Sample records for gas chromatography-electron-capture detection

  1. DETERMINATION OF ACRYLAMIDE IN RAT SERUM AND SCIATIC NERVE BY GAS CHROMATOGRAPHY-ELECTRON-CAPTURE DETECTION

    EPA Science Inventory

    A modified method for the derivatization and analysis of acrylamide as 2-bromopropenamide by gas chromatography/electron capture detection was validated in serum and sciatic nerve from rats. he method was accurate and precise over the concentration range of 2240 to 74700 ppm (w/v...

  2. Determination of acrylamide in rat serum and sciatic nerve by gas chromatography-electron-capture detection.

    PubMed

    Raymer, J H; Sparacino, C M; Velez, G R; Padilla, S; MacPhail, R C; Crofton, K M

    1993-09-22

    A modified method for the derivatization and determination of acrylamide as 2-bromopropenamide by gas chromatography-electron-capture detection was developed and applied to serum and sciatic nerve from rats. The method was accurate and precise over the calibration range 2.24-7.47 micrograms/ml in serum diluted 1:125 and 4-122 micrograms/g in sciatic nerve homogenate (5 mg/ml). limits of detection were estimated to be 1200 ng/ml in undiluted serum and 3 micrograms/g in intact sciatic nerve. The use of less dilute samples to allow for lower limits of detection appears feasible. The time-course of acrylamide in serum and sciatic nerve was studied after acute dosing and indicated elimination half-lives of 1.8 and 2.0 h for serum and sciatic nerve, respectively. A dose-effect relationship was established for each matrix after acute dosing and the measured acrylamide concentrations in serum (microgram/ml) were approximately the same as in sciatic nerve (microgram/g). PMID:8263094

  3. Quantitative detection of trace explosive vapors by programmed temperature desorption gas chromatography-electron capture detector.

    PubMed

    Field, Christopher R; Lubrano, Adam; Woytowitz, Morgan; Giordano, Braden C; Rose-Pehrsson, Susan L

    2014-01-01

    The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive vapor samples. The direct liquid deposition method yields a higher fidelity between the analysis of vapor samples and the analysis of solution standards than using separate injection methods for vapors and solutions, i.e., samples collected on vapor collection tubes and standards prepared in solution vials. Additionally, the method can account for instrumentation losses, which makes it ideal for minimizing variability and quantitative trace chemical detection. Gas chromatography with an electron capture detector is an instrumentation configuration sensitive to nitro-energetics, such as TNT and RDX, due to their relatively high electron affinity. However, vapor quantitation of these compounds is difficult without viable vapor standards. Thus, we eliminate the requirement for vapor standards by combining the sensitivity of the instrumentation with a direct liquid deposition protocol to analyze trace explosive vapor samples. PMID:25145416

  4. [Analysis of organochlorine pesticides and pyrethroid pesticides in vegetables by gas chromatography-electron capture detection coupled with solid-phase extraction using multiwalled carbon nanotubes as adsorbent].

    PubMed

    Zhao, Haixiang; Jia, Yanxia; Ding, Mingyu; Sun, Dajiang; Zhao, Mengbin

    2011-05-01

    A multi-residue analytical method based on solid-phase extraction (SPE) with multiwalled carbon nanotubes (MWCNTs) as adsorbent was developed. The determination of 6 organochlorine pesticides and 7 pyrethroid pesticides in vegetables (including cucumber, cherry tomato, cabbage, lettuce, purple cabbage, leek, shallot and onion) was carried out by gas chromatography-electron capture detection (GC-ECD). The GC-ECD method used two columns (HP-50 and HP-1) and two ECD detectors. The HP-50 column was used for the analysis and the HP-1 column for validation. The clean-up conditions were optimized. The analytes were extracted by acetonitrile, and the extract was cleaned up by the MWCNTs SPE cartridge. The extract was re-dissolved by hexane, eluted with acetone-hexane (7:3, v/v) from the columns. The recoveries were over 70% for the 11 pesticides in the 13 pesticides. The results indicated that the MWCNTs SPE cartridge was efficient for 8 vegetable samples, because it reduced the contamination of the coloring materials to GC-ECD. The experimental results showed the MWCNTs SPE cartridge can adsorb the coloring materials and the eluant was nearly colorless. PMID:21847981

  5. Analysis of corky off-flavour compounds at ultra trace level with multidimensional gas chromatography-electron capture detection.

    PubMed

    Slabizki, Petra; Schmarr, Hans-Georg

    2013-01-01

    A robust method for routine quality control of corky off-flavour compounds in wine and cork soak matrices has been established. Based on an automated headspace solid phase microextraction (HS-SPME), the method needs only marginal sample preparation and achieves low (sub-ng L(-1)) trace level detection limits (LODs) for the most relevant off-flavour compounds, such as 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA) and 2,4,6-tribromoanisole (TBA). Particularly for wine matrix, reliable trace level quantification had only been achieved after applying heart-cutting multidimensional gas chromatography (MDGC). Using a halogen-sensitive electron capture detector (ECD) and quantification with a stable isotope dilution assay (SIDA), LODs of 0.1ng L(-1) for TCA, TeCA and TBA could be obtained. Since a SIDA based quantification method is used with a non-mass spectrometric detector, the necessary chromatographic resolution of internal standard and target analyte peaks resulted from the use of highly deuterated [(2)H(5)]-isotopologues. PMID:23219330

  6. Optimization of matrix solid phase dispersion coupled with gas chromatography electron capture detection for determination of chlorinated pesticides in soil.

    PubMed

    Salemi, Amir; Shafiei, Elham; Vosough, Maryam

    2012-11-15

    A fast, simple and efficient technique based on matrix solid phase dispersion has been presented for extraction and clean-up of some chlorinated pesticides and derivative products; ?-BHC, ?-BHC, ?-BHC, ?-BHC, heptachlor, aldrin, dieldrin, endrin, endosulfan 1, endosulfan 2, 4,4'-DDT, 4,4'-DDE, 4,4'-DDD, heptachlor epoxide, endrin aldehyde, endosulfan sulfate. Box-Behnken response surface methodology was employed for optimization of the extraction efficiency. As the optimized procedure, 0.5 g of dried and sieved soil samples were mixed with 2.0 g of 10% C18 in silica (w/w) as dispersant and after transferring into the extraction tube they were extracted with 8 mL of dichloromethane-n-hexane (1:1, v/v). Gas chromatography with electron capture detector was used for selective and sensitive determination of the analytes. Recoveries for the extraction of the proposed analytes were calculated and were satisfying (more than 75%), except for endrin aldehyde (59%) and endosulfan sulfate (62%). Also the method was linear over the calibration range (R(2)>0.991) and the quantitative results were reasonably reproducible and sensitive (LODs ranged between 0.3 and 1.8 ng g(-1)). PMID:23158355

  7. Validation of a headspace solid-phase microextraction procedure with gas chromatography-electron capture detection of pesticide residues in fruits and vegetables

    Microsoft Academic Search

    Mee Kin Chai; Guan Huat Tan

    2009-01-01

    Headspace solid-phase microextraction (HS-SPME) was evaluated for the determination of pesticide residues in fruits and vegetables by gas chromatography with an electron capture detector (GC-ECD). The fibre used was coated with polydimethylsiloxane (100?m thickness) and the analytical conditions employed have been developed and optimised in a previous work [Chai, M. K., Tan, G. H., & Asha, L. (2008). Optimisation of

  8. Use of green coating (cork) in solid-phase microextraction for the determination of organochlorine pesticides in water by gas chromatography-electron capture detection.

    PubMed

    Dias, Adriana Neves; Simão, Vanessa; Merib, Josias; Carasek, Eduardo

    2015-03-01

    A novel method for the determination of organochlorine pesticides in water samples with extraction using cork fiber and analysis by gas chromatography with electron capture detector was developed. Also, the procedure to extract these pesticides with DVB/Car/PDMS fiber was optimized. The optimization of the variables involved in the extraction of organochlorine pesticides using the aforementioned fibers was carried out by multivariate design. The optimum extraction conditions were sample temperature 75 °C, extraction time 60 min and sodium chloride concentration 10% for the cork fiber and sample temperature 50 °C and extraction time 60 min (without salt) for the DVB/Car/PDMS fiber. The quantification limits for the two fibers varied between 1.0 and 10.0 ng L(-1). The linear correlation coefficients were >0.98 for both fibers. The method applied with the use of the cork fiber provided recovery values between 60.3 and 112.7 and RSD?25.5 (n=3). The extraction efficiency values for the cork and DVB/Car/PDMS fibers were similar. The results show that cork is a promising alternative as a coating for SPME. PMID:25618687

  9. Simultaneous analysis of polychlorinated biphenyls and organochlorine pesticides in seawater samples by membrane-assisted solvent extraction combined with gas chromatography-electron capture detector and gas chromatography-tandem mass spectrometry.

    PubMed

    Shi, Xizhi; Tang, Zigang; Sun, Aili; Zhou, Lei; Zhao, Jian; Li, Dexiang; Chen, Jiong; Pan, Daodong

    2014-12-01

    A highly efficient and environment-friendly membrane-assisted solvent extraction system combined with gas chromatography-electron capture detector was applied in the simultaneous determination of 17 polychlorinated biphenyls and organochlorine pesticides in seawater samples. Variables affecting extraction efficiency, including extraction solvent used, stirring rate, extraction time, and temperature, were optimized extensively. Under optimal extraction conditions, recoveries between 76.9% and 104.6% in seawater samples were achieved, and relative standard deviation values below 10% were obtained. The limit of detection (signal-to-noise ratio=3) and limit of quantification (signal-to-noise ratio=10) of 17 polychlorinated biphenyls and organochlorine pesticides in seawater ranged from 0.14ngL(-1) to 0.36ngL(-1) and 0.46ngL(-1) to 1.19ngL(-1), respectively. Matrix effects on extraction efficiency were evaluated by comparing with the results obtained using tap water. The extraction effect of developed membrane-assisted solvent extraction method was further demonstrated by gas chromatography-tandem mass spectrometry which can provide structural information of the analytes for more accurate identification, and results identical to those produced by gas chromatography-electron capture detector were obtained. These findings demonstrate the applicability of the developed membrane-assisted solvent extraction determination method for coupling to gas chromatography-electron capture detector or tandem mass spectrometry for determining polychlorinated biphenyls and organochlorine pesticides in seawater samples. PMID:25310709

  10. Gas chromatography-electron capture determination of styrene-7,8-oxide enantiomers.

    PubMed

    Kezi?, S; Jakasa, I; Wenker, M A; Boogaard, P J; Monster, A C; de Wolff, F A

    2000-12-01

    The enantiomers of styrene-7,8-oxide (phenyloxirane, SO) were determined using a method based on base catalysed hydrolysis with sodium methoxide. The oxirane ring opening resulted in formation, without racemisation, of the enantiomeric pairs of the two regional isomers, 2-methoxy-1-phenylethanol and 2-methoxy-2-phenylethanol. The structure of these regional isomers was confirmed by gas chromatography-mass spectrometry (GC-MS) and proton nuclear magnetic resonance (1H-NMR). To improve sensitivity of determination, the formed methoxy alcohols were subsequently derivatised with pentafluoropropionic anhydride enabling electron capture detection. This derivatization proceeded also without racemisation and the formed pentafluoropropionyl derivatives were separated on two serially coupled columns, a non-chiral AT 1705 and a chiral CP Chirasil-Dex-CB. As internal standard 2S,3S-(-)-2-methyl-3-phenyloxirane was used. The limit of quantitation of the method was 0.2 microM. The repeatability of the method was assessed at two concentration levels (2.5 and 25 microM) and ranged from 6 to 9% for both enantiomers. The method was applied to the determination of the rate and enantioselectivity of the cytochrome P-450 dependent oxidation of styrene to SO enantiomers in human liver microsomes. PMID:11145063

  11. Simultaneous determination of amitraz and its metabolite residue in food animal tissues by gas chromatography-electron capture detector and gas chromatography–mass spectrometry with accelerated solvent extraction

    Microsoft Academic Search

    Huan Yu; Yanfei Tao; Tao Le; Dongmei Chen; Awais Ishsan; Yu Liu; Yulian Wang; Zonghui Yuan

    2010-01-01

    A new method has been developed for determination and confirmation of amitraz and its main metabolite, 2,4-dimethylaniline, in food animal tissues using gas chromatography-electron capture detector (GC-ECD) and gas chromatography–mass spectrometry detector (GC–MS). This method is based on a new extraction procedure using accelerated solvent extraction (ASE). It consists of an n-hexane\\/methanol extraction step, a cleaning-up step by BakerBond octadecyl

  12. Analysis of C(14)-C(17) Polychloro-n-alkanes in Environmental Matrixes by Accelerated Solvent Extraction-High-Resolution Gas Chromatography/Electron Capture Negative Ion High-Resolution Mass Spectrometry.

    PubMed

    Tomy, G T; Stern, G A

    1999-11-01

    A method for quantifying medium-chain (C(14)-C(17)) polychloroalkanes (mPCAs) in environmental matrixes by accelerated solvent extraction high-resolution gas chromatography/electron capture negative ion high-resolution mass spectrometry in the selected ion monitoring mode is presented. The formula group abundance profiles of industrial mPCA mixtures, which are used as standards, and of samples are first determined by monitoring [M - Cl](-) ions of specific m/z values corresponding to the molecular formulas present and by correcting the integrated ion signals for the fractional abundance of the specific m/z value monitored and the number of chlorine atoms in the formula group. mPCA concentrations in environmental samples are then determined by comparing the response of a specific m/z peak in the sample to that in the standard. Extraction recoveries of mPCAs from spiked fish and sodium sulfate (in place of sediment) were >79%. Method detection limits were 13 ng/g for fish and 1.4 ng/?L for sediment, while the analytical detection limit was ?200 pg, at a signal-to-noise ratio of 4:1. By this method, mPCAs were detected in biota and sediment from the mouth of the Detroit River (MI) and ranged from 70 to 900 ng/g. The simultaneous quantitation of C(10)-C(13) (sPCAs) and C(14)-C(17) PCAs, based on monitoring two specific m/z peaks, one characteristic of sPCAs and the other of mPCAs, is also demonstrated. PMID:21662834

  13. Determination of chlorophenols in soil samples by microwave-assisted extraction coupled to headspace solid-phase microextraction and gas chromatography–electron-capture detection

    Microsoft Academic Search

    Ming-Chi Wei; Jen-Fon Jen

    2003-01-01

    Microwave-assisted extraction coupled to headspace solid-phase microextraction was studied and applied for one-step in-situ sample preparation prior to analysis of chlorophenols (CPs) in soil samples. The CPs in soil sample were extracted into the aqueous solution and then directly onto the solid-phase microextraction (SPME) fiber in headspace under the aid of microwave irradiation. After being desorbed from SPME fiber in

  14. Solidphase extraction on sorbents of different retention mechanisms followed by determination by gas chromatography–mass spectrometric and gas chromatography–electron capture detection of pesticide residues in crops

    Microsoft Academic Search

    Anna Balinova; Rositsa Mladenova; Deyana Shtereva

    2007-01-01

    Implementation of a mixed-mode solid-phase extraction is discussed as a promising approach for matrix clean-up in multiresidue\\/multimatrix methods. Sorbents characterized by different mechanisms of sorption such as reversed-phase (graphitized carbon), weak anion exchange (primary–secondary amine) and strong anion exchange (quaternary amine) were studied for their effectiveness in the removal of the matrix co-extractives in grains, fruits and vegetables for trace

  15. Multiresidue method for the simultaneous determination of four groups of pesticides in ground and drinking waters, using solid-phase microextraction–gas chromatography with electron-capture and thermionic specific detection

    Microsoft Academic Search

    C Gonçalves; M. F Alpendurada

    2002-01-01

    A common sample preparation procedure capable of efficiently concentrating various groups of pesticides, taking advantage of universal detectors like the mass spectrometer or combined techniques of group selective detectors like gas chromatography–electron capture detection (ECD)\\/thermionic specific detection (TSD), is desirable in environmental analysis. Six solid-phase microextraction fibres available for analysis of semi-volatiles (7, 30 and 100 ?m poly(dimethylsiloxane) (PDMS), 85

  16. Identification of dominant odor chemicals emanating from explosives for use in developing optimal training aid combinations and mimics for canine detection

    Microsoft Academic Search

    Ross J. Harper; José R. Almirall; Kenneth G. Furton

    2005-01-01

    Despite the recent surge in the publication of novel instrumental sensors for explosives detection, canines are still widely regarded as one of the most effective real-time field method of explosives detection. In the work presented, headspace analysis is performed by solid phase microextraction (SPME)\\/gas chromatography–mass spectrometry (GC–MS), and gas chromatography–electron capture detection (GC-ECD), and used to identify dominant explosive odor

  17. Photolytic clean-up of biological samples for gas chromatographic analysis of chlorinated paraffins.

    PubMed

    Fridén, Ulrika; Jansson, Bo; Parlar, Harun

    2004-02-01

    A method based on gas chromatography electron capture detection (GC-ECD) for the analysis of chlorinated paraffins (CPs) in biological samples has been investigated. The method includes photolytic destruction of halogenated aromatic compounds, such as PCBs, to eliminate some of the interferences in the analysis of CPs in environmental samples. Gel permeation chromatography was used to isolate CPs from the interfering components of Toxaphene and chlordane after the photolysis. GC-ECD gave a detection limit of 20 ng CPs/g fresh muscle tissue. The recovery of CPs from a spiked moose liver sample was estimated to 94%. PMID:14664836

  18. Rapid determination of DDT and related compounds in soils via carbon skeleton gas chromatography-mass spectrometry.

    PubMed

    Cooke, M; Khallef, K D; Nickless, G; Roberts, D J

    1979-10-19

    The levels of DDT and related compounds in soil samples from an apple orchard have been determined. Extraction of residues was achieved by cyclic steam extraction and by conventional solvent extraction methods allowing comparison of the two methods. Determination of the organochlorine residues present in the extracts was performed by gas-liquid chromatography-electron-capture detection and by carbon skeleton gas chromatograph-mass spectrometry. Excellent agreement between the two determination techniques was achieved. Prior to application of p,p'-DDT, a value of approximately 0.4 ppm was obtained for Delta DDT in the soil. The major component of this total was DDE. After spraying the apple trees with technical grade, p,p'-DDT, Delta DDT for the soil rose to 0.6 ppm. This increase was due to translocation of p,p'-DDT from the trees. PMID:528650

  19. Detection of gas leakage

    DOEpatents

    Thornberg, Steven (Peralta, NM); Brown, Jason (Albuquerque, NM)

    2012-06-19

    A method of detecting leaks and measuring volumes as well as an apparatus, the Power-free Pump Module (PPM), that is a self-contained leak test and volume measurement apparatus that requires no external sources of electrical power during leak testing or volume measurement, where the invention is a portable, pneumatically-controlled instrument capable of generating a vacuum, calibrating volumes, and performing quantitative leak tests on a closed test system or device, all without the use of alternating current (AC) power. Capabilities include the ability is to provide a modest vacuum (less than 10 Torr), perform a pressure rise leak test, measure the gas's absolute pressure, and perform volume measurements. All operations are performed through a simple rotary control valve which controls pneumatically-operated manifold valves.

  20. 78 FR 40027 - Novaluron; Pesticide Tolerances

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-03

    ...consumption data from the USDA under the National Health and Nutrition Examination Survey, What We Eat in America (NHANES/WWEIA...methodology (gas chromatography/electron- capture detection (GC/ECD) method and a high-performance liquid...

  1. 46 CFR 154.1345 - Gas detection.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED...Construction and Equipment Instrumentation § 154.1345 Gas...flammable gas detection system that meets § 154.1350...fixed gas detection system that is not located...fixed gas detection system that meets §...

  2. 46 CFR 154.1345 - Gas detection.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED...Construction and Equipment Instrumentation § 154.1345 Gas...flammable gas detection system that meets § 154.1350...fixed gas detection system that is not located...fixed gas detection system that meets §...

  3. 46 CFR 154.1345 - Gas detection.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED...Construction and Equipment Instrumentation § 154.1345 Gas...flammable gas detection system that meets § 154.1350...fixed gas detection system that is not located...fixed gas detection system that meets §...

  4. 46 CFR 154.1345 - Gas detection.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED...Construction and Equipment Instrumentation § 154.1345 Gas...flammable gas detection system that meets § 154.1350...fixed gas detection system that is not located...fixed gas detection system that meets §...

  5. 46 CFR 154.1345 - Gas detection.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED...Construction and Equipment Instrumentation § 154.1345 Gas...flammable gas detection system that meets § 154.1350...fixed gas detection system that is not located...fixed gas detection system that meets §...

  6. 33 CFR 127.1203 - Gas detection.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 2 2011-07-01 2011-07-01 false Gas detection. 127.1203 Section 127.1203 ...FACILITIES WATERFRONT FACILITIES HANDLING LIQUEFIED NATURAL GAS AND LIQUEFIED HAZARDOUS GAS Waterfront Facilities Handling Liquefied...

  7. 33 CFR 127.1203 - Gas detection.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 2 2012-07-01 2012-07-01 false Gas detection. 127.1203 Section 127.1203 ...FACILITIES WATERFRONT FACILITIES HANDLING LIQUEFIED NATURAL GAS AND LIQUEFIED HAZARDOUS GAS Waterfront Facilities Handling Liquefied...

  8. 33 CFR 127.1203 - Gas detection.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 2 2013-07-01 2013-07-01 false Gas detection. 127.1203 Section 127.1203 ...FACILITIES WATERFRONT FACILITIES HANDLING LIQUEFIED NATURAL GAS AND LIQUEFIED HAZARDOUS GAS Waterfront Facilities Handling Liquefied...

  9. 33 CFR 127.1203 - Gas detection.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 2 2014-07-01 2014-07-01 false Gas detection. 127.1203 Section 127.1203 ...FACILITIES WATERFRONT FACILITIES HANDLING LIQUEFIED NATURAL GAS AND LIQUEFIED HAZARDOUS GAS Waterfront Facilities Handling Liquefied...

  10. Rapid determination of dichlorodiphenyltrichloroethane and its main metabolites in aqueous samples by one-step microwave-assisted headspace controlled-temperature liquid-phase microextraction and gas chromatography with electron capture detection.

    PubMed

    Vinoth Kumar, Ponnusamy; Jen, Jen-Fon

    2011-03-01

    A rapid and sensitive analytical method for the determination of dichlorodiphenyltrichloroethane (DDT) and its main metabolites in environmental aqueous samples has been developed using one-step microwave-assisted headspace controlled-temperature liquid-phase micro-extraction (MA-HS-CT-LPME) technique coupled with gas chromatography-electron-capture detection (GC-ECD). In this study, the one-step extraction of DDT and its main metabolites was achieved by using microwave heating to accelerate the evaporation of analytes into the controlled-temperature headspace to form a cloudy mist vapor zone for LPME sampling. Parameters influencing extraction efficiency were thoroughly optimized, and the best extraction for DDT and its main metabolites from 10-mL aqueous sample at pH 6.0 was achieved by using 1-octanol (4-?L) as the LPME solvent, sampling at 34°C for 6.5 min under 249W of microwave irradiation. Under optimum conditions, excellent linear relationship was obtained in the range of 0.05-1.0 ?g/L for 1-dichloro-2,2-bis-(p'-chlorophenyl)ethylene (p,p'-DDE), 0.1-2.0 ?g/L for o,p'-DDT, 0.15-3.0 ?g/L for 1,1-dichloro-2,2-bis-(p'-chlorophenyl)ethane (p,p'-DDD) and p,p'-DDT, with detection limits of 20 ng/L for p,p'-DDE, and 30 ng/L for o,p'-DDT, p,p'-DDD and p,p'-DDT. Precision was in the range of 3.2-11.3% RSD. The proposed method was validated with environmental water samples. The spiked recovery was between 95.5% and 101.3% for agricultural-field water, between 94% and 99.7% for sea water and between 93.5% and 98% for river water. Thus the established method has been proved to be a simple, rapid, sensitive, inexpensive and eco-friendly procedure for the determination of DDT and its main metabolites in environmental water samples. PMID:21251695

  11. [Determination of 28 organochlorine and synthetic pyrethroid pesticides in greasy wool using accelerated solvent extraction technique and gas chromatography].

    PubMed

    Fan, Yuanmu; Huang, Shaotang; Yu, Xuejun; Gu, Xiaojun; Qiu, Yajun; Zhan, Jia; Chen, Shubing; He, Xiaoyu; Chen, Jun; Wang, Shijie; Li, Yaping; Li, Zhongbang

    2008-09-01

    A method for the simultaneous determination of 28 organochlorine and synthetic pyrethroid pesticides in greasy wool was developed by accelerated solvent extraction (ASE) coupled with gas chromatography-electron capture detection (GC-ECD). The organochlorine and synthetic pyrethroid pesticides in greasy wool were extracted with acetonitrile saturated with n-hexane at 80 degrees C, 10.34 MPa by ASE. The extract was pretreated by a series of procedures such as freezing-lipid filtration, concentration and purification by solid-phase extraction prior to the determination with GC-ECD. The linear ranges were 0.005-1.0 mg/L for 16 organochlorines, 0.02-4.0 mg/L for flumethrin and 0.01-2.0 mg/L for the others. There were good linear relationships between the peak area and concentration in the linear ranges. The average recoveries of 28 organochlorine and synthetic pyrethroid pesticides were 67.2%-107.7%, and the relative standard deviations were 2.6%-29.0%. The method is simple, sensitive and suitable for preliminary screening of organochlorine and synthetic pyrethroid pesticides in greasy wool. PMID:19160757

  12. Gas-influx Detection With MWD Technology

    Microsoft Academic Search

    T. M. Bryant; D. S. Grosso; S. N. Wallace

    1991-01-01

    This paper describes a new gas-influx detection technique that monitors the acoustic responses of annular measurement-while-drilling (MWD) pulses to provide a rapid, early warning of the development of potential gas-kick situations. The technique has been evaluated in both water- and oil-based muds during about 40 gas-kick simulations at two full-scale testing facilities. Free gas is identified by amplitude attenuation and

  13. 46 CFR 154.1350 - Flammable gas detection system.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...Flammable gas detection system. 154.1350 Section...DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED...Construction and Equipment Instrumentation § 154.1350 Flammable gas detection system. (a) The vessel...flammable gas detection system that has sampling...

  14. 46 CFR 154.1350 - Flammable gas detection system.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Flammable gas detection system. 154.1350 Section...DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED...Construction and Equipment Instrumentation § 154.1350 Flammable gas detection system. (a) The vessel...flammable gas detection system that has sampling...

  15. 46 CFR 154.1350 - Flammable gas detection system.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...Flammable gas detection system. 154.1350 Section...DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED...Construction and Equipment Instrumentation § 154.1350 Flammable gas detection system. (a) The vessel...flammable gas detection system that has sampling...

  16. 46 CFR 154.1350 - Flammable gas detection system.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...Flammable gas detection system. 154.1350 Section...DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED...Construction and Equipment Instrumentation § 154.1350 Flammable gas detection system. (a) The vessel...flammable gas detection system that has sampling...

  17. 46 CFR 154.1350 - Flammable gas detection system.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...Flammable gas detection system. 154.1350 Section...DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED...Construction and Equipment Instrumentation § 154.1350 Flammable gas detection system. (a) The vessel...flammable gas detection system that has sampling...

  18. Gas-influx detection with MWD technology

    SciTech Connect

    Bryant, T.M.; Grosso, D.S.; Wallace, S.N. (Teleco Oilfield Services (US))

    1991-12-01

    This paper describes a new gas-influx detection technique that monitors the acoustic responses of annular measurement-while-drilling (MWD) pulses to provide a rapid, early warning of the development of potential gas-kick situations. The technique has been evaluated in both water- and oil-based muds during about 40 gas-kick simulations at two full-scale testing facilities. Free gas is identified by amplitude attenuation and phase delay of MWD fundamentals and their harmonic frequencies. Detection is independent of influx location because the entire length of the annulus between the bit nozzles and a surface-pressure transducer is sampled. Detection of potential gas-kick situations generally occurred within minutes of influx initiation, before any significant gas expansion. Some tests also evaluated a downhole MWD mud-resistivity sensor. Results indicated that both these techniques, and particularly the pulse acoustics, can provide unequivocal confirmation of gas and an earlier warning of gas-kick situations than conventional kick- detection techniques.

  19. 49 CFR 192.736 - Compressor stations: Gas detection.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Compressor stations: Gas detection. 192.736 Section...PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY...192.736 Compressor stations: Gas detection. (a) Not later...

  20. 49 CFR 192.736 - Compressor stations: Gas detection.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Compressor stations: Gas detection. 192.736 Section...PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY...192.736 Compressor stations: Gas detection. (a) Not later...

  1. 49 CFR 192.736 - Compressor stations: Gas detection.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Compressor stations: Gas detection. 192.736 Section...PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY...192.736 Compressor stations: Gas detection. (a) Not later...

  2. 49 CFR 192.736 - Compressor stations: Gas detection.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Compressor stations: Gas detection. 192.736 Section...PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY...192.736 Compressor stations: Gas detection. (a) Not later...

  3. Air Monitoring for Hazardous Gas Detection

    NASA Technical Reports Server (NTRS)

    Arkin, C. Richard; Griffin, Timothy P.; Adams, Frederick W.; Naylor, Guy; Haskell, William; Floyd, David; Curley, Charles; Follistein, Duke W.

    2004-01-01

    The Hazardous Gas Detection Lab (HGDL) at Kennedy Space Center is involved in the design and development of instrumentation that can detect and quantify various hazardous gases. Traditionally these systems are designed for leak detection of the cryogenic gases used for the propulsion of the Shuttle and other vehicles. Mass spectrometers are the basis of these systems, which provide excellent quantitation, sensitivity, selectivity, response times and detection limits. A Table lists common gases monitored for aerospace applications. The first five gases, hydrogen, helium, nitrogen, oxygen, and argon are historically the focus of the HGDL.

  4. Gas cell photoacoustic detection of ultrasound absorption

    NASA Astrophysics Data System (ADS)

    Netzelmann, U.

    2010-03-01

    The photoacoustic signal generated by a 2 MHz ultrasound transducer has been detected at 500 Hz modulation frequency by an attached photoacoustic cell. A dominant mechanism for signal generation is the ultrasound absorption in the gas of the cell, where strong acoustic resonances are excited. The periodic heating by ultrasound absorption in the transducer buffer rod and subsequent thermal diffusion into the gas is a second mechanism. Experiment and theory are in reasonable accordance.

  5. Gas sensitive materials for gas detection and methods of making

    DOEpatents

    Trakhtenberg, Leonid Israilevich; Gerasimov, Genrikh Nikolaevich; Gromov, Vladimir Fedorovich; Rozenberg, Valeriya Isaakovna

    2014-07-15

    A gas sensitive material comprising SnO.sub.2 nanocrystals doped with In.sub.2O.sub.3 and an oxide of a platinum group metal, and a method of making the same. The platinum group metal is preferably Pd, but also may include Pt, Ru, Ir, and combinations thereof. The SnO.sub.2 nanocrystals have a specific surface of 7 or greater, preferably about 20 m2/g, and a mean particle size of between about 10 nm and about 100 nm, preferably about 40 nm. A gas detection device made from the gas sensitive material deposited on a substrate, the gas sensitive material configured as a part of a current measuring circuit in communication with a heat source.

  6. Semiconducting polymers for gas detection

    NASA Technical Reports Server (NTRS)

    Byrd, N. R.; Sheratte, M. B.

    1975-01-01

    Conjugated polyenes, and polyesters containing phthalocyanine in their backbone, were synthesized. These polymers were characterized by chemical analysis, thermogravimetric analysis, spectral analysis, and X-ray diffraction studies for crystallinity, as well as for their film-forming capability and gas/polymer interactions. Most of the polymers were relatively insensitive to water vapor up to 50 percent relative humidity, but the polyester/phthalocyanine (iron) polymer was relatively insensitive up to 100 percent RH. On the other hand, poly(p-dimethylaminophenylacetylene) was too conductive at 100 percent RH. Of the gases tested, the only ones that gave any evidence of interacting with the polymers were SO2, NOx, HCN and NH3. Poly(imidazole)/thiophene responded to each of these gases at all relative humidities, while the other polymers gave varying response, depending upon the RH. Thus, since most of these gases were electron-accepting, the electron-donating character of poly(imidazole)/thiophene substantiates the concept of electronegativity being the operating principle for interaction effects. Of the six polymers prepared, poly(imidazole)/thiophene first showed a very good response to smoldering cotton, but it later became nonresponsive; presumably due to oxidation effects.

  7. Heterodyne method for high specificity gas detection.

    NASA Technical Reports Server (NTRS)

    Dimeff, J.; Donaldson, R. W.; Gunter, W. D., Jr.; Jaynes, D. N.; Margozzi, A. P.; Deboo, G. J.; Mcclatchie, E. A.; Williams, K. G.

    1971-01-01

    This paper describes a new technique for measuring trace quantities of gases. The technique involves the use of a reference cell (containing a known amount of the gas being sought) and a sample cell (containing an unknown amount of the same gas) wherein the gas densities are modulated. Light passing through the two cells in sequence is modulated in intensity at the vibrational-rotational lines characteristic of the absorption spectrum for the gas of interest. Since the absorption process is nonlinear, modulating the two absorption cells at two different frequencies gives rise to a heterodyning effect, which in turn introduces sum and difference frequencies in the detected signal. Measuring the ratio of the difference frequency signal for example, to the signal introduced by the reference cell provides a normalized measure of the amount of the gas in the sample cell. The readings produced are thereby independent of source intensity, window transparency, and detector sensitivity. Experimental evaluation of the technique suggests that it should be applicable to a wide range of gases, that it should be able to reject spurious signals due to unwanted gases, and that it should be sensitive to concentrations of the order of 10 to the minus 8th power when used with a sample cell of only 20 cm length.

  8. Air Monitoring for Hazardous Gas Detection

    NASA Technical Reports Server (NTRS)

    Arkin, C. Richard; Naylor, Guy; Haskell, William; Floyd, David; Curley, Charles; Griffin, Timothy P.; Adams, Frederick; Follistein, Duke

    2003-01-01

    The Hazardous Gas Detection Lab is involved in the design and development of instrumentation that can detect and quantify various hazardous gases. Traditionally these systems are designed for leak detection of the cryogenic gases used for the propulsion of the Shuttle and other vehicles. Mass spectrometers are the basis of these systems, which provide excellent quantitation, sensitivity, selectivity, response and limits of detection. Unfortunately, these systems are large, heavy and expensive. This feature limits the ability to perform gas analysis in certain applications. Smaller and lighter mass spectrometer systems could be used in many more applications primarily due to the portability of the system. Such applications would include air analysis in confined spaces, in-situ environmental analysis and emergency response. In general, system cost is lowered as size is reduced. With a low cost air analysis system, several systems could be utilized for monitoring large areas. These networked systems could be deployed at job-sites for worker safety, throughout a community for pollution warnings, or dispersed in a battlefield for early warning of chemical or biological threats. Presented will be information on the first prototype of this type of system. Included will be field trial data, with this prototype performing air analysis autonomously from an aircraft.

  9. A photoacoustic spectrometer for trace gas detection

    NASA Astrophysics Data System (ADS)

    Telles, E. M.; Bezerra, E.; Scalabrin, A.

    2005-06-01

    A high-resolution external laser photoacoustic spectrometer has been developed for trace gas detection with absorption transitions in coincidence with CO2 laser emission lines (9,2-10,9 ?m: 920-1086 cm-1). The CO2 laser operates in 90 CW lines with power of up to 15 W. A PC-controlled step motor can tune the laser lines. The resonance frequency of first longitudinal mode of the photoacoustic cell is at 1600 Hz. The cell Q-factor and cell constant are measured close to 50 and 28 mVcmW-1, respectively. The spectrometer has been tested in preliminary studies to analyze the absorption transitions of ozone (O_3). The ethylene (C_2H_4) from papaya fruit is also investigated using N2 as carrier gas at a constant flow rate.

  10. Sensor array for toxic gas detection

    DOEpatents

    Stetter, Joseph R. (Naperville, IL); Zaromb, Solomon (Hinsdale, IL); Penrose, William R. (Naperville, IL)

    1987-01-01

    A portable instrument for use in the field in detecting and identifying a hazardous component in air or other gas including an array of small sensors which upon exposure to the gas from a pattern of electrical responses, a source of standard response patterns characteristic of various components, and microprocessor means for comparing the sensor-formed response pattern with one or more standard patterns to thereby identify the component on a display. The number of responses may be increased beyond the number of sensors by changing the operating voltage, temperature or other condition associated with one or more sensors to provide a plurality of responses from each of one or more of the sensors. In one embodiment, the instrument is capable of identifying anyone of over 50-100 hazardous components.

  11. NHEXAS PHASE I ARIZONA STUDY--STANDARD OPERATING PROCEDURE FOR ANALYSIS OF PESTICIDE SAMPLES BY GC/ECD (BCO-L-24.0)

    EPA Science Inventory

    The purpose of this SOP is to describe the methods used for detection and quantification by gas chromatography electron capture detector (GC/ECD) of pesticides in a variety of matrices, including air, house dust, soil, handwipes, and surface wipes. Other SOP's detail the extract...

  12. Gas correlation lidar for methane detection

    NASA Technical Reports Server (NTRS)

    Galletti, E.; Zanzottera, E.; Draghi, S.; Garbi, M.; Petroni, R.

    1986-01-01

    A new type of DIAL system for the detection of methane in the atmosphere is being developed. The main feature of this lidar is the use of a gas correlation technique to obtain the reference signal by means of a single laser pulse, instead of two shots at different wavelengths. This fact is useful to make measurements on fast moving platforms. To meet the infrared absorption band of methane an optical parametric oscillator (OPO) was used with a LiNbO3 crystal as active element, and a tuning range between 1.5 divided by 4 microns. As known, the major problem to overcome in parametric oscillators are the pump beam quality and the difficulty in reducing the linewidth. The first requirement is met by using, as a pump, a Nd-YAG laser based on a new type of resonator cavity, named SFUR (Self Filtering Unstable Resonator). The laser emits, with high efficiency, near diffraction limited pulsed beams of about 250 mJ of energy, 20 ns of duration at 10 pps of frequency repetition rate. On the other hand, the gas correlation technique allows the operation with a bandwidth as large as 1/cm, which is obtainable using only a diffraction grating as a dispersive element in the OPO cavity.

  13. ENVIRONMENTAL APPLICATION OF GAS CHROMATOGRAPHY/ATOMIC EMISSION DETECTION

    EPA Science Inventory

    A gas chromatography/atomic emission detector (GC/AED) system has been evaluated for its applicability to environmental analysis. Detection limits, elemental response factors, and regression analysis data were determined for 58 semivolatile environmental contaminants. Detection l...

  14. Detectivity of gas leakage based on electromagnetic radiation transfer

    NASA Astrophysics Data System (ADS)

    Long, Yunting; Wang, Lingxue; Li, Jiakun; Zhang, Changxing; Zhang, Bei

    2011-05-01

    Standoff detection of gas leakage is a fundamental need in petrochemical and power industries. The passive gas imaging system using thermal imager has been proven to be efficient to visualize leaking gas which is not visible to the naked eye. The detection probability of gas leakage is the basis for designing a gas imaging system. Supposing the performance parameters of the thermal imager are known, the detectivity based on electromagnetic radiation transfer model to image gas leakage is analyzed. This model takes into consideration a physical analysis of the gas plume spread in the atmosphere-the interaction processes between the gas and its surrounding environment, the temperature of the gas and the background, the background surface emissivity, and also gas concentration, etc. Under a certain environmental conditions, through calculating the radiation reaching to the detector from the camera's optical field of view, we obtain an entity "Gas Equivalent Blackbody Temperature Difference (GEBTD)" which is the radiation difference between the on-plume and off-plume regions. Comparing the GEBTD with the Noise Equivalent Temperature Difference (NETD) of the thermal imager, we can know whether the system can image the gas leakage. At last, an example of detecting CO2 gas by JADE MWIR thermal imager with a narrow band-pass filter is presented.

  15. Gas pipeline leak detection system using the online simulation method

    Microsoft Academic Search

    Reiko Maeshima; Akira Kinoshita; Hitoshi Shiraishi; Ichiro Koshijima

    2000-01-01

    Management of natural gas pipeline is an important task for economical and safety operation, loss prevention and environmental protection from methane emission. A leak detection of gas pipeline, therefore, plays a key role in the overall integrity management for a pipeline system. Especially for a long pipeline operated alongside of densely populated areas, a leak detection system is an indispensable

  16. Gas leak detection by diode laser absorption spectrometry

    Microsoft Academic Search

    R. Uhl; T Reinhardt; U Haas; J Franzke

    1999-01-01

    Diode laser atomic absorption measurements of argon traces in low-pressure discharges were carried out to detect and measure gas leaks in a test chamber. Helium flows as a carrier gas through the test chamber and the discharge. In the case of a leak, air and thus also its natural content of argon is mixed to the helium gas-flow through the

  17. Comparison of the limulus amebocyte lysate test and gas chromatography-mass spectrometry for measuring lipopolysaccharides (endotoxins) in airborne dust from poultry-processing industries.

    PubMed Central

    Sonesson, A; Larsson, L; Schütz, A; Hagmar, L; Hallberg, T

    1990-01-01

    The lipopolysaccharide (endotoxin) content in airborne dust samples from three different poultry slaughterhouses was determined with both the chromogenic Limulus amebocyte lysate assay and gas chromatography-mass spectrometry analysis of lipopolysaccharide-derived 3-hydroxy fatty acids. Gram-negative cell walls were also measured by using two-dimensional gas chromatography/electron-capture analysis of diaminopimelic acid originating from the peptidoglycan. The correlation between the results of the Limulus assay and those of gas chromatography-mass spectrometry for determination of the lipopolysaccharide content in the dust samples was poor, whereas a good correlation was obtained between lipopolysaccharide and diaminopimelic acid concentrations with the gas chromatographic methods. The results suggest that it is predominantly cell-wall-dissociated lipopolysaccharides that are measured with the Limulus assay, whereas the gas chromatographic methods allow determination of total concentrations of lipopolysaccharide, including Limulus-inactive lipopolysaccharide, gram-negative cells, and cellular debris. PMID:2187411

  18. Gas detection by correlation spectroscopy employing a multimode diode laser.

    PubMed

    Lou, Xiutao; Somesfalean, Gabriel; Zhang, Zhiguo

    2008-05-01

    A gas sensor based on the gas-correlation technique has been developed using a multimode diode laser (MDL) in a dual-beam detection scheme. Measurement of CO(2) mixed with CO as an interfering gas is successfully demonstrated using a 1570 nm tunable MDL. Despite overlapping absorption spectra and occasional mode hops, the interfering signals can be effectively excluded by a statistical procedure including correlation analysis and outlier identification. The gas concentration is retrieved from several pair-correlated signals by a linear-regression scheme, yielding a reliable and accurate measurement. This demonstrates the utility of the unsophisticated MDLs as novel light sources for gas detection applications. PMID:18449306

  19. Passive acoustic detection of gas leaks in buried pipes

    Microsoft Academic Search

    A. Soom; H. R. Martin; J. A. Lea

    1981-01-01

    A study of the practical aspects and limitations of an acoustic leak-detection method has shown that sounds caused by small gas leaks in buried pipes are detectable underground to distances of 7-10 ft and beyond for line pressures greater than 9 psi. Fairly severe range limitations to detection do exist, however, because of low source strengths and high attenuation rates

  20. Detection of a simulated gas leak in a wind tunnel

    Microsoft Academic Search

    J. Hodgkinson; Q. Shan; R. D. Pride

    2006-01-01

    This paper brings together considerations of gas leak behaviour and leak detector design and use, with a view to improving the detection of low-pressure natural gas leaks. An atmospheric boundary layer wind tunnel has been used to study ground-based releases of methane at full scale over distances of up to 3 m, under controlled conditions. These scales are relevant to

  1. Naturally fractured tight gas reservoir detection optimization

    SciTech Connect

    NONE

    1998-11-30

    The goal of the work this quarter has been to partition and high-grade the Greater Green River basin for exploration efforts in the Upper Cretaceous tight gas play and to initiate resource assessment of the basin. The work plan for the quarter of July 1-September 30, 1998 comprised three tasks: (1) Refining the exploration process for deep, naturally fractured gas reservoirs; (2) Partitioning of the basin based on structure and areas of overpressure; (3) Examination of the Kinney and Canyon Creek fields with respect to the Cretaceous tight gas play and initiation of the resource assessment of the Vermilion sub-basin partition (which contains these two fields); and (4) Initiation analysis of the Deep Green River Partition with respect to the Stratos well and assessment of the resource in the partition.

  2. Detection of Individual Gas Molecules Absorbed on Graphene

    Microsoft Academic Search

    F. Schedin; A. K. Geim; S. V. Morozov; D. Jiang; E. H. Hill; P. Blake; K. S. Novoselov

    2006-01-01

    The ultimate aspiration of any detection method is to achieve such a level of sensitivity that individual quanta of a measured value can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity.

  3. Fire detection in coal mines based on semiconductor gas sensors

    Microsoft Academic Search

    Peter Reimann; Andreas Schütze

    2012-01-01

    Purpose – Due to the environmental conditions, the detection and identification of hazardous situations in coal mines is a challenge. The purpose of this research is to focus on the underground fire detection, especially of smoldering fires, which are characterized by the outgassing of CO and C2H4. Design\\/methodology\\/approach – The study developed a system based on a single semiconductor gas

  4. Detection of Individual Gas Molecules Absorbed on Graphene

    Microsoft Academic Search

    Andre Geim; Kostya Novoselov; Fred Schedin; Sergey Morozov; Da Jiang; Ernie Hill

    2007-01-01

    The ultimate aspiration of any detection method is to achieve such a level of sensitivity that individual quanta of a measured value can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity.

  5. Detection of individual gas molecules adsorbed on graphene

    Microsoft Academic Search

    F. Schedin; A. K. Geim; S. V. Morozov; E. W. Hill; P. Blake; M. I. Katsnelson; K. S. Novoselov

    2007-01-01

    The ultimate aim of any detection method is to achieve such a level of sensitivity that individual quanta of a measured entity can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity.

  6. Research on airborne infrared leakage detection of natural gas pipeline

    NASA Astrophysics Data System (ADS)

    Tan, Dongjie; Xu, Bin; Xu, Xu; Wang, Hongchao; Yu, Dongliang; Tian, Shengjie

    2011-12-01

    An airborne laser remote sensing technology is proposed to detect natural gas pipeline leakage in helicopter which carrying a detector, and the detector can detect a high spatial resolution of trace of methane on the ground. The principle of the airborne laser remote sensing system is based on tunable diode laser absorption spectroscopy (TDLAS). The system consists of an optical unit containing the laser, camera, helicopter mount, electronic unit with DGPS antenna, a notebook computer and a pilot monitor. And the system is mounted on a helicopter. The principle and the architecture of the airborne laser remote sensing system are presented. Field test experiments are carried out on West-East Natural Gas Pipeline of China, and the results show that airborne detection method is suitable for detecting gas leak of pipeline on plain, desert, hills but unfit for the area with large altitude diversification.

  7. Naturally fractured tight gas reservoir detection optimization

    SciTech Connect

    NONE

    1998-09-30

    During this quarter, work began on the regional structural and geologic analysis of the greater Green River basin (GGRB) in southwestern Wyoming, northwestern Colorado and northeastern Utah. The ultimate objective of the regional analysis is to apply the techniques developed and demonstrated during earlier phases of the project to sweet-spot delineation in a relatively new and underexplored play: tight gas from continuous-type Upper Cretaceous reservoirs of the GGRB. The primary goal of this work is to partition and high-grade the greater Green River basin for exploration efforts in the Cretaceous tight gas play. The work plan for the quarter of January 1, 1998--March 31, 1998 consisted of three tasks: (1) Acquire necessary data and develop base map of study area; (2) Process data for analysis; and (3) Initiate structural study. The first task and second tasks were completed during this reporting period. The third task was initiated and work continues.

  8. Detection system for a gas chromatograph

    DOEpatents

    Hayes, John M. (Ames, IA); Small, Gerald J. (Ames, IA)

    1984-01-01

    A method and apparatus are described for the quantitative analysis of vaporizable compounds, and in particular of polycyclic aromatic hydrocarbons which may be induced to fluoresce. The sample to be analyzed is injected into a gas chromatography column and is eluted through a narrow orifice into a vacuum chamber. The free expansion of the eluted sample into the vacuum chamber creates a supersonic molecular beam in which the sample molecules are cooled to the extent that the excited vibrational and rotational levels are substantially depopulated. The cooled molecules, when induced to fluoresce by laser excitation, give greatly simplified spectra suitable for analytical purposes. The laser induced fluorimetry provides great selectivity, and the gas chromatograph provides quantitative transfer of the sample to the molecular beam.

  9. Naturally fractured tight gas reservoir detection optimization

    SciTech Connect

    NONE

    1999-04-30

    In March, work continued on characterizing probabilities for determining natural fracturing associated with the GGRB for the Upper Cretaceous tight gas plays. Structural complexity, based on potential field data and remote sensing data was completed. A resource estimate for the Frontier and Mesa Verde play was also completed. Further, work was also conducted to determine threshold economics for the play based on limited current production in the plays in the Wamsutter Ridge area. These analyses culminated in a presentation at FETC on 24 March 1999 where quantified natural fracture domains, mapped on a partition basis, which establish ''sweet spot'' probability for natural fracturing, were reviewed. That presentation is reproduced here as Appendix 1. The work plan for the quarter of January 1, 1999--March 31, 1999 comprised five tasks: (1) Evaluation of the GGRB partitions for structural complexity that can be associated with natural fractures, (2) Continued resource analysis of the balance of the partitions to determine areas with higher relative gas richness, (3) Gas field studies, (4) Threshold resource economics to determine which partitions would be the most prospective, and (5) Examination of the area around the Table Rock 4H well.

  10. Trace gas detection using nanostructured graphite layers

    NASA Astrophysics Data System (ADS)

    Qazi, Muhammad; Vogt, Thomas; Koley, Goutam

    2007-12-01

    Nanostructured graphite (NG) has been investigated as a sensing material using a highly sensitive potentiometric detection technique. NO2 concentration down to 60ppb was detected in ambient conditions using NG functionalization layer. Simultaneous current and surface work function (SWF) change transients measured using NG functionalization layer reveal much shorter response time for the later, which is attributed to its dependence solely on surface molecular adsorption. The gradient of SWF with respect to the current transient was found to be independent of gaseous concentration and fraction of preoccupied surface states.

  11. Gas Transport and Detection Following Underground Nuclear Explosions

    NASA Astrophysics Data System (ADS)

    Carrigan, C. R.; Sun, Y.; Wagoner, J. L.; Zucca, J. J.

    2011-12-01

    Some extremely rare radioactive noble gases are by-products of underground nuclear explosions, and the detection of significant levels of these gases (e.g., Xe-133 and Ar-37) at the surface is a very strong indicator of the occurrence of an underground nuclear event. Because of their uniqueness, such noble gas signatures can be confirmatory of the nuclear nature of an event while signatures from other important detection methods, such as anomalous seismicity, are generally not. As a result, noble gas detection at a suspected underground nuclear test site is considered to be the most important technique available to inspectors operating under the On-Site-Inspection protocol of the Comprehensive Nuclear Test Ban Treaty. A one-kiloton chemical underground explosion, the Non-Proliferation Experiment (NPE), was carried out at the Nevada Test Site in 1993 and represented the first On-Site-Inspection oriented test of subsurface gas transport with subsequent detection at the surface using soil gas sampling methods. A major conclusion of the experiment was that noble gases from underground nuclear tests have a good possibility of being detected even if the test is well contained. From this experiment and from computer simulations, we have also learned significant lessons about the modes of gas transport to the surface and the importance of careful subsurface sampling to optimize the detected noble gas signature. Understanding transport and sampling processes for a very wide range of geologic and testing scenarios presents significant challenges that we are currently addressing using sensitivity studies, which we attempt to verify using experiments such as the NPE and a new subsurface gas migration experiment that is now being undertaken at the National Center for Nuclear Security. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  12. Detect, troubleshoot gas-turbine blade failures

    SciTech Connect

    Meher-Homji, C.B. [Boyce Engineering International Inc., Houston, TX (United States)

    1995-12-01

    Approximately 40% of all gas-turbine failures stem from blading problems. This article describes state-of-the-art condition monitoring technologies that can help avoid or minimize the damage, and troubleshoot failures when they occur. In today`s gas-turbine (GT) fleet, predominant blade-failure mechanism and commonly affected components include: low-cycle fatigue--compressor and turbine disks; high-cycle fatigue--compressor and turbine blades and disks, compressor stator vanes; thermal fatigue--nozzles, combustors; environmental attack, such as oxidation, sulfidation, hot corrosion, and standby corrosion--hot-section blades and stators, transition pieces, and combustors; creep damage--hot-section nozzles and blades; erosion and wear; impact overload damage; thermal aging; combined failure mechanisms, such as creep/fatigue corrosion/fatigue, oxidation/erosion, and so on. Avoiding GT blade problems requires that two conditions be met: first, and most important, the basic design has to be sound, with adequate safety factors incorporates. Second, the proper operating regime must be maintained. Properly applied, condition monitoring can help maintain the operating regime and minimize blade distress. Should blade failures occur, data captured in a monitoring program may provide valuable clues to help identify the root causes. Reviewed here are the latest GT condition monitoring techniques, as well as several case histories that illustrate their importance.

  13. Wide-band gas leak imaging detection system using UFPA

    NASA Astrophysics Data System (ADS)

    Jin, Wei-qi; Li, Jia-kun; Dun, Xiong; Jin, Minglei; Wang, Xia

    2014-11-01

    The leakage of toxic or hazardous gases not only pollutes the environment, but also threatens people's lives and property safety. Many countries attach great importance to the rapid and effective gas leak detection technology and instrument development. However, the gas leak imaging detection systems currently existing are generally limited to a narrow-band in Medium Wavelength Infrared (MWIR) or Long Wavelength Infrared (LWIR) cooled focal plane imaging, which is difficult to detect the common kinds of the leaking gases. Besides the costly cooled focal plane array is utilized, the application promotion is severely limited. To address this issue, a wide-band gas leak IR imaging detection system using Uncooled Focal Plane Array (UFPA) detector is proposed, which is composed of wide-band IR optical lens, sub-band filters and switching device, wide-band UFPA detector, video processing and system control circuit. A wide-band (3µm~12µm) UFPA detector is obtained by replacing the protection window and optimizing the structural parameters of the detector. A large relative aperture (F#=0.75) wide-band (3?m~12?m) multispectral IR lens is developed by using the focus compensation method, which combining the thickness of the narrow-band filters. The gas leak IR image quality and the detection sensitivity are improved by using the IR image Non-Uniformity Correction (NUC) technology and Digital Detail Enhancement (DDE) technology. The wide-band gas leak IR imaging detection system using UFPA detector takes full advantage of the wide-band (MWIR&LWIR) response characteristic of the UFPA detector and the digital image processing technology to provide the resulting gas leak video easy to be observed for the human eyes. Many kinds of gases, which are not visible to the naked eyes, can be sensitively detected and visualized. The designed system has many commendable advantages, such as scanning a wide range simultaneously, locating the leaking source quickly, visualizing the gas plume intuitively and so on. The simulation experiment shows that the gas IR imaging detection has great advantages and widely promotion space compared with the traditional techniques, such as point-contact or line-contactless detection.

  14. Methods for gas detection using stationary hyperspectral imaging sensors

    DOEpatents

    Conger, James L. (San Ramon, CA); Henderson, John R. (Castro Valley, CA)

    2012-04-24

    According to one embodiment, a method comprises producing a first hyperspectral imaging (HSI) data cube of a location at a first time using data from a HSI sensor; producing a second HSI data cube of the same location at a second time using data from the HSI sensor; subtracting on a pixel-by-pixel basis the second HSI data cube from the first HSI data cube to produce a raw difference cube; calibrating the raw difference cube to produce a calibrated raw difference cube; selecting at least one desired spectral band based on a gas of interest; producing a detection image based on the at least one selected spectral band and the calibrated raw difference cube; examining the detection image to determine presence of the gas of interest; and outputting a result of the examination. Other methods, systems, and computer program products for detecting the presence of a gas are also described.

  15. Naturally fractured tight gas reservoir detection optimization

    SciTech Connect

    NONE

    1998-11-30

    The work plan for October 1, 1997 to September 30, 1998 consisted of investigation of a number of topical areas. These topical areas were reported in four quarterly status reports, which were submitted to DOE earlier. These topical areas are reviewed in this volume. The topical areas covered during the year were: (1) Development of preliminary tests of a production method for determining areas of natural fracturing. Advanced Resources has demonstrated that such a relationship exists in the southern Piceance basin tight gas play. Natural fracture clusters are genetically related to stress concentrations (also called stress perturbations) associated with local deformation such a faulting. The mechanical explanation of this phenomenon is that deformation generally initiates at regions where the local stress field is elevated beyond the regional. (2) Regional structural and geologic analysis of the Greater Green River Basin (GGRB). Application of techniques developed and demonstrated during earlier phases of the project for sweet-spot delineation were demonstrated in a relatively new and underexplored play: tight gas from continuous-typeUpper Cretaceous reservoirs of the Greater Green River Basin (GGRB). The effort included data acquisition/processing, base map generation, geophysical and remote sensing analysis and the integration of these data and analyses. (3) Examination of the Table Rock field area in the northern Washakie Basin of the Greater Green River Basin. This effort was performed in support of Union Pacific Resources- and DOE-planned horizontal drilling efforts. The effort comprised acquisition of necessary seismic data and depth-conversion, mapping of major fault geometry, and analysis of displacement vectors, and the development of the natural fracture prediction. (4) Greater Green River Basin Partitioning. Building on fundamental fracture characterization work and prior work performed under this contract, namely structural analysis using satellite and potential field data, the GGRB was divided into partitions that will be used to analyze the resource potential of the Frontier and Mesaverde Upper Cretaceous tight gas play. A total of 20 partitions were developed, which will be instrumental for examining the Upper Cretaceous play potential. (5) Partition Analysis. Resource assessment associated with individual partitions was initiated starting with the Vermilion Sub-basin and the Green River Deep (which include the Stratos well) partitions (see Chapter 5). (6) Technology Transfer. Tech transfer was achieved by documenting our research and presenting it at various conferences.

  16. Surface Ionization Gas Detection on Platinum and Metal Oxide Surfaces

    Microsoft Academic Search

    A. Hackner; A. Habauzit; G. Muller; E. Comini; G. Faglia; G. Sberveglieri

    2009-01-01

    Surface ionization (SI) gas detection experiments have been performed on platinum (Pt) and metal oxide (MOX) films. The probability of surface ion emission varies with temperature in an Arrhenius-type manner. Among all hydrocarbons studied so far those with amine functional groups exhibited the lowest activation energies allowing detection in the ppm concentration range at emitter operation temperatures of about 400degC.

  17. Aging impairs the ability to detect gas odor

    Microsoft Academic Search

    Joseph C. Stevens; William S. Cain; David E. Weinstein; John B. Pierce

    1987-01-01

    Weakened smelling is common in age. Two studies here show that this phenomenon frequently reveals itself in inability to detect ethyl mercaptan, the warning agent most commonly added to propane (LP-gas). The first study compared 21 young (18–25 years) with 21 old (70–85 years) persons for (a) detection threshold (average ten times higher in the elderly), (b) suprathreshold odor strength

  18. VOC gas leak detection using Pyroelectric Infrared sensors

    Microsoft Academic Search

    Fatih Erden; Emin Birey Soyer; B. Ugur Töreyin; A. Enis Çetin

    2010-01-01

    In this paper, we propose a novel method for detecting and monitoring Volatile Organic Compounds (VOC) gas leaks by using a Pyro-electric (or Passive) Infrared (PIR) sensor whose spectral range intersects with the absorption bands of VOC gases. A continuous time analog signal is obtained from the PIR sensor. This signal is discretized and analyzed in real time. Feature parameters

  19. Hyperspectral trace gas detection using the wavelet packet transform

    NASA Astrophysics Data System (ADS)

    Salvador, Mark Z.; Resmini, Ronald G.; Gomez, Richard B.

    2008-04-01

    A method for trace gas detection in hyperspectral data is demonstrated using the wavelet packet transform. This new method, the Wavelet Packet Subspace (WPS), applies the wavelet packet transform and selects a best basis for pattern matching. The wavelet packet transform is an extension of the wavelet transform, which fully decomposes a signal into a library of wavelet packet bases. Application of the wavelet packet transform to hyperspectral data for the detection of trace gases takes advantage of the ability of the wavelet transform to locate spectral features in both scale and location. By analyzing the wavelet packet tree of specific gas, nodes of the tree are selected which represent an orthogonal best basis. The best basis represents the significant spectral features of that gas. This is then used to identify pixels in the scene using existing matching algorithms such as spectral angle or matched filter. Using data from the Airborne Hyperspectral Imager (AHI), this method is compared to traditional matched filter detection methods. Initial results demonstrate a promising wavelet packet subspace technique for hyperspectral trace gas detection applications.

  20. Pattern recognition for selective odor detection with gas sensor arrays.

    PubMed

    Kim, Eungyeong; Lee, Seok; Kim, Jae Hun; Kim, Chulki; Byun, Young Tae; Kim, Hyung Seok; Lee, Taikjin

    2012-01-01

    This paper presents a new pattern recognition approach for enhancing the selectivity of gas sensor arrays for clustering intelligent odor detection. The aim of this approach was to accurately classify an odor using pattern recognition in order to enhance the selectivity of gas sensor arrays. This was achieved using an odor monitoring system with a newly developed neural-genetic classification algorithm (NGCA). The system shows the enhancement in the sensitivity of the detected gas. Experiments showed that the proposed NGCA delivered better performance than the previous genetic algorithm (GA) and artificial neural networks (ANN) methods. We also used PCA for data visualization. Our proposed system can enhance the reproducibility, reliability, and selectivity of odor sensor output, so it is expected to be applicable to diverse environmental problems including air pollution, and monitor the air quality of clean-air required buildings such as a kindergartens and hospitals. PMID:23443378

  1. Pattern Recognition for Selective Odor Detection with Gas Sensor Arrays

    PubMed Central

    Kim, Eungyeong; Lee, Seok; Kim, Jae Hun; Kim, Chulki; Byun, Young Tae; Kim, Hyung Seok; Lee, Taikjin

    2012-01-01

    This paper presents a new pattern recognition approach for enhancing the selectivity of gas sensor arrays for clustering intelligent odor detection. The aim of this approach was to accurately classify an odor using pattern recognition in order to enhance the selectivity of gas sensor arrays. This was achieved using an odor monitoring system with a newly developed neural-genetic classification algorithm (NGCA). The system shows the enhancement in the sensitivity of the detected gas. Experiments showed that the proposed NGCA delivered better performance than the previous genetic algorithm (GA) and artificial neural networks (ANN) methods. We also used PCA for data visualization. Our proposed system can enhance the reproducibility, reliability, and selectivity of odor sensor output, so it is expected to be applicable to diverse environmental problems including air pollution, and monitor the air quality of clean-air required buildings such as a kindergartens and hospitals. PMID:23443378

  2. Optical sensing for gas detection in enclosed roadways

    NASA Astrophysics Data System (ADS)

    Chachich, Alan C.

    1995-01-01

    Detection of vehicle emissions and other gases will be an important part of the future ITS infrastructure, especially for enclosed roadways. The recently passed Intermodal Surface Transportation Efficiency Act and the Clean Air Amendments provide great incentive for the collection of emissions data. Enclosed roadways can use such data to control ventilation systems and detect hazardous substances. This paper examines the feasibility of using optical gas sensors for real-time control of enclosed roadways as well as regional environmental monitoring of mobile source emissions.

  3. Speciation analysis by gas chromatography with plasma source spectrometric detection

    NASA Astrophysics Data System (ADS)

    ?obi?ski, Ryszard; Adams, Freddy C.

    State-of-the-art species-selective analysis by gas chromatography (GC) with plasma source spectrometric detection is discussed for organometal and organometalloid compounds. Various plasmas, inductively coupled plasma, microwave induced plasma, capacitatively coupled plasma, direct current plasma and alternating current plasma, are characterized and critically compared as sources of radiation for atomic emission spectrometry and sources of ions for mass spectrometry. Interfaces between gas chromatography (packed, wide-bore, capillary and multicapillary) and plasma source spectrometry are characterized. Particular emphasis is given to applications of GC with plasma source detection to real-world analytical problems, which are comprehensively reviewed. The use of plasmas for the acquisition of auxiliary molecular information such as empirical formulae and structural information is discussed. Recent developments relating to sample preparation and presentation to the hyphenated system are addressed. The most significant trends in speciation analysis are highlighted.

  4. Gas detection by carbon nanotube gas-ionization sensor based on Lyapunov exponent

    Microsoft Academic Search

    Guohua Hui

    2010-01-01

    In this paper, a novel method utilizing a multi-walled carbon nanotube (MWNT) gas-ionization sensor based on Lyapunov exponent algorithm was proposed for argon, ethanol, acetone, and ammonia detection. The sensor was used as anodic sensor. Responses of MWNT sensor to four gases was measured and processed by Lyapunov exponent. Experimental results showed that the MWNT sensor array based on Lyapunov

  5. 46 CFR 154.709 - Cargo boil-off as fuel: Gas detection equipment.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...boil-off as fuel: Gas detection equipment. 154.709 Section 154...BULK LIQUEFIED GASES Design, Construction and Equipment Cargo Pressure and Temperature...boil-off as fuel: Gas detection equipment. (a) The continuous...

  6. Leak detection and location for gas transmission pipelines

    SciTech Connect

    Delarue, V. [Gaz de France, La Plaine Saint Denis (France). Research and Development Div.

    1996-12-31

    For legal, economic or safety reasons, gas transmission companies must look for leaks. The most widely used leak detection method is a planned survey of the network. It can be a simple visual inspection of the pipe`s environment. It can also be done with hand held gas detectors or aboard vehicles. New methods are being developed to improve productivity. The most promising are those based on the absorption of methane in the infrared which can be airborne. The first one is based on lidars that scan the pipe and measure the backscattered light. New lasers will permit great sensitivity for gas detection. The other is a camera measuring the absorption of the light emitted by the ground. On-line detection exists, but it is seldom used nowadays. The rare onshore applications use the data collected by SCADA systems that are processed by more or less sophisticated statistical methods. For off-shore applications, many systems are currently used: acoustic gates, echography or hydrophones. Promising new developments by many companies are under way. The first that has shown good results if based on the vibratory waves emitted by a leak. Acoustic waves can also be used.

  7. C$^+$ detection of warm dark gas in diffuse clouds

    E-print Network

    Langer, W D; Pineda, J L; Goldsmith, P F; Li, D; Yorke, H W

    2010-01-01

    We present the first results of the Herschel open time key program, Galactic Observations of Terahertz C$^+$ (GOT C+) survey of the [CII] fine-structure line at 1.9 THz (158 microns) using the HIFI instrument on Herschel. We detected 146 interstellar clouds along sixteen lines-of-sight towards the inner Galaxy. We also acquired HI and CO isotopologue data along each line-of-sight for analysis of the physical conditions in these clouds. Here we analyze 29 diffuse clouds (A$_{V}$ < 1.3 mag.) in this sample characterized by having [CII] and HI emission, but no detectable CO. We find that [CII] emission is generally stronger than expected for diffuse atomic clouds, and in a number of sources is much stronger than anticipated based on their HI column density. We show that excess [CII] emission in these clouds is best explained by the presence of a significant diffuse warm H$_2$, dark gas, component. This first [CII] 158 micron detection of warm dark gas demonstrates the value of this tracer for mapping this gas...

  8. A MINI MULTI-GAS DETECTION SYSTEM BASED ON INFRARED PRINCIPLE

    Microsoft Academic Search

    Xie Zhijian; Tan Qiulin

    2006-01-01

    To counter the problems of gas accidents in coal mines, family safety resulted from using gas, a new infrared detection system\\u000a with integration and miniaturization has been developed. The infrared detection optics principle used in developing this system\\u000a is mainly analyzed. The idea that multi gas detection is introduced and guided through analyzing single gas detection is got\\u000a across. Through

  9. Flight Testing of an Advanced Airborne Natural Gas Leak Detection System

    Microsoft Academic Search

    Dawn Lenz; Raymond T. Lines; Darryl Murdock; Jeffrey Owen; Steven Stearns; Michael Stoogenke

    2005-01-01

    ITT Industries Space Systems Division (Space Systems) has developed an airborne natural gas leak detection system designed to detect, image, quantify, and precisely locate leaks from natural gas transmission pipelines. This system is called the Airborne Natural Gas Emission Lidar (ANGEL) system. The ANGEL system uses a highly sensitive differential absorption Lidar technology to remotely detect pipeline leaks. The ANGEL

  10. Long-wave infrared imaging of vegetation for detecting leaking CO2 gas

    E-print Network

    Lawrence, Rick L.

    Long-wave infrared imaging of vegetation for detecting leaking CO2 gas Jennifer E. Johnson Joseph A of vegetation for detecting leaking CO2 gas Jennifer E. Johnson,a Joseph A. Shaw,a Rick Lawrence,b Paul W specific novel use of these calibrated imagers is imaging of vegetation for CO2 gas leak detection. During

  11. Optimization of SolidPhase Microextraction Procedure Coupled to GC-ECD for Triazole Fungicides Determination in Juice Samples

    Microsoft Academic Search

    Ane Bordagaray; Rosa Garcia-Arrona; Esmeralda Millán

    2011-01-01

    A solid-phase microextraction (SPME) procedure followed by gas chromatography electron capture detection (GC\\/ECD) for the\\u000a determination of triazole residues was developed. An experimental design with two steps was done. Firstly, a 26?2 fractional factorial design for screening several experimental variables (fiber-coating type, extraction temperature, extraction\\u000a time, stirring rate, desorption temperature, and desorption time) was done. After, a two-factor central composite

  12. Organochlorine Pesticides in Placentas from Southern Spain and Some Related Factors

    Microsoft Academic Search

    M.-J. Lopez-Espinosa; A. Granada; J. Carreno; M. Salvatierra; F. Olea-Serrano; N. Olea

    2007-01-01

    During pregnancy, lipophilic xenobiotics stored in maternal adipose tissue can be mobilized and enter her blood circulation and reach the placenta. This study measured residues of oestrogen-mimicking organochlorine pesticides (OCs) in 150 placenta samples from women in Southern Spain. OCs were extracted from placenta by solid–liquid technique and purified by preparative liquid chromatography. Gas chromatography\\/electron-capture detection and mass spectrometry were

  13. Determination of endocrine disruptors in Kafue lechwe ( Kobus leche kafuensis) samples from the Lochinvar National Park of Zambia

    Microsoft Academic Search

    Kwenga Sichilongo; Nelson Torto

    2006-01-01

    Analysis of serum, whole blood and liver tissue samples from Kafue lechwe in the Lochinvar National Park of Zambia for suspected endocrine disrupting compounds revealed high concentrations for some of the compounds. 45 samples of serum, whole blood and liver tissue were extracted by liquid–liquid extraction followed by an analysis using Gas Chromatography-Electron Capture Detection (GC-ECD). The following endocrine disruptors

  14. Determination of some organochlorine pesticide residues in honeys from Konya, Turkey

    Microsoft Academic Search

    Halil Yavuz; Gokalp O. Guler; Abdurrahman Aktumsek; Yavuz S. Cakmak; Haluk Ozparlak

    2010-01-01

    In this study, 24 organochlorine pesticide residues in 109 different honey samples collected from stores and open markets\\u000a in Konya, Turkey were analyzed by gas chromatography-electron capture detection. Aldrin, cis-chlordane, trans-chlordane, oxy-chlordane, 2,4? -DDE, and 4,4? -DDE were found in all honey samples. The mean value was 0.0540 ?g g???1 for oxy-chlordane. In the 55 samples of 109, levels of organochlorine

  15. Sensitive gas chromatographic detection of acetaldehyde and acetone using a reduction gas detector

    NASA Technical Reports Server (NTRS)

    O'Hara, Dean; Singh, Hanwant B.

    1988-01-01

    The response of a newly available mercuric oxide Reduction Gas Detector (RGD-2) to subpicomole and larger quantities of acetaldehyde and acetone is tested. The RGD-2 is found to be capable of subpicomole detection for these carbonyls and is more sensitive than an FID (Flame Ionization Detector) by an order of magnitude. Operating parameters can be further optimized to make the RGD-2 some 20-40 times more sensitive than an FID. The detector is linear over a wide range and is easily adapted to a conventional gas chromatograph (GC). Such a GC-RGD-2 system should be suitable for atmospheric carbonyl measurements in clean as well as polluted environments.

  16. Detection of individual gas molecules adsorbed on graphene.

    PubMed

    Schedin, F; Geim, A K; Morozov, S V; Hill, E W; Blake, P; Katsnelson, M I; Novoselov, K S

    2007-09-01

    The ultimate aim of any detection method is to achieve such a level of sensitivity that individual quanta of a measured entity can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity. The fundamental reason limiting the resolution of such sensors is fluctuations due to thermal motion of charges and defects, which lead to intrinsic noise exceeding the sought-after signal from individual molecules, usually by many orders of magnitude. Here, we show that micrometre-size sensors made from graphene are capable of detecting individual events when a gas molecule attaches to or detaches from graphene's surface. The adsorbed molecules change the local carrier concentration in graphene one by one electron, which leads to step-like changes in resistance. The achieved sensitivity is due to the fact that graphene is an exceptionally low-noise material electronically, which makes it a promising candidate not only for chemical detectors but also for other applications where local probes sensitive to external charge, magnetic field or mechanical strain are required. PMID:17660825

  17. Wireless gas detection with a smartphone via rf communication

    PubMed Central

    Azzarelli, Joseph M.; Mirica, Katherine A.; Ravnsbæk, Jens B.; Swager, Timothy M.

    2014-01-01

    Chemical sensing is of critical importance to human health, safety, and security, yet it is not broadly implemented because existing sensors often require trained personnel, expensive and bulky equipment, and have large power requirements. This study reports the development of a smartphone-based sensing strategy that employs chemiresponsive nanomaterials integrated into the circuitry of commercial near-field communication tags to achieve non-line-of-sight, portable, and inexpensive detection and discrimination of gas-phase chemicals (e.g., ammonia, hydrogen peroxide, cyclohexanone, and water) at part-per-thousand and part-per-million concentrations. PMID:25489066

  18. Wireless gas detection with a smartphone via rf communication.

    PubMed

    Azzarelli, Joseph M; Mirica, Katherine A; Ravnsbæk, Jens B; Swager, Timothy M

    2014-12-23

    Chemical sensing is of critical importance to human health, safety, and security, yet it is not broadly implemented because existing sensors often require trained personnel, expensive and bulky equipment, and have large power requirements. This study reports the development of a smartphone-based sensing strategy that employs chemiresponsive nanomaterials integrated into the circuitry of commercial near-field communication tags to achieve non-line-of-sight, portable, and inexpensive detection and discrimination of gas-phase chemicals (e.g., ammonia, hydrogen peroxide, cyclohexanone, and water) at part-per-thousand and part-per-million concentrations. PMID:25489066

  19. Atypical Applications for Gas-coupled Laser Acoustic Detection

    NASA Astrophysics Data System (ADS)

    Caron, J. N.; Kunapareddy, P.

    2014-06-01

    Gas-coupled laser acoustic detection (GCLAD) was primarily developed to sense laser-generated ultrasound in composite materials. In a typical setup, a laser beam is directed parallel to the material surface. Radiated ultrasound waves deflect or displace the probe beam resulting from changes in the air's index of refraction. A position-sensitive photodetector senses the beam movement, and produces a signal proportional to the ultrasound wave. In this paper, we discuss three applications of GCLAD that take advantage of the unique detection characteristics. Directivity patterns of ultrasound amplitude in water demonstrate the use of GCLAD as a directional hydrophone. We also demonstrate the sensing of waveforms from a gelatin. The gelatin mimics ultrasound propagation through skin tissues. Lastly, we show how GCLAD can be used as a line receiver for continuous laser generation of ultrasound. CLGU may enable ultrasound scanning at rates that are orders of magnitude faster than current methods.

  20. High Altitude Aerial Natural Gas Leak Detection System

    SciTech Connect

    Richard T. Wainner; Mickey B. Frish; B. David Green; Matthew C. Laderer; Mark G. Allen; Joseph R. Morency

    2006-12-31

    The objective of this program was to develop and demonstrate a cost-effective and power-efficient advanced standoff sensing technology able to detect and quantify, from a high-altitude (> 10,000 ft) aircraft, natural gas leaking from a high-pressure pipeline. The advanced technology is based on an enhanced version of the Remote Methane Leak Detector (RMLD) platform developed previously by Physical Sciences Inc. (PSI). The RMLD combines a telecommunications-style diode laser, fiber-optic components, and low-cost DSP electronics with the well-understood principles of Wavelength Modulation Spectroscopy (WMS), to indicate the presence of natural gas located between the operator and a topographic target. The transceiver transmits a laser beam onto a topographic target and receives some of the laser light reflected by the target. The controller processes the received light signal to deduce the amount of methane in the laser's path. For use in the airborne platform, we modified three aspects of the RMLD, by: (1) inserting an Erbium-doped optical fiber laser amplifier to increase the transmitted laser power from 10 mW to 5W; (2) increasing the optical receiver diameter from 10 cm to 25 cm; and (3) altering the laser wavelength from 1653 nm to 1618 nm. The modified RMLD system provides a path-integrated methane concentration sensitivity {approx}5000 ppm-m, sufficient to detect the presence of a leak from a high capacity transmission line while discriminating against attenuation by ambient methane. In ground-based simulations of the aerial leak detection scenario, we demonstrated the ability to measure methane leaks within the laser beam path when it illuminates a topographic target 2000 m away. We also demonstrated simulated leak detection from ranges of 200 m using the 25 cm optical receiver without the fiber amplifier.

  1. Trace gas monitoring with infrared laser-based detection schemes

    NASA Astrophysics Data System (ADS)

    Sigrist, M. W.; Bartlome, R.; Marinov, D.; Rey, J. M.; Vogler, D. E.; Wächter, H.

    2008-02-01

    The success of laser-based trace gas sensing techniques crucially depends on the availability and performance of tunable laser sources combined with appropriate detection schemes. Besides near-infrared diode lasers, continuously tunable midinfrared quantum cascade lasers and nonlinear optical laser sources are preferentially employed today. Detection schemes are based on sensitive absorption measurements and comprise direct absorption in multi-pass cells as well as photoacoustic and cavity ringdown techniques in various configurations. We illustrate the performance of several systems implemented in our laboratory. These include time-resolved multicomponent traffic emission measurements with a mobile CO2-laser photoacoustic system, a diode-laser based cavity ringdown device for measurements of impurities in industrial process control, isotope ratio measurements with a difference frequency (DFG) laser source combined with balanced path length detection, detection of methylamines for breath analysis with both a near-IR diode laser and a DFG source, and finally, acetone measurements with a heatable multipass cell intended for vapor phase studies on doping agents in urine samples.

  2. Microfabricated planar glass gas chromatography with photoionization detection.

    PubMed

    Lewis, Alastair C; Hamilton, Jacqueline F; Rhodes, Christopher N; Halliday, Jaydene; Bartle, Keith D; Homewood, Philip; Grenfell, Robin J P; Goody, Brian; Harling, Alice M; Brewer, Paul; Vargha, Gergely; Milton, Martin J T

    2010-01-29

    We report the development of a microfabricated gas chromatography system suitable for the separation of volatile organic compounds (VOCs) and compatible with use as a portable measurement device. Hydrofluoric acid etching of 95x95mm Schott B270 wafers has been used to give symmetrical hemi-spherical channels within a glass substrate. Two matching glass plates were subsequently cold bonded with the channels aligned; the flatness of the glass surfaces resulted in strong bonding through van der Waals forces. The device comprised gas fluidic interconnections, injection zone and 7.5 and 1.4m long, 320microm internal diameter capillaries. Optical microscopy confirmed the capillaries to have fully circular channel profiles. Direct column heating and cooling could be achieved using a combination of resistive heaters and Peltier devices. The low thermal conductivity of glass allowed for multiple uniform temperature zones to be achieved within a single glass chip. Temperature control over the range 10-200 degrees C was achieved with peak power demand of approximately 25W. The 7.5m capillary column was static coated with a 2microm film of non-polar dimethylpolysiloxane stationary phase. A standard FID and a modified lightweight 100mW photoionization detector (PID) were coupled to the column and performance tested with gas mixtures of monoaromatic and monoterpene species at the parts per million concentration level. The low power GC-PID device showed good performance for a small set of VOCs and sub ng detection sensitivity to monoaromatics. PMID:20022335

  3. Hydrocarbon gas detection with microelectromechanical Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Mannila, Rami; Tuohiniemi, Mikko; Mäkynen, Jussi; Näkki, Ismo; Antila, Jarkko

    2013-05-01

    VTT Technical Research Centre of Finland has developed microelectromechanical (MEMS) Fabry-Perot interferometer (FPI) for hydrocarbon measurements. Fabry-Perot interferometer is a structure where is two highly reflective surfaces separated by a tunable air gap. The MEMS FPI is a monolithic device, i.e. it is made entirely on one substrate in a batch process, without assembling separate pieces together. The gap is adjusted by moving the upper mirror with electrostatic force, so there are no actual moving parts. The manufactured MEMS FPIs have been characterized. The tuning wavelength range of the MEMS FPI is 2.8-3.5 ?m and its spectral resolution is 50-60 nm. VTT has designed and manufactured a handheld size demonstrator device based on the technology presented in this abstract. This device demonstrates gas detecting by measuring cigarette lighter gas and various plastic materials transmission spectra. The demonstrator contains light source, gas cell, MEMS FPI, detector and control electronics. It is connected to a laptop by USB connection, additional power supply or connection is not needed.

  4. Detection of gas hydrates by the measurement of instantaneous temperature

    E-print Network

    Dinakaran, Srikanth

    1994-01-01

    Natural gas hydrates are icelike crystalline substances formed by gas molecules trapped in a water lattice. Suitable thermodynamic conditions and the presence of gas are required for the formation of natural gas hydrates in ocean sediments. Several...

  5. Liquefied Noble Gas (LNG) detectors for detection of nuclear materials

    NASA Astrophysics Data System (ADS)

    Nikkel, J. A.; Gozani, T.; Brown, C.; Kwong, J.; McKinsey, D. N.; Shin, Y.; Kane, S.; Gary, C.; Firestone, M.

    2012-03-01

    Liquefied-noble-gas (LNG) detectors offer, in principle, very good energy resolution for both neutrons and gamma rays, fast response time (hence high-count-rate capabilities), excellent discrimination between neutrons and gamma rays, and scalability to large volumes. They do, however, need cryogenics. LNG detectors in sizes of interest for fissionable material detection in cargo are reaching a certain level of maturity because of the ongoing extensive R&}D effort in high-energy physics regarding their use in the search for dark matter and neutrinoless double beta decay. The unique properties of LNG detectors, especially those using Liquid Argon (LAr) and Liquid Xenon (LXe), call for a study to determine their suitability for Non-Intrusive Inspection (NII) for Special Nuclear Materials (SNM) and possibly for other threats in cargo. Rapiscan Systems Laboratory, Yale University Physics Department, and Adelphi Technology are collaborating in the investigation of the suitability of LAr as a scintillation material for large size inspection systems for air and maritime containers and trucks. This program studies their suitability for NII, determines their potential uses, determines what improvements in performance they offer and recommends changes to their design to further enhance their suitability. An existing 3.1 liter LAr detector (microCLEAN) at Yale University, developed for R&}D on the detection of weakly interacting massive particles (WIMPs) was employed for testing. A larger version of this detector (15 liters), more suitable for the detection of higher energy gamma rays and neutrons is being built for experimental evaluation. Results of measurements and simulations of gamma ray and neutron detection in microCLEAN and a larger detector (326 liter CL38) are presented.

  6. Silicon Carbide-Based Hydrogen and Hydrocarbon Gas Detection

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Neudeck, Philip G.; Chen, Liang-Yu; Knight, D.; Liu, C. C.; Wu, Q. H.R

    1995-01-01

    Hydrogen and hydrocarbon detection in aeronautical applications is important for reasons of safety and emissions control. The use of silicon carbide as a semiconductor in a metal-semiconductor or metal-insulator-semiconductor structure opens opportunities to measure hydrogen and hydrocarbons in high temperature environments beyond the capabilities of silicon-based devices. The purpose of this paper is to explore the response and stability of Pd-SiC Schottky diodes as gas sensors in the temperature range from 100 to 400 C. The effect of heat treating on the diode properties as measured at 100 C is explored. Subsequent operation at 400 C demonstrates the diodes' sensitivity to hydrogen and hydrocarbons. It is concluded that the Pd-SiC Schottky diode has potential as a hydrogen and hydrocarbon sensor over a wide range of temperatures but further studies are necessary to determine the diodes' long term stability.

  7. Long-wave infrared imaging of vegetation for detecting leaking CO2 gas

    E-print Network

    Shaw, Joseph A.

    Long-wave infrared imaging of vegetation for detecting leaking CO2 gas Jennifer E. Johnson Joseph A for detecting leaking CO2 gas Jennifer E. Johnson,a Joseph A. Shaw,a Rick Lawrence,b Paul W. Nugent,a Laura M of these calibrated imagers is imaging of vegetation for CO2 gas leak detection. During a four-week period

  8. Contact tube wear detection in gas metal arc welding

    SciTech Connect

    Quinn, T.P.; Madigan, R.B.; Mornis, M.A.; Siewert, T.A. [National Inst. of Standards and Technology, Boulder, CO (United States). Materials Reliability Division

    1995-04-01

    A real-time algorithm has been developed to detect contact tube wear during gas metal arc welding. The integral from 0.3 to 4 Hz of the power spectral density of voltage (constant current and pulsed current power sources) or current (constant voltage power sources) is called the wear parameter and is used to measure wear. The contact tube is predicted to be worn when the parameter grows nonlinearly or exceeds a threshold. For 11 contact tubes worn by welding on a rotating pipe, the wear parameter predicted the observed increase in the area of the contact tube`s exit bore of 140% of the original area within a standard deviation of 20%. Welds were made with a constant voltage power source and with a pulsed current power source at two different voltages. The pulsed current welds were made with and without automatic voltage control by wire feed speed and with and without weaving in a V-groove. No significant differences were detected between the wear parameters for all test welds, indicating that the algorithm can be used under these welding conditions.

  9. Miniaturized Hollow-Waveguide Gas Correlation Radiometer (GCR) for Trace Gas Detection in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Wilson, Emily L.; Georgieva, E. M.; Melroy, H. R.

    2012-01-01

    Gas correlation radiometry (GCR) has been shown to be a sensitive and versatile method for detecting trace gases in Earth's atmosphere. Here, we present a miniaturized and simplified version of this instrument capable of mapping multiple trace gases and identifying active regions on the Mars surface. Reduction of the size and mass of the GCR instrument has been achieved by implementing a lightweight, 1 mm inner diameter hollow-core optical fiber (hollow waveguide) for the gas correlation cell. Based on a comparison with an Earth orbiting CO2 gas correlation instrument, replacement of the 10 meter mUltipass cell with hollow waveguide of equivalent pathlength reduces the cell mass from approx 150 kg to approx 0.5 kg, and reduces the volume from 1.9 m x 1.3 m x 0.86 m to a small bundle of fiber coils approximately I meter in diameter by 0.05 m in height (mass and volume reductions of >99%). This modular instrument technique can be expanded to include measurements of additional species of interest including nitrous oxide (N2O), hydrogen sulfide (H2S), methanol (CH3OH), and sulfur dioxide (SO2), as well as carbon dioxide (CO2) for a simultaneous measure of mass balance.

  10. Gas-detection instrument based on external-cavity diode lasers and photoacoustic detectors

    Microsoft Academic Search

    Zoltan Bozoki; Janos Sneider; Miklos Szakall; Arpad Mohacsi; Gergely Toth; Zsolt Bor; Gabor Szabo

    1998-01-01

    Among the numerous detection methods applicable in spectroscopic gas detection systems photoacoustics is probably the simplest, most cost effective, yet a highly sensitive one. By using a properly designed photoacoustic cell, equipped with a commercial microphone and electronics for phase sensitive detection, absorbed electromagnetic radiation as low as 10 nW can be easily detected. The choice of a suitable light

  11. Recent Developments in Modulation Spectroscopy for Trace Gas Detection Using Tunable Diode Lasers

    Microsoft Academic Search

    Kyuseok Song; Euo Chang Jung

    2003-01-01

    The need for higher sensitive detection technology for trace gas samples, either in the laboratory setup or in the atmospheric remote sensing has been a goal for several decades. The development of the tunable diode laser has propelled the progress of trace detection technology, and modulation technology enables the improvement of the detection sensitivity. As a result, the detection of

  12. MRGC performance evaluation model of gas leak infrared imaging detection system.

    PubMed

    Li, Jiakun; Jin, Weiqi; Wang, Xia; Zhang, Xu

    2014-12-15

    Gas leak infrared imaging detection technology has become one of the most effective means to detect gas leaks. We propose a novel MRGC (minimum resolvable gas concentration) model that is suitable for evaluating the performance of passive GLIIDSs (gas leak infrared imaging detection systems). An MRGC equivalent calculation method and a direct MRGC measurement method based on the MRTD (minimum resolvable temperature difference) model are also proposed. The MRGC measurement system is designed and built. The measured and calculated results are in good agreement, which verifies the MRGC model's correctness and demonstrates the effectiveness of the MRGC performance evaluation method. PMID:25607484

  13. Project uses microphones to detect underwater gas leaks Published: 14 Oct 2011

    E-print Network

    Sóbester, András

    Project uses microphones to detect underwater gas leaks Published: 14 Oct 2011 Source: The Engineer Key Topics: Technology Scientists at Southampton University are employing hydrophones to monitor leaks from underwater gas pipelines. In addition to monitoring ruptured gas pipelines, the hydrophones could

  14. Factors affecting PD detection in GIS using a carbon nanotube gas sensor

    Microsoft Academic Search

    Weidong Ding; Kohei Ochi; Junya Suehiro; Kiminobu Imasaka; Ryota Hayashi; Masanori Hara

    2007-01-01

    The authors have previously demonstrated that a carbon nanotube (CNT) gas sensor can detect SF6 decomposition byproducts generated by partial discharges (PDs). There are several factors to be considered, however, before applying the CNT gas sensor to practical diagnosis of a gas-insulated switchgear (GIS). In this paper, three major factors, namely, the effects of operating temperature and installation location of

  15. Naturally fractured tight gas: Gas reservoir detection optimization. Quarterly report, January 1--March 31, 1997

    SciTech Connect

    NONE

    1997-12-31

    Economically viable natural gas production from the low permeability Mesaverde Formation in the Piceance Basin, Colorado requires the presence of an intense set of open natural fractures. Establishing the regional presence and specific location of such natural fractures is the highest priority exploration goal in the Piceance and other western US tight, gas-centered basins. Recently, Advanced Resources International, Inc. (ARI) completed a field program at Rulison Field, Piceance Basin, to test and demonstrate the use of advanced seismic methods to locate and characterize natural fractures. This project began with a comprehensive review of the tectonic history, state of stress and fracture genesis of the basin. A high resolution aeromagnetic survey, interpreted satellite and SLAR imagery, and 400 line miles of 2-D seismic provided the foundation for the structural interpretation. The central feature of the program was the 4.5 square mile multi-azimuth 3-D seismic P-wave survey to locate natural fracture anomalies. The interpreted seismic attributes are being tested against a control data set of 27 wells. Additional wells are currently being drilled at Rulison, on close 40 acre spacings, to establish the productivity from the seismically observed fracture anomalies. A similar regional prospecting and seismic program is being considered for another part of the basin. The preliminary results indicate that detailed mapping of fault geometries and use of azimuthally defined seismic attributes exhibit close correlation with high productivity gas wells. The performance of the ten new wells, being drilled in the seismic grid in late 1996 and early 1997, will help demonstrate the reliability of this natural fracture detection and mapping technology.

  16. Numerical investigation of coal seam gas detection using airborne electromagnetics

    NASA Astrophysics Data System (ADS)

    Abdulla, Mohamed

    The use of airborne electromagnetic (AEM) techniques has been mostly utilized in the mining industry. The various AEM systems enable fast data acquisition to detect zones of interest in exploration and in some cases are used to delineate targets on a production scale. For coal seam gas (CSG) reservoirs, reservoir thickness and the resistivity contrast present a new challenge to the present AEM systems in terms of detectability. Our research question began with the idea of using AEM methods in the detection of thin reservoirs. CSG reservoirs resemble thin reservoirs that have been and are currently being produced. In this thesis we present the results of a feasibility analysis of AEM study on coal seam reservoirs using synthetic models. The aim of the study is to contribute and bridge the gap of the scientific literature on AEM systems in settings such as CSG exploration. In the models we have chosen to simulate both in 1-D and 3-D, the CSG target resistivity was varied from a resistive to a conductive target (4 ohm.m, 150 ohm.m, and 667 ohm.m) to compare the different responses while the target thickness was fixed to resemble a stack of coal seams at that interval. Due to the differences in 1-D and 3-D modelling, we also examine the differences resulting from each modelling set up. The results of the 1-D forward modeling served as a first order understanding of the detection depths by AEM for CSG reservoirs. Three CSG reservoir horizontally layered earth model scenarios were examined, half-space, conductive/resistive and resistive/conductive. The response behavior for each of the three scenarios differs with the differing target resistivities. The 1-D modeling in both the halfspace and conductive/resistive models shows detection at depths beyond 300 m for three cases of target resistivity outlined above. After the 300-m depth, the response falls below the assumed noise floor level of 5% response difference. However, when a resistive layer overlies a conductive host, the resistive/conductive model, the signal is reduced for the resistive target cases, but the response is unchanged for the conductive target layer. For a better understanding of the responses from more complex reservoirs, a 3-D model was developed to incorporate additional geology. The 3-D models were based on the 1-D models and the modeling parameters were not altered except for the finite extent of the layers. The system properties such as the transmitter waveform, moment and time gates did not change. For the 3-D coal seam reservoir models, the same level of response is not observed for the 240 × 240 m areal extent target. For the halfspace and conductive/resistive model, the AEM response is small. Also noticeable is the decreased response below 50-m target depth. For the assumed noise floor level, the different targets would not be detectable in these instances beyond 50-m when compared to detection depths of up to 300-m in the 1-D scenario. If, however, a resistive overburden exists, i.e. the resistive/conductive model scenario, the 3-D response for the conductive case target is strong compared to the other target cases due to the preferential current flow. In this scenario, a conductive target seam can be detected at a depth of 150-m and possibly deeper depending on the thickness of the overburden layer. In contrast, for the case of the resistive targets, the anomalous body would be undetectable beyond 50-m depth. I apply the same modeling techniques to a more complex model adopted from the Queensland Surat Basin CSG reservoir. I simulate responses in both 1-D and 3-D. The 1-D responses show promise for detecting targets at up to 500 m deep. The 3-D models with an embedded a target with an areal extent of 240 × 240m display small responses and indicate shallow detection depths. However when I increased the target's areal extent to 480 × 480 m, a stronger response is observed that is larger then the 5% noise floor level for all three target cases. This is a good indication that the size of the CSG target is important for AEM application. (Abstract sh

  17. Thermally modulated nano-trampoline material as smart skin for gas molecular mass detection

    NASA Astrophysics Data System (ADS)

    Xia, Hua

    2012-06-01

    Conventional multi-component gas analysis is based either on laser spectroscopy, laser and photoacoustic absorption at specific wavelengths, or on gas chromatography by separating the components of a gas mixture primarily due to boiling point (or vapor pressure) differences. This paper will present a new gas molecular mass detection method based on thermally modulated nano-trampoline material as smart skin for gas molecular mass detection by fiber Bragg grating-based gas sensors. Such a nanomaterial and fiber Bragg grating integrated sensing device has been designed to be operated either at high-energy level (highly thermal strained status) or at low-energy level (low thermal strained status). Thermal energy absorption of gas molecular trigs the sensing device transition from high-thermal-energy status to low-thermal- energy status. Experiment has shown that thermal energy variation due to gas molecular thermal energy absorption is dependent upon the gas molecular mass, and can be detected by fiber Bragg resonant wavelength shift with a linear function from 17 kg/kmol to 32 kg/kmol and a sensitivity of 0.025 kg/kmol for a 5 micron-thick nano-trampoline structure and fiber Bragg grating integrated gas sensing device. The laboratory and field validation data have further demonstrated its fast response characteristics and reliability to be online gas analysis instrument for measuring effective gas molecular mass from single-component gas, binary-component gas mixture, and multi-gas mixture. The potential industrial applications include fouling and surge control for gas charge centrifugal compressor ethylene production, gas purity for hydrogen-cooled generator, gasification for syngas production, gasoline/diesel and natural gas fuel quality monitoring for consumer market.

  18. Detecting the gas bubbles in a liquid metal coolant by means of magnetic flowmeters

    NASA Astrophysics Data System (ADS)

    Mogilner, A. I.; Morozov, S. A.; Zakharov, S. O.; Uralets, A. Yu.

    Solution of some problems of control and diagnosis of circuits with a liquid-metal coolant (LMC) often requires the detection of gas bubbles penetrating the circulation loop. The sources of gas intake can be presented by failed fuel elements in reactor core, failed heat-exchange surfaces in sodium-water steam generators in the secondary circuits, gas capture by circulating coolant from gas circuits. Sometimes the gas is especially injected into circulating coolant to study the dynamics of accumulation and extraction of gas bubbles and to solve research problems related to simulations of emergency situations. The most commonly used methods for gas bubble detection include methods based on measuring coolant electric conductivity. A method for detecting gas bubbles in LMC, based on revealing the change of its electric conductivity is considered. Magnetic flowmeter is used as a detecting element of these changes. Approximate theory for describing spectral and energy noises in signals of a magnetic flowmeter, controlling the flow rate of LMC with gas bubbles is suggested. A new method for signal reading is suggested. Experimental results illustrating the possibility of using the method for measuring the rate of bubble movement and studying the dependence of gas bubble volume on the flow rate of injected gas are presented.

  19. [A review of mixed gas detection system based on infrared spectroscopic technique].

    PubMed

    Dang, Jing-Min; Fu, Li; Yan, Zi-Hui; Zheng, Chuan-Tao; Chang, Yu-Chun; Chen, Chen; Wang, Yi-Din

    2014-10-01

    In order to provide the experiences and references to the researchers who are working on infrared (IR) mixed gas detection field. The proposed manuscript reviews two sections of the aforementioned field, including optical multiplexing structure and detection method. At present, the coherent light sources whose representative are quantum cascade laser (QCL) and inter-band cascade laser(ICL) become the mainstream light source in IR mixed gas detection, which replace the traditional non-coherent light source, such as IR radiation source and IR light emitting diode. In addition, the photon detector which has a super high detectivity and very short response time is gradually beyond thermal infrared detector, dominant in the field of infrared detector. The optical multiplexing structure is the key factor of IR mixed gas detection system, which consists of single light source multi-plexing detection structure and multi light source multiplexing detection structure. Particularly, single light source multiplexing detection structure is advantages of small volume and high integration, which make it a plausible candidate for the portable mixed gas detection system; Meanwhile, multi light source multiplexing detection structure is embodiment of time division multiplex, frequency division multiplexing and wavelength division multiplexing, and become the leading structure of the mixed gas detection system because of its wider spectral range, higher spectral resolution, etc. The detection method applied to IR mixed gas detection includes non-dispersive infrared (NDIR) spectroscopy, wavelength and frequency-modulation spectroscopy, cavity-enhanced spectroscopy and photoacoustic spectroscopy, etc. The IR mixed gas detection system designed by researchers after recognizing the whole sections of the proposed system, which play a significant role in industrial and agricultural production, environmental monitoring, and life science, etc. PMID:25739237

  20. Gross error detection and data reconciliation in natural gas distribution systems: A feasibility study

    SciTech Connect

    Heenan, W.A.; Cardiel, M.G.; Serth, R.W.

    1987-01-01

    The feasibility of applying gross error detection and data reconciliation techniques to the problem of ''unaccounted for'' gas in natural gas distribution systems is investigated. To this end, computer simulation tests are performed using data from the gas distribution system for the city of Franklin, Texas. The economic feasibility of installing additional gas meters in the system to provide redundancy in the measured data is also considered.

  1. Gas detection techniques with fiber optical spectrum absorption at near-IR wavelength

    NASA Astrophysics Data System (ADS)

    Liu, Tiegen; Liu, Kun; Jiang, Junfeng; Peng, Gangding; Wang, Yan; Jia, Dagong; Zhang, Hongxia; Jing, Wencai; Zhang, Yimo

    2010-04-01

    Detection of pollution gas is important in environmental and pollution monitoring, which can be used widely in mining and petrochemical industry. Fiber optical spectrum absorption (FOSA) at near-IR wavelength is widely used in gas detection due to its essential advantages. It has attracted considerable attention, and there are several types and methods in FOSA. Wavelength modulation technique (WMT) is one of them, which will improve the gas detection sensitivity dramatically. This technique can be realized by detecting the intensity of the second-harmonic component signal. Intra-cavity laser spectroscopy (ICLS) is another alternative technique for high sensitivity absorption measurement. With an absorber directly placed within the laser cavity, a short absorption cell can be transformed into a high sensitivity system. But the practical sensitivity is obviously less than the theoretical value. The authors did some works in these fields and have obtained some remarkable progress. With broad reflectors instead of FBG as mirror of the cavity and wavelength sweep technique (WST), several absorption spectra of detected gas can be collected. And the detection sensitivity can be enhanced sharply by averaging the results of each spectrum, with acetylene sensitivity less than 100 ppm . When ICLS is used combined with WST and WMT, the detection sensitivity of acetylene can be enhanced further. The sensitivity is less than 75 ppm. By using FBGs as wavelength references, the absorption wavelength of the detected gas is obtained, which can be used to realize gas recognition. The system is capable of accessing into fiber intelligent sensing network.

  2. Portable instrument and method for detecting reduced sulfur compounds in a gas

    DOEpatents

    Gaffney, J.S.; Kelly, T.J.; Tanner, R.L.

    1983-06-01

    A portable real time instrument for detecting concentrations in the part per billion range of reduced sulfur compounds in a sample gas. Ozonized air or oxygen and reduced sulfur compounds in a sample gas stream react to produce chemiluminescence in a reaction chamber and the emitted light is filtered and observed by a photomultiplier to detect reduced sulfur compounds. Selective response to individual sulfur compounds is achieved by varying reaction chamber temperature and ozone and sample gas flows, and by the use of either air or oxygen as the ozone source gas.

  3. Partial discharge detection in gas insulation load breaker switch

    Microsoft Academic Search

    Chien-Yi Chen; Yu-Hsun Lin; Ching-Chau Su; Ju-Chu Hsieh; Cheng-Chi Tai

    2011-01-01

    This paper aims to discuss the measurement and recognition of partial discharge (PD) signals in gas insulation load breaker switch (GILBS) by using high frequency current transformer (HFCT) and acoustic emission (AE) sensors. Three kinds of fault were made purposely within the GILBS that sealed up with SF 6 gas. Then we increase the voltage onto the GILBS until it

  4. Gas hydrate detection and mapping on the US east coast

    SciTech Connect

    Ahlbrandt, T.S.; Dillon, W.P.

    1993-12-31

    Project objectives are to identify and map gas hydrate accumulations on the US eastern continental margin using remote sensing (seismic profiling) techniques and to relate these concentrations to the geological factors that-control them. In order to test the remote sensing methods, gas hydrate-cemented sediments will be tested in the laboratory and an effort will be made to perform similar physical tests on natural hydrate-cemented sediments from the study area. Gas hydrate potentially may represent a future major resource of energy. Furthermore, it may influence climate change because it forms a large reservoir for methane, which is a very effective greenhouse gas; its breakdown probably is a controlling factor for sea-floor landslides; and its presence has significant effect on the acoustic velocity of sea-floor sediments.

  5. Gas phase chemical detection with an integrated chemical analysis system

    SciTech Connect

    CASALNUOVO,STEPHEN A.; FRYE-MASON,GREGORY CHARLES; KOTTENSTETTE,RICHARD; HELLER,EDWIN J.; MATZKE,CAROLYN M.; LEWIS,PATRICK R.; MANGINELL,RONALD P.; BACA,ALBERT G.; HIETALA,VINCENT M.

    2000-04-12

    Microfabrication technology has been applied to the development of a miniature, multi-channel gas phase chemical laboratory that provides fast response, small size, and enhanced versatility and chemical discrimination. Each analysis channel includes a sample preconcentrator followed by a gas chromatographic separator and a chemically selective surface acoustic wave detector array to achieve high sensitivity and selectivity. The performance of the components, individually and collectively, is described.

  6. Development of an electrical resistivity cone for the detection of gas hydrates in marine sediments

    E-print Network

    McClelland, Martha Ann

    1994-01-01

    DEVELOPMENT OF AN ELECTRICAL RESISTIVITY CONE FOR THE DETECTION OF GAS HYDRATES IN MARINE SEDIMENTS A Thesis by MARTHA ANN McCLELIAND Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... (Member) Ignacio Rodriguez-Iturbe (I(cad oi' Department) May 1994 Major Subject: Civil Engineering ABSTRACT Development of an Electrical Resistivity Cone for the Detection of Gas Hydrates in Marine Sediments. (May 1994) Martha Ann McClelland, B. S...

  7. A gas chromatography-thermal conductivity detection method for helium detection in postmortem blood and tissue specimens.

    PubMed

    Schaff, Jason E; Karas, Roman P; Marinetti, Laureen

    2012-03-01

    In cases of death by inert gas asphyxiation, it can be difficult to obtain toxicological evidence supporting assignment of a cause of death. Because of its low mass and high diffusivity, and its common use as a carrier gas, helium presents a particular challenge in this respect. We describe a rapid and simple gas chromatography-thermal conductivity detection method to qualitatively screen a variety of postmortem biological specimens for the presence of helium. Application of this method is demonstrated with three case examples, encompassing an array of different biological matrices. PMID:22337780

  8. Underwater natural gas pipeline leakage detection based on interferometric fiber optic sensor in experiment-scale

    Microsoft Academic Search

    Qiang Wang; Xiaowei Wang

    2010-01-01

    A distributed optical fiber sensor of underwater gas transmission pipeline leak detector is demonstrated based on spectrum analysis of hybrid interferometer OTDR system. The feasibility of separately locating underwater pipe leaky source and phase signal demodulation scheme were theoretically analyzed. The system is capable of detecting simulated gas pipeline leakage acoustic signal. In underwater waveguide laboratory, the interferometer was used

  9. Photoacoustic spectrometry for trace gas analysis and leak detection using different cell geometries

    Microsoft Academic Search

    M. A. Gondal; A. Dastageer; M. H. Shwehdi

    2004-01-01

    A photoacoustic (PA) spectrometer with high selectivity and sensitivity has been developed for trace gas analysis and for the detection of gas leak at part per trillion by volume (pptV) level. This PA system comprises of a resonant photoacoustic cell, a pulsed line tunable CO2 laser as an excitation source and a sensitive electret microphone as a photoacoustic detector with

  10. Propane gas leak detection by infrared absorption using carbon infrared emitter and infrared camera

    Microsoft Academic Search

    Naoya Kasai; Chihiro Tsuchiya; Takabumi Fukuda; Kazuyoshi Sekine; Takeru Sano; Tatsumi Takehana

    2011-01-01

    The present study investigated the ability of a system using a carbon infrared emitter (CIE) and an infrared (IR) camera to detect a combustible gas, propane. The CIE transmitted infrared at wavelengths ranging from 1 to 5?m, and the infrared absorption band of propane gas (3.37?m) was obtained using a bandpass filter to remove other infrared wavelengths. The intensity of

  11. Good odorant practices ensure safer operations. [Natural gas odorant detection methods

    Microsoft Academic Search

    Oudman

    1993-01-01

    Regulations in Canada and the US require that combustible gas used as a fuel be odorized at such a level that a concentration in air of one-fifth the lower explosive limit the gas can be readily detected and recognized by a person with a normal sense of smell. These regulations do not specify how the odorant level should be determined.

  12. RAPID COMMUNICATION CW DFB RT diode laser-based sensor for trace-gas detection

    E-print Network

    RAPID COMMUNICATION CW DFB RT diode laser-based sensor for trace-gas detection of ethane using- moelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy

  13. Determining detection limits and minimum detectable concentrations for noble gas detectors utilizing beta-gamma coincidence systems

    Microsoft Academic Search

    K. M. Foltz Biegalski; S. R. Biegalski

    2001-01-01

    Beta-gamma coincidence counting is one of two acceptable noble gas monitoring measurement modes for Comprehensive Nuclear-Test-Ban-Treaty (CTBT) verification purposes defined in CTBT\\/PC\\/II\\/WG.B\\/1. Rigorous derivations of detection limits and minimum detectable activity concentrations for - coincidence data are derived in this paper. Different sampling methodologies are modeled to show how the MDC is affected by different sample collection times, spectral collection

  14. Evaluating Gas-Phase Transport And Detection Of Noble Gas Signals From Underground Nuclear Explosions Using Chemical Tracers

    NASA Astrophysics Data System (ADS)

    Carrigan, C. R.; Hunter, S. L.; Sun, Y.; Wagoner, J. L.; Ruddle, D.; Anderson, G.; Felske, D.; Myers, K.; Zucca, J. J.; Emer, D. F.; Townsend, M.; Drellack, S.; Chipman, V.; Snelson, C. M.

    2013-12-01

    The 1993 Non-Proliferation Experiment (NPE) involved detonating 1 kiloton of chemical explosive in a subsurface cavity which also contained bottles of tracer gases (ref 1). That experiment provided an improved understanding of transport processes relevant to the detection of noble gas signals at the surface emanating from a clandestine underground nuclear explosion (UNE). As an alternative to performing large chemical detonations to simulate gas transport from UNEs, we have developed a test bed for subsurface gas transport, sampling and detection studies using a former UNE cavity. The test bed site allows for the opportunity to evaluate pathways to the surface created by the UNE as well as possible transport mechanisms including barometric pumping and cavity pressurization (ref 2). With the test bed we have monitored long-term chemical tracers as well as newly injected tracers. In order to perform high temporal resolution tracer gas monitoring, we have also developed a Subsurface Gas Smart Sampler (SGSS) which has application during an actual On Site Inspection (OSI) and is available for deployment in OSI field exercises planned for 2014. Deployment of five SGSS at the remote test bed has provided unparalleled detail concerning relationships involving tracer gas transport to the surface, barometric fluctuations and temporal variations in the natural radon concentration. We anticipate that the results of our tracer experiments will continue to support the development of improved noble gas detection technology for both OSI and International Monitoring System applications. 1. C.R. Carrigan et al., 1996, Nature, 382, p. 528. 2. Y. Sun and C.R. Carrigan, 2012, Pure Appl. Geophys., DOI 10.1007/s00024-012-0514-4.

  15. Detection of sulfur-free odorants in natural gas using ion mobility spectrometry.

    PubMed

    Ruzsanyi, V; Sielemann, S; Baumbach, J I

    2007-01-01

    Beside the primary motivation of the public gas suppliers for odorizing natural gas with a sulfur-free odorant, which relates to the image of the environment-friendly fuel, natural gas, competing with low-sulfur heating fuel and diesel, a question of crucial importance of how to detect such sulfur-free odorants comes up. Concerning the replacement of sulfur-containing by sulfur-free odorization, the availability of a fast and sensitive detection method that can, further, be used on-site plays a key role. The minimum concentration of the new sulfur-free odorant Gasodor S-Free (S-Free) in natural gas should be added at a level of at least 8.8 mg m(-3) to assure a significant warning smell. Therefore, a dynamic range between 0 and approx. 25 mg m(-3) must be realised in the rather complex matrix of natural gas. By means of a handheld ion mobility spectrometer, the odorant content in natural gas is determined within less than 80 s total analysis time directly at the gas pipe. The concentration of S-Free is monitored between 4 and 23 mg m(-3) respecting the quality of the natural gas (high- and low-caloric gas). Results of the validation using a gas chromatograph as a reference standard will be discussed in detail. PMID:17213943

  16. Noxious gas detection using carbon nanotubes with Pd nanoparticles

    PubMed Central

    2011-01-01

    Noxious gas sensors were fabricated using carbon nanotubes [CNTs] with palladium nanoparticles [Pd NPs]. An increase in the resistance was observed under ammonia for both CNTs and CNT-Pd sensors. Under carbon monoxide [CO], the two sensors exhibited different behaviors: for CNT sensors, their resistance decreased slightly with CO exposure, whereas CNT-Pd sensors showed an increase in resistance. The sensing properties and effect of Pd NPs were demonstrated, and CNT-Pd sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective noxious gas sensor at room temperature. PMID:22115357

  17. Gas Phase Chemical Detection with an Integrated Chemical Analysis System

    SciTech Connect

    Baca, Albert G.; Casalnuovo, Stephen A.; Frye-Mason, Gregory C.; Heller, Edwin J.; Hietala, Susan L.; Hietala, Vincent M.; Kottenstette, Richard J.; Lewis, Patrick R.; Manginell, Ronald P.; Matzke, Carloyn M.; Reno, John L.; Sasaki, Darryl Y.; Schubert, W. Kent

    1999-07-08

    Microfabrication technology has been applied to the development of a miniature, multi-channel gas phase chemical laboratory that provides fast response, small size, and enhanced versatility and chemical discrimination. Each analysis channel includes a sample concentrator followed by a gas chromatographic separator and a chemically selective surface acoustic wave detector array to achieve high sensitivity and selectivity. The performance of the components, individually and collectively, is described. The design and performance of novel micromachined acoustic wave devices, with the potential for improved chemical sensitivity, are also described.

  18. Fault detection system in gas lift well based on artificial immune system

    Microsoft Academic Search

    Manana Araujo; Jose Aguilar; Hugo Aponte

    2003-01-01

    In this paper we propose an Artificial Immune System for fault detection in gas lift oil well. Our novel approach inspired by the Immune System allows the application of a pattern recognition model to perform fault detection. A significant feature of our approach is its ability to dynamically learning the fluid patterns of the 'self' and predicting new patterns of

  19. Model-based Fault Detection and Isolation Using Neural Networks: An Industrial Gas Turbine Case Study

    Microsoft Academic Search

    Hasan Abbasi Nozari; Hamed Dehghan Banadaki; Mehdi Aliyari Shoorehdeli; Silvio Simani

    2011-01-01

    This study proposed a model based fault detection and isolation (FDI) method using multi-layer perceptron (MLP) neural network. Detection and isolation of realistic faults of an industrial gas turbine engine in steady-state conditions is mainly centered. A bank of MLP models which are obtained by nonlinear dynamic system identification is used to generate the residuals, and also simple thresholding is

  20. Limit of detection of 15{sub N} by gas-chromatography atomic emission detection: Optimization using an experimental design

    SciTech Connect

    Deruaz, D.; Bannier, A.; Pionchon, C.

    1995-08-01

    This paper deals with the optimal conditions for the detection of {sup 15}N determined using a four-factor experimental design from [2{sup 13}C,-1,3 {sup 15}N] caffeine measured with an atomic emission detector (AED) coupled to gas chromatography (GC). Owing to the capability of a photodiodes array, AED can simultaneously detect several elements using their specific emission lines within a wavelength range of 50 nm. So, the emissions of {sup 15}N and {sup 14}N are simultaneously detected at 420.17 nm and 421.46 nm respectively. Four independent experimental factors were tested (1) helium flow rate (plasma gas); (2) methane pressure (reactant gas); (3) oxygen pressure; (4) hydrogen pressure. It has been shown that these four gases had a significant influence on the analytical response of {sup 15}N. The linearity of the detection was determined using {sup 15}N amounts ranging from 1.52 pg to 19 ng under the optimal conditions obtained from the experimental design. The limit of detection was studied using different methods. The limits of detection of {sup 15}N was 1.9 pg/s according to the IUPAC method (International-Union of Pure and Applied Chemistry). The method proposed by Quimby and Sullivan gave a value of 2.3 pg/s and that of Oppenheimer gave a limit of 29 pg/s. For each determination, and internal standard: 1-isobutyl-3.7 dimethylxanthine was used. The results clearly demonstrate that GC AED is sensitive and selective enough to detect and measure {sup 15}N-labelled molecules after gas chromatographic separation.

  1. Porous One-Dimensional Photonic Crystal Coatings for Gas Detection

    Microsoft Academic Search

    Nuria Hidalgo; Mauricio Ernesto Calvo; Silvia Colodrero; Hernán Miguez

    2010-01-01

    Herein, we present an overview of recent progress on the development of different types of porous 1-D photonic crystal coatings which are optically responsive to gas pressure changes in the environment. Modification of the surrounding vapor pressure gives rise to adsorption and condensation phenomena within the porous networks of the photonic crystal building blocks, varying their refractive index and hence

  2. Optical methods and systems for detecting a constituent in a gas containing oxygen in harsh environments

    DOEpatents

    Carpenter, Michael A. (Scotia, NY); Sirinakis, George (Bronx, NY)

    2011-01-04

    A method for detecting a gas phase constituent such as carbon monoxide, nitrogen dioxide, hydrogen, or hydrocarbons in a gas comprising oxygen such as air, includes providing a sensing material or film having a metal embedded in a catalytically active matrix such as gold embedded in a yttria stabilized zirconia (YSZ) matrix. The method may include annealing the sensing material at about 900.degree. C., exposing the sensing material and gas to a temperature above 400.degree. C., projecting light onto the sensing material, and detecting a change in the absorption spectrum of the sensing material due to the exposure of the sensing material to the gas in air at the temperature which causes a chemical reaction in the sensing material compared to the absorption spectrum of the sensing material in the absence of the gas. Systems employing such a method are also disclosed.

  3. Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection

    PubMed Central

    Kanan, Sofian M.; El-Kadri, Oussama M.; Abu-Yousef, Imad A.; Kanan, Marsha C.

    2009-01-01

    A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented. PMID:22408500

  4. Comparison of extraction methods and detection systems in the gas chromatographic analysis of volatile carbonyl compounds

    Microsoft Academic Search

    Elena E. Stashenko; María Constanza Ferreira; Luis Gonzalo Sequeda; Jairo René Martínez; Jon W. Wong

    1997-01-01

    High-resolution gas chromatography (HRGC) with electron-capture detection (ECD), nitrogen-phosphorus detection (NPD), flame ionization detection (FID) or with mass spectrometry-selected ion monitoring (MS-SIM) was used in the analysis of volatile carbonyl compounds. Eighteen carbonyl compounds that are typically produced during lipid peroxidation were derivatized quantitatively with pentafluorophenylhydrazine (PFPH) at room temperature, to afford their corresponding water-insoluble hydrazones. These derivatives were extracted

  5. Fault detection and isolation in aircraft gas turbine engines. Part 2: validation on a simulation test bed

    E-print Network

    Ray, Asok

    319 Fault detection and isolation in aircraft gas turbine engines. Part 2: validation of fault detection and isolation (FDI) in aircraft gas turbine engines. The FDI algorithms are built upon,onasimulationtestbed.Thetestbedisbuiltuponanintegratedmodelofageneric two-spool turbofan aircraft gas turbine engine including the engine control system. Keywords: aircraft

  6. False-alarm characterization in hyperspectral gas-detection applications

    NASA Astrophysics Data System (ADS)

    DiPietro, Robert S.; Truslow, Eric; Manolakis, Dimitris G.; Golowich, Steven E.; Lockwood, Ronald B.

    2012-09-01

    Chemical cloud detection using long-wave infrared (LWIR) hyperspectral-imaging sensors has many civilian and military applications, including chemical warfare threat mitigation, environmental monitoring, and emergency response. Current capabilities are limited by variation in background clutter as opposed to the physics of photon detection, and this makes the statistical characterization of clutter and clutter-induced false alarms essential to the design of practical systems. In this exploratory work, we use hyperspectral data collected both on the ground and in the air to spectrally and spatially characterize false alarms. Focusing on two widely-used detectors, the matched filter (MF) and the adaptive cosine estimator (ACE), we compare empirical false-alarm rates to their theoretical counterparts - detector output under Gaussian, t and t-mixture distributed data - and show that these models often underestimate false-alarm rates. Next, we threshold real detection maps and show that true detections and false alarms often exhibit very different spatial behavior. To exploit this difference and understand how spatial processing affects performance, the spatial behavior of false alarms must be understood. We take a first step in this direction by showing that, although the behavior may `look' quite random, it is not well captured by the complete-spatial-randomness model. Finally, we describe how our findings impact the design of real detection systems.

  7. Visual detection of gas shows from coal core and cuttings using liquid leak detector

    USGS Publications Warehouse

    Barker, C.E.

    2006-01-01

    Portions of core or cutting samples that have active gas shows can be identified by applying a liquid leak detector to the core surface. Although these gas shows can be caused by manmade changes to the coals' internal structure and surface of the core during the coring process, in many cases, the marked gas shows overlie changes in maceral composition, subtle fractures or coal, coal structure and so forth that seemingly are places where natural primary permeability is higher and gas shows would be favored. Given the limited time available for core description before a core is closed in a canister, using the liquid leak detector method to mark gas shows enhances core description by providing a photographic record of places of apparently increased gas flow likely related to enhanced coal permeability that cannot be easily detected otherwise.

  8. Fabry-Pérot cavity sensors for multipoint on-column micro gas chromatography detection.

    PubMed

    Liu, Jing; Sun, Yuze; Howard, Daniel J; Frye-Mason, Greg; Thompson, Aaron K; Ja, Shiou-Jyh; Wang, Siao-Kwan; Bai, Mengjun; Taub, Haskell; Almasri, Mahmoud; Fan, Xudong

    2010-06-01

    We developed and characterized a Fabry-Pérot (FP) sensor module based micro gas chromatography (microGC) detector for multipoint on-column detection. The FP sensor was fabricated by depositing a thin layer of metal and a layer of gas-sensitive polymer consecutively on the endface of an optical fiber, which formed the FP cavity. Light partially reflected from the metal layer and the polymer-air interface generated an interference spectrum, which shifted as the polymer layer absorbed the gas analyte. The FP sensor module was then assembled by inserting the FP sensor into a hole drilled in the wall of a fused-silica capillary, which can be easily connected to the conventional gas chromatography (GC) column through a universal quick seal column connector, thus enabling on-column real-time detection. We characterized the FP sensor module based microGC detector. Sensitive detection of various gas analytes was achieved with subnanogram detection limits. The rapid separation capability of the FP sensor module assembled with both single- and tandem-column systems was demonstrated, in which gas analytes having a wide range of polarities and volatilities were well-resolved. The tandem-column system obtained increased sensitivity and selectivity by employing two FP sensor modules coated with different polymers, showing great system versatility. PMID:20441156

  9. LOW COST IMAGER FOR POLLUTANT GAS LEAK DETECTION - PHASE I

    EPA Science Inventory

    Infrared (IR) imaging is the best method for detecting leaks of pollutant gases, but current technology based on cooled IR imagers is far too expensive ($75,000 to $150,000) for everyday field use by those who need it to meet regulatory limits—electric and petrochemical ...

  10. Gas detection for alternate-fuel vehicle facilities.

    PubMed

    Ferree, Steve

    2003-05-01

    Alternative fuel vehicles' safety is driven by local, state, and federal regulations in which fleet owners in key metropolitan [table: see text] areas convert much of their fleet to cleaner-burning fuels. Various alternative fuels are available to meet this requirement, each with its own advantages and requirements. This conversion to alternative fuels leads to special requirements for safety monitoring in the maintenance facilities and refueling stations. A comprehensive gas and flame monitoring system needs to meet the needs of both the user and the local fire marshal. PMID:12754860

  11. An integrated knowledge system for the Space Shuttle hazardous gas detection system

    NASA Technical Reports Server (NTRS)

    Lo, Ching F.; Shi, George Z.; Bangasser, Carl; Fensky, Connie; Cegielski, Eric; Overbey, Glenn

    1993-01-01

    A computer-based integrated Knowledge-Based System, the Intelligent Hypertext Manual (IHM), was developed for the Space Shuttle Hazardous Gas Detection System (HGDS) at NASA Marshall Space Flight Center (MSFC). The IHM stores HGDS related knowledge and presents it in an interactive and intuitive manner. This manual is a combination of hypertext and an expert system which store experts' knowledge and experience in hazardous gas detection and analysis. The IHM's purpose is to provide HGDS personnel with the capabilities of: locating applicable documentation related to procedures, constraints, and previous fault histories; assisting in the training of personnel; enhancing the interpretation of real time data; and recognizing and identifying possible faults in the Space Shuttle sub-systems related to hazardous gas detection.

  12. Possible influence of breathing on detection frequency and intensity rating in gas chromatography-olfactometry

    Microsoft Academic Search

    Karine Hanaoka; Nadine Vallet; Pierre Giampaoli; Bertrand Heyd; Patrick MacLeod

    2001-01-01

    Gas chromatography-olfactometry (GCO) is a useful method to screen potent odorants in food aromas. In this technique, the human olfactory sense is used to detect the odor-active compounds eluted from a gas chromatograph. A particularity of GCO, compared to other sensory analyses, is to combine two discontinuous phenomena:the aperiodic and unpredictable elution of odorous compounds from the chromatographic column and

  13. Field-test system for underground fire detection based on semiconductor gas sensor

    Microsoft Academic Search

    Peter Reimann; Stephan Horras; Andreas Schütze

    2009-01-01

    Based on a single semiconductor (sc) gas sensor and sensors for temperature, relative humidity and gas flow we developed a system for fire detection in coal mines. These sensors are read-out by a high-dynamic-range hardware control and data acquisition platform, in which the sc-sensor is operated with an application-optimized temperature cycle to improve the stability and selectivity. A hierarchical evaluation

  14. Naturally fractured tight gas reservoir detection optimization. Quarterly report, January 1, 1997--March 31, 1997

    SciTech Connect

    NONE

    1998-04-01

    This document contains the quarterly report dated January 1-March 31, 1997 for the Naturally Fractured Tight Gas Reservoir Detection Optimization project. Topics covered in this report include AVOA modeling using paraxial ray tracing, AVOA modeling for gas- and water-filled fractures, 3-D and 3-C processing, and technology transfer material. Several presentations from a Geophysical Applications Workshop workbook, workshop schedule, and list of workshop attendees are also included.

  15. Metal-oxide Nanowires for Toxic Gas Detection

    SciTech Connect

    Devineni, D. P.; Stormo, S.; Kempf, W.; Schenkel, J.; Behanan, R.; Lea, Alan S.; Galipeau, David W.

    2007-01-02

    The feasibility of using Electric field enhanced oxidation (EFEO) to fabricate metal-oxide nanowires for sensing toxic gases was investigated. The effects of fabrication parameters such as film thickness, ambient relative humidity, atomic force microscope (AFM) tip bias voltage, force, scan speed and number of scans on the growth of nanowires were determined. The chemical composition of indium-oxide nanowires was verified using Auger electron spectroscopy. It was found that oxygen to indium ration was 1.69, 1.72, 1.71 and 1.84 at depths of 0, 1.3, 2.5, and 3.8 nm, which was near the 1.5:1 expected for stoichiometric indium-oxide film. Future work will include characterizing the electrical and gas sensing properties of the metal-oxide nanowires.

  16. Chemoresistive Gas Sensors for the Detection of Colorectal Cancer Biomarkers

    PubMed Central

    Malagù, Cesare; Fabbri, Barbara; Gherardi, Sandro; Giberti, Alessio; Guidi, Vincenzo; Landini, Nicolò; Zonta, Giulia

    2014-01-01

    Numerous medical studies show that tumor growth is accompanied by protein changes that may lead to the peroxidation of the cell membrane with consequent emission of volatile organic compounds (VOCs) by breath or intestinal gases that should be seen as biomarkers for colorectal cancer (CRC). The analysis of VOCs represents a non-invasive and potentially inexpensive preliminary screening technique. An array of chemoresistive gas sensors based on screen-printed metal oxide semiconducting films has been selected to discriminate gases of oncological interest, e.g., 1-iodononane and benzene, widely assumed to be biomarkers of colorectal cancer, from those of interference in the gut, such as methane and nitric oxide. PMID:25313496

  17. Multiple headspace extraction for gas detection in ionic liquids.

    PubMed

    Müller, D; Fühl, M; Pinkwart, K; Baltes, N

    2014-10-16

    In this study multiple headspace extraction was used for the first time to measure the saturation concentration of carbon monoxide and oxygen in various ionic liquids (ILs). Many processes in ILs involve the reaction of gases so that the reactant solubility is not a mere characteristical parameter, but understanding the solubility of gases in ILs is required for assessing the feasibility of possible applications. Multiple headspace extraction has proofed to be a powerful tool to obtain solubilities in good accordance with literature data. The measured saturation concentration for carbon monoxide and oxygen in ILs based on rarely researched tetracyanoborates and other anions was in the range of 1.5-6.5mmol/L. The great advantage of multiple headspace extraction is that it is a nonexpensive method that can be realised in most analytical laboratories by combination of a simple gas chromatograph and an eligible headspace injector. PMID:25458524

  18. Application of backscatter absorption gas imaging to the detection of chemicals related to drug production

    NASA Astrophysics Data System (ADS)

    Kulp, Thomas J.; Garvis, Darrel G.; Kennedy, Randall B.; McRae, Thomas G.

    1991-08-01

    The application of backscatter absorption gas imaging (BAGI) to the detection of gaseous chemical species associated with the production of illegal drugs is considered. BAGI is a gas visualization technique that allows the imaging of over 70 organic vapors at minimum concentrations of a few to several hundred ppm-m. Present BAGI capabilities at Lawrence Livermore National Laboratory and Laser Imaging Systems are discussed. Eighteen different species of interest in drug-law enforcement are identified as being detectable by BAGI. The chemical remote sensing needs of law enforcement officials are described, and the use of BAGI in meeting some of these needs is outlined.

  19. Development of an intelligent hypertext manual for the space shuttle hazardous gas detection system

    NASA Technical Reports Server (NTRS)

    Lo, Ching F.; Shi, George Z.; Bangasser, Carl; Fensky, Connie

    1992-01-01

    A computer-based Integrated Knowledge System (IKS), the Intelligent Hypertext Manual (IHM), is being developed for the Space Shuttle Hazardous Gas Detection System (HGDS) at the Huntsville Operations Support Center (HOSC). The IHM stores all HGDS related knowledge and presents them in an interactive and intuitive manner. The IHM's purpose is to provide HGDS personnel with the capabilities of: enhancing the interpretation of real time data; recognizing and identifying possible faults in the Space Shuttle sub-system related to hazardous gas detections; locating applicable documentation related to procedures, constraints, and previous fault histories; and assisting in the training of personnel.

  20. Surface Ionization Gas Detection at SnO{sub 2} Surfaces

    SciTech Connect

    Krenkow, A.; Oberhuettinger, C.; Habauzit, A.; Kessler, M.; Goebel, J.; Mueller, G. [EADS Innovation Works, D-81663 Muenchen (Germany)

    2009-05-23

    In surface ionization (SI) gas detection adsorbed analyte molecules are converted into ionic species at a heated solid surface and extracted into free space by an oppositely biased counter electrode. In the present work we consider the formation of positive and negative analyte gas ions at SnO{sub 2} surfaces. We find that SI leads to positive ion formation only, with the SI efficiency scaling with the ionization energy of the analyte gas molecules. Aromatic and aliphatic hydrocarbons with amine functional groups exhibit particularly high SI efficiencies.

  1. ZnO:Al Thin Film Gas Sensor for Detection of Ethanol Vapor

    PubMed Central

    Chou, Shih Min; Teoh, Lay Gaik; Lai, Wei Hao; Su, Yen Hsun; Hon, Min Hsiung

    2006-01-01

    The ZnO:Al thin films were prepared by RF magnetron sputtering on Si substrate using Pt as interdigitated electrodes. The structure was characterized by XRD and SEM analyses, and the ethanol vapor gas sensing as well as electrical properties have been investigated and discussed. The gas sensing results show that the sensitivity for detecting 400 ppm ethanol vapor was ?20 at an operating temperature of 250°C. The high sensitivity, fast recovery, and reliability suggest that ZnO:Al thin film prepared by RF magnetron sputtering can be used for ethanol vapor gas sensing.

  2. High sensitive gas detection and isotopic measurement for the applications of industrial emission online monitoring and air pollution source tracking

    NASA Astrophysics Data System (ADS)

    Dong, Fengzhong; Zhang, Zhirong; Xia, Hua; Cui, Xiaojuan; Pang, Tao; Wu, Bian; Chen, Weidong; Sigrist, Markus

    2015-04-01

    High sensitive gas detection and isotopic measurements have been widely employed in the industrial and safety production. The recent progress made by our group on high sensitive gas detection with technologies of TDLAS, off-axis integrated cavity output spectroscopy (OA-ICOS) and cavity ring-down spectroscopy (CRDS) will be briefly summarized in this report. Some works for field applications of industrial emission online monitoring and gas leakage detection in oil tank farm with TDLAS are first presented, and then part of our most recent researches on isotopic gas detection with OA-ICOS and CRDS for tracking of pollution sources are also introduced.

  3. [Long optical path gas detection based on MEMS infrared light source].

    PubMed

    Du, Bin-Bin; Zhang, Peng; Gao, Wen-Hong; Shi, Yun-Bo; Zhu, Lin-Quan

    2014-04-01

    According to the requirements of infrared gas sensor for the light source, a broad wavelength, high modulation frequency, low power consumption and small size MEMS infrared light source is chosen as the radiation source, whose performance meets the requirements of infrared sensing system for the light source greatly. However, the infrared light source with the lamberation radiation characteristics is a surface light source, which is still with a large numerical aperture after shaping. It is difficult to increase the detection sensitivity by using a traditional long optical gas cell in a MEMS infrared light source detection system. Based on the dual-wavelength single beam differential detection method, an integrating sphere as the gas cell for long optical path is designed, which is able to realize long optical path for high sensitivity gas detection. The physical dimension is deduced for the equivalent optical path according to the flux conservation principle in the process of light transmission, solving the calculation problem of equivalent optical path of the integrating sphere cell. Using FPGA control chip, the MEMS infrared light source is droved at high frequency modulation and the detector output signal is processed, which makes the external circuit design much simple and flexible. It turns out that 166.7 cm equivalent optical path and the minimum concentration of methane of 0.001 x 10(-6) are achieved by the use of a 5 cm diameter integrating sphere in the research, improving the sensitivity of infrared detection system greatly. PMID:25007612

  4. The Detection Rate of Molecular Gas in Elliptical Galaxies: Constraints on Galaxy Formation Theories

    E-print Network

    Yutaka Fujita; Masahiro Nagashima; Naoteru Gouda

    2000-05-15

    In order to constrain parameters in galaxy formation theories, especially those for a star formation process, we investigate cold gas in elliptical galaxies. We calculate the detection rate of cold gas in them using a semi-analytic model of galaxy formation and compare it with observations. We show that the model with a long star formation time-scale (~20 Gyr) is inconsistent with observations. Thus, some mechanisms of reducing the mass of interstellar medium, such as the consumption of molecular gas by star formation and/or reheating from supernovae, are certainly effective in galaxies. Our model predicts that star formation induced when galaxies in a halo collide each other reduces the cold gas left until the present. However, we find that the reduction through random collisions of satellite (non-central) galaxies in mean free time-scale in a halo is not required to explain the observations. This may imply that the collisions and mergers between satellite galaxies do not occur so often in clusters or that they do not stimulate the star formation activity as much as the simple collision model we adopted. For cD galaxies, the predicted detection rate of cold gas is consistent with observations as long as the transformation of hot gas into cold gas is prevented in halos whose circular velocities are larger than 500 km s^-1. Moreover, we find that the cold gas brought into cDs through captures of gas-rich galaxies is little. We also show that the fraction of galaxies with observable cold gas should be small for cluster ellipticals in comparison with that for field ellipticals.

  5. Gas chromatographic identification of Clostridium difficile and detection of cytotoxin from a modified selective medium.

    PubMed Central

    Levett, P N; Phillips, K D

    1985-01-01

    A modification of an existing selective medium for Clostridium difficile is described. Inclusion in the medium of DL nor-leucine and p-hydroxyphenylacetic acid enables identification of C difficile to be made directly from primary isolation plates by gas chromatographic detection of caproic acid and p-cresol. Plugs of agar withdrawn from the selective medium also allow the detection of cytotoxin production in vitro. PMID:3968212

  6. Granular gas of ellipsoids: analytical collision detection implemented on GPUs

    NASA Astrophysics Data System (ADS)

    Rubio-Largo, S. M.; Lind, P. G.; Maza, D.; Hidalgo, R. C.

    2015-05-01

    We present a hybrid GPU-CPU implementation of an accurate discrete element model for a system of ellipsoids. The ellipsoids have three translational degrees of freedom, their rotational motion being described through quaternions and the contact interaction between two ellipsoids is described by a force which accounts for the elastic and dissipative interactions. Further we combine the exact derivation of contact points between ellipsoids (Wang et al. in Computing 72(1-2):235-246, 2004) with the advantages of the GPU-NVIDIA parallelization strategy (Owens et al. in Comput Graph Forum 26:80-113, 2007). This novelty makes the analytical algorithm computationally feasible when dealing with several thousands of particles. As a benchmark, we simulate a granular gas of frictionless ellipsoids identifying a classical homogeneous cooling state for ellipsoids. For low dissipative systems, the behavior of the granular temperature indicates that the cooling dynamics is governed by the elongation of the ellipsoids and the restitution coefficient. Our outcomes comply with the statistical mechanical laws and the results are in agreement with previous findings for hard ellipsoids (Bereolos et al. in J Chem Phys 99:6087, 1993; Villemot and Talbot in Granul Matter 14:91-97, 2012). Additionally, new insight is provided namely suggesting that the mean field description of the cooling dynamics of elongated particles is conditioned by the particle shape and the degree of energy equipartition.

  7. Fourier transform Raman lidar for trace gas detection and quantification

    SciTech Connect

    Sentell, J.C. [Coleman Research Corp., Huntsville, AL (United States)

    1994-12-31

    The Raman technique, while a valuable tool in chemical and combustion research, is limited in many remote sensing applications because of the low Raman scattering cross-section, which may be three to five orders of magnitude below the Rayleigh (elastic) values. Two concepts for increasing the signal level are discussed. First, use a range-gated Fourier transform spectrometer to increase the system throughput and allow multiplexing advantages. The spectrum is obtained by performing a FFT on the resulting interferogram. Second, since the cross section goes as the fourth power of the optical frequency, use ultra-violet laser illumination, and separate the resulting fluorescence radiation by placing a known dispersion on the transmitted waveform. The techniques for achieving this function, and the mathematical formulation for the phase-modulated auto-correlation which result, are not evaluated in this paper. However, the approach does not appreciably lower the available resolution because the limits are imposed by the sampling function inherent to the finite-duration Michelson mirror scan. A conceptual design using a long-pulse, flashlamp-pumped dye laser is shown, and typical performance equations in the detection of Freon 12, CCl{sub 2}F{sub 2}, are presented. For a one joule laser and a thirty (30) cm aperture operating in darkness, a concentration of 10{sup 23} molecules/m{sup 3} can be detected in a 60 km visibility at a range of 3.4 km. Much greater performance is obtained against molecules exhibiting the resonance Raman effect, such as nitrogen dioxide.

  8. Mid-infrared VIPA Spectrometer for Rapid and Broadband Trace Gas Detection

    E-print Network

    Nugent-Glandorf, Lora; Adler, Florian; Fleisher, Adam J; Cossel, Kevin C; Bjork, Bryce; Dinneen, Tim; Ye, Jun; Diddams, Scott A

    2015-01-01

    We present and characterize a 2-D imaging spectrometer based on a virtually-imaged phased array (VIPA) disperser for rapid, high-resolution molecular detection using mid-infrared (MIR) frequency combs at 3.1 and 3.8 \\mu m. We demonstrate detection of CH4 at 3.1 \\mu m with >3750 resolution elements spanning >80 nm with ~600 MHz resolution in a <10 \\mu s acquisition time. In addition to broadband detection, rapid, time-resolved single-image detection is demonstrated by capturing dynamic concentration changes of CH4 at a rate of ~375 frames per second. Changes in absorption above the noise floor of 5\\times 10-4 are readily detected on the millisecond time scale, leading to important future applications such as real time monitoring of trace gas concentrations and detection of reactive intermediates.

  9. IV-VI semiconductor lasers for gas phase biomarker detection

    NASA Astrophysics Data System (ADS)

    McCann, Patrick; Namjou, Khosrow; Roller, Chad; McMillen, Gina; Kamat, Pratyuma

    2007-09-01

    A promising absorption spectroscopy application for mid-IR lasers is exhaled breath analysis where sensitive, selective, and speedy measurement of small gas phase biomarker molecules can be used to diagnose disease and monitor therapies. Many molecules such as nitric oxide, ethane, formaldehyde, acetaldehyde, acetone, carbonyl sulfide, and carbon disulfide have been connected to diseases or conditions such as asthma, oxidative stress, breast cancer, lung cancer, diabetes, organ transplant rejection, and schizophrenia. Measuring these and other, yet to be discovered, biomarker molecules in exhaled breath with mid-IR lasers offers great potential for improving health care since such tests are non-invasive, real-time, and do not require expensive consumables or chemical reagents. Motivated by these potential benefits, mid-IR laser spectrometers equipped with presently available cryogenically-cooled IV-VI lasers mounted in compact Stirling coolers have been developed for clinical research applications. This paper will begin with a description of the development of mid-IR laser instruments and their use in the largest known exhaled breath clinical study ever performed. It will then shift to a description of recent work on the development of new IV-VI semiconductor quantum well materials and laser fabrication methods that offer the promise of low power consumption (i.e. efficient) continuous wave emission at room temperature. Taken together, the demonstration of compelling clinical applications with large market opportunities and the clear identification of a viable pathway to develop low cost mid-IR laser instrumentation can create a renewed focus for future research and development efforts within the mid-IR materials and devices area.

  10. Diagnosis of diabetes by image detection of breath using gas-sensitive laps

    Microsoft Academic Search

    Qintao Zhang; Ping Wang; Jianping Li; Xiaoguang Gao

    2000-01-01

    Gaseous respiratory acetone detection using LAPS (Light Addressable Potentiometric Sensors) is proposed as a supplementary method for the diagnosis of diabetes. First, electric simulation of the LAPS systern is studied to obtain the optimum sensitivity of tested odours. Gas phase chromatography is used to obtain correlations between blood sugar levels and acetone from the breath. Then several experiments are carried

  11. Gas phase detection of cyclic B3 : 2 2 A1 electronic origin band

    E-print Network

    Maier, John Paul

    Gas phase detection of cyclic B3 : 2 2 E ]X 2 A1 electronic origin band P. Cias, M. Araki, A in the 2 2 E X 2 A1 electronic spectrum of cyclic B3 has been observed by cavity ring down spectroscopy. EXPERIMENT This consists of a standard cavity ring down setup sam- pling a plasma generated in a pulsed

  12. Naturally fractured tight gas reservoir detection optimization. Quarterly report, January 1 - March 31, 1996

    SciTech Connect

    NONE

    1996-12-31

    The objective is to determine methods for detection and mapping of naturally fractured systems for economic production of natural gas from fractured reservoirs. This report contains: 3D P-wave alternate processing; down hole 3C geophone analysis; fracture pattern analysis of the Fort Union and Wind River Basin; 3D-3C seismic processing; and technology transfer.

  13. Compact Electronic Nose Systems Using Metal Oxide Gas Sensors for Fire Detection Systems

    Microsoft Academic Search

    Bancha Charumporn; Toru Fujinaka; Michifumi Yoshioka; Sigeru Omatu

    2006-01-01

    In this paper, a reliable electronic nose (EN) system designed from the combination of various metal oxide gas sensors (MOGS) is applied to the detection of fire resulting from various sources at an early stage. The time series signals obtained from the same source of lire are highly correlated, and different sources of lire exhibit unique patterns in the time

  14. Fire detection systems by compact electronic nose systems using metal oxide gas sensors

    Microsoft Academic Search

    B. Charumporn; S. Omatu; M. Yoshioka; T. Fujinaka; T. Kosaka

    2004-01-01

    In this paper, a reliable electronic nose (EN) system designed from the combination of various metal oxide gas sensors (MOGS) is applied to detect the early stage of fire from various sources. The time series signals of the same source of fire in every repetition data are highly correlated and each source of fire has a unique pattern of time

  15. Naturally fractured tight gas reservoir detection optimization. Quarterly technical progress report, April 1995--June 1995

    SciTech Connect

    NONE

    1995-08-01

    Research continued on methods to detect naturally fractured tight gas reservoirs. This report contains a seismic survey map, and reports on efforts towards a source test to select the source parameters for a 37 square mile compressional wave 3-D seismic survey. Considerations of the source tests are discussed.

  16. Novel technology for flame and gas detection in the petrochemical industry

    NASA Astrophysics Data System (ADS)

    Spector, Yechiel; Jacobson, Esther

    1999-01-01

    A reliable and high performance novel method of flame and gas optical spectral analysis was developed to meet the specific flame and gas detection of the petrochemical industry. Petrochemical industries, especially the offshore and unmanned areas in onshore refineries, pose a major safety hazard with respect to potential explosions and fire events. Unwanted fuel spills or fugitive flammable vapor clouds, migrating along congested pipe lines and hot production areas may cause upon ignition significant loss or damage. To help prevents events like the catastrophic fire that destroyed the offshore oil platform Piper Alpha in July 1988, a reliable and fast gas and flame detection system can be used to trigger effective risk management actions. The present paper describes a patented method of Triple Optical Spectral Analysis employed for the detection of various gases in the air according to their unique 'spectral finger print' absorption characteristics of radiation, as well as for analysis of emission and absorption radiation from combustion processes for flame detection purpose. The method has been applied in the development of unique gas and flame monitoring system designed for 'high risk - harsh/extreme weather conditions continuous operation'. These systems have been recently installed on several offshore platforms and oil rigs as well as on 'floating production Storage and Offloading' - FPSO vessels. The systems advantages and limitations as well as several installations and test data are presented. Various atmospheric conditions as well as false alarm stimulus are discussed.

  17. Absolute detection of metastable rare gas atoms by a cw laser photoionization method

    Microsoft Academic Search

    S. Schohl; D. Klar; T. Kraft; H. A. J. Meijer; M.-W. Ruf; U. Schmitz; S. J. Smith; H. Hotop

    1991-01-01

    A novel, accurate method for the absolute detection of metastable rare gas atoms is described and demonstrated. It involves a direct in situ determination of the electron emission coefficient ? for impact of the respective metastable atom on a conducting surface. ? is reliably obtained by a cw two-photon ionization — depletion technique: the reduction ?IS in electron current from

  18. First results from a marine controlled-source electromagnetic survey to detect gas hydrates offshore Oregon

    E-print Network

    Key, Kerry

    sounding at Hydrate Ridge, Oregon, USA, in August, 2004. Electromagnetic fields transmitted by a deepFirst results from a marine controlled-source electromagnetic survey to detect gas hydrates electromagnetic surveys have the potential to provide an estimate of the total hydrate volume fraction more

  19. Naturally fractured tight gas reservoir detection optimization. Quarterly report, January--March 1995

    SciTech Connect

    NONE

    1995-05-01

    The objective is to determine methods for detection and mapping of natural fracture systems for economic production of natural gas from fractured reservoirs. This progress report covers: 3D P-wave survey; additional processing of 3D P-wave survey; review of multicomponent recording feasibility tests; minivibrator studies; and modeling of 3D-3C acquisition parameters.

  20. Detection of gas leaks along pipelines by spectrally tuned infrared imaging

    Microsoft Academic Search

    Werner Gross; Thomas Hierl; H. Scheuerpflug; U. Schirl; Max J. Schulz

    1998-01-01

    We present a novel method developed for the localization of leaks along natural gas pipelines. Methane distributions in the atmosphere around the leaky pipeline are detected and visualized by spectrally tuned IR imaging. In contrast to conventional techniques which utilize laser radiation sources or scanning, we irradiate the overall region under investigation by 1 kW halogen lamps. The scene background

  1. A Nasicon CO2 gas sensor with drift-detection electrode

    Microsoft Academic Search

    Song Chen; De-Yin Jeng; Hironori Hadano; Yoshiaki Ishiguro; Masakatsu Nakayama; Kenzo Watanabe

    2003-01-01

    A Nasicon (sodium super ion conductor) CO2 gas sensor with a new structure is developed for monitoring CO2 levels in the atmospheric air. In addition to the sensing and reference electrodes of a conventional Nasicon sensor, an auxiliary electrode, referred to as the base electrode, is provided with the new structure. The principle of CO2 detection is the same as

  2. Metal oxide gas sensor array for the detection of diesel fuel in engine oil

    Microsoft Academic Search

    Simonetta Capone; Marzia Zuppa; Dominique S. Presicce; Luca Francioso; Flavio Casino; Pietro Siciliano

    2008-01-01

    We developed a novel method to detect the presence of unburned diesel fuel in lubricating oil for internal combustion engine. The method is based on the use of an array of different gas microsensors based on metal oxide thin films deposited by sol–gel technique on Si substrates. The sensor array, exposed to the volatile chemical species of different diesel fuel

  3. A highly selective and sensitive "turn-on" fluorescence chemodosimeter for the detection of mustard gas.

    PubMed

    Raghavender Goud, D; Purohit, Ajay Kumar; Tak, Vijay; Dubey, Devendra Kumar; Kumar, Pravin; Pardasani, Deepak

    2014-10-21

    A new chemodosimetric protocol based on a tandem S-alkylation followed by desulfurisation reaction of rhodamine-thioamide with mustard gas is reported. The chemodosimeter is highly selective for potential DNA alkylating agents like sulfur mustard, over other simple alkyl halides with the limit of detection of 4.75 ?M. PMID:25186207

  4. Simultaneous detection of multiple-gas species by correlation spectroscopy using a multimode diode laser.

    PubMed

    Lou, X T; Somesfalean, G; Chen, B; Zhang, Y G; Wang, H S; Zhang, Z G; Wu, S H; Qin, Y K

    2010-06-01

    Simultaneous detection of multiple-gas species has for the first time (to our knowledge) been demonstrated by using a multimode diode-laser-based correlation spectroscopy (MDL-COSPEC) scheme. Concentration measurements of a mixture of CO(2) and CO gas were performed by probing overlapping line spectra around 1.57microm using an MDL. Species identification and corresponding quantitive analysis were implemented by correlating the recorded absorption signals of the sample gas mixtures with those of the reference gases of particular interest, attaining accuracies of 2% and 1%, respectively. MDL-COSPEC is a generic technique with potential application for simultaneous detection of multiple gases having resolvable narrow lines. PMID:20517403

  5. A Detection of Molecular Gas Emission in the Host Galaxy of GRB 080517

    NASA Astrophysics Data System (ADS)

    Stanway, E. R.; Levan, A. J.; Tanvir, N. R.; Wiersema, K.; van der Laan, T. P. R.

    2015-01-01

    We have observed the host galaxy of the low-redshift, low-luminosity Swift GRB 080517 at 105.8 GHz using the IRAM Plateau de Bure interferometer. We detect an emission line with integrated flux S?? = 0.39 ± 0.05 Jy km s-1—consistent both spatially and in velocity with identification as the J = 1-0 rotational transition of carbon monoxide (CO) at the host galaxy redshift. This represents only the third long gamma-ray burst (GRB) host galaxy with molecular gas detected in emission. The inferred molecular gas mass, MH_2˜ 6.3× 10^8 M ?, implies a gas consumption timescale of ~40 Myr if star formation continues at its current rate. Similar short timescales appear characteristic of the long GRB population with CO observations to date, suggesting that the GRB in these sources occurs toward the end of their star formation episode.

  6. Effect of Background Emissivity on Gas Detection in Thermal Hyperspectral Imagery

    SciTech Connect

    Walsh, Stephen J.; Tardiff, Mark F.; Chilton, Lawrence K.; Metoyer, Candace N.

    2008-10-02

    Detecting and identifying weak gaseous plumes using thermal imaging data is complicated by many factors. These include variability due to atmosphere, ground and plume temper- ature, and background clutter. This paper presents an analysis of one formulation of the physics-based radiance model, which describes at-sensor observed radiance. The background emissivity and plume/ground temperatures are isolated, and their effects on net chemical signal are described. This analysis shows that the plume’s physical state, emission or absorption, is directly dependent on the background emissivity. It then describes what conditions on the background emissivity have inhibiting effects on the net chemical signal. These claims are illustrated by analyzing synthetic hyperspectral imaging data with the Adaptive Matched Filter using four chemicals and three distinct background emissivities. Two chemicals (Carbontetrachloride and Tetraflourosilane) in the analysis had a very strong relationship with the background emissivities: they exhibited absorbance over a small range of wavenumbers and the background emissivities showed a consistent ordering at these wavenumbers. Analysis of simulated hyperspectral images containing these chemicals showed complete agreement with the analysis of the physics-based model that described when the background emissivities would have inhibiting effects on gas detection. The other chemicals considered (Ammonia and Tributylphosphate) exhibited very complex absorbance structure across the longwave infrared spectrum. Analysis of images containing these chemicals revealed that the the analysis of the physics-based model did not hold completely for these complex chemicals but did suggest that gas detection was dominated by their dominant absorbance features. These results provide some explanation of the effect of the background emissivity on gas detection and a more general exploration of gas absorbance/background emissivity variability and their effects on gas detection is warranted. i

  7. A probe for in situ, remote, detection of defects in buried plastic natural gas pipelines.

    PubMed

    Mathur, M P; Spenik, J L; Condon, C M; Monazam, E R; Fincham, W L

    2007-12-01

    Several techniques are available to determine the integrity of in situ metal pipeline but very little is available in the literature to determine the integrity of plastic pipelines. Since the decade of the 1970s much of the newly installed gas distribution and transmission lines in the United States are fabricated from polyethylene or other plastic. A probe has been developed to determine the in situ integrity of plastic natural gas pipelines that can be installed on a traversing mechanism (pig) to detect abnormalities in the walls of the plastic natural gas pipeline from the interior. This probe has its own internal power source and can be deployed into existing natural gas supply lines. Utilizing the capacitance parameter, the probe inspects the pipe for flaws and records the data internally which can be retrieved later for analysis. PMID:18163747

  8. Good odorant practices ensure safer operations. [Natural gas odorant detection methods

    SciTech Connect

    Oudman, P. (Canada Western Natural Gas Co. Ltd., Calgary, Alberta (Canada))

    1993-12-01

    Regulations in Canada and the US require that combustible gas used as a fuel be odorized at such a level that a concentration in air of one-fifth the lower explosive limit the gas can be readily detected and recognized by a person with a normal sense of smell. These regulations do not specify how the odorant level should be determined. However, since the requirement is related to smell, the level should be determined by an olfactory method. There are two odorant monitoring methods commonly used by gas companies, the olfactory (odorometer) and the instrumentation (gas chromatograph) methods. The instrument method provides only quantitative results, which somehow must be related to an olfactory response. This paper discusses these methods.

  9. Detection of Clostridium difficile in faeces by direct gas liquid chromatography.

    PubMed Central

    Levett, P N

    1984-01-01

    Stool specimens examined for the presence of Clostridium difficile and its cytotoxin were screened by gas liquid chromatography for the presence of volatile fatty acids and p-cresol. Twenty seven of 110 (25%) stools yielded C difficile or cytotoxin; iso-valeric acid was detected in 63/110 (57%) and iso-caproic acid in 18/110 (16%) stools. Para-cresol was found in 24/71 (34%) stools examined. Iso-valeric acid was detected in 85% of stools positive for C difficile, whereas iso-caproic acid (41%) and p-cresol (52%) were found in much lower numbers of C difficile-positive stools. It is concluded that gas chromatographic detection of volatile fatty acids or p-cresol in faeces are not satisfactory screening tests for the presence of C difficile. PMID:6693575

  10. AIRBORNE, OPTICAL REMOTE SENSNG OF METHANE AND ETHANE FOR NATURAL GAS PIPELINE LEAK DETECTION

    SciTech Connect

    Jerry Myers

    2005-04-15

    Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. The scope of the work involved designing and developing an airborne, optical remote sensor capable of sensing methane and, if possible, ethane for the detection of natural gas pipeline leaks. Flight testing using a custom dual wavelength, high power fiber amplifier was initiated in February 2005. Ophir successfully demonstrated the airborne system, showing that it was capable of discerning small amounts of methane from a simulated pipeline leak. Leak rates as low as 150 standard cubic feet per hour (scf/h) were detected by the airborne sensor.

  11. Dispersion modeling approach for quantification of methane emission rates from natural gas fugitive leaks detected by infrared imaging technique

    Microsoft Academic Search

    Anisa Safitri; Xiaodan Gao; M. Sam Mannan

    2011-01-01

    Recently, infrared optical imaging has been applied in the oil and gas industry as a method to detect potential leaks in pipelines, components and equipment. The EPA suggested that this impending technique is considered as a smart gas LDAR (leak detection, monitoring and repair) for its rapid recognition of leaks, accuracy and robustness. In addition, compared to the conventional method

  12. Supercritical fluid extraction and clean-up of organochlorine pesticides in Chinese herbal medicine

    Microsoft Academic Search

    Y.-C Ling; H.-C Teng; C Cartwright

    1999-01-01

    A method involving the simultaneous extraction and clean-up of 13 organochlorine pesticides (OCPs) from Chinese herbal medicines (CHMs) was developed using supercritical fluid extraction (SFE) followed by gas chromatography–electron capture detection and mass spectrometric confirmation. The pesticides in the study consisted of ?-, ?-, ?-, and ?-benzene hexachloride, heptachlor, aldrin, heptachlor epoxide, endosulfan I, 4,4?-DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethene), dieldrin, endrin, 4,4?-DDD (1,1-dichloro-2,2-bis(p-chlorophenyl)ethane),

  13. Polychlorinated biphenyls (PCB) analysis report for solid sample from 219S tank 104

    SciTech Connect

    Ross, G.A.

    1998-03-27

    A sample of solids was obtained from tank 104 of 219S via a peristaltic pump equipped with a stainless steel tube and Norprenel tubing (Phthalate free). The sample obtained in a glass jar with Teflon 2 lid, was analyzed for PCBs as Aroclor mixtures. A soxhlet extraction procedure was used to extract the Aroclors from the sample. Analysis was performed using dual column confirmation gas chromatography/electron capture detection (GC/ECD). The extraction method closely follows SW-846 method 3540C and the analysis follows SW-846 method.

  14. Polychlorinated biphenyls (PCB) analysis report for solid sample from 219S tank 101

    SciTech Connect

    Diaz, L.A.

    1998-02-04

    One waste sample that was obtained with solids from tank 101 of 219S via a peristaltic pump equipped with a stainless steel tube and Norprene tubing (Phthalate free) was obtained in a glass jar with teflon lid was analyzed (with duplicate, matrix spike, and matrix spike duplicate) for PCBs as Aroclor mixtures by the Inorganic/Organic Chemistry Group. A soxhlet extraction procedure was used for extraction of the Aroclors from the sample. Analysis was performed using dual column confirmation gas chromatography/electron capture detection (GC/ECD). Results are presented.

  15. Generalized average of signals (GAS) - a new method for denoising and phase detection

    NASA Astrophysics Data System (ADS)

    Malek, J.; Kolinsky, P.; Strunc, J.; Valenta, J.

    2007-12-01

    A novel method called Generalized Average of Signals (GAS) was developed and tested during the last two years (Málek et al., in press). This method is designed for processing of seismograms from dense seismic arrays and is convenient mainly for denoising and weak phase detection. The main idea of the GAS method is based on non-linear stacking of seismograms in frequency domain, which considerably improves signal-to-noise ratio of coherent seismograms. Several synthetic tests of the GAS method are presented and the results are compared with the PWS method of Schimell and Paulssen (1997). Moreover, examples of application on real data are presented. These examples were chosen to show a broad applicability of the method in experiments of different scales. The first one shows identification of S-waves on seismograms from shallow seismic. The second one concerns identification of converted waves from local earthquakes registered at the WEBNET local network in western Bohemia. Finally, the third one depicts identification of PKIKP onsets on seismograms of teleseismic earthquakes. Schimmel, M., Paulssen H. (1997): Noise reduction and detection of weak, coherent signals through phase- weighted stacks. Geophys. J. Int. 130, 497-505. Málek J., Kolínský P., Strunc J. and Valenta J. (2007): Generalized average of signals (GAS) - a new method for detection of very weak waves in seismograms. Acta Geodyn. et Geomater., in press.

  16. An integrated GPS-FID system for airborne gas detection of pipeline right-of-ways

    SciTech Connect

    Gehue, H.L.; Sommer, P.

    1996-12-31

    Pipeline integrity, safety and environmental concerns are of prime importance in the Canadian natural gas industry. Terramatic Technology Inc. (TTI) has developed an integrated GPS/FID gas detection system known as TTI-AirTrac{trademark} for use in airborne gas detection (AGD) along pipeline right-of-ways. The Flame Ionization Detector (FID), which has traditionally been used to monitor air quality for gas plants and refineries, has been integrated with the Global Positioning System (GPS) via a 486 DX2-50 computer and specialized open architecture data acquisition software. The purpose of this technology marriage is to be able to continuously monitor air quality during airborne pipeline inspection. Event tagging from visual surveillance is used to determine an explanation of any delta line deviations (DLD). These deviations are an indication of hydrocarbon gases present in the plume that the aircraft has passed through. The role of the GPS system is to provide mapping information and coordinate data for ground inspections. The ground based inspection using a handheld multi gas detector will confirm whether or not a leak exists.

  17. Cholesteric liquid crystal-carbon nanotube hybrid architectures for gas detection

    NASA Astrophysics Data System (ADS)

    Chang, Chin-Kai; Chiu, Shih-Wen; Kuo, Hui-Lung; Tang, Kea-Tiong

    2012-01-01

    The ability of a hybrid material that is based on cholesteric liquid crystal and carbon nanotube to detect acetone vapor is investigated. We find that the phase transition in this cholesteric liquid crystal-carbon nanotube hybrid will enable carbon nanotube to form conducting networks under the higher vapor concentration. This cholesteric liquid crystal-carbon nanotube hybrid exhibits an obvious change in reflected color and electrical resistance in the early and later stages of gas diffusion, respectively. This hybrid architecture has potential application as a gas sensor with a high dynamic range.

  18. Gas detection and migration in geological media: lessons learned from the Roselend Natural Laboratory (Invited)

    NASA Astrophysics Data System (ADS)

    Pili, E.; Guillon, S.; Agrinier, P.; Sabroux, J.; Adler, P. M.

    2013-12-01

    The Roselend Natural Laboratory (French Alps) is a unique facility for studying gas transport in the subsurface and across the geosphere-atmosphere interface. At 55 m depth, a sealed cavity allows for gas release experiments across fractured porous rocks in the unsaturated zone. While many parameters controlling the state of the geological system are known, analogous gas-tracer experiments were conducted at the field-scale with SF6 and 3He. Water infiltration, permeability and the concentrations of many gases, naturally occurring or injected, are recorded via long-term and high-resolution monitoring. The fracture network is characterized thanks to extensive drilling, logging and modeling. These experiments are used to determine the physical and chemical processes that would control the noble gas source term after an underground nuclear explosion in the framework of the Comprehensive nuclear-Test-Ban Treaty (CTBT) and to develop and validate the corresponding numerical models. The Roselend Natural Laboratory also provides a test bed for sampling protocols and instrument developments. Detection of gases relevant to CTBT issues requires that their baseline concentration is understood. Experiments and subsequent modeling demonstrated that baselines are a highly dynamical process resulting from gas sources, sinks and modulation by barometric pressure and water movements. Gas migration from underground cavities occurs as early venting through fractures due to advection driven by gas overpressure. It is associated with very large dilution which requires very low detection limits. Late-time seepage occurs through fractured porous media thanks to barometric pumping, which is only efficient for a narrow window of parameter values. Full calculation for real fractured porous media is now available.

  19. Gas-liquid chromatography technique for detection of hippurate hydrolysis and conversion of fumarate to succinate by microorganisms.

    PubMed Central

    Kodaka, H; Lombard, G L; Dowell, V R

    1982-01-01

    A gas-liquid chromatography technique which allows simultaneous detection of hippuric acid (N-benzoylglycine) hydrolysis and conversion of fumaric acid to succinic acid by microorganisms uses a new medium, hippurate-formate-fumarate broth, and a gas chromatograph equipped with a thermal conductivity detector. This technique gave more reproducible results than other tests used in the study for detecting hippurate hydrolysis and also gave consistent results in detecting succinic acid produced from utilization of fumaric acid. PMID:7153346

  20. Quantification of L-tryptophan and L-kynurenine by liquid chromatography/electron capture negative ion chemical ionization mass spectrometry.

    PubMed

    Boni, R L; Simpson, J T; Naritsin, D B; Saito, K; Markey, S P

    1994-01-01

    In a number of infectious and inflammatory diseases, stimulation of the immune system can lead to increased accumulation of tryptophan metabolites via induction of kynurenine pathway enzymes in extrahepatic tissues. We developed a liquid chromatographic/mass spectrometric (LC/MS) method suitable for tracing the disposition of 13C isotopomers of L-tryptophan and L-kynurenine in various cultured cell, tissue slice, and whole animal model systems used to investigate tryptophan flux through the kynurenine pathway. The method employs extractive derivatization of the analytes and their 2H internal standards with pentafluorobenzyl bromide in order to enhance the negative ion chemical ionization (NICI) mass spectrometric response. Normal-phase liquid chromatographic separation of derivatized analytes was optimized using a silica column with organic solvents, followed by particle beam transfer and NICI-MS. Standard curves were linear over the range 1-250 ng per sample. Particle beam and mass spectrometric operating parameters were optimized with direct flow injections of 1-(methylamino) anthraquinone, which is an ideal test compound for the evaluation of LC/NICI-MS. The developed method was used to quantify the conversion of (13C6)L-tryptophan to (13C6)L-kynurenine by human monocytes (THP-1) stimulated with interferon-gamma, lung and brain tissue slices obtained from gerbils immune-stimulated with pokeweed mitogen. The effect of whole body immune stimulation on the plasma levels of endogenous L-kynurenine in mice stimulated with interferon-gamma was also quantified. PMID:8155745

  1. Wavelength modulation spectroscopy-digital detection of gas absorption harmonics based on Fourier analysis.

    PubMed

    Mei, Liang; Svanberg, Sune

    2015-03-20

    This work presents a detailed study of the theoretical aspects of the Fourier analysis method, which has been utilized for gas absorption harmonic detection in wavelength modulation spectroscopy (WMS). The lock-in detection of the harmonic signal is accomplished by studying the phase term of the inverse Fourier transform of the Fourier spectrum that corresponds to the harmonic signal. The mathematics and the corresponding simulation results are given for each procedure when applying the Fourier analysis method. The present work provides a detailed view of the WMS technique when applying the Fourier analysis method. PMID:25968506

  2. Detection and recognition threshold values of odorants used in the odorization of natural gas

    SciTech Connect

    Moschundreas, D.J.; Jones, D.; Martinus, J.

    1982-06-01

    This study was designed to determine if odorization practices provide adequate warning for detecting and reacting to gas leakage and involves direct sensory measurements under totally controlled conditions with experienced panelists, indirect measurements by randomly selected panelists exposed to varying odorant levels inside a specially built chamber, and other-directed measurements that test the of the other measurements. This paper reports the findings of the direct sensory measurements and also measurements of odor detection and recognition threshold values, dose-response curves and an assessment of the capabilities of currently used odorants to serve as warning agents.

  3. Innovative high pressure gas MEM's based neutron detector for ICF and active SNM detection.

    SciTech Connect

    Martin, Shawn Bryan; Derzon, Mark Steven; Renzi, Ronald F.; Chandler, Gordon Andrew

    2007-12-01

    An innovative helium3 high pressure gas detection system, made possible by utilizing Sandia's expertise in Micro-electrical Mechanical fluidic systems, is proposed which appears to have many beneficial performance characteristics with regards to making these neutron measurements in the high bremsstrahlung and electrical noise environments found in High Energy Density Physics experiments and especially on the very high noise environment generated on the fast pulsed power experiments performed here at Sandia. This same system may dramatically improve active WMD and contraband detection as well when employed with ultrafast (10-50 ns) pulsed neutron sources.

  4. Derivatization of pinacolyl alcohol with phenyldimethylchlorosilane for enhanced detection by gas chromatography-mass spectrometry.

    PubMed

    Albo, Rebecca L F; Valdez, Carlos A; Leif, Roald N; Mulcahy, Heather A; Koester, Carolyn

    2014-08-01

    A derivatization procedure for the qualitative gas chromatography-mass spectrometry (GC-MS) analysis of pinacolyl alcohol (PA) that employs phenyldimethylchlorosilane (PhDMClS) and the promoter N-methylimidazole is described. While PA, underivatized, can be detected using conventional gas chromatographic methods, its polarity and low boiling point make its detection in complex matrices challenging. The silylation procedure described herein generates a PA-derivative exhibiting an increased on-column retention time, thus shifting its GC-MS signal away from commonly encountered, volatile, interfering analytes. Derivatized PA could be distinguished from other PhDMClS-derivatized isomeric alcohols by its unique retention time and mass spectrum. The derivatization was demonstrated to perform well in the GC-MS analysis and identification of PA in samples from Proficiency Tests administered by the Organisation for the Prohibition of Chemical Weapons (OPCW). PMID:24481624

  5. Detection of gas leaks along pipelines by spectrally tuned infrared imaging

    NASA Astrophysics Data System (ADS)

    Gross, Werner; Hierl, Thomas; Scheuerpflug, H.; Schirl, U.; Schulz, Max J.

    1998-12-01

    We present a novel method developed for the localization of leaks along natural gas pipelines. Methane distributions in the atmosphere around the leaky pipeline are detected and visualized by spectrally tuned IR imaging. In contrast to conventional techniques which utilize laser radiation sources or scanning, we irradiate the overall region under investigation by 1 kW halogen lamps. The scene background is subtracted by a real-time computer evaluation of the image. The methane gas emitted from the leak creates a flickering cloud in the image which is easily recognized. Methane concentrations as low as 0.03 percent by volume are visible. The method was successfully tested under realistic conditions on a buried pipeline by a natural gas provider.

  6. The development of a pulsed laser imaging system for natural gas leak detection

    SciTech Connect

    Kulp, T.J.

    1995-05-01

    The detection of gas leaks represents a critical operation performed regularly by the gas industry to maintain the integrity and safety of its vast network of piping, both above and below the ground. We are developing a technology that allows the real-time imaging of gas plumes in a television format. Termed backscatter absorption gas imaging (BAGI), the technique operates by illuminating a scene with infrared laser radiation having a wavelength that is absorbed by the gas to be detected (in this case, methane). Backscattered laser radiation is used to create a video image of the scene. If a leak of the target gas is present in the field-of-view of the camera, it attenuates a portion of the backscatter and creates a dark cloud in the video picture. The specific purpose of this project is to investigate a new method of accomplishing BAGI using a pulsed laser source. The efficacy of using BAGI to detect natural gas leaks has already been demonstrated using a first-generation gas imaging technology that was developed at Lawrence Livermore National Laboratories. That technique accomplishes imaging by scanning a continuous-wave infrared laser (infrared helium-neon laser, emitting at 3.39 {mu}m) across a scene at real-time video rates as the scene is imaged by a scanned infrared camera. The primary limitation to the use of that system is the weak output energy of the helium neon laser (30 mW). The pulsed laser imager under development in this project is expected to have a range ({ge}40 m) and sensitivity (<10 ppm-m) that will surpass the respective attributes of the scanned imager. The pulsed system will operate by flooding (rather than scanning) the imaged scene with pulses of laser radiation. Imaging will be accomplished using a focal-plane array camera that operates in a snapshot format. The higher power of the pulsed laser source and the more effective collection optics of the focal-plane array-based receiver will allow the performance enhancements to be achieved.

  7. High-voltage onsite commissioning tests for gas-insulated substations using UHF partial discharge detection

    Microsoft Academic Search

    Raymond Bell; Chris Charlson; Shaun Paul Halliday; Terry Irwin; Jose Lopez-Roldan; John Nixon

    2003-01-01

    This paper describes the practical application of the ultra-high-frequency (UHF) partial discharge (PD) detection method which VA TECH Reyrolle has routinely applied to high-voltage onsite commissioning tests on gas-insulated substations (GISs) for more than 10 yr. The location of the PD sensors has a significant effect on the sensitivity of the UHF method, and research has been undertaken to quantify

  8. Widely tunable quantum cascade lasers with coupled cavities for gas detection

    Microsoft Academic Search

    Peter Fuchs; Jochen Seufert; Johannes Koeth; Julia Semmel; Sven Höfling; Lukas Worschech; Alfred Forchel

    2010-01-01

    The authors report the fabrication of widely tunable monolithic quantum cascade lasers (QCLs) with coupled Fabry-Pérot (FP) cavities on indium phosphide. Quasicontinuous tuning of the single mode emission over a total spectral range of 242 nm was realized at two regions between 8.394 and 8.785 mum. An absorption experiment with ammonia shows principle feasibility of gas detection with multisegment QCL

  9. Diamond Film Gas Sensors for Leak Detection of Semiconductor Doping Gases

    Microsoft Academic Search

    Kazushi Hayashi; Yoshihiro Yokota; Takeshi Tachibana; Koichi Miyata; Koji Kobashi; Tetsuya Fukunaga; Tadashi Takada

    2000-01-01

    Gas sensors for leak detection of toxic semiconductor doping gases such as PH3, B2H6, and AsH3 were fabricated using diamond films. The sensors have a double-layered structure composed of undoped and B-doped polycrystalline diamond layers with Pt electrodes. The relative changes in the resistance of the sensors were typically 10-20% for 0.2 ppm PH3 in air, and the highest value

  10. Room-temperature mid-infrared laser sensor for trace gas detection

    Microsoft Academic Search

    Thomas Töpfer; Konstantin P. Petrov; Yasuharu Mine; Dieter Jundt; Robert F. Curl; Frank K. Tittel

    1997-01-01

    Design and operation of a compact, portable, room-temperature mid-infrared gas sensor is reported. The sensor is based on continuous-wave difference-frequency generation (DFG) in bulk periodically poled lithium niobate at 4.6 m, pumped by a solitary GaAlAs diode laser at 865 nm and a diode-pumped monolithic ring Nd:YAG laser at 1064.5 nm. The instrument was used for detection of CO in

  11. The development of a pulsed laser imaging system for natural gas leak detection

    NASA Astrophysics Data System (ADS)

    Kulp, Thomas J.

    The detection of gas leaks represents a critical operation performed regularly by the gas industry to maintain the integrity and safety of its vast network of piping, both above and below the ground. We are developing a technology that allows the real-time imaging of gas plumes in a television format. Termed backscatter absorption gas imaging (BAGI), the technique operates by illuminating a scene with infrared laser radiation having a wavelength that is absorbed by the gas to be detected (in this case, methane). Backscattered laser radiation is used to create a video image of the scene. If a leak of the target gas is present in the field-of-view of the camera, it attenuates a portion of the backscatter and creates a dark cloud in the video picture. The specific purpose of this project is to investigate a new method of accomplishing BAGI using a pulsed laser source. The pulsed laser imager under development in this project is expected to have a range (greater than or equal to 40 m) and sensitivity (less than 10 ppm-m) that will surpass the respective attributes of a scanned continuous wave laser imager. The pulsed system will operate by flooding (rather than scanning) the imaged scene with pulses of laser radiation. Imaging will be accomplished using a focal-plane array camera that operates in a snapshot format. The higher power of the pulsed laser source and the more effective collection optics of the focal-plane array-based receiver will allow the performance enhancements to be achieved.

  12. New laser sources for photoacoustic trace gas detection with applications in biomedical science

    NASA Astrophysics Data System (ADS)

    Oomens, Jos; Bisson, Scott E.; Harting, Matthew; Kulp, Thomas J.; Harren, Frans J. M.

    2000-05-01

    Photoacoustic spectroscopy is a sensitive, on-line and non- invasive tool to monitor concentrations of trace gases in ambient air. With the appropriate high power lasers in the mid-IR wavelength region gas mixtures can be analyzed, at and below the part per billion level. Within the development of novel IR laser sources, a continuous wave optical parametric oscillator based on periodically poled lithium niobate in combination with photoacoustic detection has been applied to detect traces of several hydrocarbons in nitrogen. At an idler wavelength of around 3.3 micrometers , the cw OPO produced approximately 300 mW of single mode radiation. Preliminary results show detection limits on methane, ethane, butane and pentane of around 1 ppb. This trace gas detector will be used within medical applications. E.g., the trace gas composition of exhaled air is able to give information about a wide variety of processes in human body. In addition, such analysis has the potential to monitor processes non-invasive, on-line and fast for diagnostic purposes related to acute or chronic diseases.

  13. Development of a van-portable remote-sensing laser system for selective detection of natural gas leaks

    NASA Astrophysics Data System (ADS)

    Rosengreen, A.; Vanderlaan, J.

    1984-04-01

    A mobile leak-survey system was developed for gas mains buried in the street that is faster and more efficient than existing systems. The feasibility of the laser remote-sensing technique for selective detection of leaking natural gas was demonstrated. A laser breadboard system was developed using a spectral differential absorption technique for detection of ethane from natural gas leaks. The system was then successfully demonstrated using an outdoor simulated gas leak. To estimate system performance, a preliminary system analysis was performed.

  14. Determination of acoustic speed for improving leak detection and location in gas pipelines.

    PubMed

    Li, Shuaiyong; Wen, Yumei; Li, Ping; Yang, Jin; Yang, Lili

    2014-02-01

    The commonly used cross-correlation technique for leak location requires that the acoustic speed is known and invariable. In practice, the gas leakage-induced acoustic waves propagate along multiple paths including in-pipe gas and pipe wall, and the acoustic waves in different transmission paths exhibit different acoustic speeds and different dispersive behaviors, which bring a great challenge for leak detection and location in the gas pipelines. In this study, based on the vibration theory of cylindrical elastic thin shell, the wavenumber formulae in different transmission paths are derived to predict the acoustic speeds and the acoustical coupling between the in-pipe gas and the pipe wall is analyzed to determine the dominant transmission path. In addition, the velocity dispersions in the dominant transmission path are suppressed by selection of a characteristic frequency band of the gas leakage-induced acoustic waves. The theoretical predictions are verified in the experiment and the results show that the theoretical acoustic speed is slightly larger than the measured acoustic speed. Thus, the theoretical acoustic speed formula is modified considering the effect of the structural loss factor and consequently the location error using the modified acoustic speed is reduced by two times compared to that using the theoretical acoustic speed. PMID:24593385

  15. An overview of micromachined platforms for thermal sensing and gas detection

    SciTech Connect

    Manginell, R.P.; Smith, J.H.; Ricco, A.J.

    1997-03-01

    Micromachined hotplates, membranes, filaments, and cantilevers have all been used as platforms for thermal sensing and gas detection. Compared with conventional devices, micromachined sensors are characterized by low power consumption, high sensitivity, and fast response time. Much of these gains can be attributed to the size reductions achieved by micromachining. In addition, micromachining permits easy, yet precise tailoring of the heat transfer characteristics of these devices. By simple alterations in device geometry and materials used, the relative magnitudes of radiation, convection and conduction losses and Joule heat gains can be adjusted, and in this way device response can be optimized for specific applications. The free-standing design of micromachined platforms, for example, reduces heat conduction losses to the substrate, thereby making them attractive as low power, fast-response heaters suitable for a number of applications. However, while micromachining solves some of the heat transfer problems typical of conventionally produced devices, it introduces some of its own. These trade-offs will be discussed in the context of several micromachined thermal and gas sensors present in the literature. These include micromachined flow sensors, gas thermal conductivity sensors, pressure sensors, uncooled IR sensors, metal-oxide and catalytic/calorimetric gas sensors. Recent results obtained for a microbridge-based catalytic/calorimetric gas sensor will also be presented as a means of further illustrating the concepts of thermal design in micromachined sensors.

  16. DETECTION OF HIGHLY IONIZED C IV GAS WITHIN THE LOCAL CAVITY

    SciTech Connect

    Welsh, Barry Y.; Wheatley, Jonathan; Siegmund, Oswald H. W. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720 (United States); Lallement, Rosine [IPSL/LATMOS, Versailles (France)

    2010-04-01

    We present high resolution (R = 114,000) ultraviolet measurements of the interstellar absorption line profiles of the C IV (1550 A) high ionization doublet recorded toward the nearby B2Ve star HD 158427 (d {approx} 74 pc). These data, which were recorded with the recently re-furbished Space Telescope Imaging Spectrograph instrument on the Hubble Space Telescope, represent the most convincing detection yet of highly ionized C IV absorption that can be associated with interstellar gas located within the boundary of the Local Cavity (LC). Two highly ionized gas clouds at V {sub 1} = -24.3 km s{sup -1} and V {sub 2} = -41.3 km s{sup -1} are revealed in both C IV absorption lines, with the V {sub 1} component almost certainly being due to absorption by the Local Interstellar Cloud (d < 5 pc). Although the observed column densities for both cloud components can be explained by the predictions of current theoretical models of the local interstellar medium, the narrow Doppler width of the V {sub 2} line profile (b = 6.8 km s{sup -1}) indicates an unusually low gas temperature of {<=}34,000 K for this highly ionized component. It is conjectured that the V {sub 2} cloud may be due to an outflow of highly ionized and hot gas from the nearby Loop I superbubble. These new data also indicate that absorption due to highly ionized gas in the LC can be best described as being 'patchy' in nature.

  17. Detecting benzodiazepines: immunoassays compared with negative chemical ionization gas chromatography/mass spectrometry.

    PubMed

    Fitzgerald, R L; Rexin, D A; Herold, D A

    1994-03-01

    We tested 231 urine samples by six immunoassay methods--EMIT d.a.u., EMIT II, Roche Abuscreen Online, Abbott TDx, Diagnostic Products Corp. (DPC) double-antibody radioimmunoassay (RIA), and Biosite Triage--and by negative chemical ionization gas chromatography/mass spectrometry to determine how the immunoassays performed on samples selected for suspected benzodiazepine use (n = 100) and in random urine drug screening (n = 131). In general, all of the assays were successful in detecting oxazepam and related metabolites, even at concentrations below the stated cutoffs. However, the negative predictive value of benzodiazepine immunoassays for samples selected for suspected benzodiazepine use ranged from 86% to 96%. A primary difference between the test kits was the ability of DPC RIA and Triage to detect lorazepam when other assays did not. Contrary to previous reports, pretreatment of specimens with glucuronidase was not necessary to detect oxazepam-related metabolites with these immunoassays. PMID:8131270

  18. Tunable photonic cavities for in-situ spectroscopic trace gas detection

    DOEpatents

    Bond, Tiziana; Cole, Garrett; Goddard, Lynford

    2012-11-13

    Compact tunable optical cavities are provided for in-situ NIR spectroscopy. MEMS-tunable VCSEL platforms represents a solid foundation for a new class of compact, sensitive and fiber compatible sensors for fieldable, real-time, multiplexed gas detection systems. Detection limits for gases with NIR cross-sections such as O.sub.2, CH.sub.4, CO.sub.x and NO.sub.x have been predicted to approximately span from 10.sup.ths to 10s of parts per million. Exemplary oxygen detection design and a process for 760 nm continuously tunable VCSELS is provided. This technology enables in-situ self-calibrating platforms with adaptive monitoring by exploiting Photonic FPGAs.

  19. Multiresidue analysis of pesticides in soil by gas chromatography with nitrogen-phosphorus detection and gas chromatography mass spectrometry.

    PubMed

    Fenoll, José; Hellín, Pilar; Marín, Cristóbal; Martínez, Carmen M; Flores, Pilar

    2005-10-01

    A rapid multiresidue method for the simultaneous determination of 25 fungicides and insecticides in soil was developed. Soil samples are extracted by sonication with a water-acetonitrile mixture, and the pesticides are partitioned into dichloromethane. Final determination was made by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). Confirmation analysis of pesticides was carried out by GC-MS in the selected ion monitoring (SIM) mode. The identification of compounds was based on retention time and on comparison of the primary and secondary ions. The average recovery by the GC-NPD method obtained for these compounds varied from 68.5% to 112.1% with a relative standard deviation between 1.8% and 6.2%. The GC-NPD method presents good linearity over the range assayed 50-2000 microg/L, and the detection limit for the pesticides studied varied from 0.1 to 10.4 microg/kg. The proposed method was used to determine pesticide levels in soil samples from experimental greenhouse pepper cultivation. PMID:16190613

  20. Issues Involving The OSI Concept of Operation For Noble Gas Radionuclide Detection

    SciTech Connect

    Carrigan, C R; Sun, Y

    2011-01-21

    The development of a technically sound protocol for detecting the subsurface release of noble gas radionuclides is critical to the successful operation of an on site inspection (OSI) under the CTBT and has broad ramifications for all aspects of the OSI regime including the setting of specifications for both sampling and analysis equipment used during an OSI. With NA-24 support, we are investigating a variety of issues and concerns that have significant bearing on policy development and technical guidance regarding the detection of noble gases and the creation of a technically justifiable OSI concept of operation. The work at LLNL focuses on optimizing the ability to capture radioactive noble gases subject to the constraints of possible OSI scenarios. This focus results from recognizing the difficulty of detecting gas releases in geologic environments - a lesson we learned previously from the LLNL Non-Proliferation Experiment (NPE). Evaluation of a number of important noble gas detection issues, potentially affecting OSI policy, has awaited the US re-engagement with the OSI technical community. Thus, there have been numerous issues to address during the past 18 months. Most of our evaluations of a sampling or transport issue necessarily involve computer simulations. This is partly due to the lack of OSI-relevant field data, such as that provided by the NPE, and partly a result of the ability of LLNL computer-based models to test a range of geologic and atmospheric scenarios far beyond what could ever be studied in the field making this approach very highly cost effective. We review some highlights of the transport and sampling issues we have investigated during the past year. We complete the discussion of these issues with a description of a preliminary design for subsurface sampling that is intended to be a practical solution to most if not all the challenges addressed here.

  1. Detection of disturbances in pulmonary gas exchanges during exercise from arterialized earlobe PO2.

    PubMed

    Aguilaniu, Bernard; Maitre, Jocelyne; Diab, Samia; Perrault, Hélène; Péronnet, François

    2011-06-30

    Blood sampling from the arterialized earlobe is widely used in clinical exercise testing but Fajac et al. (1998) (Eur. Respir. J. 11, 712-715) have shown that arterialized P(O2) Pc(CO2) is not a valid surrogate for Pa(O2). In the present study, in order to detect disturbances in pulmonary gas exchanges during clinical exercise testing from the alveolar-arterial gradient of P(O2) (P[Ai-a](O2)), a correction factor for Pc(O2) was validated from data on a large cohort (107 patients at one or two levels of exercise: 172 pairs of samples). Pulmonary gas exchanges and pH, P(O2), P(CO2), PA(iO2) and P(Ai-a)(O2) from arterial and arterialized blood were measured or computed. Arterial and arterialized pH and P(CO2) (and thus PA(iO2)) were similar but P(CO2) was lower than arterial P(O2) (Pa(O2)). However, when corrected for the systematic bias between Pa(O2) and Pc(O2), which increased with Pc(O2), Pc(O2) adequately detected disturbances in pulmonary gas exchanges with a very high sensibility and specificity (predictive values of a negative or positive test ?95%). PMID:21397053

  2. On autonomous detection of pressured air and gas leaks using passive IR-thermography for mobile robot application

    Microsoft Academic Search

    Andreas Kroll; Werner Baetz; Daniel Peretzki

    2009-01-01

    Today, pressured air and gas leaks are typically detected using in-situ sensor technology. In this contribution the application of passive IR-thermography is proposed to permit remote leak detection by assessing the resulting temperature profile disturbance due to expansion of pressured gas. Remote measurements are advantageous as they are easier and safer to conduct. Scanning high-rise objects can be achieved using

  3. Development of a High-Resolution Human-Specific Breath Gas Sensor for Survivor Detection in Disaster Zones

    Microsoft Academic Search

    Hideki Toda; Genci Capi

    2012-01-01

    This paper presents a new type of ultrasonic gas molecule concentration sensor for rescue robotics. This device can measure the change of gas concentration with a sampling rate of over 400 kHz. The performance is evaluated by measuring the CO2 concentration in human respiration gas. The experiments show that the proposed sensor could detect a difference between 5% CO2-containing air,

  4. Characterization of the gas sensors based on polymer-coated resonant microcantilevers for the detection of volatile organic compounds

    Microsoft Academic Search

    Ying Dong; Wei Gao; Qin Zhou; Yi Zheng; Zheng You

    2010-01-01

    The gas sensors based on polymer-coated resonant microcantilevers for volatile organic compounds (VOCs) detection are investigated. A method to characterize the gas sensors through sensor calibration is proposed. The expressions for the estimation of the characteristic parameters are derived. The effect of the polymer coating location on the sensor's sensitivity is investigated and the formula to calculate the polymer–analyte partition

  5. Development of gprs-based leak detection system for pipe pushing crossing part of nature gas pipeline

    Microsoft Academic Search

    Fujun Liu; Shuai Kong; Zhangwei Ling; Mulin Zheng; Yueqiang Qian

    2011-01-01

    There would be a sealed space, called culvert box, between the nature gas pipeline and the concrete pipe when the nature gas pipeline crossing highways, railways and rivers using the trenchless pipe pushing technology. To deal with the problem of leak detection and monitoring for these culvert boxes, which were located in the field and scattered, a GPRS-based (GPRS: general

  6. The Beta Pictoris Phenomenon in A-Shell Stars: Detection of Accreting Gas

    NASA Technical Reports Server (NTRS)

    Grady, C. A.; Perez, Mario R.; Talavera, A.; McCollum, B.; Rawley, L. A.; England, M. N.; Schlegel, M.

    1996-01-01

    We present the results of an expanded survey of A-shell stars using IUE high-dispersion spectra and find accreting, circumstellar gas in the line of sight to nine stars, in addition to the previously identified beta Pic, HR 10, and 131 Tau, which can be followed to between +70 and 100 km/s relative to the star. Two of the program stars, HD 88195 and HD 148283, show variable high-velocity gas. Given the small number of IUE spectra for our program stars, detection of high-velocity, accreting gas in 2/3 of the A-shell stars sampled indicates that accretion is an intrinsic part of the A-shell phenomenon and that beta Pic is not unique among main-sequence A stars in exhibiting such activity. Our program stars, as a group, have smaller column densities of high-velocity gas and smaller near-IR excesses compared with beta Pic. These features are consistent with greater central clearing of a remnant debris disk, compared with beta Pic, and suggest that the majority of field A-shell stars are older than beta Pic.

  7. The Detection Rate of Molecular Gas in Elliptical Galaxies Constraints on Galaxy Formation Theories

    E-print Network

    Fujita, Y; Gouda, N; Fujita, Yutaka; Nagashima, Masahiro; Gouda, Naoteru

    2000-01-01

    In order to constrain parameters in galaxy formation theories, especially those for a star formation process, we investigate cold gas in elliptical galaxies. We calculate the detection rate of cold gas in them using a semi-analytic model of galaxy formation and compare it with observations. We show that the model with a long star formation time-scale (~20 Gyr) is inconsistent with observations. Thus, some mechanisms of reducing the mass of interstellar medium, such as the consumption of molecular gas by star formation and/or reheating from supernovae, are certainly effective in galaxies. Our model predicts that star formation induced when galaxies in a halo collide each other reduces the cold gas left until the present. However, we find that the reduction through random collisions of satellite (non-central) galaxies in mean free time-scale in a halo is not required to explain the observations. This may imply that the collisions and mergers between satellite galaxies do not occur so often in clusters or that t...

  8. Nanofiber-net-binary structured membranes for highly sensitive detection of trace HCl gas

    NASA Astrophysics Data System (ADS)

    Wang, Xianfeng; Wang, Jialin; Si, Yang; Ding, Bin; Yu, Jianyong; Sun, Gang; Luo, Wenjing; Zheng, Gang

    2012-11-01

    This work describes the detection of trace hydrogen chloride (HCl) gas through analyses of the resonance frequency signal from quartz crystal microbalance (QCM) sensors coated with polyaniline (PANI) functionalized polyamide 6 (PA 6) (PANI-PA 6) nanofiber-net-binary (NNB) structured membranes. The PA 6 NNB substrate comprising nanofibers and spider-web-like nano-nets fabricated by a versatile electro-spinning/netting (ESN) process offered an ideal interface for the uniform PANI functionalization and enhanced sensing performance. Benefiting from the large specific surface area, high porosity, and strong adhesive force to the QCM electrode of the PANI-PA 6 NNB membranes, the developed HCl-selective sensors exhibited a rapid response, good reproducibility and stability, and low detection limit (7 ppb) at room temperature. Additionally, the PANI-PA 6 NNB sensing membranes presented visible color changes upon cycled exposure to HCl and ammonia, suggesting their potential application in the development of colorimetric sensors. The PANI-PA 6 NNB coated QCM sensors are considered to be a promising candidate for trace HCl gas detection in practical applications.

  9. Fast gas chromotography with luminol detection for measurement of nitrogen dioxide and PANs.

    SciTech Connect

    Gaffney, J. S.; Marley, N. A.; Drayton, P. J.

    1999-09-30

    Fast capillary gas chromatography has been coupled to a luminol-based chemiluminescence detection system for the rapid monitoring of nitrogen dioxide and peroxyacyl nitrates. A first-generation instrument was described recently (Gaffney et al., 1998). This system is capable of monitoring nitrogen dioxide and peroxyacyl nitrates (PANs; to and including the C4 species) with 1-min time resolution. This is an improvement by a factor of five over gas chromatography methods with electron capture detection. In addition, the luminol method is substantially less expensive than laser fluorescent detection or mass spectroscopic methods. Applications in aircraft-based research have been published electronically and will appear shortly in Environmental Science and Technology (Gaffney et al., 1999a). An improved version of the instrument that has been designed and built makes use of a Hammamatsu photon-counting system. Detection limits of this instrumentation are at the low tens of ppt. The range of the instrument can be adjusted by modifying sampling volumes and detection counting times. A review of past work and of recent application of the instrumentation to field measurements of nitrogen dioxide and PANs is presented. The data clearly indicate that the luminol approach can determine the target species with time resolution of less than 1 min. Examples of applications for estimation of peroxyacetyl radical concentrations and nitrate radical formation rates are also presented. This instrumentation can further be used for evaluation of surfaces for loss of nitrogen dioxide and PANs, phenomena of possible importance for sampling interfaces and chamber wall design. Our high-frequency field data clearly indicate that the ''real world'' is not well mixed and that turbulent mixing and plume-edge chemistries might play an important role in urban- and regional-scale interactions. Dynamic flow systems might be required to evaluate such effects in new-generation chamber studies.

  10. Detection of deuterium and hydrogen using laser-induced helium gas plasma at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Kurniawan, Koo Hendrik; Lie, Tjung Jie; Suliyanti, Maria Margaretha; Hedwig, Rinda; Abdulmadjid, Syahrun Nur; Pardede, Marincan; Idris, Nasrullah; Kobayashi, Takao; Kusumoto, Yoshihumi; Kagawa, Kiichiro; Tjia, May On

    2005-11-01

    An experimental study on gas analysis by means of laser-induced breakdown spectroscopy was conducted using a Nd-yttrium aluminum garnet laser (1,064 nm, 120 mJ, 8 ns) and helium host gas at atmospheric pressure on a sample of mixed water (H2O) and heavy water (D2O) in vapor form. It was shown that completely resolved hydrogen (H?) and deuterium (D?) emission lines that are separated by only 0.179 nm could be obtained at a properly delayed detection time when the charged particles responsible for the strong Stark broadening effect in the plasma have mostly disappeared. It is argued that the helium metastable excited state plays an important role in the hydrogen excitation process.

  11. Detection of accreting gas toward HD 45677: A newly recognized, Herbig Be proto-planetary system

    NASA Technical Reports Server (NTRS)

    Grady, C. A.; Bjorkman, K. S.; Shepherd, D.; Schulte-Ladbeck, R. E.; Perez, M. R.; Dewinter, D.; The, P. S.

    1993-01-01

    We report detection of high velocity, accreting gas toward the Be star with IR excess and bipolar nebula, HD 45677. High velocity (+200 to +400 km/s), variable column density gas is visible in all IUE spectra from 1979-1992 in transitions of Si II, C II, Al III, Fe III, Si IV, and C IV. Low-velocity absorption profiles from low oscillator-strength transitions of Si II, Fe II, and Zn II exhibit double-peaked absorption profiles similar to those previously reported in optical spectra of FU Orionis objects. The UV absorption data, together with previously reported analyses of the IR excess and polarization of this object, suggest that HD 45677 is a massive, Herbig Be star with an actively accreting circumstellar, proto-planetary disk.

  12. Detection of accreting gas toward HD 45677 - A newly recognized, Herbig Be proto-planetary system

    NASA Technical Reports Server (NTRS)

    Grady, C. A.; Bjorkman, K. S.; Shepherd, D.; Schulte-Ladbeck, R. E.; Perez, M. R.; De Winter, D.; The, P. S.

    1993-01-01

    We report the detection of high-velocity, accreting gas toward the BE(e) star with IR excess and bipolar nebula, HD 45677. High-velocity (+200 to +400 km/s), variable column density gas is visible in all IUE spectra from 1979 to 1992 in transitions of Si II, C II, Al III, Fe III, Si IV, and C IV. Low-velocity absorption profiles from low oscillator strength transitions of Si II, Fe II, and Zn II exhibit double-peaked absorption profiles similar to those previously reported in optical spectra of FU Orionis objects. The UV absorption data, together with previously reported analyses of the IR excess and polarization of this object, suggest that HD 45677 is a massive, Herbig Be star with an actively accreting circumstellar, protoplanetary disk.

  13. Fire Detection Using tin Oxide Gas Sensors Installed in an Indoor Space

    NASA Astrophysics Data System (ADS)

    Shibata, Shin-Ichi; Higashino, Tsubasa; Sawada, Ayako; Oyabu, Takashi; Takei, Yoshinori; Nanto, Hidehito; Toko, Kiyoshi

    Many lives and facilities were lost by fire. Especially, there are many damages to elderly, toddlers and babies. In Japan, number of deaths over 65 years old reached to 53% in 2004. Number of over 81 years olds went to 20%. It takes for the elderly person more time to sense fire and also to evacuate to safe places. Although it is important to prevent the fire, it also needs to inform the fire breaking as early as possible. Human sense decreases with age and it is difficult to perceive the fire at an early stage. It is desired to develop a higher sensitive element for fire and its system which can detect fire at an early stage. In this experiment, tin oxide gas sensors were adopted to detect a smoldering fire at the early stage. Most common case of fire is the smoldering fire. The reliability of the sensor is higher and it is adopted in a gas alarm detector. The sensor can also detect slight amount of odor molecule. In our previous experiment, it became obvious that it was better to install the sensor to the ceiling to detect odor components generating from smoldering fire. Therefore, five sensors were installed in the ceiling away from each other and the method to detect the fire was examined. As a result, a characteristic was newly derived by adding the sensor outputs for one minute. The sensor output was input every 0.1s. The characteristic is called as the integrated characteristic. After that, the differential characteristic was derived using the integrated characteristic. The fire was determined using the differential characteristics. The materials causing a smoldering fire were woodchip, wallpaper and carpet as subjects. The system could detect the fire in several minutes for whole materials. The sensor is effective to detect the smoldering fire at an early stage. It is necessary to detect a cigarette smoke to distinguish as non fire. In this study, the discrimination was also examined using a quadratic function (ax2+b). The coefficients a and b were effective to identify smoldering fire and cigarette smoke. Principal component analysis for the arrival speed S which meant a kind of odor-speed was also useful to distinguish fire from non fire.

  14. Simultaneous determination of lincomycin and spectinomycin residues in animal tissues by gas chromatography-nitrogen phosphorus detection and gas chromatography-mass spectrometry with accelerated solvent extraction

    Microsoft Academic Search

    Y. Tao; D. Chen; G. Yu; H. Yu; Y. Pan; Y. Wang; L. Huang; Z. Yuan

    2011-01-01

    A new multi-dimensional analytical method using gas chromatography-nitrogen phosphorus detection (GC-NPD) and gas chromatography-mass spectrometry (GC-MS) was developed for qualitative and quantitative measurement of lincomycin and spectinomycin residues in food animal tissues. This method is based on a new extraction procedure using accelerated solvent extraction (ASE). The analytes were extracted by phosphate buffer with trichloroacetic acid de-proteinisation and clean-up by

  15. ROSAT detection of diffuse hot gas in the edge-on galaxy NGC 4631

    NASA Technical Reports Server (NTRS)

    Wang, Q. David; Walterbos, Rene A. M.; Steakley, Michael F.; Norman, Colin A.; Braun, Robert

    1994-01-01

    ROSAT observation is presented of the edge-on spiral galaxy NGC 4631, a nearby Sc/SBd galaxy best known for its extended radio halo. Because of the low foreground Galactic X-ray-absorbing gas column density, N(sub H) approximately 1.4 x 10(exp 20)cm(exp -2), this observation is sensitive to gas of temperature greater than or equal to a few times 10(exp 5) K. A soft (approximately 0.25 keV) X-ray radiation out to more than 8 kpc above the midplane of the galaxy was detected. The strongest X-ray emission in the halo is above the central disk, a region of about 3 kpc radius which shows high star formation activity. The X-ray emission in the halo is bordered by two extended filaments of radio continuum emission. Diffuse X-ray emission from hot gas in the galaxy's disk was found. The spectrum of the radiation can be characterized by a thermal plasma with a temperature of 3 x 10(exp 6) K and a radiative cooling rate of approximately 8 x 10(exp 39) ergs s(exp -1). This rate is only a few percent of the estimated supernova energy release in the interstellar medium of the galaxy. Analysis of the X-ray spectrum shows evidence for the presence of a cooler (several times 10(exp 5) K) halo gas component that could consume a much larger fraction of the supernova energy. Strong evidence was found for disk/halo interaction. Hot gas apparently blows out from supershells in the galaxy's disk at a rate of approximately 1 solar mass yr(exp -1). This outflow of hot gas drags magnetic field lines up in the halo and forms a magnetized gaseous halo. If the magnetic field lines are still anchored to the disk gas at large disk radii, the outflowing gas may be confined high above the disk by magnetic pressure. A strong X-ray source which coincides spatially with an H I supershell has been identified. However, the source is likely an extremely luminous X-ray binary with L(sub chi)(0.1 - 2 keV) approximately 5 x 10(exp 39) ergs s(exp -1), which makes it a stellar mass black hole candidate.

  16. Tentative detection of warm intervening gas towards PKS 0548-322 with XMM-Newton

    SciTech Connect

    Barcons, X.

    2005-03-17

    We present the results of a long ({approx} 93 ksec) XMM-Newton observation of the bright BL-Lac object PKS 0548-322 (z = 0.069). Our Reflection Grating Spectrometer (RGS) spectrum shows a single absorption feature at an observed wavelength {lambda} = 23.33 {+-} 0.01 {angstrom} which we interpret as OVI K{alpha} absorption at z = 0.058, i.e., {approx} 3000 km s{sup -1} from the background object. The observed equivalent width of the absorption line {approx} 30m {angstrom}, coupled with the lack of the corresponding absorption edge in the EPIC pn data, implies a column density N{sub OVI} {approx} 2 x 10{sup 16} cm{sup -2} and turbulence with a Doppler velocity parameter b > 100 km s{sup -1}. Within the limitations of our RGS spectrum, no OVII or OV K{alpha} absorption are detected. Under the assumption of ionization equilibrium by both collisions and the extragalactic background, this is only marginally consistent if the gas temperature is {approx} 2.5 x 10{sup 5} K, with significantly lower or higher values being excluded by our limits on OV or OVII. If confirmed, this would be the first X-ray detection of a large amount of intervening warm absorbing gas through OVI absorption. The existence of such a high column density absorber, much stronger than any previously detected one in OVI, would place stringent constraints on the large-scale distribution of baryonic gas in the Universe.

  17. Sensitivity of detection of fugitive methane emissions from coal seam gas fields

    NASA Astrophysics Data System (ADS)

    Feitz, A. J.; Berko, H.; Wilson, P.; Jenkins, C.; Loh, Z. M.; Etheridge, D.

    2013-12-01

    There is increasing recognition that minimising methane emissions from the oil and gas sector is a key step in reducing global greenhouse gas emissions in the near term. Atmospheric monitoring techniques are likely to play an important future role in measuring the extent of existing emissions and verifying emission reductions. They can be very suitable for monitoring gas fields as they are continuous and integrate emissions from a number of potential point and diffuse sources that may vary in time. Geoscience Australia and CSIRO Marine & Atmospheric Research have collected three years of continuous methane and carbon dioxide measurements at their atmospheric composition monitoring station ('Arcturus') in the Bowen Basin, Australia. Methane signals in the Bowen Basin are likely to be influenced by cattle production, landfill, coal production, and conventional and coal seam gas (CSG) production. Australian CSG is typically 'dry' and is characterised by a mixed thermogenic-biogenic methane source with an absence of C3-C6+ alkanes. The range of ?13C isotopic signatures of the CSG is similar to methane from landfill gas and cattle emissions. The absence of standard in-situ tracers for CSG fugitive emissions suggests that having a comprehensive baseline will be critical for successful measurement of fugitive emissions using atmospheric techniques. In this paper we report on the sensitivity of atmospheric techniques for the detection of fugitive emissions from a simulated new CSG field against a three year baseline signal. Simulation of emissions was performed for a 1-year period using the coupled prognostic meteorological and air pollution model TAPM at different fugitive emission rates (i.e. estimates of <1% to up to 10% of production lost) and distances (i.e. 10 - 50 km) from the station. Emissions from the simulated CSG field are based on well density, production volumes, and field size typical of CSG fields in Australia. The distributions of the perturbed and baseline signals were evaluated and statistically compared to test for the presence of fugitive methane emissions. In addition, a time series model of the methane baseline was developed in order to generate alternative realizations of the baseline signal. These were used to provide measures of both the likelihood of detecting fugitive emissions at various emission levels and of the false alarm rate. Results of the statistical analysis and an indicative minimum fugitive methane emission rate that can be detected using a single monitoring station are presented.

  18. Miniaturized Gas Correlation Radiometer for the Detection of Trace Gases in the Martian Atmosphere

    NASA Astrophysics Data System (ADS)

    Melroy, H.; Wilson, E. L.; Georgieva, E.

    2012-12-01

    We present a miniaturized and simplified version of a gas correlation radiometer (GCR) capable of simultaneously mapping multiple trace gases and identifying active regions on the Mars surface. Gas correlation radiometry (GCR) has been shown to be a sensitive and versatile method for detecting trace gases in Earth's atmosphere. Reduction of the size and mass of the GCR was achieved by implementing compact, light-weight 1 mm inner diameter hollow-core optical fibers (hollow waveguides) as the gas correlation cells. In a comparison with an Earth orbiting CO2 GCR instrument, exchanging the 10 m multipass cells with hollow waveguide gas correlation cells of equivalent pathlength reduces the mass from ~150 kg to ~0.5 kg, and reduces the volume from 1.9 m x 1.3 m x 0.86 m to a small bundle of fiber coils approximately 1 meter in diameter by 0.05 m in height (mass and volume reductions of >99%). A unique feature of this instrument is its stackable module design, with a single module for each trace gas. Each of the modules is self-contained, and fundamentally identical; differing by the bandpass filter wavelength range and gas mixtures inside the hollow-waveguide absorption cells. The current configuration contains four stacked modules for simultaneous measurements of methane (CH4), formaldehyde (H2CO), water vapor (H2O), and deuterated water vapor (HDO) but could easily be expanded to include measurements of additional species of interest including nitrous oxide (N2O), hydrogen sulfide (H2S), methanol (CH3OH), and sulfur dioxide (SO2), as well as carbon dioxide (CO2) for a simultaneous measure of mass balance. Preliminary results indicate that a 1 ppb detection limit is possible for both formaldehyde and methane with one second of averaging. Using non-optimized components, we have demonstrated an instrument sensitivity equivalent to ~30 ppb for formaldehyde, and ~500 ppb for methane. We expect custom bandpass filters and 6 m long waveguides to significantly improve these promising results. Ongoing testing is being conducted on water vapor and deuterated water vapor.

  19. Miniaturized Gas Correlation Radiometer for the Detection of Trace Gases in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Melroy, Hilary R.; Wilson, Emily L.; Georgieva, Elena

    2012-01-01

    We present a miniaturized and simplified version of a gas correlation radiometer (GCR) capable of simultaneously mapping multiple trace gases and identifying active regions on the Mars surface. Gas correlation radiometry (GCR) has been shown to be a sensitive and versatile method for detecting trace gases in Earth's atmosphere. Reduction of the size and mass of the GCR was achieved by implementing compact, light-weight 1 mm inner diameter hollow-core optical fibers (hollow waveguides) as the gas correlation cells. In a comparison with an Earth orbiting CO2 GCR instrument, exchanging the 10 m multipass cells with hollow waveguide gas correlation cells of equivalent path length reduces the mass from approximately 150 kg to approximately 0.5 kg, and reduces the volume from 1.9 m x 1.3 m x 0.86 m to a small bundle of fiber coils approximately 1 meter in diameter by 0.05 m in height (mass and volume reductions of greater than 99%). A unique feature of this instrument is its stackable module design, with a single module for each trace gas. Each of the modules is self-contained, and fundamentally identical; differing by the bandpass filter wavelength range and gas mixtures inside the hollow-waveguide absorption cells. The current configuration contains four stacked modules for simultaneous measurements of methane (CH4), formaldehyde (H2CO), water vapor (H2O), and deuterated water vapor (HDO) but could easily be expanded to include measurements of additional species of interest including nitrous oxide (N2O), hydrogen sulfide (H2S), methanol (CH3OH), and sulfur dioxide (SO2), as well as carbon dioxide (CO2) for a simultaneous measure of mass balance. Preliminary results indicate that a 1 ppb detection limit is possible for both formaldehyde and methane with one second of averaging. Using non-optimized components, we have demonstrated an instrument sensitivity equivalent to approximately 30 ppb for formaldehyde, and approximately 500 ppb for methane. We expect custom bandpass filters and 6 m long waveguides to significantly improve these promising results. Ongoing testing is being conducted on water vapor and deuterated water vapor.

  20. Detection of pristine gas two billion years after the Big Bang.

    PubMed

    Fumagalli, Michele; O'Meara, John M; Prochaska, J Xavier

    2011-12-01

    In the current cosmological model, only the three lightest elements were created in the first few minutes after the Big Bang; all other elements were produced later in stars. To date, however, heavy elements have been observed in all astrophysical environments. We report the detection of two gas clouds with no discernible elements heavier than hydrogen. These systems exhibit the lowest heavy-element abundance in the early universe, and thus are potential fuel for the most metal-poor halo stars. The detection of deuterium in one system at the level predicted by primordial nucleosynthesis provides a direct confirmation of the standard cosmological model. The composition of these clouds further implies that the transport of heavy elements from galaxies to their surroundings is highly inhomogeneous. PMID:22075722

  1. Analyzing the emission self-organized structure in gas discharge by photoelectric detect method

    NASA Astrophysics Data System (ADS)

    Liu, Shuhua; Yang, Fan; Song, Jianmin; Gu, Yanxia; Zhu, Lingxin; Ma, Hengxin

    2010-10-01

    In gas discharge, various self-organized structures are formed as the applied voltage is increased. A noticeable phenomenon is that the system undergoes twice hexagon structure. One is observed in the lower voltage range and the other is in the higher voltage range. To study the intrinsic mechanism, the light signal, electric signal, and the emission spectrum of the two hexagons is measured by photoelectric detect method. The electric signal is detected by high-voltage probe. The light signal is measured distinguished in time and space by using diaphragm. The electron excitation temperature is measured using spectrum method. It is conclude that the forming mechanism of the two kinds of hexagon is different. The lower-voltage hexagon is a dynamic multiplex structure, while the higher-voltage hexagon is a single static structure. The excitation temperature of higher-voltage hexagon is higher than that of lower-voltage hexagon.

  2. Gas temperature measurements using the dual-line detection Rayleigh scattering technique

    NASA Technical Reports Server (NTRS)

    Otugen, M. Volkan; Seasholtz, Richard G.; Annen, Kurt D.

    1992-01-01

    A new laser-induced Rayleigh scattering method is presented for the improved temperature diagnostics of gas flows. In the present technique, the two lines of a copper vapor laser are used to obtain the time and space resolved temperature. A single set of optics is used to form the optical probe and to collect the signal simultaneously from both the 510 nm and the 578 nm lines. The dual-line detection allows for the determination and removal of surface-scattered laser light from a Rayleigh signal thereby improving the applicability of Rayleigh scattering to near wall flows with a high degree of glare. An optical system using the dual-line detection technique is built, calibrated and tested in a hot air jet under various levels of background contamination. The results indicate that highly accurate temperature measurements are possible even when the laser-line background intensity, captured by the collecting optics, is five times that of the Rayleigh signal.

  3. A COST EFFECTIVE MULTI-SPECTRAL SCANNER FOR NATURAL GAS DETECTION

    SciTech Connect

    Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan

    2004-10-25

    The objective of this project is to design, fabricate and field demonstrate a cost effective, multi-spectral scanner for natural gas leak detection in transmission and distribution pipelines. During the first year of the project, a laboratory version of the multi-spectral scanner was designed, fabricated, and tested at En'Urga Inc. The multi-spectral scanner was also evaluated using a blind DoE study at RMOTC. The performance of the scanner was inconsistent during the blind DoE study. However, most of the leaks were outside the view of the multi-spectral scanner. Therefore, a definite evaluation of the capability of the scanner was not obtained. Despite the results, sufficient number of plumes was detected fully confirming the feasibility of the multi-spectral scanner. During the second year, a rugged prototype scanner will be developed and evaluated, both at En'Urga Inc. and any potential field sites.

  4. Identification of volatiles by headspace gas chromatography with simultaneous flame ionization and mass spectrometric detection.

    PubMed

    Tiscione, Nicholas B; Yeatman, Dustin Tate; Shan, Xiaoqin; Kahl, Joseph H

    2013-10-01

    Volatiles are frequently abused as inhalants. The methods used for identification are generally nonspecific if analyzed concurrently with ethanol or require an additional analytical procedure that employs mass spectrometry. A previously published technique utilizing a capillary flow technology splitter to simultaneously quantitate and confirm ethyl alcohol by flame ionization and mass spectrometric detection after headspace sampling and gas chromatographic separation was evaluated for the detection of inhalants. Methanol, isopropanol, acetone, acetaldehyde, toluene, methyl ethyl ketone, isoamyl alcohol, isobutyl alcohol, n-butyl alcohol, 1,1-difluoroethane, 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane (Norflurane, HFC-134a), chloroethane, trichlorofluoromethane (Freon®-11), dichlorodifluoromethane (Freon®-12), dichlorofluoromethane (Freon®-21), chlorodifluoromethane (Freon®-22) and 1,2-dichlorotetrafluoroethane (Freon®-114) were validated for qualitative identification by this method. The validation for qualitative identification included evaluation of matrix effects, sensitivity, carryover, specificity, repeatability and ruggedness/robustness. PMID:24005155

  5. Fault detection and isolation in aircraft gas turbine engines. Part 2: validation on a simulation test bed

    Microsoft Academic Search

    S Sarkar; S Gupta; K Mukherjee; A Ray

    2008-01-01

    The first part of this two-part paper, which is a companion paper, has developed a novel concept of fault detection and isolation (FDI) in aircraft gas turbine engines. The FDI algorithms are built upon the statistical pattern recognition method of symbolic dynamic filtering (SDF) that is especially suited for real-time detection and isolation of slowly evolving anomalies in engine components,

  6. THE INVISIBLE MAJORITY? EVOLUTION AND DETECTION OF OUTER PLANETARY SYSTEMS WITHOUT GAS GIANTS

    SciTech Connect

    Mann, Andrew W. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Gaidos, Eric [Department of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822 (United States); Gaudi, B. Scott [Department of Astronomy, Ohio State University, 140 W. 18th Avenue, Columbus, OH 43120 (United States)

    2010-08-20

    We present 230 realizations of a numerical model of planet formation in systems without gas giants. These represent a scenario in which protoplanets grow in a region of a circumstellar disk where water ice condenses and the surface density of solids is enhanced (the 'ice line'), but fail to accrete massive gas envelopes before the gaseous disk is dispersed. Each simulation consists of a small number of gravitationally interacting oligarchs (protoplanets) and a much larger number of small bodies that represent the natal disk of planetesimals. Time zero of each simulation represents the epoch at which the gas has disappeared, and the dynamics are integrated for 5 billion years (Gyr). We investigate systems with varying initial number of oligarchs, oligarch spacing, location of the ice line, total mass in the ice line, and oligarch mean density. Systems become chaotic in {approx}1 Myr but settle into stable configurations in 10-100 Myr. We find: (1) runs consistently produce a 5-9 M {sub +} planet at a semimajor axis of 0.25-0.6 times the position of the ice line, (2) the distribution of planets' orbital eccentricities is distinct from, and skewed toward lower values than the observed distribution of (giant) exoplanet orbits, (3) Inner systems of two dominant planets (e.g., Earth and Venus) are not stable or do not form because of the gravitational influence of the innermost icy planet. The planets predicted by our model are unlikely to be detected by current Doppler observations. Microlensing is currently sensitive to the most massive planets found in our simulations, and may have already found several analogs. A scenario where up to 60% of stars host systems such as those we simulate is consistent with all the available data. We predict that, if this scenario holds, the NASA Kepler spacecraft will detect about 120 planets by two or more transits over the course of its 3.5 yr mission. Furthermore, we predict detectable transit timing variations exceeding 20 minutes due to the presence of additional outer planets. Future microlensing surveys will detect {approx}130 analogs over a 5 yr survey, including a handful of multiple-planet systems. Finally, the Space Interferometry Mission (SIM-Lite) should be capable of detecting 96% of the innermost icy planets over the course of a 5 yr mission.

  7. A quantum gas microscope for detecting single atoms in a Hubbard-regime optical lattice.

    PubMed

    Bakr, Waseem S; Gillen, Jonathon I; Peng, Amy; Fölling, Simon; Greiner, Markus

    2009-11-01

    Recent years have seen tremendous progress in creating complex atomic many-body quantum systems. One approach is to use macroscopic, effectively thermodynamic ensembles of ultracold atoms to create quantum gases and strongly correlated states of matter, and to analyse the bulk properties of the ensemble. For example, bosonic and fermionic atoms in a Hubbard-regime optical lattice can be used for quantum simulations of solid-state models. The opposite approach is to build up microscopic quantum systems atom-by-atom, with complete control over all degrees of freedom. The atoms or ions act as qubits and allow the realization of quantum gates, with the goal of creating highly controllable quantum information systems. Until now, the macroscopic and microscopic strategies have been fairly disconnected. Here we present a quantum gas 'microscope' that bridges the two approaches, realizing a system in which atoms of a macroscopic ensemble are detected individually and a complete set of degrees of freedom for each of them is determined through preparation and measurement. By implementing a high-resolution optical imaging system, single atoms are detected with near-unity fidelity on individual sites of a Hubbard-regime optical lattice. The lattice itself is generated by projecting a holographic mask through the imaging system. It has an arbitrary geometry, chosen to support both strong tunnel coupling between lattice sites and strong on-site confinement. Our approach can be used to directly detect strongly correlated states of matter; in the context of condensed matter simulation, this corresponds to the detection of individual electrons in the simulated crystal. Also, the quantum gas microscope may enable addressing and read-out of large-scale quantum information systems based on ultracold atoms. PMID:19890326

  8. Detection of a CO and NH3 gas mixture using carboxylic acid-functionalized single-walled carbon nanotubes

    PubMed Central

    2013-01-01

    Carbon nanotubes (CNT) are extremely sensitive to environmental gases. However, detection of mixture gas is still a challenge. Here, we report that 10 ppm of carbon monoxide (CO) and ammonia (NH3) can be electrically detected using a carboxylic acid-functionalized single-walled carbon nanotubes (C-SWCNT). CO and NH3 gases were mixed carefully with the same concentrations of 10 ppm. Our sensor showed faster response to the CO gas than the NH3 gas. The sensing properties and effect of carboxylic acid group were demonstrated, and C-SWCNT sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective detection method of CO and NH3 mixture gas. PMID:23286690

  9. Detection of Greenhouse Gas Precursors from Diesel Engines Using Electrochemical and Photoacoustic Sensors

    PubMed Central

    Mothé, Geórgia; Castro, Maria; Sthel, Marcelo; Lima, Guilherme; Brasil, Laisa; Campos, Layse; Rocha, Aline; Vargas, Helion

    2010-01-01

    Atmospheric pollution is one of the worst threats to modern society. The consequences derived from different forms of atmospheric pollution vary from the local to the global scale, with deep impacts on climate, environment and human health. Several gaseous pollutants, even when present in trace concentrations, play a fundamental role in important processes that occur in atmosphere. Phenomena such as global warming, photochemical smog formation, acid rain and the depletion of the stratospheric ozone layer are strongly related to the increased concentration of certain gaseous species in the atmosphere. The transport sector significantly produces atmospheric pollution, mainly when diesel oil is used as fuel. Therefore, new methodologies based on selective and sensitive gas detection schemes must be developed in order to detect and monitor pollutant gases from this source. In this work, CO2 Laser Photoacoustic Spectroscopy was used to evaluate ethylene emissions and electrochemical analyzers were used to evaluate the emissions of CO, NOx and SO2 from the exhaust of diesel powered vehicles (rural diesel with 5% of biodiesel, in this paper called only diesel) at different engine rotation speeds. Concentrations in the range 6 to 45 ppmV for ethylene, 109 to 1,231 ppmV for carbon monoxide, 75 to 868 ppmV for nitrogen oxides and 3 to 354 ppmV for sulfur dioxide were obtained. The results indicate that the detection techniques used were sufficiently selective and sensitive to detect the gaseous species mentioned above in the ppmV range. PMID:22163437

  10. A Cost Effective Multi-Spectral Scanner for Natural Gas Detection

    SciTech Connect

    Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan; Seonghyeon Park

    2005-12-07

    The objective of this project is to design, fabricate and field demonstrate a cost effective, multi-spectral scanner for natural gas leak detection in transmission and distribution pipelines. During the first year of the project, a laboratory version of the multi-spectral scanner was designed, fabricated, and tested at EnUrga Inc. The multi-spectral scanner was also evaluated using a blind DoE study at RMOTC. The performance of the scanner was inconsistent during the blind DoE study. However, most of the leaks were outside the view of the multi-spectral scanner. Therefore, a definite evaluation of the capability of the scanner was not obtained. Despite the results, sufficient number of plumes was detected fully confirming the feasibility of the multi-spectral scanner. During the second year, the optical design of the scanner was changed to improve the sensitivity of the system. Laboratory tests show that the system can reliably detect small leaks (20 SCFH) at 30 to 50 feet. Electronic and mechanical design of the scanner to make it a self standing sensor was completed during the last six months of the project. The prototype scanner was tested with methane leaks at 15 feet and 30 feet, at a flow rate of 25 SCFH. The prototype scanner successfully detected the leaks. This concluded the project.

  11. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Remote laser detection of natural gas leakages from pipelines

    NASA Astrophysics Data System (ADS)

    Petukhov, V. O.; Gorobets, V. A.; Andreev, Yu M.; Lanskii, G. V.

    2010-02-01

    A differential absorption lidar based on a tunable TEA CO2 laser emitting at 42 lines of the 'hot' 0111 — 1110 band in the range from 10.9 to 11.4 ?m is developed for detecting natural gas leakages from oil pipelines by measuring the ethane content in the atmosphere. The ethane detection sensitivity is 0.9 ppm km. The presence of methane does not distort the measurement results. The developed lidar can detect the natural gas leakage from kilometre heights at the flying velocities up to 200 km h-1 and a probe pulse repetition rate of 5 Hz.

  12. Development of an optical gas leak sensor for detecting ethylene, dimethyl ether and methane.

    PubMed

    Tan, Qiulin; Pei, Xiangdong; Zhu, Simin; Sun, Dong; Liu, Jun; Xue, Chenyang; Liang, Ting; Zhang, Wendong; Xiong, Jijun

    2013-01-01

    In this paper, we present an approach to develop an optical gas leak sensor that can be used to measure ethylene, dimethyl ether, and methane. The sensor is designed based on the principles of IR absorption spectrum detection, and comprises two crossed elliptical surfaces with a folded reflection-type optical path. We first analyze the optical path and the use of this structure to design a miniature gas sensor. The proposed sensor includes two detectors (one to acquire the reference signal and the other for the response signal), the light source, and the filter, all of which are integrated in a miniature gold-plated chamber. We also designed a signal detection device to extract the sensor signal and a microprocessor to calculate and control the entire process. The produced sensor prototype had an accuracy of ±0.05%. Experiments which simulate the transportation of hazardous chemicals demonstrated that the developed sensor exhibited a good dynamic response and adequately met technical requirements. PMID:23539025

  13. Detection of free radicals in low-temperature gas-grain reactions of astrophysical interest

    NASA Astrophysics Data System (ADS)

    Zhitnikov, R. A.; Dmitriev, Yu. A.

    2002-05-01

    For laboratory detection and investigation of free radicals which often appear in chemical reactions of astrophysical interest either as important intermediate or as final products, we pioneered the use of the electron paramagnetic resonance (EPR) technique, which is very effective in observing these substances. This has allowed both formyl (HCO and DCO) and methyl (CH3 and CD3) free radicals to be detected in a sequence of low-temperature gas-grain reactions of H and D atom addition in solid CO. The solid samples subjected to the EPR study were obtained by simultaneous independent deposition of CO molecules and either H or D atoms on the substrate cooled to liquid helium temperatures. The sequence of the H-atom addition gas-grain reactions in solid CO is acknowledged to be among the fundamental processes responsible for the synthesis of organic molecules in interstellar cloud dust grains. The present observation of the above free radicals confirms that the solid-state gas-grain sequence of the reactions is efficient at low temperatures; it also suggests that there should be considerable concentrations of formyl and methyl radicals in the ISM. Another study concentrated on the formation of ethyl free radicals (C2H5) in a low-temperature gas-grain reaction of H-atom abstraction from a C2H6 molecule by free H-atom in solid CH4. These experiments were carried out by deposition onto a substrate, cooled by liquid helium, of a flow of CH4 molecules containing a small amount of impurities such as ethane molecules (C2H6), free H-atoms and CH3 radicals formed in a discharge in a pure gaseous methane. EPR spectra of CH3 radicals, H-atoms, and C2H5 radicals matrix-isolated in solid CH4 were detected. The relative concentrations of the radicals were found to depend on the experimental conditions. The abstraction reaction, C2H6 + H -> C2H5 + H2, took place in CH4-ice.

  14. Solid state gas sensors for detection of explosives and explosive precursors

    NASA Astrophysics Data System (ADS)

    Chu, Yun

    The increased number of terrorist attacks using improvised explosive devices (IEDs) over the past few years has made the trace detection of explosives a priority for the Department of Homeland Security. Considerable advances in early detection of trace explosives employing spectroscopic detection systems and other sensing devices have been made and have demonstrated outstanding performance. However, modern IEDs are not easily detectable by conventional methods and terrorists have adapted to avoid using metallic or nitro groups in the manufacturing of IEDs. Instead, more powerful but smaller compounds, such as TATP are being more frequently used. In addition, conventional detection techniques usually require large capital investment, labor costs and energy input and are incapable of real-time identification, limiting their application. Thus, a low cost detection system which is capable of continuous online monitoring in a passive mode is needed for explosive detection. In this dissertation, a thermodynamic based thin film gas sensor which can reliably detect various explosive compounds was developed and demonstrated. The principle of the sensors is based on measuring the heat effect associated with the catalytic decomposition of explosive compounds present in the vapor phase. The decomposition mechanism is complicated and not well known, but it can be affected by many parameters including catalyst, reaction temperature and humidity. Explosives that have relatively high vapor pressure and readily sublime at room temperature, like TATP and 2, 6-DNT, are ideal candidate for vapor phase detection using the thermodynamic gas sensor. ZnO, W2O 3, V2O5 and SnO2 were employed as catalysts. This sensor exhibited promising sensitivity results for TATP, but poor selectivity among peroxide based compounds. In order to improve the sensitivity and selectivity of the thermodynamic sensor, a Pd:SnO2 nanocomposite was fabricated and tested as part of this dissertation. A combinatorial chemistry techniques were used for catalyst discovery. Specially, a series of tin oxide catalysts with continuous varying composition of palladium were fabricated to screen for the optimum Pd loading to maximize specificity. Experimental results suggested that sensors with a 12 wt.% palladium loading generated the highest sensitivity while a 8 wt.% palladium loading provided greatest selectivity. XPS and XRD were used to study how palladium doping level affects the oxidation state and crystal structure of the nanocomposite catalyst. As with any passive detection system, a necessary theme of this dissertation was the mitigation of false positive. Toward this end, an orthogonal detection system comprised of two independent sensing platforms sharing one catalyst was demonstrated using TATP, 2, 6-DNT and ammonium nitrate as target molecules. The orthogonal sensor incorporated a thermodynamic based sensing platform to measure the heat effect associated with the decomposition of explosive molecules, and a conductometric sensing platform that monitors the change in electrical conductivity of the same catalyst when exposed to the explosive substances. Results indicate that the orthogonal sensor generates an effective response to explosives presented at part per billion level. In addition, with two independent sensing platforms, a built-in redundancy of results could be expected to minimize false positive.

  15. Detecting Hazardous Gas Analytes Using Porous Silicon Sensors Coated with Metal Oxide Nanoparticles Eddie Goude, University of Florida Georgia Tech SURF 2011

    E-print Network

    Li, Mo

    Detecting Hazardous Gas Analytes Using Porous Silicon Sensors Coated with Metal Oxide Nanoparticles platform with two probes connected to the gold contacts on the sensor and a gas pipe on top of the sensor Graduate Mentor: William Laminack Introduction Gas detectors are utilized to detect odorless and

  16. Technical Note: Detection of gas bubble leakage via correlation of water column multibeam images

    NASA Astrophysics Data System (ADS)

    Schneider von Deimling, J.; Papenberg, C.

    2012-03-01

    Hydroacoustic detection of natural gas release from the seafloor has been conducted in the past by using singlebeam echosounders. In contrast, modern multibeam swath mapping systems allow much wider coverage, higher resolution, and offer 3-D spatial correlation. Up to the present, the extremely high data rate hampers water column backscatter investigations and more sophisticated visualization and processing techniques are needed. Here, we present water column backscatter data acquired with a 50 kHz prototype multibeam system over a period of 75 seconds. Display types are of swath-images as well as of a "re-sorted" singlebeam presentation. Thus, individual and/or groups of gas bubbles rising from the 24 m deep seafloor clearly emerge in the acoustic images, making it possible to estimate rise velocities. A sophisticated processing scheme is introduced to identify those rising gas bubbles in the hydroacoustic data. We apply a cross-correlation technique adapted from particle imaging velocimetry (PIV) to the acoustic backscatter images. Temporal and spatial drift patterns of the bubbles are assessed and are shown to match very well to measured and theoretical rise patterns. The application of this processing to our field data gives clear results with respect to unambiguous bubble detection and remote bubble rise velocimetry. The method can identify and exclude the main source of misinterpretations, i.e. fish-mediated echoes. Although image-based cross-correlation techniques are well known in the field of fluid mechanics for high resolution and non-inversive current flow field analysis, we present the first application of this technique as an acoustic bubble detector.

  17. Technical Note: Detection of gas bubble leakage via correlation of water column multibeam images

    NASA Astrophysics Data System (ADS)

    Schneider von Deimling, J.; Papenberg, C.

    2011-07-01

    Hydroacoustic detection of natural gas release from the seafloor has been conducted in the past by using singlebeam echosounders. In contrast modern multibeam swath mapping systems allow much wider coverage, higher resolution, and offer 3-D spatial correlation. However, up to the present, the extremely high data rate hampers water column backscatter investigations. More sophisticated visualization and processing techniques for water column backscatter analysis are still under development. We here present such water column backscattering data gathered with a 50 kHz prototype multibeam system. Water column backscattering data is presented in videoframes grabbed over 75 s and a "re-sorted" singlebeam presentation. Thus individual gas bubbles rising from the 24 m deep seafloor clearly emerge in the acoustic images and rise velocities can be determined. A sophisticated processing scheme is introduced to identify those rising gas bubbles in the hydroacoustic data. It applies a cross-correlation technique similar to that used in Particle Imaging Velocimetry (PIV) to the acoustic backscatter images. Tempo-spatial drift patterns of the bubbles are assessed and match very well measured and theoretical rise patterns. The application of this processing scheme to our field data gives impressive results with respect to unambiguous bubble detection and remote bubble rise velocimetry. The method can identify and exclude the main driver for misinterpretations, i.e. fish-mediated echoes. Even though image-based cross-correlation techniques are well known in the field of fluid mechanics for high resolution and non-inversive current flow field analysis, this technique was never applied in the proposed sense for an acoustic bubble detector.

  18. Oil and gas exploration system and method for detecting trace amounts of hydrocarbon gases in the atmosphere

    DOEpatents

    Wamsley, Paula R. (Littleton, CO); Weimer, Carl S. (Littleton, CO); Nelson, Loren D. (Evergreen, CO); O'Brien, Martin J. (Pine, CO)

    2003-01-01

    An oil and gas exploration system and method for land and airborne operations, the system and method used for locating subsurface hydrocarbon deposits based upon a remote detection of trace amounts of gases in the atmosphere. The detection of one or more target gases in the atmosphere is used to indicate a possible subsurface oil and gas deposit. By mapping a plurality of gas targets over a selected survey area, the survey area can be analyzed for measurable concentration anomalies. The anomalies are interpreted along with other exploration data to evaluate the value of an underground deposit. The system includes a differential absorption lidar (DIAL) system with a spectroscopic grade laser light and a light detector. The laser light is continuously tunable in a mid-infrared range, 2 to 5 micrometers, for choosing appropriate wavelengths to measure different gases and avoid absorption bands of interference gases. The laser light has sufficient optical energy to measure atmospheric concentrations of a gas over a path as long as a mile and greater. The detection of the gas is based on optical absorption measurements at specific wavelengths in the open atmosphere. Light that is detected using the light detector contains an absorption signature acquired as the light travels through the atmosphere from the laser source and back to the light detector. The absorption signature of each gas is processed and then analyzed to determine if a potential anomaly exists.

  19. Limited Streamer Tube System for Detecting Contamination in the Gas Used in the BaBar Instrumented Flux Return

    SciTech Connect

    Huntley, L.I.; /Franklin - Marshall Coll.

    2006-08-30

    The Resistive Plate Chambers (RPCs) initially installed in the Instrumented Flux Return (IFR) of the BABAR particle detector have proven unreliable and inefficient for detecting muons and neutral hadrons. In the summer of 2004, the BABAR Collaboration began replacing the RPCs with Limited Streamer Tubes (LSTs). LST operation requires a mixture of very pure gases and an operating voltage of 5500 V to achieve maximum efficiency. In the past, the gas supplies obtained by the BABAR Collaboration have contained contaminants that caused the efficiency of the IFR LSTs to drop from approximately 90% to approximately 60%. Therefore, it was necessary to develop a method for testing this gas for contaminants. An LST test system was designed and built using two existing LSTs, one placed 1 cm above the other. These LSTs detect cosmic muons in place of particles created during the BABAR experiment. The effect of gas contamination was mimicked by reducing the operating voltage of the test system in order to lower the detection efficiency. When contaminated gas was simulated, the coincidence rate and the percent coincidence between the LSTs in the test system dropped off significantly, demonstrating that test system can be used as an indicator of gas purity. In the fall of 2006, the LST test system will be installed in the gas storage area near the BABAR facility for the purpose of testing the gas being sent to the IFR.

  20. Chandra Detects Halo Of Hot Gas Around Milky Way-Like Galaxy

    NASA Astrophysics Data System (ADS)

    2001-07-01

    The first unambiguous evidence for a giant halo of hot gas around a nearby, spiral galaxy much like our own Milky Way was found by astronomers using NASA's Chandra X-ray Observatory. This discovery may lead to a better understanding of our own Galaxy, as well the structure and evolution of galaxies in general. A team of astronomers, led by Professor Daniel Wang of the University of Massachusetts, Amherst, observed NGC 4631, a spiral galaxy approximately 25 million light years from Earth with both Chandra and NASA's Hubble Space Telescope. While previous X-ray satellites have detected extended X-ray emission from this and other spiral galaxies, because of Chandra's exceptional resolution this is the first time that astronomers were able to separate the individual X-ray sources from the diffuse halo. Chandra found the diffuse halo of X-ray gas to be radiating at a temperature of almost 3 million degrees and extending some 25,000 light years from the galactic plane. "Scientists have debated for over 40 years whether the Milky Way has an extended corona, or halo, of hot gas," said Wang, lead author of the paper which appeared this month in The Astrophysical Journal Letters. "Of course since we are within the Milky Way, we can't get outside and take a picture. However, by studying similar galaxies like NGC 4631, we can get an idea of what's going on within our own Galaxy." The Chandra image reveals a halo of hot gas that extends for approximately 25,000 light years above the disk of the galaxy. One important feature of the X-ray emission from NGC 4631 is that it closely resembles the overall size and shape seen in the radio emission from the galaxy. This indicates that there may be a close connection between the outflows of hot gas, seen in X-rays, and the galaxy's magnetic field, revealed by radio emission. The Hubble image of NGC 4631 shows filamentary, loop-like structures enclosing enhanced X-ray-emitting gas and emanating from regions of recent star formation in the galaxy's disk. These data clearly show the hot gas is heated by clusters of massive stars and is now expanding into the halo of the galaxy. NGC 4631 X-ray: NASA/CXC/UMass/D.Wang et al. UV: NASA/GSFC/UIT "What we see in NGC 4631 can be thought of as the bursting flames of a gigantic cosmic camp fire," said Wang. "Using Chandra and Hubble together, we really get a complete story of what is happening in this galaxy." NGC 4631 is a galaxy that has high amounts of star formation, possibly triggered by interaction with neighboring galaxies. Such star formation might have created the conditions necessary to heat the gas seen by Chandra, as vast amounts of energy are released from supernovas and massive stars in star-forming regions - enough to lift the gas out of the plane of the galaxy. These new results provide important clues about the cycling of energy and mass in a galaxy like our own Milky Way and about the evolutionary history of galaxies, which are thought to be more active in star formation in the past than at the present. Other members of the research team include: Stefan Immler, University of Massachusetts; Rene Walterbos, New Mexico State University; James Lauroesch, Northwestern University, Evanston, IL, and Dieter Breitschwerdt, Max Plank Institute, Germany. Chandra observed NGC 4631 with its Advanced CCD Imaging Spectrometer (ACIS) instrument, which was developed for NASA by Pennsylvania State University, University Park, and Massachusetts Institute of Technology, Cambridge. NASA's Marshall Space Flight Center in Huntsville, AL, manages the Chandra program, and TRW, Inc., Redondo Beach, CA, is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, MA.

  1. Application of gas-coupled laser acoustic detection to gelatins and underwater sensing

    SciTech Connect

    Caron, James N. [Research Support Instruments, Lanham, MD 20706, USA and Quarktet, Silver Spring, MD 20901 (United States); Kunapareddy, Pratima [Research Support Instruments, Lanham, MD 20706 (United States)

    2014-02-18

    Gas-coupled Laser Acoustic Detection (GCLAD) has been used as a method to sense ultrasound waves in materials without contact of the material surface. To sense the waveform, a laser beam is directed parallel to the material surface and displaced or deflected when the radiated waveform traverses the beam. We present recent tests that demonstrate the potential of using this technique for detecting ultrasound in gelatin phantoms and in water. As opposed to interferometric detection, GCLAD operates independently of the optical surface properties of the material. This allows the technique to be used in cases where the material is transparent or semi-transparent. We present results on sensing ultrasound in gelatin phantoms that are used to mimic biological materials. As with air-coupled transducers, the frequency response of GCLAD at high frequencies is limited by the high attenuation of ultrasound in air. In contrast, water has a much lower attenuation. Here we demonstrate the use of a GCLAD-like system in water, measuring the directivity response at 1 MHz and sensing waveforms with higher frequency content.

  2. A COST EFFECTIVE MULTI-SPECTRAL SCANNER FOR NATURAL GAS DETECTION

    SciTech Connect

    Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan; Seonghyeon Park

    2005-04-15

    The objective of this project is to design, fabricate and field demonstrate a cost effective, multi-spectral scanner for natural gas leak detection in transmission and distribution pipelines. During the first year of the project, a laboratory version of the multi-spectral scanner was designed, fabricated, and tested at En'Urga Inc. The multi-spectral scanner was also evaluated using a blind DoE study at RMOTC. The performance of the scanner was inconsistent during the blind DoE study. However, most of the leaks were outside the view of the multi-spectral scanner. Therefore, a definite evaluation of the capability of the scanner was not obtained. Despite the results, sufficient number of plumes was detected fully confirming the feasibility of the multi-spectral scanner. During the second year, the optical design of the scanner was changed to improve the sensitivity of the system. Laboratory tests show that the system can reliably detect small leaks (20 SCFH) at 30 to 50 feet. Electronic design of the scanner to make it a self standing sensor is currently in progress. During the last six months of the project, the electronic and mechanical design will be completed and evaluated at En'Urga Inc.

  3. Strategies for Detecting Hidden Geothermal Systems by Near-Surface Gas Monitoring

    SciTech Connect

    Lewicki, Jennifer L.; Oldenburg, Curtis M.

    2004-12-15

    ''Hidden'' geothermal systems are those systems above which hydrothermal surface features (e.g., hot springs, fumaroles, elevated ground temperatures, hydrothermal alteration) are lacking. Emissions of moderate to low solubility gases (e.g., CO2, CH4, He) may be one of the primary near-surface signals from these systems. Detection of anomalous gas emissions related to hidden geothermal systems may therefore be an important tool to discover new geothermal resources. This study investigates the potential for CO2 detection and monitoring in the subsurface and above ground in the near-surface environment to serve as a tool to discover hidden geothermal systems. We focus the investigation on CO2 due to (1) its abundance in geothermal systems, (2) its moderate solubility in water, and (3) the wide range of technologies available to monitor CO2 in the near-surface environment. However, monitoring in the near-surface environment for CO2 derived from hidden geothermal reservoirs is complicated by the large variation in CO2 fluxes and concentrations arising from natural biological and hydrologic processes. In the near-surface environment, the flow and transport of CO2 at high concentrations will be controlled by its high density, low viscosity, and high solubility in water relative to air. Numerical simulations of CO2 migration show that CO2 concentrations can reach very high levels in the shallow subsurface even for relatively low geothermal source CO2 fluxes. However, once CO2 seeps out of the ground into the atmospheric surface layer, surface winds are effective at dispersing CO2 seepage. In natural ecological systems in the absence of geothermal gas emissions, near-surface CO2 fluxes and concentrations are primarily controlled by CO2 uptake by photosynthesis, production by root respiration, and microbial decomposition of soil/subsoil organic matter, groundwater degassing, and exchange with the atmosphere. Available technologies for monitoring CO2 in the near-surface environment include (1) the infrared gas analyzer (IRGA) for measurement of concentrations at point locations, (2) the accumulation chamber (AC) method for measuring soil CO2 fluxes at point locations, (3) the eddy covariance (EC) method for measuring net CO2 flux over a given area, (4) hyperspectral imaging of vegetative stress resulting from elevated CO2 concentrations, and (5) light detection and ranging (LIDAR) that can measure CO2 concentrations over an integrated path. Technologies currently in developmental stages that have the potential to be used for CO2 monitoring include tunable lasers for long distance integrated concentration measurements and micro-electronic mechanical systems (MEMS) that can make widespread point measurements. To address the challenge of detecting potentially small-magnitude geothermal CO2 emissions within the natural background variability of CO2, we propose an approach that integrates available detection and monitoring methodologies with statistical analysis and modeling strategies. Within the area targeted for geothermal exploration, point measurements of soil CO2 fluxes and concentrations using the AC method and a portable IRGA, respectively, and measurements of net surface flux using EC should be made. Also, the natural spatial and temporal variability of surface CO2 fluxes and subsurface CO2 concentrations should be quantified within a background area with similar geologic, climatic, and ecosystem characteristics to the area targeted for geothermal exploration. Statistical analyses of data collected from both areas should be used to guide sampling strategy, discern spatial patterns that may be indicative of geothermal CO2 emissions, and assess the presence (or absence) of geothermal CO2 within the natural background variability with a desired confidence level. Once measured CO2 concentrations and fluxes have been determined to be of anomalous geothermal origin with high confidence, more expensive vertical subsurface gas sampling and chemical and isotopic analyses can be undertaken. Integrated analysis of all measurements will d

  4. Non-Invasive Timing of Gas Gun Projectiles with Light Detection and Ranging

    NASA Astrophysics Data System (ADS)

    Goodwin, Peter; Wu, Ming; Dattelbaum, Dana

    2013-06-01

    We have developed a Light Detection and Ranging (LIDAR) diagnostic to track the position of a projectile inside of the gas gun barrel in real-time. This capability permits the generation of precisely timed trigger pulses useful for pre-triggering high-latency diagnostics such as a flash lamp-pumped laser. An initial feasibility test was performed using a 72 mm bore single-stage gas gun routinely used for dynamic research at Los Alamos National Laboratory. A 655-nm pulsed (~100 ps) diode laser operating at a pulse repetition rate of ~100 kHz was used to interrogate the position of the moving projectile in real-time. The position of the projectile in the gun barrel was tracked over a distance of ~3 meters prior to impact. The position record showed that the projectile moved at a constant velocity (483 m/s) prior to impacting the target. This velocity was in good agreement with independent measurements of the projectile velocity by photon Doppler velocimetry, and timing of the passage of the projectile through optical marker beams positioned at the muzzle of the gun. The LIDAR return can be processed in real-time to generate pre-trigger pulses at preset separations between the projectile and target. We have developed a Light Detection and Ranging (LIDAR) diagnostic to track the position of a projectile inside of the gas gun barrel in real-time. This capability permits the generation of precisely timed trigger pulses useful for pre-triggering high-latency diagnostics such as a flash lamp-pumped laser. An initial feasibility test was performed using a 72 mm bore single-stage gas gun routinely used for dynamic research at Los Alamos National Laboratory. A 655-nm pulsed (~100 ps) diode laser operating at a pulse repetition rate of ~100 kHz was used to interrogate the position of the moving projectile in real-time. The position of the projectile in the gun barrel was tracked over a distance of ~3 meters prior to impact. The position record showed that the projectile moved at a constant velocity (483 m/s) prior to impacting the target. This velocity was in good agreement with independent measurements of the projectile velocity by photon Doppler velocimetry, and timing of the passage of the projectile through optical marker beams positioned at the muzzle of the gun. The LIDAR return can be processed in real-time to generate pre-trigger pulses at preset separations between the projectile and target. Work funded by LANL Laboratory Directed Research Project 2011012DR. LA-UR-13-21121, approved for public release.

  5. Detecting Organic Compounds in Martian Soil Analogues Using Gas Chromatography Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Buch, A.; Mahaffy, P. R.

    2004-01-01

    One of the primary objectives of the 1976 Viking missions was to determine whether organic compounds, possibly of biological origin, were present in the Martian surface soils. The Viking gas chromatography mass spectrometry (GCMS) instruments found no evidence for any organic compounds of Martian origin above a few parts per billion in the upper 10 cm of surface soil [l], suggesting the absence of a widely distributed Martian biota. However, Benner et d. have suggested that significant amounts of non-volatile organic compounds, possibly including oxidation products of bioorganic molecules (e.g. carboxylic acids) would not have been detected by the Viking GCMS [2]. Moreover, other key organic compounds important to biology, such as amino acids and nucleobases, would also likely have been missed by the Viking GCMS as these compounds require chemical derivatization to be stable in a GC column [3]. Recent pyrolysis experiments with a Mars soil analogue that had been innoculated with Escherichia coli bacteria have shown that amino acid decomposition products (amines) and nucleobases are among the most abundant products generated after pyrolysis of the bacterial cells [4,5]. At the part per billion level (Viking GCMS detection limit), these pyrolysis products generated from several million bacterial cells per gram of Martian soil would not have been detected by the Viking GCMS instruments [4]. Analytical protocols are under development for upcoming in situ lander opportunities to target several important biological compounds including amino acids and nucleobases. For example, extraction and chemical derivatization techniques [3] are being adapted for space flight use to transform reactive or fragile molecules that would not have been detected by the Viking GCMS instruments, into species that are sufficiently volatile to be detected by GCMS. Recent experiments carried out at NASA Goddard have shown that using this derivatization technique all of the targeted compounds mentioned above can be separated on a GC column and detected by MS at sub-picomole (< 10(exp -l2 mole) levels. With these methods, the detection limit for amino acids, carboxylic acids and nucleobases is several orders of magnitude more sensitive than the Viking GCMS instruments for these compounds. Preliminary results using this analytical technique on a variety of Martian soil analogues will be presented.

  6. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experimentsa)

    NASA Astrophysics Data System (ADS)

    Herrmann, H. W.; Kim, Y. H.; Young, C. S.; Fatherley, V. E.; Lopez, F. E.; Oertel, J. A.; Malone, R. M.; Rubery, M. S.; Horsfield, C. J.; Stoeffl, W.; Zylstra, A. B.; Shmayda, W. T.; Batha, S. H.

    2014-11-01

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ?400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ˜400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

  7. He-Ne and CW CO2 laser long-path systems for gas detection

    NASA Technical Reports Server (NTRS)

    Grant, W. B.

    1986-01-01

    This paper describes the design and testing of a laboratory prototype dual He-Ne laser system for the detection of methane leaks from underground pipelines and solid-waste landfill sites using differential absorption of radiation backscattered from topographic targets. A laboratory-prototype dual CW carbon dioxide laser system also using topographic backscatter is discussed, and measurement results for methanol are given. With both systems, it was observed that the time-varying differential absorption signal was useful in indicating the presence of a gas coming from a nearby source. Limitations to measurement sensitivity, especially the role of speckle and atmospheric turbulence, are described. The speckle results for hard targets are contrasted with those from atmospheric aerosols. The appendix gives appropriate laser lines and values of absorption coefficients for the hydrazine fuel gases.

  8. A COST EFFECTIVE MULTI-SPECTRAL SCANNER FOR NATURAL GAS DETECTION

    SciTech Connect

    Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan

    2004-04-01

    The objective of this project is to design, fabricate and field demonstrate a cost effective, multi-spectral scanner for natural gas leak detection in transmission and distribution pipelines. During the first six months of the project, the design for a laboratory version of the multispectral scanner was completed. The optical, mechanical, and electronic design for the scanner was completed. The optical design was analyzed using Zeemax Optical Design software and found to provide sufficiently resolved performance for the scanner. The electronic design was evaluated using a bread board and very high signal to noise ratios were obtained. Fabrication of a laboratory version of the multi-spectral scanner is currently in progress. A technology status report and a research management plan was also completed during the same period.

  9. Possible Detection of Perchlorates by Evolved Gas Analysis of Rocknest Soils: Global Implication

    NASA Technical Reports Server (NTRS)

    Archer, P. D., Jr.; Sutter, B.; Ming, D. W.; McKay, C. P.; Navarro-Gonzalez, R.; Franz, H. B.; McAdam, A.; Mahaffy, P. R.

    2013-01-01

    The Sample Analysis at Mars (SAM) instrument suite on board the Mars Science Laboratory (MSL) recently ran four samples from an aeolian bedform named Rocknest. Rocknest was selected as the source of the first samples analyzed because it is representative of both windblown material in Gale crater as well as the globally-distributed dust. The four samples analyzed by SAM were portioned from the fifth scoop at this location. The material delivered to SAM passed through a 150 m sieve and should have been well mixed during the sample acquisition/ preparation/handoff process. Rocknest samples were heated to 835 C at a 35 C/minute ramp rate with a He carrier gas flow rate of 1.5 standard cubic centimeters per minute and at an oven pressure of 30 mbar. Evolved gases were detected by a quadrupole mass spectrometer (QMS).

  10. Detection of nerve agents using proton transfer reaction mass spectrometry with ammonia as reagent gas.

    PubMed

    Ringer, Joachim M

    2013-01-01

    The chemical warfare agents (CWA) Sarin, Soman, Cyclosarin and Tabun were characterised by proton transfer mass spectrometry (PTRMS). It was found that PTRMS is a suitable technique to detect nerve agents highly sensitively, highly selectively and in near real-time. Methods were found to suppress molecule fragmentation which is significant under PTRMS hollow cathode ionisation conditions. In this context, the drift voltage (as one of the most important system parameters) was varied and ammonia was introduced as an additional chemical reagent gas. Auxiliary chemicals such as ammonia affect ionisation processes and are quite common in context with detectors for CWAs based on ion mobility spectrometry (IMS). With both, variation of drift voltage and ammonia as the reagent gas, fragmentation can be suppressed effectively. Suppression of fragmentation is crucial particularly concerning the implementation of an algorithm for automated agent identification in field applications. On the other hand, appearance of particular fragments might deliver additional information. Degradation and rearrangement products of nerve agents are not distinctive for the particular agent but for the chemical class they belong to. It was found that switching between ammonia doped and ordinary water ionisation chemistry can easily be performed within a few seconds. Making use of this effect it is possible to switch between fragment and molecular ion peak spectra. Thus, targeted fragmentation can be used to confirm identification based only on single peak detection. PTRMS turned out to be a promising technique for future CWA detectors. In terms of sensitivity, response time and selectivity (or confidence of identification, respectively) PTRMS performs as a bridging technique between IMS and GC-MS. PMID:24308198

  11. Calorimetric thermoelectric gas sensor for the detection of hydrogen, methane and mixed gases.

    PubMed

    Park, Nam-Hee; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

    2014-01-01

    A novel miniaturized calorimeter-type sensor device with a dual-catalyst structure was fabricated by integrating different catalysts on the hot (Pd/?-Al2O3) and cold (Pt/?-Al2O3) ends of the device. The device comprises a calorimeter with a thermoelectric gas sensor (calorimetric-TGS), combining catalytic combustion and thermoelectric technologies. Its response for a model fuel gas of hydrogen and methane was investigated with various combustor catalyst compositions. The calorimetric-TGS devices detected H2, CH4, and a mixture of the two with concentrations ranging between 200 and 2000 ppm at temperatures of 100-400 °C, in terms of the calorie content of the gases. It was necessary to reduce the much higher response voltage of the TGS to H2 compared to CH4. We enhanced the H2 combustion on the cold side so that the temperature differences and response voltages to H2 were reduced. The device response to H2 combustion was reduced by 50% by controlling the Pt concentration in the Pt/?-Al2O3 catalyst on the cold side to 3 wt%. PMID:24818660

  12. Designing a reliable leak bio-detection system for natural gas pipelines.

    PubMed

    Batzias, F A; Siontorou, C G; Spanidis, P-M P

    2011-02-15

    Monitoring of natural gas (NG) pipelines is an important task for economical/safety operation, loss prevention and environmental protection. Timely and reliable leak detection of gas pipeline, therefore, plays a key role in the overall integrity management for the pipeline system. Owing to the various limitations of the currently available techniques and the surveillance area that needs to be covered, the research on new detector systems is still thriving. Biosensors are worldwide considered as a niche technology in the environmental market, since they afford the desired detector capabilities at low cost, provided they have been properly designed/developed and rationally placed/networked/maintained by the aid of operational research techniques. This paper addresses NG leakage surveillance through a robust cooperative/synergistic scheme between biosensors and conventional detector systems; the network is validated in situ and optimized in order to provide reliable information at the required granularity level. The proposed scheme is substantiated through a knowledge based approach and relies on Fuzzy Multicriteria Analysis (FMCA), for selecting the best biosensor design that suits both, the target analyte and the operational micro-environment. This approach is illustrated in the design of leak surveying over a pipeline network in Greece. PMID:21177031

  13. Detection of abundant molecular gas in the UV-excess quasar Mrk 1014

    SciTech Connect

    Sanders, D.B.; Scoville, N.Z.; Soifer, B.T.

    1988-01-01

    Carbon dioxide (1 yields 0) emission has been detected from the UV-excess quasar Mrk 1014 (=PG 0157+001=IRAS 01572+0009) at z=0.163. Assuming the same empirical relationship between CO brightness and H2 surface mass density as has been found for giant molecular clouds in the Milky Way, the mass of H2 gas is approximately 4 x 10 to the 10th solar masses, i.e., more than ten times the H2 content of our Galaxy. The infrared and molecular gas properties of Mrk 1014 are similar to other warm, ultraluminous infrared galaxies such as Mrk 231, and IRAS 15206+3342 (z=0.125) from which CO(1 yields 0) emission is also reported. The trigger for the intense infrared activity in both Mrk 1014 and IRAS 15206+3342 appears to be a recent galaxy merger. It is suggested that objects such as these represent an important link in the evolution of ultraluminous infrared galaxies into UV-excess quasars.

  14. Detection of abundant molecular gas in the UV-excess quasar Markarian 1014

    SciTech Connect

    Sanders, D.B.; Scoville, N.Z.; Soifer, B.T.

    1988-12-01

    CO(1-0) emission has been detected from the UV-excess quasar Mrk 1014 ( = PG 0157+001 = IRAS 01572+0009) at z = 0.163. Assuming the same empirical relationship between CO brightness and H2 surface mass density as has been found for giant molecular clouds in the Milky Way, the mass of H2 gas is about 4 x 10 to the 10th solar masses more than 10 times the H2 content of the Galaxy. The infrared and molecular gas properties of Mrk 1014 are similar to other warm, ultraluminous infrared galaxies such as Mrk 231, and IRAS 15206+3342 (z = 0.125) from which CO(1-0) emission is also reported. The trigger for the intense infrared activity in both Mrk 1014 and IRAS 15206+3342 appears to be a recent galaxy merger. It is suggested that objects such as these represent an important link in the evolution of ultraluminous infrared galaxies into UV-excess quasars. 37 references.

  15. Non-invasive timing of gas gun projectiles with light detection and ranging

    NASA Astrophysics Data System (ADS)

    Goodwin, P. M.; Bartram, B. D.; Gibson, L. L.; Wu, M.; Dattelbaum, D. M.

    2014-05-01

    We have developed a Light Detection and Ranging (LIDAR) diagnostic to track the position of a projectile inside of a gas gun launch tube in real-time. This capability permits the generation of precisely timed trigger pulses useful for triggering high-latency diagnostics such as a flash lamp-pumped laser. An initial feasibility test was performed using a 72 mm bore diameter single-stage gas gun routinely used for dynamic research at Los Alamos. A 655 nm pulsed diode laser operating at a pulse repetition rate of 100 kHz was used to interrogate the position of the moving projectile in real-time. The position of the projectile in the gun barrel was tracked over a distance of ~ 3 meters prior to impact. The position record showed that the projectile moved at a velocity of 489 m/s prior to impacting the target. This velocity was in good agreement with independent measurements of the projectile velocity by photon Doppler velocimetry and timing of the passage of the projectile through optical marker beams positioned at the muzzle of the gun. The time-to-amplitude conversion electronics used enable the LIDAR data to be processed in real-time to generate trigger pulses at preset separations between the projectile and target.

  16. Detection of Dense Molecular Gas in Inter-Arm Spurs in M51

    E-print Network

    S. A. Corder; K. Sheth; N. Z. Scoville; J. Koda; S. N. Vogel; E. Ostriker

    2008-11-18

    Spiral arm spurs are prominent features that have been observed in extinction and 8$\\mu$m emission in nearby galaxies. In order to understand their molecular gas properties, we used the Owens Valley Radio Observatory to map the CO(J=1--0) emission in three spurs emanating from the inner northwestern spiral arm of M51. We report CO detections from all three spurs. The molecular gas mass and surface density are M$_{H2} \\sim3\\times10^6$ M$_{\\sun}$ and $\\Sigma_{H2} \\sim$50 M$_{\\sun}$ pc$^{-2}$. Thus, relative to the spiral arms, the spurs are extremely weak features. However, since the spurs are extended perpendicular to the spiral arms for $\\sim$500 pc and contain adequate fuel for star formation, they may be the birthplace for observed inter-arm HII regions. This reduces the requirement for the significant time delay that would be otherwise needed if the inter-arm star formation was initiated in the spiral arms. Larger maps of galaxies at similar depth are required to further understand the formation and evolution of these spurs and their role in star formation - such data should be forthcoming with the new CARMA and future ALMA telescopes and can be compared to several recent numerical simulations that have been examining the evolution of spiral arm spurs.

  17. Determination of sulfur dioxide in wine using headspace gas chromatography and electron capture detection.

    PubMed

    Aberl, A; Coelhan, M

    2013-01-01

    Sulfites are routinely added as preservatives and antioxidants in wine production. By law, the total sulfur dioxide content in wine is restricted and therefore must be monitored. Currently, the method of choice for determining the total content of sulfur dioxide in wine is the optimised Monier-Williams method, which is time consuming and laborious. The headspace gas chromatographic method described in this study offers a fast and reliable alternative method for the detection and quantification of the sulfur dioxide content in wine. The analysis was performed using an automatic headspace injection sampler, coupled with a gas chromatograph and an electron capture detector. The method is based on the formation of gaseous sulfur dioxide subsequent to acidification and heating of the sample. In addition to free sulfur dioxide, reversibly bound sulfur dioxide in carbonyl compounds, such as acetaldehyde, was also measured with this method. A total of 20 wine samples produced using diverse grape varieties and vintages of varied provenance were analysed using the new method. For reference and comparison purposes, 10 of the results obtained by the proposed method were compared with those acquired by the optimised Monier-Williams method. Overall, the results from the headspace analysis showed good correlation (R = 0.9985) when compared with the conventional method. This new method requires minimal sample preparation and is simple to perform, and the analysis can also be completed within a short period of time. PMID:23176364

  18. Detecting Methane From Leaking Pipelines and as Greenhouse Gas in the Atmosphere

    NASA Technical Reports Server (NTRS)

    Riris, Haris; Numata, Kenji; Li, Steven; Wu, Stewart; Ramanathan, Anand; Dawsey, Martha

    2012-01-01

    Laser remote sensing measurements of trace gases from orbit can provide unprecedented information about important planetary science and answer critical questions about planetary atmospheres. Methane (CH4) is the second most important anthropogenically produced greenhouse gas. Though its atmospheric abundance is much less than that of CO2 (1.78 ppm vs. 380 ppm), it has much larger greenhouse heating potential. CH4 also contributes to pollution in the lower atmosphere through chemical reactions, leading to ozone production. Atmospheric CH4 concentrations have been increasing as a result of increased fossil fuel production, rice farming, livestock, and landfills. Natural sources of CH4 include wetlands, wild fires, and termites, and perhaps other unknown sources. Important sinks for CH4 include non-saturated soils and oxidation by hydroxyl radicals in the atmosphere. Remotely measuring CH4 and other biogenic molecules (such as ethane and formaldehyde) on Mars also has important implications on the existence of life on Mars. Measuring CH4 at very low (ppb) concentrations from orbit will dramatically improve the sensitivity and spatial resolution in the search for CH4 vents and sub-surface life on other planets. A capability has been developed using lasers and spectroscopic detection techniques for the remote measurements of trace gases in open paths. Detection of CH4, CO2, H2O, and CO in absorption cells and in open paths, both in the mid- IR and near-IR region, has been demonstrated using an Optical Parametric Amplifier laser transmitter developed at GSFC. With this transmitter, it would be possible to develop a remote sensing methane instrument. CH4 detection also has very important commercial applications. Pipeline leak detection from an aircraft or a helicopter can significantly reduce cost, response time, and pinpoint the location. The main advantage is the ability to rapidly detect CH4 leaks remotely. This is extremely important for the petrochemical industry. This capability can be used in manned or unmanned airborne platforms for the detection of leaks in pipelines and other areas of interest where a CH4 leak is suspected.

  19. Development of a multiple gas analyzer using cavity ringdown spectroscopy for use in advanced fire detection.

    PubMed

    Fallows, Eric A; Cleary, Thomas G; Miller, J Houston

    2009-02-01

    A portable cavity ringdown spectroscopy (CRDS) apparatus was used to detect effluents from small test fires in the Fire Emulator/Detector Evaluator (FE/DE) and a small room in the Building Fire and Research Laboratory at the National Institute of Standards and Technology (NIST). The output from two lasers is combined to detect four combustion gases, CO, CO(2), HCN, and C(2)H(2), near simultaneously using CRDS. The goal of this work was to demonstrate the feasibility of using a CRDS sensor as a fire detector. Fire effluents were extracted from several test facilities and measurements of CO, CO(2), HCN, and C(2)H(2) were obtained every 25-30 s. In the FE/DE test, peak concentrations of the gases from smoldering paper were 420 parts in 10(6) (ppm) CO, 1600 ppm CO(2), 530 parts in 10(9) (ppb) HCN, and 440 ppb C(2)H(2). Peak gas concentrations from the small room were 270 ppm CO, 2100 ppm CO(2), and 310 ppb C(2)H(2). PMID:19183595

  20. Nonlinear Bayesian Algorithms for Gas Plume Detection and Estimation from Hyper-spectral Thermal Image Data

    PubMed Central

    Heasler, Patrick; Posse, Christian; Hylden, Jeff; Anderson, Kevin

    2007-01-01

    This paper presents a nonlinear Bayesian regression algorithm for detecting and estimating gas plume content from hyper-spectral data. Remote sensing data, by its very nature, is collected under less controlled conditions than laboratory data. As a result, the physics-based model that is used to describe the relationship between the observed remote-sensing spectra, and the terrestrial (or atmospheric) parameters that are estimated is typically littered with many unknown “nuisance” parameters. Bayesian methods are well-suited for this context as they automatically incorporate the uncertainties associated with all nuisance parameters into the error estimates of the parameters of interest. The nonlinear Bayesian regression methodology is illustrated on simulated data from a three-layer model for longwave infrared (LWIR) measurements from a passive instrument. The generated LWIR scenes contain plumes of varying intensities, and this allows estimation uncertainty and probability of detection to be quantified. The results show that this approach should permit more accurate estimation as well as a more reasonable description of estimate uncertainty. Specifically, the methodology produces a standard error that is more realistic than that produced by matched filter estimation.

  1. Fingerprinting of vegetable oil minor components by multidimensional comprehensive gas chromatography with dual detection.

    PubMed

    Purcaro, Giorgia; Barp, Laura; Beccaria, Marco; Conte, Lanfranco S

    2015-01-01

    The potentiality of a multidimensional comprehensive gas chromatographic (GC?×?GC) method, employing a simultaneous dual detection (FID and mass spectrometer), to generate peculiar two-dimensional chromatograms to be used as a chemical fingerprint, was investigated to characterize minor compounds in edible oil, particularly olive oil. The best column combination for this application was investigated comparing two column sets (orthogonal or reverse-type), equivalent in terms of theoretical plate number, but differing in stationary phase combination. The apolar?×?mid-polar set gave a superior separation power, thus was used for further characterization. Different levels of information were extrapolated from the two-dimensional chromatogram. Using the FID, reliable quantification of the alkyl esters fatty acids and waxes was obtained, comparable to the results obtained using the official method, as required by the European legislation. However, thanks to a slight modification of the sample preparation method, the increased separation power obtained using the GC?×?GC method, and the support of the mass spectrometer detector, further diagnostic information was extrapolated considering the free sterol and tocopherol fractions. In particular, the profiles of extra virgin olive oil samples were compared with a hazelnut oil sample, highlighting that the latter was characterized by a larger number of compounds, completely absent in the extra virgin olive oil samples, which can be used to detect illegal admixtures. PMID:25209809

  2. Selective determination of volatile sulfur compounds in wine by gas chromatography with sulfur chemiluminescence detection.

    PubMed

    Siebert, Tracey E; Solomon, Mark R; Pollnitz, Alan P; Jeffery, David W

    2010-09-01

    Volatile sulfur compounds can be formed at various stages during wine production and storage, and some may impart unpleasant "reduced" aromas to wine when present at sensorially significant concentrations. Quantitative data are necessary to understand factors that influence the formation of volatile sulfur compounds, but their analysis is not a trivial undertaking. A rapid and selective method for determining 10 volatile sulfur-containing aroma compounds in wine that have been linked to "off-odors" has been developed. The method utilizes static headspace injection and cool-on-column gas chromatography coupled with sulfur chemiluminescence detection (GC-SCD). Validation demonstrated that the method is accurate, precise, robust, and sensitive, with limits of quantitation around 1 microg/L or better, which is below the aroma detection thresholds for the analytes. Importantly, the method does not form artifacts, such as disulfides, during sample preparation or analysis. To study the contribution of volatile sulfur compounds, the GC-SCD method was applied to 68 commercial wines that had reductive sensory evaluations. The analytes implicated as contributors to reductive characters were hydrogen sulfide, methanethiol, and dimethyl sulfide, whereas carbon disulfide played an uncertain role. PMID:20707415

  3. A hierarchical strategy for underground early fire detection based on a T-cycled semiconductor gas sensor

    Microsoft Academic Search

    Thorsten Conrad; Peter Reimann; Andreas Schütze

    2007-01-01

    Based on a single semiconductor gas sensor device operated in a T-cycled mode we developed a hierarchical identification strategy for the use in under-ground early fire detection systems, i.e. in coal mines. This strategy not only provides the identification of the alarm scenario to be detected (CO and ethene in a specific ratio) but is also suitable for identifying or

  4. Comparison of Detection Capability for Acoustic Thermography, Visual Inspection and Fluorescent Penetrant Inspection on Gas Turbine Components

    NASA Astrophysics Data System (ADS)

    Guo, Y.; Ruhge, F. R.

    2009-03-01

    The innovative NDE inspection system Acoustic Thermography is developed with Sonic Infrared (Sonic IR) technology. Since the probability of detection is sensitive to the flaw characteristics, the fabricated flaws could not simulated the nature flaws with accuracy. The study is focus on gas turbine blades with service induced fatigue cracks. The detection capability of this innovative NDE inspection system is compared with two traditional NDE methods: Visual Inspection and Fluorescent Penetrant Inspection. POD curves for each technique were generated and compared.

  5. Nano Sensors for Gas Detection in Space and Ground Support Applications

    NASA Technical Reports Server (NTRS)

    Medelius, Pedro J.

    2006-01-01

    Personnel living in a space environment as well as technicians and engineers preparing spacecraft for launch can potentially be exposed to small amounts of hazardous gases. It is therefore important to be able to detect, identify and quantify the presence of a gas especially when its presence could lead to a fatal situation. The use of small and sensitive sensors can allow for the placement of these devices over a large area, thus allowing for a more precise and timely determination of a gas leak. ASRC Aerospace and its research partners are developing nano sensors for detection of various gases, including but not limited to: H2, NH3, N2O4, hydrazine and others. Initial laboratory testing has demonstrated the capability to detect the gases in concentrations lower than parts per million. Testing and development is continuing to improve the response and recovery times, to increase the sensitivity of the devices. Different coatings and electrodes are currently being evaluated to determine the optimum configuration of a variety of gases. The small footprint of the Nano sensors allows for several devices, each responsive in a different way to different gases, to be placed into a single substrate. Multiple devices embedded into a single substrate results in increased reliability and in a decrease for periodic calibrations. The use of different coatings will result in a small electronic nose capable of distinguishing between different gases. A multi-channel signal conditioner amplifier built on a small multi chip module is used to process the output of the sensors and to deliver a signal that can be remotely monitored. All the data is digitized and transmitted over the same cable pair used to power the amplifier. Multiple outputs can be connected to a single cable pair in order to minimize the added weight and expense associated with cabling in a spacecraft. The sensors will be run through a qualification process to evaluate their suitability for space applications we are expecting to have fully functional sensors available for initial field deployment and testing by the end of the year 2006.

  6. Detection of cold gas releases in space via low energy neutral atom imaging

    SciTech Connect

    McComas, D.J.; Funsten, H.O.; Moore, K.R.; Scime, E.E.; Thomsen, M.F.

    1993-01-01

    Low energy neutral atoms (LENAs) are produced in space plasmas by charge exchange between the ambient magnetospheric plasma ions and cold neutral atoms. Under normal conditions these cold neutrals come from the terrestrial geocorona, a shroud of few-ev hydrogen atoms surrounding the Earth. As a consequence of this charge exchange, it has become possible to remotely image many regions of the magnetosphere for the first time utilizing recently developed LENA imaging technology. In addition to the natural hydrogen geocorona, conventional explosions and maneuvering thruster firings can also introduce large amounts of cold gas into the space environment. In this paper we examine whether such potentially clandestine activities could also be remotely observed for the first time via LENA imaging. First, we examine the fluxes of LENAs produced in the space environment from a conventional explosion. Then we review the present state of the art in the emerging field of LENA detection and imaging. Recent work has shown that LENAs can be imaged by first converting the neutrals to ions with ultra-thin (10s of [Angstrom]) foils and then electrostatically analyzing these newly created ions to reject the large (>10[sup 10] cm[sup [minus]2] [sup [minus]1]) UV background to which the low energy detectors are sensitive. We conclude that the sensitivities for present LENA imager designs may be just adequate for detecting some man-made releases. With additional improvements in LENA detection capabilities, this technique could become an important new method for monitoring for conventional explosions, as well as other man-made neutral releases, in the space environment.

  7. Detection of cold gas releases in space via low energy neutral atom imaging

    SciTech Connect

    McComas, D.J.; Funsten, H.O.; Moore, K.R.; Scime, E.E.; Thomsen, M.F.

    1993-04-01

    Low energy neutral atoms (LENAs) are produced in space plasmas by charge exchange between the ambient magnetospheric plasma ions and cold neutral atoms. Under normal conditions these cold neutrals come from the terrestrial geocorona, a shroud of few-ev hydrogen atoms surrounding the Earth. As a consequence of this charge exchange, it has become possible to remotely image many regions of the magnetosphere for the first time utilizing recently developed LENA imaging technology. In addition to the natural hydrogen geocorona, conventional explosions and maneuvering thruster firings can also introduce large amounts of cold gas into the space environment. In this paper we examine whether such potentially clandestine activities could also be remotely observed for the first time via LENA imaging. First, we examine the fluxes of LENAs produced in the space environment from a conventional explosion. Then we review the present state of the art in the emerging field of LENA detection and imaging. Recent work has shown that LENAs can be imaged by first converting the neutrals to ions with ultra-thin (10s of {Angstrom}) foils and then electrostatically analyzing these newly created ions to reject the large (>10{sup 10} cm{sup {minus}2} {sup {minus}1}) UV background to which the low energy detectors are sensitive. We conclude that the sensitivities for present LENA imager designs may be just adequate for detecting some man-made releases. With additional improvements in LENA detection capabilities, this technique could become an important new method for monitoring for conventional explosions, as well as other man-made neutral releases, in the space environment.

  8. ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT, EXPLOSIVES DETECTION TECHNOLOGY, SRI INSTRUMENTS, MODEL 8610C, GAS CHROMATOGRAPH/THERMIONIC IONIZATION DETECTION

    EPA Science Inventory

    The SRI Model 86 1 OC gas chromatograph (GC) is a transportable instrument that can provide on-site analysis of soils for explosives. Coupling this transportable gas chromatograph with a thermionic ionization detector (TID) allows for the determination of explosives in soil matri...

  9. Hydroacoustic detection and quantification of free gas -methane bubbles in the ocean

    Microsoft Academic Search

    J. Greinert; Y. Artemov; P. Gimpel

    2003-01-01

    Extensive methane release as a free gas phase from cold vents is well known from deep (>2000m) and shallow (10s of meters) water depths. Supposedly, much more methane is transported into the water column by free gas than by dissolved gas, which is oxidized by anaerobic and aerobic processes and partly precipitated as carbonate. Rising gas bubbles are not affected

  10. Separation of corona using wavelet packet transform and neural network for detection of partial discharge in gas-insulated substations

    Microsoft Academic Search

    C. S. Chang; J. Jin; C. Chang; Toshihiro Hoshino; Masahiro Hanai; Nobumitsu Kobayashi

    2005-01-01

    It is essential to detect partial discharge (PD) as a symptom of insulation breakdown in gas-insulated substations (GIS). However, the accuracy of such measurement is often degraded due to the existence of noise in the signal. In this paper, a method using wavelet packet transform and neural network is proposed to separate the PD pulses from corona in air, which

  11. Gas chromatography with surface ionization detection: a highly sensitive method for determining underivatized codeine and dihydrocodeine in body fluids

    Microsoft Academic Search

    H. Seno; H. Hattori; S. Kurono; T. Yamada; T. Kumazawa; A. Ishii; O. Suzuki

    1995-01-01

    Underivatized codeine and dihydrocodeine in human plasma and urine have been determined with a high degree of accuracy by capillary gas chromatography (GC) with surface ionization detection (SID). The drugs were extracted with the aid of Sep-Pak C18 cartridges. Recovery of both drugs was ? 90%. The calibration curves obtained with dimemorfan as an internal standard showed linearity in the

  12. Potentialities of gaseous biomarkers detection against the main atmospheric components with gas analyzer based on CO II laser

    NASA Astrophysics Data System (ADS)

    Nikiforova, O. Yu.; Ptashnik, I. V.

    2006-11-01

    Potentialities of detection of minor gases characterizing the biosystem-atmosphere gas exchange, such as C IIH 4, N IIO, NH 3, H IIO II, using a gas-analyzer based on waveguide CO II laser with discrete frequency tuning are studied numerically. The measured signal is recorded over the whole laser frequency scan for 9-?m or 10-?m transitions, i.e. for 25-30 generation lines. An effect of interference of the main gaseous atmospheric components H IIO and CO II on the minor gas detection limit and the uncertainty in the retrieved concentration is analyzed. Absorption coefficients of atmospheric gases at CO II laser lines are calculated using the HITRAN-2004 spectral database and the CKD water vapor continuum model. Aerosol effect is not taken into account.

  13. Physical conditions of gas in high-redshift (z > 4.4) ALMA-detected submillimeter galaxies

    NASA Astrophysics Data System (ADS)

    Huynh, Minh; Norris, Ray; Emonts, Bjorn; Swinbank, Mark; Ivison, Rob; Coppin, Kristen; Smail, Ian; Smolcic, Vernesa

    2014-04-01

    This proposal aims to complete a project to measure CO(2-1) emission in two high-redshift (z > 4.4) submm selected galaxies (SMGs) that have been detected in [CII] 157.74 micron emission by ALMA. These high-z galaxies trace the most intense stellar build-up in massive galaxy formation. These observations will allow us to measure the gas mass and dynamics of these ultra-luminous infra-red galaxies, and help us determine whether z > 4 SMGs have the baryonic masses and gas consumption timescales necessary to be the progenitors of the massive red galaxies seen at z ~ 3. We will combine the CO(2-1) measurement with the [CII] detection from ALMA to constrain physical conditions of gas in the early universe.

  14. Molecular gas in NUclei of GAlaxies (NUGA): VI. Detection of a molecular gas disk/torus via HCN in the Seyfert 2 galaxy NGC 6951?

    NASA Astrophysics Data System (ADS)

    Krips, M.; Neri, R.; García-Burillo, S.; Combes, F.; Schinnerer, E.; Baker, A. J.; Eckart, A.; Boone, F.; Hunt, L.; Leon, S.; Tacconi, L. J.

    2007-06-01

    Context: Several studies of nearby active galaxies indicate significantly higher HCN-to-CO intensity ratios in AGN (e.g., NGC 1068) than in starburst (e.g., M 82) environments. HCN enhancement can be caused by many different effects, such as higher gas densities and/or temperatures, UV/X-ray radiation, and non-collisional excitation. As active galaxies often exhibit intense circumnuclear star formation, high angular resolution/high sensitivity observations are of paramount importance to disentangling the influence of star formation from that of nuclear activity on the chemistry of the surrounding molecular gas. The tight relation of HCN enhancement and nuclear activity may qualify HCN as an ideal tracer of molecular gas close to the AGN, providing complementary and additional information to that gained via CO. Aims: NGC 6951 houses nuclear and starburst activity, making it an ideal testbed in which to study the effects of different excitation conditions on the molecular gas. Previous lower angular resolution/sensitivity observations of HCN(1-0) carried out with the Nobeyama Millimeter array by Kohno et al. (1999a, ApJ, 511, 157) led to the detection of the starburst ring, but no central emission has been found. Our aim was to search for nuclear HCN emission and, if successful, for differences of the gas properties of the starburst ring and the nucleus. Methods: We used the new A, B, C and D configurations of the IRAM PdBI array to observe HCN(1-0) in NGC 6951 at high angular resolution (1'' ?96 pc) and sensitivity. Results: We detect very compact (?50 pc) HCN emission in the nucleus of NGC 6951, supporting previous hints of nuclear gas structure. Our observations also reveal HCN emission in the starburst ring and resolve it into several peaks, leading to a higher coincidence between the HCN and CO distributions than previously reported by Kohno et al. (1999a). Conclusions: We find a significantly higher HCN-to-CO intensity ratio (?0.4) in the nucleus than in the starburst ring (0.02-0.05). As for NGC 1068, this might result from a higher HCN abundance in the centre due to an X-ray dominated gas chemistry, but a higher gas density/temperature or additional non-collisional excitation of HCN cannot be entirely ruled out, based on these observations. The compact HCN emission is associated with rotating gas in a circumnuclear disk/torus. Based on observations carried out with the IRAM Plateau de Bure Interferometer (PdBI). IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

  15. Development of a Chemiluminescence Method for Gas-Phase HO2 Detection

    NASA Astrophysics Data System (ADS)

    Zheng, J.; Lloyd, J.; Springston, S.

    2003-12-01

    Hydroperoxyl Radical (HO2) is a highly reactive intermediate species that participates in photochemical processes in the troposphere. Accurate measurement of HO2 will facilitate the verification of the ozone production mechanism used by the atmospheric chemistry community. HO2 is also the major source of H2O2, which is responsible for the oxidation of SO2 in droplets. Here, we describe a new HO2 detection method based on flow injection analysis (FIA) with a chemiluminescence detector. Gas-phase HO2 is first scrubbed into a pH 9 borax buffer solution, then injected into a chemiluminescence detector, where HO2 and its conjugate base O2- react with MCLA, a synthetic analog of the luciferin from the crustacean Cypridina, to emit light at 465 nm. This technique shows high sensitivity (DL = 0.1 nM in liquid phase or 1 pptv in gas phase) and selectivity for the HO2 / O2- system. A unique feature of our technique is the calibration with a radiolytic method that uses a 60Co gamma ray source to quantitatively produce stable aqueous HO2 / O2- standards. This calibration method is highly reproducible, producing an instrument response that varies less than 5% from day to day. We tested our instrument in the meteorology field at Brookhaven National Laboratory (BNL), which is considered a clean remote rural site with background ozone levels about 30 ppbv. On July 17, 2003, a clear sunny day, with a steady NW wind, HO2 started to build up after sunrise and reached a maximum of 9 pptv at about 3 pm local time, approximately two hours after the maximum solar intensity. Our technique has the advantages of simplicity, low cost and ease of operation. It is especially suitable for field measurements, where space and energy resources are usually limited.

  16. Selective Detection of Formaldehyde Gas Using a Cd-Doped TiO2-SnO2 Sensor

    PubMed Central

    Zeng, Wen; Liu, Tianmo; Wang, Zhongchang; Tsukimoto, Susumu; Saito, Mitsuhiro; Ikuhara, Yuichi

    2009-01-01

    We report the microstructure and gas-sensing properties of a nonequilibrium TiO2-SnO2 solid solution prepared by the sol-gel method. In particular, we focus on the effect of Cd doping on the sensing behavior of the TiO2-SnO2 sensor. Of all volatile organic compound gases examined, the sensor with Cd doping exhibits exclusive selectivity as well as high sensitivity to formaldehyde, a main harmful indoor gas. The key gas-sensing quantities, maximum sensitivity, optimal working temperature, and response and recovery time, are found to meet the basic industrial needs. This makes the Cd-doped TiO2-SnO2 composite a promising sensor material for detecting the formaldehyde gas. PMID:22291551

  17. Measurement of nitrogen content in a gas mixture by transforming the nitrogen into a substance detectable with nondispersive infrared detection

    DOEpatents

    Owen, Thomas E.; Miller, Michael A.

    2007-03-13

    A method of determining the amount of nitrogen in a gas mixture. The constituent gases of the mixture are dissociated and transformed to create a substance that may measured using nondispersive infrared adsorption techniques.

  18. Measurement of nitrogen content in a gas mixture by transforming the nitrogen into a substance detectable with nondispersive infrared detection

    DOEpatents

    Owen, Thomas E. (Helotes, TX); Miller, Michael A. (San Antonio, TX)

    2010-08-24

    A method of determining the amount of nitrogen in a gas mixture. The constituent gases of the mixture are dissociated and transformed to create a substance that may measured using nondispersive infrared adsorption techniques.

  19. Naturally fractured tight gas reservoir detection optimization. Annual report, September 1993--September 1994

    SciTech Connect

    NONE

    1994-10-01

    This report is an annual summarization of an ongoing research in the field of modeling and detecting naturally fractured gas reservoirs. The current research is in the Piceance basin of Western Colorado. The aim is to use existing information to determine the most optimal zone or area of fracturing using a unique reaction-transport-mechanical (RTM) numerical basin model. The RTM model will then subsequently help map subsurface lateral and vertical fracture geometries. The base collection techniques include in-situ fracture data, remote sensing, aeromagnetics, 2-D seismic, and regional geologic interpretations. Once identified, high resolution airborne and spaceborne imagery will be used to verify the RTM model by comparing surficial fractures. If this imagery agrees with the model data, then a further investigation using a three-dimensional seismic survey component will be added. This report presents an overview of the Piceance Creek basin and then reviews work in the Parachute and Rulison fields and the results of the RTM models in these fields.

  20. Nonlinear Bayesian Algorithms for Gas Plume Detection and Estimation from Hyper-spectral Thermal Image Data

    SciTech Connect

    Heasler, Patrick G.; Posse, Christian; Hylden, Jeff L.; Anderson, Kevin K.

    2007-06-13

    This paper presents a nonlinear Bayesian regression algorithm for the purpose of detecting and estimating gas plume content from hyper-spectral data. Remote sensing data, by its very nature, is collected under less controlled conditions than laboratory data. As a result, the physics-based model that is used to describe the relationship between the observed remotesensing spectra, and the terrestrial (or atmospheric) parameters that we desire to estimate, is typically littered with many unknown "nuisance" parameters (parameters that we are not interested in estimating, but also appear in the model). Bayesian methods are well-suited for this context as they automatically incorporate the uncertainties associated with all nuisance parameters into the error estimates of the parameters of interest. The nonlinear Bayesian regression methodology is illustrated on realistic simulated data from a three-layer model for longwave infrared (LWIR) measurements from a passive instrument. This shows that this approach should permit more accurate estimation as well as a more reasonable description of estimate uncertainty.

  1. Multi-colorimetric sensor array for detection of explosives in gas and liquid phase

    NASA Astrophysics Data System (ADS)

    Kostesha, N.; Alstrøm, T. S.; Johnsen, C.; Nielsen, K. A.; Jeppesen, J. O.; Larsen, J.; Boisen, A.; Jakobsen, M. H.

    2011-05-01

    In the framework of the research project "Xsense" at the Technical University of Denmark (DTU) we are developing a simple colorimetric sensor array which can be useful in detection of explosives like DNT, TATP, HMX, RDX and identification of reagents needed for making homemade explosives. The technology is based on an array of chemoselective compounds immobilized on a solid support. Upon exposure to the analyte in suspicion the colorimetric array changes color. Each chosen compound reacts chemo-selectively with analytes of interest. A change in a color signature indicates the presence of unknown explosives and volatile organic compounds (VOCs). We are working towards the selection of compounds that undergo color changes in the presence of explosives and VOCs, as well as the development of an immobilization method for the molecules. Digital imaging of the colorimetric array before and after exposure to the analytes creates a color difference map which gives a unique fingerprint for each explosive and VOCs. Such sensing technology can be used for screening relevant explosives in a complex background as well as to distinguish mixtures of volatile organic compounds distributed in gas and liquid phases. This sensor array is inexpensive, and can potentially be produced as single use disposable.

  2. Coupling gas chromatography and electronic nose detection for detailed cigarette smoke aroma characterization.

    PubMed

    Rambla-Alegre, Maria; Tienpont, Bart; Mitsui, Kazuhisa; Masugi, Eri; Yoshimura, Yuta; Nagata, Hisanori; David, Frank; Sandra, Pat

    2014-10-24

    Aroma characterization of whole cigarette smoke samples using sensory panels or electronic nose (E-nose) devices is difficult due to the masking effect of major constituents and solvent used for the extraction step. On the other hand, GC in combination with olfactometry detection does not allow to study the delicate balance and synergetic effect of aroma solutes. To overcome these limitations a new instrumental set-up consisting of heart-cutting gas chromatography using a capillary flow technology based Deans switch and low thermal mass GC in combination with an electronic nose device is presented as an alternative to GC-olfactometry. This new hyphenated GC-E-nose configuration is used for the characterization of cigarette smoke aroma. The system allows the transfer, combination or omission of selected GC fractions before injection in the E-nose. Principal component analysis (PCA) and discriminant factor analysis (DFA) allowed clear visualizing of the differences among cigarette brands and classifying them independently of their nicotine content. Omission and perceptual interaction tests could also be carried out using this configuration. The results are promising and suggest that the GC-E-nose hyphenation is a good approach to measure the contribution level of individual compounds to the whole cigarette smoke. PMID:25260341

  3. Automated thermochemolysis reactor for detection of Bacillus anthracis endospores by gas chromatography-mass spectrometry.

    PubMed

    Li, Dan; Rands, Anthony D; Losee, Scott C; Holt, Brian C; Williams, John R; Lammert, Stephen A; Robison, Richard A; Tolley, H Dennis; Lee, Milton L

    2013-05-01

    An automated sample preparation system was developed and tested for the rapid detection of Bacillus anthracis endospores by gas chromatography-mass spectrometry (GC-MS) for eventual use in the field. This reactor is capable of automatically processing suspected bio-threat agents to release and derivatize unique chemical biomarkers by thermochemolysis (TCM). The system automatically controls the movement of sample vials from one position to another, crimping of septum caps onto the vials, precise delivery of reagents, and TCM reaction times and temperatures. The specific operations of introduction of sample vials, solid phase microextraction (SPME) sampling, injection into the GC-MS system, and ejection of used vials from the system were performed manually in this study, although they can be integrated into the automated system. Manual SPME sampling is performed by following visual and audible signal prompts for inserting the fiber into and retracting it from the sampling port. A rotating carousel design allows for simultaneous sample collection, reaction, biomarker extraction and analysis of sequential samples. Dipicolinic acid methyl ester (DPAME), 3-methyl-2-butenoic acid methyl ester (a fragment of anthrose) and two methylated sugars were used to compare the performance of the autoreactor with manual TCM. Statistical algorithms were used to construct reliable bacterial endospore signatures, and 24 out of 25 (96%) endospore-forming Bacillus species were correctly identified in a statistically designed test. PMID:23601976

  4. Remote detection NMR imaging of gas phase hydrogenation in microfluidic chips.

    PubMed

    Zhivonitko, Vladimir V; Telkki, Ville-Veikko; Leppäniemi, Jarmo; Scotti, Gianmario; Franssila, Sami; Koptyug, Igor V

    2013-04-21

    The heterogeneous hydrogenation reaction of propene into propane in microreactors is studied by remote detection (RD) nuclear magnetic resonance (NMR). The reactors consist of 36 parallel microchannels (50 × 50 ?m(2) cross sections) coated with a platinum catalyst. We show that RD NMR is capable of monitoring reactions with sub-millimeter spatial resolution over a field-of-view of 30 × 8 mm(2) with a steady-state time-of-flight time resolution in the tens of milliseconds range. The method enables the visualization of active zones in the reactors, and time-of-flight is used to image the flow velocity variations inside the reactor. The overall reaction yields determined by NMR varied from 10% to 50%, depending on the flow rate, temperature and length of the reaction channels. The reaction yield was highest for the channels with the lowest flow velocity. Propane T1 relaxation time in the channels, estimated by means of RD NMR images, was 270 ± 18 ms. No parahydrogen-induced polarization (PHIP) was observed in experiments carried out using parahydrogen-enriched H2, indicating fast spreading of the hydrogen atoms on the sputtered Pt surface. In spite of the low concentration of gases, RD NMR made imaging of gas phase hydrogenation of propene in microreactors feasible, and it is a highly versatile method for characterizing on-chip chemical reactions. PMID:23435499

  5. Valid internal standard technique for arson detection based on gas chromatography-mass spectrometry.

    PubMed

    Salgueiro, Pedro A S; Borges, Carlos M F; Bettencourt da Silva, Ricardo J N

    2012-09-28

    The most popular procedures for the detection of residues of accelerants in fire debris are the ones published by the American Society for Testing and Materials (ASTM E1412-07 and E1618-10). The most critical stages of these tests are the conservation of fire debris from the sampling to the laboratory, the extraction of residues of accelerants from the debris to the activated charcoal strips (ACS) and from those to the final solvent, as well as the analysis of sample extract by gas chromatography-mass spectrometry (GC-MS) and the interpretation of the instrumental signal. This work proposes a strategy for checking the quality of the sample conservation, the accelerant residues transference to final solvent and GC-MS analysis, using internal standard additions. It is used internal standards ranging from a highly volatile compound for checking debris conservation to low volatile compound for checking GC-MS repeatability. The developed quality control (QC) parameters are not affected by GC-MS sensitivity variation and, specifically, the GC-MS performance control is not affected by ACS adsorption saturation that may mask test performance deviations. The proposed QC procedure proved to be adequate to check GC-MS repeatability, ACS extraction and sample conservation since: (1) standard additions are affected by negligible uncertainty and (2) observed dispersion of QC parameters are fit for its intended use. PMID:22920302

  6. TechNotes November 2014www.ll.mit.edu The detection and localization of gas

    E-print Network

    Williams, Brian C.

    such as methane from leaking natural gas pipelines or nitrogen oxides from failing electrical equipment require high sensitivity to the target gas and insensitivity to non-target gases. Infrared (IR) absorption

  7. Gas chromatography analysis with olfactometric detection (GC-O) as a useful methodology for chemical characterization of odorous compounds.

    PubMed

    Brattoli, Magda; Cisternino, Ezia; Dambruoso, Paolo Rosario; de Gennaro, Gianluigi; Giungato, Pasquale; Mazzone, Antonio; Palmisani, Jolanda; Tutino, Maria

    2013-01-01

    The gas chromatography-olfactometry (GC-O) technique couples traditional gas chromatographic analysis with sensory detection in order to study complex mixtures of odorous substances and to identify odor active compounds. The GC-O technique is already widely used for the evaluation of food aromas and its application in environmental fields is increasing, thus moving the odor emission assessment from the solely olfactometric evaluations to the characterization of the volatile components responsible for odor nuisance. The aim of this paper is to describe the state of the art of gas chromatography-olfactometry methodology, considering the different approaches regarding the operational conditions and the different methods for evaluating the olfactometric detection of odor compounds. The potentials of GC-O are described highlighting the improvements in this methodology relative to other conventional approaches used for odor detection, such as sensoristic, sensorial and the traditional gas chromatographic methods. The paper also provides an examination of the different fields of application of the GC-O, principally related to fragrances and food aromas, odor nuisance produced by anthropic activities and odorous compounds emitted by materials and medical applications. PMID:24316571

  8. Gas Chromatography Analysis with Olfactometric Detection (GC-O) as a Useful Methodology for Chemical Characterization of Odorous Compounds

    PubMed Central

    Brattoli, Magda; Cisternino, Ezia; Dambruoso, Paolo Rosario; de Gennaro, Gianluigi; Giungato, Pasquale; Mazzone, Antonio; Palmisani, Jolanda; Tutino, Maria

    2013-01-01

    The gas chromatography-olfactometry (GC-O) technique couples traditional gas chromatographic analysis with sensory detection in order to study complex mixtures of odorous substances and to identify odor active compounds. The GC-O technique is already widely used for the evaluation of food aromas and its application in environmental fields is increasing, thus moving the odor emission assessment from the solely olfactometric evaluations to the characterization of the volatile components responsible for odor nuisance. The aim of this paper is to describe the state of the art of gas chromatography-olfactometry methodology, considering the different approaches regarding the operational conditions and the different methods for evaluating the olfactometric detection of odor compounds. The potentials of GC-O are described highlighting the improvements in this methodology relative to other conventional approaches used for odor detection, such as sensoristic, sensorial and the traditional gas chromatographic methods. The paper also provides an examination of the different fields of application of the GC-O, principally related to fragrances and food aromas, odor nuisance produced by anthropic activities and odorous compounds emitted by materials and medical applications. PMID:24316571

  9. Development of a magnetic coating for gas pipe detection. Final report, May 1987June 1988

    Microsoft Academic Search

    1989-01-01

    The inability to accurately locate plastic gas pipe after it is buried has been a troublesome problem since plastic pipe began being used for natural gas distribution. Electromagnetic pipe locaters have been available to the gas industry for decades. However, this technology cannot locate plastic pipe without the use of a metallic wire or tape buried with the pipe. To

  10. A telescope with microstrip gas chambers for the detection of charged products in heavy-ion reactions

    NASA Astrophysics Data System (ADS)

    Gramegna, F.; Abbondanno, U.; Andreano, A.; Bassini, R.; Bonutti, F.; Bruno, M.; Casini, G.; D'Agostino, M.; Manzin, G.; Margagliotti, G. V.; Mastinu, P. F.; Milazzo, P. M.; Moroni, A.; Squarcini, M.; Tonetto, F.; Vannini, G.; Vannucci, L.

    1997-02-01

    Prototypes of a ?E-E telescope, designed to detect and identify with low-energy threshold both light charged particles and heavy fragments, are described. They are based on a gas drift chamber which conveys primary ionization electrons on gas microstrip devices where multiplication occurs and the energy loss signals are generated. Silicon detectors or CsI(T1) crystals operate as residual energy detectors. The prototypes were tested both with a source and heavy ion beams. Performances, mainly related to energy resolution, charge identification and angle resolution, are reported.

  11. Rapid and selective detection of acetone using hierarchical ZnO gas sensor for hazardous odor markers application.

    PubMed

    Jia, Qianqian; Ji, Huiming; Zhang, Ying; Chen, Yalu; Sun, Xiaohong; Jin, Zhengguo

    2014-07-15

    Hierarchical nanostructured ZnO dandelion-like spheres were synthesized via solvothermal reaction at 200°C for 4h. The products were pure hexagonal ZnO with large exposure of (002) polar facet. Side-heating gas sensor based on hierarchical ZnO spheres was prepared to evaluate the acetone gas sensing properties. The detection limit to acetone for the ZnO sensor is 0.25ppm. The response (Ra/Rg) toward 100ppm acetone was 33 operated at 230°C and the response time was as short as 3s. The sensor exhibited remarkable acetone selectivity with negligible response toward other hazardous gases and water vapor. The high proportion of electron depletion region and oxygen vacancies contributed to high gas response sensitivity. The hollow and porous structure of dandelion-like ZnO spheres facilitated the diffusion of gas molecules, leading to a rapid response speed. The largely exposed (002) polar facets could adsorb acetone gas molecules easily and efficiently, resulting in a rapid response speed and good selectivity of hierarchical ZnO spheres gas sensor at low operating temperature. PMID:24892776

  12. [Mid-infrared distributed-feedback quantum cascade laser-based photoacoustic detection of trace methane gas].

    PubMed

    Tan, Song; Liu, Wan-feng; Wang, Li-jun; Zhang, Jin-chuan; Li, Lu; Liu, Jun-qi; Liu, Feng-qi; Wang, Zhan-guo

    2012-05-01

    There have been considerable interests in methane detection based on infrared absorption spectroscopy for industrial and environment monitoring. The authors report on the realization of photoacoustic detection of methane (CH4) using mid-infrared distributed-feedback quantum cascade laser (DFB-QCL). The absorption line at 1316.83 cm(-1) was selected for CH4 detection, which can be reached by the self-manufactured DFB-QCL source operating in pulsed mode near 7.6 microm at room-temperature. The CH4 gas is filled to a Helmholtz resonant photoacoustic cell, which was equipped with a commercial electret microphone. The DFB-QCL was operated at 234 Hz with an 80 mW optical peak power. A detection limit of 189 parts per billion in volume was derived when the signal-to-noise ratio equaled 1. PMID:22827065

  13. Warm-Hot Gas in and around the Milky Way: Detection and Implications of OVII Absorption toward LMC X-3

    E-print Network

    Q. D. Wang; Y. Yao; T. M. Tripp; T. -T. Fang; W. Cui; F. Nicastro; S. Mathur; R. J. Williams; L. Song; R. Croft

    2005-08-30

    X-ray absorption lines of highly-ionized species such as OVII at about zero redshift have been firmly detected in the spectra of several active galactic nuclei. However, the location of the absorbing gas remains a subject of debate. To separate the Galactic and extragalactic contributions to the absorption, we have obtained Chandra LETG-HRC and FUSE observations of the black hole X-ray binary LMC X--3. A joint analysis of the detected OVII and Ne IX Kalpha lines, together with the non-detection of the OVII Kbeta and OVIII Kalpha lines, gives the measurements of the temperature, velocity dispersion, and hot oxygen column density. The X-ray data also allow us to place a 95% confidence lower limit to the Ne/O ratio as 0.14. The OVII line centroid and its relative shift from the Galactic OI Kalpha absorption line, detected in the same observations, are inconsistent with the systemic velocity of LMC X--3 ($+310 {\\rm km s^{-1}}$). The far-UV spectrum shows OVI absorption at Galactic velocities, but no OVI absorption is detected at the LMC velocity at $> 3\\sigma$ significance. Both the nonthermal broadening and the decreasing scale height with the increasing ionization state further suggest an origin of the highly-ionized gas in a supernova-driven galactic fountain. In addition, we estimate the warm and hot electron column densities from our detected OVII Kalpha line in the LMC X--3 X-ray spectra and from the dispersion measure of a pulsar in the LMC vicinity. We then infer the O/H ratio of the gas to be $\\gtrsim 8 \\times 10^{-5}$, consistent with the chemically-enriched galactic fountain scenario. We conclude that the Galactic hot interstellar medium should in general substantially contribute to zero-redshift X-ray absorption lines in extragalactic sources.

  14. A broadband absorption spectrometer using light emitting diodes for ultrasensitive, in situ trace gas detection.

    PubMed

    Langridge, Justin M; Ball, Stephen M; Shillings, Alexander J L; Jones, Roderic L

    2008-12-01

    A broadband absorption spectrometer has been developed for highly sensitive and target-selective in situ trace gas measurements. The instrument employs two distinct modes of operation: (i) broadband cavity enhanced absorption spectroscopy (BBCEAS) is used to quantify the concentration of gases in sample mixtures from their characteristic absorption features, and (ii) periodic measurements of the cavity mirrors' reflectivity are made using step-scan phase shift cavity ringdown spectroscopy (PSCRDS). The latter PSCRDS method provides a stand-alone alternative to the more usual method of determining mirror reflectivities by measuring BBCEAS absorption spectra for calibration samples of known composition. Moreover, the instrument's two modes of operation use light from the same light emitting diode transmitted through the cavity in the same optical alignment, hence minimizing the potential for systematic errors between mirror reflectivity determinations and concentration measurements. The ability of the instrument to quantify absorber concentrations is tested in instrument intercomparison exercises for NO(2) (versus a laser broadband cavity ringdown spectrometer) and for H(2)O (versus a commercial hygrometer). A method is also proposed for calculating effective absorption cross sections for fitting the differential structure in BBCEAS spectra due to strong, narrow absorption lines that are under-resolved and hence exhibit non-Beer-Lambert law behavior at the resolution of the BBCEAS measurements. This approach is tested on BBCEAS spectra of water vapor's 4v+delta absorption bands around 650 nm. The most immediate analytical application of the present instrument is in quantifying the concentration of reactive trace gases in the ambient atmosphere. The instrument's detection limits for NO(3) as a function of integration time are considered in detail using an Allan variance analysis. Experiments under laboratory conditions produce a 1sigma detection limit of 0.25 pptv for a 10 s acquisition time, which improves with further signal averaging to 0.09 pptv in 400 s. Finally, an example of the instrument's performance under field work conditions is presented, in this case of measurements of the sum of NO(3)+N(2)O(5) concentrations in the marine boundary layer acquired during the Reactive Halogens in the Marine Boundary Layer field campaign. PMID:19123548

  15. A broadband absorption spectrometer using light emitting diodes for ultrasensitive, in situ trace gas detection

    SciTech Connect

    Langridge, Justin M.; Shillings, Alexander J. L.; Jones, Roderic L. [Department of Chemistry, University Chemical Laboratory, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Ball, Stephen M. [Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

    2008-12-15

    A broadband absorption spectrometer has been developed for highly sensitive and target-selective in situ trace gas measurements. The instrument employs two distinct modes of operation: (i) broadband cavity enhanced absorption spectroscopy (BBCEAS) is used to quantify the concentration of gases in sample mixtures from their characteristic absorption features, and (ii) periodic measurements of the cavity mirrors' reflectivity are made using step-scan phase shift cavity ringdown spectroscopy (PSCRDS). The latter PSCRDS method provides a stand-alone alternative to the more usual method of determining mirror reflectivities by measuring BBCEAS absorption spectra for calibration samples of known composition. Moreover, the instrument's two modes of operation use light from the same light emitting diode transmitted through the cavity in the same optical alignment, hence minimizing the potential for systematic errors between mirror reflectivity determinations and concentration measurements. The ability of the instrument to quantify absorber concentrations is tested in instrument intercomparison exercises for NO{sub 2} (versus a laser broadband cavity ringdown spectrometer) and for H{sub 2}O (versus a commercial hygrometer). A method is also proposed for calculating effective absorption cross sections for fitting the differential structure in BBCEAS spectra due to strong, narrow absorption lines that are under-resolved and hence exhibit non-Beer-Lambert law behavior at the resolution of the BBCEAS measurements. This approach is tested on BBCEAS spectra of water vapor's 4v+{delta} absorption bands around 650 nm. The most immediate analytical application of the present instrument is in quantifying the concentration of reactive trace gases in the ambient atmosphere. The instrument's detection limits for NO{sub 3} as a function of integration time are considered in detail using an Allan variance analysis. Experiments under laboratory conditions produce a 1{sigma} detection limit of 0.25 pptv for a 10 s acquisition time, which improves with further signal averaging to 0.09 pptv in 400 s. Finally, an example of the instrument's performance under field work conditions is presented, in this case of measurements of the sum of NO{sub 3}+N{sub 2}O{sub 5} concentrations in the marine boundary layer acquired during the Reactive Halogens in the Marine Boundary Layer field campaign.

  16. A broadband absorption spectrometer using light emitting diodes for ultrasensitive, in situ trace gas detection

    NASA Astrophysics Data System (ADS)

    Langridge, Justin M.; Ball, Stephen M.; Shillings, Alexander J. L.; Jones, Roderic L.

    2008-12-01

    A broadband absorption spectrometer has been developed for highly sensitive and target-selective in situ trace gas measurements. The instrument employs two distinct modes of operation: (i) broadband cavity enhanced absorption spectroscopy (BBCEAS) is used to quantify the concentration of gases in sample mixtures from their characteristic absorption features, and (ii) periodic measurements of the cavity mirrors' reflectivity are made using step-scan phase shift cavity ringdown spectroscopy (PSCRDS). The latter PSCRDS method provides a stand-alone alternative to the more usual method of determining mirror reflectivities by measuring BBCEAS absorption spectra for calibration samples of known composition. Moreover, the instrument's two modes of operation use light from the same light emitting diode transmitted through the cavity in the same optical alignment, hence minimizing the potential for systematic errors between mirror reflectivity determinations and concentration measurements. The ability of the instrument to quantify absorber concentrations is tested in instrument intercomparison exercises for NO2 (versus a laser broadband cavity ringdown spectrometer) and for H2O (versus a commercial hygrometer). A method is also proposed for calculating effective absorption cross sections for fitting the differential structure in BBCEAS spectra due to strong, narrow absorption lines that are under-resolved and hence exhibit non-Beer-Lambert law behavior at the resolution of the BBCEAS measurements. This approach is tested on BBCEAS spectra of water vapor's 4v+? absorption bands around 650 nm. The most immediate analytical application of the present instrument is in quantifying the concentration of reactive trace gases in the ambient atmosphere. The instrument's detection limits for NO3 as a function of integration time are considered in detail using an Allan variance analysis. Experiments under laboratory conditions produce a 1? detection limit of 0.25 pptv for a 10 s acquisition time, which improves with further signal averaging to 0.09 pptv in 400 s. Finally, an example of the instrument's performance under field work conditions is presented, in this case of measurements of the sum of NO3+N2O5 concentrations in the marine boundary layer acquired during the Reactive Halogens in the Marine Boundary Layer field campaign.

  17. A systems level characterization and tradespace evaluation of a simulated airborne Fourier transform infrared spectrometer for gas detection

    NASA Astrophysics Data System (ADS)

    Weiner, Aaron

    The remote sensing gas detection problem is one with no straightforward solution. While success has been achieved in detecting and identifying gases released from industrial stacks and other large plumes, the fugitive gas detection problem is far more complex. Fugitive gas represents a far smaller target and may be generated by leaking pipes, vents, or small scale chemical production. The nature of fugitive gas emission is such that one has no foreknowledge of the location, quantity, or transient rate of the targeted effluent which requires one to cover a broad area with high sensitivity. In such a scenario, a mobile airborne platform would be a likely candidate. Further, the spectrometer used for gas detection should be capable of rapid scan rates to prevent spatial and spectral smearing, while maintaining high resolution to aid in species identification. Often, insufficient signal to noise (SNR) prevents spectrometers from delivering useful results under such conditions. While common dispersive element spectrometers (DES) suffer from decreasing SNR with increasing spectral dispersion, Fourier Transform Spectrometers (FTS) generally do not and would seemingly be an ideal choice for such an application. FTS are ubiquitous in chemical laboratories and in use as ground based spectrometers, but have not become as pervasive in mobile applications. While FTS spectrometers would otherwise be ideal for high resolution rapid scanning in search of gaseous effluents, when conducted via a mobile platform the process of optical interferogram formation to form spectra is corrupted when the input signal is temporally unstable. This work seeks to explore the tradespace of an airborne Michelson based FTS in terms of modeling and characterizing the performance degradation over a variety of environmental and optical parameters. The major variables modeled and examined include: maximum optical path distance (resolution), scan rate, platform velocity, altitude, atmospheric and background emissivity variability, gas target parameters such as temperature, concentration-pathlength, confuser gas presence, and optical effects including apodization effects, single and double-sided interferograms, internal mirror positional accuracy errors, and primary mirror jitter effects. It is through an understanding of how each of the aforementioned variables impacts the gas detection performance that one can constrain design parameters in developing and engineering an FTS suitable to the airborne environment. The instrument model was compared to output from ground-based FTS instruments as well as airborne data taken from the Airborne Hyperspectral Imager (AHI) and found to be in good agreement. Monte Carlo studies were used to map the impact of the performance variables and unique detection algorithms, based on common detection scores, were used to quantify performance degradation. Scene-based scenarios were employed to evaluate performance of a scanning FTS under variable and complex conditions. It was found that despite critical sampling errors and rapidly varying radiance signals, while losing the ability to reproduce a radiometrically accurate spectrum, an FTS offered the unique ability to reproduce spectral evidence of a gas in scenarios where a dispersive element spectrometer (DES) might not.

  18. Monitoring Requirements and Methods for Greenhouse Gas Management and Climate Change Detection

    NASA Astrophysics Data System (ADS)

    Birdsey, R.; Pan, Y.; Clark, K.; Hom, J.

    2007-12-01

    Climate change policy and management require monitoring data to support decision making. Availability of good data about past trends, and projections based on reasonable assumptions and models, can support debate about response options and avoid the pitfall of arguing about information quality. A hierarchical or multi-tier approach to environmental monitoring has been used efficiently for many decades, and can be linked with experiments and process modeling to improve natural resource assessments. Consideration of spatial and temporal scale can align data requirements with the information needed to facilitate separation of causal factors, e.g., factoring out natural effects from human-induced effects on the carbon cycle. Here we describe a 3-tier integrated monitoring hierarchy: intensive process-level monitoring, landscape-scale monitoring, and regional monitoring. Information at each tier may be used independently or integrated across tiers. Methods to integrate information include statistical techniques for diagnostic analysis, and ecosystem models for prognostic analysis. We illustrate the methods and results for each tier using data and analyses for the Pinelands Management Area of New Jersey, a reserved area of 360,000 ha. A cluster of flux towers and associated intensive-site measurements comprises the process monitoring. A network of biometric monitoring sites represents the landscape conditions, and forest inventory with remote sensing is used to characterize the region. This approach is capable of closing the regional carbon budget, i.e., accounting for all exchanges of carbon between the land, atmosphere, and ocean. It is also an excellent platform for monitoring the effects of climate change and factoring out different effects -- the system was designed to provide information about dangerous fire weather and identify needs to manage wildfire fuels. The New Jersey Pinelands site is part of a national network of multi-scale monitoring sites that can meet many of the emerging needs for greenhouse gas management and climate change detection.

  19. Determination of methyl bromide in foods by headspace capillary gas chromatography with electron capture detection.

    PubMed

    Page, B D; Avon, R J

    1989-01-01

    Methyl bromide (MB, bromomethane) is determined in a variety of foods by headspace capillary gas chromatography with electron capture detection. The comminuted food sample as an aqueous sodium sulfate slurry is equilibrated with stirring for 1 h at room temperature before a 1 mL headspace aliquot is removed and injected using a modified on-column syringe needle. Methyl bromide is cryogenically focussed at -60 degrees C and then eluted by temperature programming. The procedure requires blending of soft samples, e.g. raisins, prunes, or oranges, and ultrasonic homogenization of hard samples, e.g. wheat, cocoa beans, corn, or nuts, with portions of water and ice so the final temperature of the food-water slurry is less than 1 degree C. A 20 g aliquot (4 g food) is then added to a cold headspace vial containing 4 g sodium sulfate. Losses of MB during a 3.5 min ultrasonic homogenization of wheat were 11% at 0.95 ppb and 4.4% at 4.8 ppb. For flour, cocoa, and finely divided spices, which do not require blending, 4 g is added to the cold headspace vial containing 16 mL cold water and 4 g sodium sulfate. Studies show that comminution of wheat or peanuts must be carried out to release MB trapped within the food so the headspace equilibrium can be attained in 1 h as well as to obtain homogeneous samples and representative sampling. No interferences were noted with the above foods or with many grain-based baking mixes analyzed.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2808244

  20. Gas reservoir sweet spot detection and delineation in Rocky Mountain laramide basins. Topical report, May 1993March 1996

    Microsoft Academic Search

    R. C. Surdam; W. O. Iverson; P. Yin

    1995-01-01

    The determination of the position and configuration of the pressure boundary between normal and anomalously pressured regimes, and the detection and delineation of porosity\\/permeability `sweet spots` below this boundary are the two most important elements in exploring for basin-center or deep-basin gas in Rocky Mountain Laramide Basins. These two exploration elements from the basis for a new exploration paradigm. To

  1. High-Voltage on-Site Commissioning Tests for Gas-Insulated Substations Using UHF Partial Discharge Detection

    Microsoft Academic Search

    R. Bell; C. Charlson; S. Halliday; T. Irwin; J. Lopez-Roldan; J. Nixon

    2002-01-01

    This paper describes the practical application of the UHF Partial Discharge Detection method that VA TECH Reyrolle has routinely applied to high-voltage on-site commissioning tests on gas-insulated substations (GIS) for over 10 years. The location of the partial discharge (PD) sensors has a significant effect on the sensitivity of the UHF method. Research has been undertaken to quantify the parameters

  2. Kinetics of Ethanol and Acetaldehyde Production in Fermenting Wheat Dough by Laser-Based Trace Gas Detection

    Microsoft Academic Search

    S. Tomás; F. J. M. Harren

    2001-01-01

    The fermentation process of wheat dough was studied by laser-based trace gas detection. A CO-laser-driven photoacoustic spectrometer was used to monitor simultaneously, in real time, the ethanol and acetaldehyde production rates of two commercial types of active dry yeast (Saccharomyces cerevisiae) in wheat dough substrates. Both types of yeast, Oand B, produced ethanol for 5 hours. Acetaldehyde was yielded only

  3. Acoustic detection of gas emissions within the submerged section of the North Anatolian Fault Zone in the Sea of Marmara

    Microsoft Academic Search

    L. Géli; P. Henry; S. Dupré; D. Voelker; T. Zitter; X. Le Pichon; M. Tryon; N. Cagatay

    2007-01-01

    The 38 kHz, single beam, echo-sounder SIMRAD EK-60 was operated during the Marnaut cruise (May-June 2007) onboard the RV L'Atalante to detect acoustic anomalies related to the presence of gas bubbles in the water column. In the south Cinarcik Basin, strong acoustic anomalies have been found along N140 normal faults within a 3 km wide swath oriented N100. The swath

  4. Nuclear magnetic resonance applied to gas detection in a highly laminated Gulf of Mexico turbidite invaded with synthetic oil filtrate

    SciTech Connect

    Moore, M.A.; Akkurt, R.

    1996-12-31

    A recently developed time-domain nuclear magnetic resonance (NMR) technique applying matched filters to the difference of raw echo trains acquired with different wait times has proven effective in detecting and quantifying free gas in a highly laminated Gulf of Mexico (GOM) turbidite deposit expected to be badly invaded by synthetic oil-base drilling fluid. This case history is the first documented use of this approach under these conditions, and it clearly met objectives where the more conventional differential spectrum method (DSM) failed. The technique was applied to data acquired in the Shell-operated Tahoe Field. The VK783 No. 5 penetration encountered one-hundred-seventy gross feet of laminated turbidite reservoir averaging 50% net to gross through much of the interval. The well was thirteen-hundred psi overbalanced, and this, combined with the miscible filtrate made severe invasion and near residual gas saturations a certainty near the wellbore. Conventional wireline gas indicators such as neutron-density crossover and the various cross plots fail in this environment due to tool inability to resolve the sand beds and to the abundance of shale laminae, and is aggravated by the invasion. Fluid typing is primarily done with fluid pressure gradients established via formation tester. For this well, the logging program included quad-combo, NMR (MRIL-C{reg_sign}) and formation tester. The formation tester proved gas to base in the reservoir, showing a .0951 psi/ft fluid pressure gradient. The conventional DSM analysis carried out in the T{sub 2} domain showed a strong signal from the invading filtrate, but was ambiguous with respect to gas detection. Careful examination of the raw echo train data using matched filters showed clearly both heavy filtrate invasion, and the presence of gas in low saturations.

  5. Gas Solubility in Oil-Based Drilling Fluids: Effects on Kick Detection

    Microsoft Academic Search

    David Thomas; E. A. Turek

    1984-01-01

    This paper describes the effects of gas solubility on the properties of oil-based drilling fluids. Prediction methods for gas solubility in oil-based muds were tested by experimental work and found acceptable. Expansion of discrete mixtures of mud and gas are predicted. A blowout simulation program was written and used to predict the effects of a kick on the surface-observable indicators

  6. Gas chromatography negative ion chemical ionization mass spectrometry: application to the detection of alkyl nitrates and halocarbons in the atmosphere.

    PubMed

    Worton, David R; Mills, Graham P; Oram, David E; Sturges, William T

    2008-08-01

    Alkyl nitrates and very short-lived halocarbon species are important atmospheric trace gas species that are present in the low to sub parts per trillion concentration range. This presents an analytical challenge for their detection and quantification that requires instrumentation with high sensitivity and selectivity. In this paper, we present a new in situ gas chromatograph negative ion chemical ionization mass spectrometer (GC/NICI-MS) coupled to a non-cryogen sample pre-concentration system. This instrument, with detection limits of <0.01 ppt, is capable of detecting and quantifying a large suite of alkyl nitrate and halocarbon species with high sensitivity and precision. The effects of ion source temperature and reagent gas pressure on the ionization efficiency of the NICI mode are investigated and the results are used to optimize the sensitivity. The NICI mode is compared to the more frequently used electron impact (EI) ionization and the enhancements in sensitivity are presented for all the calibrated compounds. PMID:18586255

  7. An optical sensor for detecting the contact location of a gas-liquid interface on a body.

    PubMed

    Belden, Jesse; Jandron, Michael

    2014-08-01

    An optical sensor for detecting the dynamic contact location of a gas-liquid interface along the length of a body is described. The sensor is developed in the context of applications to supercavitating bodies requiring measurement of the dynamic cavity contact location; however, the sensing method is extendable to other applications as well. The optical principle of total internal reflection is exploited to detect changes in refractive index of the medium contacting the body at discrete locations along its length. The derived theoretical operation of the sensor predicts a signal attenuation of 18 dB when a sensed location changes from air-contacting to water-contacting. Theory also shows that spatial resolution (d) scales linearly with sensor length (L(s)) and a resolution of 0.01L(s) can be achieved. A prototype sensor is constructed from simple components and response characteristics are quantified for different ambient light conditions as well as partial wetting states. Three methods of sensor calibration are described and a signal processing framework is developed that allows for robust detection of the gas-liquid contact location. In a tank draining experiment, the prototype sensor resolves the water level with accuracy limited only by the spatial resolution, which is constrained by the experimental setup. A more representative experiment is performed in which the prototype sensor accurately measures the dynamic contact location of a gas cavity on a water tunnel wall. PMID:25173325

  8. Gas

    MedlinePLUS

    ... and pain in the belly—especially after a big meal. Foods that can cause gas Some people naturally produce ... your stomach or throw up . Your breasts are big and sore . The area around your nipples gets darker. You crave certain foods. Or you really dislike certain foods. You feel ...

  9. Fault detection and isolation in aircraft gas turbine engines. Part 1: underlying concept

    E-print Network

    Ray, Asok

    life due to degradation of the gas path components such as fan, compressor, combustor, and turbines. Com- mon causes of degradation of the gas path com- ponents include compressor fouling, increase of the blade-tip clearance in the turbine, labyrinth seal leakage, wear and erosion, and corrosion in the hot

  10. Infrared active imaging for the remote detection of fugitive gas emissions

    Microsoft Academic Search

    T. J. Kulp; R. P. Bambha; T. A. Reichardt; R. Schmitt

    2003-01-01

    In this paper, a compact active imaging system that allows real-time video visualization of methane plumes is described. The development of this instrument is motivated by the need for technology to allow the rapid identification and localization of natural gas leaks by the Japanese gas industry. Because it yields an instantaneous view of a three-dimensional volume, the described device provides

  11. Calculating the detection limits of chamber-based greenhouse gas flux measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chamber-based measurement of greenhouse gas emissions from soil is a common technique. However, when changes in chamber headspace gas concentrations are small over time, determination of the flux can be problematic. Several factors contribute to the reliability of measured fluxes, including: samplin...

  12. Gas chromatographic method for detection of urinary sucralose: application to the assessment of intestinal permeability

    Microsoft Academic Search

    Ashkan Farhadi; Ali Keshavarzian; Earle W Holmes; Jeremy Fields; Lei Zhang; Ali Banan

    2003-01-01

    We developed a capillary column gas chromatography (CCGC) method for the measurement of urinary sucralose (S) and three other sugar probes including, sucrose, lactulose (L) and mannitol (M) for use in in vivo studies of intestinal permeability. We compared the capillary method with a packed column gas chromatography (PCGC) method. We also investigated a possible role for sucralose as a

  13. Realization of rapid debugging for detection circuit of optical fiber gas sensor: Using an analog signal source

    NASA Astrophysics Data System (ADS)

    Tian, Changbin; Chang, Jun; Wang, Qiang; Wei, Wei; Zhu, Cunguang

    2015-03-01

    An optical fiber gas sensor mainly consists of two parts: optical part and detection circuit. In the debugging for the detection circuit, the optical part usually serves as a signal source. However, in the debugging condition, the optical part can be easily influenced by many factors, such as the fluctuation of ambient temperature or driving current resulting in instability of the wavelength and intensity for the laser; for dual-beam sensor, the different bends and stresses of the optical fiber will lead to the fluctuation of the intensity and phase; the intensity noise from the collimator, coupler, and other optical devices in the system will also result in the impurity of the optical part based signal source. In order to dramatically improve the debugging efficiency of the detection circuit and shorten the period of research and development, this paper describes an analog signal source, consisting of a single chip microcomputer (SCM), an amplifier circuit, and a voltage-to-current conversion circuit. It can be used to realize the rapid debugging detection circuit of the optical fiber gas sensor instead of optical part based signal source. This analog signal source performs well with many other advantages, such as the simple operation, small size, and light weight.

  14. A New Method for Ultrasound Detection of Interfacial Position in Gas-Liquid Two-Phase Flow

    PubMed Central

    Coutinho, Fábio Rizental; Ofuchi, César Yutaka; de Arruda, Lúcia Valéria Ramos; Jr., Flávio Neves; Morales, Rigoberto E. M.

    2014-01-01

    Ultrasonic measurement techniques for velocity estimation are currently widely used in fluid flow studies and applications. An accurate determination of interfacial position in gas-liquid two-phase flows is still an open problem. The quality of this information directly reflects on the accuracy of void fraction measurement, and it provides a means of discriminating velocity information of both phases. The algorithm known as Velocity Matched Spectrum (VM Spectrum) is a velocity estimator that stands out from other methods by returning a spectrum of velocities for each interrogated volume sample. Interface detection of free-rising bubbles in quiescent liquid presents some difficulties for interface detection due to abrupt changes in interface inclination. In this work a method based on velocity spectrum curve shape is used to generate a spatial-temporal mapping, which, after spatial filtering, yields an accurate contour of the air-water interface. It is shown that the proposed technique yields a RMS error between 1.71 and 3.39 and a probability of detection failure and false detection between 0.89% and 11.9% in determining the spatial-temporal gas-liquid interface position in the flow of free rising bubbles in stagnant liquid. This result is valid for both free path and with transducer emitting through a metallic plate or a Plexiglas pipe. PMID:24858961

  15. Wavelet analysis used in UHF partial discharge detection in GIS [gas insulated substations

    Microsoft Academic Search

    Z. M. Li; Y. P. Feng; J. Q. Chen; X. G. Zheng

    1998-01-01

    One of the most important subjects in monitoring GIS is PD detection. The issue is that the PD signal is weak and sensitive to external noise. In this paper, the experiments of detection PD in GIS using UHF technique is described. The results show that UHF method is effective in detecting PD in GIS and avoiding the disturbance of corona.

  16. Determination of halogenated mono-alcohols and diols in water by gas chromatography with electron-capture detection.

    PubMed

    Matthew, B M; Anastasio, C

    2000-01-01

    We have developed an analytical method for the detection of halogenated alcohols in water with particular focus on 3-chloro-1,2-propanediol and 3-bromo-1,2-propanediol. In this method the target analytes are extracted from water, derivatized with heptafluorobutyric anhydride, and then analyzed with gas chromatography with electron-capture detection. The effects of water, pH and seawater constituents on the method were investigated. Method detection limits for a 5 ml aqueous sample ranged from 0.14 microg l(-1) for 2-bromo-1,3-propanediol to 1.7 microg l(-1) for 1,3-dichloro-2-propanol (1,3DCP). PMID:10681010

  17. Detection and quantification of adulteration of sesame oils with vegetable oils using gas chromatography and multivariate data analysis.

    PubMed

    Peng, Dan; Bi, Yanlan; Ren, Xiaona; Yang, Guolong; Sun, Shangde; Wang, Xuede

    2015-12-01

    This study was performed to develop a hierarchical approach for detection and quantification of adulteration of sesame oil with vegetable oils using gas chromatography (GC). At first, a model was constructed to discriminate the difference between authentic sesame oils and adulterated sesame oils using support vector machine (SVM) algorithm. Then, another SVM-based model is developed to identify the type of adulterant in the mixed oil. At last, prediction models for sesame oil were built for each kind of oil using partial least square method. To validate this approach, 746 samples were prepared by mixing authentic sesame oils with five types of vegetable oil. The prediction results show that the detection limit for authentication is as low as 5% in mixing ratio and the root-mean-square errors for prediction range from 1.19% to 4.29%, meaning that this approach is a valuable tool to detect and quantify the adulteration of sesame oil. PMID:26041212

  18. Fire Detections and Fire Radiative Power Intercomparison Using Multiple Sensor Products over a Predominantly Gas Flaring Region

    NASA Astrophysics Data System (ADS)

    Sharma, A.; Wang, J.

    2014-12-01

    Gas flaring is a global environmental hazard severely impacting climate, economy and public health. The associated emissions are frequently unreported and have large uncertainties. Prior studies have established a direct relationship between radiative energy released from fires and the biomass burned, making fire radiative power (FRP), i.e., the rate of radiative energy release, an important proxy to characterize emissions. In this study fire properties from four different satellite products were obtained over a 10? x 10? gas flaring region in Russia for all days of May 2013. The target area is part of Russia's biggest gas flaring region, Khanty-Mansiysk autonomous okrug. The objective of the study is to investigate the consistency of fire detections, FRP retrievals and effects of gridding FRP data from the region on a uniform grid. The four products used were: MODIS Terra level2 thermal anomalies (MOD14), MODIS Aqua level2 thermal anomalies (MYD14), VIIRS Active fire product and a recent NOAA Nightfire product. 1 km nominal resolution FRP from MOD14 AND MYD14, subpixel radiant heat (RH) from NOAA Nightfire product and fire detections from all four products were recorded on a 0.25? x 0.25? grid on a daily basis. Results revealed the Nightfire product had maximum detections, almost six times the number of detections by other products, mainly because of the use of M10 (1.6 µm) band as their primary detection band. The M10 band is highly efficient in identifying radiant emissions from hot sources during night-time. The correlation (after omitting outliers) between gridded NOAA Nightfire RH and corresponding MOD14 FRP and MYD14 FRP gave a moderate regression value, with MODIS FRP being mostly higher than RH. As an extension to this work, a comprehensive study for a larger temporal domain also incorporating viewing geometries and cloud cover would advance our understanding of flare detections and associated FRP retrievals not just for the target region but also gas flaring regions globally.

  19. Development of a Random Field Model for Gas Plume Detection in Multiple LWIR Images.

    SciTech Connect

    Heasler, Patrick G.

    2008-09-30

    This report develops a random field model that describes gas plumes in LWIR remote sensing images. The random field model serves as a prior distribution that can be combined with LWIR data to produce a posterior that determines the probability that a gas plume exists in the scene and also maps the most probable location of any plume. The random field model is intended to work with a single pixel regression estimator--a regression model that estimates gas concentration on an individual pixel basis.

  20. The Determination of Pesticidal and Non-Pesticidal Organotin Compounds in Water Matrices by in situ Ethylation and Gas Chromatography with Pulsed Flame Photometric Detection

    EPA Science Inventory

    The concurrent determination of pesticidal and non-pesticidal organotin compounds in several water matrices, using a simultaneous in situ ethylation and liquid-liquid extraction followed by splitless injection mode capillary gas chromatography with pulsed flame photometric detect...

  1. The Determination of Pesticidal and Non-Pesticidal Organotin Compounds by in situ Ethylation and Capillary Gas Chromatography with Pulsed Flame Photometric Detection

    EPA Science Inventory

    The concurrent determination of pesticidal and non-pesticidal organotin compounds in several water matrices, using a simultaneous in situ ethylation and liquid-liquid extraction followed by splitless injection mode capillary gas chromatography with pulsed flame photometric detect...

  2. Detection of Gas Hydrates in Garden Banks and Keathley Canyon from Seismic Data 

    E-print Network

    Murad, Idris

    2011-08-08

    and shallow-rooted faults were mapped throughout the area. A shallow sediment deformation map was generated that defined areas of significant faulting. We then quantified the thermal impact of shallow salt to better estimate the gas hydrate stability zone...

  3. Chemical warfare agent detection in complex environments with comprehensive two-dimensional gas chromatography

    Microsoft Academic Search

    Stephen E. Reichenbach; Mingtian Ni; Visweswara Kottapalli; Arvind Visvanathan; Edward B. Ledford Jr.; John Oostdijk; Henk C. Trap

    2003-01-01

    Comprehensive two-dimensional gas chromatography (GCxGC) is an emerging technology for chemical separation that provides an order-of-magnitude increase in separation capacity over traditional gas chromatography. GCxGC separates chemical species with two capillary columns interfaced by two-stage thermal desorption. Because GCxGC is comprehensive and has high separation capacity, it can perform multiple traditional analytical methods with a single analysis. GCxGC has great

  4. EXTENDED PERFORMANCE HANDHELD AND MOBILE SENSORS FOR REMOTE DETECTION OF NATURAL GAS LEAKS

    Microsoft Academic Search

    Michael B. Frish; B. David Green; Richard T. Wainner; Francesca Scire-Scappuzzo; Paul Cataldi; Matthew C. Laderer

    2005-01-01

    This report summarizes work performed by Physical Sciences Inc. (PSI) to advance the state-of-the-art of surveying for leaks of natural gas from transmission and distribution pipelines. The principal project goal was to develop means of deploying on an automotive platform an improved version of the handheld laser-based standoff natural gas leak detector previously developed by PSI and known as the

  5. Method and apparatus for noble gas atom detection with isotopic selectivity

    DOEpatents

    Hurst, G. Samuel (Oak Ridge, TN); Payne, Marvin G. (Harriman, TN); Chen, Chung-Hsuan (Knoxville, TN); Parks, James E. (Oak Ridge, TN)

    1984-01-01

    Apparatus and methods of operation are described for determining, with isotopic selectivity, the number of noble gas atoms in a sample. The analysis is conducted within an evacuated chamber which can be isolated by a valve from a vacuum pumping system capable of producing a pressure of 10.sup.-8 Torr. Provision is made to pass pulses of laser beams through the chamber, these pulses having wavelengths appropriate for the resonance ionization of atoms of the noble gas under analysis. A mass filter within the chamber selects ions of a specific isotope of the noble gas, and means are provided to accelerate these selected ions sufficiently for implantation into a target. Specific types of targets are discussed. An electron measuring device produces a signal relatable to the number of ions implanted into the target and thus to the number of atoms of the selected isotope of the noble gas removed from the gas sample. The measurement can be continued until a substantial fraction, or all, of the atoms in the sample have been counted. Furthermore, additional embodiments of the apparatus are described for bunching the atoms of a noble gas for more rapid analysis, and for changing the target for repetitive cycling of the gas in the chamber. The number of repetitions of the cyclic steps depend upon the concentration of the isotope of interest, the separative efficiency of the mass filter, etc. The cycles are continued until a desired selectivity is achieved. Also described are components and a method of operation for a pre-enrichment operation for use when an introduction of a total sample would elevate the pressure within the chamber to levels in excess of those for operation of the mass filter, specifically a quadrupole mass filter. Specific examples of three noble gas isotope analyses are described.

  6. Airborne detection of natural gas leaks from transmission pipelines by using a laser system operating in visual, near-IR, and mid-IR wavelength bands

    NASA Astrophysics Data System (ADS)

    Ershov, Oleg V.; Klimov, Alexey G.; Vavilov, Vladimir P.

    2006-04-01

    An airborne gas detection IR system which includes a laser, infrared imager and video-recorder is described. The sensitivity of the system to leaks from ground pipelines by the laser channel is about 100 ppm*m at 100 m (by methane). The IR thermographic channel plays an auxiliary role and the video channel allows better coordinate positioning of detected gas leaks in conjunction with a built-in GPS device.

  7. A-2005 Site environmental report appenDiX a: GloSSarY

    E-print Network

    DOECH DOEChicagoOperationsOffice DQo Data Quality objective DSB Duct Service Building DUV­FEL DeepUltraViolet­FreeElectron measurements laboratory EMP EnvironmentalMonitoringPlan emS* environmental management System epa* U and beta GC/eCD gas chromatography/electron capture detector GC/mS gas chromatography/mass spectrometry GDS

  8. A University of Texas Arlington group has developed a passive RFID tag and reader for wirelessly detecting the presence of stomach acid, gas and water in the esophagus.

    E-print Network

    Chiao, Jung-Chih

    detecting the presence of stomach acid, gas and water in the esophagus. By Claire Swedberg April 10, 2007, as well as working with simulated stomach acid in a test tube. It is now preparing to conduct testing in the esophagus. The sensor is designed to measure the presence of stomach acid, gas and water in the esophagus

  9. A sub-ppm acetone gas sensor for diabetes detection using 10 nm thick ultrathin InN FETs.

    PubMed

    Kao, Kun-Wei; Hsu, Ming-Che; Chang, Yuh-Hwa; Gwo, Shangjr; Yeh, J Andrew

    2012-01-01

    An indium nitride (InN) gas sensor of 10 nm in thickness has achieved detection limit of 0.4 ppm acetone. The sensor has a size of 1 mm by 2.5 mm, while its sensing area is 0.25 mm by 2 mm. Detection of such a low acetone concentration in exhaled breath could enable early diagnosis of diabetes for portable physiological applications. The ultrathin InN epilayer extensively enhances sensing sensitivity due to its strong electron accumulation on roughly 5-10 nm deep layers from the surface. Platinum as catalyst can increase output current signals by 2.5-fold (94 vs. 37.5 ?A) as well as reduce response time by 8.4-fold (150 vs. 1,260 s) in comparison with bare InN. More, the effect of 3% oxygen consumption due to breath inhalation and exhalation on 2.4 ppm acetone gas detection was investigated, indicating that such an acetone concentration can be analyzed in air. PMID:22969342

  10. Determination of Trichlorfon Pesticide Residues in Milk via Gas Chromatography with ?-Electron Capture Detection and GC-MS

    PubMed Central

    Hem, Lina; Khay, Sathya; Choi, Jeong-Heui; Morgan, E.D.; El-Aty, A.M. Abd

    2010-01-01

    The pesticide trichlorfon is readily degraded under experimental conditions to dichlorvos. A method has therefore been developed by which residues of trichlorfon in milk are determined as dichlorvos, using gas chromatography with ?-electron capture detection. The identification of dichlorvos was confirmed by mass spectrometry. Milk was extracted with acetonitrile followed by centrifugation, freezing lipid filtration, and partitioning into dichloromethane. The residue after partitioning of dichloromethane was dissolved in ethyl acetate for gas chromatography. Recovery concentration was determined at 0.5, 1.0, and 2.0 of times the maximum permitted residue limits (MRLs) for trichlorfon in milk. The average recoveries (n = 6) ranged from 92.4 to 103.6%. The repeatability of the measurements was expressed as relative standard deviations (RSDs) ranging from 3.6%, to 6.7%. Limit of detection (LOD) and limit of quantification (LOQ) were 3.7 and 11.1 ?g/l, respectively. The accuracy and precision (expressed as RSD) were estimated at concentrations from 25 to 250 ?g/l. The intra- and inter-day accuracy (n = 6) ranged from 89.2%to 91% and 91.3% to 96.3%, respectively. The intra- and inter-day precisions were lower than 8%. The developed method was applied to determine trichlorfon in real samples collected from the seven major cities in the Republic of Korea. No residual trichlorfon was detected in any samples. PMID:24278518

  11. A Sub-ppm Acetone Gas Sensor for Diabetes Detection Using 10 nm Thick Ultrathin InN FETs

    PubMed Central

    Kao, Kun-Wei; Hsu, Ming-Che; Chang, Yuh-Hwa; Gwo, Shangjr; Yeh, J. Andrew

    2012-01-01

    An indium nitride (InN) gas sensor of 10 nm in thickness has achieved detection limit of 0.4 ppm acetone. The sensor has a size of 1 mm by 2.5 mm, while its sensing area is 0.25 mm by 2 mm. Detection of such a low acetone concentration in exhaled breath could enable early diagnosis of diabetes for portable physiological applications. The ultrathin InN epilayer extensively enhances sensing sensitivity due to its strong electron accumulation on roughly 5–10 nm deep layers from the surface. Platinum as catalyst can increase output current signals by 2.5-fold (94 vs. 37.5 ?A) as well as reduce response time by 8.4-fold (150 vs. 1,260 s) in comparison with bare InN. More, the effect of 3% oxygen consumption due to breath inhalation and exhalation on 2.4 ppm acetone gas detection was investigated, indicating that such an acetone concentration can be analyzed in air. PMID:22969342

  12. Element-selective detection of gas chromatographic eluates by near infrared Échelle optical emission spectrometry on microwave-induced plasmas

    NASA Astrophysics Data System (ADS)

    Koch, J.; Okruss, M.; Franzke, J.; Florek, S. V.; Niemax, K.; Becker-Ross, H.

    2004-02-01

    Specific analytical characteristics of near-infrared Échelle microwave-induced plasma atomic emission spectrometry (NIR-Échelle-MIP-OES) with respect to the quantification of organic compounds were examined. Matrices consisting of halogenated and sulfureous hydrocarbons were gas chromatographically separated and subsequently H-, C-, F-, Cl-, Br-, I- and S-selectively analyzed. For these purposes, a compact Échelle spectrometer, designed for the high-repetitive, high-resolved and simultaneous spectra acquisition between 640 and 990 nm was used. Depending on the plasma gas applied and element considered, detection limits typically varied from 200-2200 pg/s for Ar to 70-660 pg/s for He. Furthermore, strategies to improve the over-all sensitivity are discussed. In this context, a concept, which rests on simultaneous multi-line analysis is described and experimentally proofed.

  13. Detection of HCN, HCO+, and HNC in the Mrk 231 molecular outflow. Dense molecular gas in the AGN wind

    NASA Astrophysics Data System (ADS)

    Aalto, S.; Garcia-Burillo, S.; Muller, S.; Winters, J. M.; van der Werf, P.; Henkel, C.; Costagliola, F.; Neri, R.

    2012-01-01

    Aims: Our goal is to study gas properties in large-scale molecular outflows and winds from active galactic nuclei (AGNs) and starburst galaxies. Methods: We obtained high-resolution (1.''55 × 1.''28) observations of HCN, HCO+, HNC 1-0 and HC3N 10-9 of the ultraluminous galaxy (ULIRG) Mrk 231 with the IRAM Plateau de Bure Interferometer. Results: We detect luminous emission from HCN, HCO+ and HNC 1-0 in the QSO ULIRG Mrk 231. All three lines show broad line wings - which are particularly prominent for HCN. Velocities are found to be similar ( ? ± 750 km s-1) to those found for CO 1-0. This is the first time bright HCN, HCO+ and HNC emission has been detected in a large-scale galactic outflow. We find that both the blue- and red-shifted line wings are spatially extended by at least 0.''75 (>700 pc) in a north-south direction. The line wings are brighter (relative to the line center intensity) in HCN than in CO 1-0 and line ratios suggest that the molecular outflow consists of dense (n > 104 cm-3) and clumpy gas with a high HCN abundance X(HCN) > 10-8. These properties are consistent with the molecular gas being compressed and fragmented by shocks in the outflow. Alternatively, HCN is instead pumped by mid-IR continuum, but we propose that this effect is not strong for the spatially extended outflowing gas. In addition, we find that the rotation of the main disk, in east-west direction, is also evident in the HCN, HCO+ and HNC line emission. An unexpectedly bright HC3N 10-9 line is detected inside the central 400 pc of Mrk 231. This HC3N emission may emerge from a shielded, dust-enshrouded region within the inner 40-50 pc where the gas is heated to high temperatures (200-300 K) by the AGN. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

  14. Natural gas

    NSDL National Science Digital Library

    N/A N/A (None; )

    2003-07-27

    Natural gas is used as a means of power in households. Natural gas has no natural odor, so an odor is added to the gas. This is useful because gas leaks can be detected better and it also reduces the risk of accidents in homes.

  15. Detection of hydrogen gas-producing anaerobes in refuse-derived fuel (RDF) pellets.

    PubMed

    Sakka, Makiko; Kimura, Tetsuya; Ohmiya, Kunio; Sakka, Kazuo

    2005-11-01

    Recently, we reported that refuse-derived fuel (RDF) pellets contain a relatively high number of viable bacterial cells and that these bacteria generate heat and hydrogen gas during fermentation under wet conditions. In this study we analyzed bacterial cell numbers of RDF samples manufactured with different concentrations of calcium hydroxide, which is usually added to waste materials for the prevention of rotting of food wastes and the acceleration of drying of solid wastes, and determined the amount of hydrogen gas produced by them under wet conditions. Furthermore, we analyzed microflora of the RDF samples before and during fermentation by denaturing gradient gel electrophoresis of 16S rDNA followed by sequencing. We found that the RDF samples contained various kinds of clostridia capable of producing hydrogen gas. PMID:16306688

  16. Multiphase imaging of gas flow in a nanoporous material usingremote detection NMR

    SciTech Connect

    Harel, Elad; Granwehr, Josef; Seeley, Juliette A.; Pines, Alex

    2005-10-03

    Pore structure and connectivity determine how microstructured materials perform in applications such as catalysis, fluid storage and transport, filtering, or as reactors. We report a model study on silica aerogel using a recently introduced time-of-flight (TOF) magnetic resonance imaging technique to characterize the flow field and elucidate the effects of heterogeneities in the pore structure on gas flow and dispersion with Xe-129 as the gas-phase sensor. The observed chemical shift allows the separate visualization of unrestricted xenon and xenon confined in the pores of the aerogel. The asymmetrical nature of the dispersion pattern alludes to the existence of a stationary and a flow regime in the aerogel. An exchange time constant is determined to characterize the gas transfer between them. As a general methodology, this technique provides new insights into the dynamics of flow in porous media where multiple phases or chemical species may be present.

  17. Further lipophilic flavonols in Vellozia graminifolia (Velloziaceae) by high temperature gas chromatography: quick detection of new compounds.

    PubMed

    Branco, A; Pereira, A S; Cardoso, J N; de Aquino Neto, F R; Pinto, A C; Braz-Filho, R

    2001-01-01

    Further lipophilic flavonols present in Vellozia graminifolia have been determined by high temperature high resolution gas chromatography (HTHRGC) and by HTHRGC coupled to mass spectrometry (MS). These methods resulted in the detection, isolation and characterisation of a monoisoprenylated flavonol 3,5,4'-trimethoxy-3'-hydroxy-6,7-(2"-isopropenyldihydrofurano)flavone from the ethyl acetate extract of the whole plant. The structural elucidation was accomplished using spectral data, including two-dimensional NMR, and on chemical transformations. Both HTHRGC and HTHRGC-MS were shown to be alternative and extremely valuable methods for the quick screening of flavonoid aglycones and other chemical metabolites of the Velloziaceae. PMID:11708300

  18. DETECTION OF OUTFLOWING AND EXTRAPLANAR GAS IN DISKS IN AN ASSEMBLING GALAXY CLUSTER AT z = 0.37

    SciTech Connect

    Freeland, Emily; Tran, Kim-Vy H.; Irwin, Trevor [George P. and Cynthia W. Mitchell Institute, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Giordano, Lea [Institute for Theoretical Physics, University of Zuerich, CH-8057 Zuerich (Switzerland); Saintonge, Amelie [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Zaritsky, Dennis; Just, Dennis, E-mail: freeland@physics.tamu.edu [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

    2011-12-15

    We detect ionized gas characteristics indicative of winds in three disk-dominated galaxies that are members of a super-group at z = 0.37 that will merge to form a Coma-mass cluster. All three galaxies are IR luminous (L{sub IR} > 4 Multiplication-Sign 10{sup 10} L{sub Sun }, SFR > 8 M{sub Sun} yr{sup -1}) and lie outside the X-ray cores of the galaxy groups. We find that the most IR-luminous galaxy has strong blueshifted and redshifted emission lines with velocities of {approx} {+-} 200 km s{sup -1} and a third, blueshifted ({approx}900 km s{sup -1}) component. This galaxy's line widths (H{beta}, [O III]{lambda}5007, [N II], H{alpha}) correspond to velocities of 100-1000 km s{sup -1}. We detect extraplanar gas in two of the three galaxies with SFR >8 M{sub Sun} yr{sup -1} whose orientations are approximately edge-on and which have integral field unit (IFU) spaxels off the stellar disk. IFU maps reveal that the extraplanar gas extends to r{sub h} {approx} 10 kpc; [N II] and H{alpha} line widths correspond to velocities of {approx}200-400 km s{sup -1} in the disk and decrease to {approx}50-150 km s{sup -1} above the disk. Multi-wavelength observations indicate that the emission is dominated by star formation. Including the most IR-luminous galaxy we find that 18% of supergroup members with SFR >8 M{sub Sun} yr{sup -1} show ionized gas characteristics indicative of outflows. This is a lower limit as showing that gas is outflowing in the remaining, moderately inclined, galaxies requires a non-trivial decoupling of contributions to the emission lines from rotational and turbulent motion. Ionized gas mass loss in these winds is {approx}0.1 M{sub Sun} yr{sup -1} for each galaxy, although the winds are likely to entrain significantly larger amounts of mass in neutral and molecular gases.

  19. Persistence behaviour of deltamethrin on tea and its transfer from processed tea to infusion.

    PubMed

    Paramasivam, M; Chandrasekaran, S

    2014-09-01

    The dynamics and residues of deltamethrin in a tea grown in an open field ecosystem were investigated. The quantification was performed using gas chromatography-electron capture detection (GC-ECD) and confirmed by gas chromatograph-mass spectrometry (GC-MS) in selective ion monitoring (SIM) mode. The method was validated using blank samples spiked at three levels and the results showed that recoveries ranged from 87% to 101% with relative standard deviations (RSD) ranging of 0.7-7.1%. The residues of deltamethrin were found to dissipate following first order kinetics with half-life ranging between 3.04 and 3.54d for two different rates of foliar application. The deltamethrin residues are present in the processed tea are not transferred into the tea infusion during the infusion process, since their water solubility is extremely low. These results can be utilized in formulating the spray schedule and safety evaluation on deltamethrin tea crop. PMID:24997931

  20. Detection and tracking of gas clouds in an urban area by imaging infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Sabbah, Samer; Rusch, Peter; Gerhard, Jörn-Hinnrich; Harig, Roland

    2013-05-01

    The release of toxic industrial compounds in urban areas is a threat for the population and the environment. In order to supply emergency response forces with information about the released compounds after accidents or terrorist attacks, monitoring systems such as the scanning imaging spectrometer SIGIS 2 or the hyperspectral imager HI 90 were developed. Both systems are based on the method of infrared spectroscopy. The systems were deployed to monitor gas clouds released in the harbor area of Hamburg. The gas clouds were identified, visualized and quantified from a distance in real time. Using data of two systems it was possible to identify contaminated areas and to determine the source location.

  1. Gas reservoir sweet spot detection and delineation in Rocky Mountain laramide basins. Topical report, May 1993-March 1996

    SciTech Connect

    Surdam, R.C.; Iverson, W.O.; Yin, P.

    1995-10-01

    The determination of the position and configuration of the pressure boundary between normal and anomalously pressured regimes, and the detection and delineation of porosity/permeability `sweet spots` below this boundary are the two most important elements in exploring for basin-center or deep-basin gas in Rocky Mountain Laramide Basins. These two exploration elements from the basis for a new exploration paradigm. To utilize this new paradigm, the following tasks need to be included in the exploration strategy: (1) determine the position of the pressure boundary; (2) evaluate the three-dimensional aspects of the pressure boundary surface; (3) determine which depositional facies has the greatest potential for enhances storage capacity and deliverability below the pressure boundary; (4) document the determinative factors that control sweet spot development in the targeted lithofacies; and (5) detect and delineate sweet spots using 2-D and 3-D models of eletric log responses and seismic data.

  2. Detection of gaseous compounds by needle trap sampling and direct thermal-desorption photoionization mass spectrometry: concept and demonstrative application to breath gas analysis.

    PubMed

    Kleeblatt, Juliane; Schubert, Jochen K; Zimmermann, Ralf

    2015-02-01

    A fast detection method to analyze gaseous organic compounds in complex gas mixtures was developed, using a needle trap device (NTD) in conjunction with thermal-desorption photoionization time-of-flight mass spectrometry (TD-PI-TOFMS). The mass spectrometer was coupled via a deactivated fused silica capillary to an injector of a gas chromatograph. In the hot injector, the analytes collected on the NTD were thermally desorbed and directly transferred to the PI-TOFMS ion source. The molecules are softly ionized either by single photon ionization (SPI, 118 nm) or by resonance enhanced multiphoton ionization (REMPI, 266 nm), and the molecular ion signals are detected in the TOF mass analyzer. Analyte desorption and the subsequent PI-TOFMS detection step only lasts ten seconds. The specific selectivity of REMPI (i.e., aromatic compounds) and universal ionization characteristics render PI-MS as a promising detection system. As a first demonstrative application, the alveolar phase breath gas of healthy, nonsmoking subjects was sampled on NTDs. While smaller organic compounds such as acetone, acetaldehyde, isoprene, or cysteamine can be detected in the breath gas with SPI, REMPI depicts the aromatic substances phenol and indole at 266 nm. In the breath gas of a healthy, smoking male subject, several xenobiotic substances such as benzene, toluene, styrene, and ethylbenzene can be found as well. Furthermore, the NTD-REMPI-TOFMS setup was tested for breath gas taken from a mechanically ventilated pig under continuous intravenous propofol (2,6-diisopropylphenol, narcotic drug) infusion. PMID:25517186

  3. Quantum Cascade Laser-Based Photoacoustic Sensor for Trace Detection of Formaldehyde Gas

    PubMed Central

    Elia, Angela; Di Franco, Cinzia; Spagnolo, Vincenzo; Lugarà, Pietro Mario; Scamarcio, Gaetano

    2009-01-01

    We report on the development of a photoacoustic sensor for the detection of formaldehyde (CH2O) using a thermoelectrically cooled distributed-feedback quantum cascade laser operating in pulsed mode at 5.6 ?m. A resonant photoacoustic cell, equipped with four electret microphones, is excited in its first longitudinal mode at 1,380 Hz. The absorption line at 1,778.9 cm?1 is selected for CH2O detection. A detection limit of 150 parts per billion in volume in nitrogen is achieved using a 10 seconds time constant and 4 mW laser power. Measurements in ambient air will require water vapour filters. PMID:22574040

  4. Detection of clenbuterol at trace levels in doping analysis using different gas chromatographic-mass spectrometric techniques.

    PubMed

    Yang, Sheng; Liu, Xin; Xing, Yanyi; Zhang, Dapeng; Wang, Shan; Wang, Xiaobing; Xu, Youxuan; Wu, Moutian; He, Zhenwen; Zhao, Jian

    2013-01-01

    This study demonstrates the development of a gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS-MS) assay to detect clenbuterol in human urine and the comparison of this method with GC-MS techniques and gas chromatography-high resolution mass spectrometry (GC-HRMS) techniques. Urine samples were hydrolyzed with ?-glucuronidase, extracted with methyl tert-butyl ether and dried under nitrogen. The derivative reagent was N-methyl-N-(trimethylsilyl)-trifluoroacetamide with NH4I and was analyzed by GC-MS, GC-MS-MS and GC-HRMS. A validation study was conducted by GC-MS-MS. The analyses of clenbuterol using different mass spectrometric techniques were compared. The limit of detection (LOD) for clenbuterol in human urine was 2 ng/mL by GC-MS (selected ion monitoring mode: SIM mode), 0.06 ng/mL by GC-HRMS and 0.03 ng/mL by GC-MS-MS, respectively, while the LOD by GC-HRMS was 0.06. With GC-MS-MS, the intra-assay and inter-assay precisions were less than 15%, the recoveries were 86 to 112% and the linear range was 0.06 to 8.0 ng/mL. The GC-MS under SIM mode can be used as a screening tool to detect clenbuterol at trace levels in human urine. The GC-MS-MS and GC-HRMS methods can confirm clenbuterol when its concentration is below 2 ng/mL. The results demonstrate that the GC-MS-MS method is quite sensitive, specific and reliable for the detection of clenbuterol in doping analysis. PMID:23042839

  5. Electromagnetic wave radiated from an insulating spacer in gas insulated switchgear with partial discharge detection

    Microsoft Academic Search

    Shuhei Kaneko; Shigemitsu Okabe; Hirotaka Muto; Manabu Yoshimura; Chieko Nishida; Mitsuhito Kamei

    2009-01-01

    As a means of diagnosing partial discharge (PD) signals propagate inside a gas insulated switchgear (GIS), a study for the leakage of electromagnetic waves (EM-waves) emitted from the insulating spacer was implemented. The EM-waves leaking out from the solid insulator have the resonance frequencies depend on the spacing between adjacent bolts in the direction of the flange circumference, because the

  6. REVIEW OF METHODS OF OPTICAL GAS Detection by Direct Optical Spectroscopy, with Emphasis on Correlation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Dakin, John P.; Chambers, Paul

    This chapter reviews the development of optical gas sensors, starting with an initial emphasis on optical-fibre remoted techniques and finishing with a particular focus on our own group's work on highly selective methods using correlation spectroscopy. This latter section includes extensive theoretical modelling of a correlation spectroscopy method, and compares theory with practice for a CO2 sensor.

  7. Michelson interferometry for gas density measurement by detecting frequency variations independent of light fluctuations

    Microsoft Academic Search

    F. Seiler; A. George; G. Mathieu

    1991-01-01

    The Laser Doppler Velocimeter, commonly used for flow velocity measurement, was improved in sensitivity in order to determine the temporal variation of the refractive index distribution caused by density changes in a gas volume crossed by a laser beam. For light processing a Michelson interferometer with different legs is used. The interferometer output informs about the changes in time of

  8. New laser sources for photoacoustic trace gas detection with applications in biomedical science

    Microsoft Academic Search

    Jos Oomens; Scott E. Bisson; Matthew Harting; Thomas J. Kulp; Frans J. Harren

    2000-01-01

    Photoacoustic spectroscopy is a sensitive, on-line and non- invasive tool to monitor concentrations of trace gases in ambient air. With the appropriate high power lasers in the mid-IR wavelength region gas mixtures can be analyzed, at and below the part per billion level. Within the development of novel IR laser sources, a continuous wave optical parametric oscillator based on periodically

  9. Rapid, automated gas chromatographic detection of organic compounds in ultra-pure water

    Microsoft Academic Search

    CURTIS DALE MOWRY; DIANNA S. BLAIR; DENNIS J. MORRISON; STEPHEN D. REBER; PHILIP J. RODACY

    2000-01-01

    An automated gas chromatography was used to analyze water samples contaminated with trace (parts-per-billion) concentrations of organic analytes. A custom interface introduced the liquid sample to the chromatography. This was followed by rapid chromatographic analysis. Characteristics of the analysis include response times less than one minute and automated data processing. Analytes were chosen based on their known presence in the

  10. Low-cost multispectral vegetation imaging system for detecting leaking CO2 gas

    E-print Network

    Shaw, Joseph A.

    verification in geological carbon sequestration, which has been proposed as a way to reduce atmospheric 153096); published 31 January 2012 As a component of a multisensor approach to monitoring carbon sequestration sites for possible leaks of the CO2 gas from underground reservoirs, a low-cost multispectral

  11. Separation and Detection of Toxic Gases with a Silicon Micromachined Gas Chromatography System

    NASA Technical Reports Server (NTRS)

    Kolesar, Edward S.; Reston, Rocky R.

    1995-01-01

    A miniature gas chromatography (GC) system was designed and fabricated using silicon micromachining and integrated circuit (IC) processing techniques. The silicon micromachined gas chromatography system (SMGCS) is composed of a miniature sample injector that incorporates a 10 microliter sample loop; a 0.9 meter long, rectangular shaped (300 micrometer width and 10 micrometer height) capillary column coated with a 0.2 micrometer thick copper phthalocyanine (CuPc) stationary phase; and a dual detector scheme based upon a CuPc-coated chemiresistor and a commercially available 125 micrometer diameter thermal conductivity detector (TCD) bead. Silicon micromachining was employed to fabricate the interface between the sample injector and the GC column, the column itself, and the dual detector cavity. A novel IC thin-film processing technique was developed to sublime the CuPc stationary phase coating on the column walls that were micromachined in the host silicon wafer substrate and Pyrex (r) cover plate, which were then electrostatically bonded together. The SMGCS can separate binary gas mixtures composed of parts-per-million (ppm) concentrations of ammonia (NH3) and nitrogen dioxide (NO2) when isothermally operated (55-80 degrees C). With a helium carrier gas and nitrogen diluent, a 10 microliter sample volume containing ammonia and nitrogen dioxide injected at 40 psi ((2.8 x 10(exp 5)Pa)) can be separated in less than 30 minutes.

  12. Noble gas detection using resonance ionization spectroscopy and a quadrupole mass spectrometer

    Microsoft Academic Search

    C. H. Chen; G. S. Hurst

    1983-01-01

    The technique of Resonance Ionization Spectroscopy (RIS) is being extended to develop a means for counting individual atoms of a selected isotope of a noble gas. In this method, lasers are used for RIS to obtain atomic species (Z) selectivity and a small quadrupole mass spectrometer provides isotopic (A) selectivity. A progress report on the objective of counting each atom

  13. Method and apparatus for noble gas atom detection with isotopic selectivity

    Microsoft Academic Search

    G. Samuel Hurst; Marvin G. Payne; Chung-Hsuan Chen; James E. Parks

    1984-01-01

    Apparatus and methods of operation are described for determining, with isotopic selectivity, the number of noble gas atoms in a sample. The analysis is conducted within an evacuated chamber which can be isolated by a valve from a vacuum pumping system capable of producing a pressure of 10.sup.-8 Torr. Provision is made to pass pulses of laser beams through the

  14. Method and apparatus for noble gas atom detection with isotopic selectivity

    Microsoft Academic Search

    G. S. Hurst; M. G. Payne; C. H. Chen; J. E. Parks

    1984-01-01

    Apparatus and methods of operation are described for determining, with isotopic selectivity, the number of noble gas atoms in a sample. The analysis is conducted within an evacuated chamber which can be isolated by a valve from a vacuum pumping system capable of producing a pressure of 10[sup [minus]8] Torr. Provision is made to pass pulses of laser beams through

  15. Multiphase imaging of gas flow in a nanoporous material using remote-detection NMR

    Microsoft Academic Search

    Elad Harel; Josef Granwehr; Juliette A. Seeley; Alex Pines

    2006-01-01

    Pore structure and connectivity determine how microstructured materials perform in applications such as catalysis, fluid storage and transport, filtering or as reactors. We report a model study on silica aerogel using a time-of-flight magnetic resonance imaging technique to characterize the flow field and explain the effects of heterogeneities in the pore structure on gas flow and dispersion with 129Xe as

  16. Multiphase imaging of gas flow in a nanoporous material usingremote detection NMR

    Microsoft Academic Search

    Elad Harel; Josef Granwehr; Juliette A. Seeley; Alex Pines

    2005-01-01

    Pore structure and connectivity determine how microstructured materials perform in applications such as catalysis, fluid storage and transport, filtering, or as reactors. We report a model study on silica aerogel using a recently introduced time-of-flight (TOF) magnetic resonance imaging technique to characterize the flow field and elucidate the effects of heterogeneities in the pore structure on gas flow and dispersion

  17. A NASICON CO2 gas sensor with drift-detection electrode

    Microsoft Academic Search

    Song Chen; Hironori Hadano; Yoshiaki Ishiguro; Masakatsu Nakayama; Kenzo Watanabe

    2002-01-01

    A Nasicon (sodium super ion conductor) CO2 gas sensor with a new structure is developed for monitoring CO2 level in the atmospheric air. In addition to the sensing and reference electrodes of a conventional Nasicon sensor, an auxiliary electrode, referred to as the base electrode, is provided with the new structure. Characterization has revealed that the output voltage at the

  18. Detection of Griseofulvin and Dechlorogriseofulvin by Thin-Layer Chromatography and Gas-Liquid Chromatography

    PubMed Central

    Cole, R. J.; Kirksey, J. W.; Holaday, C. E.

    1970-01-01

    A rapid and accurate method is described for the determination of griseofulvin and dechlorogriseofulvin extracted from Penicillium urticae with chloroform. Thinlayer chromatography was used to tentatively identify griseofulvin or dechlorogriseofulvin, or both. Two gas-liquid chromatographic systems provided additional qualitative information and simultaneous quantitation of the individual compounds. PMID:5415206

  19. Detection of soot particles in gas turbine engine combustion gases using nonintrusive FTIR spectroscopy

    Microsoft Academic Search

    Moira Hilton; John D. Black

    1998-01-01

    Fourier transform IR (FTIR) spectroscopy for making non- intrusive measurements of gas turbine exhaust gases and laser induced incandescence for measuring soot content are being evaluated in EU Brite EuRam project AEROJET. Soot concentrations in modern aero-engine exhausts are very low with mean particle sizes < 100 nm. The standard extractive filter paper soot measurement gives results expressed in terms

  20. Fault detection and diagnosis for gas turbines based on a kernelized information entropy model.

    PubMed

    Wang, Weiying; Xu, Zhiqiang; Tang, Rui; Li, Shuying; Wu, Wei

    2014-01-01

    Gas turbines are considered as one kind of the most important devices in power engineering and have been widely used in power generation, airplanes, and naval ships and also in oil drilling platforms. However, they are monitored without man on duty in the most cases. It is highly desirable to develop techniques and systems to remotely monitor their conditions and analyze their faults. In this work, we introduce a remote system for online condition monitoring and fault diagnosis of gas turbine on offshore oil well drilling platforms based on a kernelized information entropy model. Shannon information entropy is generalized for measuring the uniformity of exhaust temperatures, which reflect the overall states of the gas paths of gas turbine. In addition, we also extend the entropy to compute the information quantity of features in kernel spaces, which help to select the informative features for a certain recognition task. Finally, we introduce the information entropy based decision tree algorithm to extract rules from fault samples. The experiments on some real-world data show the effectiveness of the proposed algorithms. PMID:25258726

  1. Detection of Potato Storage Disease via Gas Analysis: A Pilot Study Using Field Asymmetric Ion Mobility Spectrometry

    PubMed Central

    Rutolo, Massimo; Covington, James A.; Clarkson, John; Iliescu, Daciana

    2014-01-01

    Soft rot is a commonly occurring potato tuber disease that each year causes substantial losses to the food industry. Here, we explore the possibility of early detection of the disease via gas/vapor analysis, in a laboratory environment, using a recent technology known as FAIMS (Field Asymmetric Ion Mobility Spectrometry). In this work, tubers were inoculated with a bacterium causing the infection, Pectobacterium carotovorum, and stored within set environmental conditions in order to manage disease progression. They were compared with controls stored in the same conditions. Three different inoculation time courses were employed in order to obtain diseased potatoes showing clear signs of advanced infection (for standard detection) and diseased potatoes with no apparent evidence of infection (for early detection). A total of 156 samples were processed by PCA (Principal Component Analysis) and k-means clustering. Results show a clear discrimination between controls and diseased potatoes for all experiments with no difference among observations from standard and early detection. Further analysis was carried out by means of a statistical model based on LDA (Linear Discriminant Analysis) that showed a high classification accuracy of 92.1% on the test set, obtained via a LOOCV (leave-one out cross-validation). PMID:25171118

  2. Sensitive detection of black powder by stand-alone ion mobility spectrometer with chlorinated hydrocarbon modifiers in drift gas.

    PubMed

    Liang, Xixi; Wang, Xin; Wang, Weiguo; Zhou, Qinghua; Chen, Chuang; Peng, Liying; Wen, Meng; Qu, Tuanshuai; Wang, Zhenxin; Zhao, Kun; Li, Jinghua; Li, Haiyang

    2014-04-01

    This paper introduces a simple method for selective and sensitive detection of black powder by adding chlorinated hydrocarbons in the drift gas instead of changing the structure of conventional ion mobility spectrometer (IMS). The function of chloride modifiers was to substitute Cl(-)(H?O)n for [O?? (H?O)(n)] in the drift region so as to avoid the overlap between O?? (H?O)(n) and sulfur ion peaks. Among CH?Cl?, CHCl? and CCl?, CCl? was chosen as the modifier due to the best peak-to-peak resolution and stability towards the fluctuation of modifier concentration. With 1.4 ppm CCl? as the modifier, the minimum detectable quantity of 0.1 ng for sulfur was achieved. Moreover, this method showed the ability for detection of common explosives at sub-nanogram level, such as black powder (BP), ammonium nitrate fuel oil (ANFO), 2,4,6-trinitrotoluene (TNT), and pentaerythritol tetranitrate (PETN). In summary, this method requiring no configuration modification has high sensitivity and selectivity, and consumes trace amount of modifier. And these characteristics make it easy to be adopted in current deployed IMS to detect black powder explosives. PMID:24607130

  3. Detection of potato storage disease via gas analysis: a pilot study using field asymmetric ion mobility spectrometry.

    PubMed

    Rutolo, Massimo; Covington, James A; Clarkson, John; Iliescu, Daciana

    2014-01-01

    Soft rot is a commonly occurring potato tuber disease that each year causes substantial losses to the food industry. Here, we explore the possibility of early detection of the disease via gas/vapor analysis, in a laboratory environment, using a recent technology known as FAIMS (Field Asymmetric Ion Mobility Spectrometry). In this work, tubers were inoculated with a bacterium causing the infection, Pectobacterium carotovorum, and stored within set environmental conditions in order to manage disease progression. They were compared with controls stored in the same conditions. Three different inoculation time courses were employed in order to obtain diseased potatoes showing clear signs of advanced infection (for standard detection) and diseased potatoes with no apparent evidence of infection (for early detection). A total of 156 samples were processed by PCA (Principal Component Analysis) and k-means clustering. Results show a clear discrimination between controls and diseased potatoes for all experiments with no difference among observations from standard and early detection. Further analysis was carried out by means of a statistical model based on LDA (Linear Discriminant Analysis) that showed a high classification accuracy of 92.1% on the test set, obtained via a LOOCV (leave-one out cross-validation). PMID:25171118

  4. Detecting naphthenic acids in waters by gas chromatography–mass spectrometry

    Microsoft Academic Search

    Mireya Merlin; Selma E. Guigard; Phillip M. Fedorak

    2007-01-01

    Naphthenic acids (general formula CnH2n+ZO2) are water-soluble, toxic compounds found in petroleum and bitumen. Some of the current methods for detecting these acids in waters depend on measuring the presence of the carboxylic acid functional group, and therefore many of these methods also detect naturally occurring carboxylic acids that are not naphthenic acids. We report a procedure that includes liquid–liquid

  5. A method for detecting breakthrough of organic solvent vapors in a charcoal tube using semiconductor gas sensors

    SciTech Connect

    Hori, Hajime; Noritake, Yuji; Murobushi, Hisako; Higashi, Toshiaki; Tanaka, Isamu

    1999-08-01

    This study developed a method for detecting organic vapors that break through charcoal tubes, using semiconductor gas sensors as a breakthrough detector of vapors. A glass column equipped with two sensors was inserted in Teflon tubing, and air containing organic vapor was introduced at a constant flow rate. After the output signal of the sensors became stable, a charcoal tube was inserted into the tubing at the upstream of the sensors. The resistance of the sensors was collected temporally in an integrated circuit (IC) card. The vapor concentration of the air near the sensors was measured with a gas chromatograph (GC) equipped with a flame ionization detector (FID) at intervals of 5 minutes to obtain the breakthrough curve. When the relative humidity was zero, the output signals of the sensors began to change before the breakthrough point (1% breakthrough time). This tendency was almost the same for methyl acetate, ethyl acetate, isopropyl alcohol (IPA), toluene, and chloroform. For dichloromethane and 1,1,1-trichloroethane, the time when the sensor output signals began to rise was almost the same as the breakthrough point. When the relative humidity was 80 percent, the sensors could also detect many vapors before the breakthrough point, but they could not perceive dichloromethane and chloroform vapors. A personal sampling system with a breakthrough detector was developed and its availability is discussed.

  6. Multi-scale Detection of Organic and Inorganic Signatures Provides Insights into Gas Shale Properties and Evolution

    SciTech Connect

    Bernard, S.; Horsfield, B; Schultz, H; Schreiber, A; Wirth, R; Thi AnhVu, T; Perssen, F; Konitzer, S; Volk, H; et. al.

    2010-01-01

    Organic geochemical analyses, including solvent extraction or pyrolysis, followed by gas chromatography and mass spectrometry, are generally conducted on bulk gas shale samples to evaluate their source and reservoir properties. While organic petrology has been directed at unravelling the matrix composition and textures of these economically important unconventional resources, their spatial variability in chemistry and structure is still poorly documented at the sub-micrometre scale. Here, a combination of techniques including transmission electron microscopy and a synchrotron-based microscopy tool, scanning transmission X-ray microscopy, have been used to characterize at a multiple length scale an overmature organic-rich calcareous mudstone from northern Germany. We document multi-scale chemical and mineralogical heterogeneities within the sample, from the millimetre down to the nanometre-scale. From the detection of different types of bitumen and authigenic minerals associated with the organic matter, we show that the multi-scale approach used in this study may provide new insights into gaseous hydrocarbon generation/retention processes occurring within gas shales and may shed new light on their thermal history.

  7. Detection of shocked atomic gas in the Kleinmann-Low nebula

    NASA Technical Reports Server (NTRS)

    Werner, M.; Crawford, M. K.; Genzel, R.; Hollenbach, D. J.; Townes, C. H.; Watson, F. M.

    1984-01-01

    The 63 micrometer (3)p(1)-(3)P(2) fine structure line emission of neutral atomic oxygen at the center of the Orion nebula with a resolution of 30" is presented. There are three main emission peaks. One is associated with the region of strongest thermal radio continuum radiation close to the Trapezium cluster, and probably arises at the interface between the HII region and the dense Orion molecular cloud. The other two line emission peaks, associated with the Kleinmann Low nebula, are similar in both distribution and velocity to those of the 2 micrometer S(1) line of molecular hydrogen and of the high velocity wings of rotational CO emission. The OI emission from the KL nebula can be produced in the shocked gas associated with the mass outflows in this region and is an important coolant of the shocked gas.

  8. Carbon14 based biomass fraction detection in power plant flue gas CO2: validation and results

    Microsoft Academic Search

    S. W. L. Palstra; H. A. J. Meijer

    2009-01-01

    Replacing non-renewable fossil fuels by renewable fuels like biomass-based ones is one of the tools to combat increasing atmospheric CO2 concentrations. In order to promote biofuel-based electricity generation, a tool must be available to reliably quantify the bio-based CO2 fraction in the flue gas of a power plant. For traditional power plants, such as coal-fired ones to which wood is

  9. S-MAyHEM: A Spectroscopic Microanalytical Hollow Enhanced Magnetron for Explosive Gas Detection

    Microsoft Academic Search

    Rajesh Yalavarthy; Chester G. Wilson

    2006-01-01

    This paper reports on S-MAyHEM, a new magnetic microdevice that magnetically confines on-chip microplasmas (small-scale electric discharges) for spectroscopic molecular gas analysis. Micromagnets in an epoxy casing form the shell of an on-chip hollow cathode. Voltage is applied to this structure under vacuum, creating an on-chip discharge, which is found to be an order of magnitude brighter than seen in

  10. Multiresidue analysis of seventeen pesticides in wine by gas chromatography with mass-selective detection

    Microsoft Academic Search

    George J Soleas; Joe Yan; Kirby Hom; David M Goldberg

    2000-01-01

    We have developed a multiresidue method permitting the simultaneous quantitation of 17 pesticides in wine: dicloran, dimethoate, diazinon, chlorpyrifos-methyl, vinclozolin, carbaryl, methiocarb, dichlofluanid, parathion-ethyl, triadimefon, procymidone, myclobutanil, iprodione, imidan, dicofol, phosalone and azinphos-methyl. Solid-phase extraction of 0.5 ml of wine sample is followed by direct injection of 1 ?l of the eluent onto a DB-5 MS gas chromatographic column followed

  11. A bulk silicon micromachined structure for gas microdischarge-based detection of beta-particles

    Microsoft Academic Search

    Christine K Eun; Chester Wilson; Yogesh B Gianchandani

    2008-01-01

    This paper describes two Si micromachined structures for sensing beta-particles. The basic device (the micro-detector) includes a square silicon cathode surrounded by a concentric anode, and is formed by stacks of glass and Si wafers. Incident beta-particles ionize the gas encapsulated between the electrodes, resulting in an avalanche current pulse or ‘count’. It is shown experimentally that devices with 8

  12. A bulk silicon micromachined structure for gas microdischarge-based detection of beta-particles

    Microsoft Academic Search

    Christine K. Eun; Chester Wilson; Yogesh B. Gianchandani

    2008-01-01

    This paper describes two Si micromachined structures for sensing beta-particles. The basic device (the micro-detector) includes a square silicon cathode surrounded by a concentric anode, and is formed by stacks of glass and Si wafers. Incident beta-particles ionize the gas encapsulated between the electrodes, resulting in an avalanche current pulse or 'count'. It is shown experimentally that devices with 8

  13. The detection of molecular gas in the ring galaxy Arp 143

    NASA Technical Reports Server (NTRS)

    Higdon, James L.; Smith, Beverly J.; Lord, Steven D.; Rand, Richard J.

    1995-01-01

    We have used the NRAO 12 m telescope to map the inner 10 kpc of NGC 2445, the ring galaxy in Arp 143, in CO-12(J = 1-0). Emission is peaked near the ring galaxy nucleus, but we find evidence for an additional asymmetric and extended CO component. This extended CO distribution is consistent with an approximately 8 kpc diameter crescent-shaped ring of molecular gas, similar to the one seen in H I, accounting for approximately half of the total CO flux. Assuming this distribution, we derive a total H2 mass for NGC 2445 of 0.4-2.4 x 10(exp 10) solar mass, depending on whether a Galactic or low-metallicity Large Magellanic Cloud (LMC) conversion factor is used, and an H2/H I mass ratio between 0.9 and 5. The ring is experiencing low rates of massive star formation despite very high gas column densities. We find that the gas surface density exceeds the critical threshold for star formation throughout the ring, even without a possible contribution from a significant molecular component. The absence of vigorous star formation is most simply understood in terms of its youth (approximately 30 Myr): massive stars have not had time to form in large numbers. Our results support the interpretation that NGC 2445 is a nascent ring galaxy, seen prior to its ring starburst phase.

  14. Detection of accreting circumstellar gas around weak emission-line Herbig Ae/Be stars

    NASA Technical Reports Server (NTRS)

    Grady, C. A.; Perez, M. R.; The, P. S.

    1993-01-01

    Archival and recent International Ultraviolet Explorer (IUE) high dispersion spectra of late B stars which reveal the presence of accreting gas with velocities as high as 350 km/s, collisional ionization of the accreting gas to temperatures above the stellar T(sub eff), and column densities intermediate between those observed toward classical Herbig Ae/Be stars and the nearby proto-planetary system beta Pictoris are presented. One of the stars HD 176386, while lacking obvious optical signatures of youth, is a member of the R CrA star formation region, and with an inferred age of 2.8 Myr has not yet arrived on the zero-age main sequence (ZAMS). The other object, an isolated, field B star with pronounced IR excess due to warm, circumstellar dust, 51 Oph, exhibits only modest H(alpha) emission. The combination of high velocity, accreting gas in systems with IR excesses due to circumstellar dust suggests that not only are these objects candidate proto-planetary systems, but that they may represent an extension to higher stellar masses of the weak-emission pre-main sequence (PMS) stars.

  15. Fiber Optic Sensing Technology for Detecting Gas Hydrate Formation and Decomposition

    SciTech Connect

    Rawn, Claudia J [ORNL; Leeman, John R [University of Oklahoma, Norman; Ulrich, Shannon M [ORNL; Alford, Jonathan E [ORNL; Phelps, Tommy Joe [ORNL; Madden, Megan Elwood [University of Oklahoma, Norman

    2011-01-01

    A fiber optic-based distributed sensing system (DSS) has been integrated with a large volume (72 L) pressure vessel providing high spatial resolution, time resolved, 3-D measurement of hybrid temperature-strain (TS) values within experimental sediment gas hydrate systems. Areas of gas hydrate formation (exothermic) and decomposition (endothermic) can be characterized through this proxy by time series analysis of discrete data points collected along the length of optical fibers placed within a sediment system. Data is visualized as a 'movie' of TS values along the length of each fiber over time. Experiments conducted in the Seafloor Processing Simulator (SPS) at Oak Ridge National Laboratory show clear indications of hydrate formation and dissociation events at expected P-T conditions given the thermodynamics of the CH4-H2O system. The high spatial resolution achieved with fiber optic technology makes the DSS a useful tool for visualizing time resolved formation and dissociation of gas hydrates in large-scale sediment experiments.

  16. Nonequilibrium and local detection of the normal fraction of a trapped two-dimensional Bose gas

    NASA Astrophysics Data System (ADS)

    Carusotto, Iacopo; Castin, Yvan

    2011-11-01

    We propose a method to measure the normal fraction of a two-dimensional Bose gas, a quantity that generally differs from the noncondensed fraction. The idea is based on applying a spatially oscillating artificial gauge field to the atoms. The response of the atoms to the gauge field can be read out either mechanically from the deposited energy into the cloud or optically from the macroscopic optical properties of the atomic gas. The local nature of the proposed scheme allows one to reconstruct the spatial profile of the superfluid component; furthermore, the proposed method does not require having established thermal equilibrium in the gas in the presence of the gauge field. The theoretical description of the system is based on a generalization of the Dum-Olshanii theory of artificial gauge fields to the interacting many-body context. The efficiency of the proposed measurement scheme is assessed by means of classical field numerical simulations. An explicit atomic level scheme minimizing disturbing effects such as spontaneous emission and light shifts is proposed for 87Rb atoms.

  17. Detecting floating black holes as they traverse the gas disk of the Milky Way

    E-print Network

    Wang, Xiawei

    2014-01-01

    A population of intermediate-mass black holes (BHs) is predicted to be freely floating in the Milky Way (MW) halo, due to gravitational wave recoil, ejection from triple BH systems, or tidal stripping in the dwarf galaxies that merged to make the MW. As these BHs traverse the gaseous MW disk, a bow shock forms, producing detectable radio synchrotron emission from accelerated electrons. We calculate the synchrotron flux to be $\\sim \\rm 0.01-10\\, mJy$ at GHz frequency, detectable by JVLA, and $\\sim0.1-1\\,\\mu\\rm Jy$ in the infrared, detectable by HST and JWST. The discovery of the floating BH population will provide insights on the formation and merger history of the MW as well as on the evolution of massive BHs in the early Universe.

  18. Selectivity enhancement in photoacoustic gas analysis via phase-sensitive detection at high modulation frequency

    NASA Technical Reports Server (NTRS)

    Kosterev, Anatoliy (Inventor)

    2010-01-01

    A method for detecting a target fluid in a fluid sample comprising a first fluid and the target fluid using photoacoustic spectroscopy (PAS), comprises a) providing a light source configured to introduce an optical signal having at least one wavelength into the fluid sample; b) modulating the optical signal at a desired modulation frequency such that the optical signal generates an acoustic signal in the fluid sample; c) measuring the acoustic signal in a resonant acoustic detector; and d) using the phase of the acoustic signal to detect the presence of the target fluid.

  19. Method Development for the Determination of Pesticide Residues in Vegetables and Fruits by using SolidPhase Microextraction

    Microsoft Academic Search

    Chai Mee Kin; Tan Guan Huat; Asha Kumari

    A headspace solid phase microextraction (HS-SPME) method in combination with Gas Chromatography -Electron Capture Detector (GC-ECD) was used for the extraction and quantification of diazinon, chlorothalonil, malathion, chlorpyrifos, quinalphos, alpha endosulfan, profenofos and beta endosulfan. The method was developed using a 100 ?m poly dimethylsiloxane (PDMS) fiber. The results showed higher responses of the pesticides after addition of aliquots of

  20. Human hair as a potential biomonitor for assessing persistent organic pollutants

    Microsoft Academic Search

    Hong Zhang; Zhifang Chai; Huibin Sun

    2007-01-01

    To explore human biomonitor of persistent organic pollutants (POP) for public health risk assessment, extractable organohalogens (EOX), extractable persistent organohalogens (EPOX) and some selected organochlorine pesticides (OCP) and polychlorinated biphenyls (PCB) in children hair from urban and rural regions of Beijing, China, were measured by instrumental neutron activation analysis (INAA) and gas chromatography–electron capture detector (GC–ECD). The results indicated that

  1. Mid-infrared virtually imaged phased array spectrometer for rapid and broadband trace gas detection

    E-print Network

    - tually imaged phased array (VIPA) disperser [6­8] that operates with an InSb array detector in the MIR grating. This provides a two dimensional (2D) image recorded with a liquid N2 cooled InSb array detector above the noise floor of 5 × 10-4 are readily detected on the millisecond time scale, leading

  2. Systems and methods of monitoring acoustic pressure to detect a flame condition in a gas turbine

    DOEpatents

    Ziminsky, Willy Steve (Simpsonville, SC); Krull, Anthony Wayne (Anderson, SC); Healy, Timothy Andrew (Simpsonville, SC), Yilmaz, Ertan (Glenville, NY)

    2011-05-17

    A method may detect a flashback condition in a fuel nozzle of a combustor. The method may include obtaining a current acoustic pressure signal from the combustor, analyzing the current acoustic pressure signal to determine current operating frequency information for the combustor, and indicating that the flashback condition exists based at least in part on the current operating frequency information.

  3. Derivation of new emission factors for quantification of mass emissions when using optical gas imaging for detecting leaks.

    PubMed

    Lev-On, Miriam; Epperson, David; Siegell, Jeffrey; Ritter, Karin

    2007-09-01

    This paper describes the development of new "leak/no-leak" emission factors that are suitable for estimating facilities' fugitive emissions when using an alternative work practice (AWP) that is based on optical gas imaging technology for detecting leaking piping system components. These emission factors were derived for valves, pumps, and connectors/flanges for instrument leak detection thresholds ranging from 3 to 60 g/hr using a combination of field data and Monte Carlo statistical simulation techniques. These newly derived leak/no-leak emission factors are designed to replace the U.S. Environment Protection Agency (EPA) 1995 Protocol factors, which were based on Method 21 monitoring of leaks at "uncontrolled" facilities. The emission factors published in the 1995 Protocol have not been updated since the 1970s. This derivation is based on results where the authors document the use of a Monte Carlo simulation technique to quantify the required leak detection thresholds that provide equal--or better--environmental benefits for an AWP. The use of these newly derived emission factors is demonstrated for different methods of computing fugitive emissions from a hypothetical model refinery. The resulting facility emissions calculated by using these new emission factors is compared with the existing emission estimation methods provided in the EPA 1995 Protocol. The results demonstrate that the new emission factors provide an emission estimate that is the closest to that obtained from the direct determination of total emissions by Monte Carlo simulations. PMID:17912925

  4. Spectroscopic ultra-trace detection of nitroaromatic gas vapor on rationally designed two-dimensional nanoparticle cluster arrays.

    PubMed

    Wang, Jing; Yang, Linglu; Boriskina, Svetlana; Yan, Bo; Reinhard, Björn M

    2011-03-15

    Nanoparticle cluster arrays (NCAs) are engineered two-dimensional plasmonic arrays that provide high signal enhancements for critical sensing applications using surface enhanced Raman spectroscopy (SERS). In this work we demonstrate that rationally designed NCAs are capable of detecting ultra-traces of 2,4-dinitrotoluene (DNT) vapor. NCAs functionalized with a thin film of an aqueous NaOH solution facilitated the detection of DNT vapor at a concentration of at least 10 ppt, even in the presence of an excess of potential interferents, including Diesel fuel, fertilizers, and pesticides. Both in the presence and in the absence of this complex background the SERS signal intensity of the NO(2) stretching mode showed a continuous, concentration dependent response over the entire monitored concentration range (10 ppt-100 ppb). The small size, superb sensitivity, and selectivity, as well as the fast response time of <5 min, make NCAs a valuable photonic sensor platform for ultra-trace nitroaromatic gas vapor detection with potential applications in landmine removal and homeland security. PMID:21332229

  5. Qualitative and quantitative analysis of pyrolysis oil by gas chromatography with flame ionization detection and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry.

    PubMed

    Sfetsas, Themistoklis; Michailof, Chrysa; Lappas, Angelos; Li, Qiangyi; Kneale, Brian

    2011-05-27

    Pyrolysis oils have attracted a lot of interest, as they are liquid energy carriers and general sources of chemicals. In this work, gas chromatography with flame ionization detector (GC-FID) and two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) techniques were used to provide both qualitative and quantitative results of the analysis of three different pyrolysis oils. The chromatographic methods and parameters were optimized and solvent choice and separation restrictions are discussed. Pyrolysis oil samples were diluted in suitable organic solvent and were analyzed by GC×GC-TOFMS. An average of 300 compounds were detected and identified in all three samples using the ChromaToF (Leco) software. The deconvoluted spectra were compared with the NIST software library for correct matching. Group type classification was performed by use of the ChromaToF software. The quantification of 11 selected compounds was performed by means of a multiple-point external calibration curve. Afterwards, the pyrolysis oils were extracted with water, and the aqueous phase was analyzed both by GC-FID and, after proper change of solvent, by GC×GC-TOFMS. As previously, the selected compounds were quantified by both techniques, by means of multiple point external calibration curves. The parameters of the calibration curves were calculated by weighted linear regression analysis. The limit of detection, limit of quantitation and linearity range for each standard compound with each method are presented. The potency of GC×GC-TOFMS for an efficient mapping of the pyrolysis oil is undisputable, and the possibility of using it for quantification as well has been demonstrated. On the other hand, the GC-FID analysis provides reliable results that allow for a rapid screening of the pyrolysis oil. To the best of our knowledge, very few papers have been reported with quantification attempts on pyrolysis oil samples using GC×GC-TOFMS most of which make use of the internal standard method. This work provides the ground for further analysis of pyrolysis oils of diverse sources for a rational design of both their production and utilization process. PMID:21036362

  6. Low-Dimensional Palladium Nanostructures for Fast and Reliable Hydrogen Gas Detection

    PubMed Central

    Noh, Jin-Seo; Lee, Jun Min; Lee, Wooyoung

    2011-01-01

    Palladium (Pd) has received attention as an ideal hydrogen sensor material due to its properties such as high sensitivity and selectivity to hydrogen gas, fast response, and operability at room temperature. Interestingly, various Pd nanostructures that have been realized by recent developments in nanotechnologies are known to show better performance than bulk Pd. This review highlights the characteristic properties, issues, and their possible solutions of hydrogen sensors based on the low-dimensional Pd nanostructures with more emphasis on Pd thin films and Pd nanowires. The finite size effects, relative strengths and weaknesses of the respective Pd nanostructures are discussed in terms of performance, manufacturability, and practical applicability. PMID:22346605

  7. Low cost, disposable colorimetric sensor for quantitative detection of ammonia gas

    NASA Astrophysics Data System (ADS)

    Srivastava, Ruchi; Verma, Abhishek; Jain, V. K.

    2012-10-01

    The development of a simple, fast, disposable and low cost method for sensing and differentiating a wide range of concentration of toxic ammonia vapor by using colorimetric sensor is reported. A large dynamic range from 10 ppm to 1,00,000 ppm is successfully classified at ambient temperature with reproducible results. The CSA strip is consists of the dots of chemo-responsive materials, which are environmental friendly and react specifically with ammonia at different thresholds. The pattern of color change of colorimetric sensor array is unique for reported concentration range of ammonia gas.

  8. Detection of ethene and other hydrocarbons in gas turbine engine exhaust using non-intrusive FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Arrigone, Giovanni M.; Welch, Michael A.; Hilton, Moira; Miller, Michael N.; Wilson, Christopher W.

    2003-04-01

    As part of the EU funded project AEROJET2, a number of gas turbine engine tests were performed in different facilities around Europe. At Farnborough, UK a Spey engine was used to test a suite of prototype optically based instrumentation designed to measure exhaust gas emissions without using extractive probe systems. In addition to the AEROJET 2 prototype instrumentation, a Bruker Equinox 55 Fourier transform infrared (FTIR) spectrometer was used to obtain infrared spectra of the exhaust plume both in emission and absorption mode. The Bruker FTIR spectrometer was fitted with a periscope system so that different lines of sight could be monitored in the plume in a vertical plane 25 cm downstream from the nozzle exit and 20 cm upstream of the center line of sight of the AEROJET 2 prototype instrumentation. DERA (now QinetiQ) provided exhaust gas analysis data for different engine running conditions using samples extracted from the plume with an intrusive probe. The probe sampled along a horizontal plane across the centerline of the engine 45 cm downstream of the nozzle exit. The Bruker spectrometer used both InSb (indium antimonide) and MCT (mercury-cadmium-telluride) detectors to maximize the sensitivity across the IR range 600-4000 cm-1. Typically, CO2 and H2O IR signatures dominate the observed spectra of the plume. However, the engine tests showed that at low power engine conditions spectral features associated with CO around 2147 cm-1 and with hydrocarbons could be observed at around 3000 cm-1. In particular the presence of ethene (C2H2) was detected from observation of its characteristic in and out of plane vibration mode at 949 cm-1. At high engine powers the presence of NO was detected at 1900.3 cm-1. Species concentrations were calculated using a slab model for each line of sight compared against reference spectra. The engine plume was assumed to be symmetric about the centerline. On this basis, data from the extractive sampling gas analysis that had been obtained by traversing the probe across a horizontal plane through the centerline could be compared with non-intrusive measurements made by scanning vertically. Adjustments have been made to account for the 20 cm downstream offset in measurement planes of the probe and the spectrometer behind the nozzle exit.

  9. A Detection of Gas Associated with the M31 Stellar Stream

    NASA Astrophysics Data System (ADS)

    Koch, Andreas; Danforth, Charles W.; Rich, R. Michael; Ibata, Rodrigo; Keeney, Brian A.

    2015-07-01

    Detailed studies of stellar populations in the halos of the Milky Way and the Andromeda (M31) galaxies have shown increasing numbers of tidal streams and dwarf galaxies, attesting to a complicated and on-going process of hierarchical structure formation. The most prominent feature in the halo of M31 is the Giant Stellar Stream, a structure ?4.°5 in extent along the sky, which is close to, but not coincident with the galaxy's minor axis. The stars that make up this stream are kinematically and chemically distinct from the other stars in the halo. Here, we present Hubble Space Telescope/Cosmic Origins Spectrograph high-resolution ultraviolet absorption spectra of three active galactic nuclei sight lines which probe the M31 halo, including one that samples gas in the main southwestern portion of the Giant Stream. We see two clear absorption components in many metal species at velocities typical of the M31 halo and a third, blueshifted component which arises in the stream. Photoionization modeling of the column density ratios in the different components shows gas in an ionization state typical of that seen in other galaxy halo environments and suggests solar to slightly super-solar metallicity, consistent with previous findings from stellar spectroscopy. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  10. Mesenchymal stem cells detect and defend against gammaherpesvirus infection via the cGAS-STING pathway

    PubMed Central

    Yang, Kun; Wang, Jinli; Wu, Minhao; Li, Meiyu; Wang, Yi; Huang, Xi

    2015-01-01

    Mesenchymal stem cells (MSCs) are widely used in clinical settings to treat tissue injuries and autoimmune disorders due to their multipotentiality and immunomodulation. Long-term observations reveal several complications after MSCs infusion, especially herpesviral infection. However, the mechanism of host defense against herpesviruses in MSCs remains largely unknown. Here we showed that murine gammaherpesvirus-68 (MHV-68), which is genetically and biologically related to human gammaherpesviruses, efficiently infected MSCs both in vitro and in vivo. Cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) was identified as the sensor of MHV-68 in MSCs for the first time. Moreover, the cytosolic DNA sensing pathway mediated a potent anti-herpesviral effect through the adaptor STING and downstream kinase TBK1. Furthermore, blockade of IFN signaling suggested that cytosolic DNA sensing triggered both IFN-dependent and -independent anti-herpesviral responses. Our findings demonstrate that cGAS-STING mediates innate immunity to gammaherpesvirus infection in MSCs, which may provide a clue to develop therapeutic strategy. PMID:25592282

  11. Do we need exercise tests to detect gas exchange impairment in fibrotic idiopathic interstitial pneumonias?

    PubMed

    Wallaert, Benoit; Wemeau-Stervinou, Lidwine; Salleron, Julia; Tillie-Leblond, Isabelle; Perez, Thierry

    2012-01-01

    In patients with fibrotic idiopathic interstitial pneumonia (f-IIP), the diffusing capacity for carbon monoxide (DLCO) has been used to predict abnormal gas exchange in the lung. However, abnormal values for arterial blood gases during exercise are likely to be the most sensitive manifestations of lung disease. The aim of this study was to compare DLCO, resting PaO(2), P(A-a)O(2) at cardiopulmonary exercise testing peak, and oxygen desaturation during a 6-min walk test (6MWT). Results were obtained in 121 patients with idiopathic pulmonary fibrosis (IPF, n = 88) and fibrotic nonspecific interstitial pneumonias (NSIP, n = 33). All but 3 patients (97.5%) had low DLCO values (35?mmHg) and 100 (83%) demonstrated significant oxygen desaturation during 6MWT (>4%). Interestingly 27 patients had low DLCO and normal P(A-a)O(2), peak and/or no desaturation during the 6MWT. The 3 patients with normal DLCO also had normal PaO(2), normal P(A-a)O(2), peak, and normal oxygen saturation during 6MWT. Our results demonstrate that in fibrotic IIP, DLCO better defines impairment of pulmonary gas exchange than resting PaO(2), exercise P(A-a)O(2), peak, or 6MWT SpO(2). PMID:22900170

  12. Electrochemical Noise Sensors for Detection of Localized and General Corrosion of Natural Gas Transmission Pipelines. Final Report for the Period July 2001-October 2002

    SciTech Connect

    Bullard, Sophie J.; Covino, Jr., Bernard S.; Russell, James H.; Holcomb, Gordon R.; Cramer, Stephen D.; Ziomek-Moroz, Margaret

    2002-12-01

    The U.S. Department of Energy, National Energy Technology Laboratory funded a Natural Gas Infrastructure Reliability program directed at increasing and enhancing research and development activities in topics such as remote leak detection, pipe inspection, and repair technologies and materials. The Albany Research Center (ARC), U.S. Department of Energy was funded to study the use of electrochemical noise sensors for detection of localized and general corrosion of natural gas transmission pipelines. As part of this, ARC entered into a collaborative effort with the corrosion sensor industry to demonstrate the capabilities of commercially available remote corrosion sensors for use with the Nation's Gas Transmission Pipeline Infrastructure needs. The goal of the research was to develop an emerging corrosion sensor technology into a monitor for the type and degree of corrosion occurring at key locations in gas transmission pipelines.

  13. Development of an indirect enzyme linked immunoassay for abscisic acid. [Pisum sativum

    SciTech Connect

    Ross, G.S.; Elder, P.A.; McWha, J.A.; Pearce, D.; Pharis, R.P.

    1987-09-01

    AN INDIRECT METHOD OF ENZYME-LINKED-IMMUNOSORBENT-ASSAY (ELISA) IS REPORTED FOR ABSCISIC ACID (ABA), UTILIZING A THYROGLOBULIN-ABA CONJUGATE FOR COATING WELLS. THE ASSAY CAN USE COMMERCIALLY AVAILABLE MONOCLONAL ANTIBODIES, IS SENSITIVE TO AS LITTLE AS 20 PICOGRAMS ABA PER WELL, AND IS MUCH MORE CONSERVATIVE OF ANTIBODY THAN DIRECT METHODS. THE MOST DILUTE ABA STANDARDS DID NOT RETAIN THEIR ANTIGENICITY DURING STORAGE, SO ABA STANDARD SETS WERE DILUTED IMMEDIATELY PRIOR TO USE. THE INDIRECT ELISA WAS USED SUCCESSFULLY TO ESTIMATE ABA CONCENTRATIONS IN DEVELOPING COTYLEDONS OF PISUM SATIVUM L., AFTER ONLY LITTLE PRELIMINARY PURIFICATION. IT WAS VALIDATED FOR THIS TISSUE THROUGH THE USE OF GAS CHROMATOGRAPHY-ELECTRON CAPTURE DETECTION (GC-EC), AND CAPILLARY GC-SELECTED ION MONITORING (GC-MS-SIM) USING LABELLED ABA AS AN INTERNAL STANDARD. FULL SPECTRUM GC-MASS SPECTROMETRY WAS ALSO USED TO VERIFY THAT ABA WAS PRESENT IN A SAMPLE ASSAYED QUANTITATIVELY BY BOTH ELISA AND GC-MS-SIM.

  14. Determination of PCBs in fish using enzyme-linked immunosorbent assay (ELISA)

    USGS Publications Warehouse

    Lasrado, J.A.; Santerre, C.R.; Zajicek, J.L.; Stahl, J.R.; Tillitt, D.E.; Deardorff, D.

    2003-01-01

    Polychlorinated biphenyls (PCBs) were determined in fish tissue using an enzyme-linked immunosorbent assay (ELISA). Standard curves for Aroclor 1248, 1254, and 1260 in catfish tissue were developed with ranges from 0.05 to 0.5 ppm and 0.5 to 5.0 ppm. Wild fish were initially analyzed using gas chromatography/electron-capture detection (GC/ECD) and those having residues within the standard curve ranges were analyzed with ELISA. Results obtained using ELISA and GC/ECD were not significantly different (p < 0.05) from 0.05 to 0.5 ppm. From 0.5 to 5.0 ppm, the standard curve for Aroclor 1254 was the best predictor of total PCB in wild fish samples.

  15. Stereoisomeric Specificity and Soil Gas Disequilibria: Implications for Martian Life Detection

    PubMed Central

    Keeley, Lee M.; Meyer, Edward D.; Zumberge, John E.; Bandurski, Eric L.; Nagy, Bartholomew

    1975-01-01

    Variations in the atmospheric composition of soil samples were monitored by mass spectrometry after the addition of mixtures of D- and L-carbohydrates and/or amino acids. The changes in concentrations of CO2 in these experiments were found to be related to the stereoisomeric configurations of the compounds with which the soil samples were enriched. The potential of this relationship provides a comparatively simple approach for detecting life in extraterrestrial soils. PMID:1115497

  16. Electronic subtracter for trace-gas detection with InGaAsP diode lasers

    NASA Astrophysics Data System (ADS)

    Zhu, Xiang; Cassidy, Daniel T.

    1995-12-01

    An electronic noise-cancellation scheme has been developed and tested for second-harmonic (2f) detection with short-external-cavity and distributed-feedback InGaAsP diode lasers and wavelength modulation. The 2f background signal and noise from, e.g., optical feedback, optical fringes, and power-supply pickup are effectively reduced by subtraction of a measure of the signal-beam photocurrent from a measure of the reference-beam photocurrent. The dynamic range required for the lock-in amplifier is also reduced because the signal owing to modulation of the laser output at the first harmonic is canceled. Reduction of the 2f background and dynamic range are important for atmospheric-pressure detection where a large wavelength modulation is necessary. The detector noise was minimized by the use of zero-biased detectors in the subtraction circuit. A beam-noise level (defined as 2 \\times the rms value) equivalent to a line-center absorption of 1.6 \\times 10-6 was achieved with an equivalent-noise bandwidth of 1.25 Hz for 2f detection at 10 kHz. The electronic circuit is easy to construct and low cost.

  17. A study of an electronic nose for detection of lung cancer based on a virtual SAW gas sensors array and imaging recognition method

    Microsoft Academic Search

    Xing Chen; Mingfu Cao; Yi Li; Weijun Hu; Ping Wang; Kejing Ying; Hongming Pan

    2005-01-01

    In this paper, we propose an electronic nose for non-invasive detection and diagnosis of lung cancer based on a kind of virtual array of surface acoustic wave (SAW) gas sensors and an imaging recognition method. It includes a gas path constructed from a two-bag system, solid phase micro extraction (SPME) and a capillary column to pre-concentrate and separate volatile organic

  18. Application of comprehensive two-dimensional gas chromatography with nitrogen-selective detection for the analysis of fungicide residues in vegetable samples

    Microsoft Academic Search

    Weeraya Khummueng; Craige Trenerry; Gavin Rose; Philip J. Marriott

    2006-01-01

    Comprehensive two-dimensional gas chromatography (GCxGC) with nitrogen-phosphorus detection (NPD) has been investigated for the separation and quantitation of fungicides in vegetable samples. The detector gas flows (H2, N2 and air) were adjusted to achieve maximum response of signal whilst minimizing peak width. The comparison of different column sets and selection of the temperature program were carried out with a mixture

  19. Field detection and identification of a bioaerosol suite by pyrolysis-gas chromatography-ion mobility spectrometry

    NASA Astrophysics Data System (ADS)

    Snyder, A. Peter; Tripathi, Ashish; Maswadeh, Waleed M.; Ho, Jim; Spence, Mel

    2002-06-01

    Improvements were made to a pyrolysis-gas chromatography-ion mobility spectrometry stand-alone biodetector to provide more pyrolyzate compound information to the IMS detector module. Air carrier gas flowing continuously through the pyrolysis tube, the rate of air flow, and pyrolysis rate were found to improve the relative quality and quantity of pyrolyzate compounds detected by the IMS detector compare to earlier work. These improvements allowed a greater degree of confidence in the correlation of biological aerosols obtain in outdoor testing scenarios to a standard GC-IMS biological aerosol dataset. The airflow improvement allowed more biomarker compounds to be observed in the GC-IMS data domain for aerosols of Gram-negative Erwinia herbicola (EH) and ovalbumin protein as compared to previous studies. Minimal differences were observed for Gram-positive spores of Bacillus subtilis var. globigii (BG) from that of earlier work. Prior outdoor aerosol challenges dealt with the detection of one organism, either EH or BG. Biological aerosols were disseminated in a Western Canadian prairie and the Py-GC-IMS was tested for its ability to detect the biological aerosols. The current series of outdoor trials consisted of three different biological aerosol challenges. Forty-two trials were conducted and a simple area calculation of the GC-IMS data domain biomarker peaks correlated with the correct bioaerosol challenge in 30 trials. In another 7 trials, the status of an aerosol was determined to be biological in origin. Two additional trials had no discernible, unambiguous GC-IMS biological response, because they were black water sprays. Reproducible limits of detection were at a concentration of less than 0.5 bacterial analyte-containing particles per liter of air (ACPLA). In order to realize this low concentration, an aerosol concentrator was used to concentrate 2000 liters of air in 2.2 minutes. Previous outdoor aerosol trials have shown the Py-GC-IMS device to be a credible detector with response to determining the presence of a biological aerosol. The current series of outdoor trials has provided a platform to show that the Py-PC-IMS can provide information more specific than a biological or non-biological analysis to an aerosol when the time of dissemination is unknown to the operator. The Py-GC-IMS is shown to be able to discriminate between aerosols of a Gram-positive spore, a Gram-negative bacterium and a protein.

  20. Detecting ozone- and greenhouse gas-driven wind trends with observational data.

    PubMed

    Lee, Sukyoung; Feldstein, Steven B

    2013-02-01

    Modeling studies suggest that Antarctic ozone depletion and, to a lesser degree, greenhouse gas (GHG) increase have caused the observed poleward shift in the westerly jet during the austral summer. Similar studies have not been performed previously with observational data because of difficulties in separating the two contributions. By applying a cluster analysis to daily ERA-Interim data, we found two 7- to 11-day wind clusters, one resembling the models' responses to GHG forcing and the other resembling ozone depletion. The trends in the clusters' frequency of occurrence indicate that the ozone contributed about 50% more than GHG toward the jet shift, supporting the modeling results. Moreover, tropical convection apparently plays an important role for the GHG-driven trend. PMID:23372010

  1. The C3N- anion: first detection of its electronic luminescence in rare gas solids.

    PubMed

    Turowski, Micha?; Gronowski, Marcin; Boyé-Péronne, Séverine; Douin, Stéphane; Monéron, Laurence; Crépin, Claudine; Ko?os, Robert

    2008-04-28

    The 193 nm laser irradiation of cyanoacetylene (HCCCN) that was isolated in rare gas solids led to a long-lived luminescence (origin at 3.58 eV), which was assigned to the a (3)Sigma(+)-X (1)Sigma(+) system of cyanoacetylide (CCCN(-)). The identification, which involved (15)N and (2)H isotopic substitution studies, is based on vibronic spacings in the phosphorescence spectrum (compared to previous infrared absorption measurements and to theoretical results regarding CCCN(-) vibrational frequencies), as well as on a BD(T)/cc-pVTZ prediction for the singlet-triplet energy gap in this anion (3.61 eV). The same emission was also generated from KrHC(3)N mixtures subjected to a glow electric discharge immediately before the solidification (cold-window-radial-discharge technique). PMID:18447436

  2. Detection of ergot (Claviceps purpurea) in a dairy feed component by gas chromatography and mass spectrometry.

    PubMed

    Mantle, P G

    1996-11-01

    A dairy feed that contained barley malt screenings caused hyperthermia in dairy cattle. The feed was suspected of containing ergot and was subsequently analyzed to determine the ricinoleate component, a special and prominent feature of oil-rich ergot tissue. Triglyceride oil was extracted by organic solvents from the dairy feed, and the oil was saponified to release fatty acids. Ricinoleate, as a methyl ester, was selectively resolved from other fatty acids by silica gel chromatography and was analyzed by capillary gas chromatography coupled with chemical ionization mass spectrometry, which demonstrated the presence of the methyl ricinoleate molecule and proved that the feed contained ergot. The methodology may be refined to monitor for ergot in powdered dairy feed more routinely. PMID:8961105

  3. Self-detection of x-ray Fresnel transmittivity using photoelectron-induced gas ionization

    E-print Network

    Stoupin, Stanislav

    2015-01-01

    Electric response of an x-ray mirror enclosed in a gas flow ionization chamber was studied under the conditions of total external reflection for hard x-rays. It is shown that the electric response of the system as a function of the incidence angle is defined by x-ray Fresnel transmittivity and photon-electron attenuation properties of the mirror material. A simple interpretation of quantum yield of the system is presented. The approach provides non-invasive in-situ diagnostics of hard x-ray optics, easy access to complementary x-ray transmittivity data in x-ray reflectivity experiments and can also pave the way to novel schemes for angle and energy resolving x-ray detectors.

  4. Laser system for natural gas detection. Phase 1: Laboratory feasibility studies

    NASA Technical Reports Server (NTRS)

    Grant, W. B.; Hinkley, E. D., Jr.

    1982-01-01

    This project demonstrated the feasibility of using laser remote sensing technology as a tool for leak survey work in natural gas distribution systems. A laboratory device was assembled using a pair of helium neon (HeNe) lasers to measure methane. One HeNe laser emits radiation at a wavelength of 3.3922 micrometers, which corresponds to a strong absorption feature of methane, while the other emits radiation at a wavelength of 3.3911 micrometers, which corresponds to a weak absorption by methane. As a particular area is scanned for leaks, the laser is pointed at convenient topographic targets within its operating range, about 25 m. A portion of the backscattered radiation is collected by a receiver and focused onto an indium antimonide (InSb) photodetector, cooled to 77K. Methane concentrations were determined from the differential absorption at the two wavelengths for the backscattered radiation.

  5. Detection of discoloration in diesel fuel based on gas chromatographic fingerprints.

    PubMed

    Krakowska, Barbara; Stanimirova, Ivana; Orzel, Joanna; Daszykowski, Michal; Grabowski, Ireneusz; Zaleszczyk, Grzegorz; Sznajder, Miroslaw

    2015-02-01

    In the countries of the European Community, diesel fuel samples are spiked with Solvent Yellow 124 and either Solvent Red 19 or Solvent Red 164. Their presence at a given concentration indicates the specific tax rate and determines the usage of fuel. The removal of these so-called excise duty components, which is known as fuel "laundering", is an illegal action that causes a substantial loss in a government's budget. The aim of our study was to prove that genuine diesel fuel samples and their counterfeit variants (obtained from a simulated sorption process) can be differentiated by using their gas chromatographic fingerprints that are registered with a flame ionization detector. To achieve this aim, a discriminant partial least squares analysis, PLS-DA, for the genuine and counterfeit oil fingerprints after a baseline correction and the alignment of peaks was constructed and validated. Uninformative variables elimination (UVE), variable importance in projection (VIP), and selectivity ratio (SR), which were coupled with a bootstrap procedure, were adapted in PLS-DA in order to limit the possibility of model overfitting. Several major chemical components within the regions that are relevant to the discriminant problem were suggested as being the most influential. We also found that the bootstrap variants of UVE-PLS-DA and SR-PLS-DA have excellent predictive abilities for a limited number of gas chromatographic features, 14 and 16, respectively. This conclusion was also supported by the unitary values that were obtained for the area under the receiver operating curve (AUC) independently for the model and test sets. PMID:25407430

  6. The determination by gas chromatography with atomic emission detection of total sulfur in fuels used as forensic evidence.

    PubMed

    Kaneko, Tsuyoshi; Yoshida, Hiroaki; Suzuki, Shinichi

    2008-05-20

    In Japan, taxed diesel fuel from non-taxed fuel oil-A is illegally produced by removing coumarin, which is added as a non-taxed marker. The coumarin is removed using concentrated sulfuric acid and this produces a high viscosity and hazardous material, called "sulfuric acid pitch", as a by-product. This compound has a detrimental effect on the environment and is hazardous to humans. The actions have been associated with organized crime with the illegally gained taxes becoming financial bases. To discriminate legal and diesel oil from illegal product, the peak area ratio R(SC), the ratio of total sulfur to carbon (>C(14)), was used. R(SC) is calculated by the total areas of sulfur and carbon (>C(14)) from the gas chromatogram obtained by gas chromatography-atomic emission detection (GC-AED). Sulfur in legal diesel fuels is strictly regulated by a maximum limit, which was 50ppm (and is now 10ppm), but in the preparation of illegal diesel oil, in which coumarin is eliminated, sulfur cannot be removed. Therefore, the R(SC) of fuel oil-A and illegal fuel oil is over 15, whereas those for legal fuel oil and diesel fuel are under 2.0. Furthermore, these ratios do not change in weathering experiments. GC-AED was applied to an actual arson case and was found to be effective for the determination of total sulfur in trace amounts of accelerants detected in fire debris at the arson scene, and hence was effective for the characterization of the ignitable liquids used. PMID:18160239

  7. THE DIRECT DETECTION OF COOL, METAL-ENRICHED GAS ACCRETION ONTO GALAXIES AT z {approx} 0.5

    SciTech Connect

    Rubin, Kate H. R.; Xavier Prochaska, J. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, 69117 Heidelberg (Germany); Koo, David C. [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High St, Santa Cruz, CA 95064 (United States); Phillips, Andrew C., E-mail: rubin@mpia.de [UCO/Lick Observatory, University of California, 1156 High St, Santa Cruz, CA 95064 (United States)

    2012-03-10

    We report on the discovery of cool gas inflow toward six star-forming galaxies with redshifts z {approx} 0.35-1. Analysis of Mg II and Fe II resonance-line absorption in Keck/LRIS spectroscopy of the galaxies reveals positive velocity shifts for cool gas of 80-200 km s{sup -1} with respect to the host galaxy velocity centroids, and equivalent widths for this inflow of {approx}> 0.6 A in five of the six objects. The host galaxies exhibit a wide range of star formation rates (SFRs {approx}1-40 M{sub Sun} yr{sup -1}) and have stellar masses similar to that of the Milky Way (log M{sub *}/M{sub Sun} {approx} 9.6-10.5). Imaging from the Hubble Space Telescope Advanced Camera for Surveys indicates that five of the six galaxies have highly inclined (i > 55 Degree-Sign ), disk-like morphologies. These data represent the first unambiguous detection of inflow into isolated, star-forming galaxies in the distant universe. We suggest that the inflow is due to the infall of enriched material from dwarf satellites and/or a galactic fountain within the galaxies. Assuming that the material has been enriched to 0.1 Z{sub Sun} and has a physical extent approximately equal to that of the galaxies (implied by the high observed gas covering fractions), we infer mass inflow rates of dM{sub in}/dt {approx}> 0.2-3 M{sub Sun} yr{sup -1} for four of these systems. Finally, from comparison of these absorption lines to the profiles of Mg II and Fe II absorption in a larger spectroscopic sample of {approx}100 objects, we measure a covering fraction of cool inflow of at least 6%, but cannot rule out the presence of enriched infall onto as many as {approx}40 of these galaxies.

  8. Controlled growth of conical nickel oxide nanocrystals and their high performance gas sensing devices for ammonia molecule detection.

    PubMed

    Wang, Jian; Yang, Fan; Wei, Xiaowei; Zhang, Yafei; Wei, Liangming; Zhang, Jianjun; Tang, Qifeng; Guo, Biao; Xu, Lei

    2014-08-21

    NiO nanocones with good symmetry and highly ordered structure on NiO foil substrate have been successfully fabricated via a facile wet chemical approach combined with subsequent high temperature oxidation. These organized conical superstructures grow only along a certain direction and be controlled via the self-assembly and oriented attachment of a nucleus, which mainly rely on the similar surface energies and the extent of lattice matching of the oriented attached surfaces. During high temperature oxidation, the electric field created via the Ni(2+) and O(2-) facilitates Ni(2+) diffusion outward along the grain boundaries and O(2-) diffusion inward toward to meet the Ni(2+) ions, forming NiO. The as-grown NiO nanocones are 50-350 nm in diameter and 50-400 nm in height. The tip diameter of the nanocone is about 30 nm and the apex angle of the nanocone is about 40°. Meanwhile, we systematically investigated the gas sensing properties of the sensors based on the as-fabricated NiO foil covered with nanocone arrays for ammonia detection at room temperature. The results show that the gas sensing devices have outstanding sensitivity, reproducibility and selectivity, which are mainly because of the excellent connection between the NiO sensing materials and the Au electrodes, the strong electron donating ability of ammonia and the large active surface of selective physisorption for ammonia. PMID:25000512

  9. Detection of molecular gas in an ALMA [C II]-identified submillimetre galaxy at z = 4.44

    NASA Astrophysics Data System (ADS)

    Huynh, M. T.; Kimball, A. E.; Norris, R. P.; Smail, Ian; Chow, K. E.; Coppin, K. E. K.; Emonts, B. H. C.; Ivison, R. J.; Smol?i?, V.; Swinbank, A. M.

    2014-09-01

    We present the detection of 12CO(2-1) in the z = 4.44 submillimetre galaxy ALESS65.1 using the Australia Telescope Compact Array. A previous Atacama Large Millimeter/submillimeter Array study of submillimetre galaxies (SMGs) in the Extended Chandra Deep Field South determined the redshift of this optically and near-infrared undetected source through the measurement of [C II] 157.74 ?m emission. Using the luminosity of the 12CO(2-1) emission, we estimate the gas mass to be Mgas ˜ 1.7 × 1010 M?. The gas depletion time-scale of ALESS65.1 is ˜ 25 Myr, similar to other high-redshift SMGs and consistent with z > 4 SMGs being the progenitors of massive `red-and-dead' galaxies at z > 2. The ratio of the [C II], 12CO and far-infrared luminosities implies a strong far-ultraviolet field of G0 ˜ 103.25, which is at the high end of the far-ultraviolet fields seen in local starbursts, but weaker than the far-ultraviolet fields of most nearby ultraluminous infrared galaxies (ULIRGs). The high ratio of L_{[{C II}]}/L_FIR = 1.0 × 10^{-3} observed in ALESS65.1, combined with L_{[{C II}]}/L_CO ˜ 2300, is consistent with ALESS65.1 having more extended regions of intense star formation than local ULIRGs.

  10. Loading and detecting a three-dimensional Fermi gas in a one-dimensional optical superlattice

    NASA Astrophysics Data System (ADS)

    Sheikhan, Ameneh; Kollath, Corinna

    2015-04-01

    We investigate the procedures of loading and detecting three-dimensional fermionic quantum gases in a one-dimensional optical superlattice potential subjected to a trapping potential. Additionally, we consider the relaxation dynamics after a sudden change of the superlattice potential. We numerically simulate the time-dependent evolution of the continuous system using exact diagonalization of noninteracting fermions. During the loading procedure we analyze the occupation of the instantaneous energy levels and compare the situation in a homogeneous system with the trapped one. Strong differences are found in particular in the evolution of excitations which we trace back to the distinct global density distribution. Starting from an imbalanced state in the superlattice potential, we consider the relaxation dynamics of fermions after a slow change of the superlattice potential and find a bimodal distribution of excitations. To be able to compare with the experimental results we also simulate the measurement sequence of the even and odd local density and find a strong dependence of the outcome on the actual ramp procedure. We suggest how the loading and detecting procedure can be optimized.

  11. SIM PlanetQuest Key Project Precursor Observations to Detect Gas Giant Planets Around Young Stars

    NASA Technical Reports Server (NTRS)

    Tanner, Angelle; Beichman, Charles; Akeson, Rachel; Ghez, Andrea; Grankin, Konstantin N.; Herbst, William; Hillenbrand, Lynne; Huerta, Marcos; Konopacky, Quinn; Metchev, Stanimir; Mohanty, Subhanjoy; Prato, L.; Simon, Michal

    2008-01-01

    We present a review of precursor observing programs for the SIM PlanetQuest Key project devoted to detecting Jupiter mass planets around young stars. In order to ensure that the stars in the sample are free of various sources of astrometric noise that might impede the detection of planets, we have initiated programs to collect photometry, high contrast images, interferometric data and radial velocities for stars in both the Northern and Southern hemispheres. We have completed a high contrast imaging survey of target stars in Taurus and the Pleiades and found no definitive common proper motion companions within one arcsecond (140 AU) of the SIM targets. Our radial velocity surveys have shown that many of the target stars in Sco-Cen are fast rotators and a few stars in Taurus and the Pleiades may have sub-stellar companions. Interferometric data of a few stars in Taurus show no signs of stellar or sub-stellar companions with separations of <5 mas. The photometric survey suggests that approximately half of the stars initially selected for this program are variable to a degree (1(sigma) >0.1 mag) that would degrade the astrometric accuracy achievable for that star. While the precursor programs are still a work in progress, we provide a comprehensive list of all targets ranked according to their viability as a result of the observations taken to date. By far, the observable that removes the most targets from the SIM-YSO program is photometric variability.

  12. Hydroacoustic methodology for detection, localization, and quantification of gas bubbles rising from the seafloor at gas seeps from the eastern Black Sea

    NASA Astrophysics Data System (ADS)

    Nikolovska, Aneta; Sahling, Heiko; Bohrmann, Gerhard

    2008-10-01

    Detailed acoustic investigation of bubble streams rising from the seafloor were conducted during R/V Meteor cruise M72/3a at a deep submarine hydrocarbon seep environment. The area is located offshore Georgia (eastern part of the Black Sea) at a water depth between 840 m and 870 m. The sediment echosounder Parasound DS-3/P70 was used for detecting bubbles in the water column that causes strong backscatter in the echographs ("flares"). Employing the swath echsounder Kongsberg EM710 flares in the water column were mapped along the entire swath width of approximately 1000 m at high spatial resolution. The exact location of the flares could be extracted manually. Subsequently, the horizontally looking sonar Kongsberg digital telemetry MS1000 mounted on a remotely operated vehicle (ROV) was utilized to quantify the flux of bubbles. A model was developed that is based on the principle of finding the "acoustic mass" in order to quantify the bubble flux at various seeps. The acoustic approach from the backscatter data of the ROV sonar resulted in bubble fluxes in the range of 0.01 to 5.5 L/min (corresponding to 0.037 to 20.5 mol CH4/min) at in situ conditions (˜850 m water depth, ˜9°C). Independent flux estimations using a funnel-shaped device showed that the acoustic model consistently produced lower values but the offset is less than 12%. Furthermore, the deviation decreased with increasing flux rates. A field of bubble streams was scanned three times from different directions in order to reveal the reproducibility of the method. Flux estimations yielded consistent fluxes of about 2 l/min (7.4 mol CH4/min) with variations of less than 10%. Although gas emissions have been found at many sites at the seafloor in a range of geological settings, the amount of escaping gas is still largely unknown. With this study presenting a novel method of quantifying bubble fluxes employing a horizontally looking sonar system, it is intended to contribute to the global effort of better constraining bubble fluxes at deep-sea settings.

  13. A NEW METHOD OF PEAK DETECTION FOR ANALYSIS OF COMPREHENSIVE TWO-DIMENSIONAL GAS CHROMATOGRAPHY MASS SPECTROMETRY DATA.

    PubMed

    Kim, Seongho; Ouyang, Ming; Jeong, Jaesik; Shen, Changyu; Zhang, Xiang

    2014-06-01

    We develop a novel peak detection algorithm for the analysis of comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOF MS) data using normal-exponential-Bernoulli (NEB) and mixture probability models. The algorithm first performs baseline correction and denoising simultaneously using the NEB model, which also defines peak regions. Peaks are then picked using a mixture of probability distribution to deal with the co-eluting peaks. Peak merging is further carried out based on the mass spectral similarities among the peaks within the same peak group. The algorithm is evaluated using experimental data to study the effect of different cut-offs of the conditional Bayes factors and the effect of different mixture models including Poisson, truncated Gaussian, Gaussian, Gamma, and exponentially modified Gaussian (EMG) distributions, and the optimal version is introduced using a trial-and-error approach. We then compare the new algorithm with two existing algorithms in terms of compound identification. Data analysis shows that the developed algorithm can detect the peaks with lower false discovery rates than the existing algorithms, and a less complicated peak picking model is a promising alternative to the more complicated and widely used EMG mixture models. PMID:25264474

  14. Detection of an Extended Human Volatome with Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometry

    PubMed Central

    Phillips, Michael; Cataneo, Renee N.; Chaturvedi, Anirudh; Kaplan, Peter D.; Libardoni, Mark; Mundada, Mayur; Patel, Urvish; Zhang, Xiang

    2013-01-01

    Background Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF MS) has been proposed as a powerful new tool for multidimensional analysis of complex chemical mixtures. We investigated GCxGC-TOF MS as a new method for identifying volatile organic compounds (VOCs) in normal human breath. Methods Samples of alveolar breath VOCs and ambient room air VOC were collected with a breath collection apparatus (BCA) onto separate sorbent traps from 34 normal healthy volunteers (mean age = 40 yr, SD = 17 yr, male/female = 19/15). VOCs were separated on two serial capillary columns separated by a cryogenic modulator, and detected with TOF MS. The first and second dimension columns were non-polar and polar respectively. Results BCA collection combined with GC×GC-TOF MS analysis identified approximately 2000 different VOCs in samples of human breath, many of which have not been previously reported. The 50 VOCs with the highest alveolar gradients (abundance in breath minus abundance in ambient room air) mostly comprised benzene derivatives, acetone, methylated derivatives of alkanes, and isoprene. Conclusions Collection and analysis of breath VOCs with the BCA-GC×GC-TOF MS system extended the size of the detectable human volatile metabolome, the volatome, by an order of magnitude compared to previous reports employing one-dimensional GC-MS. The size of the human volatome has been under-estimated in the past due to coelution of VOCs in one-dimensional GC analytical systems. PMID:24086492

  15. [A trace gas sensor using mid-infrared quantum cascaded laser at 4.8 microm to detect carbon monoxide].

    PubMed

    Chen, Chen; Wang, Biao; Li, Chun-Guang; Li, Jian; Wang, Yi-Ding

    2014-03-01

    Presented in the present paper is a compact instrument developed for rapid, sensitive and continuous monitoring of trace gases in air, with results shown for carbon monoxide concentration. This instrument takes advantage of recent technology in mid-infrared quantum cascaded laser (QCL) operating at 4.8 microm and mercury cadmium telluride (HgCdTe) mid-infrared (MIR) detector, combing MIR multipass herriott cell with 76 m absorption path length to obtain low detection sensitivity down to 50 nmol x mol(-1) level in 4 s acquisition time. Meanwhile, in order to eliminate the instability induced by electrically modulated light source and effectively improve detection limit of the instrument, an optical structure with dual channel path was designed which is based on differential optical absorption spectroscopy method. The experimental results show that the instrument integrated with gas concentration inversion algorithm can be applied to in-situ measurements of trace gases without calibration. Additionally, operator could substitute a QCL operating at a different wavelength to measure other gases. PMID:25208424

  16. Solidphase microextraction combined with gas chromatography and atomic emission detection for the determination of cyclopentadienylmanganese tricarbonyl and (methylcyclopentadienyl)manganese tricarbonyl in soils and seawaters

    Microsoft Academic Search

    Natalia Campillo; Rosa Peñalver; Manuel Hernández-Córdoba

    2007-01-01

    A method based on solid-phase microextraction with capillary gas chromatography and microwave-induced plasma atomic emission detection (SPME-GC-MIP-AED) for the determination of cyclopentadienylmanganese tricarbonyl (CMT) and its methyl derivative, (methylcyclopentadienyl)manganese tricarbonyl (MMT) in seawaters and soils was optimized and evaluated. The solvent-free preconcentration step was carried out in the headspace (HS) mode. Element-specific detection and quantification was carried out by monitoring

  17. COMPLETE IONIZATION OF THE NEUTRAL GAS: WHY THERE ARE SO FEW DETECTIONS OF 21 cm HYDROGEN IN HIGH-REDSHIFT RADIO GALAXIES AND QUASARS

    SciTech Connect

    Curran, S. J. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Whiting, M. T., E-mail: sjc@physics.usyd.edu.au [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)

    2012-11-10

    From the first published z {approx}> 3 survey of 21 cm absorption within the hosts of radio galaxies and quasars, Curran et al. found an apparent dearth of cool neutral gas at high redshift. From a detailed analysis of the photometry, each object is found to have a {lambda} = 1216 A continuum luminosity in excess of L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}, a critical value above which 21 cm has never been detected at any redshift. At these wavelengths, and below, hydrogen is excited above the ground state so that it cannot absorb in 21 cm. In order to apply the equation of photoionization equilibrium, we demonstrate that this critical value also applies to the ionizing ({lambda} {<=} 912 A) radiation. We use this to show, for a variety of gas density distributions, that upon placing a quasar within a galaxy of gas, there is always an ultraviolet luminosity above which all of the large-scale atomic gas is ionized. While in this state, the hydrogen cannot be detected or engage in star formation. Applying the mean ionizing photon rate of all of the sources searched, we find, using canonical values for the gas density and recombination rate coefficient, that the observed critical luminosity gives a scale length (3 kpc) similar that of the neutral hydrogen (H I) in the Milky Way, a large spiral galaxy. Thus, this simple yet physically motivated model can explain the critical luminosity (L {sub 912} {approx} L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}), above which neutral gas is not detected. This indicates that the non-detection of 21 cm absorption is not due to the sensitivity limits of current radio telescopes, but rather that the lines of sight to the quasars, and probably the bulk of the host galaxies, are devoid of neutral gas.

  18. Complete Ionization of the Neutral Gas: Why There are So Few Detections of 21 cm Hydrogen in High-redshift Radio Galaxies and Quasars

    NASA Astrophysics Data System (ADS)

    Curran, S. J.; Whiting, M. T.

    2012-11-01

    From the first published z >~ 3 survey of 21 cm absorption within the hosts of radio galaxies and quasars, Curran et al. found an apparent dearth of cool neutral gas at high redshift. From a detailed analysis of the photometry, each object is found to have a ? = 1216 Å continuum luminosity in excess of L 1216 ~ 1023 W Hz-1, a critical value above which 21 cm has never been detected at any redshift. At these wavelengths, and below, hydrogen is excited above the ground state so that it cannot absorb in 21 cm. In order to apply the equation of photoionization equilibrium, we demonstrate that this critical value also applies to the ionizing (? <= 912 Å) radiation. We use this to show, for a variety of gas density distributions, that upon placing a quasar within a galaxy of gas, there is always an ultraviolet luminosity above which all of the large-scale atomic gas is ionized. While in this state, the hydrogen cannot be detected or engage in star formation. Applying the mean ionizing photon rate of all of the sources searched, we find, using canonical values for the gas density and recombination rate coefficient, that the observed critical luminosity gives a scale length (3 kpc) similar that of the neutral hydrogen (H I) in the Milky Way, a large spiral galaxy. Thus, this simple yet physically motivated model can explain the critical luminosity (L 912 ~ L 1216 ~ 1023 W Hz-1), above which neutral gas is not detected. This indicates that the non-detection of 21 cm absorption is not due to the sensitivity limits of current radio telescopes, but rather that the lines of sight to the quasars, and probably the bulk of the host galaxies, are devoid of neutral gas.

  19. Pt- and Pd-decorated MWCNTs for vapour and gas detection at room temperature.

    PubMed

    Baccar, Hamdi; Thamri, Atef; Clément, Pierrick; Llobet, Eduard; Abdelghani, Adnane

    2015-01-01

    Here we report on the gas sensing properties of multiwalled carbon nanotubes decorated with sputtered Pt or Pd nanoparticles. Sputtering allows for an oxygen plasma treatment that removes amorphous carbon from the surface of the carbon nanotubes and creates oxygenated surface defects in which metal nanoparticles nucleate within a few minutes. The decoration with the 2 nm Pt or the 3 nm Pd nanoparticles is very homogeneous. This procedure is performed at the device level (i.e., for carbon nanotubes deposited onto sensor substrates) for many devices in one batch, which illustrates the scalability for the mass production of affordable nanosensors. The response to selected aromatic and non-aromatic volatile organic compounds, as well as pollutant gases has been studied. Pt- and Pd-decorated multiwalled carbon nanotubes show a fully reversible response to the non-aromatic volatile organic compounds tested when operated at room temperature. In contrast, these nanomaterials were not responsive to the aromatic compounds studied (measured at concentrations up to 50 ppm). Therefore, these sensors could be useful in a small, battery-operated alarm detector, for example, which is able to discriminate aromatic from non-aromatic volatile organic compounds in ambient. PMID:25977863

  20. A Detection of Gas Associated with the M 31 Stellar Stream

    E-print Network

    Koch, Andreas; Rich, R Michael; Ibata, Rodrigo; Keeney, Brian A

    2015-01-01

    Detailed studies of stellar populations in the halos of the Milky Way and the Andromeda (M 31) galaxies have shown increasing numbers of tidal streams and dwarf galaxies, attesting to a complicated and on-going process of hierarchical structure formation. The most prominent feature in the halo of M 31 is the Giant Stellar Stream, a structure ~4.5 degrees in extent along the sky, which is close to, but not coincident with the galaxy's minor axis. The stars that make up this stream are kinematically and chemically distinct from the other stars in the halo. Here, we present HST/COS high-resolution ultraviolet absorption spectra of three Active Galactic Nuclei sight lines which probe the M 31 halo, including one that samples gas in the main southwestern portion of the Giant Stream. We see two clear absorption components in many metal species at velocities typical of the M 31 halo and a third, blue-shifted component which arises in the stream. Photoionization modeling of the column density ratios in the different ...

  1. Hydrothermally carbonized plant materials: patterns of volatile organic compounds detected by gas chromatography.

    PubMed

    Becker, Roland; Dorgerloh, Ute; Helmis, Mario; Mumme, Jan; Diakité, Mamadou; Nehls, Irene

    2013-02-01

    The nature and concentrations of volatile organic compounds (VOCs) in chars generated by hydrothermal carbonization (HTC) is of concern considering their application as soil amendment. Therefore, the presence of VOCs in solid HTC products obtained from wheat straw, biogas digestate and four woody materials was investigated using headspace gas chromatography. A variety of potentially harmful benzenic, phenolic and furanic volatiles along with various aldehydes and ketones were identified in feedstock- and temperature-specific patterns. The total amount of VOCs observed after equilibration between headspace and char samples produced at 270°C ranged between 2000 and 16,000?g/g (0.2-1.6wt.%). Depending on feedstock 50-9000?g/g of benzenes and 300-1800?g/g of phenols were observed. Substances potentially harmful to soil ecology such as benzofurans (200-800?g/g) and p-cymene (up to 6000?g/g in pine wood char) exhibited concentrations that suggest restrained application of fresh hydrochar as soil amendment or for water purification. PMID:23334019

  2. Pt- and Pd-decorated MWCNTs for vapour and gas detection at room temperature

    PubMed Central

    Baccar, Hamdi; Clément, Pierrick; Abdelghani, Adnane

    2015-01-01

    Summary Here we report on the gas sensing properties of multiwalled carbon nanotubes decorated with sputtered Pt or Pd nanoparticles. Sputtering allows for an oxygen plasma treatment that removes amorphous carbon from the surface of the carbon nanotubes and creates oxygenated surface defects in which metal nanoparticles nucleate within a few minutes. The decoration with the 2 nm Pt or the 3 nm Pd nanoparticles is very homogeneous. This procedure is performed at the device level (i.e., for carbon nanotubes deposited onto sensor substrates) for many devices in one batch, which illustrates the scalability for the mass production of affordable nanosensors. The response to selected aromatic and non-aromatic volatile organic compounds, as well as pollutant gases has been studied. Pt- and Pd-decorated multiwalled carbon nanotubes show a fully reversible response to the non-aromatic volatile organic compounds tested when operated at room temperature. In contrast, these nanomaterials were not responsive to the aromatic compounds studied (measured at concentrations up to 50 ppm). Therefore, these sensors could be useful in a small, battery-operated alarm detector, for example, which is able to discriminate aromatic from non-aromatic volatile organic compounds in ambient. PMID:25977863

  3. Diagnostic organometallic and metallodendritic materials for SO2 gas detection: reversible binding of sulfur dioxide to arylplatinum(II) complexes

    PubMed

    Albrecht; Gossage; Lutz; Spek; van Koten G

    2000-04-14

    A series of square-planar platinum(II) complexes of the N,C,N'-terdentate-coordinating monoanionic "pincer" ligand, [PtX(4-E-2,6-[CH2NRR']2-C6H2](X=Cl, Br, I, tolyl; R, R'=Et, Me; E=H, OH, OSiMe2tBu) has been prepared. In the presence of sulfur dioxide, these complexes spontaneously adsorb this gas to form penta-coordinated adducts. Solid-state crystal-structure analyses of the SO2 adducts 8c (X=I, R=R=Me, E=OSiMe2tBu) and 11 (X=Cl, R=R'=Me, E=OH) show a square-pyramidal geometry around the metal center with SO2 in the apical position. Most interestingly. the adduct 11 forms similar Pt-Cl... H-O hydrogen-bonded alpha-type networks as the corresponding SO2-free complex 5. The conservation of the supramolecular information (hydrogen-bonded self-assembly) throughout a reaction (SO2 adsorption) is unprecedented in crystal engineering. Adduct formation in the solid state or in solution is fast and reversible and is indicated by a characteristic color change of the material from colorless to bright orange. Since facile methods have been developed to remove SO2 from the adducts and to regenerate the square-planar starting complexes, these complexes fulfill several essential prerequisites of sensor materials for repeated diagnostic SO2 detection. The platinum sensors have been found to be highly selective for sulfur dioxide and particularly sensitive for submilimolar to molar gas quantities. Their response capacity is tuneable by electronic and steric modifications of the ligand array by introduction of, for example, different substituents on the nitrogen donors. The periphery of dendrimers is shown to be an appropriate macromolecular support for anchoring the detection-active sites, thus allowing full recovery of the sensor materials for repeated use. By using this concept, metallo-dendrimers 3 and 15 have been prepared. Owing to the dendritic connectivity, these sensors are suitable for repetitive qualitative and quantitative detection of small amounts of SO2. PMID:10840966

  4. Residue analysis of organophosphorus and organochlorine pesticides in fatty matrices by gas chromatography coupled with electron-capture detection.

    PubMed

    Park, Jae-Woo; Abd El-Aty, A M; Lee, Myoung-Heon; Song, Sung-Ok; Shim, Jae-Han

    2006-01-01

    A multiresidue method for the simultaneous determination of 22 organochlorine (OCs) and organophosphorus (Ops) pesticides (including isomers and metabolites), representing a wide range of physicochemical properties, was developed in fatty matrices extracted from meat. Pesticides were extracted from samples with acetonitrile/n-hexane (v:v, 1:1). The analytical screening was performed by gas chromatography coupled with electron-capture detection (ECD). The identification of compounds was based on their retention time and on comparison of the primary and secondary ions. The optimized method was validated by determining accuracy (recovery percentages), precision (repeatability and reproducibility), and sensitivity (detection and quantitation limits) from analyses of samples fortified at 38 to 300 ng/g levels. Correlation coefficients for the 22 extracted pesticide standard curves (linear regression analysis, n = 3) ranged from 0.998 to 1.000. Recovery studies from 2 g samples fortified at 3 levels demonstrated that the GC-ECD method provides 64.4-96.0% recovery for all pesticides except 2,4'-DDE (44.6-50.4%), 4,4'-DDE (51.1-57.5%) and 2,4'-DDT (50.0-51.2%). Both repeatability and reproducibility relative standard deviation values were < 20% for all residues. Detection limits ranged from 0.31 to 1.27 ng/g and quantification limits were between 1.04 and 4.25 ng/g. The proposed analytical method may be used as a simple procedure in routine determinations of OCs and Ops in meat. It can also be applied to the determination of pesticide multi-residues in other animal products such as butter and milk. PMID:16869490

  5. Optimizing Installation and Operation Properties of an AUV-Mounted Swath Sonar Sensor for Automated Marine Gas Seep Detection - a Modelling Approach

    NASA Astrophysics Data System (ADS)

    Wenau, S.; Fei, T.; Tóth, Z.; Keil, H.; Spiess, V.; Kraus, D.

    2014-12-01

    The detection of gas bubble streams in the water column by single- and multibeam sonars has been a common procedure in the research of marine seep sites. In the framework of the development of an AUV capable of automatic detection and sampling of gas bubble streams, such acoustic flares were modelled in MATLAB routines to assess the optimal sonar configuration for flare detection. The AUV development (IMGAM-project) is carried out as a cooperation of the company ATLAS Hydrographic and the MARUM at the University of Bremen. The combination of sensor inclination, sonar carrier frequency and pulse characteristics affect the ability of the system to detect bubble streams of different sizes and intensities. These variations in acoustic signal return from gas bubble streams depending on acquisition parameters can affect the detectability and acoustic properties of recorded acoustic flares in various seepage areas in the world's oceans. We show several examples of acoustic signatures of previously defined bubble streams under varying acquisition parameters and document the effects of changing sensor parameters on detection efficiency.

  6. Fish freshness detection by a computer screen photoassisted based gas sensor array.

    PubMed

    Alimelli, Adriano; Pennazza, Giorgio; Santonico, Marco; Paolesse, Roberto; Filippini, Daniel; D'Amico, Arnaldo; Lundström, Ingemar; Di Natale, Corrado

    2007-01-23

    In the last years a large number of different measurement methodologies were applied to measure the freshness of fishes. Among them the connection between freshness and headspace composition has been considered by gas chromatographic analysis and from the last two decades by a number of sensors and biosensors aimed at measuring some characteristic indicators (usually amines). More recently also the so-called artificial olfaction systems gathering together many non-specific sensors have shown a certain capability to transduce the global composition of the fish headspace capturing the differences between fresh and spoiled products. One of the main objectives related to the introduction of sensor systems with respect to the analytical methods is the claimed possibility to distribute the freshness control since sensors are expected to be "portable" and "simple". In spite of these objectives, until now sensor systems did not result in any tool that may be broadly distributed. In this paper, we present a chemical sensor array where the optical features of layers of chemicals, sensitive to volatile compounds typical of spoilage processes in fish, are interrogated by a very simple platform based on a computer screen and a web cam. An array of metalloporphyrins is here used to classify fillets of thawed fishes according to their storage days and to monitor the spoilage in filleted anchovies for a time of 8 h. Results indicate a complete identification of the storage days of thawed fillets and a determination of the storage time of anchovies held at room temperature with a root mean square error of validation of about 30 min. The optical system produces a sort of spectral fingerprint containing information about both the absorbance and the emission of the sensitive layer. The system here illustrated, based on computer peripherals, can be easily scaled to any device endowed with a programmable screen and a camera such as cellular phones offering for the first time the possibility to fulfil the sensor expectation of diffused and efficient analytical capabilities. PMID:17386509

  7. Free surface microfluidic/SERS for detection of gas-phase DNT

    NASA Astrophysics Data System (ADS)

    Piorek, Brian D.; Lee, Seung Joon; Judy, Nick; Meinhart, Carl D.; Moskovits, Martin; Fountain, Augustus; Christesen, Steven; Guicheteau, Jason

    2010-04-01

    A novel microfluidic/SERS platform has been developed for real time sensing of 2,4-DNT. The fundamental research is being conducted at UCSB, commercialized by SpectraFluidics, and validated at ECBC. The system leverages phenomena at multiple length scales, ranging from tens of micrometers to several nanometers. The key enabling technology is a newly developed invention termed Free-Surface Fluidics (FSF), where one or more fluidic surfaces are confined by surface tension forces, and exposed to the surrounding atmosphere. The free-surface fluidic architecture is combined with surface-enhanced Raman spectroscopy (SERS) for detection of 2,4-DNT. Once 2,4-DNT analyte molecules are absorbed into the flow, they can interact with gold or silver colloidal particles. This architecture allows for analysis and deterministic control of SERS 'hot spot' aggregation, which can increase Raman scattering signal strength by up to 10 orders in magnitude. We have successfully measured DNT vapor at concentrations as low as ~1 ppb. This sensitivity value is confirmed by orthogonal measurements using GC-mass spectroscopy at ECBC.

  8. Portable fiber-coupled diode-laser-based sensor for multiple trace gas detection

    NASA Technical Reports Server (NTRS)

    Lancaster, D. G.; Richter, D.; Tittel, F. K.

    1999-01-01

    Tunable narrowband mid-infrared radiation from 3.25 to 4.4 micrometers is generated by a compact fiber-coupled, difference-frequency-based spectroscopic source. A 20-mW external cavity diode laser (with a tuning range from 814 to 870 nm) and a 50-mW distributed-Bragg-reflector diode-laser-seeded ytterbium-doped fiber amplifier operating at 1083 nm are difference-frequency mixed in a multi-grating, temperature-controlled periodically poled LiNbO3 crystal. A conversion efficiency of 0.44 mW/(W2cm) (corresponding to a power of approximately equal to 3 microW at 3.3 micrometers) represents the highest conversion efficiency reported for a portable device. Performance characteristics of such a sensor and its application to spectroscopic detection of CO2, N2O, H2CO, HCl, NO2, and CH4 will be reported in this work.

  9. Application of gas-sensor array technology for detection and monitoring of growth of spoilage bacteria in milk: A model study

    Microsoft Academic Search

    John Erik Haugen; Knut Rudi; Solveig Langsrud; Sylvia Bredholt

    2006-01-01

    The aim of this study was to develop a novel, rapid system for detection and monitoring of growth of undesirable bacteria in food using gas-sensor array technology. Three spoilage bacteria isolated from a cheese-processing hall were identified as Serratia marcescens, Serratia proteamacufans and Pseudomonas putida. The growth of these bacteria in milk was investigated using a commercial solid state based

  10. Trace analysis of residual methyl methanesulfonate, ethyl methanesulfonate and isopropyl methanesulfonate in pharmaceuticals by capillary gas chromatography with flame ionization detection

    Microsoft Academic Search

    Weiyong Li

    2004-01-01

    A capillary gas chromatographic method using flame ionization detection was developed and validated for the trace analysis (ppm level) of methyl methanesulfonate, ethyl methanesulfonate, and isopropyl methanesulfonate in pharmaceutical drug substance. The method utilizes a megabore capillary column with bonded and crosslinked polyethylene glycol stationary phase. A dissolve-and-injection approach was adopted for sample introduction in a splitless mode. The investigated

  11. On the copper oxide neutral cluster distribution in the gas phase: Detection through 355 nm and 193 nm multiphoton and 118 nm single photon ionization

    Microsoft Academic Search

    Y. Matsuda; D. N. Shin; E. R. Bernstein

    2004-01-01

    The distribution of neutral copper oxide clusters in the gas phase created by laser ablation is detected and characterized through time-of-flight mass spectroscopy (TOFMS). The neutral copper oxide clusters are ionized by two different approaches: Multiphoton absorption of 355 and 193 nm radiation; and single photon absorption of 118 nm radiation. Based on the observed cluster patterns as a function

  12. Preparation and Gas Sensing Properties of In2O3/Au Nanorods for Detection of Volatile Organic Compounds in Exhaled Breath.

    PubMed

    Xing, Ruiqing; Xu, Lin; Song, Jian; Zhou, Chunyang; Li, Qingling; Liu, Dali; Wei Song, Hong

    2015-01-01

    A series of In2O3/Au nanorods (NRs) were fabricated and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The length to diameter ratios of In2O3/Au NRs was periodically modulated in the range of 2.9-4.5 through controlling the initial content of indium salt and reaction time. Their gas sensing properties to volatile organic compounds (VOCs) were carefully studied and then applied in exhaled breath detection. The results demonstrate that In2O3/Au NRs gas sensor can effectively detect acetone at 250?°C and ethanol at 400?°C. The corresponding actual detection limit is as low as 0.1?ppm to acetone and 0.05?ppm to ethanol, respectively. Moreover, by using humidity compensation method, In2O3/Au NRs gas sensor can clearly distinguish the acetone and ethanol biomarkers in human breath. The main reason of the enhanced gas sensing properties was attributed to the "spillover effects" between Au and In2O3 NRs. The excellent sensing performance indicates that In2O3/Au NRs is a promising functional material to actual application in monitoring and detecting diabetes and safe driving area in a noninvasive and more accurate way. PMID:26030482

  13. Simultaneous detection of multiple hydroxylated polychlorinated biphenyls from a complex tissue matrix using gas chromatography/isotope dilution mass spectrometry.

    PubMed

    Eguchi, Akifumi; Nomiyama, Kei; Ochiai, Mari; Mizukawa, Hazuki; Nagano, Yasuko; Nakagawa, Katsuhiro; Tanaka, Kouki; Miyagawa, Haruhiko; Tanabe, Shinsuke

    2014-01-01

    In this study, we developed a comprehensive, highly sensitive, and robust method for determining 53 congeners of three to eight chlorinated OH-PCBs in liver and brain samples by using isotope dilution gas chromatography (GC) coupled with electron capture negative ionization mass spectrometry (ECNI-MS). These results were compared with those from GC coupled with electron ionization high-resolution mass spectrometry (EI-HRMS). Clean-up procedures for analysis of OH-PCBs homologs in liver and brain samples involve a pretreatment step consisting of acetonitrile partition and 5% hydrated silica-gel chromatography before derivatization. Recovery rates of tri- and tetra-chlorinated OH-PCBs in the acetonitrile partition method followed by the 5% hydrated silica-gel column (82% and 91%) were higher than conventional sulfuric acid treatment (2.0% and 3.5%). The method detection limits of OH-PCBs for each matrix obtained by GC/ECNI-MS and GC/EI-HRMS were 0.58-2.6 pg g(-1) and 0.36-1.6 pg g(-1) wet wt, respectively. Recovery rates of OH-PCB congeners in spike tests using sample matrices (10 and 50 pg) were 64.7-117% (CV: 4.7-14%) and 70.4-120% (CV: 2.3-12%), respectively. This analytical method may enable the simultaneous detection of various OH-PCBs from complex tissue matrices. Furthermore, this method allows more comprehensive assessment of the biological effects of OH-PCB exposure on critical organs. PMID:24274296

  14. Detection of 3-nitrotyrosine in human platelets exposed to peroxynitrite by a new gas chromatography/mass spectrometry assay.

    PubMed

    Jiang, H; Balazy, M

    1998-01-01

    A new sensitive and specific assay was developed and applied for the quantitative determination of 3-nitrotyrosine in proteins of human platelets. 3-Nitrotyrosine was quantitatively converted into a new pentafluorobenzyl derivative in a single step and detected as an abundant carboxylate anion at m/z 595 using negative ion chemical ionization gas chromatography/mass spectrometry. The internal standard, [13C6]-3-nitrotyrosine, was prepared via a new and efficient method using nitronium borofluorate dissolved in hydrochloric acid. The assay showed excellent linearity and sensitivity. Intact human platelets contained 1.4+/-0.6 ng of 3-nitrotyrosine per milligram of protein. Peroxynitrite increased 3-nitrotyrosine levels 4- to 535-fold at the concentration range of 10 to 300 microM. Decomposed peroxynitrite was without the effect. Nitrogen dioxide (43 microM) was also a potent tyrosine nitrating molecule, increasing the levels of 3-nitrotyrosine 153-fold. HOCl (50 microM) in the presence of nitrite (50 microM) increased the 3-nitrotyrosine levels 3-fold. Exposure of platelets to nitric oxide, nitrite, thrombin, adenosine diphosphate, platelet activating factor, and arachidonic acid had no effect on platelet 3-nitrotyrosine levels. PMID:10100490

  15. [Determination of triazolam and midazolam in human plasma using gas chromatography with microelectron capture detection for clinical application].

    PubMed

    Tsutsumi, Kimiko; Iwao, Miyuki; Kotegawa, Tsutomu; Imai, Hiromitsu; Ohashi, Kyoichi; Nakano, Shigeyuki

    2014-01-01

    A method for the simple and reliable determination of triazolam and midazolam in human plasma using gas chromatography with microelectron capture detection has been developed. Samples (0.5 mL of plasma) were prepared using a simple solvent extraction with 3% isoamyl alcohol/benzene in the presence of NaOH. Two microlitres of the extract were injected onto the capillary column ((5%-phenyl)-methylpolysiloxane). The method was found to be valid in terms of selectivity, linearity, precision, accuracy, and recovery over the concentration range of 0.2 to 20 ng/mL for triazolam, and from 0.5 to 200 ng/mL for midazolam, respectively. Intra- and inter-day precisions determined at three concentrations were from 4.1 to 9.3% for triazolam and from 2.9 to 13.0% for midazolam. The accuracies were within 17.7% for triazolam and within 13.0% for midazolam. This proposed method was successfully applied to a pharmacokinetic study of triazolam or midazolam in healthy volunteers. PMID:24389624

  16. Proposal for the award of an industrial services contract for maintenance of fire and gas detection and evacuation alarm systems

    E-print Network

    2001-01-01

    This document concerns the award of an Industrial Services contract for maintenance of fire and gas detection and evacuation alarm systems. Following a market survey carried out among 48 firms in fourteen Member States, a call for tenders (IT-2818/ST) was sent on 15 December 2000 to four firms and three consortia, each consisting of two firms, in five Member States. By the closing date, CERN had received tenders from one firm and three consortia in four Member States. The Finance Committee is invited to agree to the negotiation of a contract with the consortium SCHRACK SECONET (AT) - SOTEB (FR), the lowest bidder, for an initial period of three years from 1 October 2001 for an amount not exceeding 5 800 000 Swiss francs, not subject to revision. The contract will include options for two one-year extensions beyond the initial three-year period. The consortium has indicated the following distribution by country of the contract value covered by this adjudication proposal: AT-50%, FR-50%.

  17. Simultaneous determination of chloramphenicol, florfenicol, and thiamphenicol residues in milk by gas chromatography with electron capture detection.

    PubMed

    Pfenning, A P; Madson, M R; Roybal, J E; Turnipseed, S B; Gonzales, S A; Hurlbut, J A; Salmon, G D

    1998-01-01

    A gas chromatographic (GC) method is described for determining residues of chloramphenicol (CAP), florfenicol (FF), and thiamphenicol (TAP) in raw milk, with meta-nitrochloramphenicol (mCAP) as internal standard. Milk is extracted with acetonitrile, centrifuged, evaporated, reconstituted in water, and passed through a C18 solid-phase extraction (SPE) column. The SPE column is eluted with 60% methanol, and then the eluate is evaporated and derivatized with Sylon BFT ¿N,O-bis(trimethylsilyl)trifluoroacetamide [BSTFA]-trimethylchlorosilane [TMCS], 99 + 1¿. After derivatization, toluene is added directly to the sample, followed by water, to quench the derivatization process. After centrifugation, the organic layer is carefully removed. Analytes are determined by GC with electron capture detection (ECD). Milk was fortified with fenicols (the collective name for CAP, FF, and TAP) at 5, 10, 20, 40 and 80 ng/mL (target level = 10 ng/mL). Overall recoveries were 92, 100, and 104% for CAP, FF, and TAP, respectively. Overall interassay (between-day) variabilities were 6.1, 6.7, and 6.0% for CAP, FF, and TAP, respectively. Raw milk samples containing incurred residues of FF were also analyzed. PMID:9680695

  18. Intracavity CO laser photoacoustic trace gas detection: cyclic CH 4 , H 2 O and CO 2 emission by cockroaches and scarab beetles

    NASA Astrophysics Data System (ADS)

    Bijnen, F. G. C.; Harren, F. J. M.; Hackstein, J. H. P.; Reuss, J.

    1996-09-01

    A liquid-nitrogen-cooled CO laser and an intracavity resonant photoacoustic cell are employed to monitor trace gases. The setup was designed to monitor trace gas emissions of biological samples on line. The arrangement offers the possibility to measure gases at the 10 9 by volume (ppbv) level (e.g., CH 4 , H 2 O) and to detect rapid changes in trace gas emission. A detection limit of 1 ppbv for CH 4 in N 2 equivalent to a minimal detectable absorption of 3 10 9 cm 1 can be achieved. Because of the kinetic cooling effect we lowered the detection limit for CH 4 in air is decreased to 10 ppbv. We used the instrument in a first application to measure the CH 4 and H 2 O emission of individual cockroaches and scarab beetles. These emissions could be correlated with CO 2 emissions that were recorded simultaneously with an infrared gas analyzer. Characteristic breathing patterns of the insects could be observed; unexpectedly methane was also found to be released.

  19. DETECTION OF WEAK CIRCUMSTELLAR GAS AROUND THE DAZ WHITE DWARF WD 1124-293: EVIDENCE FOR THE ACCRETION OF MULTIPLE ASTEROIDS

    SciTech Connect

    Debes, J. H. [Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States); Kilic, M. [Homer L. Dodge Department of Physics and Astronomy, The University of Oklahoma, 440 W. Brooks St., Norman, OK 73019 (United States); Faedi, F. [Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast, BT7 1NN (United Kingdom); Shkolnik, E. L. [Lowell Observatory, Flagstaff, AZ 86001 (United States); Lopez-Morales, M. [Institut de Ciencies de l'Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, Torre C5, parell, 2a pl, E-08193 Bellaterra, Barcelona (Spain); Weinberger, A. J.; Slesnick, C. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5249 Broad Branch RD, N.W., Washington, DC 20015 (United States); West, R. G. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom)

    2012-07-20

    Single metal-polluted white dwarfs with no dusty disks are believed to be actively accreting metals from a circumstellar disk of gas caused by the destruction of asteroids perturbed by planetary systems. We report, for the first time, the detection of circumstellar Ca II gas in absorption around the DAZ WD 1124-293, which lacks an infrared excess. We constrain the gas to >7 R{sub WD} and <32000 AU, and estimate it to be at {approx}54 R{sub WD}, well within WD 1124-293's tidal disruption radius. This detection is based on several epochs of spectroscopy around the Ca II H and K lines ({lambda} = 3968 A, 3933 A) with the MIKE spectrograph on the Magellan/Clay Telescope at Las Campanas Observatory. We confirm the circumstellar nature of the gas by observing nearby sightlines and finding no evidence for gas from the local interstellar medium. Through archival data we have measured the equivalent width of the two photospheric Ca lines over a period of 11 years. We see <5%-7% epoch-to-epoch variation in equivalent widths over this time period, and no evidence for long term trends. The presence of a circumstellar gas implies a near edge-on inclination to the system, thus we place limits to short period transiting planetary companions with R > R{sub Circled-Plus} using the Wide Angle Search for Planets survey. The presence of gas in orbit around WD 1124-293 implies that most DAZs could harbor planetary systems. Since 25%-30% of white dwarfs show metal line absorption, the dynamical process for perturbing small bodies must be robust.

  20. Comparison of two derivatization reagents for the simultaneous determination of organolead and organomanganese compounds using solid-phase microextraction followed by gas chromatography with atomic emission detection.

    PubMed

    Peñalver, Rosa; Campillo, Natalia; Hernández-Córdoba, Manuel

    2011-12-15

    Two procedures for the simultaneous determination of organolead (tetraethyllead, triethyllead and trimethyllead) and organomanganese compounds (cyclopentadienyl manganese tricarbonyl (CMT) and methylcyclopentadienyl manganese tricarbonyl (MMT)) are studied. Both procedures involve sample preconcentration by solid-phase microextraction and capillary gas chromatography coupled to atomic emission detection, the main difference being the derivatizing agent used for the ionic alkylated lead species: sodium tetrapropylborate (NaBPr(4)) and sodium tetraphenylborate (NaBPh(4)). The parameters affecting the derivatization and preconcentration steps, chromatographic separation as well as detection of the compounds were optimized. Higher sensitivity was attained for all compounds with the method involving propylation derivatization. In this case, detection limits ranged between 0.04 and 0.1 ng L(-1), depending on the compound. Detection limits of between 0.1 and 24.5 ng L(-1) were obtained, when using phenylation derivatization. A low CMT concentration was found in one of the seawater samples analyzed. PMID:22099678

  1. Ram pressure stripping of hot coronal gas from group and cluster galaxies and the detectability of surviving X-ray coronae

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, Rukmani; Ricker, Paul M.

    2015-05-01

    Ram pressure stripping can remove hot and cold gas from galaxies in the intracluster medium, as shown by observations of X-ray and H I galaxy wakes in nearby clusters of galaxies. However, ram pressure stripping, including pre-processing in group environments, does not remove all the hot coronal gas from cluster galaxies. Recent high-resolution Chandra observations have shown that ˜1-4 kpc extended, hot galactic coronae are ubiquitous in group and cluster galaxies. To better understand this result, we simulate ram pressure stripping of a cosmologically motivated population of galaxies in isolated group and cluster environments. The galaxies and the host group and cluster are composed of collisionless dark matter and hot gas initially in hydrostatic equilibrium with the galaxy and host potentials. We show that the rate at which gas is lost depends on the galactic and host halo mass. Using synthetic X-ray observations, we evaluate the detectability of stripped galactic coronae in real observations by stacking images on the known galaxy centres. We find that coronal emission should be detected within ˜10 arcsec, or ˜5 kpc up to ˜2.3 Gyr in the lowest (0.1-1.2 keV) energy band. Thus, the presence of observed coronae in cluster galaxies significantly smaller than the hot X-ray haloes of field galaxies indicates that at least some gas removal occurs within cluster environments for recently accreted galaxies. Finally, we evaluate the possibility that existing and future X-ray cluster catalogues can be used in combination with optical galaxy positions to detect galactic coronal emission via stacking analysis. We briefly discuss the effects of additional physical processes on coronal survival, and will address them in detail in future papers in this series.

  2. New gas chromatographic-electron-capture detection method for the determination of atmospheric aldehydes and ketones based on cartridge sampling and derivatization with 2,4,6-trichlorophenylhydrazine

    Microsoft Academic Search

    David W. Lehmpuhl; John W. Birks

    1996-01-01

    The derivatizing reagent 2,4,6-trichlorophenylhydrazine (TCPH) was applied for the first time to the determination of atmospheric aldehydes and ketones using gas chromatography (GC) with electron-capture detection. TCPH is volatile enough to be used with GC without the problems of thermal decomposition or complex procedures associated with other derivatives such as 2,4-dinitrophenylhydrazine. Small cartridges packed with octadecyl silica impregnated with TCPH

  3. Comparison of two derivatization reagents for the simultaneous determination of organolead and organomanganese compounds using solid-phase microextraction followed by gas chromatography with atomic emission detection

    Microsoft Academic Search

    Rosa Peñalver; Natalia Campillo; Manuel Hernández-Córdoba

    Two procedures for the simultaneous determination of organolead (tetraethyllead, triethyllead and trimethyllead) and organomanganese compounds (cyclopentadienyl manganese tricarbonyl (CMT) and methylcyclopentadienyl manganese tricarbonyl (MMT)) are studied. Both procedures involve sample preconcentration by solid-phase microextraction and capillary gas chromatography coupled to atomic emission detection, the main difference being the derivatizing agent used for the ionic alkylated lead species: sodium tetrapropylborate (NaBPr4)

  4. Volatile organo-selenium speciation in biological matter by solid phase microextraction–moderate temperature multicapillary gas chromatography with microwave induced plasma atomic emission spectrometry detection

    Microsoft Academic Search

    C. Dietz; J. Sanz Landaluze; P. Ximénez-Embún; C. Cámara

    2004-01-01

    Microwave induced plasma atomic emission spectrometry (MIP-AES) in combination with multicapillary (MC) gas chromatography could be proven to be useful for element specific detection of volatile species. Solid phase microextraction (SPME) was used for preconcentration and sample-matrix separation. The fiber desorption unit as well as the heating control for the MC column were in-house developed and multicapillary column was operated

  5. Method for analysis of exhaled air by microwave energy desorption coupled with gas chromatography-flame ionization detection-mass spectrometry.

    PubMed

    Mueller, W; Schubert, J; Benzing, A; Geiger, K

    1998-09-25

    A method for chemical analysis of volatile constituents in exhaled air of mechanically ventilated patients is described. Exhaled substances are adsorbed and concentrated onto activated charcoal, desorbed by microwave energy and transferred into a gas chromatograph for separation without prior cryofocusing. Substances are identified by flame ionisation detection and mass spectrometry. This method yields reproducible results and is well suited for clinical studies. PMID:9824215

  6. Toxicological detection of pholcodine and its metabolites in urine and hair using radio immunoassay, fluorescence polarisation immunoassay, enzyme immunoassay and gas chromatography-mass spectrometry

    Microsoft Academic Search

    Hans H. Maurer; Christian F. Fritz

    1990-01-01

    Summary Pholcodine (3-O-(2'-morpholinoethyl)-morphine) is used in many countries as an antitussive without analgesic or addictive properties. It is of forensic relevance that pholcodine interferes with opiate immunoassays. In this paper a gas chromatographic-mass spectrometric (GC-MS) procedure for the precise and sensitive detection of pholcodine and its metabolites in urine and hair, after acid hydrolysis, extraction and acetylation, is presented. Furthermore,

  7. Controlled inert gas environment for enhanced chlorine and fluorine detection in the visible and near-infrared by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Asimellis, George; Hamilton, Stephen; Giannoudakos, Aggelos; Kompitsas, Michael

    2005-08-01

    Efficient quantitative detection for halogens is necessary in a wide range of applications, ranging from pharmaceutical products to air polluting hazardous gases or organic compounds used as chemical weapons. Detection of the non-metallic elements such as fluorine (F) and chlorine (Cl) presents particular difficulty, because strong emission lines originating from their resonance states lie in the VUV spectral range (110-190 nm). In the present work we detect F and Cl in the upper visible and in the near IR (650-850 nm) under controlled inert gas ambient atmosphere. Investigation of the controlled atmosphere effects suggests that there exists an optimum pressure range that optimizes signal strength and quality. Ablation and ionization were achieved with a UV laser at 355 nm, and a gated GaAs photocathode-based detector was used for detection with quantum efficiency in the range of 20% in the wavelengths of interest. Our results indicate that our approach provides quantitative detection with linearity over at least two orders of magnitude that is achieved without the need for Internal Standardization Method, and improved limits of detection. In particular, fluorine has been detected for concentration values down to 0.03 wt.% Definite spectral assignment revealing all major emission lines centered around 837 nm for F and 687 nm for Cl has been obtained for the first time in Laser-induced breakdown spectroscopy application.

  8. Modified gas gauge

    SciTech Connect

    Potvin, M.J.

    1990-12-11

    This paper discusses a method of testing the reliability of a gas meter presenting an input end, an output end, and a gas flow detecting mechanism between the ends. It comprises providing a conduit having a gas inlet and a gas outlet end; operably coupling the gas inlet end of the conduit; manipulating the valve means to a first flow condition; thereafter changing the level of gas flow; and inspecting the gas meter flow.

  9. HIGH FREQUENCY RESPONSE OF A FLUID-FILLED CYLINDRICAL SHELL WITH AN INTERNAL COLUMN OF GAS BUBBLES: APPLICATION TO ACTIVE ACOUSTIC GAS LEAK DETECTION

    Microsoft Academic Search

    B. J. Brévart; C. Journeau; C. R. Fuller

    1996-01-01

    The high frequency response to a point force excitation of an infinite elastic cylindrical shell, filled with a liquid including a column of gas bubbles, is investigated. A state vector approach is used for the shell theory to include the effects of shear deformation and rotary inertia. The far field mobility of the shell for each propagating circumferential modenis calculated

  10. Detection of [SiLL] (34.8 micron) emission in Orion-KL: A measurement of the silicon abundance in dense interstellar gas

    NASA Technical Reports Server (NTRS)

    Haas, M. R.; Hollenbach, D. J.; Erickson, E. F.

    1985-01-01

    The first detection of the ground state fine structure transition of Si+ at a rest wavelength determined to be 34.815 + or - 0.004 micron are reported. These observations were obtained with the facility spectrometer on NASA's Kuiper Airborne Observatory. A 6' NW-SE strip scan across the Orion-KL region shows SiII emission from both the extended photodissociation region surrounding theta 1 Ori C and from the shocked gas NW of BN-KL. The inferred gas-phase silicon elemental abundance relative to hydrogen in the dense 10 to the 5/cc primarily neutral photodissociation region is approximately 2.6 x to the -6, a factor of 0.075 times the solar value and 3.4 times greater than the abundance in the moderate density approx. 10 to the 3/cc cloud toward zeta Oph. The silicon abundance in the shocked gas is approximately solar, indicating that any pre-existing grains have been destroyed in the shock wave or that the preshock gas carries a near solar abundance of gas phase silicon. The shock-excited SiII (34.8 micron) emission may arise from shocked wind material in the outflow around IRc2, with wind velocities approx. 100 km/s.

  11. Laboratory Evaluation of an Electrochemical Noise System for Detection of Localized and General Corrosion of Natural Gas Transmission Pipelines

    SciTech Connect

    Bullard, S.J.; Covino, B.S., Jr.; Russell, J.H.; Holcomb, G.R.; Cramer, S.D.; Ziomek-Moroz, M.; Eden, D.

    2003-03-16

    Gas transmission pipelines are susceptible to both internal (gas side) and external (soil side) corrosion attack. Internal corrosion is caused by the presence of salt laden moisture, CO{sub 2}, H{sub 2}S, and perhaps O{sub 2} in the natural gas. Internal corrosion usually manifests itself as general corrosion. However, the presence of chlorides in entrained water also can lead to pitting corrosion damage. The electrochemical noise technique can differentiate general from localized corrosion and provide estimates of corrosion rates without external perturbation of the corroding system. It is increasingly being applied to field and industrial installations for in situ corrosion monitoring. It has been used here to determine its suitability for monitoring internal and external corrosion damage on gas transmission pipelines. Corrosion measurements were made in three types of environments: (1) aqueous solutions typical of those found within gas pipelines in equilibrium with th e corrosive components of natural gas; (2) biologically-active soils typical of wetlands; and (3) a simulated, unpressurized, internal gas/liquid gas pipeline environment. Multiple sensor designs were evaluated in the simulated pipe environment. Gravimetric measurements were conducted in parallel with the electrochemical noise measurements to validate the results.

  12. Detection of ethene and other hydrocarbons in gas turbine engine exhaust using non-intrusive FTIR spectroscopy

    Microsoft Academic Search

    Giovanni M. Arrigone; Michael A. Welch; Moira Hilton; Michael N. Miller; Christopher W. Wilson

    2003-01-01

    As part of the EU funded project AEROJET2, a number of gas turbine engine tests were performed in different facilities around Europe. At Farnborough, UK a Spey engine was used to test a suite of prototype optically based instrumentation designed to measure exhaust gas emissions without using extractive probe systems. In addition to the AEROJET 2 prototype instrumentation, a Bruker

  13. Metering Research Facility Program: Detection of pulsation effects on gas turbine meters. Topical report, April 1993August 1994

    Microsoft Academic Search

    McKee

    1994-01-01

    Research concerning pulse period modulation measurements for detection of pulsation effects on turbine meters has been conducted as part of the GRI Metering Research Facility Program. Previous research indicated that pulsation influences turbine meter accuracy; however, a practical method for detection of pulsation effects was not available. In these tests, the monitoring of period variations between pulses to detect pulsation-induced

  14. Determination of dimethylselenide and dimethyldiselenide in milk and milk by-products by solid-phase microextraction and gas chromatography with atomic emission detection.

    PubMed

    Campillo, Natalia; Peñalver, Rosa; Hernández-Córdoba, Manuel

    2010-03-15

    A method based on solid-phase microextraction (SPME) followed by gas chromatography with microwave-induced plasma atomic emission detection for determining dimethylselenide (DMSe) and dimethyldiselenide (DMDSe) in milk and milk by-products is proposed. Parameters affecting the SPME, such as sample volume or mass, ionic strength, adsorption and desorption times and temperatures were optimized in the headspace mode. The matrix effect was evaluated for the different samples studied, concluding that standard additions calibration was required for quantification purposes. The detection limits ranged from 70 to 110 pg mL(-1) for DMSe and from 80 to 400 pg mL(-1) for DMDSe, depending on the sample under analysis. None of the twenty-three samples analyzed contained the studied compounds at concentrations above the corresponding detection limits. PMID:20152423

  15. Detection of optical asymmetry in amino acids by gas chromatography for extraterrestrial space exploration - Results of a new soil processing scheme with breadboard instrumentation

    NASA Technical Reports Server (NTRS)

    Pollock, G. E.; Day, R.; Kinsey, S.; Miller, S. L.

    1977-01-01

    The life-detection experiments of the Viking spacecraft are of an active biology type that will attempt to elicit metabolic responses from soil samples. Because bioresponses may be difficult to stimulate, it is desirable also to devise a purely chemical life-detection experiment. The unique chemical property of living systems on which such an experiment could be based is the optical activity of the amino acids that compose its protein. We have devised a new soil processing scheme which has been laboratory tested and for which we have built semi-automated breadboard instrumentation. The system involves the operations of heating, filtering, evaporation, conversion of the isolated amino acids to volatile diastereomers, injection onto a gas chromatographic column, and detection using a flame ionization detector. The breadboard form of the soil processing scheme and instrumentation has been successfully end-to-end tested.

  16. Comparison of enzyme-linked immunosorbent assay and gas chromatography procedures for the detection of cyanazine and metolachlor in surface water samples

    USGS Publications Warehouse

    Schraer, S.M.; Shaw, D.R.; Boyette, M.; Coupe, R.H.; Thurman, E.M.

    2000-01-01

    Enzyme-linked immunosorbent assay (ELISA) data from surface water reconnaissance were compared to data from samples analyzed by gas chromatography for the pesticide residues cyanazine (2-[[4-chloro-6-(ethylamino)-l,3,5-triazin-2-yl]amino]-2-methylpropanenitrile ) and metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide). When ELISA analyses were duplicated, cyanazine and metolachlor detection was found to have highly reproducible results; adjusted R2s were 0.97 and 0.94, respectively. When ELISA results for cyanazine were regressed against gas chromatography results, the models effectively predicted cyanazine concentrations from ELISA analyses (adjusted R2s ranging from 0.76 to 0.81). The intercepts and slopes for these models were not different from 0 and 1, respectively. This indicates that cyanazine analysis by ELISA is expected to give the same results as analysis by gas chromatography. However, regressing ELISA analyses for metolachlor against gas chromatography data provided more variable results (adjusted R2s ranged from 0.67 to 0.94). Regression models for metolachlor analyses had two of three intercepts that were not different from 0. Slopes for all metolachlor regression models were significantly different from 1. This indicates that as metolachlor concentrations increase, ELISA will over- or under-estimate metolachlor concentration, depending on the method of comparison. ELISA can be effectively used to detect cyanazine and metolachlor in surface water samples. However, when detections of metolachlor have significant consequences or implications it may be necessary to use other analytical methods.

  17. Detection of hot, metal-enriched outflowing gas around z ? 2.3 star-forming galaxies in the Keck Baryonic Structure Survey

    NASA Astrophysics Data System (ADS)

    Turner, Monica L.; Schaye, Joop; Steidel, Charles C.; Rudie, Gwen C.; Strom, Allison L.

    2015-06-01

    We use quasar absorption lines to study the physical conditions in the circumgalactic medium of redshift z ? 2.3 star-forming galaxies taken from the Keck Baryonic Structure Survey. In Turner et al. we used the pixel optical depth technique to show that absorption by H I and the metal ions O VI, N V, C IV, C III, and Si IV is strongly enhanced within |?v| ? 170 km s-1 and projected distances |d| ? 180 proper kpc from sightlines to the background quasars. Here we demonstrate that the O VI absorption is also strongly enhanced at fixed H I, C IV, and Si IV optical depths, and that this enhancement extends out to ˜350 km s-1. At fixed H I the increase in the median O VI optical depth near galaxies is 0.3-0.7 dex and is detected at 2-3? confidence for all seven H I bins that have log _{10}?_{H I} ? -1.5. We use ionization models to show that the observed strength of O VI as a function of H I is consistent with enriched, photoionized gas for pixels with ?_{H I} ? 10. However, for pixels with ?_{H I} ? 1 this would lead to implausibly high metallicities at low densities if the gas were photoionized by the background radiation. This indicates that the galaxies are surrounded by gas that is sufficiently hot to be collisionally ionized (T > 105 K) and that a substantial fraction of the hot gas has a metallicity ?10-1 of solar. Given the high metallicity and large velocity extent (out to ˜1.5 vcirc) of this gas, we conclude that we have detected hot, metal-enriched outflows arising from star-forming galaxies.

  18. Detection and quantification of methane and VOC emissions from oil and gas production operations using remote measurements, Interim report

    EPA Science Inventory

    Improved understanding of air pollutant emissions from oil and gas production operations is needed. With a steadily increasing number of production sources, the impact of emitted volatile organic compounds (VOCs) on regional ozone is potentially significant. As the separation dis...

  19. Gas Sensitivity and Sensing Mechanism Studies on Au-Doped TiO2 Nanotube Arrays for Detecting SF6 Decomposed Components

    PubMed Central

    Zhang, Xiaoxing; Yu, Lei; Tie, Jing; Dong, Xingchen

    2014-01-01

    The analysis to SF6 decomposed component gases is an efficient diagnostic approach to detect the partial discharge in gas-insulated switchgear (GIS) for the purpose of accessing the operating state of power equipment. This paper applied the Au-doped TiO2 nanotube array sensor (Au-TiO2 NTAs) to detect SF6 decomposed components. The electrochemical constant potential method was adopted in the Au-TiO2 NTAs' fabrication, and a series of experiments were conducted to test the characteristic SF6 decomposed gases for a thorough investigation of sensing performances. The sensing characteristic curves of intrinsic and Au-doped TiO2 NTAs were compared to study the mechanism of the gas sensing response. The results indicated that the doped Au could change the TiO2 nanotube arrays' performances of gas sensing selectivity in SF6 decomposed components, as well as reducing the working temperature of TiO2 NTAs. PMID:25330053

  20. Detection of volatile organic compounds (VOCs) using SnO 2 gas-sensor array and artificial neural network

    Microsoft Academic Search

    A. K. Srivastava

    2003-01-01

    This paper presents design and development of an electronic nose system based on tin oxide gas-sensors array and artificial neural network (ANN) for the identification of some of the volatile organic compounds (VOCs) relevant to environmental monitoring such as propane-2-ol, methanol, acetone, ethyl methyl ketone, hexane, benzene and xylene. An array of SnO2-based thick-film gas sensors doped with Pd, Pt

  1. Detection of hydrocarbon microseepage in a rain forest environment (Jurua Gas field, northern Brazil) using Landsat MSS data

    SciTech Connect

    Miranda, F.P.; Cunha, F.M.B. (Petrobras, New York, NY (USA))

    1990-05-01

    The Jurua gas field is the first important hydrocarbon accumulation found in the jungle-covered Solimoes basin. The tectonic framework in this area is characterized by a right-lateral transpressional zone (Jurua structural trend). Hydrocarbon traps are anticlines developed along the upthrown block of a reverse fault. The prospective 2,200-m-thick Paleozoic section is unconformably covered by a 2,800-m-thick pile of Mesozoic and Cenozoic continental sediments. Anomalous concentrations of hydrocarbons (C{sub 2}-C{sub 4}) in soil samples are concordantly aligned with the trace of the reverse fault crossing the gas field, indicating that this feature acted as a conduit for hydrocarbon microseepage. Gas-producing wells are located over a tabular watershed which coincides with the northeast-southwest Jurua structural trend. An unsupervised classification of Landsat MSS data over the gas field area reveals that one spectral class of vegetation is aligned with the Jurua structural trend. Field checking shows that the vegetation near the gas-producing well 1-JR-1-AM is not as dense as the forest outside the limits of the Jurua gas field. Two geologic factors may account for the vegetation anomaly over the gas field. (1) The northeast-southwest tabular watershed corresponds to a Pleistocene erosional surface associated with weathering products such as bauxite and laterite. The resulting soil is impermeable and low in nutrients. (2) The spectral behavior of vegetation may represent the response of plants to long-term anaerobic soil conditions brought about by gas leakage from the Paleozoic reservoir.

  2. Concentrating materials covered by molecular imprinted nanofiltration layer with reconfigurability prepared by a surface sol-gel process for gas-selective detection.

    PubMed

    Imahashi, Masahiro; Hayashi, Kenshi

    2013-09-15

    Sensors that recognize molecules are acquired for the comprehensive detection of great many kinds of gases. Adsorbents with high molecular recognition and condensation ability were developed for selective gas sensing with a molecular imprinting technique. Developed adsorbents have multilayer structures consisted of a chemically modified polymer layer on the surface of a substrate covered by a TiO2 gel monolayer by the surface sol-gel process. Ellipsometry measurements showed that the 6-nm-thick layers deposited on the substrate. Cavities of molecular templates were imprinted on these layers, and thus, the film acts as a molecular gas filter without concentrating ability, which could form specific binding sites for various molecules that confirmed using solid-phase microextraction and gas chromatography-mass spectrometry. Gases were selectively absorbed into an accumulating adsorption layer and other gas molecules were blocked by the nanofiltration. These developed adsorbents enabled effective concentration ability and the filtration of gases or odors. In addition, these filters possess the flexibility to be easily configured with specific surface properties to interact with volatile molecules under appropriate conditions. A successful multiplex filter, imprinted simultaneously on an adsorbent with different sites, was demonstrated. PMID:23800374

  3. Proposal for the award of a blanket contract for automatic air-sampling systems for fire and gas detection in the LHC experiments

    E-print Network

    2004-01-01

    This document concerns the award of a blanket contract for automatic air-sampling systems for fire and gas detection in the LHC experiments. Following a market survey carried out among 119 firms in ten Member States, a call for tenders (IT-2891/ST) was sent on 1 August 2003 to four firms, in three Member States. By the closing date, CERN had received two tenders from one firm and one consortium, in three Member States. The Finance Committee is invited to agree to the negotiation of a blanket contract with ICARE (FR), the lowest bidder, for the supply of automatic air-sampling systems for fire and gas detection in the LHC experiments for a total amount not exceeding 1 750 000 euros (2 714 000 Swiss francs), subject to revision for inflation from 1 January 2007 with options for air-sampling smoke detection systems for electrical racks, for an additional amount of 400 000 euros (620 000 Swiss francs), subject to revision for inflation from 1 January 2007, bringing the total amount to a maximum of 2 150 000 euros...

  4. HST/COS detection of a Ne VIII absorber towards PG 1407+265: An unambiguous tracer of collisionally ionized hot gas?

    E-print Network

    Hussain, Tanvir; Narayanan, Anand; Srianand, Raghunathan; Wakker, Bart P; Charlton, Jane C; Pathak, Amit

    2014-01-01

    We report the detection of Ne VIII in a z_abs = 0.59961 absorber towards the QSO PG 1407+265 (z_em = 0.94). Besides Ne VIII, absorption from HI Lyman series lines (HI 1025 - 915), several other low (C II, N II, O II, and S II), intermediate (C III, N III, N IV, O III, S IV, and S V) and high (S VI, O VI, and Ne VIII) ionization metal lines are detected. Disparity in the absorption line kinematics between different ions implies that the absorbing gas comprises of multiple ionization phases. The low and the intermediate ions (except S V) trace a compact (~ 410 pc), metal-rich (Z ~ Z_sun) and over-dense (log n_H ~ -2.6) photoionized region that sustained star-formation for a prolonged period. The high ions, Ne VIII and O VI, can be explained as arising in a low density (-5.3 Z_sun) and diffuse (~ 180 kpc) photoionized gas. The S V, S VI and C IV (detected in the FOS spectrum) require an intermediate photoionization phase with -4.2 < log n_H < -3.5. Alternatively, a pure collisional ionization model, as us...

  5. Liquid/Gas Vortex Separator

    NASA Technical Reports Server (NTRS)

    Morris, B. G.

    1986-01-01

    Liquid/gas separator vents gas from tank of liquid that contains gas randomly distributed in bubbles. Centrifugal force separates liquid and gas, forcing liquid out of vortex tube through venturi tube. Gas vented through exhaust port. When liquid detected in vent tube, exhaust port closed, and liquid/gas mixture in vent tube drawn back into tank through venturi.

  6. On-line novelty detection by recursive dynamic principal component analysis and gas sensor arrays under drift conditions

    Microsoft Academic Search

    Alexandre Perera; Niko Papamichail; Nicolae Bârsan; Udo Weimar; Santiago Marco

    2006-01-01

    Leakage detection is a common chemical-sensing application. Leakage detection by thresholds on a single sensor signal suffers from important drawbacks when sensors show drift effects or when they are affected by other long-term cross sensitivities. In this paper, we present an adaptive method based on a recursive dynamic principal component analysis (RDPCA) algorithm that models the relationships between the sensors

  7. Simultaneous determination of amitriptyline, nortriptyline and four hydroxylated metabolites in serum by capillary gas-liquid chromatography with nitrogen-phosphorus-selective detection

    Microsoft Academic Search

    S. Ulrich; T. Isensee; U. Pester

    1996-01-01

    A method for the simultaneous quantification of the antidepressant drug amitriptyline, its demethylated metabolite nortriptyline and four hydroxy metabolites (E-10-hydroxyamitriptyline, Z-10-hydroxyamitriptyline, E-10-hydroxynortriptyline, Z-10-hydroxynortriptyline) in human serum or plasma has been developed. The method is based on a three-step liquid-liquid extraction followed by gas-liquid chromatography (split-splitless injection, HP-5, 25 m×0.2 mm I.D., 0.33 ?m capillary) with nitrogen phosphorus-selective detection (GLC-NPD). The

  8. Identification and confirmation of traces of chlorinated fatty acids in fish downstream of bleached kraft pulp mills by gas chromatography with halogen-specific detection.

    PubMed

    Zhuang, Wenshan; McKague, Bruce; Reeve, Douglas; Carey, John

    2003-04-25

    Methyl esters of threo-9,10-dichlorooctadecanoic, threo-7,8-dichlorohexadecanoic, and threo-5,6-dichlorotetradecanoic acids, present in transesterified extracts of filets, gonad, intestinal fat and carcass of white sucker (Catostomus commersoni) sampled in receiving waters of bleached kraft pulp mill effluents, were identified by gas chromatography with halogen-specific detection (XSD). Identification was based on (1) a comparison of the retention times of a sample peak with a prospective reference standard on two stationary phases of very different polarities by spiking, and (2) elution behavior of configurational and positional isomers of dichloro fatty acid methyl esters. PMID:12779225

  9. Three sources and three components of success in detection of ultra-rare alpha decays at the Dubna Gas-Filled Recoil separator

    E-print Network

    Tsyganov, Y S

    2015-01-01

    General philosophy of procedure of detecting rare events in the recent experiments with 48Ca projectile at the Dubna Gas-Filled Recoil Separator(DGFRS) aimed to the synthesis of superheavy elements (SHE) has been reviewed. Specific instruments and methods are under consideration. Some historical sources of the successful experiments for Z=112-118 are considered too. Special attention is paid to application of method of active correlations in heavy-ion induced complete fusion nuclear reactions. Example of application in Z=115 experiment is presented. Brief description of the 243Am + 48Ca -> 291-x115+xn experiment is presented too. Some attention is paid to the role of chemical experiments in discoveries of SHEs. The DGFRS detection/monitoring system is presented in full firstly.

  10. Three sources and three components of success in detection of ultra-rare alpha decays at the Dubna Gas-Filled Recoil separator

    E-print Network

    Y. S. Tsyganov

    2015-06-05

    General philosophy of procedure of detecting rare events in the recent experiments with 48Ca projectile at the Dubna Gas-Filled Recoil Separator(DGFRS) aimed to the synthesis of superheavy elements (SHE) has been reviewed. Specific instruments and methods are under consideration. Some historical sources of the successful experiments for Z=112-118 are considered too. Special attention is paid to application of method of active correlations in heavy-ion induced complete fusion nuclear reactions. Example of application in Z=115 experiment is presented. Brief description of the 243Am + 48Ca -> 291-x115+xn experiment is presented too. Some attention is paid to the role of chemical experiments in discoveries of SHEs. The DGFRS detection/monitoring system is presented in full firstly.

  11. Repeated detection of gas in the portal vein after liver transplantation: A sign of EBV-associated post-transplant lymphoproliferation?

    PubMed

    Wallot, Michael A; Klepper, Jörg; Clapuyt, Philippe; Dirsch, Olaf; Malagó, Max; Reding, Raymond; Otte, Jean Bernard; Sokal, Etienne M

    2002-08-01

    A 1-yr-old child presented with intractable right sided pleural effusion and progressive clinical deterioration 3 weeks after liver transplantation for Alagille Syndrome. He had been treated successfully for severe acute rejection before. Ultrasound and Doppler mode studies repeatedly demonstrated air in the portal vein. Intra-abdominal and intra-thoracic lymphoproliferation was detected, and EBV virus load and serology were suggestive of primary EBV infection. Liver biopsy revealed blast-like infiltrates of B-cells, considered diagnostic for post-transplant lymphoproliferative disease. The disease resolved upon reduction of immunosuppression. We suggest that the detection of portal vein gas in pediatric liver transplant recipients beyond the early post-operative period may be a sign of intra-abdominal post-transplant lymphoproliferative disease. PMID:12234275

  12. Determination of microbial fatty acid profiles at femtomolar levels in human urine and the initial marine microfouling community by capillary gas chromatography-chemical ionization mass spectrometry with negative ion detection

    Microsoft Academic Search

    Goran Odham; Anders Tunlid; Gunilla Westerdahl; Lennart Larsson; James B. Guckert; David C. White

    1985-01-01

    Summary Room temperature esterification with the electron capturing pentafluorobenzyl bromide in glass capillaries, with analysis by capillary gas-liquid chromatography coupled with chemical ionization mass spectrometry and negative ion detection in the selected ion mode, allowed detection and identification of fatty acids from micro- bial biofilms at the femtomolar level. This sensitivity was achieved without loss of specificity of the mass

  13. Detection of Caribbean fruit fly [(Anastrepha suspensa Loew (Diptera: Tephritidae)]-infested grapefruit with portable gas chromatography

    Technology Transfer Automated Retrieval System (TEKTRAN)

    New technologies are being sought by plant protection officials to more quickly and efficiently identify concealed pests in imported commodities. The zNose portable gas chromatography unit was investigated as a tool for identifying organic volatile signatures indicative of Caribbean fruit fly infest...

  14. DENSE MOLECULAR GAS EXCITATION AT HIGH REDSHIFT: DETECTION OF HCO{sup +}(J = 4 {yields} 3) EMISSION IN THE CLOVERLEAF QUASAR

    SciTech Connect

    Riechers, Dominik A. [Astronomy Department, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Walter, Fabian [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Carilli, Christopher L. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Cox, Pierre [Institut de RadioAstronomie Millimetrique, 300 Rue de la Piscine, Domaine Universitaire, 38406 Saint Martin d'Heres (France); Weiss, Axel; Menten, Karl M. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, Bonn (Germany); Bertoldi, Frank, E-mail: dr@caltech.edu [Argelander-Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, Bonn (Germany)

    2011-01-01

    We report the detection of HCO{sup +}(J = 4 {yields} 3) emission in the Cloverleaf Quasar at z = 2.56, using the IRAM Plateau de Bure Interferometer. HCO{sup +} emission is a star formation indicator similar to HCN, tracing dense molecular hydrogen gas (n(H{sub 2}) {approx_equal} 10{sup 5} cm{sup -3}) within star-forming molecular clouds. We derive a lensing-corrected HCO{sup +}(J = 4 {yields} 3) line luminosity of L'{sub HCO}{sup +}{sub (4-3)} = (1.6 {+-} 0.3) x 10{sup 9}, ({mu}{sub L}/11){sup -1} K km s{sup -1} pc{sup 2}, which corresponds to only 48% of the HCO{sup +}(J = 1 {yields} 0) luminosity, and {approx}<4% of the CO(J = 3 {yields} 2) luminosity. The HCO{sup +} excitation thus is clearly subthermal in the J = 4 {yields} 3 transition. Modeling of the HCO{sup +} line radiative transfer suggests that the HCO{sup +} emission emerges from a region with physical properties comparable to that exhibiting the CO line emission, but 2x higher gas density. This suggests that both HCO{sup +} and CO lines trace the warm, dense molecular gas where star formation actively takes place. The HCO{sup +} lines have only {approx}2/3 the width of the CO lines, which may suggest that the densest gas is more spatially concentrated. In contrast to the z = 3.91 quasar APM 08279+5255, the dense gas excitation in the Cloverleaf is consistent with being purely collisional, rather than being enhanced by radiative processes. Thus, the physical properties of the dense gas component in the Cloverleaf are consistent with those in the nuclei of nearby starburst galaxies. This suggests that the conditions in the dense, star-forming gas in active galactic nucleus-starburst systems at early cosmic times like the Cloverleaf are primarily affected by the starburst itself, rather than the central active black hole.

  15. Detection of volatile nitrosamines in waste water from chemical plants by combined capillary gas chromatography-mass spectrometry

    Microsoft Academic Search

    G. Hartmetz; J. Slemrova

    1980-01-01

    Detection of carcinogenic nitrosamines in foodstuffs has been reported in a large number of publications (e.g., see WALKER et al. 1976), while searches for these compounds in drinking, surface or waste water have only seldom been reported.

  16. Detection of hydrogen fluoride absorption in diffuse molecular clouds with Herschel\\/HIFI: an ubiquitous tracer of molecular gas

    Microsoft Academic Search

    P. Sonnentrucker; D. A. Neufeld; T. G. Phillips; M. Gerin; D. C. Lis; M. de Luca; J. R. Goicoechea; J. H. Black; T. A. Bell; F. Boulanger; J. Cernicharo; A. Coutens; E. Dartois; M. Kazmierczak; P. Encrenaz; E. Falgarone; T. R. Geballe; T. Giesen; B. Godard; P. F. Goldsmith; C. Gry; H. Gupta; P. Hennebelle; E. Herbst; P. Hily-Blant; C. Joblin; R. Kolos; J. Krelowski; J. Martín-Pintado; K. M. Menten; R. Monje; B. Mookerjea; J. Pearson; M. Perault; C. M. Persson; R. Plume; M. Salez; S. Schlemmer; M. Schmidt; J. Stutzki; D. Teyssier; C. Vastel; S. Yu; E. Caux; R. Güsten; W. A. Hatch; T. Klein; I. Mehdi; P. Morris; J. S. Ward

    2010-01-01

    We discuss the detection of absorption by interstellar hydrogen fluoride (HF) along the sight line to the submillimeter continuum sources W49N and W51. We have used Herschel's HIFI instrument in dual beam switch mode to observe the 1232.4762 GHz J = 1-0 HF transition in the upper sideband of the band 5a receiver. We detected foreground absorption by HF toward

  17. Detectability enhancement by the use of large-volume injections in gas chromatography-cryotrapping-Fourier transform infrared spectrometry

    Microsoft Academic Search

    Th. Hankemeier; H. T. C. van der Laan; J. J. Vreuls; M. J. Vredenbregt; T. Visser; U. A. Th. Brinkman

    1996-01-01

    The use of large-volume injections via a loop-type interface in GC-cryotrapping-FT-IR has been studied. n-Alkanes and polycyclic aromatic hydrocarbons (PAHs) were used as test compounds. When using 100-?l injections the analyte detectability was enhanced by two to three orders of magnitude compared with conventional split\\/splitless injections. For the alkanes, the absolute detection limits were nearly independent of the injected volume

  18. USE OF MAILBOX APPROACH, VIDEO SURVEILLANCE, AND SHORT-NOTICE RANDOM INSPECTIONS TO ENHANCE DETECTION OF UNDECLARED LEU PRODUCTION AT GAS CENTRIFUGE ENRICHMENT PLANTS.

    SciTech Connect

    BOYER, B.D.; GORDON, D.M.; JO, J.

    2006-07-16

    Current safeguards approaches used by the IAEA at gas centrifuge enrichment plants (GCEPs) need enhancement in order to detect undeclared LEU production with adequate detection probability. ''Mailbox'' declarations have been used in the last two decades to verify receipts, production, and shipments at some bulk-handling facilities (e.g., fuel-fabrication plants). The operator declares the status of his plant to the IAEA on a daily basis using a secure ''Mailbox'' system such as a secure tamper-resistant computer. The operator agrees to hold receipts and shipments for a specified period of time, along with a specified number of annual inspections, to enable inspector access to a statistically large enough population of UF{sub 6} cylinders and fuel assemblies to achieve the desired detection probability. The inspectors can access the ''Mailbox'' during randomly timed inspections and then verify the operator's declarations for that day. Previously, this type of inspection regime was considered mainly for verifying the material balance at fuel-fabrication, enrichment, and conversion plants. Brookhaven National Laboratory has expanded the ''Mailbox'' concept with short-notice random inspections (SNRIs), coupled with enhanced video surveillance, to include declaration and verification of UF{sub 6} cylinder operational data to detect activities associated with undeclared LEU production at GCEPs. Since the ''Mailbox'' declarations would also include data relevant to material-balance verification, these randomized inspections would replace the scheduled monthly interim inspections for material-balance purposes; in addition, the inspectors could simultaneously perform the required number of Limited-Frequency Unannounced Access (LFUA) inspections used for HEU detection. This approach would provide improved detection capabilities for a wider range of diversion activities with not much more inspection effort than at present.

  19. Detection of [O I] ?6300 and Other Diagnostic Emission Lines in the Diffuse Ionized Gas of M33 with Gemini-North

    NASA Astrophysics Data System (ADS)

    Voges, E. S.; Walterbos, R. A. M.

    2006-06-01

    We present spectroscopic observations of diffuse ionized gas (DIG) in M33 near the H II region NGC 604. We present the first detection of [O I] ?6300 in the DIG of M33, one of the critical lines for distinguishing photoionization from shock ionization models. We measure [O I]/H? in the range of 0.04-0.10 and an increase in this ratio with decreasing emission measure. Our measurements of [S II]/H? and [N II]/H? also rise with decreasing emission measure, while our [O III]/H? measurements remain fairly constant. We have one tentative detection of He I in the region of brightest emission measure, with a ratio of He I/H? = 0.033 +/- 0.019, indicating that the helium is at least partially ionized. We compare our observed emission-line ratios to photoionization models and find that field star ionization models do not fit our data well. Leaky H II region models are consistent with our data, without the need to invoke additional ionization mechanisms to fit our [O I] or [O III] measurements. The closest large H II region is NGC 604 and is therefore a likely candidate for the source of the ionizing photons for the gas in this region.

  20. Enhancing the sensitivity of chemiresistor gas sensors based on pristine carbon nanotubes to detect low-ppb ammonia concentrations in the environment.

    PubMed

    Rigoni, Federica; Tognolini, Silvia; Borghetti, Patrizia; Drera, Giovanni; Pagliara, Stefania; Goldoni, Andrea; Sangaletti, Luigi

    2013-11-12

    The possibility of using novel architectures based on carbon nanotubes (CNTs) for a realistic monitoring of the air quality in an urban environment requires the capability to monitor concentrations of polluting gases in the low-ppb range. This limit has been so far virtually neglected, as most of the testing of new ammonia gas sensor devices based on CNTs is carried out above the ppm limit. In this paper, we present single-wall carbon nanotube (SWCNT) chemiresistor gas sensors operating at room temperature, displaying an enhanced sensitivity to NH3. Ammonia concentrations in air as low as 20 ppb have been measured, and a detection limit of 3 ppb is demonstrated, which is in the full range of the average NH3 concentration in an urban environment and well below the sensitivities so far reported for pristine, non-functionalized SWCNTs operating at room temperature. In addition to careful preparation of the SWCNT layers, through sonication and dielectrophoresis that improved the quality of the CNT bundle layers, the low-ppb limit is also attained by revealing and properly tracking a fast dynamics channel in the desorption process of the polluting gas molecules. PMID:24171188