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1

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

PubMed

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

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

2014-01-01

2

Part-per-trillion determination of chlorobenzenes in water using dispersive liquid–liquid microextraction combined gas chromatography–electron capture detection  

Microsoft Academic Search

In this study, a simple, rapid and efficient method, dispersive liquid–liquid microextraction (DLLME) combined gas chromatography–electron capture detection (GC–ECD), for the determination of chlorobenzenes (CBs) in water samples, has been described. This method involves the use of an appropriate mixture of extraction solvent (9.5?l chlorobenzene) and disperser solvent (0.50ml acetone) for the formation of cloudy solution in 5.00ml aqueous sample

Reyhaneh Rahnama Kozani; Yaghoub Assadi; Farzaneh Shemirani; Mohammad-Reza Milani Hosseini; Mohammad Reza Jamali

2007-01-01

3

Part-per-trillion determination of chlorobenzenes in water using dispersive liquid-liquid microextraction combined gas chromatography-electron capture detection.  

PubMed

In this study, a simple, rapid and efficient method, dispersive liquid-liquid microextraction (DLLME) combined gas chromatography-electron capture detection (GC-ECD), for the determination of chlorobenzenes (CBs) in water samples, has been described. This method involves the use of an appropriate mixture of extraction solvent (9.5 microl chlorobenzene) and disperser solvent (0.50 ml acetone) for the formation of cloudy solution in 5.00 ml aqueous sample containing analytes. After extraction, phase separation was performed by centrifugation and the enriched analytes in sedimented phase were determined by gas chromatography-electron capture detection (GC-ECD). Our simple conditions were conducted at room temperature with no stiring and no salt addition in order to minimize sample preparation steps. Parameters such as the kind and volume of extraction solvent, the kind and volume of disperser solvent, extraction time and salt effect, were studied and optimized. The method exhibited enrichment factors and recoveries ranging from 711 to 813 and 71.1 to 81.3%, respectively, within very short extraction time. The linearity of the method ranged from 0.05 to 100 microgl(-1) for dichlorobenzene isomers (DCB), 0.002-20 microgl(-1) for trichlorobenzene (TCB) and tetrachlorobenzene (TeCB) isomers and from 0.001 to 4 microgl(-1) for pentachlorobenzene (PeCB) and hexachlorobenzene (HCB). The limit of detection was in the low microgl(-1) level, ranging between 0.0005 and 0.05 microgl(-1). The relative standard deviations (R.S.D.s) for the concentration of DCB isomers, 5.00 microgl(-1), TCB and TeCB isomers, 0.500 microgl(-1), PeCB and HCB 0.100 microgl(-1) in water by using the internal standard were in the range of 0.52-2.8% (n=5) and without the internal standard were in the range of 4.6-6.0% (n=5). The relative recoveries of spiked CBs at different levels of chlorobenzene isomers in tap, well and river water samples were 109-121%, 105-113% and 87-120%, respectively. It is concluded that this method can be successfully applied for the determination of CBs in tap, river and well water samples. PMID:19071629

Kozani, Reyhaneh Rahnama; Assadi, Yaghoub; Shemirani, Farzaneh; Hosseini, Mohammad-Reza Milani; Jamali, Mohammad Reza

2007-04-30

4

Simultaneous determination of cyanide and carbonyls in cyanogenic plants by gas chromatography-electron capture/photoionization detection.  

PubMed

A new method to simultaneously detect cyanide and carbonyl compounds arising from cyanogenic glycosides in plants is described. A portable gas chromatograph.housing two detectors using a single carrier gas is employed to measure the carbonyl compounds (photoionization detector) and cyanide as its cyanogen chloride derivative (electron capture detector) from the headspace of a plant sample. This method affords in-field, rapid screening of plants to determine cyanogenicity. Good agreement was seen between this method for cyanide determination and two traditional field cyanide test kits. Detection of both the cyanide and the carbonyl compound(s) allows for confirmation of the presence of cyanogenic glycosides and eliminates the problem of false positives often seen in traditional cyanide test kits. Gas phase limits of detection for cyanide, acetone, butanone, and benzaldehyde were 69, 41, 105, and 0.39 parts per billion by volume (ppbv), respectively, allowing sensitive detection of cyanogenic glycoside breakdown products. The method's utility for screening cyanogenic plants is demonstrated, and it should be useful for screening cyanogenic foodstuffs to determine suitability for consumption. PMID:12475032

Curtis, Abigale J; Grayless, C Charles; Fall, Ray

2002-11-01

5

Group-selective enrichment and determination of pyrethroid insecticides in aquaculture seawater via molecularly imprinted solid phase extraction coupled with gas chromatography-electron capture detection.  

PubMed

Two types of molecularly imprinted polymers (MIPs) for the simultaneous determination of six pyrethroid insecticides have been developed using deltamethrin (D-MIPs) and cypermethrin (C-MIPs) as template molecules. A comparison of the performance of D-MIPs, C-MIPs, and the corresponding non-imprinted polymers (NIPs) were conducted. Stronger group-selective interactions between the C-MIPs and the six pyrethroid insecticides were achieved. The MISPE method based on the C-MIPs displayed higher extraction recoveries (86.4-96.0%) with RSD values ranging from 2.4 to 7.8% for the six pyrethroid insecticides in aquaculture seawater. After the C-MIP cartridge procedure, the limits of detection and quantification for fenvalerate, deltamethrin, cypermethrin, cyfluthrin, and bifenthrin were in the 16.6-37.0 and 55.3-109.1 ng L?¹ ranges, respectively, and 0.68 and 2.26 ?g L?¹ for phenothrin, respectively. The proposed MISPE method coupled with gas chromatography-electron capture detection was successfully used for the determination of the six pyrethroid insecticides in aquaculture seawater. PMID:22265776

Shi, Xizhi; Liu, Jinghua; Sun, Aili; Li, Dexiang; Chen, Jiong

2012-03-01

6

A study of the suitability of gas chromatography-electron capture detection for the analysis of deoxynivalenol in cereals  

Microsoft Academic Search

A gas chromatographic-electron capture detection (GC-ECD) method for the analysis of deoxynivalenol (DON) in cereals was investigated.\\u000a The sample was extracted with a mixture of acetonitrile-water and purified with a MycoSep #225 column. The silylation was\\u000a performed with Tri-Sil-TBT reagent, followed by dilution with hexane and a washing step with buffer. By using Tri-Sil-TBT\\u000a reagent no double peaks were observed

M Eskola; G Boonzaaijer; WA van Osenbruggen; A Rizzo; G Tijmensen

2000-01-01

7

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

PubMed

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

Slabizki, Petra; Schmarr, Hans-Georg

2013-01-01

8

Dispersive liquid-liquid microextraction followed by gas chromatography-electron capture detection for determination of polychlorinated biphenyls in fish.  

PubMed

A new method of dispersive liquid-liquid microextraction (DLLME) combined with GC-electron capture detection (GC-ECD) was proposed for the extraction and determination of four polychlorinated biphenyls (PCBs) congeners in fish samples. Acetone was used as extraction solvent for the extraction of PCBs from fish samples. The target analytes in the acetone solvent were rapidly transferred to chlorobenzene, which was used as extraction solvent in DLLME procedures. Under the optimum conditions, linearity was obtained in the concentration range from 1.25 to 1250 microg/kg for PCB 52, and 0.25 to 250 microg/kg for PCB 101, 138 and 153. Coefficients of correlation (r2) ranged from 0.9993 to 0.9999. The repeatability was tested by spiking fish samples at 10 microg/kg PCBs, and RSD% (n = 8) varied between 2.2 and 8.4%. The LODs were between 0.12 and 0.35 microg/kg. The enrichment factors of PCBs were from 87 to 123. The relative recoveries of the four PCB congeners for the perch, pomfret and yellow-fin tuna at spiking levels of 10, 20 and 50 microg/kg were in the range of 81.20-100.6%, 85.00-102.7% and 87.80-108.4%, respectively. The results demonstrated that DLLME combined with GC-ECD was a simple, rapid, and efficient technique for the extraction and determination of PCBs in fish samples. PMID:19548213

Hu, Jia; Li, Yanyan; Zhang, Wei; Wang, Huili; Huang, Changjiang; Zhang, Minghua; Wang, Xuedong

2009-06-01

9

Determination of pyrethroid metabolites in human urine using liquid phase microextraction coupled in-syringe derivatization followed by gas chromatography/electron capture detection.  

PubMed

Metabolites of synthetic pyrethroids such as cis-3-(2,2-dibromovinyl)-2,2-di-methylcyclo-propane-1-carboxylic acid, cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid), 3-phenoxybenzoic acid (3-PBA), and 4-fluoro-3-PBA are biomarkers for exposure to phenothrin, tetramethrin, cyfluthrin, cypermethrin, deltamethrin, and permethrin. In this study, the pyrethroid metabolites in workers' urine samples were monitored for the first time with a novel sample pretreatment process combining hollow fiber liquid phase microextraction (HF-LPME) and in-syringe derivatization (ISD) followed by gas chromatography-electron capture detector (GC-ECD) analysis. A micro-syringe pre-filled with derivatizing agents and syringe needle connected to an extracting solvent impregnated hollow fiber segment was used as the LPME probe. Pyrethroid metabolites were extracted and enriched simultaneously from urine samples by HF-LPME sampling and acid hydrolysis at 70 °C for 10 min. After sampling, the ISD was performed by mixing the extracting solution and derivatizing agents through plunger movements, followed by GC-ECD analysis. Parameters influencing the HF-LPME efficiency and ISD were investigated and optimized. Under optimum conditions, the method provided enrichment factors of 69.8-154.6, repeatability from 5.0 to 12% (n = 5), and good linearity (R(2) = 0.9980-0.9998) for interested analytes spiked in urine samples. The method detection limits ranged from 1.6 to 17 ng/mL. A comparison was performed between the proposed method and conventional methods. The proposed method was applied to analyze pyrethroid metabolites in the urine samples collected from workers of pesticide formulation plants. The results suggested that the proposed HF-LPME coupled ISD method was a rapid, simple, efficient, and eco-friendly technique in the biomonitoring of metabolites of pyrethroids in workers' urine. PMID:21667061

Lin, Chiu-Hwa; Yan, Cheing-Tong; Kumar, Ponnusamy Vinoth; Li, Hong-Ping; Jen, Jen-Fon

2011-08-01

10

2-Phosphoglycolate and glycolate-electrophore detection, including detection of 87 zeptomoles of the latter by gas chromatography-electron-capture mass spectrometry  

Microsoft Academic Search

As a first stage towards a goal of studying some aspects of oxidative damage to DNA and its subsequent repair, we set up three techniques for the detection of 2-phosphoglycolate (PG). This compound is released as a metabolite from the DNA in certain cases of this process. We explored three techniques because we wanted to learn which one(s) would be

Poguang Wang; Veeravagu Murugaiah; Bernice Yeung; Paul Vouros; Roger W. Giese

1996-01-01

11

Determination of 2,4,6-trichloroanisole in wines by headspace solid-phase microextraction and gas chromatography-electron-capture detection.  

PubMed

One of the most important problems in the wine world, today, is cork taint, which often has been chemically identified as 2,4,6-trichloroanisole (TCA). The perception limit of this compound is very low (close to 10 and 40 ng/l for white and red wines, respectively), so, even at such low concentrations, its presence becomes a problem in wine quality. A method for the analysis of TCA in white and red wines has been developed in our laboratory, using headspace solid-phase microextraction and gas chromatography with electron-capture detection. The method, which has been optimized using an experimental design, involves the use of fibres coated with polydimethylsiloxane (PDMS) and allows the analysis of TCA at very low concentrations (under 500 ng/l) with good accuracy (RSD < or = 10%). The limits of quantification of the method are 5 and 8 ng/l for white and red wines, respectively, while the limit of detection is 1 ng/l for both types of wine. PMID:12456090

Riu, M; Mestres, M; Busto, O; Guasch, J

2002-11-15

12

Miniaturized membrane-assisted solvent extraction combined with gas chromatography/electron-capture detection applied to the analysis of volatile organic compounds.  

PubMed

A new module of membrane-assisted solvent extraction (MASE) with miniaturized membrane bags was applied to the determination of seven volatile organic compounds (VOCs): chloroform, 1,1,1-trichloroethane, trichloroethylene, 1,1,2-trichloroethane, tetrachloroethene, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane with boiling points between 61 and 147 degrees C in aqueous samples. Different from the known procedure the new, shortened membrane bags were filled with 100 microl of an organic solvent. The membrane bags were placed in a 20 ml headspace vial and filled with 15 ml of the aqueous sample. The vial was transferred into an autosampler where it was stirred for a definite time at elevated temperature. After the extraction, 1 microl of the organic extract was transferred into the spilt/splitless injector of a GC system equipped with an electron-capture detector. This work included optimization of the membrane device, the determination of the optimized extraction conditions such as stirring rate, extraction time and the impact of salt addition. The validation of the method involved repeatability, recovery and detection limit studies, followed of its application towards real water samples. The repeatability, expressed as the relative standard deviation of the peak areas of six extractions was below 10%. The detection limits (LODs) were between 5 ng/l (tetrachloroethene) and 50 ng/l (chloroform). Calibration was performed in a range from 5 ng/l to 150 microg/l, since the concentration in the aqueous samples was expected quite various in this concentration range. Five river water samples of Bitterfeld, Saxony-Anhalt, Germany were analyzed with miniaturized-MASE and the results were compared with those obtained with Headspace-Analysis. The method can be fully automated and moreover, it allows the simultaneous determination of volatile and semi volatile compounds. PMID:16325836

Schellin, Manuela; Popp, Peter

2006-01-27

13

Rapid analysis of organochlorine and pyrethroid pesticides in tea samples by directly suspended droplet microextraction using a gas chromatography-electron capture detector.  

PubMed

A simple and efficient directly suspended droplet microextraction (DSDME) has been developed to extract and pre-concentrate organochlorine and pyrethrin pesticides from tea samples prior to analysis by a gas chromatography-electron capture detector (GC-ECD). The optimal experimental conditions of DSDME were: 100 ?L isooctane exposed for 15 min to 5 mL of the tea aqueous sample stirred at 1100 rpm. For most of the target analytes, the optimal pretreatment of DSDME processes led to no significant interference of tea matrices. The approach was applied to the determination of organochlorine and pyrethroid pesticides in tea samples, with a linearity range of 0.0005-2 ?g/mL. The relative recoveries of all the pesticides ranged between 80.0% and 120.8% with relative standard deviations (RSDs) in the range of 0.8-19.9% (n=5). The limits of detections (LODs) ranged between 0.04 and 1 ?g/L for all the target pesticides. PMID:22440664

Liu, Dan; Min, Shungeng

2012-04-27

14

Rapid analysis of cyclamate in foods and beverages by gas chromatography-electron capture detector (GC-ECD).  

PubMed

A rapid method for determination of sodium cyclamate in foods and beverages was developed. Sodium cyclamate was converted to N,N-dichloridecyclohexylamine by reaction with sodium hypochlorite under acid condition. N,N-dichloridecyclohexylamine was subsequently extracted by n-hexane and determined by gas chromatography. Conditions such as derivatization time, the concentration of sodium hypochlorite and sulphuric acid were optimised. Amino acids, aliphatic amines, and food additives such as preservatives, dyes and sweeteners showed no interference for quantification of cyclamate. The correlation coefficient of calibration curve was 0.9993 in the range of 5.0-250mg/L. The limits of detection (LOD) and limits of quantification (LOQ) were calculated as three or ten times the signal-to-noise ratio (S/N), respectively. The LOD and LOQ for yellow wine and fruit juice were 0.05 and 0.2mg/L, respectively. The LOD and LOQ for cake and preserved fruit were 0.25 and 0.8mg/kg, respectively. The intra-day and inter-day RSD were 0.28% and 1.1% (n=5), respectively. The method was successfully applied for determination of cyclamate in yellow wine, cake, fruit juice and preserved fruit. This method was simple, fast, and sensitive. It was suitable for the determination of cyclamate in foods and beverages for safety and quality control inspections. PMID:23442705

Yu, Shengbing; Zhu, Binghui; Lv, Fen; Li, Shaoxiao; Huang, Weixiong

2012-10-15

15

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.  

PubMed

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 C(18) silica bonded cartridge, hydrolysis and derivatization to 2,4-dimethyl-7-F-butyramide for GC-ECD analysis. For confirmation using GC-MS, hydrolysis and derivatization were not needed. Parameters for extraction pressure, temperature and cycle of ASE, clean-up, derivatization and analysis procedure have been optimized. Spike recoveries from 50 to 300 microg/kg levels were found to be between 72.4 and 101.3% with relative standard deviation less than 11.5% in GC-ECD, from 5 to 20 microg/kg levels were found to be between 77.4 and 107.1% with relative standard deviation less than 11.6% in GC-MS. The LOD and LOQ are 5 and 10 microg/kg, respectively, for these two analytes using GC-ECD. For GC-MS, LOD and LOQ were 2 and 5 microg/kg, respectively. The rapid and reliable method can be used for characterization and quantification of residues of amitraz and its main metabolite, 2,4-dimethylaniline, in liver and kidney samples of swine, sheep and bovine. PMID:20554255

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

2010-07-01

16

Simultaneous determination of bisphenol A, triclosan, and tetrabromobisphenol A in human serum using solid-phase extraction and gas chromatography-electron capture negative-ionization mass spectrometry  

Microsoft Academic Search

This study aimed at optimizing and validating a sensitive method for simultaneous determination of bisphenol A (BPA), triclosan\\u000a (TCS), and tetrabromobisphenol A (TBBPA) in human serum using solid-phase extraction (SPE) and gas chromatography coupled\\u000a to electron-capture negative-ionization mass spectrometry (GC-ECNI\\/MS). Sample preparation involved denaturation of serum\\u000a proteins with formic acid followed by SPE on an Oasis HLB cartridge. Fractionation was

Alin C. Dirtu; Laurence Roosens; Tinne Geens; Adriana Gheorghe; Hugo Neels; Adrian Covaci

2008-01-01

17

Homogeneous liquid–liquid extraction combined with gas chromatography–electron capture detector for the determination of three pesticide residues in soils  

Microsoft Academic Search

In this study, a new method was developed for analyzing malathion, cypermethrin and lambda-cyhalothrin from soil samples by using homogeneous liquid–liquid extraction (HLLE) and gas chromatography with electron capture detector (GC–ECD). Acetone was used as extraction solvent for the extraction of target pesticides from soil samples. When the extraction process was finished, the target analytes in the extraction solvent were

Xuedong Wang; Xinna Zhao; Xiujuan Liu; Yanyan Li; Lingyan Fu; Jia Hu; Changjiang Huang

2008-01-01

18

Measurement of Low Picomolar Levels of Triamcinolone Acetonide in Human Bronchoalveolar Lavage Fluid by Gas Chromatography-Electron-Capture Negative-Ion Mass Spectrometry  

Microsoft Academic Search

The intense inherent electron-capture properties of the C21 acetate derivative of triamcinolone acetonide (TAA) under methane chemical ionization mass spectrometric conditions were exploited for the development of a highly sensitive and selective gas chromatography-mass spectrometric (GC-MS) technique for measurement of levels of TAA in human bronchoalveolar lavage (BAL) fluid. After the addition of 3.0 ng of a heptadeuterated analog of

Walter C. Hubbard; Mark C. Liu; Carol Bickel; Domenick Argenti; Don Heald; Robert P. Schleimer

2001-01-01

19

Construction and validation of a cryogen free gas chromatography–electron-capture detection system for the measurement of ambient halocarbons  

Microsoft Academic Search

A fully automated GC–ECD system was constructed to perform unattended on site measurement of airborne halocarbons. To adequately manage water vapor during analysis a retractable thermoelectric cooling device was built and incorporated into the automated GC–ECD system for retaining water vapor during sample preconcentration. This device allows the trap tubing to engage with the cooling block when trapping, or disengage

Jia-Lin Wang; Cheng-Hsiu Wu

2002-01-01

20

Determination of pyrethroid metabolites in human urine using liquid phase microextraction coupled in-syringe derivatization followed by gas chromatography\\/electron capture detection  

Microsoft Academic Search

Metabolites of synthetic pyrethroids such as cis-3-(2,2-dibromovinyl)-2,2-di-methylcyclo-propane-1-carboxylic acid, cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid), 3-phenoxybenzoic acid (3-PBA), and 4-fluoro-3-PBA are\\u000a biomarkers for exposure to phenothrin, tetramethrin, cyfluthrin, cypermethrin, deltamethrin, and permethrin. In this study,\\u000a the pyrethroid metabolites in workers’ urine samples were monitored for the first time with a novel sample pretreatment process\\u000a combining hollow fiber liquid phase microextraction (HF-LPME) and in-syringe

Chiu-Hwa Lin; Cheing-Tong Yan; Ponnusamy Vinoth Kumar; Hong-Ping Li; Jen-Fon Jen

21

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

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

C Gonçalves; M. F Alpendurada

2002-01-01

22

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

Microsoft Academic Search

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

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

2005-01-01

23

Rapid determination of the isomeric truxillines in illicit cocaine via capillary gas chromatography/flame ionization detection and their use and implication in the determination of cocaine origin and trafficking routes.  

PubMed

The isomeric truxillines are a group of minor alkaloids present in all illicit cocaine samples. The relative amount of truxillines in cocaine is indicative of the variety of coca used for cocaine processing, and thus, is useful in source determination. Previously, the determination of isomeric truxillines in cocaine was performed with a gas chromatography/electron capture detection method. However, due to the tedious sample preparation as well as the expense and maintenance required of electron capture detectors, the protocol was converted to a gas chromatography/flame-ionization detection method. Ten truxilline isomers (alpha-, beta-, delta-, epsilon-, gamma-, omega, zeta-, peri-, neo-, and epi-) were quantified relative to a structurally related internal standard, 4',4?-dimethyl-?-truxillic acid dimethyl ester. The method was shown to have a linear response from 0.001 to 1.00mg/mL and a lower detection limit of 0.001mg/mL. In this method, the truxillines are directly reduced with lithium aluminum hydride and then acylated with heptafluorobutyric anhydride prior to analysis. The analysis of more than 100 cocaine hydrochloride samples is presented and compared to data obtained by the previous methodology. Authentic cocaine samples obtained from the source countries of Colombia, Bolivia, and Peru were also analyzed, and comparative data on more than 23,000 samples analyzed over the past 10 years with the previous methodology is presented. PMID:25219521

Mallette, Jennifer R; Casale, John F

2014-10-17

24

Estimation of measurement uncertainty of polychlorinated biphenyls, polycyclic aromatic hydrocarbons and organochlorine pesticides in the atmosphere using gas chromatography-mass spectrometry and gas chromatography-electron capture detector.  

PubMed

Estimation of uncertainty of measurement is a crucial issue to achieve accurate measurement results. When the target has adverse environmental and health effects, accuracy of the results become more important. POPs are the pollutants that have toxic effects and unfortunately, there is a lack of information about uncertainty of the method for determining POPs in air samples. In this work, uncertainty calculations were carried out for PCBs, OCPs, and PAHs in air samples analyzed by using GC-MS and GC-ECD. The main dominant sources for combined uncertainty were calibration curve, recovery and repeatability. The relative uncertainties were found to be in the range of 23-52% for PCBs, 24-59% for OCPs and 23-90% for PAHs. PMID:24369999

Aslan-Sungur, Güler; Gaga, Eftade O; Yenisoy-Karaka?, Serpil

2014-01-17

25

46 CFR 154.1345 - Gas detection.  

...154.1345 Gas detection. (a) Each vessel carrying a cargo that...space. (c) A vessel that carries...have a fixed gas detection system that is...space. (d) A vessel that carries sulfur...have a fixed gas detection system that...

2014-10-01

26

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2011 CFR

...154.1345 Gas detection. (a) Each vessel carrying a cargo that...space. (c) A vessel that carries...have a fixed gas detection system that is...space. (d) A vessel that carries sulfur...have a fixed gas detection system that...

2011-10-01

27

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2013 CFR

...154.1345 Gas detection. (a) Each vessel carrying a cargo that...space. (c) A vessel that carries...have a fixed gas detection system that is...space. (d) A vessel that carries sulfur...have a fixed gas detection system that...

2013-10-01

28

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2012 CFR

...154.1345 Gas detection. (a) Each vessel carrying a cargo that...space. (c) A vessel that carries...have a fixed gas detection system that is...space. (d) A vessel that carries sulfur...have a fixed gas detection system that...

2012-10-01

29

Detection of Gas Slugs in Heat Pipes  

NASA Technical Reports Server (NTRS)

Temperature sensing system detects presence of gas slugs in heat pipes. System designed for operation between zero and 70 degrees C and detects noncondensable pockets of gas that result from decomposition of ammonia cooling fluid. Slugs 1 in. (25mm) in length detected.

Jones, J. A.

1985-01-01

30

Method of detecting oxygen in a gas  

NASA Technical Reports Server (NTRS)

The presence of oxygen in a gas is detected by contacting an article, such as a film, comprising poly(ethylenenaphthalene-dicarboxylate) with a gas and simultaneously exposing the article to ultraviolet light. The article is subsequently heated and the presence of oxygen in the gas is indicated by thermoluminescence.

Hendricks, H. D. (inventor)

1973-01-01

31

Development and application of an indirect competitive enzyme-linked immunosorbent assay for the detection of p,p'-DDE in human milk and comparison of the results against GC-ECD.  

PubMed

1,1-Dichloro-2,2-bis(p-chlorophenyl) ethylene (p,p'-DDE) is the major metabolite of insecticide 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (p,p'-DDT) and a persistent organic pollutant (POPs) with concerns regarding its bioaccumulation and persistence in the environment and food chain. In the present study, an indirect competitive enzyme-linked immunosorbant assay (ic-ELISA) specific for the detection of p,p'-DDE is described. In hapten synthesis, 2,2'-bis(4-chlorophenyl)ethanol and glutaric anhydride were used as precursor and spacer arm, respectively. The hapten was then conjugated to bovine serum albumin (BSA) as immunogen for mouse immunization and also conjugated to ovalbumin as coating antigen for ELISA. The developed ic-ELISA was used for detecting p,p'-DDE in human milk samples and validated against the results from conventional gas chromatography-electron capture detection (GC-ECD). Coefficients of variation (%CV) of ELISA were 5.7-10.4% for intra-assay and 10.6-19.6% for interassay variations. The Pearson correlation coefficient of p,p'-DDE concentrations between ic-ELISA and GC-ECD was r = 0.766, which was in an acceptable range. The results indicate that the developed assay could be an alternative analytical tool for monitoring p,p'-DDE in lipimic matrices such as human milk. PMID:22122759

Hongsibsong, Surat; Wipasa, Jiraprapa; Pattarawarapan, Mookda; Chantara, Somporn; Stuetz, Wolfgang; Nosten, Francois; Prapamontol, Tippawan

2012-01-11

32

46 CFR 154.1350 - Flammable gas detection system.  

...1350 Flammable gas detection system. (a) The vessel must have a fixed flammable gas detection system that has sampling...can be removed during vessel operation, unless it...Each flammable gas detection system in a...

2014-10-01

33

Detection of hydrogen chloride gas in air  

NASA Technical Reports Server (NTRS)

Launch vehicle effluent (LVE) monitoring is part of NASA's overall tropospheric and stratospheric environmental program. Following nine techniques are evaluated and developed in report: bubbler method, pH measurements, indicator tubes, microcoulometers, modified condensation nuclei counter, dual-isotope absorption, gas-filter correlation, chemiluminescent nitric oxide detection, chemiluminescent luminol-oxidation detection.

Gregory, G. L.

1978-01-01

34

Mass spectrometric detection and measurement of N 2-(2?-deoxyguanosin-8-yl)PhIP adducts in DNA  

Microsoft Academic Search

Capillary column gas chromatography–electron-capture mass spectrometry (GC–MS) and microbore liquid chromatography–positive ion electrospray mass spectrometry (LC–MS) have been used to measure the carcinogenic, food-derived, heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) adducted at C-8 of deoxyguanosine in DNA. For GC–MS analysis, PhIP was released from adducted DNA by alkaline hydrolysis and analysed as the di(3,5-bistrifluoromethylbenzyl) derivative, while for LC–MS analysis, the nucleoside N2-(2?-deoxyguanosin-8-yl)PhIP

Sarah J Crosbie; Stephen Murray; Alan R Boobis; Nigel J Gooderham

2000-01-01

35

Heterodyne method for high specificity gas detection.  

NASA Technical Reports Server (NTRS)

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.

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

36

Novel gas-based detection techniques  

NASA Astrophysics Data System (ADS)

This year we celebrate the 100th birthday of gaseous detectors: Hans Geiger operated the first gas-filled counter in Manchester in 1908. The thin wires, essential for obtaining gas amplification, have been replaced by Micro Pattern Gas Detectors (MPGDs): Micromegas (1995) and GEM (1996). In the GridPix detector, each of the grid holes of a MPGD is equipped with its own electronic readout channel in the form of an active pixel in suitable pixel CMOS chips. By means of MEMS technology, the grid has been integrated with the chip, forming a monolithic readout device for gas volumes. By applying a protection layer made of hydrogenated amorphous silicon, the chips can be made spark proof. New protection layers have been made of silicon nitride. The use of gas as detection material for trackers is compared to Si, and the issue of chamber aging is addressed. New developments are set out: the development of Micro Channel Plates, integrated on pixel chips, the development of electron emission foil, and the realization of TimePix-2: a general-purpose pixel chip with time and amplitude measurement, per pixel, of charge signals.

van der Graaf, Harry

2009-06-01

37

49 CFR 192.736 - Compressor stations: Gas detection.  

Code of Federal Regulations, 2010 CFR

...station must have a fixed gas detection and alarm system, unless the...of this section, each gas detection and alarm system required by...than 25 percent of the lower explosive limit; and (2) If that...danger. (c) Each gas detection and alarm system...

2010-10-01

38

49 CFR 192.736 - Compressor stations: Gas detection.  

Code of Federal Regulations, 2011 CFR

...station must have a fixed gas detection and alarm system, unless the...of this section, each gas detection and alarm system required by...than 25 percent of the lower explosive limit; and (2) If that...danger. (c) Each gas detection and alarm system...

2011-10-01

39

49 CFR 192.736 - Compressor stations: Gas detection.  

Code of Federal Regulations, 2012 CFR

...station must have a fixed gas detection and alarm system, unless the...of this section, each gas detection and alarm system required by...than 25 percent of the lower explosive limit; and (2) If that...danger. (c) Each gas detection and alarm system...

2012-10-01

40

49 CFR 192.736 - Compressor stations: Gas detection.  

Code of Federal Regulations, 2013 CFR

...station must have a fixed gas detection and alarm system, unless the...of this section, each gas detection and alarm system required by...than 25 percent of the lower explosive limit; and (2) If that...danger. (c) Each gas detection and alarm system...

2013-10-01

41

Sensor array for toxic gas detection  

DOEpatents

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.

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

1987-01-01

42

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2010 CFR

...4 must have: (1) Two portable gas detectors that show if the concentration...for that cargo; and (2) Fixed gas sampling tubes in each hold space and interbarrier...unless it is connected to a fixed toxic gas detector; (iii) If the...

2010-10-01

43

Gas concentration detection with FBGs and compensation method  

NASA Astrophysics Data System (ADS)

A novel scheme of gas concentration detection based on a frequency modulation technique is introduced in this paper, which resolves the problems of centric wavelength drift and variations of modulation amplitude by using an ASE source, FBG and a specific mechanical vibration device. A wavelength Scanning optical source for gas detection can be easily achieved.

Zhong, Chunlan; Dong, Xiaopeng; Li, Junjun; Qi, Jie; Li, Sensen; Li, Weiwen

2008-12-01

44

Gas in soil; 1: Detection an [eta]profiling  

Microsoft Academic Search

Increasing offshore construction activities in areas where marine sediments contain gas (either in dissolved or free from) have generated an interest in developing in situ test equipment capable of detecting and quantifying the amount of in situ gases ([eta]-profiling). This is important since: (1) Failure to detect gas pockets ahead of the drill bit during soil investigation of drilling operations

Nader S. Rad; Tom Lunne

1994-01-01

45

ANALYSIS OF SOIL AND DUST SAMPLES FOR POLYCHLORINATED BIPHENYLS BY ENZYME LINKED IMMUNOSORBENT ASSAY (ELISA)  

EPA Science Inventory

An inhibition enzyme-linked immunosorbent assay (ELISA) was used to determine polychlorinated biphenyls (PCBs) in house dust and soil. Soil and house dust samples were analyzed for PCB by both gas chromatography/electron capture detection (GC/ECD) and ELISA methods. A correlati...

46

Validation of proton transfer reaction-mass spectrometry (PTR-MS) measurements of gas-phase organic compounds in the atmosphere during the New England Air Quality Study (NEAQS) in 2002  

NASA Astrophysics Data System (ADS)

Organic compounds were measured by proton transfer reaction-mass spectrometry (PTR-MS) on board the National Oceanic and Atmospheric Administration's research ship Ronald H. Brown during the New England Air Quality Study (NEAQS) in July and August of 2002. PTR-MS has the potential to measure many important organic species with a fast time response, but its validity has not been proven sufficiently. The results obtained by PTR-MS during NEAQS were compared with those from (oxygenated) hydrocarbon measurements by gas chromatography/mass spectrometry (GC-MS), peroxyacyl nitrate measurements by gas chromatography/electron capture detection, and carboxylic acid measurements by mist chamber/ion chromatography. The PTR-MS and GC-MS data for methanol, acetonitrile, acetone, isoprene, benzene, and toluene agreed within the measurement uncertainties. The comparison for C8 aromatics and acetaldehyde was less quantitative due to calibration inaccuracies. In addition, PTR-MS measured the sum of methyl vinyl ketone and methacrolein at 71 amu, the sum of C9 aromatics at 121 amu, and the sum of monoterpenes at 81 and 137 amu. The PTR-MS signal at 61 amu was found to correlate well with data for acetic acid. The signal at 73 amu correlated reasonably well with methyl ethyl ketone data, but the quantitative disagreement suggested interference from other species, possibly methyl glyoxal. The signal at 77 amu correlated well with data for peroxyacetyl nitrate, and the sensitivity inferred from the field data agreed within 30% with the results from laboratory calibrations. Finally, the signal at 105 amu was attributed to styrene and peroxy isobutyryl nitrate. These results prove that many important organic species can be measured accurately and with a fast response time by PTR-MS.

de Gouw, J. A.; Goldan, P. D.; Warneke, C.; Kuster, W. C.; Roberts, J. M.; Marchewka, M.; Bertman, S. B.; Pszenny, A. A. P.; Keene, W. C.

2003-11-01

47

Detecting gas molecules via atomic magnetization.  

PubMed

Adsorptions of gas molecules were found to alter the directions and magnitudes of magnetic moments of transition metal (Co, Fe) atoms adsorbed on graphene. Using first-principles calculations, we demonstrated that magnetism of surface atoms can be used to identify the kind of existing gas molecules via spin-reorientation and/or demagnetizations caused by the reconfigurations of 3d electron energy levels of Co and Fe. We suggest for the first time that magnetic properties of transition metal-embedded nanostructures can be used in highly selective gas-sensing applications. PMID:25036241

Choi, Heechae; Lee, Minho; Kim, Seungchul; Lee, Kwang-Ryeol; Chung, Yong-Chae

2014-09-14

48

Dynamic photoacoustic spectroscopy for trace gas detection  

NASA Astrophysics Data System (ADS)

We present a method of photoacoustic spectroscopy in which a laser beam tuned to an absorption feature of a gas is swept through its plume at the speed of sound. The resulting coherent addition of acoustic waves leads to an amplification of the signal without the need for a resonant chamber, thus enhancing the ability to remotely sense the gas. We demonstrate the concept using a tunable CO2 laser and SF6 gas in conjunction with a microphone. Sound pressure levels of 83 dB (relative to 20 ?Pa) are generated from a 15-ppm plume.

Wynn, C. M.; Palmacci, S.; Clark, M. L.; Kunz, R. R.

2012-10-01

49

Detection of Greenhouse-Gas-Induced Climatic Change  

SciTech Connect

The objective of this report is to assemble and analyze instrumental climate data and to develop and apply climate models as a basis for (1) detecting greenhouse-gas-induced climatic change, and (2) validation of General Circulation Models.

Jones, P.D.; Wigley, T.M.L.

1998-05-26

50

Naturally fractured tight gas reservoir detection optimization  

SciTech Connect

Building upon the partitioning of the Greater Green River Basin (GGRB) that was conducted last quarter, the goal of the work this quarter has been to conclude evaluation of the Stratos well and the prototypical Green River Deep partition, and perform the fill resource evaluation of the Upper Cretaceous tight gas play, with the goal of defining target areas of enhanced natural fracturing. The work plan for the quarter of November 1-December 31, 1998 comprised four tasks: (1) Evaluation of the Green River Deep partition and the Stratos well and examination of potential opportunity for expanding the use of E and P technology to low permeability, naturally fractured gas reservoirs, (2) Gas field studies, and (3) Resource analysis of the balance of the partitions.

NONE

1999-06-01

51

Naturally fractured tight gas reservoir detection optimization  

SciTech Connect

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.

NONE

1998-11-30

52

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

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

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

1990-01-01

53

Miniature fiber-tip photoacoustic spectrometer for trace gas detection.  

PubMed

We demonstrate a fiber-tip photoacoustic spectrometric sensor for trace gas detection. The sensor head is a miniature fiber-tip hollow-cavity with a deflectable polymer diaphragm. Periodic light absorption of gas molecules within the cavity generates an acoustic pressure wave, which causes deflection of the diaphragm. The hollow cavity also is a Fabry-Perot interferometer with which the diaphragm deflection is detected with high sensitivity. Experimental test around the P(9) absorption line of C(2)H(2) achieved a minimum detectable gas concentration of 4.3 ppm with an excitation laser power of 8 mW. The miniature sensor head and fiber optic detection system make this type of spectrometers ideally suited for remote and space-limited applications as well as for multipoint detection in a multiplexed fiber optic sensor network. PMID:23455093

Cao, Yingchun; Jin, Wei; Ho, Hoi Lut; Ma, Jun

2013-02-15

54

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

Code of Federal Regulations, 2011 CFR

...boil-off as fuel: Gas detection equipment. 154.709...STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED...boil-off as fuel: Gas detection equipment. (a) The continuous gas detection system required...

2011-10-01

55

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

Code of Federal Regulations, 2013 CFR

...boil-off as fuel: Gas detection equipment. 154.709...STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED...boil-off as fuel: Gas detection equipment. (a) The continuous gas detection system required...

2013-10-01

56

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

Code of Federal Regulations, 2012 CFR

...boil-off as fuel: Gas detection equipment. 154.709...STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED...boil-off as fuel: Gas detection equipment. (a) The continuous gas detection system required...

2012-10-01

57

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

...boil-off as fuel: Gas detection equipment. 154.709...STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED...boil-off as fuel: Gas detection equipment. (a) The continuous gas detection system required...

2014-10-01

58

Fire detection using smoke and gas sensors  

Microsoft Academic Search

Fire detection systems located in aircraft cargo compartments are currently based only on smoke detectors. They generate about 200 false alarms per year for US registered aircraft. The number of false alarms is growing as more planes are outfitted with smoke detectors and air travel expands. Moreover, the survivability of an aircraft in a fire scenario depends on the early

Shin-Juh Chen; David C. Hovde; Kristen A. Peterson; André W. Marshall

2007-01-01

59

Metal oxide nanostructures for gas detection  

NASA Astrophysics Data System (ADS)

Currently, most of gas sensors on the market are produced in thin or thick film technologies with the use of ceramic substrates. It is expected that the miniature sensors needed in portable applications will be based on one-dimensional structures due to their low power consumption, fast and stable time response, small dimensions and possibility of embedding in integrated circuit together with signal conditioning electronics. The authors manufactured resistance type gas sensors based on ZnO and WO3 nanostructures. ZnO:Al nanorods with good cristallinity were obtained with electrodeposition method, while ZnO:Al nanofibres with varying diameters were obtained by electrospinning method. The sensors were built as a nanowire network. WO3 films with nanocrystalline surface were manufactured by deposition of a three layer WO3/W/WO3 structure by RF sputtering and successive annealing of the structure in appropriate temperature range. In effect a uniform nanostructurized metal oxide layer was formed. Investigation of sensors characteristics revealed good sensitivity to nitrogen dioxide at temperatures lower than these for conventional conductometric type sensors.

Maziarz, Wojciech; Pisarkiewicz, Tadeusz; Rydosz, Artur; Wysocka, Kinga; Czyrnek, Grzegorz

2013-07-01

60

Naturally fractured tight gas reservoir detection optimization  

SciTech Connect

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.

NONE

1998-11-30

61

Gas Transport and Detection Following Underground Nuclear Explosions  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

62

Methods for gas detection using stationary hyperspectral imaging sensors  

DOEpatents

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.

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

2012-04-24

63

Infrared thermography to detect residual ceramic in gas turbine blades  

Microsoft Academic Search

A serious problem in the production of gas turbine blades is the detection of residual ceramic cores inside the cooling passages;\\u000a in fact, the presence of even small ceramic pieces affects turbine performance and may cause difficulties in successive manufacturing.\\u000a Therefore, it is important to have a non-destructive technique that must be capable of detecting tiny ceramic fragments in\\u000a a

C. Meola; G. M. Carlomagno; M. Di Foggia; O. Natale

2008-01-01

64

Gas-self-filter-based erbium-doped fiber loop laser for gas detection.  

PubMed

An erbium-doped fiber (EDF) loop laser, based on a gas-self-filter (GSF), is developed with single or multiple wavelength emission. The GSF is a type of Mach-Zehnder interferometer with a gas cell in one arm. By matching the destructive wavelength of the interferometer with the gas absorption line, the self-filtering function is achieved. A GSF-based multi-wavelength laser with a side-mode suppression ratio of ~50??dB is performed. As an example, C?H? gas is detected using a single-wavelength GSF-based laser with correlation spectroscopy, and a good linearity of the measurement is obtained. The present laser has the potential advantage for multiple gas detection, e.g., being free of wavelength calibration. PMID:25090309

Guo, Kaikai; Lou, Xiutao; Yan, Chunsheng; Mei, Liang

2014-08-01

65

Summary of gas release events detected by hydrogen monitoring  

SciTech Connect

This paper summarizes the results of monitoring tank headspace for flammable gas release events. In over 40 tank years of monitoring the largest detected release in a single-shell tank is 2.4 cubic meters of Hydrogen. In the double-shell tanks the largest release is 19.3 cubic meters except in SY-101 pre mixer pump installation condition.

MCCAIN, D.J.

1999-05-18

66

Position sensitive radioactivity detection for gas and liquid chromatography  

DOEpatents

A method and apparatus are provided for the position sensitive detection of radioactivity in a fluid stream, particularly in the effluent fluid stream from a gas or liquid chromatographic instrument. The invention represents a significant advance in efficiency and cost reduction compared with current efforts.

Cochran, Joseph L. (Knoxville, TN); McCarthy, John F. (Loudon, TN); Palumbo, Anthony V. (Oak Ridge, TN); Phelps, Tommy J. (Knoxville, TN)

2001-01-01

67

Pattern Recognition for Selective Odor Detection with Gas Sensor Arrays  

PubMed Central

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

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

2012-01-01

68

Detection of greenhouse-gas-induced climatic change  

SciTech Connect

The aims of the US Department of Energy's Carbon Dioxide Research Program are to improve assessments of greenhouse-gas-induced climatic change and to define and reduce uncertainties through selected research. This project will address: The regional and seasonal details of the expected climatic changes; how rapidly will these changes occur; how and when will the climatic effects of CO[sub 2] and other greenhouse gases be first detected; and the relationships between greenhouse-gas-induced climatic change and changes caused by other external and internal factors. The present project addresses all of these questions. Many of the diverse facets of greenhouse-gas-related climate research can be grouped under three interlinked subject areas: modeling, first detection and supporting data. This project will include the analysis of climate forcing factors, the development and refinement of transient response climate models, and the use of instrumental data in validating General Circulation Models (GCMs).

Wigley, T.M.L.; Jones, P.D.

1992-07-15

69

Gas detection with micro- and nano-engineered optical fibers  

NASA Astrophysics Data System (ADS)

This paper overviews recent development in gas detection with micro- and nano-engineered optical fibers, including hollow-core fibers, suspended-core fibers, tapered optical micro/nano fibers, and fiber-tip micro-cavities. Both direct absorption and photoacoustic spectroscopy based detection schemes are discussed. Emphasis is placed on post-processing stock optical fibers to achieve better system performance. Our recent demonstration of distributed methane detection with a ˜75-m long of hollow-core photonic bandgap fiber is also reported.

Jin, W.; Ho, H. L.; Cao, Y. C.; Ju, J.; Qi, L. F.

2013-12-01

70

Development of a gas leak detection method based on infrared spectrum imaging utilizing microbolometer camera  

NASA Astrophysics Data System (ADS)

Development of an early gas leak detection system is essential for safety of energy storage tank fields or chemical plants. Contact-type conventional gas sensors are not suitable for remote surveillance of gas leakage in wide area. Infrared camera has been utilized for gas leak detection, however it is limited only for detecting particular gas. In this study a gas leak identification system, which enables us to detect gas leakage and to identify gas type and density, is developed based on infrared spectrum imaging system utilizing low cost and compact microbolometer infrared camera. Feasibility of the proposed system was demonstrated by experimental results on identification of hydrofluorocarbon gas.

Sakagami, Takahide; Anzai, Hiroaki; Kubo, Shiro

2011-05-01

71

Remote laser detection of natural gas leakages from pipelines  

SciTech Connect

A differential absorption lidar based on a tunable TEA CO{sub 2} laser emitting at 42 lines of the 'hot' 01{sup 1}1 - 11{sup 1}0 band in the range from 10.9 to 11.4 {mu}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{sup -1} and a probe pulse repetition rate of 5 Hz. (laser applications and other topics in quantum electronics)

Petukhov, V O; Gorobets, V A [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus); Andreev, Yu M [Institute of Monitoring of Climatic and Ecological Systems, Siberian Division of the Russian Academy of Sciences, Tomsk (Russian Federation); Lanskii, G V

2010-02-28

72

Neutron detection by scintillation of noble-gas excimers  

NASA Astrophysics Data System (ADS)

Neutron detection is a technique essential to homeland security, nuclear reactor instrumentation, neutron diffraction science, oil-well logging, particle physics and radiation safety. The current shortage of helium-3, the neutron absorber used in most gas-filled proportional counters, has created a strong incentive to develop alternate methods of neutron detection. Excimer-based neutron detection (END) provides an alternative with many attractive properties. Like proportional counters, END relies on the conversion of a neutron into energetic charged particles, through an exothermic capture reaction with a neutron absorbing nucleus (10B, 6Li, 3He). As charged particles from these reactions lose energy in a surrounding gas, they cause electron excitation and ionization. Whereas most gas-filled detectors collect ionized charge to form a signal, END depends on the formation of diatomic noble-gas excimers (Ar*2, Kr*2,Xe* 2) . Upon decaying, excimers emit far-ultraviolet (FUV) photons, which may be collected by a photomultiplier tube or other photon detector. This phenomenon provides a means of neutron detection with a number of advantages over traditional methods. This thesis investigates excimer scintillation yield from the heavy noble gases following the boron-neutron capture reaction in 10B thin-film targets. Additionally, the thesis examines noble-gas excimer lifetimes with relationship to gas type and gas pressure. Experimental data were collected both at the National Institute of Standards and Technology (NIST) Center for Neutron Research, and on a newly developed neutron beamline at the Maryland University Training Reactor. The components of the experiment were calibrated at NIST and the University of Maryland, using FUV synchrotron radiation, neutron imaging, and foil activation techniques, among others. Computer modeling was employed to simulate charged-particle transport and excimer photon emission within the experimental apparatus. The observed excimer scintillation yields from the 10B( n, alpha)7Li reaction are comparable to the yields of many liquid and solid neutron scintillators. Additionally, the observed slow triplet-state decay of neutron-capture-induced excimers may be used in a practical detector to discriminate neutron interactions from gamma-ray interactions. The results of these measurements and simulations will contribute to the development and optimization of a deployable neutron detector based on noble-gas excimer scintillation.

McComb, Jacob Collin

73

Development of trace gas detection instrumentation. [using the heterodyne principle  

NASA Technical Reports Server (NTRS)

Breadboard hardware was constructed to demonstrate detection of a gaseous species by the heterodyne principle. The characteristics of the component parts were investigated and preliminary measurements were made to establish the sensitivity and selectivity of the method for gas analysis of CO, CO2, and N2O. A prototype heterodyne gas analyzer was designed, built, and brought into operational condition. Performance parameters of the prototype analyzer were investigated and its sensitivity to CO2 measured. Further development was undertaken for both the optical bench and the electronic processor components. A three-gas prototype analyzer, capable of measuring the gases CO, CO2, and CH4 was also constructed and tested. Detailed descriptions of the work and results are presented.

1973-01-01

74

Broadband cavity-enhanced absorption spectroscopy for trace gas detection  

NASA Astrophysics Data System (ADS)

We present an overview of incoherent broadband cavity-enhanced absorption spectroscopy (BBCEAS) and discuss its relevance to monitoring atmospherically important gases. Adavantages of the method include its high sensitivity, portability, and good spatial resolution. We present the visible absorption spectra of NO2 and NO3 between 600 nm and 720 nm and address issues relating to spectral deconvolution and the simultaneous measurement of multiple gases. The sensitivity of our system is compared to that of other trace gas detection techniques.

Venables, Dean S.; Staak, Michael; Ruth, Albert A.

2005-06-01

75

Sulfur gas geochemical detection of hydrothermal systems. Final report  

SciTech Connect

The purpose of this investigation was to determine whether a system of exploration using sulfur gases was capable of detecting convecting hydrothermal systems. Three surveying techniques were used at the Roosevelt Hot Springs KGRA in Utah. These were (a) a sniffing technique, capable of instantaneous determinations of sulfur gas concentration, (b) an accumulator technique, capable of integrating the sulfur gas emanations over a 30 day interval, and (c) a method of analyzing the soils for vaporous sulfur compounds. Because of limitations in the sniffer technique, only a limited amount of surveying was done with this method. The accumulator and soil sampling techniques were conducted on a 1000 foot grid at Roosevelt Hot Springs, and each sample site was visited three times during the spring of 1980. Thus, three soil samples and two accumulator samples were collected at each site. The results are shown as averages of three soil and two accumulator determinations of sulfur gas concentrations at each site. Soil surveys and accumulator surveys were conducted at two additional KGRA's which were chosen based on the state of knowledge of these hydrothermal systems and upon their differences from Roosevelt Hot Springs in an effort to show that the exploration methods would be effective in detecting geothermal reservoirs in general. The results at Roosevelt Hot Springs, Utah show that each of the three surveying methods was capable of detecting sulfur gas anomalies which can be interpreted to be related to the source at depth, based on resistivity mapping of that source, and also correlatable with major structural features of the area which are thought to be controlling the geometry of the geothermal reservoir. The results of the surveys at Roosevelt did not indicate that either the soil sampling technique or the accumulator technique was superior to the other.

Rouse, G.E.

1984-01-01

76

Optical fiber gas sensor for remote detection of methane gas in coal mines  

NASA Astrophysics Data System (ADS)

Characteristic molecular and atomic absorption spectra in the middle infrared and near infrared regions are extensively used for chemical analysis and spectroscopic detection of gases. The absorption of electromagnetic radiation in this spectral region is due to the vibration-rotational bands of molecular structure. Various techniques have been developed for high resolution and high sensitivity absorption spectroscopic detection. Optical gas sensors based on absorption of light by the vibrational-rotational energy levels of gas molecules at near-IR (1-1.8mum) wavelength have attracted considerable attention recently [1]-[4]. The advantages of fiber sensors are remote detection capability, safety in hazardous environments, immunity to electromagnetic fields, etc. The possible gases that can be detected are methane, acetylene, hydrogen sulphide, carbon dioxide, carbon monoxide, etc. In this Dissertation, a particular one-channel optical-fiber-based CH 4 gas real-time monitoring system which can be deployed in mining complexes has been developed. A long-distance silica fiber link with double-pass gas sensor head has been employed in conjunction with a wavelength-tunable InGaAsP DFB laser diode at 1.64 mum (at R(6)line of the 2nu3 absorption band of methane) to realize highly sensitive remote interrogation of CH 4. By wavelength modulation with the DFB laser diode together with a self-designed processing circuit and data processing software, sensitivities of less than 0.1% (volume) and response time of less than 6 sec. have been achieved. Extensive tests have been carried out, and comparisons made with existing conventional CH4 gas detection systems, it is shown, that the performance of the optical fiber sensor system is generally better and is completely qualified for application in the coal mine safety monitoring.

Li, Sanguo

77

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

Code of Federal Regulations, 2010 CFR

...equipment. (a) The continuous gas detection system required under...volume; and (ii) Closes the master gas fuel valve required under § 154...b) The number and arrangement of gas sampling points must be specially...

2010-10-01

78

Method of detecting a fault of an exhaust gas recirculation system  

Microsoft Academic Search

This patent describes a method of detecting a fault of an exhaust gas recirculation system of an internal combustion engine, wherein a temperature relating to a temperature of the exhaust gas recirculating through the exhaust gas recirculation system is detected when the exhaust gas recirculation system is in a condition in which the system should be operated to return part

T. Hashimoto; A. Takahashi; T. Imaizuma; S. Saito; H. Tanaka; T Jimbo

1989-01-01

79

ACOUSTIC DETECTING AND LOCATING GAS PIPE LINE INFRINGEMENT  

SciTech Connect

The West Virginia University natural gas transmission line leak detection research is only considering using readily available 1/2 inch pipeline access ports for the detection of leak generated signals. The main problem with leak signals is the low signal to noise ratio. One of the acoustic signals associated with gas escaping through a leak is only temporary and is in the form of a rarefaction wave originating when the leak is formed. Due to pipeline friction, over distance such a step function transitions to a ramp function. The ability to identify a leak by pipeline monitoring and signal processing depends a great deal on the quality and signal to noise ratio of the characteristics of the detectors used. Combinations of sensing devices are being used for the WVU sensor package and are contained in a removable sensor housing. The four sensors currently installed are a 1/2 inch 3 Hz-40 Khz microphone, an audible range moving coil sensor, a piezo-electric pressure transducer, and the WVU designed floating 3 inch diameter diaphragm to detect flow transient induced pressure ramp type signals. The WVU diaphragm sensor, which is currently under development, uses the same diaphragm principle as a high quality capacitance type microphone, but utilizes aerodynamic signal amplification. This type of amplification only amplifies the ramp-signal itself, not the random pipeline noise.

John L Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Deepak Mehra

2003-04-01

80

Exposure to Pesticides at Sublethal Level and Their Distribution Within a Honey Bee ( Apis mellifera ) Colony  

Microsoft Academic Search

Honey bee colonies were exposed to pesticides used in agriculture or within bee hives by beekeepers: coumaphos; diazinon;\\u000a amitraz or fluvalinate. Samples of bee workers, larvae and royal jelly were analysed using Gas Chromatography-Electron Capture\\u000a Detection (GC-ECD). Amitraz was quantified using High Performance Liquid Chromatography (HPLC), and Gas Chromatography-Tandem\\u000a Mass Spectrometry (GC\\/MS\\/MS) was used for quantification of diazinon. Sixth day

Maja Ivana Smodiš Škerl; Veronika Kmecl; Aleš Gregorc

2010-01-01

81

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

NASA Technical Reports Server (NTRS)

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.

O'Hara, Dean; Singh, Hanwant B.

1988-01-01

82

Naturally fractured tight gas reservoir detection optimization. Final report  

SciTech Connect

This DOE-funded research into seismic detection of natural fractures is one of six projects within the DOE`s Detection and Analysis of Naturally Fractured Gas Reservoirs Program, a multidisciplinary research initiative to develop technology for prediction, detection, and mapping of naturally fractured gas reservoirs. The demonstration of successful seismic techniques to locate subsurface zones of high fracture density and to guide drilling orientation for enhanced fracture permeability will enable better returns on investments in the development of the vast gas reserves held in tight formations beneath the Rocky Mountains. The seismic techniques used in this project were designed to capture the azimuthal anisotropy within the seismic response. This seismic anisotropy is the result of the symmetry in the rock fabric created by aligned fractures and/or unequal horizontal stresses. These results may be compared and related to other lines of evidence to provide cross-validation. The authors undertook investigations along the following lines: Characterization of the seismic anisotropy in three-dimensional, P-wave seismic data; Characterization of the seismic anisotropy in a nine-component (P- and S-sources, three-component receivers) vertical seismic profile; Characterization of the seismic anisotropy in three-dimensional, P-to-S converted wave seismic data (P-wave source, three-component receivers); and Description of geological and reservoir-engineering data that corroborate the anisotropy: natural fractures observed at the target level and at the surface, estimation of the maximum horizontal stress in situ, and examination of the flow characteristics of the reservoir.

NONE

1997-11-19

83

A novel microelectronic gas sensor utilizing carbon nanotubes for hydrogen gas detection  

Microsoft Academic Search

A novel microelectronic gas sensor utilizing carbon nanotubes (CNTs) in a thin-layered Pd\\/CNTs\\/n+-Si structure for hydrogen detection has been achieved. The sensor is fabricated on an n-type silicon wafer, which is needed as an ohmic supporting substrate. Multiwalled CNTs were grown selectively on the substrate via catalytic activation with microwave plasma enhanced chemical vapor deposition. The I–V characteristics of the

Y. M. Wong; W. P. Kang; J. L. Davidson; A. Wisitsora-at; K. L. Soh

2003-01-01

84

Trace gas detection and monitoring with the Digital Array Gas-correlation Radiometer (DAGR)  

NASA Astrophysics Data System (ADS)

We present the first results from a Digital Array Gas-correlation Radiometer (DAGR) prototype sensor, and discuss applications in remote sensing of trace gases. The sensor concept is based on traditional and reliable Gas Filter Correlation Radiometry (GFCR), but overcomes the limitations in solar backscatter applications. The DAGR sensor design can be scaled to the size of a digital camera and is ideal for downlooking detection of gases in the boundary layer, where solar backscatter measurements are needed to overcome the lack of thermal contrast in the IR. Ground-based portable DAGR sensors can monitor carbon sequestration sites or industrial facilities. Aircraft or UAV deployment can quickly survey large areas and are particularly well suited for gas leak detection or carbon monitoring. From space-based platforms, Doppler modulation can be exploited to produce an extremely fine spectral resolution with effective resolving power exceeding 100,000. Such space-based DAGR observations could provide near-global sensing of climatically important species such as such as CO2, CO, CH4, O3 and N2O. Planetary science applications include detection and mapping of biomarkers in the Martian atmosphere.

Gordley, Larry L.; Hervig, Mark E.; Fish, Chad; McHugh, Martin J.

2011-05-01

85

Hydrocarbon gas detection with microelectromechanical Fabry-Perot interferometer  

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

86

Detection of gas hydrates by the measurement of instantaneous temperature  

E-print Network

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...

Dinakaran, Srikanth

2012-06-07

87

SELECTIVE FILTER FOR SnO2 BASED GAS SENSOR : APPLICATION TO HYDROGEN TRACE DETECTION  

E-print Network

1 SELECTIVE FILTER FOR SnO2 BASED GAS SENSOR : APPLICATION TO HYDROGEN TRACE DETECTION G dioxide, silicon oxide, filter, hydrogen, selectivity. #12;2 I INTRODUCTION Today hydrogen gas sensors safety problems due to the extremely explosive hydrogen gas. In other cases, hydrogen trace detection

Paris-Sud XI, Université de

88

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

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

89

Gas detection mechanism for single-walled carbon nanotube networks  

NASA Astrophysics Data System (ADS)

We study field-effect transistors fabricated with carbon nanotube (CNT) networks to determine whether the gas sensing mechanism is due to molecules adsorbed on the nanotubes, or changes at the interface between the nanotubes and the contacts. Our previous work showed that in devices made with isolated CNT, the response to nitrogen dioxide was mainly due to the contact interfaces [1]. Here, we focus on CNT networks and use SU-8 layers patterned with e-beam lithography to passivate the contact interfaces, while leaving the network exposed. We look to investigate possible differences in sensing mechanism for devices made with isolated tubes versus networks. [4pt] [1] J. Zhang, A. Boyd, A. Tselev, M. Paranjape, and P. Barbara, Mechanism of NO2 detection in carbon nanotube field effect transistor chemical sensors, Applied Physics Letters 88, 123112-123115 (2006)

Boyd, Anthony; Dube, Isha; Fedorov, Georgy; Paranjape, Makarand; Barbara, Paola

2011-03-01

90

Silicon Carbide-Based Hydrogen and Hydrocarbon Gas Detection  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

91

Conductive polymers as new media for solid-phase extraction: Isolation of chlorophenols from water sample  

Microsoft Academic Search

Three different conductive polymers, poly-N-methylaniline (PNMA), polyaniline and polydiphenylamine were synthesised and used as sorbents for the solid-phase extraction of some phenolic compounds from water. The separation and determination was, subsequently, performed by gas chromatography–electron-capture and flame ionization detection. Among these easy-made polymers, PNMA gave better recovery for the extraction of the studied analytes. The capability of the PNMA to

Habib Bagheri; Mohammad Saraji

2003-01-01

92

Digital array gas radiometer (DAGR): a sensitive and reliable trace gas detection concept  

NASA Astrophysics Data System (ADS)

The Digital Array Gas Radiometer (DAGR) concept is based on traditional and reliable Gas Filter Correlation Radiometry (GFCR) for remote trace gas detection and monitoring. GFCR sensors have been successful in many infrared remote sensing applications. Historically however, solar backscatter measurements have not been as successful because instrument designs have been susceptible to natural variations in surface albedo, which induce clutter and degrade the sensitivity. DAGR overcomes this limitation with several key innovations. First, a pupil imaging system scrambles the received light, removing nearly all spatial clutter and permitting a small calibration source to be easily inserted. Then, by using focal plane arrays rather than single detectors to collect the light, dramatic advances in dynamic range can be achieved. Finally, when used with the calibration source, data processing approaches can further mitigate detector non-uniformity effects. DAGR sensors can be made as small as digital cameras and are well suited for downlooking detection of gases in the boundary layer, where solar backscatter measurements are needed to overcome the lack of thermal contrast in the IR. Easily integrated into a satellite platform, a space-based DAGR would provide near-global sensing of climatically important species such as such as CO, CH4, and N2O. Aircraft and UAV measurements with a DAGR could be used to monitor agricultural and industrial emissions. Ground-based or portable DAGRs could augment early warning systems for chemical weapons or toxic materials. Finally, planetary science applications include detection and mapping of biomarkers such as CH4 in the Martian atmosphere.

Gordley, Larry L.; McHugh, Martin J.; Marshall, B. T.; Thompson, Earl

2009-05-01

93

On-Column Micro Gas Chromatography Detection with Capillary-Based Optical Ring Resonators  

E-print Network

On-Column Micro Gas Chromatography Detection with Capillary-Based Optical Ring Resonators Siyka I their utility. In contrast, in gas chromatography (GC), gaseous samples are separated based on their interaction

Fan, Xudong "Sherman"

94

a Mini Multi-Gas Detection System Based on Infrared Principle  

NASA Astrophysics Data System (ADS)

To counter the problems of gas accidents in coal mines, family safety resulted from using gas, a new infrared detection system with integration and miniaturization has been developed. The infrared detection optics principle used in developing this system is mainly analyzed. The idea that multi gas detection is introduced and guided through analyzing single gas detection is got across. Through researching the design of cell structure, the cell with integration and miniaturization has been devised. The way of data transmission on Controller Area Network (CAN) bus is explained. By taking Single-Chip Microcomputer (SCM) as intelligence handling, the functional block diagram of gas detection system is designed with its hardware and software system analyzed and devised. This system designed has reached the technology requirement of lower power consumption, mini-volume, big measure range, and able to realize multi-gas detection.

Zhijian, Xie; Qiulin, Tan

2006-12-01

95

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

E-print Network

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

Shaw, Joseph A.

96

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

97

Exhaust gas recirculation control system having a function of automatically correcting detected zero opening value of exhaust gas recirculation valve  

Microsoft Academic Search

An exhaust gas recirculation control system is disclosed which is adapted to control the valve opening of the exhaust gas recirculation valve so as to minimize the difference between a detected value of the valve opening of the above valve and a command value read from a memory as a function of operating condition of the engine. The system includes

S. Hasegawa; Y. Otobe; A. Yamato

1983-01-01

98

Gas Chromatographic – Mass Spectrometric Cardiotonic Glycosides Detection in Equine Urine Doping Analysis  

Microsoft Academic Search

A screening method for the detection of cardiotonic glycosides in horse’s urine is presented in this paper. This method is based on the detection by gas chromatography -mass spectrometry (GC -MS) and gas chromatography -high resolution mass spectrometry (GC -HRMS) of the trimethylsilyl (TMS) derivatives of the aglycon moieties of these compounds after solid phase extraction and methanolysis, according to

P. Kiousi; Y. S. Angelis; M. Koupparis; D. Kouretas; N. Diakakis; A. Desiris; C. G. Georgakopoulos

2004-01-01

99

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

SciTech Connect

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.

NONE

1997-12-31

100

Evaluation of Gas Chromatography/Mini-IMS to Detect VOCs  

NASA Technical Reports Server (NTRS)

The Toxicology Laboratory at Johnson Space Center (JSC) has pioneered the use of gas chromatography-ion mobility spectrometry (GC/IMS) for measuring target volatile organic compounds (VOCs) aboard spacecraft. Graseby Dynamics, under contract to NASA/Wyle, has built several volatile organic analyzers (VOA) based on GC/IMS. Foremost among these have been the volatile organic analyzer-risk mitigation unit and the two flight VOA units for International Space Station (ISS). The development and evaluation of these instruments has been chronicled through presentations at the International Conference on Ion Mobility Spectrometry over the past three years. As the flight VOA from Graseby is prepared for operation on ISS at JSC, it is time to begin evaluations of technologies for the next generation VOA, Although the desired instrument characteristics for the next generation unit are the same as the current unit, the requirements are much more stringent. As NASA looks toward future missions beyond Earth environs, a premium will be placed upon small, light, reliable, autonomous hardware. It is with these visions in mind that the JSC Toxicology Laboratory began a search for the next generation VOA. One technology that is a candidate for the next generation VOA is GC/IMS. The recent miniaturization of IMS technology permits it to compete with other, inherently small, technologies such as chip-sized sensor arrays. This paper will discuss the lessons learned from the VOA experience and how that has shaped the design of a potential second generation VOA based upon GC/IMS technology. Data will be presented from preliminary evaluations of GC technology and the mini-IMS when exposed to VOCs likely to be detected aboard spacecraft. Results from the evaluation of an integrated GC/mini-IMS system will be shown if available.

Limero, Thomas; Reese, Eric; Peters, Randy; James, John T.; Billica, Roger (Technical Monitor)

1999-01-01

101

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

NASA Astrophysics Data System (ADS)

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.

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

102

3 dimensionally combined pyrolyzed polymer sensor and heater toward all polymeric gas detection system  

Microsoft Academic Search

This paper proposes for the first time all polymeric gas detection system consisting of the 3 dimensionally combined carbon structures and the gas regulator with the three-stage pneumatic valves. The pyrolyzed photo-resist structure as an absorbent of nitrogen dioxide sensor and 3D bridge-type resistive heater are fabricated and assembled with the gas regulator. The valve efficiency of the gas regulator

Ok Chan Jeong; Satoshi Konishi

2007-01-01

103

SOIL-GAS MEASUREMENT FOR DETECTION OF SUBSURFACE ORGANIC CONTAMINATION  

EPA Science Inventory

The Lockheed Gas Analysis System (LGAS) grab-sampling method and the PETREX Static Surface Trapping Pyrolysis/Mass Spectrometry (SST-Py/MS) passive sampling technique for soil-gas measurement have been field tested at the Pittman Lateral near Henderson, Nevada. This site has unco...

104

Slow neutron detection without 3He: far ultraviolet noble-gas-excimer radiation  

E-print Network

Slow neutron detection without 3He: far ultraviolet noble-gas-excimer radiation induced by neutron (NIST) 3 Nuclear Engineering Program, UMD 4 Joint Quantum Institute, NIST and UMD Slow neutron detection. 3 He, 6 Li or 10 B initiator Slow neutron detection without 3He Eighth Ultracold Neutron Workshop

Titov, Anatoly

105

Single-Walled Carbon Nanotube Thin-Film Sensor for Ultrasensitive Gas Detection  

NASA Astrophysics Data System (ADS)

We demonstrated a gas sensor fabricated by growing a single-walled carbon nanotube (SWNT) thin film directly on a conventional sensor substrate. NO2 and Cl2 were detected down to the ppb level under room-temperature operation with a fast response. Using an electrical breakdown technique, gas response sensitivity was improved by an order of magnitude. The relationship between gas concentration and sensor response was derived based on the Langmuir adsorption isotherm, predicting a detection limit of 8 ppb for NO2. The SWNT thin-film gas sensor exhibits merits over other types of sensors by virtue of its simplicity in fabrication and feasible application.

Wongwiriyapan, Winadda; Honda, Shin-ichi; Konishi, Hirofumi; Mizuta, Tomoaki; Ikuno, Takashi; Ito, Tatsuya; Maekawa, Toru; Suzuki, Kengo; Ishikawa, Hiroshi; Oura, Kenjiro; Katayama, Mitsuhiro

2005-04-01

106

Gas phase chemical detection with an integrated chemical analysis system  

SciTech Connect

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.

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

107

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

PubMed

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

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

2012-03-01

108

Improved low concentration gas detection system based on intracavity fiber laser.  

PubMed

The improvement of a low concentration gas detection system based on the intracavity fiber laser is proposed in this paper. The sensitivity of the system is deduced based on Lambert-Beer law. The optimized system was established with the gas cell made elaborately. In order to apply the wavelength sweeping technique, the fiber Bragg grating reflector was substituted by the wavelength independent Faraday rotation reflector. The sensitivity of the system for acetylene detection is reduced to less than 100 ppm by using the average of three absorption spectra. The acetylene detection coefficients of variation with different concentrations are measured. The gas measurement system is validated to detect low concentration gas effectively. PMID:21361570

Zhang, Hongxia; Liu, Kun; Jia, Dagong; Xu, Tianhua; Liu, Tiegen; Peng, Gangding; Jing, Wencai; Zhang, Yimo

2011-02-01

109

Multi-species trace gas detection by rapidly swept cavity ringdown spectroscopy  

Microsoft Academic Search

A cavity ringdown spectrometer, based on a rapidly swept optical cavity and multiple-wavelength coherent radiation, detects several gas-phase molecules simultaneously. This comprises a compact, high-performance instrument for efficient spectroscopic sensing of gases.

Yabai He; Florian V. Englich; Brian J. Orr

2007-01-01

110

ACOUSTIC DETECTING AND LOCATING GAS PIPE LINE INFRINGEMENT  

SciTech Connect

The power point presentation for the Natural Gas Technologies II Conference held on February 8-11, 2004 in Phoenix AZ, published the presentations made at the conference, therefore required all presenters to submit their presentation prior to November 2003. However in the remainder of year, significant new test data became available which were incorporated in the actual presentation made at the Natural Gas Technologies II Conference. The 6th progress report presents the updated actual slide show used during the paper presentation by Richard Guiler.

John L. LOTH; GARY J. MORRIS; GEORGE M. PALMER; RICHARD GUILER

2004-01-05

111

Gas Phase Chemical Detection with an Integrated Chemical Analysis System  

SciTech Connect

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.

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

112

Single-Walled Carbon Nanotube Thin-Film Sensor for Ultrasensitive Gas Detection  

Microsoft Academic Search

We demonstrated a gas sensor fabricated by growing a single-walled carbon nanotube (SWNT) thin film directly on a conventional sensor substrate. NO2 and Cl2 were detected down to the ppb level under room-temperature operation with a fast response. Using an electrical breakdown technique, gas response sensitivity was improved by an order of magnitude. The relationship between gas concentration and sensor

Winadda Wongwiriyapan; Shin-ichi Honda; Hirofumi Konishi; Tomoaki Mizuta; Takashi Ikuno; Tatsuya Ito; Toru Maekawa; Kengo Suzuki; Hiroshi Ishikawa; Kenjiro Oura; Mitsuhiro Katayama

2005-01-01

113

Design and implementation of a reliable gas leak detection system for domestic environments  

Microsoft Academic Search

Gas leaks represent the cause of many accidents both in the industry sector and domestic environments. Due to the deployment of complex supervisory control and data acquisition (SCADA) systems, accident rates have decreased in the industry sector but they are still high in domestic environments. Here, we propose a gas leak detection system based on redundant sensing units and investigate

Pal-Stefan Murvay; Ioan Silea

2011-01-01

114

Low-cost multispectral vegetation imaging system for detecting leaking CO2 gas  

E-print Network

Low-cost multispectral vegetation imaging system for detecting leaking CO2 gas Justin A. Hogan,1 sequestration sites for possible leaks of the CO2 gas from underground reservoirs, a low-cost multispectral are then flagged for closer inspection with in-situ CO2 sensors. The system is entirely self

Shaw, Joseph A.

115

Characterization of a purely thermal wave based photopyroelectric gas sensor for hydrogen detection  

E-print Network

Characterization of a purely thermal wave based photopyroelectric gas sensor for hydrogen detection and Optoelectronic Diagnostics Laboratory, Department of Mechanical Engineering and Center for Hydrogen; accepted for publication 16 March 1994) A study towards the characterization of a new photopyroelectric gas

Mandelis, Andreas

116

Surface Coatings for Gas Detection via Porous Silicon  

NASA Astrophysics Data System (ADS)

Nanopore covered microporous silicon interfaces have been formed via an electrochemical etch for gas sensor applications. Rapid reversible and sensitive gas sensors have been fabricated. The fabricated porous silicon (PS) gas sensors display the advantages of operation at room temperature as well as at a single, readily accessible temperature with an insensitivity to temperature drift; operation in a heat-sunk configuration, ease of coating with gas-selective materials; low cost of fabrication and operation, and the ability to rapidly assess false positives by operating the sensor in a pulsed mode. The PS surface has been modified with unique coatings on the basis of a general theory in order to achieve maximum sensitivity and selectivity. Sensing of NH3, NOx and PH3 at or below the ppm level have been observed. A typical PS nanostructure coated microstructured hybrid configuration when coated with tin oxide (NOx, CO) and gold nanostructures (NH3) provides a greatly increased sensitivity to the indicated gases. Al2O3 coating of the porous silicon using atomic layer deposition and its effect on PH3 sensing has been investigated. 20-100 nm TiO2 nanoparticles have been produced using sol-gel methods to coat PS surfaces and the effects on the selectivity and the sensitivity have been studied.

Ozdemir, Serdar; Li, Ji-Guang; Gole, James

2009-03-01

117

LOW COST IMAGER FOR POLLUTANT GAS LEAK DETECTION - PHASE II  

EPA Science Inventory

An inexpensive imaging Instrument to quickly locate leaks of methane and other greenhouse and VOC gases would reduce the cost and effort expended by industry to comply with EPA regulations. In Phase I, of this WBIR program, a new gas leak visualization camera was demonstrated...

118

Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection  

PubMed Central

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

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

2009-01-01

119

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

SciTech Connect

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.

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

1995-08-01

120

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

NASA Astrophysics Data System (ADS)

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.

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

121

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

PubMed

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

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

2007-01-01

122

[Gas pipeline leak detection based on tunable diode laser absorption spectroscopy].  

PubMed

The principle of tunable diode laser absorption spectroscopy and harmonic detection technique was introduced. An experimental device was developed by point sampling through small multi-reflection gas cell. A specific line near 1 653. 7 nm was targeted for methane measurement using a distributed feedback diode laser as tunable light source. The linearity between the intensity of second harmonic signal and the concentration of methane was determined. The background content of methane in air was measured. The results show that gas sensors using tunable diode lasers provide a high sensitivity and high selectivity method for city gas pipeline leak detection. PMID:19839297

Zhang, Qi-Xing; Wang, Jin-Jun; Liu, Bing-Hai; Cai, Ting-Li; Qiao, Li-Feng; Zhang, Yong-Ming

2009-08-01

123

Detection of metabolically produced labeled gas - The Viking Mars Lander.  

NASA Technical Reports Server (NTRS)

A qualitative, nonspecific method will test for life on Mars in 1976 by supplying radioactive substrates to samples of the planetary surface material. If microorganisms are present, they may assimilate one or more of the simple labeled compounds and produce radioactive gas. The compounds have been selected on the basis of biological theory and terrestrial results. The measurement of radioactive gas evolved as a function of time constitutes evidence for life. A control performed on a duplicate, but heat sterilized, sample will confirm the biological nature of the results. The shape of the response curve obtained from the viable sample may provide information on the physiological state and generation period of the organisms. Data obtained from a wide variety of terrestrial soils demonstrate a rapid response and high sensitivity for the experiment. Its ability to make comparative studies of soil microorganisms is also demonstrated.

Levin, G. V.

1972-01-01

124

Gas detection by structural variations of fluorescent guest molecules in a flexible porous coordination polymer  

Microsoft Academic Search

The development of a new methodology for visualizing and detecting gases is imperative for various applications. Here, we report a novel strategy in which gas molecules are detected by signals from a reporter guest that can read out a host structural transformation. A composite between a flexible porous coordination polymer and fluorescent reporter distyrylbenzene (DSB) selectively adsorbed CO2 over other

Nobuhiro Yanai; Koji Kitayama; Yuh Hijikata; Hiroshi Sato; Ryotaro Matsuda; Yoshiki Kubota; Masaki Takata; Motohiro Mizuno; Takashi Uemura; Susumu Kitagawa

2011-01-01

125

Multiwavelength and triple CO2 lidars for trace gas detection  

NASA Astrophysics Data System (ADS)

SRI International has developed two infrared differential absorption lidar (IR DIAL) systems to detect infrared-absorbing trace gases and environmental monitoring applications. The multiwavelength DIAL system operates at 10.6 microns and performs both path-integrated (column-content) and range-resolved measurements. The multiwavelength DIAL system has demonstrated path-integrated measurements to a range of 9 km and range-resolved measurements to 4 km. The triple CO2 DIAL system operates at 3.4 microns and utilizes three mini-TEA CO2 lasers and nonlinear crystals in a novel frequency-mixing technique to detect and discriminate selective hydrocarbons.

Leonelli, Joseph; Holland, Peter L.; van der Laan, Jan E.

1989-01-01

126

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

DOEpatents

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.

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

2011-01-04

127

On-chip gas detection in silicon optical microcavities  

E-print Network

.6010) Sensors. References and links 1. W. Yang, D. B. Conkey, B. Wu, D. Yin, A. R. Hawkins, and H. Schmidt nanoparticle detection," App. Phys. Lett. 85, 4854 (2004). 5. A. M. Armani, R. P. Kulkarni, S. E. Fraser, R. C. Hendrickson, G. Khitrova, H. M. Gibbs, G. Rupper, C. Ell, O. B. Shchekin, and D. G. Deppe, "Vacuum rabi

Lipson, Michal

128

Study of gas detection based on integrated cavity output spectroscopy  

NASA Astrophysics Data System (ADS)

A trace gases detection system based on integrated cavity output spectroscopy (ICOS) was developed, where a NIR tunable diode laser (TDL) was used as light source, an optical cavity composed by two plan-concave mirrors with reflection near 99.7% was used as the absorption cell. Trace water vapour (H2O), carbon dioxide (CO2), methane (CH4), carbon monoxide (CO) and mixture of CO2 and CO were tested by ICOS based on the characteristics absorption. The wavelength calibration, cavity transmission characteristics, quantitative measurement ability and sensitivity of the TDL-ICOS were also studied, and a evaluated minimum detectable sensitivity of 1.15 × 10-7 cm-1 was obtained when the system was used to CH4 detection. The experiment results show that TDL-ICOS is expected to be a reliable and promising system for the detection of trace gases since it has some advantages such as real-time monitoring, simple device, easy operation, high sensitivity, good stability and quantitative ability.

Pei, Shixin; Cui, Fenping; Su, Jing; Xu, Linhua; Sun, Tingting

2013-08-01

129

Detection of Clostridium difficile from an enhancement broth by gas-liquid chromatography.  

PubMed

Gas-Liquid chromatography (GLC) was used to detect the presence of isocaproic acid produced by Clostridium difficile from 54 stool samples grown in cycloserine-cefoxitin broth. Isocaproic acid was detected in 12 samples of which 5 were confirmed to be Clostridium difficile by culture and biochemical tests. The detection of isocaproic acid by GLC together with the presence of presumptive colonies on primary selective culture media provides a more rapid laboratory diagnosis for Clostridium difficile. PMID:1795558

Hassan, H; Cheng, S C

1991-06-01

130

Plastic optical fiber sensor system for detecting multi-point gas leakages  

NASA Astrophysics Data System (ADS)

Combustible gases such as propane gas and methane gas are widely used in many homes and factories. However, accidents caused by gas leakage become a menace to everyday life. Therefore, development of quick and highly sensitive gas leakage sensor is required strongly. From these backgrounds, we have studied about plastic optical fiber (POF) gas leakage sensor because the POF have many advantages such as low-cost, light weight, immunity to electromagnetic noise. In this paper, the POF sensing system for multi-point gas leakages and its long term stability have been studied. In the experiment, gas concentration below 1% was detected for both propane gas and methane gas. This operation does not depend on a light wavelength. So, using several LED light sources with different wavelength, the POF sensing system for multi-point gas leakages was constructed. In the experiment using blue-, green- and red-LED, sensing of three-point gas leakages could successfully be obtained. Further more, considering its system for real application, long term stability of the sensor head was also checked and it was confirmed that the sensitivity does not change over 15 days.

Suzumori, Hirofumi; Honma, Satoshi; Morisawa, Masayuki; Muto, Shinzo

2008-03-01

131

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

USGS Publications Warehouse

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.

Barker, C.E.

2006-01-01

132

Fiber optic TDLAS-based multi-gas remote detection system for mine goaf fire  

NASA Astrophysics Data System (ADS)

Spontaneous combustion in coal goaf area is one of major disasters in coal mines. Detection technology based on signature Gas is the primary means of spontaneous combustion forecasting of coal goaf area. A real-time remote fire gas detection system is proposed based on tunable diode laser absorption spectroscopy technology, to achieve valid test of signature gas (CO, CO2, CH4, C2H2 and C2H4). The System uses the wavelength, respectively 1.567um, 1.608um, 1.653um, 1.530um, 1.623um near-infrared band fiber-coupled distributed feedback laser (DFB) as the light source, Combined wavelength modulation spectroscopy and harmonic detection technique, developed a fiber-coupled white-type long-path gas absorption cell, to achieve high sensitivity detection of gas concentration. The system achieved a remote on-line monitoring of multi-component gas concentration,to meet the fire forecast need for Coal goaf area. There are obvious advantages Compared with the existing beam tube monitoring system in coal mine.

Wei, Yubin; Li, Yanfang; Shang, Ying; Zhang, Tingting; Song, Zhiqiang; Wang, Chang; Liu, Tongyu

2010-10-01

133

[Study on high accuracy detection of multi-component gas in oil-immerse power transformer].  

PubMed

In order to solve the problem of low accuracy and mutual interference in multi-component gas detection, a kind of multi-component gas detection network with high accuracy was designed. A semiconductor laser with narrow bandwidth was utilized as light source and a novel long-path gas cell was also used in this system. By taking the single sine signal to modulate the spectrum of laser and using space division multiplexing (SDM) and time division multiplexing (TDM) technique, the detection of multi-component gas was achieved. The experiments indicate that the linearity relevance coefficient is 0. 99 and the measurement relative error is less than 4%. The system dynamic response time is less than 15 s, by filling a volume of multi-component gas into the gas cell gradually. The system has advantages of high accuracy and quick response, which can be used in the fault gas on-line monitoring for power transformers in real time. PMID:24611396

Fan, Jie; Chen, Xiao; Huang, Qi-Feng; Zhou, Yu; Chen, Gang

2013-12-01

134

Metal-oxide Nanowires for Toxic Gas Detection  

SciTech Connect

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.

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

2007-01-02

135

Chemoresistive Gas Sensors for the Detection of Colorectal Cancer Biomarkers  

PubMed Central

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

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

2014-01-01

136

Compact Resonance ?-Shaped Photoacoustic Cell for Gas Detection  

NASA Astrophysics Data System (ADS)

A compact resonance photoacoustic cell with a ?-shaped internal cavity and a volume of ~0.2 cm3 is developed. The design of the cell and an experimental setup for testing its operational capabilities are described. Results are presented from tests of the photoacoustic cell in experiments to detect light absorption by ammonia in nitrogen flows using a single-mode diode laser with a wavelength of ~1.53 ?m. The amplitude-frequency characteristics of the photoacoustic absorption response with and without ammonia are analyzed. The operation of the cell under conditions of resonance with the second longitudinal acoustic mode of the inner cavity of the cell (resonant frequency 4.38 kHz, Q-factor 13.9) is analyzed. The measured background signal level from the cell windows corresponds to an absorption coefficient of ~2.8·10-7 cm-1. The microphone-noise limited minimum detectable absorption is ~1.44·10-9 cm-1·W·Hz1/2.

Ulasevich, A. L.; Gorelik, A. V.; Kouzmouk, A. A.; Starovoitov, V. S.

2014-07-01

137

Electrochemical noise sensors for detection of localized and general corrosion of natural gas transmission pipelines  

SciTech Connect

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.

Holcomb, Gordon R.; Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Russell, James H.; Ziomek-Moroz, Margaret

2002-09-01

138

Nanostructure Engineered Chemical Sensors for Hazardous Gas and Vapor Detection  

NASA Technical Reports Server (NTRS)

A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs) and metal oxides nanowires or nanobelts, on a pair of interdigitated electrodes (IDE) processed with a silicon based microfabrication and micromachining technique. The IDE fingers were fabricated using thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to hazardous gases and vapors, such as acetone, benzene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing in our sensor platform can be understood by electron modulation between the nanostructure engineered device and gas molecules. As a result of the electron modulation, the conductance of nanodevice will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost.

Li, Jing; Lu, Yijiang

2005-01-01

139

Active acoustic detection of subsea oil and gas leaks; model prediction and measurements.  

PubMed

There is a need in the oil and gas industry for technology for real time monitoring of subsea structures. National research strategies emphasize the need to develop innovative solutions to detect, contain, and clean up spills. The technology should ideally cover a large area and be able to detect leaks up to 500 m from the sensor. As part of a project where a leak detection technology based on active acoustics is developed, effective medium models have been used to predict the acoustic signal from small oil and gas leaks. Model results were compared with multifrequency data from controlled in situ measurements of oil and gas releases, collected with scientific echosounders. The measurements also include stereo camera images for bubble/droplet and plume size estimation. The models generally predict the measurements within 3 dB, when taking into account the variability in plume dimensions and bubble sizes the difference is smaller. PMID:25235639

Pedersen, Geir; Hauge, Rune; Kubilius, Rokas

2014-04-01

140

Gas sensor arrays for early detection of infection in mammalian cell culture.  

PubMed

The detection of bacterial infections in a mammalian cell culture process is realised using a gas sensor array. In production-scale and laboratory-scale cultivations of a perfused recombinant CHO-cell culture producing human blood coagulation Factor VIII, we show that the gas sensor array identifies bacterial contamination earlier than conventional methods. The sensitivity of the instrument is verified by inoculation of a blank cell culture medium with defined bacterial cell counts. PMID:11888730

Bachinger, Thomas; Riese, Ulrich; Eriksson, Rolf K; Mandenius, Carl Fredrik

2002-05-01

141

Naturally fractured tight gas reservoir detection optimization. Quarterly report, July 1, 1996--September 30, 1996  

SciTech Connect

This document contains the status report for the Naturally Fractured Tight Gas-Gas Reservoir Detection Optimization project for the contract period July 1 to September 30, 1996. Data from seismic surveys are analyzed for structural imaging of reflector units as part of a 3-D basin modeling effort. The main activities of this quarter were 3-D, 3-C processing, correlation matrix, and paraxial ray-tracing modeling.

NONE

1998-12-31

142

TREFEX: Trend Estimation and Change Detection in the Response of MOX Gas Sensors  

PubMed Central

Many applications of metal oxide gas sensors can benefit from reliable algorithms to detect significant changes in the sensor response. Significant changes indicate a change in the emission modality of a distant gas source and occur due to a sudden change of concentration or exposure to a different compound. As a consequence of turbulent gas transport and the relatively slow response and recovery times of metal oxide sensors, their response in open sampling configuration exhibits strong fluctuations that interfere with the changes of interest. In this paper we introduce TREFEX, a novel change point detection algorithm, especially designed for metal oxide gas sensors in an open sampling system. TREFEX models the response of MOX sensors as a piecewise exponential signal and considers the junctions between consecutive exponentials as change points. We formulate non-linear trend filtering and change point detection as a parameter-free convex optimization problem for single sensors and sensor arrays. We evaluate the performance of the TREFEX algorithm experimentally for different metal oxide sensors and several gas emission profiles. A comparison with the previously proposed GLR method shows a clearly superior performance of the TREFEX algorithm both in detection performance and in estimating the change time. PMID:23736853

Pashami, Sepideh; Lilienthal, Achim J.; Schaffernicht, Erik; Trincavelli, Marco

2013-01-01

143

IV-VI semiconductor lasers for gas phase biomarker detection  

NASA Astrophysics Data System (ADS)

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.

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

2007-09-01

144

Sensor Array Devices Utilizing Nano-structured Metal-oxides for Hazardous Gas Detection  

NASA Astrophysics Data System (ADS)

Methane and carbon monoxide are two hazardous gases which require continuous monitoring by gas sensors in underground coal mines for explosion prevention and toxicity, respectively. This work explored implementing miniaturized gas sensors in this area to simultaneously detect both gases for benefits of increased portability and reduced power consumption of the chemiresistive gas sensor device. The focus of this research was to understand how the particle size, morphology, and microstructure of the metaloxide film affected the gas sensor performance to the two gases of interest on miniaturized gas sensor devices in the form of microhotplate platforms. This was done through three main research studies. The first was conducted by growing SnO2 nanowires from SnO 2 particles using an Au-catalyst. Growth conditions including temperature, time, and oxygen partial pressure were explored to determine the formation aspects of the SnO2 nanowires. Gas sensor studies were completed that provided evidence that the SnO2 nanowires increased detection to a fixed concentration of carbon monoxide compared to SnO2 particles without nano-structure formation. A second research study was performed to compare the gas sensor performance of SnO2 nanoparticles, hierarchical particles, and micron-size particles. The nanoparticles were developed into an ink and deposited via ink-jet printing on the microhotplate substrates to control the microstructure of the metal-oxide film. By preventing agglomeration of the nanoparticle film, the SnO2 nanoparticles displayed similar gas sensor performance to methane and carbon monoxide as the hierarchical particles. Both nano-structures had much higher gas sensor response than the micron-size particles which confirms the surface area of the metal-oxide film is critical for reaction of the analyte gas at the surface. The last research study presented in the dissertation describes an oxide nanoparticle array developed for detecting methane and carbon monoxide in the presence of one another. A design of experiments was constructed and principal component analysis was used for determining the optimum temperatures of the metal-oxide elements. A four element array was developed with the SnO 2 and TiO2 sensor elements able to detect methane concentrations of interest and the ZnO and NiO sensor elements able to detect the carbon monoxide concentrations. A linear based prediction model was developed and tested for accuracy and reproducibility of the model to a series of random gas concentrations.

Andio, Mark A.

145

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

146

A Micro Gas Sensor Using TiO2 Nanotubes to Detect Volatile Organic Compounds  

NASA Astrophysics Data System (ADS)

To develop a portable gas sensor with low power consumption, we deposited a micro size sensing film (100×100 µm2) on a Si substrate with an integrated micro heater and electrodes constructed using micro-electro-mechanical system (MEMS) technology. TiO2 nanotubes ca. 500 nm long with a 50 nm diameter were used to sense and detect volatile organic compounds (VOCs). We demonstrate that the MEMS sensor responded well to ethanol and toluene in air at elevated temperatures, such as 500 °C, which suggests that it is a promising battery-operable micro gas sensor for detecting VOCs.

Kida, Tetsuya; Seo, Min-Hyun; Suematsu, Koichi; Yuasa, Masayoshi; Kanmura, Yuichi; Shimanoe, Kengo

2013-04-01

147

Detection of dideuterium in diprotium gas at infinitesimal concentration using a trace reduction detector.  

PubMed

An analyzer able to detect extremely small concentrations of dideuterium in diprotium gas was developed. To examine its performance, four gas samples of pure diprotium with dideuterium concentrations of 0.25, 0.5, 1, and 5 cm(3)/m(3) were measured using the analyzer, and peak areas and retention times from 18 chromatograms were determined. Results indicated that the peaks were distributed within a relative standard deviation of approximately 15% and a linear correlation existed between peak area and concentration. Retention times were stable, showing a relative standard deviation of 1% with repeated tests and having no correlation with concentration of the four gas samples. PMID:17521662

Kawano, Takao; Tsuboi, Naohiro; Tsujii, Hirotsugu; Uda, Tatsuhiko

2007-07-20

148

Naturally fractured tight gas reservoir detection optimization. Quaterly report, October 1, 1996--December 31, 1996  

SciTech Connect

This document contains the status report for the Naturally Fractured Tight Gas-Gas Reservoir Detection Optimization project for the contract period October 1 to December 31, 1996. Data from seismic surveys are analyzed for structural imaging of reflector units as part of a 3-D basin modeling effort. The goal of this task is to assess the effects of structural complexity and regional anisotropy on a seismic attribute taken to indicate local fracturing and/or gas concentrations. The main activities of this quarter included basin modeling, 3-D, 3-C processing, correlation matrix, dipole sonic logging, and technology transfer.

NONE

1998-12-31

149

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

PubMed

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

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

2014-04-01

150

40 CFR 141.131 - Analytical requirements.  

...Protection of Environment 23 2014-07-01 2014-07-01 false Analytical...Drinking Water by Liquid-liquid Microextraction, Derivatization, and Gas Chromatography...electron capture detector; SPE = solid phase extraction; IC = ion...

2014-07-01

151

EXTENDED PERFORMANCE HANDHELD AND MOBILE SENSORS FOR REMOTE DETECTION OF NATURAL GAS LEAKS  

SciTech Connect

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 Remote Methane Leak Detector or RMLD. A laser beam which interrogates the air for methane is projected from a spinning turret mounted upon a van. As the van travels forward, the laser beam scans an arc to the front and sides of the van so as to survey across streets and to building walls from a moving vehicle. When excess methane is detected within the arc, an alarm is activated. In this project, we built and tested a prototype Mobile RMLD (MRMLD) intended to provide lateral coverage of 10 m and one lateral scan for every meter of forward motion at forward speeds up to 10 m/s. Using advanced detection algorithms developed as part of this project, the early prototype MRMLD, installed on the back of a truck, readily detected simulated gas leaks of 50 liters per hour. As a supplement to the originally planned project, PSI also participated in a DoE demonstration of several gas leak detection systems at the Rocky Mountain Oilfield Testing Center (RMOTC) during September 2004. Using a handheld RMLD upgraded with the advanced detection algorithms developed in this project, from within a moving vehicle we readily detected leaks created along the 7.4 mile route of a virtual gas transmission pipeline.

Michael B. Frish; B. David Green; Richard T. Wainner; Francesca Scire-Scappuzzo; Paul Cataldi; Matthew C. Laderer

2005-05-01

152

Thin-film-bulk-acoustic-resonator gas sensor for the detection of organophosphate vapor detection  

Microsoft Academic Search

A novel design of an organophosphate vapor sensor based on a thin film bulk acoustic resonator (TFBAR) is presented. The TFBAR device is consisted of an AlN piezoelectric stack and a Mo\\/AlN Bragg reflector. Poly (vinylidene fluoride) (PVDF) is coated on the surface of the piezoelectric stack as the special sensitive layer. The concentration of the target gas can be

Jing-jing Wang; Da Chen; Lu-yin Zhang; Yan Xu

2011-01-01

153

Detection of chlorinated pesticides on the surface of fungus using ToF-SIMS  

NASA Astrophysics Data System (ADS)

Chlorinated organic compounds are commonly used as pesticides (e.g. Lindane or DDT); unfortunately these compounds have the ability to be concentrated in aquatic and terrestrial food chains causing environmental problems due to their toxicity. Therefore there is a need for their removal using wastewater treatment plants. It is known that these pollutants adsorb on to the surface of the fungi Rhizopus arrizus from a water solution. However the actual mode of biosorption is unknown. We aim to investigate this interaction further using time-of-flight (ToF)-SIMS. Samples of fungus were grown in aqueous solutions containing Lindane then freeze-dried, the presence of Lindane was independently quantified by a gas chromatography-electron capture detector technique. The samples were then subjected to ToF-SIMS analysis. Evidence for Lindane was seen on the surface of the fungus, however it became apparent that the Lindane was too volatile for such an analysis. This rapid deterioration of signal is preventing a more in depth study of the interaction between Lindane and R. arrhizus. However it is anticipated that by utilising a frozen-hydrated sample preparation technique, of a type currently being developed at UMIST, that these challenges would be overcome.

Cliff, B.; Weibel, D. E.; Lockyer, N. P.; Jungnickel, H.; Stephens, G.; Vickerman, J. C.

2003-01-01

154

Metal Oxide Nanowire and Thin-Film-Based Gas Sensors for Chemical Warfare Simulants Detection  

Microsoft Academic Search

This work concerns with metal oxide (MOX) gas sensors based on nanowires and thin films. We focus on chemical warfare agents (CWAs) detection to compare these materials from the functional point-of-view. We work with different chemicals including simulants for Sarin nerve agents, vescicant gases, cyanide agents, and analytes such as ethanol, acetone, ammonia, and carbon monoxide that can be produced

Andrea Ponzoni; Camilla Baratto; Sebastiano Bianchi; Elisabetta Comini; Matteo Ferroni; Matteo Pardo; Marco Vezzoli; Alberto Vomiero; Guido Faglia; Giorgio Sberveglieri

2008-01-01

155

Detection of Accelerants in Fire Debris using Headspace Solid Phase Microextraction-Capillary Gas Chromatography  

Microsoft Academic Search

The detection of fire accelerants such as gasoline and diesel using solid phase microextraction-capillary gas chromatography (SPME-GC) for the forensic analyses of fire debris has been carried out. A special glass apparatus was designed to hold the fire debris and to optimize the position of the SPME needle for the adsorption of analytes in the headspace. Using polydimethylsiloxane (PDMS) fibre

Umi K. Ahmad; Chin K. Voon

156

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

E-print Network

. Res. Lett., 33, L03304, doi:10.1029/2005GL024896. 1. Introduction [2] Natural gas hydrates hydrates; a bottom simulating reflector (BSR) sometimes marks the phase boundary of solid hydrate above of the hydrate stability field with the local geothermal gradient. While seismic methods are often able to detect

Key, Kerry

157

Hot gas in the nucleus of IC 342 - Detection of J = 3-2 CO emission  

Microsoft Academic Search

The J = 3-2 CO line is detected for the first time in an external galaxy, in the nearby spiral IC 342. It is shown that in contrast to the J = 1-0 CO line, which favors optically thick and cool gas, the J = 3-2 CO line can be used to study a hot component in extragalactic nuclear environment.

Paul T. P. Ho; Jean L. Turner; Robert N. Martin

1987-01-01

158

Development of high sensitivity tin oxide based sensors for gas\\/odour detection at room temperature  

Microsoft Academic Search

An effort has been made to develop thick film tin oxide gas sensors which could detect various gases\\/odours at room temperature. To achieve this, the fabricated sensors were annealed in oxygen plasma for various durations. It was then found that, the room temperature sensitivity of such sensors was increased to about ten times as compared to the sensitivity of the

Roopali Srivastava; R Dwivedi; S. K Srivastava

1998-01-01

159

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

SciTech Connect

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.

NONE

1995-08-01

160

Flight Testing of an Advanced Airborne Natural Gas Leak Detection System  

SciTech Connect

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 System is operated from a fixed wing aircraft and includes automatic scanning, pointing system, and pilot guidance systems. During a pipeline inspection, the ANGEL system aircraft flies at an elevation of 1000 feet above the ground at speeds of between 100 and 150 mph. Under this contract with DOE/NETL, Space Systems was funded to integrate the ANGEL sensor into a test aircraft and conduct a series of flight tests over a variety of test targets including simulated natural gas pipeline leaks. Following early tests in upstate New York in the summer of 2004, the ANGEL system was deployed to Casper, Wyoming to participate in a set of DOE-sponsored field tests at the Rocky Mountain Oilfield Testing Center (RMOTC). At RMOTC the Space Systems team completed integration of the system and flew an operational system for the first time. The ANGEL system flew 2 missions/day for the duration for the 5-day test. Over the course of the week the ANGEL System detected leaks ranging from 100 to 5,000 scfh.

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

2005-10-01

161

[System design of open-path natural gas leakage detection based on Fresnel lens].  

PubMed

Based on the technology of tunable diode laser absorption spectroscopy (TDLAS) in conjunction with second harmonic wave detection, a long open-path TDLAS system using a 1.65 microm InGaAsP distributed feedback laser was developed, which is used for detecting pipeline leakage. In this system, a high cost performance Fresnel lens is used as the receiving optical system, which receives the laser-beam reflected by a solid corner cube reflector, and focuses the receiving laser-beam to the InGaAs detector. At the same time, the influences of the concentration to the fluctuation of light intensity were taken into account in the process of measurement, and were eliminated by the method of normalized light intensity. As a result, the measurement error caused by the fluctuation of light intensity was made less than 1%. The experiment of natural gas leakage detection was simulated, and the detection sensitivity is 0.1 x 10(-6) (ratio by volume) with a total path of 320 m. According to the receiving light efficiency of the optical system and the detectable minimum light intensity of the detector, the detectable maximal optical path of the system was counted to be 2 000 m. The results of experiment show that it is a feasible design to use the Fresnel lens as the receiving optical system and can satisfy the demand of the leakage detection of natural gas. PMID:19455840

Xia, Hui; Liu, Wen-Qing; Zhang, Yu-Jun; Kan, Rui-Feng; Cui, Yi-Ben; Wang, Min; He, Ying; Cui, Xiao-Juan; Ruan, Jun; Geng, Hui

2009-03-01

162

Development and application of a milli-whistle for use in gas chromatography detection.  

PubMed

A simple milli-whistle was developed for the use in GC (gas chromatography) detection, in which, compared to a thermal conductivity detector (TCD), 1 order of magnitude superior sensitivity can be obtained. The milli-whistle can be connected to the outlet of a GC capillary. The gas and makeup gas passing through the capillary produces a sound as it passes through the milli-whistle (i.e., the gas of the GC eluate). The sound can easily be detected by a microphone, which, after a Fourier transform (FT) by means of a LabVIEW (Laboratory Virtual Instrumentation Engineering Workbench) built-in program, a very sharp frequency peak (full width at half-maximum, approximately 1.6 Hz) can be simultaneously observed. As a result, GC elutes can be qualitatively determined on the basis of their retention times, and a quantitative analysis can be achieved on the basis of the frequency shifts. When the makeup and carrier gases used were nitrogen, in the case of gas samples, including hydrogen, helium, argon, and carbon dioxide, the limits of detection were found to be approximately 3 microL/each injection; in the case of liquid samples, including methanol, cyclohexane, tetrahydrofuran, hexane, and acetone, the limits of detection were determined to be approximately 10 microg/each injection, respectively. When the gases were changed to hydrogen, the limits of detection were dramatically improved. When acetone was selected as the model sample, a linear relationship was found in the range of 0.2-200 microg/injection. PMID:20690658

Lin, Cheng-Huang; Lin, Chien-Hung; Li, Yi-Shiuan; He, Yi-San

2010-09-01

163

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

PubMed

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

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

2007-12-01

164

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

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

165

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

SciTech Connect

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.

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

1993-12-01

166

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

SciTech Connect

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.

Jerry Myers

2005-04-15

167

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

PubMed

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

Levett, P N

1984-02-01

168

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

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

169

Cholesteric liquid crystal-carbon nanotube hybrid architectures for gas detection  

NASA Astrophysics Data System (ADS)

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.

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

2012-01-01

170

Detection of room air contamination of angiographic CO2 with use of a gas analyzer.  

PubMed

The purpose of this study was to describe a practical method to detect room air contamination in CO2 used for angiography. Samples of CO2 with known room air contamination levels were used in a "bag system" of CO2 delivery and sampled by a gas analyzer commonly used in anesthesia. Nitrogen levels were reliably detected indicating contamination with as little as 2% air. Oxygen levels were reliably detected, indicating contamination with as little as 5% air. Measured CO2 values were unreliable with higher-than-true values at all levels except 100%. All clinically important amounts of N2 and O2 contamination were readily detected by this practical method. PMID:12119334

Culp, William C; Culp, William C

2002-07-01

171

Periodically porous top electrodes on vertical nanowire arrays for highly sensitive gas detection  

NASA Astrophysics Data System (ADS)

Nanowires of various materials and configurations have been shown to be highly effective in the detection of chemical and biological species. In this paper, we report a novel, nanosphere-enabled approach to fabricating highly sensitive gas sensors based on ordered arrays of vertically aligned silicon nanowires topped with a periodically porous top electrode. The vertical array configuration helps to greatly increase the sensitivity of the sensor while the pores in the top electrode layer significantly improve sensing response times by allowing analyte gases to pass through freely. Herein, we show highly sensitive detection to both nitrogen dioxide (NO2) and ammonia (NH3) in humidified air. NO2 detection down to 10 parts per billion (ppb) is demonstrated and an order-of-magnitude improvement in sensor response time is shown in the detection of NH3.

In, Hyun Jin; Field, Christopher R.; Pehrsson, Pehr E.

2011-09-01

172

Tunable fiber laser and fiber amplifier based photoacoustic spectrometer for trace gas detection.  

PubMed

A new wavelength modulated photoacoustic spectrometer based on a near-infrared tunable erbium doped fiber laser (TEDFL) and an erbium doped fiber amplifier (EDFA) is first developed for trace gas detection. This sensor has been applied to the detection of ammonia using a first longitudinal resonant photoacoustic cell with double absorption optical path (L=20cm) and lock-in harmonic detection technique. The minimum detectable limit of 3 parts-per-billion volume (signal-to-noise ratio=1) and response time of approximately 1min is achieved at room temperature and atmospheric pressure with 100ms time constant and 500mW optical power at the 1531.7nm transition line. PMID:19781982

Peng, Yong; Zhang, Wang; Li, Liang; Yu, Qingxu

2009-11-01

173

Intracavity phase-matched coherent anti-Stokes Raman spectroscopy for trace gas detection.  

PubMed

We present a novel, cavity-enhanced spectroscopic technique based on a phase-matched Raman process to detect trace quantities of gas. The essence of this technique is the careful control of cavity dispersion to satisfy the phase-matching condition of coherent anti-Stokes Raman scattering (CARS) enhanced in a high-finesse optical cavity. A 6000-fold improvement of the CARS signal is observed under optimized conditions, indicating that this is a promising tool to quantify Raman-active molecules with an extremely low detection limit. PMID:24420247

Zaitsu, Shin-ichi; Imasaka, Totaro

2014-01-01

174

Evaluation of an Interferometric Sensor for In-Space Detection of Gas Leaks  

NASA Technical Reports Server (NTRS)

Space mission planning often involves long-term storage of volatile liquids or high-pressure gases. These may include cryogenic fuels and oxidizers, high-pressure gases, and life-support-critical consumables. The risk associated with the storage of fluids and gases in space systems has long been an issue and the ability to retain these fluids is often tied to mission success. A leak in the storage or distribution system can cause many different problems, including a simple, but mission endangering, loss of inventory or, in severe cases, unbalanced thrust loads on a flight vehicle. Cryogenic propellants are especially difficult to store, especially over a long duration. The propellant can boil off and be lost through the insulating walls of the tank or simple thermal cycling of the fittings, valves, and propellant feed lines may unseat seals allowing the fluid to escape. Current NASA missions call for long-duration in-space storage of propellants, oxidizers, and life support supplies. Leaks of a scale detectable through a pressure drop in the storage tank are often catastrophic and have long been the focus of ground-based mitigation efforts where redundant systems are often employed. However, there is presently no technology available for detecting and monitoring low-level, but still mission-endangering, gas leaks in space. Standard in-space gas detection methods either have a very limited pressure range over which they operate effectively or are limited to certain gases. Mass spectrometer systems are able to perform the detection tasks, but their size, mass and use of high voltage, which could potentially lead to an arc that ignites a combustible propellent, severely limit their usefulness in a space system. In this paper, we present results from testing of the light-based interferometric gas monitoring and leak detection sensor shown in Fig. 1. The output of the sensor is an interference fringe pattern that is a function of the gas density, and commensurate index of refraction, in the sample region. Changes in the density of gas cause the interference fringes to move across a photodiode detector, providing a temporal history of the leak. The sensor is fiber coupled and constructed from solid optics, allowing for placement almost anywhere on the spacecraft. It is also advantageous in that it consumes very little power and does not introduce an ignition source. Data are presented demonstrating the capability of the sensor to measure density variations in different gas species. In addition, the transient response of the sensor in vacuum is demonstrated. These data extend and improve upon the results previously presented by the authors in Ref. [1].

Polzin, Kurt A.; Korman, Valentin; Sinko, John; Hendrickson, Adam

2009-01-01

175

One-Dimensional Nanostructure Field-Effect Sensors for Gas Detection  

PubMed Central

Recently; one-dimensional (1D) nanostructure field-effect transistors (FETs) have attracted much attention because of their potential application in gas sensing. Micro/nanoscaled field-effect sensors combine the advantages of 1D nanostructures and the characteristic of field modulation. 1D nanostructures provide a large surface area-volume ratio; which is an outstanding advantage for gas sensors with high sensitivity and fast response. In addition; the nature of the single crystals is favorable for the studies of the response mechanism. On the other hand; one main merit of the field-effect sensors is to provide an extra gate electrode to realize the current modulation; so that the sensitivity can be dramatically enhanced by changing the conductivity when operating the sensors in the subthreshold regime. This article reviews the recent developments in the field of 1D nanostructure FET for gas detection. The sensor configuration; the performance as well as their sensing mechanism are evaluated. PMID:25090418

Zhao, Xiaoli; Cai, Bin; Tang, Qingxin; Tong, Yanhong; Liu, Yichun

2014-01-01

176

Microstrip gas chamber with individual read-out using two-level discriminators for neutron detection  

Microsoft Academic Search

The microstrip gas chamber (MSGC) with an individual read-out and using two-level discriminators for each strip is proposed for neutron detection with a high spatial resolution. The system identifies secondary particles—protons and tritons—created in the nuclear reaction 3He+n?p+T based on the difference in their track lengths, and determines the incident position of neutrons using suprathreshold signals from tritons. The new

H. Yamagishi; T. Nakamura; S. Masaoka; K. Soyama; K. Aizawa

2004-01-01

177

Detection of Quiescent Molecular Hydrogen Gas in the Circumstellar Disk of a Classical T Tauri Star  

Microsoft Academic Search

We have detected emission from the quiescent, molecular hydrogen gas in the disk around the X-ray bright, classical T Tauri star TW Hya in the 1-0 S(1) line at 2.1218 mum through high-resolution spectroscopy using CSHELL on NASA's Infrared Telescope Facility. The brightness of the observed emission line is consistent with that predicted from models for X-ray excitation of the

David A. Weintraub; Joel H. Kastner; Jeffrey S. Bary

2000-01-01

178

Fiber-optic photo-acoustic spectroscopy sensor for harsh environment gas detection  

Microsoft Academic Search

Photo-acoustic spectroscopy (PAS) has been successfully applied to detect various gases and chemicals due to its high selectivity and sensitivity. However, the performance of the conventional acoustic sensors prohibits the application of PAS for harsh environment gas species real-time monitoring. By replacing conventional acoustic sensors, such as microphone and piezo-transducers, with a high-temperature Fiber Bragg Grating (FBG) vibration sensor, we

Juntao Wu; Kung-Li Deng; Renato Guida; Boon Lee

2007-01-01

179

Detection of very large ions in aircraft gas turbine engine combustor exhaust: charged small soot particles?  

Microsoft Academic Search

Small electrically charged soot particles (CSP) present in the exhaust of a jet aircraft engine combustor have been detected by a Large Ion Mass Spectrometer and quantitatively measured by an Ion Mobility Analyzer. The size and concentration measurements which took place at an aircraft gas-turbine engine combustor test-rig at the ground covered different combustor conditions (fuel flow=FF, fuel sulphur content=FSC).

S Wilhelm; H Haverkamp; A Sorokin; F Arnold

2004-01-01

180

Prospects of Optical Single Atom Detection in Noble Gas Solids for Measurements of Rare Nuclear Reactions  

NASA Astrophysics Data System (ADS)

Optical detection of single atoms captured in solid noble gas matrices provides an alternative technique to study rare nuclear reactions relevant to nuclear astrophysics. I will describe the prospects of applying this approach for cross section measurements of the ^22Ne,,),25Mg reaction, which is the crucial neutron source for the weak s process inside of massive stars. Noble gas solids are a promising medium for the capture, detection, and manipulation of atoms and nuclear spins. They provide stable and chemically inert confinement for a wide variety of guest species. Because noble gas solids are transparent at optical wavelengths, the guest atoms can be probed using lasers. We have observed that ytterbium in solid neon exhibits intersystem crossing (ISC) which results in a strong green fluorescence (546 nm) under excitation with blue light (389 nm). Several groups have observed ISC in many other guest-host pairs, notably magnesium in krypton. Because of the large wavelength separation of the excitation light and fluorescence light, optical detection of individual embedded guest atoms is feasible. This work is supported by DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

Singh, Jaideep; Bailey, Kevin G.; Lu, Zheng-Tian; Mueller, Peter; O'Connor, Thomas P.; Xu, Chen-Yu; Tang, Xiaodong

2013-04-01

181

DETECTION OF HIGHLY IONIZED C IV GAS WITHIN THE LOCAL CAVITY  

SciTech Connect

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.

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

182

An overview of micromachined platforms for thermal sensing and gas detection  

SciTech Connect

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.

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

1997-03-01

183

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

184

Development of a detection sensor for lethal H2S gas.  

PubMed

The gas which may be lethal to human body with short-term exposure in common industrial fields or workplaces in LAB may paralyze the olfactory sense and impose severe damages to central nervous system and lung. This study is concerned with the gas sensor which allows individuals to avoid the toxic gas that may be generated in the space with residues of organic wastes under 50 degrees C or above. This study investigates response and selectivity of the sensor to hydrogen sulfide gas with operating temperatures and catalysts. The thick-film semiconductor sensor for hydrogen sulfide gas detection was fabricated WO3/SnO2 prepared by sol-gel and precipitation methods. The nanosized SnO2 powder mixed with the various metal oxides (WO3, TiO2, and ZnO) and doped with transition metals (Au, Ru, Pd Ag and In). Particle sizes, specific surface areas and phases of sensor materials were investigated by SEM, BET and XRD analyses. The metal-WO3/SnO2 thick films were prepared by screen-printing method. The measured response to hydrogen sulfide gas is defined as the ratio (Ra/R,) of the resistance of WO3ISnO2 film in air to the resistance of WO3/SnO2 film in a hydrogen sulfide gas. It was shown that the highest response and selectivity of the sensor for hydrogen sulfide by doping with 1 wt% Ru and 10 wt% WO3 to SnO2 at the optimum operating temperature of 200 degrees C. PMID:22966558

Park, Young-Ho; Kim, Yong-Jae; Lee, Chang-Seop

2012-07-01

185

Nonlinear Raman spectroscopy without tunable laser for sensitive gas detection in the atmosphere  

NASA Astrophysics Data System (ADS)

A new technique for photo-acoustic Raman spectroscopy (PARS) and coherent anti-Stokes Raman spectroscopy (CARS) is proposed and demonstrated for the detection of H 2 and CH 4 at atmospheric pressure. Conventionally, these types of nonlinear Raman spectroscopy require two lasers whose frequency difference is tuned to the Raman frequency. In the proposed scheme, only a pulsed Nd:YAG laser is used as a pumping source, and a Raman shifter filled with the same gas to be detected is combined. This allows automatic generation of the Raman-shifted radiation. In the case of CH 4, the measurement with the optimized scheme shows that detection limits up to 1 ppm for PARS and 15 ppm for CARS are achieved. The proposed PARS technique allows the measurement of the CH 4 concentration in the natural air. Although the sensitivity of CARS is lower than that of PARS, the signal to noise ratio (S/N) for higher concentrations is better.

Oki, Yuji; Kawada, Noriyuki; Abe, Yoshiteru; Maeda, Mitsuo

1999-03-01

186

Tunable photonic cavities for in-situ spectroscopic trace gas detection  

DOEpatents

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.

Bond, Tiziana; Cole, Garrett; Goddard, Lynford

2012-11-13

187

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

SciTech Connect

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.

Diaz, L.A.

1998-02-04

188

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

SciTech Connect

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.

Ross, G.A.

1998-03-27

189

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

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

190

Trace gas detection of molecular hydrogen H(2) by photoacoustic stimulated Raman spectroscopy (PARS).  

PubMed

Photoacoustic stimulated Raman spectroscopy (PARS) has been used for sensitive and selective trace gas detection of molecular hydrogen under ambient conditions. In one experiment, 532 nm output of a seeded pulsed Nd:YAG laser is employed as Raman pump source and a Raman shifter filled with gaseous H(2) to obtain Stokes shifted radiation at 683 nm, suitable to stimulate H(2) Raman detection in a photoacoustic cell. A noise equivalent detection limit of 40 ppm by volume H(2) in 1 atm N(2) is obtained (14 mJ at 532 nm, 18 mJ at 683 nm, 10 Hz repetition rate, 58 s measurement time). Another experiment employs a dye laser for stimulating Raman radiation between 681-684 nm, allowing tuneable PARS. A Gaussian spectral fitting procedure has been applied giving a noise equivalent detection limit of 4.6 ppm by volume H(2) in 1 atm N(2) (35 mJ pulse energy at 532 nm, 45 mJ at 681-684 nm, 10 Hz repetition rate, 256 s measurement time). Spectroscopic detection offers the advantage of high selectivity along with the ability to obtain temperature and dynamic information from the rotational population and a line shape analysis, and also allows the discrimination between ortho- and para-H(2). PMID:22302187

Spencer, Claire Louise; Watson, Verity; Hippler, Michael

2012-03-21

191

Gas-CT cisternography for detection of small acoustic nerve tumors  

SciTech Connect

Gas-CT cisternography is a simple and accurate procedure for detection of small acoustic nerve tumors. Review of one of the largest series in a single institution found that 98% of the studies clearly showed the presence or absence of tumors. The diagnostic pitfalls of the small number of studies in which significant errors were made, or could have been made, are discussed. It is concluded that certain situations appear to call for extra caution: (a) when the filling defect does not show a convex surface, (b) when the amount of cisternal gas is marginal, and (c) when the canal is small. In such situations careful attention to details and healthy skepticism may avert potential errors.

Solti-Bohman, L.G.; Magaram, D.L.; Lo, W.W.M.; Wade, C.T.; Witten, R.M.; Shimizu, F.H.; McMonigle, E.M.; Raja Rao, A.K.

1984-02-01

192

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

SciTech Connect

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 (H{sub 2}O) and heavy water (D{sub 2}O) in vapor form. It was shown that completely resolved hydrogen (H{sub {alpha}}) and deuterium (D{sub {alpha}}) 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.

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 [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia); Department of Fiber Amenity, Graduate School of Engineering, Fukui University, 9-1 Bunkyo 3-chome, Fukui 910 (Japan); Department of Chemistry and Bio-Science, Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan); Department of Physics, Faculty of Education and Regional Studies, 9-1 Bunkyo 3-chome, Fukui 910 (Japan); Department of Physics, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, 10 Ganesha, Bandung 40132 (Indonesia)

2005-11-01

193

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

NASA Astrophysics Data System (ADS)

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.

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

194

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

195

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

196

Electrically Detected Magnetic Resonance of Neutral Donors Interacting with a Two-Dimensional Electron Gas  

SciTech Connect

We have measured the electrically detected magnetic resonance of donor-doped silicon field-effect transistors in resonant X- (9.7 GHz) and W-band (94 GHz) microwave cavities. The two-dimensional electron gas (2DEG) resonance signal increases by two orders of magnitude from X- to W-band, while the donor resonance signals are enhanced by over one order of magnitude. Bolometric effects and spin-dependent scattering are inconsistent with the observations. We propose that polarization transfer from the donor to the 2DEG is the main mechanism giving rise to the spin resonance signals.

Lo, C. C.; Lang, V.; George, R. E.; Morton, J. J. L.; Tyryshkin, A. M.; Lyon, A.; Bokor, J.; Schenkel, T.

2011-04-20

197

Intelligent hypertext manual development for the Space Shuttle hazardous gas detection system  

NASA Technical Reports Server (NTRS)

This research is designed to utilize artificial intelligence (AI) technology to increase the efficiency of personnel involved with monitoring the space shuttle hazardous gas detection systems at the Marshall Space Flight Center. The objective is to create a computerized service manual in the form of a hypertext and expert system which stores experts' knowledge and experience. The resulting Intelligent Manual will assist the user in interpreting data timely, in identifying possible faults, in locating the applicable documentation efficiently, in training inexperienced personnel effectively, and updating the manual frequently as required.

Lo, Ching F.; Hoyt, W. Andes

1989-01-01

198

Microsecond fiber laser pumped, single-frequency optical parametric oscillator for trace gas detection.  

PubMed

We report on the first microsecond doubly resonant optical parametric oscillator (OPO). It is based on a nested cavity OPO architecture allowing single longitudinal mode operation and low oscillation threshold (few microjoule). The combination with a master oscillator-power amplifier fiber pump laser provides a versatile optical source widely tunable in the 3.3-3.5 ?m range with an adjustable pulse repetition rate (from 40 to 100 kHz), high duty cycle (~10(-2)) and mean power (up to 25 mW in the idler beam). The potential for trace gas sensing applications is demonstrated through photoacoustic detection of atmospheric methane. PMID:23811865

Barria, Jessica Barrientos; Roux, Sophie; Dherbecourt, Jean-Baptiste; Raybaut, Myriam; Melkonian, Jean-Michel; Godard, Antoine; Lefebvre, Michel

2013-07-01

199

Circumstellar Gas-Disk Variability Around A-Type Stars: The Detection of Exocomets?  

NASA Astrophysics Data System (ADS)

We present medium spectral resolution (R˜60,000) observations of the CaII K-line (3,933 Å) absorption profiles observed toward 21 nearby A-type stars thought to possess circumstellar gas debris disks. The stars were repeatedly observed over two observing runs on the 2.1 m Otto Struve telescope at the McDonald Observatory, Texas in 2011 May and 2012 November. Nightly changes in the absorption strength of the CaII K-line near the stellar radial velocity were observed in four of the stars (HD 21620, HD 110411, HD 145964 and HD 183324). This type of absorption variability indicates the presence of a circumstellar gas disk around these stars. We also have detected weak absorption features that sporadically appear with velocities in the range ±100 km s-1 of the main circumstellar K-line in the spectra of HD 21620, HD 42111, HD 110411 and HD 145964. Due to the known presence of both gas and dust disks surrounding these four stars, these transient absorption features are most probably associated with the presence of Falling Evaporated Bodies (FEBs, or exocomets) that are thought to liberate gas on their grazing trajectory toward and around the central star. This now brings the total number of A-type stars in which the evaporation of CaII gas from protoplanetary bodies (i.e., exocomets) has been observed to vary on a nightly basis to 10 systems. A statistical analysis of the 10 A-stars showing FEB-activity near the CaII K-line compared to 21 A-type stars that exhibit no measurable variability reveals that FEB-activity occurs in significantly younger stellar systems that also exhibit chemical peculiarities. The presence of FEB-activity does not appear to be associated with a strong mid-IR excess. This is probably linked to the disk inclination angle, since unless the viewing angle is favorable the detection of time-variable absorption may be unlikely. Additionally, if the systems are more evolved then the evaporation of gas due to FEB activity could have ceased, whereas the circumstellar dust disk may still remain.

Welsh, Barry Y.; Montgomery, Sharon

2013-07-01

200

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

201

Continuous wave, distributed feedback diode laser based sensor for trace-gas detection of ethane  

NASA Astrophysics Data System (ADS)

The development of a continuous wave (CW), thermoelectrically cooled (TEC), distributed feedback (DFB) laser diode based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) based on a 2f wavelength modulation (WM) detection technique. TDLAS was performed with a 100 m optical path length astigmatic Herriott cell. For an interference free C2H6 absorption line located at 2976.8 cm-1 a 1 ? minimum detection limit of 240 pptv (part per trillion by volume) with a 1 second lock-in amplifier time constant was achieved. In addition, reliable and long-term sensor performance was obtained when operating the sensor in an absorption line locked mode.

Krzempek, K.; Lewicki, R.; Nähle, L.; Fischer, M.; Koeth, J.; Belahsene, S.; Rouillard, Y.; Worschech, L.; Tittel, F. K.

2012-02-01

202

Detection of the greenhouse gas signal from space - A progress report  

NASA Technical Reports Server (NTRS)

The spatial distribution of the expected changes in the atmospheric water vapor content and cloud cover, as predicted by the transient greenhouse gas (GHG) simulation of Hansen et al. (1988), are examined to determine whether the signals would be large enough and unique enough to be useful in a GHG detection study. The nature of the predicted GHG signal was first examined using the transient CO2 run from the GISS ocean/atmosphere general circulation model. Next, the remotely sensed irradiance characteristics data (as the measure of water vapor content) supplied by the HIRS/MSU sensors for the area of the equatorial cold tongue region (the region in which there are no measurement stations). It is shown that HIRS/MSU signals can provide data necessary for detecting GHS signals in atmospheric moisture for regions where ground observations are not possible.

Barnett, T. P.; Haskins, R.; Chahine, M.

1991-01-01

203

Detection of Several Classes of Pesticides and Metabolites in Meconium by Gas Chromatography-Mass Spectrometry  

PubMed Central

A solid phase extraction method was developed to isolate multiple classes of parent pesticides from meconium. A methanolic/hydrochloric acid methyl ester derivatization with liquid-liquid extraction technique was also developed for the analysis of metabolites. Identification and quantitation was by electron impact gas chromatography-mass spectrometry. For the parent compounds and metabolites, recoveries in spiked meconium ranged between 72–109%, with coefficients of variation ranging from 1.55–16.92% and limits of detection between 0.01–4.15 ?g g?1. Meconium samples obtained from infants in the Philippines were assayed using these methods, and propoxur, cypermethrin, pretilachlor, malathion, 4,4?-dichlorodiphenyltrichloroethylene, bioallethrin, and cyfluthrin were detected. PMID:17664958

Bielawski, D.; Ostrea, E.; Posecion, N.; Corrion, M.; Seagraves, J.

2007-01-01

204

Detection of Pristine Gas Two Billion Years after the Big Bang  

E-print Network

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.

Fumagalli, Michele; Prochaska, J Xavier

2011-01-01

205

Gas detection with evanescent-wave quartz-enhanced photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

Evanescent-wave gas sensing with tapered optical fibers (TOFs) and quartz-enhanced photoacoustic spectroscopy (QEPAS) is reported. The evanescent field of TOFs with diameter down to sub-wavelength is utilized for photoacoustic excitation in photoacoustic spectroscopy. A quartz tuning fork (QTF) with resonant frequency about ~32.75 kHz is used to detect the generated pressure wave. A normalized noise equivalent absorption coefficient of 1.5×10-6 cm-1 W/?Hz is achieved for acetylene detection with a fiber taper with a waist diameter of 1.1 ?m. It is found that QEPAS with TOFs of sub-wavelength diameters exhibit comparable sensitivities with open path QEPAS but with additional advantages of lower insertion loss, easier alignment, and multiplexing capability.

Cao, Yingchun; Jin, Wei; Ho, Hoi Lut

2012-02-01

206

Potential application of microsensor technology in radioactive waste management with emphasis on headspace gas detection.  

SciTech Connect

Waste characterization is probably the most costly part of radioactive waste management. An important part of this characterization is the measurements of headspace gas in waste containers in order to demonstrate the compliance with Resource Conservation and Recovery Act (RCRA) or transportation requirements. The traditional chemical analysis methods, which include all steps of gas sampling, sample shipment and laboratory analysis, are expensive and time-consuming as well as increasing worker's exposure to hazardous environments. Therefore, an alternative technique that can provide quick, in-situ, and real-time detections of headspace gas compositions is highly desirable. This report summarizes the results obtained from a Laboratory Directed Research & Development (LDRD) project entitled 'Potential Application of Microsensor Technology in Radioactive Waste Management with Emphasis on Headspace Gas Detection'. The objective of this project is to bridge the technical gap between the current status of microsensor development and the intended applications of these sensors in nuclear waste management. The major results are summarized below: {sm_bullet} A literature review was conducted on the regulatory requirements for headspace gas sampling/analysis in waste characterization and monitoring. The most relevant gaseous species and the related physiochemical environments were identified. It was found that preconcentrators might be needed in order for chemiresistor sensors to meet desired detection {sm_bullet} A long-term stability test was conducted for a polymer-based chemresistor sensor array. Significant drifts were observed over the time duration of one month. Such drifts should be taken into account for long-term in-situ monitoring. {sm_bullet} Several techniques were explored to improve the performance of sensor polymers. It has been demonstrated that freeze deposition of black carbon (CB)-polymer composite can effectively eliminate the so-called 'coffee ring' effect and lead to a desirable uniform distribution of CB particles in sensing polymer films. The optimal ratio of CB/polymer has been determined. UV irradiation has been shown to improve sensor sensitivity. {sm_bullet} From a large set of commercially available polymers, five polymers were selected to form a sensor array that was able to provide optimal responses to six target-volatile organic compounds (VOCs). A series of tests on the response of sensor array to various VOC concentrations have been performed. Linear sensor responses have been observed over the tested concentration ranges, although the responses over a whole concentration range are generally nonlinear. {sm_bullet} Inverse models have been developed for identifying individual VOCs based on sensor array responses. A linear solvation energy model is particularly promising for identifying an unknown VOC in a single-component system. It has been demonstrated that a sensor array as such we developed is able to discriminate waste containers for their total VOC concentrations and therefore can be used as screening tool for reducing the existing headspace gas sampling rate. {sm_bullet} Various VOC preconcentrators have been fabricated using Carboxen 1000 as an absorbent. Extensive tests have been conducted in order to obtain optimal configurations and parameter ranges for preconcentrator performance. It has been shown that use of preconcentrators can reduce the detection limits of chemiresistors by two orders of magnitude. The life span of preconcentrators under various physiochemical conditions has also been evaluated. {sm_bullet} The performance of Pd film-based H2 sensors in the presence of VOCs has been evaluated. The interference of sensor readings by VOC has been observed, which can be attributed to the interference of VOC with the H2-O2 reaction on the Pd alloy surface. This interference can be eliminated by coating a layer of silicon dioxide on sensing film surface. Our work has demonstrated a wide range of applications of gas microsensors in radioactive waste management. Such applications can poten

Davis, Chad Edward; Thomas, Michael Loren; Wright, Jerome L.; Pohl, Phillip Isabio; Hughes, Robert Clark; Wang, Yifeng; McGrath, Lucas K.; Ho, Clifford Kuofei; Gao, Huizhen

2004-09-01

207

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

PubMed

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

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

2009-11-01

208

A Cost Effective Multi-Spectral Scanner for Natural Gas Detection  

SciTech Connect

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.

Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan; Seonghyeon Park

2005-12-07

209

Clipping of TE-CO2 laser pulse using gas breakdown technique for high spatial resolution gas plume detection  

NASA Astrophysics Data System (ADS)

High stability and energy-efficient TE-CO2 laser pulse clipper using gas breakdown techniques for high spatial resolution chemical plume detection is presented. The most dominant time constant, attributed to TE-CO2 unclipped laser pulses, is its nitrogen tail which extends for several microseconds beyond the gain-switched spike. Near-field scattered signal, produced by unclipped laser pulses, interferes with the weak signal backscattered from the long range and far field atmospheric aerosols which ultimately degrades the range resolution of LIDARS to some hundreds of meters. Short laser pulses can be obtained by various techniques such as mode locking, free induction decay, pulse slicing with electro-optic switched. However, output pulses from these require further amplification for any useful application due to their very low energy content. This problem is circumvented in this work by the use of a plasma clipper that achieves high range-resolved remote sensing in the atmosphere. Complete extinction of the nitrogen tail is obtained at pressures extending from 375 up to 1500 Torr for nitrogen and argon gases and approximately 105, for helium. Optimum pressures for helium, argon, and nitrogen, that provide the best stability of the transmitted energy and complete extinction of the nitrogen tail, are identified. Excellent range resolutions can be achieved with TE-CO2 laser-based LIDAR systems. Clipped laser pulses are also field tested.

Gasmi, Taieb

2014-06-01

210

Development of an Optical Gas Leak Sensor for Detecting Ethylene, Dimethyl Ether and Methane  

PubMed Central

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

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

2013-01-01

211

Detection of trace gas emissions from point sources using shortwave infrared imaging spectrometry  

NASA Astrophysics Data System (ADS)

Existing spaceborne remote sensing provides an effective means of detecting continental-scale variation in trace gas concentrations, but does not permit mapping of local emissions from point sources. Point source emissions of methane (CH4), nitrous oxide (N2O) and particulates, often associated with combustion and carbon dioxide (CO2) emissions, have significant impacts on air quality. Using Airborne Visible InfraRed Imaging Spectrometer (AVIRIS) data and a cluster-tuned matched filter technique, we have mapped local CH4, N2O and CO2 emissions from terrestrial sources in the Los Angeles basin. CH4 anomalies were in close proximity to known and probable emission sources, including hydrocarbon storage tanks and gas flares. Multiple N2O and CH4 anomalies were detected at a wastewater treatment facility, while CH4 and CO2 anomalies were also identified at a large oil refinery. We discuss ongoing efforts to estimate CH4 concentrations using radiative transfer modeling and potential application of this technique to additional trace gasses with distinct absorption features. This method could be applied to data from existing airborne sensors and planned satellite missions like HyspIRI, thereby improving high resolution mapping of trace gasses and better constraining local sources.

Thorpe, A. K.; Roberts, D. A.; Dennison, P. E.; Bradley, E. S.; Funk, C. C.

2011-12-01

212

Xenon Additives Detection in Helium Micro-Plasma Gas Analytical Sensor  

NASA Astrophysics Data System (ADS)

Electron energy spectra of Xe atoms at He filled micro-plasma afterglow gas analyzer were observed using Collisional Electron Spectroscopy (CES) method [1]. According to CES, diffusion path confinement for characteristic electrons makes it possible to measure electrons energy distribution function (EEDF) at a high (up to atmospheric) gas pressure. Simple geometry micro-plasma CES sensor consists of two plane parallel electrodes detector and microprocessor-based acquisition system providing current-voltage curve measurement in the afterglow of the plasma discharge. Electron energy spectra are deduced as 2-nd derivative of the measured current-voltage curve to select characteristic peaks of the species to be detected. Said derivatives were obtained by the smoothing-differentiating procedure using spline least-squares approximation of a current-voltage curve. Experimental results on CES electron energy spectra at 10-40 Torr in pure He and in admixture with 0.3% Xe are discussed. It demonstrates a prototype of the new miniature micro-plasma sensors for industry, safety and healthcare applications. [1]. A.A.Kudryavtsev, A.B.Tsyganov. US Patent 7,309,992. Gas analysis method and ionization detector for carrying out said method, issued December 18, 2007.

Tsyganov, Alexander; Kudryavtsev, Anatoliy; Mustafaev, Alexander

2012-10-01

213

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

PubMed Central

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

2013-01-01

214

A poly(vinylidene fluoride)-coated ZnO film bulk acoustic resonator for nerve gas detection  

NASA Astrophysics Data System (ADS)

We apply the film bulk acoustic resonator for the detection of nerve gas. The resonator is consisted of a ZnO piezoelectric stack and a W/SiO2 Bragg reflector. Poly(vinylidene fluoride) (PVDF) is used as the sensing coating to adsorb the analyte under test. The testing results show that our proposed sensor can yield a sensitive, reversible and reproducible response to nerve gas. The relationship between the frequency shifts and the concentrations of the nerve gas exhibits a perfect linear correlation in the range of 10-50 ppm. The gas sensitivity of the proposed sensor is 718 kHz ppm-1, which is several orders of magnitude higher than that of a quartz crystal microbalance with the same sensitive coating. This study proves that it is feasible to use the PVDF-coated thin film bulk acoustic resonator for the detection of the traced nerve gas.

Chen, Da; Wang, Jingjing; Li, Dehua; Liu, Yijian; Song, Hongwei; Liu, Qixin

2011-08-01

215

Hierarchical Leak Detection and Localization Method in Natural Gas Pipeline Monitoring Sensor Networks  

PubMed Central

In light of the problems of low recognition efficiency, high false rates and poor localization accuracy in traditional pipeline security detection technology, this paper proposes a type of hierarchical leak detection and localization method for use in natural gas pipeline monitoring sensor networks. In the signal preprocessing phase, original monitoring signals are dealt with by wavelet transform technology to extract the single mode signals as well as characteristic parameters. In the initial recognition phase, a multi-classifier model based on SVM is constructed and characteristic parameters are sent as input vectors to the multi-classifier for initial recognition. In the final decision phase, an improved evidence combination rule is designed to integrate initial recognition results for final decisions. Furthermore, a weighted average localization algorithm based on time difference of arrival is introduced for determining the leak point’s position. Experimental results illustrate that this hierarchical pipeline leak detection and localization method could effectively improve the accuracy of the leak point localization and reduce the undetected rate as well as false alarm rate. PMID:22368464

Wan, Jiangwen; Yu, Yang; Wu, Yinfeng; Feng, Renjian; Yu, Ning

2012-01-01

216

Estimation of seismically detectable portion of a gas plume: CO2CRC Otway project case study  

NASA Astrophysics Data System (ADS)

CO2CRC Otway project comprises of several experiments involving CO2/CH4 or pure CO2 gas injection into different geological formations at the Otway test site (Victoria, Australia). During the first stage of the project, which was finished in 2010, more than 64,000 t of gas were injected into the depleted gas reservoir at ~2 km depth. At the moment, preparations for the next stage of the project aiming to examine capabilities of seismic monitoring of small scale injection (up to 15,000 t) into saline formation are ongoing. Time-lapse seismic is one of the most typical methods for CO2 geosequestration monitoring. Significant experience was gained during the first stage of the project through acquisition and analysis of the 4D surface seismic and numerous time-lapse VSP surveys. In order to justify the second stage of the project and optimise parameters of the experiment, several modelling studies were conducted. In order to predict seismic signal we populate realistic geological model with elastic properties, model their changes using fluid substitution technique applied to the fluid flow simulation results and compute synthetic seismic baseline and monitor volumes. To assess detectability of the time-lapse signal caused by the injection, we assume that the time-lapse noise level will be equivalent to the level of difference between the last two Otway 3D surveys acquired in 2009 and 2010 using conventional surface technique (15,000 lbs vibroseis sources and single geophones as the receivers). In order to quantify the uncertainties in plume imaging/visualisation due to the time-lapse noise realisation we propose to use multiple noise realisations with the same F-Kx-Ky amplitude spectra as the field noise for each synthetic signal volume. Having signal detection criterion defined in the terms of signal/time- lapse noise level on a single trace we estimate visible portion of the plume as a function of this criterion. This approach also gives an opportunity to attempt to evaluate probability of the signal detection. The authors acknowledge the funding provided by the Australian government through its CRC program to support this CO2CRC research project. We also acknowledge the CO2CRC's corporate sponsors and the financial assistance provided through Australian National Low Emissions Coal Research and Development (ANLEC R&D). ANLEC R&D is supported by Australian Coal Association Low Emissions Technology Limited and the Australian Government through the Clean Energy Initiative.

Pevzner, Roman; Caspari, Eva; Bona, Andrej; Galvin, Robert; Gurevich, Boris

2013-04-01

217

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

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

218

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

NASA Technical Reports Server (NTRS)

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).

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

219

A novel gas sensor used for C2H2 trace detection in power transformer  

NASA Astrophysics Data System (ADS)

A novel gas sensor has been presented using tunable diode laser absorption spectroscopy (TDLAS) technique for incipient faults monitoring in power transformer. In this sensor, near infrared distribute feedback laser diode (DFB LD) is used as light source, a 0.5m short optical path cell is used as absorbing cell , two InGaAs PIN photo diodes are used as detector. Applying TDLAS technique and Wavelength modulation spectroscopy (WMS) technique, and combining with ARM9 S3C2140 processor controlling, the system has been implemented compact and flexible. The concentration monitoring based on TDLAS method is obtained in situ and in real time, and the detected precision is below ppm degree, which can meet the requirement for power transformer incipient faults.

Ding, Zhiqun; Bao, Jilong; Fang, Xiaohui; Zhao, Hongxia; Ja, Hui

2010-10-01

220

Recent Advances in Gas and Chemical Detection by Vernier Effect-Based Photonic Sensors  

PubMed Central

Recently, the Vernier effect has been proved to be very efficient for significantly improving the sensitivity and the limit of detection (LOD) of chemical, biochemical and gas photonic sensors. In this paper a review of compact and efficient photonic sensors based on the Vernier effect is presented. The most relevant results of several theoretical and experimental works are reported, and the theoretical model of the typical Vernier effect-based sensor is discussed as well. In particular, sensitivity up to 460 ?m/RIU has been experimentally reported, while ultra-high sensitivity of 2,500 ?m/RIU and ultra-low LOD of 8.79 × 10?8 RIU have been theoretically demonstrated, employing a Mach-Zehnder Interferometer (MZI) as sensing device instead of an add drop ring resonator. PMID:24618728

La Notte, Mario; Troia, Benedetto; Muciaccia, Tommaso; Campanella, Carlo Edoardo; De Leonardis, Francesco; Passaro, Vittorio M. N.

2014-01-01

221

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

NASA Astrophysics Data System (ADS)

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.

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

222

Mobile spectroscopic system for trace gas detection using a tunable mid-IR laser.  

PubMed

We describe a mobile spectroscopic system for trace gas analysis based on the open path differential absorption spectrometer and the photoacoustic spectrometer. The first method allows long distance measurements (up to a few kilometers) while the second one provides local in situ detection of pollutants. The open path system is based on the nanosecond (f = 10 Hz, tau = 5 ns) lamp pumped Nd:YAG laser and a tunable two cascade optical parametric generator operating in the 5-12 microm spectral region. This source was mounted into the lidar setup based on the coaxial transmitter/receiver. The photoacoustic system was constructed using the same laser as well as a nonresonant photoacoustic cell. PMID:17578102

Vaicikauskas, V; Kaucikas, M; Svedas, V; Kuprionis, Z

2007-02-01

223

Sensitive trace gas detection with near-infrared laser diodes and an integrating sphere.  

PubMed

We describe a simple spectrometer for sensitive trace gas detection in the atmosphere. A communication laser diode is used as a light source, and a commercial integrating sphere is used as a multipass absorption cell. We developed a theoretical formulation of the relative absorption of the optical power by trace gases in the sphere and applied it to two kinds of experimental result: one that is concerned with a structureless broad absorption band of butane with the use of a 1.2-?m multimode laser diode, and one that is related to the study of an isolated and sharp rovibrational line of water vapor in air at atmospheric pressure with the use of an 830-nm single-mode laser diode. With equivalent path lengths of several meters obtained with a 10-cm-i.d. integrating sphere we can demonstrate the usefulness of such a device as a broadband multipass cell for the measurement of small absorptions. PMID:21151310

Tranchart, S; Bachir, I H; Destombes, J L

1996-12-20

224

Sensitive trace gas detection with near-infrared laser diodes and an integrating sphere  

NASA Astrophysics Data System (ADS)

We describe a simple spectrometer for sensitive trace gas detection in the atmosphere. A communication laser diode is used as a light source, and a commercial integrating sphere is used as a multipass absorption cell. We developed a theoretical formulation of the relative absorption of the optical power by trace gases in the sphere and applied it to two kinds of experimental result: one that is concerned with a structureless broad absorption band of butane with the use of a 1.2- m multimode laser diode, and one that is related to the study of an isolated and sharp rovibrational line of water vapor in air at atmospheric pressure with the use of an 830-nm single-mode laser diode. With equivalent path lengths of several meters obtained with a 10-cm-i.d. integrating sphere we can demonstrate the usefulness of such a device as a broadband multipass cell for the measurement of small absorptions.

Tranchart, Sébastien; Bachir, Ikhlef Hadj; Destombes, Jean-Luc

1996-12-01

225

A COST EFFECTIVE MULTI-SPECTRAL SCANNER FOR NATURAL GAS DETECTION  

SciTech Connect

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.

Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan

2004-04-01

226

Detection of very large ions in aircraft gas turbine engine combustor exhaust: charged small soot particles?  

NASA Astrophysics Data System (ADS)

Small electrically charged soot particles (CSP) present in the exhaust of a jet aircraft engine combustor have been detected by a Large Ion Mass Spectrometer and quantitatively measured by an Ion Mobility Analyzer. The size and concentration measurements which took place at an aircraft gas-turbine engine combustor test-rig at the ground covered different combustor conditions (fuel flow=FF, fuel sulphur content=FSC). At the high-pressure turbine stage of the engine, CSP-diameters were mostly around 6 nm and CSP-concentrations reached up to 4.8×10 7 cm -3 (positive and negative) corresponding to a CSP-emission index ECSP=2.5×10 15 CSP kg -1 fuel burnt. The ECSP increased with FF but did not increase with FSC. The latter indicates that sulphur was not a major component of the large ions. Possible CSP-sources and CSP-sinks as well as CSP-roles are discussed.

Wilhelm, S.; Haverkamp, H.; Sorokin, A.; Arnold, F.

227

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

NASA Technical Reports Server (NTRS)

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.

Grant, W. B.

1986-01-01

228

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

PubMed

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

Ringer, Joachim M

2013-01-01

229

Calorimetric Thermoelectric Gas Sensor for the Detection of Hydrogen, Methane and Mixed Gases  

PubMed Central

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

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

2014-01-01

230

Chemical warfare agent detection in complex environments with comprehensive two-dimensional gas chromatography  

NASA Astrophysics Data System (ADS)

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 potential for a wide variety of environmental sensing applications, including detection of chemical warfare agents (CWA) and other harmful chemicals. This paper demonstrates separation of nerve agents sarin and soman from a matrix of gasoline and diesel fuel. Using a combination of an initial column separating on the basis of boiling point and a second column separating on the basis of polarity, GCxGC clearly separates the nerve agents from the thousands of other chemicals in the sample. The GCxGC data is visualized, processed, and analyzed as a two-dimensional digital image using a software system for GCxGC image processing developed at the University of Nebraska - Lincoln.

Reichenbach, Stephen E.; Ni, Mingtian; Kottapalli, Visweswara; Visvanathan, Arvind; Ledford, Edward B., Jr.; Oostdijk, John; Trap, Henk C.

2003-08-01

231

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

232

CO Gas Detection of Al-Doped ZnO Nanostructures with Various Shapes  

NASA Astrophysics Data System (ADS)

Nanostructure of semiconductor type gas sensors that are high sensitivity, fast response time, inexpensive, and easily fabricated, is suggested. One-dimensional (1D) nanostructures, such as nanorods, and hollow spheres, are attracting particularly great interest because of their large specific surface area and their inherent physical properties. This study combined with ZnCl2 (6.95 g, Sigma-Aldrich), Al(NO3)3.9H2O (Junsei), NaOH, ethanol, and deionized water (DI) by hydrothermal synthesis to manufacture, spherical, hollow, hierarchical, and nanorod. The same Al-doped ZnO (AZO) were prepared by a colloidal template on a Si wafer to make a 3D igloo structure as well. Sensitivity to carbon monoxide at 50 ppm was tested at 250 °C the compare the sensing properties. Gas sensitivity of the hierarchical structure showed the highest sensitivity at 31.8, a figure 7 times that of the packed spherical sphere, whereas the igloo structure gave the fastest response speed of 32 s. The results of various shapes of the AZO nanostructures demonstrated high sensitivity and quick response time, which is useful in the detection of harmful gases in automobiles and the atmosphere.

Wang, Byung-Yong; Lim, Dae-Soon; Oh, Young-Jei

2013-10-01

233

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

PubMed

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

Aberl, A; Coelhan, M

2013-01-01

234

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

PubMed

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

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

2014-01-01

235

Detection of human butyrylcholinesterase-nerve gas adducts by liquid chromatography–mass spectrometric analysis after in gel chymotryptic digestion  

Microsoft Academic Search

To verify the exposure to nerve gas, a method for detecting human butyrylcholinesterase (BuChE)-nerve gas adduct was developed using LC–electrospray mass spectrometry (ESI-MS). Purified human serum BuChE was incubated with sarin, soman or VX, and the adduct was purified by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and digested in gel by treatment with chymotrypsin. The resulting peptide mixture was subjected

Kouichiro Tsuge; Yasuo Seto

2006-01-01

236

Detection of liquid petroleum gas using mixed nanosized tungsten oxide-based thick-film semiconductor sensor  

Microsoft Academic Search

The thick-film semiconductor sensor for liquid petroleum gas (LPG) detection was fabricated using a mixed WO3-based sensor. We present the characterization of both their structural properties by means of XRD measurements and the electrical characteristics by using gas-sensing properties. The sensing characteristics such as sensitivity, working range, cross-sensitivity and response time were studied by using nanosized WO3-based mixed with different

G. N. Chaudhari; A. M. Bende; A. B. Bodade; S. S. Patil; S. V. Manorama

2006-01-01

237

Determination of acrylonitrile in foods by headspace gas-liquid chromatography with nitrogen-phosphorus detection.  

PubMed

A general procedure is described for the determination of acrylonitrile (AN) in foods such as margarine, honey butter, cold-pack cheese, and peanut butter, which are likely to be packaged in AN-based plastic. The entire sample is blended with water and salt at less than 5 degrees C, aliquots are sealed in crimp-top vials, and the vials are equilibrated in a boiling water bath. The headspace is sampled by using a heated syringe, and AN is determined by gas chromatography with a nitrogen-phosphorus selective detector. The inclusion of propionitrile as an internal standard allows quantitation of AN with detection at 4,4, and 10 ppb for margarine, honey butter, and cold-pack cheese, respectively. A peak corresponding to about 5 ppb apparent AN in all non-AN-packaged peanut butter samples examined limits detection in peanut butter to about 15 ppb. The coefficients of variation at 20 ppb for margarine, honey butter, cold-pack cheese, and peanut butter were 7.5, 8.3, 7.3, and 10.2%, respectively. PMID:6630123

Page, B D; Charbonneau, C F

1983-09-01

238

A ground-based trace gas observing system for detection of Arctic and Boreal change  

NASA Astrophysics Data System (ADS)

The large reservoir of below-ground organic carbon in the Arctic and Boreal region (ABR) permafrost, combined with large observed and predicted temperature changes leads to the expectation of increasing surface emissions of CO2 and/or CH4 this century. However, the near-term response of northern ecosystems could be enhanced ecosystem productivity and carbon sequestration via, among other causes, longer growing seasons and encroachment of woody species into Arctic tundra. Regardless of the temporal evolution of carbon (both CO2 and CH4) sources and sinks in the ABR, monitoring these changes at regional (~10^5 - 10^6 km^2) scales using trace gas mixing and isotopic ratios will be a critical complement to detailed process-based studies at the plot scale and remote sensing of the land surface. Turbulent mixing in the lower few kilometers of the atmosphere naturally integrates emissions from all known and unknown processes and can provide a powerful bottom-line constraint on the net result of both sources and sinks. We will present the first year of results of a trace-gas measurement system capable of daily or more frequent observations of more than 50 trace gas species, including CO2, CH4 and their stable and radio isotope ratios. The measurements were initiated as part of the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) and come from a 30 m tower located on a ridge in central Alaska. Central Alaska is dominated by discontinuous permafrost, which is likely to undergo significant changes in the coming decades. Footprint analysis suggests that mixing ratios measured at the tower are influenced by large swaths of central Alaska, although in winter, anthropogenic emissions form the city of Fairbanks are evident. In summer, as expected, we observe a large drawdown of CO2. The seasonal cycle of CH4 is dominated by the large-scale destruction of methane by hydroxyl radical (OH). However, based on previous measurements from other ABR sites, we expect summer/fall wetland emissions to be evident as a late summer/early fall bulge. Moreover, analysis of ?13C of CH4 has also indicated that methane consumption by OH masks a substantial biogenic (mostly wetland) source in summer. Starting summer 2012, 14C of CH4 measurements were initiated to help determine the age of the biogenic emissions. In addition to biogenic tracers, a large suite of measured anthropogenic tracers can be used to identify periods of transport from both local (i.e. Fairbanks) and mid-latitude sources of pollutant CO, CO2 and CH4. As a whole, our tower measurements represent an important component of detecting trace gas emissions from permafrost.

Karion, A.; Miller, J. B.; Sweeney, C.; Bruhwiler, L.; Newberger, T.; Miller, C. E.; Dinardo, S. J.; Wolter, S.; Ledlow, L.

2012-12-01

239

Nano Sensors for Gas Detection in Space and Ground Support Applications  

NASA Technical Reports Server (NTRS)

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.

Medelius, Pedro J.

2006-01-01

240

Gas-coupled laser acoustic detection at ultrasonic and audio frequencies  

NASA Astrophysics Data System (ADS)

Airborne acoustic waves have been detected by a laser-beam deflection technique in both the ultrasonic and audio frequency ranges. For ultrasonic applications, a probe beam is directed parallel to the surface of a sample. Ultrasonic waves in the solid are detected when an acoustic wave is radiated from the surface into the ambient air, where the density variations cause a beam deflection. Gas-coupled laser acoustic detection (GCLAD) has been used to record well-resolved through-transmission and surface-acoustic wave forms in various materials. GCLAD has also been incorporated into a C-scanning system where it has been used to image subsurface flaws in graphite/polymer composite panels. Because the laser beam is not reflected from the sample surface, the technique is not dependent upon the surface optical properties of the material under investigation. It is particularly useful for testing graphite/polymer composites and other materials with rough surfaces. The beam-deflection technique has been tested quantitatively in the kHz frequency range by passing a probe beam through a cylindrical resonator. The acoustic spectrum of the resonator was measured from 4 to 13.5 kHz by scanning the frequency of a source and recording the acoustic field with both a microphone and the beam-deflection system. The acoustic fields of the lower-frequency modes are well known and enable both qualitative and quantitative tests of the beam-deflection technique. Measurements on the lowest-frequency plane-wave mode were used for absolute calibration of the microphone. The noise level of the beam-deflection measurements at 4.3 kHz was found to be 0.05 nrad (rms), corresponding to an acoustic pressure of 0.005 Pa (rms).

Caron, James N.; Yang, Yuqiao; Mehl, James B.; Steiner, Karl V.

1998-08-01

241

Solid phase extractive preconcentration coupled to gas chromatography–atomic emission detection for the determination of chlorophenols in water samples  

Microsoft Academic Search

Solid-phase extraction (SPE) followed by derivatization and gas chromatography-atomic emission detection (GC–AED) was evaluated for the determination of five chlorophenols (CPs) in water samples. The derivatization was based on the esterification of phenolic compounds with ferrocenecarboxylic acid. The determination of the derivatized phenols was performed by GC–AED in the iron selective detection mode at 302nm. The described method was tested

Latif Elci; Nina Kolbe; Sukru G. Elci; Jan T. Anderson

2011-01-01

242

Derivation of New Emission Factors for Quantification of Mass Emissions When Using Optical Gas Imaging for Detecting Leaks  

Microsoft Academic Search

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

Miriam Lev-On; David Epperson; Jeffrey Siegell; Karin Ritter; Norman Robinson; Dana Trimble; Steven Kohl; John Watson; L.-W. Chen; M. C. Chang; Hsing-Wang Li; Yee-Lin Wu; Wen-Jhy Lee; Guo-Ping Chang-Chien; Joao Gomes; Joana Nascimento; Helena Rodrigues; David Schaad; James Halley; Vince Alaimo; Hal Taback; Yu Zhou; Lixin Fu; Linglin Cheng; Pao-Wen Liu; Daniel Brady; Gregory Pratt; Qingzhong Yuan; Kalliat Valsaraj; Danny Reible; Clinton Willson; Wipada Sanongraj; Yongsheng Chen; John Crittenden; Hugo Destaillats; David Hand; David Perram; Roy Taylor; Sangil Lee; Armistead Russell; Karsten Baumann

2007-01-01

243

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

DOEpatents

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.

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

2010-08-24

244

Development of a Chemiluminescence Method for Gas-Phase HO2 Detection  

NASA Astrophysics Data System (ADS)

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.

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

2003-12-01

245

Detection of exhaled hydrogen sulphide gas in healthy human volunteers during intravenous administration of sodium sulphide  

PubMed Central

INTRODUCTION Hydrogen sulphide (H2S) is an endogenous gaseous signaling molecule and potential therapeutic agent. Emerging studies indicate its therapeutic potential in a variety of cardiovascular diseases and in critical illness. Augmentation of endogenous sulphide concentrations by intravenous administration of sodium sulphide can be used for the delivery of H2S to the tissues. In the current study, we have measured H2S concentrations in the exhaled breath of healthy human volunteers subjected to increasing doses sodium sulphide in a human phase I safety and tolerability study. METHODS We have measured reactive sulphide in the blood via ex vivo derivatization of sulphide with monobromobimane to form sulphide-dibimane and blood concentrations of thiosulfate (major oxidative metabolite of sulphide) via ion chromatography. We have measured exhaled H2S concentrations using a custom-made device based on a sulphide gas detector (Interscan). RESULTS Administration of IK-1001, a parenteral formulation of Na2S (0.005–0.20 mg kg?1, i.v., infused over 1 min) induced an elevation of blood sulphide and thiosulfate concentrations over baseline, which was observed within the first 1–5 min following administration of IK-1001 at 0.10 mg kg?1 dose and higher. In all subjects, basal exhaled H2S was observed to be higher than the ambient concentration of H2S gas in room air, indicative of on-going endogenous H2S production in human subjects. Upon intravenous administration of Na2S, a rapid elevation of exhaled H2S concentrations was observed. The amount of exhaled H2S rapidly decreased after discontinuation of the infusion of Na2S. CONCLUSION Exhaled H2S represents a detectable route of elimination after parenteral administration of Na2S. PMID:20565454

Toombs, Christopher F; Insko, Michael A; Wintner, Edward A; Deckwerth, Thomas L; Usansky, Helen; Jamil, Khurram; Goldstein, Brahm; Cooreman, Michael; Szabo, Csaba

2010-01-01

246

Gas chromatographic/electron capture detection method for determination of chlorinated acids in water: collaborative study.  

PubMed

A U.S. Environmental Protection Agency (USEPA) interlaboratory method validation study was conducted on USEPA Method 515.1, "Determination of Chlorinated Acids in Water by Gas Chromatography with an Electron Capture Detector." This method is one of the 6 pesticide methods developed for the USEPA National Pesticide Survey (NPS). Method recovery and precision for analyses of sub-ppb to low-ppb concentrations of chlorinated acids were determined in reagent water and finished drinking waters. The analytes evaluated in the study included the 12 pesticides that were quantitatively measured in the National Pesticide Survey (bentazon, 2,4-D, 2,4-DB, 3,5-dichlorobenzoic acid, DCPA-diacid, dicamba, dichlorprop. 5-hydroxydicamba, pentachlorophenol, picloram, 2,4,5-T, and 2,4,5-TP) and 5 pesticides (acifluorfen, chloramben, dalapon, dinoseb, and 4-nitrophenol) that were only qualitatively assessed in the National Pesticide Survey because of recognized method imprecision. The study design was based on Youden's nonreplicate plan for collaborative tests of analytical methods. The waters were spiked with 17 chlorinated acids, each at 6 concentration levels, prepared as 3 Youden pairs. Eight laboratories extracted the spiked test waters at pH < 2 with ethyl ether, performed a solvent exchange with methyl tert-butyl ether, prepared methyl esters of the extracted acids using diazomethane, and analyzed an aliquot of each derivatized extract by gas chromatography with electron capture detection. The submitted data were analyzed using a USEPA computer program, which measured recovery and precision for each of the 17 compounds and compared the performance of the method between water types. Method 515.1 was judged acceptable for the 12 NPS analytes recovered quantitatively; mean percent recoveries at 10-15 times the method detection limits ranged from 79 to 105% in reagent water and from 75 to 123% in finished drinking water. In reagent water, overall precision (reproducibility relative standard deviation, RSDR) ranged from 9.6 to 34.2% and in finished drinking water, the RSDR ranged from 11.9 to 37.0%. Single-analyst precision (RSD for repeatability, RSDr) ranged from 5.8 to 17.7% in reagent water and from 4.6 to 27.9% in drinking water. Results for the 5 other NPS analytes were too inaccurate or imprecise and, for these compounds, supported use of the method for qualitative measurements only; the 5 compounds are not included in the adopted method. The method has been adopted first action by AOAC INTERNATIONAL for determination of residues of 12 chlorinated acids in finished drinking water. PMID:8241813

Edgell, K W; Erb, E J; Wesselman, R J; Longbottom, J E

1993-01-01

247

Part-per-million gas detection from long-baseline THz spectroscopy S. A. Harmon and R. A. Chevillea)  

E-print Network

Part-per-million gas detection from long-baseline THz spectroscopy S. A. Harmon and R. A. Chevillea (Received 10 May 2004; accepted 6 July 2004) We report a long-baseline THz time domain spectrometer based. [DOI: 10.1063/1.1788896] Optically generated pulses of electromagnetic radiation with terahertz THz

248

Determination of ethyl carbamate in alcoholic beverages by capillary multi-dimensional gas chromatography with thermionic specific detection  

Microsoft Academic Search

A specific, sensitive capillary multi-dimensional gas chromatographic method with thermionic specific detection (TSD) combined with internal standard methodology to identify ethyl carbamate (EC), a well known carcinogen, in various fermented alcoholic beverages is described. The basic procedures for sample preparation were similar to a modification of the LCBO (Liquor Control Board of Ontario) procedure, except that isopropyl carbamate (i-PC) was

Ya-Ping Ma; Fu-Quan Deng; Dai-Zhou Chen; Shou-Wei Sun

1995-01-01

249

The detection and determination of some chlorinated pesticide residues in crops, soils and animal tissues by gas-liquid chromatography  

Microsoft Academic Search

Summary A rapid method for the identification and determination of traces of chlorinated pesticides in crops, soils and animal tissues by gas-liquid chromatography with electron capture ionisation detection will be outlined. Only conventional G. L. C. equipment is required and neither preliminary „clean-up” nor concentration of the extract solution of the pesticide is, in general, necessary. In most cases the

R. Goulden

1964-01-01

250

SIMULTANEOUS DETERMINATION OF ORGANOTIN, ORGANOLEAD, AND ORGANOMERCURY COMPOUNDS IN ENVIRONMENTAL SAMPLES USING CAPILLARY GAS CHROMATOGRAPHY WITH ATOMIC EMISSION DETECTION  

EPA Science Inventory

As part of a continuing evaluation of new analytical and sample preparation techniques conducted by the US Environmental Protection Agency (EPA), the use of capillary gas chromatography with atomic emission detection (GC-AED) for the simultaneous determination of organotin, organ...

251

CAPILLARY GAS CHROMATOGRAPHY-ATOMIC EMISSION DETECTION METHOD FOR THE DETERMINATION OF PENTYLATED ORGANOTIN COMPOUNDS: INTERLABORATORY STUDY  

EPA Science Inventory

A capillary gas chromatography-atomic emission detection (GC-AED) method was developed for the U. S. Environmental Protection Agency's Environmental Monitoring Systems Laboratory in Las Vegas, NV, for determination of selected organotin compounds. Here we report on an interlabora...

252

Detection of greenhouse-gas-induced climatic change. Progress report, 1 December 1991--30 June 1992  

SciTech Connect

The aims of the US Department of Energy`s Carbon Dioxide Research Program are to improve assessments of greenhouse-gas-induced climatic change and to define and reduce uncertainties through selected research. This project will address: The regional and seasonal details of the expected climatic changes; how rapidly will these changes occur; how and when will the climatic effects of CO{sub 2} and other greenhouse gases be first detected; and the relationships between greenhouse-gas-induced climatic change and changes caused by other external and internal factors. The present project addresses all of these questions. Many of the diverse facets of greenhouse-gas-related climate research can be grouped under three interlinked subject areas: modeling, first detection and supporting data. This project will include the analysis of climate forcing factors, the development and refinement of transient response climate models, and the use of instrumental data in validating General Circulation Models (GCMs).

Wigley, T.M.L.; Jones, P.D.

1992-07-15

253

DEVELOPMENT OF NOVEL CERAMIC NANOFILM-FIBER INTEGRATED OPTICAL SENSORS FOR RAPID DETECTION OF COAL DERIVED SYNTHESIS GAS  

SciTech Connect

The overall goal of this project is to conduct fundamental studies on advanced ceramic materials and fiber optic devices for developing new types of high temperature (>500{degree}C) fiber optic chemical sensors (FOCS) for monitoring fossil (mainly coal) and biomass derived gases in power plants. The primary technical objective is to investigate and demonstrate the nanocrystalline doped-ceramic thin film enabled FOCS that possess desired stability, sensitivity and selectivity for in-situ, rapid gas detection in the syngas streams from gasification and combustion flue gases. This report summarizes research works of two integrated parts: (1) development of metal oxide solid thin films as sensing materials for detection and measurement of important gas components relevant to the coal- and biomass-derived syngas and combustion gas streams at high temperatures; and (2) development of fiber optic devices that are potentially useful for constructing FOCS in combination with the solid oxide thin films identified in this program.

Junhang Dong; Hai Xiao; Xiling Tang; Hongmin Jiang; Kurtis Remmel; Amardeep Kaur

2012-09-30

254

Short-Time-Response measurements of nitrogen dioxide and peroxyacetyl nitrate by fast capillary gas chromatography with luminol detection.  

SciTech Connect

The interaction of hydrocarbons and nitrogen oxides in sunlight to produce photochemical smog has been well studied over the years. In the past, the workhorse for the measurement of NO{sub 2}and NO was the chemiluminescent reaction with ozone. This method has detection limits of approximately 0.5 ppb in most commercial instruments, but it cannot detect NO{sub 2} directly; the instrument detects NO and uses hot catalytic surfaces to decompose all other nitrogen oxides (including NO{sub 2}) to NO for detection (l). The main problem with the method is the inherent difficulty in detecting excited NO{sub 2}, which emits over a broad region beginning at approximately 660 nm and has a maximum at 1270 nm, thus requiring a red-shifted photomultiplier for detection. The use of luminol for direct chemiluminescent detection of NO{sub 2} was demonstrated to have greater inherent sensitivity (detection limits of 5 ppt) than the indirect ozone chemiluminescence detection (2). In the luminol system, a gas-liquid reaction leads to light emission with a maximum at approximately 425 nm, at the maximum sensitivity for most photomultiplier tubes. This emission is responsible for the increased detection sensitivities. The biggest problem with this method for direct measurement of NO{sub 2} has been interference due to other soluble oxidants, particularly peroxyacyl nitrates (PANs).

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

2000-12-07

255

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

PubMed

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

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

2012-09-28

256

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

SciTech Connect

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.

NONE

1994-10-01

257

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

PubMed

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

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

2014-10-24

258

Lyapunov-Based Sensor Failure Detection And Recovery For The Reverse Water Gas Shift Process  

NASA Technical Reports Server (NTRS)

Livingstone, a model-based AI software system, is planned for use in the autonomous fault diagnosis, reconfiguration, and control of the oxygen-producing reverse water gas shift (RWGS) process test-bed located in the Applied Chemistry Laboratory at KSC. In this report the RWGS process is first briefly described and an overview of Livingstone is given. Next, a Lyapunov-based approach for detecting and recovering from sensor failures, differing significantly from that used by Livingstone, is presented. In this new method, models used are in terms of the defining differential equations of system components, thus differing from the qualitative, static models used by Livingstone. An easily computed scalar inequality constraint, expressed in terms of sensed system variables, is used to determine the existence of sensor failures. In the event of sensor failure, an observer/estimator is used for determining which sensors have failed. The theory underlying the new approach is developed. Finally, a recommendation is made to use the Lyapunov-based approach to complement the capability of Livingstone and to use this combination in the RWGS process.

Haralambous, Michael G.

2001-01-01

259

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

SciTech Connect

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.

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

2007-06-13

260

First detection of [N II] 205 micrometer absorption in interstellar gas  

E-print Network

We present high resolution [NII] 205 micrometer ^3P_1-^3P_0 spectra obtained with Herschel-HIFI towards a small sample of far-infrared bright star forming regions in the Galactic plane: W31C (G10.6-0.4), W49N (G43.2-0.1), W51 (G49.5-0.4) and G34.3+0.1. All sources display an emission line profile associated directly with the HII regions themselves. For the first time we also detect absorption of the [NII] 205 micrometer line by extended low-density foreground material towards W31C and W49N over a wide range of velocities. We attribute this absorption to the Warm Ionised Medium (WIM) and find N(N^+)\\approx 1.5x10^17 cm^-2 towards both sources. This is in agreement with recent Herschel-HIFI observations of [CII] 158 micrometer, also observed in absorption in the same sight-lines (Gerin et al. 2012, 2014), if ~10-13% of all C^+ ions exist in the WIM on average. Using an abundance ratio of [N]/[H] = 6.76x10^-5 in the gas-phase we find that the mean electron and proton densities are ~0.2-2 cm^-3 assuming a WIM fil...

Persson, C M; Mookerjea, B; Black, J H; Olberg, M; Goicoechea, J R; Hassel, G E; Falgarone, E; Levrier, F; Menten, K M; Pety, J

2014-01-01

261

LYAPUNOV-Based Sensor Failure Detection and Recovery for the Reverse Water Gas Shift Process  

NASA Technical Reports Server (NTRS)

Livingstone, a model-based AI software system, is planned for use in the autonomous fault diagnosis, reconfiguration, and control of the oxygen-producing reverse water gas shift (RWGS) process test-bed located in the Applied Chemistry Laboratory at KSC. In this report the RWGS process is first briefly described and an overview of Livingstone is given. Next, a Lyapunov-based approach for detecting and recovering from sensor failures, differing significantly from that used by Livingstone, is presented. In this new method, models used are in t e m of the defining differential equations of system components, thus differing from the qualitative, static models used by Livingstone. An easily computed scalar inequality constraint, expressed in terms of sensed system variables, is used to determine the existence of sensor failures. In the event of sensor failure, an observer/estimator is used for determining which sensors have failed. The theory underlying the new approach is developed. Finally, a recommendation is made to use the Lyapunov-based approach to complement the capability of Livingstone and to use this combination in the RWGS process.

Haralambous, Michael G.

2002-01-01

262

Development of Oxide Semiconductor Thick Film Gas Sensor for the Detection of Total Volatile Organic Compounds  

NASA Astrophysics Data System (ADS)

After an amendment of Building Standards Law in 2003, the installation of the ventilator is compulsory in the newly built house. Because many persons suffer from indoor-air pollutants caused by the volatile organic compounds (VOCs). The final purpose of this research is to develop the gas sensor which can monitor the gross weight of VOC gases indoors and then to control the ventilator efficiently using the sensor. In order to develop the sensor which detects total VOC, the responses of 4 oxide semiconductor materials to 37 kinds of VOC gases were studied. Those materials showed small responses to halogenated and aliphatic hydrocarbon gases. As a result of improving the response to these gases, among 4 metal oxides examined, SnO2 and WO3 showed high sensitivities by the addition of Pd and Pt. The sensing properties of SnO2 for halogenated hydrocarbon gases were extremely improved by the addition of 0.5wt% Pd. Also, the sensing properties of SnO2 for aliphatic hydrocarbon gases were improved by the addition of 0.7wt% Pt. In addition, the doubly promoted element, Pt(0.5wt%)-Pd(0.5wt%)-SnO2, showed a large response to many kinds of VOC gases examined.

Kadosaki, Masahiro; Sakai, Yuichi; Tamura, Ikuo; Matsubara, Ichiro; Itoh, Toshio

263

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

PubMed

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

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

264

Trace gas detection using 1.3-microm InGaAsP diode laser transmitter modules.  

PubMed

The detection of small absorptions using a laser absorption spectrometer (LAS) based on InGaAsP diode laser transmitter modules has been investigated. The modules are normally employed in optical communication systems and as such operate at 1.3 microm and have single-mode-fibor pigtails to couple the light out. The minimum detectable absorption of the LAS wasfound tobe ~5 x 10(-5) with harmonic detection and ~1 x 10(-4) with sweep integration. The dominant noise source was caused by reflections off the cleaved end of the fiber pigtail. The strength and number of absorption lines in the 0.7-1.6-microm spectral region which are free from interference is considered for the major constituents of the atmosphere. It is found that there arc sufficient strong isolated lines for trace gas detection and monitoring purposes usinga LAS based on InGaAsP lasers and the reported minimum detectable absorption. PMID:20523648

Cassidy, D T

1988-02-01

265

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

E-print Network

INTRODUCTION Performance and reliability of aircraft gas turbine engines gradually deteriorate over the service 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

Ray, Asok

266

High-resolution seismic detection of shallow natural gas beneath Hutchinson, Kansas  

USGS Publications Warehouse

Two high-resolution seismic reflection surveys were conducted to identify shallow natural gas that had caused explosions in Hutchinson, Kansas, in January 2001. Gas presence is associated with both a bright spot and a dim-out on the seismic reflection profiles. Core and log data from wells drilled to vent the gas indicate that the gas-bearing interval corresponds to thin dolomite layers, which have higher P-wave velocities than the surrounding shales. Gas in fractures can reduce the velocity of the dolomite interval to that of the shales (or lower). Depending on the magnitude of the velocity change, either a dim-out or bright spot is produced. Sonic logs from gas-bearing vent wells, recorded after venting of gas, show no anomalous velocity, indicating that as gas dissipates, any associated seismic anomaly will be reduced. Lateral variations in the seismic properties of the gas-bearing interval and adjacent strata (namely, variations in dolomite and shale content) also have a significant effect on the seismic signature of the interval, mimicking the effect of a small amount of gas. Only where the gas zone is relatively thick (2-3 m; 7-10 ft), creating a high-amplitude negative seismic reflection, is the seismic signature diagnostic of gas. Therefore, whereas the dim-outs observed on the seismic reflection profiles may be the result of gas presence, they are equally well explained by lateral variations in lithology. Dim-outs should not be used in the Hutchinson area as an indicator of gas. The observed bright spot, however, is most likely a unique gas response. Copyright ?? 2004. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

Nissen, S.E.; Watney, W.L.; Xia, J.

2004-01-01

267

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

PubMed Central

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

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

2013-01-01

268

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

PubMed

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

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

2013-01-01

269

[Investigation of the limit of detection of an infrared passive remote sensing and scanning imaging system for pollution gas].  

PubMed

NECL could be used to estimate the limit of detection of the infrared passive remote sensing system. It was an important indicator of the sensitivity of the system. The theoretical equation of the NECL according to the atmospheric infrared radiation transfer model showed that NECL related to NESR, the brightness temperature of background and pollution gas, and the absorption coefficient of pollution gas. The remote sensing of SF6 was done. The limit of detection of the system at the different brightness temperature of background and pollution gas could be calculated. False color image of NECL was given from the measured data. The results show that NECL decreases rapidly by increasing the difference in brightness temperature of the background and pollution gas, the value of NECL was down to 10(-2) order of magnitude when the brightness temperature difference was equal to 30 K. False color image of NECL contributes to the discrimination of the limit of detection of the system in the complex background. PMID:24409702

Jiao, Yang; Xu, Liang; Gao, Min-Guang; Jin, Ling; Tong, Jing-Jing; Li, Sheng; Wei, Xiu-Li

2013-10-01

270

Noise studies in CW cavity ring-down spectroscopy and its application in trace gas detection  

NASA Astrophysics Data System (ADS)

The traditional uncorrelated least squares fit can be generalized to the situation with data correlation (e.g. caused by data filtering which is essential to minimize noise), which has been applied to cavity ring-down spectroscopy (CRDS). The ideal accuracy limit of the extracted decay rate k was derived from the exponential decay signal for both white noise dominated and shot noise dominated CRDS. Different algorithms of single exponential fitting in CRDS were reviewed by comparing the bias and variance estimation of the extracted k, and computation efficiency of different fitting methods. In continuous wave (CW) CRDS, it was found that the very high order (˜ 60th) transverse mode can be excited simultaneously with the TEM00 mode through mirror surface scattering coupling when they are near degenerate. This will lead to mode beating noise in ring-down transients even when the intensity coupling strength is extremely small, ˜ 10-12 per reflection. Putting an intracavity aperture of the right size will remove this noise by suppressing the excitation of high order transverse modes. Linear residual or strain induced birefringence (10-7 ˜ 10-6 rad) in high reflective (HR) coatings of supermirrors will lift the degeneracy of TEM00 mode between two polarizations, generating two new eigen polarization states, which are very close to linear polarization and have a typical splitting of 0.1 kHz. Because of the polarization dependent loss (linear dichroism, ˜ 10-8) of HR coatings of supermirrors, these two new eigenstates are no longer orthogonal with each other, producing mode beating noise in ring-down signal. By controlling the polarization state of the incident light or in the detection, this noise can be removed. Because of finite extinction ratio of the light modulator in CW-CRDS, the small light leakage will interfere with the exponential decay of intracavity light power, generating excess noise in the signal. A linear relation between (sigmak/k)2 and the extinction ratio has been found both theoretically and experimentally, with excellent agreement. In order to realize the ideal sensitivity (See Chapter 2) in CW-CRDS, light modulator with very high extinction ratio is needed. The efficacy of using a semiconductor optical amplifier (SOA) as light modulator in CW-CRDS was demonstrated. SOA has the highest extinction ratio (>80 dB). For ring-down transients with S/N of 1400:1, the SOA and acousto-optic modulator (AOM) are found to give equivalent performance. The Allan variance was applied to characterize the drifting of the decay rate in CW-CRDS experiments. With differential measurements by two lasers between k and k0, the decay rates with and without absorption, the drifting between them will cancel out with each other greatly. A sensitivity of 5.6 x 10-12 cm -1 has been reached within an integration time of 15.4 minutes, which corresponds to trace methane detection limit (3sigma) of 0.3 parts per billion by volume (ppbv) at 20 torr or 15 parts per trillion by volume (pptv) at one atm measurement pressure around 1652 nm. By converting CO, CO2, ethane, propane and n-butane into methane with 100% conversion efficiency under the condition of excess H2 gas and nickel (or ruthenium) catalyst (for isobutane, the conversion efficiency is about 80%), each trace gas has been measured in nitrogen separately down to the level of sub parts per million by volume (ppmv), limited by ˜ 0.5 ppmv methane background in the conversion caused by the carbon contamination of both catalysts.

Huang, Haifeng

271

Comparison of Thermal Neutron Detection Efficiency of $^{6}$Li Scintillation Glass and $^{3}$He Gas Proportional Tube  

E-print Network

We report on a comparison study of the $^{3}$He gas proportional tube and the $^{6}$Li incorporated scintillation glasses on thermal neutron detection efficiency. Both $^{3}$He and $^{6}$Li are used commonly for thermal neutron detection because of their high neutron capture absorption coefficient. By using a neutron source $^{252}$Cf and a paraffin moderator in an alignment system, we can get a small beam of thermal neutrons. A flash ADC is used to measure the thermal neutron spectrum of each detector, and the detected number of events is determined from the spectrum, then we can calculate the detection efficiency of different detectors. Meanwhile, the experiment have been modeled with GEANT4 to validate the results against the Monte Carlo simulation.

Ming Xu; Zhi-Cheng Tang; Guo-Ming Chen; Jun-Quan Tao

2013-04-22

272

Element-specific detection of organosilicon compounds by gas chromatography/atmospheric pressure microwave induced helium plasma spectrometry  

SciTech Connect

The gas chromatographic, element-specific detection of organosilicon compounds by atmospheric pressure microwave induced helium plasma spectrometry (GC/MIP) is investigated. At plasma temperatures, silicon is continuously removed from the walls of a quartz discharge tube. This results in a high silicon background response and poor experimental repeatability. Alumina and boron nitride are examined as discharge tubes. Background emission spectra are compared for helium plasmas contained within alumina, boron nitride, and quartz discharge tubes. Silicon detection limits, sensitivity, and selectivity are determined at optimized MIP conditions. A 4.5-pg silicon detection limit is obtained. Simultaneous multielement detection and empirical formula determinations are demonstrated for silicon-, carbon-, hydrogen-, and chlorine-containing compounds. 39 references, 6 figures, 4 tables.

Slatkavitz, K.J.; Hoey, L.D.; Uden, P.C.; Barnes, R.M.

1985-08-01

273

Upconversion enhanced degenerate four-wave mixing in the mid-infrared for sensitive detection of acetylene in gas flows  

NASA Astrophysics Data System (ADS)

We present a new background free method for in situ gas detection that combines degenerate four-wave mixing with an infra-red light detector based on parametric frequency upconversion of infra-red light. The system is demonstrated at mid infrared wavelengths for low concentration measurements of acetylene diluted in a N2 gas flow at ambient conditions. It is demonstrated that the system is able to cover more than 100 nm in scanning range and detect concentrations as low as 3 ppm based on the R9e line. A major issue in small signal measurements is scattered light and it is showed how a spatial analysis can be used to reduce this level.

Høgstedt, Lasse; Dam, Jeppe Seidelin; Sahlberg, Anna-Lena; Li, Zhongshan; Aldén, Marcus; Pedersen, Christian; Tidemand-Lichtenberg, Peter

2014-02-01

274

Detection of martian amino acids by chemical derivatization coupled to gas chromatography: in situ and laboratory analysis.  

PubMed

If there is, or ever was, life in our solar system beyond the Earth, Mars is the most likely place to search for. Future space missions will have then to take into account the detection of prebiotic molecules or molecules of biological significance such as amino acids. Techniques of analysis used for returned samples have to be very sensitive and avoid any chemical or biological contamination whereas in situ techniques have to be automated, fast and low energy consuming. Several possible methods could be used for in situ amino acid analyses on Mars, but gas chromatography would likely be the most suitable. Returned samples could be analyzed by any method in routine laboratory use such as gas chromatography, already successfully performed for analyses of organic matter including amino acids from martian meteorites. The derivatization step, which volatilizes amino acids to perform both in situ and laboratory analysis by gas chromatography, is discussed here. PMID:11605632

Rodier, C; Vandenabeele-Trambouze, O; Sternberg, R; Coscia, D; Coll, P; Szopa, C; Raulin, F; Vidal-Madjar, C; Cabane, M; Israel, G; Grenier-Loustalot, M F; Dobrijevic, M; Despois, D

2001-01-01

275

Simultaneous Photoacoustic and Photopyroelectric Detection of Trace Gas Emissions from Some Plant Parts and Their Related Essential Oils in a Combined Detection Cell  

NASA Astrophysics Data System (ADS)

The aim of this work was to establish the feasibility of the combined photoacoustic (PA) and photopyroelectric (PPE) detection of the vapours emitted from essential oils and their corresponding uncrushed leaves or flowers. Gas traces of jasmine (Jessamine (Jasminum)), mint (Mentha arvensis L.) and Damask rose (Rosa damascena Miller) and their essential oils were tested using a combined cell fitted with both a photopyroelectric film (PVDF) and a microphone in conjunction with a pulsed wideband infrared source (PWBS) source. Infrared PA and PPE absorbances were obtained simultaneously at room temperatures with excellent reproducibility and high signal-to-noise ratios. Significant similarities found between the PA and PPE spectra of the trace gas emissions of plant parts, i.e., flowers or leaves and their related essential oils show the good correlation of their emissions and that both effects are initiated by the same absorbing molecules.

Abu-Taha, M. I.; Abu-Teir, M. M.; Al-Jamal, A. J.; Eideh, H.

276

Long-term detection of clenbuterol in human scalp hair by gas chromatography–high-resolution mass spectrometry  

Microsoft Academic Search

A method for the detection of clenbuterol in human scalp hair by gas chromatography–high-resolution mass spectrometry (GC–HRMS) is described. The sample preparation involved chemical digestion of the protein structure, which was achieved by incubating the hair with 1 M KOH at 70°C. A single extraction step with tert.-butyl methyl ether provided approximately 90% of the analyte, which was dried and

M. Machnik; H. Geyer; S Horning; A. Breidbach; P. Delahaut; W. Schänzer

1999-01-01

277

Development of a high-performance microstrip gas chamber with a capability of track discrimination for neutron detection  

Microsoft Academic Search

A microstrip gas chamber (MSGC) with a capability of track discrimination for neutron detection was developed whilst ensuring the stability of the MSGC and fulfilling the specifications required for detectors used in high-flux reactors and high-intensity pulsed-neutron sources. The developed two-dimensional detector system comprises an MSGC with individual signal channel read-outs and a new instrument system with a capability of

T. Nakamura; H. Yamagishi; S. Masaoka; K. Soyama; K. Aizawa

2004-01-01

278

Hyphenation of a near-infrared Echelle spectrometer to a microplasma for element-selective detection in gas chromatography.  

PubMed

The coupling of a near-infrared Echelle spectrometer (NIRES) with a gas chromatograph for element-selective detection is introduced. The miniaturized capacitive plasma device is operated at a frequency of 40.68 MHz and is mounted directly on an Hewlett-Packard HP6890 GC. First results with a mixture of halogenated standard compounds are presented and discussed in terms of the advantages and problems with this system. PMID:11798094

Cziesla, K; Platzer, B; Okruss, M; Florek, S; Otto, M

2001-12-01

279

A poly(vinylidene fluoride)-coated ZnO film bulk acoustic resonator for nerve gas detection  

Microsoft Academic Search

We apply the film bulk acoustic resonator for the detection of nerve gas. The resonator is consisted of a ZnO piezoelectric stack and a W\\/SiO2 Bragg reflector. Poly(vinylidene fluoride) (PVDF) is used as the sensing coating to adsorb the analyte under test. The testing results show that our proposed sensor can yield a sensitive, reversible and reproducible response to nerve

Da Chen; Jingjing Wang; Dehua Li; Yijian Liu; Hongwei Song; Qixin Liu

2011-01-01

280

Development of a broadly tunable mid-infrared laser source for highly sensitive multiple trace gas detection  

Microsoft Academic Search

A room-temperature broadly tunable mid-infrared difference frequency laser source for highly sensitive trace gas detection has been developed recently in our laboratory. The mid-infrared laser system is based on quasi-phase-matched (QPM) difference frequency generation (DFG) in a multi-grating, temperature-controlled periodically poled LiNbO3 (PPLN) crystal and employs two near-infrared diode lasers as pump sources. The mid-infrared coherent radiation generated was tunable

Xiao-juan Cui; Feng-zhong Dong; Yu-jun Zhang; Rui-feng Kan; Yi-ben Cui; Min Wang; Dong Chen; Jian-guo Liu; Wen-qing Liu

2008-01-01

281

MEASUREMENT AND ANALYSIS OF ADSISTOR AND FIGARO GAS SENSORS USED FOR UNDERGROUND STORAGE TANK LEAK DETECTION  

EPA Science Inventory

Two different sensor technologies and their properties were analyzed. he nalysis simulated a leak which occurs from an underground storage tank. igaro gas sensors and the Adsistor gas sensor were tested in simulated underground storage tank nvironments using the Carnegie Mellon R...

282

THE RADIO JET INTERACTION IN NGC 5929: DIRECT DETECTION OF SHOCKED GAS  

SciTech Connect

We report on the discovery of kinematic shock signatures associated with a localized radio jet interaction in the merging Seyfert galaxy NGC 5929. We explore the velocity-dependent ionization structure of the gas and find that low-ionization gas at the interaction site is significantly more disturbed than high-ionization gas, which we attribute to a local enhancement of shock ionization due to the influence of the jet. The characteristic width of the broad low-ionization emission is consistent with shock velocities predicted from the ionization conditions of the gas. We interpret the relative prominence of shocks to the high density of gas in the nuclear environment of the galaxy and place some constraints of their importance as feedback mechanisms in Seyferts.

Rosario, D. J. [Astronomy Department, University of California, Santa Cruz, CA 95064 (United States); Whittle, M. [Astronomy Department, University of Virginia, Charlottesville, VA 22903 (United States); Nelson, C. H. [Physics and Astronomy Department, Drake University, Des Moines, IA 50311-4505 (United States); Wilson, A. S. [Astronomy Department, University of Maryland, College Park, MD 20742 (United States)], E-mail: rosario@ucolick.org, E-mail: dmw8f@virginia.edu, E-mail: charles.nelson@drake.edu

2010-03-10

283

CW DFB RT diode laser based sensor for trace-gas detection of ethane using novel compact multipass gas absorption cell  

NASA Astrophysics Data System (ADS)

The development of a continuous wave (CW), thermoelectrically cooled (TEC), distributed feedback (DFB) laser diode based spectroscopic trace-gas sensor for ultra sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable laser diode absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS) as the detection technique. TDLAS was performed with an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm. For an interference free C2H6 absorption line located at 2976.8 cm-1 a 1? minimum detection limit of 130 pptv with a 1 second lock-in amplifier time constant was achieved.

Jahjah, Mohammad; Lewicki, Rafal; Tittel, Frank K.; Krzempek, Karol; Stefanski, Przemyslaw; So, Stephen; Thomazy, David

2013-01-01

284

CW DFB RT diode laser-based sensor for trace-gas detection of ethane using a novel compact multipass gas absorption cell  

NASA Astrophysics Data System (ADS)

The development of a continuous wave, thermoelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy as the detection technique. TDLAS was performed using an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm and optimized for the 2.5-4 ?m range TEC mercury-cadmium-telluride detector. For an interference-free C2H6 absorption line located at 2,976.8 cm-1, a 1 ? minimum detection limit of 740 pptv with a 1 s lock-in amplifier time constant was achieved.

Krzempek, Karol; Jahjah, Mohammad; Lewicki, Rafa?; Stefa?ski, Przemys?aw; So, Stephen; Thomazy, David; Tittel, Frank K.

2013-09-01

285

A New Method for Ultrasound Detection of Interfacial Position in Gas-Liquid Two-Phase Flow  

PubMed Central

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

Coutinho, Fabio Rizental; Ofuchi, Cesar Yutaka; de Arruda, Lucia Valeria Ramos; Jr., Flavio Neves; Morales, Rigoberto E. M.

2014-01-01

286

Development of a Random Field Model for Gas Plume Detection in Multiple LWIR Images.  

SciTech Connect

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.

Heasler, Patrick G.

2008-09-30

287

Sulphur-bearing Compounds Detected by MSL SAM Evolved Gas Analysis of Materials from Yellowknife Bay, Gale Crater, Mars  

NASA Technical Reports Server (NTRS)

The Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments on the Mars Science Laboratory (MSL) analysed several subsamples of sample fines (<150 µm) from three sites in Yellowknife Bay, an aeolian bedform termed Rocknest (hereafter "RN") and two samples drilled from the Sheepbed mudstone at sites named John Klein ("JK") and Cumberland ("CB"). SAM's evolved gas analysis (EGA) mass spectrometry detected H2O, CO2, O2, H2, SO2, H2S, HCl, NO, OCS, CS2 and other trace gases. The identity of evolved gases and temperature (T) of evolution can support mineral detection by CheMin and place constraints on trace volatile-bearing phases present below the CheMin detection limit or difficult to characterize with XRD (e.g., X-ray amorphous phases). Here, we focus on potential constraints on phases that evolved SO2, H2S, OCS, and CS2 during thermal analysis.

McAdam, A. C.; Franz, H. B.; Archer, P. D. Jr.; Sutter, B.; Eigenbrode, J. L.; Freissinet, C.; Atreya, S. K.; Bish, D. L.; Blake, D. F.; Brunner, A.; Mahaffy, P. R.; Ming, D. W.; Morris, R. V.; Navarro-Gonzalez, R.; Rampe, E. B.; Steele, A.; Wray, J. J.

2014-01-01

288

Detection of Gas Hydrates in Garden Banks and Keathley Canyon from Seismic Data  

E-print Network

, where the sub-seafloor is a complex structure of shallow salt diapirs and sheets underlying heavily deformed shallow sediments and surrounding diverse minibasins. Here, we consider the effect these structural factors have on gas hydrate occurrence...

Murad, Idris

2011-08-08

289

The development of a curb valve flow meter for gas theft detection  

E-print Network

As the supply of natural gas continues to dwindle, and government decontrol of pricing progresses, the rising cost of this essential natural resource will drive more individuals to consider various forms of pilferage as a ...

Fitzgerald, Kevin Francis

1984-01-01

290

Detection of Ethylene Gas by Fluorescence Turn-On of a Conjugated Polymer  

E-print Network

Ripe fruits: The fluorescence of a conjugated polymer is quenched by the presence of copper(I) moieties. Upon exposure to ethylene gas the copper complexes bind to ethylene and no longer quench the polymer fluorescence ...

Swager, Timothy Manning

291

An imaging gas scintillation proportional counter for the detection of subkiloelectron-volt x-rays  

SciTech Connect

A large area imaging gas scintillation proportional counter (IGSPC) was constructed for use in X-ray astronomy. The IGSPC consists of a gas scintillation proportional counter (GSPC) with a micron polyprotylene window coupled to a multiwire proportional counter (MWPC) via a calcium fluoride window. Over a sensitive area of 21 cu cm the instrument has a measured energy resolution of 17.5% (FWHM) and 1.9 mm (FWHM) spatial resolution at 1.5 keV.

Hailey, C.J.; Ku, W.H.M.; Vartanian, M.H.

1981-11-01

292

Determination of antimony in environment samples by gas phase chemiluminescence detection following flow injection hydride generation and cryotrapping.  

PubMed

A novel method for the determination of antimony in environmental samples was developed with gas phase chemiluminescence detection following flow injection hydride generation and cryotrapping. The stibine, generated from samples by borohydride reduction of antimony using flow injection technique, was separated by using a new gas-liquid separator, dried with an ice-salt cryogenic bath and concentrated in a glass U-tube immersed in liquid nitrogen. Re-vaporization of stibine based on its boiling point was achieved by allowing the tube to warm at room temperature. A gas phase chemiluminescence signal was produced during the ozonation of the hydride in a reflective chamber. Under optimal conditions, the proposed method was characterized by a wide linear calibration range from 1.0microgL(-1) to 10.0mgL(-1) with a detection limit of 0.18microgL(-1) (n=11). The relative standard deviation for 10.0microgL(-1) antimony was 3.56% (n=11) and the sampling rate was 15 samples h(-1). Blank signal was reduced by the purification of reagents and the interference from transition metal ions was eliminated by the addition of L-cysteine into samples. The method was applied to the determination of antimony in environmental samples with satisfactory results. PMID:20441930

Ye, Yousheng; Sang, Jianchi; Ma, Hongbing; Tao, Guanhong

2010-06-15

293

Fracture detection, mapping, and analysis of naturally fractured gas reservoirs using seismic technology. Final report, November 1995  

SciTech Connect

Many basins in the Rocky Mountains contain naturally fractured gas reservoirs. Production from these reservoirs is controlled primarily by the shape, orientation and concentration of the natural fractures. The detection of gas filled fractures prior to drilling can, therefore, greatly benefit the field development of the reservoirs. The objective of this project was to test and verify specific seismic methods to detect and characterize fractures in a naturally fractured reservoir. The Upper Green River tight gas reservoir in the Uinta Basin, Northeast Utah was chosen for the project as a suitable reservoir to test the seismic technologies. Knowledge of the structural and stratigraphic geologic setting, the fracture azimuths, and estimates of the local in-situ stress field, were used to guide the acquisition and processing of approximately ten miles of nine-component seismic reflection data and a nine-component Vertical Seismic Profile (VSP). Three sources (compressional P-wave, inline shear S-wave, and cross-line, shear S-wave) were each recorded by 3-component (3C) geophones, to yield a nine-component data set. Evidence of fractures from cores, borehole image logs, outcrop studies, and production data, were integrated with the geophysical data to develop an understanding of how the seismic data relate to the fracture network, individual well production, and ultimately the preferred flow direction in the reservoir. The multi-disciplinary approach employed in this project is viewed as essential to the overall reservoir characterization, due to the interdependency of the above factors.

NONE

1995-10-01

294

Measurement techniques investigated for detection of hydrogen chloride gas in ambient air  

NASA Technical Reports Server (NTRS)

Nine basic techniques are discussed, ranging from concentration (parts per million) to dosage only (parts per million-seconds) measurement techniques. Data for each technique include lower detection limit, response time, instrument status, and in some cases, specificity. Several techniques discussed can detect ambient hydrogen chloride concentrations below 1 part per million with a response time of seconds.

Gregory, G. L.

1976-01-01

295

Recent developments in the applications of mid-infrared lasers, LEDs, and other solid state sources to gas detection  

NASA Astrophysics Data System (ADS)

Although mid infrared research into sources and detectors has made considerable progress in recent years, requirements for gas sensing purposes for source power and the detectivity of diode detectors - particularly in combination - remain to be convincingly demonstrated in an industrial context. Published results are often confusing in that they apply to a variety of pulse lengths and duty cycles. We suggest a standardized approach in terms of an averaged cw power output. Parameters such as radiance, drive current and electrical power are also important. We discuss the relative merits of lasers and LEDs, i.e. use of line or band absorption on gas sensing. We report recent advances in the use of immersion optics leading to detectors with D*~5x109 cmHz1/2W-1 at 5.4micrometers , LEDs with outputs improved by a factor of 5 and an LED/Diode/White cell gas sensing demonstration giving 2ppm sensitivity for NO2 with an electrical power requirement of only 0.25mW. Further consideration includes sensitivity of gas sensing, path length and volume, time constant and temperature stability. Latest results are assessed on the basis of the above and combined with some market indications.

Smith, Stanley D.; Hardaway, Harvey R.; Crowder, J. G.

2002-05-01

296

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...

297

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...

298

A Sub-ppm Acetone Gas Sensor for Diabetes Detection Using 10 nm Thick Ultrathin InN FETs  

PubMed Central

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

Kao, Kun-Wei; Hsu, Ming-Che; Chang, Yuh-Hwa; Gwo, Shangjr; Yeh, J. Andrew

2012-01-01

299

A sub-ppm acetone gas sensor for diabetes detection using 10 nm thick ultrathin InN FETs.  

PubMed

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

Kao, Kun-Wei; Hsu, Ming-Che; Chang, Yuh-Hwa; Gwo, Shangjr; Yeh, J Andrew

2012-01-01

300

Detection of Noble Gas Radionuclides from an Underground Nuclear Explosion During a CTBT On-Site Inspection  

NASA Astrophysics Data System (ADS)

The development of a technically sound approach to detecting the subsurface release of noble gas radionuclides is a critical component of the on-site inspection (OSI) protocol under the Comprehensive Nuclear Test Ban Treaty. In this context, we are investigating a variety of technical challenges that have a 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 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 non-proliferation experiment (NPE). 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 computer-based models to test a range of geologic and atmospheric scenarios far beyond what could ever be studied by field experiments, making this approach very highly cost effective. We review some highlights of the transport and sampling issues we have investigated and complete the discussion of these issues with a description of a preliminary design for subsurface sampling that addresses some of the sampling challenges discussed here.

Carrigan, Charles R.; Sun, Yunwei

2014-03-01

301

Solid phase extractive preconcentration coupled to gas chromatography-atomic emission detection for the determination of chlorophenols in water samples.  

PubMed

Solid-phase extraction (SPE) followed by derivatization and gas chromatography-atomic emission detection (GC-AED) was evaluated for the determination of five chlorophenols (CPs) in water samples. The derivatization was based on the esterification of phenolic compounds with ferrocenecarboxylic acid. The determination of the derivatized phenols was performed by GC-AED in the iron selective detection mode at 302 nm. The described method was tested on spiked water samples.The overall method gave detection limits of 1.6-3.7 ng L(-1) and recoveries of 90.9-104.5% for the examined mono- to trichlorophenols in 10 mL water samples. The CPs extracted from a 10 mL water sample with SPE were concentrated into 100 ?L of organic solvent, a preconcentration factor of 100. The method was applied to lake and tap water samples, and CP contents between 6 and 51 ng L(-1) in lake water and between below the detection limit and 8 ng L(-1) in tap water were found for different CPs. The method is quick, simple and gives excellent recoveries, limits of detection and standard deviations. PMID:21645740

Elci, Latif; Kolbe, Nina; Elci, Sukru G; Anderson, Jan T

2011-07-15

302

Multiphase imaging of gas flow in a nanoporous material usingremote detection NMR  

SciTech Connect

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.

Harel, Elad; Granwehr, Josef; Seeley, Juliette A.; Pines, Alex

2005-10-03

303

Gas sensors based on carbon nanoflake/tin oxide composites for ammonia detection.  

PubMed

Carbon nanoflake (CNFL) was obtained from graphite pencil by using the electrochemical method and the CNFL/SnO2 composite material assessed its potential as an ammonia gas sensor. A thin film resistive gas sensor using the composite material was manufactured by the drop casting method, and the sensor was evaluated to test in various ammonia concentrations and operating temperatures. Physical and chemical characteristics of the composite material were assessed using SEM, TEM, SAED, EDS and Raman spectroscopy. The composite material having 10% of SnO2 showed 3 times higher sensor response and better repeatability than the gas sensor using pristine SnO2 nano-particle at the optimal temperature of 350°C. PMID:24473403

Lee, Soo-Keun; Chang, Daeic; Kim, Sang Wook

2014-03-15

304

Thin film transistors gas sensors based on reduced graphene oxide poly(3-hexylthiophene) bilayer film for nitrogen dioxide detection  

NASA Astrophysics Data System (ADS)

Reduced graphene oxide (RGO)/poly(3-hexylthiophene) (P3HT) bilayer films were firstly utilized as active layers in OTFT gas sensors for nitrogen dioxide (NO2) detection. The OTFT with RGO/P3HT bilayer film exhibited the typical transistor characteristics and better gas sensing properties at room temperature. The electrical parameters of OTFTs based on pure P3HT film and RGO/P3HT bilayer film were calculated. The threshold voltage of OTFT was positively shifted due to the high concentration carriers in RGO. The sensing properties of the sensor with RGO/P3HT bilayer film were also investigated. Moreover, the sensing mechanism was analyzed as well.

Xie, Tao; Xie, Guangzhong; Zhou, Yong; Huang, Junlong; Wu, Mei; Jiang, Yadong; Tai, Huiling

2014-10-01

305

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

PubMed

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 coefficient without knowing the polymer coating features is presented for the first time. Three polymers: polyethyleneoxide (PEO), polyethylenevinylacetate (PEVA) and polyvinylalcohol (PVA) are used to perform the experiments. Six organic solvents: toluene, benzene, ethanol, acetone, hexane and octane are used as analytes. The response time, reversibility, hydrophilicity, sensitivity and selectivity of the polymer layers are discussed. According to the results, highly sensitive sensors for each of the analytes are proposed. Based on the characterization method, a convenient and flexible way to the construction of electric nose system by the polymer-coated resonant microcantilevers can be achieved. PMID:20541647

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

2010-06-25

306

Detection of HCN, HCO+, and HNC in the Mrk 231 molecular outflow. Dense molecular gas in the AGN wind  

NASA Astrophysics Data System (ADS)

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).

Aalto, S.; Garcia-Burillo, S.; Muller, S.; Winters, J. M.; van der Werf, P.; Henkel, C.; Costagliola, F.; Neri, R.

2012-01-01

307

Compression as a Tool to Detect Bose Glass in a Cold Atomic Gas  

SciTech Connect

We suggest that measuring the variation of the radius of an atomic cloud when the harmonic trap confinement is varied makes it possible to monitor the disappearance of the insulating Mott phase of an ultracold atomic gas trapped in a disordered optical lattice. This paves the way for an unambiguous identification of a Bose glass phase in the system.

Delande, Dominique [Laboratoire Kastler-Brossel, Universite Pierre et Marie Curie-Paris 6, ENS, CNRS, 4 Place Jussieu, F-75005 Paris (France); Zakrzewski, Jakub [Laboratoire Kastler-Brossel, Universite Pierre et Marie Curie-Paris 6, ENS, CNRS, 4 Place Jussieu, F-75005 Paris (France); Instytut Fizyki imienia Mariana Smoluchowskiego and Mark Kac Complex Systems Research Center, Uniwersytet Jagiellonski, ulica Reymonta 4, PL-30-059 Krakow (Poland)

2009-02-27

308

Separation and Detection of Toxic Gases with a Silicon Micromachined Gas Chromatography System  

NASA Technical Reports Server (NTRS)

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.

Kolesar, Edward S.; Reston, Rocky R.

1995-01-01

309

Fault detection and diagnosis for gas turbines based on a kernelized information entropy model.  

PubMed

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

Wang, Weiying; Xu, Zhiqiang; Tang, Rui; Li, Shuying; Wu, Wei

2014-01-01

310

Fault Detection and Diagnosis for Gas Turbines Based on a Kernelized Information Entropy Model  

PubMed Central

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

Wang, Weiying; Xu, Zhiqiang; Tang, Rui; Li, Shuying; Wu, Wei

2014-01-01

311

REVIEW OF METHODS OF OPTICAL GAS Detection by Direct Optical Spectroscopy, with Emphasis on Correlation Spectroscopy  

NASA Astrophysics Data System (ADS)

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.

Dakin, John P.; Chambers, Paul

312

Tin oxide nanowire sensors for highly sensitive detection of the toxic gas H2S  

NASA Astrophysics Data System (ADS)

We have realized gas sensor devices, which are based on a single SnO2-nanowire or a multiple SnO2-nanowire network as gas sensing components and are very sensitive to the toxic gas H2S. The nanowires are fabricated in a two-step atmospheric pressure synthesis process directly on the Si-chip by spray pyrolysis and subsequent annealing. Exposure of the single SnO2-nanowire sensor H2S with a concentration of only 1.4 ppm decreases the resistance by ~ 30%, while the multiple SnO2-nanowire network sensor exhibits a resistance decrease by ~ 90%. The nanowire sensors have extraordinary sensitivity with resolution limit in the ppb range and are able to measure concentrations well below the threshold limit value of 10 ppm. Due to their high performance the nanowire based sensors are basically suited for the realization of smart gas sensing devices for personal safety issues as well as industrial applications.

Köck, A.; Brunet, E.; Mutinati, G. C.; Maier, T.; Steinhauer, S.

2011-05-01

313

Inflations prior to Vulcanian eruptions and gas bursts detected by tilt observations at Semeru Volcano, Indonesia  

NASA Astrophysics Data System (ADS)

We examine the basic characteristics of inflations at Semeru Volcano, Indonesia, to clarify the pressurization process prior to two different styles of explosive eruptions: Vulcanian eruptions and gas bursts. Analysis of data obtained from tilt meters installed close to the active crater allows clarification of the common features and the differences between the two styles of eruptions. To improve the signal-to-noise ratio and to determine the mean characteristics of the inflations, we stack tilt signals obtained from eruptions of different magnitudes and evaluate the maximum amplitude of the seismic signal associated with these eruptions. Vulcanian eruptions, which explosively release large amounts of ash, are preceded by accelerating inflation about 200-300 s before the eruption, which suggests volume expansion of the gas phase. In contrast, gas bursts, which rapidly effuse water steam accompanied by explosive sounds, follow non-accelerating changes of inflation starting 20 s before each emission. Tilt amplitudes increase with the magnitude of eruptions for both eruption styles. This suggests that the volume and/or pressure of magma or gas stored in the conduit before eruptions controls the magnitude of volcanic eruptions. These results further suggest that the magnitude of eruptions can be predicted from geodetic measurements of volcano inflation.

Nishimura, Takeshi; Iguchi, Masato; Kawaguchi, Ryohei; Surono; Hendrasto, Muhamad; Rosadi, Umar

2012-05-01

314

Detection of greenhouse-gas-induced climatic change. Progress report, 1 December 1992--30 June 1993  

SciTech Connect

The aims of the US Department of Energy`s Carbon Dioxide Research Program are to improve assessments of greenhouse-gas-induced climatic change and to define and reduce uncertainties through selected research. The main research areas covered by this proposal are (b), First Detection and (c) Supporting Data. The project will also include work under area (a), Modeling: specifically, analysis of climate forcing factors, the development and refinement of transient response climate models, and the use of instrumental data in validating General Circulating Models (GCMs).

Wigley, T.M.L.; Jones, P.D.

1993-07-09

315

Detection of Breast Masses in Mammogram Images Using Growing Neural Gas Algorithm and Ripley's K Function  

Microsoft Academic Search

Breast cancer is a serious public health problem in several countries. Computer-aided detection\\/diagnosis systems (CAD\\/CADx)\\u000a have been used with relative success in aid of health care professionals. The goal of such systems is not to replace the professionals,\\u000a but to join forces in order to detect the different types of cancer at an early stage. The main contribution of this

Leonardo De Oliveira Martins; Aristófanes Corrêa Silva; Anselmo Cardoso De Paiva; Marcelo Gattass

2009-01-01

316

Determination of beryllium in natural waters in real time using electron capture detection gas chromatography  

Microsoft Academic Search

A method is described for the determination of Be in seawater at oceanic concentration levels (2-30 pM). The technique uses electron capture detection of the 1,1,1-trifluoro-2,4-pentanedione derivative and has a detection limit of approximately 2 pM and a relative precision of ca +\\/-5% at 23 pM. The method has been utilized in the laboratory on stored acidified seawater samples as

Chris I. Measures; J. M. Edmond

1986-01-01

317

Broad-spectrum determination of pesticides in groundwater by gas chromatography with electron capture detection, nitrogen-phosphorus detection, and tandem mass spectrometry.  

PubMed

Gas chromatography with electron capture detector (ECD), nitrogen-phosphorus detector (NPD), and tandem mass spectrometry (MS/MS) was used to identify 36 pesticides, widely used to control various pest and diseases in vegetables, in water after a preconcentration step on C18 cartridges. The recoveries obtained ranged from 70 to 135% at a fortification level of 100 ng/L with relative standard deviations of <36.2%. The limits of detection and quantitation were < or =48 and < or =160 ng/L, respectively. Important advantages of MS/MS over ECD and NPD in the determination of pesticides are also presented. The proposed analytical methodology was applied to the determination of pesticides in groundwater samples from an agricultural area, the Campo de Dalías (Almería, Spain). The most frequently encountered pesticides were endosulfan sulfate and metalaxyl, whereas the pesticide found at the highest concentration was fenamiphos. PMID:11767142

Frenich, A G; Pablos Espada, M C; Martínez Vidal, J L; Molina, L

2001-01-01

318

Detection of clenbuterol at trace levels in doping analysis using different gas chromatographic-mass spectrometric techniques.  

PubMed

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

Yang, Sheng; Liu, Xin; Xing, Yanyi; Zhang, Dapeng; Wang, Shan; Wang, Xiaobing; Xu, Youxuan; Wu, Moutian; He, Zhenwen; Zhao, Jian

2013-01-01

319

Detection of Potato Storage Disease via Gas Analysis: A Pilot Study Using Field Asymmetric Ion Mobility Spectrometry  

PubMed Central

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

Rutolo, Massimo; Covington, James A.; Clarkson, John; Iliescu, Daciana

2014-01-01

320

Detection system for a gas chromatograph. [. cap alpha. -methylnaphthalene,. beta. -methylnapthalene  

DOEpatents

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. 3 figures, 2 tables.

Hayes, J.M.; Small, G.J.

1982-04-26

321

Methane gas detection in environment using shape dependent ?-MoO3 nanosensor  

NASA Astrophysics Data System (ADS)

In this work, one dimensional (1-D) orthorhombic molybdenum trioxide (?-MoO3) nanostructures were synthesized using sol-gel technique and deposited on alumina substrates pre-patterned with interdigitated gold electrodes. Microstructure characterization was done using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and Micro Raman spectroscopy techniques. Different morphology viz nanospheres, nanoplatelets (300-600 nm) and nanobars (average length of 1?m, width of 100 nm and thickness of 100 nm) which are predominantly orthorhombic (?-MoO3) were obtained. The growth along (001) direction of the nanobars was enhanced by increasing the annealing temperature to 550°C. The fabricated sensors were tested with methane gas at elevated temperatures of 300°C. The structural and gas sensing properties of ?-MoO3 nanostructures are correlated.

Rakkesh, R. Ajay; Prasad, A. K.; Dash, S.; Tyagi, A. K.; Balakumar, S.

2012-06-01

322

The detection of evaporating hazardous material released from moving sources using a gas sensor network  

Microsoft Academic Search

Sensor information resulting from distributed locations and\\/or a multitude of instruments and heterogeneous sensors can increase the reliability of safety and security applications.A gas-sensing platform was developed, communicating via a wireless sensor network based on IEEE 802.15.4 and\\/or Ethernet. Data from this network are aggregated via a central server feeding its information via TCP\\/IP into subsequent data fusion software. The

C. Becher; P. Kaul; J. Mitrovics; J. Warmer

2010-01-01

323

Detection of water or gas entry into horizontal wells by using permanent downhole monitoring systems  

E-print Network

REVIEW One of the earliest works on temperature prediction was done by Ramey 7 . Ramey’s method approximates the pressure gradient of vertical wellbores by the hydrostatic difference, neglecting frictional pressure drop, and assumes steady-state heat...-phase ideal gas in vertical injection and production wells. Sagar 8 extended Ramey’s work to inclined wellbores. Hasan et al. 9 applied an energy equation for multi-phase flow and calculated temperature profile and history numerically. Hagoort 10...

Yoshioka, Keita

2007-09-17

324

Dopants in Tin Oxide Gas Sensor for Enhancing Detection of Alcohol  

Microsoft Academic Search

SnO2 films were prepared from sol-gel by spinning on substrate, with various dopants at 0.5-4 mole%. The dopants included Al, La, Nd, Mn, Ni, Cu, Sb, In, Pd, Pt, Nb, Si and Fe. The effects of these dopants towards the alcohol sensitivity of SnO2 gas sensor were investigated. Only four dopants , Al, Pt ,Pd and Si, have shown the

Paisan Setasuwon

325

Evaluation of time-of-flight mass spectrometric detection for fast gas chromatography  

Microsoft Academic Search

Separations below 1 s of a mixture of organic compounds ranging from C5 to C8 have been performed to investigate the performance of a time-of-flight mass spectrometer in fast gas chromatography. The gaseous samples were focussed on a cold trap, and then injected after thermal desorption to obtain the required narrow input band-widths. Also, to obtain a very fast separation,

M. M. van Deursen; J. Beens; H.-G. Janssen; P. A. Leclercq; CAMG Cramers

2000-01-01

326

S-MAyHEM: A Spectroscopic Microanalytical Hollow Enhanced Magnetron for Explosive Gas Detection  

Microsoft Academic Search

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

Rajesh Yalavarthy; Chester G. Wilson

2006-01-01

327

Laboratory Gas-phase Detection of the Cyclopropenyl Cation (C-C3H3 +)  

NASA Astrophysics Data System (ADS)

The cyclopropenyl cation (c-C3H3 +) is the smallest aromatic hydrocarbon molecule and considered to be a pivotal intermediate in ion-molecule reactions in space. An astronomical identification has been prohibited so far, because of a lack of gas-phase data. Here we report the first high resolution infrared laboratory gas-phase spectrum of the ? 4 (C-H asymmetric stretching) fundamental band of c-C3H3 +. The c-C3H3 + cations are generated in supersonically expanding planar plasma by discharging a propyne/helium gas pulse, yielding a rotational temperature of ~35 K. The absorption spectrum is recorded in the 3.19 ?m region using sensitive continuous-wave cavity ring-down spectroscopy. The analysis of about 130 ro-vibrational transitions results in precise spectroscopic parameters. These constants allow for an accurate comparison with high-level theoretical predictions, and provide the relevant information needed to search for this astrochemically relevant carbo-cation in space.

Zhao, Dongfeng; Doney, Kirstin D.; Linnartz, Harold

2014-08-01

328

Erratum: Detecting floating black holes as they traverse the gas disc of the Milky Way  

NASA Astrophysics Data System (ADS)

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 and mm/sub-mm synchrotron emission from accelerated electrons. We calculate the synchrotron flux to be $\\sim \\rm 0.01-10\\, mJy$ at GHz frequency, detectable by Jansky Very Large Array, and $\\sim 10-100\\,\\mu\\rm Jy$ at $\\sim10^{10}-10^{12} \\,\\rm Hz$ frequencies, detectable by Atacama Large Millimeter/sub-millimter Array. 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.

Wang, Xiawei; Loeb, Abraham

2014-12-01

329

Detecting floating black holes as they traverse the gas disk of the Milky Way  

E-print Network

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.

Wang, Xiawei

2014-01-01

330

Headspace gas chromatography with flame ionization detection (HS-GC-FID) for the determination of dissolved methane in wastewater.  

PubMed

There is currently a need for a simple, accurate and reproducible method that quantifies the amount of dissolved methane in wastewater in order to realize the potential methane that can be recovered and account for any emissions. This paper presents such a method, using gas chromatography with flame ionization detection fitted with a GS-Gas PRO column coupled with a headspace auto sampler. A practical limit of detection for methane of 0.9 mg L(-1), with a retention time of 1.24 min, was obtained. It was found that the reproducibility and accuracy of the method increased significantly when samples were collected using an in-house constructed bailer sampling device and with the addition of 100 ?L hydrochloric acid (HCl) and 25% sodium chloride (NaCl) and sonication for 30 min prior to analysis. Analysis of wastewater samples and wastewater sludge collected from a treatment facility were observed to range from 12.51 to 15.79 mg L(-1) (relative standard deviation (RSD) 8.1%) and 17.56 to 18.67 mg L(-1) (RSD 3.4%) respectively. The performance of this method was validated by repeatedly measuring a mid-level standard (n = 8; 10 mg L(-1)), with an observed RSD of 4.6%. PMID:25225939

Beale, D J; Tjandraatmadja, G; Toifl, M; Goodman, N

2014-01-01

331

Process-based approach to CO2 leakage detection by vadose zone gas monitoring at geologic CO2 storage sites  

NASA Astrophysics Data System (ADS)

A critical issue for geologic carbon sequestration is the ability to detect CO2 in the vadose zone. Here we present a new process-based approach to identify CO2 that has leaked from deep geologic storage reservoirs into the shallow subsurface. Whereas current CO2 concentration-based methods require years of background measurements to quantify variability of natural vadose zone CO2, this new approach examines chemical relationships between vadose zone N2, O2, CO2, and CH4 to promptly distinguish a leakage signal from natural vadose zone CO2. The method uses sequential inspection of the following gas concentration relationships: 1) O2 versus CO2 to distinguish in-situ vadose zone background processes (biologic respiration, methane oxidation, and CO2 dissolution) from exogenous deep leakage input, 2) CO2 versus N2 to further distinguish dissolution of CO2 from exogenous deep leakage input, and 3) CO2 versus N2/O2 to assess the degree respiration, CH4 oxidation and atmospheric mixing/dilution occurring in the system. The approach was developed at a natural CO2-rich control site and successfully applied at an engineered site where deep gases migrated into the vadose zone. The ability to identify gas leakage into the vadose zone without the need for background measurements could decrease uncertainty in leakage detection and expedite implementation of future geologic CO2 storage projects.

Romanak, K. D.; Bennett, P. C.; Yang, Changbing; Hovorka, Susan D.

2012-08-01

332

Detection of greenhouse-gas-induced climatic change. Progress report, 1 December 1991--30 June 1994  

SciTech Connect

In addition to changes due to variations in greenhouse gas concentrations, the global climate system exhibits a high degree of internally-generated and externally-forced natural variability. To detect the enhanced greenhouse effect, its signal must be isolated from the ``noise`` of this natural climatic variability. A high quality, spatially extensive data base is required to define the noise and its spatial characteristics. To facilitate this, available land and marine data bases will be updated and expanded. The data will be analyzed to determine the potential effects on climate of greenhouse gas concentration changes and other factors. Analyses will be guided by a variety of models, from simple energy balance climate models to ocean General Circulation Models. Appendices A--G contain the following seven papers: (A) Recent global warmth moderated by the effects of the Mount Pinatubo eruption; (B) Recent warming in global temperature series; (C) Correlation methods in fingerprint detection studies; (D) Balancing the carbon budget. Implications for projections of future carbon dioxide concentration changes; (E) A simple model for estimating methane concentration and lifetime variations; (F) Implications for climate and sea level of revised IPCC emissions scenarios; and (G) Sulfate aerosol and climatic change.

Wigley, T.M.L.; Jones, P.D.

1994-07-01

333

Selectivity enhancement in photoacoustic gas analysis via phase-sensitive detection at high modulation frequency  

NASA Technical Reports Server (NTRS)

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.

Kosterev, Anatoliy (Inventor)

2010-01-01

334

Atmospheric gas detection using broadband mid-IR thulium fiber-based sources  

NASA Astrophysics Data System (ADS)

We present a Tm:fiber based broadband ASE source which was used for atmospheric CO2 detection. The average spectral power of this source was limited to ~6.1 ?W/nm which was the main limitation in detection of trace concentrations of gases. This shortcoming was overcome by using an ultrashort pulsed Raman amplifier system with maximum of ~127 ?W/nm of spectral power density which was able to provide sensitivity better than 300 ppm for CO2. In addition, improving the average power of the ASE provided an essential tool in lab to characterize optical elements with sharp spectral features around 2 ?m.

Kadwani, Pankaj; Sims, Robert A.; Chia, Jeffrey; Altal, Falah; Shah, Lawrence; Richardson, Martin C.

2011-06-01

335

Detection of low concentration formaldehyde gas by photonic crystal sensor fabricated by nanoimprint process in polymer material  

NASA Astrophysics Data System (ADS)

This paper describes experimental measurement results for photonic crystal sensor devices which have been functionalized for gas sensing applications. The sensor consists of a two dimensional photonic crystal etched into a slab waveguide having a refractive index of 1.7-1.9. Test devices were fabricated from SiON material on silicon / silicon dioxide platform, and also in polymer materials on silicon platform. The inorganic photonic crystals were made using direct write electron-beam lithography and reactive ion etching. The polymeric devices were made by nano-imprint lithography using the SiON structure as the imprint master. The high refractive index polymer was composed of a TiO2 - UV resin nanocomposite having a nanoparticle fraction between 50 and 60 wt%. This resulted in a tunable refractive index between 1.7 and 1.85. Devices were functionalized for gas sensing applications by coating the surface with a chemical receptor. This responsive layer reacts with the target gas and changes its refractive index. This change causes the angle of out-coupling to change slightly. In this paper we report successful detection of formaldehyde in air at sub ppm levels, and discuss details of chemical functionalization of the PC sensor.

Boersma, A.; van Ee, Renz J.; Stevens, Ralph S. A.; Saalmink, Milan; Charlton, Martin D. B.; Pollard, Michael E.; Chen, Ruiqi; Kontturi, Ville; Karioja, Pentti; Alajoki, Teemu

2014-05-01

336

Detecting Low-Frequency Seismic Signals From Surface Microseismic Monitoring of Hydraulic Fracturing of a Tight-Sand Gas Reservoir  

NASA Astrophysics Data System (ADS)

For both surface and downhole microseismic monitoring, generally geophones with resonance frequency greater than 4.5 Hz are used. Therefore, useful information below 4.5 Hz may not be detected. In a recent experiment, we installed14 3-component broadband seismic sensors on the surface to monitor the process of hydraulic fracturing of tight sand gas reservoirs. The sensor has a broad frequency range of 30 s to 100 Hz with a very high sensitivity of 2400 m/v/s. The reservoirs are located around 1.5 km depth. There are two fracturing stages along a vertical well, lasting for about 2 hours. We recorded the data continuously during the fracturing process at a sampling rate of 50 Hz. From time-frequency analysis of continuous data, we found some high-energy signals at resonance frequencies between 10 and 20 Hz and a relatively weaker signal at a resonance frequency of ~27 Hz during the hydraulic fracturing. These signals with various resonance frequencies are likely caused by vibrations of high-pressure pipes. In addition to the resonance frequencies, the time-frequency analysis also showed consistent low frequency signals between 3 and 4 Hz at different time. The move-out analysis showed that these signals traveled at shear-wave speeds. We have detected 77 effective low frequency events during the 2-hour hydraulic fracturing process, among which 42 were located by a grid-search location method. The horizontal distribution of the events aligns with the maximum horizontal compressive stress direction. Because of the uncertainty in the velocity model, the low-frequency seismic events are not located in the fracturing depths. Recently, long-period, long-duration seismic events in the frequency band of 10 to 80 Hz were detected during hydraulic fracture stimulation of a shale gas reservoir, which may be caused by slow slip along faults/fractures (Das and Zoback, 2011). In the active volcanic areas, monochromatic events that are related to circulation of hydrothermal fluids are often detected. Our detected low frequency seismic signals have waveforms and frequency contents resembling the monochromatic events detected in volcanic areas, therefore we believe they are also likely caused by movement of fracturing fluids.

Yu, H.; Zhang, H.; Zeng, X.

2013-12-01

337

Detection of soil microorganism in situ by combined gas chromatography mass spectrometry  

NASA Technical Reports Server (NTRS)

Experimental tests were made to determine whether analysis of volatile metabolic products, formed in situ, is a viable procedure for an extraterrestrial life detection system. Laboratory experiments, carried out under anaerobic conditions with addition of carbon source, extended to include a variety of soils and additional substrates. In situ experiments were conducted without amendment using a vacuum sampling system.

Alexander, M.; Duxbury, J. M.; Francis, A. J.; Adamson, J.

1972-01-01

338

Systems and methods of monitoring acoustic pressure to detect a flame condition in a gas turbine  

DOEpatents

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.

Ziminsky, Willy Steve (Simpsonville, SC); Krull, Anthony Wayne (Anderson, SC); Healy, Timothy Andrew (Simpsonville, SC), Yilmaz, Ertan (Glenville, NY)

2011-05-17

339

Gas detection using low-temperature reduced graphene oxide sheets Ganhua Lu,1  

E-print Network

of hydrophilic graphite oxide in water. GO is electrically insu- lating but it can become conductive by exposing it to reduc- ing agents, such as hydrazine,13 NaBH4,14 through high- temperature treatment,15 or via UVGas detection using low-temperature reduced graphene oxide sheets Ganhua Lu,1 Leonidas E. Ocola,2

Chen, Junhong

340

Determination of C 1 ?C 4 fatty acids as p-bromophenacyl esters using glass-capillary gas chromatography and electron-capture detection  

Microsoft Academic Search

Summary  A method for the determination of low relative molecular mass carboxylic acids (C1–C4) in water is reported. The acids are converted to p-bromophenacyl esters prior to a glass-capillary gas chromatographic separation. By utilizing electron-caputre detection the detectability is substantially improved compared to flame-ionization detection. A comparison of three different ways to treat the water samples and to produce the derivatives

M. Larsson; C. Roos

1983-01-01

341

CO-laser-based photoacoustic trace-gas detection: applications in postharvest physiology  

NASA Astrophysics Data System (ADS)

A sensitive CO-laser-based photoacoustic trace-gas detector has been applied to study physiological processes in biological samples. A continuous flow-through system at atmospheric pressure leads the released trace gases from the sample to the photoacoustic resonator cells at flow rates where these processes can be studied with high time resolution. We focus here on transient effects that were found during fermentation of red bell peppers and apples, yielding in particular ethanol and acetaldehyde. Results are discussed also in the light of simultaneous O2 measurements using polarographic oxygen sensors.

Oomens, J.; Zuckermann, H.; Persijn, S.; Parker, D. H.; Harren, F. J. M.

1998-10-01

342

Low-Dimensional Palladium Nanostructures for Fast and Reliable Hydrogen Gas Detection  

PubMed Central

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

Noh, Jin-Seo; Lee, Jun Min; Lee, Wooyoung

2011-01-01

343

Do We Need Exercise Tests to Detect Gas Exchange Impairment in Fibrotic Idiopathic Interstitial Pneumonias?  

PubMed Central

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 PaO2, P(A-a)O2 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)O2, peak and/or no desaturation during the 6MWT. The 3 patients with normal DLCO also had normal PaO2, normal P(A-a)O2, peak, and normal oxygen saturation during 6MWT. Our results demonstrate that in fibrotic IIP, DLCO better defines impairment of pulmonary gas exchange than resting PaO2, exercise P(A-a)O2, peak, or 6MWT SpO2. PMID:22900170

Wallaert, Benoit; Wemeau-Stervinou, Lidwine; Salleron, Julia; Tillie-Leblond, Isabelle; Perez, Thierry

2012-01-01

344

Continuous-wave terahertz by photomixing: applications to gas phase pollutant detection and quantification  

NASA Astrophysics Data System (ADS)

Recent advances in the development of monochromatic continuous-wave terahertz sources suitable for high resolution gas phase spectroscopy and pollution monitoring are reviewed. Details of a source using an ultra fast opto-electronic photomixing element are presented. The construction of a terahertz spectrometer using this source has allowed spectroscopic characterisation and application studies to be completed. Analysis of H 2S and OCS under laboratory conditions are used to demonstrate the spectrometer performance, and the determination of the transition line strengths and pressure self broadening coefficients for pure rotational transitions of OCS. The spectral purity 5 MHz, tunability 0.3 to 3 THz, and long wavelength ?200 ?m of this source have been exploited to identify and quantify numerous chemical species in cigarette smoke. The key advantages of this frequency domain are its high species selectivity and the possibility to make reliable measurements of gas phase samples heavily contaminated by aerosols and particles. To cite this article: F. Hindle et al., C. R. Physique 9 (2008).

Hindle, Francis; Cuisset, Arnaud; Bocquet, Robin; Mouret, Gaël

2008-03-01

345

Near infrared frequency comb vernier spectrometer for broadband trace gas detection.  

PubMed

We present a femtosecond frequency comb vernier spectrometer in the near infrared with a femtosecond Er doped fiber laser, a scanning high-finesse cavity and an InGaAs camera. By utilizing the properties of a frequency comb and a scanning high-finesse cavity such a spectrometer provides broad spectral bandwidth, high spectral resolution, and high detection sensitivity on a short time scale. We achieved an absorption sensitivity of ~8 × 10-8 cm-1Hz-1/2, corresponding to a detection limit of ~70 ppbv for acetylene, with a resolution of ~1.1 GHz in single images taken in 0.5 seconds and covering a frequency range of ~5 THz. Such measurements have broad applications for sensing greenhouse gases in this fingerprint near infrared region with a simple apparatus. PMID:25321773

Zhu, Feng; Bounds, James; Bicer, Aysenur; Strohaber, James; Kolomenskii, Alexandre A; Gohle, Christoph; Amani, Mahmood; Schuessler, Hans A

2014-09-22

346

On the use of quadrupole mass spectrometric detection for flow modulated comprehensive two-dimensional gas chromatography.  

PubMed

Flow modulated comprehensive two-dimensional gas chromatography with simultaneous flame ionization detection (FM GC×GC-FID) and quadrupole mass spectrometric detection (FM GC×GC-qMSD) was applied to the analysis of a quantitative reference standard sample covering the C5-C14 hydrocarbon range and a kerosene sample. This study reports the influence of the data acquisition frequency (DAF) of the qMSD on the qualitative and quantitative data. The DAF was varied between 5.27 and 25.45Hz. In GC×GC-qMSD, the characterization of peaks is getting worse with decreasing qMSD frequencies which deteriorate the quality of the 2D contour plots of the separations. It is, however, demonstrated that the improved characterization of the peaks at high qMSD frequencies is combined with loss in sensitivity and in spectral quality. Dependences of a (2)D hydrocarbon peak area (?Ai of all corresponding (2)D peaks) on the DAFs show negative slopes which testify the conclusion that the sensitivity of GC×GC-qMSD determinations decreases with the increase of DAF. Consequently, the limits of detection (LOD) and quantification (LOQ) increase with the increase of DAF. Moreover, quality criteria on recorded spectral data also indicate that the lower the DAF is, the higher is the spectral quality. PMID:24461452

Gorovenko, Roman; Krup?ík, Ján; Špánik, Ivan; Bo?ková, Ingrid; Sandra, Pat; Armstrong, Daniel W

2014-02-21

347

Gas sensors based on deposited single-walled carbon nanotube networks for DMMP detection  

NASA Astrophysics Data System (ADS)

Sensors based on single-walled carbon nanotube (SWNT) networks were fabricated and their sensitive properties for the nerve agent stimulant dimethyl methylphosphonate (DMMP) vapor were investigated at room temperature. The SWNT networks were deposited on oxidized silicon surface functionalized with 3-aminopropyltrimethysilane (APS). Combining with a traditional silicon process, SWNT-based gas sensors were made at a wafer scale. The effects of the density of deposited SWNTs on the sensor response were studied. The excellent response is obtained under a density of 30-40 tubes µm-2. The sensors exhibit high resistance response, fast response time, rapid recovery and good reproducibility for DMMP vapor. The deposited SWNT sensors will be potentially extended to large-scale fabrication.

Wang, Yanyan; Zhou, Zhihua; Yang, Zhi; Chen, Xiaohang; Xu, Dong; Zhang, Yafei

2009-08-01

348

QCM gas phase detection with ceramic materials—VOCs and oil vapors  

Microsoft Academic Search

Titanate sol–gel layers imprinted with carbonic acids were used as sensitive layers on quartz crystal microbalance. These\\u000a functionalized ceramics enable us detection of volatile organic compounds such as ethanol, n-propanol, n-butanol, n-hexane, n-heptane, n-\\/iso-octane, and n-decane. Variation of the precursors (i.e., tetrabutoxy titanium, tetrapropoxy titanium, tetraethoxy titanium) allows us to\\u000a tune the sensitivity of the material by a factor of

Usman Latif; Andreas Rohrer; Peter A. Lieberzeit; Franz L. Dickert

2011-01-01

349

SIM PlanetQuest Key Project Precursor Observations to Detect Gas Giant Planets Around Young Stars  

E-print Network

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 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 moves the most targets from the SIM-YSO program is photometric variability.

Angelle Tanner; Charles Beichman; Rachel Akeson; Andrea Ghez; Konstantin N. Grankin; William Herbst; Lynne Hillenbrand; Marcos Huerta; Quinn Konopacky; Stanimir Metchev; Subhanjoy Mohanty; L. Prato; Michal Simon}

2007-05-25

350

SIM PlanetQuest Key Project Precursor Observations to Detect Gas Giant Planets Around Young Stars  

NASA Technical Reports Server (NTRS)

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.

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

351

The determination by gas chromatography with atomic emission detection of total sulfur in fuels used as forensic evidence.  

PubMed

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

Kaneko, Tsuyoshi; Yoshida, Hiroaki; Suzuki, Shinichi

2008-05-20

352

THE DIRECT DETECTION OF COOL, METAL-ENRICHED GAS ACCRETION ONTO GALAXIES AT z {approx} 0.5  

SciTech Connect

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.

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

353

Comprehensive two-dimensional gas chromatography coupled with fast sulphur-chemiluminescence detection: implications of detector electronics.  

PubMed

Within the petrochemical industry, there has been a growing interest in methods capable of providing detailed information on the distribution of sulphur-containing compounds in various product streams, going down to the level of separating and quantifying individual sulphur species. Since no single capillary gas chromatographic column is able to perform this separation, a refuge to multi-dimensional separation techniques has to be taken. In this respect, comprehensive two-dimensional gas chromatography (GC x GC) coupled with sulphur chemiluminescence detection (SCD) has shown to be highly promising. It has been suggested, however, that the detector volume of an SCD restricts its potential to keep up with the fast second-dimension separations of contemporary GC x GC. In this paper, we will demonstrate that the lack of speed of the SCD does not originate from its physical dimensions, but is largely determined by the speed of the electronics used. Additionally, some typical examples will be presented to illustrate the potential of GC x GC coupled with fast SCD. PMID:15503928

Blomberg, Jan; Riemersma, Toby; van Zuijlen, Manfred; Chaabani, Hassan

2004-09-24

354

Controlled growth of conical nickel oxide nanocrystals and their high performance gas sensing devices for ammonia molecule detection.  

PubMed

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

Wang, Jian; Yang, Fan; Wei, Xiaowei; Zhang, Yafei; Wei, Liangming; Zhang, Jianjun; Tang, Qifeng; Guo, Biao; Xu, Lei

2014-08-21

355

Detection and Mapping of Decoupled Stellar and Ionized Gas Structures in the Ultraluminous Infrared Galaxy IRAS 12112+0305.  

PubMed

Integral field optical spectroscopy with the INTEGRAL fiber-fed system and Hubble Space Telescope optical imaging are used to map the complex stellar and warm ionized gas structure in the ultraluminous infrared galaxy IRAS 12112+0305. Images reconstructed from wavelength-delimited extractions of the integral field spectra reveal that the observed ionized gas distribution is decoupled from the stellar main body of the galaxy, with the dominant continuum and emission-line regions separated by projected distances of up to 7.5 kpc. The two optical nuclei are detected as apparently faint emission-line regions, and their optical properties are consistent with being dust-enshrouded weak [O i] LINERs. The brightest emission-line region is associated with a faint (mI=20.4), giant H ii region of 600 pc diameter, in which a young ( approximately 5 Myr) massive cluster of about 2x107 M middle dot in circle dominates the ionization. Internal reddening toward the line-emitting regions and the optical nuclei ranges from 1 to 8 mag in the visual. Taking the reddening into account, the overall star formation in IRAS 12112+0305 is dominated by starbursts associated with the two nuclei and corresponds to a star formation rate of 80 M middle dot in circle yr-1. PMID:10727379

Colina; Arribas; Borne; Monreal

2000-04-10

356

Naturally fractured tight gas reservoir detection optimization. Annual report, August 1994--July 1995  

SciTech Connect

This report details the field work undertaken Blackhawk Geosciences and Lynn, Inc. during August 1994 to July 1995 at a gas field in the Wind River Basin in central Wyoming. The work described herein consisted of four parts: 9C VSP in a well at the site; additional processing of the previously recorded 3D P-wave survey on the site and Minivibrator testing; and planning and acquisition of a 3-D, 3-C seismic survey. The objectives of all four parts were to characterize the nature of anisotropy in the reservoir. With the 9C VSP, established practices were used to achieve this objective in the immediate vicinity of the well. The additional processing of the 3-D uses developmental techniques to determine areas of fractures in 3-D surveys. With the multicomponent studies, tests were conducted to establish the feasibility of surface recording of the anisotropic reservoir rocks. The 3-D, 3-C survey will provide both compressional and shear wave data sets over areas of known fracturing to verify the research.

NONE

1995-09-01

357

Gas sensor based on nano ZSM-5 zeolite films for the nerve agent simulant dimethylmethylphosphonate detection  

NASA Astrophysics Data System (ADS)

The piezoelectric sensor device coated with nanosize ZSM-5 zeolite films has beem fabricated. The Nerve agent simulant Dimethylmethylphosphonate has been tested with this piezoelectric sensor devices. The frequency shifts to time at 1 ppm, 5ppm and 20ppm DMMP are examined respectively. The minimum detection concentration of 1ppm DMMP has been obtained in the N2 at 293K. 1 ppm is lower than the EC50 concentration value (where EC50 is the airborne concentration sufficient to induce severe effects in 50% of those exposed for 30 min). The frequency sensitivity was found to be about 60HZ / ppm. The effect of acetone on the ZSM-5 zeolite film was also investigated for the selectivity test. Using principle component analysis (PCA), we can qualify and quantify these testing gases.

Xie, Haifen; Ting, Yu; Sun, Xiaoxiang; Jia, Zhou; Huang, Yiping

2004-12-01

358

Synthesis of Inorganic-Organic Hybrid Materials Designed for Radiation Detection, Luminescence, and Gas Storage  

NASA Astrophysics Data System (ADS)

Materials discovery is the driving force behind the research presented herein. Basic research has been conducted in order to obtain a better understanding of coordination chemistry and structural outcomes, particularly within the area of trivalent lanthanides. Discovering new materials is one route to further advancement of technology; another one is the focus on incremental changes to already existing materials. Often the building blocks of a compound are chosen in an effort to synthesize a material that makes use of the properties of each individual component and may result in a better, more robust, applicable material. The combination of organic and inorganic components for the synthesis of novel materials with potential applications such as scintillation photoluminescence, catalysis, and gas storage are the focus of the research presented herein. The first part focuses on lanthanide organic hybrid materials, where the synthesis of a new family of potential scintillating materials was undertaken and yielded improved understanding of the control that can be achieved over the topological structure of these materials by controlling the coordinating crystallization solvents. This research has led to the synthesis of an array of unique motifs, ranging from dimeric complexes, tetrameric complexes, to 1-D chains, and most intriguing of all, catenated tetradecanuclear rings. These rings represent the largest lanthanide rings synthesized to date, the next largest multinuclear rings, until now, were dodecanuclear complexes of alkoxides. From a basic research standpoint this is an exciting new development in lanthanide coordination chemistry and illustrates the importance of steric effects upon a system. These complexes are potential scintillators, supported by their luminescence and measurements of similar compounds that demonstrate surprising scintillation efficiencies. In the second part, other hybrid materials that have also been prepared are discussed, including the synthesis of a polyoxometallate compound (POM) containing a typical Keggin ion, which is charge-balanced via protonated organic ligands. POMs are one of the most studied inorganic clusters owing to their potential catalytic capabilities. A third part concerns a pseudo hybrid material consisting of boron, a metalloid, and a polymeric network, which includes a site of contortion, provided by the incorporation of a disulfide linkage and polymerized through boronate ester linkages. Tuning of this disulfide-linked polymer of intrinsic microporosity has the potential to lead to a dynamic material that may have gas sorption properties. The fourth part describes research in which the goal was to synthesize novel metal organic frameworks (MOFs) for solid state lighting applications via the synthesis of long, rigid, highly conjugated ligands. The successful synthesis of these ligands and optimization of the reaction conditions through the use of cyano derivatives as intermediates was discovered. Subsequent incorporation into coordination polymers with the transition elements was unsuccessful. This is believed to be the case due to the rigidity of the ligands and their inability to be flexible enough to successfully coordinate to a metal cation in a crystalline form.

Vaughn, Shae Anne

359

Fish freshness detection by a computer screen photoassisted based gas sensor array.  

PubMed

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

Alimelli, Adriano; Pennazza, Giorgio; Santonico, Marco; Paolesse, Roberto; Filippini, Daniel; D'Amico, Arnaldo; Lundström, Ingemar; Di Natale, Corrado

2007-01-23

360

Determination of nitrogen dioxide in air compressed gas mixtures by quantitative tunable diode laser absorption spectrometry and chemiluminescence detection  

SciTech Connect

Tunable diode laser absorption spectrometry (TDLAS) and chemiluminescence detection (CD) were both employed for the determination of seven NO/sub 2//air compressed gas mixtures in the 2.3-2500 ppm (by mole) concentration range. In the diode laser determinations, they employed a variety of different measurement and calibration approaches based upon direct absorption and second harmonic detection. Such redundancy enabled them to carry out a careful analysis thus minimizing systematic errors. After HNO/sub 3/ was accounted for, measured in all but one cylinder examined, the TDLAS and CD NO/sub 2/ determinations were generally found to agree to better than 3%. Fourier transform infrared absorption spectrometry was also employed in the determination of one particular cylinder, the nominal 2500 ppm cylinder. The resulting NO/sub 2/ determination was within 0.2% of that obtained by TDLAS. However, a small remaining discrepancy on the order of 5-8% was still observed between these two results and those determined by CD even after HNO/sub 3/ was accounted for. Further studies pointed to the presence of an additional nitrogen-containing compound in this cylinder.

Fried, A.; Sams, R.; Dorko, W.; Elkins, J.W.; Cai, Z.

1988-03-01

361

Simultaneous detection and quantitation of diethylene glycol, ethylene glycol, and the toxic alcohols in serum using capillary column gas chromatography.  

PubMed

Determination of toxic glycols and alcohols in an emergency setting requires a rapid yet accurate and reliable method. To simultaneously determine diethylene glycol (DEG) along with ethylene glycol, methanol, isopropanol, acetone, and ethanol, we modified a previously developed gas chromatographic (GC) method. The system used a Hewlett-Packard 6890 GC with EPC, a Gooseneck splitless liner, and an Rtx-200 capillary column (30 m x 0.53-mm i.d., 3 mm). After serum samples were deproteinized using ultrafiltration (Millipore Ultrafree-MC), 1 mL of the protein-free filtrate was manually injected into the GC. Internal standards for alcohols (and acetone) and glycols were n-propanol and 1,3-butanediol, respectively. All compounds eluted within 3.5 min (linear temperature gradient from 40 to 260 degrees C); total run time was 6.5 min. Limit of detection and linear range for all compounds were 1 or 2.5 mg/dL and 0-500 mg/dL, respectively. In addition, there was no interference from propionic acid, propylene glycol, and 2,3-butanediol. The modifications in the equipment and temperature program allowed increased resolution and thus, detection and reliable quantitation of DEG and other common toxic glycols and alcohols of clinical interest. PMID:11043669

Williams, R H; Shah, S M; Maggiore, J A; Erickson, T B

2000-10-01

362

Detection of an Extended Human Volatome with Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometry  

PubMed Central

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

Phillips, Michael; Cataneo, Renee N.; Chaturvedi, Anirudh; Kaplan, Peter D.; Libardoni, Mark; Mundada, Mayur; Patel, Urvish; Zhang, Xiang

2013-01-01

363

A NEW METHOD OF PEAK DETECTION FOR ANALYSIS OF COMPREHENSIVE TWO-DIMENSIONAL GAS CHROMATOGRAPHY MASS SPECTROMETRY DATA*  

PubMed Central

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.

Kim, Seongho; Ouyang, Ming; Jeong, Jaesik; Shen, Changyu; Zhang, Xiang

2014-01-01

364

Determination of mercaptans at microgram-per-cubic-meter levels in air by gas chromatography with photoionization detection  

SciTech Connect

A method for the gas chromatographic (GC) determination of ethyl, tert-butyl, propyl, sec-butyl, and n-butyl mercaptans in air using a photoionization detector (PID) was established by using air sampling bags. Up to 5 mL of sample was injected into a Hewlett-Packard Model 588OA GC fitted with a 9 ft glass column packed with 100/120 mesh Chromosorb W AW DMCS and coated with 15% SF-96 and 6% OV-225. The oven was held at 65 /sup 0/C and the nitrogen flow rate was 30 mL/min. The photoionization detector was attached to the GC and held at 200 /sup 0/C. The GC detection limit was determined to be 0.06 ng for n-butyl mercaptan and 0.02 ng for the remaining mercaptans with precisions (n = 8, 1sigma, 4 ng) of +/- 7.3, +/- 8.5, +/- 8.1, and +/- 10% for ethyl, tert-butyl, propyl, sec-butyl, and n-butyl mercaptan, respectively. With a 5-mL injection volume, sensitivity is about 2 ..mu..g/m/sup 3/ which is as sensitive as detection by smell since the oder threshold is about 2-4 ..mu..g/m/sup 3/.

Stein, V.B.; Narang, R.S.

1982-05-01

365

Portable fiber-coupled diode-laser-based sensor for multiple trace gas detection  

NASA Technical Reports Server (NTRS)

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.

Lancaster, D. G.; Richter, D.; Tittel, F. K.

1999-01-01

366

Parameter optimization of a microfabricated surface acoustic wave sensor for inert gas detection  

SciTech Connect

This work is related to designing, fabricating, and testing a surface acoustic wave sensor to be used for detecting metastable inert gases, particularly helium. The assembly consists of two microsensor configurations: (a) a reference device with no deposition at the delay line and (b) a sensing device with an Au-activated TiO{sub 2} e-beam-deposited thin film on the delay line. The interdigitated transducers and delay lines are fabricated by photolithography techniques on a single Y-cut LiNbO{sub 3} substrate oriented for Z-propagation of the acoustic waves. Variation in electrical conductivity of the Au-activated TiO{sub 2} film due to exposure to metastable He is translated as a frequency change in the assembly. Various characteristics of the surface acoustic microsensor have been studied to better understand and optimize the variation of acoustic wave velocity and the operating frequency of the microdevice. Methods for the TiO{sub 2} thin-film deposition are discussed.

Ahuja, S.; Ross, C.; Chien, H.T.; Raptis, A.C. [and others

1996-12-31

367

Detecting Intracluster Gas Motion in Galaxy Clusters: Mock Astro-E2 Observations  

E-print Network

We explore the detectability of bulk motions in the X-ray emitting intracluster medium (ICM) using a catalog of 1,836 mock Astro-E2 observations of simulated clusters of galaxies. We generate high resolution mock spectra for two observing strategies: a four-pointing mosaic and a single central pointing. Normalizing to 200 (400) photons in the iron K-alpha region for the mosaic (central) study, we fit Poisson realizations of each simulated spectrum to a velocity broadened isothermal plasma emission model. We confirm that the velocity characteristics (mean and dispersion) returned by the spectral fittings are unbiased measures of the emission-weighted values within the observed region, with scatter 55 km/s. The maximum velocity difference between mosaic element pairs $\\Delta v_{\\rm max}$ has ~ 6% likelihood of being transonic ($\\Delta v_{\\rm max} \\ge 0.5 c_s$), and the likelihood falls steeply, $p \\spropto (\\Delta v_{\\rm max}/c_s)^{-4}$, at high Mach number. The velocity broadening parameter $\\sigma_v$ from the central pointing fit exceeds the thermal value in 49% of the cases, with again a $\\sigma_v^{-4}$ tail at large dispersion. We present as case studies the clusters that yield the strongest signal for each observing strategy.

Andrew Pawl; August E. Evrard; Renato A. Dupke

2005-03-12

368

Membrane oxygenator heat exchanger failure detected by unique blood gas findings.  

PubMed

Failure of components integrated into the cardiopulmonary bypass circuit, although rare, can bring about catastrophic results. One of these components is the heat exchanger of the membrane oxygenator. In this compartment, unsterile water from the heater cooler device is separated from the sterile blood by stainless steel, aluminum, or by polyurethane. These areas are glued or welded to keep the two compartments separate, maintaining sterility of the blood. Although quality control testing is performed by the manufacturer at the factory level, transport presents the real possibility for damage. Because of this, each manufacturer has included in the instructions for use a testing procedure for testing the integrity of the heat exchanger component. Water is circulated through the heat exchanger before priming and a visible check is made of the oxygenator bundle to check for leaks. If none are apparent, then priming of the oxygenator is performed. In this particular case, this procedure was not useful in detecting communication between the water and blood chambers of the oxygenator. PMID:24779125

Hawkins, Justin L

2014-03-01

369

Evaluation of gas-liquid chromatography (GLC) for rapid detection of Clostridium difficile in fecal specimens.  

PubMed

Clostridium difficile intestinal infection is a major nosocomial hazard in patients receiving antimicrobial therapy. Rationale for rapid diagnosis include lifesaving antimicrobial therapy in patients with severe colitis and early isolation measures for transmission control. We have therefore analysed the sensitivity, specificity and predictive value of GLC identification of isocaproic acid in diarrheic stools from adult hospitalized patients in comparison with selective fecal culture on Cycloserine Cefoxitin Fructose Agar. During the study period, the prevalence of positive culture for C. difficile was 38/595 fecal specimens (6.4%). Compared with culture, GLC had a sensitivity of 24/38 (63%) and a specificity of 524/557 (94%). The predictive value of a positive GLC was 24/57 (42%) and of a negative GLC was 524/538 (97%). Measurement of the isocaproic acid peak height did not allow determination of a cutt-off value improving the test accuracy. The sensitivity of detection of isocaproic acid in stools by GLC is too low to be used as screening test for C. difficile infection. However, in a low prevalence population, a positive GLC test increased the pre-test probability of infection sevenfold. PMID:7597879

Nonhoff, C; Struelens, M J; Serruys, E

1995-01-01

370

Detection of designer steroid methylstenbolone in "nutritional supplement" using gas chromatography and tandem mass spectrometry: elucidation of its urinary metabolites.  

PubMed

The use of "nutritional supplements" containing unapproved substances has become a regular practice in amateur and professional athletes. This represents a dangerous habit for their health once no data about toxicological or pharmacological effects of these supplements are available. Most of them are freely commercialized online and any person can buy them without medical surveillance. Usually, the steroids intentionally added to the "nutritional supplements" are testosterone analogues with some structural modifications. In this study, the analyzed product was bought online and a new anabolic steroid known as methylstenbolone (2,17?-dimethyl-17?-hydroxy-5?-androst-1-en-3-one) was detected, as described on label. Generally, anabolic steroids are extensively metabolized, thus in-depth knowledge of their metabolism is mandatory for doping control purposes. For this reason, a human excretion study was carried out with four volunteers after a single oral dose to determine the urinary metabolites of the steroid. Urine samples were submitted to enzymatic hydrolysis of glucuconjugated metabolites followed by liquid-liquid extraction and analysis of the trimethylsilyl derivatives by gas chromatography coupled to tandem mass spectrometry. Mass spectrometric data allowed the proposal of two plausible metabolites: 2,17?-dimethyl-16?,17?-dihydroxy-5?-androst-1-en-3-one (S1), 2,17?-dimethyl-3?,16?,17?-trihydroxy-5?-androst-1-ene (S2). Their electron impact mass spectra are compatible with 16-hydroxylated steroids O-TMS derivatives presenting diagnostic ions such as m/z 231 and m/z 218. These metabolites were detectable after one week post administration while unchanged methylstenbolone was only detectable in a brief period of 45 h. PMID:23200734

Cavalcanti, Gustavo de Albuquerque; Leal, Felipe Dias; Garrido, Bruno Carius; Padilha, Monica Costa; de Aquino Neto, Francisco Radler

2013-02-01

371

Rapid and sensitive optochemical nitrogen dioxide detection: Silicone-containing amphiphilic co-networks as well suited immobilization matrices for gas sensing  

Microsoft Academic Search

We present a new optical polymer thin film sensor for high sensitivity and rapid response gas detection. Amphiphilic polymer co-networks (APCN) are used as sensor matrices for fast nitrogen dioxide detection. The sensor consists of an APCN in which the indicator has been embedded. The APCNs were synthesized by free radical induced photo polymerization and result in poly(2-(dimethylamino)ethyl acrylate)-1-polydimethylsiloxane(PDMAEA-l-PDMS). Thin

Stephan Meskath; G. Urban; Jürgen Heinze

2010-01-01

372

Cross validation of gas chromatography-flame photometric detection and gas chromatography-mass spectrometry methods for measuring dialkylphosphate metabolites of organophosphate pesticides in human urine.  

PubMed

We report two analytical methods for the measurement of dialkylphosphate (DAP) metabolites of organophosphate pesticides in human urine. These methods were independently developed/modified and implemented in two separate laboratories and cross validated. The aim was to develop simple, cost effective, and reliable methods that could use available resources and sample matrices in Thailand and the United States. While several methods already exist, we found that direct application of these methods required modification of sample preparation and chromatographic conditions to render accurate, reliable data. The problems encountered with existing methods were attributable to urinary matrix interferences, and differences in the pH of urine samples and reagents used during the extraction and derivatization processes. Thus, we provide information on key parameters that require attention during method modification and execution that affect the ruggedness of the methods. The methods presented here employ gas chromatography (GC) coupled with either flame photometric detection (FPD) or electron impact ionization-mass spectrometry (EI-MS) with isotopic dilution quantification. The limits of detection were reported from 0.10ng/mL urine to 2.5ng/mL urine (for GC-FPD), while the limits of quantification were reported from 0.25ng/mL urine to 2.5ng/mL urine (for GC-MS), for all six common DAP metabolites (i.e., dimethylphosphate, dimethylthiophosphate, dimethyldithiophosphate, diethylphosphate, diethylthiophosphate, and diethyldithiophosphate). Each method showed a relative recovery range of 94-119% (for GC-FPD) and 92-103% (for GC-MS), and relative standard deviations (RSD) of less than 20%. Cross-validation was performed on the same set of urine samples (n=46) collected from pregnant women residing in the agricultural areas of northern Thailand. The results from split sample analysis from both laboratories agreed well for each metabolite, suggesting that each method can produce comparable data. In addition, results from analyses of specimens from the German External Quality Assessment Scheme (G-EQUAS) suggested that the GC-FPD method produced accurate results that can be reasonably compared to other studies. PMID:24280209

Prapamontol, Tippawan; Sutan, Kunrunya; Laoyang, Sompong; Hongsibsong, Surat; Lee, Grace; Yano, Yukiko; Hunter, Ronald Elton; Ryan, P Barry; Barr, Dana Boyd; Panuwet, Parinya

2014-01-01

373

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

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.

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

374

GC/HRSIR as a Complementary Technique to GC/ECNIMS  

EPA Science Inventory

Gas chromatography/electron capture negative ion mass spectrometry (GC/ECNIMS) is a highly selective and sensitive technique for the analysis of appropriate analytes in complex matrices. Its major drawback is often the lack of fragmentation indicative of structure that can be use...

375

Determination of Residues of the Fungicide Metalaxyl in Water by SolidPhase Extraction with Gas Chromatography and Nitrogen–Phosphorus Detection  

Microsoft Academic Search

A rapid and sensitive method for the determination of metalaxyl residues in water samples has been developed. The metalaxyl residues were preconcentred from the sample by solid-phase extraction and determination by gas chromatography and nitrogen–phosphorus detection. The developed method was applied to water samples from an area under influence of highway accident in Brazil. After optimization of the extraction and

Renato Zanella; Clóvia Marozzin Mistura; Márcia Helena Scherer Kurz; Ednei Gilberto Primel; Fábio Ferreira Gonçalves

2003-01-01

376

Determination of PCBs in fish using enzyme-linked immunosorbent assay (ELISA)  

USGS Publications Warehouse

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.

Lasrado, J.A.; Santerre, C.R.; Zajicek, J.L.; Stahl, J.R.; Tillitt, D.E.; Deardorff, D.

2003-01-01

377

Determination of Pyrethroids through Liquid-Liquid Extraction and GC-ECD  

NASA Astrophysics Data System (ADS)

Storm water samples from various locations in San Diego Creek and Newport Bay watershed, southern California, were taken to study the occurrence and fate of pyrethroids. This study focused on four commonly used pyrethroids: bifenthrin, cypermethrin, permethrin, and fenpropathrin. Since the ban of DDT, usage of pyrethroids became an effective second choice. However, pyrethroids are extremely toxic to fish and aquatic organisms. They can pass through secondary wastewater treatment system, causing the final effluent to be in lethal doses to aquatic invertebrates and some insects such as mayflies. Hence, it is necessary to monitor the amount of pyrethroid concentration in storm water. As a part of this study, I attended the RISE internship program at Stanford University in this summer. In the seven weeks, I learned liquid-liquid extraction, water-bath evaporation, nitrogen evaporation, and gas chromatography-electron capture detector techniques to extract and detect the pyrethroid residues in the water sample.

Ding, B.

2010-12-01

378

Development and validation of an analytical method to determine Fipronil and its degradation products in soil samples.  

PubMed

The aim of this study was to develop a methodology for identifying and quantifying Fipronil and its degradation products in soil by gas chromatography-electron capture detector previously extracted using a focused ultrasound probe. This methodology was obtaining a range of recovery between 85% and 120%, decreasing approximately solvent used time and cost, respect to other methodologies such as bath ultrasonic, solid-phase extraction, liquid-liquid extraction and soxhlet. The method was validated in fortified matrix, presented linearity in the range of 25-400 ?g kg(-1), and limit of detection for Fipronil and their products desulfinyl, sulfide and sulfone was 14.7, 9.8, 8.9 and 10.7 ?g kg(-1), respectively. This process was applied to samples of agricultural soils, where two degradation products desulfinyl and sulfone were found. PMID:22893178

Flores-Ramírez, R; Batres-Esquivel, L E; Díaz-Barriga Martínez, F; López-Acosta, I; Ortiz-Pérez, M D

2012-10-01

379

Field detection of bacillus spore aerosols with stand-alone pyrolysis-gas chromatography and ion mobility spectrometry  

NASA Astrophysics Data System (ADS)

A commercially available, hand-held chemical vapor detector was modified to detect Gram-positive Bacillus subtilis var. globigii spores (BG) in outdoor field scenarios. An Airborne Vapor Monitor (AVM) ion mobility spectrometry (IMS) vapor detector was interfaced to a biological sample processing and transfer introduction system. The biological sample processing was accomplished by quartz tube pyrolysis (Py), and the resultant vapor was transferred by gas chromatography (GC) to the IMS detector. The Py-GC/IMS system can be described as a hyphenated device where two analytical dimensions, in series, allow the separation and isolation of individual components from the pyrolytic decomposition of biological analytes. Gram positive spores such as BG contain 5 - 15% by weight of dipicolinic acid (DPA), and picolinic acid is a pyrolysis product of DPA. Picolinic acid has a high proton affinity, and it is detected in a sensitive fashion by the atmospheric pressure-based IMS device. Picolinic acid occupies a unique region in the GC/IMS data domain with respect to other bacterial pyrolysis products. A 1000 to 1, air-to-air, aerosol concentrator was interfaced to the Py-GC/IMS instrument, and the system was placed in an open-air, Western United States desert environment. The system was tested with BG spore aerosol releases, and the instrument was remotely operated during a trial. A Met-One aerosol particle counter was placed next to the Py-GC/IMS so as to obtain a real-time record of the ambient and bacterial aerosol challenges. The presence/absence of an aerosol event, determined by an aerosol particle counter and a slit sampler-agar plate system, was compared to the presence/absence of a picolinic acid response in a GC/IMS data window at selected times in a trial with respect to a BG challenge. In the 21 BG trials, the Py-GC/IMS instrument experienced two true negatives, no false positives, and the instrument developed a software failure in one trial. The remaining 18 trials were true positive determinations for the presence of BG aerosol, and a limit of detection for the Py-GC/IMS instrument was estimated at approximately 3300 BG spore-containing particles.

Snyder, A.; Maswadeh, Waleed M.; Parsons, John A.; Tripathi, Ashish; Meuzelaar, Henk L. C.; Dworzanski, Jacek P.; Kim, Man-Goo

1999-12-01

380

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  

Microsoft Academic Search

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

Themistoklis Sfetsas; Chrysa Michailof; Angelos Lappas; Qiangyi Li; Brian Kneale

2011-01-01

381

DETECTION OF WEAK CIRCUMSTELLAR GAS AROUND THE DAZ WHITE DWARF WD 1124-293: EVIDENCE FOR THE ACCRETION OF MULTIPLE ASTEROIDS  

SciTech Connect

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.

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

382

Detection of synthetic testosterone use by novel comprehensive two-dimensional gas chromatography combustion-isotope ratio mass spectrometry.  

PubMed

We report the first demonstration of comprehensive two-dimensional gas chromatography combustion-isotope ratio mass spectrometry (GC×GCC-IRMS) for the analysis of urinary steroids to detect illicit synthetic testosterone use, of interest in sport doping. GC coupled to IRMS (GCC-IRMS) is currently used to measure the carbon isotope ratios (CIRs, ?(13)C) of urinary steroids in antidoping efforts; however, extensive cleanup of urine extracts is required prior to analysis to enable baseline separation of target steroids. With its greater separation capabilities, GC×GC has the potential to reduce sample preparation requirements and enable CIR analysis of minimally processed urine extracts. Challenges addressed include online reactors with minimized dimensions to retain narrow peak shapes, baseline separation of peaks in some cases, and reconstruction of isotopic information from sliced steroid chromatographic peaks. Difficulties remaining include long-term robustness of online reactors and urine matrix effects that preclude baseline separation and isotopic analysis of low-concentration and trace components. In this work, steroids were extracted, acetylated, and analyzed using a refined, home-built GC×GCC-IRMS system. 11-Hydroxyandrosterone and 11-ketoetiocolanolone were chosen as endogenous reference compounds because of their satisfactory signal intensity, and their CIR was compared to target compounds androsterone and etiocholanolone. Separately, a GC×GC-quadrupole MS system was used to measure testosterone (T)/epitestosterone (EpiT) concentration ratios. Urinary extracts of urine pooled from professional athletes and urine from one individual that received testosterone gel (T-gel) and one individual that received testosterone injections (T-shots) were analyzed. The average precisions of ?(13)C and ??(13)C measurements were SD(?(13)C) approximately ±1‰ (n = 11). The T-shot sample resulted in a positive for T use with a T/EpiT ratio of >9 and CIR measurements of ??(13)C > 5‰, both fulfilling World Anti-Doping Agency criteria. These data show for the first time that synthetic steroid use is detectable by GC×GCC-IRMS without the need for extensive urine cleanup. PMID:21846122

Tobias, Herbert J; Zhang, Ying; Auchus, Richard J; Brenna, J Thomas

2011-09-15

383

Determination of total sulfur compounds and benzothiazole in asphalt fume samples by gas chromatography with sulfur chemiluminescence detection.  

PubMed

As part of a collaborative project between the National Institute for Occupational Safety and Health and the Federal Highway Administration to evaluate asphalt pavers' exposures to asphalt fume and their potential health effects, a method was developed for the determination of total sulfur compounds and benzothiazole in asphalt fume samples. Asphalt fume samples were collected from asphalt mixtures with and without the addition of ground-up rubber tires. The asphalt fume samples were collected with sampling trains that consisted of a Teflon membrane filter and an XAD-2 adsorbent tube. Filter and sampling tube media were extracted with hexane and subsequently analyzed by gas chromatography with a sulfur chemiluminescence detector. Separation was achieved with a 100 percent dimethyl polysiloxane fused silica column. Typical calibration curves had linear correlation coefficients of 0.99 or better with a relative standard deviation (RSD) of 5 percent. Benzothiazole desorption efficiency (DE) determined using spiked sampling tubes ranged from 96.5 percent at 5.0 micrograms to 89.4 percent at 40 micrograms with RSD values from 0.9 to 4.0 percent. Benzothiazole storage recovery determined using sampling tubes spiked at 20 micrograms and refrigerated for 30 days at 4 degrees C was 89.8 percent when corrected for the DE with an RSD of 1.1 percent. The limit of detection for the method determined using spiked sampling tubes was 0.30 microgram. Quantitation for total sulfur compounds and benzothiazole was against benzothiazole standards in hexane. Because of detector selectivity, sample preparation consisted of a simple hexane extraction even when samples had a high background due to hydrocarbon overload. Detector sensitivity provided quantitation in the sub-microgram region. Because of the sample preparation step and because benzothiazole was determined during the same analysis run, this method is straightforward and analytically efficient. The method has been used to analyze asphalt fume samples collected at several asphalt paving and roof operations. PMID:10983404

Jaycox, L B; Olsen, L D

2000-09-01

384

Absorption-line Detections of 105-106 K Gas in Spiral-rich Groups of Galaxies  

NASA Astrophysics Data System (ADS)

Using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope, the COS Science Team has conducted a high signal-to-noise survey of 14 bright QSOs. In a previous paper, these far-UV spectra were used to discover 14 "warm" (T >= 105 K) absorbers using a combination of broad Ly? and broad O VI absorptions. A reanalysis of a few of this new class of absorbers using slightly relaxed fitting criteria finds as many as 20 warm absorbers could be present in this sample. A shallow, wide spectroscopic galaxy redshift survey has been conducted around these sight lines to investigate the warm absorber environment, which is found to be spiral-rich groups or cluster outskirts with radial velocity dispersions ? = 250-750 km s-1. While 2? evidence is presented favoring the hypothesis that these absorptions are associated with the galaxy groups and not with the individual, nearest galaxies, this evidence has considerable systematic uncertainties and is based on a small sample size so it is not entirely conclusive. If the associations are with galaxy groups, the observed frequency of warm absorbers (d {N}/dz = 3.5-5 per unit redshift) requires them to be very extended as an ensemble on the sky (~1 Mpc in radius at high covering factor). Most likely these warm absorbers are interface gas clouds whose presence implies the existence of a hotter (T ~ 106.5 K), diffuse, and probably very massive (>1011 M ?) intra-group medium which has yet to be detected directly. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

Stocke, John T.; Keeney, Brian A.; Danforth, Charles W.; Syphers, David; Yamamoto, H.; Shull, J. Michael; Green, James C.; Froning, Cynthia; Savage, Blair D.; Wakker, Bart; Kim, Tae-Sun; Ryan-Weber, Emma V.; Kacprzak, Glenn G.

2014-08-01

385

Optical sensing elements for nitrogen dioxide (NO.sub.2) gas detection, a sol-gel method for making the sensing elements and fiber optic sensors incorporating nitrogen dioxide gas optical sensing elements  

DOEpatents

A sensing element, a method of making a sensing element, and a fiber optic sensor incorporating the sensing element are described. The sensor can be used for the quantitative detection of NO.sub.2 in a mixture of gases. The sensing element can be made by incorporating a diazotizing reagent which reacts with nitrous ions to produce a diazo compound and a coupling reagent which couples with the diazo compound to produce an azo dye into a sol and allowing the sol to form an optically transparent gel. The sensing element changes color in the presence of NO.sub.2 gas. The temporal response of the absorption spectrum at various NO.sub.2 concentrations has also been recorded and analyzed. Sensors having different design configurations are described. The sensing element can detect NO.sub.2 gas at levels of parts per billion.

Mechery, Shelly John (Mississippi State, MS); Singh, Jagdish P. (Starkville, MS)

2007-07-03

386

Nanoparticle engineering for gas sensor optimisation: improved sol–gel fabricated nanocrystalline SnO 2 thick film gas sensor for NO 2 detection by calcination, catalytic metal introduction and grinding treatments  

Microsoft Academic Search

The control of the technological steps such as calcination temperature and introduction of catalytic additives are accepted to be key points in the obtaining of improved sol–gel fabricated SnO2 thick film gas sensors with different sensitivity to NO2 and CO. In this work, after proving that the undoped material calcined at 1000°C is optimum for NO2 detection, grinding is added

A. Diéguez; A. Romano-Rodr??guez; J. R. Morante; J. Kappler; N. Bârsan; W. Göpel

1999-01-01

387

Determination of 266 pesticide residues in apple juice by matrix solid-phase dispersion and gas chromatography–mass selective detection  

Microsoft Academic Search

A macro matrix solid-phase dispersion (MSPD) method was developed to extract 266 pesticides from apple juice samples prior to gas chromatography–mass selective detection (GC–MSD) determination. A 10g samples was mixed with 20g diatomaceous earth. The mixture was transferred into a glass column. Pesticide residues were leached with a 160mL hexane–dichloromethane (1:1) at 5mL\\/min. Two hundred and sixty-six pesticides were divided

Xiao-Gang Chu; Xiao-Zhong Hu; Hui-Yuan Yao

2005-01-01

388

Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection applied to the determination of pesticides in food extracts  

Microsoft Academic Search

The separation provided by conventional gas chromatography (1D-GC) can be significantly enhanced by using comprehensive two-dimensional GC (GC×GC) instead. Combination with mass spectrometric detection is desirable for unambiguous confirmation of target compounds and the provisional identification of unknowns. A GC×GC system using a cryogenic modulator was coupled to a time-of-flight mass spectrometric (TOF MS) detector. With the determination of pesticides

Jens Dallüge; Martijn van Rijn; Jan Beens; René J. J Vreuls; Udo A. Th Brinkman

2002-01-01

389

Determination of chromium(III) in water by solid-phase microextraction with a polyimide-coated fiber and gas chromatography-flame photometric detection  

Microsoft Academic Search

A method for the determination of trace Cr(III) in aqueous solution by solid-phase microextraction (SPME) coupled with gas chromatography (GC)-flame photometric detection (FPD) was developed. Aqueous Cr(III) was first converted to the volatile chromium trifluoroacetylacetonate (Cr(tfa)3) by derivatization with 1,1,1-trifluoroacetylacetone (Htfa), followed by SPME extraction using a polyimide-coated silica fiber. The distribution constants (K) of derivatized cis- and trans-Cr(tfa)3 between

Tzuoo-Huei Ding; Huang-Huei Lin; Chen-Wen Whang

2005-01-01

390

Detection of testosterone misuse: comparison of two chromatographic sample preparation methods for gas chromatographic-combustion\\/isotope ratio mass spectrometric analysis  

Microsoft Academic Search

Two chromatographic methods, reversed-phase liquid chromatography (LC) and immunoaffinity chromatography (IAC), were compared in the preparation of purified testosterone extracts suitable for gas chromatography-combustion\\/isotope ratio mass spectrometry (GC-C-IRMS) analysis. We have shown previously that GC-C-IRMS is a promising means of detection of testosterone misuse in sport. The two clean-up procedures afford sufficient recovery and adequate purity of testosterone. LC presents

R. Aguilera; M. Becchi; C. Grenot; H. Casabianca; C. K. Hatton

1996-01-01

391

Laboratory Evaluation of an Electrochemical Noise System for Detection of Localized and General Corrosion of Natural Gas Transmission Pipelines  

SciTech Connect

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.

Bullard, S.J.; Covino, B.S., Jr.; Russell, J.H.; Holcomb, G.R.; Cramer, S.D.; Ziomek-Moroz, M.; Eden, D.

2003-03-16

392

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)

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.

Haas, M. R.; Hollenbach, D. J.; Erickson, E. F.

1985-01-01

393

Double-pulse laser induced breakdown spectroscopy with ambient gas in the vacuum ultraviolet: Optimization of parameters for detection of carbon and sulfur in steel  

NASA Astrophysics Data System (ADS)

Laser induced breakdown spectroscopy (LIBS) in the vacuum ultraviolet (VUV) has been applied to calibrated steel samples for the low concentration level detection of the light elements, carbon and sulfur in steel. Experimental optimization parameters, aimed at enhancing the sensitivity of the technique, included short wavelength spectral detection, double-pulse (DP) operation, variable focusing conditions and different ambient environments in terms of gas type and pressure. Two lasers were employed respectively as an ablation laser (Spectron: 1.06 ?m/200 mJ/15 ns) and a reheating laser (Surelite: 1.06 ?m/665 mJ/6 ns) in a collinear geometry. The results include insight into the most salient experimental variables and limits of detection in the parts per million range.

Jiang, X.; Hayden, P.; Costello, J. T.; Kennedy, E. T.

2014-11-01

394

Analytical Method for the Detection of Ozone Depleting Chemicals (ODC) in Commercial Products Using a Gas Chromatograph with an Electron Capture Detector (GC-ECD)  

SciTech Connect

This document describes an analytical procedure that was developed for the trace level detection of residual ozone depleting chemicals (ODC) associated with the manufacture of selected commercial products. To ensure the United States meets it obligation under the Montreal Protocol, Congress enacted legislation in 1989 to impose an excise tax on electronic goods imported into the United States that were produced with banned chemicals. This procedure was developed to technically determine if residual ODC chemicals could be detected on electronic circuit boards. The analytical method utilizes a “purge and trap” technique followed by gas chromatography with electron capture detection to capture and analyze the volatile chemicals associated with the matrix. The method describes the procedure, the hardware, operating conditions, calibration, and quality control measures in sufficient detail to allow the capability to be replicated. This document corresponds to internal Standard Operating Procedure (SOP) EFL-130A, Rev 4.

Lee, Richard N.; Dockendorff, Brian P.; Wright, Bob W.

2008-08-01

395

Comparison of enzyme-linked immunosorbent assay and gas chromatography procedures for the detection of cyanazine and metolachlor in surface water samples  

USGS Publications Warehouse

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.

Schraer, S.M.; Shaw, D.R.; Boyette, M.; Coupe, R.H.; Thurman, E.M.

2000-01-01

396

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...

397

Gas Sensitivity and Sensing Mechanism Studies on Au-Doped TiO2 Nanotube Arrays for Detecting SF6 Decomposed Components.  

PubMed

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

Zhang, Xiaoxing; Yu, Lei; Tie, Jing; Dong, Xingchen

2014-01-01

398

Gas Sensitivity and Sensing Mechanism Studies on Au-Doped TiO2 Nanotube Arrays for Detecting SF6 Decomposed Components  

PubMed Central

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

Zhang, Xiaoxing; Yu, Lei; Tie, Jing; Dong, Xingchen

2014-01-01

399

Portable sick house syndrome gas monitoring system based on novel colorimetric reagents for the highly selective and sensitive detection of formaldehyde.  

PubMed

Formaldehyde (HCHO) emitted from the furniture and the walls in the rooms injures the eyes, nose, and respiratory organs and causes allergies, which is called sick house syndrome. We designed and synthesized novel colorimetric HCHO-sensing molecules (KD-XA01 and KD-XA02) which possess an enaminone structure and developed a hand-held instrument to monitor indoor HCHO gas with the use of KD-XA01. These sensing molecules produced speedy color changes from colorless to yellow under mild conditions, which was caused by the fact that the enaminone structure in the reagent reacts with HCHO to give a lutidine derivative. This reaction took place not only in the solution phase but also in the solid phase (surface of the cellulose paper). To take advantage of this phenomena, a handy and rapid monitoring system has been developed for detecting indoor HCHO gas using a highly sensitive and selective detection tablet constructed from the porous cellulose paper that contains silica gel as an adsorbent, KD-XA01, and phosphoric acid under optimum conditions. This instrument detected the surface color change of the tablet from white to yellow, which was monitored as a function of the intensity of the reflected light illuminated by an LED (475 nm). The response was proportional to the HCHO concentration at a constant sampling time and flow rate; 0.05 ppm HCHO, which is under the standard value set by the World Health Organization, was able to be detected in 5 min. The detection limit was 0.005 ppm. This monitoring system was not interfered by carbonyl compounds such as acetaldehyde and acetone, alcohols, hydrocarbons, and typical gases such as carbon monoxide, carbon dioxide, nitrogen dioxide, etc., which contributes to the measurement of correct HCHO concentrations. It was possible to monitor the HCHO gas in the room of a new apartment and school using this instrument; the response values were in good agreement with those obtained by the standard DNPH method. This highly sensitive, selective, and handy HCHO gas monitor is widely applicable and convenient for users who are not specialists in this field. PMID:14717182

Suzuki, Yoshio; Nakano, Nobuo; Suzuki, Koji

2003-12-15

400

Empirical Methods for Detecting Regional Trends and Other Spatial Expressions in Antrim Shale Gas Productivity, with Implications for Improving Resource Projections Using Local Nonparametric Estimation Techniques  

USGS Publications Warehouse

The primary objectives of this research were to (1) investigate empirical methods for establishing regional trends in unconventional gas resources as exhibited by historical production data and (2) determine whether or not incorporating additional knowledge of a regional trend in a suite of previously established local nonparametric resource prediction algorithms influences assessment results. Three different trend detection methods were applied to publicly available production data (well EUR aggregated to 80-acre cells) from the Devonian Antrim Shale gas play in the Michigan Basin. This effort led to the identification of a southeast-northwest trend in cell EUR values across the play that, in a very general sense, conforms to the primary fracture and structural orientations of the province. However, including this trend in the resource prediction algorithms did not lead to improved results. Further analysis indicated the existence of clustering among cell EUR values that likely dampens the contribution of the regional trend. The reason for the clustering, a somewhat unexpected result, is not completely understood, although the geological literature provides some possible explanations. With appropriate data, a better understanding of this clustering phenomenon may lead to important information about the factors and their interactions that control Antrim Shale gas production, which may, in turn, help establish a more general protocol for better estimating resources in this and other shale gas plays. ?? 2011 International Association for Mathematical Geology (outside the USA).

Coburn, T.C.; Freeman, P.A.; Attanasi, E.D.

2012-01-01

401

Determination of a sulfur-containing drug in human plasma by an improved method for sulfur chemiluminescence detection in combination with capillary gas chromatography.  

PubMed

An improved method for sulfur chemiluminescence detection in combination with capillary gas chromatography was established. The method was applied to the analysis of a sulfur-containing antiasthma drug, S-1452, and its nine metabolities in human plasma. The high selectivity and sensitivity of the method allowed accurate quantitation of trace levels of these compounds in human plasma with no interferences from the biological components present. To enable stable measurements and maintain reproducibility over a long period, the performance characteristics of a commercially available instrument were investigated. The gas seal in the injection port was found to easily corrode through interaction of the sulfur analyte with the metal gas seal. To prevent this, a disk made from an alloy of platinum and gold (60:40) was mounted on the gas seal. The reproducibility of the measurement was improved remarkably by using the disk. The use of compressed air of high purity significantly lowered the signal-to-noise ratio. The optical filter was kept clean by using a nickel catalyst to trap ozone in place of copper manganese oxide (CuMn2O4). These improvements raised the sensitivity and selectivity with the lower quantitation limits of 0.5-1.0 ng/mL in human plasma. PMID:10695154

Okamoto, J; Matsubara, T; Kitagawa, T; Umeda, T

2000-02-01

402

Fast, sensitive and cost-effective detection of nerve agents in the gas phase using a portable instrument and an electrochemical biosensor.  

PubMed

The nerve agents are chemical warfare agents known to be used during terrorist attacks. An inexpensive and portable system to be used by first responders and military personnel is of interest owing to the continuing threat of possible terrorist attacks. Amperometric biosensors based on cholinesterase inhibition show such potentialities. In this work butyrylcholinesterase was immobilized onto screen-printed electrodes modified with Prussian blue and the nerve agent detection was performed by measuring the residual activity of enzyme. The optimized biosensor was tested with sarin and VX standard solutions, showing detection limits of 12 and 14 ppb (10% of inhibition), respectively. The enzymatic inhibition was also obtained by exposing the biosensors to sarin in gas phase. Two different concentrations of sarin gas (0.1 and 0.5 mg m(-3)) at different incubation times (from 30 s up to 10 min) were tested. It is possible to detect sarin at a concentration of 0.1 mg m(-3) with 30-s incubation time, with a degree of inhibition of 34%, which match the legal limits (immediate danger to life and health). PMID:17508205

Arduini, Fabiana; Amine, Aziz; Moscone, Danila; Ricci, Francesco; Palleschi, Giuseppe

2007-07-01

403

All-optical pump-and-probe detection of two-time correlations in a Fermi gas  

SciTech Connect

We propose an all-optical scheme to probe the dynamical correlations of a strongly interacting gas of ultracold atoms in an optical lattice potential. The proposed technique is based on a pump-and-probe scheme: a coherent light pulse is initially converted into an atomic coherence and later retrieved after a variable storage time. The efficiency of the proposed method to measure the two-time one-particle Green function of the gas is validated by numerical and analytical calculations of the expected signal for the two cases of a normal Fermi gas and a BCS superfluid state. Protocols to extract the superfluid gap and the full quasiparticle dispersions are discussed.

Dao, T.-L. [Centre de Physique Theorique, Ecole Polytechnique, CNRS, F-91128 Palaiseau (France); Laboratoire Charles Fabry de l'Institut d'Optique, CNRS and Univ. Paris-Sud, Campus Polytechnique, RD 128, F-91127 Palaiseau cedex (France); Kollath, C. [Centre de Physique Theorique, Ecole Polytechnique, CNRS, F-91128 Palaiseau (France); Carusotto, I. [CNR-INFM BEC Center and Dipartimento di Fisica, Universita di Trento, I-38050 Povo (Italy); Koehl, M. [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

2010-04-15

404

Differentiation of wines according to grape variety using multivariate analysis of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection data.  

PubMed

Headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detection (GC×GC/TOFMS) was used to analyse the volatiles in five types of wines elaborated with grapes of Cabernet Sauvignon, Merlot, Chardonnay, Sauvignon Blanc and Pinot Noir varieties. Fisher ratio, principal component analysis (PCA) and stepwise linear discriminant analysis (SLDA) were used to develop a discriminant model and, as a result, 12 volatile compounds enabled differentiation and classification of wines according to grape cultivars. A detailed examination of GC×GC/TOFMS data showed that the use of one-dimensional gas chromatography with a mass spectrometric detector (1D-GC/MS) would probably result in misidentification of some of these 12 compounds, as they showed partial coelution with other components in the first chromatographic dimension. PMID:23993563

Welke, Juliane Elisa; Manfroi, Vitor; Zanus, Mauro; Lazzarotto, Marcelo; Alcaraz Zini, Cláudia

2013-12-15

405

Development of criteria for the detection of adrenosterone administration by gas chromatography-mass spectrometry and gas chromatography-combustion-isotope ratio mass spectrometry for doping control.  

PubMed

Adrenosterone (androst-4-ene-3,11,17-trione, 11-oxoandrostenedione) is an endogenous steroid hormone that has been promoted as a dietary supplement capable of reducing body fat and increasing muscle mass. It is proposed that adrenosterone may function as an inhibitor of the 11beta-hydroxysteroid dehydrogenase type 1 enzyme (11beta-HSD1), which is primarily responsible for reactivation of cortisol from cortisone. The urinary metabolism of adrenosterone was investigated, after a single oral administration in two male subjects, by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Substantially increased excretion of 11beta-hydroxyandrosterone, 11beta-hydroxyetiocholanolone, 11-oxoandrosterone and 11-oxoetiocholanolone was observed. Minor metabolites such as 3alpha,17beta-dihydroxy-5beta-androstan-11-one, 3alpha-hydroxyandrost-4-ene-11,17-dione and 3alpha,11beta-dihydroxyandrost-4-en-17-one were also identified. The exogenous origin of the most abundant adrenosterone metabolites was confirmed by GC-C-IRMS according to World Anti-Doping Agency criteria. Through analysis of a reference population data set obtained from urine samples provided by elite athlete volunteers (n = 85), GC-MS doping control screening criteria are proposed: 11beta-hydroxyandrosterone concentration greater than 10 000 ng/mL (specific gravity adjusted to 1.020) or 11beta-hydroxyandrosterone/11beta-hydroxyetiocholanolone ratio greater than 20.Urine samples fulfilling these screening criteria may be subjected to GC-C-IRMS analysis for confirmation of adrenosterone administration. PMID:20355175

Brooker, Lance; Parr, Maria Kristina; Cawley, Adam; Flenker, Ulrich; Howe, Christopher; Kazlauskas, Rymantas; Schänzer, Wilhelm; George, Adrian

2009-11-01

406

Detection and identification of phenazone-type drugs and their microbial metabolites in ground and drinking water applying solid-phase extraction and gas chromatography with mass spectrometric detection  

Microsoft Academic Search

A new analytical method applying in situ derivatization was developed to enable the extraction of polar drug metabolites from water samples by solid-phase extraction (SPE). An additional derivatization by silylation was used to enhance the sensitivity of analyte detection by gas chromatography–mass spectrometry (GC–MS). Thus, the two metabolites 1,5-di-methyl-1,2-dehydro-3-pyrazolone (DP) and 4-(2-methylethyl)-1,5-dimethyl-1,2-dehydro-3-pyrazolone (PDP), postulated for the degradation of phenazone and

Sebastian Zühlke; Uwe Dünnbier; Thomas Heberer

2004-01-01

407

Renaissance of gas chromatography-time-of-flight mass spectrometry. Meeting the challenge of capillary columns with a beam deflection instrument and time array detection.  

PubMed

This report describes the use of a unique beam deflection time-of-flight mass spectrometer to address some of the demands made on mass spectrometry by new developments in high-resolution capillary column gas chromatography. An integrating transient recorder is used in combination with this beam deflection time-of-flight instrument to apply the concept of time array detection in capturing all of the mass spectral information available from the ion source, thereby greatly enhancing the signal-to-noise ratio quality of the mass spectral data. The applicability of the time array detection approach to gas chromatography-mass spectrometry is demonstrated in the context of an analysis of the standard Grob mixture for assessing performance of capillary column chromatography. During analysis of the Grob mixture by gas chromatography-mass spectrometry, mass spectra were recorded at a rate of 20 scan files per second. The data indicate that this rate of mass spectral scan file generation is adequate to provide a suitable data base for reconstruction of the chromatographic profile. In addition, the effective scan rate is high enough that there is no distortion in the relative peak intensities throughout the individual mass spectra of components regardless of the relatively high dynamic changes in partial pressure of the analyte as reflected by the sharp peaks in the chromatographic profile. The experimental results indicate that the beam deflection time-of-flight mass spectrometer can provide mass spectra at a scan file generation rate much higher than that possible with the conventional quadrupole or magnetic sector mass spectrometer, but at comparable detection limits. PMID:2254386

Watson, J T; Schultz, G A; Tecklenburg, R E; Allison, J

1990-10-01

408

Determination of sulphite in wines by gas-diffusion flow injection analysis utilizing spectrophotometric pH-detection  

Microsoft Academic Search

A photometric flow injection analysis (FIA) method, using a gas-diffusion cell, has been developed for the determination of sulphite in wines. The method is based on the change of the absorbance of an indicator solution when sulphur dioxide, liberated from the matrix, diffuses via a permeable membrane into the indicator solution and locally shifts the pH. As indicator, bromocresol green

L. G. Decnop-Weever; J. C. Kraak

1997-01-01

409

Sensors and Actuators B, 2 (1990) 19-81 79 Photopyroelectric (P'E) Sensor for Trace Hydrogen Gas Detection  

E-print Network

(SAW) sensor [9], an optical fiber sensor [lo] and a piezo- electric crystal detector [ll reported. Furthermore, a variety of other hydrogen sensors have been developed: a surface acoustic waveSensors and Actuators B, 2 (1990) 19-81 79 Photopyroelectric (P'E) Sensor for Trace Hydrogen Gas

Mandelis, Andreas

410

Effect of heat pretreatment on the electrical conductance of lead phthalocyanine films for NO 2 gas detection  

Microsoft Academic Search

The phthalocyanines are organic semiconductors which exhibit high chemical and thermal stability. Their semiconducting behaviour is p-type both in terms of the effects of common dopants and temperature. Phthalocyanines have been studied as prototype organic semiconductors and used as active elements in oxidizing gases [1-3]. Some work on a semiconductive gas sensor using phthalocyanines has been published recently [4, 5].

Y. Sadaoka; T. A. Jones; W. Göpel

1989-01-01

411

Determination of dimethoate and fenitrothion in estuarine samples by C-18 solid-phase extraction and high-resolution gas-chromatography with nitrogen-phosphorus detection  

Microsoft Academic Search

Dimethoate [S-((2-(methylamino)ethyl)-2-oxoethyl)phosphorodithioate] and fenitrothion [O,O-dimethyl O-(4-nitro-m-tolyl)phosphorothioate], both organophosphorus pesticides (OPs), have been successfully enriched on monofunctional C-18 solid-phase extraction (SPE) cartridges and quantified by high-resolution capillary gas-chromatography with nitrogen-phosphorus detection (GC-NPD). The method was optimised for estuarine conditions. The recoveries varied significantly with the pH values of spiked seawater samples in the range pH 6.5–9.0 for both compounds. Salinity did

V. K. Karamfilov; T. W. Fileman; K. M. Evans; R. F. C. Mantoura

1996-01-01

412

Simultaneous determination of two human urinary metabolites of N, N-dimethylformamide using gas chromatography–thermionic sensitive detection with mass spectrometric confirmation  

Microsoft Academic Search

Two human urinary metabolites of the industrial solvent N,N-dimethylformamide (DMF), N-hydroxymethyl-N-methylformamide (HMMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC), were assayed using a new analytical method (gas chromatography and thermionic sensitive detection). Clean-up of urine samples includes a liquid–liquid extraction step followed by a solid-phase extraction step to separate HMMF and AMCC from other urine components. During clean-up, AMCC is converted into ethyl-N-methylcarbamate (EMC),

Heiko U Käfferlein; Jürgen Angerer

1999-01-01

413

Trace analysis of residual methyl methanesulfonate, ethyl methanesulfonate and isopropyl methanesulfonate in pharmaceuticals by capillary gas chromatography with flame ionization detection.  

PubMed

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 sample solvents include acetonitrile, ethyl acetate, methylene chloride, 1,2-dichloromethane, and toluene. Aqueous mixtures of acetonitrile and water can also be used as sample solvent. A limit of detection of about 1 microg/g (1 ppm) and limit of quantitation of 5 microg/g (5 ppm) were achieved for the mesylate esters in drug substance samples. The method optimization and validation are also discussed in this paper. PMID:15387202

Li, Weiyong

2004-08-13

414

Sensitive and selective flow injection analysis of hydrogen sulfite/sulfur dioxide by fluorescence detection with and without membrane separation by gas diffusion.  

PubMed

Highly sensitive and selective FIA flow injection analysis procedures for the determination of sulfite/hydrogen sulfite/sulfur dioxide were developed on the basis of an in situ-generated o-phthalaldehyde (OPA)/ammonium reagent and fluorescence detection. The highest sensitivity was achieved at an excitation wavelength of 330 nm, an emission wavelength of 390 nm, and at pH 6.5. Sulfite concentrations between 2.5 nM and 5 microM can be determined with relative standard deviations between 10.5 and 1.0% (n = 5, confidence level alpha = 0.05) by utilization of a reagent that contains 0.2 mM OPA and 0.4 M NH4Cl in 50 mM potassium phosphate buffer. A concentration of 0.1 mM sulfite can be selectively detected in the presence of thiosulfate, thioglycolate, tetrathionate, cysteine, and ascorbate. The fluorometric sulfite detection was combined with a membrane gas diffusion step to improve the selectivity with respect to nonvolatile fluorescing substances. The total sulfite content can be quantitatively separated as sulfur dioxide into an acceptor solution before its flow detection. Between 40 nM and 0.1 mM sulfite can be determined. After 1,000-fold dilution, the total sulfite content can be determined in white and red wines. PMID:11467572

Mana, H; Spohn, U

2001-07-01

415

Mechanism of ammonia detection by chemically functionalized single-walled carbon nanotubes: in situ electrical and optical study of gas analyte detection.  

PubMed

We provide definitive evidence for the mechanism of electronic detection of ammonia by monitoring in situ changes in the electrical resistance and optical spectra of films of poly(m-aminobenzenesulfonic acid)-functionalized SWNTs (SWNT-PABS). The increase of resistance during exposure to ammonia is associated with deprotonation of the PABS side chain that in turn induces electron transfer between the oligomer and the valence band of the semiconducting SWNTs. Near IR spectroscopy is used to demonstrate that the charge transfer is a weakly driven process, and this accounts for the high reversibility of the sensor. We show that the sensitivity of the chemiresistors increases as the film thickness is reduced to the percolation threshold and that the SWNT-PABS film thickness provides a simple means to enhance the electronic response. PMID:17696430

Bekyarova, Elena; Kalinina, Irina; Itkis, Mikhail E; Beer, Leanne; Cabrera, Nelson; Haddon, Robert C

2007-09-01

416

DENSE MOLECULAR GAS EXCITATION AT HIGH REDSHIFT: DETECTION OF HCO{sup +}(J = 4 {yields} 3) EMISSION IN THE CLOVERLEAF QUASAR  

SciTech Connect

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.

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

417

Determination of dissolved nitrous oxide inaquatic systems by gas chromatography using electron-capture detection and multiple phase equilibration  

SciTech Connect

An accurate method for the determination of small concentrations of dissolved nitrous oxide (N/sub 2/0) in fresh and seawater systems using electron capture detector gas chromatography is discussed. Successive analyses are made of the head space after repeated equilibrations of solution and an equal volume of ultra-pure gas. Precision better than 2% can be achieved on sample sizes as small as 60 mL. Possible sources of error of this method are enumerated. Six samples can be analyzed per hour with this method. The variations of measured dissolved N/sub 2/0 concentration during long term storage of samples are small (2.3%) using the procedures discussed here. 4 figures.

Elkins, J.W.

1980-02-01

418

Whole Microorganisms Studied by Pyrolysis-Gas Chromatography-Mass Spectrometry: Significance for Extraterrestrial Life Detection Experiments 1  

PubMed Central

Pyrolysis-gas chromatography-mass spectrometric studies of two microorganisms, Micrococcus luteus and Bacillus subtilis var. niger, indicate that the majority of thermal fragments originate from the principal classes of bio-organic matter found in living systems such as protein and carbohydrate. Furthermore, there is a close qualitative similarity between the type of pyrolysis products found in microorganisms and the pyrolysates of other biological materials. Conversely, there is very little correlation between microbial pyrolysates and comparable pyrolysis studies of meteoritic and fossil organic matter. These observations will aid in the interpretation of a soil organic analysis experiment to be performed on the surface of Mars in 1975. The science payload of this landed mission will include a combined pyrolysis-gas chromatography-mass spectrometry instrument as well as several “direct biology experiments” which are designed to search for extraterrestrial life. PMID:16349890

Simmonds, Peter G.

1970-01-01

419

Detection of [OI] 6300 and Other Diagnostic Emission Lines in the Diffuse Ionized Gas of M33 with Gemini-North  

E-print Network

We present spectroscopic observations of diffuse ionized gas (DIG) in M33 near the HII region NGC 604. We present the first detection of [OI] 6300 in the DIG of M33, one of the critical lines for distinguishing photo- from shock ionization models. We measure [OI]/Ha in the range of 0.04 to 0.10 and an increase in this ratio with decreasing emission measure. Our measurements of [SII]/Ha and [NII]/Ha also rise with decreasing emission measure, while our [OIII]/Hb 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/Ha = 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 HII region models are consistent with our data, without the need to invoke additional ionization mechanisms to fit our [OI] or [OIII] measurements. The closest large HII region is NGC 604 and is therefore a likely candidate for the source of the ionizing photons for the gas in this region.

E. S. Voges; R. A. M. Walterbos

2006-05-09

420

Determination of trihalomethanes in soil matrices by simplified quick, easy, cheap, effective, rugged and safe extraction and fast gas chromatography with electron capture detection.  

PubMed

A method based on QuEChERS extraction is proposed for the determination of trihalomethanes (chloroform, bromodichloromethane, dibromocloromethane and bromoform) in soil samples. The new version of QuEChERS adapted to soil samples consists of liquid extraction with ethyl acetate, the addition of water to moisten the samples, salting-out partitioning of the water with anhydrous MgSO4, and direct injection of the organic extract, obtained after the centrifugation step, into the gas chromatograph. This simplified extraction procedure maintains the advantages of the original method and avoids some steps, making the final procedure simpler, faster, and cheaper, with the consequent reduction in errors associated with sample manipulation. The experimental conditions of the analytical method, based on fast gas chromatography (FGC) and micro-electron capture detection (microECD), were optimized. The column and oven program used allowed fast separation of the compounds in less than 4 min and the total analysis cycle time was as short as 10 min. The existence of a matrix effect was checked and the analytical conditions of the method were studied in a fortified garden soil sample. The highly sensitive and selective detector used afforded to detection limits in the order of ng/kg for the target compounds. To validate the proposed method two certified reference materials (CRMs) were analyzed. PMID:20554286

Herrero Martín, Sara; García Pinto, Carmelo; Pérez Pavón, José Luis; Moreno Cordero, Bernardo

2010-07-23

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