Abstract:
A portable chemical analytical apparatus to analyze a test swipe includes a heater to warm the test swipe to a predetermined temperature; a clamp to secure the test swipe to the heater; one or more pumps to dispense one or more chemicals onto the test swipe from a disposable cartridge; a fan to remove chemical vapors rising a predetermined distance from the test swipe; and a camera to capture an image of the test swipe for automated analysis.

Description:
This application is a continuation of U.S. application Ser. No. 12/354,960 filed Jan. 16, 2009 now U.S. Pat. No. 8,071,385, the content of which is incorporated by reference. 
    
    
     BACKGROUND 
     This invention relates to systems for the detection of explosives and other controlled substances such as drugs or narcotics as well as other chemicals used in clandestine activities. 
     Recent terror attacks have changed the dynamics of the explosive detection systems across the globe. Terrorists, acting singly or in concert, instill immense fear and apprehension in civilians and governments alike with their technical knowledge about explosives. In parallel, the world has experienced an increase in the transportation of contraband substances such as drugs or narcotics. 
     With advances in explosives technology, such as the advent of the plastic explosives, which can be disguised as common items, it is becoming increasingly difficult to detect these substances. The problems that must be overcome in the detection of these substances as well as others, include low vapor pressure of the particular vapors escaping from the particular substance, the search time and the throughput of the various systems, the low concentration of vapor or particulate emissions from the particular substance, isolation of the particular substance with a high degree of reliability, and maintaining the integrity of the systems environment. 
     Various techniques for detecting substances such as explosives and drugs or narcotics have been developed, ranging from explosives/drug sniffing dogs to highly sophisticated vapor detection devices. Machine detection of the aforementioned substances can be accomplished through non-vapor detection or vapor detection. Non-vapor detection methods include x-ray detection, gamma-ray detection, neutron activation detection and nuclear magnetic resonance detection. These methods of detection are more applicable to the detection of the various substances when the substances are concealed and are carried or associated with non-living items such as baggage as these techniques might pose a threat to living items. Vapor detection methods include electron capture detection, gas chromatography detection, mass spectroscopy detection, plasma chromatography detection, bio-sensor detection and laser photo-acoustic detection. These methods of detection are more applicable to the detection of substances that are concealed and associated with living specimens. 
     Conventional systems tend to be large and immobile. Further, current systems can require users to manually apply toxic chemicals as testing agents. As a result, conventional systems are not mobile and hard to use. Hence, their adoption for field use has been limited. 
     SUMMARY 
     In one aspect, a portable handheld chemical analytical apparatus to analyze a test swipe for chemicals such as household, drug, and clandestine, and explosive chemicals is disclosed. The apparatus includes a heater to warm the test swipe to a predetermined temperature; a clamp to secure the test swipe to the heater; one or more pumps to dispense one or more chemicals onto the test swipe; a fan to circulate chemical vapors rising from the test swipe; and a camera to capture an image of the test swipe for analysis. 
     In another aspect, a method to analyze a swiped sample to identify a chemical composition, includes automatically pumping a series of chemical solution agents into the swiped sample; heating the swiped sample to one or more predetermined temperatures to accelerate the chemical reactions; capturing one or more images of the chemical reaction; sending the images to the a display screen for operator observation; and analyzing the images to identify the chemical composition based on a chemical reaction database. 
     Advantages of the system may include one or more of the following. The system tests the presence of chemical materials or compounds using a number of factors or parameters singly or in concert. The factors can include heat, volume, time, temperature, and vapor control, among others and sequences these factors over time. The sequences can be in unique intervals. As a result, the system is highly reliable and reduces “false positives” due to its multi-factor, multi-step diagnostic operations. 
     The system significantly enhances the possibility of accurately and quickly screening personnel, equipment, and materials at security checkpoints, military operations, law enforcement, or other screening scenarios, and for detecting trace of explosive materials. The system allows users to precisely and quickly detect different explosive chemical agents. 
     The system operates in a real-time fashion. It automatically dispenses a precise volume of chemical solutions over time when requested. The system optionally allows users to manually control the sequence of the pumping process. The system provides users with pump controls for dispensing chemical solutions. Through the built-in heater, the system automatically heats up the swiped sample to predetermined temperatures over specific time parameters using an automatic ramped heating feedback control. The system automatically and continually performs self-check and monitors fluid levels, temperature and time. The system automatically chronologically stores data and arranges according to positive results versus negative results. The system automatically tells the operator to remove the analyzed swipe. The system delivers a unique sequence of precise chemical volumes under time, heat, and vapor parameters. The system has detachable and expendable chemical(s) in cartridge form for ease of replacement. The system uses a high-resolution digital camera for data collection and analysis. 
     By use of a wired or wireless transceiver, detected information can be easily transmitted to anywhere in the world. By replacing disposable swipes/pads/swabs and disposable chemical test reservoirs, the system can detect a wide range of explosives, clandestine material, drugs, and household products used to manufacture explosives, a range of controlled chemical agents, drugs, and narcotics etc. By allowing the user to swap test materials and running a computerized diagnostics, the user can easily and effectively change the system to meet what is considered to be the threat at that time. By having all components under program control and by arranging for a known input to the system such as a controlled injection of target material, the system can perform self-calibration and self-diagnostic. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features, and advantages of the present invention will be better understood from the following detailed descriptions taken in conjunction with the accompanying drawings, all of which are given by way of illustration only, and are not imitative of the present invention, in which: 
         FIG. 1  shows an exemplary portable chemical detection device. 
         FIGS. 2A and 2B  show in more details major components of the device. 
         FIG. 3  shows in more details a swipe receiving port. 
         FIG. 4A  shows a perspective view of a chemical supply cartridge. 
         FIG. 4B  shows an exemplary perspective top view of a pump assembly. 
         FIG. 4C  shows an exemplary perspective view of a micro-pump array. 
         FIG. 5A  shows an exemplary perspective view of a camera in a test chamber. 
         FIG. 5B  shows an exemplary perspective view of tubing and camera actuator in the test chamber. 
         FIG. 6  shows an exemplary block diagram of processing electronics for the system of  FIG. 1 . 
         FIGS. 7A-7D  show an exemplary operational flow chart executed by the system of  FIG. 1 . 
         FIG. 8  shows an exemplary image analysis process executed by the processor of  FIG. 5  to detect chemical agents automatically. 
     
    
    
     DESCRIPTION 
     The following detailed description of the invention is provided to aid those skilled in the art in practicing the present invention. Even so, the following detailed description of the invention should not be construed to unduly limit the present invention, as modifications and variations in the embodiments herein discussed may be made by those of ordinary skill in the art without departing from the spirit or scope of the present inventive discovery. 
       FIG. 1  shows an exemplary portable chemical detection device  10 . The device  10  has a housing  20  that supports a display  22  and input devices such as an on-off button  24  and navigation/selection buttons  26 . In one embodiment, the system has six buttons. The first button is the On/Off button. This button allows user to turn the unit on or off. The remaining five buttons (Left, Right, Down, Up, and Enter) allows user to interact with a Graphical User Interface (GUI) of the system. The GUI is flexible, efficient and user friendly. 
     The device  10  also has an input/output port  28  such as a USB port or Firewire port to communicate with a remote computer, and AC power port, among others. In one embodiment, the I/O port  28  is a weather proof PC interface. The PC interface can set up operation parameters and recover analyzed data. In another embodiment, the I/O port  28  can include a flash memory card interface. 
     The device  10  also includes two ports  30  and  40  to receive user replaceable media and chemical. The device  10  also includes a port  41 A to receive user replaceable DC battery cartridge. Port  30  receives a test swipe  32 . The port  40  receives a chemical cartridge, which can house one or more chemical containers. An electronic controller  58  (shown in  FIGS. 2A AND 2B ) receives inputs from the buttons or keys and controls the display  22  and other electronics in the device  10 . The system can work with different power sources including battery port  41 A port and/or a DC input port  41 B such as a car jack or an AC/DC adaptor. 
     The system of  FIG. 1  is preferably a hand-held unit, which can most preferably be operated easily in real time by one operator. Moreover, the operation of such detectors should preferably be simple so that non-technical persons can operate the instrument properly, efficiently, and easily. 
       FIGS. 2A and 2B  are two perspective top views that show in more details major components of the device  10 . In the embodiment of  FIG. 2A , a plurality of chemical containers or reservoirs  42  are mounted in a disposable cartridge  44  that is inserted into the unit  10 . The reservoirs  42  are punctured via safety needles with a side port and the chemicals are automatically or manually pumped from the reservoirs  42  by one or more micro-pumps  46 . The chemicals are delivered through one or more short length and narrow ID delivery tubes connected to the outputs of the micro-pumps  46  to the test swipe  32  during testing. 
     To test a contaminate collection swipe, a user opens the port  30  and places a test swipe  32  into a swipe holder  34 . The swipe holder  34  moves along sliding rails  36  when the user closes the port  30  to place the test swipe  32  under a test chamber  38 . The test chamber  38  includes a chamber with two openings  52  that face a variable speed fan  54  to draw air across the test swab  32  while under test. The test chamber also includes a heating element  56  connected to a PID loop that can warm up the test swab  32  to multiple predetermined temperature settings during test. The test chamber also contains a camera  39  ( FIGS. 2A ,  2 B, and  5 A) 
       FIG. 3  shows in more detail port  30  that receives the test swipe  32  in the swipe holder  44   34 . The swipe holder  34  includes a door  60  by which a user can press against to open or close the port  30 . The swipe holder  34  also includes an open face press-fit clamp  62  that secures the swipe  32  against a heating element  64  under the swipe  32  upon closure. The swipe holder  34  is attached to rails  66  that slide within rails  68  to enable the swipe holder  34  carrying the test swab  32  to move in and out of the device  10 . An enclosure for the swipe holder  34  is formed by positioning a lid  70  with an opening  72  between the sliding rails  68 . The opening  72  allows movable tubes from the micro-pumps  46  to dispense test chemicals onto the  32 . The opening  72  also allows a camera  39  ( FIG. 5A ) to capture images of the test results for automatic real-time analysis of the test. A white-light source such as an LED is positioned near the camera can be turned on to provide lighting if needed and turned off when not used to conserve power. In one embodiment, the camera output is shown on the display  22  so that the user or operator can visually determine the test result(s) while the automated determination is in progress. The opening  72  also allows a variable speed fan  54  to gently move vapor away from the camera lens to avoid fogging the lens (anti-fogging). 
       FIG. 4A  shows a perspective view of a disposable chemical supply cartridge  44  that can be inserted into the port  40 . The disposable cartridge  44  contains one or more reservoirs  80 , each having an inlet  82  that can be punctured and is re-sealable so that the chemical in each reservoir  80  can be accessed by a tip or safety needle  84 . The disposable cartridge  44  also has a key  86  cooperating with a recess  87  ( FIG. 4B ) to ensure that the cartridge  44  can only be inserted in a predetermined orientation. 
       FIG. 4B  shows a pump assembly with the cartridge  44 . The needles  84  provide chemicals through short length, narrow gauge tubes (not shown) to their respective inputs  90  at the micro-pumps  46 . 
       FIG. 4C  shows an exemplary perspective view of a micro-pump array. As shown therein, a plurality of micro-pumps  46  are provided to pump a series of respective chemicals from the array of reservoirs  80 . Each micro-pump has an inlet  90  that is connected to the needles that may or may not include safety tips and that are inserted into each reservoir  80  when the user inserts the cartridge  44  into the device  10 . Another set of tubes are connected to the outputs of the micro-pumps  46  to deliver the chemicals in precise volume, sequence and timing as controlled by the processing electronic controller  58 . 
       FIGS. 5A and 5B  show an exemplary perspective view of a camera  39  in conjunction with the test chamber  38 . The chamber  38  includes a motor  92  driving a gear  94 . The gear  94  cooperates with a moveable arm  96  that moves test tubing fixture  98  back and forth over the test swab  32  during testing. The test tubing fixture  96  moves very closely to the swipe  32  for chemical deposit onto the swipe when the device  10  is held in any orientation. The arm  96  includes a plurality of openings that receive a plurality of tubes from the output of the micropumps  46 . The arm  96  also moves the fixture  98  out of the way for the camera  39  to capture changes on the test swipe  32  during testing. The camera images are then analyzed, and the result can then be displayed on the display  22 . In one embodiment, the camera  39  can capture raw images with 65,536 colors. The camera is protected with an anti-fog feature using the adjustable speed fan  54 . The image data can be shown continuously throughout the entire process on a flip-up display  22  with high fidelity. In one embodiment, the system provides a software JPEG encoder and decoder for storing and viewing previous results and images. The system also includes white light LEDs (not shown) located within the test chamber  38  that provides even, shadow free, and uniform lighting during camera  39 &#39;s operation with a programmable white light intensity. The LEDs minimize shadows in the camera viewing area. 
     The swipe holder  34  moves along rugged sliding rails  66  when the user closes the port  30  to place the test swipe  32  under the test chamber  38 . The test chamber  38  includes a chamber with two openings  52  that face the fan  54  to draw air across the test swipe  32  while under test. The test chamber also includes a heating element  56  that can warm up the test swipe  32  to a predetermined temperature during test. 
       FIG. 6  shows an exemplary block diagram of processing electronics for the system of  FIG. 1 . A processor  200  controls all tasks done by the system. The processor  200  communicates over a bus  202  to various devices, including buttons interface  204 , fan driver  206 , speaker driver  208 , display controller  210 , micro-pump driver  212 , and USB controller  214 . The processor  200  also communicates with embedded memory  220  and a programmable ROM  224  that contains boot code as well as application code. The processor  200  also drives buffers  226 ,  228  and  230  which controls the LED, infrared sensor that informs the operator if a swipe has been loaded into the test chamber  38 , and heat filament, respectively. The infrared sensor is positioned under the swipe and acts as a proximity sensor to detect the presence or absence of a swipe by the amount of light reflected back. The processor  200  or controller actuates the motor to drive a solution delivery manifold to the center of the swipe and in close proximity to the swipe to dispense the solution without dripping, regardless orientation. The controller can monitor fluid levels within each reservoir contained in the disposable cartridge. This is done by decrementing available volume each time the pump is actuated and when the count reaches a low threshold, the controller can indicate that the reservoir is out of chemical. 
     The system is powered by a 12-volt DC source, which can be generated from an AC/DC converter, a car outlet or from eight 1.5-volt batteries in series. The highest prioritized energy source is from an AC/DC converter followed by the one from a car outlet, then the energy from batteries. The 12-volt DC power source will supply current to the heater and the pump. It is also connected to the low drop voltage regulator to generate different voltage levels such as 5 V, 2.8 V and 3.3 V, which are necessary for the processor and for other peripherals as well. 
     In one embodiment as a Portable Explosive Trace Detector (PETD), the system of  FIG. 6  significantly enhances the detection of the explosive materials as well as speeding up the screening and detecting procedures at security checkpoints. First, the PETD automatically pumps a series of chemical solution agents into the swiped sample and heats up to specific temperature to accelerate the chemical reactions. Second, an internal CMOS camera captures the chemical reaction images at its highest resolution, raw data for better image analysis. Third it then sends these raw images data to the LCD (Liquid Crystal Display) screen for the purpose of observation. Moreover, the JPEG codec will be develop for storing and replaying image functions. The LCD screen provides a high quality image for human viewing. The LCD can analyze the image to identify explosive materials based on the provided chemical reaction database. Last but not least, the PC interfaces can be used to update software and firmware as well as to backup the data. 
     In one implementation, to start the analysis process, the system turns the micro-pump(s) N (i.e., N=1, 2, 3 . . . or a combination thereof) to disperse the chemical solution into the Swiped Sample. The pumping rate is set to 2 Hz. After dispersing chemical solution, the system starts heating the sample to excite the chemical reactions under controlled vapor, time, temperature, and chemical volume conditions specific to a particular analyte or group of analytes. A current of about one ampere is applied to heat up the heating filament. During the heating process, the fluctuation of the temperature is controlled by a feedback circuit with a thermistor. 
     When the temperature of the sample swipe reaches a predefined value, the system turns the heater off, the white light LED on and the fan on. The speed of the fan is adjustable using pulse width modulation control in one embodiment. 
     Before commanding the camera&#39;s CMOS image sensor to capture an image, the system waits for the chemical reaction to complete for around 1 ms. The captured image is then displayed on the LCD. 
     The system creates a result image by subtracting the captured image from the background one. Then the result image is compared with the color patterns in the lookup table stored in the system. If the results image matches some color pattern, the result probability will be displayed and an optional audible alarm is given or not. Otherwise, an appropriate message is displayed on the LCD. 
     During the process of writing to the memory, (e.g., saving results or updating database), the system is able to detect the memory capacity and give the user a warning of full memory. In such a case, the user needs to clear the memory by deleting certain files before commanding the system to continue its work. 
     In one embodiment, the system executes a prime pump procedure to clear up air and chemical bubbles in the tubes of minimized length and diameter once the system has been idled for more than 12 hours. If the system has not been used for the past 12 hours then the system prompts the user to place an empty swipe sample into a clamp holder. Once a swipe sample is secured on the clamp holder, the system prompts user to do the prime pump procedure by pumping chemical solutions onto swipe sample. During the prime pumps, the camera captures the image from the swipe and displays it on the LCD screen. During the prime pumps, no heat is applied to the swipe. 
     In one embodiment, in the main menu, user can see the date, the time and current status of the system. The system can generate a warning alarm once battery, chemical level and memory reach their minimal levels. The menu also contains three (3) software programmable buttons, namely New Analysis, Previous Results, and Settings. User can interact with these soft buttons by using the five hard buttons. The New Analysis option is highlighted as default. The usage of these soft buttons is as follows:
         New Analysis: allows user to perform a new test.   Previous Results: allows user to trace back the data tested in the past.   Settings: allows user to set parameters such as date, time, to test the system reliability, or to connect to PC for firmware and/or database update.       

     The user can see the images taken by the camera. The system status is also displayed. In addition, three (3) soft buttons (Start, Stop, and Status) are provided. The Start option is highlighted as default. 
       FIGS. 7A-7D  (collectively  FIG. 7 ) show an exemplary operational flow chart executed by the system of  FIG. 1 . When the system is turned on by pressing the Start Power On button, it will stay in IDLE state  304 . In this state, the system waits for user commands. By default, both the camera lighting LED and the fan are turned off. The system sends an appropriate message alarm to operator once chemical, battery, and memory reach their minimal level. User may command the system to perform a new test by selecting New Analysis, to view previous results and images by selecting Previous Results, or to update the firmware and/or database. 
     When the option of performing a new test is selected, the system checks whether the Slide Door Switch closed or not ( 360 ). If the door is not closed, it will display a warning message ( 400 ) and return to IDLE state  304 . Otherwise, it looks for a loaded Swiped Sample using the infrared sensor ( 362 ). The presence of the sample allows the system to move to the next state, where it checks for the fluid levels of the three reservoirs to ensure that the fluids are enough for the entire test process ( 364 ). The amount of fluid is determined by the number of dispersing (i.e., a full bottle is enough for a predetermined number of dispersals and the number is decremented during each dispersing). 
     Before continuing, the system checks the temperature of the filament if it is equal to 35° C. in one embodiment. Otherwise, it will have to heat the filament until the temperature of the filament reaches 35° C. ( 374 ). At this temperature, the user is allowed to choose different options. If the user presses the Stop button ( 368 ), the system will stop the work and return to the IDLE state. If the user chooses the Status button ( 370 ), the system will temporarily display its current task to turn the system status on/off. After that it returns and continues the previous work. When the user presses Start button ( 372 ), the system turns the Fan on to blow the fog or vapor away from the camera, turns the LEDs on, turns the fan  39  to a low speed and takes a background image using the camera ( 378 ). Then, the system will select a particular micro-pump N=1 or a series of micro-pumps (N=1, 2, 3 . . . or a combination thereof) and start analyzing the sample based on the image analysis process ( 380 - 386 ). Once the New Analysis operation is in process, it takes a number of different tests (in one embodiment seven tests) non-stop and summarizes the test results after the last test has completed. The image results are saved automatically as a group by a time date stamp and can be further sorted by positive or negative results for ease of viewing recall ( 392 - 394 ). Different audible sounds can be played at the end of each test to catch the operators attention. The image result is obtained by subtracting the current image from its initial background image. After finishing this analysis, the system asks user if he/she wants to review the test summary or else return to the main menu. 
     When the option of viewing previous results is selected, the user can select his/her desired filename and presses Display button to command the system to decompress and display the image and/or other necessary information ( 402 - 408 ). 
     When the option of updating date, time, database and/or firmware is selected ( 306 ), the system shows a menu to allow the user to choose different options such as update date, time, or upgrade the firmware, or test the reliability of the system. For example, when the user presses the date button ( 308 ), the system allows the user to change the date via the buttons of the system. After the date is confirmed to be changed, the system will store the change in its memory and return to the previous menu to allow the user to choose other options. The change of the time functions in the same manner as the change of the date ( 310 ). 
     In case the user wants to update the database by pressing Database button ( 316 ), the system communicates with the PC in order to set up a channel for data transfer ( 312 ). Upon a successful connection the user can update database and/or firmware. After the firmware or database is updated, the user presses the Ok button to return to the main menu. When the system connects to the PC unsuccessfully, it warns the user to check the connection ( 316 ). 
     When the user wants to test the reliability of the system, the user can press the Test button ( 322 ). As soon as this button is pressed, the user can test different system parameters. He/she can save the changed parameter or restore default parameter. When the user presses Exit button, system returns to the main menu. 
     By having all components under program control and by arranging for a known input to the system such as a controlled injection of target material, the system can perform self-calibration and self-diagnostic. The function of this program is to calibrate the entire system and determine and store the required time, and temperature parameter, among others. If these parameters are not within specified limits for any reason, the program can alert the user. Guided by a service program the user response can range from immediate shutdown to scheduling service at a later date, to simply noting the circumstances. 
       FIG. 8  shows an exemplary image analysis process executed by the processor  200  to detect chemical agents automatically. To start the analysis process, the system turns the micro-pump(s) N (i.e., N=1, 2, 3 . . . or a combination thereof) to disperse the chemical solution into the Swiped Sample. The pumping rate is set to 2 Hz. After dispersing chemical solution, the system starts heating the sample to excite the chemical reactions. A current of about 1 Ampere is required to heat up the filament. When the temperature of the sample reaches to a predefined value, the system turns the heater off, the LED and the fan on. In one embodiment, before commanding the CMOS image sensor to capture an image, the system waits for the chemical reaction under optimized: time, temperature, volume dispensed, and vapor to complete for around 1 ms. The captured image is then displayed on the LCD. The system creates a result image by subtracting the captured image from the background one. Then the result image is compared with the color patterns in the lookup table stored in the memory. If the results image matches some pattern, the result will be displayed and an audible alarm is given. Otherwise, an appropriate message is displayed on the LCD. 
     Due to the automated analysis, the system provides an objective indication of potential threats with more accurate results and more convenience. 
     The invention may be implemented in hardware, firmware or software, or a combination of the three. Preferably the invention is implemented in a computer program executed on a programmable computer having a processor, a data storage system, volatile and non-volatile memory and/or storage elements, at least one input device and at least one output device. 
     By way of example, a block diagram of a computer to support the system is discussed next. The computer preferably includes a processor, random access memory (RAM), a program memory (preferably a writable read-only memory (ROM) such as a flash ROM) and an input/output (I/O) controller coupled by a CPU bus. The computer may optionally include a hard drive controller which is coupled to a hard disk and CPU bus. Hard disk may be used for storing application programs, such as the present invention, and data. Alternatively, application programs may be stored in RAM or ROM. I/O controller is coupled by means of an I/O bus to an I/O interface. I/O interface receives and transmits data in analog or digital form over communication links such as a serial link, local area network, wireless link, and parallel link. Optionally, a display, a keyboard and a pointing device (mouse) may also be connected to I/O bus. Alternatively, separate connections (separate buses) may be used for I/O interface, display, keyboard and pointing device. Programmable processing system may be preprogrammed or it may be programmed (and reprogrammed) by downloading a program from another source (e.g., a floppy disk, CD-ROM, or another computer). 
     Each computer program is tangibly stored in a machine-readable, removable storage media or device (e.g., program memory or magnetic disk) readable by a general or special purpose programmable computer, for configuring and controlling operation of a computer when the storage media or device is read by the computer to perform the procedures described herein. The inventive system may also be considered to be embodied in a computer-readable storage medium, configured with a computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner to perform the functions described herein. 
     The 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 details and operating procedures, can be accomplished without departing from the scope of the invention itself. 
     Although specific embodiments of the present invention have been illustrated in the accompanying drawings and described in the foregoing detailed description, it will be understood that the invention is not limited to the particular embodiments described herein, but is capable of numerous rearrangements, modifications, and substitutions without departing from the scope of the invention. The following claims are intended to encompass all such modifications.