.g., 1,2,4-triazol-1-yl); 1.42 Any of formulae 1.1-1.22, wherein F is diazolyl (e.g., pyrazolyl (for example, pyrazol-1-yl) or imidazolyl (for example, imidazol-1-yl, 4-methylimidazolyl, 1-methylimidazol-2-yl); 1.43 Any of formulae 1.1-1.22, wherein F is C- 1-6 alkyl-oxadiazolyl (e.g., 5-methyl-1,2,4-oxadiazolyl); 1.44 Any of formulae 1.1-1.22, wherein F is amino (e.g., —NH 2 ); 1.45 Any of formulae 1.1-1.22, wherein F is C 1-6 alkoxy; 1.46 Any of formulae 1.1-1.22, wherein F is —O-haloC 1-6 alkyl (e.g., —O—CF 3 ); 1.47 Any of formulae 1.1-1.22, wherein F is —C(O)—R 13 ; 1.48 Any of formulae 1.1-1.22, wherein F is —N(R 14 )(R 15 ); 1.49 Any of formulae 1.1-1.22, wherein F is C 1-6 alkylsulfonyl; 1.50 Any of formulae 1.1-1.22, wherein F is methylsulfonyl or —S(O) 2 CH 3 ; 1.51 Formula I or any of 1.1-1.21, wherein R 3 is a substituted heteroarylaklyl, e.g., substituted with haloalkyl; 1.52 Formula I or any of 1.1-1.21, wherein R 3 is attached to one of the nitrogens on the pyrazolo portion of Formula I and is a moiety of Formula A wherein X, Y and Z are, independently, N or C, and R 8 , R 9 , R 11 and R 12 are independently H or halogen (e.g., Cl or F); and R 10 is halogen, alkyl, cycloalkyl, haloalkyl (e.g., trifluoromethyl), aryl (e.g., phenyl), heteroaryl (e.g., pyridyl, (for example, pyrid-2-yl) or e.g., thiadiazolyl (for example, 1,2,3-thiadiazol-4-yl), diazolyl, triazolyl (e.g., 1,2,4-triazol-1-yl), tetrazolyl (e.g., tetrazol-5-yl), alkoxadiazolyl (e.g., 5-methyl-1,2,4-oxadiazol), pyrazolyl (e.g., pyrazol-1-yl), alkyl sulfonyl (e.g., methyl sulfonyl), arylcarbonyl (e.g., benzoyl), or heteroarylcarbonyl, alkoxycarbonyl, (e.g., methoxycarbonyl), aminocarbonyl; preferably phenyl or pyridyl, e.g., 2-pyridyl; provided that when X, Y or X is nitrogen, R 8 , R 9 or R 10 , respectively, is not present; 1.53 Formula 1.52, wherein R 3 is a moiety of Formula A, R 8 , R 9 , R 11 and R 12 are each H and R 10 is phenyl; 1.54 Formula 1.52, wherein R 3 is a moiety of Formula A, R 8 , R 9 , R 11 and R 12 are each H and R 10 is pyridyl or thiadizolyl; 1.55 Formula 1.52, wherein R 3 is a moiety of Formula A, R 8 , R 9 , R 11 and R 12 are each H and R 10 is pyrid-2-yl optionally substituted with halo (e.g., fluoro); 1.56 Formula 1.52, wherein R 3 is a moiety of Formula A and X, Y and Z are all C; 1.57 Formula 1.52, wherein R 10 is pyrimidinyl; 1.58 Formula 1.52, wherein R 10 is 5-fluoropyrmidinyl; 1.59 Formula 1.52, wherein R 10 is pyrazol-1-yl; 1.60 Formula 1.52, wherein R 10 is 1,2,4-trazol-1-yl; 1.61 Formula 1.52, wherein R 10 is aminocarbonyl; 1.62 Formula 1.52, wherein R 10 is methylsulfonyl; 1.63 Formula 1.52, wherein R 10 is 5-methyl-1,2,4-oxadiazol-3-yl; 1.64 Formula 1.52, wherein R 10 is 5-fluoropyrimidin-2-yl, 1.65 Formula 1.52, wherein R 10 is trifluoromethyl; 1.66 Formula 1.52, wherein R 3 is a moiety of Formula A, X and Z are C, and Y is N; 1.67 Formula I or any of 1.1-1.66, wherein R 2 is H; C 1-6 alkyl (e.g., isopropyl, isobutyl, neopentyl, 2-methylbutyl, 2,2-dimethylpropyl) wherein said alkyl group is optionally substituted with halo (e.g., fluoro) or hydroxy (e.g., 1-hydroxypropan-2-yl, 3-hydroxy-2-methylpropyl); —C 0-4 alkyl-C 3-8 cycloalkyl (e.g., cyclopentyl, cyclohexyl) optionally substituted with one or more amino (e.g., —NH 2 ), for example, 2-aminocyclopentyl or 2-aminocyclohexyl), wherein said cycloalkyl optionally contains one or more heteroatom selected from N and O and is optionally substituted with C 1-6 alkyl (e.g., 1-methyl-pyrrolindin-2-yl, 1-methyl-pyrrolindin-3-yl, 1-methyl-pyrrolindin-2-yl-methyl or 1-methyl-pyrrolindin-3-yl-methyl); C 3-8 heterocycloalkyl (e.g., pyrrolidinyl, for example, pyrrolidin-3-yl) optionally substituted with C 1-6 alkyl (e.g., methyl), for example, 1-methylpyrrolidin-3-yl; C 3-8 cycloalkyl-C 1-6 alkyl (e.g.,cyclopropylmethyl); haloC 1-6 alkyl (e.g., trifluoromethyl, 2,2,2-trifluoroethyl); —N(R 14 )(R 15 )—C 1-6 alkyl (e.g., 2-(dimethylamino)ethyl,2-aminopropyl); hydroxyC 1-6 alkyl (e.g., (e.g., 3-hydroxy-2-methylpropyl, 1-hydroxyprop-2-yl); arylC 0-6 alkyl (e.g., benzyl); heteroarylC 1-6 alkyl (e.g., pyridinylmethyl); C 1-6 alkoxyarylC 1-6 alkyl (e.g., 4-methoxybenzyl); -G-J wherein: G is a single bond or, alkylene (e.g., methylene) and J is cycloalkyl or heterocycloalkyl (e.g., oxetan-2-yl, pyrolyin-3-yl, pyrolyin-2-yl) optionally substituted with C 1-6 alkyl (e.g., (1-methylpyrolidin-2-yl)); 1.68 Formula 1.66, wherein R 2 is H; 1.69 Formula 1.66, wherein R 2 is C 1-6 alkyl (e.g., isopropyl, isobutyl, neopentyl, 2-methylbutyl, 2,2-dimethylpropyl) wherein said alkyl group is optionally substituted with halo (e.g., trifluoroethyl) or hydroxy (e.g., 1-hydroxypropan-2-yl, 3-hydroxy-2-methylpropyl); 1.70 Formula 1.66, wherein R 2 is isobutyl; 1.71 Formula 1.66, wherein R 2 is 3-hydroxy-2-methylpropyl; 1.72 Formula 1.66, wherein R 2 is 1-hydroxypropan-2-yl; 1.73 Formula 1.66, wherein R 2 is —C 0-4 alkyl-C 3-8 cycloalkyl (e.g., cyclopentyl, cyclohexyl) optionally substituted with one or more amino (e.g., —NH 2 ), for example, 2-aminocyclopentyl or 2-aminocyclohexyl), wherein said cycloalkyl optionally contains one or more heteroatom selected from N and O and is optionally substituted with C 1-6 alkyl (e.g., 1-methyl-pyrrolindin-2-yl, 1-methyl-pyrrolindin-3-yl, 1-methyl-pyrrolindin-2-yl-methyl or 1-methyl-pyrrolindin-3-yl-methyl); 1.74 Formula 1.66, wherein R 2 is 1-methyl-pyrrolindin-2-yl, 1-methyl-pyrrolindin-3-yl, 1-methyl-pyrrolindin-2-yl-methyl or 1-methyl-pyrrolindin-3-yl-methyl; 1.75 Formula 1.66, wherein R 2 is C 3-8 heterocycloalkyl (e.g., pyrrolidinyl, for example, pyrrolidin-3-yl) optionally substituted with C 1-6 alkyl (e.g., methyl), for example, 1-methylpyrrolidin-3-yl; 1.76 Formula 1.66,wherein R 2 is 1-methylpyrrolidin-3-yl; 1.77 Formula 1.66, wherein R 2 is C 3-8 cycloalkyl-C 1-6 alkyl (e.g., cyclopropylmethyl); 1.78 Formula 1.66, wherein R 2 is —N(R 14 )(R 15 )—C 1-6 alkyl (e.g., 2-(dimethylamino)ethyl, 2-aminopropyl); 1.79 Formula 1.66, wherein R 2 is heteroarylC 1-6 alkyl (e.g., pyridinylmethyl), 1.80 Formula 1.66, wherein R 2 is C 1-6 alkoxyarylC 1-6 alkyl (e.g., 4-methoxybenzyl; 1.81 Formula 1.66, wherein R 2 is arylC 0-6 alkyl (e.g., benzyl); 1.82 Formula 1.66, wherein R 2 is cyclopentyl or cyclohexyl; 1.83 Formula I or any of 1.1-1.66, wherein R 2 is -G-J; G is a single bond or, alkylene (e.g., methylene); and J is cycloalkyl or heterocycloalkyl (e.g., oxetan-2-yl, pyrolyin-3-yl, pyrolyin-2-yl) optionally substituted with C 1-6 alkyl (e.g., (1-methylpyrolidin-2-yl)); 1.84 Formula 1.83, wherein G is alkylene (e.g., methylene); 1.85 Formula 1.83, wherein G is methylene; 1.86 Formula 1.83, wherein J is cycloalkyl or heterocycloalkyl (e.g., oxetan-2-yl, pyrolyin-3-yl, pyrolyin-2-yl) optionally substituted with alkyl (e.g., 1-methylpyrolidin-2-yl); 1.87 Formula 1.83, wherein J is oxetan-2-yl, pyrolyin-3-yl, pyrolyin-2-yl; 1.88 Formula 1.83, wherein J is (1-methylpyrolidin-2-yl); 1.89 Any of the preceding formulae wherein R 4 is selected from H, C 1-6 alkyl (e.g., methyl, isopropyl), C 3-8 cycloalkyl (e.g., cyclopentyl), C 3-8 heterocycloalkyl (e.g., pyrrolidin-3-yl), or aryl (e.g., phenyl) or heteroaryl (e.g., pyrid-4-yl, pyrid-2-yl or pyrazol-3-yl) wherein said aryl or heteroaryl is optionally substituted with halo (e.g., 4-fluorophenyl), hydroxy (e.g., 4-hydroxyphenyl), C 1-6 alkoxy C 1-6 alkyl, or C 1-6 alkoxy or another aryl group (e.g., biphenyl-4-ylmethyl); 1.90 Formula 1.89, wherein either R 4 is H; 1.91 Formula 1.89, wherein either R 4 or R 5 is C 1-6 alkyl (e.g., methyl, isopropyl); 1.92 Formula 1.89, wherein either R 4 is isopropyl; 1.93 Formula 1.89, wherein either R 4 or R 5 is C 3-8 cycloalkyl (e.g., cyclopentyl); 1.94 Formula 1.89, wherein either R 4 or R 5 is C 3-8 heterocycloalkyl (e.g., pyrrolidin-3-yl); 1.95 Formula 1.89, wherein either R 4 or R 5 is aryl (e.g., phenyl) optionally substituted with halo (e.g., 4-fluorophenyl), hydroxy (e.g., 4-hydroxyphenyl), C 1-6 alkyl, C 1-6 alkoxy or another aryl group (e.g., biphenyl-4-ylmethyl); 1.96 Formula 1.89, wherein either R 4 or R 5 is 4-hydroxyphenyl; 1.97 Formula 1.89, wherein either R 4 or R 5 is 4-fluorophenyl; 1.98 Formula 1.89, wherein either R 4 or R 5 is heteroaryl (e.g., pyrid-4-yl, pyrid-2-yl or pyrazol-3-yl) optionally substituted with halo (e.g., 4-fluorophenyl), hydroxy (e.g., 4-hydroxyphenyl), C 1-6 alkyl, C 1-6 alkoxy or another aryl group (e.g., biphenyl-4-ylmethyl); 1.99 Formula 1.89, wherein either R 4 or R 5 is phenyl; 1.100 Any of the foregoing formulae, wherein R 13 is —N(R 14 )(R 15 ), C 1-6 alkyl (e.g., methyl), —OC 1-6 alkyl (e.g., —OCH 3 ), haloC 1-6 alkyl, aryl (for example phenyl), or heteroaryl; 1.101 Formula 1.100, wherein R 13 is —N(R 14 )(R 15 ); 1.102 Formula 1.100, wherein R 13 is —NH 2 ; 1.103 Formula 1.100, wherein R 13 is C 1-6 alkyl (e.g., methyl); 1.104 Formula 1.100, wherein R 13 is —OC 1-6 alkyl (e.g., —OCH 3 ), 1.105 Formula 1.100, wherein R 13 is —OCH 3 ; 1.106 Formula 1.100, wherein R 13 is haloC 1-6 alkyl (e.g., trifluoromethyl); 1.107 Formula 1.100, wherein R 13 is trifluoromethyl; 1.108 Formula 1.100, wherein R 13 is aryl (e.g., phenyl); 1.109 Formula 1.100, wherein R 13 is heteroaryl (e.g., pyridiyl); 1.110 Any of the preceding formulae, wherein R 14 and R 15 are independently H or C 1-6 alkyl (e.g., methyl); 1.111 Formula I or any of 1.1-1.110, wherein either R 14 or R 15 is independently H; 1.112 Formula I or any of 1.1-1.110, wherein either R 14 or R 15 is C 1-6 alkyl (e.g., methyl); 1.113 Formula I or any of 1.1-1.110, wherein either R 14 or R 15 is methyl; 1.114 Formula I or any of 1.1-1.110, wherein R 14 and R 15 are methyl; 1.115 any of the preceding formulae wherein R 3 is selected from a group consisting of 4-(pyrimidin-2-yl)benzyl, 4-(1,2,4-triazol-1-yl)benzyl, 4-(1-methylpyrrolidin-2-yl)benzyl, 4-(1-methylpiperid-2-yl)benzyl, 4-(pyrid-2-yl)benzyl, 4-(pyrazol-1-yl)benzyl, 4-(pyrrolidin-3-yl)benzyl, (6-chloropyridin-3-yl)methyl, (6-fluoropyridin-3-yl)methyl, 4-(imidazol-1-yl)benzyl, 4-(pyrimidin-4-yl)benzyl), 4-(oxazol-2-yl)benzyl, 4-(dimethylamino)benzyl, 4-(methylsulfonyl)benzyl, 4-(pyrrolidin-3-yl)benzyl, (1-isopropylpyiperidin-4-yl)methyl, and —CH 2 —C 2 H 4 —C(O)—NH 2 ; 1.116 formula 1.115 wherein R 3 is 4-(pyrimidin-2-yl)benzyl; 1.117 formula 1.115 wherein R 3 is 4-(1,2,4-triazol-1-yl)benzyl; 1.118 formula 1.115 wherein R 3 is 4-(1-methylpyrrolidin-2-yl)benzyl; 1.119 formula 1.115 wherein R 3 is 4-(1-methylpiperid-2-yl)benzyl; 1.120 formula 1.115 wherein R 3 is 4-(pyrid-2-yl)benzyl; 1.121 formula 1.115 wherein R 3 is 4-(pyrazol-1-yl)benzyl; 1.122 formula 1.115 wherein R 3 is 4-(pyrrolidin-3-yl)benzyl; 1.123 formula 1.115 wherein R 3 is (6-chloropyridin-3-yl)methyl or (6-fluoropyridin-3-yl)methyl; 1.124 formula 1.115 wherein R 3 is 4-(imidazol-1-yl)benzyl; 1.125 formula 1.115 wherein R 3 is 4-(pyrimidin-4-yl)benzyl); 1.126 formula 1.115 wherein R 3 is 4-(oxazol-2-yl)benzyl; 1.127 formula 1.115 wherein R 3 is 4-(dimethylamino)benzyl; 1.128 formula 1.115 wherein R 3 is 4-(methylsulfonyl)benzyl; 1.129 formula 1.115 wherein R 3 is 4-(pyrrolidin-3-yl)benzyl; 1.130 formula 1.115 wherein R 3 is (1-isopropylpyiperidin-4-yl)methyl; 1.131 formula 1.115 wherein R 3 is —CH 2 —C 2 H 4 —C(O)—NH 2 ; 1.132 any of the preceding formulae wherein compound of formula I is 1.133 any of the preceding formulae wherein compound of formula I is 1.134 any of the preceding formulae wherein compound of formula I is selected from a group consisting of: 1.135 any of the preceding formulae wherein the compounds inhibit phosphodiesterase-mediated (e.g., PDE1-mediated, especially PDE1B-mediated) hydrolysis of cGMP, e.g., with an IC 50 of less than 10 μnM, preferably less than 1 μM, preferably less than 500 nM, preferably less than 200 nM in an immobilized-metal affinity particle reagent PDE assay, for example, as described in Example 16, in free or salt form. In a further embodiment, the Compound of the Invention is a Compound of Formula I, wherein R 3 is C 5-6 heteroarylC 1-6 alkyl optionally substituted with halo, C1-6alkyl (e.g., (6-fluoropyrid-3-yl)methyl, (6-chloropyrid-3-yl)methyl). In another embodiment, the Compound of the Invention is a Compound of Formula I, wherein R 3 is pyridylC 1-6 alkyl (e.g., pyridylmethyl) optionally substituted with halo, haloalkyl alkyl sulfonyl, —C(O)N(C 0-6 alkyl)(C 0-6 alkyl), heteroaryl (e.g., pyridyl, pyrimidinyl, oxazole, imidazole, triazolyl, pyrazolyl), amino, C 1-6 alkylamino, and heterocycloalkyl (e.g., piperidinyl, pyrrolidinyl) which heterocycloalkyl, heteroaryl are further optionally substituted with C 1-6 alkyl or halo. In still another embodiment, the Compound of the Invention is a Compound of Formula I, wherein R 3 is benzyl substituted with aryl, heteroaryl (e.g., pyridyl, pyrimidinyl, oxazole, imidazole, triazolyl, pyrazolyl), C 3-7 cycloalkyl, heteroC 3-7 cycloalkyl (e.g., piperidinyl, pyrrolidinyl), alkyl sulfonyl, —C(O)N(C 0-6 alkyl)(C 0-6 alkyl), amino, C 1-6 alkylamino, which aryl, heterocycloalkyl, heteroaryl are further optionally substituted with C 1-6 alkyl or halo. In a another embodiment, the Compound of the Invention is a Compound of Formula I wherein (ii) R 1 is H or alkyl (e.g., methyl); (iii) R 2 is H, alkyl (e.g., isobutyl, 2-methylbutyl, 2,2-dimethyl propyl), cycloalkyl (e.g., cyclopentyl, cyclohexyl), haloalkyl (e.g., trifluoromethyl, 2,2,2-trifluoroethyl), alkylaminoalkyl (e.g., 2-(dimethylamino)ethyl), hydroxyalkyl (e.g., 3-hydroxy-2-methyl propyl), arylalkyl (e.g., benzyl), heteroarylalkyl (e.g., pyridylmethyl), or alkoxyarylalkyl (e.g., 4-methoxybenzyl); (iv) R 3 is a substituted heteroarylaklyl, e.g., substituted with haloalkyl or R 3 is attached to one of the nitrogens on the pyrazolo portion of Formula 1 and is a moiety of Formula A wherein X, Y and Z are, independently, N or C, and R 8 , R 9 , R 11 and R 12 are independently H or halogen (e.g., Cl or F); and R 10 is halogen, alkyl, cycloalkyl, haloalkyl (e.g., trifluoromethyl), aryl (e.g., phenyl), heteroaryl (e.g., pyridyl, (for example, pyrid-2-yl) or e.g., thiadiazolyl (for example, 1,2,3-thiadiazol-4-yl), diazolyl, triazolyl (e.g., 1,2,4-triazol-1-yl), tetrazolyl (e.g., tetrazol-5-yl), alkoxadiazolyl (e.g., 5-methyl-1,2,4-oxadiazol), pyrazolyl (e.g., pyrazol-1-yl), alkyl sulfonyl (e.g., methyl sulfonyl), arylcarbonyl (e.g., benzoyl), or heteroarylcarbonyl, alkoxycarbonyl, (e.g., methoxycarbonyl), aminocarbonyl; preferably phenyl or pyridyl, e.g., 2-pyridyl; provided that when X, Y or X is nitrogen, R 8 , R 9 or R 10 , respectively, is not present; (v) R 4 is aryl (e.g., phenyl) or heteroaryl; (vi) R 5 is H, alkyl, cycloalkyl (e.g., cyclopentyl), heteroaryl, aryl, p-benzylaryl (e.g., biphenyl-4-ylmethyl); (vii) R 6 is H, C 1-6 alkyl (e.g., methyl) or C 3-8 cycloalkyl; (viii) R 13 is —N(R 14 )(R 15 ), C 1-6 alkyl (e.g., methyl), —OC 1-6 alkyl (e.g., —OCH 3 ), haloC 1-6 alkyl (trifluoromethyl), aryl (e.g., phenyl), or heteroaryl; and (vii) R 10 and R 15 are independently H or C 1-6 alkyl, in free or salt form (hereinafter, Compound of Formula I(i)). In still another embodiment, the Compound of the Invention is a Compound of Formula I wherein (i) R 1 is H or alkyl (e.g., methyl); (ii) R 2 is H, alkyl (e.g., isopropyl, isobutyl, 2-methylbutyl, 2,2-dimethyl propyl), cycloalkyl (e.g., cyclopentyl, cyclohexyl), haloalkyl (e.g., trifluoromethyl, 2,2,2-trifluoroethyl), alkylaminoalkyl (e.g., 2-(dimethylamino)ethyl), hydroxyalkyl (e.g., 3-hydroxy-2-methyl propyl), arylalkyl (e.g., benzyl), heteroarylalkyl (e.g., pyridylmethyl), or alkoxyarylalkyl (e.g., 4-methoxybenzyl); (iii) R 3 is D-E-F wherein 1. D is single bond, alkylene (e.g., methylene), or arylalkylene (e.g., benzylene or —CH 2 C 6 H 4 —); 2. E is a alkylene (e.g., methylene, ethynylene, prop-2-yn-1-ylene), arylene (e.g., phenylene or —C 6 H 4 —), alkylarylene (e.g., -benzylene- or —CH 2 C 6 H 4 —), aminoalkylene (e.g., —CH 2 N(H)—) or amino (e.g., —N(H)—); and 3. F is alkyl (e.g., isobutyl), aryl (e.g., phenyl), heteroaryl (e.g., pyrid-2-yl, 1,2,4-triazolyl), heteroC 3-8 cycloalkyl (e.g., pyrolidin-1-yl), amino (e.g., —NH 2 ), C 1-6 alkoxy, or —O-haloalkyl (e.g., —O—CF 3 ); (iv) R 4 is aryl (e.g., phenyl), heteroaryl (e.g., pyrid-4-yl, pyrid-2-yl or pyrazol-3-yl) or heterocycloalkyl (e.g., pyrrolidin-3-yl); and (v) R 5 is H, alkyl, cycloalkyl (e.g., cyclopentyl), heteroaryl, aryl, p-benzylaryl (e.g., biphenyl-4-ylmethyl); (vi) R 6 is H, C 1-6 alkyl (e.g., methyl) or C 3-8 cycloalkyl; (vii) R 13 is —N(R 14 )(R 15 ), C 1-6 alkyl (e.g., methyl), —OC 1-6 alkyl (e.g., —OCH 3 ), haloC 1-6 alkyl (trifluoromethyl), aryl (e.g., phenyl), or heteroaryl; and (viii) R 10 and R 15 are independently H or alkyl, wherein “alk”, “alkyl”, “haloalkyl” or “alkoxy” refers to C 1-6 alkyl and “cycloalkyl” refers to C 3-8 cycloalkyl unless specifically specified; in free or salt form (hereinafter, Compound of Formula I(ii)). If not otherwise specified or clear from context, the following terms herein have the following meanings: (a) “Alkyl” as used herein is a saturated or unsaturated hydrocarbon moiety, preferably saturated, preferably having one to six carbon atoms, which may be linear or branched, and may be optionally mono-, di- or tri- substituted, e.g., with halogen (e.g., chloro or fluoro), hydroxy, or carboxy. (b) “Cycloalkyl” as used herein is a saturated or unsaturated nonaromatic hydrocarbon moiety, preferably saturated, preferably comprising three to eight carbon atoms, at least some of which form a nonaromatic mono- or bicyclic, or bridged cyclic structure, and which may be optionally substituted, e.g., with halogen (e.g., chloro or fluoro), hydroxy, or carboxy. Wherein the cycloalkyl optionally contains one or more atoms selected from N and O and/or S, said cycloalkyl may also be a heterocycloalkyl. (c) “Heterocycloalkyl” is, unless otherwise indicated, saturated or unsaturated nonaromatic hydrocarbon moiety, preferably saturated, preferably comprising three to nine carbon atoms, at least some of which form a nonaromatic mono- or bicyclic, or bridged cyclic structure, wherein at least one carbon atom is replaced with N, O or S, which heterocycloalkyl may be optionally substituted, e.g., with halogen (e.g., chloro or fluoro), hydroxy, or carboxy. (d) “Aryl” as used herein is a mono or bicyclic aromatic hydrocarbon, preferably phenyl, optionally substituted, e.g., with alkyl (e.g., methyl), halogen (e.g., chloro or fluoro), haloalkyl (e.g., trifluoromethyl), hydroxy, carboxy, or an additional aryl or heteroaryl (e.g., biphenyl or pyridylphenyl). (e) “Heteroaryl” as used herein is an aromatic moiety wherein one or more of the atoms making up the aromatic ring is sulfur or nitrogen rather than carbon, e.g., pyridyl or thiadiazolyl, which may be optionally substituted, e.g., with alkyl, halogen, haloalkyl, hydroxy or carboxy. (f) Wherein E is phenylene, the numbering is as follows: (g) It is intended that wherein the substituents end in “ene”, for example, alkylene, phenylene or arylalkylene, said substitutents are intended to bridge or be connected to two other substituents. Therefore, methylene is intended to be —CH 2 — and phenylene intended to be —C 6 H 4 — and arylalkylene is intended to be —C 6 H 4 —CH 2 — or —CH 2 —C 6 H 4 —. Compounds of the Invention may exist in free or salt form, e.g., as acid addition salts. In this specification unless otherwise indicated, language such as “Compounds of the Invention” is to be understood as embracing the compounds of Formula I, or any of 1.1-1.135, a Compound of Formula I(i) or I(ii), in any form, for example free or acid addition salt form, or where the compounds contain acidic substituents, in base addition salt form. The Compounds of the Invention are intended for use as pharmaceuticals, therefore pharmaceutically acceptable salts are preferred. Salts which are unsuitable for pharmaceutical uses may be useful, for example, for the isolation or purification of free Compounds of the Invention or their pharmaceutically acceptable salts, are therefore also included. Compounds of the Invention may in some cases also exist in prodrug form. A prodrug form is compound which converts in the body to a Compound of the Invention. For example, when the Compounds of the Invention contain hydroxy or carboxy substituents, these substituents may form physiologically hydrolysable and acceptable esters. As used herein, “physiologically hydrolysable and acceptable ester” means esters of Compounds of the Invention which are hydrolysable under physiological conditions to yield acids (in the case of Compounds of the Invention which have hydroxy substituents) or alcohols (in the case of Compounds of the Invention which have carboxy substituents) which are themselves physiologically tolerable at doses to be administered. Therefore, wherein the Compound of the Invention contains a hydroxy group, for example, Compound-OH, the acyl ester prodrug of such compound, i.e., Compound-O—C(O)—C 1-4 alkyl, can hydrolyze in the body to form physiologically hydrolysable alcohol (Compound-OH) on the one hand and acid on the other (e.g., HOC(O)—C 1-4 alkyl). Alternatively, wherein the Compound of the Invention contains a carboxylic acid, for example, Compound-C(O)OH, the acid ester prodrug of such compound, Compound-C(O)O—C 1-4 alkyl can hydrolyze to form Compound-C(O)OH and HO—C 1-4 alkyl. As will be appreciated, the term thus embraces conventional pharmaceutical prodrug forms. The invention also provides methods of making the Compounds of the Invention and methods of using the Compounds of the Invention for treatment of diseases and disorders as set forth below (especially treatment of diseases characterized by reduced dopamine D1 receptor signaling activity, such as Parkinson's disease, Tourette's Syndrome, Autism, fragile X syndrome, ADHD, restless leg syndrome, depression, cognitive impairment of schizophrenia, narcolepsy and diseases that may be alleviated by the enhancement of progesterone-signaling such as female sexual dysfunction), or a disease or disorder such as psychosis or glaucoma). This list is not intended to be exhaustive and may include other diseases and disorders as set forth below. In another embodiment, the invention further provides a pharmaceutical composition comprising a Compound of the Invention, e.g., a Compound of Formula I, or any of 1.1-1.135, or a Compound of Formula I(i) or I(ii), or any described in this specification, in free or pharmaceutically acceptable salt form, in admixture with a pharmaceutically acceptable carrier. DETAILED DESCRIPTION OF THE INVENTION Methods of Making Compounds of the Invention The Compounds of the Invention and their pharmaceutically acceptable salts may be made using the methods as described and exemplified herein and by methods similar thereto and by methods known in the chemical art. Such methods include, but not limited to, those described below. If not commercially available, starting materials for these processes may be made by procedures, which are selected from the chemical art using techniques which are similar or analogous to the synthesis of known compounds. In particular, the intermediates and starting materials for the Compounds of the Invention may be prepared by methods and processes as described in PCT/US2007/070551. All references cited herein are hereby incorporated by reference in their entirety. The Compounds of the Invention include their enantiomers, diastereoisomers, tautomers and racemates, as well as their polymorphs, hydrates, solvates and complexes. Some individual compounds within the scope of this invention may contain double bonds. Representations of double bonds in this invention are meant to include both the E and the Z isomer of the double bond. In addition, some compounds within the scope of this invention may contain one or more asymmetric centers. This invention includes the use of any of the optically pure stereoisomers as well as any combination of stereoisomers. It is also intended that the Compounds of the Invention encompass their stable and unstable isotopes. Stable isotopes are nonradioactive isotopes which contain one additional neutron compared to the abundant nuclides of the same species (i.e., element). It is expected that the activity of compounds comprising such isotopes would be retained, and such compound would also have utility for measuring pharmacokinetics of the non-isotopic analogs. For example, the hydrogen atom at a certain position on the Compounds of the Invention may be replaced with deuterium (a stable isotope which is non-radioactive). Examples of known stable isotopes include, but not limited to, deuterium, 13 C, 15 N, 18 O. Alternatively, unstable isotopes, which are radioactive isotopes which contain additional neutrons compared to the abundant nuclides of the same species (i.e., element), e.g., 123 I, 131 I, 125 I, 11 C, 18 F, may replace the corresponding abundant species of I, C and F. Another example of useful isotope of the compound of the invention is the 11 C isotope. These radio isotopes are useful for radio-imaging and/or pharmacokinetic studies of the compounds of the invention. Melting points are uncorrected and (dec) indicates decomposition. Temperature are given in degrees Celsius (° C.); unless otherwise stated, operations are carried out at room or ambient temperature, that is, at a temperature in the range of 18-25° C. Chromatography means flash chromatography on silica gel; thin layer chromatography (TLC) is carried out on silica gel plates. NMR data is in the delta values of major diagnostic protons, given in parts per million (ppm) relative to tetramethylsilane (TMS) as an internal standard. Conventional abbreviations for signal shape are used. Coupling constants (J) are given in Hz. For mass spectra (MS), the lowest mass major ion is reported for molecules where isotope splitting results in multiple mass spectral peaks Solvent mixture compositions are given as volume percentages or volume ratios. In cases where the NMR spectra are complex, only diagnostic signals are reported. Terms and abbreviations: BuLi=n-butyllithium ButOH=tert-butyl alcohol, CAN=ammonium cerium (IV) nitrate, DIPEA=diisopropylethylamine, DMF=N,N-dimethylforamide, DMSO=dimethyl sulfoxide, Et20=diethyl ether, EtOAc=ethyl acetate, equiv.=equivalent(s), h=hour(s), HPLC=high performance liquid chromatography, LDA=lithium diisopropylamide MeOH=methanol, NBS=N-bromosuccinimide NCS=N-chlorosuccinimide NaHCO 3 =sodium bicarbonate, NH 4 OH=ammonium hydroxide, Pd2(dba) 3 =tris[dibenzylideneacetone]dipalladium(0) PMB=p-methoxybenzyl, POCl 3 =phosphorous oxychloride, SOCl 2 =thionyl chloride, TFA=trifluoroacetic acid, THF=tetrahedrofuran. The synthetic methods in this invention are illustrated below. The significances for the R groups are as set forth above for formula I unless otherwise indicated. In an aspect of the invention, intermediate compounds of formula IIb can be synthesized by reacting a compound of formula IIa with a dicarboxylic acid, acetic anhydride and acetic acid mixing with heat for about 3 hours and then cooled: wherein R 1 is H or C 1-4 alkyl [e.g., methyl]. Intermediate IIe can be prepared by for example reacting a compound of IIb with for example a chlorinating compound such as POCl 3 , sometimes with small amounts of water and heated for about 4 hours and then cooled: Intermediate IId may be formed by reacting a compound of IIe with for example a P 1 —X in a solvent such as DMF and a base such as K 2 CO 3 at room temperature or with heating: wherein P 1 is a protective group [e.g., p-methoxybenzyl group (PMB)]; X is a leaving group such as a halogen, mesylate, or tosylate. Intermediate IIe may be prepared by reacting a compound of IId with hydrazine or hydrazine hydrate in a solvent such as methanol and refluxed for about 4 hours and then cooled: Alternatively, Intermediate IIIa may be formed by reacting a compound of IIe with for example a R 2 —X wherein X is a leaving group such as a halogen, mesylate, or tosylate, in a solvent such as DMF and a base such as K 2 CO 3 at room temperature or with heating: Intermediate IIIb may be prepared by reacting a compound of IIIa with hydrazine or hydrazine hydrate in a solvent such as methanol and heated for several hours and then cooled: Intermediate IVa may be formed by for example reacting a compound of IIIb with POCl 3 and DMF. Intermediate IVb may be formed by reacting a compound of IVa with for example a R 3 —X wherein X here is a leaving group, e.g., halogen, mesylate, or tosylate, in a solvent such as DMF and a base such as K 2 CO 3 at room temperature or with heating. The thio Compounds of the Invention, e.g., Formula I wherein L is S or Compound (I)-E may be prepared by reacting a compound (IVb) with a disulfide R 4 -L-L-R 4 or a thiol R 4 -LH in the presence of a strong base, such as a lithium reagent (e.g. LiHMDS) in a solvent such as THF. The sulfinyl or sulfonyl derivative, e.g. Formula I wherein L is SO or SO 2 , may be formed by reacting a 3-thio compounds (I)-E with an oxidizer such as a peroxide (e.g. oxone or hydrogen peroxide) at room temperature in a solvent such as acetonitrile and methanol. Alternatively, a compound of Formula (I)-E can be prepared by reacting, for example, Compounds 1-A with, for example, R 3 —X, in a solvent such as DMF and a base such as K 2 CO 3 at room temperature or with heating: wherein all the substituents are as defined previously; X is a leaving group such as a halogen, mesylate, or tosylate. Methods of Using Compounds of the Invention The Compounds of the Invention are useful in the treatment of diseases characterized by disruption of or damage to cAMP and cGMP mediated pathways, e.g., as a result of increased expression of PDE1 or decreased expression of cAMP and cGMP due to inhibition or reduced levels of inducers of cyclic nucleotide synthesis, such as dopamine and nitric oxide (NO). By preventing the degradation of cAMP and cGMP by PDE1B, thereby increasing intracellular levels of cAMP and cGMP, the Compounds of the Invention potentiate the activity of cyclic nucleotide synthesis inducers. The invention provides methods of treatment of any one or more of the following conditions: (i) Neurodegenerative diseases, including Parkinson's disease, restless leg, tremors, dyskinesias, Huntington's disease, Alzheimer's disease, and drug-induced movement disorders; (ii) Mental disorders, including depression, attention deficit disorder, attention deficit hyperactivity disorder, bipolar illness, anxiety, sleep disorders, e.g., narcolepsy, cognitive impairment, dementia, Tourette's syndrome, autism, fragile X syndrome, psychostimulant withdrawal, and drug addiction; (iii) Circulatory and cardiovascular disorders, including cerebrovascular disease, stroke, congestive heart disease, hypertension, pulmonary hypertension, and sexual dysfunction; (iv) Respiratory and inflammatory disorders, including asthma, chronic obstructive pulmonary disease, and allergic rhinitis, as well as autoimmune and inflammatory diseases; (v) Any disease or condition characterized by low levels of cAMP and/or cGMP (or inhibition of cAMP and/or cGMP signaling pathways) in cells expressing PDE1; and/or (vi) Any disease or condition characterized by reduced dopamine D1 receptor signaling activity, comprising administering an effective amount of a Compound of the Invention, e.g., a compound according to any of Formula I or 1.1-1.135, or a composition comprising a Compound of the Invention, e.g., a compound according to any of Formula I or 1.1-1.135, or any described in this specification, in free or pharmaceutically acceptable salt form, to a human or animal patient in need thereof. In another aspect, the invention provides a method of treatment of the conditions disclosed above comprising administering a therapeutically effective amount of a Compound of Formula II as hereinbefore described, in free or pharmaceutically acceptable salt form, to a human or animal patient in need thereof. In an especially preferred embodiment, the invention provides methods of treatment or prophylaxis for narcolepsy. In this embodiment, PDE 1 Inhibitors may be used as a sole therapeutic agent, but may also be used in combination or for co-administration with other active agents. Thus, the invention further comprises a method of treating narcolepsy comprising administering simultaneously, sequentially, or contemporaneously administering therapeutically effective amounts of (i) a PDE 1 Inhibitor of the Invention, e.g., a compound according to any of Formula I or any of 1.1-1.135, or I(i) or I(ii), or any described in this specification; and (ii) a compound to promote wakefulness or regulate sleep, e.g., selected from (a) central nervous system stimulants-amphetamines and amphetamine like compounds, e.g., methylphenidate, dextroamphetamine, methamphetamine, and pemoline; (b) modafinil, (c) antidepressants, e.g., tricyclics (including imipramine, desipramine, clomipramine, and protriptyline) and selective serotonin reuptake inhibitors (including fluoxetine and sertraline); and/or (d) gamma hydroxybutyrate (GHB), in free or pharmaceutically acceptable salt form, to a human or animal patient in need thereof. In another embodiment, the invention provides methods of treatment or prophylaxis for narcolepsy as herein before described, wherein the PDE1 inhibitor is in a form of a pharmaceutical composition. In still another embodiment, the methods of treatment or prophylaxis for narcolepsy as hereinbefore described, comprises administering a therapeutically effective amount of a Compound of Formula II as hereinbefore described, in free or pharmaceutically acceptable salt form, as a sole therapeutic agent or use in combination for co-administered with another active agent. In another embodiment, the invention further provides methods of treatment or prophylaxis of a condition which may be alleviated by the enhancement of the progesterone signaling comprising administering an effective amount of a Compound of the Invention, e.g., a compound according to any of Formula 1.1-1.135 or Formula I, I(i) or I(ii), or any described in this specification, in free or pharmaceutically acceptable salt form, to a human or animal patient in need thereof. The invention also provides methods of treatment as disclosed here, comprising administering a therapeutically effective amount of a Compound of Formula II, in free or pharmaceutically acceptable salt form. Disease or condition that may be ameliorated by enhancement of progesterone signaling include, but are not limited to, female sexual dysfunction, secondary amenorrhea (e.g., exercise amenorrhoea, anovulation, menopause, menopausal symptoms, hypothyroidism), pre-menstrual syndrome, premature labor, infertility, for example infertility due to repeated miscarriage, irregular menstrual cycles, abnormal uterine bleeding, osteoporosis, autoimmmune disease, multiple sclerosis, prostate enlargement, prostate cancer, and hypothyroidism. For example, by enhancing progesterone signaling, the PDE 1 inhibitors may be used to encourage egg implantation through effects on the lining of uterus, and to help maintain pregnancy in women who are prone to miscarriage due to immune response to pregnancy or low progesterone function. The novel PDE 1 inhibitors, e.g., as described herein, may also be useful to enhance the effectiveness of hormone replacement therapy, e.g., administered in combination with estrogen/estradiol/estriol and/or progesterone/progestins in postmenopausal women, and estrogen-induced endometrial hyperplasia and carcinoma. The methods of the invention are also useful for animal breeding, for example to induce sexual receptivity and/or estrus in a nonhuman female mammal to be bred. In this embodiment, PDE 1 Inhibitors may be used in the foregoing methods of treatment or prophylaxis as a sole therapeutic agent, but may also be used in combination or for co-administration with other active agents, for example in conjunction with hormone replacement therapy. Thus, the invention further comprises a method of treating disorders that may be ameliorated by enhancement of progesterone signaling comprising administering simultaneously, sequentially, or contemporaneously administering therapeutically effective amounts of (i) a PDE 1 Inhibitor, e.g., a compound according to any of Formula I, any of 1.1-1.135 or I(i) or I(ii), or any described in this specification and (ii) a hormone, e.g., selected from estrogen and estrogen analogues (e.g., estradiol, estriol, estradiol esters) and progesterone and progesterone analogues (e.g., progestins) in free or pharmaceutically acceptable salt form, to a human or animal patient in need thereof. In another embodiment, the invention provides the method described above wherein the PDE 1 inhibitor is a Compound of Formula II, in free or pharmaceutically acceptable salt form. The invention also provides a method for enhancing or potentiating dopamine D1 intracellular signaling activity in a cell or tissue comprising contacting said cell or tissue with an amount of a Compound of the Invention sufficient to inhibit PDE1B activity. The invention also provides a method for enhancing or potentiating progesterone signaling activity in a cell or tissue comprising contacting said cell or tissue with an amount of a Compound of the Invention sufficient to inhibit PDE1B activity. The invention also provides a method for treating a PDE1-related, especially PDE1B-related disorder, a dopamine D1 receptor intracellular signaling pathway disorder, or disorders that may be alleviated by the enhancement of the progesterone signaling pathway in a patient in need thereof comprising administering to the patient an effective amount of a Compound of the Invention that inhibits PDE1B, wherein PDE1B activity modulates phosphorylation of DARPP-32 and/or the GluR 1 AMPA receptor. In another aspect, the invention also provides a method for the treatment for glaucoma or elevated intraocular pressure comprising topical administration of a therapeutically effective amount of a phospodiesterase type I (PDE1) Inhibitor of the Invention, in free or pharmaceutically acceptable salt form, in an opthalmically compatible carrier to the eye of a patient in need thereof. However, treatment may alternatively include a systemic therapy. Systemic therapy includes treatment that can directly reach the bloodstream, or oral methods of administration, for example. The invention further provides a pharmaceutical composition for topical ophthalmic use comprising a PDE1 inhibitor; for example an ophthalmic solution, suspension, cream or ointment comprising a PDE1 Inhibitor of the Invention, in free or ophthamalogically acceptable salt form, in combination or association with an ophthamologically acceptable diluent or carrier. Optionally, the PDE1 inhibitor may be administered sequentially or simultaneously with a second drug useful for treatment of glaucoma or elevated intraocular pressure. Where two active agents are administered, the therapeutically effective amount of each agent may be below the amount needed for activity as monotherapy. Accordingly, a subthreshold amount (i.e., an amount below the level necessary for efficacy as monotherapy) may be considered therapeutically effective and also may also be referred alternatively as an effective amount. Indeed, an advantage of administering different agents with different mechanisms of action and different side effect profiles may be to reduce the dosage and side effects of either or both agents, as well as to enhance or potentiate their activity as monotherapy. The invention thus provides the method of treatment of a condition selected from glaucoma and elevated intraocular pressure comprising administering to a patient in need thereof an effective amount, e.g., a subthreshold amount, of an agent known to lower intraocular pressure concomitantly, simultaneously or sequentially with an effective amount, e.g., a subthreshold amount, of a PDE1 Inhibitor of the Invention, in free or pharmaceutically acceptable salt form, such that amount of the agent known to lower intraocular pressure and the amount of the PDE1 inhibitor in combination are effective to treat the condition. In one embodiment, one or both of the agents are administered topically to the eye. Thus the invention provides a method of reducing the side effects of treatment of glaucoma or elevated intraocular pressure by administering a reduced dose of an agent known to lower intraocular pressure concomitantly, simultaneously or sequentially with an effective amount of a PDE1 inhibitor. However, methods other than topical administration, such as systemic therapeutic administration, may also be utilized. The optional additional agent or agents for use in combination with a PDE1 inhibitor may, for example, be selected from the existing drugs comprise typically of instillation of a prostaglandin, pilocarpine, epinephrine, or topical beta-blocker treatment, e.g. with timolol, as well as systemically administered inhibitors of carbonic anhydrase, e.g. acetazolamide. Cholinesterase inhibitors such as physostigmine and echothiopate may also be employed and have an effect similar to that of pilocarpine. Drugs currently used to treat glaucoma thus include, e.g., 1. Prostaglandin analogs such as latanoprost (Xalatan), bimatoprost (Lumigan) and travoprost (Travatan), which increase uveoscleral outflow of aqueous humor. Bimatoprost also increases trabecular outflow. 2. Topical beta-adrenergic receptor antagonists such as timolol, levobunolol (Betagan), and betaxolol, which decrease aqueous humor production by the ciliary body. 3. Alpha 2 -adrenergic agonists such as brimonidine (Alphagan), which work by a dual mechanism, decreasing aqueous production and increasing uveo-scleral outflow. 4. Less-selective sympathomimetics like epinephrine and dipivefrin (Propine) increase outflow of aqueous humor through trabecular meshwork and possibly through uveoscleral outflow pathway, probably by a beta 2 -agonist action. 5. Miotic agents (parasympathomimetics) like pilocarpine work by contraction of the ciliary muscle, tightening the trabecular meshwork and allowing increased outflow of the aqueous humour. 6. Carbonic anhydrase inhibitors like dorzolamide (Trusopt), brinzolamide (Azopt), acetazolamide (Diamox) lower secretion of aqueous humor by inhibiting carbonic anhydrase in the ciliary body. 7. Physostigmine is also used to treat glaucoma and delayed gastric emptying. For example, the invention provides pharmaceutical compositions comprising a PDE1 Inhibitor of the Invention and an agent selected from (i) the prostanoids, unoprostone, latanoprost, travoprost, or bimatoprost; (ii) an alpha adrenergic agonist such as brimonidine, apraclonidine, or dipivefrin and (iii) a muscarinic agonist, such as pilocarpine. For example, the invention provides ophthalmic formulations comprising a PDE-1 Inhibitor of the Invention together with bimatoprost, abrimonidine, brimonidine, timolol, or combinations thereof, in free or ophthamalogically acceptable salt form, in combination or association with an ophthamologically acceptable diluent or carrier. In addition to selecting a combination, however, a person of ordinary skill in the art can select an appropriate selective receptor subtype agonist or antagonist. For example, for alpha adrenergic agonist, one can select an agonist selective for an alpha 1 adrenergic receptor, or an agonist selective for an alpha 2 adrenergic receptor such as brimonidine, for example. For a beta-adrenergic receptor antagonist, one can select an antagonist selective for either β 1 , or β 2 , or β 3 , depending on the appropriate therapeutic application. One can also select a muscarinic agonist selective for a particular receptor subtype such as M 1 -M 5 . The PDE 1 inhibitor may be administered in the form of an ophthalmic composition, which includes an ophthalmic solution, cream or ointment. The ophthalmic composition may additionally include an intraocular-pressure lowering agent. In yet another example, the PDE-1 Inhibitors disclosed may be combined with a subthreshold amount of an intraocular pressure-lowering agent which may be a bimatoprost ophthalmic solution, a brimonidine tartrate ophthalmic solution, or brimonidine tartrate/timolol maleate ophthalmic solution. In addition to the above-mentioned methods, it has also been surprisingly discovered that PDE1 inhibitors are useful to treat psychosis, for example, any conditions characterized by psychotic symptoms such as hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, e.g., schizophrenia, schizoaffective disorder, schizophreniform disorder, psychotic disorder, delusional disorder, and mania, such as in acute manic episodes and bipolar disorder. Without intending to be bound by any theory, it is believed that typical and atypical antipsychotic drugs such as clozapine primarily have their antagonistic activity at the dopamine D2 receptor. PDE1 inhibitors, however, primarily act to enhance signaling at the dopamine D1 receptor. By enhancing D1 receptor signaling, PDE1 inhibitors can increase NMDA receptor function in various brain regions, for example in nucleus accumbens neurons and in the prefrontal cortex. This enhancement of function may be seen for example in NMDA receptors containing the NR 2 B subunit, and may occur e.g., via activation of the Src and protein kinase A family of kinases. Therefore, the invention provides a new method for the treatment of psychosis, e.g., schizophrenia, schizoaffective disorder, schizophreniform disorder, psychotic disorder, delusional disorder, and mania, such as in acute manic episodes and bipolar disorder, comprising administering a therapeutically effective amount of a phosphodiesterase-1 (PDE1) Inhibitor of the Invention, in free or pharmaceutically acceptable salt form, to a patient in need thereof. PDE 1 Inhibitors may be used in the foregoing methods of treatment prophylaxis as a sole therapeutic agent, but may also be used in combination or for co-administration with other active agents. Thus, the invention further comprises a method of treating psychosis, e.g., schizophrenia, schizoaffective disorder, schizophreniform disorder, psychotic disorder, delusional disorder, or mania, comprising administering simultaneously, sequentially, or contemporaneously administering therapeutically effective amounts of: (i) a PDE 1 Inhibitor of the invention, in free or pharmaceutically acceptable salt form; and (ii) an antipsychotic, e.g., Typical antipsychotics, e.g., Butyrophenones, e.g. Haloperidol (Haldol, Serenace), Droperidol (Droleptan); Phenothiazines, e.g., Chlorpromazine (Thorazine, Largactil), Fluphenazine (Prolixin), Perphenazine (Trilafon), Prochlorperazine (Compazine), Thioridazine (Mellaril, Melleril), Trifluoperazine (Stelazine), Mesoridazine, Periciazine, Promazine, Triflupromazine (Vesprin), Levomepromazine (Nozinan), Promethazine (Phenergan), Pimozide (Orap); Thioxanthenes, e.g., Chlorprothixene, Flupenthixol (Depixol, Fluanxol), Thiothixene (Navane), Zuclopenthixol (Clopixol, Acuphase); Atypical antipsychotics, e.g., Iozapine (Clozaril), Olanzapine (Zyprexa), Risperidone (Risperdal), Quetiapine (Seroquel), Ziprasidone (Geodon), Amisulpride (Solian), Paliperidone (Invega), Aripiprazole (Abilify), Bifeprunox; norclozapine, in free or pharmaceutically acceptable salt form, to a patient in need thereof. In a particular embodiment, the Compounds of the Invention are particularly useful for the treatment or prophylaxis of schizophrenia. Compounds of the Invention, in free or pharmaceutically acceptable salt form, are particularly useful for the treatment of Parkinson's disease, schizophrenia, narcolepsy, glaucoma and female sexual dysfunction. In still another aspect, the invention provides a method of lengthening or enhancing growth of the eyelashes by administering an effective amount of a prostaglandin analogue, e.g., bimatoprost, concomitantly, simultaneously or sequentially with an effective amount of a PDE1 inhibitor of the Invention, in free or pharmaceutically acceptable salt form, to the eye of a patient in need thereof. In yet another aspect, the invention provides a method for the treatment or prophylaxis of traumatic brain injury comprising administering a therapeutically effective amount of a PDE1 inhibitor of the invention, in free or pharmaceutically acceptable salt form, to a patient in need thereof. Traumatic brain injury (TBI) encompasses primary injury as well as secondary injury, including both focal and diffuse brain injuries. Secondary injuries are multiple, parallel, interacting and interdependent cascades of biological reactions arising from discrete subcellular processes (e.g., toxicity due to reactive oxygen species, overstimulation of glutamate receptors, excessive influx of calcium and inflammatory upregulation) which are caused or exacerbated by the inflammatory response and progress after the initial (primary) injury. Abnormal calcium homeostasis is believed to be a critical component of the progression of secondary injury in both grey and white matter. For a review of TBI, see Park et al., CMAJ (2008) 178(9):1163-1170, the contents of which are incorporated herein in their entirety. Studies have shown that the cAMP-PKA signaling cascade is downregulated after TBI and treatment of PDE IV inhibitors such as rolipram to raise or restore cAMP level improves histopathological outcome and decreases inflammation after TBI. As Compounds of the present invention is a PDE1 inhibitor, it is believed that these compounds are also useful for the treatment of TBI, e.g., by restoring cAMP level and/or calcium homeostasis after traumatic brain injury. The present invention also provides (i) a Compound of the Invention for use as a pharmaceutical, for example for use in any method or in the treatment of any disease or condition as hereinbefore set forth, (ii) the use of a Compound of the Invention in the manufacture of a medicament for treating any disease or condition as hereinbefore set forth, (iii) a pharmaceutical composition comprising a Compound of the Invention in combination or association with a pharmaceutically acceptable diluent or carrier, and (iv) a pharmaceutical composition comprising a Compound of the Invention in combination or association with a pharmaceutically acceptable diluent or carrier for use in the treatment of any disease or condition as hereinbefore set forth. Therefore, the invention provides use of a Compound of the Invention for the manufacture of a medicament for the treatment or prophylactic treatment of the following diseases: Parkinson's disease, restless leg, tremors, dyskinesias, Huntington's disease, Alzheimer's disease, and drug-induced movement disorders; depression, attention deficit disorder, attention deficit hyperactivity disorder, bipolar illness, anxiety, sleep disorder, narcolepsy, cognitive impairment, dementia, Tourette's syndrome, autism, fragile X syndrome, psychostimulant withdrawal, and/or drug addiction; cerebrovascular disease, stroke, congestive heart disease, hypertension, pulmonary hypertension, and/or sexual dysfunction; asthma, chronic obstructive pulmonary disease, and/or allergic rhinitis, as well as autoimmune and inflammatory diseases; and/or female sexual dysfunction, exercise amenorrhoea, anovulation, menopause, menopausal symptoms, hypothyroidism, pre-menstrual syndrome, premature labor, infertility, irregular menstrual cycles, abnormal uterine bleeding, osteoporosis, multiple sclerosis, prostate enlargement, prostate cancer, hypothyroidism, estrogen-induced endometrial hyperplasia or carcinoma; and/or any disease or condition characterized by low levels of cAMP and/or cGMP (or inhibition of cAMP and/or cGMP signaling pathways) in cells expressing PDE1, and/or by reduced dopamine D1 receptor signaling activity; and/or any disease or condition that may be ameliorated by the enhancement of progesterone signaling. The invention also provides use of a Compound of the Invention, in free or pharmaceutically acceptable salt form, for the manufacture of a medicament for the treatment or prophylactic treatment of: a) glaucoma or elevated intraocular pressure, b) psychosis, for example, any conditions characterized by psychotic symptoms such as hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, e.g., schizophrenia, schizoaffective disorder, schizophreniform disorder, psychotic disorder, delusional disorder, and mania, such as in acute manic episodes and bipolar disorder, c) traumatic brain injury. The phrase “Compounds of the Invention” or “PDE 1 inhibitors of the Invention” encompasses any and all of the compounds disclosed within this specification. The words “treatment” and “treating” are to be understood accordingly as embracing prophylaxis and treatment or amelioration of symptoms of disease as well as treatment of the cause of the disease For methods of treatment, the word “effective amount” is intended to encompass a therapeutically effective amount to treat a specific disease or disorder. The term “pulmonary hypertension” is intended to encompass pulmonary arterial hypertension. The term “patient” include human or non-human (i.e., animal) patient. In particular embodiment, the invention encompasses both human and nonhuman. In another embodiment, the invention encompasses nonhuman. In other embodiment, the term encompasses human. The term “comprising” as used in this disclosure is intended to be open-ended and does not exclude additional, unrecited elements or method steps. Compounds of the Invention are in particular useful for the treatment of Parkinson's disease, narcolepsy and female sexual dysfunction. Compounds of the Invention may be used as a sole therapeutic agent, but may also be used in combination or for co-administration with other active agents. For example, as Compounds of the Invention potentiate the activity of D1 agonists, such as dopamine, they may be simultaneously, sequentially, or contemporaneously administered with conventional dopaminergic medications, such as levodopa and levodopa adjuncts (carbidopa, COMT inhibitors, MAO-B inhibitors), dopamine agonists, and anticholinergics, e.g., in the treatment of a patient having Parkinson's disease. In addition, the novel PDE 1 inhibitors of the Invention, e.g., the Compounds of the Invention as described herein, may also be administered in combination with estrogen/estradiol/estriol and/or progesterone/progestins to enhance the effectiveness of hormone replacement therapy or treatment of estrogen-induced endometrial hyperplasia or carcinoma. Dosages employed in practicing the present invention will of course vary depending, e.g. on the particular disease or condition to be treated, the particular Compound of the Invention used, the mode of administration, and the therapy desired. Compounds of the Invention may be administered by any suitable route, including orally, parenterally, transdermally, or by inhalation, but are preferably administered orally. In general, satisfactory results, e.g. for the treatment of diseases as hereinbefore set forth are indicated to be obtained on oral administration at dosages of the order from about 0.01 to 2.0 mg/kg. In larger mammals, for example humans, an indicated daily dosage for oral administration will accordingly be in the range of from about 0.75 to 150 mg, conveniently administered once, or in divided doses 2 to 4 times, daily or in sustained release form. Unit dosage forms for oral administration thus for example may comprise from about 0.2 to 75 or 150 mg, e.g. from about 0.2 or 2.0 to 50, 75 or 100 mg of a Compound of the Invention, together with a pharmaceutically acceptable diluent or carrier therefor. Pharmaceutical compositions comprising Compounds of the Invention may be prepared using conventional diluents or excipients and techniques known in the galenic art. Thus oral dosage forms may include tablets, capsules, solutions, suspensions and the like. EXAMPLES The synthetic methods for various Compounds of the Present Invention are illustrated below. Other compounds of the Invention and their salts may be made using the methods as similarly described below and/or by methods similar to those generally described in the detailed description and by methods known in the chemical art. Example 1 2-(4-(1H-1,2,4-triazol-1-yl)benzyl)-5-methyl-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione 1) 2-(4-(1H-1,2,4-triazol-1-yl)benzyl)-5-methyl-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione 5-methyl-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione (200 mg, 0.847 mmol), 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole (202 mg, 0.847 mmol) and K 2 CO 3 (117 mg, 0.847 mmol) are suspended in 5 mL of anhydrous DMF. The reaction mixture is stirred at room temperature for 5 h, and then evaporated to dryness under reduced pressure. The residue is treated with water, and then extracted with dichloromethane three times. The combined organic phase is dried with anhydrous sodium sulfate, filtered, and then evaporated to dryness to give 337 mg of crude product, which is used in the next step without further purification. MS (ESI) m/z 394.2 [M+H] + . 2) 2-(4-(1H-1,2,4-triazol-1-yl)benzyl)-5-methyl-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione 2-(4-(1H-1,2,4-triazol-1-yl)benzyl)-5-methyl-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione (52 mg, 0.132 mmol) and methyl disulfide (12 μL, 0.13 mmol) are dissolved in 2 mL of anhydrous CH 2 Cl 2 , and then 1.0 M LiHMDS (190 μL, 0.19 mmol) in THF is added dropwise. The reaction mixture is stirred at room temperature for 30 min, and then quenched with saturated ammonium chloride aqueous solution. After routine workup, the obtained crude product is purified by silica gel column chromatography to give pure product as off-white solids. MS (ESI) m/z 440.2 [M+H] + . Example 2 5-methyl-3-(methylthio)-7-neopentyl-2-(4-(trifluoromethyl)benzyl)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is analogous to EXAMPLE 1 wherein 1-(bromomethyl)-4-(trifluoromethyl)benzene is used in step 1 instead of 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole. MS (ESI) m/z 441.2 [M+H] + . Example 3 5-methyl-7-neopentyl-3-(phenylthio)-2-(4-(trifluoromethyl)benzyl)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is analogous to EXAMPLE 1 wherein 1-(bromomethyl)-4-(trifluoromethyl)benzene is used in step 1 instead of 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole, and phenyl disulfide is used in step 2 instead of methyl disulfide. MS (ESI) m/z 503.2 [M+H] + . Example 4 2-(4-methoxybenzyl)-5-methyl-7-neopentyl-3-(phenylthio)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is analogous to EXAMPLE 1 wherein 4-methoxybenzyl bromide is used in step 1 instead of 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole, and phenyl disulfide is used in step 2 instead of methyl disulfide. MS (ESI) m/z 465.2 [M+H] + . Example 5 2-(4-(1H-1,2,4-triazol-1-yl)benzyl)-5-methyl-7-neopentyl-3-(phenylthio)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione 2-(4-methoxybenzyl)-5-methyl-7-neopentyl-3-(phenylthio)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione (2.7 g, 5.9 mmol) is dissolved in CH 2 Cl 2 (20 mL) containing TFA (4.2 mL) and TFMSA (1.0 mL). The mixture is stirred at room temperature overnight. Solvents are removed, and the residue is dissolved in ethyl acetate (250 mL), followed by washing with saturate NaHCO 3 and water successively. After dried over anhydrous sodium sulfate, the organic phase is evaporated to dryness. The obtained crude product is used in the next step without further purification. Crude 5-methyl-7-neopentyl-3-(phenylthio)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione (40 mg, 0.12 mmol), 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole (28 mg, 0.12 mmol) and K 2 CO 3 (16 mg, 0.12 mmol) are suspended in 5 mL of anhydrous DMF. The reaction mixture is stirred at room temperature overnight, and then evaporated to dryness under reduced pressure. The residue is purified by silica gel column chromatography to give pure product as white solids. MS (ESI) m/z 502.2 [M+H] + . Example 6 2-(4-methoxybenzyl)-5-methyl-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is analogous to EXAMPLE 1 wherein 4-methoxybenzyl bromide is used in step 1 instead of 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole. MS (ESI) m/z 403.2 [M+H] + . Example 7 2-(4-(1H-pyrazol-1-yl)benzyl)-5-methyl-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is analogous to EXAMPLE 5 wherein 2-(4-methoxybenzyl)-5-methyl-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione is used instead of 2-(4-methoxybenzyl)-5-methyl-7-neopentyl-3-(phenylthio)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione, and 1-(4-(bromomethyl)phenyl)-1H-pyrazole is used instead of 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole. MS (ESI) m/z 439.2 [M+H] + . Example 8 5-methyl-2-(4-(methylsulfonyl)benzyl)-7-neopentyl-3-(phenylthio)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is analogous to EXAMPLE 5 wherein 1-(bromomethyl)-4-(methylsulfonyl)benzene is used instead of 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole. MS (ESI) m/z 513.2 [M+H] + . Example 9 5-methyl-7-neopentyl-3-(phenylthio)-2-(4-(pyridin-2-yl)benzyl)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is analogous to EXAMPLE 1 wherein 2-(4-(bromomethyl)phenyl)pyridine is used in step 1 instead of 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole, and phenyl disulfide is used in step 2 instead of methyl disulfide. MS (ESI) m/z 512.3 [M+H] + . Example 10 5-methyl-2-(4-(1-methylpiperidin-2-yl)benzyl)-7-neopentyl-3-(phenylthio)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is analogous to EXAMPLE 5 wherein 2-(4-(chloromethyl)phenyl)-1-methylpiperidine is used instead of 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole. MS (ESI) m/z 532.3 [M+H] + . Example 11 5-methyl-2-(4-(methylsulfonyl)benzyl)-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is analogous to EXAMPLE 5 wherein 2-(4-methoxybenzyl)-5-methyl-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione is used instead of 2-(4-methoxybenzyl)-5-methyl-7-neopentyl-3-(phenylthio)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione, and 1-(bromomethyl)-4-(methylsulfonyl)benzene is used instead of 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole. MS (ESI) m/z 451.1 [M+H] + . Example 12 5-methyl-3-(methylsulfinyl)-2-(4-(methylsulfonyl)benzyl)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione 5-methyl-2-(4-(methylsulfonyl)benzyl)-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione (11.4 mg, 0.022 mmol) is dissolved in CH 2 Cl 2 (200 μL) and CH 3 CN (100 μL), and then 30% H 2 O 2 aqueous solution (75 μL, 0.66 mmol) is added, followed by acetic acid (6.6 mg, 0.11 mmol). The reaction mixture is stirred at room temperature over a weekend, and then purified by a semi-preparative HPLC to give 6 mg of product as white solids. MS (ESI) m/z 467.1 [M+H] + . Example 13 2-(4-(1H-1,2,4-triazol-1-yl)benzyl)-5-methyl-3-(methylsulfinyl)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione 2-(4-(1H-1,2,4-triazol-1-yl)benzyl)-5-methyl-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione (16 mg, 0.036 mmol) is dissolved in CH 2 Cl 2 (500 μL) and MeOH (500 μL), and then an aqueous solution of Oxone (22.4 mg, 0.036 mmol) is added. The reaction mixture is stirred at room temperature for 2 days, and then purified by a semi-preparative HPLC to give 8 mg of product as off-white solids. MS (ESI) m/z 456.2 [M+H] + . Example 14 2-(4-(1H-1,2,4-triazol-1-yl)benzyl)-5-methyl-3-(methylsulfonyl)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is the same as EXAMPLE 13. 2-(4-(1H-1,2,4-triazol-1-yl)benzyl)-5-methyl-3-(methylsulfonyl)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione is obtained as a minor product of the reaction. MS (ESI) m/z 472.2 [M+H] + . Example 15 5-methyl-2-(4-(1-methylpiperidin-2-yl)benzyl)-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione The synthetic procedure of this compound is analogous to EXAMPLE 5 wherein 2-(4-methoxybenzyl)-5-methyl-3-(methylthio)-7-neopentyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione is used instead of 2-(4-methoxybenzyl)-5-methyl-7-neopentyl-3-(phenylthio)-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione, and 2-(4-(chloromethyl)phenyl)-1-methylpiperidine is used instead of 1-(4-(bromomethyl)phenyl)-1H-1,2,4-triazole. MS (ESI) m/z 439.2 [M+H] + . Example 16 Measurement of PDE1B Inhibition In Vitro Using IMAP Phosphodiesterase Assay Kit Phosphodiesterase 1B (PDE1B) is a calcium/calmodulin dependent phosphodiesterase enzyme that converts cyclic guanosine monophosphate (cGMP) to 5′-guanosine monophosphate (5′-GMP). PDE1B can also convert a modified cGMP substrate, such as the fluorescent molecule cGMP-fluorescein, to the corresponding GMP-fluorescein. The generation of GMP-fluorescein from cGMP-fluorescein can be quantitated, using, for example, the IMAP (Molecular Devices, Sunnyvale, Calif.) immobilized-metal affinity particle reagent. Briefly, the IMAP reagent binds with high affinity to the free 5′-phosphate that is found in GMP-fluorescein and not in cGMP-fluorescein. The resulting GMP-fluorescein-IMAP complex is large relative to cGMP-fluorescein. Small fluorophores that are bound up in a large, slowly tumbling, complex can be distinguished from unbound fluorophores, because the photons emitted as they fluoresce retain the same polarity as the photons used to excite the fluorescence. In the phosphodiesterase assay, cGMP-fluorescein, which cannot be bound to IMAP, and therefore retains little fluorescence polarization, is converted to GMP-fluorescein, which, when bound to IMAP, yields a large increase in fluorescence polarization (Δmp) Inhibition of phosphodiesterase, therefore, is detected as a decrease in Δmp. Enzyme Assay Materials: All chemicals are available from Sigma-Aldrich (St. Louis, Mo.) except for IMAP reagents (reaction buffer, binding buffer, FL-GMP and IMAP beads), which are available from Molecular Devices (Sunnyvale, Calif.). Assay: 3′,5′-cyclic-nucleotide-specific bovine brain phosphodiesterase (Sigma, St. Louis, Mo.) is reconstituted with 50% glycerol to 2.5 U/ml. One unit of enzyme will hydrolyze 1.0 μmole of 3′,5′-cAMP to 5′-AMP per min at pH 7.5 at 30° C. One part enzyme is added to 1999 parts reaction buffer (30 μM CaCl 2 , 10 U/ml of calmodulin (Sigma P2277), 10 mM Tris-HCl pH 7.2, 10 mM MgCl 2 , 0.1% BSA, 0.05% NaN 3 ) to yield a final concentration of 1.25 mU/ml. 99 μl of diluted enzyme solution is added into each well in a flat bottom 96-well polystyrene plate to which 1 μl of test compound dissolved in 100% DMSO is added. Selected Compounds of the Invention are mixed and pre-incubated with the enzyme for 10 min at room temperature. The FL-GMP conversion reaction is initiated by combining 4 parts enzyme and inhibitor mix with 1 part substrate solution (0.225 μM) in a 384-well microtiter plate. The reaction is incubated in dark at room temperature for 15 min The reaction is halted by addition of 60 μl of binding reagent (1:400 dilution of IMAP beads in binding buffer supplemented with 1:1800 dilution of antifoam) to each well of the 384-well plate. The plate is incubated at room temperature for 1 hour to allow IMAP binding to proceed to completion, and then placed in an Envision multimode microplate reader (PerkinElmer, Shelton, Conn.) to measure the fluorescence polarization (Δmp) A decrease in GMP concentration, measured as decreased Δmp, is indicative of inhibition of PDE activity. IC 50 values are determined by measuring enzyme activity in the presence of 8 to 16 concentrations of compound ranging from 0.0037 nM to 80,000 nM and then plotting drug concentration versus ΔmP, which allows IC 50 values to be estimated using nonlinear regression software (XLFit; IDBS, Cambridge, Mass.). The Compounds of the Invention may be selected and tested in an assay as described or similarly described herein for PDE1 inhibitory activity. The exemplified compounds of the invention generally have IC 50 values of less than 5 μM, some less than 1 μM, some less than 250 nM, some with PDE1A activities. Example 17 PDE1 Inhibitor Effect on Sexual Response in Female Rats The effect of PDE1 inhibitors on Lordosis Response in female rats is measured as described in Mani, et al., Science (2000) 287: 1053. Ovariectomized and cannulated wild-type rats are primed with 2 μg estrogen followed 24 hours later by intracerebroventricular (icy) injection of progesterone (2 μg), PDE1 inhibitors of the present invention (0.1 mg, 1.0 mg or 2.5 mg) or sesame oil vehicle (control). The rats are tested for lordosis response in the presence of male rats. Lordosis response is quantified by the lordosis quotient (LQ=number of lordosis/10 mounts×100). The LQ for estrogen-primed female rats receiving Compounds of the Invention, at 0.1 mg, will likely be similar to estrogen-primed rats receiving progesterone and higher than for estrogen-primed rats receiving vehicle.

Optionally substituted (5- or 7- amino)-3,4-dihydro-(optionally 4-oxo, 4-thioxo or 4-imino)- 1H-pyrrolo [3,4-d]pyrimidin-2(6H)-ones, Compounds of Formula I, processes for their production, their use as pharmaceuticals and pharmaceutical compositions comprising them.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation application of International Application No. PCT/US2015/015294, filed on Feb. 10, 2015, which claims the benefit of U.S. Provisional Patent Application 61/938,120, filed on Feb. 10, 2014, the content of each application of which is hereby incorporated by reference in its entirety. BACKGROUND OF THE INVENTION [0002] Purposes for using multiple network connections between terminals and remote servers include attaining higher network availability. A multi-network router connects terminals and servers via at least one of multiple network sessions that the router establishes with remote network components such as servers, switches or gateways. If a network connection being used for data communication fails, the multi-network router selects a network connection that is available for use at the time, and fails over the data traffic to the selected network connection. [0003] In some multi-network routers, at least one of multiple networks is designated as a primary network. Data traffic fails over from the primary network to another network upon failure of the primary network. Such failure can be detected by monitoring the bearer network or sending data packets with the “ping” command to some remote server. When the primary network later recovers from failure, for example, upon the router determining that the bearer network as operational or the “ping” test succeeding, the router fails backs to route data through the primary network. [0004] Stability of data communication networks is influenced by a variety of factors. In case of cellular and other radio networks, for example, these factors include the distance between a radio tower and a terminal, weather, buildings, both stationary and moving obstacles at premises, and many other conditions. Congestion due to excessive traffic with a cell as well as on the core network can also interrupt communications. Some of these interruptions can be quite prolonged, but even momentary or transitory events can disrupt digital communications, particularly if the event is repetitive. [0005] Use of wide area data networks such as cellular wireless include data communication between ATMs (automatic teller machines) or POS (Point Of Sales) terminals and financial institutions for financial transactions among many other applications. To provide connectivity that is highly available and/or reliable, some implementations connect more than one network routers, each connecting to a cellular network. Some other implementations employ a cellular network router that contains more than one cellular network modem modules, each connecting to a cellular network. Typically, there is a routing table inside a switch that connects with one or more network routers or within a multiple-network router. When data is transmitted over a network to a remote location, the routing table can be looked up, which specifies the network through which data needs to be routed. The data can then be transmitted via the specified network interface associated with the specified network. [0006] In case of using multiple cellular network connections to provide highly available network service, cost management becomes a significant factor in selecting which network to use primarily. Simple failover and failback of data traffic may not minimize operating costs. For example, different types of cellular networks such as, but not limited to, different generations of cellular network implementations (e.g., 2G, 3G, 4G, etc.) may have different operating costs given data traffic. In addition, cost structure of data communication may depend on how network operators procure interconnection with other telecommunication operators. In some cases, the cost is based on a monthly flat-rate per bandwidth or a variable rate per data volume. If the primary network is designated based on operating costs, it is important to maximize the use of the primary network. [0007] A preferred network needs to be designated from both cost and network quality perspectives, and it is expected that the system maximize the use of the preferred network. Improvement on failback technology is needed to minimize the cost. [0008] In addition, there are cases of rapid cycles of failover and failback, sometimes referred as rapid “flapping” among multiple network interfaces, occurring among multiple networks when quality level of the preferred network fluctuates just above and below the threshold level. In such a situation, it is desirable for the system not to use the preferred network until quality of the preferred network no longer fluctuates. [0009] There has also been a need to remotely manage preferred networks, as cost structures of respective networks may change over time. The preference needs to be changed without requiring changing network selection settings at terminals such as ATMs and POS. INCORPORATION BY REFERENCE [0010] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. BRIEF DESCRIPTION OF THE DRAWINGS [0011] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which: [0012] FIG. 1 depicts an embodiment of prior arts as a multi-network router with two cellular network interface modules, connecting to a server via the Internet or via a private cloud. [0013] FIG. 2 depicts an embodiment of prior arts as a multi-network router with one LAN network interface module along with three cellular WAN interface modules. [0014] FIG. 3 depicts exemplary computing components for implementing the present invention, according to an embodiment. [0015] FIG. 4 depicts exemplary logical components for implementing the present invention, according to an embodiment. [0016] FIG. 5 depicts an exemplary process for deciding data routing among multiple networks to transmit data, according to an embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION [0017] The present invention discloses methods and systems provided for a multi-network router, which maintains and enforces use of a preferred network while executing failovers and failbacks among multiple networks to maximize service availability and to minimize operating costs. The multi-network router determines which network to use for data traffic, and dynamically changes the priority of available networks based on conditions of the respective networks. [0018] According to an aspect of the present invention, a method is provided for selecting, from a plurality of networks, an optimal network through which data is to be routed. The plurality of networks may be reachable by a multi-network router as described herein. The router may be configured to perform the selection dynamically based on a variety of factors such as system or user preference (e.g., primary versus secondary network, operating costs), real-time network status (e.g., availability, traffic status, error rate, delays, latency), status report provided by an external or internal Intrusion Detection System (IDS) or module, and the like. Each of these factors may be associated with a plurality of possible weight values indicative of the relative weight or severity of the factor. The weight values for a particular network may be statically and/or dynamically assigned. Thus, for each of the plurality of networks reachable by the router, a total weight value may be calculated by combining (e.g., via multiplication) the weight values for each of the plurality of factors. The plurality of networks can then be ranked according to the calculated total weight values to determine the optimal network to route the data and the routing table associated with the router can be updated accordingly. [0019] According to another aspect of the present invention, a method is provided for preventing route “flapping” such as described above. To this end, a dampening effect may be introduced to change the way that the routing table is updated. In particular, the dampening effect may be used to delay the update of some or all of the weight values described herein for a predetermined period of time. Additionally or alternatively, the updates may progress as scheduled, but with reduced or modified weight value for a predetermined period of time. In various embodiments, such dampening effect may be introduced for some or all of the factors at any stage in the route ranking or selection process. The length of the predetermined period of time and/or the modified weight values used within the period of time can be selected based on a variety of factors such as the duration of time since a network becomes available, the minimum and/or maximum bandwidth available on the network, an amount of data volume over the network, or other statistics or characteristics associated with the network. [0020] Some or all aspects of the functionalities and features described herein may be implemented individually or collectively by one or more physical or logical components such as described herein. [0021] FIG. 1 depicts an embodiment of prior arts as a multi-network router with two cellular network interface modules, connecting to a server via the Internet or via a private cloud. [0022] FIG. 2 depicts an embodiment of prior arts as a multi-network router with one LAN network interface module along with three cellular WAN interface modules. [0023] In some embodiments, such as described in FIG. 3 , the invention can be implemented in a multi-network router. In particular, FIG. 3 illustrates a system 300 for communication between a client terminal and a server using a multi-network router as provided in embodiments of the present invention. FIG. 3 includes client terminal 310 . Client terminal 310 of FIG. 3 represents an entity, such as an ATM or a POS terminal, which communicates with remote servers to execute financial transactions. FIG. 3 also includes a multi-network router 320 . Router 320 includes network interface modules 322 referenced as “PPP 99 ”, “PPP 0 ”, “PPP 1 ”, and “PPP 2 ”. In particular, network interface module PPP 99 interfaces with client terminal 310 . Additionally, network interface module PPP 99 interfaces with network interface modules PPP 0 , PPP 1 , and PPP 2 . Further, network interface modules 322 may connect with cellular networks 340 . In particular, as seen in FIG. 3 , network interface module PPP 0 connects with cellular network A; network interface module PPP 1 connects with cellular network B, and network interface module PPP 2 connects with cellular network C. As shown in FIG. 3 , cellular networks 340 connect to gateway 350 and gateway 350 connects to server 360 . Accordingly, in this embodiment shown in FIG. 3 , data traffic between client terminal 310 and server 360 can connect through at least one cellular network 340 . In FIG. 3 , a bus connects the network interface modules 322 with processing unit 324 and memory 330 . Processing unit 324 processes computations and programs on the router 320 . Memory 330 stores programs including a data transmission program 334 as well as a routing table 332 and an operating system 336 . Routing table 332 may contain a list of network interfaces available for data transmission from the router 320 , and may also specify over which network interface to transmit data. [0024] Memory 330 may include a non-transitory computer readable medium or transitory computer readable medium. For example, the memory can include random access memory (“RAM”), read only memory (“ROM”), disk drive, floppy disc, tape, DVD/CD-ROM drive, memory card, USB flash drive, solid state drive (SSD) or the like. The memory can be configured to store data received from the processing unit, an input device (not shown), or other modules of the computing device. The memory may also store program code or program instructions executable by the processing unit to perform any suitable embodiments of the methods described herein. For example, the program code can include an operating system, Data Transmission Program, and the like. In some embodiments, program code may be located into Memory using a drive mechanism associated with a non-transient computer readable storage medium such as discussed above. In other embodiments, the program code may alternatively be loaded via the network interface, rather than via a non-transient computer readable storage medium. [0025] As indicated in FIG. 4 , the methods and systems described herein may be implemented by the following logical components: process monitor 410 , WAN monitor 420 , WAN manager 430 , configuration manager 440 , routing decision engine 450 , and routing table manager 460 . In some embodiments, Process monitor 410 may manage the order that the system starts components during a boot process within the multi-network router 320 . Process manager 410 may also re-start any component that has inexplicably stopped. [0026] Additionally, a WAN monitor 420 may exist for every physical WAN interface such as an interface for a specific cellular network carrier. WAN monitor 420 monitors and determines if its assigned interface is available for transmitting and receiving data. For example, WAN monitor 410 may perform monitoring of a network for a configurable time period, such as every 10 seconds. The monitoring activity can also be triggered by an external event to start performing monitoring immediately. Further, WAN monitor 420 may feed its findings to the Routing decision engine 450 . [0027] WAN manager 430 may manage connectivity status of a WAN interface, and may reset and remedy connections when a problem occurs on network connectivity. WAN manager 430 has the ability to reinitialize and reactivate a cellular module that is associated with the cellular network. WAN manager 430 may receive interface status from an associated WAN monitor 420 . [0028] Additionally, Configuration manager 440 may accept and manage configuration attributes and their values. For example, Configuration manager 440 may maintain a list of preferred interfaces from a configuration file and produce weighted values for processing by the Routing decision engine 450 . [0029] In some embodiments, Routing decision engine 450 receives input from WAN monitors 420 and Configuration manager 440 to decide how data needs to be routed when the terminal transmits data. Routing decision engine 450 may compile and manage a list of network interfaces that are available for use based on status information from WAN monitors, such as WAN monitor 420 . Routing decision engine 450 may receive input from Configuration manager 440 and compile a prioritized list of network interfaces to use for data communications. Routing decision engine 450 may use these two lists and identify a network interface that is the most desirable to use for data communication. Routing decision engine 450 may then specify this interface to the Routing table manager 460 . [0030] Routing table manager 460 may be capable of adjusting routing tables and other networking parameters. The objective of routing table manager 460 may be to route networking traffic over a singular WAN interface reported to it from the Routing decision engine 450 . Routing of data may be determined based on which network the Routing table 460 specifies. [0031] Process monitor 410 may be the first service initiated when router 320 starts. Process monitor 410 may manage the start-up of the remaining service components in router 320 . The Process monitor 410 may assure that an applicable WAN monitor 420 and WAN manager 430 have been started for every interface detected. Process monitor 410 may also maintain a list of service components and their initialization sequence. Process monitor 410 may also serve as a “Watchdog” service, for example re-starting any service component that may have stopped. [0032] WAN monitor 420 may bind to a specific interface and then attempt a connection. In order to override a possible modification on the routing table by the operating system upon its connection test, WAN monitor 420 may bypass the network interface control functionality provided by the underlying operating system and directly bind itself to the network interface port. [0033] In some embodiments, the network connectivity tests on all network interfaces that WAN monitor 420 binds to may be repeated at a specified or unspecified interval. The test can be triggered by external services to be performed immediately. In some embodiments, the test consists of an initial verification that an IP address has been assigned to each network interface, transmission of at least one data packet to a specified network address of a remote network entity such as a remote server, and then a verification of a receipt of data by the remote entity. [0034] WAN monitor 420 may feed test results directly to Routing decision engine 450 . WAN monitor 420 may repeat feeding a status at a specified interval regardless of any change in that status. This may serve as a status heartbeat for the interface. Additionally, a network monitoring status report can be triggered by external services to perform an immediate check, rather than waiting for its next specified time. [0035] In some embodiments, WAN monitor 420 counts and maintains status data, such as but not limited to the time duration that its network interface has been active, in order to determine the stability of network connections. WAN monitor 420 may use the time duration value to generate different weighed values depending on whether the network interface has just become active or has been active for more than a preconfigured threshold time period. By WAN monitor 420 feeding weighted values accordingly to Routing decision engine 450 , the Routing decision engine 450 may effectively prevent rapid “flapping” among multiple network interfaces as the Routing decision engine 450 . [0036] In some embodiments, components other than the ones described herein may also be used to implement the present invention. In some embodiments, the components may be executed asynchronously, allowing the components to communicate with one another asynchronously. In some embodiments, the components may be executed sequentially. [0037] The components may be implemented as a set of logics on a digital signal processor, such as an application-specific integrated circuit (ASIC), or stored on memory for execution inside a cellular router that contains one or more network modems connected to respective networks. Additionally, the components may be implemented and stored on a computer or server, which is connected to one or more network routers. [0038] In some embodiments the invention is implemented as logic on a gate array, an application-specific integrated circuit (ASIC), or on a digital signal processor. [0039] In some embodiments, WAN manager 430 may perform a tiered set of recovery steps against its associated interface. For example, in a first step, if a connection is down for 30 seconds an attempt may be made to reinitialize a module. In a second step, if a connection is down for an additional 30 seconds beyond the first step, an attempt may be made to re-activate the module. In a third step, if a connection is down for an additional 30 seconds beyond the second step, an attempt may be made to power down the module completely, wait a predetermined amount of time (such as 10 seconds), and then power the module back up. [0040] Configuration manager 440 may receive external inputs on network interface preference. For example, configuration manager 440 may parse input from a discrete source, such as a configuration file, or from external intrusion detection services. Configuration manager 440 may encapsulate the specific output generated by its bound process and distill it into information usable by the system as a whole. In an example, an external service may detect a possible hacker attack on one of the network interfaces. In this example, configuration manager 440 may notify Routing decision engine 450 or WAN manager 430 that the interface in question needs to be changed in the preference hierarchy, allowing a different interface to be used for network data traffic. [0041] Additionally, Routing decision engine 450 may compile a list of interfaces that are actively available to route traffic, based on results of network monitoring by WAN monitor 420 . Routing decision engine 450 may also determine a list of the most desirable interfaces to be used for routing traffic based on a weighting algorithm, based on preference settings from Configuration manager 440 . Routing decision engine 450 may pass the at least one name of the most desirable available interface to the Routing table manager 460 , where the at least one name may listed on a routing table such as routing table 332 . [0042] The list of interfaces that are actively available to route traffic and/or the list of interfaces that are most desirable to be used for routing traffic may be reevaluated when Routing decision engine 450 receives new information from a Configuration manager 440 and/or when Routing decision engine 450 receives differing information from a WAN monitor 420 (e.g., a status change on an interface from “available” to “unavailable”). [0043] A weighting algorithm that may be used to determine a list of the most desirable interfaces to be used for routing traffic may rely on “weights” being assigned to specific events and conditions. These weights may be used by configuration manager 440 and WAN monitor 420 . For example, an interface that is available may be assigned a weight of “1” while an interface that is down may receive a weight of “0.” Additionally, an interface that is deemed primary may be given a weight of “1” while an interface that is deemed secondary or otherwise below primary may be given a weight that is less than 1, such as “0.5”. These weights may be used in calculating which interface is the most desirable through which to route traffic. As such, based on weighting calculations of the interfaces using a weighting algorithm, Routing decision engine 450 may specify the “winning” interface to Routing table manager 460 for updating a Routing table. [0044] In the event that the routing decision engine 450 is unable to propose a usable interface (e.g., because no interface is listed as available), a series of steps can be taken to remedy the problem, including escalating the severity level up to the action where the Routing decision engine 450 issues a reboot of the routing device, such as router 320 . [0045] Routing table manager 460 may be implemented as a trigger-based process, activated only when it receives information from another service, such as the routing decision engine 450 . The Routing table manager 460 may receive from the Routing decision engine 450 the name of the interface that traffic should be routed across. This change can be effected by modification of the Routing table 332 . The routing table manager 460 may compile a proposed route table which it compares with the existing Route Table 332 . If there are any differences between the two, Routing table manager 460 may replace parts of the existing table with the proposed one. [0046] While embodiments of the present invention may be practiced utilizing multiple network interface ports, examples are provided to illustrate fail overs that may take place utilizing two network interface ports. [0047] In a first example of the present invention, a fail over is described that takes place when a connection of a first interface port is down. In this example, a system has two interfaces: PPP 0 and PPP 1 . A WAN monitor, such as WAN monitor 420 , continuously reports the status of interfaces PPP 0 and PPP 1 to a Routing decision engine, such as Routing decision engine 450 . Initially, both interfaces PPP 0 and PPP 1 are working correctly. Additionally, configuration manager 440 reads a configuration file, which contains a list of the interfaces on the system in order of preference. [0048] In this example, the defined preference is that PPP 0 is primary and PPP 1 is secondary. The Configuration manager 440 translates this into a weighted list, assigning PPP 0 a weighted value of 1 for being a primary interface and assigning PPP 1 a weighted value of 0.5 for being a secondary interface. Further, the WAN monitor 420 determines that both interfaces PPP 0 and PPP 1 are up and translates this into a weighted list, assigning PPP 0 and PPP 1 a value of 1. The Routing decision engine 450 then takes the values from both lists, multiplies them to determine a resultant weighted value for each interface, then assesses the resultant weighted values of the interfaces to determine a most desirable interface through which to communicate data traffic. In particular, the Routing decision engine 450 may determine that the interface having the highest weighted value is the most desirable interface through which to communicate data traffic. [0049] As the contributing weighted values for PPP 0 are “1” from the configuration manager 440 and “1” from the WAN monitor 420 , the resultant weighted value of PPP 0 is 1×1=1. As the contributing weighted values for PPP 1 are “0.5” from the configuration manager 440 and “1” from the WAN monitor 420 , the resultant weighted value of PPP 1 is 1×0.5=0.5. [0050] In this example the Routing decision engine 450 may determine that the interface having the highest weighted value is the most desirable interface through which to communicate data traffic. Accordingly, the Routing decision engine 450 may initially determine that PPP 0 is the most desirable interface through which to communicate data traffic in this example. The Routing decision engine 450 may report to Routing table manager 460 that interface PPP 0 is the most desirable interface. In response, Routing table manager 460 may adjust a routing table, such as routing table 332 , to direct pertinent traffic across PPP 0 . [0051] However, in the event that PPP 0 loses its connections, WAN monitor 420 may perceive the outage and send this new status to the Routing decision engine 450 . Based on receiving the new status, Routing decision engine 450 may perform another calculation. In this new calculation, the weighting values assigned by configuration manager 440 may stay at “1” and “0.5” for PPP 0 and PPP 1 , respectively, as PPP 0 is considered a primary network interface. The weighting values assigned by WAN monitor 420 , however, may change. In particular, WAN monitor 420 may determine that interface PPP 0 is down and interface PPP 1 is up and may translate this into a weighted list, assigning PPP 0 a value of 0 and PPP 1 a value of 1. The Routing decision engine 450 may then take the values from both lists, multiply them to determine a recalculated resultant weighted value for each interface, then assesses the resultant weighted values of the interfaces to determine a most desirable interface through which to communicate data traffic. In particular, the Routing decision engine 450 may determine that the interface having the highest weighted value is the most desirable interface through which to communicate data traffic. [0052] As the contributing weighted values for PPP 0 are “ 1 ” from the configuration manager 440 and “0” from the WAN monitor 420 , the resultant weighted value of PPP 0 is 1×0=0. As the contributing weighted values for PPP 1 are “0.5” from the configuration manager 440 and “1” from the WAN monitor 420 , the resultant weighted value of PPP 1 is 1×0.5=0.5. In this example the Routing decision engine 450 may determine that the interface having the highest weighted value is the most desirable interface through which to communicate data traffic. Accordingly, the Routing decision engine 450 may determine that PPP 1 is the most desirable interface through which to communicate data traffic based on the recalculated values. [0053] The Routing decision engine 450 may report to Routing table manager 460 that interface PPP 1 is the most desirable interface. In response, Routing table manager 460 may adjust a routing table, such as routing table 332 , to redirect pertinent traffic from PPP 0 to PPP 1 . [0054] While the first example provided a description of a fail over that occurs when PPP 0 becomes disconnected, a second example is provided to analyze a fail over that occurs when PPP 0 regains its network connectivity. In particular, in the second example, configuration manager still has PPP 0 defined as Primary, and PPP 1 as Secondary. In the discussion of example 1, PPP 0 was reported as down from the WAN monitor, resulting in PPP 1 as having a higher resultant weighted value. [0055] If the weights assigned to PPP 1 stay the same but PPP 0 begins to regain connectivity, then WAN monitor 420 may assign PPP 0 a diminished value of 0.25. Even if PPP 0 regains full connectivity, WAN monitor 420 may provide only a diminished value for a predetermined period of time to reflect that PPP 0 has only recently regained network connectivity. If a network interface has only recently regained network connectivity, the network interface may be more likely to lose network connectivity again as the source of the network connectivity may not be fully resolved. [0056] As such, based on the new status of PPP 0 as recently regaining network connectivity (e.g., regaining network connectivity but being within a predetermined period of time after the network connectivity has been established), the Routing decision engine 450 may recalculate the weighted values of the network interfaces PPP 0 and PPP 1 . [0057] In this new calculation, the weighting values assigned by configuration manager 440 may stay at “1” and “0.5” for PPP 0 and PPP 1 , respectively, as PPP 0 is considered a primary network interface. The weighting values assigned by WAN monitor 420 , however, may change. In particular, WAN monitor 420 may determine that interface PPP 0 is recently reconnected and interface PPP 1 is up and may translate this into a weighted list, assigning PPP 0 a value of 0.25 and PPP 1 a value of 1. The Routing decision engine 450 may then take the values from both lists, multiply them to determine a recalculated resultant weighted value for each interface, then assess the resultant weighted values of the interfaces to determine a most desirable interface through which to communicate data traffic. In particular, the Routing decision engine 450 may determine that the interface having the highest weighted value is the most desirable interface through which to communicate data traffic. [0058] As the contributing weighted values for PPP 0 are “1” from the configuration manager 440 and “0.25” from the WAN monitor 420 , the resultant weighted value of PPP 0 is 1×0.25=0.25. As the contributing weighted values for PPP 1 are “0.5” from the configuration manager 440 and “1” from the WAN monitor 420 , the resultant weighted value of PPP 1 is 1×0.5=0.5. In this example the Routing decision engine 450 may determine that the interface having the highest weighted value is the most desirable interface through which to communicate data traffic. Accordingly, the Routing decision engine 450 may determine that PPP 1 is the most desirable interface through which to communicate data traffic based on the recalculated values. Since the Routing decision engine 450 previously reported to Routing table manager 460 that interface PPP 1 is the most desirable interface, Routing decision engine 450 may choose to not update Routing table manager 460 since there has been no change in the most desirable interface through which to communicate data traffic. [0059] The use of assigning PPP 0 a diminished value from WAN monitor 420 for a predetermined amount of time after a network connection has been re-established is used to avoid “flapping” of connections among multiple networks. In this way, if PPP 0 is intermittently losing network connection, the assigning of a reduced value from WAN monitor 420 gives extra weight to the alternative interface of PPP 1 . Accordingly, even though the first portion of the second example provides that PPP 0 has resumed a network connection, PPP 1 is still the highest ranked calculation based on weighted values. As such, Routing table manager 460 maintains PPP 1 as the interface for pertinent traffic while PPP 0 has a diminished value assigned from WAN monitor 420 . [0060] After PPP 0 has become available for data transmission and active for longer than a predetermined period of time, the WAN monitor 420 may again assign PPP 0 its full value of “1” for network connectivity and report this updated status to the Routing decision engine 450 . This updated status may trigger the Routing decision engine 450 to recalculate the resultant weighted values of the interfaces PPP 0 and PPP 1 . [0061] In this new calculation, the weighting values assigned by configuration manager 440 may stay at “1” and “0.5” for PPP 0 and PPP 1 , respectively, as PPP 0 is considered a primary network interface. The weighting values assigned by WAN monitor 420 , however, may return back to the initialized values discussed in the first example where WAN monitor 420 determines that both interfaces PPP 0 and PPP 1 are up and assigned a value of 1. [0062] The Routing decision engine 450 then takes the values from both lists, multiplies them to determine a recalculated resultant weighted value for each interface, then assesses the resultant weighted values of the interfaces to determine a most desirable interface through which to communicate data traffic. As the contributing weighted values for PPP 0 are “1” from the configuration manager 440 and “1” from the WAN monitor 420 , the resultant weighted value of PPP 0 is 1×1=1. As the contributing weighted values for PPP 1 are “0.5” from the configuration manager 440 and “1” from the WAN monitor 420 , the resultant weighted value of PPP 1 is 1×0.5=0.5. In this example the Routing decision engine 450 may determine that the interface having the highest weighted value is the most desirable interface through which to communicate data traffic. Accordingly, the Routing decision engine 450 may determine that PPP 0 is the most desirable interface through which to communicate data traffic based on the recalculated values. The Routing decision engine 450 may report to Routing table manager 460 that interface PPP 0 is the most desirable interface. In response, Routing table manager 460 may adjust the routing table, to redirect pertinent traffic from PPP 1 to PPP 0 . [0063] As discussed above, a predetermined amount of time may be set after an interface has regained connectivity before the interface is assigned a full value from the WAN monitor 420 . During the predetermined amount of time, the WAN monitor 420 may assign the recently reconnected interface a diminished value. The value assigned by the WAN monitor 420 to the interface may be used in determining a resultant weighted value that is calculated by the Routing decision engine 450 . However, while a threshold for keeping the recently connected interface assigned to a diminished value may be based on a predetermined amount of time, threshold for changing the interface's assigned WAN monitor 420 value from diminished to full may not be based on time—rather, or in addition, the threshold for adjusting the value of the interface may be based on a minimum or maximum bandwidth available on the network. In another example, the threshold can be based on an amount of data volume that has been transmitted to test data traffic over the newly connected network interface or the network channel since data connection over the network interface has resumed. [0064] A third example is provided to describe how an interface may have a weighted value assigned to it demoted. For example, there may be a third-party intrusion detection program feeding configuration data to Configuration manager 440 . This program may have detected a possible attack directed at interface PPP 0 . In response to the detection of a possible attack, the Configuration manager may translate this potential threat into a weight adjustment for PPP 0 , thereby demoting priority of the interface. In particular, the configuration manager 440 may adjust the preference of PPP 0 from 1 to 0.1. [0065] The configuration manager 440 may communicate the change in status of PPP 0 to the Routing decision engine 450 which may then initiate recalculations based on the new status information. If the weighted values assigned to PPP 0 and PPP 1 from WAN monitor 420 stay at 1 each, and the weighted values assigned to PPP 0 and PPP 1 from configuration manager 440 are adjusted to 0.1 and 0.5, respectively, based on the potential threat of an attack on PPP 0 , the resultant calculated weights of PPP 0 and PPP 1 would be 0.1 (1×0.1=1) and 0.5 (1×0.5=0.5) respectively. As such, the Routing decision engine 450 may determine that PPP 1 is the most desirable interface through which to communicate data traffic, and may provide this information to the Routing table manager 460 . The Routing table manager 460 may then update the routing table accordingly. [0066] Additionally, the configuration manager 440 may restore its full weighted value to PPP 0 after a predetermined condition has been met. In particular, the configuration manager 440 may retract its demotion (in whole or in part) after a specified amount of time has passed without the configuration manager 440 receiving an indication of an attack to PPP 0 . The amount of time that elapses between the configuration manager 440 demoting the weighted value of PPP 0 based on a potential threat and the configuration manager 440 restoring the weighted value of PPP 0 based on a lack of threatening information (or, in another example, based on affirmative assurances that no attack has been detected) may vary based on a number of factors. For instance, the severity of the potential attack may affect the amount of time that the configuration manager 440 waits before restoring its full weighted value to PPP 0 . [0067] While the first, second, and third examples were directed towards a system having two ports, the fourth example is directed towards a system having three ports for network interface: PPP 0 , PPP 1 , and PPP 2 . The WAN monitors may continuously report the status of these interfaces to the Routing decision engine. Configuration manager 440 may receive input on configuration settings from two sources: from a configuration file and from a 3 rd party performance/intrusion monitor. The configuration file associated with the Configuration manager may be a simple ordered list, intended to convey interface preference. In particular, the configuration file may list the interfaces from most to least desirable. In this example, the list reads: PPP 0 , PPP 1 , PPP 2 . The Configuration manager 440 may translate the list into a weighted list, assigning values of 1, 0.5, and 0.25 for interfaces PPP 0 , PPP 1 , and PPP 2 , respectively. Further, WAN monitors may determine that all three interfaces are up, and accordingly may assign the interfaces values of 1, 1, 1 to interfaces PPP 0 , PPP 1 , and PPP 2 , respectively. [0068] The Routing decision engine 450 may take the values from both lists and multiply the weighted values to determine the most desirable interface for communication data traffic. In this example, the Routing decision engine 450 may calculate resultant weighted values of 1 (1×1=1), 0.5 (0.5×1=0.5) and 0.25 (0.25×1=0.25) for interfaces PPP 0 , PPP 1 , and PPP 2 , respectively. [0069] As such, in this example, the Routing decision engine 450 may determine that PPP 0 is the most desirable interface to communication data traffic. [0070] In some embodiments, a third party intrusion detection system may notice something anomalous happening on PPP 0 and notify the configuration manager 440 . The configuration manager may adjust the value of PPP 0 accordingly by demoting the value. For example, the configuration manager may demote the value from 1 to 0.1. This change in status may be reported to the Routing decision engine 450 which may then recalculate resultant weighted values based on this change of status. If the values of the other interfaces remain the same but the value of PPP 0 is changed based on the demotion from the configuration manager 440 , the new resultant weighted value of PPP 0 may be 0.1 (1×0.1=0.1). Based on this new calculation, the Routing decision engine 450 may determine that PPP 1 having a resultant weighted value of 0.5 is the most desirable interface over which to communicate data. [0071] In some embodiments, the WAN monitor attached to PPP 1 may notice that it has lost connection. It may send this new status to the Routing decision engine, forcing another recalculation. Under the new recalculation, the WAN monitor 420 may assign weighted values of 1, 0, 1 to interfaces PPP 0 , PPP 1 , and PPP 2 , respectively. If the assigned weighted values from the configuration manager 440 stay the same as in the most recent example concerning a potential threat to PPP 0 , the recalculated weighted values are 0.1 (1×1×0.1=0.1), 0 (0×0.5=0.5), and 0.25 (1×0.25=0.25) for PPP 0 , PPP 1 , and PPP 2 , respectively. In this example, PPP 2 has the highest value (0.25) and the Routing decision engine may report this to the Routing table manager. [0072] In some embodiments, the network fails back to the original connection state as follows. PPP 1 has regained connection. Consequently, the WAN monitor reports this status change to the Routing decision engine. In order to prevent rapid flapping of connections, however, the WAN monitor is configured to report “Reduced” functionality for a given amount of time after a connection resumes. [0073] For example, after PPP 1 establishes network connectivity, WAN monitor 420 may assign PPP 1 a reduced value of 0.25. As the Routing decision engine has received new data, it may calculate the results again. In particular, WAN may assign weighted values of 1, 0.25, and 1 to PPP 0 , PPP 1 , and PPP 2 , respectively. If the values for the configuration manager 440 stay the same, then the resultant weighted values are 0.1 (1×1×0.1=0.1), 0.125 (0.25×0.5=0.125), and 0.25 (1×0.25=0.25) for PPP 0 , PPP 1 , and PPP 2 , respectively. [0074] In this example, even though PPP 1 is operational, it may be beneficial to wait a predefined amount of time before switching back to it. This is reflected by PPP 2 still having the lead after the latest calculation. When that predefined amount of time has expired, PPP 1 may regain its rightful place in the hierarchy. [0075] Meanwhile, the Intrusion Detection system is no longer noticing any attacks. It has been some configurable duration since the last evidence of an attack, so the Configuration manager may revoke its demotion of PPP 0 . As such, configuration manager may assign weighted values of 1, 0.5, and 0.25 to interfaces PPP 0 , PPP 1 , and PPP 2 , respectively. If the WAN monitor weighted values assigned to the interfaces stay the same, then the newly recalculated resultant values are 1 (1×1=1), 0.125 (0.25×0.5=0.125), and 0.25 (1×0.25=0.25) for interfaces PPP 0 , PPP 1 , and PPP 2 , respectively. This change of status places PPP 0 back as the most desirable interface over which to transmit communication data. [0076] At a later period of time, once interface PPP 1 has had network connectivity for a threshold period of time (and/or another threshold condition has been met), WAN monitor 420 may assign PPP 1 a weighted value of 1 to indicate that the interface PPP 1 is up. This change of status may be provided to the Router Decision Engine 450 which may recalculate weighted values. Based on the previous values, with the WAN monitor 420 may update to PPP 1 from 0.25 to 1 as the only change, the recalculated values are 1, 0.5, and 0.25 for interfaces PPP 0 , PPP 1 , and PPP 2 , respectively. In some examples, if there is a tie in the resultant weighted values, a preference may be given to whichever interface has the higher value reported by the Configuration manager. In other examples, if there is a tie in the resultant weighted values, a preference may be given to which interface has the higher value reported by the WAN monitor. In other examples, if there is a tie in the resultant weighted values, a preference may be given to which interface has the lowest value reported by a third-party threat assessment. [0077] In some embodiments, decision making on which network to use for data traffic may be based on integer arithmetic to minimize table look-ups, as described in further detail below. In particular, as each WAN monitor detects network connection, the WAN monitor may notify the Routing decision engine of the connection status. As the Routing decision engine receives notifications from WAN monitors, the Routing decision engine may create a link back to the WAN monitors to watch for changes. As Routing decision engine detects a change in any of the network interfaces based on notifications from WAN monitors, the Routing decision engine may re-evaluate immediately its preference list on a network interface. [0078] Whenever WAN monitor sets or changes connection status, the status may be set in code as a string. This string may be compared to a list of known strings in the system. If the status does not exist in the list, this is considered an error. Additionally, the lists of strings that describe different statuses may be ranked from least to most desired status. [0079] Once the status is set, the “Status” may note its order in the list and assign this as its “index.” The lower the index of a status is, the more usable the network. For example, a list of statuses may include: “Available”, “Diminished”, “Compromised”, “Startup”, “Failures in confirming connection”, and “Network Down.” Additionally, the configuration file may contain a list of all interfaces in the order of preference. As different WAN monitors register a network interface, the Routing decision engine may maintain a list of current network interfaces. [0080] In an example, the routing decision engine may calculate a rank for each interface by first getting the index for the interfaces status (i.e. Available=0, Diminished=1, etc) and then multiplying this index by the number of interfaces present in the system. The Routing decision engine may then get the index of this interface in the preference list from the configuration file (i.e. primary=0, backup=1), and may then set this new information to the previous calculation. In this calculation, the network interface having the lowest score may be determined to be the winner. [0081] In an example of the steps of processing, interfaces PPP 0 and PPP 1 may both be assigned values of 1 based on their status as being available. However, information may then be received to update PPP 0 as having a diminished value. This may be reflected in PPP 0 being assigned a “compromised” status. The “Compromised” status may be used to indicate when the system, such as the intrusion detection service, determines that the network interface is compromised. In examples, this algorithm may not change if additional interfaces are added. As this status list grows, the list of multipliers may grow as well, effectively eliminating the floating point calculations needed. The Routing decision engine may rank the currently connected interfaces from most preferred, to least preferred. The Routing table manager uses the results, and may set the default routes accordingly. [0082] An exemplary process for deciding data routing among multiple networks to transmit data is provided in FIG. 5 . As seen in FIG. 5 , the exemplary process starts at block 510 , where a determination is made of “Does a process monitor detect any process that has inexplicitly stopped?” If the answer to this is “Yes,” the process continues to block 520 where an action is taken such that “Process monitor resets and restarts process and services to recover from system anomaly.” After this action is completed the process moves to block 530 . If the answer to block 510 is No, the process continues directly to block 530 . [0083] At block 530 , a determination is made of “Does WAN monitor detect disconnect on any of WAN interfaces?” If the answer to this is “Yes,” the process continues to block 540 where an action is taken such that “WAN session manager resets and restarts WAN session to resume connection.” After this action is completed the process moves to block 550 . If the answer to block 530 is No, the process moves direction to block 550 . [0084] At block 550 , a determination is made of “Does Configuration manager detect any update on system configuration (e.g. weighted values for processing)?” If the answer to this is “Yes,” the process continues to block 560 where an action is taken such that “Configuration manager sets configuration values used by Routing decision engine.” After this action is completed, the process moves to block 570 . If the answer to block 550 is No, the process moves directly to block 570 . [0085] At block 570 , Routing decision engine specifies which WAN interface data traffic is to use, based on weighted configuration values and WAN interface conditions. Subsequently, at block 580 , Routing table manager updates Route Table to specify data routing (e.g. which WAN interface to use) as specified by Routing decision engine. Subsequently, at block 590 , Data Transmission Program looks up Routing table, and Transmits Data using the WAN interface that is specified by the Routing table. After block 590 , the process returns to the start at block 510 . [0086] Although preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

A computer-implemented method for providing data communication between two or more host systems is provided. The method comprises designating a first network as a primary network by updating a routing table, monitoring network connections on the first network channel and a second network channel, transmitting data on the first network channel according to the routing table, detecting termination of network connection on the first network channel, determining to transmit data traffic on the first network channel, modifying the routing table, transmitting data traffic on the second network channel according to the routing table, detecting connection on the first network channel, and in response to the detection of data traffic on the first network channel, measuring a network attribute and comparing against a satisfactory threshold, and selecting the first network channel for data communication if the network attribute value satisfies the threshold.

FIELD OF THE INVENTION This invention relates to conductive connecting elements and, in particular, to nanoscale connectors for microdevices such as integrated circuit components and to methods for making such connectors. BACKGROUND OF THE INVENTION As integrated circuits become smaller, structures for electrically connecting microscopic electronic devices become increasingly important. Integrated circuits can now be made with hundreds of thousands of devices of submicron dimension requiring at least as many conductive interconnections among the devices and hundreds of interconnections with packaging leads. As the circuits become smaller and more complex, the difficulties of making sufficiently small, uniform metal wires and metal stripes become increasingly a limitation on circuit design and performance. The standard gold wires used to bond IC pads to package leads are relatively bulky, limiting the minimum size of IC bonding pads, and the metal stripes used to interconnect microdevices within an IC are subject to cross sectional nonuniformities. Accordingly there is a need for nanoscale connectors which provide high, uniform conduction. SUMMARY OF THE INVENTION In accordance with the invention, nanoscale connectors particularly useful for connecting microscale devices comprise free-standing nanoscale conductors. The nanoscale conductors are conveniently fabricated in sets of controlled, preferably equal length by providing a removable substrate, growing conductive nanotubes or nanowires on the substrate, equalizing the length of the nanoscale conductors, and removing the substrate. Preferably the removable substrate is soluble, leaving a collection of free standing nanoscale connectors in suspension or solution. BRIEF DESCRIPTION OF THE DRAWINGS The nature, advantages and various additional features of the invention will appear more fully upon consideration of the illustrative embodiments now to be described in detail with the accompanying drawings. In the drawings: FIGS. 1 ( a )-( c ) schematically illustrates various configuration of nanoscale conductors grown on a substrate; FIG. 2 schematically illustrates an exemplary process of preparing equal length, free-standing nanoscale conductors; FIG. 3 illustrates aligned nanoscale conductors grown on a removable substrate; FIGS. 4 and 5 illustrate an exemplary process of equalizing the length of nanoscale connectors; FIG. 6 shows apparatus for removal of the substrate; FIG. 7 shows an example of functionalized, equal length, free-standing nanoscale connectors; FIGS. 8 ( a ) and 8 ( b ) schematically illustrates circuit device interconnections by nanoscale connectors. It is to be understood that the drawings are for purposes of illustrating the concepts of the invention and are not to scale. DETAILED DESCRIPTION This description is divided into three parts. Part I describes the conventional growth of substrate-supported nanoscale conductors. Part II describes the fabrication of free-standing nanoscale conductive connectors; and Part III describes the use of nanoscale conductive connectors. I. Nanoscale Conductors and Their Conventional Growth To understand the invention, it is useful to understand some of the properties of nanoscale conductors (“nanoconductors”) and how they are conventionally grown. Nanoconductors are tiny conductive tubes (hollow) or wires (solid) with a very small size scale of the order of 1.0-100 nanometers in diameter and 0.5-10 μm in length. Carbon nanotubes are representative. Their structure and fabrication are reported in J. Liu et al., Science , Vol. 280, p. 1253 (1998); Z. F. Ren et al., Science , Vol. 282, p. 1105 (1998); W. Z. Li, et al., Science , Vol. 274, p. 1701 (1996); S. Frank et al., Science , Vol. 280, p. 1744 (1998); S. J. Tans et al., Nature , Vol. 36, p. 474 (1997); S. Fan, et al., Science , Vol. 283, p. 512 (1999); P. G. Collins et al., Science , Vol. 278, p. 100 (1997); J. Kong et al., Nature , Vol. 395, p. 878 (1998); and T. W. Ebbesen et al., Nature , Vol. 382, p. 54 (1996), all of which are incorporated herein by reference. The synthesis of conductive nanowires based on semiconductor materials such as Si or Ge has also been reported. See, for example, A. M. Morales et al., Science , Vol. 279, p. 208 (1998) which is incorporated herein by reference. Carbon nanotubes exhibit unique atomic arrangements, having useful physical properties such as one-dimensional electrical behavior, quantum conductance, and ballistic electron transport. The ballistic transport in carbon nanotubes, as reported by Frank et al, permits the passage of huge electrical currents, with the magnitude of current density comparable to or better than those in superconductors. Carbon nanotubes are among the smallest dimensioned nanotubes materials with generally high aspect ratio and small diameter of about ˜1.0 nm in the case of single-wall nanotubes and less than ˜50 nm in the case of multi-wall nanotubes. See A. G. Rinzler et al, Applied Physics , Vol. A67, p. 29 (1998); Kiang et al, J. Physical Chemistry , Vol. 98, p. 6612, (1994); and Kiang et al, Physical Review Letters , Vol. 81, p. 1869 (1998), which are incorporated herein by reference. High-quality single-walled carbon nanotubes are typically grown as randomly oriented, needle-like or spaghetti-like, tangled tubules. They can be grown by chemical vapor deposition (CVD), laser ablation or electric arc growth. CVD methods such as used by Ren et al., Fan et al., and Li et al can produce multiwall nanotubes attached onto a substrate, often with aligned, parallel growth perpendicular to the substrate. Carbon nanotubes are grown on a substrate by catalytic decomposition of hydrocarbon-containing precursors such as ethylene, methane, or benzene. Nucleation layers, such as thin coatings of Ni, Co, or Fe, are often intentionally added onto the substrate surface in order to nucleate a multiplicity of isolated nanotubes. Carbon nanotubes can also be nucleated and grown on a substrate without a metal nucleating layer, by using a precursor including one or more of these metal atoms. During CVD the metal atoms serve to nucleate the nanotubes on the substrate surface. See H. M. Cheng et al., Chem. Physics Letters , Vol. 289, p. 602 (1998), which is incorporated herein by reference. Semiconductor nanowires are grown on substrates by similar processes. Referring to the drawings, FIGS. 1 ( a )-( c ) schematically illustrate various configurations of nanoconductors conductors 10 grown on a substrate 11 . The nanoconductors 10 can be carbon nanotubes or Si or GaAs nanowires, synthesize by any one of a variety of methods. In the absence of alignment processing the nanoconductors tend to grow with the random orientation morphology shown in FIG. 1 ( a ) or with the tangled growth morphology shown in FIG. 1 ( b ). Such a tangled morphology of nanoconductors is also obtained in laser ablation synthesis. By using CVD growth in the presence of an applied electric field, a vapor concentration gradient, a temperature gradient, or recessed pores containing catalysts in the substrate, the nanoconductors can be grown with an aligned morphology substantially perpendicular to the substrate. Such aligned nanoconductors 10 are schematically illustrated in FIG. 1 ( c ). II. Fabrication of Free-Standing Nanoconductors Nanoscale conductive connectors for connecting microdevices (“nanoconnectors”) should be free-standing and preferably of equal length. For reliable circuit interconnections such connectors should be prepared as a collection of free-standing nanoconductors so that they can be placed and bonded for circuit interconnections. They should be of approximately equal length to avoid unwanted short circuits from connectors that are too long and unwanted open circuits from connectors that are too short. Referring to the drawings, FIG. 2 is a schematic flow diagram of the steps involved in making a collection of free-standing nanoconnectors of controlled, substantially equal length. The first step, shown in block A of FIG. 2, is to provide a removable substrate for nanoconductor growth. Preferably the substrate is removable by dissolving in water or another solvent. The substrate can be a sodium chloride crystal or another water-soluble material. Acid-dissolvable metals such Cu, Ni, Co, Mo, Fe, V, Au, Ag, and their alloys, or base-dissolvable metals such as Al may also be used. Or the substrate can be made of a soluable polymer such as polyvinyl alcohol, polyvinyl acetate, polyacrylamide, acrylonitrile-butadiene-styrene. The removable substrate, alternatively, can be a volatile (evaporable) material such as PMMA polymer. The removable substrate can be a layered combination of metals or compounds. For example, a solvent-soluble material such as polyacrylamide or an acid-soluable metal such as Cu can be coated with a thin film of nucleating material for nanoconductor growth and used as a substrate during CVD growth. The coating can be a catalyst metal such as Ni, Fe or Co, and can be deposited as a continuous, spotly or patterned film by sputtering, vacuum evaporation or electrochemical deposition. The next step shown in Block B is to grow aligned nanoconductors on the removable substrate. For example, aligned carbon nanotubes can be grown using CVD growth in the direction of an applied electric field, vapor concentration gradient, temperature gradient, or recessed pores in the substrate to produce aligned nanotubes as discussed in Ren et al., Fan et al. and Li et al. Aligned nanoconductors 10 on a substrate 11 are schematically illustrated in FIG. 1 ( c ). Advantageously the average deviation from vertical growth is less than 25 degrees and preferably less than 15 degrees. The third step (Block C of FIG. 2) is to equalize the lengths of the grown nanoconductors. Ideally, length equality is achieved by careful growth, but equal length growth is difficult to achieve in practice. FIG. 3 schematically illustrates equal length, aligned nanoconductors 10 on a removable substrate 11 . For aligned nanoconductors grown on a substrate with non-uniform lengths, the third step of FIG. 2 (length-equalization) can be effected by adding to the substrate a sacrificial layer of uniform thickness which will bury the nanoconductors to an equal height level while leaving exposed the nanoconductor material beyond the desired length. This is illustrated in FIG. 4 which shows the nanoconductors 10 partially buried by the sacrificial layer 12 . Such a sacrificial locking layer 12 temporarily protects the buried nanoconductor regions 10 A while the exposed extra length regions 10 B are removed. The sacrificial layer 12 is desirably a material that can be relatively easily removed after the length equalization, i.e., by dissolving in water or in a solvent, by chemically or electrochemically etching, or by vaporizing through heating. Exemplary sacrificial layer materials include water-soluble or solvent-soluble salts such as sodium chloride, silver chloride, potassium nitrate, copper sulfate, and indium chloride, or soluble organic materials such as sugar and glucose. The sacrificial layer material can also be a chemically etchable metal or alloy such as Cu, Ni, Fe, Co, Mo, V, Al, Zn, In, Ag, Cu—Ni alloy, Ni—Fe alloy and others. These materials can be dissolved in an acid such as hydrochloric acid, aqua regia, or nitric acid, or can be dissolved away in a base solution such as sodium hydroxide or ammonia. The sacrificial layer 12 may also be a vaporizable material such as Zn which can be decomposed or burned away by heat. The sacrificial layer 12 can be added by chemical deposition such as electroplating or electroless plating, by physical vapor deposition such as sputtering, evaporation, laser ablation, ion beam deposition, or by chemical vapor decomposition. An advantageous method is to electroplate in an electrolyte containing the ions of a metal to be deposited, e.g., Ni from a NiSO 4 solution or Cu from a CuSO 4 -containing solution. The substrate 11 desirably has a catalyst metal coating 13 such as Ni, Co, or Fe. The electrodeposition of the metal preferentially occurs on the catalyst metal coating rather than on the nanoconductors because of chemical affinity. As is well known, the thickness of the electroplated metal is controlled by the processing variables such as the time, temperature, electrolyte concentration, and current density. The thickness of the uniformly deposited sacrificial layer 12 determines the nanoconductor length. For interconnection applications, the desired average length (region 10 A) is typically in the range of 10-10,000 nm. Preferably the lengths of at least 90% of the nanoconductors should not deviate more than 20% from the average length. In the next step of the equalization process, the exposed portions 10 B of the nanotubes are removed. In the case of carbon nanotubes, the exposed portion can be burned away by heating in an oxidizing atmosphere at temperatures in the range of 200-1000° C. for 0.1-10,000 minutes. The exposed portion 10 B can also be removed by mechanical polishing or chemical etching so that only their buried, equal-length part 10 A remains. FIG. 5 schematically illustrates the workpiece after removal of the exposed portions. The third step of FIG. 2 (length eqaulization) may also be achieved by alternative methods without employing a sacrificial layer. For example, equalization can be achieved by laser cutting or hot blade cutting, as disclosed in U.S. patent application Ser. No. 09/236,933 filed by S. Jin on Jan. 25, 1999 and entitled “Article Comprising Aligned Truncated Carbon Nanotubes” now allowed, which is incorporated herein by reference. The next step in the process of FIG. 2 (Block D) is to remove the substrate. This includes removing any sacrificial layers used in the length equalization process and any catalyst metal film added for nanoconductor nucleation. Removal is advantageously obtained by dissolving the substrate materials, and the particular solvent used depends on the materials. As shown in FIG. 6, the workpiece comprising the substrate 11 and the equal height nanoconductors 10 A is typically placed in a bath of solvent 14 . The result of this step is a collection of free-standing, equal length nanoconductors. They typically have diameters averaging less than 100 nm, and the lengths of at least 90% of the nanoconductors in the collection do not deviate by more than 20 percent from the average length. The free-standing, equal-length nanoconductors obtained by the process of FIG. 2 are advantageously dispersed in liquid or functionalized and dissolved in liquid so that the collection remains separated without agglomeration. Carbon nanotubes allow various chemical modifications of their open ends, outside walls, or the tube-interior cavity by functionalization chemistry. For example, single-wall carbon nanotubes can be made soluable in common organic solvents such as chloroform, dichloromethane, toluene, CS 2 , chlorobenzene, etc. by attaching long-chain molecules such as octadecylamin, NH(CH 2 ) 17 CH 3 , to the open ends of the nanotubes. This can be accomplished via formation of amide functionality. FIG. 7 illustrates carbon nanotubes 10 A modified for solution. Other types of functionalization can induce modification of the electronic bandgap structure (and hence the electrical properties) of the nanoconductors, for example, by dichlorocarbene covalent bonding onto nanotube walls. See J. Chen et al., Science , Vol. 282, p.95, (1998); J. Chen et al., Journal of Materials Research , Vol. 13, p. 2423 (1998); and J. Liu et al., Science , Vol. 280, p. 1253 (1998), which are incorporated herein by reference. III. Nanoscale Connection The free-standing, equal-length dispersed nanoconductors can be applied to an electronic circuit and for interconnection and bonding. We will refer to such connectors as nanoconnectors. As shown in FIG. 8 ( a ) the nanoconnectors 10 A can be placed on circuit pads 80 by individual micro-manipulation or nano-manipulation under high resolution microscope. Alternatively, as shown in FIG. 8 ( b ) the nanoconnectors 10 A are placed by random dropping such as by sedimentation from a thin layer of solution. Because of the equal-length of the nanoconnectors without undesirably long nanoconnectors, unwanted electrical shorting is avoided. The nanoconnectors 10 A are then dried and bonded onto the underlying pads 80 , as by soldering. The pad surface can be pre-coated with a solder layer and heated together with the contacting nanoconnectors). The device surface can be washed then to remove non-bonded nanoconnectors, i.e. those in FIG. 8 ( b ) which are sitting on the surface of the circuit device without touching any of the contact pads 80 . The sedimentation and the solder bonding process can be repeated until all the desired electrical interconnections between adjacent contact pads are obtained. It is to be understood that the above-described embodiments are illustrative of only a few of the many possible specific embodiments which can represent applications of the principles of the invention. Numerous and varied other arrangements can be readily devised by those skilled in the art without departing from the spirit and scope of the invention.

In accordance with the invention, nanoscale connectors particularly useful for connecting microscale devices comprise free-standing nanoscale conductors. The nanoscale conductors are conveniently fabricated in sets of controlled, preferably equal length by providing a removable substrate, growing conductive nanotubes or nanowires on the substrate, equalizing the length of the nanoscale conductors, and removing the substrate. Preferably the removable substrate is soluble, leaving a collection of free standing nanoscale connectors in suspension or solution.

CROSS-REFERENCE TO RELATED APPLICATIONS This non-provisional patent application is a continuation of U.S. Pat. No. 9,208,221, issued Dec. 8, 2015, which is a continuation of U.S. Pat. No. 8,650,190, issued Feb. 11, 2014, which is a continuation of U.S. Pat. No. 8,402,026, issued Mar. 19, 2013, which is a continuation of U.S. Pat. No. 6,778,995, issued Aug. 17, 2004, the priority dates of which are claimed and the disclosures of which are incorporated by reference. FIELD OF THE INVENTION The present invention relates in general to text mining and, in particular, to a computer-implemented system and method for generating clusters for placement into a display. BACKGROUND OF THE INVENTION Document warehousing extends data warehousing to content mining and retrieval. Document warehousing attempts to extract semantic information from collections of unstructured documents to provide conceptual information with a high degree of precision and recall. Documents in a document warehouse share several properties. First, the documents lack a common structure or shared type. Second, semantically-related documents are integrated through text mining. Third, essential document features are extracted and explicitly stored as part of the document warehouse. Finally, documents are often retrieved from multiple and disparate sources, such as over the Internet or as electronic messages. Document warehouses are built in stages to deal with a wide range of information sources. First, document sources are identified and documents are retrieved into a repository. For example, the document sources could be electronic messaging folders or Web content retrieved over the Internet. Once retrieved, the documents are pre-processed to format and regularize the information into a consistent manner. Next, during text analysis, text mining is performed to extract semantic content, including identifying dominant themes, extracting key features and summarizing the content. Finally, metadata is compiled from the semantic context to explicate essential attributes. Preferably, the metadata is provided in a format amenable to normalized queries, such as database management tools. Document warehousing is described in D. Sullivan, “Document Warehousing and Text Mining, Techniques for Improving Business Operations, Marketing, and Sales,” Chs. 1-3, Wiley Computer Publishing (2001), the disclosure of which is incorporated by reference. Text mining is at the core of the data warehousing process. Text mining involves the compiling, organizing and analyzing of document collections to support the delivery of targeted types of information and to discover relationships between relevant facts. However, identifying relevant content can be difficult. First, extracting relevant content requires a high degree of precision and recall. Precision is the measure of how well the documents returned in response to a query actually address the query criteria. Recall is the measure of what should have been returned by the query. Typically, the broader and less structured the documents, the lower the degree of precision and recall. Second, analyzing an unstructured document collection without the benefit of a priori knowledge in the form of keywords and indices can present a potentially intractable problem space. Finally, synonymy and polysemy can cloud and confuse extracted content. Synonymy refers to multiple words having the same meaning and polysemy refers to a single word with multiple meanings. Fine-grained text mining must reconcile synonymy and polysemy to yield meaningful results. In particular, the transition from syntactic to semantic content analysis requires a shift in focus from the grammatical level to the meta level. At a syntactic level, documents are viewed structurally as sentences comprising individual terms and phrases. In contrast, at a semantic level, documents are viewed in terms of meaning. Terms and phrases are grouped into clusters representing individual concepts and themes. Data clustering allows the concepts and themes to be developed more fully based on the extracted syntactic information. A balanced set of clusters reflects terms and phrases from every document in a document set. Each document may be included in one or more clusters. Conversely, concepts and themes are preferably distributed over a meaningful range of clusters. Creating an initial set of clusters from a document set is crucial to properly visualizing the semantic content. Generally, a priori knowledge of semantic content is unavailable when forming clusters from unstructured documents. The difficulty of creating an initial clusters set is compounded when evaluating different types of documents, such as electronic mail (email) and word processing documents, particularly when included in the same document set. In the prior art, several data clustering techniques are known. Exhaustive matching techniques fit each document into one of a pre-defined and fixed number of clusters using a closest-fit approach. However, this approach forces an arbitrary number of clusters onto a document set and can skew the meaning of the semantic content mined from the document set. A related prior art clustering technique performs gap analysis in lieu of exhaustive matching. Gaps in the fit of points of data between successive passes are merged if necessary to form groups of documents into clusters. However, gap analysis is computational inefficient, as multiple passes through a data set are necessary to effectively find a settled set of clusters. Therefore, there is a need for an approach to forming clusters of concepts and themes into groupings of classes with shared semantic meanings. Such an approach would preferably categorize concepts mined from a document set into clusters defined within a pre-specified range of variance. Moreover, such an approach would not require a priori knowledge of the data content. SUMMARY OF THE INVENTION The present invention provides a system and method for generating logical clusters of documents in a multi-dimensional concept space for modeling semantic meaning. Each document in a set of unstructured documents is first analyzed for syntactic content by extracting literal terms and phrases. The semantic content is then determined by modeling the extracted terms and phrases in multiple dimensions. Histograms of the frequency of occurrences of the terms and phrases in each document and over the entire document set are generated. Related documents are identified by finding highly correlated term and phrase pairings. These pairings are then used to calculate Euclidean distances between individual documents. Those documents corresponding to concepts separated by a Euclidean distance falling within a predetermined variance are grouped into clusters by k-means clustering. The remaining documents are grouped into new clusters. The clusters can be used to visualize the semantic content. An embodiment provides a computer-implemented system and method for generating clusters for placement into a display. A set of clusters is generated from a document set. A single cluster of related documents from the document set is obtained and at least one new cluster is added. One such document in the set is compared to the cluster. A difference in distance is determined between the document and a common origin and the cluster and the common origin. The document is designated as the new cluster when the difference fails to satisfy a predetermined threshold. One or more cluster spines each having two or more clusters placed along a vector are placed into a display. The clusters along each spine are identified as similar and the clusters of one such spine are also similar to further clusters located along a further spine having a small cosine rotation from that cluster spine. Still other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein is described embodiments of the invention by way of illustrating the best mode contemplated for carrying out the invention. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, all without departing from the spirit and the scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a system for efficiently generating cluster groupings in a multi-dimensional concept space, in accordance with the present invention. FIG. 2 is a block diagram showing the software modules implementing the document analyzer of FIG. 1 . FIG. 3 is a process flow diagram showing the stages of text analysis performed by the document analyzer of FIG. 1 . FIG. 4 is a flow diagram showing a method for efficiently generating cluster groupings in a multi-dimensional concept space, in accordance with the present invention. FIG. 5 is a flow diagram showing the routine for performing text analysis for use in the method of FIG. 4 . FIG. 6 is a flow diagram showing the routine for creating a histogram for use in the routine of FIG. 5 . FIG. 7 is a data structure diagram showing a database record for a concept stored in the database 30 of FIG. 1 . FIG. 8 is a data structure diagram showing, by way of example, a database table containing a lexicon of extracted concepts stored in the database 30 of FIG. 1 . FIG. 9 is a graph showing, by way of example, a histogram of the frequencies of concept occurrences generated by the routine of FIG. 6 . FIG. 10 is a table showing, by way of example, concept occurrence frequencies generated by the routine of FIG. 6 . FIG. 11 is a graph showing, by way of example, a corpus graph of the frequency of concept occurrences generated by the routine of FIG. 5 . FIG. 12 is a flow diagram showing the routine for creating clusters for use in the routine of FIG. 5 . FIG. 13 is a table showing, by way of example, the concept clusters created by the routine for FIG. 12 . FIG. 14 is a data representation diagram showing, by way of example, a view of overlapping cluster generated by the system of FIG. 1 . DETAILED DESCRIPTION Glossary Keyword: A literal search term which is either present or absent from a document. Keywords are not used in the evaluation of documents as described herein. Term: A root stem of a single word appearing in the body of at least one document. Phrase: Two or more words co-occurring in the body of a document. A phrase can include stop words. Concept: A collection of terms or phrases with common semantic meanings Theme: Two or more concepts with a common semantic meaning Cluster: All documents for a given concept or theme. The foregoing terms are used throughout this document and, unless indicated otherwise, are assigned the meanings presented above. FIG. 1 is a block diagram showing a system 11 for efficiently generating cluster groupings in a multi-dimensional concept space, in accordance with the present invention. By way of illustration, the system 11 operates in a distributed computing environment 10 , which includes a plurality of heterogeneous systems and document sources. The system 11 implements a document analyzer 12 , as further described below beginning with reference to FIG. 2 , for evaluating latent concepts in unstructured documents. The system 11 is coupled to a storage device 13 , which stores a document warehouse 14 for maintaining a repository of documents and a database 30 for maintaining document information. The document analyzer 12 analyzes documents retrieved from a plurality of local sources. The local sources include documents 17 maintained in a storage device 16 coupled to a local server 15 and documents 20 maintained in a storage device 19 coupled to a local client 18 . The local server 15 and local client 18 are interconnected to the system 11 over an intranetwork 21 . In addition, the document analyzer 12 can identify and retrieve documents from remote sources over an internetwork 22 , including the Internet, through a gateway 23 interfaced to the intranetwork 21 . The remote sources include documents 26 maintained in a storage device 25 coupled to a remote server 24 and documents 29 maintained in a storage device 28 coupled to a remote client 27 . The individual documents 17 , 20 , 26 , 29 include all forms and types of unstructured data, including electronic message stores, such as electronic mail (email) folders, word processing documents or Hypertext documents, and could also include graphical or multimedia data. Notwithstanding, the documents could be in the form of structured data, such as stored in a spreadsheet or database. Content mined from these types of documents does not require preprocessing, as described below. In the described embodiment, the individual documents 17 , 20 , 26 , 29 include electronic message folders, such as maintained by the Outlook and Outlook Express products, licensed by Microsoft Corporation, Redmond, Wash. The database is an SQL-based relational database, such as the Oracle database management system, release 8, licensed by Oracle Corporation, Redwood Shores, Calif. The individual computer systems, including system 11 , server 15 , client 18 , remote server 24 and remote client 27 , are general purpose, programmed digital computing devices consisting of a central processing unit (CPU), random access memory (RAM), non-volatile secondary storage, such as a hard drive or CD ROM drive, network interfaces, and peripheral devices, including user interfacing means, such as a keyboard and display. Program code, including software programs, and data are loaded into the RAM for execution and processing by the CPU and results are generated for display, output, transmittal, or storage. FIG. 2 is a block diagram showing the software modules 40 implementing the document analyzer 12 of FIG. 1 . The document analyzer 12 includes three modules: storage and retrieval manager 41 , text analyzer 42 , and display and visualization 44 . The storage and retrieval manager 41 identifies and retrieves documents 45 into the document warehouse 14 (shown in FIG. 1 ). The documents 45 are retrieved from various sources, including both local and remote clients and server stores. The text analyzer 42 performs the bulk of the text mining processing. The cluster 43 generates clusters 49 of highly correlated documents, as further described below with reference to FIG. 12 . The display and visualization 44 complements the operations performed by the text analyzer 42 by presenting visual representations of the information extracted from the documents 45 . The display and visualization 44 can also generate a graphical representation which preserves independent variable relationships, such as described in common-assigned U.S. Pat. No. 6,888,548, issued May 3, 2005, the disclosure of which is incorporated by reference. During text analysis, the text analyzer 42 identifies terms and phrases and extracts concepts in the form of noun phrases that are stored in a lexicon 18 maintained in the database 30 . After normalizing the extracted concepts, the text analyzer 42 generates a frequency table 47 of concept occurrences, as further described below with reference to FIG. 6 , and a matrix 48 of summations of the products of pair-wise terms, as further described below with reference to FIG. 10 . The cluster 43 generates logical clusters 49 of documents in a multi-dimensional concept space for modeling semantic meaning. Similarly, the display and visualization 44 generates a histogram 50 of concept occurrences per document, as further described below with reference to FIG. 6 , and a corpus graph 51 of concept occurrences over all documents, as further described below with reference to FIG. 8 . Each module is a computer program, procedure or module written as source code in a conventional programming language, such as the C++ programming language, and is presented for execution by the CPU as object or byte code, as is known in the art. The various implementations of the source code and object and byte codes can be held on a computer-readable storage medium or embodied on a transmission medium in a carrier wave. The document analyzer 12 operates in accordance with a sequence of process steps, as further described below with reference to FIG. 5 . FIG. 3 is a process flow diagram showing the stages 60 of text analysis performed by the document analyzer 12 of FIG. 1 . The individual documents 45 are preprocessed and noun phrases are extracted as concepts (transition 61 ) into a lexicon 46 . The noun phrases are normalized and queried (transition 62 ) to generate a frequency table 47 . The frequency table 47 identifies individual concepts and their respective frequency of occurrence within each document 45 . The frequencies of concept occurrences are visualized (transition 63 ) into a frequency of concepts histogram 50 . The histogram 50 graphically displays the frequencies of occurrence of each concept on a per-document basis. Next, the frequencies of concept occurrences for all the documents 45 are assimilated (transition 64 ) into a corpus graph 51 that displays the overall counts of documents containing each of the extracted concepts. Finally, the most highly correlated terms and phrases from the extracted concepts are categorized (transition 65 ) into clusters 49 . FIG. 4 is a flow diagram showing a method 70 for efficiently generating cluster groupings in a multi-dimensional concept space 44 (shown in FIG. 2 ), in accordance with the present invention. As a preliminary step, the set of documents 45 to be analyzed is identified (block 71 ) and retrieved into the document warehouse 14 (shown in FIG. 1 ) (block 72 ). The documents 45 are unstructured data and lack a common format or shared type. The documents 45 include electronic messages stored in messaging folders, word processing documents, hypertext documents, and the like. Once identified and retrieved, the set of documents 45 is analyzed (block 73 ), as further described below with reference to FIG. 5 . During text analysis, a matrix 48 (shown in FIG. 2 ) of term-document association data is constructed to summarize the semantic content inherent in the structure of the documents 45 . The semantic content is represented by groups of clusters of highly correlated documents generated through k-means clustering. As well, the frequency of individual terms or phrases extracted from the documents 45 are displayed and the results, including the clusters 43 , are optionally visualized (block 74 ), as further described below with reference to FIG. 14 . The routine then terminates. FIG. 5 is a flow diagram showing the routine 80 for performing text analysis for use in the method 70 of FIG. 4 . The purpose of this routine is to extract and index terms or phrases for the set of documents 45 (shown in FIG. 2 ). Preliminarily, each document in the documents set 44 is preprocessed (block 81 ) to remove stop words. These include commonly occurring words, such as indefinite articles (“a” and “an”), definite articles (“the”), pronouns (“I”, “he” and “she”), connectors (“and” and “or”), and similar non-substantive words. Following preprocessing, a histogram 50 of the frequency of terms (shown in FIG. 2 ) is logically created for each document 45 (block 82 ), as further described below with reference to FIG. 6 . Each histogram 50 , as further described below with reference to FIG. 9 , maps the relative frequency of occurrence of each extracted term on a per-document basis. Next, a document reference frequency (corpus) graph 51 , as further described below with reference to FIG. 10 , is created for all documents 45 (block 83 ). The corpus graph 51 graphically maps the semantically-related concepts for the entire documents set 44 based on terms and phrases. A subset of the corpus is selected by removing those terms and phrases falling outside either edge of predefined thresholds (block 84 ). For shorter documents, such as email, having less semantically-rich content, the thresholds are set from about 1% to about 15%, inclusive. Larger documents may require tighter threshold values. The selected set of terms and phrases falling within the thresholds are used to generate themes (and concepts) (block 85 ) based on correlations between normalized terms and phrases in the documents set. In the described embodiment, themes are primarily used, rather than individual concepts, as a single co-occurrence of terms or phrases carries less semantic meaning than multiple co-occurrences. As used herein, any reference to a “theme” or “concept” will be understood to include the other term, except as specifically indicated otherwise. Next, clusters of concepts and themes are created (block 86 ) from groups of highly-correlated terms and phrases, as further described below with reference to FIG. 12 . The routine then returns. FIG. 6 is a flow diagram showing the routine 90 for creating a histogram 50 (shown in FIG. 2 ) for use in the routine of FIG. 5 . The purpose of this routine is to extract noun phrases representing individual concepts and to create a normalized representation of the occurrences of the concepts on a per-document basis. The histogram represents the logical union of the terms and phrases extracted from each document. In the described embodiment, the histogram 48 need not be expressly visualized, but is generated internally as part of the text analysis process. Initially, noun phrases are extracted (block 91 ) from each document 45 . In the described embodiment, concepts are defined on the basis of the extracted noun phrases, although individual nouns or tri-grams (word triples) could be used in lieu of noun phrases. In the described embodiment, the noun phrases are extracted using the LinguistX product licensed by Inxight Software, Inc., Santa Clara, Calif. Once extracted, the individual terms or phrases are loaded into records stored in the database 30 (shown in FIG. 1 ) (block 92 ). The terms stored in the database 30 are normalized (block 93 ) such that each concept appears as a record only once. In the described embodiment, the records are normalized into third normal form, although other normalization schemas could be used. FIG. 7 is a data structure diagram showing a database record 100 for a concept stored in the database 30 of FIG. 1 . Each database record 100 includes fields for storing an identifier 101 , string 102 and frequency 103 . The identifier 101 is a monotonically increasing integer value that uniquely identifies each term or phrase stored as the string 102 in each record 100 . The frequency of occurrence of each term or phrase is tallied in the frequency 103 . FIG. 8 is a data structure diagram showing, by way of example, a database table 110 containing a lexicon 111 of extracted concepts stored in the database 30 of FIG. 1 . The lexicon 111 maps out the individual occurrences of identified terms 113 extracted for any given document 112 . By way of example, the document 112 includes three terms numbered 1, 3 and 5. Concept 1 occurs once in document 112 , concept 3 occurs twice, and concept 5 occurs once. The lexicon tallies and represents the occurrences of frequency of the concepts 1, 3 and 5 across all documents 45 . Referring back to FIG. 6 , a frequency table is created from the lexicon 111 for each given document 45 (block 94 ). The frequency table is sorted in order of decreasing frequencies of occurrence for each concept 113 found in a given document 45 . In the described embodiment, all terms and phrases occurring just once in a given document are removed as not relevant to semantic content. The frequency table is then used to generate a histogram 50 (shown in FIG. 2 ) (block 95 ) which visualizes the frequencies of occurrence of extracted concepts in each document. The routine then returns. FIG. 9 is a graph showing, by way of example, a histogram 50 of the frequencies of concept occurrences generated by the routine of FIG. 6 . The x-axis defines the individual concepts 121 for each document and the y-axis defines the frequencies of occurrence of each concept 122 . The concepts are mapped in order of decreasing frequency 123 to generate a curve 124 representing the semantic content of the document 45 . Accordingly, terms or phrases appearing on the increasing end of the curve 124 have a high frequency of occurrence while concepts appearing on the descending end of the curve 124 have a low frequency of occurrence. FIG. 10 is a table 130 showing, by way of example, concept occurrence frequencies generated by the routine of FIG. 6 . Each concept 131 is mapped against the total frequency occurrence 132 for the entire set of documents 45 . Thus, for each of the concepts 133 , a cumulative frequency 134 is tallied. The corpus table 130 is used to generate the document concept frequency reference (corpus) graph 51 . FIG. 11 is a graph 140 showing, by way of example, a corpus graph of the frequency of concept occurrences generated by the routine of FIG. 5 . The graph 140 visualizes the extracted concepts as tallied in the corpus table 130 (shown in FIG. 10 ). The x-axis defines the individual concepts 141 for all documents and the y-axis defines the number of documents 45 referencing each concept 142 . The individual concepts are mapped in order of descending frequency of occurrence 143 to generate a curve 144 representing the latent semantics of the set of documents 45 . A median value 145 is selected and edge conditions 146 a - b are established to discriminate between concepts which occur too frequently versus concepts which occur too infrequently. Those documents falling within the edge conditions 146 a - b form a subset of documents containing latent concepts. In the described embodiment, the median value 145 is document-type dependent. For efficiency, the upper edge condition 146 b is set to 70% and the 64 concepts immediately preceding the upper edge condition 146 b are selected, although other forms of threshold discrimination could also be used. FIG. 12 is a flow diagram 150 showing the routine for creating clusters for use in the routine of FIG. 5 . The purpose of this routine is to build a concept space over a document collection consisting of clusters 49 (shown in FIG. 2 ) of individual documents having semantically similar content. Initially, a single cluster is created and additional clusters are added using a k-mean clustering technique, as required by the document set. Those clusters falling outside a pre-determined variance are grouped into new clusters, such that every document in the document set appears in at least one cluster and the concepts and themes contained therein are distributed over a meaningful range of clusters. The clusters are then visualized as a data representation, as further described below with reference to FIG. 14 . Each cluster consists of a set of documents that share related terms and phrases as mapped in a multi-dimensional concept space. Those documents having identical terms and phrases mapped to a single cluster located along a vector at a distance (magnitude) d measured at an angle θ from a common origin relative to the multi-dimensional concept space. Accordingly, a Euclidean distance between the individual concepts can be determined and clusters created. Initially, a variance specifying an upper bound on Euclidean distances in the multi-dimensional concept space is determined (block 151 ). In the described embodiment, a variance of five percent is specified, although other variance values, either greater or lesser than five percent, could be used as appropriate to the data profile. As well, an internal counter num_clusters is set to the initial value of 1 (block 152 ). The documents and clusters are iteratively processed in a pair of nested processing loops (blocks 153 - 164 and 156 - 161 ). During each iteration of the outer processing loop (blocks 153 - 164 ), each document i is processed (block 153 ) for every document in the document set. Each document i is first selected (block 154 ) and the angle θ relative to a common origin is computed (block 155 ). During each iterative loop of the inner processing loop (block 156 - 161 ), the selected document i is compared to the existing set of clusters. Thus, a cluster j is selected (block 157 ) and the angle σ relative to the common origin is computed (block 158 ). Note the angle σ must be recomputed regularly for each cluster j as documents are added or removed. The difference between the angle θ for the document i and the angle σ for the cluster j is compared to the predetermined variance (block 159 ). If the difference is less than the predetermined variance (block 159 ), the document i is put into the cluster j (block 160 ) and the iterative processing loop (block 156 - 161 ) is terminated. If the difference is greater than or equal to the variance (block 159 ), the next cluster j is processed (block 161 ) and processing continues for each of the current clusters (blocks 156 - 161 ). If the difference between the angle θ for the document i and the angle σ for each of the clusters exceeds the variance, a new cluster is created (block 162 ) and the counter num_clusters is incremented (block 163 ). Processing continues with the next document i (block 164 ) until all documents have been processed (blocks 153 - 164 ). The categorization of clusters is repeated (block 165 ) if necessary. In the described embodiment, the cluster categorization (blocks 153 - 164 ) is repeated at least once until the set of clusters settles. Finally, the clusters can be finalized (block 165 ) as an optional step. Finalization includes merging two or more clusters into a single cluster, splitting a single cluster into two or more clusters, removing minimal or outlier clusters, and similar operations, as would be recognized by one skilled in the art. The routine then returns. FIG. 13 is a table 180 showing, by way of example, the concept clusters created by the routine 150 of FIG. 12 . Each of the concepts 181 should appear in at least one of the clusters 182 , thereby insuring that each document appears in some cluster. The Euclidean distances 183 a - d between the documents for a given concept are determined. Those Euclidean distances 183 a - d falling within a predetermined variance are assigned to each individual cluster 184 - 186 . The table 180 can be used to visualize the clusters in a multi-dimensional concept space. FIG. 14 is a data representation diagram 14 showing, by way of example, a view 191 of overlapping clusters 193 - 196 generated by the system of FIG. 1 . Each cluster 193 - 196 has a center c 197 - 200 and radius r 201 - 204 , respectively, and is oriented around a common origin 192 . The center c of each cluster 193 - 196 is located at a fixed distance d 205 - 208 from the common origin 192 . Cluster 194 overlays cluster 193 and clusters 193 , 195 and 196 overlap. Each cluster 193 - 196 represents multi-dimensional data modeled in a three-dimensional display space. The data could be visualized data for a virtual semantic concept space, including semantic content extracted from a collection of documents represented by weighted clusters of concepts, such as described in commonly-assigned U.S. Pat. No. 6,978,274, issued Dec. 20, 2005, the disclosure of which is incorporated by reference. For each cluster 193 , the radii r 201 - 204 and distances d 197 - 200 are independent variables relative to the other clusters 194 - 196 and the radius r 201 is an independent variable relative to the common origin 192 . In this example, each cluster 193 - 196 represents a grouping of points corresponding to documents sharing a common set of related terms and phrases. The radii 201 - 204 of each cluster 193 - 196 reflect the relative number of documents contained in each cluster. Those clusters 193 - 197 located along the same vector are similar in theme as are those clusters located on vectors having a small cosign rotation from each other. Thus, the angle θ relative to a common axis' distance from a common origin 192 is an independent variable within a correlation between the distance d and angle θ relative similarity of theme. Although shown with respect to a circular shape, each cluster 193 - 196 could be non-circular. At a minimum, however, each cluster 193 - 196 must have a center of mass and be oriented around the common origin 192 and must define a convex volume. Accordingly, other shapes defining each cluster 193 - 196 are feasible. While the invention has been particularly shown and described as referenced to the embodiments thereof, those skilled in the art will understand that the foregoing and other changes in form and detail may be made therein without departing from the spirit and scope of the invention.

A computer-implemented system and method for generating clusters for placement into a display is provided. A set of clusters is generated from a document set. A single cluster of related documents from the document set is obtained and at least one new cluster is added. One such document in the set is compared to the cluster. A difference in distance between the document and a common origin and the cluster and the common origin is determined. The document is designated as the new cluster when the difference fails to satisfy a predetermined threshold. One or more cluster spines each having two or more clusters placed along a vector are placed into a display. The clusters along each spine are identified as similar and the clusters of one such spine are also similar to further clusters located along a further spine having a small cosine rotation from that cluster spine.

FIELD OF THE INVENTION This invention relates to a catalyst system comprising a catalyst compound and an activator used in an olefin polymerization process, preferably in the gas or slurry phase to produce polyolefins. The catalyst system preferably includes an activator, and a catalyst compound comprising a transition metal complexed with a facially coordinating tridentate bisamide ligand. BACKGROUND OF THE INVENTION Advances in polymerization and catalysis have resulted in the capability to produce many new polymers having improved physical and chemical properties useful in a wide variety of superior products and applications. With the development of new catalysts the choice of polymerization (solution, slurry, high pressure or gas phase) for producing a particular polymer has been greatly expanded. Also, advances in polymerization technology have provided more efficient, highly productive and economically enhanced processes. Especially illustrative of these advances is the development of technology utilizing bulky ligand metallocene catalyst systems. In a slurry or gas phase process typically a supported catalyst system is used, however, more recently unsupported catalyst systems are being used in these processes. For example, U.S. Pat. Nos. 5,317,036 and 5,693,727 and European publication EP-A-0 593 083 and PCT publication WO 97/46599 all describe various processes and techniques for introducing liquid catalysts to a reactor. There is a desire in the industry using this technology to reduce the complexity of the process, to improve the process operability, to increase product characteristics and to vary catalyst choices. Thus, it would be advantageous to have a process that is capable of improving one or more of these industry needs. EP 0 893 454 A1 discloses bisamide based catalyst compounds that can be used for ethylene polymerization. WO 98/45039 discloses polymerization catalysts containing electron withdrawing amide ligands combined with group 3-10 or lanthanide metal compounds used with co-catalysts to polymerize olefins. SUMMARY OF THE INVENTION This invention relates to a catalyst system and polymerization processes using that catalyst system. In one aspect, the invention relates to a catalyst system comprising one or more activators and at least one catalyst compound. The catalyst compound preferably comprises a group 3, 4, 5 lanthanide, or actinide metal atom bound to at least one anionic leaving group and also bound to at least three group 15 atoms, at least one of which is also bound to a group 15 or 16 atom through another group which may be a C 1 to C 20 hydrocarbon group, a heteroatom containing group, silicon, germanium, tin, or phosphorus, wherein the group 15 or 16 atom may also be bound to nothing or a hydrogen, a group 14 atom containing group, a halogen, or a heteroatom containing group, and wherein each of the two group 15 atoms are also bound to a cyclic group and may optionally be bound to hydrogen, a halogen, a heteroatom or a hydrocarbyl group, or a heteroatom containing group. In a preferred embodiment, the catalyst compound is represented by the formula: wherein M is a group 3, 4 or 5 transition metal or a lanthanide or actinide group metal, each X is independently an anionic leaving group, n is the oxidation state of M, a is 0 or 1, m is the formal charge of the YZL ligand, Y is a group 15 element, Z is a group 15 element, J is a C 1 to C 20 hydrocarbon group, a heteroatom containing group, silicon, germanium, tin, or phosphorus, L is a group comprising a group 15 or 16 element, R 1 and R 2 are independently a C 1 to C 20 hydrocarbon group, a heteroatom containing group, silicon, germanium, tin, or phosphorus, R 1 and R 2 may also be interconnected to each other, R 3 is hydrogen, a hydrocarbyl group or a heteroatom containing group, R 4 and R 5 are independently an aryl group, a substituted aryl group, a cyclic alkyl group, a substituted cyclic alkyl group, or multiple ring system, and R 6 and R 7 are independently absent or hydrogen, halogen, heteroatom or a hydrocarbyl group, or a heteroatom containing group. By “formal charge of the YZL ligand” is meant the charge of the entire ligand absent the metal and the leaving groups X. By “R 1 and R 2 may also be interconnected to each other” is meant that R 1 and R 2 may be bound to each other through other groups. The activator is preferably an alumoxane, a modified alumoxane, a non-coordinating anion, a borane, a borate, a combination thereof or a conventional-type cocatalyst as described below. It appears preferably however, to use the alumoxanes and boranes together as the inventors have observed that alumoxanes alone and boranes alone do not appear activate the catalysts compounds nearly as well. BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE INVENTION In a preferred embodiment, one or more activators are combined with a catalyst compound represented by the formula: M is a group 3, 4, or 5 transition metal or a lanthanide or actinide group metal, preferably a group 4, preferably zirconium or hafnium, each X is independently an anionic leaving group, preferably hydrogen, a hydrocarbyl group, a heteroatom or a halogen, n is the oxidation state of M, preferably +3, +4, or +5, preferably +4, m is the formal charge of the YZL ligand, preferably 0, −1, −2 or −3, preferably −2, L is a group 15 or 16 element, preferably nitrogen; J is a C 1 to C 20 hydrocarbon group, a heteroatom containing group having up to twenty carbon atoms, preferably a C 1 to C 6 hydrocarbon group, preferably a C 1 to C 20 alkyl, aryl or aralkyl group, preferably a linear, branched or cyclic C 1 to C 20 alkyl or group, wherein the alkyl aryl or aralkyl group may be substituted or un-substituted and may contain heteroatoms, and J may form a ring structure with L; Y is a group 15 element, preferably nitrogen or phosphorus, Z is a group 15 element, preferably nitrogen or phosphorus, R 1 and R 2 are independently a C 1 to C 20 hydrocarbon group, a heteroatom containing group having up to twenty carbon atoms, silicon, germanium, tin, or phosphorus, preferably a C 1 to C 6 hydrocarbon group, preferably a C 1 to C 20 alkyl, aryl or aralkyl group, preferably a linear, branched or cyclic C 1 to C 20 alkyl group, R 1 and R 2 may also be interconnected to each other, R 3 is a hydrocarbon group, hydrogen, a halogen, a heteroatom containing group, preferably a linear, cyclic or branched alkyl group having 1 to 20 carbon atoms; a is 1; R 4 and R 5 are independently an aryl group, a substituted aryl group, a cyclic alkyl group, a substituted cyclic alkyl group, a cyclic aralkyl group, a substituted cyclic aralkyl group or multiple ring system, preferably having up to 20 carbon atoms, preferably between 3 and 10 carbon atoms, preferably a C 1 to C 20 hydrocarbon group, a C 1 to C 20 aryl group or a C 1 to C 20 aralkyl group, and R 6 and R 7 are independently absent, or hydrogen, halogen, heteroatom or a hydrocarbyl group, preferably a linear, cyclic or branched alkyl group having 1 to 20 carbon atoms, more preferably absent. An aralkyl group is defined to be a substituted aryl group. In a preferred embodiment, R 4 and R 5 are independently a group represented by the following formula: wherein R 8 to R 12 are each independently hydrogen, a C 1 to C 40 alkyl group, a heteroatom, a heteroatom containing group containing up to 40 carbon atoms, preferably a C 1 to C 20 linear or branched alkyl group, preferably a methyl, ethyl, propyl or butyl group, any two R groups may form a cyclic group and/or a heterocyclic group. The cyclic groups may be aromatic. In a preferred embodiment, R 9 and R 10 are independently a methyl, ethyl, propyl or butyl group, in a preferred embodiment, R 9 and R 10 are methyl groups, and R 8 , R 11 and R 12 are hydrogen. In this embodiment, M is preferably zirconium or hafnium, most preferably zirconium; each of L, Y, and Z is nitrogen; each of R 1 and R 2 is —CH 2 —; R 3 is methyl; and R 6 and R 7 are absent. The catalyst compounds described herein are preferably combined with one or more activators to form an olefin polymerization catalyst system. Preferred activators include alumoxanes, modified alumoxanes, non-coordinating anions, non-coordinating group 13 metal or metalliod anions, boranes, borates and the like. It is within the scope of this invention to use alumoxane or modified alumoxane as an activator, and/or to also use ionizing activators, neutral or ionic, such as tri (n-butyl) ammonium tetrakis (pentafluorophenyl) boron or a trisperfluorophenyl boron metalloid precursor which ionize the neutral metallocene compound. Other useful compounds include triphenyl boron, triethyl boron, tri-n-butyl ammonium tetraethylborate, triaryl borane and the like. Other useful compounds include aluminate salts as well. In a preferred embodiment, MMAO3A (modified methyl alumoxane in heptane, commercially available from Akzo Chemicals, Inc. under the trade name Modified Methylalumoxane type 3A, (See U.S. Pat. No. 5,041,584) is combined with the metal compounds to form a catalyst system. There are a variety of methods for preparing alumoxane and modified alumoxanes, non-limiting examples of which are described in U.S. Pat. Nos. 4,665,208, 4,952,540, 5,091,352, 5,206,199, 5,204,419, 4,874,734, 4,924,018, 4,908,463, 4,968,827, 5,308,815, 5,329,032, 5,248,801, 5,235,081, 5,157,137, 5,103,031, 5,391,793, 5,391,529, 5,041,584 5,693,838, 5,731,253, 5,041,584 and 5,731,451 and European publications EP-A-0 561 476, EP-B1-0 279 586 and EP-A-0 594-218, and PCT publication WO 94/10180, all of which are herein fully incorporated by reference. Ionizing compounds may contain an active proton, or some other cation associated with but not coordinated to or only loosely coordinated to the remaining ion of the ionizing compound. Such compounds and the like are described in European publications EP-A-0 570 982, EP-A-0 520 732, EP-A-0 495 375, EP-A-0 426 637, EP-A-500 944, EP-A-0 277 003 and EP-A-0 277 004, and U.S. Pat. Nos. 5,153,157, 5,198,401, 5,066,741, 5,206,197, 5,241,025, 5,387,568, 5,384,299, 5,502,124 and 5,643,847, all of which are herein fully incorporated by reference. Other activators include those described in PCT publication WO 98/07515 such as tris (2,2′,2″- nonafluorobiphenyl) fluoroaluminate, which is fully incorporated herein by reference. Combinations of activators are also contemplated by the invention, for example, alumoxanes and ionizing activators in combinations, see for example, PCT publications WO 94/07928 and WO 95/14044 and U.S. Pat. Nos. 5,153,157 and 5,453,410 all of which are herein fully incorporated by reference. Also, methods of activation such as using radiation and the like are also contemplated as activators for the purposes of this invention. Useful activators include those selected from the group consisting of: trimethylammonium tetraphenylborate, triethylammonium tetraphenylborate, tripropylammonium tetraphenylborate, tri(n-butyl)ammonium tetraphenylborate, tri(t-butyl)ammonium tetraphenylborate, N,N-dimethylanilinium tetraphenylborate, N,N-diethylanilinium tetraphenylborate, N,N-dimethyl-(2,4,6-trimethylanilinium) tetraphenylborate, trimethylammonium tetrakis(pentafluorophenyl)borate, triethylammonium tetrakis(pentafluorophenyl)borate, tripropylammonium tetrakis(pentafluorophenyl)borate, tri(n-butyl)ammonium tetrakis(pentafluorophenyl)borate, tri(sec-butyl)ammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N-diethylanilinium tetrakis(pentafluorophenyl)borate, N,N-dimethyl-(2,4,6-trimethylanilinium) tetrakis(pentafluorophenyl)borate, trimethylammonium tetrakis-(2,3,4,6-tetrafluorophenylborate, triethylammonium tetrakis-(2,3,4,6-tetrafluorophenyl)borate, tripropylammonium tetrakis-(2,3,4,6-tetrafluorophenyl)borate, tri(n-butyl)ammonium tetrakis-(2,3,4,6-tetrafluoro-phenyl)borate, dimethyl(t-butyl)ammonium tetrakis-(2,3,4,6-tetrafluorophenyl)borate, N,N-dimethylanilinium tetrakis-(2,3,4,6-tetrafluorophenyl)borate, N,N-diethylanilinium tetrakis-(2,3,4,6-tetrafluoro-phenyl)borate, N,N-dimethyl-(2,4,6-trimethylanilinium)tetrakis-(2,3,4,6-tetrafluorophenyl)borate; di-(i-propyl)ammonium tetrakis(pentafluorophenyl)borate, dicyclohexylammonium tetrakis(pentafluorophenyl)borate; triphenylphosphonium tetrakis(pentafluorophenyl)borate, tri(o-tolyl)phosphonium tetrakis(pentafluorophenyl)borate, tri(2,6-dimethylphenyl)phosphonium tetrakis(pentafluorophenyl)borate, and mixtures thereof. In another embodiment, a second catalyst compound may be present. The second catalyst compound mat be another compound as described above or may comprise a conventional-type transition metal catalyst. Conventional-Type Transition Metal Catalysts Conventional-type transition metal catalysts are those traditional Ziegler-Natta, vanadium and Phillips-type catalysts well known in the art. Such as, for example Ziegler-Natta catalysts as described in “Ziegler-Natta Catalysts and Polymerizations”, John Boor, Academic Press, New York, 1979. Examples of conventional-type transition metal catalysts are also discussed in U.S. Pat. Nos. 4,115,639, 4,077,904, 4,482,687, 4,564,605, 4,721,763, 4,879,359 and 4,960,741 all of which are herein fully incorporated by reference. The conventional-type transition metal catalyst compounds that may be used in the present invention include transition metal compounds from Groups 3 to 17, preferably 4 to 12, more preferably 4 to 6 of the Periodic Table of Elements. These conventional-type transition metal catalysts may be represented by the formula: MR x , where M is a metal from Groups 3 to 17, preferably Group 4 to 6, more preferably Group 4, most preferably titanium; R is a halogen or a hydrocarbyloxy group; and x is the oxidation state of the metal M. Non-limiting examples of R include alkoxy, phenoxy, bromide, chloride and fluoride. Non-limiting examples of conventional-type transition metal catalysts where M is titanium include TiCl 4 , TiBr 4 , Ti(OC 2 H 5 ) 3 Cl, Ti(OC 2 H 5 )Cl 3 , Ti(OC 4 H 9 ) 3 Cl, Ti(OC 3 H 7 ) 2 Cl 2 , Ti(OC 2 H 5 ) 2 Br 2 , TiCl 3 .1/3AlCl 3 and Ti(OC 12 H 25 )Cl 3 . Conventional-type transition metal catalyst compounds based on magnesium/titanium electron-donor complexes that are useful in the invention are described in, for example, U.S. Pat. Nos. 4,302,565 and 4,302,566, which are herein fully incorporate by reference. The MgTiCl 6 (ethyl acetate) 4 derivative is particularly preferred. British Patent Application 2,105,355 and U.S. Pat. No. 5,317,036, herein incorporated by reference, describes various conventional-type vanadium catalyst compounds. Non-limiting examples of conventional-type vanadium catalyst compounds include vanadyl trihalide, alkoxy halides and alkoxides such as VOCl 3 , VOCl 2 (OBu) where Bu=butyl and VO(OC 2 H 5 ) 3 ; vanadium tetra-halide and vanadium alkoxy halides such as VCl 4 and VCl 3 (OBu); vanadium and vanadyl acetyl acetonates and chloroacetyl acetonates such as V(AcAc) 3 and VOCl 2 (AcAc) where (AcAc) is an acetyl acetonate. The preferred conventional-type vanadium catalyst compounds are VOCl 3 , VCl 4 and VOCl 2 -OR where R is a hydrocarbon radical, preferably a C 1 to C 10 aliphatic or aromatic hydrocarbon radical such as ethyl, phenyl, isopropyl, butyl, propyl, n-butyl, iso-butyl, tertiary-butyl, hexyl, cyclohexyl, naphthyl, etc., and vanadium acetyl acetonates. Conventional-type chromium catalyst compounds, often referred to as Phillips-type catalysts, suitable for use in the present invention include CrO 3 , chromocene, silyl chromate, chromyl chloride (CrO 2 Cl 2 ), chromium-2-ethyl-hexanoate, chromium acetylacetonate (Cr(AcAc) 3 ), and the like. Non-limiting examples are disclosed in U.S. Pat. Nos. 3,709,853, 3,709,954, 3,231,550, 3,242,099 and 4,077,904, which are herein fully incorporated by reference. Still other conventional-type transition metal catalyst compounds and catalyst systems suitable for use in the present invention are disclosed in U.S. Pat. Nos. 4,124,532, 4,302,565, 4,302,566, 4,376,062, 4,379,758, 5,066,737, 5,763,723, 5,849,655, 5,852,144, 5,854,164 and 5,869,585 and published EP-A2 0 416 815 A2 and EP-A1 0 420 436, which are all herein incorporated by reference. Other catalysts may include cationic catalysts such as AlCl 3 , and other cobalt, iron, nickel and palladium catalysts well known in the art. See for example U.S. Pat. Nos. 3,487,112, 4,472,559, 4,182,814 and 4,689,437 all of which are incorporated herein by reference. Typically, these conventional-type transition metal catalyst compounds excluding some conventional-type chromium catalyst compounds are activated with one or more of the conventional-type cocatalysts described below. Conventional-Type Cocatalysts Conventional-type cocatalyst compounds for the above conventional-type transition metal catalyst compounds may be represented by the formula M 3 M 4 v X 2 c R 3 b-c , wherein M 3 is a metal from Group 1 to 3 and 12 to 13 of the Periodic Table of Elements; M 4 is a metal of Group 1 of the Periodic Table of Elements; v is a number from 0 to 1; each X 2 is any halogen; c is a number from 0 to 3; each R 3 is a monovalent hydrocarbon radical or hydrogen; b is a number from 1 to 4; and wherein b minus c is at least 1. Other conventional-type organometallic cocatalyst compounds for the above conventional-type transition metal catalysts have the formula M 3 R 3 k , where M 3 is a Group IA, IIA, IIB or IIIA metal, such as lithium, sodium, beryllium, barium, boron, aluminum, zinc, cadmium, and gallium; k equals 1, 2 or 3 depending upon the valency of M 3 which valency in turn normally depends upon the particular Group to which M 3 belongs; and each R 3 may be any monovalent hydrocarbon radical. Non-limiting examples of conventional-type organometallic cocatalyst compounds useful with the conventional-type catalyst compounds described above include methyllithium, butyllithium, dihexylmercury, butylmagnesium, diethylcadmium, benzylpotassium, diethylzinc, tri-n-butylaluminum, diisobutyl ethylboron, diethylcadmium, di-n-butylzinc and tri-n-amylboron, and, in particular, the aluminum alkyls, such as tri-hexyl-aluminum, triethylaluminum, trimethylaluminum, and tri-isobutylaluminum. Other conventional-type cocatalyst compounds include mono-organohalides and hydrides of Group 2 metals, and mono- or di-organohalides and hydrides of Group 3 and 13 metals. Non-limiting examples of such conventional-type cocatalyst compounds include di-isobutylaluminum bromide, isobutylboron dichloride, methyl magnesium chloride, ethylberyllium chloride, ethylcalcium bromide, di-isobutylaluminum hydride, methylcadmium hydride, diethylboron hydride, hexylberyllium hydride, dipropylboron hydride, octylmagnesium hydride, butylzinc hydride, dichloroboron hydride, di-bromo-aluminum hydride and bromocadmium hydride. Conventional-type organometallic cocatalyst compounds are known to those in the art and a more complete discussion of these compounds may be found in U.S. Pat. Nos. 3,221,002 and 5,093,415, which are herein fully incorporated by reference. The second catalyst compound may also be compound referred to as a metallocene, i.e. those mono-and bis-cyclopentadienyl group 4, 5 and 6 compounds described in U.S. Pat. Nos. 4,530,914, 4,805,561, 4,871,705, 4,937,299, 5,096,867, 5,120,867, 5,210,352, 5,124,418, 5,017,714, 5,057,475, 5,064,802, 5,278,264, 5,278,119, 5,304,614, 5,324,800, 5,347,025, 5,350,723, 5,391,790, 5,391,789, 5,399,636, 5,539,124, 5,455,366, 5,534,473, 5,684,098, 5,693,730, 5,698,634, 5,710,297, 5,712,354, 5,714,427, 5,714,555, 5,728,641, 5,728,839, EP-A-0 591 756, EP-A-0 520 732, EP-A-0 578,838, EP-A-0 638,595, EP-A-0 420 436, EP-B1-0 485 822, EP-B1-0 485 823, EP-A-0 743 324, EP-B1-0 518 092, WO 91/04257, WO 92/00333, WO 93/08221, WO 93/08199, WO 94/01471, WO 94/07928, WO 94/03506 WO 96/20233, WO 96/00244, WO 97/15582, WO 97/15602, WO 97/19959, WO 97/46567, WO 98/01455, WO 98/06759 and WO 95/07140, all of which are fully incorporated by reference herein. Supports, Carriers and General Supporting Techniques The catalyst and/or the activator may be placed on, deposited on, contacted with, incorporated within, adsorbed, or absorbed in a support. Typically the support can be of any of the solid, porous supports, including microporous supports. Typical support materials include talc; inorganic oxides such as silica, magnesium chloride, alumina, silica-alumina; polymeric supports such as polyethylene, polypropylene, polystyrene, cross-linked polystyrene; and the like. Preferably the support is used in finely divided form. Prior to use the support is preferably partially or completely dehydrated. The dehydration may be done physically by calcining or by chemically converting all or part of the active hydroxyls. For more information on how to support catalysts please see U.S. Pat. No. 4,808,561 which discloses how to support a metallocene catalyst system. The techniques used therein are generally applicable for this invention. For example, in a most preferred embodiment, the activator is contacted with a support to form a supported activator wherein the activator is deposited on, contacted with, vaporized with, bonded to, or incorporated within, adsorbed or absorbed in, or on, a support or carrier. Support materials of the invention include inorganic or organic support materials, preferably a porous support material. Non-limiting examples of inorganic support materials include inorganic oxides and inorganic chlorides. Other carriers include resinous support materials such as polystyrene, functionalized or crosslinked organic supports, such as polystyrene divinyl benzene, polyolefins or polymeric compounds, or any other organic or inorganic support material and the like, or mixtures thereof. The preferred support materials are inorganic oxides that include those Group 2, 3, 4, 5, 13 or 14 metal oxides. The preferred supports include silica, fumed silica, alumina (WO 99/60033), silica-alumina and mixtures thereof. Other useful supports include magnesia, titania, zirconia, magnesium chloride (U.S. Pat. No. 5,965,477), montmorillonite (EP-B1 0 511 665), phyllosilicate, zeolites, talc, clays (U.S. Pat. No. 6,034,187) and the like. Also, combinations of these support materials may be used, for example, silica-chromium, silica-alumina, silica-titania and the like. Additional support materials may include those porous acrylic polymers described in EP 0 767 184 B1, which is incorporated herein by reference. Other support materials include nanocomposites as described in PCT WO 99/47598, aerogels as described in WO 99/48605, spherulites as described in U.S. Pat. No. 5,972,510 and polymeric beads as described in WO 99/50311, which are all herein incorporated by reference. A preferred support is fumed silica available under the trade name Cabosil™ TS-610, available from Cabot Corporation. Fumed silica is typically a silica with particles 7 to 30 nanometers in size that has been treated with dimethylsilyldichloride such that a majority of hydroxyl groups are capped. It is preferred that the support material, most preferably an inorganic oxide, has a surface area in the range of from about 10 to about 700 m 2 /g, pore volume in the range of from about 0.1 to about 4.0 cc/g and average particle size in the range of from about 5 to about 500 μm. More preferably, the surface area of the support is in the range of from about 50 to about 500 m 2 /g, pore volume of from about 0.5 to about 3.5 cc/g and average particle size of from about 10 to about 200 μm. Most preferably the surface area of the support is in the range from about 100 to about 1000 m 2 /g, pore volume from about 0.8 to about 5.0 cc/g and average particle size is from about 5 to about 100 μm. The average pore size of the support material of the invention typically has pore size in the range of from 10 to 1000 Å, preferably 50 to about 500 Å, and most preferably 75 to about 450 Å. There are various methods known in the art for producing a supported activator or combining an activator with a support material. In an embodiment, the support material is chemically treated and/or dehydrated prior to combining with the catalyst compound, activator and/or catalyst system. In one embodiment, an alumoxane is contacted with a support material, preferably a porous support material, more preferably a inorganic oxide, and most preferably the support material is silica. In an embodiment, the support material having a various levels of dehydration, preferably 200° C. to 600° C. dehydrated silica, that is then contacted with an organoaluminum or alumoxane compound. In specifically the embodiment wherein an organoaluminum compound is used, the activator is formed in situ in or on the support material as a result of the reaction of, for example, trimethylaluminum and water. In yet another embodiment, a Lewis base-containing support substrates will react with a Lewis acidic activator to form a support bonded Lewis acid compound. The Lewis base hydroxyl groups of silica are exemplary of metal/metalloid oxides where this method of bonding to a support occurs. This embodiment is described in U.S. patent application Ser. No. 09/191,922, filed Nov. 13, 1998, which is herein incorporated by reference. Other embodiments of supporting an activator are described in U.S. Pat. No. 5,427,991, where supported non-coordinating anions derived from trisperfluorophenyl boron are described; U.S. Pat. No. 5,643,847 discusses the reaction of Group 13 Lewis acid compounds with metal oxides such as silica and illustrates the reaction of trisperfluorophenyl boron with silanol groups (the hydroxyl groups of silicon) resulting in bound anions capable of protonating transition metal organometallic catalyst compounds to form catalytically active cations counter-balanced by the bound anions; immobilized Group IIIA Lewis acid catalysts suitable for carbocationic polymerizations are described in U.S. Pat. No. 5,288,677; and James C. W. Chien, Jour. Poly. Sci.: Pt A: Poly. Chem, Vol. 29, 1603-1607 (1991), describes the olefin polymerization utility of methylalumoxane (MAO) reacted with silica (SiO 2 ) and metallocenes and describes a covalent bonding of the aluminum atom to the silica through an oxygen atom in the surface hydroxyl groups of the silica. In an embodiment, the weight percent of the activator to the support material is in the range of from about 10 weight percent to about 70 weight percent, preferably in the range of from 20 weight percent to about 60 weight percent, more preferably in the range of from about 30 weight percent to about 50 weight percent, and most preferably in the range of from 30 weight percent to about 40 weight percent. In another embodiment, the catalyst compounds and/or the activators are preferably combined with a support material such as a particulate filler material and then spray dried, preferably to form a free flowing powder. Spray drying may be by any means known in the art. Please see EP A 0 668 295 B1, U.S. Pat. No. 5,674,795 and U.S. Pat. No. 5,672,669 which particularly describe spray drying of supported catalysts. In general one may spray dry the catalysts by placing the catalyst compound and the optional activator in solution (allowing the catalyst compound and activator to react, if desired), adding a filler material such as silica or fumed silica, such as Gasil™ or Cabosil™, then forcing the solution at high pressures through a nozzle. The solution may be sprayed onto a surface or sprayed such that the droplets dry in midair. The method generally employed is to disperse the silica in toluene, stir in the activator solution, and then stir in the catalyst compound solution. Typical slurry concentrations are about 5-8 wt %. This formulation may sit as a slurry for as long as 30 minutes with mild stirring or manual shaking to keep it as a suspension before spray-drying. In one preferred embodiment, the makeup of the dried material is about 40-50 wt % activator (preferably alumoxane), 50-60 SiO 2 and about ˜2 wt % catalyst compound. The first and second catalyst compounds may be combined at molar ratios of 1:1000 to 1000:1, preferably 1:99 to 99:1, preferably 10:90 to 90:10, more preferably 20:80 to 80:20, more preferably 30:70 to 70:30, more preferably 40:60 to 60:40. The particular ratio chosen will depend on the end product desired and/or the method of activation. One practical method to determine which ratio is best to obtain the desired polymer is to start with a 1:1 ratio, measure the desired property in the product produced and adjust the ratio accordingly. The melt index (and other properties) of the polymer produced may be changed by manipulating hydrogen concentration in the polymerization system by: 1) changing the amount of the first catalyst in the polymerization system, and/or 2) changing the amount of the second catalyst, if present, in the polymerization system, and/or 3) adding hydrogen to the polymerization process; and/or 4) changing the amount of liquid and/or gas that is withdrawn and/or purged from the process; and/or 5) changing the amount and/or composition of a recovered liquid and/or recovered gas returned to the polymerization process, said recovered liquid or recovered gas being recovered from polymer discharged from the polymerization process; and/or 6) using a hydrogenation catalyst in the polymerization process; and/or 7) changing the polymerization temperature; and/or 8) changing the ethylene partial pressure in the polymerization process; and/or 9) changing the ethylene to hexene ratio in the polymerization process; and/or 10) changing the activator to transition metal ratio in the activation sequence. In a preferred embodiment, the hydrogen concentration in the reactor is about 200-2000 ppm, preferably 250-1900 ppm, preferably 300-1800 ppm, preferably 350-1700 ppm, preferably 400-1600 ppm, preferably 500-1500 ppm, preferably 500-1400 ppm, preferably 500-1200 ppm, preferably 600-1200 ppm, preferably 700-1100 ppm, more preferably 800-1000 ppm. In general the catalyst compound(s) and the activator(s) are combined in ratios of about 1000:1 to about 0.5:1. In a preferred embodiment, the metal compounds and the activator are combined in a ratio of about 300:1 to about 1:1, preferably about 150:1 to about 1:1, for boranes, borates, aluminates, etc. the ratio is preferably about 1:1 to about 10:1 and for alkyl aluminum compounds (such as diethylaluminum chloride combined with water) the ratio is preferably about 0.5:1 to about 10:1. The catalyst system, the catalyst compounds and or the activator (whether spray dried or not) are preferably introduced into the reactor in one or more solutions or one or more slurries. In one embodiment, a solution of the activated catalyst compound(s) in an alkane such as pentane, hexane, toluene, isopentane or the like is introduced into a gas phase or slurry phase reactor. In another embodiment, a slurry of the activated catalyst compound(s) is introduced into a gas phase or slurry phase reactor. The slurry is preferably a suspension of particulate materials in a diluent medium. Preferably the slurry comprises mineral oil or other hydrocarbon as the diluent, typically an alkane having from 3 to 7 carbon atoms, preferably a branched alkane can be used as the diluent. The medium employed should be liquid under the conditions of polymerization and relatively inert. When a propane medium is used the process must be operated above the reaction diluent critical temperature and pressure. Preferably, a hexane or an isobutane medium is employed. In another embodiment, a slurry of the catalyst compound(s) in mineral oil or an alkane such as pentane, hexane, toluene, isopentane or the like is combined with a solution of the activator and is introduced into a gas phase or slurry phase reactor. In another embodiment, the catalysts system or the components can be introduced into the reactor in a suspension or an emulsion. In one embodiment, the catalyst compound(s) are contacted with the activator in a solvent and just before the solution is fed into a gas or slurry phase reactor. Solutions of the catalyst compounds are prepared by taking the catalyst compound and dissolving it in any solvent such as an alkane, toluene, xylene, etc. The solvent may first be purified in order to remove any poisons that may affect the catalyst activity, including any trace water and/or oxygenated compounds. Purification of the solvent may be accomplished by using activated alumina and activated supported copper catalyst, for example. The catalyst is preferably completely dissolved into the solution to form a homogeneous solution. Multiple catalysts may be dissolved into the same solvent, if desired. Once the catalysts are in solution, they may be stored indefinitely until use. A slurry used in the process of this invention is typically prepared by suspending the activator and/or catalyst compound in a liquid diluent. The liquid diluent is typically an alkane having from 3 to 7 carbon atoms, preferably a branched alkane or an organic composition such as mineral oil The diluent employed should be liquid under the conditions of polymerization and relatively inert. The concentration of the components in the slurry is controlled such that a desired ratio of catalyst compound(s) to activator, and/or catalyst compound to catalyst compound is fed into the reactor. The components are generally fed into the polymerization reactor as a mineral oil slurry. Solids concentrations in oil are about 10 to 15 weight %, preferably 11-14 weight %. In some embodiments, the spray dried particles are <˜10 micrometers in size from the lab-scale Buchi spray-dryer, while the scaled up rotary atomizers can create particles ˜25 micrometers, compared to conventional supported catalysts which are ˜50 micrometers. In a preferred embodiment, the particulate filler has an average particle size of 0.001 to 1 microns, preferably 0.001 to 0.1 microns. Polymerization Process The metal compounds and catalyst systems described above are suitable for use in any polymerization process, including solution, gas or slurry processes or a combination thereof, most preferably a gas or slurry phase process. In one embodiment, this invention is directed toward the polymerization or copolymerization reactions involving the polymerization of one or more monomers having from 2 to 30 carbon atoms, preferably 2-12 carbon atoms, and more preferably 2 to 8 carbon atoms. The invention is particularly well suited to the copolymerization reactions involving the polymerization of one or more olefin monomers of ethylene, propylene, butene-1, pentene-1,4-methyl-pentene-1, hexene-1, octene-1, decene-1,3-methyl-pentene-1,3,5,5-trimethyl-hexene-1 and cyclic olefins or a combination thereof. Other monomers can include vinyl monomers, diolefins such as dienes, polyenes, norbornene, norbornadiene monomers. Preferably a copolymer of ethylene is produced, where the comonomer is at least one alpha-olefin having from 4 to 15 carbon atoms, preferably from 4 to 12 carbon atoms, more preferably from 4 to 8 carbon atoms and most preferably from 4 to 7 carbon atoms. In another embodiment, ethylene or propylene is polymerized with at least two different comonomers to form a terpolymer. The preferred comonomers are a combination of alpha-olefin monomers having 4 to 10 carbon atoms, more preferably 4 to 8 carbon atoms, optionally with at least one diene monomer. The preferred terpolymers include the combinations such as ethylene/butene-1/hexene-1, ethylene/propylene/butene-1, propylene/ethylene/hexene-1, ethylene/propylene/norbornene and the like. In a particularly preferred embodiment, the process of the invention relates to the polymerization of ethylene and at least one comonomer having from 4 to 8 carbon atoms, preferably 4 to 7 carbon atoms. Particularly, the comonomers are butene-1,4-methyl-pentene-1, hexene-1 and octene-1, the most preferred being hexene-1 and/or butene-1. Typically in a gas phase polymerization process a continuous cycle is employed where in one part of the cycle of a reactor system, a cycling gas stream, otherwise known as a recycle stream or fluidizing medium, is heated in the reactor by the heat of polymerization. This heat is removed from the recycle composition in another part of the cycle by a cooling system external to the reactor. Generally, in a gas fluidized bed process for producing polymers, a gaseous stream containing one or more monomers is continuously cycled through a fluidized bed in the presence of a catalyst under reactive conditions. The gaseous stream is withdrawn from the fluidized bed and recycled back into the reactor. Simultaneously, polymer product is withdrawn from the reactor and fresh monomer is added to replace the polymerized monomer. (See for example U.S. Pat. Nos. 4,543,399, 4,588,790, 5,028,670, 5,317,036, 5,352,749, 5,405,922, 5,436,304, 5,453,471, 5,462,999, 5,616,661 and 5,668,228 all of which are fully incorporated herein by reference.) The reactor pressure in a gas phase process may vary from about 10 psig (69 kPa) to about 500 psig (3448 kPa), preferably in the range of from about 100 psig (690 kPa) to about 400 psig (2759 kPa), preferably in the range of from about 200 psig (1379 kPa) to about 400 psig (2759 kPa), more preferably in the range of from about 250 psig (1724 kPa) to about 350 psig (2414 kPa). The reactor temperature in the gas phase process may vary from about 30° C. to about 120° C., preferably from about 60° C. to about 115° C., more preferably in the range of from about 75° C. to 110° C., and most preferably in the range of from about 85° C. to about 110° C. Altering the polymerization temperature can also be used as a tool to alter the final polymer product properties. The productivity of the catalyst or catalyst system is influenced by the main monomer partial pressure. The preferred mole percent of the main monomer, ethylene or propylene, preferably ethylene, is from about 25 to 90 mole percent and the monomer partial pressure is in the range of from about 75 psia (517 kPa) to about 300 psia (2069 kPa), which are typical conditions in a gas phase polymerization process. In one embodiment, the ethylene partial pressure is about 220 to 240 psi (1517-1653 kPa). In another embodiment, the molar ratio of hexene to ethylene in the reactor is 0.03:1 to 0.08:1. In a preferred embodiment, the reactor utilized in the present invention and the process of the invention produce greater than 500 lbs of polymer per hour (227 Kg/hr) to about 200,000 lbs/hr (90,900 Kg/hr) or higher of polymer, preferably greater than 1000 lbs/hr (455 Kg/hr), more preferably greater than 10,000 lbs/hr (4540 Kg/hr), even more preferably greater than 25,000 lbs/hr (11,300 Kg/hr), still more preferably greater than 35,000 lbs/hr (15,900 Kg/hr), still even more preferably greater than 50,000 lbs/hr (22,700 Kg/hr) and most preferably greater than 65,000 lbs/hr (29,000 Kg/hr) to greater than 100,000 lbs/hr (45,500 Kg/hr). Other gas phase processes contemplated by the process of the invention include those described in U.S. Pat. Nos. 5,627,242, 5,665,818 and 5,677,375, and European publications EP-A-0 794 200, EP-A-0 802 202 and EP-B-634 421 all of which are herein fully incorporated by reference. A slurry polymerization process generally uses pressures in the range of from about 1 to about 50 atmospheres and even greater and temperatures in the range of 0° C. to about 120° C. In a slurry polymerization, a suspension of solid, particulate polymer is formed in a liquid polymerization diluent medium to which ethylene and comonomers and often hydrogen along with catalyst are added. The suspension including diluent is intermittently or continuously removed from the reactor where the volatile components are separated from the polymer and recycled, optionally after a distillation, to the reactor. The liquid diluent employed in the polymerization medium is typically an alkane having from 3 to 7 carbon atoms, preferably a branched alkane. The medium employed should be liquid under the conditions of polymerization and relatively inert. When a propane medium is used the process must be operated above the reaction diluent critical temperature and pressure. Preferably, a hexane or an isobutane medium is employed. In one embodiment, a preferred polymerization technique of the invention is referred to as a particle form polymerization, or a slurry process where the temperature is kept below the temperature at which the polymer goes into solution. Such technique is well known in the art, and described in for instance U.S. Pat. No. 3,248,179 which is fully incorporated herein by reference. The preferred temperature in the particle form process is within the range of about 185° F. (85° C.) to about 230° F. (110° C.). Two preferred polymerization methods for the slurry process are those employing a loop reactor and those utilizing a plurality of stirred reactors in series, parallel, or combinations thereof. Non-limiting examples of slurry processes include continuous loop or stirred tank processes. Also, other examples of slurry processes are described in U.S. Pat. No. 4,613,484, which is herein fully incorporated by reference. In another embodiment, the slurry process is carried out continuously in a loop reactor. The catalyst as a solution, as a suspension, as an emulsion, as a slurry in isobutane or as a dry free flowing powder is injected regularly to the reactor loop, which is itself filled with circulating slurry of growing polymer particles in a diluent of isobutane containing monomer and comonomer. Hydrogen, optionally, may be added as a molecular weight control. The reactor is maintained at pressure of about 525 psig to 625 psig (3620 kPa to 4309 kPa) and at a temperature in the range of about 140° F. to about 220° F. (about 60° C. to about 104° C.) depending on the desired polymer density. Reaction heat is removed through the loop wall since much of the reactor is in the form of a double-jacketed pipe. The slurry is allowed to exit the reactor at regular intervals or continuously to a heated low pressure flash vessel, rotary dryer and a nitrogen purge column in sequence for removal of the isobutane diluent and all unreacted monomer and comonomers. The resulting hydrocarbon free powder is then compounded for use in various applications. In an embodiment, the reactor used in the slurry process of the invention is capable of and the process of the invention is producing greater than 2000 lbs of polymer per hour (907 Kg/hr), more preferably greater than 5000 lbs/hr (2268 Kg/hr), and most preferably greater than 10,000 lbs/hr (4540 Kg/hr). In another embodiment, the slurry reactor used in the process of the invention is producing greater than 15,000 lbs of polymer per hour (6804 Kg/hr), preferably greater than 25,000 lbs/hr (11,340 Kg/hr) to about 100,000 lbs/hr (45,500 Kg/hr). In another embodiment, in the slurry process of the invention the total reactor pressure is in the range of from 400 psig (2758 kPa) to 800 psig (5516 kPa), preferably 450 psig (3103 kPa) to about 700 psig (4827 kPa), more preferably 500 psig (3448 kPa) to about 650 psig (4482 kPa), most preferably from about 525 psig (3620 kPa) to 625 psig (4309 kPa). In yet another embodiment, in the slurry process of the invention the concentration of ethylene in the reactor liquid medium is in the range of from about 1 to 10 weight percent, preferably from about 2 to about 7 weight percent, more preferably from about 2.5 to about 6 weight percent, most preferably from about 3 to about 6 weight percent. A preferred process of the invention is where the process, preferably a slurry or gas phase process is operated in the absence of or essentially free of any scavengers, such as triethylaluminum, trimethylaluminum, tri-isobutylaluminum and tri-n-hexylaluminum and diethyl aluminum chloride, dibutyl zinc and the like. This preferred process is described in PCT publication WO 96/08520 and U.S. Pat. No. 5,712,352, which are herein fully incorporated by reference. In another preferred embodiment, the one or all of the catalysts are combined with up to 10 weight % of a metal stearate, (preferably a aluminum stearate, more preferably aluminum distearate) based upon the weight of the catalyst system (or its components), any support and the stearate. In an alternate embodiment, a solution of the metal stearate is fed into the reactor. In another embodiment, the metal stearate is mixed with the catalyst and fed into the reactor separately. These agents may be mixed with the catalyst or may be fed into the reactor in a solution or a slurry with or without the catalyst system or its components. More information on using aluminum stearate type additives may be found in U.S. Ser. No. 09/113,261 filed Jul. 10, 1998, which is incorporated by reference herein. In another preferred embodiment, the supported catalysts combined with the activators are tumbled with 2 weight % of an antistat, such as a methoxylated amine, such as Witco's Kemamine AS-990 from ICl Specialties in Bloomington Del. Polyolefins, particularly polyethylenes, having a density of 0.89 to 0.97g/cm 3 can be produced using this invention. In particular polyethylenes having a density of 0.910 to 0.965, preferably 0.915 to 0.960, preferably 0.920 to 0.955 can be produced. In some embodiments, a density of 0.915 to 0.940 g/cm 3 would be preferred, in other embodiments densities of 0.930 to 0.970 g/cm 3 are preferred. The polyolefins then can be made into films, molded articles (including pipes), sheets, wire and cable coating and the like. The films may be formed by any of the conventional techniques known in the art including extrusion, co-extrusion, lamination, blowing and casting. The film may be obtained by the flat film or tubular process which may be followed by orientation in an uniaxial direction or in two mutually perpendicular directions in the plane of the film to the same or different extents. Orientation may be to the same extent in both directions or may be to different extents. Particularly preferred methods to form the polymers into films include extrusion or coextrusion on a blown or cast film line. The films produced may further contain additives such as slip, antiblock, antioxidants, pigments, fillers, antifog, UV stabilizers, antistats, polymer processing aids, neutralizers, lubricants, surfactants, pigments, dyes and nucleating agents. Preferred additives include silicon dioxide, synthetic silica, titanium dioxide, polydimethylsiloxane, calcium carbonate, metal stearates, calcium stearate, zinc stearate, talc, BaSO 4 , diatomaceous earth, wax, carbon black, flame retarding additives, low molecular weight resins, hydrocarbon resins, glass beads and the like. The additives may be present in the typically effective amounts well known in the art, such as 0.001 weight % to 10 weight %. EXAMPLES In order to provide a better understanding of the present invention including representative advantages thereof, the following examples are offered. The following compounds are well know in the art and are available from many different suppliers: TIBA is triisobutyl aluminum; MMAO is modified methyl alumoxane; and MAO is methyl alumoxane. Ph is phenyl. Me is methyl. Example 1 Preparation of 2-(2-Pyridyl)-1,3-propane-bis(2,6-dimethyl)aniline 1.50 gms of 2-(2-pyridyl)-1,3-propaneditosylate (3.15 mmol) was combined with 5.0 mls 2,6-dimethylaniline in a 100 ml Schlenk flask with a stir bar. The flask was heated under nitrogen at 110° C. for 16 hrs, then was allowed to cool to room temperature. ˜20 mis diethyl ether was added and swirled until the viscous oil became miscible. The ether solution was extracted three times with water, followed by removal of the solvent in vacuo. The oil was transferred to a short path distillation apparatus and heated under full vacuum. The initial fraction distilling over at 35° C. was discarded. The remaining viscous oil was isolated. 1H NMR THF-d 8 8.64 (1H, m, py), 7.71 (1H, t, py), 7.51 (1H, d, py), 7.21 (1H, m, py), 6.86 (4H, d, meta-aniline), 6.68 (2H, t, para-aniline), 3.80 (2H, br, NH), 3.47 (2H, d, ArN(H)CHH), 3.26 (2H, d, ArN(H)CHH), 2.18 (12H, s, aniline Me), 1.66 (3H, s, MeC(CH 2 ) 2 (py)). Example 2 Preparation of 2-(2-Pyridyl)-1,3-propane-bis(2,6dimethyl)aniline Zirconium Dimethyl) 0.234 gms (1.0 mmol) of ZrCl 4 was combined with 0.378 gms (1.0 mmol) 2-(2-pyridyl)-1,3-propane-bis(2,6-dimethyl)aniline and ˜10 mls toluene in a 100 ml Schlenk flask under a nitrogen atmosphere. The contents were heated to 90-100° C. for 20 hrs with stirring. The solids produced were filtered in the drybox and washed with additional toluene. Yield (0.523 gms, 86%) All of this material (0.86 mmol) was suspended in 15 mls diethyl ether and cooled to ˜78° C. under nitrogen in a Schlenk flask. 2.46 mls of 1.4 M MeLi in diethyl ether (3.44 mmol) was added dropwise. The flask was allowed to warm to room temperature over 3 hours. Solvent was removed in vacuo. The product was extracted with toluene followed by filtration to remove solids. 1H NMR C6D6 8.76 (1H, m, pyridyl), 6.53-7.11 (9H, m, pyridyl and aniline), 3.92 (2H, d, CHH), 2.74 (2H, d, CHH), 2.26 (12H, s, aniline Me), 0.96 (3H, s, MeC(CH 2 ) 2 (py)), 0.19 (6H, br, ZrMe). Over time, another resonance appeared at 0.156 ppm, presumably due to methane formation. The product was stable when stored as a solid under nitrogen. This is a representation of the complex of Example 2: Examples 3 to 12 Ethylene polymerizations using 2-(2-pyridyl)-1,3-propane-bis(2,6-dimethyl)aniline zirconium dimethyl were performed. Polymerizations in a slurry reactor were conducted as follows. After an appropriate bake-out period and subsequent cool-down under nitrogen, 500 cc's of hexanes were charged to a 1 liter autoclave reactor. 1-Hexene, if any, and scavenger, if any, were added to the reactor prior to heating. The reactor contents were heated to the desired temperature. A mixture of the catalyst and cocatalyst were prepared in the glovebox in an airtight syringe, removed to the reactor and injected into the reactor once it had reached reaction temperature. Ethylene immediately filled the system to obtain a total pressure of 150 psig (1.03 MPa) and was fed on demand thereafter. Polymerizations were conducted for 30 minutes. BBF indicates butyl branching frequency (per 1000 C). TABLE 1 umol yield BBF Example Zr activator Ratio scavenger ratio temp hexene (gms) (IR) 3 2 MAO + MMAO 1000 none 85 0 0 4 10 B(C6F5)3 1.2 TIBA 50 85 0 0 5 5 B(C6F5)3 7.5 MMAO 350 85 0 2 6 5 Ph3C B(C6F5)4 1.2 TIBA 50 65 0 0.8 7 5 Ph3C B(C6F5)4 1.2 TIBA 50 85 0 4.5 8 5 Ph3C B(C6F5)4 1.2 TIBA 50 95 0 0.1 9 5 Ph3C B(C6F5)4 1.2 TIBA 50 85 20 3.2 22.5 10 5 PhN(Me)2H B(C6F5)4 1.2 TIBA 50 65 0 0 11 5 PhN(Me)2H B(C6F5)4 1.2 TIBA 50 85 0 4.5 12 5 PhN(Me)2H B(C6F5)4 1.2 TIBA 50 85 20 5 19.9 Temperature in Table 1 is in ° C. Example 13 to 18 Hexene polymerizations using 2-(2-pyridyl)-1,3-propane-bis(2,6-dimethyl)aniline zirconium dimethyl). In a glovebox, five mis 1-hexene, stored over Na/K alloy under nitrogen, were purified by passing through an activated basic alumina column directly into 20 ml scintillation vials, each equipped with a stir bar. To each was added 0.25 ml of a 4.2 M stock solution of 2-(2-pyridyl)-1,3-propane-bis(2,6-dimethyl)aniline zirconium dimethyl in toluene. Stock solutions of the appropriate activator were prepared as follows and added to the appropriate vial: 1.15 ml of 0.865M TIBA/heptane solution to example 13; 0.31 ml of a 3.5M MAO/toluene solution for example 14, 0.57 ml of a 1.73M MMAO/heptane solution for example 15, and 1.0 ml of 1.2 mM B(C 6 F 5 ) 3 , or PhN(Me) 2 H B(C 6 F 5 ) 4 , or Ph 3 C B(C 6 F 5 ) 4 toluene solution for 16-18, respectively. The mixtures were capped and allowed to stir overnight. Observations were noted. Workup of 17 and 18 constituted stripped off the remaining 1-hexene. SEC analysis was conducted in THF using a polystyrene standard. TABLE 2 umols Mw PDI Example Zr Activator ratio comments (SEC) (SEC) 13 1 TIBA 1000 no apparent reaction 14 1 MAO 1000 no apparent reaction 15 1 MMAO 1000 no apparent reaction 16 1 B(C6F5)3 1.2 no apparent reaction 17 1 PhN(Me)2H B(C6F5)4 1.2 solution viscous after overnight stirring 544,000 2.17 18 1 Ph3C (C6F5)4 1.2 solution most viscous after overnight stirring 691,000 1.99 All documents described herein are incorporated by reference herein, including any priority documents and/or testing procedures. As is apparent form the foregoing general description and the specific embodiments, while forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly it is not intended that the invention be limited thereby.

This invention relates to a composition of matter comprising the catalyst compound comprising a transition metal complexed with a facially coordinating tridentate bisamide ligand. The invention is also directed to a catalyst system or a supported catalyst system comprising this compound and an activator and to a process for using the catalyst system or supported catalyst system in a process for polymerizing olefin(s).

FIELD OF THE INVENTION [0001] The invention relates principally but not exclusively to Raman spectroscopy, in particular surface enhanced Raman spectroscopy (SERS). BACKGROUND OF THE INVENTION [0002] Raman spectroscopy is used for a variety of applications, most commonly to study vibrational quanta, such as vibrations in molecules or phonons in solids, although other quantised entities can also be studied. Raman spectroscopy can provide detailed information relating to the physical state of sample materials and can be used to distinguish various states of otherwise chemically identical molecules, such as various molecular isomers, from one another. [0003] Raman spectroscopy finds wide ranging use in numerous different industries. By way of example, Raman spectroscopy finds application in the pharmaceutical, chemical, bio-analysis, medical, materials science, art restoration, polymer, semiconductor, gemology, forensic, research, military, sensing and environmental monitoring fields. [0004] Although Raman spectroscopy is an extremely useful analytical tool, it does suffer from a number of disadvantages. The principal drawbacks associated with Raman spectroscopy arise because of the small scattering cross-section. Typically, only 10 −7 of the photons incident on the sample material will undergo Raman scattering. Hence, in order to detect Raman scattered photons, Raman spectrometers typically employ high power laser sources and high sensitivity detectors. Not only is the scattering cross-section small in an absolute sense, but it is small relative to Rayleigh scattering in which the scattered photon is of the same energy as the incident photon. This means that there are often problems related to separating out the small Raman signal from the large Rayleigh signal and the incident signal, especially when the Raman signal is close in energy to the incident signal. [0005] High power sources are not only both bulky and expensive, but at very high power the intensity of the optical radiation itself can destroy the sample material, thus placing an upper limit on the optical radiation source intensity. Similarly, high sensitivity detectors are often bulky and expensive, and even more so where forced cooling, such as with liquid nitrogen, is necessary. Additionally, detection is often a slow process as long integration periods are required to obtain a Raman spectrum signal having an acceptable signal-to-noise ratio (SNR). [0006] The problems associated with Raman spectrometry have been known long since C. V. Raman discovered the effect itself in 1928. Since that date, various techniques have been applied to improve the operation of Raman spectrometers. [0007] Certain of the techniques involve the use of metal surfaces to induce surface plasmon resonance (SPR) for more efficient coupling of energy into the sample material. One refinement of this technique involves placing sample material on or near a roughened surface. Such a surface can be formed by the deposition of metallic/dielectric particles, sometimes deposited in clusters [1-3]. The roughened surface is found to give rise to an enhanced Raman signal, and the technique of using the roughened surface to obtain a Raman spectrum is known as surface enhanced Raman spectroscopy (SERS). [0008] However, whilst SERS devices can lead to an improved SNR when compared to previous conventional Raman spectrometers, they still suffer to a lesser extent with various of the same disadvantages. For example, SERS devices are still not efficient enough to provide a Raman signal without fairly long detector integration times, and can still require the use of bulky and expensive detectors. Even at present, an acquisition time for a Raman spectrum of some five seconds is considered to be extremely good. SUMMARY OF THE INVENTION [0009] According to a first aspect of the invention, there is provided a spectrometer for obtaining a Raman spectrum from a sample material. The spectrometer comprises an optical source for generating optical radiation, a substrate for receiving the optical radiation, and a spectral analyser for analysing the Raman scattered radiation emerging from the substrate. The substrate comprises a metallic film that incorporates a plurality of voids of a predetermined size. These voids are suitable for confining surface plasmons. The surface plasmons couple energy from incident optical radiation to a sample material when the sample material is located proximal the substrate. The surface plasmons are also responsible for converting scattered energy emitted from the sample material into the Raman scattered radiation. The substrate may be incorporated into existing Raman spectrometers in order to improve their performance. [0010] The substrate provides an enhanced Raman signal. Therefore to obtain an acceptable SNR, less incident optical radiation or a lower sensitivity detector can be used, or both. In various embodiments, the spectral analyser makes use of detectors that do not need to be cooled, such as a photodiode array. Certain embodiments can make use of high efficiency compact optical source devices, such as a laser diode or laser diode array. By employing such detectors and arrays, a high efficiency, low-power, portable, and compact Raman spectrometer can be provided. Moreover, embodiments employing, for example, a laser diode array provide optical radiation that can be used to illuminate large area of substrate. In various such embodiments, it is not always necessary to focus the optical radiation, thereby further improving the compactness and reducing the cost of these spectrometer. [0011] Moreover, because of the enhanced Raman signal, input channel optics provided with the spectral analyser to collect Raman scattered radiation may be made to differ from optics used in conventional Raman spectrometers. In particular, various embodiments avoid the need to use a high numerical aperture lens system to collect Raman scattered radiation. This allows the collection optics to be spaced away from the substrate. Such spacing is particularly beneficial as it enables fluids containing sample material to be analysed to freely flow over the substrate without being impeded by the collection optics. The fluid may be liquid or gas. The input channel optics may comprise a fibre optic input channel oriented towards the substrate. As in various embodiments the direction of emerging Raman signal can be predicted, use of a fibre optic input channel can be used to cut down on any background signal from the optical source that reaches the spectral analyser. [0012] Further, since the signal is strong, alignment and focusing tolerances of the optical components are much relaxed so that, for example, the need to provide for adjustability of the optical components to allow signal optimisation before each experimental series can in some cases be dispensed with entirely. [0013] Furthermore, since the Raman signal is enhanced, a Raman spectrometer incorporating the substrate is able to acquire a Raman spectrum having an acceptable SNR using a reduced integration time. Not only does this enable faster processing of sample materials, but it also opens up the exciting possibility of using Raman spectroscopy to monitor processes in real-time, such as chemical reactions and catalysis processes. [0014] Although the applicants have for several years been involved in research relating to producing and investigating the optical properties of metallic films which include voids [4, 5, 6, 9], the fact that these films were capable of delivering huge SERS enhancement was not previously realised since their physical structure differs greatly from that of any surfaces previously used. [0015] However, when it was tried out, the results showed huge enhancements in the Raman signals. These initial experiments indicated that the Raman signal could be increased by a factor of between some 10 4 to 10 14 when compared to non-SERS apparatus. [0016] Moreover, experimental and theoretical investigations detailed below have indicated that the Raman signal can be increased by at least a factor of two when compared to conventional SERS apparatus by careful design of the voids to optimise them for particular wavelengths of incident optical energy. [0017] Additionally, the theoretical and experimental studies show that by careful design of the voids, the Raman signal can be concentrated to be emitted at a predetermined angular direction, thereby allowing appropriately positioned low NA collection optics to be used to collect the signal. [0018] Whilst the origins of the enhanced Raman signal are not completely understood, it is believed that it may be due to the effect of localised plasmons that form at the surfaces of the voids. It is thought that the localised plasmons increase the coupling efficiency between the incident optical radiation and any sample material located proximal the surface of the metallic film, and subsequently give rise to the dramatic enhancements in Raman signal strength that are seen by the applicant. [0019] In various embodiments, the voids have the shape of a truncated sphere. By controlling the diameter of the sphere and the thickness of the truncation, the emission direction of a particular wavelength of Raman signal can be tailored in a known and predictable manner detailed further below. Additionally, by providing part-spherical voids with truncation parallel to a surface of the substrate, the emission direction remains predictable and constant even if the substrate is rotated about an axis normal to the surface. Alignment of the substrate within the spectrometer is thereby facilitated. [0020] The size of the voids may be selected depending upon the wavelength of the optical radiation that is to be used with a particular sample material. Substrate responses may thus be tailored to suit a particular sample material. The voids may range from about a few nanometres to about many tens of microns in size. For example, the size of the voids may range from about 10 nm to 50 nm for working with deep ultraviolet radiation, to about tens of microns for working with mid-infrared radiation tuned to be resonant to molecular vibrational transitions. In other examples, a void may be provided with a diameter from about 100 nm to about 900 nm due to the ease of manufacturing voids of this size. For still further examples, the size of the voids may correspond substantially to the wavelength of visible optical radiation. Voids may be used with optical radiation that is selected so to be non-ionising and so as not to induce extraneous molecular vibrations for a particular sample material. This allows the optical radiation merely to probe the sample material without unduly influencing it. [0021] Certain embodiments include a substrate that is generally planar in shape and in which the voids are uniformly spaced over at least part of a planar surface of the substrate. Efficient use can thus be made of the surface, and a uniform signal for Raman spectra can be obtained from different parts of the substrate surface. [0022] Various embodiments incorporate a substrate that further comprises a waveguide structure for coupling the optical radiation to a sample material through the metallic film. Where such a waveguide structure is provided, the spectral analyser may also be configured to collect Raman scattered radiation that emerges from the waveguide. [0023] According to a second aspect of the invention, there is provided a method of obtaining a Raman spectrum from sample material. The method comprises introducing sample material into the spectrometer according to the first aspect of the invention proximal to the substrate, activating the optical source and operating the spectral analyser to provide the Raman spectrum of the sample material. [0024] The method may comprise a step of introducing sample material by flowing a fluid containing the sample material across the substrate in a region illuminated by the optical radiation. The substrate is particularly good for this because, besides being positionable away from any light collecting optics, it may be provided with a smooth surface. [0025] In various embodiments, the method comprises varying the electric potential of the metallic film of the substrate. Applying a electric potential to the metallic film allows the dynamics of the sample material proximal the surface of the voids to be monitored. Moreover, it can permit real-time surface reaction monitoring, enable chemical reactions to be initiated, enable the breakdown of various molecules to be monitored, and be used to provide information about how Raman spectra are modified by the presence of electric fields. [0026] According to a third aspect of the invention, there is provided a method of making a substrate having an enhanced efficiency of coupling optical energy to surface plasmons at a predetermined wavelength of optical radiation incident upon the substrate. The method comprises determining the size and shape of voids which when formed in a metallic film efficiently couple optical energy at the predetermined wavelength to surface plasmons that form in the voids, and forming a substrate comprising a metallic film that includes a plurality of voids of the determined size and shape. [0027] The size and shape of the voids determines whether optical radiation of a particular predetermined energy will couple into plasmons that form at the surface of the voids. Furthermore, the applicant has found that by modifying the size and shape of the voids and the incident direction of the optical radiation, both optical-to-plasmon and plasmon-to-optical energy couplings can be controlled as well as the orientation of optical radiation emitted from the metallic film. [0028] Voids may be formed in the metallic film that are uniformly spaced over a surface of the substrate. A waveguide structure may be formed in the substrate for coupling optical radiation from the substrate through the metallic film. [0029] In various embodiments, the voids are in the shape of a truncated spherical void. The size of these voids are determined in dependence upon the desired wavelength of the optical radiation. The diameter of the truncated spherical void may be chosen to be of the same order of magnitude as the predetermined wavelength of optical radiation. For example, the diameter of the truncated spherical void may be chosen to be about equal to the wavelength of optical radiation. In various examples, the diameter of the truncated sphere is from about 50 nm to about 10,000 nm, or about 100 nm to about 900 nm. The thickness of the truncated spherical void may be chosen to couple optical energy at the predetermined wavelength to zero-dimensional plasmons that form in the void. [0030] The substrate may be formed by depositing a template of ordered spherical particles on a substrate surface, and passing a predetermined amount of charge though a metallic ion containing solution that surrounds the template so as to deposit the metallic film on the substrate surface. [0031] The third aspect of the invention relates to how to apply the experimental and theoretical information obtained by the applicant so as to design and manufacture substrates having tailored emission characteristics. Through the applicant's investigations, the applicant has come to understand how to produce the metallic films necessary for efficient use in various applications or with various sample materials. Numerous applications for such substrates are envisaged. For example, applications are envisaged in spectrometry, such as Raman spectrometry, and in optical filtering. [0032] According to a fourth aspect of the invention, there is provided a substrate made according to the method of the third aspect of the invention. Such substrates may incorporate a metallic film that comprises one or more of the following materials: gold, platinum, silver, copper, palladium, cobalt and nickel. It will be appreciated that the metallic film may be made of any one of these elements alone or in combination with each other or other materials to form an alloy. Materials that have catalytic properties, inert properties, optically beneficial properties, etc. may be preferred depending upon the application of the substrate. For example, silver may be used to provide a high Raman enhancement signal in applications where it is unlikely to be placed in contact with oxidising materials that would otherwise degrade its optical performance. The substrates may be encapsulated. [0033] In various embodiments the substrate may be provided already with a sample material for analysis provided in the voids of the metallic film. In certain embodiments, the sample material is an organic material. Provision of substrates with sample materials is convenient for users, particularly where the sample materials have undesirable chemical or biological properties, such as high toxicity. [0034] According to a fifth aspect of the invention, there is provided an optical device incorporating the substrate according to the fourth aspect of the invention. A sixth aspect of the invention relates to the use of the optical device according to the fifth aspect of the invention. For example, such an optical device may be a filter device, an analysis device or a device other than a Raman spectrometer. BRIEF DESCRIPTION OF THE DRAWINGS [0035] For a better understanding of the invention and to show how the same may be carried into effect reference is now made by way of example to the accompanying drawings in which: [0036] FIG. 1 shows a conventional Raman spectrometer; [0037] FIG. 2 shows a first embodiment of a Raman spectrometer according to the present invention; [0038] FIG. 3 shows a second embodiment of a Raman spectrometer according to the present invention; [0039] FIG. 4 shows a third embodiment of a Raman spectrometer according to the present invention; [0040] FIG. 5 is a flow diagram illustrating a method of obtaining a Raman spectrum from a sample material according to an embodiment of the invention; [0041] FIG. 6 shows a Raman spectrum of benzenethiol obtained using the first embodiment of a Raman spectrometer according to the present invention; [0042] FIG. 7 shows a set of Raman spectra of pyridine obtained with different electric potentials applied in solution to the metallic film of the first embodiment of a Raman spectrometer according to the present invention; [0043] FIG. 8 shows modelled data indicating predicted Raman signal enhancement factors for substrates incorporating metallic films made using various metals in accordance with the present invention; [0044] FIG. 9 is a flow diagram illustrating a method of making a substrate having an enhanced efficiency of coupling optical energy to surface plasmons at a predetermined wavelength of optical radiation according to an embodiment of the present invention; [0045] FIG. 10A shows a schematic illustration of a plasmon formed in a void according to various embodiments of the present invention; [0046] FIG. 10B shows a schematic illustration of a void having a truncated spherical shape for use in various embodiments of the present invention; [0047] FIG. 10C shows a perspective view of a metallic film in a substrate according to an embodiment of the present invention; [0048] FIG. 10D shows a plan view of the metallic film of FIG. 10C taken using a scanning electron microscope (SEM); [0049] FIG. 11 schematically shows the first embodiment of a Raman spectrometer according to the present invention in one mode of operation; [0050] FIG. 12 schematically illustrates the process of surface enhanced Raman spectroscopy used for various embodiments of the present invention; [0051] FIG. 13A schematically shows plasmon field strength on a metallic sphere; [0052] FIGS. 13B to 13G schematically show plasmon field strengths in a perfect spherical void for plasmons of varying angular momentum; [0053] FIG. 14A shows a reflection spectrum for different thickness truncated spherical voids in a gold metallic film used in various embodiments of the present invention; [0054] FIG. 14B shows plasmon modes for different thickness truncated spherical voids in a gold metallic film used in various embodiments of the present invention; [0055] FIG. 15 shows data indicating how the reflectivity of a gold metallic film of varying thickness varies according to the wavelength of incident optical radiation and for different angles of incidence, polarisation and metallic film orientation; [0056] FIG. 16A is a schematic illustration of a plasmon formed in a void by coupling of optical radiation from a waveguide formed in a substrate for use in various embodiments of the present invention; [0057] FIG. 16B is a schematic illustration of a plasmon formed in a void decaying to generate optical radiation in the waveguide shown in FIG. 16A ; [0058] FIG. 17A is a schematic illustration of a combined void and metal sphere for enhancing Raman signal in various embodiments of the present invention; [0059] FIG. 17B is a schematic illustration of a microcavity formed by a void and a reflector for selectively enhancing Raman signal in various embodiments of the present invention; [0060] FIG. 17C is a schematic illustration of a void bounded by an overhanging layer for enhancing Raman signal in various embodiments of the present invention; [0061] FIG. 17D is a schematic illustration of a void bounded by an over-etched layer for enhancing Raman signal in various embodiments of the present invention; [0062] FIG. 18 is an optical device for filtering optical radiation incorporating a substrate according to an embodiment of the present invention; and [0063] FIG. 19 is a flow diagram illustrating a method of using the optical device of FIG. 18 . DETAILED DESCRIPTION [0064] FIG. 1 shows a conventional Raman spectrometer 100 . For example, the spectrometer 100 may comprise various elements of the in Via range of Raman microscopes available from Renishaw plc of Wotton-under-Edge, Gloucestershire, UK. The spectrometer 100 comprises an optical source 120 , a spectral analyser 180 and input channel optics 160 for collecting Raman scattered radiation 142 and directing it to the spectral analyser 180 . The optical source 120 generates a beam of optical radiation 122 which is filtered by a first filter 124 . The filtered optical radiation 122 is directed by beam splitter 126 on to a sample 140 . Raman scattered radiation 142 generated by the sample 140 is collected by input channel optics 160 for analysis by the spectral analyser 180 . [0065] The input channel optics 160 comprises a microscope objective lens 162 a second filter 164 and a lens 166 . The microscope objective lens 162 has a high numerical aperture (typically 0.4 or more) in order to gather as much Raman scattered radiation 142 as possible from the sample 140 . The second filter 164 is designed to block any reflected optical radiation 122 that is not Raman scattered. The lens 166 focuses the Raman scattered radiation 142 in to the spectral analyser 180 . [0066] The spectral analyser 180 comprises a spectrum separator 182 and a CCD detector 184 . The spectrum separator 182 spatially separates different frequencies of Raman scattered radiation 142 . A rotating grating (not shown) may be used to sweep different wavelengths of Raman scattered radiation 142 across an aperture placed in front of the CCD detector 184 . The CCD detector 184 is cooled in order to be able to detect low levels of Raman scattered radiation 142 . Other parallel or single channel detectors may be used. [0067] The microscope objective lens 162 needs to be placed close to the sample 140 in order to collect as much Raman scattered radiation 142 as possible. The microscope objective lens 162 collects Raman scattered radiation 142 from an area having a diameter of about Δ 1 . Typically, Δ 1 is less than 10 micrometers. Additionally, the microscope objective lens 162 needs to be placed close to the sample 140 . The microscope objective lens 162 and the sample 140 are separated by a distance L 1 which is typically less than 1 mm. [0068] FIG. 2 shows a Raman spectrometer 200 according to a first embodiment of the invention. The spectrometer 200 comprises a source/detector package 290 and a substrate 240 . The source/detector package 290 comprises an optical source 220 and a first filter 224 for filtering optical radiation 222 generated by the optical source 220 . The package 290 also includes input channel optics 260 and a spectral analyser 286 . [0069] The input channel optics 260 comprises a first lens 262 for gathering Raman scattered radiation 242 and a second filter 264 for rejecting any non-Raman scattered radiation. The input channel optics directs Raman scattered radiation to the spectral analyser 286 . [0070] The source/detector package 290 is configured to direct optical radiation 222 on to the surface of the substrate 240 and to collect Raman scattered radiation 242 that is generated by a sample that is placed proximal to the surface of the substrate 240 . The substrate 240 comprises a support layer 244 with a metallic film 246 formed thereon. The metallic film 246 comprises a plurality of voids 248 . The voids 248 generate and confine surface plasmons that couple energy from the optical radiation 222 to a sample material (not shown). The plasmons also convert scattered energy emitted from the sample material into Raman scattered radiation 242 . The plasmons give rise to a surface enhanced effect which increases significantly the amount of Raman scattered radiation 242 . This in turn means that the optical radiation 222 does not necessarily need to be tightly focused in order to generate a significant Raman signal. Additionally, it also allows use of a lens 262 which need not have a high numerical aperture. [0071] The focal spot size of the optical radiation 222 , Δ 2 , can be greater than 100 micrometers. This further enhances the Raman scattered radiation 242 since it enables a large number of sample material molecules to be illuminated at any one time. Moreover, as will be seen later on, careful design of the size and shape of the voids 248 enables the direction at which the Raman scattered radiation 242 emerges to be controlled and predicted so that appropriately positioned small solid angle collection optics is capable of collecting a high proportion of the Raman scattered signal. [0072] The optical source 220 can be a small laser diode having an output power of several tens of milliwatts. A laser diode array may also be used. The input channel lens 262 is separated from the substrate 240 by a distance L 2 . Since the lens 262 need not have a high numerical aperture it can be separated from the substrate 240 by distances of 1 cm or more. Preferably, the lens 262 (or an alternative optical radiation gathering aperture such as, for example, a fibre optic) will have a numerical aperture of less than 0.4. More preferably, the numerical aperture will be less than 0.1. This allows the Raman spectrometer 200 to be used to analyse fluids (liquids/gasses) flowing over the substrate 240 . [0073] The spectral analyser 286 comprises apparatus for spectral separation of the Raman scattered radiation 242 and a detector for measuring the Raman scattered radiation 242 . In this embodiment, the spectral analyser 286 comprises a fixed grating and an array of diodes (not shown) for detecting the spectral components of the Raman scattered radiation 242 . It is understood that conventional scanning spectrum separators may be used to detect Raman scattered radiation 242 . For example, a precision grating stage and optionally a detector from Renishaw plc's in Via Raman microscope range may be used. However, an advantage of the present embodiment is that the spectrometer 200 can be made to be ultra compact and portable. In addition reliability and detection speed are improved with respect to conventional spectrometers since it is not necessary to use a mechanically operated spectrum separator to sweep across the range of Raman scattered radiation wavelengths. [0074] FIG. 3 shows a Raman spectrometer 300 according to a second embodiment of the invention. The spectrometer 300 comprises an optical source 320 , a substrate 340 and a detector package 380 . [0075] The optical source 320 comprises a laser diode. The laser diode generates a beam of optical radiation 322 that is filtered by a first filter 324 to provide a monochromatic beam. The optical radiation 322 is coupled in to an optically transparent support layer 344 of the substrate 340 . A blazed grating is written in to the support layer 344 for coupling the optical radiation 322 from the support layer 344 in to a metallic film 346 formed on the support layer 344 . Optical radiation 322 excites plasmons in voids 348 that are formed in metallic film 346 . [0076] Sample material is placed in the voids 348 and excites Raman scattered radiation 342 in response to the plasmons generated by the optical radiation 322 . The Raman scattered radiation 342 is emitted from the metallic film 346 in a direction that depends upon the shape and size of the voids 348 . Raman scattered radiation 342 is captured by the detector package 380 and converted in to a Raman signal that represents the spectrum of the Raman scattered radiation 342 . Raman scattered radiation 342 is captured by a lens 362 which is separated from the substrate 340 by a distance L 3 . L 3 can be a distance greater than 1 cm. Raman scattered radiation collected by the lens 362 is filtered by a second filter 364 used to reject non-scattered light emerging from the substrate 340 . The filtered Raman scattered radiation is converted by a spectral analyser 386 in to a Raman signal. [0077] A spectral analyser 386 comprises a spectrum separator. In this case, the spectrum separator includes a fixed grating which separates the Raman scattered radiation 342 into various spectral components. The spectral components are angularly separated and impinge upon a diode array contained within the spectral analyser 386 . Each diode of the diode array is used to measure a spectral component of the Raman scattered radiation 342 . [0078] Electronic circuitry coupled to the diode array logs the spectrum for the Raman scattered radiation 342 . The electronic circuitry (not shown) can be coupled to a computer system for logging and manipulating the Raman spectrum data. Software may be provided to identify a particular type of substrate material in dependence upon the measured Raman spectrum. [0079] FIG. 4 shows a Raman spectrometer 400 according to a third embodiment of the invention. The Raman spectrometer 400 comprises an optical source 420 for generating optical radiation 422 . The optical radiation 422 is filtered by a first filter 424 and guided in to an optically transparent support layer 444 formed in a substrate 440 . The optical radiation 422 couples in to a metallic film 446 formed upon the support layer 444 over a distance of Δ 4 . The distance Δ 4 can be greater than 100 micrometers. [0080] Optical radiation 422 excites plasmons in voids 448 that are formed in the metallic film 446 . The plasmons couple energy to sample materials that are located near the voids 448 . The excited sample material gives rise to Raman scattered energy that couples via plasmons back in to the optically transparent support layer 444 . The support layer 444 acts as a waveguide that guides Raman scattered radiation 442 through the support layer 444 . [0081] Detector package 480 is provided to detect the Raman scattered radiation 442 that emerges from the support layer 444 . Detector package 480 comprises input channel optics 460 and a spectral analyser 486 . The input channel optics 460 comprises a lens 462 and a second filter 464 that is used to reject elastically scattered photons generated by the optical source 420 . The spectral analyser 486 comprises a fixed grating and a diode array. Each of the diodes in the diode array is used to detect a spectral component of the Raman scattered radiation 442 . [0082] Electronic circuitry (not shown) gathers data from each of the diodes in the diode array in order to reconstruct a Raman spectrum. The electronic circuitry can be configured to provide data relating to the Raman spectrum to a computer system for further analysis, identification or storage. For example, software running on such a computer system may be used to identify a particular sample material according to the measured Raman spectrum. [0083] FIG. 5 is a flow diagram illustrating method 500 of obtaining a Raman spectrum from a sample material. The method 500 can be used in conjunction with the Raman spectrometers described in connection with FIGS. 2 to 4 . [0084] Step 502 comprises flowing a fluid containing a sample material across the surface of a substrate that contains a plurality of voids. [0085] Step 504 is a step of activating an optical source to generate optical radiation for generating surface plasmons that are confined by the voids. The surface plasmons excite an enhanced Raman scattered radiation signal from the sample material. [0086] Step 506 is a step of operating a spectral analyser to determine a Raman spectrum of the Raman scattered radiation generated in response to the activation of the optical source by the sample material. Operation of the spectral analyser may entail rotating a grating and recording a signal from a single photodetector. Alternatively, a photo diode array may be used with a fixed spectral separator. [0087] Step 508 is a decision step. The decision step entails deciding whether further Raman spectra are required. This operation may for example be pre-programmed into a computer system which is operable to generate a plurality of Raman spectra and to control a Raman spectrometer. Where such a computer system determines that further spectra are to be obtained then the method moves on to step 510 . Otherwise the method is ended. [0088] Step 510 is a step at which the electric potential of the metallic film is varied. By varying the electric potential applied to the metallic film the physical properties of the sample material can be changed. Chemical reactions of an adsorbed species can be initiated at the substrate surface at a specific bias applied potential. Subsequently, variations in the adsorbed molecules can be tracked from a time sequence of their Raman spectra, obtained in real time using fast detection. [0089] Once the potential of the metallic film has been incrementally changed, the method moves again to step 506 so that a further Raman spectrum can be obtained for the sample material which will be subject to a modified electric potential. [0090] FIG. 6 shows Raman spectra 600 of a sample material containing benzenethiol obtained using the Raman spectrometer of FIG. 2 . The Figure shows a set of Raman spectra obtained from benzenethiol placed on a substrate having a gold metallic film incorporating a plurality of voids. The voids had a truncated spherical shape 600 nm in diameter. Various thicknesses of films were used to produce the curves A to H shown in this Figure: A—100 nm; B—160 nm; C—220 nm; D—280 nm; E—340 nm; F—460 nm; G—52 nm; and H—400 nm. The spectra indicate how by varying the properties of the voids large enhancements of the Raman cross section can be provided. For a flat gold surface no signal was observed at all. However, as the physical properties of the voids were changed a maximum intensity enhancement of some 10 4 was observed. Moreover, when the substrate was placed in a standard Raman spectrometer to obtain the results, the integration time for deriving each spectrum was only 50 milliseconds as compared to a standard conventional integration time of 5 seconds. [0091] FIG. 7 shows a set of Raman spectra of pyridine obtained with different electric potentials applied to the metallic film in solution. Raman spectra curves A-G are shown vertically offset with respect to each other for clarity. The Raman spectra 620 were obtained using the Raman spectrometer shown in FIG. 2 operated according to the method shown in FIG. 5 . The Raman spectra are enhanced by the effect of the structured substrate. In this case, by a factor of some 10 5 . As the electric potential applied to the metallic film is varied, it is noticeable that the spectra evolved to develop clearly defined sharp enhanced peaks. The main peaks in the curve when a potential of −1.0 volt is applied to the metallic film derive from the large number of molecules in solution (curve G). New peaks are observed to appear at critical potentials from 0.2 volts to −0.2 volts (curves A-C) which derive from just a few molecules adsorbed on the substrate, and which show the initiation of their chemical reaction directly observed as a change in molecular structure. [0092] FIGS. 8A and 8B show modelled data indicating predicted Raman signal enhancement factors for substrates incorporating metallic films having a plurality of voids. The predicted enhancement factors are calculated using the following equation [4]: [0000] ∈ i H l ( k m a )[ k i aJ l ( k i a )]′=∈ m J l ( k i a )[ k m aH l ( k m a]′   (1) [0000] where J l and H l are spherical Bessel and Hankel functions, and the prime denotes differentiation with respect to the argument (ka). ∈ i and ∈ m are the dielectric constants inside and outside the sphere, with k i =√{square root over (∈ i )}ω/c and k m =√{square root over (∈ m )}ω/c the corresponding wave numbers. We take ∈ i =1 and assuming that the external material is an “ideal” metal with ∈ m (ω)=1−ω p 2 /ω 2 , where ω p is the three dimensional plasmon frequency. Where frequencies are expressed in units of ω p , the solutions to Equation (1) for a sphere then depend only on the angular momentum quantum number 1, and the normalised sphere radius R=aω p /c. Symmetry requires that they are degenerate with respect to the azimuthal quantum number, m. [0093] Known tabulated complex dielectric constants for various metals were taken from the established literature. Equation (1) is the denominator for the rate of plasmon interactions. An estimate of the enhancement is produced by taking the inverse of the mismatch of this equation at each wavelength. This is an estimate because if Equation (1) is satisfied exactly for both real and imaginary parts, an infinite enhancement is predicted. In practice, the imaginary part of Equation (1) is never exactly satisfied, thus limiting the maximum enhancement. Use of such theoretically-derived estimates is relatively well respected by the scientific community. [0094] FIG. 8A shows predicted enhancement factors for a variety of different metals in which the angle and momentum of the plasmons is confined to the l=1 mode, where 1 is the angular momentum quantum number. [0095] FIG. 8 b shows predicted Raman enhancement factors for various metals in which voids confine plasmons to the l=2 mode. [0096] Both FIGS. 8A and 8B indicate that by carefully selecting the size of the voids to match the plasmon modes that form in the voids, enhanced coupling can be obtained beyond that already found from our experiments. Enhancement factors ranging from about 10 9 to about 10 15 are predicted from the theoretical studies. [0097] FIG. 9 is a flow diagram 700 illustrating a method of making a substrate having an enhanced efficiency of coupling optical energy to surface plasmons at a predetermined wavelength of optical radiation. The method relies upon using experimental and theoretical studies in order to optimise the performance of the substrate for any particular application by ensuring that voids provided in a metallic film give rise to strong plasmon generation for a particular desired wavelength of incident optical radiation. [0098] Step 702 entails selecting a wavelength and a metal type for a particular application. Where the substrate is to be used for Raman spectroscopy this will depend on the sample material that is to be used. For example, the sample material will often have known peaks in its Raman spectra that are generally stronger than others. In this case, the wavelength can thus be selected in order to excite the various Raman spectral features of most interest. Further, the metal type may be selected in order to provide for minimal reactivity with the sample material so as to ensure that the spectral properties derive solely from the sample material and not from a combination of the sample material and the metal used to form the substrate. [0099] Step 704 requires the matching of the wavelength selected for the sample material to the available void sizes that can be fabricated. In the technique used to manufacture the substrates according to this invention, a predetermined range of materials for forming the voids may be available. For example, the latex spheres used to manufacture the voids may only be available with a predetermined number and range of sizes. In order to form a matrix, one size that best matches the properties of the voids to the size of a void that can be made needs to be selected. For example, 700 nanometer diameter latex spheres are readily available and these can be used to form the voids. [0100] Step 706 involves ascertaining the thickness of the film needed to produce the desired optical response. Ascertaining the optimised thickness involves using the data shown in FIG. 14B in a normalised form to determine at what wavelength the localised plasmon resonance occurs for a particular void diameter. Since it is desirable to tune the exciting wavelength (and/or the SERS emission wavelength) to the localised plasmons, the film thickness may be selected using this technique. [0101] Step 708 involves calculating the charge that needs to be used to provide the metallic film having the optical characteristics desired for use in the particular application for which the substrate is designed. The applicants have calibrated the charge/unit area required to grow films of particular thickness with particular void size. However, this calculation can also be derived from first principles by associating the deposition of each metal with a certain number of electrons, and then calculating from the geometry of the voids how many metal atoms need to be deposited to occupy a certain thickness. [0102] Step 710 involves depositing latex spheres upon a substrate base to form a template. The technique of depositing the latex spheres and subsequently forming the metallic film on the substrate is described by the applicant in References 7, 10 and 11. The content of References 7, 10 and 11 are hereby incorporated herein by reference in their entirety. [0103] Step 712 involves introducing an electrolyte solution to surround the latex spheres that form the template. The electrolyte solution comprises ions of the metal type previously chosen to form a metallic film. The electrolyte solution permeates the template. [0104] At step 714 the electrolyte solution is electrolysed. A predetermined charge corresponding to that previously calculated is passed through the solution so that the metallic ions come out of solution and form the metallic film. The amount of charge determines the thickness of the metallic film that is deposited. [0105] Step 716 the latex sphere template is dissolved using an organic solvent. Dissolving of the latex sphere template leaves a metallic substrate including voids formed where the latex spheres previously existed. [0106] At step 718 the substrate is rinsed and dried in order to remove any traces of organic solvent and to provide a clean optically active surface for the metallic film. [0107] Optionally, following the manufacture of various substrates, they can be coated with various sample materials. This allows ready made substrates to be provided that can be used to analyse specific sample materials. Various organic materials may be provided with substrates that selectively bind to specific target molecules. For example, various oligonucleotides (fragments of DNA or RNA) which target specific DNA or RNA sequences for selective binding may be provided along with the substrates. [0108] FIG. 10A shows a schematic illustration of a plasmon energy states 752 , 754 formed in a void 748 . The void 748 is defined by a void surface 750 that is formed in a metallic film 746 . The voids 748 are shaped like part-spherical dishes of metal, and may be formed by electrochemically growing metal around a latex spherical former. The plasmons, which are electromagnetic modes, sit predominantly localised inside the spherical voids. Once the plasmons are excited, they decay either by radiating light or by transferring their energy to individual electrons in the surface 750 of the metal. [0109] Void surfaces 750 can be designed so as to obtain plasmon resonances at a particular angle of incidence, based on the physical parameters of a metallic film. Light of a particular wavelength couples to localised plasmons in the voids only at particular angles of incidence, which can be predicted. The coupling depends upon the thickness of the film, the diameter of the spherical void, the type of metal and the optical polarisation. [0110] FIG. 10B shows a schematic illustration of a void 748 having a truncated spherical shape. [0111] FIG. 10C shows a perspective view of a metallic film 746 including a plurality of voids 748 . The metallic film 746 can be incorporated in a substrate used in various embodiments of the invention. [0112] FIG. 10D shows a plan view of the metallic film 746 shown in FIG. 10C . The plan view was obtained by imaging the metallic film 746 using a scanning electron microscope. The diameter of the latex spheres that were used as a template to form the metallic film 746 was 700 nanometers. [0113] FIG. 11 schematically shows the Raman spectrometer 200 shown in FIG. 2 in one mode of operation. Optical radiation 722 is focussed through a first lens 762 onto a metallic film 746 . The metallic film 746 comprises a plurality of voids 748 . A fluid containing sample material flows over the metallic film 746 in the direction of the arrow 756 . Raman scattered radiation 742 is generated by the sample material. The Raman scattered radiation 742 is collected by a second lens 766 and subsequently analysed to derive the Raman spectrum. The emission of the surface enhanced Raman scattered light is at a different angle (θ 2 ) from the incident optical radiation (θ 1 ). The metallic film 746 can be engineered to provide a spectrometer in which it is not necessary to use high numerical aperture lenses. High numerical aperture lenses have a short working distance from the sample so as to capture light emerging from the sample from as many angles of emission as possible. Embodiments of the invention enable larger areas of the substrate to be examined simultaneously. This also increases the Raman signal that is observed because more photons are gathered. Furthermore, the Raman signal can be collected by optics that do not necessarily need to be placed close to the substrate surface. [0114] We have also shown that it is possible directly to observe real time changes in the chemistry of a sample material monolayer at the surface of the substrate. The substrate is placed in a solution containing sample material. The optical radiation passes through the solution and excites the sample material proximal to the substrate. By applying a potential to the solution by placing an electric potential on the substrate surface, molecules of sample material can be selectively electrochemically bound to the surface. Previously this was impractical because it was difficult to separate Raman scattered photons generated close to the surface from Raman scattered photons generated by molecules in solution remote from the surface. However, now since the surface molecules provide an enhanced Raman signal, Raman signal arising from sample material near the surface dominates, swamping any Raman signal arising from the body of the solution away from the surface. [0115] The invention therefore enables real time tracking of the progress of surface chemical reactions with the possibility of initiating the surface chemical reactions using laser pulses to excite sample material molecules via plasmons generated in the voids. The study of small numbers of molecules contained in a single void is also made possible by the enhanced Raman signal. In addition, our theoretical studies predicted that enhanced Raman signals are also derivable using a platinum-based substrate or a palladium-based substrate. This allows for the direct study of catalysis. [0116] FIG. 12 schematically illustrates the process of surface enhanced Raman spectroscopy. A photon of optical radiation 822 is incident on the metallic surface of the substrate 840 . The photon is incident on the metallic surface and gives rise to an electromagnetic disturbance in the form of a surface plasmon 852 . The surface plasmon 852 couples energy from the surface of the substrate 840 into sample material 858 . The plasmon energy couples with the energy of a phonon and converts into a further surface plasmon 854 . The plasmon 854 subsequently transfers energy to a Raman scattered photon 842 . [0117] A flat metal film does not efficiently convert incident light to plasmons or plasmons into emitted photons. The voids of the present invention, however, provide a controlled way of doing this by careful choice of the void size and shape. [0118] FIG. 13A schematically shows the plasmon field strength on a metallic sphere. The plasmon intensity on the surface of the sphere, and in its vicinity, is not high and decays only slowly. This means that plasmons generated on the surface of metallic spheres are not best suited to coupling energy from incident photons to any sample material that is placed near to the spheres in order to obtain an enhanced Raman signal. This is one reason why various roughened surfaces used in existing SERS devices are less effective. [0119] FIGS. 13B to 13G schematically show plasmon field strengths for a perfect spherical void. FIGS. 13C to 13G show how the plasmon field strengths appear as different modes depending on the angular momentum (l,m) of the plasmons that are excited. In each case it can be seen that at least one high field strength “hot spot” develops, as indicated by the light coloration regions shown within the voids. The high field strength enables energy to be coupled efficiently from incident optical radiation into sample materials that are placed in or near to the voids. [0120] FIG. 14A shows a reflection spectrum for different thickness voids as the thickness increases from near zero (thin) to about 700 nanometres (thick). Optical radiation is incident normal to the substrate surface. [0121] FIG. 14B shows plasmon modes for different thickness truncated spherical voids in a gold metallic film. The metallic film is the same as that used to provide the results shown in FIG. 14A . The plasmon modes have been extracted from the reflectivity data and their energies are compared with the energy of the plasmon on a flat gold film, i.e. a two-dimensional (2D) plasmon. The energies of the plasmons are also compared to those of a perfect spherical void, i.e. a zero-dimensional (0D) plasmon, for different angular momentum values l=1 and l=2. The localised plasmons (known as Mie modes, M 1 and M 2 ) start out with an energy equal to the 2D plasmons for a very shallow void. As the void gets thicker the energy drops, tending to the energy of a complete spherical void as the thickness approaches 700 nanometers. This is clearly seen in the data, which also shows the theoretical limits (2D and 0D), and the experimental data moving smoothly between them. This information is useful as it enables tailored metallic films to be produced that efficiently couple optical radiation of a particular wavelength into plasmons. [0122] Two additional modes are also seen in the data. These are known as a localised mode (L 3 ) and a Bragg mode (B 4 ). The localised mode (L 3 ) arises from 2D plasmons which move along the flat gold surface in between the voids. These can become localised in the gaps above the voids rather than on the gold in between the voids. It is expected that this mode will also give rise to an enhanced Raman signal. [0123] FIG. 15 shows data indicating how the reflectivity of a gold metallic film of varying thickness varies according to the wavelength of incident optical radiation and for different angles of incident polarisation and metallic film orientation. [0124] The substrate comprises metallic film made of gold. The metallic film was some 5 mm long. Voids formed in the metallic film varied in depth from zero (i.e. flat) at the zero mm position to 700 nanometers at the 5 mm position. The angle φ represents the angle of rotation of the sample about the surface normal. The surface has sixfold symmetry due to the hexagonal packing of the truncated spherical voids, and hence rotation was made between 0° and 30°. The angle θ corresponds to the angle of incidence of the optical radiation with respect to the surface of the substrate. Normal incidence is at 0° and measurements were made up to 27° incrementally in steps of 3°. Measurements were made for both the transverse electric and the transverse magnetic field. Further details of the optical set-up for obtaining these results can be found in Reference 8. [0125] The data indicates that whereas a perfectly spherical void has no angular dependence, truncated spherical voids give rise to localised plasmons that emit at different wavelengths in different directions. Each mode changes wavelength with angle in a way that can be predicted from a comparison with experimental results or from modified experimental results derived from theory. By truncating spherical voids a coupling together of dipole, quadruple, hexapole, etc. plasmons occurs which shifts the coupled plasmon modes to a higher energy and introduces angular dependence. The presence of a strong optical field for some of these modes on a metal boundary (for example (l, m)=(1, 0), (2, 0)) is what allows light impinging on the structure to couple strongly to the localised plasmons. This process can be modelled. (For example, see FIGS. 8A and 8B .) Moreover, using the applicant's data, it has been possible to produce substrates with voids that confine plasmons in both platinum and nickel. Both of these materials are interesting because of their catalytic properties. [0126] FIG. 16A shows a schematic illustration of a plasmon formed in a void by coupling of optical radiation from a waveguide formed in a substrate. The substrate 940 comprises a support layer 944 made using low refractive index glass. A high refractive index glass waveguide layer 947 is formed over the support layer 944 . Metallic film 946 incorporating a plurality of voids 948 is formed on the waveguide layer 947 . Optical radiation 922 is guided in the waveguide layer 947 . [0127] Where the voids 948 are in close proximity to the waveguide layer 947 optical radiation 922 can couple to the surface of the voids 948 . This coupling generates plasmons in a void 948 . The plasmons 952 are able to couple to sample material in the voids 948 and generate Raman scattered radiation 942 . Some of the Raman scattered radiation 942 couples back into the waveguide layer 947 and can be detected remote from the voids 948 . [0128] By combining the voids with an optical waveguide, either the input optical radiation or the output surface enhanced Raman signal, or both, can be injected/collected through the waveguide. In a first version, optical radiation is fed in through the optical waveguide and couples to the localised plasmons via evanescent coupling. The applicants have made such a device using a gold metallic film formed on an indium tin oxide (ITO) layer forming a waveguide over a glass support layer. [0129] FIGS. 17A to 17D show various schemes for improving the coupling of optical radiation into sample materials by modifying the geometry of the voids. In FIG. 17A a metal sphere 1049 is placed in the void 1048 . The metal sphere can be a gold, silver or copper sphere which is either solid or which has a dielectric core. Theoretical predictions indicate that use of such a sphere 1049 will give rise to a further enhanced Raman signal. [0130] FIG. 17B shows a mirror device 1149 placed above the void 1148 in order to form a microcavity. The microcavity enhances the Raman signal by selecting certain wavelength bands for amplification. By adjusting the length of the cavity, a particular set of wavelength bands can be amplified. The mirror device 1149 can be a dielectric Bragg reflector, or a thin metallic layer. Additionally, this geometry allows MEMS devices to be constructed in conjunction with the substrate. [0131] FIGS. 17C and 17D illustrate how electrochemically grown metal over-layers can be provided to produce a modified void. In FIG. 17C gold layer 1246 is provided with an overhanging silver layer 1249 . In FIG. 17D gold layer 1346 is provided with an over-etched silver layer 1349 . [0132] FIG. 18 shows an optical device 1400 for filtering optical radiation 1422 . The optical device 1400 comprises a substrate 1440 having a metallic film 1446 that includes a plurality of voids 1448 . The voids 1448 are designed to emit radiation of a particular wavelength at a particular angle. The optical device 1400 incorporates an optical aperture 1470 for blocking radiation which does not emerge from the substrate 1440 at a particular predetermined angle. Only radiation 1442 having a predetermined wavelength is able to emerge from the optical device 1400 . Thus, the optical device 1400 acts to filter the optical radiation 1422 . [0133] FIG. 19 is a flow diagram 1500 illustrating a method of using the optical device 1400 shown in FIG. 18 . [0134] Step 1502 requires the generation of radiation which is to be filtered. The optical radiation is provided to the optical device. [0135] Step 1504 entails reflecting of the radiation to be filtered from a substrate. The substrate disperses the radiation according to its wavelength. Radiation of a particular predetermined wavelength leaves a surface of the substrate at a particular predetermined angle. [0136] Step 1506 comprises collimating reflected radiation in order to remove the components of the incident radiation that do not emerge from the substrate at a particular predetermined angle. In one example, a pinhole or the like may be used to selectively block dispersed optical radiation. The angular dispersion and collimation of the radiation reflected from the substrate therefore enables the incident optical radiation to be filtered. [0137] Whilst the invention has been described in relation to various embodiments, many variations will be envisaged by the skilled person. For example, one possibility is to take an existing fibre optic probe and create a semitransparent substrate on top of this so that light can couple from the fibre optic onto the substrate and so that SERS photons can be detected in a direction back down the fibre optic. Such a probe can be fabricated as an immersible probe without a microscope objective or other lens. Moreover, those skilled in the art will realise that various features of different embodiments may be combined as necessary to obtain still further embodiments of the invention. REFERENCES [0000] 1. U.S. Pat. No. 6,242,264 2. US 2003/0157732 3. U.S. Pat. No. 5,376,556 4. “Confined Plasmons in Metallic Nanocavities,” S. Coyle, M. C. Netti, J. J. Baumberg, M. A. Ghanem, P. R. Birkin, P. N. Bartlett and D. M. Whittaker, Physical Review Letters , Volume 87, Number 17, 176801 (2001) 5. “Confined Plasmons in Gold Photonic Nanocavities,” M. C. Netti, S. Coyle, J. J. Baumberg, M. A. Ghanem, P. R. Birkin, P. N. Bartlett and D. M. Whittaker, Advanced Materials , Volume 13, Number 18, 1368 (2001) 6. “Spherical micromirrors from templated self-assembly: Polarization rotation on the micron scale,” S. Coyle, G. V. Prakash, J. J. Baumberg, M. Abdelsalem and P. N. Bartlett, Applied Physics Letters , Volume 83, Number 4, 767 (2003) 7. “Highly Ordered Macroporous Gold and Platinum Films Formed by Electrochemical Deposition through Templates Assembled from Submicron Diameter Monodisperse Polystyrene Spheres,” P. N. Bartlett, J. J. Baumberg, P. R. Birkin, M. A. Ghanem and M. C. Netti, Chemical Materials , Volume 14, Number 5, 2199 (2002) 8. Baumberg et al, Applied Physics Letters , Volume 76, 991 (2000) 9. WO-A1-02/42836 10. “Optical properties of nanostructured metal films,” P. N. Bartlett, J. J. Baumberg, S. Coyle and M. Abdelsalem, Faraday Discussions, 125/19 (2003) 11. “Preparation of Arrays of Isolated Spherical Cavities by Self-Assembly of Polystyrene Spheres on Self-Assembled Pre-patterned Macroporous Films,” M. Abdelsalem, P. N. Bartlett, J. J. Baumberg and S. Coyle, Advanced Materials , Volume 16, Number 1, 90 (2004)

It has been discovered that specially structured metallic films containing voids can deliver a hugely enhanced surface enhanced Raman spectroscopy (SERS) effect. By selecting a particular size and geometry for the voids, metallic films can be provided which have an enhanced photon-to-plasmon conversion efficiency for incident radiation of a predetermined wavelength. Controllable surface-enhanced absorption and emission characteristics may thus be provided, which are useful for SERS and potentially also other optical spectrometry and filtering applications. With such a large Raman signal, the invention enables fast, compact and inexpensive Raman spectrometers to be provided opening up many new application possibilities.

CROSS-REFERENCE TO RELATED APPLICATION The present patent application is related to co-pending and commonly owned The present patent application is related to co-pending and commonly owned U.S. patent application Ser. No. 10/380,581, entitled “Pitch Quantization For Distributed Speech Recognition”, filed on even date with the present patent application, the entire teachings of which being hereby incorporated by reference. FIELD OF THE INVENTION The present invention generally relates to the field of distributed speech recognition systems, and more particularly relates to distributed speech recognition for narrow bandwidth communications and wireless communications. BACKGROUND OF THE INVENTION With the advent of pagers and mobile phones the wireless service industry has grown into a multi-billion dollar industry. The bulk of the revenues for Wireless Service Providers (WSPs) originate from subscriptions. As such, a WSP's ability to run a successful network is dependent on the quality of service provided to subscribers over a network having a limited bandwidth. To this end, WSPs are constantly looking for ways to mitigate the amount of information that is transmitted over the network while maintaining a high quality of service to subscribers. Recently, speech recognition has enjoyed success in the wireless service industry. Speech recognition is used for a variety of applications and services. For example, a wireless service subscriber can be provided with a speed-dial feature whereby the subscriber speaks the name of a recipient of a call into the wireless device. The recipient's name is recognized using speech recognition and a call is initiated between the subscriber and the recipient. In another example, caller information (411) can utilize speech recognition to recognize the name of a recipient to whom a subscriber is attempting to place a call. As speech recognition gains acceptance in the wireless community, Distributed Speech Recognition (DSR) has arisen as an emerging technology. DSR refers to a framework in which the feature extraction and the pattern recognition portions of a speech recognition system are distributed. That is, the feature extraction and the pattern recognition portions of the speech recognition system are performed by two different processing units at two different locations. Specifically, the feature extraction process is performed on the front-end, i.e., the wireless device, and the pattern recognition process is performed on the back-end, i.e., by the wireless service provider. DSR enhances speech recognition for more complicated tasks such as automated airline booking with spoken flight information or brokerage transactions with similar features. The European Telecommunications Standards Institute (ETSI) promulgates a set of standards for DSR. The ETSI DSR standards ES 201 108 (April 2000) and ES 202 050 (July 2002) define the feature extraction and compression algorithms at the front-end. These standards, however, do not incorporate speech reconstruction at the back-end, which may be important in some applications. As a result, new Work Items WI-030 and WI-034 have been released by ETSI to extend the above standards (ES 201 108 and ES 202 050, respectively) to include speech reconstruction at the back-end as well as tonal language recognition. In the current DSR standards, the features that are extracted, compressed, and transmitted to the back-end are 13 Mel Frequency Cepstral Coefficients (MFCC), C0-C12, and the logarithm of the frame-energy, log-E. These features are updated every 10 ms or 100 times per second. In the proposals for the extended standards (i.e., in response to the Work Items described above), pitch and class (or voicing) information are also derived for each frame and transmitted in addition to the MFCC's and log-E. This increases the amount of information that is transmitted by the wireless device over the network and consumes additional bandwidth. Thus, it is desirable that the representation of class and pitch information be as compact as possible in order to keep the bit rate low. In speech coders, the normal practice has been to quantize the pitch information and the class information separately. In some coders, “unvoiced” class is represented by a “zero pitch value”, e.g., the Mixed Excitation Linear Predictive (MELP) coder, which is the U.S. Federal Standard at 2400 bps. Unfortunately, the multiple types of classes proposed for the extended standards require increased amount of information to represent, and increased bandwidth to transmit, the class information. Therefore a need exists to overcome the problems with the prior art as discussed above. SUMMARY OF THE INVENTION Briefly, in accordance with the present invention, disclosed is a system, method and computer readable medium for quantizing class information and pitch information of audio. In an embodiment of the present invention, the method on an information processing system includes receiving audio and capturing a frame of the audio. The method further includes determining a pitch of the frame and calculating a codeword representing the pitch of the frame, wherein a first codeword value indicates an indefinite pitch. The method further includes determining a class of the frame, wherein the class is any one of at least two classes indicating an indefinite pitch and at least one class indicating a definite pitch. The method further includes calculating a codeword representing the class of the frame, wherein the codeword length is the maximum of the minimum number of bits required to represent the at least two classes indicating an indefinite pitch and the minimum number of bits required to represent the at least one class indicating a definite pitch. The pitch and the class of the frame are represented by the two codewords. In another embodiment of the present invention, an information processing system for quantizing class information and pitch information of audio, includes a microphone for receiving audio and capturing a frame of the audio. The information processing system further includes a digital signal processor for determining a pitch of the frame and calculating a codeword representing the pitch of the frame, wherein a first codeword value indicates an indefinite pitch. The digital signal processor further determines a class of the frame, wherein the class is any one of at least two classes indicating an indefinite pitch and at least one class indicating a definite pitch. The digital signal processor further calculates a codeword representing the class of the frame, wherein the codeword length is the maximum of the minimum number of bits required to represent the at least two classes indicating an indefinite pitch and the minimum number of bits required to represent the at least one class indicating a definite pitch. The pitch and the class of the frame are represented by the two codewords. The preferred embodiments of the present invention are advantageous because they serve to decrease the amount of bits used to transmit audio information over a communications network. This is beneficial because communications networks possess limited bandwidth. The bit savings are translated into making more bandwidth available for current or additional subscribers. Thus, the present invention provides both an improvement in network performance and an increase in communications quality. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a network for distributed speech recognition according to a preferred embodiment of the present invention. FIG. 2 is a detailed block diagram of a wireless communication system for distributed speech recognition according to a preferred embodiment of the present invention. FIG. 3 is a block diagram illustrating a wireless device for a wireless communication system according to a preferred embodiment of the present invention. FIG. 4 is a block diagram illustrating data exchange of a wireless device with the wireless service provider. FIG. 5 is an operational flow diagram showing the overall distributed speech recognition process according to a preferred embodiment of the present invention. FIG. 6 is an operational flow diagram showing a class and pitch quantization process according to a preferred embodiment of the present invention. FIG. 7 is a block diagram illustrating the conventional bit allocations for the class and pitch quantization process. FIG. 8 is a block diagram illustrating the bit allocations for the class and pitch quantization process according to a preferred embodiment of the present invention. FIGS. 9A , 9 B and 9 C are an operational flow diagram showing another pitch quantization process according to a preferred embodiment of the present invention. FIG. 10 is a block diagram of an information processing system useful for implementing a preferred embodiment of the present invention. DETAILED DESCRIPTION The present invention, according to a preferred embodiment, advantageously overcomes problems with the prior art by effectively reducing the number of bits used in class quantization, as will be discussed in detail below. I. Overview FIG. 1 is a block diagram illustrating a network for Distributed Speech Recognition (DSR) according to a preferred embodiment of the present invention. FIG. 1 shows a network server or wireless service provider 102 operating on a network 104 , which connects the server/wireless service provider 102 with clients 106 and 108 . In one embodiment of the present invention, FIG. 1 represents a network computer system, which includes a server 102 , a network 104 and client computers 106 through 108 . In a first embodiment, the network 104 is a circuit switched network, such as the Public Service Telephone Network (PSTN). Alternatively, the network 104 is a packet switched network. The packet switched network is a wide area network (WAN), such as the global Internet, a private WAN, a local area network (LAN), a telecommunications network or any combination of the above-mentioned networks. In another alternative, the network 104 is a wired network, a wireless network, a broadcast network or a point-to-point network. In the first embodiment, the server 102 and the computer clients 106 and 108 comprise one or more Personal Computers (PCs) (e.g., IBM or compatible PC workstations running the Microsoft Windows 95/98/2000/ME/CE/NT/XP operating system, Macintosh computers running the Mac OS operating system, PCs running the LINUX operating system or equivalent), or any other computer processing devices. Alternatively, the server 102 and the computer clients 106 and 108 include one or more server systems (e.g., SUN Ultra workstations running the SunOS or AIX operating system, IBM RS/6000 workstations and servers running the AIX operating system or servers running the LINUX operating system). In another embodiment of the present invention, FIG. 1 represents a wireless communication system, which includes a wireless service provider 102 , a wireless network 104 and wireless devices 106 through 108 . The wireless service provider 102 is a first-generation analog mobile phone service, a second-generation digital mobile phone service or a third-generation Internet-capable mobile phone service. In this embodiment, the wireless network 104 is a mobile phone network, a mobile text messaging device network, a pager network, or the like. Further, the communications standard of the wireless network 104 of FIG. 1 is Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), Frequency Division Multiple Access (FDMA) or the like. The wireless network 104 supports any number of wireless devices 106 through 108 , which are mobile phones, text messaging devices, handheld computers, pagers, beepers, or the like. In this embodiment, the wireless service provider 102 includes a server, which comprises one or more Personal Computers (PCs) (e.g., IBM or compatible PC workstations running the Microsoft Windows 95/98/2000/ME/CE/NT/XP operating system, Macintosh computers running the Mac OS operating system, PCs running the LINUX operating system or equivalent), or any other computer processing devices. In another embodiment of the present invention, the server of wireless service provider 102 is one or more server systems (e.g., SUN Ultra workstations running the SunOS or AIX operating system, IBM RS/6000 workstations and servers running the AIX operating system or servers running the LINUX operating system). As explained above, DSR refers to a framework in which the feature extraction and the pattern recognition portions of a speech recognition system are distributed. That is, the feature extraction and the pattern recognition portions of the speech recognition system are performed by two different processing units at two different locations. Specifically, the feature extraction process is performed by the front-end, e.g., the wireless devices 106 and 108 , and the pattern recognition process is performed by the back-end, e.g., by a server of the wireless service provider 102 . The feature extraction process, as performed on the front-end by the wireless devices 106 and 108 , is described in greater detail below. FIG. 2 is a detailed block diagram of a wireless communication system for DSR according to a preferred embodiment of the present invention. FIG. 2 is a more detailed block diagram of the wireless communication system described with reference to FIG. 1 above. The wireless communication system of FIG. 2 includes a controller 201 coupled to base stations 202 , 203 , and 204 . In addition, the wireless communication system of FIG. 2 is interfaced to an external network through a telephone interface 206 . The base stations 202 , 203 , and 204 individually support portions of a geographic coverage area containing subscriber units or transceivers (i.e., wireless devices) 106 and 108 (see FIG. 1 ). The wireless devices 106 and 108 interface with the base stations 202 , 203 , and 204 using a communication protocol, such as CDMA, FDMA, CDMA, GPRS and GSM. The geographic coverage area of the wireless communication system of FIG. 2 is divided into regions or cells, which are individually serviced by the base stations 202 , 203 , and 204 (also referred to herein as cell servers). A wireless device operating within the wireless communication system selects a particular cell server as its primary interface for receive and transmit operations within the system. For example, wireless device 106 has cell server 202 as its primary cell server, and wireless device 108 has cell server 204 as its primary cell server. Preferably, a wireless device selects a cell server that provides the best communication interface into the wireless communication system. Ordinarily, this will depend on the signal quality of communication signals between a wireless device and a particular cell server. As a wireless device moves between various geographic locations in the coverage area, a hand-off or hand-over may be necessary to another cell server, which will then function as the primary cell server. A wireless device monitors communication signals from base stations servicing neighboring cells to determine the most appropriate new server for hand-off purposes. Besides monitoring the quality of a transmitted signal from a neighboring cell server, the wireless device also monitors the transmitted color code information associated with the transmitted signal to quickly identify which neighbor cell server is the source of the transmitted signal. FIG. 3 is a block diagram illustrating a wireless device for a wireless communication system according to a preferred embodiment of the present invention. FIG. 3 is a more detailed block diagram of a wireless device described with reference to FIGS. 1 and 2 above. FIG. 3 shows a wireless device 106 , such as shown in FIG. 1 . In one embodiment of the present invention, the wireless device 106 is a two-way radio capable of receiving and transmitting radio frequency signals over a communication channel under a communications protocol such as CDMA, FDMA, CDMA, GPRS or GSM. The wireless device 106 operates under the control of a controller 302 which switches the wireless device 106 between receive and transmit modes. In receive mode, the controller 302 couples an antenna 316 through a transmit/receive switch 314 to a receiver 304 . The receiver 304 decodes the received signals and provides those decoded signals to the controller 302 . In transmit mode, the controller 302 couples the antenna 316 , through the switch 314 , to a transmitter 312 . The controller 302 operates the transmitter and receiver according to instructions stored in memory 310 . The stored instructions include a neighbor cell measurement scheduling algorithm. Memory 310 is Flash memory, other non-volatile memory, random access memory (RAM), dynamic random access memory (DRAM) or the like. A timer module 311 provides timing information to the controller 302 to keep track of timed events. Further, the controller 302 can utilize the time information from the timer module 311 to keep track of scheduling for neighbor cell server transmissions and transmitted color code information. When a neighbor cell measurement is scheduled, the receiver 304 , under the control of the controller 302 , monitors neighbor cell servers and receives a “received signal quality indicator” (RSQI). RSQI circuit 308 generates RSQI signals representing the signal quality of the signals transmitted by each monitored cell server. Each RSQI signal is converted to digital information by an analog-to-digital converter 306 and provided as input to the controller 302 . Using the color code information and the associated received signal quality indicator, the wireless device 106 determines the most appropriate neighbor cell server to use as a primary cell server when hand-off is necessary. Processor 320 in FIG. 3 performs various functions such as the functions attributed to distributed speech recognition, described in greater detail below. In various embodiments of the present invention, the processor 320 in FIG. 3 is a single processor or more than one processor for performing the tasks described above. II. Distributed Speech Recognition FIG. 4 is a block diagram illustrating data exchange of a wireless device 106 with the wireless service provider 102 . FIG. 4 is a more detailed block diagram of a wireless device 106 described with reference to FIGS. 1 and 2 above. Some of the functions that are performed at the wireless device 106 are also shown. FIG. 4 shows a wireless device 106 and the wireless network 104 , such as shown in FIG. 1 . Also shown are the processor 320 and the transmitter 312 of the wireless device 106 , as shown in FIG. 3 . In one embodiment of the present invention, the wireless device 106 also includes a microphone 404 for receiving audio 402 . The received audio 402 is then processed by the processor 320 . Among the processes performed by processor 320 , the class and pitch of a frame of audio 402 are quantized by the processor 320 . The class and pitch of a frame of audio 402 is embodied in at least one codeword that is included in a packet 406 . The packet 406 is then transmitted by the transmitter 312 via the network 104 to a server or wireless service provider 102 . The processes of quantizing the class and pitch of a frame of audio 402 and generating at least one codeword are described in greater detail below. FIG. 5 is an operational flow diagram showing the overall distributed speech recognition process according to a preferred embodiment of the present invention. The operational flow diagram of FIG. 5 depicts the process, on a client 106 , of performing feature extraction of incoming audio and the process, at the server or wireless service provider 102 , of performing pattern recognition. The operational flow diagram of FIG. 5 begins with step 502 and flows directly to step 504 . In step 504 , the client 106 receives audio for transmission to the server 102 . In an embodiment where the system of FIG. 1 represents a wireless network, such as described in FIG. 2 , in step 504 the wireless device 106 receives audio 404 (see FIG. 4 ) via a microphone 404 . Next, in step 506 , the client 106 , proceeds to perform feature extraction on the audio that was received. Feature extraction includes the quantization of pitch and class values for one frame. Feature extraction is described in greater detail below. In the wireless network embodiment, in step 506 the processor 320 (see FIG. 3 ) of wireless device 106 proceeds to perform feature extraction on the audio 402 . In step 508 , the client 106 generates packet data including the extracted features for transmission to the server 102 . Data packet generation is described in greater detail below. In the wireless network embodiment, in step 508 the wireless device 106 generates data packet 406 including the extracted features. Next, in step 510 , the client 106 , proceeds to transmit the data packet to the server 102 . In the wireless network embodiment, in step 510 the transmitter 312 of wireless device 106 proceeds to transmit the data packet 406 to the wireless network provider or server 102 via wireless network 104 . In step 512 , the server 102 receives the packet data sent by client 106 and, in step 514 , the server 102 proceeds to reconstruct the audio based on the packet data. In step 516 , the server 102 performs speech recognition based on the packet data received from the client 106 . In the wireless network embodiment, in step 512 , the wireless service provider or server 102 receives the data packet 406 sent by wireless device 106 and, in step 514 , the wireless service provider or server 102 proceeds to reconstruct the audio based on the data packet 406 . In step 516 , the wireless service provider or server 102 performs speech recognition based on the data packet 406 received from the wireless device 106 . In step 518 , the operational flow of FIG. 5 stops. III. Data Packet Creation A. First Quantization Scheme In the proposals for the extended DSR standards (in response to Work Items WI- 030 and WI- 034 ), the class (or voicing) information for a frame can take four possible values: 1) non-speech, i.e., silence or background noise, 2) unvoiced, 3) mixed voiced, and 4) fully voiced. These four values can be generally divided into two categories: not voiced (including the non-speech and unvoiced classes) and voiced (including the mixed voiced and fully voiced classes). To quantize class information for one frame, 2 bits are normally needed since there are four class values to represent and 2 bits can represent four values. The pitch information for a frame can take any value ranging from about 19 to about 140 samples. To quantize pitch information for one frame, e.g., as integer values, 7 bits are normally needed since there are 122 pitch values to represent and 7 bits can represent 128 values. In one preferred embodiment of the present invention, by combining the class information and the pitch information, one bit per frame can be saved as follows. One of the 7-bit pitch codewords (the all-zero codeword, for example) is used to indicate that the class is not voiced (i.e., either non-speech or unvoiced). The remaining 127 non-zero 7-bit pitch codewords are used to represent different pitch values as well as the information that the class is voiced (i.e., either mixed-voiced or fully-voiced). That is, one of the 7-bit pitch codewords indicates that the class is not voiced while the remaining codewords indicate that the class is voiced. Consequently, one class bit is now sufficient to remove the ambiguity among the two not voiced classes (i.e., between non-speech and unvoiced classes) and among the two voiced classes (i.e., between mixed-voiced and fully-voiced classes). The table below shows one example of 7-bit pitch codeword values and 1-bit codeword values used to indicate pitch and class information, as described above. Class Type 7-bit Pitch Codeword 1-bit Class Codeword Non-speech all-zero 0 Unvoiced all-zero 1 Mixed-voiced non-zero 0 Fully-voiced non-zero 1 Thus, in summary, according to the present example, the total number of bits used to represent the class and pitch information is 8 bits. This is opposed to the 9 bits that would have been necessary to represent the class and pitch information, if the class and pitch information had been quantized separately (i.e., 7-bits for pitch and 2-bits for class; see above). The penalty incurred for such a scheme is that one out of the 128 pitch codewords has been used to indicate class information. Because of the relative unimportance of one codeword, this has very little (and insignificant) impact on the accuracy of pitch quantization. FIG. 6 is an operational flow diagram showing a class and pitch quantization process according to a preferred embodiment of the present invention. The operational flow diagram of FIG. 6 depicts the process, on a client 106 , of calculating pitch and class information and generating a data packet representing the same. FIG. 6 describes in more detail the steps 506 and 508 of FIG. 5 . The operational flow diagram of FIG. 6 begins with step 602 and flows directly to step 604 . In step 604 , the client 106 calculates the pitch value of the audio that was received. In the wireless network exemplary embodiment, in step 604 , the wireless device 106 (more specifically, the processor 320 of wireless device 106 ) calculates the pitch value of the audio 402 that was received via microphone 404 . In step 606 , the client 106 performs pitch quantization based on the pitch value of the audio. In one example, 7-bit pitch quantization is performed, as described above. In the wireless network embodiment, in step 606 , the wireless device 106 performs pitch quantization based on the pitch value of the audio 402 . In step 608 , the client 106 performs class calculation of the audio. In step 610 , the client 106 determines whether the class that was calculated in step 608 is of the not voiced category, i.e., either non-speech class or unvoiced class. If the result of the determination of step 610 is positive, then control flows to step 612 . If the result of the determination of step 610 is negative, then control flows to step 616 . In step 612 , the client 106 sets a pitch codeword to a predefined pitch codeword indicating a not voiced class category (i.e., non-speech class or unvoiced class) frame. In one example, the client 106 sets a 7-bit pitch codeword to all zeroes—the predefined pitch codeword indicating a non-speech class or unvoiced class frame. In step 614 , the client 106 sets a class codeword to indicate the class of a not voiced class category (i.e., either non-speech class or unvoiced class) frame. In one example, the client 106 sets a 1-bit class codeword indicating either non-speech class or unvoiced class. In step 616 , the client 106 sets a pitch codeword to the pitch value generated for the pitch quantization performed in step 604 . In one example, the client 106 sets a 7-bit pitch codeword to the pitch value generated for the pitch quantization performed in step 604 . In step 618 , the client 106 sets a class codeword to indicate the class of a voiced class category (i.e., either mixed voiced or fully voiced) frame. In one example, the client 106 sets a 1-bit class codeword indicating either mixed voiced class or fully voiced class. In step 620 , the operational flow of FIG. 6 stops. FIG. 7 is a block diagram illustrating the conventional bit allocations for a class and pitch quantization process. FIG. 7 shows that seven bits represent pitch quantization 702 . Thus, 128 possible values are used to represent a pitch period data of one frame of audio. FIG. 7 also shows that two bits represent class quantization 704 . Thus, four possible values are used to represent the class of one frame of audio. Four classes are defined: non-speech, unvoiced, mixed voiced and fully voiced. Therefore, according to FIG. 7 , a total of nine bits are used to represent pitch and class quantization values for one frame of audio. FIG. 8 is a block diagram illustrating the bit allocations for the class and pitch quantization process according to a preferred embodiment of the present invention. FIG. 8 shows the bit allocations for class and pitch quantization according to the present invention. FIG. 8 shows that seven bits represent pitch quantization 802 . However, of the 128 possible values available with the seven bits, only 127 values are used to represent pitch period data of one frame of audio. The remaining one value is used to indicate class information, specifically, the not voiced class category (i.e., non-speech class or unvoiced class). Preferably, the one value of 802 used to indicate class category is all zeroes and this value indicates a not voiced class category frame (i.e., non-speech class or unvoiced class). The other 127 values of 802 are used to indicate the pitch value of a voiced category frame (i.e., mixed voiced class or fully voiced class). FIG. 8 also shows that one bit represents class quantization 804 . This is a significant advantage of the present invention. Thus, two possible values, or codewords, are used to further represent the class of one frame of audio. The two possible values are used to differentiate among the not voiced class category (i.e., non-speech class or unvoiced class) and among the voiced category frame (i.e., mixed voiced class or fully voiced class). Preferably, a zero value of 804 is used to indicate a non-speech class if 802 is all zeroes, a zero value of 804 is used to indicate a mixed voice class if 802 is not all zeroes, a value of one of 804 is used to indicate an unvoiced class if 802 is all zeroes, and a value of one of 804 is used to indicate a fully voiced class if 802 is not all zeroes (see table above). Therefore, according to FIG. 8 , a total of eight bits are used to represent pitch and class quantization values for one frame of audio. B. Second Quantization Scheme In the proposals for the extended DSR standards, the pitch period is estimated for each frame and is updated every 10 ms (or 100 times per second). The estimated pitch period can take fractional values and ranges from about 19 to about 140 samples at an 8 kHz sampling rate. Therefore, the estimated pitch frequency ranges from about 57 Hz to about 420 Hz. When performing the pitch quantization process, it is desirable to achieve accuracy, i.e., low quantization error, a low bit rate, and robustness against channel errors. In a preferred embodiment of the present invention, all even-numbered frames (starting with the first frame numbered zero) are quantized using 7 bits and all odd-numbered frames are quantized using 5 bits. Considered as frame-pairs, the first frame in a frame-pair is quantized using 7 bits and the second frame in a frame-pair is quantized using 5 bits. Thus the average number of bits per frame is six. This corresponds to a bit rate of 600 bps due to pitch quantization alone. An absolute quantization scheme is used for the even-numbered frames. Out of the 128 codewords available, one codeword (i.e., the all-zero codeword) is used for transmitting not voiced category class information, i.e., to indicate that the frame is non-speech or unvoiced. The remaining 127 codewords are used for quantization of the pitch period. This scheme is described in greater detail above. The pitch range from about 19 to about 140 samples is equally divided (in the logarithmic domain) into 127 regions and the midpoints of these regions are chosen as the reconstruction levels. For any given pitch value, the corresponding quantized pitch value is chosen as the nearest reconstruction level in the linear domain. The 127 codewords are assigned one-to-one to the 127 reconstruction levels. The maximum quantization error with this quantizer design is about 0.8%. For the odd-numbered frames, a differential quantization scheme is used a majority of the time. However, under certain situations (as shown in the table below), an absolute quantization scheme is also used. For the differential quantization scheme, a reference has to be selected so that the difference between the current frame's pitch period value and the reference value (or more appropriately, the ratio of the two values) can be quantized. Although the quantized pitch period of the previous frame provides the best possible reference, this frame may not always be a voiced class category (i.e., either mixed voiced or fully voiced). Therefore, the quantized pitch period value of one of the preceding three frames is selected as the reference. That is, the differential quantization of the second frame of a frame-pair is performed using the quantized pitch period value of the first frame of the frame-pair or either of the two quantized pitch period values of the previous frame-pair as the reference. At the server side, it is important to limit the propagation of errors due to an error in one of the decoded pitch period values. For this purpose, we identify each quantized pitch value at the client side as being either reliable (R) or unreliable (U) to serve as a reference. Each absolutely quantized pitch value is regarded as reliable. Each differentially quantized pitch value is considered reliable if the reference used for its quantization is the quantized pitch period value of the first frame of the same frame-pair. Since the pitch period values of neighboring frames are generally close to each other, pitch period values near the reference value are finely quantized and pitch period values farther away from the reference are coarsely quantized. The quantization levels chosen for differential quantization depend on which of the three preceding quantized pitch values has been chosen as the reference as well as the reference value. The table below illustrates how the pitch period values of odd-numbered frames are quantized. P(−2) P(−1) P(0) Action Taken 0 0 0 Absolute Quantization 0 1U 0 Absolute Quantization * * 1 Differential Quantization: Reference P(0) * 1R 0 Differential Quantization: Reference P(−1) 1 0 0 Differential Quantization Reference P(−2) 1 1U 0 Differential Quantization Reference P(−2) In the above table, the value to be quantized is P( 1 ), the pitch period value of the second frame of a frame pair. The reference value is the quantized pitch period value of one of the three preceding frames, i.e., P( 0 ), the quantized pitch period value of the first frame of the same frame-pair, P(− 1 ), the quantized pitch period value of the second frame of the previous frame-pair, and P(− 2 ), the quantized pitch period value of the first frame of the previous frame-pair. In the table, a value of “0” indicates that the corresponding frame is a not voiced category class (i.e., non-speech class or unvoiced class). A value of “1” indicates that the corresponding frame is a voiced class category (i.e., mixed-voiced class or fully-voiced class) and its quantized pitch period value can be used as a reference. For the differentially quantized P(− 1 ), we also have “ 1 R” and “ 1 U” to indicate whether the quantized pitch period value is reliable or unreliable respectively. A “*” indicates that the quantized pitch period is inconsequential, i.e., the value can be a “0” or “1” and it does not make a difference. As initial conditions, we assume that P(− 1 )=0 and P(− 2 )=0 both at the encoder (i.e., client 106 ) and decoder (i.e., server 102 ). The last column indicates whether the pitch was quantized absolutely or differentially and if differentially, the reference frame used. When the three preceding frames are of a not voiced category class or when the only reference value available is unreliable P(− 1 ), P( 1 ) is absolutely quantized using 5 bits. One codeword, such as the all-zero codeword, is used to indicate that the frame is of a not voiced category class. The remaining 31 codewords are used to quantize the pitch period P( 1 ) in a manner similar to that used for quantizing the pitch period values of even-numbered frames. The absolute quantization option using 5 bits is chosen typically for the first frame of a voiced segment or for some misclassified frames belonging to a noisy background condition. In either case, the slightly larger quantization error resulting from the use of only 5 bits does not cause any significant loss of speech quality or intelligibility. The use of only 5 bits helps limit the propagation of decoding errors as we will explain later. When the first frame of a frame-pair is of a voiced category class, then the corresponding quantized pitch period value is always chosen as the reference irrespective of the values of P(− 1 ) and P(− 2 ). According to an exemplary embodiment, out of 32 possible codewords (using 5 bits quantization of pitch period value), one codeword, such as the all-zero codeword, is used to indicate that the current frame is non-speech/unvoiced. Twenty seven codewords are used to cover a small pitch range around the reference value in a logarithmic fashion (similar to the 7-bit absolute quantization discussed above). Both of the end points of the pitch range represent reconstruction levels. The remaining four levels are used to coarsely quantize the rest of the pitch range as indicated in the table. Notice that the four levels chosen depend on the value of P( 0 ). For example, if P( 0 ) is small, then the four levels are greater than P( 0 ). On the other hand, if P( 0 ) is large, then all four levels are smaller than P( 0 ). When the first frame of a frame-pair is of the not voiced category class, then either P(− 1 ) or P(− 2 ),is chosen as the reference. If P(− 1 ) corresponds to a frame of the voiced category class and is reliable, then it is chosen as the reference irrespective of the value of P(− 2 ). If P(− 1 ) corresponds to a not voiced category class frame or corresponds to a voiced category class frame but is unreliable, and P(− 2 ) corresponds to a voiced category class frame, then P(− 2 ) is chosen as the reference. Whether P(− 1 ) or P(− 2 ) is chosen as the reference, the quantization method is similar. One of the codewords, such as the all-zero codeword, is used to indicate that the current frame is of the not voiced category class. Twenty-five codewords are used to cover a small pitch range around the reference value in a logarithmic fashion (similar to the 7-bit absolute quantization discussed above). Both the pitch range end values represent reconstruction levels. The remaining six levels are used to coarsely quantize the rest of the pitch range. The above quantization scheme satisfies the requirements for accuracy, low bit rate, and robustness as follows. By quantizing the pitch period values of the even-numbered frames with 7 bits and those of the odd-numbered frames with 5 bits, an average of 1 bit per frame is saved, i.e., 100 bits per second. At the same time, accuracy is not compromised. Seven-bit absolute quantization is sufficiently accurate. Five-bit absolute quantization is used typically for the first frame of a voiced segment and for some noisy background frames. In either case, the lack of accuracy is not critical and does not affect the quality or intelligibility of the reconstructed speech in any significant way. With 5-bit differential quantization, the pitch period values, which are close to the reference value, are quantized rather accurately. These are the high probability pitch period values. The pitch period values, which are farther away from the reference value are of low probability and are quantized coarsely. Once again, the larger error in the quantization of these values is not critical and does not significantly affect the quality or intelligibility of the reconstructed speech. Error propagation in the present invention is limited by identifying differentially quantized pitch period values as reliable and unreliable and by using 5-bit absolute quantization for odd-numbered frames whenever there is no reference value available or the only reference value available is unreliable. For example, consider the situation where a number of frame-pairs have been erased. This is the most common type of channel error situation for a DSR channel. Assume that the bits corresponding to the frames following the erasures have been received correctly. If the first frame of the frame-pair following the erasures is a voiced frame, then there is no propagation of error at all. This is because the first frame is always absolutely quantized (using 7 bits) and the second frame is differentially quantized using the quantized pitch period value of the first frame as the reference. Also, the following frames do not depend on any of the erased frames. If the first frame is of a not voiced category class, then the second frame cannot be decoded correctly unless it is also a not voiced category class. This is because the second frame's pitch value could have been differentially quantized using the quantized pitch value of one of the last erased frame as reference. In this case, the error has propagated to the second frame following the erasures. If the third frame is of a voiced category class, then the error propagation ceases because the quantized pitch period values of all the frames following the third frame do not depend on the erased frames or the correctly received frame-pair following the erasures. If the third frame is of a not voiced category class, then the quantized pitch period value of the fourth frame can be successfully decoded because it must have been absolutely quantized given that the first and third frames are of a not voiced category class and the second frame is unreliable. Therefore, the error propagation following the erasure of one or more frame-pairs ceases after two frames at the most. Similarly, it can be shown that any error in the decoded pitch period value of an even-numbered frame (due to random bit errors) can propagate up to three frames at most. In addition, any error in the decoded pitch period value of an odd-numbered frame (due to random bit errors) can propagate up to two frames at most. FIGS. 9A , 9 B and 9 C are an operational flow diagram showing another pitch quantization process according to a preferred embodiment of the present invention. The operational flow diagram of FIGS. 9A , 9 B and 9 C depicts the process, on a client 106 , of calculating pitch information for one frame, generating a data packet representing the same and continuing with the next frame. FIGS. 9A , 9 B and 9 C describe in more detail the steps 506 and 508 of FIG. 5 . The operational flow diagram of FIGS. 9A , 9 B and 9 C begins with step 902 (in FIG. 9A ) and flows directly to step 904 . In step 903 , the client 106 calculates the pitch value of the audio for the current frame. In the wireless network embodiment, in step 903 , the wireless device 106 (more specifically, the processor 320 of wireless device 106 ) calculates the pitch value of the audio 402 that was received via microphone 404 . In step 904 , the client 106 determines whether the current frame is an even or odd frame. If the result of the determination of step 904 is even, then control flows to step 910 . If the result of the determination of step 904 is odd, then control flows to step 905 . In step 905 , the current frame is an odd frame and thus, the client 106 proceeds to find an adequate reference frame to utilize for differential pitch quantization. In step 906 , control flows directly to step 916 (B) of FIG. 9 B. In step 910 , the client 106 performs absolute pitch quantization based on the pitch value of the audio. In one example, 7-bit absolute pitch quantization is performed, as described above. In the wireless network embodiment, in step 910 , the wireless device 106 performs absolute pitch quantization based on the pitch value of the audio 402 . In step 912 , the client 106 sets a pitch codeword to the pitch value generated for the absolute pitch quantization performed in step 910 . In one example, the client 106 sets a 7-bit pitch codeword to the pitch value generated for the absolute pitch quantization performed in step 910 . In step 915 (E), control flows directly to step 914 . In step 914 , the pitch quantization process advances to the next frame and the control flows directly back to step 903 . In step 916 (B) of FIG. 9B , control flows directly to step 917 . In step 917 , the client 106 determines whether the class of the frame immediately preceding the current frame “0” is of the voiced category class (i.e., mixed voiced class or fully voiced class). Note that in FIGS. 9B and 9C , the current frame is designated frame “0”, the frame immediately preceding frame “0” is frame “−1”, the frame immediately preceding frame “−1” is frame “−2” and the frame immediately preceding frame “−2” is frame “−3.” If the result of the determination of step 917 is positive, then control flows to step 940 . If the result of the determination of step 917 is negative, then control flows to step 920 . In step 920 , the client 106 proceeds to the previous frame to continue to seek an adequate reference frame to utilize for differential pitch quantization. In step 927 , the client 106 determines whether the class of frame “−2” is of the voiced category class (i.e., mixed voiced class or fully voiced class). If the result of the determination of step 927 is positive, then control flows to step 928 . If the result of the determination of step 927 is negative, then control flows to step 930 . In step 928 , the client 106 determines whether the pitch value of frame “−2” was absolutely quantized. If the result of the determination of step 928 is positive, then control flows to step 940 . If the result of the determination of step 928 is negative, then control flows to step 929 . In step 929 , the client 106 determines whether the pitch value of frame “−2” was differentially quantized and is reliable (that is, it was differentially quantized and referenced the frame immediately preceding it). If the result of the determination of step 929 is positive, then control flows to step 940 . If the result of the determination of step 929 is negative, then control flows to step 930 . In step 930 , the client 106 proceeds to the previous frame to continue to seek an adequate reference frame to utilize for differential pitch quantization. In step 937 , the client 106 determines whether the class of frame “−3” is of the voiced category class (i.e., mixed voiced class or fully voiced class). If the result of the determination of step 937 is positive, then control flows to step 940 . If the result of the determination of step 937 is negative, then control flows to step 942 . Step 940 flows directly to step 960 (C) of FIG. 9 C and step 942 flows directly to step 950 (D) of FIG. 9 C. In step 950 (D) of FIG. 9C , control flows directly to step 952 . In step 952 , it is determined that no adequate reference frame has been found for differentially quantizing the current frame “0.” In step 956 , the client 106 performs absolute pitch quantization based on the pitch value of the audio. In one example, 5-bit absolute pitch quantization is performed, as described above. In the wireless network embodiment, in step 956 , the wireless device 106 performs absolute pitch quantization based on the pitch value of the audio 402 . In step 958 , the client 106 sets a pitch codeword to the pitch value generated for the absolute pitch quantization performed in step 956 . In one example, the client 106 sets a 5-bit pitch codeword to the pitch value generated for the absolute pitch quantization performed in step 956 . In step 960 (C) of FIG. 9C , control flows directly to step 962 . In step 962 , it is determined that an adequate reference frame has been found for differentially quantizing the current frame “0.” In step 966 , the client 106 performs differential pitch quantization referencing the identified reference frame. In one example, 5-bit differential pitch quantization is performed, as described above. In step 968 , the client 106 sets a pitch codeword to the pitch value generated for the differential pitch quantization performed in step 966 . In one example, the client 106 sets a 5-bit pitch codeword to the pitch value generated for the differential pitch quantization performed in step 966 . In step 970 , the control flows directly back to step 915 (E) of FIG. 9 A. In step 915 (E), control flows directly to step 914 . In step 914 , the pitch quantization process advances to the next frame and the control flows directly back to step 903 . C. Review of Prior Art In the Mixed Excitation Linear Prediction (MELP) standard (a telecommunications standard), there is no distinction between non-speech and unvoiced speech frames. Both classes are combined together and indicated by a zero pitch period value. An additional 4 bits are used for quantizing class information when the pitch period is greater than zero, i.e., when a frame is of the voiced category class (e.g., mixed voiced or fully voiced). These 4 bits identify voicing in different bands of speech spectrum. The pitch value is quantized absolutely using 7 bits. Therefore, there is no bit saving in MELP, such as described in the present invention. In LPC-10 (another telecommunications standard), 7 bits are used to indicate a voiced category class frame and pitch. There are 60 pitch period levels and 3 levels used to indicate that: 1) both half-frames are of the not voiced category class (i.e., non-speech class and unvoiced class), 2) only the second half-frame is of the voiced category class (i.e., mixed voiced class and fully voiced class) or 3) only the first half-frame is of the voiced category class. Therefore, LPC-10 only distinguishes between the voiced category class and the unvoiced category class. LPC-10 does not distinguish among the voiced category class (i.e., between non-speech and unvoiced classes) or among the unvoiced category class (i.e., between the mixed voiced and fully voiced classes). The present invention extends LPC-10 with the introduction of non-speech and unvoiced classes under the not voiced category class and mixed voiced and fully voiced classes under the voiced category classes. IV. Exemplary Implementations The present invention can be realized in hardware, software, or a combination of hardware and software in clients 106 , 108 or server 102 of FIG. 1. A system according to a preferred embodiment of the present invention, as described in FIGS. 5 , 6 , 9 A, 9 B and 9 C, can be realized in a centralized fashion in one computer system, or in a distributed fashion where different elements are spread across several interconnected computer systems. Any kind of computer system—or other apparatus adapted for carrying out the methods described herein—is suited. A typical combination of hardware and software could be a general-purpose computer system with a computer program that, when being loaded and executed, controls the computer system such that it carries out the methods described herein. An embodiment of the present invention can also be embedded in a computer program product (in clients 106 and 108 and server 102 ), which comprises all the features enabling the implementation of the methods described herein, and which, when loaded in a computer system, is able to carry out these methods. Computer program means or computer program as used in the present invention indicates any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following a) conversion to another language, code or, notation; and b) reproduction in a different material form. A computer system may include, inter alia, one or more computers and at least a computer-readable medium, allowing a computer system, to read data, instructions, messages or message packets, and other computer-readable information from the computer-readable medium. The computer-readable medium may include non-volatile memory, such as ROM, Flash memory, Disk drive memory, CD-ROM, and other permanent storage. Additionally, a computer-readable medium may include, for example, volatile storage such as RAM, buffers, cache memory, and network circuits. Furthermore, the computer-readable medium may comprise computer-readable information in a transitory state medium such as a network link and/or a network interface, including a wired network or a wireless network, that allow a computer system to read such computer-readable information. FIG. 10 is a block diagram of a computer system useful for implementing an embodiment of the present invention. The computer system of FIG. 10 is a more detailed representation of clients 106 and 108 and server 102 . The computer system of FIG. 10 includes one or more processors, such as processor 1004 . The processor 1004 is connected to a communication infrastructure 1002 (e.g., a communications bus, cross-over bar, or network). Various software embodiments are described in terms of this exemplary computer system. After reading this description, it will become apparent to a person of ordinary skill in the relevant art(s) how to implement the invention using other computer systems and/or computer architectures. The computer system can include a display interface 1008 that forwards graphics, text, and other data from the communication infrastructure 1002 (or from a frame buffer not shown) for display on the display unit 1010 . The computer system also includes a main memory 1006 , preferably random access memory (RAM), and may also include a secondary memory 1012 . The secondary memory 1012 may include, for example, a hard disk drive 1014 and/or a removable storage drive 1016 , representing a floppy disk drive, a magnetic tape drive, an optical disk drive, etc. The removable storage drive 1016 reads from and/or writes to a removable storage unit 1018 in a manner well known to those having ordinary skill in the art. Removable storage unit 1018 , represents a floppy disk, magnetic tape, optical disk, etc., which is read by and written to by removable storage drive 1016 . As will be appreciated, the removable storage unit 1018 includes a computer usable storage medium having stored therein computer software and/or data. In alternative embodiments, the secondary memory 1012 may include other similar means for allowing computer programs or other instructions to be loaded into the computer system. Such means may include, for example, a removable storage unit 1022 and an interface 1020 . Examples of such may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM, or PROM) and associated socket, and other removable storage units 1022 and interfaces 1020 which allow software and data to be transferred from the removable storage unit 1022 to the computer system. The computer system may also include a communications interface 1024 . Communications interface 1024 allows software and data to be transferred between the computer system and external devices. Examples of communications interface 1024 may include a modem, a network interface (such as an Ethernet card), a communications port, a PCMCIA slot and card, etc. Software and data transferred via communications interface 1024 are in the form of signals which may be, for example, electronic, electromagnetic, optical, or other signals capable of being received by communications interface 1024 . These signals are provided to communications interface 1024 via a communications path (i.e., channel) 1026 . This channel 1026 carries signals and may be implemented using wire or cable, fiber optics, a phone line, a cellular phone link, an RF link, and/or other communications channels. In this document, the terms “computer program medium,” “computer-usable medium,” “machine-readable medium” and “computer-readable medium” are used to generally refer to media such as main memory 1006 and secondary memory 1012 , removable storage drive 1016 , a hard disk installed in hard disk drive 1014 , and signals. These computer program products are means for providing software to the computer system. The computer-readable medium allows the computer system to read data, instructions, messages or message packets, and other computer-readable information from the computer-readable medium. The computer-readable medium, for example, may include non-volatile memory, such as Floppy, ROM, Flash memory, Disk drive memory, CD-ROM, and other permanent storage. It is useful, for example, for transporting information, such as data and computer instructions, between computer systems. Furthermore, the computer-readable medium may comprise computer-readable information in a transitory state medium such as a network link and/or a network interface, including a wired network or a wireless network, that allow a computer to read such computer-readable information. Computer programs (also called computer control logic) are stored in main memory 1006 and/or secondary memory 1012 . Computer programs may also be received via communications interface 1024 . Such computer programs, when executed, enable the computer system to perform the features of the present invention as discussed herein. In particular, the computer programs, when executed, enable the processor 1004 to perform the features of the computer system. Accordingly, such computer programs represent controllers of the computer system. V. Conclusion Although specific embodiments of the invention have been disclosed, those having ordinary skill in the art will understand that changes can be made to the specific embodiments without departing from the spirit and scope of the invention. The scope of the invention is not to be restricted, therefore, to the specific embodiments. Furthermore, it is intended that the appended claims cover any and all such applications, modifications, and embodiments within the scope of the present invention.

A system, method and computer readable medium for quantizing class information and pitch information of audio is disclosed. The method on an information processing system includes receiving audio and capturing a frame of the audio. The method further includes determining a pitch of the frame and calculating a codeword representing the pitch of the frame, wherein a first codeword value indicates an indefinite pitch. The method further includes determining a class of the frame, wherein the class is any one of at least two classes indicating an indefinite pitch and at least one class indicating a definite pitch. The method further includes calculating a codeword representing the class of the frame, wherein the codeword length is the maximum of the minimum number of bits required to represent the at least two classes and the minimum number of bits required to represent the at least one class.

CROSS REFERENCE TO RELATED APPLICATIONS The present application is a continuation of application Ser. No. 09/750,040, filed Dec. 29, 2000; now U.S. Pat. No. 6,359,812 which is a continuation of application Ser. No. 09/428,925, filed Oct. 28, 1999, now U.S. Pat. No. 6,198,665; which is a continuation of application Ser. No. 09/303,442, filed May 3, 1999, now U.S. Pat. No. 6,028,795; which is a continuation of Ser. No. 09/055,327, filed Apr. 6, 1998, now U.S. Pat. No. 5,923,591; which is a continuation of Ser. No. 08/853,713, filed May 9, 1997, now U.S. Pat. No. 5,781,479; which is a continuation of application Ser. No. 08/694,599, filed Aug. 9, 1996, now U.S. Pat. No. 5,719,809; which is a continuation of application Ser. No. 08/582,906, filed Jan. 4, 1996, now U.S. Pat. No. 5,615,155; which is a continuation of application Ser. No. 08/435,959, filed May 5, 1995, now U.S. Pat. No. 5,493,528; which is a continuation of application Ser. No. 08/294,407, filed Aug. 23, 1994, now U.S. Pat. No. 5,448,519; which is a continuation of application Ser. No. 07/855,843, filed Mar. 20, 1992, now U.S. Pat. No. 5,450,342; which is a continuation-in-part of application Ser. No. 07/349,403, filed May 8, 1989, now U.S. Pat. No. 5,175,838; which is a continuation of application Ser. No. 07/240,380, filed Aug. 29, 1988, now U.S. Pat. No. 4,868,781; which is a continuation of application Ser. No. 06/779,676, filed Sep. 24, 1985, now abandoned; said U.S. Pat. No. 4,868,781 being reissued by application Ser. No. 07/542,028, filed Jun. 21, 1990 now Pat. No. Re. 33,922; said application Ser. No. 07/855,843, filed Mar. 20, 1992, now U.S. Pat. No. 5,450,342 also being a continuation-in-part of Ser. No. 07/816,583, filed Jan. 3, 1992, now abandoned; which is a continuation of application Ser. No. 07/314,238, filed Feb. 22, 1989 now U.S. Pat. No. 5,113,487; which is a continuation of application Ser. No. 06/864,502, filed May 19, 1986, now abandoned, said application Ser. No. 07/816,583, filed Jan. 3, 1992, now abandoned, also being a continuation-in-part of application Ser. No. 07/349,403, filed May 8, 1989 now U.S. Pat. No. 5,175,383; which is a continuation of application Ser. No. 06/779,676, filed Sep. 24, 1985, now abandoned. BACKGROUND OF THE INVENTION The present invention relates to a memory device, and in particular, to a memory device suitable for a graphic memory to be utilized in high-speed image processing. The prior art technique will be described by referring to graphic processing depicted as an example in FIGS. 1-2. For example, the system of FIG. 1 comprises a graphic area M 1 having a one-to-one correspondence with a cathode ray tube (CRT) screen, a store area M 2 storing graphic data to be combined, and a modify section FC for combining the data in the graphic area M 1 with the data in the store area M 2 . in FIG. 2, a processing flowchart includes a processing step S 1 for reading data from the graphic area M 1 , a processing step S 2 for reading data from the store area M 2 , a processing step S 3 for combining the data read from the graphic area M 1 and the data read from the store area M 2 , and a processing step S 4 for writing the composite data generated in the step S 3 in the graphic area M 1 . In the graphic processing example, the processing step S 3 of FIG. 2 performs a logical OR operation only to combine the data of the graphic area M 1 with that of the store area M 2 . On the other hand, the graphic area M 1 to be subjected to the graphic processing must have a large memory capacity ranging from 100 kilobytes to several megabytes in ordinary cases. Consequently, in a series of graphic processing steps as shown in FIG. 2, the number of processing iterations to be executed is on the order of 10 6 or greater even if the processing is conducted on each byte one at a time. Similarly referring to FIGS. 2-3, graphic processing will be described in which the areas M 1 and M 2 store multivalued data such as color data for which a pixel is represented by the use of a plurality of bits. Referring now to FIG. 3, a graphic processing arrangement comprises a memory area M 1 for storing original multivalued graphic data and a memory area M 2 containing multivalued graphic data to be combined therewith. For the processing of multivalued graphic data shown in FIG. 3, addition is adopted as the operation to ordinarily generate composite graphic data. As a result, the values of data in the overlapped portion become larger, and hence a thicker picture is displayed as indicated by the crosshatching. in this case, the memory area must have a large memory capacity. The number of iterations of processing from the step S 1 to the step S 4 becomes on the order of 10 6 or greater, as depicted in FIG. 2 . Due to the large iteration count, most of the graphic data processing time is occupied by the processing time to be elapsed to process the loop of FIG. 2 . In graphic data processing, therefore, the period of time utilized for the memory access becomes greater than the time elapsed for the data processing. Among the steps S 1 -S 4 of FIG. 2, three steps S 1 , S 2 , and S 4 are associated with the memory access. As described above, in such processing as graphic data processing in which memory having a large capacity is accessed, even if the operation speed is improved, the memory access time becomes a bottleneck of the processing, which restricts the processing speed and does not permit improving the effective processing speed of the graphic data processing system. In the prior art examples, the following disadvantages take place. (1) In the graphic processing as shown by-use of the flowchart of FIG. 2, most of the processing is occupied by the steps S 1 , S 2 , and S 4 which use a bus for memory read/write operations consequently, the bus utilization ratio is increased and a higher load is imposed on the bus. (2) The graphic processing time is further increased, for example, because the bus has a low transfer speed, or the overhead becomes greater due to the operation such as the bus control to dedicatedly allocate the bus to CRT display operation and to memory access. (3) Moreover, although the flowchart of FIG. 2 includes only four static processing steps, a quite large volume of data must be processed as described before. That is, the number of dynamic processing steps which may elapse the effective processing time becomes very large, and hence a considerably long processing time is necessary. Consequently, it is desirable to implement a graphic processing by use of a lower number of processing steps. A memory circuit for executing the processing described above is found in the Japanese Patent Unexamined Publication No. 55-129387, for example. Recent enhanced resolution of graphic display units is now demanding a large-capacity memory for use as a frame buffer for holding display information. In displaying a frame of graphic data, a large number of access operations to a capacious frame buffer take place, and therefore high-speed memory read/write operations are required. A conventional method for coping with this requirement is the distribution of processings. An example of the distributed process is to carry out part of the process with a frame buffer. FIG. 26 shows, as an example, the arrangement of the frame buffer memory circuit, used in the method. The circuit includes an operation unit 1 , a memory 2 , an operational function control register 23 , and a write mask register 26 . The frame buffer writes data in bit units regardless of the word length of the memory device. On this account, the frame buffer writing process necessitates to implement operation and writing both in bit units. In the example of FIG. 26 , bit operation is implemented by the operation unit I and operational function control register 23 , while bit writing is implemented by the mask register 6 only to bits effective for writing. This frame buffer is designed to implement the memory read-modify-write operation in the write cycle for data D from the data processor, eliminating the need for the reading of data DO out of the memory, which the usual memory necessitates in such operation, whereby speedup of the frame buffer operation is made possible. FIG. 27 shows another example of distributed processing which is applied to a graphic display system consisting of two data processors 20 and 20 ′, linked through a common bus 21 with a frame buffer memory 9 ″. The frame buffer memory 9 ″ is divided into two areas a and b which are operated for display by the data processors 20 and 20 ′, respectively. FIG. 28 shows an example of a display made by this graphic system. The content of the frame buffer memory 9 ″ is displayed on the CRT screen, which is divided into upper and lower sections in correspondence with the divided memory areas a and b as shown in FIG. 28 . When it is intended to set up the memory 9 ″ for displaying a circle, for example, the data processor 20 produces an arc aa′a″ and the data processor 20 ′, produces a remaining arc bb′b″ concurrently. The circular display process falls into two major processings of calculating the coordinates of the circle and writing the result into the frame buffer. In case the calculation process takes a longer time than the writing process, the use of the two processors 20 and 201 for the process is effective for the speedup of display. If, on the other hand, the writing process takes a longer time, the two processors conflict over the access to the frame buffer memory 9 ″, resulting in a limited effectiveness of the dual processor system. The recent advanced LSI technology has significantly reduced the computation time of data processors relative to the memory write access time, which fosters the use of a frame buffer memory requiring less access operations such as one 9 ′ shown in FIG. 26 . In application of the frame buffer memory 9 ′ shown in FIG. 26 to the display system shown in FIG. 27, when both processors share in the same display process as shown in FIG. 28, the memory modification function is consistent for both processors and no problem will arise. In another case, however, if one processor draws graphic display a′ and another processor draws character display b′ as shown in FIG. 29, the system is no longer uneventful. In general, different kinds of display are accompanied by different memory modification operations, and if two processors make access to the frame buffer memory alternately, the setting for the modification operation and the read-modify-write operation need to take place in each display process. Setting for modification operation is identical to memory access when seen from the processor, and such double memory access ruins the attempt of speedup. A conceivable scheme for reducing the number of computational settings is the memory access control in which one processor makes access to the frame buffer several times and then hands over the access right to another processor, instead of the alternate memory access control. However, this method requires additional time for the process of handing over the access right between the processors as compared with the display process using a common memory modification function. Namely, the conventional scheme of sharing in the same process among more than one data processor as shown in FIG. 28 is recently shifting to the implementation of separate processes as shown in FIG. 29 with a plurality of data processors as represented by the multi-window system, and the memory circuit is not designed in consideration of this regard. An example of the frame buffer using the read-modify-write operation is disclosed, for example, in an article entitled “Designing a 1280-by-1024 pixel graphic display frame buffer in a 64K RAM with nibble mode”, Nikkei electronics, pp. 227-245, published on Aug. 27, 1984. SUMMARY OF THE INVENTION It is therefore an object of the present invention to-provide a method for storing graphic data and a circuit using the method which enables a higher-speed execution of dyadic and arithmetic operations on graphic data. Another object of the present invention is to provide a memory circuit which performs read, modify, and write operations in a write cycle so that the number of dynamic steps is greatly reduced in the software section of the graphic processing. Still another object of the present invention is to provide a memory circuit comprising a function to perform the dyadic and arithmetic operations so as to considerably lower the load imposed on the bus. Further another object of the present invention is to provide a memory circuit which enables easily to implement a priority processing to be effected when graphic images are overlapped. Further another object of the present invention is to provide a memory circuit with logical functions for use in constructing a frame buffer suitable for the multiple processors, parallel operations with the intention of realizing a high-speed graphic display system. According to the present invention, there is provided a memory circuit having the following three functions to effect a higher-speed execution of processing to generate composite graphic data. (1) A function to write external data in memory elements. (2) A function to execute a logical operation between data previously stored in memory elements and external data, and to write the resultant data in the memory elements. (3) A function to execute an arithmetic operation between data previously stored in memory elements and external data and to write the resultant data, in the memory elements. A memory circuit which has these functions and which achieves a portion of the operation has been, implemented with emphasis placed on the previous points. Also, many operations other than processing to generate composite multivalued graphic data as described above, a dyadic logic operation is required in which two operands are used. That is, the operation format is as follows in such cases. D—D op s; where op stands for operator. On the other hand, the polynomial operation and multioperand operation as shown below are less frequently used. D−S i opS z op . . . opS n when the dyadic and two-operand operation is conducted between data in a central processing unit (CPU) an data in the memory elements, memory elements need be accessed only once if the operation result is to be stored in a register of the CPU (in a case where the D is a register and the S is a unit of memory elements) Contrarily, if the D indicates the memory elements unit and the S represents a register, the memory elements unit must be accessed two times. In most cases of data Processing including the multivalued graphic data processing, the number of data items is greater than the number of registers in the CPU; and hence the operation of the latter case where the D is the data element unit is frequently used; furthermore, each of two operands is stored in a memory element unit in many cases. Although the operation to access the S is indispensable to read the data, the D is accessed twice for read and write operations, that is, the same memory element unit is accessed two times for an operation. To avoid this disadvantageous feature, the Read-Modify-Write adopted in the operation to access a dynamic random access memory (DRAM) is utilized so as to provide the memory circuit with an operation circuit so that the read and logic operations are carried out in the memory circuit, whereby the same memory element unit is accessed only once for an operation. The graphic data is modified in this fashion, which unnecessitates the operation to read the graphic data to be stored in the CPU and reduces the load imposed on the bus. In accordance with the present invention there is provided a unit of memory elements which enables arbitrary operations to read, write, and store data characterized by including a control circuit which can operate in an ordinary write mode for storing in the memory elements unit a first data supplied externally based on first data and second data in the memory elements unit, a logic operation mode for storing an operation result obtained from a logic operation executed between the first and second data, and an arithmetic operation mode for storing in the memory element unit result data obtained from an arithmetic operation executed between the first data and the second data. In general, when it is intended to share a resource by a plurality of processors, the resource access arbitration control is necessary, and when it is intended for a plurality of processors to share in a process for the purpose of speedup, they are required to operate and use resources in unison. These controls are generally implemented by the program of each processor, and it takes some processing time. Resources used commonly among processors include peripheral units and a storage unit. A peripheral unit is used exclusively for a time period once a processor has begun its use, while the storage unit is accessed by processors on a priority basis. The reason for the different utilization modes of the resources is that a peripheral unit has internal sequential operating modes and it is difficult for the unit to suspend the process in an intermediate mode once the operation has commenced, while the storage unit completes the data read or write operation within the duration of access by a processor and its internal operational mode does not last after the access terminates. When it is intended to categorize the aforementioned memory implementing the read-modify-write operation in the above resource classification, the memory is a peripheral unit having the internal modification function, but the internal operating mode does not last beyond the access period, and operates faster than the processor. Accordingly, the memory access arbitration control by the program of the low-speed processor results in an increased system overhead for the switching operation, and therefore such control must be done within the memory circuit. The memory circuit implementing the read-modify-write operation does not necessitate internal operating modes dictated externally and it can switch the internal states to meet any processor solely by the memory internal operation. The present invention resides in a memory circuit including a memory device operative to read, write and hold data, an operator which performs computation between first data supplied from outside and second data read out of the memory device, means for specifying an operational function from outside, and means for controlling bit writing from outside, wherein the operational function specifying means issues a selection control signal to a selector which selects one of a plurality of operational function specifying data supplied from outside, and wherein the bit writing control means issues a selection control signal to a selector which selects one of a plurality of bit writing control data supplied from outside, so that a frame buffer memory which implements the read-modify-write operation can be used commonly. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram for explaining an operation to generate a composite graphic image in a graphic data processing system. FIG. 2 is a flowchart of processing applied to the prior art technique to generate composite graphic data. FIG. 3 is a schematic block diagram for explaining multivalued graphic data processing. FIG. 4 is a timing chart illustrating the ordinary operation of a memory. FIG. 5 is an explanatory diagram of a memory having a logic function. FIG. 6 is a table for explaining the operation modes of the memory of FIG. 5 . FIG. 7 is schematic circuit diagram for implementing the logic function. FIGS. 8-9 are tables for explaining truth values in detail. FIG. 10 is a block diagram depicting the configuration of a memory having a logic function. FIG. 11 is a flowchart of processing to generate composite graphic data by use of the memory of FIG. 10 . FIG. 12 is an explanatory diagram of processing to generate composite graphic data by use of an EOR logic function. FIGS. 13-14 are schematic diagrams for explaining the processing to generate composite graphic data according to the present invention. FIG. 15 is an explanatory diagram of an embodiment of the present invention. FIG. 16 is a table for explaining in detail the operation logic or the present invention. FIG. 17 is a schematic circuit diagram of an embodiment of the present invention. FIG. 18 is a circuit block diagram for explaining an embodiment applied to color data processing. FIG. 19 is a block diagram illustrating a memory circuit of an embodiment of the present invention. FIG. 20 is a table for explaining the operation modes of a control circuit. FIG. 21 is a schematic diagram illustrating an example of the control circuit configuration. FIG. 22 is a circuit block diagram depicting an example of a 4-bit operational memory configuration. FIGS. 23 a to 23 c are-diagrams for explaining an application example of an embodiment. FIG. 24 is a schematic diagram for explaining processing to delete multivalued graphic data. FIG. 25 is a block diagram showing the memory circuit embodying the present invention; FIG. 26 is a block diagram showing the conventional memory circuit; FIG. 27 is a block diagram showing the conventional graphic display system; FIG. 28 is a diagram explaining a two processor graphic display; FIG. 29 is a diagram showing a graphic display by one processor a character display by another processor; FIG. 30 is a block diagram showing the multi-processor graphic display system embodying the present invention; FIG. 31 is a table used to explain the operational function of the embodiment shown in FIG. 30; FIG. 32 is a block diagram showing the arrangement of the conventional frame buffer memory; FIG. 33 is a block diagram showing the arrangement of the memory circuit embodying the present invention; FIG. 34 is a schematic logic diagram showing the write mask circuit in FIG. 33; FIG. 35 is a diagram used to explain the frame buffer constructed using the memory circuit shown in FIG. 33; FIG. 36 is a block diagram showing the arrangement of the graphic display system for explaining operation code setting according to this embodiment; FIG. 37 is a timing chart showing the memory access timing relationship according to this embodiment; FIG. 38 is a timing chart showing the generation of the selection signal and operation code setting signal based on the memory access timing relationship; and FIG. 39 is a timing chart showing the memory write timing relationship derived from FIG. 37, but with the addition of the selection signal. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, the following paragraphs describe embodiments of the present invention in detail. FIG. 4 is a timing chart of a DRAM. First, the operation to access the memory will be briefly described in conjunction with FIG. 4 . In this timing chart, ADR is an address signal supplied from an external device and WR indicates a write request signal. These two signals (ADR and WR) are fed from a microprocessor, for example. In addition, RAS is a row address strobe signal, CAS is a column address strobe signal, A indicates an address signal representing a column or row address generated in the timesharing fashion, WE stands for a write enable signal, and Z is a data item supplied from an external device (microprocessor). Excepting the Z signal, they are control signals generated by a DRAM controller, for example. The memory access outlined in FIG. 4 can be summarized as follows. (i) As shown in FIG. 4, a memory access in a read/write cycle generally commences with a read cycle (I) and ends with a write cycle (III) due to a write enable signal, WE. (ii) Between the read cycle (I) and the write cycle (III), there appears an interval (II) in which a read data Do and an external data Z (to be written) exist-simultaneously. (iii) This interval (ii) is referred to as the operation enabled interval. As described above, the store data Do and the external write data Z exist simultaneously in the interval (II). As a consequence, the store data Do and the external data Z can be subjected to an operation during a memory cycle in this interval by use of the memory circuit having an operation function, thereby enabling the operation result to be written in the memory circuit. FIG. 5 is a block diagram illustrating a first embodiment of the present invention, FIG. 6 is an explanatory diagram of the operation principle of the embodiment shown in FIG. 5, FIG. 7 is a circuit example implementing the operation principle of FIG. 6, and FIG. 8 is a table for explaining in detail the operation of the circuit shown in FIG. 7 . The circuit configuration of FIG. 5 comprises a control logic circuit 1 , a unit of memory elements 2 , a DRAM controller 3 , external data X and Y, a write data Z to the memory elements unit 2 , a read data Do from the memory elements unit 2 , and signals A, CAS, RAST ADR, and WR which are the same as those described in conjunction with FIG. 4 . The external data Z of FIG. 4 is replaced with the write data Z delivered via the control circuit to the memory elements unit 2 in FIG. 5 . In accordance with an aspect of the present invention as shown in FIG. 5, the control circuit I controls the read data Do by use of the external data signals X and Y, and the modified read data is written in the memory elements unit 2 . FIG. 6 is a table for explaining the control operation. In this table, mode I is provided to set the external data Y as the write data Z, whereas mode II is provided to set the read data Do as the write data Z. As shown in FIG. 6, the external data signals X and Y, namely, the external control is used to control two modes, that is, the read data of the memory elements unit 2 is altered and written (mode II), or the external data Y is written (mode I). For the control of two modes, (i) mode I or II is specified by the external data X and (ii) the modification specification to invert or not to invert the read data Do is made by use of an external data. The control and modification are effected in the interval (II) described in conjunction with FIG. 4 . A specific circuit example implementing the operation described above is shown in FIG. 7 . The control logic circuit comprises an AND gate 10 and an EOR gate 11 and operates according to the truth table of FIG. 8, which illustrates the relationships among two external data signals X and Y, store data Do, -and output Z from the control circuit 1 . As can be seen from FIG. 8, the control circuit 1 operates primarily in the following two operation modes depending on the external data X. (i) When the external data X is ‘0’, it operates in the operation mode I in which the external data Y is processed as the write data Z. (ii) When the external data X is ‘1’, it operates in the operation mode II in which the data obtained by modifying the read data Do based on the external data Y is used as the write data Z. As already shown in FIG. 4, the operation above is executed during a memory cycle. Consequently, the principle of the present invention is described as follows. (i) The output Do from the memory elements unit 2 is fed back as an input signal to the control circuit as described in conjunction with FIG. 4; and (ii) The write data to, the memory elements unit 2 is controlled by use of the input data signals X and Y (generated from the write data from the CPU) as shown in FIG. 5 . These operations (i) and (ii) are executed during a, memory cycle. That is, a data item in the memory elements is modified with an external input data (namely, an operation is conducted between these two data items) during a memory cycle by use of three data items including (i) feedback data from the memory elements, (ii) data inputted from an external device, and (iii) control data from an external device (a portion of external input data is also used as the control data). These operations imply that an external device (for example, a graphic processing system, a CPU available at present, or the like) can execute a logic operation only by use of a write operation. The operation of the circuit shown in FIG. 7, on the other hand, is expressed as follows Z=X·Do Y+X·Do·Y=Do·Y+X·Y+X·Do·Y =( X+Y )· Do·Y+X·Y+X·DO·Y=X·Y+X ·( YÅDo )  (1) Substituting the externally controllable data items X and Y with the applicable values of a signal “O”, a signal “1”, the bus data Di fed from the microprocessor, and the reversed data thereof appropriately Di, the operation results of the dyadic logic operations as shown in FIG. 9 will be obtained. FIG. 10 . is a circuit diagram implemented by combining the dyadic operations of FIG. 9 with the processing system of the FIG. 5 embodiment. The system of FIG. 10 comprises four-input selectors SELf and SEL 1 , input select signals SO and S 1 to the selector SELf, input select signals S 2 and S 3 to the selector SEL 1 , and an inverter element INV. Referring now to FIG. 1, and FIGS. 9-11, an operation example of a logic operation will be specifically described. As shown in FIG. 9, the input select signals SO and S 1 are used as the select signals of the selector SELf to determine the value of data X. Similarly, the input select signals S 2 and S 3 are used to determine the value of data Y. The values that can be set to these data items X and Y include a signal “O”, a signal “1”, the bus data Di, and the inverted data thereof Di as described before. The selectors SELf and SEL 1 each select one of these four signal values depending on the input select signals S 0 to S 3 as shown in FIG. 10 . FIG. 9 is a table illustrating the relationships between the input select signals SO to S 3 and the data items X and Y outputted from the selectors SELf and SEL 1 , respectively, as well as the write data Z outputted from the control circuit 1 . In graphic processing as shown in FIG. 1 (OR operation: Case 1 ), for example, the data items X and Y are selected as Di and Di, respectively when the input select signals are set as follows: SO, SI=(11) and S z , S 3 =(10). Substituting these values of X and Y in the expression (1) representing the operation of the control circuit 1 , the OR operation, namely, Z=Di+Di Do=Di·(1+Do)+Di Do=Di+(Di+Di) Do=Di+Do is executed. In accordance with an aspect of the present invention, therefore, the graphic processing of FIG. 1 can be performed as shown in FIG. 11 in which the input select signals S 0 to S 1 are specified in the first step (function specification), a graphic data item to be combined is thereafter read from the storage area M 2 , and the obtained data item is stored in the graphic area only by use of a write operation. Various logic functions can be effected by changing the values of SO to S 3 as depicted in FIG. 9 . Consequently, an operation to draw a picture, for example, by use of a mouse cursor which is arbitrarily moved can be readily executed as shown in FIG. 12 . Even when the mouse cursor (M 2 ) overlaps with a graphic image in the graphic area M 1 as illustrated in FIG. 12, the cursor must be displayed, and hence a function of the EOR operation is necessary. In this cursor display, when the input select signals are set as SO, S 1 =(10) and S 2 , S 3 =(01), the processing can be achieved as depicted in FIG. 11 in the same manner as the case of—the composite graphic 7 c data generation described before. The various logic functions as listed in the table of FIG. 9 can be therefore easily implemented; furthermore, the Read-Modify-Write operation on the memory element unit 2 can—be accomplished only by a write operation. By use of the circuit configuration of FIG. 10, the dyadic logic operations of FIG. 9 can be executed as a modify operation to be conducted between the data Di from the microprocessor and the read data Do from the memory elements unit 2 . Incidentally, the input select signals are used to specify a dyadic logic operation. In accordance with the embodiment described above, the prior art processing to generate a composite graphic image can be simplified as depicted by the flowchart of FIG. 11 . The embodiment of the present invention described above comprises three functions as shown in FIG. 10, namely, a memory section including memory elements unit 2 , a control section having the control circuit 1 , and a selector section including the selectors SEIA and SELI. However, the function implemented by a combination of the control and selector sections is identical to the dyadic logic operation function described in conjunction with FIG. 9 . Although this function can be easily achieved by use of other means, the embodiment above is preferable to simplify the circuit configuration. On the other hand, graphic processing is required to include processing in which graphic images and the like are overlapped as illustrated in FIGS. 13 14 . In the first case, the graphic image in the store area M 2 takes precedence over the graphic image in the graphic image area M 1 when they are displayed as depicted in FIG. 13 . In the second case, the graphic image in the graphic image area M 1 takes precedence over the graphic image in the store area M 2 as shown in FIG. 14 . The priority processing to determine the priority of graphic data as illustrated in FIGS. 13-14 cannot be achieved only by the logical function implemented by the FC section of FIG. 10) described above. This function, however, can be early implemented by use of the memory circuit in an embodiment of the present invention namely, only simple logic and selector circuits need by added to the graphic processing system. An embodiment for realizing such a function will be described by referring to FIGS. 15-17. The FC section of FIG. 15 corresponds to a combination of the control circuit and the selectors SELf and SEL 1 . In this embodiment, the logic operation function (FC) section operates in the pass mode with the input select signals so to S 3 of the selectors SELf and SEL 1 set as (0, 0, 1, 0), for example. The circuit block diagram of FIG. 15 includes a priority control section 4 , a two-input selector SEL 2 , a priority specification signal P, an input select signal S 4 to-the selector SEL 2 , a graphic data signal Di′ from the store area M 2 , a graphic image area M 1 , a selected signal Di from selector SEL 2 , a graphic data signal Do from the graphic image area M 1 (identical to the read data signal from the memory elements unit 2 shown in FIG. 10 ), and an output signal Z from the FC section (identical to the output signal from the control circuit I of FIG. 4 ). For the convenience of explanation, the graphic area is set to a logic value “1” and the background area is set to a logic value “O” as shown in FIG. 15 . In this processing, the priority control section 4 and the selector SEL 2 operate according to the contents of the truth table of FIG. 16 . The relation-ships between the input select signal S 4 and the input data Di to the logic operation function (FC) section are outlined in FIG. 16, where the signal S 4 is determined by a combination of the priority specification signal P, the data Di′ in the area M 2 , and the data Do from the area M 1 , and the input data Di is set by the signal S 4 . In other words, the truth table of FIG. 16 determines an operation as follows. For example, assume that the graphic area to be used as the background is Mi. If the data items Do and Di′ in the areas M 1 and M 2 , respectively, are set to the effective data (“1”), the priority specification signal P is used to deter-mine whether the data Do of the background area M 1 takes precedence (P=1), or the data Di′ of the area M 2 takes precedence (P=0). That is, if a graphic image in the store area M 2 is desired to be displayed over the graphic image of the graphic area M 1 , as illustrated in FIG. 13, the priority specification signal P is set to “0”. Then, if the graphic data items Di′ and Do, are in the graphic areas (“1”) as depicted in FIG. 15, the data Di′ of the store area M 2 is preferentially selected by the selector SEL 2 . If the priority specification signal P is set to “1”, the graphic processing is similarly executed according to the truth table of FIG. 16 as shown in FIG. 14 . In FIG. 16, if the graphic areas (“1”) are overlapped, the graphic area of the graphic area M 1 , or the store area M 2 , is selected depending on the priority specification signal P, and the data of the graphic area M 1 is selected as the background for the area in which the graphic area does not exist. FIG. 17 is a specific circuit diagram of the priority control section 4 depicted in FIG. 15 . In this circuit diagram, reference numerals 40 and 41 indicate a three-input NAND circuit and a two-input NAND circuit respectively. In order to apply the principle of priority decision to color data in which each pixel comprises a plurality of bits, the circuit must be modified as illustrated in FIG. 18 . The circuit of FIG. 18 includes a compare and determine section 5 for determining the graphic area (COL 3 ) of the graphic area M 1 and a compare and determine section 6 for determining the graphic area (COL 1 ) of the store area M 1 . As described above, the priority comprises a plurality of bits, it is different from the circuit for processing information for which a pixel comprises a bit as shown in FIG. 15 in that the priority determination between significant data items is achieved by use of the code information (COLf to COL 3 ) because the graphic data is expressed by the code information. Consequently, in the case of color data, the overlapped graphic images can be easily processed by adding the compare and determine sections which determine the priority by comparing the code information. The preceding paragraphs have described the priority determine circuit applied to an embodiment of the memory circuit having an operation function, however, it is clear that such embodiment can be applied to a simple memory circuit, or a memory circuit which has integrated shift register and serial outputs. In accordance with this embodiment, the following effect is developed. (1) When executing the processing as shown in FIG. 1, the processing flowchart of FIG. 11 can be utilized, and hence the memory cycle can be minimized. (2) Three kinds of processing including the read, modify, and write operations can be executed only during a write cycle, which enables an increase in the processing speed. (3) As depicted in FIGS. 16-18, the priority processing to be conducted when the graphic images are overlapped can be effected by the use of a plurality of simple logic gates. (4) The graphic processing of color data can be also easily implemented by externally adding the compare and determine circuits for determining the graphic areas (code data comprising at least two bits). (5) The size of the circuit configuration necessary for implementing the memory circuit according to the invention is quite small as compared with that of a group of memory elements, which is considerably advantageous to manufacture a large scale integration circuit in the same memory chip. Next, another embodiment will be described in which processing to generate a composite graphic data represented as the multivalued data of FIG. 3 is executed. FIG. 19 is a circuit block diagram of a memory circuit applied to a case in which multivalued data is processed. This circuit is different from the memory circuit of FIG. 5 in the configuration of a control circuit 1 ′. The configuration of FIG. 19 is adopted because the processing to generate a composite graphic data from the multivalued data indispensably necessitates an arithmetic operation, not a simple logic operation. As shown in FIG. 19, however, the basic operation is the same as depicted in FIG. 5 . In the following paragraphs, although the arithmetic operation is described, the circuit configuration includes the sections associated with the logic operation because the logic operation is also used for the multivalued graphic data processing. The circuit arrangement of FIG. 19 includes a control circuit 11 , memory elements unit 2 , a DRAM controller 3 , external control signals CNT and Cr, data Y supplied from an external device, write data Z to the memory elements unit 2 , read data Do from the memory elements unit 2 , and signals A, WE, CAS, RAS, ADR, and WR which are the same as those shown in FIG. 5 . In the embodiment as shown in FIG. 19, the control circuit 11 performs an operation on the read data Do and the external data Y according to the external control signals CRT and Cr; and the operation result, write data Z is written in the memory elements 2 . FIG. 20 is a table illustrating the control operation modes of the control circuit 1 ′. When the external control signals CRT and Cr are set to f, the control circuit 1 ′ operates in a mode where the external data Y is used as a control signal to determine whether or not the read data Do is subjected to an inversion before it is outputted; when the signals CRT and Cr are set to 0 and 1, respectively, the control circuit 1 ′ operates in a mode where the external data Y is outputted without change; and when the signals are set to 1, the control circuit 1 ′ operates in a mode where the read data Do, the external data Y, and the external control signal Cr are arithmetically added. FIG. 21 is a specific circuit diagram of a circuit implementing the control operation modes. In this circuit arrangement, the arithmetic operation is achieved by use of the ENOR gates G 1 and G 2 , and the condition that the external control signals CRT and Cr are f and 1 , respectively is detected by the gates G 6 to G 8 , and the output from the ENOR gate or the external data Y is selected by use of a selector constituted from the gates G 3 to G 5 . This circuit configuration further includes a NAND gate G 9 for outputting a generate signal associated with the carry lookahead function provided to minimize the propagation delay of the carry and an AND gate GIO for generating a propagate signal similarly associated with the carry lookahead function. The logical expressions of the output signals Z, P, and G from the control circuit I′ are as listed in FIG. 21, where the carry lookahead signals P and G each are set to fixed values (P=0, G=1) if the external control signal CNT is f. FIG. 22 is the configuration of a four-bit operation memory utilizing four memory circuits for the embodiment. For simplification of explanation, only the sections primarily associated with the arithmetic operation mode are depicted in FIG. 22 . The circuit diagram includes the memory circuits 11 - 14 shown in FIG. 19, gates G 11 to G 28 constituting a carry lookahead circuit for achieving a carry operation, and a register F for storing the result of a carry caused by an arithmetic operation. The memory circuits 11 and 14 are associated with the least and most-significant bits, respectively. Although not shown in this circuit configuration to simplify the circuit arrangement, the register F is connected to an external circuit which sets the content to f or 1 . The logical expression of the carry result, namely, the output from the gate G 29 is as follows. G 4 +G 3 ·P 4 +G 2 ·P 3 ·P 4 +G 1 ·P 2 ·P 3 ·P 4 +Cr·P 1 ·P 2 ·P 3 ·P 4 When the external control signal CNT is f, Pi and Gi are set to 1 and f, respectively (where, i indicates an integer ranging from one to four), and hence the logical expression includes only the signal Cr, which means that the value of the register F is not changed by a write operation. Since the intermediate carry signals Gr 2 to Gr 4 are also set to the value of the signal Cr, three operation states are not changed by a write operation when the external control signal CNT is f. If the external control signal CNT is 1, the carry control signals P 1 to P 4 and G 1 to G 4 of the memory circuits 11 - 14 , respectively function as the carry lookahead signals, so an ordinary addition can be conducted. As shown in FIG. 20, although the control circuit has a small number of operation modes, the operation functions can be increased by selecting the logic value f, the logic value 1, the write data D to a microprocessor or the like, and the inverted data D of the write data D as the inputs Of the external control signal Cr and the external data Y. FIGS. 23 a to 23 c illustrate an example in which the above-mentioned circuits are combined. FIG. 23 a is a specific representation of a circuit for the least significant bit, whereas FIG. 22 b is a table outlining the operation functions of the circuit of FIG. 23 a. In the following paragraphs, the circuit operation will be described only in the arithmetic operation mode with the external control signal CNT set to 1. Gates G 29 -G 33 constitute a selector (SEL 3 ) for the external control signal Cr, while gates G 34 -G 37 configure a selector (SEL 4 ) for the external data Y. The circuit arrangement of FIG. 23 a comprises select control signals Sf and S 1 for selecting the external control signal Cr and select control signals S 2 and S 3 for selecting the external data Y. FIG. 23 c depicts a circuit for the most-significant bit. This circuit is different from that of FIG. 23 a in that the selector for the signal Cr is constituted from the gates G 38 -G 44 so that a carry signal Cri-I from the lower-order bit is inputted to the external control signal Cr when the external control signal CNT is 1. The selector for the external data Y is of the same configuration of that of FIG. 23 a. In the circuit configuration of FIG. 23 c, the memory circuit arrangement enables to achieve 16 kinds of logical operations and six kinds of arithmetic operations by executing a memory write access. For example, the processing to overlap multivalued graphic data as shown in FIG. 3 is carried out as follows. First, the select signals SO to S 3 are set to 0, 0, 0, and 1, respectively and the write data Z is specified for an arithmetic operation of Do Plus 1. A data item is read from the multivalued graphic data memory M 2 and the obtained data item is written in the destination multivalued graphic data area M 1 , which causes each data to be added and the multivalued graphic data items are overlapped at a higher speed. Similarly, if the select signals Sf to S 3 are set to 1 and the write data Z is specified for a subtraction of Do Minus Di, the unnecessary portion (such as the noise) of the multivalued graphic data can be deleted as depicted in FIG. 24 . Like the case of the overlap processing, this processing can be implemented only by executing a read operation on the data memory M 3 containing the data from which the unnecessary portion is subtracted and by repeating a write operation thereafter on the destination data memory M 3 , which enables higher-speed graphic processing. According to the above embodiments, (1) The multivalued graphic data processing is effected by repeating memory access two times, and hence the processing such as the graphic data overlap processing and subtraction can be achieved at a higher speed; (2) Since the data operation conducted between memory units is implemented on the memory side, the multivalued graphic processing can be implemented not only in a device such as a microprocessor which has an operation function but also in a device such as a direct memory access (DMA) controller which has not an operation function; and (3) The carry processing is conducted when a memory write access is executed by use of the circuit configuration as shown in FIG. 22, so the multiple-precision arithmetic operation can be implemented only by using a memory write operation, thereby enabling a multiple-precision arithmetic operation to be achieved at a higher speed. It is also possible to perform the dyadic operation and the arithmetic operation on graphic data at a higher speed. Moreover, the priority processing to be utilized when graphic images overlap and processing for color data can be readily implemented. FIG. 25 shows a frame buffer memory circuit including an operation unit (LU) 1 for implementing the modification functions for the read-modify-write operation, a data memory 2 , operational function specifying registers 23 and 24 for specifying an operational function of the operation unit, an operational function selector 25 for selecting an operational function, write mask registers 26 and 27 for holding write mask data, and a write mask selector 28 for selecting write mask data. Symbol D denotes write data sent over the common bus, and symbol C denotes a selection signal for controlling the operational function selector 5 and write mask selector 28 . FIG. 30 is a block diagram showing the application of the inventive frame buffer memory circuit 9 shown in FIG. 25 to the multi-processor system, in which are included data processors 20 and 20 ′, a common bus 21 and an address decoder 22 . The following describes, as an example, the operation of this embodiment. For clarification purposes, FIGS. 25 and 30 do not show the memory read data bus, memory block address decoder and read-modify-write control circuit, all of which are not essential for the explanation of this invention In this embodiment, the memory circuit 9 is addressed from 800000H to 9FFFFFH. The memory circuit 9 itself has a 1M byte capacity in a physical sense, but it is addressed double in the range 800000H-9FFFFFH to provide a virtual 2M byte address space. The method of double addressing is such that address 800000H and address 900000H contain the same byte data, and so on, and finally address 8FFFFFH and address 9FFFFFH contain the same byte data. Accordingly, data read by the processor 20 at address 8 xxxxxH is equal to data read at address 9 xxxxxH, provided that the address—section xxxxx is common. The reason for double addressing the memory circuit 9 beginning with address 800000H and address 900000H is to distinguish accesses by the data processors 20 and 201 . Namely, the data processor 20 is accessible to a 1M byte area starting with 800000H, while the-processor 20 , is accessible to a 1M byte area starting with 900000H. The address decoder 22 serves to control the double addressing system, and it produces a “O” output in response to an address signal having an even (8H) highest digit, while producing a “1” output in response to an address signal having an odd (9H) highest digit. The operation unit I has a function set of 16 logical operations as listed in FIG. 31 . In order to specify one of the 16 kinds of operations, the operation code data FC is formatted in 4 bits, and the operational function specifying registers 23 and 24 and operational function selector 25 are all arranged in 4 bits. Since the memory 2 is of the 16-bit word length, the write mask registers 26 and 27 and mask selector 28 also have 16 bits. Next, the operation of the data processor 20 in FIG. 30 in making write access to the frame buffer memory 9 will be described. The data processor 20 has a preset of function code FO in the operational function specifying register 23 and mask data MO in the write mask register 26 . When the data processor 20 makes write access to address 800000H, for example. the memory access operation takes place in the order of reading, modifying and writing in the timing relationship as shown in FIG. 39 . In response to the output of address 800000H onto the address bus by the data processor 20 , the address decoder 22 produces a “O” output, the operational function selector 25 selects the operational function specifying register 23 , and the operation unit 1 receives F 0 as operation code data FC. At this time, the write mask selector 28 selects the write mask register 26 , and it outputs MO as WE to the memory 2 . In FIG. 39, data in address SOOOOOH is read out in the read period, which is subjected to calculation with write data D from the data processor 20 by the operation unit 1 in accordance with the calculation code data FO in the modification period, and the result is written in accordance with data MO in the write period. The write mask data inhibits writing at “O” and enables writing at “1”, and the data MO is given value FFH for the usual write operation. When another data processor 20 ′ makes-access to the frame buffer 9 , function code F 1 is preset in the operational function specifying register 24 and mask data M 1 is preset in the write mask register 27 . In order for the data processor 201 to access the same data as one in address 800000H for the data processor 20 , it makes write access to address 900000H. The write access timing relationship for the data processor 201 is similar to that shown in FIG. 39, but differs in that the output signal C of the address decoder 22 is “1” during the access, the function code for modification is F 1 , and the write mask is M 1 in this case. Accordingly, by making the data processors 20 and 20 ′ access different addresses, the calculation and mask data can be different, and the operational functions need not be set at each time even when the processors implement different display operations as shown in FIG. 29 . Next, the arrangement of the frame buffer memory 9 and the method of setting the operational function according to this embodiment will be described. FIG. 32 shows a typical arrangement of the frame buffer. Conventionally, a memory has been constructed using a plurality of memory IC (Integrated Circuit) components with external accompaniments of an operation unit 1 , operational function specifying register 23 and write mask register 26 . The reason for the arrangement of the memory using a plurality of memory IC components is that the memory capacity is too large to be constructed by a single component. The memory is constructed divisionally, each division constituting 1, 3 or 4 bits or the like of data words (16-bit word in this embodiment). For example, when each division forms a bit of data words, at least 16 memory IC components are used. For the same reason when it is intended to integrate the whole frame buffer shown in FIG. 32, it needs to be divided into several IC components. The following describes the method of this embodiment for setting the operational function and write mask data for the sliced memory structure. The setting method will be described on the assumption that a single operational function specifying register and write mask register are provided, since the plurality of these register sets is not significant for the explanation. Currently used graphic display units are mostly arranged to have operational functions of logical bit operations, and therefore it is possible to divide the operation unit into bit groups of operation data. It is also possible in principle to divide the operation unit on a bit slicing basis also for the case of implementing arithmetic operations, through the additional provision of a carry control circuit. The write mask register 26 is a circuit controlling the write operation in bit units, and therefore it can obviously be divided into bit units. The operational function specifying register 23 stores a number in a word length determined from the type of operational function of the operation unit 1 , which is independent of the word length of operation data (16 bits in this embodiment), and therefore it cannot be divided into bit groups of operation data. On this account, the operational function specifying register 23 needs to be provided for each divided bit group. Although it seems inefficient to have the same functional circuit for each divided bit group, the number of elements used for the peripheral circuits is less than 1% of the memory elements, and the yearly increasing circuit integration density makes this matter insignificant. However, in contrast to the case of slicing the operational function specifying register 23 into bit groups, partition of the frame buffer-shown in FIG. 32 into bit groups of data is questionable. The reason is that the operational function specifying register 23 is designed to receive data signals D 15 -DO. When the frame buffer is simply sliced into 1-bit groups, the operational function specifying register 23 can receive 1-bit data and it cannot receive a 4-bit specification code listed in FIG. 31 . If, on the other hand, it is designed to supply a necessary number of 1-bit signals to the operational function specifying register 23 , the frame buffer must have terminals effective solely for the specification of operational functions, and this will result in an increased package size when the whole circuit is integrated. If it is designed to specify the operational function using the data bus, the number of operational functions becomes dependent on bit slicing of data, and to avoid this the frame memory of this embodiment is intended to specify operational functions using the address but which is independent of bit slicing. FIG. 33 shows, as an example, the arrangement of the frame buffer memory which uses part of the address signals for specifying operational functions. Symbol Dj denotes a 1-bit signal in the 16-bit data signals to the graphic display data processor, A 23 -A 1 are address signals to the data processor, WE is the write control signal to the data processor, FS is the data setting control signal for the operational function specifying register 3 and write mask register 26 , DOj is a bit of data read out of the memory device 2 , DIj is a bit of data produced by the operation unit 1 , and Wj is the write control signal to the memory device 2 . FIG. 34 shows, as an example, the arrangement of the write mask register, which includes a write mask data register 61 and a gate 62 for disabling the write control signal WE. FIG. 35 shows the arrangement of the frame buffer constructed by using the memory circuit shown in FIG. 33 . The figure shows a 4-bit arrangement for clarifying the connection to each memory circuit. FIG. 36 shows the memory circuit of this embodiment applied to a graphic display system, with the intention of explaining the setting of the operation code. Reference number 20 denotes a data processor, and 23 denotes a decoder for producing the set signal FS. The following describes the operation of the memory circuit. In this embodiment, an address range 800000H-9FFFFFH is assigned to the memory circuit 9 . The decoder 23 produces the set signal FS in response to addresses AOOOOOH-AOOOIFH. The operation unit 1 has the 16 operational functions as listed in FIG. 31 . When the data processor 20 operates to write data FOFFH in address A00014H, for example, the decoder 23 produces the set signal FS to load the address bit signals A 4 -A 1 , i.e., 0101B (B signifies binary), in the operational function specifying register 3 . Consequently, the operation unit 2 selects the logical-sum operation in compliance with the table in FIG. 31 . In the write mask register 26 , a bit of 16-bit data OFOOH from the data processor 20 , the bit position being the same as the bit position of the memory device, is set in the write mask data register 61 . As a result, FOFFH is set as write mask data. Next, the operation of the data processor 20 for writing F3FFH in address 800000H will be described. It is assumed that the address BOOOOOH has the contents of 0512H in advance. FIG. 37 shows the timing relation-ship of memory access by the data processor 10 . The write access to the memory circuit 9 by the data processor 20 is the read-modify-write operation as shown in FIG. 37 . In the read period of this operation, data 0512H is read out onto the DO bus, and the D bus. receives F3FFH. In the subsequent modification period, the operation unit 1 implements the operation between data on the D bus and DO bus and outputs the operation result onto the DI bus. In this example, the D bus carries F3FFH and the DO bus carries 0512H, and the DI bus will have data F7FFH as a result of the logical-sum operation which has been selected for the operation unit 1 . Finally, in the write period of the read-modify-write operation, data F7FFH on the DI bus is written in the memory device. In this case, FOFFH has been set as write mask data by the aforementioned setting operation, and a “O” bit of mask data enables the gate 62 , while “1” bit disables the gate 62 as shown in FIG. 34, causing only 4 bits (D 11 -D 8 ) to undergo the actual write operation, with the remaining 12 bits being left out of the write operation. Consequently, data in address 800000H is altered to 0712H. The foregoing embodiment of this invention provides the following effectiveness. Owing to the provision of the operation specifying registers 23 and 24 and the write mask registers 26 and 27 in correspondence to the data processors 20 and 20 ′, specification of a modification function for the read-modify-write operation and mask write specification are done for each data processor even in the case of write access to the frame buffer memory 9 by the data processors 20 and 20 ′ asynchronously and independently, which eliminates the need for arbitration control between the data processors, whereby both processors can implement display processings without interference from each other except for an access delay caused by conflicting accesses to the frame buffer memory 9 . The above embodiment is a frame buffer memory for a graphic display system, and the data processors 20 and 20 ′ mainly perform the coordinate calculations for pixels. The two data processors can share in the coordinate calculation and other processes in case they consume too much time, thereby reducing the processing time and thus minimizing the display wait time. For the case of a time-consuming frame buffer write processing, the use of the read-modify-write operation reduces the frequency of memory access, whereby a high-speed graphic display system operative with a minimal display wait time can be realized. The above embodiment uses part of the address signal for the control signal, and in consequence a memory-circuit operative in read-modify-write mode with the ability of specifying the operational function independent of data slicing methods can be realized. On this account, when all functional blocks are integrated in a circuit component, the arrangement of the memory section can be determined independently of the read-modify-write function. Although in the foregoing embodiment two data processors are used, it is needless to say that a system including three or more data processors can be constructed in the same principle. The present invention is obviously applicable to a system in which a single data processor initiates several tasks and separate addresses are assigned to the individual tasks for implementing parallel display processings. The memory circuit of the above embodiment differs from the usual memory IC component in that the set signal FS for setting the operational function and w-rite-mask data and the signal C for selecting an operational function and write mask are involved. These signals may be provided from outside at the expense of two additional IC pins as compared with the usual memory device, or may be substituted by the aforementioned signals by utilization of the memory access timing relationship for the purpose of minimizing the package size. FIG. 38 shows the memory access timing relation-ship for the latter method, in which a timing unused in the operation of a usual dynamic RAM is used to distinguish processors (the falling edge of RAS causes the WE signal to go low) and to set the operation code and write mask data (the rising edge of RAS causes CAS and WE signals to go low), thereby producing the FS and C signals equivalently. Although in the above embodiment a 16-bit data word is sliced into 1-bit groups, these values can obviously be altered. Although in the above embodiment the operational function and write mask are specified concurrently, they may be specified separately. It is obvious that the word length for operational function specification may be other than 4 bits. The above embodiment can also be applied to a memory with a serial output port by incorporating a shift register. According to the above embodiments, the coordinate calculation process in the display process is shared by a plurality of processors so that the calculation time is reduced, and the frame buffer memory operative in a read-modify-write mode can be shared among the processors without the need of arbitration control so that the number of memory accesses is reduced, whereby a high-speed graphic display system can be constructed. Moreover, the modification operation for the read-modify-write operation is specified independently of the word length of write data, and this realizes a memory circuit incorporating a circuit which implements the read-modify-write operation in arbitrary word lengths, whereby a frame buffer used in a high-speed graphic display system, for example, can be made compact.

A memory device which includes dynamic random access memories for effecting data read and write operations, first and second data terminals for receiving data, and a controller having a first data input connected to receive first data, a second data input connected to receive second data, a third data input connected to receive a function mode signal, and operation unit for executing operations between the first data and the second data. The operation unit includes a function setting unit for setting a function indicated by a function mode signal prior to receipt of the first data. The second data is read out of a selected part of the storage locations. The operation corresponding to the set function is executed for the first and second data. The operation result is written into the selected part of the storage locations during one memory cycle.

FIELD OF THE INVENTION The present invention pertains to a joint for the movable connection of two components of a motor vehicle, which are movable in relation to one another. BACKGROUND OF THE INVENTION Such joints are currently used, e.g., as “sleeve joints” for mounting stabilizers in motor vehicles. The designation “sleeve joint” is derived from the mount body present in the mount, which is designed as a sleeve in prior-art embodiments, so that it has a through hole. The sleeve joints known from the state of the art have a mount body with a spherically shaped bearing surface. This is accommodated in a complementarily shaped bearing shell inner surface of the bearing shell and is guided therein in a slidingly movable manner. For example, a bolt, which is used to fasten the joint to a motor vehicle component, is passed through the through hole of the mount body. However, the problem arises that the space necessary for introducing and fixing the bolt in the area of the wheel suspension is very limited. Thus, the installation of prior-art joints in the motor vehicle is rather difficult. Moreover, it was observed that the cross section of the prior-art sleeve joints is weakened due to the through hole prepared in the mount body, and this weakening must be compensated by the application of additional material on the outer circumference of the mount body in order to reach the required strength values of the component. The prior-art joint designs correspondingly have a considerable overall volume and consequently require more space for installation in the area of the wheel suspension than would be desirable. SUMMARY OF THE INVENTION The basic object of the present invention is to make available a joint that has a compact design and can be preferably connected to a motor vehicle component from one side, so that its installation is simplified. Accordingly, a joint according to the present invention for the movable connection of two components of a motor vehicle, which are movable in relation to one another, has a housing and a bearing shell accommodated in the housing for the slidingly movable mounting of a mount body. The mount body is provided with a bearing surface curved complementarily to the bearing shell inner surface and is thus accommodated in the bearing shell in a slidingly movable manner. On at least one side, the mount body has a pin neck, and the bearing surface passes over into the pin neck. The pin neck has a connection area for connecting the mount body to a bearing journal. Due to a mount body being equipped with a connection area, it becomes possible to connect a bearing journal to be mounted on the mount body to the mount body in a very short time, so that the time needed for installing a joint according to the present invention becomes shorter. In addition, the installation of the joint in the motor vehicle is simplified. The joint has a small overall size and is consequently very compact. In a preferred embodiment of the present invention, the mount body has two pin necks arranged diametrically to each other, and the curved bearing surface is a joint ball. Thus, the mount body has an outer geometry similar to the prior-art sleeve joint inner parts. Unlike in the prior-art designs of the sleeve joint inner parts, the mount body is not provided with a through hole in the joint according to the present invention, but it has only a connection area for connection to the bearing journal, which is preferably provided on the pin neck. Both connections by material bonding (to integrate structurally) and positive-locking connections may be selected for connecting the pin neck of the mount body to the bearing journal. Moreover, a combination of connection by material bonding and positive-locking connection is possible and can be embodied in the sense of the present invention. Thus, corresponding to a variant of the present invention, the connection by material bonding between the pin neck and the bearing journal may be a welded connection or a bonded connection. Processes such as friction welding or resistance pressure welding are possible for preparing the welded connection. A positive-locking connection between the pin neck and the bearing journal may, moreover, be designed such that at least one pin, which passes through an opening of a flange present at the bearing journal and is placed on the flange on the opposite side of the flange by means of deformation of the material, is made in one piece with the pin neck. A nondetachable connection, which meets very high requirements in terms of fatigue strength, is thus obtained between the bearing journal and the pin neck. Another possibility of preparing the connection between the pin neck and the bearing journal is to make a connection pin, whose geometry, which deviates from a regular cylindrical shape at least in some sections, is fitted into a complementary recess of the bearing journal, in one piece with the pin neck. The reverse case can also be readily embodied in the sense of the present invention. Thus, a recess may be prepared in the pin neck, and a connection pin having a geometry deviating from the regular cylindrical shape at least in some sections is then introduced into the said recess. In other words, the pin neck of the mount body is thus connected to the bearing journal by a connection pin being present on the first component and by a corresponding recess being prepared in the other component. Thus, a deformation process may be used as the manner of connecting the components indicated. Furthermore, it is possible to prepare the connections by means of a press fit or, in the simplest case, to provide a thread on the connection pin, which thread can be screwed into a fitting internal thread of the recess. Moreover, combined with the positive-locking connection, a connection by material bonding may be selected for the permanent, nondetachable fixation of the mount body on the bearing journal. This is possible, but not absolutely necessary in the sense of the present invention. Moreover, a variant of the present invention is seen in that a contour for the action of a tool or a tool engagement contour is provided on the bearing journal and/or the mount body. This tool action contour or tool engagement contour permits the simplified mounting of the joint according to the present invention as well as facilitated installation in the wheel suspension of a motor vehicle. The tool action contour or tool engagement contour is used as a holder for a tool while the bearing journal is being connected to the bearing body. If this connection comprises the above-mentioned threaded connection, the tool engagement contour or tool action contour offers an ideal possibility of holding the components in this case. Two preferred embodiments of a joint according to the present invention will be described in greater detail below on the basis of the views in the figures. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial sectional view through a first joint according to the present invention; FIG. 2 is a partially cut-away mount body as an individual part; FIG. 3 is a partially cut-away view of a bearing journal; FIG. 4 is a sectional view through another embodiment of a joint according to the present invention; FIG. 5 is a section through the mount body of a joint according to FIG. 4 ; FIG. 6 is a partially cut-away bearing journal of the joint shown in FIG. 4 ; and FIG. 7 shows a partial section through another joint. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings in particular, FIG. 1 shows an embodiment of a joint according to the present invention. This joint comprises a housing 1 and a bearing shell 2 inserted into the housing. The bearing shell accommodates a curved, here spherically shaped bearing surface 4 of a mount body 3 , which said bearing surface is rotatably or tiltably movable. The bearing shell 2 has a bearing shell inner surface curved complementarily to the bearing surface 4 for this purpose. The housing 1 of the joint shown in FIG. 1 has two housing openings 23 , 24 and is open on both sides. The housing 1 has on one side a collar, which is directed toward the inside of the joint and at which the bearing shell 2 is supported in the axial direction of the joint. On the opposite side, the bearing shell 2 is fixed in the housing 1 by means of a securing ring 17 . The bearing shell 2 is fixed in the known manner by the deformation of an edge of the housing, so that the securing ring is thus locked in a groove of the housing. The mount body 3 has a pin neck 5 each on both sides of the curved bearing surface 4 designed as a joint ball. As can be recognized in the upper part of FIG. 1 , a tool engagement contour 15 was prepared in the pin neck 5 of the mount body 3 . This tool engagement contour 15 comprises in this case a hexagonal recess or a hexagonal round recess (Torx) for attaching a corresponding tool wrench. In the lower part of the mount body 3 , the mount body is provided with a connection area 6 . In the embodiment of a joint according to the present invention shown in FIG. 1 , the connection area comprises a connection pin 12 , which is made in one piece with the mount body 3 and is made integrally with the mount body 3 and is screwed with a corresponding external thread 20 (see FIG. 2 ) intro a corresponding internal thread 21 (see FIG. 3 ) of the bearing journal 7 . To prepare the internal thread 21 in the bearing journal 7 , a recess 13 is prepared in the bearing journal in advance. To improve the contact between the mount body 3 and the bearing journal 7 , a flange 8 is present in the contact area of the said components. A sealing bellows 14 , on the one hand, and, on the other hand, another sealing bellows 16 are used to seal the sensitive components of the joint. The sealing bellows 14 and 16 are fixed directly on the pin neck 5 by means of respective straining rings 18 and 19 , on the one hand, and in a groove of the housing, on the other hand. The pin necks 5 of the mount body pass through the housing openings 23 and 24 in the axial direction and project from the housing 1 on both sides, so that the tool engagement contour 15 and the connection area 6 can be used here to mount the joint as well as to install it in the motor vehicle. A mount body 3 of the joint according to the present invention, which is described in FIG. 1 , is shown as an individual part once again in FIG. 2 for better illustration. This mount body 3 has on one side a connection pin 12 , which was provided with an external thread 20 . This connection pin 12 is made integrally with the mount body 3 and is made on one side in one piece with a part of the mount body 3 , which part is designed as a pin neck 5 . On the side of the mount body 3 located opposite the connection pin 12 , the mount body has, moreover, a tool engagement contour 15 for attaching a tool wrench. Moreover, FIG. 3 shows a partially cut-away view of a bearing journal 7 of the embodiment of a joint shown in FIG. 1 . The partial section clearly shows the blind hole 22 prepared in the bearing journal 7 , in which blind hole an internal thread 21 was prepared. To improve the contact between the pin neck 5 of the mount body 3 and the bearing journal 7 , a flange 8 is made in one piece with the bearing journal 7 . Furthermore, a tool engagement contour 15 , which has a shape similar to that of the tool engagement contour shown in FIG. 2 , is prepared on the side located opposite the flange 8 in the embodiment of a bearing journal 7 shown here. Another possible embodiment of a joint according to the present invention is shown in a partial sectional view in FIG. 4 . The design of this joint is basically similar to that of the joint shown, and the same reference will therefore also be used to designate identical components. Unlike in the view in FIG. 1 , the mount body 3 has a recess 13 , which was prepared only to a defined depth in the mount body 3 . This recess 13 , prepared as a blind hole 22 , has, moreover, an internal thread 21 . A connection pin 12 , on which a corresponding external thread 20 is present, can be screwed into this internal thread until the face of the pin neck 5 of the mount body 3 comes into contact with the flange 8 of the bearing journal 7 , on which the connection pin is present and secure locking of the components to be connected is thus made possible as a consequence of the self-locking of the thread. As is apparent from FIG. 5 , in which a sectional view of the mount body 3 of a joint according to FIG. 4 is shown, the mount body 3 also has a tool engagement contour 15 on the side located opposite the connection area 6 . Since the recess 13 is not a through hole, higher strength values can be obtained with the embodiments being shown here along with reduced dimensions than was hitherto possible in prior-art joints. FIG. 6 once again shows a bearing journal 7 , which has in the partial section a tool engagement contour 15 , on the one hand, and, located opposite this above the flange 8 , a connection pin 12 , whose external thread 20 can be screwed into the above-described internal thread 21 of the mount body 3 until the face of the pin neck 5 of the mount body 3 comes into contact with the flange 8 . Moreover, the tool engagement contour 15 is used to facilitate the installation of the joint in the wheel suspension of a motor vehicle. Furthermore, FIG. 7 shows a detail of the connection area between the bearing journal 7 and the mount body 3 , as can also be applied in a meaningful manner. The pin neck 5 has a recess 13 here, into which a connection pin 12 is inserted. The connection pin and the recess have complementary regular cylindrical contours. A plurality of openings 10 , through which pins 9 made in one piece with the pin neck 5 pass, are prepared in the flange 8 on the bearing journal 7 , distributed over its circumference. On the side located opposite the pin neck 5 , these pins 9 have a material deformation 11 , so that they guarantee a permanent connection between the bearing journal 7 and the mount body 3 . While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

A joint for the movable connection of two components of a motor vehicle, which are movable in relation to one another, with a housing ( 1 ) and with a bearing shell ( 2 ) accommodated in the housing ( 1 ) for the slidingly movable mounting of a mount body ( 3 ) is presented, wherein the mount body ( 3 ) has a bearing surface ( 4 ) curved complementarily to the bearing shell inner surface and passes over at least on one side into a pin neck ( 5 ), which has a connection area ( 6 ) for connection to a bearing journal ( 7 ).

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit under 35 U.S.C. Section 371, of PCT International Application No. PCT/JP2005/013626, filed Jul. 26, 2005 and Japanese Application No. 2004-256597, filed Sep. 3, 2004 in Japan, the contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of exhaust gas purification and an exhaust gas purification system having a catalyst unit carrying a NOx (nitrogen oxides) occlusion-reduction type catalyst that reduces and purifies NOx in exhaust gas from internal combustion engines. 2. Description of the Related Art Various research and proposals have been made regarding NOx (nitrogen oxides) catalysts to reduce and remove NOx in exhaust gas from internal combustion engines such as diesel engines and certain types of gasoline engines and various combustion units. One of such catalysts is a NOx occlusion-reduction type catalyst, which is a catalyst for decreasing NOx from diesel engines. By using a catalyst unit carrying the NOx occlusion-reduction type catalyst, NOx in exhaust gas can be purified effectively. This catalyst unit is constructed, having a monolith honeycomb 30 M whose structure is as shown in FIG. 7 . The monolith-honeycomb 30 M, as shown in FIG. 8 , is constructed by forming multiple of polygonal cells 30 S on a support 31 that is a structural material made of cordierite or stainless steel. On the walls of the cells 30 S, as shown in FIGS. 8 and 9 , a porous catalyst coat layer 34 , which is a catalyst carrying layer, made of alumina (Al 2 O 3 ) or zeolite is provided. The catalyst coat layer 34 increases the contact surface area with exhaust gas. On the surface of the catalyst coat layer 34 , there are carried precious metal (catalytically active metal) 32 and NOx occlusion material (NOx occlusion substance: NOx occlusion agent; NOx absorbent) 33 . A catalytic function is provided by the construction described above. FIGS. 10 and 11 show the configuration and occlusion-reduction mechanism of catalytic substances 32 and 33 on the surface of the carrying layer of the catalyst unit. In the catalyst unit, precious metal 32 having an oxidation function and NOx occlusion material 33 having a NOx occlusion function, are carried on the catalyst coat layer 34 . The precious metal 32 is platinum (Pt) or the like. The NOx occlusion material 33 is made of some of alkaline metals such as potassium (K), sodium (Na), lithium (Li) and cesium (Cs), alkaline earth metals such as barium (Ba) and calcium (Ca) and rare-earth metals such as lanthanum (La) and yttrium (Y). Depending on the oxygen concentration in exhaust gas, the catalyst unit having the above described construction will perform the function of NOx occlusion or NOx release with purification of the released NOx. As shown in FIG. 10 , in normal diesel engines, lean-burn gasoline engines and the like, the exhaust gas contains oxygen (O 2 ). In such cases where the air/fuel ratio of exhaust gas is in a lean air/fuel condition, nitrogen monoxide (NO) emitted from engines is oxidized into nitrogen dioxide (NO 2 ) with oxygen contained in exhaust gas by the oxidation catalytic function of precious metal 32 . Then, the nitrogen dioxide is occluded in the form of nitrate to the NOx occlusion material 33 such as barium having a NOx occlusion function, thus purifying NOx. However, if the above reaction continues, the entire portion of the NOx occlusion material 33 having a NOx occlusion function will turn into nitrate, and will therefore lose the NOx occlusion function eventually. Therefore, exhaust gas with high fuel concentration (rich spike gas) is generated by changing the operating conditions of an engine or by injecting fuel into an exhaust passage, and then fed into the catalyst. The rich spike gas has no oxygen and a high carbon monoxide (CO) concentration with a high temperature. Then, as shown in FIG. 11 , in the rich air/fuel condition where there is no oxygen and a high concentration of carbon monoxide with a raised exhaust gas temperature, the nitrate formed after occluding NOx, releases nitrogen dioxide and returns to the original barium and the like. The released nitrogen dioxide, since no oxygen exists in the exhaust gas, is reduced by the oxidation function of carried precious metal 32 , thus purifying the exhaust gas. That is, nitrogen dioxide is reduced into water (H 2 O), carbon dioxide (CO 2 ) and nitrogen (N 2 ) by using carbon monoxide, carbon hydride (HC) and hydrogen (H 2 ) that are reductants in exhaust gas. For the purpose described above, in an exhaust gas purification system having a catalyst unit carrying a NOx occlusion-reduction type catalyst, as described in Japanese Patent Application Kokai Publication No. 1994-336916, for example, the following regeneration operation is performed. When an estimated NOx occlusion amount reaches a NOx saturation amount, the air/fuel ratio in exhaust gas is made rich, thus decreasing the oxygen concentration in inflowing exhaust gas. That is, a rich control is performed for restoring a NOx occlusion capacity. The rich control causes occluded NOx to be released and the released NOx to be reduced with a precious metal catalyst. However, in the conventional rich combustion control for regenerating the NOx occlusion capacity of the catalyst unit carrying a NOx occlusion-reduction type catalyst, the rich control is performed at the excess air ratio λ of 1.0 i.e. at the theoretical air/fuel ratio in the initial stage of rich combustion as shown in FIG. 12 . At the beginning, the oxygen adsorbed onto the surface of the catalyst is released. The released oxygen consumes reductant in exhaust gas. Therefore, sufficient amount of reductant does not remain to reduce released NOx, so that the NOx reduction reaction is insufficiently activated. As a result, the NOx concentration at a catalyst outlet Cnoxex is remarkably higher compared to the NOx concentration at a catalyst inlet Cnoxin, and a large amount of unpurified NOx is released into the downstream of the catalyst unit. That is, the air/fuel ratio adjacent to the catalyst surface does not become rich because of the oxygen adsorbed on the catalyst surface. Therefore, NOx cannot be reduced and flows out. As a result, there is a problem that the overall performance of NOx purification is degraded. In addition, in this regeneration control of the catalyst unit, the release of oxygen adsorbed onto the catalyst surface occurs more easily, compared to the release of NOx due to the decomposition of nitrate. As a result, in the initial stage of the regeneration control, NOx remain in a NOx occlusion agent at a high degree. This causes a problem that the restoration of a NOx occlusion capacity becomes insufficient, unless the regeneration control time is set, taking the above described issue into consideration. In order to solve the problem, there is considered making the exhaust gas more fuel-rich. That can be attained by measuring the amount of oxygen adsorbed onto the catalyst unit in an experiment in advance and increasing the amount of reductant corresponding to the amount of oxygen released from the adsorbed oxygen. An example close to this consideration is proposed in Japanese Patent Application Kokai Publication No. 2000-27677, which is an exhaust gas purification unit for a lean-burn internal combustion engine. In this exhaust gas purification unit, a catalyst unit having an oxygen (O 2 ) storage function is placed in the upstream of a catalyst unit carrying a NOx occlusion-reduction type catalyst. The catalyst unit in the upstream works as a catalyst unit for startup time and its main purpose is to remove HC and CO components that are released in large amounts from an engine at startup. In this exhaust gas purification unit, the catalyst unit for startup time releases oxygen during a rich spike operation for regenerating the catalyst unit carrying a NOx occlusion-reduction type catalyst. By releasing oxygen, it is intended to solve the problem that unpurified NOx are flowed out toward the downstream of the catalyst unit in the initial stage of the regeneration. This exhaust gas purification unit comprises a means for decreasing storage that makes an air/fuel ratio even richer than that during the rich spike operation for regenerating a NOx occlusion-reduction type catalyst by adding reductant to consume the entire amount of oxygen released from the catalyst unit in the upstream for startup time. The means for decreasing storage prevents the air/fuel ratio adjacent to a NOx occlusion-reduction type catalyst from becoming less rich than the theoretical air/fuel ratio in the initial stage of the rich spike operation, thus preventing NOx from being unpurified. However, if the regeneration control of increasing the amount of reductant corresponding to the amount of released oxygen is employed, NOx continue to be released even after the completion of oxygen release. Because of this, the amounts of HC and CO that are reductant in exhaust gas become excessive, after oxygen that has been absorbed by an oxygen storage function, is released from the surface of a catalyst. As a result, there arises a problem that the exhaust gas is extremely deteriorated since HC and CO that have not been used for the reduction of NOx are flowed out in unpurified state toward the downstream of the catalyst unit carrying a NOx occlusion-reduction type catalyst. That is, as shown in FIG. 13 , when the more fuel-rich control whose excess air ratio λ is smaller than 1.0, i.e. whose air/fuel ratio is smaller than the theoretical air/fuel ratio is performed, the NOx concentration at a catalyst outlet Cnoxex in the initial stage becomes lower. However, the HC concentration at the catalyst outlet Chcex becomes extremely high since the consumption of reductant is decreased when oxygen is no longer released. As a result, after oxygen adsorbed on the surface of a catalyst is consumed, a large amount of HC flows out (or slips) unused toward the downstream of the catalyst unit. Meanwhile, an exhaust gas purification unit for an internal combustion engine is proposed, for example, as described in Japanese Patent Application Kokai Publication No. 2002-188430. In this exhaust gas purification unit, the feedback control for the supply amount of reductant is performed by using an air/fuel ratio sensor placed in the downstream of a catalyst unit carrying a NOx occlusion-reduction type catalyst. In the initial stage of regeneration control, the feedback control is stopped during a predetermined period until the output value from the air/fuel ratio sensor reaches a certain predetermined value, i.e. during a period until oxygen (O 2 ) storage effect converges. This prevents unnecessary supply of reductant caused by the oxygen occlusion function of a NOx occlusion material (NOx absorbent). At the same time, this prevents the deterioration of exhaust emissions caused by excessive supply of reductant and the useless consumption of reductant. However, in this exhaust gas purification unit for an internal combustion engine, in the downstream of a catalyst unit, an air/fuel ratio is considered to exhibit a high apparent air/fuel ratio temporarily due to the release of oxygen caused by oxygen storage effect. Based on this consideration, the unit prevents the supply amount of reductant from exceeding the amount of reductant that should be supplied to the catalyst unit. Accordingly, the consumption of reductant by released oxygen is not taken into consideration. As a result, there arises a problem that unpurified NOx cannot be prevented from flowing out toward the downstream of the catalyst unit in the initial stage of rich spike operation. SUMMARY OF THE INVENTION The present invention has been made to solve the above mentioned problems, and therefore an object of this invention is to provide a method of exhaust gas purification and an exhaust gas purification system using a NOx occlusion-reduction type catalyst for purifying NOx in exhaust gas, which can prevent both the outflow of unpurified NOx in the initial stage of regeneration and the outflow of unused reductant such as HC and CO in the later-stage of regeneration, by performing the generation control that supplies an appropriate amount of reductant into exhaust gas, taking an oxygen storage function into consideration during the regeneration control of the NOx occlusion-reduction type catalyst. A method of exhaust gas purification for achieving the above-described object is a method of exhaust gas purification in a purification system for nitrogen oxides in exhaust gas, having a catalyst unit carrying a NOx occlusion-reduction type catalyst, which occludes NOx when an air/fuel ratio in exhaust gas is in a lean condition, and releases and reduces the occluded NOx when an air/fuel ratio in exhaust gas is in a rich condition, and performing the regeneration control to restore a capacity of the catalyst unit for occluding NOx when it is determined that an estimated amount of NOx occluded in the catalyst unit reaches a predetermined determination value, wherein said regeneration control comprising; performing a first rich control whose target air/fuel ratio is smaller than the theoretical air/fuel ratio by adding an amount of reductant meeting an amount of oxygen released from the catalyst unit in the initial stage of regeneration control to an amount of reductant supplied in order to reduce NOx released from the catalyst unit; determining completion of the oxygen release on the basis of an oxygen concentration in a downstream of the catalyst unit in said first rich control and performing a second rich control whose target air/fuel ratio is higher than that of the first rich control and closer to the theoretical air/fuel ratio when the oxygen release is determined to have been completed. The above mentioned air/fuel ratio in exhaust gas does not necessarily represent the air/fuel ratio in a cylinder, but represents the ratio between an amount of air and an amount of fuel (including the amount combusted in the cylinder) that are supplied into the exhaust gas flowing into the catalyst unit carrying a NOx occlusion-reduction type catalyst. In addition, it is preferable to set the target air/fuel ratio of the first rich control to 0.70 to 0.98 in terms of an excess air ratio λ, and the target air/fuel ratio of the second rich control to 0.98 to 1.02 in terms of an excess air ratio λ respectively. The relation between an air/fuel ratio (=amount of air/amount of fuel) and an excess air ratio λ is expressed as an excess air ratio=(air/fuel ratio/theoretical air/fuel ratio). According to the above mentioned method of exhaust gas purification, the first rich control is performed with an increased amount of reductant required to consume oxygen released in the initial stage of regeneration, taking into consideration the oxygen storage function of the catalyst unit. This enables the air/fuel ratio adjacent to a NOx occlusion-reduction type catalyst to be maintained in a rich condition close to the theoretical air/fuel ratio, despite of oxygen release. In addition, unpurified NOx can be prevented from flowing out toward the downstream of the catalyst unit since the sufficient amount of reductant is supplied to reduce NOx released. Furthermore, even after the completion of oxygen release, the second rich control with a reductant amount changed appropriately, enables the air/fuel ratio adjacent to a NOx occlusion-reduction type catalyst to be maintained in a rich condition close to the theoretical air/fuel ratio. Furthermore, unused HC and CO can be prevented from flowing out toward the downstream of a NOx occlusion-reduction type catalyst since unused reductant does not remain when released NOx are reduced. Also, in the above described method of exhaust gas purification, a regeneration control can be performed with a relatively simple algorithm, by determining the amount of reductant meeting the oxygen amount released from the catalyst unit from the map data showing the relation between catalyst unit temperatures and oxygen occlusion amounts, and also by performing a feedback control so that the oxygen concentration at the inlet of the catalyst unit becomes the oxygen concentration of the target air/fuel ratio in the first and second rich controls. The map data, showing the relation between catalyst unit temperatures and oxygen occlusion amounts, is obtained by an experiment in advance, input into a control unit and referred to during the regeneration control. Furthermore, in the above described method of exhaust gas purification, in determining the completion of oxygen release, the oxygen release is determined to have been completed when an output value of an excess air ratio sensor that detects an oxygen concentration in the downstream of the catalyst unit is reversed. This excessive air ratio sensor has a large output change near the stoichiometric air/fuel ratio (the theoretical air/fuel ratio) and thus can determine the completion of oxygen release easily and accurately. An O 2 sensor that has a characteristic of changing the output value rapidly at λ=1.0 between the rich side and the lean side, is used as the excess air ratio sensor. The O 2 sensor is calibrated to set λ=1.0 to zero point, so that the output value is reversed at λ=1.0 between positive and negative, thus enabling On/Off output. In addition, in the above described method of exhaust gas purification, the control time of the second rich control can be determined by a relatively simple algorithm if the control time is calculated from the map data based on an engine load and an engine speed or the map data based on an engine load and a catalyst unit temperature. These map data, are obtained by an experiment in advance, input into a control unit and referred to during the regeneration control. Alternatively, in the above described method of exhaust gas purification, the control time of the second rich control is determined by a relatively simple algorithm if the control time is calculated from the amount of the NOx remaining in the catalyst unit and the amount of the HC detected in the downstream of the catalyst unit. The amount of the remaining NOx is determined from a map, obtained from an experiment in advance and the like, and the exhaust gas temperature and regeneration time of the pervious regeneration. The amount of the HC is calculated from the value of the excess air ratio sensor placed at the catalyst outlet, using a map showing the relation between O 2 concentrations and the amount of the HC obtained from an experiment in advance. The control time of the second rich control is determined from these maps. Also, an exhaust gas purification system for achieving the above-mentioned object is an exhaust gas purification system, having a catalyst unit carrying a NOx occlusion-reduction type catalyst, which occludes NOx when an air/fuel ratio in exhaust gas is in a lean condition, and releases and reduces the occluded NOx when an air/fuel ratio in exhaust gas is in a rich condition, and further comprising a regeneration control means for performing regeneration control in order to restore a capacity of the catalyst unit for occluding NOx when an estimated amount of NOx occluded into the catalyst unit reaches a predetermined determination value, and the generation control means comprising: a first control means for performing a first rich control whose target air/fuel ratio is smaller than the theoretical air/fuel ratio by adding the amount of reductant meeting the amount of oxygen released from the catalyst unit in the initial stage of regeneration control to an amount of ruductant supplied to reduce NOx released from the catalyst unit; a oxygen-release completion determination means for determining completion of the oxygen release from an oxygen concentration in a downstream of the catalyst unit during the first rich control; and a second rich control means for performing a second rich control whose target air/fuel ratio is higher than that of the first rich control and closer to the theoretical air/fuel ratio when the oxygen release is determined to have been completed. In addition, in the above described exhaust gas purification system, the first rich control means has an additional reductant amount calculation means for calculating an amount of additional reductant that determines an amount of reductant meeting an amount of oxygen released from the catalyst unit based on map data showing a relation between catalyst unit temperatures and oxygen occlusion amounts, and also the first rich control and the second rich control are subjected to a feedback control so that each oxygen concentration at an inlet side of the catalyst unit becomes each oxygen concentration of the target air/fuel ratio respectively. Furthermore, in the above described exhaust gas purification system, in determining completion of the oxygen release, the oxygen-release completion determination means determines that oxygen release has been completed when an output value of an excess air ratio sensor that detects an oxygen concentration in a downstream of the catalyst unit, changes substantially and is reversed at an point of an excess air ratio equal to 1. Furthermore, in the above described exhaust gas purification system, the second rich control means calculates the control time of the second rich control, from the map data based on an engine load and an engine speed or from the map data based on an engine load and a catalyst unit temperature. Alternatively, in the above described exhaust gas purification system, the second rich control means determines a control time of the second rich control from an amount of NOx remaining in the catalyst unit and an amount of HC detected in the downstream of the catalyst unit. As described above, a method of exhaust gas purification and an exhaust gas purification system according to the present invention can exhibit the following effects. In the regeneration control of the catalyst unit carrying a NOx occlusion-reduction type catalyst, since the first rich control is performed with the added amount of reductant required to consume oxygen released in the initial stage of regeneration, taking into consideration the oxygen storage function of the catalyst unit, the air/fuel ratio can be maintained in a rich condition and close to the theoretical air/fuel ratio despite of the oxygen released from the catalyst unit. Furthermore, since the amount of reductant consumed by the released oxygen is taken into consideration, the NOx released from the catalyst unit can be reduced with a sufficient amount of reductant. In addition, after the completion of oxygen release, since the second rich control is performed with the amount of reductant appropriately changed, the air/fuel ratio adjacent to the NOx occlusion-reduction type catalyst can be maintained in a rich condition and close to the theoretical air/fuel ratio and the NOx released from the catalyst unit can be reduced with an appropriate amount of reductant even after oxygen release has been completed. Therefore, the outflow of unpurified NOx in the initial stage of regeneration control can be decreased, thus improving the performance of the NOx purification. Furthermore, after the completion of oxygen release, i.e. in the later-stage of regeneration control, the outflow (or slip) of unused reductant such as HC and CO can be decreased. In addition, the appropriate regeneration control against the lowering of NOx occlusion capacity can be performed, with an appropriate combustion of unused HC and CO by the function of oxidation catalyst of the NOx occlusion-reduction type catalyst, and thus preventing the localized heating of the catalyst due to the heat of the reaction. Therefore, the heat deterioration of the catalyst can be decreased. Thus, the exhaust gas purification system of the present invention can cope with low activities due to the deterioration of the catalyst and exhibits a high performance and long life. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a drawing showing a configuration of an exhaust gas purification system of an embodiment in accordance with the present invention. FIG. 2 is a block diagram showing a construction of the control means for an exhaust gas purification system of an embodiment in accordance with the present invention. FIG. 3 is a block diagram showing an example of the control flow for regenerating a catalyst unit carrying a NOx occlusion-reduction type catalyst. FIG. 4 is a schematic diagram showing a construction of the map data for the control time of a second rich control based on an engine load and an engine speed. FIG. 5 is a schematic diagram showing the relation between remaining NOx amount and HC outflow amount. FIG. 6 is a schematic diagram showing the temporal changes in fuel injection control, control of injection into an exhaust pipe, an estimated NOx occlusion amount, degree of opening of an EGR valve, degree of throttle opening of an intake valve, an intake air amount, an excess air ratio at a catalyst inlet and an excess air ratio at a catalyst outlet in the flow control shown in FIG. 3 . FIG. 7 is a drawing showing a monolith-honeycomb. FIG. 8 is an enlarged view of a part of a monolith-honeycomb. FIG. 9 is an enlarged view of the cell wall of a monolith-honeycomb. FIG. 10 is a schematic drawing showing a configuration of a catalyst unit and a purification mechanism during a lean control condition. FIG. 11 is a schematic drawing showing a configuration of a catalyst unit and a purification mechanism during a rich control condition. FIG. 12 is a schematic diagram showing the relations in a very low temperature. FIG. 13 is a diagram showing the relation between catalyst unit temperatures and purification rates. DETAILED DESCRIPTION OF THE INVENTION A method of exhaust gas purification and an exhaust gas purification system of the present invention will hereinafter be described with reference to the drawings. The term “rich condition of exhaust gas” herein used does not represent rich combustion in the cylinder, but represents a condition where the ratio between the amount of air and the amount of fuel (including the amount combusted in the cylinder) that are supplied into exhaust gas flowing into a catalyst unit carrying a NOx occlusion-reduction type catalyst, is close to the theoretical air/fuel ratio, or in a rich condition where the amount of fuel is larger than that of the theoretical air/fuel ratio. An exhaust gas purification system 10 shown in FIG. 1 is configured to place a catalyst unit 50 carrying a NOx occlusion-reduction type catalyst in an exhaust passage 20 of an engine (internal combustion) 1 . The catalyst unit 50 is formed with a monolith catalyst. In the catalyst unit 50 , a catalyst coat layer is formed on a support made of aluminum oxide, titanium oxide and the like. On the catalyst coat layer, there are carried a precious metal catalyst (catalyst metal) such as platinum (Pt) and palladium (Pd) and a NOx occlusion material (NOx occlusion substance) such as barium (Ba). In the catalyst unit 50 , NOx in exhaust gas are occluded by a NOx occlusion material when the exhaust gas has a high concentration of oxygen (lean air/fuel condition). Thereby, the NOx in exhaust gas are purified. When the oxygen concentration in exhaust gas is low or zero, the occluded NOx are released, and the released NOx are reduced by the catalytic function of a precious metal catalyst. Thereby, the outflow of NOx into the atmosphere is prevented. In the upstream of the catalyst unit 50 , an exhaust pipe fuel-admission valve 22 is provided. Fuel sent via a line (not shown) is supplied into exhaust gas as a reductant for NOx, through the exhaust pipe fuel-admission valve 22 . Thereby, the air/fuel ratio in exhaust gas is made smaller than the theoretical air/fuel ratio, and the exhaust gas is made into a more fuel-rich condition. Then, in the regeneration control of the catalyst unit 50 , a feedback control is performed so that the oxygen concentration of exhaust gas flowing into the catalyst unit 50 becomes that of the target air/fuel ratio (or excess air ratio λ). The supply amount of reductant is controlled in the feedback control. For the purpose of the feedback control, a catalyst inlet λ (excess air ratio) sensor 51 is provided on the inlet side of the catalyst unit 50 . In addition, there is provided a catalyst outlet λ sensor 52 that detects oxygen concentration in the downstream of the catalyst unit 50 , in order to determine the completion of oxygen release in the initial stage of regeneration, based on the oxygen storage function of the NOx occlusion-reduction type catalyst of the catalyst unit 50 . As the catalyst outlet λ sensor 52 , there is used an excess air ratio sensor that has a remarkably large change of output near the stoichiometric air/fuel ratio (the theoretical air/fuel ratio) and is able to determine the completion of oxygen release in a simple and accurate manner. As the excess air ratio sensor 52 , there is employed a sensor having a characteristic of reversing the output value between positive and negative at λ=1.0 when the sensor output conversion is calibrated to set λ=1.0 to zero point. The excess air ratio sensor has a characteristic of changing the output value rapidly between a rich side and a lean side at λ=1.0. The excess air ratio sensor outputs ON/OFF signals. Furthermore, on the inlet side of the catalyst unit 50 , there are disposed a catalyst inlet NOx sensor 53 and a catalyst inlet exhaust gas temperature sensor 54 that detects the temperature of the catalyst unit 50 . In addition, on the outlet side of the catalyst unit 50 , a catalyst outlet NOx sensor 55 is disposed. A turbine 21 a of a turbocharger 21 is placed on the exhaust passage 20 in the upstream of the catalyst unit 50 . On the other hand, in an intake passage 30 , there are provided a mass air flow (MAF) sensor 31 , a compressor (not shown) of the turbocharger 21 , an intercooler (not shown) and an intake throttle valve 32 . Also there is provided an EGR passage 40 that connects the exhaust passage 20 in the upstream of the turbine 21 a and the air-intake passage 30 . In the EGR passage 40 , an EGR cooler 41 and an EGR valve 42 are provided. Furthermore, a control unit (ECU: Engine Control Unit) 60 is provided, which not only controls the overall operation of the engine 1 , but also controls the regeneration of the NOx purification ability of the catalyst unit 50 . Into this control unit 60 , detected values are input from the catalyst inlet λ sensor 51 , the catalyst outlet λ sensor 52 , the catalyst inlet NOx sensor 53 , the catalyst inlet exhaust gas temperature sensor 54 , the catalyst outlet NOx sensor 55 and the like. Also, from the control unit 60 , control signals are output, which control the EGR valve 42 of the engine 1 , the fuel-injection valve 61 of a common-rail electronically controlled fuel injection apparatus for fuel injection, the intake throttle valve 32 and the like. In the exhaust gas purification system 10 , air A passes through the mass air flow sensor (MAF sensor) 31 of the intake passage 30 and the compressor (not shown) of the turbocharger 21 , and enters into a cylinder with its amount adjusted by the intake throttle valve 32 . Exhaust gas G, generated in the cylinder, drives the turbine 21 a of the turbocharger 21 in the exhaust passage 20 . Thereafter, the exhaust gas G passes through the catalyst unit 50 , thus being changed to purified exhaust gas Gc, and flows out into the atmosphere through a silencer (not shown). In addition, a part of the exhaust gas G passes through the EGR cooler 41 in the exhaust passage 40 as the EGR gas Ge, and is recirculated into the intake passage 30 with its amount adjusted by the EGR valve 42 . The control unit of the exhaust gas purification system 10 is built into the control unit 60 of the engine 1 , and the control of the exhaust gas purification system 10 is performed along with the operation control of the engine 1 . The control unit of the exhaust gas purification system 10 comprises a control means C 1 for a NOx occlusion-reduction type catalyst, as shown in FIG. 2 . The control means C 1 for a NOx occlusion-reduction type catalyst is a means for controlling the regeneration, desulfurization (sulfur purge) and the like for the catalyst unit 50 carrying a NOx occlusion-reduction type catalyst, and comprises a regeneration control means C 10 and a desulfurization regeneration control means C 20 . Furthermore, the regeneration control means C 10 is a means for controlling the regeneration of the NOx occlusion capacity of the catalyst unit 50 when the estimated NOx occlusion amount, which has been estimated to be occluded into the catalyst unit 50 , reaches a predetermined determination value. The regeneration control means C 10 comprises a NOx concentration detection means C 11 , a catalyst temperature detection means C 12 , a regeneration start determination means C 13 , a first rich control means C 14 , an oxygen-release completion determination means C 15 and a second rich control means C 16 . The NOx concentration detection means C 11 is a means for detecting a NOx concentration in exhaust gas and has a catalyst inlet NOx sensor 53 and a catalyst outlet NOx sensor 55 . If an exhaust component concentration sensor, in which a NOx concentration sensor and an oxygen concentration (or an excess air ratio) sensor are combined, is used, an oxygen concentration (or excess air ratio) can be detected along with a NOx concentration. The catalyst temperature detection means C 12 is a means for detecting a catalyst unit temperature, based on the exhaust gas temperature Tg detected by the catalyst inlet exhaust gas temperature sensor 54 . In the strict sense, the catalyst unit temperature differs from the exhaust gas temperature Tg and has to be corrected. However, the exhaust gas temperature Tg is regarded as the catalyst unit temperature in many cases for the ease of control and therefore the exhaust gas temperature (catalyst inlet gas temperature) Tg is regarded herein as the catalyst unit temperature. If a catalyst unit temperature sensor is provided and measures the catalyst unit temperature, the measured temperature is taken as the catalyst unit temperature. In the regeneration start determination means C 13 , a catalyst inlet NOx concentration Cnoxin and a catalyst outlet NOx concentration Cnoxex are input from the NOx concentration detection means C 11 , and a fuel injection amount (fuel weight) Qg and an intake air amount (intake air weight) Ag are input based on the degree of control of the engine. The NOx occlusion amount per unit time Rnox 1 is calculated from these values showing the condition of exhaust gas, using the expression Rnox 1 =(Qg+Ag)×(Cnoxin−Cnoxex). In this calculation, since the NOx occlusion amount is affected by a temperature to some extent, it is corrected to some extent, using the temperature as a function. The corrected amount is accumulated to determine the estimated NOx occlusion amount Rnox. The estimated NOx occlusion amount Rnox is compared to a determination value R 0 for the start of regeneration control. The timing of the start of regeneration control is determined when the estimated NOx occlusion amount Rnox reaches the predetermined determination value R 0 or more. The determination value R 0 for the start of regeneration control is calculated from map data for the start of regeneration control, predetermined from an engine speed Ne, which represents the operating condition of the engine, and engine load Q. The map data showing the determination value R 0 for the start of regeneration control are based on data obtained from an experiment in advance and the like and are mapped based on the engine speed Ne and the engine load Q. The first rich control means C 14 comprises an additional reductant amount calculation means C 141 for determining the amount of reductant meeting the oxygen released from the catalyst unit 50 (additional reductant amount) from map data showing the relation between catalyst unit temperatures and oxygen occlusion amounts. The first rich control means C 14 is a means for performing a first rich control in a more fuel-rich condition by adding the additional reductant amount to the amount supplied to reduce the NOx released from the catalyst unit (standard reductant amount) in the initial stage of regeneration control to make the target air/fuel ratio smaller than the theoretical air/fuel ratio. The rich control means C 14 performs a feedback control to make the inlet oxygen concentration of the catalyst unit 50 the oxygen concentration of the target air/fuel ratio, through a large amount EGR by intake throttling, fuel injection into an exhaust pipe, fuel injection control and the like. In the intake throttling, the intake throttle valve 22 and the EGR valve 42 are controlled. In the fuel injection control, fuel injection through the exhaust pipe fuel-admission valve 22 is performed in addition to post injection or main injection increase and the like. As for the additional reductant amount, the amount of reductant meeting the oxygen amount released from the catalyst unit 50 is calculated in such a way that an oxygen occlusion amount is calculated from the catalyst unit temperature detected and with reference to the map data showing the relation between catalyst unit temperatures and oxygen occlusion amounts, a released oxygen amount is calculated from the calculated oxygen occlusion amount and then an additional reductant amount meeting the released oxygen amount is calculated. On the other hand, the standard reductant amount, which does not consider the amount of oxygen released, is calculated from the map data for calculating the standard reductant amount, predetermined by an experiment in advance and the like, from the relation between an engine speed Ne and an engine load Q, which represent the operating condition of the engine. The map data is based on the relation between the engine speed Ne and the engine load Q, and sets the value of the amount of reductant that gives the minimum outflow of NOx toward the downstream of the catalyst unit when there is no oxygen released as the value of the standard reductant amount. The map data is set up based on the data obtained from an experiment in advance and the like. The oxygen-release completion determination means C 15 is a means for determining the completion of oxygen release in a first rich control, based on the oxygen concentration in the downstream of the catalyst unit 50 . The oxygen-release completion determination means C 15 determines that the oxygen release has been completed when the output value of the excess air ratio sensor 52 , which detects the oxygen concentration in the downstream of the catalyst unit 50 , is reversed. The second rich control means C 16 is a means for performing the second rich control whose target air/fuel ratio is higher than that of the first rich control and is closer to the theoretical air/fuel ratio, which is less fuel-rich than the first rich control. In the second rich control, a feedback control is performed so that the inlet oxygen concentration of the NOx occlusion-reduction type catalyst 50 becomes the oxygen concentration of the target air/fuel ratio. In the feedback control, a large amount EGR by intake throttling, as well as post injection or main injection increase are performed, without fuel injection into an exhaust pipe. In the second rich control, the target oxygen concentration is calculated based on the standard reductant amount that does not consider the amount of oxygen released. In the second rich control means C 16 , the control time Tr of the second rich control is calculated from a first control-time map data based on an engine load and an engine speed, or from a second control-time map data based on an engine load and a catalyst unit temperature. As shown in FIG. 4 , in the first control-time map data, the control-times Tr of the second rich control are arrayed in a matrix and mapped, based on an engine load and an engine speed. The first control-time map data is made in such a way that the control time can be selected corresponding to the engine load and engine speed detected. The second control-time map data is made in the same manner as the first control-time map data. In addition, as shown in FIG. 5 , the optimum time (the intersecting point in FIG. 5 ) can be made to the termination time of the second rich control Re, since the NOx amount remaining in the catalyst unit 50 decreases, while the HC outflow amount toward the downstream of the catalyst unit 50 increases with the time passing of the second rich control. That is, the control time Tr of the second rich control can be determined from the NOx amount remaining in the catalyst unit 50 and the HC outflow amount detected in the downstream of the catalyst unit 50 . The desulfurization regeneration control means C 20 comprises a desulfurization start determination means C 21 and a desulfurization control means C 22 . The desulfurization start determination means C 21 is a means for determining if sulfur purge control should be started, depending on if an amount of sulfur is accumulated to such an extent to decrease the NOx occlusion capacity, by calculating the amount of sulfur accumulated, and the like. The desulfurization regeneration control means C 20 starts desulfurization when the accumulated amount of sulfur reaches a predetermined determination value or more. The desulfurization control means C 22 is a means for performing desulfurization efficiently, while suppressing the emissions of carbon monoxide (CO) into the atmosphere. The desulfurization control means C 22 controls the air/fuel ratio in exhaust gas by fuel injection into an exhaust pipe, or by post injection, and raises the temperature of the catalyst unit 50 by EGR control, intake throttling control or the like, to the temperature at which desulfurization can be performed. In this exhaust gas purification system 10 , the regeneration control of the catalyst unit 50 is performed by the exhaust gas purification system control means C 1 of the control unit for the exhaust gas purification system 10 , which is built into the control unit 60 of the engine 1 , following an exemplary flow shown in FIG. 3 . The flow in FIG. 3 is shown to be performed in parallel with other control flows of the engine at the time of the operation of the engine 1 . Once the control flow shown in FIG. 3 is started, the regeneration start determination means C 13 calculates an estimated NOx occlusion amount Rnox, from the catalyst inlet NOx concentration Cnoxin, the catalyst outlet NOx concentration Cnoxex, the fuel injection amount (fuel weight) Qg and the intake air amount (intake air weight) Ag at step S 11 . At the following step S 12 , the estimated NOx occlusion amount Rnox is compared to a determination value R 0 for the start of regeneration control and the timing of the start of regeneration control is determined when the estimated NOx occlusion amount Rnox reaches the determination value R 0 or more. The determination value R 0 for the start of regeneration control is calculated from the map data for determining the start of regeneration control, predetermined from an engine speed Ne and an engine load Q, which represent the operating condition of the engine. If the determination at step 12 determines that it is not the time to start regeneration control, controls other than regeneration control are performed at step S 40 . After passing through the routine of the controls other than the regeneration control, the process returns to step S 11 . In the controls other than regeneration control, the controls other than regeneration control such as desulfurization are performed if various conditions are satisfied. The process returns without performing the controls, if each condition is not satisfied. If the determination at step S 12 determines that it is the time to start regeneration control, the process proceeds to step S 20 where a first rich control is performed by the first rich control means C 14 of the regeneration control means C 10 . In the first rich control, firstly, at step S 21 , the target air/fuel ratio of the first rich control (or the target excess air ratio of λ 1 ) is calculated based on the amount that is obtained by adding the additional reductant amount meeting the amount of oxygen released from the catalyst unit 50 to the standard reductant amount that does not consider the amount of oxygen released from the catalyst unit 50 in the initial stage of regeneration control. This target air/fuel ratio is smaller than the theoretical air/fuel ratio. Alternatively, the map data of the target air/fuel ratio (or the target excess air ratio of λ 1 ) of the first rich control based on an engine load and an engine speed may be prepared in advance. In this case, the target air/fuel ratio of the first rich control (or the target excess air ratio of λ 1 ) is determined from the engine load and engine speed detected, with reference to the map data. For the preparation of the map data, the engine load and engine rotational speed may be used as the base via the exhaust gas temperature instead of using the catalyst unit temperature, since the adsorption amount of oxygen is determined essentially by the catalyst unit temperature, and the exhaust gas temperature, which has a close relation to the catalyst unit temperature, is determined by the engine load and the engine speed. Next, at step S 22 , feedback control is performed so that the inlet oxygen concentration of the catalyst unit 50 becomes the oxygen concentration of the target air/fuel ratio, through controls such as a large amount EGR by intake throttling, fuel injection into an exhaust pipe, as well as post injection or main injection increase. With this control, the air/fuel ratio of the exhaust gas before the catalyst is set to 0.70 to 0.98 (for example, 0.90) in terms of an excess air ratio (λ). At the same time, the exhaust gas temperature is set within a certain range (about 200 to 600 deg C., depending on the type of a catalyst) to restore the NOx occlusion capacity, i.e. the NOx purification ability, thus regenerating the NOx catalyst. The first rich control at step S 22 is performed for a predetermined time period of Δt that is related to the interval of determining the completion of oxygen release, and then proceeds to step S 23 . At the step S 23 , the completion of release of the oxygen that has been adsorbed and stored by the oxygen storage function of the catalyst unit 50 , is determined by the oxygen-release completion determination means C 15 during the first rich control. Oxygen release has been completed when it has been determined that the output value (voltage) Vλ2 from the excess air ratio sensor 52 changes substantially and is reversed at the value λ=1. At step 23 , if the oxygen release is determined to have not been completed, the process returns to step S 22 , and steps S 22 and S 23 are repeated until the oxygen release is determined to have been completed at step S 23 . At step S 23 , if the oxygen release is determined to have been completed, the process proceeds to a second rich control at step S 30 . In the second rich control at step S 30 , the second rich control means C 16 performs the second rich control whose target air/fuel ratio is higher than that of the first rich control and closer to the theoretical air/fuel ratio. First of all, at step S 31 , the target air/fuel ratio (target excess air ratio λ 2 ) of the second rich control is determined based on the standard reductant amount that does not consider the amount of oxygen released. Furthermore, at step S 32 , the control time Tr of the second rich control is calculated. The control time Tr is calculated from the first control-time map data based on an engine load and an engine speed, or from the second control-time map data based on an engine load and a catalyst unit temperature. Alternatively, the control time Tr of the second rich control is determined from the amount of NOx remaining in the catalyst unit 50 and the amount of HC detected in the downstream of the catalyst unit 50 . The amount of NOx remaining in the catalyst unit 50 is determined from the map obtained from an experiment in advance and the like, as well as the exhaust gas temperature and regeneration time of the previous regeneration. As for the HC amount, the relation between O 2 concentrations and HC amounts is mapped based on a result of an experiment in advance. The HC amount is then calculated from the value of an excess air ratio sensor 52 at the catalyst outlet and the control time Tr of the second rich control is determined from the maps. Next, at step S 33 , feedback control is performed so that the inlet oxygen concentration of the catalyst unit 50 becomes the oxygen concentration of the target air/fuel ratio (target excess air ratio λ 2 ), through controls such as, a large amount EGR by intake throttling, fuel injection into an exhaust pipe, as well as post injection or main injection increase. With the controls, the air/fuel ratio of the exhaust gas before the catalyst inlet is set to 0.98 to 1.02 (for example, 1.0) in terms of an excess air ratio (λ). At the same time, the exhaust gas temperature is set within a certain range (about 200 to 600 deg C., depending on the type of a catalyst) to restore the NOx occlusion capacity, i.e. the NOx purification ability, regenerating the NOx catalyst. The second rich control at step S 33 is performed for the control-time Tr of the second rich control that has been calculated at step S 32 and then terminates. The regeneration control is performed in the first rich control at step S 20 and the second rich control at step S 30 , and after the second rich control terminates, the process returns to step S 11 . The control flow shown in FIG. 3 is repeated until the engine stops. If the engine is turned off during the control, an interruption of step S 13 occurs. After the termination processing (not shown) required is performed at the step where the interruption occurs, the process returns. Then the control flow is terminated at the same time of the termination of the main control. According to this control flow, in regeneration control for an exhaust gas NOx purification system, the first rich control whose target air/fuel ratio (excess air ratio λ 1 ) is smaller than the theoretical air/fuel ratio, is performed by adding the amount of reductant meeting the amount of oxygen released from the catalyst unit 50 in the initial stage of the regeneration control, to the amount of reductant supplied to reduce NOx released from the catalyst unit 50 . In the first rich control, the completion of oxygen release is determined based on the oxygen concentration in the downstream of the catalyst unit 50 , and when the oxygen release is determined to have been completed, the second rich control whose target air/fuel ratio (excess air ratio λ 2 ) is larger than the first rich control and closer to the theoretical air/fuel ratio, is performed. The catalyst unit 50 is thus regenerated. FIG. 6 is a schematic diagram showing an example of the temporal changes in the fuel injection control A such as post injection or main injection increase, control for fuel injection into an exhaust pipe B, an estimated NOx occlusion amount (Rnox) C, degree of opening of a EGR valve D, degree of the throttle opening of an intake valve E, an intake air amount F, a catalyst inlet excess air ratio λ in, and a catalyst outlet excess air ratio λ ex, according to the control flow of FIG. 3 . In FIG. 6 , regeneration control starts at the time Rs 1 , when the estimated NOx occlusion amount (Rnox) C exceeds a threshold value R 0 . In the first rich control, fuel injection through the exhaust pipe fuel-admission valve 22 is performed in addition to fuel injection control such as post injection, setting the target excess air ratio λ 1 to 0.70 to 0.98 (for example, 0.90). At the same time, the degree of opening of the EGR valve D is made open and the degree of the throttle opening of the intake valve E is made close to decrease the intake air amount F. Feedback control is performed so that the catalyst inlet excess air ratio λ in becomes the target excess air ratio λ 1 . The catalyst inlet excess air ratio λ in becomes the target excess air ratio λ 1 after an overshoot, and the first rich control continues until the completion of oxygen release Oe. This first rich control causes the estimated NOx occlusion amount (Rnox) C to be decreased. Then, at the completion of oxygen release Oe, the catalyst outlet excess air ratio λ ex starts to decrease rapidly. At the time Rs 2 when this decrease is detected, the first rich control is terminated and the second rich control is started. In the second rich control, setting the target excess air ratio λ 2 to 0.98 to 1.02 (for example, 1.0), fuel injection control such as post injection, continues, but the fuel injection into an exhaust pipe from an exhaust pipe fuel-admission valve 22 is discontinued. Then, feedback control is performed so that the catalyst inlet excess air ratio λ in becomes the target excess air ratio λ 2 . After the catalyst inlet excess air ratio λ in becomes the target excess air ratio λ 2 and is maintained for a predetermined time period of Tr, at the time Re the fuel injection control such as post injection, is discontinued. At the same time, the intake air amount F is recovered by making the degree of opening of an EGR valve D close, and the degree of the throttle opening of an intake valve E open. Then the second rich control terminates. With the first and second rich controls, the estimated NOx occlusion amount (Rnox) C becomes approximately zero, that is, the NOx occlusion capacity is restored and the regeneration control is completed. Furthermore, according to the exhaust gas purification system 10 of the above construction, the air/fuel ratio in a catalyst unit 50 is maintained in a rich condition near the theoretical air/fuel ratio, despite of the oxygen released from the catalyst unit 50 , during the regeneration control to restore the NOx occlusion capacity of the catalyst unit 50 carrying a NOx occlusion-reduction type catalyst. This is because a first rich control is performed with the additional amount of reductant required to consume the oxygen released in the initial stage of regeneration, taking into consideration the oxygen storage function of the NOx occlusion-reduction type catalyst 50 . In addition, since the consumption of the reductant by the oxygen released is taken into consideration, the NOx released from the catalyst unit 50 can be reduced with a sufficient amount of reductant. In addition, after the oxygen release, since a second rich control is performed with the amount of reductant changed appropriately, the air/fuel ratio adjacent to the NOx occlusion-reduction type catalyst of the catalyst unit 50 can be maintained to be close to the theoretical air/fuel ratio even after the completion of the oxygen release and the NOx released from the catalyst unit 50 can be reduced with an appropriate amount of reductant. Accordingly, the outflow of unpurified NOx in the initial stage of regeneration control can be decreased, improving the NOx purification performance, and furthermore, the outflow (slip) of HC and CO, after the completion of oxygen release, can be decreased. INDUSTRIAL APPLICABILITY A method of exhaust gas purification and an exhaust gas purification system according to the present invention have excellent effects as described above, and can be very effectively utilized as the method and system for purifying the exhaust gas from internal combustion engines on automobiles, as well as for purifying exhaust gas from various industrial machines and stationary internal combustion engines, factory emissions, power plant emissions and the like.

In an exhaust gas purification system, including a catalyst unit carrying an NOx occlusion-reduction type catalyst, a first-stage rich control having a target air-fuel ratio lower than theoretical air-fuel ratio and which is conducted through addition of an amount of a reducing agent meeting an amount of oxygen emitted in the initial stage of regeneration control. In the first-stage rich control a completion of oxygen emission is judged on the basis of an oxygen concentration on the downstream side of the catalyst unit. Upon determination of the completion of the oxygen emission, a later-stage rich control close to the theoretical air-fuel ratio with the target air-fuel ratio increased over that of the first-stage rich control is conducted to thereby accomplish regeneration of the catalyst unit. As a result, there can be prevented not only any outflow of unpurified NOx occurring in the initial stage of regeneration but also any outflow of virgin reducing agents, such as HC and CO, occurring in the later stage of regeneration.

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of US Provisional Patent Application 60/698,024, filed Jul. 11, 2005 and also claims the benefit of US Provisional Patent Application 60/739,247, filed Nov. 23, 2005. BACKGROUND [0002] Conventional water heaters for residential and mixed use buildings typically keep the water in the tank between about 140-150°, and a thermostat is usually used to control the water temperature. (Note that all temperatures mentioned herein are specified in degrees Fahrenheit.) However, since thermostats do not provide a high a degree of accuracy, the water temperature can often fluctuate by up to 10° before the heating system switches on. In many cases, the inaccurate nature of the temperature control in conventional water heaters is not a problem, because the user can compensate for temperature variations by mixing in more or less cold water at the tap. In other cases, e.g., when small children or infirm adults may be using the hot water, the 140-150° temperature posses a potential risk of scalding the user. This risk can be eliminated by reducing the temperature of the water in the tank at all times (e.g., to 110°). However, keeping the temperature that low makes it very likely that the users will run out of hot water during high demand periods (e.g., in the morning, when many members of the household may be showering). Moreover, for low temperature operation, the large fluctuations of conventional temperature controls becomes more of an issue, since a 10° increase would increase the risk of scalding, and a 10° decrease would cause the users to run out of hot water during high demand periods. SUMMARY [0003] A controller monitors the temperature of water in a tank and switches between a high temperature mode of operation and a low temperature mode of operation based on time. During the low temperature mode of operation, the controller generates signals to selectively activate a water heater to keep the water's temperature within a first range of values (most preferably within a 4° or 6° subset of the 105°-113° F. range). During the high temperature mode of operation, the controller generates signals that cause the water heater to heat the water to a temperature that is above the first range of values. BRIEF DESCRIPTION OF THE DRAWINGS [0004] FIG. 1 is a block diagram of a gas-fired water heater with a controller that is configured to provide a high temperature mode of operation and a low temperature mode of operation. [0005] FIG. 2 is a schematic diagram of an alternative temperature control circuit for the system shown in FIG. 1 . [0006] FIG. 3 is a pictorial representation of the FIG. 1 embodiment, with the controller mounted on the water tank. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0007] FIG. 1 is a block diagram of a gas-fired water heater that has a high temperature mode of operation and a low temperature mode of operation. The water heater maintains accurate control over the water temperature in the low temperature mode of operation. The water heater uses a programmable controller/timer for switching between the high temperature and the low temperature modes at regular intervals. Note that the invention is described herein in the context of a gas-fired heater. However, the present invention is not limited to gas-fired heaters, and may be used with other types of water heating systems (e.g., electric and oil-fired water heaters) to provide similar results. [0008] A water tank 30 of any conventional construction may be used. One example of a suitable water tank is the Bradford White M-I series of upright residential gas water heaters. The water in the water tank 30 is heated by a gas burner 45 which is configured with a suitable valve 46 to control the flow of gas from the gas supply 48 into the burner 45 . One example of a suitable gas valve is the Robertshaw 722 series. The gas burner 45 and valve 46 are hooked up to the gas supply 48 using conventional techniques that are well known to persons skilled in the relevant art. A gas ignition controller 40 is hooked up to valve 46 , also using conventional techniques that are well known to persons skilled in the relevant art. One example of a suitable gas ignition controller is the Robertshaw 780 series. Taken together, the ignition controller 40 , the valve 46 , and the burner 45 are configured so that an electrical input signal to the ignition controller 40 provides control over the flow of gas through the valve 46 into the burner 45 in order to heat the water 32 in the tank 30 . [0009] The decision to turn on the burner 45 or turn off the burner 45 is made by a controller 20 , which sends appropriate electrical signals to the ignition controller 40 to control the flow of gas into the burner 45 . More specifically, when the controller 20 receives information indicating that the temperature of the water 32 in the tank 30 is too low, the controller 20 sends appropriate electrical signals to the ignition controller 40 which will, in turn, cause the burner 45 to turn on, thereby raising the temperature of the water 32 . If the controller 20 receives information indicating that the temperature of the water 32 in the tank 30 is at or above the desired temperature at any given moment, the controller 20 turns off the signal to the ignition controller 40 , which causes the valve 46 to turn off so that the burner 45 will stop heating the water 32 in the tank 30 . [0010] The controller 20 receives information about the temperature of the water 32 from a temperature probe 25 . The temperature-sensing portion of the probe 25 is in thermal contact with the water 32 in the tank 30 . For the application described below, the water temperature must be sensed with a higher degree of accuracy than in conventional water heaters. Accordingly, the temperature probe 25 must be designed to provide relatively high accuracy. One preferred approach for implementing a temperature probe with sufficiently high accuracy is to use a thermistor such as the Invensys-Robertshaw 54584-006. Alternative temperature sensors that can provide sufficient accuracy include RTDs and integrated circuit temperature sensors, such as the LM34 analog temperature sensor or the LM92 digital temperature sensor, both made by National Semiconductor. The latter can sense temperatures between 60 and 120° F. to an accuracy of less than 1° F. [0011] The interface between the temperature probe 25 and the controller 20 will depend on the particular sensor technology that is selected for use in the temperature probe 25 . However, for any given sensor technology, the interface between the controller 20 and the temperature probe 25 is preferable implemented using conventional techniques that are well known to persons skilled in the relevant art. Based on the signals arriving from the temperature probe 25 , the controller 20 obtains information about the temperature of the water 32 in the tank 30 . The controller 20 using this information to decide whether or not to turn on the burner 45 by sending appropriate control signals to the ignition controller 40 . Circumstances when the controller 20 turns the burner 45 on or off are described below. [0012] One useful application for the dual-mode water heater depicted in FIG. 1 would be a day care center in mixed-use building. At night and in the morning, when the residents will likely be taking showers and using a lot of hot water, the controller 20 selects the high temperature mode and maintains the temperature of the water in the tank at about 140°. This is accomplished by reading the signals arriving from the temperature sensor 25 to sense the temperature of the water in the tank 30 , and sending appropriate signals to the ignition controller 40 to turn the burner 45 on or off The temperature monitoring via the sensor 25 may be done constantly or periodically, but in the latter case it should be done often enough so that the temperature cannot change too much between measurements, based on to the thermal inertia of the water in the tank 30 . [0013] When the controller 20 recognizes that it is time for the day care center to open (e.g., based on a time schedule that has been programmed into the controller 20 ), the controller 20 sets the system to operate in the low temperature mode. Optionally, the switch to the low temperature mode is programmed to occur an interval of time before the lower temperature water is actually required, since the tank will not cool instantly as soon as the mode is switched. For example, if the day care center opens at 8 AM, the controller may be programmed to switch to the low temperature mode a half hour in advance of that time, at 7:30 AM. The temperature will drop between 7:30 and 8 as hot water is drawn out of the tank (by ordinary use of hot water) and replaced by incoming cold water. [0014] Optionally, after the low temperature mode has been selected, hot water may be drained from the tank under control of the controller 20 in order to rapidly reduce the temperature of the water to the desired level. One way to accomplish this is by having the controller 20 send appropriate signals to an electrically operated valve (not shown) that draws hot water from any hot water pipe that is fed by the tank 30 . Of course, appropriate plumbing must be provided between the hot water supply, the valve, and an appropriate drain. [0015] A suitable program of operation for the controller 20 for use in a day care center that operates on weekdays only is set forth in Table 1 below. TABLE 1 Day 5:00 AM-7:30 AM 7:30 AM-6:00 PM 6:00 PM-5:00 AM Sunday 140° 140° 140° Monday 140° 110° 140° Tuesday 140° 110° 140° Wed- 140° 110° 140° nesday Thurs- 140° 110° 140° day Friday 140° 110° 140° Satur- 140° 140° 140° day [0016] Another useful application for the dual-mode water heater depicted in FIG. 1 would be in residential homes. In the evening and in the morning, when the residents will likely be taking showers and using a lot of hot water, the controller selects the high temperature mode and maintains the temperature of the water in the tank at a desired high temperature (e.g., 130°). At night and during portions of the day when nobody is home, the temperature may be set to a desired low temperature (e.g., 90°) in order to save energy. Temperature control is implemented in the same way as in the day care application discussed above, except that the timing of the transitions and the temperature set points are different. A suitable program of operation for the controller 20 for achieving energy savings in residential homes is set forth in Table 2 below. TABLE 2 Day 6-8 AM 8 AM-5 PM 5-11 PM 11 PM-6 AM Sunday 130° 130°  130° 90° Monday 130° 90° 130° 90° Tuesday 130° 90° 130° 90° Wednesday 130° 90° 130° 90° Thursday 130° 90° 130° 90° Friday 130° 90° 130° 90° Saturday 130° 130°  130° 90° [0017] A third example of a suitable application for the dual-mode water heater depicted in FIG. 1 would be for use in the homes of people who observe the Jewish law that prohibits heating liquids beyond a certain threshold temperature on the Sabbath. Many Jewish legal authorities that were contacted by the inventor maintain that the threshold temperature is 113° F., and others maintain that the threshold temperature is as low as 106° F. However, all these authorities agree that heating liquids on Sabbath is not prohibited by Jewish law when the liquid is not heated beyond the threshold temperature. [0018] In a conventional water heater, when the water temperature is set at about 140°, when a person draws hot water from the tank, cold water flows into the tank via the cold water inlet pipe. When that cold water mixes with the hot water that is already present in the tank, its temperature will be raised above the threshold, which would violate the prohibition of heating liquids on the Sabbath. To avoid this, some observant Jews refrain from using hot water on the Sabbath, so that the incoming cold water is never heated beyond the threshold temperature. [0019] If, however, the hot water that is contained in the tank is always kept at or below 112°, which is below the threshold temperature according to the aforementioned Jewish legal authorities, when the cold water flows into the tank via the cold water inlet pipe, it will not be heated past the threshold temperature. Under these circumstances, Jewish law permits people to draw hot water out of the tank on Sabbath, even though cold water will flow into the hot water tank as the hot water leaves. [0020] Thus, for this application, the controller 20 is programmed to switch into the low temperature mode of operation about one hour before Sabbath (to provide a period of cool-down time), and to switch back to the normal high temperature mode when Sabbath is over. In the embodiment described above with rapid cooling, that time can be reduced. Since the Jewish Sabbath starts at sundown on Friday evening and lasts until the stars come out on Saturday night, and since the sun sets at different times during the year, a suitable program for the controller 20 for automatically entering the low temperature mode before Sabbath begins is shown in Table 3: TABLE 3 start low temp. mode end low temp mode. Month Friday at Saturday at January 3:30 PM 5:30 PM February 4:00 PM 6:00 PM March 4:30 PM 6:30 PM April 5:00 PM 7:00 PM May 5:30 PM 7:30 PM June 6:00 PM 8:00 PM July 6:00 PM 8:00 PM August 5:30 PM 7:30 PM September 4:30 PM 7:00 PM October 4:00 PM 6:30 PM November 3:30 PM 6:00 PM December 3:00 PM 5:30 PM [0021] Preferably, the controller is programmed to make suitable adjustments in regions that observe daylight savings time, to adjust for the changed time of sunset. [0022] Alternatively, instead of roughly estimating the time when Sabbath begins based on the month, a more precise start time for switching to the low temperature mode can be determined based on the date. The controller 20 can obtain knowledge of the date by keeping track of time after being set once by the user in any conventional manner. In alternative embodiments, an appropriate receiver (not shown) that receives the atomic clock signals broadcast by the National Institute of Standards and Technology in Boulder, Colorado, may be added so the system to determine the date and time. The controller 20 would then determine the correct time to switch modes based on the expected time of sunset on the day in question (e.g., by using an appropriate look-up table indexed by the date). [0023] Optionally, a Jewish calendar may be programmed into the controller 20 , and the controller may be programmed to select the low temperature mode during those Jewish holidays when similar prohibitions on heating water are applicable. [0024] Controlling the temperature with a high degree of accuracy is particularly important in the first and third applications described above, especially in the low-temperature mode of operation. For example, in the context of a daycare center, if the water is 10° too hot while the daycare center is opened, it would increase the risk of accidentally scalding, and temperatures above 113° are problematic for the Jewish Sabbath. (Note that for those users who choose to comply with a lower threshold temperature, such as 106°, all the relevant temperature values set forth herein must be adjusted accordingly). Conversely, if the water temperature drops too far (e.g., to 100°), it may not be hot enough for the user's desired use (e.g. washing hands or doing dishes), especially during periods of high demand. Accordingly, the controller 20 should make appropriate and timely adjustments to minimize the temperature fluctuations, preferably to within a 6° F. range, and more preferably to within a 4° range (e.g., to manage the temperature fluctuations within the tank 30 so that it always stays between 105° and 111°, or more preferably between 107° and 111°). [0025] In the embodiment illustrated in FIG. 1 , the controller 20 turns the burner 45 on and off as required in both the low temperature mode and the high temperature mode by sending appropriate signals to the ignition controller 40 . Thus, the controller 20 has direct control over the burner 45 in both the low temperature and the high temperature modes. In an alternative embodiment, the controller 20 retains direct control over the burner 45 in low temperature mode, but passes responsibility for controlling the temperature to another device (e.g., a conventional thermostat) in the high temperature mode where accuracy is less important. This may be accomplished as shown in FIG. 2 , for example, by having the controller 20 ′ selectively actuate a relay 90 to connect a thermostat 92 to the control input of the ignition controller 40 in high temperature mode, and to connect the control output of the controller 20 to the ignition controller 40 in low temperature mode. In that case, the controller 20 ′ would have direct control over the burner 45 in low temperature mode, but would have indirect control over the burner in the high temperature mode (by letting the thermostat bring the temperature up to a range that is higher than the temperatures associated with the low temperature mode). [0026] FIG. 3 shows how the system can be physically connected to a water heater. A control panel 80 is shown mounted to the body of the water heater 30 at a convenient height. The control panel 80 preferably houses the controller 20 (shown in FIG. 1 ), as well as a display and buttons for implementing a user interface, which may be implemented in any of a variety of ways that will be apparent to persons skilled in the relevant arts. For example, a user interface similar to those used for programmable air conditioning thermostats may be used, preferably including a digital display that displays the current temperature of the water in the tank and/or the temperature setting. The control panel 80 may be mounted to the tank's wall using any suitable approach including but not limited to screws, glues, magnets, straps that surround the tank, etc. A magnetic mount may make it easier to install the above-described embodiments in retrofits of existing tanks. Preferably, the control panel 80 is relatively small and as lightweight to facilitate easy mounting. [0027] The tank 30 has a utility compartment 82 , which may be used to house the gas ignition controller. In electric heat embodiments, the utility compartment 82 may be used to house components like a controller power module, a transformer, a heating element control switch, and the connection to the temperature probe. Optionally, a cover for the utility compartment 82 may be shaped to accommodate the control cable connection, and the power module may be fixed to the cover itself to simplify the installation and retrofitting of existing tanks. A cable 84 connects the control panel 80 to the components housed in the utility compartment 82 . Optionally, the cable 84 may be coiled to simplify installation onto different sized tanks or at other locations that may be preferred by the user.

The temperature in a water tank (e.g., a residential water tank) is monitored, and a controller switches between a high temperature mode of operation and a low temperature mode of operation (e.g., based on a daily or weekly program). During the low temperature mode of operation, the controller generates signals to selectively activate a water heater to keep the water's temperature within a first range of values, (e.g., between 105 and 113° F). During the high temperature mode of operation, the controller generates signals that cause the water heater to heat the water to a temperature that is above the first range of values. This arrangement may be used for saving energy by operating in the low temperature mode at night and during those parts of the day when nobody is home, and by operating in the high temperature mode in the morning and evening when the demand for hot water is typically high. This arrangement is also well-suited for day-care centers and nursing homes, in which case the low temperature mode is used to reduce the risk of scalding. It is also useful in the homes of people who wish to avoid violating a religious injunction that prohibits heating liquids beyond a threshold temperature on the Sabbath.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates generally to systems and methods for providing media content for mobile communication devices and, more particularly, to systems and methods for supporting the production, management and delivery of media content for wireless devices. 2. Description of the Related Art A typical system for distributing media content, such as audio-based ringtones, to mobile communication devices over a communication network includes a library of media content stored in a file server and a means for sending the media content to a device. Each piece of media content is stored in a format compatible with one or more communication devices. For example, an audio file stored in a Nokia proprietary format is considered to be compatible with all models of Nokia telephones. Among the various models of Nokia telephones, however, there may be different types of media capabilities. For example, one telephone model may be capable of playing an audio file such as “ringtones” of a certain byte duration and note range while another model has different duration and range capabilities. Existing media content distribution systems do not account for these differences in device capabilities. Thus, a piece of media content associated with Nokia telephones may be sent to any Nokia telephone regardless of the capabilities of the particular telephone model. If the particular model receiving the content does not have the proper capabilities, the content may not be able to be played or, if it can be played, will be limited by the model capabilities. For example, the duration of the ringtone may be truncated or the note range modified to accommodate the capability of the particular telephone. Thus, the user of the device is not able to hear the “true” ringtone. In view of the foregoing limitations of existing media distribution systems, those skilled in the art have recognized a need for a system that is capable of providing media content to a variety of communication devices operating over various communications networks and with various media content capabilities such that the possibility of providing incompatible media content to an end-user device is substantially eliminated. The invention fulfills these needs and others. SUMMARY OF THE INVENTION Briefly, and in general terms, the invention is directed to various systems and methods for providing media content for mobile communication devices. The systems and methods take the media content capabilities of the device into consideration when determining which media content is available for a given device. The distribution channel over which a device operates may also be taken into consideration. In a first aspect, the invention relates to a system for making one or more pieces of media content available for delivery to an end-user device. The system includes a file server with a plurality of media content files stored therein and a database. The database associates content type attributes with each of the media content files and attribute capability constraints with the end-user device. The attribute capability constraints prescribe a range of acceptable values for content type attributes. The system also includes a first rules engine that creates an available library of media content that excludes all media content that have content type attributes outside the range of acceptable values. In another aspect of the system, the database associates a carrier network with the end-user device. The carrier network, in turn, has an associated delivery channel capacity. The system further includes a second rules engine adapted to refine the available library to exclude all media content not supported by the delivery channel of the end-user device. A key differentiator between the prior system and the system of the present invention is the capacity for the system to determine whether media content of a particular type is viable for delivery to a given device or class of devices. Existing systems operate on the premise that all content marked as active in a database is viable for the devices it is associated with. In accordance with the system of the present invention, content availability is determined from a combination of rules for device capabilities and rules for distribution capabilities. The device capabilities determination is made by a rules-based engine that compares content attributes (typically metadata derived by content examination programs) with constraints on those attributes for a device. There are effectively two main steps to this process: firstly, metadata describing the content is derived and entered into the database; secondly, as the specifications of different devices are entered into the system, corresponding constraints are associated with the devices that tell the rules engine what the valid range of values for each content attribute is. As output of this process, the rules engine creates an available content library for each class of devices by excluding all instances of media content that have attributes outside the range of values prescribed in the constraints. A similar rule set determines whether the content can be distributed through a particular delivery channel, based on factors such as territory-based licensing of content, distribution channel capacity to support the given media type, and business agreements with third-party distributors and networks that would allow or disallow content of that type to be distributed. The subset of content that passes both the device capabilities tests described above and the distribution capability tests can be determined to be viable for delivery to a given end-user device over a particular distribution channel. Thus, the system substantially eliminates the possibility of providing incompatible media content to an end-user device and instead provides only the most viable media content in view of the operating parameters, i.e., content constraints, delivery channel capacity, etc., associated with a given device. These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings which illustrate by way of example the features of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an exemplary communications system configured in accordance with the invention and including an engine with a database, file servers and client-server interface interfacing with a number of client servers; FIG. 2 is a block diagram of the functions performed by the system of FIG. 1 including media production, media management and media delivery; FIG. 3 is a conceptual model related to the media production function of FIG. 2 ; FIG. 4 is an exemplary listing of the information associated with a performance of FIG. 3 , including media type, performance type, performance attributes and content tree; FIGS. 5 and 6 are exemplary listings of the information associated with two of the contents listed in the content tree of FIG. 4 , including content type, content attribute values and child content tree; FIG. 7 a is a conceptual model related to the content to device mapping (C2DMA) function depicted in FIG. 2 ; FIG. 7 b is a conceptual model related to the content to payload mapping performed by the media delivery function in FIG. 2 ; FIG. 7 c is a conceptual model related to the project configurator aspect of the media management function of FIG. 2 ; FIGS. 8 a - 8 c are exemplary user interfaces associated with the project configurator aspect of the media management function of FIG. 2 ; FIGS. 9-15 are exemplary user interfaces associated with the catalog designer aspect of the media management function of FIG. 2 ; FIG. 16 provides an exemplary code listing for a catalog request; FIGS. 17 a - 17 d provide an exemplary code listing for a catalog response; FIG. 18 is a conceptual model related to the billing interface aspect of the media delivery function of FIG. 2 ; FIGS. 19 a and 19 b provide an exemplary code listing for a content delivery request; FIG. 20 provides an exemplary code listing for a content delivery response; FIG. 21 is a conceptual model related to the distributor aspect of the media delivery function of FIG. 2 ; FIG. 22 is a conceptual model related to the customer service tools aspect of the media delivery function of FIG. 2 ; FIG. 23 provides an exemplary code listing for an account status request; and FIG. 24 provides an exemplary code listing for an account status response. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, particularly to FIG. 1 , there is shown a block diagram of a communications system configured to deliver media content to an end-user device over a wireless carrier network. “Media content”, as used herein includes, but is not limited to, ringtones, graphics, photographs, text messages and other audio, video, audiovisual, textual or interactive content as well as actual software applications such as games, alert applications and media players. An “end-user device” includes, but is not limited to, cellular telephone handsets, such as those manufactured by Nokia, Motorola, Sony Ericsson, Samsung and Kyocera. End-user devices may also include personal digital assistants (PDA), pagers, wireless e-mail devices, wireless calenders, GPS enabled devices and wireless game devices. The system includes an engine 10 with various database related components and server related components working in conjunction to provide a library of media content. Database related components include a database system 12 which stores metadata of the media content while the server system includes a file server system 13 which stores the actual media content. The metadata in the database system 12 includes a uniform resource locator (URL) to the media content in the file server system 13 . In a preferred configuration of the system, the database system 12 includes at least two production databases 12 a to provide a level of redundancy and an additional replication server database 12 b to manage and synchronize the redundant databases. In one configuration, the redundant databases are Sun 420 RS boxes running on the Sun Solaris operating system and the replication server database is a Sun 220 box running Sybase database software. The filer servers 13 are Intel 2U, 1 GHz dual processor CPUs running the Linux operating system. The system also includes a client-server interface 14 for providing communication between the engine 10 and one or more client servers 16 . The client-server interface 14 is housed within a triple redundant CPU system comprised of Intel 2U, 1 GHz dual processor CPUs, and interfaces with the client servers 16 through a network of switches 15 and routers 17 . The client servers 16 themselves, interface with one or more end-users through an end-user interface 18 . The end-user interface 18 may be a browser running on a personal computer or the end-user device itself, e.g., cellular telephone or a client application. The system or platform is built as a layered multitier server application. The Sybase relational database management system is used for data storage but application code components are implemented in the Java programming language using Java 2 as the platform. A Java Database Connectivity (JDBC) driver provided by the database vendor is used to connect the datastore to the application. The lowest-level component of the Java core of the application is a toolkit called XORM (an acronym for eXtensible Object-Relational Mapping). XORM is an open source implementation of the Java Data Objects (JDO) specification which allows application developers to work with the relational data in the database as if it were native Java data objects. XORM facilitates the automatic generation of Structure Query Language (SQL) statements and queries in order to perform operations on persistent data. The central part of the application consists of logic classes that provide shared business logic to the externally facing parts of the system. The logic classes include components to manage the complex relationships between different types of data and are broken down into core divisions based on their responsibilities. One contains functions that enable the available library of content, one provides methods to navigate the complexities of the content to device mapping application (C2DMA), and so on. The external face of the application is created using the Java Servlet and Java Server Pages application programming interfaces defined by Sun Microsystems. The open source Jakarta Tomcat servlet engine created by the Apache Group is used to host these components. In addition, many of the web-based interfaces in the system rely on the Jakarta Struts template engine, which adds a Model-View-Controller paradigm to the servlet and JSP model. Other components that provide XML (eXtensible Markup Language) output are built similarly but use the open source JDOM API for generating and managing data using the XML document object model. The external connectivity pieces of the application, including the content distributors and delivery mechanisms, use the core services provided by the business logic classes and database connectivity layers. They also rely on additional proprietary software and components provided by third-party vendors to provide Java code access to complex communication protocols. With reference to FIG. 2 , the system includes various functionally interrelated operating modules and database components, including a media production aspect 20 , a content-to-device-mapping application (C2DMA) module 22 , a media management aspect 24 and a media delivery aspect 26 . The media production portion 20 is responsible for the creation and storage of media content. The media management portion 24 is responsible for the management of content catalogs and associated projects and clients through the client-server interface 14 ( FIG. 1 ). The media delivery aspect 26 of the system is responsible for the delivery of content through any available channel to any addressable end-user device. The C2DMA 22 handles the management and selection of appropriate media content for users based on a variety of factors described in detail below. A detailed description of each portion of the system follows. The operating modules described below are contained within the various redundant processing unit systems shown in FIG. 1 . Each of these processing units is an Intel 2U, 1 GHz dual processor CPU. Common numeric identifiers in FIGS. 1 and 2 show the relationship between the functional modes ( FIG. 2 ) and the system hardware ( FIG. 1 ). Media Production With the continued reference to FIG. 2 , the media production aspect 20 of the system includes a production tools module 28 and a master media content library 30 , referred to herein as the “master library”. The media production aspect may also include a licensing tools module 32 . With reference to the conceptual model of FIG. 3 , the media production aspect 20 allows for the creation of a piece of content 34 from an original piece of media 36 . The content 34 is made by a producer 38 using production tools 40 . Production tools 40 include algorithms which are specific for end-user devices. In the case of ringtones, these algorithms manipulate a source file, e.g., MIDI file, of the media 36 into a piece of content 34 that is compatible with a particular end-user device. The algorithms used by the producer 38 are based on the operation attributes of the end-user device and are often provided by the manufacturer of the end-user device. For example, some end-user devices cannot reproduce a musical note above high “C”. The algorithm associated with this end-user device takes this into account when manipulating the source file. A description and example of the major blocks of the media production portion 20 of the system follows. Media 36 is an original work, such as the written music of a song or a piece of art created by an author 44 . A piece of media 36 may have several performances 42 . An example of a piece of media 36 is “Dock of the Bay” written by Steve Cropper and Otis Redding. A performance 42 is a unique rendering of a piece of media 36 . Performances 42 have their own set of attributes such as album name, track length, etc. Thus, for the media “Dock of the Bay”, performances might be “Dock of the Bay” by Otis Redding and “Dock of the Bay” by Glen Campbell. Content 34 is a generic container of all forms of digital media. For example, a ringtone's original MIDI, its Real Audio preview, its Motorola ringtone string, its WAV preview—are all unique pieces of content 34 that relate to a performance 42 . Thus, for the performance, “Dock of the Bay” by Otis Redding, a piece of content might be “the Motorola ringtone for the Otis Redding performance of Dock of the Bay.” Licensing system 46 refers to the process by which a performance 42 is associated with specific licensing requirements. For example, a performance 42 may be limited to use in a specific geographical region. Post production 48 is performed by someone who has authority to approve content 34 from the standpoint of quality, licensing, etc. A producer 38 is someone who manipulates content 34 into various formats using the production tools 40 . A producer may also create the original performance using standard media production tools. With reference to FIG. 4 , various pieces of information are associated with a particular performance, including media type (audio), performance type (song) and rating filter. Each performance is a record in a performance database file stored in the database 12 a ( FIG. 1 ). The pieces of information are fields in the performance record. The rating filter assigns a G, PG, PG-13, R, NC-17 or X content rating to the performance. As described further below, this rating filter may be used to limit access to the performance. Each performance has an associated set of attributes, which may include album, genre, label, year and country information. These attributes are fields in the performance record. The attributes may identify one or more geographical territories (not shown) for licensing purposes. As explained further below, the licensing attribute acts as a filter to limit access to a performance based on licensing criteria such as geographical territories and approved clients. Regarding approved clients, certain clients may have the exclusive rights to certain performances based on distributor agreements. Associated with each performance is one or more pieces of content, as listed under the content tree. The pieces of content are associated with the performance record. Content records contain paths to individual media files stored on the content servers 13 ( FIG. 1 ). With reference to FIGS. 5 and 6 , various pieces of information are associated with each piece of content, including content type (audio/Nokia Proprietary, audio/Motorola Proprietary) status (active), deliverable (yes), performance (Who Let the Dogs Out) and several content attributes. These pieces of information are fields in the content record. The content attributes relate to the content media file itself and include, for example, the byte count of the content file and the highest and lowest notes within a media file and dimensions and bit depth in the case of graphics. A content file also may include attributes related to territorial licensing. Each content file's associated attributes and information are stored in a content database file in the database 12 a ( FIG. 1 ). The actual data is stored on a file server referenced from the database. Additional details on the content field entries are described under the following C2DMA section. Content-to-Device-Mapping Application (C2DMA) With reference to FIG. 2 , as previously mentioned, the C2DMA 22 handles the management and selection of appropriate content for users. In general, the system is capable of managing, serving and delivering correctly formatted content to heterogeneous devices over heterogenous networks. To this end, the system supports multiple makes and models of end-user devices. The system also differentiates between differing makes and models of end-user devices; supports differing functional capabilities of end-user devices that may share the same make and model; recognizes and handles carrier networks that may not allow or support the same functionality, even on the same device; defines the set of products available to a given end-user device and the media constraints for a piece of content to qualify as a product for a device; and associates specific users with specific devices which they own and use. With reference to the conceptual model of FIG. 7 a , the C2DMA maps content to end-users using the following subtasks: Content Description: The C2DMA provides a metadata model allowing each unique piece of content 34 in the system to be described in such a way that it can be reused. A content type 50 represents a formal declaration of a specific type of content 34 along with a generic description of its possible attributes. Each of the attributes is defined by an instance of the content type attribute 52 class. A content type attribute 52 has a name, a datatype, and a field denoting whether the attribute must be assigned to all content of that type. Note that content type attributes 52 are not meant to provide metadata for the original media title (such as artist, album, etc.), but instead describe details of the electronic media produced. For example, an MP3 file can be stereo or mono, has a bit rate in Kbps or has a variable bit rate with a maximum. In this case a content type “audio/mp3” would be created, with content type attributes named “stereo” (type boolean), “bitRateKbps” (type integer), and “variableBitRate” (type boolean). All three would most likely be marked as required database entries. As a piece of content 34 is produced and entered into the system, content attribute value 54 items are created to describe the values for content type attributes 52 of its content type 50 . All content type attributes 52 marked as required must be specified; others are optional. For example, the “Working in a Coal Mine” MIDI is of type “audio/midi”. As content attribute values, it specifies that “numNotes=25”, “highNote=G4”, “lowNote=E3”, etc. User Device Customization: The C2DMA architecture supports the possibility of unique capabilities for each individual end-user device. A user 56 owns one or more devices 58 . The user 56 may know the make 60 and model 62 of each device 58 . In the object model, make 60 and model 62 are simply entities with a name, where a single make can be associated with many models. For example, end-user Barbara owns a Kyocera 3035. “Barbara” is the name of a user; her device object references a model with the name “3035” which in turn references the “Kyocera” make. A device 58 is the entity that binds a user 56 to a model 62 . In some cases, model 62 may not be known, so the device 58 to model 62 mapping is optional. Both models 62 and devices 58 can support any number of platforms 64 . A platform 64 is a semantic grouping of distinct platform product 66 definitions, as described below. Multiple models 62 that support the same functionality may be part of the same platform 64 . For example, the Nokia 5125 model and the Nokia 5165 model both reference the “Nokia 51 xx” platform. Platform Product Support: The C2DMA describes platforms 64 that support specific media products 68 . A product 68 is a formal definition of deliverable content that implies both media type and intended use. Two examples of products 68 are “Screen Saver” and “Operator Logo”. While these products 68 use the exact same piece of content 34 defined by the exact same size constraints, i.e., content attribute values 54 , they represent different uses of the media. A platform product 66 describes the media type and constraints that specify products 68 deliverable to the platform 64 . This is done via a set of media capability 70 objects. The ability for a phone to support ringtones is captured, in the object model, by a platform product 66 that references the product 68 named “Ringtone”. Other platform products 66 for the same phone platform may reference “Operator Logo”, “Screen Saver”, etc. A media capability 70 references a content type 50 and capability constraints 72 for that content type. A capability constraint 72 specifies the required value or range of acceptable values for a particular content type attribute 52 . For example, the Nokia 3390 can utilize operator logos that are monochrome bitmaps exactly 72 pixels wide by 72 pixels high. Here, the “3390” model is linked to a platform 64 . This platform 64 references a platform product 66 entry. The platform product 66 references the product 68 named “Operator Logo” and specifies that it is composed of a single media capability 70 for content type 50 , “image/ING”. Attached to the media capability 70 object are three capability constraints 72 , specifying “width=72”, “height=72”, and “color Depth=1”. Device to Network Mapping: The C2DMA provides a means of associating specific end-user devices with the carrier networks that service them. A device 58 is on a network 74 , which is provided by an operator 76 . For example, Steve's Motorola phone (the device) is serviced by Verizon (the operator) on the “Verizon US TDMA” network. A network 74 can deliver content 34 via a set of delivery channels 78 . Delivery channels 78 define a protocol and means of addressing a device 58 . Examples of delivery channels 78 include the following: HTTP: user or agent acquires content by requesting a URL SMS: requires a phone number EMS: requires a phone number Carrier Proprietary: requires a phone number (there might be many of these for different custom protocols) Email: requires an email address Manual Entry/user Install: denotes that the content must be acquired by the user via a different channel, for example downloading a PRC application from a PC and later synching with a PDA. WAP push/pull: user or agent acquires content by requesting a URL BREW: user must have appropriate client software The relationship between a specific device 58 and a delivery channel 78 is the device's delivery address 80 . The format of a delivery address 80 may vary based on the delivery channel 78 . For example, the delivery address for the “SMS” delivery channel on Steve's phone contains an address data field with the value “13105551234”. Network Product Support: The C2DMA describes the ability for specific media products to be delivered via particular network connections and protocols, both public (the Internet) and proprietary SMSCs). Each delivery channel 78 can provide delivery of a set of products 68 . For example, the Nokia 51xx line supports delivery of ringtones via SMS. Associated with each delivery channel 78 for a network 74 is one or more acceptable encodings, provided by subtypes of the converter class. For example, for a specific SMS delivery channel, the ringtones must be sent as hexadecimal sequences with colons between each pair of characters and segmented into data packets or “frames” for SMPP delivery. Some examples of encodings are: binary, hexadecimal encoded, hexadecimal encoded escaped, ZIPped and Base64/UUEncoded. With reference to FIG. 7 b , each specific converter 142 encapsulates business logic for translating raw content 34 data to the format specified by the encoding, taking into account the details of the end-user device 58 ( FIG. 7 a ) and network 74 . The transformed content is an instance of the payload 160 class. A payload 160 is the customized version of media content 34 for a particular end-user device on a particular delivery network. Media Management With reference to FIG. 2 , the media management aspect 24 of the system includes an available media content library 82 which is a subset of the master library 30 . The available media content library is not a physical entity, i.e., its content resides in the master library. As described further below, attributes, such as content type and territory designation, assigned to a piece of content within the master library 30 determine whether the content may be mapped to a particular available media content library 82 . The media management portion 24 of the system provides the tools to create catalogs 86 of media content using the content stored in the master library 30 . These catalogs 86 are defined by various parameters, described below, which are stored in system processors ( FIG. 1 ). The media content itself, remains in the file servers 13 . Attributes associated with a piece of content and a catalog are used to map content to a catalog. A conceptual model of this mapping relationship is shown in FIG. 7 c . As previously mentioned, an available media content library 82 is derived from the master library. This derivation process involves one or more rules engines which act as filters to exclude certain media content in the master library 30 from being associated with the available media content library 82 . In one configuration, a rules engine uses the territory 88 and country 90 associated with a particular catalog 86 to limit the available content for the catalog to those pieces of content having licensing related attributes that match or exceed those of the catalog. For example, if a catalog has North America as a territorial designation, only those pieces of content with a North America territorial designation or greater designation, e.g., worldwide, are mapped to the available media content library 82 of the catalog 86 . Other licensing-related parameters, such as approved clients, may be used to limit the available content. The available media content library 82 may also be refined by another rules engine based on the media capabilities, i.e., platform 64 , make (not shown), model (not shown), associated with the catalog 86 and the media capabilities associated with the content of the existing available media content library 82 . Thus, the limiting factors in an available media content library 82 are the end-user devices that are supported by the catalog. For example, if a catalog 86 has an associated media capability of “audio/Nokia Proprietary”, only those pieces of content within the existing available media content library 82 of the catalog having an associated media capability of “audio/Nokia Proprietary” are mapped to the available media content library 82 of the catalog. With reference to FIG. 2 , the media management portion 24 of the system also includes a project configurator 92 which provides an integrated interface between a project manager (PM) and the master library 30 through the C2DMA 22 . The project configurator 92 allows for the creation of client accounts and catalog permissions using standard technologies including Java Server Pages (JSP) and Struts. Data related to the client accounts is stored in system processors ( FIG. 1 ). Various interfaces of the project configurator 92 and the functions provided thereby are described below, with reference to FIG. 7 c. Create New Client: With reference to FIG. 8 a , the PM enters client 96 information which adds a new record to the system database. Client information contains the name of the client and contact 94 information. The first screen of the graphical user interface (GUI) allows the PM to go to “client operations.” This screen has a list of current clients. When a new client is created, a form appears for obtaining client information. After filling out the information and selecting “OK,” the previous screen appears and the new client now appears on the client list. Delete (or Disable) Existing Client: At the “client operations” screen, a client is selected on the list and the delete button is selected. After an “are you sure?” popup ensures that this is not a mistake, the client is marked as “deleted,” i.e., is no longer on the list of clients. Client information, however, is not permanently deleted from the system database; it is merely hidden. Change Client Information: Basic client information is modified. For example: addresses, contacts, etc. The user navigates to the “client operations” screen, selects a specific client, and selects the modify button. A screen just like the form for creating a new client appears, but information is already filled in. The PM can change this information and hit “OK.” The fields are then updated in the system database. Manage Contacts for the Client: Contact information is added, including names, phone numbers, etc. At the “client operations” screen, there is a list of contacts 94 , and “add”, “modify”, and “remove” buttons. The add and modify buttons navigate to a screen with client contact information. This information can be added or modified. By selecting “OK,” a new database record is created or the existing one is modified. Create Extranet Logins: An extranet login 98 allows a client 96 to have limited access to the system. At the “client operations” screen, there is a list of contacts 94 . The PM must choose from this list and select the “Create Extranet Login” button. This brings up a screen that asks for the username and password. The system knows who the contact 94 is and what client 96 he is associated with. When this information is entered, a new record is created which is used to validate client logins and initialize the session. Manage Catalogs: With reference to FIG. 8 b , a client 96 may want changes made to its catalog 86 . Such changes may involve the name and catalog limit 100 , or even deleting a catalog 86 . The system provides an interface for a PM to manage these changes. When a PM chooses to manage catalogs 86 for a client 96 , he is presented with a list of catalogs currently defined for the client. Each catalog 86 in the list has an edit and delete link next to it. Selecting delete causes the system to disable (not physically remove) the catalog 86 by marking it as inactive. The PM is returned to the manage catalogs interface with the selected catalog 86 no longer showing. Selecting edit takes the PM to the change catalog setup details. On the same interface, a button is provided to create new catalogs. When selected, the system presents a create new catalogs screen. Create New Catalogs: With reference to FIG. 8 c , the system provides an interface allowing a PM to create new catalogs 86 for a client 96 . The catalog 86 provides the basis for the client's product 68 offerings to end users. The interface has a text field for entering a name of the catalog 86 and a drop down box with all currently defined territories 88 in it. The interface provides a list of available networks 74 . At least one network must be assigned to the catalog 86 , optionally multiple networks can be assigned. The system responds with an interface providing a list of platforms 64 supported by the assigned networks 74 , to be assigned to the catalog 86 . At least one platform 64 must be assigned, optionally multiple platforms can be selected. The system responds with a list of products 68 to be assigned to the catalog 86 . The list of products available for assignment are those capable of being deployed to the previously assigned platforms 64 . When the PM assigns a product 68 to a catalog 86 , a catalog limit 100 can be specified. If set, the limit sets the maximum amount of the product 68 the client 96 can add to his catalog 86 from the available library for each supported platform 64 . If a limit is not set, no limit is enforced. The system creates the catalog 86 with the chosen territory 88 , networks 74 , platforms 64 , and products 68 associated with it. In addition, a root category is created in the catalog 86 to store default values for the catalog. A default price code 102 for “free” is created. All categories 106 entered by the client 96 , as explained below, are created under this default root category. After creating the catalog 86 and default root category, the PM is returned back to the client management page ( FIG. 8 b ). If more than one network 74 is going to be supported in one catalog 86 , the client 96 appends the target network when querying for the XML list of available titles 104 , allowing the system to respond with just the titles 104 available for the selected network 74 . This is because if the catalog 86 supports multiple networks 74 , it may have selected content 108 that can be deployed to one network 74 but not to others. A catalog 86 may have price codes 102 in one or more currencies. Different price codes can be associated with different catalog categories. Change Catalog Setup Details: The client 96 may want to change the name of the catalog 86 , adjust the catalog limits 100 or even change the networks 74 , platforms 64 , and products 68 associated with a catalog. This interface shows the name of the catalog 86 in a text box for editing. Below the name a table shows columns containing the supported networks 74 , platforms 64 , and products 68 . At the bottom of each column a link is provided to change the information above the link. If the PM chooses to change the networks 74 , he is taken to interfaces to select the networks, and must reselect the platforms 64 and products 68 since the available platforms and products may have changed when the networks changed. Similarly, if the platforms 64 are changed, the products 68 must be reselected. The interfaces for selecting the networks 74 , platforms 64 , and products 68 are identical to the interfaces specified in the create new catalog section. If the networks 74 , platforms 64 , and or products 68 are changed, the system traverses the current selected content 108 and unselects all content not currently supported by the new configuration. Once the system is updated, the PM is taken back to the manage catalogs interface. Associate Client Logins with Catalogs: The PM, having created extranet logins 98 for contacts 94 and one or more catalogs 86 for the clients 96 , now needs to associate which contacts can edit the catalogs in question. The PM is presented with a grid with catalogs 86 listed across and contacts 94 with extranet logins 98 listed down. Each intersection of a contact 94 and catalog 86 is represented by a checkbox. The PM can check or uncheck each checkbox; upon this action, the system creates or removes the corresponding mapping from the extranet login 98 to the catalog 86 . With reference to FIG. 2 , the media management aspect 24 of the system also includes a catalog designer 110 which provides an integrated interface between a client user and the available library through the C2DMA 22 . The catalog designer 110 allows for the creation of catalogs using standard technologies including JSP and Struts. Various interfaces of the catalog designer 110 and the functions provided thereby are described below. As previously mentioned, data related to catalogs is stored in system processors ( FIG. 1 ). Client Login/Logout: A contact 94 accesses the system home page, which has a hyperlink to the login page. The login page has text fields for username and password, and a login button. The contact 94 gives name/password which is checked against the system database. If correct, a session is created for that contact 94 . The contact 94 is then able to create and modify catalogs 86 . All pages have a logout button. Also, when the session times out, the contact 94 is automatically logged out of the system. Catalog Manager/Category Manager: After a contact 94 has successfully logged into the system, he is taken to the catalog manager ( FIG. 9 ). The contact 94 is presented with a list of catalogs 86 that have been defined by the PM for the client 96 . Each catalog 86 provides a link to a category manager interface, which displays the categories associated with the catalog. ( FIG. 10 ). If the system determines the contact 94 has authorized access to only one catalog 86 , the contact is immediately presented to the category manager for that catalog. Create New Category: From the category manager, the contact 94 can choose to add new categories 106 to an existing catalog 86 . In response to a request to create a new category, the system presents an interface screen ( FIG. 11 ), whereby attributes are assigned to the new category. Relevant data about the new category 86 includes: Category name Product types (choose from list of available product types for catalog) Default price code (choose from list of available price codes) Rating filter Choose if the category is seasonal; if so, enter start and end dates. Choose whether the auto-add feature is enabled and if so, what existing category should be used as a template. Upon completion of this form, the system creates a new category 106 object with the appropriate relationships and presents an updated category manager screen with the newly created category ( FIG. 12 ). If the auto-add feature is enabled, the category 106 is immediately populated with the titles 104 from the auto-add source category. The category 106 name does not have to be unique throughout a catalog 86 . Default values for price code, rating filter and seasonal status are inherited from the parent category. Manage Categories: Once a contact 94 has chosen a catalog 86 to manage, he is taken to the category manager interface ( FIG. 12 ). This interface presents a list of all the subcategories defined under the root category of the catalog. Each category has links next to it to edit, create subcategories, manage content, and delete. If the contact chooses to edit a category 106 , he is taken to the edit category interface ( FIG. 13 ) and presented with all of the category attributes. The category name is displayed in an editable text box through which it can be changed. Under the category name, other category attributes are presented including: default price code, rating filter, start date and end date. The contact 94 can save or cancel the changes. If he saves the changes, the system modifies the category 106 to reflect the new attribute values. If the rating filter has been lowered, the system removes all selected titles 104 from the category 106 that no longer meet the rating requirements. In one configuration of the system, the titles are left in place, thus allowing the client to see what titles have been removed. In either case (save or cancel) the contact is returned to the category manager interface ( FIG. 12 ). If the contact 94 chooses to manage category or subcategory content, the system presents a manage content interface, which is described below. If he chooses to delete the category 106 , he is given a popup to confirm the action. If he confirms it, the system deletes the category and its dependent objects permanently. Add Content to Category: The manage content interface ( FIG. 14 ) provides a list of titles currently in the category, and allows for the addition of titles. Selecting the “add titles” option causes the system to present a title selector interface ( FIG. 15 ). This interface allows the contact 94 to select a title from the list of available content for the platforms, products and networks associated with this category and catalog. The available list is further restricted based on the rating for the title. The contact can view this available list of titles in a number of ways: Sorted alphabetically and paginated via a query containing one of the following: Artist name (substring match) Title (substring match) Exact rating (G, PG, PG-13, R, NC-17, X) Product type (choice of products configured for category) Platform type (choice of platforms configured for catalog) Template category—show content as grouped in an existing template category The contact 94 can select one or more titles 104 from this list to import into the category 106 . The system creates a title 104 instance linked to each chosen title and assigns it the default price code 102 . In addition, subject to catalog limit 100 constraints, selected content 108 entries are created for each platform product 66 ( FIG. 7 a ) that matches the title with the category's configuration. The performances listed in a category 106 are unique, i.e., the same item cannot be added twice. As a default function, a single price applies to all selected versions of a title. Add/Remove Selected Content by Platform: A manage catalog interface allows a contact 94 to look at an existing catalog 86 and add or remove titles 104 . The contact 94 goes to this page and sees a list of catalogs. A specific catalog can be selected and the “modify” button pressed. This brings up a page that displays the titles for that catalog. Specific titles can be selected and deleted. There may also be titles in this “active catalog” that are shown, but not selected as active. The contact activates these by selecting the title line item (for a specific device). Also, the contact can go to a screen that shows the entire catalog of available items, select one or more items, and have them added to the active catalog. Manage Price/Code Settings for Each Title: Each title can be given a price code 102 . Also, the price codes 102 can be modified globally, which automatically changes the price for all items using that code. The active catalog page contains a dropdown combo box for each line item title. The contact 94 can select from a list of price codes 102 . The current price for that code is also displayed. To change pricing, the contact 94 goes to a pricing page and sees a list of all price codes 102 . An individual price code can be selected and modified. Also, existing price codes 102 can be deleted, and new ones created. If a price code 102 is deleted, all titles 104 that are set to that price code revert to the default price code. There is a default price code for the entire catalog 86 . This is selected from a list of available price codes on a “pricing” page. Manage Price Codes: When a contact 94 chooses to manage price codes 102 , he is taken to the manage price codes interface (not shown). The interface presents the contact with a list of all currently defined price codes, in an editable text box, with the set of prices (one price for each currency) to the right of the code in text boxes. The name of the price code can be changed, as can each of the prices. Below the list of price codes the list continues with several lines of the same text boxes, all of which are blank. The contact can add new price codes by filling in the blank boxes. When the contact selects save, the system renames any price codes, resets any changed prices and adds any new price codes and prices. Next to each price code in the list is a button to delete the price code. If the contact chooses to delete a price code, a pop-up confirmation is presented. If confirmed, the system checks if any titles are using the price code and returns an error page if the price code is currently in use. Otherwise, the price code and all associated prices are permanently deleted. If the price code being deleted was the default price code of any categories or subcategories, the category is modified to use the default “free” price code. With continued reference to FIG. 2 , the media management aspect 24 of the system also includes a Web services application tool 112 or content export tool which is part of the client-server interface 14 ( FIG. 1 ) and provides an integrated interface between client servers 16 ( FIG. 1 ) and a particular project catalog 86 . The Web services application tool 112 is built utilizing XML and HTTP protocols and provides XML feeds of catalogs and the previews and content associated with a catalog in response to an HTTP request by a client server. The following is generally needed to retrieve content information from the system servers: a client account in the system, one or more created catalogs within the system, and an Internet protocol (IP) address from which the client accesses the system. A client requests (via browser manually or server originated request), receives (via browser copy and paste or server catch), parses (to flat file or database importer), and stores (in flat file or database) catalog and content feeds. Using the catalog and content feeds, the client creates an HTML/Wireless Applications Protocol (WAP) display (flat file served to end-user interface or dynamically displayed from system database) interface (Storefront) for use by end-users. A client accesses the content of a project catalog 86 with an XML request via HTTP. Once this is successfully passed into the system server, a response is generated and pushed to the client server 16 for display to the end user. In other embodiments, the responses may be provided to the client server by WAP pulling and other browser based delivery. The process is as follows: The client sends a server 16 XML request via HTTP to the system server 10 to access its client-specific catalog 86 . The code for an exemplary catalog request and its related schema is shown in FIG. 16 . The following fields are in the request: Catalog Request—the enclosing tag denoting that this is a catalog request Client Id—the assigned client ID for the partner Storefront Id—the storefront ID the partner requests Model Id—a device model ID, for which the partner is requesting content The Web services application tool 112 responds to HTTP POST requests and looks for a parameter with name XML to contain the actual request XML. The Web services application tool 112 uses a standard approach to error messaging. Since it is built on the top of HTTP, it utilizes the robust and extensible platform of HTTP error messaging. All successful requests return HTTP status code 200 . If an error occurs, the response will have error code 4xx. If an XML request is detected by the Web services application tool 112 , the catalog request is sent to the system server 10 . The catalog request is handled via the system server 10 and a catalog response is generated as shown in FIGS. 17 a and 17 b . The code for an exemplary catalog response and its related schema is shown in FIGS. 17 a through 17 d. Catalog Response—the enclosing tag denoting that this is a catalog response Model—an end-user device, for which a client is requesting content Id—a model Id as assigned by the system operator Name—model's name Make—model's manufacturer Product—describes the media types supported by the model Id—a platform product Id as assigned by the system operator Name—a formal definition of deliverable content that implies both media type and intended use Platform—a media type supported by the model Category—a logical grouping of content within a catalog; category can contain other categories Name—name of the category Description—description of the category Title—a title of a given performance as stored in the catalog Name—name of this performance Type—performance type of the piece of content Artist—artist or band Price—price for all types of content with this title Title Attribute—additional attributes describing the above title Type—attribute type Value—attribute value Content Delivery Code—a unique Id for a piece of content that is derived via the storefront from which the content is being requested Id—id of the content delivery code Product—product for which this title is available and supported by at least one of the requested models Id—id for the product Preview—a URI pointing to a preview of the requested piece of content; one piece of content might have several previews with different media types MediaType—media type of the preview URI—URI of the selected piece of content Upon receipt of the catalog response, the client server 16 unwinds the XML within the response and builds an HTML or WAP storefront. The storefront may be a Web page displaying the content available within the requested catalog and end-user devices compatible with at least one of the displayed content types. With reference to FIG. 2 , the media management aspect 24 of the system also includes billing interfaces 114 which provide for the payment of content by the end user. A conceptual model of an exemplary billing interface is shown in FIG. 18 . The billing manager 116 is the central object that reconciles billing reports 118 generated from a billing channel 120 with delivery reports generated by a network's 74 delivery of content 34 through a delivery path 122 . The billing channel 120 may include any one of a 900 toll Interactive Voice Response (IVR) 124 , 800 toll free IVR, credit card 126 , carrier direct billing (CDB) 128 a prepaid card or other billing forms, such as Paypal. From the billing report 118 and the network 74 delivery information, commissions 130 are calculated for the various entities in the sales pipeline. The sales pipeline is a conceptual model that includes all primary entities involved in the delivery of a particular piece of content 34 , such as distributors, operators, billing partners, etc. The system calculates a commission share for each entity within the sales pipeline. In addition to commissions, royalties 132 are generated for use of the content 34 that was delivered. Of note is the price list 134 , generated from a client contract 136 involving a point of sale (EPOS) 138 and the system operator. The contract drives which content 34 is available for sale at an EPOS, and the price that will be charged at the EPOS. Possible EPOSs include the Web, Wireless Applications Protocol (WAP), Mobile Originated Short Message Service (MOSMS), a prepaid card, print, advertising and IVR. Media Delivery With reference to FIG. 2 , the media delivery aspect 26 of the system includes a request handler 140 , a broker/converter 142 , a distributor 144 , monitoring tools 146 and customer service tools 148 . The request handler 140 hosts the Web services application 14 ( FIG. 1 ) and receives content requests from a client server. In one embodiment, the content requests sent to the request handler 140 by the client server may contain the fields listed below. In other embodiments, less fields may be included. For example, the delivery address, content delivery code Id and operator Id are sufficient to deliver content. The code for an exemplary content request and its related schema is shown in FIGS. 19 a and 19 b. Content Delivery Request—the enclosing tag denoting that this is a content delivery request Delivery Address—destination phone number or e-mail address where content is to be sent Content Delivery Code Id—the requested content id; content Id uniquely identifies a piece of content as a part of a catalog; it doesn't represent the actual content; this is a unique id that is determined by matching the content with the storefront to which it will be delivered Picture Message Text—this is a special case of product—picture message, which along with a graphic can contain a text message Price—price of the requested piece of content; this is defined by combining the storefront and the billing method to calculate the cost to the end user Operator Id—the id assigned by the system operator that designates which mobile operator the piece of content will be sent through Storefront Id—The store front where the request is coming from Sales Channel Id—The sales channel used for this request; this helps determine how the client will pay for a piece of content; it identifies uniquely billing method which will be used, e.g., credit card, and point of sale, e.g., 800, Web site Client Transaction Id—the id tracked by the client for this content request Request Type—paid/free/resend, etc. Billing Address—in case when someone sends a content to a buddy, the billing address will be different from the delivery address Model Id—the model of a device that the piece of content will be sent to; the system operator provides the client with a separate document detailing the ids of the models it supports Upon receiving the request, the request handler 140 repackages the requests into a standard form and forwards it to the broker/converter 142 . The request handler 140 also sends a content delivery response to the client-server, which contains the following fields. The code for an exemplary content response and its related schema is shown in FIG. 20 . Content Delivery Response—the enclosing tag denoting that this is a content delivery response Moviso Transaction—a transaction associated to this content delivery request Id—the transaction id Client Transaction—a transaction Id used by the client for tracking this content delivery request Id—the transaction id With reference to FIG. 7 b , the broker/converter 142 translates the raw content 34 into a payload 160 , i.e., a format specified by the encoding requirements/delivery format 162 used by the delivery channel 78 of the carrier network identified in the content request. The final payload 160 is placed in a que in the broker/converter 142 before being forwarded to the distributor 144 for transmission over the carrier's delivery network 74 . A conceptual model of media distribution is shown in FIG. 21 . The following abbreviations are used in the figure: SMPP: Short Message Peer to Peer SM/ASI: Short Message/Application Service Interface SMTP: Simple Mail Transfer Protocol ESME: External Short Message Entity SMSC: Short Message Service Center IVR: Interactive Voice Response Delivery network: global system for mobile communication (GSM), time division multiple access (TDMA) or code division multiple access (CDMA) for second generation (2G) systems MOSMS: Mobile Short Message Service Though not shown in the diagram, the system may be used with other delivery networks including the following third generation systems: third generation code division multiple access (3GCDMA), wideband code division multiple access (WCDMA), universal mobile telecommunication system (UMTS) and freedom of mobile multimedia access (FOMMA). With reference to FIG. 2 , the system may also include a customer service (CS) tool 148 through which it provides various reports to the client and notifications to the end users. A conceptual model of the CS tool 148 is shown in FIG. 22 . An exemplary content delivery/accounting report 150 contains the following information: Content download transaction identifier Content download date Content type (ringtone,picture message,etc) Content id Content name Accounting type (free,paid,credit,charge,etc) Content download originator type (customer,cs rep,etc) Delivery status (phoneset delivered,smsc delivered,buffered,rejected,etc) Billing status (billed, not billed, refunded) A service request 152 generates a notification 154 , e.g. an email, which is sent to an appropriate notification receiver. The receiver searches for this service request in the CS tool 148 and resolves it, resulting in a service request resolution 156 and an associated notification delivery to an appropriate user 158 . As an additional feature, the request handler 140 provides an account status service to those clients using a pre-paid or MIN accounting system to bill the end user. To use this feature, the client sends an account status request which includes the following fields. The code for an account status request and its related schema is shown in FIG. 23 . Account Status Request—the enclosing tag denoting that this is an account status request Billing Address—this can be either an e-mail address, telephone number, home address, etc. that is being used to charge for delivery of the content; when someone sends a ringtone to a buddy, the billing address will be different from the delivery address Sales Channel Id—The sales channel used for this request. This is the means by which the user is charged, such as 800 IVR, 900 IVR, pre-paid, etc. Store Front Id—The store front from which the request is coming In response to the account status request, the request handler 140 generates an account status response which includes the following fields. The code for an account status request and its related schema is shown in FIG. 24 . Account Status Response—the enclosing tag denoting that this is an account status response Balance—the balance of the requested account While the foregoing description of the system has focused on the provision of audio-based media content, particularly ringtones, to cellular telephones, the system may be used to provide any type of media content including visual-based and audiovisual-based media content to any one of a variety of communication devices, such as those described earlier. It will be apparent from the foregoing that while particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.

In a system for providing media content to a communication device, a device capabilities determination is made by a rules engine that compares content attributes with constraints on those attributes for a device. Metadata describing the content is derived and entered into a database. As the specifications of different devices are entered into the system, corresponding constraints are associated with the devices that tell the engine the valid range of values for the content attributes. The engine creates an available content library for each class of devices by excluding all instances of content that have attributes outside the range of values prescribed in the constraints. A similar rule set determines whether the content can be distributed through a particular delivery channel, based on the distribution channel capacity to support a media type. The subset of content that passes both the device capabilities tests and the distribution capability tests is viable for delivery to a device over a particular distribution channel.

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a development apparatus of an electrophotographic image forming apparatus utilizing electrophotographic type such as copying machine, laser beam printer, facsimile and complex machine (hereafter referred simply to as “image forming apparatus”). [0003] 2. Related Background Art [0004] In an image forming apparatus utilizing electrophotographic type, or electrostatic recording type, a latent image is formed on a electrostatic latent image bearing member, for example, a photosensitive drum, and a visible image is obtained by attaching a developer (toner) to this latent image. Particularly, in a color image forming apparatus for forming chromatic color images, development method using two-component developer including toner and carrier is used widely since stability of image quality and durability of the apparatus are superior to those of other development method. [0005] In development method using two-component developer, of nonmagnetic one component toner and magnetic carrier (hereafter referred simply to as “toner and carrier”) being charged in the development apparatus, toner alone is being consumed for development of electrostatic latent image. Therefore, toners should be replenished freshly one by one to the development apparatus for each of colors. In order to maintain an electrostatic latent image at a predetermined development concentration all the time, an amount of the toner to be replenished should be controlled strictly. For example, when the toner is replenished from toner cartridges corresponding to each of Y, M, C and K colors to the development apparatus, generally, those with such a structure that the toner is fed in pushing manner by rotating a powder conveyance screw having spiral structure which is provided for every color, and the conveyance amount is controlled, have been frequently used. Reasons why the powder conveyance screw is frequently used are that the conveyance amount per one rotation of the screw can be determined easily with simple structure thereof and that necessary controls can be accomplished with reduced costs. [0006] In recent years, it has been requested that images with various image ratios, from large images having large image area such as photographs to small images having small image area such as one-point-color, should be output at high speed and with stable manner. In this case, use of above-mentioned powder conveyance screw for toner replenishment (hereafter referred to as “toner conveyance screw”) involves the following problems: [0007] As for the toner conveyance screw, a screw shaft equipped with a blade in spiral form is penetrated thorough a screw pipe and is rotated to feed the toner in pushing manner by the spiral blade in the pipe. A minimal allowance clearance is provided between outside diameter of the spiral blade and inside diameter of the screw pipe so as to enable rotating the spiral blade. In some cases, so-called flashing phenomenon in which the toner leaks out from such clearance and is supplied more than necessary to the development apparatus, is generated, thereby posing a problem. In order to solve this flashing phenomenon problem, a toner replenishment apparatus which regulates toner amount by adjusting the clearance is proposed (see, for example, Patent Document 1). [Patent Document 1] Japanese Patent Application Laid-Open No. 5-224530 [0008] However, even when toner amount is regulated by adjusting the clearance as is the case of the toner replenishment apparatus disclosed in the patent publication of above-mentioned patent document, there still remain unresolved problems. [0009] In recent years, from view points of higher image quality, energy saving and speeding up of copying operation, there has been a tendency towards smaller diameter particles and lower melting point for the toner. Therefore, toners with higher degree of cohesive force (or sticking power) which is one of factors for determining the powder fluidity, namely, higher cohesion degree toners, have been frequently used. Therefore, when runout or eccentricity is caused to the toner conveyance screw under rotating, toner is ground in the clearance with regard to the screw pipe, thereby generating toner cohesion clusters. These toner cohesion clusters result in defective images such as void image or stain on the image. Particularly, with copying machines in which a toner conveyance screw is used frequently to replenish toner from a toner cartridge to a development apparatus, suppression of generation of cohesion cluster as mentioned poses a significant problem. [0010] In addition, as a known development method in color image forming apparatus, rotary type development unit is mentioned. For example, this method has such a configuration that a plurality of development apparatuses corresponding to each of Y, M, C, K are equally distributed on the same circumference in a radial pattern and are displaced in rotational manner and are rotated to a position facing with an electrophotographic photosensitive drum (hereafter referred simply to as “photosensitive drum”) that is a latent image bearing member to initiate development. In this case, for example, cartridges to which each color of Y, M, C, K toner are charged are arranged in one row in tandem manner and are provided at upper portion of a rotary type development unit to increase the amount of toner accommodation as much as possible. [0011] In this case, each of the development apparatus corresponding to Y, M, C, K arranged in radial manner in the rotary type development unit which is a rotating body is connected through a toner replenishment path to each of those corresponding to a plurality of cartridges arranged in one row at upper portion thereof. Therefore, it is natural from geometrical viewpoints that there is a dimensional difference between each of length of the replenishment path corresponding to Y, M, C, and K. Thus, a toner conveyance screw is arranged to each of toner replenishment paths having dimensional differences to form a part of the replenishment path, and therefore, length of the screw shaft and length of the screw pipe are also different for Y, M, C, and K. If length of toner conveyance screw is different for Y, M, C, K, there is also a difference of the time for the toner to pass through the screw pipe resulting in a difference of generation of toner cohesion clusters. In other words, replenishing the toner of the same component uniformly from the toner cartridge to each of development apparatuses does not constitute a fundamental solution for suppression of generation of toner cohesion clusters and for prevention of defective images due to void image or stain. SUMMARY OF THE INVENTION [0012] An object of the present invention is to provide a development apparatus capable of obtaining a stable image by suppressing effectively generation of cohesion clusters of the toner thereby preventing occurrence of defective images. [0013] A development apparatus to accomplish the above-mentioned object comprises: [0014] a plurality of development devices which develops an electrostatic image; [0015] a plurality of replenishment developer containers each of which accommodates a replenishment developer containing a toner to be replenished to each of the plurality of development devices; [0016] a plurality of replenishment developer conveyance paths which communicates the plurality of replenishment developer containers with the plurality of development devices, and which replenishes the replenishment developer in the plurality of replenishment developer containers to each of the plurality of development devices; and [0017] a plurality of conveyance members which are provided in each of the plurality of replenishment developer conveyance paths for conveying the replenishment developer; [0018] wherein a length of at least one conveyance path, of the plurality of replenishment developer conveyance paths, is different from that of other conveyance paths, and cohesion degree of replenishment developer to be conveyed by a longest conveyance path, of the plurality of replenishment developer conveyance paths, is lower than cohesion degree of replenishment developer to be conveyed by other conveyance path. BRIEF DESCRIPTION OF THE DRAWINGS [0019] FIG. 1 is a drawing illustrating a part of an image forming apparatus equipped with a development unit according to an embodiment. [0020] FIG. 2 is a drawing illustrating a toner replenishment path for every color from a toner cartridge which is a main part in the development unit according to the present embodiment, to a rotary type development unit. [0021] FIG. 3 is a drawing schematically illustrating replenishment of toners with preferred cohesion degree capable of preventing toner cohesion clusters corresponding to hopper replenishment screws having different length for each of colors. [0022] FIG. 4 shows Table 1, Table 2, Table 3 in which measurements in the first embodiment are summarized. [0023] FIG. 5 shows Table 4, Table 5 in which measurements in the first embodiment are summarized. [0024] FIG. 6 shows Table 6, Table 7 in which measurements in the second embodiment are summarized. DETAILED DESCRIPTION OF THE EMBODIMENTS [0025] Now, referring to drawings, each one exemplary embodiment of the development unit and the image forming apparatus according to the present embodiment is described in detail hereafter. [0026] FIG. 1 illustrates an image forming apparatus having a rotary type development apparatus 18 which has cylindrical form and is rotatable (hereafter referred simply to as “development unit”). On the circumference about a rotating shaft 18 a of the development unit 18 , for example, development devices 1 Y, 1 M, 1 C and 1 K corresponding to each color of Y (yellow), M (magenta), C (cyan), K (black), development device 1 LM for light magenta, development device 1 LC for light cyan are equally distributed in radial manner. Meanwhile, light magenta and light cyan are color having the same hue with regard to magenta and cyan, respectively, and low density (light color). By performing development with a combination of such a light color toner and deep color toner, granularity of images can be improved. Hereafter, these are collectively named as a development device 1 except otherwise necessary. The development unit 18 is rotated upon receiving rotational power from a motor (not shown) which serves as a rotational power source. By the rotation, an arbitrary development device 1 is displaced to a proximity position for process action to a photosensitive drum 28 which is a latent image bearing member while the another development devices 1 are retreated from a photosensitive drum 28 . [0027] The image forming apparatus operates follows: [0028] In FIG. 1 , a primary charger 21 applies a charged bias voltage to charge the surface of the photosensitive drum 28 and forms an electrostatic latent image on the photosensitive drum 28 by exposure unit such as a laser scanner 22 . The development apparatus 1 forms a toner image on the electrostatic latent image on the photosensitive drum 28 , and this toner image is transferred on an intermediate transfer belt 24 by a first transfer bias by a first transfer charger 23 a. [0029] When a full color image is to be formed, for example, first, a toner image of light magenta is formed on the photosensitive drum 28 by a development apparatus 1 LM for light magenta, and the light magenta toner image is then primary transferred on the intermediate transfer belt 24 . Subsequently, a rotary type development body 18 is displaced in rotational manner by an angle of 60° to bring the development apparatus 1 LC for light cyan to a development position P 1 . A toner image of light cyan is formed on the photosensitive drum 28 , and the toner image of light cyan is superimposed onto the toner image of light magenta mentioned above on the intermediate transfer belt 24 by way of primary transfer. Such operations are executed sequentially in the development apparatuses 1 Y, 1 M, 1 C, 1 K to form full color images based on chromatic toner onto the intermediate transfer belt 24 . [0030] Following this, by second transfer bias by way of a second transfer charger 23 b, images on the intermediate transfer body belt 24 are collectively secondary transferred onto a sheet 27 such as recording paper on a transfer paper conveyance belt 25 , and the sheet 27 is released from the transfer paper conveyance belt 25 . It is then fed to a fixing device 26 and fixed by pressurizing and heating to obtain a permanent image. Further, toner remained on the photosensitive drum 28 after primary transfer is removed by a first cleaner 29 a, and toner remained on the intermediate transfer belt 24 after secondary transfer is removed by a second cleaner 29 b, to be in stand-by state for the next image forming. [0031] Referring to FIG. 1 and FIG. 2 , the conveyance path for conveying the toner by the replenishment developer conveyance path from a toner cartridge (replenishment developer container) 51 , in which toner of each color LM, LC, Y, M, C, K is charged, to the rotary type development unit 18 will be described. [0032] At upper portion of the development unit 18 , large capacity toner cartridges 51 is arranged in single horizontal row in tandem manner in the order of, for example, image forming by each color LM, LC, Y, M, C, K. Besides, a hopper 53 for replenishing the toner to each development apparatus 1 is provided for every toner cartridge 51 , and a piezo-sensor 52 for detecting the toner is provided inside of each hopper. When output of a toner detection signal from the piezo-sensor 52 is ceased, control is made so that the toner is fed from the toner cartridge 51 to the hopper 53 inside. The toner in the hopper 53 is supplied to inside the development unit 18 by rotational driving of a hopper replenishment screw (conveyance member) 54 in pushing manner. In other words, the hopper replenishment screw 54 has a screw shaft onto which a blade is formed in spiral form, rotational speed (revolution: rpm) of the shaft is controlled by an automatic toner replenishment apparatus (ATR), and the toner is replenished to the target development unit 18 while rotating at a desired rotational speed. [0033] As shown in FIG. 2 , the toner being fed from the hopper replenishment screw 54 in pushing manner is delivered to a rotary replenishment screw (conveyance member) 55 corresponding to each of the development device 1 in the development unit 18 . The toner is replenished thoroughly to each of the development device 1 by the rotary replenishment screw 55 thereof. In this way, the replenishment developer conveyance path communicates the developer replenishment container 51 with the development device 1 , provides with conveyance members ( 54 , 55 ) therein, and serves as the replenishment route ( 54 a, 55 a ) for replenishment of the replenishment developer in the developer replenishment container to the development device 1 . Meanwhile, length of the replenishment conveyance path corresponds to a length of the replenishment route ( 54 a, 55 a ). [0034] As for toner replenishment method for the above-mentioned case, it is possible to employ a video counting type ATR which predicts toner consumption by measuring laser exposure time. As for performance of toner replenishment of this type, replenishment accuracy represented by variation of amount of replenishment per unit number of times of replenishment or by unit time affects image density and particularly affects tint stability. For this reason, an encoder is disposed at the most upperstream side of the hopper replenishment screw 54 , and rotational speed of the hopper replenishment screw 54 is controlled based on the signal from this encoder. [0035] The amount of toner replenishment obtained when the hopper replenishment screw 54 is rotated one time is defined to be “One replenishment unit”. When replenishment time is controlled by above-mentioned toner replenishment method, variation of the replenishment amount expressed by thus defined unit can be reduced to approximately 1/10 of variation of the replenishment amount by conventional method. To attain this level, it is necessary to charge an equal amount of replenishment toner all the time to every screw pitch of the hopper replenishment screw 54 . In addition, the replenishment toner should be being charged while inside of the screw pipe 54 a, through which screw shaft of the hopper replenishment screw 54 is penetrated, is sealed reasonably all the time. In the meantime, with allowable tolerance clearance provided between outside diameter of spiral blade of screw shaft of the hopper replenishment screw 54 and inside diameter of the screw pipe 54 a, it has been reported that rubbing and grinding of the replenishment toner occur. On the other hand, the replenishment toner fed from the rotary replenishment screw 55 to inside the development unit 18 is being fed entirely to the development apparatus 1 at the time of replenishment. Therefore, rubbing and grinding of the replenishment toner at the clearance between outside diameter of spiral blade of the rotary replenishment screw 55 and inside diameter of the screw pipe 55 a occur very rarely. [0036] Next, toner cohesion clusters which may cause defective images due to void image or stain are generated by rubbing with inner circumference of the screw pipe 54 a, 55 a, or generated by electrostatic cohesion of toner themselves. In general, when rubbing time is long, defective images are caused more easily under low-humidity environments than high-humidity environments. As for size of cohesion clusters, cohesion clusters more than 1 mm in diameter are present while particle diameter of ordinary toner is 5.5 μm. If these cohesion clusters are replenished to inside the development unit 18 , although majority of clusters can be crushed by the rotary replenishment screw 55 , larger particles or cohesion clusters with higher cohesiveness can not be crushed, but are subjected to development. As a result, images with drip-drop stain appear as defective images. If it is extremely difficult to eliminate cohesion clusters thoroughly, allowable extent of generation of the cohesion clusters will be analyzed hereafter based on the measurements. (Measurement of Cohesion Degree) [0037] As one of methods to know the degree of cohesion, flow characteristics of a sample representing the replenishment developer are measured. The basis of determination is such that the greater the cohesion degree is, the more likely the sample has “Defective fluidity” as the replenishment developer. The sample as the replenishment developer denotes in some cases a single body including non-magnetic toner alone, or an admixture of non-magnetic toner and magnetic carrier, or in another case, toner containing external additive. The external additive is fine powders and is used as the toner surface modifier, and in recent years, it is used, in some cases, as the image density improving agent. The object of cohesion degree in the present invention is a state as the toner containing the additive. With a developer in which magnetic carrier and no-magnetic toner are mixed, measurement of the cohesion degree is performed for non-magnetic toner excluding magnetic carrier. EMBODIMENT 1 [0038] Powder tester (Hosokawa Micron Corporation) equipped with digital vibration meter (Digivibro Model 1332) was used as the measuring device. On the vibration stand sieves having 380 mesh, 200 mesh, 100 mesh in the order of finer mesh were laminated so that 100 mesh sieve may be positioned at the uppermost. 5 g of precisely weighed sample was added on the 100 mesh sieve thus set, displacement of the digital vibration meter was set to 0.5 mm (peak-to-peak), and vibrations were exerted for 15 sec. After that, weight of the sample left on each of sieves was measured and measurement was substituted in Equation (1) shown below to calculate cohesion degree. Samples used were left under 23° C./60% RH environment for about 12 hours, and measurement environment was 23° C./60% RH. [0000] Cohesion degree (%)=(Weight of sample on 100 mesh sieve/5 g)×100×(1/1)+(Weight of sample on 200 mesh sieve/5 g)×100×(3/5)+(Weight of sample on 380 mesh sieve/5 g)×100×(1/5)   (1) (Measurement of Cohesion Clusters in Replenishment Developer Sample) [0039] The number of cohesion clusters is measured to know how many cohesion clusters, which result in defective images such as void image or stain in the sample. [0040] First, a sieve having 75 μm of opening was set on the vibration stand, 1 g (gram) of precisely weighed sample toner was added onto this mesh sieve, amplitude of vibration was adjusted to 5 mm, and vibrations were exerted 800 cycles in 30 sec. Following this, the number of cohesion clusters left on the mesh sieve was counted. This measurement was repeated 10 times and the number of cohesion clusters (sampling average) was calculated. [0041] In the meantime, in order to know possible correlation between the number of such clusters, and defects and imperfections on the image, cohesion clusters collected at actual measurement are mixed directly into the development apparatus, 20 sheets of halftone images were output, and the number of stains appeared on images was actually measured. In this case, cohesion cluster(s) of about 1 mm in size were mixed 1 piece, 5 pieces, 10 pieces with regard to toner replenishment amount of 1 g. Results of the measurement are normalized with respect to the number of pieces of cohesion clusters present in 1 g of the sample toner and are shown in Table 1. [0042] Table 2 through Table 7 described herein as well as Table 1 mentioned above are shown in the separate sheets. [0043] The material used as the sample of replenishment developer was prepared such that resin binders made primarily of polyester were kneaded together with wax and pigments, which were then crushed and classified to obtain ones having average volumetric particle diameter of around 5.5 μm. After that, appropriate amount of additives were added to yield cyan toner having 500 cohesion degree to be used for assessment. It is understood from measurement results shown in Table 1 that the number of cohesion clusters to be mixed in the development apparatus 1 should be less than 5 pieces. [0044] Next, in order to know toner cohesion degree at which cohesion clusters are generated, using toners with cohesion degree of 30%, 50%, 70% (this difference of cohesion degree was generated by changing amount of the additives appropriately), the number of cohesion clusters under room temperature/low-humidity environments (23° C./5%) was measured. For assessment, sample toner to be used as the assessment object was charged in the cartridge, and the number of cohesion clusters in the cartridge was used as the basis of assessment. Results of assessment are shown in Table 2. [0045] It is understood from assessment results shown in Table 2 that samples with higher cohesion degree tend to generate cohesion clusters easily. Therefore, it is possible to suppress generation of cohesion clusters effectively, if toner with cohesion degree less than 30% is used as replenishment developer. However, when toner with lower cohesion degree (less than 30%) is used as the replenishment developer, defective images such as varied transfer at the primary transfer portion due to high fluidity occur and changes in sealed state in the screw pipe 54 a of the hopper replenishment screw 54 become excessive, which easily results in variation of the amount of replenishment. On the other hand, when toner with higher cohesion degree (more than 70%) as replenishment developer is used, defective images such as white void due to reduction in development efficiency occur and toner transport efficiency in the screw pipe 54 a is reduced remarkably. [0046] In other words, toner as the optimum replenishment developer would be obtained if toner cohesion degree is adjusted to 30% or more and 70% or less, preferably 40% or more and 60% or less. Meanwhile, there are several methods for adjustment of cohesion degree of toners. First, adjustment by toner particle diameter is mentioned. In general, the greater the toner particle diameter is, the lower the cohesion degree is. Further, adjustment by the amount of addition of external additives, for example, SiO 2 , is available. In general, the greater the weight ratio with regard to the toner is, the lower the cohesion degree is. Furthermore, cohesion degree is depending on materials of pigments added to the toner to develop toner color. Therefore, it is possible to obtain a desired particle diameter by combining these several factors. It goes without saying that, since alteration of the combination would affect image quality, good balance should be maintained with regard to the image quality. The method for changing cohesion degree is not limited to those mentioned herein. [0047] Meanwhile, in order to identify the place of cohesion cluster generation, the number of cohesion clusters generated was assessed at cyan (C) station in the image forming apparatus. Assessment results are shown in Table 3. It has been confirmed from these assessment results that generation of cohesion clusters is remarkable in the hopper replenishment screw 54 where toner charging rate is the highest and inner circumference of the screw pipe 54 a is rubbed intensively. Further, as mentioned previously, since the number of cohesion clusters which permits occurrence of stains in the image forming apparatus is less than 5 pieces, there is no possibility of occurrence of defective images under this condition. [0048] Meanwhile, overall length of the hopper replenishment screw 54 (length of screw pipe 54 a ) acts as the factor for the difference of degree of generation of cohesion clusters. The primary object of the present invention is to resolve this problem. [0049] As shown in FIG. 1 , each of hopper replenishment screws 54 extending from each of toner cartridges 51 for LM, LC, Y, M, C, K arranged in one row in tandem manner are gathered together at a screw assembly portion 56 to form one complete unit. One common replenishment pipe 57 from the screw assembly portion 56 goes down perpendicularly and is connected to one portion at the top of the development unit 18 which is a rotating body. The most downstream side outlet end of the common replenishment pipe 57 is connected to the rotary replenishment screw 55 of the development apparatus 1 which reached that position by rotational displacement. Thus, “replenishment path” which serves as one replenishment route is formed. [0050] Therefore, each of hopper replenishment screws 54 extending from each of toner cartridges 51 for LM, LC, Y, M, C, K are different in their length to the screw assembly portion 56 . Namely, length of the screw shaft and length of the screw pipe 54 a composing a part of the replenishment path for every color are different. In order to know how generation of cohesion clusters is affected by each of screw length, the following selection was made: [0051] A screw for magenta which has the shortest length (for example, screw pipe length 50 mm), a screw for cyan having intermediate length (for example, screw pipe length 150 mm), a screw for light magenta having the longest length (for example, screw pipe length 300 mm) were selected. Cyan toner adjusted to have cohesion degree of 50 was charged to each of these screw pipes 54 a, and the number of cohesion clusters generated in the toner was observed at the most downstream of the hopper replenishment screws 54 and then subjected to comparing investigation. Comparison results are shown in Table 4. It is known from the comparison results that the number of cohesion clusters generated is greatly associated with screw length. [0052] Next, cyan toner with 50% cohesion degree was charged actually to all color stations and durability assessment of as many as 5,000 sheets was carried out for the sake of image assessment. It was then found that drip-drop stain was caused at stations for LC, K, LM which are longer than the screw length (150 mm) for cyan. [0053] Taking these results into considerations, as Embodiment 1, toners (replenishment developer) with different cohesion degree corresponding to the screw pipe length of the hopper replenishment screw 54 were supplied and investigation was made. [0054] Table 5 shows relationships among characteristics of each toner (cohesion degree, toner particle diameter, amount of addition of SiO 2 (weight ratio of additives with regard to toner weight), length of screw pipe, number of cohesion clusters, and number of stain occurrence during durability assessment. [0055] As it is seen from this table, in Embodiment 1 where length of screw pipe of the hopper replenishment screw 54 is different for each color, light magenta toner (cohesion degree of 40%), which is adjusted so that the cohesion degree might become the lowest, was arranged for light magenta screw which had the longest screw pipe 54 a. Particle diameter of light magenta toner was set to 7 μm, which was greater than particle diameter of magenta toner of 5.5 μm, to reduce cohesion degree to be lower than that of magenta toner. Although the amount of addition of SiO 2 for magenta toner was greater, lower cohesion degree was obtained since the factor of particle diameter was dominant. The difference in cohesion degree of the magenta toner from that of light cyan toner is attributable to the difference of pigments added to the toner. Besides, for K, LC toners which exceeded the allowable level of the number of cohesion clusters for stain occurrence, generation of toner cohesion clusters could be suppressed and defective images such as void image or stain could be prevented by adjusting the cohesion degree of K, LC toners appropriately. [0056] FIG. 3 is a drawing schematically illustrating construction of exemplary Embodiment 1 for the development unit according to the present embodiment. EMBODIMENT 2 [0057] A development unit, in which replenishment developer (mixture of toner and carrier) is charged to the toner cartridge 51 , is frequently provided to a real machine of image forming apparatus. In this case, by replenishing a mixture of the toner and carrier, carrier deteriorated from durability viewpoints is replaced with new carrier thereby lengthening toner service life. [0058] When toner is solely used as the replenishment developer, and is compared to the replenishment developer based on mixing of the toner and carrier, since carriers having negative charge of the toner and toners attract each other by Coulomb attraction, electrostatic cohesion is easily caused, and cohesion clusters are easily generated. Then, for cases where a mixture of the toner and carrier is used, and where toner is solely used as the replenishment developer, the number of cohesion clusters generated was compared in relation to toner cohesion degree. Specifically, the number of cohesion clusters was measured using cyan toners with above-mentioned cohesion degree of 30, 50, 70. Assessment toner, and mixture of assessment toner and carrier were charged in the cartridge for assessment, and the number of cohesion clusters in the cartridge was counted. [0059] Assessment results are shown in Table 6. It was found from the assessment results that, in the case of replenishment developer based on mixing of the toner and carrier, the toner with higher cohesion degree generate cohesion clusters more remarkably than the case of replenishment developer including toner only. The fact that the place of cohesion cluster generation is the hopper replenishment screw 54 and that there is a tendency that cohesion degree is fixed, the longer the screw length, the more cohesion clusters are generated, are identical for both cases; replenishment developer is based on mixing of the toner and carrier, and replenishment developer including toner only. [0060] In Embodiment 2, similarly to above-mentioned Embodiment 1, investigation was made by supplying a replenishment developer which is a mixture of a toner having different cohesion degree depending on screw length of the toner replenishment screw 54 and carrier. As a result, 4 pieces of cohesion clusters or more are generated at each of stations LM, K, LC. Durability assessment using 5, 000 sheets was carried out, drip-drop stain occurs. Then, further investigation was made using toners with lower cohesion degree prepared depending on length of the screw. Table 7 shows relationships among toner of each color, screw length, number of cohesion clusters, and number of stain occurrence during durability assessment. In the present embodiment, these cohesion degrees were obtained by adjusting the added amount of SiO 2 with regard to Embodiment 1. As a result, it was found that in the case where replenishment developer is a mixture of the toner and carrier, cohesion degree of the toner should be reduced much more than that necessary f or the case where replenishment developer includes toner alone. From above discussions, while screw pipe length of the hopper replenishment screw 54 is different for each of colors, for light magenta screw having the longest screw pipe length, a mixture of light magenta including light magenta toner (cohesion degree 35%) which is adjusted to attain the minimal cohesion degree, and carrier was applied. For K and LC toners which exceeded the allowable level of the number of cohesion clusters for stain occurrence, generation of toner cohesion clusters could be suppressed and defective images such as void image or stain could be avoided by adjusting cohesion degree appropriately. [0061] Although the embodiment of the development unit according to the present invention is described as mentioned above by citing Embodiments 1, 2, it is to be understood that the present invention is not limited thereto, and covers other embodiments, modifications, variations and combination thereof as long as they come within the scope of the present invention. Further, although concrete examples of the measurements are shown as Embodiments 1, 2, the present invention is of course not represented by these measurements. [0062] This application claims the benefit of priority from the prior Japanese Patent Application No. 2006-093254 filed on Mar. 30, 2006 the entire contents of which are incorporated by reference herein.

There is provided a development apparatus including a plurality of replenishment developer containers which accommodates a replenishment developer containing a toner to be replenished to a plurality of development devices, a plurality of replenishment developer conveyance paths which replenishes the replenishment developer in the plurality of replenishment developer containers to the plurality of development devices, a plurality of conveyance members provided in the plurality of replenishment developer conveyance paths, wherein a length of at least one conveyance path, of the plurality of replenishment developer conveyance paths, is different from that of other conveyance paths, and cohesion degree of a replenishment developer conveyed by the longest conveyance path, of the plurality of replenishment conveyance paths, is lower than cohesion degree of there plenishment developer conveyed by other conveyance paths.

[0001] This is a continuation application of and claims priority of U.S. patent application Ser. No. 11/287,976, filed Nov. 27, 2005, entitled “Particle Accelerator and Methods Therefor”, recently allowed. This application is incorporated by reference herein. BACKGROUND OF THE INVENTION [0002] The present invention relates to particle accelerators. More particularly, the present invention relates to cost effective particle accelerators for applications including industrial applications such as radiography, cargo inspection and food sterilization, and also medical applications such as radiation therapy and imaging. [0003] Particle accelerators operate by generating charged particles having a particular energy depending on the application. One exemplary particle accelerator is the standing-wave (SW) electron linear accelerator (linac) used in medical and industrial applications. FIG. 1A shows a simplified functional representation of a linac 100 which receives electrons from an electron gun 112 . The electrons are accelerated to produce a high-energy electron beam 114 along an axial bore hole 140 . Beam 114 is focused and accelerated in a series of accelerating cavities 120 a , 120 b . . . 120 n by forces exerted on the electrons by microwave fields which are fed from an external microwave source 116 such as a klystron or a magnetron. The microwave fields resonate inside accelerating cavities 120 a , 120 b . . . 120 n and also resonate inside auxiliary cavities 113 a , 113 b . . . 113 m. [0004] For example, in some medical applications, the high-energy beam 114 produced by the linac 100 may be applied directly to a cancer therapy volume on a patient, or beam 114 may be used to generate photons (x-rays) 130 by colliding with a suitable target 122 such as tungsten or gold. The resulting x-ray beam 130 may be used to image cancerous tumors and/or to destroy the cancerous cells within the tumors by its ionizing effect (see Section 1.2, pages 29-32 of “Biomedical Particle Accelerators” by W. H. Scharf, AIP Press, 1994, ISBN 1-56396-089-3). [0005] FIG. 1B illustrates the phases of the microwave fields along the accelerating cavities 120 a , 120 b . . . 120 n and the auxiliary cavities 113 a , 113 b . . . 113 m . SW linacs capable of generating electron beams with an energy level of up to 25 MeV require approximately 50 resonant cavities for stable operation. In addition, in order to accelerate the electrons efficiently along an axial bore 140 , the microwave fields in the accelerating cavities 120 a , 120 b . . . 120 n should have a phase difference of 180 degrees from one accelerating cavity to the adjacent accelerating cavity, e.g., from cavity 120 a to cavity 120 b. [0006] FIG. 2 is a graph 200 showing the different resonant frequency modes for an exemplary approximate model of a linac constituting of 51 resonant cavities with attendant frequency mode separation or spacing 251 , 255 between adjacent modes. Around the π-mode 245 , the mode frequency separation 255 is relatively small, and hence not ideal for stable operation of this exemplary linac. For this reason, the mode at the center of the graph, mode 241 , also known as the π/2-mode, is generally the preferred mode of operation. This is because the π/2-mode provides the maximum frequency spacing, as measured along the vertical frequency axis, between adjacent modes, i.e. at mode frequency separation 251 . Operation at the π/2-mode is conventionally realized through the use of a bi-periodic arrangement to ensure that the phase difference of the microwave fields is 180 degrees between adjacent accelerating cavities for efficient electron beam acceleration (see pages 76-82 of “Medical Electron Accelerators” by T. J. Karzmark, et al., McGraw-Hill, Inc., 1993, ISBN 0-07-105410-3) (see also pages 113-117 of T. P. Wangler, “Principles of RF Linear Accelerators”, John Wiley & Sons, Inc., ISBN 0-471-16814-9). [0007] Referring back to FIG. 1A , in addition to the set of accelerating cavities 120 a , 120 b . . . 120 n , a conventional bi-periodic structure for linac 100 requires an additional corresponding set of auxiliary cavities 113 a , 113 b . . . 113 m . Each auxiliary cavity couples the microwave power to an adjacent pair of accelerating cavities through a corresponding pair of coupling irises. The number of frequency modes in a bi-periodic linac is equal to the number of the combined resonant cavities, i.e., the total number of the accelerating cavities 120 a , 120 b . . . 120 n and the auxiliary cavities 113 a , 113 b . . . 113 m . For efficient operation of the linac 100 , all the constituent resonant cavities should resonate at specific frequencies to ensure synchrony between the electrons being accelerated in the accelerating cavities and the electromagnetic field oscillating in all the resonant cavities. [0008] One conventional SW bi-periodic linac configuration is the side-coupled SW linac 300 , shown in FIG. 3A , wherein the auxiliary cavities 313 a , 313 b . . . 313 m are placed on the sides of the accelerating cavities 320 a , 320 b , . . . 320 n , away from the axis of beam 314 . Auxiliary cavity 313 a is coupled to the adjacent accelerating cavities 320 a , 320 b through a corresponding pair of coupling irises 317 a , 317 b . Similarly, auxiliary cavity 313 b is coupled to the adjacent accelerating cavity 320 b through a coupling iris 318 b . FIG. 3B is a cross-sectional view of linac 300 illustrating accelerating cavity 320 a , auxiliary cavities 313 a , 313 b and coupling irises 317 a , 318 b. [0009] Another conventional SW bi-periodic linac configuration is the on-axis SW linac 400 shown in FIG. 4A , wherein the auxiliary cavities 413 a , 413 b . . . 413 m are placed along the axis of beam 414 . The auxiliary cavity 413 a is coupled to the adjacent accelerating cavity 420 a through a pair of irises 416 a , 418 a . Auxiliary cavity 413 a is also coupled to adjacent accelerating cavity 420 b through a pair of irises 417 a , 419 a . FIG. 4B is a cross-sectional view of linac 400 illustrating accelerating cavity 420 b , auxiliary cavity 413 b and coupling irises 416 b , 418 b. [0010] In one conventional method of manufacturing linacs, e.g., for linacs 100 , 300 , 400 , constituent sub-assembly components are stacked and brazed together to ensure vacuum tight joints. These joints are also required to provide continuity of the linac inner walls hosting the microwave current associated with the electromagnetic fields hosted in the cavities. The brazing process involves the use of alloy brazing foils that are inserted into the joints between adjacent cavities. A brazing furnace provides heat to melt the brazing foils that solidify later to form the vacuum tight joints. During brazing, some of the molten brazing alloy can make its way inside the cavities, resulting in a change in the volume of the cavity(s) which in turn can change the resonant frequency characteristics of the linac. [0011] For this reason, it is a common practice to manually tune the individual cavities after the brazing step in order to bring the frequencies of individual cavities to their nominal frequencies. This is usually done by a skilled tuning technician who has to affix the linac on a fixture, perform a series of measurements, and modify the cavities as needed by deforming the physical structure of each cavity until the desired frequency is achieved. This process is a time consuming and substantially increases the manufacturing cost of the linacs. [0012] Hence there is a need for improved linacs which are less costly to manufacture, more efficient to operate and more compact in size. SUMMARY OF THE INVENTION [0013] To achieve the foregoing and in accordance with the present invention, linear accelerators (linac) having a plurality of accelerating cavities and which do not have any auxiliary cavities are provided. Such linacs are useful for industrial applications such as radiography, cargo inspection and food sterilization, and also for medical applications such as radiation therapy and imaging. [0014] In one embodiment, a standing-wave linear accelerator includes an electron gun for generating an electron beam, and a plurality of accelerating cavities which accelerates the electron beam by applying electromagnetic fields generated by a microwave source. At least two adjacent accelerating cavities of the plurality of accelerating cavities are coupled together by at least one coupling iris. The electromagnetic fields resonate through the plurality of accelerating cavities, and the operating frequency of the electromagnetic fields is selected so that the linear accelerator is operating at a π-mode or a mode close to the π-mode. [0015] In another embodiment, the frequency of the electromagnetic fields is selected so that the linear accelerator is operating at a π/2-mode or a mode close to the π/2-mode. This more stable mode of operation is possible because at least two adjacent accelerating cavities of the plurality of accelerating cavities are coupled together by at least one coupling iris which also functions as a resonator for the electromagnetic fields. [0016] In some embodiments, the linear accelerator also includes a target made from a suitable material such as tungsten or gold. The target produces x-rays when the electron beam collides with the target. [0017] Note that the various features of the present invention can be practiced alone or in combination. These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures. BRIEF DESCRIPTION OF THE DRAWINGS [0018] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: [0019] FIG. 1A shows a simplified functional representation of a bi-periodic linear accelerator. [0020] FIG. 1B illustrates the phases of the microwave fields along the accelerating cavities and the auxiliary cavities of the linear accelerator of FIG. 1A . [0021] FIG. 2 is a graphical model showing the different resonant frequency modes for an exemplary linear accelerator constituting of 51 resonant cavities. [0022] FIGS. 3A and 3B illustrate a conventional standing-wave bi-periodic linac having side-coupled auxiliary cavities. [0023] FIGS. 4A and 4B illustrate a conventional standing-wave bi-periodic linac having on-axis auxiliary cavities. [0024] FIG. 5A is an approximate graphical model showing the frequency mode spacing for an exemplary bi-periodic linac with 13 resonant cavities. [0025] FIG. 5B is a graphical model illustrating the approximate frequency mode spacing for a lower-energy linac with 7 resonant cavities. [0026] FIGS. 6A and 6B show one embodiment of a lower-energy π-mode linear accelerator 600 in accordance with the present invention. [0027] FIG. 6C is a block diagram showing the phases of the microwave fields along the accelerating cavities of linear accelerator of FIG. 6A . [0028] FIGS. 7A , 7 B and 8 A, 8 B show two additional embodiments of lower-energy π-mode linear accelerators. [0029] FIGS. 9A and 9B illustrate an embodiment of a higher-energy π/2-mode linear accelerator with accelerating cavities coupled to each other by resonating irises. [0030] FIG. 9C is a microwave phase diagram for a linear accelerator operating in the relatively more stable π/2-mode without the need for auxiliary cavities. [0031] FIGS. 9D and 9E depict the pre-assembly and the post-assembly, respectively, of the linear accelerator of FIG. 9A . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0032] The present invention will now be described in detail with reference to a few preferred embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention. The features and advantages of the present invention may be better understood with reference to the drawings and discussions that follow. [0033] To facilitate discussion, FIGS. 5A , 5 B, 6 A- 6 C, 7 A, 7 B, 8 A, 8 B, and 9 A- 9 E include block diagrams, graphs and sectional views which illustrate several embodiments of the linear accelerators of the present invention. [0034] Historically, the prevailing approach to the design and manufacture of industrial and medical linear accelerators resulted in the commercialization of standing-wave (SW) bi-periodic linear accelerators (linacs). With the recent advent of more sensitive imaging technology and more accurate targeting technology, lower-energy compact linacs in the 4 to 8 MeV range are now in greater demand. FIG. 5A is an approximate graphical model showing the frequency mode spacing for an exemplary bi-periodic linac with 13 resonant cavities. A typical 13 resonant cavity bi-periodic linac may have 7 accelerating cavities and 6 auxiliary cavities. [0035] In contrast, the graphical model of FIG. 5B illustrates the approximate frequency mode spacing for a lower-energy linac with 7 resonant cavities. Unlike the relatively narrower frequency mode spacing of the higher-energy linacs as illustrated by FIG. 2 above, because the lower-energy linacs have fewer resonant cavities and hence fewer frequency modes, the frequency mode spacing as measured in the vertical frequency axis, e.g., mode spacing 555 of FIG. 5B , of lower-energy linacs operating at the π-mode 545 is sufficient for stable operation because the stability of such lower-energy linacs is not seriously degraded. Note that the frequency mode spacing 555 (see FIG. 5B ) at the π-mode 545 is comparable with the frequency mode spacing 551 (see FIG. 5A ) at the π/2-mode 541 for a bi-periodic linac with 13 resonant cavities. [0036] In accordance with the present invention, FIGS. 6A and 6B show one embodiment of a lower-energy π-mode linac 600 which includes accelerating cavities 620 a , 620 b , 620 . . . 620 g and does not include any auxiliary cavities. Linac 600 also includes a corresponding set of irises 617 a , 617 b , 617 . . . 617 f which provides improved coupling for the microwave power between accelerating cavities 620 a , 620 b , 620 . . . 620 g , thereby allowing most of the microwave power to bypass axial bore 640 . For example, adjacent accelerating cavities 620 a , 620 b are coupled to each other via iris 617 a , while adjacent accelerating cavities 620 b , 620 c are coupled to each other via iris 617 b . Hence, irises 617 a , 617 b , 617 . . . 617 f facilitate the overall flow of the microwave power thereby enabling linac 600 to operate efficiently in the π-mode. [0037] The simplified configuration of linac 600 is particularly useful for linacs producing electron beams with output energies less than 10 MeV where the total number of resonant cavities can be about 10 or less, thereby permitting stable operation in the π-mode. As a result, by eliminating the need for auxiliary cavities in linac 600 , the total number of resonant cavities is equal to the number of accelerating cavities. Hence, the total number of resonant cavities in exemplary linac 600 is about one-half of that needed in the conventional bi-periodic linacs of comparable energy output described above. [0038] FIG. 6C is a block diagram showing the phases of the microwave fields along the accelerating cavities 620 a , 620 b . . . 620 g of linac 600 operating in the π-mode. In this embodiment, the coupling of the microwave power between accelerating cavities 620 a , 620 b . . . 620 g is accomplished mainly through irises 617 a , 617 b , 617 . . . 617 f and partially through the axial bore 640 . Other design considerations such as high shunt impedance, may limit on how large axial bore 640 can be to maintain stable and efficient operation. [0039] In some industrial and medical applications, the electron beam of linac 600 can be directed at a suitable target such as tungsten or gold to generate x-rays. These x-rays are useful, for example, for the inspection of cargo, or for the imaging and/or treatment of medical diseases and conditions such as cancers. [0040] As illustrated by FIG. 5B , linac 600 can operate at multiple frequency modes depending on the frequency of the microwave fields fed from the microwave source. For example, the operating frequency of linac 600 can be selected to match the frequency corresponding to the π-mode, i.e., the microwave fields should at approximately 3.01 GHz (3010 MHz). The corresponding wavelength of microwave fields operating at 3 GHz is approximately 10 cm. Accordingly, the accelerating cavities 620 a , 620 b . . . 620 g should be approximately 5 cm in length in order to ensure synchrony between the electrons being accelerated and the electromagnetic fields. [0041] Note that accelerated electrons travel at a speed very close to the speed of light once these electrons attain energies higher than 1 MeV. Hence, the cavity length of the first one or two linac cavities, e.g., cavities 620 a , 620 b , at the up-stream of the linac, where the electrons have not attained enough energy yet to be relativistic (close to the speed of light), can be between 2 and 5 cm depending on the energy of the electrons, emitted by the electron gun, as the electrons enter linac 600 . Detailed dimensions of linac configuration can be obtained using computer simulation programs such as “Maxwell's Equations by the Finite Integration Algorithm” (MAFIA) available from “Computer Simulation Technology (CTS), or “ANALYST” available from Simulation Technology and Applied Research, Inc. [0042] Another embodiment of a lower-energy π-mode linac 700 useful for industrial and medical application is depicted in FIGS. 7A and 7B . A set of staggered coupling irises 718 a , 717 b , 718 . . . 717 f provides improved coupling for the microwave power between accelerating cavities 720 a , 720 b , 720 . . . 720 g , thereby allowing most of the microwave power to bypass axial bore 740 . For example, adjacent accelerating cavities 720 a , 720 b are coupled to each other via iris 718 a , while adjacent accelerating cavities 720 b , 720 c are coupled to each other via iris 717 b . Hence, irises 718 a , 717 b , 718 . . . 717 f facilitate the overall flow of the microwave power thereby enabling linac 700 to operate efficiently in the π-mode. Note that the microwave fields phases for linac 700 are similar to that shown in FIG. 6C for linac 600 . Accordingly, by operating in the π-mode, the total number of cavities in linac 700 is advantageously reduced to about one-half of that needed in a conventional bi-periodic linac of equivalent power. [0043] Yet another embodiment of lower-energy π-mode linac 800 useful for industrial and medical application is depicted in FIGS. 8A and 8B . A set of paired coupling irises 817 a & 818 a , 817 b & 818 b . . . 817 f & 818 f provides improved coupling for the microwave power between accelerating cavities 820 a , 820 b , 820 . . . 820 g , thereby allowing most of the microwave power to bypass axial bore 840 . For example, adjacent accelerating cavities 820 a , 820 b are coupled to each other via a pair of irises 817 a , 818 a . Irises 817 a & 818 a , 817 b & 818 b . . . 817 f & 818 f greatly facilitate the overall flow of the microwave power thereby enabling linac 800 to operate more efficiently in the π-mode. The microwave fields phases for linac 800 are also similar to that shown in FIG. 6C for linac 600 . As discussed above, the total number of cavities in π-mode linac 800 needs to be about one-half of that required in an equivalent conventional bi-periodic linac. [0044] In some industrial and medical applications, higher-energy SW linacs are needed to produce electron beams with output energies greater than 10 MeV. Such higher-energy linacs would require a relative large number of accelerating cavities, and it may not be feasible to operate these higher-energy linacs in a stable π-mode because of insufficient frequency mode spacing as illustrated by FIG. 2 . Conventionally, the solution for designing stable higher-energy linacs is to incorporate auxiliary cavities as described above for bi-periodic linacs 300 , 400 . [0045] In contrast, FIGS. 9A and 9B illustrate an exemplary linac 900 with a relatively large number of accelerating cavities 920 a , 920 b , 920 e . . . 920 n capable of generating output energies substantially greater than 10 MeV, and without the need for auxiliary cavities. Accelerating cavities 920 a , 920 b , 920 e . . . 920 n of linac 900 are coupled to each other by a set of staggered coupling irises 918 a , 917 b . . . 917 m . For example, adjacent accelerating cavities 920 a , 920 b are coupled to each other via an iris 918 a. [0046] In accordance with the present invention, in addition to coupling the microwave fields between accelerating cavities, coupling irises 918 a , 917 b . . . 917 m also function as microwave resonators thereby enabling linac 900 to operate in the relatively more stable π/2-mode, as shown in the microwave phase diagram of FIG. 9C . In other words, coupling irises 918 a , 917 b . . . 917 m also advantageously function as resonant irises. Thus, resonant irises 918 a , 917 b . . . 917 m enable linac 900 to achieve bi-periodic performance without the need for a corresponding set of auxiliary cavities, thereby reducing the total number of cavities by half the number of that needed for a conventional bi-periodic linac with a similar energy output. [0047] To achieve efficient resonating microwave fields, the dimensions of resonant irises 918 a , 917 b . . . 917 m can be mathematical functions of operating microwave frequency of linac 900 . In this embodiment, the length of resonant irises 918 a , 917 b . . . 917 m is a function of the microwave wavelength such as one half or one quarter of the wavelength of the operating microwave. For example, for operation at 3 GHz, the iris length is approximately 5 cm. The width and the thickness of resonant irises 918 a , 917 b . . . 917 m are design parameters that can be selected to optimize the efficiency of linac 900 . Hence, linac 900 is capable of operating in a stable bi-periodic manner without the need for auxiliary cavities. By operating in this bi-periodic manner, i.e., in the π/2-mode, linac 900 is able to generate upwards of about 25 MeV, while operating in a stable manner and permitting relaxation of manufacturing tolerances. [0048] By eliminating the need for auxiliary cavities, linacs 600 , 700 , 800 and 900 advantageously maintain a simplified structure and a cylindrical cross-sectional shape. FIGS. 9D and 9E depict the pre-assembly and the post-assembly, respectively, of exemplary linac 900 . While linacs 600 , 700 , 800 and 900 can be assembled using the brazing process described above, the cylindrical cross-sectional shape of linacs 600 , 700 , 800 and 900 makes assembly easier, enabling linacs 600 , 700 , 800 and 900 to be manufactured using a more cost effective diffusion bonding described below for exemplary linac 900 . [0049] First, the constituent sub-assembly components 900 a , 900 b , 900 e . . . 900 y are machined to the nominal design dimensions. The joining surfaces of components 900 a , 900 b , 900 . . . 900 y are also machined to the required flatness and surface roughness. In linac 900 , joints 950 a , 950 b . . . 950 x should be vacuum tight to ensure linac vacuum integrity. Joints 950 a , 950 b . . . 950 x are also required to provide the microwave continuity for the inner cavity walls of linac 900 hosting the microwave currents associated with the electromagnetic fields. In diffusion bonding, the stacked assembly for linac 900 , comprising of components 900 a , 900 b , 900 c . . . 900 y , is placed in a furnace which provides the heat for bonding joints 950 a , 950 b . . . 950 x at a temperature close to, but lower than, the melting point of the linac material, e.g., copper. During the heating process, the stacked assembly for linac 900 is kept under the required pressure for proper bonding. [0050] Since diffusion bonding does not involve the melting of a brazing alloy, the problem of having foreign material deposited inside the cavity walls of linacs 600 , 700 , 800 and 900 has now been eliminated. For this reason, post assembly tuning of the individual accelerating cavities of linacs 600 , 700 , 800 and 900 should no longer be needed. Hence, the simpler and more cost effective diffusion bonding process can replace the more expensive brazing and tuning steps. This result in advantageous savings associated with cost of material, manufacturing time, and capital and operating cost of multiple brazing furnaces. In addition, this cylindrical cross-sectional configuration allows for potential robotic stacking of cavities and automated assembly of linacs 600 , 700 , 800 and 900 . [0051] The cylindrical cross-sectional profile of linacs 600 , 700 , 800 , 900 also advantageously allows for the easy placement of magnetic coils around linacs 500 , 700 , 800 , 900 . This is because for some applications, linacs 600 , 700 , 800 , 900 may require magnetic coils for beam focusing and/or beam steering as to better control of the beam spot size and beam position. A well-controlled electron beam colliding on the x-ray target will result in more accurate x-rays. [0052] Many modifications to linacs 600 , 700 , 800 , 900 are also possible. For example, instead of operating at the π-mode, the exemplary 7 cavity linac 600 can operate at a mode adjacent to the π-mode such as the 6/7 π-mode. [0053] Although the above description uses exemplary microwave frequencies, exemplary linac energy levels, exemplary linac dimensions, and exemplary industrial and medical applications, these examples are not intended to limit the scope of the invention. For example, while assembly techniques such as brazing and diffusion bonding has been described in this application, it is possible to use other assembly techniques known to one skilled in the art. [0054] While this invention has been described in terms of several preferred embodiments, there are alterations, modifications, permutations, and substitute equivalents, which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, modifications, permutations, and substitute equivalents as fall within the true spirit and scope of the present invention.

Standing-wave linear accelerators (linac) having a plurality of accelerating cavities and which do not have any auxiliary cavities are provided. Such linacs are useful for industrial applications such as radiography, cargo inspection and food sterilization, and also medical applications such as radiation therapy and imaging. In one embodiment, the linac includes an electron gun for generating an electron beam, and a plurality of accelerating cavities which accelerates the electron beam by applying electromagnetic fields generated by a microwave source. At least two adjacent accelerating cavities of the plurality of accelerating cavities are coupled together by at least one resonant iris. The electromagnetic fields resonate through the plurality of accelerating cavities and the at least one resonant iris.

BACKGROUND OF THE INVENTION This invention is directed to a method of transmitting a signal using digital compression techniques. The transmission of an audio signal, for example, radio broadcast transmission, cable transmission, satellite transmission and with recording devices entails converting the analog signal into a digital signal with a certain resolution. The digital signal is transmitted and reconverted into an analog signal upon reproduction. The signal-to-noise ratio is enhanced, particularly upon reproduction, by using digital transmission. The band width required for the transmission of such a signal is essentially determined by the number of scanning values per time unit which are to be transmitted. The resolution is also a function of the number of scanning values transmitted. In practice, it is preferable to keep the transmission band width as small as possible in order to be able to transmit as many audio signals as possible simultaneously via a wide band channel would appear that the necessary band width can be reduced by decreasing the number of scanning values or the number of hits per scanning value. However, as a rule this measure results in a deterioration in the quality of the reproduction. A method described in DE-OS 35 06 912, improves the reproduction quality by separating the digital audio signal into successive temporal segments and transforming the audio signal into a short-time spectrum which represents the spectral components of the signal for the respective time segments. Generally, in the short-time spectrum, for reasons of psycho-acoustic laws, components which are not perceived by the listener, i.e. are irrelevant from a communications technology viewpoint, can be discovered more readily than in the time domain. Upon transmission, these components are given less weight, or are left out entirely. This allows a considerable part of the otherwise necessary data to be left out and the average bit rate can be considerably reduced. However, the formation of time segments impairs the frequency resolution because the spectral components brought about by the signal rise and fall at the start and finish of the window are also fed to the spectrum of the original signal. An improvement in the frequency resolution can be attained by having the edge gradient of the window function less steep, also by extending the edge region within the window. These measures require overlapping of adjacent time segments. If the edge region is expanded so far that the window functions no longer have a constant value in any region, then adjacent temporal segments must overlap each other by 50 per cent. This means that the number of scanning values and, accordingly the quantity of data, is doubled. The publications of J. P. Princen and A. B. Bradley "Analysis Synthesis Filter Bank Design Based On Time Domain Aliasing Cancellation", IEEE Transactions, ASSP-34, No. 5, Oct. 1986, pp 1153 through 1161, and of J. P. Princen, A. W. Johnson and A. B. Bradley "Subband/Transform Coding Using Filter Bank Design Based On Time Domain Aliasing Cancellation", IEEE Int. Conference on Acoustics, Speech and Signal Processing 1987, pp 2161 through 2164, teach that for a 50 per cent overlap of successive temporal segments the quantity of data is reduced to the original value by encoding only every second scanning value. The aliasing components resulting from the subsampling cancel each other out by using the method described in the above citation after inverse transformation upon assembling the time segments. It has become apparent that with amplitude fluctuations within a time segment, in particular with signals first appearing from a silence during the course of a block, these signals are superimposed with perceivable disturbances after transmission. The cause of the perceivability lies in the fact that the disturbances also appear before the signals start to appear and, therefore, are insufficiently masked. These disturbances can, for example, ensue through quantization noise which superimposes the short-time spectrum. After inverse transformation, the noise components then appear within the total block in the time domain. In order to reduce these disturbances, the signals in the block in which the level change appears can be subjected to a compression and, after the inverse transformation, an expansion. However, if the raising of the level for executing the compression does not extend over the entire block, then the signal components are linked with aliasing components, which cannot be cancelled by the expansion, in another block region. SUMMARY OF THE INVENTION It is the object of the invention, with a method of the aforementioned type, to combine an improvement in the analysis sharpness of the signal to be transformed with an improvement in the signal-to-noise ratio with strong signal changes. With the inventive method, signals which are subjected to only small changes in level are coded in overlapping blocks with window functions which produce a high analysis sharpness. When an increase in level which exceeds a predetermined threshold value is detected the window functions are modified. The modified window functions have a small of no overlap. The short-time spectra appearing after transformation no longer undergo sub-sampling but, on the contrary, are scanned in full. Accordingly, no aliasing components can occur. Using this method it is accepted that the spectral values which occur twice within the overlap region increase the quantity of data to be coded. The signals weighted with the modified window functions can be subjected to a compression with subsequent complementary expansion. In this manner, the disturbances, also referred to as pre-echo, which appear after the inverse transformation before the increase in level are lowered. Following the increase in level, the signal is again processed in overlapping blocks. BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a flow diagram with the main procedure steps of the invention. FIG. 2 is a representation of wanted signal and aliasing components upon application of the method according to the citation "Princen & Bradley". FIG. 3 is a representation of the temporal sequence of window functions at an increase in the signal. FIG. 4 is a representation similar to FIG. 3 but with different window functions. FIG. 5 shows window functions suitable for the application of the "time domain aliasing cancellation" method. FIG. 6 depicts are representations of a signal starting in the course of a block in original as well as after inverse transformation. FIG. 7 shows the subdivision into sub-blocks. FIG. 8 shows a window function in which the blocks are superimposed. FIG. 9 shows the energy progression within a block with and without compression. FIG. 10 is a representation of the non-raised and raised signal at an increase in the signal with non-overlapping windows for the energy calculations of the sub-blocks. FIG. 11 is a representation similar to FIG. 10 but with 50 per cent overlapping windows for the energy calculations of the sub-blocks. DESCRIPTION OF THE PREFERRED EMBODIMENTS The individual procedure steps for executing the method of the invention are represented in the flow diagram of FIG. 1. The starting variable of the method forms an analog audio signal which is converted in procedure step 1 into a digital signal, in which amplitude values are present as scanning values in digital coded form. In procedure step 2 the continuous signal is windowed, in that a series of successive scanning values is selected, in the example presented here 1024 scanning values are selected. In procedure step 3 a decision is made regarding an increase in level which exceeds a predetermined threshold level. If no increase in level is present the next procedural step is procedure step 4. In procedure step 4, blocks with temporal overlaps of 50 per cent are formed from the selected scanning values. The same scanning values sometimes are present, in adjacent blocks, albeit in different places. Therefore, the scanning values present in the first half of a current block correspond to the scanning values present in the second half of the preceding block. In procedure step 5 the signal segments contained in the blocks are assessed using analysis windows. In this manner a soft signal start and run-out are generated at the boundaries of the block to increase the analysis sharpness for the subsequent transformation. Procedure step 6 forms the transformation of the present discrete-time signal into a discrete-frequency signal. Instead of amplitude values, spectral values now appear, each of which encompass a real and an imaginary part. A conversion of the spectral values into a presentation with pseudoquantities and phases takes place in procedure step 7. The spectral values are then prepared and suited for a transmission method such as is described in DE-OS 35 06 912. A sub-scanning is also performed at the same time in connection with the conversion of the spectral values. The result is that the number of values to be transmitted again coincides with the number of original scanning values. The doubling of the data caused by the 50 per cent overlapping of the blocks is thus cancelled. In the procedure step 8, the steps of coding, if applicable the data reduction, transmission and decoding are combined. These procedure steps can be carried out using the method described in DE-OS 35 06 912. In procedure step 9 a transformation inverse to trial in procedure step 6 takes place. However, with the preceding data reduction, the signal to be inversely transformed is a modified signal freed from psycho-acoustically redundant components. The result of the inverse transformation is again discrete-time signals in the form of blocks representing signal segments of a continuous signal. However, only half the original scanning values are present in the blocks. In the procedure step 10, the blocks are weighted with synthesis windows. The synthesis window functions are so designed that they again compensate the signal distortions which have come about as a result of the weighting with the analysis windows in procedure step 5. The synthesis window functions used here fulfill two criteria. Firstly, they complement themselves to unity in the overlap region using the corresponding analysis windows. Secondly, the difference between the analysis window reflected in the center of the overlap region, multiplied by the synthesis window for the block n, and the analysis window reflected in the center of the overlap region multiplied by the synthesis window for the block n+1 in the overlap region, is equal to zero. This latter criterion contains the compensation for the aliasing components. In procedure step 11 the blocks overlapping by 50 per cent are added, whereby the aliasing components in the two blocks to be superimposed appear with reversed preceding signs so that upon addition it compensates to zero. In procedure step 12 the formation of continuous scanning values through combining the blocks to each other with the windowed signal segments is illustrated. Finally, in procedure step 13, a conversion of the digital, coded scanning values into an analog signal is carried out, whereby, objectively, components are in fact missing but which, subjectively, is experienced as identical with the original signal. When an increase in level above a preselected value is detected in procedure step 3, the process continues to procedure step 14. In procedure step 14 blocks with no temporal overlaps with each other or, temporal overlaps of much less than 50 per cent, are formed from the selected scanning values. In procedure step 15 the signal segments contained in the blocks are assessed using analysis windows which have a steep gradient course. Compression takes place in procedure step 16. Procedure step 17, which corresponds to procedure step 6, constitutes the transformation of the existing discrete-time signal into a discrete-frequency signal. Instead of amplitude values, spectral values appear each of which has a real and an imaginary part. In procedure step 18, conversion of the spectral values into a representation with pseudoquantities and pseudophases takes place. The spectral values are then prepared and suited for transmission by some known method, such as that described in DE-OS 35 06 912. However, in contrast to procedure step 7, sub-sampling is not performed. In procedure step 19, which corresponds to procedure step 8, several individual steps are combined encompassing the coding, if applicable the data reduction, transmission and decoding. These procedure steps can be carried out according to the method described in DE-OS 35 06 912. In procedure step 20 a transformation inverse to that in procedure step 17 takes place. However, because of the preceding data reduction, the signal to be inversely transformed is a modified signal which is free from psycho-acoustically redundant components. The result of the inverse transformation is again discrete-time signals in the form of blocks representing signal segments of a continuous signal. However, only half the original scanning values are present in the blocks. An expansion takes place in the subsequent procedure step 21. In procedure step 22 the blocks are weighted with synthesis windows. The synthesis window functions are so designed that they again compensate the signal distortions which have come about as a result of the weighting with the analysis windows in procedure step 15. The block, insofar as they overlap each other, are added in procedure step 23. The common procedure steps 12 and 13 described above are completed. FIG. 2 shows the wanted signal and the aliasing components with a transformation block that results by employing the "time domain aliasing cancellation" method according to Princen and Bradley. The aliasing components result from reflecting the wanted signal of a block half at the line of symmetry tb/4 or 3tb/4. By using the 50 per cent overlapping of adjacent blocks the aliasing component is clearly distinguished because it has sign reversed from that of the wanted signal. Therefore, the correct wanted signal is recovered after normal transformation and inverse transformation. If a block were to be separately subjected to a compression and subsequently processed according to the "time domain aliasing cancellation" method, the compression process could not be cancelled by expansion. If, for example, signals in the first quarter of a block are increased the increased signal components appear as aliasing components in the second quarter of the block and are combined additively with the wanted signal. This aliasing component modified by the compressor can no longer be compensated using the aliasing components of the neighboring blocks. Before executing a compression, therefore, switchover to another window is made when an increase in the signal is detected, a window which does not generate blocks with major overlaps, and the "time domain aliasing cancellation" method can no longer be applied to these blocks. The temporal sequence of such blocks is illustrated in FIGS. 3 and 4. FIG. 3 shows the temporal sequence of blocks with presentation of the window functions used for the weighting upon detection of an increase in the signal, whereby no overlapping blocks appear during the increase in the signal. Line 1 shows a block which overlaps the preceding and following blocks by 50%. Aliasing components appear in both halves of the block. Line 2 shows an initial block for 0% overlap with the following block. Aliasing components only appear in the first half of the block because the final quarter of the block is identical to zero. Line 3 shows a block of the same length but without overlapping assessed using a rectangular window function. In this block compression and expansion of the signal extending over a part of the block length can be carried out. Line 4 shows an end block for 0% overlap with the preceding block. Aliasing components appear only in the second half of the block because the first quarter of the block is identical to zero. Line 5 shows a block corresponding to the block shown in line 1. This block has a 50% overlap with the preceding and following blocks. FIG. 4 shows the temporal sequence of blocks with presentation of the window functions used for the weighting upon the detection of an increase in the signal. Blocks overlapping by 6.25% appear during the increase in the signal. Line 1 shows a block which overlaps the preceding and following blocks by 50%. Aliasing components appear in both halves of the block. Line 2 shows an initial block having 6.25% overlap with the following block. Aliasing components appear only in the first half of the block because the final quarter of the block is identical to zero. Line 3 shows a block of the same length but without overlapping assessed using a rectangular window function. In this block compression and expansion of the signal extending over a part of the block length can be carried out. Line 4 shows an end block for 6.25 per cent overlap with the preceding block. Aliasing components only appear in the second half of the block because the first quarter of the block is identical to zero, In line 5 a block corresponding to the block shown in line 1 is again illustrated. This block has a 50 per cent overlap with the preceding and following blocks. The windows used in the region of the increase in the signal have an average constant progression and edges corresponding to a cosine function. Because of the overlapping of the blocks in the region of the edges, after transformation a number of spectral values, increased by 12.5% compared to the overlap-free rectangular blocks shown in FIGURE 3, result. In order to take this into account with the coding, multiple-block-encompassing bit allocation, more coarse quantizing or suppression of less relevant spectral values can be employed. FIG. 5 shows window functions suitable for the "time domain aliasing cancellation" method, namely an analysis and a synthesis window with which the synthesis window function was calculated from the freely chosen analysis window function according to the invention in accordance with the following equations: ##EQU1## where: a n (t) is the analysis window function for the block n, s n (t) is the synthesis window function for the block n, a n +1(t) is the analysis window function for the block n+1, s n +1(t) is the synthesis window function for the block n+1, and T B is the block time. When applying these equations, the signals evaluated with the analysis and synthesis windows, which together exhibit a complementary unity response, complement each other and aliasing components are compensated. An example of the inventive method where a signal suddenly appears from silence somewhere within a block, for example in its second half, is described with respect to FIGS. 6a through 6d. FIG. 6a shows the example for the time domain. The transformed signal is shown in FIG. 6b. Because of quantization errors with the coding, an interference spectrum is superimposed on the spectrum shown in FIG. 6b and the spectrum shown in FIG. 6c results. After inverse transformation this interference spectrum influences the course of the signal from the start of the signal, and also at the beginning of the block as FIG. 6d shows. The pre-masking effect is less than the post-masking effect, and therefore the interference may become audible. Appropriate compression within the block before the transformation and transmission, and expansion after the transmission and inverse transformation can substantially improve the signal-to-noise ratio. For this purpose, as shown in FIG. 7, every block 116, 117, . . . is subdivided into sub-blocks. These sub-blocks 119, 120, 121, . . . have, apart from on the block edges, equal temporal expansions such that they overlap each other by half. On the block edges there is an overlap with sub-block 118 amounting to half a temporal expansion. The average signal energies are determined in these overlapping rectangular sub-blocks (energy in the time segment divided by the expansion of the time segment). In a following step, as shown in FIG. 8, the initially rectangular sub-blocks 119, 120, 121, . . . are evaluated with cos 2 window functions 122. The time segments on the block edges, which only have half the temporal expansion of the remaining sub-blocks, are weighted with a cos 2 half-window 123. The overlapping weighting functions complement each other at every point in time of the signal block to produce a unity response. FIG. 9 shows how the signals in the sub-blocks 119, 120, 121, corresponding to the detected average energies, represented by the full lines are amplified or attenuated, so that the average energies in the sub-blocks 119, 120, 121, . . . become roughly equal, as represented by the dotted lines. For reasons of clarity, the blocks are not shown with dotted lines. The amplification and attenuation of the signals leaves the relationship between the block's useful energy and the block's interference energy, resulting from the coding, unaltered. On the other hand, through the use of these measures the same signal-to-noise ratio exists in all sub-blocks. The same signal-to-noise ratio is realized that would have been realized if blocks corresponding to the Size of the sub-blocks, had been selected from the very beginning by windowing. The aforementioned disadvantages of shorter blocks are, however, avoided. It is advisable, for psycho-acoustic reasons, to make the size of a temporal expansion in the overlapping sub-blocks approximately 2 to 4 ms. This corresponds to the formation of some 10 to 20 sub-blocks for blocks with about 1000 scanning values and a scanning frequency of 44.1 kHz. Furthermore, it is advisable, for psycho-acoustic reasons, to limit the signal amplification to a maximum value of, for example, 40 dB. It is sufficient to quantize the amplification factors, whereby the quantization can be performed relatively coarsely in order to limit the additional data required for the quantizing stages. The quantization can be so executed that smaller quantization step sizes can be chosen for smaller amplification factors than for larger. In doing this, the quantization is so dimensioned that the average energy in the boosted sub-block does not exceed that of the sub-block with the highest detected energy, i.e. the reference block. In this way it is possible, in fact, to even gain an increase in the ratio of the block's wanted energy to the block's interference energy. However, in this case the signal-to-noise ratio of all sub-blocks is no longer identical, rather only nearly the same. If only the sub-blocks in which the compression of the signal takes place are weighted through overlapping window functions, but not the sub-blocks which serve for determining the average signal energies for calculating the amplification factors, then magnified amplification factors can result with certain signal increases. This case is illustrated in FIG. 10 for an ideal rectangular increase. The non-boosted signal progression is designated 126, the boosted signal progression 127. The lower-case letters a0 through a8 represent the boosting factors, also referred to as amplification factors. The magnification then appears if the edge of the increase and the edge of the sub-block do not coincide. In order to keep the magnification small, according to a further development, the determination of the average signal energies is also carried out with blocks overlapping by 50 per cent, albeit with rectangular windows in this case. They correspond directly to the sub-blocks in which the signals are amplified. The result of this measure is illustrated in FIGURE; 11 for the same signal increase. The non-boosted signal progression is again designated 126 and the boosted, modified signal progression is designated 128. If the method explained up to this point is applied to the entire audio signal, the amplification factors are only correct for the high-energy spectral components because it is essentially these which determine the factors. In audio signals, the spectral components up to approximately 3 kHz are almost always those with the highest energy. If the method for the high-energy spectral components up to about 3 kHz has the greatest presentation accuracy, then increases in the signals at higher frequencies With lower-energy components lead to greater inaccuracies upon coding, possibly leading to audible interference. The signal can also be subjected to pre-emphasis prior to transmission and coding, and de-emphasis after transmission and decoding.

A method of transmitting an analog signal including the steps of converting the analog signal into a digital signal and using windows to subdivide the digital signal into successive blocks. The blocks are evaluated for level changes, and when a level change is below a predetermined level the blocks are overlapped by 50%. The signal segments within the blocks assessed using analysis windows. The signal segments are transformed using subsampling and time domain aliasing cancellation to compensate for aliasing components. The signal segments are inverse transformed and assessed using synthesis windows. The blocks are rejoined in overlapping fashion. When the level change is above the predetermined level the signals are subdivided into blocks and the blocks are overlapped by less than 50%, or not overlapped at all. The signal segments are fully scanned, compressed and transformed. The signal segments are finally inverse transformed and expanded.

This application claims the benefit of provisional application No. 60/250,523 filed Nov. 30, 2000. FIELD OF THE INVENTION The present invention relates to a signal driver circuit for a liquid crystal display (LCD), and, more particularly, to a dual mode thin film transistor liquid crystal display (TFT-LCD) source driver circuit having low power consumption. BACKGROUND OF THE INVENTION Due to the increased demands for data, handheld communication and portable electronics equipment, such as radios, cellular and cordless telephones, pagers, personal digital assistants (PDAs) and the like, must display greater amounts of information. Equipment must provide displays which feature visual messages that include graphics and printed information as well as a means to access and manipulate such messages. Accordingly, equipment must provide displays that accommodate text and icon information, as well as graphic and video data. Most circuitry used to implement these and other features expend relatively large amounts of power. As a result, power consumption is a major concern for many handheld communication and portable electronics manufacturers. Conventional liquid crystal displays (LCDs) provide these features using two sheets of polarizing material having a liquid crystal solution between the two, such that when an electric current passes through the liquid, the crystals align to block or pass light. Each crystal, therefore, acts like a switch, either allowing light to pass or blocking light. Source driver circuits are commonly employed with liquid crystal displays. The driver circuit typically accepts digital video data as an input and provides an analog voltage output to each particular LCD pixel column. Generally, each column in the LCD must be uniquely addressed by a signal or column driver and given the proper analog voltage in order to achieve the desired transmissivity (i.e., the desired shade of gray or color). Moreover, it is desirable that the output voltage range of a driver circuit be wide to allow for a high pixel contrast ratio. For color LCDs, each pixel is composed of 3 sub-pixel elements representing the primary colors of red, green and blue. For example, a color VGA panel having a resolution of 640 columns×480 rows of uniquely addressable pixels will have 3×640 columns, or 1920 columns. Typically, the signal driver circuit has one driver output for each column. Thus, controlling an LCD panel requires a large number of driver outputs that consume considerable circuit area and power. Since this large number of circuitry size impacts power consumption, it is desirable to provide stages of operation in which the operation of each driver circuit is suspended. Conventionally, there are two modes of operation: standby and gray scale mode. There are two types of standby mode where operation of parts of the source driver is suspended. The first type of standby mode powers down all of the internal circuitry with the exception of some input signal detection circuitry. Given this mode, however, the driver provides no output signal. The second type of standby mode powers down some of the internal circuitry during normal operation of the circuit to save power, not altering the overall system behavior. In gray scale mode, a full color display is present at the LCD providing up to 262144 colors. Since it is common for the communications equipment to remain in standby mode or text mode, where only text or icon display on the panel, it is not necessary to display full color display quality. An approach to lower power consumption may include the use of a color super-twisted nematic liquid crystal display (STN-LCD). Although this implementation provides the greatest benefit, there exists slow display response time. In addition, using STN-LCD makes it difficult to generate high resolution colors. Both of these problems contribute to the complexity of displaying real time video or graphic information. Another approach to lower power consumption may include the use of color LCD displays using the thin film transistor (TFT) technology which produce color images that are as sharp as traditional CRT displays. The TFT-LCD is a type of LCD flat-panel display screen, in which each pixel is controlled by one to four transistors. Conventional, TFT-LCDs can provide higher display response time and high resolution colors, but the power consumption is ten times that of STN-LCD. As a further limitation to the TFT-LCD implementation, the light transmission curve shown in FIG. 4 illustrates that the conventional TFT-LCD source driver is useful during a limited range of the voltages. Thus, there exists a need for a dual mode TFT-LCD source driver circuit having low power consumption that is operable in response to a large range of voltages having at least one type of standby mode where operation of a portion of the driver circuit is suspended to lower power consumption such that the LCD is still capable of providing text, icon, graphic and video information on the display without using the full scale of colors available in the gray scale mode. SUMMARY OF THE INVENTION To address the above-discussed deficiencies of the dual mode thin film transistor liquid crystal display source driver circuit, the present invention teaches dual mode thin film transistor liquid crystal display source driver circuit having low power consumption. A first embodiment of the source driver circuit including a data inputs which connect to sample registers. An N-bit shift register containing N is the uniquely addressable channels couples to the sample registers. The input data is indicative of an image to be displayed on the LCD. Hold registers couple to the sample registers to store the sampled data. The hold register receives a transfer signal to determine when the data from the sample register should be transferred to the hold register. A resister string can provide up to 64 voltage levels for example which couple to a set of decoder cells that are programmable to decode the input data to select respective output voltage levels. Output cells couple between the hold register a set of driver outputs. A set of switches connect each respective decoder cell to the driver outputs. Both the set of switches and output cells couple to receive a mode signal, such that two modes of operation exists. In the first mode, when each switch is closed, the output cells are bypassed and, in the second mode, when each switch is open, the decoder cells are bypassed. This provides for a gray scale mode having full color display resolution and a standby mode that decreases the amount of power dissipated yet presents voltage output for the LCD to provide text, icon, graphic and video data. In an alternative embodiment, latch circuits are employed which vary the level of voltage output during the standby mode. Thus, video displays may be programmed to have a specified resolution while still conserving power. The latch circuits may couple between the sample registers and the hold registers or between the hold registers and the output cells. Advantages of this design include but are not limited to dual mode thin film transistor liquid crystal display source driver circuit having low power consumption. BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numbers indicate like features and wherein: FIG. 1 is a block diagram of a known embodiment of TFT-LCD source driver; FIG. 2 is a block diagram of a first embodiment of a dual mode TFT-LCD source driver circuit in the gray scale mode in accordance with the present invention; FIG. 3 is a block diagram of a first embodiment of a dual mode TFT-LCD source driver circuit in the standby mode in accordance with the present invention; FIG. 4 is a voltage vs. light transmission diagram of the TFT-LCD source driver of FIG. 1; FIG. 5 is a voltage vs. light transmission diagram of the dual mode TFT-LCD source driver of FIG. 2; FIG. 6 is a circuit diagram of a resistive string voltage reference coupled to a ROM decoder output buffer cell; FIG. 7 is a schematic of the output cell of FIGS. 3, 8 , and 12 ; FIG. 8 is a block diagram of a second embodiment of a dual mode TFT-LCD source driver circuit in the gray scale mode in accordance with the present invention; FIG. 9 is a schematic of a first embodiment of the latch circuit of FIGS. 8, and 12 ; FIG. 10 is a schematic of a second embodiment of the latch circuit of FIGS. 8 and 12; FIG. 11 is a schematic of a third embodiment of the latch circuit of FIGS. 8, and 12 ; and FIG. 12 is a block diagram of a third embodiment of a dual mode TFT-LCD source driver circuit in the gray scale mode in accordance with the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention is best understood by comparison with the prior art. Hence this detailed description begins with a discussion of a known source driver 100 as illustrated in FIG. 1 . Driver 100 includes a shift register 104 which contains an N-bit shift register, where N is the number of uniquely addressable channels within the source driver. The shift register 104 is clocked with the CLK signal. The sample registers 106 receive serial video data from the serial video data bus to store channels of six-bit display data for one line period, enabling the internal resistive digital-to-analog converter (DAC) 102 coupled to the decoder/output voltage drivers 110 to use the display data from line time x while the next line of data (from line time x+1) is loaded into the sample registers 106 . The contents of the sample registers 106 are transferred to the hold registers 108 before being over-written with the next line of six-bit words of display data from the serial video data bus after a low to high transition of the transfer signal occurs at the end of line x+1. An internal resistor string 102 used for voltage dividing which may comprise a string of 64 resistors, produces 64 distinct voltage levels from the 9 voltage reference inputs. Linear voltage levels are generated between each pair of adjacent reference voltage inputs, utilizing the string of resistors between the reference voltages. Decoder/output voltage drivers 110 select the desired output voltage based upon the data in the hold register 108 for each of the channels. As the display data for line x+1 is loaded into the sample registers 106 , decoder/output voltage drivers 110 use the data for line x stored in the hold registers 108 . Each of the output voltage drivers 110 outputs one of the 64 analog voltages based upon the corresponding decode of the display data. A detailed schematic of a known ROM decoder connect to a internal resistive DAC 102 may be found in FIG. 6 . As illustrated 8 reference voltages supplied across 64 resistors provide the voltage levels necessary for the ROM decoder to decode the six-bit data supplied from hold register 108 , where each ‘’ represents a transistor. FIG. 2 displays a source driver circuit 200 in accordance with the present invention as it operates in the gray scale mode. Driver 200 includes a shift register 204 which contains an N-bit shift register, where N is the number of uniquely addressable channels within the source driver. The shift register 204 is clocked with the CLK signal. The sample registers 206 receive serial video data from the serial video data bus to store channels of six-bit display data for one line period, enabling the internal resistive digital-to-analog converter (DAC) 202 coupled to the decoder/output voltage drivers 210 to use the display data from line time x while the next line of data (from line time x+1) is loaded into the sample registers 206 . The contents of the sample registers 206 are transferred to the hold registers 208 before being over-written with the next line of six-bit words of display data from the serial video data bus after a low to high transition of the transfer signal occurs at the end of line x+1. An internal resistor string 202 used for voltage dividing which may comprise a string of 64 resistors, produces 64 distinct voltage levels from the 9 voltage reference inputs. Linear voltage levels are generated between each pair of adjacent reference voltage inputs, utilizing the string of resistors 202 between the reference voltages. Decoder/output voltage drivers 210 select the desired output voltage based upon the data in the hold register 208 for each of the channels. As the display data for line x+1 is loaded into the sample registers 206 , decoder/output voltage drivers 210 use the data for line x stored in the hold registers 208 . Each of the output voltage drivers 210 outputs one of the 64 analog voltages to output buffers 212 based upon the corresponding decode of the display data. Switches 214 are closed during gray scale mode to enable the full color resolution voltage levels to be provided at the LCD. FIG. 3 displays a source driver circuit 200 in accordance with the present invention as it operates in the standby mode. Driver 200 includes a shift register 204 which contains an N-bit shift register, where N is the number of uniquely addressable channels within the source driver. The shift register 204 is clocked with the CLK signal. The sample registers 206 receive serial video data from the serial video data bus to store channels of six-bit display data for one line period, enabling the hold registers 208 to hold three-bit display data from line time x while the next line of data (from line time x+1) is loaded into the sample registers 206 . The contents of the sample registers 206 are transferred to the hold registers 208 before being over-written with the next line of six-bit words of display data from the serial video data bus after a low to high transition of the transfer signal occurs at the end of line x+1. Output cells 216 produces distinct voltage levels using 2 reference voltage reference inputs, a mode signal and data transferred by hold register 208 . Switches 214 are open during standby mode to power down the resistive string 202 , decoder/output voltage drivers 210 and buffers 212 . FIG. 7 illustrates output cell 216 of FIGS. 2 and 3. The one-bit data signal HRO from each respective hold register connects to inverter 272 and NAND gate 274 . The mode signal MODE couples to the NAND gate 274 and AND gate 276 . NAND gate 274 connects to transistor 278 which is coupled between the output OUT and power supply VH. AND gate 276 connects to transistor 280 which couples between the output OUT and power supply rail VL. In operation, during gray scale mode the output is kept at high impedance. This occurs when the mode signal MODE is low. During standby mode, when the mode signal is high, voltage VL is provided at output OUT when the active bit of the hold register 208 is low. In the alternative, when the active bit of the hold register 208 is high, voltage VH is provided at the output OUT. In accordance with the present invention in FIGS. 2 and 3, a TFT-LCD source driver circuit for driving source signal line of a liquid crystal display panel includes two driving modes: gray scale mode and monochrome mode. Gray scale modes applies selected voltage to source signal line. The selected voltage proportion to liquid crystal light transmission factor. Standby mode applies only two voltage levels to source signal line which drives the liquid crystal light transmission factor on 100% or 0% as shown in FIG. 5 . There is a mode signal to select between gray scale mode and standby mode. In standby mode, digital to analog converter portion and output circuit is shut down. In addition, most of registers and latches are shut down as well. Only one bit of the register and latch data for each output channel is left operable. Thus, the line data connects to output stage from line register directly. Major power consumption portions are shutdown such that only the digital circuits are active. Logic gate transaction frequency and data line charge and discharge current of the sample register 206 , hold register 208 and output cell 216 may be used determine the source driver's total power consumption. In order to save TFT-LCD power consumption, source driver in accordance with the present invention provides both a full color display (gray scale) mode and a standby display modes. With this solution, TFT-LCD could provide both full color and low power consumption for handheld or communication application i.e. PDA or mobile phone. During most of the time that the handheld communication device is in use, the device will be in standby mode which provides 8 colors at display quality (resolution in pixels). This mode is of substantial quality to display text and icons. When the need arises to display a video or more colors within an image, the TFT-LCD can switch to gray scale mode which provides more colors (i.e. 64 gray scale source driver produce 262144 colors). The TFT-LCD source driver in accordance with the present invention not only provides colors of display quality, but also saves power consumption in the monochrome and gray scale modes. Signal driver circuit 200 shown in FIGS. 2 and 3 provides up to sixty four voltage levels on each of two hundred one LCD columns. It will be recognized, though that more or less voltages or columns may be utilized. Within signal driver 200 , decoder/output voltage drivers 24 are used to provide a specific voltage output to each column. As shown in FIG. 3, the added switches 214 shut-down the analog circuits in the standby mode. The first power down mode includes powering down the internal resistive digital-to-analog converter (DAC) 202 where there will be no gamma reference voltage; thus, no power consumption. The second power down mode includes powering down the output buffer amplifiers 212 where the switches 214 control the switching of modes whether standby or gray scale. In standby mode, the two output transistors (not shown) may function as switches to control using a single bit of data to the driver output two different voltage levels. Such that the TFT-LCD displays only 100% brightness for the red, green and blue pixels. FIG. 8 represents the standby mode of a second embodiment of a driver circuit 800 in accordance with the present invention. Driver 800 includes a shift register 802 which contains an N-bit shift register, where N is the number of uniquely addressable channels within the source driver 800 . The shift register 802 is clocked with the CLK signal. The sample registers 804 receive serial video data from the serial video data bus to store channels of six-bit display data for one line period, enabling the hold registers 806 to hold three-bit display data from line time x while the next line of data (from line time x+1) is loaded into the sample registers 804 . The contents of the sample registers 804 are transferred to the hold registers 806 before being over-written with the next line of six-bit words of display data from the serial video data bus after a low to high transition of the transfer signal occurs at the end of line x+1. Programmable latch circuits 807 couple between each respective hold register 806 and output cell 808 to decipher from the six-bit data transferred from hold register 807 and provide a one-bit signal to the output cell 808 . Output cells 808 produces distinct voltage levels using 2 reference voltage reference inputs, a mode signal and data transferred by latch circuit 807 . Switches 810 are open during standby mode to power down the resistive string, decoder/output voltage drivers and output buffers (not shown). FIGS. 9, 10 and 11 illustrate a variety of ways in which the latch circuit 807 of FIG. 8 may be implemented. Specifically, in FIG. 9, OR gate 902 only provides the two most significant bits of six-bit data bit as output. Thus, pixel dot data corresponding to 16 and above will be represented at the LCD. In FIG. 10, OR gate 1002 only provides the three most significant bits of six-bit data bit as output. Thus, pixel dot data corresponding to 8 and above will be represented at the LCD. Moreover, in FIG. 11, AND gate 1106 and OR gates 1102 and 1104 only provides the four most significant bits of six-bit data bit as output. Thus, pixel dot data corresponding to 4 and above will be represented at the LCD. FIG. 12 represents the standby mode of a third embodiment of a driver circuit 1200 in accordance with the present invention. Driver 1200 includes a shift register 1202 which contains an N-bit shift register, where N is the number of uniquely addressable channels within the source driver 1200 . The shift register 1202 is clocked with the CLK signal. The sample registers 1204 receive serial video data from the serial video data bus to store channels of six-bit display data for one line period, enabling the programmable latch circuits 1206 to decipher from the six-bit data transferred from sample register 1204 and provide a one-bit signal to the hold register 1208 . Hold registers 1208 will hold the one-bit display data from line time x while the next line of data (from line time x+1) is loaded into the sample registers 1204 . The contents of the sample registers 1204 are transferred through the latch circuits 1206 to the hold registers 1208 before being over-written with the next line of six-bit words of display data from the serial video data bus after a low to high transition of the transfer signal occurs at the end of line x+1. Output cells 1210 receive the one-bit data from hold register 1208 and produces distinct voltage levels using 2 reference voltage reference inputs, a mode signal and data transferred by hold register 1208 . Switches 810 are open during standby mode to power down the resistive string, decoder/output voltage drivers and output buffers (not shown). The present invention finds application in video systems including digital still cameras, digital video cameras, digital video processing systems. The reader's attention is directed to all papers and documents which are filed concurrently with this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All the features disclosed in this specification (including any accompany claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.

The present invention relates to a source driver circuit ( 200 ) for driving a thin film transistor liquid crystal display (TFT-LCD) panel. The source driver circuit ( 200 ) provides several different operating modes for the driver to lower the power consumption of a TFT-LCD module while still providing a wide analog voltage range to the liquid crystal display elements. A mode signal (MODE) switches the driver from gray scale to standby mode wherein the internal resistive digital to analog converter ( 202 ), decoder/output voltage drivers ( 210 ) and output buffer amplifiers ( 212 ) are powered down. In addition, only the most significant bit of data corresponding to red, green and blue are transferred to a sample and hold register ( 206, 208 ). Output cells ( 216 ), substituting for the decoder/output voltage drivers, receive one-bit data from hold registers ( 208 ) and provide voltage at the output of the driver circuit ( 200 ).

BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to a new and useful sawdust removal device for attachment to the exterior housing of a saber saw, i.e. a portable hand-held saw having a reciprocating blade and powered by an electric motor. With appropriate modifications, the device can be used with other electric-powered saws and electric-powered drills. Saber saws are widely used by cabinet makers, carpenters and other persons engaged in the woodworking trades or metalworking trades, or both. In addition, saber saws are very popular with persons engaged in woodworking activities as a hobby. Most of these persons use a saber saw for similar purposes. Normally, a saber saw is used for precision cutting along a line drawn or scribed on the surface of the wood or other material being cut. Since a saber saw is hand held and guided, it is important for the person using the saw to have a clear and unobstructed view of the line which he or she is following during the cutting operation. It is well known by both professional and amateur users of saber saws that sawdust, chips and other debris accumulate on the surface of the wood or other material being cut during normal operation of a saber saw. In general, such accumulations take place immediately in front of the saw blade. If such accumulations are not removed, the user of the saw will not be capable of seeing the line which he or she is attempting to follow. Under such circumstances, it is very probable that the user of the saw will make one or more cutting errors. Such errors are often very costly in terms of both lost time and materials. Various means for removing sawdust, chips and other debris which accumulates on the surface of the wood or other material being cut are known in the art. For example the user of a saber saw can stop operation of the saw and tilt the wood or other material being cut to cause the sawdust, chips and other debris to fall from the surface of the wood or other material. Also, the user of a saber saw can brush the sawdust, chips and other debris from the surface of the wood or other material being cut with a cloth or a small brush. For safety reasons, it is preferable to stop operation of the saw when removing the sawdust, chips and other debris from the surface of the wood or other material being cut. And, of course, the user of a saber saw can either blow the sawdust, chips and other debris from the surface of the wood or other material being cut with compressed air or remove such accumulations with a shop vacuum cleaner. Unfortunately, many users of a saber saw do not have access to either a source of compressed air or a shop vacuum cleaner. All of the above-described means for removing sawdust, chips and other debris from the surface of the wood or other material being cut with a saber saw have the disadvantage of requiring the user of the saw to interrupt his cutting operation to remove such accumulations. It is desirable to have a means for continuously removing such accumulations during operation of a saber saw. Continuous means for removing sawdust, chips and other debris from the surface of the wood or other material being cut during operation of a saber saw are described in U.S. Pat. Nos. 2,668,567, U.S. Pat. No. 2,902,067, and U.S. Pat. No. 3,033,252. Each of these patents discloses a means for diverting a portion of the discharged cooling air of the electric motor powering a saber saw through interior passageways in the saw housing to the immediate area of the reciprocating blade to blow away sawdust, chips and other debris. At times, a mild suction action occurs at the diverted air discharge opening of some known saber saws having such interior passageways causing the sawdust to be pulled into the face and eyes of the saw user. Even if this undesirable operating characteristic is not present with known means for continuously removing sawdust, chips and other debris, known means require substantial structural modifications to the design of conventional saber saws. It is desirable to have a device which can be attached to the exterior of the housing of a conventional saber saw. Ideally, no structural modifications to the design of the saw should be required for use of such a device. The sawdust removal device of the present invention can be attached to the exterior of the housing of a conventional saber saw by traditional fastening means. No structural modifications to the design of the saw are required for use of this device. The sawdust removal device of the present invention traps air which is discharged from one of the two exhaust openings in the housing of a conventional saber saw and diverts the trapped air through an air delivery tube to a nozzle and diffuser located behind the reciprocating saw blade. This trapped and diverted air is discharged through the nozzle and diffuser and continuously blows sawdust, chips and other debris from the surface of the wood or other material being cut during use of the saber saw. The device can be attached to new saber saws during assembly operations at the manufacturing facility or attached to older saber saws by saw owners. These and many other advantages and features of the present invention will be apparent from the following description of drawings, description of the preferred embodiment and the appended claims. DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of a saber saw having the sawdust removal device of the present invention attached to the exterior of the saw housing. FIG. 2 is a side view of the sawdust removal device of the present invention. FIG. 3 is a sectional view through lines 3--3 in FIG. 2. FIG. 4 is a sectional view through lines 4--4 in FIG. 2. DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of the sawdust removal device of the present invention is illustrated in FIGS. 1-4. The sawdust removal device is comprised of two major components, namely, exhaust port cover 10 and air delivery tube 12. In the preferred embodiment, exhaust port cover 10 is a solid body having an air trapping depression 14 which cooperates with an interior air passageway 16 to trap exhaust air discharged from one of the exhaust ports of a conventional saber saw and divert said air to air delivery tube 12. Air trapping depression 14 has an appropriate geometrical configuration for cooperation with the exhaust port to be covered. In FIGS. 2 and 4, air trapping depression 14 is shown as an elongated rectangular depression which gradually increases in depth from the upper end of the depression to the lower end of the depression. This particular geometrical configuration for air trapping depression 14 is suitable for exhaust port cover 10 when the sawdust removal device of the present invention is attached to the exterior of the housing of a saber saw having an elongated rectangular exhaust port. In FIGS. 2 and 4, interior air passageway 16 is shown as a cylindrical hole interconnecting air trapping depression 14 and air delivery tube 12. In the preferred embodiment, air delivery tube 12 is a hollow tube having one end interconnected with the exit opening of interior air passageway 16. In FIGS. 1-4, this interconnection is shown as a force fit between one end of air delivery tube 12 and the exit opening of interior air passageway 16. Air nozzle 18 and air diffuser 20 are provided at the lower end of air delivery tube 12 to discharge and direct trapped and diverted exhaust air to continuously blow sawdust, chips and other debris from the surface of the wood or other material being cut by the saber saw. Exhaust port cover 10 has been fabricated by machining the desired geometrical configuration from a solid block of plastic material. But, exhaust port cover 10 could be either machined or cast from an aluminum alloy or other suitable metal alloy. Also, it is possible to fabricate exhaust port 10 from a suitable plastic material by an injection molding process. Air delivery tube 12 has been fabricated by cutting and bending copper tubing of the desired internal diameter to obtain the desired geometrical configuration. But, other types of tubing could be cut and bent to obtain the desired geometrical configuration for air delivery tube 12. Also, it is possible to fabricate air delivery tube 12 from a suitable plastic material by an injection molding process. While inexpensive, lightweight structural materials are desirable for fabrication of the components of the sawdust removal device of the present invention, it is not intended that the present invention be limited in scope by the materials selected to fabricate the sawdust removal device. Furthermore, it is not intended that the present invention be limited in scope by the methods used to fabricate the sawdust removal device. In fact, it will be readily seen by those skilled in the manufacturing arts related to the fabrication of the sawdust removal device that the device could be fabricated as a single component rather than as two components in the manner described herein. Traditional fastening means can be used to attach the sawdust removal device of the present invention to the exterior of the housing of a conventional saber saw. FIG. 1 illustrates the use of screw means 22 and 24 to attach the sawdust removal device to existing screw holes in the housing of a conventional saber saw. FIGS. 2, 3 and 4 illustrate the use of adhesive means 26 to attach the sawdust removal device to the housing of a conventional saber saw. Rivet means may be desirable if the sawdust removal device is attached during assembly of a new saber saw at the manufacturing facility. The operation of the sawdust removal device of the present invention can best be understood by referring to FIG. 1 which shows the device attached to the exterior of the housing of saber saw 30. Saber saw 30 is equipped with a reciprocating saw blade 32. During operation of the saber saw, sawdust, chips and other debris are deposited on the upper surface of wooden board 34 after each upward stroke of reciprocating saw blade 32. But, the air which is continuously discharged from air nozzle 18 and distributed by diffuser 20 flows from its discharge point immediately behind reciprocating saw blade 32 and blows the sawdust, chips and other debris from that portion of the surface of wooden board 34 which is in the immediate vicinity of reciprocating saw blade 32. Accordingly, the user of saber saw 30 has a clear and unobstructed view of line 36 at all times during operation of saber saw 30. While the present invention has been disclosed in connection with the preferred embodiment thereof, it should be understood that there may be other embodiments which fall within the spirit and scope of the invention as defined by the following claims:

A sawdust removal device for attachment to the exterior housing of a saber saw or other electric-powered saw or drill. The device traps air discharged from an exhaust port in the saw or drill housing and diverts that air to continuously blow away sawdust, chips and other debris which accumulates on the surface of the material being cut or drilled during operation of the saw or drill.

FIELD OF THE INVENTION [0001] The present invention relates generally to decoding techniques for turbo codes, and more particularly, to methods and apparatus for scaling values in a turbo decoder. BACKGROUND OF THE INVENTION [0002] Error correction techniques are used in a number of communication and storage systems. Error correction codes, such as Reed-Solomon codes, add one or more redundant bits to a digital stream prior to transmission or storage, so that a decoder can detect and possibly correct errors caused by noise or other interference. One class of error correction codes are referred to as “turbo” codes. Generally, turbo codes employ a combination of two or more systematic convolutional or block codes. Typically, an iterative decoding technique is employed where the output of each decoding step, for example, from an inner receiver, serves as an input to the subsequent decoding step performed by an outer receiver. In many implementations, the inner receiver generates log-likelihood ratios (LLRs) that are processed by the outer receiver. [0003] In a CDMA receiver, for example, an inner receiver typically demodulates the received signal into symbols and the outer receiver forms, processes and decodes each frame, comprised of a collection of symbols. The output signal of the inner receiver is often quantized to a smaller number of bits and then processed by a soft input/soft output decoder. U.S. patent application Ser. No. 10/387,876, entitled “Method and Apparatus for Decoder Input Scaling Based on Interference Estimation in CDMA,” for example, discloses a technique for scaling the decoder input for a CDMA receiver to a smaller number of bits to reduce the memory requirement. In order to maintain the decoder performance for a smaller number of input bits, the disclosed method estimates the interference of the inner receiver output and scales the decoder input such that its variance is maintained. [0004] A number of techniques have been proposed or suggested for adjusting various parameters of a turbo decoder to improve the throughput or Bit Error Rate (BER) performance. Y. Wu and B. Woerner, “The Influence of Quantization and Fixed Point Arithmetic Upon the BER Performance of Turbo Codes,” Proc. IEEE Veh. Tech. Conf., Houston, Tex. (May, 1999), for example, evaluates the influence of quantization and fixed point arithmetic upon the BER performance of turbo decoders. Wu and Woemer demonstrate that with proper scaling of the received signal prior to quantization, there is no degradation of the BER performance with eight bit quantization (or even four bit quantization). [0005] Generally, the inner receiver in such conventional turbo decoding techniques generates floating point LLRs (soft bits) that are scaled in a linear manner, and then mapped to a fixed point. Most known techniques for scaling decoder inputs have used a gain control method. For example, the mean square or mean absolute values of the inner receiver output have been employed. The technique disclosed in the above-referenced U.S. patent application Ser. No. 10/387,876 employ a noise variance of the channel in order to scale the decoder input. A need exists for methods and apparatus for scaling or shaping the LLR distribution in a manner that improves the BER performance. A further need exists for methods and apparatus for scaling or shaping the LLR distribution in a non-linear manner. SUMMARY OF THE INVENTION [0006] Generally, methods and apparatus are provided for non-linear scaling of log likelihood ratio (LLR) values in a decoder, such as a universal mobile telecom system (UMTS) receiver. According to one aspect of the invention, a decoder processes a received signal by generating a plurality of log-likelihood ratios having a first resolution; applying a non-linear function to the plurality of log-likelihood ratios to generate a plurality of log-likelihood ratios having a lower resolution; and applying the plurality of log-likelihood ratios having a lower resolution to a decoder. The non-linear function can distribute the log-likelihood ratios, for example, such that the frequency of each LLR value is more uniform than a linear scaling. [0007] The plurality of log-likelihood ratios having a first resolution may be generated by an inner receiver, such as a Rake receiver, a minimum mean squared error (MMSE) receiver, a decorrelating receiver, an equalizer or an interference canceller. The plurality of log-likelihood ratios having a lower resolution can be processed by an outer decoder, such as a Turbo decoder or a Viterbi decoder. [0008] A more complete understanding of the present invention, as well as further features and advantages of the present invention, will be obtained by reference to the following detailed description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0009] FIG. 1 is a schematic block diagram of an exemplary receiver incorporating features of the present invention; [0010] FIG. 2 illustrates an example of an LLR mapping performed by the correction block of FIG. 1 in accordance with the present invention; and [0011] FIG. 3 illustrates the frequency of each LLR value for both a conventional linear mapping and a non-linear mapping in accordance with the present invention. DETAILED DESCRIPTION [0012] The present invention provides methods and apparatus for scaling or shaping the LLR distribution in a manner that improves the BER performance. According to one aspect of the present invention, the LLR distribution is shaped in a non-linear manner. [0013] FIG. 1 is a schematic block diagram of an exemplary receiver 100 incorporating features of the present invention. While the present invention is illustrated in the context of a universal mobile telecom system (UMTS) receiver, in accordance with a 3rd Generation Partnership Project (3GPP) standard, the present invention may be implemented in any decoder employing soft decision decoding, as would be apparent to a person of ordinary skill in the art. For a detailed discussion of the 3GPP specification, see, for example, 3GPP TS 25.212, “Multiplexing and Channel Coding (FDD),” and 3GPP TS 25.101, “User Equipment (UE) Radio Transmission And Reception (FDD),” http://www.3gpp.org/specs/specs.htm, incorporated by reference herein [0014] As shown in FIG. 1 , the exemplary receiver 100 comprises an inner receiver 110 , a correction block 120 , a bit rate processing block 130 and a decoder 140 . The inner receiver 110 may be implemented, for example, as a Rake receiver, a minimum mean squared error (MMSE) receiver, a decorrelating receiver, an equalizer or an interference canceller, or some combination of the foregoing, as would be apparent to a person of ordinary skill. Generally, the inner receiver 110 generates log-likelihood ratios (LLRs), in a known manner, that are processed by the decoder 140 . The inner receiver 110 operates at the chip rate, while the bit rate processing block 130 and decoder 140 operate at the bit rate. [0015] As previously indicated, it is known to quantize the output signal of the inner receiver 110 from a set of LLRs with a first resolution to a set of LLRs with a lower resolution (i.e., having a smaller number of bits). The LLRs with a lower resolution are then processed by bit rate processing block 130 and the decoder 140 . Generally, the inner receiver 110 in conventional turbo decoding techniques generates LLRs that are scaled in a linear manner, for example, using a gain control method. [0016] According to one aspect of the present invention, the correction block 120 maps the LLR values into a lower resolution using a non-linear function. The present invention recognizes that the LLRs generated by the inner receiver 110 may not have the right shape for optimal processing in the bit rate processing block 130 . In this manner, the correction block 120 can apply a non-linear function to the LLRs to shape them such that the bit and block error rate performance metrics (BER and BLER) are improved. [0017] In one exemplary implementation, the non-linear correction block 120 applies the following non-linear function to the LLRs generated by the inner receiver 110 : [0018] LLRout=(−0.5+sqrt(0.5**2+4/30*LLRin) for LLRin>=0, [0019] LLRout=−(−0.5+sqrt(0.5**2+4/30*−LLRin) for LLRin<0. [0020] It is noted that the LLRout values produced by the correction block 120 are typically fixed point values up to five bits and the LLRin values are typically higher resolution fixed point values. The step size for each step can be optimized for the intended scenario, as would be apparent to a person of ordinary skill. A heuristic process is employed to identify a suitable non-linear function. Generally, the LLRs are skewed in such a way that distributes the LLRs a bit more evenly, and thus provides additional information to the turbo decoder 140 about the different LLRs. [0021] The bit rate processing block 130 implements a number of bit rate processing steps in accordance with the exemplary 3GPP standard, such as rate matching, HARQ processing and buffering. The decoder 140 may be implemented, for example, as a Turbo or Viterbi decoder. [0022] FIG. 2 illustrates the LLR mapping performed by the correction block 120 in accordance with the present invention. As shown in FIG. 2 , the correction block 120 applies a non-linear function 220 to the LLRs generated by the inner receiver 110 (LLR IN ). In addition, a conventional linear mapping 210 is also shown. [0023] It is noted that the correction block 120 could be implemented in hardware or software. For a hardware implementation, the non-linear function 220 could be implemented, for example, in the form of a lookup table. If the higher resolution LLR (LLR IN ) has a 7 bit resolution including one bit sign, and assuming the lookup table is symmetrical around 0, the lookup table can be implemented with 6 bits input and 4 bits output and the sign bit would be maintained from input to output. [0024] FIG. 3 is a plot 300 illustrating the frequency of each LLR value for both a conventional linear mapping and a non-linear mapping in accordance with the present invention. As shown in FIG. 3 , each data point for a conventional linear mapping is shown using a square bullet and each data point for a non-linear mapping is shown using a diamond bullet. Thus, FIG. 3 illustrates the LLR distribution before and after reshaping. It is noted that the frequency of the LLR value at zero (0) is approximately 6500 in the exemplary embodiment, although not shown in the scale presented in FIG. 3 . [0025] Among other benefits, the present invention optimizes the BER/BLER over the whole receiver processing chain. In addition, the throughput with the non-linear reshaping of the present invention has been observed to perform better than without an LLR reshaping. [0026] System and Article of Manufacture Details [0027] As is known in the art, the methods and apparatus discussed herein may be distributed as an article of manufacture that itself comprises a computer readable medium having computer readable code means embodied thereon. The computer readable program code means is operable, in conjunction with a computer system, to carry out all or some of the steps to perform the methods or create the apparatuses discussed herein. The computer readable medium may be a recordable medium (e.g., floppy disks, hard drives, compact disks, or memory cards) or may be a transmission medium (e.g., a network comprising fiber-optics, the world-wide web, cables, or a wireless channel using time-division multiple access, code-division multiple access, or other radio-frequency channel). Any medium known or developed that can store information suitable for use with a computer system may be used. The computer-readable code means is any mechanism for allowing a computer to read instructions and data, such as magnetic variations on a magnetic media or height variations on the surface of a compact disk. [0028] The computer systems and servers described herein each contain a memory that will configure associated processors to implement the methods, steps, and functions disclosed herein. The memories could be distributed or local and the processors could be distributed or singular. The memories could be implemented as an electrical, magnetic or optical memory, or any combination of these or other types of storage devices. Moreover, the term “memory” should be construed broadly enough to encompass any information able to be read from or written to an address in the addressable space accessed by an associated processor. With this definition, information on a network is still within a memory because the associated processor can retrieve the information from the network. [0029] It is to be understood that the embodiments and variations shown and described herein are merely illustrative of the principles of this invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention.

Methods and apparatus are provided for non-linear scaling of log likelihood ratio (LLR) values in a decoder. A decoder according to the present invention processes a received signal by generating a plurality of log-likelihood ratios having a first resolution; applying a non-linear function to the plurality of log-likelihood ratios to generate a plurality of log-likelihood ratios having a lower resolution; and applying the plurality of log-likelihood ratios having a lower resolution to a decoder. The non-linear function can distribute the log-likelihood ratios, for example, such that the frequency of each LLR value is more uniform than a linear scaling.

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is the US National Stage of International Application No. PCT/EP2013/055914 filed 21 Mar. 2013, and claims the benefit thereof. The International Application claims the benefit of German Application No. DE 102012205771.4 filed 10 Apr. 2012. All of the applications are incorporated by reference herein in their entirety. FIELD OF INVENTION [0002] The present invention relates to a heat accumulator for storing at least 100 MWh of thermal energy from a relatively hotter gas in a charging state and for yielding this thermal energy to a relatively colder gas in a discharging state. The invention also relates to a method for charging and discharging such a heat accumulator. BACKGROUND OF INVENTION [0003] Heat accumulators for storing large quantities of thermal energy from power plant capacities are typically used as seasonal accumulators for the temporary storage of surplus energy from the power generation. Thus, for economical reasons it can be proved to be advantageous to temporarily store surplus energy—which is generated outside of the peak load times—in thermal form. The surplus energy can be extracted from conventional power generation or also be provided by means of regenerative power generation, especially thermosolar power generation. [0004] From DE 10 2004 019 801 A1 it is known, for example, to temporarily store thermal energy from a gas flow by means of a gas-sand heat exchanger. The heat transfer is carried out in this case in a shaft which has porous walls which are connected to a gas inlet or gas outlet. Located inside the shaft is a sand section which ensures that the sand located therein is moved through the shaft at an adjustable speed. During operation of the gas-sand heat exchanger hot gas flows through the porous shaft wall into the chamber which is filled with sand and via direct heat contact partially transfers the heat energy to the sand grains. After that, the thereby heated sand can then be stored in a suitable manner and made available again to a heat extraction at a later time for a thermal reconversion application, for example. [0005] However, the relatively cost-intensive operation of such a plant is disadvantageous to such a heat accumulator since the sand also has to be re-manipulated during extraction of the thermal energy in order to transfer its thermal energy to a flowing medium. Furthermore, an only relatively small quantity of heat can be transferred to the sand as heat storage medium, i.e. a relatively high power loss is to be taken into consideration. What is proved to be a further disadvantage of such a plant which is known from the prior art is that it has movable machine parts which can be vulnerable and therefore very maintenance intensive. This in turn results in undesirable downtimes and therefore financial losses on the part of the operator of such a plant. [0006] Further disadvantages of the heat accumulators which are known from the prior art lie in their high costs for achieving an adequate thermal insulation. Even in the storage of thermal energy at a relatively high temperature level (>100° C.) in comparison to typically prevailing ambient temperatures the costs for the provision of an adequate insulation proves to be high. Since, moreover, heat accumulators for the storage of surplus energy from power plant capacities are of relatively large dimensions, the costs for achieving an adequate thermal insulation are sometimes crucial to whether the heat accumulator can be operated economically or not. SUMMARY OF INVENTION [0007] It is therefore an object of the present invention to provide a suitable heat accumulator which can enable a cost-effective seasonal storage of surplus energy produced in a power plant but to avoid the disadvantages which are known from the prior art. It is a further object of the invention to propose a heat accumulator, the costs of which for the provision of an adequate thermal insulation do not call into question the economical operation. [0008] The objects upon which this invention is based are achieved by a heat accumulator and also by a method for operating such a heat accumulator according to the claims. [0009] The objects of the invention are especially achieved by means of a heat accumulator for storing at least 100 MWh of thermal energy from a relatively hotter gas in a charging state and for yielding thermal energy to a relatively colder gas in a discharging state, which heat accumulator in the charging state has at least one inflow surface, provided with inflow openings, for introduction of the gas, and also at least one outflow surface, provided with outflow openings, for discharging the gas after yielding heat to a granular heat storage medium, wherein the inflow surface is formed at least in certain sections to form a passage which is especially completely enclosed by the outflow surface, and wherein an interspace, in which the granular heat storage medium is located, is defined between the inflow surface and the outflow surface. [0010] Here, and in the following text, the granularity of the heat storage medium is to be understood in such way that the heat storage medium is loose, but at the same time offers sufficient space to a gas for this to flow through it. Furthermore, the granularity is not to be limited in principle with regard to size distribution of the grains. Apart from preferred embodiments, the shape and volume distribution of individual grains is to be optional. According to the invention, however, it is essential that the shape and volume distribution of individual grains are sufficient to allow a gas flow between the individual grains. This gas flow, moreover, has to be large enough in order to be able to deposit the desired thermal energy in the heat accumulator. [0011] In addition, the object according to the invention is achieved by means of a method for charging and discharging such a heat accumulator, wherein for the charging of the heat accumulator a relatively hotter gas is introduced into the passage so that this flows through the inflow openings of the inflow surface and on its way to the outflow openings of the outflow surface yields heat to the granular heat storage medium, wherein it flows out of the outflow openings as relatively colder gas and is discharged from the heat accumulator, and that for the discharging of the heat accumulator a relatively colder gas is introduced through the outflow openings and on its way through the granular heat storage medium absorbs heat from the granular heat storage medium, and after discharging from the inflow openings of the inflow surface is available as a relatively hotter gas. [0012] The surplus energy which is generated by a power plant is therefore to be transferred according to the invention by means of a gaseous heat transfer medium to a suitable solid heat storage medium. The heat transfer medium may have obtained the heat transported by it in a different way. Therefore, it is conceivable, for example, that the gaseous heat transfer medium is extracted from an exhaust gas and so transfers the surplus process heat, for example of a combustion process, to the heat storage medium. By the same token, it is also conceivable that the thermal energy which is to be stored is sourced from a secondary generation process, for example from a compressor process for heat generation, wherein this generation process itself is supplied with surplus energy. [0013] According to aspects of the invention, the heat accumulator is to be suitable for storing at least 100 MWh of thermal energy. Such large quantities of energy typically result only in conjunction with capacities which are generated by power plants within the field of application into which the present invention also falls. [0014] After storage has been carried out, the temporarily stored quantity of heat can be fed again to a further power plant process or power generation process for utilization. In this way, with a time delay the energy can be retrieved from the heat accumulator and be available for renewed power generation when required. [0015] The heat accumulator according to aspects of the invention is described from the point of view of the charging state with regard to its component parts. This, however, does not constitute any restriction with regard to the disclosure of the heat accumulator since to the person skilled in the art it is understandable that with reversal of the charging state, that is to say in a discharging state, the individual component parts of the heat accumulator maintain their basic functionality. If gas therefore flows through the inflow openings of the inflow surface during the charging state, then to the person skilled in the art it is understandable that during the discharging state the inflow surface fulfills the function of an outflow surface and the inflow openings fulfill the functions of outflow openings. For improved comprehensibility, the description of individual component parts of the heat accumulator may therefore be described from the point of view of the charging state. [0016] The heat accumulator according to aspects of the invention, by means of direct heat transfer, allows energy to be extracted from the relatively hotter gas, and to be transferred to the granular heat storage medium. In this case, the relatively hotter gas flows through the inflow openings of the inflow surface into the interspace in which is arranged the granular heat storage medium. On account of a gas pressure which is to be set as desired, the relatively hotter gas flows through the free spaces which the heat storage medium has on account of its granularity. After the relatively hotter gas has flown through the entire interspace, yielding heat, it makes its way to the outflow surface and is discharged via the outflow openings in this. On account of a continuous heat yield, in the regions of the heat storage medium which are located closer to the passage of the inflow surface a temperature level is formed which is higher than in the regions which are located closer to the outflow surface. As a result, a desired temperature gradient is established as long as complete charging of the heat accumulator is not achieved. [0017] Since the heat accumulator is provided for the temporary storage of quantities of generated surplus energy, a complete charging of the heat accumulator is typically not achieved. Rather, the heat accumulator during its operation has a desired temperature distribution, which is described above, in the heat storage medium. Consequently, however, the regions which are located closer to the outflow surface of the interspace act as a heat insulator with regard to the heat losses from the regions which are located closer to the passage of the inflow surface. The outer, relatively colder regions of this interspace which is filled with the granular heat storage medium therefore prevent a heat transfer from the relatively hotter, inner regions which are located closer to the passage of the inflow surface. This, on the one hand, has the result that the heat accumulator altogether requires a lower insulation cost since a smaller heat transfer through the outer regions of the interspace which is filled with the heat storage medium is to be expected. [0018] Especially when the heat accumulator has been charged with a predetermined quantity of heat—but a further feed of heat via a gas is no longer carried out—is it necessary to hold back the energy absorbed in the heat accumulator as efficiently as possible until this energy can be yielded again to a relatively colder gas at a later point in time during discharging of the heat accumulator. [0019] The storage of the generated surplus energy, however, can sometimes necessitate the storage of these quantities of heat for many hours or even days. Since the surplus energy from power plant capacities involves comparatively large quantities of energy, the energy storage is typically also carried out at a relatively high temperature level (>100° C.). In order to also be able to provide these quantities of heat energy for steam generation in a power plant process, for example, storage at a temperature level of typically more than 400° C. is required. On account of the large temperature difference in comparison to the natural ambient temperature, noticeable heat energy losses from the heat accumulator are to be feared if a suitable insulation cannot be selected. In this respect, it is also proved to be essential to efficiently insulate the heat accumulators—which is sometimes already relatively large anyway—against such a heat loss. On account of the geometry or relative arrangement of inflow surface to outflow surface provided according to the invention, a heat distribution is created in the granular heat storage medium which is arranged in the interspace, having an additional desired insulating effect with regard to the regions which already have a relatively high temperature level. [0020] According to a further embodiment, the heat accumulator is intended for arranging on the ground. On account of the quantities of heat energy to be stored therein, the heat accumulator is to be filled with relatively large quantities of granular heat storage medium, wherein such material is preferably to be provided as heat storage medium which is common to the site and locally available. [0021] According to a still further embodiment of the heat accumulator according to aspects of the invention, it can be provided that the passage of the inflow surface has a first symmetry which coincides with a second symmetry of at least one predetermined section of the outflow surface which encloses the passage of the inflow surface. On account of the coinciding symmetry of the inflow surface and of the outflow surface an also symmetrically formed temperature field can be established, at least in certain areas, in the granular heat storage medium. [0022] The symmetry of this temperature field furthermore reduces a heat loss since the regions of relatively higher temperature and regions of relatively lower temperature of the granular heat storage medium are localized better. Therefore, for example the forming of hot spots, which could bring about an undesirable effective heat yield to the outside, is also less likely than in the case of a non-symmetrical overall construction. [0023] An also suitable temperature distribution can be established if according to the embodiment the passage of the inflow surface has a first symmetry axis, the arrangement of which in the heat accumulator coincides with a second symmetry axis of at least one predetermined section of the outflow surface which encloses the passage of the inflow surface. This also preferred embodiment ensures an additionally improved symmetrical design of the temperature field inside the interspace which is filled with the granular heat storage medium. As a result of the coinciding of both symmetry axes (first symmetry axis and second symmetry axis), a temperature distribution field which is also symmetrical to these symmetry axes is formed and ensures a desired, defined temperature distribution. Therefore, it is advantageous, for example, if the relatively hotter region of the interspace which is located closer to the passage of the inflow surface is symmetrically enclosed by the relatively colder regions closer to the outflow surface in order to therefore effect a uniform insulating action upon the relatively hotter regions. [0024] In another embodiment, it is provided that the passage of the inflow surface, as well as the at least one section of the outflow surface enclosing this, have a cylindrical symmetry and the section of the outflow surface is arranged coaxially relative to the inflow surface. The cylindrical symmetrical forming of inflow surface and outflow surface in conjunction with a coaxial arrangement of both relative to each other, ensures an especially uniform temperature distribution inside the granular heat storage medium in the interspace of the heat accumulator. As a result, a relatively uniform and defined colder zone, which is located closer to the outflow surface, is also formed around a relatively hotter zone which is arranged closer to the passage of the inflow surface and counteracts the heat loss in a way comparable to an insulation layer. Furthermore, during a discharging state of the heat accumulator a uniform gas temperature can also be ensured since a uniform heat yield from the heat accumulator is ensured regardless of the direction from which the gas flows into the passage of the inflow surface. [0025] According to a further embodiment of the heat accumulator according to aspects of the invention, the passage of the inflow surface can be closed off at the end on one side, wherein the end closure especially has inflow openings. On account of the closure, it is ensured that all the gas which flows into the passage of the inflow surface is transferred through the inflow openings into the interspace of the heat accumulator. As a result of the geometric arrangement of the closure, moreover, influence is exerted upon the temperature profile which develops in the heat accumulator during the charging state. By the provision of inflow openings in the closure, regions which are arranged beneath the closure and filled with the granular heat storage medium can therefore also be used for heat storage. In this case, it is to be noted that in the case of an arrangement of the heat accumulator on the ground the height level of the closure should not reach the level of the ground. The suitable height at which the closure can be arranged in order to therefore ensure a heat transfer which is as efficient as possible into the heat accumulator results from numerous geometric and also process parameters. [0026] According to a further embodiment of the invention, the number of inflow openings per unit area in the passage increases in the flow direction of the inflowing gas. Therefore, relatively more inflow openings per unit area are arranged in the passage on the outflow side. As a result, convection phenomena in the heat accumulator, which bring about a deformation of the temperature distribution field, can be counteracted. If, for example, the passage of the inflow surface, following the direction of the earth's gravitational field, extends from the top downwards in a heat accumulator which is arranged on the ground, a broadening of the temperature distribution profile is preferably established further up in the interspace since the relatively hotter air, in comparison to the heavier, relatively colder air, rises upwards. Convection phenomena make themselves felt in the developing temperature profile especially when the flow velocities of the relatively hotter gas in the granular heat storage medium are comparatively low (e.g. 0.1 to 0.2 m/sec). In order to therefore supply these regions with less heat, in the passage according to the embodiment less gas volume per time flows directly into these regions. Relatively more gas is delivered into the heat accumulator through the increased number of inflow openings per unit area in the outflow-side region of the passage. As a result, a higher temperature preferably develops in these regions as a result of an increased heat transfer to the granular heat storage medium. The gas which is present in these regions admittedly also flows as a result of convection into the regions located thereabove, but altogether less heat is deposited in the regions of the interspace of the heat exchanger which lie relatively higher up. Consequently, a temperature profile which is less distorted as a result of the convection influence is established. [0027] According to an alternative embodiment, it can also be provided that the size of the inflow openings per unit area in the passage increases in the flow direction of the inflowing gas. The advantages of such an arrangement correspond to those of the preceding embodiments. [0028] According to a further embodiment of the heat accumulator, it is provided that the passage, which is formed by the inflow surface, has a rectilinear progression which is especially oriented in the heat accumulator parallel to the direction of the earth's gravitational field. As a result of this orientation, the effects of convection inside the heat accumulator are distributed relatively symmetrically and equally, and they can be counteracted by measures which are simple to apply. Consequently, such an arrangement again allows the forming of a relatively equally distributed or symmetrical temperature distribution field inside the heat accumulator. [0029] According to a further embodiment of the invention, it is provided that the inflow surface is a metal surface, especially a surface made from steel, which is provided with first cutouts as inflow openings. Alternative materials for this can be brick, ceramic or glass. A metal surface is preferred, however, since this on the one hand is to be provided inexpensively and on the other hand also satisfies the demands on the operating temperature and the mechanical properties. Therefore, it is a requirement, for example, that the inflow surface at least partially supports the granular heat storage medium which is located in the interspace. As a result of the large quantities of granular heat storage medium which are sometimes held by the heat accumulator, the forces upon the inflow surface which occur in the process are considerable so that this has to be of a mechanically very resilient design. Metal is especially suitable for this purpose. [0030] According to a further embodiment of the heat accumulator according to the invention, the granular heat storage medium can comprise a bulk consisting of stones. Therefore, pebbles, for example, can be used as well as fragments of stone or brick chippings. These are easy to acquire and are inexpensive. Even metal chippings may be suitable as granular heat storage medium, however, since on the one hand they have a large heat capacity, but on the other hand can also provide sufficient free spaces for the gas flow. Locally available media are preferably used in the heat accumulator. On account of the relatively large quantities of heat storage medium which are held by the heat accumulator, waste or inexpensive building materials, such as stones, are especially suitable. In order to therefore advantageously distribute these in the heat accumulator or in the interspace of the heat accumulator, it is necessary that these are loose or at least distributable. A loose and at the same time granular heat storage medium comprises individual grains, or a fragment of stone, which are individualized by other component parts. [0031] According to a further embodiment of the present invention, it can be provided that the bulk of granular heat storage medium has an average grain size of at least 1 cm in diameter, preferably an average grain size of at least 3 cm in diameter. Such grain sizes allow the forming of sufficiently large free spaces between individual grains so that the relatively hotter gas, which is introduced for heat yield into the heat accumulator, can flow through the granular heat storage medium without excessive flow resistance. This especially applies to flow resistances at flow velocities of the gas of 0.1 to 0.5 msec. [0032] A further advantageous embodiment of the heat accumulator according to the invention is achieved when the bulk of granular heat storage medium is arranged in the heat accumulator in layers and a gas-impermeable convection barrier for the gas is provided between the individual layers. The layers can extend in this case over the entire interspace of the heat accumulator, or only over parts, however. The convection barriers, moreover, can be also be designed as partially gas-permeable convection barriers. It is only essential that the convection barriers enable a deflection of the convecting gas. Therefore, the convection barriers are provided, for example, so that the gas during the convection process impinges upon the convection barriers and is diverted by these into other areas. Especially when the convection barriers are arranged horizontally can an efficient convection prevention be achieved by means of the barriers. As a result of the convection barriers, the gas which is introduced into the heat accumulator is diverted in such a way that it counteracts the forming of a temperature distribution level which is excessively deformed as a result of the convection. The forming of a suitable temperature distribution profile can be encouraged specifically owing to the fact that the relatively hotter gas, which flows in through the inflow openings of the inflow surface, cannot move freely against the gravitational force as a result of the convection, but is directed through the convection barriers. [0033] According to a further embodiment of the present invention, the outflow surface can be a metal surface, especially a surface made from steel, which is provided with second cutouts as outlet openings. As previously in the case of the inflow surface, the outflow surface can alternatively also consist of brick, ceramic or glass. On account of the high costs which are to be foreseen for the outflow surface when using other materials, metal is the preferred material. [0034] According to a further embodiment, it can be provided that the inflow surface and/or the outflow surface supports the granular heat storage medium by contact. The inflow surface or the outflow surface therefore has to therefore be able to absorb sufficient mechanical supporting force in order to support the granular heat storage medium. In this case, it is naturally understandable to the person skilled in the art that the inflow openings which are incorporated in the inflow surface and the outflow openings which are incorporated in the outflow surface may be selected to be of only such size that on the one hand the gas flow is not significantly obstructed and on the other hand the granular heat storage medium cannot pass through the inflow surface or outflow surface. The selection of a suitable size of the inflow openings and of the outflow openings is understandable to the person skilled in the art. According to the embodiment, the inflow openings or outflow openings could also be lined with suitable grids. [0035] According to a further embodiment of the present invention, the heat accumulator is at least 10 m, preferably at least 15 m, in its vertical extent and at least 30 m, preferably at least 45 m, in its horizontal extent. The horizontal extent of the heat accumulator is especially greater than its vertical extent. According to another embodiment, the horizontal extent corresponds to a diametrical horizontal extent. Therefore, on the one hand it can be ensured that the heat accumulator can store sufficient quantities of heat for storing surplus energy from a power plant process, but on the other hand it can be minimized by and large with regard to its space requirement. It can also be conceivable to sink the heat accumulator far enough in a recess in the ground so that it no longer projects from this. [0036] According to a further embodiment of the heat accumulator, it is provided that the outflow surface is enclosed by a thermal insulation which is at a distance from the side of the outflow surface which faces away from the granular heat storage medium and so determines an outflow passage between the outflow surface and itself, by means of which the gas issuing from the outflow openings can be discharged. In this outflow passage, the relatively colder gas issuing from the interspace of the heat accumulator is discharged. Formed on account of the typically issuing quantities of gas is a gas flow which surrounds the outflow surface and at the same time exerts an insulating effect upon this. Particularly when the gas issuing from the outflow openings is distributed uniformly through the outflow openings can the developing air flow be advantageously taken into consideration as an additional insulation layer within the overall insulation concept of the heat accumulator. [0037] Also to be taken into consideration is that the relatively colder gas issuing from the outflow openings has already at least partially yielded its energy on its way through the interspace of the heat accumulator, and therefore has a lower temperature level. Therefore, the demands upon the thermal insulation are also lower to the effect that they are to ensure insulation of the heat accumulator at relatively lower temperatures without damage. The situation can sometimes prove to be different in the case of thermal insulations which have to limit the interspace of the heat accumulator towards the top against the upwardly convecting gas. Since higher temperatures are established in the interspace, typically in the upper regions, on account of the gas convection, thermal insulation means, which can withstand these higher temperatures but at the same time ensure good insulation, are also to be provided there. [0038] According to a further embodiment of the present invention, it can be provided that the thermal insulation is also enclosed by a housing which is gas tight at least in certain areas. This housing which is gas tight at least in certain areas ensures that the gas issuing from the outflow openings of the outflow surface cannot flow out of the heat accumulator in an uncontrolled manner even in the event of an undesirable penetration through the thermal insulation. The housing especially assists the forming of a defined gas flow between the outflow surface and the thermal insulation or between the outflow surface and the gas tight housing. [0039] According to a further embodiment of the invention, it is provided that the side of the passage of the inflow surface facing the outflow surface is at a distance of at least 15 m, preferably of at least 20 m, from the outflow surface. According to this, the distance which is to be covered by the relatively hotter gas in the interspace of the heat accumulator is at least 15 m, or preferably 20 m. On account of the large flow distances, it can be ensured that the relatively hotter gas transfers a large part of its energy to the granular heat storage medium when flowing into the interspace of the heat accumulator. Moreover, these flow distances ensure the storage of large quantities of heat energy which are also able to drive power plant processes during a discharging process. [0040] According to an embodiment of the method according to the invention, it is provided that for charging the heat accumulator the relatively hotter gas is introduced into the heat accumulator with a mass flow of at least 10 kg/sec, especially of at least 40 kg/sec. These mass flow values are especially preferred for air as the gas. As a result, it can be ensured on the one hand when the heat accumulator is being charged that sufficiently large quantities can be introduced into the heat accumulator, and on the other hand the efficiency of a heat accumulator operated in such a way can be noticeably increased. [0041] According to a further embodiment of the method, it can be provided that the heat accumulator when being charged is not fully charged up, especially charged at most to 70% of the possible amount of energy absorption at a predetermined temperature level of the relatively hotter gas. According to other suitable embodiments, the charging of the heat accumulator to 90% or 80% at most, or even to 60% or 50% at most, of the maximum possible amount of energy absorption, can be carried out. These upper limits correspond according to the embodiment to a maximum desired charging of the heat accumulator. By avoiding the complete charging up of the heat accumulator, it can especially be ensured that the regions of the interspace filled with the granular heat storage medium which are located closer to the outflow surface can constitute a suitable heat insulation layer for the regions which are located closer to the inflow surface since they are relatively colder and therefore have lower exergetic losses. If the charging according to the embodiment is not progressed up to a maximum possible value (i.e. a complete charging with essentially an equal distribution of temperature inside the interspace which is filled with the granular heat storage medium), the relatively colder regions of the interspace which is filled with the granular heat storage medium can exert an advantageous thermal insulation with regard to the relatively hotter regions of the interspace which is filled with the granular heat storage medium. [0042] According to a further embodiment of the method, it can also be provided that during the charging, or in a charged state, a temperature drop is formed, or has formed, towards the outflow surface between the inflow surface and the outflow surface. The charging state in this case is especially a state in which the charging is not carried out to a maximum possible value (i.e. essentially to the equal distribution of temperature inside the interspace which is filled with the granular heat storage medium). According to the embodiment, relatively colder regions are then formed and have a heat insulating effect on the relatively hotter regions of the interspace which is filled with the granular heat storage medium and can thereby counteract an exergetic energy loss. According to the embodiment, the temperature drop can be such that there is a temperature difference of at least 25%, preferably of at least 50%, between the inflow surface and the outflow surface. [0043] According to a further embodiment of the invention, it is provided that during the charging, or in a charged state, a temperature distribution, which does not have a linear characteristic, is formed, or has formed, between the inflow surface and the outflow surface. Such a characteristic can again contribute to relatively colder regions in the interspace which is filled with the granular heat storage medium having a heat insulating effect on the relatively hotter regions of the interspace and so being able to counteract an exergetic energy loss. As a result of a suitable temperature distribution, the exergetic energy loss can be advantageously adjusted. [0044] With reference to figures, specific exemplary embodiments of the present invention are described in detail below. In this case, the invention is not limited to these embodiments but claims the inventive idea in its most general form. Moreover, the individual features which are represented in the subsequent figures are claimed in combination with the other depicted features and also as individual features. [0045] Furthermore, reference is to be made to the fact that the embodiments which are shown in the subsequent figures are purely schematic representations. Limitations with regard to the functionality or specificality cannot be derived therefrom. BRIEF DESCRIPTION OF THE DRAWINGS [0046] In this case, in the drawing: [0047] FIG. 1 shows a first embodiment of the heat accumulator according to the invention in a lateral cross-sectional view; [0048] FIG. 2 shows a cross-sectional view from the top through the heat accumulator which is shown in FIG. 1 ; [0049] FIG. 3 shows the passage of the inflow surface, as can used, for example, in the depicted embodiments; [0050] FIG. 4 shows a further embodiment of the heat accumulator according to the invention in a lateral cross-sectional view; [0051] FIG. 5 shows the characteristic curve of two different heat distribution profiles, which can ensue after charging of the heat accumulator, inscribed into the outer limits of the heat accumulator; [0052] FIG. 6 shows a schematic flow diagram for representing a first embodiment of the method according to the invention; [0053] FIG. 7 shows a schematic flow diagram for representing a second embodiment of the method according to the invention. DETAILED DESCRIPTION OF INVENTION [0054] FIG. 1 shows a lateral cross-sectional view through a first embodiment of a heat accumulator 1 according to the invention, which for the introduction of a relatively hotter gas 2 has an inflow surface 10 , provided with inflow openings 11 , which is formed to produce a passage 12 . During a charging process, gas 2 flows into the passage 12 and enters the interspace 30 of the heat accumulator 1 through the inflow openings 11 . On account of direct heat transfer, the thermal energy of the gas is at least partially transferred to the heat storage medium 40 which is located in the interspace 30 . The heat storage medium 40 has a suitable granularity so that the gas 2 can stream through or flow through the free spaces between the individual grains of the heat storage medium 40 . The passage 12 , depending on the embodiment, can have suitable inflow openings. The passage 12 can especially be closed off at the end by a closure 13 , wherein the closure 13 itself can be provided with cutouts or openings for outflow of the gas 2 . [0055] The gas 2 which has been discharged from the passage 12 and transferred into the interspace 30 flows into the regions of the interspace 30 which are located further away from the passage 12 —on account of a gas pressure building up in the heat accumulator—and finally reaches the outflow surface 20 in which outflow openings 21 are provided. On its way to there, the originally relatively hotter gas 2 partially yields its heat energy to the granular heat storage medium 40 and as relatively colder gas 2 issues from the outflow openings of the outflow surface 20 , in order to be discharged. For suitable heat insulation, the outflow surface 20 is enclosed by a thermal insulation 50 and between it and the thermal insulation 50 forms an outflow passage 60 . In this outflow passage 60 , the relatively colder gas 2 issuing from the outflow openings 21 is discharged and consequently forms a flow layer which additionally exerts an insulating effect upon the interspace. In order to prevent gas loss from the heat accumulator 1 , the thermal insulation 50 can furthermore be enclosed by an at least partially gas-impermeable housing 70 which in addition to the function of a mechanical protection can also ensure the gas tightness. [0056] As can be seen in the illustration, the passage 12 has a cylindrical symmetrical shape which has a first symmetry axis SA1. The outflow surface 20 also has a cylindrical symmetry, the second symmetry axis SA2 of which coincides with the first symmetry axis SA1 of the passage 12 . The cylindrical symmetrical passage 12 and the cylindrical symmetrical outflow surface 20 are therefore arranged coaxially to each other. As a result, it is ensured that when the heat accumulator 1 is being charged a similarly cylindrical symmetrical temperature distribution profile is established in the interspace 30 of the heat accumulator 1 . On the one hand, this has the advantage that the relatively colder regions of the heat storage medium 40 in the interspace 30 which are located close to the outflow surface 20 are distributed uniformly around the hotter regions of the heat storage medium 40 which are close to the passage 12 . The advantageous insulating effect which results therefrom prevents a heat loss from the relatively hotter regions which are located close the passage 12 . Consequently, fewer demands are to be made on the thermal insulation 50 than would be the case if the relatively hotter regions of the heat storage medium 40 were located close to the inflow surface 20 . As a result of this, the material costs and also the provisioning costs are reduced. A higher-quality insulation is to be selected according to the embodiment, however, for the thermal cover 55 which is subjected to higher temperatures. These higher temperatures primarily ensue as a result of convection of the gas which is introduced into the passage 12 during the charging state. Since much hotter gas accumulates under the thermal cover 55 as a result of the convection of the gas in the interspace 30 , a higher temperature level is also achieved in these regions. As a result of this, the demands upon the thermal cover 55 are higher than upon the thermal insulation 50 . If, therefore, for example the thermal insulation 50 is achieved by means of a plastic coating, then only fire-resistant stones (chamotte) can sometimes be provided for the thermal cover 55 . [0057] FIG. 2 shows a cross-sectional view from the top through the heat accumulator 1 which is shown in FIG. 1 . Clearly to be seen here is the cylindrical symmetrical forming of the passage 12 and also of the outflow surface 20 . The grains of the heat storage medium 40 which are arranged in the interspace 30 are shown only schematically. These grains of the heat storage medium 40 can represent a suitable bulk of stones, for example. The entire interspace 30 between the inflow surface of the passage 12 and the outflow surface 20 is typically filled by the heat storage medium 40 . The filling can essentially be carried out uniformly. Also conceivable, however, is the provision of passages in the heat storage medium 40 which promote a faster flow of the gas 2 . As a result, the heat transfer to the heat storage medium 40 may admittedly no longer be carried out in a comparably efficient manner, but in this way the flow resistance can be suitably reduced. [0058] FIG. 3 shows a schematic view from the side of a passage 12 of the inflow surface 10 which has a number of inflow openings 11 . The depicted passage can, for example, be used in the embodiment of the heat accumulator 1 which is shown in the preceding FIGS. 1 and 2 . Especially shown on the passage 12 is an increase in inflow openings 11 per unit area extending from the top downwards according to the featured view. If the passage 12 is provided in conformance with an orientation in the heat accumulator 1 according to FIGS. 1 and 2 , comparatively less gas would discharge in the upper regions upon entering the passage 12 but more gas would discharge in the lower regions of the passage 12 . Therefore, a lower heat input into the regions which are located close to the inflow openings 11 in the upper region of the passage 12 can be ensured, but in relation to this a higher input into the regions which are located close the inflow openings 11 in the lower region of the passage 12 can be ensured. On account of the convection of the flow gradient which ensues in the interspace 30 , relatively hotter gas rises from the bottom upwards, wherein at the same time it flows from the passage 12 towards the outflow surface 20 . As a result, heat from the lower regions is transferred into the upper regions, wherein taking into consideration the originally lower input as a result of the lower number of inflow openings 11 per unit area in the upper region of the passage 12 , a more uniform temperature profile can develop. [0059] In order to counteract these convection effects, it can also be provided to fill the interspace 30 of the heat accumulator 1 in layers, wherein convection barriers 45 are provided between individual layers. Such convection barriers are shown in FIG. 4 . These convection barriers 45 can consist of gas-impermeable, or only partially gas-permeable, material. In order to suitably direct the quantities of relatively hotter gas 2 which are introduced into the interspace 30 , in order to counteract the convection effects, the convection barriers 45 can be arranged equidistantly from each other or even at irregular distances from each other. Furthermore, the convection barriers 45 can extend over the entire widths of the interspace of the heat accumulator 1 or only over partial areas thereof. Moreover, it can be advantageous not to align the convection barriers horizontally in relation to each other but to undertake an angled arrangement in relation to each other. As a result, a directed guiding of the relatively hotter gas 2 which is present in the interspace 30 can be possible in a better way. [0060] FIG. 5 shows two different heat distribution curves (WV1 and WV2) which are schematically inscribed in an embodiment of the heat accumulator 1 according to the heat accumulator 1 which is shown in FIG. 1 and FIG. 4 . [0061] The first heat distribution curve WV1 as well as the second heat distribution curve WV2 are produced as isotherms through the interspace 30 of the heat accumulator 1 in cross section. These isotherms correspond, for example, to the temperature level of 200° C., or another temperature which is to be specified. As is easy to see, the first heat distribution curve WV1 extends close to the thermal cover 55 further towards the outflow surface 20 than the second heat distribution curve WV2. This effect ensues, for example, if the gas rises upwards on account of stronger convection of the relatively hotter gas in the interspace 30 , and in regions which are located relatively further up is moved in the direction of the outflow surface 20 by the gas pressure which prevails in the interspace 30 . This convection movement of the hotter gas 2 can be opposed by provision being made in the interspace 30 —as shown in FIG. 4 , for example, —for convection barriers 45 which no longer permit free convection from the bottom upwards but guide the gas in a directed manner in predetermined directions. If such convection barriers 45 are provided, the effect of more heat being transported by convection from the lower regions into the upper regions of the interspace 30 can therefore be avoided. The second heat distribution curve WV2, which thus illustrates a case with improved heat distribution, shows that close to the thermal cover 55 the curve reaches a point which is less close to the outflow surface 20 in comparison to the first heat distribution curve. In contrast to this, these quantities of heat, however, which are not transported by convection are deposited in the lower regions of the interspace 30 . As a result of this, the second heat distribution curve WV2 also has a more pronounced lateral extent beneath the passage 12 in comparison to the first heat distribution curve WV1. [0062] The heat distribution curves WV1 and WV2 shown in FIG. 5 are to be only schematically understood and do not originate from a thermodynamically accurate calculation. However, they adequately illustrate what influence the convection can impose upon the heat distribution inside the heat accumulator. [0063] As already indicated in the preceding FIGS. 1 and 4 by the double arrows—which are to illustrate the flow of the gas 2 —the heat accumulator 1 can be operated both in a charging state and in a discharging state. In the charging state, relatively hotter gas 2 flows into the passage 12 and flows through the interspace 30 towards the outflow surface 20 . If the heat accumulator 1 is operated in the discharging state, however, relatively colder gas flows in via the outflow passage 60 through the outflow openings 21 of the outflow surface 20 and during its path through the interspace 30 absorbs heat from the heat storage medium 40 , after which a relatively hotter gas flows into the passage 12 of the inflow surface 10 and can be extracted from this. For reasons of clarity, however, the charging state has preferably been considered. [0064] FIG. 6 shows a schematic flow diagram for representing a first embodiment of the method according to the invention. In this case, for charging the heat accumulator relatively hotter gas 2 is introduced into the passage 12 of the inflow surface 10 of a heat exchanger 1 . The introduction is terminated at a point in time which lies before a point in time at which the heat accumulator 1 would be fully charged. This state is the charging state according to the embodiment. As a result, it is ensured that the granular heat storage medium 40 in the interspace 30 has regions between the inflow surface 10 and the outflow surface 20 which are relatively colder than others. These relatively colder regions are suitable for thermally insulating the relatively hotter regions which are located closer to the inflow surface 10 . [0065] FIG. 7 shows a schematic flow diagram for representing a second embodiment of the method according to the invention. According to this, for charging the heat accumulator relatively hotter gas 2 is introduced into the passage 12 of the inflow surface 10 . The introduction is terminated at a point in time at which there is a temperature drop in the heat storage medium 40 between the inflow surface 10 and the outflow surface 20 . This state is the charging state according to the embodiment. As a result, it is ensured that the granular heat storage medium 40 in the interspace 30 has regions between the inflow surface 10 and the outflow surface 20 which are relatively colder than others. These relatively colder regions are suitable for thermally insulating the relatively hotter regions which are located closer to the inflow surface 10 . [0066] Further embodiments come from the dependent claims.

A heat store for storing at least 100 MWh of thermal energy of a relatively warmer gas in a charging state and for giving off thermal energy to a relatively colder gas in a discharging state is provided. In the charging state, the heat store has at least one inflow surface, provided with inflow openings, for introducing the gas, and at least one outflow surface, provided with outflow openings, for discharging the gas after giving off heat to a granular heat storage medium, wherein the inflow surface is formed at least in certain portions into a channel which is surrounded, in particular completely, by the outflow surface, and wherein an intermediate space in which the granular heat storage medium is arranged is defined between the inflow surface and the outflow surface.

FIELD OF INVENTION This invention is related to oxide dispersion strengthened (ODS) iron-base alloys. More particularly, this invention is related to an improved method of forming mechanically alloyed (MA) oxide dispersion strengthened sheet with controlled grain size. BACKGROUND OF THE INVENTION Iron-base oxide dispersion strengthened alloys (iron-base ODS alloys) have been developed for high temperature applications. Chromium and aluminum are typically added to an iron-base alloy for resistance to oxidation, carburization and hot corrosion. The alloy is strengthened with an oxide stable at high temperature, such as yttrium oxide. The oxide is uniformly distributed throughout the alloy as a finely distributed dispersoid by mechanically alloying the powder. Iron-base ODS alloys in the form of sheet are particularly useful for gas-turbine combustion chambers, components of advanced energy-conversion systems and high temperature vacuum furnaces. Generally, very coarse grains are desired in MA iron-base ODS alloys for high temperature rupture strength. The coarsening of the grains provides for increased rupture strength and decreased ductility. In sheet products, a minimum number of grains traversing the thickness may be required to provide optimal high temperature rupture strength. Typically, MA iron-base ODS alloys produced by a combination of extrusion and rolling have less than 3 to 4 grains comprising the sheet thickness. The small number of grains may cause mechanical properties to be quite variable depending on the number of grains, the orientation of the grain boundaries with respect to the axis of loading, and the orientation of the grains themselves. Variability in properties means that the designer must lower the design stresses to below that for the weakest experienced material. In addition, alloy ductility with coarse grains may also be erratic. Properties of sheet iron-base alloys are extremely process dependent. The forming history of sheet controls ultimate strength properties produced. For high temperature rupture strength it is desired to form a coarse pancake type grain structure by performing a combination of longitudinal and cross rolling. The pancake structure provides isotropic properties in the rolling and transverse directions. Forming MA iron-base powder into sheet has required a combination of hot working operations and cold working operations. Between cold rolling operations, an intermediate temperature anneal is typically used to increase ductility. Suarez et al, is U.S. Pat. No. 5,032,190 an improved process for achieving isotropic properties in the rolling and transverse directions. MA iron-base alloys have been formed into sheet using a multi-step process. First, iron-base alloys have been prepared by mechanical alloying metal powder components to form a suitable MA powder. MA powder was then encased in steel cladding to form a billet. The billet was then extruded at 1066° C. and hot rolled at elevated temperature. A pickling operation was then used to remove the can. To finish the sheet, the sheet was cold rolled at a temperature slightly above room temperature such as 100° C. to final size. Cold working is defined as rolling at a temperature at which work hardening occurs during deformation with very little, if any, work softening or relaxation. Cold rolling at temperatures slightly above room temperature was required because iron-base ODS alloys may have a ductile to brittle transition temperature at about room temperature. Optionally, an intermediate temperature anneal at about 1090° C. may be used in between a series of cold rolling operations to increase ductility. It is recognized that an intermediate temperature anneal may also affect the transition temperature. Cold working is desired to produce a sheet as close to finished gage as possible and to prevent oxide formation. However, cold working of ODS iron-base sheet has often produced sheet having less than 3 to 4 grains per thickness after a final anneal at about 1370° C. This large grain size increases stress rupture strength, but it does not provide the often desired properties of decreased dependence upon grain orientation. It is an object of this invention to provide a method for increasing control of ultimate grain size formed of annealed MA iron-base alloy. It is an object of this invention to decrease final grain size of annealed MA iron-base alloy that has been hot worked and cold worked to finished size. It is further an object of this invention to provide a method for decreasing grain orientation dependence and to increase sheet ductility of MA iron-base alloys. SUMMARY OF INVENTION The process of the invention relates to forming MA iron-base ODS alloy. A billet of iron-base ODS alloy is provided. The billet is consolidated at a temperature within a predetermined range of sufficient temperature for formation of coarse and fine grain sizes. The consolidated billet is worked into final form. The object is annealed to recrystallize grains to a size determined by the temperature of the consolidation and the working of the extruded billet. DESCRIPTION OF PREFERRED EMBODIMENT The method of the invention provides for controlling the grain size of an iron-base alloy. Control of consolidation temperature is used to increase the range of grain size ultimately producible. A combination of consolidation temperature and work history is used to control grain size and the number of grains across a given thickness of MA iron-base ODS alloy after a final anneal at a temperature of at least about 1340° C. Iron-base alloys that are particularly subject to excess coarsening include about 10 to 40% chromium and about 1 to 10% aluminum. In particular, the method of the invention would be especially successful for alloy MA 956. Alloy MA 956 is an iron-base ODS alloy having the following nominal composition by weight percent: ______________________________________Iron 74Chromium 20Aluminum 4.5Titanium 0.5Yttrium Oxide (Y.sub.2 O.sub.3) 0.5______________________________________ To produce alloys having decreased grain size, mechanically alloyed iron-base ODS alloy powder is introduced into a container. This operation consists of packing powder into a steel can. The steel canned powder is then consolidated at a temperature above about 1100° C. For purposes of the specification and claims, consolidation refers to methods of increasing density such as hot pressing, hot isostatic pressing and extrusion. For a further decrease in grain size, temperatures between 1121° C. and 1232° C. are used to consolidate the alloy. The consolidated MA iron-base ODS alloy is then preferably rolled at elevated temperature for initial thickness reduction. After rolling at elevated temperature, cold rolling at a temperature slightly above ambient is used to reduce to final thickness. The cold rolled material is work hardened with a very fine grain structure. For purposes of this specification, a coarse grain size is defined as a grain size above 10 micrometers and a fine grain size is defined a grain size below 10 micrometers. A final anneal is then used to recrystallize grains and relieve the stress from work hardening and coarsen the grains. For iron-base ODS alloys such as alloy MA 956 a combination of work history and high temperature is used to achieve grain coarsening. Work history from conventional hot consolidation, hot rolling and cold rolling provides conditions for producing coarse grains upon final anneal. However, billet consolidating at temperatures above 1100° C. provides flexibility in processing allowing production of coarse or fine grains. Samples were prepared using a 4 S attritor operated at 288 rpm under an argon atmosphere with a flow rate of 330 cm 3 /min. A processing time of 30 hours was used at a ball-to-powder ratio of 20:1. MA iron-base alloy produced had the composition (in weight percent) of: ______________________________________Cr Al Co Y.sub.2 O.sub.3 C O N Fe______________________________________20.8 5.5 0.98 0.86 0.02 0.49 0.093 Balance______________________________________ The attrited powders were canned and extruded through a 2.06 cm×5.72 cm die having a 6 to 1 extrusion ratio. Samples were extruded at 38.1 cm/sec at 982° C. and 1065° C. A sample extruded at 982° C. was elevated temperature rolled to a thickness of 1.27 cm, 0.635 cm and 0.318 cm in sequential elevated temperature rolling operations at 1093° C. A sample extruded at 1065° C. was elevated temperature rolled to a thickness of 1.27 cm, 0.635 cm and 0.318 cm in sequential elevated temperature rolling operations at 1204° C. The sample extruded at 1065° C. had a 1 mm grain length much shorter than the 10 mm grain length of samples extruded at 982° C. Subsequent testing has attributed grain size control primarily to consolidation temperature rather than rolling temperature. However, it is recognized that through modified or additional working, a coarse grain structure may be produced. Two samples of MA-Fe-Cr-Al alloy containing 0.5% Y 2 O 3 were prepared in 4000 gram batches in a 4 S attritor using 0.79 cm diameter 52100 steel balls. A pure argon atmosphere was used with a flow rate of approximately 200 cc/min to maintain a tank pressure of approximately 21 KPa. Powders were canned in cleaned 8.89 cm diameter mild steel cans which were sealed without evacuation. Powder cans were extruded at 982° C. and 1065° C. to a 6.03×1.90 cm cross section using oil and glass lubrication and graphite follower blocks. Samples were given a 1 hour heat treatment at 1316° C. followed by air cooling. Samples extruded at 982° C. recrystallized and grew to a coarse structure. Samples extruded at 1065° C. produced a grain structure much finer than samples extruded at 982° C. An extrusion of an iron-base MA956 alloy at 1270° C. followed by cold rolling and a heat treatment at 1371° C. yielded a strip with a 2-5 micrometer grain size. This 2-5 micrometer grain size provides thin sheet that is not as dependent upon on individual grain orientations. Generally, the greater the forming temperature of the billet, the smaller the grain size of the annealed product. Cold working an alloy after consolidation at temperature of at least 1100° C., has been found to be capable of producing a fine controlled ultimate grain size after recrystallization. It has been found that higher consolidating temperatures (at least 1100° C.) improve control of the final annealed grain size. When consolidating at temperatures of at least 1100° C., subsequent elevated temperature working and final annealing conditions may be adjusted to produce coarse or fine grains. In contrast, an extrusion consolidating step at 871° C.-927° C. followed by cold work and annealing at 1340° C.-1400° C. provides for a large grain structure. The maximum final grain size for eliminating crystal orientation dependency is determined by sheet thickness. It is desired that grains have a thin flat pancake structure in the sheet plane. This provides for the longest grain path across the sheet thickness. For example, a sheet thickness of 1.27 mm preferably has an average grain thickness of about 0.127 mm or less and a sheet thickness of 0.05 mm preferably has an average grain thickness of 5 microns or less. This maintains the average number of grains across a thickness at 8 to 10 or more. The lower limit for thickness of MA iron-base ODS alloys is about 0.05 mm. The process of the invention has been successfully used to provide grains having an average grain thickness as fine as 2-5 microns. This would provide an average of about 10 grains across a sheet having a thickness as thin as 0.02 mm. In conclusion, the invention provides for increased grain size control after final annealing. Most advantageously, the invention provides a method for decreasing final grain size of iron-base ODS alloy by increasing consolidating temperature prior to working. The invention facilitates the use of a final cold working operation to reduce sheets final thickness without forming coarse grains upon recrystallization. A fine grain product maintains low temperature ductility. The process of the invention has been used to produce grains as small as about 2-5 micrometers. This small grain size allows for thin sheets of MA 956 to be formed using initial hot working and final cold working operations. While in accordance with the provisions of the statute, there is illustrated and described herein specific embodiments of the invention. Those skilled in the art will understand that changes may be made in the form of the invention covered by the claims and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.

The process of the invention relates to forming MA iron-base ODS alloys. A billet of iron-base ODS alloy is provided. The billet is consolidated at a temperature within a predetermined range of sufficient temperature for formation of coarse and/or fine grain sizes during a final heat treatment. The consolidated billet is worked into final form. The object is annealed to recrystallize grains to a size determined by the temperature of the consolidation and the working of the extruded billet.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of and claims the benefit of priority under 35 U.S.C. §120 from U.S. patent application Ser. No. 09/630,971, filed Aug. 1, 2000, the entire contents of which is incorporated herein by reference. U.S. application Ser. No. 09/630,971 claims the benefit of priority under 35 U.S.C. §119 from United Kingdom Patent Application No. 9918284.2, filed Aug. 3, 1999. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data broadcast system and method and, more particularly, to a method of broadcasting data services with broadcast signals and a system for selectively providing portions of the broadcast data service to the user. 2. Description of the Related Art Digital television systems have become widely used for broadcast systems. The digital television systems provide digitisation and compression of the image to be broadcast with technologies such as MPEG-2 compression. The broadcast pictures are hence encoded and conveyed to the digital television receivers in the home as a digital data sequence. Digital television has a number of advantages over conventional analogue television, such as increased capacity and increased robustness to noise and interference. Digital television systems also allow many kinds of data to be carried seamlessly within broadcasts carrying audio and visual data. Hence, many new services can be provided through the digital TV receiver to the viewer. A popular analogue service that uses additional data carried within the broadcast transmission is the teletext service. The teletext service is carried as digital data within certain transmission lines of the vertical blanking interval (VBI) of the TV signal. The VBI is the time allowed for the raster scan to return to the top of the screen and hence this time is not used to carry any useful picture information. Some lines are set aside for teletext data and the digital data is modulated onto the broadcast TV signal. Teletext systems broadcast a number of “pages” of data in cycles with a page being typically updated every 2 to 3 minutes. The update cycle time depends on how many pages are broadcast in the cycle, there being only a small bandwidth available for the teletext data. Upon selecting a page, the viewer has to then wait for the page to be delivered as part of the cycle—this time will be on average half the total cycle time for all the pages. Typical teletext systems provide the latest news, sport and TV guide information and also reference information and advertising. Teletext systems are very useful for providing “headline” information such as sports results when there is no other means of obtaining the information. A very popular use for the teletext systems is to find out the latest information for some rapidly changing event such as a sports event. Often this can be the only way the viewer can obtain this information, because sports events are often not screened live, are carried as part of a pay-per-view service or have finished such that the programs are now carrying other content. Hence, this allows the viewer to catch up with “missed” content such as sports events or news broadcasts by other means using the data services. A problem with previous broadcast data services is that they communicate very little information—perhaps just the score of a football match for instance. The user, although not wanting to see the whole sports event, would like a little more information than just the score—maybe to see video of the goals or near misses in the example of a football match. However, to provide a service like this there are further problems. Simple data services such as teletext can be provided easily with a low bandwidth. Providing an enhanced data service with audio and visual data would require more bandwidth or take a lot longer to update and cycle the information. Viewers have different interests and priorities, so what is important to one viewer is of little interest to another. Screening news “highlights” in a sequence that repeats and updates every 15 minutes is not appealing to a viewer if they have one item they would like to see and have to wait an average of 7.5 minutes to see this item. Digital broadcast systems can provide more bandwidth for program content. However, this bandwidth is still at a premium. Using some of the bandwidth to provide broadcast data services can be considered wasteful, particularly if there is other content that could be screened at the same time to a reasonable audience. Indeed, screening live video and audio as a broadcast data service will still take up approximately 2 Mbit/s of bandwidth using MPEG-2 compression. OBJECTS AND SUMMARY OF THE INVENTION It is an object of the present invention to overcome the problems identified above. According to the present invention, there is provided a method of broadcasting a broadcast data service together with broadcast digital television data as part of a broadcast signal, the broadcast data service including television data. The method comprises broadcasting the television data of the broadcast data service as non-real time data. In this way, it is possible to allocate a relatively small bandwidth to the broadcast data service and yet allow television clips to be replayed by a receiver as part of the broadcast data service. The television clips may be transmitted in non-real time over an extended period and the data assembled in the receiver for display. The method may further comprise processing and/or compressing a block of the television data as a whole. Thus, compared to continuous processing or compression processes such as MPEG, a television clip or sequence may be taken as a whole before compression. This may enable much greater compression to be achieved than for the continuous processes used in normal broadcasting. The block may comprise data requiring off-line decoding. In particular, it is possible to compress a block of data representing a television or video sequence, broadcast it in non-real time and then store the data in a memory associated with the receiver. It is then possible to post process or decompress the data off line. Preferably, the method comprises, during normal broadcasting, only broadcasting portions of the broadcast data service required to replace previous respective portions which have been changed such that receivers of the broadcast signal may store all of the current portions of the broadcast data service and update the stored portions according to replacement portions received with the broadcast signal. In this way, the bandwidth required for maintaining an enhanced broadcast data service may be reduced, such that the cycle time may also be kept to a minimum. Furthermore, since receivers may use a memory to store the entire broadcast data service, near instantaneous access is possible for the users. According to the present invention, there is also provided a system for selectively providing portions of a broadcast data service transmitted together with broadcast digital television data as part of a broadcast signal, the portions including data portions having digital television data in non-real time. The system comprises a processor for extracting portions of the broadcast data service available from the broadcast signal, a memory for storing all of the current portions of the broadcast data service and a controller responsive to a selection signal to cause the memory to output selected portions of the broadcast data service. The processor is also for converting the digital television data of data portions into real time data. In this way, the system can receive television clips, video sequences and the like over the relatively narrow bandwidth used for the broadcast data service and, by storing the relevant portions in the memory, can process those portions to return the data to real time. Preferably, the digital television data of the data portions is compressed and/or processed and the processor processes the data portions off line. In this way, it is possible to make further use of the relatively narrow bandwidth available for the broadcast data service. Television data can be compressed to the maximum amount with little regard for the time required for decompression. Preferably, the processor processes the portions at times of low usage. The processor may be provided as a separate processor in the storage device. Thus, the processor can fit in decompression and processing of any previously received compressed/processed television data in amongst its other duties in the operation of the system. The processor may operate directly on the data in the memory. However, it is also possible for the processor to operate in a batch processing method with data loaded locally from the memory in small chunks. This may be particularly appropriate where the memory is provided separately from the processor and the processor has its own working memory. The processor may conduct processing using a predefined protocol. Thus, any processing or compression of the data might make use of an existing protocol such as “WinZip”. Alternatively, the processor could conduct processing using a downloaded protocol. This might provide greater flexibility to a system and/or prevent unauthorised decompression of the data. Similarly, the processor could conduct off line decryption of data using a key. The key could be downloaded by broadcast or other means such as a memory stick or smartcard. Preferably the controller is also for identifying corresponding extracted and stored portions and for replacing data portions stored in the memory with respective portions extracted from the broadcast signal. Thus, at the receiving end, a user's device continually updates the stored complete broadcast data service and is able to retrieve any desired selected portions of the broadcast data service in a near instantaneous manner. Preferably, the method of broadcasting includes additionally broadcasting all of the current portions of the broadcast data service to enable a user to obtain all portions of the broadcast data service soon after initial connection. This may be achieved by using a separate dedicated channel or by periodically using an expanded bandwidth at a time of low demand for the broadcast digital television data. The system may be provided with additional means for accessing the complete broadcast data service from a different channel. In this way, after a receiving system has been disabled for some time or has first been connected, the memory can be filled with the current version of the broadcast data service for future update. The receiving system may be constructed as a single integral unit comprising a digital television receiver. Alternatively, various components of the system may be constructed separately and linked by means of a network, such as using an IEEE 1394 interface. In this way, a single television receiver/display could provide all of the functions of the present invention. Alternatively, a television/display could be connected by means of an IEEE 1394 interface with a broadcast data service unit which either has its own receiver or makes use of the receiver of the television display to obtain the broadcast data service portions. Similarly, the memory could be provided in the broadcast data service unit or separately, for instance again connected with an IEEE 1394 interface. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a system for receiving broadcast data services according to the present invention; FIG. 2 illustrates a system for receiving broadcast data services according to the present invention; and FIG. 3 illustrates the periodic transmission of a complete broadcast service. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be more clearly understood from the following description, given by way of example, with reference to the accompanying drawings. The MPEG video and audio compression system is designed to provide a maximum amount of compression in a broadcast environment. The MPEG video and audio compression system is also designed to allow the decompression to be carried out with a limited amount of memory in the receiver. This allows the decompression system in the receiver to be implemented with less memory and processing—and hence more cheaply—than the compression system in the transmission head-end. Even though the digital encoding of information allows many more channels to be transmitted, there is still a limited bandwidth for the transmission of the information. Hence MPEG audio and video channels are constrained to a certain bit rate dependent on the bit rate available. There is a trade off between the number of channels carried and the video quality (dependent on the bit rate of the compressed video and audio signals) of the channels. Many new services other than just audio and video services can now also be provided using the digital television broadcasts. Data and information on the transmitted programs and other entirely new services such as home banking or shopping can be provided. Many of the data services are also carried in a “carousel” where the data is broadcast in a cycle. At any one time only one part of the data service is being broadcast, but over a fixed period—say fifteen seconds or three minutes, all the data will be broadcast. After this period the data is repeated either exactly the same, or with changes if any of the data needs to be changed. This method allows receivers to receive all the data for a service, but allows the data to be transmitted in a relatively small bandwidth. It is considered that in the broadcast environment, many of the systems used presently are designed to make use of the limited bandwidth available and also assume a limited amount of storage and processing resource in the receiver. This is indeed true for current systems as the bandwidth is fixed and the receivers have to be implemented as cheaply as possible to be affordable for the average consumer. Hence the data is broadcast assuming or knowing that the receiver has a certain limited amount of storage and processing power. This constrains the format and type of data that can be sent. For instance, data requires much processing power at the receiver, or data requiring a large amount of storage for processing at the receiver cannot be sent, since it is not practical to provide a receiver It is now proposed to use storage media such as magnetic disks and semiconductor storage devices to provide storage for the transmitted digital broadcasts. The use of digital storage devices provides many enhanced applications for the user, providing a far better user experience than that of present using conventional analogue storage technologies. The AV devices in the home can be in separate physical enclosures and needing interconnection. The key technology for interconnection of digital devices in the home is the IEEE1394 Serial Bus interface which provides a low cost, user friendly method to send audio, visual and control data between devices in the home. Hence a typical digital TV system arrangement in the home could have a digital TV receiver, display device, magnetic storage and DVD player all connected using IEEE1394 Serial Bus connections. Mass storage can also be alternatively or additionally provided integrated into a consumer device—for instance an integrated digital television receiver may incorporate a large magnetic storage. Finally, it is also possible to use a “Memory Stick”. This is a non-volatile memory held in a small package to allow data to be transferred between cameras, camcorders, PCs and other home AV devices. There are other formats also supported by other consumer electronics manufacturers. FIG. 1 illustrates schematically various components of a system for receiving a broadcast data service. A receiver 2 is provided for obtaining and demodulating transmitted data from an aerial, cable, satellite or the like. The demodulated data includes digital television data, together with associated broadcast service data. Under the control of a control panel 4 or remote control, a video processor 6 extracts data from a received signal for a selected video channel and displays that video channel on the display 8 . A processor 10 is also provided for extracting any broadcast service data from the received signal. The processor 10 may be provided together with the receiver 2 , together with the memory 12 , together with the controller 14 or separately. The data is stored in a memory 12 under the control of a controller 14 . A user may then select (possibly using the control panel 4 ) desired portions of the data broadcast service. Under the control of the controller 14 , the memory 12 then outputs appropriate data for display on the display 8 . The memory 12 can be provided as a magnetic disc, for instance as is commonly known as a hard disc drive, a semiconductor memory or other means. The system of FIG. 1 can be provided integrally within a television unit. However, it is also possible for various components of the system to be distributed around a network, for instance using the IEEE 1394 interface. This is illustrated in FIG. 2 . The system may be provided merely with an external storage device. Similarly, the system may be provided as a broadcast service unit for connection to a television display and the broadcast service unit may itself have an internal memory or use an external memory and may itself have a processor. Just as with an integral design, the broadcast service unit can obtain received digital data from the receiver, process portions of the data appropriately and provide selected portions to the television display upon demand. With regard to transmission bandwidth of a broadcast service, an audio/visual stream can typically consume 2 Mbit/s using current MPEG-2 compression technologies. This could be construed as wasteful. By making use of the memory of the system, it is possible to broadcast the audio and visual data at a rate slower than real time. The audio and visual data is extracted from the broadcast data service and stored in the memory 12 of the system. When the audio/visual data is required for playback, the system can then retrieve the data at the required data rate allowing replay in real-time. In this way, by halving the broadcast rate of the audio/visual data, the bandwidth consumption of that portion of the service would also be halved. Although the cycle time would therefore also be doubled, by means of the memory of the system, access would be immediate unless a user happened to request a portion while it was being broadcast. With the proposed mass storage technologies now being implemented in consumer audio/video devices in the home, there are significant changes in the processing potential and storage available to the digital television receiver. Increased storage can allow different and possibly more effective compression and pre-processing to be applied to broadcast data. A large amount of storage allows broadcast to be downloaded as a whole block of data. This block of data is then processed as a whole, rather as a broadcast stream, where only a small fraction of the broadcast data is processed as it passes through the receiver. Thus, the video data can be compressed using a completely different non-streaming algorithm other than MPEG and be subjected to off-line compression/decompression as discussed. The increased storage also allows data to be stored for later processing. This effectively increases the processing power available in the receiver. Since the data is stored “offline” the receiver can then process the data as a background task or times of low usage. When the data is fully processed then it can be made available to the user. The video need not only be sent at slower than real time (for “trickle feed”). It could also be sent faster than real time, for instance for a mass video dump during the night. Additionally, the data can be sent in a more interactive manner. For instance, there can be an almost permanent return channel connection from the receiver to the broadcast headend. This headend can field the requests from the receiver population and broadcast the data (video or whatever) according to the demand for each item. In this case, heavily requested items are broadcast first. Once broadcast, the item is cached locally so that, if requested again, the receiver displays it locally. Thus, a popular item is broadcast a lot to start with and then the requests fall off and allow less popular items to be broadcast. For a broadcast video program, it is also possible for certain sections to be marked as “highlights”. Just these can then be stored, or the whole video stored, so that the highlights can be skipped between by the user later. The “offline” processing can be carried out in different ways It can be carried out by the processor of the digital TV receiver operating directly on the data on the mass storage device. It can be carried out by the processor of the digital TV receiver in a “batch” processing method with the data loaded locally from the mass storage device in small chunks. It can be performed by a processor local to the mass storage device. There are a variety of ways of processing the data on the mass storage device to provide “post-processed” data that can then be used by the digital TV receiver. Post-processing or decompression of data can be conducted using an existing pre-defined protocol such as “WinZip”. Post-processing or decompression of data can be conducted using a downloaded protocol. Post processing of data can be conducted to provide a new set of data. For example, processing two video streams to provide a new video stream—perhaps a “reverse angle” or “birds eye” view of a video sequence. Offline decryption of a file can be conducted using a key provided to the user by broadcast or other means (on memory stick or smart card). Data may be input from another source that is then post processed using broadcast data. Offline compression or processing of video data can be conducted (perhaps DV format data from a digital camcorder) for later re-transmission by e-mail, memory stick, i.LINK, or other means. It could also be construed as wasteful using bandwidth to cycle the same content only with slight updates each time rather than for “real” live content such as films, news and sports broadcasts. In a service where portions of the broadcast data service are cycled, there is a trade off between the bandwidth consumed by the service and the cycle rate. The service can offer a rapid update rate if it consumes a large amount of bandwidth. That bandwidth can be reduced, but will result in cycle time being increased. For the broadcast of broadcast data services, such as teletext, data is cyclically processed and provided to the user. It is now proposed to provide enhanced broadcast data services which will include more data. Unless substantial bandwidth is used, this will result in extended cycle times. In particular, if an enhanced service showing audio/video clips and data has a very long cycle time, then the service will be undesirable for the intended application of a quick newsflash style update on the days news or sports events. To overcome this problem, it is proposed to store an entire cycle of a broadcast data service such that the user can display any portion of the service instantaneously at any time. All portions of the broadcast data service of the cycle are stored in a memory. Indeed, the data portions may be obtained when a user is not viewing the broadcast data service or has the receiver on standby. For the user of the service, the most visible parameter is the cycle rate. The viewer will want to have up-to-date information as soon as possible and will not want to have to wait. Hence, this is one of the key requirements for the service. On the other hand, for the service provider, the bandwidth consumed is probably the most important parameter. The bandwidth consumed by, in particular, data broadcast service affects the bandwidth available for other broadcast data services and television data itself. A reduction in the bandwidth available for other services is hence likely to affect the revenue available to the service provider. For many broadcast data services, large numbers of the portions of a broadcast data service remain the same for each cycle. For instance, for traditional style pages as used with teletext, most pages might remain the same from one cycle to the next. Similarly, when transmitting audio/visual news or sports clips with a broadcast data service, it is likely that the same clips will be provided for an extended period of time during the day. In order to take advantage of this fact, it is proposed to transmit only portions of the data broadcast service which have changed from one cycle to the next. In this way, there may be provided a relatively fast update rate for information on the service with an efficient use of bandwidth for the service provider. A broadcast data service may take many different forms. It may be transmitted cyclically as a carousel of main information topics. It is also possible that, within each topic, further data portions are transmitted cyclically as a sub-carousel. Each data portion may consist of a traditional style page of data or may consist of other data such as image data or audio/visual data. An entire page or audio/visual data sequence can be considered as a portion or a page or audio/visual sequence can be made up of a number of portions. Irrespective, the system should provide the data in portions which can be replaced individually in such a way as to update the overall broadcast service. Hence, individual bytes of data or groups of bytes could be considered as “portions” provided that the system allows individual replacement of such portions. However, for very small portions, such as individual bytes, the protocol overhead for embodying the system is likely to be undesirably high. For a receiver that has no previously stored content, the “differential” content will not be useful, as it will not comprise the full service. This situation will arise for instance when the memory of the broadcast service unit is first connected to the system. It is possible to configure the system such that over time, by storing all of the updated portions, the complete broadcast data service will be established. Alternatively, however, the full service could be broadcast either on a different dedicated channel (possibly by means of a non-broadcast download service) or at times when the demand for other conventional broadcast is lower. Referring to FIG. 3 , it will be seen that, at these times, the bandwidth allocated for those conventional services can be reduced. As a result, the bandwidth available for the broadcast data services can be increased. This allows a receiver to quickly update its stored broadcast service information with the full information service. Subsequently, in the normal way, the system can keep up to date with the service using the differential update stream. The service provided using this system could not only carry MPEG-2 encoded audio and video data, but, as discussed above, could also carry information which has been compressed and encoded using other more suitable or efficient protocols. For instance, a football match could take advantage of the fact that most of the content features a lot of green with only a few small moving areas. In this situation, an algorithm for decompressing and decoding could be delivered to the receiver and then executed by the receiver under a pre-defined protocol. Since received broadcast service data is being stored off line and the decoding operation does not need to be executed in real time, the processing requirements for the decompression and decoding are not so great. Hence, the receiver processor can decode the content as a background task for display later. It should be appreciated that the data content of the broadcast data service need not be limited to audio/visual data or traditional data pages. The content can be suitable for use by an interactive engine in the receiver/broadcast service data unit. In this way, a mixed service could be provided featuring text, graphics and audio/visual clips. Data portions may also comprise data requiring off-line decoding. The data need not necessarily be a program, but could be any sort of data. MPEG compression and decompression systems are designed to be used in a broadcast system with limited decompression memory in the receiver, a small delay (of the order of a second) in decode delay and a limited “pick-up” delay (where “pick-up” delay is the delay when a receiver is turned on and has to wait a few frames for a full “I-frame” when it can pick-up the transmission and start decoding). By virtue of the present invention, it is possible to use compression/decompression programs which rely on having the whole data file present to be able to execute. In particular, by storing the data off-line, such compression/decompression becomes possible and it is possible to provide alternative compression and decompression algorithms to provide better performance than with current MPEG based schemes.

A system for providing requested data sets of broadcast data service transmitted as part of a broadcast signal, including a broadcast headend configured to receive a data request from a receiver, and configured to broadcast requested data sets to the receiver in response to the data request from the receiver, a processor configured to periodically extract all of the requested data sets of the broadcast data service from a broadcast carousel included in the broadcast signal, a memory configured to store all of the requested data sets of the broadcast data service, defining a plurality of digital-audio/video-data-sets including television clips, a first controller configured to allow selection from a list of the plurality of sets of the digital-audio/video-data-sets, and a second controller responsive to a user initiated selection signal to cause the memory to output a user selected one of the plurality of digital-audio/video-data sets selected from the list, wherein the processor converts the digital-audio/video-data of the requested data sets of the broadcast data service into real time audio/video data.

CROSS-REFERENCE TO RELATED APPLICATION This application claims the priority benefit of Japanese Patent Application No. 11-369811, filed Dec. 27, 1999, the entire subject matter of which is incorporated herein of reference. This application is a continuation of co-pending application Ser. No. 09/625,178, filed Jul. 25, 2000. BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a semiconductor device, which has at least one dummy pattern to protect wiring patterns from corrosion. 2. Description of the Related Art A semiconductor device having a metalized wiring pattern in the related art is formed by the process described below with reference to FIGS. 8A through 8C. Referring to FIG. 8A, a semiconductor substrate 101 having circuit elements, such as transistors, in a circuit area of a chip area on its surface is prepared, and then, a metal layer which is formed of Aluminum are formed on the entire main-surface of the semiconductor substrate 101 . Then, metalized wiring patterns 102 are formed by etching the metal layer to make an interconnection of the circuit elements. Next, referring to FIG. 8B, a first insulating layer 103 , such as a silicon oxide layer, is formed on the entire main-surface of the semiconductor substrate 101 and on the exposed surface of the metalized wiring patterns 102 by the CVD process. After that, a SOG (Spin On Grass) layer 104 as a second insulating layer is coated on the first insulating layer 103 to planarized its surface. According to the spin coating process, the thick SOG layer is formed in an area where no wiring patterns is formed, and the thin SOG layer is formed on the wiring patterns. Then, a third insulating layer 105 , such as a silicon oxide layer, is formed on the SOG layer by the CVD process. After that, referring to FIG. 8C, the first insulating layer 103 , the SOG layer 104 , the third insulating 105 layer only in an grid line area is removed to make an opening 106 until the surface of the semiconductor is exposed. This process is very important to avoid cracking the semiconductor device at the scribing process. However, as the SOG layer is exposed at an edge 1000 of the opening 106 , moisture comes into the semiconductor device because the SOG layer has hygroscopicity. As a result, the metalized wiring patterns are corroded. SUMMARY OF THE INVENTION An objective of the invention is to resolve the above-described problem and to provide a semiconductor device having a dummy pattern to protect wiring patterns formed in the semiconductor device from corrosion. The objective is achieved by a semiconductor device including a semiconductor substrate having a grid-line area and a chip area, the chip area having a circuit area and a dummy area surrounding the circuit area, circuit patterns formed on the substrate in the circuit area, a first dummy pattern which is formed of the same material as the circuit pattern, formed in the dummy area, the dummy pattern encompassing the circuit area, a first insulating layer formed on an entire surface of the semiconductor substrate, a second insulating layer formed only on the first insulating layer which is formed on the semiconductor substrate and on the circuit patterns; and a third insulating layer formed on the exposed first insulating layer and the second insulating layer. The objective is further achieved by a method for manufacturing a semiconductor device including a step for preparing a semiconductor substrate having a grid-line area and a chip area, the chip area having a circuit area and a dummy area surrounding the circuit area, a step for forming a conductivity layer on the semiconductor substrate, a step for forming circuit patterns in the circuit area and a dummy pattern encompassing the circuit area in the dummy area by etching the conductivity layer, a step for forming a first insulating layer formed on an entire surface of the semiconductor substrate, a step for forming a second insulating layer on the first insulating layer, a step for removing the second insulating layer which is formed on the first insulating layer on the dummy pattern until the surface of the first insulating layer is exposed, a step for forming a third insulating layer formed on the exposed first insulating layer and on the second insulating layer; and, a step for removing the first, second and third insulating layers in the grid-line area. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more particularly described with reference to the accompanying drawings in which: FIGS. 1A through 1C are sequential sectional views for forming a semiconductor device of a first of fifth illustrative embodiments of the invention; FIG. 2A is a graph showing a relationship between the thickness of a SOG layer formed on the dummy pattern and the width (Lw) of the dummy pattern or the length (LS) between the dummy pattern and metalized wiring pattern, of the first embodiment; FIG. 2B is an enlarged sectional view at the edge of the circuit area to indicate the width (Lw) and the length (Ls 1 ) which is used in FIG. 2A; FIGS. 3A through 3C are sequential sectional views for forming a semiconductor device of a second of fifth illustrative embodiments of the invention; FIG. 4A is a graph showing a relationship between the thickness of a SOG layer formed on the second dummy pattern and the width (Lw) of the second dummy pattern or the length (Ls 1 ) between the second dummy pattern and metalized wiring pattern, of the second embodiment; FIG. 4B is an enlarged sectional view at the edge of the circuit area to indicate the width (Lw) and the length (Ls 1 ) which is used in FIG. 4A FIGS. 5A through 5E are sequential sectional views for forming a semiconductor device of a third of fifth illustrative embodiments of the invention; FIG. 6 is a sectional view of a semiconductor device of a fourth of fifth illustrative embodiments of the invention; FIG. 7 a is a sectional view of a semiconductor device of a fifth of fifth illustrative embodiments of the invention; FIG. 7 b is a enlarged plan view of the semiconductor device shown in FIG. 7 a ; and FIGS. 8A through 8C are sequential sectional views for forming a semiconductor device in the related art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1A, unillustrated circuit elements, such as transistors, are formed in a circuit area of the chip area on a main-surface of the semiconductor substrate 201 , and then, an unillustrated insulating layer is formed on the surface of the semiconductor substrate 201 . Next, a metal layer having a thickness of 600 nm, which is formed of Aluminum, is formed on the entire main-surface of the semiconductor substrate 201 , and then, metalized wiring patterns 202 are formed in the circuit area by etching the metal layer to make an interconnection of the circuit elements. Simultaneously, a dummy pattern 202 a , which is electrically isolated from the wiring pattern 202 , is formed in a dummy area by etching the metal layer. The dummy area is disposed between the circuit area and the grid-line area. A manufacturing margin area is located on either side of the dummy area from the circuit area and grid-line area, respectively. For example, a frame-shaped dummy area having a width of ((1000−0.05)−(800+0.05))/2 μm is formed, providing that the chip area has 1000×1000 μm, the circuit area whose center is correspondence to a center of the chip area, has 800×800 μm, and width of the manufacturing margin is 0.05 μm. Therefore, the circuit area is encompassed with the dummy area. Although the dummy pattern 202 a can be formed in the dummy area, preferably, the distance (L) between the edge 1000 of the chip area and an outer edge of the dummy pattern 202 a is set for over 10 μm. Next, referring to FIG. 1B, a first insulating layer 203 , such as silicon oxide layer, having a thickness of 200 nm is formed by CVD on the entire surface of the semiconductor substrate 201 . Then, a SOG layer 204 as a second insulating layer is coated only on the first insulating layer 203 which is directly formed on the semiconductor substrate 201 and which is formed on the metalized wiring patterns 202 to planarize the surface. That is, the SOG layer is not formed on the first insulating layer 203 , which is formed on the dummy pattern 202 a . The condition not to be formed the SOG layer on the dummy pattern is explained later. Then, a third insulating layer 205 having a thickness of 400 nm is formed by CVD on the SOG layer 204 and the exposed first insulating layer 203 which is formed on the dummy pattern 202 a. Then, referring to FIG. 1C, the first insulating layer 203 , the SOG layer 204 , and the third insulating layer 205 on the grid line area are removed until the surface of the semiconductor substrate 201 is exposed. In the process shown in FIG. 1B, the SOG layer is coated in the following condition and the thickness of the SOG layer 204 on the dummy pattern 202 a is measured in changing the width (Lw) of the dummy pattern 202 a or the length (Ls 1 ) between the dummy pattern 202 a and metalized wiring pattern 202 . A result of the measurement is shown in FIG. 2 A. (1) the material of the SOG layer: Concentration of Solid content is 5.2 wt % (2) the material of the SOG layer: Viscosity is 1.03 mPa.sec. (3) Rotary speed: 5000 rpm Referring to FIGS. 2A and 2B, the X axis shows the thickness of the SOG layer on the dummy pattern 202 a , and Y axis shows the width (Lw) of the dummy pattern 202 a or length (Ls 1 ) between the dummy pattern 202 a and metalized wiring pattern 202 . In FIG. 2A, the black circles shows the relationship between the thickness of the SOG layer and the width (Lw) of the dummy pattern 202 a where the length (Ls 1 ) is fixed to 2.6 μm and the width (Lw) is changed from 1 to 100 μm. In this case, it is found that if the width (Lw) is getting wider, the SOG layer becomes thicker. The with circles shows the relationship between the thickness of the SOG layer and the length (Ls 1 ) where the width (Lw) is fixed to 1.0 μm and the length (Ls 1 ) is changed from 0.9 to 5 μm. In this case, it is found that the thickness of the SOG layer on the dummy pattern 202 a is maintained to nearly zero even if the length (Ls 1 ) is set until 5 μm. As a result form this experimentation, if the width (Lw) is designed to 1.0 μm, the SOG layer is not formed on the dummy pattern 202 a . Therefore, if the dummy pattern 202 a having a width of 1.0 μm is formed, the SOG layer 204 which is adjacent to the grid-line area is completely isolated from the SOG layer 204 which is formed in the circuit area by the first insulating layer 203 formed on the dummy pattern 203 . According to the first embodiment of the invention, as the SOG layer 204 which is adjacent to the grid-line area is completely isolated from the SOG layer 204 which is formed in the circuit area by the first insulating layer 203 formed on the dummy pattern 203 , it is possible to protect the semiconductor device from moisture which comes into the semiconductor device through the SOG layer 204 . Further, as the dummy pattern 202 a can be formed with the metalized wiring patterns, simultaneously, it is not necessary to add some additional process. Furthermore, since the dummy pattern is formed outside of the circuit area, the surface of the semiconductor device at the peripheral area is planarized as the additional effect of the dummy pattern. The second embodiment is described below with reference to FIGS. 3A through 3C and FIGS. 4A through 4B. Referring to FIG. 3A, unillustrated circuit elements, such as transistors, are formed in a circuit area of the chip area on a main-surface of the semiconductor substrate 201 , and then, an unillustrated insulating layer is formed on the surface of the semiconductor substrate 201 . Next, a tungsten polycide layer having a thickness of about 3000 μm is formed on the insulating layer, and then, a lower dummy pattern 300 a (a second dummy pattern) is formed in a dummy area by etching the tungsten polycide layer. As well as the dummy area decried in the first embodiment, the dummy area of the second embodiment is disposed between the circuit area and the grid-line area. A manufacturing margin area is located on either side of the dummy area from the circuit area and grid-line area, respectively. Further, as well as the first dummy patterns 202 a in the first embodiment, the lower dummy pattern 300 a of the second embodiment having the width (Lw) can be formed anywhere in the dummy area, preferably, the distance (L) between the edge 1000 of the chip area and an outer edge of the lower dummy pattern 300 a is set for over 10 μm. Also, the circuit area is encompassed with the lower dummy pattern 300 a . Next, a borophosphosilicate glass (BPSG) layer 302 having a thickness of 800 nm is formed on the silicon substrate and the lower dummy pattern 300 a . The impurity concentrations of P2O5 and B2O3 in BPSG layer are 15 wt % and 10 wt %, respectively. Then, a thermal treatment is performed to the BPSG layer 302 for thirty minutes at 900 C in the nitrogen atmosphere to planarize its surface. After that, an aluminum layer having a width of 600 nm is formed on the BPSG layer 302 , and then, metalized wiring patterns 304 are formed in the circuit area by etching the metal layer to make an interconnection of the circuit elements. Simultaneously, an upper dummy pattern 304 a (first dummy pattern), which is electrically isolated from the wiring pattern 304 , is formed above the lower dummy pattern 300 a . The shape and side of the upper dummy pattern 304 a are almost the same as the lower dummy pattern 302 a. Next, referring to FIG. 3B, a first insulating layer 306 , such as silicon oxide layer, having a thickness of 200 nm is formed by CVD on the surface of the BPSG layer 302 , on the surface of metalized wiring patterns 304 and on the upper dummy pattern 304 a . Then, a SOG layer 308 as a second insulating layer is coated only on the first insulating layer 306 which the lower dummy pattern 300 a is not formed thereunder to planarize the surface. That is, the SOG layer is not formed on the first insulating layer 306 which is formed on the upper dummy pattern 304 a . The condition not to be formed the SOG layer on the upper dummy pattern 304 a is explained later. Then, a third insulating layer 310 having a thickness of 400 nm is formed by CVD on the SOG layer 308 and on the exposed first insulating layer 306 which is formed on the upper dummy pattern 304 a. Then, referring to FIG. 3C, the first insulating layer 306 , the SOG layer 308 , and the third insulating layer 310 on the grid line area are removed until the surface of the BPSG layer 302 is exposed. In the process shown in FIG. 3B, the SOG layer 308 is coated in the following condition and the thickness of the SOG layer 308 on the upper dummy pattern 304 a is measured in changing the width (Lw) of the lower and upper dummy pattern 302 a , 304 a or the length (Ls 1 ) between the lower and upper dummy pattern 302 a , 304 a and metalized wiring pattern 304 . A result of the measurement is shown in FIG. 4 A. (4) the material of the SOG layer: Concentration of Solid content is 5.2 wt % (5) the material of the SOG layer: Viscosity is 1.03 mPa.sec. (6) Rotary speed: 5000 rpm Referring to FIGS. 4A and 4B, the X axis shows the thickness of the SOG layer on the upper dummy pattern 304 a , and Y axis shows the width (Lw) of the lower and upper dummy pattern 302 a , 304 a or length (Ls 1 ) between the lower and upper dummy pattern 302 a , 304 a and metalized wiring pattern 304 . In FIG. 4A, the black circles shows the relationship between the thickness of the SOG layer and the width (Lw) of the lower and upper dummy pattern 302 a , 304 a where the length (Ls 1 ) is fixed to 2.6 μm and the width (Lw) is changed from 1 to 7 μm. In this case, it is found that the SOG layer becomes thicker if the width (Lw) is designed for over 2 μm,. The with circles shows the relationship between the thickness of the SOG layer and the length (Ls 1 ) where the width (Lw) is fixed to 1.0 μm and the length (Ls 1 ) is changed from 0.9 to 5 μm. In this case, it is found that the thickness of the SOG layer on the second dummy pattern 304 a is maintained to nearly zero even if the length (Ls 1 ) is designed until 5 μm. As a result form this experimentation, if the width (Lw) is set to 1 μm-2 μm the SOG layer is not formed on the upper dummy pattern 304 a . Therefore, if the upper dummy pattern 304 a having a width of 1 μm-2 μm is formed, the SOG layer 308 which is adjacent to the grid-line area is completely isolated from the SOG layer 308 which is formed in the circuit area by the first insulating layer 306 formed on the upper dummy pattern 304 a. According to the second embodiment of the invention, in addition to the benefits of the first embodiment, the following advantages can be obtained. Although the material of the lower dummy pattern 302 a is not limited for the metal such as tungsten polycide, if it is formed of the conductivity material, metalized wiring patterns can be formed with the lower dummy pattern 302 a . Further, the second embodiment of the invention can be adapted to any semiconductor device having multi-wiring layers without any additional processes. Furthermore, as the width (Lw) of the lower and upper dummy pattern 302 a , 304 a can be designed with a range from 1 μm to 2 μm, it becomes easier to design the total semiconductor device. The third embodiment is described below with reference to FIGS. 5A through 5D. Referring to FIG. 5A, unillustrated circuit elements, such as transistors, are formed in a circuit area of the chip area on a main-surface of the semiconductor substrate 201 , and then, an unillustrated insulating layer is formed on the surface of the semiconductor substrate 201 . Next, a metal layer which, is formed of Aluminum, is formed on the entire main-surface of the semiconductor substrate 201 , and then, metalized wiring patterns 402 are formed in the circuit area by etching the metal layer to make an interconnection of the circuit elements. Simultaneously, a first dummy pattern 402 a , which is electrically isolated from the wiring pattern 402 , is formed in a dummy area by etching the metal layer. As well as in the first and second embodiment, the dummy area is disposed between the circuit area and the grid-line area. A manufacturing margin area is located on either side of the dummy area from the circuit area and grid-line area, respectively. Further, as well as in the first embodiment, the first dummy pattern 402 a of the third embodiment having the width (Lw) can be formed anywhere in the dummy area, preferably, the distance (L) between the edge 1000 of the chip area and an outer edge of the first dummy pattern 402 a is set for over 10 μm. Also, the circuit area is encompassed with the first dummy pattern 402 a. Next, referring to FIG. 5B, a first insulating layer 404 , such as silicon oxide layer, having a thickness of 200 nm is formed by CVD on the entire surface of the semiconductor substrate 201 . Then, a multi-SOG layer 406 as a second insulating layer is formed on the first insulating layer 404 to planarize its surface. The multi-SOG layer 406 is formed by coating a SOG layer few times. That is, a first SOG layer is coated on the first insulating layer 404 . Then, after it is dried up, a second SOG layer is coated on the dried SOG layer. Next, referring to FIG. 5C, the multi-SOG layer is etched by the well-known RIE method under the conditions below until the surface of the first insulating layer 404 on the first dummy pattern 402 a is exposed. (a) Gas flow rate: CHF3/CF4/Ar=20/15/200 [sccm] (b) Pressure: 40 [Pa] (c) RF power: 200 [W] (d) Etching rate of the multi-SOG layer: 7.5 [nm/sec] Next, referring to FIG. 5D, the third insulating layer 408 having a thickness of 400 nm is formed by CVD on the multi-SOG layer 406 and the exposed first insulating layer 404 which is formed on the first dummy pattern 402 a. Then, referring to FIG. 5E, the first insulating layer 404 , the multi-SOG layer 406 , and the third insulating layer 408 on the grid line area are removed until the surface of the semiconductor substrate 201 is exposed. According to the third embodiment of the invention, in addition to the benefits of the first embodiment, the following advantages can be obtained. In the first and second embodiments, the SOG layer can not be formed thick. If it were formed thick, it would be formed on the first insulating layer on the first dummy pattern. However, as the multi-SOG layer can be formed thick in the third embodiment, the planarized surface can be obtained in the circuit area. The fourth embodiment is described below with reference to FIG. 7 . Referring to FIG. 7, a pair of inner and outer dummy patterns 500 a , 500 b (a third dummy pattern and a first dummy pattern) are formed in the dummy area. Each dummy pattern has a same width (Lw), and formed in the same method with the same size described in the first embodiment. The length (Ls 2 ) between the dummy patterns 500 a , 500 b is designed for over 0.9 μm. According to the fourth embodiment, in addition to the benefits of the first embodiment, the following advantages can be obtained. Even If the SOG layer 504 is formed on the first insulating layer 502 on the outer dummy pattern 500 b by accident, the semiconductor device can be protected from the moisture because the SOG layer 504 formed on the outer dummy pattern 500 b is isolated from the SOG layer 504 formed in the circuit are by the insulating layer formed on the inner dummy pattern 500 a. The fifth embodiment is described below with reference to FIGS. 7A and 7B. A bonding pad 601 is formed in a circuit area, and an outer dummy pattern 600 a (a first dummy pattern) is formed in a dummy area. The size, location and manufacturing process of the outer dummy pattern is the same as the dummy pattern described in the first embodiment. That is, a width of the outer dummy pattern is designed for 1 μm, and the length (L) is designed for 10 μm. A frame-shaped fourth dummy pattern 600 b is formed for surrounding the bonding pad 601 in the circuit area. The distance (Ls 3 ) between the bonding pad 601 and the fourth dummy pattern 600 b or the outer dummy pattern 600 a is designed for over 0.9 μm. The distance (Ls 1 ) between the metalized wiring pattern 600 and the outer dummy pattern 600 a or the fourth dummy pattern is designed for over 0.5 μm because of the same reason described in the first embodiment. The metalized wiring pattern 600 , the outer dummy pattern 600 b and the fourth dummy pattern 600 a are formed simultaneously by etching a conductive layer. According to the fifth embodiment, in addition to the benefits of the first embodiment, the following advantages can be obtained. As the bonding pad 601 is surrounded by the fourth dummy pattern 600 a , an SOG layer 606 , which is exposed to an opening 602 for the bonding pad 601 is isolated to the SOG layer 606 which is formed in the circuit area. Therefore, it is possible to protect the semiconductor device from moisture which comes into the semiconductor device through the SOG layer 204 exposed to the opening 602 . While the invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. For example, although silicon oxide layers are used for the first and third insulating layer in the first through fifth embodiment, a silicon nitride layer, a PSG layer, a BPSG layer can be used. Further, it is possible to change the width of the dummy patterns in the first through fifth embodiment based on the concentration of solid content of the SOG layer. If a high concentrate material for the SOG layer is used, the dummy pattern having a wide width may be formed. On the contrary, If a low concentrate material for the SOG layer is used, the dummy pattern having a short width may be formed. Also, in the third embodiment, it is possible to change the etching time based on the concentration of solid content of the SOG layer. Furthermore, in the second embodiment, the BPSG layer can be changed to other layer having thermal plagiarizing characteristics, such as a PSG layer. Various modifications of the illustrated embodiments, as well as other embodiments of the invention, will be apparent to those skilled in the art on reference to this description. Therefore, the appended claims are intended cover any such modifications or embodiments as fall within the true scope of the invention.

A semiconductor device includes a semiconductor substrate having a center area where an IC is formed and a peripheral area surrounding the center area, a first wiring pattern formed on the substrate in the center area, a second wiring pattern formed in the peripheral area wherein the second wiring pattern encompasses the center area, a first insulating layer formed over the center and peripheral areas, and a second insulating layer formed on the first insulating layer which is formed on the semiconductor substrate wherein the second insulating layer is not formed over the second wiring pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 62/221,660 filed on Sep. 22, 2015 which is hereby incorporated by reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH [0002] Not Applicable. APPENDIX [0003] Not Applicable. BACKGROUND OF THE INVENTION [0004] Field of the Invention [0005] The present invention relates to roof racks, and more particularly to clamping devices used to hold items to roof racks. [0006] Related Art [0007] Vehicle roof racks are more prevalent today than ever. Many vehicles have factory-installed roof racks on their base models. Vehicle owners have tremendous numbers of options for different types of roof racks and various accessories that clamp on or are otherwise affixed to the roof racks. However, current roof rack systems are restrictive in what they can carry, components are challenging to put on and take off, and roof rack accessories are expensive. In addition, roof racks differ widely from vehicle to vehicle, and manufacturer to manufacturer which results in a wide array of components and options that make it difficult for the consumer, and an inventory and logistics challenge for distributors and retailers. Accordingly, there remains a need for a simpler roof rack clamping system that is more economical, provides versatility and is easier to use than the currently available accessories. [0008] Roof racks systems contain roof rails, crossbars, and the accessories that are used to hold items to the roof racks. The roof rack side rails are positioned parallel to the sides of the vehicle, while the crossbars are positioned transverse between the side rails across the vehicle (from side-to-side). Roof rails attach to the vehicle in a variety of ways and the crossbars connect to these roof rails. Some vehicles and systems eliminate the roof rails and have the crossbars mounted directly to the vehicle roof. The roof rack accessories connect to the crossbars by a variety of methods, and typically include a clamp with jaws on opposite sides of the crossbar (top to bottom or front to back), one end which may be permanently closed (such as disclosed in U.S. Pat. No. 6,793,186) or could be used to adjust the distance between the top side and bottom side for crossbars having different thicknesses (such as disclosed in U.S. Pat. No. 8,210,407), and another end which has a closure and adjustment mechanism. [0009] Current roof rack clamping systems use different types of closure and adjustment mechanisms; many of the clamping devices having a threaded bolt connector that close and lock the jaws of the clamp, and other clamping devices use a buckle or strap. To adjust the tightness of the jaws and lock the closure in place, most clamping systems may use a device that is permanently connected to the clamp, such as a ratchet, a lever, a wing nut or nut with a knob, and some require the use of a separate tool such as a wrench to tighten a standard nut. In most designs, the clamping jaws fit around the front and back end of the crossbar (such as disclosed in the '186 and '407 Patents); in some other designs, the jaws fit around the front and back end of the crossbar rather than clamping around the top and bottom, such as disclosed in U.S. Pat. No. 8,496,145, and in at least one design, the jaws fit around the side rail, such as disclosed in U.S. Pat. No. 5,779,116. In yet another alternative design, a clamping device may have a strap and ratchet in which the strap actually serves both the role of one jaw of the clamp and the role of the closure mechanism, such as disclosed in U.S. Pat. No. 6,322,279. [0010] The clamping systems connect the accessories to the roof racks, and the accessories hold the items being transported such as bikes, skis, canoes, kayaks, roof boxes, and cargo bins. Accordingly, the clamping devices have attachment mechanisms to which the accessories are connected. In many current roof racks, the accessories are limited to mostly function for one particular type of sports equipment (carry bikes, canoes, skis, or some other type of sports equipment) but not all types of sports equipment or function to hold cargo carriers on the roof rack which results in additional expense when different types of equipment need to be carried. In many instances, the accessory has an equipment-specific connector, such as a skewer for securing bicycle forks or straps for securing a bicycle tire (as disclosed in the '407 Patent), or the accessory may have a universal connector that could be used to hold different accessory parts for various types of cargo. Universal connectors can be a threaded bolt, such as disclosed in the '186 Patent, or by some other type of mount, such as disclosed in U.S. Pat. Nos. 6,322,279 and 7,357,283. [0011] Most current clamping systems do not offer accessories for transporting large items that do not fit in the cargo carriers, and the accessories that are used to hold sports equipment are not suitable for large items such as lumber, piping, conduit, ladders, rugs, Christmas trees, etc. Even in those roof racks which have universal connectors and which may be used for oversized items, the accessories are often hard to attach and remove from the roof rack, resulting in most users leaving the components on the roof rack even when not in use. Currently known designs with a universal roof rack clamp which can be used for sports equipment, cargo carriers or oversized items are difficult to use, take significant time to install and remove, require two hands to operate, and/or are insecure. None of the prior art clamps have an elongated handgrip and a trigger handle that extend in the same direction to allow for single-handed installation of the clamp on the roof rack's crossbar and to provide for an actuated clamping mechanism. It would be beneficial to have a roof rack clamp that can be installed onto the roof rack with a single hand. It would be an additional benefit to have a roof rack clamp with an elongated handgrip and a trigger handle to provide a mechanical advantage for an actuated clamping mechanism. SUMMARY OF THE INVENTION [0012] A clamping system having opposing jaws, an elongated handgrip, an actuator, a trigger handle, and a mount. The opposing jaws are comprised of a fixed jaw and a movable jaw, where jaws can be opened and connected to a roof rack crossbar and closed onto the roof rack crossbar to secure the clamp and mounted accessories to the roof rack. The actuator can be a ratchet or a lever that is operated by the trigger handle. The jaws have one connection at their proximal ends where they extend from the handgrip, the trigger handle, and the actuator and can also have a second connection at their distal ends. A locking fastener, locking tabs or other locking means prevents the jaws from being opened when the lock is engaged and the jaws are closed. [0013] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. In particular, each one of the various embodiments of the present invention have various orientations, configurations, and arrangements of the components that provide additional advantages over the prior art references. Accordingly, it should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0014] The present invention will become more fully understood from the detail description and the accompanying drawings. The drawings constitute a part of this specification and include exemplary embodiments of the invention, which may be embodied in various forms. It is to be understood that in some instances, various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention; therefore the drawings are not necessarily to scale. In addition, in the embodiments depicted herein, like reference numerals in the various drawings refer to identical or near identical structural elements. [0015] FIGS. 1A-1C are side views of a slide ratchet bar clamp according to the present invention. [0016] FIGS. 2A-2E display the clamp of FIGS. 1A-1C as it is used with various mounting accessories to hold objects to the roof rack. [0017] FIG. 3A is an isometric view of an alternative slide ratchet bar clamp with a latching mechanism. [0018] FIG. 3B shows the clamp of FIG. 3A in a progression of orientations between the jaws relative to the roof rack crossbar. [0019] FIGS. 3C and 3D are an isometric view and side view, respectively, showing a modular mount and a progression of positions relative to the clamp of FIG. 3A . [0020] FIG. 4A is an isometric view of an alternative slide ratchet bar clamp. [0021] FIG. 4B shows clamp of FIG. 4A in a progression of orientations between the jaws relative to the roof rack crossbar. [0022] FIGS. 4C and 4D are an isometric view and side view, respectively, showing an accessory mount in a progression of positions relative to the clamp of FIG. 4A . [0023] FIGS. 5A and 5B are side views of another alternative slide ratchet bar clamp. [0024] FIGS. 6A and 6B are side views of a fulcrum ratchet clamp according to the present invention in an opened configuration and a closed configuration, respectively. [0025] FIGS. 7A and 7B are side views of a vice grip lever clamp according to the present invention in an opened configuration and a closed configuration, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0026] The following description of the preferred embodiment(s) is exemplary in nature rather than being limiting and corresponds with the drawings shown below and attached hereto. [0027] The present invention provides a secure clamping system that is significantly easier to use than currently known systems and takes much less time to install and remove from the roof rack. Additionally, the clamping devices of the present invention allow for single-handed operation when installing the clamps onto roof rack crossbars. Several embodiments of the roof rack clamps according to the present invention are particularly described below, including a bar clamp, a ratchet clamp and a vice grip clamp. Various orientations of the clamps are possible with the jaws of the clamp. For example, as explained in detail below, the bar clamp can be in a vertical or horizontal orientation relative to the jaws. [0028] As shown in each one of the embodiments, the clamp 10 of the present invention includes a pair of opposing jaws 12 , an elongated handgrip 14 , a trigger handle 18 , a clamp actuator 16 , and a mount 30 . The jaws include a fixed jaw 12 a and a movable jaw 12 b opposing the fixed jaw 12 a. The movable jaw 12 b has a spaced apart position 24 a and a proximate position 24 b relative to the fixed jaw 12 a, and the pair of jaws 12 has an opened configuration 26 and a closed configuration 28 when the movable jaw 12 b is in its spaced apart position 24 a and proximate position 24 b, respectively. Each one of the jaws 12 has an interior surface 32 a and an outer surface, and the interior surface 32 a preferably has a resilient pad 44 . The crossbar 500 fits through an opening 34 between the pair of jaws 12 when they are in their opened configuration 26 , and the crossbar 500 is contacted by the interior surface 32 a when the jaws are in their closed configuration 28 . When the pair of jaws 12 are in the closed configuration 28 , the elongated handgrip 14 has a longitudinal length or span (L) that is on the same order of magnitude as the length (l) of the interior space 22 and may almost be equal (L≈1). The trigger handle 18 has a span (s) is preferably at least half as long as the elongated handgrip 14 (s≧½S). [0029] As explained below for the various embodiments of the clamp, the mount 30 is preferably formed as a part of either of the jaws or is attached to one of the jaws. For example, as an example of mounts that are integrally formed with the jaws, a slot 48 can extend through the sides of the jaws or the interior surface 32 a of the upper jaw 12 b can have a notch 50 . A strap 54 can be passed through slot, and the either a strap 54 or an accessory foot 56 can be positioned within the notch. The mount 30 may alternatively be a bracket 52 or other fastener that mates with and attaches to a section of the jaw, and the bracket of the present invention can be modular brackets or a bracket that mates with different accessory mount inserts that connect to different accessory mounts. [0030] The elongated handgrip 14 connects to the fixed jaw 12 a at the proximate side of the fixed jaw 12 a, and the handgrip 14 extends away from the proximate side of the fixed jaw 12 a. Depending on the particular embodiment, the trigger handle 18 is pivotally mounted to the proximal end of either the fixed jaw 12 a or the movable jaw 12 b. Regardless of the particular embodiment, the trigger handle 18 is connected to the actuator mechanism 16 and is moved relative to the elongated handgrip 14 to operate the actuator 16 . The trigger handle also extends outwardly away from the fixed jaw in the same general direction as the handgrip such that the longitudinal axes 40 of the trigger handle and the handgrip are either close to being parallel or are at a very shallow acute angle relative to each other when the clamp is in its closed configuration, preferably less than 10°, and is at a small acute angle when the clamp is in its opened configuration, preferably less than 30°. The orientation of the trigger handle relative to the handgrip allows for single-handed operation of the clamp by a user. [0031] The actuator 16 is connected between the elongated handgrip 14 and the trigger handle 18 and also connects the pair of jaws 12 to each other. The components of the actuator assembly may directly connect the jaws to each other as in the embodiments of the slide ratchet clamp and fulcrum ratchet clamp as described below or may indirectly connect the jaws to each other, such as through the trigger handle, such as in the locking lever clamp embodiment that is also described below. In each one of the embodiments, the actuator assembly also has a clamp release and a handle spring. Depending on the particular clamp embodiment, the clamp release is connected to the slide ratchet, the fulcrum ratchet, or the locking lever, and the handle spring is in operative engagement between the trigger handle and either the handgrip or the locking lever such that it biases the trigger handle away from the handgrip. [0032] The particular components of the actuator assemblies are described for each one of the clamp embodiments below. It will be appreciated that the clamp release can be a braking lever 80 , a thumb slider 106 , a ratchet locking pin 146 , or a release lever 158 , and these optional structures for the clamp release can be situated at different locations depending on the particular type of actuator mechanism being used. Similarly, it will be appreciated that the particular types of handle spring, such as a compression spring 72 or a tension spring 132 , and its location within the clamp also varies depending on the particular type of actuator mechanism. [0033] FIGS. 1A-1C show the vertical bar clamp 10 a with two interconnected and interlocking parts, an upper fixed jaw 12 a and a lower movable jaw 12 b. The upper clamp part has a ratcheting mechanism 86 with a flat-sided bar 76 serving as the connecting member 68 between the upper and lower clamp parts. The flat-sided bar 76 moves in the vertical direction through the handgrip 14 when the lever handle 18 is compressed. As the lever handle 18 is compressed, a driving lever 70 engages the connecting member 68 and forces it in the vertical direction to close the clamp 10 . The ratcheting mechanism 86 and the connecting member 68 force the upper and lower clamp parts together against the top and bottom of the crossbar 500 to hold the clamp 10 securely in place on the vehicle roof rack 502 . The two clamp parts connect on one side of the crossbar in a pivoting connection point 90 and on the other side of the crossbar they connect via the connecting member 68 . [0034] One embodiment of the ratcheting mechanism 86 is comprised of a cavity 92 . The connecting member 68 is a flat-sided bar 76 that passes through a hole in the elongated grip 14 , into the cavity 92 , and through a hole in the trigger handle. Within the cavity, a driving lever 70 is situated on the connecting member and proximate to the top of the trigger handle 18 . A compression coil spring 72 is situated around the flat-sided bar 76 and is compressed between the driving lever 70 on the trigger handle 18 and the top of the cavity 92 in the elongated grip 14 . In the standby position, the driving lever is perpendicular to the connecting member. When the trigger handle is compressed, the driving lever engages the connected member and moves from perpendicular to a position towards vertical. The force of the driving lever to the connected member incrementally moves the connecting member upwards, creating a compression between the upper and lower jaw. In the standby position 94 , the driving lever 70 rests on the trigger handle 18 within the cavity 92 and the flat-sided bar 76 is free to move. [0035] The flat-sided bar 76 extends through the bottom via the hole of the trigger handle 18 and through an opening in a braking lever 80 . The braking lever 80 is held within a recess of the trigger handle 18 and extends outwardly away from the upper jaw 12 b. A braking spring 98 is located within the trigger handle 18 and applies a force to the braking lever 80 that keeps the braking lever 80 in place. The braking lever 80 is biased to bind against the flat-sided bar 76 to prevent movement, keeping the flat-sided bar 76 in place. When the braking spring 98 is compressed by the breaking lever 80 and disengaged from the flat-sided bar 76 , the flat-sided bar 76 is free to slide in either direction. [0036] Connection points 90 a, 90 b between the upper and lower clamps may take various forms. As shown in FIGS. 1A and 1B , the lower clamp part 12 a may have a hook 100 that engages a pin 102 or a similar component in the upper clamp 12 b part for fastening. Once the lower clamp 12 a part is put in place, then lever handle 18 is compressed to tighten the clamp 10 on to the crossbar 500 . One or both of the connection points 90 a, 90 b between the may be detachable upper and lower clamps. In the case where both connection points are detachable, such as shown in FIG. 1B , the entire lower clamp part 12 a can be removed from the upper clamp part 12 b. At least one side of the jaws are detachable from each other to produce an opening 34 for the crossbar 500 . As shown in FIG. 1C , the connection point 90 b to the connecting member 68 can be a removable pin 88 , while the other connection point 90 a is a pivot point 102 that is not detachable. A user can remove the pin 88 to open the back of the clamp 10 for placing on the crossbar 500 , and then the handle 18 is compressed to tighten the clamp 10 . [0037] The pivoting connection point 90 between the upper and lower clamp parts may be a fixed pivot point 102 a, or a detachable pivot point 102 b. This connecting point 90 may also be adjustable to allow the size of the clamp's opening 34 to be varied. Different size openings allow the clamp to be used with a wide variety of crossbar 500 sizes. These features allow the user to easily and quickly attach and remove the clamp 10 from the crossbars 500 . In this embodiment, the longitudinal axis 40 a of the flat-sided bar is substantially perpendicular to the longitudinal axis 40 b of the interior space, and the longitudinal axes 40 of the trigger handle and the handgrip are substantially aligned with the longitudinal axis 40 b of the interior space. [0038] The clamp 10 can have a strap 54 that is integral to the clamp or may be added to the clamp. When the clamp 10 is attached securely to the rack 500 , the strap 54 can be used to securely hold items to the roof rack 502 . The strap 54 can be connected to the clamp 10 at a fixed end 54 a and may have a free end 54 b that can be wrapped around and/or through the item or items to be secured to the roof rack and transported. The free end 54 b is then passed through a locking mechanism 110 within the clamp 10 or on another free end of the strap. When the clamp 10 is moved into its closed configuration, it secures the strap to the crossbar. [0039] The use of the clamp 10 with various mounting accessories is shown in FIGS. 2A-2E as it holds objects to the roof rack. Common items and equipment may be secured to roof racks using the clamp, including lumber 512 , piping 516 , molding, ladders, and rugs. It will be appreciated that many other oversized and/or irregular shaped items can be held in place using the clamps 10 and straps 54 , such as Christmas trees, canoes, kayaks and mattresses. The strap may be weather-resistant webbing (such as nylon), rope, or stainless-steel cabling. In a variation, the strap 54 and its locking mechanism 110 is a separate mechanism from the ratcheting mechanism 86 and secures the strap 54 alternately with a cam lock, buckle, or other similar device. As shown in FIG. 2A , a separate strap ratchet 524 can also be connected to the strap 54 to pull the strap taut around the items being secured to the roof rack. As shown in FIG. 2B , the strap 54 can be used with the clamp 10 alone to secure items to the roof rack 502 . [0040] As the popularity of roof rack systems has increased, so has the variation in the profile of the crossbars 500 . The clamp is adapted to fit on a wide variety of crossbar 500 profiles (round, rectangular, and aero, for example). The cross-sectional opening 22 of the clamp 10 can accept inserts with profiles that match specifically shaped crossbars 500 . The inserts preferably snap securely into the upper and lower clamp parts. At the interface between the insert and the crossbar, the inserts have an appropriate material, such as rubber or another resilient and flexible material, which allows for good compression and fit while protecting the crossbars 500 from damage or scratching. [0041] The clamp 10 has an accessory notch 50 in the upper jaw 12 b, allowing the clamp 10 to securely hold the roof rack accessories. Accessories such as roof boxes and other cargo bins 510 , bike racks 520 , kayak/canoe holders, etc, could have an accessory foot 56 which fits into the clamp 10 , such as by fitting within the notch 50 in the clamp. The notch 50 and foot 56 fit together so that once the clamp 10 is secured to the crossbar 500 , the clamp 10 holds the accessory securely to the crossbar 500 . The notch 50 and foot 56 connection may be formed through a variety of shapes (flat, rectangular, or round). Examples of the accessory notch 50 being used for a base foot accessory to secure bike rack 520 that holds bicycle tire and a skewer accessory 522 that holds bicycle forks 524 are shown in FIGS. 2C and 2D , respectively. The skewer accessory could have a locking mechanism to prevent it from being opened when it is holding the bicycle forks. As explained below, the mount 30 may be a bracket 52 that is held within a cavity 46 in one of the jaws or other type of fastener which mates with and holds an accessory mount insert 58 . [0042] The entire assembly uses materials that are appropriate for use outdoors, such as plastics, rubber, and treated or stainless steel. Different types of locks 170 , 514 can be used with the clamp 10 to prevent unwanted removal. For example, a padlock 514 that is separate from the clamp body can be used with locking tabs that extend from the jaws or from one or both of the handgrip and the trigger handle to keep the clamp in its closed configuration. Another type of lock fastener 170 can be integral to the clamp body and is actuated using a key or other security device. [0043] The modular system described above allows a wide variety of roof rack accessories to be securely attached to a vehicle roof. These accessories may utilize the roof rack clamp 10 as the method of attachment, and other methods are also possible. Some accessories have a universal foot 56 that integrates with the accessory notch 50 in the clamp 10 . However, the foot 56 is able to connect to other components that attach to roof rack crossbars 500 . The accessory foot 56 can also contain an alternate connection point which allows it to connect different types of crossbar clamps. The alternate connection point in the accessory foot 56 may be a hole, a slot, or other appropriately sized space to accept the connection method between the crossbar clamp 10 and the accessory foot 56 . FIG. 2E depicts the accessory foot 56 as it can secure a cargo carrier 510 to the crossbar 500 . In one configuration, the accessory foot is connected to the cargo carrier directly. In another configuration, the cargo carrier could have an accessory mount that mates with a threaded bolt connector 114 . The threaded bolt connector 114 has a base plate or other bracket 164 with a threaded bolt 166 that extends upward from the bracket. It will also be appreciated that a threaded bolt connector 114 can be attached directly to the upper surface of the upper jaw 12 b. [0044] For a roof box accessory 510 , current products and patents contain integral clamps, usually four, which are accessed from within the roof box or below it at the crossbar. In this invention, as shown in FIG. 2E , the roof box 510 simply contains four feet 56 which extend out from both sides (two per side) and at each of two crossbars 500 (for a total of four). These feet 56 could be formed as integral parts of the molded plastic roof box 510 construction, or the feet 56 could be separate components that bolt onto the roof box during initial assembly. The roof box 510 is then secured to the crossbars 500 by one of a variety of methods such as threaded bolt connector 114 or using the roof rack clamp 10 described in this invention. Canoe or kayak accessories and other accessories can also use an accessory foot 56 that is inserted into the notch and secured to the crossbar 500 . [0045] An alternative slide ratchet bar clamp with a latching mechanism is shown in FIGS. 3A-3D . This embodiment has many of the same features as the slide ratchet bar clamp shown in FIGS. 1A and 1B and described above. Rather than using a removable pin as the connection point between the pair of jaws, this embodiment of the invention uses a spring-loaded latch 64 that releasably engages with a catch 66 when the clamp 10 is in the closed configuration 28 . FIG. 3B illustrates how the spring-loaded latch 64 and catch 66 disengage from each other to allow the jaws to separate and engage with each other to close the jaws 12 of the clamp 10 . A lower jaw lever 118 can be pulled upwards to unlock the lower jaw and pushed downwards to lock the lower jaw. The distal end of the upper jaw has a latch release 38 . When the latch release is depressed, it pushes the latch back to release the catch so that the distal end of the lower jaw rotates away from the distal end of the upper jaw, thereby producing an opening 34 for the pair of jaws to be placed around the crossbar. When the latch release is no longer depressed, the spring pushes the latch into the catch to lock the lower jaw to the upper jaw. The trigger handle is then operated relative to the handgrip similarly to the clamp as described in FIG. 1 to tighten and secure the clamp around the crossbar. [0046] Since the distal ends of the jaws can be readily opened and closed with the releasable connection point 90 a provided by the latching mechanism, the connection point 90 b between the proximal end of the bottom jaw and the ratchet bar 76 can be a fixed pivot point 102 that is not detachable. In particular, the hinge 62 between the lower jaw and the ratchet bar can be a nondetachable hinged connection. [0047] A locking fastener 170 can be used to prevent the breaking lever 80 from being actuated when the clamp is in its closed configuration. This will prevent the jaws of the clamp from moving into their opened configuration when the lock is engaged with the breaking lever to secure the clamp to the roof rack. The locking fastener 170 may also be used to lock a bracket 52 and an accessory mount insert 58 into the recess 50 on the topside of the top jaw. To further protect the closed clamp from being opened and removed from the roof rack, the distal ends of the pair of jaws may also have a respective pair of tabs 168 that can be locked. The pair of tabs can have holes for the shackle of a padlock 514 . [0048] The interior surfaces 32 a of the jaws preferably have a resilient surface 44 , such as silicon rubber. The resilient surface may be formed as inserts with different shapes to serve for crossbars that have different cross-sectional shapes. As with the embodiment described above with reference to FIGS. 1A-1C , the longitudinal axis 40 a of the flat-sided bar is substantially perpendicular to the longitudinal axis 40 b of the interior space, and the longitudinal axes 40 of the trigger handle and the handgrip are substantially aligned with the longitudinal axis 40 b of the interior space. The external surfaces of one or both of the jaws may also have a resilient surface to help prevent scratching or scuffing of the vehicle's paint and preventing potential damage to the items being secured to the roof rack. [0049] FIGS. 3C and 3D show a mount 30 in the form of a depression or cavity 46 and a mating bracket 52 that can be used with straps 54 or with an accessory mount insert 58 or directly with an accessory mount. The bracket is preferably secured within the cavity 46 on the topside of the top jaw. In the particular embodiment shown in FIGS. 3C and 3D , the bracket fits within the cavity and has a protrusion with a flange on its end which extends through a hole in the bottom of the recess and engages a spring pin lock 120 where it clicks into place. The spring pin lock may be accessed from a port in the interior surface of the upper jaw. When the jaws 12 are in their closed configuration around the roof rack's crossbar, the spring pin 120 cannot be accessed on the underside, thereby locking the bracket 52 in place. The bracket can have one or more slots 48 through which one or more straps 54 pass through. The accessory mount insert 58 mates with and is held by the bracket and may be locked in place by the locking fastener. It will be appreciated that the bracket 52 and/or the accessory mount insert 58 can have different configurations, and various mating connections can be used between the bracket 52 and the jaws. Examples of various inserts include locking threaded connectors 114 , male/female connectors 116 a, and threaded holes 116 b, and it will be appreciated that other fasteners and mating features could be used for the inserts or the brackets 52 a, 52 b, 52 c could be formed with these different types of mating features. Accordingly, the modular bracket mount of the present invention can be used with different types of accessory mounting systems from a number of different manufacturers. [0050] The horizontal bar clamp, as shown in FIGS. 4A and 4B and in FIGS. 5A and 5B , has similar components as the vertical bar clamp 10 a. However, rather than having top and bottom jaws, the horizontal bar clamp 10 b has a front jaw 12 b and a back jaw 12 a. The back clamp 12 a part has a ratcheting mechanism 86 that allows a connecting member 68 to move in the horizontal direction when a lever handle 18 is depressed. As the lever handle is depressed 18 , a driver bar or a ratcheting pawl engages the connecting member 68 and forces it in the horizontal direction thus closing the clamp 10 . The ratcheting mechanism 86 and the connecting member 68 facilitate the front 12 b and back clamp 12 a parts to compress together against the sides of the crossbar 500 becoming tighter with each squeeze of the lever handle 18 , thus holding the clamp 10 securely in place on a vehicle roof rack 500 . The ratcheting mechanism 86 may use friction or gear teeth or other method of operation. [0051] The clamp has a mount 30 on the front clamp 12 b part in the form of an accessory attachment bracket 122 , allowing the clamp 10 to securely hold roof rack accessories. Accessories such as roof boxes and other cargo bins 510 , bike racks 520 , kayak/canoe holders, etc, have a corresponding connector piece 124 which attach to the bracket. The accessory attachment bracket 122 has a recess 128 a and a pair of side arms 128 b that each surround attachment holes 128 c. The accessory connector 124 has a pair of side clips 126 a at one end that respectively snap into the attachment holes and has a hook 126 b at the other end with a channel 126 c in the hook that is situated around the connecting member 68 . FIG. 4B shows the progression of how the accessory attachment 122 is secured to the front clamp 12 b. The connector piece 124 fits onto the front clamp 12 b part so that once the clamp 10 is secured to the crossbar 500 , the clamp holds the accessory securely to the crossbar 500 . The connector piece 124 hooks onto the front clamp 12 b part and is rotated downward to snap into place using side clips 126 a that engage with the clamp body 10 . The connector piece 124 is released from the accessory attachment bracket 122 by inwardly depressing the side clips 126 c directly or disengagement tabs 126 d that are connected to the side clips. It will be appreciated that a similar accessory adapter with side clips could be used with the clamp embodiment shown in FIGS. 1A and 1B with the side clips being releasably secured within the slots 48 and the body of the adapter fitting between the sidewalls of the top jaw. [0052] The clamp 10 can be locked by means of inserting the shackle of a padlock 514 in the lock hole 104 . Preferably, the lock hole 104 is located at the release lever 106 so that the padlock prevents the release lever from moving. Alternatively, the end of the slide bar may have a hole that aligns with a locking fastener when the clamp is in its closed configuration so that the locking fastener can engage the hole to prevent any movement of the slide bar back to the opened configuration. Alternatively or in combination with the padlock or the locking fastener, a pair of tabs with center holes could extend from the corresponding pair of jaws, and the shackle of the padlock can be placed through the center holes. It will also be appreciated that the latching mechanism shown in FIGS. 3A and 3B and described in detail above could also be incorporated into the jaws of the clamps shown in FIGS. 4A-4D and FIGS. 5A and 5B ; in particular, the latch would be situated on one of the jaws opposite from the slide bar and the catch would be situated on the other one of the jaws also opposite from the slide bar. [0053] Similar to the clamps shown in FIGS. 1A-1C and in FIGS. 3A-3D , the slide connector 68 may be a flat-sided slide bar 76 or a toothed slide bar 78 . Also similar to the embodiments described above, the trigger handle pivotably mounts to the fixed jaw and the actuator includes a clamp release 106 and a compression coil spring situated between the trigger handle and the handgrip to bias the trigger handle away from the handgrip. However, unlike the embodiments described above, the horizontal slide clamp shown in FIGS. 4A-4D can position the handle spring with its axis perpendicular to the longitudinal axis of the slide bar rather than having aligned axes so the spring would not surround the slide bar. In this embodiment, the clamp release 106 is connected either to the ratchet's one-way driver mechanism 108 or to a ratchet locking pin (not shown) that would be similar to the pin described below for the fulcrum ratchet clamp. The clamp release can be operated to disengage the one-way driver mechanism 108 from the slide ratchet 78 or to disengage the ratchet locking pin. The slide connector 68 extends between the fixed jaw 12 a and the movable jaw 12 b and connects the pair of jaws 12 . [0054] In the embodiment shown in FIGS. 4A-4D , the longitudinal axis 40 a of the slide ratchet is substantially parallel to the longitudinal axis 40 b of the interior space so that both of these axes are substantially aligned with the longitudinal axes 40 of the trigger handle and the handgrip. In the embodiment shown in FIGS. 5A and 5B , the longitudinal axis 40 a of the slide ratchet is substantially parallel to the longitudinal axis 40 b of the interior space, and these axes are substantially perpendicular to the longitudinal axes 40 of the trigger handle and the handgrip. [0055] FIGS. 6A and 6B show the fulcrum ratchet clamp 10 c that has a many of the same basic components as the other ratchet clamp embodiments described above. In particular, the clamp 10 has a pair of jaws 12 , a handgrip 14 , a trigger handle 18 , and an actuator 16 . In this embodiment the actuator is a ratcheting mechanism 16 b with gear teeth along a curve 144 rather than having teeth on a straight bar. The lower jaw 12 a contains the ratchet gear 134 , and the trigger handle 18 contains the pawl 136 with a handle spring. As the trigger handle is rotated toward the lower handle by squeezing it, the pawl engages the gear teeth and rotation causes the lower jaw 12 a to close. As the ratchet gear rotates around its pivot point to close the lower jaw, a spring-loaded ratchet locking pin 146 engages the gear teeth as they pass by in the closing direction. When the ratchet locking pin is engaged with the gear teeth, it prevents the ratchet gear from rotating in the opening direction. The ratchet locking pin has a tab that can be pulled back to pull the ratchet locking pin away from the teeth and which allows the jaws to move into the opened configuration. [0056] In the closing action, with the locking pin engaging the gear teeth, when trigger handle is released, the internal handle spring forces it away from the handgrip, and the pawl resets. This motion is repeated until the lower jaw 12 a and upper jaw 12 b are tightly closed onto the roof rack crossbar 500 . Since the ratchet locking pin holds the ratchet gear and the jaws in the closed configuration, the pawl and handle spring assembly can be released from the ratchet gear using a thumb slider 106 which allows the trigger handle to be closed against the handgrip. A retainer clip 142 attached to the handgrip can be rotated into engagement with the trigger handle to hold it in its closed position adjacent to the handgrip. [0057] Similar to the embodiments described above, the clamp has a slot 48 and an accessory notch 50 in the upper jaw 12 b, allowing the clamp 10 to securely hold roof rack accessories. The notch 50 and foot 56 fit together so that once the clamp 10 is secured to the cross bar 500 the clamp 10 holds the accessory securely to the cross bar 500 . The notch 50 and foot 56 connection may be formed through a variety of shapes (flat, rectangular, or round). The clamp can be locked by means of inserting the shackle of a padlock 514 in lock holes in a pair of tabs that extend from the distal ends of the jaws. It will also be appreciated that the latching mechanism shown in FIGS. 3A and 3B and described in detail above could also be incorporated into the jaws of the clamps shown in FIGS. 6A and 6B ; in particular, the latch and catch would be situated at the distal ends of the jaws opposite from the actuator. [0058] As shown in FIGS. 7A and 7B , the locking lever clamp 10 d operates in a similar manner as locking pliers, often called vice-grip pliers and wrenches. Similar to the ratchet clamp embodiments described above, the clamp 10 has a pair of jaws 12 , a handgrip 14 , a trigger handle 18 , and an actuator 16 . In this embodiment the actuator is a lever actuator 16 c as compared to the ratchet actuators 16 a, 16 b described above. The trigger handle is rotated away from the handgrip when the jaws are in their opened configuration. As the trigger handle is rotated toward the handgrip, a linkage 148 between the handgrip and the trigger handle forces the jaw connected to the trigger handle to rotate toward the jaw fixedly connected to the handgrip until it reaches the closed configuration. The linkage 148 is positioned within recesses 150 in the handgrip and the trigger handle, and a tension coil spring 132 is connected between the linkage and the trigger handle. The tension spring biases the trigger handle away from the handgrip and is extended in the closed configuration and contracted in the opened orientation. An adjustment knob 152 at the back of the handgrip adjusts the longitudinal distance of the distal end of the linkage from the back end of the handgrip which varies the extent to which the movable jaw closes relative to the fixed jaw. Accordingly, the adjustment knob can be rotated so that when the clamp is in its closed configuration, the claim tightly fits on the cross bar. [0059] A release lever 158 is situated at the distal end of the trigger handle in the recess and rotates around a pivot point 160 . In the closed configuration, the linkage pushes the proximal end of the release lever upward further into the interior portion 162 of the recess and the distal end of the release lever rotates away from the interior portion of the recess. When the distal end of the release lever is pushed into the interior portion of the recess, the proximal end of the release lever is forced away from the interior portion and pushes the linkage away from its locked position and the spring forces the linkage to rotate the trigger handle away from the handgrip, thereby rotating the jaws apart into the opened configuration. [0060] Similar to the ratchet clamp embodiments described above, the locking lever clamp has a slot 48 and an accessory notch 50 in the upper jaw 12 b, allowing the clamp 10 to securely hold roof rack accessories. The notch 50 and foot 56 fit together so that once the clamp 10 is secured to the cross bar 500 the clamp 10 holds the accessory securely to the cross bar 500 . The notch 50 and foot 56 connection may be formed through a variety of shapes (flat, rectangular, or round). The clamp can be locked by means of inserting the shackle of a padlock 514 in lock holes in a pair of tabs that extend from the distal ends of the jaws. It will also be appreciated that the latching mechanism shown in FIGS. 3A and 3B and described in detail above could also be incorporated into the jaws of the clamps shown in FIGS. 7A and 7B with the latch and catch being situated at the distal ends of the jaws opposite from the actuator. [0061] As indicated above, different types of clamp actuators 16 can be used in the present invention. The actuator mechanisms 16 that are used in slide ratchet clamps, fulcrum ratchet clamps, and vice grip locking pliers and other similar tools which hold workpieces in place can be incorporated into the clamp actuator 16 of the present invention. Examples of such actuator mechanisms are described in the following patents which are incorporated by reference herein: U.S. Pat. Nos. 952,079, 1,036,093, 2,514,130, 3,354,759, 3,427,016, 4,220,322, 4,926,722, 5,005,449, 6,000,686, 6,240,815, 7,784,774, and 8,177,203. Although the clamping and ratcheting mechanisms for these known hand tools can be incorporated into the roof rack clamp 10 of the present invention, these known tools as they currently exist would not satisfactorily serve as a roof rack clamp according to several features and aspects of the present invention as it is used for roof rack crossbars on vehicles or on other types of cargo carriers. The existing tools would not satisfactorily perform the clamping functions on the crossbars of vehicle roof racks 500 because they do not have a mount feature that is important to the operation of the roof rack clamp 10 . The hand tools only have one connection point at the proximal end of the jaws, adjacent to the handgrip and trigger handle; they do not have a second connection point at the distal end of the jaws as in the preferred embodiments of the present invention to provide for additional clamping strength and security. Additionally, the hand tools do not have any type of locking fastener, locking tabs or other means for locking the clamps to prevent theft of the object being held to the roof rack. Further, the orientations and relative sizes of the clamping surfaces for the jaws that would provide sufficient stability for a secure connection to crossbars. For example, many of the hand tools have a width that is too narrow relative to the length and height of the interior space between the jaws so they would likely rock or rotate if placed on a crossbar. [0062] Additionally, if known hand tool clamps were to be modified according to the teachings of the present invention, they would no longer satisfactorily perform the clamping functions necessary to hold workpieces that they are designed to hold in place because they require a different orientation of the jaws with a relatively smaller surface area for the workpieces. According to the teachings for hand tool clamps, when the pressure of one or both jaws is to be distributed on a particular type of workpiece, a clamping caul is typically placed between the jaw and the workpiece rather than modifying the design of the clamp. Therefore, although the general teaching of these clamping and ratcheting mechanisms of these tools are incorporated by reference herein, modifications of these mechanisms must be made according to the present invention to satisfactorily perform the necessary clamping function in a roof rack clamp. [0063] The present invention has a number of benefits over current roof rack clamps and other cargo carrier clamps. Although there are many known clamps that have a pair of adjustable jaws that connect a particular type of accessory mount or a universal accessory mount to the crossbar of a roof rack, none of the prior art clamps use both a handgrip and a trigger handle that allows for single-handed installation of the clamp on the roof rack's crossbar. Additionally, none of the of prior art references combine a handgrip and a trigger handle with an actuator that provide a mechanical advantage of the lever action of the trigger handle. Other benefits of the present invention include the handle spring situated between the handgrip and the trigger handle which allows for single-handed tightening of the jaws on the crossbar and the quick clamp release of the present invention which permits for the efficient repositioning of the clamp on the crossbar. [0064] The embodiments were chosen and described to best explain the principles of the invention and its practical application to persons who are skilled in the art. As various modifications could be made to the exemplary embodiments, as described above with reference to the corresponding illustrations, without departing from the scope of the invention, it is intended that all matter contained in the foregoing description and shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.

A roof rack system has a clamping system comprised of handles, a ratcheting mechanism, and a pair of jaws. The jaws provide a universal clamping system that will attach to most roof rack cross bars with an easy-on/easy-off, quick-release actuator, such as a ratcheting mechanism or lever system, that will integrate with a wide variety of accessories. The ratcheting mechanism provides compression of the attached accessory, securing it to a roof rack cross bar. This system is easier to use, more versatile, and less expensive than conventional roof rack accessory systems.

BACKGROUND OF THE INVENTION [0001] The present application pertains to an oral care implement, in particular to a toothbrush with mechanical energy harvesting device and circuitry. Tooth brushing is part of a daily oral hygiene activity. Proper dental care involves regular flossing, brushing and dental checkups. Dentists generally recommend that an individual brush his or her teeth for a minimum interval per cleaning, such as two minutes. Despite such recommendations, many individuals, especially young children, do not regularly brush their teeth for the recommended minimum interval. Such habits often can be attributed to the individual regarding tooth brushing as a mundane duty with few pleasurable aspects. BRIEF SUMMARY OF THE INVENTION [0002] The present invention pertains to an oral care implement with mechanical energy harvesting device and circuitry. In one aspect, the oral care implement can signal to a user when a suitable level of brushing has been accomplished. [0003] A number of mechanical energy harvesting circuits may be used in an oral care implement to capture mechanical energy from brushing, and to convert that mechanical energy into electrical energy that can be used at a later time. For example, an oral care implement may have a handle, head with tooth cleaning elements, a mechanical energy harvesting device or circuit (to convert mechanical energy into electrical energy), an electrical energy storage device (to store the electrical energy) and a switching circuit to close an electrical connection with the storage device when a predetermined voltage has been reached. [0004] In one aspect, the predetermined voltage may be determined by taking into account typical brush stroke length, stroke number and force of brushing. [0005] In one aspect, the mechanical energy harvesting circuit can include one or more piezoelectric devices positioned to generate electricity in response to deflections or bending of the toothbrush head and/or tooth cleaning elements. [0006] In one aspect, the harvesting circuit can include one or more electromagnetic generators, having wire coils and moveable magnets, to induce an electric current as the magnets pass through the coils due to movement of the toothbrush during brushing. [0007] In another aspect, a rectifier circuit may be used to rectify the electricity generated by the harvesting circuit before storage in the storage device, and a voltage regulator may be used to provide a constant level output when the storage device is being discharged. [0008] Other features and embodiments are described in the sections that follow. BRIEF DESCRIPTION OF THE DRAWINGS [0009] The features herein will become more fully understood from the detailed description given herein below, and the accompanying drawings, which are given by way of non-limiting illustration only. [0010] FIG. 1A is a longitudinal cross-sectional view of a toothbrush construction in accordance with at least one aspect of the invention. [0011] FIG. 1B is a longitudinal cross-sectional view of an alternative toothbrush construction in accordance with at least one aspect of the invention. [0012] FIG. 1C is a longitudinal cross-sectional view of an alternative toothbrush construction in accordance with at least one aspect of the invention. [0013] FIG. 1D is a longitudinal cross-sectional view of an alternative toothbrush in accordance with at least one aspect of the invention. [0014] FIG. 2 is an electrical schematic illustrating an exemplary circuit configuration in accordance with at least one aspect of the invention. [0015] FIG. 3 is a cross-section view of an alternative head construction taken along the width of a toothbrush in accordance with at least one aspect of the invention. [0016] FIG. 4 is an electrical schematic illustrating an alternative circuit configuration. DETAILED DESCRIPTION OF THE INVENTION [0017] The following detailed description refers to the accompanying drawings. The same reference numbers in different figures identify the same or similar elements. [0018] As illustrated in FIGS. 1A-1D , an oral care implement, such as toothbrush construction 100 , 300 , 400 , 500 , may include a brush head 101 and a handle 102 . The head 101 may be a refill head that is removably connected to handle 102 , or it may be integrally formed and attached to the handle 102 . [0019] The head 101 may include one or more tooth cleaning elements, such as a field of bristles 103 . As used herein, the term “tooth cleaning elements” or “cleaning elements” includes any type of structure that is commonly used or is suitable for use in providing oral health benefits (e.g., tooth cleaning, tooth polishing, tooth whitening, massaging, stimulating, etc.) by making contact with portions of the teeth and gums. Such tooth cleaning elements include but are not limited to tufts of bristles that can be formed to have a number of different shapes and sizes and elastomeric cleaning members that can be formed to have a number of different shapes and sizes, or a combination of both tufts of bristles and elastomeric cleaning members. [0020] Referring to the toothbrush construction 100 of FIG. 1A , the head 101 may also include one or more energy producing devices, such as piezoelectric devices 104 . The piezoelectric devices 104 may be arranged in contact with, or proximate to, the bristles 103 , so that movement of the bristles causes stress or strain on the devices 104 . For example, a given bristle may be attached to a cantilever portion of a micro-electro-mechanical system (MEMS) device to stress or strain the device 104 . MEMS cantilevers are conventionally fabricated from silicon nitride (SiN), silicon (Si), or various polymers. In a cantilever MEMS device, the proximal end of the cleaning element (e.g., bristle or elastomeric element) is attached to the “cantilevered” portion of the MEMS device. In this construction, z-axis movement of the cleaning element causes deflections in the MEMS device which invokes electrical potential. Nevertheless, the amount of electrical energy depends on the modulus of elasticity of the material, the thickness of the cantilevered portion and the piezo-resistive material of the MEMS device. [0021] The stress or strain causes the piezoelectric device 104 to generate a small amount of electrical energy, such as a voltage. As will be explained below, the head 101 may also include wiring and circuitry to carry this voltage to other parts of the toothbrush 100 , and that electrical energy may eventually be used to power one or more output devices 105 . [0022] Referring to the toothbrush construction 300 of FIG. 1B , the head 101 may also include one or more piezoelectric devices 106 that are stressed or strained by the natural bending of the head 101 along the longitudinal axis X-X that occurs during a normal tooth brushing operation. The amount of bending or deflection along the longitudinal axis can depend on the type of material and thickness of the head 101 . For example, rigid plastics or resins, such as polypropylene, may be used to form the head 101 . To provide a controlled deflection profile and/or focus the bending in regional areas, the head 101 may include one or more flexing joints 107 disposed transverse (e.g., along a Y-axis) to the longitudinal axis X-X. In the one construction, the joints 107 may be disposed perpendicular to the longitudinal axis of the toothbrush. In other constructions, the joints 107 may be notches or grooves, having less head material in the area than in the immediate surrounding portion of the head 101 . In the alternative construction, the joints 107 may be formed of a less rigid material than other portions of the head (e.g., rubberized or elastomeric sections at the joints 107 ). The flexibility of the head 101 (e.g., Z-axis movement) facilitates enhanced cleaning of the lingual and facial surfaces with dentifrice on the tooth cleaning elements. In addition, Z-axis movement of the tooth cleaning elements facilitates improved interproximal cleaning as well as cleaning of the crowns of the molars of the teeth of a human. In this way, a toothbrush provides improved cleaning capabilities and energy harvesting features. [0023] The piezoelectric devices 106 may be placed near the joints 107 to maximize the stress or strain experienced by the device 106 as the head deflects or bends along the longitudinal axis X-X during brushing. Nevertheless, the head 101 may twist to have a torsional component which causes strain on the piezoelectric device 106 . The changes in strain on device 106 invoke an electrical response in the piezoelectric device. Hence, during a brushing operation, piezoelectric devices 106 can experience a combination of different types of movements including, for example, a deflection along the longitudinal axis and a twisting component about the same longitudinal axis. [0024] As illustrated in FIG. 1B , the piezoelectric devices 106 may be placed directly above and centered relative a flexing joint 107 . In alternative head construction shown in FIG. 3 , the joints or grooves 308 may be disposed along or generally parallel to the longitudinal axis X-X of the toothbrush. In this construction, the grooves 308 are disposed across the width W of the head. Piezoelectric device 304 may be placed directly above and centered with respect to a flexing joint 308 . Alternatively, the device 304 may be placed under the bristle field similar to device 104 . In these longitudinal joint constructions, the head 101 may flex in side-to-side motions (e.g., width) and provide improved energy harvesting features. [0025] Referring to FIGS. 1A and 1B , with the piezoelectric devices 104 , 106 , the amount of electrical energy generated will vary proportionally with the amount of force used to brush a user's teeth. Individual performance ranges will depend on the piezoelectric material type and configuration chosen, and any piezoelectric material type and configuration may be used as desired. Additionally, different types of piezoelectric devices may be used. The device 106 may be larger in structure than device 104 . In one construction, device 104 , 106 may be a microelectromechanical system (MEMS) device that includes a cantilever portion attached to each of a plurality of the bristles 103 . [0026] Referring to the toothbrush construction 400 of FIG. 1C , the toothbrush 400 may also include one or more electromagnetic generators 108 . Each generator 108 may include a wire coil 109 and a magnet 110 that is configured to freely move through the coil 109 as the toothbrush 100 is moved back and forth along its longitudinal axis (horizontal, as depicted in FIG. 1 ). This configuration may be accomplished in a variety of ways. For example, the coil 109 may be embedded within a tube of a non-conducting material having a low coefficient of friction, and the magnet 110 (which may also be encased in a similar material) may be centrally aligned within the tube. The non-conducting material having a low friction should be biocompatible. An example of such a material is polycarbonate. [0027] As the toothbrush 400 is moved back and forth, the magnet 110 moves back and forth through the coil 109 , inducing a small amount of current in the coil 109 . The amount of current generated will depend on several factors, such as the strength of the magnet, the number of loops in the coil, and the speed at which the magnet travels. The head 101 may include additional wiring and circuitry to convey this current to other parts of the toothbrush, as will be explained below. [0028] Referring to FIG. 1D , toothbrush construction 500 may include a combination of the features of toothbrush constructions 100 , 300 , and 400 for energy harvesting. [0029] FIG. 2 illustrates an electrical schematic that can be used with the toothbrush 100 . As illustrated, an energy harvesting device 201 represents the devices 104 , 106 and/or electromagnetic generators 108 that are in the toothbrush 100 . The toothbrush 100 may have one, some, or all of these as energy harvesting devices, and they are generically represented in FIG. 2 . [0030] The energy harvesting device 201 may generate an alternating current (AC) output due to the back-and-forth motion of the toothbrush 100 and/or bending of the head 101 and/or bristles 103 . For example, the generator 108 may generate an alternating current (AC) output in use (e.g., generating a positive current when the toothbrush is moved in one direction, and a negative current when the toothbrush is moved in an opposite direction). This output may be supplied to a rectifier circuit 202 to convert the AC output to a DC output. Any type of rectifier circuit 202 may be used, depending on the type of output generated by the particular piezoelectric devices 104 , 106 and/or the generator 108 , and on the type of output desired. [0031] The rectifier circuit 202 may then be coupled to an electrical energy storage device 203 . Device 203 may be any type of device that can receive electrical energy (a charge) and store it for later use. For example, a capacitor or rechargeable battery may be used to store the electrical energy from the rectifier 202 in the form of a stored charge. The actual amount of charge stored will depend on the type and number of energy harvesting devices 201 used in the toothbrush, and the electrical energy storage device 203 may act as an integrator summing the charges generated by each movement, bending, or stroke of the toothbrush. [0032] The energy stored in energy storage device 203 will accumulate as the toothbrush is used, and a switch circuit 204 may be used to regulate the release of that energy. The switch circuit 204 may keep an electrical connection between the storage device 203 and an output load 206 in an open state until the voltage level in the storage device 203 reaches a predetermined level, and then close that connection when the voltage reaches that predetermined level to discharge the device 203 and to allow the output load 206 to use the stored energy. One example embodiment of the switch circuit 204 is a silicon-controlled rectifier (SCR), or a thyristor, configuration, as illustrated in FIG. 2 . By knowing the SCR's turn-on voltage, and the desired predetermined voltage for the storage device 203 , the ratio of resistor values R 1 /R 2 can be chosen so that the SCR turns on when the voltage across the device 203 has reached that predetermined voltage level. [0033] That predetermined voltage level can be chosen to reflect a suitable amount of tooth brushing. For example, this can be based on a typical stroke length and/or force of brushing. If a typical tooth brushing is expected to run for S strokes at a force of F Newtons before the switch 204 is to be closed, and a typical stroke is L m in length, then it is known that the typical brushing will generate (S strokes)*(L m/stroke)*F N=X Joules of energy. When the accumulated voltage in the storage device 203 corresponds to that amount of work done during the brushing, the switch will close. [0034] During brushing, the piezoelectric devices 104 , 106 will generate a known amount of voltage for a given amount of bending force, and the electromagnetic generator 108 will generate a known amount of current for each time the magnet 110 passes through coil 109 . This energy will be stored in the storage device 203 , and accordingly, the storage device 203 acts as a form of integrator, totaling up the mechanical work performed by the user's brushing. If the user brushes faster, or harder, the storage device 203 will accumulate charge faster than if the user brushes slower or with less force. [0035] When the predetermined voltage has been accumulated, the switch circuit 204 may close the electrical connection, and the stored voltage in device 203 may be discharged and used for a variety of purposes. For example, output devices 206 may include devices that signal to the user when sufficient brushing has occurred. Such signaling devices may take many forms, such as a light-emitting diode (LED) or other illuminated display, a speaker generating an audible tone, and/or a mechanical vibrator. For example, a display may be placed on the toothbrush to assist in reporting output. The display may include light-emitting diode (LED) displays, an alphanumeric display screen, individual lights, or any other desired form of visual output. For example, the display may be an Organic LED or electroluminescent sheet that can be tuned to provide a desired luminescent characteristic such as color, temperature, intensity etc. OLED or EL (electroluminescent) technology can be embedded into the toothbrush molding, or can be applied to the surface of the toothbrush body. It should be understood by those skilled in the art that the present invention is not limited to any particular type of display. [0036] In some implementations, the toothbrush relies entirely on the mechanically-harvested energy to run these output devices, so the devices may be configured to be very low power devices. For example, an energy-efficient LED with a current limiting resistor may be used, or a DC piezoelectric buzzer as an audio device, or a piezoelectric vibrator as a vibrating device. [0037] Output devices 206 can perform other functions besides informing the user when brushing is complete. For example, the energy can be used to power components, such as micro pumps and pump valves, to deliver actives at predetermined stages during brushing. For example, a separate active or flavor can be automatically delivered midway through the brushing. The energy can alternatively be used as a supplement to energy provided by another battery on the toothbrush (e.g., for playing video games, playing music, or any other battery-operated function), or to recharge such a separate battery. In some configurations, toothbrush 100 , 300 , 400 , 500 may be a traditional electric vibratory toothbrush (with vibrating head/bristles, motor, power supply, etc.), and the energy harvesting circuitry may be used as a supplement to recycle some of the mechanical energy in the brushing and vibration of the toothbrush and use that energy to assist in powering and/or recharging a battery of the device. [0038] The toothbrush may include a voltage regulator 205 to provide a constant voltage to the output device 206 . For example, National Instrument's LM2674 or LM3670 integrated circuit may be used for this purpose. [0039] Other embodiments will be apparent to those skilled in the art from consideration of the specification disclosed herein. For example, the FIG. 2 schematic is merely an example. While FIG. 2 represents energy harvesting devices 201 generically, and shows a single example rectifier 202 , storage 203 , switch, 204 , etc., multiple devices 201 may be used and separate circuitry can be supplied for different types of devices 201 . [0040] FIG. 4 illustrates an alternate circuit configuration. This alternate configuration can use an integrated circuit (e.g., part no. LM3670_SOT23 — 5 U1), instead of the SCR in FIG. 2 , to control the switching of the circuit. The use of this integrate circuit for the switching may allow the easier turning on/off of the device at the enable pin (labeled pin 3 , or “EB”, in the Figure), allowing for a more efficient system. The FIG. 3 configuration also shows the addition of a Zener diode D 5 . The Zener diode may protect against the generation of too much voltage, by short-circuiting the source if too much voltage is generated. Such a component may help prevent damage to the circuitry if, for example, the user vigorously brushes or shakes the toothbrush for an extended period of time. [0041] It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

A mechanical energy harvesting toothbrush may employ circuits and devices to convert mechanical energy into electrical energy. Such conversion can be done using piezoelectric devices to convert stresses and strains from bending of the toothbrush head and/or bristles during use, and can be done using electromagnetic generators involving passing a magnet through a coil to induce current. The resulting electric energy may be rectified, and stored in a storage device, such as a capacitor or rechargeable battery. A switching circuit may be configured to detect the level of energy stored in the storage device, and to close an electrical connection when a predetermined level of energy (e.g., a charge) has been reached. The predetermined level may correspond to a desired amount of brushing (e.g., taking into account stroke length and force, and the number of strokes), and the closing of the electrical connection may be used to power output devices when that desired amount of brushing has been reached.

CROSS-REFERENCE TO RELATED APPLICATION This application is a divisional of U.S. Pat. application No. 09/290,094, now pat. No. 6,368,272 B1, filed Apr. 12, 1999; which claims the benefit of U.S. Provisional Application No. 60/081,290, filed Apr. 10, 1998. Each of these applications is hereby incorporated by reference in their entireties, including all figures and tables. The invention described herein was made in the performance of work under National Institutes of Health (Contract Number LR43 DR47730-01A2) and Department of Defense (Contract Number DASG60-97-M-0066) contracts. The federal government may have certain rights in this invention. BACKGROUND OF INVENTION In health, all events taking place inside living bodies are controlled by a myriad of minute processes, each having outcomes preordained by their DNA templates. One such process is the blood glucose metabolism, which is optimized to achieve normoglycemia even for wide swings in the predominant effect inputs, food and physical exercise. Illness, on the other hand, is characterized by the body's inability to maintain control over one or more biological processes. Unless correctable by surgery, medication, or other means, the out-of-control condition extends to other processes and results in poor patient prognosis. The only alternative left to people suffering from “incurable” afflictions is disease management, that is, careful monitoring of the parameters of interest, coupled with corrective actions such as insulin injections, dialysis, etc. For example, diabetes patients have little or no endogenous blood glucose (BG) control capability, and many must inject insulin to compensate for swings outside the acceptable serum glucose range. Similarly, end-stage renal disease patients have lost the ability to control their nitrogen metabolism, and must undergo dialysis, typically for the rest of their lives. The reader will appreciate that many other situations sadly exist, however, because they are representative of this entire class of problems, we will limit the examples presented here to glucose control and diabetes, and their spin-off, long-term weight management. Diabetes mellitus is a significant chronic disease with no cure, affecting more than 16 million Americans and 100 to 150 million people worldwide. In the U.S. it is the fourth-leading cause of death each year. (National Institutes of Health/National Institute of Diabetes and Digestive and Kidney Diseases: Diabetes in America/Second Edition, NIH Publication No. 95-1468 (1995)) Its incidence rate among children and teenagers in the U.S. increased several fold during the last thirty years, and more than 30,000 new cases are identified each year. It is a $156 billion problem for the US economy. A problem of this magnitude naturally generates intense efforts to alleviate it, and one landmark study has altered the course of treatment. The results of the Diabetes Control and Complications Trial (DCCT) indicate that tight control of blood glucose levels results in a dramatic reduction of complications, including 76% lower incidence of diabetic retinopathy, 60% less neuropathy, and as much as 56% fewer cases of nephropathy. The costs to society could be drastically reduced, but at the expense of intensive management (more frequent blood sugar measurements, multiple daily injections). Technological advances have made it possible for patients to administer insulin at home, and to monitor the blood glucose levels (self monitoring of blood glucose, or SMBG) with equipment that costs less than $100; test strips and accessories run about $2,000 per year per patient, but of course this expense will double with intensive management as suggested by the DCCT results. To further improve ease of control, intense product development efforts have led to the introduction of a new, rapid insulin (HUMALOG™), and non-invasive blood glucose measurement equipment could be marketed within the next few years. However, currently available equipment does not take into account the blood glucose dynamics, and invasive blood glucose measurement techniques discourage frequent testing. The blood glucose values are therefore known only to a minute extent, because even the most compliant patients will only draw blood and test the glucose concentration less than ten times a day. The data available is therefore much too far from the Nyquist sampling rate, and very little in formation results from the individual blood tests. Again, intense product development efforts have led to the introduction of statistical process control concepts in blood glucose meters, and many now can store several hundred measurements, including the time of day and date each value was measured. For a rigid regimen, whereby the patient always eats the same meals at the same time, and injects the same amounts and types of insulin every day at the same time, the statistical information thus gathered helps with the metabolic control and gives the physician the means to assess the patient compliance and adequacy of the regimen. The main draw-back of this methodology is that it is all after the fact, while also severely restricting the patients ' freedom of action in the most basic are as, such as food and exercise, and rest. This too has a solution, albeit an imperfect one: the “gold standard” in diabetes nutrition is carbohydrate counting, a method that allows the patients with insulin-dependent diabetes to eat any higher carbohydrate meal, so long as the equivalent amount of insulin is administered. There are problems with this also, the two most important being that most patients cannot do the conversion, and that not all carbohydrates are equal in terms of their speed of conversion to blood glucose. (An extensive amount of information exists on the glycemic index of different types of food.) Intense efforts to introduce non-invasive blood glucose testers will soon bring to market equipment that will make frequent testing convenient, but still no predictive capability will be added by non-invasive SMBG. The burden of understanding the temporal characteristics of the physiological mechanisms of glucose regulation depends on the patients. Those equipped with the knowledge and willingness to devote time are able to achieve a good overall level of control, but most patients are overwhelmed and find themselves unable to understand what has caused the lack of blood glucose control. For patients who are not equipped with the ability to understand such issues, the only way to stay in control is to adhere to a very stringent schedule of daily insulin, food and exercise that does not vary from one day to another. Such a regimen poses serious compliance and lifestyle problems. For these patients, solutions based on mathematical modeling are available: The body of a healthy person has the endogenous control capability to minimize the glycemic challenge to the body, but the diabetes patient has little or no endogenous control capability. Maintaining blood glucose levels within normal limits can be treated as a control systems engineering problem, which was, and continues to be the object of much research. Those who published their work in this field (Heinonen, Porumbescu, etc.) considered the body's blood glucose system a classic control system, consisting of a plant whose aim is to maintain control over an output (Blood Glucose), in the presence of zero or non-zero inputs (food, physical exercise, insulin), and of perturbations (emotional status, illness). The euglycemic output is achieved by feedback: continuously measuring the output values, comparing them to the desired state (set point), and initiating compensatory action. By contrast, in diabetes this is an open-loop system, in need of an external feedback loop, therefore attempts were made to provide it through mechanical means. After more than twenty years of trying, it can be safely said that attempts to devise mathematical models for blood glucose metabolism have failed. The reasons are numerous, but one of the most important is that models that will work properly for an entire population are very complicated and include nonlinear equations. Some degree of success has been reported with developing adaptive individual-specific models, which will work in conjunction with a strict regimen that does not vary from one day to another. For example, U.S. Pat. No. 5,840,020 (Heinonen et al.) addresses the adaptive model shown in FIG. 4, whereby the error between a predicted value and the actually measured value is used to optimize (converge) a dynamical model in a recursive fashion, using Widrow's Adaptive Least Means Square algorithm. Similarly, Porumbescu et al. (“Patient Specific Expert System For IDDM Control” in Proceedings of the Fourth Conference of the International Federation of Automatic Control/System Structure and Control, October 1997) report on the development of an Expert Equipment that optimizes a dynamical model using Kalman recursive filtering. The rapid spread of increasingly affordable high speed computers gives this type of research more impetus, and several researchers have recently reported significant progress. One commercial software package, based on a very simple prediction model has been introduced in 1995 (Insulin Therapy Analysis, by ITA Software Inc.). The AIDA Interactive Diabetes Advisor, which uses a similar modeling and prediction approach is available over the internet. Yet another system, KADIS, is in use in Germany as a model-aided education tool for IDDM patients. What all these solutions have in common is the inability to process the information and generate predictions in an on-going manner. For this reason they are more in the nature of educational tools, than of assistive devices. While they may, to some extent, be able to generate sufficiently accurate predictions, those predictions apply only to a known and very rigid, set of inputs. And, while with a good model, the patient will likely be able to generate a close enough prediction for one different input one time, the performance cannot generally be repeated several times in a row, because the initial conditions have changed. The complicating factor is that to achieve contemporaneous control, the modeled external feedback loop must include not only static corrections, but also predictive elements relative to the dynamics of the patient's body. BRIEF SUMMARY The present invention relates to decision support equipment and improved methods for providing individuals with means to proactively control their health. The invention subject also relates to computing equipment suitable for processing data to simulate the dynamics of the metabolic processes and their inputs, in order to generate real time predictions of the metabolic status. The subject invention further relates to knowledge-based apparata used in controlling management-intensive medical conditions, including apparata for noninvasive assays of metabolic analytes. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 : A flow chart and block diagram of the software and steps involved. FIG. 2 : Diagram showing the system, including software, hardware, and patient. FIG. 3 : Graph illustrating the differences in glucose bio-availability for different types of food, computed according to the invention. FIG. 4 : Prior art illustration of “static” adaptive model. FIG. 5 : Principle of operation of the wedge-and-Strip position-sensitive detector (prior art): The centroid position computation in Wedge-and-Strip patterns is based on the following property of the wedge-and-strip inter-digital pattern: An electron cloud, having diameter larger than the pitch, lands on the pattern. With the collected charges Q s , Q w as shown, and Q 0 for the substrate, the [X,Y] coordinates of the centroid of the cloud are simply computed as: X=2 . Q s /( Q s +Q w+ Q 0 ) Y=2 . Q w /( Q s +Q w+ Q 0 ) FIG. 6 : Optical Spectroscopy apparatus having a wedge-and-strip array as photodetector. DETAILED DESCRIPTION Decreasing costs for computers and communications and increasing pressures to contain health care costs promote technology-intensive proactive approaches to health care, especially in diabetes, but the invention is also applicable to any other medical condition where measurements are routinely made. The main benefit is that the patient has the ability to implement proactive actions that do not affect his or her life style in a major way, which leads to greatly improved health outcomes and compliance. The invention puts control ahead of measurement, giving people the means to understand what is happening with their bodies with respect to a set of parameters of interest, relying on the fact that proactive control is more desirable than the current test-fix-test (an approach with which one is instinctively comfortable). To that end, the invention provides a group of software programs and ancillary equipment to compute an individual patient's profile and make contemporaneous accurate predictions regarding how the patient's biological system will respond to individual stimuli: predictions are communicated in real time, enabling plans for future actions by verification of good control status, or signaling the need for corrective action. Thus, contemporaneous decision support is provided to the patient. The subject invention provides for customizing traditional population-based solutions to an individual patient's needs and adding the time dimension (i.e., attaching a time function to each variable of interest). This approach is superior because it allows prevention-driven proactive care at the health care consumer level, when the consumer needs the information, not after the fact. It is also more accurate and effective: The invention is based on three basic concepts: 1) Control is more relevant than measurement. Devices of the future, which will mimic life itself, must target the overall success of metabolic control—keeping the parameters of interest within the target range—to know any value with accuracy and precision is less relevant. A patient-specific system model converges much quicker to “good enough” approximations of the outputs of the real system than one that only uses general population data; 2) Proactive control mimics life. In control systems parlance, these are “feedforward” systems as opposed to measure-and-correct, or “feed back” that we accept instinctively. Unlike current devices that test something and generate a value that must be processed to generate information, our noninvasive measurement devices aim to use the prior knowledge about the dynamics of the system being measured, in order to generate “heads up, in or out of control” signals, usable directly by the consumer; and 3) Living things reflect the dynamics of their inputs—this is borne by research in system control theory, which indicates that stable feedforward systems have structures that are actually governed by the dynamics of their input functions. Ultimately, these basic concepts mean that the invention addresses the problem from a duality point of view: Dualities between control and estimation problems are useful concepts in optimal control theory because by demonstrating a duality, the solution to one set of problems can be applied also to the dual set of problems. As discussed by Bernhardsson et al. “A duality is demonstrated between optimal feedforward control and optimal deconvolution, or input estimation. These two problems are normally discussed separately in the literature, but have close similarities.” Managing a management-intensive disease such as diabetes involves an individual about whom considerable knowledge exists, and knowing when to test is usually more important than the test results. With careful consideration of all major inputs and outputs, total system models can predict much of what is occurring; therefore total system individual-specific modeling is as important as the measurement method, be it invasive or noninvasive. Blood glucose and interstitial fluid glucose dynamics are dominated by smooth time functions that describe the temporal transformation of a food input to glucose (the output): To that end, using carbohydrate counting to simulate the system input in conjunction with a feedback model, no matter how accurately the carbohydrates are counted, is like hitting a radio with a hammer and calculating its Dirac pulse response in order to understand how it's built. The methodology to describe the exogenous glucose dynamics for various foods which is part of this invention is the direct result of this challenge. Rather than aiming for measurement accuracy and precision, the objective of the invention is to provide the individual with sufficient information to achieve proactive metabolic control, including the optimal timing and specifics of key activities such as insulin injections, blood glucose measurements, meals, exercise, etc. That is, to pursue regimen flexibility instead of rigidity. Using the models for the input dynamics results in a drastic simplification of the complexity of the models of the metabolic system. Progress in the area of non-invasive SMBG will complement the methodology by providing more frequent clinical data points and thus helping the model converge to a sufficient prediction accuracy within a shorter time period. For IDDM patients who will not be able to afford the non-invasive SMBG equipment, the use of predictive technology in conjunction with a HUMALOG™ (lispro) type of insulin will be able to achieve euglycemia. The subject invention provides methods of generating ongoing status predictions for improved decision support in metabolic control, comprising at least one of the following steps: (a) entering ongoing information from the user-patient and from biomedical assay equipment according to an interactive, time-stamped mode which includes at least one of the following sub-steps: (a)(1) selecting and specifying inputs to the living system being controlled, plus specific descriptors and quantifiers of said inputs, wherein the said inputs may include nutrients, medication, physical activity, illness, or hormonal challenges; (a)(2) recording individual-specific anthropometrical, medication prescriptions, and treatment regimen data, wherein the said treatment regimen data also includes physician-prescribed metabolic control guidelines, including rules that define the “in-control range” and “sufficiently close” terms; (a)(3) selecting output parameters and entering their measured values; and (a)(4) selecting hypothetical inputs, wherein the user can evaluate a course of action over other possible actions. (b) accepting or rejecting said input and output values and storing the information contained therein in appropriate memory areas, wherein each associated time stamp is properly stored as well; (c) assigning to each said specified input an appropriate time function describing its dynamic characteristics and computing the predicted values thereof in an ongoing manner, starting said predictions from the time of the appropriate time stamp data; (d) assigning to each said output parameter a mathematical model describing its dynamic interactions with the said inputs and improving said mathematical model by making it individual-specific by the following sub-steps: (d)(1) accepting individual-specific anthropometrical data and storing the information contained therein in appropriate memory areas; (d)(2) performing appropriate computations, wherein said anthropometrical data is incorporated in each said output parameter mathematical model; (e) generating ongoing metabolic status predictions by combining all previous relevant said inputs with said individual-specific mathematical models, wherein the accuracy of the said predictions is improved by one or more of the following substeps: (e)(1) selecting from the universe of possible mathematical models only those that meet physiologically meaningful periodicity criteria, wherein they reflect circadian, menstrual and other applicable cycles that affect the process; and (e)(2) further improving the said mathematical models by selecting from the universe of possible mathematical models only those that lead to predicted values that are “sufficiently close” to the actual measured values. (f) recording, revising and storing the prescribed individual-specific medication and control parameter limits, wherein a health practitioner sets boundaries on the type of actions the patient can take; and (g) communicating to the patient the need for proactive corrective action, wherein any such need is determined by considering steps (e) and (f). The subject invention also provides methods for estimating the ongoing “dynamic bio-availability” of metabolites subject to control, comprising at least one of the following steps: (a) dividing the intake matter into distinct components, whereas each component is uniquely characterized by the dynamics of its transformation into a metabolite; (b) assigning each said distinct component to an elementary category, wherein each category is described mathematically by a category-specific time function; (c) calculating the time functions corresponding to the said distinct components, by accounting for all relevant quantifiers available for the intake matter; and (d) calculating the combined effect of said elementary components as a function of time. The intake matter may be food, and the metabolites are “exogenous glucose” from food. Category-specific time functions are described by a time function having a general form such as would be required to describe mathematically the output from a chain of N compartments connected with one-way fluxes of the same rate a, given for example by, but not limited to, the expression: EG ( t )= a N t N−1 c −nt /( N −1)! wherein “EG(t)” is elementary food component glucose activity time function; “t” is a length of time measured from the time stamp of entered data, such as the time the food was consumed; “a” is the flux rate of elementary food categories; and “N” is the number of compartments. In various embodiments, “a” is a population averaged value, “a” is specific for a given individual, or a=12 for all sugars, a=1/1.5 for starchy glucose, a=1/2 for starchy galactose, a=1/3 for starchy fructose, a=1/5 for protein, and a=1/8 for fats and N=1 to 5. Some embodiments provide for N=4. Elementary food categories are simple sugars, starches, protein, and fat, wherein each of the said elementary categories is described by a unique pair of coefficients a and N. The elementary food categories are further refined by executing at least one of the following steps: (a) dividing each food category into sub-categories, each said sub-category being described by its unique pair of coefficients a and N; (b) dividing the food category “starches” into three sub-categories corresponding to glucose-based, galactose-based, and fructose-based carbohydrates; and (c) adjusting the values of any said pair of coefficients a and N to reflect any individual-specific differences in ability to process the said category or sub-category of food. Contemporaneous decision support in metabolic control may be achieved for diabetes, by pursuing two or more of the following steps: (a) generating time functions describing the time course of the exogenous glucose following a meal, according to the methods provided herein; (b) generating time functions describing the time course of the exogenous insulin following an injection or infusion pump action, according to the following method: (b)(1) generating specific time functions having a general form such as would be required to describe mathematically the output from a chain of N compartments connected with one-way fluxes of the same rate by, given for example by, but not limited to, the expression: I ( t )= b N t N−1 e −bt /( N −1)!  wherein “I(t)” is an exogenous insulin time function; “t” is a length of time measured from the time stamp of entered data, such as the time the particular insulin was injected; “a” is the flux rate of various insulin types; and “N” is the number of compartments. In various embodiments, “b” is a population averaged value, “b” is specific for a given individual, or b=1.0 for regular insulin, b=0.5 for NPH insulin, b=0.25 for lente insulin, and b=0.2 for ultralente insulin. N can be a value from 1 to 5. Some embodiments provide for N=4; (b)(2) refining said exogenous insulin time functions by accounting for the differences in insulin bio-availability experienced by the patient depending on the injection site; and (b)(3) refining said exogenous insulin time functions by accounting for the differences in insulin bio-availability experienced by the patient depending on the patient's degree of insulin resistance. (c) generating time functions describing the time course of the physical exercise and other manually-entered inputs, according to the following method: (c)(1) generating specific time functions having a general form such as would be required to describe mathematically the output from a chain of N compartments connected with one-way fluxes of the same rate c, given for example by, but not limited to, the expression: PE ( t )= C N t N−1 e −c(t−d) /( N −1)!  wherein c takes specific values for each different type of exercise, and d is a delay factor; and (c)(2) refining said physical exercise time functions by accounting for the differences in insulin bio-availability experienced by the patient depending on the injection site; and (c)(3) accounting for the additive or subtractive effect of illness, medication, or hormonal challenges by correcting the insulin input information accordingly. The subject invention also provides a personal assistive apparatus for contemporaneous metabolic control, wherein a health practitioner programs the prescription and limits the type and extent of actions a patient is allowed to take by means of a hierarchical software structure. The invention also provides an apparatus for computing the bioavailability of exogenous glucose and other nutrients contained in food, consisting of: (a) an interface and control device that accepts user input and provides information for the assessment and control of the ongoing metabolic state of the individual user; (b) a data storage device containing an addressable food data base, and software wherein each element in the said food data base is decomposed vectorially into elementary food categories; (c) a data storage device that contains a plurality of coefficient values and time function formats, wherein such coefficients and time functions appropriately describe the expected variation in time of one or more metabolites in vivo, under certain input conditions; and (d) software and means for computing and storing the predicted input time functions for the characteristics of the specified inputs. The personal assistive apparatus for contemporaneous metabolic control may further comprise a means for determining the current values for at least one output parameter, such as the blood glucose level, wherein such determination results from direct input by the individual patient, or from direct download from an instrument measuring the concentration of said blood glucose; software and means for computing the estimated current values for the said blood glucose level; software and means for comparing the estimated current values for the said blood glucose level with their contemporaneous measured correspondent values, in order to optimize the mathematical model of the metabolic control system; software and means for predicting values for the future state of the blood glucose level, including means to decide if and when said blood glucose values are expected to fall outside the range defined by the “in-control” rules; and/or a means for alerting the user whenever any such predicted output parameter values fall outside the range defined by the “in-control” rules. The device may also present information to the user, through a graphical user interface, a color-coded or pictorial representation of the time course of the blood glucose, enabling the user to assess how every new action taken will modify the said representation. The personal assistive apparatus for contemporaneous metabolic control may further comprise a means to compute and store functions indicative of the degree of control achieved by the individual patient over a period of time, such functions consisting typically of the aggregation of the severity-weighted time integrals of all out-of-control situations likely to have been experienced by the patient over the reporting period. Additionally, the personal assistive apparatus for contemporaneous metabolic control can further comprise at least one of the following devices: an insulin infusion pump; a blood glucose meter; a modem for communicating with other computers; wireless communication means for emergency situations; a meter that can test both glucose and fructosamine in the blood; a non-invasive blood glucose meter; a minimally-invasive blood glucose meter; a transdermal glucose measurement system. Alternatively, the personal assistive apparatus for contemporaneous metabolic control may further comprise an intelligent sensor consisting of at least: an optical spectroscopy apparatus employing at least one Wedge-and-Strip Position-Sensitive Photo-Detector, including means to detect the location of light pulses by employing analog decoding means; a means to illuminate a portion of a patient's body and onward the said Wedge-and-Strip Position-Sensitive Photo-Detector with light in certain portions of the infrared spectrum, wherein such illumination may be applied in a pulsatory fashion; a means to synchronize such light pulses with certain biological events, such as the heart beats; a means to accumulate the pulses read by the Wedge-and-Strip Position-Sensitive Photo-Detector into a histogram; means to calibrate the said optical spectroscopy apparatus by correlating the number of counts per second recorded in a certain portion of the histogram with the glucose concentration; a means to modify the duration of the measurement; and/or software for adapting the duration of the measurement according to the degree of prior knowledge about the analyte. The personal assistive apparatus for contemporaneous metabolic control can further comprise software for optimizing the peritoneal dialysis prescription of patients with diabetes who suffer from kidney disease or for optimizing the metabolic control regimen of pancreatic or protected beta-cells transplantation patients. The software can be optimized for the metabolic control regimen of newly diagnosed diabetes patients in a hospital or clinic setting. Alternatively, the software for optimizing the metabolic control regimen of astronauts during space flights or for optimizing the metabolic control regimen of people with special glucose metabolism needs, including but not limited to patients under intensive care, patients who have suffered trauma, premature babies, or people involved in performance sports. Definitions The term “acceptable serum glucose range” is intended to mean glucose levels above 50 mg/dl and below 300 mg/dl more preferably 80 mg/dl to 200 mg/dl and most preferably about 100 mg/dl. It will be understood by those skilled in the art that levels of about 50 mg/dl are considered low and that levels of about 300 mg/dl are considered high, although acceptable in the sense that these levels are generally not fatal. Insulin Dependent Diabetes Mellitus, or IDDM is a syndrome of disordered metabolism, leading to hyperglycemia due to an absolute deficiency of insulin secretion. The only known way to prevent the patient's death is by administering insulin. The term “metabolism” is used here in its general sense, and it summarizes the activities each living cell carries on. The term “dynamic bio-availability” reflects the time course of a certain metabolite, typically expressed as the changes in its quantity in blood. The term “exogenous blood glucose” means glucose appearing in the blood stream as a result of the steps involved in assimilating food. The term “in-control range” is a patient-specific term, reflecting the physician's assessment of the range of values within which a patient must try to maintain the metabolite being controlled. Insulin Dependent Diabetes Mellitus, or IDDM is a syndrome of disordered metabolism, leading to hyperglycemia due to an absolute deficiency of insulin secretion. The only known way to prevent the patient's death is by administering insulin. Normoglycemia is a patient-specific state, which can be thought of as a metabolic set point of 100 mg/dl, within a “normal range of 60 to 120 mg/dl. The specificity means that, for example, a person's blood glucose may never exceed 120 mg/dl, while another's may exceed 150 after every meal due to that person's increased resistance to the counter-regulatory hormone insulin, or it may go below 50 mg/dl every day, due to some prolonged physical strain at work, or due to over-excretion of insulin. The term “sufficiently close” is used here in the following sense: a confidence band of physiologically-significant width around the measured metabolite values, that must contain all the predicted values for that metabolite for the same time stamp and input history combinatoin The term “time-stamped”, as used in conjunction with information events entered into the device, means associating each such event with the correct time it has occurred, either through mechanical means or by having the user actually enter the correct time into the device. While there have been described what are believed to be the preferred software and hardware embodiments of the invention, those skilled in the art will recognize that other and further motifications may by made hereto without departing from the spirit of the invention, and it is intended to claim all such embodiments as fall within the true scope of the invention. References U.S. Patent Documents: U.S. Pat. No. 5,840,020 Nov. 24, 1998 Heinonen et al. U.S. Pat. No. 4,731,051 Feb. 15, 1983 Fischell, R. Other References: Bernhardsson, B.; Sternad, M.; “Feedforward Control is Dual to Deconvolution” in International Journal of Control (February 1993). Porumbescu, A.; Dobrescu, R.; Jora, B.; Popeea, C.; “Patient Specific Expert System For Iddm Control” in Proceedings of the Fourth Conference of the International Federation of Automatic Control/System Structure and Control (October 1997). Salzsieder, E.; Albrecht, U.; Freise, E.; “Kinetic Modeling of the Glucoregulatory System to Improve Insulin Therapy” in IEEE Trans. In Biomedical Engineering BME-32, 846-855 (1985). Berger, M.; Rodbard, D.; “Computer Simulation of Plasma Insulin and Glucose Dynamics after Subcutaneous Insulin Injection” in Diabetes Care 12(10), 725—736 (1989).

The invention addresses hardware and software products capable to make contemporaneous accurate predictions regarding how a person's biological system will respond to a series of stimuli. The predictions can be communicated in real time, enabling confirmation if good control status, need for corrective action, planning future actions, or even outside intervention in case of emergency. Also addressed by the invention is a family of diagnostic hardware base on intelligent optoelectronic sensors that incorporate one or more Wedge-and-Strip Position-Sensitive Photo-Detectors optimized for probabilistic real time evaluation of spectroscopy data from living subjects.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application is a continuation of U.S. patent application Ser. No. 12/811,361 (published as US 2011/0315757), filed on Jun. 30, 2010, which is the U.S. National Stage of International Application No. PCT/IL2007/001632, filed Dec. 31, 2007, the content of each of which are expressly incorporated herein in its entirety by this reference. BACKGROUND [0002] Various analyzing devices, such as, for example, medical devices, use various types of connectors that are used as mediators for connecting between the medical device interface (the instruments itself) and external constituents, such as tubes, cannules, and the like that may be of the disposable type. An example of such medical device is a capnograph, which is an instrument for analyzing exhaled breath. A capnograph samples air that is exhaled by a subject by using a small tube, also known as sample line. One end of the sample line may be connected to an air passageway of a respirator or to a cannula attached to, for example, the subject nostril. The other end of the sampling line is connected, through a connector to the instrument itself. The sampling line, including the tube, the connector and other constituents, such as filters, and the like is, in most cases disposable and is replaced for each patient and for each patient type. For example, a subject which is a child will have a sampling line which is different (for example, in size) than a sampling line of an adult subject. [0003] In general, the shape of a connector is standardized throughout the industry, such that tube assemblies of various manufacturers may be interchangeably used with any analyzing instrument. Hence, the manufacturer of a particular type of analyzing instrument has generally no control over which type of tube is used with his instrument. Therefore, to ensure optimal functioning of the instrument, and for commercial reasons, the manufacturer of an analyzing instrument may want to exert such control. In particular, he may want to stipulate that only a certain class, type and/or model of tube assemblies be connected to, and used with, his instrument. Such a class may, for example, consist of tube assemblies that include a specific constituent, such as, for example, a filter, or such that are manufactured directly by him or to his specifications or under his supervision or license. [0004] Enforcing such stipulation may be performed by various means, such as, for example, by using a unique interlocking key arrangement between the connector and the instrument; having a system by which the correct tube assembly would be identified as such by the instrument, whereupon its operation would be enabled, and to disable the instrument otherwise, such as for example, by using electro-mechanical fitting, electrical fitting, and the like. Benefits of such arrangement would be that the instrument would be prevented from operation also when no tube is connected at all or when even a correct tube is improperly connected, thus avoiding damage to sensitive parts of the instrument and also causing incorrect readings. Yet another purpose may be served by such a system, namely identifying the tube assembly as belonging to one of a number of classes and informing the instrument of the particular identity detected, so as to enable it to automatically operate differently for the different classes. [0005] There is thus a widely recognized need for, and it would be highly advantageous to have, a fluid analysis system that includes the capability of determining that a tube assembly has been properly connected to the analyzing instrument and that the tube is of a certain class. Such a capability should be compatible with the standard shape of connectors being used, as well as with the medical environment, and should be reliable and inexpensive. SUMMARY [0006] The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other advantages or improvements. [0007] Medical analyzing devices may use various types of connectors that may be used for connecting between the medical device and external constituents, such as tubes, cannules, and the like that are usually disposable and are replaced for each patient. In general, the shape of a connector is standardized, such that tube assemblies of various manufacturers may be interchangeably used with any analyzing device. However, to ensure optimal functioning of the device and for commercial reasons, the manufacturer of an analyzing device may want to stipulate that only a certain class, type and/or model of tube assemblies be connected to and used with his instrument. Such stipulation may be achieved by having an identification and verification means between the medical device and the tube attached to the device. Such capability of determining that a tube assembly has been properly connected to the analyzing instrument and that the tube is of a certain class may further ensure optimal functioning of the medical device. Moreover, the identification and verification means may include any type of information that may be encoded on the end face of the tube connector and identified by the medical device. Accordingly, there is thus provided, according to some embodiments, one or more identification and verification means that may allow increased amount of information to be encoded on the end face of the connector and transferred between the connector and the device. The information encoded may improve the safety of using the device, simplify the use of the device and optimize the use of the device by ensuring an optimal operating mode of the device in accordance with the tube connector (and hence the tube/sampling line) attached to the device. For example, the information encoded on the end face of the connector may be used to determine the type/class and/or model of the connector, such as for example the patient interface, patient size, patient specific parameters, and the like. For example, the information may be used to determine if the connector type is a children's connector (a connector of sampling line that is to be used with children), an adult connector (a connector of sampling lines that is to be used with adults), and the like. This information may be used by the medical device to determine the optimized mode of operation for that type/class/model/manufacturer of connectors and patient interface. This may be achieved, for example, by use of optimized software algorithm to be used for that type of connector and sampling line. [0008] According to some embodiments, there is provided a tube connector for connecting between a fluid sampling tube and a fluid analyzer, the tube connector includes an end face adapted to identify the tube connector, said end face comprising a reflecting surface having one or more reflective regions adapted to reflect light at a predetermined range of wavelengths. [0009] According to some embodiments, the surface of the tube connector may be adapted to reflect light at one or more distinct wavelengths. The surface may further be adapted to selectively reflect light having different intensities. The surface may further include one or more reflective regions having distinct reflective properties. The surface may be patterned, wherein the pattern may include geometrical shapes, non-geometrical shapes, horizontal lines, vertical lines or any combination thereof. [0010] According to some embodiments, the fluid analyzer to which the tube connector is connected to may include a capnograph. [0011] According to further embodiments, the fluid analyzer may include a verification system adapted to identify the connector, wherein the verification system may include one or more light sources and one or more optical detectors. The one or more light sources may include a light emitting diode (LED), a lamp or any combination thereof. The one or more optical detector may include an RGB detector. [0012] According to other embodiments, the end face of the tube connector may further include a Radio Frequency Identifier (RFID) tag adapted to provide further identification of the connector type. The end face of the tube connector may further include a barcode tag adapted to provide further identification of the connector type. [0013] According to additional embodiments, the verification system of the fluid analyzer may further include a Radio Frequency Identifier (RFID) reader, a barcode scanner or both. [0014] According to some embodiments there is provided a device for analyzing fluid, the device includes: a device connector adapted to receive a tube connector and a verification system for identifying the tube connector, wherein said system comprises one or more light sources adapted to transmit light towards an end face of the tube connector, one or more optical detectors adapted to detect reflected light from the end face and to produce a signal indicative of the reflected light and a processor adapted to identify the tube connector type based on a signal received from the detector. [0015] According to some embodiments, the tube connector is adapted to connect between a fluid sampling tube and the fluid analyzer. [0016] According to additional embodiments, the end face of the connector includes a reflecting surface having one or more reflective regions adapted to reflect light at a predetermined range of wavelengths. The end face surface may be adapted to reflect light at one or more distinct wavelengths. The surface may be adapted to selectively reflect light having different intensities. The surface may include one or more reflective regions having distinct reflective properties. The surface may further be patterned, wherein the pattern may include geometrical shapes, non-geometrical shapes, horizontal lines, vertical lines or any combination thereof. [0017] According to additional embodiments, the fluid analyzing device may include a capnograph. The one or more light sources of the verification system may include a light emitting diode (LED), a lamp or any combination thereof. The one or more optical detector of the verification system may include an RGB detector. [0018] According to other embodiments, the end face of the tube connector may further include a Radio Frequency Identifier (RFID) tag adapted to provide further identification of the connector type. The end face of the tube connector may further include a barcode tag adapted to provide further identification of the connector type. [0019] According to additional embodiments, the verification system of the fluid analyzer may further include a Radio Frequency Identifier (RFID) reader, a barcode scanner or both. [0020] According to some embodiments, there is provided a verification system for identifying a tube connector attached to a fluid analyzer, the system includes one or more light sources adapted to transmit light towards an end face of the tube connector; one or more optical detectors adapted to detect reflected light from the end face and to produce a signal indicative of the reflected light; and a processor adapted to identify the tube connector type based on a signal received from the detector. [0021] According to additional embodiments, the verification system may be functionally associated with a device connector adapted to receive the tube connector. [0022] According to additional embodiments, there is further provided a method for identifying a tube connector type attached to a fluid analyzer, the method includes transmitting light from one or more light sources towards an end face of the tube connector; detecting reflected light from the end face by one or more optical detectors, producing a signal indicative of the reflected light and identifying the tube connector based on the signal. [0023] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the figures and by study of the following detailed descriptions. BRIEF DESCRIPTION OF THE FIGURES [0024] Examples illustrative of embodiments of the disclosure are described below with reference to figures attached hereto. In the figures, identical structures, elements or parts that appear in more than one figure are generally labeled with a same numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below. [0025] FIG. 1-A perspective view of a connector, according to some embodiments; [0026] FIG. 2A-A front view of exemplary end face patterns of a connector, according to some embodiments; [0027] FIG. 2B-A front view of exemplary end face patterns of a connector, according to some embodiments; [0028] FIG. 2C-A front view of exemplary end face patterns of a connector, according to some embodiments; [0029] FIG. 2D-A front view of exemplary end face patterns of a connector, according to some embodiments; [0030] FIG. 2E-A front view of exemplary end face patterns of a connector, according to some embodiments; [0031] FIG. 2F-A front view of exemplary end face patterns of a connector, according to some embodiments; [0032] FIG. 2G-A front view of exemplary end face patterns of a connector, according to some embodiments; [0033] FIG. 2H-A front view of exemplary end face patterns of a connector, according to some embodiments; [0034] FIG. 2I-A front view of exemplary end face patterns of a connector, according to some embodiments; [0035] FIG. 2J-A front view of exemplary end face patterns of a connector, according to some embodiments; [0036] FIG. 2K-A front view of exemplary end face patterns of a connector, according to some embodiments; [0037] FIG. 3A-A perspective schematic of a closeup side view of a connector and verification system, according to some embodiments, and [0038] FIG. 3B-A perspective schematic of a closeup side view of a connector and verification system, according to some embodiments. DETAILED DESCRIPTION [0039] In the following description, various aspects of the disclosure will be described. For the purpose of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the disclosure. However, it will also be apparent to one skilled in the art that the embodiments may be practiced without specific details being presented herein. Furthermore, well-known features may be omitted or simplified in order not to obscure the invention. [0040] According to some embodiments, there is provided an end face of a connector, the surface of which may have an annular, ring like shape. The surface of the end face of the connector may be an integral part of the connector, or may be permanently attached to the connector. The surface may include a flat, uniform surface. The surface may include a concave and/or convex surface. The surface may include a patterned surface, wherein the patterns may include recurring patterns of any desired shape. The surface may be a discontinuous surface. The surface may be divided to various regions/areas, wherein at last two areas have different characteristics. By characteristics may include different texture, different compositions, different chemical properties, different optical properties, different electrical properties, different magnetic properties, different surface concaveness, and the like. [0041] According to some embodiments, there is provided a connector, such as a tube connector that may be used to connect a tube to a medical device, such as for example a capnograph. Reference is now made to FIG. 1 , which illustrates a perspective view of a connector, according to some embodiments. The connecter, such as connector ( 2 ), may include 2 ends: a tube end ( 4 ), which is the end that may be connected to a tube; and a device end ( 6 ), which is the end that may be used to connect the connector to a device/instrument. Connector, such as, connector ( 2 ) may be a male or a female type connector that may be received/connected/attached/ to a matching female or male connector (referred to herein as a “device connector”), respectively, located on the device, such as, for example, on the device panel. The connector, such as connector ( 2 ), may have an elongated cylindrical-like shape. Spiral threads, such as threads ( 8 ), may be found at the outer surface of the connector in close proximity to the device end ( 6 ) of the connector ( 2 ) and may be used to secure the connector to its matching connector on the device (the device connector). At the tube end ( 4 ) of the connector ( 2 ), gripping wings, (such as, gripping wings 10 A-B in FIG. 1 ) are located. The end face ( 12 ) of the device end ( 6 ) of the connector ( 2 ) may have a circular, annular shape. The end face may form as an integral part of the connector ( 2 ), or may be an external surface that is permanently attached to the device end ( 6 ) of the connector ( 2 ). The end face ( 12 ) surface may be a continuous or discontinuous surface, which may include at least two regions/areas that are distinct from each other. By distinct from each other may relate to physical, mechanical, electrical, optical, and chemical properties, such as, for example, but not limited to: shape, pattern, texture, color, size, electrical properties, reflectivity, composition, magnetic properties, and the like, and any combination thereof. The distinct regions of the end face of the connector may be used as an identifying means to the medical device to which the connector is to be connected and consequently to affect a decision process in the device and hence the operation mode of the medical device. The distinct regions of the end face of the connectors may be used to encode data that may be read/identified and used by the medical device. The encoded data may include, for example, the type/class of the connector, the model of the connector, manufacturer of the connector, preferred mode of operation with that connector, and the like. [0042] Prior art, such as that described in U.S. Pat. No. 6,437,316 teaches that the annular end face of the device end may be specularly reflective to light. The reflectivity may be obtained, for example, by coating the surface with a suitable reflective layer, by polishing the surface to a glossy, by hot-pressing a reflective foil and the like. In particular, the reflective surface need not extend over the entire width of the end face, but it must form a complete annular ring. However, such a connector may be identified by the device by only one verification way (meaning—reflection of light at one range of wavelengths). There is thus a need to combine additional verification ways in order to allow the connector to be used with various types/models of devices and also to allow increased amount of information to be encoded on the end face of the connector and transferred between the connector and the device. This may allow a more accurate, efficient, simple and safer mode of operation of medical device. [0043] As referred to herein, the term “the end face of the connector” relates to the end face of the device end of a connecter, such as connector 2 of FIG. 1 , unless otherwise stated. [0044] As referred to herein, the terms “amplitude” and “intensity” may interchangeably be used. [0045] As referred to herein the term “type”, “model”, “class” of the connector may interchangeably be used and may relate to the interface to be used with the tube connector and/or manufacturer of the tube connector. [0046] According to some embodiments, the end face of the connector may include more than one region with distinct reflectivity characteristics. The regions may be adjacent to each other or may be spatially separated. Each of the regions may be reflective at a different range of wavelength and/or possess different level (amplitude, intensity) of reflectivity and/or may be non-reflective (such as, for example, colored black, which absorb all light and does not reflect back). For example, the end face may include two spectrally distinct reflective regions. Each of the regions may comprise about half of the annular circumference of the end face. For example, one region may be spectrally reflective such that when light is emitted at the end face, this region may reflect at one amplitude, while the second region may reflect at a second amplitude. For example, one region may be spectrally reflective such that when light is emitted at the end face, this region may reflect light at one wavelength (for example, at the green color range of wavelength), while the second region may reflect light at a second wavelength (for example, at the red color range of wavelengths). The reflected lights may be detected by matching detectors located in the medical device and then further processed/analyzed to confirm the connection between the connector and the medical device, as further detailed below herein. The distinct regions of reflectivity of the connector end face may be coated or comprised of various materials that possess different reflectivity characteristics. For example, the distinct regions may have reflective materials that contain dyes or pigments. For example, the distinct regions may be coated with suitable spectral filters. For example, the distinct regions may have different surface areas, such as, for example, a flat surface, a concaved surface, a convex surface or any combination thereof. [0047] According to some embodiments, in addition to determining various wavelength ranges of reflectivity of connectors with more than one reflective region at their end face, the amplitude and the threshold levels of reflectivness may also be determined. The threshold levels of reflectiveness may be used as an additional data encoding means that may be used to distinguish between various types/models of connectors. For example, a connector that exhibits reflectivity of above a predetermined threshold value may belong to a certain type of connector (for example, connectors of sampling lines that are to be used with children), while connectors with a lower threshold (that may include, for example, at least two distinct regions of reflectivity at the connector end face) may belong to a different type of connector (for example, connectors of sampling line to be used with adults). For example, the threshold levels may be used to distinguish between connectors manufactured by different manufacturers. [0048] According to further embodiments, the end face of the connector may include various patterns that may be distinguished by their characteristics/properties. The patterns may include any shape, such as geometrical shapes (such as circles, triangles, squares, and the like), non-geometrical shapes, such as hearts, droplets, waves, and the like. The patterns may further include any combination of shapes. The shapes may include any size and any number of shapes that may be distributed evenly or non-evenly over the surface of the end face of the connector. The patterns may include recurrent patterns. The patterned regions on the surface of the end face connector may exhibit different characteristics than the non-patterned region surface. Different characteristics may include, for example, optical characteristics, such as, for example, various reflectivness properties. [0049] According to additional embodiments, the end face of the connector may include any combination of lines, dots, spots and the like that may be distributed evenly or non evenly over the surface of the end face of the connector. For example, the lines may include straight lines, curved lines, checkered lines, and the like. Areas/regions defined by the combination of lines may possess different characteristics than other regions. Different characteristics may include, for example, optical characteristics, such as, for example, various reflectivness levels, various wavelength ranges of the reflected light, and the like. According to further embodiments, the surface of the end face of the connector may include one or more concave regions and one or more convex regions. The concave regions may focus the reflected light and the convex regions may defocus the reflected light and thus different levels of reflectivity from different regions of the end face of the connector may be obtained. [0050] Reference is now made to FIGS. 2A-K , which illustrate exemplary end faces of a connector according to some embodiments. For example, end face A illustrates an annular end face of a connector with two regions with distinct reflective properties. For example, end face B illustrates an annular end face divided into three equal regions, wherein at least one of the regions has distinct reflective properties. For example, end face C illustrates an annular end face divided into four equal regions, wherein at least one of the regions has distinct reflective properties. For example, end face D illustrates an annular end face of a connector with a reflective surface and spots, at least one of which is with distinct reflective characteristics. For example, end face E illustrates an annular end face of a connector with a reflective surface and circles distributed over the surfaces, at least one of the circles exhibits distinct reflective characteristics. For example, end face F illustrates an annular end face of a connector with a reflective surface and heart shaped regions distributed over the surfaces, at least one of the heart shaped regions exhibits distinct reflective characteristics. For example, end face G illustrates an annular end face of a connector with a reflective surface and squares distributed over the surfaces, at least one of the squares exhibits distinct reflective characteristics. For example, end face H illustrates an annular end face of a connector with a reflective surface and horizontal lines stretched over the surface, at least one of the areas bound between the lines exhibits distinct reflective characteristics. For example, end face I illustrates an annular end face of a connector with a reflective surface and horizontal and vertical lines distributed over the surface, at least one of the areas bound between the lines exhibits distinct reflective characteristics. For example, end face J illustrates an annular end face of a connector divided into two separate, non-continuous regions, wherein at least one of the regions has distinct reflective properties. For example, end face K illustrates an annular end face of a connector divided into three separate, non-continuous regions, wherein at least one of the regions has distinct reflective properties. For example, end face L illustrates an annular end face of a connector divided into four separate, non-continuous regions, wherein at least one of the regions has distinct reflective properties. [0051] According to some embodiments, the medical device may include a verification system that may be used to detect/identify the connector (and hence the tube) attached to the medical device. Identification/detection of the connector that is attached to the medical device may be performed by detection/identification of any of the properties/parameters of the end face of the connector that are described herein. For example, the verification system of the medical device may detect/identify the optical properties (as determined by the reflectiveness properties) of the end face of the connector. The verification system may include one or more optical light source emitters (such as, for example, Light Emitting Diodes (LEDs)) that may emit light at various individual wavelengths and/or at a wide spectral range of wavelengths. For example, the light source may include a Light Emitting Diode (LED) that may emit light at the visible white light spectral range (for example, at the range of 0.4 to 0.7 mm). The verification system may further include one or more optical receivers that may be adapted to receive light reflected from the end face surface of the connector. The optical receivers may be spatially separated from the light source emitters so as to ensure that light detected by the optical receivers is the light reflected from the end face surface of the connector. Spatial separation may be performed, for example by placing an optical barrier between the light source and the optical receiver. The spatial separation may be performed, for example, by use of optical wave guides that may be used to create a channel/chamber, at the bottom of which the optical detector is situated. The use of such a chamber may ensure that only light that is reflected from the end face surface of the connector reaches the optical receiver, while light, such as scattered light from the environment, direct light from the light source, and the like, is prevented from reaching the optical detector. The reflected light from the end face of the connector may be at various wavelengths and at various amplitudes (intensity levels), which may be determined by the reflective properties of the surface of the end face connector. The optical receiver may include any type of light and/or color detector. The optical receiver may include more than one optical receiver, which may be adapted to receive light at the wavelengths, which correspond to the wavelengths of the light reflected from the various regions of the end face of the connector. For example, the optical receiver may include one or more light detectors that may be used to detect intensity of reflected light. The optical receiver may include a light detector that may be further equipped with an optical filter that may allow the optical detector to identify a specific, predetermined range of wavelengths that correspond to the optical filter. For example, the optical detector may include an RGB detector, which is well known in the art. Briefly, an RGB detector may be basically described as a multi-element photodiode coupled to red, green, and blue filters, that enable the photodiode to generate separate response curves for the three colors and hence determine the color (wavelength) and the amplitude (intensity) of the light detected by the photodiode. As such, the RGB color detector that may be used to detect light of various wavelengths (which correspond to different colors) may be reflected from one or more surfaces of the end face of the connector. The RGB detector may further be used to detect the amplitude (level) of the reflected light from one or more surfaces of the end face of the connector. According to additional embodiments, the optical receiver may be adapted to receive light at a wavelength which corresponds to the wavelength of the light reflected from a region of the end face of the connector and to further receive light at a second wavelength, which may correspond to the wavelength of the light reflected from other region(s) of different reflectivity of the end face surface. According to other embodiments, the light reflected from the regions of different reflectivity on the surface of the end face of the connector may be conveyed by the use of, for example, optical fibers that may collect the signals reflected from the individual spots into one optical signal that may be received by the second receiver. [0052] Reference is now made to FIGS. 3A and 3B , which illustrate a schematic drawing of a close up side view of an end face of a tube connector and the medical device verification system, according to some embodiments. As shown in FIG. 3A , verification system 100 , includes one or more light sources (shown as one light source, 102 ). The light source may include, for example, a LED that may emit light a the white light spectral range. The verification system further includes one or more optical receivers (shown in FIG. 3A as one optical receiver, 104 ). The optical receiver may include, for example an RGB detector. The verification system may further include an optical barrier, such as optical barrier 106 , that may be used to prevent light emitted from a light source (such as light source 102 ) from directly reaching the optical receiver (such as optical receiver 104 ). Also shown in FIG. 3A , the end of connector, (such as connector 108 ) and the end face surface of the connector, (end face 110 ). When operating, the verification system light source may emit light (illustrated as arrow 112 ). The light emitted from the light source may be reflected (illustrated as reflected light (arrow 114 )), depending on the reflectiveness properties of the connector end face ( 110 ). Reflected light 114 may reach the optical receiver 104 , that may consequently determine the optical properties of the reflected light (such as color (wavelength) and amplitude (intensity). According to the determined optical properties of the reflected light, the verification system (as detailed below herein) may determine the type/model of the connector attached and further determine the operation mode of the medical device. As shown in FIG. 3B , verification system 200 , may include one or more light sources (shown as one light source, 202 ). The light source may include, for example, a LED that may emit light at the white light spectral range. The verification system further includes one or more optical receivers (shown in FIG. 3B as one optical receiver, 204 ). The optical receiver may include, for example an RGB detector. The verification system may further include one or more optical guides, such as optical guides 206 A-B that may form a tunnel/chamber, such as chamber 209 , at the bottom of which, optical receiver ( 204 ) is positioned. The optical guides may be used to prevent light emitted from a light source (such as light source 202 ) from directly reaching the optical receiver (such as optical receiver 204 ), as well as other light that is not reflected from the connector end face. Also shown in FIG. 3B is the end of connector, (such as connector 208 ) and the end face surface of the connector, end face 210 ). When operating, the verification system light source may emit light (illustrated as arrow 212 ). The light emitted from the light source may be reflected (illustrated as reflected lights (arrow 214 A-B)), depending on the reflectiveness properties of the connector end face ( 210 ). Only light that is reflected at an acute angle (such as reflected light 214 A) may enter chamber 209 and reach the optical receiver. Other reflected light (such as 214 B) is prevented from reaching the optical receiver. Likewise, light that may originate from other sources, such as scattered light from the environment (demonstrated as arrow 216 ) is prevented from reaching the optical receiver. The optical receiver that may consequently determine the optical properties of the detected reflected light (such as color (wavelength) and amplitude (intensity)). According to the determined optical properties of the reflected light, the verification system (as detailed below herein) may determine the type/model of the connector attached and further determine the operation mode of the medical device. Additional elements/constituents of the verification system that are detailed below herein, such as wires, fibers, power sources, electrical circuits, comparators, integrators, and the like are omitted from drawings 3 A and 3 B for clarification purposes. [0053] According to some embodiments, and as mentioned above herein, the medical device may include a verification system that may be used to de-encode the data encoded on and by the end face of the connector. The verification system may be used to analyze the properties and characteristics of the connector attached to the medical device, and accordingly change the mode of operation of the device. For example, in relation to detection of reflected light by the end face of the connector, the medical device may include the various electrical circuits that may further include various constituents for generating and processing optical signals transmitted to the connector end face and received therefrom and based upon the analyzed results determine if the connector is properly connected to the medical device and identify what is the type, class, model and/or interface of the connector (and hence the tube attached thereto). According to some embodiments, the electronic circuits may include several constituents, such as, for example, but not limited to: one or more light sources (such as, for example, LED adapted to emit light at various wavelengths, Infra Red light source, Ultraviolet light source, laser light source, and the like); photodiodes adapted to receive emitted and reflected light and convert the signal to electrical signal; RGB detector; fibers, such as optical fibers adapted to transfer light (emitted and reflected) between the medical device and the connector; one or more amplifiers adapted to specifically amplify the light reflected from the connector end face; filters, adapted to emit and/or receive reflected light of a specific wavelength; one or more synchronous detectors adapted to synchronize light pulses emitted from the one or more light sources, respectively; one or more integrators adapted to receive a voltage signal from the one or more synchronous detectors and integrate the voltages over a certain time period to yield voltage values (for each of the light sources); one or more comparators/processors which are adapted to compare/process the voltage value obtained by the one or more integrators to predetermined threshold values that correspond to the various light reflections from the connector. The one or more processors may be adapted to process the information received from the detectors and to provide identification of the tube connector based on the signals received from the detector. The one or more comparators/processors may yield a signal that may be used by the medical device to determine if the connector is properly attached to the device and if the connector is of the right type, class and/or model and accordingly modify the operation of the medical device. If, for example, the binary signal received indicates that improper connection is detected between the device and the connector, the device may not operate until the attachment is corrected. For example, if the signal indicates that the connector is attached to a sampling line (tube) adapted for children, than the device may operate accordingly and be adjusted (for example, automatically) to operate under “children” mode. For example, if the calculated/measured signal is indicative that the connector is attached to a sampling line that is to be used with intubated patients, the device may operate accordingly and be adjusted to operate under “intubated patient” mode. In addition, the verification system of the medical device may further include one or more additional detectors/receivers that may be used to detect/sense/measure/receive additional features/characteristics/properties/information that may be encoded on and by the end face of the connector, as further detailed below herein. [0054] According to some embodiments, the identification of the connector (and hence the tube) being attached to the medical device may be performed in various ways, such as, for example, while the connectors are being attached (“on the “fly”), after the connectors have been attached (“final position”) or any combination thereof. For example, the identification (and verification) of the tube connector being attached may be performed on the fly, during the attachment (connection) of the tube connector to its corresponding connector on the device. The connection may be performed, for example by pushing and/or turning and/or screwing the tube connector to its location in the device connector. During the time of insertion, the tube connector may be identified by the verification system by any of the methods described herein, such as, for example, by identifying distinct regions of reflectivity (amplitude and/or wavelength) of the end face of the connector; by identifying recurring changes of reflectivity during the revolving of the tube connector relative to the device connector, and the like. The identification (and verification) of the tube connector attached to the device may be performed after the tube connector is attached to its respective device connector, while the connectors are at their final (resting) position. Such identification may be performed by the verification system of the medical device by any of the methods described herein. [0055] According to some embodiments, the relative final location (alignment) of the end face of the connector with respect to the detectors/receivers of the verification system of the medical device may be determined. For example, the relative location (alignment) of the end face of the connector with respect to its matching device connector may be determined. Determining a desired relative location of the end face of the connector to its matching device connector may be used to allow proper alignment between the respective locations of the two connectors and hence, a desired respective location between the end face of the connector to the verification system of the medical device. Proper alignment may be used to allow matching between regions of the end face of the connector and, for example, respective receivers/detectors (such as, for example, optical receivers) of the verification system of the medical device. Determination of the desired relative location (alignment) between the end face connector and the verification system of the medical device may be performed by various means, such as, for example but not limited to physical barriers, mechanical fitting, visual fitting, manual fitting, and the like. For example, proper alignment may be achieved by matching projection(s) and depression(s) on the end face connectors and its matching device connector; key and lock fittings on the end face connector and its matching device connector; markings on the end face connector and its matching device connector, to which it is to be attached, and the like. For example, the end face connector may include projection at the circumference of the device end of the connector. The device connector may include a matching depression. In order to physically attach the two connectors, the respective projection and depression must match. Matching the respective projections and depression of the connectors ensures the proper relative alignment of the end face of the connector with the corresponding receivers/detectors of the verification system of the medical device. In such a manner, different regions of the end face of the end face connector may be distinguishable and may allow identification and/or verification of the end face and further, the tube being used. For example, the end face connector may include a marking, such as a line, at the circumference of the device end of the connector. Likewise, the connector device may include a marking, such as a line, at the circumference of the device connector. After (or during) attaching the connectors, the two markings on the two connectors must be aligned. Alignment of the markings on the connectors ensures proper relative alignment of the end face of the connector with the corresponding receivers/detectors of the verification system of the medical device. In such a manner, different regions of the end face of the connector may be distinguishable and may allow identification and/or verification of the end face and hence the tube being used. [0056] According to some embodiments, the threshold values may be chosen to be such that would discriminate between integrated voltage values that result from the reflection of light from various regions of the end face of the connector and other sources of light. The threshold values may further be used to discriminate between various types of connectors, such as, for example, between connectors that may have only one reflective region on the end face and connectors that may have more than one reflective region on their end face. In addition, the threshold values may be used to discriminate between connectors that have one or more reflective regions on their end face and connectors that have no reflective regions on their end face. In addition, the threshold values may be used to discriminate between various types, classes and/or models of connectors, that may be adapted for various uses (for example, use with children sampling lines, adults sampling lines, and the like). [0057] According to some embodiments, the end face of the connector may include an additional distinguishing feature in addition to being reflective. For example, the additional feature may include radioactive labeling of at least a distinct region of the end face. The radioactive labeling may include spots deposited along the annular circumference of the end face of the connector. The radioactive spots may include radioactive labeling using any common radioisotope, such as, for example, deuterium (H 3 ), C 14 , P 32 , S 35 and the like. In addition, the medical device verification system may include an appropriate matching radioactive detector, such as a radioactive counter that may be used to detect radioactive energy emitted from the connector end face. [0058] According to some embodiments, the end face of the connector may include an additional distinguishing feature in addition to being reflective. For example, the end face of the connector may include an electronic identification means, such as, for example, a Radio Frequency Identification (RFID). RFID is known as an automatic identification method, that stores and remotely retrieves data using RFID tags or transponders. An RFID tag is an identification tag that may be identified wirelessly using radio waves. Most RFID tags include at least two parts: an integrated circuit for storing and processing information, modulating and demodulating a radio frequency signal; and an antenna for receiving and transmitting the signal. In addition, a technology called chipless RFID allows for discrete identification of tags without an integrated circuit. According to some embodiments, an RFID tag may be implemented with the connector. The RFID tag may preferably be implemented at the end face of the connector, for example, by using a chipless RFID that may be printed on at least a region of the end face of the connecter. The RFID tag may be of the passive type, which is a tag that does not need an autonomous power supply. The RFID tag may include specific information characteristic of the connector, such as type, class and model of the connector. In addition, the verification system of the medical device may include an antenna and an RFID reader that may identify the RFID tag and read/process the information encoded within the RFID tag. For example, the RFID tag may include information regarding the type, class and model of the connector (for example, for what type of patient it is to be used with: a child or an adult; intubated patient or non-intubated patient; who is the manufacturer that produced the connector, and the like). [0059] According to some embodiments, the end face of the connector may include an additional distinguishing feature in addition to being reflective. For example, the end face of the connector may include a barcode pattern that may be present on at least one region of the end face of the connector. The barcode may be used to identify the connector type/model to the medical device to which it is to be connected. In addition, the medical device verification system may further include an appropriate barcode reader, such as, for example, a barcode scanner, that may be used to detect the presence of a barcode on the end face and to further interpret the barcode. The bar code may be read “on the fly”, while the connector is being turned/screwed into its location towards its final position. Identification of the barcode by the medical device verification system may allow proper identification of the connector that is connected to the medical device and accordingly, adjust the operation mode of the medical device. [0060] According to some embodiments, the end face of the connector may include an additional distinguishing feature in addition to being reflective. For example, the end face of the connector may include one or more regions that include distinct magnetic field characteristics. The one or more regions with the distinct magnetic properties may be of any shape and size. The distinct magnetic properties may be achieved by, for example, using a coating, which has magnetic properties, that may be applied to the appropriate region on the end face. In addition, the medical device verification system may further include an appropriate magnetic field detector, that may be used to detect the presence and/or force of the magnetic field created by the one or more regions of the end face. [0061] According to some embodiments, the end face of the connector may include an additional distinguishing feature in addition to being reflective. For example, the end face of the connector may include one or more regions that include distinct electrical field characteristics. The one or more regions with the distinct electrical properties may be of any shape and size. The distinct electrical properties may include, for example, regions with different electrical conductance, different electrical field, different electrical energy produced thereby, and the like. The distinct electrical properties may be applied by, for example, applying small electrical power to specified one or more regions on the end face. In addition, the medical device verification system may further include an appropriate electrical detector, that may be used to detect the presence and/or force of the electrical energy and/or current and/or conductance and/or electrical filed created by the one or more regions of the end face with distinct electrical properties. [0062] According to some embodiments, the end face of the connector may include an additional distinguishing feature in addition to being reflective. For example, the use of pressure drop detection across the sampling line used may also be used as a verification method to determine if the connector is of the appropriate class, type, an/or model. Detection of pressure drop may be performed, for example, initiating operation of the medical device upon first verification of correct attachment between the connector and the medical device. Then, different pressure drops across the sampling line are created and detected. The different pressure drops, which are characteristics of a sampling line, may be detected and may thus identify the sampling line used with the attached connecter. If the pressure drop identifies a connector/sampling line that is not of the required/desired type (such as, for example, not by the desired manufacturer), the operation of the medical device may stop until a proper connector and sampling line are attached to the device. [0063] According to further embodiments, the end face of the connector may include one or more light sources. The light sources may include, for example, one or more LED that may emit light at various, distinct wavelengths. The one or more LED may receive power from an internal power supply, such as, for example, small batteries located within the cavity of the connector. The LEDs may emit light at predetermined wavelength ranges that may match corresponding light detectors, such as, for example, photodiodes, located in the verification system of the medical device. The light detectors may convert the detected light to a binary signal, as detailed above herein to determine the type, class and/or model, of the connector and to determine the correct assembly of the connector to the medical device. If the connector is properly attached to the medical device and is of the appropriate type, the device may operate in an operation mode that is suitable for the detected connector. [0064] While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced be interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.

There is provided a tube connector for connecting between a fluid sampling tube and a fluid analyzer, the tube connector includes an end face adapted to identify the tube connector, said end face comprising a reflecting surface having one or more reflective regions adapted to reflect light at a predetermined range of wavelengths.

[0001] This application claims priority to provisional patent application 60/215,608 filed on Jun. 30, 2000. BACKGROUND OF THE INVENTION [0002] This invention relates generally to a guitar strap capable of securely connecting to a stringed instrument. REVIEW OF PRIOR ART [0003] Typical guitar straps have end tabs that are comprised of leather or some other similar material, and each of these end tabs has a slit with a small circular opening at one end of the slit, capable of receiving and, therefore, connecting to a guitar button. These straps are not capable of securely connecting the guitar strap to the guitar button and pose the risk of accidental disengagement that could cause damage to a guitar. Additionally, after significant use, the circular opening in the end tab is subject to wear and tear, which further decreases its ability to securely maintain the guitar button. [0004] Other strap locking devices consist of an externally mounted apparatus placed onto the guitar button. These externally mounted apparatuses are often bulky and are not easily transferred from one guitar to another. They also pose the risk of scratching the surface of the guitar body. SUMMARY OF THE INVENTION [0005] The locking guitar strap of the present invention provides a means to safely and securely attach a guitar strap to a guitar button by means of a locking mechanism internally mounted within the end tabs of the guitar strap. The end tabs each have a keyhole opening with a wider first end and a narrower second end. The locking mechanism is comprised of an opening with a short narrow first section, a wider second section and a narrow third section. The wider second section and the narrow third section are aligned with the keyhole openings in the end tabs. A flexible tongue extends transversely from the short narrow first section through the entire wider second section and a portion of the narrow third section of the locking mechanism. The tongue is capable of being deflected so as to allow a guitar button to be inserted into the wider second section of the opening of the locking mechanism and the wider first end of the keyhole opening of the end tabs. The narrower second end of the keyhole opening in the end tabs and narrow third section of the locking mechanism allow only for the neck of the guitar button to be fitted within the opening. Once the guitar button is fitted into the narrow second end of the keyhole opening and the narrow third section of the locking mechanism, the tongue returns to its original position and serves to “lock” the guitar button to the locking guitar strap. In the locked position, the guitar button is prevented from returning to the wider first opening of the keyhole opening and the wider second section of the locking mechanism and thus disengaging from the locking guitar strap. The guitar button is released by deflecting the tongue to enable the head of the guitar button to slide underneath the tongue and into the wider first end of the keyhole opening and wider second section of the locking mechanism, thus releasing the locking guitar strap. [0006] The locking mechanism does not experience the wear and tear experienced by the leather end tabs of typical guitar straps and, thus, consistently maintains the secure attachment of the guitar strap to the guitar button, preventing the possibility of accidental disengagement. The internal mounting of the locking mechanism within the leather end of the guitar strap virtually eliminates the possibility of scratching the surface of the body of the guitar. Finally, the locking guitar strap will accommodate most standard guitar buttons without a need for modification of the guitar button. This versatile feature allows the owner of the locking guitar strap to utilize one locking guitar strap with any number of guitars. BRIEF DESCRIPTION OF THE DRAWINGS [0007] [0007]FIG. 1 is a top view of the locking mechanism. [0008] [0008]FIG. 2 is a top view of the present invention. [0009] [0009]FIG. 3 is a cross sectional view of a guitar button engaged with the locking guitar strap in the locked position, FIG. 3 being taken substantially along lines 3 - 3 of FIG. 2. [0010] [0010]FIG. 4 is a cross sectional view of a locking guitar strap disengaging from a guitar button, FIG. 4 being taken substantially along lines 3 - 3 of FIG. 2. [0011] [0011]FIG. 5 shows an alternative embodiment of the locking mechanism used with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0012] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended; such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. [0013] Referring now to the drawings in detail, an end tab 10 of the locking guitar strap 15 is shown in FIG. 2. Each locking guitar strap 15 has at least two end tabs 10 . The end tab 10 is typically made of a leather or leather-like material. The end tab 10 may also be made of any similar durable material. The end tab 10 contains a keyhole opening 13 that has a wider first end 11 and a narrower second end 12 . [0014] A locking mechanism 20 is internally mounted into the end tab 10 of the locking guitar strap 15 as is shown in FIG. 2. This locking mechanism 20 , as is shown in FIG. 1, is typically comprised of a flat sheet metal, but could be comprised of a variety of semi-rigid materials. The outer shape of the locking mechanism 20 is shown as an oval, but could be of numerous different shapes capable of fitting within the end tab 10 . A locking mechanism has an opening 25 that consists of a short narrow first section 21 , a wider second section 22 and a narrow third section 23 . Attached to the short narrow first section 21 is a flexible tongue 24 that extends through the entire short narrow first section 21 and the wider second section 22 and through a small portion of the narrow third section 23 . [0015] [0015]FIG. 5 shows an alternative embodiment of the locking mechanism 40 . In this alternative embodiment, the opening 45 also has a short narrow first section 41 , a wider second section 42 and a narrow third section 43 . A flexible tongue 44 is also connected to the short narrow first section 41 and extends through the entire short narrow first section 41 and the entire wider second section 42 and does not extend into the narrow third section 43 of the opening 45 . [0016] When internally mounted into the end tab 10 , the wider second section 22 and the narrow third section 23 of the locking mechanism 20 are aligned with the keyhole opening 13 of the end tab 10 . The only exposed portion of the internally mounted locking mechanism 20 is the flexible tongue 24 . This minimum exposure of metal or other semi-rigid material serves to minimize any possibility that damage may occur to the surface of the guitar body as a result of contact with metal. [0017] A typical guitar button 30 has a head 31 and a neck 32 portions. The head 31 is larger in diameter, while the neck 32 more narrow. FIG. 4 shows how a guitar button 30 is attached to the locking guitar strap 15 . The first end 11 of the keyhole opening 13 of the end tab 10 , which is aligned with the wider second section 22 of the opening 25 on the locking mechanism 20 , is capable of receiving the head 31 of a guitar button 30 . The flexible tongue 24 is capable of deflecting to allow insertion of the head 31 of the guitar button 30 . [0018] The neck 32 of the guitar button 30 is moved into the second end 12 of the keyhole opening 13 of the end tab 10 , which is aligned with the narrow third section 23 of the locking mechanism 20 . Once this occurs, FIG. 3 illustrates how the flexible tongue 24 returns to its original position and serves to lock the guitar button 30 into the second end 12 of the keyhole opening 13 of the end tab 10 . The flexible tongue 24 prevents the guitar button 30 from sliding back into the first end 11 of the keyhole opening 13 of the end tab 10 . [0019] To release or “unlock” the guitar button 30 from the locking guitar strap 15 , the flexible tongue 24 is deflected by the user of the locking guitar strap 15 to allow the guitar button 30 to be moved into the first end 11 of the keyhole opening 13 of the end tab 10 . Once moved into this position, the guitar button 30 is capable of being released or unlocked from the locking guitar strap 15 .

The locking guitar strap is a guitar strap, which can be securely attached to the button of a guitar or other stringed instrument by means of a locking mechanism mounted internally into the end tab of the guitar strap, thus preventing damage to the instrument by accidental disengagement of the strap from the instrument.

[0001] This Application claims the benefit of the filing date of U.S. Provisional Application No. 60/663,027 filed Mar. 18, 2005, which is owned by the assignee of the present Application. CROSS REFERENCE TO RELATED APPLICATIONS [0002] Reference is made to commonly assigned co-pending patent application Docket No. F-986-O1 filed herewith entitled “Method For Predicting When Mail Is Received By A Recipient” in the name of John H. Winkelman and Kenneth G. Miller, Alla Tsipenyuk and James R. Norris, Jr. Docket No. F-986-O2 filed herewith entitled “Method For Controlling When Mail Is Received By A Recipient” in the names of John H. Winkelman Kenneth G. Miller, John H. Winkleman, John W. Rojas, Alla Tsipenyuk and James R. Norris, Jr. Docket No. F-986-O4 filed herewith entitled, “Method for Dynamically Controlling Call Center Volumes,” in the names of Alla Tsipenyuk, John H. Winkleman, John W. Rojas, Kenneth G. Miller and James R. Norris, Jr. Docket No. F-986-O5 filed herewith entitled, “Method for Determining the best Day of the week For a Recipient to receive a mail piece” in the names of John H. Winkleman, John W. Rojas, Kenneth G. Miller, Alla Tsipenyuk and James R. Norris, Jr. FIELD OF THE INVENTION [0003] This invention relates to making predictions based upon in-home mail volumes and more particularly to predicting call center volumes based on predicting in-home mail volumes. BACKGROUND OF THE INVENTION [0004] Companies have used the mail to sell products to customers for almost as long as there has been mail. Responses from these solicitations happen over multiple channels such as by phone, mail, fax, internet, email. Etc. Response volumes are tied to the mail volumes of direct marketing campaigns. Response volumes associated with a direct marketing campaign will usually have peak and the peak happens at some period of time after the direct marketing campaign has been mailed. Response peaks that happen via mail, fax, internet and email can be handled over multiple days. Response peaks that happen through calls can not, they must be handled in a timely manner or else the caller will hang up. Sometimes peaks in response volumes will overwhelm a call center and the call will not be handled in a timely manner. When this happens potential orders are lost. [0005] A direct marketing campaign is divided into two parts. The first part is the planning, creation and execution of the campaign and the second part is handling the responses and orders associated with the campaign. On the other hand there is normally a strong coupling between the response and order data from a previous campaign and the planning of the current campaign. There is normally a weak coupling between the execution of the campaign and the handling of the responses for that campaign. This weak coupling is partly due to there not being accurate data that can determine when response volumes associated with a direct marketing campaign will happen. Usually rules of thumb are used to tie response volumes to mailing drop dates, but the problem is that responses are more closely associated with when the recipient receives the mail piece, instead of when the mailing is dropped. Thus, the direct marketer is not able to confidently determine when the recipient who receives the mail piece will respond. [0006] A mailing drop date is when the mail leaves the mail production facility to be shipped to the USPS. The mail can be shipped to the USPS facility nearest to the production facility (local induction) or to the USPS facilities closest to where the mail is to be delivered (drop ship induction). The time delay is 1 day for local induction and 1 to 8+ days for drop ship induction. Once the USPS accepts the mail, either through local induction or through multiple drop ship inductions, the time to process and deliver can be from 1 to 10+ days. So mail in a direct marketing campaign will be arriving in home for a period of 1 to 18+ days in some seemingly random pattern to the direct marketer. Since the in home delivery patterns for the mailing are seemingly random, the call volumes associated with the mailing will be impossible to determine. Thus, the mailer is reacting to call center volumes by itself. Hence, the mailer may have staff sitting idle or staff being over-whelmed with too many phone calls. [0007] Another disadvantage of the prior art is that a mailer is unable to predict when the mail will be delivered to a recipients home or place of business henceforth the mailer may have the appropriate staff at a call center to take orders or answer questions at the time when the recipient places the call. SUMMARY OF THE INVENTION [0008] This invention overcomes the disadvantages of the prior art by predicting when a recipient will receive a mail piece and determining an expected and actual recipient response to a call center. The foregoing is accomplished by: determining the mail in home volumes by day for the duration of the mailing using mail prediction algorithm; determining the expected and then actual delay from when a mail piece arrives to when a call response is received for previous and the current campaign using the response delay algorithm; determining the expected and then actual call response rate for the campaign for previous and the current campaign; and predicting call volumes based initially on previous campaign data and as the campaign progresses updating prediction based on current campaign data. [0009] An advantage of this invention is that it allows the call center management to dynamically allocate sufficient staffing resources, based on call response prediction. [0010] An additional advantage of this invention is that it allows a call center to handle the call volumes for each day of a campaign. On peak days this can be done either by hiring temporary resources or taking resources from other areas, such as staff tasked with placing is doing follow up calls. On slow days call response staff can be allocated to other areas of the call center. [0011] A further advantage of this invention is that by having sufficient staff on peak days all calls can be handled in a timely manner thereby eliminating dropped calls. Since more calls will be placed and many calls lead to orders this will lead to an increase in orders, order rate and hence will reduce the cost per order. [0012] A still further advantage of this invention is that on slow days it increases call center productivity by not having staff sitting idle. Increased productivity of call center staff directly correlates to an increase in profits. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 is a flow chart of a prior art direct mail marketing process; [0014] FIG. 2 is a flow chart showing how to predict recipient delivery distribution for a mailing; [0015] FIG. 3 is a flow chart that generates the actual mail shipment induction date and triggers a prediction update. [0016] FIG. 4 is a flow chart that loads facility conditions and status information and triggers prediction updates if changes are detected. [0017] FIG. 5 is an actual vs. predicted in-home curve for controlled mailing. [0018] FIG. 6 is a drawing showing the predicted vs. partial actual in-home curves for a controlled mailing. [0019] FIG. 7A is a mailing facility condition plant report. [0020] FIG. 7B is a mailing facility loading plant report. [0021] FIG. 8 is a flow chart showing how to compile historic USPS container level delivery data. [0022] FIG. 9A is a drawing showing curves generated for the Dallas Tex. BMC. [0023] FIG. 9B is a drawing showing curves generated for the Denver Colo. BMC. [0024] FIG. 9C is a drawing showing curves generated for the Los Angles Calif. BMC. [0025] FIGS. 10A-10F is a table showing sample mail piece historic delivery times for the North Metro facility which is used to create container level data shown in step 1580 ( FIG. 8 ). [0026] FIGS. 11A-11D depicts sample data,representative of the mailing container level data shown in step 1580 ( FIG. 8 ) in tabular form. [0027] FIG. 12 is a flow chart showing how to determine the in-home date for a mail piece. [0028] FIGS. 13A-13B is a table of drop shipment appointment close out dates. [0029] FIG. 14A is a flow chart of a Process for controlling a mailing campaign. [0030] FIG. 14B is a flow chart of an algorithm for controlling the mail. [0031] FIG. 15 is a flow chart showing how to determine the best shipment induction date as used by the algorithm in FIG. 14B . [0032] FIG. 16 is a flow chart showing how to predict daily call center volumes for a mailing. [0033] FIG. 17 is a flow chart showing how to control daily in-home mail volumes in order to achieve daily call volumes. [0034] FIG. 18 is daily response curve showing call center response delays associated with in home mail pieces. [0035] FIG. 19 is a table showing the information in FIG. 18 in tabular form. [0036] FIG. 20 is a table showing how the historical response delay curve is applied to the in home volume for each day in the mailing campaign. [0037] FIG. 21A and 21B depicts an offset in the data in FIG. 20 and then sums the in-home quantities and multiplies the sum by the response rate, which obtains the predicted calls per day. DETAILED DESCRIPTION OF THE INVENTION [0038] Referring now to the drawings in detail and, more particularly, to Prior Art FIG. 1 , the process begins in step 100 , where the direct mail marketer plans the campaign. Inputs into campaign planning include planning the creative, i.e., the design of the mail piece, offer and incentive in step 130 and acquiring mailing lists in step 120 ; then selecting prospects in step 112 by comparing respondent profiles in step 111 from different marketing tests, i.e., previous campaigns in step 110 . Once the marketer has created the artwork, selected the prospects to be mailed from the lists available, the campaign is actually created in step 200 . Step 200 involves having the various components of the mailing campaign printed, assembled and printing the addresses on the mail pieces and the address presorted. From there, the direct mail marketer mails, i.e., drop ships the mail to the appropriate USPS facility, the offer to all prospective customers in step 300 . Once the prospective customers receive the offer, some prospects place orders in step 400 . When the prospect orders, the direct mail marketer captures order processing data in step 410 and correlates the data with demographic information. That data is fed back into the order history database in step 110 and used to profile prospective customers for upcoming campaigns. [0039] FIG. 2 is a flow chart showing how to predict recipient delivery distribution for a mailing. The process begins in step 1180 where the mailing prediction process begins and goes to retrieve shipments in mailing step 1000 or the process may also begin if it is triggered by the update prediction of step 1190 . The anticipated induction date of the mailing from step 1200 is used with the retrieve shipment level data in step 1020 and with the mailing container level data from step 1220 by step 1210 to obtain the mailing shipment level data. Step 1020 uses mailing shipment level data from step 1210 including the anticipated induction date in step 1200 and the induction facility to prepare a prediction for a shipment. In step 1040 the containers in the shipment are retrieved. [0040] In step 1050 the process iterates through each container in the shipment and in step 1060 the process retrieves the container level data. Then the process will go to step 1070 to retrieve a historical container level delivery curve from step 1230 . Then in step 1080 the container delivery distribution is calculated based upon the historical delivery curve by applying the container piece count for each day in the distribution and using Sundays, holidays and other postal delivery processing exceptions. Then in step 1090 the information from step 1080 and the drop ship appointment facility condition data from step 1240 is utilized to retrieve container induction and processing facility condition. Step 1091 determines whether or not the information from step 1240 is available. If step 1091 determines the information is available the next step in the process is step 1100 to calculate facility condition offset. If step 1091 determines the information is not available the next step in the process is step 1120 . [0041] Then step 1120 adds the container delivery curve to the shipment prediction curve. Then if step 1130 determines that there are no more containers in the shipment, the process goes to step 1140 to add a shipment prediction curve to a mailing prediction curve. If step 1130 determines that there are more containers in the shipment the next step will be step 1050 . Now if step 1150 determines that there are no more shipments in the mailing the next step will be step 1160 to save the mailing prediction. If step 1150 determines that there are more shipments in the mailing the next step will be step 1010 . Step 1170 ends the predict mailing process. [0042] FIG. 3 is a flow chart that generates the actual mail shipment induction date and triggers the prediction update. The process begins at step 1400 via an automated or user driven request. Two independent events are detected, in step 1410 , mail arrives at a USPS facility as a Drop Shipment and in step 1415 , mail arrives at a USPS facility for local induction. Step 1411 follows step 1410 where the USPS scans Drop Shipment Form 8125 and produces an Entry Scan. Step 1416 follows step 1415 where the USPS scans Local Entry Form 3602 and also produces an Entry Scan. The Entry Scans are stored in Step 1420 by the USPS Confirm System for later retrieval. In addition, step 1410 is also followed by step 1430 , where the Drop Shipment Appointment System stores information associated with the drop shipment, such as the truck arrival, status, load time, etc. Step 1420 and step 1430 are followed by Step 1440 , where the Actual Induction Date is calculated using the best possible date from the entry scan or the drop shipment information that is available (If both sets of data are available, the appointment data is used). Then in step 1450 the Actual Induction Date is stored and in step 1460 a trigger is generated to update the mailing campaign prediction. [0043] FIG. 4 is a flow chart that loads facility conditions and status information and triggers prediction updates if changes are detected. The process begins at step 1300 , via an automated or user driven request. The facility conditions are then loaded in step 1315 from step 1310 and stored in step 1317 . At the same time, Facility Loading data is loaded in step 1316 from step 1311 and stored in step 1317 . Step 1320 follows step 1315 , where changes to the facility conditions are detected. In a similar fashion, step 1322 follows step 1316 and detects changes to the facility loading data. In either case, if changes are detected, steps 1320 and 1322 will trigger a Prediction Update in step 1330 . [0044] FIG. 5 is an actual vs. predicted in-home curve for controlled mailing. [0045] FIG. 6 is a drawing showing the predicted vs. partial actual in-home curves for a controlled mailing. [0046] FIGS. 5 and 6 illustrate the variability encountered when dealing with high volume direct mail marketing campaigns through the standard approach of controlling drop dates (the date that the mail leaves the facility that created it). [0047] In the case of FIG. 6 the mailer elected to create the mail all at once then drop the 4.5 million or so pieces over 3 days. The result was a elongated bell curve. The resultant impact was that the inbound call center, where the prospect called to order the item, could not handle the call volume. To remediate the situation, the mailer decided to go to a 4 week induction schedule, targeting Tuesday, Wednesday and Thursday for receipt of most of the mail for each week as shown in FIG. 5 , where the mailer elected to drop the mail over a four (4) week period. The expected result was that ¼ of the mail would arrive each week for a period of four weeks. The mail control module was used to create the induction plan and the result was as seen in FIG. 5 . By knowing the daily in-home piece count for the mail and understanding the likely response to those volumes the mailer was able to staff the call center correctly and the result yielded a higher order conversion rate for each inbound call. [0048] FIG. 7A is a mailing facility condition plant report. Block 20 is the legend block for the report. Spaces 21 , 22 and 23 indicate the code used in the report. Space 24 indicates the condition represented by the code indicated in space 21 and space 25 indicates the condition represented by the code indicated in space 22 . Space 26 indicates the condition represented by the code indicated in space 23 . Space 27 indicates when the report was last updated. Column 28 indicates the facility name and column 29 indicates the condition of the facility indicated in lines 31 shown in rows 30 at the date indicated at the top of the column. [0049] FIG. 7B is a mailing facility loading report that shows facility appointments over a date range. This report provides information on the amount or quantity of mail processed by a specific facility over time and the amount of mail that is scheduled to be processed by a facility in the near future. Space 900 is the header for the search criteria, including space 901 which is the Facility name header and space 902 which is the facility name. Space 903 is the Date Range header and space 904 is the date range for the report. [0050] The data for the report is defined as follows. Space 905 is the column header for the Date and space 906 is date for each row of data. [0051] Space 907 is the row where the Totals are tallied for each column. [0052] Space 908 is the header for the Total Scheduled Appointments, and space 909 is the total appointments for each date, and space 910 is the total scheduled appointments for the facility over the date range specified in space 904 , Date Range above. Space 911 is the header for the columns related to Pallets scheduled and space 912 is the column header for the total count of pallets containing parcels scheduled and space 913 is the count of pallets containing parcels scheduled for each day. Space 914 is the total count of pallets containing parcels scheduled for all days and space 915 is the column header for the total count of pallets containing bundles scheduled. Space 916 is the count of pallets containing bundles scheduled for each day and space 917 is the total count of pallets containing bundles scheduled for all days. [0053] Space 918 is the column header for the total count of pallets containing trays scheduled and space 919 is the count of pallets containing trays scheduled for each day. Space 920 is the total count of pallets containing trays scheduled for all days. Space 921 is the column header for the total count of pallets containing bundles scheduled. Space 922 is the count of pallets containing bundles scheduled for each day and space 923 is the total count of pallets containing bundles scheduled for all days. Space 924 is the column header for the total count of pallets scheduled and space 925 is the total count of pallets scheduled for each day. Space 926 is the total count of pallets scheduled for all days and space 927 is the header for the columns related to cross docked mail scheduled. Space 928 is the column header for the total count of cross docked mail containing parcels scheduled and space 929 is the count of cross docked mail containing parcels scheduled for each day. Space 930 is the total count of cross docked mail containing parcels scheduled for all days and space 931 is the column header for the total count of cross docked mail containing bundles scheduled. Space 932 is the count of cross docked mail containing bundles scheduled for each day and space 933 is the total count of cross docked mail containing bundles scheduled for all days. Space 934 is the column header for the total count of cross docked mail containing trays scheduled and space 935 is the count of cross docked mail containing trays scheduled for each day. Space 936 is the total count of cross docked mail containing trays scheduled for all days and space 937 is the column header for the total count of cross docked mail containing bundles scheduled. Space 938 is the count of cross docked mail containing bundles scheduled for each day and space 939 is the total count of cross docked mail containing bundles scheduled for all days. Space 940 is the column header for the total count of cross docked mail scheduled and space 941 is the total count of cross docked mail scheduled for each day. Space 942 is the total count of cross docked mail scheduled for all days. Space 943 is the header for the columns related to bed loads scheduled and space 944 is the column header for the total count of bed loads containing parcels scheduled. Space 945 is the count of bed loads containing parcels scheduled for each day and space 946 is the total count of bed loads containing parcels scheduled for all days. Space 947 is the column header for the total count of bed loads containing bundles scheduled and space 948 is the count of bed loads containing bundles scheduled for each day. Space 949 is the total count of bed loads containing bundles scheduled for all days and space 950 is the column header for the total count of bed loads containing trays scheduled. Space 951 is the count of bed loads containing trays scheduled for each day and space 952 is the total count of bed loads containing trays scheduled for all days. Space 953 is the column header for the total count of bed loads containing bundles scheduled and space 954 is the count of bed loads containing bundles scheduled for each day. Space 955 is the total count of bed loads containing bundles scheduled for all days and space 956 is the column header for the total count of bed loads scheduled. Space 957 is the total count of bed loads scheduled for each day and space 958 is the total count of bed loads scheduled for all days. [0054] FIG. 8 is a flow chart showing how to compile historic USPS container level delivery data. The process begins at either step 1500 or step 1510 . If the process began at step 1500 where the USPS scans drop shipment form 8125 . Drop shipment form 8125 is used by the USPS for registering when the drop shipment arrives at a USPS facility. If the process began at step 1510 the USPS scans entry form 3062 . Drop shipment form 3062 is used by the USPS for registering when mail is locally inducted by the USPS. In step 1530 the USPS confirm system is utilized. The confirm system receives the information scanned by the USPS from the mail piece in step 1520 and the information from steps 1500 and 1510 . Then entry scan data from step 1530 is sent to step 1570 mailing shipment level data and planet code data is sent to step 1590 as mail piece level data. In addition drop shipment close out data is sent from the USPS Drop Shipment Appointment System (DSAS) to step 1570 as mailing shipment level data. In step 1580 mailing container level data is correlated from shipment level data tied in 1600 and mail piece level data tied in step 1610 . [0055] Step 1560 utilizes mailing container level data from step 1580 to compile historical mailing delivery data. Step 1550 utilizes historical mailing delivery data from step 1560 to produce historical container level delivery curves. Step 1540 stores the historical delivery data for predicting and/or controlling mailings [0056] FIGS. 9A-9C show example curves generated for BMC's and SCF's in three different regions: Dallas Tex., Denver Colo., and Los Angeles, Calif. The curves show the high variability of in home mail distributions, both volumes and timing, across BMC and SCF in the same region. Furthermore, the figures also show the high variability across different BMC's and/or SCF across different regions. [0057] Each of the FIGS. 9A-9C shows graphs for a specific facility, displaying average distribution of in home mail volumes from the day of induction to the day of delivery, over a 10 month period, January to October 2004. In each chart, the x axis is the number of days since induction and the y axis is the percentage of the mail delivered on that day. [0058] FIGS. 10A-10F is a table showing sample mail piece historic delivery times for the North Metro facility which is used to create container level data shown in step 1580 ( FIG. 8 ). [0059] In FIG. 10A the shipment ID, i.e., the identification of the mailing shipment is shown in column 43 . The city and state that the shipment is delivered to is respectively shown in columns 44 and 45 . The three digit zip code is shown in column 46 . The zip code and the zip code plus four are respectively shown in columns 47 and 48 . The carrier route for the shipment is shown in column 49 . The delivery point code (DPC) is shown in column 50 and the cell i.e., identifies mail with different creative formats within a mailing is shown in column 51 . The mail sequence i.e., internal/identifier for each mail piece is shown in column 52 . [0060] In FIG. 10B the CLASS of mail is shown in column 53 . Column 54 is the name DMLAYOUT_TABLE, the name of the table holding the address information for this mail piece. Column 55 (IND_FACILITY_NAME) holds the name of the induction facility. Column 56 (IND_FACILITY_TYPE) holds the type of facility, i.e. BMC, SCF, etc. Column 57 (IND_FACILITY) holds the zip code for the induction facility, and column 58 (FIRST_IND_DATE) is the time stamp of the first scan that occurs in the induction facility. Column 59 (LAST_IND_DATE) is the optional time stamp of the last scan that occurs in the induction facility. [0061] In FIG. 10C column 60 (DS_SCHEDULE_DATE) is the date when the shipment was scheduled for drop shipment. Column 61 (IND_REC_PK) is a foreign key to the shipment record for this mail piece and column 62 (FIRST_SCAN_FACILITY) is the zip code of the facility where the mail piece was first scanned—after induction and column 63 (FIRST_SCAN_DATE) is the time stamp of the first scan at the processing facility. Column 64 (FIRST_OP_NO) is the operation that was performed on the mail piece during the first scan, i.e. first pass sort, second pass sort, etc. and column 65 (LAST_SCAN_FACILTY) is the zip code of the facility where the mail piece was last scanned. [0062] In FIG. 10D column 66 ((LAST_SCAN_DATE) is the time stamp of the last scan at a processing facility and column 67 (LAST_OP_NO) is the operation that was performed on the mail piece during the last scan. Column 68 (NUMBER_SCANS) is a count of the total number of planetcode scans (or operations) detected on the mail piece and column 69 (IN_HOME_DATE) is the calculated in home date for the mail piece, see FIG. 12 . Column 70 (IND_FIRST_SCAN_HRS) is the number of hours between the FIRST_IND_DATE and the FIRST_SCAN_DATE and column 71 (IND_LAST_SCAN_HRS) is the number of hours between the FIRST_IND_DATE and the LAST_SCAN_DATE. [0063] In FIG. 10E column 72 (FIRST_LAST_SCAN_HRS) is the number of hours between the FIRST_SCAN_DATE and the LAST_SCAN_DATE and column 73 (REC_ID_PK) is the primary key for this mail piece record. Column 74 (PROBLEM_DATA) is used to flag if there is problem data for this mail piece and Column 75 (IND_FIRST_SCAN_DAYS) is the IND_FIRST_SCAN_HRS represented as days. Column 76 (IND_LAST_SCAN_DAYS) is the IND_LAST_SCAN_HRS represented as days and column 77 (PALLET) identifies the pallet the mail piece is in for the mailing. Column 78 (BAG) identifies the bag the mail piece is in for the mailing. [0064] In FIG. 10F column 79 (BUNDLE) identifies the bundle the mail piece is in Column 80 (TIER) i.e., C=carrier route, P=presort 3 or 5 digit, R=residential and column 81 (AUTO_NON_AUTO) indicates if the mail piece has an automation compatible post-net code, where A=zipcode plus 4 plus 2 and N=zip code. Column 82 (PRESORT_TYPE) is the presort order assigned to the mail piece and column 83 (PRESORT_ZIP) is the zip code for the specific presort type in column 82 . Column 84 (MODELED_IN_HOME_DATE) is the calculated in home date, see FIG. 12 . [0065] Mail piece level data ( FIGS. 10A-10F ) is combined or aggregated into container level data and tabulated as shown in FIGS. 11A-11D . [0066] FIGS. 11A-11D depicts sample data representative of the mailing container level data shown in step 1580 ( FIG. 8 ) in tabular form. In FIG. 11A the location of the induction facility for the mailing shipment is shown in column 85 . Each row in FIGS. 11A-11D is representative of an aggregation of containers of mail pieces represented in rows in FIGS. 10A-10F (belonging to the container). The location of the processing facility of the mailing shipment is shown in column 86 . The type of induction facility i.e., BMC, Auxiliary Sectional Facility (ASF) or SCF is shown in column 87 . The sort level performed on the mail pieces, i.e., Enhanced Carrier Route (ECROLT), three digit sort level (AUTO**3-Digit), Auto Carrier Route (AUTOCR), five digit sort level (AUTO**5-Digit) are shown in column 88 . The induction date of the shipment for the container is shown in column 89 . The induction day of week (DOW) is shown in column 90 . [0067] In FIG. 11B is the induction tour when the shipment was inducted Foreign Key (FK) for the container is shown in column 91 and the induction Day Of Week (DOW) for the container is shown in column 92 . The induction MOY month of year (MOY) for the container is shown in column 93 and the induction year-FK for the container is shown in column 94 . The mail piece count for the shipment is shown in column 95 . The percentage of the container mail pieces that arrived on the induction day (Day0) In home is shown in column 96 . [0068] In FIG. 11C the percent of mail pieces that are in the home one day after postal induction is shown in column 97 and the percent of mail pieces that are in the home two days after postal induction is shown in column 98 . The percent of mail pieces that are in the home three days after postal induction is shown in column 99 and the percent of mail pieces that are in the home four days after postal induction is shown in column 100 . The percent of mail pieces that are in the home five days after postal induction is shown in column 101 and the percent of mail pieces that are in the home six days after postal induction is shown in column 102 . The percent of mail pieces that are in the home seven days after postal induction is shown in column 103 and the percent of mail pieces that are in the home eight days after postal induction is shown in column 104 . [0069] In FIG. 11D the percent of mail pieces that are in the home nine days after postal induction is shown in column 105 and the percent of mail pieces that are in the home ten days after postal induction is shown in column 106 . The percent of mail pieces that are in the home eleven days after postal induction is shown in column 107 and the percent of mail pieces that are in the home twelve days after postal induction is shown in column 108 . The percent of mail pieces that are in the home beyond the second week of postal induction is shown in column 109 and the ready for training flag shown in column 110 indicates when the record can be used as historical container level delivery curves as shown in step 1550 ( FIG. 8 ). [0070] FIG. 12 is a flowchart indicating how the In Home Date is calculated for a mail piece, and saved in space 69 , IN_HOME_DATE, in FIG. 10D and is also used to calculate MODELED_IN_HOME_DATE in space 84 in FIG. 10F . [0071] The process is applied to each mail piece that is scanned and starts in step 3000 and is followed by step 3020 , where the last scan for the mail piece is loaded from step 3010 , Mail piece Last Scan Date from USPS Confirm System. Next, step 3030 initializes the In Home Date for the mail piece as the Last Scan Date and then if step 3040 determines if the mail piece scan occurred after the delivery cut-off time for that facility, step 3050 will add 24 hours to the in home date, since the mail piece will not be delivered on the same day. Next if step 3060 determines that the In Home Date falls on a no-delivery date, such as a Sunday, Holiday, or exception date, etc, step 3070 will use the next available delivery date is used as the In Home Date for the mail piece. [0072] The process continues at step 3080 where the calculated In Home Date is saved to space 69 in FIG. 10D , as shown in step 3090 . Finally, the process ends in step 3095 . [0073] FIG. 13A and 13B is a table of drop shipment appointment close out data, which is used to calculate the actual mail shipment induction date as described in FIG. 3 . Space 33 indicates the shipment confirmation number and space 34 indicates the appointment status of the shipment, with states of Closed, No Show, or Open, etc. Space 35 indicates the header for space 35 a , the name of the facility where the shipment is scheduled to arrive. Space 36 is the header for space 36 a , the date and time when the truck arrived. Space 37 is the header for space 37 a , the date and time when the truck started to be unloaded [0074] Space 38 is the header for space 38 a , the date and time when the truck completed unloading. Space 39 a is the header for Space 39 a , the Trailer Number, identifying the truck that delivered the mail. [0075] FIG. 14A is a flow chart of a Process for controlling a mailing campaign. [0076] In FIG. 14 A , the customer provides mailing campaign data file in step 500 describing the mail pieces in each shipment of the mailing campaign. A mailing campaign consists of one or more shipments. Each shipment consists of a number of trays or containers of mail sorted to some density for instance 3-digit zip code level, 5-digit zip code level, or AADC level. Further, each shipment is to be inducted at a specific BMC of Sectional Control Facility (SCF). Each tray or container consists of one or more mail pieces. Of those mail pieces, one or more mail piece in each tray are uniquely identified with a bar code or bar codes uniquely identifying that mail piece. Those bar codes are in a format that is scanned and stored by the USPS. The mail campaign data include may custom formats such as a comma delimited flat file or an XML formatted data file, or may follow an industry standard such as Mail.dat. The customer also inputs to the system the desired days that the recipient is to receive the mail piece in step 530 . The recipient target interval may be specific days of a week or specific dates. For instance, the recipient population is to receive the mail piece on a Tuesday or Wednesday or the recipient is to receive the mail piece on the 13 th or 14 th of January, 2005. The system shall accept inputs spanning one or more desired in-home days or dates. [0077] The induction planner in step 510 using a model of the processing pattern of all facilities in the system determines the best day of the week to induct the mail at each of the target facilities. Step 510 is described in more detail in FIG. 14B . The system also accepts manual or automated exception event inputs containing postal holidays in step 575 and in step 570 catastrophic events that may shut down or seriously impede the postal system's ability to process mail. In step 580 the data is stored in an exception data file or database and accessed by the induction planner. Further, the system takes as an input the logistics schedule of the shipping provider for the mailer in step 550 and stores that data in step 560 using a method that allows access by the induction planning software. The logistics schedule of the shipping provider is the route schedule for that transportation firm. The system, is able to plan the induction schedule for the mail around the dates that the logistics provider actually inducts mail with the destination facility or facilities. It is not uncommon for the logistics providers to take mail to some facilities daily and some other facilities as infrequently as once per week. [0078] Given all of the inputs, the system calculates an induction plan in step 510 containing the date to induct the mail for each destination facility within the USPS. Further, the system outputs an anticipated arrival curve for each container or shipment or the mailing campaign as a whole or a part of the campaign. The anticipated arrival curve provides the mailer with a realistic idea for when the mail will arrive with the recipient population given logistics constraints, postal processing variability, postal holidays and catastrophic events. [0079] Once the mailer instructs the shipper when to induct the shipments at each destination processing facility the system monitors the USPS system in step 590 to measure when the shipment(s) were actually inducted. Step 590 is described in further detail in FIG. 3 and step 620 in described in further detail in FIG. 4 . Additionally, the system monitors the DSAS system in step 620 for facility status information which may delay the processing and ultimately delivery of mail to the recipients of that mail. Periodically, the system accesses the stored induction and facility status data in step 600 and updates the anticipated in-home curves in step 610 . [0080] Once the mail is accepted, those pieces containing scannable bar codes are processed and tracked through the USPS. The USPS reports that scan information for each scannable piece. The scanned data in step 650 is downloaded to the system and tied to the customer mail piece data in step 670 through an appropriate database in step 660 . The system then uses that data to generate reports containing when the prospect population is in fact receiving the mail pieces. Further that data is used to create conformance reporting back to the mailer in step 640 demonstrating how much mail was in-homed within the desired window. [0081] The delivery results of the mailing campaign including shipment and mail piece information are then used to update the induction planning model in step 540 thus refining the induction planner's in step 510 future capability to accurately determine when mail is to be inducted to achieve desired delivery dates. [0082] FIG. 14B is a flow chart of an algorithm for controlling the mail. The process begins in step 2000 control mailing. Then in step 2005 mailing shipments are retrieved from step 2110 . Now in step 2010 each shipment from step 2065 is processed one shipment at a time. Then in step 2020 the data associated with the make up of the shipment from step 2110 is retrieved. The retrieved data includes the induction facility and the mail piece count. In step 2030 the identity of the containers in the shipment are retrieved from step 2120 mailing container level data. [0083] Now in step 2040 each container in the shipment is processed. Then step 2050 the data associated with the make up of the container from step 2120 is retrieved. This data includes the container processing facility, destination facility, sort level, mail pieces in the container and make up of the mail piece. Then in step 2060 the historical level delivery curve associated with the container in step 2050 is retrieved from step 2130 historical delivery data. The historical delivery curve is conveyed as a proportional curve that indicates the percentage of mail pieces delivered each day. [0084] In step 2070 the mail pieces delivered per day for this container is calculated by multiplying the mail piece counts in the container by the historical container delivery curve. Then, step 2080 adds the container delivery curve calculated in step 2070 to the shipment delivery curve. Now step 2090 determines whether or not there are more containers to be processed in the shipment. If step 2090 determines there are more containers in the shipment to be processed, the next step will be step 2040 . If step 2090 determines there are no more containers in the shipment to be processed, the next step will be step 2300 to determine the best shipment induction date. Step 2300 is more fully described in the description of FIG. 15 . [0085] Then the process goes to step 2100 to determine whether or not there are more shipments in the mailing campaign. If step 2100 determines that there are more shipments in the mailing campaign the next step is step 2010 . If step 2100 determines that there are no more shipments in the mailing campaign the next step is step 2140 which prints an induction plan for execution. Now in step 2150 the mailing control algorithm is completed. [0086] FIG. 15 is a flow chart showing how to determine the best shipment induction date as used by the algorithm in FIG. 14B . The process begins at step 2300 determine best shipment induction date. Then in step 2310 data is retrieved for the desired in home window. At this time data is exchanged between step 2310 and step 2430 desired in home window to specify the date range when most of the mail needs to be delivered. Now in step 2320 the process builds a list of all the possible in home window locations over the shipment delivery curve, calculating the percentage of mail delivered inside the window for each window location. The in house window locations are sorted from best to worst, i.e., from most mail delivered to least mail delivered in the window. [0087] In step 2330 , the induction date is determined for each in home window location taking into account Sundays and holidays. Then step 2340 retrieves the USPS facility acceptance schedule. Step 2340 exchanges information with step 2440 USPS facility acceptance schedule. At this point the process goes to step 2350 . Step 2350 determines whether or not the USPS facility accepts mail on the induction date. If step 2350 determines that mail is accepted on the induction date, the process goes to step 2360 to retrieve the drop ship schedule. Step 2360 exchanges information with step 2450 drop shipper schedule. Then the process goes to step 2370 . Step 2370 determines whether or not the drop shipper can deliver the shipment to the induction facility on the induction date. If step 2370 determines that the shipper can deliver the shipment on the induction date the process goes to step 2400 update shipment desired induction date. The next step will be step 2460 return. If step 2370 determines the drop shipper can not deliver the shipment on the induction date or if step 2350 determines that the USPS facility does not accept mail on the induction date then, the next step is 2390 . [0088] If decision step 2390 , determines that the next highest in home window location does not exist, the process goes to step 2420 , where the shipment is flagged as there is no known induction for the specified in home window. Then the process goes to step 2460 return. [0089] FIG. 16 is a flow chart showing how to predict daily call center volumes for a mailing. The process begins in step 2501 , predict call center volumes. Then in step 2511 , the mailing prediction is retrieved from step 2581 , Mailing Prediction. The Mailing Prediction that is provided is an updated Mailing Prediction accounting for any known changes in the mailing campaign, including updated induction dates, facility status, etc. The updated Mailing Prediction is merged with the Actual In Home curve as it is determined to date; and gradually, predicted in home volumes are replaced with actual results. Therefore, the Mailing Prediction allows predicted call center volumes to be updated as the campaign progresses so that corrective action can be taken at the call center with staffing or resources if necessary. Now in step 2551 , the historical call response delay curve is retrieved from step 2601 , the historical call response behavior. The historical call response delay curve provides daily rates for responses to mail pieces arriving on a specific day; that is, some recipients will respond the day that the mailpiece arrives, others on the next day, others two days later, and so on. [0090] Now the process goes to step 2561 , to calculate the predicted calls per day curve. The historical call response delay curve is applied to the mail pieces that were predicted to arrive on each day of the campaign. In other words, the mail pieces arriving each day are distributed across a range of days, based on the call response delay curve, in order to determine the call response delay distribution for that day. The predicted calls per day curve (i.e. call response delay distribution for the entire campaign) is calculated by adding the call response delay distribution for each in-home day of the campaign. See FIGS. 21A and 21B . [0091] At this point, the predicted calls per day indicates that all of the recipients will respond to the mailing, the next step will scale the results by applying one or more historical call response rates. Now in step 2521 , the historical call response rates are retrieved from step 2591 , historical call response rates. Then in step 2541 , anticipated calls are calculated by multiplying predicted calls per day by the response rate. Next in step 2542 create calls per day prediction will merge the anticipated calls calculated in step 2541 with the daily actual call volumes measured at the center in step 2543 , by giving higher priority to the actual call results. Finally, in step 2571 , the calls per day prediction is produced, based on the merged anticipated calls and actual calls that were calculated in steps 2541 and 2543 respectively. After producing the calls per day prediction, the process ends in step 2561 end predict call center volumes. [0092] FIG. 17 is a flow chart showing how to control daily in-home mail volumes in order to achieve daily call volumes. The process begins in step 2499 call center control, then the process continues in step 2500 , retrieve desired daily call center volume (how many call center calls do you want a day). Then the process goes to step 2510 , to retrieve historical call response rate from historical call response rate, step 2580 . Now the process goes to step 2520 , divide desired daily call center volume by historical call response rate (desired responses per day). In step 2540 , the historical call response delay curve is retrieved from step 2590 , historical call response behavior. Then in step 2545 , the process sums the response delays based on the length of the desired campaign in home window. In step 2550 , the process calculates the required in home window mail volume, by dividing desired responses per day by the sum of the response delays. Now in step 2555 the mailing campaign control algorithm is executed to produce an induction plan that will generate the in home volumes that were calculated in step 2550 . Step 2555 is described in further detail in FIG. 14B . Step 2555 will also take into account placing the in home volumes at the correct tome and date so that the required call volumes are generated when expected, i.e., if you want the call center volumes to peak on February 15 th to February 16 th , the peak mail volumes must arrive some time before February 16 th . Then in step 2560 , the required daily in home mail volume curve is produced. Then step 2600 ends the call center control. [0093] FIG. 18 is a daily response curve showing call center response delays associated with in-home mail pieces. The curve shows. the probability of a recipient responding X days after receiving a mail piece. The X axis is the number of days after receiving the mail piece and the Y axis is the likelihood that a recipient will respond on that day. This curve is applied in step 2561 of FIG. 16 to calculate the predicted distribution of calls for the mail pieces arriving on each one of the in-home days of a mailing. This curve can be further divided based on seasonality, day of week, geographical location, weather conditions, etc. [0094] FIG. 19 is a table showing the information in FIG. 18 in tabular form. The table illustrates the percentage of respondents per day for mail pieces arriving in home on a given day. The historical response delay curve need not be limited to 10 days of delay, instead, it can long enough to account for a specific amount of responses, such as 90%. [0095] FIG. 20 is a table showing how the historical response delay curve is applied to the in home volume for each day in the mailing campaign. The rows in the table show the mail for each day in the mailing campaign, totaling 11 days, where 100,000 pieces arrived in home on each day. The columns in the table show the distribution of responses for each in home day, by applying the historical response delay curve. It is important to note though, that the delayed response volumes will need to be shifted based on the day when mail pieces arrived. This is explained in FIG. 21A and FIG. 21B . [0096] FIG. 21A and 21B depicts an offset in the data in FIG. 20 and then sums the in-home quantities and multiplies the sum by the response rate, which obtains the predicted calls per day. The rows are the same as shown in FIG. 20 , except that they have been shifted so that the response distribution starts on the day when the mail pieces arrived, for each in home day. The 21 columns represent each day when calls are predicted to arrive into the call center, and the response rate is used to calculate the predicted number of calls for each day in the predicted response curve. The table uses a sample response rate of 0.03%, but in application, the response rate can be applied based on historical analysis, for example, based on day of week, geographical location, weather, etc. [0097] It should be understood that although the present invention was described with respect to mail processing by the USPS, the present invention is not so limited and can be utilized in any application in which mail is processed by any carrier. The present invention may also be utilized for mail other than direct marketing mail, for instance, transactional mail, i.e., bills, charitable solicitations, political solicitations, catalogues etc. Also the expression “in-home” refers to the recipient's residence or place of business. [0098] The above specification describes a new and improved method for predicting call center volumes. It is realized that the above description may indicate to those skilled in the art additional ways in which the principles of this invention may be used without departing from the spirit. Therefore, it is intended that this invention be limited only by the scope of the appended claims.

A computer method that is used to predict when recipients of mail pieces will contact a call center in response to information contained in the mail pieces. The method involves, utilizing previous mailing campaign data to determine when the mail piece arrives in the home and when a call center is contacted in response to information in the mail piece; and predicting call volumes based initially on previous campaign data and as the mailing campaign progresses updating call center predictions based on current mailing campaign data.

CROSS REFERENCES TO RELATED APPLICATIONS [0001] The present invention contains subject matter related to Japanese Patent Application JP 2005-030675 filed in the Japanese Patent Office on Feb. 7, 2005, the entire contents of which being incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] The present invention relates to a recording/reproducing apparatus and a method and a program thereof and, more particularly, to a recording/reproducing apparatus and a method and a program thereof that are suitably applicable to a reproducing apparatus for reproducing externally obtained music data for example. [0003] Recently, reproducing apparatuses of this type are adapted to get music data from servers providing music data through the Internet. [0004] The music data thus obtained through the Internet generally includes symbol images visually representing impressions of that music data for example. A symbol image in this case is a symbol image of the jacket of a particular CD (Compact Disc) to which that music data is recorded, for example. [0005] If an operation for reproducing music data obtained through the Internet is executed for example, such a reproducing apparatus as mentioned above may display, on a display monitor thereof, a jacket image for example related to a title of music data specified by that reproducing operation or to the music data itself, thereby letting a user recognize an image and various kinds of information of the music data to be reproduced at that time (refer to Japanese Patent Laid-Open No. 2001-175624, corresponding U.S. Patent Application No. 2002-159304). SUMMARY OF THE INVENTION [0006] The above-mentioned reproducing apparatus having the configuration described above is adapted to get music data also from each CD to which music data is recorded. However, the music data thus obtained from each CD is generally not related with a jacket image of that music data. [0007] Consequently, when an operation is executed for reproducing music data from a CD, the above-mentioned reproducing apparatus can hardly display the jacket image corresponding to the music data specified by that reproducing operation, thereby making it difficult for the user to visually recognize the impression of that music data. [0008] Therefore, present invention addresses the above-identified and other problems associated with related-art methods and apparatuses by providing a recording/reproducing apparatus, a method thereof, and a program thereof. [0009] In carrying out the invention and according to one aspect thereof, there is provided a recording/reproducing apparatus having a recording device configured to record content data to a storage medium; a reproduction device configured to reproduce the content data from the storage medium; an image data storage device configured to store image data corresponding to each of a plurality of pieces of attribute information; an attribute information detector configured to detect, if no image data is related with the content data, attribute information related with the content data; an image data detector configured to detect image data corresponding the attribute information detected by the attribute information detector from the image data storage device; and a controller configured to control such that the image data detected by the image data detector be outputted at least during reproduction of the content data by the reproduction device. [0010] The above-mentioned novel configuration allows the outputting of image data corresponding to the information attribute of content data if the content data is related with no image data. [0011] As described and according to the invention, if no image data is related with content data, image data corresponding to the attribute information of that content data may be outputted. Consequently, symbol images associated with content data may be surely displayed. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIG. 1 is a block diagram illustrating an exemplary circuit configuration of a reproducing apparatus practiced as one embodiment of the invention; [0013] FIG. 2 is a diagram for describing genres defined in the above-mentioned embodiment; [0014] FIG. 3 is a diagram for describing a main genre vs. symbol image table; [0015] FIG. 4 is a flowchart indicative of an image display processing procedure; [0016] FIG. 5 is a diagram for describing attribute information related with music data; [0017] FIG. 6 is a flowchart indicative of an image display processing procedure; [0018] FIG. 7 is a diagram for describing an artist vs. symbol image table; [0019] FIG. 8 is a flowchart indicative of an image display processing procedure; [0020] FIG. 9 is a flowchart indicative of another image display processing procedure; [0021] FIG. 10 is a flowchart indicative of still another image display processing procedure; and [0022] FIG. 11 is a flowchart indicative of yet another image display processing procedure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0023] This invention will be described in further detail by way of embodiments thereof with reference to the accompanying drawings. (1) First Embodiment [0024] Referring to FIG. 1 , reference number 1 denotes a reproducing apparatus as a whole. If a user thereof executes music data acquisition operation through an operation block 2 for acquiring music data from a music provision server SV for providing music data for example, a CPU (Central Processing Unit) 3 that controls the reproducing apparatus 1 in its entirety transmits accordingly a music data request signal for requesting the music data corresponding to that music data acquisition operation to a music provision server SV via a communication processing block 4 , a network interface 5 , and the Internet NT sequentially. Receiving the music data request signal, the music provision server SV transmits the music data requested by the music data request signal to the reproducing apparatus 1 via the Internet NT. The reproducing apparatus 1 receives, through the network interface 5 and the communication processing block 4 in this order, the music data from the music provision server SV, storing the received music data into a hard disc drive 6 . Thus, the reproducing apparatus 1 is able to get music data from the music provision server SV. Likewise, the reproducing apparatus 1 is also able to get a plurality of pieces of music data bundled in one group as one album work from the music provision server SV. An album work herein denotes a unit in which music is sold as one piece of CD (Compact Disc), for example. [0025] When an operation for acquiring music data from a CD is executed on the operation block 2 of the reproducing apparatus 1 , the CPU 3 of the reproducing apparatus 1 accordingly controls a media drive block 7 on which the CD is loaded to read the music data therefrom and stores the retrieved music data into the hard disc drive 6 . Thus, the reproducing apparatus 1 is able to get music data from a CD. [0026] The music data thus acquired from a music provision server SV or a CD is related with attribute information for each piece of music. This music data attribute information may include symbol image data visually representing an impression associated with that music data (in this case, jacket image data equivalent to a CD jacket image) and a genre name indicative of a field to which that music image belongs. [0027] The attribute information for each piece of music, music data title, album name, artist name, lyrics, and genre for example, may be manually entered by the user through the operation block 2 . Also, it is practicable that, when a CD is reproduced through the media drive block 7 , for example, identification information generated on the basis of reproduced TOC and music data be transferred to an external server under the control of the CPU 3 , the attribute information corresponding to that identification information be received from that external server through the network interface 5 and the communication processing block 4 , the received attribute information being recorded to the hard disc drive 6 as related with that music data along therewith read from that CD. The external server may be a CDDB (trademark) of Gracenote, Inc. for example. [0028] The present embodiment defines main genres indicative of major classifications and sub genres indicative of specific genres below the main genres as shown in FIG. 2 for example. In the example shown in FIG. 2 , main genres are “punk,” “metal,” and so on. Main genre “punk” has sub genres “pop punk” and “metal punk.” Main genre “metal” has sub genres “pop metal” and “country metal.” Therefore, if the acquired music data belongs to sub genre “pop punk” of main genre “punk,” the attribute information of that music data indicates character string “poppunk” for example indicative of sub genre “pop punk” as a genre name. It should be noted that the character string indicated in this attribute information as a genre name is editable by the user, so that the character string may be other than “poppunk.” [0029] If an operation for reproducing acquired music data is executed through the operation block 2 of the reproducing apparatus 1 , the CPU 3 of the reproducing apparatus 1 accordingly reads music data corresponding to the reproduction operation done from the hard disc drive 6 to reproduce the music data, thereby supplying a resultant audio signal to an audio processing block 8 . Consequently, the audio processing block 8 sounds the supplied audio signal through a speaker 9 . Thus, the reproducing apparatus 1 is able to reproduce acquired music data. [0030] At the same time, the CPU 3 of the reproducing apparatus 1 reads the attribute information related with the currently reproduced music data (hereafter referred to as in-reproduction music data) from the hard disc drive 6 to determine whether the attribute information includes jacket image data. [0031] If jacket image data is found included in the attribute information, then the CPU 3 of the reproducing apparatus 1 displays a jacket image on a display block 10 on the basis of that jacket image data. Then, visually recognizing the jacket image displayed on the display block 10 , the user is able to visually recognize the impression of the in-reproduction music data being reproduced at that moment. [0032] On the other hand, if no jacket image data is found included in the attribute information, the CPU 3 of the reproducing apparatus 1 determines whether the attribute information includes a genre name. [0033] If a genre name, “poppunk” for example, is found included in the attribute information, then the CPU 3 of the reproducing apparatus 1 recognizes, from this genre name “poppunk,” main genre “punk” to which in-reproduction music data belongs and executes alternate symbol image display processing for displaying a symbol image corresponding to recognized main genre “punk.” [0034] In this alternate symbol image display processing, main genre vs. symbol image table TB 1 ( FIG. 3 ) stored in the hard disc drive 6 for example is used. [0035] In the case of the present embodiment, this main genre vs. symbol image table TB 1 shows “punk,” “metal,” and so on as main genres. In this main genre vs. symbol image table TB 1 , symbol image data D (1, 2, . . . , N) symbolizing main genres “punk,” “metal,” and so on are related with main genres “punk,” “metal,” and so on. [0036] In addition, this main genre vs. symbol image table TB 1 relates a comparison character string with each main genre. For this comparison character string, a character string is selected which is high in the possibility in which the character sting appears in the genre name in the attribute information of the music data belonging to that genre name. For example, “punk” is selected for the comparison character string corresponding to main genre “punk.” This is because character strings “poppunk” and “metalpunk” for example are often set as genre names in the attribute information of the music data belonging to main genre “punk,” making it high possible that character string “punk” appears in the genre name in the attribute information of the music data belonging to main genre “punk.” [0037] Consequently, the CPU 3 of the reproducing apparatus 1 compares genre name “poppunk” indicated in the attribute information of in-reproduction music data with comparison character string “punk” for example in main genre vs. symbol image table TB 1 . If the CPU 3 recognizes that this comparison character string “punk” is found included in genre name “poppunk,” the CPU 3 recognizes main genre “punk” corresponding to this comparison character string “punk” as the main genre of the in-reproduction music data. Then, the CPU 3 of the reproducing apparatus 1 reads symbol image data D 1 corresponding to the recognized main genre “punk” from the main genre vs. symbol image table TB 1 and displays a symbol image on the display block 10 on the basis of the read symbol image data. [0038] Thus, if jacket image data is not related with the in-reproduction music data being reproduced at that moment, the CPU 3 of the reproducing apparatus 1 is able to display a symbol image symbolizing the main genre to which this in-reproduction music data belongs instead of displaying a jacket image. As a result, the reproducing apparatus 1 may be realized that is surely able to display symbol images associated with in-reproduction music data being reproducing at that time. [0039] In the case of the present embodiment, main genre vs. symbol image table TB 1 shows, for each comparison character sting, a comparison sequence in the comparison between genre names in the attribute information of in-reproduction music data and comparison character strings. In the present embodiment for example, comparison character string “punk” corresponding to main genre “punk” may be assumed if determined with reference to FIG. 2 for example that the frequency of inclusion in genre names (“popmetal,” “countrymetal,” etc.) of other main genres “metal” and so on than this main genre “punk” be low, so that the comparison sequence is set to “1” for prioritized comparison. On the other hand, comparison sequence “metal” may be assumed if determined with reference to FIG. 2 for example that the frequency of inclusion in genre names (“poppunk,” “metal punk,” etc.) of other main genres “punk” and so on than this main genre “metal” be high, so that the comparison sequence is set to “ 2 ” for lower comparison priority. [0040] Thus, on the basis of a comparison sequence shown in main genre vs. symbol image table TB 1 , the CPU 3 of the reproducing apparatus 1 compares a genre name in the attribute information of in-reproduction music data preferentially with comparison character strings assumed to have a smaller frequency of inclusion in the genre names of other main genres among a plurality of comparison character strings shown in main genre vs. symbol image table TB 1 . Consequently, the reproducing apparatus 1 starts comparison with a comparison character string small in the possibility of inclusion in the genre names of other main genres (in this case, “punk”). This allows more accurate recognition of the main genre of that in-reproduction music data from among the genre names of the attribute information of that in-reproduction music data. [0041] The following describes image display processing procedure RT 1 of the first embodiment with reference to the flowchart shown in FIG. 4 . [0042] When an operation for reproducing acquired music data is executed through the operation block 2 of the reproducing apparatus 1 , the CPU 3 of the reproducing apparatus 1 accordingly goes to step SP 1 to read the music data corresponding to the reproduction operation from the hard disc drive 6 , thereby starting reproduction processing. [0043] Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 2 to read the attribute information related with the in-reproduction music data being reproduced from the hard disc drive 6 , determining whether jacket image data is included in the read attribute information. [0044] If the decision in step SP 2 is YES, it indicates that jacket image data is included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 3 . In step SP 3 , the CPU 3 of the reproducing apparatus 1 displays a jacket image on the display block 10 on the basis of the jacket image data included in the attribute information of the in-reproduction music data and then goes to step SP 9 to end image display processing procedure RT 1 . [0045] On the other hand, if the decision in step SP 2 is NO, it indicates that jacket image data is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 4 . In step SP 4 , the CPU 3 of the reproducing apparatus 1 determines whether a genre name is included in the attribute information of the in-reproduction music data. [0046] If the decision is NO in step SP 4 , it indicates that a genre name is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 5 . In step SP 5 , the CPU 3 of the reproducing apparatus 1 displays a default image on the display block 10 on the basis of predetermined default image data DN defined in main genre vs. symbol image table TB 1 shown in FIG. 3 and then goes to step SP 9 to end image display processing procedure RT 1 . [0047] On the other hand, if the decision is YES in step SP 4 , it indicates that “popmetal” for example is included as a genre name in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 6 . [0048] In step SP 6 , the CPU 3 of the reproducing apparatus 1 sequentially compares each of comparison character strings “punk,” “metal,” and so on with genre name “popmetal” in the attribute information of the in-reproduction music data in accordance with the comparison sequence shown in main genre vs. symbol image table TB 1 . If the CPU 3 of the reproducing apparatus 1 consequently finds comparison character string “metal” compared second for example in the genre name “popmetal,” then the CPU 3 of the reproducing apparatus 1 goes to step SP 7 to recognize main genre “metal” corresponding to this comparison character string “metal” as the main genre of the in-reproduction music data. [0049] Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 8 to read, from the hard disc drive 6 , symbol image data D 2 corresponding to main genre “metal” recognized in step SP 7 and displays a symbol image on the display block 10 on the basis of this symbol image data D 2 , upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 9 to end image display processing procedure RT 1 . [0050] It should be noted that, if, in step SP 6 , none of character strings “punk,” “metal” and so on is found included in this genre name after sequentially comparing comparison character strings “punk,” “metal” and so on shown in main genre vs. symbol image table TB 1 with the genre name in the attribute information of the in-reproduction music data, then the CPU 3 of the reproducing apparatus 1 goes to step SP 5 . In step SP 5 , the CPU 3 of the reproducing apparatus 1 displays a default image on the display block 10 on the basis of default image data DN and then goes to step SP 9 to end image display processing procedure RT 1 . [0051] As described above, if jacket image data indicative of the symbol of the in-reproduction music data being reproduced at that moment is not related therewith, the reproducing apparatus 1 recognizes the main genre of that in-reproduction music data on the basis of the genre name information related with that in-reproduction music data, reads the symbol image data symbolizing the recognized main genre from main genre vs. symbol image table TB 1 , and displays the symbol image on the basis of the read symbol image data. Consequently, the reproducing apparatus 1 is able to surely display the symbol image associated with the in-reproduction music data being reproduced at that moment. (2) Second Embodiment [0052] A second embodiment of the invention is different from the above-mentioned first embodiment in the contents of attribute information related with music data acquired from music provision server SV or a CD. On the other hand, the second embodiment is substantially the same as the first embodiment in the configuration ( FIG. 1 ) of the reproducing apparatus 1 , the genre definition ( FIG. 2 ), and main genre vs. symbol image table TB 1 ( FIG. 3 ). Therefore, the following describes the contents of the attribute information related with music data with reference to FIG. 5 . [0053] To be more specific, the attribute information of music data is configured by track information (“TRACK INFO” in the figure) indicative of information about the music data itself, album information (“ALBUM INFO” in the figure) indicative of information about an album to which the music data belongs, and data information (“DATA INFO” in the figure) indicative of information about compression algorithm for example used for the music data. The track information in this attribute information may include jacket image data (hereafter referred to as track jacket image data) indicative of a symbol of that music data, a genre name (hereafter referred to as a track genre name) indicative of a genre to which that music data belongs, and an artist name (hereafter referred to as a track artist name) indicative of a player or an editor of that music data, for example. The album information in this attribute information may include a jacket image (hereafter referred to as album jacket image data) indicative of a symbol of a particular album to which that music data belongs and a genre name (hereafter referred to as an album genre name) indicative of a genre to which that album belongs, and an artist name (hereafter referred to as an album artist name) indicative of a creator or an editor of that album, for example. [0054] The following describes image display processing procedure RT 2 ( FIG. 6 ) in the second embodiment. [0055] When an operation for reproducing acquired music data is executed through the operation block 2 of the reproducing apparatus 1 , the CPU 3 of the reproducing apparatus 1 accordingly goes to step SP 21 to read the music data corresponding to the reproduction operation from the hard disc drive 6 , thereby starting reproduction processing. [0056] Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 22 to read attribute information related with in-reproduction music data being reproduced from the hard disc drive 6 , thereby determining whether track jacket image data is included in the read attribute information. [0057] If the decision is YES in step SP 22 , it indicates that track jacket image data is included in the attribute information of in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 23 . In step SP 23 , the CPU 3 of the reproducing apparatus 1 displays a track jacket image on the display block 10 on the basis of the track jacket image data included in the attribute information of the in-reproduction music data and then goes to step SP 31 to end image display processing procedure RT 2 . On the other hand, if the decision in step SP 22 is NO, it indicates that the track jacket image data is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 24 . [0058] In step SP 24 , the CPU 3 of the reproducing apparatus 1 determines whether album jacket image data is included in the attribute information related with the in-reproduction music data. [0059] If the decision is YES in step SP 24 , it indicates that album jacket image data is included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 23 . In step SP 23 , the CPU 3 of the reproducing apparatus 1 displays an album jacket image on the display block 10 on the basis of the album jacket image data included in the attribute information of the in-reproduction music data and then goes to step SP 31 to end image display processing procedure RT 2 . On the other hand, if the decision is NO in step SP 24 , it indicates that album jacket image data is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 25 . [0060] In step SP 25 , the CPU 3 of the reproducing apparatus 1 determines whether a track genre name is included in the attribute information of the in-reproduction music data. [0061] If the decision is YES in step SP 25 , it indicates that “popmetal” for example is included in the attribute information of the in-reproduction music data as a track genre name, upon which the CPU 3 of the reproducing apparatus 1 goes to step S 26 . In step SP 26 , the CPU 3 of the reproducing apparatus 1 sequentially compares comparison character strings “punk,” “metal,” and so on with track genre name “popmetal” in the attribute information of the in-reproduction music data in accordance with a comparison sequence indicated in main genre vs. symbol image table TB 1 . If comparison character string “metal” compared second is found included in track genre name “popmetal,” then the CPU 3 of the reproducing apparatus 1 goes to step SP 27 to recognize that main genre “metal” corresponding to this comparison character string “metal” as the main genre of the in-reproduction music data. Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 28 to display a symbol image on the display block 10 on the basis of symbol image data D 2 corresponding to main genre “metal” recognized in step SP 27 and then goes to step SP 31 to end image display processing procedure RT 2 . It should be noted that, if, in step SP 26 , none of character strings “punk,” “metal” and so on is found included in this genre name after sequentially comparing comparison character strings “punk,” “metal” and so on shown in main genre vs. symbol image table TB 1 with the track genre name in the attribute information of the in-reproduction music data, then the CPU 3 of the reproducing apparatus 1 goes to step SP 30 . In step SP 30 , the CPU 3 of the reproducing apparatus 1 displays a default image on the display block 10 on the basis of default image data DN and then goes to step SP 31 to end image display processing procedure RT 2 . [0062] On the other hand, if the decision is NO in step S 25 , it indicates that a track genre name is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 29 . [0063] In step S 29 , the CPU 3 of the reproducing apparatus 1 determines whether an album genre name is included in the attribute information of the in-reproduction music data. [0064] If the decision in YES in step SP 29 , it indicates that “countrymetal” for example is included in the attribute information of the in-reproduction music data as an album genre name, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 26 . In step SP 26 , the CPU 3 of the reproducing apparatus 1 sequentially compares comparison character strings “punk,” “metal,” and so on with album genre name “country metal” in the attribute information of the in-reproduction music data in accordance with a comparison sequence indicated in main genre vs. symbol image table TB 1 . If comparison character string “metal” compared second for example is found included in album genre name “countrymetal,” then the CPU 3 of the reproducing apparatus 1 goes to step SP 27 to recognize main genre “metal” corresponding to this comparison character string “metal” as the main genre of the in-reproduction music data. Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 28 to display a symbol image on the display block 10 on the basis of symbol image data D 2 corresponding to main genre “metal” recognized in step SP 27 and then goes to step SP 31 to end image display processing procedure RT 2 . It should be noted that, if, in step SP 26 , none of character strings “punk,” “metal” and so on is found included in this genre name after sequentially comparing comparison character strings “punk,” “metal” and so on shown in main genre vs. symbol image table TB 1 with the album genre name in the attribute information of the in-reproduction music data, then the CPU 3 of the reproducing apparatus 1 goes to step SP 30 . In step SP 30 , the CPU 3 of the reproducing apparatus 1 displays a default image on the display block 10 on the basis of default image data DN and then goes to step SP 31 to end image display processing procedure RT 2 . [0065] On the other hand, if the decision is NO in step S 29 , it indicates that an album genre name is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 30 to display a default image on the display block 10 on the basis of default image data DN and then goes to step SP 31 to end image display processing procedure RT 2 . [0066] As described above, if track jacket image data indicative of a symbol of that in-reproduction music data and album jacket image data indicative of a symbol of an album to which that in-reproduction music data belongs are not related with the in-reproduction music data being reproduced at that moment, this reproducing apparatus 1 may recognize the main genre that in-reproduction music data or the main genre of the album to which that in-reproduction music data belongs on the basis of track genre name information or album genre name information related with that in-reproduction music data, read symbol image data symbolizing the recognized main genre from main genre vs. symbol image table TB 1 , and display the symbol image on the basis of the read symbol image data. Consequently, this reproducing apparatus 1 may surely display the symbol image associated with the in-reproduction music data being reproduced at that moment. (3) Third Embodiment [0067] A third embodiment of the invention is substantially the same in configuration as the above-mentioned first and second embodiments. On the other hand, the third embodiment uses a table that is different from main genre vs. symbol image table TB 1 ( FIG. 3 ). The following mainly describes differences between the third embodiment and the foregoing embodiments. [0068] In this case, the attribute information related with the music data acquired from music provision server SV or a CD may include jacket symbol data of that music data and an artist name indicative of a player or an editor of that music data. [0069] If the artist who played music data is “Dekoboko Sayaka” for example, “Dekoboko Sayaka” for example is displayed as one of artist names included in the attribute information of this music data. It should be noted that each character string indicated as an artist name in the attribute information may be edited by the user for example, so that the character string in this example may be other than “Dekoboko Sayaka.” If an artist who played music data is “Toba Outotsu” for example, “Toba Outotsu” for example is displayed as an artist name included in the attribute information of this music data. [0070] When an operation for reproducing acquired music data is executed through the operation block 2 of the reproducing apparatus 1 , the CPU 3 of the reproducing apparatus 1 accordingly reads the specified music data from the hard disc drive 6 , starting reproduction processing. [0071] At the same time, the CPU 3 of the reproducing apparatus 1 reads the attribute information related with the in-reproduction music data being reproduced from the hard disc drive 6 to determine whether jacket symbol data is included in the read attribute information. [0072] If jacket symbol data is found included in the attribute information, then the CPU 3 of the reproducing apparatus 1 displays a jacket symbol on the display block 10 on the basis of this jacket symbol data. Consequently, by visually recognizing the jacket symbol displayed on the display block 10 , the user is able to recognize the symbol of the in-reproduction music data being reproduced at that moment. [0073] On the other hand, if jacket symbol data is found not included in the attribute information, then the CPU 3 of the reproducing apparatus 1 determines whether an artist name is included in this attribute information. [0074] Recognizing that “Dekoboko Sayaka” for example is included in the attribute information as an artist name, the CPU 3 of the reproducing apparatus 1 recognizes artist “Dekoboko Sayaka” of the in-reproduction music data from this artist name “Dekoboko Sayaka” to execute alternate symbol image display processing for displaying the symbol image corresponding to recognized artist “Dekoboko Sayaka.” [0075] In this alternate symbol image display processing, artist vs. symbol image table TB 2 ( FIG. 7 ) stored in the hard disc drive 6 , for example. [0076] In the second embodiment, artist vs. symbol image table TB 2 shows “Dekoboko Sayaka,” “Toba Outotsu,” and so on as artists. Artist vs. symbol image table TB 2 relates these artists “Dekoboko Sayaka,” “Toba Outotsu,” and so on with symbol image data Dx (1, 2, . . . , N) symbolizing these artists. It should be noted that, for these symbol image data Dx, jacket symbol data related with past music data by these artists may be applied, for example. [0077] Artist vs. symbol image table TB 2 also relates artists with comparison character strings. For these comparison character strings, those which are high in the possibility of appearing in the artist names in the attribute information of the music data played by these artists are selected. In this case for example, “Dekoboko Sayaka” is selected as the character string corresponding to artist “Dekoboko Sayaka” and “Toba Outotsu” is selected as the character string corresponding to artist “Toba Outotsu.” [0078] Consequently, the CPU 3 of the reproducing apparatus 1 compares artist name “Dekoboko Sayaka” indicated in the attribute information of the in-reproduction music data with comparison character string “Dekoboko Sayaka” for example in artist vs. symbol image table TB 2 . If this comparison character string “Dekoboko Sayaka” is found included in artist name “Dekoboko Sayaka” in this attribute information, then the CPU 3 recognizes artist “Dekoboko Sayaka” corresponding to this comparison character string “Dekoboko Sayaka” as the artist who played the in-reproduction music data. Then, the CPU 3 of the reproducing apparatus 1 reads symbol image data Dx 1 corresponding to recognized artist “Dekoboko Sayaka” from artist vs. symbol image table TB 2 and displays a symbol image on the display block 10 on the basis of read symbol image data Dx 1 . [0079] As described above, if jacket symbol data is not related with the in-reproduction music data being reproduced at that moment, the CPU 3 of the reproducing apparatus 1 may display a symbol image symbolizing the artist of this in-reproduction music data instead of displaying a jacket image. As a result, the reproducing apparatus 1 is capable of surely displaying a symbol image associated with the in-reproduction music data being reproduced at that time may be realized. [0080] The following describes image display processing procedure RT 3 to be executed in the third embodiment with reference to the flowchart shown in FIG. 8 . [0081] When an operation for reproducing acquired music data is executed through the operation block 2 of the reproducing apparatus 1 , the CPU 3 of the reproducing apparatus 1 accordingly goes to step SP 41 to read the music data corresponding to the reproduction operation from the hard disc drive 6 , thereby starting reproduction processing. [0082] Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 42 to read attribute information related with in-reproduction music data being reproduced from the hard disc drive 6 , thereby determining whether jacket image data is included in the read attribute information. [0083] If the decision is YES in step SP 42 , it indicates that jacket image data is included in the attribute information of in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 43 . In step SP 43 , the CPU 3 of the reproducing apparatus 1 displays a jacket image on the display block 10 on the basis of the jacket image data included in the attribute information of the in-reproduction music data and then goes to step SP 49 to end image display processing procedure RT 3 . [0084] On the other hand, if the decision in step SP 42 is NO, it indicates that the jacket image data is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 44 . In step SP 44 , the CPU 3 of the reproducing apparatus 1 determines whether an artist name is included in the attribute information of the in-reproduction music data. [0085] If the decision is NO in step SP 44 , it indicates that an artist name is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 45 . In step S 45 , the CPU 3 of the reproducing apparatus 1 displays a default image on the display block 10 on the basis of predetermined default image data DxN defined in artist vs. symbol image table TB 2 shown in FIG. 7 and then goes to step SP 49 to end image display processing procedure RT 3 . [0086] On the other hand, if the decision is YES in step SP 44 , it indicates that “Toba Outotsu” for example is included in the attribute information of the in-reproduction music data as an artist name, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 46 . [0087] In step SP 46 , the CPU 3 of the reproducing apparatus 1 sequentially compares comparison character strings “Dekoboko Sayaka,” “Toba Outotsu,” and so on shown in artist vs. symbol image table TB 2 with artist name “Toba Outotsu” in the attribute information of the in-reproduction music data. If comparison character string “Toba Outotsu” is found in artist name “Toba Outotsu” in the attribute information of the in-reproduction music data, for example, then the CPU 3 of the reproducing apparatus 1 goes to step SP 47 to recognize artist “Toba Outotsu” corresponding to this comparison character string “Toba Outotsu” as the artist who played the in-reproduction music data. [0088] Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 48 , displays a symbol image on the display block 10 on the basis of symbol image data Dx 2 corresponding to artist “Toba Outotsu” recognized in step SP 47 , and then goes to step SP 49 to end image display processing procedure RT 3 . [0089] It should be noted that, if none of comparison character strings “Dekoboko Sayaka,” “Toba Outotsu,” and so on is found included in the artist names in this attribute information as a result of the sequential comparison between comparison character strings shown in artist vs. symbol image table TB 2 and the artist name in the attribute information of the in-reproduction music data, then the CPU 3 of the reproducing apparatus 1 goes to step SP 45 . In step SP 45 , the CPU 3 of the reproducing apparatus 1 displays a default image on the display block 10 on the basis of default image data DxN and goes to step SP 49 to end image display processing procedure RT 3 . [0090] As described above, if jacket image data indicative of an image of that in-reproduction music data is not related with the in-reproduction music data being reproduced at that moment, the reproducing apparatus 1 recognizes the artist who played that in-reproduction music data on the basis of the artist name information related with that in-reproduction music data, reads a symbol image data symbolizing the recognized artist from artist vs. symbol image table TB 2 , and displays the symbol image on the basis of the read symbol image data. Consequently, the reproducing apparatus 1 is able to surely display a symbol image associated with the in-reproduction music data being reproduced at that moment. (4) Fourth Embodiment [0091] A fourth embodiment of the invention is substantially the same in the configuration ( FIG. 1 ) of the reproducing apparatus 1 as the above-mentioned first, second, and third embodiments. Also, the fourth embodiment is substantially the same as the second embodiment in the contents of attribute information related with music data acquired from music provision server SV or a CD (refer to FIG. 5 ). The fourth embodiment also uses artist vs. symbol image table TB 2 shown in FIG. 7 . [0092] The following describes image display processing procedure RT 4 ( FIG. 9 ) to be executed in the fourth embodiment. [0093] When an operation for reproducing acquired music data is executed through the operation block 2 of the reproducing apparatus 1 , the CPU 3 of the reproducing apparatus 1 accordingly goes to step SP 51 to read the music data corresponding to the reproduction operation from the hard disc drive 6 , thereby starting reproduction processing. [0094] Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 52 to read attribute information of the in-reproduction music data being reproduced from the hard disc drive 6 to determine whether track jacket image data is included in the read attribute information. [0095] If the decision in step SP 52 is YES, it indicates that track jacket image data is included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 53 . In step SP 53 , the CPU 3 of the reproducing apparatus 1 displays a track jacket image on the display block 10 on the basis of the track jacket image data included in the attribute information of the in-reproduction music data and then goes to step SP 61 to end image display processing procedure RT 4 . On the other hand, if the decision is NO in step SP 52 , it indicates that track jacket image data is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 54 . [0096] In step SP 54 , the CPU 3 of the reproducing apparatus 1 determines whether album jacket image data is included in the attribute information related with the in-reproduction music data. [0097] If the decision is YES in step SP 54 , it indicates that album jacket image data is included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 53 . In step SP 53 , the CPU 3 of the reproducing apparatus 1 displays an album jacket image on the display block 10 on the basis of the album jacket image data included in the attribute information of the in-reproduction music data and then goes to step SP 61 to end image display processing procedure RT 4 . On the other hand, if the decision is NO in step S 54 , it indicates that album jacket image data is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 55 . [0098] In step SP 55 , the CPU 3 of the reproducing apparatus 1 determines whether a track artist name is included in the attribute information of in-reproduction music data. [0099] If the decision is YES in step SP 55 , it indicates that “Toba Outotsu” for example is included in the attribute information of the in-reproduction music data as a track artist name, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 56 . In step SP 56 , the CPU 3 of the reproducing apparatus 1 sequentially compares comparison character strings “Dekoboko Sayaka,” “Toba Outotsu,” and so on shown in artist vs. symbol image table TB 2 with track artist name “Toba Outotsu” in the attribute information of the in-reproduction music data. If comparison character string “Toba Outotsu” is found included in track artist name “Toba Outotsu,” then the CPU 3 of the reproducing apparatus 1 goes to step SP 57 to recognize artist “Toba Outotsu” corresponding to comparison character string “Toba Outotsu” as the artist who played the in-reproduction music data. Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 58 to display a symbol image on the display block 10 on the basis of symbol image data Dx 2 corresponding to artist “Toba Outotsu” recognized in step SP 57 . Then, the CPU 3 of the reproducing apparatus 1 goes to step SP 61 to end image display processing procedure RT 4 . It should be noted that, if none of comparison character strings “Dekoboko Sayaka,” “Toba Outotsu,” and so on is found included in this track artist name, then the CPU 3 of the reproducing apparatus 1 goes to step SP 60 . In step SP 60 , the CPU 3 of the reproducing apparatus 1 displays a default image on the display block 10 on the basis of default image data DxN and goes to step SP 61 to end image display processing procedure RT 4 . [0100] On the other hand, if the decision is NO in step SP 55 , it indicates that a track artist name is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 59 . [0101] In step SP 59 , the CPU 3 of the reproducing apparatus 1 determines whether an album artist name is included in the attribute information of the in-reproduction music data. [0102] If the decision is YES in step SP 59 , it indicates that “Dekoboko Sayaka” for example is included in the attribute information of the in-reproduction music data as an album artist name, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 56 . In step SP 56 , the CPU 3 of the reproducing apparatus 1 sequentially compares comparison character strings “Dekoboko Sayaka,” “Toba Outotsu,” and so on shown in artist vs. symbol image table TB 2 with album artist name “Dekoboko Sayaka” in the attribute information of the in-reproduction music data. If comparison character string “Dekoboko Sayaka” is found included in this album artist name “Dekoboko Sayaka” for example, then CPU 3 of the reproducing apparatus 1 goes to step SP 57 to recognize artist “Dekoboko Sayaka” corresponding to this comparison character string “Dekoboko Sayaka” as the artist who played this in-reproduction music data. Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 58 to display a symbol image on the display block 10 on the basis of symbol image data Dx 1 corresponding to artist “Dekoboko Sayaka” recognized in step SP 57 and goes to step SP 61 to end image display processing procedure RT 4 . It should be noted that, none of comparison character strings “Dekoboko Sayaka,” “Toba Outotsu,” and so on is found included in this album artist name, the CPU 3 of the reproducing apparatus 1 goes to step SP 60 to display a default image on the display block 10 on the basis of default image data DxN and then goes to step SP 61 to end image display processing procedure RT 4 . [0103] On the other hand, if the decision is NO in step SP 59 , it indicates that an album artist name is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 or the reproducing apparatus 1 goes to step SP 60 . In step SP 60 , the CPU 3 of the reproducing apparatus 1 displays a default image on the display block 10 on the basis of default image data DxN and then goes to step SP 61 to end image display processing procedure RT 4 . [0104] As described above, if track jacket image data indicative of an image of that in-reproduction music data and album jacket image data indicative of an image of an album to which that in-reproduction music data belongs are not related with the in-reproduction music data being reproduced at that moment, the reproducing apparatus 1 recognizes the artist who played that in-reproduction music data or the artist of an album to which that in-reproduction music data belongs on the basis of the artist name information related with that in-reproduction music data, reads a symbol image data symbolizing the recognized artist from artist vs. symbol image table TB 2 , and displays the symbol image on the basis of the read symbol image data. Consequently, the reproducing apparatus 1 is able to surely display a symbol image associated with the in-reproduction music data being reproduced at that moment. (5) Fifth Embodiment [0105] A fifth embodiment of the invention is substantially the same in the configuration ( FIG. 1 ) of the reproducing apparatus 1 as the above-mentioned first, second, third, and fourth embodiments. [0106] However, the fifth embodiments differs from the foregoing embodiments in that, every time music data stored in the hard disc drive 6 is reproduced, it is counted and reproduction count information indicative of the reproduction count is stored in the hard disc drive 6 . The hard disc drive 6 of the reproducing apparatus 1 also stores a plurality of pieces of symbol image data corresponding to the reproduction count, such as symbol image data indicative of a high reproduction count and symbol image data indicative of a low reproduction count, for example. [0107] The following describes image display processing procedure RT 5 ( FIG. 10 ) to be executed in the fifth embodiment. [0108] When an operation for reproducing acquired music data is executed through the operation block 2 of the reproducing apparatus 1 , the CPU 3 of the reproducing apparatus 1 accordingly goes to step SP 71 to read the music data corresponding to the reproduction operation from the hard disc drive 6 , thereby starting reproduction processing. [0109] Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 72 to read attribute information of the in-reproduction music data being reproduced from the hard disc drive 6 to determine whether jacket image data is included in the read attribute information. [0110] If the decision is YES in step SP 72 , it indicates that jacket image data is included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 73 . In step SP 73 , the CPU 3 of the reproducing apparatus 1 displays a jacket image on the basis of the jacket image data included in the attribute information of the in-reproduction music data and then goes to step SP 75 to end image display processing procedure RT 5 . [0111] On the other hand, if the decision is NO in step SP 72 , it indicates jacket image data is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 74 . [0112] In step SP 74 , the CPU 3 of the reproducing apparatus 1 reads reproduction count information corresponding to the in-reproduction music data from the hard disc drive 6 to recognize the reproduction count so far of that in-reproduction music data on the basis of the read reproduction count information, reads symbol image data corresponding to the recognized reproduction count from the hard disc drive 6 , displays a symbol image on the display block 10 on the basis of the read symbol image data, and then goes to step SP 75 to end image display processing procedure RT 5 . [0113] Thus, if jacket image data is not related with the in-reproduction music data being reproduced at that moment, the CPU 3 of the reproducing apparatus 1 is able to display a symbol image symbolizing the reproduction frequency of that in-reproduction music data instead of displaying a jacket image. As a result, the reproducing apparatus 1 is capable to surely displaying a symbol image associated with the in-reproduction music data being reproduced at that moment may be realized. (6) Sixth Embodiment [0114] A sixth embodiment of the invention is substantially the same in the configuration ( FIG. 1 ) of the reproducing apparatus 1 as the above-mentioned first, second, third, fourth, and fifth embodiments. The sixth embodiment is also substantially the same in the contents of the attribute information related with music data as the above-mentioned second embodiment for example (refer to FIG. 5 ). [0115] Like the above-mentioned fifth embodiment, the CPU 3 of the reproducing apparatus 1 in the sixth embodiment counts the reproduction of each piece of music data stored in the hard disc drive 6 and stores the reproduction count information indicative of the obtained reproduction count into the hard disc drive 6 . The hard disc drive 6 of the reproducing apparatus 1 also stores a plurality of pieces of symbol image data corresponding to the reproduction count, such as symbol image data indicative of a high reproduction count and symbol image data indicative of a low reproduction count, for example. [0116] The following describes image display processing procedure RT 6 ( FIG. 11 ) to be executed in the sixth embodiment. [0117] When an operation for reproducing acquired music data is executed through the operation block 2 of the reproducing apparatus 1 , the CPU 3 of the reproducing apparatus 1 accordingly goes to step SP 81 to read the music data corresponding to the reproduction operation from the hard disc drive 6 , thereby starting reproduction processing. [0118] Next, the CPU 3 of the reproducing apparatus 1 goes to step SP 82 to read attribute information of the in-reproduction music data being reproduced from the hard disc drive 6 to determine whether track jacket image data is included in the read attribute information. [0119] If the decision is YES in step SP 82 , it indicates that track jacket image data is included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 83 . In step SP 83 , the CPU 3 of the reproducing apparatus 1 displays a track jacket image on the display block 10 on the basis of the track jacket image data included in the attribute information of the in-reproduction music data and then goes to step SP 86 to end image display processing procedure RT 6 . [0120] On the other hand, if the decision is NO in step S 82 , it indicates that track jacket image data is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 84 . [0121] In step SP 84 , the CPU 3 of the reproducing apparatus 1 determines whether album jacket image data is included in the attribute information related with the in-reproduction music data. [0122] If the decision is YES in step SP 84 , it indicates that album jacket image data is included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 83 . In step SP 83 , the CPU 3 of the reproducing apparatus 1 displays an album jacket image on the display block 10 on the basis of the album jacket image data included in the attribute information of the in-reproduction music data and then goes to step SP 86 to end image display processing procedure RT 6 . [0123] On the other hand, if the decision is NO in step SP 84 , it indicates that album jacket image data is not included in the attribute information of the in-reproduction music data, upon which the CPU 3 of the reproducing apparatus 1 goes to step SP 85 . [0124] In step SP 85 , the CPU 3 of the reproducing apparatus 1 reads reproduction count information corresponding to the in-reproduction music data to recognize the reproduction count so far of the in-reproduction music data on the basis of the read reproduction count information, reads symbol image data corresponding to the recognized reproduction count from the hard disc drive 6 to display a symbol image on the display block 10 on the basis of the read symbol image data, and goes to step SP 86 to end image display processing procedure RT 6 . [0125] Thus, if track jacket image data and album jacket image data are not related with the in-reproduction music data being reproduced at that moment, the CPU 3 of the reproducing apparatus 1 is able to display a symbol image symbolizing the reproduction frequency of that in-reproduction music data instead of displaying a track jacket image and an album jacket image. As a result, the reproducing apparatus 1 is capable to surely displaying a symbol image associated with the in-reproduction music data being reproduced at that moment may be realized. (7) Other Embodiments [0126] In the above-mentioned first and second embodiments, genre names in the attribute information of music data are subject to editing by user and therefore not fixed, so that main genre vs. symbol image table TB 1 defines that character strings high in the possibility of appearing in genre names be related with symbol image data as comparison character strings, thereby comparing the defined comparison character strings with the genre name in the attribute information of in-reproduction music data. However, if the genre name in the attribute information of music data remains unchanged, it is also practicable to define that this genre name itself be related with symbol image data as a comparison character string in main genre vs. symbol image table TB 1 , thereby comparing the defined comparison character strings with the genre name in the attribute information of in-reproduction music data. [0127] In the above-mentioned third and fourth embodiments, artist names in the attribute information of music data are subject to editing by user and therefore not fixed, so that artist vs. symbol image table TB 2 defines that character strings high in the possibility of appearing in artist names be related with symbol image data as comparison character strings, thereby comparing the defined comparison character strings with the artist name in the attribute information of in-reproduction music data. However, if the artist name in the attribute information of music data remains unchanged, it is also practicable to define that this artist name itself be related with symbol image data as a comparison character string in artist vs. symbol image table TB 2 , thereby comparing the defined comparison character strings with the artist name in the attribute information of in-reproduction music data. [0128] In the above-mentioned first through sixth embodiments, the application of music data for sounding music as content data has been described. The embodiments of the present invention are not limited to this application. For example, video data (movies and TV programs), still image data, game programs, text data (e.g. book data), and program data may also be applied as content data. [0129] In the above-mentioned first through sixth embodiments, jacket images for example that are still images are applied as symbol images visually indicative of images associated with music data. It is also practicable to apply various other kinds of images such as moving pictures (or video), icon images, and so on. [0130] In the above-mentioned first through sixth embodiments, the reproducing apparatus 1 having a recording capability of recording music data acquired from music provision server SV and CD to the hard disc drive 6 and a reproducing capability of reproducing music data from the hard disc drive 6 is applied to a recording/reproducing apparatus. It is also practicable to apply various other configurations for the reproducing apparatus 1 . [0131] In the above-mentioned first through sixth embodiments, the CPU 3 adapted to execute various processing operations by expanding programs stored in the ROM 11 into the RAM 12 is used as a recording means for recording content data to recording media (or the hard disc drive 6 ). It is also practicable to apply various other configurations. For example, each of components recited in claims hereto may be implemented with a separate hardware block. [0132] In the above-mentioned first through sixth embodiments, the hard disc drive 6 for storing main genre vs. symbol image table TB 1 and artist vs. symbol image table TB 2 is applied as an image data storage device for storing image data in correspondence with particular attribute information. It is also practicable to apply various other configurations. [0133] In the above-mentioned first through sixth embodiment, the CPU 3 of the reproducing apparatus 1 is applied as a reproducing means for reproducing content data from recording media, attribute information detection means for detecting attribute information related with content data if no image data (or jacket image data) is related with content data, image data detection means for detecting, from the image data storage means, image data (or symbol image data) related with attribute information (or sub genre information, artist name information, and reproduction count information) detected by the attribute information detection means, and control means for controlling such that image data detected by the image data detection means during the reproduction of content data by the reproduction means be outputted (or displayed). It is also practicable to apply various other configurations. For example, if a particular piece of content data is selected by user through the operation block 2 , the image data thereof may be outputted. At this moment, that content data may not be reproduced. When the reproduction of content data has ended and the reproducing operation ends, the output of the image data corresponding to that content data may be continued. [0134] In the above-mentioned first through sixth embodiments, the CPU 3 of the reproducing apparatus 1 executes the above-mentioned image display processing procedures RT 1 through RT 6 in software approach in accordance with programs stored in the hard disc drive 6 and so on. It is also practicable to apply hardware circuits for executing image display processing procedures RT 1 through RT 6 to the reproducing apparatus 1 , thereby realizing these procedures in hardware approach. [0135] While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purpose only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

A recording/reproducing apparatus and method and program are preferably applicable to a reproducing apparatus for reproducing externally acquired music data for example. The recording/reproducing apparatus has a recording device configured to record content data to a storage medium; a reproduction device configured to reproduce the content data from the storage medium; an image data storage device configured to store image data corresponding to each of a plurality of pieces of attribute information; an attribute information detector configured to detect, if no image data is related with the content data, attribute information related with the content data; an image data detector configured to detect image data corresponding the attribute information detected by the attribute information detector from the image data storage device; and a controller configured to control such that the image data detected by the image data detector be outputted at least during reproduction of the content data by the reproduction device.

RELATED APPLICATIONS This is a Continuation-In-Part of application U.S. Ser. No. 08/354,237, filed Dec. 12, 1994, and entitled "Headset Amplifier With Automatic Log On/Log Off Detection," which issued as U.S. Pat. No. 5,926,543, which is a Continuation of application U.S. Ser. No. 08/062,614, filed May 11, 1993, and entitled "Apparatus for and Method of Operating an Automatic Log On/Log Off Circuit In a Telephone System By Disconnecting a Headset," which issued as U.S. Pat. No. 5,488,657, which is a Continuation of application U.S. Ser. No. 07/844,739, filed Mar. 2, 1992, and entitled "Headset Amplifier With Automatic Log On/Log Off Detection," which issued as U.S. Pat. No. 5,226,077 on Jul. 6, 1993. BACKGROUND OF THE INVENTION Telephone headsets are an important element of modern business equipment. They provide hands-free communication, and improve productivity, in a variety of applications, such as operator and information services. One of the main applications of telephone headsets is in connection with automatic in-bound and out-bound telephone systems. Such systems generally include an Automatic Call Distributor (ACD). In a telephone system with an ACD, a computer automatically routes telephone calls to workstations connected to the system in a way that balances the call load equally between the workstations. Each workstation can be occupied by a telephone representative. For a telephone system with ACD to work properly, each telephone representative is required to log on to the system each time he/she occupies his/her workstation, and to log off the system each time he/she leaves his/her workstation. This is necessary so that the ACD will route calls to all occupied workstations, and will not route calls to any unoccupied workstations. If a representative leaves his/her workstation without logging off, the ACD system will continue to route calls to that workstation. Such calls are not responded to, or a response is delayed. A representative failing to log on to the system increases the load on the other representatives, and increases the time required to respond to incoming calls. The failure of a representative either to log on to or log off the system consequently results in a reduced quality of service. The need for a telephone system to determine whether a workstation is occupied is not restricted to telephone systems with an ACD. For example, the sole telephone operator in a small office is also required to log off when away from his/her workstation so that incoming calls do not go unanswered. To improve the quality of service provided by telephone systems in which the presence of a representative or operator at a workstation impacts the quality of service, it is desirable that logging on and logging off be automated. A typical workstation includes a telephone headset connected to an amplifier. The amplifier is, in turn, connected to the workstation, which is connected to the telephone system. The amplifier is powered by current drawn from the telephone system. Automated log on/log off systems are known in which the representative has to unplug the amplifier from the workstation to log off automatically. The automatic log on/log off system monitors each workstation to determine whether or not an amplifier is connected to the workstation. The system logs the representative off when it determines that the amplifier has been disconnected from the workstation. Some types of automatic log on/log off system log the representative back on when it determines that the amplifier has been re-connected to the workstation. Other types require the representative to log back in manually. Such automatic log on/log off systems determine whether the amplifier is connected to the workstation by monitoring some parameter that depends on whether or the amplifier is connected, such as the current drawn from the telephone system by the amplifier, or the resistance between a pair of contacts. The log on/log off system just described is regarded as automatic, even though the representative has to connect or disconnect the amplifier, because operators prefer to continue to wear their headsets when away from their workstations, especially if the time away from the workstation is short. To be able to leave the workstation while wearing the headset, the representative has to unplug the amplifier, and has to carry the amplifier around while away from the workstation. Recently, headset manufacturers have made it easier for a representative to leave his/her workstation while wearing his/her headset by providing a connector in the cord between the headset and the amplifier. The representative can then wear the headset while he/she is away from the workstation and no longer has to carry the amplifier. However, disconnecting the headset using the connector in the cord defeats the known automatic log in/log out systems, because the representative can leave the workstation without unplugging the amplifier, and disconnecting the headset using the connector in the cord does not change any of the parameters monitored by the known automatic log on/log off systems. SUMMARY OF THE INVENTION In accordance with the present invention, wireless communication is provided between a telephone headset and conventional automatic in-bound and out-bound telephone systems, including those with an ACD, while maintaining full automated log on/log off capability. A wireless telephone headset system in accordance with the present invention includes an amplifier and a telephone headset. The amplifier is for connecting to a telephone system which includes a monitor for monitoring when a peripheral device is connected thereto and detecting a change in a parameter which occurs when the peripheral device is disconnected therefrom. Together, the amplifier and telephone headset are for establishing a wireless communication link therebetween for communicating signals between the telephone headset and the telephone system. One embodiment of the amplifier in accordance with the present invention includes a detector and an activator. The detector is for detecting an interruption of a wireless communication link between the telephone headset and the amplifier and providing an output signal in accordance therewith. The activator, coupled to the detector, is for receiving the output signal and in accordance therewith changing the parameter in a manner which emulates a disconnection of a peripheral device from the telephone system even though the amplifier remains connected to the telephone system. In another embodiment of the amplifier, where the telephone system monitor is further for detecting a change in the parameter which occurs when the peripheral device is reconnected to the telephone system, the detector is further for detecting when the wireless communication link is reestablished between the telephone headset and the amplifier and in accordance therewith providing another output signal, and the activator is further for changing the parameter, in accordance with the other output signal, in a manner which emulates a reconnection of the peripheral device to the telephone system even though the amplifier has not been disconnected. One embodiment of the telephone headset in accordance with the present invention includes a detector and a controller. The detector is for detecting an interruption of the wireless communication link between the telephone headset and the amplifier and providing an output signal in accordance therewith. The controller, coupled to the detector, is for receiving the output signal and in accordance therewith providing one or more control signals for controlling one or more operating parameters of the telephone headset. In another embodiment of the telephone headset, where the telephone system monitor is further for detecting a change in the parameter which occurs when the peripheral device is reconnected to the telephone system, the detector is further for detecting when the wireless communication link is reestablished between the telephone headset and the amplifier and in accordance therewith providing another output signal, and the controller is further for providing one or more other control signals, in accordance with the other output signal, for further controlling the one or more operating parameters of the telephone headset. These and other features and advantages of the present invention will be understood upon consideration of the following detailed description of the invention and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a telephone system with a conventional automatic log on/log off system that determines whether or not the amplifier is connected by sensing the current drawn from the telephone system. FIG. 2 is a block diagram of a telephone system with a conventional automatic log on/log off system that determines whether or not the amplifier is connected by sensing the resistance or voltage difference between two additional contacts. FIG. 3 is a block diagram of a wireless telephone headset system with automatic log on/log off detection according to the invention connected to a telephone system. FIG. 4 is a block diagram of the activator part of a wireless telephone headset system with automatic log on/log off detection according to the invention in which the activator activates a current sensing type of automatic log on/log off system. FIG. 5 is a block diagram of the activator part of a wireless telephone headset system with automatic log on/log off detection according to the invention in which the activator activates a current sensing type of automatic log on/log off system with a low current sensing threshold. FIG. 6 is a block diagram of the activator part of a wireless telephone headset system with automatic log on/log off detection according to the invention in which the activator activates a resistance/voltage sensing type of automatic log on/log off system and the activator can activate both current sensing and resistance/voltage sensing automatic log on/log off systems. FIG. 7 is a block diagram of the activator part of a wireless telephone headset system with automatic log on/log off detection according to the invention showing how a different interconnect can be used to adapt the base unit for use with a different type of telephone system. FIG. 8 is a block diagram of the base unit of a wireless telephone headset system with automatic log on/log off detection in accordance with one embodiment of the present invention. FIG. 9 is a block diagram of the headset unit of a wireless telephone headset system with automatic log on/log off detection in accordance with one embodiment of the present invention. FIG. 10A is a block diagram of one embodiment of the base unit of FIG. 8 with a radio frequency transmitter and receiver. FIG. 10B is a block diagram of another embodiment of the base unit of FIG. 8 with an infrared transmitter and receiver. FIG. 11A is a block diagram of one embodiment of the headset unit of FIG. 9 with a radio frequency transmitter and receiver. FIG. 11B is a block diagram of another embodiment of the headset unit of FIG. 9 with an infrared transmitter and receiver. DETAILED DESCRIPTION OF THE INVENTION A typical telephone system with an automatic log on/log off system is shown in FIG. 1. The workstation 1, which is normally one of several workstations connected to the telephone system 16, has an amplifier 6 to provide an interface between the telephone system 16 and the headset 46. The cord 11 connects the amplifier to the telephone system 16. The amplifier is powered by the telephone system, and draws a current of several milliamps from the telephone system. The cord 11 includes the conductor 21 for DC power and the conductor 31, which provides the ground connection. The transmit signal from the amplifier 6 is normally superimposed on the conductor 21. Alternatively, an additional conductor (not shown) in the cord 11 may be used for the transmit signal. Finally the cord 11 includes receive conductors, which have been omitted for clarity. The cord 11 is interrupted by the connector 36, comprising the plug 36A and the socket 36B, which is normally mounted on the workstation 1. The connector 36 allows the amplifier 6 and the headset 46 to be disconnected from the workstation. The headset 46 includes an earphone (not shown) and a microphone (not shown). Typically, an electret microphone is used, which requires that the amplifier 6 supply DC power of a few volts at between 25 and several hundred microamps to the headset. The cord 51 interconnects the headset and the amplifier. The cord 51 includes the conductor 56 for DC power and the conductor 66, which provides the ground connection. The transmit signal from the microphone in the headset (not shown) is normally superimposed on the conductor 56. Alternatively, an additional conductor (not shown) may be used for the transmit signal. Finally, the cord 51 includes receive conductors, which have been omitted for clarity. The cord 51 is interrupted by the connector 71, comprising the plug 71A and the socket 71B. The connector 71 enables the representative to disconnect the headset from the amplifier when he/she leaves the workstation 1. Normally, the connector 71 is mounted in the cord 51 close to the headset, but it can be an integral part of the headset or an integral part of the amplifier. Applications handling a large volume of telephone calls, such as telemarketing, bank customer service, or airline reservations, have a plurality of workstations, each with its own telephone connector 36, amplifier 6, headset 46 and necessary interconnecting cords. The workstations are connected to the telephone system 16. The telephone system may include an Automatic Call Distributor (ACD) for distributing the calls evenly between occupied workstations, i.e., workstations at which a representative is logged on. Smaller telephone systems lack an ACD, but the invention can be applied to a telephone system without an ACD. The telephone system 16 includes an automatic log on/log off system 76 that automatically logs a workstation off the telephone system when the occupant leaves the workstation. Some automatic log-on/log off systems automatically log the workstation back onto the telephone system when the occupant returns. Other automatic log on/log off systems require the occupant to log back in manually. The cord 11 connects the amplifier 6 to the telephone system 16. When the amplifier 6 is disconnected from the telephone system 16, the automatic log on/log off system 76 causes the telephone system to take an action that is appropriate in view of the fact that the workstation is no longer occupied. For example, in a small office system with a single telephone operator, it can cause the telephone system to go temporarily into its night service mode so that incoming calls do not go unanswered. In a large system with ACD, it prevents the telephone system from directing calls to the unoccupied workstation. When the amplifier 6 is re-connected to the telephone system 16, the automatic log on/log off system 76 may cause the telephone system to reverse the action previously taken, or the occupant may have to log back in manually. FIG. 1 shows a telephone system 16 with an automatic log on/log off system controlled by the current sensor 86 that detects whether or not the amplifier 6 is connected to the telephone system by monitoring the current drawn by the amplifier from the telephone system. Current from a power supply 81 in the telephone system is supplied to the conductor 21, and to the amplifier 6, through the current sensor 86. The current sensor 86 provides an output signal to the automatic log on/log off system 76. When the current supplied to the amplifier is greater than a threshold value, typically about one milliamp, the current sensor 86 provides an output signal in a first state that indicates that the amplifier is connected to the telephone system. When the current supplied to the amplifier is less than the threshold value, the current sensor provides an output signal in a second state that indicates that the amplifier has been disconnected from the telephone system. The state of the output signal from the current sensor thus informs the automatic log on/log off system 76 whether or not the amplifier 6 is connected to the telephone system 16, and the automatic log on/log off system can thus cause the telephone system to take appropriate action. The connector 71 in the cord 51 between the amplifier 6 and the headset 46 enables the occupant to leave the workstation while continuing to wear his/her headset without having to disconnect the amplifier from the telephone system 16. This defeats the automatic log on/log off system. Because the current drawn from the telephone system 16 by the headset 46 is small compared with the total current drawn from the telephone system by the amplifier 6, it is not practical to change the threshold of the current sensor 86 to detect the change in the current drawn by the amplifier resulting from disconnecting the headset. FIG. 2 shows the telephone system of FIG. 1 fitted with a known alternative to the current sensor 86 (FIG. 1) for determining whether or not the amplifier 6 is connected to the telephone system 11. The cord 11 is provided with two additional conductors 91 and 96. The conductors are interconnected on the amplifier side of the connector 36. Inside the telephone system 16, the additional conductors 91 and 96 are connected to the sensor 186, which measures a parameter relating to the two additional conductors that depends on whether the amplifier 6 is connected to the telephone system 16. This could be the resistance between the conductors, a voltage difference between the conductors, an a.c. signal level, or some other suitable parameter. The sensor 186 provides an output signal to the automatic log on/log off system 76. When, for example, the resistance between the additional conductors 91 and 96 is less than a threshold value, the sensor 186 provides an output signal in a first state that indicates that the amplifier is connected to the telephone system. When the resistance between the conductors is greater than the threshold value, the sensor 186 provides an output signal in a second state that indicates that the amplifier has been disconnected from the telephone system. The state of the output signal of the sensor 186 thus indicates to the automatic log on/log off system 76 whether or not the amplifier 6 is connected to the telephone system 16, and the automatic log on/log off system can thus cause the telephone system to take appropriate action. As a common alternative to the arrangement shown in FIG. 2, the additional conductors 91 and 96 can be connected to the contacts of a switch on the socket 36B. The contacts are actuated by plugging the plug 36A into the socket 36B. When the plug 36A (typically a 1/4 inch phone jack) is not plugged into the socket 36B, the contacts are in first condition, e.g., open; when the plug 36A is plugged into the socket 36B, the contacts change to a second condition, e.g., closed. As an alternative to providing two additional conductors 91 and 96, the additional conductor 96 can be omitted. The sensor 186 would then monitor a parameter relating to the single conductor 91 and one of the other conductors 21 and 31 of the cord 11 that depends on whether the amplifier 6 is connected to the telephone system 16. For example, the additional conductor 91 can be connected to the power/signal conductor 21 on the plug 36A of the connector 36, which is connected to the amplifier. The sensor 186 then determines whether or not the voltage on the additional conductor 91 is substantially the same as the amplifier power supply voltage. The connector 71 in the cord 51 between the amplifier 6 and the headset 46 enables the occupant of the workstation to leave the workstation while continuing to wear his/her headset without having to disconnect the amplifier 6 from the telephone system 16. This defeats the automatic log on/log off system because it does not change any parameter relating to the additional conductors 91 and 96, or relating to the additional conductor 91 and another conductor in the cord 11. FIG. 3 shows a block diagram of an amplifier 100 according to the invention. As discussed in more detail below, the amplifier 100 communicates with the headset 146 over a wireless communication link 151 via wireless signal radiators (e.g. antennas) 156, 158, 166, 168. The amplifier is connected to the telephone system by the cord 111 that includes the connector 136, comprising the plug 136A and the socket 136B, the two conductors 121 and 131 for power/signal and ground, respectively. The cord 111 may also include the additional conductors 191 and 196. The conductors in the cords 111 and 151 are directly or indirectly connected to the amplifier electronics 105, and provides the necessary interface between the headset 146 and the telephone system 116. The amplifier electronics 105 are known and consequently details of them will not be shown. The amplifier 100 according to the invention additionally includes the detector 110, to which wireless signal radiators 156 and 158 are connected for wireless signal transmission and reception, respectively, and the activator 115 to which one or more of the conductors of the cord 111 are connected. As discussed in more detail below, the detector 110 monitors the wireless communication link 151 for detecting interruption and reestablishment thereof, i.e., to determine whether or not the workstation at which the amplifier 100 is located is occupied. The detector output 120 is connected to the control input 119 of the activator. The detector output 120 preferably provides a signal having one state when the headset 146 and amplifier 100 are communicating, and a second state when the headset 146 and amplifier 100 are not communicating. Further, as also discussed in more detail below, the detector 110 and headset 146 each include transmitter and receiver circuits for transmitting and receiving wireless signals over the wireless communication link 151 via their respective wireless signal radiators 156, 158, 166, 168. In accordance with one embodiment of the present invention, the detector 110 and headset 146 transmit and receive radio frequency (RF) signals. In this embodiment, the receive signal radiator 158 and transmit signal radiator 168 for the detector 110 and headset 146, respectively, are each an RF antenna (preferably directional), while the transmit signal radiator 156 and receive signal radiator 166 for the detector 110 and headset 146, respectively, are each a magnetic antenna (preferably directional). In accordance with another embodiment of the present invention, the detector 110 and headset 146 each include transmitter and receiver circuits suitable for transmitting and receiving infrared (IR) signals. In this embodiment, the transmit signal radiators 156, 168 are IR-emitting elements, while the receive signal radiators 158, 166 are IR-sensitive elements. The activator 115 activates the existing automatic log on/log off system in the telephone system 116 in response to the detector output 120. One or more of the conductors of the cord 111 are connected to the activator 115. Depending on the state of the output 120 of the detector 110, the activator 115 makes it appear to the automatic log on/log off system in the telephone system 116 as if the amplifier 100 is connected to or disconnected from the telephone system 116. The action of the activator 115 depends on what parameter the sensor controlling the automatic log on/log off system in the telephone system 116 monitors to determine whether or not the amplifier 100 is connected. For example, the activator 115 can include a controlled switch that is responsive to the detector output for emulating the effect of disconnecting the amplifier 100 from the telephone system 116. The controlled switch in the activator 115 switches the parameter that the sensor in the automatic log on/log off system in the telephone system 116 monitors to determine whether or not the amplifier 100 is connected to the telephone system 116. For further example, an activator 115 for use with the telephone system 16 with the current sensing automatic log on/log off system shown in FIG. 1 changes the current drawn by the amplifier 100 from the telephone system 116 in response to the detector 110. When the detector 110 indicates that the headset 146 and amplifier 100 are not communicating, the activator 115 reduces the current drawn by the amplifier 100 to less than the threshold level of the current sensor 86 (FIG. 1) in the telephone system 116. When the amplifier 100 draws less current than the threshold level of the current sensor, it appears to the current sensor, and hence to the automatic log on/log off system in the telephone system 116, as if the amplifier 100 has been disconnected from the telephone system 116. Accordingly, the automatic log on/log off system in the telephone system 116 logs off the workstation to which the amplifier 100 is connected. A version of the amplifier 100 for use with a telephone system having an automatic log on/log off system having a current sensor that senses the current drawn by the amplifier from the telephone system is shown in FIG. 4. In FIG. 4, the ground conductor 131 is connected directly from the telephone system 116 to the amplifier electronics 105. The conductor 121 is connected to the power supply input connections 180 and 185 of the activator 115 and the detector 110, respectively. The capacitor 126 couples the transmit output of the amplifier electronics to the power supply/signal conductor 121. The conductor 121 is also connected to one of the switched terminals 104 of the controlled switch 190 in the activator 115. The other switched terminal 109 of the controlled switch is connected to the power supply input terminal 114 of the amplifier electronics 105. The detector output 120 is connected to the control input terminal 119 of the controlled switch. The controlled switch 190 can be a relay, a transistor, an opto-relay or any other suitable switching device that can be controlled by a suitable control signal. When detector output 120 is in one of its states, the controlled switch 190 is in its ON (conducting) state, and when the detector output 120 is in the other of its states, the controlled switch 190 is in its OFF (non-conducting) state. When the controlled switch is in its ON state, the amplifier electronics 105 draw current from the conductor 121 (and hence from the telephone system) through the controlled switch. To the current sensor 86 in the telephone system 116 that monitors the flow of current through the conductor 121, this appears the same as if the amplifier 100 were connected to the telephone system. When the controlled switch is in its OFF state, the amplifier electronics 105 draw no current from the conductor 121. To the current sensor 86 in the telephone system that monitors the flow of current through the conductor 121, this appears the same as if the amplifier 100 were disconnected from the telephone system. Thus, by controlling the current drawn from the telephone system 116 by the amplifier 100, the controlled switch 190 is able to control the automatic log on/log off system in the telephone system. When the controlled switch 190 is in its OFF state, the detector 110 and the activator 115 continue to draw current from the telephone system 116. These circuits must therefore be designed such that together they draw significantly less current than the threshold current level of the current sensor 86 in the telephone system. The current drawn by the detector and the activator must be minimized especially when the controlled switch is in its OFF state, i.e., when the headset 146 is disconnected. For example, if a relay is used for the controlled switch 190, the normally-open contacts of the relay should be used to provide the switched contacts 104 and 109 so that the relay does not draw current in its OFF state. As an alternative to switching the power supply to the amplifier electronics 105, the controlled switch 190 can switch the ground connection to the amplifier electronics. This enables an NPN transistor to be used for the controlled switch. If the current sensor 86 controlling the automatic log on/log off system in the telephone system has a very low threshold, the detector 110 and the activator 115 should be connected to a power source that is not sensed by the current sensor 86 in the telephone system. Alternatively, the detector 110, the activator 115, and the amplifier electronics 105 all can be powered from a power source that is not sensed by the current sensor 86 in the telephone system 116, as shown in FIG. 5. An additional conductor 124 is added to the cord 111. In the amplifier, the conductor 124 is connected to the power supply input terminals 185, 180, and 114 of the detector, the activator, and the amplifier electronics 105, respectively. The conductor 124 is connected directly to the power supply 81 in the telephone system, bypassing the current sensor 86. Alternatively, the additional conductor 124 can be dispensed with, and the amplifier 100 can be provided with its own internal DC power supply powered from the a.c. line. In versions of the amplifier 100 in which the power supply to the amplifier electronics is not switched, a load resistor 129 is connected between the conductor 121, carrying the power supply current that is sensed by the current sensor 86, and one of the switched terminals 104 of the controlled switch 190. The other switched terminal 109 of the controlled switch is connected to the conductor 131 that carries the ground connection. The control input terminal 119 of the controlled switch is connected to the detector output 120. The value of the load resistor 129 is chosen so that when the controlled switch 190 is in its ON state, the current through the conductor 121, and hence through the current sensor 86, is well above the threshold current of the current sensor 86. This arrangement has the following advantages: an NPN transistor with a suitable current rating can be used for the controlled switch 190; the current drawn from the conductor 121 can be made completely independent of the current requirements of the amplifier 100; and the amplifier electronics 105 remain powered when the headset 146 is disconnected, which avoids unpleasant and potentially harmful transients in the earphone of the headset when the headset is reconnected. A version of the activator 115 for use with a telephone system having an automatic log on/log off system that senses the change in resistance between two additional conductors in the cord 111 is shown in FIG. 6. In FIG. 6, the conductors 121, carrying the positive power supply, and 131, carrying the ground connection, are connected from the telephone system 116 to the amplifier electronics 105. The additional conductors 191 and 196 in the cord 111 are connected to the switched terminals 104 and 109 of the controlled switch 195. The control input terminal 119 of the controlled switch 195 is connected to the detector output 120. When the detector output 120 is in one of its states, the controlled switch 195 is in its ON (conducting) state, and when the detector output is in the other of its states, the controlled switch 195 is in its OFF (non-conducting) state. When the controlled switch is ON, the conductor 191 is connected to the conductor 196 which, to the sensor 102 in the telephone system 116 appears the same as the amplifier being connected to the telephone system. When the controlled switch is OFF, the conductor 191 is not connected to the conductor 196 which, to the sensor in the telephone system appears the same as the amplifier not being connected to the telephone system. Thus, controlling the resistance between the conductors 191 and 196 by the controlled switch 195 activates the automatic log on/log off system in the telephone system. When the telephone system has an automatic log on/log off system that senses the resistance or voltage between the contacts of a switch mounted on the socket 136B, the switch being operated by plugging the plug 136A into the socket, the additional conductors 191 and 196 must be connected either in series or in parallel with the switch, depending on the operating sense of the switch. Thus, if the switch is open when the plug 136 is plugged in, the additional conductors 191 and 196 must be connected in parallel with the switch. If the switch is closed when the plug 136 is plugged in, the additional conductors 191 and 196 must be connected in series with the switch. The controlled switch 195 can be a relay, a transistor, an opto-relay or any other suitable switching device that can be controlled by a suitable control signal. Preferably, the controlled switch is of the type that has switched contacts that are isolated from the control terminal so that the amplifier can used with telephone systems having any type of automatic log on/log off sensor. The ability of the amplifier according to the invention to work with telephone systems having different types of automatic log on/log off systems by using a different interconnect 213 is shown in FIG. 7. The telephone system 216 is connected to the socket 236B on the workstation 1 by a three-wire cord that includes the conductors 321 and 331 for power/signal and ground, respectively, and the additional conductor 391. The automatic log on/log off system in the telephone system 216 senses whether the additional conductor 391 is at the same potential as the positive supply conductor 321. The interconnect 213 enables the amplifier 100 to operate the automatic log on/log off system of the telephone system 216, which is different from the automatic log on/log off systems in the telephone systems 116 shown in FIGS. 4-6. The interconnect 213 has the plug 108B that plugs into the socket 108A on the amplifier 100, and the plug 236A that is of the correct type to mate with the socket 236B on the workstation 1. The cord 118 has the conductors 121 and 131 for power supply/signal and ground, respectively, and the additional conductors 191 and 196. The additional conductors 191 and 196 are connected through the connector 108 to the switched contacts 134 and 139, respectively, of the second controlled switch 195 in the activator 115. So that the second controlled switch 195 can change the voltage on the additional conductor 391, the interconnect 218 includes a link 183 between the conductor 121 carrying the positive supply voltage and the additional conductor 196. The link is shown mounted on the plug 236A, but it could alternatively be mounted on the plug 108B, or in the cord 118 between the plug 108B and the plug 136A. When the second controlled switch 195 is ON, the additional conductor 191 is connected to the additional conductor 196, which is at the potential of the positive supply voltage. When the second controlled switch is OFF, the additional conductor 191 is at a voltage different from the voltage of the positive supply. The second controlled switch 195, together with the appropriate interconnect 218, controls the potential on the additional conductor 191 in such a way as to activate the voltage sensing automatic log on/log off system of the telephone system 216. Referring to FIG. 8, an amplifier 100 forming the base unit of a wireless telephone headset system in accordance with one embodiment of the present invention includes the amplifier electronics 105 and activator 115, as discussed above, plus a detector 110 having a base transmitter 112 and base receiver 113, and a power controller 117. The power controller 117 can be a power source such as a battery or an AC-to-DC power supply, or circuitry used for distributing power or controlling power otherwise provided to the amplifier electronics 105, activator 115, base transmitter 112 and base receiver 113. As discussed in more detail below, the base transmitter 112 receives the audio signal 127 relayed by the amplifier electronics 105 from the telephone system 116 (FIG. 3) and appropriately converts it to an outgoing signal 130 for transmission (e.g. via RF or IR) to the headset via the transmit signal radiator 156 over the wireless communication link 151. Meanwhile, the base receiver 113 receives an incoming signal 132 via its receive signal radiator 158 from the headset 146 via the wireless communication link 151 and extracts (e.g. demodulates) the outgoing audio signal 125 for relaying to the telephone system 116 via the amplifier electronics 105 and activator 115. The base receiver 113 also provides the above-discussed detector output signal 120, a communication status signal 122 to the base transmitter 112 and a power control signal 123 to the power controller 117. Additionally, the base transmitter 112 and receiver 113 operate to detect when the wireless communication link 151 is interrupted, or after such interruption has already occurred, to detect when the communication link 151 is reestablished. This detection function can be done in any of several ways. For example, in one embodiment, the base receiver 113 monitors the signal strength of its incoming signal 132. When the strength of this signal 132 falls below a predetermined threshold, the receiver 113 will have detected that the headset 146 has moved outside the range of communication. Accordingly, the receiver 113 provides the above-discussed output signal 120 to the activator 115. In another embodiment, the receiver 113 provides a control signal 122 to the transmitter 112 for the purpose of altering or discontinuing transmission of the outgoing signal 130 by the transmitter 112. In yet another embodiment, the receiver 113 generates a control signal 123 for the power controller 117 which, in turn, provides individual control or controlled-power signals 128A, 128B, 128C, 128D for selectively powering down portions of the transmitter 112, receiver 113, activator 115 and amplifier electronics 105, thereby saving on power and preventing spurious emission of wireless signals from the detector 110. In still another embodiment, the base transmitter 112 also participates in the detection of interruption and reestablishment of the wireless communication link 151 with the headset 146. For example, the transmitter 112, as part of its output signal 130, includes an encoded query signal intended to query the corresponding headset 146 with which it is communicating. As long as the headset 146 continues to receive such a query signal, a corresponding response signal is sent by the headset 146 for reception by the base receiver 113 as part of its incoming signal 132. However, whenever the headset 146 is removed from communicating range with respect to the amplifier 100, it will no longer receive the query signal from the base transmitter 112 with sufficient signal strength and, accordingly, will alter or cease transmission of its response signal to the base receiver 113. When this happens (similar to the above-discussed case of receiving insufficient signal strength from the headset 146), the base receiver 113 provides the aforementioned output/control signals 120, 122, 123. Referring to FIG. 9, the headset 146 includes a headset transmitter 140, receiver 142, power controller 143, audio amplifier 144, speaker 147, microphone 148 and audio processor 145 (in addition to the above-discussed signal radiators 166, 168). From the incoming signal 155, the receiver 142 provides an audio signal 157 which is amplified by the audio amplifier 144, with the amplified audio signal 159 then used to drive the speaker 147. An outgoing audio signal 152 generated by the microphone 148 is processed (e.g. amplified and filtered) by the audio processor 145, with the processed audio signal 153 then appropriately converted by the transmitter 140 for transmission via the transmit signal radiator 166. Additionally, as discussed above, the headset receiver 142 can be used to detect an interruption in the wireless communication link 151. In one embodiment, the signal strength of its incoming signal 155 is monitored. When this signal strength falls below a predetermined threshold, e.g. when the headset 146 has moved outside of its range of communication with the amplifier 100, the receiver 142 generates a control signal 141 for the transmitter 140 and a control signal 149 for the audio amplifier 144 and power controller 143. In accordance with this control signal 141, the transmitter 140 alters or terminates its signal 154 transmission. The other control signal 149 operates as a squelch control for the audio amplifier 144 (e.g. to squelch static emissions from the speaker 147) and as a power control for the power controller 143 for providing individual control or controlled-power signals 150A, 150B, 150C, 150D for selectively powering down portions of the receiver 142, transmitter 140, audio processor 145 and audio amplifier 144, thereby conserving power and preventing spurious signal emissions from the headset 146. In another embodiment, in accordance with the discussion above, the receiver 142, as part of its incoming signal 155 receives a query signal from the amplifier 100. When the receiver 142 stops receiving such query signal, e.g. when the wireless communication link 151 is interrupted, it sends the control signal 141 to the transmitter 140 to instruct it to so inform the amplifier 100 via the response signal portion of the outgoing signal 154. It should be understood that the above-discussed query and response signals transmitted by the amplifier 100 and headset 146, respectively, can be in any of a number of well known forms. For example, they can be in the form of subcarrier signals or pilot tones or, where digital signals are used, in the form of one or more encoded bits embedded within the signals. In a preferred embodiment of the present invention, the range within which the wireless communication link 151 between the amplifier 100 and headset 146 remains established is approximately 1.5-3 meters, with such range capable of being increased or decreased as desired by appropriately increasing or decreasing the signal strength of the signals communicated between the amplifier 100 and headset 146. When the wireless communication link 151 is interrupted, the telephone system 116 blocks calls from being routed to this particular amplifier 100, or where a call has already been routed, places such call on hold. As discussed above, this has the effect of emulating the unplugging, or disconnecting, of the amplifier 100 from the telephone system 116, even though the amplifier 100 remains connected to the telephone system 116. Referring to FIG. 10A, one embodiment of the base unit of FIG. 8 includes an RF transmitter 112A and RF receiver 113A. The receiver 113A includes a low noise amplifier (LNA) 204, mixer 206, frequency synthesizer 208, IF amplifier 210, automatic gain-controlled (AGC) amplifier 212, amplitude modulation (AM) demodulator 214 and time-varying modulation (TVM: a form of pulse-width modulation) demodulator 216, connected substantially as shown. The transmitter 112A includes a TVM modulator 220 and power amplifier 222, connected substantially as shown. In the receiver 113A, the LNA 204 receives the incoming signal 132 from an RF antenna 158A. The amplified signal 205 is frequency down converted in the mixer 206 with the local oscillator signal 209 provided by the frequency synthesizer 208, which is controlled by a crystal 218. The intermediate frequency (IF) signal 207 is amplified by the IF amplifier 210, with the amplified signal 211 further amplified with gain control by the AGC amplifier 212. The gain-controlled signal 213 is demodulated by the AM demodulator 214. The resulting signal 215 is further demodulated in the TVM demodulator 216 to produce the above-discussed detector output signal 120, power control signal 123 and outgoing audio signal 125. In the transmitter 112A, the audio signal 127 from the amplifier electronics 105 (FIG. 8) is modulated by the TVM modulator 220. The modulated signal 221 is amplified by the power amplifier 222 to produce the outgoing signal 130 for transmission via a magnetic antenna 156A. The above-discussed communication status signal 122 is provided to the TVM modulator 220 and power amplifier 222 by the AM demodulator 214 in the receiver 113A. Referring to FIG. 10B, another embodiment of the base unit of FIG. 8 includes an IR transmitter 112B and IR receiver 113B. The receiver 113B includes an LNA 224, AGC amplifier 226, AM demodulator 228 and TVM demodulator 232, connected substantially as shown. The transmitter 112B includes a TVM modulator 234 and light-emitting diode (LED) driver 236, connected substantially as shown. In the receiver 113B, the incoming signal 132 is received from an IR-sensitive element (e.g. photodiode) 158B. The amplified signal 225 is further amplified with gain control by the AGC amplifier 226. The gain-controlled signal 227 is then sequentially demodulated by the AM demodulator 228 and TVM demodulator 232 to produce the above-discussed detector output signal 120, power control signal 123 and outgoing audio signal 125. In the transmitter 112B, the TVM modulator 234 modulates the audio signal 127 from the amplifier electronics 105 (FIG. 8). The modulated signal 235 drives the LED driver 236 which provides the outgoing signal 130 to an IR-emitting element (e.g. photodiode) 156B. The above-discussed communication status signal 122 is provided to the TVM modulator 234 and LED driver 236 by the AM demodulator 228 in the receiver 113B. Referring to FIG. 11A, one embodiment of the headset unit of FIG. 9 includes an RF transmitter 140A and an RF receiver 142A. The receiver 142A includes an LNA 238, TVM demodulator 240 and comparator 242, connected substantially as shown. The transmitter 140A includes a TVM modulator 230, AM modulator 244 and power amplifier 246, connected substantially as shown. In the receiver 142A, the incoming signal 155 from the RF antenna 168A is amplified by the LNA 238. The LNA 238 provides an amplified signal 239 which is demodulated by the TVM demodulator 240 to provide the audio signal 157 to the audio amplifier 144 (FIG. 9). The LNA 238 also provides a receive signal strength indicator (RSSI) signal 241 which is compared to a reference 243 by the comparator 242 to provide an output signal suitable for use as a control signal 141 for the transmitter 140A (e.g. a "mute" signal) and/or a control signal 149 for the audio amplifier 144 and power controller 143, as discussed above. In the transmitter 140A, the processed audio signal 153 from the audio processor 145 (FIG. 9) is sequentially modulated by the TVM modulator 230 and AM modulator 244. The resulting modulated signal 245 is amplified by the power amplifier 246 to provide the outgoing signal 154 to the magnetic antenna 166A. Referring to FIG. 11B, another embodiment of the headset unit of FIG. 9 includes an IR transmitter 140B and an IR receiver 142B. The receiver 142B includes an LNA 248, AGC amplifier 250, TVM demodulator 252 and comparator 254, connected substantially as shown. The transmitter 140B includes a TVM modulator 260, AM modulator 256 and LED driver 258, connected substantially as shown. In the receiver 142B, the incoming signal 155 from an IR-sensitive element (e.g. photodiode) 168B is amplified by the LNA 248. The amplified output 249 is further amplified with gain control by the AGC amplifier 250, with the resulting signal 251 being demodulated by the TVM demodulator 252 to provide the audio signal 157. The LNA 248 further provides an RSSI signal 253 for comparison with a reference 255 by the comparator 254 to provide a control signal suitable for the above-discussed control signals 141, 149 for the transmitter 140B and/or audio amplifier 144 and power controller 143 (FIG. 9). In the transmitter 140B, the processed audio signal 153 is sequentially modulated by the TVM modulator 260 and AM modulator 256. The resulting modulated signal 257 is used by the LED driver 258 to provide the outgoing signal 154 for transmission via an IR-emitting element (e.g. photodiode) 166B. Various other modifications and alterations in the structure and method of operation of this invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. It is intended that the following claims define the scope of the present invention and that structures and methods within the scope of these claims and their equivalents be covered thereby.

Existing automatic log on/log off systems in telephone systems determine whether or not a workstation is occupied and whether calls can be directed to that workstation by determining whether or not the amplifier that provides the interface between the telephone system and the occupant's headset is plugged into the workstation. Recent headsets have included a connector in the cord between the headset and the amplifier, enabling the occupant to leave the workstation without unplugging the amplifier. However, this defeats the sensing mechanism of the existing automatic log on/log off system. A wireless telephone headset system according to the present invention replaces the existing wired amplifier and headset assembly and includes a detector for determining whether a wireless communication link exists between the headset and the amplifier, and an activator for activating the existing automatic log on/log off system in the telephone system. In the preferred embodiment, the detector senses both interruption and reestablishment of the wireless communication link between the headset and the amplifier, and the activator activates both current-sensing and voltage/resistance-sensing automatic log on/log off systems.

BACKGROUND OF THE INVENTION This invention relates to an immunoassay method which permits specific, rapid and accurate quantitation of trace components in body fluids such as serum, plasma and urine. In recent years, autoanalyzers capable of analyzing many samples for many items at the same time have spread, and attempts have been made to apply a method for immunoassay of a trace component utilizing antigen-antibody reaction to the autoanalyzers. Typical examples of method applicable to the autoanalyzers are so-called immunoturbidimetry in which an objective component is measured by measuring a turbidity change caused by antigen-antibody reaction, and so-called immunonephelometry in which an objective component is measured by measuring a scattered light intensity change caused by antigen-antibody reaction. These methods, however, are disadvantageous in that when the amount of an analyte to be measured in a sample is small (namely, when the concentration of the analyte is low), the measured value of the analyte is lower than its theoretical value, so that the analyte cannot be accurately measured. In the above methods, for removing such a defect, there are investigated, for example, a method of adding a large amount of an antigen-antibody reaction accelerator such as polyethylene glycol (PEG) or chondroitin sulfate to a measuring system, and a method of increasing the absolute amount of a sample. Both of these methods, however, are disadvantageous in that measurement errors are caused by substances present in a sample together with an analyte to be measured or by an insoluble material produced by a nonspecific reaction. Therefore, there is a desire to seek further improvement in the methods. SUMMARY OF THE INVENTION This invention was made in view of such conditions and is intended to provide an immunoassay method which permits accurate, highly-reproducible, rapid and easy measurement of an analyte to be measured, even in a low concentration range and is applicable to autoanalyzers. This invention provides a method for immunoassay of a trace component (analyte) on the basis of a change of turbidity or scattered light intensity caused by antigen-antibody reaction, which uses an antigen previously modified with a hapten, as antigen against an antibody to be measured. This invention also provides a method for immunoassay of a trace component (analyte) on the basis of a change of turbidity or scattered light intensity caused by antigen-antibody reaction, which uses an antibody previously modified with a hapten, as antibody against an antigen to be measured. This invention also provides a reagent composition for immunoassay comprising an antigen against an antibody to be measured, said antigen being previously modified with a hapten. This invention also provides a reagent composition for immunoassay comprising an antibody against an antigen to be measured, said antibody being previously modified with a hapten. This invention also provides a reagent composition for immunoassay comprising a combination of a reagent comprising an antigen against an antibody to be measured, said antigen being previously modified with biotin; and a reagent comprising avidin or streptoavidin. In addition, this invention provides a reagent composition for immunoassay comprising a combination of a reagent comprising an antibody against an antigen to be measured, said antibody being previously modified with biotin; and a reagent comprising avidin or streptoavidin. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a calibration curve obtained in Example 1. FIG. 2 shows a calibration curve obtained in Example 2. FIG. 3 shows a calibration curve obtained in Example 3. FIG. 4 shows a calibration curve obtained in Example 4. FIG. 5 shows a calibration curve obtained in Example 5. FIG. 6 shows a calibration curve obtained in Example 6. DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to find a method for enhancing measuring sensitivity for an analyte to be measured, in a low concentration range without any influence of substances present together with the analyte and measurement error caused by a nonspecific reaction, the present inventors earnestly investigated and consequently found that a high reaction sensitivity and a calibration curve showing good linearity can be obtained even in a low concentration range by modifying an antigen against an antibody to be measured (or an antibody against an antigen to be measured), which is added to a reagent, with a hapten such as a compound having a benzene ring or a compound having a heterocyclic ring. Thus, the present invention has been accomplished. As the hapten used in this invention for modifying an antigen (or antibody), any material may be used without particular limitation so long as it is generally known as hapten. Particularly preferable examples of the hapten are compounds having a benzene ring and compounds having a heterocyclic ring. As the compounds having a benzene ring which can be used as hapten in this invention, there can be exemplified compounds having, for example, a substituted or unsubstituted phenyl, tolyl, xylyl or naphthyl group. The substituent includes, for example, unsubstituted alkyl groups such as methyl group, ethyl group, propyl group and butyl group (which may be either linear or branched), substituted alkyl groups (having as the substituent a hydroxyl group, alkoxy group such as methoxy group, ethoxy group, propoxy group and butoxy group (which may be either linear or branched), carboxyl group, sulfo group, halogen atom such as chlorine, bromine and iodine, or the like), alkoxy groups such as methoxy group, ethoxy group, propoxy group and butoxy group (which may be either linear or branched), nitro group, acetyl group, carboxyl group, sulfo group, and halogen atoms such as chlorine, bromine and iodine. Preferable specific examples of the compounds having a benzene ring which can be used in this invention are p-nitrophenylacetic acid, 4-methylbenzoic acid and 3-(1-naphthyl)propionic acid. Preferable examples of the compounds having a heterocyclic ring which can be used as hapten in this invention are compounds having a heterocyclic group such as thiazolyl, thienyl, furanyl, pyranyl, pyrrolyl, imidazolyl, pyrazolyl, isothiazolyl, isoxazolyl, pyrimidinyl, pyridazinyl, indolyl, purinyl, quinolyl, isoquinolyl, pyrazolinyl, indolinyl, morpholino, biotinyl or the like (all of these groups may have a substituent). As the substituent on the heterocyclic group, there can be exemplified unsubstituted alkyl groups such as methyl group, ethyl group, propyl group and butyl group (which may be either linear or branched), substituted alkyl groups (having as the substituent a hydroxyl group, alkoxy group such as methoxy group, ethoxy group, propoxy group and butoxy group (which may be either linear or branched), carboxyl group, sulfo group, halogen atom such as chlorine, bormine and iodine; or the like), alkoxy groups such as methoxy group, ethoxy group, propoxy group and butoxy group (which may be either linear or branched), nitro group, acetyl group, carboxyl group, sulfo group, and halogen atoms such as chlorine, bromine and iodine. Preferable specific examples of the compounds having a heterocyclic ring which can be used in this invention are biotin, 2-thienylacetic acid, indole-butyric acid and pyrrole-2-carboxylic acid. In the present invention, as a method for modifying an antigen or antibody with the compound having a benzene ring, the following methods, for example, can be exemplified. For example, modification of an antigen or antibody with p-nitrophenylacetic acid can easily be carried out by introducing a succinimide group into p-nitrophenylacetic acid by a conventional method for instance, J. Amer. Chem. Soc., vol. 85, 3039(1963) and J. Amer. Chem. Soc., vol. 86, 1839(1964)!, and reacting the resulting compound with the antigen or antibody by a conventional method for instance, Z. Anal. Chem., vol. 279,143(1976); J. Clin. Endocrinol. Metab., vol. 44, 91(1977); and Biochem. Biophys. Acta., vol. 403, 131(1975)!. When a commercially available SNPA (N-succinimidyl-p-nitrophenylacetate) reagent manufactured by DOJINDO LABORATORIES by introducing a succinimide group into p-nitrophenylacetic acid is used, the succinimide group introduction step can be omitted, so that the modification procedure can be simplified. Examples of other methods are a method of introducing a maleimide group into the compound having a benzene ring by a conventional method for example, J. Pharm. Dyn., vol. 4, 812-819(1981)! and reacting the resulting compound with the thiol group of an antigen or antibody for example, Annals of the New York Academy of Science, vol. 254, 203(1975)!; and a method of introducing a hydrazino group into the compound having a benzene ring by a conventional method for example, J. Biol. Chem., vol. 172, 71(1948)!, and reacting the resulting compound with an aldehyde-modified antigen or antibody for example, Biotech. Appln. Biochem., vol. 9, 488-496(1987)!. As to the degree of the modification of an antigen or antibody with the compound having a benzene ring, the amount of the compound is usually about 0.2 to about 10 moles, preferably about 1 to about 5 moles, per mole of the antigen or antibody. When the degree of the modification with the compound having a benzene ring is too high, there is a problem, for example, in that the insolubility of the antigen or antibody is increased or that the antigen-antibody reaction is inhibited. When the degree of the modification is too low, there is a problem, for example, in that the sensitivity does not reach a desired value. Therefore, care should be taken in the modification. Preferable examples of method for attaching the compound having a heterocyclic ring, such as biotin to an antigen or antibody are a method of reacting a commercially available biotinylation reagent for example, biotin having a succinimide group introduced thereinto (e.g. N-hydroxysuccunimidobiotin) or a product obtained by combining N-hydroxysuccinimide (NHS) and biotin through a spacer! with the amino group of an antibody or antigen protein; a method of reacting, for example, a commercially available N- 6-(biotinamide)hexyl!-3'-(2'-pyridyldithio)propionamide (biotin-HPDP) or N-iodoacetyl-N-biotinylhexylenediamine with the thiol group of an antigen or antibody for instance, Annals of the New York Academy of Science, vol. 254, 203(1975)!; and a method of reacting biotin (or other compound having a heterocyclic ring) having a hydrazino group introduced thereinto with the aldehyde group of an aldehyde-modified antigen or antibody for instance, J. Biol. Chem., vol. 172, 71(1948) and Biotech. Appl. Biochem., vol. 9, 488-496(1987)!. As to the degree of the modification of an antigen or antibody with the compound having a heterocyclic ring, the amount of the compound is usually about 0.2 to about 10 moles, preferably about 1 to about 5 moles, per mole of the antigen or antibody. When the degree of the modification with the compound having a heterocyclic ring is too high, there is a problem, for example, in that the insolubility of the antigen or antibody is increased or that the antigen-antibody reaction is inhibited. When the degree of the modification is too low, there is a problem, for example, in that the sensitivity does not reach a desired value. Therefore, care should be taken in the modification. In the method of this invention, preferable examples of the antigen used after being modified with a hapten are streptolysin O (SLO), rheumatoid factor (RF) and hepatitis B type virus surface antigen (HBs). The antibody used after being modified with a hapten is not critical and may be either a monoclonal antibody or a polyclonal antibody. Preferable specific examples of the antibody are anti-C-reactive protein (anti-CRP) antibody, anti-immunoglobulin G (anti-IgG) antibody, anti-immunoglobulin A (anti-IgA) antibody, anti-immunoglobulin M (anti-IgM) antibody, anti-albumin antibody, anti-C3 antibody, anti-C4 antibody and anti-α-fetoprotein (anti-AFP) antibody. It is sufficient that all of other reagents, measuring conditions (reaction temperature, reaction time, measuring wavelength, measuring apparatus, etc.) and the like which are employed for practicing the measuring method of this invention are selected from those employed in a conventional immunoturbidimetry or immunonephelometry method. That is, it is sufficient that the measuring method of this invention is practiced according to a measuring procedure used in a conventional immunoturbidimetry or immunonephelometry method, except for using an antigen or antibody modified with a hapten in the manner described above. In the measuring method of this invention, there can be used without exception all of autoanalyzers, spectrophotometers and the like which are usually used in the art. Specific examples of buffer solution used in the measuring method of this invention are all of those usually used in measuring methods using antigen-antibody reaction, such as Tris buffers, phosphate buffers, veronal buffers, borate buffers, Good's buffers, etc. The pH of the buffer solution is not critical so long as it does not inhibit the antigen-antibody reaction. Usually, the pH is preferably in the range of 5 to 9. According to the method of this invention, a calibration curve showing good linearity even in a low concentration range can be obtained because the reaction sensitivity is high even when the concentration of an analyte to be measured is low. Although the reason is unexplained, the following, for example, is conjectured. By the modification of an antigen or antibody, which participates the reaction, with a hapten such as a compound having a benzene ring or a compound having a heterocyclic ring, the hydrophobicity of the antigen or antibody is increased and the hydrophobicity of the antigen-antibody complex produced by the reaction is also inevitably increased. Therefore, the precipitation of the desired antigen-antibody complex as insoluble material from the reaction solution is facilitated even at a low concentration. In this invention, when an amount of an analyte to be measured is small (such as rheumatoid factor, C-reactive protein, etc), it is possible to enhance the reaction sensitivity in a low concentration range and obtain a calibration curve showing good linearity by carrying out an objective measurement using an antigen against an antibody to be measured (or an antibody against an antigen to be measured) which is modified using biotin as hapten in the presence of avidin or streptoavidin. Avidin-biotin reaction is highly specific and the bonding strength between avidin and biotin is strong. Therefore, in enzyme immunoassay and radio-immunoassay, avidin-biotin reaction is used for combining a solid phase with an antigen-antibody reaction product or combining an antibody or the like with a labeling substance. In latex photometric immunoassay and carrier agglutination method, avidin-biotin reaction is used for combining a carrier with an antigen (or antibody). However, few cases are known where avidin-biotin reaction is used together with antigen-antibody reaction in carrying out immuno-turbidimetry or immunonephelometry, which utilizes the antigen-antibody reaction. It is really surprising that the co-use of avidin-biotin reaction markedly enhances the measuring sensitivity attained when the amount of an analyte to be measured in a sample is small (namely, the measuring sensitivity in a low concentration range). As the avidin or streptoavidin used in this invention, a commercially available one may be used as it is. The quality and purity of the avidin or streptoavidin are not particularly limited. The amount of the avidin or streptoavidin used is not critical and is varied depending on the amount of biotin used for modifying an antigen (or antibody) against an analyte to be measured, and measurement items. Usually, the concentration of the avidin or streptoavidin in the reaction solution is properly chosen in the range of 0.01 to 1,000 μg/ml, preferably 0.1 to 100 μg/ml, more preferably 5 to 100 μg/ml. When an objective measurement is carried out in the presence of avidin or streptoavidin, the present invention's reagent composition for immunoassay in which the reaction of avidin (or streptoavidin) with biotin is utilized can be used in the form of a single reagent. But since turbidity on the basis of the reaction of avidin (or streptoavidin) with biotin is produced slowly, it is preferable for reagent stability to prepare the composition as a reagent form composed of two separate groups, i.e., a reagent group containing avidin or streptoavidin and a reagent group containing a biotin-modified antigen or a biotin-modified antibody. In the present inventions, a method without using an avidin (or streptavidin) is preferable comparing with a method of using an avidin (or streptavidin). That is, since turbidity on the basis of the reaction of avidin (or streptavidin) with biotin is produced slowly, the method of using an avidin (or streptavidin) is disadvantageous in that the reagent for the method is low in stability, a blank value of the reagent increases slowly, etc. This invention is more concretely explained below with reference to Examples, which are not by way of limitation but by way of illustration. EXAMPLE 1 Measurement of anti-streptolysin O (ASO) value (1) Modification of streptolysin O (SLO) In 10 ml of 100 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer (pH 8.5) was dissolved commercial SLO (available from Wako Pure Chemical Industries, Ltd.) to a concentration of 1.3 mg protein/ml. To the resulting solution was added 1 ml of a 40 mM solution of N-succinimidyl-4-nitrophenylacetate (SNPA, mfd. by DOJINDO LABORATORIES) in N,N-dimethylformamide, and the reaction was carried out at 37° C. for 2 hours. After completion of the reaction, the reaction solution was dialyzed against a 0.9% NaCl solution to remove the unreacted SNPA, whereby a modified SLO solution was obtained. (2) Measurement of anti-streptolysin O (ASO) value Preparation of reagent solutions! 1 First reagent solution As a first reagent solution, there was used 50 mM 3-(N-morpholino)propanesulfonic acid (MOPS)-NaOH buffer (pH 7.4) containing 3.5% polyethylene glycol 6,000, 0.9% NaCl and 0.1% NAN 3 . 2 Second reagent solution As a second reagent solution, there was used a solution prepared by adding the modified SLO obtained in (1) above to the first reagent solution to adjust the protein concentration to 150 μg/ml. Measuring instrument! An Autoanalyzer Hitachi Model 7070 was used. Measuring procedure! After 20 μl of a sample containing a predetermined concentration of ASO and 350 μl of the first reagent solution were mixed and then incubated at 37° C. for 5 minutes, absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured (sample blank value). Then, 50 μl of the second reagent solution was added and the resulting mixture was incubated at 37° C. for 5 minutes, after which absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured. Absorbance difference (absorbance due to reaction) was calculated by subtracting the sample blank value corrected for solution volume from the thus obtained absorbance. For comparison, absorbance due to reaction was measured by the same procedure as above by use of the same sample and reagent solutions as above except for using a second reagent solution prepared in the same manner as above except for using unmodified SLO. Results! FIG. 1 shows calibration curves each showing a relationship between the obtained absorbance due to reaction and ASO concentration. In FIG. 1, + shows the results obtained by use of the second reagent solution containing the modified SLO, and □ the results obtained by use of the second reagent solution containing unmodified SLO. As is clear from FIG. 1, when unmodified SLO is used (a conventional method), the reaction sensitivity is lowered in a concentration range of 200 U/ml or less, so that the measurement becomes impossible. 0n the other hand, when the present invention's method using the modified SLO is employed, the reaction sensitivity is sufficient to carry out the measurement, even in a concentration range of 100 U/ml or less. EXAMPLE 2 Measurement of rheumatoid factor (RF) (1) Preparation of biotin-modified human IgG In 9 ml of 50 mM carbonate buffer (pH 9) was dissolved 100 mg of commercially available human IgG, followed by adding thereto a solution of 9 mg of biotinamidocaproate-N-hydroxysuccinimidoester (BAHS, mfd. by Pierce Chemical Co.) in 1 ml of N,N-dimethylformamide. The reaction was carried out at 5° C. for 24 hours. After completion of the reaction, the reaction solution was dialyzed against a 0.9% NaCl solution to remove unreacted BAHS, whereby biotin-modified human IgG was obtained. (2) Measurement of rheumatoid factor (RF) Preparation of reagent solutions! 1 First reagent solution The same as the first reagent solution used in Example 1. 2 Second reagent solution As a second reagent solution, there was used a solution prepared by adding the biotin-modified human IgG to physiological saline (0.9% NaCl) to adjust the protein concentration to 1 mg/ml. Measuring instrument! An Autoanalyzer Hitachi Model 7070 was used. Measuring procedure! After 14 μl of a sample containing a predetermined concentration of RF and 250 μl of the first reagent solution were mixed and then incubated at 37° C. for 5 minutes, absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured (sample blank value). Then, 125 μl of the second reagent solution was added and the resulting mixture was incubated at 37° C. for 5 minutes, after which absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured. Absorbance difference (absorbance due to reaction) was calculated by subtracting the sample blank value corrected for solution volume from the thus obtained absorbance. For comparison, absorbance due to reaction was measured by the same procedure as above by use of the same sample and reagent solutions as above except for using a second reagent solution prepared in the same manner as above except for using human IgG not modified with biotin. Results! FIG. 2 shows calibration curves each showing a relationship between the obtained absorbance due to reaction and rheumatoid factor (RF) concentration. In FIG. 2, + shows the results obtained by use of the second reagent solution containing the biotin-modified human IgG, and □ the results obtained by use of the second reagent solution containing unmodified human IgG. As is clear from FIG. 2, when unmodified human IgG is used (a conventional method), measurement of RF is difficult. On the other hand, when the present invention's method using the biotin-modified human IgG is employed, it becomes possible to measure RF with high sensitivity. EXAMPLE 3 Measurement of anti-streptolysin O (ASO) value (1) Preparation of biotin-modified streptolysin O (SLO) In 30 mM phosphate buffer (pH 7.5) was dissolved commercially available SLO to a concentration of 1.3 mg protein/ml. To 5 ml of the resulting solution was added 0.5 ml of a 30 mM solution of N-hydroxysuccinimidobiotin (NHS-Biotin, mfd. by Pierce Chemical Co.) in N,N-dimethylformamide, and the reaction was carried out at 37° C. for 1 hours. After completion of the reaction, the reaction solution was dialyzed against a 0.9% NaCl solution to remove the unreacted NHS-Biotin, whereby biotin-modified SLO was obtained. (2) Measurement of ASO Preparation of reagent solutions! 1 First reagent solution The same as in Example 1 was used. 2 Second reagent solution As a second reagent solution, there was used a solution prepared by adding the biotin-modified SLO obtained in (1) above to the first reagent solution to adjust the protein concentration to 150 μg/ml. Measuring instrument! An Autoanalyzer Hitachi Model 7070 was used. Measuring procedure! After 20 μl of a sample containing a predetermined concentration of ASO and 350 μl of the first reagent solution were mixed and then incubated at 37° C. for 5 minutes, absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured (sample blank value). Then, 50 μl of the second reagent solution was added and the resulting mixture was incubated at 37° C. for 5 minutes, after which absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured. Absorbance difference (absorbance due to reaction) was calculated by subtracting the sample blank value corrected for solution volume from the thus obtained absorbance. For comparison, absorbance due to reaction was measured by the same procedure as above by use of the same sample and reagent solutions as above except for using a second reagent solution prepared in the same manner as above except for using unmodified SLO. Results! FIG. 3 shows calibration curves each showing a relationship between the obtained absorbance due to reaction and ASO concentration. In FIG. 3, + shows the results obtained by use of the second reagent solution containing the biotin-modified SLO, and □ the results obtained by use of the second reagent solution containing unmodified SLO. As is clear from FIG. 3, when unmodified SLO is used (a conventional method), the reaction sensitivity is lowered in a concentration range of 150 U/ml or less, so that the measurement becomes impossible. On the other hand, when the present invention's method using the biotin-modified SLO is employed, the reaction sensitivity is sufficient even in a concentration range of 100 U/ml or less, so that a calibration curve showing good linearity can be obtained. EXAMPLE 4 Measurement of anti-streptolysin O (ASO) value (1) Modification of streptolysin O (SLO) In 10 ml of 30 mM phosphate buffer (pH 7.5) was dissolved commercial SLO (available from Wako Pure Chemical Industries, Ltd.) to a concentration of 1.3 mg protein/ml. To the resulting solution was added 1 ml of a 30 mM solution of N-hydroxysuccinimidobiotin (NHS-biotin, mfd. by Pierce Chemical Co.) in N,N-dimethylformamide, and the reaction was carried out at 37° C. for 1 hours. After completion of the reaction, the reaction solution was dialyzed against a 0.9% NaCl solution to remove the unreacted NHS-biotin, whereby a biotin-modified SLO solution was obtained. (2) Measurement of anti-streptolysin O (ASO) value Preparation of reagent solutions! 1 Buffer solution for measurement As a buffer solution for measurement, there was used 50 mM 3-(N-morpholino)propanesulfonic acid (MOPS)-NaOH buffer (pH 7.4) containing 3.5% polyethylene glycol 6,000, 0.9% NaCl and 0.1% NAN 3 . 2 First reagent solution As a first reagent solution, there was used a solution prepared by dissolving avidin (available from Wako Pure Chemical Industries, Ltd.) in the aforesaid buffer solution for measurement to adjust the protein concentration to 20 μg/ml. 3 Second reagent solution As a second reagent solution, there was used a solution prepared by adding the biotin-modified SLO obtained in (1) above to the aforesaid buffer solution for measurement to adjust the protein concentration to 150 μg/ml. Measuring instrument! An Autoanalyzer Hitachi Model 7070 was used. Measuring procedure! After 20 μl of a sample containing a predetermined concentration of ASO and 350 μl of the first reagent solution were mixed and then incubated at 37° C. for 5 minutes, absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured (sample blank value). Then, 50 μl of the second reagent solution was added and the resulting mixture was incubated at 37° C. for 5 minutes, after which absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured. Absorbance difference (absorbance due to reaction) was calculated by subtracting the sample blank value corrected for solution volume from the thus obtained absorbance. For comparison, absorbance due to reaction was measured by the same procedure as above by use of the same sample and reagent solutions as above except for using a second reagent solution prepared in the same manner as above except for using unmodified SLO. Results! FIG. 4 shows calibration curves each showing a relationship between the obtained absorbance due to reaction and ASO concentration. In FIG. 4, + shows the results obtained by use of the second reagent solution containing the modified SLO, and □ the results obtained by use of the second reagent solution containing unmodified SLO. As is clear from FIG. 4, when unmodified SLO is used (a conventional method), the reaction sensitivity is lowered in a concentration range of 200 U/ml or less, so that the measurement becomes impossible. On the other hand, when the present invention's method using the modified SLO is employed, the reaction sensitivity is sufficient to carry out the measurement, even in a concentration range of 100 U/ml or less. Referential Example 1 Preparation of anti-human C-reactive protein (anti-CRP) monoclonal antibody (1) immunization immunization was carried out by inoculating a mouse with commercial human CRP (available from Wako Pure Chemical Industries, Ltd.) three times at 2-week intervals (amount of human CRP per inoculating operation: 50 μg/mouse). (2) Preparation of hybridoma Three days after the final immunization, cell fusion between spleen cells removed from the mouse and myeloma cells (P3/NS1-1-Ag4-1) was carried out according to the method of Kohler and Milstein Nature, vol. 256, 495(1975)!. Screening was carried out in the following manner. Each well of a 96-wells microtiter plate was fed with 50 μl of a 0.2% solution of human CRP in 50 mM carbonate buffer (pH 9.6), followed by incubation at 37° C. for 1 hour, whereby the human CRP was fixed to the microtiter plate. Each well was washed with 10 mM phosphate buffered saline (pH 7.4) and then fed with 50 μl of each of the culture supernatants of hybridoma obtained by the cell fusion, and the reaction was carried out at 37° C. for 1 hour. Each well was washed with 10 mM phosphate buffered saline (pH 7.4) and then fed with 50 μl of peroxidase-labeled anti-mouse immunoglobulin antibody (available from DAKOPATTS, Denmark) properly diluted with 10 mM phosphate buffered saline (pH 7.4), and the reaction was carried out at 37° C. for 1 hour. After washing with 10 mM phosphate buffered saline (pH 7.4), each well was fed with 50 μl of citrate buffer (pH 4.9) containing 2 mg/ml of o-phenylenediamine and 0.017% of hydrogen peroxide and allowed to stand at room temperature for 10 minutes to carry out coloration reaction. Then, each well was fed with 6N sulfuric acid to stop the coloration reaction. On the basis of the results obtained above, hybridoma capable of producing a culture supernatant reactive with human CRP was selected as parent hybridoma. The parent hybridoma was cloned by limiting dilution to establish clones 1-3 and 2-6 of hybridoma capable of producing anti-human CRP monoclonal antibody. (3) Preparation of monoclonal antibodies Three days after having been intraperitoneally injected with 0.5 ml of pristane (2,6,10,14-tetramethylpentadecane, mfd. by Wako Pure Chemical Industries, Ltd.), a mouse was intraperitoneally inoculated with 1×106 cells of the clone 1-3 or 2-6 obtained in (2) above. Twelve days after the inoculation with the hybridoma, the ascites accumulated in the abdominal cavity was collected. Then, 10 ml of the obtained ascites was subjected to 40% ammonium sulfate fractionation, followed by dyalysis against 10 mM phosphate buffered saline (pH 7.4) (1 liter×3 times). Thus, anti-human CRP monoclonal antibody solutions were obtained. EXAMPLE 5 Measurement of C-reactive protein (CRP) (1) Preparation of biotin-modified anti-human CRP monoclonal antibody Biotin-modified anti-human CRP monoclonal antibody was obtained by the same procedure with the same reagents as in Example 4 except for using the anti-human CRP monoclonal antibody (the clone 1-3) obtained in Referential Example 1, in place of SLO. (2) Measurement of C-reactive protein (CRP) Preparation of reagent solutions! 1 Buffer solution for measurement The same as in Example 4. 2 First reagent solution As a first reagent solution, there was used a solution prepared by dissolving avidin (available from Wako Pure Chemical Industries, Ltd.) in the aforesaid buffer solution for measurement to adjust the protein concentration to 50 μg/ml. 3 Second reagent solution As a second reagent solution, there was used a solution prepared by adding the biotin-modified anti-human CRP monoclonal antibody obtained in (1) above and the anti-human CRP monoclonal antibody (the clone 2-6) obtained in Referential Example 1 to the aforesaid buffer solution for measurement to adjust the concentration of each protein to 1 μg/ml. Measuring instrument! An Autoanalyzer Hitachi Model 7070 was used. Measuring procedure! After 15 μl of a sample containing a predetermined concentration of CRP and 350 μl of the first reagent solution were mixed and then incubated at 37° C. for 5 minutes, absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured (sample blank value). Then, 50 μl of the second reagent solution was added and the resulting mixture was incubated at 37° C. for 5 minutes, after which absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured. Absorbance difference (absorbance due to reaction) was calculated by subtracting the sample blank value corrected for solution volume from the thus obtained absorbance. For comparison, absorbance due to reaction was measured by the same procedure as above by use of the same sample and reagent solutions as above except for using a second reagent solution prepared in the same manner as above except for using the unmodified anti-human CRP monoclonal antibody (the clone 1-3) in place of the biotin-modified anti-human CRP monoclonal antibody. Results! FIG. 5 shows calibration curves each showing a relationship between the obtained absorbance due to reaction and CRP concentration. In FIG. 5, + shows the results obtained by use of the second reagent solution containing the biotin-modified anti-human CRP monoclonal antibody, and □ the results obtained by use of the second reagent solution containing the unmodified anti-human CRP monoclonal antibody alone. As is clear from FIG. 5, when the second reagent solution containing the unmodified anti-human CRP monoclonal antibody alone is used (a conventional method), measurement of 5 mg/dl or less of CRP is difficult. On the other hand, when the present invention's method using the second reagent solution containing the biotin-modified anti-human CRP monoclonal antibody is employed, measurement of 5 mg/dl or less of CRP becomes possible. EXAMPLE 6 Measurement of anti-human IgG antibody (1) Preparation of biotin-modified human IgG In 9 ml of 50 mM carbonate buffer (pH 9) was dissolved 100 mg of commercially available human IgG, followed by adding thereto a solution of 9 mg of biotinamidocaproate-N-hydroxysuccinimidoester (BHS, mfd. by Pierce Chemical Co.) in 1 ml of N,N-dimethylformamide. The reaction was carried out at 5° C. for 24 hours. After completion of the reaction, the reaction solution was dialyzed against a 0.9% NaCl solution to remove unreacted BHS, whereby biotin-modified human IgG was obtained. (2) Measurement of anti-human IgG antibody Preparation of reagent solutions! 1 Buffer solution for measurement The same as in Example 1. 2 First reagent solution As a first reagent solution, there was used a solution prepared by dissolving avidin (available from Wako Pure Chemical Industries, Ltd.) in the aforesaid buffer solution for measurement to adjust the protein concentration to 10 μg/ml. 3 Second reagent solution As a second reagent solution, there was used a solution prepared by adding the biotin-modified human IgG obtained in (1) above to the aforesaid buffer solution for measurement to adjust the protein concentration to 75 μg/ml. Measuring instrument! An Autoanalyzer Hitachi Model 7070 was used. Measuring procedure! After 20 μl of a sample containing a predetermined concentration of anti-human IgG antibody and 350 μl of the first reagent solution were mixed and then incubated at 37° C. for 5 minutes, absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured (sample blank value). Then, 50 μl of the second reagent solution was added and the resulting mixture was incubated at 37° C. for 5 minutes, after which absorbance using dual wavelength (λ 1 =700 nm, λ 2 =340 nm) was measured. Absorbance difference (absorbance due to reaction) was calculated by subtracting the sample blank value corrected for solution volume from the thus obtained absorbance. For comparison, absorbance due to reaction was measured by the same procedure as above by use of the same sample and reagent solutions as above except for using a second reagent solution prepared in the same manner as above except for using unmodified human IgG. Results! FIG. 6 shows calibration curves each showing a relationship between the obtained absorbance due to reaction and anti-human IgG antibody concentration. In FIG. 6, + shows the results obtained by use of the second reagent solution containing the biotin-modified human IgG, and □ the results obtained by use of the second reagent solution containing unmodified human IgG. As is clear from FIG. 6, the calibration curve obtained by the present invention's method using the second reagent solution containing the biotin-modified human IgG does not show curvature in a low concentration range, as compared with the calibration curve obtained in the case of using the second reagent solution containing unmodified human IgG (a conventional method). From the results shown in FIG. 6, it can also be seen that the method of this invention permits measurement of 0.2 mg/ml or less of anti-human IgG antibody. As described above, this invention provides a method which permits accurate, highly-reproducible, rapid and easy measurement of an analyte to be measured, even in a low concentration range in which the analyte cannot be measured by a conventional method. Therefore, this invention contributes greatly to the art.

The use of an antigen (or antibody) previously modified with a hapten makes the immunoassay of a trace component (analyte) on the basis of a change of turbidity or scattered light intensity caused by antigen-antibody reaction rapid and easy with high accuracy and high reproduction.

CONTINUITY [0001] This is a continuation-in-part of my U.S. patent application Ser. No. 08/058,197, filed May 4, 1994, which is a continuation of my U.S. patent application Ser. No. 826,491, filed Jan. 27, 1992, now U.S. Pat. No. 5,233,773, which issued Aug. 10, 1993, which is a continuation-in-part of U.S. patent application Ser. No. 07/536,765, filed Jun. 11, 1990, now U.S. Pat. No. 5,111,606, which issued May 12, 1992. FIELD OF INVENTION [0002] The present invention relates to lighted merchandising display devices for advertising purposes in stores and, more particularly, provides a flexible display device having a battery supply mount. The device is engineered and employed principally for locations in mercantile establishments such as grocery stores, supermarkets, discount centers, and the like. BACKGROUND AND BRIEF DESCRIPTION OF PRIOR ART [0003] In the past there have been several different types of approaches taken in advertising merchandise carried on grocery store shelves, in refrigerator cabinets, and so forth. Advertising media are important, of course, to draw the attention of shoppers to various specials, new items, and featured items for a particular sale. Merchandisers have noted the advantages of having lighted signs or sign displays proximate merchandise such as canned goods to be placed on special. Many conventional signs have their electrical circuits connected to an AC source; this is impractical, however, because the provision of multiple AC outlets along a very long shelf display becomes prohibitively expensive. Certain display signs carry a battery pack proximate the display area; however, this does interfere with the viewing of the sign, especially bidirectional viewing to accommodate customers. A further problem in the prior art is presented in the case of rigid signs which might be inadvertently bumped and possibly damaged should a rigid connection be maintained between the outwardly projecting sign and its mount to a shelf, for example. A certain flexibility feature relative to the sign and its mount to the shelf has been adopted in the past as is evidenced by U.S. Pat. Nos. 4,881,707 and 4,805,331; also, certain approaches have been taken in supplying battery power to signs, but which exclude practical application relative to the sign for bidirectional viewing, see U.S. Pat. Nos. 4,317,303 and 4,924,363. [0004] For several reasons, and not believed disclosed in the prior art, what is needed is a battery supply proximate, i.e., at the mount of the device at the shelf proper, or the refrigerator enclosure which is to incorporate the sign. In this way both forward and rear surfaces of the outwardly projecting signs are completely free and unobstructed for viewing in either direction; this magnifies the uses of the sign for traffic in both directions in stores utilizing the device. A further feature which is needed, and not believed shown in the prior art, is the concept of having electrical connection from the battery station fixed adjacent to the shelf, to and through the flexible or articulative structure to the electrical circuit board of the sign proper. There is no art currently known to the inventor which teaches the concept of supplying electrical leads, for example, or other electrical connections between a battery supply mount and a flexible lighted sign, through a tongue, or spring, or articulative joint, so as to preserve resilience to the structure, and yet not interfere with sign lighting or the displacements and automatic restoration of the sign relative to its mount. A number (24) of U.S. patents are known which bear upon signs in general, however, and will be of interest and, to some small degree, relevant. These are as follows: 1. Des 243,639  9. 3,070,911 17. 4,096,656 2. Des 245,945 10. 3,084,463 18. 4,317,303 3.   469,487 11. 3,226,866 19. 4,682,430 4.   900,590 12. 3,517,937 20. 4,805,331 5. 2,654,172 13. 3,696,541 21. 4,819,353 6. 2,817,131 14. 3,931,689 22. 4,881,707 7. 2,924,902 15. 4,028,828 23. 4,924,363 8. 3,041,760 16. 4,055,014 24. 4,984,693 [0005] A primary difficulty with respect to traditional sign displays, particularly bi-directionally viewable sign displays located within aisles of a store, has been a need for the sign display to be flexible and resilient. It is desirable for the sign display to be deflectable in a horizontal or side-to-side direction in addition to being deflectable in an up-and-down or vertical direction. As such, the sign can be deflected regardless of the angle of impact (either from a shopping cart or a person) and resiliently returned to its original position. [0006] Another traditional problem with respect to sign displays, again particularly bi-directionally viewable sign displays within an aisle of a shopping area, involves the impediment created by the sign display in stacking shelves and removing items from shelves. Such sign displays that are rectangular may extend above and below the particular shelf area to which it is attached. This can impede access to the shelf. [0007] Still another problem with respect to sign displays relates to the presentation angle of the sign display so that it is pleasing from a marketing standpoint. Since particular sign displays may vary in terms of shape and size, it is desirable to have an ability to change the angle at which the sign display is positioned to provide a desirable presentation angle for marketing purposes. [0008] With respect to illuminated sign displays in particular, the power supply, similar to the sign display, may impede access to shelf storage areas depending on the orientation of the power supply. There is therefore a need to incorporate a power supply into a sign display that minimizes impedance with access to shelf storage areas. [0009] Another problem with respect to lighted sign displays is the light necessary for illuminating the sign display. Traditional sign displays have required several light sources. Therefore, each light source is susceptible to failure, which requires repair and/or replacement. The fewer light sources incorporated into the sign display, the fewer number of potential failures involved. [0010] Another primary design concern with respect to sign displays is the attention it provides to the particular shelf to which it is attached. In a typical shopping aisle, there are so-called primary shelves and secondary shelves. The primary shelves are typically eye level and are the easiest, most convenient shelves for the shopper to view. The present invention is designed to overcome primary/secondary shelf distinction by rendering any shelf to which the sign display of the present invention is attached a primary shelf. BRIEF DESCRIPTION AND OBJECTS OF THE INVENTION [0011] In the present invention a lighted merchandising display includes its own individual electrical circuit such as a circuit board for powering lights disposed at the margins or about the periphery of the display, this preferably at opposite sides of the frame of the display. The display is of a slim-line design and has viewing windows on opposite sides of the frame so that advertising matter may be viewed from both sides of the display as customers are approaching the display. A battery pack, case or holder is provided and is directly mounted to the shelf molding of the display shelf, or also to the transparent door of a refrigerator or freezer, by way of example. The display frame relative to the battery pack is flexibly connected so as to allow for temporary deflections of the sign should passersby inadvertently bump the same and thus deflect the sign from its usual orthogonal position. [0012] Accordingly, a coil deflection spring, a torsion spring, or a flexible resilient tongue is provided to contribute the flexibility needed relative to the display and its fixedly mounted battery pack. Electrical leads proceed through the tongue, spring, or articulative pivotal joint incorporating the torsion spring, so that electrical connection is always maintained between the battery pack and the sign whatever the temporary disposition of the frame of the device. Perforated ears and a pin element positioned therethrough are designed to releasably secure advertising cards within the frame of the display as well as serve other functions. The circuit board is preferably U-configured so as to provide for a convenient receptacle and the support for cards to be inserted in the frame and within the circuit board. The battery is maintained outside of the frame and its advertising display, and is proximate the mounting of the unit to external structure. This mounting is preferably adjustable but may be fixed and secure so as to eliminate the chancing of inadvertent dislodgment of the batteries, or its case. Of prime importance, and whether an articulative or pivotal joint is incorporated or some type of tongue, whether resilient and/or spring, the electrical connectors from the battery support maintain continuous communication via the tongue or spring, etc. whereby to facilitate continuous connection to the circuit board or other lighting circuit of the frame. In the above manner the frame of the device is made free of the battery pack so that it can insure a slim-line design and be functional bi-directionally at opposite sides of the frame as well as be flexible. [0013] Another aspect of the present involves a tapered sign display having a relatively small section at a proximal end of the sign display and a relatively tall section at a distal end of the sign display. The tapered frame portion of the sign display is mounted to a battery pack oriented to coincide with the horizontal plane of the shelf to which the sign display is attached. As such, the sign display creates minimal interference with access to storage areas above and below the shelf. [0014] Still another aspect of the present invention involves a resilient flexion joint interconnecting the sign display and the mounting mechanism for the sign display. The flexion joint allows for resilient movement of the sign display in side-to-side directions and in up-and-down directions. [0015] Yet another aspect of the present invention involves an adjustment mechanism that allows the orientation of the sign display to be adjusted. That is, the presentation angle of the bi-directionally observable sign can be changed as desired. [0016] Another aspect of the invention involves mounting a pair of lights within the tubular frame members of the sign display, and mounting respective parabolic reflectors at opposite ends of the tubes for illuminating the tubular frame portions of the sign display. [0017] In view of the foregoing, it is a principal object of the present invention to provide a new and improved advertising display device. [0018] A further object is to provide an advertising display device carrying its own battery pack and being suitable for attachment to the molding of a merchandise shelf, to the transparent door of a refrigerator or freezer, and so forth. [0019] A further object is to provide a device having an articulative pivotal joint suitably spring-biased to provide a restoring force for the device frame to return the same to orthogonal projection subsequent to inadvertent bumping or displacements by customers, shopping carts, and the like. [0020] An additional object is to provide a battery pack or battery holder mount for outwardly projecting display signs, wherein the battery pack mount includes the electrical connections which are maintained with the lighting circuit of the sign provided, even though such sign may be temporarily displaced from its intended orthogonal position. [0021] A further object is to provide a means for securing cards in display signs, wherein the structure provided may also serve as a tag- or other sign-support. [0022] Still another object of the invention is to provide a sign display that minimizes impedance with respect to access to shelf areas adjacent the sign display. [0023] Another object of the invention is to provide an adjustment device for changing the presentation angle of the sign display. [0024] Yet another object of the invention is to provide a sign display that is resiliently moveable in the side-to-side directions as well as the up-and-down directions. [0025] Still another object of the invention is to provide a sign display that includes an integral power source aligned to correspond with the shelf area to which the sign display is attached. [0026] Another object of the invention is to provide a sign display that minimizes the number of light sources used in connection with the sign display. [0027] Still yet another object of the invention is to provide a sign display that renders the shelf to which it is attached a primary shelf in terms of customer attention and focus. [0028] Other objects, features, and advantages of the present invention may best be understood by reference to the following detailed description, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0029] Preferred embodiments of the invention are described below with reference to the accompanying drawings: [0030] [0030]FIG. 1 is a fragmentary perspective view of a shelf incorporating the display device of the present invention. [0031] [0031]FIG. 1A is an enlarged fragmentary detail of a corner of the display device of FIG. 1 wherein the same contains a single card receiving slot. [0032] [0032]FIG. 2 is an enlarged fragmentary elevation taken along the arrow 2 in FIG. 1. [0033] [0033]FIG. 2A is a cross-sectional detail taken along the arcuate lines 2 A- 2 A in FIGS. 2 and 11, illustrating that the attachment construction of the display device may be modified so that the same can be adapted for direct attachment to the front panel of the glass door of a display cabinet a fragmentary detail of a portion of which is shown. [0034] [0034]FIG. 3 is a vertical section taken along the line 3 - 3 in FIG. 2. [0035] [0035]FIG. 4 is an elevation taken along the arrow 4 in FIG. 1. [0036] [0036]FIG. 5 is a vertical transverse section taken along the line 5 - 5 in FIG. 4. [0037] [0037]FIG. 6 is an enlarged section detail taken along the lines 6 - 6 in FIG. 4. [0038] [0038]FIG. 7 is a schematic diagram of a representative electrical circuit that can be employed in conjunction with the subject advertising display device. [0039] [0039]FIG. 8 is similar to FIG. 4 but illustrates this time that the display device can contain in its frame directly the electrical circuit means including its battery. [0040] [0040]FIG. 9 is an enlarged fragmentary section taken along the line 9 - 9 in FIG. 8. [0041] [0041]FIG. 10 is an enlarged vertical section taken along the line 10 - 10 in FIG. 8. [0042] [0042]FIG. 11 is a perspective view of a conventional display cabinet, but with the same having the display device of the invention attached to the cabinet's transparent door. [0043] [0043]FIG. 12 is a fragmentary side elevation, shortened horizontally for convenience of illustration, of another embodiment of the invention illustration usage of a horizontal battery case which is part of the mount of the device, and incorporating a coil-spring tongue or extension connected to the device frame, carrying electrical leads to the circuit of the frame, and lending flexibility to the structure. [0044] [0044]FIG. 12A is an enlarged fragmentary cross-section, taken along the line 12 A- 12 A in FIG. 12, illustrating circuit-board insertion-receipt of the advertising card employed. [0045] [0045]FIG. 12B is a partial end view, taken along the line 12 B- 12 B, illustrating the slot receiving the advertising card for positioning within the frame of the device. [0046] [0046]FIG. 13 is an enlarged horizontal section, taken along the line 13 - 13 in FIG. 12, illustrating the battery pack or holder and its mounting to a display shelf and its flexible securement to the display sign. [0047] [0047]FIG. 14 is a side elevation of another embodiment of the invention. [0048] [0048]FIG. 14A is an enlarged fragmentary cross-section taken along the line 14 A- 14 A in FIG. 14. [0049] [0049]FIG. 15 is a vertical transverse section taken along the line 15 - 15 in FIG. 14. [0050] [0050]FIG. 16 is an enlarged fragmentary top plan taken along the line 16 - 16 in FIG. 14. [0051] [0051]FIG. 16A is a longitudinal vertical section taken along the line 16 A- 16 A in FIG. 16. [0052] [0052]FIGS. 17 and 17A are essentially identical to FIGS. 16 and 16A, respectively, but illustrate a re-arrangement of conductive leads to accommodate single, centralized, screw-attachment placement. [0053] [0053]FIG. 18 is a top plan of a circuit board which may be used in the frame of the device to power its lights. [0054] [0054]FIG. 19 is a schematic of one of several electrical circuits which can be used in powering the lights of the advertising display sign. [0055] [0055]FIG. 20 is an isometric view of an alternative embodiment of a sign display apparatus according to the present invention. [0056] [0056]FIG. 21 is a right side elevation view, partly in section, of the sign display apparatus of FIG. 20. [0057] [0057]FIG. 22 is a top view of the sign display apparatus of FIG. 20. [0058] [0058]FIG. 23 is a sectional side elevation view, taken along the line 23 - 23 , of FIG. 22. [0059] [0059]FIG. 24 is an exploded isometric view of the mounting bracket portion of the sign display apparatus of FIG. 20. [0060] [0060]FIG. 25 is a sectional view, taken along the line 25 - 25 , of the display frame portion of FIG. 23. [0061] [0061]FIG. 26 is a sectional top view of the power source housing and attachment bracket, taken along the line 26 - 26 of FIG. 20. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0062] In FIG. 1 advertising or merchandising display device 10 comprises a panel 11 , a resilient flexible tongue 12 integral therewith, and a mounting bracket or clip 13 . The panel 11 has a peripheral edge 14 which is contiguous with frame portions 15 at opposite sides of the panel, the frame portions comprising respective peripheral margins 16 at opposite sides of panel 11 . Panel 11 includes also a central portion or partition 17 , from which tongue 12 extends, that serves as a backing for a pair of display cards 18 , by way of example, which may be contained in respective pockets 19 and 20 in panel 11 . Small interior detents as at 20 A can be employed to aid in keeping the advertising cards in place. The tab portion or tongue at 12 is designed to be flexible and may be comprised of a coil spring, a resilient, flexible metallic rubber or resilient plastic member, and so forth, this to insure that any jarring of the panel as produced by the movement of a shopping cart will not damage the display device but will rather allow it to give, in the direction of motion of the cart, such that when the cart passes, the display device will spring back to its normal, perpendicular condition relative to the shelf edge of the display shelf. [0063] The display shelf 19 is customarily made of metal and has a forward lip 20 which is vertical in orientation. The lip 20 serves as a backing for channel or edge molding 21 . The channel 21 includes upper and lower channel slots 22 and 23 , each of which receive a respective foot portion 24 and 25 of upper and lower legs 26 and 27 . Legs 26 and 27 form integral portions of, and comprise flanges of the composite mounting clip 13 . Battery container 28 is secured to tongue or tongue portion 12 by any conventional means and is also made integral, preferably, with mounting clip 13 . The battery container 28 is shown in greater detail in FIG. 6 wherein a nine volt battery, by way of example, is included at 29 , having its battery terminals 30 and 31 engaging electrical connections 32 and 33 , respectively, of the battery housing or container 28 . The left end 28 A of battery container 28 is closed off excepting for a central aperture 34 , designed to receive an implement such as a pencil 35 which can be used to eject the battery 29 from its container 28 in the direction of arrows 36 and 37 . A series of screws or rivets 38 can be employed to secure the channel 21 directly to the front lip or portion 20 of the display shelf 19 . FIG. 1 thus shows the display shelf as containing a series of cans or other containers at 39 , the display device 10 being employed to draw the attention of shoppers to particular specials or other advertising information relative to such goods at 39 . [0064] Comparison of FIGS. 1 and 4 indicate that different types of signs may be employed concurrently in the respective forward and rear pockets 19 and 20 of the display device, see also FIG. 3. [0065] A circuit which may be employed in the display device 10 is shown as circuit 39 in FIG. 7. The same includes battery 29 and, with the same, flasher control circuit 40 as well as a series of lights 41 such as parallel connected LEDs (light emitting diodes). A push button on/off switch 42 is preferably included in the circuit, see FIG. 7 and also FIGS. 1 and 10. An optional way of including the battery in the structure is shown in FIG. 8, wherein a disc-type battery 29 A is simply dropped into slot 43 , engages electrical connections 44 and 45 leading to the lighting circuit, and wherein the slot 43 is permissibly covered by a cover 46 that is hinged or pivoted at 47 in FIG. 8. The inclusion of the battery at 29 A in FIG. 8, corresponding to battery 29 in FIGS. 6 and 7, will this time power the circuit, leaving the mounting clip 13 A, corresponding to mounting clip 13 in the other figures, free of battery inclusion; instead the legs and feet may be designed simply to spring outwardly, as is also the case with mounting clip 13 , to engage the upper and lower channel portions 48 and 49 of channel 21 , see FIGS. 1 and 8. For most type of grocery shelves that are presently used, and which do include, generally, the channel 21 , then the upper and lower flanges of the mounting clip 13 , comprising upper and lower legs 26 and 27 with their respective feet, will be made resilient such that the legs can be depressed inwardly so that the outer ends of the feet can slip past the upper and lower lips of the channel, this such that these legs can spring outwardly, with the feet engaging slots 22 and 23 . [0066] If desired, the clip and the battery container, with an exposed portion of the tongue 12 , may be plastic encased for protection purposes. [0067] [0067]FIG. 1A illustrates that panel 11 A, corresponding to panel 11 in FIG. 1, may include simply a single slot 50 that can receive a display card 51 containing advertising indicia on both sides, by way of example. [0068] The several lights 41 , 52 may comprise, again, light emitting diodes or LEDs, or any other type of light. Included is the concept of employing HID (high intensity discharge) lights which customarily comprise U-shaped tubes having suitable terminal and filled with xenon gas. Other types of gases such as argon, etc., may be employed. Typical xenon HID lights may be employed and are shown at 52 A in FIGS. 8 and 9. These, or other lights can include parabolic or other concave reflectors as at 53 , which may be either integrally formed with the panel 11 or comprise separate elements tending to concentrate light emissions from the various light elements. The lights themselves are preferably electrically connected together in parallel and, to prolong battery life, and on/off switch as at 42 can be employed. In the structure shown it is preferable that there be two pockets on either side of the central portion of the panel; these pockets contain their respective cards which can be inserted from the tongue or clip side of the device. The tongue, or tongue tab-portion 12 , is bendable and resilient so that the cards are not exposed to inadvertent vandalism or withdrawal by young shoppers. [0069] It will of course be understood that the device of the present invention, see the fragmentary cross-sectional view of FIG. 2A, may be used in conjunction with display shelves where the shelves themselves are close to but separated by passersby by means of a glass or plastic door 53 of a refrigerated display cabinet 54 . Cabinet 54 , see also FIG. 11, thus has door 53 which is provided with door knob 61 and hinge mounts 62 secured to the cabinet proper in a conventional manner. The cabinet may include shelves 55 and 56 , and the display device 10 this time includes a plastic or even a metal channel length 57 that can simply be glued or otherwise secured at surface 58 , see also FIG. 2A, to the door 53 . Accordingly, the display device will highlight the contents of the cabinet, yet the door can be opened in customary fashion so that the shopper achieves easy access to the shelves. [0070] Where the battery and battery container form a portion of or are contained by the mounting clip 13 and the same made integral with tongue, tongue or tab-portion 12 , then it is preferred that the electrical wire leads from the battery as at 59 and 60 , see FIG. 4, be actually encased in the tongue 12 . In this way the wire leads are protected from passersby; yet, their nature permits their flexing with the tab portion or tongue in response to inadvertent movement of display device 10 . [0071] Accordingly, what the present invention offers is an at-or-proximate shelf merchandising display device which is illuminated, battery powered, and which serves to draw attention to a variety of store goods. The battery is either self-contained in the panel of the display device or is encased within the clip used to mount the flexible tongue of such device to a forward lip channel associated with a given store shelf. [0072] Rather than, or in addition to plural lights, the subject advertising panel may include battery powered, electrically energized alpha-numeric, liquid crystal or other display indicia, as is conventional with various battery-powered readouts in watches, etc. on the market. Again, the invention is suitable not only for shelves per se, but also for frozen food cabinets, refrigerators, freezers and the like. [0073] In FIG. 12, an advertising display device 63 is shown and includes a frame 64 having outer edge 65 and rear and front rectangular frame margins 66 and 67 , these respectively being disposed on opposite sides of the frame. Such margins form opposite windows 68 which display the faces of one or more advertising cards 69 . The frame 64 can include an electrical circuit 70 , as before, which is coupled to and electrically powers the several display lights 52 and may take the form of electrical circuit board 102 in FIG. 18. [0074] It is noted that the frame 64 includes a slot 71 serving as an admittance slot relative to card insertion of card 69 . The interior slot formed by the inner edges of circuit board 102 forms a support receptacle for card 69 . The light powering electrical circuit 70 may include electrical leads 59 and 60 , see FIG. 1, which pass through a new design of tongue 72 . The latter is formed of a flexible resilient sheath 73 which encases deflection restoring coil spring 74 . Spring 74 is seated at its opposite end turns 75 and 76 to and within recesses 77 and 78 of battery case 79 and frame 64 , respectively. Again, the wires 59 and 60 project through the tongue, i.e., through the interior of spring 74 to connect to the electrical circuit 70 powering lights 52 . This will be in the same fashion in connection with the electrical circuit shown in the embodiment of FIG. 1, etc. Battery case 79 may include an end aperture 80 for receiving a battery push-out tool such as pencil 35 in FIG. 6. Optional to this of course may be included a battery rejection spring within battery case 79 for enabling a battery retrieval. The inner circuit 81 of battery case or holder 79 includes a pair of conductor strips 82 and 83 which are electrically connected to leads 59 and 60 . Conductive strip 82 leads to battery end contact 84 which is secured at 85 to the battery case in a manner conventional with battery case constructions. Conductive strip 83 is connected to a conductive threaded ring 86 at the remaining end of the battery, and a plug or cap 87 is provided with a contact 88 and a conductive strip 89 leading to matching conductive threaded ring 90 . Accordingly, insertion of batteries 91 and 92 within the cavity 93 of the battery case, and the securement of the cap 87 , produces an electrical contact circuit and hence an electrical energy supply circuit, via the battery and its conductive strips to electrical circuit leads 59 and 60 . [0075] Mounting clip 93 can be designed similarly to clip 13 in FIG. 2 and, in any event, will be secured by attachments 94 to battery case 79 . The clip may be designed to be resilient, whereby the up-turned ends thereof 95 and 96 will be releasably and selectively received into the upper and lower recesses of channel molding 97 that corresponds to molding 21 in FIG. 1. Molding 97 of course will be secured in the usual manner to shelf 98 of any description which corresponds to shelf 19 in FIG. 1. In the preferred form of the invention, the mounting clip 93 will be locked in place relative to the channel molding. This will be accomplished by the locking structure shown in FIG. 14 whereby the securement of the mounting clip relative to the channel molding is made permanent or is of a semi-permanent character. The securement of the channel molding 97 to the outer-shelf edge may be effected by attachment 99 . [0076] Accordingly, FIGS. 12, 12A, 12 B and 13 illustrate the incorporation of a horizontal battery case with contained batteries with the same being supplied an electrical circuit leading through a tongue or extension such as, this time, a coiled deflection-restoring spring 74 , to the electrical circuit of the frame 64 of advertising display device 63 . What is accomplished, therefore, is the provision of a battery pack, i.e., case and batteries, which is separate from the frame proper, but constructed for selected mounting to a shelf molding. More importantly, the leads powered by the batteries in the case project through the tongue, i.e., this time through the spring 74 and its protective sheath, to connect to the electrical circuit of the device. An on-off switch may be provided for the electrical circuit if desired, and in accordance with the teaching of the prior figures. [0077] [0077]FIGS. 14, 14A, 15 , 16 , and 16 A, with FIGS. 18 and 19 constitute another embodiment of the invention. However, other than being U-shaped to accommodate insertion and support for card insertion in the frame, the circuit board of FIG. 18 and its representative circuit as shown in schematic form in FIG. 19 are strictly conventional and may take any one of a number of forms, familiar to all skilled in the art. Representations as inverters U 1 and counter U 2 . VCC (voltage common cathode) connection is had at the customary points for the circuit components. LED light positioning, D 1 -D 20 , for lights 52 , is also illustrated. Standard resistors are utilized at R 1 , R 2 as well as capacitor C 1 , all selected in accordance with conventional established design procedures. The particular circuit design selected for the circuit board forms no part of the invention. [0078] [0078]FIGS. 17 and 17A illustrate yet another embodiment of the advertising display device that is closely similar to that shown in FIG. 14, e.g., but illustrates certain minor modifications. [0079] In FIG. 14 the advertising display device 100 is shown to include a frame 101 that is interiorly provided with a circuit board 102 , having conventional elements as seen in circuit 103 in FIG. 19, but which will be encased within the frame to supply electrical power therefore to the several lights 52 and, additionally, provide a slot 104 for the reception of advertising card 105 . Where desired, the frame 101 may be constituted by separate halves 106 and 106 A which can be secured together by male, female connectors 107 , 108 , by screws, or by other means. Frame half 106 A can be integral with body 137 . Card 105 is designed to slip into end slot 109 which can be similar to slot 71 in FIG. 12B. A tag 110 may be one of several provided, the same incorporating an aperture 111 which receives a hook-shaped pin 112 . This pin proceeds through apertures 113 and 114 of ears 115 , protruding outwardly on both sides of the frame. Accordingly, pin 112 is operative not only to support “special” or other tags, for promotional purposes, but also releasably secures the card 105 within the frame of the advertising display device. The shelf 98 in FIG. 14 is provided with channel edge molding 97 A, corresponding to channel molding 97 in FIG. 12. [0080] [0080]FIGS. 16 and 16A illustrate that the embodiment introduced by FIG. 14 includes a fixed securement member 116 and also a sliding securement member 117 . The sliding securement member 117 includes a central aperture 118 having a threaded metal insert 119 that receives adjustment screw 120 . Access to adjustment screw 120 is had through the bore or aperture 118 by an elongated screw driver, Allen wrench fitting or the like. Channel edge molding 97 A is also seen. Thus, as to member 119 , the same provides a locking mechanism for locking the entire display device 100 in position by simply tightening down on the screw 120 , which is recessed to be tamper-proof. Member 117 may be configured as shown in FIG. 16 with outer ribs 121 , 122 . Therefore, the sliding securement member is retained in slide disposition by the undercut slots or grooves 123 and 124 as the same is adjusted up and down by screw 120 . FIG. 16A illustrates that the fixed securement member 116 includes an interior circular cavity 125 which receives serially connected batteries 126 and 127 . A battery spring 128 serves to retain the batteries together and also provides electrical contact to conductive strip 129 which leads to lead 136 of the electrical circuit powering lights 52 . Correspondingly, battery spring 130 is supplied to the cap member 131 and connects to conductive strip 132 which leads to spring 133 . Spring 133 in turn is connected to conductor strip 134 connected to lead 135 which is associated with the electrical lighting circuit of the display sign. Thus, the ground and VCC (power) lines, see FIG. 19, will be coupled to the electricity supply leads 135 and 136 . [0081] Body 137 forms an extension of and moves with frame 101 and includes a recessed seat 138 which accommodates the bearing engagement of end 139 of member 116 . The raised boss 140 is recessed to provide for the battery spring 128 . Accordingly, and relative to the engagement of fixed securement member 116 with body 137 , it is seen that the latter can be rotationally displaced about pivot access R in accordance with temporary deflections of the frame as occasioned by inadvertent impact by passengers or carts in the direction of arrows S and T in FIG. 16. More will be said about this in conjunction with the return torsion spring feature of the invention at a later point. [0082] At this point it is important to note the cap member 140 A and its provision with electrical current conducting battery spring 130 in the latter engagement with batteries 126 and 127 . Cap member 140 A likewise includes the spring 133 as previously mentioned which provides for electrical connection between conductive strip 132 and strip 134 coupled to lead 135 . The depending portion 142 of cap member 140 A is illustrated and additionally serves to hold down and hold in place the batteries 126 and 127 . Importantly, see FIG. 16, the upper portion 143 of cap member 140 A includes a circularly arcuate enlarged major recess 145 and, contiguous therewith, the arcuate minor recess 146 . These are seen in both FIGS. 16 and 16A. The arcuate major recess or travel path 145 accommodates the movement of the outwardly turned extremities 147 and 148 of circular torsion spring 151 as the sign is laterally deflected according to forces S and T in FIG. 16. Shoulder stop 149 and shoulder stop 150 respectively retain the remaining end of the torsion spring 151 . Upstanding pins 152 and 153 co-act with the torsion spring and are upstanding from fixed securement member 116 . Screws 155 and 156 are provided in FIG. 16 to retain the cap member 140 A in position. Thus, these screws will be threaded into apertures, not shown, positioned in body 137 . [0083] The remainder of the operation of the embodiments shown in FIGS. 14, 16 and 16 A is as follows: The batteries 126 and 127 with their electrical circuit elements, comprising springs 128 and 130 and conductive strips before mentioned leading to leads 135 and 136 , supply power to the circuit board in the frame of the display device. The apparatus is assembled as heretofore indicated, with cap member 140 A finally being positioned in place and fixed to the frame and screws 155 and 156 tightened. [0084] In referring to FIG. 16, an inadvertent and temporary deflection in the direction of, e.g., arrow S will produce a clockwise rotation of the sign about axis R. This is simultaneously accompanied by a rotational displacement of cap member 140 A, and hence of its shoulder stops 149 and 150 . The upstanding pins 152 and 153 , upstanding from fixed securement member 116 , are stationary, however, relative to the shelf edge molding, so that there will be a temporary torsional tightening of the spring by one of the pins 152 , 153 , depending upon the direction of frame displacement and thus producing a potential restoring force in the spring. Once temporary pressure is relieved relative to arrows S and/or T, then the spring will operate against its associated pin 152 , 153 to restore the sign to orthogonal relationship relative to the shelf. It is important to note that the pivoting functioning is accomplished proximate the battery case enclosure and that the unit may be clamped to the molding strip, remain stationary, and yet provide for the flexibility and circuit connection needed for the sign proximate the battery enclosure. The display device 100 A in FIGS. 17 and 17A is essentially identical with that shown at 100 in FIGS. 14, 16 and 16 A, but with the following exceptions. A single screw 155 A is employed to secure cap member 140 A, corresponding to cap 140 in FIG. 16A, to the body 137 of the unit. Conductive strips 170 and 171 this time are secured to the spring 130 , see FIG. 16A, and are angulated in dog-leg configuration to connect at 172 to the electrical circuit of the sign. In this manner but a single screw can be used at 155 , can be centered, and the electrical circuit required, with its connections, still be supplied. Metal conductive pin 173 may be employed at the point indicated in FIG. 17A to complete the circuit. [0085] Hence, what is provided in this invention are a plurality of embodiments of advertising display signs having sufficient flexibility to allow for a restoring force and yet temporary relief for inadvertent forces acting on the sign. Furthermore, the several embodiments illustrate that the display sign can be releasably or securely engaged with the molding strip of a store shelf, and a battery case supplied at the mount for powering the sign. In a preferred form of the invention the battery case itself incorporates structure whereby to facilitate a pivotal displacement of the sign as may be occasioned. [0086] At all events, the electrical circuit requirement is met for the displacement sign, whether a spring, a resilient member, or other structure is employed. [0087] [0087]FIG. 20 shows a particular alternative embodiment of the present invention. Specifically, a sign display 200 for point-of-purchase advertising is shown. The sign display generally includes a frame portion 202 , a power supply housing 204 , and an attachment bracket assembly 206 . A yieldable, resilient flexion joint 208 couples the frame portion 202 with the combined power supply housing 204 and attachment bracket assembly 206 . [0088] The frame portion 202 is best described with reference to FIGS. 20, 23, and 25 . The frame portion 202 includes a top frame member 210 , a bottom frame member 212 , a proximal frame member 214 , and a distal frame member 216 . In one embodiment, the frame portion 202 is generally configured such that the proximal frame member 214 defines a relatively small proximal sign segment 218 and the distal frame member 216 defines a relatively large distal sign segment 220 . The relatively small sign segment 218 provides for substantially unrestricted access to shelf areas above and below the sign display, while the relatively large distal sign segment 220 provides ample sign surface area for effective point-of-purchase advertising. [0089] The distal frame member 216 further defines a slot 222 for inserting advertising materials 224 , such as a rigid paperboard or the like, into operative position within the sign display 200 . The slot 222 is sized to accommodate the largest vertical dimension of the advertising material 224 . It should be understood that the advertising material 224 may comprise a substantially opaque material such as paperboard, cardboard, paper, or like material. Alternatively, the advertising material 224 may comprise a partially transparent material (e.g., polycarbonate or glass) with specific advertising indicia affixed thereon. As yet another alternative, the advertising material 224 may comprise a series of sheets, such as a pair of transparent sheets of material (e.g., glass or polycarbonate) and an opaque sheet of material positioned in between. Still another alternative embodiment may include a substantially transparent material (e.g., glass or plastic) with indicia provided on at least one surface of the transparent material. [0090] In the embodiment shown in FIGS. 20 - 23 , the shape of the advertising material 224 is substantially pie-shaped or triangularly shaped with a relatively short vertical dimension provided adjacent the small proximal segment 218 and a relatively tall vertical dimension corresponding with the large distal segment 220 of the sign display 200 . Indicia provided on the advertising material 224 may require that the orientation of the sign be adjusted to a particular presentation angle β (FIG. 21). To adjust the presentation angle β, the attachment bracket assembly 206 includes a worm gear assembly 226 (FIGS. 23 - 24 ) specifically comprising a stationary gear 228 having a plurality of teeth and a rotating adjustment screw 230 having a plurality of threads 232 . The threads 232 rotate through the teeth of the stationary gear 228 to move the frame portion 202 through a plurality of presentation angles until the desired angle β is achieved. The rotatable adjustment screw 230 includes a head 234 into which an adjustment device, such as a straight-slot screwdriver, can be inserted to adjust the presentation angle. The presentation angle is preferably set to orient the advertising material in a manner that will be easy for a purchaser to read. [0091] The attachment bracket assembly 206 still further comprises a mounting base 236 , formed by two mirror halves 236 A and 236 B. A sliding block 238 is slidably mounted between the halves 236 A and 236 B. An upper clip 240 is mounted to the sliding block 238 . A lower clip 242 is mounted to the base 236 so as to be inserted through slots created by a tongue member 244 (FIG. 24). A rotatable adjustment screw 246 is disposed between the tongue member 244 and the sliding block 238 . Rotation of the screw 246 moves the sliding block 238 relative to the base 236 to adjust the spacial relationship of upper clip 240 and lower clip 242 for securing or releasing the sign display from a shelf or other advertising area. As the sliding block 238 moves away from tongue member 244 , the upper clip 240 and lower clip 242 lock into an attachment bracket associated with the shelf or other display structure. As shown in FIGS. 20, 22, and 24 , a pair of sidewalls 248 are mounted to the base members 236 A and 236 B to prevent lateral displacement of the power supply housing 204 relative to the attachment assembly 206 . The first base member 236 A is secured to the second base member 236 B by means of conventional fasteners 250 . The sidewalls 248 include male posts 249 inserted into corresponding apertures 251 (only one shown in FIG. 24) in the base 236 . The posts allow articulation of the frame portion 202 relative to the mounting base portion 206 upon movement of the adjustment screw 230 . [0092] With reference to FIGS. 22, 23, and 26 , the power supply housing 204 comprises a main compartment structure 254 and an end cap 256 threadedly received by the main housing structure 254 . Conventional batteries 258 are held within the power supply housing 204 . Lead wires 260 extend from the power supply housing through an opening 262 formed in the main housing structure 254 . The lead wires supply power to the light display associated with the frame section 202 . The lead wires are protected by a yieldable, resilient flexion joint 208 . As shown in FIG. 26, the flexion joint more specifically comprises a resilient spring-bias member 264 surrounded by a rubber boot 266 . The boot 266 allows the resilient bias member 264 to yield and bend while protecting the lead wires 260 . Mounted within the proximal section 218 is the circuitry 270 used in illuminating the frame section 202 . The circuitry 270 may comprise any conventional circuitry to illuminate light sources 272 . The circuitry may provide differentiating illumination for the light sources 272 , alternating the supply of power to the light sources 272 , or any other desired result. The light sources 272 are provided to direct light through the upper frame section 210 and the lower frame section 212 . A pair of parabolic mirrors 274 are mounted within the upper and lower frame sections 210 , 212 , respectively, to provide enhanced illumination within the tubular areas. The frame sections 210 , 212 are preferably made of a translucent material so that light is emitted to catch the attention of shoppers. A benefit of the present invention is that with the illumination as proposed, only two light sources are required to fully illuminate the top and bottom frame sections 210 , 212 . [0093] With reference to FIG. 25, the frame portion 202 is formed by joining a first frame half 202 A and a second frame half 202 B. A slot is formed between the two frame halves which enables the sign 224 to be inserted therein, as shown in FIG. 20. [0094] In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not to be limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.

A lighted flexible display device or sign, useful for advertising purposes, and having a battery supply mount. The display device herein is a lighted display and is constructed to be flexible in the presence of inadvertent bumping or deflection thereof. The mounting is resilient such that, when the deflecting force is removed, the sign springs back to its normal lateral position. The mount for the display device includes a battery supply, with such supply being electrically connected to the electrical circuit of the sign proper. This is accomplished by means of electrical leads passing through a deflection restoration spring, by such leads passing through a resilient tongue, or with connectors used in a spring-biased pivotal construction for connecting the battery supply to the electrical lighting circuit of the sign.

This is a continuation of application Ser. No. 08/092,137, filed Jul. 15, 1993, now abandoned which is a continuation of application Ser. No. 06/654,377, filed Sep. 26, 1984 which is issued as U.S. Pat. No. 5,279,838. FIELD OF THE INVENTION This invention is directed to a feed grain conditioning composition and a method for tempering feed grains for livestock in association with other processing, or for both tempering and adding digestive benefits to the grain. More specifically, the invention is directed to a method for processing feed grains by the addition of wetting agents such as saponins, preferably sarsasaponins, extracted from Yucca plants. BACKGROUND OF THE INVENTION Animal scientists and cattle feeders have evolved numerous grain processing methods in an attempt to optimize the efficiency of animal growth per unit of grain fed. Some of the methods employed in processing feed grains are grinding, rolling, reconstituting, and steam flaking. Water is often added as a tempering agent before or during the processing by direct liquid application and/or as steam. Processing is disruptive to the grain kernel organization. Grinding and rolling reduce the particle size of the grain kernels. Steam flaking, micronizing (dry heating) and reconstitution disrupt the microscopic integrity of the kernel structure. Animals masticate grain kernels mixing the feed with saliva as they do so. Digestion of the feed takes place at the sub-microscopic level and involves the biochemical breaking of molecular structures. Macroscopic and microscopic disruption of the kernel, along with wetting, are predigestive steps which can be achieved by the mechanical and physical processing techniques already described. By achieving the predigestive disruption prior to feeding the feedstuffs, the amount of feed required to produce a unit of animal body tissue is reduced. Fuel efficiency is increased. Feed processing is an added cost to the feedstuff due to the cost of energy expended, equipment maintenance, person hours, etc. Processing is economically feasible only when the increased cost of the feedstuff is more than offset by the reduced pounds of the feedstuff required to yield a pound of animal weight gain. Energy requirements of processing contributes much of the added cost. Steam flaking represents one of the most costly processing methods employed on a large scale in beef cattle feeding operations. Steam flaking also effects the largest increase in feed efficiency. The quantity of steam injected into the feed is minimized and the through-put (tons per hour) is maximized to hold down the added cost. Wetting agents are used to facilitate the absorption of moisture into the grain. A flaking aid, such as a wetting agent, is employed by a large majority of feedlots. Saponins in general and sarsasaponins, and their sapogenin and sarsasapogenin derivatives, are well known substances (The Merk Index, Tenth Edition, Monographs Nos. 4509, 8215, 8218, 8228 and 8393). Saponins are known to be wetting agents. They have not been employed as flaking aids or otherwise in the treatment of grain for processing. Sarsasaponins are a special class of saponins. The sarsasaponins contain asteroid whereas other saponins do not. The steroid portion of saponins (sapogenins) are not wetting agents. Steroids are fat soluble, making them ideally suited for promoting moisture penetration of oil containing feed grains, most of which are protected by a wax-like coating. Steroids (sapogenins) are not readily soluble in water. Saponins are polar, readily water soluble, and reduce the surface tension of water and exhibit the classic Characteristics of wetting agents. Sarsasaponins are known to enhance gain and feed efficiency when incorporated into the rations of feedlot cattle. It is one of the sarsasaponins extracted from the plants of the family: Lillaecae, genus: Yucca to increase the rate of moisture uptake by feed grains prior to and during processing. It is a further objective of this invention to introduce sarsasaponins into the rations without destruction of their chemical characteristics, thus leaving them intact in the diet where they may serve as feed and gain enhancers. The increase in feed efficiency due to the addition of sarsasaponins during processing of the feed grain is at least as great as that which has been demonstrated when they are introduced into the ruminant diet by inclusion in protein supplements. THE PRIOR ART Hale et al (Proc. Soc. Exp. Biol. Med. 106:486, 1961) have demonstrated that the steroid portions (sapogenins) of some of the sarsasaponins improve gain and feed efficiency when included in the diets of ruminant animals. McKeen et al (Pfizer U.S. Pat. No. 3,144,337) disclose among others that sarsasaponins, in the form of its glycoside sarsasaponin, may be admixed with a component (grain) of an animal's feed in amount from 0.1 to 24 grams per ton of feed to promote animal growth. However, use of saponins is discouraged because of possible toxicity of saponins. Use of sapogenins is advised. Sapogenins are not readily soluble in water and are not wetting agents. Accordingly, McKeen et al do not and cannot rely on the non-existent wetting agent property of their sapogenins in achieving their claimed stimulated animal growth. Since they advise against use of saponins, there is no accidental or inherent use of the wetting agent property of sarsasaponin. The biological activity of sapogenins is not a function of a wetting agent. SUMMARY OF THE INVENTION Broadly stated, the invention comprises the method of processing livestock animal feed grains which comprises adding a small but effective amount of a sarsasaponin to the grain as a wetting agent in association with mechanical processing of the grain. The preferred sarsasaponin is extracted from the Yucca plant of the family Lillaecae. The sarsasaponin may be added at two weight levels, a lower level for its wetting agent and tempering functions, or a higher level for enhancing the digestibility of the grain in addition to its wetting agent and tempering functions. For thorough uniform admixture, the sarsasaponin is desirably added to the grain form a liquid aqueous medium, preferably including an antifreeze agent. Typical mechanical processing steps to which the grain is subjected includes, grinding or rolling to disrupt the kernel organization, steam flaking to add moisture, and mixing with other feed ingredients and components. Although the wetting agent is preferably added prior to mechanical processing, it may be added at any stage in the preparation of the grain for feeding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The addition of sarsasaponin to feed grain for livestock animals performs two functions. It acts as a wetting agent to facilitate the addition of moisture to render the feed more palatable, more digestible and more stable. It also permits faster weight gains with less feed. When applied in preferred liquid form, a more uniform distribution is assured increasing the chance of uniform sarsasaponin intake. Ration sorting, which often occurs with pelleted supplements, is eliminated. All cattle or other livestock in the pen are exposed to sarsasaponin's special increased feed efficiency benefits. For feed grain processing sarsasaponins are unique in providing both improved wetting agent function and benefits to improved feed conversion in a single project. The introduction of the sarsasaponins prior to processing by steam flaking, dry rolling, etc. with the unexpected result of maintaining compound integrity is heretofore unknown. Analytical procedures show that these sarsasaponins exhibit the same chemical characteristics before and after being subjected to feed grain processing methods. The sarsasaponins are more water soluble, and thus are more capable of mitigating the stresses exerted on a microbial fermentation than the sapogenins. In the preferred form, the sarsasaponins are added to the grain in a liquid medium. An exemplary liquid from of sarsasaponin is sold under the trademark SarTemp by SarTec Corporation of Anoka, Minn. It is prepared by blending an aqueous extract of the plants of the family: Lillaecae, genus: Yucca, or other appropriate Yucca plants containing 10 solids with antifreeze agents such as calcium chloride, propylene glycol, and the like, to depress the freezing point to -30° F. The final concentration of Yucca soluble solids is 8.25%. Its physical data are: ______________________________________Bulk Density 10.4 lbs. per gallonColor Dark brownFreezing Point -30° F.Sarsasaponin 390 grams per gallonContent (3 grams per ounce)pH 5.5-6.0Total solids 33%Water 67%______________________________________ For grain tempering this liquid material is applied at the rate of 3-4 fluid ounces (9 to 12 grams dry weight) per ton of grain. For grain tempering plus sarsasaponin digestive benefits, it is applied at the rate of 5-6.5 fluid ounces (15 to 20 grams dry weight) per ton of grain. Even when applied at the lower grain tempering rate, the growth improving properties of the sarsasaponins are retained in the treated grain, but at a lower level. Lesser amounts of sarsasaponin, as low as 1 gram per ton dry weight may be used but with decreased effectiveness. Larger amounts than 20 grams per ton may also be used, but are not cost effective. It can be added to grain either at the roller mill, before entering the surge bin of the steam flaker, directly to grain before storage, or directly to the mixer. It should be blended with enough water to achieve the desired moisture level in the processed grain. The solution may then be applied as a surface spray. Shrinkage is a loss incurred while conveying and processing feed grain. Such losses are the result of dust and fines. Not only are these dusts an economic loss of physical property, but they are atmospheric pollutants. Workers in and around the processing facilities and animals consuming such dusty rations are stressed. The fines also tend to blow out of the feed bunk. Sarsasaponins, because of their wetting properties, permit the application of smaller amounts of water than would otherwise be required to reduce the fines and dust problems. If enough water is applied to reduce the dustings, etc., freezing, molding and other physical handling problems arise. By inclusion of the sarsasaponin, less water is required. Shrinkage and pollution can thus be controlled. Most wetting formulas commercially available as flaking aids contain volatile organic acids (propionic acid) to ensure stability of the formula against spoiling and molding. These volatile acids are corrosive to processing equipment and are released into the atmosphere. Sarsasaponins, in general, and the exemplary SarTemp formulation, specifically, are non-volatile and, therefore, are not lost as corrosive agents into the atmosphere. Feedlot research has clearly demonstrated the benefits derived when sarsasaponin is introduced directly into cattle rations. More than 10% weight gain has been achieved with more than 2.5% less feed. In steam chest trials, moisture uptake in sarsasaponin treated corn increased as much as 63% to over 300% as compared with untreated grain. Sarsasaponins useful in the present invention may also be extracted from plants of the family: Amaryllidaccae, genus: Agave, which grows extensively in the southwestern United States and in Mexico. The invention is further illustrated by the following examples: Example I The moisture uptake of treated and untreated corn was measured. A spray dried water soluble extract of the plants of the family: Lillaecae, genus: Yucca, (1.3 grams) was dissolved in water and diluted to a total volume of one liter (Solution SA). One ml of water and one ml of SA were added to 100 g of whole corn and mixed. The sample was then exposed to steam at the prevailing atmospheric pressure for ten minutes and two minutes. Other samples of corn were treated with 2 ml of water and mixed. These samples were also subsequently exposed to steam for 10 and 2 minutes. Increased moisture content as measured by weight increase was determined and listed: ______________________________________Weight increase (grams) per 100 g cornExposure (Min) SA Water______________________________________10 6.1 5.7 2 4.7 4.1______________________________________ At 10 minutes exposure the moisture uptake of the sarsasaponin treated samples was 70.2% greater than that of the untreated samples. At 2 minutes exposure and moisture uptake was only 14.6%. Example II The moisture uptake of larger samples of treated and untreated corn exposed to greater amounts of sarsasaponin (SA) and water was measured. The corn samples were treated with water or SA and exposed to steam for 2 minutes. The weight increase of the samples were determined and are listed: ______________________________________Sample: Treatment: Weight increase: (grams)Corn (grams) SA (ml) Water (ml) SA Water______________________________________200 2 -- 20.7 --200 -- 2 -- 11.8500 5 -- 23.1 --500 -- 5 -- 13.7______________________________________ The moisture uptake of the sarsasaponin treated samples was 75.4% and 68.5% greater than the untreated samples of 200 and 500 grams, respectively. Example III The moisture uptake of corn samples treated with sarsasaponin from Yucca extract as in Example I (SA) and the proprietary material SarTemp (ST) was compared with untreated samples. A diluted solution of SarTemp (1.39 g/l) was prepared. Corn samples (500 g) were treated with water, SA, or ST and exposed to steam for 2 minutes. The increase in weight was determined and is tabulated: ______________________________________Water (ml) SA (ml) ST (ml) Weight increase (grams)______________________________________15 -- -- 710 5 -- 22.7 5 -- 10 10.2______________________________________ The moisture uptake of the sarsasaponin extract treated sample was 324% greater than untreated samples. The moisture uptake of the SarTemp treated sample was 145% greater than the untreated sample. However, the SA solution was about 4.5 times more concentrated than the ST solution. Example IV The increase in moisture in 500 g samples of corn in a laboratory scale steam chest was between that which was untreated and that treated with SarTemp (ST) was compared in several trials. Liquid ST was added to the corn at the rate of 6.6 ounces per ton equal to 20.1 grams sarsasaponin dry weight per ton of corn. 1% moisture was added to the corn prior to introduction into the steam chamber. The results were as follows: ______________________________________Trial Untreated ST______________________________________1 2.1 3.92 1.8 5.03 3.8 4.04 2.9 4.6Average 2.7 ± 0.7 4.4 ± 0.5Difference +1.7% Increase 62.9______________________________________ Adding sarsasaponin in liquid medium from SarTemp increased moisture approximately 63% over uptake in corn grain by untreated samples. Example V The possible effect of steam flaking on the chemical characteristic of sarsasaponin was evaluated. Wheat grain was treated with SarTemp (ST) and processed by steam flaking. A thin layer chromatogram of the butanol extract of ST and wheat (6.6 oz/ton ST) have identical moving concentrations of saponin, relative to the solvent front. Steam flaking has not alerted the chemical characteristic of this saponin fraction of the ST. Example VI The performance of steers fed sarsasaponin treated and untreated flaked corn rations was compared in an extensive feedlot test. A total of 40 steers were fed over a period of 130 days. The results of the trial are shown: ______________________________________ Average Weights Control Sarsasaponin______________________________________Initial weight lbs. 746 746Final weight lbs. 1063 1095Total gain lbs. 317 349Average daily gain lbs. 2.44 2.69Total air dry feed lbs. 21.5 23.06Feed/lb. Gain lbs. 8.19 7.96______________________________________ Whereas control group cattle required 8.19 pounds of feed per pound of gain, sarsasaponin-fed cattle required only 7.96 pounds of feed per pound of gain. The sarsasaponin-fed cattle showed 10.1% greater gain which was achieved with only 97.2% as much feed. It is apparent that many modifications and variations of this invention as hereinbefore set forth may be made without departing from the spirit and scope thereof. The specific embodiments described are given by way of example only and the invention is limited only by the terms of the appended claims.

A feed grain conditioning composition including an aqueous tempering agent including a Yucca extract containing saponin and an antifreeze agent. Preferably, the Yucca extract contains sarsasaponin. The antifreeze agent is preferably selected from the group consisting of calcium chloride and propylene glycol. In a preferred embodiment, the amount of antifreeze agent is sufficient to depress the freezing point of the tempering agent to about -30° F. or less. A method of tempering feed grain by applying the feed grain conditioning composition to feed grain is also disclosed.

This is a division of application Ser. No. 08/326,335, filed Oct. 20, 1994. FIELD OF THE INVENTION This application claims the priority of Japanese Patent Application No. 287358 filed Oct. 21, 1993, which is incorporated herein by reference. This invention relates to an ohmic electrode of n-type semiconductor cubic boron nitride (c-BN) and a method for producing an ohmic electrode on a c-BN crystal. In particular, this invention proposes an ohmic electrode and a method of fabricating the ohmic electrode of c-BN which is suitable for making semiconductor devices favored with high resistance against heat. BACKGROUND OF THE INVENTION N-type semiconductor cubic boron nitride (c-BN) has high resistance against heat (stable up to about 1300° C.), a wide band gap (7 eV) and excellent stability against chemical reactions. N-type c-BN has been attracting strong attention as a promising material of heat resistant semiconductor devices, or optoelectronic devices for emitting the light ranging from ultraviolet to visible light. However, cubic boron nitride is not yielded as a natural resource. Ultra high pressure method synthesizes bulk crystals of c-BN. Furthermore, vapor phase synthesis method fabricates thin films of c-BN on some substrate. Non-doped c-BN is an insulator with high resistivity. P-type c-BN is obtained by doping with beryllium (Be). Doping with silicon (Si) or sulfur (S) brings about n-type c-BN. Application to semiconductor devices necessitates a pn-Junction. A pn-junction can be fabricated on a c-BN by synthesizing an n-type c-BN crystal on a p-type c-BN crystal as a seed by the ultra high pressure synthesizing method, although it is difficult. Since a pn-Junction can be produced on a c-BN, some applications have been suggested regarding the semiconductor devices of c-BN. 1 Japanese Patent Laying Open No. 4-11688 proposed an application of c-BN to semiconductor devices. 2 Japanese Patent Laying Open No. 3-112177 made an offer of an application of unifying c-BN with diamond. 3 Japanese Patent Laying Open No. 1-259257 also suggested a complex of c-BN and diamond as a semiconductor device. 4 Japanese Patent Laying Open No. 4-29375 proposed an ohmic electrode of c-BN by the same inventors of the present invention. An ohmic electrode is one of the most important parts in order to produce semiconductor devices. However there was no ohmic electrode of c-BN due to the too short history of c-BN as a semiconductor. Nobody except the Inventors has suggested a method of fabricating ohmic electrodes of c-BN. Only the Inventors of the present invention have suggested an ohmic electrode on a c-BN crystal in the above application. An ohmic electrode was produced with titanium (Tl), zirconium (Zr), hafnium (Hf) or an alloy including Ti, Zr and Hf. 5 Japanese Patent Laying Open No. 4-29376 suggested a method of producing an ohmic electrode with a metal including silicon (Si)or sulfur (S), or an alloy containing silicon (Si) or sulfur (S) by the same inventors. 6 Japanese Patent Laying Open No. 4-29377 made an offer of forming ohmic electrode of c-BN with boron (B), aluminum (Al), gallium (Ga), indium (In) or an alloy of B, Al, Ga or In. 7 Japanese Patent Laying Open No. 4-29378 mentioned a method of producing an ohmic electrode with vanadium (V), niobium (Nb) or tantalum (Ta) or an alloy including V, Nb or Ta. An ohmic electrode is an electrode formed on a substrate or a film which is in ohmic contact with the substrate or the film crystal. "ohmic" means bilateral current-voltage property unlike diodes or rectifiers. The forward resistance is equal to the rear resistance at an ohmic electrode. Further, an ohmic electrode demands both small forward resistance and small rear resistance in order to minimize the loss of signal power at the electrode. Besides the inherent resistance at the electrode, it is also desirable to reduce the resistance of the circuits following the electrode in order to produce good devices. Therefore, the ohmic electrode shall preferably adopt a multilayer structure in which more conductive Au or Al layer covers an ohmic contact metal in order to connect the contact metal with circuit patterns with little resistance. The higher layer metal (Au or Al) may be called an extraction electrode, since the layer connects the higher resistive electrode with outer circuit patterns or outer wires. Prior art from 4 to 7 suggested ohmic electrodes of titanium (Ti), zirconium (Zr), hafnium (Hf), a metal containing Si or S, boron (B), aluminum (Al), gallium (Ga), indium (In), vanadium (V), niobium (Nb), tantalum (Ta) or so on. These materials can all form an ohmic contact with cubic boron nitride (c-BN). The contact has the bilateral character. The forward resistance and the rear resistance are nearly equal. Thus the electrodes can be called "ohmic". However, these prior art did not satisfy the other requirement of ohmic electrodes. The metals or half-metals recommended as ohmic contact materials have resistivities more than ten times as high as that of gold (Au). Simple use of these high resistive metals or semi-metals would raise the resistance of the electrodes. Thus the prior structure adopted the extraction electrode (Au or Al) to reduce the resistance between the circuit patterns and the ohmic electrodes. The deposition of Au on the resistive material is also useful for wire-bonding between the electrodes and the pattern circuit pads. Prevention of oxidization of the ohmic electrodes necessitates the coating with Au. High heat resistance is also required for the ohmic electrodes in order to apply c-BN to heat-resistant semiconductor devices or optoelectronic devices for emitting the light ranging from ultraviolet rays to visible rays. However it has been noticed that the electrodes suggested by 4 to 7 lack the heat resistance. Titanium (Ti), zirconium (Zr) and hafnium (Hf) are metals with a high melting point among the ohmic electrodes proposed by 4 to 7. Thus someone may suppose that the ohmic electrodes fabricated with the high melting point metals should enjoy high resistance against heat. However the fact was otherwise to their surprise. The electrode of (c-BN)/(ohmic electrode of Ti, Zr or Hf)/(Au) in strata has a drawback that Ti, Zr or Hf atoms easily diffuse into the Au surface layer by heating at about 300° C. which is far lower than the melting points of the materials. Diffusing through the Au layer, the refractory metal atoms attain the surface of the Au layer and cover the Au layer surface. The segregation of the refractory metal on the Au layer raises the contact resistance of the ohmic electrode. A moderate temperature such as about 300° C. impairs the property of the ohmic electrode by the precipitation of the metal on the extraction layer of Au. These devices are useless even at about 300° C. because of to the increment of resistance by the diffusion of the metal in the Au layer. Furthermore, even when the devices are operated by a large driving current at room temperature, the ohmic electrode Is heated at a temperature as high as 300° C by the generation of Joule's heat. The heat facilitates the diffusion of the high melting point metals in Au. Thus the drive of the devices even at room temperature degrades the performance of the device by increasing the extraction resistance by the deposition of metals on the top surface of the Au layer. A purpose of the present invention is to provide an ohmic electrode of c-BN which prevents the refractory metal Ti, Zr or Hf composing the electrode from diffusing in the Au layer till the top surface. Another purpose of this invention is to provide an ohmic electrode immune from the segregation of the high melting point metal on the Au layer. Another object of the invention is to provide a c-BN semiconductor device with high heat resistance by an ohmic electrode endowed with low resistance at high temperature. Still further object of this invention is to provide an optoelectronic device which can emit highly luminous rays from ultraviolet wavelength to visible light wavelength by a big current injection. SUMMARY OF THE INVENTION This invention proposes an ohmic electrode of an n-type cubic boron nitride comprising a first layer of a boride or a nitride of anyone selected from metals of Ti, Zr and Hf or of a boride or a nitride of an alloy including anyone selected from metals of Ti, Zr and Hf and a second layer of Au. This electrode is called type A. This invention further proposes anther ohmic electrode of an n-type cubic boron nitride comprising a first layer of low contact resistance, a second layer of diffusion-barrier layer and a third layer of Au. This electrode is called type B. Both types A and B are similar in the purpose and the function. First, type A is now explained. Type A of this invention has two layers. The first layer is borides or nitrides of Ti, Zr or Hf. The second layer is an Au layer. [TYPE A] First Layer: borides of Ti, Zr or Hf: TiB, TiB 2 , ZrB 2 , ZrB, HfB 2 , etc. nitrides of Ti, Zr or Hf: TiN, ZrN, HfN, etc. borides of alloys including at least a metal chosen from among Ti, Zr and Hf Second Layer: Au One way of producing the electrode is to make the two layers in succession. The first layer Is produced by depositing a film of a boride or a nitride of Ti, Zr or Hf, or a boride or a nitride of an alloy including Ti, Zr or Hf on an n-type cubic boron nitride crystal, and by alloying the film with the c-BN crystal in order to come into an ohmic contact. The reason of adopting Ti, Zr or Hf is that these materials enable the electrode to make an ohmic contact with the n-type cubic boron nitride. The reason for employing borides or nitrides is that borides or nitrides effectively prevent the atoms of Ti, Zr or Hf from diffusing into the upper Au layer. It Is desirable to form the first layer at a substrate temperature higher than 300° C. in order to make an ohmic contact and reduce the contact resistance of the electrode. Otherwise it is preferable to anneal the crystal at a temperature higher than 300° C., when the electrode has been formed on the n-type c-BN crystal at a temperature lower than 300° C. The heating of the electrode enables the metal Ti, Zr or Hf to diffuse downward into the n-type c-BN and to produce an alloy of BN and a metal of Ti, Zr or Hf partially on the surface. If the first layer were made only of metal Ti, Zr or Hf instead of borides or nitrides, the metal atoms would freely diffuse also upward into the top Au layer and would make a low-conductive alloy with Au, when the crystal is annealed at a temperature higher than 300° C. The electrode would be useless because of the increment of the resistance at the top layer. Another way to make the electrode is to produce the first electrode, process the first electrode and fabricate the second layer. In this case, a single element metal of Ti, Zr or Hf is deposited on an n-type cubic boron nitride crystal at a substrate temperature either higher than 300° C. or lower than 300° C. The high temperature coating of the monoelement metal forms a compound of the metal and the bottom BN crystal. Then the first layer naturally becomes a mixture of a boride and a nitride of the deposited metal. If the monoelement metal Is replenished on the n-type c-BN below 300° C., the BN crystal shall be heated above 300° C. in order to yield a boride and a nitride of the deposited metal. This way produces a nitride and a boride from a single element metal on the crystal. Then unreacted metal may remain in the surface of the first layer. The residual, unreacted metal Ti, Zr or Hf should be eliminated by solving selectively with an acid. If the metal remained in the first layer, the resistance of the electrode would increase by the formation of alloys of Au with Ti, Zr or Hf which diffused into the top Au layer by heating. Then the second layer becomes a mixture of a boride and a nitride. Finally Au is deposited on the first layer. The Au forms the second top layer. Second, type B is explained. The second layer of borides or nitrides is separated into two layers In type B. Thus type B electrode has three layers. [TYPE B] First layer: low contact resistance layer: a single element or an alloy of Ti, Zr, Hf, B, Al, Ga, In, V, Nb or Ta or a metal Including Si or S. Second layer: diffusion barrier layer: a single element metal or an alloy of W, Mo, Ta or Pt Third layer: Au layer The low contact resistance layer is made from a material which enables n-type BN to make an ohmic contact of a low resistance with it. In particular, a metal of Ti, Zr or Hf or an alloy including Ti, Zr or Hf is suitable for the low contact resistance first layer. The diffusion barrier layer inhibits the material of the first layer from diffusing through the second layer. This name does not signify that the layer prevents the material of the second layer itself from diffusing out of the own layer. The second layer prohibits the low contact resistant material from diffusing upward into the top Au layer. The transference of the first layered material is forbidden by the diffusion barrier layer. The diffusion barrier layer is made from a single element metal of W, Mo, Ta or Pt or an alloy of W, Mo, Ta or Pt. Since the diffusion barrier layer plays the role of inhibiting Ti, Zr, Hf, etc., too thin layer is useless. The barrier layer requires more than 100 nm of thickness. The more thick second layer can suppress the diffusion of Ti, Zr, Hf, etc. more rigorously. However, a too thick barrier layer pushes up the cost of material. Further, the resistance of the barrier layer increases in proportion to the thickness of the layer. The lower resistance is more favorable for an ohmic electrode. Less than 2 μ m is preferable for the thickness of the diffusion barrier layer. Thus the optimum thickness of the diffusion barrier layer is 100 nm to 2 μ m. The low contact resistance is achieved either by forming the low contact resistant material metal layer on the n-type c-BN (n-c-BN in short) substrate at a temperature higher than 300° C. or by forming the low contact resistant material layer on the n-c-BN substrate at a temperature lower than 300° C. and by annealing the layer at a temperature higher than 300° C. The formation or annealing above 300° C. produces an alloy of the material with the n-c-BN, and makes an ohmic contact with low resistance. The function of the electrodes is now clarified. The Inventors have discovered the fact that the barrier layer can prohibit the mutual diffusion between Au and a low contact resistant material by interposing the barrier layer between the Au layer and the low contact resistance layer for the first time. The structure B is based upon this discovery. The first layer shall be built by the materials of a single element of Ti, Zr, Hf, B, Al, Ca, In, V, Nb or Ta and an alloy of same or a metal including SI or S. A sufficiently low contact resistance ohmic electrode can be made, in particular, by a metal or an alloy of Ti, Zr or Hr. The diffusion barrier layer is formed by a metal selected from the group of W, Mo, Ta and Pt. The barrier layer made from these materials can prevent the reciprocal diffusion of Au and the low contact resistant material. It is not fully clear yet why the material can suppress the mutual thermal diffusion between Au and one of Ti, Zr, Hf, etc. However, the following explanation may outline the function of a barrier. W, Mo, Ta and Pt are all refractory metals of high melting points. Atoms build up a strong lattice structure with high cohesion energy. It is difficult to replace a host atom with an alien atom in the high melting point metal, because the replacement requires a break of the strong bonds between the host atoms. Diffusion is a phenomenon of the pervasion of foreign atoms from low concentration regions to high concentration regions along the gradient of the concentration by thermal agitation. The bonds are successively exchanged between the host atoms and the impurity atoms in a metal bond. The exchange of the bonds is gradually progressing from the surface to the inner portion. Replacement of the strong coupling in a high melting point metal demands an extremely high temperature. A temperature of 300° C. or a temperature slightly more than 300° C. for annealing or practical use is still insufficient to induce such a replacement of matrix atoms by alien atoms in the refractory metal. The strong atomic coupling enables W, Ta, Mo or Pt to forbid alien atoms invading in the metal. Thus W, Ta, Mo or Pt effectively inhibits the mutual diffusion between Au and one of Ti, Zr, Hf, etc. The heating for forming or annealing the low contract resistance layer does not induce the thermal diffusion of the low contact resistive material to the Au layer. The Au top layer is not degraded by alloying with Ti, Zr, Hf, etc. The ohmic electrodes still maintain the reciprocal, symmetric low resistance in spite of the high temperature invited by the production of Joule's heat by a big current flow. The above is the function of the structure B. The function of the structure A is further clarified. The structure B features contrivance on the composition of materials for impeding the low contact resistance material from diffusing instead of the interposition of the diffusion barrier layer. The inventors have discovered that what diffuses into the Au layer is the unreacted remains of Ti, Zr or Hf, when ohmic electrodes are made on n-c-BN with one of Ti, Zr, Hf, etc. if no unreacted metal remained in the bottom layer of the electrode, no diffusion would occur. Thus the structure B adopts borides or nitrides in order to avoid the diffusion. In the structure B, a boride or a nitride of Ti, Zr, Hf, etc. composes the first layer with a low contact resistance instead of a single element metal of Zr, Ti, Hf, etc. The atoms of Zr, Ti, Hf, etc., In borides or nitrides are far more stable and immovable than a single element metal of Zr, Ti, Hf, etc., because borides or nitrides have strong bonds between B atoms or N atoms and other metal atom. If the atoms would diffuse, the atoms must transfer as a molecule of a boride or a nitride. The big size of the compounds makes it more difficult to move in the crystal structures. The Ti, Zr, Hf, etc., do not diffuse into the Au top layer during the annealing or the practical use. Thus Ti, Zr, Hf, etc. do not reveal on the top surface of the Au layer. On the contrary, there may be a probability of an increase of the contact resistance or a conversion to a non-ohmic contact by the boridation or nitridation of the low contact resistant materials, i.e. Ti, Zr, Hf, etc. This may be a big problem. However the inventors have confirmed that the ohmic contact and the low contact resistance are maintained in spite of the nitridation or boridation. The electrodes with the boride or nitride first layers exhibit sufficiently low and reciprocal resistances. Two methods are available for making the layers of borides or nitrides as the first layers. Starting from a boride or nitride itself, one method makes boride layers or nitride layers by evaporating, sputtering or ion-plating the boride or nitride of a metal of Ti, Zr, Hf, etc. Starting from a metal of Ti, Zr, Hf, etc., the other method either forms metal layers on a n-type c-BN substrate at a sufficiently high temperature for inducing boridation or nitridation with the substrate elements, or forms metal layers at a lower temperature and anneals the metal layers into boride or nitride layers by letting the metal react with the substrate elements. In the latter case, if the metal of Ti, Zr, Hf, etc., remained, the active metal atoms would diffuse and appear on the top surface of the Au layer. Thus the probable residual metal should be removed. Then the metal atoms are eliminated by an acid treatment. The Au is further evaporated on the cleaned surface without metal atoms. This invention succeeds in fabricating a highly heat resistant ohmic contact electrode with low resistance on n-type c-boron nitride crystals. This invention is, in particular, suitable for the production of heat-resistant semiconductor devices which are used in a high temperature atmosphere. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a c-BN substrate with a pair of electrodes of structure A on both surfaces to measure the resistance of the electrodes. FIG. 2 is a sectional view of a c-BN substrate with a pair of electrodes of structure B on both surfaces to measure the resistance of the electrodes. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [EMBODIMENTS AND COMPARISONS] Various electrodes are fabricated with different materials, thicknesses, methods of production, substrate temperatures, anneal temperatures and acid treatment. These embodiments correspond to structure A and structure B. Besides the embodiments, comparison examples are also produced. In every sample, the top layer is an Au film which is made by vacuum evaporation. In order to inspect the influence of heating on the contact resistance, all the samples are annealed in 30 minutes at 500° C. at a pressure of 1×10 -5 Torr. The resistances of all the samples are measured before and after the annealing treatment. The resistances are measured by the four terminal method. Table 1 and Table 2 show the results of the measurements. Table 1 corresponds to structure A. Samples 1 to 15 are embodiments of structure A of the invention. Samples 16 to 20 are comparison examples. Table 1. Structure A: Dependence of the change of resistance of electrodes upon materials, thicknesses, production methods, substrate temperatures, annealing temperatures, or acid treatment TABLE 1__________________________________________________________________________Structure A substrate annealing acid treatment change thickness temperature temperature before ofNo. electrode (nm) method (°C.) (°C.) Au evaporation registance__________________________________________________________________________1 TiN 20 sputtering 300 Non Non 1.12 TiB.sub.2 15 sputtering 350 Non Non 1.83 ZrN 20 sputtering 300 Non Non 1.54 ZrB.sub.2 20 sputtering 400 Non Non 1.25 HfN 15 sputtering 300 Non Non 1.36 HfB.sub.2 20 sputtering 350 Non Non 1.17 TiN 20 sputtering room temp. 400 Non 1.28 ZrB.sub.2 15 sputtering room temp. 300 Non 1.39 HfN 20 sputtering room temp. 350 Non 1.810 Ti 30 sputtering 300 non Non 1.511 Zr 25 sputtering room temp. 350 Fluoric acid 1.412 Hf 30 sputtering 350 Non Fluoric acid 1.213 TiC 25 sputtering 350 Non Fluoric acid 1.614 ZrB.sub.2 20 sputtering room temp. 300 Fluoric acid 1.815 HfSi 25 sputtering room temp. 400 Fluoric nitric acid 1.416 Ti 20 sputtering 250 Non Non 1117 Ti 20 sputtering room temp. 250 Non 1018 Ti 30 sputtering 350 Non Non 1219 Zr 25 sputtering 250 Non Non 1620 HfSi 25 sputtering room temp. 400 Non 14__________________________________________________________________________ The first column denotes sample numbers. The second column signifies the materials of the contact layer of electrodes. The third column designates the thicknesses (nm) of the contact layers. The fourth column is the methods of producing ohmic electrodes. The fifth column denotes the temperatures of n-type c-BN substrates at the formation of the contact layers. The sixth column means the temperatures of annealing. "Non" signifies that the sample is not annealed. The seventh column designates whether the contact layer is treated with an acid or not, before the evaporation of Au. "Non" means that the sample is not treated with an acid. If the samples are treated with acid, the names of the acid are listed. The eighth column signifies the change of contact resistances by the heating test. The change of the resistance is defined by a quotient of the post-heating resistance divided by the pre-heating resistance. The effects of the anneal will now be clarified for each sample. [Samples 1 to 6] Samples 1 to 6 make the first layer by sputtering a target of a boride or a nitride of Ti, Zr or Hf into particles and depositing the sputtered particles on a cubic boron nitride substrate heated at a temperature more than 300° C. Sample 1 has a TiN first layer of a thickness of 20 nm. Sample 2 makes a TiB 2 film of a 15 nm thickness. Sample 3 is provided with a ZrN film of a thickness of 20 nm. Sample 4 produces a ZrB 2 film of a 20 nm thickness. Sample 5 has a 15nm HfN layer. Sample 6 covers c-BN with a 20 nm HfB 2 film. Samples 1, 3 and 5 are heated at 300° C. Samples 2 and 6 are heated at 350° C. Sample 4 is heated at 400° C. The purpose of heating the substrate above 300° C. is to lower the contact resistance between the first layer and the c-BN substrate. Since the films have been yielded at a high temperature, samples 1 to 6 are annealed no more. No metal remains on the layer, because metal is not employed as a starting material. This fact enables the omission of the acid treatment. Samples 1 to 6 hardly increase the contact resistances of electrodes in spite of the heating of 500° C. in 30 minutes under a pressure of 10 -5 Torr. Sample 1 raises the resistance only by 1.1 times by the heat-treatment. Sample 2 heightens the resistance 1.8 times as large as the pre-heating resistance. Sample 3 has a post-heating resistance 1.5 times as large as the pre-heating resistance. Sample 4 (ZrB 2 ) submits to a slight increase of 1.2 times in a contact resistance. Sample 5 reveals only a 1.3 times increment. Sample 6 (HfB 2 ) shows a smallest increase of 1.1 times. The increases of the contact resistance by the heating test are commonly less than 1.8 times for all samples 1 to 6. [Samples 7 to 9] Samples 7 to 9 fabricate a boride or nitride first layer on a c-BN substrate at room temperature by sputtering a boride or nitride of Ti, Zr or Hf, anneal the first layer at a temperature higher than 300° C. and deposit an Au layer on the first boride or nitride layer. The formation at a low temperature requires annealing of above 300° C. to reduce the contact resistance. Sample 7 makes a TiN film at room temperature and anneals it at 400° C. Sample 7 increases the resistance only by 1.2 times by the heat treatment of 500° C. for 30 minutes. Sample 8 produces a ZrB 2 film at room temperature and anneals it at 300° C. The heating-test of 500° C. for 30 minutes only heightens the resistance by 1.3 times of sample 8. Sample 9 produces an HfN film at room temperature and anneals it at 350° C. The multiplier of resistance by the heating test is 1.8 for sample 9. The increments of resistance are all less than 1.8 for samples 7 to 9. [Samples 10 to 12] Samples 10 to 12 once deposit a single element metal film of Ti, Zr or Hf on a c-BN crystal by sputtering a target of Ti, Zr or Hf and convert the metal film into a boride or a nitride by the reaction with the c-BN substrate. Samples 10 to 12 either sputter the metal film at a temperature more than 300° C. or anneal the film at a temperature higher than 300° C. Heating above 300° C. at the film formation or at the annealing enables the metal to react with the element atoms of c-BN substrates. Since unreacted metal atoms remained on the first layer, the metal would diffuse to the top of the Au layer. Therefore the residual metal atoms are eliminated from the surface of the first layer by fluoric acid or fluoric nitric acid. Sample 10 makes a Ti film by sputtering a Ti target on a c-BN substrate at 300° C. and treats the substrate with fluoric acid. Then an Au layer is produced on the first layer. The constant resistance increases 1.5 times by the heat-treatment test of 500° C. for 30 minutes in sample 10. Sample 11 coats a c-BN substrate at room temperature with a Zr film by sputtering a Zr target and subjects the first layer with the c-BN to heat at 350° C. The Zr reacts with boron or nitride atoms of the BN crystal and makes compounds of ZrN and ZrB 2 . Metal Zr is completely removed by fluoric acid from the surface. Then an Au film is deposited on the layer. Sample 11 submits to a 1.4 times increase of resistance by the heat-test. Sample 12 sputters Hf metal, piles Hf atoms on a c-BN substrate at 350° C. and makes a boride and nitride film of Hf by the reaction induced by the high temperature. The resultant Hf metal is eliminated by fluoric acid. Finally an Au layer is made on the first layer. The heat-test of 500° C. for 30 minutes induces only a 1.2 times increase of the contact resistance in sample 12. [Samples 13 to 15] Samples 13 to 15 start from a compound of Ti, Zr or Hf, e.g. TiC, ZrB 2 or HfSi. Samples 13 to 15 either make a film of an alloy of Ti, Zr or Hf on a c-BN crystal at a high temperature by sputtering or deposit a film of the alloy on a c-BN crystal at room temperature and subject it to heat above 300° C. The high temperature transforms the alloys into borides or nitrides. Either fluoric acid or fluoric, nitric acid eliminates the resultant metal atoms from the surface of the first layer. Then an Au film is evaporated. Sample 13 sputters a TiC target into TiC molecules and piles the TiC molecules on a c-BN substrate at 350° C. and makes a film of TiN and TiB 2 . The extra TiC is removed by fluoric acid. An Au layer is deposited on the TiC layer. The resistance of sample 13 becomes 1.6 times as large as the pre-heating resistance the heat-test of 500° C. for 30 minutes. Sample 14 forms a ZrB 2 layer on a BN substrate at room temperature by sputtering a ZrB 2 target, subjects the electrode to heat at 300° C., and treats the first layer with fluoric acid. Finally the first is covered with an Au layer. The resistance increases by 1.8 times due to the heating test. Sample 15 makes an HfSi film on a BN substrate at room temperature by sputtering, anneals it at 400° C. in order to convert the HfSi to an HfB 2 and HfN layer. Then sample 15 is treated with fluoric, nitric acid. The heating test raises the resistance by 1.4 times. [Comparison examples: samples 16 to 18] Samples 16 to 18 produce metal Ti films on BN substrates and cover the layers with Au layers without acid treatment. What is sputtered is neither boride nor nitride but single element metal Ti. Heating test allows Ti atoms to diffuse into the Au top layer owing to either the reaction temperature less than 300° C. or the lack of the acid treatment. Sample 16 falls in converting metal Ti into a boride or a nitride, since Ti is deposited on a substrate of a low temperature of 250° C. But the Ti layer is neither annealed above 300° C. nor treated with an acid. Metal Ti remains on the TiB 2 and TiN surface. The heat-test of 500° C. for 30 minutes raises the resistance of sample 16 by 11 times. Sample 16 is useless as an ohmic electrode, since the contact resistance is raised by heating. The residual metal Ti incurs the weak heat resistance of sample 16. Sample 17 deposits Ti on a BN substrate at room temperature and subjects the Ti film to heat at 250° C. Acid treatment is omitted. The low temperature annealing leaves some part of metal Ti unreacted on the surface. Heating facilitates the diffusion of metal Ti into the Au top layer. The diffusing Ti lowers the conductivity of Au by making an alloy of Au and Ti. Thus the heating test raises the resistance to a big extent. The post-heating resistance is ten times as large as the pre-heating resistance. Sample 18 sputters a Ti target and plies sputtered Ti atoms on a BN substrate at 350° C. The Ti layer experiences neither annealing nor acid treatment. The deposition of 350° C. transforms most of the Ti atoms into TiB 2 and TiN. But some part of Ti is left and unreacted as metal atoms. The metal Ti is no more eliminated, since acid treatment is not done. The post-heating resistance is 12 times as big as the pre-heating resistance. The enhancement of resistance results from the diffusion of Ti in the Au layer. Sample 19 sputters a Zr target and deposits Zr atoms on a BN substrate heated at 250° C. Zr partially changes into ZrB 2 and ZrN. However some portion of Zr remains as a single element. The Zr film is neither annealed nor treated with an acid. Omission of the acid treatment allows metal Ti to diffuse into the Au top layer. The heating test enhances the contact resistance by 16 times. Sample 20 sputters HfSi and piles HfSi molecules on a BN substrate at room temperature. The HfSi layer is annealed at 400° C. Without acid treatment, an Au layer is fabricated on the first layer of Hf. The contact resistance is heightened about 14 times bigger by the heating test of 500° C. for 30 minutes. The annealing of 400° C. converts almost all Hf into HfN and HfB 2 . But some portion of Hf remains movable atoms. The heating test expedites the diffusion of Hf to the top layer. Alloying Au with Hf decreases the conductivity. Samples 16 to 20 are inappropriate for ohmic contact electrodes of semiconductor devices which will be used in a hot atmosphere, because heating induces a big increase of the resistance of the electrodes. Table 2. Structure B: Dependence of the change of resistance of electrodes upon metals, thicknesses, production methods, substrate temperatures, annealing temperatures, or acid treatment. TABLE 2__________________________________________________________________________Structure B substrate annealing change thickness temperature temperature ofNo. electrode (nm) method (°C.) (°C.) registance__________________________________________________________________________21 Ti/W 20/200 sputtering 300 Non 1.222 Ti/W 20/200 sputtering room temp. 300 1.623 Ti/Mo 35/100 sputtering 350 Non 1.524 Zr/Ta 25/250 sputtering 300 Non 1.825 Hf/Pt 20/200 sputtering room temp. 400 1.626 V/Mo 30/350 sputtering room temp. 300 1.127 Nb/W 30/150 sputtering 400 Non 1.228 Al/W 25/200 sputtering 300 Non 1.129 B/Mo 20/100 sputtering room temp. 350 1.530 TaSi/Pt 30/250 sputtering 350 Non 1.231 Ti/WC 20/150 sputtering 300 Non 1.832 Zr/MoSi 25/300 sputtering room temp. 350 1.633 Hf/TaB 25/250 sputtering 400 Non 1.434 Zr/W 20/100 sputtering room temp. 300 1.2 (after Zr formation before W formation)35 Ti/W 20/50 sputtering 300 Non 5.136 Ti/Mo 25/70 sputtering 350 Non 4.637 Zr/Mo 30/80 sputtering room temp. 400 4.238 B 30 sputtering 350 Non 15__________________________________________________________________________ Then structure B is clarified in accordance with embodiments and comparison examples. Table 2 shows the examples of structure B. The first column is sample numbers. The second column denotes materials of the first layer and the second layer of the electrode. The first layer is a low contact resistance layer. The second layer is a diffusion barrier layer. The third column designates the thicknesses of the first and the second layers. The fourth column signifies the methods of producing the layers. The fifth column means the substrate temperatures (°C.) at the formation of the layers. The sixth column denotes whether the sample is annealed or not and the annealing temperature, if annealed. "Non" means that the sample is not annealed. The seventh column is the ratios of the post-heating resistance divided by the pre-heating resistance. The resistances of the electrodes are measured by the four probe method. The heating test is a test examining the change of the samples by heating samples at 500° C. for 30 minutes under a pressure of 10 -5 Torr. The second layer is covered with an Au layer of a 200 nm thickness by evaporation. Samples 21 to 34 are embodiments. Samples 35 to 38 are comparison examples. [Samples 21 to 25] The first layer (low contact resistance layer) is any one of Ti, Zr and Hf. The first layer is either deposited at a temperature higher than 300° C. or annealed at a temperature higher than 300° C. The second (diffusion barrier) layer is made from W, Mo Ta or Pt. The third layer is an Au layer of a 200 nm thickness in common. Sample 21 sputters Ti into particles, piles the Ti particles of a thickness of 20 nm on a c-BN heated at 300° C. Then W is sputtered and deposited into a 200 nm thick film on the Ti layer. Without annealing, Au is finally evaporated on the W layer. The heating test of 500° C. for 30 minutes multiplies the resistance of the three-layered electrode by 1.2. This proves the fact that W is suitable for stopping diffusion of Ti atoms. The small multiplier exhibits an excellent heat-resistance of sample 21. Sample 22 makes a 20 nm thick Ti layer on a c-BN substrate kept at room temperature by sputtering a Ti target, subjects the first layer to heat at 300° C. and forms a W (barrier) layer of a 200 nm thickness by sputtering. Finally an Au layer of a 200 nm thickness is evaporated on the W layer. The resistance is raised by 1.6 times by the heating test of 30 minutes at 500° C. Sample 23 heats a c-BN substrate at 350° C., forms a 35 nm thick Ti layer on the BN substrate and makes a 100 nm thick Mo (barrier) layer on the Ti layer. Then the W layer is covered with an Au layer of a 200 nm thickness. The ratio of the post-heating resistance to the pre-heating resistance is only 1.5. The result signifies that W is also useful for a barrier against the diffusion. Sample 24 makes a 25 nm thick Zr layer on a c-BN substrate heated at 300° C. as a low contact film. Without annealing, a 250 nm thick Ta barrier layer is produced on the Zr layer. Then Au is evaporated into a 200 nm thick film on the Ta layer. The heating test of 500° C. for 30 minutes reveals a 1.8 times increase of the resistance of the electrode. Sample 24 exhibits the usefulness of Zr as the low contact material and the probability of Ta as a barrier. Sample 25 makes a 20 nm Hf film on a c-BN substrate at room temperature and produces a 200 nm W film on the Hf film at room temperature. Then the films are annealed at 400° C. The resistance rises by 1.6 times by the heating--test. Sample 25 shows that Zr is also suitable for a low contact material and W is pertinent to a barrier. [Samples 26 and 27] V and Nb are employed as the material of the first low contact layer. V and Nb have been proposed by 7 Japanese Patent Laying Open No. 4-29378. Sample 26 forms a V layer of a 30 nm thickness on a C-BN substrate at room temperature by sputtering and subjects the layer to heat at 300° C. Sputtering makes a 350 nm thick Mo layer as a barrier layer. Then an Au top layer of a 200 nm thickness is produced on the Mo layer. The heating test of 500° C. for 30 minutes invites only a 1.1 times increase of the resistance. Sample 26 signifies that V is useful for a low contact metal and that Mo is effective as a barrier. Sample 27 heats a c-BN substrate to 400° C., sputters Nb into particles, deposits Nb particles on the c-BN crystal and further makes a W layer by sputtering. Without annealing, an Au layer is produced on the W barrier film. The heating test of 500° C. for 30 minutes invites only a 1.1 rise of the resistance. Sample 27 exhibits the excellency of Nb as a low contact material and of W as a barrier. [Samples 28 to 29] The first low contact layer is made from Al or B, which has suggested by 6Japanese Patent Laying Open No. 4-29377. Sample 28 makes an Al contact layer of a 25 nm thickness on a c-BN heated at 300° C. by sputtering. An Mo layer is deposited till a 100 nm thickness on the Al layer by sputtering. A 200 nm Au layer at 300° C. is formed on the Mo layer. The heating test brings about a slight increase of resistance of 1.6 times. Sample 29 makes a 20 nm B film and a 100 nm Mo film on a c-BN substrate at room temperature, and anneals the films at 350 ° C. Then an Au layer is deposited on the films. 1.5 is the multiplier of the change of resistance before and after the heating test of 500° C. for 30 minutes. Sample 29 exhibits the effective use of B as a low contact material and the excellency of Mo as a barrier. [Sample 30] An alloy of Ta is adopted as a material of the first layer. The use of a Ta alloy has been suggested by 7 Japanese Patent Laying Open No. 4-29378. Sample 30 forms a 30 nm thick TaSi layer on a c-BN substrate heated at 350° C. by sputtering, covers the TaSi by a Pt layer of a 250 nm thickness and deposits an Au layer of a 200 nm thickness. The resistance rises by 1.2 times by the heating test of 500° C. for 30 minutes. This proves the suitability of Ta as a low contact material and of Mo as a barrier. [Samples 31 to 33] The first (low contact resistance) layers are made from any one of single element metals Ti, Zr and Hf, which have been proposed by 4 Japanese Patent Laying Open No. 4-29375. The second layer is built with an alloy of any one of W, Mo, Ta and Pt. Sample 31 makes a 20 nm thick Ti layer on a c-BN substrate heated to 300° C. by sputtering, forms a WC barrier layer of 150 nm on the Ti layer by sputtering, and finally covers the WC layer with an Au layer of 200 nm. The heat test of 500° C. for 30 minutes multiplies a resistance by 1.8 times. Sample 31 clarifies the adequacy of the low contact layer of Ti and the barrier of WC. Sample 32 yields a Zr layer of 25 nm by sputtering on a c-BN substrate at room temperature, anneals the Zr film at 350° C., makes an MoSi film on the Zr layer by sputtering, and covers the MoSi film with an Au film of a 200 nm thickness. The annealing forms an ohmic contact of Zr with the n-type BN. The post-heating resistance is 1.6 times as big as the pre-heating one. This proves the suitability of MoSi as a candidate for a barrier. Sample 33 makes an Hf layer of 25 nm by sputtering on a c-BN substrate at 400° C. Without annealing, another sputtering makes a TaB barrier layer on the Hf layer. An Au layer is deposited on the TaB layer. The change of the resistance is 1.4 times by the heating test. This example clarifies the capability of boride of tantalum (TAB) for a barrier material. [Sample 34] The first layer is a single element metal of Zr. The second layer is made from W. Sputtering makes a 20 nm thick Zr layer on a cool BN substrate, and subjects the Zr layer to heat at 300° C., and another sputtering process forms a 100 nm W layer on the Zr layer. Finally Au is deposited on the V/layer. The heat test multiplies the resistance only by 1.2 times. [Samples 35 to 38: comparison examples] Samples 35 to 38 have a too thin diffusion barrier layer to prohibit the low contact resistant material from diffusing upward to the Au layer. Sample 35 makes a 20 nm thick Ti layer by sputtering on a c-BN substrate at 300° C. and produces a 50 nm thick W layer on the Ti layer. The heating test of 500° C. for 30 minutes raises the resistance by 5.1 times. This result signifies that too thin barrier layer is insufficient to impede Ti atoms from diffusing. The barrier requires a sufficient thickness. In sample 36, sputtering makes a 25 nm Ti layer on a c-BN substrate at 350° C. Another sputtering makes a 70 nm thick Mo barrier on the Ti layer. The contact resistance is multiplied by 4.6 by the heating test of 500° C. for 30 minutes in sample 36. The 70 nm thick Mo layer is impotent to hinder the diffusion of Ti atoms entirely. Sample 37 makes a Zr layer of a 30 nm thickness on a cool c-BN substrate, anneals the Zr layer at 400° C., and produces an Mo layer of a 80 nm thickness on the Zr layer by sputtering. An Au layer is produced on the Mo layer. The resistance is raised by 4.2 times by the heating test of 500° C. for 30 minutes. The Mo barrier of 80 nm is too thin to forbid Zr diffusing to the Au layer. Sample 38 heats a c-BN substrate at 350° C., sputters a B target, and forms a 30 nm thick B layer on the heated BN substrate. Without building a barrier layer, an Au layer is deposited on the B layer. The resistance of the electrode is multiplied by 15 times by the heating test of 500° C. for 30 minutes. The big increase of resistance is caused by the diffusion of B atoms into the Au layer. The diffused B atoms make an alloy with Au having a high resistivity. Sample 38 proves the importance of the barrier layer in the ohmic electrodes. All samples 1 to 38 have been explained till now. The electrodes of this invention are commonly favored with a low resistance similar to the resistance of a bulk Au metal. The electrodes maintain the golden color in spite of the heating test of 500° C. for 30 minutes. This means that the low contact resistive materials do not diffuse into the Au top layer by the heating test. The Au layer is left unpolluted with the metals of Ti, Zr, Hf or other materials of the first layer. No diffusion into the Au layer is proved by the fact that the resistance is hardly increased by the heating test in the embodiments of samples 1 to 15 and samples 21 to 34. The multipliers are all less than 1.8 in the embodiments. On the contrary, comparison examples (16 to 20 and 35 to 38) have all experienced a big increase of the resistance by the heating test. All samples lose the golden color from the surface of the top layer due to alloying of Au with other metals. The contact resistances are raised by more than 5 times by the heating test of 500° C. for 30 minutes. Samples 35 to 37 with a barrier layer, even if imperfect, still suppress the increase less than ten times. However sample 38 which lacks the barrier suffers from the big resistance increase of more than 10 times. Then the components of the surfaces of the electrodes have been analyzed for comparison examples 16 to 20 and 35 to 38. The component analysis clarifies that the top layers have lost almost all Au and are occupied by the material of lower layers. This fact signifies that the materials of lower layers have diffused directly or indirectly through the intermediate layers into the Au top layers. Furthermore, samples 1 to 15 and samples 20 to 34, embodiment of this invention are estimated by the absolute resistance. In order to measure the absolute value of the resistances, a pair of two-layered electrodes are fabricated on both surfaces of samples 1 to 15 as shown in FIG. 1. Similarly a pair of three-layered electrodes are produced on both surfaces of samples 21 to 34 as shown in FIG. 2. In the sandwich structure, the current is measured for the applied voltage on both electrodes. The total resistance is deduced from the voltage and the current. The contact resistance of the electrodes is calculated by subtracting the inherent resistance of the BN substrate. All the embodiments have very low contact resistances less than 6×10 -1 Ω cm. This is one of a preferable region of the contact resistance of an ohmic electrode. The sandwich structure of electrodes of FIG. 1 or FIG. 2 is again heated at 500° C. for 30 minutes under a pressure less than 10 -5 Torr. The resistances do not increase by the heating test. The resistance is stable despite the heating test. This fact proves an excellent heat-resistance of the electrodes of this invention. This invention is suitable for the electrodes of the devices which will be used in a high temperature atmosphere.

N-type c-BN is a heat-resistant material with a wide band gap. Ohmic electrodes are indispensable for making semiconductor devices utilizing n-type c-BN. The electrodes proposed so far are likely to deteriorate in an atmosphere of high temperature. The degradation of electrodes hinders the production of semiconductor devices utilizing c-BN. A heat-resistant ohmic electrode is produced by forming a low contact resistance layer of a boride or a nitride of Ti, Zr or Hf on a heated c-BN and by covering the low resistance layer by an Au layer. Otherwise an ohmic electrode is produced by forming a low contact resistance layer of one of Ti, Zr, Hf, etc. on c-BN, making a diffusion barrier layer of W, Mo, Ta or Pt and depositing an Au layer on the diffusion barrier layer.

SUMMARY The present invention relates to cyclopentanophenanthrene derivatives and to certain novel compounds obtained as intermediates. More particularly, the present invention relates to compounds represented by the formula: ##STR1## wherein R 11 is chloro or hydroxy; R 16 independently is methyl; R 17 independently is hydroxy or acyloxy having 2 to 8 carbon atoms or R 16 and R 17 taken together are 16α,17α-isopropylidenedioxy; R 21 is lower alkyl having 1 to 8 carbon atoms; X 1 and X 2 are independently hydrogen, chloro or fluoro, with the proviso that when R 11 is chloro, X 2 is chloro; Y is OR 21 , SR 21 ' , bromo, chloro, cyano, thiocyano or azido in which R 21 ' is lower alkyl having 1 to 8 carbon atoms or phenyl and R 21 is defined as above, but independent thereof, and Z is a single or double bond. A preferred subclass of compounds within the class defined by formula (A) are those compounds wherein Y is OR 21 . Preferred compounds within this subclass are the symmetrical 21,21-bis-alkyl esters. Particularly preferred compounds are the 21,21-bis-methyl ethers. In addition, the present invention relates to certain compounds obtained as intermediates in the preparation of compounds of Formula (A) and exhibiting similar pharmacological activity. These novel intermediates are represented by the formulas: ##STR2## wherein X 1 ' is hydrogen, chloro and fluoro when Z is a single bond and chloro or fluoro when Z is a double bond; R 11 , R 16 , R 17 , R 21 and X 2 are as previously defined and all R 21 s are identical. Preferred compounds embraced by Formulas (B) and (C) are those wherein R 21 is methyl or ethyl. The compounds of the instant invention are potent topical anti-inflammatory agents. Although the instant compounds exhibit low systemic activity in the rat as measured in standard assays, e.g. Rat Thymolytic Assay and the Anti-inflammatory Assay Utilizing Carrageenan-induced Rat Paw Edema, they exhibit high topical activity in humans as measured in the Stoughton-McKenzie Assay (Human Vasoconstrictor Assay). In spite of the fact that systemic effects such as adrenal atrophy, mineralocorticoid effects and collagen disorders may be produced by large doses of the instant compounds if administered for long periods of time, the favorable topical/systemic activity ratio of the instant compounds permits the use of such small doses that these systemic effects are minimized. This combination of high topical anti-inflammatory activity coupled with negligible systemic activity renders the instant compounds highly suitable for the alleviation of inflammatory disorders. The present invention further relates to a method for treating symptoms associated with inflammatory disorders, which method comprises administering an effective amount of a compound selected from those represented by formulas (A), (B), and (C), or a pharmaceutical composition incorporating such a compound as an active ingredient. The present invention still further relates to pharmaceutical compositions useful for treating inflammatory disorders. These compositions comprise an effective amount of a compound selected from those represented by formulas (A), (B), and (C) in admixture with a pharmaceutically acceptable non-toxic carrier. Suitable carriers or medicament vehicles for topical application of the novel steroids of the instant invention include creams, ointments, lotions, emulsions, solutions, and the like. For example, a suitable ointment for topical application of compounds of the instant invention contains 15 to 45 percent of a saturated fatty alcohol having 16 to 24 carbon atoms such as cetyl alcohol, stearyl alcohol, behenyl alcohol, and the like and 45 to 85 wt. percent of a glycol solvent such as propylene glycol, polyethylene glycol, dipropylene glycol, and the mixtures thereof. The ointment can also contain 0 to 15 wt. percent of a plasticizer such as polyethylene glycol, 1,2,6-hexanetriol, sorbitol, glycerol, and the like; 0 to 15 wt. percent of a coupling agent such as a saturated fatty acid having from 16 to 24 carbon atoms, e.g., stearic acid, palmitic acid, behenic acid, a fatty acid amide e.g., oleamide, palmitamide, stearamide, behenamide and an ester of a fatty acid having from 16 to 24 carbon atoms such as sorbitol monostearate, polyethylene glycol monostearate, polypropylene glycol or the corresponding mono-ester of other fatty acids such as oleic acid and palmitic acid; and 0 to 20 wt. percent of the penetrant such as dimethyl sulfoxide, dimethylacetamide, dimethylformamide, and the like. The concentration of cortical steroid in pharmaceutical compositions suitable for topical application will vary depending upon the particular activity of the steroid used in conjunction with the condition and subject to be treated. In general, topical preparations containing 0.005 to 1% by weight of the active steroid are advantageously employed. In the specification and claims the following definitions apply: The wavy line ( ) used in the depicted formulas indicates that the substituent attached to those positions can be in either the (α) or (β) configuration. The broken line ( - - - ) used in the depicted formulas indicates that the substituent attached to those positions is in the α configuration. The unbroken line (--) used in the depicted formulas indicates that the substituent attached to those positions is in the β configuration. The term "lower alkyl" defines aliphatic hydrocarbons containing from 1 to 8 carbon atoms including all isomers thereof. Typical lower alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, n-amyl, n-hexyl, n-heptyl, n-octyl, and so forth. The term "acyloxy" refers to those esters employed in the cortical steroid art having from 2 to 8 carbon atoms and being derived from alkanoic or phenyl carboxylic acids. Typical acyloxy groups expressed as the ester include for example acetate, propionate, butyrate, valerate, caproate, enanthate, carpyrlate, benzoate and the like. Compounds of Formula (A) wherein Y and OR 21 are not identical exist in two epimeric forms, i.e., the 21(R) and 21(S) forms. Accordingly, all nomenclature, formulas and discussion herein is intended to refer to both forms and mixtures thereof unless otherwise specified. DETAILED DESCRIPTION The present invention, in a further aspect, is directed to methods for the preparation of compounds of Formulas (A), (B), and (C) according to the following reaction sequences: ##STR3## In the above formulas R 11 , R 16 , R 17 , R 21 , X 1 , X 2 , and Z are as previously defined; Y is OR 21 , SR 21 ' cyano, thiocyano or azido in which R 21 and R 21 ' are as previously defined; X is chloro or bromo; and X 1 ' is hydrogen, chloro or fluoro when Z is a single bond and chloro and fluoro when Z is a double bond. With reference to reaction steps 1-5, a 21-hydroxy steroid (1) is contacted with air in the presence of a copper (II) catalyst such as cupric acetate to yield the 21-aldehyde hydrate (2). The reaction is preferably conducted in methanol at a temperature of 50° to 30° C. for a period of 30 minutes to 6 hours. The 21-aldehyde hydrate (2) is then heated under vacuum at a temperature of 100° C. for a period of 30 minutes to 3 hours to yield the 21-aldehyde (3) which is reacted with a lower alkanol containing 1 to 8 carbon atoms at a temperature of 20° to 60° C. for a period of 15 minutes to 1 hour to yield the 21-aldehyde heniacetal (4). Reaction of the 21-aldehyde hemiacetal (4) with a suitable halogenating agent such as methane sulfonyl chloride, thionyl chloride, or thionyl bromide in the presence of an organic base such as triethylamine, pyridine and the like yields the 21-halo-21-alkyl ether (5). The reaction is preferably conducted in a chlorinated organic solvent such as methylene chloride, chloroform, 1,1-dichloroethane and the like for a period of 1 to 16 hours and a temperature of -20° to +10° C. The thus obtained 21-halo-21-alkyl ether (5) is then used to prepare the 21-aldehyde acetal ((6), Y=OR 21 ), the 21-azido-21-alkyl ether ((6), Y=azido), the 21-thiocyano-21-alkyl ether ((6), Y=thiocyano), the 21-cyano-21-alkyl ether ((6), Y=cyano), the 21-thiophenyl-21-alkyl ether ((6), Y=thiophenyl), and the 21-thioalkyl-21-alkyl ether ((6), Y=thioalkyl). Preparation of the 21-aldehyde acetal ((6), Y=OR 21 ) is accomplished by treating the 21-halo-21-alkyl ether (5) with an alkali metal alkoxide, preferably a sodium alkoxide such as sodium methoxide, sodium ethoxide, etc. The reaction is conducted in a solvent medium usually containing the alkanol corresponding to the alkoxide utilized although a solvent inert to the other reactants may be employed. Reaction temperatures are peferably maintained at 20° to 60° C. for a period of 2 to 6 hours. The 21-azido-21-alkyl ether ((6), Y=azido) is prepared by treating the 21-halo-21-alkyl ether (5) with an alkali metal azide, preferably sodium azide, in an aprotic inert organic solvent such as dimethylformamide, acetone, hexamethylphosphoramide, dimethyl sulfoxide and the like. The reaction is preferably conducted at a temperature of 20° to 60° C. for a period of 2 to 12 hours. Preparation of the 21-thiocyano-21-alkyl ether ((6), Y=thiocyano), the 21-cyano-21-alkyl ether ((6), Y=cyano), the 21-thiophenyl-21-alkyl ether, ((6), Y=thiophenyl) and the 21thioalkyl-21-alkyl ether ((6), Y=thioalkyl) is accomplished according to the procedure outlined in the previous paragraph, i.e., the 21-halo-21-alkyl ether (5) is treated with a suitable alkali metal salt such as potassium thiocyanate, sodium cyanide, sodium thiophenylate or a sodium thioalkylate in an aprotic inert organic solvent such as dimethylformamide, acetone, hexamethylphosphoramide, dimethyl sulfoxide and the like at a temperature of 20 to 80° C. for a period of 2 to 16 hours. Compounds of Formula (A) having identical R 21 groups are conveniently prepared via reaction steps 6-8 as follows: A 21-aldehyde hydrate (2) is treated with a trialkyl orthoformate such as trimethyl orthoformate, triethyl orthoformate, tri-n-propyl orthoformate and the like in the presence of a strong acid such as perchloric acid, p-toluenesulfonic acid, sulfuric acid and the like to obtain the 3-alkoxy-3,5-dien-21-acetal (B). The reaction is conducted in the presence of an alkanol corresponding to the trialkyl orthoformate employed at a temperature of 50° to 100° C. for a period of 2 to 12 hours. Treatment of the thus obtained 3-alkoxy compound (B) with a dilute inorganic acid such as hydrochloric acid, sulfuric acid and the like yields the 3-oxo-5-en-21-acetal (C). This reaction is preferably conducted in aqueous acetone at a temperature of 50° to 80° C. for a period of 30 minutes to 4 hours. Thereafter, the 3-oxo-5-en-21-acetal (C) is treated with a base such as sodium hydroxide, potassium hydroxide, ammonium hydroxide and the like to yield the 3-oxo-4-en-21-acetal (7). This reaction is preferably conducted in a solvent such as methylene chloride/methanol, aqueous acetone or methanol at a temperature of 30° to 60° C. for a period of 30 minutes to 4 hours. Alternatively, the 3-alkoxy-3,5-dien-21-acetal (B) can be treated with a higher concentration of a strong acid such as hydrochloric acid, perchloric acid, sulfuric acid and the like to yield directly the 3-oxo-4-en-21-acetal (7). This reaction is preferably conducted in aqueous acetone. For those 21-aldehyde hydrates (2) wherein Z is a double bond and X 1 is hydrogen, the reaction conditions of step 6 lead directly to compounds of formula (7). The 21-hydroxy steroid starting materials (1) used to prepare the 21-acetal and 21-difunctional compounds of the instant invention are available commercially or can be prepared according to known procedures. Information concerning the preparation of 21-hydroxy steroids suitable for use in the preparation of compounds of Formulas (A), (B), and (C) and be obtained, for example for U.S. Pat. Nos. 3,048,581 and 3,126,375; and from Fried et al., J. Am. Chem. Soc., 802, 338 (1958) and Mills et al., J. Am. Chem. Soc., 82, 3399 (1960). Additional information concerning the preparation of 21-hydroxy steroids suitable for use in the preparation of compounds of Formulas (A), (B), and (C) can be found for example, in U.S. Pat. Nos. 2,894,963, 3,013,033 and 3,119,748; and Edwards et al., Proc. Chem. Soc. (London), p. 87 (1959), Edwards et al., J. Am. Chem. Soc., 82, 2318 (1960), and Taub et al., J. Am. Chem. Soc., 80, 4435 (1958). DESCRIPTION OF SPECIFIC EMBODIMENTS The following specific description is given to enable those skilled in the art to more clearly understand and practice the present invention. It should not be considered as a limitation upon the scope of the invention but merely as being illustrative and representative thereof. EXAMPLE 1 6α,9α-difluoro-11β,16α,17α, 21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide To a slurry of 12.0 g. of 6α,9α-difluro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide in 130 ml. of dry methanol is added a solution of 0.68 g. of cupric acetate hydrate in 40 ml. methanol. Air is then sparged through the mixture for 2 hours. Thereafter, the mixture is evaporated to dryness and the residue is taken up in ethyl acetate and washed with water and then with a dilute aqueous solution of potassium bicarbonate and then again with water. The solution is evaporated to dryness and the resulting residue is then dissolved in acetone. The acetone solution is diluted with a substantial volume of water whereupon the resulting precipitate is filtered and dried under vacuum to yield 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide. EXAMPLE 2 6α,9α-difluoro-11β,16α,17α-trihydroxypregna-1,4-diene-3,20,21-trione-16,17-acetonide 6α,9α-difluoro-11β,16α ,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide (4.0 g.) is heated under high vacuum in an oil bath at 100° C. for 1 hour to yield 6α,9α-difluoro-11β,16α,17α-trihydoxypregna-1,4-diene-3,20,21-trione-16,17-acetonide. EXAMPLE 3 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether 6α,9α-difluoro-11β,16α,17α-trihydroxypregna-1,4-3,20,21-trione-16,17-acetonide (obtained above in Example 2) is dissolved in 50 ml. of dry methanol. After stirring for approximately 15 minutes at room temperature the solution color changes from yellow to colorless. The solution is then evaporated and dried at 50° C. under vacuum to yield 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether. Replacing methanol in the above procedure with other lower alkanols, e.g., ethanol, isopropanol, n-butanol, sec-butanol, amyl alcohol etc., is productive of the corresponding 21-aldehyde hemiacetals, for example, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-butyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-butyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, and so forth. EXAMPLE 4 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether (2.5 g.) is dissolved in 100 ml. of dry methylene chloride and 1.2 ml. of triethylamine is added to the solution which is cooled to -15° C. under a nitrogen atmosphere. Methane sulfonyl chloride (1.2 ml.) is then added and the solution is allowed to warm to 0° C. with stirring. After 16 hours at 0° C. there is obtained 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, m.p. 207°-213° C. The product can be recovered by evaporation of the solvent or used directly in solution in the next example. Repeating the above procedure but substituting thionyl bromide for methane sulfonyl chloride is productive of the corresponding 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether. In like manner, other 21-halo-21-alkyl ether steroids are prepared, for example: 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-butyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-sec-butyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahdroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-octyl ether, and also the corresponding 21-bromo-21-alkyl ether steroids, e.g., 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl ether, 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-butyl ether, 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-sec-butyl ether, 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl ether, and 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-octyl ether. EXAMPLE 5 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether To the methylene chloride solution of 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, obtained in Example 4, is added 200 ml. of dry methanol and the methylene chloride is then removed by distillation. The resulting solution is heated under nitrogen at 60° C. while a 0.5 normal solution of sodium methoxide in methanol is added dropwise at a rate sufficient to maintain a pH of 8. After approximately 4 hours the reaction is complete whereupon the reaction mixture is concentrated to approximately 50 ml. by evaporation. The the resultant precipitates is filtered, washed with water and vacuum dried. The precipitate is recrystallized from a mixture of methanol and methylene chloride to yield 6α,9α-difluoro-11β,17α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, m.p. 291°-292° C. Repeating the above procedure, but substituting other alkoxides for sodium methoxide and using an alkanol corresponding to the alkoxide used is productive of the corresponding 21-methyl-21-alkyl ether steroids, for example, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-ethyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-isopropyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-butyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-sec-butyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-amyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-hexyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-heptyl ether, and 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-octyl ether, empimer A m.p. 189°-193° C.; epimer B m.p. 113°-116° C. In like manner, other 21,21-bis-alkyl ether steroids and 21-mixed alkyl ether steroids are pepared, for example 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, m.p. 269°-275° C., 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, m.p. 244°-248° C., 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna- 1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-isopropyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-butyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-sec-butyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-amyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-hexyl ether, 6α,9α-difluoro-11β,16α, 17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-heptyl ether, 6α,9α-difluoro-11β,16α, 17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-octyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21-n-butyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl-21-n-butyl ether, 6α,9α-difluoro-11β,16α,17α-21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21-n-hexyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21-n-heptyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21-n-octyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl-21-n-amyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl-21-n-hexyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl-21-n-heptyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl-21-n-octyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl-21-n-hexyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl-21-n-heptyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl-21-n-octyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl-21-n-hexyl ether, and 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl-21-n-octyl ether, EXAMPLE 6 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether To a solution of 100 mg. of 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether in 50 ml. of methylene chloride (obtained in Example 4) is added 10 ml. of dry dimethylformamide and the methylene chloride is then removed from the solution by distillation. Sodium azide (40 mg.) is added to the resulting solution and the mixture is stirred at room temperature for 16 hours. The reaction mixture is then poured into water and the resulting mixture extracted with chloroform. The chloroform extracts are washed with water and dried over sodium sulfate, and evaporated to dryness. The resulting impure product is chromatographed on a silica GF plate (1 m. × 20 cm. × 0.5 mm.) which is developed twice with 12% acetone in hexane. The product is removed from the plate to yield 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, m.p. 220°-222° C. In like manner, other 21-azido-21-alkyl ether steroids are prepared, for example 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl ether, 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-butyl ether, 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-sec-butyl ether, 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl ether, and 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-octyl ether. EXAMPLE 7 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether To a solution of 160 mg. of 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether in 80 ml. of methylene chloride (obtained in Example 4) is added 30 ml. of dry dimethylformamide and the methylene chloride is removed by distillation. Thereafter, 265 mg. of potassium thiocyanate is added and the mixture is heated under nitrogen at 70° C. After 4 hours the mixture is poured into water and the resulting aqueous mixture extracted with ethyl acetate. The organic phase is washed with water, dried over sodium sulfate and evaporated to dryness. The product is then chromatographed on a silica GF plate (1 m. × 20 cm. × 0.5 mm.) which is developed with 15% acetone and hexane. The product is removed from the plate to yield 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, m.p. 233°-237° C. In like manner, other 21-thiocyano-21-alkyl ether steroids are prepared, for example 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21 isopropyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-butyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21-sec-butyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl ether, and 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-octyl ether. EXAMPLE 8 21-Cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether To a solution of 160 mg. of 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether in 80 ml. of methylene chloride (obtained in Example 4) is added 30 ml. of dry dimethylformamide and the methylene chloride is removed by distillation. Thereafter, 200 mg. of sodium cyanide is added and the mixture is heated under nitrogen at 70° C. After 4 hours the reaction mixture is poured into water and the product extracted with ethyl acetate. The organic phase is then washed with water, dried over sodium sulfate and evaporated to dryness. The residue is purified by preparative thin layer chromatography to yield 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, epimer A m.p. 272°-275° C.; epimer B m.p. 219°-222° C. In like manner, other 21-cyano-21-alkyl ether steroids are prepared, for example 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl ether, 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-butyl ether, 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-sec-butyl ether, 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl ether, and 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-octyl ether. EXAMPLE 9 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether To a solution of 140 mg. of 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether in 70 ml. of methylene chloride (obtained in Example 4) is added 30 ml. of acetone and the methylene chloride is removed by distillation. Approximately 0.5 g. of sodium thiophenylate is added and the mixture is stirred at room temperature for 16 hours. The reaction mixture is then poured into water and the product extracted with ethyl acetate. The combined extracts are washed with water, dried over sodium sulfate and evaporated to dryness. The resulting impure product is chromatographed on a silica GF plate (1 m. × 20 cm. × 0.5 mm.) which is developed with 20% ethyl acetate in benzene to yield 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, epimer A m.p. 247°-250° C., epimer B m.p. 219°-222° C. In like manner, other 21-thiophenyl-21-alkyl ether steroids are prepared, for example 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-butyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-sec-butyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl ether, and 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-octyl ether. EXAMPLE 10 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thioethylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether To a solution of 140 mg. of 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether in 70 ml. of methylene chloride (obtained in Example 4) is added 30 ml. of acetone and the methylene chloride is removed by distillation. Approximately 0.5 g. of sodium thioethylate is added and the mixture is stirred at room temperature for a period of 16 hours. The reaction mixture is then poured into water and the product extracted with ethyl acetate. The combined extracts are washed with water, dried over sodium sulfate and evaporated to dryness. The resulting impure product is chromatographed on a silica GF plate (1 m. × 20 cm. × 0.5 mm.) which is developed twice with 12% acetone in benzene to yield 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, epimer A m.p. 280°-282° C., epimer B m.p. 254°-256° C. In like manner, other 21-thioalkyl-21-alkyl ether steroids are prepared, for example 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiomethylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,16α,17α,21tetrahydroxy-21-thio-n-butyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-butyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-hexyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 6α,9α-difluoro-11β, 16α,17α,21-tetrahydroxy-21-thiomethylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiomethylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-octyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thioethylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-octyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether. EXAMPLE 11 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether a. 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide (300 mg.) is dissolved in a mixture of 8 ml. of trimethyl orthoformate and 2 ml. of methanol. Two drops of concentrated perchloric acid is then added to the mixture which is stirred and heated at 50° C. under nitrogen. After 2 hours, the reaction mixture is diluted with ethyl acetate, washed with water until neutral, dried over sodium sulfate and evaporated to dryness to yield 6,9α-difluoro-3,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-triene-20-one-16,17-acetonide-3,21,21-tris-methyl ether, m.p. 168°-176° C. b. 30 mg. of the crude triene obtained above is dissolved in 5 ml. of acetone and 2 ml. of water and 1 drop of concentrated HCl is added. After refluxing for 30 minutes under nitrogen, water is added to the reaction mixture and the acetone was removed by distillation. The resulting precipitate is filtered off and dried under vacuum to yield 6,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, m.p. 267°-270° C. c. 100 mg. of the crude 1,5-diene obtained above is dissolved in 15 ml. of a 2:1 mixture of methylene chloride and methanol and 1 drop of aqueous 3N sodium hydroxide is added. After 15 minutes at room temperature, the reaction mixture is diluted with ethyl acetate. The organic phase is then separated, washed with water and dried over sodium sulfate. The product is recrystallized from a mixture of methanol and methylene chloride to yield 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether. Repeating the above procedures but substituting other alkyl orthoformates in paragraph (a) for trimethyl orthoformate, e.g. triethyl orthoformate, tri-n-propyl orthoformate, tri-n-butyl orthoformate, and so forth is productive of the corresponding 1,4-diene-3,20-dione-21,21-bis-alkyl ether steroids and also the 1,3,5-trien-20-dione-3,21,21-trialkyl ether steroids, for example 6α,9α-difluoro-3β,11β,16α,17α,21,21-hexyhydroxypregna-1,3,5-trien-20-dione-16,17-acetonide-3,21,21-tris-ethyl ether, 6α,9α-difluoro-3β,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-trien-20-dione-16,17-acetonide-3,21,21-tris-n-propyl ether, 6α,9α-difluoro-3β,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-trien-20-dione-16,17-acetonide-3,21,21-tris-n-butyl ether, and so forth, and also the 1,5-diene-3,20-dione-21,21-bis-alkyl ether steroids for example 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-dien-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-dien-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-dien-3,20-dione-16,17-acetonide-21,21-bis-n-butyl ether, and so forth. EXAMPLE 12 In similar manner to the procedures of Examples 1-10, using reactants as dictated by the particular 21-acetal or 21-mixed acetal desired, the following compounds are prepared: 21-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 21-chloro-6α-fluoro-11β, 16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 9α,11β,21-trichloro-6α-fluoro-16α,17α,21-trihydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 9α,21-dichloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, decomp. 180°-190° C., 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-21-methyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-methyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-methyl ether, 21-chloro-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, 21-chloro-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregn-4-ene-3,20-dione-21-methyl ether, 21-chloro-9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-acetate-21-methyl ether, 21-chloro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 21-chloro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,21-dichloro-11β,16α,17α-21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-2-methyl ether, 21-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 9α,11β,21-trichloro-6α-fluoro-16α,17α,21-trihydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 9α,21-dichloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-21-ethyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-ethyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-ethyl ether, 21-chloro-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-ethyl ether, 21-chloro-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregn-4-ene-3,20-dione-21-ethyl ether, 21-chloro-9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-acetate-21-ethyl ether, 21-chloro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-chloro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,21-dichloro-11β,16α,17α,21-tetrahydroxypreg-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 21-chloro-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 21-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-octyl ether, 9α,11β,21-trichloro-6α-fluoro-16α,17α,21-trihydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl ether, 9α,21-dichloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-butyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-21-n-propyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-n-propyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-n-amyl ether, 21-chloro-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-n-amyl ether, 21-chloro-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregn-4-ene-3,20-dione-21-n-butyl ether, 21-chloro-9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 21-chloro-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-acetate-21-n-hexyl ether, 21-chloro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-octyl ether, 21-chloro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl ether, 21-bromo-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-bromo-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-propyl ether, 21-bromo-6α-fluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-bromo-9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 21-bromo-9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-bromo-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-21-n-propyl ether, 21-bromo-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-methyl ether, 21-bromo-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-methyl ether, 21-bromo-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-ethyl ether, 21-bromo-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregn-4-ene-3,20-dione -21-isopropyl ether, 21-bromo-9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-bromo-6α,9α-difluoro-11β,17α,21-trihydroxypregna-1,4-diene-3,20-dione-17-acetate-21-n-propyl ether, 21-bromo-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-bromo-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 21-bromo-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 21-bromo-6α-fluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 21-bromo-9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-octyl ether, 21-bromo-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-n-heptyl ether, 21-bromo-9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 21-bromo-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-octyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, m.p. 297°-299° C., 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, m.p. 246°-250° C., 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, m.p. 270°-273° C., 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, m.p. 179°-181° C., 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-21,21-bis-methyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-caprylate-21,21-bis-methyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-benzoate-21,21-bis-methyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21,21-bis-methyl ether, m.p. 202°-204° C., 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregn-4-ene-3,20-dione-21,21-bis-methyl ether, 9α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, m.p. 280°-282° C., 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-acetate-21,21-bis-methyl ether, m.p. 226°-228° C., 11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, m.p. 250°-253° C., 11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, m.p. 154°-158° C., 6α-chloro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-21,21-bis-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-caprylate-21,21-bis-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-benzoate-21,21-bis-ethyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21,21-bis-ethyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregn-4-ene-3,20-dione-21,21-bis-ethyl ether, 9α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-acetate-21,21-bis-ethyl ether, 11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, m.p. 224°-227° C., 11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 6α-chloro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-1,4-diene-3,20-dione-21,21-bis-n-propyl ether, m.p. 202°-204° C., 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-caprylate-21,21-bis-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α,methylpregna-1,4-diene-3,20-dione-17-benzoate-21,21-bis-n-propyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21,21-bis-n-propyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregn-4-ene-3,20-dione-21,21-bis-n-propyl ether, 9α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-acetate-21,21-bis-n-propyl ether, 11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α-chloro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-amyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-n-hexyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-octyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21,21-bis-n-heptyl ether, 9α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21,21-bis-n-butyl ether, 11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21,21-bis-n-octyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-ethyl ether, 6α,9α-difluoro-11β,16α,17α, 21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21-ethyl ether, 6α-fluoro-11β,16α,17α, 21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21-ethyl ether, 9α, 11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-ethyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-21-methyl-21-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-methyl-21-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-methyl-21-ethyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-1,4-diene -3,20-dione-17-valerate-21-methyl-21-ethyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregn-4-ene-3,20-dione-21-methyl-21ethyl ether, 9α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17acetate-21-methyl-21-ethyl ether, 11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21-ethyl ether, 11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-ethyl ether, 6α-chloro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21-ethyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 60α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21-n-propyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21-n-propyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-propyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-21-methyl-21-n-propyl ether, m.p. 172°-175° C., 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-methyl-21-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-methyl-21-n-propyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-methyl-21-n-propyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregn-4-ene-3,20-dione-21-methyl-21-n-propyl ether, 9α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-acetate-21-methyl-21-n-propyl ether, 11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21-n-propyl ether, 11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl-21-n-propyl ether, 6α-chloro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21-n-propyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl-21-n-propyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-propyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21-n-propyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16αmethylpregna-1,4-diene-3,20-dione-21-ethyl-21-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-ethyl-21-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-ethyl21n-propyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-ethyl-21n-propyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregn-4-ene- 3,20-dione-21-ethyl-21n-propyl ether, 9α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-acetate-21-ethyl-21-n-propyl ether, 11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl-21-n-propyl ether, 11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21-n-propyl ether, 6α-chloro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl-21-n-propyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21n-butyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-6α-methylpregna-1,4-diene-3,20-dione-21-ethyl-21-n-butyl ether, 9α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl-21-n-butyl ether, 6α-fluoro- 11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl-21-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21n-octyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl-21-n-hexyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl-21-n-heptyl ether, 9α-chloro-6α-fluoro-11β,16;60 ,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione=16,17-acetonide-21-methyl-21-n-hexyl ether, 6α,9α-difluoro-11β,17α, 21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-21-ethyl-21-n-heptyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-methyl-21-n-octyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-methyl-21-n-octyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-n-octyl-21-n-propyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregn-4-ene-3,20-dione-21-n-heptyl ether, 9α-fluoro-11β,16α,17;60 ,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl-21-n-octyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17acetate-21-n-amyl-21-n-propyl ether, 11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl-21-n-octyl ether, 11β,16α,17α,21,21-pentahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl-21-n-octyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-amyl-21n-hexyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl-21-n-hexyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-21-n-amyl-21-n-heptyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregn-4-ene-3,20-dione-21-n-hexyl -n-octyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-acetate-21n-amyl-21-n-octyl ether, 21-azido-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 21-azido-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-azipo-9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-azido-9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-azido-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna 1,4-diene-3,20-dione-21-methyl ether, 21-azido-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-methyl ether, 21-azido-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-methyl ether, 21-azido-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, 21-azido-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregn-4ene-3,20-dione-21-methyl ether, 21-azido-9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-21-methyl ether, 21-azido-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17 -acetate-21-methyl ether, frothing 199°-204° C.; decomp. 235°- 245° C., 21-azido-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 21-azido-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-azido-6α-chloro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 21-azido-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-azido-6α,9α-difluoro- 11β,16;60 ,17α,21-tetrahydroxypregn-4-ene- 3,20-dione-16,17-acetonide-21-ethyl ether, 21-azido-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-azido-9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-azido-9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-azido-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-21-ethyl ether, 21-azido-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-ethyl ether, 21-azido-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-ethyl ether, 21-azido-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-ethyl ether, 21-azido-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregn-4-ene-3,20-dione-21-ethyl ether, 21-azido-9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-21-ethyl ether, 21-azido-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-acetate-21-ethyl ether, 21-azido-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-azido-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-azido-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-propyl ether, 21-azido-11β,16α,17α,21-tetrahydroxypregna-1,4-diene- 3,20-dione-16,17-acetonide-21-n-propyl ether, 21-azido-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 21-azido-9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl ether, 21-azido-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-21-sec-butyl ether, 21-azido-9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-21-n-hexyl ether, 21-azido-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-acetate-21-n-octyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyanopregn-4-ene-3,20 -dione-16,17-acetonide-21-methyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiocyano-pregna-1,4-diene-3,20-dione-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiocyano-pregna-1,4-diene-3,20-dione-17-caprylate-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiocyano-pregna-1,4-diene-3,20-dione-17-benzoate-21-methyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiocyano-pregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiocyano-pregn-4-ene-3,20-dione-21-methyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-21-thoicyano-pregna-1,4-diene-3,20-dione-17-acetate-21-methyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α-chloro-11β,16α,17α,21-tetrahydroxy-16 43,5-dien- -methyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 9α-chloro-6α;l -fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,43,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiocyano-pregna-1,4-diene-3,20-dione-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiocyano-pregna-1,4-diene-3,20-dione-17-caprylate-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiocyano-pregna-1,4-diene-3,20-dione-17-benzoate-21-ethyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiocyano-pregna-1,4-diene-3,20-dione-17-valerate-21-ethyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiocyano-pregn-4-ene-3,20-dione-21-ethyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,4-diene-3,20-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-17-acetate-21-ethyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether 6α-chloro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-sec-butyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregn-4-ene-3,20-dione-16,17-acetonide-21-n-octyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21n-propyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiocyano-pregna-1,4-diene-3,20-dione-17-caprylate-21-n-octyl ether, 9α-fluoro-11α,17α,21-trihydroxy-16β-methyl-21-thiocyano-pregna-1,4-diene-3,20-dione-17-valerate-21-n-hexyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiocyano-pregn-4-ene-3,20-dione-21-n-propyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregn-4-ene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiocyano-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 21-cyano-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 21-cyano-6α-fluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 21-cyano-9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxy-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-cyano-9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-cyano-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-21-methyl ether, 21-cyano6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20 -dione-17-caprylate-21-methyl ether, 21-cyano-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-methyl ether, 21-cyano-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, 21-cyano9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregn-4-ene-3,20-dione-21-methyl ether, 21-cyano-9α-fluoro-11β,16α,17α21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-cyano-6α,9α-difluoro-11β,17α,21-trihydroxypregna-1,4-diene-3,20-dione-17-acetate-21-methyl ether, 21-cyano-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 21-cyano-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 21-cyano-6α-chloro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 21-cyano-6α-fluoro-11β, 16,60 ,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-cyano-6α-fluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-cyano-9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-21-ethyl ether 21-cyano-9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-cyano-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-21-ethyl ether, 21-cyano-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-caprylate-21-ethyl ether, 21-cyano-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-17-benzoate-21-ethyl ether, 21-cyano-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregna-1,4-diene-3,20-dione-17-valerate-21-ethyl ether, 21-cyano-9α-fluoro-11β,17α,21-trihydroxy-16β-methylpregn-4-ene-3,20-dione-21-ethyl ether, 21-cyano-9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-cyano-6α,9α-difluoro-11β,17α,21-trihydroxypregna-1,4-diene-3,20-dione-17-acetate-21-ethyl ether, 21-cyano-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-cyano-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-cyano-6α-chloro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 21-cyano-6α,9α-difluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-octyl ether, 21-cyano-6α-fluoro-11β,16α,17α,21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-propyl ether, 21-cyano-9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-butyl n-butyl ether, 21-cyano-6α,9α-difluoro-11β,17α,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-dione-21-n-hexyl ether, 21-cyano-9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl ether, ether, 21-cyano-6α,9α-difluoro-11β,17α,21-trihydroxypregna-1,4-diene-3,20-dione-17-acetate-21-n-propyl ether, 21-cyano-11β,16α,17α21-tetrahydroxypregn-4-ene-3,20-dione-16,17-acetonide-21-n-amyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β, 16α,17α,21-tetrahydroxy-21-thiophenyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiophenyl-pregna-1,4-diene-3,20-dione-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21 -thiophenyl-pregna-1,4-diene-3,20-dione-17-caprylate-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiophenyl-pregna-1,4-diene-3,20-dione-17-benzoate-21-methyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiophenylpregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiophenyl-pregn-4-ene-3,20-dione-21-methyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-17-acetate-21-methyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α-chloro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahdyroxy-21-thiophenyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiophenyl-pregna-1,4-diene-3,20-dione-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiophenyl-pregna-1,4-diene-3,20-dione-17-caprylate-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiophenyl-pregna-1,4-diene-3,20-dione-17-benzoate-21-ethyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiophenyl-pregna-1,4-diene-3,20-dione-17-valerate-21-ethyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiophenyl-pregn-4-ene-3,20-dione-21-ethyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-17-acetate-21-ethyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α-chloro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-n-amyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenylpregn-4-ene-3,20-dione-16,17-acetonide-21-n-octyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-isopropyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiophenyl-pregn-4-ene-3,20-dione-21-n-octyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-21-thiophenylpregna-1,4-diene-3,20-dione-17-acetate-21-sec-butyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiophenyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiomethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thiomethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiomethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxy-21-thiomethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 9α-chloro- 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiomethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiomethyl-pregna-1,4-diene-3,20-dione-17-caprylate-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiomethyl-pregna-1,4-diene-3,20-dione-17-caprylate-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thiomethyl-pregna-1,4-diene-3,20-dione-17-benzoate-21-methyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiomethyl-pregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thiomethyl-pregn-4-ene-3,20-dione-21-methyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thiomethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-21-thiomethyl-pregna-1,4-diene-3,20-dione-17-acetate-21-methyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiomethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 11β,16α,17α,21-tetrahydroxy-21-thiomethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α-chloro-11β,16α,17α,21-tetrahydroxy-21-thiomethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thioethyl-pregna-1,4-diene-3,20-dione-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thioethyl-pregna-1,4-diene-3,20-dione-17-caprylate-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thioethyl-pregna-1,4-diene-3,20-dione-17-benzoate-21-ethyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thioethyl-pregna-1,4-diene-3,20-dione-17-valerate-21-ethyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thioethyl-pregn-4-ene-3,20-dione-21-ethyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-17-acetate-21-ethyl ether, 11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α-chloro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-n-propyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-17-valerate-21-n-propyl ether, 11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-propyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-octyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-octyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-sec-butyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-sec-butyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-heptyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-heptyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-hexyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-hexyl ether, 11β,16α,17α,21-tetrahydroxy-21-thio-n-amyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-n-amyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregn-4-ene-3,20-dione-16,17-aceotnide-21-methyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahdyroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thioethyl-pregna-1,4-diene-3,20-dione-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thioethyl-pregna-1,4-diene-3,20-dione-17-caprylate-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thioethyl-pregna-1,4-diene-3,20-dione-17-benzoate-21-methyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thioethyl-pregna-1,4-diene-3,20-dione-17-acetate-21-methyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thioethyl-pregn-4-ene-3,20-dione-21-methyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-17-acetate-21-methyl ether, 11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α-chloro-11β,16α,17α,21-tetrahydroxy-21-thioethyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-propylpregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 6α-fluoro-11β,16α,17α ,21-tetrahydroxy-21-thio-n-propyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21-trihydroxy-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-21-methyl ether, 6α,9α-difluoro-11β,17α ,21-trihydroxy-16α-methyl-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-17-caprylate-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-17-benzoate-21-methyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-17-acetate-21-methyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thio-n-propyl-pregn-4-ene-3,20-dione-21-methyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,17α,21-trihydroxy-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-17-acetate-21-methyl ether, 11β,16α ,17α,21-tetrahydroxy-21-thio-n-propyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-methyl ether, 6α-chloro-11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether, 6α,9α-difluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-ethyl ether, 6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-heptyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-21-n-propyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether 6α,9α-difluoro-11β,17α,21-trihydroxy-16α-methyl-21-thio-n-heptyl-pregna-1,4-diene-3,20-dione-17-benzoate-21-isopropyl ether, 9α-fluoro-11β,17α,21-trihydroxy-16β-methyl-21-thio-n-hexyl-pregna-1,4-diene-3,20-dione-17-acetate-21-ethyl ether, 9α-fluoro-11β,16α,17α,21-tetrahydroxy-21-thio-n-propyl-pregna-1,4-diene-3,20-dione-16,17-acetonide-21-ethyl ether, 11β,16α,17α,21-tetrahydroxy-21-thio-n-octyl-pregn-4-ene-3,20-dione-16,17-acetonide-21-methyl ether. 21-chloro-11β,17α,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, 21-chloro-11β,17α,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-valerate-21-ethyl ether, 21-chloro-11β,17α,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-valerate-21-n-propyl ether, 11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-valerate-21,21-bis-methyl ether, 11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-valerate-21,21-bis-ethyl ether, 11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-valerate-21,21-bis-n-propyl ether, 11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-valerate-21-methyl-21-ethyl ether, 11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-valerate-21-methyl-21-n-propyl ether, 21-azido-11β,17α,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, 11β,17α,21-trihydroxy-16α-methyl-21-thiocyano-pregna-1,4-diene-3-20-dione-17-valerate -21-methyl ether, 21-cyano-11β,17α,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, 11β,17α,21-trihydroxy-16α-methyl-21-thiophenyl-pregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, 11β,17α,21-trihydroxy-16α-methyl-21-thiophenyl-pregna-1,4-diene-3,20-dione-17-valerate-21-ethyl ether, 11β,17α,21-trihydroxy- 16α-methyl-21-thiomethyl-pregna-1,4-diene-3,20-dione-17-valerate-21-methyl ether, EXAMPLE 13 In similar manner to procedures a) and b) of Example 11, using reactants as dictated by the particular 3-alkoxy-3,5-dien-21-acetal or 3-oxo-5- en-21-acetal desired, the following compounds are prepared: 6α-fluoro-3,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-trien-20-one-16,17-acetonide-3,21,21-tris-methyl ether, 6α,9α-difluoro-3,11β,16α,17α,21,21-hexahydroxypregna-3,5 -dien-dien-20-one-16,17-acetonide-3,21,21-tris-methyl ether, 6α-fluoro-3,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien-20-one-16,17-acetonide-3,21,21-tris-methyl ether, 9α,11β-dichloro-6α-fluoro-3,16α,17α,21,21-pentahydroxy-pregna-1,3,5 -trien-20-one-16,17-acetonide-3,21,21-tris-methyl ether, 9α-chloro-6α-fluoro-3,11β,16α,17α,21-21-hexahydroxypregna-1,3,5 -trien-20-one-16,17-acetonide-3,21,21-tris-methyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16 -methylpregna-1,3,5-trien- 20-one-3,21,21-tris-methyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16 -methylpregna-1,3,5-trien- 20-one-17-caprylate-3,21,21-tris-methyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16-methylpregna-1,3,5-trien- 20-one-17-benzoate-3,21,21-tris-methyl ether, 9α-fluoro-3,11β,17α,21,21-pentahydroxy-16 -methylpregna-3,5 - dien-20-one-3,21,21-tris-methyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16 -methylpregna-1,3,5 -trien-20-one-17-acetate-3,21,21-tris-methyl ether, 3,11β,16α,17α,21,21-hexahydroxypregna-3,5 -dien- 20one-16,17-acetonide-3,21,21-tris-methyl ether, 6α-chloro-3,11β,16α,17α,21,21-hexahydroxyprenga-3,5-dien-20-one-16,17-acetonide-3,21,21-tris-methyl ether, 6α-fluoro-3,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-trien-20-one-16,17-acetonide-3,21,21-tris-ethyl ether, 6α,9α-difluoro-3,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien- 20-one-16,17-acetonide-3,21,21-tris-ethyl ether, 6α-fluoro-3,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien- 20-one-16,17-acetonide-3,21,21-tris-ethyl ether, 9α,11β-dichloro-6α-fluoro-3.16α,17α,21,21-pentahydroxypregna-1,3,5-trien- 20-one-16,17-acetonide-3,21,21-tris-ethyl ether, 9α-chloro-6α-fluoro-3,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-trien- 20-one-16,17-acetonide-3,21,21-tris-ethyl ether. 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpregna-1,3,5-trien- 20-one-3,21,21-tris-ethyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpregna-1,3,5-trien- 20-one-17-caprylate-3,21,21-tris-ethyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpegna-1,3,5-trien- 20-one-17-benzoate-3,21,21-tris-ethyl ether, 9α-fluoro-3,11β,17α,21,21-pentahydroxy-16β-methylpregna-3,5-dien- 20-one-3,21,21-tris-ethyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpregna-1,3,5-trien- 20-one-17-acetate-3,21,21-tris-ethyl ether, 3,11β,16α,17α,21,21-hexahydroxyprena-3,5-dien- 20-one-16,17-acetonide-3,21,21-tris-ethyl ether, 3β,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-trien--20-one-16,17-acetonide-3,21,21-tris-ethyl ether, 6α-chloro-3,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien-20-one-16,17-acetonide-3,21,21-tris-ethyl ether, 60α-fluoro-3,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-trien-20-one-16,17-acetonide-3,21,21-tris-isopropyl ether, 6α,9α-difluoro-3,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien-20-one-16,17-acetonide-3,21,21-tris-n-propyl ether, 60α6α-fluoro - 3,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien-20-one-16,17-acetonide-3,21,21-tris-n-propyl ether, 9α,11β-dichloro-6α-fluoro-3,16α,17α,21,21-pentahydroxypregna-1,3,5-trien-20-one-16,17-acetonide-3,21,21-tris-n-propyl ether, 9α-chloro-6α-fluoro-3,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-trien-20-one-16,17-acetonide-3,21,21-tris-n-propyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpregna-1,3,5-trien-20-one-3,21,21-tris-n-propyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-mthylpregna-1,3,5-trien-20-one-17-caprylate-3,21,21-tris-n-propyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpregna-1,3,5-trien-20-one-17-benzoate-3,21,21-tris-n-propyl ether, 9α-fluoro-3,11β,17α,21,21-pentahydroxy-16β-methylpregna-3,5-dien-20-one-3,21,21-tris-n-propyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpregna-1,3,5-trien-20-one-17-acetate-3,21,21-tris-n-propyl ether, 3,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien-20-one-16,17-acetonide-3,21,21-tris-n-propyl ether, 6α-chloro-3,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien-20-one-16,17-acetonide-3-21,21-tris-n-propyl ether, 6α-fluoro-3,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-trien-20-one-16,17-acetonide-3,21,21-tris-n-butyl ether, 6α,9α-difluoro-3,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien-20-one-16,17-acetonide-3,21,21-tris-n-butyl ether, 6α-fluoro-3,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien-20-one-16,17-acetonide-3,21,21-tris-n-butyl ether, 9α,11β-dichloro-6α-fluoro-3,16α,17α,21,21-pentahydroxypregna-1,3,5-trien-20-one-16,17-acetonide-3,21,21-tris-n-butyl ether, 9α-chloro-6α-fluoro-3,11β,16α,17α,21,21-hexahydroxypregna-1,3,5-trien-20-one-16,17-acetonide-3,21,21-tris-n-butyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpregna-1,3,5-trien-20-one-3,21,21-tris-n-butyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpregna-1,3,5-trien-20-one-17-caprylate-3,21,21-tris-n-butyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpregna-1,3,5-trien-20-one-17-benzoate-3,21,21-tris-n-butyl ether, 9α-fluoro-3,11β,17α,21,21-pentahydroxy-16β-methylpregna-3,5-dien-20-one-3,21,21-tris-n-butyl ether, 6α,9α-difluoro-3,11β,17α,21,21-pentahydroxy-16.alpha.-methylpregna-1,3,5-trien-20-one-17-acetate-3,21,21-tris-n-butyl ether, 3β,11β,16α,17α,21,21-hexahydroxypregna-3,5-dien-20-one-16,17-acetonide-3,21,21-tris-n-butyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-21,21-bis-methyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-caprylate-21,21-bis-methyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-benzoate-21,21-bis-methyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-5-ene-3,20-dione-21,21-bis-methyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-acetate-21,21-bis-methyl ether, 11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, 6α-chloro-11β,16α,17α,21,21-pentahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-methyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-diene-3,20dione-16,17-acetonide-21,21-bis-ethyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-21,21-bis-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-caprylate-21,21-bis-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-benzoate-21,21-bis-ethyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-5-ene-3,20-dione-21,21-bis-ethyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-acetate-21,21-bis-ethyl ether, 11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 6α-chloro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-ethyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-isopropyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-21,21-bis-isopropyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-caprylate-21,21-bis-isopropyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-benzoate-21,21-bis-isopropyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregn-5(6)-ene-3,20-dione-21,21-bis-isopropyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-acetate-21,21-bis-n-propyl ether, 11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α-chloro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-n-propyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-n-butyl ether, 6α,9α-difluoro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-n-butyl ether, 6α-fluoro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-n-butyl ether, 9α,11β-dichloro-6α-fluoro-16α,17α,21,21-tetrahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-n-butyl ether, 9α-chloro-6α-fluoro-11β,16α,17α,21,21-pentahydroxypregna-1,5-diene-3,20-dione-16,17-acetonide-21,21-bis-n-butyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-21,21-bis-n-butyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-caprylate-21,21-bis-n-butyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-benzoate-21,21-bis-n-butyl ether, 9α-fluoro-11β,17α,21,21-tetrahydroxy-16β-methylpregna-5-ene-3,20-dione-21,21-bis-n-butyl ether, 6α,9α-difluoro-11β,17α,21,21-tetrahydroxy-16α-methylpregna-1,5-diene-3,20-dione-17-acetate-21,21-bis-n-butyl ether, 11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-n-butyl ether, and 6α-chloro-11β,16α,17α,21,21-pentahydroxypregn-5-ene-3,20-dione-16,17-acetonide-21,21-bis-n-butyl ether.

21-ACETALS AND MIXED ACETALS OF STEROIDS OF THE CORTICOID SERIES ARE PREPARED FROM THE CORRESPONDING 21-HYDROXY STEROIDS AND HAVE UTILITY AS ANTI-INFLAMMATORY AGENTS.

CROSS-REFERENCE TO RELATED APPLICATION [0001] This is a continuation of application, filed under 35 U.S.C. §111(a) of International Application PCT/JP2011/060604, filed on May 6, 2011, the contents of which are herein wholly incorporated by reference. FIELD [0002] The present invention relates to a stereoscopic moving picture generating apparatus, a moving picture generating method and a moving picture generating program. BACKGROUND [0003] There is a moving picture generating apparatus for generating images that can be stereoscopically viewed by making use of a parallax between the images captured by two cameras adjacent to each other. The moving picture generating apparatus generates and displays the image captured by one camera as an image for a left eye and the image captured by the other camera as an image for a right eye in the images captured by the two adjacent cameras, thereby making a viewer perceive the stereoscopic image. [0004] With respect to the same physical object, a difference between a position in the image for the left eye and a position in the image for the right eye is referred to as a parallax. When parallax quantities are different between two physical objects existing within the image (picture), one physical object appears to exist nearer or farther than the other physical object. The parallax quantity is defined as a magnitude of the parallax. [0005] FIG. 1 is a diagram illustrating an example of the stereoscopic picture. In FIG. 1 , an image 910 is an image for a left eye, and an image 920 is an image for a right eye. Herein, an object A, an object B and an object C exist in each of the image 910 as the image for the left eye and the image 920 as the image for the right eye. Due to parallaxes of these objects between the image 910 and the image 920 , a person looking at the stereoscopic picture in FIG. 1 views the object A, the object B and the object C as if existing in this sequence from the near side. DOCUMENTS OF PRIOR ARTS Patent Document [0000] [Patent document 1] Japanese Patent Application Laid-Open Publication No. 11-088910 [Patent document 2] Japanese Patent Application Laid-Open Publication No. H08-331598 [Patent document 3] Japanese Patent Application Laid-Open Publication No. H09-074573 [Patent document 4] Japanese Patent Application Laid-Open Publication No. 2001-016620 [Patent document 5] Japanese Patent Application Laid-Open Publication No. H09-224267 [Patent document 6] Japanese Patent Application Laid-Open Publication No. 2010-206774 SUMMARY [0012] In a stereoscopic picture, if a ratio of a distance from a camera to a physical object on this side (closer to the camera in a depthwise direction) to a distance from a camera to a backface is approximate to “1”, even the stereoscopic picture becomes a planar picture with none of the stereoscopic sense. Moreover, in a plurality of objects (physical objects) within the picture, if there is no difference between the distances from the camera, even the stereoscopic picture becomes the planar picture exhibiting no stereoscopic sense. The stereoscopic picture is, however, requested to emphasize the stereoscopic sense even when there is no difference between the distances from the camera to the plurality of objects (physical objects). [0013] According to one aspect of the disclosure, a stereoscopic picture generating apparatus includes: [0014] a storage unit to get stored with a first image containing a plurality of partial images and a second image containing a plurality of partial images corresponding respectively to the plurality of partial images contained in the first image; and an arithmetic unit to extract a first position defined as an existing position of a first partial image contained in the first image and a second position defined as an existing position of a second partial image contained in the first image, to calculate a first differential quantity defined as a difference between the first position and the second position, to calculate a third position defined as a new existing position of a third partial image contained in the second image that corresponds to the first partial image on the basis of the first differential quantity, and to generate a third image on the basis of the third position of the third partial image. [0016] The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. [0017] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. BRIEF DESCRIPTION OF THE DRAWINGS [0018] FIG. 1 is a diagram illustrating an example of a stereoscopic picture. [0019] FIG. 2 is an explanatory diagram of a parallax in the stereoscopic picture. [0020] FIG. 3 is a diagram depicting an example of a stereoscopic picture generating apparatus. [0021] FIG. 4 is a diagram illustrating an example of a hardware configuration of an information processing apparatus. [0022] FIG. 5 is a flowchart illustrating an example (1) of an operation flow of the stereoscopic picture generating apparatus. [0023] FIG. 6 is a flowchart illustrating an example (2 of the operation flow of the stereoscopic picture generating apparatus. [0024] FIG. 7 is a diagram depicting a concrete example of processes in step S 105 and step S 106 . [0025] FIG. 8 is a diagram illustrating an example of parallax phase angle information. [0026] FIG. 9 is a diagram depicting an example of coordinates of a reference object, coordinates of another object in an image for a left eye and coordinates of another object in an image for a right eye. [0027] FIG. 10 is a diagram depicting an example of the coordinates of the reference object, the coordinates of another object in the image for the left eye and the coordinates of another object in the image for the right eye after a process in step S 110 . DESCRIPTION OF EMBODIMENTS [0028] Embodiments will hereinafter be described with reference to the drawings. Configurations of the embodiments are exemplifications, and the present invention is not limited to the configurations of the embodiments of the disclosure. [0029] Herein, the discussion is made by using a stereoscopic picture based on images captured by two adjacent cameras, however, the stereoscopic picture is not limited to this type of images but may be based on two frames of artificially generated images, and so on. Moreover, the stereoscopic picture may also be a stereoscopic moving picture. First Embodiment [0030] (Parallax) [0031] FIG. 2 is an explanatory diagram illustrating a parallax in the stereoscopic picture. In FIG. 2 , for instance, in images of the same physical object captured by the two adjacent cameras, an image 10 is defined as an image for a left eye, while an image 20 is defined as an image for a right eye. In the example of FIG. 2 , the image 10 and the image 20 contain an object 1 defined as the same physical object. Herein, a point P1 is set as a point representative of a position of the object 1 in the image 10 . A point P2 is set as a point representative of a position of the object 1 in the image 20 . The point representative of the position of the object 1 may be set to, e.g., a central point of the object 1 and also a point located at a rightward lower edge of the object 1. The point representative of the position of the object 1 is not limited to these points. The point P1 and the point P2 are points each indicating the same position of the object 1. The point P1 and the point P2 are also referred to as the position of the object 1 in the image 10 and as the position of the object 1 in the image 20 , respectively. [0032] The parallax in the stereoscopic picture is a difference between the position in the image for the left eye and the position in the image for the right eye with respect to the same physical object. A parallax quantity is a magnitude of the parallax. [0033] In the image 10 and the image 20 of FIG. 2 , the parallax quantity of the object 1 is a difference between the position (point P1) of the object 1 in the image 10 and the position (point P2) of the object 1 in the image 20 . To be specific, let (XL, YL) be a coordinate of the point P1 in the image 10 and (XR, YR) be a coordinate of the point P2 in the image 20 , and the parallax quantity of the object 1 is expressed as follows. [0000] Δ X=XL−XR [0000] Δ Y=YL−YR   [Mathematical Expression 1] [0034] Herein, ΔX represents the parallax quantity in a crosswise direction, and ΔY denotes the parallax quantity in a lengthwise direction. [0035] For example, the parallax of the object 1 in the stereoscopic picture disappears by moving the image for the right eye in parallel to a degree corresponding to this parallax quantity. [0036] (Configuration) [0037] FIG. 3 is a diagram illustrating an example of a stereoscopic picture generating apparatus. A stereoscopic picture generating apparatus 100 includes an acquiring unit 110 , an arithmetic unit 120 and a storage unit 130 . [0038] The acquiring unit 110 acquires the images from an external or internal input device. The images acquired by the acquiring unit 110 are the image for the left eye and the image for the right eye in the stereoscopic picture. The images acquired by the acquiring unit 110 are stored in the storage unit 130 . [0039] The image for the left eye and the image for the right eye are stored in the storage unit 130 in the way of being associated with each other. Each image has a pixel value per dot within the image. The pixel value is information representing a color etc of the dot. The pixel values are expressed by, e.g., an R (Red) value, a G (Green) value and a B (Blue) value of RGB color coordinate system. As a substitute for the RGB color coordinate system, parameters (values) of other color coordinate systems (e.g., a YUV color coordinate system) may also be employed. In the case of using the parameters of the YUV color coordinate system, a Y (Yellow) value may be used as a luminance value. [0040] The arithmetic unit 120 calculates the parallax quantity with respect to the images acquired by the acquiring unit 110 , thereby generating the stereoscopic picture. The stereoscopic picture generated by the arithmetic unit 120 is stored in the storage unit 130 . [0041] The storage unit 130 gets stored with the images acquired by the acquiring unit 110 , the stereoscopic picture generated by the arithmetic unit 120 , the parallax quantity calculated by the arithmetic unit 120 , an offset quantity predetermined with respect to the stereoscopic picture to be generated, and so on. [0042] A display unit 140 displays the images etc stored in the storage unit 130 . [0043] A receiving unit 150 accepts an input such as a selection of the reference object from a user. [0044] FIG. 4 is a diagram illustrating an example of a hardware configuration of an information processing apparatus 300 . The stereoscopic picture generating apparatus 100 is realized by, e.g., the information processing apparatus 300 as depicted in FIG. 4 . The information processing apparatus 300 includes a CPU (Central Processing Unit) 302 , a memory 304 , a storing unit 306 , an input unit 308 , an output unit 310 and a communication unit 312 . [0045] The CPU 302 loads a program stored in a recording unit 306 into an operation area of a memory 304 and executes this program, whereby the information processing apparatus 300 can actualize functions conforming to predetermined purposes by controlling peripheral devices through the execution of the program. [0046] The CPU 302 performs processes according to the program stored in the storing unit 306 . The memory 304 caches the program and the data and also deploys the operation area. The memory 304 includes, e.g., a RAM (Random Access Memory) and a ROM (Read Only Memory). [0047] The storing unit 306 stores various categories of programs and various items of data on a readable/writable recording medium. The storing unit 306 is exemplified by a solid-state drive device, a hard disk drive device, a CD (Compact Disc) drive device, a DVD (Digital Versatile Disc) drive device, a +R/+RW drive device, an HD DVD (High-Definition Digital Versatile Disc) drive device or a BD (Blu-ray Disc) drive device. Furthermore, the recording medium is exemplified by a silicon disk including a nonvolatile semiconductor memory (flash memory), a hard disk, a CD, a DVD, a +R/+RW, an HD DVD or a BD. The CD is exemplified by a CD-R (Recordable), a CD-RW (Rewritable) and a CD-ROM. The DVD is exemplified by a DVD-R and a DVD-RAM (Random Access Memory). The BD is exemplified by a BD-R, a BD-RE (Rewritable) and BD-ROM. [0048] The input unit 308 accepts an operating instruction etc from the user etc. The input unit 308 is exemplified by input devices such as a keyboard, a pointing device, a wireless remote controller, a microphone and a plurality of cameras. The CPU 302 is notified of information inputted from the input unit 308 . The camera may be equipped with an infrared-ray sensor etc for measuring a distance. [0049] The output unit 310 outputs the data processed by the CPU 302 and the data stored in the memory 304 . The output unit 310 is exemplified by output devices such as a CRT (Cathode Ray Tube) display, an LCD (Liquid Crystal Display, a PDP (Plasma Display Panel), an EL (Electroluminescence) panel, a printer and a loudspeaker. [0050] The communication unit 312 transmits and receives the data to and from the external device. The communication unit 312 is connected to the external device via, e.g., a signal line. The communication unit 312 is exemplified such as a LAN (Local Area Network) interface board and a wireless communication circuit for wireless communications. [0051] In the information processing apparatus 300 , the storing unit 306 is stored with an operating system (OS), the various categories of programs and a variety of tables. [0052] The OS is software that handles in-between operations between the software components and the hardware components, manages a memory space, manages files and manages processes and tasks. The OS includes a communication interface. The communication interface is defined as a program for transferring and receiving the data to and from another external device etc connected via the communication unit 312 . [0053] The information processing apparatus 300 capable of realizing the stereoscopic picture generating apparatus 100 actualizes functions as the acquiring unit 110 , the arithmetic unit 120 and the receiving unit 150 in such a way that the CPU 302 loads the programs stored in the storing unit 306 into the memory 304 and executes the programs. Further, the storage unit 130 is provided in storage areas of the memory 304 , the storing unit 306 , etc. The display unit 140 is realized by the CPU 302 , the output unit 310 , etc. The receiving unit 150 is realized by the CPU 302 , the input unit 308 and so on. Operational Example [0054] An operational example of the stereoscopic picture generating apparatus 100 will be described. In the following discussion, the left and the right are employed, however, there is neither superiority nor inferiority between the left eye and the right, and the both are interchangeable. For example, in the following discussion, the image for the left eye and the image for the right eye are used, however, there is neither superiority nor inferiority between the image for the left eye and the image for the right eye, and the both are interchangeable. [0055] The stereoscopic picture generating apparatus 100 acquires the image for the left eye and the image for the right eye, and settles objects contained in the images. Further, the stereoscopic picture generating apparatus 100 determines a reference object, and calculates the parallax quantities of other objects on the basis of a positional relation between each of these other objects and the reference object and phase angles of the parallaxes. The stereoscopic picture generating apparatus 100 determines the parallax quantity of each object so that the parallax quantity of each object does not exceed a limit value of the parallax quantity. [0056] FIGS. 5 and 6 are flowcharts illustrating an example of an operation flow of the stereoscopic picture generating apparatus 100 . A symbol [A] in FIG. 5 is continued to [A] in FIG. 6 . Symbols [B] and [C] in FIG. 8 connect to [B] and [C] in FIG. 9 . A start of the operation flow in FIGS. 5 and 6 is triggered by, e.g., powering ON the stereoscopic picture generating apparatus 100 . [0057] The arithmetic unit 120 of the stereoscopic picture generating apparatus 100 acquires the limit value of the parallax quantity (S 101 ). The limit value of the parallax quantity is stored in e.g., the storage unit 130 . The limit value of the parallax quantity is defined as a maximum value of the parallax quantity of the same physical object between the image for the left eye and the image for the right eye. The limit value of the parallax quantity is set by use of a pixel count (the number of pixels). The limit value of the parallax quantity is a quantity depending on a size of the display unit 140 , the pixel count, etc. If there is a parallax quantity exceeding the limit value of the parallax quantity with respect to the same physical object, such a possibility exists that a person cannot recognize the same physical object. The limit value of the parallax quantity depends on the size of the display unit 140 . For instance, the limit value of the parallax quantity is set so that a length in the display unit 140 becomes equal to or smaller than an interval between human eyes. Accordingly, in the case of comparing the display units 140 having the same pixel count with each other, the display unit 140 having a larger size of screen exhibits a smaller limit value of the parallax quantity. The arithmetic unit 120 of the stereoscopic picture generating apparatus 100 may also calculate the limit value of the parallax quantity on the basis of the size and the pixel count of the display unit 140 , which are stored in the storage unit. Moreover, the arithmetic unit 120 of the stereoscopic picture generating apparatus 100 may also prompt a user to input the limit value of the parallax quantity to the accepting unit 150 . [0058] The acquiring unit 110 acquires the image for the left eye and the image for the right eye (S 102 ). The acquiring unit 110 may acquire the image for the left eye and the image for the right eye from a built-in camera of the stereoscopic picture generating apparatus 100 , may also acquire these images from the external device. The acquired images for the left and right eyes are stored in the storage unit 130 . The image for the left eye and the image for the right eye may also be stored previously in the storage unit 130 . [0059] The arithmetic unit 120 extracts all the objects (physical objects) contained in common to the image for the left eye and the image for the right eye, which are acquired in step S 102 (S 103 ). The extraction of the common objects involves using, e.g., pattern matching. The arithmetic unit 120 stores, in the storage unit 130 , positions of the respective images (the image for the left eye and the image for the right eye) of the common physical objects (objects). Further, the arithmetic unit 120 stores the images of the common objects in the storage unit 130 . The object (physical object) in the image for the left eye (or the image for the right eye) is also referred to as a partial image. [0060] The pattern matching is conducted, e.g., in a manner described below. The arithmetic unit 120 superposes a moving image in the image for the left eye on a moving image in the image for the right eye in a certain position, and takes a difference between pixel values in the superposed region. The arithmetic unit 120 obtains a position and a size of an area with the difference being “0” in the superposed region. The position of this area can be set to a central position of the region of each image. Further, the arithmetic unit 120 similarly takes the difference of the superposed region in each of the positions by arbitrarily moving the superposed position in parallel, and obtains the position and the size of the area with the difference being “0” in the superposed region. The arithmetic unit 120 extracts the area having the largest size with the difference being “0”. The arithmetic unit 120 can deem the area having the largest size with the difference being “0” (the area with the difference being “0”) as the common physical object and the position of the area (the area with the difference being “0”) as the position of the moving object. This area can be considered to be the same object in the same form in the image for the left eye and the image for the right eye. Note that the pattern matching method is not limited to the method described above, but other known methods are applicable. These common physical objects are recognized by the user who views the stereoscopic picture as the same object in the stereoscopic picture. [0061] Herein, the images (which are referred to as predetermined images) of the common physical objects may be stored beforehand in the storage unit 130 . At this time, the arithmetic unit 120 may extract the common physical objects by performing the pattern matching of the image for the left eye and the image for the right eye with the predetermined images stored in the storage unit 130 . Moreover, the images of the once-extracted common physical objects may also be stored as the predetermined images in the storage unit 130 . [0062] The arithmetic unit 120 determines the reference object from within the objects extracted in step S 103 (S 104 ). The reference object can be set to the image closest to the center (middle) of, e.g., the image for the right eye. Further, the arithmetic unit 120 displays the image for the right eye on the display unit 140 and may prompt the user to select a range serving as the reference object. The user selects the range serving as the reference object from the image displayed on the display unit 140 , and may input the selected range through the accepting unit 150 . The arithmetic unit 120 extracts the image of the selected range and stores the extracted image as the reference object in the storage unit 130 . This operation enables the arithmetic unit 120 to specify the reference object. Moreover, the image serving as the reference object may also be stored previously in the storage unit 130 . The range of the reference object may also be selected in each of the image for the left eye and the image for the right eye. At this time, the user selects the range of the reference object about the same physical object with respect to the image for the left eye and the image for the right eye. The reference object is one example of a predetermined image. [0063] The arithmetic unit 120 calculates the parallax quantity between the image for the left eye and the image for the right eye with respect to the reference object determined in step S 104 . Herein, the arithmetic unit 120 obtains the position of the reference object in the image for the left eye. Further, the arithmetic unit 120 obtains the position of the reference object in the image for the right eye. The position of the reference object in the image is specified by, e.g., coordinates of the center of the reference object. The reference objects of the image for the left eye and the image for the right eye have been determined in step S 104 . [0064] The arithmetic unit 120 calculates a difference between the position of the reference object in the image for the left eye and the position of the reference object in the image for the right eye. The thus-obtained difference is the parallax quantity. In the obtained difference, the difference given in the crosswise direction is a parallax quantity ΔX, while the difference given in the lengthwise direction is a parallax quantity ΔY. The arithmetic unit 120 stores the parallax quantity ΔX in the crosswise direction and the parallax quantity ΔY in the lengthwise direction in the storage unit 130 . [0065] Further, the arithmetic unit 120 may obtain the parallax quantity by superposing the image for the left eye and the image for the right eye on each other and moving one image (e.g., the image for the right eye) in parallel so that the range of the reference object specified in step S 104 becomes coincident with the image for the left eye and the image for the right eye. The parallax quantity is equivalent to a distance (a moving quantity in an X-axis direction and a moving quantity in a Y-axis direction) at which one image (e.g., the image for the right eye) moves in parallel). At this time, the arithmetic unit 120 stores, with respect to the distance given when moved in parallel, the distance in the crosswise direction as the parallax quantity ΔX and the distance in the lengthwise direction as the parallax quantity ΔY in the storage unit 130 . The parallax quantity contains positive and negative signs. That is, for instance, in the case of making the parallel movement in a −X direction, the parallax quantity ΔX takes a negative quantity. [0066] Moreover, the arithmetic unit 120 may also obtain the parallax quantity as below. The arithmetic unit 120 displays the image for the left eye and the image for the right eye in superposition on the display unit 140 . The user moves one image in parallel with the aid of the accepting unit 150 while looking at the images displayed on the display unit 140 so that the range of the reference object specified in step S 102 becomes coincident with the image for the left eye and the image for the right eye. The parallax quantity is the distance given when one image (e.g., the image for the right eye) moves in parallel. The arithmetic unit 120 stores, with respect to the distance given when moved in parallel, the distance in the crosswise direction as the parallax quantity ΔX and the distance in the lengthwise direction as the parallax quantity ΔY in the storage unit 130 . [0067] The arithmetic unit 120 aligns the positions of the reference objects in the image for the left eye and the image for the right eye (S 105 ). In the process of S 105 , the arithmetic unit 120 extracts, e.g., the image for the right eye from the storage unit 130 . Then, the arithmetic unit 120 sets an image, which is given by moving the whole image for the right eye in parallel by the parallax quantity, as a new image for the right eye. The parallax quantities involve using the parallax quantities (ΔX and ΔY) stored in the storage unit 130 . Thus, when moving the whole image of the image for the right eye in parallel by the parallax quantities (ΔX and ΔY) obtained beforehand, the position of the reference object in the image for the right eye becomes coincident with the position of the reference object in the image for the left eye. Namely, the parallax of the reference object between the image for the left eye and the image for the right eye substantially disappears. The arithmetic unit 120 stores the new image for the right eye in the storage unit 130 . Furthermore, the arithmetic unit 120 moves the position of the image for the right eye, which is stored in the storage unit 130 , in parallel by the parallax quantities (ΔX and ΔY), and sets this parallel-moved position as a new position of the object of the image for the right eye. [0068] The arithmetic unit 120 adjusts Y-coordinates of all the objects in the image for the left eye and the image for the right eye (S 106 ). In the process of S 106 , the arithmetic unit 120 makes the Y-coordinates of all the objects in the image for the left eye coincident with the Y-coordinates of all the objects in the image for the right eye. This is because, if the Y-coordinates of the same object in the image for the left eye differ from the Y-coordinates thereof in the image for the right eye, there is a possibility that the object might not be recognized to be identical. The arithmetic unit 120 extracts the image for the left eye and the image for the right eye from the storage unit 130 . Further, the arithmetic unit 120 extracts, with respect to all the objects, the positions of the objects in the image for the left eye and the positions of the objects in the image for right eye from the storage unit 130 . The arithmetic unit 120 compares the Y-coordinates of each object. The arithmetic unit 120 , if the same object has a difference of the Y-coordinates between the image for the left eye and the image for the right eye, adjusts the Y-coordinates in the image for the right eye to the Y-coordinates in the image for the left eye. Moreover, the arithmetic unit 120 may apply, with respect to the same object, an average of the Y-coordinates in the image for the left eye and the Y-coordinates in the image for the right eye to the Y-coordinates in the image for the left eye and the Y-coordinates in the image for the right eye. With this contrivance, the Y-coordinates in the image of the object for the left eye is identical to the Y-coordinates in the image of the object for the right eye. The arithmetic unit 120 stores the new image for the left eye (and the new image for the right eye) in the storage unit 130 . Further, the arithmetic unit 120 stores the position of each of objects in the new image for the left eye and the position of each of objects in the new image for the right eye in the storage unit 130 . The new image for the left eye and the new image for the right eye are used in the subsequent processes. [0069] FIG. 7 is a diagram illustrating a concrete example of the processes in step S 105 and step S 106 . An image 811 for the left eye and an image 812 for the right eye correspond to the image for the left eye and the image for the right eye before being processed in step S 105 and step S 106 . Moreover, an image 821 for the left eye and an image 822 for the right eye correspond to the image for the left eye and the image for the right eye after being processed in step S 105 and step S 106 . Herein, the image for the left eye is fixed, while the image for the right eye is moved, whereby the processes in step S 105 and step S 106 are carried out. In step S 105 , the position of the reference object of the image 812 for the right eye is moved to get coincident with the position of the reference object of the image 811 for the left eye. In step S 106 , the Y-coordinates of all the objects of the image for the right eye are moved to become coincident with the Y-coordinates of the corresponding objects of the image 811 for the left eye. The objects depicted by solid lines in the image 822 for the right eye represent objects after being moved. Moreover, the objects depicted by dotted lines in the image 822 for the right eye represent objects before being moved. Herein, the image for the left eye is fixed, and hence the image 811 for the left eye is identical with the image 821 for the left eye. [0070] Referring back to FIG. 5 , the arithmetic unit 120 acquires parallax phase angle information in the stereoscopic picture (S 107 ). The parallax phase angle is a quantity used when calculating the new position of the object of the image for the left eye. The parallax phase angle is a quantity depending on a distance between the position of the reference object and the position of another object in the image for the right eye. The parallax phase angle may also be a quantity depending on a difference between the Y-coordinates of the reference object and the Y-coordinates of another object in the image for the right eye. The parallax phase angle is an angle made by a straight line extending from the position of the reference object to the position of another object in the image for the right eye and by a straight line extending therefrom to the position of another object in the image for the left eye when the image for the left eye and the image for the right eye are expressed on the same screen. In the subsequent processes, the position of another object in the image for the left eye is calculated in a way that fixes the position of the reference object and the position of another object in the image for the right eye. [0071] FIG. 8 is a diagram illustrating an example of the parallax phase angle information. FIG. 8 illustrates an example of a table depicting an associative relation between the distance between the position of the reference object and the position of another object in the image for the right eye and the parallax phase angle. This table is stored in, e.g., the storage unit 130 . At this time, the arithmetic unit 120 can acquire the parallax phase angle information from the storage unit 130 . Moreover, the parallax phase angle may also be given as a function of the distance between the position of the reference object and the position of another object in the image for the right eye. [0072] The user may adjust the associative relation between the distance between the position of the reference object and the position of another object in the image for the right eye and the parallax phase angle. For example, the associative relation may also be adjusted in a way that multiplies a value of the parallax phase angle in the table of FIG. 8 by an arbitrary value. For instance, the arithmetic unit 120 may prompt the user to input this value. The user can adjust the parallax phase angle by inputting the value through the accepting unit 150 . Further, the parallax phase angle may also be adjusted by other methods. The parallax phase angle is adjusted, whereby a stereoscopic sense in the stereoscopic picture is adjusted. For example, the stereoscopic sense in the stereoscopic picture is emphasized by increasing the parallax phase angle. Namely, the parallax phase angle is adjusted, thereby further emphasizing or de-emphasizing the stereoscopic sense in the stereoscopic picture. [0073] The arithmetic unit 120 acquires the parallax phase angle information defined as the associative relation between the distance between the position of the reference object and the position of another object in the image for the right eye and the parallax phase angle from the table as in FIG. 8 , through the user's input and by the function. [0074] In step S 108 , the arithmetic unit 120 calculates the parallax quantity defined as the difference between the position of one object in the image for the left eye and the position of this object in the image for the right eye (S 108 ). The arithmetic unit 120 extracts information on the position of a certain single object in the image for the left eye and information on the position of this object in the image for the right eye from the storage unit 130 . Herein, owing to the process in step S 106 , the Y-coordinates of one object in the image for the left eye are the same as the Y-coordinates thereof in the image for the right eye. Hence, the parallax quantity is calculated based on a difference between X-coordinates in the image for the left eye and X-coordinates in the image for the right eye. [0075] FIG. 9 is a diagram illustrating an example of the coordinates of the reference object, the coordinates of another object in the image for the left eye and the coordinates thereof in the image for the right eye. In the example of FIG. 9 , the coordinates of the reference object are indicated by a point A0 (Xa0, Ya0). Further, the coordinates of another object in the image for the left eye are indicated by a point BL0 (Xbl0, Ybl0), and the coordinates thereof in the image for the right eye are indicated by a point BR0 (Xbr0, Ybr0). Herein, the Y-coordinate of the point BL0 is the same as the Y-coordinate of the point BR0 owing to the process in step S 106 . Moreover, the parallax quantity is a difference between the X-coordinate of the point BL0 and the X-coordinate of the point BR0. [0076] Referring back to FIG. 6 , the arithmetic unit 120 checks whether or not the parallax quantity of the object that is processed in step S 108 is equal to or smaller than the limit value of the parallax quantity that is acquired in step S 101 (S 109 ). If the parallax quantity of the object exceeds the limit value of the parallax quantity, such a possibility exists that the user, who views the stereoscopic picture, cannot recognize this object as one object (physical object). Therefore, the arithmetic unit 120 checks whether the parallax quantity of the object is equal to or smaller than the limit value of the parallax quantity or not. [0077] If the parallax quantity of the object is equal to or smaller than the limit value of the parallax quantity that is acquired in step S 101 (S 109 ; YES), the arithmetic unit 120 calculates a new position of the object in the image for the left eye (S 110 ). The arithmetic unit 120 calculates, based on the following formula, a new position (a point BL1 (Xbl1, Ybl1)) of the object in the image for the left eye. [0000] L 1 2 =L 2 2 +L 3 2 +2· L 2 ·L 3 ·cos θ 0 [0000] L 1 =√{square root over (( Xbl 1 −Xbr 0) 2 +( Ybl 1 −Ybr 0) 2 )}{square root over (( Xbl 1 −Xbr 0) 2 +( Ybl 1 −Ybr 0) 2 )}=√{square root over (( Xbl 1 −Xbr 0) 2 )}♯ Ybl 1 =Ybr 0 [0000] L 2 =√{square root over (( Xbr 0 −Xa 0) 2 +( Ybr 0 −Ya 0) 2 )}{square root over (( Xbr 0 −Xa 0) 2 +( Ybr 0 −Ya 0) 2 )} [0000] L 3 =√{square root over (( Xbl 1 −Xa 0) 2 +( Ybl 1 −Ya 0) 2 )}{square root over (( Xbl 1 −Xa 0) 2 +( Ybl 1 −Ya 0) 2 )}=√{square root over (( Xbl 1 −Xa 0) 2 =( Ybl 1 −Ya 0) 2 )}{square root over (( Xbl 1 −Xa 0) 2 =( Ybl 1 −Ya 0) 2 )}  [Mathematical Expression 2] [0078] An angle θ 0 is the parallax phase angle based on the parallax phase angle information acquired in step S 107 . The parallax phase angle depends on a distance between, e.g., the point A0 and the point BR0. [0079] Herein, the angle θ 0 , the coordinates of the point A0 and the coordinates of the point BR0 take given values. The Y-coordinate (Ybl1) of the point BL1 shall be the same as the Y-coordinate (Ybl10) of the point BR0. Hence, the formula given above is a quadratic equation with respect to the X-coordinate (Xbl1) of the point BL1, and hence the X-coordinate (Xbl1) of the point BL1 is obtained. When solving the quadratic equation, two solutions for Xbl1 are obtained, however, there is taken the solution by which the sign (the positive sign or the negative sign) of (Xbl0−Xbr0) is identical with the sign of (Xbl1−Xbr0). Namely, the solution of Xbl1 involves adopting Xbl1 with which a product of (Xbl0−Xbr0) and (Xbl1−Xbr0) is positive. The arithmetic unit 120 thus calculates the point BL1 (Xbl1,Ybl1). If the difference (parallax quantity) between the point BL1 and the point BR1 exceeds the limit value of the parallax quantity, the arithmetic unit 120 does not, however, adopt the value calculated herein as the point BL1. In this case, the new position (the point BL1(Xbl1,Ybl1)) of the object in the image for the left eye shall be a position moved by the limit value of the parallax quantity toward the point BL0 from the position (the point BR0(Xbr0,Ybr0)) of the object in the image for the right eye. Further, if the Y-coordinates of the point A0 are the same as the Y-coordinates of the point BR0, the arithmetic unit 120 shall set the new position of the object to be coincident with the original position (the point BR0 and the point BL0). The arithmetic unit 120 stores information on the positions calculated herein in the storage unit 130 . The method of calculating the position of the point BL1 is not limited to this method, but the position of the point BL1 may also be calculated by other calculation methods using a function of the distance between the reference object and the calculation target object. [0080] FIG. 10 is a diagram illustrating an example of the coordinates of the reference object, the coordinates of another object in the image for the left eye and the coordinates thereof in the image for the right eye. In the example of FIG. 10 , the coordinates of the reference object are indicated by a point A1(Xa1,Ya1). The position of the point A1 is the same as the position of the point A0. Further, the coordinates of another object in the image for left eye are indicated by the point BL1(Xbl1,Ybl1), and the coordinates of another object in the image for right eye are indicated by the point BR1(Xbr1,Ybr1). The position of the point BR1 is the same as the position of the point BR0. The angle θ 0 is the parallax phase angle. The angle θ 0 is an angle made by the point BR1—the point A0—the point BL1 (made by a line segment A0-BR1 and by a line segment A0-BL1). [0081] Referring back to FIG. 6 , if the parallax quantity of the object is not equal to or smaller than the limit value of the parallax quantity acquired in step S 101 (S 109 ; NO), the arithmetic unit 120 calculates a new position of the object in the image for the left eye (S 111 ). Herein, the new position (the point BL1(Xbl1,Ybl1)) of the object in the image for the left eye becomes a position moved by the limit value of the parallax quantity toward the point BL0 from the position (the point BR0(Xbr0,Ybr0)) of the object in the image for the right eye. The arithmetic unit 120 stores information on the position calculated herein in the storage unit 130 . [0082] The arithmetic unit 120 checks whether the new positions of all the objects are calculated or not (S 112 ). If there are some objects of which the new positions are not yet calculated (S 112 ; NO), the processing loops back to step S 108 , in which the objects with their new positions not yet being calculated, are processed. Whereas if the new positions of all the objects are calculated (S 112 ; YES), the processing advances step S 113 . [0083] In step S 113 , the arithmetic unit 120 generates the stereoscopic picture (S 113 ). The arithmetic unit 120 lays out the respective objects in the image for the left eye and the image for the right eye on the basis of the positions of all the objects that are calculated in step S 110 or step S 111 , and stores these objects as one (one set) stereoscopic picture in the storage unit 130 . Moreover, the arithmetic unit 120 may also display the generated stereoscopic picture on the display unit 140 . [0084] The stereoscopic picture stored in the storage unit 130 can be displayed on a display device for a stereovision. The display device for the stereovision is a display device configured so that the image for the left eye is inputted to the left eye, while the image for the right eye is inputted to the right eye. [0085] Herein, the processing of the stereoscopic picture generating apparatus 100 terminates. If the image for the left eye and the image for the right eye are consecutively inputted, however, the processing loops back to step S 102 and is repeated. Further, if the image to be inputted is a moving picture, similarly the processing loops back to step S 102 and is iterated. Modified Example [0086] The arithmetic unit 120 may calculate the position of the point BL1 on the basis of the following formula in place of calculating the position of the point BL1 in step S 110 . [0000] Xbl 1 =α·L 2 ·( Xbl 0 −Xbr 0)+ Xbr 0 [0000] L 2 =√{square root over (( Xbr 0 −Xa 0) 2 +( Ybr 0 −Ya 0) 2 )}{square root over (( Xbr 0 −Xa 0) 2 +( Ybr 0 −Ya 0) 2 )}  [Mathematical Expression 3] [0087] Herein, α value α is a constant. For example, the value α can be adjusted in place of prompting the user to adjust the parallax phase angle. The value α is adjusted, thereby enabling the stereoscopic sense in the stereoscopic picture to be adjusted. An increase in value a leads to a rise in parallax quantity, and hence the stereoscopic sense in the stereoscopic picture can be further emphasized. A difference (Ybr0−Ya0) between the Y-coordinates may also be used as a substitute for a distance L 2 . [0088] A value (Xbl0−Xbr0) is the parallax quantity of the object in step S 110 . The parallax quantity depends on the position (coordinates) in the depthwise direction (Z-direction). Let Zb be the position (coordinates) of the object in the Z-direction (a direction of an optical-axis of the camera) with the camera position serving as an origin, and the parallax quantity takes a linear to Zb to the power of −1 (Zb̂(−1)). Namely, when the position of the object gets distanced from the camera (when Zb increases), the parallax quantity becomes approximate to a predetermined value. The Z-directional position Zb of the object can be calculated based on the parallax quantity. Moreover, the Z-directional position Zb of the object may also be obtained by, e.g., an infrared-ray sensor etc attached to the camera. The position of the point BL1 of the object may also be calculated based on the following formula by use of the Z-directional position Zb of the object. [0000]  Xbl   1 = ( α · L 2 Zb - β ) + Xbr   0   L 2 = ( Xbr   0 - Xa   0 ) 2 + ( Ybr   0 - Ya   0 ) 2 [ Mathematical   Expression   4 ] [0089] Herein, a value β is a constant. For instance, the parallax quantity ΔX in the crosswise direction, which is used in step S 105 , can take the value β. At this time, if the Z-directional position of the object is coincident with the Z-directional position of the reference object, the parallax quantity of this object is “0”. A new parallax quantity of each object is calculated based on a difference from the Z-directional position of the reference object. The difference between the Z-directional position of the object and that of the reference object gets smaller, the new parallax quantity is affected to a greater degree. Further, the value β may also be “0”. [0090] Moreover, according to these formulae, the new parallax quantity of each object can take a value depending on a distance (a distance on the image) from the reference object and on the original parallax quantity or a value depending on the distance from the reference object and on Z-directional position of each object. According to this contrivance, it is feasible to generate a new stereoscopic picture depending on a back-and-forth relation (in the depthwise direction) of the original image. Operation and Effect of Embodiment [0091] The stereoscopic picture generating apparatus 100 acquires the image for the left eye and the image for the right eye, and settles the objects contained in the images. Further, the stereoscopic picture generating apparatus 100 determines the reference object, and calculates the parallax quantities of other objects on the basis of the positional relations between other objects and the reference object, the parallax phase angles, etc. Moreover, the stereoscopic picture generating apparatus 100 determines each object so as not to exceed the limit value of the parallax quantity. [0092] The stereoscopic picture generating apparatus 100 is capable of generating the stereoscopic picture having the stereoscopic sense depending on the distance on the screen between the reference object and each object. Namely, the stereoscopic picture generating apparatus 100 can generate the stereoscopic picture emphasizing the stereoscopic sense of even the picture based on the plurality of objects with no difference between their distances from the camera. [0093] [Non-Transitory Computer Readable Recording Medium] [0094] A program for making a computer, other machines and devices (which will hereinafter be referred to as the computer etc) realize any one of the functions can be recorded on a non-transitory recording medium readable by the computer etc. Then, the computer etc is made to read and execute the program on this non-transitory recording medium, whereby the function thereof can be provided. [0095] Herein, the non-transitory computer-readable recording medium connotes a recording medium capable of accumulating information such as data and programs electrically, magnetically, optically, mechanically or by chemical action, which can be read from the computer. Such a medium is provided inside with components such as the CPU and the memory that configure the computer, in which the CPU may also be made to execute the program. [0096] Further, among these recording mediums, for example, a flexible disc, a magneto-optic disc, a CD-ROM, a CD-R/W, a DVD, a DAT, an 8 mm tape, a memory card, etc. are given as those removable from the computer. [0097] Furthermore, a hard disc, a ROM (Read-Only Memory), etc. are given as the recording mediums fixed within the computer. [0098] All examples and conditional language provided herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.

A stereoscopic picture generating apparatus comprising: a storage unit to get stored with a first image containing partial images and a second image containing partial images corresponding respectively to the partial images contained in the first image; and an arithmetic unit to extract a first position defined as an existing position of a first partial image contained in the first image and a second position defined as an existing position of a second partial image contained in the first image, to calculate a first differential quantity defined as a difference between the first position and the second position, to calculate a third position defined as a new existing position of a third partial image contained in the second image that corresponds to the first partial image based on the first differential quantity, and to generate a third image based on the third position of the third partial image.

CROSS-REFERENCE TO RELATED APPLICATIONS This is a continuation, under 35 U.S.C. §120, of copending German Application 103 24 889.1, filed May 30, 2003, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of International Patent Application No. PCT/EP2004/005766, filed May 28, 2004; the prior applications are herewith incorporated by reference in their entirety. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a metal sheet, in particular for use as a carrier body for a catalytically active material for the purification of exhaust gases from mobile internal combustion engines. The metal sheet has at least one slit that extends only in an inner region of the metal sheet and at least partially delimits a microstructure of the metal sheet. The microstructure projects out of a surface structure of the metal sheet. The invention also relates to a carrier body having a plurality of sheets, and an exhaust system having the carrier body. In the treatment of exhaust gas from mobile internal combustion engines such as, for example, gasoline and diesel engines, it is known that components or structures which provide a relatively large surface may be placed in the exhaust gas line. Those components are conventionally provided with an adsorbing, catalytically active or similar coating, with intimate contact with exhaust gas flowing past being implemented due to the large surface of the components. Such components are, for example, filter elements for filtering out particles containing the exhaust gas, adsorbers for the at least time-limited storage of pollutants (for example, NO x ) contained in the exhaust gas, catalytic converters (for example, three-way catalytic converters, oxidation catalytic converters, reduction catalytic converters, etc.), diffusers for influencing the flow or the swirling of the exhaust gas flowing through, or else heating elements which heat the exhaust gas to a predetermined temperature just after the cold starting of the internal combustion engine. In light of the conditions of use in the exhaust system of an automobile, basically the following carrier substrates have proved appropriate: ceramic honeycomb bodies, extruded honeycomb bodies and honeycomb bodies formed of metal sheets. Due to the fact that such carrier substrates always have to be adapted to their functions, metal sheets resistant to high temperature and to corrosion are especially suitable for serving as initial material. It is known to produce honeycomb bodies with a plurality of at least partially structured metal sheets which are subsequently introduced into a housing and thus form a carrier body that may be provided with one or more of the above-mentioned coatings. The at least partially structured metal sheets in that case are disposed in such a way that channels or ducts disposed substantially parallel to one another are formed. In order to ensure that, for example, some of the metal sheets are provided with a primary structure or surface structure which is distinguished, inter alia, by a regular repetitive structure, in particular a kind of sinusoidal undulation, a sawtooth structure, a rectangular undulation, a triangular undulation, an omega undulation or the like. Those metal sheets provided with a primary structure are then stacked one on the other (if appropriate, alternating with smooth intermediate layers), are connected to one another and are introduced into a housing. A honeycomb body is thereby formed which has channels or ducts substantially parallel to one another. It is known, further, to introduce a second structure into metal sheets of that kind which is intended, in particular, to prevent the formation of a laminar flow directly after entry of the exhaust gas into the honeycomb body. A gas exchange of regions of the partial exhaust gas stream which lie in the center of such a channel or duct with the, for example, catalytically active channel or duct wall regions, does not take place. That secondary structure or microstructure therefore provides inflow surfaces which result in a kind of swirling of the partial exhaust gas streams inside such a channel or duct. That leads to an intensive mixing of the partial exhaust gas streams themselves, so that intimate contact with the pollutants contained in the exhaust gas with the channel or duct wall is ensured. Furthermore, it is possible, through the use of such secondary structures, to form flow passages transversely with respect to the channel or duct, which allow a gas exchange of partial exhaust gas streams in adjacent channels or ducts. For that reason, secondary structures are known which include, for example, guide surfaces, microstructures, bosses, projections, wings, tabs, holes or the like. That, to an extent, results in a markedly increased diversity of variation in the production of such metallic honeycomb bodies, as compared with those formed of ceramic material, since, in that ccase, such a complex channel or duct wall cannot be implemented or can be implemented only at a particularly high outlay in technical terms. Further, in the treatment of exhaust gas, it is particularly useful if a conversion of the pollutants contained in the exhaust gas takes place virtually immediately after the starting of the engine. In that case, according to the statutory provisions or directives, that should take place with particularly high effectiveness. For that reason, increasingly thin metal sheets have been used in the past. The result of very thin metal sheets is that there is a very low surface-specific heat capacity. That is to say, relatively little heat is extracted from the exhaust gas flowing past or the metal sheets themselves experience a temperature rise relatively quickly. That is important because the catalytically active coatings used at the present time in the exhaust system begin to convert the pollutants only from a specific light-off temperature which lies approximately around temperatures of 230° C. to 270° C. Metal sheets have been used which have a sheet thickness that, for example, is smaller than 20 μm, with the aim of converting the pollutants with at least 98% effectiveness even after a few seconds. The above-mentioned objectives, however, result in a series of problems with regard to manufacture and to use. The production of such filigree structures, in particular secondary structures or microstructures, requires tools which operate especially accurately and which are normally very costly, and therefore they should have long service lives. It must be remembered, in this context, that, on one hand, forming and, on the other hand, if appropriate, also separating manufacturing steps have to be carried out. In order to save tool costs, as many machining steps as possible have been integrated into one tool, and because of the configuration of the secondary structure an increasing wear was to be seen on the tool. Furthermore, there is the problem that the relatively thin metal sheets have to be supplied at a suitable speed, if possible without being exposed to undesirable cold forming. Strain hardening may adversely influence the forming behavior of the metal sheet. Moreover, due to the small material thickness, there is the risk that the metal sheet tends to crease, to roll up and/or to tear. Those undesirable deformations may occur or be intensified even during production as well as during transport or during use in an exhaust system of an automobile. The result of creases, for example, is that, under certain circumstances, channels or ducts are blocked or cracks are formed which are propagated as a result of the high thermal and dynamic loads in the exhaust system of an automobile and therefore put the structural integrity of the honeycomb body at risk. Furthermore, it must be remembered that primary and/or secondary structures creased or deformed in that way present opposition to the exhaust gas in an undesirable way, so that, under certain circumstances, an increased dynamic pressure upstream of the honeycomb body is to be noted, which may possibly lead to a reduction in engine power. SUMMARY OF THE INVENTION It is accordingly an object of the invention to provide a metal sheet having a microstructure relieved of notching, a carrier body, in particular for a catalytically active material, having a plurality of sheets, and an exhaust system having the carrier body, which overcome the hereinafore-mentioned disadvantages of the heretofore-known products and devices of this general type, in which the carrier body can permanently withstand the high thermal and dynamic loads in the exhaust system of an automobile and in which the metal sheet, although having a complex construction and being provided with a large relatively rigid surface, is nevertheless highly durable. In particular, it is to be ensured that the structures of the metal sheet inside the carrier body are preserved as far as possible for a long period of time in use, in order to thereby provide a particularly effective device for the purification of exhaust gases. With the foregoing and other objects in view there is provided, in accordance with the invention, a metal sheet, comprising an inner region and a surface structure. At least one slit is disposed in the inner region. The at least one slit has at least one edge region and a recess in the at least one edge region. A microstructure is at least partially delimited by the at least one slit. The microstructure projects out of the surface structure. It may be pointed out, in the first place, that a plurality or multiplicity of slits may be located in the metal sheet, at least one extending into an inner region of the metal sheet. That is to say in particular, the slit is not in contact with the edge of the metal sheet, hence is bordered by the material of the metal sheet. It is also possible, however, for the slit to be constructed in a more complex way, that is to say in which it does not extend in only one direction (instead of I-shaped, for example, V-shaped, W-shaped, T-shaped, X-shaped or shaped in a similar way), although then at least two and preferably all edge regions of the complex slit are provided with a recess. Such a slit, lying particularly completely in the inner region of the metal sheet, is introduced into the material, in order, on one hand, to allow fluid exchange through the metal sheet itself, and, on the other hand, to enable the slit to also serve for the formation of microstructures or secondary structures, such as are described in the introduction hereto. The term “microstructures” is to be understood to also mean, in particular, protuberances, crimpings, upbends or the like which, as a rule, are delimited locally in or on the metal sheet. The microstructures may also form, for example, bosses, wings, cants or similar structures. The microstructure serves, inter alia, for influencing a fluid flow routed along the surface of the metal sheet, thus giving rise to swirling and calming zones in which a kind of turbulent flow or a reduced flow velocity is generated with respect to the fluid. With regard to the action or configuration of such microstructures, reference may be made, for example, to International Publication No. WO 01/80978 A1, corresponding to U.S. Patent Application Publication No. US 2003/0072694 A1, the content of which is incorporated in full into the subject matter of the disclosure of the instant application. Moreover, in addition to this microstructure, the metal sheet has what is known as a surface structure or primary structure. What is meant by this is that the metal sheet itself is not planar, but has an overriding structure. As is known, metal sheets which are used as carrier bodies for catalytically active material in the exhaust system of automobiles are provided with a surface structure which forms a multiplicity of channels or ducts when this metal sheet is assembled together with other metal sheets to form a carrier body. Conventionally, these surface structures have a wave-like or zigzag-shaped structure. Where the wave shapes or forms are concerned, for example, a kind of sinusoidal undulation or an omega-shaped undulation has proved particularly appropriate. These surface structures extend, as a rule, over the entire length of the metal sheet or of the resulting carrier body. Under certain circumstances, continuous or abrupt changes in the height or in the width of the surface structure over the lengths are also known. In summary, therefore, it is to be assumed, herein, that the surface structure serves for forming channels or ducts in an axial direction of the carrier body through which a fluid is capable of flowing, while the microstructure is intended, foremost, to bring about an influencing of the flow inside these channels or ducts formed by the surface structure. It is therefore to be assumed that the microstructures are constructed in such a way that they extend into the inner region of such a channel or duct and, of course, are not made larger or higher than the channel or duct allows. Depending on the form of the channel or duct, the microstructure may extend from any desired point into the inner region, that is to say both from a bottom face and from the side faces or else from a ceiling region. According to the invention, it is proposed that the slit have a recess in at least one edge region. Preferably, all of the edge regions of the slit have a recess, in particular with the same configuration of the recess. Conventionally, the slit has a linear (I-shaped) configuration. This means that the edge regions normally terminate in a point or with an extremely small radius (for example, smaller than 0.05 mm). Such a slit is conventionally produced by stamping since the manufacturing method and has a straight (I-shaped) run. In order to produce the microstructures, that region of the metal sheet which is located directly in the vicinity of the slit is bent up through the use of suitable tools, so that, for example, guide surfaces are obtained. As a result of this bending operation, the material in the edge region around the slit is subjected to high stress. Thus, for example, strain-hardening processes may lead to a changed thermal and dynamic behavior of the metal sheet around the slit. The sometimes considerable loads which act on such a guide surface or the metal sheet during use in the exhaust system of an automobile may result in pronounced notching in the edge region of the slit. A crack which, starting from this edge region of the slit, would be propagated further into the material of the metal sheet, would put the entire functionality of the carrier body at risk, and detached fragments might even be accelerated considerably due to the exhaust gas stream flowing through and impinge onto the following components for exhaust gas purification. There, too, they would block the channels or ducts, clog pores, strip off material, destroy coatings or the like. Such effects are reliably avoided by the provision of recesses in at least one edge region of the slit. These recesses have a relatively large radius, so that a notch effect does not arise even in sometimes considerably deformed regions of the metal sheet. Preferably, the slit has such a recess on each of its edge regions. In this case, it is also conceivable that, for example, crossed slits are provided, with such a recess being provided at the respective end regions. The recess means, in other words, a widening of the linear slit, so that a wider slit is provided in the end regions. Round cross sections, wider grooves with rounded end sides or flanks, undercuts or similar shapes are appropriate for this purpose. Further, the recess may also be constructed in the form of one or more buckled or angled end region of the slit. In this case, it is also possible for the edge regions to be configured with different shapes relating to the recess. The production of such slits with recesses can be carried out in a simple way through the use of separating manufacturing methods such as, for example, (laser beam) cutting, stamping, spinning or similar methods for the separation of metal sheets. In accordance with another feature of the invention, the surface structure of the metal sheet has a wave-like or corrugated configuration with wave crests and wave troughs extending in a longitudinal direction. A wave-like configuration also embraces, in particular, a sinusoidal form which can be seen when the metal sheet is viewed from one edge. The wave crests or wave troughs preferably extend over the entire axial length of the metal sheet, and they preferably run substantially parallel to one another. In accordance with a further, particularly advantageous feature of the invention, the wave-like configuration can be described by a wavelength and a wave height. The ratio of wavelength to wave height lies in a range of 3.0 to 1.0, in particular in a range of 2.5 to 1.1 or preferably in a range of 2.0 to 1.3. The terms wave crest and wave trough, as a rule, respectively mean the highest and the lowest point of the wave-like configuration. The wavelength in this case designates the distance between two directly adjacent identical extremes of the surface structure such as, for is example, between two directly adjacent wave crests or between two directly adjacent wave troughs. The wave height describes the height difference between two different extremes, that is to say, for example, the height difference from wave crest to wave trough. As a result, the wave height and wavelength are measured perpendicularly to one another. In this case, it may be pointed out that, basically, deviations with regard to wave height or to wavelength occur which are unavoidable for manufacturing reasons. The characteristic values specified herein thus constitute a statistical mean value, and manufacturing tolerances always have to be remembered. The ratio of wavelength to wave height specified herein also describes the degree of deformation of the metal sheet. If it is assumed that the metal sheet is in the first place substantially planar, and the surface structure is subsequently introduced, for example through the use of a wave-rolling method, then a low ratio of wavelength to wave height, for example lower than 2.0, means that the wave crests or the wave troughs are disposed relatively closely next to one another, while the height difference from wave crest to wave trough is relatively large. As a result, relatively slender channels or ducts are formed, which have sides or flanks running very steeply. Precisely where so highly deformed metal sheets are concerned, there is the risk of material fatigue, even during production, so that, for example in the case of increasing wear of the tool, cracks may even arise which may subsequently spread. Consequently, precisely for such metal sheets, it is particularly useful to provide recesses in the edge regions of the slits. In accordance with an added feature of the invention, the microstructure includes a guide surface which is set or flared out from the surface structure of the metal sheet, in particular obliquely in the longitudinal direction. An angle which lies in a range of 10° to 35° is preferably formed. Such a guide surface is particularly suitable for peeling off partial flows on the surface of the metal sheet and steering them toward desired regions. Such a guide surface may also be gathered in detail from German Utility Model 201 17 873 U1, corresponding to U.S. Patent Application Publication No. US 2004/0013580 A1, the content of the disclosure of which is incorporated herein in full by reference. In accordance with an additional feature of the invention, the metal sheet has two slits which in each case at least partially delimit a microstructure. This means, in other words, that at least one of the microstructures is delimited in two directions by a pair of slits, and that region of the metal sheet which lies between them is set out, pressed out or otherwise deformed with respect to the general surface structure. In this case, as a rule, surfaces are formed which, for example, are not oriented so obliquely with respect to the direction of flow of the exhaust gas, that a lower diversion of the gas stream is brought about in this case. This may result in an advantageous effect on the pressure loss which is generated, because such microstructures present lower flow resistance. In accordance with yet another feature of the invention, the at least one recess has a rounded shape, in particular an arc of a circle with a radius of curvature. The radius of curvature preferably amounts to at least 0.1 mm. Tests have shown that, with a radius of curvature larger than 0.1 mm, in particular larger than or equal to 0.2 mm, crack formation or crack propagation, starting from the slits, is markedly reduced. The cause of this is, inter alia, a markedly reduced material stress of the metal sheet during use, which is sometimes only in the region of less than 30%, as compared with the simple slit. A reduced stress in the edge regions of the slit prevents the formation of cracks. In accordance with yet a further feature of the invention, there is provided a multiplicity of microstructures, which are disposed in lines parallel to the longitudinal direction of the metal sheet and/or in rows transvers to the longitudinal direction. The microstructures are preferably disposed in such a way that they are located on the wave crests or in the wave troughs. The microstructures disposed on the wave crests extend toward the wave troughs, and the microstructures disposed on the wave troughs extend toward the wave crests. That is to say, in other words, that the microstructures are disposed within two planes which are defined in each case either by the wave crests or by the wave troughs when such a metal sheet is positioned flat on a planar base. The microstructures are later disposed thus inside the flow channels or ducts in the case of a carrier body. With regard to their configuration in relation to one another, it may also be pointed out that, if appropriate, an offset of the lines or rows over the length or width of the metal sheet is also possible. In accordance with yet an added feature of the invention, the metal sheet is formed from a steel which contains aluminum and chromium and which has high thermal load-bearing capacities and is corrosion-resistant. The metal sheet preferably has a metal sheet thickness in a range of 0.015 to 0.15 mm, in particular in a range of 0.03 to 0.08 mm. Alternatively thereto, it is basically also possible to use a metal sheet which has a nickel base or alloys thereof. The materials specified herein have proved appropriate precisely for use under the aggressive conditions in the exhaust system of an automobile. The metal sheet thickness in this case is to be selected as a function of the place of use or of the intended use of the metal sheet in the exhaust system. It is to be noted, in principle, that a higher metal sheet thickness represents an increased heat capacity, so that such metal sheets may also be used, for example, as heat storage devices. Furthermore, the increased sheet thickness also results, of course, in increased stability, so that these metal sheets can be exposed to particularly high dynamic loads. The relatively thin metal sheets in the range of 0.015 to approximately 0.05 mm have only a relatively low heat capacity, so that these sheets, for example, adapt quickly to the ambient temperature. This means that, after the cold starting of the internal combustion engine, these are heated quickly by the exhaust gas flowing past and therefore make it possible to quickly activate the catalyst adhering to them. In accordance with yet an additional feature of the invention, the microstructure has a maximum extent out of the surface structure which lies in a range of 0.3 to 0.95 (30%-95%) of the wave height, preferably in a range of 0.5 to 0.8 (50%-80%) of the wave height. That is to say, in other words, that the microstructure stands out from the surface structure of the metal sheet in a clearly perceivable way. It is only in this way that the exhaust gas quantity flowing past the metal sheet in a normally laminar flow can be transformed into a turbulent flow. With the objects of the invention in view, there is also provided a carrier body for a component for the purification of exhaust gases. The carrier body comprises a plurality of at least partially structured metal sheets being stacked and/or wound to permit a fluid to flow through the carrier body. At least one of the metal sheets is a metal sheet according to the invention as described above. In accordance with another feature of the invention, the carrier body has a multiplicity of channels or ducts which extend substantially in a longitudinal direction and which are at least partially formed by the surface structure of the metal sheet. The at least one microstructure preferably influences the flow of the fluid, so that the fluid, when it flows through the carrier body, is steered toward adjacent channels or ducts. In other words, therefore, flow influencing takes place in a direction which is at least partially oblique or perpendicular to the longitudinal direction of the channels or ducts or to the main flow direction of the exhaust gas. The microstructure may in this case also have a plurality of measures for flow influencing. Thus, it is possible for the microstructure to be formed by a guide surface which brings about a defined deflection of the exhaust gas, for example through the use of bosses, orifices, steps, upsets or the like. In accordance with a further feature of the invention, the carrier body has a channel or duct density in a range of 100 to 1,000 cpsi (cells per square inch; 6.45 channels or ducts per square inch corresponds to 1 channel or duct per square centimeter), preferably in a range of 300 to 600 cpsi. In this case, the metal sheets preferably have a ratio of wavelength to wave height which lies in a range of 2.0 to 1.3. In accordance with an added feature of the invention, the carrier body has, at least in a partial region (in the longitudinal direction), a uniform distribution of microstructures over a cross section perpendicular to the longitudinal direction. The multiplicity of channels or ducts are preferably oriented in the longitudinal direction of the carrier body which coincides substantially with the main flow direction of the exhaust gas through the carrier body. If a cross section perpendicular thereto is considered, then, the channels or ducts can be perceived as a kind of honeycomb structure. In light of such a cross section, then, it is proposed that there be a uniform distribution of microstructures (in the statistical sense). This means, in other words, that there is substantially the same distance toward adjacent microstructures and/or that in each case only a specific number of channels or ducts are disposed per unit of cross-sectional area. This results in a particularly symmetrical load on the metal sheet or on the carrier body, so that stress peaks can be reduced in this case. In accordance with an additional feature of the invention, a multiplicity of microstructures is disposed in a cross section perpendicular to the longitudinal direction of the carrier body. These microstructures are configured in such a way that the fluid flowing through is deflected partially in different directions. What is meant thereby is, in particular, that a radially outward deflection can take place through the use of the microstructures in one partial region of the cross section, while a deflection of the fluid or exhaust gas into an opposite direction running obliquely thereto or a skew direction can take place in an adjacent partial region of the cross section. The orientation of the microstructures or the resulting deflection of the fluid flowing through the carrier body is also codetermined substantially by the configuration of the metal sheet in the carrier body itself. Thus, where spirally wound metal sheets are concerned, as a rule, only deflections in a radial direction take place, whereas, in the case of stacked or simply bent, involute, S-shaped or similar configurations of the metal sheets, different orientations of the microstructures in adjacent regions are possible. This results in a markedly more complex flow mixing pattern. In accordance with still another feature of the invention, the carrier body includes, in addition to the at least one metal sheet, at least one element from the following group of elements: at least one smooth metal layer which, in particular, bears substantially against the extremes of the surface structure of the metal sheet, and preferably is connected thereto; at least one porous fiber layer which, in particular, bears substantially against the extremes of the surface structure of the metal sheet, and preferably is connected thereto; at least one housing which surrounds the carrier body at least in a portion; at least one sleeve which surrounds the carrier body at least in a connection or tie-up region and serves for connection or tying up to a housing; at least one coating which is provided in at least one sector of the carrier body; and at least one measuring device. With regard to the smooth metal layer, it must be mentioned that, as is known, smooth metal layers and structured metal sheets are stacked alternately with one another and thus in each case delimit channels or ducts. Such a stack of smooth metal layers and structured metal sheets is subsequently wound or bent in such a way that they are given the cross section of the desired carrier body form. Known carrier body forms are round, oval, polygonal as well as cylindrical, conical or rectangular configurations. The provision of a porous fiber layer is appropriate particularly when such a carrier body is used as the filter for particles or other solid, liquid or gaseous constituents in the exhaust gas stream. At this juncture, too, reference may be made to German Utility Model 201 17 873 U1, corresponding to U.S. Patent Application Publication No. US 2004/0013580 A1, the content of the disclosure of which is also presented herein with respect to the porous fiber layer. All known technical joining manufacturing methods are considered in general as a technique for connecting the smooth metal layer or the porous fiber layer to the metal sheet, but welding or brazing is preferably proposed herein. The preferred manner of producing the technical joining connection is by brazing. However, a sintering process or even welding may be used as well. A sleeve provides an additional sheet which surrounds the carrier body or the stack of metal sheets about a circumference and which serves for connecting or tying up to a housing. A direct technical joining connection from the metal layers or metal sheets forming the channels or ducts toward the housing is thus prevented. In order to explain the function of the sleeve, reference may be made, for example, to International Publication No. WO 01/79670 A1, corresponding to U.S. Patent Application Publication No. US 2003/0007906 A1, the disclosure content of which is fully incorporated herein. The coating is to be selected in each case in dependence on the function of the carrier body. Thus, coatings are known which bring about a catalytic conversion of pollutants that are contained in the exhaust gas and which are formed substantially by precious metals or rare earths. Furthermore, coatings are customary which assume a kind of storage function, in particular with regard to nitrogen oxides. It is also possible for the coating to be used for a further enlargement of the surface of the metal sheet, with a washcoat normally being employed. The statement that such a coating is provided at least in a sector of the carrier body means, in particular, that the carrier body: is constructed with different coatings (for example, with regard to type, layer thickness, surface roughness, etc.) and/or is provided even only partially with a coating, in which case this sector may be located in the inner region of the carrier body without contact with the circumferential surface and (additionally or alternatively) may extend over only part of the axial length. The provision of a measuring device, in particular of sensors or the like, serves, for example, for checking the functionality of the carrier body. The sensors used are often, inter alia, what are known as lambda probes or also temperature sensors. A measurement value located in the exhaust gas or present in the carrier body is normally transferred through the housing toward an engine control or another control or regulating unit. With the objects of the invention in view, there is additionally provided, in an exhaust system, a component, comprising a carrier body according to the invention as described above, for purification of exhaust gases. The component is selected from the group consisting of a catalytic converter, a flow mixer, an adsorber, and a particle trap. The various fields of use or structures for catalytic converters, flow mixers, adsorbers or particle traps are known to a person skilled in this art, so that, as a rule, it is possible in a simple way for him or her to adapt the carrier bodies described herein to the respective tasks as components in the exhaust system. Since the thermal and dynamic loads for the carrier body are always high and crack propagation with regard to the slits for the microstructure can be markedly reduced in this manner, all of the above-mentioned components have a markedly prolonged useful life. The statutorily required limit values with regard to exhaust gas purification can thus be maintained for a long time without high maintenance or repair costs. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a metal sheet having a microstructure relieved of notching, a carrier body having a plurality of sheets, and an exhaust system having the carrier body, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims, in which the features recited individually therein can be combined with one another in any appropriate way desired. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic, perspective view of a portion of a metal sheet with a microstructure; FIG. 2.1 is a fragmentary, perspective view of a microstructure with a slit without a recess; FIG. 2.2 is a fragmentary, perspective view of a microstructure with a slit which has a first exemplary embodiment of a recess; FIG. 2.3 is a fragmentary, perspective view of a microstructure with a slit which has a further exemplary embodiment of a recess; FIG. 3 is a reduced perspective view showing the construction of a carrier body with a first embodiment of the metal sheets; FIG. 4 is a fragmentary, perspective view of a portion of a carrier body including metal sheets with microstructures and a fiber layer; FIG. 5 is an enlarged, longitudinal-sectional view showing the construction of a carrier body; FIG. 6 is a cross-sectional view showing the construction of a further embodiment of the carrier body; FIG. 7 is a perspective view showing the construction of an exhaust system in an automobile; FIGS. 8A , 8 B, 8 C and 8 D are perspective views illustrating the production of an embodiment of the metal sheet according to the invention; and FIG. 9 is a fragmentary, perspective view of a portion of a metal sheet with a microstructure causing a swirl. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a diagrammatic and perspective view of part of a metal sheet 1 with a microstructure 4 . In this illustrated portion, the metal sheet 1 includes a microstructure 4 which is partially delimited by two slits 2 . These slits 2 extend only into an inner region 3 of the metal sheet 1 . The microstructure 4 projects out of a surface structure 5 of the metal sheet 1 . The surface structure 5 is constructed with wave crests 9 and wave troughs 10 . As indicated by reference numeral 11 , edge regions 6 of the slits 2 are illustrated in an enlarged manner in the following FIGS. 2.1 , 2 . 2 and 2 . 3 . FIGS. 2.1 , 2 . 2 and 2 . 3 show views of a portion of a microstructure 4 which is delimited by a slit 2 . The slit 2 makes it possible for the microstructure 4 to be formed from the metal sheet 1 in such a way that the microstructure emerges from the surface structure 5 . FIG. 2.1 in this case illustrates the edge region 6 as a simple slit 2 , that is to say without a recess 7 according to the invention. Tip transitions in the edge region 6 constitute a notch, so that during a relative movement of the microstructure 4 with respect to the metal sheet 1 , a continuing widening of the slit 2 may take place in the edge region 6 . Entire microstructures 4 may therefore ultimately be loosened from the metal sheet 1 . In order to avoid something such as that occurring, recesses 7 are provided in the edge region 6 of the slit 2 , as is illustrated by way of example in FIGS. 2.2 and 2 . 3 . The recess 7 in FIG. 2.2 forms an arc of a circle 15 with a radius of curvature 16 which preferably lies in the range of 0.2 mm to 0.4 mm. In FIG. 2.3 , the recess 7 is illustrated as an undercut. Other forms of the recess 7 which reduce the notch effect may likewise be employed. FIG. 3 is a diagrammatic and perspective view of a configuration of two metal sheets 1 with microstructures 4 which can be assembled to form a carrier body according to the invention. The metal sheets 1 again have the surface structure 5 with wave crests 9 and wave troughs 10 which extend preferably over the entire length in longitudinal direction 8 . The microstructures 4 of the metal sheet 1 are disposed “reciprocally” and “equidirectionally”. In this respect, “reciprocally” means that the microstructures 4 extend alternately upward and downward (with respect to the surface structure 5 of the metal sheet 1 ), as is seen in the longitudinal direction 8 . In addition, in this respect, “equidirectionally” means that the slits 2 which delimit the microstructure 4 point in one (common) direction, that is to say precede the microstructure 4 or delimit the latter upstream. The microstructures 4 are formed as guide surfaces 13 with an orifice 45 . The guide surfaces 13 have the effect that the flow running substantially in the longitudinal direction 8 is deflected in transverse direction 47 . The recess 7 is also clearly illustrated, enlarged, in the edge regions 6 of the slits 2 . FIG. 4 shows, in a perspective and sectional-view, a portion of an embodiment of a carrier body 21 as a filter body or particle trap. Two metal sheets 1 disposed adjacent one another are illustrated, between which a fiber layer 27 is disposed. The metal sheets 1 have a multiplicity of guide surfaces 13 to deflect a flow direction, which is illustrated in this case by an arrow 25 . This ensures that the exhaust gas, together with particles 46 contained in it, penetrates through the filter layer 27 , so that the particles 46 are retained on the surface or inside the fiber layer 27 until they can be converted into gaseous components. For this purpose, discontinuous regeneration (a considerable supply of heat) may be carried out or continuous regeneration according to the CRT method may take place. The dwell time of the particles in the filter body is advantageously prolonged so that the required reaction partners for chemical conversion are present. The microstructures 4 or guide surfaces 13 are set or flared out of the surface 5 of the metal sheet 1 . A configuration which is oblique in the longitudinal direction 8 is illustrated, with an angle 14 being formed which lies in a range of 10° to 35°. The guide surface 13 or microstructure 4 has a maximum extent 20 out of the surface structure 5 which lies in a range of 0.3 to 0.95 of the wave height 12 (shown in FIGS. 8B and 8D ). A recess 7 is again provided in the edge region 6 of the slits 2 . The metal sheets 1 have a surface structure 5 which forms channels or ducts 22 through which a fluid is capable of flowing in the direction of flow indicated by the arrow 25 . FIG. 5 is a diagrammatic, longitudinal-sectional view, which shows a carrier body 21 having a plurality of metal sheets 1 that form channels or ducts 22 through which the exhaust gas is capable of flowing in the direction of flow indicated by the arrow 25 . The carrier body 21 illustrated herein is constructed as a flow mixer which serves the function of equalizing a flow profile 48 of the oncoming exhaust gas stream. The flow profile is substantially parabolic. The carrier body 21 has a multiplicity of metal sheets 1 with microstructures 4 which form orifices 45 , so that the exhaust gas can flow into adjacent channels or ducts 22 . In this case, the configuration of the microstructures 4 in the carrier body 21 is selected in such a way that, in a partial region 23 in the longitudinal direction 8 , a uniform distribution of microstructures 4 is provided perpendicularly to the longitudinal direction 8 over a cross section 24 (shown in FIG. 6 ). The metal sheets 1 or the carrier body 21 are or is surrounded in a portion 29 by a housing 28 . In this case, the portion 29 includes the entire axial length of the carrier body 21 and the housing 28 and even extends beyond the axial length of the carrier body 21 . The metal sheets 1 are connected or tied to the housing 28 through the use of a sleeve 30 which is disposed relatively centrally in a connecting or tying region 32 . The illustrated carrier body 21 or flow mixer furthermore has a sector 33 in which a coating 31 is provided. However, the sector 33 may extend over the entire axial length of the carrier body 21 in exactly the same way as the portion 29 . FIG. 6 shows a diagrammatic, cross-sectional view of a further embodiment of a carrier body 21 with a housing 28 . The metal sheets 1 in this case are wound in an S-shaped manner, with layers formed of the structured metal sheets 1 and a smooth metal layer 26 being formed. The surface structure 5 of the metal sheet 1 and the smooth metal layers 26 together form channels or ducts 22 into which the microstructures 4 or guide surfaces 13 project. The microstructures 4 or guide surfaces 13 bring about a deflection of the fluid flowing through the carrier body 21 , so as to give rise, transversely thereto, in particular within the cross section 24 , to transverse flows which are identified in this case by the arrow 25 . The ends of (preferably all) the metal layers 26 or metal sheets 1 are connected to the sleeve 30 which likewise has a surface structure 5 . The sleeve 30 is disposed over the entire circumference of the outer contour of the carrier body 21 . As a result of a partial connection or tying of the sleeve 30 to the housing 28 and of a connection or tying to the metal sheets 1 or metal layers 26 which, if appropriate, is offset (axially and/or in the circumferential direction), the different expansion behavior of the housing 28 and of the metal sheets 1 or metal layers 26 is compensated. FIG. 7 diagrammatically shows the construction of an exhaust system 35 for an automobile. The automobile has an internal combustion engine 40 , and the fuel used may be gasoline, diesel, rape or rape oil or other energy carriers. An exhaust gas which is produced in a displacement or piston volume 43 (or combustion chamber), where appropriate, runs through the following components before it is ultimately discharged into the surroundings: a turbocharger 42 for compressing intake air for the internal combustion engine 40 , a flow mixer 37 with a measuring device 34 , a particle trap 39 , a catalytic converter 36 , an adsorber 38 , a further catalytic converter 36 (for example, a three-way catalytic converter), and an exhaust gas line 41 through which the individual components for the purification of the exhaust gas are connected to one another. In order to influence the combustion operations or the action of the exhaust system 35 or of the internal combustion engine 40 , data are transferred to an engine control 44 . FIGS. 8A , 8 B, 8 C and 8 D diagrammatically illustrates the manufacturing steps which may be used in order to produce the metal sheet according to the invention. Step (A): As is seen in FIG. 8A , starting from a substantially planar metal sheet 1 , slits 2 lying in the inner region 3 of the metal sheet 1 are introduced in rows 18 and/or in lines 17 . The slits 2 in this case are configured in such a way that a recess or opening 7 is provided in each of their edge regions 6 . Step (B): As is seen in FIG. 8B , the metal sheet 1 which is thus pretreated is then subjected to a shaping manufacturing method, for example wave-rolling, so that the surface structure 5 is formed. The surface structure 5 illustrated is distinguished by wave crests 9 and wave troughs 10 which are propagated substantially parallel to one another. The surface structure 5 or the wave-like configuration can be described through the use of the parameters of a wavelength 11 and wave height 12 . In the illustrated embodiment of the metal sheet 1 , the ratio of wavelength 11 to wave height 12 is approximately 3.0. Step (C): As is seen in FIG. 8C , step C shows the metal sheet 1 as it appears after a second shaping manufacturing method for forming the microstructures 4 . For this purpose, the slits 2 positioned on the wave crests 9 or in the wave troughs 10 have been provided as a delimitation for the microstructure 4 and upsets have been carried out in the material of the metal sheet 1 . The upsets form the guide surfaces 13 with the orifices 45 . The guide surfaces 13 extend upward from the wave troughs 10 , and the guide surfaces 13 project downward from the wave crests 9 . Step (D): As is seen in FIG. 8D , in a last step, a particularly low ratio of wavelength 11 to wave height 12 is formed. In this case, for example, it is possible for the metal sheet 1 to be compressed, so that the surface structure 5 has markedly smaller wavelengths 11 . With regard to the production of such metal sheets, reference may also be made to German Patent DE 103 04 814 B3, corresponding to U.S. patent application Ser. No. 11/199,396, filed Aug. 8, 2005. FIG. 9 is a diagrammatic and perspective view of a portion of a metal sheet 1 with a microstructure 4 which causes a swirl of the fluid stream (as is indicated diagrammatically by the arrow 25 ). A metal sheet 1 is shown which includes at least one slit 2 disposed in an inner region 3 of the metal sheet 1 . The at least one slit 2 at least partially delimits a microstructure 4 of the metal sheet 1 which projects out of a surface structure 5 of the metal sheet 1 that is distinguished by the microstructure 4 forming a spherical area 53 . This area 53 or the surface formed has the property of causing the onflowing fluid or exhaust gas, which often flows in laminar form, to be not (only) simply deflected in one direction, but to have a flow thread which is provided with at least one swirl, rotation or turbulence. Whereas considerable pressure losses are generated in the channel or duct in the case of a predominant deflection of the flow thread toward a channel or duct wall, this is markedly reduced through the use of the helical flow of the fluid in the channel or duct after corresponding excitation by the spherical area 53 . It is precisely in automobile construction where pressure loss plays an important part and indeed has a direct influence on engine power. It must be pointed out, at this juncture, that this metal sheet 1 with a microstructure 4 having a spherical area 53 can also be produced independently of the recesses 7 according to the invention in the edge region 6 of the slit 2 , and may also be combined advantageously with all aspects of the metal sheets and carrier bodies described herein or may be employed for the same use. The spherical area 53 can be described, for example, by stating that the microstructure 4 is not planar, but (when a sectional plane parallel to the transverse direction 47 , as illustrated in FIG. 9 , is considered) has at least one high point 51 and one low point 50 . This applies particularly at edges 54 of the microstructure 4 . The high points 51 and low points 50 can be distinguished from one another by the amounts of the height 52 , in particular meaning local extreme points. The height 52 in this case describes, in particular, a vertical distance to a channel or duct bottom 55 or a plane through the wave troughs 10 of the metal sheet 1 . According to a preferred embodiment, then, the spherical area 53 is shaped in such a way that at least the high points 51 or the low points 50 of various sectional planes (parallel to the transverse direction 47 and through the microstructure 4 ) are not disposed in alignment in the longitudinal direction 8 . This means, for example, that a distance 56 of the high points 51 and/or the low points 50 from a transitional region 49 of the microstructure 4 changes in the longitudinal direction 8 . According to one embodiment, it is also possible that (additionally) high points 51 and low points 50 are provided in at least one sectional plane through the microstructure 4 parallel to the longitudinal direction 8 . In other words, in particular, there is no rectilinear run of the microstructure 4 . Preferably, in this case too, the distances of the high points 51 and/or the low points 50 from the edges 54 are not identical in all the sectional planes parallel to the longitudinal direction 8 . According to the embodiment illustrated in FIG. 9 , the low points 50 form a contour 57 which is distinguished in that it does not run parallel to the longitudinal direction 8 , but preferably corresponds to a three-dimensional path which has at least portions transverse to the longitudinal direction 8 . This contour 57 preferably constitutes a continuous path, that is to say it has no corners, edges, etc. The contour 57 advantageously has a varying height 52 along its run. It is particularly advantageous if the contour 57 starts, with a first height 52 and a first distance 56 from the transitional region 49 disposed nearest, at the edge 54 onto which the fluid flows, and finally, at the other edge 54 , has a second distance 56 which is greater. In particular, there too, the contour 57 has a second height 52 which is different from the first height 52 . Through the use of such a configuration of the microstructure 4 , the fluid flow which has come into contact with it undergoes a deviation simultaneously in both transverse directions 47 (horizontal and vertical) perpendicularly to the longitudinal direction 8 , with an eddy, vortex, swirl, etc. being generated.

A metal sheet having a microstructure relieved of notching, a carrier body having a plurality of sheets, and an exhaust system having the carrier body, are distinguished by a particularly long useful life in an automobile. Moreover, it is possible to bring about flow profiles coordinated exactly with the respective fields of use, so that a particularly efficient or extremely adaptable carrier body for purifying the exhaust gas of automobiles is provided.

FIELD OF THE INVENTION [0001] The invention is related to whole empty viral particles of the infectious bursal disease virus (IBDV), with immunogenic activity against IBDV, their production by means of genetic engineering and applications thereof, particularly in the production of animal health vaccines, for example, in the manufacture of vaccines against the avian disease called infectious bursal disease caused by IBDV and in the manufacture of gene therapy vectors. BACKGROUND OF THE INVENTION [0002] During the last four decades of the 20 th century, the appearance and global spreading of an avian disease called infectious bursal disease (IBD) has occurred. IBD is characterized by the destruction of pre-B lymphocyte populations residing in the bursa of Fabricius of infected animals (Sharma J M et al. 2000. Infectious bursal disease virus of chickens: pathogenesis and immunosuppression. Dev Comp Immunol. 24:223-35). This disease is caused by the infectious bursal disease virus (IBDV) belonging to the Birnaviridae family (Leong J C et al. 2000. Virus Taxonomy Seventh Report of International Committee on Taxonomy of Viruses. Academic Press, San Diego, Calif.). In spite of the implementation of intensive vaccination programs, based on the use of combinations of live and inactivated vaccines, outbreaks of IBD are still reported in all chicken meat-producing countries (van den Berg T P et al. 2000. Infectious bursal disease (Gumboro disease). Rev Sci Tech. 19:509-43). [0003] The virions of the infectious bursal virus lack a lipid envelope, have an icosahedral structure (symmetry T=13) and have a diameter of 65-70 nm (Bottcher B. et al. 1997. Three-dimensional structure of infectious bursal disease virus determined by electron cryomicroscopy. J. Virol. 71:325-30; Castón J. R., et al. 2001. C terminus of infectious bursal disease virus major capsid protein VP2 is involved in definition of the t number for capsid assembly. J. Virol. 75:10815-28). The capsid is formed by a single protein layer containing four different polypeptides called VPX, VP2, VP3 and VP1, respectively. The VPX, VP2 and VP3 proteins are produced by means of proteolytic processing of a precursor, referred to as viral polyprotein, encoded by genomic segment A. The VP1 protein is produced by means of expression of the corresponding gene encoded by segment B. [0004] The viral polyprotein, synthesized as a precursor of 109 kDa, is processed cotranslationally, giving rise to the formation of three polypeptides referred to as VPX, VP3 and VP4. VP4 is responsible for this processing (Birghan C. et al. 2000. A non-canonical Ion proteinase lacking the ATPase domain employs the Ser-Lys catalytic dyad to exercise broad control over the life cycle of a double-stranded RNA virus. Embo J. 19:114-23). VP3 is a polypeptide of 29 kDa forming trimeric subunits coating the inner layer of the capsid. VPX (also known as pVP2) undergoes a second proteolytic processing giving way to the mature form of the protein called VP2. The outer surface of the virions is formed by trimeric subunits constituted of a variable ratio of VPX and VP2 (Chevalier C et al. 2002. The maturation process of pVP2 requires assembly of infectious bursal disease virus capsids. J. Virol. 76:2384-92; Lombardo, E., et al. 1999. VP1, the putative RNA-dependent RNA polymerase of infectious bursal disease virus, forms complexes with the capsid protein VP3, leading to efficient encapsidation into virus-like particles. J. Virol. 73:6973-83). It has been suggested that the conversion of VPX to VP2 is associated with the formation of mature capsids (Chevalier, C., et al. 2002. The maturation process of pVP2 requires assembly of infectious bursal disease virus capsids. J. Virol. 76:2384-92; Martínez-Torrecuadrada, J. L. 2000. Different architectures in the assembly of infectious bursal disease virus capsid proteins expressed in insect cells. Virology. 278:322-31). The polyprotein proteolytic processing sites have been characterized (Da Costa, B., et al. 2002. The capsid of infectious bursal disease virus contains several small peptides arising from the maturation process of pVP2. J. Virol. 76:2393-402; Sánchez, A. B. and Rodríguez, J. F. 1999. Proteolytic processing in infectious bursal disease virus: identification of the polyprotein cleavage sites by site-directed mutagenesis. Virology. 262:190-9), which allows for a reliable expression of the polypeptides of the capsid. The viral RNA-dependent RNA polymerase (RdRp) viral, called VP1, interacts with the VP3 protein, giving rise to a complex facilitating its encapsidation (Lombardo E et al. 1999. VP1, the putative RNA-dependent RNA polymerase of infectious bursal disease virus, forms complexes with the capsid protein VP3, leading to efficient encapsidation into virus-like particles. J. Virol. 73:6973-83; Tacken, M., et al. 2000. Interactions in vivo between the proteins of infectious bursal disease virus: capsid protein VP3 interacts with the RNA-dependent RNA polymerase, VP1. J. Gen. Virol. 81 Pt 1:209-18). The domain of the protein VP3 responsible for this interaction is located in its 16 C-terminal residues (Maraver, A., et al. Identification and molecular characterization of the RNA polymerase-binding motif of the inner capsid protein VP3 of infectious bursal disease virus. J. Virol. 77:2459-2468). The protein VP3 interacts with RNA non-specifically. This reaction does not require the existence of specific sequences in the RNA molecule (Kochan, G., et al. 2003. Characterization of the RNA binding activity of VP3, a major structural protein of IBDV. Archives of Virology 148:723-744). As with that observed with other internal capsid proteins of other viruses, it seems likely that VP3 stabilizes the genomic RNA in the viral particle. [0005] Conventional vaccines used for controlling infectious bursal disease are based on the use of strains, with different degrees of virulence, of the IBDV itself grown in cell culture or in embryonated eggs. The extracts containing the infectious material are subjected to chemical inactivation processes to produce inactivated vaccines, or else are used directly to produce live attenuated vaccines (Sharma, J. M., et al. 2000. Infectious bursal disease virus of chickens: pathogenesis and immunosuppression. Developmental and Comparative Immunology 24:223-235; van den Berg, T. P., et al. 2000. Rev. Sci. Tech. 2000, 19:509-543). This latter type of vaccine has the typical drawbacks associated with the use of live attenuated vaccines, specifically, the risk of mutations reverting the virulence of the virus or causing it to lose its immunogenicity. [0006] Recombinant subunit vaccines containing the IBDV protein VP2 expressed in several expression systems, for example, bacteria, yeasts or baculovirus, usually in fusion protein form, have been disclosed. The results obtained in chicken immunization tests with said vaccines have not been completely satisfactory. [0007] Empty viral capsids or virus-like particles (VLPs,) constitute an alternative to the use of live attenuated vaccines and of recombinant subunit vaccines. VLPs are obtained by self-assembly of the subunits constituting the viral capsid and mimicking the structure and antigenic properties of the native virion, even thought they lack genetic material, as a result of which they are incapable of replicating themselves. Apart from their application for vaccination purposes, VLPs can be used as vectors of molecules of biological interest, for example, nucleic acids, peptides or proteins. By way of illustration, parvovirus VLPs (U.S. Pat. No. 6,458,362) or human immunodeficiency virus (HIV) VLPs (U.S. Pat. No. 6,602,705), can be mentioned. [0008] Morphogenesis is a vital process for the viral cycle requiring successive steps associated to modifications in the polypeptide precursors. As a result, viruses have developed strategies allowing the sequential and correct interaction between each one of its components. One of these strategies, frequently used by icosahedral viruses, is the use of polypeptides coming from a single polyprotein as the base of its structural components. In these cases, the suitable proteolytic processing of such polyprotein plays a crucial role in the assembly process. [0009] The production of several IBDV VLPs by means of expression of the viral polyprotein using different expression systems have been disclosed. In 1997, Vakharia disclosed for the first time, obtainment of IBDV VLPs in insect cells (Vakharia, V. N. 1997. Development of recombinant vaccines against infectious bursal disease. Biotechnology Annual Review 3:151-68). Later, in 1998, the research group to which the inventors belonged proved the possibility of obtaining IBDV VLPs in mammalian cells (Fernández-Arias A et al. 1998. Expression of ORF A1 of infectious bursal disease virus results in the formation of virus-like particles. J. Gen. Virol. 79:1047-54). In 1999, an article was published disclosing the obtaining of IBDV VLPs in insect cells by another research group (Kibenge, F. S., et al. 1999. Formation of virus-like particles when the polyprotein gene (segment A) of infectious bursal disease virus is expressed in insect cells. Can. J. Vet. Res. 63:49-55). A subsequent study, published by the laboratory to which the inventors belong, in collaboration with INGENASA S. A., proved that the morphogenesis of IBDV VLPs in insect cells infected with recombinant baculoviruses expressing the IBDV polyprotein is very ineffective and leads to the major accumulation of abnormal tubular structures (Martínez-Torrecuadrada, J. L., et al. 2000. Different architectures in the assembly of infectious bursal disease virus capsid proteins expressed in insect cells. Virology 278:322-331). These results were subsequently corroborated (Chevalier, C., et al. 2002. The maturation process of pVP2 requires assembly of infectious bursal disease virus capsids. J. Virol. 76:2384-92). In that same article, that group of researchers proved the possibility of obtaining an efficient morphogenesis by means of the expression of a chimeric polyprotein formed by the fusion of the open reading frame (ORF) corresponding to the green fluorescent protein (GFP) and to 3′ end of the open reading phase of the IBDV polyprotein. The expression of this chimeric polyprotein leads to the formation of recombinant IBDV VLPs, containing in their interior a VP3-GFP recombinant fusion protein, different from the one present in the IBDV virions. On the other hand, the results disclosed in this latter research project do not provide information concerning the mechanism responsible for the ineffectiveness of the morphogenetic process of the IBDV VLPs in insect cells. [0010] It is important to stress that all the VLPs disclosed previously lack the VP1 protein, which is present in the IBDV virions. The only reference to the obtaining of IBDV VLPs including VP1 have been carried out by researchers of the laboratory to which the inventors belong (Lombardo, E., et al. 1999. VP1, the putative RNA-dependent RNA polymerase of infectious bursal disease virus, forms complexes with the capsid protein VP3, leading to efficient encapsidation into virus-like particles. J. Virol. 73:6973-83), using the vaccine virus as the vector, which prevents the possible use of said VLPs for vaccination purposes. [0011] The different processes of producing IBDV VLPs previously described suffer from different defects that reduce or prevent their applicability for the generation of vaccines against IBDV, given that: i) the production of IBDV VLPs in mammalian cells is based on the use of recombinants of the vaccine virus; however, that production system has a very high cost and, as it uses a recombinant virus capable of infecting both mammals and birds, it does not meet the biosafety conditions necessary for its use as a vaccine; ii) the production of IBDV VLPs in insect cells using conventional expression systems, i.e. recombinant baculoviruses only expressing the viral polyprotein, is very inefficient, leading to practically no production of VLPs; iii) the production of IBDV VLPs in insect cells by means of the expression of a chimeric polyprotein (formed by the fusion of the ORF corresponding to the GFP at the 3′ end of the ORF corresponding to the IBDV polyprotein) results in the production of IBDV VLPs containing a fusion protein VP3-GFP, which introduces a protein element not present in IBDV virions, of unknown effect and of doubtful applicability in the chicken food chain for human consumption, and iv) none of the systems described above for the production of IBDV VLPs based on the use of recombinant baculoviruses allows for obtaining IBDV VLPs containing all the antigens present in the IBDV virions. SUMMARY OF THE INVENTION [0016] The invention generally is aimed at the problem of providing new effective and safe vaccines against the infectious bursal disease virus (IBDV). [0017] The solution provided by this invention is based on it being possible to obtain IBDV VLPs correctly assembled by means of the simultaneous expression of the viral polyprotein and the IBDV VP1 protein from two independent open reading frames (ORFs) in suitable host cells. In a particular embodiment, the expression of said ORFs is controlled by different promoters. Said IBDV VLPs are formed by auto-assembly of the IBDV VPX, VP2, VP3 and VP1 proteins, whereby they contain all the antigenically relevant protein elements present in the purified and infective IBDV virions and, for this reason, are called “whole IBDV VLPs” in this description. Given that such whole (complete) IBDV VLPs contain all the antigenically relevant protein elements present in the purified and infective virions of IBDV so as to induce an immunogenic or antigenic response, such whole IBDV VLPs can be used for therapeutic purposes, for example, in the development of vaccines, such as vaccines for protecting birds from the infection caused by IBDV or in the development of gene therapy vectors; for diagnostic purposes, etc. [0018] The obtained results clearly show that: (i) IBDV VP3 protein, expressed in insect cells from the expression of the viral polyprotein, undergo a proteolytic processing eliminating the last 13 amino acid residues from its C-terminal end; (ii) the resulting VP3 protein (called VP3T) is incapable of forming oligomers, which produces a virtually complete blocking of the morphogenetic process inducing virtually no production of VLPs; and (iii) the association of the VP3 protein with the VP1 protein protects the first one (VP3) against the proteolytic processing. [0019] These results have allowed for designing a new strategy or process for the efficient production of whole IBDV VLPs and which, unlike the previously described methods, have an effective morphogenesis while at the same time the presence therein of heterologous protein elements inexistent in purified viral particles is prevented. This strategy is based on the use of a gene expression vector or system allowing the coexpression of the viral polyprotein and of the VP1 protein as independent ORFs, which assures the presence of the viral polyprotein and of the IBDV VP1 protein during the assembly process of the whole IBDV VLPs. Under these conditions, the VP3 and VP1 proteins form stable complexes hindering the proteolytic degradation of VP3, assuring its proper functioning, and leading to the incorporation of VP1 in the IBDV VLPs. [0020] In a particular embodiment, said gene expression system is based on the use of a dual recombinant baculovirus simultaneously expressing the viral polyprotein and the IBDV VP1 protein from two independent ORFs controlled by different promoters. In another particular embodiment, such whole IBDV VLPs are obtained as a result of the coinfection of host cells, such as insect cells, with two recombinant baculoviruses, one of them capable of expressing the viral polyprotein and the other one, the IBDV VP1 protein. [0021] The vaccines obtained by using said whole IBDV VLPs have a number of advantages since it prevents the handling of highly infectious material, it prevents the potential risk of the occurrence of new IBDV mutants, and eliminates the use of a live virus on poultry farms, thus preventing the risk of spreading IBDV vaccine strains to the environment. [0022] Consequently, one aspect of the present invention is related to a whole IBDV VLP made up by assembly of the IBDV PVX, VP2, VP3 and VP1 proteins. Said whole IBDV VLP has antigenic or immunogenic activity against the infection caused by IBDV. [0023] A further aspect of this invention is related to a process for the production of said whole IBDV VLPs provided by this invention, based on the gene coexpression of the viral polyprotein and of the IBDV VP1 as two independent ORFs in suitable host cells. In a particular embodiment, the expression of said ORFs is controlled by different promoters. [0024] The gene constructs, expression systems and host cells developed for the implementation of said production process of said whole IBDV VLPs, as well as their use for the production of said whole IBDV VLPs, constitute further aspects of the present invention. [0025] Such whole IBDV VLPs have the ability to immunize animals, particularly, birds, against the avian disease caused by IBDV, as well as the ability to vectorize or incorporate into vehicles molecules of biological interest, for example, polypeptides, proteins, nucleic acids, etc. In a particular embodiment, said whole IBDV VLPs can be used in the development of vaccines to protect birds against the virus causing the avian disease known as infectious bursal disease (IBDV). Virtually any bird, preferably those avian species of economic interest, for example, chickens, turkeys, ganders, geese, pheasants, partridges, ostriches, etc., can be immunized against the infection caused by IBDV with the vaccines provided by this invention. In another particular embodiment, said whole IBDV VLPs can internally incorporate into vehicles products with biological activity, for example, nucleic acids, peptides, proteins, drugs, etc., whereby they can be used in the manufacture of gene therapy vectors. [0026] Therefore, in a further aspect, the present invention is related to the use of said whole IBDV VLPs in the manufacture of medicaments, such as vaccines and gene therapy vectors. Said vaccines and vectors constitute further aspects of the present invention. In a particular embodiment, said vaccine is a vaccine useful for protecting birds from the infection caused by IBDV. In a specific embodiment, said birds are selected from the group formed by chickens, turkeys, ganders, geese, pheasants, partridges, ostriches, preferably chickens. [0027] In another aspect, the invention is related to a process for the production of recombinant baculoviruses useful for the production of whole IBDV VLPs. In a particular embodiment, the recombinant obtained baculoviruses are dual, i.e., the same recombinant baculovirus is able to express in suitable host cells the viral polyprotein and the IBDV VP1 protein from two ORFs, independent and controlled by promoters of different baculoviruses. In another particular embodiment, recombinant baculoviruses are obtained which are able to express in suitable host cells the viral polyprotein from a nucleic acid sequence comprising the ORFs corresponding to the IBDV polyprotein under the control of a promoter, and recombinant baculoviruses able to express in suitable host cells the IBDV VP1 protein from a nucleic acid sequence comprising the ORF corresponding to the IBDV VP1 under the control of a promoter, the same as or different from the one controlling the expression of the viral polyprotein in said recombinant baculoviruses able to express the viral polyprotein. The resulting recombinant baculoviruses (rBVs) constitute a further aspect of the present invention. Such rBVs can be used for the production of whole IBDV VLPs. BRIEF DESCRIPTION OF THE FIGURES [0028] FIG. 1 shows the effect of the C-terminal deletion of the IBDV VP3 in the morphogenesis of VLPs. FIG. 1A shows a diagram which graphically represents the genes derived from IBDV expressed by the different recombinants of the vaccine virus [VT7/Poly (Poly), disclosed by Fernández-Arias et al. (Fernández-Arias, A., et al. 1998. Expression of ORF A1 of infectious bursal disease virus results in the formation of virus-like particles. J. Gen. Virol. 79:1047-1054), VT7/PolyΔ907-1012 (PolyΔ907-1012) and VT7VP3 (VP3)] used for checking the effect of the C-terminal end deletion of VP3 in the formation of IBDV VLPs in mammal cells. VT7/Poly (Poly) expresses the whole polyprotein. VT7/PolyΔ907-1012 (PolyΔ907-1012) expresses a deleted form of the polyprotein lacking the 150 C-terminal residues. VT7/VP3 (VP3) expresses the whole VP3 polyprotein. FIG. 1B illustrates the effect of the deletion of the C-terminal end of the IBDV polyprotein on the subcellular distribution of the VPX (pVP2) and VP2 proteins, and includes digital confocal microscopy images obtained from infected cells with the recombinants VT7/Poly (Poly), VT7/PolyΔ907-1012 (PolyΔ907-1012) and VT7/VP3 (VP3), respectively. The cells were fixed at 24 hours post-infection (h.p.i.) and incubated with anti- IBDV VPX/2 (anti-pVP2VP2) rabbit serum and with anti-IBDV VP3 rat serum, followed by incubation with anti-rabbit IgG goat immunoglobulin coupled to Alexa 488 (green) and with anti-rat IgG goat immunoglobulin coupled to Alexa 594 (red). FIG. 1C shows the effect of the deletion of the C-terminal end of the IBDV polyprotein on the assembly of the capsids; cell extracts infected with VT7/Poly (Poly), VT7/PolyΔ907-1012 (PolyΔ907-1012) or coinfected with VT7/PolyΔ907-1012 (PolyΔ907-1012) and VT7/VP3 (VP3) were subjected to fractioning on sucrose gradient. An aliquot of each one of the fractions was placed on an electron microscopy grid, negatively stained and viewed by means of electron microscopy. The images represent the assemblies detected in equivalent fractions of the different gradients. [0029] FIG. 2 shows the results of a comparative analysis by means of Western blot of the IBDV VP3 protein expressed in different expression systems; cell extracts infected with IBDV, VT7/Poly and FB/Poly, respectively, were subjected to sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis using anti-IBDV VP3 rabbit serum, followed by incubation with goat immunoglobulin coupled to peroxidase (HRPO: horse radish peroxidase). The signal was detected by means of ECL (Enhanced Chemioluminescence). The position of the immunoreactive bands and those of the molecular weight markers are indicated. [0030] FIG. 3 shows the characterization of C-terminal proteolysis of the IBDV VP3 protein expressed in insect cells. FIG. 1A shows a diagram graphically representing the his-VP3 gene containing a histidine tag fused to the N-terminal end of VP3 expressed by the recombinant baculovirus FB/his-VP3 [occasionally referred to in this description as FB/his-VP3 wt (wild type)]. The sequence corresponding to the histidine tag and the first amino acid residue corresponding to VP3 (underlined) is indicated. Samples corresponding to whole H5 cell extracts (GIBCO), also identified in this description as H5 cells, infected with FB/his-VP3, or to the his-VP3 protein purified by affinity were subjected to SDS-PAGE and Western blot analysis using anti-VP3 rabbit serum ( FIG. 1B ) or anti-histidine tag (anti-his tag) ( FIG. 1C ) followed by incubation with goat immunoglobulin coupled to peroxidase. The signal was detected by means of ECL. The position of the immunoreactive bands and those of the molecular weight markers are indicated. [0031] FIG. 4 shows the location of the proteolytic cutting site of the IBDV VP3 protein in insect cells. FIG. 1A is a diagram graphically representing the group of deleted his-VP3 proteins used in the determination of the position of the proteolytic cutting site of the IBDV VP3 protein in insect cells. FIG. 1B shows the result of a Western blot analysis of the different deleted his-VP3 proteins expressed in H5 cells and purified by immobilized metal affinity chromatography (IMAC). H5 cell culture extracts infected with each one of the recombinant baculoviruses were subjected to purification in HiTrap affinity columns (Amersham Pharmacia Biotech). The purified proteins were subjected to SDS-PAGE and Western blot analysis using anti-VP3 rabbit serum, followed by incubation with goat immunoglobulin coupled to peroxidase. The signal was detected by means of ECL. The position of the immunoreactive bands and those of the molecular weight markers are indicated. The arrows indicate the position of the whole protein (F) and the one corresponding to the proteolyzed form (T). [0032] FIG. 5 illustrates that the proteolytic processing of IBDV VP3 in insect cells causes the elimination of a peptide of 1.560 Da from the C-terminal end of his-VP3. H5 cell extracts infected with FB/his-VP3 were subjected to purification by means of IMAC and the resulting purified protein was analyzed by means of mass spectrophotometry in triplicate. FIG. 5A shows the results of one of these experiments. The presence of two polypeptides of 32.004 and 30.444 Da, respectively, was determined, which proves that the proteolytic processing produces the elimination of a peptide of 1.560 Da from the C-terminal end of his-VP3, size which fits with the molecular mass (1.576 Da) corresponding to the 13 C-terminal residues of IBDV VP3, the sequence of which is shown in FIG. 5B . [0033] FIG. 6 shows the effect of the coexpression of IBDV VP1 on the proteolysis of his-VP3. FIG. 6A shows the detection of VP3/VP1 complexes. H5 cells were infected with FB/his-VP3 or with FBD/his-VP3-VP1. At 72 h.p.i., the cells were harvested and the corresponding extracts subjected to purification in HiTrap affinity columns (Amersham Pharmacia Biotech). Samples corresponding to total extracts (T) or to purified proteins were subjected to SDS-PAGE. The gels were subsequently stained with silver nitrate. The position of the molecular weight markers is indicated. FIG. 6B shows the results of a Western blot analysis of extracts of H5 cells infected with FB/his-VP3, FBD/his-VP3-VP1, or coinfected with FB/his-VP3 and FB/VP1, respectively. The infected cells were harvested at 72 h.p.i. and homogenized. The corresponding extracts were subjected to SDS-PAGE and Western blot analysis using anti-VP3 rabbit serum, followed by incubation with goat immunoglobulin coupled to peroxidase. The signal was detected by means of ECL. The position of the molecular weight markers is indicated. [0034] FIG. 7 shows the location of the oligomerization domain. FIG. 7A is a diagram graphically representing the group of deleted his-VP3 proteins used in the determination of the VP3 oligomerization domain position. The deleted regions are indicated with the dotted line. The name of each mutant indicates the location of eliminated amino acid remains in the sequence of the IBDV VP3 protein. FIG. 7B shows the detection of VP3 oligomers. The different his-VP3 deletion proteins, purified by HiTrap affinity columns (Amersham Pharmacia Biotech), were subjected to SDS-PAGE and Western blot analysis using anti-VP3 rabbit serum, followed by incubation with goat immunoglobulin coupled to peroxidase. FIG. 1C shows the results of a Western blot analysis. The samples described in the previous paragraph ( FIG. 7B ) were subjected to non-denaturing electrophoresis followed by Western blot analysis using anti-VP3 rabbit serum, followed by incubation with goat immunoglobulin coupled to peroxidase. FIG. 7D shows the detection of VP3 oligomers produced by VP3 C-terminal deletion mutants. The purified proteins were subjected to SDS-PAGE and Western blot analysis using anti-VP3 rabbit serum, followed by incubation with goat immunoglobulin coupled to peroxidase. The signal was detected by means of ECL. The position of the molecular weight markers is indicated. [0035] FIG. 8 shows the determination of the effect of the coexpression of IBDV VP1 on the proteolytic processing of IBDV VP3 and the subcellular distribution of the proteins of the capsid. FIG. 8A illustrates the detection of the IBDV VP1 and VP3 proteins accumulated in H5 cells infected with FB/Poly and FBD/Poly-VP1, respectively. Infected cells were harvested at 24, 48 and 72 h.p.i. The samples were subjected to SDS-PAGE and Western blot analysis using anti-VP3 or anti-VP1 rabbit serum, followed by incubation with goat immunoglobulin coupled to peroxidase. The position of the molecular weight markers is indicated. The subcellular distribution of the VPX/2 (pVP2/VP2) and VP3 proteins in cells infected with FB/Poly and FBD/Poly-VP1 was analyzed by confocal microscopy ( FIG. 8B ). The cells were fixed at 60 h.p.i., and then incubated with anti-VPX rabbit serum (anti-pVP2) and anti-VP3 rat serum followed by incubation with anti-rabbit IgG goat immunoglobulin coupled to Alexa 488 (green) and with anti-rat IgG goat immunoglobulin coupled to Alexa 594 (red). The arrows indicate the position of the viroplasms formed by VPX/2 (pVP2/VP2) and VP3. [0036] FIG. 9 illustrates the characterization of the structures formed by expression of the IBDV polyprotein in cells infected with FB/Poly-VP1. FIG. 9A shows a set of micrographs of the structures obtained in the different fractions. H5 cells were infected with FB/Poly (Poly) or with FBD/Poly-VP1 (Poly-VP1). The cells were harvested at 90 h.p.i. and the corresponding extracts were used for the purification of structures by means of sucrose gradients. After centrifugation, 6 aliquots of 2 ml were taken. One part of the aliquot was placed on a grid, negatively stained with uranyl acetate, and analyzed by means of observation in the electron microscope. Fractions #1 correspond to the bottom of the gradients. Fractions #6, which contained soluble protein and de-assembled structures, are not shown. The bar corresponding to 200 nm. FIG. 9B is a micrograph showing purified VLPs from cells infected with FBD/Poly-VP1. The image corresponds to fraction #5 of the gradient obtained from cells infected with FBD/Poly-VP1. The enlarged boxes show 2 VLPs at a larger amplification. FIG. 9C shows the characterization of the polypeptides present in fraction #5 of both gradients. An aliquot of fraction #5 of each gradient was subjected to SDS-PAGE and Western blot analysis using anti-VP1, anti-VPX (anti-pVP2/VP2) or anti-VP3 rabbit serum, followed by incubation with goat immunoglobulin coupled to peroxidase. The position of VPX (pVP2), VP2, whole VP3 (F) and proteolyzed VP3 (T) is shown. DETAILED DESCRIPTION OF THE INVENTION [0037] In a first aspect, the invention provides a whole empty viral capsid of the infectious bursal disease virus (IBDV), hereinafter whole IBDV VLP (whole VLPs in plural form) of the invention, characterized in that it contains all the proteins present in purified and infective IBDV virions, specifically the IBDV VPX, VP2, VP3 and VP1 proteins. [0038] The term “IBDV”, as it is used in the present invention, refers to the different IBDV strains belonging to any of the serotypes (1 or 2) known [by way of illustration, see the review carried out by van den Berg, T. P., Eterradossi, N., Toquin, D., Meulemans, G., in Rev Sci Tech 2000 19:509-43]. [0039] The terms “viral polyprotein” or “IBDV polyprotein” are generally used in this description and refer to the product resulting from the expression of the A segment of the IBDV genome the proteolytic processing of which gives rise to the VPX (pVP2), VP3 and VP4 proteins, and include the different forms of the polyproteins representative of any of the mentioned IBDV strains [NCBI protein databank], according to the definition carried out by Sánchez and Rodríguez (1999) (Sánchez, A. B. and Rodríguez, J. F. Proteolytic processing in infectious bursal disease virus: identification of the polyprotein cleavage sites by site-directed mutagenesis. Virology. 1999 Sep. 15; 262(1):190-199), as well as proteins substantially homologous to said IBDV polyprotein, i.e., proteins the amino acid sequences of which have a degree of identity regarding said IBDV polyprotein of at least 60%, preferably of at least 80%, more preferably of at least 90% and even more preferably of at least 95%. [0040] The term “IBDV VP1 protein” refers to the product resulting from the expression of segment B of the IBDV genome and includes the different forms of the VP1 proteins representative of any of the mentioned IBDV strains [NCBI protein databank], according to the definition carried out by Lombardo, E., et al. 1999. VP1, The putative RNA-dependent RNA polymerase of infectious bursal disease virus, forms complexes with the capsid protein VP3, leading to efficient encapsidation into virus-like particles. J. Virol. 73:6973-83) as well as proteins substantially homologous to said IBDV VP1 protein, i.e., proteins the amino acid sequences of which have a degree of identity regarding said IBDV VP1 of at least 60%, preferably of at least 80%, more preferably of at least 90% and even more preferably of at least 95%. [0041] The IBDV VPX (pVP2), VP2 and VP3 proteins present in the whole IBDV VLPs of the invention can be any of the VPX, VP2 and VP3 proteins representative of any IBDV strain obtained by proteolytic processing of the viral polyprotein, for example the IBDV Soroa strain VPX, VP2 and VP3 proteins [NCBI, access number AAD30136]. [0042] The IBDV VP1 protein present in the whole IBDV VLPs of the invention can be any VP1 protein representative of any IBDV strain, for example, the whole length, Soroa strain VP1 protein, the amino acid sequence of which is shown in SEQ. ID. NO: 2. [0043] In a particular embodiment, the whole IBDV VLPs of the invention have a diameter of 65-70 nm and a polygonal contour indistinguishable from the IBDV virions. [0044] The whole IBDV VLPs of the invention can be obtained by means of the simultaneous expression of said IBDV viral polyprotein and VP1 protein in suitable host cells. Said suitable host cells are cells containing the encoding nucleotide sequence of the IBDV polyprotein under the control of a suitable promoter and the encoding nucleotide sequence of the IBDV VP1 protein under the control of another suitable promoter, either in a single gene construct or in two different gene constructs. In a particular embodiment, said suitable host cells are cells that are transformed, transfected or infected with a suitable expression system, such as (1) an expression system comprising a gene construct, in which such gene construct comprises the nucleotide sequence encoding for the IBDV polyprotein under the control of a promoter and the encoding nucleotide sequence of the IBDV VP1 protein under the control of another promoter different from the one which is operatively bound to the nucleotide sequence encoding the viral polyprotein, or, alternatively, (2) an expression system comprising a first gene construct comprising the nucleotide sequence encoding for the IBDV polyprotein, and a second gene construct comprising the nucleotide sequence encoding for the IBDV VP1 protein, each one of them under the control of a suitable promoter. In a particular embodiment, said host cell is an insect cell and said promoters are baculovirus promoters. [0045] Therefore, in another aspect, the invention is related to a gene construct comprising the nucleotide sequence encoding for said IBDV polyprotein and the nucleotide sequence encoding for said IBDV VP1 protein, in the form of two independent ORFs, the expression of which is controlled by respective different promoters controlling the gene expression of each one of said IBDV viral polyprotein and VP1 protein. Therefore, the invention provides a gene construct comprising (i) a nucleotide sequence comprising the open reading frames corresponding to the polyprotein of the infectious bursal disease virus (IBDV) operatively bound to a nucleotide sequence comprising a first promoter and (ii) a nucleotide sequence comprising the open reading frame corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence comprising a second promoter, in which such first promoter is different from such second promoter. The use of such different promoters allows the independent and simultaneous control of the gene expression of such IBDV polyprotein and VP1 protein. [0046] A feature of the gene construct provided by this invention is that it comprises the nucleotide sequences encoding for all the protein elements present in the purified and infective IBDV virions, specifically, the VPX, VP2, VP3 and VP1 proteins. [0047] As it is used in this description, the term “ORFs (or open reading frames) corresponding to the IBDV polyprotein” or “ORF (open reading frame) corresponding to the IBDV VP1 protein” includes, in addition to the nucleotide sequences of said ORFs, other ORFs analogous to the same encoding sequences of the IBDV viral polyprotein and of the IBDV VP1. The term “analogous”, as it is used herein, intends to include any nucleotide sequence which can be isolated or constructed on the base of the encoding nucleotide sequence of the viral polyprotein and the IBDV VP1, for example, by means of the introduction of conservative or non-conservative nucleotide replacements, including the insertion of one or more nucleotides, the addition of one or more nucleotides at any end of the molecule, or the deletion of one or more nucleotides at any end or inside of the sequence. Generally, a nucleotide sequence analogous to another nucleotide sequence is substantially homologous to said nucleotide sequence. In the sense used in this description, the expression “substantially homologous” means that the nucleotide sequences in question have a degree of identity, at the nucleotide level, of at least 60%, advantageously of at least 70%, preferably of at least 80%, more preferably of at least 85%, even more preferably of at least 90%, and yet even more preferably of at least 95%. [0048] The promoters which can be used in the implementation of the present invention generally comprise a nucleic acid sequence to which the RNA polymerase is bound so as to begin the mRNA transcription and to express said ORFs corresponding to the viral polyprotein and to the IBDV VP1 protein in suitable host cells. Although virtually any promoter meeting these conditions can be used to implement the present invention, for example, promoters of a viral, bacterial, yeast, animal, plant origin, etc., in a particular embodiment such promoters are viral promoters, for example, baculovirus promoters. [0049] The expression of each one of said nucleotide sequence encoding for said viral polyprotein and IBDV VP1 protein, in the form of two independent ORFs, is controlled by respective different promoters controlling the gene expression of each one of such proteins. In a particular embodiment, the gene expression of such an viral polyprotein and IBDV VP1 protein is carried out in insect cells infected or coinfected with recombinant baculoviruses (rBVs) containing the encoding nucleotide sequences of said proteins, either in a single rBV (dual rBV) or in two rBVs (in which case one of such rBVs contains the encoding sequence of the IBDV polyprotein and the other one, the encoding sequence of the IBDV VP1 protein) under the control of baculovirus promoters. [0050] Virtually any baculovirus promoter can be used as long as it is able to effectively control the expression of the encoding sequence to which it is operatively bound. By way of illustration, the first baculovirus promoter can be the promoter of the p10 protein of the baculovirus Autographa californica nucleopolyhedrovirus (AcMNV), the promoter of the polyhedrin of the AcMNPV baculovirus, etc. and the second baculovirus promoter can be the promoter of the p10 protein of AcMNPV and the promoter of the AcMNPV polyhedrin. More specifically, in a particular embodiment, the first baculovirus promoter is the promoter of the p10 protein of AcMNPV and the second baculovirus promoter is the promoter of the AcMNPV polyhedrin, whereas in another particular embodiment, the first baculovirus promoter is the promoter of the AcMNPV polyhedrin and the second baculovirus promoter is the promoter of the protein 10 of AcMNPV. [0051] In a particular embodiment, the gene construct provided by this invention comprises: (i) a nucleotide sequence comprising the open reading frames corresponding to the IBDV polyprotein operatively bound to a nucleotide sequence comprising a first promoter of a baculovirus, and (ii) a nucleotide sequence comprising the ORF corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence comprising a second promoter of a baculovirus, wherein said first and second baculovirus promoters are different. [0054] The use of different baculovirus promoters allows for the independent and simultaneous control of the gene expression of said IBDV polyprotein VP1 protein in insect cells. [0055] In a specific embodiment, the gene construct provided by this invention comprises the encoding sequence of the IBDV polyprotein under the control of a first baculovirus promoter and the encoding sequence of the IBDV VP1 protein under the control of a second baculovirus promoter, different from the first one, such as the gene construct referred to as “Poly-VP1” in this description, comprising the nucleotide sequence identified as SEQ. ID. NO: 1; the Poly-VP1 gene construct contains the encoding sequence of the IBDV polyprotein under the control of the promoter of the AcMNV polyhedrin and the encoding sequence of the IBDV VP1 protein under the control of the promoter of the AcMNV p10 protein. [0056] In another aspect, the invention provides an expression vector or system selected from: a) an expression system comprising a gene construct provided by this invention, operatively bound to transcription, and optionally translation, control elements, wherein such gene construct includes (i) a nucleotide sequence comprising the ORFs corresponding to the IBDV polyprotein operatively bound to a nucleotide sequence comprising a first promoter and (ii) a nucleotide sequence comprising the ORF corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence comprising a second promoter, wherein the first promoter is different from the second promoter; and b) an expression system including (1) a first gene construct, operatively bound to transcription, and optionally translation, control elements, wherein the first gene construct comprises a nucleotide sequence comprising the ORFs corresponding to the IBDV polyprotein operatively bound to a nucleotide sequence including a first promoter, and (2) a second gene construct, operatively bound to transcription, and optionally translation, control elements, wherein the second gene construct includes a nucleotide sequence including the ORF corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence comprising a second promoter. [0059] In the second case [b)], the first promoter and the second promoter, as they are in different gene constructs, can be equal to or different from one another. [0060] The features of the ORFs corresponding to the IBDV polyprotein and to the IBDV VP1 protein have previously been defined in relation to the gene construct provided by this invention. The promoters which can be used in the expression system provided by this invention have been previously defined in relation to the gene construct provided by this invention. By way of illustration, such promoters can be promoters of a viral, bacterial, yeast, animal, plant origin, etc. [0061] In a particular embodiment, the expression system provided by this invention comprises a gene construct, operatively bound to transcription, and optionally translation, control elements, wherein the gene construct includes (i) a nucleotide sequence including the ORFs corresponding to the IBDV polyprotein operatively bound to a nucleotide sequence including a first baculovirus promoter, such as, for example, the promoter of the AcMNV p10 protein or the promoter of the AcMNV polyhedrin, and (ii) a nucleotide sequence including the ORF corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence including a second baculovirus promoter, such as, for example, the promoter of the AcMNV p10 protein or the promoter of the AcMNV polyhedrin, wherein the first baculovirus promoter is different from the second baculovirus promoter. [0062] In another particular embodiment, the expression system provided by this invention includes (1) a first gene construct, operatively bound to transcription, and optionally translation, control elements, wherein the first gene construct includes a nucleotide sequence including the ORFs corresponding to the IBDV polyprotein operatively bound to a nucleotide sequence comprising a first baculovirus promoter, such as, for example, the promoter of the AcMNV p10 protein or the promoter of the AcMNV polyhedrin, and (2) a second gene construct, operatively bound to transcription, and optionally translation, control elements, wherein the second gene construct comprises a nucleotide sequence comprising the ORF corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence including a second baculovirus promoter, such as, for example, the promoter of the AcMNV p10 protein or the promoter of the AcMNV polyhedrin. In this particular embodiment, the first baculovirus promoter and the second baculovirus promoter, as they are in different gene constructs, can be equal to or different from one another. [0063] The transcription, and optionally translation, control elements present in the expression system provided by this invention include the necessary or suitable sequences for the transcription and its suitable control in time and place, for example, beginning and termination signals, cleavage sites, polyadenylation signals, replication origin, transcriptional activators (enhancers), transcriptional silencers (silencers), etc. [0064] Virtually any suitable expression system or vector can be used in the generation of the expression system provided by this invention depending on the conditions and requirements of each specific case. By way of illustration, said suitable expression systems or vectors can be plasmids, bacmids, yeast artificial chromosomes (YACs), bacteria artificial chromosomes (BACs), bacteriophage P1-based artificial chromosomes (PACs), cosmids, viruses, which can further have, if so desired, an origin of heterologous replications, for example, bacterial, so that it may be amplified in bacteria or yeasts, as well as a marker usable for selecting the transfected cells, etc., preferably plasmids, bacmids or viruses. [0065] These expression systems or vectors can be obtained by conventional methods known by persons skilled in the art [Sambrook, J., Fritsch, E. F., and Maniatis, T. (1989). Molecular cloning: a laboratory manual, 2nd ed. Cold Spring Harbor Laboratory] and form part of the present invention. In a particular embodiment, the expression system or vector is a plasmid, such as the plasmid referred to as pFBD/Poly-VP1 in this description, or a bacmid, such as the recombinant bacmid referred to as Bac/pFBD/Poly-VP1 in this description, which contain the previously defined gene construct Poly-VP1, or a virus, such as the recombinant baculovirus (rBV) referred to as FBD/Poly-VP1 in this description, which contains the gene construct Poly-VP1 and expresses during its replication cycle both proteins (polyprotein and IBDV VP1 protein) simultaneously in insect cells, or the rBVs expressing the IBDV polyprotein and the IBDV VP1 protein, separately and simultaneously, when coinfecting insect cells, whole IBDV VLPs being obtained. [0066] In another aspect, the invention provides a host cell containing the encoding nucleotide sequence of the IBDV polyprotein and the encoding nucleotide sequence of the IBDV VP1 protein, each one of them under the control of a suitable promoter allowing the simultaneous and independent control of said IBDV polyprotein and VP1 protein, either in a single gene construct (in which case the promoters bound to each one of said encoding sequences would be different from one another), or in two different gene constructs. Therefore, said host cell can contain either a gene construct provided by this invention or an expression system provided by this invention. [0067] The host cell provided by this invention can be a host cell transformed, transfected or infected with an expression system provided by this invention. [0068] In a particular embodiment, the host cell provided by this invention is a host cell transformed, transfected or infected with an expression system provided by this invention comprising a gene construct, operatively bound to transcription, and optionally translation, control elements, wherein the gene construct includes (i) a nucleotide sequence including the ORFs corresponding to said IBDV polyprotein operatively bound to a nucleotide sequence comprising a first promoter and (ii) a nucleotide sequence comprising the open reading frame corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence comprising a second promoter, wherein the first promoter is different from the second promoter. [0069] Alternatively, in another particular embodiment, the host cell is a host cell transformed, transfected or infected with an expression system provided by this invention comprising (1) a first gene construct, operatively bound to transcription, and optionally translation, control elements, wherein the first gene construct comprises a nucleotide sequence comprising the ORFs corresponding to said IBDV polyprotein operatively bound to a nucleotide sequence including a first promoter, and (2) a second gene construct, operatively bound to transcription, and optionally translation, control elements, wherein the second gene construct comprises a nucleotide sequence comprising the ORF corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence comprising a second promoter; in this particular embodiment, the first promoter and the second promoter, as they are in different gene constructs, can be equal to or different from one another. [0070] Although in any of the previously mentioned embodiments, virtually any promoter could be used, it is preferred in practice that such promoters are useful in bacteria, yeasts, viruses, animal cells, for example, in mammal cells, bird cells, insect cells, etc.; in a particular embodiment, the promoters are baculovirus promoters, such as, for example, the promoter of the AcMNV polyhedrin or the promoter of the AcMNV p10 protein. [0071] Virtually any host cell susceptible to being transformed, transfected or infected by an expression system provided by this invention can be used, for example, bacteria, mammal cells, bird cells, insect cells, etc. [0072] In a particular embodiment, the host cell is a bacteria transformed with an expression system provided by this invention including a gene construct provided by this invention comprising (i) a nucleotide sequence comprising the ORFs corresponding to the IBDV polyprotein and (ii) a nucleotide sequence comprising the ORFs corresponding to the IBDV VP1 protein, each one of them operatively bound to a different promoter, such as the gene construct identified as Poly-VP1. A culture of Escherichia coli bacteria strain DH5, transformed with such gene construct Poly-VP1, and identified as DH5-pFBD/Poly-VP1 has been deposited in the Spanish Type Culture Collection (hereinafter, CECT) with deposit number CECT 5777. [0073] Alternatively, the host cell is an insect cell. Insect cells are suitable when the expression system comprises one or more rBVs. The use of rBVs is advantageous due to biosafety issues related to the host range of the baculoviruses, incapable of replicating in other cell types which are not insect cells. [0074] Therefore, in a particular embodiment, the invention provides a host cell, such as an insect cell, infected with an expression system provided by this invention, such as a rBV, comprising a gene construct provided by this invention including (i) a nucleotide sequence including the ORFs corresponding to the IBDV polyprotein and (ii) a nucleotide sequence including the ORF corresponding to the IBDV VP1 protein, each one of them operatively bound to a different baculovirus promoter, such as the gene construct identified as Poly-VP1. [0075] In another particular embodiment, the invention provides host cell, such as an insect cell, coinfected with an expression system including (1) a first rBV comprising a gene construct comprising the ORFs corresponding to the IBDV polyprotein and (2) a second rBV comprising a gene construct comprising the nucleotide sequence comprising the ORF corresponding to the IBDV VP1 protein, each one of the encoding sequences being operatively bound to a baculovirus promoter, equal to or different from one another. [0076] In another aspect, the invention provides a process for producing whole IBDV VLPs of the invention including culturing a host cell provided by this invention containing a nucleotide sequence comprising the ORFs corresponding to said IBDV polyprotein and a nucleotide sequence comprising the ORF corresponding to said IBDV VP1 protein, either in a single gene construct or in two different gene constructs, and simultaneously expressing said viral polyprotein and IBDV VP1 protein, and if so desired, recovering said whole IBDV VLPs of the invention. [0077] In a particular embodiment, the host cell provided by this invention is a cell transformed, transfected or infected with a suitable expression system provided by this invention, such as an expression system comprising a gene construct provided by this invention, wherein such gene construct comprises (i) a nucleotide sequence including the ORFs corresponding to the IBDV polyprotein operatively bound to a nucleotide sequence including a first promoter and (ii) a nucleotide sequence comprising the ORF corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence comprising a second promoter, wherein either the first promoter is different from the second promoter; or alternatively, with an expression system provided by this invention including (1) a first gene construct comprising a nucleotide sequence comprising the ORFs corresponding to the IBDV polyprotein and (2) a second gene construct comprising a nucleotide sequence comprising the ORF corresponding to the IBDV VP1 protein, each one of the nucleotide sequences comprising the ORFS corresponding to the viral polyprotein and to the IBDV VP1 protein being under the control of respective nucleotide sequences including respective promoters, equal to or different from one another. [0078] Such process therefore includes the simultaneous gene coexpression of the viral polyprotein and IBDV VP1 protein as two independent ORFs. After the simultaneous expression of the viral polyprotein and VP1 protein in such cells, the polyprotein is proteolytically processed and the resulting proteins are assembled and form the whole IBDV VLPs of the invention, made up of VPX, VP2, VP3 and VP1, which can be isolated or withdrawn from the medium and, if desired, purified. The isolation or purification of such whole IBDV VLPs of the invention can be carried out by means of conventional methods, for example, by means of fractioning on sucrose gradients. [0079] Although the host cell to culture can be any of those previously defined, in a particular embodiment, the host cell is an insect cell. [0080] Therefore, in a specific embodiment, the simultaneous gene coexpression of the viral polyprotein and of the IBDV VP1 protein in a suitable host cell, such as an insect cell, is carried out by means of the use of a dual rBV allowing the simultaneous expression of such proteins from two independent ORFs, each one of them under the control of a different baculovirus promoter able to simultaneously and independently control the expression of such proteins in insect cells. In this case, the production of the whole IBDV VLPs of the invention can be carried out by means of a process including, first, the obtaining of a gene expression system made up of a dual rBV containing a gene construct simultaneously including the ORFS corresponding to the viral polyprotein and IBDV VP1 protein, such as the rBV referred to as FBD/Poly-VP1 in this description, or else, alternatively, the obtaining of a rBV containing a gene construct including the ORF corresponding to the IBDV polyprotein and the obtaining of another rBV containing a gene construct comprising the ORF corresponding to the IBDV VP1 protein, followed by the infection of insect cells with the expression system based on such rVB(s), expression of the recombinant proteins and, if so desired, isolation of- the formed whole IBDV VLPs of the invention, and optionally, subsequent purification of the whole IBDV VLPs of the invention. [0081] More specifically, in a particular embodiment, the process for obtaining whole VLPs of the invention is characterized in that the host cell is an insect cell and includes the steps of: a) preparing an expression system provided by this invention made up of (1) a first recombinant baculovirus comprising a gene construct comprising a nucleotide sequence including the ORFs corresponding to the IBDV polyprotein operatively bound to a baculovirus promoter, such gene construct being operatively bound to transcription, and optionally translation, control elements, and of (2) a second recombinant baculovirus comprising a gene construct including a nucleotide sequence including the ORF corresponding to the IBDV VP1 protein operatively bound to a promoter of a baculovirus, such gene construct being operatively bound to several transcription, and optionally translation, control elements; b) infecting insect cells with said expression system prepared in step a); c) culturing the infected insect cells obtained in step b) under conditions allowing the expression of the recombinant proteins and their assembly so as to form whole IBDV VLPs; and d) if so desired, isolating and optionally purifying such whole IBDV VLPs. [0086] Likewise, in another particular embodiment, the process for obtaining whole VLPs of the invention is characterized in that the host cell is an insect cell and includes the steps of: a) preparing an expression system made up of a dual recombinant baculovirus including a gene construct including (i) a nucleotide sequence including the ORFs corresponding to the IBDV polyprotein operatively bound to a nucleotide sequence including a first baculovirus promoter, such gene construct being operatively bound to transcription, and optionally translation, control elements, and (ii) a nucleotide sequence comprising the ORF corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence including a second baculovirus promoter, such gene construct being operatively bound to transcription, and optionally translation, control elements, wherein the baculovirus promoter is different from the second baculovirus promoter; b) infecting insect cells with said expression system prepared in step a); c) culturing the infected insect cells obtained in step b) under conditions allowing the expression of the recombinant proteins and their assembly so as to form whole IBDV VLPs; and d) if so desired, isolating and optionally purifying the whole IBDV VLPs. [0091] The construct of a dual rBV simultaneously allowing expression of the IBDV polyprotein and of the IBDV VP3 protein can be carried out by a person skilled in the art based on that herein described and on the state of the art on this technology (Cold Spring Harbor, N.Y.; Leusch, M. S., Lee, S. C., Olins, P. O. 1995. A novel host-vector system for direct selection of recombinant baculoviruses (bacmids) in Escherichia coli . Gene 160:191-4; Luckow, V. A., Lee, S. C., Barry, G. F., Olins, P. O. 1993. Efficient generation of infectious recombinant baculoviruses by site-specific transposon-mediated insertion of foreign genes into a baculovirus genome propagated in Escherichia coli . J. Virol. 67:4566-79). A rBV containing the gene construct comprising the ORFs corresponding to the IBDV polyprotein and a rBV containing a gene construct including the ORF corresponding to the IBDV VP1 protein can be similarly obtained. [0092] In relation to this, the invention provides a process for obtaining a dual rBV allowing the simultaneous expression of the IBDV polyprotein and of IBDV VP1 protein from two independent ORFs and each one of them controlled by a different baculovirus promoter, in insect cells, including: a) constructing a plasmid carrier of a gene construct containing (i) a nucleotide sequence including the open reading frames corresponding to the IBDV polyprotein operatively bound to a nucleotide sequence including a first promoter of a baculovirus, and (ii) a nucleotide sequence including the open reading frame corresponding to the IBDV VP1 protein operatively bound to a nucleotide sequence including a second promoter of a baculovirus, wherein the first baculovirus promoter is different from the second baculovirus promoter and they allow the simultaneous control of the gene expression of the polyprotein and IBDV VP1 protein; b) obtaining a recombinant bacmid, simultaneously allowing the expression during its replicative cycle of the polyprotein and the IBDV VP1 protein under the transcriptional control of the baculovirus promoters, by means of the transformation of competent bacteria with the plasmid obtained in a); and c) obtaining a dual recombinant baculovirus, allowing the simultaneous expression of the open reading frames corresponding to the polyprotein and the IBDV VP1 protein under the transcriptional control of the baculovirus promoters, by means of the transformation of insect cells with the recombinant bacmid of b). [0096] As used in this description, the term “competent bacteria” refers to bacteria which can contain the genome of a baculovirus, for example, AcMNV, optionally genetically modified, allowing the recombination with donor plasmids. [0097] In a particular embodiment, the process of obtaining dual rBVs is characterized in that: the first baculovirus promoter sequence comprises the promoter of the AcMNV p10 protein and the second baculovirus promoter sequence includes the promoter of the AcMNPV polyhedrin, or vice versa; the plasmid obtained in a) is the one identified as pFBD/Poly-VP1 in this description; the competent bacteria transformed in b) are Escherichia coli DH10Bac; the recombinant bacmid obtained in b) is the one identified as Bac/pFBD/Poly-VP1 in this description; and the dual rBV obtained is the one identified as FBD/Poly-VP1. [0103] The dual rBV thus obtained can be used, if so desired, to obtain whole IBDV VLPs of the invention. To that end, insect cells are infected with the dual rBV. Virtually any insect cell can be used; however, in a particular embodiment, the insect cells are H5 cells or Spodoptera frugiperda Sf9 cells. [0104] Alternatively, as previously mentioned, whole VLPs of the invention can be obtained by means of the combined infection (coinfection) of insect cells with a rBV allowing expression of the IBDV polyprotein in insect cells and with a rBV allowing expression of the IBDV VP1 protein in insect cells. Such rBVs can be obtained as previously described. Virtually any insect cell can be used; however, in a particular embodiment, the insect cells are H5 cells or Spodoptera frugiperda Sf9 cells. [0105] Accordingly, in another aspect, the invention is related to a process for the production of rBVs useful for the production of whole IBDV VLPs. In a particular embodiment, the recombinant baculoviruses obtained are dual, i.e., the same recombinant baculovirus is able to express in suitable host cells the viral polyprotein and the IBDV VP1 protein from two independent ORFs and controlled by different baculovirus promoters. The simultaneous expression in the same host cell of the viral polyprotein and IBDV VP1 protein allows the formation of whole IBDV VLPs. In another particular embodiment, recombinant baculoviruses are obtained which are able to express in suitable host cells the viral polyprotein from a nucleic acid sequence comprising the ORFs corresponding to the IBDV polyprotein under the control of a baculovirus promoter and several recombinant baculoviruses able to express in suitable host cells the IBDV VP1 protein from a nucleic acid sequence comprising the ORF corresponding to the VP1 of IBDV under the control of a promoter that is equal to or different from the one regulating the expression of the viral polyprotein in the recombinant baculoviruses able to express the viral polyprotein. The combined infection (coinfection) of suitable host cells, such as insect cells, with the recombinant baculoviruses able to express the viral polyprotein and with the recombinant baculoviruses able to express the IBDV VP1 protein, allows for the simultaneous expression in the coinfected cells of the viral polyprotein and of the IBDV VP1 protein, which allows for the formation of whole IBDV VLPs. The resulting recombinant baculoviruses constitute a further aspect of the present invention. [0106] In another aspect, the invention is related to the use of the gene expression system provided by this invention for the production of whole IBDV VLPs of the invention, which constitute a further aspect of this invention. [0107] The whole IBDV VLPs of the invention can be used to immunize animals, particularly birds, per se or as vectors or vehicles of molecules with biological activity, for example, polypeptides, proteins, nucleic acids, drugs, etc., whereby they can be used for therapeutic or diagnostic purposes. In a particular embodiment, the molecules with biological activity include antigens or immune response inducers in animals or humans to whom they are supplied, or drugs which can be released in their specific action site, or nucleic acid sequences, all being useful in gene therapy and intended for being introduced inside the suitable cells. [0108] Therefore, in another aspect, the invention is related to the use of the whole IBDV VLPs of the invention in the manufacture of medicaments such as vaccines, gene therapy vectors (delivery systems), etc. In a particular embodiment, the medicament is a vaccine intended for conferring protection to animals, particularly birds, against the infectious bursal disease virus (IBDV). In another particular embodiment, the medicament is a gene therapy vector. [0109] In another aspect, the invention provides a vaccine comprising a therapeutically effective amount of whole IBDV VLPs of the invention, optionally together with one or more pharmaceutically acceptable adjuvants and/or vehicles. Such vaccine is useful for protecting animals, particularly birds, against the infectious bursal disease virus (IBDV). In a particular embodiment, such birds are selected from the group formed by chickens, turkeys, geese, ganders, pheasants, partridges and ostriches. In a preferred embodiment, the vaccine provided by this invention is a vaccine useful for protecting chickens from the infection caused by IBDV. [0110] In the sense used in this description, the expression “therapeutically effective amount” refers to the amount of whole IBDV VLPs of the invention calculated for producing the desired effect and will generally be determined, among others, by the characteristics of the whole IBDV VLPs of the invention and the immunization effect to be achieved. [0111] The pharmaceutically acceptable adjuvants and vehicles which can be used in such vaccines are those adjuvants and vehicles known by the persons skilled in the art and normally used in the manufacture of vaccines. [0112] In a particular embodiment, the vaccine is prepared in form of an aqueous solution or suspension in a pharmaceutically acceptable diluent, such as saline solution, phosphate-buffered saline solution (PBS), or any other pharmaceutically acceptable diluent. [0113] The vaccine provided by this invention can be administered by any suitable administration route that results in a protective immune response against the heterologous sequence or epitope used, to which end the vaccine will be formulated in the dosage form suited to the chosen administration route. In a particular embodiment, the administration of the vaccine provided by this invention is carried out parenterally, for example, intraperitoneally, subcutaneously, etc. [0114] The following Examples illustrate the invention and should not be considered limiting of the scope thereof. Example 1 clearly shows that the deletion of the C-terminal end of the IBDV VP3 protein hinders formation of IBDV VLPs, whereas Example 2 describes the generation of a recombinant baculovirus coexpressing the A1 and B1 open reading frames of the IBDV genome, and Example 3 illustrates obtaining whole IBDV VLPs from H5 cells infected with the recombinant baculovirus FBD/Poly-VP1. The materials and methods described below were used to implement the Examples. Materials and Methods [0115] Cells and viruses. The recombinant viruses VT7/VP3, VT7/PolyΔ907-1012, FB/Poly, FB/his-VP3 (wt), FB/his-VP3Δ253-257, FB/his-VP3Δ1-25, FB/his-VP3Δ26-52, FB/his-VP3Δ53-77, FB/his-VP3Δ78-100, FB/his-VP3Δ101-124, FB/his-VP3Δ125-150, FB/his-VP3Δ151-175, FB/his-VP3Δ176-200, FB/his-VP3Δ201-224 and FB/his-VP3Δ216-257 were disclosed previously (Fernández-Arias A et al. 1997. The major antigenic protein of infectious bursal disease virus, VP2, is an apoptotic inducer. J. Virol. 71:8014-8; Kadono-Okuda, K., et al. 1995. Baculovirus-mediated production of the human growth hormone in larvae of the silkworm, Bombyx mori. Biochem. Biophys. Res. Commun. 213:389-96; Kochan, G., et al. Characterization of the RNA binding activity of VP3, a major structural protein of IBDV. 2003. Archives of Virology 148:723-744; Martínez-Torrecuadrada, J. L., et al. 2000. Different architectures in the assembly of infectious bursal disease virus capsid proteins expressed in insect cells. Virology. 278:322-31). [0116] The expression experiments were carried out with BSC-1 cells (American Type Culture Collection, ATCC; Catalogue CCL26), H5 [HighFive™ (GIBCO)] and Sf9 cells (GIBCO). The BSC-1 cells were cultured in Eagle modified Dulbecco medium supplemented with 10% fetal bovine serum. The H5 and Sf9 cells were cultured in TC-100 medium (GIBCO) supplemented with 10% fetal bovine serum. The viruses were amplified and titrated following previously disclosed protocols (Lombardo, E., et al. 2000. VP5, the nonstructural polypeptide of infectious bursal disease virus, accumulates within the host plasma membrane and induces cell lysis. Virology. 277:345-57; Martínez-Torrecuadrada, J. L., et al. 2000. Different architectures in the assembly of infectious bursal disease virus capsid proteins expressed in insect cells. Virology. 278:322-31). [0117] The isolate of IBDV used was IBDV Soroa strain. [0118] Generation of recombinant baculoviruses. The previously disclosed plasmid pFB/his-VP3 was used as a mold in the generation, by means of polymerase chain reaction (PCR), of the DNA fragments used in the construction of the plasmid vectors needed for the construction of the recombinant baculoviruses FB/his-VP3Δ248-257, FB/his-VP3Δ243-257, FB/his-VP3Δ238-257, FB/his-VP3Δ233-257, and FB/his-VP3Δ228-257. The PCR reactions were carried out using a common 5′ primer (SEQ. ID. NO: 4) and 3′ primer specific for each mutant (Table 1). TABLE 1 Generation of deletion mutants of the terminal carboxy end of His-VP3 Mutant Sequence His-VP3Δ248-257 SEQ. ID. NO: 5 His-VP3Δ243-257 SEQ. ID. NO: 6 His-VP3Δ238-257 SEQ. ID. NO: 7 His-VP3Δ233-257 SEQ. ID. NO: 8 His-VP3Δ228-257 SEQ. ID. NO: 9 [0119] After the PCR reactions, the corresponding DNA fragments were purified and digested with the restriction enzymes ApaI and KpnI and ligated to the plasmid pFB/his-VP3 (Kochan, G., et al. 2003. Characterization of the RNA binding activity of VP3, a major structural protein of IBDV. Archives of Virology 148:723-744) previously digested with the same enzymes. The plasmid series generically referred to as pFB/his-ΔVP3 (pFB/his-VP3Δn-n′ more specifically, wherein n and n′ indicate the deleted region borders) containing deletions in the 5′ end of the encoding region of VP3, were thus generated. [0120] The construction of the plasmid vectors required for the generation of the recombinant baculoviruses FB/PolyΔ1008-1012, FB/PolyΔ1003-1012 and FB/PolyΔ998-1012 was carried out by means of the substitution of the Xba I fragment (343 base pairs) with its homologs, containing the desired deletions, deriving from the plasmids FB/his-VP3Δ233-257, FB/his-VP3Δ248-257, and FB/his-VP3Δ243-257, respectively. [0121] The construction of the plasmid vector pFB/VP1 was carried out by means of cloning a DNA fragment, which contains the open reading frame of the gene of the IBDV VP1 protein, from the plasmid pBSKVP1 (Lombardo E et al. 1999. VP1, the putative RNA-dependent RNA polymerase of infectious bursal disease virus, forms complexes with the capsid protein VP3, leading to efficient encapsidation into virus-like particles. J. Virol. 73:6973-83) by means of digestion of the plasmid with the restriction enzyme ClaI, followed by treatment with the Klenow fragment of DNA polymerase I and subsequent treatment with the enzyme NotI. This fragment was subcloned into the vector pFastBac1 (Invitrogen) previously digested with the restriction enzymes Stul and NotI. The resulting plasmid was called pFB/VP1. [0122] The plasmid vectors pFBD/his-VP3-VP1 and pFBD/Poly-VP1 were constructed by means of the insertion of the open reading frames of the genes of the VP3 and VP1 proteins in the vector pFastBacDual (Invitrogen). pFBD/VP1 was generated by means of the insertion of a fragment containing the open reading frame of VP1 obtained by means of digestion with the enzyme NotI, followed by treatment with the Klenow fragment of DNA polymerase I and subsequent treatment with the enzyme XhoI, in the vector pFastBacDual (Invitrogen) previously digested with the enzymes XhoI and PvuII. Next, the plasmid pFB/his-VP3 (Kochan, G., et al. 2003. Characterization of the RNA binding activity of VP3, a major structural protein of IBDV. Archives of Virology 148:723-744) was digested with the enzymes NotI and RsrII, and the resulting fragment containing the open reading frame of his-VP3 was inserted in the plasmid pFBD/VP1 previously digested with the enzymes NotI and RsrII. The resulting plasmid was called pFBD/his-VP3-VP1. Similarly, the open reading frame corresponding to the IBDV polyprotein was isolated from the plasmid pCIneoPoly (Maraver, A., et al. Identification and molecular characterization of the RNA polymerase-binding motif of the inner capsid protein VP3 of infectious bursal disease virus. J. Virol. 77:2459-2468) by means of digestion with the enzymes EcoRI and NotI. The corresponding DNA fragment was cloned into the plasmid pFBD/VP1 previously digested with the enzymes EcoRI and NotI, giving rise to the vector referred to as pFBD/Poly-VP1. [0123] The recombinant baculoviruses described above were generated using the Bac-to-Bac system, following the protocols described by the manufacturer (Invitrogen). [0124] Purification by means of sucrose gradients and characterization of the structures derived from the expression of the IBDV polyprotein. BSC-1 or H5 cells were infected with the described vaccine viruses or recombinant baculoviruses. The infected cells were harvested, lysed and processed as described above (Lombardo, E., et al. 1999. VP1, the putative RNA-dependent RNA polymerase of infectious bursal disease virus, forms complexes with the capsid protein VP3, leading to efficient encapsidation into virus-like particles. J. Virol. 73:6973-83; Castón, J. R., et al. 2001. C terminus of infectious bursal disease virus major capsid protein VP2 is involved in definition of the number for capsid assembly. J. Virol. 75:10815-28). [0125] Electron microscopy. Aliquots of 5 μl of the different fractions of the analyzed sucrose gradients were placed in electron microscopy grids. The samples thus prepared were negatively stained with a 2% uranyl acetate solution. The micrographs were obtained with a Jeol 1200 EXII microscope operating at 100 kV with magnifications of 20,000 or 40,000×. [0126] Purification of his-VP3 fusion proteins and derivatives by means of immobilized metal affinity chromatography (IMAC). H5 or Sf9 cells infected with the different recombinant viruses described were harvested at 72 h.p.i. Alter washing twice in phosphate buffered saline (PBS), the cells were resuspended in lysis buffer (Tris-HCI 50 mM, pH 8.0; NaCl 500 mM) supplemented with protease inhibitors (Complete Mini, Roche) and kept on ice for 20 minutes. Then the samples were subjected to centrifugation at 13,000×g for 10 minutes at 4° C. The corresponding supernatants were subjected to purification by means of IMAC using a resin bound to cobalt (Talon, Clontech Laboratories, Inc., Palo Alto, Calif.) following the manufacturer instructions. [0127] Electrophoresis and Western blot. The protein samples were resuspended in Laemmli buffer (King J & Laemmli UK. 1973. Bacteriophage T4 tail assembly: structural proteins and their genetic identification. J Mol Biol. 1973 Apr. 5;75(2):315-37) and subjected to heating at 100° C. for 5 minutes. The electrophoreses were carried out in 11% polyacrylamide gels. Then the proteins were transferred to nitrocellulose membranes by means of electroblotting. Prior to the incubation with specific antisera, the membranes were blocked by means of incubation for 1 hour at room temperature, with 5% powdered milk diluted in PBS. [0128] Immunofluorescence (IF) and confocal microscopy (CLSM). BSC-1 or H5 cells were grown on slide covers and infected with the recombinant baculoviruses or vaccine viruses. At the post-infection times indicated, the cells were washed two times with PBS and fixed with methanol at −20° C. for 10 minutes. After the fixing, the slide covers were air dried, blocked in a 20% solution of recently born calf serum in PBS 45 minutes at room temperature and incubated with the indicated anti-sera. The samples were viewed by means of epifluorescence using a Zeiss Axiovert 200 microscope equipped with a Bio-Rad Radiance 2100 confocal system. The images were obtained using the Laser Sharp software package programs (Bio-Rad). [0129] Mass spectrophotometry (MS) analysis. The proteins were passed through C-18 ZipTip tips minicolumns (Millipore, Bedford, Mass., USA) and eluted in matrix solution (3,5-dimethoxy-4-hydroxycinnamic acid saturated in aqueous solution of 33% acetonitrile and 0.1% trifluoroacetic acid). An aliquot of 0.7 μl of the resulting mixture was placed in a steel MALDI probe which was subsequently air dried. The samples were analyzed using a Bruker Reflex™ IV MALDI-TOF mass spectrometer (Bruker-Franzen Analytic GmbH, Bremen, Germany) equipped with a SCOUT™ reflector source in positive ion reflector mode using delayed extraction. The acceleration voltage was 20 kV. The equipment was externally calibrated using mass signals corresponding to BSA and BSA dimers ranging from 20-130 m/z. EXAMPLE 1 Deletion of the C-terminal End of the VP3 Protein Eliminates the Formation of IBDV VLPs [0130] It has recently been disclosed that the C-terminal end of VP3 contains the domain responsible for the interaction of this protein with the VP1 protein (Maraver, A., et al. Identification and molecular characterization of the RNA polymerase-binding motif of the inner capsid protein VP3 of infectious bursal disease virus). As a result, it was decided to analyze the possible role of the C-terminal region of VP3 in the morphogenesis of IBDV VLPs. As a starting ground for this analysis, the recombinant vaccine virus referred to as VT7/PolyΔ907-1012, expressing a deleted form of VP3 lacking the 105 C-terminal end residues (Sánchez Martínez, A. B. 2000. “Caracterización de las modificaciones co y post-traduccionales de la poliproteína del virus de la bursitis infecciosa”. Doctoral Thesis. Universidad Autónoma of Madrid. Facultad of Ciencias Biológicas), was used ( FIG. 1A ). The SDS-PAGE and Western blot analysis showed that the deletion does not affect the cotranslational proteolytic processing of the polyprotein (Sánchez Martínez, A. B. 2000. Doctoral Thesis cited supra). Expression of the PolyΔ907-1012 protein gives rise to the formation of tubular structures similar to the type I tubules formed in cells infected with IBDV (Kaufer, I., and E. Weiss 1976. Electron-microscope studies on the pathogenesis of infectious bursal disease after intrabursal application of the causal virus. Avian Dis. 20:483-95). The tubular structures formed by expression of PolyΔ907-1012 were detected by means of immunofluorescence using antibodies anti-VPX/2 (anti-pVP2NP2) and anti-VP3 ( FIG. 1B ), and by means of electron microscopy of fractions obtained by means of purification on sucrose gradients ( FIG. 1C ). The Western blot analysis confirmed the presence of VPX and VP3 in the tubules. [0131] For the purpose of confirming that the mentioned phenotype was due to the deletion within the region corresponding to VP3, an experiment was carried out coinfecting BSC-1 cells with VT7/PolyΔ907-1012 and VT7VP3. VT7/VP3 is a virus vaccine recombinant expressing the whole VP3 protein (Fernández-Arias, A., et al. 1997. The major antigenic protein of infectious bursal disease virus, VP2, is an apoptotic inducer. J. Virol. 71:8014-8). A confocal microscopy analysis showed that the coexpression of the whole VP3 protein produces a significant reduction in the formation of type I tubules. In the coinfected cells, the subcellular distribution of the VPX/VP3 proteins is characterized by the formation of short tubules and viroplasms similar to those detected in cells infected with the whole polyprotein ( FIG. 1B ). This observation indicates that the coexpression of the whole VP3 protein partially salvages the ability of the PolyΔ907-1012 protein to form VLPs. The electron microscopy analysis of fractions derived from the coinfection confirmed this hypothesis. Therefore, the top fractions of the gradient were highly enriched in short tubules and quasi-spherical assemblies, called capsoids, with a diameter of 60-70 nm, together with a small proportion of VLPs of polygonal contour ( FIG. 1C ). The Western blot analysis of the top fractions of the gradient, which contained the highest concentration of capsoids, clearly showed that they contained a larger ratio of whole VP3 protein than of VP3Δ907-1012 protein (data not shown). This result indicated that the incorporation of the whole VP3 protein in these structures is more efficient than that of the deleted form. These results show that the C-terminal end of VP3 plays a fundamental role in the morphogenesis of the IBDV capsid. [0132] The VP3 protein undergoes a proteolytic processing in insect cells. It has previously been disclosed that the expression of the IBDV polyprotein in insect cells produces the assembly of long tubules formed by VPX trimer hexamers (Da Costa, B., C. Chevalier, C. Henry, J. C. Huet, S. Petit, J. Lepault, H. Boot, and B. Delmas 2002. The capsid of infectious bursal disease virus contains several small peptides arising from the maturation process of pVP2. J. Virol. 76:2393-402; Martínez-Torrecuadrada, J. L., et al. 2000. Different architectures in the assembly of infectious bursal disease virus capsid proteins expressed in insect cells. Virology. 278:322-31). The similarity between the tubules observed in mammalian cells infected with VT7/PolyΔ907-1012 and those detected in insect cells infected with recombinant baculoviruses expressing the whole polyprotein led to the analysis of the condition of the VP3 protein accumulated in insect cells. To that end, cell extracts infected with IBDV, VT7/Poly (Fernández-Arias, A., et al. 1998. Expression of ORF A1 of infectious bursal disease virus results in the formation of virus-like particles. J. Gen. Virol. 79: 1047-54) and FB/Poly, respectively, were analyzed by means of Western blot using anti-VP3 serum (Fernández-Arias. A., et al. 1997. The major antigenic protein of infectious bursal disease virus, VP2, is an apoptotic inducer. J. Virol. 71:8014-8). In cells infected with IBDV and VT7/Poly, the presence of a single band of 29 kDa, the expected size of the whole VP3 protein, was detected by means of Western blot ( FIG. 2 ). On the contrary, in insect cells infected with FB/Poly, the presence of two bands corresponding to polypeptides of 29 and 27 kDa, respectively, was detected by means of Western blot ( FIG. 2 ). An analysis of the time expression showed that even though the appearance of the product of 27 kDa is slightly delayed with regard to the appearance of the product of 29 kDa, it becomes predominant in the later stage of infection ( FIG. 8A ). A similar analysis carried out in Sf9 cells produced identical results (data not shown). These results show that in insect cells, the VP3 protein undergoes a post-translational modification giving rise to the accumulation of a product of 27 kDa. [0133] The infection of insect cells with a recombinant baculovirus, FB/his-VP3, expressing a version of VP3 containing a six-histidine residue tag (6xhis), called his-VP3 ( FIG. 3A ), gives rise to the accumulation of two molecular forms of the protein of 32 and 30 kDa, respectively, similar to those observed in cells infected with FB/Poly (Kochan, G., et al. 2003. Characterization of the RNA binding activity of VP3, a major structural protein of IBDV. Archives of Virology 148:723-744). Therefore, FB/his-VP3 was used as a tool to determine the origin of the smaller VP3 protein. To that end, both total cell extracts infected with FB/his-VP3 and protein purified by means of IMAC were analyzed by means of SDS-PAGE and Western blot using anti-VP3 serum ( FIG. 3B ) and anti-6xhis ( FIG. 3C ). As shown in FIG. 3B , the polyprotein of the 30 kDa is present in the purified protein sample, which shows that its N-terminal end remains intact. On the other hand, both the product of 32 kDa and that of 30 kDa are recognized by both antisera ( FIGS. 3B and 3C ). These results strongly indicate that in insect cells, the VP3 protein undergoes proteolysis, giving rise to a product lacking a fragment of 2 kDa at its C-terminal end. For the purpose of firmly determining this possibility, six recombinant baculoviruses called his-VP3Δ253-257, his-VP3Δ248-257, his-VP3Δ243-257, his-VP3Δ238-257, his-VP3Δ233-257 and his-VP3Δ228-257, respectively ( FIG. 4A ) were used [they correspond to those defined in the section of Materials and Methods, sub-section Cells and Virus, with an identical nomenclature, but. preceded by “FB/” (indicative of the name of the plasmid used for generating the viruses (pFastBac1)]. These recombinant baculoviruses express a series of deletion forms of VP3 containing a histidine tag. The deletions were generated to progressively eliminate groups of 5 amino acid residues and thus generate a collection with growing deletions at the C-terminal end of the VP3 protein, as shown in FIG. 4A . The expression of these proteins was analyzed by means of Western blot using anti-VP3 serum. As shown in FIG. 4B , the expression of the his-VP3 (his-VP3 wt) whole protein and of the his-VPΔ253-257 mutant protein gave rise to the formation of doublets. On the other hand, the proteins containing deletions of 10 or more residues migrated according to their expected size, giving way to a single band ( FIG. 4B ). This result shows that the C-terminal end of the VP3 protein is proteolytically processed and that the deletion of the cleavage site prevents proteolysis. The electrophoretic mobility of the his-VP3Δ248-257 protein is slightly less than that of the polypeptides generated by proteolytic processing of his-VP3 and his-VP3Δ253-257, which indicates that the processing occurs in the region located between residues 243 and 248. The C-terminal end of the his-VP3Δ248-257 protein is probably too short so as to allow the recognition on the part of the protease, and therefore it would not undergo proteolytic processing. [0134] For the purpose of confirming the results obtained with the his-VP3 deletion mutants and precisely establishing the proteolytic cleavage site in the VP3 protein, H5 cell extracts infected with FB/his-VP3 were subjected to purification by means of IMAC. The resulting purified protein was analyzed by means of mass spectrometry. The experiment was repeated three times using independent purifications. The obtained results were similar in all cases (a difference in mass of less than 0.03%). FIG. 5A shows the results of one of these experiments. The presence of two polypeptides of 32,004 and 30,444 Da, respectively, was determined. These results show that the proteolytic processing causes the elimination of a peptide of 1,560 Da from the C-terminal end of his-VP3. This size fits with the molecular mass (1,576 Da) corresponding to the 13 C-terminal residues of VP3 (SEQ. ID. NO: 3) ( FIG. 5B ). [0135] These results as a whole show that the VP3 protein is proteolytically processed in insect cells between the L244 and G245 residues, giving rise to a polypeptide lacking the 13 C-terminal residues. EXAMPLE 2 Generation of a Recombinant Baculovirus Coexpressing the A1 and B1 Open Reading Frames of the IBDV Genome 2.1 Construction of the Plasmid PFBD/VP1 [0136] The nucleotide sequence corresponding to the B1 open reading frame of the IBDV genome was obtained from the plasmid pBSKVP1 described above (Lombardo, E., et al. 1999. VP1, the putative RNA-dependent RNA polymerase of infectious bursal disease virus, forms complexes with the capsid protein VP3, leading to efficient encapsidation into virus-like particles. J. Virol. 73:6973-83). The plasmid was purified and subjected to the following enzymatic treatments: i) digestion with the restriction enzyme NotI; ii) incubation with the Klenow fragment of DNA polymerase of E. coli in the presence of dNTPs; and iii) digestion with the restriction enzyme XhoI. Then the corresponding DNA fragment was purified and used for its cloning into the vector pFastBacDual (Invitrogen) previously treated with restriction enzymes XhoI and PvuII. For this, the DNA fragment and the linearized plasmid were incubated in the presence of T4 DNA ligase to generate the plasmid pFBD/VP1. 2.2 Construction of the Plasmid pFBD/Poly-VP1 [0137] The nucleotide sequence corresponding to the Al open reading frame of the IBDV genome was obtained from the plasmid pCIneoPoly described above (Lombardo, E., et al. 1999. VP1, the putative RNA-dependent RNA polymerase of infectious bursal disease virus, forms complexes with the capsid protein VP3, leading to efficient encapsidation into virus-like particles. J. Virol. 73:6973-83). The plasmid was purified and incubated with the restriction enzymes EcoRI and NotI. The corresponding DNA fragment was purified and incubated with the plasmid pFBD/VP1, previously digested with the restriction enzymes EcoRI and NotI, in the presence of T4 DNA ligase to generate the plasmid pFBD/Poly-VP1. A bacteria culture transformed with said plasmid pFBD/Poly-VP1 has been deposited in the CECT with deposit number CECT 5777. 2.3 Obtaining the Bacmid Bac/pFBD/Poly-VP1 [0138] This was carried out by means of the transformation of competent bacteria DH10Bac (Invitrogen), positive colony selection in selective medium and purification following the methodology disclosed by Invitrogen (catalog numbers 10359016 and 10608016). 2.4 Obtaining the Recombinant Baculovirus FBD/Poly-VP1 [0139] The virus was obtained by means of transfection of H5 cells (Invitrogen) with the bacmid Bac/pFBD/Poly-VP1 previously purified following the methodology disclosed by Invitrogen (catalog numbers 10359016 and 10608016). EXAMPLE 3 Obtaining Whole IBDV VLPs from H5 Cells Infected with the Recombinant Baculovirus FBD/Poly-VP1 [0140] H5 cell cultures were infected with the recombinant virus FBD/Poly-VP1 (Example 2) using a multiplicity of infection of 5 plaque forming units per cell. The cultures were harvested at 72 hours post-infection (h.p.i). The cells were settled by means of centrifugation (1.500×g for 10 minutes). The cellular sediment was resuspended in PES buffer (PIPES (1,4-piperazine ethanesulfonic acid) 25 mM, pH 6.2, NaCl 150 mM, CaCl 2 20 mM). Then the cells were homogenized by means of three consecutive freezing/thawing cycles (−70° C./+37° C.). The corresponding homogenate was centrifuged (10,000×g for 15 minutes at 4° C.). The resulting supernatant was harvested and used for the purification of the VLPs. To that end, a centrifuge tube with a 25% sucrose cushion (weight/volume), diluted in PES buffer of 4 ml, was prepared, depositing 8 ml of supernatant thereon. The tube was centrifuged (125,000×g for 3 hours at 4° C.). The resulting sediment was resuspended in 1 ml of PES buffer. Then a continuous 25-50% sucrose gradient in PES buffer was prepared in a centrifuge tube, depositing the resuspended sediment thereon. The tube was centrifuged (125,000×g for 1 hour at 4° C.). Then the gradient was fractioned into aliquots of 1 ml. [0141] The different aliquots were analyzed by means of transmission electron microscopy. To that end, a volume of 5 μl of each sample was placed on a microscope grid. The samples were negatively stained with an aqueous solution of 2% uranyl acetate. A Jeol 1200 EXII microscope operating at 100 kV and at a nominal magnification of 40,000× was used. This analysis showed the presence of whole VLPs structurally identical to the IBDV virions in the analyzed samples. [0142] For the purpose of determining the protein composition of the VLPs detected by means of electron microscopy, the samples were analyzed by means of Western blot. To that end, the samples were subjected to polyacrylamide gel electrophoresis. The gels were subsequently transferred to nitrocellulose and incubated with anti-VPX/2 antibodies (anti-pVP2VP2), anti-VP3 and anti-VP1. The results showed the presence of the VPX, VP2, VP3 and VP1 proteins in the fractions containing VLPs. [0000] Microorganism Deposit [0143] A culture of the bacteria derived from DH5, carrier of a plasmid containing the IBDV polyprotein-VP1 genetic construction (pFBD/Poly-VP1), DH5-pFBD/poly-VP1, has been deposited in the Spanish Culture Type Collection (CECT), University of Valencia, Research Building, Burjasot Campus, 46100 Burjasot, Valencia, Spain, on Mar. 8, 2003, with deposit number CECT 5777.

Whole empty viral particles of infectious bursal disease virus (IBDV), which contain all of the antigenically-relevant proteinaceous constituents present in determinant IBDV virions. The whole empty virus particles are readily produced in suitable expression systems to provide capsids that can be used in the production of vaccines against avian disease, e.g., infectious bursitis caused by IBDV, and in the development of gene therapy vectors.

BACKGROUND OF THE INVENTION This invention relates in general to artificial hearts and more particularly to an artificial heart system that will respond to varying physiological demand and includes mechanisms accommodating the actual flow imbalance between pulmonary and systemic circulations. Over the last several years progress in developing a permanent artificial heart for implantation in a patient as a substitute for a failed natural heart has been steady. Initial clinical application of total artificial heart as a bridge to transplantation was done in 1969. This has been followed by several additional cases at various institutions. In 1982 the first pneumatically driven tethered artificial heart intended for permanent replacement was implanted. Among the issues that need to be addressed in an untethered artificial heart system are control strategies that respond to varying physiological demand, and mechanisms for accommodating the natural flow imbalance between the pulmonary and systemic circulations. The left-right cardiac output differences have been well established. Normally this difference appears to be ten to fifteen percent with the left side flow always greater than the right side flow. Artificial heart systems must account for this inherent physiological characteristic. For externally actuated pneumatic systems the external drive system can be set to accommodate this flow difference. In permanent systems, however, this flow difference compensation has to be considered in conjunction with the system compliance and control. In the prior art two approaches, control valve regurgitation and a gas compliance chamber have been used in experimental systems. In particular a controlled outflow valve regurgitation in the artificial right heart has been employed. (Lioi, A. P.; Kolff, W. D.; Olsen, D. B.; Crump, K.; Isaacson, M. S.; and Nielson, S. D.; "Physiological Control of Electric Total Artificial Hearts", in Devices and Contractors Branch Contractors Meeting 1985, Program and Abstracts, Dec. 1985, 89.) In this approach the left and right sides of the heart are pumped alternately by a reversing hydraulic pump. A deliberate outflow leakage designed into the right pump is intended to accommodate the flow difference and obviate the need for a compensating chamber. However the regurgitant flow is only a function of the square root of the difference between the pulmonary diastolic pressure and the right atrial pressure. This results in a near constant compensating flow which may well be inadequate to accommodate time varying flow differences. Also, changes in the orifice size over the long duration can cause this flow imbalance to drift from the preset value. A second prior art approach has employed a gas compliance chamber (with its problems of gas composition and pressure changes) and passive filling to accommodate the flow difference in conjunction with a stroke-time division scheme. (Rosenberg, G.; Snyder, J.; Landis, D. L.; Geselowitz, D. B.; Donachy, J. H.; and Pierce, W. S., "An Electric Motor-Driven Total Artificial Heart: Seven Months Survival In The Calf", Trans Am Soc Artif Intern Organ, 15, 69, 1984.) In addition to the left-right balance problem, the prior art has actively worked on a control system for controlling the artificial heart. Externally actuated pneumatic systems have commonly been operated under preset drive parameters: drive pressure, vent pressure, beat rate, and systolic/diastolic ratio. SUMMARY OF THE INVENTION It is therefore an object of this invention to provide an artificial heart which is an alternately left-right pumping device in which the basic control strategy is to adjust hydraulic fluid flow and beat rate on a beat-by-beat basis so that the device is stable and sensitive to both left and right atrial pressures. It is a further object of this invention to provide for the left-right blood flow imbalance by incorporating in a hydraulically pumped system, a hydraulic imbalance chamber positioned to respond physiologically through the blood flows in the right and left side of the heart to maintain an appropriate imbalance. Broadly speaking, the present invention utilizes an alternately left-right pumping device with the left and right pumping chambers, each including a membrane or diaphragm separating the chamber into a blood flow section and a hydraulic section. During left-side blood pump ejection, hydraulic fluid is being pumped from the right hydraulic section through a hydraulic pump into the left hydraulic section, resulting in concurrent filling of the right side blood pump while left side ejection is taking place. The hydraulic flow is reversed for right side ejection and left side filling. A third hydraulic chamber small in volume compared to the left side hydraulic section and right side hydraulic section of the blood pumping chambers and having fluid communication with the right side hydraulic section is preferably incorporated on the proximal (atrial) side of the left pump inflow valve and includes its own flexible diaphragm in contact with blood inflow through the left pump. This third chamber serves to maintain the natural imbalance in the left and right side flows by changing the right hydraulic section fluid volume during a beat. Without this additional balancing hydraulic section, the left and right blood pumping chambers would always provide equal stroke volumes. With the incorporation of this additional hydraulic balance chamber, the volume pumped by the right side pump is reduced by the balancing chamber. The distribution of hydraulic fluid between the right side chamber volume and the balancing chamber volume is altered dynamically by the physiological pressure in the pulmonary artery and in the left atrium, thus adjusting the volume pumped by the right side fluid flow chamber on a beat-by-beat basis. The flow resistance between the hydraulic section on the right side chamber and the hydraulic balancing chamber is designed to maintain the overall natural flow imbalance. The balancing chamber is placed in the left atrial inflow to provide a negative feedback on the right chamber fluid volume. A high left atrial pressure, indicating too much flow from the right side, will decrease the hydraulic volume in the balancing chamber and increase the hydraulic volume in the right side chamber. The result is to reduce the flow on the right side. Conversely, a low left atrial pressure will increase the right side flow. This provides a stable feedback to maintain the desired right side flow relative to the left side flow. The primary factor is that the membrane of the balancing factor be in contact with blood flow somewhere in the system or in the patient's connecting atria or arteries so that a variation in blood pressure will produce a positioned change in the membrane. While the left atrium is the preferred site for this balancing chamber, other suitable sites include distal to the right side outflow valve, or right atrial inflow. An electrohydraulic energy system drives the blood pumps employing a hydraulic fluid, typically methyl silicone, operating at physiological pressures. This hydraulic coupling between the blood pumps and the energy converter allows geometric flexibility. There is a 1:1 correspondence between blood and hydraulic fluid displacement. The hydraulic fluid and blood are immiscible with negligible fluid transfer across the interface. The energy converter consists of an unidirectional axial pump driven by a brushless d.c. motor with flow reversal accomplished by a two-position, sliding sleeve valve. There are, then, essentially two moving parts, the pump motor and one of the valving sleeves. The motor sits immersed in the hydraulic fluid which fills the energy system housing. This ensures temperature uniformity of the system. Waste heat is transferred to the blood across the pump diaphragms and from the housing to contacting body fluid and surfaces. A simple two-level control strategy results in a system responsive to physiological demands. Sensors in the hydraulic fluid are indicators of the atrial filling pressures. Other sensors detect full stroke of the left blood pumps. Thus there are two inputs and they control two outputs: motor speed or rate of filling/ejection, and beat rate. In this system the systolic/diastolic ratio is held constant. The rate of ejection is incrementally increased for a given beat rate until the pump is ejecting completely. If, in addition to complete ejection full stroke is achieved, then the beat rate is increased. The reverse occurs if fill volumes are too low. The strategy is independent of outflow impedances. The artificial heart system reacts (both stroke volume and beat rate) to changes in the available fill volume and adjusts the outflow pressure to accommodate the outflow impedance. Similarly since each pump is filled by active withdrawal of hydraulic flow, fill characteristics are not determined by mechanical impedances, but can be tailored to a desired characteristic. DESCRIPTION OF THE DRAWING In the drawing: FIG. 1 is an illustration generally in perspective view of an artificial heart constructed in accordance with the principles of this invention placed orthotopically in the thoraic space; FIG. 2 is an illustration generally in diagrammatic form of one embodiment of an artificial heart system constructed in accordance with the principles of this invention; FIGS. 3a and 3b are a diagrammatic illustration of the operation of the embodiment of FIG. 2.; FIG. 4a is an illustration in perspective view of the artificial heart embodiment of FIG. 2; and FIG. 4b is an illustration in top view of the embodiment of FIG. 4a; FIG. 5 is a diagram of an algorithm hierarchy for the control system of the artificial heart embodiment of FIG. 1; FIG. 6 is an illustration in diagrammatic form of the interrelationships of the sensed parameters and the control parameters, together with the resultant physiological parameter of the artificial heart embodiment of FIG. 2; FIG. 7 is an illustration generally in cross sectional view of a detachable blood pump construction suitable for employment in the embodiment of FIG. 2; FIG. 8 is an illustration generally in perspective view and partially broken away to show a balancing chamber construction suitable for use in the embodiment of FIG. 2; and FIGS. 9a and 9b are illustrations in cross sectional view of an energy converter suitable for use in the embodiment of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION The Figures generally illustrate a preferred embodiment of the artificial heart system of this invention. In FIG. 1 the anatomical placement of the system components is illustrated. The system is intended to replace the ventricles of the natural heart and is inserted within the thoracic cavity in place of the natural heart and coupled to the natural heart right and left atria and also to the pulmonary artery and the aorta. The cylindrical energy converter 8 and the blood pumps 5 and 6 approximate the shape and volume of the natural heart and are implanted in the pericardial volume vacated by the excised natural heart. The blood pumps 5 and 6 are seamless with no steps or connectors from proximal to the inflow valve through to the outflow graft distal to the outflow valve. The valves (not shown) are trileaflet valves placed at the flow inputs and outputs of each of the ventricles. The internal blood pump surfaces including the integral trileaflet valves are fabricated from a non-toxic, non-mutagenic polyetherurethane material made by Abiomed, Inc., Danvers, Mass. under the trademark Angioflex. A block diagram of an artificial heart system in accordance with the principles of this invention is illustrated in FIG. 2. The two blood pumps 10 and 20, each with a stroke volume typically of 85cc, are connected to the energy converter 32, which includes both a fluid switch and a hydraulic pump. As illustrated in FIG. 2 the left side pump 10 includes a blood flow pumping chamber 11 having a blood input section 18 from the left atrium and a blood output port 14 to the aorta. Trileaflet valves 40 and 41 have the normal valving function for the blood flow from the pump volume 11. The pump 10 also includes a hydraulic pumping section 16 which is fluidically coupled to the hydraulic pump 32. The right side pump 20 is similarly constructed and is coupled between the right atrium at its blood input port 22 and the pulmonary artery at its blood output port 24. This pump also includes a hydraulic pumping section 26 fluidically coupled to the energy converter 32. In addition to the parts described the left pump 10 includes at input cuff 18 a hydraulic section 28 which is fluidically coupled through conduit 30 to the right side hydraulic section 26. The volume of hydraulic section 28 is small compared to the volume of hydraulic sections 16 and 26 (typically a 1:5 ratio). The energy converter 32 includes a hydraulic pump which is coupled through a fluid switch to the sections 16 and 26. The fluid switch and hydraulic pump in energy converter 32 are controlled by a controller 34 which receives electrical power from internal battery 35 and an external battery (not shown) and control signals from sensors 36. The converter is more completely described in conjunction with FIG. 9, but provides for an axial flow pump with a sleeve valve which can be electrically switched. Depending upon the position of the sleeve valve, fluid is pumped either in the direction away from hydraulic section 16 and toward hydraulic section 26 or in the other position, away from hydraulic section 26 and toward hydraulic section 16. The controller 34 controls the position of this switch in accordance with the response to its program and input signals from the sensors 36. The pump cycle is as follows. During left side systole, blood is being ejected from the left blood chamber 11 into the aorta. Concurrently the right side blood chamber 21 is being filled from the right atrium. If the blood volume filling the right pump from the right atrium is less than the volume ejected from the left side blood chamber the compensating chamber 28 adjusts the compensating chamber volume formed in the cuff 18 to accommodate this volume difference by virtue of hydraulic fluid flowing from the compensating hydraulic chamber 28 into the right hydraulic section 26. The resultant volume change in the balance chamber in cuff 18 is naturally compensated for by the compliant left atrium during its filling phase. During right side ejection and left pump filling, the process is reversed, and the blood volume displaced by the compensating chamber 18 in the left atrium is transferred into the left side of the blood chamber 11 in addition to the remainder of the blood volume in the left atrium. This has the added advantage of aiding left atrial filling during left pump systole and left pump filling during left pump diastole. As will be described in more detail below the flow resistance of the hydraulic conduit 30 is selected to maintain the necessary natural left-right flow imbalance. The advantages of this compensation technique are: (1) its sensitivity to physiological pressure changes, thus providing stable feedback, and its insensitivity to valve performance changes, (2) no tissue encapsulation or gas composition changes on the moving diaphragm as would be the case of a gas compliance bag, and (3) simple integration into the left side inflow cuff of the compensating device. The basic control philosophy, implemented on a beat-by-beat basis, is to pump as much blood volume as is available in the atria. This can be achieved by first controlling the hydraulic motor speed to pump the available blood volume at a fixed beat rate. When the available atrial volume exceeds the pump stroke volume, the beat rate is increased. Similarly, in a fill limited situation, the motor speed and the beat rate are reduced to avoid overpumping. The motor speeds are controlled by pressure sensing, while the beat rate is controlled by stroke volume sensing. The atrial pressures govern the motor speeds during the respective fill cycles. By indirectly sensing the pressure in the atrium (by placing the pressure sensors in the hydraulic section 16 and 26), the motor speed is adjusted to insure that the end diastolic atrial pressure is near zero at the end of a fill cycle. The flexible bladder 17 separating blood and hydraulic fluid is tension-free during fill and ejection, and pressure sensors in the hydraulic chambers reflect the atrial pressures. At the end of filling, the bladder rests on a base plate, thus decoupling the hydraulic and the blood pressures. A second parameter which indicates the current stroke volume is used to determine the beat rate of the artificial heart. The control for the beat rate is as follows: when the left pump 10 indicates a full stroke, the beat rate is increased, otherwise the beat rate is decreased. For blood pumps of 85 cc volume, a compensation volume of 13 cc will accommodate up to 15% difference between the left and the right side flows. The compensating hydraulic volume 28 communicates with the right hydraulic section 26. At the initiation of right side filling, the right hydraulic chamber section 26 has 85 cc of fluid and the compensation volume 28 has 13 cc of fluid. At the end of filling, the right side blood chamber 21 can contain 72 to 85 cc of blood depending upon how many cubic centimeters of fluid in the compensating volume 28 have transferred to the hydraulic chamber 26. This determines the stroke volume, provided that at the end of right pump ejection the compensation volume 28 is replenished and readied for the next cycle. The hydraulic flow (Fc) in and out of this compensation volume 28 is governed by the following equation, F.sub.c =(P.sub.H -P.sub.b)/R where P H is the hydraulic pressure in the right chamber 26 and P b is the blood pressure in cuff 18 in contact with the flexing bladder of the compensation volume, and R is the fluidic resistance of the conduit 30 connecting the two chambers. For F c <o, fluid is flowing into the right hydraulic chamber 26. To insure a full compensation chamber prior to right side filling, |F c | S >|F c | D , that is the filling rate of the chamber should be greater than its draining rate. (The subscripts S and D denote right side systole and diastole respectively.) Under these physiological circumstances, |F c | S >|F c | D . More importantly, |F c | D is sensitive to the left atrial pressure. A high left atrium pressure, indicative of high right side flows, results in higher |F c | D , which in turn reduces the right side flow. This negative feedback is very desirable for stable operation. In order to maintain a mean flow difference of 7.5% at a left atrium pressure of 7.5 mmHg and a median beat of 80 BPM, the required flow resistance, R, is given by R=ΔP/Q=(8μL)/(πr.sup.4) where μ=viscosity of silicone fluid =0.01 poise L=length of the connecting conduit r=radius of the conduit. Q at 80 BPM, 50% diastole, and 7.5% flow difference (6.5 cc/per beat) is approximately 17.3 cc/sec. Thus R=0.43 mmHg/cc/sec, for L=3 cm, and P b =7.5 mmHg, R is 0.11 cm. Thus a 0.22 cm diameter conduit, 3 cm in length, can maintain a flow difference of 7.5%. At left atrium pressure of 15 mmHg, 15% flow difference can be maintained. The time constant for this feedback depends on R and the pulmonary venous compliance (c). Using a compliance of 6.5 cc/mmHg, the response time of this feedback mechanism is=RC=2.8 sec. Thus changes in the right side flow that deviates from the "normal" requirement can be compensated for rapidly. The design criteria for this balance compensation chamber are: (1) the hydraulic fluid volume must be limited to and not exceed the desired value, and 2) the diaphragm in contact with blood must be free of any supporting structures on the blood-facing side. An annular baseplate sandwiched between two flexible diaphragms will satisfy these criteria. The atrial pressure sensors are placed within the hydraulic section 16 and 26 and, because the hydraulic pressure is in equilibrium with the pressure of the blood in the chambers, these provide for accurate reading of the atrial fill pressure during fill. The stroke sensors are devices which measure the position of the diaphragm 17 which forms the interface between the flow volume and the hydraulic section in the left blood pump, as indicative of whether there is a full stroke. FIG. 3a illustrates the operation of this system when the right pump 20 is pumping by virtue of the hydraulic pump forcing hydraulic fluid into the hydraulic section 26, while the left pump is filling with blood returned from the lung under the influence of the membrane 17 withdrawing as the hydraulic fluid is pumped from the left hydraulic section toward the right. FIG. 3b is the opposite configuration, in which the left pump is ejecting blood into the aorta under the influence of hydraulic fluid pumped from the right pump section 26 into the left pump section 16, once again aiding the right pump chamber 20 in filling. At the same time the amount of hydraulic fluid in the flow balance compensation chamber 26 is determined by the pressure in the left atrium due to return blood flow. In FIG. 4a and 4b there is illustrated the physical configuration of the pumping chambers together with the energy converter showing the location of the inflow and outflow ports. The complete control algorithm decision tree is illustrated in FIG. 5. The control hierarchy is first fill governed (pressure sensing) followed by beat rate adjustment (full stroke indicator). Addressing first the left side diastolic phase, if the end diastolic pressure in the left chamber (P L is greater than some preset level (P o ) indicating that there is blood remaining in the left atrium, the motor speed during left side diastole and right side systole is incremented such that during the next beat the flow rate is increased to insure faster filling. Conversely, for P L <P o , overpumping is indicated and the motor speed is decremented. However, two situations can be encountered. In one case, if the left atrial blood volume is less than the blood pump stroke volume (fill limited), and complete filling did not occur (derived from the stroke indicator S D =0), and if during the subsequent left side systole only partial ejection (S s =0) occurred (right-side fill limited), the beat rate will be decremented. The second case occurs when the bladder bottoms on the hydraulic baseplate (full fill condition). Since the pressure is measured in the hydraulic chamber, P L will be less than P o . The left stroke indicator will show a full bladder starting position (S D =1) prior to ejection. During the subsequent left side systole, if the left stroke indicator shows full ejection (S S =1), the beat rate will be incremented. The beat rate remains unchanged when neither of the above conditions occur. Similarly, during right side filling (left side ejection), the hydraulic pressure in the right chamber is sensed to determine the right motor speed for the next beat. Beat rate changes occur only when both sides are fill limited (S D =0; S s =0) or when both sides are volume-limited by the prosthetic ventricles (S D =3); (S s =1). This control mechanism, coupled with the flow-pressure characteristics of the axial flow pump, can automatically accommodate aortic and pulmonary pressure variations. For example, if the aortic pressure increases while the right side fill pressure remains unchanged, the motor speed for this half of the cycle will increase during the next beat to yield similar flow but at a higher aortic pressure. This algorithm does not assume that the peripheral resistance varies inversely with the cardiac output. It is well known that both arterial pressure and cardiac output can increase during exercise. This control mechanism does not assume any specific relationship between arterial pressure and vascular resistance. Up to the system performance limit, the device will adjust to variations in both the arterial pressure and the vascular resistance. FIG. 6 shows interrelated plots of parameter changes on a beat-by-beat basis. Adjacent plots share common axes. This plot allows fill pressure, flow, motor speeds (left and right) and beat rate to be intercorrelated and illustrates the behavior of the parameters through a transition from a fill limited case to a stroke volume limited situation. The motor speed immediately increases due to the high filling pressure. Concurrently, the end diastolic pressure decreases and the flow increases. If after the 2nd increment, the pump is at full stroke, the beat rate will increment by one unit every other beat to maintain full stroke. This is accompanied by a further increase in the flow and decrease in the end diastolic pressure, while the motor speed decrements and increments on alternate beats. If after another six beats, the end diastolic pressure is negative, the motor speed will again operate on a beat-by-beat crossing and recrossing the zero pressure boundary at constant beat rate as illustrated. During this transition, flow increases due to increase in both the motor speed and the beat rate. Table I shows the conditions governing motor speed and beat rate changes in accordance with the logic set forth in the algorithm hierarchy illustrated in FIG. 5. TABLE I______________________________________CONDITIONS GOVERNING MOTOR SPEED ANDBEAT RATE CHANGES Left Right Side Filling Side FillingControl Parameters* Motor Speed Motor Speed Beat Rate______________________________________P.sub.L > P.sub.o Increase Increase N.CP.sub.R > P.sub.oP.sub.L > P.sub.o Increase Decrease N.C.P.sub.R > P.sub.oP.sub.L > P.sub.o Decrease Increase N.C.P.sub.R > P.sub.o ##STR1## Decrease Decrease ##STR2## Increase ##STR3## Decrease ##STR4## N.C. ##STR5## N.C.______________________________________ *P.sub.L --Left ventricular end diastolic pressure P.sub.R --Right ventricular end diastolic pressure P.sub.o --Reference pressure S.sub.D --Left side fill indicator; S.sub.D = 1 is full fill; S.sub.D = 0 is partial fill. S.sub.S --Left side ejection indicator; S.sub.S = 1 is full ejection; S.sub.S = 0 is partial ejection. In FIG. 7 there is illustrated in cross sectional view a suitable configuration of a pumping chamber existing in the art. The baseplate 50 has passages 52 therein to permit flow of the hydraulic fluid against the first diaphragm 55. In operation the base plate 50 is snapped over a base plate on the energy converter to allow the converter to provide for the flow of hydraulic fluid to extend the diaphragm 55 during systole of the chamber. An upper pump diaphragm 57 defines the flexible boundary of chamber 11. The sealed space (exaggerated for illustration purposes) between the hydraulic diaphragm 55 and the blood pump diaphragm 57 is lubricated with hydraulic fluid and thus the change of position of the hydraulic diaphragm 55 under the influence of hydraulic pressure pump in the converter 32 results in a corresponding displacement of the blood pump diaphragm 57. The materials used in a circulatory system must be durable and biocompatible. The tissue contacting the materials must be non-mutagenic and non-toxic. In addition the blood contacting materials must be hemocompatible. The materials used for fabricating the pump diaphragms as illustrated in FIG. 7 at 55 and 57, must retain their hemocompatibility and mechanical integrity under the mechanical stresses. Suitable biocompatible materials are medical grade silicones, epoxy, titanium, glass fiber reenforced, epoxy composite, and polyetherurethane, made by Abiomed, Inc. of Danvers, Mass. under the trademark Angioflex. FIG. 8 is a view of the left inflow cuff 22 containing the imbalance compensation chamber. As shown, the compensation chamber contains a blood contacting diaphragm 60, a hydraulic diaphragm 64 and annular base plate 66 sandwiched between the two diaphgrams. FIGS. 9a and 9b illustrate the energy converter in cross sectional view. FIG. 9a shows the converter in condition to pump hydraulic fluid from the left hydraulic chamber 16 to the right hydraulic chamber 26, while FIG. 9b shows the converter in condition to pump hydraulic fluid from the right hydraulic chamber 26 to the left hydraulic chamber 16. The converter consists of a unidirectional axial pump 60 having impeller blades to drive fluid from the left chamber 68 into the right chamber 70. The direction of outflow from the converter is controlled by the position of sliding sleeve 64 which can be moved axially in response to actuation of the solenoid actuators 65. The pump element 60 is fitted into a porting sleeve 61, which has slots on both sides of chamber 70, as well as slots on both sides of chamber 68. The sliding sleeve 64 is formed so that in one position, as shown in 9a, it blocks the slots in the lower portion of the outflow chamber 70 while opening the lower slots in the inflow chamber 68. The sleeve also, in this position, blocks the inflow chamber 68 slots in the upper portion of chamber 68 while opening the outflow slots in the upper portion of chamber 70. In its other position, shown in FIG. 9b, the exact opposite situation occurs. This arrangement provides for the hydraulic fluid to move, as indicated by the arrows, in one direction when the sliding sleeve is positioned as in FIG. 9a and in the opposite direction when the sleeve is positioned as in 9b. Signals from the control circuit actuate the solenoid actuator 65 and thus control the switching of the direction of flow from the pump. While a specific embodiment of the artificial heart has been described above, it will be understood that many of the elements can be substituted for by other conventional parts.

An artificial heart system employing left and right pumping chambers each divided by a membrane into a blood pumping chamber and a hydraulic pumping chamber and a hydraulic pumping system for alternately pumping hydraulic fluid from said left hydraulic chamber toward said right hydraulic chamber and vice versa. A balancing chamber including a flexible membrane placed in the left atrium so that the membrane changes position with changes in the patient's blood pressure, the hydraulic portion of said balancing chamber being fluidically coupled to the right hydraulic pumping chamber in order to allow for a different pumping volume between the left blood pumping chamber and the right blood pumping chamber. A control system employing an algorithm to control the speed of the hydraulic pumping and the direction of flow of the hydraulic pumping in response to sensors sensing the left atrial pressure and the completeness of stroke of the left blood pumping chamber.

This application claims priority of provisional application Serial No. 60/341,178 filed on Dec. 13, 2001, the disclosure of which is hereby incorporated by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to systems for treating water containing unwanted contaminants. More particularly, the present invention relates to waste water treatment systems including biological media used to aerobically and anaerobically treat solid and liquid waste in the water. Still more particularly, the present invention relates to such treatment systems for large and small-scale waste water systems. The present invention includes novel methods for effectively treating waste water in a way that minimizes the size of the system required to output high-quality, environmentally-suitable, water depleted of ammonia, nitrites, nitrates, perchlorates and other contaminants. 2. Description of the Prior Art Waste water treatment systems are ubiquitous, from the smallest single-family residence septic system, to industrial facilities for commercial operations and municipalities large and small. It is always the object of such systems to treat for total suspended solids (TSS), biochemical oxygen demand (BOD), nitrogen compounds, E - coli , phosphorous, and virtually any other bacteria, so as to minimize the quantity of such undesirables output by the system. Various well known means have been devised for achieving such goals, with varying degrees of success and efficiency. An overriding general problem, for the most part, with such prior systems has been the scale of operation required to effectively treat that water with high-quality output. That is, for the volumes of water to be treated, the sizes of these systems are correspondingly large. This may be particularly true for relatively small-scale systems, such as single-family residences and small groupings of homes and/or buildings, where coupling to a municipal treatment system may be unsuitable. In the array of systems designed to treat waste water, many include the use of biological treatments to accelerate the breakdown of solids and the various contaminants associated with waste water. This biological treatment involves the use of microbes having an affinity for the pollutants contained in the water. That is, rather than simply permit solids to slowly decant from the waste water, and then apply a hazardous chemical treatment designed to destroy the pollutants—along with virtually everything else in the water—these microbes are permitted to act upon the waste water. In relative terms, they act to remove the pollutants faster than if nothing were used, and do so without the hazardous and difficulties associated with chemical treatment. They must, however, be permitted to reside in some type of holding tank, filter, fixed film or media in order to multiply and feed on the contaminants. Upon completion of their ingestion of the pollutants, the microbes simply die and end up as waste solids that fall to the bottom of the treatment tank or unit for subsequent removal. Some microbes may partially block the availability of surface area or volume resulting in voids of inactivity. The treated water then passes to the next stage, which may simply be some form of a leach bed, or it may be a more complex system, such as a reactor, including, but not limited to, an ultraviolet disinfection means, ozone treatment, or membrane filtration for subsequent transport to a body of water, or for recycling in non-critical uses, such as horticulture. Unfortunately, while aerobic and anaerobic microbe treatment has significant advantages, it is not exceedingly effective in that it is necessary to provide sufficient “dwell time” or “residence time” for the microbes to “eat” enough of the pollutants so that the waste water is rendered satisfactorily contaminant-free. Of course, the extent to which contaminant removal is satisfactory is a function of governmental regulation. In any case, the volume of water that must be treated can often lead to the need for a rather large-scale treatment unit for a relatively small waste-water-generating facility. As a result, there is often a compromise in the prior systems, which compromise is associated with the contamination-removal requirements, the space available to treat the waste water output, and the cost associated with both. Some of these problems have been addressed by recirculation of the partially treated waste water for repeated treatments. Traditional wastewater treatment systems rely on effective treatment by the gradual accumulation of bacteria. This is common to all treatment schemes but especially pronounced in systems relying on vessels or containers in which air is introduced. Such systems, relying on the gradual accumulation of bacteria for treatment, inevitably will experience failure during hydraulic overload, power failure, temporary shutdown for maintenance or in response to seasonal flows. Often, during such events, the bacteria providing treatment wash through the system and after such an event, treatment efficiency is compromised. Another problem with such prior systems has been their efficiency over a period of time of use. When the waste water to be treated requires the use of a considerable amount of biological mass, there results a problem of “plugging” of the mass. That is, as waste solids build up on the surface of the mass, or as microbes ingest the pollutants and die they do not always fall to the bottom of the tank. Instead, they become trapped at or near the surface of the mass. This plugging or blocking of the mass significantly reduces the pathways by which subsequent pollutants may pass through to underlying active microbes that are located below the surface of the mass. There are two negative results: 1) the acceleration of pollutant decay caused by microbe ingestion is canceled; and 2) water flow through the mass is reduced and possibly even stopped. It is therefore necessary to either build a substantially larger unit than would otherwise be required—in order to account for this plugging—or to expend the effort to clean the clogged system. Such maintenance may include the introduction of agitation means or the use of pressurized water for removal of dead microbes. Several prior waste-water treatment systems have been described. These systems have apparently been designed for large- and/or small-scale treatment using biological media to accelerate contaminant reduction. For the most part, they include biological treatment as well as mechanisms designed to enhance the effectiveness of the microbial action. However, each in turn suffers from one or more deficiencies that significantly affect the ability to provide the most effective and relatively inexpensive waste treatment system. Nitrogen in its oxidized states (e.g. as nitrates or nitrites) can seep into ground waters, causing problems in drinking water. Drinking water standards generally limit the concentration of nitrate to 5 to 10 mg/l, yet effluent from a modern treatment plant may have natural levels greater than 20 mg/l. Nitrogen in its reduced state, as ammonia, is toxic to fish, and severe limits are in effect on many streams to control the maximum concentration. A conventional method of nitrogen removal is by biological means. With sufficient time, oxygen, and the proper mass of microorganisms, organic nitrogen is biologically converted to ammonia and then further oxidized to nitrate forms. This conversion occurs under aerobic (with oxygen) conditions, and is relatively easy to accomplish, resulting naturally under different known types of waste treatment processes. At this point the nitrogen has not been reduced in concentration, only converted to a different form. A practical means to remove nitrate is to convert them to nitrogen gas. At this point N.sub.2 will evolve from the water and become atmospheric nitrogen. As atmospheric nitrogen, it is not a water pollutant. Nitrates are best converted to nitrogen gas by microbial action. Under anoxic conditions (without free dissolved oxygen), many common bacteria with a demand for oxygen are able to biochemically remove the oxygen from the nitrate ion, leaving nitrogen gas. This process is called biological denitrification. For denitrification to occur, the nitrogen must first be converted to nitrates and then the bacteria must have a food source to create a demand for oxygen. This food source may be from outside, like a chemical addition of methanol, by the addition of sewage, or by the natural demand of the organisms (endogenous respiration). This natural demand must occur under conditions where free oxygen is absent. In the conversion of organic nitrogen and ammonia to nitrates adequate aeration must be provided, and this aerobic process also results in removal of carbon. However, carbon must be present during the denitrification by dentrifying bacteria. Accordingly carbon has to be reintroduced into the system, and this is commonly done by addition of methanol in the art. The biochemical reaction which occurs when methanol is used as the carbon source results in production of nitrogen gas, carbon dioxide and water. The amount of methanol required is about three times the weight of nitrogen compounds to be removed. As is known in the art, other carbon sources can be used. U.S. Pat. No. 4,005,010 issued to Lunt describes the use of mesh sacks containing the biological medium. The sacks are apparently designed to hold the microbes while allowing fluids to pass through. This unit nevertheless may still result in plugging in that the biological medium will likely become clogged during the course of its usage. Furthermore, the capacity of the unit is directly dependent on the wetted surface area that can be produced for microbial growth. U.S. Pat. No. 4,165,281 Kuriyama et al. describes a waste water treatment system that includes a mat designed to contain the microorganisms. A plurality of mats is disposed vertically and waste water is supposed to pass therethrough. The likelihood of plugging is greater in this unit than in the Lunt device because of the orientation of the mats and the difficulty in maintaining and/or replacing them. U.S. Pat. No. 4,279,753 issued to Nielson et al. describes the arrangement of a plurality of treatment reactors, alternating from aerobic to anaerobic action. There may be some advantage in using a plurality of small tanks rather than one large tank to achieve the decontamination required in that dwell time is increased; however, this is certainly more costly than is necessary. Moreover, while Nielson indicates that it is necessary to address plugging problems, the technique for doing so is relatively crude and likely not completely effective. U.S. Pat. No. 4,521,311 issued to Fuchs et al. teaches the use of a filtering bed through which the waste water passes and which includes support bedding to suspend the biological medium. The device has a rather complex recirculation process required in order to ensure cleaning of the bedding and the microbes. This device may experience clogging of another sort, and the bedding particles described by Fuchs are required to go through a costly operation for maintenance. U.S. Pat. No. 5,202,027 issued to Stuth describes a sewage treatment system that includes a buoyant medium in the shape of large hollow balls designed to provide a site for microbial growth. The buoyant balls form but a small portion of the system, which includes a series of complex turbulent mixing sections. The Stuth device is relatively complex and likely requires considerable energy to operate in order to ensure the mixing apparently required. U.S. Pat. No. 5,221,470 issued to McKinney describes a waste water treatment plant having a final filter made of a sheet of plastic. The sheet of plastic is wrapped about itself so as to form passageways designed for microbe growth. While this design may increase the surface area and, therefore, the dwell time available for microbial action, it is likely that plugging will occur as the passageway will likely fill with dead microbes over a period of time. U.S. Pat. No. 5,342,522 relates to a method for the treatment of (raw) sewage in a package plant consisting of three bioreactors in series. The treatment is being carried out using three types of biomass. In a first step phosphate is removed by biological means and, at the same time, the chemical and biological oxygen demand is lowered in a highly loaded active sludge system, in a second step a nitrification is carried out, ammonium being converted to nitrate, and in a third step a denitrification is carried out using a carbon source such as methanol or natural gas. The nitrifying and denitrifying bioreactors are both fixed film processes. The thickness of the biofilm on the support material in the nitrifying bioreactor can be influenced by adjusting the aeration system or by adjusting the hydraulic loading. In the denitrifying bioreactor the thickness of the biofilm can be adjusted by raising the shear by means of raising the superficial velocity in the support material. The system according to the invention makes possible effective treatment of raw sewage in a highly loaded system resulting in the far-reaching removal of COD, nitrogen and phosphate. The process can be operated in an alternative mode, where the nitrifying and denitrifying bioreactors are exchanged. The mixing in the nitrifying step is advantageously maintained by aeration under the packages of support material. The denitrifying step was accomplished by means of a propeller stirrer or impeller stirrer, which may be placed centrally in the vessel, was preferably used for active proper mixing. Polacel, reticulated polyurethane or any other carrier material were described as support material for the biomass. U.S. Pat. No. 5,185,080 describes that in the denitrification chamber, pre-measured quantities of a composite material, containing bacteria and a source of carbon as food, is introduced daily or even bi-daily to the treated wastewater. The bacteria are heterotrophic, laboratory cultured and packaged, as a loose particulate material, capsules, pellets, tablets or other shaped forms. The bacteria Pseudomonas, normally present in the ground, is claimed to be prevalent in this material. The Pseudomonas microorganism has the capability of transforming nitrates to nitrogen gas. The technology of this conversion is well known. The preferred pre-measured microbial tablet includes a carbon supply (source) for biological synthesis. The need for a carbon source is discussed in Handbook of Biological Wastewater Treatment by Henry H. Benjes, Jr., Garland STPM Press, 1980. Denitrification using suspended or fixed growth systems is also discussed in the foregoing reference. All the above prior art methods attempt to increase the surface area or volume available to microbes for nitrification and denitrification, and thereby increase the productivity of the treatment system. The above systems are generally referred to as fixed film media or suspended media systems in that surface area for bacteria to grow are provided by the addition of surface. The suspended media bacteria that prefer surfaces would generally predominate such surfaces. However, such surfaces are still subject to failures due to system poisonings and upsets, and may not be easily restarted after such failures, as the surfaces are then contaminated or plugged with dead microbes. U.S. Pat. No. 4,693,827 describes the addition of a rapidly metabolized soluble or miscible organic material to be added to the carbon consuming step of the process. Heterotrophic organisms consume the added material together with soluble ammonia to generate additional organisms, resulting in the reduction of the soluble ammonia concentration in the wastewater. The rapidly metabolized material comprises one or more short chain aliphatic alcohols, short chain organic acids, aromatic alcohols, aromatics, and short chain carbohydrates. However, if too much of the rapidly metabolizing material is not introduced in a controlled manner, the heterotrophic organism will proliferate detrimentally. On the other hand if too little is added or in the absence of carbon, the organism will slowly die. Therefore, there is a need for an efficient delivery system for introducing independently carbon and rapidly metabolizing material, bacteria, nutrients and air to such systems. In addition, there is also a need for monitoring the performance of the system as to the extent of the treatment, and feedback from the monitoring detectors to the delivery system for efficient and optimum delivery of carbon, bacteria, nutrients and air. In U.S. Pat. Nos. 5,863,435 and 6,183,642 issued to Heijen et. al. a method is described for the biological treatment of ammonium-rich wastewater in at least one reactor which involves the wastewater being passed through the said reactor(s) with a population, obtained by natural selection in the absence of sludge retention, in the suspended state of nitrifying and denitrifying bacteria to form, in a first stage with the infeed of oxygen, a nitrite-rich wastewater and by the nitrite-rich wastewater thus obtained being subjected, in a second stage without the infeed of oxygen, to denitrification in the presence of an electron donor of inorganic or organic nature, in such a way that the contact time between the ammonium-rich wastewater and the nitrifying bacteria is at most about two days, and the pH of the medium is controlled between 6.0 and 8.5 and the excess, formed by growth, of nitrifying and denitrifying bacteria and the effluent formed by the denitrification are extracted. In addition the growth rate of the nitrifying and denitrifying bacteria is expediently controlled by means of the retention time, in the reactor, of the wastewater to be treated which is fed in. The electron donor of inorganic nature is selected from the group consisting of hydrogen gas, sulfide, sulfite and iron (III) ions, and said electron donor of organic nature is selected from the group consisting of glucose and organic acids, aldehydes and alcohols having 1-18 carbon atoms. However, such a system could fail based on washouts, introduction of toxic substances, and there will be lag time before the system performs properly. In addition, while organic solvents such as methanol are liquid, and can be introduced as liquid, they are flammable and toxic, and not preferred by many waste water system operators. Lower carbohydrates such as glucose and dextrose while non-toxic, are solids, and require special solid delivery methods to introduce into water treatment systems, and therefore not generally used in the industry. Aqueous solutions of lower carbohydrates may be used; however, such solutions are subject to premature biological degradation, and generally require introduction of antibacterial agents which are harmful for the nitrifiers and denitrifiers. U.S. Pat. Nos. 4,465,594 and 5,588,777 disclose a wastewater treatment system that use grey water and soaps for denitrification in two different designs of wastewater systems. U.S. patent application 20020270857 by McGrath et al. published Nov. 21, 2002 discloses the use of a detergent or a detergent like compound for the denitrification of wastewater or nitrified water of U.S. Pat. No. 5,588,777. the application also discloses heating the denitrified wastewater as well as the addition of bacteria to the mixing tank. However, soaps, detergents and detergent like compounds are generally surface active and tend to damage the cell walls of bacteria, adhere to surfaces, interfere with bacterial functions, and are more expensive than methanol. In addition, the metabolism rate of such compounds would be low and would require longer dwell times in the denitrification zones, reactors or media. Therefore, there is a need for aqueous solution compositions of electron donor or carbon containing material which are non-flammable, liquid; stable to storage, non-toxic to the environment and wastewater microorganisms, readily metabolized, such as carbohydrates and mixtures thereof, and which can be readily introduced to defined locations in wastewater treatment systems to assist in the nitrification and denitrification of wastewaters. In addition, such compositions may also be used for the removal of perchlorates and other pollutants. The prior art has many examples of teachings that employ bacterial compositions to accomplish, or aid in accomplishing, the biologically mediated purification of wastewater. Hiatt U.S. Pat. No. 6,025,152 describe a methods and mixtures of bacteria for aerobic biological treatment of aqueous systems polluted by nitrogen waste products. Denitrifying bacterial compositions are used in combination with solid column packings in the teachings of Francis, U.S. Pat. No. 4,043,936. These compositions are believed to belong to the family of Pseudomonas. Hater, et al U.S. Pat. No. 4,810,385 teaches a wastewater purification process involving bacterial compositions comprising, in addition to non-ionic surfactants and the lipid degrading enzymes Lipase, three strains of Bacillus subtillis, 3 strains of Pseudomonas aeruginosa , one strain of Pseudomonas stutzeri , one strain of Pseudomonas putida , and one strain of Eschericia hermanii grown on a bran base. Wong, et. al., U.S. Pat. No. 5,284,587 teaches a bacterial composition, that is in combination with enzymes and a gel support is necessary to achieve satisfactory waste treatment. Bacterial species mentioned in Wong et al are Bacillus subtillis, Bacillus licheniformis , Cellulomonas and acinetobacter lwoffi . Similarly, Wong and Lowe, U.S. Pat. No. 4,882,059 teach a process for biological treatment of wastewater comprising bacterial species that aid in the solubilization of the solid debris. The bacterial species used in the teaching of Wong and Lowe are of the following bacterial types: Bacillus amyloliquefaciens and aerobacter aerogenes . These bacterial types are taught to be employed primarily for solubilization and biodegradation of starches, proteins, lipids and cellulose present in the waste product. Hiatt U.S. Pat. No. 6,025,152 describes the addition of bacterial mixtures in the spore form. Most water treatment systems have residence or dwell times of 2 days or less, and addition of bacteria in the spore form will lead to a substantial portion of bacteria being washed out of the system before it has time to establish, because the environment is not always conducive for bacterial growth. U.S. Pat. No. 5,185,080 issued to Boyle discloses a system for the treatment of nitrate containing wastewater from home or commercial, not municipal, in which the wastewater is contacted underground by denitrifying bacteria introduced to the treatment zone periodically; the treatment zone being maintained at or above the temperature at which the bacteria are active on a year-round basis by the ground temperature. U.S. Pat. No. 5,811,289 issued to Lewandowski et al. discloses an aerobic waste pretreatment process which comprises inoculating a milk industry effluent with a mixture of bacteria and yeasts both classes of microorganisms capable of living and growing in symbiosis in the effluent, the population of the bacteria being, in most cases, several times greater than the population of the yeasts, maintaining the temperature and pH of the inoculated effluent between 0.degree. C. and 50.degree. C. and between 1.7 and 9, aerating the effluent while varying, if necessary, the pH at maximum rate of 1.5 pH units per minute and also, if required, modulating the aeration of the inoculated effluent at a maximum rate of 130 micromoles of oxygen per minute. U.S. Pat. No. 6,077,432 issued to Coppola et al. discloses a method and system for carrying out the bio-degradation of perchlorates, nitrates, hydrolysates and other energetic materials from wastewater, including process groundwater, ion exchange effluent brines, hydrolyzed energetics, drinking water and soil wash waters, which utilizes at least one microaerobic reactor having a controlled microaerobic environment and containing a mixed bacterial culture. It is claimed that using the method of invention, perchlorates, nitrates, hydrolysates and other energetics can be reduced to non-detectable concentrations, in a safe and cost effective manner, using readily available non-toxic low cost nutrients. The temperature of the reactor was maintained at 10 to 42 degrees centigrade. European Patent Application EP 1151967A1 published Nov. 7, 2001, to Nakamura discloses a liquid microorganism preparation which contains enzymes generated by anaerobic microorganisms, facultative anaerobic microorganisms and aerobic microorganisms will be propagated in a growth tank to make microorganism enzyme water. The obtained enzyme water will be added to a grease trap that retains kitchen water which includes macromolecular organic matter, such as animal and vegetable waste oil, and will be stirred with aeration so that the enzymes and the organic materials will be in contact in order to decompose the organic matter. The decomposition residue and sludge will be separated so as to flow the supernatant water to the sewer pipe. U.S. patent application Ser. No. 2002170857 published Nov. 21, 2002 to McGrath et al. describe a system for nitrified water that comprises a plurality of interconnected tanks including a mixing tank which feeds detention tanks which in combination provide a detention time period for the effluent. A controller determines the amount of detergent dispensed into the mixing tank in accordance with the measured volume of effluent to be treated. The mixing tank comprises a heater for maintaining the nitrified effluent temperature above 50 degrees F. The application also discloses the addition of small doses of bacteria into the mixing tank for denitrification, and heating means to heat the effluent in the mixing tank to accelerate denitrification. An optional line filter can be added to the output of the system for further reducing organic nitrogen concentration. Addition of bacteria or heating means for nitrification was not disclosed, and may be construed as being not necessary for the disclosure. Therefore, there is a need for bacterial compositions which are not in the spore form or low growth phase, but are in the growth phase when added to the water treatment systems, will continue their growth in the water treatment systems after addition, and delivery means for such addition. Therefore, there is a need for a waste water treatment apparatus and process that takes advantage of the useful characteristics of biological treatment in an effective manner of existing systems or new systems to be constructed. There is also a need for such an apparatus and process that maximizes the contact between contaminants from the waste water and the microbes without the need for a relatively large processing tank or unit, while providing the best conditions for the microbes to grow. Further, there is a need for an apparatus and process that is simple, energetically efficient, and sufficiently effective to reduce to desirable levels the TSS, BOD, E - Coli , nitrogen-containing compounds, phosphorus-containing compounds, and bacteria of wastewater in a cost-effective manner. In addition, there is a need for a treatment system and apparatus that can deliver microbes and nutrients optimally to enhance the efficiency and performance of the large number of water treatment systems already in operation for nitrification and denitrification without costly reengineering. There are a large number of existing systems and apparatuses that are not performing efficiently in removing ammonia, nitrite and nitrate which could be made to perform efficiently by the current invention with relatively little cost. In addition, new systems could be made to perform efficiently by following the process described in the present invention. SUMMARY OF THE INVENTION The present invention relates to a system and method for treating wastewater from any mechanical or gravity system. This generally relates to placement of bacteria, enzymes, biological and chemical catalysts, such as nitrifying and denitrifying, carbon or electron donor sources and nutrients, and heating means in a system relative to oxygen and nitrogen sources, oxic, aerobic, anoxic, and anaerobic zones, using an apparatus. The apparatus may be in one or more parts. It refers to the placement of bacteria, enzymes, biological and chemical catalysts, nutrients and or electron donor, carbon sources or heating means in waste water systems in industrial, agricultural, commercial, residential, and other waste water systems; and the methods for treating pollutants or undesirable materials in waste water or polluted sites. These ingredients are frequently limiting in the efficient and proper functioning of the wastewater systems. Frequently, the bacterial species which are specific for the pollutant to be removed is not always present, or have a short life or not present in high concentrations to be effective. This will also be the case for suspended media as well as fixed film media. Therefore, there is a need for the delivery of the bacteria and electron donors in high concentration to allow for system efficiency and capacity without increasing the size or volume of the system. Furthermore, frequent testing and monitoring for the presence of the microbes is desirable to establish efficient system performance. The findings of constant demand for microbes and electron donor/carbon and micronutrients show the need for controlled addition. The volume available for fixed or suspended film surface area is small and limiting, and not all the microbes grow on surfaces. Solid media (materials) used as carbon or electron donor is not always adequate to supply the necessary electron donors due to solubility limitations, and could be supplemented by this invention. The invention also includes stable compositions of carbon and carbon containing nutrient liquid mixtures of low viscosity which can be easily pumped, non-flammable, less damaging to beneficial bacteria, safer to handle than currently used organic solvents and less toxic to the environment when released and not subject to premature growth of bacteria and other microorganisms during storage and use. These bioremediation processes may be considered as fermentation processes applicable to pollutants, and the location placement of additives is important for the efficient functioning of these processes. The microbes can be bacteria or yeast, and other biological catalysts such as enzymes may also be used. For example, in the case of nitrification and denitrification, methanol and other organic solvents are used as electron donors or carbon sources. However, these solvents are flammable and toxic, and its large scale use causes handling difficulties including special storage. In addition, methanol metabolism rate by many bacteria would be too slow for some systems, resulting in longer residence times and reduced productivity of treatment. Therefore there is a need for carbon sources that overcome the limitations of methanol and other carbon sources. The invention also includes alternative electron donor or carbon sources and compositions, that are less toxic and non-flammable than pure methanol and other solvents and allow for the addition of other micronutrients without precipitation, if needed to the carbon source, is not subject to premature degradation during use and storage by bacteria and other microorganisms, and possess the ability to reduce nitrates to nitrogen in the presence of denitrifying bacteria. Such alternate carbon sources include, but are not limited to carbohydrates such as glucose, fructose, dextrose, maltose, sucrose, other sugars, maltodextrins (CAS No. 9050-36-6), corn syrup solids (CAS No.68131-37-3) starches, and cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose and other carbon containing compounds. Methanol in the above invention is used as a carbon source as well as a bacteriostat for the prevention of premature growth of extraneous bacteria and other microorganisms in the liquid carbon source. However, at low concentrations, methanol is generally not harmful for bacteria. In addition to methanol, a number of additives can be used to prevent premature microbial growth in the present invention. These additives can be used in addition to methanol or in the absence of methanol as a single component or combinations thereof. They include sodium hydroxide, sodium carbonate and sodium bicarbonate, and other bases with pH greater than 9. Other additives are nitro substituted compounds such as 2-Bromo-2-nitropropane-1,3-diol (CAS#52-51-7), 5-Bromo-5-nitro-1,3-dioxane (CAS#30007-47-7)-Bromo-nitropropane-1,3-diol (CAS#52-51-7); Isothiazolones such as 5-Chloro-2-methyl-4-isothiazolin-3-one (CMI) (CAS#26172-55-4), 2-Methyl-4-isothiazolin-3-one (MI) (CAS#2682-20-4), Mixture of CMI:MI 3:1 (CAS #55965-84-9, 1,2-Benzisothiazolin-3-one (CAS#2634-33-5); Quaternary ammonium compounds such as benzyl-C8-18 alkyldimethyl ammonium chloride and Benzylalkonium chloride (CAS #, 61789-74-7,8001-54-5,68393-01-5,68424-85-1,85409-22-9), N,N,N,-trimethyl-1-hexadecane ammonium bromide (CAS #57-09-0), N,N,N,-trimethyl-1-hexadecane ammonium chloride (CAS #112-02-7), 1-(3-Chloro-2-propenyl)-3,5,7-triaza-1-azoniatricyclo(3.3.1.1) decane chloride (CAS #9080-31-3,4080-31-3,51229-78-8); parabans such as Butyl-4-hydroxybenzoate (CAS #94-26-8), Ethyl-4-hydroxybenzaote (CAS #120-47-8), Methyl-4-hydroxybenzoate (CAS #99-76-3), Propyl-4-hydroxybenzoate (CAS #94-13-3). Other substances that may be used are 2,2,4′-Trichloro-2′-hydroxyphenylether (CAS #3380-34-5), Sodium Benzoate (CAS #532-32-1), Benzyl alcohol (CAS #100-51-6), Chloroacetamide (CAS #79-07-2), N-(1,3-Bis hydroxy methyl)-2,5-dioxo-4-imidazolidinyl)N,N′-bis(hydroxy-methyl) urea(Diazolidinyl urea) (CAS #35691-65-7); 1,2-Dibromo-2,4-dicyanobutan (CAS #35691-65-7), 4,4-Dimethyl oxazolidin (CAS #51200-87-4), Glutarldehyde (CAS #111-30-8), formalin, 37% formaldehyde (CAS #50-00-0). Other additives that may be also be used are sodium hydroxymethyl glycinate (CAS#7732-18-5), imidazolidnyl urea (CAS #39236-46-9), diazolidinyl urea (CAS #78491-02-8) and 3-iodo-2-propynyl butyl carbamate (CAS #55406-53-6). The above additives are added at a concentration such that premature bacterial growth is prevented in the aqueous carbon solution, and yet will not kill or inhibit the bacteria when added for the microbiological remediation reactions. The useful concentration range will vary for each compound, and may be expected to be in the 0.01% to 5% range. Another embodiment of the invention is the use of enzymes, biological and chemical catalysts, and bacteria that will convert a useful precursor carbon or electron donor source, such as cellulose, grease, fat, oils, aliphatic and aromatic hydrocarbons, to a useful carbon or electron donor source, such as glucose, fructose, glycerol, fatty acids, alcohols, by the use of the respective enzymes, biological or chemical catalysts, or microbes. For cellulose, the enzyme cellulases or microbial cellulases may be used. These cellulases and microbial cellulases may also be added along with the nitrifiers to the anaerobic or aerobic zone, or even into the settling tanks before the aerobic zones. Other enzymes that may be used in addition to cellulase are amylase, protease, lipase, carbohydrases and combinations thereof. For esters, fats and oils, enzyme esterases may be used. Grease, fats and oils are discharged into water treatment systems, and grease and fat traps are sometimes employed to remove these materials. Costs are incurred at regular intervals for the removal and disposal of grease and fats from these traps, especially by users processing food. For the treatment of grease, fats and oils, the enzyme lipases, lipase releasing bacteria or bacteria capable of breaking down grease and fats could be used. These would convert the grease, fats and oils to glycerine, fatty acids, mono- and diglycerides. The breakdown products can then be diverted to the aerobic or anaerobic regions of the waste water treatment system, and can perform as an additional source of electron donor or carbon for nitrification or denitrification. For aliphatic and aromatic hydrocarbons, and compounds, enzymes and bacteria which convert these materials may be used. The products of these transformations may then be directed to another zone of the water treatment process as a reactant. The pollutant may be a process waste product such as cyanide. In such a case a cyanide converting enzyme, a cyanidase may be used, as described in U.S. Pat. No. 5,116,744 issued to Ingvorsen et al. The carbon or electron donor source preferably should be in the liquid form so that the apparatus can deliver known volumes at predefined flow rates. If the carbon or electron donor source is in the solid form, solid or powder delivery methods should be employed. In the liquid form the carbon or electron donor source provides flexibility as to the addition of micronutrients without precipitation or undue agglomeration. In the case of methanol which is commonly used, micronutrients cannot generally be added without precipitation, and many other components are not soluble in methanol. Even though pure or concentrated methanol or other organic solvents may be used as the carbon or electron donor source in the present invention, the apparatus may still be used with modifications for appropriate use. The electron donor source is not limited to carbon containing compounds. Any electron donor source, including inorganic electron donors such as hydrogen gas, methane, natural gas, sulfide, sulfite, and iron (III) may be used. Another embodiment is the use of enzymes which can be genetically modified to be present in crops such as potatoes, corm and other crops, so that these can convert starch directly into electron donors, and used without further treatment. The liquid carbon sources are made by dissolving solid or liquid carbon sources in water, and adding bacterial stabilizers to prevent premature bacterial growth, and micronutrients as needed. An example of a useful composition is about 100 g of carbohydrates mixture containing about 7.6% monosaccharides, 6.9% disaccharides, 7.0% trisaccharides, 6.8% tetrascaacahrides and 71.7% tetrasaccharides and higher saccharides dissolved in 100 ml water. In addition, stabilizing agents to prevent premature microbiological growth described earlier, may be added, as well as other carbon sources which will increase the carbon content, and increase stability to microbiological growth. Examples are methanol, ethanol, ethylene glycol and glycerol, which may be added from about 3% to 40% or more as needed, without compromising flammability and solubility. Furthermore, micronutrients such as minerals, vitamins, other carbohydrates, and amino acids may be added to the aqueous carbon mixture, as needed, without precipitation. The composition and concentration of the mono and polysaccharides may be changed depending on the requirements of viscosity and concentration of the carbon or electron donor source. The monosccharides that can be used are glucose, galactose and fructose. The disaccharides that may be used are sucrose, lactose and maltose. Monosaccharides and disaccharides will provide a carbon solution with lower viscosity, whereas the use of oligo and polysaccharides will provide a higher viscosity for the same carbon concentration. While it is convenient to use soluble carbon or electron donor sources, in cases, it may be useful to use partially soluble carbon or electon donors which gradually dissolve or breakdown by microbes or enzymes to release material at a controlled release rate. An example would be the use of soluble oligosaccharides, polysaccharides as well as insoluble polysccharides, such as starch, or monosaccharides and polysaccharides formulated for controlled release in aerobic and anaerobic zones. For nitrification, the apparatus is set to deliver growing nitrifying bacteria in the rapidly growing phase of growth or the end of the rapidly growing phase of growth, called the log phase of growth, to the inlet of the aerobic tank or chamber of the wastewater treatment process, but after the settling tank or the primary treatment. In addition, the apparatus has an air pump to deliver additional air to the aerobic tank or chamber. The air pump may input air by means of a distributing means such as an air diffuser. The apparatus can optionally deliver carbon and nutrients if needed for the particular process or system, based on the composition of the waste water and the stage of the treatment. Since the bacteria are grown on the liquid carbon source of the invention, the liquid carbon source and composition may be considered to be a nitrifying and denitrifing bacterial induction media. The bacteria specifically grown in this invention is expected to be more efficient in the nitrification and denitrification metabolism This invention also relates to a method for selecting for enzyme function in nitrifiers and denitrifiers to be available down stream in a septic system when re-exposed to the same carbon carbohydrate source. It is well known in the field of microbiology that specific requirements are needed to grow and maintain microbes. It has been shown that maintaining microbes on the same carbon source maintains a high level of induction of the appropriate enzymes needed to utilize that carbon source at a high rate of efficiency. This manifests itself in competitive utilization of the carbon source. More specifically this invention using specific carbohydrates and other nutrients such as nucleic acid fragments may be used to transform microbial communities towards nitrification and denitrification in a more consistent and rapid manner. The invention is of significant interest for the nutritional improvement of sewage related microorganisms as well as methods for obtaining the expression of particular enzymes in sewage related nitrifying and denitrifying microorganisms. For denitrification, the apparatus is set to deliver growing denitrifying bacteria in the rapidly growing phase of growth or the end of the rapidly growing phase of growth, called the log phase of growth, to the inlet of the anaerobic tank or chamber of the wastewater treatment process where anoxic conditions are present, but after the aerobic tank or chamber. The apparatus can optionally deliver carbon and nutrients if needed for the particular process or system, based on the composition of the waste water entering the anoxic or anaerobic chamber. In some waste water systems the aerobic or oxic and anoxic or anaerobic chambers may not be clearly separated. In such systems, mixtures of nitrifying and denitrifying bacteria are added along with carbon and nutrient sources if the system lacks such ingredients. The location of the delivery of the bacteria and carbon sources in the reaction zones is important. For nitrification and denitrification, nitrifying bacteria and electron donors, if needed, should be added in the aerobic zone; for denitrification, in the anaerobic zone, in those regions where the oxygen concentration is lower than other regions in the zone. In addition, both the aerobic and anaerobic zones may contain mixing means such as stirrers or mixers for dispersion of the contents. It is therefore an object of the present invention to provide a waste water treatment apparatus and process that takes advantage of the useful characteristics of biological treatment in an effective manner. It is also an object of the present invention to provide such an apparatus and process that maximizes the contact between contaminants from the waste water and the microbes. This allows inefficient systems to become efficient without the need for a relatively large processing tank or unit for smaller systems. Another object of the present invention is to provide a waste water treatment apparatus and process that is sufficiently effective so as to reduce to desirable levels the Total Suspended Solids (TSS), Biological Oxygen Demand (BOD), E - Coli , nitrogen-containing compounds, phosphorus-containing compounds, bacteria and viruses of waste water in a cost-effective manner. These and other objectives are achieved in the present invention through an aerobic and anaerobic treatment process including the addition of specific microbes and carbon to specific locations in the aerobic and anaerobic process so that the aerobic and anaerobic processes are made efficient. The aerobic and anaerobic process may be homogeneous such as the absence of any fixed film or added suspended media, or in addition may contain fixed film or other added suspended media for a heterogeneous process, for extra locations (surface area) for the added microbes to attach and grow. In such systems, either microfiltration or ultrafiltration membranes may be used to contain the bacteria within the aerobic or anaerobic zone and remove the effluent through the membrane. If suspended media is used, screens or filters may be employed at the end of the aerobic and anaerobic zones or tanks to contain the added suspended media within the zone or tank and prevent washout, and membranes may also be used to separate suspended microbes. In addition to the specific microbes, specific carbon sources and nutrients also can be added which provide additional efficiencies to the waste treatment process. The microbes and nutrients may be added at the specific locations in a batchwise, periodic or a continuous process using an apparatus. The microbes, carbon sources, nutrients and if necessary oxygen from air may be added together or separately in the process. Heating means may be provided to maintain the aerobic and anaerobic zones in a desirable temperature range of between 10 and 37 degrees F. In addition, the timing and delivery of the microbes, nutrients and temperature are optimized for the particular process. An example of the micronutrients that may be used is described in Micronutrient Bacterial Booster, N-100, Bio-systems Corporation, Roscoe, Ill., containing the minerals described. Minerals, vitamins, carbohydrates, and amino acids may be added together, separately, or mixed with the carbon source, or microbes as needed. The efficient timing and delivery of the microbes, carbon and nutrients are achieved by the use of a specific apparatus, a controller, which forms part of the invention. This efficiency in the process results in efficient depletion of wastewater contaminants from existing systems and meet regulatory requirements imposed by regulatory agencies. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration of the apparatus in accordance with one embodiment of the present invention; FIGS. 2A and 2B are a schematic illustration of a suitable apparatus for introducing bacteria in accordance with one embodiment of the present invention; FIG. 3 is a schematic illustration of another waste treatment system including one embodiment of the apparatus of the present invention; FIG. 4 is a schematic illustration of yet another waste treatment system including one embodiment of the apparatus of the present invention; FIG. 5 is a schematic illustration of still another waste treatment system including one embodiment of the apparatus of the present invention; FIG. 6 is a schematic illustration of still another waste treatment system including one embodiment of the apparatus of the present invention; FIG. 7 is a schematic illustration of another waste treatment system including one embodiment of the apparatus of the present invention; FIG. 8 is a schematic illustration of yet another waste treatment system including one embodiment of the apparatus of the present invention; FIG. 9 is a schematic illustration of still another waste treatment system including one embodiment of the apparatus of the present invention; FIG. 10 is a schematic illustration of still another waste treatment system including one embodiment of the apparatus of the present invention; FIG. 11 is a schematic illustration of another waste treatment system including one embodiment of the apparatus of the present invention; FIG. 12 is a schematic illustration shown an oxic and anoxic reactor with Apparatus (“Tommy Box”) for the introduction of bacteria, carbon and air in accordance with one embodiment of the present invention; FIGS. 13A and 13B are a schematic illustration of an embodiment of the invention for a filter system; FIG. 14A is a schematic illustration of an embodiment of the invention for a modified nitrification/denitrification filter system; FIG. 14B is a schematic illustration of an embodiment of the invention for a modified nitrification/denitrification filter system; FIG. 15 is a schematic illustration of an embodiment of the invention for 1 liter reactors; FIG. 16 is a schematic illustration of an embodiment of the invention for 1 liter reactors with fixed media in the oxic and anoxic reactors; FIG. 17 is a comparison of the performance of the Mini OAR 1 (Fixed Film Media) and Mini OAR 2 for combined nitrogen, under different operating conditions; and FIG. 18 is a schematic illustration of an alternative embodiment of the controller, where the layout of the different components are shown. DETAILED DESCRIPTION OF THE INVENTION The introduction of bacteria before or in the initial settling phase of treatment requires the bacteria to survive a significant time period, usually measured in days, in a hostile environment. The settling period provides significant challenges to survival due to the physical processes during settling. Settling also promotes the removal of larger particles that can significantly delay complete treatment due to the large mass of the particle to the size of the bacteria. After settlement, the volume to be treated is dampened in peaks and easier to treat because particle size is reduced. Typically in the art batch pulses are fed into a system on the input end through either sinks or toilets. In accordance with the present invention, a (small) pump and actively growing microbes are placed in the post settling tank or primary treatment area as shown in FIG. 1 . The process uses a combination of nitrifiers to convert ammonia to nitrites and nitrates, and denitrifiers to convert the nitrites and nitrates to nitrogen. Preferably the microbes are in log growth phase at the time of delivery, and growing microbes and nutrients are delivered either in a batch wise, periodic or continuous manner. This is different from prior art methods where microbes in static state, non-actively growing phase or spore form are added at the input locations, where growth is slow, and the microbes may have insufficient time or nutrients to grow before they are washed out of the holding and settling tanks due to insufficient “dwell” or “residence” times. Many of these systems also require either fixed or suspended media for functioning. The use of growing microbes ensures that the density of microbes available per unit volume is very high, and therefore the volume of the tanks needed for a particular treatment will be much smaller than current waste water systems. In addition, for the same treatment tank size, the efficiency of removal of nitrogen would be enhanced, resulting in cost savings. Furthermore, in fixed film and suspended film media, there will be continuous replacement of dead and buried bacteria on the surface with fresh and growing bacteria to enhance the performance of the wastewater treatment. The tanks, in addition may contain mixing means, either by mechanical mixers or fluid mixers, for uniformly dispersing the contents added by the controller. An additional feature of this invention is the use of heating means to maintain the temperature of the tanks or containers at the optimum temperature for the transformation and removal of the unwanted contaminants. The control means for maintaining the temperature at the optimum temperature is either included in the controller, or is provided separately, and forms part of this invention In addition, because the microbes and nutrients are added in a controlled process, there is less likelihood of microbes not surviving. The problem of runaway growth when excessive microbes are added to settling tanks resulting in plugs and blocks of filters or tanks also is minimized. Furthermore, a particular amount of active microbes is always present, making the system catastrophic failure proof, such as in the case when toxic chemicals react with the microbes, or when the microbes are washed out in the case of rainstorms or flushes. The particular microbes chosen depend on the nature of the waste to be cleaned, and are within the skill in the art. Generally the microbes include nitrifying bacteria for the conversion of ammonia to nitrites and nitrates. The denitrifying microbes are denitrifying bacteria that convert the nitrates and nitrites to nitrogen in the presence of the carbon sources and nutrients added in a controlled process. Those skilled in the art know the nature of the nutrients most effective for supporting the microbes chosen. The examples below provide examples of suitable microbes. Some of the microbes can be microbes that transform phosphorus to another form that may be easily removed for example by precipitation or sedimentation. Some others will be specific for impurities such as the removal of biological oxygen demand by the removal of carbon or other oxidizable impurities which can interfere with the nitrification. The invention is equally applicable for the remediation of waterbodies, such as ponds, lakes, aquaculture facilities, landfills, industrial wastes, and contaminated sites. A homogeneous system or a heterogeneous fixed film or suspended media may be used as appropriate. In the case of waterbodies the water can be recycled through a series of aerobic reactors aerobic to convert ammonia to nitrates and nitrites, and an anaerobic reactor to convert the nitrates and nitrites to nitrogen. In the case of industrial wastes, an appropriate microbe specific to the pollutant should be employed. In the case of contaminated soils and waste sites, water would be used to wash or percolate the site and sent to one or more vessels containing microbes and receiving growing microbes introduced by the controller. In addition, the containers and the controllers may be mounted on mobile platforms. In the case of contaminated waste sites, such as perchlorates and chlorinated hydrocarbons, the concentrations of the contaminant may be too high in general for microbes to survive for longer periods. The continuous or periodic addition of growing microbes as described in the invention overcomes this deficiency. Any growing microbe that transforms a particular contaminant can be used. Microbes may be modified genetically to contain genes encoding enzymes that are effective in transforming the contaminants. Some examples of contaminants that may be removed or transformed by the invention by the controlled addition of microbes and if needed other nutrients are, Acetone, Ammonia, Aniline, Aromatic compounds, Nitrate, Nitrite, Carbon disulphide, Chlorinated solvents, Chlorobenzenes, Chloroform, Dichloroethanes, Dinitrotoluene, Dioxane, Ethanol, Ethylene, Explosives, Glycols, Hydrocarbons, Hydrogen sulfide, Isopentane, Isobutanes, Methanol, Methyl chloride, Methylene chloride, Tri nitro toluenes, Naththalene, Nitraamines, Nitrate, Nitroaromatics, Nitrites, Nitrobenzene, Perchlorates, Perchloroethylene, Pesticides, Phenol, Solvents, Styrene, Sulfur compounds, Tetrahydrofuran, Trichloroethane, Trichlorotoluene, Bromoform, Nitrobenzene, Methyl tertiarybutyl ether, Tertiary butyl alcohol, Chlorinated ethenes, Chlorinated ethanes, Vinyl chloride, Ammonium perchlorate and perchlorates. The preferred carbon/electron donor source is methanol, carbohydrates and sugars and mixtures thereof. Other carbon sources that may be used are ethanol, polysaccharides, soluble starches, oils, fats, dairy and food waste, and other sources of organic carbon. The amount of carbon that should be added is about 0.2 to about 5 times the total nitrogen present in the waste water, preferably about 2 times the total nitrogen present in the waste water. The preferred nutrients are amino acids, phosphates, and other minerals needed by bacteria for growth. The preferred bacteria to be used are specific for the pollutant to be treated. For denitrification, denitrifying bacteria are used. If nitrification of ammonia is the need, nitrifying bacteria would be used, and for cyanide removal “cyanidase” enzyme or bacteria capable of converting cyanide can be used. For denitrification, a mixture of Enterobacter Sakazaki (ATCC 29544), Bacillus coagulans (ATCC7050), Bacillus subtillis (ATCC 6051), Bacillus subtillis (ATCC 6051), Bacillus megatarium (ATCC7052), Bacillus licheniformis (ATCC14580), Bacillus cerus (ATCC4513) and Bacillus pasytereurii (ATCC 11859) may be used. Other bacteria that may be used are described in U.S. Pat. No. 6,025,152. For nitrification, the bacteria include Nitrobacter and Nitrocococcus spp available from Cape Cod Biochemicals, 21 Commerce Road, Bourne, Mass. These bacteria are available from a number of commercial suppliers which are specific for the specific pollutant. The bacteria are used in an amount effective to treat (and preferably eliminate) the contaminants. Turning now to FIG. 1, there is shown a simplified diagrammatic illustration of a preferred arrangement of the basic components of the waste water treatment system of the present invention for a small system such as a single family home. (Title V System). Waste generated in toilet ( 1 ) and water waste generator ( 2 ) enters the settling tank ( 3 ), and after a certain residence or “dwell” time enters the distribution box ( 4 ) which distributes to the leaching field. The distribution box can be a large tank with two zones, one for receiving oxygen and be oxic and result in nitrification, and another anoxic for denitrification, or it could simply be one tank. In the present invention an apparatus ( 31 ), shown in greater detail in FIG. 2, is used to add growing microbes, nutrients including carbon sources, and oxygen after the settling tank, but before the distribution box for efficient nitrification and denitrification of waste. The distribution box can be made large or small depending on the flow rate of waste water and the rate of addition of components from the apparatus ( 3 ). FIG. 2A is an expanded view of the apparatus called controller “Tommy Box”, used for the addition of the carbon or electron donor source, nutrient, the biological microbial medium, and air used to accomplish effective aerobic and anaerobic waste water treatment. Growing microbes in bacteria holding tank ( 5 ) are pumped using bacteria pump ( 15 ) controlled by a controller-timer ( 7 ), to the exit point ( 56 ). Nutrient and carbon/electron donor source holding tank ( 6 ) feeds into the carbon/electron donor pump ( 10 ), controlled by the controller-timer ( 7 ), to the exit point ( 56 ). Air pump ( 26 ) controlled by the controller-timer also pumps air to the exit point ( 56 ). The exit point ( 56 ) of the apparatus is placed on line before the distribution box in FIG. 1 . This allows for controlled predetermined feed of air, carbon, nutrients, and bacteria into the waste water flow before the distribution box. The controller timer allows for measured addition of microbes, nutrients, carbon and air. If needed, additional tanks and pumps may be installed in the apparatus for controlled addition of other ingredients for any other specific treatment. FIG. 2B is another design of the apparatus called controller “Tommy Box”. The timer, the carbon pump, and the bacteria pump, the carbon storage container, and the bacteria storage container are installed inside a box to protect from the elements. Additionally, a small thermostatically controlled heater is provided to keep the box at an optimum temperature for the bacteria and carbon. FIG. 3 is another embodiment of the invention where waste water flow into settling tank or septic tank ( 1 ), and flows into a distribution box ( 4 ) connected to receive input from Apparatus ( 31 ), which delivers controlled quantities of carbon, nutrient, bacteria, and air. The treated water finally flows into the soil absorption system ( 6 ). FIG. 4 is a preferred embodiment of the invention where waste water flow into settling tank or septic tank ( 1 ) and flows into a dosing mechanism section ( 2 ). A septic tank 1 , or other form of primary settling tank or unit may be used for initial settling of large solids from the waste water initially transferred from some type of facility, whether a single-family residence, a grouping of buildings, or an industrial facility. The septic tank 1 may be an existing unit, or it may be provided as part of an integrated treatment system of the present invention. The present invention includes a primary treatment unit that is a dosing zone or mechanism, which receives the controlled addition of carbon or electron donor, nutrients, bacteria, oxygen and any other additive, using the apparatus ( 31 ) at the specific location or zone. For aerobic zones oxygen is provided, whereas for anaerobic zones, oxygen is not provided. The output from the apparatus ( 31 ) is preferentially introduced at the input side of the dosing mechanism. In some cases it may be advantageous to introduce the output of the apparatus midway into a zone or close to the bottom of the zone. The dosing mechanism may be replaced by a distribution box for a single-family residence, as shown in FIG. 3, or could be a dosing tank as described in FIG. 7 . The output can then be further treated by a sand filter or sent to the environment or the soil absorption system. The treated water that passes through the treatment system is then drawn off or otherwise moved to another site, such as a leach field, a secondary water user, such as a toilet, to a final usable water site, such as via a soak hose system, or it can be discharged to nearby water bodies. The apparatus (Tommy Box) ( 31 ) introduces controlled quantities of carbon, nutrient, bacteria, and air into the dosing mechanism ( 2 ) section. The waste water then flows through a sand filter ( 3 ). A portion of the treated water may be diverted to the soil absorption system ( 6 ). Another portion of the treated water may be re-circulated using a flow mechanism to the input of the settling tank ( 1 ), and flows into a dosing mechanism section ( 2 ). FIG. 5 is another embodiment of the invention where waste water flow into settling tank or septic tank ( 1 ) and flows into a reactor ( 9 ). The apparatus (Tommy Box) ( 31 ) introduces controlled quantities of carbon/electron donor, nutrient, bacteria, and air into the input of the reactor vessel ( 9 ). A portion of the treated water may be diverted to the soil absorption system ( 6 ). Another portion of the treated water may be re-circulated using a flow mechanism to the input of the settling tank ( 1 ), and flows into a reactor ( 9 ). The apparatus (Tommy Box) ( 31 ) introduces controlled quantities of carbon, nutrient, bacteria, and air into the input of the reactor vessel ( 9 ). This process is repeated, and gives additional treatment time for the waste water. FIG. 6 is another embodiment of the invention where waste water flow into settling tank or septic tank ( 1 ) and flows into a dosing tank mechanism section ( 2 ). The apparatus (Tommy Box) ( 31 ) introduces controlled quantities of carbon, nutrient, bacteria, and air into the dosing mechanism ( 2 ) section. The waste water then flows through an aeration structure ( 12 ) and is discharged to the environment. A variation is to treat the output using a sand filter before being discharged to the environment. FIG. 7 is another embodiment of the invention where waste water flow into settling tank or septic tank ( 1 ), and flows into a dosing tank ( 2 ) connected to receive input from apparatus ( 31 ), (Tommy Box), which delivers controlled quantities of carbon, nutrient, bacteria, and air. The treated water finally flows into a RUKK Filter system ( 13 ), described in U.S. Pat. No. 4,465,594 and 5,588,777 (incorporated herein by reference) and finally to the environment. FIG. 8 is another embodiment of the invention where wastewater is treated using a series of alternating aerobic and anaerobic reactors or zones. The series of alternating aerobic and anaerobic reactors or zones can be any number as desired. At the inlet to one or all of the aerobic zones or reactors, the apparatus 31 , “Tommy Box” delivers nitrifying microbes and oxygen. In this zone, ammonia is converted to nitrite and nitrate. If needed, carbon, nutrient or electron donors may also be added, if the waste water is deficient in the above ingredients. Denitrifying microbes, may also be added, if there are zones in the reactors that are anaerobic, and therefore can participate in denitrification, and thereby increase the efficiency of the nitrogen removal process. At the inlet to one or all of the anaerobic zones or reactors, the apparatus 31 , “Tommy Box” would be set to deliver denitrifying microbes, carbon or electron donor and nutrients. No oxygen is delivered to the anaerobic rectors or zones. The amount of carbon, electron donors, and nutrient added is related to the needs of the system. In this zone denitrification of nitrates and nitrites to nitrogen gas takes place. The discharge from the final anaerobic reactor could then be sent to the environment or for tertiary treatment. U.S. Pat. No. 4,279,753 issued to Nielson et al. describe multiple series of alternating aerobic-anaerobic bioreactors in series can utilize the current invention to improve the efficiency and dependability of such a wastewater treatment system. U.S. Pat. No. 6,235,196 issued to Zhou also describe multiple reactors which can utilize the improvements of the invention. In FIG. 9, if only two aerobic and anaerobic zones are needed, then only two apparatuses ( 31 ) feeding the inlets to the aerobic and anaerobic zones would be used. The size of the apparatus could be scaled based on the size of the reactors 90 , 91 , zones and the wastewater flow rates. The discharge from the anaerobic reactor could then be sent to the environment ( 6 ) or for tertiary treatment. FIG. 10 . is a dual spherical reactor vessel embodiment where liquid wastewater flows into a settling tank or septic tank ( 1 ), and flows into a primary spherical reactor vessel ( 102 ) connected to receive input from apparatus ( 31 ), (Tommy Box), which delivers controlled quantities of nutrient, bacteria, and air. The output then flows to a secondary spherical reactor vessel ( 103 ) where nutrients and bacteria can be delivered into said vessel near the bottom, middle and top of the fluid. In the preferred example the reactor vessels should hold between 2 and 8 days of retained daily flow volume. The output of the secondary reactor vessel leads to the soil absorption system ( 6 ). FIG. 11 is another embodiment of the invention wherein wastewater is treated using a single reactor ( 110 ) which contains both an aerobic ( 95 ) and an anaerobic ( 96 ) zone. The two zones may be separated by some mechanical means, or may be a two fluid regions not separated by mechanical means. At the inlet to the aerobic zone the apparatus ( 31 ), “Tommy Box” delivers nitrifying microbes and oxygen. If needed, carbon, nutrient or electron donors may also be added, if the waste water is deficient in the above ingredients. In this zone, ammonia is converted to nitrite and nitrate. At the beginning of the anaerobic zone ( 96 ) where the two zones meet, a second apparatus 31 , “Tommy Box” would be set to deliver denitrifying microbes, carbon or electron donor and nutrients using transfer means ( 97 ), which could be a tube. No oxygen is delivered to the anaerobic zone. The amount of carbon, electron donors, and nutrient added is related to the needs of the system. In this zone denitrification of nitrate and nitrites to nitrogen gas takes place. U.S. Pat. No. 6,086,765 issued to Edwards. describe a single aerobic-anaerobic reactor that can utilize the current invention to improve the efficiency and dependability of such a wastewater treatment system. FIG. 12 shows the Oxic and Anoxic reactor with Apparatus (“Tommy Box”) with lines for the introduction of bacteria, carbon and air, the use of a heating means to heat the aerobic zone, and the use of filters in the fluid exit from the aerobic and anaerobic zones. Optional heating means may be introduced to the anoxic zone. Optionally, an additional reactor or zone may be added where the effluent leaving the anaerobic reactor or zone is aerobically treated with air to reduce the BOD before it is released to the soil absorption system or environment. Optional tanks for additional aeration, filtration by sand filter or other soil absorption system, ultraviolet treatment, ozone treatment and membrane filtration are not drawn. In the aerobic and anaerobic zones a membrane filter (hollow fiber or other) may be used to remove effluent by filtration. The membrane prevents the loss of microbes from the anoxic reactor. FIGS. 13A and 13B. Embodiment of the invention for a filter system. The system includes a holding tank 10 having an outlet 14 that draws nitrifying bacteria (from transfer apparatus) leading to a leaching field 16 . A porous bed of sand or fine gravel is provided below the leaching field 16 , and includes an in-drain 18 having a core 20 surrounded by an outer envelope 22 of geotextile fabric material. Conduit means 24 having a lower branch 24 a that draws denitrifying bacteria (from transfer apparatus) is provided. The upper end of the conduit means 24 communicates with pump 26 that draws liquid carbon from a reservoir 28 in response to the output of a timer 30 . FIG. 14 A. Embodiment of the invention for a modified nitrification denitrification filter system. FIG. 14 B. Improved embodiment of the invention for a modified nitrification denitrification filter system. FIG. 15 . Another layout for the apparatus for 1 liter reactors. FIG. 16 . Layout for Apparatus shown for 1 liter reactors with fixed media in the oxic and anoxic reactors. FIG. 17 . Comparison of the performance of the Mini OAR 1 (Fixed Film Media) and Mini OAR 2 for combined nitrogen, under different operating conditions. FIG. 18 . Another embodiment of the controller, where the layout of the different components are shown. The bacteria pump, the carbon pump and the air pump are controlled by a timer/controller. The controllers may be optionally connected to a master controller for external remote control by a computer. The master controller can also receive inputs from sensors in the OAR system to monitor temperature, flow rates, ammonia, oxygen, nitrate and bacteria. These inputs may be programmed using a controller to reset the pumping rates for bacteria, carbon and air. EXAMPLE 1 Preparation of Nitrification and Denitrification Bacteria Mixture: Bacteria mixtures useful in nitrification and denitrification were prepared by mixing bacterial mixtures containing various bacterial strains known to nitrify and denitrify. For nitrification, a mixture of Enterobacter Sakazaki (ATCC 29544), Bacillus coagulans (ATCC7050), Bacillus subtillis (ATCC 6051), Bacillus subtillis (ATCC 6051), Bacillus megatarium (ATCC7052), Bacillus licheniformis (ATCC14580), Bacillus cerus (ATCC4513) and Bacillus pasytereurii (ATCC 11859) was used. For nitrification, the bacteria were not easy to identify, and include Nitrobacter and Nitrocococcus spp obtained from Cape Cod Biochemicals, 21 Commerce Road, Bourne, Mass. Bacterial growth media was prepared in 1 liter batches by dissolving 20 g Bacto Tryptose, 2 g Bacto Dextrose, (Difco Laboratories, Detroit, Mich.), 5 g sodium chloride, and 2.5 g disodium phosphate (Sigma-Aldrich Corp., St. Louis, Mo., USA) in 1 liter of deionized water, and sterilizing at 250° F. for 15 minutes in an autocloave. The bacteria, 0.1 ml, if in liquid form, and 0.5 g, if in dry form, was added to 100 ml of media prepared above, and grown at 37° C. for 3 days. At the end of 3 days, 100 ml of the grown bacteria were added to 4 liters of growth media, and grown for 3 days before use. The bacterial mixtures were then used in field testing. EXAMPLE 2 Preparation of Carbon Nutrient Mixtures Carbon mixtures that are non-flammable, have low viscosity and are readily pumpable liquids, and stable to premature microbial growth were prepared by adding to 100 ml of deionized water, 50 g Maltrin M250 (Grain Processing Corporation, Muscatine, Iowa, USA), dissolving the solids, and adding 10 ml of methanol (Sigma-Aldrich). In addition to the carbon sources, other micronutrients generally used for growth of bacteria, and described in Handbook of Microbiological Media by R. N. Atlas, CRC Press, Cleveland, Ohio and Media Formulations described in the ATCC catalog ATCC 12301 Park Lane Drive, Rockville, Md., were added in the generally recommended quantities. The carbon and nutrient mixtures were found to be stable, as measured by unwanted premature growth for over 4 weeks. The bacterial mixtures and carbon/nutrient mixtures were tested for viability using solutions made up of ammonium chloride for ammonia conversion, and sodium nitrate for nitrate conversion. The nitrifying and denitrifying bacteria were found to be effective for conversion of ammonia and nitrate, respectively. Ammonia was measured using a Hanna Instruments Inc, 584 Park East Drive, Woonsocket, R.I. 02895, High Range Ammonia Calorimeter, Catalog No, HI 93733, and the ammonia testing reagents kits. Nitrate was measured using a Hanna Instruments Inc., 584 Park East Drive, Woonsocket, R.I. 02895, Nitrate Calorimeter, Catalog No. HI93728, and the nitrate testing reagents kit. The nutrient carbon mixtures were scaled up to 10 gallons, by dissolving 42 pounds of Maltin M250 in 10 gallons of deionized water using a paddle, and adding 3,785 ml of methanol (Doe and Ingals, Medford, Mass.). In addition, other micronutrients generally used for growth of bacteria described in Handbook of Microbiological Media by R. N. Atlas, CRC Press, Cleveland, Ohio and Media Formulations described in the ATCC catalog, ATCC 12301 Park Lane Drive, Rockville, Md. were added in the recommended quantities. In addition to deionized water, tap water also may be used. The carbon nutrient mixtures prepared above were used in the field testing described below. Leaching Field Test EXAMPLE 3 The bacterial and carbon/nutrient mixtures were then tested in a field test in a system as described in FIG. 2 and FIG. 3, in a sewage treatment testing facility. The waste water exciting the settling tank had 36 ppm nitrate, and was flowing at a rate of 78 gallons/day, and the septic/settling tank was 1500 gallons. The bacteria mixture of nitrifiers and denitrifiers was fed at a rate of 11 ml/hr for 1 hour, each 6 hours, 4 times/day. The carbon/nutrient was added at a rate of 110 ml/hr, for 1 hr every 4 hours, for a total of 660 ml/day. Samples were taken after 14 days under the leaching field at a depth of 1 ft, and 2 ft and tested for nitrate nitrogen. The results are given in Table 1. TABLE 1 FIG. 2 Field Testing of Waste Water Nitrate nitrogen, ppm Before treatment 1 ft 2 ft under the leaching field 29-37 ppm 29-37 ppm With treatment as in FIG. 2 1 ft 2 ft under the leaching field 10 ppm 2 ppm Ammonia was measured using a Hanna Instruments Inc, 584 Park East Drive, Woonsocket, R.I. 02895, High Range Ammonia Calorimeter, Catalog No, HI 93733, and the ammonia testing reagents kits. Nitrate was measured using a Hanna Instruments Inc, 584 Park East Drive, Woonsocket, R.I. 02895, Nitrate Calorimeter, Catalog No, HI93728, and the nitrate testing reagents kit. Reactor System Test EXAMPLE 4 The bacterial and nutrient mixtures described in examples 2 and 3 were then tested in a field test in a system as described in FIG. 5 in a sewage treatment system facility. The discharge from the treatment system reactor system had Total Nitrogen (TN) in the range 91-135 ppm, prior to the field test, and not discharging final concentrations of TKN generally required for discharge limits in waste water treatment facilities. The waste water exiting the septic/settling tank had about 91-135 ppm TN and was flowing at a rate of about 3,500 gallons/day, and the septic tank was about 5000 gallons. The reactor vessel was about 5000 gallons. The bacteria mixture, containing denitrifiers and nitrifiers capable of converting ammonia to nitrate and nitrite, and further nitrate and nitrite to nitrogen, was added continuously at the entrance to the reactor vessel at a rate of 1 liter/day for 1 week. At the end of one week, the bacterial addition was changed to 250 ml/day. Samples were taken 12 and 19 days after the initial addition of the bacteria. at the point of discharge, and tested for TN by an outside water testing laboratory. The results are given in Table 2. TABLE 2 Reactor System (FIG. 5) Field Testing of Waste Water TN, Before treatment 91-135 ppm In the discharge TN With treatment as in FIG. 5 12 days 19 days In the discharge 31 ppm 4-6 ppm Sludge Reduction EXAMPLE 5 The reactor described in example 4, which was approximately 8 feet by 8 feet by 8 feet before the treatment with the bacterial mixture had sludge to a height of about 4 feet. The sludge in the reactor when measured at the end of about 90 days was approximately 1 foot. EXAMPLE 6 Dual reactors as shown in FIG. 10 could be used for nitrification and denitrification by fermentation of waste water. Waste flow enters a 1,500 gallon settling tank that has a “T” at the effluent end that leads to a 750 gallon plastic sphere (Zabel Environmental Technology, PO Box 1520, Crestwood, Ky., 40014). House wastewater enters the settling tank in a range of 80-200 gallons per day. Settled fluid enters the primary reactor where nitrifying bacteria as described in example 3 are introduced into the system using the apparatus “Tommy Box” as shown in FIG. 10 . Nutrients could be added to primary reactor to stabilize the pH and micro nutrient levels. In addition to bacteria and nutrients, optionally air may be used to aerate the system. The aerated effluent from the primary reactor flows into the secondary reactor. The secondary 750 gallon Zabel spherical reactor receives denitrifying bacteria and carbon as described in example 3. The carbon and bacteria are added into the system on or near the bottom where little or no oxygen is available. The output of the secondary reactor flows directly into the soil absorption system. EXAMPLE 7 The Oxic Anoxic Reactor (OAR) system as shown in FIG. 12 was installed at the Massachusetts Alternative Septic Test Center, Otis Mass. This is a variation of FIG. 9, where two apparatuses are shown. Extra pumps as needed may be installed inside the apparatus (“Tommy Box”) for delivering two or more different mixtures of bacteria to specified locations in the OAR system. A larger air aerator and diffuser capable of producing oxygen concentrations in the 3 to 8 mg/liter was used. These dual tank stepwise multi tank systems are used for reducing TSS, COD, phosphate, nitrification and denitrification of the wastewater. The OAR system is a gravity fed continuous reactor where primary effluent first enters a settling tank (Massachusetts Title V or equivalent regulations). Flow rates entering the tank ranged from 100-550 gallons per day. Over one year the influent temperature and oxygen levels ranged 2 to 28 degrees Celsius, and 0.0-0.5 mg/l respectively. The second stage flows into the first OAR tank, aerobic reactor, (T1) where temperature and oxygen are monitored by sensors. The sensor information is used to control the temperature and oxic conditions. The air is purged into T1 using a diffuser for better aeration. The need for bacteria is also monitored and added as needed. Residence time or dwell in T1 is designed to average about 1-6 or more days depending on the level of nitrification needed. Oxygen concentration and temperature are held between 3.0-8.0 mg/l and about 20-40 degrees Celsius respectively, by means of an aerator and a heating means inserted into the tank T1. The preferred temperature is 24 degrees Celsius. The heating means may be by electrical heating or solar heating with temperature controls. Growing nitrifying bacteria and denitrifying bacteria are introduced at a rate of 1 to 10 ml per 100 gallons of raw effluent flow. Bacterial concentrations ranged from 10 exponent 12 to 10 exponent 17 cells per ml. Nitrified effluent passes through T1 into an optional filter and into Tank 2 (T2). T2 contains injection ports to deliver the non-flammable carbon source of the invention, as well as nitrifying bacteria from the apparatus. While other sources of carbon may be used, it is preferable to use the non-flammable liquid carbon source of the invention as the bacteria have been specifically grown in that carbon source, and the carbon source contains the preferred nutrients for the optimum performance of the bacteria. The carbon pump is set to deliver carbon at a rate sufficient to decrease the nitrogen level desired by the local wastewater regulations. Generally for 1 mg of nitrogen, 1-4 mg of carbon would be needed for bringing the level of nitrogen to below 10 mg/l, depending on the content of carbon present in the nitrified wastewater. The wastewater flow rate and the concentration of nitrogen in the influent dictate the flow rate and volume of carbon to be delivered. The outlet of the tank T1 can have an optional filter for removing particulates and any large media particles or suspended media introduced. T1 can also contain fixed film media if desired. The oxygen level in T2 rapidly approached near undetectable values from top to bottom of the tank for anoxic conditions. Residence time is designed to average 1-4 days, preferably 2 to 3 days. Denitrifying bacteria that had been previously added in T1 where they begin their initial growth under aerobic conditions can migrate to T2 and continue the denitrification under anoxic conditions. Optionally, denitrifying bacteria can be added to T2 as needed for denitrification. The OAR system allows the separation of various microbiological functions to enable complete system control and testing capabilities. Optionally, a filter is placed at the end of the tank T2 for particulate removal as well as for holding any suspended media introduced to the system for bacteria growing on surfaces. Fixed film media may also be introduced into T2 as desired. Optionally, a membrane filter, such as a hollow fiber or flat sheet membrane may be used to filter the effluent, by applying a vacuum to the lumen side, leaving the bacteria in the tank T2. The effluent finally travels to a distribution box where it is distributed to a soil absorption system such as a leaching field. The effluent may also be directed to a sand filter or modified sand filter for additional removal of suspended solids, bacteria, and in addition can be treated using ultraviolet light, ozone or chlorine to provide tertiary treated water or recycled water, and further treated by reverse osmosis as needed. The tanks T1 and T2 are placed in the ground such that T1 is at a lower level compared to the settling tank outflow, and T2 is at a lower level relative to T1 so that there is gravity flow. This avoids the need for pumping of wastewater required in many commercial systems and is energetically favourable. The OAR system was started on day 1 receiving 150 gal/day with influent from a trench that was fed from a septic tank. Influent levels were for Ammonia of about 35 mg/l, Nitrate close to 0 mg/l, Oxygen close to 0 mg/l, Total Suspended Solids (TSS) in the range 150-230 mg/l, Chemical and Biological Oxygen Demand (CBOD), in the range 235-339 mg/ml. On day 17, the OAR effluent exciting from T2 had TSS<30 mg/l, CBOD<20 mg/l, Total Nitrogen (Ammonia plus Nitrate) was generally below 10 mg/l. Sample measurements for each data point were taken 3 times a week. For the oxic and anoxic reactors, additional mixing means such as stirrers and mixes can be added to improve the performance of the system, and keep especially suspended fixed film media in suspension. In addition, if activated sludge is used, the controlled addition of bacteria can improve the performance of the activated sludge system over and above its normal performance. EXAMPLE 8 FIG. 13 shows the use of the invention to improve the performance of U.S. Pat. No. 5,588,777 incorporated herein by reference. The apparatus (not shown) introduces nitrifying bacteria after the septic tank, so that the bacteria are dispersed in the sand filter. Optionally denitrifying bacteria may also be introduced and additional aeration provided. Instead of the liquid soap, the non-flammable carbon source can be used. Denitrifiers may also be added in the anoxic bottom zone of the filter. EXAMPLE 9 FIG. 14A shows the use of the invention to improve the performance of U.S. Pat. No. 4,465,594 incorporated by reference. The apparatus (not shown) introduces nitrifying bacteria after the septic tank to the holding tank ( 10 ), so that the bacteria are dispersed in the (aerobic) nitrification filter ( 12 ). An optional mixing tank may be provided between the nitrification filter and the holding tank for receiving the nitrifying bacteria. This holding tank is optionally heated to between 10 and 35 degrees Celsius for improved nitrification. The heated nitrified effluent is collected in the chamber 18 . Denitrifying bacteria is introduced to chamber ( 18 ) along with non-explosive carbon described in this invention. The chamber can optionally have mixing means for better dispersion of denitrifying bacteria and carbon. The bacteria and carbon flows to the anoxic detention tanks where denitrification takes place. EXAMPLE 10 FIG. 14B is another embodiment of the invention where the apparatus is used to introduce nitrifying bacteria into a pump chamber before the nitrification filter. Optionally, the pump chamber may also be aerated for efficient nitrification in addition to that provided by the air vent. Furthermore, the pump chamber may be heated to maintain a temperature of between 10 and 35 degrees Celsius for efficient nitrification. The apparatus is used to introduce denitrifying bacteria and a carbon source into the mixing chamber. The use of the denitrifying bacteria grown with the non-flammable carbon source is preferred. EXAMPLE 11 The effluent from the septic tanks (the primary treatment) were tested using a scaled down version of the Oxic Anoxic Reactor (OAR) scaled down to 1 liter, with and without a fixed film media. The effluent from the sepic tank is the same effluent used in example 7, and had combined nitrogen in the 35 mg/l range. The fixed film media used was a fibrous filter used for air filtration produced by Flanders Precision Aire, St. Petersburg, Fla. FIGS. 15 and 16 show different layout for the apparatus to be used with the OAR system. Air was introduced to the aerobic reactors in FIGS. 15 (Mini OAR 1) and 16 (Mini OAR 2). The flow rate of the effluent entering the aerobic tank was between 100-300 ml/day. Growing nitrifying bacteria was added to the aerobic reactor at the rate of 1 ml/day, once a day because of the small volume. The liquid carbon was added at the rate of 0.1 ml/day, once a day. The temperature of this system was kept at room temperature of between 16 to 20 degrees Celsius. FIG. 17 gives the combined nitrogen data under various conditions. From Jun. 17, 2002 to Jul. 3, 2002 growing bacteria and liquid carbon were added as described above. The combined nitrogen stayed below 12 mg/l during this period. On Jul. 3, 2002, the addition of growing bacteria and liquid carbon was stopped, and resulted in an increase of the combined nitrogen to between 20 and 30 mg/l. On Jul. 10, 2002, the addition of bacteria and carbon was resumed. Within one week, the combined nitrogen in both OAR systems was below 10 mg/l and trending towards the values before the disruption in the addition of bacteria and carbon. Use of a suspended film media is expected to produce a similar result. EXAMPLE 12 Power Failure Stress Test Power shut off stress test of the 220 gallon per day OAR (Oxic Anoxic Reactors) as shown in FIG. 12 was carried out as follows. The OAR installed at the Massachusetts Alternative Septic Test Center, Otis Mass. Nitrification and denitrification of the waste water was monitored to determine the effects of 4 days of complete power shut down. During 4 days from May 24 to May 28, 2002 all electrical power was shut off on the OAR System. Effluent continued to be sent into the system. Throughout the 4-day period air, carbon, heat and bacteria were not functional. Total Nitrogen (Ammonia and Nitrate) during the shut off the system was still below 20 mg/liter. Three days after restoring power the Total Nitrogen began to drop back to below 10 mg/liter in 7 days. EXAMPLE 13 Stability of non-flammable liquid carbon to microbial stability was tested. Non-flammable liquid carbon was made by dissolving 1000 ml of deionized water 500 g of Maltrin M250 and micronutrients described in example 2 without methanol. The liquid carbon solution was divided into 5 aliquots of 100 ml each by transferring into 100 ml sterile glass bottles baked at 250 degrees Celsius. One bottle was kept as a control. To the second bottle 5 ml methanol was added to bring the methanol concentration to 5%. To the third 5 ml of formalin (10% formaldehyde solution) was added to bring the formalin concentration to 5% of the added formalin. To the fourth 2 ml of Iodopropynyl Bulycarbamate (Germal) was added to bring the Iodopropynyl Bulycarbamate concentration to 2%. To the fourth bottle 10 ml sodium hypochlorite solution (Americas Choice Bleach Compass Foods, Modale N.J. USA) was added to bring the added bleach concentration to 10%. To the fifth bottle 3 ml 1M sodium hydroxide was added to bring the pH of the solution to 12.6. Each bottle was then spiked with 0.1 ml of bacteria cultures grown for 4 days on Difco TPD Media. The samples were stored at 18 to 20 degrees Celsius for one week and observed daily. The control liquid carbon carbohydrate solution with no additive was cloudy with stringy mass and pale yellow color. The methanol, formalin and Germal were all clear with pale yellow color, the bleach was clear with no color, and the bottle with sodium hydroxide was clear with dark yellow color. The control showed rapid growth in less than 2 days, whereas none of the others showed any growth. In addition to the use of nitrifying and denitrifying bacteria, a wide variety bacteria and bacterial mixtures can be used to modify or remove a many pollutants, contaminants from many sources. Several of the bacteria mixtures are available commercially, such as from Bio-Systems Corporation, 1238 Inman Parkway, Beloit, Wis. 53511, and incorporated by reference. The bacteria may treat municipal, industrial, commercial, and residential waste. Some of these users are for degradation of complex chemicals such as phenols, benzene compounds, surfactants, alcohols, aliphatic compounds, aromatic compounds, and other ionic waste such as chlorates, perchlorates, cyanides, nitrites, nitrates or any other pollutant that can be reacted and removed by bacteria. Other users for contaminant and pollutant control and removal are in chemical waste, grease removal, grease control, chlorinated organics, dairy waste, refinery waste, hydrocarbon soil remediation, marine pollutant control, hydrocarbon oil sump treatment, municipal activated sludge, fish farming, pulp and paper bio-augmentation, municipal lagoons, manure waste, portable toilet treatments, drain and grease traps, odor control, and septic tank treatments. Additional potential uses are in aquaculture, aquariums, food waste and grease traps, pond reclamation and farm waste remediation. The invention is equally applicable to any wastewater system that suffers from frequent failure, and that has separate oxic, aerobic, anoxic and anaerobic regions. This invention can be used with recirculating sand filters, trickling filters, and any aerobic and anaerobic treatment systems. The applicability of this invention is not restricted to nitrification and denitrification, and equally applicable to other pollutants which can be microbiologically treated.

Systems for treating water containing unwanted contaminants. More particularly, the present invention relates to waste water treatment systems including biological media used to aerobically or anaerobically treat solid and liquid waste in water for large and small-scale waste water systems in a way that minimizes the size of the system required to output high-quality, environmentally suitable water that is depleted of ammonia, nitrites, nitrates and other contaminants.

BACKGROUND OF THE INVENTION 1. Technical Field of the Invention This invention relates to an improved process for reducing the sulfur content in flue gas generated by the combustion of a sulfur-containing fuel. More particularly, the present invention relates to the combined addition of formate and thiosulfate, magnesium, sodium or other calcium concentration reduction agent to improve the performance of and reduce costs in wet, calcium based flue gas desulfurization processes. 2. Description of the Prior Art Over the past two decades, the consumption of electrical power generated by power generation sources which use sulfur-containing fuels, particularly coal for the generation of steam for producing such electrical power, has increased tremendously while the restrictions placed on the flue gases which emanate from the burning of such sulfur-containing fuels have been tightened nationwide and particularly in areas where a heavy concentration of such gases develop. Therefore, there have been a variety of systems developed for treating the flue gases which emanate from the power generation plant such that the stringent standards promulgated by the Environmental Protection Agency can be met. These various systems include processes which attempt to reduce or eliminate the sulfur content in the fuel prior to its combustion. Other systems include processes which require the addition of chemical compounds into the combustion zone which change the nature of the sulfur compounds produced, thereby aiding in their removal from the combustion products. Still other systems include scrubbers which require the addition of compounds into the flue gas generated by the combustion of the sulfur-containing fuels to remove the sulfur compounds from the flue gas by way of a chemical reaction. The after treatment of flue gas may be accomplished by a variety of known processes; namely, wet scrubbing, spray drying or dry treatment of the flue gas in a contact zone of a flue gas flow passage. Illustrative of the wet scrubber approach is U.S. Pat. No. 3,928,537, issued Dec. 23, 1975 to Saitoh et al., which discloses contacting the exhaust gas with an aqueous solution of an organic acid to form a soluble sulfite or sulfate. The sulfite or sulfate is removed, and the organic acid regenerated, by a second step comprising reaction with a calcium compound such as an inorganic or an organic acid salt, for example calcium hydroxide or calcium formate. The spray dryer approach is illustrated for example by U.S. Pat. No. 4,279,873, issued July 21, 1981 to Felsvang et al., which discloses spraying a suspension of fresh slaked lime and recycled fly ash plus spent calcium compound into the hot flue gas in such a manner as to evaporate the slurry droplets to dryness; the resulting powdered solids are removed from the flue gas by a downstream electrostatic precipitator or bag filter. U.S. Pat. No. 4,178,349, issued Dec. 11, 1979 to Wienert illustrates the dry treatment; it discloses mixing a dry, powdered lime-bearing material in a reactor, and subsequently separating the solids from the treated flue gas. Another example of a dry process is the flue gas desulfurization process set forth in U.S. Pat. No. 4,615,871 issued to Yoon which utilizes calcium formate to remove sulfur compounds from combustion exhaust gas in a dry treatment system. In doing so, a finely divided dry solid is formed and subsequently separated from the flue gas. However, systems employing dry injection FGD processes differ from that of wet calcium-based FGD processes in that it is necessary to control the humidity of the flue gas and consequently requires that the environment within the contact zone of the flue gas passage be maintained at a particular optimum level which is both costly and difficult to accomplish. Many additives have been proposed for improving the performance of various aspects of wet calcium based gas desulfurization (FGD) processes. For example, U.S. Pat. No. 4,670,236 issued to Thomas et al. introduces a 50:50 diisobutylene-maleic anhydride copolymer having an average molecular weight of 11,000, However, the introduction of diisobutylenemaleic anhydride does nothing to enhance the desulfurization of the flue gasses and only reduces the formation of calcium scale on the surfaces of the system to reduce maintenance costs. In U.S Pat. No. 4,454,101 issued to Garrison et al., relatively small amounts of a sodium thiosulfate additive or additives derived from or related to sodium thiosulfate are added into the scrubber liquid slurry. As a result, the thiosulfate ion alters the conglomerative characteristics of the spent slurry crystals making them settle from suspension faster and dewater more readily when filtered. However, the Garrison et al. process is not intended to improve the desulfurization process. Rather, it operates only to improve the dewatering capabilities of sulfite sludges from flue gas desulfurization facilities. Clearly, there is a pressing need for a flue gas desulfurization process which will improve the efficiency and cost effectiveness of wet, calcium-based FGD systems by reducing the sulfur dioxide content of flue gases being discharged into the atmosphere while minimizing the downtime and replacement costs necessitated by the formation of calcium scale within the system. Also, with the cost of chemical additives increasing, there is a need for a system which will effectively reduce the sulfur dioxide level of the flue gas while consuming a minimal amount of reactive chemical. Further, with the more stringent environmental restrictions which have been implemented by the Environmental Protection Agency, there is a need for a cost-effective and reliable wet, calcium-based flue gas desulfurization process which is capable of meeting current environmental standards. SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to overcome the shortcomings associated with those prior processes discussed above and to provide an improved, more reliable and cost efficient wet, calcium-based flue gas desulfurization process wherein the loss of formate in the form of precipitated solids from the system is reduced while also eliminating the potential for the formation of gypsum scale. Another object of the present invention is to provide a wet, calcium-based FGD process to which there is added an additive comprising formate ions and a dissolved calcium concentration reduction agent. Still another object of the present invention is to provide a flue gas desulfurization process which includes the addition of formate ions to the flue gas Which minimizes the quantity of formate which must be added to the system to maintain an optimal formate concentration. These, as well as other advantages of the present invention, are achieved by providing a flue gas desulfurization process including the step of adding to the flue gas an additive comprising formate ions and an agent which reduces the dissolved calcium concentration therein. Such an agent may include, but is not limited to, the soluble compounds of thiosulfate, magnesium, sodium and ammonium. In a preferred embodiment of the present invention, the additive comprises formate ions and thiosulfate ions. It has been found that each of these ions enhance the performance of the other, resulting in a reduction in the dissolved calcium concentration and consequently a reduction in formate coprecipitation. Moreover, it has been found that with the addition of thiosulfate, the coprecipitation of formate is reduced independent of the calcium concentration. Further objects of the subject invention will become apparent from the following description of the preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graphical illustration of the effect of the addition of both formate and thiosulfate on sulfur dioxide removal in wet, calcium-based flue gas desulfurization processes in accordance with the present invention FIG. 2 is a graphical illustration comparing formate coprecipitation as a function of formate activity product with the addition of thiosulfate vs. without the addition of thiosulfate. FIG. 3 is a graphical illustration of the relationship between formate concentration and the loss rate of formate in a wet, calcium-based flue gas desulfurization process for systems which include the addition of magnesium and systems which do not include the addition of magnesium. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A common by-product of electrical power generating plants which burn fossil fuels such as coal is a flue gas which contains dangerous amounts of sulfur dioxide. Inasmuch as environmental regulations restrict the discharge of the sulfur dioxide into the atmosphere, the flue gas must be treated to remove sulfur dioxide and other environmental contaminants. Most typically, the flue gas is directed from the combustion chamber where the burning occurs through heat recovery exchangers into the treatment zone and, following flue gas clean-up, by way of duct work to a stack where the cleaned flue gas is expelled into the atmosphere. Because this flue gas includes solid particles in the form of fly ash, the flue gas is initially treated for solids removal in any of several well known manners. This initial treatment removes only the solid particles and, consequently, the flue gas containing sulfur dioxide is unaffected thereby. It is the subsequent process for the removal of sulfur dioxide from the flue gas which constitutes the essence of the present invention. In accordance with the present invention, sulfur dioxide removal is accomplished in a wet, calcium-based flue gas desulfurization (FGD) process wherein a sulfur dioxide-containing flue gas is passed in contact with an aqueous calcium-bearing (e.g., calcium oxide or carbonate) scrubbing liquor whereby the sulfur dioxide is removed from the flue gas by being absorbed by the scrubbing liquor. An aqueous reagent slurry is sprayed into contact with the flue gas, for example by admixture with the liquor at a point downstream from the point at which the solid separation takes place and upstream of the flue gas discharge to the atmosphere. The solution useful in the present invention comprises both the formate ion (HCOO - which can be added as formic acid or a soluble salt of formic acid) and an ion of a dissolved calcium concentration reduction compound, such as thiosulfate ion (S 2 O 3 = added as a soluble salt of thiosulfate or formed insitu through the addition of elemental sulfur), magnesium ion, sodium ion, ammonium ion, or any other ionic agent which can be used to reduce the dissolved calcium concentration in a wet, calcium-based FGD system. Use of solutions such as are described hereinabove enhances, both the resultant performance and reliability of the flue gas desulfurization process and significantly reduces the cost of the process by virtue of minimizing the amount of formate added to the system. This is accomplished by reducing the dissolved calcium concentration which, in turn, reduces the calcium ion activity, reducing the calcium formate activity product and the corresponding rate of formate coprecipitation. Also, with the use of formate and thiosulfate, the formate coprecipitation is reduced independently of the calcium concentration as will be described in greater detail below. Inasmuch as the coprecipitation of calcium formate within the calcium sulfite crystal represents 70 to 90% of the nonsolution losses of formate from the system, it can be seen that reduction of dissolved calcium concentration is a key element in conserving formate within the system. Many additives have been proposed for improving the performance and/or reliability of wet, calcium based Flue Gas Desulfurization processes. However, as can be seen from the foregoing discussions, few of these additives have been considered for use in combination with one another. Moreover, the combination of additives in some instances may be detrimental to the performance and reliability of the wet, calcium-based flue gas desulfurization processes. As will be described in greater detail hereinbelow, the combination of particular additives herein-described have been found to both improve the performance of flue gas desulfurization processes as well as improve the reliability and economics of such processes while eliminating the potential for gypsum scaling for providing a substantially maintenance-free environment within the flue gas flow passages. It has been found that the use of sodium formate in combination with thiosulfate, magnesium, sodium, ammonium or any other additive which can be used to reduce the dissolved calcium concentration in a wet, calcium-based FGD system has proven to be more cost effective than using sodium formate alone. This is because the combination of sodium formate with these and other dissolved calcium concentration reducing agents has resulted in a significant reduction in the loss of sodium formate from the system due to coprecipitation of the compound. This discovery of the source of formate loss in FGD processes has resulted in the development of a process which, as described above, improves the performance, reliability and cost effectiveness of such processes. Sodium formate acts to buffer the pH in the FGD process in a range which promotes increased sulfur dioxide removal. At the same time, the additive which reduces the dissolved calcium concentration increases the solubility of the sulfite ion which also acts as a buffer. In the preferred embodiment, the additive comprises thiosulfate or emulsified elemental sulfur which will produce thiosulfate ions when added to wet, calcium-based FGD systems. In the presence of thiosulfate, the oxidation of sulfite ions to sulfate ions is inhibited. If the sulfite oxidation fraction can be reduced to less than 15 percent, it has been shown that the wet, calcium-based FGD system can be operated at a subsaturated level with respect to the formation of calcium sulfate dihydrate (gypsum scale). Operation of the FGD process in this manner eliminates the potential for the deposition of gypsum scale within the flue gas passages, a problem which often requires the system to be shut down for maintenance purposes and significantly affects the reliability of the FGD system. Further, with the sulfite oxidation fraction reduced to a level below 15 percent, the dissolved calcium concentration is also reduced. For systems with low dissolved chloride concentrations, the reduction in calcium concentration which occurs when sulfite oxidation is reduced represents a substantial reduction in the total dissolved calcium concentration. As will be seen more clearly hereinafter, this, in turn, aids in the performance and reliability of the FGD process. The most significant formate loss mechanism naturally oxidized, in wet, calcium-based FGD systems is the coprecipitation of calcium formate within the calcium sulfite crystal. It has been found that this loss represents between 70 and 90 percent of the nonsolution losses of formate from the system. The rate of formate coprecipitation is dependent on the calcium sulfite precipitation rate and on the activity product of calcium formate in the system. This activity product may be calculated as follows: Ca(HCOO).sub.2 activity product=(a.sub.Ca ++)×(a.sub.HCOO -).sup.2 where the a Ca++ is the activity of the calcium ion in the solution and a HCOO - represents the activity of the formate ion. This activity of the calcium ion is calculated directly using an FGD liquid phase equilibrium computer model and the activity of the formate ion is estimated from the product of the formate ion concentration and the chloride ion activity coefficient which is also calculated using the aforementioned computer model. The chloride activity coefficient is used to determine the activity of the formate ion because the computer model does not currently include formate ions and the chloride activity coefficient is directly proportionate thereto. With reference now to FIG. 1, it can be noted that the introduction of thiosulfate into the FGD process does not adversely affect the sulfur dioxide removal efficiency and in actuality enhances this removal process. This desired result will be discussed in greater detail with reference to the examples which follow. As can be seen from FIG. 2, the calcium formate coprecipitation rate per mole of calcium sulfite precipitated can change by a factor of five or more depending solely on the calcium formate activity product. This is illustrated by the upper curve of FIG. 2. Therefore, by reducing the calcium concentration and thus the calcium activity, the formate consumption rate can be reduced substantially. It should be noted from FIG. 2 that there is a significant reduction in formate coprecipitation with the use of thiosulfate. This may be due to the selective coprecipitation of calcium thiosulfate rather than calcium formate in the calcium sulfite crystal lattice, or perhaps a change in the morphology of the sulfite crystal in the presence of thiosulfate. Whichever scenario may apply, the resultant effect is significant and the loss of formate from the wet, calcium-based FGD system is reduced. It should be noted that the tests represented by FIG. 2 were carried out under constant calcium concentration levels. Significant benefits have been realized with the use of these additives in combination with one another. The addition of sulfur to a system already using formate in a wet, calcium-based flue gas desulfurization process can significantly reduce the quantity of formate which must be added to the system to maintain an optimal formate concentration level. This is brought about by the formation of thiosulfate which reduces the oxidation of sulfite ions to sulfate ions which in turn reduces the dissolved calcium concentration. Consequently, because it is the dissolved calcium concentration which reduces the formate concentration, a reduction of the dissolved calcium concentration in turn reduces the rate of formate loss from the system. Moreover, it has been found that through the use of formate and thiosulfate, formate coprecipitation is reduced independent of the calcium concentration level. As discussed previously, it is possible to reduce the calcium concentration in a wet, calcium-based FGD system by the use of additives which reduce such calcium concentration. These additives may include but are not limited to thiosulfate, magnesium, sodium or ammonium ions and may include such other ions as have been proven to reduce the calcium concentration in FGD processes. Their effect is to significantly reduce the formate coprecipitation rate when applied. In order that those skilled in the art to which the present invention pertains may better understand the present invention, it will now be particularly illustrated by the following examples which are shown only by way of illustration and are not to be limiting of the present invention. EXAMPLE I A conventional wet, calcium-based flue gas desulfurization process was run initially under baseline conditions; i.e., without additives. It can be noted from Table I that a baseline or constant run was performed to illustrate the significance of the addition of formate to the system. With the addition of Formate-01 (formate only), a significant increase in SO 2 removal is experienced (90%); however, the non-solution losses of formate in this system is also significant (1104 meq/hr). With the additive of Formate-02 (formate plug thiosulfate), the SO 2 removal rate was slightly enhanced while the formate non-solution loss amount dropped over 50% to 525 meq/hr. Therefore, by the addition of thiosulfate to a wet, calcium-based FGD process which utilizes formate for SO 2 removal, the consumption of formate can be significantly reduced. TABLE I______________________________________FORMATE/THIOSULFATE TEST RESULTS SUMMARYTEST ID Baseline Formate-01 Formate-02______________________________________Formate (ppm) 0 1785 1849Thiosulfate (ppm) 0 0 1376SO.sub.2 Removal (%) 74 90 91Utilization (%) 94 98 99Oxidation (%) 24 8 6Waste Solids (%) 55 55 70Non-Solution Loss -- 1104 525(meg/hr)______________________________________ EXAMPLE II As with the previous example, a conventional wet, calcium-based flue gas desulfurization process was run initially under baseline conditions (Test AD-1) as shown in Table II. Next, the system was run with the addition of formate, resulting in a substantial increase in the removal of SO 2 (Test AD-5). The system was also run with the addition of 500 ppm of thiosulfate (Test AD-11) which evidenced results similar to that discussed above. Subsequently, 1962 ppm of magnesium and sodium were added (Tests AD-15a and AD-15b) resulting in a significant decrease in the calcium concentration while increasing the SO 2 removal. Also tested was the addition of both thiosulfate and Magnesium (Test AD-17) the results of which are consistent with those previously discussed. TABLE II__________________________________________________________________________FORMATE/THIOSULFATE, FORMATE/MAGNESIUMTEST RESULTS SUMMARY SO.sub.2 Rem. Limestone Solids Gypsum CaSO.sub.3 Ca++ SO.sub.3 =. SO.sub.4 =.Test Description pH Eff. % Loading, g/l Ox. % R.S. R.S. mM mM mM__________________________________________________________________________AD-1 Baseline 5.7 77.0 5.5 27 0.66 3.03 25.5 6.6 38.2AD-5 30 mM Formate 5.7 87.7 6.0 13 0.44 2.18 14.0 8.0 43.6AD-11 60 mM Formate 5.7 90.5 4.1 8 0.14 2.00 6.2 16.6 35.3 500 ppm ThioAD- 30 mM Formate 5.7 91.0 4.4 8 0.19 1.86 5.2 26.2 85.715a 1962 ppm Added Mg and NaAD- 30 mM Formate 6.0 93.5 14.0 9 0.13 1.87 3.7 23.7 81.515b 1962 ppm Added Mg and NaAD-17 12 mM Formate 5.7 92.5 6.0 7 0.08 1.97 3.0 51.0 60.9 1000 ppm Thio 1510 ppm Added Mg and Na__________________________________________________________________________ As can be seen from FIG. 3, which is a graphical representation of formate loss rate as a function of formate concentration for various dissolved calcium concentration reduced agents, when read in conjunction with Table II, as the calcium concentration decreased, the loss rate of formate is reduced, resulting in a reduction in formate loss and, thus, in operating costs. It should be noted from the above examples that the reduction in formate loss is greater with the use of thiosulfate; however, any calcium reducing additive will reduce the formate loss to an appreciable degree. The particular amounts of formate and the calcium concentration reduction agent will be directly dependent upon the type of system, the environmental restrictions which are in effect in the operating area as well as the operating parameters of the system and the environmental effects on the system. These values need be determined on an application-by-application basis and will be readily ascertainable by one skilled in the art. Various additional calcium reducing additives may be used in addition to those mentioned above and will become apparent to those skilled in the art. Accordingly, the foregoing detailed description of the invention and examples are considered exemplary in nature, and it should be appreciated by those skilled otherwise than as specifically described herein without departing from the spirit and scope of the invention. It is, therefore, to be understood that the spirit and scope of the present invention be limited only by the appended claims.

A wet, calcium-based, flue gas desulfurization process for reliably and cost effectively removing sulfur dioxide from the flue gas generated by the combustion of fossil flues containing sulfur includes the step of contacting the combustion flue gas preferably as a part of the scrubbing liquor, with an aqueous solution containing formate ions and a dissolved calcium concentration reduction agent. The latter reduces the dissolved calcium concentration present in the flue gas which, in turn reduces the coprecipitation and loss of formate within and from the system. Also, by contacting the flue gas with an aqueous solution comprising formate and thiosulfate ions, the formate coprecipitation within the system is reduced independent of the calcium concentration level within the system.

BACKGROUND OF THE INVENTION This invention relates to a process for filling cavities, in particular the cavity between a conduit pipe and its jacket, with insulating material by introducing a liquid foamable reaction mixture, in particular one which forms a polyurethane foam, into the cavity. The apparatus used for this process consists of containers for the reactants from which pipes with pumps lead to a mixing head. It is known to fill narrow cavities and insulate pipe conduits by using a mixing head with an insertion lance which is pushed into the gap between a pipe and its jacket and to slowly withdraw the mixing head while the cavity is filled with the reaction mixture. Although this method ensures that the mixture will always be introduced at the correct position so that it flows directly to the points where it is required to foam up, such an apparatus is very inconvenient to handle and is only suitable for short pipes of up to about 5 meters in length. For longer pipes additional equipment is needed to support the lance. Additionally, the lance must not be too long because the reaction may start to take place in the lance. Another serious problem with this apparatus is the cleaning of the lance between the individual operations. The loss of material and time is relatively high and consequently the apparatus is uneconomical. It is therefore an object of this invention to provide a process which is suitable for filling longer cavities and which is designed such that the time at which the reaction mixture starts to react is accelerated from the beginning of the filling procedure to its end so that the mixture foams up simultaneously over the length of the cavity. The process may be employed, for example, for filling long, slender hollow bodies such as structural elements, safety planks or tubes with foam. When used for insulating pipes, the foam will adhere on all sides to both the pipe enclosed by it and to the jacket around it. In addition, the process should be applicable to seamless pipe jackets. STATEMENT OF THE INVENTION According to the invention, this problem is solved by introducing the reaction mixture through the outlet nozzle of a mixing head which is drawn lengthwise through the cavity by accelerating the reactivity of the reaction mixture during the filling procedure so that the mixture foams up simultaneously over the length of the cavity. This is caused by increasing the amount of catalyst in the reaction mixture. Apart from the insulating material based on polyurethane already mentioned above, the process may also be used for producing insulating materials based on polyester resins, phenol resins and epoxy resins. Thermoplasts containing blowing agents may also be used as insulating materials in this process by mixing the thermoplast with the blowing agent inside the mixing head. The hollow body is preferably kept inclined at an angle of about 3° to 20° during introduction of the mixture. This ensures that the air in the cavity can be expelled and that the mixture introduced into the cavity will not flow against the mixing head. An example of the apparatus according to the invention for carrying out the process comprises containers for the reactants, from which pipes with pumps connected along their lengths lead to a mixing head. A section of the pipes adjusted to the maximum length of a cavity which is to be filled with foam consists of flexible tubes and the mixing head is constructed as a carriage. A rigid bearing is preferably provided for the hollow body. The novelty of the apparatus is that the pump for the catalyst is supplied with a servomotor adapted to vary (accelerate) the throughput of the pump from the beginning of the filling procedure to its end. Instead of flexible tubes a section of the pipes adjusted to the maximum length of hollow body which is to be filled with foam may consist of a rigid transverse arm and may be provided with a displaceable bearing for the hollow body. In the first embodiment, the mixing head can be pulled through the hollow body. In the second embodiment, the bearing, together with the hollow body, is displaced during introduction of the reaction mixture. This embodiment is clearly not suitable for pipe conduits which have already been laid. In both cases, relative movement between the hollow body and the mixing head takes place. It is, therefore, in principle immaterial whether it is the mixing head or the hollow body which is displaced. In contrast to the known method of introducing the reaction mixture with a lance, in this process and apparatus the mixture is applied directly from the mixing head, i.e. immediately after mixing, to that position in the cavity where it is required to foam up. Long flow paths with superimposition of different layers resulting in an uneven foam are thereby avoided. The flexible tubes are preferably equipped with a winding device which can be driven at an adjustable velocity so that the rate of feed of the mixing head which consists of a carriage can be accurately adjusted and maintained constant during the foaming process. Alternatively, according to the second embodiment of the apparatus, the bearing for the hollow body can be driven at an adjustable velocity. The mixing head is preferably provided with rollers. But it may alternatively be equipped with skids. When insulating fairly short lengths of pipe, the pipe can be centered in the jacket at both ends. In the case of long pipes, the pipe and the jacket are liable to sag by different amounts if the pipe is centered only at the ends. The pipe is, therefore, preferably covered with spacer pins which are arranged so that they do not obstruct the movement of the mixing head. For example, they may be so arranged that there are three pins at intervals of 120° in one cross-section. The uppermost pin would then be placed vertically so that the lower part of the cavity is left free for the mixing head. The mixing head is in this case preferably provided with suitable chamfered surfaces so that in the event of contact with the pins it will be centered in the correct position. These spacer pins are preferably also made of insulating material or at least of material with a low thermal conductivity. They may be glued to the pipe or inserted in holders welded to the pipe. Considerable lengths of pipe or even pipes which have already been laid can be insulated with foam produced in situ by this method. Introduction of the mixing head with the flexible tubes into the pipe jacket is most simply achieved by holding the pipe and jacket obliquely and letting the mixing head slide into the cavity. It is also very advantageous to introduce the mixing head by securing it at the end of the conduit pipe which is to be introduced into the jacket and then pushing it into the jacket together with the pipe. At the end of the foaming process, it is then withdrawn by pulling it in the opposite direction. An apparatus for carrying out the process according to the invention is illustrated in the drawing and described below with reference to the example of filling a cavity between a conduit pipe and a jacket with foam. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of a first example of the apparatus, FIG. 2 is a rear view of the mixing head constructed as a carriage in a cavity between a conduit pipe and its jacket, FIG. 3 is a top plan view of the mixing head of FIG. 2, FIG. 4 is a schematic view of a second example of the apparatus. DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 to 3, the reactants flow from containers 1 and 2 through pipes 3 and 4 which contain pumps 5 and 6 to a winding device 7 for the flexible tubes 8 and 9. A catalyst flows from the container 10 through pipe 11 into pipe 4. The pump 12 is supplied with a servomotor adapted to vary the throughput during working. The pipes 3 and 4 open into this winding device 7, and the components enter their respective flexible tubes 8 and 9 through slide ring packings known per se. The winding device 7 is adapted to be driven by a drive 14 in such a manner that the mixing head 15 into which the tubes 8 and 9 open can be pulled at a uniform velocity. The mixing head 15 comprises a mixing chamber into which the components can be injected and an outlet nozzle 16 from which the finished mixture is ejected. In enters a cavity 17 which is enclosed by a conduit pipe 18 and a jacket 19 around it. This cavity 17 is filled with such a quantity of reaction mixture that it will be filled with insulating foam after completion of the reaction. The two pipes 18 and 19 are mounted on bearing blocks 20 in such a manner that they are inclined at an angle of between 3° and 20°. Supports 21 are welded to the conduit pipe 18 and spacer pins 22 are held in these supports (see FIG. 2). The mixing head 15 is equipped with wheels 23 which are mounted in such a manner that they automatically keep to their track when the mixing head is withdrawn. In FIG. 4, the reactants flow from the containers 24 and 25 through pipes 26 and 27 which contain pumps 28 and 29. The catalyst flows from container 30 through pipe 31 into pipe 27. The pump 32 is supplied with a servomotor 33 adapted to vary the throughput of the pump. The pipes 26 and 27 continue into a transverse arm 34 which is rigidly clamped in a bearing 35 and carries a slim mixing head 36 at its free end. The arm 34 with mixing head 36 extends into cavity 37 of a hollow body 30. The hollow body 38 rests on a displaceable bearing 39 which is equipped with a drive 40 and is displaced during introduction of the reaction mixture so that the hollow body is continuously filled with foam. While the invention has been described in conjunction with specific embodiments thereof, it is evident that other alternatives, modifications, and variations may be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and scope of the appended claims. EXAMPLE 1 By use of the aforementioned process and apparatus, an insulated pipe is produced. The pipe has a length of 3 m. The conveying (inner) pipe is of steel with 50.8 mm inner diameter and of 60.3 mm outer diameter. The jacket pipe is of rigid polyethylene with an outer diameter of 160 mm and an inner diameter of 141.8 mm. The thickness of insulation layer is about 40 mm and made of polyurethane with a density of 50 kg/m 3 . The following recipe was used: 100 parts by weight of a polyol formulation consisting of 80 parts by weight of polyether started on 1,1,1-trimethylolpropane (OH-number 550), 10 parts by weight of polyether started on ethylenediamine (OH-number 470), 10 parts by weight of 1,1,1-trimethylolpropane (OH-number 1250), 20 parts by weight of trichloro-ethylphosphate, 0.75 parts by weight of Na-salt of sulphonated castor oil, 0.75 parts by weight of water, 2 parts by weight of silicone stabilizer (L 520 of UNION CARBIDE CORPORATION); 20 parts by weight of blowing agent monofluortrichloro-methane; 1 part by weight of dimethylbenzylamine as catalyst; 130 parts by weight of polymethylene-polyphenyl-polyisocyanate, NCO-content of approximately 31%. The time for start of reaction was 16 sec., the reaction time 85 sec. A machine of the type HK 165 of MASCHINENFABRIK HENNECKE GMBH of St. Augustin, Federal Republic of Germany, was used. The machine has a total output of 18,900 g/min. The throughput of the polyol pump was 9,025 g/min, that of the catalyst pump 75 g/min and that of the isocyanate pump 9,800 g/min. The travel speed of the mixing head was 30 m/min. The time for filling the pipe with the reaction mixture was 6 sec. The advance movement of the mixing head was continuous. In view of the relative short length of the pipe, it was not necessary to change the activity of the reaction mixture during the filling procedure. EXAMPLE 2 The same process and apparatus as in Example 1 is used. The pipe has a length of 6 m. The conveying (inner) pipe is of steel with 77.2 mm inner diameter and 88.9 mm outer diameter. The jacket pipe is of rigid polyvinylchloride with 200 mm outer diameter and 192 mm inner diameter. The thickness of the insulation layer is 51.5 mm. The insulation material is polyurethane foam with a raw density of 45 kg/m 3 . The following recipe was used: 100 parts by weight of the polyol formulation described in Example 1; 25 parts by weight blowing agent monofluortrichloro-methane; 0.5 - 2 parts by weight of dimethylbenzylamine as catalyst (variable); 130 parts by weight of the isocyanate described in Example 1. The time for start of the reaction is 22 sec. with 0.5 parts by weight of catalyst and 10 sec. with 2 parts by weight. The reaction time is 100 sec. with 0.5 parts by weight of catalyst and 55 sec. with 2 parts by weight. The same machine as in Example 1 is used. The machine has a total output of 31,800 g/min, that of the polyol pump is 15,550 g/min, that of the catalyst pump is 62 to 248 g/min which is continuously variable. The isocyanate pump delivers 16,150 g/min. The travel speed of the mixing head is 30 m/min. The time for filling the pipe with the reaction mixture is 12 sec. The advance movement of the mixing head is continuous. To ensure that the reaction mixture foams up simultaneously the amount of catalyst is accelerated during the filling time from 0.5 to 2.0 parts by weight. The catalyst pump is supplied with a servomotor so that the output can be varied during the time of 12 sec. from 62 to 248 g/min. The pipe to be insulated is in horizontal position during the filling procedure. EXAMPLE 3 A security plank for highways of a metal sheet profile must be filled with polyurethane foam for stiffening. The length of the plank is 16 m; the free cross-section 415 cm 2 , the foam raw density is 40 kg/m 3 . The following recipe was used: 100 parts by weight of a polyol formulation consisting of 80 parts by weight of polyether started on 1,1,1-trimethylolpropane (OH-number 380), 10 parts by weight of polyether started on 1,1,1-trimethylolpropane and propanediol-(1,2) (OH-number 56), 10 parts by weight of trichloro-diphenylphosphate, 0.5 parts by weight of Na-salt of sulphonated castor oil, 0.5 parts by weight of water, 1 part by weight of silicone stabilizer; 30 parts by weight of blowing agent monofluortrichloromethane; 0.1 - 2.5 parts by weight of dimethylbenzylamine as catalyst (variable); 130 parts by weight of the isocyanate described in Example 1. The start time for reaction is 45 sec. with 0.1 parts by weight of catalyst and 8 sec. with 2.5 parts. The reaction time is 250 sec. with 0.1 parts by weight of catalyst and 37 sec. with 2.5 parts. The same type of foaming machine was used (HENNECKE HK 245). The total output was 43,500 g/min. The output of the polyol pump was 21,750 g/min, that of the catalyst pump 17 to 420 g/min (variable), that of the isocyanate pump 21 to 750 g/min. The travel speed of the mixing head is 25 m/min. The time for filling is 38 sec. The advance movement of the mixing head is continuous. The amount of catalyst is accelerated from 0.1 to 2.5 parts by weight. Therefore, the output of the amount of catalyst must be varied within 38 sec. from 17 to 420 g/min by the servomotor.

Cavities are filled with a foam insulating material by introducing the reaction mixture through the outlet nozzle of a mixing head which is drawn lengthwise through the cavity at a rate adapted to the rate of foaming, wherein the reactivity of the reaction mixture is accelerated during the filling procedure so that the reaction mixture is foaming up simultaneously over the length of the cavity.

CROSS REFERENCE TO RELATED APPLICATION This application is a continuation application of U.S. patent application Ser. No. 12/633,969, filed on Dec. 9, 2009, which is a divisional application of U.S. patent application Ser. No. 11/765,156, filed on Jun. 19, 2007, which claims priority to Korean Patent Application No. 10-2006-0057874, filed on Jun. 27, 2006, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lamp socket, a backlight assembly including the lamp socket, and a liquid crystal display including the backlight assembly. More particularly, the present invention relates to a lamp socket capable of easy assembly and a reduction in manufacturing costs, a backlight assembly including the lamp socket, and a liquid crystal display including the backlight assembly. 2. Description of the Related Art Liquid crystal displays are one of the most commonly used flat panel displays. Liquid crystal displays, which include two panels having a plurality of electrodes thereon and a liquid crystal layer interposed between the two panels, control the transmittance of incident light by applying voltages to the electrodes to rearrange liquid crystal molecules of the liquid crystal layer. The liquid crystal molecules may be oriented to allow light to pass therethrough, may be oriented to block light from passing therethrough, or may be oriented to allow only a portion of the light to pass therethrough. Liquid crystal displays include a backlight assembly for supplying light to the liquid crystal layer. The backlight assembly typically includes lamps, various types of optical sheets, and a housing unit for receiving the lamps and the optical sheets. Conventionally, sockets are used to fasten the lamps into the housing unit. With respect to conventional liquid crystal displays using a plurality of lamps arranged in an ordered fashion, an alignment plate is used for securing the sockets coupled with the lamps to the housing unit. The sockets are secured to the housing unit with an alignment plate after being inserted into holes formed in the housing unit. According to the above-described conventional liquid crystal displays, an alignment plate is separately used to secure sockets to a housing unit, thereby complicating the liquid crystal display assembly process. Furthermore, the arrangement of sockets may need to be changed according to the type of liquid crystal display used, which requires the fabrication of a new alignment plate configured for the arrangement of sockets, thereby resulting in an increase in both manufacturing costs and manufacturing time. BRIEF SUMMARY OF THE INVENTION The present invention provides a lamp socket capable of achieving easy assembling and a reduction in manufacturing costs. The present invention also provides a backlight assembly including the lamp socket. The present invention also provides a liquid crystal display including the backlight assembly These and other aspects of the present invention will be described in or be apparent from the following description of the exemplary embodiments. According to an exemplary embodiment of the present invention, a lamp socket includes a lamp connection unit which is electrically connected to a lamp, a power connection unit which is disposed below and adjacent to the lamp connection unit along a longitudinal axis and is electrically connected to an electric source which supplies power to the lamp, and a fastening member which is disposed on the power connection unit, wherein the power connection unit comprises at least one sub-component which has a surface area perpendicular to the longitudinal axis which is larger than the largest surface area of the lamp connection unit perpendicular to the longitudinal axis and wherein the sub-component of the power connection unit with the largest surface area perpendicular to the longitudinal axis is located proximate to the lamp connection unit. According to another exemplary embodiment of the present invention, a lamp socket includes a power connection unit which is electrically connected to an electric source which supplies power to a lamp, a lamp connection unit which is disposed above and adjacent to the power connection unit along a longitudinal axis and is electrically connected to the lamp, and a fastening member which is disposed on the lamp connection unit, wherein the lamp connection unit comprises at least one sub-component which has a surface area perpendicular to the longitudinal axis which is larger than the largest surface area of the power connection unit perpendicular to the longitudinal axis and wherein the sub-component of the lamp connection unit with the largest surface area perpendicular to the longitudinal axis is located proximate to the power connection unit. According to still another exemplary embodiment of the present invention, a backlight assembly includes at least one lamp, a housing unit which receives the at least one lamp and has socket holes corresponding to ends of the at least one lamp, and lamp sockets which are inserted into the socket holes and are connected to the lamps, wherein each of the lamp sockets comprises a lamp connection unit which is electrically connected to a lamp, a power connection unit which is disposed below and adjacent to the lamp connection unit along a longitudinal axis and is electrically connected to an electric source which supplies power to the lamp, and a fastening member which is disposed on the power connection unit and is secured to the socket hole, wherein the power connection unit comprises at least one sub-component which has a surface area perpendicular to the longitudinal axis which is larger than the largest surface area of the lamp connection unit perpendicular to the longitudinal axis and wherein the sub-component of the power connection unit with the largest surface area perpendicular to the longitudinal axis is located proximate to the lamp connection unit. According to a further exemplary embodiment of the present invention, a backlight assembly includes at least one lamp, a housing unit which receives the at least one lamp and has socket holes corresponding to ends of the at least one lamp, and lamp sockets which are inserted into the socket holes and are connected to the at least one lamp, wherein each of the lamp sockets comprises a power connection unit which is electrically connected to an electric source which supplies power to a lamp, a lamp connection unit which is disposed above and adjacent to the power connection unit along a longitudinal axis and is electrically connected to the lamp, and a fastening member which is disposed on the lamp connection unit and is secured to the socket hole, wherein the lamp connection unit comprises at least one sub-component which has a surface area perpendicular to the longitudinal axis which is larger than the largest surface area of the power connection unit perpendicular to the longitudinal axis and wherein the sub-component of the lamp connection unit with the largest surface area perpendicular to the longitudinal axis is located proximate to the power connection unite. According to yet another exemplary embodiment of the present invention, a liquid crystal display includes a liquid crystal panel which displays an image signal, and a backlight assembly including at least one lamp, a housing unit which receives the at least one lamp and has socket holes corresponding to ends of the at least one lamp, and lamp sockets which are inserted into the socket holes and are connected to the at least one lamp, wherein each of the lamp sockets comprises a power connection unit which is electrically connected to an electric source which supplies power to a lamp, a lamp connection unit which is disposed above and adjacent to the power connection unit along a longitudinal axis and is electrically connected to the lamp, and a fastening member which is disposed on the lamp connection unit and is secured to the socket hole, wherein the lamp connection unit comprises at least one sub-component which has a surface area perpendicular to the longitudinal axis which is larger than the largest surface area of the power connection unit perpendicular to the longitudinal axis and wherein the sub-component of the lamp connection unit with the largest surface area perpendicular to the longitudinal axis is located proximate to the power connection unit which supplies light to the liquid crystal panel. According to yet another exemplary embodiment of the present invention a method of manufacturing a lamp socket includes; forming a lamp connection unit which is electrically connected to a lamp, forming a power connection unit which is disposed below and adjacent to the lamp connection unit along a longitudinal axis and is electrically connected to an electric source which supplies power to the lamp, and forming a fastening member which is disposed on the power connection unit, wherein the forming a power connection unit comprises forming at least one sub-component to have a surface area perpendicular to the longitudinal axis which is larger than the largest surface area of the lamp connection unit perpendicular to the longitudinal axis and wherein the sub-component of the power connection unit with the largest surface area perpendicular to the longitudinal axis is formed proximate to the lamp connection unit. According to yet another exemplary embodiment of the present invention a method of manufacturing a lamp socket includes; forming a power connection unit which is electrically connected to an electric source which supplies power to a lamp, forming a lamp connection unit which is disposed above and adjacent to the power connection unit along a longitudinal axis and is electrically connected to the lamp, and forming a fastening member which is disposed on the lamp connection unit, wherein the forming a lamp connection unit comprises forming at least one sub-component to have a surface area perpendicular to the longitudinal axis which is larger than the largest surface area of the power connection unit perpendicular to the longitudinal axis and wherein the sub-component of the lamp connection unit with the largest surface area perpendicular to the longitudinal axis is formed proximate to the power connection unit. BRIEF DESCRIPTION OF THE DRAWINGS The above and other aspects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings in which: FIG. 1 is an exploded perspective view illustrating a first exemplary embodiment of a liquid crystal display according to the present invention; FIG. 2 is a top front perspective view illustrating a first exemplary embodiment of a lamp socket according to the present invention; FIG. 3 is a perspective view, as seen from below, of the exemplary embodiment of the lamp socket of FIG. 2 ; FIG. 4 is a top perspective view illustrating the assembly of an exemplary embodiment of a lower housing unit and a lamp with the exemplary embodiment of the lamp socket of FIG. 2 ; FIG. 5 is a front view illustrating an exemplary embodiment of a lower housing unit and the exemplary embodiment of the lamp socket of FIG. 2 , in an assembled state; FIG. 6 is a front perspective view, as seen from below, illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the exemplary embodiment of the lamp socket of FIG. 2 , in an assembled state; FIG. 7 is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the exemplary embodiment of the lamp socket of FIG. 2 in an assembled state; FIG. 8 is a front view illustrating an exemplary embodiment of a lower housing unit with a relatively thin thickness and an exemplary embodiment of the lamp socket of FIG. 2 , in an assembled state; FIG. 9A is a top front perspective view illustrating a second exemplary embodiment of a lamp socket according to the present invention; FIG. 9B is a front perspective view, as seen from below, of the exemplary embodiment of the lamp socket of FIG. 9A ; FIG. 9C is a front view illustrating an exemplary embodiment of a lower housing unit and the second exemplary embodiment of the lamp socket of FIG. 9A , in an assembled state; FIG. 9D is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the second exemplary embodiment of the lamp socket of FIG. 9A , in an assembled state; FIG. 10A is a top front perspective view illustrating a third exemplary embodiment of a lamp socket according to the present invention; FIG. 10B is a front perspective view, as seen from below, of the third exemplary embodiment of the lamp socket of FIG. 10A ; FIG. 10C is a front view illustrating an exemplary embodiment of a lower housing unit and the third exemplary embodiment of the lamp socket of FIG. 10A , in an assembled state; FIG. 10D is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the third exemplary embodiment of the lamp socket of FIG. 10A , in an assembled state; FIG. 11A is a top front perspective view illustrating a fourth exemplary embodiment of a lamp socket according the present invention; FIG. 11B is a front perspective view, as seen from below, of the fourth exemplary embodiment of the lamp socket of FIG. 11A ; FIG. 11C is a front view illustrating an exemplary embodiment of a lower housing unit and the fourth exemplary embodiment of the lamp socket of FIG. 11A , in an assembled state; FIG. 11D is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the fourth exemplary embodiment of the lamp socket of FIG. 11A , in an assembled state; FIG. 12A is a top elevated front perspective view illustrating a fifth exemplary embodiment of a lamp socket according to the present invention; FIG. 12B is a front perspective view, as seen from below, of the fifth exemplary embodiment of the lamp socket of FIG. 12A ; FIG. 12C is a front view illustrating an exemplary embodiment of a lower housing unit and the fifth exemplary embodiment of the lamp socket of FIG. 12A , in an assembled state; FIG. 12D is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the fifth exemplary embodiment of the lamp socket of FIG. 12A , in an assembled state; and FIG. 13A is a top front perspective view illustrating a sixth exemplary embodiment of a lamp socket according to the present invention; FIG. 13B is a front perspective view, as seen from below, of the sixth exemplary embodiment of the lamp socket of FIG. 13A ; FIG. 13C is a front view illustrating an exemplary embodiment of a lower housing unit and the sixth exemplary embodiment of the lamp socket of FIG. 13A , in an assembled state; and FIG. 13D is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the sixth exemplary embodiment of the lamp socket of FIG. 13A , in an assembled state. DETAILED DESCRIPTION OF THE INVENTION Aspects, advantages and features of the present invention and methods of accomplishing the same may be understood more readily by reference to the following detailed description of preferred embodiments and the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art, and the present invention will only be defined by the appended claims. Like reference numerals refer to like elements throughout the specification. It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Exemplary embodiments of the present invention are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments of the present invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, exemplary embodiments of the present invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present invention. A first exemplary embodiment of a lamp socket according to the present invention, an exemplary embodiment of a backlight assembly including the lamp socket, and an exemplary embodiment of a liquid crystal display including the backlight assembly will now be described more fully with reference to FIGS. 1 through 8 . FIG. 1 is an exploded perspective view illustrating a first exemplary embodiment of a liquid crystal display 100 according to the present invention. Referring to FIG. 1 , a liquid crystal display 100 includes a liquid crystal panel assembly 130 , a backlight assembly 140 , and an upper housing unit 110 . The liquid crystal panel assembly 130 includes a liquid crystal panel 136 including a thin film transistor (“TFT”) array panel 133 and a common electrode panel 134 , liquid crystals (not shown), gate tape carrier packages 131 , data tape carrier packages 132 , and a printed circuit board 135 . In the liquid crystal panel 136 , the TFT array panel 133 includes gate lines (not shown), data lines (not shown), an array of TFTs (not shown), pixel electrodes (not shown), and other various components. The common electrode panel 134 includes black matrices (not shown), a common electrode (not shown), and other various components, and is disposed opposite to the TFT array panel 133 . The gate tape carrier packages 131 are respectively connected to the gate lines in the TFT array panel 133 , and the data tape carrier packages 132 are respectively connected to the data lines in the TFT array panel 133 . In one exemplary embodiment driving devices for processing gate driving signals and data driving signals are mounted on the printed circuit board 135 to apply the gate driving signals and the data driving signals to the gate tape carrier packages 131 and the data tape carrier packages 132 , respectively. Alternative exemplary embodiments include configurations wherein the driving devices are mounted on the TFT array panel 133 . The backlight assembly 140 includes optical sheets 141 , an optical plate 142 , lamps 143 , and a reflective plate 144 . The lamps 143 may be light emitting diodes (“LEDs”), cold cathode fluorescent lamps (“CCFLs”), external electrode fluorescent lamps (“EEFLs”), or various other types of light emitting devices. The lamps 143 generate light using a lamp driving voltage applied to the lamps 143 from an external source (not shown). According to the present exemplary embodiment the lamps 143 are spaced apart from each other by a predetermined distance and positioned in parallel to each other in the same plane. The lamps 143 may form a structure which supplies light directly to the liquid crystal panel 136 . In order to achieve uniformity of brightness by uniformly distributing a discharge gas in the lamps 143 , the lamps 143 may be arranged horizontally with respect to the liquid crystal panel 136 . Lamp sockets 200 are securely inserted into socket holes 162 formed in a lower housing unit 160 . The lamp sockets 200 are positioned to correspond to end portions of the lamps 143 and securely support the lamps 143 . The lamp sockets 200 will be descried in more detail below. The optical plate 142 may be disposed on the lamps 143 , and serves to enhance the brightness uniformity of light generated from the lamps 143 . The optical plate enables a more uniform distribution of light to the liquid crystal panel 136 . The reflective plate 144 is disposed below the lamps 143 and reflects light upward from below the lamps 143 . In one exemplary embodiment the reflective plate 144 may be formed integrally with the bottom surface of the lower housing unit 160 . If the lower housing unit 160 is made of a highly reflective material, exemplary embodiments of which include aluminum (Al) or aluminum alloy, the lower housing unit 160 itself can serve as the reflective plate 144 . The optical sheets 141 are disposed on the optical plate 142 , and serve to diffuse and focus light coming from the lamps 143 . Exemplary embodiments of the optical sheets 141 include a diffusion sheet, a first prism sheet, a second prism sheet, and various other sheets with similar properties. In the exemplary embodiment wherein the optical sheets include a diffusion sheet, the diffusion sheet is disposed above the lamps 143 and serves to enhance the brightness and brightness uniformity of incident light from the lamps 143 . In the exemplary embodiment wherein the optical sheets include a prism sheet, the first prism sheet is disposed on the diffusion sheet. Exemplary embodiments of the prism sheet include triagonal prism patterns (not shown) uniformly arranged on a surface of the first prism sheet to focus light diffused from the diffusion sheet and to output the focused light. In one exemplary embodiment the first prism sheet may be a brightness enhancement film (“BEF”). In the exemplary embodiment wherein the optical sheets include a prism sheet the second prism sheet is disposed on the first prism sheet, and is a multi-layered, reflective, polarization prism sheet for focusing, polarizing, and outputting light. In one exemplary embodiment the second prism sheet may be a dual brightness enhancement film (“DBEF”). In the exemplary embodiment where the first prism sheet provides sufficient brightness and viewing angle, the second prism sheet may be omitted. The backlight assembly 140 includes a receiving frame 150 and the lower housing unit 160 for receiving the optical sheets 141 , the optical plate 142 , the lamps 143 , and the reflective plate 144 . The liquid crystal panel assembly 130 is disposed on the optical sheets 141 , and is received in the lower housing unit 160 in a state in which it is supported by the receiving frame 150 . The receiving frame 150 has sidewalls extending from the edges of a bottom surface. In one exemplary embodiment the receiving frame 150 is structured such that the liquid crystal panel assembly 130 can be supported by stepped portions or projections formed inside the sidewalls. The lower housing unit 160 has a substantially flat bottom surface, and receives the optical sheets 141 , the optical plate 142 , the lamps 143 , the reflective plate 144 , and the liquid crystal panel assembly 130 in an area defined by sidewalls extending from the edges of its bottom surface. The lower housing unit 160 also serves to prevent bending of the optical sheets 141 . In one exemplary embodiment the printed circuit board 135 of the liquid crystal panel assembly 130 is folded along an outer edge of the lower housing unit 160 so that it is disposed on a sidewall or a rear surface of the lower housing unit 160 . The shape of the lower housing unit 160 can be changed according to how the optical sheets 141 , the optical plate 142 , the lamps 143 , the reflective plate 144 , or the liquid crystal panel assembly 130 are placed in the lower housing unit 160 . The lower housing unit 160 is coupled to the upper housing unit 110 so that a periphery of an upper surface of the liquid crystal panel assembly 130 received in the lower housing unit 160 is covered. A window for exposing the liquid crystal panel assembly 130 to the outside is disposed on an upper surface of the upper housing unit 110 . Exemplary embodiments of the coupling between the upper housing unit 110 and the lower housing unit 160 can be accomplished by hooking (not shown) and/or screwing (not shown). The coupling between the upper housing unit 110 and the lower housing unit 160 may also be achieved in various other ways. Hereinafter, an exemplary embodiment of a lamp socket according to the present invention will be described in more detail with reference to FIGS. 2 through 7 . FIG. 2 is a top front perspective view illustrating a first exemplary embodiment of a lamp socket ( 200 ) according to the present invention, FIG. 3 is a front perspective view, as seen from below, of the exemplary embodiment of a lamp socket of FIG. 2 , FIG. 4 is a top front perspective view illustrating the assembly of an exemplary embodiment of the lower housing unit and a lamp with the exemplary embodiment of the lamp socket of FIG. 2 , FIG. 5 is a front view illustrating an exemplary embodiment of the lower housing unit and the exemplary embodiment of the lamp socket of FIG. 2 , in an assembled state, FIG. 6 is a front perspective view, as seen from below, illustrating an exemplary embodiment of the lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the exemplary embodiment of the lamp socket of FIG. 2 , in an assembled state, and FIG. 7 is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of the inverter printed circuit board, and the exemplary embodiment of the lamp socket of FIG. 2 , in an assembled state. First, referring to FIGS. 2 and 3 , together with FIG. 1 , the lamp socket 200 includes a lamp connection unit 210 which is electrically connected to the lamp 143 , a power connection unit 220 which is disposed below the lamp connection unit 210 and electrically connected to a power source (not shown) for supplying power to the lamp 143 , and a fastening member 230 , which is disposed on the power connection unit 220 at the boundary between the lamp connection unit 210 and the power connection unit 220 and secures the lamp socket 200 to the lower housing unit 160 . The lamp connection unit 210 includes a first housing 212 made of an insulating material, a guide groove 214 formed in the first housing 212 to permit the lamp 143 to be inserted into the first housing 212 , and a lamp connection terminal 216 to electrically connect to the lamp 143 . The lamp connection terminal 216 has a pair of convexly curved opposing surfaces and is made of a conductive material. The lamp connection terminal 216 is electrically connected to the lamp 143 by elastically and securely gripping the lamp 143 . The power connection unit 220 includes a stepped structure protruding outwardly with respect to the lamp connection unit 210 and adjoining the lamp connection unit 210 . The power connection unit 220 may be electrically connected to an inverter printed circuit board for supplying power. In more detail, the power connection unit 220 includes a light-shielding plate 222 constituting the bottom portion of the stepped structure, a board support 224 disposed below the light-shielding plate 222 , a second housing 226 disposed below the board support 224 , and a power connection terminal 228 which is disposed in the second housing 226 and electrically may be connected to the inverter printed circuit board. The light-shielding plate 222 adjoins the lamp connection unit 210 and constitutes the bottom portion of the stepped structure. The fastening member 230 is disposed on the side of the light-shielding plate opposite the board support. The fastening member 230 extends upward away from the stepped structure of the power connection unit 220 . Therefore, as shown in FIGS. 4 and 5 , the lamp socket 200 can be easily and securely inserted into the socket hole 162 of the lower housing unit 160 using the fastening member 230 disposed on the light-shielding plate 222 without using an additional fastener. In one exemplary embodiment the fastening member 230 may have a hook-like shape with an outwardly protruding portion. One or more fastening members may be disposed on the light-shielding plate 222 . In the present exemplary embodiment, two fastening members are disposed to be opposite to each other with respect to the lamp connection unit 210 . Alternative exemplary embodiments include configurations wherein only one fastening member 230 or more than two fastening members 230 are used. Meanwhile, in order to prevent external light from passing through the socket hole 162 , light-shielding plate 222 may have a larger area than the socket hole 162 . As shown in FIGS. 6 and 7 , a portion of the inverter printed circuit board is inserted into the power connection terminal 228 disposed in the second housing 226 , and the power connection terminal 228 is electrically connected to the lamp connection terminal 216 through the pair of convexly curved opposing surfaces made of a conductive material which run internally through the lamp socket down from the lamp connection terminal in the lamp connection unit to the power connection terminal in the power connection unit. Thus, lamp power from the inverter printed circuit board is supplied through the power connection terminal 228 and the lamp connection terminal 216 and into the lamp 143 . The board support 224 interposed between the power connection terminal 228 and the light-shielding plate 222 serves to support the inverter printed circuit board inserted into the power connection terminal 228 . Referring again to FIGS. 4 and 5 , when the lamp socket 200 is inserted upward into the socket hole 162 , it is secured to the lower housing unit 160 by the fastening member 230 disposed on the power connection unit 220 . The lamp connection unit 210 of the lamp socket 200 is disposed inside the lower housing unit 160 , and the power connection unit 220 of the lamp socket 200 is disposed outside the lower housing unit 160 . Next, the lamp 143 is inserted into the lamp connection unit 210 , which has been insertedly disposed in the lower housing unit 160 , to electrically connect the lamp 143 to the lamp connection unit 210 . The lamp 143 includes a lamp tube 320 internally coated with a fluorescent material and lead lines 310 connected to both ends of the lamp tube 320 . Exemplary embodiments of the fluorescent material coated in the lamp tube 320 include a rare earth element with high fluorescence efficiency, e.g., yttrium (Y), cerium (Ce), or terbium (Tb). In one exemplary embodiment the lamp 143 may be a three-wavelength type fluorescent lamp made of red, green, and blue fluorescent materials. The lead lines 310 supply an external power to electrodes (not shown) disposed inside the lamp tube 320 . When the lamp tube 320 of the lamp 143 is inserted along the guide groove 214 of the lamp connection unit 210 , the lamp connection terminal 216 of the lamp connection unit 210 is connected to the lead line 310 of the lamp 143 . Referring to FIGS. 6 and 7 , with respect to the lamp socket 200 securely inserted into a socket hole 162 by the fastening member 230 , a pad 410 of an inverter printed circuit board 400 disposed below the lower housing unit 160 is electrically connected to the lamp socket 200 by inserting the pad 410 into the power connection terminal 228 of the lamp socket 200 . Heat may be generated from any of several devices (e.g., a transformer) mounted on the inverter printed circuit board 400 . Thus, the inverter printed circuit board 400 may be disposed to be separated from the lower housing unit 160 by a predetermined distance. Accordingly, the power connection terminal 228 connected to the pad 410 of the inverter printed circuit board 400 may be disposed to be separated from the light-shielding plate 222 by a predetermined distance determined by the spacing between the lower housing unit 160 and the inverter printed circuit board 400 . Furthermore, in order to support the inverter printed circuit board 400 inserted into the power connection terminal 228 , the board support 224 may be interposed between the power connection terminal 228 and the light-shielding plate 222 . In addition, an auxiliary projection 165 for supporting the inverter printed circuit board 400 may be disposed on a lower surface of the lower housing unit 160 . In another exemplary embodiment, the auxiliary projection 165 may be disposed on an upper surface of the inverter printed circuit board 400 . Hereinafter, the application of a lamp socket to different types of lower housing units with different thicknesses will be described with reference to FIGS. 5 and 8 . FIG. 8 is a front view illustrating an exemplary embodiment of a lower housing unit having a relatively thin thickness and an exemplary embodiment of the lamp socket of FIG. 2 , in an assembled state. First, referring to FIG. 5 illustrating the lamp socket 200 securely inserted into the socket hole 162 of the lower housing unit 160 , the position of a protruding portion of the fastening member 230 is determined by the thickness d 1 of the lower housing unit 160 . In the exemplary embodiment shown in FIG. 8 , when the lamp socket 200 is inserted into a lower housing unit 160 ′ with a thinner thickness d 2 than the thickness d 1 , the thickness d 2 of the lower housing unit 160 ′ is thinner than a gap between the protruding portion and the light-shielding plate 222 , and thus, the lamp socket 200 may not be secured to the lower housing unit 160 ′. In this regard, as shown in FIG. 8 , an embossing 164 is formed around a socket hole 162 of the lower housing unit 160 ′, to enable the lamp socket 200 to be securely fastened to the lower housing unit 160 ′. The first housing 212 , the light-shielding plate 222 , the board support 224 , and the second housing 226 constituting the lamp connection unit 210 or the power connection unit 220 have been separately described and can be formed separately as in the above-described exemplary embodiment of the present invention. However, alternative exemplary embodiments include configurations wherein all or some of the components constituting the lamp connection unit 210 or the power connection unit 220 may also be formed integrally with each other. Hereinafter, a second exemplary embodiment of a lamp socket according to the present invention will be described in more detail with reference to FIGS. 9A through 9D . FIG. 9A is a top front perspective view illustrating a second exemplary embodiment of a lamp socket 500 according to the present invention, FIG. 9B is a front perspective view, as seen from below, of the exemplary embodiment of a lamp socket of FIG. 9A , FIG. 9C is a front view illustrating an exemplary embodiment of a lower housing unit and the second exemplary embodiment of the lamp socket of FIG. 9A , in an assembled state, and FIG. 9D is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the second exemplary embodiment of the lamp socket of FIG. 9A , in an assembled state. For convenience of illustration, the same functional elements as those in the first exemplary embodiment, shown in FIGS. 2 through 8 , are represented by the same reference numerals, and thus, a detailed description thereof will be omitted. The second exemplary embodiment of a lamp socket of the present invention has substantially the same structure as that of the first exemplary embodiment of the present invention except for the points described below. Referring to FIGS. 9A through 9D , a power connection unit 520 of a second exemplary embodiment of a lamp socket 500 includes a light-shielding plate 522 which constitutes a stepped structure protruding outwardly with respect to a lamp connection unit 210 and adjoining the lamp connection unit 210 , a second housing 226 which is disposed on a lower surface of the light-shielding plate 522 , and a power connection terminal 228 which is disposed in the second housing 226 and which may be electrically connected to an inverter printed circuit board 400 . A fastening member 230 is disposed on the light-shielding plate 522 . When the second exemplary embodiment of a lamp socket 500 is inserted into a socket hole 162 , the light-shielding plate 522 can serve to prevent the incidence of external light through the socket hole 162 . The second exemplary embodiment of a lamp socket 500 is structured such that the light-shielding plate 522 supports the inverter printed circuit board 400 . This second exemplary embodiment differs from the first exemplary embodiment in that the light-shielding plate 522 provides support for the inverter printed circuit board 400 , whereas the first exemplary embodiment requires a board support 224 to perform the same function. Hereinafter, a third exemplary embodiment of a lamp socket according to the present invention will be described in more detail with reference to FIGS. 10A through 10D . FIG. 10A is a top front perspective view illustrating a third exemplary embodiment of a lamp socket 600 according to the present invention, FIG. 10B is a front perspective view, as seen from below, of the third exemplary embodiment of the lamp socket of FIG. 10A , FIG. 10C is a front view illustrating an exemplary embodiment of a lower housing unit and the third exemplary embodiment of the lamp socket of FIG. 10A , in an assembled state, FIG. 10D is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the third exemplary embodiment of the lamp socket of FIG. 10A , in an assembled state. For convenience of illustration, the same functional elements as those in the first exemplary embodiment, shown in FIGS. 2 through 8 , are represented by the same reference numerals, and thus, a detailed description thereof will be omitted. The third exemplary embodiment of a lamp socket of the present invention has substantially the same structure as that of the first exemplary embodiment of the present invention except for the points described below. Referring to FIGS. 10A through 10D , a power connection unit 620 of a third exemplary embodiment of a lamp socket 600 includes a second housing 626 which protrudes outwardly with respect to a lamp connection unit 210 and adjoins the lamp connection unit 210 , and a power connection terminal 228 which is disposed in the second housing 626 and may be electrically connected to an inverter printed circuit board 400 . A fastening member 230 is disposed on the second housing 626 . When the third exemplary embodiment of a lamp socket 600 is inserted into a lamp hole 162 , the second housing 626 can serve to prevent the incidence of external light through the socket hole 162 . The third exemplary embodiment of a lamp socket 600 is structured such that the second housing 626 supports the inverter printed circuit board 400 . This third exemplary embodiment of a light socket 600 differs from the first exemplary embodiment of a light socket 200 in that the second housing 626 provides support for the inverter printed circuit board 400 , whereas the first exemplary embodiment of a light socket 200 requires a board support 224 to perform the same function. Hereinafter, a fourth exemplary embodiment of a lamp socket according to the present invention will be described in more detail with reference to FIGS. 11A through 11D . FIG. 11A is a top front perspective view illustrating a fourth exemplary embodiment of a lamp socket 700 according to the present invention, FIG. 11B is a front perspective view, as seen from below, of the fourth exemplary embodiment of a lamp socket of FIG. 11A , FIG. 11C is a front view illustrating an exemplary embodiment of a lower housing unit and the fourth exemplary embodiment of the lamp socket of FIG. 11A , in an assembled state, and FIG. 11D is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the fourth exemplary embodiment of the lamp socket of FIG. 11A , in an assembled state. For convenience of illustration, the same functional elements as those in the first exemplary embodiment shown in FIGS. 2 through 8 , are represented by the same reference numerals, and thus, a detailed description thereof will be omitted. The fourth exemplary embodiment of a lamp socket of the present invention has substantially the same structure as that of the first exemplary embodiment of the present invention except for the points described below. Referring to FIGS. 11A through 11D , a fourth exemplary embodiment of a lamp socket 700 includes a power connection unit 720 which is electrically connected to an inverter printed circuit board 400 , a lamp connection unit 710 which is disposed on the power connection unit 720 and electrically connected to a lamp (not shown), and a fastening member 230 , disposed on the lamp connection unit 710 at a border between the lamp connection unit 710 and the power connection unit 720 , securing the lamp socket 700 to a lower housing unit 160 . In more detail, the lamp connection unit 710 includes a stepped structure protruding outwardly with respect to the power connection unit 720 and adjoining the power connection unit 720 . In more detail, the lamp connection unit 710 includes a light-shielding plate 718 constituting the widest part of the stepped structure, and a first housing 212 disposed on the light-shielding plate 718 . The first housing 212 has a guide groove 214 and a lamp connection terminal 216 . The power connection unit 720 includes a board support 224 which is connected to the lamp connection unit 710 , a second housing 226 which is disposed on the board support 224 , and a power connection terminal 228 which is disposed in the second housing 226 and may be electrically connected to the inverter printed circuit board 400 . The light-shielding plate 718 adjoins the power connection unit 720 . The fastening member 230 is disposed on the lamp connection unit 710 . The fastening member 230 extends downward from the side of the light-shielding plate 718 opposite the lamp connection unit 710 . Therefore, the fourth exemplary embodiment of a lamp socket 700 can be easily and securely inserted into a socket hole 162 of the lower housing unit 160 using the fastening member 230 disposed on a lower surface of the light-shielding plate 718 without using an additional fastener. Meanwhile, when the fourth exemplary embodiment of a lamp socket 700 is inserted into the lamp hole 162 , the light-shielding plate 718 may have a larger area than the socket hole 162 to prevent external light from becoming incident on the liquid crystal panel 136 . The fourth exemplary embodiment of a lamp socket 700 is inserted downward into the socket hole 162 , it is secured to the lower housing unit 160 by the fastening member 230 disposed on the lower surface of the lamp connection unit 710 . The lamp connection unit 710 of the fourth exemplary embodiment of a lamp socket 700 is disposed inside the lower housing unit 160 , and the power connection unit 720 of the lamp socket 700 is disposed outside the lower housing unit 160 . According to the fourth exemplary embodiment of a lamp socket 700 of the present invention, the fastening member 230 is disposed on a lower surface of the light-shielding plate 718 and the light-shielding plate 718 is disposed inside the lower housing unit 160 . Even though the insertion direction of the lamp socket 700 into the lower housing unit 160 is opposite to that of the first exemplary embodiment of the present invention, the fourth exemplary embodiment of a lamp socket 700 of the present invention can provide substantially the same functions and effects as that of the first exemplary embodiment of the present invention. Hereinafter, a fifth exemplary embodiment of a lamp socket according to the present invention will be described in more detail with reference to FIGS. 12A through 12D . FIG. 12A is an elevated front perspective view illustrating a fifth exemplary embodiment of a lamp socket 800 according to the present invention, FIG. 12B is a front perspective view, as seen from below, of the fifth exemplary embodiment of a lamp socket of FIG. 12A , FIG. 12C is a front view illustrating an exemplary embodiment of a lower housing unit and the fifth exemplary embodiment of the lamp socket of FIG. 12A , in an assembled state, and FIG. 12D is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the fifth exemplary embodiment of a lamp socket of FIG. 12A , in an assembled state. For convenience of illustration, the same functional elements as those in the fourth exemplary embodiment are represented by the same reference numerals, and thus, a detailed description thereof will be omitted. The lamp socket of the fifth exemplary embodiment of the present invention has substantially the same structure as that of the fourth exemplary embodiment of the present invention except for the points described below. Referring to FIGS. 12A through 12D , a power connection unit 820 of a fifth exemplary embodiment of a lamp socket 800 includes a second housing 826 which is connected to a lamp connection unit 710 , and a power connection terminal 228 which is disposed in the second housing 826 and may be electrically connected to an inverter printed circuit board 400 . The fifth exemplary embodiment of a lamp socket 800 is structured such that the power connection terminal 228 of the power connection unit 820 may provide support for supporting the inverter printed circuit board 400 . This fifth exemplary embodiment of a lamp socket 800 differs from the sixth exemplary embodiment of a lamp socket 700 in that a separate board support 224 is not provided. Hereinafter, a sixth exemplary embodiment of a lamp socket according to the present invention will be described in more detail with reference to FIGS. 13A through 13D . FIG. 13A is a top front perspective view illustrating a sixth exemplary embodiment of a lamp socket 900 according to the present invention; FIG. 13B is a front perspective view, as seen from below, of the sixth exemplary embodiment of a lamp socket of FIG. 13A ; FIG. 13C is a front view illustrating an exemplary embodiment of a lower housing unit and the sixth exemplary embodiment of a lamp socket of FIG. 13A , in an assembled state, and FIG. 13D is a side view illustrating an exemplary embodiment of a lower housing unit, an exemplary embodiment of an inverter printed circuit board, and the sixth exemplary embodiment of the lamp socket of FIG. 13A , in an assembled state. For convenience of illustration, the same functional elements as those in the fourth exemplary embodiment, as shown in FIGS. 11A through 11D , are represented by the same reference numerals, and thus, a detailed description thereof will be omitted. The sixth exemplary embodiment of a lamp socket of the present invention has substantially the same structure as that of the fourth exemplary embodiment of the present invention except for the points described below. Referring to FIGS. 13A through 13D , a lamp connection unit 910 of a sixth exemplary embodiment of a lamp socket 900 includes a first housing 912 made of an insulating material, which constitutes a stepped structure protruding outwardly with respect to a power connection unit 720 and adjoining the power connection unit 720 , and a guide groove 214 and a lamp connection terminal 216 which are formed in the first housing 912 . The lamp socket 900 is structured to prevent the incidence of external light through a socket hole 162 by disposing the first housing 912 around the socket hole 162 . This sixth exemplary embodiment of a lamp socket 900 prevents the incidence of external light without using a light-shielding plate as shown in the previous exemplary embodiments (the third exemplary embodiment of the lamp socket 600 shown in FIGS. 10A-10D also blocks the incidence of external light to the liquid crystal panel 136 without using a separate light-shielding plate, but does so using an enlarged second housing 626 ). As described above, a lamp socket according to the present invention can be easily assembled with a backlight assembly, can be applied to various types of liquid crystal displays, and can reduce the manufacturing costs of liquid crystal displays. While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. It is therefore desired that the present exemplary embodiments be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than the foregoing description to indicate the scope of the present invention.

A lamp socket includes a lamp connection unit which is electrically connected to a lamp, a power connection unit which is disposed below and adjacent to the lamp connection unit along a longitudinal axis and is electrically connected to an electric source which supplies power to the lamp, and a fastening member which is disposed on the power connection unit, wherein the power connection unit comprises at least one sub-component which has a surface area perpendicular to the longitudinal axis which is larger than the largest surface area of the lamp connection unit perpendicular to the longitudinal axis and wherein the sub-component of the power connection unit with the largest surface area perpendicular to the longitudinal axis is located proximate to the lamp connection unit.

FIELD OF THE INVENTION The invention which is the subject of this application relates to apparatus for a toy which allows an article such as, but not exclusively, a model of a person, an animal or the like, to be moved around a play base and environment created thereon without any direct physical force being applied thereto. BACKGROUND OF THE INVENTION Conventionally it is known for toys to be movable and it is easily understood that movement of toys renders the same significantly more attractive to children. This attractiveness is further enhanced if the movement of the article, such as a model of a human character, is not directly controlled in that the child does not have to physically touch the model. For this reason puppets which are controlled by strings are attractive to children and also give the child a degree of fascination and the models a life like quality. The problem with puppets however is that the control strings can become tangled or break and furthermore the ability to incorporate the same into particular environments or to produce the same on a small scale is limited due to the requirement to have no barriers over the puppet so that the strings can be freely moved and if the model is too small the complexity of the controls is too great. A further method for providing movement is to provide the model to be movable along a base having a predefined track such that the model can be slid along the track to move in a predefined and selected direction or path. The main disadvantage with this arrangement is that the model can only ever move in a predefined path and therefore the toy soon loses its appeal to children as their interest level wanes. Also known is the ability to provide a model with a magnet and to provide a control means with a magnet and to use the magnetic field to cause movement of the model by movement of one or both of the magnets. However, the movement in these conventional toys is only movement of the model while the model remains at the same point on the toy base. SUMMARY OF THE INVENTION The aim of the present invention is to provide a toy which includes an article which is movable around an environment created on a base along which the article moves in a selected but not predetermined path without the need for physical contact with the article by the child. A further aim is to provide a control means for the movement of the article which is arranged to be controlled for movement from a point remote to the article and also to provide the control means with mechanical advantage thereby increasing the scope of movement of the article. In a first aspect of the invention there is provided apparatus for a toy, said apparatus comprising a play base of substantially planar material having a first, upper side along which an article is provided for movement and on the second, under, side, control means for movement of the article and wherein the article includes mounted therein at least a first magnet and the control means includes at least a second magnet and said first or second magnet is arranged to be movable relative to the other magnet to cause the article to move along the base in a selected direction by selected movement of the control means. Typically the relative movement of the magnets is arranged such that the condition of the magnetic field between said magnets changes during movement and thus creates movement of the article in addition to the movement of the article along the base. It should be noted that it may be possible that one of the first or second magnets is replaced by a magnetically attracted material and reference hereonin to magnets includes this arrangement. In one embodiment the condition of the magnetic field is altered by the movement of the magnet such that the first or second magnet is moved to position the same to have a peak polar strength at one instant when the particular magnet pole is positioned close to the underside of the play base and a minimum polar strength when the particular magnet pole is positioned at the furthest possible point away from the other magnet. Movement between the peak and minimum positions is preferably of substantially constant speed and the variation between peak and minimum conditions is sufficient to cause a visual effect on the movement of the article but is always sufficiently strong to allow the article to be magnetically attracted to stay on the surface of the base so that it continues to be moved along the base. By rotating the magnet said peak and minimum conditions are repeated for each polarity of the magnet in turn and in one embodiment the magnet is arranged such that there is never a sole north or south polarity acting on the other magnet. Thus the extent of the effect on the article can be controlled by controlling the extent of change between north and south polarity of the magnet as it rotates and this can be achieved by determining the angle of the magnet relative to the axis of rotation. The movable magnet may also, or alternatively, be provide to rotate relative to the other magnet such that the polarity of the moving magnet changes more quickly and to a greater extent between poles relative to the other magnet thereby creating a greater visual effect on the movement of the article. In certain arrangements it is possible that both the first and second magnets can be arranged to rotate. In whichever arrangement it is envisaged that the magnet which is movable is preferably mounted on the control means and is provided to rotate as the control means moves along or adjacent to the underside of the base and as it does so causes the at least first magnet and hence the article to which it is attached to move along the upper surface of the play base. In one embodiment the control means comprises a roller upon which a disc magnet is mounted at an angle to the axis of rotation of the roller which is in itself substantially parallel with the base. Thus as the roller rotates so the position of the poles of the disc magnet to the base and hence the article on the other side of the base alters and so the condition of the magnetic field alters on an alternating basis. The roller on which the magnet is mounted is driven via a gear arrangement by movement of the control means along the underside of the play base and typically a second roller with a sleeve which contacts the play base is provided and the roller is connected to the magnet roller to turn the same and said magnet and second rollers are mounted in a common bracket. Preferably a resilient member acts on the bracket to bias the sleeve on the roller into contact with the base underside and said resilient member, magnet and second rollers are mounted in a housing which in turn is connected via an arm to a lever and disc drive arrangement, typically a pantograph arrangement, which allows control of the movement of the magnet relative to the base, from a common single position. Typically the control means is provided in a form which provides mechanical advantage to the article movement. Typically the toy is provided with a cover which encloses the control means between said cover and the underside of the play base. Typically the cover also includes raised protrusions which act as guide means for the area of movement of the housing and in particular a pin protruding below the housing. Typically said protrusions are linked to the position of objects on the upper side of the base and in relation to which the article is movable. By providing the pin to contact the protrusions rather than the housing so the position of the article on the play base can be more accurately determined and more finely controlled. This is especially important where the article is required to pass along relatively narrow spaces and said control is further improved by providing the pin directly below the position of the magnet of the control means. Alternatively the magnet on the control means can be arranged with an axis of rotation such that the polarity of the magnet acting on the magnet or magnets in the article alternates between substantially wholly North and South poles as the magnet rotates. In a further aspect of the invention there is provided an article for a toy, said article arranged for movement along a base and wherein said article is provided with at least one magnet mounted thereon and is movable along said play base by control means arranged to operate under the play base and physically separate from the article by said base, said control means including at least a second magnet and movement of the control means causes the article to move under the influence of the magnetic field created between the article and control means. In one arrangement the article is a human character or an animal and the at least first magnet is mounted in the area of the article depicting the feet of the same. In one preferred embodiment the article is provided with two, separate, legs and at the base of each leg there is provided a magnet. Typically the magnets are arranged so that one of the magnets has a north polarity adjacent the base and the other has a south polarity adjacent the base. Typically the legs are rigidly interconnected with the ends of the same, in one embodiment, lying in the same plane or alternatively, arranged such that when one of the legs is in contact with the base the end of the other leg lies out of contact and at an angle to the base so that when the article moves alternate leg ends contact the base and thereby mimic a walking effect. By providing the magnets with opposite polarities so the walking effect is increased as, as one magnet is attracted to the magnet of the control means at any one instant so the other magnet is being repelled at that instant. The extent of attraction and repulsion is dependent upon the relative position of the control means at that instant. In one arrangement the body and/or head portions of the article are pivotally mounted on the legs portion of the article such that as the legs move so the body and/or head portion can rotate freely or at least between designated end positions thereby enhancing the walking effect when the same moves. Typically the article is a model and may be as small as 10-20 mm in height and preferably the play base is provided on its upper side with a model environment into and through which the article can be moved by the control means as described previously. It is also possible that the control means can be used to manipulate and move items in the environment and this is described in the applicant's co-pending application. In a further aspect of the invention there is provided a toy including an article provided with a base portion to be movable along a playbase and a control means including a housing with, mounted therein, at least one magnet with one designated pole facing towards the underside of said playbase and said article including first and second magnets mounted in or adjacent to the base portion of the same each arranged with the opposing pole to that of the first designated pole lying closest to the playbase in use. Typically the magnet in the housing is mounted to be movable between a first position in contact with the underside of the playbase and a second position withdrawn from contact with the underside. The magnet is arranged to be drawn to the first position by attraction of the magnet to the magnets on the article on the top side of the playbase thereby allowing the movement assembly to influence the movement of the article thereafter and withdrawn from contact with the underside due to lack of attraction. Preferably the article includes a third magnet arranged to the rear of and preferably intermediate the first and second magnets relative to the direction of movement of the article and is of reverse polarity to the first and second magnets. Preferably the underside of the base portion is angled and in one embodiment portions of said base portion are arranged to lie at substantially equal but opposing angles relative to the playbase. The first and second magnets can be arranged to lie at equal but opposing angles relative to the playbase and especially if they form the underside of the base portion which contacts with the playbase. The provision of the base in the angled configuration causes movement of the object parts from and to the playbase as the article moves therealong thereby mimicking a walking effect. In a further aspect of the invention there is provided an article for use to be moved along a playbase of a toy and wherein said article comprises at least two parts, a base portion on which is mounted an upper part and said upper part is pivotally mounted on said base part to allow relative pivotal movement between said parts and thereby provide axial articulation of the same. In one embodiment the base portion is provided with a relatively narrow upstanding portion and onto the top face of which a face of an interior port of the upper part sits to be pivotally movable in relation thereto. In one preferred embodiment stops are provided to prevent 360 degree rotation of the parts and also to impart a reverse rotational action on the upper part relative to the base part when the stops are contacted. In one typical embodiment the base portion comprises the viewable feet and legs of the article which depicts a figure of a person and the upper part defines the arms, head and chest of the figure. This aspect allows the article to be animated when the same is moved along the play surface. Additionally the relative movement of the parts allows the movement of the article to be more realistic than if the article was one solid part as in this form the movement of the article tends to be relatively unrealistic and does not give the effect of, for example, a normal walking action. A further advantage is that the provision of the movable parts adds significantly to the stability of the article as it moves and is especially advantageous when the article depicts a figure as this has a relatively small base area and a relatively large height. The pivotal movement tends to disengage the effects of the upper part from acting on the base as the article moves and the jerking movement of the base as it moves is converted into pivotal movement of the parts rather than causing the article to topple over as may be the case if the article was provided as one part. It is envisaged that the assembly herein described can be used with apparatus described in the co-pending application number GB9615506.4. Thus the present invention provides in the various aspects described an article which is movable on a base to and between various positions on the base without the need for physical moving forces to be applied to the article and furthermore without the need for any form of control means to be physically connected thereto. Thus, the scope of possible movement of the article is greatly increased and the visual appearance of the same is such that it appears, especially to a child, that the article is moving of its own accord and, importantly, in a random manner throughout the environment on the base. Furthermore the arrangement of the control means allows the visual effect of the movement of the article to be that it is walking rather than simply sliding along the base surface. Thus, the toy and movable article which are the subject of this application provide for the article to be moved along a play base by control means which are remote from and not in physical contact with the article thereby giving the article the effect of being independently movable. The exertion of the movement is via a magnetic arrangement between the control means and article and which, if the article is a scale model of a human character can be arranged in conjunction with the shape of the article, to impart a walking effect on the article as it moves thereby adding to the realism of the toy and article. BRIEF DESCRIPTION OF THE DRAWINGS Specific embodiments of the invention will now be described with reference to the accompanying drawings; wherein FIG. 1A-1C illustrate an embodiment of the control means in one arrangement; FIG. 2 illustrates a detailed view of the roller arrangement of the control means of FIG. 1; FIG. 3A-3D illustrate an embodiment of an article according to the invention; FIG. 4A illustrates the legs portion of the article of FIG. 3 in more detail; FIG. 4B illustrates an alternative embodiment of the legs portion; FIG. 5 illustrates the control means and article of the previous Figures in an in use position; and FIG. 6 illustrates the article provided with the base as would be viewed by a child playing with the toy formed according to the invention. FIG. 7 illustrates a schematic view of the movement assembly detail of the invention and object; FIG. 8 illustrates a front view of the object, surface and movement assembly in section; and FIG. 9 illustrates a side view of the object, surface and movement assembly in section. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring firstly to FIG. 1 there is illustrated the components of a control means according to the invention, said control means comprising an actuation rod 2 which is viewable in the complete toy and may therefore be of any required shape to fit in with the environment created on the play base of the toy and movement of the same causes a 4 multiplication of the movement of the control means magnet around the base 54. The rod is in turn connected through a cover disc 4 to lever arm 6 via pins 8, 10 and said cover disc is mounted in a mover disc 12 which in turn controls the extent of movement of the actuating rod relative to the same and acts in conjunction with lever arm 6 to control the movement of a control rod 14 along the underside of the play base with which the control rod is held in close proximity and substantially parallel therewith. At the free end of the control rod 14 is formed a housing 16 and in said housing is provided a bracket 18 and a resilient means in the form of a spring plate 20 which acts to bias the bracket toward the base underside. The bracket includes a first roller with a magnet mounted thereon and second roller with a sleeve thereon and these, and their relationship, are described with reference to FIG. 2. The bracket 18 is however pivotally movable within the housing and the pivot point 17 is provided to be located directly under the roller on which the magnet is mounted thereby allowing the position of the article on the upper side of the base to be accurately determined and preventing the movement of the article in an arc which is the case if the pivot point is offset relative to the magnet. The housing 16 also includes a pin which prevents the article on the upper surface of the play base from coming into contact with objects on that side as there is provided a cover which encloses the underside of the play base with the control means therebetween and the cover is provided with protrusions which are described hereafter with which the pin contacts and stops before the article reaches the corresponding objects on that side of the base and this is another advantage of having the pin which also acts as the pivot point of the bracket below the magnet 26 so that the position of the article can be accurately determined to be within the confines of the housing 16. Turning now to FIG. 2 the bracket 18 and associated parts are illustrated in greater detail. The bracket 18 includes an end stop 22 and between said end stop and bracket are mounted a roller 24 with a magnet 26 mounted in a swash relationship at an angle relative to the axis of rotation 28 and a second roller 30 which is provided with a sleeve 32 on the outer surface thereof. The roller 24 and second roller 30 are drivingly connected via gears 34, 36, 38 such that the second roller drives the roller 24 and there is a ratio of 2.5 between the same. The second roller 30 is arranged to contact with the underside of the base via the sleeve which can be of a suitable gripping material such as rubber so that when the control means is moved so the movement of the roller 30 along the underside of the base causes the roller 24 and hence magnet to be rotated. The housing also includes pin 25 which protrudes below the housing which has a chamfered underside to allow the same to ride over protrusions on the cover with which the pin contacts, if sufficient force is applied. Turning now to FIGS. 3A-3D and 4A there are shown views of an article 39 according to one embodiment of the invention. In this embodiment the article comprises a head portion 40 which is in engagement with a body portion 42 and said portions are mounted on a legs portion 44. The portions 40, 42 are pivotally mounted on a pivot 46 which is part of the legs portion and are provided with stops 47, indicated in broken lines which allow rotation of the portions through 280 degrees. The legs portion 44 includes the pivot point 46 at one end and at the other end of each leg there is provided a magnet 50, 52. The magnets 50, 52 in FIG. 4A are arranged such that the bottom faces 54, 56 respectively are relatively angled such that when one magnet face 56 is in contact with the base as shown in FIG. 4A the bottom face 54 of the other magnet is out of contact and lies at an angle to the base and this increases the visual effect by increasing movement of the article as a whole and of the legs in particular. In FIG. 4B the legs are shown with the magnets 50, 52 in a flat arrangement wherein both contact the surface and this produces a more gentle visual movement effect and thus the appropriate arrangement can be selected to suit the character of the article depicted. In whichever embodiment one of the magnets 50, 52 is provided with a bottom face having a north polarity and the other is provided with a bottom face having a south polarity and this, in conjunction with the rotation of the magnet 26 and the changing degree of influence of the north and south poles caused by this as the control means moves causes the article to have a walking effect as it moves along the base with one leg attracted to contact the base and the other repelled followed by vice versa and so on as the control means magnet rotates and the article moves. Furthermore the ability of the body and head portions to rotate during this movement further mimics the walking effect of a real person. The separation of the head and body portions from the legs portion also reduces the mass of the article connected to the legs portion which can rotate by freeing the head and body portions to rotate separately and independently and thereby minimises the possibility of the article toppling over as it is caused to move by the influence of the magnet 26. Turning now to FIG. 5 there is illustrated part of the control means with the housing 16 in section and the article 39 in an use position relative to the play base 54 and cover 55 which are shown in section. The article 39 is provided with at least one of the magnets 50,52 in contact with the base 54 and this is achieved by ensuring that the magnetic attraction between the magnets 50, 52 and magnet 26 is sufficiently high to maintain the article 39 in this position. As the control means is moved so the sleeve 32 contacts the underside of the base 54 and rotates the second roller 30 which in turn rotates the roller 24 and magnet 26 mounted in a swash manner thereon. Thus the influence of the north 26N and South 26S poles on the magnet varies in relation to the magnets 50,52 of the article 39 as the magnet rotates serving to attract and repel the magnets as the polarity influence changes. It is believed that the change in influence on the magnets changes in a substantially sinusoidal fashion as the magnet 26 is rotated. The extent of the visual effect created in mimicking the walking action of the article 39 is dependent to an extent on the angle of the mounting of the magnet 26. In the example shown the magnet is mounted at 30 degrees to vertical and this provides a relatively smooth and relaxed walking effect as the effect that is created is of an increasing in effect of one polarity followed by the other but there is never a single polarity acting on the magnets on the article and thus only a gradual but still visible effect is created as in this case the article depicts a small girl. However if the walking effect was required to be significantly more dramatic, perhaps for example for a boys toy including a model of a robot or the like, then the position of the magnet 26 can be adjusted to create a more dramatic effect by increasing the influence of each pole as the magnet rotates so that at one instant the magnet 26 when adjacent the base 54 has a substantially north polarity and then changes when it rotates to a substantialy south polarity and so on such that the changes of the condition of the magnetic field created during rotation are significantly more marked. The cover 55 is also shown to have a series of protrusions 56 thereon and these protrusions are located to define the area in which the control means can operate and hence define the area on the upper surface of the base about which the article can be moved. The protrusions define the area in that the pin 25 protruding from the housing 16 contacts the same and stops but the protrusions 56 do not define a particular path of movement of the article and hence the article is free to move in whichever direction selected within the defined area. Typically the protrusions are located in areas which match with particular features of the environment which are created on the upper side of the base 54 such as houses, shops, parks, lakes and the like. Typically the guide pin 25 is bevelled so that a firm tug on the control means can release the housing from any area thereby preventing the article from being stuck. FIG. 6 illustrates the toy in a condition for purchase and use and it is immediately apparent that only the article 39 is visible to the child playing with the toy and thus it appears that the toy is independently movable within the environment. As the article does not have any direct physical control contact it is possible for the article 39 to go through doorways, under arches and actually to move about "inside" the environments and this has a significant effect on the realism and overall attractiveness of the toy formed. Referring to the FIGS. 7-9, a further movement assembly actuating means is shown which is similar to that previously described with an arm 214 and housing 216. However the arrangement of the interior of the housing is significantly different and comprises a magnet 210 which is fixed to a tube 215 which is slidable along a pin 225 in the housing 216. It should also be appreciated that this is an example of only one possible embodiment. In use the magnet 210 is laid flat in relation to the playbase 204 and in sliding contact with the underside of the same. The article which in this case is a figure of a girl, is provided on the base, with first and second magnets 230, 240 each mounted at or adjacent the surface of the base 231, 241 of the figure. The undersides 231, 241 and/or magnets are arranged with their outer surface angularly displaced relative to the surface 204 with which they contact as shown in FIG. 8. A third magnet 250 is also provided to the rear of the first and second magnets and this acts to stabilise the object in movement in a manner as is herein described. In use, the magnet 210 is attracted to the magnets 230, 240, and repelled by the smaller strength magnet 250 of the figure when the assembly and article are in proximity on either side of the surface 204 as shown. As the magnet 210 is attracted it rises up the pin 225 toward the playbase and can engage with the edges of any protrusions 220 formed on the underside of the playbase 204. This allows interaction of the movement of the article in relation to features on the top of the surface 204 the position of which are linked to the position of the protrusions on the underside. When the figure is removed from or misplaced from the playbase so the magnet 210 is no longer attracted and therefore retracts and the movement assembly is then freely movable about the underside of the playbase without contacting any of the protrusions 220 and thus the movement assembly can be moved to "pick up" the article in a particular area of the playbase and then cause the same to move. This is found to increase the effect of the article being independently movable with no visible control acting thereon. In movement, the first and second magnets, 230, 240 ate provided with the same polarity facing the playbase and the surfaces 231, 241 are angled relative to the playbase 204 in front view. The magnet 210 of the movement assembly is arranged with the opposite polarity facing the underside of the surface and so as it is moved the magnetic attraction between the magnets on either side of the playbase 204 causes the article to be dragged in the direction of movement of the magnet 210. The friction caused when the article is moved from rest, the effect of which is increased by the magnetic attraction loading, prevents a sliding movement of the article until the magnet 210 is a distance in front of the article. At the same time one of the magnets, 230 or 240, for example 230, is attracted towards the magnet 210 and is in contact with the playbase while the other magnet 240 is forced into the air due to the angling of the surfaces 231, 241 as shown in FIG. 8. Further movement of magnet 210 causes the magnet 240 to move more freely towards the magnet 210 than magnet 230 as no friction acts thereon and as it does so it pivots around the position of the magnet 230. As the movement continues so the magnet 240 becomes closer to the magnet 210 than magnet 230 whereupon the increased attraction causes the figure to fall or "topple" and change from contact with the playbase via the base 231 and/or magnet 230 to contact via the magnet 240 and/or base 241 which in turn raises the magnet 230 in the air and thus mimics a "step" taken by a real person which the object, in this embodiment, is provided to imitate. This process repeats between respective magnets 230, 240 and so the walking effect is created. To prevent the article pivoting backwardly due to the attraction forces created the third magnet 250 is provided with a similar polarity facing the surface to that of the magnet 210 thereby repelling the same and as the magnet 250 is located to the rear of the first and second magnets 230, 240, backwards movement is prevented. To further increase the visual effect created the body portion 260 can be separate to the legs and bases portion 270 in which the magnets 230, 240, 250 are mounted and said body portion and base portion pivotally movable as illustrated in FIGS. 8 and 9.

The toy and movable article which are the subject of this application provide for the article to be moved along a playbase by mechanical assembly and/or variable magnetic field which are remote from and not in physical contact with the article thereby giving the article the effect of being independently movable. The exertion of the movement is via a magnetic arrangement between the mechanical assembly and/or variable magnetic field and article and which, if the article is a scale model of a human character can be arranged in conjunction with the shape of the article, to impart a walking effect on the article as it moves thereby adding to the realism of the toy and article.

RELATED APPLICATIONS This application is a continuation in part of U.S. Ser. No. 10/952,530, filed Sep. 28, 2004 now U.S. Pat. No. 7,419,680, which claims priority from U.S. Provisional Patent Application Ser. No. 60/507,593, filed Oct. 1, 2003. FIELD OF THE INVENTION This invention relates generally to compositions and methods useful in the prevention and treatment of osteoporosis and for bone and fracture repair. More specifically, the invention relates to slow-releasing calcium phosphate-based materials incorporating Mg, Zn, F, carbonate and optionally other ions such as, for instance, boron, strontium, manganese, copper, silicate, etc. or organic moieties such as, for instance, proteins, amino acids, nutraceuticals, etc. that may promote bone formation and inhibit bone resorption. BACKGROUND OF THE INVENTION Osteoporosis is a progressive and debilitating metabolic bone disease characterized by low bone mass (bone loss) and structural deterioration (thinning of the cortical bone and disorganization of the trabecular bone) leading to increased bone fragility and susceptibility to fractures especially of the hip (femoral head), spine (vertebrae) and the wrist. Osteoporosis is a ‘silent’ disease because related bone loss occurs without symptoms until the individual suffers a bone fracture. Worldwide, the number of hip fractures due to osteoporosis was projected to rise from 1.7 million in 1990 to 6.3 million by 2050. In the U.K., it was estimated that the National Health Service cost associated with osteoporosis is over L600 million ($1.02 billion) per year in 1991 and projected to increase considerably. In Japan, estimated number of hip fracture in 1998 was about 90,000/year with associated hospital cost of about $120 million per year. In the U.S., osteoporosis is responsible for more than 1.5 million fractures/year including: 300,000 hip fractures and approximately 700,000 vertebral fractures, 200,000 wrist fractures and 300,000 fractures in ribs and other sites. 12% to 20% of patients with hip fracture die within a year after the fracture, usually from complications related to either the fracture or surgery. In 2001, the estimated health care cost (hospitals and nursing homes) related to osteoporosis and associated fractures were $17 billion ($47 million/day!) and projected to increase to $30 to $40 billion annually in the next decade. Bone tissue consists of two types: cortical (or compact bone) and trabecular (or spongy bone), differing in architecture, properties and function. The cortical bone provides mechanical strength and protective functions while cancellous or trabecular bone provides the metabolic functions. Two major processes are responsible for the development and maintenance of the bone tissue: bone formation (bone build-up) and bone resorption (bone modeling). During skeletal development in humans (birth to adulthood), the rate of bone formation is much greater than the rate of bone resorption until maximum bone mass (peak bone mass) is reached (at about age 35 for cortical bone and earlier for trabecular bone). After the peak bone mass is reached, the bone turnover per year is about 25% in trabecular bone and 3% in cortical bone. A bone remodeling process (bone turnover) in which the rates of bone formation and bone resorption are equal in the same site maintains the skeletal mass in adulthood. When these two processes are in equilibrium or are “coupled,” there is no net gain or loss in bone mass. It is believed that the bone loss associated with primary type of osteoporosis results from the uncoupling of these two processes; with the rate of bone formation being much lower than the rate of resorption. A secondary type of osteoporosis is observed after prolonged immobilization and prolonged periods of bed rest or under glucocorticoid treatment for pulmonary disorders. In such conditions the mechanism of bone loss include both increased bone resorption and decreased bone formation. Reduction in bone formation leads to inadequate bone replacement during remodeling and to gradual bone loss resulting in the thinning of the cortical bone and reduction in cancellous bone formation. Two major bone cells are involved—osteoblasts for bone formation and osteoclasts for bone resorption. Bone formation is reflected in osteoblast activities involving matrix (collagen, protein, DNA) formation and mineralization. Bone resorption is determined by the rate of osteoclast recruitment and the intensity of osteoclast activity manifested by the appearance of resorption pits. Most conditions leading to osteoporosis (including estrogen deficiency, hyperparathyroidism and hyperthyroidism) are associated with increased osteoclastic bone resorption and the inability of the bone formation process to keep up with the resorption process. Bone is a composite of about 25 wt % biopolymer (organic matrix), 70 wt % mineral or inorganic phase, and 5 wt % water. The organic matrix is principally (about 95%) of Type I collagen with non-collageneous proteins. Osteoporosis is characterized by bone loss, decreased bone strength, lower bone density, poorer bone quality (e.g., porous cortical bone), thinning cortical bone and disorganized trabecular bone. Bone loss is often a predictor of future fracture risk. In bone resorption, dissolution of the bone mineral occurs before the degradation of the collagen fibers. The rate of osteoclastic destruction of mineralized tissues was observed to be inversely proportional to bone mineral density. The bone mineral or inorganic component of bone is a calcium phosphate idealized as a calcium hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 . However, comprehensive studies on synthetic and biologic apatites demonstrate convincingly that biologic apatites (mineral phases of enamel, dentin, cementum and bone) are apatites containing minor constituents (carbonate and magnesium) and are more accurately described as carbonate hydroxyapatite, approximated by the formula, (Ca,Na,Mg) 10 (PO 4 ,HPO 4 ,CO 3 ) 6 (OH) 2 . Changes in the composition of the apatite affect its lattice parameters, morphology, crystallinity (reflecting crystal size and/or perfection) and dissolution properties. For example, Mg-for-Ca or CO 3 -for-PO 4 substitution decreases crystallinity (crystal size) and increases solubility while F-for-OH substitution increases crystal size and decreases the solubility of synthetic apatites. Osteoporotic bones were observed to have lower magnesium (Mg) and carbonate (CO 3 ) concentrations. Along with decreased Mg and CO 3 contents, larger bone apatite crystals (based on infrared spectroscopic measurements of ‘crystallinity index’) were reported in bones from patients with postmenopausal osteoporosis and alcoholic osteoporosis. Smaller bone apatite crystals were observed in bones of rats fed excess Mg while bone apatite crystals increased in size in bones from Mg-deficient rats. Enamel crystals of rats injected with Mg were smaller than those of the controls. On the other hand, bone apatite crystals from rats drinking high levels of fluoride (F) were larger and less soluble. Increase in width of bone apatite crystals were also observed in the bones of F-treated rabbits. Larger enamel apatite crystals in rat's teeth were observed after F administration. Although there is still no known cure for osteoporosis, some medications have been approved by the FDA for postmenopausal women to prevent and/or treat osteoporosis. These include biphosphonates such as alendronate (Fosamax) and Risedmate (Actonel), Calcitonin (e.g., Miacalcin), estrogen (e.g., Climara, Estrace, Estraderm, Estratab, Ogen, Orto-Es, Viovlle, Premarin, etc) and hormones (estrogens and progestins (e.g., Activella, FemJHrt, Premphase, Prempro, etc); and selective estrogen receptor modulators, SERMs such as ralozifene (Evista). Sodium fluoride (NaF) treatment is pending approval. Treatments under investigation include parathyroid hormone (PTH), vitamin D metabolites, other biphosphonates, and SERMs. These therapeutic agents, except F therapy, are described as anti-resorptive agents because they principally target bone resorption. These therapeutic agents are associated with some serious side effects. For example, estrogen therapy is associated with cancer while bisphosphonate-based drugs are associated with osteonecrosis of the jaw and delayed healing. Currently, experimental fluoride compounds recommended for osteoporosis therapy include sodium fluoride (NaF), monosodiumfluorophosphate, MFP, (Na 2 PO 3 F) and slow release preparation of NaF (SR—NaF). There is general agreement that F stimulates bone formation directly without the need for prior bone resorption and that it is this uncoupling of resorption and formation that makes this element so effective in increasing bone mass. However, fluoride therapy has also been associated with increased fracture risk despite increased bone mass. The bone mineral can best be described as a carbonate hydroxyapatite, approximated by the formula: (Ca,Na,Mg) 10 (PO 4 ,CO 3 ,HPO 4 ) 6 (OH,Cl) 2 containing about 40% calcium. Calcium is stored in bone in the process of mineralizing newly deposited tissue and it is withdrawn from bone only by resorption of old bone tissue. The biological fluids are metastable with respect to apatite, maintaining the integrity of the bone and tooth mineral (apatite). Ca deficiency in the diet induces osteoporosis in rats. Ca supplementation is strongly recommended for optimum bone health. Ca supplementation has been reported to reduce cortical bone loss during the first 5 years of menopause and produce a sustained reduction in the rate of total body bone loss at least 3 years after menopause. However, by itself, Ca supplementation does not appear to slow the rapid loss of trabecular bone during the first few years of menopause nor does it prevent the menopause-related lumbar bone loss. A study on spinal bone loss in postmenopausal women supplemented with Ca and trace minerals (zinc, manganese and copper) showed that bone loss was arrested by intake of Ca plus trace minerals while no difference was observed between the placebo group or group receiving Ca alone. Magnesium (Mg) is an important element in biological systems. 50% to 60% of Mg in the body is associated with the bone mineral. The rest of the Mg in the body is intracellular, a required co-factor in more than 300 enzyme systems. Mg is critical for cellular functions that include oxidative phosphorylation, glycolysis, DNA transcription and protein and nucleic acid synthesis. Mg deficient diet in rats was shown to have impaired bone growth (reduction in bone formation and bone volume), decreased bone strength and increased fragility. These and other animal studies implicate Mg deficient diet as a possible risk factor for osteoporosis. In humans, Mg deficiency in the diet was also associated with osteoporosis. Mg therapy was reported to increase bone mass in postmenopausal osteoporosis. Other studies suggest that Mg supplementation suppresses bone turnover rates in young adult males. On the cellular level, in vitro, an isolated report indicates that Mg directly stimulated osteoblast proliferation. Zn is an essential trace element in the activity of more than 300 enzymes and affects basic processes of cell division, differentiation, and development and is required in collagen biosynthesis and in the biosynthesis and repair of DNA, in matrix and protein synthesis and plays an important role in bone metabolism and growth. It is the most abundant trace metal in bone mineral, being present at a concentration of up to 300 ppm. Zn deficiency in rats was shown to result in a 45% reduction in cancellous bone mass and to a deterioration of trabecular bone architecture, with fewer and thinner trabeculae and therefore may be considered as a risk factor in the development of osteoporosis. In vivo, Zn was shown to stimulate bone formation in weanling rats and in aged rats. On the cellular level in vitro, Zn has been shown to have a stimulatory effect on bone formation and an inhibitory or biphasic effect on osteoclastic bone resorption. Studies on Zn-releasing compounds such as b-alanyl-L-histadanato zinc and Zn-TCP demonstrated that Zn promoted greater bone formation in vitro and was effective in increasing bone density or in preventing bone loss in vivo. On the crystal level in synthetic systems, the presence of Zn causes the formation of apatite with low crystallinity, promoting the formation of Zn-substituted . β-TCP or even amorphous calcium phosphate (ACP), depending on the solution Zn/Ca molar ratio. Both Mg and Zn were shown to inhibit the growth of apatite. The relevant literature suggests that Mg or Zn separately may have beneficial effects on bone matrix but may cause the formation of bone apatite with low crystallnity (small crystal size). On the other hand, F may improve crystallinity (larger crystal size) and reduce solubility of bone apatite, but may cause impaired or abnormal mineralization. Separately, Mg, Zn and F ions have been associated with promotion of osteoblastic activity (bone formation) and/or inhibition of osteoclastic activity (bone resorption). Zn-releasing compounds, such as b-alanyl-l-histadano zinc compounds and Zn-TCP have been shown to have therapeutic effect on osteoporosis in rats induced by zinc-deficiency. Mg and Zn deficiencies have been reported as risk factors for osteoporosis. F compounds (NaF, monofluorophosphate and slow-releasing NaF) are used in the management of osteoporosis. SUMMARY OF THE INVENTION The present invention provides novel biomaterials comprising one or more of the following ions: magnesium (Mg), zinc (Zn) and fluoride (F) ions in a carbonate-containing apatite or biphasic calcium phosphate, BCP system. The present invention may consist of carbonate apatite and tricalcium phosphate incorporating Mg, Zn, F or other ions. In some embodiments, the biomaterial contains Mg, in some embodiments Zn, in some embodiments F, in some embodiments Mg and Zn, in some embodiments Mg and F, in some embodiments Zn and F, and in some embodiments Mg, Zn and F. In some embodiments, the biomaterial may contain one or more additional ions, for instance, strontium, boron, manganese, copper, silicate, etc. In yet other embodiments, the biomaterial may contain one or more additional compounds, such as, for instance, nutraceuticals that have anti-inflammatory, antibacterial or anti-oxidant properties or activity. In still further embodiments, the biomaterial may contain one or more additional protein or peptide. In preferred embodiments, the biomaterial is substantially free of serious side effects or deleterious effects on bone strength and fracture incidence such as those associated with the presently FDA-approved anti-resorptive agents. The biomaterial may be substantially similar in composition to bone mineral (a carbonate apatite). In some embodiments, the biomaterial features slow release of Mg, Zn, F, Ca, and P ions. In other embodiments, the biomaterial combines ions in preferred concentrations known separately to promote bone formation and minimize or prevent bone resorption. In yet other embodiments, the biomaterial allows the incorporation of lower levels of these ions thus avoiding deleterious effects observed with higher levels. In still other embodiments, the biomaterial provides beneficial effects of Mg and Zn on collagen and protein formation to balance the F effect on bone apatite formation and crystal size thereby promoting formation of bone with higher mineral density and greater bone mass. In yet other embodiments, the biomaterial provides synergistic effects of the three elements on bone resorption to allow the rate of bone formation to catch up with the rate of bone resorption, resulting in a net gain in bone mass. The biomaterials of the present invention may be useful for reducing the development of osteoporosis or even preventing osteoporosis, increasing cancellous bone mass and arresting the progress of osteoporosis, reversing bone loss and repairing fractures such as those caused by osteoporosis. The biomaterials may also be used in treating other bone deficiency caused by mineral deficiency or diseases such as cancer or osteopenia or therapies such as steroid treatments or radiation or conditions such as immobilization). The biphasic calcium phosphate, BCP, may be, in one embodiment, a mixture of unsubstituted hydroxyapatite (HA) or substituted HA or substituted carbonate apatite and unsubstituted -TCP, Ca 3 (PO 4 ) 2 or substituted -TCP. BCP of varying HA -TCP ratios may be produced directly or by sintering calcium-deficient apatite, for instance having a Ca/P<1.67, that has been prepared either by a precipitation or by a hydrolysis method or by a solid-state reaction. In some embodiments, the amount of each component (by weight %) present in the biomaterials of the invention may be as follows: Mg, 0.0.05 to 20 wt %, Zn, 0.02 to 20 wt %, F, 0.0 to 4 wt %, calcium (Ca commonly designated “C” herein as in “TCP” or “BCP”) 10 to 50 wt %, phosphate (commonly designated “P” herein, as in “TCP” or “BCP”) 5 to 30 wt %, carbonate (CO 3 ) 0.5 to 25 wt %. In other embodiments, the amount of each component (by weight %) present in the biomaterials of the invention may be as follows: Mg, 0.05 to 12 wt %; Zn, 0.02 to 12 wt %; F, 0.0 to 4 wt %, calcium (Ca commonly designated “C” herein as in “TCP” or “BCP”), 20 to 40 wt %; phosphate, (commonly designated “P” herein, as in “TCP” or “BCP”) 10 to 20 wt %; carbonate (CO 3 ). 1 to 20 wt %. In some embodiments, the biomaterial contains Ca, P, and CO 3 . The biomaterial may also be combined with one or more organic moieties such as proteins, amino acids, nutraceuticals with antibacterial, antioxidante and anti-inflammatory properties known to inhibit osteoclastic activity or promote osteoblastic activity. The biomaterial may be unsintered or sintered (heated) at temperatures of, for instance, about 200° to 1000° C. The biomaterial may be used as a diet supplement representing from about 0.01 to 5 wt. % of the total diet, or as bone-graft material or scaffold for tissue engineering. The biomaterial may be in any form including: powder, granule, block, in a carrier (e.g., a saline solution or a polymer solution) for injection at local sites, and may be in the form of an injectable cement. In a second aspect, the invention provides methods of inhibiting bone resorption by administering a biomaterial comprising one or more of Mg, Zn and F ions in a carbonate-containing apatite or in a biphasic calcium phosphate (BCP) system. In some embodiments, the biomaterial contains Mg, in some embodiments Zn, in some embodiments F, in some embodiments Mg and Zn, in some embodiments Mg and F, in some embodiments Zn and F, and in some embodiments Mg, Zn and F. In some embodiments, the biomaterial may contain one or more additional ions, for instance, strontium, boron, manganese, copper, silicate, etc. In yet other embodiments, the biomaterial may contain one or more additional compounds such as, for instance, nutraceuticals that have anti-oxidant, anti-inflammatory or antibacterial properties or activity. In still further embodiments, the biomaterial may contain one or more additional proteins or peptides. The biomaterial may be substantially similar in composition to bone mineral (a carbonate apatite). In some embodiments, the biomaterial features slow release of Mg, Zn, F, Ca, and P ions. The biphasic calcium phosphate, BCP, may be, in one embodiment, a mixture of unsubstituted hydroxyapatite (HA) or substituted HA or substituted carbonate apatite and unsubstituted -TCP, Ca 3 (PO 4 ) 2 or substituted -TCP. BCP of varying HA -TCP ratios may be produced directly or by sintering calcium-deficient apatite, for instance having a Ca/P<1.5, 1.6, 1.67, 1.75 or 1.8 that has been prepared either by a precipitation or by a hydrolysis method or by a solid-state reaction. In some embodiments, the amount of each component (by weight %) present in the biomaterials of the invention may be as follows: Mg 0.5 to 12 wt %, Zn 1 to 12 wt %, F 0.1 to 4 wt %, calcium (Ca commonly designated “C” herein as in “TCP” or “BCP”) 20 to 40 wt %, phosphate (commonly designated “P” herein, as in “TCP” or “BCP”) 10 to 20 wt %, carbonate (CO 3 ) 1 to 20 wt %. In some embodiments, the biomaterial contains Ca, P, and CO 3 . The biomaterial may also be combined with one or more organic moieties such as moieties known to inhibit osteoclast activity. The biomaterial may be unsintered or sintered at 100 to 1000° C. The biomaterial may be used as a diet supplement or as bone-graft material or scaffold for tissue engineering. The biomaterial may be in any form including: powder, granule, a block, in a carrier (e.g., a saline solution or a polymer solution) for injection at local sites, and may be in the form of an injectable cement. In a third aspect, the invention provides methods of treating osteoporosis or delaying the onset of osteoporosis by administering a biomaterial comprising one or more of Mg, Zn and F ions in a carbonate-containing apatite or biphasic calcium phosphate (BCP) system consisting of carbonate apatite and substituted β-TCP. In some embodiments, the biomaterial contains Mg, in some embodiments Zn, in some embodiments F, in some embodiments Mg and Zn, in some embodiments Mg and F, in some embodiments Zn and F, and in some embodiments Mg, Zn and F. The biomaterial may be substantially similar in composition to bone mineral (a carbonate apatite). In some embodiments, the biomaterial may contain one or more additional ions, for instance, strontium, boron, manganese, copper, silicate etc. In yet other embodiments, the biomaterial may contain one or more additional compounds that have anti-oxidant, anti-inflammatory, antibacterial, anti-oxidant properties or activity such as, for instance, a nutraceutical. In still further embodiments, the biomaterial may contain one or more additional protein or peptide. In some embodiments, the biomaterial features slow release of Mg, Zn, F, Ca, and P ions. The biphasic calcium phosphate, BCP, may be, in one embodiment, a mixture of unsubstituted hydroxyapatite (HA) or substituted HA or substituted carbonate apatite and unsubstituted -TCP, Ca 3 (PO 4 ) 2 or substituted -TCP. BCP of varying HA -TCP ratios may be produced directly or by sintering calcium-deficient apatite, for instance having a Ca/P<1.5, 1.6, 1.67, 1.75 or 1.8 that has been prepared either by a precipitation or by a hydrolysis method or by a solid-state reaction. In some embodiments, the amount of each component (by weight %) present in the biomaterials of the invention may be as follows: Mg 0.5 to 12 wt %, Zn 1 to 12 wt %, F 0.1 to 4 wt %, calcium (Ca commonly designated “C” herein as in “TCP” or “BCP”) 20 to 40 wt %, phosphate (commonly designated “P” herein, as in “TCP” or “BCP”) 10 to 20 wt %, carbonate (CO 3 ) 1 to 20 wt %. In some embodiments, the biomaterial contains Ca, P, and CO 3 . The biomaterial may also be combined with one or more organic moieties such as moieties known to inhibit osteoclastic activity or promote osteoblastic activity. The biomaterial may be unsintered or sintered (heated) at temperatures of from about 100° to 1000° C. The biomaterial may be used as a diet supplement or as bone-graft material or scaffold for tissue engineering. The biomaterial may be in any form including a powder, granule, a block, in a carrier (e.g., a saline solution or a polymer solution) for injection at local sites, and may be in the form of an injectable cement. In a fourth aspect, the invention provides methods of treating a bone fracture by administering a biomaterial comprising one or more of Mg, Zn and F ions in a carbonate-containing apatite or in a biphasic calcium phosphate (BCP) system. In some embodiments, the biomaterial contains Mg, in some embodiments Zn, in some embodiments F, in some embodiments Mg and Zn, in some embodiments Mg and F, in some embodiments Zn and F, and in some embodiments Mg, Zn and F. In some embodiments, the biomaterial may contain one or more additional ions, for instance, strontium, boron, manganese, etc. In yet other embodiments, the biomaterial may contain one or more additional compounds that have anti-oxidant properties or activity. In still further embodiments, the biomaterial may contain one or more additional protein or peptide. The biomaterial may be substantially similar in composition to bone mineral (a carbonate apatite). In some embodiments, the biomaterial features slow release of Mg, Zn, F, Ca, and P ions. The biphasic calcium phosphate, BCP, may be, in one embodiment, a mixture of unsubstituted hydroxyapatite (HA) or substituted HA or substituted carbonate apatite and unsubstituted and substituted -TCP, Ca 3 (PO 4 ) 2 . BCP of varying HA/ -TCP ratios may be produced directly or by sintering calcium-deficient apatite, for instance having a Ca/P<1.5, 1.6, 1.67, 1.75 or 1.8 that has been prepared either by a precipitation or by a hydrolysis method or by a solid-state reaction. In some embodiments, the amount of each component (by weight %) present in the biomaterials of the invention may be as follows: Mg, 0.05 to 12 wt %; Zn, 0.01 to 12 wt %; F, 0.0 to 4 wt %; calcium (Ca commonly designated “C” herein as in “TCP” or “BCP”), 20 to 40 wt %; phosphate (commonly designated “P” herein, as in “TCP” or “BCP”), 10 to 20 wt %; carbonate (CO 3 ), 1 to 20 wt %. In some embodiments, the biomaterial contains Ca, P, and CO 3 . The biomaterial may also be combined with one or more organic moieties such as proteins, peptides or nutraceuticals with antibacterial, antioxidant, anti-inflammatory properties known to inhibit osteoclastic activity or promote osteoblastic activity. The biomaterial may be unsintered or sintered (heated) at temperatures from about 100° to 1000° C. The biomaterial may be used as a diet supplement or as bone-graft material or scaffold for tissue engineering. The biomaterial may be in any form including a powder, granule, a block, in a carrier (e.g., a saline solution or a polymer solution) for injection at local sites, and may be in the form of an injectable cement. In a fifth aspect, the invention provides methods of inhibiting osteoclast activity by administering a biomaterial comprising one or more of Mg, Zn and F ions in a carbonate-containing apatite or in a biphasic calcium phosphate (BCP) system consisting of carbonate apatite and substituted β-TCP. In some embodiments, the biomaterial contains Mg, in some embodiments Zn, in some embodiments F, in some embodiments Mg and Zn, in some embodiments Mg and F, in some embodiments Zn and F, and in some embodiments Mg, Zn and F. In some embodiments, the biomaterial may contain one or more additional ions, for instance, strontium, boron, manganese, copper, silicate, etc. In yet other embodiments, the biomaterial may contain one or more additional compounds such as, for example a neutraceutical that may have anti-oxidant, anti-inflammatory or antibacterial properties. In still further embodiments, the biomaterial may contain one or more additional protein or peptide. The biomaterial may be substantially similar in composition to bone mineral (a carbonate apatite). In some embodiments, the biomaterial features slow release of Mg, Zn, F, Ca, and P ions. The biphasic calcium phosphate, BCP, may be, in one embodiment, a mixture of unsubstituted hydroxyapatite (HA) or substituted HA or substituted carbonate apatite and unsubstituted and substituted -TCP, Ca 3 (PO 4 ) 2 . BCP of varying HA/ -TCP ratios may be produced directly or by sintering calcium-deficient apatite, for instance having a Ca/P<1.5, 1.6, 1.67, 1.75 or 1.8 that has been prepared either by a precipitation or by a hydrolysis method or by a solid-state reaction. In some embodiments, the amount of each component (by weight %) present in the biomaterials of the invention may be as follows: Mg 0.5 to 12 wt %, Zn 1 to 12 wt %, F 0.1 to 4 wt %, calcium (Ca commonly designated “C” herein as in “TCP” or “BCP”) 20 to 40 wt %, phosphate (commonly designated “P” herein, as in “TCP” or “BCP”) 10 to 20 wt %, carbonate (CO 3 ) 1 to 20 wt %. In some embodiments, the biomaterial contains Ca, P, and CO 3 . The biomaterial may also be combined with one or more organic moieties such as moieties known to inhibit osteoclastic activity and promote osteoblastic activity. The biomaterial may be unsintered or sintered (heated) at 100 to 1000° C. The biomaterial may be used as a diet supplement or as bone-graft material or scaffold for tissue engineering. The biomaterial may be in any form including a powder, granule, a block, in a carrier (e.g., a saline solution or a polymer solution) for injection at local sites, and may in the form of an injectable cement. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows XRD patterns of precipitated carbonate apatite which has been substituted with ion combinations in accordance with the invention. XRD patterns of precipitated carbonate apatite containing: (A) F, (B) Mg+F; (C) Zn+F; and (D) Mg+Zn+F. The differences in the sharpness of the diffraction peaks (line broadening) at about 25.8° 2Θ reflect the difference in their crystallite size. Mg and Zn have additive effects on reducing crystallinity of apatite (B & C vs D). FIG. 2 shows XRD patterns of Mg/Zn/F—CaP: (A) before and after sintering (B) at 600° C.; and (C) at 800° C. T=Mg- and Zn-substituted . β-TCP; H═F-substituted apatite. FIG. 3 shows dissolution reflected by the release of Ca 2+ ions with time from the synthetic calcium phosphates: (A) F—CaP; (B) Zn/F—CaP; (C) Mg/F—CaP and (D) Mg/Zn/F—CaP. FIG. 4 shows dissolution reflected by release of Ca 2+ ions with time of Mg/Zn/F—CaP: before (C, D) and after ignition at 600° C. (B) and at 800° C. (A). C and D have similar concentrations of Mg and Zn but different concentrations of F, with (D) having the lower F concentration. The initial dissolution rate is decreased with increasing sintering temperature (A and B vs. C and D) and with increasing F concentration (A vs. B, C vs. D). FIG. 5 shows the enhancing effect of MZF-CaPs on the proliferation of human osteoblast-like cells (MG-63) compared to control. FIG. 6 shows the effect of MZF-CaPs on the phenotype expression of bone growth markers by the osteoblast-like cells (MG-63). Bone markers expressed are: osteocalcin (OSC), alkaline phosphatase (AP), collagen type 1 (Col 1), osteopontin (OSP). FIG. 7 shows the effect of BCPs on expression of proteoglycans (versican, deconsin, biglycan) by human osteoblast cells. FIG. 8 shows XRD profiles (A,B,C,D) and FT-IR spectra (E). XRD profiles: (A) F—CaP; (B) Mg—CaP; (C) Zn—CaP; (D1,D2) MZF-CaPs compared to that of (D3) bone. When Mg or Zn concentrations in the CaP is higher than 5 wt %, two phases are observed: apatite and Mg- or Zn-TCP (C). FT-IR spectra: (EC, EB) MZF-CaPs compared to that of rat bone (EA), showing that the matrix of MZF-CaPs (EC,EB) is a carbonate apatite similar to bone (EA). FIG. 9 shows dissolution expressed as release of Ca 2+ ions with time from: (A) F—CaP containing high and low concentrations of F; (B) Mg-TCP; and (C) Zn-TCP. (B) and (C) contain different levels of Mg or Zn, respectively. Dissolution rates of Mg-TCP and Zn-TCP decrease with increasing Mg (B) or Zn (C) and dissolution rate of F—CaP decreases with increasing F (A). FIG. 10 demonstrates that Zn-TCP compared to β-TCP, suppressed the activity of mature osteoclasts through: (A) reduction in actin ring formation, (B) down-regulation of CAII and cathepsin K expressions without significant change in the expression of TRAP, and (C) increased cell apoptosis, in a dose dependent manner. FIG. 11 represents bone fracture strength of femur of rats on (A) basic diet; (B) mineral deficient (MD) diet; on MD supplemented with: (C) Mg—CaP; (D) Zn—CaP; (E) F—CaP; and (F) MZF-CaP. Bone strength was significantly reduced by mineral deficient (MD) diet (B vs. A) and improved by the MZF-CaP supplemented diets (C,D,E,F vs. B). FIG. 12 shows SEM images of cortical bone from rat on: ( 12 A) normal diet; ( 12 B) mineral deficient (MD) diet; ( 12 C, 12 D, 12 E, 12 F) MD supplemented with Mg—CaP, Zn—CaP, F—CaP and MZF-CaP, respectively. The cortical bone loss induced by MD diet ( 10 B vs 10 A) was prevented by the supplemented diets ( 12 C, 12 D, 12 E, 12 F compared to 12 B). FIG. 13 shows SEM images of trabecular bone from rat on: ( 13 A) basic diet; ( 13 B) mineral deficient (MD) diet; ( 13 C, 13 D, 13 E, 13 F) MD diet supplemented with Mg—CaP, Zn—CaP, F—CaP and MZF-CaP, respectively. The trabecular bone loss induced by MD diet ( 13 B vs 13 A) was prevented by the supplemented diets ( 13 C, 13 C, 13 E, 13 F compared to 13 B). FIG. 14 depicts bone mineral density, BMD of left and right femurs of (A) non-OVX, (B) OVX, (C) OVX injected with Zn-TCP; and OVX injected with MZF-CaPs (D,E,F,G) Ovariectomy induced reduction in BMD (B vs. A), injection with MZF-CaPs prevented the loss in BMD (D,E,F, G compared to B) ( 14 A) Wistar rats after 12 weeks. ( 14 B) Sprague-Dawley rats after 16 weeks. FIG. 15 depicts bone strengths of OVX rats on (A 1 ) basic (BD) for 3 months; (A 2 ) BD, 3 months, then BD+MZF-CaP for 2 additional months; (A 3 ) BD+MZF-CaP for 5 months; and non-OVX on (A 4 ) BD for 5 months; and (A 5 ) BD+MZF for 5 months showing increased bone strength in bones from rats (OVX or non-OVX) on diet supplemented with MZF-CaP. FIG. 16 shows microCT images of L-5 vertebra (one slice, 10μ) from: (A) OVX rat on basic diet, 5 months; and (B) OVX rat on basic diet supplemented with MZF-CaP showing prevention of bone loss induced by ovariectomy or estrogen-deficiency ( 16 B vs 16 A). FIG. 17 shows microCT images of L-5 vertebra (261 slices, 10μ/slice, standard resolution) of OVX rats on (A) basic diet, and (B) basic diet supplemented with MZF-CaP MZF-CaP increased bone volume, trabecular thickness and decreased bone porosity. FIG. 18 depicts the extent of dissolution (expressed as release of Ca 2+ ions with time) of rat bones in acidic buffer (0.1M KAc, pH 6 at 37° C.). The dissolution is lower in bones from OVX and non-OVX rats on a basic diet supplemented with MZF-CaP (B vs. A; D vs. C). FIG. 19 shows Faxitron images of the femoral heads from (A) non-ovariectomized rats on a basic diet, (B) ovariectomized rats on a basic diet after two months, and (C) ovariectomized rats on a basic diet for two months then on basic diet supplemented with Mg/Zn/F—CaP supplements for one month. Bone loss induced by ovarietomy (B vs A) was recovered when the diet was supplemented with MZF-CaP was administered for one month (C vs B). FIG. 20 shows microCT images of femur head demonstrating further the recovery of bone loss that may be achieved by providing Mg/Zn/F—CaP as a dietary supplement. MicroCT images of femur head of rat: (A) on a basic diet, (B) on a mineral-deficient diet for two months, and (C) on mineral-deficient diet for two months followed by a diet having a Mg/Zn/F—CaP dietary supplement for one month. The bone loss induced by mineral deficiency (B vs A) was recovered by adding MZF-CaP supplement to the mineral-deficient diet for one month (C vs B). DESCRIPTION OF PREFERRED EMBODIMENTS The rationale for incorporating Mg, Zn and F in a carbonate apatite matrix was to combine these ions that had been separately associated with biomineralization in a matrix that is similar to bone mineral. Bone mineral is a carbonate apatite. (LeGeros R Z (1981) Prog Crystal Growth Charact 4:145). Preparation of MZF-CaPs. Mg/F—CaP, Zn/F—CaP, Mg/Zn/F—CaP were prepared by a hydrolysis method at 90° C. from solutions with known Mg/Ca, Zn/Ca, CO 3 /P and F/P molar ratios. X-ray diffraction (XRD) analysis confirmed earlier observations on the effect of Mg or Zn on the crystallinity of the apatite ( FIG. 1 ), i.e., Mg or Zn tends to lower the crystallinity of apatite. Sintering at 600° C. increased the crystallinity (crystal size). When the concentration of either Mg or Zn in the CaP is higher than 5 wt %, sintering at 800° C., resulted in the formation of biphasic calcium phosphate, BCP, consisting of a mixture of apatite and Mg- and/or Zn-substituted β-TCP ( FIG. 2C ). Composition of MZF-CaPs. Elemental analyses using inductive coupled plasma (ICP) showed that the amount of Mg, Zn or F incorporated in the precipitated apatite depended on the solution concentrations of these ions (Table 1). The crystallinity, composition (Table 1, FIG. 8 ) and dissolution rates (release of ions) of the Mg/Zn/F—CaPs can be adjusted by manipulation of reaction condition, ion concentrations and sintering temperatures. TABLE 1 Composition (wt %) and of MX + ZF—CaP preparations tested in animals Prep# Ca P Mg Zn F CO 3 Ca/P Mg/Ca Zn/Ca F/P C/P XRD* #51 27.71 16.44 1.10 2.90 1.10 3.24 1.30 0.08 0.06 0.11 0.10 AP #52 27.57 15.73 0.18 0.01 1.21 4.32 1.38 0.01 0.00 0.13 0.14 AP #53 26.75 17.74 4.10 0.01 0.05 4.41 1.17 0.25 0.00 0.00 0.13 AP #54 21.94 14.71 0.16 8.40 0.05 5.48 1.17 0.01 0.19 0.00 0.19 BCP #68 27.71 16.44 2.70 2.85 2.31 3.62 1.30 0.17 0.06 0.03 0.12 AP #74 27.19 16.76 2.00 2.24 1.50 3.60 1.26 0.12 0.09 0.15 0.11 AP #76 28.54 15.98 1.95 2.44 3.00 2.39 1.38 0.11 0.05 0.31 0.08 AP #86 22.19 13.64 2.26 2.23 1.00 3.69 1.25 0.17 0.06 0.12 0.14 AP *XRD: AP, apatite; BCP, biphasic calcium phosphate (mixture of Xn-substituted tricalcium phosphate and AP Dissolution Properties of MZF-CaPs. It has been demonstrated that an acidic microenvironment is fundamental to the resorptive process by the osteoclasts. Therefore, in vitro dissolution properties of the Mg/Zn/F-BCP materials under acidic conditions is predictive of in vivo degradation of these materials. For example β-TCP shown to be more soluble than HA in vitro and was also shown to have greater degradation in vivo. The rate of release of the essential elements (Mg, Zn and F) obtained in vitro gives an insight into their rate of release in vivo. Incorporation of Mg or Zn increased while incorporation of F decreased extent of dissolution of MZF-CaPs as measured by the Ca release ( FIG. 3 ). The extent of dissolution decreased with increasing sintering temperature and with increasing amount of F ( FIG. 4 ). Maximum release was observed after 10-minute exposure in the acidic buffer (0.1M NaAc, pH 5, 37° C.). Results from the in vitro dissolution study of experimental synthetic materials provides information on the rate of release of Mg, Zn, F, Ca and P from the Mg/Zn/F—CaP materials and give insight into their release and availability in vivo. The dissolution is affected by the following factors: composition (the greater the F content, the lower the dissolution rate); sintering temperature (sintered materials have a slower rate of dissolution than uncalcined or unsintered materials), particle size, porosity and surface area and possibly physical form (e.g., powder vs. discs). The slow release of these ions from the Mg/Zn/F-BCP materials avoids the side effects observed for the fast releasing materials such as those reported for NaF. Effect of MZF-CaPs on Bone Cell Activities. Bones are constantly being remodeled throughout life. Under normal conditions, bones are being dissolved by osteoclasts and rebuilt by osteoblasts under exquisite regulatory control. In pathologic conditions such as osteoporosis, the tightly controlled bone remodeling process is disrupted and osteoclast activity outpaces bone production by osteoblasts. Laboratory models that can characterize the behavior of osteoclasts and osteoblasts at the cellular and molecular level provide critical insights into the pathophysiology of bone remodeling. In vitro cell models are important tools that address this problem. Osteoblast-like cells that exhibit characteristics of normal osteoblasts including synthesis of bone matrix component: collagen type I, osteocalcin, osteopontin and osteonectin help evaluate the effects of Mg/Zn/F-BCPs on cellular events involved in bone formation. Similarly, osteoclast-like cells derived from the bone marrow help clarify the effect of Mg/Zn/F-BCPs on bone resorption. In vitro cell models have also been instrumental in screening various agents and biomaterials for clinical application in a cost-effective way. Results from in vitro studies demonstrated that MZF-CaPs (releasing Ca, P, Mg, Zn and F ions) promoted proliferation, differentiation and phenotypic expression of bone markers and protoglycans by osteoblast-like cells (bone forming) showing stimulation of bone formation (FIGS. 4 , 5 , 6 ). In vitro studies on osteoclasts showed that Zn—CaP (releasing Ca, P and Zn ions) and carbonate-F-apatite (releasing Ca, P and F ions) inhibited osteoclast (bone resorbing) activities ( FIG. 10 ). Mg, Zn, F simultaneously present at optimum concentrations in a calcium phosphate system (Mg/Zn/F—CaPs) enhance osteoblast activity (bone formation) as well as inhibit osteoclast activity (bone resorption) in vitro to a greater degree than when present separately. Cell response to materials with combined incorporation of Mg, Zn and F is more favorable than to materials incorporating these ions separately. Ovariectomized Rat Model. Ovariectomized rats have been used as an animal model for postmenopausal bone loss. The justification for this model is the observed similarities between ovariectomy-induced bone loss in rats and postmenopausal bone loss in humans, e.g., increased bone turnover, greater bone resorption than bone formation, greater loss of trabecular bone compared to cortical bone. The ovariectomized rats are given deficient diets to accelerate the onset of osteoporosis. Diet deficiency or immobilization and immobilization and calcium-deficient diet have been associated as risk factors for osteoporosis. Prevention of Bone Loss by MZF-CaP Administered as Daily an Oral Supplement. Results of initial studies demonstrated that mineral deficiency or estrogen deficiency (ovariectomy) in a rat model causes bone loss, thinning of cortical and trabecular bone, reduction in trabecular bone density and connectivity ( FIGS. 12 , 13 ) and decrease in bone strength ( FIG. 11 ). All these features are similar to that observed in osteoporotic bone. The newly developed biomaterial, MZF-CaPs or synthetic bone mineral (SBM), when administered as a daily supplement to a mineral deficient diet or administered to OVX rats prevented bone loss in cortical and trabecular bones (FIGS. 12 , 13 , 16 , 17 ) (LeGeros et al, Key Eng Mater 2008; 361-363:43-46; IADR 2006, abstract no. 270; IADR 2007, abstract no. 2176). The bone seeking ions (Mg, Zn and F) in MZFCaP were incorporated in the cortical and trabecular bones (Table 2). TABLE 2 Composition (wt %) of rat cortical bones (not ashed). Phase 1. Diet Ca P Mg Zn F Basic 26.44 12.121 0.50 0.05 0.02 Mineral deficient (MD) 25.77 11.96 0.26 0.05 0.02 MD + Mg—CaP (#53) 26/14 12/03 0.44 0.05 0.02 MD + Zn—CaP(#54) 25.93 11.78 0.31 0.24 0.02 MD + F—CaP(#52) 25.87 11.62 0.40 0.08 0.21 MD + MZF—CaP (#51) 27.09 12.43 0.45 0.10 0.12 Prevention of Bone Loss by MZF-CaP Administered by Weekly Injection. Parallel studies also showed that MZF-CaP administered as a weekly injection for 4, 12 or 16 weeks also increased bone strength ( FIG. 14 ) and prevented bone loss induced by estrogen deficiency (Otsuka et al. J. Pharm Sci 2008; 97:421-432; Key Eng Mater 2006, 254-256:343-346; Tokudome et al., IADR 2006 abstract No. 1138). Recovery of Bone Loss. Current FDA approved drugs have been shown to prevent further bone loss but were not shown to recover or restore bone already lost to the disease (Mohan et al., (1996) In: Principles of Bone Biology Ch 80 Academic Press: New York, pp. 1111-1124). These preliminary results demonstrate that MZF-CaP administered as oral supplement restored bone loss induced by either mineral deficiency or estrogen deficiency (ovariectomy) as shown in FIGS. 19 and 20 . Dissolution Properties of Rat Bones. Osteoclastic activity results in bone resorption. Such activity occurs in an acidic environment. In vitro dissolution (in acidic buffer) rates of bone obtained from animals receiving MZF-CaP supplement were shown to be lower than those from controls (not receiving MZF-CaP supplement untreated) as shown in FIG. 18 . Treatment results in compositional changes in the bone mineral making it less susceptible to acid challenge (bone resorption) EXAMPLES The following examples are provided to further demonstrate particular embodiments of the invention and are not considered to limit the scope of the invention. Example 1 Cell Response to Mg/Zn/F-BCP Materials Unsintered materials used for studies on in vitro cell response included Mg—CaP, Zn—CaP, F—CaP, Mg/Zn/F—CaP. Effect on Proliferative Capacity of Osteoblast-Like (Bone-Forming) Cells. The effect on the proliferative capacity of human osteoblast-like cells was studied by incubating human MG-63 (10 5 cells/well/ml) in the presence or absence of materials at 37° C., 5% CO 2 for 5 days. The cells were radiolabeled with 1 mCi of 3 H-thymidine, and the proliferation rate was determined by scintillation counting of TCA precipitable DNA. The materials significantly increased the proliferative capacity of osteoblast-like cells. Higher proliferative effect compared to control in cells exposed to the synthetic materials was observed. Effect on Phenotype Expression of Bone Growth Markers. The effect on the phenotype expression and growth markers of human bone-derived osteoblasts was studied by incubating 10 5 cells/well/ml in the presence or absence of the materials at 37° C., 5% CO 2 for 5 days. Total RNA was isolated and specific transcript levels for osteocalcin (OSC), alkaline phosphatase (AP), collagen type I (Col 1), osteopontin (OSP) and growth markers cyclin D1 (CD1) and CDk5 were determined by reverse transcriptase polymerase chain reaction (RT-PCR). The levels of OSC mRNA were low and expression was not detectable in osteoblasts incubated in control medium alone. Incubation with four different preparations enhanced OSC expression to detectable level ( FIG. 5 ). OSC is documented to play a critical role in mineralization. FIG. 5 depicts the effect of the present synthetic materials on proliferation of human osteoblast-like cells (MG-63) compared to control. All the materials, especially ( 2 ), ( 4 ), ( 5 ) and ( 6 ) caused increased cell proliferation compared to control. ( 1 ) and ( 6 ) have similar F concentrations, ( 1 ) has lower Mg and Zn concentrations. FIG. 6 shows the effect of the present synthetic materials on the phenotype expression: osteocalcin, OSC; alkaline phosphatase, AP; collagen type I, Col I; and osteopontin, OSP and growth markers: cyclin D1 (CD1) and CDk4. OSC becomes detectable from materials ( 4 ), ( 5 ) and ( 6 ). The expression for OSP is stronger for materials ( 4 ), ( 5 ) and ( 6 ). The materials used for both tests: ( 1 ) Mg/Zn/F—CaPa, ( 2 ) Mg/CHA, ( 3 ) Zn/CHA, ( 4 ) CHA, ( 5 ) CFA, and ( 6 ) Mg/Zn/F—CaPb. ( 1 ) and ( 6 ) have equivalent levels of F and CO 3 , Mg and Zn levels lower in ( 1 ) compared to ( 6 ). The levels of Mg in ( 2 ) and that of Zn in ( 3 ) are equivalent to that in ( 6 ). The levels of F in ( 1 ), ( 4 ) and ( 6 ) are similar and the levels of CO 3 in ( 10 to ( 6 ) are similar. MZF-CaPs also affect the human osteoblasts expression of proteoglycans. Analysis of proteoglycan transcripts showed no distinct pattern in versican expression whereas decorin expression appeared to be modulated by the CaPs. Biglycan expression was profoundly increased by CaPs containing Mg, Zn and F. Example 2 Preparation and Characterization of Unsintered and Highly Sintered (Ceramic) Materials Incorporating Mg, Zn, and F in a Calcium Phosphate Matrix The materials are designated herein as Mg/Zn/F—CaP. Mg/Zn/F—CaP will consist of one phase (Mg-, Zn- and/or F-substituted carbonate apatite) or of biphasic calcium phosphate, BCP, an intimate mixture of β-TCP (Mg- and Zn-substituted) and carbonate apatite (Mg-, Zn- and F-substituted). (Mg, Zn, F and Ca have been separately associated with bone formation, bone resorption, biomineralization). Studies on synthetic and biologic apatites (mineral phases of enamel, dentin and bone) using a combination of analytical techniques (x-ray diffraction, infrared spectroscopy, chemical analysis) demonstrated that biologic apatites (the mineral phases of enamel, dentin, cementum and bone) are not pure hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 (stoichiometric Ca/P molar ratio, 1.67) but are associated with minor constituents (most important of which are magnesium and carbonate) and trace elements. Therefore, biologic apatite such as bone apatite, may be more accurately described as carbonate apatite, approximated by the formula: (Ca,Mg,Na) 10 (PO 4 ,CO 3 ,HPO 4 ) 6 (OH,Cl,F) 2 where Mg, Na and CO 3 are minor constituents and Cl and F may be present in trace amounts. Substitutions or incorporation of different ions in the apatite lattice cause changes in properties: lattice parameters, crystallinity (reflecting crystal size or perfection), and solubility. For example, partial CO 3 -for-PO 4 substitution (coupled with Na-for-Ca substitution) or partial Mg-for-Ca substitution causes an increase in solubility and decrease in crystallinity. Mg and CO 3 have synergistic effects on the properties of apatite. F-for-OH substitution causes a decrease in solubility and increase in crystallinity of synthetic and biologic apatite and promotes formation of less Ca-deficient synthetic apatites. Pure . -TCP cannot be obtained from solution. However, when Mg or Zn ions are present, Mg- or Zn-substituted -TCP are formed. The formation of partially substituted Mg or Zn in apatite or in -TCP or Mg- or Zn-containing amorphous calcium phosphate (ACP) depends on the solution Mg/Ca or Zn/Ca or (Mg+Zn)/Ca molar ratios. Mg- and Zn-deficiencies have been implicated as risk factors in the development of osteoporosis. Separately, Mg, Zn or F has been recommended for osteoporosis therapy. Also, separately, these ions have also been shown to promote bone formation and increase bone mass. In rats, at the biologic apatite crystal level, Mg supplementation was shown to cause the formation of smaller bone apatite crystals and smaller enamel apatite crystals while F-incorporation in bone from the drinking water caused the formation of larger and less soluble bone apatite crystals. F has been shown to consistently increase bone mass. However, other studies have reported increased bone fracture with prolonged use of F compounds. F was shown to affect the orientation of collagen and decrease the level of collagen synthesis, modify bone matrix components and was associated with abnormal mineralization. On the other hand, Zn ions were shown to increase collagen and DNA synthesis. The material of the present invention, by combining relatively optimum concentrations of F, Mg and Zn ions in a calcium phosphate matrix, combines the beneficial effects of F of these ions on the bone mineral (increasing crystallinity and decreasing solubility) and of Mg and Zn on the organic matrix components thus minimizing deleterious effects of Mg and/or Zn on the bone mineral or deleterious effect of F on bone matrix components. In addition, since these ions appear to act additively or synergistically, the dose for each ion can be reduced to a level that will not be harmful after prolonged use. Example 3 Preparation and Characterization of Uncalcined or Unsintered Material Incorporating Mg+F (M/F—CaP), Zn+F (Zn/F—CaP), and Mg+Zn+F (Mg/Zn/F—CaP) in a Calcium Phosphate Matrix Materials and Methods. All chemicals used in the preparation of MZF-CaPs or SBM were reagent grade (Fischer Chemicals, New Jersey). MZF-CaP or SBM were prepared by hydrolysis method. Preparations incorporating only Mg, (MgCaP) or Zn (ZnCaP), F (FCaP) and all three ions (MZFCaP) in a calcium phosphate matrix were made. The preparations were characterized using Xray diffraction (X'Pert, Philips), FTIR (Nicolet 500), thermogravimetry, TGA, and inductive coupled plasma, ICP (ThermalJarrel Ash) for Ca, Mg, Zn, P, Na contents; and F for F ion selective electrode. The MZFCaP or SBM preparations showed XRD profiles shown in FIGS. 1 and 8 . F—CaP, MgCaP and CaP incorporating all three ions, MZFCaP showed only the apatite XRD profiles, with FCAP showing the higher crystallinity (larger crystalsize); while Zn—CaP showed two phases: Zn-substituted tricalciumphosphate (Zn-CP) and apatite. The composition of these preparations is listed in Table 1. Ca and P ion concentrations were not significantly different in bones of rats in all diets. However, Zn ion concentration was highest in bone from rats given mineral deficient (md)+Zn—CaP; F ion concentration highest in bones given F—CaP and MZF-CaP; Mg ion concentration was lowest in bones of rats on md diet and not significantly different in bones of rats on normal or supplemented diets. (Table 2). The crystallinity (reflecting crystal size) of bones from rats on basic or supplemented diets were significantly higher (larger crystal size) than those from rats on mineral deficient diets. Example 4 The release of ions (Ca, Mg, Zn and P) in acidic buffer (0.1M Kac, pH 6, 37 C) with time, depends on the composition of MZF-CaP. With similar CO 3 concentrations, the higher the F concentration, the lower the rate of release, the higher the Mg and Zn concentrations, the higher the rate of release ( FIGS. 3 and 4 ). Compared to OTC (over the counter) calcium supplements (e.g., CALTRATE® or calcium carbonate) that only released Ca ions in larger amounts at a shorter time, MZF-CaP simultaneously released Ca, P, Mg, Zn and F ions. High Temperature (800° C. to 1100° C.) Preparations. The conditions for high temperature preparation of F-containing carbonate apatites (CFA), Mg-substituted β-TCP (Mg-TCP) and Zn-substituted β-TCP (Zn-TCP) were optimized. Determination of some of the chemical properties (composition, dissolution properties) showed the following: (a) CFA prepared at high temperatures (800° C.) containing high F and low CO 3 contents had lower dissolution rate than that with low F and high CO 3 ( FIG. 9A ) confirming results obtained with CFA's prepared at low temperatures (95° C.); (b) increasing amounts of Mg or Zn in the β-TCP decreased their dissolution rates (FIGS. 9 B, 9 C) similar to that observed with Mg-TCP prepared at low temperature. Example 5 Determination of In Vitro Cell Response to MZF-CaPs Osteoblast-Like Cell Response. More than forty MZF-CaP formulations were screened for their effect on the (i) proliferative capacity, (ii) type I collagen production and (iii) phenotype expression of bone markers of osteoblast-like cells (MG-63). Response of osteoblast-like cells on all the MZF-CaPs tested showed increased proliferation, higher production of type I collagen and phenotypic expression of bone markers, including alkaline phosphatase, extracellular matrx (ECM) constituents such as alkaline phosphatase, type I collagen, osteocalcin and proteoglycans. Inhibitory Effect of Zn-TCP on Osteoclastic Activity. 10-day-old Japanese white rabbits were used in this study. Cell response to β-TCP with increasing amounts of Zn was determined from formation of an actin ring and expression of the following genes analyzed by quantitative RT-PCR: carbonic anhydrase II (CAII), cathepsin K/OC2, TRAP and glyceraldehydes-3-phosphate dehydrogenase (GAPDH). The resorbing activity of osteoclasts was assessed by measuring the morphological parameters of resorption pits. Results showed that Zn-TCP compared to β-TCP, suppressed the activity of mature osteoclasts through reduction in actin ring formation ( FIG. 10A ), down-regulation of CAII and cathepsin K expressions ( FIG. 10B ) without significant change in the expression of TRAP and increased cell apoptosis ( FIG. 10C ), in a dose dependent manner. Example 6 Determine the Effect of Orally Administered Various Mg/Zn/F—CaPs on Bone Properties of Mineral Deficient Rats Sprague-Dawley rats (Charles River Labs), 2 months old (average weight, 165 g) were randomly distributed into the following groups (10 per group for female or male rats): GA: on basic diet; GB: on mineral deficient diet (MD); GC: on MD diet+Mg—CaP; GD: MD diet+Zn—CaP; GE: MD diet+F—CaP; and GF: on MD+Mg/Zn/F—CaP (MZF-CaP) for 3 months. Rat food pellets (basic, mineral deficient and supplemented mineral deficient diets) were prepared by Purina Test Diets. Compositions of the MZF-CaP preparations and of the diets are summarized in Tables 1 and 3, respectively. Animal protocol was approved by NYU IUCAC and adhered to the NIH guidelines for the care and use of laboratory animals. The rats were sacrificed by CO 2 inhalation. The bones (femurs, tibias, vertebras, jawbones) were separated, cleaned of soft tissues and stored according to type of analyses: femurs for bone strength analyses were wrapped in wet gauze and directly frozen; other bones were stored in 70% alcohol and stored at °20° C. Bones for x-ray diffraction (X'Pert Philips), SEM (Hitachi S3500N), radiography (Faxitron Series 43805 N X-ray System, Hewlett-Packard), and microcomputed tomography, microCT (μCT 40, Scanco Medical, Switzerland). Tibias for compositional analysis (by inductive coupled plasma for Ca, Mg, Zn, and P and by F-ion selective electrode for F) were ashed at 600° C. Other tibias were enzyme treated and analyzed as unashed samples. Composition of unashed cortical bone is summarized in Table 2. Bone strength ( FIG. 11 ) was determined by 3-point bending using universal testing machine (Instron). SEM images showed that mineral-deficient (MD) diet caused thinning of the cortical bone ( FIG. 12B ), and MD diet supplemented with Mg—CaP ( FIG. 12C ), Zn—CaP ( FIG. 12D ), F—CaP and especially ( FIG. 12E ), MZF-CaP ( FIG. 12F ), prevented bone loss. Similar effects on trabecular bone thickness ( FIG. 13 ), bone density and trabecular bone connectivity were observed. TABLE 3 Composition of the diets given to the rats. Diet wt % Ca wt % P wt % Mg ppmZn ppmF Basic 0.6 0.57 0.07 21 0.0 Mineral deficient(MD) 0.0 0.0 0.17 0.0 0.0 MD + Mg—CaP(#53) 0.17 0.29 0.07 1.0 0.0 MD + Zn—CaP 0.17 0.21 0.0 370 0.0 MD + F—CaP 0.19 0.27 0.0 0.0 67.2 MD + MZF—CaP 0.18 0.27 0.02 276 66.3 Example 7 Prevention of Bone Loss Induced by Ovariectomy Non-OVX and OVX Sprague-Dawley rats (3 months old, average weight, 225 g) were distributed into the following groups: G1: control (non-Ovx Rats); G2: OVX rats on basic diet (BD); G3: OVX rats on BD supplemented with MZF-CaP for 5 months. After sacrifice, femurs, tibia, vertebra, and jawbones were collected, cleaned of extraneous tissues and stored according to what type of analyses will be performed. Mechanical test (3-point bending) were determined using femurs. TGA, XRD and FT-IR analyses were made on tibia and vertebra, SEM and microCT on femurs that were cleaned of extraneous soft tissues; Ca, P, Mg, Zn, Na and F determinations were made on ashed (800° C.) bones. Faxitron, (radiography), SEM and microCT images showed that bone loss induced by estrogen deficiency was prevented when diet was supplemented with MZF-CaP. Results from these studies demonstrated that MZF-CaPs administered daily as supplement to mineral deficient or basic diets were effective in preventing bone loss enhancing bone strength induced by mineral deficiency or estrogen deficiency (ovariectomy) in rats. Example 8 Determine Therapeutic Effect of MZF-CaP Administered by Weekly Injection on Ovariectomized Rats on Enhancing Bone Properties (Bone Density and Bone Strength) Sprague Dawley rats (4 weeks old) were used. The rats were randomly assigned to 6 groups (6 rats per group): GN—normal (non-OVX); GC: control (OVX rats on Zn-deficient diet); G1, G2, G3 and G4 were OVX. Rats receiving weekly injections of Zn-TCP (G1), MZF-CaP #51 (G2), MZF-CaP#68 (G3) and MZF-CaP#76 (G4). The compositions of these MZF-CaPs are listed in Table 1. The composition of Zn-TCP: 6.17 wt % Zn; 34.1 wt % Ca and 19.5 wt % P. 10 mg of MZF-CaP or Zn-TCP in 0.1 mL saline solution was injected intramuscularly in the right thighs of the OVX rats in all groups once a week for 12 weeks and 16 weeks. Results showed that the bone mineral densities (BMD) of the treated groups (G1 to G4) were greater than the OVX groups (GC) ( FIG. 14 ). Example 9 Determine the Effect of MZF-CaP Supplement in Preventing Bone Loss Induced by Estrogen Deficiency (Ovariectomy) Non-OVX and OVX Sprague-Dawley rats (3 months old, average weight, 225 g) were randomly distributed in the following groups (4 rats per group): G1: control (non-Ovx rats) on basic diet (BD), 5 months; G2: non-OVX rats on BD+MZF-CaP (#74); G3: OVX rats on BD for 3 months, then BD+#74 for 2 months; G4: OVX rats on BD supplemented with MZF-CaP, 5 months. Improved bone strength ( FIG. 15 ), improved microarchitecture ( FIG. 16B vs 16 A; 17 B vs 17 A), and decreased susceptibility to acid dissolution in acidic buffer ( FIG. 18 ) were observed in bones from rats with basic diets supplemented with MZF-CaP. In a continuing study, the effect of MZF-CaP (with low fluoride) and of MZ-CaP/FF on preventing bone loss induced by ovariectomy will be evaluated using larger number of rats and correlating bone strength with bone quality. FIGS. 19 and 20 represent the effect of Mg/Zn/F—CaP dietary supplements on recovery of bone loss induced by estrogen deficiency (ovariectomy) in rats. FIG. 19 represents microCT images of the femoral heads from (A) non-ovariectomized rats on a basic diet, (B) ovariectomized rats on a basic diet after two months, and (C) ovariectomized rats on a basic diet supplemented with Mg/Zn/F—CaP supplements after one month. FIG. 20 provides microCT images of femur head that demonstrate further the recovery in bone loss that may be achieved by providing a Mg/Zn/F—CaP dietary supplement. (A) is a microCT demonstrating the femur head of a rat on a basic diet, (B) is a microCT demonstrating bone loss in the femur head of a rat fed a mineral-deficient diet for two months, and (C) is a microCT demonstrating recovery of bone in the femur head of a rat fed a mineral-deficient diet for two months followed by a diet having a Mg/Zn/F—CaP dietary supplement for one month. While the present invention has been described in terms of specific embodiments thereof, it will be understood in view of the present disclosure, that numerous variations upon the invention are now enabled to those skilled in the art. Accordingly, the invention is limited only by the scope and spirit of the claims appended.

The present invention provides novel biomaterials comprising one or more of Mg, Zn and F ions in a carbonate-containing biphasic calcium phosphate (BCP) system. The biomaterial may contain Mg, Zn, F, Mg and Zn, Mg and F, Zn and F, or Mg, Zn and F. The biomaterial may be substantially similar in composition to bone mineral (a carbonate apatite). The biomaterial may feature slow release of Mg, Zn, F, Ca, and P ions. The biphasic calcium phosphate, BCP, may be a mixture of unsubstituted hydroxyapatite (HA) and unsubstituted.-TCP, Ca 3 (PO 4 ) 2 . BCP of varying HA/.-TCP ratios may be produced by sintering calcium-deficient apatite, for instance having a Ca/P<1.5, 1.6, 1.67, 1.75 or 1.8 that has been prepared either by a precipitation or by a hydrolysis method or by a solid-state reaction. The amount of each component (by weight %) present in the biomaterials may be as follows: Mg 0.5 to 12 wt %, Zn 1 to 12 wt %, F 0.1 to 4 wt %, calcium 20 to 40 wt %, phosphate 10 to 20 wt %, and carbonate (CO 3 ) 1 to 20 wt %. The biomaterial may further comprise one or more other ion such as strontium, manganese, copper, boron or silicate, or one or more other organic moiety such as a protein, a peptide, or a nutraceutical which may provide antioxidant, anti-bacterial or anti-inflammatory properties. The invention also provides methods of inhibiting bone resorption, methods of treating osteoporosis or delaying the onset of osteoporosis, methods of treating a bone fracture, and methods of inhibiting osteoclast activity. Further, the invention provides methods of treating or reversing bone deficiencies such as bone loss, similar to osteoporosis, caused all or in part by a mineral deficient diet, a disease such as cancer or osteopenia, a treatment such as steroid therapy or radiation therapy, or a physical condition such as immobilization.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 11/281/151, filed Nov. 17, 2005, which is a continuation of U.S. patent application Ser. No. 10/678,774, filed Oct. 3, 2003, now abandoned, which is a continuation of U.S. patent application Ser. No. 10/201,112, filed Jul. 22, 2002, now abandoned, which is a continuation of U.S. patent application Ser. No. 09/668,067, filed Sep. 22, 2000, now U.S. Pat. No. 6,425,887 issued Jul. 30, 2002, which is a divisional of U.S. patent application Ser. No. 09/457,844, filed on Dec. 9, 1999, now U.S. Pat. No. 6,592,559 issued Jul. 15, 2003, which claims the benefit of U.S. Provisional Patent Application Ser. Nos. 60/111,624, filed Dec. 9, 1998 and 60/130,597 filed Apr. 22, 1999, each of which is hereby incorporated herein by reference. TECHNICAL FIELD [0002] This invention relates generally to medical devices and more particularly to needles that are curved for indirect infusion access within the body. BACKGROUND [0003] Medical procedures involving the vertebrae are typically complicated because of the preciseness required to avoid both neural damage and injury to major blood vessels, as well as the indirect path that is usually required to access the treatment site. [0004] This is certainly the case when performing a vertebroplasty, a procedure whereby bone cement, most commonly methyl methacrylate, is injected into a vertebral body to provide stabilization and/or pain relief in selected patients having a spinal condition such as osteolytic metastasis and myeioma, painful or aggressive hemangiome (benign lesions of the spine), or painful osteoporotic vertebral collapse. [0005] Standard treatment practice depends on the region of the spine being treated. For the cervical vertebrae, anterolateral access is used with a 15 gauge needle. The large vessels adjacent to the vertebra are laterally manipulated by the radiologist to provide an access site between the vessels and the pharyngolarynx. An upward access route is required because the needle must be introduced below the mandible. [0006] When accessing the thoracic or lumbar vertebrae, typically a large 10 gauge needle is used following a transpedicular or posterolateral approach. The transpedicular route is preferred to avoid spinal nerve injury and to decrease the probability of the cement leaking into tissues adjacent to the vertebral body. [0007] To obtain complete fill of a damaged vertebral body, it is often required that a second transpedicular access be made from the opposite side. A single infusion usually cannot fill the entire target area because the needle tip cannot be redirected from the original plane of entry. Continued infusion of cement from the first access site will usually not result in an adequate infusion due to the tendency of the material to set before it fills all of the affected area, thereby becoming a baffle to itself. Furthermore, the thick density of the marrow and structures, such as veins, usually acts to impede free flow of the cement within the vertebral body. [0008] Another concern during the procedure is accidental puncture of the these veins. Because vertebral veins lead directly to the lungs, there is a significant risk of pulmonary embolism if cement is accidentally introduced therein. [0009] The inability to adequately maneuver the needle cannula tip within a body or around structures is a major limitation of the straight needle. Additional needle sticks to complete a medical procedure result in discomfort to the patient and additional risk of leakage and other complications. [0010] To sufficiently access a vertebral body for complete infusion of cement, the needle tip must be capable of being deflected at significantly large angles from the original axis. This would require that the needle have a distal bend so that the needle could be rotated to selectively direct the material. [0011] Rigid curved needles are well known for suturing applications; however, adding anything more than a slight bend to an infusion needle limits its access path and ability to deeply penetrate tissue, especially bone. For example, a rigid curved needle is unsuitable for use in a vertebroplasty procedure where the needle cannula must be driven through the bone and deep into the vertebral body using a relatively straight approach and maintained in place to avoid additional damage to the entry site. While the initial needle access must be done with a straight needle of sufficient strength to penetrate bone, the ideal approach would be to direct a lateral infusion of cement following needle penetration, and then to withdraw the needle along its original path. [0012] Accomplishing this is problematic. The tissue density and resistance of the tissue to penetration at the treatment site can require that the inner infusion member be nearly as stiff as the outer piercing cannula. A certain degree of needle rigidity is required in order to be able to maneuver the needle and accurately direct flow of material. [0013] While stainless steel needles having a slight distal bend are known, the amount of needle curvature necessary to provide adequate lateral infusion is not possible—the needle plasticly deforms once inside the outer restraining cannula and hence is unable to return resiliently to its preformed shape. Thus, a second needle access would still be required to provide adequate filling. [0014] Other medical procedures present similar problems when a single straight needle is used. One example is tumor ablation where percutaneous ethanol injection is used to treat carcinoma of the liver and kidney. Originally introduced as a palliative treatment for inoperable hepatocellular carcinoma of the liver, ethanol injection has now been shown to have curative potential comparable to resection in many patients, especially for smaller tumors. [0015] Practice has been to inject ethanol directly into masses using a straight needle and to allow the ethanol to infuse from one or more side holes into the tissue. The problem is that the infusion may not penetrate any deeper than the needle tract; thus portions of the tumor are not effectively treated. It is desirable to provide a device for more effective infusion of ethanol into the tumor mass. SUMMARY OF THE INVENTION [0016] The foregoing problems are solved and a technical advance is achieved in an infusion needle made of rigid superelastic material and having at least one performed bend along the distal portion of its length. The needle is used as an inner cannula coaxially with a second hollow cannula for restraining the inner needle cannula in a substantially straight orientation during percutaneous introduction to the target site, whereby the inner needle cannula is deployed to resiliently return to its preformed configuration. [0017] The ability of the preformed inner needle cannula to deflect laterally upon exiting the outer cannula allows the inner needle cannula to infuse or aspirate material at multiple points within different planes in the body as the inner infusion needle rotates about its longitudinal axis. This helps to reduce or eliminate the need for additional “sticks” with the outer cannula; it also allows the operator to make an entry from one direction, then to deploy the curved inner cannula to reach a site that cannot be accessed directly, such as where another structure lies along the access path, thereby blocking the target site. [0018] The preferred material for the inner cannula is a superelastic, shape memory alloy such as sold under the trademark Nitinol (Ni—Ti); however, there are other non Ni Ti alloys that may be used. A Nitinol alloy is desirably selected that has properties whereby the temperature at which the martensitic to austenitic phase change occurs is lower than the working temperature of the device (i.e. room temperature). [0019] As described in U.S. Pat. No. 5,597,378, incorporated herein by reference, a permanent bend may be heat set in a superelastic Nitinol cannula by maintaining the cannula in the desired final shape while subjecting it to a prescribed high temperature for a specific time period. The resulting cannula can be elastically manipulated far beyond the point at which stainless steel or other metals would experience plastic deformation. Nitinol and other superelastic materials when sufficiently deformed undergo a local phase change at the point of stress to what is called “stress-induced martensite” (SIM). When the stress is released, the material resiliently returns to the austenitic state. [0020] A second method of imparting a permanent bend to the needle material is by a process commonly known as “cold working.” Cold working involves mechanically overstressing or overbending the superelastic cannula. The material within the bending region undergoes a localized phase shift from austenite to martensite and does not fully return to its original shape. In the case of the cold-worked cannula, the result is a permanent curve about the bending zone which has been locked in to at least a partial martensitic crystalline state. [0021] In contrast, when heat treating is used, the entire heat-annealed cannula is in a austenitic condition, even in the curved region, and is only temporarily transformed to martensite under sufficient bending stresses. Therefore, the flexural properties of the annealed cannula vary little across its length. [0022] Conversely, the bend of a cold-worked cannula, which contains martensite, has increased resistance to deformation and therefore holds its shape better than the more flexible bend of the pure austenitic cannula This increased rigidity can be an advantage for certain clinical applications. [0023] In one aspect of the invention, an introducer trocar or stylet is used with either the outer or inner needle cannula, depending on the luminate size of the needle, to facilitate access to tissue and/or prevent coring tissue into the distal tip of the needle device. The infusion needle or inner cannula is introduced through the outer cannula after access has been established and the trocar or stylet is removed. [0024] Depending on the size of the cannulas, the degree of the preformed bend, or the method used to form the bend, the inner cannula or needle may slightly deform the outer cannula as the preformed bend present in the inner needle or cannula is constrained within the outer cannula. As a result, the outer cannula may be deflected a few degrees from its normal longitudinal axis at a point corresponding to the bend of the inner cannula. As the inner cannula is deployed from the outer cannula, the inner cannula deflects laterally until the entire region of the bend is unsheathed. The distal opening of the inner cannula is oriented at a large angle (preferably within the range of 60-90°) from the original longitudinal axis when the inner needle is fully deployed. [0025] The ability of the inner cannula to deflect at a significant angle from the original longitudinal axis has great utility in a number of applications where straight access is required followed by redirection of the distal opening. This deflection permits access to a different site without the necessity of withdrawing and reintroducing the needle. [0026] A primary example of such a procedure is vertebroplasty in which infusion of the stabilizing cement with a straight needle often requires a second stick to provide complete filling to stabilize the vertebral body while avoiding damage to delicate structures such as veins. As with the standard single-needle procedure involving the thoracic or lumbar regions of the spine, a transpedicular approach is normally used whereby the larger outer needle cannula, such as a coaxial Jamshldi-type needle, is introduced into the damaged or diseased vertebral body. The outer needle includes an inner introducer trocar which is then replaced with a inner curved needle for infusion of the cement. [0027] The ability of the curved needle to deflect laterally and rotate to reach multiple planes gives it a significant advantages over straight needles which have a limited range of movement. Because of this additional range of movement, the curved needle can usually complete the vertebroplasty procedure with a single access of the vertebral body. This avoids additional discomfort and risks to the patient, which include complications from leakage of cement or inadvertent infusion into non-target areas. [0028] In addition to using the coaxial needle for infusion of cement as above, the device can also be adapted for aspirating material or serving as a conduit for the introduction of other devices. The apparatus may be used for a percutaneous corpectomy, a procedure which involves fusion and decompression of two or more vertebrae by first aspirating tissue from the damaged vertebral bodies, then introducing a prosthesis having a carbon fiber composite cage packed with bone graft material to serve as scaffolding for the affected vertebrae. Once the cage is properly positioned, methyl methacrylate or another suitable material is infused into the vertebral bodies to secure the prosthesis. The percutaneous corpectamy offers less trauma, and with the reinforcement cage, provides superior rigidity over a conventional corpectomy utilizing bone graft material alone. [0029] In another aspect of the invention, the coaxial needle can be adapted for paraspinal use to inject medicaments within the neural canal or epidural space as part of management and/or diagnosis of pain. Preferably, the outer cannula has a tip adapted for piercing soft tissue. This outer needle cannula, preferably about twenty-one (21) gauge, is introduced percutaneously parallel to the spinal column along with an internal stylet with matched bevel to prevent coring tissue into the distal opening. The stylet is removed and the curved needle, about twenty-five (25) gauge, is inserted into the outer cannula. The needle assembly is then maneuvered to contact a nerve root during a diagnostic procedure to help recreate pain symptoms of the patient. The inner infusion needle also includes a stylet which is situated within the passageway of the needle as it is directed to the target site. The stylet is then removed from the infusion needle and medicaments, commonly steroids such as celestone (injected with lidocaine), kenalog, or methylprednisone are introduced to the treatment site. The inner needle is then withdrawn into the outer sheathing cannula and both are withdrawn from the patient. [0030] Another use of the smaller gauge paraspinal needle is for diskography which consists of injecting a contrast agent (preferably nonionic contrast media) directly into the patient's disk to delineate the extent of any malformation or injury to the vertebral body. [0031] Yet another aspect of the invention solves the problem of infusion of ethanol into a tumor mass by utilizing a plurality of curved needle cannulae deployed within an cannula introduced into the tumor where the curved needle cannulae radiate outward into an umbrella-shaped configuration. Infusion can take place at multiple points within the tumor to provide wider dispersion of the ethanol. Following treatment, the curved needle cannulae are withdrawn into the cannula and the device is removed from the patient. [0032] In a related aspect, one or more needle cannulae are located proximal to the distal end of the infusion needle. These proximally-located cannulae allow infusion of medicaments at different points along the length of the device. By having multiple sets of needles arranged in the umbrella configuration, the volume of tissue treated is increased. The coaxial outer cannula includes a plurality of side apertures that allow the proximally-located needle cannulae to deploy after the infusion needle is placed at the desired location in the body and the outer cannula is withdrawn. An outer sheath over the coaxial outer cannula selectively exposes the side apertures to permit the appropriate alignment of needle cannulae and apertures when there are multiple rows of each. [0033] The invention has applicability in any clinical situation where a straight approach is dictated and there is a need to avoid an obstructing structure (a large vessel, bowel loop, etc.) in the entry path, or the need to redirect the approach to a more lateral pathway to infuse medicaments or aspirate, such as to drain an abscess. [0034] In addition to infusion or aspiration, the invention can provide a conduit for introducing and/or directing the path of other medical devices within the body such as radio-frequency ablation catheters or wire guides. This would allow a straight approach to a critical juncture whereafter the curved infusion needle can be deployed to precisely proceed to the desired anatomical site, especially in situations such as a luminal bifurcation or when access to an ostium is required. [0035] Another use of the invention is to place the infusion needle in a bronchoscope or colonoscope which can serve as the outer constraining device. Under visualization, the inner needle then can be directed to perform a biopsy or other type of procedure. BRIEF DESCRIPTION OF THE DRAWINGS [0036] FIG. 1 is an isometric view of an illustrative embodiment of the curved needle inner cannula; [0037] FIG. 2 is a top view of an outer needle cannula with an introducer trocar and the inner curved needle cannula; [0038] FIG. 3 is a top view of the assembly of the inner curved needle cannula inside the outer needle cannula; [0039] FIG. 4 is an exploded isometric view of a second embodiment of the inner and outer cannula; [0040] FIG. 5 depicts a pictorial view of the inner cannula of FIG. 4 with an introducer stylet; [0041] FIG. 6 is a side view of the inner cannula of FIG. 4 being initially deployed from the outer cannula; [0042] FIG. 7 is a side view of the inner cannula of FIG. 4 being further deployed from the outer cannula; [0043] FIG. 8 is a side view of the inner cannula of FIG. 4 being still further deployed from the outer cannula; [0044] FIG. 9 is a partially sectional view depicting the apparatus of FIG. 2 being introduced into a vertebral body; [0045] FIG. 10 is a partially sectional view similar to FIG. 9 , depicting of the apparatus of FIG. 2 infusing cement into a vertebral body. [0046] FIG. 11 is a broken, partially sectioned view similar to FIGS. 9 and 10 , depicting of the apparatus of FIG. 2 infusing additional cement into a vertebral body. [0047] FIG. 12 is an isometric view of a third embodiment of the apparatus; [0048] FIG. 13 is a side view of the multi-directional infusion needle illustrated in of FIG. 12 ; [0049] FIG. 14 is a broken, side view of the needle of FIG. 13 partially showing the needle deployed; [0050] FIG. 15 is a side view of a trocar introducer used with the embodiment of FIG. 12 ; [0051] FIG. 16 is a side view of the proximal assembly portion of the apparatus illustrated in FIG. 12 ; [0052] FIG. 17 is a side view of a fourth embodiment of the apparatus; [0053] FIG. 18 is a broken, partially-sectioned side view of the apparatus illustrated in FIG. 17 prior to deployment; [0054] FIG. 19 is a transverse cross-sectional view of coaxial outer cannula depicted in FIG. 17 ; [0055] FIG. 20 depicts cross-sectional views of two embodiments of coaxial outer cannula depicted in FIG. 17 ; [0056] FIG. 21 is an isometric view of a fifth embodiment of the present apparatus; and [0057] FIG. 22 is an isometric view similar to that of FIG. 21 showing the apparatus fully deployed. DETAILED DESCRIPTION [0058] FIG. 1 depicts a needle assembly 10 comprising an infusion needle 11 with a preformed bend 16 for lateral infusion or aspiration of medicaments and other materials. As defined herein, the “needle assembly 10 ” can comprise infusion needle 11 alone or infusion needle 11 in combination with other components. The “infusion needle 11 ” as defined herein comprises one or more needle cannulae having a preformed bend 16 . [0059] The infusion needle 11 of FIG. 1 is comprised of a superelastic alloy needle cannula 13 , preferably the alloy sold under the trademark Nitinol, that is soldered or otherwise affixed to a well-known needle hub 14 using one of a selected number of well-known techniques, including that of Hall described in U.S. Pat. No. 5,354,623 whose disclosure is expressly incorporated herein by reference, and a flange 23 which has a first tapered or pointed end 24 whose shape is readily distinguishable from the second, squared end 42 . [0060] First end 24 corresponds to the direction of preformed bend 16 in needle cannula 13 of infusion needle 11 . Bend 16 is formed in the Nitinol needle cannula 13 by either the well-known process of deforming the cannula under extreme heat for a prescribed period of time, which produces a cannula entirely in the austenitic state, or by cold working the cannula, which involves applying a large amount of mechanical stress to deflect the 15 cannula well beyond the desired amount of permanent bend. Cold working permanently locks a crystalline structure in the bending zone into at least a partial martensitic condition while the unstressed portions of the cannula remain in the austenitic state. [0061] Cold worked Ni—Ti alloys are discussed in “Linear Superelasticity In Cold-Worked Ni—Ti”, (Zadno and Duerig) pp. 414 to 419, in Engineering Aspects of Shape Memory Alloys, Butterworth-Heineman, Boston, Mass. (Duerig et al, editors) which is incorporated herein by reference. In addition to Nitinol, superelastic or pseudoelastic copper alloys, such as Cu—Al—Ni, Cu—Al—Zi, and Cu—Zi, are available as alternative needle cannula materials. Flexible polymeric materials with sufficient rigidity for both deployment and shape memory to assume a desired curve may also be used in certain applications, either alone or in combination with reinforcing metal components such as a metal braid or tip. [0062] Preformed bend 16 of infusion needle 11 forms a distal portion of needle cannula 13 , preferably close to about 25% of the length of needle cannula 13 in the embodiment shown in FIG. 1 . The large size of the infusion needle, preferably 10 to 18 gauge, makes this particular embodiment suitable for penetrating a vertebral body to perform a vertebroplasty or percutaneous corpectomy procedure. A more preferred range is 12 to 17 gauge, with the most preferred cannula size being 13 to 15 gauge. [0063] With regard to a vertebroplasty and corpectomy procedures, the larger gauge cannula has both the strength to penetrate dense bone material as well as a sufficient lumen diameter to aspirate material from the vertebral body and to infuse highly viscous bone cement, such as methyl methacrylate. The preferred preformed bend 16 of the infusion needle 11 has a constant radius. For the embodiment of FIG. 1 , the preferred radius of distal bend 16 is approximately 3.0 cm for a 13 gauge needle, and approximately 2.5 cm for a 14 gauge needle. Although the illustrative embodiment has a constant bend radius, an increasing or decreasing radius bend could be employed for certain clinical applications. Furthermore, it is possible to introduce more than one bend into the superelastic cannula for applications requiring a special needle configuration. [0064] The primary purpose of using a Nitinol or other superelastic alloy cannula is that the cannula can be constrained into one shape during passage to the treatment site, then deployed into the preformed configuration without experiencing any plastic deformation. [0065] FIG. 2 depicts a pair of needles to be used coaxially in that manner, including the infusion needle 11 of FIG. 1 and a coaxial outer cannula 12 for maintaining inner infusion needle 11 in a substantially straight configuration while being introduced to the treatment site. The embodiment depicted in FIG. 2 is Jamshidi-type needle (Manan Inc., Northbrook, Ill.) which is a two-part needle assembly 43 , and is most commonly used for accessing dense, hard tissue such as bone, fibrous material, etc. Thus, it is well suited for penetrating the wall of a vertebral body wherein the infusion needle 11 can be deployed. [0066] The two-part needle assembly 43 includes a coaxial outer cannula 12 having a stainless steel cannula 19 with an inner passageway 21 that is sufficiently large to accommodate inner infusion needle 11 . For example, the standard 11 gauge Jamshidi-type needle suitable for accessing a vertebral body would be used with thirteen (13) gauge inner curved needle. Stainless steel cannula 19 is affixed proximally to a handle 26 and a connector hub 31 (shown in FIG. 3 ). The connector hub 31 receives the second part of the two-part needle assembly 43 , the coaxial outer cannula introducer 52 which preferably comprises a trocar 25 . The trocar hub 27 locks into handle 26 of coaxial outer cannula 12 . The beveled tip 30 of trocar 25 extends approximately 5 mm beyond the distal tip 22 of coaxial outer cannula 12 and assists in penetration. Trocar 25 also serves to prevent the coaxial outer cannula 12 from coring a sample of bone or other material during access. [0067] After outer needle assembly 43 has been directed to the target site, trocar 25 is removed from coaxial outer cannula 12 and infusion needle 11 is inserted into passageway 21 of the coaxial outer cannula 12 , as shown in FIG. 3 . To maintain openness of the infusion needle passageway 15 and to prevent tissue coring during deployment, an inner needle introducer stylet 46 can be introduced coaxially inside the infusion needle. Inner needle introducer stylet 45 includes a handle 83 and a shaft 46 which is made of a flexible, high-tensile. polymeric material such as polyetherethylketone (PEEK) to allow stylet 45 to assume the contour of preformed bend 16 after deployment. [0068] Inner infusion needle 11 straightens as it is loaded into coaxial outer cannula 12 . As the portion including preformed bend 16 of infusion needle 11 extends out from tip 22 of coaxial outer cannula 12 as depicted in FIG. 3 , infusion needle 11 assumes the preformed shape due to the superelastic properties of needle cannula 13 . For infusion, inner needle introducer stylet 52 , which helps prevent coring of tissue into passageway 21 of coaxial outer cannula 12 , is removed. The tapered or “arrow” end 24 of flange 23 of proximal hub 14 corresponds with the deflection plane 29 of infusion needle 11 . [0069] By maneuvering flange 28 , the inner curved needle 13 can be rotated in either direction 28 to reorient the plane of deflection 29 and place the tip opening 17 at multiple locations within the area being treated. [0070] In FIG. 3 , tip 17 is deflected at an angle 44 of approximately 60° to 70° from the device longitudinal axis 18 . This gives, for example, with a thirteen (13) gauge infusion needle 11 , a lateral reach, measured from tip 17 to longitudinal axis 18 , of nearly thirty (30) millimeters in any direction. [0071] While the degree of deflection required is determined by the application and desired lateral reach of the device, it is also limited by the size of the cannula if the permanent bend is cold worked into the material. Cold working provides a stiffer bend which can be advantageous in certain applications such as vertebroplasty and biopsy of dense tissue; it is more difficult to permanently deform a larger gauge Nitinol cannula without application of extreme heat. For the embodiments contemplated, the angle of deflection 44 can encompass a range of 30° to 110°, with a preferred range of 40 to 90° for most applications. [0072] FIG. 4 depicts a second version of the inner curved needle and sheathing outer needle adapted for use in the injection of medicaments, contrast media, or other non-viscous agents. The infusion needle 11 is comprised of a smaller gauge needle cannula 13 , preferably around twenty-five (25) gauge, mounted to a proximal hub 14 . The preformed bend 16 of individual needle cannula 13 has a slightly tighter radius than that illustrated in FIGS. 1 through 3 . [0073] Still referring to FIG. 4 , the coaxial outer cannula 12 includes a correspondingly sized needle cannula 19 , preferably around twenty-one (21) gauge, attached to a standard needle hub that is adapted to receive proximal hub 14 of infusion needle 11 . The embodiment of FIG. 4 is used with a plurality of stylets that are inserted within both the inner and outer needles during their respective introduction into the body. The first is an outer cannula introducer stylet 52 that is inserted into the passageway 21 of coaxial outer cannula 12 . The coaxial outer cannula 12 and outer cannula introducer stylet 52 are inserted together into the patient. The stylet, which is preferably a stainless steel stylet wire 46 with an attached standard plastic needle hub 47 , prevents the coaxial outer cannula 12 from coring tissue into passageway 21 at distal tip 22 . [0074] Once coaxial outer cannula 12 is in position, outer cannula introducer stylet 52 is withdrawn from coaxial outer cannula 12 and infusion needle 11 and second introducer stylet 45 are inserted together into outer needle passageway 21 . The inner needle introducer stylet 45 , which is longer than outer cannula introducer stylet 52 in order to fit the longer infusion needle 11 , serves a similar function to the outer cannula introducer stylet 52 by preventing coring of tissue when infusion needle 11 is deployed from coaxial outer cannula 12 . [0075] As illustrated in FIGS. 4 and 5 , proximal hub 14 of infusion needle 11 is adapted such that hub 53 of inner needle introducer stylet 45 locks together with proximal hub 14 to keep the two in alignment. This locking mechanism includes a molded protuberance 49 on hub 53 that fits within a recess 50 on proximal hub 14 . The purpose of maintaining alignment of hub 53 and proximal hub 14 is to match the beveled surface 51 at the tip of the inner needle introducer stylet 45 , shown in FIG. 5 , with the beveled edge at the tip 17 of infusion needle 11 . [0076] FIGS. 6 through 8 depict the deployment of infusion needle 11 from within outer needle cannula 12 . FIG. 6 shows infusion needle 11 during initial deployment from coaxial outer cannula 12 . The preformed bend 16 of the infusion needle 11 is constrained by the cannula 19 ; however, as illustrated in FIG. 6 , preformed bend 16 may be of sufficient stiffness to slightly deform outer cannula 19 while infusion needle 11 is inside coaxial outer cannula 12 . Despite this slight deformation, coaxial outer cannula 12 is still substantially straight. [0077] As depicted in FIG. 7 , stress preformed bend 16 places on outer cannula 19 relaxes as infusion needle 11 is further deployed and the angle of deflection 44 (measured from longitudinal axis 18 of coaxial outer cannula 12 to the opening at tip 17 of infusion needle 11 ) is increased. As infusion needle 11 is further deployed as depicted in FIG. 8 , fully exposing preformed bend 16 to produce the largest angle of deflection 44 , the unstressed outer cannula returns to a straight configuration. [0078] The phenomenon depicted in FIGS. 6 through 8 is most noticeable when using smaller gauge cannulae, such as shown in FIGS. 4 and 5 . The larger gauge outer cannula of FIGS. 1 to 3 is more resistant to deformation than that of FIGS. 4 and 5 . Naturally, the tendency of the stressed outer cannula to deform is also very much dependent on the stiffness and radius of the preformed bend 16 as well as the thickness of the cannula wall and material used. To eliminate this deformation during introduction of the device into the body, stylet 45 , as depicted in FIG. 5 , can be used as a stiffener until removed immediately before the portion having preformed bend 16 is deployed. [0079] FIGS. 9 through 11 depict the use of the device illustrated in FIG. 3 to perform a vertebroplasty procedure on a pathological vertebral body 33 using a transpedicular approach. As depicted in FIG. 9 , coaxial outer cannula 12 with introducer trocar 25 is introduced through the wall 38 and into the marrow 37 of the vertebral body 33 . The transpedicular route of access places the needle between the mammillary process 34 and accessory process 35 of the vertebral arch 55 . The vertebral arch 55 is attached posteriorly to the vertebral body 33 and together they comprise the vertebra 54 and form the walls of the vertebral foremen 36 . [0080] Once coaxial outer cannula 12 and inner introducer trocar 25 are within the internal region or marrow 37 of the vertebral body, trocar 25 is withdrawn from the coaxial outer cannula 12 and infusion needle 11 is inserted in its place. FIG. 10 depicts infusion needle 11 infusing bone cement 41 , commonly methyl methacrylate, into vertebral body 33 to provide it with improved structural integrity. As depicted in FIG. 11 , infusion needle 11 can be partially withdrawn or rotated to obtain more complete filling or to avoid the network of vertebral veins. Even though the vertebral body may not need to be completely filled, the density of marrow 37 would still necessitate a second transpedicular stick in the absence of the instant apparatus infusing cement within multiple planes within vertebral body 33 . Upon completion of the procedure, infusion needle 11 is withdrawn back into coaxial outer cannula 12 and both are removed from vertebral body 33 . [0081] The utility of the hollow, curved superelastic needles is certainly not limited to procedures involving the spine. Such needles are useful at many sites within the body that might require straight access by a needle, followed by indirect or lateral infusion, aspiration, or sampling. For example, the inner needle could be adapted to take biopsy samples from dense tissue, such as a breast lesion, especially where indirect access is might be desirable. [0082] FIG. 12 is an isometric view of hollow, curved superelastic needles in which needle assembly 10 comprises a multiple needle assembly 70 useful in infusion of ethanol or other medicaments into a tumor. In FIG. 12 , needle assembly 10 comprises an infusion needle 11 , which includes a multiple needle assembly 70 comprising a plurality of needle cannulae 13 , each having a preformed bend 16 , a proximal assembly 58 for constraining the multiple needle assembly 70 , and a coaxial outer cannula 12 for introducing the multiple needle assembly 70 to its anatomical target. [0083] The multiple needle assembly 70 in FIG. 13 includes a base cannula 56 affixed to a proximal hub 14 such as a standard female luer fitting. A plurality of needle cannulae 13 are manifolded into base cannula 56 , preferably evenly spaced in an umbrella configuration 75 , and affixed in place with a solder joint 57 . In the structure illustrated in FIG. 12 , five needle cannulae 13 are used; from two to as many as appropriate for the given cannula size can be used. As with the other versions, needle cannulae 13 are preferably made of Nitinol that is either annealed or cold-worked to produce the preformed bend 16 . In the structure illustrated in FIG. 12 , the coaxial outer cannula 12 has an outer diameter of approximately 0.072 inches and an inner diameter of around 0.06 inches, while the individual curved needle cannulae 13 have an outer diameter of 0.02 inches and an inner diameter of about 0.12 inches. As shown in FIG. 14 , the tips 17 of the needle cannulae 13 may be beveled to better penetrate tissue. [0084] Deployment of curved needle cannulae 13 of multiple needle assembly 70 is depicted in FIG. 14 . Needle cannulae 13 are restrained by coaxial outer cannula 12 until multiple needle assembly 70 is advanced, exposing the distal end portions of needle cannulae 13 at distal end 22 of coaxial outer cannula 12 , whereby they radiate outward to assume, when fully advanced, the umbrella configuration 75 shown in FIG. 13 . [0085] FIG. 15 depicts a side view of an outer needle assembly comprising a coaxial outer cannula 12 and outer cannula introducer stylet 52 used in placement of the multiple needle assembly 70 of FIGS. 12 through 14 . The outer cannula introducer stylet 52 is inserted into passageway 21 of coaxial outer cannula 12 with the male proximal hub 47 of the outer cannula introducer stylet 52 fitting into the female proximal hub 20 of coaxial outer cannula 12 when the outer cannula introducer stylet 52 is fully advanced. Outer cannula introducer stylet 52 includes a sharp tip 63 , such as the diamond-shape tip depicted, for penetrating tissue. [0086] The outer cannula introducer stylet 52 and coaxial outer cannula 12 may be introduced percutaneously into the liver or kidney and placed at the desired treatment location. The outer cannula introducer stylet 52 is then removed. The proximal assembly 58 with the preloaded multiple needle assembly is then advanced into the coaxial outer cannula 12 which remains in the patient. In the version illustrated in FIGS. 12 through 15 , the coaxial outer cannula preferably has an outer diameter of about 0.095 inches and an inner diameter of about 0.076 inches, while the outer diameter of the inner stylet is preferably about 0.068 inches. [0087] FIG. 16 a side view of the proximal assembly 58 shown of FIG. 12 . The Proximal assembly 58 includes a distal male adaptor 60 connected to an intermediate cannula 59 that is sufficiently large to accommodate multiple needle assembly 70 . At the proximal end of the intermediate cannula 59 is proximal assembly female adaptor 61 which is connected proximally to a proximal assembly hub 62 , such as a Tuohy-Borst adaptor. Proximal assembly hub 62 is utilized by the physician during manipulation of the device. [0088] The multiple needle assembly 70 of FIG. 13 is loaded into lumen 64 at the proximal end 65 of the proximal assembly hub 62 , with the needle cannulae 13 remaining within intermediate cannula 59 . Distal end 66 of proximal assembly 58 with preloaded multiple needle assembly 70 is then inserted into proximal hub 20 of the coaxial outer cannula as depicted in FIG. 12 . The multiple needle assembly 70 is then advanced from the proximal assembly 58 into the coaxial outer cannula 12 where it is deployed as depicted in FIGS. 12 to 14 . Ethanol is infused into multiple needle assembly 70 via the proximal hub 14 of the infusion needle 11 . Following treatment, the multiple needle assembly 70 is withdrawn into coaxial outer cannula 12 and the entire needle assembly 10 is removed from the patient. [0089] FIGS. 21 and 22 depict a variation of needle assembly 10 of FIG. 12 in which infusion needle 11 and coaxial outer cannula 12 are connected to a coaxial handle 76 used to advance and deploy multiple needle assembly 70 releasably from constraint of coaxial outer cannula 12 . As shown, coaxial handle 76 comprises a stationary outer component 77 that fits over base cannula 56 of multiple needle assembly 70 and attaches to proximal hub 20 . A slidable inner component 78 further comprises a thumb piece 79 used by the physician to advance or retract the coaxial outer cannula 12 as the slidable inner component 78 retracts into stationary outer component 77 . [0090] In FIG. 21 , the needle assembly is depicted in the introducer position with the thumb piece 79 advanced fully forward within a slot 80 in outer slidable component 77 . [0091] FIG. 22 depicts the deployment state of needle assembly 10 in which thumb piece 79 has been moved to the most proximal position within slot 80 . In this position, coaxial outer cannula 12 is retracted to fully expose the plurality of needle cannulae 13 which can assume their unconstrained configuration with the preformed bends 16 . [0092] This type of handle can be used with both the multiple and single infusion needle where a introducer trocar or stylet is not required. Other well-known types of coaxial handles 76 include, but are not limited to, screw-type, rachet-type, or trigger-activated handles which allow coaxial outer cannula 12 to be longitudinally displaced relative to infusion needle 11 . To reduce the need for a trocar or stylet for facilitating tissue penetration, distal tip 22 of coaxial outer cannula 12 can be shaped into a needle point such as depicted, or into a non-coring point to help maintain an open outer cannula passageway 21 . [0093] A syringe or other reservoir container can be attached to proximal hub 14 as an infusate source or for collection of aspirated material. In addition, a reservoir, such as a syringe, can be incorporated internally within coaxial handle 76 of needle assembly 10 or integrally attached thereto. [0094] Another version of multiple needle assembly 70 is depicted in FIGS. 17-20 whereby there are one or more groupings of proximally-located needles 73 in addition to the distally-located needles 74 that are similar to those illustrated in of FIG. 12 . By locating the additional needle cannulae 13 proximal to those at the distal end, wider dispersal and coverage is attained for infusion of medicaments. [0095] In the version illustrated in FIG. 17 , there is an arrangement of four needle cannulae comprising the distally-located needles 74 , while at least one other group comprising proximally-located needles 73 located along the length of infusion needle 11 provides for simultaneous infusion in a more proximal location. The needle cannulae 13 of the proximally-located and distally-located needles 73 , 74 can vary in configuration, length, number, and how they are attached to a base cannula 56 such as that shown in FIG. 13 . For example, individual needle cannulae 13 within an umbrella configuration 75 or between proximally-located and distally-located needles 73 , 74 can be longer, or have a different radius than others, to vary the distribution pattern of the infusate. [0096] As depicted in FIGS. 17 and 18 , each pair of oppositely-disposed needle cannulae 13 within a grouping of four proximally-located needles 73 are longitudinally offset with respect to the adjacent pair located ninety degrees (90°) therefrom, as are the side apertures 67 from which they emerge. With regard to attachment, possibilities include, but are not limited to, having all needle cannulae 13 attaching to a single base cannula 56 ; dividing base cannula 56 such that a separate portion extends distally from the proximally-located needles 73 to join the distally-located needles 74 , or eliminating the base cannula 56 such that needle cannulae 13 of multiple needle assembly 70 are separate and run the length of infusion needle 11 . [0097] To constrain needle cannulae 13 for introduction along a single pathway into the body, a coaxial outer cannula 12 is used that has side apertures 67 in the cannula to permit the proximally-located needles 73 to deploy outward therethrough for lateral infusion. FIG. 18 shows a sectioned view of the needle assembly of. FIG. 17 in which the needle cannulae 13 are constrained in the introduction position. An introducer cannula 68 is used to selectively expose side apertures 67 in versions where the arrangement of needles is such that individual needle cannulae 13 may prematurely exit a non-designated hole or row, preventing or delaying proper deployment of the multiple needle assembly 70 . By maintaining the introducer sheath over side apertures 67 until distally-located needles 73 are deployed, proper deployment of all needle cannulae 13 is easier. [0098] FIGS. 19 and 20 illustrate intraluminal guides 69 to help facilitate proper alignment of needle cannulae 13 with a designated side aperture 67 . In FIG. 19 , a series of ridges 71 within passageway 21 of coaxial outer cannula 12 guide the needle cannulae 13 to align with a designated side aperture 67 . FIG. 20 depicts an alternative intraluminal guide 69 in which the needle cannulae 13 travel longitudinally within grooves 72 formed in the inner wall of passageway 21 .

A needle assembly 10 compromising an infusion needle 11 that includes a needle cannula 13 made of a superelastic material such as Nitinol. The needle cannula is cold-worked or heat annealed to produce a preformed bend 16 that can be straightened within passageway 21 of a coaxial outer cannula 12 for introduction into the body of a patient. Upon deployment from the outer cannula, the needle cannula substantially returns to the preformed configuration for the introduction or extraction of materials at areas lateral to the entry path of the needle assembly. The needle assembly can compromise a plurality of needle cannulae than can be variably arranged or configured for attaining a desired infusion pattern.

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of Korean Patent Application No. 10-2007-0076556 filed on Jul. 30, 2007 with the Korea Intellectual Property Office, the contents of which are incorporated here by reference in their entirety. BACKGROUND 1. Technical Field The present invention relates to a method for manufacturing metal nanoparticles and more particularly, to a method for manufacturing metal nanoparticles which provides uniform particle size and allows mass production. 2. Description of the Related Art There is a large demand for metal patterning of a thin film and forming a fine wiring on a substrate through the inkjet method in response to trends for electronic devices with greater densifications and smaller sizes. To this end, it is necessary to develop conductive ink made of metal nanoparticles having uniform shape, a narrow particle distribution, and excellent dispersibility. There are various methods for manufacturing metal nanoparticles such as mechanical grinding method, co-precipitation method, spray, sol-gel method, electro-deposition method, and microemulsion method, etc. A problem associated with the co-precipitation method is that the method may difficult to control particle size, shape and particle distribution and problems associated with the sol-gel method are high production costs and difficulties in mass production. On the other hand, the microemulsion method provides easy control of particle size, shape and particle distribution but the process is complicate and thus not suitable for practical uses. A conventional method for manufacturing nanoparticles in a solution has a limitation of concentration. That is, only a concentration of less than 0.01 M is used to produce nanoparticles having uniform size and even its production yield is very low. Thus, at least 1000 liter of a reactor is required to produce gram(g) volumes of nanoparticles having uniform size. Silver nanoparticles have been produced by using thiol or fatty acid compound. The thiol compound has a strong bond with novel metals such as gold and silver and is able to control the particle size. The fatty acid compound is also able to control the particle size even though the bond with novel metals is less that the thiol compound. However, the amine compound has a weak bond with silver, so that it is difficult to produce stable silver nanoparticles. Recently, a method for manufacturing gold or silver nanoparticles using silver acetate, oleylamine, and an organic solvent has been introduced. However, a reaction time is more than 8 hours and a yield is about 10% which is very low. In this method, phenylhydrazine can be used as a reducing agent to produce silver nanoparticles but it is a carcinogenic compound and thus not applicable for industrial production. Further, silver acetate is very costly and thus not suitable for mass production. Accordingly, such conventional methods are not suitable for mass production of metal nanoparticles having high dispersion stability in high yield. SUMMARY An aspect of the present invention is to provide a method for manufacturing metal nanoparticles in high yield by using a low price of a precursor in high concentration. In order to resolve the problems associated with the conventional methods, the present invention provides a method for manufacturing metal nanoparticles, the method including: dissociating at least one metal precursor chosen from silver, gold and palladium; reducing the dissociated metal precursor; and isolating the capped metal nanoparticles with an alkyl amine. According to an embodiment of the present invention, the metal precursor may be a silver precursor. According to an embodiment of the present invention, the silver precursor may be at least one chosen from silver nitrate, silver acetate, and silver oxide. According to an embodiment of the present invention, the metal precursor is added in a mole ratio of 0.1 to 1 with respect to the alkyl amine. According to an embodiment of the present invention, the step of dissociating the metal precursor is performed by using C10 to C20 alkyl amine at a temperature of 60 to 150° C. According to an embodiment of the present invention, the C10 to C20 alkyl amine may be at least one chosen from decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine and oleylamine. According to an embodiment of the present invention, the step of dissociating the metal precursor is performed by additionally adding C2 to C8 alkyl amine at a temperature of room temperature to 150° C. According to an embodiment of the present invention, the C2 to C8 alkyl amine may be at least one chosen from ethylamine, propylamine, butylamine, hexylamine, and octylamine. According to an embodiment of the present invention, the alkyl amine may be added in a mole ratio of 1 to 10 with respect to the metal precursor. According to an embodiment of the present invention, the step of dissociating the metal precursor may further include adding a non-polar solvent. According to an embodiment of the present invention, the non-polar solvent may be at least one chosen from toluene, hexane, cyclohexane, decane, dodecane, tetradecane, hexadecane, octadecane and octadecene. According to an embodiment of the present invention, the non-polar solvent may be added in a mole ratio of 1 to 100 with respect to the metal precursor. According to an embodiment of the present invention, in the step of reducing the dissociated metal precursor, a reducing agent or a catalyst may be added. According to an embodiment of the present invention, the reducing agent may be at least one chosen from formic acid, ammonium formate, dimethylamine borane, ter-butylamine borane, and triethylamine borane. According to an embodiment of the present invention, the reducing agent may be added in a mole ratio of 1 to 4 with respect to the metal precursor. According to an embodiment of the present invention, the catalyst may be at least one chosen from Sn, Cu, Fe, Mg and Zn. According to an embodiment of the present invention, the catalyst may be added in a mole ratio of 0.05 to 0.5 with respect to the metal precursor. According to an embodiment of the present invention, the step of isolating the metal nanoparticles may be performed by using methanol or acetone or a mixture thereof. The present invention provides a method for manufacturing metal nanoparticles which can be performed with a simpler equipment compared to the gas phase method, can provide metal nanoparticles in high yield by only using alkyl amine without using any surfactant in high concentration which further allows mass production, can provide metal nanoparticles having high dispersion stability and uniform size of 1-40 nm. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a TEM image of silver nanoparticles produced in Example 1. FIG. 2 is a PXRD analysis of silver nanoparticles produced in Example 1. FIG. 3 is a TGA graph illustrating a content of an organic compound in silver nanoparticles produced in Example 1. DETAILED DESCRIPTION Hereinafter, preferred embodiments will be described in detail of the method of producing metal nanoparticles according to the present invention. A method for manufacturing metal nanoparticles according to the present invention include dissociating at least one metal precursor chosen from silver, gold and palladium; reducing the dissociated metal precursor; and isolating the capped metal nanoparticles with an alkyl amine. Here, the metal precursor may be a metal salt in which the metal is at least one chosen form gold, silver, and palladium. According to an embodiment, the metal precursor may be chosen from AgBF 4 , AgCF 3 SO 3 , AgNO 3 , AgClO 4 , Ag(CH 3 CO 2 ), AgPF 6 and Ag 2 O. The metal precursor is added in a mole ratio of 0.1 to 1 with respect to the alkyl amine. When a content of the metal precursor is less than 0.1 mole ratio, the metal precursor is not sufficiently dissociated, while it is more than 1 mole ratio, it brings excess use of alkyl amine which is not economical and lowers the productivity. The step of dissociating the metal precursor may be divided into (i) direct using of alkyl amine used as capping molecule and (ii) additional adding of a small molecule of alkyl amine. In the former case, alkyl amine, which can be used as a capping molecule, may have at least 10 carbons including decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine and oleylamine, etc. This alkyl amine may not only function as a capping molecule but also dissociate the metal precursor. A content of the alkyl amine used also as a capping molecule may be in a mole ratio of 1 to 10 with respect to the metal precursor. When the content is less than 1 mole ratio, the metal precursor is not sufficiently dissociated, while when it is more than 10 mole ratio, it brings excess use of alkyl amine which is not economical and lowers the productivity. In case that the alkyl amine having at least 10 carbons is used to dissociate the metal precursor, when the temperature is lower than 60° C., the metal precursor may not be sufficiently dissociated, while it is higher than 150° C., it may cause severe exothermic reaction. In the latter case, the small molecule of alkyl amine may be ethylamine, propylamine, butylamine, hexylamine, and octylamine, etc which has less than C8 carbons. The small molecule of alkyl amine may be added in a mole ratio of 1 to 10 with respect to the metal precursor. When the content is less than 1 mole ratio, the metal precursor is not sufficiently dissociated, while when it is more than 10 mole ratio, it brings excess use of alkyl amine which is not economical. In case that the small molecule of alkyl amine is used to dissociate the metal precursor, when the temperature is lower than room temperature, the metal precursor may not be sufficiently dissociated, while it is higher than 150° C., it may cause severe exothermic reaction. Further, a non-polar solvent may be added additionally in the step of dissociating the metal precursor and its example may be toluene, hexane, cyclohexane, decane, dodecane, tetradecane, hexadecane, octadecane and octadecene. The non-polar solvent may control the reaction temperature and dilute the reaction mixture. The non-polar solvent may be added in a mole ratio of 1 to 100 with respect to the metal precursor. When the content is less than 1 mole ratio, it may not form a homogenous reaction solution, while when it is more than 100 mole ratio, it brings excess use of non-polar solvent which is not economical. Any kind of reducing agent may be used in the step of reducing the dissociated metal precursor, a weak reducing agent may be preferably used and its example includes formic acid, ammonium formate, dimethylamine borane, ter-butylamine borane, and triethylamine borane, preferably a formate compound such as formic acid and ammonium formate. The reducing agent may be added in a mole ratio of 1 to 4 with respect to the metal precursor. When the content of reducing agent is less than 1 mole ratio, it may lower the production yield due to insufficient reduction, while it is more than 4 mole ratio, it brings excess use of reducing agent which is not economical. Any kind of catalyst may be used in the step of reducing the dissociated metal precursor, and metal examples of the catalyst include each salt of Sn, Cu, Fe, Mg, and Zn, etc. Since the metal catalyst has lower standard reduction potential than the metal of the metal precursor, the metal catalyst itself is oxidized and efficiently reduces the metal ions such as silver ions as shown in the following reaction equation. Ag + +M +z →Ag 0 +M +(Z+1) Particular metal catalyst may be Sn(NO 3 ) 2 , Sn(CH 3 CO 2 ) 2 , Sn(acac) 2 , Cu(NO 3 ) 2 , Cu(CH 3 CO 2 ) 2 , Cu(acac) 2 , FeCl 2 , FeCl 3 , Fe(acac) 2 , Mg(NO 3 ) 2 , Mg(CH 3 CO 2 ) 2 , Mg(acac) 2 , Zn(CH3CO2) 2 , ZnCl 2 , Zn(acac) 2 , etc but is not limited to them. The catalyst may be used in a mole ratio of 0.05 to 0.5 with respect to the metal precursor. When the content is less than 0.05 mole ratio, it lowers the production yield, while when the content is more than 0.5 mole ratio, it brings excess use of metal catalyst which is not economical. A non-solvent such as methanol, acetone or a mixture of methanol and acetone may be used to isolate the metal nanoparticles in the step of isolating the capped metal nanoparticles with the alkyl amine but it is not limited to them. The metal nanoparticles produced by the above described method are produced in high yield and have high dispersion stability of 1-40 nm, compared the metal nanoparticles produced by the conventional method. EXAMPLE While the present invention has been described with reference to particular embodiments, it is to be appreciated that various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention, as defined by the appended claims and their equivalents. Throughout the description of the present invention, when describing a certain technology is determined to evade the point of the present invention, the pertinent detailed description will be omitted. Hereinafter, although more detailed descriptions will be given by examples, those are only for explanation and there is no intention to limit the invention. Example 1 Preparation of Metal Nanoparticles Silver nitrate 34 g and oleylamine 300 g were stirred and heated to dissolve the silver nitrate to 80° C. The reaction mixture was yellow color and after the silver nitrate was completely dissolved, formic acid 8 g was added at room temperature. As soon as adding formic acid, the reaction mixture turned to dark brown with exothermic reaction. The reaction was performed for about 2 hours and then a mixture of acetone and methanol was added. Silver nanoparticles were obtained through a centrifuge and the produced silver nanoparticles were determined to have a size of about 7 nm. Example 2 Preparation of Metal Nanoparticles using a Small Molecule of Alkyl Amine Silver nitrate 34 g, oleylamine 120 g and toluene 250 ml were stirred and butylamine 30 g was added to easily dissociate silver nitrate while stirring. The reaction mixture was stirred and heated to 80° C. till turned to a clear solution. As soon as formic acid 8 g was added, the reaction mixture was turned to dark brown with exothermic reaction. The reaction was performed for about 2 hours and then a mixture of acetone and methanol was added. Silver nanoparticles were obtained through a centrifuge and the produced silver nanoparticles were determined to have a size of about 10 nm. Example 3 Preparation of Metal Nanoparticles using a Metal Catalyst Silver nitrate 34 g and oleylamine 300 g were stirred and heated to dissolve the silver nitrate to 80° C. The reaction mixture was yellow color and after the silver nitrate was completely dissolved, Sn(ac) 2 10 g was added at room temperature. As soon as adding Sn(ac) 2 , the reaction mixture turned to dark brown with exothermic reaction. The reaction was performed for about 2 hours and then a mixture of acetone and methanol was added. Silver nanoparticles were obtained through a centrifuge and the produced silver nanoparticles were determined to have a size of about 5 nm. A TEM image of the silver nanoparticles produced in Example 1 is shown in FIG. 1 . It is noted that the silver nanoparticles has uniform size of less than 10 nm as shown in FIG. 1 . A PXRD analysis of the silver nanoparticles produced in Example 1 is shown in FIG. 2 . It is noted that the silver nanoparticles having FCC (face-centered cubic) structure are produced as shown in FIG. 2 . In addition, a TGA (thermogravimetric analysis) graph which provides a content of an organic compound in the silver nanoparticles produced in Example 1 is shown in FIG. 3 . It is noted that the content of an organic compound in the silver nanoparticles, which is the capping molecule, is 15 wt % and when size of the silver nanoparticles changes from 1 nm to 20 nm, the content of an organic compound is reduced from 30 wt % to 5 wt %. It is also noted that the silver nanoparticles exhibit high dispersion stability.

The present invention provides a method for manufacturing metal nanoparticles, comprising: dissociating at least one metal precursor selected from the group consisting of silver, gold and palladium; reducing the dissociated metal precursor; and isolating the capped metal nanoparticles with an alkyl amine. The present invention provides a method for manufacturing metal nanoparticles which can be performed with simpler equipment compared to the gas phase method, can provide metal nanoparticles in high yield by only using alkyl amine without using any surfactant in high concentration which further allows mass production, and can provide metal nanoparticles having high dispersion stability and uniform size of 1-40 nm.

FIELD OF THE INVENTION The present invention relates to certain pyrazolo-triazolo-pyrimidine, triazolo-triazolo-pyrimidine and imidazolo-triazolo-pyrimidine derivatives and their use in the practice of medicine as modulators of adenosine A 3 receptors. BACKGROUND OF THE INVENTION Three major classes of adenosine receptors, classified as A 1 , A 2 , and A 3 , have been characterized pharmacologically. A 1 receptors are coupled to the inhibition of adenylate cyclase through G i proteins and have also been shown to couple to other second messenger systems, including inhibition or stimulation of phosphoinositol turnover and activation of ion channels. A 2A receptors are further divided into two subtypes, A 2A and A 2B , at which adenosine agonists activate adenylate cyclase with high and low affinity, respectively. The A 3 receptor sequence was first identified in a rat testes cDNA library, and this sequence, later cloned by homology to other G-protein coupled receptors from a rat brain cDNA library, was shown to correspond to a novel, functional adenosine receptor. The discovery of the A 3 receptor has opened new therapeutic vistas in the purine field. In particular, the A 3 receptor mediates processes of inflammation, hypotension, and mast cell degranulation. This receptor apparently also has a role in the central nervous system. The A 3 selective agonist IB-MECA induces behavioral depression and upon chronic administration protects against cerebral ischemia. A 3 selective agonists at high concentrations were also found to induce apoptosis in HL-60 human leukemia cells. These and other findings have made the A 3 receptor a promising therapeutic target. Selective antagonists for the A 3 receptor are sought as potential anti inflammatory or possibly antiischemic agents in the brain. Recently, A 3 antagonists have been under development as antiasthmatic, antidepressant, antiarrhythmic, renal protective, antiparkinson and cognitive enhancing drugs. It is therefore an object of the present invention to provide compounds and methods of preparation and use thereof, which are agonists, partial agonists, and/or antagonists of the adenosine A 3 receptor. SUMMARY OF THE INVENTION Compounds useful as potent, yet selective modulators of the adenosine A 3 receptor, with activity as antagonists of this receptor, and methods of preparation and use thereof, are disclosed. The compounds have the following general formula: wherein: A is imidazole, pyrazole, or triazole; R is —C(X)R 1 , —C(X)—N(R 1 ) 2 , —C(X)OR 1 , —C(X)SR 1 , —SO n R 1 , —SO n OR 1 , —SO n SR 1 or SO n —N(R 1 ) 2 ; R 1 is hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, heteroaryl, heterocyclic, lower alkenyl, lower alkanoyl, or, if linked to a nitrogen atom, then taken together with the nitrogen atom, forms an azetidine ring or a 5-6 membered heterocyclic ring containing one or more heteroatoms such as N, O, S; R 2 is hydrogen, alkyl, substituted alkyl, aralkyl, substituted aralkyl, heteroaryl, substituted heteroaryl or aryl; R 3 is furan, pyrrole, thiophene, benzofuran, benzopyrrole, benzothiophene, optionally substituted with one or more substituents as described herein for substituted heteroaryl rings; X is O, S, or NR 1 ; n is 1 or 2; and and pharmaceutically acceptable salts thereof. Preferably, R 1 is hydrogen; C1 to C8 alkyl; C3 to C7 alkenyl, C3 to C7 alkynyl; C3 to C7 cycloalkyl; C1 to C5 alkyl substituted with one or more halogen atoms, hydroxy groups, C1 to C4 alkoxy, C3 to C7 cycloalkyl or groups of formula —NR 1 2 , —CO NR 1 2 ; aryl, substituted aryl wherein the substitution is selected from the group consisting of C1 to C4 alkoxy, C1 to C4 alkyl, nitro, amino, cyano, C1 to C4 haloalkyl, C1 to C4 haloalkoxy, carboxy, carboxyamido; C7 to C10 aralkyl in which the aryl moiety can be substituted with one or more of the substituents indicated above for the aryl group; a group of formula —(CH 2 )m-Het, wherein Het is a 5-6 membered aromatic or non aromatic heterocyclic ring containing one or more heteroatoms selected from the group consisting of N, O, and S and m is an integer from 1 to 5; Preferred C1 to C8 alkyl groups are methyl, butyl and isopentyl. Examples of C3 to C7 cycloalkyl groups include cyclopropyl, cyclopentyl, and cyclohexyl. Examples of C1 to C5 alkyl groups substituted with C3 to C7 cycloalkyl groups include cyclohexylmethyl, cyclopentylmethyl, and 2-cyclopentylethyl. Examples of substituted C1 to C5 alkyl groups include 2-hydroxyethyl, 2-methoxyethyl, trifluoromethyl, 2-fluoroethyl, 2-chloroethyl, 3-aminopropyl, 2-(4methyl-1-piperazine)ethyl, 2-(4-morpholinyl)ethyl, 2-aminocarbonylethyl, 2-dimethylaminoethyl, 3-dimethylaminopropyl. Aryl is preferably phenyl, optionally substituted with Cl, F, methoxy, nitro, cyano, methyl, trifluoromethyl, difluoromethoxy groups. Examples of 5 to 6 membered ring heterocyclic groups containing N, O and/or S include piperazinyl, morpholinyl, thiazolyl, pyrazolyl, pyridyl, furyl, thienyl, pyrrolyl, triazolyl, tetrazolyl. Examples of C7 to C10 aralkyl groups comprise benzyl or phenethyl optionally substituted by one or more substituents selected from Cl, F, methoxy, nitro, cyano, methyl, trifluoromethyl, and difluoromethoxy. Preferably, R is hydrogen, C1 to C8 alkyl, aryl or C7 to C10 aralkyl, optionally substituted, preferably with halogen atoms. Particularly preferred compounds are those in which R is a phenethyl group in which the phenyl ring is substituted with one or more substituents selected from the group consisting of chlorine, fluorine atoms, methoxy, nitro, cyano, methyl, trifluoromethyl, and difluoromethoxy groups. The possible meanings of A can be represented by the following structural formulae: The compounds can be used in a method for modulating adenosine A 3 receptors in a mammal, including a human. The methods involve administering an effective amount of a compound of formula I sufficient to modulate adenosine A 3 receptors in the mammal. Uses for the compounds include: treating hypertension; treating inflammatory disorders such as rheumatoid arthritis and psoriasis; treating allergic disorders such as hay fever and allergic rhinitis; mast cell degranulation; antitumor agents; treating cardiac hypoxia; and protection against cerebral ischemia; diagnostic uses, for example, to determine the presence of one or more of the above described medical conditions, or in a screening assay to determine the effectiveness of other compounds for binding to the A 3 Ado receptor (i.e., through competitive inhibition as determined by various binding assays), as described in Jacobson and Van Rhee, Purinergic approaches to experimental therapy, Jacobson and Jarvis, ed., Wiley, N.Y., 1997, pp. 101-128; Mathot et al., Brit. J. Pharmacol ., 116:1957-1964 (1995); van der Wenden et al., J. Med. Chem ., 38:4000-4006 (1995); and van Calenbergh, J. Med. Chem ., 40:3765-3772 (1997), the contents of which are hereby incorporated by reference. The compounds can also be used in a method for fully or partially inhibiting adenylate cyclase (A 3 ) in a mammal, including a human. The methods involve administering an effective amount of a compound of formula I sufficient to fully or partially inhibiting adenylate cyclase in the mammal. The compounds can be used in a pharmaceutical formulation that includes a compound of formula I and one or more excipients. Various chemical intermediates can be used to prepare the compounds. BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a graph showing the saturation of [ 125 I]AB-MECA binding (fmol/mg protein) to human A 3 receptors expressed in HEK 293 cells versus the molar concentration of [ 125 I]AB-MECA. DETAILED DESCRIPTION OF THE INVENTION The present application discloses compounds useful as potent, yet selective modulators of adenosine receptors, with activity as A 3 agonists, and in some cases, A 3 antagonists, and methods of preparation and use thereof. The compounds can be used in a method for modulating adenosine A 3 receptors in a mammal, including a human. The methods involve administering an effective amount of a compound of formula I sufficient to moderate adenosine A 3 receptors to the mammal. The compounds can be used in a pharmaceutical formulation that includes a compound of formula I and one or more excipients. Various chemical intermediates can be used to prepare the compounds. Definitions As used herein, a compound is an agonist of an adenosine A 1 receptor if it is able to fully inhibit adenylate cyclase (A 3 ) and is able to displace [ 125 I]-AB-MECA in a competitive binding assay. As used herein, a compound is a partial agonist of an adenosine A 3 receptor if it is able to partially inhibit adenylate cyclase (A 3 ) and is able to displace [ 125 I]-AB-MECA in a competitive binding assay. As used herein, a compound is an antagonist of an adenosine A 3 receptor if it is able to prevent the inhibition due to an agonist and is able to displace [ 125 I]-AB-MECA in a competitive binding assay. As used herein, a compound is selective for the A 3 receptor if the ratio of A 1 /A 3 and A 2 /A 3 activity is greater than about 50, preferably between 50 and 100, and more preferably, greater than about 100. As used herein, the term “alkyl” refers to monovalent straight, branched or cyclic alkyl groups preferably having from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms (“lower alkyl”) and most preferably 1 to 6 carbon atoms. This term is exemplified by groups such as methyl, ethyl, n-propyl, iso-propyl, -butyl, iso-butyl, n-hexyl, and the like. The terms “alkylene” and “lower alkylene” refer to divalent radicals of the corresponding alkane. Further, as used herein, other moieties having names derived from alkanes, such as alkoxyl, alkanoyl, alkenyl, cycloalkenyl, etc when modified by “lower,” have carbon chains of ten or less carbon atoms. In those cases where the minimum number of carbons are greater than one, e.g., alkenyl (minimum of two carbons) and cycloalkyl, (minimum of three carbons), it is to be understood that “lower” means at least the minimum number of carbons. As used herein, the term “substituted alkyl” refers to an alkyl group, preferably of from 1 to 10 carbon atoms (“substituted lower alkyl”), having from 1 to 5 substituents, and preferably 1 to 3 substituents, selected from the group consisting of alkoxy, substituted alkoxy, cycloalkyl, substituted cycloalkyl, cycloalkenyl, substituted cycloalkenyl, acyl, acylamino, acyloxy, amino, substituted amino aminoacyl, aminoacyloxy, oxyacylamino, cyano, halogen, hydroxyl, keto, thioketo, carboxyl, carboxylalkyl, thiol, thioalkoxy, substituted thioalkoxy, aryl, aryloxy, heteroaryl, heteroaryloxy, heterocyclic, hydroxyamino, alkoxyamino, nitro, —SO-alkyl, —SO-substituted alkyl, —SO-aryl, —SO-heteroaryl, —SO 2 -alkyl, —SO 2 -substituted alkyl, —SO 2 -aryl, —SO 2 -heteroaryl, and mono- and di-alkylamino, mono- and di-(substituted alkyl)amino, mono- and di-arylamino, mono- and di-heteroarylamino, mono- and di-heterocyclic amino, and unsymmetric di-substituted amines having different substituents selected from alkyl, aryl, heteroaryl and heterocyclic. As used herein, other moieties having the prefix “substituted” are intended to include one or more of the substituents listed above. As used herein, the term “alkoxy” refers to the group “alkyl-O—”, where alkyl is as defined above. Preferred alkoxy groups include, by way of example, methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, tert-butoxy, sec-butoxy, n-pentoxy, n-hexoxy, 1,2-dimethylbutoxy, and the like. As used herein, the term “alkenyl” refers to alkenyl groups preferably having from 2 to 10 carbon atoms and more preferably 2 to 6 carbon atoms and having at least 1 and preferably from 1-2 sites of alkenyl unsaturation. Preferred alkenyl groups include ethenyl (—CH═CH 2 ), n-propenyl (—CH 2 CH═CH 2 ), iso-propenyl (—C(CH 3 )═CH 2 ), and the like. As used herein, the term “alkynyl” refers to alkynyl groups preferably having from 2 to 10 carbon atoms and more preferably 2 to 6 carbon atoms and having at least 1 and preferably from 1-2 sites of alkynyl unsaturation. As used herein, the term “acyl” refers to the groups alkyl-C(O)—, substituted alkyl-C(O)—, cycloalkyl-C(O)—, substituted cycloalkyl-C(O)—, aryl-C(O)—, heteroaryl-C(O)— and heterocyclic-C(O)— where alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, aryl, heteroaryl and heterocyclic are as defined herein. As used herein, the term “acylamino” refers to the group —C(O)NRR where each R is independently hydrogen, alkyl, substituted alkyl, aryl, heteroaryl, or heterocyclic wherein alkyl, substituted alkyl, aryl, heteroaryl and heterocyclic are as defined herein. As used herein, the term “aryl” refers to an unsaturated aromatic carbocyclic group of from 6 to 14 carbon atoms having a single ring (e.g., phenyl) or multiple condensed (fused) rings (e.g., naphthyl or anthryl). Preferred aryls include phenyl, naphthyl and the like. Unless otherwise constrained by the definition for the aryl substituent, such aryl groups can optionally be substituted with from 1 to 5 substituents and preferably 1 to 3 substituents selected from the group consisting of hydroxy, acyl, alkyl, alkoxy, alkenyl, alkynyl, substituted alkyl, substituted alkoxy, substituted alkenyl, substituted alkynyl, amino, substituted amino, aminoacyl, acyloxy, acylamino, alkaryl, aryl, aryloxy, azido, carboxyl, carboxylalkyl, cyano, halo, nitro, heteroaryl, heteroaryloxy, heterocyclic, heterocyclooxy, aminoacyloxy, oxyacylamino, thioalkoxy, substituted thioalkoxy, thioaryloxy, thioheteroaryloxy, —SO-alkyl, —SO-substituted alkyl, —SO-aryl, —SO-heteroaryl, —SO 2 -alkyl, —SO 2 -substituted alkyl, —SO 2 -aryl, —SO 2 -heteroaryl, trihalomethyl. Preferred substituents include alkyl, alkoxy, halo, cyano, nitro, trihalomethyl, and thioalkoxy. As used herein, the term “cycloalkyl” refers to cyclic alkyl groups of from 3 to 12 carbon atoms having a single cyclic ring or multiple condensed rings. Such cycloalkyl groups include, by way of example, single ring structures such as cyclopropyl, cyclobutyl, cyclopentyl, cyclooctyl, and the like, or multiple ring structures such as adamantyl, and the like. As used herein, the terms “halo” or “halogen” refer to fluoro, chloro, bromo and iodo and preferably is either fluoro or chloro. As used herein, the term “heteroaryl” refers to an aromatic carbocyclic group of from 1 to 15 carbon atoms and 1 to 4 heteroatoms selected from the group consisting of oxygen, nitrogen and sulfur within at least one ring (if there is more than one ring). Unless otherwise constrained by the definition for the heteroaryl substituent, such heteroaryl groups can be optionally substituted with from 1 to 5 substituents and preferably 1 to 3 substituents selected from the group consisting of hydroxy, acyl, alkyl, alkoxy, alkenyl, alkynyl, substituted alkyl, substituted alkoxy, substituted alkenyl, substituted alkynyl, amino, substituted amino, aminoacyl, acyloxy, acylamino, alkaryl, aryl, aryloxy, azido, carboxyl, carboxylalkyl, cyano, halo, nitro, heteroaryl, heteroaryloxy, heterocyclic, heterocyclooxy, aminoacyloxy, oxyacylamino, thioalkoxy, substituted thioalkoxy, thioaryloxy, thioheteroaryloxy, —SO-alkyl, —SO-substituted alkyl, —SO-aryl, —SO-heteroaryl, —SO 2 -alkyl, —SO 2 -substituted alkyl, —SO 2 -aryl, —SO 2 -heteroaryl, and trihalomethyl. Preferred substituents include alkyl, alkoxy, halo, cyano, nitro, trihalomethyl, and thioalkoxy. Such heteroaryl groups can have a single ring (e.g., pyridyl or furyl) or multiple condensed rings (e.g., indolizinyl or benzothienyl). “Heterocycle” or “heterocyclic” refers to a monovalent saturated or unsaturated group having a single ring or multiple condensed rings, from 1 to 15 carbon atoms and from 1 to 4 hetero atoms selected from the group consisting of nitrogen, sulfur and oxygen within the ring. Unless otherwise constrained by the definition for the heterocyclic substituent, such heterocyclic groups can be optionally substituted with 1 to 5 substituents selected from the group consisting of alkyl, substituted alkyl, alkoxy, substituted alkoxy, aryl, aryloxy, halo, nitro, heteroaryl, thiol, thioalkoxy, substituted thioalkoxy, thioaryloxy, trihalomethyl, and the like. Such heterocyclic groups can have a single ring or multiple condensed rings. As to any of the above groups that contain 1 or more substituents, it is understood, of course, that such groups do not contain any substitution or substitution patterns which are sterically impractical and/or synthetically non-feasible. As used herein, “carboxylic acid derivatives” and “sulfonic acid derivatives” refer to —C(X)R 1 , —C(X)—N(R 1 ) 2 , —C(X)OR 1 , —C(X)SR 1 , —SO n R 1 , —SO n OR 1 , —SO n SR 1 or —SO n —N(R 1 ) 2 ; where X is O, S or NR 1 , where R 1 is hydrogen, alkyl, substituted alkyl or aryl, and activated derivatives thereof, such as anhydrides, esters, and halides such as chlorides, bromides and iodides, which can be used to couple the carboxylic acid and sulfonic acid derivatives to the 5′-amine using standard coupling chemistry. “Pharmaceutically acceptable salts” refers to pharmaceutically acceptable salts of a compound of Formulas IA, IB, or IC, which salts are derived from a variety of organic and inorganic counter ions well known in the art and include, by way of example only, sodium, potassium, calcium, magnesium, ammonium, tetraalkylammonium, and the like; and when the molecule contains a basic functionality, salts of organic or inorganic acids, such as hydrochloride, hydrobromide, tartrate, mesylate, acetate, maleate, oxalate and the like can be used as the pharmaceutically acceptable salt. The term “protecting group” or “blocking group” refers to any group which when bound to one or more hydroxyl, amino or carboxyl groups of the compounds (including intermediates thereof such as the aminolactams, aminolactones, etc.) prevents reactions from occurring at these groups and which protecting group can be removed by conventional chemical or enzymatic steps to reestablish the hydroxyl, amino or carboxyl group. Preferred removable amino blocking groups include conventional substituents such as t-butyoxycarbonyl (t-BOC), benzyloxycarbonyl (CBZ), and the like which can be removed by conventional conditions compatible with the nature of the product. The following abbreviations are used herein: Abbreviations: [ 125 I]AB-MECA, [ 125 I]N 6 -(4-amino-3-iodobenzyl)adenosine-5-N-methyluronamide;(R)-PIA, (R)-N 6 -(phenylisopropyl)adenosine; DMSO, dimethysulfoxide; I-AB-MECA, N 6 -(4-amino-3-iodobenzyl)adenosine-5-N-methyluronamide; IB-MECA, N 6 -(3-iodobenzyl)adenosine-5-N-methyluronamide; Ki, equilibrium inhibition constant; NECA, 5-N-ethylcarboxamido adenosine; THF, tetrahydrofuran; Tris, tris(hydroxymethyl)aminomethane. Compound Preparation Those skilled in the art of organic chemistry will appreciate that reactive and fragile functional groups often must be protected prior to a particular reaction, or sequence of reactions, and then restored to their original forms after the last reaction is completed. Usually groups are protected by converting them to a relatively stable derivative. For example, a hydroxyl group may be converted to an ether group and an amine group converted to an amide or carbamate. Methods of protecting and de-protecting, also known as “blocking” and “de-blocking,” are well known and widely practiced in the art, e.g., see T. Green, Protective Groups in Organic Synthesis , John Wiley, New York (1981) or Protective Groups in Organic Chemistry , Ed. J. F. W. McOmie, Plenum Press, London (1973). The compounds are preferably prepared by reacting a compound of Formula II below with a suitable carboxylic acid or sulfonic acid derivative using known chemistry. Compounds of Formula II can be prepared using the following Schemes I and II, illustrated where R 3 is furan. Reagents: A) triethyl orthoformate; B) 2-furoic acid hydrazide, 2-methoxyethanol; C) PhOPh, 260° C.; D) 10% HCl, under reflux; E) cyanamide, pTsOH, N-methylpyrrolidone Reagents: F) furoic acid hydrazide, diphenyl ether; E) cyanamide, pTsOH, N-methylpyrrolidone. The compounds of formula II can be prepared through either an indirect route described in Scheme I or a direct route described in Scheme II. Suitable starting materials for both schemes are the heterocyclic ortho-amino nitriles of formula III, generally prepared according to synthetic procedures known in literature and reported in the book by E. C. Taylor and A. McKillop (vol. 7 of the series Advances in Organic Chemistry, Ed. Interscience, 1970). Ortho-amino nitrites III are transformed into the corresponding imidates of formula IV by reaction with an ethyl orthofornate excess at the reflux temperature for 8 to 10 h. The reaction, after evaporation of the ethyl orthoformate, leads to the substantially pure corresponding imidates IV in a high yield as evidenced by the IR and 1 H NMR analysis on the crude reaction products. The imidates of formula IV are then subjected to a sequence of two reactions allowing to obtain the tricyclic structures of formula VI in a high yield. The reaction sequence includes: a) reaction with 2-furoic acid hydrazide in a 2-methoxyethanol solution at the reflux temperature for 8-10 h, to obtain the intermediates compounds of formula V; b) thermal cyclization of the latter to corresponding compounds of formula VI, by heating in diphenyl ether at the temperature of 260° C. for 0.5 to 1 h. The tricyclic compounds VI are then hydrolyzed with HCl at reflux for 1 to 3 h to give triazoles VII, which are finally cyclized to desired compounds II with cyanamide in N-methyl pyrrolidone at reflux and in the presence of para-toluenesulfonic acid (Scheme I). In some cases, triazoles VII can be obtained directly heating in diphenyl ether ortho-amino nitrile III with 2-furoic acid hydrazide. Triazoles VII are then cyclized as described above in Scheme II. In the following schemes III, IV and V, the synthesis of the compounds of formula II in which A is a triazole ring are reported in more detail. Scheme III Synthesis of 5-amino-7-substituted-2(2-furyl)-1,2,3-triazolo[5,4-e)1,2,4-triazolo[1,5-c]pyrimidine Derivatives Scheme IV Synthesis of 5-amino-8-substituted-2(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine Derivatives Reagents: A) furoic acid hydrazide, PhOph, 260° C., B) NH 2 CN, pTsOH, N-methylpyrrolidone. Scheme V Synthesis of 5-amino-9-substituted-2(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine Derivatives Reagents: A) furoic acid hydrazide, PhOph, 260° C., B) NH 2 CN, pTsOH, N-methylpyrrolidone. Finally, the 5-amine-containing compounds II are reacted with carboxylic acids, sulfonic acids, activated carboxylic acids, activated sulfonic acids, thiocarboxylic acids, activated thiocarboxylic acids, and the like, to form the desired compounds. Activated carboxylic acids include acid halides, esters, anhydrides and other derivatives known to react with amines to form amides. Activated sulfonic acids include sulfonyl halides such as sulfonyl chlorides. It is not necessary in all cases to use activated carboxylic acid and sulfonic acid derivatives. The acids themselves can be coupled to the amines using standard coupling chemistry, for example, using dicyclohexyl diimide (DCI) and other routinely used coupling agents. Suitable coupling conditions for forming amide linkages are well known to those of skill in the art of peptide synthesis. Generally, the chemistry above can be used to prepare 8-(Ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo[1,5c]pyrimidines when 3-cyano-2-aminopyrazoles are used as starting materials. The 3-cyano-2-aminopyrazoles can be reacted with an alkyl halide (RX) in a polar aprotic solvent such as dimethyl formamide (DMF) to provide an R group on one of the ring nitrogens. The resulting compound can be refluxed with triethyl orthoformate to provide an imine ethyl ester, which can be reacted with furoic hydrazide, preferably using a Dean-Stark trap for the azeotropic elimination of water produced in the reaction, to provide 8-(Ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo[1,5c]pyrimidines. The products can be purified by chromatography, for example, in (EtOAc/hexane 1:1), for use in subsequent chemistry. The product of this reaction can be reacted with a suitable acid, such as HCl, at reflux, followed by reaction with cyanamide in a solvent such as N-methyl pyrrolidone with catalytic para-toluene sulfonic acid at elevated temperatures to provide 5-amino-8-(Ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo[1,5c]pyrimidines. These amine-substituted compounds can be reacted with appropriate isocyanates to form urea compounds, activated carboxylic acids such as acid halides to provide amides, activated sulfonic acids such as sulfonic acid halides to form sulfonamides, or other reactive carboxylic acid or sulfonic acid derivatives to form other desired compounds. Triazolo-triazolo-pyrimidine compounds can be prepared using similar chemistry, but starting with a suitably functionalized azide, and reacting the azide with H 2 NC(O)CH 2 CN to form the initial heterocyclic ring, followed by reaction of the amide group with a dehydrating agent such as POCl 3 to form a nitrile. The resulting cyano-aminotriazole can be reacted in the same manner as the 3-cyano-2-aminopyrazoles discussed above to prepare triazolo-triazolo-pyrimidines. Methods of Using the Compounds The compounds can be used for all indications for which agonists and antagonists of the A3 receptor, including: treating hypertension; treating inflammatory disorders such as rheumatoid arthritis and psoriasis; treating allergic disorders such as hay fever and allergic rhinitis; mast cell degranulation; antitumor agents; treating cardiac hypoxia; and protection against cerebral ischemia; as described, for example, in Jacobson, TIPS May 1998, pp. 185-191, the contents of which are hereby incorporated by reference. The compounds can be administered via any medically acceptable means. Suitable means of administration include oral, rectal, topical or parenteral (including subcutaneous, intramuscular and intravenous) administration, although oral or parenteral administration are preferred. The amount of the compound required to be effective as an allosteric modulator of an adenosine receptor will, of course, vary with the individual mammal being treated and is ultimately at the discretion of the medical or veterinary practitioner. The factors to be considered include the condition being treated, the route of administration, the nature of the formulation, the mammal's body weight, surface area, age and general condition, and the particular compound to be administered. However, a suitable effective dose is in the range of about 0.1 μg/kg to about 10 mg/kg body weight per day, preferably in the range of about 1 mg/kg to about 3 mg/kg per day. The total daily dose may be given as a single dose, multiple doses, e.g., two to six times per day, or by intravenous infusion for a selected duration. Dosages above or below the range cited above are within the scope of the present invention and may be administered to the individual patient if desired and necessary. For example, for a 75 kg mammal, a dose range would be about 75 mg to about 220 mg per day, and a typical dose would be about 150 mg per day. If discrete multiple doses are indicated, treatment might typically be 50 mg of a compound given 3 times per day. Formulations The compounds described above are preferably administered in formulation including an active compound, i.e., a compound of formula I, together with an acceptable carrier for the mode of administration. Suitable pharmaceutically acceptable carriers are known to those of skill in the art. The compositions can optionally include other therapeutically active ingredients such as antivirals, antitumor agents, antibacterials, anti-inflammatories, analgesics, and immunosuppresants. The carrier must be pharmaceutically acceptable in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof. The formulations can include carriers suitable for oral, rectal, topical or parenteral (including subcutaneous, intramuscular and intravenous) administration. Preferred carriers are those suitable for oral or parenteral administration. Formulations suitable for parenteral administration conveniently include sterile aqueous preparation of the active compound which is preferably isotonic with the blood of the recipient. Thus, such formulations may conveniently contain distilled water, 5% dextrose in distilled water or saline. Useful formulations also include concentrated solutions or solids containing the compound of formula (I) which upon dilution with an appropriate solvent give a solution suitable for parental administration above. For enteral administration, the compound can be incorporated into an inert carrier in discrete units such as capsules, cachets, tablets or lozenges, each containing a predetermined amount of the active compound; as a powder or granules; or a suspension or solution in an aqueous liquid or non-aqueous liquid, e.g., a syrup, an elixir, an emulsion or a draught. Suitable carriers may be starches or sugars and include lubricants, flavorings, binders, and other materials of the same nature. A tablet may be made by compression or molding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active compound in a free-flowing form, e.g., a powder or granules, optionally mixed with accessory ingredients, e.g., binders, lubricants, inert diluents, surface active or dispersing agents. Molded tablets may be made by molding in a suitable machine, a mixture of the powdered active compound with any suitable carrier. A syrup or suspension may be made by adding the active compound to a concentrated, aqueous solution of a sugar, e.g., sucrose, to which may also be added any accessory ingredients. Such accessory ingredients may include flavoring, an agent to retard crystallization of the sugar or an agent to increase the solubility of any other ingredient, e.g., as a polyhydric alcohol, for example, glycerol or sorbitol. The compounds can also be administered locally by topical application of a solution, ointment, cream, gel, lotion or polymeric material (for example, a Pluronic™, BASF), which may be prepared by conventional methods known in the art of pharmacy. In addition to the solution, ointment, cream, gel, lotion or polymeric base and the active ingredient, such topical formulations may also contain preservatives, perfumes, and additional active pharmaceutical agents. Formulations for rectal administration may be presented as a suppository with a conventional carrier, e.g., cocoa butter or Witepsol S55 (trademark of Dynamite Nobel Chemical, Germany), for a suppository base. Alternatively, the compound may be administered in liposomes or microspheres (or microparticles). Methods for preparing liposomes and microspheres for administration to a patient are well known to those of skill in the art. U.S. Pat. No. 4,789,734, the contents of which are hereby incorporated by reference, describes methods for encapsulating biological materials in liposomes. Essentially, the material is dissolved in an aqueous solution, the appropriate phospholipids and lipids added, along with surfactants if required, and the material dialyzed or sonicated, as necessary. A review of known methods is provided by G. Gregoriadis, Chapter 14, “Liposomes,” Drug Carriers in Biolopy and Medicine , pp. 287-341 (Academic Press, 1979). Microspheres formed of polymers or proteins are well known to those skilled in the art, and can be tailored for passage through the gastrointestinal tract directly into the blood stream. Alternatively, the compound can be incorporated and the microspheres, or composite of microspheres, implanted for slow release over a period of time ranging from days to months. See, for example, U.S. Pat. Nos. 4,906,474, 4,925,673 and 3,625,214, the contents of which are hereby incorporated by reference. Preferred microparticles are those prepared from biodegradable polymers, such as polyglycolide, polylactide and copolymers thereof. Those of skill in the art can readily determine an appropriate carrier system depending on various factors, including the desired rate of drug release and the desired dosage. The formulations may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy. All methods include the step of bringing the active compound into association with a carrier which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing the active compound into association with a liquid carrier or a finely divided solid carrier and then, if necessary, shaping the product into desired unit dosage form. In addition to the aforementioned ingredients, the formulations may further include one or more optional accessory ingredient(s) utilized in the art of pharmaceutical formulations, e.g., diluents, buffers, flavoring agents, binders, surface active agents, thickeners, lubricants, suspending agents, preservatives (including antioxidants) and the like. Determination of the Degree of Activity for the Compounds The activity of the compounds can be readily determined using no more than routine experimentation using any of the following assays. Rat A 1 and A 2A Adenosine Receptor Binding Assay Membrane preparations: Male Wistar rats (200-250 g) can be decapitated and the whole brain (minus brainstem, striatum and cerebellum) dissected on ice. The brain tissues can be disrupted in a Polytron (setting 5) in 20 vols of 50 mM Tris HCl, pH 7.4. The homogenate can then be centrifuged at 48,000 g for 10 min and the pellet resuspended in Tris-HCL containing 2 IU/ml adenosine deaminase, type VI (Sigma Chemical Company, St. Louis, Mo., USA). After 30 min incubation at 37° C., the membranes can be centrifuged and the pellets stored at −70° C. Striatal tissues can be homogenized with a Polytron in 25 vol of 50 mM Tris HCL buffer containing 10 mM MgCI 2 pH 7.4. The homogenate can then be centrifuged at 48,000 g for 10 min at 4° C. and resuspended in Tris HCl buffer containing 2 IU/ml adenosine deaminase. After 30 min incubation at 37° C., membranes can be centrifuged and the pellet stored at −70° C. Radioligand binding assays: Binding of [ 3 H]-DPCPX (1,3-dipropyl-8-cyclopentylxanthine) to rat brain membranes can be performed essentially according to the method previously described by Bruns et al., Proc. Natl. Acad. Sci . 77, 5547-5551 1980. Displacement experiments can be performed in 0.25 ml of buffer containing 1 nM [ 3 H]-DPCPX, 100 μl of diluted membranes of rat brain (100 μg of protein/assay) and at least 6-8 different concentrations of examined compounds. Non specific binding can be determined in the presence of 10 μM of CHA (N 6 cyclohexyladenosine) and this is always ≦10% of the total binding. Incubation times are typically 120 min at 25° C. Binding of [ 3 H]-SCH 58261 (5-amino-7-(2-phenylethyl)-2-(2-furyl)pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine) to rat striatal membranes (100 μg of protein/assay) can be performed according to methods described in Zocchi et al., J. Pharm. and Exper. Ther . 276:398-404 (1996). In competition studies, at least 6-8 different concentrations of examined compounds should be used. Non specific binding can be determined in the presence of 50 μM of NECA (5′-(N-ethylcarboxamido)adenosine). Incubation time is typically 60 min at 25° C. Bound and free radioactivity can be separated by filtering the assay mixture through Whatman GF/B glass-fiber filters using a Brandel cell harvester (Gaithersburg, Md., USA). The incubation mixture can be diluted with 3 ml of ice-cold incubation buffer, rapidly vacuum filtered and the filter can be washed three times with 3 ml of incubation buffer. The filter bound radioactivity can be measured, for example, by liquid scintillation spectrometry. The protein concentration can be determined, for example, according to a Bio-Rad method (Bradford, Anal. Biochem . 72:248 (1976)) with bovine albumin as reference standard. Human cloned A 3 Adenosine Receptor Binding Assay Receptor binding assays: Binding assays can be carried out according to methods described in Salvatore et al., Proc. Natl. Acad. Sci . 90:10365-10369 (1993). In saturation studies, an aliquot of membranes (8 mg protein/ml) from HEK-293 cells transfected with the human recombinant A 3 adenosine receptor (Research Biochemical International, Natick, Mass. USA) can be incubated with 10-12 different concentrations of [ 125 I]AB-MECA ranging from 0.1 to 5 nM. Competition experiments can be carried out in duplicate in a final volume of 100 μl in test tubes containing 0.3 nM [ 125 I]AB-MECA, 50 mM Tris HCL buffer, 10 mM MgCI 2 , pH 7.4 and 20 μl of diluted membranes (12.4 mg protein/ml) and at least 6-8 different concentrations of examined ligands. Incubation time was 60 min at 37° C., according to the results of previous time-course experiments. Bound and free radioactivity were separated by filtering the assay mixture through Whatiman GF/B glass-fiber filters using a Brandel cell harvester. Non-specific binding was defined as binding in the presence of 50 μM R-PIA and was about 30% of total binding. The incubation mixture was diluted with 3 ml of ice-cold incubation buffer, rapidly vacuum filtered and the filter was washed three times with 3 ml of incubation buffer. The filter bound radioactivity was counted in a Beckman gamma 5500B γ counter. The protein concentration can be determined according to a Bio-Rad method (3) with bovine albumin as reference standard. Data Analysis Inhibitory binding constant, K i , values can be calculated from those of I C 50 according to the Cheng & Prusoff equation (Cheng and Prusoff, Biochem. Pharmacol . 22:3099-3108 (1973)), K i =IC 50 /(I+[C*]/K D *), where [C*] is the concentration of the radioligand and K D * its dissociation constant. A weighted non linear least-squares curve fitting program LIGAND (Munson and Rodbard, Anal. Biochem . 107:220-239 (1990)) can be used for computer analysis of saturation and inhibition experiments. Data are typically expressed as geometric mean, with 95% or 99% confidence limits in parentheses. EXAMPLES The following examples illustrate aspects of this invention but should not be construed as limitations. The symbols and conventions used in these examples are intended to be consistent with those used in the contemporary, international, chemical literature, for example, the Journal of the American Chemical Society (“ J.Am.Chem.Soc .”) and Tetrahedron. Example 1 Preparation of 8-(Ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]]1,2,4-triazolo[1,5-c]pyrimidines (Compounds 18-25) 8-(Ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidines were prepared according to the synthetic strategy shown in the following Scheme VI. Scheme VI General procedures for the preparation of 8-(Ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (18-25) Reagents: a) NaH, DMF, R 2 X; b) HC(OEt) 3 , reflux; c) 2-Furoic hydrazide, MeO(CH 2 ) 2 OH; d) Ph 2 O, 260° C., flash chromatography In the preparation of compounds 18-25, a solution of 1 (10 mmol) in 40 ml of DMF cooled to 0° C. was treated with NaH (60% in oil, 12 mmol) in several portions over 10 minutes. After 45 minutes, the appropriate (ar)alkyl halide (12 mmol), was added and the reaction mixture was allowed to warm to 25° C. and stirred for 3-5 h (TLC: EtOAc 1:1). The reaction was quenched by addition of H 2 O (80 ml), and the aqueous layer was extracted with EtOAc (5×25 ml). The organic layers were recombined, dried (Na 2 SO 4 ), filtered and concentrated at reduced pressure, to afford the alkylated pyrazole (2-9) as inseparable mixture of N 1 and N 2 isomers (ratio approximately 1:4). This mixture of N 1 and N 2 -substituted-4-cyano-5-amino pyrazoles (2-9) was then dissolved in triethyl orthoformate (60 ml) and the solution was refluxed under nitrogen for 8 h. The solvent was then removed under vacuum and the oily residue constituted by the mixture of imidates (10-17) was dissolved in 2-methoxyethanol (50 ml) and 2-furoic acid hydrazide (13 mmol) was added. The mixture was refluxed for 5-10 h, then, after cooling, the solvent was removed under reduced pressure and the dark oily residue was cyclized further any other purification in diphenyl ether (50 ml) at 260° C. using a Dean-Stark apparatus for the azeotropic elimination of water produced in the reaction. After 1.5 h, the mixture was cooled and poured onto hexane (300 ml). The precipitate was collected by filtration and purified by chromatography (EtOAc/hexane 1:1). In this way, the major product (N 8 alkylated) (18-25) was obtained in a good overall yield. Following this general procedure the following compounds have been prepared: 8-Methyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (18) yield 45%; yellow solid, m.p. 155-156° C. (EtOAc-light petroleum); IR (KBr): 1615, 1510 cm −1 ; 1 H NMR (DMSO d 6 ) δ 4.1 (s, 1H); 6.32 (m, 1H); 7.25 (m, 1H); 8.06 (m, 1H); 8.86 (s, 1H), 9.38 (s, 1H). 8-Ethyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (19) yield 50%; pale yellow solid m.p. 188-189° C. (EtOAc-light petroleum); IR (KBr): 1620, 1500 cm −1 ; 1 H NMR (DMSO d 6 ) δ 1.67 (t, 2H, J=7); 4.53 (q, 2H, J=7); 6.59 (m, 1H); 7.23 (m, 1H); 7.64 (s, 1H); 8.34 (s, 1H); 9.10 (s, 1H). 8-Propyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (20) yield 60%; yellow solid m.p. 189-190° C. (EtOAc-light petroleum); IR (KBr): 1600, 1505 cm −1 ; 1 H NMR (DMSO d 6 ) δ 0.98 (t, 2H, J=7); 2.03-2.10 (m, 2H); 4.41 (q, 2H, J=7); 6.60 (m, 1H); 7.24 (m, 1H); 7.64 (s, 1H); 8.32 (s, 1H); 9.10 (s, 1H). 8-Butyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (21) yield 50%, pale yellow solid m.p. 245-247° C. (EtOAc-light petroleum); IR (KBr): 1610, 1500 cm −1 ; 1 H NMR (DMSO d 6 ) δ 0.9 (m, 3H); 1.3 (m, 2H); 1.9 (m, 2H); 4.5 (t, 2H, J=7.2); 6.2 (m, 1H); 7.3 (m, 1H); 8.0 (m, 1H); 8.9 (s, 1H); 9.4 (s, 1H). 8-Isopentyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (22) yield 54%; pale yellow solid m.p. 235-237° C. (EtOAc-light petroleum); IR (KBr): 1635, 1510, 1450 cm −1 ; 1 H NMR (DMSO d 6 ) δ 1.0 (d, 6H, J=6.2); 1.5-1.9 (m, 3H); 4.6 (t, 2H, J=7.4); 6.6 (m, 1H), 7.3 (m, 1H); 7.7 (m, 1H); 8.8 (s, 1H); 9.1 (s, 1H). 8-(2-Isopentenyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (23) yield 48%; yellow solid map 210-212° C. (EtOAc-light petroleum); IR (KBr): 1625, 1500, 1430 cm −1 ; 1 H NMR (DMSO d 6 ) δ 1.79 (s, 3H); 1.87 (s, 3H); 1.87 (s, 3H); 5.05 (d, 2H, J=6); 5.55-5.63 (m, 1H); 6.60 (m, 1H); 7.24 (m, 1H); 7.64 (s, 1H) 8.34 (s, 1H); 9.10 (s, 1H). 8-2-Phenylethyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (24) yield 56%, m.p. 268-270° C.; (EtOAc-Light petroleum); IR (KBr): 1660, 1510, 1450 cm −1 ; 1 H NMR (DMSO d 6 ) δ 3.32 (t, 2H, J=6.7); 4.72 (t, 2H, J=6.7); 6.73 (s, 1H); 7.23 (m, 5H); 7.95 (s, 1H); 8.8 (s, 1H); 9.41 (s, 1H). Anal. (C 18 H 14 N 6 O) C, H, N. 8-(3-phenylpropyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (25) yield 63%; yellow solid m.p. 165-166° C. (EtOAc-light petroleum); IR (KBr): 1630, 1500, 1440 cm −1 ; 1 H NMR (DMSO d 6 ) δ 2.34-2.48 (m, 2H); 2.67 (t, 3H, J=7.5); 4.43 (t, 2H, J=7.5), 6.61 (m, 1H); 7.16-7.32 (m, 6H); 7.64 (d, 1H, J=2); 8.29 (s, 1H); 9.02 (s, 1H). Example 2 Preparation of 5-Amino-8-(ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidines (Compounds 33-40) 5-Amino-8-(ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidines can be prepared according to the synthetic strategy shown in the following Scheme VII. Scheme VII General procedures for the preparation of 5-Amino-8-(ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (33-40) Reagents: a) HCl, reflux; b) NH 2 CN, 1-methyl-2-pyrrolidone, pTsOH, 140° C. In the preparation of compounds 33-40, a solution of the mixture of triazolo-pyrimidine (18-25) (10 mmol) in aqueous 10% HCl (50 ml) was refluxed for 3 h. Then the solution was cooled and neutralized with a saturated solution of N a HCO 3 at 0° C. The compounds (26-33) were extracted with EtOAc (3×20 ml), the organic layers were dried with Na 2 SO 4 and evaporated under vacuum. The obtained crude amine (26-33) was dissolved in N-methyl pyrrolidone (40 ml), cyanamide (60 mmol) and p-toluene sulfonic acid (15 mmol) were added and the mixture was heated at 160° C. for 4 h. Then cyanamide (60 mmol) was added again and the solution was heated overnight. Then the solution was diluted with EtOAc (80 ml) and the precipitate (excess of cyanamide) was collected by filtration; the filtrate was concentrated under reduced pressure and washed with water (3×30 ml). The organic layer was dried (Na 2 SO 4 ) and evaporated under vacuum. The residue was purified by chromatography (EtOAc/light petroleum 2:1) to afford the desired product (34-41) as a solid, Following this general procedure the following compounds have been prepared: 5-Amino-8-methyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (34) yield 53%; yellow solid m.p. 167-168° C. (EtOAc-light petroleum); IR (KBr): 3500-2950, 1680, 1645, 1610, 1560, 1455 cm −1 ; 1H NMR (DMSO d 6 ) δ 4.12 (s, 3H); 6.70 (m, 1H); 6.99 (bs, 2H); 7.18 (m, 1H); 7.81 (s, 1H), 8.42 (s, 1H). 5-Amino-8-ethyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (35) yield 65%, yellow solid m.p. 249-250° C. (EtOAc-light petroleum); IR (KBr): 3430-2950, 1680, 1655, 1620, 1550, 1450 cm −1 ; 1 H NMR (DMSO d 6 ) δ 1.46 (t, 2H, J=7); 4.30 (d, 2H, J=7); 6.72 (m, 1H); 7.18 (m, 1H); 7.93 (bs, 2H); 7.93 (s, 1H); 8.62 (s, 1H). 5-Amino-8-propyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (36) yield 57%; pale yellow solid m.p. 209-210° C. (EtOAc-light petroleum); IR (KBr): 3400-2900, 1660, 1645, 1610, 1545, 1430 cm −1 ; 1 H NMR (DMSO d 6 ) δ 0.83 (t, 2H, J=7); 1.81-1.91 (m, 2H); 4.22 (d, 2H, J=7); 6.71 (m, 1H); 7.19 (m, 1H); 7.63 (bs, 2H); 7.93 (s, 1H); 8.61 (s, 1H). 5-Amino-8-butyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (37) yield 47%; white solid m.p. 200-203° C. (EtOAc-light petroleum); IR (KBr): 3500-2900, 1685, 1640, 1620, 1550, 1450 cm −1 ; 1 H NMR (DMSO d 6 ) δ 0.9 (t, 3H); 1.2 (m, 2H); 1.8 (m, 2H); 4.2 (t, 2H); 6.7 (m, 1H); 7.2 (m, 2H); 7.6 (s, 1H); 8.0 (s, 1H); 8.6 (s, 1H). 5-Amino-8-isopentyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[5-c]pyrimidine (38) yield 60%; off-white solid m.p. 212-213° C. (EtOAc-light petroleum); IR (KBr): 3500-2850, 1670, 1650, 1615, 1560, 1455 cm −1 ; 1H NMR (CDCl 3 ) δ 0.96 (d, 6H, J=6.4); 1.59 (m, 1H); 1.86 (m, 2H); 4.32 (t, 2H, J=6.4); 6.58 (m, 1H); 6.72 (bs, 2H); 7.21 (d, 1H, J=4.2); 7.63 (d, 1 H, J=1.2); 8.10 1H). 5-Amino-8-(2-isopentenyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (39) yield 58%; pale yellow solid m.p. 178-179° C. (EtOAc-light petroleum); IR (KBr): 3520-2950, 1665, 1640, 1610, 1555, 1450 cm −1 ; 1 H NMR (CDCl 3 ) δ 1.74 (s, 3H); 1.77 (s, 3H); 4.87 (d, 2H, J=7); 5.43-5.46 (m, 1H); 6.72 (m, 1H); 7.18 (m, 1H); 7.62 (bs, 2H); 7.93 (s, 1H); 8.55 (s, 1H). 5-Amino-8-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (40) yield 45%; white solid m.p. 183-185° C. (EtOAc-light petroleum); IR (KBr): 3500-2900, 1670, 1645, 1620, 1530, 1455 cm −1 ; 1 H NMR (DMSO d 6 ) δ 3.21 (t, 2H, J=6.4); 4.53 (t, 2H, J=6.4); 6.7 (s, 1H); 7.1-7.4 (m, 6H), 7.65 (bs, 2H); 7.93 (s,1H); 8.45 (s, 1H). 5-Amino-8-(3-phenylpropyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (41) yield 57%; yellow solid m.p. 168-170° C. (EtOAc-light petroleum); IR (KBr): 3510-2950, 1665, 1640, 1615, 1520, 1455 cm −1 ; 1H NMR (DMSO d 6 ) δ 2.14-2.21 (m, 2H); 2.54 (t, 2H, J=7); 4.29 (t, 2H, J=6.4); 6.71 (s, 1H); 7.14-7.32 (m, 6H), 7.64 (bs, 2H); 7.93 (s, 1H); 8.64 (s, 1H). Example 3 Preparation of 5-[[(Substituted phenyl)amino]carbonyl]amino-8-(ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (Compounds 42-57) 5-[[substituted phenyl)carbonyl]amino-8-(Ar)alkyl-2-(2-furyl)-pyrazolo]4,3-e]1,2,4-triazolo[1,5-c]pyrimidines can be prepared according to the synthetic strategy shown in the following Scheme VIII. Scheme VIII General Procedures for the Preparation of 5-[[(Substituted phenyl)amino]carbonyl]amino-8-(ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (42-57) In the preparation of compounds 42-57, the appropriate amino compound (34-41) (10 mmol) was dissolved in freshly distilled THF (15 ml) and the appropriate isocyanate (13 mmol) was added. The mixture was refluxed under argon for 18 hours. Then the solvent was removed under reduced pressure and the residue was purified by flash chromatography (EtOAc-light petroleum 4-6) to afford the desired compounds 42-57. Following this general procedure the following compounds have been prepared: 5-[[(3-Chlorophenyl)amino]carbonyl]amino-8-methyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (42) yield 98%; pale yellow solid m.p. 142-145° C. (Et 2 -light petroleum); I (KBr): 3210-2930, 1660, 1630, 1610, 1500 cm −1 ; 1 H NMR (CDCl 3 ) δ 4.21 (s, 3H); 6.60 (m, 1H); 7.11 (d, 1H, J=8); 7.13-7.28 (m, 2H): 7.55 (d, 1H, J=8); 7.65 (s, 1H); 7.78 (d, 1H, J=2); 8.22 (s, 1H); 8.61 (bs, 1H); 11.24 (bs, 1H). 5-[[(4-Methoxyphenyl)amino]carbonyl]amino-8-methyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (43) yield 99%; yellow solid m.p. 193-195° C. (Et 2 O-light petroleum); IR (KBr): 3200-2900, 1664, 1625, 1600, 1500 cm −1 , 1H NMR (CDCl 3 ) δ 3.81 (s, 3H); 4.20 (s, 3H); 6.61 (m, 1H); 6.85 (d, 2H, J=9); 7.26 (m, 1H); 7.55 (d, 2H, J=9); 7.65 (s, 1H); 8.21 (s, 1H); 8.59 (bs, 1H); 10.96 (bs, 1H). 5-[[(3-Chlorophenyl)amino]carbonyl]amino-8-ethyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (44) yield 98%; pale yellow solid m.p. 204-205° C. (Et 2 O-light petroleum); IR (KBr): 3220-2930, 1660, 1620, 1600, 1500 cm −1 ; 1 H NMR (CDCl 3 ) δ 1.71 (t, 3H, J=7); 4.50 (q, 2H, J=7); 6.67 (m, 1H); 7.20 (d, 1H, J=8); 7.31 (m, 1H); 7.61 (d, 1H, J=8); 7.70 (s, 1H); 7.84 (s, 1H); 8.30 (s, 1H); 8.67 (bs, 1H); 11.30(bs, 1H). 5-[[(4-Methoxyphenyl)amino]carbonyl]amino-8-ethyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (45) yield 99%; pale yellow solid m.p. 200-201° C. (Et 2 O-light petroleum); IR (KBr): 3250-2950, 1665, 1620, 1610, 1520 cm −1 ; 1 H NMR (CDCl 3 ) δ 1.71 (t, 3H, J=7); 3.85 (s, 3H); 4.49 (s, 3H); 6.65 (m, 1H); 6.88 (d, 2H, J=9); 7.26 (m, 1H); 7.58 (d, 2H, J=9); 7.69 (s, 1H); 8.28 (s, 1H); 8.63 (bs, 1H); 10.99 (bs, 1H). 5-[[(3-Chlorophenyl)amino]carbonyl]amino-8-propyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (46) yield 95%; white solid m.p. 138-139° C. (Et 2 O-light petroleum): IR (KBr): 3210-2920, 1655, 1615, 1600, 1510 cm −1 ; 1 H NMR (CDCl 3 ) δ 1.71 (t, 3H, J=7); 2.04 (m, 2H); 4.36 (q, 2H, J=7); 6.62 (m, 1H); 7.12 (d, 1H, J=8); 7.27 (m, 1H); 7.56 (d, 1H, J=8); 7.66 (s, 1H); 7.80 (s, 1H); 8.24 (s, 1H); 8.62 (bs, 1H); 11.08 (bs, 1H). 5-[[(4-Methoxyphenyl)amino]carbonyl]amino-8-propyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (47) yield 98%; pale yellow solid m.p. 146-148° C. (Et 2 O-light petroleum); IR (KBr): 3230-2950, 1660, 1620,1600, 1530 cm −1 ; 1 H NMR (CDCl 3 ) δ 0.98 (t, 3H, J=7); 2.04-2.08 (m, 2H); 3.82 (s, 3H); 4.35 (t, 2H, J=7); 6.61 (m, 1H); 6.89 (d, 2H, J=9); 7.25 (m, 1H); 7.56 (d, 2H, J=9); 7.65 (s, 1H); 8.23 (s, 1H); 8.59 (bs, 1H); 10.95 (bs, 1H). 5-[[(3-Chlorophenyl)amino]carbonyl]amino-8-butyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (48) yield 97%; white solid m.p. 210-212° C. (Et 2 O-light petroleum); IR (KBr): 3240-2970, 1650, 1610, 1510 cm −1 ; 1 H NMR (CDCl 3 ) δ 1.00 (t, 3H, J=7); 1.39-1.41 (m, 2H); 1.99-2.03 (m, 2H); 4.41 (q, 2H, J=7); 6.63 (m, 1H); 7.14 (d, 1H, J=8); 7.29 (m, 1H); 7.56 (d, 1H, J=8); 7.67 (s, 1H), 7.80 (s, 1H); 8.25 (s, 1H); 8.63 (bs, 1H); 11.26 (bs, 1H). 5-[[(4-Methoxyphenyl)amino]carbonyl]amino-8-butyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (49) yield 96%; white solid m.p. 197-198° C. (Et 2 O-light petroleum); IR (KBr): 3250-2960, 1665, 1610, 1600, 1520 cm −1 ; 1 H NMR (CDCl 3 ) δ 0.98 (t, 3H, J=7); 1.38-1.42 (m, 2H); 2.02-2.05 (m, 2H); 3.82 (s, 3H); 4.39 (t, 2H, J=7); 6.63 (m, 1H); 6.92 (d, 2H, J=9); 7.25 (m, 1H); 7.57 (d, 2H, J=9); 7.67 (s, 1H); 8.23 (s, 1H); 8.60 (bs, 1H); 10.95 (bs, 1H). 5-[[(3-Chlorophenyl)amino]carbonyl]amino-8-isopentyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (50) yield 97%; pale yellow solid m.p. 199-200° C. (Et 2 O-light petroleum); IR (KBr): 3230-2950, 1655, 1600, 1510 cm −1 ; 1 H NMR (CDCl 3 ) δ 1.01 (d, 6H, J=7.5); 1.49-1.51 (m, 1H); 1.88-2.03 (m, 2H), 4.42 (t, 2H, J=7); 6.62 (m, 1H); 7.13 (d, 1H, J=8); 7.34 (m, 1H); 7.57 (d, 1H, J=8); 7.67 (s, 1H); 7.80 (s, 1H); 8.24 (s, 1H); 8.63 (bs, 1H); 11.25 (bs, 1H). 5-[[(4-Methoxyphenyl)amino]carbonyl]amino-8-isopentyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (51) yield 98%; white solid m.p. 192-193° C. (Et 2 O-light petroleum); IR (KBr): 3230-2970, 1660, 1615, 1600, 1500 cm −1 ; 1 H NMR (CDCl 3 ) δ 0.99 (d, 6H, J=7.5); 1.58-1.22 (m, 1H); 1.87-1.97 (m, 2H); 3.82 (s, 3H); 4.40 (t, 2H, J=7); 6.62 (m, 1H); 6.91 (d, 2H, J=9); 7.23 (m, 1H); 7.58 (d, 2H, J=9); 7.66 (s, 1H); 8.23 (s, 1H); 8.59 (bs, 1H); 10.94 (bs, 1H). 5-[[(3-Chlorophenyl)amino]]carbonyl]amino-8-(2-isopentenyl)-2-(2-furyl)pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (52) yield 99%; white solid m.p. 204-205° C. (Et 2 O-light petroleum); IR (KBr): 3245-2960, 1650, 1600, 1510 cm −1 , 1 H NMR (CDCl 3 ) δ 1.84 (s, 3H); 1.88 (s, 3H); 5.01 (d, 2H, J=8); 5.57 (m, 1H); 6.62 (m, 1H); 7.12 (d, 1H, J=8); 7.29 (m, 1H); 7.56 (d, 1H, J=8); 7.66 (s, 1H); 7.80 (s, 1H); 8.26 (s, 1H); 8.60 (bs, 1H); 11.26 (bs, 1H). 5-[[(4-Methoxyphenyl)amino]carbonyl]amino-8-(2-isopentenyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (53) yield 96%; pale yellow solid m.p. 198-199° C. (Et 2 O-light petroleum); IR (KBr): 3235-2950, 1665, 1620, 1600, 1510 cm − , 1 H NMR (CDCl 3 ) δ 1.83 (s, 3H); 1.87 (s, 3H); 3.81 (s, 3H); 4.97 (d, 2H, J=7); 5.57 (m, 1H); 6.61 (m, 1H); 6.93 (d, 2H, J=9); 7.24 (m, 1H); 7.54 (d, 2H, J=9); 7.66 (s, 1H); 8.25 (s, 1H); 8,58 (bs, 1H); 10.96 (bs, 1H). 5-[[(3-Chlorophenyl)amino]carbonyl]amino-8-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (54) yield 98%; white solid m.p. 186-187° C. (Et 2 O-light petroleum); IR (KBr): 3250-2970, 1660, 1610, 1515 cm −1 ; 1 H NMR (CDCl 3 ) δ 3.33 (t, 2H, J=7); 4.62 (t, 2H, J=7); 6.60 (m, 1H); 7.19-7.35 (m, 7H); 7.57 (d, 1H, J=8); 7.61 (s, 1H); 7.81 (s, 1H); 7.89 (s, 1H); 8.63 (bs, 1H); 11.27 (bs, 1H), 5-[[(4-Methoxyphenyl)amino]carbonyl]amino-8-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (55) yield 99%; white solid m.p. 180-181° C. (Et 2 O-light petroleum); IR (KBr); 3245-2960, 1660, 1615, 1600, 1500 cm −1 ; 1 H NMR (CDCl 3 ) δ 3.42 (t, 2H, J=7); 3.82 (s, 3H); 4.60 (t, 2H, J=7); 6.60 (m, 1H); 6.93 (d, 2H, J=9); 7.09 (m, 2H); 7.20-7.28 (m, 4H); 7.56 (d, 2H, J=8); 7.60 (s, 1H); 7.89 (s, 1H); 8.59 (bs, 1H); 10.96 (bs, 1H). 5-[[(3-Chlorophenyl)amino]carbonyl]amino-8-(3-phenylpropyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (56) yield 99%; pale yellow solid m.p. 183-184° C. (Et 2 O-Light petroleum); IR (KBr); 3245-2960, 1665, 1610, 1515 cm − , 1 H NMR (CDCl 3 ) δ 2.46 (m, 2H); 2.73 (t, 2H, J=7); 4.43 (t, 2H, J=7); 6.66 (m, 1H); 7.19-7.40 (m, 8H); 7.59 (d, 1H, J=8); 7.64 (s, 1H); 7.85 (m, 1H); 8.25 (s, 1H); 8.67 (bs, 1H); 11.30 (bs, 1H). 5[[(4-Methoxyphenyl)amino]carbonyl]amino-8-(3-phenylpropyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (57) yield 98%; white solid m.p. 174-175° C. (Et 2 O-light petroleum); IR (KBr): 3240-2950, 1665, 1615, 1600, 1510 cm −1 ; 1 H NMR (CDCl 3 ) δ 2.46 (m, 2H); 2.73 (t, 2H, J=7); 4.42 (t, 2H, J=7); 6.67 (m, 1H); 6.96 (d, 2H, J=9); 7.22-7.41 (m, 6H); 7.60 (d, 2H, J=8); 7.64 (s, 1H); 8.25 (s, 1H), 8.65 (bs, 1H); 11.16 (bs, 1H). Example 4 Preparation of 5-[(Benzyl)carbonyl]amino-8-(ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (Compounds 58-59) 5-[[benzyl)carbonyl]amino-8-(Ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidines can be prepared according to the synthetic strategy shown in the following Scheme IX. Scheme IX General Procedures for the Preparation of 5-[(Benzyl)carbonyl]amino-8-(ar)alkyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (58-59) In the preparation of compounds 58-59, the appropriate amino compound (38 or 41) (10 mmol) was dissolved in freshly distilled THF (15 ml) and the appropriate acid halide (13 mmol) and triethylamine (13 mmol) were added. The mixture was refluxed under argon for 18 hours. The solvent was then removed under reduced pressure and the residue was dissolved in EtOAc (30 ml) and washed twice with water (15 ml). The organic phase was dried on Na 2 SO 4 and concentrated under reduced pressure. The residue was purified by flash chromatography (EtOAc-light petroleum 4:6) to afford the desired compounds 58, 59. Following this general procedure the following compounds have been prepared: 5-[(Benzyl)carbonyl]amino-8-isopentyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine (58) yield 85%, pale yellow solid m.p. 144-145° C. (Et 2 O-light petroleum); IR (KBr): 3255-2930, 1673, 1620, 1610, 1520 cm −1 ; 1 H NMR (CDCl 3 ) δ 0.98 (d, 6H, J=7.5); 1.60 (m, 1H); 1.91 (m, 1H); 4.40 (t, 2H, J=7); 4.53 (s, 2H); 6.60 (m, 1H); 7.18 (m, 1H); 7.26-7.39 (m, 5H); 7.64 (s, 1H); 8.22 (s, 1H); 9.11 (bs, 1H). 5-[(Benzyl)carbonyl]amino-8-(3-phenylpropyl)-2-(2-furyl)-pyrazolo[4,3-e]2,4-triazolo[1,5-c]pyrimidine (59) yield 95%, pale yellow solid m.p. 116-117° C. (Et 2 O-light petroleum); IR (KBr); 3250-2900, 1675, 1625, 1600, 1500 cm −1 ; 1 H NMR (CDCl 3 ) δ 2.39 (m, 2H); 2.67 (t, 2H, J=7); 4.37 (t, 2H, J=7); 4.53 (s, 2H); 6.61 (m, 1H); 7.16-7.43 (m, 11H); 7.65 (s, 1H); 7.64 (s, 1H); 8.19 (s, 1H); 9.12 (bs, 1H). Example 5 Preparation of 1-Substituted-4-cyano-5-aminopyrazoles According to the procedures described in J. Org. Chem . 1956, 21, 1240 ; J. Am. Chem. Soc . 1956, 78, 784 and the references herein cited, the following compounds are prepared, starting from commercially available ethoxy methylene malonodinitrile and N1-substituted hydrazines, which also are mainly commercially available: 1-methyl-4-cyano-5-aminopyrazole 1-n-butyl-4-cyano-5-aminopyrazole 1-isopentyl-4-cyano-5-aminopyrazole 1-(2-cyclopentyl)ethyl-4-cyano-5-aminopyrazole 1-hydroxyethyl-4-cyano-5-aminopyrazole 1-phenyl-4-cyano-5-aminopyrazole 1-tert-butyl-4-cyano-5-aminopyrazole. 1-phenylethyl-4-cyano-5-aminopyrazole 1-(2-chlorophenyl)-4-cyano-5-aminopyrazole. These compounds can be used as intermediates to prepare pyrazolo-triazolo-pyrimidine compounds as described herein. Example 6 Preparation of 1-substituted-4-cyano-3-aminopyrazoles Starting from 4-cyano-5-aminopyrazole, prepared according the procedure reported in Chem. Pharm. Bull . 1970, 18, 2353 or in J. Heterocyclic Chem . 1979, 16, 1113, 1-substituted 4-cyano-3-aminopyrazoles can be prepared by direct alkylation with the corresponding alkyl halide in dimethyl formamide at 80° C. for 1 to 2 h in the presence of anhydrous potassium carbonate. From the reaction mixture, containing the two N1 and N2 alkylated position isomers in an about 1:2 ratio, the N2 isomer can be isolated by a single crystallization or column chromatography on silica gel eluting with ethyl acetate and petroleum ether mixtures. Using these procedures, the following compounds were prepared: 1-methyl-4-cyano-3-aminopyrazole 1-butyl-4-cyano-3-aminopyrazole 1-benzyl-4-cyano-3-aminopyrazole 1-isopentyl-4-cyano-3-aminopyrazole 1-phenylethyl-4-cyano-3-aminopyrazole These compounds can be used as intermediates to prepare pyrazolo-triazolo-pyrimidine compounds as described herein. Example 7 Preparation of phenylethyl-4-cyano-3-aminopyrazoles a) A suspension of anhydrous potassium carbonate (30 mmols) in DMF (50 ml) is added with 3-amino-4-cyano pyrazole (20 mmols), heating to a temperature of 80° C. for 30 minutes. The suspension is added with phenethyl bromide (25 mmols) and is heated to 80° C. for 2 h. After cooling to room temperature, the mixture is evaporated to dryness under vacuum and the resulting residue is taken up with distilled water (100 ml) and extracted with ethyl acetate (3×50 ml). The combined organic extracts are dried over anhydrous sodium sulfate and evaporated to dryness under vacuum. The resulting residue consists of a 1:3 mixture of 1-phenylethyl-4-cyano-5-aminopyrazole (20%) and of 1-phenylethyl-4-cyano-3-aminopyrazole (60%) which may be used as such in Example 9 or chromatographed on silica gel column eluting with an ethyl acetate/hexane mixture to give: 1-phenylethyl-4-cyano-5-aminopyrazole M.P. 172-173° C.; (20%); 1 H-NMR (DMSO-d6): 3.04 (t, 2H); 4.12 (t, 2H); 5.85 (sb, 2H); 7.21-7.30 (m, 5H); 7.41 (s, 1H); 1-β-phenylethyl-4-cyano-3-aminopyrazole M.P. 98-100° C. (60%); 1 H NMR (CDCl 3 ): 3.07 (t, 2H); 4.10 (t, 2H); 4.23 (sb, 2H); 7.17 (s, 1H); 7.00-7.28 (m, 5H). b) A solution of 1-β-phenylethyl-4-cyano-5-aminopyrazole (20 mmol) in triethylorthoformate (40 ml) was refluxed under nitrogen for 8 h. The excess orthoformate was evaporated to dryness under vacuum and the residual yellow oil is dissolved in ethyl ether and percolated onto silica gel to give the corresponding iminoether (87% yield). The residue obtained after orthoformate evaporation is practically pure and is directly used in the following step. A solution of the iminoether (20 mmol) and 2-furoic acid hydrazide (2.5 g, 22 mmol) in 2-methoxyethanol (50 ml) was refluxed for 5 to 10 h. After cooling, the solution is evaporated to dryness to give an oily residue which is subjected to thermal cyclization in diphenylether (50 ml) using a Dean-Stark apparatus so as to azeotropically remove water formed during the reaction. After 1.5 h, the reaction is checked by TLC (ethyl acetate:petroleum ether 2:1) and when the starting compound is completely absent, the mixture is cooled and added with hexane. The resulting precipitate is filtered and crystallized to give 7-(β-phenylethyl)-2(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5c]-pyrimidine M.P. 174-175° C. (20%) 1 H NMR (DMSO-d 6): 3.23 (t, 2H) 4.74 (t, 2H); 6.75 (s, 1H); 7.14-7.17 (m, 5H); 7.28 (s, 1H); 7.98 (s, 1H); 8.53 (s, 1H); 9.56 (s, 1H). In a similar way, starting from 1-β-phenylethyl-4-cyano-3-aminopyrazole, 8-(β-phenylethyl)-2(2-furyl) pyrazolo[4,3-e]1,2,4-triazole(1,5-c)-pyrimidine was prepared; M.P. 268-270° C. (600A) 1 H NMR (DMSO-d6): 3.32 (t, 2H); 4.72 (t, 2H); 6.73 (s, 1H), 7.23 (m, 5H); 7.95 (s, 1H); 8.8 (s, 1H); 9.41 (s, 1H). c) A suspension of the product of step b) (10 mmol) in 10% HCl (5.0 ml) is refluxed under stirring for 3 h. After cooling, the solution is alkalinized with concentrated ammonium hydroxide at 0° C. and the resulting precipitate is filtered or extracted with ethyl acetate (3×100 ml), dried and evaporated to dryness under vacuum, to give the corresponding 1-β-phenylethyl)-4-[3(2-furyl)-1,2,4-triazol-5-yl]-5-amino pyrazole m.p. 175-176° C.; 1 H NMR (DMSO-d6): 3.15 (t, 2H); 4.48 (t, 2H); 5.78 (s, 1H), 6.37 (s, 1H); 6.68 (s, 1H); 7.1 (s, 1H); 7.27-7.28 (m, 5H); 7.82 (s, 1H); 14.51 (bs, 2H): in a similar way 1-(β-phenylethyl)-4-[3(2-furyl)-1,2,4-triazol-5-yl)-3-aminopyrazole (m.p. 205-206° C.); 1 H NMR (DMSO-d 6): 3.12 (t, 2H); 4.46 (t, 2H) 5.75 (s, 1H); 14.41 (bs, 2H) is obtained. d) Cyanamide (60 mmol) is added to a suspension of the amine of step c) (10 mmol in N-methylpyrrolidone (40 ml) followed by p-toluene sulfonic acid (15 mmol). The mixture is heated to 160° C. under stirring. After 4 h a second portion of cyanamide (60 mmol) is added and heating is continued overnight. The mixture is then treated with hot water (200 ml) and the precipitate is filtered, washed with water and crystallized from ethanol to give the corresponding 5-amino-7-(β-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazole[1,5-c]pyrimidine m.p. 225-226° C. 1 H NMR (DMSO-d 6): 3.21 (t, 2H); 4.51 (t, 2H); 6.65 (s, 1H); 7.1-7.44 (m, 6H); 7.78 (s, 1H); 7.89 (bs, 2H); 8.07 (s, 1H). In a similar way 5-amino-8-(β-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazole[1,5c]-pyrimidine m.p. 212-213° C. 1 H NMR (DMSO-d 6): 3.21 (t, 2H); 4.53 (t, 2H); 6.7 (s, 1H); 7.1-7.4 (m, 6H); 7.65 (sb, 2H); 7.93 (s, 1H); 8.45 (s, 1H) was obtained. Example 8 Preparation of 4-cyano-5-amino-1,2,3-triazoles A suspension of potassium carbonate (0.23 mole) in DMSO (70 ml) is added subsequently with cyanoacetamide (70 mmols) and p-fluorobenzylazide (54.5 mmols). The resulting solution is stirred at room temperature for 1 h and then poured into a large volume of water (1.5 l). The separated solid is filtered, washed with water and dried in oven at 70° C. to give 1-(p-fluorobenzyl)-4-carboxamido-5-amino-1,2,3-triazole (96.1% yield). M.P.: 198-199° C.; 1 H NMR (DMSO-d 6): 7.5-7.1 (m, 6H); 6.4 (s, 2H); 5.4 (s, 2H). An amide suspension (0.005 mole), stirred and cooled to 0° C., in DMF (5 ml) is added with phosphorous oxychloride (0.01 mole). The resulting solution is stirred for 5 minutes at 0° C., 10 minutes at 25° C. and 15 minutes at 80° C. After cooling to room temperature, 5 ml of N HCl are added and the mixture is refluxed for 5 minutes. 1-(p-fluorobenzyl)-4-cyano-5-amino-1,2,3-triazole separates from the cooled solution (90% yield). M.P. 185-186° C.; 1 H NMR (DMSO-d 6): 7.3-7.0 (m, 6H); 5.5 (s, 2H); IR (KBr): 3400, 3220, 2220, 1655 cm−1. Analogously, the following compounds were prepared: 1- or 2-benzyl-4-cyano-5-amino-1,2,3-triazole 1- or 2-(o-fluorobenzyl)-4-cyano-5-amino-1,2,3-triazole 1- or 2-(p-fluorobenzyl)-4-cyano-5-amino-1,2,3-triazole 1- or 2-butyl-4-cyano-5-amino-1,2,3-triazole 1- or 2-isopentyl-4-cyano-5-amino-1,2,3-triazole 1- or 2-(2-methoxyethyl)-4-cyano-5-amino-1,2,3-triazole 1-2-heptyl-4-cyano-5-amino-1,2,3-triazole 1- or 2-octyl-4-cyano-5-amino-1,2,3-triazole. These compounds can be used as intermediates to prepare the triazolo-triazolo-pyrimidine compounds as described herein. Example 9 Preparation of Ethoxymethyleneamino Heterocycles The preparation of ethoxymethyleneamino heterocycles of formula IV is performed refluxing the respective ortho-aminonitrile with ethyl orthoformate. By way of example, the preparation of 4-cyano-5-(ethoxymethyleneamino)-1-butylpyrazole is reported. A solution of 4-cyano-5-amino-1-butylpyrazole (20 mmols) in triethyl orthoformate (40 ml) is heated to the reflux temperature under nitrogen atmosphere for 8 h. The orthoformate excess is evaporated to dryness under vacuum and the residual yellow oil is dissolved in ethyl ether and eluted through silica gel to give the pure compound (87% yield). In many cases, the residue obtained after evaporation of the orthoformate is substantially pure and is used as such in the subsequent step. IR (nujol): 3140, 2240, 1640 cm−1; 1 H NMR (CDCl 3 ): 8.4 (s, 1H); 7.9 (s, 2H); 4.5 (t, 2H); 4.3 (q, 2H); 1.8 (m, 2H); 1.5 (m, 2H); 1.4 (t, 3H); 0.9 (t, M). Example 10 Cyclization of Ethoxymethyleneamino Heterocycles A solution of the ethoxymethyleneamino heterocycle (20 mmols) and 2-furoic acid hydrazide (2.5 g, 22 mmols) in 2-methoxyethanol (50 ml) is refluxed for 5 to 10 h. After cooling, the solution is evaporated to dryness to obtain a residual oil which is subjected to thermal cyclization in diphenyl ether (50 ml) using a round-bottom flask fitted with a Dean-Stark apparatus, to azeotropically remove the water formed during the reaction. After varying times (3 to 5 h) the reaction is checked by TLC (2:1 ethyl acetate: petroleum ether) and when the whole starting product has disappeared, the mixture is cooled and hexane is added. The resulting precipitate is filtered and crystallized from the suitable solvent. In some cases, a viscous oil separates from the solution, which is then decanted and subsequently extracted. The oily residue is then chromatographed on silica gel, eluting with ethyl acetate/petroleum ether mixtures, to give the tricyclic compound VI. By way of examples, the analytical and spectroscopical characteristics of some compounds prepared by these procedures are reported: 7-butyl-2(2-furyl)-pyrazolo-[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine. 1 H NMR (DMSO-d 6): 9.6 (s, 1H); 8.6 (s, 1H); 8.0 (m, 1H); 7.4 (m, 1H); 6.7 (m, 1H); 4.5 (t, 2H); 1.9 (m, 2H); 1.3 (m, 2H); 0.9 (t, 3H). 8-butyl-2(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine. 1 H NMR (DMSO-d 6): 9.4 (s, 1H); 8.9 (s, 1H); 8.0 (m, 1H), 7.3 (m, 1H); 6.2 (m, 1H); 4.5 (t, 2H); 1.9 (m, 2H); 1.; (m, 2H); 0.9 (m, 3H). In the 2D-NMR (NOESY) spectrum, the N—CH 2 signal resonating at 4.5 shows cross peaks with the C9-H signal resonating at 8.9. 7-isopentyl-2(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine. 1 H NMR (CDCl 3 ): 9.1 (s, 1H); 8.8 (s, 1H); 7.7 (m, 1H); 7.3 (m, 1H); 6.6 (m, 1H); 4.6 (t, 2H); 1.18-1.7 (m, 3H); 1.0 (d, 6H). 8-isopentyl-2(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine. 9.1 (s, 1H); 8.8 (s, 1H); 7.7 (m, 1H); 7.3 (m, 1H); 6.6 (m, 1H); 4.6 (t, 2H); 1.9-1.5 (m, 3H); 1.0 (d, 6H). Following this procedure, the following compounds were prepared: 7-methyl-2(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine 8-methyl-2(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine 7-(2-chlorophenyl)-2(2-furyl)-pyrazolo[4,3-e]1,2,4triazolo[1,5-c]pyrimidine 7-phenylethyl-2(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine 7-tert-butyl-2(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine 7-(2-cyclopentyl)ethyl-2(2-furyl)-pyrazolo[4,3-e]1,2,4 triazolo(1,5-c)pyrimidine 8-benzyl-2(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine 7-benzyl-2(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 7-(2-fluorobenzyl)-2(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 7-(4-fluorobenzyl)-2(2-furyl)-1,2,3-triazolo[5,4e]1,2,4-triazolo[1,5-c]pyrimidine 7-butyl-2(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 7-isopentyl-2(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 7-(2-methoxy)ethyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]-1,2,4-triazolo[1,5-c]pyrimidine 7-heptyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]-1,2,4-triazolo[1,5-c]pyrimidine 7-octyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 8-benzyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 8-(2-fluorobenzyl)-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 8-(4-fluorobenzyl)-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 8-butyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 8-isopentyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 8-hexyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 8-heptyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 8-octyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine 9-benzyl-2-(2-furyl)-1,2,3-triazolo[4,5-e]1,2,4-triazolo[1,5-c]pyrimidine 9-(2-fluorobenzyl)-2-(2-furyl)-1,2,3-triazolo[4,5-e]1,2,4-triazolo[1,5-c]pyrimidine 9-(4-fluorobenzyl)-2-(2-furyl)-1,2,3-triazolo[4,5-e]1,2,4-triazolo[1,5-c]pyrimidine These compounds can be used as intermediates to prepare the triazolo-triazolo-pyrimidines and pyrazolo-triazolo-pyrimidines as described herein. Example 11 Preparation of 5-amino-7-[aralkyl)]-2-(2-furyl)-pyrazole[4,3-e]-1,2,4-triazole[1,5-c]pyrimidines A suspension of the amines of formula VII (10 mmols) in N-methylpyrrolidone (40 ml) is added with cyanamide (60 mmols) followed by p-toluenesulfonic acid (15 mmols). The mixture is heated to 160° C. with magnetic stirring. After 4 h, a second portion of cyanamide (60 mmols) is added and heating is continued overnight. The mixture is then treated with hot water (200 ml) and the precipitated solid is filtered, washed with water and crystallized from ethanol. If no precipitations take place, the solution is extracted with ethyl acetate (4×100 ml), the extracts are washed with brine (2×50 ml), dried and evaporated to dryness under vacuum. The residue is then chromatographed on a silica gel column eluting with ethyl acetate. In the following, the analytical and spectroscopic data of some compounds prepared by this procedure are reported: 5-amino-7-butyl-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine. M.P. 157-158° C.; 1 H NMR (DMSO-d 6) 8.1 (s, 1H); 8.0 (s, 2H); 7.9 (m, 1H); 7.2 (m, 1H); 6.7 (m, 1H); 4.2 (t, 2H); 1.9 (m, 2H); 1.5 (m, 2H); 0.9 (t, 3H). 5-amino-8-butyl-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine m.p. 183-185° C.; 1 H NMR (DMSO-d 6): 8.6 (s, 1H); 8.0 (s, 1H); 7.6 (s, 2H); 7.2 (m, 1H); 6.7 (m, 1H); 4.2 (t, 2H); 1.8 (m, 2H); 1.2 (m, 2H); 0.9 (t, 3H). 5-amino-7-benzyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine. M.p. 295-297° C.; 1 H NMR (DMSO-d 6): 8.5 (s, 2H); 8.0 (s, 1H); 7.3 (m, 6H); 6.7 (m, 1H); 5.7 (s, 2H). 5-amino-7-o-fluoro-benzyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]-1,2,4-triazolo[1,5-c]pyrimidine M.p. 310-312° C.; 1 H NMR (DMSO-d 6): 8.5 (s, 2H); 8.0 (s, 1H); 7.3 (m, 5H); 6.8 (s, 1H); 5.75 (s, 2H). 5-amino-7-methyl-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4triazolo-[1,5-c]pyrimidine; m.p. 210-213° C. 5-amino-7-tert-butyl-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4triazolo-[1,5-c]pyrimidine; m.p. 238-240° C. 5-amino-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo (1,5-c)pyrimidine; m.p. 248-250° C. 5-amino-7-(2-hydroxyethyl)-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo-[1,5-c]pyrimidine; m.p. 258-260° C. 5-amino-7-phenyl-2-(2-furyl)-pyrazolo(4,3-e]-1,2,4triazolo-[1,5-c]pyrimidine; m.p. 295-297° C. 5-amino-7-isopentyl-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4triazolo-[1,5-e]pyrimidine; m.p. 208-210° C. 5-amino-8-isopentyl-2-(2-furyl)-pyrazolo(4,3-e)-1,2,4triazolo-1,5-c]pyrimidine;. m.p. 200-203° C. 5-amino-7-phenethyl-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo-[1,5-c]pyrimidine; m.p. 225° C. 5-amino-7-benzyloxyethyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo-[1,5-c]pyrimidine. 5-amino-7-[β-(4-isobutylphenethyl)]-2-(2-furyl)-pyrazole[4,3-e]-1,2,4-triazole[1,5-c]pyrimidine m.p. 207-210° C. These compounds can be reacted with a suitable acid or sulfonic acid derivative to arrive at the compounds of Formula I disclosed herein. Example 12 Preparation of Substituted-4-carboxamido-5-amino-1,2,3-triazoles p-Fluorobenzylazide (15.1 g, 0.1 mole) and cyanacetamide (10.8 g, 0.13 moles) are added in this order to a suspension of powdered potassium carbonate (57.5 g, 0.42 mole) in dimethylsulfoxide (150 ml). The mixture is stirred at room temperature, for 1 h. The mixture is poured into 3 liters of water and the solid which separates is filtered and washed thoroughly with water to give 22.47 g (96%) of 1-p-fluorobenzyl-4-carboxamido-5-amino 1,2,3-triazole. M.P.: 198-199° C.; 1 H NMR (DMSO-d 6): 7.5-7.1 (m, 6H); 6.4 (s, 2H); 5.4 (s, 2H). Analogously, 2-fluoro-6-chlorobenzyl-4-carboxamide-5-amino-1,2,3-triazole; m.p. 230-231° C.; 1 H NMR (DMSO d 6): 5.40 (s, 2H); 6.52 (bs, 2H); 7.12-7.45 (m, 5H). 3-fluoroberizyl-4-carboxamido-5-amino 1,2,3-triazole; m.p. 211-211° C. 1 H-NMR (DMSO-d 6): 5.46 (s, 2H); 6.47 (bs, 2H); 7.00-7.52 (m, 6H). 2-fluorobenzyl-4-carboxamido-5-amino-1,2,3-triazole; M.P. 195-197° C. 1-(β-phenylethyl)-4-carboxamido-5-amino-1,2,3-triazole; M.P. 181-183° C.; 1 H NMR (DMSO-d6): 3.04 (t, 2H); 4.35 (t, 2H); 6.30 (sb, 2H); 7.20-7.47 (m, 7H) are obtained. Example 13 Preparation of Substituted-4-cyano-5-amino-1,2,3-triazoles A suspension of 1-p-fluorobenzyl-4-carboxamido-5amino-1,2,3-triazole (23.4 g, 0.1 mole) in DMF (100 10 ml), magnetically stirred at 0° C., is added with 20.8 ml (0.2 mole) of POCl 3 . The solution is stirred for 5 h at 0° C., 10 h at room temperature and finally 15 h at 80° C. After cooling, 1N HCl (100 ml) is added thereto and the resulting solution is refluxed for 5 h; upon cooling 1,5 p-fluorobenzyl-4-cyano-5-amino-1,2,3-triazole (18.54 g, 90%) precipitates. M.P. 185-186° C.; 1 H NMR (DMSO-d6): 7.3-7.0 (m, 6H); 5.5 (s, 2H); IR (KBr): 3400, 3220, 2220, 1655 cm−1. Analogously, the following compounds are obtained: 2-fluoro-6-chlorobenzyl-4-cyano-5-amino-1,2,3-triazole; M.P. 181-185° C. 1 H NMR (DMSO-d 6): 5.40 (s, 2H); 7.26-7.50 (m, 5H). 3-fluorobenzyl-4-cyano-5-amino-1,2,3-triazole; M.P. 195-197° C. 1 H NMR (DMSO-d 6): 5.44 (s, 2H); 7.00-7.43 (m, 6H). 2-fluorobenzyl-4-cyano-5-amino-1,2,3-triazole; M.P.: 195-197° C. 1-(β-phenylethyl)-4-cyano-5-amino-1,2,3-triazole; M.P. 149-150° C. 1 H NMR (DMSO-d 6): 3.04 (t, 2H), 4.36 (t, 2H); 7.03 (sb, 2H); 7.23-7.28 (m, 5H). Example 14 Preparation of Substituted-4[3(2-furyl)-1,2,4-triazol-5-yl]-5-amino-1,2,3-triazoles A suspension of 1-p-fluorobenzyl-4-cyano-5-amino-1,2,3-triazole (20 mmols) and 2-furoic acid hydrazide (22 mmols) in diphenyl ether (30 ml) is stirred and heated to reflux (260° C.) with a Dean-Stark apparatus until the starting compound disappears (TLC, 1 to 2 h). After cooling, the mixture is diluted with petroleum ether and the resulting precipitate is either filtered or separated by decantation and chromatographed on a silica gel column eluting with 2:1 ethyl acetate and petroleum ether. 1-p-fluorobenzyl-4[3-(2-furyl)-1,2,4-triazol-5-yl]-5-amino-1,2,3-triazole; m.p. 266-268° C. 1 H NMR (DMSO-d 6): 14.5 (s, 1H); 7.8 (s, 1H); 7.4-7.1 (m, 5H); 6.6 (s, 1H); 6.5 (s, 2H); 5.5 (s, 2H). Analogously, 1-(β-phenylethyl)-4[3(2-furyl)-1,2,4-triazol-5-yl]-5-amino1,2,3-triazole (50%); m.p. 200-202° C. 1 H-NMR (DMSO-d6): 3.07 (t, 2H); 4.16 (t, 2H); 5.50 (sb, 2H); 6.61 (s, 1H); 6.95 (s, 1H); 7.2-7.4 (m, 5H); 7.78 (s, 1H); 13.8 (bs, 1H) is obtained. Example 15 Preparation of 5-amino-7-Substituted-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidines A suspension of 1-p-fluorobenzyl-4[3-(2-furyl)1,2,4-triazol-5-yl]-5-amino-1,2,3-triazole (0.325 g, 1 mmols) in N-methyl-pyrrolidone (4 ml) is added with cyanamide (6 mmols) followed by p-toluenesulfonic acid (1.5 mmols). The mixture is heated at 160° C. with magnetic stirring. After 4 h, a second portion of cyanamide (6 mmols) is added and heating is continued overnight. The mixture is then treated with hot water (20 ml) and the precipitated solid is filtered, washed with water and crystallized from ethanol. If no precipitations take place, the solution is extracted with ethyl acetate (4×10 ml), the extracts are washed with brine (2×5 ml), dried and evaporated to dryness under vacuum. The residue is then chromatographed on a silica gel column eluting with ethyl acetate to give 105 mg (30% yield) of 5-amino-7-p-fluoro-benzyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine M.P.: 266-268° C.; 1 H NMR (DMSO-d 6): 8.5 (sb, 2H); 7.95 (s, 1H); 7.4-7.1 (m, 6H); 6.7 (s, 1H); 5.7 (s, 2H). Analogously, were obtained: 5-amino-7-o-fluorobenzyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine; M.P. 310° C. 5-amino-7-benzyl-2-(2-furyl)-1,2,3-triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine; M.P. 295-297° C. 5-amino-7-(2-fluoro-6-chlorobenzyl)-2-(2-furyl)-1,2,3-triazolo-5,4-e]1,2,4-triazolo[1,5-c]pyrimidine; M.P. 218-220° C.; 1 H NMR (DMSO-d6): 8.51 (sb′, 2H); 7.98 (s, 1H); 7.55-7.28 (m, 4H); 6.77 (m, 1H); 5.73 (s, 2H). 5-amino-7-(m-fluorobenzyl)-2-(2-furyl) 1,2,3triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine; m.p. 280-283° C.; 1 H NMR (DMSO-d6): 8.45 (bs, 2H); 7.98 (s, 1H); 7.4-7.1 (m, 5H); 6.76 (s, 1H); 5.75 (s, 2H). 5-amino-7-(β-phenylethyl)-2-(2-furyl)-1,2,3 triazolo[5,4-e]1,2,4-triazolo[1,5-c]pyrimidine; M.P. 269-271° C.; 1 H NMR (DMSO-d6): 8.4 (sb, 2H); 7.98 (s, 1H); 7.3-7.15 (m, 6H); 6.8 (s, 1H); 4.71 (t, 2H); 3.31 (t, 2H) are obtained. Example 16 Evaluation of the Biological Activity of the Compounds Several of the compounds described above have been tested for their affinity at rat A 1 and A 2A and human A 3 receptors using the following assays. Rat A 1 and A 2A Adenosine Receptor Binding Assay Male Wistar rats (200-250 g) were decapitated and the whole brain and striatum dissected on ice. The tissues were disrupted in a polytron homogenizer at a setting of 5 for 30 s in 25 volumes of 50 mM Tris HCl, pH 7.4, containing 10 mM MgCl 2 . The homogenate was centrifuged at 48,000 for 10 min, and the pellet was resuspended in the same buffer containing 2 IU/mL adenosine deaminase. After 30 min incubation at 37° C., the membranes were centrifuged and pellets were stored at −80° C. Prior to freezing, an aliquot of homogenate was removed for protein assay with bovine albumin as reference standard. Binding assays were performed on rat brain and striatum membranes respectively, in the presence of 10 mM MgCl 2 at 25° C. All buffer solutions were adjusted to maintain a constant pH of 7.4. Displacement experiments were performed in 500 μL of Tris HCl buffer containing 1 nM of the selective adenosine A 1 receptor ligand [ 3 H]CHA (N 6 -cyclohexyladenosine) and membranes of rat brain (150-200 μg- of protein/assay). Displacement experiments were performed in 500 μL of Tris HCl buffer containing 10 mM MgCl 2 , 0.2 nM of the selective adenosine A 2A receptor ligand [ 3 H]SCH58261 (5-amino-7-(2-phenylethyl)-2(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine) and membranes of rat striatum (80-100 μg of protein/assay). To determine IC 50 values (where IC 50 is the inhibitor concentration displacing 50% of labeled ligand) the test compound was added in triplicate to binding assay samples at a minimum of six different concentrations. Separation of bound from free radio ligand was performed by rapid filtration through Whatman GF/B filters which were washed three times with ice-cold buffer. Filter bound radioactivity was measured by scintillation spectrometry after addition of 5 mL of Aquassure. Non specific binding was defined as binding in the presence of 10 μM R-PIA (N 6 -(phenylisopropyl)adenosine) and 10 μM NECA (5′-(N-ethylcarboxamido) adenosine), respectively, and was always 10% of the total binding. Incubation time ranged from 150 min. at 0° C. to 75 min at 30° C. according to the results of previous time-course experiments. Ki values were calculated from the Cheng-Prusoff equation. All binding data were analyzed using the nonlinear regression curve-fitting computer program LIGAND. Human Cloned A 3 Adenosine Receptor Binding Assays. An aliquot of membranes (8 mu of protein/mL) from HEK-293 cells transfected with the human recombinant A 3 adenosine receptor was used for binding assays. FIG. 1 shows a typical saturation of [ 125 I]AB-MECA (N 6 -(4-amino-3-iodobenzyl)-5′-(N-methylcarbamoyl)adenosine) to HEK-293 cells. Inhibition experiments were carried out in duplicate in a final volume of 100 μL in test tub containing 0.3 nM [ 125 I]AB-MECA, 50 nM Tris HCL buffer, 10 mM MgCl 2 , pH 7.4, 20 μL of diluted membranes (12.4 mg of protein/mL), and at least 6-8 different concentrations of typical adenosine receptor antagonists. Non-specific binding was defined in the presence of 50 μM R-PIA and was about 30% of total binding. Incubation time was 60 min at 37° C., according to the results of previous time-course experiments. Bound and free radioactivity was separated by filtering the assay mixture through Whatman GF/B glass-fiber filters using a Brandel cell harvester. Results and Discussion Compounds 38, 40, 41, 50, 51, and 54-57 were tested in radio ligand binding assays for affinity at rat brain A 1 , A 2A and human A 3 receptors, and the results are summarized in Table 1. The data demonstrate that compounds lacking bulky (compounds 38, 40 and 41) groups at N 5 position show great affinity for A 2A adenosine receptors with low selectivity vs. A 1 and low affinity at human adenosine A 3 receptor subtype, and that compounds with substituted phenyl carbamoyl chain at N 5 position possess affinity in nanomolar range at hA 3 receptor subtype with different degree of selectivity vs. A 1 and A 2A receptor subtype. In particular, the 4-methoxyphenylcarbamoyl moiety (compounds 51, 55 and 57) confers higher affinity, of about three order of magnitude, than 3-chlorophenylcarbamoyl residue (compounds 50, 54 and 56). Derivatives with a β-phenylethyl chain at N 8 and 4-MeO-phenylcarbamoyl chain at N 5 positions (compound 55) showed the best values in terms of affinity and selectivity. (K i hA 3 =1.47 nM, rA 1 /hA 3 =872, rA 2A /hA 3 =951). The introduction, at the N 8 position, of chains with different steric characteristics permits the design of derivatives with high potency at human A 3 adenosine receptor and better selectivity vs. A 1 and A 2A receptor subtypes. FIG. 1 shows a saturation curve of [ 125 I]AB-MECA to adenosine A 3 receptor and the linearity of the Scatchard plot in the inset is indicative, in our experimental conditions, of the presence of a single class of binding sites with K D value of 0.9±0.01 nM and Bmax value of 62±1 fmol/mg protein (n=3). TABLE 1 Binding affinity at rA 1 , rA 2A and hA 3 adenosine receptors of compounds 38, 40, 41, 50, 51, and 54-57 Compound R 2 R rA 1 (K i , nM) rA 2A (K i , nM) hA 3 (K i , nM) rA 1 /hA 3 rA 2A /hA 3 38 (CH 3 ) 2 CH—CH 2 —CH 2 H 8.09 1.20 1,163 0.007 0.001 (7.46-8.78) (1.03-1.40) (1,024-1,320) 51 (CH 3 ) 2 CH—CH 2 —CH 2 — 4-MeO—Ph—NHCO 476 376 29.57 16 13 (432-525) (332-426) (26.94-32.46) 50 (CH 3 ) 2 CH—CH 2 —CH 2 3-Cl—Ph—NHCO 1,650 1,197 81.10 20 15 (1,560-1,744) (1,027-1,396) (68.45-96.09) 40 Ph—CH 2 —CH 2 H 2.16 0.70 2,785 0.0007 0.0002  (1.9-2.47) (0.53-0.91) (2,463-3,149) 55 Ph—CH 2 —CH 2 4-MeO—Ph—NHCO 1,282 1,398 1.47 872 951 (1,148-1,432) (1,225-1,594) (1.22-1.78) 54 Ph—CH 2 —CH 2 3-Cl—Ph—NHCO 1,049 1,698 13.28 79 128   (961-1,145) (1,524-1,892) (10.87-16.23) 41 Ph—CH 2 —CH 2 —CH 2 H 11.13 0.59 2,666 0.004 0.0002  (9.34-13.27) (0.44-0.81) (2,533-2,805) 57 Ph—CH 2 —CH 2 —CH 2 4-MeO—Ph—NHCO 1,514 >10,000 19.81 76.4 >504 (1,332-1,721) (17.61-22.27) 56 Ph—CH 2 —CH 2 —CH 2 3-Cl—Ph—NHCO >10,000 3,200 42.65 >234 75 (3,025-3,385) (39.92-45.57) Example 17 Pharmaceutical Formulations (A) Transdermal System-for 1000 patches Ingredients Amount Active compound 100 g Silicone fluid 450 g Colloidal silicon dioxide 2 g (B) Oral Tablet-For 1000 Tablets Ingredients Amount Active compound 50 g Starch 50 g Magnesium Stearate 5 g The active compound and the starch are granulated with water and dried. Magnesium stearate is added to the dried granules and the mixture is thoroughly blended. The blended mixture is compressed into tablets. (c) Injection-for 1000, 1 mL Ampules Ingredients Amount Active compound 10 g Buffering Agents q.s. Propylene glycol 400 mg Water for injection q.s. 1000 mL The active compound and buffering agents are dissolved in the propylene glycol at about 50° C. The water for injection is then added with stirring and the resulting solution is filtered, filled into ampules, sealed and sterilized by autoclaving. (D) Continuous Injection-for 1000 mL Ingredients Amount Active compound 10 g Buffering agents q.s. Water for injection q.s. 1000 mL Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.

The compounds of formula I wherein R, R 1 , R 2 R 3 and A have the meanings given in the specification, are endowed with selective A 3 adenosine receptor agonist activity. These compounds can be used in a pharmaceutical composition to treat disorders caused by excessive activation of the A 3 receptor, or can be used in a diagnostic application to determine the relative binding of other compounds to the A 3 receptor.

RELATED APPLICATIONS [0001] The present application is related to U.S. Patent Application, Ser. No. 12/475,370, entitled “Method and Apparatus for Magnetic Waveguide Forming a Shaped Field Employing a Magnetic Aperture for Guiding and Controlling a Medical Device,” filed on May 29, 2009, which is incorporated herein by reference and to which priority is claimed pursuant to 35 USC 119. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The invention relates to the field of medical mapping systems, namely systems and methods for guiding, steering and advancing an invasive medical device in a patient for the purpose of defining the physical boundaries and surface properties of a chamber or orifice. [0004] 2. Description of the Prior Art [0005] All cardiac electrophysiologic procedures, as currently practiced, involve the use of intracardiac electrode catheters which are placed inside one or more of the four cardiac chambers. Occasionally one or more catheters is also placed in the pericardial space surrounding the heart. The catheters are used for recording intracardiac electrograms, and in many cases the catheters are also used for creating a 3-D representation of the relevant cardiac chamber. Mapping catheters contain an array of electrodes which are used for three purposes: (1) to record local and “far-field” intracardiac electrical activity, (2) to deliver ablative, or curative energy to endocardial surfaces, most commonly in the form of RF energy, and (3) for position location and creation of the chamber geometry. As the catheter is moved about the chamber, the geometric shell of the chamber is defined at the extreme limits of catheter travel, along with the electrical activity on that shell. When the physician determines that there is enough surface detail, the surface is considered to be fully mapped. The physician then uses the display of the endocardial electrogram on the geometric shell to determine specific locations to deliver therapeutic radiofrequency energy. Some electrophysiology laboratories deliver RF energy to specific sites, such as pulmonary vein ostia in the left atrium, without regard to the specific recorded electrogram at those sites. It is also common practiced to integrate or merge the 3-D geometry of the cardiac chamber with a pre-procedure representation of that chamber, usually obtained by a CT or MRI scan. [0006] Prior to many ablation procedures, the relevant cardiac chamber is mapped in order to facilitate the movement of the catheter to precise anatomic regions which are responsible for initiating the arrhythmia. Once a circuit or an arrhythmogenic focus are found, or a specific aberrant tract is located, the catheter is directed the relevant endocardial surface site(s) and an electrode is placed in contact with the endocardial tissue. RF energy is then delivered from the electrode to the tissue to heat and ablate the tissue, thus eliminating the source of the arrhythmia. [0007] Common problems encountered in this procedure are difficulty in precisely locating the aberrant tissue, and complications related to the ablation of the tissue. Locating the area of tissue causing the arrhythmia often involves several hours of electrically “mapping” the inner surface of the heart using a variety of mapping catheters, and once the aberrant tissue is located, it is often difficult to position or maintain the catheter at the desired position in the beating heart so that it continuously maintains contact with the desired tissue. [0008] In the manual method of mapping coronary chambers, the physicians rely on their dexterity to manipulate mapping catheters about the chamber and into the associated vasculature. The density of the mapping data varies due to the time and attention the physician gives each part of the chamber, as well as to the anatomic variability found between individual patients i.e., in some patients certain cardiac anatomic regions are more difficult to reach than in other patients. In addition, the variable amount of force used by the physician in mapping will unevenly distend the chamber walls and create “false cardiac spaces,” as well as possibly distort the relationship between the pulmonary vein ostia and the associated left atrial body. The geometric definition of such ostia is critical in determining the locations for the delivery of therapeutic radiofrequency energy. [0009] In both manual and automated mapping procedures, the catheter is swept about the inner surfaces of the cardiac chamber which is undergoing dynamic contractions under the systole/diastole cycle. The locally averaged (motion filtered) position of the catheter at its extreme limits is used to define the boundaries or endocardial surfaces of the relevant cardiac chambers. This type of catheter manipulation does not guarantee that the limit defined by the geometric map completely delineates the true anatomic borders of the cardiac chambers, but rather defines the limit of where the catheter has been. [0010] Prior and related art associated with guiding and controlling an automated mapping and therapeutic procedure are extensive in scope, the discussion outlined by this application is centered on the ability of a novel magnetic chamber enabling such modality of guiding and controlling a mapping and other therapeutic tools in an automated fashion within the heart chambers of a patient. [0011] The prior art as described by U.S. Pat. No. 3,708,772 (Le Franc) describes a highly compact magnetic lens arrangement which economically provides the highest field strength on the axis with the minimum beam half width and a minimum outer field strength of the coil winding which comprises two tubular shielding cylinder means of superconductive material coaxially aligned with the lens axis. The cylinder means each has a first end and a second end, said first ends being spaced from each other to define a unshielded lens gap between, said lens gap having a coil means positioned about the cylinder means to create a magnetic field, a cooling agent adapted to be present about the cylinder which cause a concentration of the magnetic field adjacent the particle beam, and a ferromagnetic ring-shaped pole shoe on each of said first ends of said cylinders for regulating and guiding the magnetic field. [0012] Davis U.S. Pat. No. 4,057,748 teaches a travelling wave tube having a periodic permanent magnetic focusing structure provided with ferromagnetic plates having copper inserts which conduct heat away from the electron beam path and reduce the formation of hot spots. [0013] Purnell U.S. Pat. No. 3,684,914 teaches a travelling wave tube including an envelope, an electron source for projecting an electron beam along a predetermined path in said envelope, a collector spaced from said source for intercepting and collecting electrons in the beam, a helical conductor disposed within said envelope along the path of said beam for supporting and projecting an electromagnetic wave in coupled relationship to the beam for interaction therewith, a periodic permanent magnet focusing assembly having a succession of alternate high thermal conductivity conducting bars and magnetic plates having aligned apertures to define an envelope portion which accommodates the helix support assembly and helix and a plurality of magnet bars disposed between plates to form a succession of longitudinal magnetic fields in coupled relationship with the beam to focus the same as it travels along the envelope portion. [0014] Carson, et al. U.S. Pat. No. 6,078,872 titled “Magnetic lens, method and focus volume imaging MRI” teaches methods for suppressing noise in measurements by correlating functions based on at least two different measurements of a system at two different times. In one embodiment, a measurement operation is performed on at least a portion of a system that has a memory. A property of the system is measured during a first measurement period to produce a first response indicative of a first state of the system. Then the property of the system is measured during a second measurement period to produce a second response indicative of a second state of the system. The second measurement is performed after evolution duration subsequent to the first measurement period when the system still retains a degree of memory of an aspect of the first state. Next, a first function of the first response is combined with a second function of the second response to form a second-order correlation function. Information of the system is then extracted from the second-order correlation function. [0015] In general, the prior art is centered on the ability of microscopic resonance imaging, spectrometry, and general resonance imaging to form a coherent magnetic field for use in MR imaging. Maxwell's equations place restrictions on the properties of magnetostatic fields in free space. It is impossible for the magnitudes of the components of the magnetic field vector B X , B Y , or B Z to have a local minimum or maximum in free space. Additionally, the magnetic field magnitude, |B|, cannot have a local maximum, but it can have local minimum in free space. Localized minimums have been generated with current carrying structures and used in the fields of plasma confinement, neutral particle trapping, and levitation. Others have also proposed magnetic resonance imaging techniques that were based on different physical principles for creating what the papers termed as an imaging focus point, and relied on the magnetic field gradients produced by the three-dimensional current carrying wires. See, Damadian, et al., “Field Focusing Nuclear Magnetic Resonance (FONAR): Visualization of a Tumor in a Live Animal,” Science 194, 1430 (1976); Hinshaw, “Image Formation by Nuclear Magnetic Resonance: The Sensitive Point Method,” J. Appl. Phys. 47, 3709 (1976). The current carrying structures limit practical extensions of the technique. All the above noted patents and journal publications are the results of the ability of microscopic resonance imaging, spectrometry, and general resonance imaging to form a coherent magnetic field for use in MR imaging. The novel and application of the waveguide and its magnetic aperture depart from the prior art due to the embodiments which this application teaches. [0016] What is needed is a new waveguide and magnetic aperture that enables the creation of an electroanatomic map by using an apparatus that automatically performs the task of mapping of an anatomical site. BRIEF SUMMARY OF THE INVENTION [0017] The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole. Additional objects and advantages of the current invention will become apparent to one of ordinary skill in the art upon reading the specification. [0018] Some embodiments of the method of this invention provides for automatically mapping an anatomical surface of a subject's heart with the help of a remote navigation system. One example of such a system is the Catheter Guidance, Control & Imaging Apparatus (CGCI), described by U.S. Pat. Nos. 1,521,555 and ZL03821597.7, and “System and Method for Radar-Assisted Catheter Guidance and Control”, U.S. Pat. No. 7,280,863, and “Apparatus and Method for Shaped Magnetic Field Control for Catheter, Guidance, Control, and Imaging” U.S. Pat. No. 1,895,930 and HK1111875. [0019] The invention described herein solves these and other problems by enhancing the automation of the coronary chamber mapping process with a method using constant magnetic force and position control to seek continuous tissue contact in a distinct set of locations. This method incorporates a tissue contact monitoring algorithm into the coronary chamber mapping algorithms. This contact monitoring determines both intermittent and continuous contact with the moving tissue surface. This allows the automated mapping algorithm to rapidly map out the actual chamber limits in a consistent and repeatable manner. This geometric map may then be used under automatic guidance with a CGCI system to locate ablation catheters and to deliver therapeutic radiofrequency energy. [0020] In one embodiment of the invention, the catheter is controlled by a magnetic catheter guidance, control and imaging system (CGCI) that uses tissue contact information, such as that disclosed in patent application Ser. No. 12/323,231 entitled “System and Method for a Catheter Impedance Seeking Device”, Shachar et. al., Nov. 25, 2008 which is incorporated herein by reference in its entirety. [0021] In one embodiment of the invention, the tissue contact information is recorded over several heartbeat cycles and the recording is analyzed to determine the continuity of tissue contact. [0022] In another embodiment of the invention, the catheter is advanced to the tissue surface until continuous contact is made throughout the systole/diastole cycle. [0023] In yet another embodiment of the invention, the catheter is retracted from continuous tissue contact until only partial contact is made, and then the catheter is repositioned and advanced to a new location of continuous tissue contact. [0024] In one embodiment of the invention, a set of distinct directions or coordinate points is sequentially specified to the catheter guidance control and imaging system so as to provide an optimal tissue contact mapping pattern. [0025] In another embodiment of the invention, the differences in tissue contact impedances are used to differentiate between types of tissue within the coronary chamber. [0026] In yet another embodiment of the invention, the differences in the tissue type are used to vary the mapping density of an automated mapping algorithm. [0027] In one embodiment of the invention, the system differentiates between contact with the coronary chamber wall and the associated vasculature for the purpose of locating and defining the vascular ostia. [0028] In one embodiment, the physical catheter tip (the distal end of the catheter) includes a permanent magnet that responds to the magnetic field generated externally by the waveguide. The external magnetic field pulls, pushes, turns, and holds the tip in the desired position. One of ordinary skill in the art will recognize that the permanent magnet can be replaced or augmented by an electromagnet. [0029] One embodiment provides for a waveguide and its regulating apparatus that is more intuitive and simpler to use, that displays the catheter tip location in three dimensions, that applies force at the catheter tip to pull, push, turn, or hold the tip as desired, and that is configured to producing a vibratory or pulsating motion of the tip with adjustable frequency and amplitude. [0030] An additional embodiment provides tactile feedback at the operator control to indicate an obstruction encountered by the tip. [0031] One embodiment of the waveguide and its regulator comprises a user input device called a “virtual tip” (VT). The virtual tip includes a physical assembly, similar to a joystick, which is manipulated by the surgeon/operator and delivers tactile feedback to the surgeon in the appropriate axis or axes if the actual tip encounters an obstacle. The virtual tip includes a joystick type device that allows the surgeon to guide actual surgical tool such as catheter tip through the patient's body. When the actual catheter tip encounters an obstacle, the virtual tip provides tactile force feedback to the surgeon to indicate the presence of the obstacle. [0032] In another embodiment, the waveguide multi-coil cluster is configured to generate a magnetic field gradient for exerting an orthogonal force on the tip (side-ways movement), with little or no rotating torque on the tip. This is useful for example to align the catheter's tip at narrow forks of artery passages. [0033] In one embodiment, the waveguide multi-coil cluster is configured to generate a mixed magnetic field to push/pull and/or bend/rotate the distal end of the catheter tip, so as to guide the tip while it is moving in a curved space. [0034] In one embodiment, the waveguide multi-coil cluster is configured to move the location of the magnetic field in 3D space relative to a desired area. This magnetic shape control function provides efficient field shaping to produce magnetic fields required for example in surgical tool manipulations in the operating region. [0035] In one embodiment, the waveguide symmetry (eight coil clusters) configuration, which enable a regulator to compute the desired field(s) under the doctrine of linear transformation of all matrices in the magnetic chamber so as to enable closure of all vector field operations (addition, subtraction, superposition etc.) without the need for tailoring the waveguide-regulator linearity and thus preserving symmetry within the effective space. [0036] In one embodiment, the waveguide regulator as described and disclosed by Foreign Patent Numbers 1895930 and HK1111875 entitled “Apparatus and Method for Shaped Magnetic Field Control for Catheter, Guidance, Control & Imaging,” is used to provided for a means to allow the electromagnet poles faces to form a shaped magnetic field based on a position and orientation of the catheter's travel path between the desired point (DP) and actual point (AP). This method further optimizes the necessary power requirements needed to push, pull, and rotate the surgical tool tip with a minimum of power by employing “lensing” modes of the field. The invention is further improved by the use of the magnetic aperture disclosed above by enabling the waveguide apparatus to form a shaped magnetic field (Flux Density Axis relative to the catheter tip) relative to the minimal geometrical path between AP to DP. [0037] In one embodiment, the waveguide is fitted with a sensory apparatus for real time detection of position and orientation so as to provide command inputs to a servo system that controls the tool-tip location from AP to DP. The waveguide further generates a command which results in the shaping of the magnetic field geometry based on magneto-optical principles as shall be clear when reviewing the figures and the accompanying descriptions detailed herein. [0038] In one embodiment, the waveguide's servo system has a correction input that compensates for the dynamic position of a body part, or organ, such as the heart, thereby offsetting the response such that the actual tip moves substantially in unison with the dynamic position (e.g., with the beating heart). Further, synchronization of dynamic position of a surgical tool with the appropriate magnetic field force and direction is accomplished by the response of the waveguide regulator and its resulting field's intensity and field's geometry. [0039] In another embodiment, the operator can make further adjustments to the virtual catheter tip (VT) position and repeat the sequence of operating steps. In one embodiment, the feedback from the servo system and control apparatus (the regulator) deploys command logic (AI routine) when the actual catheter tip encounters an obstacle or resistance in its path. The command logic is further used to control stepper motors which are physically coupled to the virtual catheter tip. [0040] In one embodiment, a mathematical model for predicting the magnetic field geometry (Shaped) versus magnetic field strength is established relative to the catheter tip axis of magnetization and is used by the waveguide regulator to predict and command the movements of a surgical tool from its actual position (AP) to its desired position (DP). [0041] In one embodiment, the waveguide magnetic chamber comprises a regulator coupled to a magnetically fitted tool which forms a system operated by the steps of: i) the operator adjusts the physical position of the virtual tip (VT), ii) a change in the virtual tip position is encoded and provided along with data from a position detection system, iii) the regulator generates a series of servo system commands that are sent to a servo system control circuitry, iv) the servo system control apparatus operates the servo mechanisms to adjust the condition of one or more electromagnet from the cluster by varying the power relative to distance and/or angle of the electromagnet clusters vis-a-vie the tool's permanent magnet position, further energizing the electromagnets so as to control the magnetic (catheter) tip within the patient's body, v) the new position of the actual catheter tip is then sensed by the position detection system thereby allowing, for example, a synchronization of the catheter position on an image produced by fluoroscopy, and/or other imaging modality such as ICE, MRI, CT or PET scan, vi) providing feedback to the servo system control apparatus and to the operator interface vii) updating the displayed image of the catheter tip position in relation to the patient's internal body structures, viii) once the catheter tip is positioned at the DP site, the tissue contact information in the automatic mapping function is set by the operator and the catheter is enabled to commence and perform the ablating procedure. [0050] While the apparatus and method has or will be described for the sake of grammatical fluidity with functional explanations, it is to be expressly understood that the claims, unless expressly formulated under 35 USC 112, are not to be construed as necessarily limited in any way by the construction of “means” or “steps” limitations, but are to be accorded the full scope of the meaning and equivalents of the definition provided by the claims under the judicial doctrine of equivalents, and in the case where the claims are expressly formulated under 35 USC 112 are to be accorded full statutory equivalents under 35 USC 112. The invention can be better visualized by turning now to the following drawings wherein like elements are referenced by like numerals. BRIEF DESCRIPTION OF THE DRAWINGS [0051] FIG. 1 is block diagram of a catheter guidance control and imaging system (CGCI) using tissue contact information. [0052] FIG. 1B is a block diagram of the catheter guidance control and imaging system (CGCI) used to guide the catheter into tissue contact. [0053] FIG. 2 is a cross sectional view of a coronary left atrium showing the regions of partial and continuous tissue contact with a catheter. [0054] FIG. 3 is a cross sectional view of a coronary left atrium showing the position control reference vectors used in defining an automated mapping search pattern for a catheter. [0055] FIG. 4 is a magnified view of the catheter movement pattern used in the mapping of a coronary chamber. [0056] FIG. 5 is a flowchart of the command pipeline used by the catheter guidance control and imaging system during an automatic mapping procedure. [0057] FIG. 6 is a cross sectional view of the use of tissue contact impedance values obtained by the catheter to differentiate between coronary wall tissue and vascular tissue. [0058] FIG. 7A is a perspective view of the CGCI waveguide system with the electromagnetic coils removed. [0059] FIG. 7B is a perspective view of the CGCI waveguide system shown in FIG. 7A with the electromagnetic coils installed. [0060] FIG. 7C is a perspective view of the CGCI waveguide system shown in FIG. 7B with a patient inserted between the electromagnetic coils. [0061] FIG. 8 is a block diagram of the CGCI functional elements. [0062] FIG. 9 is a block diagram of the CGCI regulator with its functional blocs. [0063] FIG. 10 is an orthographic cross section of the magnetic aperture (Lens) and its EM radiator of the CGCI. [0064] FIG. 11 is a schematic representation of the flux line geometry due to the refraction index generated by a magnetic aperture (the Lens) of the CGCI. [0065] FIG. 12 is a sectional view of the lens demonstrating its efficiency as described by the computational schema. [0066] FIG. 12A is a perspective view of the magnetic aperture of the CGCI and its adjacent structure. [0067] FIG. 13A is a schematic representation of the geometry of a magnetic field produced by the waveguide assembly. [0068] FIG. 13B is a schematic representation of the geometry of an alternative magnetic field produced by the waveguide assembly. [0069] FIG. 13C is a schematic representation of the geometry of an alternative magnetic fields produced by the waveguide assembly and its magnetic apertures. [0070] FIG. 14 is a perspective view of the Virtual Tip (VT) user input device. [0071] FIG. 15 is a perspective view of a catheter and a guide wire fitted with a magnetic pallet. [0072] The invention and its various embodiments can now be better understood by turning to the following detailed description of the preferred embodiments which are presented as illustrated examples of the invention defined in the claims. It is expressly understood that the invention as defined by the claims may be broader than the illustrated embodiments described below. Definitions [0073] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the methods, devices, and materials are now described. All publications mentioned herein are incorporated herein by reference for the purpose of describing and disclosing the materials and methodologies which are reported in the publications which might be used in connection with the invention. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention [0074] Ablation—as used herein refers to the use of a catheter to apply radiofrequency electrical energy to a specific location within the heart to necrotize (kill) tissue and block neural conduction pathways as to eliminate electrical signals that are the cause of cardiac arrhythmias. [0075] Ablation Catheter—as used herein refers to a catheter whose tip electrode is wired to deliver radiofrequency energy and also contains a thermocouple for monitoring the tip temperature during the ablation. [0076] Actual Position (AP)—as used herein refers to the six degree of freedom position and orientation of the catheter tip. The catheter tip position is measured at the center of the distal electrode. [0077] Automatic Guidance—as used herein refers to methods of automatically advancing, steering and pushing a catheter toward a desired position. [0078] Catheter—as used herein refers to a minimally invasive medical tool used for diagnostic and therapeutic medical procedures. Catheters have a wide variety of shapes, sizes and capabilities, but all are a combination of a long shaft and a functional end effector. [0079] Desired Position (DP)—as used herein refers to the desired or target six degree of freedom position and orientation of the catheter tip, or the three degree of freedom desired location for a catheter tip with an implied optimized catheter orientation which is based on the orientation of the tissue. Three degree of freedom desired positions are typically used, and the catheter guidance system adjusts the orientation of the catheter for maintaining optimal contact with a moving surface. [0080] Distal—as used herein refers to at the most distant end, or the end of the catheter furthest within the patient. [0081] Electrode—as used herein refers to a conductive ring on a catheter which is wired through the catheter line to the position detection and heart electrogram sensing hardware. [0082] Electrogram—as used herein refers to a time vs. amplitude plot of the electrical potential as measured at a specific point on, or in the body. Electrograms for each electrode pair are displayed on the mapping system and on a separate ECG system. [0083] Electrophysiology—as used herein refesr to the diagnosis and treatment of anomalies in the heart neuro-electrical system. [0084] Geometric Location—as used herein refers to a specific Cartesian point on the geometric map which represents the average position of the tissue location that passes through that point. [0085] Insert Ring—as used herein refers to a ferrous material with permeability of one order magnitude lower than the poleface. [0086] Mapping—as used herein refers to the process of sweeping a catheter about a coronary chamber to define the average location of the walls and the electrical activity of the nerves within those walls throughout the heartbeat cycle. [0087] Poleface—as used herein refers to an aperture comprising of ferrous material formed with a specific geometry and a high permeability (μ>1000) value. In this application the use of a magnetic aperture forming the lense is designated by reference as 4 . 3 x y while the “x” is a designator of the permeability μ (x=μ) value, while “y” is (y=geometry). [0088] Sheath (Introducer)—as used herein refers to a tube which is inserted through a vein and into the heart. Catheters, wires and fluids are introduced into the heart chamber through this tube. [0089] Six Degree of Freedom—as used herein refers to a coordinate set that describes both the position of an object and its orientation in space. [0090] Spiral Catheter—as used herein refers to a type of mapping catheter, typically with twenty electrodes arranged along its coiled end. Manual controls are provided to adjust the amount of coil to make it larger or smaller, as well as to bend the assembly back and forth during the manual mapping process. [0091] Tissue Contact—as used herein refers to where the tip of the catheter maintains continuous contact with the surface of the heart chamber wall throughout the heartbeat cycle. [0092] Shaped Magnetic Field—as used herein refers to a system of forming a shape magnetic field geometry (Lobe), which operates under the principles noted by the invention and as described below. [0093] Lens—as used herein refers to an apparatus used in a CGCI system which generates a DC magnetic field, with magnetic geometry on demand by the use of combination of different material permeability's. The “lens” comprises a ferromagnetic core having an anisotropy axis permanently magnetized in a direction perpendicular to the insert ring, the insert ring being disposed in the magnetic field such that the anisotropy axis is opposite the magnetization direction of the DC magnetic field, the pole face encircled by the ring having cut-outs shaped and dimensioned to create a localized minimum of the magnitude of the magnetic field vector of the combined magnetic field in a focus volume away from the aperture. [0094] Magnetic Aperture—as used herein refers to the optical behavior of ferrous materials having negative permeability at or near permeability resonance which can yield large field amplifications and can refract the flux lines through negative angles. This enhancement is guided analytically by the Biot-Savart law and the inclusion of mirror image currents. (See: An Open Magnet Utilizing Ferro - Refraction Current Magnification, by, Yuly Pulyer and Mirko I. Hrovat, Journal of Magnetic Resonance 154, 298-302 (2002)). [0095] Virtual Tip or (VT)—as used herein refers to a physical assembly, similar to a joystick, which is manipulated by the surgeon/operator and delivers tactile feedback to the surgeon in the appropriate axis or axes if the actual tip encounters an obstacle. [0096] CGCI—as used herein refers to a system for guiding and controlling a medical device within a body of a patient: composing of a set of electromagnets formed with a specific geometry and act as a waveguide to deliver electromagnetic radiation acting on a permanent magnet further delivering energy in a manner so as to push, pull, and rotate a surgical tool(s) fitted with such. The CGCI chamber is a highly compact magnetic aperture assembly which economically provides the highest field strength on the axis with the minimum DC field and minimum outer field strength of the coil winding. The assembly is fitted with a parabolic shielding antenna and eight electromagnets coaxially aligned with the lens axis, said chamber means each having a first end and a second end, said first ends being spaced from each other to define a unshielded lens gap there between, said lens gap having a coil means positioned about the chamber to create a magnetic field, a cooling agent adapted to be present about the chamber which cause a concentration of the magnetic field adjacent to a permanent magnet tool, and a ferromagnetic ring-shaped pole face on each of said first ends of said coil for regulating and guiding the magnetic field. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0097] The present invention is a method for guiding an interventional device in a magnetic environment comprising the steps of providing a magnetic navigation system, placing a catheter with an electrode array within a magnetic environment generated by a plurality electromagnets, using a sensor interface to receive signals from the catheter and, in response, generating a processed signal, using a processing and control unit to receive the processed signal and to calculate a position of the electrode array, and using the calculated position of the catheter to guide movement of the catheter within the waveguide environment. [0098] FIG. 1 is block diagram of a catheter guidance control and imaging system that uses tissue contact information. An introducing sheath 4 is inserted into a patient 1 until the distal end is within a cavity or chamber 1 . 1 to be mapped. The introducing sheath 4 comprises a plurality of position detection electrodes 4 . 1 which are used to determine both the position of the distal end and the exit direction of the sheath 4 . A catheter 3 . 2 is inserted through the sheath 4 until its distal tip 3 . 1 is within the chamber 1 . 1 . The proximal section of the catheter line 3 . 2 is inserted between the rollers of a catheter line feed device 11 that is used by a catheter position guidance and control unit or CGCI regulator 15 to adjust the length of the catheter 3 . 2 within the chamber 1 . 1 . The distal end of the catheter 3 . 2 is connected to a catheter position detection and tissue contact detection system 7 , such as a St. Jude Medical's EnSite NavX system. This catheter position detection and tissue contact detection system 7 provides the catheter position guidance and control unit 15 with real-time position feedback for the introducer sheath 4 and for the catheter tip 3 . 1 . It also gives tissue impedance readings for a plurality of catheter tip electrodes (not shown). In this embodiment, the catheter position guidance and control unit 15 controls the position of a magnetized catheter tip 3 . 1 through the use of a plurality of magnetic coils that provide both magnetic torque and force gradients, such as those described in U.S. patent application Ser. No. 11/697,690, “Method and Apparatus for Controlling Catheter Positioning and Orientation”, Shachar et. al., Mar. 7, 2008 which is incorporated herein by reference in its entirety. An automated mapping location sequence 10 is a set of targeting locations or directions that are sequentially fed into the catheter position guidance and control unit 15 . The pattern and density of the automated mapping location sequence 10 may be a user selectable fixed pattern, or the mapping density may be automatically adjusted based on the current tissue type as acquired from tissue impedance measurements. [0099] FIG. 1B is a block diagram of the catheter guidance control and imaging system 15 used to guide the catheter 3 . 2 into tissue contact, by employing a virtual tip user input device (VT) 905 (seen in FIG. 9 ). In this embodiment, the catheter guidance control and imaging system 15 is the CGCI magnetic guidance system as described in U.S. patent application Ser. No. 11/697,690, Shachar et. al., “Method and Apparatus for Controlling Catheter Positioning and Orientation”, Apr. 6, 2007 which is incorporated herein by reference in its entirety. The position detection and tissue contact detection system 7 , such as the St. Jude Medical EnSite NavX system, sends the actual position (AP) of the catheter tip 3 . 1 and its associated tissue contact impedance signal (ECI) to the CGCI regulator 15 which accepts commands to either guide the catheter tip from the AP to a desired position (DP) 3 . 6 , or to retract the catheter tip 3 . 1 from tissue contact. An automated mapping location sequence 10 sends the DP 3 . 6 through a series of target locations one at a time until the entire automated mapping targeting sequence 10 has been completed. The CGCI regulator 15 calculates a set of coil currents to shape the magnetic field within a CGCI waveguide 15 . 1 that will incrementally adjust the AP on a tissue contacting path through the DP 3 . 6 until continuous tissue contact is made. A magnetic field regulator 15 . 2 maintains these currents. In this embodiment, a catheter impedance seeking device 11 is also used which is described in U.S. patent application Ser. No. 12/323,231, Shachar et. al, “System and Method for a Catheter Impedance Seeking Device”, of Nov. 25, 2008 which is incorporated herein by reference in its entirety. The catheter impedance seeking device (CISD) 11 advances or retracts the catheter in synchronization with the CGCI regulator 15 and monitors the ECI tissue contact signal until continuous contact has been made over the desired number of heartbeats, such as to provide a repeatable level of continuous contact with the moving tissue surface that passes through the static geometric location DP 3 . 6 . [0100] FIG. 2 is an illustration of a coronary left atrium depicting regions of partial and continuous tissue contact. Typically, a geometric shell is generated by a cardiac mapping system is at the extreme limits of catheter tip 3 . 1 travel. The supplemental tissue contact data guarantees that this geometric shell is a continuous contact manifold 8 . 1 . A secondary zone within the chamber is mapped to define where intermittent tissue contact occurs. This partial contact zone 8 . 2 specifies a region where the catheter tip 3 . 1 has enough freedom of movement to adjust its position before re-seeking continuous contact. The catheter line 3 . 2 is advanced into the chamber 1 . 1 through the introducer sheath 4 . The tissue contact sensing is provided at the catheter tip 3 . 1 . The tissue contact is monitored over a user-selectable duration to differentiate between continuous and intermittent contact, and this information supplements the data received from the position detection and tissue contact sensing unit 7 . [0101] Turning to FIG. 3 , an illustration of a coronary left atrium is shown with the position control reference vectors used when defining an automated mapping search pattern. The catheter tip orientation 3 . 3 is determined from a plurality of catheter tip position detection electrodes 3 . 4 disposed on the catheter tip 3 . 1 . The introducer sheath orientation 4 . 3 is determined from the sheath position detection electrodes 4 . 1 . The desired position (DP) 3 . 6 is a Cartesian location coupled with a targeting direction that is used to regulate the actual position (AP) 3 . 5 of the catheter tip 3 . 1 on a path towards or though DP 3 . 6 until continuous tissue contact is made for a specified number of heartbeat cycles or fixed time duration. [0102] FIG. 4 is a magnified view of a catheter movement pattern used in mapping a coronary chamber. The catheter tip 3 . 1 is moved from continuous contact with the tissue surface at DP 1 3 . 6 on the continuous contact manifold 8 . 1 to a partial contact within the partial contact zone 8 . 2 while adjusting to the new position. A new position DP 2 3 . 6 is then targeted without leaving the region between the continuous contact manifold 8 . 1 and the partial contact zone 8 . 2 so as to reduce the travel time and distance while mapping the continuous contact manifold 8 . 1 . [0103] FIG. 5 is a flowchart of the command structure used by the catheter guidance control and imaging system 15 during an automatic mapping procedure. In this embodiment of the invention, an automated mapping routine 10 sends a series of target locations and retraction commands to the catheter position guidance and control unit 15 as seen in FIG. 1 . After the routine has been started 10 , and an initial target location has been set, the catheter 3 . 2 is manipulated along a target vector by the catheter guidance control system 15 to obtain continuous contact with that initial target location. If continuous contact has not been obtained at the initial target location, the catheter guidance system 15 continues to manipulate the catheter 3 . 2 until continuous contact is made. Once it is determined that continuous contact has been made at the target location, the catheter 3 . 2 is retracted until the continuous contact is lost. At this point, a new target location is acquired and the catheter guidance system 15 sends the catheter 3 . 2 along a new target vector to the new target location. The process of obtaining continuous contact described above is then repeated, with the catheter 3 . 2 being withdrawn every time improper contact has been made, until an entire location set has been acquired. If the user is satisfied with the acquired data received from the catheter 3 . 2 , the scan is considered complete and the automated mapping procedure ends. If the user is not satisfied with the acquired data or if new target locations are added to the catheter guidance system 15 , the catheter 3 . 2 is then taken through the entire process again from the beginning. [0104] FIG. 6 is a cross sectional view of how the catheter 3 . 2 uses obtained tissue contact impedance values to differentiate between the tissue of a coronary wall 20 and a vascular tissue 21 . Two tissue types are illustrated to divide the geometric map into chamber tissue 20 and vascular tissue 21 . The type of tissue at every DP may be recorded and then added to the geometric map in order to further supplement the automated mapping process. In other embodiments, the automated mapping algorithm may differentiate between tissue types other than what is listed here which can be differentiated by their dynamic impedance, including excitable tissue, scar tissue, valve tissue, etc. Each tissue type can be used to automatically generate a different mapping point density in a search algorithm, based on the level of medical significance. [0105] FIGS. 7A-7C are perspective views of the CGCI waveguide 15 . 1 and its preferred embodiments. Turning to FIG. 7A , an isometric view of the CGCI waveguide 15 . 1 and its construction comprising a plurality of cores 12 . In FIG. 7B a plurality of electromagnetic coils 517 are coupled to the core 12 . Also seen in FIGS. 7A and 7B are the relative orientations of the polefaces 4 . 3 x y disposed on the distal end of each of the plurality of cores 12 . The orientations of the poleface 4 . 3 x y are determined by the performance of electromagnetic radiation under Maxwell formalism and as modified by the wave equation for forming a shaped field 400 as described in further detail in Example 1 below. The combination of the core 12 , electromagnetic coil 517 , poleface 4 . 3 x y as well as a ring insert 5 . x y form a magnetic aperture 50 as best seen in FIG. 10 . [0106] The resulting effects of the CGCI waveguide 15 . 1 is to enable the apparatus to generate magnetic field geometries on demand, while shifting the magnetic flux density axis based on the AP to DP travel path of the catheter 3 . 2 . It can also be seen in FIGS. 7A-7C the relative locations of a plurality of parabolic antenna shields 18 that are disposed around a magnetic circuit return path ferrous skeleton 525 . The skeleton 525 preferably comprises at least four segments forming a substantially spherical chamber. Each of the cores 12 holds a coil 517 in the structure of the CGCI waveguide 15 . 1 . Each of the upper coils 517 , specifically coils 517 labeled 1 A T , 1 B T , 1 C T and 1 D T in FIG. 7B are held in place by their respective cores 12 , specifically cores 12 labeled 1 A T , 1 B T , 1 C T and 1 D T as seen in FIG. 7A . The specific structure and the orientation of the cores 12 relative to a central axis of the CGCI 15 . 1 are determined in accordance with the spherical topology of the CGCI 15 . 1 which provides linear solutions to the location of the catheter tip 3 . 1 . The spherical topology of the CGCI 15 . 1 further establishes the computing regimen necessary to solve a series partial differential equations as is known in the art by a regulator 500 seen in FIG. 8 . These and other properties associated with the spherical topology are essential to the embodiments of this invention, as it enables the formation of anisotropic EM wave propagation without the customary non-linear representation of the fields, which can result in the inefficient and time consuming use of numerical as well a finite element (FEA) modeling of the field instead of the use of an analytical model as in the current invention. [0107] FIG. 7C further illustrates the CGCI waveguide 15 . 1 and its eight coils 517 clustered and covered with the plurality of parabolic antenna shields 518 . The performance of the CGCI waveguide 15 . 1 is enhanced by the use of parabolic shields 518 because any stray magnetic flux that is radiated above and beyond the effective boundaries of the assembly footprint are prevented from escaping and thus improving the efficiency of the CGCI waveguide 15 . 1 . [0108] FIGS. 8 and 9 are two possible configurations of a regulator scheme employed by the CGCI regulator 15 comprising a command circuit 500 used to perform the tasks of moving a catheter tip 3 . 1 , from an AP 3 . 5 to a DP 3 . 6 with the necessary accuracy for delivering a medical tool in vivo. The command circuit 500 receives a command signal from an operator input 501 , a position detector 350 , a joy stick 8 , and a virtual tip user input device (VT) 905 contemporaneously. The command circuit 500 then determines a new DP 3 . 6 from the data obtained by generating a Bx, By, Bz vector for torque control, and the dBx, dBy, dBz vector gradient for force control. With these position values identified, the command circuit 500 is allowed to receive two sets of field values for comparison. [0109] The present value of the AP 3 . 5 and of the Bcath and dBcath 300 acting on the catheter tip 3 . 1 seen in FIG. 9 , are calculated from the position detector 350 and outputs B x, y, z. The new field values for the DP 3 . 6 (Bx, By, Bz, dBx, dBy, dBz) are used to advance the catheter tip 3 . 1 and are generated in the command circuit 500 with the help of a customary D/A A/D 550 , a set of IOs 551 , 552 , and a set of display controls 730 , 730 . 1 . The difference in the AP 3 . 5 and the DP 3 . 6 is translated to a matrix block 528 for setting the coil currents 300 . 1 and polarities within the electromagnetic coils 517 and cores 12 respectively. [0110] In one embodiment the matrix block 528 issues a plurality of current reference signals to a set of eight regulators (CREG) 527 seen in FIG. 9 . It is preferred that eight separate CREG units 527 be used so that they may individually respond to the needs of the path translation or rotation from AP to DP within each of the coils 517 , however fewer or additional CREG units 527 than what is shown may be used without departing from the original spirit and scope of the invention. The command circuit 500 drives an eight-channel power amplifier 625 to obtain the desired currents within the coils 517 . [0111] FIGS. 10-12 are schematic cross sections of the magnetic aperture 50 that forms a magnetic shaped field 60 seen in FIGS. 13A-13C . The magnetic aperture 50 comprises a coil 517 and a core 12 . The core 12 is comprised of material such as ASTMA848 steel with material permeability with a value set of μ>1000. The poleface 4 . 3 x y is fitted with an insert ring 5 . x y which is fitted over the poleface 4 . 3 x y as shown in FIG. 10 . The insert ring 5 . x y is comprised of material such as 1010 steel with a value set of μ>10. [0112] FIGS. 10-12 further elaborate on the preferred embodiments of the configured waveguide 15 . 1 . FIG. 10 illustrates the formation of the magnetic aperture 50 . The physical principle that governs the effects associated with shaped electromagnetic radiation and which establishes a lens 120 , is the discontinuity of material properties, such as the permeability (μ>1000) of the ferrous materials used in the core 12 and the poleface 4 . 3 x y (μ>10) coupled with the insert ring 5 . x y which has a permeability value of μ=10 and as contrasted with the permeability value of air (μ>1). The above permeability combinations generate a step change that is representative of the refractive angle at the boundaries. As the magnetic flux leaves the ferrous material of the core 12 , poleface 4 . 3 x y , and insert ring 5 . x y , they enter the operating region of air with a permeability value of μ>1. A magneto-optical transition is present within the operating region which attenuates the localized minimums of the magnetic field vector which have been long been used in the prior art for example with current carrying structures used in plasma physics, particle trapping, and levitation. Large currents are required in the prior art techniques, however applying the lens 120 of the current invention avoids the need to create such currents. The lens 120 of the current invention provides a favorable alternative that can be used, for example, in confining the flux density axis relative to the catheter tip 3 . 1 so as to push, pull, and rotate the catheter tip 3 . 1 on demand without the customary current noted by the prior art. [0113] Turning now to FIG. 12A , an orthographic representation of the magnetic aperture 50 and its adjacent structure comprising of the poleface 4 . 3 x y and the insert ring 5 . x y supported by the core 12 is shown. The entire assembly forms a lens 120 which employs the permeability difference. A detailed description of the operation of the lens 120 is described by the example noted below. [0114] FIGS. 13A-13C are top view schematic representations of the geometry of the magnetic fields produced by the CGCI waveguide 15 . 1 relative to the CGCI waveguide 15 . 1 assembly. The CGCI waveguide 15 . 1 in one preferred embodiment as disclosed above consists of eight electromagnets 517 positioned symmetrically about a substantially spherical magnetically conductive ferrous skeleton 525 such that each core 12 faces the other seven cores with a symmetrical physical perspective. Thus, each of the electromagnets 517 occupies a segment of the enclosing sphere with each segment angled at ±45° from the skeleton's 525 center coordinate system. There are no privileged positions for any of the electromagnets 517 in any direction relative to the center region which contains the catheter tip 3 . 1 to be positioned and oriented by the CGCI magnetic field 60 . [0115] Once the magnetic field 60 is generated by any number or combination of the eight electromagnets 517 , the catheter tip 3 . 1 will experience a torque aligning it to the direction of the field and a force moving it along the field's gradient. The magnetic flux generated by a single electromagnet 517 will close through all the other seven cores 12 due to the spherical symmetry of the cores 12 and the magnetic path available through the ferrous skeleton 525 which holds the magnetic aperture 50 assemblies together. An example of the direction of the magnetic flux and the distribution of the magnetic flux density is shown by the arrow seen in FIGS. 13A-13C . The flux density map will resemble a lobe shape field 60 seen in FIG. 13A , where the ‘lobe’ indicates an extension or projection of the magnetic field 60 generated by the source, namely the current density vector in the particular coil 517 shown. [0116] The CGCI magnetic skeleton 525 comprises two circular armatures crossing each other at a 90° angle. This configuration situates each of the eight coils 517 on the inside surface of a virtual sphere where the magnetic skeleton 525 provides closed flux paths on six planes with four coils 517 each. The magnetic vector-plane, shown as a shaped lobe 60 in FIG. 13A , with all eight coils 517 in operation forms a 3D magnetic volume 60 shown in FIG. 13B with uniform torque-field and high gradient-force linearity. Each coil 517 is controlled independently, thus the magnetic vector direction, magnitude and slope offers 6 degrees of control freedom. [0117] On the outside surface of CGCI ferrous skeleton 525 are a plurality of additional parabolic antenna flux shields 518 which shield the exterior area from parasitic magnetic fields escaping the CGCI waveguide 15 . 1 between the circular armature structures. The shields 518 are shaped such that any escaping flux lines are redirected onto a return path behind the coil 517 assemblies. The captured stray flux contributes to the internal flux density available at the center region and improves the overall shape of the shaped magnetic volume 60 as seen in FIG. 13C . Also shown in FIG. 13C , the paths of the stray flux lines, shown as broken line arrows, interact with the shields 518 installed on the ferrous skeleton 525 and reduce the stray magnetic fields at 5 feet from the surface of the CGCI waveguide 15 . 1 to a value of below 5 Gauss. [0118] Utilizing the spherical symmetry described above, linearity and uniformity of the generated magnetic field 60 is achieved within the center region of the CGCI waveguide 15 . 1 which can be used to accurately and quickly advance the catheter 3 . 2 position and orientation via the command circuit 500 . The closed loop guidance of the magnetically tipped catheter 3 . 1 is aided by real-time computing of a simple magnetic landscape of the changing fields and gradients within the interior of the lobe. The landscape is generated from the continuously measured magnetic boundary conditions at the polefaces 4 . 3 x y , and from the calculated field density vectors set by the current in the eight coils 517 . Thus, the command circuit 500 having obtained the desired position 3 . 6 from the operator, will not only charter a path to the target based on the physical map of the endocardial surface, but will also integrate the information available from the magnetic landscape of the lobe. Knowing the magnetic landscape allows for the computation of the highest possible field intensity and gradient available at the actual position AP 3 . 5 with the catheter 3 . 2 in route to the target DP 3 . 6 . This regulation technique complements the strictly location-based field generation and moves the catheter 3 . 2 in real-time at the maximum obtainable speed. In addition, the field-shaping performance is enhanced within the CGCI waveguide 15 . 1 with magnetic shields 518 capturing and reorienting stray magnetic fields and flux into the center region. [0119] Magnetic lensing with poleface permeability refractors is accomplished by the CGCI waveguide 15 . 1 by use of the CGCI coils 517 which are disposed around a ferrous core 12 material with polefaces 4 . 3 x y protruding into the center region. The poleface 4 . 3 x y orientation is determined by pointing it toward the catheter tip 3 . 1 such that the rounded and raised end is pointed towered the catheter tip 3 . 1 and its highest generated flux density is directed towered the catheter 3 . 2 main axis. The current invention employs these magnetic focusing enhancements by using the general laws of electromagnetic wave propagation through materials of different dialectic and magnetic properties and as described by Snell's law of refraction. In its simplest form the law states that the relative angles of wave propagation in one media through the boundary of the second media depends on both the dielectric and magnetic properties of each media, jointly defining the index of refraction coefficient n(ω). The speed of the electromagnetic wave is given by c, thus the speed of magnetic wave propagation in the media is inversely proportional to the index of refraction. This index can be expressed in terms of permittivity ε(ω) and permeability μ(ω). The permittivity and permeability of the mediums are related to the index of refraction by the relation of μ(ω)·ε(ω)=n 2 (ω)/c 2 . [0120] Snell's law states: n 1 sin(θ 1 )=n 2 sin(θ 2 ) In a static (ω≅0) magnetic structure we can write for the general relation: [0000] B 1  t μ 1 = B 2  t μ 2 if   J s = 0 , [0000] where subscript 1 t and 2 t stands for the tangential components of B on both sides of the boundary. The tangential components of B are discontinuous regardless of any current density at the interface. This discontinuity is related to the permeability of the two mediums. As a direct consequence of the above interface conditions, the magnetic field (either H or B) is refracted at the interface between the two materials (magnetic steel, such as A858 with permeability μ steel =>1000 and air with permeability μ air =1). Rearranging and substituting we obtain [0000] tan   θ 1 = H 1  t H 1  n   and tan   θ 2 = H 2  t H 2  n [0000] where t stands for tangential component and n for normal component. [0121] Substituting H=B/μ and B 1n =B 2n we obtain [0000] tan   θ 1 tan   θ 2 = μ 1 μ 2 . [0122] The above equations correspond to a common interpretation of relativistic wave propagation dynamics and its salient case of a non-relativistic static perspective. The static solution seen FIG. 12 calculates as follows: [0123] θ 1 =λ°, μ 1 −1000, μ 2 −1, [0000] tan   θ 2 = μ 2 μ 1 · tan   θ 1 , [0000] thus θ 2 <1° [0124] The resultant optical displacement associated with the discontinuity of the medium due to permeability difference between the poleface 4 . 3 x y and insert ring 5 . x y enable the formation of a lens 120 shown as flux line map in FIG. 12 . [0125] FIG. 14 is a perspective view showing one preferred embodiment of the virtual tip user input device 905 . The virtual tip 905 is a multi-axis joystick-type device which allows the surgeon to provide inputs to control the position, orientation, and rotation of the catheter tip 3 . 1 , within the CGCI waveguide 15 . 1 chamber. In one embodiment, the virtual tip 905 includes an X-direction input 3400 , a Y-direction input 3404 , a Z-direction input 3402 , and a phi rotation input 3403 for controlling the position of the catheter tip. The virtual tip 905 further comprises a tip rotation input 3405 and a tip elevation input 3404 . As described above, the surgeon manipulates the virtual tip 905 and the virtual tip 905 communicates the surgeon's movements to the command circuit 500 . The command circuit 500 then generates instructions for the proper currents 300 . 1 in the coils 517 to be produced and to effect motion of actual catheter tip 3 . 1 to follow the motions entered into the virtual tip 905 . In one embodiment, the virtual tip 905 comprises various motors and/or actuators (e.g., permanent-magnet motors/actuators, stepper motors, linear motors, piezoelectric motors, linear actuators, etc.) to provide force feedback to the operator to provide tactile indications that the catheter tip 3 . 1 has encountered an obstruction or obstacle. [0126] FIG. 15 is a representation of the medical tool(s) that may be controlled by the CGCI waveguide 15 . 1 . Once such tool is a catheter 375 fitted with a permanent magnet 3 . 1 at its distal end. The catheter 375 further comprises a catheter body 376 , which extends into a flexible section 378 that possesses sufficient flexibility for allowing the relatively more rigid responsive tip 3 . 1 to be steered through the patient's body 1 . Alternatively, the catheter may comprise an articulated set of permanent magnets in the distal end of the tool. [0127] In one embodiment, the catheter tip 3 . 1 includes a guidewire assembly 379 seen in FIG. 15 that is responsive to magnetic fields. The responsive distal tips 3 . 1 of both the catheter assembly 375 and the guidewire assembly 379 respectively, comprise a plurality of magnetic elements such as permanent magnets that respond to the external flux generated by the CGCI waveguide's 15 . 1 electromagnetic coils 517 . [0128] In one particular embodiment, the magnetic catheter assembly 375 in combination with the CGCI waveguide 15 . 1 reduces or eliminates the need for the plethora of medical tools normally needed to perform diagnostic and therapeutic procedures. During a conventional catheterization procedure, the surgeon often encounters difficulty in guiding the conventional catheter to the desired position 3 . 6 , since the process is manual and relies on manual dexterity to maneuver the catheter 3 . 2 through a tortuous path of, for example, the cardiovascular system. Thus, a plethora of catheters in varying sizes and shapes have to be made available to the surgeon in order to assist him/her in the task since such tasks require different bends in different situations due to natural anatomical variations within and between patients. By using the CGCI waveguide 15 . 1 and while manipulating the distal magnetic element 3 . 1 , only a single catheter 3 . 2 is needed for most, if not all geometries associated with the vascular or the heart chambers. The catheterization procedure is now achieved with the help of the CGCI waveguide 15 . 1 that guides the magnetic catheter 375 and/or a guidewire assembly 379 to the desired position 3 . 6 within the patient's body 1 as dictated by the surgeon's manipulation of the virtual tip 905 . The magnetic catheter 375 and guidewire assembly 379 provides the flexibility needed to overcome tortuous paths, since the CGCI waveguide 15 . 1 overcomes most, if not all the physical limitations faced by the surgeon while attempting to manually advance the catheter tip 3 . 1 through the patient's body 1 . [0129] In another embodiment, the responsive tip 3 . 1 of the catheter assembly 375 is substantially tubular in shape and is a solid cylinder. The responsive tip 3 . 1 of the catheter assembly 375 is a dipole with a longitudinal polar orientation created by the two ends of a magnetic element positioned longitudinally within it. Similarly, the responsive tip 3 . 1 of the guidewire assembly 379 is a dipole with a longitudinal polar orientation created by two ends of the magnetic element 3 . 1 positioned longitudinally within it. [0130] In another embodiment, a high performance permanent magnet is used in forming the distal end 3 . 1 of the catheter assembly 375 so as to simultaneously have a high remanence M r , a high Curie temperature T c , and a strong uniaxial anisotropy. The high performance permanent magnet in the distal tip 3 . 1 preferably comprises a coercive field H c , (defined as the reverse field required to reduce the magnetization to zero) and a (BH) max that are inversely proportional to the volume of permanent magnet material needed to produce a magnetic field in a given volume of space. [0131] FIG. 15 also shows an alternative possible formation of a catheter assembly 375 whereby the permanent magnet in the distal tip 3 . 1 is supplemented with additional set of small beads 311 . The magnet in the distal tip 3 . 1 and the beads 311 are fabricated using magnetic materials and chemical compositions having at least two different H c values which enable a formation of a universal joint as is known in the art. The magnetic field B emanating from the CGCI waveguide's 15 . 1 electromagnetic coils 517 is applied uniformly onto the axial magnetization of the magnetic tip 3 . 1 and beads 311 . The magnetic distal tip 3 . 1 and the beads 311 with distinctly different H c values will act on each other as a mechanical joint. The two different H c values having properties that are “elastic” or “plastic” will respond to the magnetic field in a fashion of simulating an action such as cantilevered beam, and the deformation will result in an angular displacement value associated with the difference in H c between the distal tip 3 . 1 and beads 311 . When the magnetic field is removed, the cantilevered moment of inertia will recover and return the distal tip 3 . 1 to the position of its natural magnetization axis. [0132] In one embodiment a permanent magnet such as Nd 2 Fe 14 B is used in forming the distal tip 3 . 1 of the catheter assembly 375 , providing for a saturation magnetization of about 16 kG. However it is to be expressly understood that other permanent magnets now known or later devised may be used in forming the distal tip 3 . 1 without departing from the original spirit and scope of the invention. [0133] Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the invention as defined by the following invention and its various embodiments. [0134] Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the invention as defined by the following claims. For example, notwithstanding the fact that the elements of a claim are set forth below in a certain combination, it must be expressly understood that the invention includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations. A teaching that two elements are combined in a claimed combination is further to be understood as also allowing for a claimed combination in which the two elements are not combined with each other, but may be used alone or combined in other combinations. The excision of any disclosed element of the invention is explicitly contemplated as within the scope of the invention. [0135] The words used in this specification to describe the invention and its various embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use in a claim must be understood as being generic to all possible meanings supported by the specification and by the word itself. [0136] The definitions of the words or elements of the following claims are, therefore, defined in this specification to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim. Although elements may be described above as acting in certain combinations and even initially claimed as such, it is to be expressly understood that one or more elements from a claimed combination can in some cases be excised from the combination and that the claimed combination may be directed to a subcombination or variation of a subcombination. [0137] Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements. [0138] The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptionally equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the invention.

The invention relates to a method for using tissue contact technology to optimize automated cardiac chamber mapping algorithms to both speed up the mapping process and guarantee the definition of the actual chamber limits. The invention further comprises a method for conveying tissue type information to such automatic mapping algorithms so as to allow them to adapt their point collection density within areas of particular interest. The method is enhanced by the use of a magnetic chamber that employs electromagnetic coils configured as a waveguide that radiate magnetic fields by shaping the necessary flux density axis on and around the catheter distal tip so as to push, pull and rotate the tip on demand and as defined by such automatic mapping algorithms.

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority to provisional patent application Serial No. 60/359,088, filed Feb. 22, 2002. BACKGROUND OF THE INVENTION [0002] I. Field of the Invention [0003] This invention relates generally to vehicle mounted roof racks for transporting loads, and more particularly to a movable ladder rack that can be used to readily raise and lower a ladder onto and from the roof of a motor vehicle, such as a truck or van. [0004] II. Discussion of the Prior Art [0005] In my earlier U.S. Pat. Nos. 5,297,912, 6,092,972, 6,099,231 and in my currently pending application Ser. No. 09/758,729, filed Jan. 11, 2001, the teachings of which are hereby incorporated by reference, there are described different designs of truck or van-mounted ladder racks that facilitate the loading and unloading of one or more ladders with respect to the vehicle's roof. These devices comprise front and rear four-bar linkage assemblies that include a stationary member which is adapted to rigidly affixed to the vehicle's roof or to cross-members that clamp to the vehicle's roof, and a ladder support member pivotally joined to the stationary member by a pair of transversely spaced links. A drive shaft is journaled for rotation in the stationary members of the front and rear four-bar linkage assemblies and is rigidly affixed to one of the pair of links of the front and rear four-bar linkage assemblies. Thus, when the drive shaft is rotated, either manually with a crank or automatically by means of a motor, ladders resting on the front and rear ladder support members are lifted and rotated from a position parallel to the vehicle's roof to a position parallel to the vehicle's side during an unloading maneuver. When reloading ladders onto the vehicle, the drive shaft is rotated in an opposite direction to raise and rotate the ladder load onto the vehicle's roof. [0006] In my earlier designs described in the aforereferenced patents, the four-bar linkages have been designed such that the top and foot of the ladders remain generally horizontal throughout their range of motion as the drive shaft is rotated. This design featured significant lowering of the ladder's center of gravity, thus requiring still significant forces. [0007] While the earlier designs reflected in the above-listed patents greatly simplify the loading and unloading of heavy extension ladders onto and from transport vehicles, it is deemed advantageous to provide a rotatable ladder rack assembly for a motor vehicle that requires less force to be applied during the unloading and reloading operations. SUMMARY OF THE INVENTION [0008] In accordance with the present invention, I have redesigned the frontmost four-bar linkage assembly so that as a ladder load is transferred from the vehicle's roof to its position alongside the vehicle, the front or top end of the ladder is at an increased elevation relative to its foot such that the ladder is inclined relative to the horizontal. The height drop from a roof top position to the lowered disposition is reduced and, therefore, requires less force to operate. With the inclined position, the ladder feet are lowered further and the user is then better able to grasp the ladder at its foot end while the top or front end thereof is still engaged and supported by the front ladder support member. The foot of the ladder can be lifted free of the rear ladder support member and lowered to the ground. Because the top end of the ladder is still being supported by the front ladder support member, less force is required to accomplish the maneuver. [0009] The user may then move to a location along the side of the vehicle to the approximate center of mass of the ladder, whereupon the front portion of the ladder is lifted to disengage it from the front ladder support member and the ladder can be carried to the worksite. DESCRIPTION OF THE DRAWINGS [0010] [0010]FIGS. 1A through 1C illustrate a sequence in lowering a ladder from the roof of a vehicle to a location along side the vehicle using my prior art ladder rack assembly; [0011] [0011]FIG. 2 is a frontal perspective view of a utility vehicle on which the ladder rack assembly of the present invention is installed with an extension ladder mounted thereon and located generally parallel to the vehicle's roof; [0012] [0012]FIG. 3 is a frontal perspective view as in FIG. 2 but showing the ladder's partially elevated and rotated relative to the top of the vehicle; [0013] [0013]FIG. 4 is a further view showing the ladder rack assembly being used to lower a ladder from the vehicle's roof at a predetermined point during its lowering sequence; [0014] [0014]FIG. 5 is a further view of a ladder and the ladder rack assembly where the ladder is now positioned adjacent the vehicle's side and with the foot of the ladder at a lower elevation than its head end; [0015] [0015]FIG. 6 is a side view of a truck on which the present invention is installed and showing the ladder rack in its lowered disposition; and [0016] FIGS. 7 (A) through 7 (E) are perspective views of the preferred embodiment of the present invention at different angular dispositions in traversing from a raised, ladder transport position to a lowered, ladder unloading position. DESCRIPTION OF THE PREFERRED EMBODIMENT [0017] Before describing the preferred embodiment of the present invention, attention is first directed to FIGS. 1 (A) through 1 (C) which show the prior art ladder rack being used to transition a ladder load from a disposition atop a vehicle's roof to a lowered disposition alongside the vehicle and where the ladder is shown as being removed and carried away as to a worksite. The important thing to note from the views of FIG. 1 is that when the ladder rack has been transitioned by rotation of the handle so that the ladder load is adjacent the side of the vehicle, the ladder is in a level or horizontal disposition, requiring the user to shift the ladder free of the ladder rack assembly onto his shoulder when carrying the ladder to a worksite. Given the fact that a conventional 12-foot extension ladder made of fiberglass may typically weigh about 60 lbs., it requires some strength and dexterity to properly remove, balance and carry the ladder once the ladder has been lowered using the prior art ladder rack. [0018] Referring next to the photographs labeled FIGS. 2 - 6 , there is illustrated the use of the ladder rack of the present invention in lifting a ladder from its stowed disposition (FIG. 2) atop the vehicle's roof to a location alongside the vehicle prior to the ladder being removed from the ladder rack assembly. Particular attention should be paid to the manner in which the ladder rack assembly of the present invention causes a ladder to be inclined to the horizontal when in its lowered disposition as in FIG. 6. [0019] When the ladder is in the disposition illustrated in FIG. 6, a workman can readily lift the foot of the ladder free of the rear ladder support member while maintaining the top portion of the ladder hooked in place on the front ladder support member. Thus, the ladder acts as a lever of the second class allowing much less effort to lower the foot of the ladder to the ground than is required to completely lift the ladder free of the ladder rack assembly as in the prior art arrangement. [0020] With the foot of the ladder resting on the ground, the workmen can move forward and lift the top end of the ladder free of the front ladder rack assembly and gently lower the ladder to the ground. [0021] Referring now to FIG. 7(A), there is indicated generally by numeral 10 a ladder rack assembly constructed in accordance with the present invention. It includes a rear four-bar linkage assembly 12 and a front four-bar linkage assembly 14 . In my prior art arrangements, the four-bar linkage assemblies 12 and 14 are substantially identical. However, in the case of the present invention, this is not true. [0022] The rear four-bar linkage assembly 12 is seen to include a first rigid tube 16 of generally rectangular cross-section. This member is usually attached to a cross-bar that extends transversely across the roof of the vehicle and is anchored at each end to the vehicle. A second rectangular bar comprises a movable ladder rest 18 and it is coupled to the stationary bar member 16 by a pair of link members, including links 20 and 22 . The link 20 is pivotally secured to the ladder rest member 18 by a pin 24 located proximate the midpoint of the member 18 . The link 22 is likewise pivotally joined to the ladder rest member 18 by a pin 26 disposed near the inner end of member 18 with the other end of the link 22 being pivotally coupled to the stationary member 16 by a pin 28 . The other end of the link 20 is rigidly affixed to a drive shaft 30 that is journaled for rotation in bearings 32 disposed in the stationary bar member 16 proximate its end. A foldable handle 34 is pivotally joined at 36 to a coupling 38 affixed to the end of the drive shaft 30 to facilitate its being rotated. Rotation of the drive shaft in a clockwise direction, when viewed as in FIG. 7(A) will apply a torque to the linkage 20 causing it to rotate clockwise to thereby lift the ladder support member 18 relative to the vehicle's roof. [0023] The four-bar linkage assembly 14 differs from the four-bar linkage assembly 12 in that the ladder rest member 40 has an offset member 42 welded to it proximate its outer end 44 . Straddling the tubular stub comprising the offset member 42 are two right angle brackets 46 and 48 that are welded to a stationary bar member 50 adapted to be affixed to a front cross-bar member whose opposite ends are clamped to the vehicle's roof. A hinge pin 52 extends through the brackets 46 and 48 and through the offset member 42 , thereby permitting the ladder rest member 40 to swing about the pin 52 as a center. [0024] The front end of the drive shaft 30 is journaled in bearings 54 disposed in the stationary member 50 . Affixed to the drive shaft is a bell crank assembly that comprises a linkage 56 and a linkage 58 , where the two are pivotally joined by a pin 60 . The linkage 56 is also pivotally joined to the ladder rest member 40 by a pin 62 . [0025] It will seen, then, that as the handle 34 is used to rotate the drive shaft in a clockwise direction, the combined action of the links 56 and 58 will be to pivot the ladder rest member 40 in a clockwise direction about the hinge pin 52 . [0026] The kinematic design of the four-bar linkages 12 and 14 is such that as the rear ladder rest member 18 rotates slightly less than 90° in going from a horizontal disposition as shown in FIG. 7(A) to a generally vertical disposition as shown in FIG. 7(E), the front ladder rest member 40 also rotates slightly less than 90° whereby a ladder suspended on the perpendicularly extending arms 19 and 41 joined to the ladder rest members of the front and rear four-bar linkage assemblies will be inclined to the horizontal. The foot end of the ladder is at a lower elevation relative to its upper end, as earlier shown in the view of FIG. 6 while the center of gravity of the ladder is lowered only slightly while going from the roof top disposition to the lowered disposition. This provides a significant reduction in force needed for operating the crank handle when raising and lowering ladders onto and from the vehicle's roof. It offers a further advantage that there is less interference with the vehicle's outside rear view mirrors because the top of the ladder does not descend as far when carried by the front 4-bar linkage assembly. [0027] This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.

To reduce the energy needed to unload and reload ladders from and onto the roof of utility vehicles, a ladder rack assembly has been devised which minimizes the movement of the center of gravity of the ladder load when going between a first position atop the vehicle to a second position along a vertical side of the vehicle. To achieve this advantage, the rear and front four-bar linkages are driven by a rotatable drive shaft such that a ladder support member of the front four-bar linkage is at a higher elevation than the ladder support member of the rear four-bar linkage when the two are aligned with the side of the vehicle.

FIELD OF INVENTION [0001] The present invention relates to a method for the isolation, purification and characterization of novel phytoprogestogenic extracts from a traditional Chinese herb, Rhizoma Ligusticum Chuanxiong and their uses for conditions requiring progestogen therapy. The present invention also provides for a novel progesterone receptor assay and to a method for its preparation and also to a method for the use thereof. PRIOR ART AND BACKGROUND OF THE INVENTION [0002] Progesterone (PG) is a steroid hormone that has an essential role in mammalian reproduction. Together with estrogen, progesterone acts on the central nervous system, ovary and uterus, to initiate changes in the female reproductive tract that are critical for fertilization of the oocyte, implantation of the embryo and maintenance of pregnancy. Progesterone is formed in the corpus luteum, adrenals, testes, and placenta during pregnancy, and regulates the proliferation, differentiation and function of the uterus, mammary gland and ovary (Clarke and Sutherland 1990). In the uterus the hormone transforms the endometrium from a proliferative to a secretory phase and together with estradiol maintains endometrial integrity in the luteal phase of the menstrual cycle and in pregnancy. Progesterone also inhibits myometrial contractility and has a key role in mammary gland development and lactation. The diverse physiological effects of progesterone are however not restricted to the female reproductive tract. Progesterone has also been implicated in the function of the cardiovascular, immune, bone and central nervous systems. Progestogens act by binding specifically to the progesterone receptor in responsive cells. The receptor-ligand complex then translocates to the cell nucleus, binds to chromosomal DNA in the promoters of progesterone-responsive genes thereby regulating gene transcription. More recently, non-receptor mediated actions of progesterone have also been described. [0003] The progesterone receptor is a member of the steroid/nuclear receptor superfamily of transcription factors (Nuclear Receptor Nomenclature Committee, 1999). The 50 or so proteins of this superfamily are involved in diverse physiological functions such as control of embryonic development, cell differentiation, and homeostasis. The progesterone receptor is encoded by a single copy gene on chromosome 11q 22-23 and has with 8 exons spanning more than 90 Kb (Misrahi et al 1993, Rousseeu-Merck et al 1987). There are 2 isoforms of the progesterone receptor, PR-A (85 KDa) and PR-B (115 KDa). PR-A and PR-B differ, in that PR-B has an additional stretch of 164 amino acids located at the amino terminus of the receptor. When both receptors are expressed in equimolar quantities, PR-A and PR-B can heterodimerize and transactivate. Like other steroid receptors, the progesterone receptor has four main functional domains, namely the N-terminal Transactivation domain, followed by the Hinge, DNA-binding, and Ligand-binding domains. The most conserved domain is the DNA-binding domain. On activation by liquid, the DNA-binding domain binds to progesterone-responsive elements (PRE) which are composed of two palindromic sequences. The consensus PRE sequence is TGTACAnnnTGTTCT, where n represents any nucleotide. The carboxyl terminal domain is the ligand-binding domain (Bourguet et. al 1995, Carson-Jurica et al 1990) which in the presence of progesterone causes nuclear translocation, dimerization and formation of the pre-initiation complex on PRE of progesterone-responsive genes. [0004] The function of progesterone acting through its receptor system is indicated by anovulatory diseases in women where the hormone is lacking. The use of mouse mutants in which expression of individual progesterone receptor genes has been specifically ablated has also led to increased appreciation of the diverse roles of progesterone. Female mice lacing both PR gene insoforms exhibit impaired sexual behaviour, impaired neuroendocrine gonadotrophin regulation, anovulation, uterine dysfunction, and impaired ductal branching and lobuloalveolar differentiation of the mammary gland. Progesterone receptors also play an essential role in regulating thymic involution during pregnancy and in the cardiovascular system through regulation of endothelial cell proliferation. Receptors for progesterone have also been identified in the central nervous system and bone suggesting that the hormone is involved in regulator cognitive function and bone maintenance. [0000] Uterine Development and Function [0005] Progesterone hormone exerts both proliferative and differentiative effects on the uterus. Progesterone receptors are expressed in epithelial, stromal and myometrial compartments of the uterus (Tibbets et al 1998). In non-pregnant women, progesterone promotes changes in the estrogen-primed endometrium in order to convert the endometrium in a secretory phase. Withdrawal of progesterone typically induces endometrial sloughing. The lack of progesterone in anovulatory conditions like perimenopause or polycystic ovarian syndrome can result in hyperplasia and cancer of the endometrium due to the action of unopposed estrogen. [0000] Mammary Gland [0006] Progesterone and estrogens are the primary steroids required in normal breast development. In pregnancy, progesterone controls the increase in the branching, alveolar proliferation as well as differentiation of alveolar lobules. Studies with the PRKO mouse model have confirmed this action of progeterone (Lydon et al 1995). [0000] Immunity [0007] There are also reports in the prior art that estradiol has a strong pro-inflammatory action in the uterus, while progesterone has a potent anti-inflammatory response. It has been shown that PG can down-regulate the expression of Interleukin 8 (IL-8). The anti-inflammatory role of PR both of which are anti-estradiol and anti-inflammatory is likely to be essential for generation of an immunologically privileged tissue to facilitate implantation of the developing embryo and prevention of embryonic rejection (Ito et al 1994, Tibbetts et al 1999). [0000] CNS Effects [0008] Estrogen and progesterone, long considered for their roles as primary hormones in reproductive and maternal behavior, are now also being studied as neuroprotective and neuroregenerative agents in stroke and traumatic brain injuries (Stein, 2001). The hormones affect neuronal function including neurobehavioural expression associated with sexual responsiveness (Lydon et al 1995) and can prevent of the death of motor neurons (Yu 1988a). Collectively, the hormones reduce the consequences of the injury cascade by enhancing anti-oxidant mechanisms, reducing excitotoxicity (altering glutamate receptor activity, reducing immune inflammation, providing neurotrophic support, stimulating axonal remyelinization), and enhancing synaptogenesis and dendritic arborization. Whereas estrogen seems more effective as a prophylactic treatment in females at risk for cardiac and ischemic brain injury, progesterone appears to be more helpful in the post-injury treatment of both male and female subjects with acute traumatic brain damage. [0009] Compounds with biological activity similar to progesterone are known as progestogens, progestins or gestogens. The majority of progestogens are steroidal compounds belonging to progesterone and its derivatives, and testosterone and 19-nortestosterones and their derivatives. A smaller number of progestogens that are non-steroidal are also known including ligands based on sesquiterpenes possessing a ligularenolid skeleton (Kurihara, 1999), tetrahydropyridazines RWJ 26819 (Palmer, 2000), 5-Aryl-1,2,3,4-tetrahydrochromeno[3,4-f]quinolin-3-ones (Zhi et al 1999) and the fluorinated phthalides (Lehman et al 2001). [0010] Progestins have a wide range of applications such as in oral contraception, hormone replacement therapy (in combination with estrogen) and to assist reproductive technology (Sengupta and Ghosh 2000). Progestins are also used to treat inoperable endometrial cancer and have been suggested to aid in the reduction of risk to endometrial cancer from postmenopausal estrogen in woman. Effective treatment of secondary amenorrhea, functional uterine bleeding as well as related menstrual disorders (caused by hormonal deficiency or imbalance) have been achieve with the use of progestins. [0011] Progestogens are commonly used in hormone replacement therapy, normally in conjunction with estrogen to protect the endometrium from hyperplasia and cancer (Skouby 2001). High doses of progestogens are used to treat irregular and abnormal menstrual bleeding, to suppress endometrial growth, and for treating endometrial hyperplasia. Progestogens have anti-neoplastic activity against endometrial hyperplasia and cancer. Other uses for progestogens include treatment of premenstrual symptoms such as headaches, depression, water retention and mastodynia. Progestogens alone or in combination with other steroid hormones are also essential for the treatment of endometriosis and are essential components in the composition of female birth control pills and hormone replacement therapy. Progestogens are also used to treat luteal phase defects and for luteal support in assisted reproduction cycles for infertile patients. After conception, progestogens are used for fetal support. [0012] Presently, the progestogens available commercially comprise synthetic products such as medroxyprogesterone acetate and progesterol acetate. Some of the progestogens available commercially also result in undesirable side effects such as excessive androgen activity. It is therefore important to develop new progestogens which overcome the above drawbacks. In addition, considering the growing popularity for drugs based on traditional systems of medicine across the world, herbs and herbal extracts are of prime importance. Thus, phytoprogestogenic compounds would open new avenues of treatment for many people. Currently there are no known phytoprogestogens and the discovery of such substances would be of great commercial value. [0013] Traditional systems of medicine such as those practiced in China, Korean, Indian, Japanese and other Asian countries offer a wide variety of solutions to several diseases/disorders. Most traditional systems of medicine rely on herbs and herbal extracts and combinations thereof. Some traditional system of medicine also rely on the use of specific dosages of minerals either alone or in combination with herbs/herbal extracts to provide relief/cure for several disorders. [0014] Ligusticum belongs to the Umbelliferae family; members of which include L Chuanxiong (Chuan Xiong), L. wallichit, L. sinese (Gao Ben), and L. brachylobum. The dried rhizome of Ligusticum Chuanxiong is a very common crude drug in traditional Chinese, Japanese and Korean medicines. In Japan, Senkyu is obtained from the dried rhizome of Ligusticum officinale KITAGAWA, a variety of L. wallichii. [0015] Ligusticum's traditional actions include invigorating blood circulation, promoting the flow of Qi, dispelling wind, and alleviating pain. It Ligusticum has traditionally been prescribed for headaches, abdominal pain, arthralgias, and menstrual disorders caused due to blood stasis. L. Chuanxiong is indicated for menstrual disorders, amenorrhoea, dysmenorrhoea, abdominal pain with mass formation, pricking pain in the chest and costal regions pain due to traumatic injury, headache and rheumatic arthralgia (Chinese Pharmacopoeia, 1997). [0016] Over 90 essential oils (Zhong et al 1996) and 20 phthalides (Naito et al 1992) have been isolated from Ligusticum species and their value to the plant is believed to be because some of these alkylphthalide derivatives have antimicrobial, anti-fungal, anti-helminthic activities (Sinclair, 1998). Major constituents include ligustilide, butylidenephthalide, coidilide, neocnidilide and butylphthalide. Pregeneolone, coniferylferulate, senkyunolide-A and their mono- and dihydroxyphthalide derivatives have also been found. Other ingredients include an alkaloid, tetramethylpyrazine, ferulic acid (a phenolic compound), chrysophanol, sedanoic acid, and 1-2% of essential oils such as ligustilide and butylphthalide. Significant amounts of minor components can be derived from the original components subsequent to processing and storage. For example the dihydroxyphthalides senkyunolide-H and I and senkyunolide-J can be synthesized from major components ligustilide and senkyunolide-A. These oxygenated phthalides were absent from the fresh herb but were shown to be derived from the major volatile phthalides during storage of the crude drug. Similarly ferulic acid is a decomposition product from coniferylferulate (Kobayashi et al 1984). [0000] Animal Studies [0000] Cardiovascular Effects [0017] Four phthalide dimers from Ligusticum Chuanxiong, tokinolide B, levistolide A, ligustilide and senkyunolide P are shown to relax KCl-induced contraction on rat thoracic aorta and reduced KCl-induced perfusion pressure of rat mesenteric arteries. Coniferylferulate reduced methoxamine-induced perfusion pressure on rat mesenteric arteries. On the other hand the phthalide dimers, tokinolode B and senkynolide P and the phthalides, senkyunolide, buthylphtalide and cnidilide decrease blood viscosity. These suggest that the herb has important functions for activating the blood circulation and removing blood stasis (Naito et al 1995). [0018] Butylidenephthalide was reported to have a selective anti-anginal effect without changing blood pressure. Experiments performed to determine the mechanism of this action suggest that Butylidenephthalide inhibits calcium release from calcium stores more selectively than calcium influx from extracellular space via voltage-dependent calcium channels. The inhibition by butylidenephthalide of calcium release from KCl-sensitive calcium stores might be similar to its inhibition of calcium release from phenylephrine-sensitive calcium stores (Ko et al 1998). Senkyu phthalides has also been described as having antiarteriosclerotic properties (Massayasu K et al 1989). Thus synthetic butylidenephthalides have been described to have inhibitory effects on mouse aorta smooth muscle cells in-vitro (Mimura et al 1995). [0019] The methanol extract from Cnidium rhizome (Senkyu) decreased the contraction and slightly increased the heart rates of the isolated atria. The methanol extract from Cnidium rhizome when fractionated with chloroform and water fractions was reported to exert potent negative inotropic and chronotropic effects in isolated atria. The contraction was attenuated by two major components in the chloroform fraction, ligustilide and senkyunolide, but the heart rates were scarcely affected by these components. The chloroform fraction induced changes in resting potentials and configurations of normal action potentials recorded in the isolated left atria; the resting potentials were depolarized, and the upstroke velocity of the action potentials decreased. Neither ligustilide nor senkyunolide exerted such effects. The upstroke velocity of action potentials recorded in partially depolarized atria was reduced by the chloroform fraction as well as ligustilide and senkyunolide (Nakazawa et al 1989). [0020] By occluding the bilateral carotid arteries of rabbits to produce bilateral partial cerebral ischemia, and by using radioimmunoassays to measure the levels of dynorphin A1-13 like immunoreactivity (ir-Dyn A1-13) in plasma and cerebrospinal fluid (CSF), Liu & Shi (1990) found that the levels of ir-Dyn A1-13 in plasma and CSF have significantly increased (P less than 0.01) after cerebral ischemia appears. The result of the Ligusticum wallichii Franch ( Ligusticum ) pretreatment to the test-group shows a definite improvement of the changes of ir-Dyn A1-13 levels in plasma and CSF. The severity of brain ischemic damage and neurologic dysfunction in Ligusticum -treated animals is lighter than that of saline-treated group, too. In this study, some new approaches are explored to explain the pathophysiology of cerebral ischemia and the mechanisms by which Ligusticum prevents and treats cerebral ischemia (Liu & Shi 1990). [0000] Anti-Inflammatory Properties: [0021] In a Japanese study, the active ingredients in Ligusticum, tetramethylpyrazine and ferulic acid, were found to have both significant anti-inflammatory and analgesic effects (Ozaki 1992). When given to guinea pigs with histamine/acetylcholine induced bronchospasm, Ligusticum was found to decrease plasma levels of thromboxane B2, relax tracheal muscle, increase the forced expiratory volume, and inhibit the synthesis and release of thromboxane A2 with no adverse side-effects. The total effective rate was 92 percent vs. 62 percent in the control group (P<0.01). [0000] Asthma and Bronchial Smooth Muscle [0022] Ligusticum wallichii mixture was also reported to inhibit bronchospasm induced by histamine and acetylcholine in guinea pigs; to decrease the plasma level of TXB2. The incubation period from antigen inhalation to asthma attack could be delayed by Ligusticum wallichii mixture and the incidence of asthma and its mortality were reduced in guinea pigs compared with control, P<0.01. (Shao et al 1994) [0000] CNS and Anticonvulsive Activities [0023] Early reports suggest that 3-n-butyl phthalide can facilitate the performance of learning and memory in rats (Yu et al 1988a) and that it has a protective effect on rat brain cells (Yu et al 1988b). [0000] Antibacterial/Antifungal Effects: [0024] Ligusticum has demonstrated in vitro effects against several strains of pathogenic bacteria including Pseudomonas aeruginosa, Shigella sonnei, Salmonella typhi, and Vibrio cholera (Bensky & Gamble 1993). The essential oil components of Ligusticum (butylphthalide) have been shown to inhibit dermatophytes in vitro (Hone 1986). [0000] Renal Effects [0025] It is believed that Ligusticum wallichii can also affect the toxicity of Cyclosporine A on renal function, renin-angiotensin system and platelet aggregation in Sprague Dolly rats (Liu 1992). Infusion of Cyclosporine A (50 mg/kg, iv) resulted in a significant fall in glomerular filtration rate and renal plasma flow and a significant increase of plasma renin activity, angiotensin II level and percentage platelet aggregation. At the same time, treatment with 20% Ligusticum wallichii (8 ml/kg, iv) before cyclosporine A infusion significantly prevented the decline of glomerular filtration rate and renal plasma flow as well as the enhancement of platelet aggregation, but had no influence on cyclosporine A mediated renin-angiotensin system activation. These results suggested that Ligusticum wallichii may be beneficial to the acute nephrotoxicity induced by cyclosporine A (Liu 1992). [0000] Skin Permeability [0026] Ligustici Chuanxiong Rhizoma (Senkyu) ether extract has been reported to enhanced permeability of moderately lipophilic compounds into the skin. (Sekiya et al 1997, Nmaba et al 1992). [0000] Human Studies on Ligusticum Herbs [0000] Cerebro-Vascular and Coagulation Effects [0027] Ligusticum has been studies in the treatment of ischemic stroke (Chen 1992b). Some injections of the medicines, including Ligusticum, Ligustrazine, Ligustylid and ferulic acid, were tested clinically and experimentally. The results showed that the effects of the drugs were the same as or even better than those of the controls, such as papaverine, dextran and aspirin-persantin. They could improve brain microcirculation through inhibiting thrombus formation and platelet aggregation as well as blood viscosity. [0028] One hundred and fifty-eight subjects with transient ischemic attack were randomly divided into a Ligusticum group (111 cases) and an aspirin group (47 cases). The total effective rate in the Ligusticum group was 89.2 percent as compared to 61.7 percent in the aspirin group (P<0.01) (Chen 1992b). Ligusticum increased cerebral blood flow, accelerated the velocity of blood flow, dilated the spastic artery, and decreased peripheral arterial resistance. In another study, Ligusticum was evaluated in the treatment of ischemic stroke. Injectable preparations were shown to improve brain microcirculation through inhibiting thrombus formation, decreasing platelet aggregation, and improving blood viscosity. The effect of Ligusticum was the same or better than the controls of papaverine, dextran and aspirin-persantin (Chen & Chen 1992). [0029] In another double-blind trial 220 patients with acute cerebral infarction were randomly divided into Ligusticum Chuanxiong group (134 cases) and low molecular weight dextran group (86 cases) to evaluate the herb's effects on neurologic function and living capability. The results showed that the total therapeutic efficacy rate in Chuanxiong group and in dextran 40 group were 86.6% and 62.8% respectively. The effect of Chuanxiong on treatment of acute cerebral infarction was superior to low molecular weight dextran. The difference between the two groups was also statistically significant (P<0.01) (Chen 1992a). [0030] By using ELISA and RIA to measure the levels of Beta-thromboglobulin (beta-TG), platelet factor 4, thromboxane B2 and 6-keto-prostaglandin F1 alpha in plasma of patients with acute cerebral infarction, Liu (1991) found that the levels of beta-TG, platelet factor 4 and thromborane B2 in plasma had significantly increased (P less than 0.01), but the level of 6-keto-prostaglandin F1 alpha in plasma showed no change (P greater than 0.05). The results of the Ligusticum wallichii treatment to the test-group showed that the levels of Beta-thromboglobulin, platelet factor 4 and T thromboxane B2 in plasma had significantly decreased (P less than 0.01), and the level of 6-keto-prostaglandin F1 alpha in plasma had significantly increased (P less than 0.05). This suggested that the Ligusticum treatment could effectively inhibit the platelet activation in vivo and correct the thromboxane A2-prostaglandin F2 imbalance in blood of the patients (Liu 1991). [0000] Toxicity: [0031] Ligusticum is prescribed in traditional Chinese decoctions at dosages up to 9 grams administered over several days. Overdose symptoms may include vomiting and dizziness (Bensky & Gamble 1993). [0032] U.S. Pat. No. 4,708,949 discloses therapetic compositions are composed of four plant extracts; ginsenoside, tetramethyl pyrazine, astragalan and atractylol. Pharmaceutical dosage units are prepared by conventional means with specific weight ranges and proportions of each of the four ingredients. The pharmaceutical dosage units are claimed to be highly effective in treating cerebral vascular disease and the sequelae thereof. The dosage units are also useful for bolstering immunofunction in healthy and diseased patients. Tetramethyl pyrazine is preferably extracted from Ligusticum Chuanxiong. [0033] There has however been no teaching in the art that associates L.C. or the Ligusticum family or their extracts or compounds contained therein with progestogenic activity. [0034] Many women consider prescription progestogens to be unnatural. As a result, there would be a demand for phyto-progestogens derived from herbs. There is a need to identify naturally occurring compounds which can activate the progesterone receptor and thus can act as phyto-progestogens. Such herbal derived progestogens are needed to develop therapeutic compositions, botanical drugs and/or nutraceutical applications. Pure chemical phyto-progestogens can be developed as pharmaceutical applications. [0000] Reporter Gene Bioassays for Steroidogenic Activity [0035] The measurement of steroid bioactivity and bioavailability in animal models is an essential part of preclinical drug evaluation. To determine whether a herbal extract or any other complex mixture is clinically effective, data on its absorption, metabolism and bioavailability in animal models is required. Unlike pure compounds, herbal extracts are mixtures of multiple compounds, many of which contribute to biological activity. Current methods used in the pharmaceutical industry to perform pharmacokinetic/dynamic studies in man or animal models, depend on the measurement and tracking of single compounds in serum using chromatography and mass spectrometric techniques. These conventional techniques are inadequate for studies of botanical or animal-derived drugs since these comprise multiple biologically active compounds. Although there are preliminary reports of bioassays to track androgenic (Paris, 2002), estrogenic (Paris, 2002) and glucocorticoid (Vermeer, 2003) bioactivities in serum using reporter genes in cells, there are not reports of bioassays to measure progestogenic activity. Furthermore, there is a need to develop methods to extract steroid-active small compounds from serum and compared their bioactivity, bioavailability and bioequivalence to reference pharmaceutical compounds in animal models. [0000] Objects of the Invention [0036] The main object of the present invention is to provide herbal extracts with progestogenic activity which substantially replicate the activity of progesterone. [0037] It is another object of the invention to provide a method for the screening of herbal extracts to determine their potential progestogenic activity, validate such activity and prepare herbal extracts which can be used as progestogens. [0038] It is another object of the invention to provide a method for the preparation of herbal extracts of Ligusticum Chuanxiong which can be used as a progestogen in crude extract form or after further purification. [0039] It is another object of the invention to provide a method for the preparation of herbal extracts of Ligusticum Chuanxiong which after purification provide enriched fractions of extract useful as progestogens. [0040] It is another object of the invention to provide for the use of extracts containing phyto-progestogens from Rhizoma Chuanxiong, to treat health problems requiring progesterone therapy, supplementation or replacement including fetal support, menstrual disorders, amenorrhoea, menorrhagia, polycystic ovarian syndrome, pregnancy complications, endometriosis, contraception, menopause, endometrial hyperplasia and endometrial cancer. [0041] It is another object of the invention to provide use of extracts containing phyto-progestogens from Rhizoma Chuanxiong, alone, or in combinations with other compounds, for oral contraception, for hormonal replacement therapy, for treating endometriosis, neuroprotective and neuroregenerative agents in stroke and traumatic brain injuries. [0042] It is another object of the invention to provide methods to separate fractions of Rhizoma Chuanxiong, enriched for 3-butyl-4,5-dihydrophthalide, 3-butyl-phthalide and components and co-eluates, with strong progestogenic activity using solvent-solvent partitioning, solid-phase fractionations and high-performance liquid chromatography (HPLC). [0043] It is another object of the invention to provide methods for standardization and fingerprinting of Rhizoma Chuanxiong extracts using solvent-solvent partitioning solid phase fractionations, HPLC, mass spectrometry (MS), and nuclear magnetic resonance imaging (NMR). [0044] It is another object of the invention to provide methods for measurement and standardization of the bioactivity Rhizoma Chuanxiong and its extracts based on the presence of 3-butyl-4,5-dihydrophthalide and 3-butyl-phthalide. SUMMARY OF THE INVENTION [0045] The present invention resides in the analysis of various herbs noted in traditional Chinese medicine for their “uterotonic” activity in order to firstly determine which of them may possess progestogenic activity, and secondly to isolate/prepare extracts therefrom with progestogenic activity. The present invention relies on screening of herbs reported to possess “uterotonic activity” in ancient pharmacopoeia, for progestogenic activity and to purify and characterize pure phyto-progestogens from bioactive herbal extracts. [0046] Accordingly the present invention provides a method for the preparation of an alcoholic extract from Rhizoma Chuanxiong useful as a progestogen, said method comprising subjecting powdered Rhizoma Chuanxiong to a first extraction with an alcoholic solvent selected from the group consisting of ethanol and methanol, separating a first Rhizoma Chuanxiong extract obtained thereby from a supernatant, subjecting the filtered first extract to a second extraction with an alcoholic solvent to obtain a second extract, separating and drying the second extract. [0047] In one embodiment of the invention, the solvent used for the first extraction is selected from ethanol in a concentration of 70% and 100%. [0048] In another embodiment of the invention, the solvent for the first extraction is selected from methanol in a concentration of 70% and 100%. [0049] In another embodiment of the invention, in the first extraction, the powdered Rhizoma Chuanxiong is mixed with the solvent and then allowed to soak for 5-7 days at 37° C. [0050] In another embodiment of the invention, the first extract is separated from the supernatant by filtration using Whatman Grade I (11 μm pore size) filter paper. [0051] In another embodiment of the invention, the second extraction is carried out over a time period in the range of 2-3-hours. [0052] In another embodiment of the invention, the second extract is separated from the solvent by filtration. [0053] In another embodiment of the invention, the separated second extract is dried in a rotary evaporator. [0054] In another embodiment of the invention, the solvent used for the second extraction is the same as the solvent used for the first extraction. [0055] In another embodiment of the invention, the solvent used for second extraction is selected from the group consisting of 50%, 70% and 100% ethanol in water; and 70% and 100% methanol in water. [0056] In another embodiment of the invention, the dried second extract is suspended in an alcoholic medium. [0057] In another embodiment of the invention, the medium used for suspending the dried second extract is selected from ethanol and methanol in a concentration of 100%. [0058] In another enbodiment of the invention, the dried extract is suspended in the alcoholic medium at a concentration in the range of 6.25 μg/ml to 100 μg/ml of medium. [0059] In another embodiment of the invention, the dried extract is suspended in the alcoholic medium at a concentration of 50 μg/ml. [0060] In another embodiment of the invention, the dried extract of Rhizoma Chuanxiong contains 3-butyl-4,5-dihydrophthalide and 3-butyl-phthalide as active constituents. [0061] In another embodiment of the invention, the 3-butyl-4,5-dihydrophthalide is present in the extract in an amount of about 95% and the 3-butyl-phthalide is present in an amount of about 2%. [0062] In another embodiment of the invention, the dried second extract of Rhizoma Chuanxiong is subjected to purification to enrich the second extract. [0063] In another embodiment of the invention, the purification is carried out by eluting the dried second extract with a solvent using reverse phase extraction in a C18 matrix contained in a glass column. [0064] In another embodiment of the invention, the solvent used for elution is selected from the group consisting of 30% methanol, 80% methanol, 100% methanol and DCM. [0065] In another embodiment of the invention, the purification is carried out using reverse phase extraction in a Diol matrix contained in a glass column. [0066] In another embodiment of the invention, the reverse phase extraction is carried out using an eluate selected from the group consisting of 30% EtoAc:70% DCM, 100% DCM and 60% EtoAc:40% DCM. [0067] In another embodiment of the invention, the dried extract is first subjected to solvent/solvent partitioning to remove tannins present in said extract. [0068] In another embodiment of the invention, the solvent/solvent partitioning is carried out by first mixing the dried second extract in ethanol, mixing the ethanolic extract obtained thereby with water to obtain an ethanolic solution, adding hexane to the solution to obtain a first hexane layer, separating the hexane layer and adjusting the ethanol:water ratio in the remaining solution to 3:2, adding equivolume of DCM to obtain a DCM layer, separating the DCM layer, adding butanol to the remaining solution after DCM layer removal to obtain a butanol layer, separating the butanol layer to leave a water layer as remnant, the tannins being partitioned to the butanol layer and the water layer, the prior separated hexane and DCM layers being enriched in Rhizoma Chuanxiong extract. [0069] The present invention also relates to the therapeutic use or a therapeutic method for progesterone replacement or supplementation comprising administering to a patient suffering from conditions requiring progesterone replacement or supplementation, a therapeutically effective dose of an extract of Rhizoma Chuanxiong. [0070] In one embodiment of the invention, the therapeutically effective dose of Rhizoma Chuanxiong extract is in the range of 6.25 μg/ml to 100 μg/ml. [0071] In another embodiment of the invention, the therapeutically effective dose of Rhizoma Chuanxiong extract is 50 μg/ml of crude extract. [0072] In another embodiment of the invention, the conditions requiring replacement/supplementation of progesterone are selected from the group consisting of menstrual disorders, amenorrhoea, menorrhagia, polycystic ovarian syndrome, pregnancy complications, endometriosis, contraception, menopause, endometrial hyperplasia and hormonal replacement. [0073] In another embodiment of the invention, the Rhizoma Chuanxiong extract is used alone or in combination with co-elutes from Rhizoma Chuanxiong. [0074] The present invention also relates to the use of Rhizoma Ligusticum chuanxiong extract for or to a method for the treatment of stroke or brain injuries in a subject suffering the same comprising administering to the subject a pharmaceutically effective amount of Rhizoma Chuanxiong extract. [0075] In one embodiment of the invention, the pharmaceutically effective dose of Rhizoma Chuanxiong extract is in the range of 6.25 μg/ml to 100 μg/ml. [0076] In another embodiment of the invention, the as claimed in claim 29 wherein the pharmaceutically effective dose of Rhizoma Chuanxiong extract is 50 μg/ml of crude extract. [0077] In another embodiment of the invention, the Rhizoma Chuanxiong extract is used alone or in combination with co-elutes from Rhizoma Chuanxiong. [0078] The present invention also provides a novel progestogen receptor assay comprising HeLa cells transiently co-transfected with a first plasmid and a second using lipofectamine. [0079] In one embodiment of the invention, the first plasmid comprises of DNA encoding the full length human progesterone receptor (FR-B) and the second plasmid comprises a progesterone reporter gene (PRE2-TATA-LUC) comprising a luciferase reporter gene driven by two copies of the progesterone response element from the aminotransferase gene. [0080] The present invention also relates to a method for preparing a kit for conducting an assay for progesterone receptor activity comprising growing HeLa cells in 24-well microtiter plates, infecting the grown HeLa cells with a first plasmid and a second plasmid using lipofectamine, the first plasmid comprising of DNA encoding the full length human progesterone receptor (PR-B), and the second plasmid comprising a progesterone reporter gene (PRE2-TATA-LUC) comprising a luciferase reporter gene driven by two copies of the progesterone response element from the aminotransferase gene, exposing the transfected cells to ligands in RPMI 1640 medium, supplemented with 10% charcoal-stripped fetal calf serum, 2 mM L-glutamine, 0.1 mM non-essential amino acids and 1 mM sodium pyruvate for 42-48 hours at 37° C. in a 5% carbon dioxide incubator, exposing the replicate wells to ethanol vehicle, rinsing the cells with a buffer selected from a PBS buffer and lysis buffer, collecting the cell lysates for measurement of luciferase activity. [0081] The present invention also provides a method for conducting assay of progestogenic activity of an extinct Ligusticum chuanxiong comprising exposing an assay kit comprising transfected cells of He—La transiently co-transfected with a first plasmid and a second using lipofectamine, to increasing doses of progesterone and the extract. BRIEF DESCRIPTION OF THE FIGURES [0082] FIG. 1 is a graphical representation of dose-response curves of progesterone (PG), and the synthetic progestogen, megesterol acetate (MA); using the cell-based progesterone reporter gene system. Progestogenic activity of the ligands was expressed as fold-increase in luciferase activity compared with control cells exposed to vehicle only. All data points were in triplicate. Error bars represented SEM. [0083] FIG. 2 is the dose-response curve of the 100% ethanol extract of Ligusticum chuanxiong (L.C.) in comparison to PG 100 nM. L.C. extract was prepared as described in example 2, and replicate wells were exposed to increasing concentration of L.C. extract for 48 hours. Progestogenic activity of the ligands was expressed as fold-increase in luciferase activity compared with control cells exposed to vehicle only. All data points were in triplicate. Error bars represent SEM. [0084] FIG. 3 is a representation of the progestogenic activity of L.C. extract in the presence of a progestogenic antagonist, FU486. Cells were exposed to the indicated concentrations of RU486 in the presence of fixed amounts of L.C. extract (50 μg/ml), or PG 100 nM for 48 hours. L.C. extract was prepared as described in example 2. Replicate wells exposed to L.C. extract (50 μg/ml) alone, or PG 100 nM alone, served as positive controls. Progestogenic activity of the ligands was expressed as fold-increase in luciferase activity compared with control cells exposed to vehicle only. All data points were in triplicate. Error bars represent SEM. [0085] FIG. 4 shows the effect of L.C. on PG action. Cells were exposed to the indicated concentrations of progesterone (PG) in the presence of fixed amounts of L.C. extract (50 μg/ml). L.C. extract was prepared as described in example 2. Replicate wells exposed to LC. extract (50 μg/ml) alone, or PG 100 nM alone, served as positive controls. Progestogenic activity of the ligands was expressed as fold-increase in luciferase activity compared with control cells exposed to vehicle only. All data points were in triplicate. Error bars represent SEM. [0086] FIG. 5 shows the effect of L.C. extract on glucocorticoid (GR), androgen (AR), estrogen (ERα and ERβ) receptors. Plasmids encoding either PR, GR or AR were co-expressed with a reporter gene (PRE2-TATA-LUC) that contains the hormone-reponse elements common to all three receptors. Estrogenic activity was measured by expressing ERα or ERβ in the presence of the estrogen-responsive ERE-MMTV-LUC reporter gene. Hormone activity of the ligands was expressed as fold-increase in luciferase activity compared with control cells exposed to vehicle only. All data points were in triplicate. Error bars represent SEM. L.C. displayed strong progestogenic activity and the absence of activity with the GR, AR, ERα and the ERβ. This indicated that L.C. has specific agonistic activity for PR. [0087] FIG. 6 (A-D) shows the effects of L.C. crude extract on GR, AR, ERα and ERβ activity in the presence of their natural ligands. The effect of increasing doses of L.C. crude extract on Hormone receptor activity was assessed as described in FIG. 5 . Luciferase activity was measured for GR ( FIG. 6A ), AR ( FIG. 6B ), ERα ( FIG. 6C ) and ERβ ( FIG. 6D ); in the presence of fixed doses of hydrocortisone (HC 1 nM), dihydrotestoterone (DHT 1 nM) and estradiol (E2 1 nM) respectively. No significant additive, synergistic, or antagonistic activity was observed. [0088] FIG. 7 (A, B) shows the progestogenic activity of L.C. fractions following solid phase extraction. L.C. crude extract was applied to A) C18 reverse phase, and B) Diol flash columns. C18 or Diol powder was obtained commercially and packed into glass columns. L.C. (50 mg/ml) was applied to the columns. Elution was performed in the order (C1 to C4) for C18 columns, and in the order (D1 to D8) for the Diol columns, using the solvents indicated. The fractions were collected separately in glass tubes, and dried down and reconstituted. Progestogenic activity was measured and expressed as fold-increase in luciferase activity compared with control cells exposed to vehicle only. Replicate wedls exposed to L.C. extract (5 & 50 μg/ml) alone, or PG 100 nM alone, served as positive controls. All data points were in triplicate. Error bars represent SEM. [0089] FIG. 8 shows the progestogenic activity of L.C. fractions after solvent/solvent partition. L.C. crude extract in 100% ethanol (50 mg/ml) was reconstituted to a mixture of 9:1 with water. 100% hexane was then added and partitioned the hexane phase was removed to form the first fraction. The next partition was conducted with the ethanol fraction in a mixture of 3:2, equal volume of DCM was added. This formed the second fraction. Following which an equal volume of Betanol was used for the final partition. Progestogenic activity was measured and expressed as fold-increase in luciferase activity compared with control cells exposed to vehicle only. Replicate wells exposed to L.C. extract (5 & 50 μg/ml) alone, or PG 100 nM alone, served as positive controls. All data points were in triplicate. Error bars represent SEM. [0090] FIG. 9 shows the progestogenic activity of Diol elution fractions following solvent/solvent extractions. The DCM fraction from solvent/solvent partition, shown in FIG. 8 , was subjected to Diol solid phase extraction and eluted with solvents (D1 to D8) as indicated. The fractions were collected separately in pre-weighed glass tubes, dried down, re-weighed and reconstituted. Progestogenic activity of indicated doses of each Diol fraction was measured and expressed as fold-increase in luciferase activity compared with control cells exposed to vehicle only. Replicate wells were exposed to L.C. extract (50 μg/ml) alone, or PG 100 nM alone, or the reconstituted extract combining all Diol fractions (D9). All data points were in duplicate or triplicate. Error bars represent SEM. [0091] FIG. 10 is a HPLC chromatogram of a bioactive Diol L.C. fraction. Diol fraction D1, eluted with 100% Hexane in Example 9, was further fractionated using HPLC. The HPLC column used was ThermoQuest Hypurity Elite C18 (5 μm 150 mm×10 mm). Isocratic conditions of 45% ACN:55% H 2 O Over a period of 40 minutes were used to effect the separation. This typical HPLC chromatogram of a purified L.C. extract, generated using a wavelength (λ) of 210 mm, displayed 7 characteristic peaks within the elution periods Fr 1-Fr 7 as indicated. [0092] FIG. 11 shows the progestogenic activity of the HPLC fractions. The 7 fractions with elution periods Fr 1-Fr 7 in Example 10 were dried down and re-constituted into 3 concentrations (5, 2.5 and 1.25 μg/ml). These were then tested for the progestogenic activity with the assay described in FIG. 1 . Fraction 6 (Fr 6) demonstrated the most potent activity from the bioassay. Replicated wells were exposed to L.C. extract (50 μg/ml) alone, or PG 100 nM alone, or the reconstituted extract combining all Diol fractions (Combi). Maximum activity was observed in Fr 6 and Fr 7. In contrast, the wash after Fr 7 was relatively inactive. All data points were in duplicate or triplicate. Error bars represent SEM. [0093] FIG. 12 (A-D) is the nuclear magnetic resonance (NMR) analyses of comounds in HPLC Fraction 6. Reconstituted Fr 6 from the preparative HPLC described in Example 10 was subjected to NMR analyses to determine the structure of their constituents. A) 1-D NMR, B) 2-D NMR, C) 1 H— 1 H COSY, D) 1 H— 13 C gHSQC. [0094] FIG. 13 (A-B) shows the structure of the constituents of HPLC Fraction 6. (A) 3-butyl-4,5-dihydrophthalide and (B) 3-butyl-phthalide. [0095] FIG. 14 shows the progestogenic activity of L.C. in serum following subcutaneous administration. One ml. of crude ethanolic L.C. extract (1 g), MPA (10 mg) and control [1,2-propanediol:PEG(400):Ethanol (1:1:1)] was subcutaneously administered to male Sprague-Dawley rats at 0 minutes. Six rats were used for each arm of the experiment. Serum samples were collected from the tail vein at indicated time points, before and after L.C. injection. Bioactive progestogens were extracted from serum and tested for progestogenic activity using the novel receptor-based bioassay of the invention. Each data point is the Mean ±SEM of samples obtained from 6 different rats. Bars indicate progestogenic activity of original MPA and L.C. extract in-vitro. Progestogenic activity is expressed as fold increase compared to cells exposed to vehicle only. [0096] FIG. 15 shows the progestogenic activity of L.C. in serum following ORAL administration. Sprague-Dawley rats were fasted overnight. Two mls of L.C. (2 g), MPA (10 mg) and vehicle (60% Ethanol) were orally fed to male rats using gavage tubes. Serum samples were collected from the tail vein at indicated time points, before and after L.C. administration. Bioactive progestogens were extracted from serum and tested for progestogenic activity using our receptor-based bioassay. Each data point is the Mean±SEM of samples obtained from 6 different rats. Bars indicate progestogenic activity of original MPA and L.C. extract in-vitro. Progestogenic activity is expressed as fold increase compared to cells exposed to vehicle only. DETAILED DESCRIPTION OF THE INVENTION [0097] Different herbs reported to have “uterotonic activity” were identified and screened for progestogenic activity using a cell-based reporter gene assay and have discovered two herbs with significant progestogenic activity. Extracts from the Rhizoma Chuanxiong, the dried rhizome of Ligusticum Chuanxiong Hort, were able to specifically activate the progesterone receptor but not the related androgen, estrogen or glucocorticoid receptors. Dose response studies in cells indicate that predicted therapeutic serum levels for Rhizoma Chuanxiong crude extract, prepared as by methods described are between 6.25 μg/ml to 100 μg/ml, and the effective oral dose would be between 31.25 mg to 500 mg. Extracts containing these phyto-progestogens from Rhizoma Chuanxiong are useful to treat health problems requiring progesterone therapy, supplementation or replacement including fetal support, menstrual disorders, amenorrhoea, menorrhagia, polycystic ovarian syndrome, pregnancy complications, endometriosis, contraception, menopause, endometrial hyperplasia and endometrial cancer. These phytoprogestogens alone, or in combinations with other compounds, are also useful for oral contraception, for hormonal replacement therapy, for treating endometriosis, neuroprotective and neuroregenerative agents in stroke and traumatic brain injuries. It was also observed that compound(s) co-eluting with two known phthalides, 3-butyl-4,5-dihydrophthalide and 3-butyl-phthalide, from Rhizoma Chuanxiong strongly activate the progesterone receptor. These compound(s), which co-elute with 3-butyl-4,5-dihydrophthalide and 3-butyl-phthalide or herbal extracts enriched therewith, are useful for harmone replacement therapy and the treatment of health problems requiring progestogenic supplementation or therapy as described above. [0098] The present invention also provides novel methods for separating fractions of Rhizoma Chuanxiong, enriched for 3-butyl-4,5-dihydrophthalide, 3-butyl-phthalide and components and co-elutes, with strong progestogenic activity using solvent-solvent partitioning, solid-phase fractionations and high-performance liquid chromatography (HPLC). These methods can be used to standardize and fingerprint Rhizoma Chuanxiong extracts using solvent-solvent partitioning solid phase fractionations, HPLC, mass spectrometry (MS), and nuclear magnetic resonance imaging (NMR). Since the bioactive compounds co-elutes with 3-butyl-4,5-dihydrophthalide and 3-butyl-phthalide, these compounds can be used for the measurement and standardization of the bioactivity Rhizoma Chuanxiong and its extracts. Novel methods have been devised to detect summated bioavailabillty and bioequivalence of multiple steroidogenic compounds in serum, following drug administration to humans and animal models. It has also been established that Rhizoma Chuanxiong extract is an effective progestogenic drug when administered both subcutaneously and orally to animal models. [0000] Validation of in-vitro Reporter Gene Assay for Progestogens [0099] In the progestogen receptor assay of the invention, HeLa cells grown in 24-well microtiter plates were transiently co-transfected with two plasmids using lipofectamine. The first plasmid consisted of DNA encoding the full length human progesterone receptor (PR—B), and the second a progesterone reporter gene (PRE2-TATA-LUC) comprising a luciferase reporter gene driven by two copies of the progesterone response element from the aminotransferase gene. Cells were exposed to the ligands in RPMI 1640 medium, supplemented with 10% charcoal-stripped fetal calf serum, 2 mM L-glutamine, 0.1 mM non-essential amino acids and 1 mM sodium pyruvate for 42-48 hours at 37° C. in a 5% carbon dioxide incubator. Replicate wells were exposed to vehicle only (ethanol) and used as negative controls. After the period of incubation, cells were rinsed with PBS buffer, lysis buffer (Promega Corp) was added, and cell lysates collected for measurement of luciferase activity. Progestogenic activity of the ligands was expressed as fold-increase in luciferase activity compared with control cells exposed to vehicle only. All data points were in triplicate. To determine the sensitivity of progesterone receptor assay, the transfected cells were exposed to increasing doses of one natural (progesterone), and one synthetic (megesterol acetate) progestogen ( FIG. 1 ). Both progesterone and megesterol acetate were able to dose-dependently increase reporter gene activity at doses ranging from 0.1 nM onwards, reaching peak activity at 10 μM, wherein a 300-fold increase in hromonal activity was observed over controls exposed to vehicle only. Thus the assay system of the invention provides an effective way to screen for nano-molar quantities of bioactive progestogens. [0000] Novel Uses of Extracts From Rhizoma Ligusticum Chuanxiong (L.C.) for Progesterone Therapy. [0100] As will be clear from Example 1 below, from among 13 herbs screened, extracts derived from Rhizoma Ligusticum Chuanxiong (L.C.) were identified as possessing strong progestogenic activity. The most potent were L.C. extracts which displayed progestogenic activity comparable to progesterone itself (Example 1). Since progesterone and its derivatives are commonly used for hormone replacement therapy and other progesterone deficient states; crude herbal extracts of Rhizoma Ligusticum Chuanxiong with defined progestogenic activity can be useful to treat health problems requiring progestogen therapy. Such conditions include menstrual disorders, amenorrhoea, menorrhagia, polycystic ovarian syndrome, pregnancy complications, endometriosis, contraception, menopause, endometrial hyperplasia and endometrial cancer. The extracts in combinations with other compounds are also useful for oral contraception, for hormonal replacement therapy, for treating endometriosis, as neuroprotective and neuroregenerative agents in stroke and traumatic brain injuries. [0000] Novel Methods to Efficiently Extract Compounds From Rhizoma Ligusticum Chuanxiong That Specifically Activate the Progesterone Receptor. [0101] Various combination of ethanol/water, methanol/water and water alone, were tested to determine the best solvent for extracting progestogenic compounds from L.C. Extraction with 100% ethanol proved to be the most effective method for producing a crude extract with the highest progestogenic activity, comparable to progesterone itself (100 nM) (Table 2). In contrast, extraction with methanol resulted in activity that was only one-third of 100% ethanol. Extraction with water resulted in an inactive extract. The method of extraction comprising soaking of powdered L.C. in 100% ethanol for 5-7 days at 37° C., that results in L.C. crude extract with maximal progestogenic activity is a novel and non-traditional method. It was also observed that while crude L.C. alcoholic extract has strong progestogenic activity, it does not have estrogenic, glucocorticoid or androgenic activity. Thus it is clear that L.C. extract contains compounds that can specifically activate the progesterone receptor but not other closely related members of the steroid receptor family. Moreover it has an additive effect on progesterone action but has no antagonistic effects on the action of progestogens, estrogens, glucocorticoids or androgens. L.C. extracts prepared in the above manner are therefore particularly useful in health conditions in which pure and specific progestogenic effects are required and where cross reaction with other steroid receptor are contraindicated. [0000] Predicted Therapeutic Serum Levels and Effective Oral Doses in Women. [0102] It is believed that the crude L.C. extract and progesterone act through the same molecular mechanisms since their activity are blocked by the progesterone antagonist RU486 in an identical manner (Example 4). Thus the amount of L.C. required to achieve therapeutic effects can be inferred by comparison with the biological activity of physiological levels of progesterone. The range of serum progesterone concentrations in the human luteal phase is 15 to 90 nM, and these doses of progesterone elicit 150- to 200-fold increases in reporter gene activity ( FIG. 1 ). Comparable 150- to 200-fold increases in reporter gene activity can be obtained with 6.25 μg/ml to 100 μg/ml of L.C. ( FIG. 2 ), suggesting that these doses of L.C. represent therapeutic serum dose ranges. [0103] Assuming 100% absorption and distribution to the total blood volume of 5000 ml, the oral dose of L.C. crude extract required for therapeutic effect is predicted to be between 31.25 mg to 500 mg. These doses of L.C. crude extract can be administered orally to treat conditions requiring progesterone replacement or supplementation as discussed above. [0000] New Methods to Purify L.C. Fractions that are Highly Enriched for Progestogenic Activity [0104] The present invention also provides a novel method to obtain L.C. fractions that are enriched for progestogenic activity. Such bioactive fractions are obtained by performing solid phase extractions using reverse phase C18 or Diol matrices in glass columns (Example 7). Using reverse phase C18 matrix, progestogenic activity is mainly present in fractions eluted with 80% to 100% methanol. With dry-packed Diol columns, maximal activity was observed with fractions eluted with 30% EtoAc:70% DCM, and lesser degrees of activation with the 100% DCM and 60% EtoAc:40% DCM elutes. Removal of unwanted annins can be achieved by first partitioning these into the butanol and water fractions, using solvent/solvent partitioning (Example 8). [0105] Further purification if desired can be achieved using preparative HPLC. In this method a ThermoQuest Hypurity Elite C18 column and a isocratic mobile phase of 45% ACN:55% water can be used. Under these conditions, purified fractions can be expected to exhibit typical HPLC chromatograms as demonstrated in Example 10. In one manifestation, crude extract is first put through solvent/solvent partition to remove tannins, and then eluted through Diol solid phase columns using polar solvents like Hexane and DCM (Example 9). The elute when subjected to HPLC, separates into highly purified subfractions with strong progestogenic activity (Example 10). The present invention also provides for reproducible novel methods to obtain L.C. extracts with defined purity, consistency and biological activity. [0106] These highly purified L.C. extracts can be use to treat conditions requiring progesterone therapy, supplementation or replacement. Such conditions include menstrual disorders, amenorrhoea, menorrhagia, polycystic ovarian syndrome, pregnancy complication, endometriosis, contraception, menopause, endometrial hyperplasia and endometrial cancer. The extracts in combinations with other compounds are also useful for oral contraception, for hormonal replacement therapy, for treating endometriosis, as neuroprotective and neuroregenerative agents in stroke and traumatic brain injuries. [0000] New Methods for Quality Control and Standardization of L.C. Extracts [0107] A key problem in botanical drugs is the lack of methods to standardize and quality control raw materials, herbal decoctions, the manufacturing process and the finished herbal products. Discovery of progestogenic properties of L.C. herbal extract will enable a person skilled in the art to use this property in appropriate cell-based or other assays to measure potency, purity and quality of the raw herbs and other manufactured herbal products derived from it. For example, progestogenic effects of the herbs can be measured with progestogenic-reporter gene assays in cell lines, and with ligand-binding assays; among others. [0108] It has also been observed that characteristic HPLC conditions can be used to fingerprint L.C. herbal extracts. In one manifestation, L.C. extracts after preliminary solvent partition and solid phase extraction, can be subjected to HPLC C18 analysis (Example 10) resulting in typical HPLC chromatograms with distinct subfraction ( FIG. 10 ). Since the biological activity of each subfraction has been documented, these characteristic HPLC patterns, especially peaks corresponding to the relative quantity and resolution of each subfraction, can be used to standardize L.C. herbal extract. [0109] If a higher level of standardization is required, these HPLC fractions can be subjected to NMR analyses, whereby characteristic patterns and chemical shifts can be observed ( FIG. 12A , B, C, D). Those skilled in the art will realize that these methods of purification of active compounds can be adapted for standardization of the biological effect of the L.C. extracts. The methods of the present invention also enable those skilled in the art to devise methods for standardization and quality control of L.C. extracts using bioassays, solid phase fractionation, HPLC and NMR fingerprinting. [0000] Discovery of the Progestogenic Effects of Senkyunolide (A) and/or 3-butyl-phthalide and/or Minor Components Co-Eluting with Them. [0110] Two known phthalides, 3-butyl-4,5-dihydrophthalide and 3-butyl-phthalide were purified, isolated and identified from L.C., along with components which co-elute with them, as potent activators of the progesterone receptor. Those skilled in the art will realize that the descriptions contained herein provides novel methods for measurement and standardization of the bioactivity L.C. and its extracts based on the presence of 3-buty-4,5-dihydrophthalide and 3-butyl-phthalide, 3-butyl-4,5-dihydrophthalide and 3-butyl-phthalide, or components which co-elute with them, or herbal extracts enriched for them, are also useful for hormone replacement therapy and the treatment of human or animal health problems requiring progestogenic supplementation or therapy. Products derived from 3-buty-4,5-dihydrophthalide and 3-butyl-phthalide, or components which co-elutes with them, are also expected to exhibit progestogenic effects and therefore can be used for progesterone therapy [0000] Novel Methods to Detect Summated Activity of Multiple Steroidogenic Compounds in Serum Following Drug Administration to Animal Models. [0111] Novel methods to perform pharmacokinetic and/or bioequivalence studies in human or in animal models have also been provided herein. These depend on the use of simple, robust techniques to precipitate proteins and extract bioactive small molecules from serum following parenteral or oral administration to animal models. The summated bioactivity of these molecules can then be tested in the receptor-based bioassay of the invention. Total biological activity of these extracted small molecules when compared to reference pharmaceutical compounds, enables the determination of bioequivalence. The assay of the present invention is useful as a biomarker of progestogenic action that can predict actual physiological changes due to progesterone in animals and in the human. The assay of the invention can measure progestogenic activity accurately and rapidly in days, compared to 4-8 weeks for traditional animal models of progestogenic activity, like the pregnancy maintenance and endometrial transformation models. The present invention is of use in the pharmaceutical industry where a rapid and discriminating biomarker to predict of the efficacy potential steroid-active drugs in-vivo is required. Since many steroidal pharmaceutical compounds are coming off patent, generic drug manufacturers need to prove bioequivalence to regulatory authorities. The present invention has great utility in this regard as a rapid and relatively inexpensive way to determine the absorption, distribution, metabolism, bioavailability and bioequivalence of pure compounds or complex mixtures compared to reference pharmaceutical compounds. [0000] Proof of Principle that L.C. Extract is an Effective Progestogenic Drug When Administered Both Subcutaneously and Orally [0112] The data in Examples 12 and 13 prove that L.C. ethanolic extract is efficiently absorbed when administered orally, that it remained biologically active in serum after absorption in the intestinal tract, and after the first-pass effect in the liver. Because the effect of L.C. declined rapidly after 5 hours (Example 13), it is believed that a 6 hourly (4 times a day) oral dosing regime will be required to maintain high progesterone activity throughout the day. MPA is used at a dose of 50 mg/weekly (7.1 mg/day) for endometriosis which is roughly equivalent to the dose of MPA (10 mg) in our experiments. Since L.C. can achieve a therapeutic equivalence of MPA 10 mg if administered at a dose of 2 gm 6 hourly, the preferred dosage for LC crude extract for therapeutic use in humans would be about 250 mg to 5 gm every 6 hours or 1 gm to 30 gm per day. The use of purified extracts enriched for bioactive progestogens would reduce the dose further. It has also been established in animal models that the progestogenic herbal LC extract is effective when administered subcutaneously or orally. The maximum progestogenic effect of the extract of the invention is equivalent to that observed with the gold standard progestogenic drug, Depo-provera. L.C. at the above doses can therefore be used for the same indications as Depo-provera, and these include abnormal menstrual bleeding, endometriosis, contraception, menopausal vasomotor symptoms, endometrial and renal carcinoma, and breast cancer. [0113] The present invention will now be described with reference to the following examples, which are illustrative and should not be construed as limiting the scope of the invention in any manner. EXAMPLE 1 Screening of Herbs for Progestogenic Activity [0114] To begin the search for phyto-progestogens in Traditional Chinese herbal medicines, The Pharmacopoeia of the People's Republic of China (1997) was consulted and 13 herbs reported to have “uterotonic activity” were selected for screening. Separate portions of the different chosen herbs were extracted with respective different concentration of solvents: 70% and 100% ethanol and 70% and 100% methanol. This was carried out by first powdering the herbs, mixing with the solvent, and allowing the mixture to soak for 5-7 days at 37° C., after which the respective extracts in the supernatant were filtered with Whatman Grade I (11 μm pore size) filter paper. The herbal residues were re-extracted a second time with the same solvent for 2-3 hours. Filtered extracts were combined and dried in a rotary evaporator. This process was repeated with different combinations of solvents, namely 50%, 70% and 100% ethanol in water; and 70% and 100% methanol in water for each of the 13 selected herbs. Dried extracts were weighed and re-suspended in 100% ethanol or methanol to a concentration 50 mg/ml. Each herbal extract was screened for progestogenic activity in-vitro at a final concentration of 50 μg/ml. [0115] Of the 13 herbal extracts screened, Rhizoma Ligusticum Chuanxiong (L.C.) displayed the greatest progestogenic activity. The herb L.C., extracted with a 100% ethanol, demonstrated a 323-fold higher activity compared to controls exposed to vehicle alone as shown in Table 1. This was about 80% of the progestogenic activity observed with progesterone (100 nM). In comparison, the other 11 extracts did not activate the PR. Thus it was discovered fro the first time that potent phyto-progestogens are present in extracts from the dried rhizome of L.C., a traditional Chinese herb. TABLE 1 Progestogenic activity of selected herbal extracts using PR and PRE2- TATA-LUC reporter gene in HeLa cells Progestongenic Percentage activity activity, (Fold-induction compared compared to 100 nM Herbal extracts to controls) Progesterone (%) Rhizonia Ligusticum Chuanxiong 323.39 79.86 Fructus Aurantii 1.81 1 Radix Glycyrrhizae 1.77 1 Rhizoma Corydalis 1.15 0.36 Rhizoma Atractylodis Marcocephalae 0.52 0.34 Radix Astragali 1.62 0.34 Radix Achyranthis Bidentatae 0.94 0.29 Herba Schizonepetae 1.31 0.27 Rhizoma seu Radix Notopterygii 0.49 0.27 Radix Peaoniae Alba 0.43 0.22 Concha Margaritifera Usta 0.39 0.12 Cortex Magnoliae Officinalis 0.27 0.05 EXAMPLE 2 Method for Extraction of Progestogenic Compound(s) From L.C. [0116] Various combinations of ethanol/water, methanol/water and water alone were tested to determine the best solvent for extracting progestogenic compounds from L.C. under conditions described in example 1. Extraction with a 100% of ethanol was the most effective method for producing a crude extract with the highest progestogenic activity, comparable to that of progesterone itself (100 nM) (Table 2). In contrast, extraction with 100% methanol resulted in activity that was only one-third of 100% of ethanol. Extraction with water resulted in an inactive extract. This established a non-traditional method for extraction using 100% ethanol and repeated soaking for 5-7 days at 37° C. that resulted in a L.C. crude extract with maximal progestogenic activity. In all subsequent experiments, extraction was performed with this method. TABLE 2 Progestogenic activity LC extracted with indicated solvents with the use of PR and PRE2-TATA-LUC reporter gene In HeLa cells. L.C. crude extracts Progestogenic adivity (% to PG 100 mM)  70% Ethanol 48.17 100% Ethanol 79.86 100% Methanol 23.39 100% Water 0.53 EXAMPLE 3 Effect of L.C. Crude Extract in Comparison with Progesterone and Predicted Therapeutic Dose Ranges [0117] The same methods as in Example 1 and 2 were adopted. The progestogenic activity of L.C. crude extract was compared to a physiological concentration of PG (100 nM) ( FIG. 2 ). Doses of L.C. from 6.25 μg/ml to 100 μg/ml resulted in a dose-dependent increase in progestogenic activity. The maximal activity of L.C. crude extract, at 50 μg/ml, was equivalent to that observed for 100 nM progesterone. Since the maximum serum concentration of progesterone in women is 90 nM, it is predicted that a serum L.C. level of 50 μg/ml would be sufficient to achieve maximal therapeutic progestogenic effect. The physiological range of progesterone concentrations in the human luteal phase is 15 to 90 nM, and these doses of progesterone elicit 150- to 200-fold increase in reporter gene activity ( FIG. 1 ). Comparable 150- to 200-fold increases in reporter gene activity are obtained with 6.25 μg/ml to 100 μg/ml of L.C. ( FIG. 2 ), suggesting that these doses of L.C. represent therapeutic serum dose ranges. Assuming 100% absorption and serum distribution to the total blood volume of 5000 ml, the oral dose of L.C. crude extract required for therapeutic effect is predicted to be between 31.25 mg to 500 mg. EXAMPLE 4 Inhibition of L.C. and Progesterone Action by the Progesterone Receptor Antagonist, RU486, and Possible Therapeutic Uses of L.C. [0118] The same methods as in Example 1 and 2 were adopted. To determine the mechanism whereby L.C. activates the progsterone receptor, the effect of RU486 (a specific progesterone receptor antagonist) on L.C. activity was examined. The progestogenic effect of L.C. was dose-dependently inhibited by RU486, in a manner similar to that observed for progesterone itself ( FIG. 3 ). Thus doses of RU486≧0.01 nM were able to completely inhibit the activity of fixed concentrations of both L.C. crude extract and progesterone. Since RU 486 acts by binding competitively to the ligand-binding pocket of the PR LBD, our data confirm that components in L.C. activate PR by specifically binding to the PR LBD in a manner similar to that for progesterone itself. Given that L.C. extract and progesterone act through similar mechanisms, L.C. herbal extract can be used for health problems for which progesterone replacement or supplementation is thereapeutically indicated. Such conditions include menstrual disorders, amenorrhoea, menorrhagia, polycystic ovarian syndrome, pregnancy complications, endometriosis, contraception, menopause, endometrial hyperplasia and endometrial cancer. The extracts or phyto-progestogens from L.C., alone, or in combinations with other compounds, are also useful for oral contraception, for hormonal replacement therapy, for treating endometriosis, neuro-protective and neuro-regenerative agents in stroke and traumatic brain injuries. EXAMPLE 5 Additive Effect of L.C. on Progesterone Activity [0119] The same methods as in Example 1 and 2 were adopted. The presence of L.C. did not block the activity of progesterone. Addition of increasing doses of PG to a fixed concentration (50 μg/ml.) of L.C. produced an additive increase in progestogenic activity ( FIG. 4 ) suggesting that L.C. can be used to boost the effects of endogenous progesterone. EXAMPLE 6 Absence of Agonistic and Antagonistic Activity on Other Steroid Receptors, GR, AR, ERα and ERβ. [0120] The same methods as in Example 1 and 2 were adopted. Although L.C. exhibits progestogenic activity in a dose-dependent manner, doses of L.C. from 3.125 μg/ml to 50 μg/ml did not result in any activation of GR, AR, ERα and ERβ reporter gene systems ( FIG. 5 ). Similarly, the introduction of increasing concentrations of L.C crude extract did not elicit significant synergistic or antagonistic effect on the GR, AR, ERα and ERβ reporter gene systems in the presence of HC (1 nM), DHT (1 nM), and E2 (1 nM) ( FIGS. 6 A , B, C and D) respectively. The absence of cross-receptor activation with closely-related steroid receptors suggests that the action of L.C. was highly specific to the progesterone receptor. EXAMPLE 7 Solid Phase Fractionation of L.C. with the Use of C18 and Diol Columns [0121] To identify the bioactive compounds in L.C. crude extract, bioassay-guided fractionation was performed. Preliminary isolation was performed with solid phase C18 and Diol columns. [0122] Reverse phase C18 powder was packed into glass columns, after which 4 mls of L.C. (50 mg/ml) was applied. Elution of L.C. fractions was performed with solvents of decreasing polarity in the following order: 30% MeOH, 80% MeOH, 100% MeOH and finally DCM. The fractions were collected separately dried down, reconstituted in ethanol and their bioactivity measured. Progestogenic activity was mainly present in fractions eluted with 80 to 100% methanol in water ( FIG. 7A ). Smaller amounts were presen tin the 30% methanol fraction. In contrast, negligible activity was observed with 100% DCM, the most hydrophobic solvent. [0123] Fractionation was also performed with Diol, a silica matrix. Diol powder was added to L.C. (50 mg/ml) extract and the mixture dry-packed on top of a Diol column. Elution was performed using a least polar solvent to the most polar solvent. The elution solvents used were, 100% Hexane (D1), 50% DCM: 50% Hexane (D2), 100% DCM (D3), 10% EtoAc: 70% DCM (D4), (D5), 100% EtoAc (D6), 20% MEOH: 80% EtoAc (D7) and finally 100% MeOH (D8). FIG. 7B shows the progestogenic activity of the fractions obtained with PR bioassay as described in FIG. 1 . Maximal activity was observed with D4 (30% EtoAc: 70% DCM) fraction, and lesser degrees of activation with D3 (100% DCM) and D5 (60% EtoAc: 40% DCM). [0124] These studies suggest that the bioactive compounds were of intermediate polarity since they co-elute with solvents of mixed polarity in both the diol and reverse phase C18 matrices. Studies herein also suggest that Diol and reverse phase C18 columns used with solvents of intermediate polarity can be used to obtain L.C. fractions that are enriched for progestogenic compounds. EXAMPLE 8 Solvent/Solvent Partition [0125] To further define the conditions under which separation of progestogenic fractions can be obtained, solvent/solvent partition of L.C. extracts was performed. Crude L.C. extract in ethanol (360 ml) was mixed with water (40 ml) to give a 90% ethaol solution, in which 400 ml of hexane was added. The hexane was removed and the ethanol:water ratio adjusted to 3:2 to obtain optimal partition of DCM/ethanol-water interface. An equi-volume of DCM was added to the mixture. After this separation, DCM layer was removed and butanol was added. The butanol layer was separated from the water layer. All 4 solvent fractions were dried down, weighed, and their constituents tested for the PR bioactivity. Under these conditions, the majority of the bioactivity resided in the DCM and hexane fractions ( FIG. 8 ). The most potent was the DCM fraction, where dose-dependent increase in PR activity was observed such that 25 μg/ml of this fraction was equivalent to 100 nM of progesterone. The hexane fraction also exhibited strong bioactivity and 50 μg/ml of this fraction was equivalent to 100 nM of progesterone. In comparison, the buanol and water fractions did not show any bioactivity. Since tannins (substances known to interfere with receptor-based assays) partition mainly to butanol and water fractions, this method is useful for removing these unwanted tannins from bioactive fractions. The method of solvent/solvent partition can therefore be used to obtain DCM and hexane L.C. fractions, enriched for progestogenic compounds, which are free of tannins. EXAMPLE 9 Second Separation Step of L.C. After Solvent Partition, with the Use of the Diol Solid Matrix [0126] As the DCM fraction obtained from solvent/solvent partition exhibited greatest activity, it was used for further bioassay-guided fractionation. The DCM fraction was subected to Diol solid-phase extraction and eluted with solvents of increasing polarity as described in Example 7. The fractions were collected and analyzed for bioactivity. Fractions D1, D2 and D3, eluted with 100% Hexane, Hexane/DCM (1:1) and 100% DCM respectively, showed the most progestogenic activity ( FIG. 9 ). Thus the combination of solvent/solvent partition (described in Example 9 above) and Diol Solid Phase Extraction, using non-polar solvents like Hexane and DCM, is useful to further purify fractions from L.C. that are enriched for progestogenic compounds. EXAMPLE 10 HPLC Finger Printing of the Fraction D1 From the Diol Column [0127] To further separate the bioactive components of L.C., the Diol fraction D1 (obtained as in Example 9) was subjected to preparative HPLC analyses using a ThermoQuest Hypurity Elite C18 column and a isocratic mobile phase of 45% ACN:55% water. Under these conditions, Diol Fraction D1 exhibited a typical HPLC chromatogram from which 7 distinct subfractions can be recognized ( FIG. 10 ). These subfractions (with elution times as noted in FIG. 10 ) were dried, weighed and their progestogenic activities determined. Progestogenic activity was greatest in subfractions 6 and 7, eluting from 23.1 min to 40 min ( FIG. 11 ). Decreasing amounts of bioactivity was observed in subfractions 5 and 1, with elution periods of 20.51 to 23 min. and 2 to 12.5 min. respectively. In contrast minimal bioactivity was detected in subfractions 2 to 4 eluting from 12.51 to 20.5 min. Our data indicate that more than one compound in L.C. is responsible for the progestogenic activity of L.C., since bioactive subfractions 1 and 5-6 are separated by inactive subfractions. The HPLC chromatogram as shown FIG. 10 can be used as a standard for biological activity of L.C. Under these HPLC conditions, the subfractions 6 and 7 (eluting from 23.1 min to 40 min) can be expected to contain the most potent progestogenic compounds. EXAMPLE 11 NMR Finger Printing of the Fraction 6 obtained From HPLC Fractionation [0128] To identify the bioactive compounds, the HPLC fraction with the highest yield (subfraction 6) was subjected to NMR analysis. A known phthalide, Senkyunolide (A) or 3-butyl-4,5-dihydrophthalide, was identified in subfraction 6, using 1D- and 2D-NMR, 1 H- 1 H COSY, 1 H- 13 C gHSQC spectral analyses ( FIG. 12A , B, C, D). Senkyunolide (A) has the molecular formula C 13 H 16 O 2 corresponding to five double-bond equivalents. The NMR data for senkyunolide (A) revealed resonances consistent with an enter carbonyl carbon ( 13 C 165.0) and a 3,4-disubstituted 1,3 cyclohexadiene ( 1 H δ 5.96, 6.10 and 13 C 130.0, 117.0, 125.0 and 137.5). Evident were resonances consistent with a butyl group ( 1 H δ 1.93, 1.38, 1.38, 0.93 and 13 C 33.0, 27.0, 24.0 and 14.5) and an oxymethine ( 13 C 84.5 and 1 H δ 5.06). Analysis of gHMBC showed important correlations from 1 H δ 2.54 to 13 C 165.0, 137.5, 130.0, 125.0 and 117.0 ppm and 1 H δ 5.06 to 13 C 165.0, 130.0, 125.0, 117.0 and 33.0 and 27.0 ppm. This allowed the gross structure of the compound to be proposed as shown ( FIG. 13A ). This data is consistent with the reported structure (Yu, 1983). Using similar analyses a related second compound, 3-butyl-phthalide ( FIG. 13B ), was characterized in subfraction 6. Analyses of 1D-NMR data show that the principal constituent of subfraction 6 is Senkyunolide (A), constituting 95% of the dried extract by weight. 3-Butyl-phthalide, forming 2% of the extract is a minor constituent. Thus it is very likely that Senkyunolide (A) and/or 3-butyl-phthalide and/or minor co-elutes, are progestogenic and can be used to treat conditions requiring progesterone replacement therapy or supplementation. Furthermore, Senkyunolide (A) and/or 3-butyl-phthalide and/or minor co-elutes, can be used as markers for progestogenic bioactivity in L.C. extracts. EXAMPLE 12 Detection of Progestogenic Activity in Serum Following Drug Administration to Animal Models [0129] L.C. extract was administered to rat models and its progestogenic effect in serum compared with vehicle (negative control) and a reference progestogenic drug, 6α-methyl-17α-hydroxy-progesterone acetate (Depo-provera, MPA). L.C. extract (1 gm/ml), vehicle (1 ml) and MPA (10 mg/ml) were injected subcutaneously to male Sprague-Dawley rats and peripheral blood (150 μl) sampled at indicated time intervals for 24 hours from tail veins. Male rats were selected because of their low endogenous progesterone levels. Collected blood samples were stored at 4° C. until processed. Whole blood was centrifuged at 4° C. for 5 minutes and serum collected. Two parts of extraction solvent, consisting of acetonitrile:methanol (3:1), was added to one part of serum and the mixture vortexed for 30 sec to precipitate proteins. The precipitate was then removed by centrifugation at 10,000G for 5 min. The clear supernatant containing bioactive small molecules was stored at −20 C for bioassay. Subsequently 6 μl of this supernatant (equivalent to 2 μl of serum from the rat) was used for the progestogenic bioassay. To increase the assay sensitivity, HeLa cells were pre-exposed to charcoal-stripped serum in phenol free RPMI for at least 7 days prior to performing the assay. As shown in FIG. 14 , progestogenic activity in serum rose to a peak within 30 min of subcutaneous injection of the reference drug MPA. The peak progestogenic activity observed with MPA was maintained for more than 24 hours and was about 5-fold higher than serum from rats administered vehicle only. This level of progestogenic activity is equivalent to the maximum bioactivity of MPA extract when tested in-vitro (black bar). Serum from rats injected with LC displayed a slower but still significant rise in progestogenic activity reaching a peak after 270 min. At its peak, LC activity was comparable to that observed with saturating doses of MPA in-vitro and in-vivo. High levels of progesterone activity was observed from 120 to 330 min after injection and declined to 31% of peak levels after 24 hours. This proves the principle that the technology described in this example can accurately quantify the summated bioactivity of progestogenic compounds in serum following administration of progestogenic drugs to animal models. EXAMPLE 13 Progestogenic Activity of LC in a Rat Model Following Oral Administration [0130] To determine the pharmacokinetics and bioequivalence of LC, we measured the progestogenic effect of rat serum sampled at defined time points after oral doses of LC (2 g/2 ml), MPA (10 mg/2 ml), and vehicle only (2 ml 60% ethanol). Serum samples were extracted and progesterone effect measured as in Example 12. Rats fed MPA exhibited a rapid and highly significant rise in serum progestogenic action reaching a peak after 120 min ( FIG. 15 ). High levels of progestogenic effect were maintained throughout the 24 hour of sampling. In contrast, rats administered vehicle only exhibited baseline progesterone activity that was about 5-fold lower than that observed with MPA. Rats fed LC showed a steady rise in progesterone activity reaching a peak after 210 min. This peak was maintained for an hour before dropping rapidly to baseline after 300 min. Rats fed either MPA or LC displayed peak progesterone activity that was comparable to that observed with saturating doses of progesterone in-vitro. Based on these pharmacokinetic/pharmacodynamic profiled, we conclude that oral doses of LC can result in maximal progesterone activity in serum. In our model, significant effects were observed after 60 min, peaks at 210 min and returns to baseline after 270 min following LC administration. These data prove that LC ethanolic extract is efficiently absorbed when administered orally and that it remains biologically active in serum after absorption in the intestinal tract and after the first-pass effect in the liver. Because the effect of LC declines rapidly after 5 hours, we conclude that a 6 hourly (4 times a day) oral dosing regime might be required to maintain high progesterone activity throughout the day. MPA is used at a dose of 50 mg/weekly (7.1 mg/day) for endometriosis which is roughly equivalent to the dose of MPA (10 mg) in our experiments. Since LC can achieve a therapeutic equivalence of MPA 10 mg if administered at a dose of 2 gm 6 hourly, the preferred dosage for LC crude extract for therapeutic use in humans would be about 250 mg to 5 gm every 6 hours, or 1 gm to 30 gm per day. The use of purified extracts enriched for bioactive progestogens would reduce the dose further. [0000] Advantages of the Invention [0000] A) Discovery of extracts from the Rhizoma Chuanxiong, the dried rhizome of Ligusticum chuanxiong Hort., a traditional Chinese herb, which specifically activates the progesterone receptor (phyto-progestogens). B) Novel methods to efficiently extract progestogenic compounds from Rhizoma Chuanxiong. C) Prediction of therapeutic serum levels for Rhizoma Chuanxiong crude extract, prepared as by methods described in (B), as being between 6.25 μg/ml to 100 μg/ml, and the effective oral dose being between 31.25 mg to 500 mg. D) Use of extracts, containing these phyto-progestogens from Rhizoma Chuanxiong, to treat health problems requiring progesterone therapy, supplementation or replacement including fetal support, menstrual disorders, amenorrhoea, menorrhagia, polycystic ovarian syndrome, pregnancy complications, endometriosis, contraception, menopause, endometrial hyperplasia and endometrial cancer. E) Use of extracts, containing these pyto-progentogens from Rhizoma Chuanxiong, alone, or in combinations with other compounds, for oral contraception, for hormonal replacement therapy, for treating endometriosis, neuroprotective and neuroregenerative agents in stroke and traumatic brain injuries. F) Discovery of compound(s) co-eluting with two known phthalides, 3-butyl-4,5-dihydrophthalide and 3-butyl-phthalide, from Rhizoma Chuanxiong which strongly activates the progesterone receptor. G) Use of compound(s), which co-elutes with 3-butyl-4,5-dihydrophthalide and 3-butyl-phthalideor or herbal extracts enriched for them, for hormone replacement therapy and the treatment of health problems requiring progestogenic supplementation or therapy as described in (B) and/or (C). H) New and simple methods to separate fractions of Rhizoma Chuanxiong, enriched for 3-butyl-4,5-dihydrophthalide, 3-butyl-phthalide and components and co-eluates, with strong progestogenic activity using solvent-solvent partitioning, solid-phase fractionations and high-performance liquid chromatography (HPLC). I) Novel methods for standardization and fingerprinting of Rhizoma Chuanxiong extracts using solvent-solvent partitioning solid phase fractionations, HPLC, mass spectrometry (MS), and nuclear magnetic resonance imaging (NMR). J) Novel methods for measurement and standardization of the bioactivity Rhizoma Chuanxiong and its extracts based on the presence of 3-butyl-4,5-dihydrophthalide and 3-butyl-phthalide. K) Novel methods to detect summated bioavailability and bioequivalence of multiple steroidogenic compounds in serum following drug administration to humans and animal models. 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A., Mendoza-Meneses M., O'Malley B. W., Conneely O. M. 1998. Mutal and intercompartmental regulation of estrogen and progesterone receptor expression in the mouse uterus. Biol. Reprod. 59:1143-52. Tibbettes T. A., Conneely O. M., O'Malley B. W. 1999. Progesterone via its receptor antagonizes the pro-inflammatory activity of esterogen i the mouse uterus. Biol. Reprod. 60:1158-65. Vermeer H, Hendriks-Stegeman B I, Van Den Brink C B, Van Der Saag P T, Van Der Burg B, Van Buul-Offers S C., Jansen M. 2003 A novel specific bioassay for the determination of glucocorticoid bioavailability in human serum. Clin Endocrinol (Oxf). 2003 July; 59(1):49-55. Yu S. R., Gao N. N., Li L. L., Wang Z. Y., Chen Y., Wang W. N. 1988a. The protective effect of 3-butyl phthalide on rat brain cells. Yao Xue Xue Bao. 23(9):656-61. Yu S. R., Gao N. N., Li L. L., Wang Z. Y., Cheu Y., Wang W. N. 1988b. Facilitated performance of learning and memory in rats by 3-n-butyl phthalide. 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A method of extracting phytoprogestogenic compounds from herbs and their use in preparing a medicament for treating humans requiring progesterone replacement or supplement. Assay systems to quantify progesterone and progestogenic receptor activity and a method for assembling a kit for the assays are also provided.

TECHNICAL FIELD [0001] The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device in which black is displayed when a vertical electric field is applied to liquid crystal with negative dielectric anisotropy, and white is displayed when a horizontal electric field is applied to this liquid crystal. BACKGROUND ART [0002] Liquid crystal display (LCD) devices are devices that control the transmission or blockage of light (turning ON/OFF the display) by controlling the orientation of liquid crystal molecules having birefringence. Examples of liquid crystal orientation modes of LCDs include the twisted nematic (TA) mode in which liquid crystal molecules having positive dielectric anisotropy are oriented so as to be twisted at 90° when viewed from a direction normal to the substrate, vertical alignment (VA) mode in which liquid crystal molecules having negative dielectric anisotropy are oriented vertically with respect to the substrate surface, and in-plane switching (IPS) mode and fringe field switching (FFS) mode in which a horizontal electric field is applied to liquid crystal layer to orient liquid crystal molecules having positive dielectric anisotropy horizontally with respect to the substrate surface. [0003] In VA mode, display is performed by using liquid crystal having negative dielectric anisotropy and applying a vertical electric field to the liquid crystal molecules, which are oriented vertically with respect to the substrate surface, such that the liquid crystal molecules take on a more horizontal orientation, but when the liquid crystal molecules are viewed at different angles, the apparent birefringence thereof differs, which results in narrow viewing angle. [0004] A method in which the orientation of the liquid crystal is partitioned by a technique of applying pretilt angles using a polymer (polymer sustained alignment (PSA)). A method of partitioning the orientation of the liquid crystal is proposed in which a voltage is applied to a liquid crystal layer containing a photocurable monomer, the liquid crystal molecules are oriented in multiple azimuth directions along slits formed in the pixel electrodes, and ultraviolet light is radiated when the orientation azimuths are stable to cure the photocurable monomers, thereby fixing the azimuth directions of the liquid crystal molecules (see Patent Document 1, for example). [0005] In IPS mode, display is performed by relying on the movement of liquid crystal molecules towards a horizontal orientation in response to a horizontal electric field formed between a pair of comb-shaped electrodes. In FFS mode, display is performed by relying on the movement of liquid crystal molecules towards the horizontal orientation in response to a horizontal electric field (fringe field) formed between a common electrode and a pixel electrode provided over the common electrode across an insulating layer. Although the viewing angle is improved in IPS mode and FFS mode, it is difficult to attain a contrast ratio comparable to that attained in VA mode. [0006] Also, in recent years, a new method has been proposed in which the driving of liquid crystal is controlled by generating a vertical electric field in addition to the conventional horizontal electric field in a liquid crystal display device that performs display using a horizontal electric field as done in IPS mode and FFS mode (see Patent Documents 2 and 3, for example). RELATED ART DOCUMENTS Patent Documents [0007] Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2007-286642 [0008] Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2002-23178 [0009] Patent Document 3: Japanese Patent Application Laid-Open Publication No. 2000-356786 SUMMARY OF THE INVENTION Problems to be Solved by the Invention [0010] The present invention takes into account the above-mentioned situation, and an object thereof is to provide a liquid crystal display device having excellent viewing angle characteristics while having a high contrast ratio in a display mode using a horizontal electric field and a vertical electric field. Means for Solving the Problems [0011] The inventors of the present invention have focused on a configuration in which a total of three types of electrodes are used in one liquid crystal display device having a liquid crystal layer containing liquid crystal having negative dielectric anisotropy: a uniformly planar first electrode, and a second electrode having a plurality of teeth and a plurality of slits, provided in a layer different from the first electrode across an insulating layer, the first electrode and the second electrode being provided on one substrate; and a third electrode provided on a substrate across the liquid crystal layer from the aforementioned substrate. [0012] The inventors of the present invention found that it is possible to change the azimuth direction of the liquid crystal molecules while keeping them horizontal with respect to the substrate surface by forming a vertical electric field (electric field formed in the thickness direction of the liquid crystal layer) in the liquid crystal layer by applying a voltage between the first electrode and the third electrode while forming a horizontal electric field by also applying a voltage between the second electrode and the first electrode. The “azimuth of the liquid crystal molecule” represents the long axis direction of the liquid crystal molecule when the substrate is viewed in a plan view. [0013] As a result of further study, the inventors of the present invention also found that by setting the potential difference between the second electrode and the first electrode to a certain value while applying a voltage between the first electrode and the third electrode, the liquid crystal molecules orient to azimuth directions parallel to the lengthwise directions of the slits, thereby displaying a black image (display with the lowest transmittance). When the potential difference between the second electrode and the first electrode is increased, the liquid crystal molecules rotate while maintaining a horizontal orientation with respect to the substrate surface, and thus, the liquid crystal molecules are at an angle with respect to the lengthwise direction of the slit formed in the second electrode, thereby displaying a grayscale image or even a white image (image with the highest transmittance). [0014] According to this method, it is possible to attain a liquid crystal display device having excellent viewing angle characteristics and high contrast ratio in a display mode differing from VA mode and FFS mode. Furthermore, the inventors of the present invention found that when the potential difference between the second electrode and the first electrode is greater than the potential difference between the first electrode and the third electrode, a vertical electric field is no longer formed and it is not possible to attain a desired orientation, and that by maintaining a state in which the potential difference between the first electrode and the third electrode is greater than the potential difference between the second electrode and the first electrode, it is possible to attain an excellent viewing angle and contrast ratio in this display mode. [0015] Thus, the inventors of the present invention have arrived at a solution that elegantly solves the above-mentioned problem, and have arrived at the present invention. [0016] In other words, one aspect of the present invention is a liquid crystal display device including: a first substrate and a second substrate opposing each other; and a liquid crystal layer sandwiched between the first and second substrates, wherein the liquid crystal layer contains liquid crystal molecules having negative dielectric anisotropy, wherein the first substrate includes a uniformly planar first electrode, a first insulating layer, and a second electrode provided in a different layer from the first electrode across the first insulating layer, wherein the second electrode has a plurality of teeth and a plurality of slits, wherein the second substrate includes a uniformly planar third electrode, and wherein V 1 , V 2 , and V 2 — B satisfy the following formula (1), where a potential between the first electrode and the third electrode is V 1 , a potential between the first electrode and the second electrode is V 2 , and a potential between the first electrode and the second electrode at a lowest gradation is V 2 — B . [0000] (Formula 1) [0000] 0<| V 2 — B |≦|V 2 |<|V 1 |  (1) [0017] The unit for V 2 — B , V 1 , and V 2 is volts (V). [0018] The liquid crystal layer contains liquid crystal molecules having negative dielectric anisotropy. The liquid crystal molecules have the characteristic of orienting in a direction perpendicular to the electric field when an electric field is applied. [0019] The second electrode has a plurality of teeth and a plurality of slits, and is provided in a layer different from the first electrode across the first insulating layer. According to this configuration, it is possible to form a horizontal electric field (fringe field) between the second electrode and the first electrode. [0020] Different potentials are supplied respectively to the first electrode and the third electrode. As a result, a potential difference is formed between the third electrode and the first electrode, between the first electrode and the second electrode, and between the third electrode and the second electrode, thereby forming a vertical electric field and an oblique electric field. [0021] By V 2 changing within a range satisfying |V 2 |<|V 1 |, the liquid crystal molecules can rotate while oriented in the horizontal direction with respect to the substrate surface, thereby allowing an image ranging in gradation from black to white to be displayed. [0022] |V 2 | is greater than 0. This means that when a black image is displayed, some potential difference is present between the first electrode and the second electrode. In a general liquid crystal display device of the VA mode, FFS mode, or the like, a black image is displayed when the potential difference between the pair of electrodes for applying a voltage to the liquid crystal layer is 0V, but in the present invention, when using both a vertical electric field and a horizontal electric field, the lowest transmittance cannot be attained when the potential difference between the first electrode and the second electrode is 0, which is why such a condition has been set. [0023] The first and second substrates included in the liquid crystal display device are a pair of substrates for sandwiching a liquid crystal layer therebetween, and are formed by using insulating substrates made of glass, resin, or the like, for example, as bases and forming on the insulating substrates wiring lines, electrodes, color filters, and the like. In order to maintain a vertical electric field, it is preferable that an overcoat layer (permittivity ∈=3 to 4) that planarizes the uneven surface be formed on the color filters. [0024] It is preferable that the first substrate be an active matrix substrate including active elements. [0025] As long as the liquid crystal display device includes such necessary components, it is possible to appropriately provide other components normally used in liquid crystal display devices. [0026] Below, preferable aspects of the liquid crystal display device will be described. Aspects combining two or more of the individual preferable aspects of the liquid crystal display device disclosed below are also considered to be preferable aspects of the liquid crystal display device. [0027] It is preferable that the value V 2 — B satisfy the following formula (2). [0000] ( Formula   2 ) 0 <  V 2  _B  ≤ ɛ ⊥  d 1 ɛ 1  d LC + ɛ ⊥  d 1   V 1  + 0.5 ( 2 ) [0028] (d LC represents the thickness of the liquid crystal layer, ∈ ⊥ represents a permittivity perpendicular to the director of the liquid crystal, d 1 represents the thickness of the first insulating layer, and ∈ 1 represents the permittivity of the first insulating layer) [0029] If the first insulating layer is made of a plurality of different materials, the permittivity ∈ 1 of the first insulating layer is calculated from the permittivity and thickness of each of the materials. If, for example, the first insulating layer has a first material “a” and a second material “b,” then the permittivity ∈ 1 of the first insulating layer is represented by the following formula (7). [0000] ( Formula   3 ) ɛ 1 = ɛ a  ɛ b  ( d a + d b ) ɛ a  d b + ɛ b  d a ( 7 ) [0030] (d a is a thickness of the first material, ∈ a is the permittivity of the first material, d b is the thickness of the second material, and ∈ b is the permittivity of the second material) [0031] It is preferable that the second substrate have an alignment film, that a second insulating layer be present between the third electrode and the alignment film, and that the value V 2 — B satisfy the following formula (3). [0000] ( Formula   4 ) 0 <  V 2  _B  ≤ ɛ 2  ɛ ⊥  d 1 ɛ 1  ɛ ⊥  d 2 + ɛ 1  ɛ 2  d LC + ɛ 2  ɛ ⊥  d 1   V 1  + 0.5 ( 3 ) [0032] (d LC represents the thickness of the liquid crystal layer, ∈ ⊥ represents the permittivity in the direction perpendicular to the director of the liquid crystal, d 1 represents the thickness of the first insulating layer, d 2 represents the thickness of the second insulating layer, ∈1 represents the permittivity of the first insulating layer, and ∈ 2 represents the permittivity of the second insulating layer) [0033] If the second insulating layer is made of a plurality of different materials, the permittivity ∈ 2 of the second insulating layer is calculated from the permittivity and thickness of each of the materials in a manner similar to the first insulating layer. [0034] By having |V 2 — B | satisfy formula (2) or (3), it is possible to attain excellent black display as described below. [0035] By having the above-mentioned second insulating layer, it is possible to attain a high transmittance even if |V 2 | is low, and thus, the liquid crystal display device can be driven at a low voltage compared to a liquid crystal display device that does not having an insulating layer between the third electrode and the alignment film, as described below. The alignment film on the second substrate has a negligible thickness, and is therefore not included in the second insulating layer. [0036] It is preferable that a width of each of the slits in the second electrode is 2 to 10 μm. Also, it is preferable that a width of each of the teeth in the second electrode be 2 to 10 μm. These ranges are preferred from the perspective of design limits and of achieving a transmittance by applying a sufficient voltage to the liquid crystal layer. [0037] It is preferable that the second electrode have a trunk portion and that the plurality of teeth extend from the trunk portion in a direction perpendicular to a lengthwise direction of the trunk portion while collectively exhibiting linear symmetry about the trunk portion. According to such a structure, when displaying a mid-gradation or white image, it is possible to orient the liquid crystal molecules horizontally in four different azimuth directions, and thus, the viewing angle characteristics can be improved. [0038] It is preferable that at least one of the first substrate and the second substrate has a vertical alignment film. If a second insulating layer is present between the third electrode and the alignment film, then it is preferable that the alignment film on the second substrate be a vertical alignment film. The vertical alignment film is an alignment film that causes liquid crystal molecules to be oriented perpendicularly with respect to the substrate surface when no voltage is being applied, and alignment treatment may be performed on the vertical alignment film. Rubbing treatment, photoalignment, and the like are examples of a method of alignment treatment. Vertical orientation refers to an orientation in which the average initial angle of inclination of liquid crystal molecules with respect to the substrate surface is 60° to 90°, and more preferably 80° to 90°. The “angle of inclination” is the angle of the long axis of the liquid crystal molecule with respect to the substrate surface in a range of 0° to 90°, and the “average angle of inclination” is sometimes referred to as the “tilt angle.” Also, the average angle of inclination of the liquid crystal molecules with respect to the substrates when no voltage is applied is referred to as the “average initial angle of inclination,” and sometimes referred to below as the “pretilt angle.” [0039] It is preferable that the first substrate have a horizontal alignment film with the second substrate having a vertical alignment film, or that the first substrate have a vertical alignment film with the second substrate having a horizontal alignment film. If a second insulating layer is present between the third electrode and the alignment film, then it is preferable that the first substrate have a vertical alignment film with the alignment film on the second substrate being a horizontal alignment film, or that the first substrate have a horizontal alignment film with the alignment film on the second substrate being a vertical alignment film. A horizontal alignment film aligns the liquid crystal molecules in the horizontal direction with respect to the substrate surface when no voltage is applied, and may be formed by applying an alignment treatment such as rubbing treatment or photoalignment. Horizontal orientation refers to an orientation in which the average initial angle of inclination of the liquid crystal molecules with respect to the substrate surface is 0° to 30°, and more preferably 0° to 10°. Effects of the Invention [0040] According to the present invention, it is possible to attain a liquid crystal display device having excellent viewing angle characteristics and high contrast in a display mode using both a vertical electric field and a horizontal electric field. BRIEF DESCRIPTION OF THE DRAWINGS [0041] FIG. 1 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 1 when no voltage is applied. [0042] FIG. 2 is a schematic plan view of one pixel of the liquid crystal display device of Embodiment 1. [0043] FIG. 3 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 when a black image is being displayed. [0044] FIG. 4 is a schematic plan view of one pixel of the liquid crystal display device according to Embodiment 1 when a black image is being displayed. [0045] FIG. 5 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 when a white image is being displayed. [0046] FIG. 6 is a schematic plan view of one pixel of the liquid crystal display device according to Embodiment 1 when a white image is being displayed. [0047] FIG. 7 is a graph showing V-T characteristics of a liquid crystal display device according to Working Example 1. [0048] FIG. 8 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 2 when no voltage is applied. [0049] FIG. 9 is a graph showing V-T characteristics of a liquid crystal display device according to Working Example 2. [0050] FIG. 10 is a cross-sectional image of the liquid crystal display device of Working Example 1 when a white image is being displayed. [0051] FIG. 11 is a cross-sectional image of the liquid crystal display device of Working Example 2 when a white image is being displayed. [0052] FIG. 12 is a graph comparing V-T characteristics of the liquid crystal display devices of Working Example 1 and Working Example 2. [0053] FIG. 13 is a schematic plan view of one pixel of the liquid crystal display device of Embodiment 3. [0054] FIG. 14 is a schematic plan view of one pixel of the liquid crystal display device of Embodiment 4. [0055] FIG. 15 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 5 when no voltage is applied. [0056] FIG. 16 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 6 when no voltage is applied. [0057] FIG. 17 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 7 when no voltage is applied. [0058] FIG. 18 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 7 when no voltage is applied. [0059] FIG. 19 is a graph showing V-T characteristics of the liquid crystal display device shown in FIG. 18 . [0060] FIG. 20 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 8 when no voltage is applied. [0061] FIG. 21 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 8 when no voltage is applied. [0062] FIG. 22 is a graph showing V-T characteristics of the liquid crystal display device shown in FIG. 21 . [0063] FIG. 23 is a schematic cross-sectional view of the liquid crystal display device according to Comparison Example 1 when a white image is being displayed. [0064] FIG. 24 is a schematic plan view of one pixel of the liquid crystal display device according to Comparison Example 1 when a white image is being displayed. [0065] FIG. 25 is a graph showing gamma characteristics at a horizontal azimuth and a polar angle of 60°. [0066] FIG. 26 is a graph showing gamma characteristics of at an oblique azimuth and a polar angle of 60°. DETAILED DESCRIPTION OF EMBODIMENTS [0067] Embodiments are shown below and the present invention is described in further detail with reference to the drawings, but the present invention is not limited to these embodiments. Embodiment 1 [0068] FIG. 1 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 1 when no voltage is applied, and FIG. 2 is a schematic plan view of one pixel of the liquid crystal display device of Embodiment 1. FIG. 1 is also a schematic cross-sectional view of FIG. 2 along the line A-B. In Embodiment 1, the first electrode and third electrode are common electrodes, and the second electrodes are pixel electrodes. [0069] The liquid crystal display device of Embodiment 1 includes a first substrate 10 , a second substrate 20 , and a liquid crystal layer 30 sandwiched between the first substrate 10 and the second substrate 20 . The liquid crystal layer 30 contains liquid crystal molecules 31 having a negative dielectric anisotropy. The first substrate 10 includes a support substrate 11 , thin film transistors (TFTs), data signal lines, scan signal lines, a first common electrode 12 (first electrode), pixel electrodes 14 (second electrodes), an insulating layer 13 (first insulating layer) that electrically separates the first common electrode 12 from the pixel electrodes 14 , and a vertical alignment film 15 . The second substrate 20 includes a support substrate 21 , a second common electrode 22 (third electrode), a vertical alignment film 25 , color filters, and a black matrix. [0070] The plurality of data signal lines 1 extend in the vertical direction of the liquid crystal display device, the plurality of scan signal lines 2 extend in the horizontal direction of the liquid crystal display device, and the TFTs 6 are respectively formed in the vicinity of the respective intersections between the data signal lines 1 and the scan signal lines 2 . The TFTs 6 are each formed of respective portions of the data signal line 1 , the scan signal line 2 , and a drain lead-out wiring line 4 , and of a semiconductor layer 3 , and function as switching elements. The pixel electrodes 14 are connected to the drain lead-out wiring lines 4 extending from the TFTs 6 through contact holes 5 . When the TFT 6 is turned ON by a scan signal supplied through the scan signal line 2 , the semiconductor layer 3 becomes conductive, and a data signal is supplied to the pixel electrode 14 through the data signal line 1 . [0071] The pixel electrode 14 is provided at each region surrounded by the data signal lines 1 and the scan signal lines 2 . The pixel electrode 14 includes a trunk portion 14 a and a plurality of teeth 14 b . The trunk portion 14 a extends to bisect the pixel vertically into two equal parts, and the plurality of teeth 14 b extend from the trunk portion 14 a in a direction perpendicular to the lengthwise direction of the trunk portion. The teeth 14 b are formed to exhibit line symmetry about the trunk portion 14 a . Slits 14 c are present between adjacent teeth 14 b . In Embodiment 1, the pixel electrode 14 has a comb structure in which one end of each slit 14 c is open. Also, in Embodiment 1, no comb-shaped electrode opposing the pixel electrode 14 is provided, and the horizontal electric field (fringe field) is formed only between the pixel electrode 14 and the first common electrode 12 . [0072] It is preferable that the width of the trunk portion 14 a and each of the teeth 14 b be 2 μm to 10 μm, and that the width of each slit 14 c be 2 μm to 10 μm. If the width of the slit is less than 2 μm, then the area of the actual transmissive portion is reduced, but if the width is greater than 10 μm, then the fringe field becomes weaker, which can result in slow switching of liquid crystal molecules. As shown with two double-headed arrows in FIG. 2 , the polarizing plates are arranged in a crossed Nicols state such that the polarizing axes are respectively parallel or perpendicular to the lengthwise direction of the slit 14 c . As for the arrangement of the polarizing axes in the present specification, “substantially parallel” and “substantially perpendicular” include a margin of error of 3°. [0073] The first common electrode 12 is formed in a uniformly planar manner on the first substrate 10 , and the pixel electrodes 14 are formed thereover across the insulating layer 13 . The insulating layer 13 can be made of an organic film including an organic material such as an acrylic resin (permittivity ∈=3 to 4), an inorganic film including an inorganic material such as silicon nitride (permittivity ∈=5 to 7), or the like. The insulating layer 13 is 0.2 to 2 μm in thickness, for example, and more preferably 0.3 to 1.5 μm in thickness. The first common electrode 12 is supplied a common potential of 0V, for example. [0074] The second common electrode 22 is formed in a uniformly planar manner on the second substrate 20 and is supplied a potential of |4|V to |15|V, for example. If the potential difference between the second common electrode 22 and the first common electrode 12 is V 1 , and the potential difference between the first common electrode 12 and the pixel electrode 14 is V 2 , then a potential of |0.3|V to |10|V is supplied to the pixel electrode 14 such that |V 2 | is less than |V 1 |. [0075] The first substrate 10 and the second substrate 20 respectively have vertical alignment films 15 and 25 on surfaces thereof facing the liquid crystal layer 30 . An alignment treatment need not be performed on the vertical alignment films 15 and 25 , but by performing alignment treatment on either or both of the vertical alignment films 15 and 25 , it is possible to define the orientation azimuth of the liquid crystal molecules when a black image is being displayed. By performing alignment treatment, the liquid crystal molecules 31 have a prescribed pretilt angle with respect to either or both of the substrate surfaces when no voltage is applied. If the pixel electrode 14 has a trunk portion 14 a that is formed across the center of the pixel as shown in FIG. 2 , for example, then the liquid crystal molecules 31 can be oriented in the up-and-down direction (azimuth parallel to the lengthwise direction of the slits) of the pixel, with the trunk portion of the pixel electrode 14 a being the symmetry axis, by performing alignment treatment in an azimuth direction parallel to the lengthwise direction of slits, and thus, it becomes possible to attain a wide viewing angle as will be described below. [0076] In Embodiment 1, a technique to apply a pretilt angle using a polymer formed in the respective boundaries between the liquid crystal layer 30 and the substrates 10 and 20 (PSA technique) may be adopted. In such a case, it is possible to orient the liquid crystal molecules 31 so as to have an azimuth parallel to the lengthwise direction of the slits 14 c of the pixel electrode when voltage is applied, without performing alignment treatment. The PSA technique may be used in addition to alignment treatment, which can improve anchoring and stabilize the orientation azimuth of the liquid crystal molecules 31 . This PSA technique can be adopted by applying a voltage to a liquid crystal layer 30 containing liquid crystal and a photopolymerizable monomer, and radiating ultraviolet light thereon in a state in which the liquid crystal molecules 31 are oriented at an azimuth parallel to the lengthwise direction of the slits 14 c of the pixel electrode, thereby polymerizing the monomer. [0077] Below, driving principles of a liquid crystal display device of Embodiment 1 of the present invention will be described. [0078] A state when no voltage is applied will be described with reference to FIG. 1 . When no voltage is applied, this means that no potential is applied to the first common electrode 12 , the second common electrode 22 , or the pixel electrodes 14 , and V 1 and V 2 are both 0V. When no voltage is applied, the liquid crystal molecules 31 are oriented perpendicularly with respect to the surfaces of the first substrate 10 and the second substrate 20 . [0079] The display of a black image will be described with reference to FIGS. 3 and 4 . FIGS. 3 and 4 are schematic drawings showing a liquid crystal display device of Embodiment 1 during black display; FIG. 3 is a schematic cross-sectional view, and FIG. 4 is a schematic plan view of one pixel. In FIG. 3 , the double-headed arrows represent the direction of the electric field. [0080] In FIG. 3 shows an example in which a 0V potential is applied to the first common electrode 12 , a ±7.5V potential is applied to the second common electrode 22 , and a ±1V potential is applied to the pixel electrode (|V 1 |=7.5 and |V 2 |=1). As shown in FIG. 3 , a vertical electric field is formed in the liquid crystal layer 30 and the liquid crystal molecules 31 have negative dielectric anisotropy, and thus, the liquid crystal molecules 31 are oriented towards a direction perpendicular to the electric field, causing the liquid crystal molecules 31 to be oriented parallel to the surfaces of the first substrate 10 and the second substrate 20 . As shown in FIG. 4 , when viewing this state in a plan view, the liquid crystal molecules 31 are oriented at an azimuth parallel to the lengthwise direction of the slits 14 c of the pixel electrode 14 . The polarizing plates are bonded to the outer surfaces of the first substrate 10 and the second substrate 20 , and these are arranged such that the polarizing axes are respectively substantially parallel or substantially perpendicular to the lengthwise direction of the slits 14 c and in a crossed Nicols state with each other, and thus, in the state shown in FIG. 3 , light from the backlight is blocked by the polarizing plates. [0081] In Embodiment 1, a potential greater than 0V is applied to the pixel electrode when a black image is being displayed. By gradually increasing the potential applied to the pixel electrode 14 from 0V, the potential difference between the pixel electrode 14 and the first common electrode 12 reaches a certain value, at which point an equipotential plane parallel to the substrate surface is formed over the teeth 14 b and the slits 14 c of the pixel electrode in the vicinity of the boundary between the first substrate 10 and the liquid crystal layer 30 , thereby forming an even vertical electric field in the liquid crystal layer 30 . [0082] If V 2 , when the even vertical electric field is applied to the liquid crystal layer 30 , is V 2 — 0 , then V 2 is represented by the following formula (4): [0000] ( Formula   5 ) V 2 = ɛ ⊥  d 1 ɛ 1  d LC + ɛ ⊥  d 1  V 1  ( = V 2  _  0 ) ( 4 ) [0083] (d LC represents the thickness of the liquid crystal layer, ∈ ⊥ represents a permittivity perpendicular to the director of the liquid crystal, d 1 represents the thickness of the first insulating layer, and ∈ 1 represents the permittivity of the first insulating layer) [0084] In the liquid crystal display device of Embodiment 1, if the potential difference between the first common electrode 12 and the pixel electrode 14 is V 2 — B when a black image is being displayed, then it is preferable that V 2 — B be within the range set in formula (5) below: [0000] (Formula 6) [0000] 0<| V 2 — B |≦V 2 — 0 |+0.5  (5) [0085] In other words, it is preferable that V 2 — B be within the range of formula (2) below: [0000] ( Formula   7 ) 0 <  V 2  _B  ≤ ɛ ⊥  d 1 ɛ 1  d LC + ɛ ⊥  d 1   V 1  + 0.5 ( 2 ) [0086] Display of a white image will be described with reference to FIGS. 5 and 6 . FIGS. 5 and 6 are schematic drawings showing a liquid crystal display device of Embodiment 1 when a white image is being displayed; FIG. 5 is a schematic cross-sectional view, and FIG. 6 is a schematic plan view of one pixel. In FIG. 5 , the double-headed arrows represent the direction of the electric field. [0087] In FIG. 5 , an example is shown in which a potential of 0V is applied to the first common electrode 12 , a potential of ±7.5V is applied to the second common electrode 22 , and a potential of ±4.5 is applied to the pixel electrode (|V 1 |=7.5, |V 2 |=4.5). As shown in FIG. 5 , a vertical electric field and a horizontal electric field (oblique electric field) are formed in the liquid crystal layer 30 , and the liquid crystal molecules 31 rotate to respectively different azimuths while maintaining a horizontal orientation with respect to the surfaces of the first substrate 10 and the second substrate 20 . As shown in FIG. 6 , when viewed in a plan view, the liquid crystal molecules 31 are at azimuths at angles with respect to the lengthwise direction of the slits 14 c of the pixel electrode. As a result, the liquid crystal molecules 31 are at an angle with respect to the polarizing axes of the polarizing plate, and thus, light from the backlight passes through, and a grayscale image or a white image can be displayed. [0088] More specifically, the liquid crystal molecules 31 are oriented to have line symmetry about the trunk portion 14 a of the pixel electrode 14 while facing the open ends of the slits 14 c of the pixel electrode. Also, the liquid crystal molecules 31 are oriented to have line symmetry about the center of the respective slits 14 c . As a result, the liquid crystal molecules 31 are at four different azimuths within one pixel, which can further improve viewing angle characteristics. This is due to the fact that the pixel electrodes 14 have a trunk portion 14 a that crosses the center of the pixel. [0089] If |V 2 | becomes greater than |V 1 | when a grayscale image or a white image is being displayed, no vertical electric field is formed in the liquid crystal layer, and the liquid crystal molecules 31 no longer maintain a horizontal orientation with respect to the surfaces of the first substrate 10 and the second substrate 20 , and thus, transmittance and contrast ratio decrease. Thus, |V 2 | must remain below |V 1 |. [0090] Thus, excellent display can be attained if V 2 changes according to the range in formula (1) below: [0000] (Formula 8) [0000] 0<| V 2 — B |≦|V 2 |<|V 1 |  (1) [0091] Materials of respective members and a manufacturing method will be described below. [0092] A transparent material such as glass or plastic is suitable for the support substrates 11 and 21 . [0093] The first common electrode 12 , the second common electrode 22 , and the pixel electrodes 14 can be made by forming a single layer or multiple layers of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and tin oxide (SnO), or an alloy thereof by sputtering, and then patterning the material by photolithography or the like, for example. The slits 14 c of the pixel electrode 14 can also be formed simultaneously to this during patterning. [0094] The first substrate 10 and the second substrate 20 manufactured in this manner are provided with a plurality of columnar spacers made of an insulating material and then bonded together by a sealing member. The liquid crystal layer 30 is formed between the first substrate 10 and the second substrate 20 , but when using the dripping method, the liquid crystal is dripped onto a substrate prior to the substrates being bonded, and when using the vacuum injection method, the liquid crystal is injected after the substrates have been bonded. By bonding polarizing plates, phase contrast films, or the like onto the surfaces of the substrates opposite to the liquid crystal layer 30 , the liquid crystal display device is completed. Furthermore, by mounting a gate driver, a source driver, a display control circuit, and the like and adding a backlight or the like, a liquid crystal display device suited to a given application is completed. [0095] The structure of the liquid crystal display device of Embodiment 1 can be confirmed using a scanning electron microscope (SEM), for example. [0096] The dielectric anisotropy of the liquid crystal molecules 31 can be confirmed by analyzing the molecular structure of the liquid crystal by gas chromatography, for example. [0097] An actual liquid crystal display device of Working Example 1 was manufactured as an example of Embodiment 1. The dielectric anisotropy (Δ∈) of the liquid crystal was −7.1, the permittivity (∈ ⊥ ) in the direction perpendicular to the director direction of the liquid crystal was 11.3, the refraction anisotropy (Δn) was 0.11, and the permittivity (∈ 1 ) of the insulating layer 13 was 6.9. Also, the thickness (d LC ) of the liquid crystal layer 30 was 3.2 μm, the thickness (d 1 ) of the insulating layer 13 was 0.3 μm, the width of each of the teeth 14 b of the pixel electrode was 6 μm, and the width of each slit 14 c was 10 μm. [0098] With a potential of 0V being applied to the first common electrode 12 and a potential of |7.5|V being applied to the second common electrode 22 , the transmittance was measured as different potentials were applied to the pixel electrode 14 . [0099] FIG. 7 is a graph representing the relation (V-T characteristics) between the potential difference between the first common electrode and the pixel electrode (V 2 ) and the transmittance in the liquid crystal display device of Working Example 1. As shown in FIG. 7 , in Working Example 1, |V 2 | at the lowest transmittance (| 2 — 0 |) is 1V, and when |V 2 | rises from |V 2 — 0 | (1V) and approaches |V 1 | (7.5V), the transmittance increases, with the maximum being when |V 2 |=4.5 V. Thus, in Working Example 1, |V 2 | during black image display (|V 2 — B |) is 1V, and |V 2 | during white image display is 4.5V. |V 2 — B | simply needs to be in the range specified by formulae (2) and (5) as in (A) of FIG. 7 . According to the conditions above, the relations of formulae (1) and (2) are satisfied, thereby achieving a liquid crystal display device having excellent viewing angle characteristics and high contrast ratio. Embodiment 2 [0100] Embodiment 2 is similar to Embodiment 1 other than that a second insulating layer is present between the second common electrode and the alignment film. FIG. 8 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 2 when no voltage is applied. [0101] As shown in FIG. 8 , the liquid crystal display device of Embodiment 2 has a second insulating layer 23 . The second insulating layer 23 can be made of an organic film including an organic material such as an acrylic resin (permittivity ∈=3 to 4), an inorganic film including an inorganic material such as silicon nitride (permittivity ∈=5 to 7), or the like. The second insulating layer 23 is 0.2 to 2 μm in thickness, for example, and more preferably 0.3 to 1.5 μm in thickness. The driving principles are similar to those of Embodiment 1. [0102] In Embodiment 2, a potential greater than 0V is applied to the pixel electrode 14 during black display. If a 0V potential is applied to the first common electrode 12 and a potential of ±7.5 is applied to the second common electrode 22 , with the potential applied to the pixel electrode 14 being gradually increased from 0V, then when the potential difference between the pixel electrode 14 and the first common electrode 12 reaches a certain value, an equipotential plane parallel to the substrate surface is formed over the teeth 14 b and the slit 14 c of the pixel electrode in the vicinity of the boundary between the first substrate 10 and the liquid crystal layer 30 , thereby forming an even vertical electric field in the liquid crystal layer 30 . [0103] If V 2 when an even vertical electric field is formed in the liquid crystal layer 30 is V 2 — 0 , then V 2 is represented by formula (6) below: [0000] ( Formula   9 ) V 2 = ɛ 2  ɛ ⊥  d 1 ɛ 1  ɛ ⊥  d 2 + ɛ 1  ɛ 2  d LC + ɛ 2  ɛ ⊥  d 1  V 1  ( = V 2  _  0 ) ( 6 ) [0104] (d LC represents the thickness of the liquid crystal layer, ∈ ⊥ represents the permittivity in the direction perpendicular to the director of the liquid crystal, d 1 represents the thickness of the first insulating layer, d 2 represents the thickness of the second insulating layer, ∈ 1 represents the permittivity of the first insulating layer, and ∈ 2 represents the permittivity of the second insulating layer) [0105] In the liquid crystal display device of Embodiment 2, if the potential difference between the first common electrode 12 and the pixel electrode 14 is V 2 — B for black image display, then it is preferable that V 2 — B be within the range set in formula (5) below, as in Embodiment 1: [0000] (Formula 10) [0000] 0<| V 2 — B |≦|V 2 — 0 |+0.5  (5) [0106] In other words, it is preferable that V 2 — B be within the range of formula (3) below: [0000] ( Formula   11 ) 0 <  V 2  _B  ≤ ɛ 2  ɛ ⊥  d 1 ɛ 1  ɛ ⊥  d 2 + ɛ 1  ɛ 2  d LC + ɛ 2  ɛ ⊥  d 1   V 1  + 0.5 ( 3 ) [0107] Similar to Embodiment 1, if, during grayscale or white image display, |V 2 | exceeds |V 1 |, then a vertical electric field is not formed in the liquid crystal layer 30 , and the liquid crystal molecules 31 no longer stay in a horizontal orientation with respect to the surfaces of the first substrate 10 and the second substrate 20 , which results in a decrease in transmittance and contrast ratio. Thus, |V 2 | must remain below |V 1 |. [0108] Thus, excellent display can be attained if V 2 changes according to the range in formula (1) below: [0000] (Formula 12) [0000] 0<| V 2 — B |≦|V 2 |<|V 1 |  (1) [0109] An actual liquid crystal display device of Working Example 2 was manufactured as an example of Embodiment 2. The dielectric anisotropy (Δ∈) of the liquid crystal was −7.1, the permittivity (∈ ⊥ ) in the direction perpendicular to the director direction of the liquid crystal was 11.3, the refraction anisotropy (Δn) was 0.11, the permittivity (∈ 1 ) of the first insulating layer 13 was 6.9, and the permittivity (∈ 2 ) of the second insulating layer 23 was 3.8. The thickness (d LC ) of the liquid crystal layer 30 is 3.2 μm, the thickness (d 1 ) of the first insulating layer 13 was 0.3 μm, the thickness (d 2 ) of the second insulating layer 23 was 1 μm, the width of each of the teeth 14 b of the pixel electrode was 6 μm, and the width of the slit 14 c was 10 μm. [0110] With a potential of 0V being applied to the first common electrode 12 and a potential of |7.5|V being applied to the second common electrode 22 , the transmittance was measured as different potentials were applied to the pixel electrode 14 . [0111] FIG. 9 is a graph representing the relation (V-T characteristics) between the potential difference between the first common electrode and the pixel electrode (V 2 ) and the transmittance in the liquid crystal display device of Working Example 2. As shown in FIG. 9 , in Working Example 2, |V 2 | at the lowest transmittance (|V 2 — 0 |) was 0.5V, and as |V 2 | increased from |V 2 — 0 | (0.5V) and approached |V 1 | (7.5V), the transmittance increased to a maximum when |V 2 |=2.2 V. Thus, in Working Example 2, |V 2 | during black image display (V 2 — B ) was 0.5V, and |V 2 | during white image display was 2.2V. |V 2 — B | simply needs to be in the range specified by formulae (3) and (5) as in (B) of FIG. 9 . According to the conditions above, the relations of formulae (1) and (3) are satisfied, thereby achieving a liquid crystal display device having excellent viewing angle characteristics and high contrast ratio. [0112] (Evaluation Test 1) [0113] Below, the results of a comparison between Working Example 1 and Working Example 2 will be described. FIGS. 10 and 11 are respectively cross-sectional images simulating the orientation of liquid crystal during white display in the liquid crystal display devices of Working Examples 1 and 2. FIGS. 10 and 11 were made using an orientation simulator “LCD master” manufactured by Shintech. FIG. 12 is a graph comparing the V-T characteristics of the liquid crystal display devices of Working Examples 1 and 2 based on FIGS. 7 and 9 . [0114] When comparing the respective boundaries between the second substrates and the liquid crystal layers in FIGS. 10 and 11 (areas surrounded by the dotted lines in FIGS. 10 and 11 ), it was found that whereas an equipotential plan parallel to the substrate surface is formed in FIG. 10 , a plurality of equipotential planes not parallel to the substrate surface are present in FIG. 11 . Also, as shown in FIG. 12 , in Working Example 2, the maximum transmittance was achieved with a smaller value for |V 2 | compared to Working Example 1, and the maximum transmittance of Working Example 2 was greater than the maximum transmittance of Working Example 1. [0115] It is thought that in the liquid crystal display device of Working Example 1, the electric field distribution is less susceptible to change in the area surrounded by the dotted line in FIG. 10 because a second insulating layer is not present between the second common electrode 22 and the vertical alignment film 25 . On the other hand, in the liquid crystal display device of Working Example 2, the second insulating layer 23 is present between the second common electrode 22 and the vertical alignment film 25 , and thus, regions where the electric field distribution varies are present in the area surrounded by the dotted line in FIG. 11 , allowing the liquid crystal molecules to move more readily, which is thought to be why the increase transmittance is steeper and the maximum transmittance is greater than in Working Example 1. [0116] Thus, according to Embodiment 2, a higher transmittance is achieved with a lower |V 2 | than in Embodiment 1, and therefore, it is possible to drive the liquid crystal display device at a lower voltage. Embodiment 3 [0117] Embodiment 3 is similar to Embodiment 1 other than the arrangement of scan signal lines. FIG. 13 is a schematic plan view of one pixel of the liquid crystal display device of Embodiment 3. [0118] As shown in FIG. 13 , in Embodiment 3, the pixel electrode 14 is provided for each pixel such that the trunk portion 14 a thereof corresponds in position to the scan signal line 2 . The plurality of data signal lines 1 extend in the vertical direction of the liquid crystal display device, the plurality of scan signal lines 2 extend in the horizontal direction of the liquid crystal display device so as to cross the middle of each pixel, and the TFTs 6 are respectively formed in the vicinity of the respective intersections between the data signal lines 1 and the scan signal lines 2 . The TFTs 6 are constituted of respective portions of the data signal line 1 and the scan signal line 2 , and the semiconductor layer 3 , and function as a switching element. The pixel electrode 14 is connected to the scan signal line 2 through a contact hole 5 . When the TFT 6 is turned ON by a scan signal supplied through the scan signal line 2 , the semiconductor layer 3 becomes conductive, and a data signal is supplied to the pixel electrode 14 through the data signal line 1 . [0119] In Embodiment 3 also, a liquid crystal display device having excellent viewing angle characteristics and high contrast can be achieved by using a design that satisfies the relations of formulae (1) and (2). Embodiment 4 [0120] Embodiment 4 is similar to Embodiment 1 other than the structure of the pixel electrodes 14 . FIG. 14 is a schematic plan view of one pixel of the liquid crystal display device of Embodiment 4. As shown in FIG. 14 , in Embodiment 4, the pixel electrode 14 has teeth 14 b and slits 14 c , but the teeth of the pixel electrodes are not connected at the middle, and the slits 14 c are closed off at the upper and lower ends of the pixel electrode. [0121] In Embodiment 4, by using a design that satisfies the relations of formulae (1) and (2), a liquid crystal display device having viewing angle characteristics that are slightly worse than Embodiment 1 but still excellent, and a high contrast ratio can be achieved. Embodiment 5 [0122] Embodiment 5 is similar to Embodiment 1 except that the first electrode is the pixel electrode and that the second electrode and the third electrode are common electrodes. FIG. 15 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 5 when no voltage is applied. [0123] As shown in FIG. 15 , the liquid crystal display device of Embodiment 5 includes a first substrate 10 , a second substrate 20 , and a liquid crystal layer 30 sandwiched between the first substrate 10 and the second substrate 20 . The liquid crystal layer 30 contains liquid crystal molecules 31 having a negative dielectric anisotropy. The first substrate 10 includes a support substrate 11 , thin film transistors (TFTs), data signal lines, scan signal lines, pixel electrodes 41 (first electrodes), a first common electrode 42 (second electrode), an insulating layer 13 (first insulating layer) that electrically separates the pixel electrodes 41 from the first common electrode 42 , and a vertical alignment film 15 . The second substrate 20 includes a support substrate 21 , a second common electrode 22 (third electrode), a vertical alignment film 25 , color filters, and a black matrix. [0124] In Embodiment 5, the configuration of the first common electrode 42 is similar to that of the pixel electrodes 12 of Embodiment 1. The pixel electrodes 41 are formed in a uniformly planar manner for each pixel and are supplied data signals through respective data signal lines. The first common electrode 42 and the second common electrode 22 are respectively applied differing common potentials. [0125] In Embodiment 5 also, a liquid crystal display device having excellent viewing angle characteristics and high contrast can be achieved by using a design that satisfies the relations of formulae (1) and (2). Embodiment 6 [0126] Embodiment 6 is similar to Embodiment 1 except that the first electrode and the second electrode are pixel electrodes and that the third electrode is a common electrode. FIG. 16 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 6 when no voltage is applied. [0127] As shown in FIG. 16 , the liquid crystal display device of Embodiment 6 includes a first substrate 10 , a second substrate 20 , and a liquid crystal layer 30 sandwiched between the first substrate 10 and the second substrate 20 . The liquid crystal layer 30 contains liquid crystal molecules 31 having a negative dielectric anisotropy. The first substrate 10 includes a support substrate 11 , thin film transistors (TFTs), data signal lines, scan signal lines, first pixel electrodes 43 (first electrodes), second pixel electrodes 44 (second electrodes), an insulating layer 13 (first insulating layer) that electrically separates the first pixel electrodes 43 from the second pixel electrodes 44 , and a vertical alignment film 15 . The second substrate 20 includes a support substrate 21 , a common electrode 45 (third electrode), a vertical alignment film 25 , color filters, and a black matrix. [0128] In Embodiment 6, the configuration of the common electrode 45 is similar to that of the second common electrode 22 of Embodiment 1, and the configuration of the second pixel electrode 44 is similar to that of the pixel electrode 12 of Embodiment 1. The first pixel electrode 43 is formed in a uniformly planar shape for each pixel. The first pixel electrode 43 and the second pixel electrode 44 may be respectively connected to different TFTs and supplied data signals through the data signal lines. [0129] In Embodiment 6 also, a liquid crystal display device having excellent viewing angle characteristics and high contrast can be achieved by using a design that satisfies the relations of formulae (1) and (2). Embodiment 7 [0130] Embodiment 7 is similar to Embodiments 1 and 2 except that the liquid crystal molecules are of a hybrid alignment type in which liquid crystal molecules close to the first substrate are oriented horizontally with respect to the surface of the first substrate and the liquid crystal molecules close to the second substrate are oriented vertically with respect to the second substrate. FIGS. 17 and 18 are schematic cross-sectional views of a liquid crystal display device according to Embodiment 7 when no voltage is applied. FIG. 19 is a graph showing V-T characteristics of the liquid crystal display device shown in FIG. 18 . The aspect shown in FIG. 17 does not have a second insulating layer between the second common electrode and the alignment film as in Embodiment 1, but the aspect shown in FIG. 18 has the second insulating layer between the second common electrode and the alignment film as in Embodiment 2. [0131] In FIGS. 17 and 18 , the first substrates 10 both have horizontal alignment films 16 , and the second substrates 20 both have vertical alignment films 25 . An alignment treatment is performed on the horizontal alignment film 16 and the vertical alignment film 25 such that the orientation azimuth of the liquid crystal molecules 31 is parallel to the lengthwise direction of the slits 14 c of the pixel electrode 14 . [0132] By controlling the azimuth of the liquid crystal molecules 31 during black image display in this manner, it is possible to control display by driving principles similar to those of Embodiments 1 and 2. The aspect of FIG. 17 is designed to satisfy the conditions of formulae (1) and (2), and the aspect of FIG. 18 is designed to satisfy the conditions of formulae (1) and (3). As shown in FIG. 19 , an excellent gradation display is attained even with the aspect of FIG. 18 . According to Embodiment 7, it is possible to attain an excellent display similar to Embodiments 1 and 2. Embodiment 8 [0133] Embodiment 8 is similar to Embodiments 1 and 2 except that the liquid crystal molecules are of a hybrid alignment type in which liquid crystal molecules close to the first substrate are oriented horizontally with respect to the surface of the first substrate and the liquid crystal molecules close to the second substrate are oriented vertically with respect to the second substrate. FIGS. 20 and 21 are schematic cross-sectional views of a liquid crystal display device according to Embodiment 8 when no voltage is applied. FIG. 22 is a graph showing V-T characteristics of the liquid crystal display device shown in FIG. 21 . The aspect shown in FIG. 20 does not have a second insulating layer between the second common electrode and the alignment film as in Embodiment 1, but the aspect shown in FIG. 21 has the second insulating layer between the second common electrode and the alignment film as in Embodiment 2. [0134] In FIGS. 20 and 21 , the first substrates 10 both have vertical alignment films 15 , and the second substrates 20 both have horizontal alignment films 26 . An alignment treatment is performed on the horizontal alignment film 26 and the vertical alignment film 25 such that the orientation azimuth of the liquid crystal molecules 31 is parallel to the lengthwise direction of the slits 14 c of the pixel electrode 14 . [0135] By controlling the azimuth of the liquid crystal molecules 31 during black image display in this manner, it is possible to control display by driving principles similar to those of Embodiments 1 and 2. The aspect of FIG. 20 is designed to satisfy the conditions of formulae (1) and (2), and the aspect of FIG. 21 is designed to satisfy the conditions of formulae (1) and (3). As shown in FIG. 22 , an excellent gradation display is attained even with the aspect of FIG. 21 . According to Embodiment 8, it is possible to attain an excellent display similar to Embodiments 1 and 2. [0136] Comparing FIGS. 19 and 22 , when adopting so-called hybrid alignment, the liquid crystal display device can be driven at a lower voltage and with a higher transmittance if the liquid crystal molecules close to the first substrate are vertically aligned with respect to the surface of the first substrate than if the liquid crystal molecules close to the first substrate are horizontally aligned with respect to the surface of the first substrate when no voltage is applied. Comparison Example 1 [0137] A liquid crystal display device of Comparison Example 1 is one aspect of a conventional vertical alignment type liquid crystal display device. FIGS. 23 and 24 are schematic views of the liquid crystal display device of Comparison Example 1 during white image display; FIG. 23 is a schematic cross-sectional view, and FIG. 24 is a schematic plan view of one pixel. FIG. 23 is also a schematic cross-sectional view of FIG. 24 along the line C-D. In FIG. 23 , the arrows in the liquid crystal layer represent the direction of the electric field. [0138] As shown in FIG. 23 , the liquid crystal display device of Comparison Example 1 includes a first substrate 110 , a second substrate 120 , and a liquid crystal layer 130 sandwiched between the first substrate 110 and the second substrate 120 . The liquid crystal layer 130 contains liquid crystal molecules 131 having a negative dielectric anisotropy. The first substrate 110 includes a support substrate 111 , thin film transistors (TFTs), data signal lines, scan signal line storage capacitance bus lines, an insulating layer 113 , pixel electrodes 114 , and a vertical alignment film 115 . Comparison Example 1 differs from Embodiment 1 in that there is no common electrode below the pixel electrodes 114 . The second substrate 120 includes a support substrate 121 , a uniformly planar common electrode 122 , color filters, a black matrix, and a vertical alignment film 125 . [0139] As shown in FIG. 24 , the pixel electrode 114 is provided for each region surrounded by the data signal lines 101 and the scan signal lines 102 . The pixel electrode 114 includes a connecting electrode 114 a , a connecting electrode 114 b , and a plurality of teeth 114 c . Slits 114 d are present between adjacent teeth 114 c . The connecting electrode 114 a is formed parallel to the longer side of the pixel to bisect the pixel horizontally. The connecting electrode 114 b is formed parallel to the shorter side of the pixel to bisect the pixel vertically. The storage capacitance bus line 108 , like the connecting electrode 114 b , is formed parallel to the shorter side of the pixel to bisect the pixel vertically, and is formed to correspond in position to the connecting electrode 114 b. [0140] The connecting electrodes 114 a and 114 b are formed to divide the pixel into four rectangles of the same shape. The plurality of teeth 114 c extend at azimuths of 45°, 135°, 225°, and 315° to form 45° angles with the longer side direction of the connecting electrode 114 a or the connecting electrode 114 b. [0141] An actual liquid crystal display device of Comparative Example 1 was manufactured as an example of Comparison Example 1. The dielectric anisotropy (Δ∈) of the liquid crystal was −7.1, the permittivity (∈ ⊥ ) in the direction perpendicular to the director direction of the liquid crystal was 11.3, and the refraction anisotropy (Δn) was 0.11. The thickness (d LC ) of the liquid crystal layer 31 was 3.2 μm, the width of each of the teeth 114 c of the pixel electrode was 3 μm, and the width of the slit 114 d was 3 μm. [0142] Also, in Comparative Example 1, a liquid crystal composition containing liquid crystal and a monomer for PSA (made by Merck) is injected between the first substrate 110 and the second substrate 120 , and sealed therein. A 17.51V potential was applied to the pixel electrode 114 , a 0V potential was applied to the common electrode 122 , and the liquid crystal molecules 131 were oriented at azimuths parallel to the lengthwise directions of the slits of the pixel electrode 114 so as to have four different orientation azimuths, thereby dividing orientation into four directions. Ultraviolet light was radiated in this state to polymerize the monomer for PSA, thereby forming a polymer on the substrate surface and fixing the azimuths of the liquid crystal molecules. Polarizing plates are bonded to the respective outer surfaces of the first substrate 110 and the second substrate 120 in a crossed Nicols state by having the respective polarizing axes be parallel or perpendicular to the lengthwise directions of the connecting electrode 114 a or the connecting electrode 114 b. [0143] During black image display, most of the liquid crystal molecules are oriented vertically with respect to the surfaces of the first substrate 110 and the second substrate 120 , but some of the liquid crystal molecules close to the respective substrates are oriented in a direction slightly inclined from the direction perpendicular to the substrate surfaces and at azimuths parallel to the lengthwise directions of the slits using the above-mentioned technique for adding pretilt angles using the polymer. In the liquid crystal display device of Comparative Example 1, the potential of both the common electrode 122 and the pixel electrode 114 is 0V during black image display. [0144] As shown in FIG. 23 , a 0V common potential is applied to the common electrode 122 and a potential gradually increasing from 0 to |7.5|V is applied to the pixel electrode 114 , and it was confirmed that the display shifted from grayscale image display to white image display. In the liquid crystal layer 130 , an electric field inclined with respect to the substrate surfaces is formed from the pixel electrode 114 towards the common electrode 122 . The liquid crystal molecules 131 have negative dielectric anisotropy and are oriented in a direction perpendicular to the electric field, and thus, the angle of inclination of the liquid crystal molecules 131 with respect to the substrate surfaces changes, which causes the display to shift from grayscale image display to white image display. As shown in FIG. 24 , when viewing the liquid crystal display panel in a plan view during white image display, the liquid crystal molecules 131 are oriented in azimuths parallel to the lengthwise directions of the slits 114 d formed in the pixel electrode 114 . In Comparative Example 1, the orientation azimuths of the liquid crystal molecules 131 are fixed by the slits 114 d formed in the pixel electrode and the above-mentioned technique for adding pretilt angles using the polymer. [0145] (Evaluation Test 2) [0146] Below, the results of a comparison between Working Example 1 and Comparative Example 1 will be described. FIG. 25 is a graph showing gamma characteristics at a horizontal azimuth (azimuth angle 0-180°) and a polar angle of 60° in the liquid crystal display devices of Working Example 1 and Comparative Example 1, and FIG. 26 is a graph showing gamma characteristics at an oblique azimuth (azimuth angle 45-225°) and a polar angle of 60° in the liquid crystal display devices of Working Example 1 and Comparative Example 1. The gamma characteristics were measured using “EZContrast.” [0147] In FIGS. 25 and 26 , the vertical axis represents the luminance ratio (normalized luminance ratio) with a gradation of 255 being 1, and the horizontal axis represents the gradation value. In FIGS. 25 and 26 , curves showing the frontal gamma characteristics (γ=2.2) are also included for the comparison. The polar angle is the angle measured between the direction normal to the surface of the substrate and a position inclined towards the substrate surface. The azimuth is an angle where a right azimuth is 0° and a left azimuth is 180° along the surface of the substrate when the surface of the substrate is viewed from the direction normal thereto. Where the azimuth is θ and the polar angle is φ, then θ=φ=0°. The closer the curve is to the front gradation (γ=2.2), the less whitening there is when the liquid crystal display device is viewed from a diagonal direction, and the viewing angle characteristics are excellent. [0148] As shown in FIGS. 25 and 26 , the liquid crystal display device of Working Example 1 has similar curves for both the horizontal azimuth and the oblique azimuth as the frontal direction curve (γ=2.2) for all gradations, and therefore has excellent viewing angle characteristics. On the other hand, in Comparative Example 1, both the horizontal azimuth and the oblique azimuth widely diverge from the frontal direction curve (γ=2.2) at mid gradation, which results in whitening being observed when the liquid crystal display device is viewed from the diagonal direction. [0149] Below, the differences in viewing angle characteristics between Embodiment 1 and Comparison Example 1 will be discussed. [0150] In Comparison Example 1, a voltage is applied to the liquid crystal layer to form a vertical electric field, thereby orienting the liquid crystal molecules to azimuths parallel to the lengthwise directions of the slits of the pixel electrode. The orientation azimuths of the liquid crystal molecules are determined by the width of the slits, and thus, if the width is the same for all slits, then the orientation azimuths of the liquid crystal molecules are also uniform. Also, there is no electrode corresponding to the first common electrode of Embodiment 1 present below the pixel electrode, and thus, it is not possible to change the electric field distribution in the liquid crystal layer. Therefore, in Comparison Example 1, grayscale image display is performed only by changing the tilt angle of the liquid crystal molecules with respect to the substrate surface, and therefore, when viewed from the diagonal direction, the apparent birefringence of the liquid crystal molecules changes. Even if alignment partitioning is performed by the PSA technique described above to orient the liquid crystal molecules at four different azimuths, as shown in FIGS. 25 and 26 , the viewing angle characteristics are not good enough. [0151] On the other hand, in Embodiment 1, the first common electrode is present below the pixel electrodes having slits, and thus, it is possible to change the electric field distribution in the liquid crystal layer by changing the potential between the first common electrode and the pixel electrodes. Therefore, even if the width is the same for all slits in the pixel electrode, it is possible to control the azimuths at which the liquid crystal molecules are oriented. In Embodiment 1, the electric field distribution is changed in the liquid crystal layer to change the azimuths of the liquid crystal molecules during gradation display, and thus, at all gradations, the liquid crystal molecules are oriented horizontally with respect to the substrate surface. Therefore, even when viewed from the diagonal direction, the apparent birefringence of the liquid crystal molecules does not change, which allows for excellent viewing angle characteristics. DESCRIPTION OF REFERENCE CHARACTERS [0000] 1 , 101 data signal line 2 , 102 scan signal line 3 semiconductor layer 4 drain lead-out wiring line 5 contact hole 6 , 106 thin film transistor (TFT) 10 , 110 first substrate 11 , 21 , 111 , 121 support substrate 12 first common electrode (first electrode) 13 , 113 insulating layer (first insulating layer) 14 pixel electrode (second electrode) 14 a trunk portion 14 b , 114 c teeth 14 c , 114 d slit 114 a , 114 b connecting electrode 15 , 25 , 115 , 125 vertical alignment film 16 , 26 horizontal alignment film 20 , 120 second substrate 22 second common electrode (third electrode) 23 second insulating layer 30 , 130 liquid crystal layer 31 , 131 liquid crystal molecules 41 pixel electrode (first electrode) 42 first common electrode (second electrode) 43 first pixel electrode (first electrode) 44 second pixel electrode (second electrode) 45 common electrode (third electrode) 108 storage capacitance bus line 114 pixel electrode 122 common electrode

Provided is a liquid crystal display device having excellent viewing angle characteristics and high contrast in a display mode using both a vertical electric field and a horizontal electric field. This liquid crystal display device is provided with a first substrate and a second substrate disposed facing each other, and a liquid crystal layer held between said first and second substrates. The liquid crystal layer contains liquid crystal molecules having a negative dielectric anisotropy. The first substrate is provided with a flat plate first electrode, a first insulating layer, and a second electrode provided in a layer other than that of the first electrode and provided separated from the first electrode by the first insulating layer. The second electrode has multiple comb-tooth sections and multiple slits, and the second substrate has a flat plate third electrode. Defining V 1 as the potential difference between the first electrode and the third electrode, V 2 as the potential difference between the first electrode and the second electrode, and V 2 — B as the potential difference between the first electrode and the second electrode when the lowest gradation is showed, V 1 , V 2 and V 2 — B satisfy 0<|V 2 — B |≦|V 2 |<|V 1 |.

FIELD OF INVENTION This invention relates to devices for supressing the boiling and channeling in fluidized beds used for phase separation, mass transfer, and chemical or biological processes in water and wastewater treatment, food, chemical and other industries. PRIOR ART For many processes, for example suspended sludge blanket clarification, absorption, ion exchange, biological processes, fluidized bed reactors demonstrate better performance than other reactor types and provide significant capital and operational savings and a greater convenience of operation. The concrete technological advantages are process specific. A fluidized bed reactor consists of the body of the reactor with one or another type of distribution system for liquid or gas fluidizing agent (sometimes liquid and gas are used simultaneously) located at the bottom of the reactor. The reactor is either charged with a certain quantity of solid particles, which are called the bed, or the bed is formed by the particles (solid or liquid) coming into the reactor with the fluidizing agent, or the bed is formed as a result of physical (condensation of vapors), chemical and physico-chemical (coagulation-flocculation, crystallization) or biological (growth of microorganisms) processes. In the upflow of the fluidizing agent the bed particles become a fluidized material. One or another type of collection system is located at the top of the reactor. The theories, applications, advantages and disadvantages of fluidized bed reactors and various elements of these reactors are discussed in the following sources: "Mechanique Des Suspensions" by A. Fortier, Masson et C-ie Editeurs 120, Boulevard Saint-Germain, Paris-VI e , 1967; "Proceedings of the International Symposium on Fluidization" June 6-9, 1967, A. A. H. Drinkenburg, Editor, Netherland University Press, Amsterdam, 1967; "Fluidization", Davidson, J. F., Harrison, D., Editors, Academic Press, London and N.Y., 1971; "Mechanics of Heterogeneous Media" by Nigmatullin, R. I., Publishing House "Nauka" (Sciences), Moscow, 1978; and articles: Anderson, T. B., Jackson, R., "A Fluid Mechanical Description of Fluidized Beds", I & EC Fundamentals, Vol. 5, No. 4, 1967, Vol. 7, No. 1, 1968, Vo. 8, No. 1, 1969; Medlin, J., Wong, H., Jackson, R., "Fluid Mechanical Description of Fluidized Beds. Convective Instabilities in Bounded Beds", Ind. Eng. Chem. Fundam. Vol. 13, No. 3, 1974; El-Kaissy, M. M., Homsy, G. M., "Instability Waves and the Origin of Bubbles in Fluidized Beds", Int. J. Multiphase Flow, Vol. 2, 1976, Vol 6, 1980; Latif, B. A. J., Rirchardson, J. F., "Circulation Patterns and Velocity Distributions for Particles in Fluidized Bed", Chemical Engineering Science, Vol. 27, No. 11-C, 1977; Vanecek, V., Hummel, R. L., "Structure of Liquid Fluidized Beds with Small Density Difference Between the solids and the Liquid", I. Chem. E. Symposium Series, No. 30, 1968; Fan, L. T., Ho, T., Hiraoka, S., Walawender, W. P., "Pressure Fluctuations in Fluidized Bed", AIChE Journal, Vol. 27, No. 3, 1981; Pigford, R. L., Baron, T., "Hydrodynamic Stability of a Fluidized Bed", I & EC Fundamentals, Vol. 4, No. 1, 1965; Happel, T., Brenner, H., "Low Reynolds Number Hydrodynamics with Special Applications to Particulate Media", Prentice-Hall, 1965; "Fluidization Technology", edited by Keairns, D. L., McGraw-Hill International Book Co., 1976. In accordance with these sources one of the major disadvantages of fluidized bed reactors is the hydrodynamic instability which is manifested through the channeling of the bed at low velocities of the fluidizing agent and the boiling of the bed at high velocities of flow. Both channeling and boiling cause shortcircuting of the fluidizing agent and consequent lowering of the retention time of fluidizing agent in the reactor. In case of boiling, intensive mixing of the fluidized material occurs. In case of channeling, only partial fluidization of the bed occurs. In both cases, the rates and efficiencies of physical, chemical, physico-chemical, and biological processes become lower. Channeling and boiling phenomena are discussed in the literature sources cited previously in this section. Based on these discussions the mechanisms of channeling and boiling can be presented as follows. Channeling of the bed occurs at lower velocities of flow of the fluidizing agent and, consequently, at lower expansions of the bed. At a certain velocity of flow the initially compact bed becomes loosened, although, the particles of the bed remain in contact with each other. The further increase of the velocity of the flow over the velocity which produces loosening of the bed causes the particles to separate from each other at the locations where cohesion or interlocking among the particles is weaker. Such separation starts at the bottom of the bed and progresses upwardly as a fast rupture of the bed. Along the ruptures in the bed channels are formed, while in the rest of the bed the particles are not fluidized. The formation of channels is primarily associated with the properties of the particles forming the bed. The channeling occurs more frequently in cohesive beds formed by flocculent particles, and in beds formed by smaller particles which tend to interlock more strongly than larger particles. Distribution devices with a nonuniform distribution of the fluidizing agent may aggravate the channeling problem. However, even the ideally uniform distribution of the fluidizing agent cannot prevent the channeling of the bed. The boiling occurs at greater velocities of flow of the fluidizing agent and consequently greater expansions of the bed. The boiling type of instability of a fluidized bed is associated with the structure of such a bed. Ideally a fluidized bed is a system of alternating horizontal layers of greater and lower concentration of fluidized material. The bottom layer in the bed is always more diluted (less concentrated) than the rest of the bed due to the continuous influx of the fluidizing agent. The thickness (the height) of this layer fluctuates with time. The diluted (less concentrated) layers are "emitted" from the bottom layer and propagate upwardly in a wave-like motion. The fluidized bed exhibits the properties of liquids. Thus, layers of lesser and higher concentration of fluidized material can be considered at layers of liquid, the layers with the greater concentration of the fluidized material being denser than the layers with the lower content of fluidized particles. The system which consists of lighter liquid layers overlayed by the densier layers is a classical example of hydrodynamically unstable system. These layers tend to flip over under the action of a small disturbance. When such a "flip-over" occurs the distribution of velocities of the fluidizing agent across the plan area of the bed becomes nonuniform, the velocity being greater at the locations of the initial upward slips of the lighter layer. At these locations the amount of the fluidized material along the vertical pathways becomes lower. This causes lower hydraulic resistances along these pathways, and therefore increased velocities of flow. Consequently, in the rest of the bed, the velocities of flow of the fluidizing agent decrease. Such changes in the velocities cause the fluidized material to become more diluted over the areas of greater velocities of liquid flow and to become more concentrated at the locations of the reduced velocities of liquid flow. The redistribution of the velocities of the flow of the fluidizing agent and the concentrations of the fluidized material makes the boiling a self-sustaining process. Distribution devices with a nonuniform distribution of the fluidizing agent may aggravate the boiling problem. However, even an ideally uniform distribution of the fluidizing agent cannot prevent the boiling of the bed. The following conclusions can be made from the preceeding two paragraphs: Both, channeling and boiling are induced by small disturbances and due to nonuniform spacial distribution of the properties of the bed. Once induced, channeling and boiling become self-sustaining and perpetuate even after the removal of the source of small disturbance. Distribution devices with a nonuniform distribution of the fluidizing agent may aggravate the channeling and boiling problems. However, ideally uniform distribution of the fluidizing agent cannot prevent the boiling of the bed. Therefore, the means intended to control the channeling and the boiling of the fluidized bed should be located within the bed itself. Various techniques which may control the distributions of the velocities of flows of the fluidizing agent and concentrations of the fluidized material in the bed have been discussed in several literature sources. Reviews on this subject are presented by D. Harrison and J. R. Grace in the book "Fluidization", Edited by Harrison and Davidson, Academic Press, London and N.Y. 1971, and by F. J. Zuiderweg in "The Proceedings of the International Symposium on Fluidization" edited by Drinkenburg, Netherland University Press, Amsterdam, 1967. The following devices are described: (1) bunches of parallel horizontal pipes and rods, (2) bunches of vertical pipes and rods, (3) fixed stone or ball packing, (4) fixed ring packing, e.g., Raschig or other ring types, (5) parallel vertical baffles, (6) parallel inclined baffles. It has been shown that these devices can lessen the boiling and/or channeling to some degree. However, they exhibit the following disadvantages: (1) vertical and horizontal pipes and rods, stone and ball, and, to a lesser degree, rings, occupy substantial space (65% for stone) and reduce the effective volume of the reactor; (2) free spaces in the stone, and ring media are not uniform and stagnation zones occur in the reactor with such packing types, (3) bunches of horizontal pipes and rods, and parallel vertical or parallel inclined baffles do not produce the bidirectional control action in the bed needed to prevent boiling and channeling, (4) bunches of vertical rods and parallel vertical baffles promote channeling of the bed, (5) parallel inclined baffles promote boiling of the bed through inducing asymmetrical flows in the bed, (6) neither of the present type packings is intended to produce a controlled nonuniform distributions of the flows of the fluidizing agent, and the concentrations of the fluidized material. Such nonuniform distributions can be desirable for specific applications such as fluidization of multiple media, or single media distributed nonuniformly in the horizontal section of the reactor. OBJECTS Accordingly it is the primary aim of the present invention to provide a packing for fluidized bed reactors which is capable of uniform bidirectional control of channeling and boiling of fluidized beds. It is another object of the present invention to provide a packing which occupies little volume in the reactor. It is further an object of the present invention to provide a packing free from dead zones. It is further an object of the present invention to provide a packing which does not promote channeling and does not induce the boiling of the fluidized bed. It is a further object of the present invention to provide a packing capable of producing controlled nonuniform distributions of the flows of the fluidizing agent and concentrations of the fluidized material in the bed which can be desirable for specific applications such as fluidization of multiple media, distributed along the height of the reactor, or a single medium distributed nonuniformly either along the height or across the reactor, or in both directions. It is also an object of the present invention to provide a packing for fluidized beds which is simple to produce and manufacture. DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of a fluidized bed reactor with the preferred packing type. FIG. 2 is a view of the portion indicated by section lines I--I in FIG. 1. FIG. 3 is a top view of a fluidized bed reactor with the preferred packing type being turned at 45° angle as compared with FIG. 1. FIG. 4 is a top view of the portion indicated by section lines II--II in FIG. 3. FIG. 5 is a persective view of a section of the preferred packing. FIG. 6 is a top view of a single layer of the preferred packing. FIG. 7 is a view of the portion indicated by section lines III--III in FIG. 6. FIG. 8 is a view of the portion indicated by section lines IV--IV in FIG. 6. FIG. 9 is a view of the portion indicated by section lines V--V in FIG. 6. FIG. 10 is a vertical section of a portion of a stack of several single layers of the preferred packing and the means for spacing and securing these layers in the reactor. FIG. 11 is a perspective view of the alternative configuration of the preferred packing type. FIG. 12 is the top view of another alternative configuration of the preferred packing type. FIG. 13 is a view of the portion indicated by section lines VI--VI in FIG. 12. FIG. 14 is a perspective view of a single element from which the preferred packing type exemplified in FIGS. 13 and 14 can be assembled. FIG. 15 is a vertical section of the alternative configuration of a single element exemplified in FIG. 14. FIG. 16 is a vertical section of the suspended sludge blanket reactor which utilizes the preferred packing type capable of producing the desirable nonuniform distributions of the flows of the fluidizing agent and the concentrations of the fluidized material. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1, 2, 3 and 4, there is shown a fluidized bed reactor comprising the body of the reactor 1, the system for distribution of the fluidizing agent 2, the system for collection of the effluent 3, and grids of packing 4, each grid forming a layer of the packing. The strings or rods 28 passing over and under the grids are the means for securing the grids in the reactor. Referring now to FIGS. 5, 6, 7, 8, 9, there is shown a single grid of the preferred packing which consists of the contracting 5 and expanding 6 cells in the direction of the flow of the fluidizing agent, the said cells being formed by inclined hexagonal baffles 7 connected with each other at the corners of the said cells 5 and 6 and forming the saddle shape surface with the nodal point 8 at these corners. Referring now to FIGS. 2 and 4, the alternative arrangement of the grids 4 when the baffles located on the same vertical are oppositely inclined. This can be achieved by placing every other grid upside down. Referring now to FIG. 10 there is shown a section of portion of a stack of the grids 4, with the holes made at some of the saddle points 8 and the vertical rods or strings 9 passing through these holes and the sliding spacers 10 put on the said rods or strings, the lengths of the said spacers being specified for a particular application, and the cross-sectional size being greater than the size of the holes at the saddle points. The vertical rods or strings 9 and sliding spacers 10 are an alternative means for securing the grids of packing in the reactors. Referring now to FIG. 11 there is shown an alternative configuration of the single grid of the preferred packing type comprising expanding cells 5 formed by conical baffles 11 and contracting cells 6 formed by the said conical baffles 11 and the vertical baffles 21 connecting the conical baffles into a grid 4. The length of the baffles 12 can vary from zero to a specified value. The grid exemplified in FIG. 12 can also be used in the upside down position. In such a case the expanding cells are formed by cones 11 and the contracting cells are formed by the cones 11 and the vertical baffles 12. Referring now to FIGS. 12, 13, and 14 there is shown another alternative configuration of the preferred packing type comprizing vertical frames 14 which are single elements from which the alternative packing type can be assembled. This frame can be stamped out of a sheet material. It consists of vertical strips 15, a horizontal connecting band 16 at the top of the frame, horizontal strips 17 connecting vertical strips 15, and inclined baffles 18 shaped as trapezoids. The frame 14 can be considered as a louvered frame with fins composited from elements 17 and 18. Four louvered frames are connected along the lengths of the vertical strips 15 into a square box 19 thus forming a stack of contracting cells 6. The boxes 19 can be assembled in a checkered position and connected along the corners into a tridimensional structure. The spaces amoung four boxes 19 form the stack of expanding cells 5. The entire tridimensional frame formed of elements 14 incorporated into the boxes 19 represents the stack of grids with the checkered expanding and contracting cells. This tridimensional frame can also be used in the upside down position. Referring now to FIG. 15 there is shown a modification 20 of the element 14 as exemplified in FIG. 14. This modification incorporates additional inclined trapezoidal baffles 21 attached to the horizontal strips 17 at their lower side and bent in the direction opposite to the plates 18. The elements 20 can be connected into a tridimensional structure similar to that formed by elements 14 but with equal sizes of expanding and contracting cells. Referring now to FIG. 16, there is shown the suspended sludge blanket reactor 22 combined with the sludge separator 23. The reactor 22 is equipped with the distribution device for water or wastewater 2, the collection devices for treated water 3 located at the top of the reactor 22 and another collection device 24 located at the top of the sludge separator 23. A sludge discharge system 25 is located at the bottom of the sludge separator 23. The reactor 22 and the sludge separator 23 are hydraulically connected by means of the opening(s) 26 located in the common wall between the reactor 22 and the sludge separator 23 at an elevation slightly lower than the top level of the suspended sludge blanket. The reactor is equipped with the packing 4 located throughout the volume occupied by the suspended sludge blanket but the zone adjacent to the opening(s) 26, where packing type 27 is placed. The packing 27 differs from the packing 4 either by a closer spacing of baffles, or by a greater angle of attack, or by other parameters producing greater resistance to the flow. If needed, the reactor 23 can be covered and equipped with the means for collecting gases produced in the reactor. The reactor 22 can be charged with the solid media, or the solid media can be formed in the reactor due to chemical or biological processes, or both the charged and the formed media can be present. OPERATION OF THE DEVICE Referring now to FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 and the preferred embodiment described above, the device would be operated as follows: The fluidizing agent fed into the reactor 1 through the distribution device 2 would fluidize the bed media either charged into the reactor or formed in the reactor. While passing across the fluidized media the fluidizing agent would be treated. Either separation of phases, or chemical, physico-chemical, biological, or other processes would occur. The treated fluidizing agent would be collected by the collection device 3 and removed from the reactor. While passing through the grids 4 of the proposed packing exemplified in FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10, the fluidizing agent would induce circulations of the fluidized material and the fluidizing agent, the said circulations being localized around the inclined baffles. In the contracting cells 5, the flow of the fluidizing agent would accelerate along the vertical pathway and the velocity of flow will become greater than the approach velocity at the bottom of the grid 4. This would cause the fluidized material to be transported upwardly across and out of the grid and, consequently, the concentration of fluidized material in the contracting cell would become lower than that at the approach to the grid 4. In the expanding cells 6, the flow of the fluidizing agent would decelerate and cause the fluidized material to be precipitated. The accumulation of the fluidized material in expanding cells 6 and the depletion of the fluidized material from the contracting cells 5 would cause a greater hydraulic pressure loss across the expanding cells than the loss across the contracting cells. This would result in a greater pressure under the expanding cells 6 than the pressure under the contracting cells 5, and in a greater pressure over the contracting cells 5 than over the expanding cells 6. These pressure differentials would cause the fluidizing material to flow in horizontal directions, from the expanding cells 6 toward the contracting cells 5 under the lower tips of the inclined baffles, and from the contracting cells 5 towards the expanding cells 6 over the upper tips of the inclined baffles. These horizontal flows and the accelerated flow in the contracting cells and the decelerated flow in the expanding cells would constitute the circulation flows around the inclined baffles. The checkered arrangement of the contracting 5 and expanding 6 cells would produce a tridimensional circulation within each grid. These circulations would be comprised of the interacting toroidal flows. In the absence of disturbances the intensity of all circulation would be equal across each of the grids 4. It was observed in the experimental testing of the preferred embodiment that the intensity of circulation increases when the velocity of the fluidizing agent increases. When a disturbance occurs, such as a localized faster flow of fluidizing agent induced by the distribution device or due to a change in the temperature of the fluidizing agent fed into the reactor, the circulations in the area of the grids 4 where the flow is greater would become more intense. This would induce a greater horizontal flows under the grids 4 towards the area of the increased flows bringing more fluidized material to this area, and increasing the hydraulic resistance at this location. This would also induce greater horizontal flows over the grids 4 from the area of the increased flows, therefore, reducing the velocities of flow approaching the higher located grids. The changes in the resistances and pressures across the reactor would cause the disturbance to be suppressed. The checkered arrangement of the contracting and expanding cells would provide the bidirectional control of the disturbances in the horizontal cross-section of the reactor. The circulation flows would break up the system of lighter and denser layers and the vertical channels in the fluidized bed and, therefore, eliminate the reasons for the boiling and channeling which are associated with the structure of the fluidized bed and the physico-chemical properties of particles. The packing of the proposed configuration would suppress channeling and boiling induced by disturbances of any origin, e.g., imperfect distribution device 2, or fluctuations in the fluidizing agent (for example, fast increase in temperature), or due to the processes occuring in the bed (for example, formation of gases in the reactor volume), or due to inherited instability of the bed itself and random small fluctuations in the bed. Referring now to FIG. 11, and the preferred embodiment described above, the modification of the proposed grid consisting of conical baffles 11 connected by vertical baffles 12 would be operated the same way as the packing described in the preceeding paragraph of this section. Referring now to FIGS. 12, 13, 14, and 15, and the preferred embodiment described above, the modification of the proposed grid formed by the louvered frames 14 with the inclined fins 18 or inclined fins 18 and 21, the said frames being assembled into a tridimensional frame 19, would be operated the same way as the packing described in the preceeding paragraphs of this section. For different applications the sizes of cells 5 and 6, the spacing of inclined baffles 7, or 11, or 18 and 21, their height, and the angle of attack (inclination) of the inclined baffles, and the vertical spacing between grids 4 would vary. For specific applications different grids and various spacing between grids can be used in the same reactor. For example, FIG. 16 illustrates the suspended sludge blanket clarifier which utilizes the proposed packing. The clarifier is operated as follows: The liquid carrying suspended solids and added with reagents, for example, coagulants, would be distributed in the suspended sludge blanket reactor 22 by the means of the distribution device 2. In the body of the reactor coagulation and formation of larger solids particles than that entering the reactor would occur. These particles would be fluidized by the incoming flow of liquid. The subsequent portions of of the liquid fed into the reactor would be treated in contact with the previously formed particles. The treated water would be collected by the collection devices 3 located at the top of the reactor 23 and devices 24 located at the top of the sludge separator 23. The liquid flow from the reactor 22 to the sludge separator 23 forced by the collecting of liquid by the collection device 24 would carry the sludge accumulated in the reactor across the opening(s) 26 into the sludge separator where the sludge precipitates. Continuously or periodically, this sludge would be removed from the sludge separator by the means of the sludge discharge system 25. The reactor 22 is packed with the proposed packing consisting of the grids 4 which are intended to suppress the boiling and channeling and grids 27 which are intended to preconcentrate the sludge prior to its transfer to the sludge separator. The spaces between inclined baffles in the grids 27 are smaller than in grids 4. This would produce a higher hydraulic resistance across the location of the grids 27 and would cause solids transport towards the location of these grids and liquid transport from the grids. The prethickened sludge would require a lower flow to be directed into the sludge separator. Therefore, the volume of the sludge separator would be reduced. The use of grids of various sizes and spacing will also be beneficial in the reactors with multiple fluidized materials, such as sand, antracite, active carbon, etc., because it will permit the simultaneous fluidization and classification of different media. Principal elements of the device have been tested. The data on testing is presented in the report "Hydrodynamics of Fluidized Bed Reactors for Wastewater Treatment" by B. M. Khudenko and R. M. Palazzolo. While the above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Many other variations are possible. For example, the proposed packing consisting of expanding and contracting cells can be formed by curvilinear baffles, the cells can be staggered in vertical directions, various means for connecting and supporting the baffles can be used; the proposed packing can be used for other applications not mentioned in this text; mixing, elimination of mist from gases, thickening of fluffy sludges, heat transfer, etc.

Packing for fluidized bed reactors, is improved by providing alternately inclined baffles connected directly to each other or by means for connecting the said baffles into grids located in one or several levels, the said baffles forming expanding and contracting cells in the direction of the flow. The size, spacing in grids and the angle of attack of these baffles and spacing of grids are the same throughout the reactor volume when uniform distributions of the fluidizing agent and the fluidized medium are required. Alternatively, a device of this type is improved by providing variable sizes, spacing in grids, and angle of attack of these baffles and spacing of grids when specified nonuniform distributions of the flow of the fluidizing agent and the concentrations of the fluidized media are desired for particular applications.