US20050210956A1 - Method of identifying and detecting the concentrations of multiple species by means of a spectrophone - Google Patents
Method of identifying and detecting the concentrations of multiple species by means of a spectrophone Download PDFInfo
- Publication number
- US20050210956A1 US20050210956A1 US11/086,280 US8628005A US2005210956A1 US 20050210956 A1 US20050210956 A1 US 20050210956A1 US 8628005 A US8628005 A US 8628005A US 2005210956 A1 US2005210956 A1 US 2005210956A1
- Authority
- US
- United States
- Prior art keywords
- chamber
- detector chamber
- frequency
- spectrophone
- gas sample
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/36—Detecting the response signal, e.g. electronic circuits specially adapted therefor
- G01N29/42—Detecting the response signal, e.g. electronic circuits specially adapted therefor by frequency filtering or by tuning to resonant frequency
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/02—Analysing fluids
- G01N29/036—Analysing fluids by measuring frequency or resonance of acoustic waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/222—Constructional or flow details for analysing fluids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
- G01N29/348—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with frequency characteristics, e.g. single frequency signals, chirp signals
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/021—Gases
- G01N2291/0215—Mixtures of three or more gases, e.g. air
Abstract
A method of identifying and determining the concentrations of multiple species in a gas sample, includes providing a spectrophone assembly having a detector chamber, supplying the gas sample to the detector chamber and simultaneously passing a plurality of radiations of different wavelengths into the detector chamber to produce multiple acoustic resonances of different frequencies. Acoustic resonances in the detector chamber are simultaneously sensed to produce corresponding electrical signals, and the electrical signals are analysed to identify the species present in the gas sample and determine the concentration of each specie.
Description
- This invention relates to the identification and determination of the concentrations of multiple species in a gas sample by means of a spectrophone.
- In laser based photo acoustic spectroscopy, each molecular specie in a detection chamber is basically detected from the response to illumination by laser radiation of a specific wavelength. Absorption of such radiation by a specie in the detector chamber at the specific wavelength produces an amplitude modulated pressure which is detected by a microphone in the detector chamber. Generally, if more than one specie is involved, with interference from unwanted species is to be taken into account, then operation at corresponding different wavelengths is required. The procedure involved ultimately sorts out different species and/or interfering components.
- Such a procedure normally requires the operation of a spectrophone at different wavelengths in time sequence, that is to say requires that the laser be tuned in time ordered sequence to different wavelengths. When each wavelength arises from a different and separate source, such as a set of semi conductor lasers each operating at a different wavelength, the illumination from each such laser is injected into the spectrophone in timed sequence. Thus, measurement of multiple species cannot be carried out simultaneously and consequently requires more time for the species to be identified and their concentrations determined.
- Further information in this respect can be found in the following references:
- Kreuzer, L. B., Journal of Applied Physics, 42, 2934 (1971).
- Rosengren, L-G., Infrared Physics, 13, 173 (1973).
- Minguzzi, P., Tonelli, M., and Carrozzi, A., Journal of Optical Spectroscopy, 96, 294 (1982).
- Morse, P. M., “Vibration and Sound” (McGraw-Hill, New York, 1968). West, G. A., Barrett, J. J., and Siebert, D. R., Review of Scientific Instruments, 54, 797 (1983).
- It is therefore an object of this invention to provide a method simultaneously identifying and determining the concentrations of multiple species by means of a spectrophone.
- According to the invention, a method of identifying and measuring the concentration of multiple species in a gas sample includes providing a spectrophone assembly having a detector chamber supplying the gas sample to the detector chamber simultaneously passing a plurality of radiations of different wavelengths into the detector chamber to produce multiple acoustic resonances of different frequencies, simultaneously sensing acoustic resonances in the detector chamber and producing corresponding electrical signals, and analyzing said electrical signals to identify the species present in the gas sample and determine the concentration of each specie.
- The acoustic resonances may be determined by internal geometry of the detector chamber. The acoustic resonances may be sensed by at least one microphone.
- The method may include providing a plurality of detector chambers each with a single or multiple acoustic resonant mode.
- The radiation may be modulated amplitude, frequency or phase or by utilizing the Stark effect to modulate the frequency of specie absorption with respect to the frequency or wavelength of the radiation passed into the chamber.
- According to one aspect of the invention, a method of identifying and measuring the concentration of multiple species in a gas sample includes providing a spectrophone with a detector chamber which is acoustically resonant at a plurality of different resonant frequencies, simultaneously illuminating the multiple species in the detector chamber with a plurality of lasers each operating at a different wavelength, the radiation from each laser being amplitude modulated at a frequency rate corresponding to a particular resonant frequency, providing microphones in the detector chamber suitably positioned therein and frequency tuned to a corresponding resonant frequency and analyzing signals from the microphones to identify the species present and determine their concentration.
- Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, of which:
-
FIG. 1 is a schematic view of a spectrophone assembly in accordance with one embodiment of the invention; -
FIG. 2 is a graph showing the separation between modulation frequencies ω1 and ω2; -
FIG. 3 a is a side view of a spectrophone in accordance with another embodiment of the invention; -
FIG. 3 b is an end view of the spectrophone chamber ofFIG. 3 a; -
FIG. 4 a is a side view of a spectrophone chamber in accordance with a still further embodiment of the invention; -
FIG. 4 b is an end view of the spectrophone chamber ofFIG. 4 a; -
FIG. 5 a is a side view of a spectrophone chamber in accordance with yet another embodiment of the invention; and -
FIG. 5 b is a side view of the spectrophone chamber ofFIG. 5 a. - Referring first to
FIG. 1 of the drawings, a spectrophone assembly includes a cell orchamber 3 which in use is illuminated by twolasers chamber 3 is formed by two cylindrical tubes with internal length and diameter L1, D1and L2, D2 respectively, the two tubes being internally connected and vacuum closed to the outside. - The
lasers modulators lock amplifiers chamber 3 by fiber optics or wave guides 4 and the two beams are combined by adichroic mirror 5 which transmits the beam fromlaser 1 and reflects the beam fromlaser 2. - The
chamber 3 is closed by tworadiation transmitting windows 6 through which the laser beams pass before being received by aradiation power meter 7 adjacent theexit window 6. Asingle power meter 7 is used to measure the exit powers for both power beams simultaneously. Thus, thepower meter 7 must have a response time fast enough to detect beams at both modulation rates ω1 and ω2. Alternatively, separate power meters each sensitive to a corresponding modulation rate may be used. - The exit power P measured by
power meter 7 is separated by afilter 8 into power components for ω1 and ω2 which are then sent to acomputer 14 for signal normalization purposes. A gas sample containing trace amounts of the species of interest is passed into and out of thechamber 3 throughvalved ports 9. The gas sample is typically air at a pressure of about 1 atmosphere. The sample may be a static gas fill or may be continuously flowed through thechamber 3. The necessary electric power supplies are of course provided as will be readily apparent to a person skilled in the art. - The
chamber 3 is provided with microphones M1, M2. The acoustic responses chosen for operation should be sufficiently separated in frequency space such that there will be no overlap in the response from the microphones. This can be effected by proper design and selection of the internal geometry of thechamber 3.FIG. 2 illustrates a typical frequency separation of the two acoustics resonances in this embodiment. Such frequency separation provides a basic filter between the responses of the microphones and also filters substantially all acoustic noise and/or erroneous signals arising from outside the bandwidths of the subject resonances. - Referring now again to
FIG. 1 , if the specie to be detected has an absorptivity at λ1, the absorption will produce gas heating which, because of the fixed chamber volume, causes a pressure change modulated at a frequency of ω1 which is sensed by internal microphone M1. The resulting electronic signal es1 from microphone M1 is fed to and measured by lock-inamplifier 10. The modulation rate ω1 corresponds to an acoustic resonance frequency at ω1 which amplifies the pressure changes at this modulation rate. The frequency bandwidth of the resonance is sufficiently narrow to effectively prevent frequency overlap, within its bandwidth, with other resonances and thereby filters out acoustic signals from any source at frequencies outside the bandwidth of the resonance at ω1. The resonance frequency is determined by the internal geometry of thechamber 3. Microphone M1 is located at or near a maximum of thepressure standing wave 12, the amplitude of which is shown inFIG. 1 . - In a similar manner, microphone M2 is located near a maximum of
pressure standing wave 13 in the side arm with length and diameter L2, D2. The resonance in this case is at frequency ω2 and outside the bandwidth of the resonance at ω1. The signals es1 and es2 from microphones M1 and M2 respectively are fed for processing to separate phase-locked (lock-in)amplifiers computer 14. The exit powers of the two beams P(ω1) and P(ω2) required for normalization of the microphone signals are also fed into thecomputer 14. The computer analyzes the computer data and produces the specie identifications and their concentrations for display. - The acoustic resonances of the
chamber 3 are defined by its internal geometry in accordance with the following equation:
ωkmn =πc[(k/L)2+(βmn /R)2]1/2 (1)
where ωkmn is the acoustic resonance frequency, the in radians per second, defined by a cylindrical section of length L between the end boundaries and of internal radius R, c is the velocity of sound for the gas at the pressure and temperature inside thechamber 3, k is an integer having values corresponding to longitudinal harmonics, and βmn is the nth root of the derivative of the Bessel function Jm(πβ), of order m, with respect to β. - It should be noted that the acoustic resonance is a pressure standing wave where the boundaries defining the length L can be any discontinuity in the cross section, such as the window boundary at each end of the
chamber 3. The windows need not even be present, i.e. the ends of the cell may be open. The basic fact is that these boundaries define the standing wave nodes of zero pressure. Each tubular section of the cell (as shown being utilized by microphones M1 and M2) has available to it a number of resonances defined by the values of k, m and n and the sum and difference resonance frequencies by various combinations of resonances arising from the two sections shown inFIG. 1 . All of the differing resonances can be used to increase the number of radiation sources of different wavelengths illuminating thechamber 3 where each source is modulated and its microphone response is processed at its resonance frequency. - There are many internal geometrical configurations of the
chamber 3 which promote acoustic resonances. To illustrate the principles involved,FIGS. 3 a, 3 b, 4 a, 4 b, 5 a and 5 b show schematics of some configurations (with the pressure profile indicated by dotted lines) for some resonant pressure standing waves. The maxima are the most desirable locations for a microphone. -
FIGS. 3 a and 3 b show fundamental resonance modes available with the geometry illustrated. Theexpansion bulbs expansion bulbs chamber 15 need not be closed at both ends. As shown, one end is open.FIG. 3 shows the best locations X for a microphone for each resonance. A single microphone of sufficient frequency bandwidth can be located in an overlapping region of two or more resonances where the pressure value in each case is non-zero. -
FIG. 4 shows a configuration with tworesonance side arms side arms -
FIG. 5 shows a configuration similar to that ofFIG. 4 except that theside arm tubes disks - Thus, as described above, a photo acoustic cell can be simultaneously illuminated by a number of radiation sources, each of different wavelength, and simultaneously analyzing a gas sample in the cell for its specie identifications and concentrations. The gas pressure in the chamber may be in the range of from about 0.1 TORR to as high as practically possible, and the detectable concentration of a specie may range from a trace to 100%.
- The advantages and other embodiments of the invention will now be readily apparent to a person skilled in the art, the scope of the invention being defined in the appended claims.
Claims (5)
1. A method of identifying and determining the concentrations of multiple species in a gas sample, the method comprising:
providing a spectrophone assembly having a detector chamber,
supplying the gas sample to the detector chamber,
simultaneously passing a plurality of radiations of different wavelengths into the detector chamber to produce multiple acoustic resonances of different frequencies,
simultaneously sensing acoustic resonances in the detector chamber and producing corresponding electrical signals, and
analyzing said electrical signals to identify the species present in the gas sample and determine the concentration of each specie.
2. A method according to claim 1 wherein the acoustic resonances are defined by internal geometry of the detector chamber.
3. A method according to claim 1 wherein the acoustic resonances are sensed by at least one microphone.
4. A method according to claim 1 including providing a plurality of detector chambers each with a single or multiple acoustic resonant mode.
5. A method according to claim 1 wherein the radiation is modulated in amplitude, frequency or phase or by utilizing the Stark effect to modulate the frequency of specie absorption with respect to the frequency or wavelength of the radiation passed into the chamber.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11/797,375 US7647815B2 (en) | 2004-03-24 | 2007-05-03 | Method of identifying and detecting the concentrations of multiple species by means of a spectrophone |
US12/629,692 US8096165B2 (en) | 2004-03-24 | 2009-12-02 | Spectrophone assembly for identifying and detecting multiple species |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA2,461,328 | 2004-03-24 | ||
CA002461328A CA2461328A1 (en) | 2004-03-24 | 2004-03-24 | A multiplexed type of spectrophone |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/797,375 Continuation US7647815B2 (en) | 2004-03-24 | 2007-05-03 | Method of identifying and detecting the concentrations of multiple species by means of a spectrophone |
Publications (1)
Publication Number | Publication Date |
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US20050210956A1 true US20050210956A1 (en) | 2005-09-29 |
Family
ID=34988168
Family Applications (3)
Application Number | Title | Priority Date | Filing Date |
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US11/086,280 Abandoned US20050210956A1 (en) | 2004-03-24 | 2005-03-23 | Method of identifying and detecting the concentrations of multiple species by means of a spectrophone |
US11/797,375 Expired - Fee Related US7647815B2 (en) | 2004-03-24 | 2007-05-03 | Method of identifying and detecting the concentrations of multiple species by means of a spectrophone |
US12/629,692 Expired - Fee Related US8096165B2 (en) | 2004-03-24 | 2009-12-02 | Spectrophone assembly for identifying and detecting multiple species |
Family Applications After (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/797,375 Expired - Fee Related US7647815B2 (en) | 2004-03-24 | 2007-05-03 | Method of identifying and detecting the concentrations of multiple species by means of a spectrophone |
US12/629,692 Expired - Fee Related US8096165B2 (en) | 2004-03-24 | 2009-12-02 | Spectrophone assembly for identifying and detecting multiple species |
Country Status (2)
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US (3) | US20050210956A1 (en) |
CA (1) | CA2461328A1 (en) |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20070284887A1 (en) * | 2006-06-13 | 2007-12-13 | Tseng-Shen Lee | Using sound waves and photic energy for electric power |
US20110088453A1 (en) * | 2009-10-21 | 2011-04-21 | Commissariat A L'energie Atomique Et Aux Energies Alternatives | Photoacoustic gas detector |
WO2012010806A1 (en) * | 2010-07-21 | 2012-01-26 | Université De Reims Champagne Ardenne | Method and device for detecting trace amounts of many gases |
AT511934A3 (en) * | 2012-12-14 | 2014-01-15 | Avl List Gmbh | Photoacoustic measuring cell |
US20140338423A1 (en) * | 2011-12-06 | 2014-11-20 | The Technology Partnership Plc. | Acoustic sensor |
CN104220864A (en) * | 2011-12-15 | 2014-12-17 | 梅特勒-托利多公开股份有限公司 | Gas measuring device |
CN106124410A (en) * | 2016-06-08 | 2016-11-16 | 中国科学院合肥物质科学研究院 | Single photoacoustic cell measures the new method of aerosol multi-wavelength absorptance simultaneously |
WO2017068301A1 (en) * | 2015-10-21 | 2017-04-27 | Aerovia | Gas-detecting device with very high sensitivity based on a helmholtz resonator |
CN112903592A (en) * | 2019-12-04 | 2021-06-04 | 财团法人金属工业研究发展中心 | Gas concentration detection system and gas concentration detection method |
CN112924388A (en) * | 2021-01-22 | 2021-06-08 | 中国科学院合肥物质科学研究院 | Orthogonal dual channel acoustic resonance module and device comprising same |
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DE102010062015B4 (en) | 2010-11-26 | 2021-09-02 | Endress+Hauser Conducta Gmbh+Co. Kg | Measuring device for measuring absorption or scattering at different wavelengths |
US8434366B2 (en) * | 2010-12-15 | 2013-05-07 | Texas Instruments Incorporated | Active detection techniques for photoacoustic sensors |
US8594507B2 (en) * | 2011-06-16 | 2013-11-26 | Honeywell International Inc. | Method and apparatus for measuring gas concentrations |
DK3535563T3 (en) * | 2016-11-04 | 2023-08-21 | Wilco Ag | METHOD AND APPARATUS FOR MEASURING A CONCENTRATION OF A GAS |
CN107064295B (en) * | 2017-01-14 | 2019-07-02 | 西安科技大学 | A kind of methane gas concentration measurement system and method |
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US6725704B2 (en) * | 2000-01-14 | 2004-04-27 | Pas Technology A/S | Gas analyzer |
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2004
- 2004-03-24 CA CA002461328A patent/CA2461328A1/en not_active Abandoned
-
2005
- 2005-03-23 US US11/086,280 patent/US20050210956A1/en not_active Abandoned
-
2007
- 2007-05-03 US US11/797,375 patent/US7647815B2/en not_active Expired - Fee Related
-
2009
- 2009-12-02 US US12/629,692 patent/US8096165B2/en not_active Expired - Fee Related
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US4818882A (en) * | 1986-05-27 | 1989-04-04 | Aktieselskabet Bruel & Kjaer | Photoacoustic gas analyzer |
US5933245A (en) * | 1996-12-31 | 1999-08-03 | Honeywell Inc. | Photoacoustic device and process for multi-gas sensing |
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US6662627B2 (en) * | 2001-06-22 | 2003-12-16 | Desert Research Institute | Photoacoustic instrument for measuring particles in a gas |
Cited By (20)
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US7358621B2 (en) * | 2006-06-13 | 2008-04-15 | Tseng-Shen Lee | Using sound waves and photic energy for electric power |
US20070284887A1 (en) * | 2006-06-13 | 2007-12-13 | Tseng-Shen Lee | Using sound waves and photic energy for electric power |
US20110088453A1 (en) * | 2009-10-21 | 2011-04-21 | Commissariat A L'energie Atomique Et Aux Energies Alternatives | Photoacoustic gas detector |
FR2951545A1 (en) * | 2009-10-21 | 2011-04-22 | Commissariat Energie Atomique | PHOTOACOUSTIC GAS SENSOR |
EP2315019A1 (en) * | 2009-10-21 | 2011-04-27 | Commissariat à l'Énergie Atomique et aux Énergies Alternatives | Photoacoustic gas detector |
US8359904B2 (en) | 2009-10-21 | 2013-01-29 | Commissariat a l'Energie Atomique et aux Energies Albernatives | Photoacoustic gas detector |
WO2012010806A1 (en) * | 2010-07-21 | 2012-01-26 | Université De Reims Champagne Ardenne | Method and device for detecting trace amounts of many gases |
FR2963102A1 (en) * | 2010-07-21 | 2012-01-27 | Univ Reims Champagne Ardenne | METHOD AND DEVICE FOR DETECTING MULTIPLE GAS TRACES |
US20140338423A1 (en) * | 2011-12-06 | 2014-11-20 | The Technology Partnership Plc. | Acoustic sensor |
US9869659B2 (en) * | 2011-12-06 | 2018-01-16 | The Technology Partnership Plc. | Acoustic sensor |
CN104220864A (en) * | 2011-12-15 | 2014-12-17 | 梅特勒-托利多公开股份有限公司 | Gas measuring device |
WO2014090518A1 (en) * | 2012-12-14 | 2014-06-19 | Avl List Gmbh | Photoacoustic measurement cell |
AT511934B1 (en) * | 2012-12-14 | 2014-06-15 | Avl List Gmbh | Photoacoustic measuring cell |
AT511934A3 (en) * | 2012-12-14 | 2014-01-15 | Avl List Gmbh | Photoacoustic measuring cell |
WO2017068301A1 (en) * | 2015-10-21 | 2017-04-27 | Aerovia | Gas-detecting device with very high sensitivity based on a helmholtz resonator |
FR3042867A1 (en) * | 2015-10-21 | 2017-04-28 | Aerovia | DEVICE FOR DETECTING GAS WITH VERY HIGH SENSITIVITY BASED ON A RESONATOR OF HELMHOLTZ |
US10876958B2 (en) * | 2015-10-21 | 2020-12-29 | Aerovia | Gas-detecting device with very high sensitivity based on a Helmholtz resonator |
CN106124410A (en) * | 2016-06-08 | 2016-11-16 | 中国科学院合肥物质科学研究院 | Single photoacoustic cell measures the new method of aerosol multi-wavelength absorptance simultaneously |
CN112903592A (en) * | 2019-12-04 | 2021-06-04 | 财团法人金属工业研究发展中心 | Gas concentration detection system and gas concentration detection method |
CN112924388A (en) * | 2021-01-22 | 2021-06-08 | 中国科学院合肥物质科学研究院 | Orthogonal dual channel acoustic resonance module and device comprising same |
Also Published As
Publication number | Publication date |
---|---|
US8096165B2 (en) | 2012-01-17 |
US20100107734A1 (en) | 2010-05-06 |
US7647815B2 (en) | 2010-01-19 |
US20070256475A1 (en) | 2007-11-08 |
CA2461328A1 (en) | 2005-09-24 |
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