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1

Determination of Acrylamide in Rat Serum and Sciatic Nerve by Gas Chromatography-Electron-Capture Detection.  

National Technical Information Service (NTIS)

A modified method for the derivatization and determination of acrylamide as 2-bromopropenamide by gas chromatography-electron-capture detection was developed and applied to serum and sciatic nerve from rats. The method was accurate and precise over the ca...

J. H. Raymer C. M. Sparacino G. R. Velez S. Padilla R. C. MacPhail

1993-01-01

2

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

EPA Science Inventory

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

3

Detection of trace levels of triclopyr using capillary gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry.  

PubMed

Triclopyr, after esterification, is shown to be a suitable candidate for detection by gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry forming a characteristic carboxylate anion which offers a high detection sensitivity. A detection limit of 70 fg reaching the ionizer is indicated. Low backgrounds and an absence of chemical interferences are shown for vegetation extracts, using a simple method of extraction and derivatisation. A similar behaviour is demonstrated for 2,4-D and 2,4,5-T. PMID:3379116

Begley, P; Foulger, B E

1988-04-01

4

Photocatalytic oxidation of aqueous trichloroethylene using dye sensitized buoyant photocatalyst monitored via micro-headspace solid-phase microextration gas chromatography\\/electron capture detection and mass spectrometry  

Microsoft Academic Search

Trichloroethylene (TCE), a useful industrial agent which unfortunately exhibits carcinogenic properties, has become an extremely prevalent environmental contaminant. As such, new rapid, sensitive, and cost effective detection methods are needed for the identification of potential point sources of contamination. A new analytic micro-headspace method is described, utilizing solid phase micro-extraction (SPME) fibers and routine gas chromatography\\/electron capture detection (GC\\/ECD) for

Matt V. Alexander; Jeffrey J. Rosentreter

2008-01-01

5

Determination of chlorophenols in water samples using simultaneous dispersive liquid–liquid microextraction and derivatization followed by gas chromatography-electron-capture detection  

Microsoft Academic Search

Simultaneous dispersive liquid–liquid microextraction (DLLME) and derivatization combined with gas chromatography-electron-capture detection (GC-ECD) was used to determine chlorophenols (CPs) in water sample. In this derivatization\\/extraction method, 500?L acetone (disperser solvent) containing 10.0?L chlorobenzene (extraction solvent) and 50?L acetic anhydride (derivatization reagent) was rapidly injected by syringe in 5.00mL aqueous sample containing CPs (analytes) and K2CO3 (0.5%, w\\/v). Within a few

Nazir Fattahi; Yaghoub Assadi; Mohammad Reza Milani Hosseini; Elham Zeini Jahromi

2007-01-01

6

Determination of pentachlorophenol residue in meat and fish by gas chromatography-electron capture detection and gas chromatography-mass spectrometry with accelerated solvent extraction.  

PubMed

A novel analytical method, using gas chromatography-electron capture detection (GC-ECD) and GC-mass spectrometry detection (MS), was developed for the qualitative and quantitative measurement of pentachlorophenol in meat and fish. The analyte was extracted by methanol-2% trichloroacetic acid (3/1, v/v) with accelerated solvent extraction (ASE). The eluted fraction was evaporated and derivatized with acetic anhydride-pyridine (1/1, v/v) for GC-ECD analysis and GC-MS confirmation. The parameters for extraction pressure, temperature and cycle of ASE, cleanup, derivatization and analysis procedure were optimized. The averaged decision limits and detection capability of the method were in the ranges of 0.25-0.41 and 0.49-1.01 µg/kg in the muscle and liver of swine and bovine and in the muscle of carp and finless eel, respectively. Spiked recoveries from levels of 0.5-2.0 µg/kg were found to be more than 71.1%, with relative standard deviation less than 14.7% in GC-ECD and GC-MS. This rapid and reliable method can be used for the characterization and quantification of residues of pentachlorophenol in animal and fish tissues. PMID:23690067

Zhao, Dongmei

2014-05-01

7

Solid phase extraction with silicon dioxide microsphere adsorbents in combination with gas chromatography-electron capture detection for the determination of DDT and its metabolites in water samples.  

PubMed

The goal of the present study was to investigate the feasibility of silicon dioxide (SiO(2)) microspheres without special modification to enrich dichlorodiphenyltrichloroethane (DDT) and its main metabolites, p,p'-dichlorodiphenyl-2,2-dichloroethylene (p,p'-DDD) and p,p'-dichlorodiphenyldichloroethylene (DDE) in combination with gas chromatography-electron-capture detection. The experimental results indicated that an excellent linear relationship between the recoveries and the concentrations of DDT and its main metabolites was obtained in the range of 0.2-30 ng mL(-1) and the correlation coefficients were in the range of 99.96-99.99%. The detection limits based on the ratio of signal to the baseline noise (S/N = 3) were 2.2, 2.9, 3.8 and 4.1 ng L(-1) for p,p'-DDD, p,p'-DDT, o,p'-DDT, and p,p'-DDE, respectively. The precisions of the proposed method were all below 10% (n = 6). Four real water samples were utilized for validation of the proposed method, and satisfactory spiked recoveries in the range of 72.4-112.9% were achieved. These results demonstrated that the developed method was a simple, sensitive, and robust analytical method for the monitoring of pollutants in the environment. PMID:23356340

Zhou, Qingxiang; Wu, Wei; Xie, Guohong

2013-01-01

8

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

9

Improved method for the in vitro assessment of antioxidant activity of plant extracts by headspace solid-phase microextraction and gas chromatography-electron capture detection.  

PubMed

The simultaneous monitoring of malondialdehyde, pentanal and hexanal, final products of lipid peroxidation is reported, using a headspace solid-phase microextraction (HS-SPME) technique with on-fibre derivatisation. The aldehydes are extracted and subjected to on-sorbent derivatisation into stable hydrazones with 2,4,6-trichlorophenylhydrazine (TCPH) and analyzed. The degree of inhibition of oxidation is performed by monitoring the chlorinated hydrazones after thermal desorption, by gas chromatography-electron capture detection. The procedure was employed to evaluate in vitro the antioxidant activity of Hypericum perforatum L. extracts and of the well-known antioxidant vitamin E following induction of oxidation of sunflower oil, as a model lipid system. Prior to the measurement of antioxidant activity, the optimal process conditions, i.e. headspace volume, temperature, agitation, extraction/derivatisation time and desorption time and temperature were properly established. Aqueous extracts of H. perforatum L. exhibited the highest antioxidative effect. The method is shown to be promising for screening purposes for antioxidant substances and natural extracts. PMID:17316667

Gioti, Eleni M; Fiamegos, Yiannis C; Skalkos, Dimitris C; Stalikas, Constantine D

2007-06-01

10

Profiling Neurosteroids in Cerebrospinal Fluids and Plasma by Gas Chromatography\\/Electron Capture Negative Chemical Ionization Mass Spectrometry  

Microsoft Academic Search

A quantitative method for the determination of allopregnanolone (5?,3?-THP) and related neurosteroids in CSF and plasma was established using gas chromatography\\/electron capture negative chemical ionization mass spectrometry (GC\\/ECNCI\\/MS). Neurosteroids were converted to carboxymethoxime, pentafluorobenzyl and trimethylsilyl derivatives and detected as intense (M-181)? fragment ions generated under the negative ion chemical ionization process. The response curves constructed using d4-dihydrotestosterone (DHT) and

Yang-Suk Kim; Hongjian Zhang; Hee-Yong Kim

2000-01-01

11

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

12

Direct and simultaneous determination of trace-level carbon tetrachloride, peroxyacetyl nitrate, and peroxypropionyl nitrate using gas chromatography-electron capture detection.  

PubMed

Gas chromatography equipped with electron capture detector (GC-ECD) has been widely used for detecting atmospheric peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN). However, to the best of our knowledge, only a few capillary columns have been adopted for separation to achieve the direct and simultaneous analysis of the two atmospheric pollutants. This paper demonstrates a novel method for directly and simultaneously measuring atmospheric carbon tetrachloride (CCl(4)), PAN, and PPN using GC-ECD with a DB-1 separation column. The responses of the GC-ECD to PAN, PPN, and CCl(4) were individually calibrated by using gas mixtures prepared via volatilization of synthesized solutions of PAN and PPN or high-purity CCl(4) reagent in a Teflon Bag. The concentrations of PAN and PPN in the synthesized solutions were quantified by ion chromatography (IC). Further calibration of the GC-ECD for PAN was conducted by in situ photochemical formation of gaseous PAN which was quantified by a NO(x) analyzer. The two calibration methods agreed well with each other, and the overall uncertainties for measuring atmospheric PAN were estimated to be ± 13% and ± 15% based on the calibrations of IC and NO(x), respectively. The detection limits (three times the signal to noise ratio) for PAN, PPN, and CCl(4) were estimated to be 22, 36, and 5 pptv (parts per trillion by volume), respectively. The atmospheric concentrations of these compounds were measured for several days in August in Beijing, and the values obtained in this study were found to be in good agreement with the data reported in the literature for Beijing using other GC-ECD methods. PMID:23107119

Zhang, Gen; Mu, Yujing; Liu, Junfeng; Mellouki, Abdelwahid

2012-11-30

13

Extraction of ultra traces of polychlorinated biphenyls in aqueous samples using suspended liquid-phase microextraction and gas chromatography-electron capture detection.  

PubMed

This study reports the feasibility of applying directly suspended liquid-phase microextraction (DSLPME)-gas chromatography detection for the pre-concentration and determination of low levels of eight polychlorinated biphenyls (PCBs) in aqueous samples. The technique requires minimal sample preparation, analysis time and solvent consumption and represents significant advantages over conventional analytical methods. The experimental parameters such as salt content, sample temperature, stirring rate, extraction time, micro-drop volume and breakthrough volume were investigated and found to have significant influences on DSLPME. Under the optimal experimental conditions, the enrichment factor ranged from 578 to 729, and the recovery was above 93 %. Calibration curves possessed good linearity (R(2) > 0.99) over a wide concentration range of 0.1-10.0 ?g L(-1) with limits of detection ranging from 0.01 to 0.07 ?g L(-1). The relative standard deviations for 1.0 ?g L(-1) of PCBs in water by using internal standard were in the range 2-14 % (n = 3). The proposed simple, accurate and sensitive analytical method was applied successfully to the determination of trace amounts of PCBs in water samples. PMID:22892997

Hassan, Jalal; Shamsipur, Mojtaba

2013-05-01

14

Ultrasonic enhancement of leaching and in situ derivatization of haloacetic acids in vegetable foods prior to gas chromatography-electron capture detection.  

PubMed

A continuous ultrasound-assisted approach to enhance the extraction of nine haloacetic acids (HAAs) from vegetables with in situ derivatization to methyl esters for their gas chromatography (GC) analysis is presented. The optimization of simultaneous extraction (using acidic methanol as extractant) and derivatization enabled the completion of both steps in 15 min. Ultrasound assistance has proved to enhance both linked steps, which results in a considerable shortening of the overall analysis time (i.e. 552.1 and 552.2 EPA methods for analysis of these compounds in drinking water require 1 and 2 h, respectively, only for derivatization). After sample preparation, the esterified HAAs were isolated by liquid-liquid extraction with n-hexane and analysed by GC-electron capture detection. The proposed method is an interesting alternative to present methods for the determination of HAAs in vegetable foods. This is an area unjustifiably forgotten by reference laboratory organisms as proved by the absence of official methods for analysis of the target compounds in these samples. The proposed method can be applied to the analysis of HAAs in any solid sample after optimization of the main variables involved in the extraction-derivatization step. PMID:18586256

Alvarez Sánchez, B; Priego Capote, F; Luque de Castro, M D

2008-08-01

15

Optimization of solid-phase extraction and solid-phase microextraction for the determination of ?- and ?-endosulfan in water by gas chromatography–electron-capture detection  

Microsoft Academic Search

Water contamination due to the wide variety of pesticides used in agriculture practices is a global environmental pollution problem. The 98\\/83\\/European Directive requires to measure residues of pesticides at a target concentration of 1.0 ?g\\/l in surface water and 0.1 ?g\\/l in drinking water. In order to reach the level of detection required, efficient extraction techniques are required. Although solid-phase

M. C López-Blanco; B Reboreda-Rodr??guez; B Cancho-Grande; J Simal-Gándara

2002-01-01

16

Detection and quantitation of fatty acid acyl conjugates of triamcinolone acetonide via gas chromatography–electron-capture negative-ion mass spectrometry  

Microsoft Academic Search

The inherent electron-capture properties of triamcinolone acetonide (TAA) fatty acid conjugates were exploited for development of a GC–MS technique for quantitation of C21 long-chain fatty esters of TAA synthesized in BEAS-2B cells, an immortalized airway epithelium cell line. TAA esters extracted from BEAS-2B cells were purified and detected via selected ion monitoring of the molecular anions generated from the TAA

Walter C Hubbard; Andrew E Blum; Carol A Bickel; Nicola M Heller; Robert P Schleimer

2003-01-01

17

Quantification of multi-residue levels in peach juices, pulps and peels using dispersive liquid-liquid microextraction based on floating organic droplet coupled with gas chromatography-electron capture detection.  

PubMed

In this paper, polychlorinated biphenyl (PCB), organochlorine pesticide (OCP) and pyrethroid pesticides in peach was investigated by comparing their residual level in peach juice, pulps and peels using dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) combined with gas chromatography-electron capture detection (GC-ECD). Extraction conditions such as the type of extractant, volume of extractant and dispersant, salt effect and extraction time were optimized. For juice samples, the linearity of the method was obtained in the range of 10-2000 ng L(-1),with determination coefficients>0.99. The limits of detection (LOD) of the method were ranged between 2.8 and 18.5 ng L(-1). For pulp and peel samples, the developed method is linear over the range assayed, 1-20 ?g kg(-1),with coefficients also >0.99. The relative recoveries of compounds analyzed from juice, pulp and peel samples were in the range of 73-106% with a relative standard deviation between 2.6 and 11.8%. The proposed method was applied to the simultaneous analysis of residues in real peach juice, pulp and peel samples. As a result, there were no target analytes found in peach juices and pulps while 3.3 ?g kg(-1) cyhalothrin and 3.5 ?g kg(-1) fenvalerate were found in peels. The experiment results revealed that the pyrethroid residues just deposited on the peels of the fruits, but did not move into pulps and juices. PMID:21703950

Matsadiq, Guzalnur; Hu, Hai-Li; Ren, Hai-Bo; Zhou, Yi-Wen; Liu, Lu; Cheng, Jing

2011-07-15

18

Confirmation of identity by gas chromatography/tandem mass spectrometry of sulfathiazole, sulfamethazine, sulfachloropyridazine, and sulfadimethoxine from bovine or swine liver extracts after quantitation by gas chromatography/electron-capture detection.  

PubMed

Four sulfonamide veterinary drug residues were quantitated by electron-capture detection (ECD) after separation by gas chromatography (GC). The identities of sulfathiazole (ST), sulfamethazine (SM), sulfachloropyridazine (SCP), and sulfadimethoxine (SDM) were confirmed in bovine or swine liver residues by tandem mass spectrometry (MS/MS). Bovine or swine liver tissues were extracted by using either the Tishler or the Manuel-Steller cleanup. The methylated residues containing ST, SM, SCP, and SDM were separated by GC prior to MS/MS daughter ion analysis. Control tissue, control tissue fortified at 0.1 ppm, and incurred tissue residues at approximately 0.1 ppm were analyzed for these 4 sulfonamides. A Finnigan Model TSQ-46 operating in the chemical ionization mode was used to perform the MS/MS daughter ion experiments. The identities of all 4 sulfonamides were confirmed in a single GC/MS/MS analysis. PMID:2211474

Matusik, J E; Sternal, R S; Barnes, C J; Sphon, J A

1990-01-01

19

Determination of indicator polychlorinated biphenyls (PCBs) by gas chromatography-electron capture detector.  

PubMed

An effective method for determination of indicator polychlorinated biphenyls (PCBs) has been validated using gas chromatography (GC) equipped with electron capture detector (ECD). The GC-ECD method was validated by determining the linear range (working range) for determination of the compounds, minimum detectable quantities (MDQ), the precision and accuracy of the method for the analysis of the compounds. MDQ obtained for the compounds ranges from 0.0005 to 0.002 ng. Indeed the method was found to be more sensitive as the number of chlorine atoms attached to the biphenyl increases. The precision and accuracy of the GC method validated ranges from 2.4% to 14.5% and -7.0% to 14.6% respectively. Coefficient of variation associated with the repeatability of the retention times and corresponding peak areas was found to be 0.0001-0.0007 for the retention times and 0.0014-0.059 for the peak areas. Percentage recoveries for the compounds were in the range of 95.7-101.0%. The validated method was then applied to determine levels of indicator PCBs in sediments sampled from eleven sampling points along the Lake Bosuntwi in Ghana and the highest PCB load of 19.17 ng g(-1) was recorded at Pipie No. 2. PCB 52 and PCB 101 were found to be the most ubiquitous indicator PCBs in the study area, both with 90.91% occurrence. PMID:24016628

Afful, Samuel; Awudza, Johannes A M; Twumasi, Stevester K; Osae, Shiloh

2013-11-01

20

Application of single-drop microextraction and comparison with solid-phase microextraction and solid-phase extraction for the determination of ?- and ?-endosulfan in water samples by gas chromatography–electron-capture detection  

Microsoft Academic Search

Water contamination due to the wide variety of pesticides used in agriculture practices is a global environmental pollution problem. The 98\\/83 European Directive requires the measurement of pesticides residues at a target concentration of 1.0 ?g\\/l in surface water and 0.1 ?g\\/l in drinking water. In order to reach the level of detection required, efficient extraction techniques are necessary. The

M. C López-Blanco; S Blanco-Cid; B Cancho-Grande; J Simal-Gándara

2003-01-01

21

An Examination of Pentafluorobenzoyl Derivatization Strategies for the Analysis of Fatty Alcohols using Gas Chromatography/Electron Capture Negative Ion Chemical Ionization-Mass Spectrometry  

PubMed Central

Gas chromatography/electron capture negative ion chemical ionization-mass spectrometry (GC/ECNICI-MS) combined with pentafluorobenzoyl derivatization (PFBoyl) is frequently used for the sensitive detection of fatty alcohols (FOH). However, this derivatization technique suffers from a lack of established reaction protocols, time-consuming reactions, and the presence of reagent artifacts or unwanted derivatization byproducts which can hinder analyte detection. Here, strategies are presented to reduce the problems associated with PFBoyl-derivatization, including 1) the optimization of reaction conditions (derivatization time and temperature) for a variety of PFBoyl-derivatized FOH, 2) an investigation of microwave-accelerated derivatization (MAD) as a rapid alternative heating mechanism for the PFBoyl-derivatization of FOH, and 3) an analysis of an alternative strategy employing a solvent extraction procedure post-derivatization to reduce the detrimental effects commonly associated with PFBoyl derivatization reagents. The optimal reaction conditions for the PFBoyl-derivatization of FOH was determined to be 60 °C for 45 min. The investigation in MAD demonstrated the potential of obtaining comparable PFBoyl-derivatizations to those obtained using traditional heating methods, albeit in a reaction time of 3 min. An examination of several solvents for post-derivatization extraction revealed improved relative response factors in comparison to those obtained without solvent extraction. The best solvents for the PFBoyl-FOH extraction, dichloromethane and tert-butyl methyl ether, were also compared to the no solvent extraction samples with standard response curves and PFBoyl-derivatized FOH in Bligh-Dyer extracted rat plasma.

Bowden, John A.; Ford, David A.

2010-01-01

22

Evaluation of BDE-47 Hydroxylation Metabolic Pathways Based on a Strong Electron-Withdrawing Pentafluorobenzoyl Derivatization Gas Chromatography/Electron Capture Negative Ionization Quadrupole Mass Spectrometry.  

PubMed

Understanding the metabolic pathways of polybrominated diphenyl ethers (PBDEs) is a key issue in the evaluation of their cytotoxicity after they enter the biota. In order to obtain more information concerning the metabolic pathways of PBDEs, we developed a strong electron-withdrawing pentafluorobenzoyl (PFBoyl) derivatization capillary gas chromatography/electron capture negative ionization quadrupole mass spectrometry (GC/ECNI-qMS). PFBoyl esterification greatly improves separation of the metabolites of PBDEs such as hydroxylated PBDEs (OH-PBDEs) and bromophenols (BPs) metabolites in rat liver microsomes (RLMs). On the other hand, the strong electron-withdrawing property of PFBoyl derivatized on OH-PBDEs and/or BPs makes cleavage of the ester bond on ECNI easier resulting in higher abundance of the structure-informative characteristic fragment ions at a high m/z region, which facilitate the identification of OH-PBDEs metabolites. Subsequent quantification can be performed by monitoring not only (79)Br(-) (or (81)Br(-)) but also their characteristic fragment ions, achieving more accurate isotope dilution quantification using GC/ECNI-qMS. These merits allow us to identify totally 12 metabolites of BDE-47, a typical example of PBDEs, in the RLMs in vitro incubation systems. In addition to the already known metabolites of BDE-47, one dihydroxylated 3,6-di-OH-BDE-47 and one dihydroxylated 3,5-di-OH-tetrabrominated dioxin were found. Moreover, the second hydroxylation took place on the same bromophenyl ring, where the first hydroxyl group was located, and was further confirmed via the identification of the dihydroxylated 2',6'-di-OH-BDE-28 of an asymmetric 2'-OH-BDE-28. This methodological development and its subsequent findings of the metabolic pathways of BDE-47 provided experimental evidence for understanding its dioxin-like behavior and endocrine disrupting risk. PMID:24925108

Zhai, Chao; Peng, Shunv; Yang, Limin; Wang, Qiuquan

2014-07-15

23

Clean-up of aqueous acetone vegetable extracts by solid-matrix partition for pyrethroid residue determination by gas chromatography—electron-capture detection  

Microsoft Academic Search

Disposable, ready-to-use cartridges filled with macroporous diatomaceous material are used to carry out a partition clean-up that, in a single step, is capable of transferring pesticide residues from aqueous acetone extracts into light petroleum-dichloromethane (75:25, v\\/v). This procedure takes the place of some functions (such as separatory-funnel partition, drying over anhydrous sodium sulphate and partial adsorption clean-up) usually performed by

Alfonso Di Muccio; Danilo Attard Barbini; Tiziana Generali; Patrizia Pelosi; Antonella Ausili; Fabio Vergori; Ivano Camoni

1997-01-01

24

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

Microsoft Academic Search

A rapid and sensitive analytical method for the determination of dichlorodiphenyltrichloroethane (DDT) and its main metabolites in environmental aqueous samples has been developed using one-step microwave-assisted headspace controlled-temperature liquid-phase micro-extraction (MA-HS-CT-LPME) technique coupled with gas chromatography–electron-capture detection (GC–ECD). In this study, the one-step extraction of DDT and its main metabolites was achieved by using microwave heating to accelerate the evaporation

Ponnusamy Vinoth Kumar; Jen-Fon Jen

2011-01-01

25

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

26

Ionic liquid-mediated molecularly imprinted solid-phase extraction coupled with gas chromatography-electron capture detector for rapid screening of dicofol in vegetables.  

PubMed

New ionic liquid-mediated molecularly imprinted polymers (IL-MIPs) were prepared by precipitation polymerization using 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM(+)PF6(-)) as the auxiliary solvent, ?-chloro-DDT as the dummy template, and they were successfully applied as the sorbents of solid-phase extraction (SPE) for rapid screening of dicofol from cabbage, tomato, and carrot samples. The IL-MIPs were characterized by FTIR, FE-SEM, static adsorption and chromatographic evaluation, and the results revealed that the IL-MIPs had higher adsorption capacity and selectivity to dicofol in aqueous solution than that of ionic liquid-mediated non-imprinted polymers (IL-NIPs) and non-imprinted polymers (NIPs). Under the optimized conditions, the IL-MIPs-SPE-GC method offered good linearity (0.4-40.0ngg(-1), r(2)=0.9995) and the average recoveries of dicofol at three spiked levels were in a range of 84.6-104.1% (n=3) with RSD?7.6%. The proposed method obviously improved the selectivity and purification effect, and eliminated the effect of template leakage on dicofol quantitative analysis. PMID:23932224

Yan, Hongyuan; Sun, Ning; Han, Yehong; Yang, Chen; Wang, Mingyu; Wu, Ruijun

2013-09-13

27

Evaluation of a multiresidue method for pesticides in cereals using supercritical fluid extraction and gas chromatographic detection  

Microsoft Academic Search

Supercritical fluid extraction (SFE) was evaluated to be applied for residue analysis of 22 gas chromatography\\/electron capture detector-nitrogen phosphorus detector (GC\\/ECD-NPD) amenable pesticides in rice, wild rice and wheat. Samples were extracted with supercritical carbon dioxide at 200 atm pressure and 50°C temperature, using methanol as a static modifier. Mean recoveries obtained with the proposed SFE method at two spiking

Antonio Valverde; Ana Aguilera; Mariano Rodriguez; Maria Brotons

2009-01-01

28

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

29

Dispersive liquid-liquid microextraction method based on solidification of floating organic drop combined with gas chromatography with electron-capture or mass spectrometry detection.  

PubMed

A simple dispersive liquid-liquid microextraction (DLLME) method based on solidification of a floating organic drop (DLLME-SFO) technique combined with gas chromatography/electron-capture detection (GC/ECD) or gas chromatography/mass spectrometry (GC/MS) has been developed. The proposed method is simple, low in cost, and of high precision. It overcomes the most important problem in DLLME, the high-toxic solvent used. Halogenated organic compounds (HOCs) in water samples were determined as the model compounds. The parameters optimized for the DLLME-SFO technique were as follows: A mixture of 0.5 mL acetone, containing 10 microL 2-dodecanol (2-DD-OH), was rapidly injected by syringe into the 5 mL water sample. After centrifugation, the fine 2-DD-OH droplets (8+/-0.5 microL) were floated at the top of the screwcap test tube. The test tube was then cooled in an ice bath. After 5 min the 2-DD-OH solvent had solidified and was then transferred into a conical vial; it melted quickly at room temperature and 3 microL (for GC/ECD) or 2 microL (for GC/MS) of it was injected into a gas chromatograph for analysis. The limit of detection (LOD) for this technique was 0.005-0.05microgL(-1) for GC/ECD and was 0.005-0.047 microgL(-1) for GC/MS, respectively. The linear range of the calibration curve of DLLME-SFO was from 0.01 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/ECD and was from 0.02 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/MS. PMID:18945435

Leong, Mei-I; Huang, Shang-Da

2008-11-21

30

Detection of gas leakage  

SciTech Connect

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

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

2012-06-19

31

Gas Flow Detection System  

NASA Technical Reports Server (NTRS)

This system provides a portable means to detect gas flow through a thin-walled tube without breaking into the tubing system. The flow detection system was specifically designed to detect flow through two parallel branches of a manifold with only one inlet and outlet, and is a means for verifying a space shuttle program requirement that saves time and reduces the risk of flight hardware damage compared to the current means of requirement verification. The prototype Purge Vent and Drain Window Cavity Conditioning System (PVD WCCS) Flow Detection System consists of a heater and a temperature-sensing thermistor attached to a piece of Velcro to be attached to each branch of a WCCS manifold for the duration of the requirement verification test. The heaters and thermistors are connected to a shielded cable and then to an electronics enclosure, which contains the power supplies, relays, and circuit board to provide power, signal conditioning, and control. The electronics enclosure is then connected to a commercial data acquisition box to provide analog to digital conversion as well as digital control. This data acquisition box is then connected to a commercial laptop running a custom application created using National Instruments LabVIEW. The operation of the PVD WCCS Flow Detection System consists of first attaching a heater/thermistor assembly to each of the two branches of one manifold while there is no flow through the manifold. Next, the software application running on the laptop is used to turn on the heaters and to monitor the manifold branch temperatures. When the system has reached thermal equilibrium, the software application s graphical user interface (GUI) will indicate that the branch temperatures are stable. The operator can then physically open the flow control valve to initiate the test flow of gaseous nitrogen (GN2) through the manifold. Next, the software user interface will be monitored for stable temperature indications when the system is again at thermal equilibrium with the test flow of GN2. The temperature drop of each branch from its "no flow" stable temperature peak to its stable "with flow" temperature will allow the operator to determine whether a minimum level of flow exists. An alternative operation has the operator turning on the software only long enough to record the ambient temperature of the tubing before turning on the heaters and initiating GN2 flow. The stable temperature of the heated tubing with GN2 flow is then compared with the ambient tubing temperature to determine if flow is present in each branch. To help quantify the level of flow in the manifolds, each branch will be bench calibrated to establish its thermal properties using the flow detection system and different flow rates. These calibration values can then be incorporated into the software application to provide more detailed flow rate information.

Moss, Thomas; Ihlefeld, Curtis; Slack, Barry

2010-01-01

32

Fission gas detection system  

DOEpatents

A device for collecting fission gas released by a failed fuel rod which device uses a filter to pass coolant but which filter blocks fission gas bubbles which cannot pass through the filter due to the surface tension of the bubble.

Colburn, Richard P. (Pasco, WA)

1985-01-01

33

Analyzing haloacetic acids using gas chromatography/mass spectrometry.  

PubMed

Haloacetic acids (HAAs) are a group of disinfection by-products formed in chlorinated water. Due to their potential health effects and widespread occurrences, HAAs are regulated in drinking water in the United States under a promulgated regulation. To better control the formation of HAAs in drinking water, a reliable and accurate analytical method is needed for HAA monitoring. In the present study, a liquid-liquid microextraction, acidic methanol derivatization, and gas chromatography/mass spectrometry (GC/MS) detection method was developed for determining HAAs and dalapon in drinking water. The newly developed method is capable of analyzing all nine HAAs and dalapon at microgram/l levels. The method performance, including the method detection limit (MDL) and spiking recovery, was evaluated. In comparison to EPA Method 552.2, which uses gas chromatography/electron capture detection (GC/ECD), this GC/MS method gave cleaner baselines and had few interfering peaks. For each of all nine HAAs and dalapon, the MDL was less than 1 microgram/l and the spiking recovery ranged from 73 to 165%. Using the GC/MS method, the run time could also be significantly reduced without compromising the analytical results. Further study is needed to fine-tune this GC/MS based analytical method, especially in the detection of brominated trihaloacetic acids and monochloroacetic acid. PMID:11317908

Xie, Y

2001-04-01

34

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Gas detection. 154.1345 Section 154...SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment Instrumentation § 154.1345 Gas detection. (a) Each vessel carrying...

2013-10-01

35

33 CFR 127.1203 - Gas detection.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

36

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2010 CFR

...A fixed flammable gas detection system that meets...is above or below the threshold limit value listed...must have a fixed gas detection system that is not located...must have a fixed gas detection system that meets...set at or below the threshold limit value listed...

2010-10-01

37

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2010 CFR

...A fixed flammable gas detection system that meets...is above or below the threshold limit value listed...must have a fixed gas detection system that is not located...must have a fixed gas detection system that meets...set at or below the threshold limit value listed...

2009-10-01

38

In situ derivatization and hollow fiber membrane microextraction for gas chromatographic determination of haloacetic acids in water.  

PubMed

An alternative method for gas chromatographic determination of haloacetic acids (HAAs) in water using direct derivatization followed by hollow fiber membrane liquid-phase microextraction (HF-LPME) has been developed. The method has improved the sample preparation step according to the conventional US EPA Method 552.2 by combining the derivatization and the extraction into one step prior to determination by gas chromatography electron captured detector (GC-ECD). The HAAs were derivatized with acidic methanol into their methyl esters and simultaneously extracted with supported liquid hollow fiber membrane in headspace mode. The derivatization was attempted directly in water sample without sample evaporation. The HF-LPME was performed using 1-octanol as the extracting solvent at 55 degrees C for 60 min with 20% Na2SO4. The linear calibration curves were observed for the concentrations ranging from 1 to 300 microg L(-1) with the correlation coefficients (R2) being greater than 0.99. The method detection limits of most analytes were below 1 microg L(-1) except DCAA and MCAA that were 2 and 18 microg L(-1), respectively. The recoveries from spiked concentration ranged from 97 to 109% with %R.S.D. less than 12%. The method was applied for determination of HAAs in drinking water and tap water samples. The method offers an easy one step high sample throughput sample preparation for gas chromatographic determination of haloacetic acids as well as other contaminants in water. PMID:17693310

Varanusupakul, Pakorn; Vora-Adisak, Narongchai; Pulpoka, Bancha

2007-08-13

39

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

PubMed

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

Vinoth Kumar, Ponnusamy; Jen, Jen-Fon

2011-03-01

40

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

41

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 Central

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.

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

2012-01-01

42

System and method for detecting gas  

DOEpatents

A system to detect a presence of a specific gas in a mixture of gaseous byproducts comprising moisture vapor is disclosed. The system includes an electrochemical cell, a transport to deliver the mixture of gaseous byproducts from the electrochemical cell, a gas sensor in fluid communication with the transport, the sensor responsive to a presence of the specific gas to generate a signal corresponding to a concentration of the specific gas, and a membrane to prevent transmission of liquid moisture, the membrane disposed between the transport and the gas sensor.

Chow, Oscar Ken (Simsbury, CT); Moulthrop, Lawrence Clinton (Windsor, CT); Dreier, Ken Wayne (Madison, CT); Miller, Jacob Andrew (Dexter, MI)

2010-03-16

43

Method for detecting gas turbine engine flashback  

DOEpatents

A method for monitoring and controlling a gas turbine, comprises predicting frequencies of combustion dynamics in a combustor using operating conditions of a gas turbine, receiving a signal from a sensor that is indicative of combustion dynamics in the combustor, and detecting a flashback if a frequency of the received signal does not correspond to the predicted frequencies.

Singh, Kapil Kumar; Varatharajan, Balachandar; Kraemer, Gilbert Otto; Yilmaz, Ertan; Lacy, Benjamin Paul

2012-09-04

44

Environmental trace gas detection using laser spectroscopy  

Microsoft Academic Search

This special issue of Applied Physics B – Lasers and Optics attempts to document the current status and trends of environmental trace gas detection through a collection of 32 invited papers motivated in part by the need for and importance of a detailed understanding of our environment. Although numerous traditional optical methods, gas chromatography, and mass spectrometry have served us

Frank K. Tittel

1998-01-01

45

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

46

Semiconducting polymers for gas detection  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

47

Air Monitoring for Hazardous Gas Detection  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

48

49 CFR 192.736 - Compressor stations: Gas detection.  

Code of Federal Regulations, 2013 CFR

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

2013-10-01

49

Gas sensitive materials for gas detection and method of making  

DOEpatents

A gas sensitive material comprising SnO2 nanocrystals doped with In2O3 and an oxide of a platinum group metal, and a method of making the same. The platinum group metal is preferably Pd, but also may include Pt, Ru, Ir, and combinations thereof. The SnO2 nanocrystals have a specific surface of 7 or greater, preferably about 20 m2/g, and a mean particle size of between about 10 nm and about 100 nm, preferably about 40 nm. A gas detection device made from the gas sensitive material deposited on a substrate, the gas sensitive material configured as a part of a current measuring circuit in communication with a heat source.

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

2012-12-25

50

Gas correlation lidar for methane detection  

Microsoft Academic Search

A new type of DIAL system for the detection of methane in the atmosphere is being developed. The main feature of this lidar is the use of a gas correlation technique to obtain the reference signal by means of a single laser pulse, instead of two shots at different wavelengths. This fact is useful to make measurements on fast moving

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

1986-01-01

51

Detection of gas atoms with carbon nanotubes  

PubMed Central

Owning to their unparalleled sensitivity resolution, nanomechanical resonators have excellent capabilities in design of nano-sensors for gas detection. The current challenge is to develop new designs of the resonators for differentiating distinct gas atoms with a recognizably high sensitivity. In this work, the characteristics of impulse wave propagation in carbon nanotube-based sensors are investigated using molecular dynamics simulations to provide a new method for detection of noble gases. A sensitivity index based on wave velocity shifts in a single-walled carbon nanotube, induced by surrounding gas atoms, is defined to explore the efficiency of the nano-sensor. The simulation results indicate that the nano-sensor is able to differentiate distinct noble gases at the same environmental temperature and pressure. The inertia and the strengthening effects by the gases on wave characteristics of carbon nanotubes are particularly discussed, and a continuum mechanics shell model is developed to interpret the effects.

Arash, B.; Wang, Q.

2013-01-01

52

Detection of gas atoms with carbon nanotubes  

NASA Astrophysics Data System (ADS)

Owning to their unparalleled sensitivity resolution, nanomechanical resonators have excellent capabilities in design of nano-sensors for gas detection. The current challenge is to develop new designs of the resonators for differentiating distinct gas atoms with a recognizably high sensitivity. In this work, the characteristics of impulse wave propagation in carbon nanotube-based sensors are investigated using molecular dynamics simulations to provide a new method for detection of noble gases. A sensitivity index based on wave velocity shifts in a single-walled carbon nanotube, induced by surrounding gas atoms, is defined to explore the efficiency of the nano-sensor. The simulation results indicate that the nano-sensor is able to differentiate distinct noble gases at the same environmental temperature and pressure. The inertia and the strengthening effects by the gases on wave characteristics of carbon nanotubes are particularly discussed, and a continuum mechanics shell model is developed to interpret the effects.

Arash, B.; Wang, Q.

2013-05-01

53

Validation of a gas chromatography–mass spectrometry method for the determination of pg\\/ml levels of 17?-estradiol and 17?-trenbolone in bovine serum  

Microsoft Academic Search

A method for the quantitation of pg\\/ml levels of 17?-estradiol and 17?-trenbolone in bovine serum by gas chromatography\\/electron-capture mass spectrometry has been developed and validated. Using the area ratios of the integrated molecular-ion peaks of the analytes to their corresponding deuterated internal standards, [2,4,16,16-2H4] 17?-estradiol (17?-estradiol-d4) and [16,16-2H2] 17?-trenbolone (17?-trenbolone-d2), and non-weighted linear regression, two calibration curves per analyte; 5–50

Rick W. Fedeniuk; Joe O. Boison; James D. MacNeil

2004-01-01

54

High sensitivity gas leak detection system  

Microsoft Academic Search

A new gas-leak-detection system owes its high sensitivity to a unique configuration of low-volume sample collectors. A corollary benefit of the arrangement is its portability: the entire unit can be easily hand-carried and rapidly attached to a rented car, for example, for use in distant or remote locations. The system incorporates numerous small-diameter flexible tubes aligned and directed toward the

Burkhart

1979-01-01

55

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

56

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

57

Air Monitoring for Hazardous Gas Detection  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

58

46 CFR 154.1350 - Flammable gas detection system.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Flammable gas detection system. 154.1350 Section...SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment Instrumentation § 154.1350 Flammable gas detection system. (a) The...

2010-10-01

59

46 CFR 154.1350 - Flammable gas detection system.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Flammable gas detection system. 154.1350 Section...SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment Instrumentation § 154.1350 Flammable gas detection system. (a) The...

2009-10-01

60

[Determination of antioxidant residues in polymer food package using gas chromatography].  

PubMed

A new method for the determination of antioxidants, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) and tertiary butylhydroquinone (TBHQ) in plastic food package by gas chromatography-electron capture detection (ECD) was developed. The antioxidants were extracted by cyclohexane with ultrasonic extraction, separated by an HP-50 + chromatographic column (30 m x 0.53 mm x 1 microm) and quantified by external standard method with an ECD detector. The average recoveries of antioxidants were 88% -93%, 92% - 101% and 83% -97% for BHT, BHA and TBHQ, respectively, at the spiking levels of 3.00 - 10.0 mg/kg. The corresponding relative standard deviations (RSDs, n = 5) were 2.01% - 2.89%, 2.11% - 3.19% and 2.99% - 4.02%, respectively. The limits of detection (S/N = 3) were 0.5, 0.5 and 0.8 mg/kg for BHT, BHA and TBHQ, respectively. The proposed method has been applied to the analysis of 5 kinds of polymer food package. The results indicated that all the above antioxidants were found in the practical polymer food package samples. Plastic food package contained BHT and BHA with the concentrations varying from 6.3 to 7.8 mg/kg and rubber food package contained all the three antioxidants with the concentrations varying from 9.3 to 28.4 mg/kg. This method is accurate, sensitive, highly reproducible and suitable for the analysis of residual antioxidants in polymer food package. PMID:21657061

Xiong, Zhongqiang; Wang, Libing; Li, Ningtao; Yu, Yanjun; Jia, Xiaochuan

2011-03-01

61

Thin film metal oxide gas sensor array for gas detection  

NASA Astrophysics Data System (ADS)

This paper presents how an array of sensors with various sensitivities can be used for reliable detection and recognition of gases. An array of six different thin film metal oxide gas sensors has been constructed and tested. The selected sensors are based on indium, zinc, tin and titanium thin film oxides deposited by reactive magnetron sputtering. Sensors operate inside a measuring chamber at elevated temperatures of 250 - 300°C. The sensors responses upon hydrogen and ammonia exposure (0 - 3000 ppm) at relative humidity (0 - 75%Rh) are studied. The results show that exploiting the cross sensitivity and different sensing performance of the sensors allows to increase the reliability of gas sensing at relatively low operating temperatures.

Gwi?d?, Patryk; Brudnik, Andrzej; Zakrzewska, Katarzyna

2013-07-01

62

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

63

A photoacoustic spectrometer for trace gas detection  

NASA Astrophysics Data System (ADS)

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

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

2005-06-01

64

Development of a sample preparation method for the analysis of current-use pesticides in sediment using gas chromatography.  

PubMed

Pyrethroid insecticides have been implicated as the cause of sediment toxicity to Hyalella azteca in both agricultural and urban areas of California; however, for a subset of these toxic sediments (approximately 30%), the cause of toxicity remains unidentified. This article describes the analytical method development for seven additional pesticides that are being examined to determine if they might play a role in the unexplained toxicity. A pressurized liquid extraction method was optimized to simultaneously extract diazinon, methyl parathion, oxyfluorfen, dicofol, fenpropathrin, pyraclostrobin, and indoxacarb from sediment, and the extracts were cleaned using a two-step solid-phase extraction procedure. The final extract was analyzed for the target pesticides by gas chromatography/nitrogen-phosphorus detector (GC/NPD), and gas chromatography/electron capture detector (GC/ECD), after sulfur was removed by shaking with copper and cold crystallization. Three sediments were used as reference matrices to assess method accuracy and precision. Method detection limits were 0.23-1.8 ng/g dry sediment using seven replicates of sediment spiked at 1.0 ng/g dry sediment. Recoveries ranged from 61.6 to 118% with relative standard deviations of 2.1-17% when spiked at 5.0 and 50 ng/g dry sediment. The three reference sediments, spiked with 50 ng/g dry weight of the pesticide mixture, were aged for 0.25, 1, 4, 7, and 14 days. Recoveries of the pesticides in the sediments generally decreased with increased aging time, but the magnitude of the decline was pesticide and sediment dependent. The developed method was applied to field-collected sediments from the Central Valley of California. PMID:19798461

Wang, Dongli; Weston, Donald P; Ding, Yuping; Lydy, Michael J

2010-02-01

65

Gas correlation lidar for methane detection  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

66

Limits of classical detection for gas  

NASA Astrophysics Data System (ADS)

The L.P.M. effect has to be taken into account in UHE-?-ray Astronomy above 1018 eV; at 1020 eV a ?-induced shower has only twice the electron size of a ?-shower with 10 times lower energy. This reduces considerably the intensity ``observed'' near 1020 eV. The e.m. component in proton induced Giant Air Showers (GAS) will be reduced according to our preliminary approach by a non Monte Carlo simulation) by 24% at 1020 eV at sea level; this implies up to those energies that spectrum measurements have to be corrected, but that the classical detection of the e.m. component is still possible. In the same time, the detection of the muon component is also considered. A realistic situation with a giant array ditributed over 104 Km2 at sea level is analysed: the equilateral triangle of the pine forest ``Landes de Gascogne'' (sides of 150 Km, Hossegor-Nerac-Carcans, centered in the south of Bordeaux).

Capdevielle, J. N.; Attallah, R.

1992-11-01

67

ENVIRONMENTAL APPLICATION OF GAS CHROMATOGRAPHY/ATOMIC EMISSION DETECTION  

EPA Science Inventory

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

68

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...

69

Detectivity of gas leakage based on electromagnetic radiation transfer  

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

70

Gas leak detection by diode laser absorption spectrometry  

Microsoft Academic Search

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

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

1999-01-01

71

Fire detection and suppression in natural gas pipeline compressor stations  

Microsoft Academic Search

The occurrence of fires in natural gas compressor stations is fortunately infrequent. The consequences, however, can be severe. This paper discusses the design concepts and experience of Pacific Gas Transmission Company (PGT) with fire detection and suppression systems in its natural gas pipeline compressor stations.

1987-01-01

72

Hybrid field-assisted solid-liquid-solid dispersive extraction for the determination of organochlorine pesticides in tobacco with gas chromatography.  

PubMed

A novel one-step sample preparation technique termed hybrid field-assisted solid-liquid-solid dispersive extraction (HF-SLSDE) was developed in this study. A simple glass system equipped with a condenser was designed as an extraction vessel. The HF-SLSDE technique was a three-phase dispersive extraction approach. Target analytes were extracted from the sample into the extraction solvent enhanced by the hybrid field. Meanwhile, the interfering components were adsorbed by dispersing sorbent. No cleanup step preceded chromatographic analysis. The efficiency of the HF-SLSDE approach was demonstrated in the determination of organochlorine pesticide (OCP) residues in tobacco with a gas chromatography-electron capture detector (GC-ECD). Various operation conditions were studied systematically. Low detection limits (0.3-1.6 ?g/kg) and low quantification limits (1.0-4.5 ?g/kg) were achieved under the optimized conditions. The recoveries of OCPs ranged from 70.2% to 118.2%, with relative standard deviations of <9.6%, except for the lowest fortification level. Because of the effect of the hybrid field, HF-SLSDE showed significant predominance compared with other extraction techniques. The dispersing sorbent with good cleanup ability used in this study was also found to be a microwave absorption medium, which could heat the nonpolar extraction solvent under microwave irradiation. Different microstructures of tobacco samples before and after extractions demonstrated the mechanism of HF-SLSDE was based on an explosion at the cell level. According to the results, HF-SLSDE was proved to be a simple and effective sample preparation method for the analysis of pesticide residues in solid samples and could potentially be extended to other nonpolar target analytes in a complex matrix. PMID:22092268

Zhou, Ting; Xiao, Xiaohua; Li, Gongke

2012-01-01

73

Oil and gas prospecting by ultra-sensitive optical gas detection with inverse gas dispersion modelling  

NASA Astrophysics Data System (ADS)

We report a new oil and gas prospecting technique based on measurements of sub-part-per-billion ethane concentration in the atmosphere and local wind data. The sensitivity of our sensor enables detection, from a range of several km, of the naturally occurring ethane seepages that accompany hydrocarbon reservoirs. Using the concentration and wind data, the gas dispersion process is inverted to provide maps of surface ethane flux over several hundred km2. Within a desert environment, we demonstrate the technique is capable of locating a controlled release and corresponds with the results from a geochemical soil sampling survey conducted over the same oil field.

Hirst, Bill; Gibson, Graham; Gillespie, Steve; Archibald, Ian; Podlaha, Olaf; Skeldon, Kenneth D.; Courtial, Johannes; Monk, Steve; Padgett, Miles

2004-06-01

74

Detect, troubleshoot gas-turbine blade failures  

Microsoft Academic Search

Approximately 40% of all gas-turbine failures stem from blading problems. This article describes state-of-the-art condition monitoring technologies that can help avoid or minimize the damage, and troubleshoot failures when they occur. In today`s gas-turbine (GT) fleet, predominant blade-failure mechanism and commonly affected components include: low-cycle fatigue--compressor and turbine disks; high-cycle fatigue--compressor and turbine blades and disks, compressor stator vanes; thermal

Meher-Homji

1995-01-01

75

Multiline absorption spectroscopy for methane gas detection  

Microsoft Academic Search

A multiline absorption spectroscopy technique was investigated based on the single-line absorption spectroscopy technique. An open-path methane-detecting system was designed. An LED was used as a broadband source, and a Fabry-Perot interferometer whose transmission peaks matched the methane R-branch absorption lines was used to enhance the detectable sensitivity. We demonstrate a minimum-detectable concentration of 7600 ± 10% ppm (parts per

Yi Qu; Zhi-Hui Kang; Yun Jiang; Jin-Yue Gao

2006-01-01

76

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

77

Gas Multiplication Ultraviolet Detector System for Fire Detection.  

National Technical Information Service (NTIS)

The patent describes a fire detection system using an ultraviolet gas multiplication detector, an amplitude discriminator to differentiate between a fire and cosmic radiation, and a time base discriminator to differentiate between a fire and background no...

T. M. Trumble

1973-01-01

78

Improvements in NDIR gas detection within the same optical chamber  

NASA Astrophysics Data System (ADS)

Non-dispersive infrared (NDIR) is a well known technique for gas concentration monitoring. Lead salt photoconductors and thermopile detectors are typically used. Together with gas filter correlation (GFC) they are the basis for a reference standard in environmental gas monitoring like carbon monoxide determination and other gas species. To increase gas sensitivity, a multi-pass optical cavity is often used. In this contribution we propose a new optical design that allows for auto-reference multiple gas detection. It basically consists of an array of White's cell multi-pass camera that allows multiple channels with independent lengths inside the same volume. We explore its performance for carbon monoxide detection and based on recent commercial developments in infrared detector and emitter technologies.

Martinez-Anton, Juan Carlos; Silva-Lopez, Manuel

2011-09-01

79

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

80

Feasibility of wireless gas detection with an FMCW RADAR interrogation of passive RF gas sensor  

Microsoft Academic Search

The feasibility of the remote measurement of gas detection from an RF gas sensor has been experimentally investigated. It consists of a Frequency-Modulated Continuous-Wave (FMCW) RADAR interrogation of an antenna loaded by the passive sensor. The frequency band of the RADAR [28.8-31GHz] allows the detection of the resonant frequencies of Whispering Gallery Modes that are sensitive to gas concentration. Reported

Hamida Hallil; F. Chebila; P. Menini; P. Pons; H. Aubert

2010-01-01

81

Gas-detecting properties of surface acoustic wave ammonia sensors  

Microsoft Academic Search

The detecting properties of l-glutamic acid hydrochloride that is deposited on 128° YX-LiNbO3 surface acoustic wave (SAW) delay lines are studied in this work. SAW gas sensors that were based on l-glutamic acid hydrochloride had good sensitivity, selectivity, reversibility, and repeatability to ammonia gas. A detection limit of 0.56ppm for gaseous ammonia was observed when using l-glutamic acid hydrochloride for

Chi-Yen Shen; Chun-Pu Huang; Wang-Tsung Huang

2004-01-01

82

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

Code of Federal Regulations, 2010 CFR

...boil-off as fuel: Gas detection equipment. 154.709...boil-off as fuel: Gas detection equipment. (a) The continuous gas detection system required under...in the wheelhouse if the methane concentration reaches...

2010-10-01

83

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

Code of Federal Regulations, 2010 CFR

...boil-off as fuel: Gas detection equipment. 154.709...boil-off as fuel: Gas detection equipment. (a) The continuous gas detection system required under...in the wheelhouse if the methane concentration reaches...

2009-10-01

84

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...boil-off as fuel: Gas detection equipment. (a) The continuous gas detection system required under...in the wheelhouse if the methane concentration reaches...

2013-10-01

85

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

86

Ultrasonic gas accumulation detection and evaluation in nuclear cooling pipes  

NASA Astrophysics Data System (ADS)

This paper presents a novel ultrasonic guided wave based inspection methodology for detecting and evaluating gas accumulation in nuclear cooling pipe system. The sensing is in-situ by means of low-profile permanently installed piezoelectric wafer sensors to excite interrogating guided waves and to receive the propagating waves in the pipe structure. Detection and evaluation is established through advanced cross time-frequency analysis to extract the phase change in the sensed signal when the gas is accumulating. A correlation between the phase change and the gas amount has been established to provide regulatory prediction capability based on measured sensory data.

Yu, Lingyu; Lin, Bin; Shin, Yong-June; Wang, Jingjiang; Tian, Zhenhua

2012-03-01

87

Detection system for a gas chromatograph  

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.

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

1984-01-01

88

Detection of Individual Gas Molecules Absorbed on Graphene  

Microsoft Academic Search

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

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

2006-01-01

89

Gas imaging detectivity model combining leakage spot size and range  

NASA Astrophysics Data System (ADS)

As to visualize the leaking gas cloud which is not visible to the naked eyes, three categories of techniques have emerged, Backscatter Absorption Gas Imaging, Passive Thermal Imaging, and Imaging Spectrometer. Among these systems, Signal to Noise Ratio (SNR) is generally used to deduce gas leakage detection limit and leads to several performance evaluation parameters, such as Noise-Equivalent Spectral Radiance and Noise-Equivalent Concentration-Path Length. However, in most cases, measuring the SNR accurately is not accessible and usually needs auxiliary instruments. Therefore, we focus on researching a gas leakage detection model according to the general parameter of a thermal imager, Noise Equivalent Temperature Difference (NETD). Firstly, the Gas Equivalent Blackbody Temperature Difference (GEBTD) is obtained by calculating the attenuated radiation of the On-plume path and that of the Off-plume path respectively. A simplified form of GEBTD was derived by our previous paper, assuming that the work range was short and the affection of atmospheric transmission was omitted. But in this paper, more factors are considered to establish a more realistic and accurate detectivity model. The radiation of the gas cloud and the attenuation of the atmosphere are taken into account as well as the size of the leakage spot which inevitably affects the concentration path length. Secondly, the NETD and the GEBTD are compared to determine the detection capability. At last, an experiment is designed to verify the accuracy and reliability of this model on the basis of the gas cloud concentration cone distribution model.

Li, Jiakun; Wang, Lingxue; Wang, Meirong; Gao, Yue; Jin, Weiqi

2012-05-01

90

Gas leak detection by diode laser absorption spectrometry  

NASA Astrophysics Data System (ADS)

Diode laser atomic absorption measurements of argon traces in low-pressure discharges were carried out to detect and measure gas leaks in a test chamber. Helium flows as a carrier gas through the test chamber and the discharge. In the case of a leak, air and thus also its natural content of argon is mixed to the helium gas-flow through the chamber. The argon content of the mixed gas flow through the discharge is determined by wavelength modulation diode laser atomic absorption spectrometry. The resulting absorption signal is a measure for the existing leak-rate. For barometric pressure of ambient air lowest detectable leak rates are typically 10 -6 mbar l s -1. By application of pure Ar with pressures above 1 bar detectable leak rates can in practice be lower than 10 -8 mbar l s -1.

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

1999-11-01

91

Detection of gas leaks in the subsurface environment  

NASA Astrophysics Data System (ADS)

Leaking valves, connections and distribution pipelines are significant sources of fugitive gas and volatile chemical emissions in chemical manufacturing, gas production, transmission, and oil refineries. A gas leak detection method has been developed based on continuous monitoring of the oxygen concentration surrounding a natural gas pipeline. The method utilizes optical fibers coated with an oxygen permeable polymeric film containing a luminescent sensor molecule. When the specialty fiber is illuminated by a light source that excites the luminophor, the functional cladding compound has the ability to detect and quantify leaks by measuring small changes in oxygen concentrations in the surrounding environment. Key features of the technology include long-term performance based on well understood platinum porphyrin chemistry, in addition to the capability of distributed sensing using fiber optic evanescent field spectroscopy. Results of leak detection in various environments namely atmospheric conditions, dry sand as well as saturated sand is reported, along with test results on long term system performance.

Ghandehari, Masoud; Khalil, Gamal; Kimura, Fletcher

2005-05-01

92

Research on airborne infrared leakage detection of natural gas pipeline  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

93

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

94

Temperature detection in a gas turbine  

DOEpatents

A temperature detector includes a first metal and a second metal different from the first metal. The first metal includes a plurality of wires and the second metal includes a wire. The plurality of wires of the first metal are connected to the wire of the second metal in parallel junctions. Another temperature detector includes a plurality of resistance temperature detectors. The plurality of resistance temperature detectors are connected at a plurality of junctions. A method of detecting a temperature change of a component of a turbine includes providing a temperature detector include ing a first metal and a second metal different from the first metal connected to each other at a plurality of junctions in contact with the component; and detecting any voltage change at any junction.

Lacy, Benjamin; Kraemer, Gilbert; Stevenson, Christian

2012-12-18

95

Early detection of combustible gas leaks using open path infrared (IR) gas detectors  

NASA Astrophysics Data System (ADS)

Open path IR gas detectors are a mainstay in the oil and gas industry. They are used in a variety of instances to identify gas accumulations or monitor gas cloud migrations. In offshore installations, open path optical gas detectors are used to monitor drilling and production operations, crude oil separation, compression, and exhaust and ventilation systems. Because they can monitor a perimeter or fence line, they are ideally suited for detecting gas in open facilities, where point gas detectors would be difficult or expensive to deploy. Despite their widespread use, open path optical gas detectors are rarely employed to detect low level concentrations of combustible gases. Standard models are typically set to alarm at 50% LEL-m (50% LEL extended over one meter), providing sufficiently early warning when gas accumulations occur. Nevertheless, in cases in which a combustible gas is diluted quickly, such as ventilation exhaust ducting, it may be necessary to set the detector to alarm at the lowest predictable level. Further, interest in low level infrared gas detection has been growing as gases such as CH4 and CO2 are greenhouse gases. The present paper describes a mid-wave infrared (MWIR) open path system designed to detect combustible and carbon dioxide gas leaks in the parts-per-million-meter (ppm-m or mg/cm2). The detector has been installed in offshore platforms and large onshore facilities to detect a variety of flammable gases and vapors. Advantages and limitations of the system are presented. False alarm immunity and resilience to atmospheric interferences are also discussed.

Naranjo, Edward; Baliga, Shankar

2012-05-01

96

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

97

[A mobile sensor for remote detection of natural gas leakage].  

PubMed

The detection of natural gas pipeline leak becomes a significant issue for body security, environmental protection and security of state property. However, the leak detection is difficult, because of the pipeline's covering many areas, operating conditions and complicated environment. A mobile sensor for remote detection of natural gas leakage based on scanning wavelength differential absorption spectroscopy (SWDAS) is introduced. The improved soft threshold wavelet denoising was proposed by analyzing the characteristics of reflection spectrum. And the results showed that the signal to noise ratio (SNR) was increased three times. When light intensity is 530 nA, the minimum remote sensitivity will be 80 ppm x m. A widely used SWDAS can make quantitative remote sensing of natural gas leak and locate the leak source precisely in a faster, safer and more intelligent way. PMID:22512213

Zhang, Shuai; Liu, Wen-qing; Zhang, Yu-jun; Kan, Rui-feng; Ruan, Jun; Wang, Li-ming; Yu, Dian-qiang; Dong, Jin-ting; Han, Xiao-lei; Cui, Yi-ben; Liu, Jian-guo

2012-02-01

98

Molecular gas in powerful radio galaxies detected by IRAS  

NASA Technical Reports Server (NTRS)

The present CO(J = 1 to 0) line survey of powerful radio galaxies has led to the detection of five sources in eight IRAS-determined radio galaxies. The range of the computed molecular gas masses is 1-7 times the H2 mass of the Milky Way and strikingly contrasts with the low molecular gas masses found in radio-quiet FIR-selected elliptical galaxies. These new CO observations lend support to the hypothesis that powerful radio galaxies result from disk galaxy collisions that evolve into gas-rich, peculiar E/S0 galaxies in the course of their merging.

Mazzarella, J. M.; Graham, J. R.; Sanders, D. B.; Djorgovski, S.

1993-01-01

99

ACOUSTIC DETECTING AND LOCATING GAS PIPE LINE INFRINGEMENT  

SciTech Connect

The extensive network of high-pressure natural gas transmission pipelines covering the United States provides an important infrastructure for our energy independence. Early detection of pipeline leaks and infringements by construction equipment, resulting in corrosion fractures, presents an important aspect of our national security policy. The National Energy Technology Laboratory Strategic Center for Natural Gas (SCVG) is and has been funding research on various applicable techniques. The WVU research team has focused on monitoring pipeline background acoustic signals generated and transmitted by gas flowing through the gas inside the pipeline. In case of a pipeline infringement, any mechanical impact on the pipe wall, or escape of high-pressure gas, generates acoustic signals traveling both up and down stream through the gas. Sudden changes in flow noise are detectable with a Portable Acoustic Monitoring Package (PAMP), developed under this contract. It incorporates a pressure compensating microphone and a signal- recording device. Direct access to the gas inside the line is obtained by mounting such a PAMP, with a 1/2 inch NPT connection, to a pipeline pressure port found near most shut-off valves. An FFT of the recorded signal subtracted by that of the background noise recorded one-second earlier appears to sufficiently isolate the infringement signal to allow source interpretation. Using cell phones for data downloading might allow a network of such 1000-psi rated PAMP's to acoustically monitor a pipeline system and be trained by neural network software to positively identify and locate any pipeline infringement.

John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Patrick Browning

2004-12-01

100

ACOUSTIC DETECTING AND LOCATING GAS PIPE LINE INFRINGEMENT  

SciTech Connect

The extensive network of high-pressure natural gas transmission pipelines covering the United States provides an important infrastructure for our energy independence. Early detection of pipeline leaks and infringements by construction equipment, resulting in corrosion fractures, presents an important aspect of our national security policy. The National Energy Technology Laboratory Strategic Center for Natural Gas (SCVG) is and has been funding research on various applicable techniques. The WVU research team has focused on monitoring pipeline background acoustic signals generated and transmitted by gas flowing through the gas inside the pipeline. In case of a pipeline infringement, any mechanical impact on the pipe wall, or escape of high-pressure gas, generates acoustic signals traveling both up and down stream through the gas. Sudden changes in flow noise are detectable with a Portable Acoustic Monitoring Package (PAMP), developed under this contract. It incorporates a pressure compensating microphone and a signal- recording device. Direct access to the gas inside the line is obtained by mounting such a PAMP, with a 1/2 inch NPT connection, to a pipeline pressure port found near most shut-off valves. An FFT of the recorded signal subtracted by that of the background noise recorded one-second earlier appears to sufficiently isolate the infringement signal to allow source interpretation. Using cell phones for data downloading might allow a network of such 1000-psi rated PAMP's to acoustically monitor a pipeline system and be trained by neural network software to positively identify and locate any pipeline infringement.

John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Patrick Browning

2004-10-31

101

Aging impairs the ability to detect gas odor  

Microsoft Academic Search

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

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

1987-01-01

102

Trace gas monitoring with infrared laser-based detection schemes  

Microsoft Academic Search

The success of laser-based trace gas sensing techniques crucially depends on the availability and performance of tunable laser\\u000a sources combined with appropriate detection schemes. Besides near-infrared diode lasers, continuously tunable midinfrared\\u000a quantum cascade lasers and nonlinear optical laser sources are preferentially employed today. Detection schemes are based\\u000a on sensitive absorption measurements and comprise direct absorption in multi-pass cells as well

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

2008-01-01

103

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

2001-01-01

104

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

105

Distributed-fibre-optic methane gas concentration detection  

Microsoft Academic Search

A novel method for detecting methane gas concentration distribution is proposed, based on the characteristics of supported catalytic sensors (SCS) and optical fibers. The feasibility, performance, and applications prospects of this system are also discussed. After analyzing the operating procedure of SCS theoretically, the linear relationship between methane concentration and its working temperature was established. The response of temperature to

Yi-Wei Shi; Yao-Cai Wang; Hong-Tao Jiang; Cheng-Shan Yao; Zhen-Chun Wu

1991-01-01

106

Large scale multiplexing a point sensor for methane gas detection  

Microsoft Academic Search

This paper has reported the design and installation of a highly multiplexed (45 point) methane gas detection system using single mode fibre optics linked to remote miniature open path absorption cells interrogated by a single DFB laser diode configured for frequency modulation spectroscopy. To our knowledge this is the first such system to be site tested. The system operates over

B. Culshaw; W. Johnstone; A. McLean; I. Mauchline; D. Moodie; G. Stewart

2002-01-01

107

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.

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

2012-01-01

108

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

109

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

110

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

111

Methane and Carbon Monoxide Gas Detection system based on semiconductor sensor  

Microsoft Academic Search

One of the most important actual problems in the gas detection field is that there are strong demands for gas methane leak detection and CO (carbon monoxide) detection to prevent explosions or CO poisoning accidents. In this sense, the present paper describes technical characteristics, test results, and a concluding application for methane and carbon monoxide based gas detection using a

E. Cordos; L. Ferenczi; S. Cadar; S. Costiug; G. Pitl; A. Aciu; A. Ghita; M. Chintoanu

2006-01-01

112

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

113

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

Microsoft Academic Search

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

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

2012-01-01

114

Improved micro-flame detection method for gas chromatography  

Microsoft Academic Search

A previously developed micro-counter-current flame method is modified to provide both sensitive photometric and ionization detection for gas chromatography (GC). A stainless steel capillary (0.254mm i.d.) supplying oxygen functions as a burner, which supports a compact flame that burns in a counter-flowing excess of hydrogen. In the “micro-flame photometric detector” (?FPD) response mode, the background emission level is reduced by

Kevin B Thurbide; Taylor C Hayward

2004-01-01

115

Surface acoustic wave gas monitor for ppm ammonia detection  

Microsoft Academic Search

A shear horizontal surface acoustic wave (SH-SAW) sensor coated with polyaniline (PANI) film was investigated in this study. The frequency shift of SH-SAW was measured to detect the presence of ammonia. In addition, an analysis of humidity interference with the ammonia was performed. The SH-SAW sensor in this study responded to the ammonia gas and could be recovered using dry

Chi-Yen Shen; Shih-Yuan Liou

2008-01-01

116

An all-optical photoacoustic spectrometer for trace gas detection  

Microsoft Academic Search

An all-optical photoacoustic spectrometer based on the diaphragm-based extrinsic Fabry–Perot interferometer (EFPI) fiber acoustic sensor for trace gas detection at atmospheric pressure and room temperature is first developed. The diaphragm-based EFPI fiber acoustic sensor is used to replace the conventional acoustic sensor in this system. Tunable erbium-doped fiber ring laser (TEDFRL) with an erbium-doped fiber amplifier (EDFA) is used as

Qiaoyun Wang; Jianwei Wang; Liang Li; Qingxu Yu

2011-01-01

117

C+ detection of warm dark gas in diffuse clouds  

NASA Astrophysics Data System (ADS)

We present the first results of the Herschel open time key program, Galactic Observations of Terahertz C+ (GOT C+) survey of the [CII] 2P3/2-2P1/2 fine-structure line at 1.9 THz (158 ?m) using the HIFI instrument on Herschel. We detected 146 interstellar clouds along sixteen lines-of-sight towards the inner Galaxy. We also acquired HI and CO isotopologue data along each line-of-sight for analysis of the physical conditions in these clouds. Here we analyze 29 diffuse clouds (AV < 1.3 mag) in this sample characterized by having [CII] and HI emission, but no detectable CO. We find that [CII] emission is generally stronger than expected for diffuse atomic clouds, and in a number of sources is much stronger than anticipated based on their HI column density. We show that excess [CII] emission in these clouds is best explained by the presence of a significant diffuse warm H2, dark gas, component. This first [CII] 158 ?m detection of warm dark gas demonstrates the value of this tracer for mapping this gas throughout the Milky Way and in galaxies. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

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

2010-10-01

118

Gas detection unit on a basis of semiconductor devices  

SciTech Connect

A gas detection unit provides for the measurement of the concentrations of methane and some other gases. The system operates when the gases studied have infrared absorption lines in the 2.6-3.9 ..mu..m range. The basic element of the unit involves optron pairs consisting of semiconductor light emitting diodes and a photodetector. A grating and concave mirror, placed directly in a gas mixture, are employed in the present work. Light from emitters travels 100 cm and is received by a PbSe detector, which yields signals in measuring and controlling channels. The test unit measures 350 x 250 x 150 mm/sup 3/, with the overall power consumption amounting to about 4 W. The methane detection limit of the analyzer is as low as 0.002 mol. %. The response of the unit of 0.2% CH/sub 4/ has a signal to noise ratio of 50, the testing range is 0.004-10 mol. % CH/sub 4/. The gas detection unit is planned to be used in coal mines, chemical industry and atmosphere monitoring.

Esina, N.P.; Zotova, N.V.; Markov, I.I.; Matveev, B.A.; Rogachyov, A.A.; Stus, N.M.; Talalakin, G.N.

1985-04-01

119

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

120

Liquid metal-to-gas leak-detection instruments. [LMFBR  

SciTech Connect

It is desirable for liquid-metal-cooled reactors that small liquid metal-to-gas leaks be reliably detected. Testing has been performed on a number of detection systems to evaluate their sensitivity, response time, and performance characteristics. This testing has been scheduled in three phases. The first phase was aimed at screening out the least suitable detectors and optimizing the performance of the most promising. In the second phase, candidates were tested in a 1500 ft/sup 3/ walk-in type enclosure in which leaks were simulated on 24-in. and 3-in. piping. In the third phase of testing, selected type detectors were tested in the 1500-ft/sup 3/ enclosure with Clinch River Breeder Reactor Plant (CRBRP) pipe insulation configurations and detector tubing configuration with cell gas recirculation simulated. Endurance testing of detection equipment was also performed as part of this effort. Test results have been shown that aerosol-type detectors will reliably detect leaks as small as a few grams per hour when sampling pipe insulation annuli.

Matlin, E.; Witherspoon, J.E.; Johnson, J.L.

1982-01-01

121

Trace Spectrometric Flame Analysis and Gas Chromatographic Detectors Related to Jet Engine Oil Analysis and Gas Detection.  

National Technical Information Service (NTIS)

The report briefly summarizes research on trace spectrometric flame analysis and gas chromatographic detectors related to jet engine oil analysis and gas detection including the University of Florida consists of fundamental, instrumental and applied studi...

J. D. Winefordner

1973-01-01

122

A photothermal interferometer for gas-phase ammonia detection.  

PubMed

Detection of gas-phase ammonia is particularly challenging because ambient ammonia concentrations may be less than 1 ppb (molecules of NH(3) per 10(9) molecules of air), ammonia sticks to many materials commonly used to sample air, and particles containing ammonium may interfere with gas-phase measurements. We have built a new and sensitive photothermal interferometer to detect gas-phase ammonia in situ, under typical atmospheric conditions. Ammonia molecules in sampled air absorb infrared radiation from a CO(2) laser at 9.22 ?m, with consequent collisional heating, expansion, and refractive index change. This change in refractive index is detected as a phase shift in one arm of a homodyne interferometer. Measurements of vibrational and electrical noise in the interferometer correlate to an instrumental lower limit of detection of 6.6 ppt ammonia in 1 s. The CO(2) laser output is modulated at 1.2 kHz, and the ac signal from the interferometer is measured with a lock-in amplifier. The detector is zeroed by sampling through a H(3)PO(4)-coated denuder tube and is calibrated by dynamic dilution of two permeation tube outputs and by standard addition. Signal gain is insensitive to CO(2) or H(2)O in the sample, and the signal is linear over 5 orders of magnitude. The instrument 2? precision is 31 ppt when the signal is integrated for 100 s and 250 ppt with a 1-s integration time. The windowless sample cell and inlet is fabricated entirely of glass to minimize sample loss and hysteresis. The instrument response time is demonstrated to be about 1 s. PMID:21662962

Owens, M A; Davis, C C; Dickerson, R R

1999-04-01

123

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

124

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

125

Gas-chromatographic determination of disopyramide with nitrogen detection.  

PubMed

A sensitive and specific method is presented for the quantification of disopyramide, a new antiarrhythmic agent, in blood plasma or serum. Aminopentamide, a chemically similar compound, is added to the biological fluid, and the two compounds are extracted with chloroform. The concentrated extract is treated with trifluoroacetic anhydride, resulting in the dehydration of the primary amide group of the drug and internal standard to the corresponding nitriles. The dehydrated derivatives are gas chromatographed and detected using a nitrogen-phosphorus detector. The method is applicable to the determination of the drug in plasma in the 1-10 microgram/mL concentration range. PMID:6927045

Gal, J; Brady, J T; Kett, J

1980-01-01

126

Atypical Applications for Gas-coupled Laser Acoustic Detection  

NASA Astrophysics Data System (ADS)

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

Caron, J. N.; Kunapareddy, P.

2014-06-01

127

High Altitude Aerial Natural Gas Leak Detection System  

SciTech Connect

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

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

2006-12-31

128

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

129

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

130

Microfabricated planar glass gas chromatography with photoionization detection.  

PubMed

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

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

2010-01-29

131

Flashback Detection Sensor for Hydrogen Augmented Natural Gas Combustion  

SciTech Connect

The use of hydrogen augmented fuel is being investigated by various researchers as a method to extend the lean operating limit, and potentially reduce thermal NOx formation in natural gas fired lean premixed (LPM) combustion systems. The resulting increase in flame speed during hydrogen augmentation, however, increases the propensity for flashback in LPM systems. Real-time in-situ monitoring of flashback is important for the development of control strategies for use of hydrogen augmented fuel in state-of-the-art combustion systems, and for the development of advanced hydrogen combustion systems. The National Energy Technology Laboratory (NETL) and Woodward Industrial Controls are developing a combustion control and diagnostics sensor (CCADS), which has already been demonstrated as a useful sensor for in-situ monitoring of natural gas combustion, including detection of important combustion events such as flashback and lean blowoff. Since CCADS is a flame ionization sensor technique, the low ion concentration produced in pure hydrogen combustion raises concerns of whether CCADS can be used to monitor flashback in hydrogen augmented combustion. This paper discusses CCADS tests conducted at 0.2-0.6 MPa (2-6 atm), demonstrating flashback detection with fuel compositions up to 80% hydrogen (by volume) mixed with natural gas. NETL’s Simulation Validation (SimVal) combustor offers full optical access to pressurized combustion during these tests. The CCADS data and high-speed video show the reaction zone moves upstream into the nozzle as the hydrogen fuel concentration increases, as is expected with the increased flame speed of the mixture. The CCADS data and video also demonstrate the opportunity for using CCADS to provide the necessary in-situ monitor to control flashback and lean blowoff in hydrogen augmented combustion applications.

Thornton, J.D.; Chorpening, B.T.; Sidwell, T.; Strakey, P.A.; Huckaby, E.D.; Benson, K.J. (Woodward)

2007-05-01

132

Verification , Dosimetry and Biomonitoring of Mustard Gas Exposure via Immunochemical Detection of Mustard Gas Adducts to DNA and Proteins.  

National Technical Information Service (NTIS)

The use of mustard gas in the Iran-Iraq War has stressed the need of reliable methods for retrospective detection of poisoning with chemical warfare agents. We are developing methods to detect adducts of mustard gas to DNA and proteins, which may have a l...

H. P. Benschop

1991-01-01

133

Verification, Dosimetry and Biomonitoring of Mustard Gas Exposure via Immunochemical Detection of Mustard Gas Adducts to DNA and Proteins.  

National Technical Information Service (NTIS)

The recent use of mustard gas in the Gulf War has stressed the need of reliable methods for retrospective detection of poisoning with chemical warfare agents. We are developing methods to detect adducts of mustard gas to DNA and proteins, which may have l...

H. P. Benschop

1990-01-01

134

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

Microsoft Academic Search

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

Ane Bordagaray; Rosa Garcia-Arrona; Esmeralda Millán

2011-01-01

135

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

136

Assessment of Dispersing Tracer Gas with Ventilation Air Stream to Detect Mine Fires.  

National Technical Information Service (NTIS)

A remote heat-activiated stench gas-tracer gas mine alarm system was developed to reduce the time between fire detection and personnel notification. The stench gas-tracer gas system contains ethyl mercaptan for personnel warning and a fluorocarbon for tra...

M. D. Marshall

1983-01-01

137

Leak detection and localization of gas pipeline system based on wavelet analysis  

Microsoft Academic Search

Pipelines are one of great important components for gas and petrochemical industries. Normally, they are used to transport gas by hundreds or even thousands of miles. It is a momentous task to keep the gas pipeline under safety operation. Leak detection and localization mechanisms play an important role in the management of a gas pipeline system. In this paper, wavelet

Lijing Dong; Senchun Chai; Baihai Zhang

2011-01-01

138

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

139

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

140

A piezoelectric-sound-resonance cavity for hydrogen gas detection.  

PubMed

A new concept for hydrogen gas (H2) detection has been developed. This concept is based on a piezoelectric-sound-resonance cavity (PSRC). Detection uses sound resonance and the acoustic property differences of gases as a sensing mechanism in which there is a significant difference in the sound velocity and acoustic impedance between H2 and air. The PSRC sensor consists of two thin piezoelectric discs, separated by a small cavity. One disc excites a weak acoustic standing wave in the cavity, and the second senses the wave by monitoring the acoustic impedance characteristics of the cavity. Changes in H2 concentration result in a shift of the sound resonance state. Investigations of a PSRC prototype have demonstrated a sensitivity limit of <10 ppm, a fast response time approximately 1 second, and a signal (phase and voltage) in proportion to the change in H2 concentration (n) over the range of 10(-5) < n < 0.2. These performance characteristics are far superior to those of other methods. PMID:14561027

Dong, Shuxiang; Bai, Feiming; Li, Jie-Fang; Viehland, Dwight

2003-09-01

141

Detection and Identification of Bacteria by Gas Chromatography1  

PubMed Central

Ether extracts of cultures of 29 strains representing 6 species of Bacillus, and of individual strains of Escherichia coli, Aerobacter aerogenes, and Pseudomonas aeruginosa were examined in a gas chromatograph by use of flame ionization and electron capture detectors. Among the products detected were compounds with the chromatographic characteristics of acetic, propionic, and butyric acids, ethyl alcohol, diacetyl, acetoin, and 2,3-butanediol. The differences in peak areas of the various products formed by the bacteria were determined statistically for the chromatograms obtained with the two detectors, and the peaks were arranged in order of decreasing areas to yield a signature for each bacterial strain. Different signatures were obtained for the various genera and species and for strains of the same species. B. licheniformis, B. subtilis, and A. aerogenes formed significant quantities of a number of volatile compounds, and qualitative and quantitative differences between strains were noted. The electron capture detector was particularly sensitive to diacetyl and acetoin as well as to unknown compounds. By use of this detector, the presence of 5 pg of diacetyl and 20 pg of acetoin could be demonstrated. The quantity of acetoin detected in B. subtilis and B. licheniformis cultures was present in as little as 6.3 × 10-3 ?liters of medium. Images Fig. 1 Fig. 2 Fig. 3

Henis, Y.; Gould, J. R.; Alexander, M.

1966-01-01

142

Non-selective NDIR array for gas detection  

NASA Astrophysics Data System (ADS)

A micro component for a non-selective NDIR (non dispersive infrared) gas detection system is presented in this work. This device consist of an IR detection module composed of a thermopile and a thin film filter array. The thermopile arrays (up to 4x4) are built on a silicon substrate by bulk micro-machining processes. The whole matrix is built on a thin freestanding silicon oxide/silicon nitride membrane of 2100x2100?m2 defined by anisotropic wet etching. To ensure the existence of hot and cold junctions for each detector we define on the insulating membrane absorbers and ribs, 6?m thick, by heavy boron doping of the silicon underneath. The ribs crisscross the membrane contacting the silicon bulk acting as a heat sink. Absorbers are located in the centre of each individual pseudo-membrane defined by the ribs intersection. Incident radiation heats up the absorber creating a temperature difference that is measured by the thermocouples that are placed between the absorber and the ribs. On a second chip, the elements of the filter array are fabricated in a matching configuration. The filters are built on a silicon substrate alternating thin films of different refraction index acting like a Fabry-Perot structure with 2-8?m silicon oxide cores. The transmitted filter peaks are not tuned for the detection of any specific substance: they configure a non selective general purpose filter array (400-4000 cm-1), making signal processing and pattern recognition techniques necessary. Both dies have been fabricated and characterized and have been successfully attached using flip-chip techniques. The measurements on these devices have been used to build an optical simulation tool that allows the assessment of the whole NDIR system behaviour in operating conditions.

Rubio, R.; Santander, J.; Marco, S.; Fonseca, L.; Fonollosa, J.; Moreno, M.

2005-07-01

143

Improved low concentration gas detection system based on intracavity fiber laser  

NASA Astrophysics Data System (ADS)

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.

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

2011-02-01

144

Igniter for gas discharge pipe with a flame detection system  

SciTech Connect

This patent describes a method of burning waste gas, using an igniter of the type having a nozzle, a main gas conduit extending to the nozzle, and an electrical spark means for creating a spark in the nozzle. It comprises: mounting the igniter to a waste gas discharge pipe with the nozzle directed across the opening of the gas discharge pipe; supplying a gaseous fuel to the main gas conduit; igniting the gaseous fuel with the electrical spark means, creating a flame for igniting the waste gas being discharged from the gas discharge pipe; providing the igniter with an auxiliary gas line extending to the vicinity of the nozzle; and supplying a second and lower volume source of waste gas to the auxiliary gas line for burning at the nozzle.

Guerra, R.E.

1990-03-06

145

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

146

Detection methods for atoms and radicals in the gas phase  

NASA Astrophysics Data System (ADS)

This report lists atoms and free radicals in the gas phase which are of interest for environmental and flame chemistry and have been detected directly. The detection methods which have been used are discussed with respect to their range of application, specificity and sensitivity. In table 1, detection methods for the five atoms of group IV (C, Si, Ge, Sn, Pb) and about 60 radicals containing at least one atom of group IV are summarized (CH, Cd, Cf, CC1, CBr, Cn, Cs, CSe, CH2, CD2, Chf, Cdf, CHC1, CHBr, CF2, CC12, CBr2, CFC1, CFBr, CH3, CD3, CF3, CH2F, CH2C1, CH2Br, CHF2, CHC12, CHBr2, Hco, Fco, CH30, CD30, CH2OH, CH3S, Nco, CH4N, CH302, CF302; C2, C2N, C2H, C20, C2HO, C2H3, C2F3, C2H5, C2HsO, C2H4OH, CH3CO, CD3CO, C2H3O, C2H502, CH3COO2, C2H4N, C2H6N, C3; Si, SiF, SiF2, SiO, SiC, Si2; Ge, GeC, GeO, GeF, GeF2, GeCl2, Sn, SnF, SnO, SnF2, Pb, PbF, PbF2, PbO, PbS). In table 2 detection methods for about 25 other atoms and 60 radicals are listed: (H, D, O, O2, Oh, Od, HO2, DO2, F, Ci, Br, I, Fo, Cio, BrO, Io, FO2, C1O2, Li, Na, K, Rb, Cs, N, N3, Nh, Nd, Nf, Nci, NBr, NH2, ND2, Nhd, Nhf, NF2, NC12, N2H3, No, NO2, NO3, Hno, Dno, P, Ph, Pd, Pf, Pci, PH2, PD2, PF2, Po, As, AsO, AsS, Sb, Bi, S, S2, Sh, Sd, Sf, SF2, So, Hso, Dso, Sn, Se, Te, Se2, SeH, SeD, SeF, SeO, SeS, SeN, TeH, TeO, Bh, BH2, Bo, Bn, B02, Cd, Hg, UF5). The tables also cite some recent kinetic applications of the various methods.

Hack, W.

147

Detection of gas and water using HHT by analyzing P- and S-wave attenuation in tight sandstone gas reservoirs  

NASA Astrophysics Data System (ADS)

A direct detection of hydrocarbons is used by connecting increased attenuation of seismic waves with oil and gas fields. This study analyzes the seismic attenuation of P- and S-waves in one tight sandstone gas reservoir and attempts to give the quantitative distinguishing results of gas and water by the characteristics of the seismic attenuation of P- and S-waves. The Hilbert-Huang Transform (HHT) is used to better measure attenuation associated with gas saturation. A formation absorption section is defined to compute the values of attenuation using the common frequency sections obtained by the HHT method. Values of attenuation have been extracted from three seismic sections intersecting three different wells: one gas-saturated well, one fully water-saturated well, and one gas- and water- saturated well. For the seismic data from the Sulige gas field located in northwest Ordos Basin, China, we observed that in the gas-saturated media the S-wave attenuation was very low and much lower than the P-wave attenuation. In the fully water-saturated media the S-wave attenuation was higher than the P-wave attenuation. We suggest that the joint application of P- and S-wave attenuation can improve the direct detection between gas and water in seismic sections. This study is hoped to be useful in seismic exploration as an aid for distinguishing gas and water from gas- and water-bearing formations.

Xue, Ya-juan; Cao, Jun-xing; Wang, Da-xing; Tian, Ren-fei; Shu, Ya-xiang

2013-11-01

148

Comparison of various detection limit estimates for volatile sulphur compounds by gas chromatography with pulsed flame photometric detection  

Microsoft Academic Search

This paper addresses the variations that presently exist regarding the definition, determination, and reporting of detection limits for volatile sulphur compounds by gas chromatography with pulsed flame photometric detection (GC-PFPD). Gas standards containing hydrogen sulphide (H2S), carbonyl sulphide (COS), sulphur dioxide (SO2), methyl mercaptan (CH3SH), dimethyl sulphide (DMS), carbon disulphide (CS2), and dimethyl disulphide (DMDS) in concentrations varying from 0.36ppb

Lionel J. J. Catalan; Victor Liang; Charles Q. Jia

2006-01-01

149

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

Microsoft Academic Search

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

Kyuseok Song; Euo Chang Jung

2003-01-01

150

Indikeringsprov med Senapsgas/Klorbensen (Detection of Mustard Gas Mixed with Chloro Benzene using Different Detection Material).  

National Technical Information Service (NTIS)

The report shows the results from detection with a mixture of mustard gas (HD) and chloro benzene. The purpose of the investigation was to see if the result is different when chloro benzene is mixed with mustard gas compared to when its not. We have found...

G. Olofsson G. Lindberg

1999-01-01

151

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

Microsoft Academic Search

A portable real time instrument for detecting concentrations in the part per billion range of reduced sulfur compounds in a sample gas. Ozonized air or oxygen and reduced sulfur compounds in a sample gas stream react to produce chemiluminescence in a reaction chamber and the emitted light is filtered and observed by a photomultiplier to detect reduced sulfur compounds. Selective

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

1983-01-01

152

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

153

Laser application in the fabrication of gas-tagged capsules. A leak detection system.  

National Technical Information Service (NTIS)

Encapsulation of a unique isotopic blend of krypton and xenon gas employs a special application of laser technology. The encapsulated gas is then used as the primary medium for detection and identification of failed nuclear fuel rods. The use of gas taggi...

R. B. McCord W. M. Lysher

1993-01-01

154

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

155

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

156

Laboratorietest och Utvaerdering av Gasindikeringsinstrument. Multi Gas Analyzer (MUGAS), Version II (Laboratory Test and Evaluation of a Gas Detection Instrument. Multi Gas Analyzer (MUGAS), Version II).  

National Technical Information Service (NTIS)

MUGAS (Multi Gas Analyzer) is a gas detection instrument developed by Telaire Europe AB, supported from the Swedish Rescue Services Agency. The instrument can be used to measure inflammable and toxic gases. The principle of measuring is based on an IR-tec...

L. Haegglund

1997-01-01

157

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...

158

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

DOEpatents

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

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

1983-06-01

159

Sensing Mechanisms for Carbon Nanotube Based NH3 Gas Detection  

SciTech Connect

There has been an argument on carbon nanotube (CNT) based gas detectors with a field-effect transistor (FET) geometry: do the response signals result from charge transfer between adsorbed gas molecules and the CNT channel and/or from the gas species induced Schottky barrier modulation at the CNT/metal contacts? To differentiate the sensing mechanisms, we employed three CNTFET structures, i.e., (1) the entire CNT channel and CNT/electrode contacts are accessible to NH3 gas; (2) the CNT/electrode contacts are passivated with a Si3N4 thin film, leaving the CNT channel open to the gas and, in contrast, (3) the CNT channel is covered with the film, while the contacts are open to the gas. We suggest that the Schottky barrier modulation at the contacts is the dominant mechanism from room temperature to 150°C. At higher temperatures, the charge transfer process contributes to the response signals. There is a clear evidence that the adsorption of NH3 on the CNT channel is facilitated by environmental oxygen.

Peng, Ning; Zhang, Qing; Chow, Chee L.; Tan, Ooi K.; Marzari, Nicola N.

2009-03-31

160

Systems and methods for detecting a flame in a fuel nozzle of a gas turbine  

DOEpatents

A system may detect a flame about a fuel nozzle of a gas turbine. The gas turbine may have a compressor and a combustor. The system may include a first pressure sensor, a second pressure sensor, and a transducer. The first pressure sensor may detect a first pressure upstream of the fuel nozzle. The second pressure sensor may detect a second pressure downstream of the fuel nozzle. The transducer may be operable to detect a pressure difference between the first pressure sensor and the second pressure sensor.

Kraemer, Gilbert Otto; Storey, James Michael; Lipinski, John; Mestroni, Julio Enrique; Williamson, David Lee; Marshall, Jason Randolph; Krull, Anthony

2013-05-07

161

Semiconductor Laser Source for Natural Gas Leak Detection. Final Report September 1, 1984 - March 31, 1985.  

National Technical Information Service (NTIS)

The feasibility of using semiconductor lasers as infrared sources for handheld natural gas leak detectors was assessed. The detection system was assumed to be based on the differential absorption (DIAL) technique and to operate at ambient temperatures. Th...

R. A. Elliott

1985-01-01

162

Acoustic Detecting and Locating Gas Pipe Line Infringement. 9th Quarterly Report.  

National Technical Information Service (NTIS)

The extensive network of high-pressure natural gas transmission pipelines covering the United States provides an important infrastructure for our energy independence. Early detection of pipeline leaks and infringements by construction equipment, resulting...

2005-01-01

163

Detectability of cosmic topology in generalized Chaplygin gas models  

Microsoft Academic Search

If the spatial section of the universe is multiply connected, repeated images or patterns are expected to be detected in observations. However, due to the finite distance to the last scattering surface, such repeated patterns could be unobservable. This raises the question of whether a given cosmic topology is detectable, depending on the values of the parameters of the cosmological

B. Mota; M. Makler; M. J. Rebouças

2006-01-01

164

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

165

Noxious gas detection using carbon nanotubes with Pd nanoparticles.  

PubMed

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

Choi, Hyang Hee; Lee, Junmin; Dong, Ki-Young; Ju, Byeong-Kwon; Lee, Wooyoung

2011-01-01

166

Noxious gas detection using carbon nanotubes with Pd nanoparticles  

PubMed Central

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

2011-01-01

167

Detection of sulfur dioxide gas with graphene field effect transistor  

NASA Astrophysics Data System (ADS)

Graphene grown by chemical vapor deposition on a Cu foil and transferred onto a Si wafer has been used to fabricate a field effect transistor device that was used to study the sensing of SO2 gas. It was found by in-situ measurements that the SO2 strongly p-dopes the graphene and dramatically shifts its Dirac point. This effect was used to monitor the SO2 gas. The detector can be completely reset by thermal annealing at 100 °C in high vacuum. The response and recovery of the detector are faster at higher temperatures. Moreover, the sensitivity of the SO2 graphene detector increases proportionally with increasing temperature.

Ren, Yujie; Zhu, Chaofu; Cai, Weiwei; Li, Huifeng; Ji, Hengxing; Kholmanov, Iskandar; Wu, Yaping; Piner, Richard D.; Ruoff, Rodney S.

2012-04-01

168

Novel technology for flame and gas detection in the petrochemical industry  

Microsoft Academic Search

A reliable and high performance novel method of flame and gas optical spectral analysis was developed to meet the specific flame and gas detection of the petrochemical industry. Petrochemical industries, especially the offshore and unmanned areas in onshore refineries, pose a major safety hazard with respect to potential explosions and fire events. Unwanted fuel spills or fugitive flammable vapor clouds,

Yechiel Spector; Esther Jacobson

1999-01-01

169

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

170

Electrochemical Corrosion Rate Sensors For Detecting Internal Corrosion Of Natural Gas Transmission Pipelines  

Microsoft Academic Search

This paper is a report on the evaluation of the use of electrochemical corrosion rate probes to detect internal corrosion in natural gas transmission pipeline environments. Flange and flush-mount probes were used in four different environments at three different sites that were selected to represent normal and upset conditions in a gas transmission pipeline. The environments consisted of humidified natural

Brenard Covino; Gordon Holcomb; Malgorzata Moroz; Russell Kane; Dawn Eden; Sophie Bullard; Steven Cramer

2005-01-01

171

Field tests of probes for detecting internal corrosion of natural gas transmission pipelines  

Microsoft Academic Search

A field study was conducted to evaluate the use of electrochemical corrosion rate (ECR) probes for detecting corrosion in environments similar to those found in natural gas transmission pipelines. Results and interpretation will be reported from four different field tests. Flange and flush-mount probes were used in four different environments at a gas-gathering site and one environment but two different

Covino Bernard S. Jr; Sophie J. Bullard; Stephen D. Cramer; Gordon R. Holcomb; M. Ziomek-Moroz; Michael S. Cayard; Russell D. Kane; Brian Meidinger

2005-01-01

172

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

Microsoft Academic Search

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.

Oudman

1993-01-01

173

Temperature and Pressure Detection System of Gas Tanks Using Fiber Bragg Grating  

Microsoft Academic Search

In order to safely test the temperature and pressure in the oil storage tanks and gas tanks, we propose a kind of method that uses fiber Bragg grating sensor to conduct real-time detection on the temperature and pressure conditions in the gas tank. Install a fiber Bragg grating as the sensor to get the temperature and pressure signal of the

Guangwei Liu; Zhenwu Guo; Fan Wu; Yang Li

2011-01-01

174

Theoretical expectations for the properties of hot gas around galaxies and prospects for future detection  

NASA Astrophysics Data System (ADS)

I will review the current theoretical predictions for the properties of hot gas around galaxies derived from cosmological simulations of galaxy formation. I will also discuss prospects for detection of such gas both at low and high redshifts with current and future X-ray emissions.

Kravtsov, Andrey

2014-08-01

175

Detection method of gas flow distribution of burden surface based on two-stage information fusion  

Microsoft Academic Search

The situation of gas flow distribution in burden surface ensures to a certain degree whether the blast furnace could be running in a way of high efficiency and low consumption, and then influences the economic benefits of the whole steel enterprises. Focusing on the difficulty of directly detecting the gas flow distribution in burden surface, a method of that distribution

An Jianqi; Wu Min; He Yong; Cao Weihua

2010-01-01

176

Laser system for natural gas detection. Phase I. Laboratory feasibility studies  

Microsoft Academic Search

Laboratory and field tests successfully proved the feasibility of laser remote sensing as a leak-survey tool in gas distribution systems. Using a pair of helium neon lasers to measure methane, the device exhibited at a 43-ft range a methane detection limit of 3 ppm in a gas plume with a 3.3-ft path length.

W. B. Grant; E. D. Hinkley

1981-01-01

177

Laser system for natural gas detection. Phase I. Laboratory Feasibility studies  

Microsoft Academic Search

Laboratory and field tests successfully proved the feasibility of laser remote sensing as a leak-survey tool in gas distribution systems, Using a pair of helium-neon lasers to measure methane, the device exhibited at a 43-ft range a methane detection limit of 3 ppm in a gas plume with a 3.3-ft path length.

W. B. Grant; E. D. Hinkley

1981-01-01

178

Fiber-Optic Based Compact Gas Leak Detection System  

NASA Technical Reports Server (NTRS)

A propellant leak detection system based on Raman scattering principles is introduced. The proposed system is flexible and versatile as the result of the use of optical fibers. It is shown that multiple species can be monitored simultaneously. In this paper oxygen, nitrogen, carbon monoxide, and hydrogen are detected and monitored. The current detection sensitivity for both hydrogen and carbon monoxide is 1% partial pressure at ambient conditions. The sensitivity for oxygen and nitrogen is 0.5% partial pressure. The response time to changes in species concentration is three minutes. This system can be used to monitor multiple species at several locations.

deGroot, Wim A.

1995-01-01

179

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...

180

Detection mechanism of metal oxide gas sensor under UV radiation  

Microsoft Academic Search

The effect of ultraviolet radiation on the sensing mechanism of polycrystalline metal oxide gas sensor has been studied analytically. The model used to describe the sensing mechanism is based on the combination of the neck mechanism and grain boundary mechanism. We found that increasing the UV radiation flux density increases the conductivity of the film by decreasing the resistance. It

Sunita Mishra; C. Ghanshyam; N. Ram; R. P. Bajpai; R. K. Bedi

2004-01-01

181

Porous One-Dimensional Photonic Crystal Coatings for Gas Detection  

Microsoft Academic Search

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

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

2010-01-01

182

Silicon Carbide-Based Hydrogen and Hydrocarbon Gas Detection.  

National Technical Information Service (NTIS)

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...

G. W. Hunter P. G. Neudeck L. Chen D. Knight C. C. Liu

1995-01-01

183

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.

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

2009-01-01

184

Instruments for Detecting Gas in Underground Mines and Tunnels.  

National Technical Information Service (NTIS)

Toxic and explosive atmospheres are described together with some of the instruments commercially available for their detection in underground mines and tunnels. Accuracy of the instruments has not been evaluated. This report should aid mine inspectors in ...

A. H. Wieser B. I. Ferber

1972-01-01

185

Gas Phase Organophosphate Detection Using Enzymes Encapsulated Within Peptide Nanotubes.  

National Technical Information Service (NTIS)

Previous work to develop biosensors that can be used to detect organophosphorus compounds (OPCs) has successfully demonstrated the potential application of enzymes encapsulated in peptide-nanotubes (PNTs) enhanced with horseradish peroxidase (HRP) to dete...

C. W. Edwards

2014-01-01

186

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

187

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

188

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

189

Detecting gas hydrate behavior in crude oil using NMR.  

PubMed

Because of the associated experimental difficulties, natural gas hydrate behavior in black oil is poorly understood despite its grave importance in deep-water flow assurance. Since the hydrate cannot be visually observed in black oil, traditional methods often rely on gas pressure changes to monitor hydrate formation and dissociation. Because gases have to diffuse through the liquid phase for hydrate behavior to create pressure responses, the complication of gas mass transfer is involved and hydrate behavior is only indirectly observed. This pressure monitoring technique encounters difficulties when the oil phase is too viscous, the amount of water is too small, or the gas phase is absent. In this work we employ proton nuclear magnetic resonance (NMR) spectroscopy to observe directly the liquid-to-solid conversion of the water component in black oil emulsions. The technique relies on two facts. The first, well-known, is that water becomes essentially invisible to liquid state NMR as it becomes immobile, as in hydrate or ice formation. The second, our recent finding, is that in high magnetic fields of sufficient homogeneity, it is possible to distinguish water from black oil spectrally by their chemical shifts. By following changes in the area of the water peak, the process of hydrate conversion can be measured, and, at lower temperatures, the formation of ice. Taking only seconds to accomplish, this measurement is nearly direct in contrast to conventional techniques that measure the pressure changes of the whole system and assume these changes represent formation or dissociation of hydrates - rather than simply changes in solubility. This new technique clearly can provide accurate hydrate thermodynamic data in black oils. Because the technique measures the total mobile water with rapidity, extensions should prove valuable in studying the dynamics of phase transitions in emulsions. PMID:16570953

Gao, Shuqiang; House, Waylon; Chapman, Walter G

2006-04-01

190

Powerful interface light emitting diodes for methane gas detection  

Microsoft Academic Search

Powerful (light emitting diodes) LEDs which exhibit more than 3.5 mW of output power at room temperature have been fabricated by liquid phase epitaxy (LPE) and characterized. These LEDs are well matched to the CH4 absorption spectrum and confirm the potential of the devices as a key component for use in an infrared CH4 gas sensor. We report on the

A. Krier; V. V. Sherstnev

2000-01-01

191

Gas Chromatographic Detection of in Vivo Activity of Equine Infectious Anaemia Virus.  

National Technical Information Service (NTIS)

By making use of the marked response of the electron capture detector, it has been possible to detect the presence of extremely small numbers of bacteria in culture media by gas chromatography. The same technique has been employed for the detection of can...

B. M. Mitruka N. L. Norcross M. Alexander

1968-01-01

192

Remote field eddy current testing for detection of stress corrosion cracks in gas transmission pipelines  

Microsoft Academic Search

Magnetic flux leakage (MFL) pigs are traditionally used for the detection of gross corrosion on steel pipelines used for the transmission of natural gas. Alternative nondestructive evaluation (NDE) modalities are required for the detection of stress corrosion cracking (SCC), which tends to exist in colonies oriented axially along the length of the pipeline. This paper describes the use of multi-phase

D. Kim; L. Udpa; S. Udpa

2004-01-01

193

Acoustic Detecting and Locating Gas Pipe Line Infringement 3rd Quarterly Report.  

National Technical Information Service (NTIS)

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...

J. L. Loth G. J. Morris

2003-01-01

194

A solenoid failure detection system for cold gas attitude control jet valves  

NASA Technical Reports Server (NTRS)

The development of a solenoid valve failure detection system is described. The technique requires the addition of a radioactive gas to the propellant of a cold gas jet attitude control system. Solenoid failure is detected with an avalanche radiation detector located in the jet nozzle which senses the radiation emitted by the leaking radioactive gas. Measurements of carbon monoxide leakage rates through a Mariner type solenoid valve are presented as a function of gas activity and detector configuration. A cylindrical avalanche detector with a factor of 40 improvement in leak sensitivity is proposed for flight systems because it allows the quantity of radioactive gas that must be added to the propellant to be reduced to a practical level.

Johnston, P. A.

1970-01-01

195

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

196

LOW COST IMAGER FOR POLLUTANT GAS LEAK DETECTION - PHASE I  

EPA Science Inventory

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

197

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

198

Gas detection for alternate-fuel vehicle facilities.  

PubMed

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

Ferree, Steve

2003-05-01

199

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

200

Design of a portable optical sensor for methane gas detection  

Microsoft Academic Search

A detailed investigation has been carried out on the design of a low-cost portable optical sensor for methane detection with a sensitivity of ?1% of the Lower Explosive Level (LEL) for methane (500ppm) and able to operate in harsh environments with temperature variation between ?20 and 50°C. The sensor design is based on the use of near-IR LEDs operating around

Crawford Massie; George Stewart; George McGregor; John R. Gilchrist

2006-01-01

201

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

PubMed

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

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

2010-06-01

202

Fiber-Laser Nice-Ohms for Trace Gas Detection  

NASA Astrophysics Data System (ADS)

Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is an absorption technique that combines frequency modulation (FM) for reduction of noise with cavity enhancement for increased interaction length with the sample to provide ultra-high detection sensitivity. The carrier of the FM triplet is locked to a mode of an external cavity and the FM modulation frequency is matched to the cavity free spectral range (FSR), thus the sidebands are transmitted through adjacent cavity modes. As a result any residual frequency noise of the laser carrier leads to the same amplitude attenuation and phase shift of the sidebands, wherefore FM spectroscopy can be performed inside the cavity without introduction of additional noise, yet benefiting from the cavity enhancement of length and laser power. The main technical difficulty of NICE-OHMS is the locking of the laser frequency to a cavity mode. We will present a recently developed compact NICE-OHMS spectrometer based on an erbium-doped fiber laser, whose narrow linewidth (1 kHz/120 ?s) simplifies the locking procedure significantly. The use of integrated-optics devices, such as a fiber-coupled electro-optic modulator, further reduces the complexity of the system. The fiber-laser-based NICE-OHMS spectrometer is capable of detecting both Doppler-broadened and sub-Doppler signals with a sensitivity in the 10^{-11} cm^{-1} range, using a cavity with a finesse of 4800. The two detection modes will be compared and experimental results from C_2H_2 and CO_2 at 1531 nm under low pressure conditions will be presented. The dependence of signal strengths and shapes on analyte concentration and other experimental parameters (such as intracavity power and pressure, cavity FSR and FM detection phase), as well as the optimum detection conditions will be discussed. J. Ye, L. S. Ma, and J. L. Hall, J. Opt. Soc. Am. B 15, 6 (1998). A. Foltynowicz, F. M. Schmidt, W. Ma, and O. Axner, Appl. Phys. B 92, 313 (2008). F. M. Schmidt, A. Foltynowicz, W. Ma, and O. Axner, J. Opt. Soc. Am. B 24, 1392 (2007). F. M. Schmidt, A. Foltynowicz, W. Ma, T. Lock, and O. Axner, Opt. Express 15, 10822 (2007). A. Foltynowicz, W. Ma, and O. Axner, Opt. Express 16, 14689 (2008).

Foltynowicz, A.; Ma, W.; Axner, O.

2009-06-01

203

Electron capture gas chromatographic detection of acethylmethylcarbinol produced by neisseria gonorrhoeae.  

PubMed Central

Acetylmethylcarbinol (acetoin) production by Neisseria gonorrhoeae and other Neisseria species was established by gas-liquid chromatography and by mass spectrometric data. Sixty-nine isolates of Neisseria were tested by incubating them in a chemically defined fluid medium. The medium was extracted with organic solvents and derivatized with heptafluorobutryic anhydride for gas chromatography and mass spectrometry. Cultures of 58 of the same strains were tested with the conventional Voges-Proskauer reagents, and results were compared with those of gas-liquid chromatography. When glucose was used as an energy source, N. gonorrhoeae, some N. meningitidis, and N. lactamica produced enough acetoin in 16 h to be detectable by either method, whereas other Neisseria species produce amounts detectable only by gas chromatography. The conventional acetylmethylcarbinol test with the chemically defined medium and maltose as an energy source might be used to develop methods that would differentiate certain members of the genus, including the pathogenic species.

Morse, C D; Brooks, J B; Kellogg, D S

1976-01-01

204

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

205

Small sodium-to-gas leak behavior in relation to LMFBR leak detection system design  

Microsoft Academic Search

Various aspects of sodium-to-gas leaks which must be considered in the design of leak detection systems for LMFBR's are discussed. Attention is focused primarily on small, weeping type leaks. Corrosion rates of steels in fused sodium hydroxide and corrosion damage observed at the site of small leaks lead to the conclusion that the sodium-gas reaction products could attack the primary

J. Hopenfeld; G. R. Taylor; L. A. James

1976-01-01

206

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

SciTech Connect

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

NONE

1998-04-01

207

A two-electrode sensor cell for CO detection in a H 2-rich gas  

Microsoft Academic Search

A two-electrode chemical cell, with a proton-conducting polymer as electrolyte, is used to detect the CO concentration in a H2-rich gas. The anode is exposed to the gas flow, while the cathode is immersed in water to retain the polymer conductivity. The disturbance of the H2-oxidation current is a measure of the partial CO pressure. The proposed model describes well

W. G. Planje; G. J. M. Janssen; M. P. de Heer

2004-01-01

208

Study on Detection of SF6 Gas Leakage Based on Photoacoustic Spectrometry  

Microsoft Academic Search

In view of the problems of using traditional monitoring method for SF6 gas leakage in electrical equipments, according to the photoacoustic spectrometry technology, the photoacoustic spectrometry experiment system is designed for detecting SF6 gas concentration. The generation of photoacoustic spectrum is presented, the photoacoustic technique is used to survey the photoacoustic characteristic of SF6 molecule at 10.6 mum wavelength, resonance

Yuanzhe Xu; Hongjing Zhou; Bo Li; Xin Zhao

2009-01-01

209

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.

210

Field evaluation of the British Gas elastic-wave vehicle for detecting stress corrosion cracking in natural gas transmission pipelines. Final report, June 1995  

SciTech Connect

The objective of this project was to provide the gas pipeline industry with a more comprehensive understanding of the capabilities of the elastic-wave, in-line inspection system developed by British Gas (BG) for detecting stress corrosion cracking (SCC) in natural gas transmission pipelines.

Culbertson, D.L.; Whitney, C.E.

1995-07-01

211

Field evaluation of the British Gas elastic-wave vehicle for detecting stress corrosion cracking in natural gas transmission pipelines. Final report, June 1995  

Microsoft Academic Search

The objective of this project was to provide the gas pipeline industry with a more comprehensive understanding of the capabilities of the elastic-wave, in-line inspection system developed by British Gas (BG) for detecting stress corrosion cracking (SCC) in natural gas transmission pipelines.

D. L. Culbertson; C. E. Whitney

1995-01-01

212

Trace gas detection based on off-beam quartz enhanced photoacoustic spectroscopy: optimization and performance evaluation.  

PubMed

A gas sensor based on off-beam quartz enhanced photoacoustic spectroscopy was developed and optimized. Specifically, the length and diameter of the microresonator tube were optimized, and the outer tube shape is modified for enhancing the trace gas detection sensitivity. The impact of the distance between the quartz tuning fork and an acoustic microresonator on the sensor performance was experimentally investigated. The sensor performance was evaluated by determining the detection sensitivity to H(2)O vapor in ambient air at normal atmospheric pressure. A normalized noise equivalent absorption coefficient (1?) of 6.2×10(-9)?cm(-1)?W/Hz(1/2) was achieved. PMID:21034071

Liu, Kun; Yi, Hongming; Kosterev, Anatoliy A; Chen, Weidong; Dong, Lei; Wang, Lei; Tan, Tu; Zhang, Weijun; Tittel, Frank K; Gao, Xiaoming

2010-10-01

213

Mass-sensitive detection of gas-phase volatile organics using disk microresonators.  

PubMed

The detection of volatile organic compounds (VOCs) in the gas phase by mass-sensitive disk microresonators is reported. The disk resonators were fabricated using a CMOS-compatible silicon micromachining process and subsequently placed in an amplifying feedback loop to sustain oscillation. Sensing of benzene, toluene, and xylene was conducted after applying controlled coatings of an analyte-absorbing polymer. An analytical model of the resonator's chemical sensing performance was developed and verified by the experimental data. Limits of detection for the analytes tested were obtained, modeled, and compared to values obtained from other mass-sensitive resonant gas sensors. PMID:21469667

Truax, Stuart B; Demirci, Kemal S; Beardslee, Luke A; Luzinova, Yulia; Hierlemann, Andreas; Mizaikoff, Boris; Brand, Oliver

2011-05-01

214

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

215

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

216

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

PubMed Central

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

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

2006-01-01

217

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

218

[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

219

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

NASA Astrophysics Data System (ADS)

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 atmospheric gases. This adsorption induced a host transformation, which was accompanied by conformational variations of the included DSB. This read-out process resulted in a critical change in DSB fluorescence at a specific threshold pressure. The composite shows different fluorescence responses to CO2 and acetylene, compounds that have similar physicochemical properties. Our system showed, for the first time, that fluorescent molecules can detect gases without any chemical interaction or energy transfer. The host-guest coupled transformations play a pivotal role in converting the gas adsorption events into detectable output signals.

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

2011-10-01

220

Picosecond standoff multiphoton detection of gas phase species: initial results  

NASA Astrophysics Data System (ADS)

In the implementation of laser-induced fluorescence (LIF) for the detection of vapor-phase organic compounds that accompany hazardous materials, multiphoton excitation offers a significant advantage over single photon methods. In particular, if the absorption spectra of unwanted background molecules overlap that of the target molecule, single photon LIF is plagued by false positives. Multiphoton methods alleviate this difficulty by requiring that the target molecule be in resonance with multiple molecular transitions. A promising multiphoton method is stimulated Raman adiabatic passage (STIRAP). This method involves a counterintuitive sequence of laser pulses which is capable of transferring 100% of the target molecules to the desired excited state from which fluorescence is to be observed. As a precursor to more complex molecules, we demonstrate the STIRAP technique on sodium vapor using the 3p (2P 1/2) <-- 3s (2S 1/2) and 5s (2S 1/2) <-- 3p (2P 1/2) transitions. This is the first time STIRAP has been achieved on a vapor using picosecond lasers. We produced light to couple the states using two synchronously pumped OPG/OPAs (pumped by the 355 nm light from a picosecond YAG). We measured the fluorescence from the 5s state to both 3p states (2P 1/2, 2P 3/2) and from both 3p states to the 3s state with monochromator using a gated CCD to eliminate Rayleigh scattered light. Our results indicate a four to five-fold increase in the transfer efficiency to the 5s state when the laser pulse that couples the 3p and 5s states precedes the laser pulse tuned to the 3p <-- 3s transition.

Johnson, J. Bruce; Lyon, Kevin; Murry, William D.; Britton, Daniel R.; Johnson, Michael J.

2008-05-01

221

Silicon Carbide Nanotubes As Potential Gas Sensors for CO and HCN Detection  

Microsoft Academic Search

Semiconducting carbon nanotubes (CNTs) have demonstrated extreme sensitivity to molecules such as NH3, NO, NO2, ans so forth. Yet, intrinsic CNTs cannot be used to detect some highly toxic molecules such as CO and HCN. In this article, we examine the possibility of silicon carbide nanotubes (SiCNTs) as a potential gas sensor for CO and HCN detection by first-principles calculations

R. Q. Wu; M. Yang; Y. H. Lu; Y. P. Feng; Z. G. Huang; Q. Y. Wu

2008-01-01

222

Community Structure Detection in Complex Networks with Applications to Gas-Liquid Two-Phase Flow  

Microsoft Academic Search

We propose an algorithm to detect community structure in complex networks based on data field theory. The efficiency and accuracy\\u000a of the algorithm for computer-simulated and real networks make it feasible to be used for the accurate detection of community\\u000a structure in complex networks. Using the conductance fluctuating signals measured from gas-liquid two-phase flow dynamic experiments,\\u000a we construct the flow

Zhongke Gao; Ningde Jin

2009-01-01

223

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

PubMed Central

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

Levett, P N; Phillips, K D

1985-01-01

224

BAGI: a technique for the detection and tracking of large gas clouds  

SciTech Connect

For the past six years the Liquefied Gaseous Fuels (LGF) Spill Effects Program at the Lawrence Livermore National Laboratory (LLNL) has been studying the possible hazards associated with large-scale spills of hazardous materials. This effort has focused primarily on modeling and measurement of the dispersion of large, heavier-than-air gas clouds. A need was discovered for the development of a system which would allow the remote detection and tracking of these large hazardous gas clouds. A passive infrared (IR) imaging system for use in monitoring liquefied natural gas (LNG) vapor cloud dispersion and vapor cloud combustion dynamics is being developed. The heart of the imaging system is the Inframetrics, Inc., Model 210 Fast Scan IR Thermal Imager. This is a two-wavelength, broadband system which when mounted in a helicopter, and with appropriate choice of interference filters, provides images of the dispersing gas cloud. These images were used to augment the LFG Program's surface gas measurement data taken during the Burro Series tests at the Naval Weapons Center (NWC), China Lake, CA. This system relies on the thermal radiation from the ground to produce a background image and the absorption bands of methane, ethane, and propane to attenuate this background image when the vapor is present. The system demonstrated the ability to image the LNG vapor cloud from an altitude of 1 km for gas concentrations down to about 1%. The BAGI technique is based on the radiation augmentation of the field of view of an imaging device by laser radiation corresponding to an absorption line of the gas species to be detected. Schematic representation of several BAGI systems as proposed both for leak detection and the tracking of a hazardous gas cloud are shown.

McRae, T.G.

1983-02-01

225

Quantum-State Detection of Molecular Hydrogen in Gas-Gas and Gas-Surface Scattering Experiments.  

National Technical Information Service (NTIS)

We have used the technique of resonance-enhanced multiphoton ionization to detect molecular hydrogen in a quantum state specific manner. We report on the use of this technique to determine accurate ro-vibrational state populations in scattering experiment...

G. O. Sitz R. S. Blake T. A. Stephenson R. N. Zare

1986-01-01

226

Nanoparticle cluster gas sensor: controlled clustering of SnO? nanoparticles for highly sensitive toluene detection.  

PubMed

Gas sensing with nanosized oxide materials is attracting much attention because of its promising capability of detecting various toxic gases at very low concentrations. In this study, using clustered SnO2 nanoparticles formed by controlled particle aggregation, we fabricated highly sensitive gas sensing films to detect large gas molecules such as toluene. A hydrothermal method using stanic acid (SnO2·nH2O) gel as a precursor produced monodispersed SnO2 nanoparticles of ca. 5 nm at pH 10.6. Decreasing the solution pH to 9.3 formed SnO2 clusters of ca. 45 nm that were assemblies of the monodispersed nanoparticles, as determined by dynamic light scattering, X-ray diffraction, and transmission electron microscopy analyses. Porous gas sensing films were successfully fabricated by a spin-coating method using the clustered nanoparticles due to the loose packing of the larger aggregated particles. The sensor devices using the porous films showed improved sensor responses (sensitivities) to H2 and CO at 300 °C. The enhanced sensitivity resulted from an increase in the film's porosity, which promoted the gas diffusivity of the sensing films. Pd loading onto the clustered nanoparticles further upgraded the sensor response due to catalytic and electrical sensitization effects of Pd. In particular, the Pd-loaded SnO2 nanoparticle clusters showed excellent sensitivity to toluene, able to detect it at down to low ppb levels. PMID:24635838

Suematsu, Koichi; Shin, Yuka; Hua, Zhongqiu; Yoshida, Kohei; Yuasa, Masayoshi; Kida, Tetsuya; Shimanoe, Kengo

2014-04-01

227

On the Use of Arc Radiation to Detect the Quality of Gas Metal Arc Welds  

Microsoft Academic Search

Gas metal arc (GMA) welding has over the years grown both in stature and strength to become a widely used welding process in the industries related to manufacturing. With sustained and noticeable developments in the technologies related to welding a need to automatically detect and even control the quality of welding has become both essential and desirable. Since defects present

Li Zhiyong; T. S. Srivatsan; Zhao Hongzhi; Yan Xiaocheng; Guo Yong

2011-01-01

228

Novel technology for flame and gas detection in the petrochemical industry  

NASA Astrophysics Data System (ADS)

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

Spector, Yechiel; Jacobson, Esther

1999-01-01

229

The detection properties of ammonia SAW gas sensors based on L-glutamic acid hydrochloride  

Microsoft Academic Search

This study has investigated an improved surface acoustic wave (SAW) ammonia gas sensor based on L-glutamic acid hydrochloride. It presents an excellent reversibility, sensitivity, and repeatability to ammonia. The frequency shift versus ammonia concentration above 40°C was a monotonic function, and the limit of detection of the sensor at 50°C was 80 ppb.

Chi-Yen Shen; Chun-Pu Huang; Wang-Tsung Huang

2005-01-01

230

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

231

Selective CO detection by using indium oxide-based semiconductor gas sensor  

Microsoft Academic Search

A compact, solid-state CO sensor has been in great demand for detecting incomplete combustion of gas appliances. Continuous CO monitoring of combustion exhaust can prevent a serious CO poisoning accident. From a screening test for the sensing properties of 26 single oxides, an InâOâ sensor element was found to exhibit rather high sensitivity to both CO and Hâ in wet

Hiroyuki Yamaura; Jun Tamaki; Norio Miura; Noboru Yamazoe; Koji Moriya

1996-01-01

232

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

Microsoft Academic Search

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

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

2007-01-01

233

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

Microsoft Academic Search

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, ?≈5 ns) lamp pumped

Z. Kuprionis

2007-01-01

234

Detection of Metal-Transfer Mode in GMAW (Gas-Metal-Arc Welding).  

National Technical Information Service (NTIS)

One of the requirements of a sensing system for feedback control of gas metal arc welding (GMAW) is the capability to detect information about the metal-transfer mode. Because the operating boundary for the desired transfer mode, expressed as a function o...

J. A. Johnson N. M. Carlson H. B. Smartt

1989-01-01

235

Detection of noble gas scintillation light with large area avalanche photodiodes (LAAPDs)  

Microsoft Academic Search

Large area avalanche photodiodes (LAAPDs) were used for a series of systematic measurements of the scintillation light in Ar, Kr, and Xe gas. Absolute quantum efficiencies are derived. Values for Xe and Kr are consistent with those given by the manufacturer. For the first time we show that argon scintillation (128nm) can be detected at a quantum efficiency above 40%.

R. Chandrasekharan; M. Messina; A. Rubbia

2005-01-01

236

Correlated column micro gas chromatography instrumentation for the vapor detection of contraband drugs in cargo containers  

Microsoft Academic Search

We have developed an instrument based on Micro Gas Chromatography ((mu) GC) for rapid, handheld detection of vapor signatures from contraband drugs in cargo containers. For this application, a key requirement is the ability to distinguish the vapor signatures of contraband drugs against the highly variable chemical backgrounds encountered in cargo containers. To achieve this, we split the sample and

Paul M. Holland; Robert V. Mustacich; James F. Everson; William Foreman; Michael Leone; Ann H. Sanders; Walter J. Naumann

1994-01-01

237

Selectivity improvement of semi-conducting gas sensors by selective filter for atmospheric pollutants detection  

Microsoft Academic Search

The monitoring of atmospheric pollution using chemical gas sensors is a challenge due to the lack of selectivity of most existing devices. However, their performances can be improved using filtering films achieving the separation or the removal of some gases. This study is focused on the detection of carbon monoxide and of oxidant pollutants (nitrogen dioxide and ozone) by sensors

J. P. Viricelle; A. Pauly; L. Mazet; J. Brunet; M. Bouvet; C. Varenne; C. Pijolat

2006-01-01

238

Zeolite-based Impedimetric Gas Sensor Device in Low-cost Technology for Hydrocarbon Gas Detection  

PubMed Central

Due to increasing environmental concerns the need for inexpensive selective gas sensors is increasing. This work deals with transferring a novel zeolite-based impedimetric hydrocarbon gas sensor principle, which has been originally manufactured in a costly combination of photolithography, thin-film processes, and thick-film processes to a low-cost technology comprising only thick-film processes and one electroplating step. The sensing effect is based on a thin chromium oxide layer between the interdigital electrodes and a Pt-loaded ZSM-5 zeolite film. When hydrocarbons are present in the sensor ambient, the electrical sensor impedance increases strongly and selectively. In the present work, the chromium oxide film is electroplated on Au screen-printed interdigital electrodes and then oxidized to Cr2O3. The electrode area is covered with the screen-printed zeolite. The sensor device is self-heated utilizing a planar platinum heater on the backside. The best sensor performance is obtained at a frequency of 3 Hz at around 350 °C. The good selectivity of the original sensor setup could be confirmed, but a strong cross-sensitivity to ammonia occurs, which might prohibit its original intention for use in automotive exhausts.

Reiss, Sebastian; Hagen, Gunter; Moos, Ralf

2008-01-01

239

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

240

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

SciTech Connect

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.

2007-12-18

241

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

242

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

243

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

PubMed Central

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.

Levett, P N

1984-01-01

244

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

245

Gas chromatography with flame photometric detection of 31 organophosphorus pesticide residues in Alpinia oxyphylla dried fruits.  

PubMed

A simple, rapid and effective gas chromatography-flame photometric detection method was established for simultaneous multi-component determination of 31 organophosphorus pesticides (OPPs) residues in Alpinia oxyphylla, which is widely consumed as a traditional medicine and food in China. Sample preparation was completed in a single step without any clean-up procedure. All pesticides expressed good linear relationships between 0.004 and 1.0?g/mL with correlation coefficients higher than 0.9973. The method gave satisfactory recoveries for most pesticides. The limits of detection varied from 1 to 10ng/mL, and the limits of quantification (LOQs) were between 4 and 30ng/mL. The proposed method was successfully applied to 55 commercial samples purchased from five different areas. Five pesticide residues were detected in four (7.27%) samples. The positive samples were confirmed by gas chromatography with tandem mass spectrometry (GC-MS/MS). PMID:24874387

Zhao, Xiangsheng; Kong, Weijun; Wei, Jianhe; Yang, Meihua

2014-11-01

246

Detection of traces of formaldehyde in pure air by gas chromatography and helium ionization detection.  

PubMed

The sensitive helium ionization detector (HID) was used for the direct determination of ppm to ppb levels of formaldehyde in air. Two methods to generate formaldehyde in an air stream were evaluated. The first method utilized a paraformaldehyde permeation tube and the second utilized a motor driven syringe and a dilute solution of formaldehyde. The two methods were evaluated using gas chromatography with HID and spectrophotometry. The paraformaldehyde permeation tube generates only about 60% of the theoretical value, while the motor driven syringe was accurate for levels below 2 ppm; however, at a concentration of 13 ppm or above, oligomers or other chemical forms of CH2O are formed to decrease the concentration of gaseous CH2O produced. PMID:6501532

Andrawes, F F

1984-11-01

247

Selective and reversible ammonia gas detection with nanoporous film functionalized silicon photonic micro-ring resonator.  

PubMed

Portable, low cost and real-time gas sensors have a considerable potential in various biomedical and industrial applications. For such applications, nano-photonic gas sensors based on standard silicon fabrication technology offer attractive opportunities. Deposition of high surface area nano-porous coatings on silicon photonic sensors is a means to achieve selective, highly sensitive and multiplexed gas detection on an optical chip. Here we demonstrate selective and reversible ammonia gas detection with functionalized silicon-on-insulator optical micro-ring resonators. The micro-ring resonators are coated with acidic nano-porous aluminosilicate films for specific ammonia sensing, which results in a reversible response to NH(3)with selectivity relative to CO(2). The ammonia detection limit is estimated at about 5 ppm. The detectors reach a steady response to NH(3) within 30 and return to their base level within 60 to 90 seconds. The work opens perspectives on development of nano-photonic sensors for real-time, non-invasive, low cost and light weight biomedical and industrial sensing applications. PMID:22714172

Yebo, Nebiyu A; Sree, Sreeprasanth Pulinthanathu; Levrau, Elisabeth; Detavernier, Christophe; Hens, Zeger; Martens, Johan A; Baets, Roel

2012-05-21

248

CO(1-0) detection of molecular gas in the massive Spiderweb Galaxy (z = 2)  

NASA Astrophysics Data System (ADS)

The high-redshift radio galaxy MRC 1138-262 (`Spiderweb Galaxy'; z = 2.16) is one of the most massive systems in the early Universe and surrounded by a dense `web' of proto-cluster galaxies. Using the Australia Telescope Compact Array, we detected CO(1-0) emission from cold molecular gas - the raw ingredient for star formation - across the Spiderweb Galaxy. We infer a molecular gas mass of MH2 = 6 × 1010 M? (for MH2/L'CO = 0.8). While the bulk of the molecular gas coincides with the central radio galaxy, there are indications that a substantial fraction of this gas is associated with satellite galaxies or spread across the intergalactic medium on scales of tens of kpc. In addition, we tentatively detect CO(1-0) in the star-forming proto-cluster galaxy HAE 229, 250 kpc to the West. Our observations are consistent with the fact that the Spiderweb Galaxy is building up its stellar mass through a massive burst of widespread star formation. At maximum star formation efficiency, the molecular gas will be able to sustain the current star formation rate (SFR ? 1400 M? yr-1, as traced by Seymour et al.) for about 40 Myr. This is similar to the estimated typical lifetime of a major starburst event in infrared luminous merger systems.

Emonts, B. H. C.; Feain, I.; Röttgering, H. J. A.; Miley, G.; Seymour, N.; Norris, R. P.; Carilli, C. L.; Villar-Martín, M.; Mao, M. Y.; Sadler, E. M.; Ekers, R. D.; van Moorsel, G. A.; Ivison, R. J.; Pentericci, L.; Tadhunter, C. N.; Saikia, D. J.

2013-04-01

249

Comparison of three lychee cultivar odor profiles using gas chromatography-olfactometry and gas chromatography-sulfur detection.  

PubMed

Odor volatiles in three major lychee cultivars (Mauritius, Brewster, and Hak Ip) were examined using gas chromatography-olfactometry, gas chromatography-mass spectrometry, and gas chromatography-pulsed flame photometric detection. Fifty-nine odor-active compounds were observed including 11 peaks, which were associated with sulfur detector responses. Eight sulfur volatiles were identified as follows: hydrogen sulfide, dimethyl sulfide, diethyl disulfide, 2-acetyl-2-thiazoline, 2-methyl thiazole, 2,4-dithiopentane, dimethyl trisulfide, and methional. Mauritius contained 25% and Brewster contained 81% as much total sulfur volatiles as Hak Ip. Cultivars were evaluated using eight odor attributes: floral, honey, green/woody, tropical fruit, peach/apricot, citrus, cabbage, and garlic. Major odor differences in cabbage and garlic attributes correlated with cultivar sulfur volatile composition. The 24 odor volatiles common to all three cultivars were acetaldehyde, ethanol, ethyl-3-methylbutanoate, diethyl disulfide, 2-methyl thiazole, 1-octen-3-one, cis-rose oxide, hexanol, dimethyl trisulfide, alpha-thujone, methional, 2-ethyl hexanol, citronellal, (E)-2-nonenal, linalool, octanol, (E,Z)-2,6-nonadienal, menthol, 2-acetyl-2-thiazoline, (E,E)-2,4-nonadienal, beta-damascenone, 2-phenylethanol, beta-ionone, and 4-vinyl-guaiacol. PMID:17266328

Mahattanatawee, Kanjana; Perez-Cacho, Pilar Ruiz; Davenport, Thomas; Rouseff, Russell

2007-03-01

250

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

251

New gas mixtures suitable for rare event detection using a Micromegas-TPC detector  

NASA Astrophysics Data System (ADS)

The aim of the presented work was to develop further techniques based on a Micromegas-TPC, in order to reach a high gas gain with good energy resolution, and to search for gas mixtures suitable for rare event detection. This paper focuses on Xenon, which is convenient for the search of neutrinoless double beta decay in 136Xe, and CF4, suitable for dark matter searches and the study of solar and reactor neutrinos. Various configurations of the Micromegas plane were investigated and are described. Gains of 105 and energy resolutions of 35-65% at 6 keV have been achieved.

Ounalli, L.; Vuilleumier, J.-L.; Schenker, D.; Vuilleumier, J.-M.

2009-01-01

252

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

PubMed

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 (NO(2)) and ammonia (NH(3)) in humidified air. NO(2) 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 NH(3). PMID:21817785

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

2011-09-01

253

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

254

Detecting errors in blood-gas measurement by analysis with two instruments.  

PubMed

We performed a two-stage prospective evaluation of the error detection capabilities of duplicate analysis of blood-gas specimens. In the first stage we analyzed 1601 specimens with a Corning Model 175 blood-gas analyzer as the test instrument and a Corning Model 178 analyzer as the reference instrument, and in the second stage we analyzed 1544 specimens with two Model 178 analyzers. In each stage the designated reference instrument underwent troubleshooting whenever an analytical error was detected; the test instrument underwent troubleshooting only when error conditions were indicated by means other than duplicate analysis. An error was considered to have occurred if the difference between the duplicate analyses exceeded 0.02 (for pH), 0.53 kPa, i.e., 4 mmHg (pCO2), or 7% (pO2). The number of specimens for which errors were detected was 97 (6.1%) in the first stage, 23 (1.5%) in the second. For each analyte more errors were detected with the Model 175 analyzer (of older design) than with the newer Model 178 analyzer. Furthermore, in certain periods associated with the use of particular electrodes there were very high error rates for individual analytes: 8% for pCO2, 18% for pO2. We conclude that duplicate analysis should be considered as a possible required standard for error detection. PMID:3829382

Metzger, L F; Stauffer, W B; Krupinski, A V; Millman, R P; Cembrowski, G S; Pack, A I

1987-04-01

255

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

SciTech Connect

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

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

2007-12-01

256

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

SciTech Connect

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

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

1982-06-01

257

Detection of internal defects in a liquid natural gas tank by use of infrared thermography  

NASA Technical Reports Server (NTRS)

The use of an infrared scanning technique to detect defects in the secondary barrier of a liquid natural gas tank is described. The method works by detecting leak-caused temperature differences as low as 0.2 K, but can provide only an approximate idea of the extent of the defect. The nondestructive method was tested in a study of a LNG tank already at its location in a ship; the secondary barrier was located inside the tank wall. Defective areas indicated by the infrared radiometric measurements were confirmed by other probe techniques and by physical examination.

Kantsios, A. G.

1978-01-01

258

Field Evaluation of the British Gas Elastic-Wave Vehicle for Detecting Stress Corrosion Cracking in Natural Gas Transmission Pipelines. Final Report, June 1995.  

National Technical Information Service (NTIS)

The objective of this project was to provide the gas pipeline industry with a more comprehensive understanding of the capabilities of the elastic-wave, in-line inspection system developed by British Gas (BG) for detecting stress corrosion cracking (SCC) i...

D. L. Culbertson C. E. Whitney

1995-01-01

259

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.

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

2013-01-01

260

Detection of polar metabolites through the use of gas chromatography-mass spectrometry.  

PubMed

Gas chromatography-mass spectrometry (GC-MS) is a highly reproducible and sensitive analytical technique that has had significant use in the area of metabolite profiling. GC-MS is able to detect a wide variety of metabolites, with highly differing chemistries. In general, extracted biological samples are volatilized prior to separation on a capillary column with a stationary phase suited to the analysis of the compounds of interest. Separated compounds are eluted into a mass spectrometer equipped with an electron impact ionization source, thereby generating a quantifiable mass spectral fingerprint. This chapter describes a method for the trimethylsilyl derivatization of polar metabolites, followed by detection and relative quantification using a gas chromatograph coupled to a single quadrupole mass spectrometer. Using this method will enable the profiling of the greatest range of polar metabolites. PMID:23963901

De Souza, David P

2013-01-01

261

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

262

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

SciTech Connect

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

Kulp, T.J.

1995-05-01

263

Assay of 3-Carboxy-Antipyrine in Urine by Capillary Gas Chromatography with Nitrogen Selective Detection  

Microsoft Academic Search

An assay procedure is described for 3-carboxy-antipyrine in urine using gas chromatography with a support coated open tubular capillary column (Carbowax 20M), a solid injection system and nitrogen selective detection. 3-Carboxy-antipyrine was analyzed after derivatization with diazomethane and using 4-bromo-antipyrine as internal standard. Following extraction of the urine samples with a mixture of organic solvents linear calibration curves were obtained

M. Danhof; A. G. de Boer; E. de Groot-van der Vis; D. D. Breimer

1979-01-01

264

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

Microsoft Academic Search

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

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

1997-01-01

265

Comparative application of sulfur chemiluminescence detection in gas and supercritical fluid chromatography  

Microsoft Academic Search

Sulfur chemiluminescence detection (SCD) for the determination of sulfur-containing compounds in gas chromatography (GC) and supercritical fluid chromatography (SFC) is described. The detector is based on the chemiluminescence reaction of ozone with sulfur monoxide which is produced in an H2\\/O2 reducing flame from sulfur-containing analytes. High selectivity over nonsulfur-containing species has been achieved for a number of mercaptans and sulfur-containing

W. F. Sye; Z. X. Zhao; M. L. Lee

1992-01-01

266

[The gas chromatography detection of fat acids in dry blood serum].  

PubMed

The article discusses the development of gas chromatography method of detecting the composition of fat acids in dry blood serum. The comparative analysis of content of fat acids in freshly selected and dry serum. The stability of composition of fat acids in dry serum under its conservation during 2 months was examined. It is demonstrated that qualitative and quantitative compound of fat acids in fresh and dry serum is identical and continue to be unchanged during one month. PMID:22946220

Petrova, I A; Kuznetsova, L P

2012-06-01

267

Determination of isoprene in human breath by thermal desorption gas chromatography with ultraviolet detection  

Microsoft Academic Search

We describe a new, highly sensitive and specific method for the analysis of isoprene (2-methyl-1,3-butadiene) in human breath. A known volume of expired air (150 ml) was drawn through a solid sorbent material to capture trace organic substances, followed by thermal desorption at 200°C and subsequent determination of isoprene by gas chromatography with diode-array ultraviolet detection. The calibration plot was

A. W. Jones; V. Lagesson; C. Tagesson

1995-01-01

268

On-chip Fabry–Pérot interferometric sensors for micro-gas chromatography detection  

Microsoft Academic Search

We fabricated and characterized on-chip Fabry–Pérot (FP) vapor sensors for the development of on-column micro-gas chromatography (?GC) detectors. The FP sensors were made by coating a thin layer of polymer on a silicon wafer. The air–polymer and polymer–silicon interfaces form an FP cavity, whose resonance wavelengths change in response to the vapor absorption\\/desorption, thus allowing for rapid detection and quantification

Karthik Reddy; Yunbo Guo; Jing Liu; Wonsuk Lee; Maung Kyaw Khaing Oo; Xudong Fan

2011-01-01

269

Dispersive liquid–liquid microextraction combined with gas chromatography-flame photometric detection  

Microsoft Academic Search

A new method was used for the extraction of organophosphorus pesticides (OPPs) from water samples: dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography-flame photometric detection (GC-FPD). In this extraction method, a mixture of 12.0?L chlorobenzene (extraction solvent) and 1.00mL acetone (disperser solvent) is rapidly injected into the 5.00mL water sample by syringe. Thereby, a cloudy solution is formed. In fact,

Sana Berijani; Yaghoub Assadi; Mansoor Anbia; Mohammad-Reza Milani Hosseini; Elham Aghaee

2006-01-01

270

Detection of gas pockets in pressurised wastewater mains using dynamic system response analysis.  

PubMed

In the Netherlands, wastewater is mostly collected in combined sewer system and transported to a WWTP through pressure mains. These pressure mains form an element of the system that did not receive much attention lately with respect to monitoring of performance and maintenance. For that reason, their state of functioning is often not known. Failure of operation is only noticed when during storm conditions the capacity of the system drops, resulting in undesirable discharge to the surface water. A recently made inventory showed that about half of the pressure mains show increased pressure loss for no obvious reason. Reduction of the systems nominal capacity can result from many causes, like increased wall roughness, scaling and the occurrence of free gas in the pipeline. The occurrence of gas-pockets may be caused by degassing of dissolved gas, but also by air entrapment at the pump inlet or at air valves. A research project is started that will be carried out from 2003 to 2005. This project focuses on three goals: the description of the gas-water transport phenomena in wastewater pressure mains, a method to detect and diagnose gas problems, and to overcome future problems by either applying remedial measures or by developing improved design methods for wastewater pressure systems. This paper describes the layout of the experimental set-up to detect and diagnose gas problems and the first results of the experiments are presented and discussed. The results are used to validate a model (Wanda) developed by Delft Hydraulics that describes the phenomena involved in surges in air/water transport. PMID:17425069

Lubbers, C; Clemens, F

2007-01-01

271

Detection of explosive analytes using a fiber-based optical Fabry-Perot gas sensor  

NASA Astrophysics Data System (ADS)

We demonstrate the rapid detection of explosive vapors based on a fiber-based optical Fabry-Pérot (FP) gas sensor. The sensing probe of the FP sensor is composed of a thin metal layer and a vapor-sensitive polymer layer that are deposited sequentially on a cleaved fiber endface to form an FP cavity. The interference spectrum generated from the reflected light at the metal-polymer and polymer-air interfaces changes upon the absorption of gas analyte. By monitoring the interference shift, we are able to obtain quantitative and knetic information of the interaction between the analyte and the polymer layer. We further assemble the FP sensor with a short fused silica capillary into a sensor module, and employ it in a gas chromotgraphy (GC) system for selevtive rapid on-column detection. In this report, we specifically target 2, 4- dinitrotoluene (DNT) and 2, 4, 6-trinitrotoluene (TNT) for their obvious defense applications. This work could lead to a portable sensor capable of detecting low concentrations of DNT, TNT, and other explosive chemicals.

Liu, Jing; Howard, Daniel J.; Whiteside, Paul; Sun, Yuze; Almasri, Mahmoud; Frye-Mason, Greg; Thompson, Aaron; Ja, Shiou-Jyh; Fan, Xudong

2010-04-01

272

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

NASA Astrophysics Data System (ADS)

We present the results of a long (~93 ks) XMM-Newton observation of the bright BL-Lac object PKS 0548-322 (z= 0.069). Our Reflection Grating Spectrometer (RGS) spectrum shows a single absorption feature at an observed wavelength ?= 23.33 +/- 0.01 Å, which we interpret as OVI K? absorption at z= 0.058, i.e. ~3000 km s-1 from the background object. The observed equivalent width of the absorption line, ~30 mÅ, coupled with the lack of the corresponding absorption edge in the EPIC pn data, implies a column density of NOVI~ 2 × 1016 cm-2 and turbulence with a Doppler velocity parameter b > 100 km s-1. Within the limitations of our RGS spectrum, no OVII or OV K? absorption are detected. Under the assumption of ionization equilibrium by both collisions and the extragalactic background, this is only marginally consistent if the gas temperature is ~2.5 × 105 K, with significantly lower or higher values being excluded by our limits on OV or OVII. If confirmed, this would be the first X-ray detection of a large amount of intervening warm absorbing gas through OVI absorption. The existence of such a high column density absorber, much stronger than any previously detected one in OVI, would place stringent constraints on the large-scale distribution of baryonic gas in the Universe.

Barcons, X.; Paerels, F. B. S.; Carrera, F. J.; Ceballos, M. T.; Sako, M.

2005-06-01

273

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

274

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

275

Characterization of dioxin-like contamination in soil and sediments from the “hot spot” area of petrochemical plant in Pancevo (Serbia)  

Microsoft Academic Search

Purpose  Combinatorial bio\\/chemical approach was applied to investigate dioxin-like contamination of soil and sediment at the petrochemical\\u000a and organochlorine plant in Pancevo, Serbia, after the destruction of manufacturing facilities that occurred in the spring\\u000a of 1999 and subsequent remediation actions.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and methods  Soil samples were analyzed for indicator polychlorinated biphenyls (PCBs) by gas chromatography\\/electron capture detection\\u000a (GC\\/ECD). Prioritized soil sample and

Sonja Kaisarevic; Klara Hilscherova; Roland Weber; Kristina L. Sundqvist; Mats Tysklind; Ernest Voncina; Stanka Bobic; Nebojsa Andric; Kristina Pogrmic-Majkic; Mirjana Vojinovic-Miloradov; John Paul Giesy; Radmila Kovacevic

2011-01-01

276

Polychlorinate biphenyls (PCB) analysis report for solid sample for 219S tank 102  

SciTech Connect

One waste sample 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). Extraction follows closely method 354 C of SW-846, analysis follows SW-846 method 8082. A cross reference of laboratory sample number to the customer identification is given in a table.

Ross, G.A.

1997-12-05

277

Research and Development of Non-Spectroscopic MEMS-Based Sensor Arrays for Targeted Gas Detection  

SciTech Connect

The ability to monitor the integrity of gas volumes is of interest to the stockpile surveillance community. Specifically, the leak detection of noble gases, at relevant concentration ranges and distinguished from other chemical species that may be simultaneously present, is particularly challenging. Aside from the laboratory-based method of gas chromatography-mass spectrometry (GC-MS), where samples may be collected by solid-phase microextraction (SPME) or cryofocusing, the other major approaches for gas-phase detection employ lasers typically operating in the mid-infrared wavelength region. While mass spectrometry can readily detect noble gases - the helium leak detector is an obvious example - laser-based methods such as infrared (IR) or Raman spectroscopy are completely insensitive to them as their monatomic nature precludes a non-zero dipole moment or changes in polarizability upon excitation. Therefore, noble gases can only be detected by one of two methods: (1) atomic emission spectroscopies which require the generation of plasmas through laser-induced breakdown, electrical arcing, or similar means; (2) non-spectroscopic methods which measure one or more physical properties (e.g., mass, thermal conductivity, density). In this report, we present our progress during Fiscal Year 2011 (FY11) in the research and development of a non-spectroscopic method for noble gas detection. During Fiscal Year 2010 (FY10), we demonstrated via proof-of-concept experiments that the combination of thermal conductivity detection (TCD) and coating-free damped resonance detection (CFDRD) using micro-electromechanical systems (MEMS) could provide selective sensing of these inert species. Since the MEMS-based TCD technology was directly adapted from a brassboard prototype commissioned by a previous chemical sensing project, FY11 efforts focused on advancing the state of the newer CFDRD method. This work, guided by observations previously reported in the open literature, has not only resulted in a substantially measureable increase in selectivity but has also revealed a potential method for mitigating or eliminating thermal drift that does not require a secondary reference sensor. The design of an apparatus to test this drift compensation scheme will be described. We will conclude this report with a discussion of planned efforts in Fiscal Year 2012 (FY12).

Loui, A; McCall, S K

2011-10-24

278

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

279

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

280

[Detection technology of methane gas concentration based on infrared absorption spectrum].  

PubMed

According to the disadvantages of current methane sensor in coal mine, the infrared methane concentration detection system based on the principle of infrared spectrum absorption was designed using differential absorption technology. In the system single light beam absorbing cell and single light beam and double wavelengths technology are adopted. Differential amplifier circuit serves as the core of faint signal processing circuit that detects the output signal of methane concentration, and linear formula fits the curve of methane concentration and output voltage, which realizes accurate and full range detection of gas concentration. Experiment shows that measurement error is less than 2%, and the system has very high measurement precision and possesses the basis of industrial applications. PMID:21510386

Luo, Da-Feng; Yang, Jian-Hua; Zhong, Chong-Gui

2011-02-01

281

Detecting naphthenic acids in waters by gas chromatography-mass spectrometry.  

PubMed

Naphthenic acids (general formula C(n)H(2n+Z)O(2)) are water-soluble, toxic compounds found in petroleum and bitumen. Some of the current methods for detecting these acids in waters depend on measuring the presence of the carboxylic acid functional group, and therefore many of these methods also detect naturally occurring carboxylic acids that are not naphthenic acids. We report a procedure that includes liquid-liquid extraction, cleanup, and derivatization to form t-butyldimethylsilyl esters prior to gas chromatography-mass spectrometry (GC-MS) analysis. Using low- and high-resolution MS to detect the ion C(15)H(27)O(2)Si(+) (nominal m/z=267) is an excellent indicator of the presence of naphthenic acids at concentrations > or =10microgL(-1). PMID:17173926

Merlin, Mireya; Guigard, Selma E; Fedorak, Phillip M

2007-01-26

282

Artificial sensing intelligence with silicon nanowires for ultraselective detection in the gas phase.  

PubMed

The use of molecularly modified Si nanowire field effect transistors (SiNW FETs) for selective detection in the liquid phase has been successfully demonstrated. In contrast, selective detection of chemical species in the gas phase has been rather limited. In this paper, we show that the application of artificial intelligence on deliberately controlled SiNW FET device parameters can provide high selectivity toward specific volatile organic compounds (VOCs). The obtained selectivity allows identifying VOCs in both single-component and multicomponent environments as well as estimating the constituent VOC concentrations. The effect of the structural properties (functional group and/or chain length) of the molecular modifications on the accuracy of VOC detection is presented and discussed. The reported results have the potential to serve as a launching pad for the use of SiNW FET sensors in real-world counteracting conditions and/or applications. PMID:24437965

Wang, Bin; Cancilla, John C; Torrecilla, Jose S; Haick, Hossam

2014-02-12

283

Detection of a noble gas molecular ion, 36ArH+, in the Crab Nebula.  

PubMed

Noble gas molecules have not hitherto been detected in space. From spectra obtained with the Herschel Space Observatory, we report the detection of emission in the 617.5- and 1234.6-gigahertz J = 1-0 and 2-1 rotational lines of (36)ArH(+) at several positions in the Crab Nebula, a supernova remnant known to contain both molecular hydrogen and regions of enhanced ionized argon emission. Argon-36 is believed to have originated from explosive nucleosynthesis in massive stars during core-collapse supernova events. Its detection in the Crab Nebula, the product of such a supernova event, confirms this expectation. The likely excitation mechanism for the observed (36)ArH(+) emission lines is electron collisions in partially ionized regions with electron densities of a few hundred per centimeter cubed. PMID:24337290

Barlow, M J; Swinyard, B M; Owen, P J; Cernicharo, J; Gomez, H L; Ivison, R J; Krause, O; Lim, T L; Matsuura, M; Miller, S; Olofsson, G; Polehampton, E T

2013-12-13

284

Terrestrial laser scanning for detection of landfill gas: a pilot study  

NASA Astrophysics Data System (ADS)

Methane built up in landfills as a result of breaking down of organic materials can be a renewable energy source if it is taken advantage of. The aim of research presented in this paper is to detect landfill gas (that contains methane) by means of terrestrial laser scanning. The hypothesis is that where no surface leakage has been reported, the landfill gas will expand or migrate. Therefore, it is possible to detect it through repeated scanning of the same area and comparison of Digital Terrain Models (DTMs) generated from the point clouds. Only the most significant movements, i.e. vertical, are of interest in this case. During September-November 2011, a small area at Forsbacka landfill in the vicinity of Gävle was scanned 10 times. Epoch-to-epoch comparisons of the resulting DTMs have shown two significant changes (-27 and +19 mm) in elevation of the surface, and it is not impossible that they are caused by migrating landfill gas. The method tested in this study is deemed to be rigorous and accurate for detecting small-scale swell-shrink behaviour of the ground surface (in our case a landfill surface). However, both data processing and interpretation of the results have been considerably complicated by presence of low vegetation (weeds) on the study site, which was dificult to filter away completely from the data. Based on our pilot study, we recommend that a larger area and a longer period of time are chosen to give basis for more grounded conclusions about presence of landfill gas.

Reshetyuk, Yuriy; Mårtensson, Stig-Göran

2014-04-01

285

Determination of Residual Epichlorohydrin in Sevelamer Hydrochloride by Static Headspace Gas Chromatography with Flame Ionization Detection  

PubMed Central

A sensitive static headspace gas chromatographic method was developed and validated for the determination of residual epichlorohydrin (ECH) in sevelamer hydrochloride (SVH) drug substance. This method utilized a Phenomenex Zebron ZB-WAX GC column, helium as carrier gas with flame ionization detection. The critical experimental parameters, such as, headspace vial incubation time and incubation temperature were studied and optimized. The method was validated as per United States Pharmacopoeia (USP) and International Conference on Harmonization (ICH) guidelines in terms of detection limit (DL), quantitation limit (QL), linearity, precision, accuracy, specificity and robustness. A linear range from 0.30 to 10 ?g/mL was obtained with the coefficient of determination (r2) 0.999. The DL and QL of ECH were 0.09 ?g/mL and 0.30 ?g/mL, respectively. The recovery obtained for ECH was between 91.7 and 96.6%. Also, the specificity of the method was proved through gas chromatography mass spectrometry (GC-MS). This method was applied successfully to determine the content of residual ECH in SVH bulk drug.

Karthikeyan, Kaliaperumal; Arularasu, Govindasamy T.; Devaraj, Perumalsamy; Pillai, Karnam Chandrasekara

2010-01-01

286

Fracture detection, mapping, and analysis of naturally fractured gas reservoirs using seismic technology  

SciTech Connect

There are a number of producing gas fields in the United States where production is controlled by natural fractures. The host rock may consist of low porosity, low permeability formations, and wells completed in the unfractured rock have low productivity. On the other hand, wells intercepting fractured rocks may show good production. The objective of the research under this contract is to improve the technology for detecting fractures by surface geophysical methods. This remote detection of fractures will allow optimum placement of vertical or horizontal wells. The critical components of the project are: (1) Selection of a gas field with known production from naturally occurring fractures. The project scope does not allow for drilling of wells, so that evidence for occurrence of fractures and gas production from fractures must be obtained from existing wells` field production history, and other data. (2) Acquisition of both surface and downhole seismic P-wave and S-wave data. The project will acquire one 9-component (9-C) VSP. In a 9-C VSP survey, seismic events are recorded by 3-C geophones from one P-wave, and two perpendicular oriented S-wave sources (SH and SV). Also, approximately 12 miles of 9-C surface seismic data will be acquired. (3) Processing and interpretation of 9-C VSP and 9-C surface seismic data, and correlating the seismic anomalies observed to all available geologic and production information to show how the variations in seismic response is related to fracture density, fracture orientation, lithology, structure, and production history.

Hoekstra, P. [Coleman Research Corp., Orlando, FL (United States); Lynn, H. [Lynn (H.) Inc. (United States)

1993-12-31

287

A RECOMBINANT Escherichia coli BIOSENSOR FOR DETECTING POLYCYCLIC AROMATIC HYDROCARBONS IN GAS AND AQUEOUS PHASES.  

PubMed

Recombinant microbial biosensors are known to be simple, cheap, and very efficient monitoring tools for detecting various environmental pollutants in the field. However, although various recombinant microbial biosensors have been developed for aqueous-phase samples, very few are applicable to the gas phase. Here, we report a recombinant Escherichia coli biosensor that can be used to monitor polycyclic aromatic hydrocarbons (PAHs) in both gas and aqueous phases by color development. Among the PAHs, naphthalene and salicylate are often used as model compounds, since they are less toxic than other options and they are widely used in various applications. Here, recombinant E. coli cells carrying nahR (encoding the NahR regulatory protein for naphthalene degradation)::lac Z fusion genes were constructed and suspended (for aqueous measurements) or co-immobilized (for gaseous measurements) with chlorophenol red-ß-D-galactopyranoside (CPRG). Biosensing was then performed by ß-galactosidase, which hydrolyzed CPRG as a substrate, developing detectable red color with the naked eye. The system showed selective responses to salicylate and naphthalene. Importantly, its response to naphthalene was much more sensitive (about 10(5)-fold) in the gas phase compared to the aqueous phase. Thus, this system could potentially be used for the instrument-free, color-change-based monitoring of gaseous pollutants. PMID:24621193

Cho, Jae Ho; Lee, Da Young; Lim, Woon Ki; Shin, Hae Ja

2014-11-17

288

Ultraviolet laser microplasma-gas chromatography detector: detection of species-specific fragment emission.  

PubMed

Characteristic laser-produced microplasma emissions from various simple carbon-containing vapors entrained in a He carrier gas have been observed and compared. A focused ArF (193-nm) excimer laser is used to induce microplasmas with modest pulse energies (15 mJ or less) in the effluent region of a gas chromatography capillary column. Strong atomic (C, H, O, Cl, and F) as well as molecular (C(2), CH, and CCI) emissions are observed with very high SNRs. A plasma emission survey indicates that different classes of molecule show unique spectra which make it relatively easy to distinguish one chemical class from another. These results suggest that a laser microplasma gas chromatography detector (LM-GCD) should offer additional discrimination/resolution for unknown sample gas mixture analysis. In addition, the LM-GCD exhibits a significant advantage over certain other GC detectors, like the widely used flame ionization detector, by readily detecting nonresponsive gases such as CO, CO(2), CCl(4) and Freons. PMID:20577495

Locke, R J; Morris, J B; Forch, B E; Miziolek, A W

1990-11-20

289

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

PubMed

This work describes the detection of trace hydrogen chloride (HCl) gas through analyses of the resonance frequency signal from quartz crystal microbalance (QCM) sensors coated with polyaniline (PANI) functionalized polyamide 6 (PA 6) (PANI-PA 6) nanofiber-net-binary (NNB) structured membranes. The PA 6 NNB substrate comprising nanofibers and spider-web-like nano-nets fabricated by a versatile electro-spinning/netting (ESN) process offered an ideal interface for the uniform PANI functionalization and enhanced sensing performance. Benefiting from the large specific surface area, high porosity, and strong adhesive force to the QCM electrode of the PANI-PA 6 NNB membranes, the developed HCl-selective sensors exhibited a rapid response, good reproducibility and stability, and low detection limit (7 ppb) at room temperature. Additionally, the PANI-PA 6 NNB sensing membranes presented visible color changes upon cycled exposure to HCl and ammonia, suggesting their potential application in the development of colorimetric sensors. The PANI-PA 6 NNB coated QCM sensors are considered to be a promising candidate for trace HCl gas detection in practical applications. PMID:23108331

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

2012-12-01

290

Semiconductor laser source for natural gas leak detection. Final report, September 1, 1984-March 31, 1985  

SciTech Connect

The feasibility of using semiconductor lasers as infrared sources for handheld natural gas leak detectors was assessed. The detection system was assumed to be based on the differential absorption (DIAL) technique and to operate at ambient temperatures. The absorption spectra of the major components of natural gas, methane and ethane, were measured in the spectral range from 1.2 to 2.0 micrometers where cryogenic cooling of detectors is not required. Both spectra exhibited absorption features due to overtones of the fundamental C-H stretching modes strong enough to be suitable for DIAL measurements. The literature on semiconductor lasers was reviewed both to determine which types emit in spectral regions overlapping the absorption bands of methane and ethane and which allow the high power pulsed operation necessary for DIAL systems. Lasers made from InGaAs emitting near 1.65 micrometers are suitable for methane detection. However, considerable materials development would be needed to develop a laser for ethane detection. Cleaved-coupled-cavity (CT) laser structures appear to be the most promising means of tuning and narrowing the linewidth of the emitted light. An experiment with a ten-emitter phased array (CT) laser showed significant line narrowing.

Elliott, R.A.

1985-06-01

291

A Cost Effective Multi-Spectral Scanner for Natural Gas Detection  

SciTech Connect

The objective of this project is to design, fabricate and 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 Department of Energy study at the Rocky Mountain Oilfield Testing Center. The performance of the scanner was inconsistent during the blind study. However, most of the leaks were outside the view of the multi-spectral scanner that was developed during the first year of the project. 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. A prototype scanner was built and evaluated during the second year of the project. Only laboratory evaluations were completed during the second year. The laboratory evaluations show the feasibility of using the scanner to determine natural gas pipeline leaks. Further field evaluations and optimization of the scanner are required before commercialization of the scanner can be initiated.

Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan; Seonghyeon Park

2005-12-07

292

[Quartz-enhanced photoacoustic spectroscopy trace gas detection system based on the Fabry-Perot demodulation].  

PubMed

An all-optical quartz-enhanced photoacoustic spectroscopy system, based on the F-P demodulation, for trace gas detection in the open environment was proposed. In quartz-enhanced photoacoustic spectroscopy (QEPAS), an optical fiber Fabry-Perot method was used to replace the conventional electronic demodulation method. The photoacoustic signal was obtained by demodulating the variation of the Fabry-Perot cavity between the quartz tuning fork side and the fiber face. An experimental system was setup. The experiment for detection of water vapour in the open environment was carried on. A normalized noise equivalent absorption coefficient of 2.80 x 10(-7) cm(-1) x W x Hz(-1/2) was achieved. The result demonstrated that the sensitivity of the all-optical quartz-enhanced photoacoustic spectroscopy system is about 2.6 times higher than that of the conventional QEPAS system. The all-optical quartz-enhanced photoacoustic spectroscopy system is immune to electromagnetic interference, safe in flammable and explosive gas detection, suitable for high temperature and high humidity environments and realizable for long distance, multi-point and network sensing. PMID:23905310

Lin, Cheng; Zhu, Yong; Wei, Wei; Zhang, Jie; Tian, Li; Xu, Zu-Wen

2013-05-01

293

[Quantitative analysis method of natural gas combustion process combining wavelength selection and outlier spectra detection].  

PubMed

The present paper uses a combination method of wavelength selection and outlier spectra detection for quantitative analysis of nature gas combustion process based on its near infrared spectra. According to the statistical distribution of partial least squares (PLS) model coefficients and prediction errors, the method realized wavelength selection and outlier spectra detection, respectively. In contrast with PLS, PLS after leave-one-out for outlier detection (LOO-PLS), uninformative variable elimination by PLS (UVE-PLS) and UVE-PLS after leave-one-out for outlier detection (LOO-UVE-PLS), the root-mean-squared error of prediction (RMSEP) based on the method for CH4 prediction model is reduced by 14.33%, 14.33%, 10.96% and 12.21%; the RMSEP value for CO prediction model is reduced by 67.26%, 72.58%, 11.32% and 4.52%; the RMSEP value for CO2 prediction model is reduced by 5.95%, 19.7%, 36.71% and 4.04% respectively. Experimental results demonstrate that the method can significantly decrease the number of selected wavelengths, reduce model complexity and effectively detect outlier spectra. The established prediction model of analytes is more accurate as well as robust. PMID:23285890

Cao, Hui; Hu, Luo-Na; Zhou, Yan

2012-10-01

294

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

295

Inflammable Gas Mixture Detection with a Single Catalytic Sensor Based on the Electric Field Effect  

PubMed Central

This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. The analysis of mixed inflammable gases results from processing the output signals obtained by adjusting the electric field parameter of the catalytic sensor. For the signal process, we designed a group of equations based on the heat balance of catalytic sensor expressing the relationship between the output signals and the concentration of gases. With these equations and the outputs of different electric fields, the gas concentration in a mixture could be calculated. In experiments, a mixture of methane, butane and ethane was analyzed by this new method, and the results showed that the concentration of each gas in the mixture could be detected with a single catalytic sensor, and the maximum relative error was less than 5%.

Tong, Ziyuan; Tong, Min-Ming; Meng, Wen; Li, Meng

2014-01-01

296

Inflammable gas mixture detection with a single catalytic sensor based on the electric field effect.  

PubMed

This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. The analysis of mixed inflammable gases results from processing the output signals obtained by adjusting the electric field parameter of the catalytic sensor. For the signal process, we designed a group of equations based on the heat balance of catalytic sensor expressing the relationship between the output signals and the concentration of gases. With these equations and the outputs of different electric fields, the gas concentration in a mixture could be calculated. In experiments, a mixture of methane, butane and ethane was analyzed by this new method, and the results showed that the concentration of each gas in the mixture could be detected with a single catalytic sensor, and the maximum relative error was less than 5%. PMID:24717635

Tong, Ziyuan; Tong, Min-Ming; Meng, Wen; Li, Meng

2014-01-01

297

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

298

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

299

Lyman Alpha Mapping Project (LAMP) Detections of LCROSS Impact Plume Gas  

NASA Astrophysics Data System (ADS)

The Lyman Alpha Mapping Project (LAMP) is an ultraviolet (UV) spectrograph on the Lunar Reconnaissance Orbiter (LRO) that is designed to map the lunar albedo at far-UV wavelengths. LAMP's spectral range of 57.5 nm to 196.5 nm includes emission line features from several known and expected lunar atmosphere constituents, including resonantly scattered Lyman-alpha (121.57 nm) emissions from hydrogen atoms and argon atom emissions at 104.82 nm and 106.67 nm. The LCROSS impact on 9 October 2009 elevated and exposed water ice and other volatiles trapped near the lunar surface (Colaprete et al., submitted, 2010). Observations with LRO/LAMP detected enhancements of volatile species in the plume shortly after impact (Gladstone et al., submitted, 2009). The plume of rapidly expanding gas includes molecular hydrogen gas seen by sunlit fluorescence. Resonantly scattered emissions from atomic Hg, Mg, and Ca in sunlight are also likely detected in a feature near 185 nm. The molecular hydrogen content within permanently shadowed regions (PSRs) is higher than possible through dissociation of water alone, which indicates that trapped hydrogen gas likely contributes to the hydrogen content of the PSRs in addition to the water detected there. The concentration of mercury in PSRs has implications for future exploration and in situ resource utilization in these regions. This investigation addresses how water and other volatiles arrive (or form) at the lunar surface, are transported through the lunar atmosphere, and are deposited within PSRs (or elsewhere), which is closely related to LAMP's primary objectives.

Retherford, Kurt; Gladstone, Randy; Stern, Alan; Hurley, Dana; Feldman, Paul; Pryor, Wayne; Hendrix, Amanda; Goldstein, David; Summy, Dustin

2010-05-01

300

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

301

Monitoring serum valproic acid by gas chromatography with electron-capture detection.  

PubMed

I have developed a procedure to monitor, by gas chromatography with electron-capture detection, the concentration of valproic acid in serum. The valproic acid is derivatized into its phenacyl ester. The assay is very sensitive, measuring as little as 100 pg of valproic acid easily and accurately. Solvent extraction and concentration of the drug are not necessary; instead, one only has to precipitate the serum proteins. n-Octanoic acid is used as the internal standard. The peak-height ratio of phenacyl valproate to phenacyl octanoate is linearly related to concentration up to 200 mg of valproic acid per liter. PMID:6774836

Chan, S C

1980-10-01

302

Selective detection of carbon-13-labeled compounds by gas chromatography/emission spectroscopy  

SciTech Connect

This paper describes a technique which also provides selective GC detection of compounds with excess {sup 13}C content. Molecular emission from CO bands in the vacuum ultraviolet region is monitored with an atomic emission detector (AED) (4,5). Samples can also be analyzed for C, H, O, N, S, P, Cl, F, etc. by changing the reagent and makeup gas flows. This combination of {sup 13}C specificity with atomic information is useful in the identification of unknown compounds, especially when combined with mass spectral data, as shown by Hooker and DeZwaan (6).

Quimby, B.D.; Dryden, P.C.; Sullivan, J.J. (Hewlett-Packard Company, Avondale, PA (USA))

1990-11-15

303

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

304

Determination of n-butylated trialkyllead compounds by gas chromatography with microwave plasma emission detection  

SciTech Connect

An analytical gas chromatographic procedure is described for the determination of trialkyllead compounds in aqueous media. The analyte compounds are extracted into benzene from an aqueous solution saturated with sodium chloride. They are then quantitatively converted into n-butyltrialkyllead derivatives by reaction with an n-butyl Grignard reagent. Precolumn Tenax trap enrichment of the derived trialkylbutylleads enables determination to low parts per billion levels to be carried out. Also investigated are extraction efficiencies and injection split ratios onto a fused silica capillary column. Lead specific detection is by atmospheric pressure microwave induced plasma spectrometric emission. Data are presented for a wastewater effluent sample. 3 figures.

Estes, S.A.; Uden, P.C.; Barnes, R.M.

1982-12-01

305

Determination of n-butylated trialkyllead compounds by gas chromatography with microwave plasma emission detection  

SciTech Connect

An analytical gas chromatographic procedure is described for the determination of trialkyllead compounds in aqueous media. The analyte compounds are extracted into benzene from an aqueous solution saturated with sodium chloride. They are then quantitatively converted into n-butyltrialkyllead derivatives by reaction with an n-butyl Grignard reagent. Precolumn Tenax trap enrichment of the derived trialkylbutylleads enables determination to low ppB levels to be carried out. Also investigated are extraction efficiencies and injection split ratios onto a fused silica capillary column. Lead specific detection is by atmospheric pressure microwave induced plasma spectrometric emission. Data are presented for a wastewater effluent sample. 21 references, 3 figures.

Estes, S.A.; Uden, P.C.; Barnes, R.M.

1982-12-01

306

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

307

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

308

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

309

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

310

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

311

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

312

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

313

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

PubMed

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

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

2013-10-01

314

Development of an Intelligent Hypertext Manual for the Space Shuttle Hazardous Gas Detection System  

NASA Technical Reports Server (NTRS)

The Intelligent Hypertext Manual (IHM) for the Hazardous Gas Detection System (HGDS) of the Space Shuttle is described as an example of an integrated knowledge system. The IHM is described in terms of its design as a system for facilitating the interpretation of real-time data regarding hazardous gases and their successful and timely detection. Hypermedia technology is employed that incorporates text, video, and sound, and the architecture of the IHM integrated knowledge system is based on knowledge elements, a basic user interface, and integrated application software. Knowledge organization enhances the retrieval of documents for launch commit criteria, operations and maintenance requirements, flight-measurement location, and hypermedia incorporation. The integration of computer and AI technologies for the HGDS IHM demonstrates the potential for enhancing efficiency in aerospace operations with aerospace data that are easy to retrieve.

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

1992-01-01

315

Determination of 17 ?-Estradiol in Rabbit Plasma by Gas Chromatography with Flame Ionization Detection  

PubMed Central

This article describes gas chromatography-flame ionization detection method for determination of 17 ?-estradiol in rabbit plasma. 17 ?-estradiol and internal standard progesterone were extracted from plasma using liquid–liquid extraction method. Linearity was found between 0.25 and 20 ?g/ml (r2=0.994) for plasma samples. Intra-day and inter-day precision, expressed as the relative standard deviation were less than 5.5%, and accuracy (relative error) was less than 3.5%. The mean recovery of 17 ?-estradiol samples was 94.4%. The limits of detection and quantification of method for plasma samples were 0.10 ?g/ml and 0.15 ?g/ml, respectively. Also, clinically used other 10 drugs were investigated to check for potential interferences and the method was successfully applied to the determination of 17 ?-estradiol in New Zealand white rabbits.

Yilmaz, B; Kadioglu, Y.

2012-01-01

316

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

317

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

SciTech Connect

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

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

2010-08-20

318

The Invisible Majority? Evolution and Detection of Outer Planetary Systems without Gas Giants  

NASA Astrophysics Data System (ADS)

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

Mann, Andrew W.; Gaidos, Eric; Gaudi, B. Scott

2010-08-01

319

Determination of alkylphenols after derivatization to ferrocenecarboxylic acid esters with gas chromatography-atomic emission detection.  

PubMed

A method is described for the rapid determination of alkylphenols in nonpolar matrixes. The alkylphenols are derivatized with ferrocenecarboxylic acid chloride so that every phenol molecule is labeled with one iron atom. The resulting esters are analyzed by gas chromatography with atomic emission detection (AED) in the iron-selective detection mode. This method utilizes the AED's low detection limit (0.05 pg/s) for iron and the high selectivity versus carbon (3.5 x 10(6)) for the detection of the alkylphenols. Because the derivatization is performed before the first step of sample preparation, the risk of analyte loss by adsorption or volatilization is minimized. The total recoveries in the lower ppm concentration range vary between 79 and 125%. The quantification of 20 C0-C3-alkylphenols in crude oils is demonstrated by analyzing a shale oil (SRM 1580) and a petroleum crude oil (SRM 1582). The complete workup is easily carried out in only 45 min/sample. PMID:11467556

Rolfes, J; Andersson, J T

2001-07-01

320

Detection of greenhouse gas precursors from diesel engines using electrochemical and photoacoustic sensors.  

PubMed

Atmospheric pollution is one of the worst threats to modern society. The consequences derived from different forms of atmospheric pollution vary from the local to the global scale, with deep impacts on climate, environment and human health. Several gaseous pollutants, even when present in trace concentrations, play a fundamental role in important processes that occur in atmosphere. Phenomena such as global warming, photochemical smog formation, acid rain and the depletion of the stratospheric ozone layer are strongly related to the increased concentration of certain gaseous species in the atmosphere. The transport sector significantly produces atmospheric pollution, mainly when diesel oil is used as fuel. Therefore, new methodologies based on selective and sensitive gas detection schemes must be developed in order to detect and monitor pollutant gases from this source. In this work, CO(2) Laser Photoacoustic Spectroscopy was used to evaluate ethylene emissions and electrochemical analyzers were used to evaluate the emissions of CO, NO(x) and SO(2) from the exhaust of diesel powered vehicles (rural diesel with 5% of biodiesel, in this paper called only diesel) at different engine rotation speeds. Concentrations in the range 6 to 45 ppmV for ethylene, 109 to 1,231 ppmV for carbon monoxide, 75 to 868 ppmV for nitrogen oxides and 3 to 354 ppmV for sulfur dioxide were obtained. The results indicate that the detection techniques used were sufficiently selective and sensitive to detect the gaseous species mentioned above in the ppmV range. PMID:22163437

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

2010-01-01

321

Leak detection in gas pipeline networks using an efficient state estimator. Part II. Experimental and field evaluation  

Microsoft Academic Search

In Part-I of this two part paper, a method is proposed for on-line leak detection and identification in gas pipeline networks using flow and pressure measurements. Simulations on two illustrative networks were used to demonstrate the applicability of the proposed method. In this paper, the performance of the proposed leak detection and identification methodology was evaluated using experiments with compressed

H. Prashanth Reddy; Shankar Narasimhan; S. Murty Bhallamudi; S. Bairagi

2011-01-01

322

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

PubMed

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

323

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

PubMed

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

Dong, Ki-Young; Choi, Jinnil; Lee, Yang Doo; Kang, Byung Hyun; Yu, Youn-Yeol; Choi, Hyang Hee; Ju, Byeong-Kwon

2013-01-01

324

Detection of unburned fuel as contaminant in engine oil by a gas microsensor array  

NASA Astrophysics Data System (ADS)

We developed a novel method to detect the presence of unburned diesel fuel in used diesel fuel engine oil. The method is based on the use of an array of different gas microsensors based on metal oxide thin films deposited by sol-gel technique on Si substrates. The sensor array, exposed to the volatile chemical species of different diesel fuel engine oil samples contaminated in different percentages by diesel fuel, resulted to be appreciable sensitive to them. Principal Component Analysis (PCA) and Self-Organizing Map (SOM) applied to the sensor response data-set gave a first proof of the sensor array ability to discriminate among the different diesel fuel diluted lubricating oils. Moreover, in order to get information about the headspace composition of the diesel fuel-contaminated engine oils used for gas-sensing tests, we analyzed the engine oil samples by Static Headspace Solid Phase Micro Extraction/Gas Chromatograph/Mass Spectrometer (SHS-SPME/ GC/MS).

Capone, Simonetta; Zuppa, Marzia; Presicce, Dominique S.; Epifani, Mauro; Francioso, Luca; Siciliano, Pietro; Distante, C.

2007-06-01

325

AIRBORNE, OPTICAL REMOTE SENSING OF METHANE AND ETHANE FOR NATURAL GAS PIPLINE 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 third six-month technical report contains a summary of the progress made towards finalizing the design and assembling the airborne, remote methane and ethane sensor. The vendor has been chosen and is on contract to develop the light source with the appropriate linewidth and spectral shape to best utilize the Ophir gas correlation software. Ophir has expanded upon the target reflectance testing begun in the previous performance period by replacing the experimental receiving optics with the proposed airborne large aperture telescope, which is theoretically capable of capturing many times more signal return. The data gathered from these tests has shown the importance of optimizing the fiber optic receiving fiber to the receiving optic and has helped Ophir to optimize the design of the gas cells and narrowband optical filters. Finally, Ophir will discuss remaining project issues that may impact the success of the project.

Jerry Myers

2004-05-12

326

A gas sensor using a multi-walled carbon nanotube sheet to detect oxygen molecules.  

PubMed

A gas sensor using a multi-walled carbon nanotube (MWCNT) sheet, which can detect oxygen (O2) gas, is presented and its output characteristics are evaluated in this study. A simple, cost effective and novel fabrication technique is described compared to dispersing CNTs into a liquid or polymer. The sheets are spun from a MWCNT forest grown on a silicon substrate; its electrical resistance decreases linearly with O2 exposure. The MWCNT sheet has a large surface area and many individual MWCNT contact points; this leads to a linear sensitivity, a fast response time, repeatability, and stability. It is well known that the surface distribution and areal density of MWCNTs have a significantly affect on their sensing characteristics. The sensors fabricated using dispersed CNTs on a substrate, either with separated CNTs of low density or with overlapping CNTs of low resistance, reveal much lower sensitivities. The large surface area and uniform distribution of the gas sensor, however, allow for the higher interaction of the MWCNTs with the O2 molecules, increasing the sensor's characteristics. Moreover, the MWCNT sheet does not need purification or a complex transfer process to be used as a sensor, making it suitable for practical applications. PMID:24266224

Jung, Daewoong; Lee, Kyung H; Kim, Donghyun; Overzet, Lawrence J; Lee, Gil S

2013-12-01

327

Solid state gas sensors for detection of explosives and explosive precursors  

NASA Astrophysics Data System (ADS)

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

Chu, Yun

328

AIRBORNE, OPTICAL REMOTE SENSING 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. This six-month technical report summarizes the progress for each of the proposed tasks, discusses project concerns, and outlines near-term goals. Ophir has completed a data survey of two major natural gas pipeline companies on the design requirements for an airborne, optical remote sensor. The results of this survey are disclosed in this report. A substantial amount of time was spent on modeling the expected optical signal at the receiver at different absorption wavelengths, and determining the impact of noise sources such as solar background, signal shot noise, and electronic noise on methane and ethane gas detection. Based upon the signal to noise modeling and industry input, Ophir finalized the design requirements for the airborne sensor, and released the critical sensor light source design requirements to qualified vendors. Responses from the vendors indicated that the light source was not commercially available, and will require a research and development effort to produce. Three vendors have responded positively with proposed design solutions. Ophir has decided to conduct short path optical laboratory experiments to verify the existence of methane and absorption at the specified wavelength, prior to proceeding with the light source selection. Techniques to eliminate common mode noise were also evaluated during the laboratory tests. Finally, Ophir has included a summary of the potential concerns for project success and has established future goals.

Jerry Myers

2003-05-13

329

Study on the micro-heater geometry in In,2O3 micro electro mechanical systems gas sensor platforms and effects on NO2 gas detecting performances.  

PubMed

Micro electro mechanical systems (MEMS) platforms for gas sensing devices with the co-planar type micro-heaters were designed, fabricated and its effects on the In2O3 gas sensors were investigated. Micro-heaters in MEMS gas sensor platforms were designed in the four-type heater patterns with different geometries. Electro-thermal characterizations showed that the designed platforms had highly thermal efficiency because the micro hot-plate structures were formed in the diaphragm and the thermal efficiencies were analyzed for all of 16 models and compared with each other, respectively. The designed micro-platforms were fabricated by MEMS process, and Indium oxide (In2O3) nanoparticles were synthesized by sol-gel process and dropped on the MEMS platforms for detecting the noxious oxide gas (NO2) Fabricated micro-platforms had a very low power consumption in the fabricated 16-type models, especially, the minimum power consumption was 41 mW at the operating temperature of 250 degrees C. After experiments on gas sensing characteristics to NO2 gases, fabricated In2O3 gas sensors had almost the same gas sensitivity (Rs) at the operation temperature of 250 degrees C. It is concluded that the micro-heater geometries, pattern shapes and sizes, can be influential on the power consumption of the devices and its gas sensing characteristics. PMID:22629914

Choi, Woo-Seok; Kim, Bum-Joon; Lee, Hoi-Jung; Choi, Jung-Woon; Kim, Si-Dong; Min, Nam-Ki

2012-02-01

330

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

NASA Astrophysics Data System (ADS)

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

2001-07-01

331

Fiber methane gas detector based on harmonic detection and application in ventilation air methane power generation  

NASA Astrophysics Data System (ADS)

A fiber methane detector based on spectrum absorption is reported. The methane monitor use a distributed feedback diode lasers(DFB) which is near infrared spectroscopy as the optic source, we realized online harmonic detection of the methane. The advantages of this detector include high precision, elimination of interference from humidity and other gases as well as long recalibration cycle. The detection of CH4 is very important in the methane power generation. Especially the detection of the tail gas with high temperature is the dependence to judge the generator. In this paper, we give some data witch gained from the local of methane power generation. The data reach an agreement with the measurements of the sensor using in mine. And the detector has the function of self reference, so the detector is more depended. This proved that the fiber methane detector can meet the needs of the generator. It have some contribution to the production safety of the mine and the energy saving and emission reduction and the environmental protection.

Li, Yanfang; Wei, Yubin; Shang, Ying; Zhao, Yanjie; Zhang, Tingting; Zhao, Weisong; Wang, Chang; Liu, Tongyu

2010-05-01

332

Hierarchical leak detection and localization method in natural gas pipeline monitoring sensor networks.  

PubMed

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

333

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.

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

2012-01-01

334

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

DOEpatents

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

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

2003-01-01

335

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

336

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

337

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

Microsoft Academic Search

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

Hirofumi Suzumori; Satoshi Honma; Masayuki Morisawa; Shinzo Muto

2008-01-01

338

Gas detection with quantum cascade lasers: An adapted photoacoustic sensor based on Helmholtz resonance  

NASA Astrophysics Data System (ADS)

A photoacoustic gas sensor exploiting a quantum cascade laser as a radiation source is demonstrated. A detection limit of ~1 ppm with 1 ms response time is found using a Peltier-cooled Fabry-Pérot InGaAs-based quantum cascade laser emitting at 9.4 ?m, and a commercial microphone as a detector. The photoacoustic cell consists of a Helmholtz resonator preceeded by a low-pass acoustic filter. This geometry is well adapted to the shape of the laser beam and allows for an effective filtering of ambient acoustical noise. The relative simplicity of the system is particularly attractive for applications where sensitivity, robustness, and ease of fabrication are all fundamental requirements.

Barbieri, Stefano; Pellaux, Jean-Paul; Studemann, Eric; Rosset, Daniel

2002-06-01

339

Recent advances in gas and chemical detection by Vernier effect-based photonic sensors.  

PubMed

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

340

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.

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

2014-01-01

341

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

342

Enantioselective gas chromatographic assay with electron-capture detection for dl-ritalinic acid in plasma.  

PubMed

Enantioselective gas chromatographic assays for the quantitation of methylphenidate and its major metabolite ritalinic acid in plasma are described. The procedures involved the extraction of methylphenidate enantiomers from alkanised plasma. The plasma was then washed to ensure complete removal of methylphenidate before saturation with sodium carbonate to promote the extraction of ritalinic acid enantiomers with ethyl acetate-isopropanol (60:40) solvent mixture. Subsequently, ritalinic acid enantiomers were converted back into methylphenidate enantiomers by Fisher-Speier esterification. N-Heptafluorobutyryl-L-prolyl chloride, a chiral acylating reagent, was used to convert the enantiomers of methylphenidate into their corresponding diastereomeric amide derivatives, which were separated cleanly on an achiral capillary column (OV-225) and quantitated with electron-capture detection. The assays were sensitive, reliable and reproducible. PMID:2079507

Srinivas, N R; Hubbard, J W; Midha, K K

1990-09-14

343

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

344

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

345

Highly Selective Probe Detects Cu(2+) and Endogenous NO Gas in Living Cell.  

PubMed

The rapid and highly sensitive detection of extremely short-lived nitric oxide (NO) gas generated in vivo by a water-soluble fluorescein derivative is developed. This assay system comprises of indole-3-carboxaldehyde functionalized fluorescein hydrazone (FI) assay which displays a typically high absorption at 492 and 620 nm in the presence of Cu(2+) and also shows FRET induced fluorescence turn-on exclusively with Cu(2+). FI selectively detects Cu(2+) in vivo and in vitro by the "turn-on" mechanism followed by fluorescence "turn-off" with NO gas generated by the lipopolysaccharide (LPS) action. The in vivo experiment performed in the cellular system indicates that FI loaded RAW264.7 cells showed bright fluorescence in the presence of Cu(2+), while other metals did not influence the FI fluorescence. In addition, the fluorescence of FI-Cu(2+) was efficiently quenched by NO generated in macrophages through LPS stimulation. FI demonstrates characteristic "turn-on" behavior in the presence of Cu(2+) via spirolactom ring-opening, while other metals such as Na(+), K(+), Ca(2+), Cr(3+), Mn(2+), Fe(3+), Fe(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+), Hg(2+), and Ag(+) did not influence FI fluorescence even at very high concentration. Further, the FI-Cu(2+) complex fluorescence was not quenched with any anions or amino acids but totally quenched by NO and the paramagnetic nature of Cu(2+) ion converted into the diamagnetic nature when reduced to Cu(1+). FI and the FI-Cu(2+) complex are nontoxic to the cellular system and have high potential for biomedical applications. PMID:24703409

Muthuraj, Balakrishnan; Deshmukh, Rohitas; Trivedi, Vishal; Iyer, Parameswar Krishnan

2014-05-14

346

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

347

A Au-functionalized ZnO nanowire gas sensor for detection of benzene and toluene.  

PubMed

A novel sensing hybrid-material of Au nanoparticles (Au NPs)-functionalized ZnO nanowires (Au-ZnO NWs) was successfully synthesized by a two-stage solution process. First, ZnO NWs were fabricated via a low-temperature one-pot hydrothermal method with SDSN introduced as a structure-directing agent. Afterward, the as-prepared ZnO NWs were used as supports to load Au NPs with small sizes via precipitating HAuCl4 aqueous solution with ammonia. The obtained samples were characterized by means of XRD, SEM, TEM and EDX. Both pristine and Au-ZnO NWs were practically applied as gas sensors to compare the effect of Au NPs on the sensing performances and the obtained results demonstrated that after functionalization by catalytic Au NPs, the hybrid sensor exhibited not only faster response and recovery speeds but also a higher response to benzene and toluene than the pristine ZnO sensor at 340 °C, especially showing high selectivity and long-term stability for low concentration toluene, which is rarely reported with this method, indicating its original sensor application in detecting benzene and toluene. To interpret the enhanced gas sensing mechanism, the strong spillover effect of the Au NPs and the increased Schottky barriers caused by the electronic interaction between Au NPs and ZnO NW support are believed to contribute to the improved sensor performance. PMID:24013527

Wang, Liwei; Wang, Shurong; Xu, Mijuan; Hu, Xiaojing; Zhang, Hongxin; Wang, Yanshuang; Huang, Weiping

2013-10-28

348

AIRBORNE, OPTICAL REMOTE SENSING 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. This second six-month technical report summarizes the progress made towards defining, designing, and developing the hardware and software segments of the airborne, optical remote methane and ethane sensor. The most challenging task to date has been to identify a vendor capable of designing and developing a light source with the appropriate output wavelength and power. This report will document the work that has been done to identify design requirements, and potential vendors for the light source. Significant progress has also been made in characterizing the amount of light return available from a remote target at various distances from the light source. A great deal of time has been spent conducting laboratory and long-optical path target reflectance measurements. This is important since it helps to establish the overall optical output requirements for the sensor. It also reduces the relative uncertainty and risk associated with developing a custom light source. The data gathered from the optical path testing has been translated to the airborne transceiver design in such areas as: fiber coupling, optical detector selection, gas filters, and software analysis. Ophir will next, summarize the design progress of the transceiver hardware and software development. Finally, Ophir will discuss remaining project issues that may impact the success of the project.

Jerry Myers

2003-11-12

349

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%.

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

2014-01-01

350

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

PubMed

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

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

2011-02-15

351

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

352

Modeling Noble Gas Transport and Detection for The Comprehensive Nuclear-Test-Ban Treaty  

NASA Astrophysics Data System (ADS)

Detonation gases released by an underground nuclear test include trace amounts of 133Xe and 37Ar. In the context of the Comprehensive Nuclear Test Ban Treaty, On Site Inspection Protocol, such gases released from or sampled at the soil surface could be used to indicate the occurrence of an explosion in violation of the treaty. To better estimate the levels of detectability from an underground nuclear test (UNE), we developed mathematical models to evaluate the processes of 133Xe and 37Ar transport in fractured rock. Two models are developed respectively for representing thermal and isothermal transport. When the thermal process becomes minor under the condition of low temperature and low liquid saturation, the subsurface system is described using an isothermal and single-gas-phase transport model and barometric pumping becomes the major driving force to deliver 133Xe and 37Ar to the ground surface. A thermal test is simulated using a nonisothermal and two-phase transport model. In the model, steam production and bubble expansion are the major processes driving noble gas components to ground surface. After the temperature in the chimney drops below boiling, barometric pumping takes over the role as the major transport process.

Sun, Yunwei; Carrigan, Charles R.

2014-03-01

353

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

354

Design of a mid-IR active imaging system for gas detection using a pulsed laser source  

Microsoft Academic Search

Summary form only given. Backscatter absorption gas imaging (BAGI) is a remote sensing technique that uses active imaging to generate real-time video images of chemical vapor plumes. As such, BAGI represents a fusion between absorptive chemical detection LIDAR and imaging laser radar. Plume imaging occurs when a gas that can absorb light at the laser wavelength enters the system field-of-view,

T. J. Kulp; P. E. Powers; R. Kennedy

1996-01-01

355

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

NASA Astrophysics Data System (ADS)

The commercial development of microbolometer uncooled long-wave thermal infrared imagers in conjuncture with advanced radiometric calibration methods developed at Montana State University has led to new uses of thermal imagery in remote sensing applications. A novel use of these calibrated imagers is imaging of vegetation for CO2 gas leak detection. During a four-week period in the summer of 2011, a CO2 leak was simulated in a test field run by the Zero Emissions Research and Technology Center in Bozeman, Montana. Thermal infrared images were acquired, along with visible and near-infrared reflectance images, of the exposed vegetation and healthy control vegetation. The increased root-level CO2 concentration causes plant stress that results in reduced thermal regulation of the vegetation, which is detectable as an increased diurnal variation of infrared emission. . In a linear regression, the infrared data were found to have a strong coefficient of determination and clearly show the effect of the CO2 on the vegetation.

Johnson, Jennifer E.; Shaw, Joseph A.; Lawrence, Rick L.; Nugent, Paul W.; Dobeck, Laura M.; Spangler, Lee H.

2012-10-01

356

Detection of metabolites of trapped humans using ion mobility spectrometry coupled with gas chromatography.  

PubMed

For the first time, ion mobility spectrometry coupled with rapid gas chromatography, using multicapillary columns, was applied for the development of a pattern of signs of life for the localization of entrapped victims after disaster events (e.g., earthquake, terroristic attack). During a simulation experiment with entrapped volunteers, 12 human metabolites could be detected in the air of the void with sufficient sensitivity to enable a valid decision on the presence of a living person. Using a basic normalized summation of the measured concentrations, all volunteers involved in the particular experiments could be recognized only few minutes after they entered the simulation void and after less than 3 min of analysis time. An additional independent validation experiment enabled the recognition of a person in a room of ?25 m(3) after ?30 min with sufficiently high sensitivity to detect even a person briefly leaving the room. Undoubtedly, additional work must be done on analysis time and weight of the equipment, as well as on validation during real disaster events. However, the enormous potential of the method as a significantly helpful tool for search-and-rescue operations, in addition to trained canines, could be demonstrated. PMID:23249433

Vautz, Wolfgang; Slodzynski, Rafael; Hariharan, Chandrasekhara; Seifert, Luzia; Nolte, Jürgen; Fobbe, Rita; Sielemann, Stefanie; Lao, Bolan C; Huo, Ran; Thomas, C L Paul; Hildebrand, Lars

2013-02-19

357

Trace detection and discrimination of explosives using electrochemical potentiometric gas sensors.  

PubMed

In this article, selective and sensitive detection of trace amounts of pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensors as the detector. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors based on lanthanum strontium chromite and Pt electrodes with yttria stabilized zirconia (YSZ) solid electrolyte were used to capture the signature of the explosives. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (1-3 ?g). Moreover, the results showed that PETN, TNT, and RDX samples could be discriminated from each other by calculating the ratio of nitrogen oxides to hydrocarbon integrated area under the peak. Further, the use of front-end technology to collect and concentrate the high explosive (HE) vapors make intrinsically low vapor pressure of the HE less of an obstacle for detection while ensuring higher sensitivity levels. In addition, the ability to use multiple sensors each tuned to basic chemical structures (e.g., nitro, amino, peroxide, and hydrocarbon groups) in HE materials will permit the construction of low-cost detector systems for screening a wide spectrum of explosives with lower false positives than present-day technologies. PMID:21435779

Sekhar, Praveen K; Brosha, Eric L; Mukundan, Rangachary; Linker, Kevin L; Brusseau, Charles; Garzon, Fernando H

2011-06-15

358

Determination of fatty acid amides as trimethylsilyl derivatives by gas chromatography with mass spectrometric detection.  

PubMed

Fatty acid amides are a newly emerging class of compounds with biological activity. The amides are formed enzymatically in vivo. Analysis of fatty acid amides has been accomplished by gas chromatography coupled with mass spectrometry. Fatty acid amides required derivatization prior to analysis at high temperatures due to thermal instability. Trimethylsilylation of fatty acid amides has been accomplished under optimum reaction conditions. The limit of detection for the silylated amides is approximately 1 pmol, with the lowest detected level being 700 fmol for the lauramide derivative. Quantitation of fatty acid amide derivatives can be accomplished by monitoring m/z 59 or m/z M-71, the only two major fragments formed in the ion trap mass spectrometer with electron impact ionization. The smaller fragment is the result of a newly reported, McLafferty-type rearrangement; M-71 resulted from loss of an n-pentyl fragment. Either peak gave four-five orders of magnitude linear dynamic range. Numerous trimethylsilylamides from C7 to C20 were separated under standard conditions. Elution was linear with the number of carbons and was systematically affected by the number and position of the double bonds. PMID:10457449

Gee, A J; Groen, L A; Johnson, M E

1999-07-23

359

Ethanol analysis by headspace gas chromatography with simultaneous flame-ionization and mass spectrometry detection.  

PubMed

Ethanol is the most frequently identified compound in forensic toxicology. Although confirmation involving mass spectrometry is desirable, relatively few methods have been published to date. A novel technique utilizing a Dean's Switch to simultaneously quantitate and confirm ethyl alcohol by flame-ionization (FID) and mass spectrometric (MS) detection after headspace sampling and gas chromatographic separation is presented. Using 100 ?L of sample, the limits of detection and quantitation were 0.005 and 0.010 g/dL, respectively. The zero-order linear range (r(2) > 0.990) was determined to span the concentrations of 0.010 to 1.000 g/dL. The coefficient of variation of replicate analyses was less than 3.1%. Quantitative accuracy was within ±8%, ±6%, ±3%, and ±1.5% at concentrations of 0.010, 0.025, 0.080, and 0.300 g/dL, respectively. In addition, 1,1-difluoroethane was validated for qualitative identification by this method. The validated FID-MS method provides a procedure for the quantitation of ethyl alcohol in blood by FID with simultaneous confirmation by MS and can also be utilized as an identification method for inhalants such as 1,1-difluoroethane. PMID:21871160

Tiscione, Nicholas B; Alford, Ilene; Yeatman, Dustin Tate; Shan, Xiaoqin

2011-09-01

360

Analysis of aromatic sulfur compounds in gas oils using GC with sulfur chemiluminescence detection and high-resolution MS.  

PubMed

The analysis of alkylbenzothiophenes (alkyl-BT) and alkyl-dibenzothiophenes (alkyl-DBT) in light cycle oil (LCO) and straight run (SR) gas oils is described. A detailed identification and quantitative analysis of alkyl-BT and alkyl-DBT present in LCO gas oils was carried out using GC-SCD. For the SR gas oils, the simultaneous presence of thiophenic and nonthiophenic compounds does not allow for a selective analysis of thiophenic compounds by GC-SCD. A new method using gas chromatography coupled with high-resolution mass spectrometry (GC-HRMS) is proposed to selectively detect and quantify the alkyl-BT and alkyl-DBT in SR gas oils. The development of the method and comparison of results between GC-SCD and GC-HRMS are presented. PMID:12175175

García, C López; Becchi, M; Grenier-Loustalot, M F; Païsse, O; Szymanskit, R

2002-08-01

361

Lung cancer detection by proton transfer reaction mass-spectrometric analysis of human breath gas  

NASA Astrophysics Data System (ADS)

Background Determination of the diagnostic usefulness of proton transfer reaction mass spectrometry (PTR-MS) for detecting primary lung cancer through analysis of volatile organic compounds (VOCs) in exhaled human breath was demonstrated in this investigation. Unlike, for example, gas-chromatographic analyses, PTR-MS can be used without time-consuming preconcentration of the gas samples.Methods By means of PTR-MS, exhaled breath samples from primary lung cancer patients (n = 17) were analyzed and compared with both an overall control collective (controls total, n = 170) and three sub-collectives: hospital personnel (controls hospital, n = 35), age-matched persons (controls age, n = 25), and smokers (controls s, n = 60), respectively.Results Among the VOCs present at reasonably high concentrations, the ones leading to the product ion at m/z = 31 (VOC-31, tentatively protonated formaldehyde) and m/z = 43 (VOC-43, tentatively a fragment of protonated iso-propanol), were found at significantly higher concentrations in the breath gas of the primary lung cancer patients as compared to the healthy controls at the following median concentrations (with interquartile distance, iqr): For VOC-31 the median concentrations were 7.0 ppb (iqr, 15.5 ppb) versus 3.0 ppb (iqr, 1.9 ppb) with P < 10-4. For VOC-43 the median concentrations were 244.1 ppb (iqr, 236.2 ppb) versus 94.1 ppb (iqr, 55.2 ppb) with P < 10-6. The discriminative power between the two collectives was further assessed by ROC-curves obtained upon variation of the chosen threshold concentration and by Fisher's Quadratic Discriminant Method.Conclusions Within the limits of pilot study, VOC-31 and -43 were found to best discriminate between exhaled breath of primary lung cancer cases and healthy controls. Simple and time-saving breath gas analysis by PTR-MS makes this method attractive for a larger clinical evaluation. It may become a new valuable tool for diagnosing primary lung cancer.

Wehinger, Andreas; Schmid, Alex; Mechtcheriakov, Sergei; Ledochowski, Maximilian; Grabmer, Christoph; Gastl, Guenther A.; Amann, Anton

2007-08-01

362

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

363

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

364

Verification, Dosimetry, and Biomonitoring of Mustard Gas Exposure via Immunochemical Detection of Mustard Gas Adducts to DNA and Proteins.  

National Technical Information Service (NTIS)

Convenient methods for diagnosis and dosimetry of exposure to chemical agents are not available, but are urgently needed. Immunochemical methods have now been developed for diagnosis and dosimetry of exposure to mustard gas. Exposure of calf-thymus DNA an...

H. P. Benschop G. P. Van Der Schans

1993-01-01

365

Muramic acid is not detectable in Chlamydia psittaci or Chlamydia trachomatis by gas chromatography-mass spectrometry.  

PubMed Central

By using the powerful separation technique of capillary gas chromatography combined with the selectivity of mass spectrometric detection, muramic acid was not detectable in purified elementary bodies of Chlamydia psittaci Cal 10 (less than or equal to 0.006%) or C. trachomatis serovar E (less than or equal to 0.02%). This confirms previous reports which suggested the absence of a typical peptidoglycan in Chlamydia spp.

Fox, A; Rogers, J C; Gilbart, J; Morgan, S; Davis, C H; Knight, S; Wyrick, P B

1990-01-01

366

Fluorescent Dye-doped Sol-gel Sensor for Highly Sensitive Carbon Dioxide Gas Detection below Atmospheric Concentrations  

Microsoft Academic Search

Optical fluorescence sol-gel sensors have been developed for the detection of carbon dioxide gas in the 0.03?30% range with a detection limit of 0.008% (or 80 ppm) and a quantitation limit of 0.02% (or 200 ppm) CO. Sol?gels were spin-coated on glass slides to create an organically modified silica-doped matrix with the 1-hydroxypyrene-3,6,8-trisulfonate (HPTS) fluorescent indicator. The luminescence intensity of

Royce N. Dansby-Sparks; Jun Jin; Shelly J Mechery; Uma Sampathkumaran; Thomas W Owens; Bi Dan Yu; Kisholoy Goswami; Kunlun Hong; Joseph Grant; Ziling Xue

2009-01-01

367

Theoretical analysis of a methane gas detection system, using the complementary source modulation method of correlation spectroscopy  

Microsoft Academic Search

Results from simulations of the response of a methane gas sensor using optical correlation spectroscopy (CoSp) are presented. Predictions of the sensor response, signal\\/noise performance and detection sensitivity are made for a typical fibre optic-coupled system. Spectral absorption data of the gases are obtained from the publicly available HITRAN database. Emphasis is placed on the effects on the detection sensitivity

Paul Chambers; Ed A D Austin; John P Dakin

2004-01-01

368

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) [Helotes, TX; Miller, Michael A. (San Antonio, TX) [San Antonio, TX

2010-08-24

369

Detection of gas hydrate with downhole logs and assessment of gas hydrate concentrations (saturations) and gas volumes on the Blake Ridge with electrical resistivity log data  

USGS Publications Warehouse

Let 164 of the Ocean Drilling Program was designed to investigate the occurrence of gas hydrate in the sedimentary section beneath the Blake Ridge on the southeastern continental margin of North America. Site 994, and 997 were drilled on the Blake Ridge to refine our understanding of the in situ characteristics of natural gas hydrate. Because gas hydrate is unstable at surface pressure and temperature conditions, a major emphasis was placed on the downhole logging program to determine the in situ physical properties of the gas hydrate-bearing sediments. Downhole logging tool strings deployed on Leg 164 included the Schlumberger quad-combination tool (NGT, LSS/SDT, DIT, CNT-G, HLDT), the Formation MicroScanner (FMS), and the Geochemical Combination Tool (GST). Electrical resistivity (DIT) and acoustic transit-time (LSS/SDT) downhole logs from Sites 994, 995, and 997 indicate the presence of gas hydrate in the depth interval between 185 and 450 mbsf on the Blake Ridge. Electrical resistivity log calculations suggest that the gas hydrate-bearing sedimentary section on the Blake Ridge may contain between 2 and 11 percent bulk volume (vol%) gas hydrate. We have determined that the log-inferred gas hydrates and underlying free-gas accumulations on the Blake Ridge may contain as much as 57 trillion m3 of gas.

Collett, T. S.; Ladd, J.

2000-01-01

370

Atmospheric Detection of Perfluorotributyl Amine, an Uncharacterized Long-Lived Greenhouse Gas  

NASA Astrophysics Data System (ADS)

Poly- and perfluoroalkyl substances (PFASs) are trace atmospheric constituents of radiative significance. In the atmosphere, PFASs may represent a class of potent long-lived greenhouse gases (LLGHGs) because they possess long lifetimes and exceptionally strong absorption bands in the infrared (IR) spectral region where other naturally occurring greenhouse gases (GHGs) do not absorb. The Intergovernmental Panel on Climate Change determined the radiative forcing (RF) of halocarbons to be +0.337 [± 0.03] W m-2, accounting for 13 % of the total RF attributed to LLGHGs. Although this value claims high certainty, it does not represent the actual perturbation from all environmentally relevant PFASs. Here we present the radiative efficiency (RE) and atmospheric concentration of a previously uncharacterized and unreported PFAS, perfluorotributyl amine (PFBAm). To assess the radiative properties of PFBAm, IR spectra were acquired by Fourier transform spectroscopy at 0.25 cm-1 resolution over the spectral range 0-2500 cm-1 at 296 K. The total integrated band strength, 7.08 x 10-16 cm2 molec-1 cm-1, was used to derive the cloudy-sky, instantaneous RE assuming a 0 to 1 ppbv change in concentration.The RE of PFBAm is calculated to be 0.86 W m-2 ppb-1, exceeding the RE of SF5CF3, the most effective GHG on a per molecule basis as reported in the literature to date. To evaluate the RF of PFBAm, a highly sensitive and selective method for detection was developed and validated. PFBAm was cryogenically extracted and pre-concentrated from bulk air samples for the offline detection by a custom-designed manifold coupled to a gas chromatograph-mass spectrometer. Quantitation was achieved by external calibration with a gravimetrically prepared, matrix-matched, authentic gaseous standard. Validation of the sampling method was performed by simultaneous measurement of several legacy chlorofluorocarbons and hydrochlorofluorocarbons. Preliminary results indicate that PFBAm is present in the atmosphere at concentrations of 0.081 [± 0.006] pptv (n=27, p<0.05, t=1.706). The potential for PFBAm to impact the Earth's energy balance will be discussed in light of its concentration and RE. The detection of PFBAm sets a precedent for the discovery of other unaccounted PFASs. PFBAm has been detected in the atmosphere for the first time. Based on its radiative properties, it has the potential to implicate the Earth's energy balance.

Hong, A. C.; Young, C. J.; Mabury, S. A.

2012-12-01

371

Optical enhancement of diode laser-photoacoustic trace gas detection by means of external Fabry-Perot cavity  

Microsoft Academic Search

An optical enhancement method applied to a diode laser photoacoustic trace gas detector is presented. In order to improve the detection sensitivity, the light intensity inside the acoustic resonator is amplified using a Fabry-Perot cavity. A feedback signal stabilizes the laser frequency to the optical cavity length, in order to maintain the light amplification constant during the probe frequency scan.

Alessandro Rossi; Roberto Buffa; Mario Scotoni; Davide Bassi; Salvatore Iannotta; Andrea Boschetti

2005-01-01

372

Assessment of technology for detection of stress corrosion cracking in gas pipelines. Final report, July 1993March 1994  

Microsoft Academic Search

The objective of the project was to assess the nondestructive evaluation (NDE) technology that may be applied to natural gas steel pipelines for the detection of stress corrosion cracking (SCC). In particular, the application of such technology would be from the inside of the pipe while the pipeline is in service, and inspection commonly called in-line inspection (ILI). The assessment

A. E. Crouch; C. M. Teller; J. L. Fisher; G. M. Light; C. M. Fortunko

1994-01-01

373

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

National Technical Information Service (NTIS)

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 ...

1995-01-01

374

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...

375

The portable gas chromatograph OralChroma™: a method of choice to detect oral and extra-oral halitosis  

Microsoft Academic Search

It is now generally accepted that the volatile sulfur compounds (VSCs) hydrogen sulfide, methyl mercaptan and dimethyl sulfide are the main contributors to halitosis when of oropharyngeal origin. Gas chromatography using a specific sulfur detector is the most appropriate method to detect halitosis of different origin (intra-oral and extra-oral halitosis) and should be considered as the gold standard. However, a

A Tangerman; E G Winkel

2008-01-01

376

Fast-Scanning Fibre-Amplified Diode Laser Pumped cw OPO for Sensitive, MultiComponent Trace Gas Detection  

Microsoft Academic Search

An 800 mW, fast scanning (100 THz\\/s), continuous wave optical parametric oscillator (3-4 mum) pumped by a fibre-amplified diode laser is used for sensitive (1.5 times 10-8 cm-1 Hz-1\\/2), multi-component trace gas detection.

S. T. Persijn; A. K. Y. Ngai; F. J. M. Harren; L. D. Lindsay; P. Gross; B. Adhimoolam; K. J. Boiler

2007-01-01

377

Cost Effective Multi-Spectral Scanner for Natural Gas Detection. (Final Report, October 1, 2003-September 30, 2005).  

National Technical Information Service (NTIS)

The objective of this project is to design, fabricate and 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 mul...

Y. Sivathanu J. Lim V. Narayanan S. Park

2005-01-01

378

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

379

Analysis of Malodorous Sulfur Gases and Volatile Organometalloid Compounds in Landfill Gas Emissions Using Capillary Gas Chromatography with Programmed Temperature Vaporization Injection and Atomic Emission Detection  

Microsoft Academic Search

Volatile compounds containing Group V and Group VI elements in landfill gases are of concern as a source of toxic pollutants and unpleasant odors. Conventional analytical techniques for these compounds e.g. ICP-MS, ICP-AES are complicated, expensive and time consuming. The use of a simple programmed temperature vaporization injection (PTV) technique coupled to gas chromatography with atomic emission detection (GC-AED) has

Suwannee Junyapoon; Keith Bartle; Andrew Ross; Michael Cooke

2002-01-01

380

Temperature-programmable resistively heated micromachined gas chromatography and differential mobility spectrometry detection for the determination of non-sulfur odorants in natural gas.  

PubMed

A portable, fast gas chromatographic method for the direct measurement of the parts per billion level of sulfur-free odorants in commercially available natural gas is introduced. The approach incorporates a resistively heated, temperature-programmable silicon micromachined gas chromatograph that employs a standard capillary column for the fast separation of methyl and ethyl acrylate from the natural gas matrix. The separation approach is coupled to a micromachined differential mobility detector to enhance analyte detectability, and the overall selectivity obtained against the matrix is described. A complete analysis can be conducted in less than 70 s. Furthermore, these two compounds can be measured accurately in the presence of other common volatile sulfur-based odorants such as alkyl mercaptans and alkyl sulfides. Repeatability of less than 3% RSD (n = 20) over a range from 0.5 to 5 ppm was obtained with a limit of detection for the target compounds at 50 ppb (v/v) and a linear range from 0.5 to 50 ppm with a correlation coefficient of at least 0.997. PMID:23427942

Luong, J; Gras, R; Cortes, H J; Shellie, R A

2013-03-19

381

Detection of the abnormal events along the oil and gas pipeline and multi-scale chaotic character analysis of the detected signals  

Microsoft Academic Search

This paper studies the monitoring principle of abnormal events along oil and gas pipelines, which is conducted by a Mach–Zehnder optical fiber interferometer based distributed optical fiber pipeline pre-warning system. The detected signals of three typical abnormal events are analyzed by a multi-scale chaotic character analysis method based on orthogonal wavelet packet decomposition. In this pre-warning system, an optical cable

Zhigang Qu; Yan Zhou; Zhoumo Zeng; Hao Feng; Yu Zhang; Shijiu Jin

2008-01-01

382

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

PubMed Central

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

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

2009-01-01

383

Detection of D-^3He Fusion ?-Rays using Gas Cherenkov Detectors  

NASA Astrophysics Data System (ADS)

The high-energy ?-ray from ^3He(d,?)^5Li reactions has drawn the attention of the nuclear physics and fusion community as a diagnostic signature to study the ^5Li nuclear structure and the D-^3He fusion reaction. In the past, the D-^3He ?-rays have been measured via accelerator-based beam-target experiments and recently in tokamak-based fusion reactors. In this work, we report the detection of D-^3He fusion ?-rays generated from inertial confinement fusion (ICF) implosions at the OMEGA laser facility. The ?-ray signal observed using Gas Cherenkov Detectors (GCD) is proportional to the independently measured 14.7-MeV fusion proton yield and provides a high-bandwidth alternative to fusion protons for D-^3He burn-history measurements. By comparing ?-rays from D-^3He and D-T implosions, we were able to examine (1) similarities in the ?-ray spectra of D-^3He and D-T and (2) disparities in the ?-to-particle branching ratios of D-^3He and D-T. This experimental work motivates further theoretical investigation of the multichannel ^5Li- and ^5He-system.

Kim, Y.; Herrmann, H. W.; Mack, J. M.; Young, C. S.; Hale, G. M.; Evans, S. C.; Sedillo, T. J.; Cahill, A.; Horsfield, C. J.; Rubery, M. S.; Grafil, E.; Stoeffl, W.; Waugh, C.; Rinderknecht, H. G.; Frenje, J. A.; Petrasso, R. D.; Miller, E. Kirk

2012-10-01

384

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

385

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

386

Profiling of soil fatty acids using comprehensive two-dimensional gas chromatography with mass spectrometry detection.  

PubMed

Profiling of phospholipid fatty acids (PLFA) represents a challenging goal for distinguishing the diversity of microbial communities and biomass in the complex and heterogeneous soil ecosystem. Comprehensive two-dimensional gas chromatography (GC×GC) coupled with simultaneous flame ionisation and mass spectrometry detection was applied as a culture-independent method for PLFA profiling of microbial classification in forest soil. A number of column sets were evaluated for the GC×GC separation of fatty acid methyl esters (FAME). Due to better isomeric separation and compound patterns on the 2D contour plot, an apolar-polar column combination was selected for soil microbial PLFA characterisation. A comprehensive view of PLFA composition with carbon chain length varying from 12 to 20 was observed in forest soil samples, with the commonly reported bacterial FAME of iso-/anteiso-, methyl-branched-, cyclopropyl-, and hydroxyl-substituted FA identified by their mass spectral and retention time according to authentic standards. Notably, some uncommon oxygenated FAME were found in high abundance and were further characterised by GC×GC coupled with high resolution mass spectrometry. This tentatively revealed geometric pairs of methyl 9,10-epoxyoctadecanoate isomers. PMID:24041509

Zeng, Annie Xu; Chin, Sung-Tong; Patti, Antonio; Marriott, Philip J

2013-11-22

387

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

388

Determination of reduced sulfur compounds in aqueous solutions using gas chromatography flame photometric detection  

SciTech Connect

A method for simultaneous analysis of hydrogen sulfide (H/sub 2/S), methyl mercaptan (CH/sub 3/SH), carbon disulfide (CS/sub 2/), dimethyl sulfide (DMS, CH/sub 3/SCH/sub 3/), and dimethyl disulfide (DMDS, CH/sub 3/SSCH/sub 3/) in aqueous solutions is described. The reduced sulfur compounds are released from the aqueous sample (50-200 mL) by purging with N/sub 2/ and then trapped cryogenically in a U-shaped sample tube with liquid nitrogen. The sample tube was sealed with end caps and placed in a portable freezer. Under stable conditions in the laboratory, the sulfur compounds are released by controlled heating and injected onto packed column gas chromatograph with a flame photometric detector. The precision of the method for environmental samples was better than +/- 5% for all compounds except for H/sub 2/S, for which the precision was +/- 25%. The detection limits for H/sub 2/S, CH/sub 3/SH, CS/sub 2/, DMS, and DMDS were 1, 0.6, 0.2, 0.2, and 0.4 ng x L/sup -1/ S, respectively, in a 200-mL natural sample. Analyses of environmental samples have been successfully performed with the described method.

Leck, C.; Baegander, L.E.

1988-09-01

389

Direct estimation of carbaryl by gas liquid chromatography with nitrogen phosphorus detection.  

PubMed

A simple and efficient analytical method was standardized for the estimation of residues of carbaryl in various substrates comprising grape berries, kinnow pulps, kinnow rind and soil. The samples were refluxed using mixture of methanol: 0.5 N HCl (1:1 v/v); diluted with brine solution, partitioned into chloroform and dried over anhydrous sodium sulfate. Further the samples were treated with anhydrous magnesium sulfate and primary secondary amine. Final clear extracts were concentrated under vacuum and reconstituted the volume into acetone. The residues were estimated directly on gas liquid chromatograph equipped with nitrogen phosphorus detection system equipped with a capillary column packed with 5 % diphenyl 95 % dimethyl polysiloxane non-polar phase. A consistent recovery from 82 % to 97 % for carbaryl was observed when samples were spiked at levels ranging from 0.05 to 1.00 mg kg(-1). The limit of quantification of the method was worked out to be 0.05 mg kg(-1) for grape berries, kinnow pulp, kinnow rind and soil. PMID:22487961

Battu, Raminderjit Singh; Mandal, Kousik; Urvashi; Pandher, Suneet; Takkar, Reenu; Singh, Balwinder

2012-07-01

390

High Sensitivity Gas Detection Using a Macroscopic Three-Dimensional Graphene Foam Network  

PubMed Central

Nanostructures are known to be exquisitely sensitive to the chemical environment and offer ultra-high sensitivity for gas-sensing. However, the fabrication and operation of devices that use individual nanostructures for sensing is complex, expensive and suffers from poor reliability due to contamination and large variability from sample-to-sample. By contrast, conventional solid-state and conducting-polymer sensors offer excellent reliability but suffer from reduced sensitivity at room-temperature. Here we report a macro graphene foam-like three-dimensional network which combines the best of both worlds. The walls of the foam are comprised of few-layer graphene sheets resulting in high sensitivity; we demonstrate parts-per-million level detection of NH3 and NO2 in air at room-temperature. Further, the foam is a mechanically robust and flexible macro-scale network that is easy to contact (without Lithography) and can rival the durability and affordability of traditional sensors. Moreover, Joule-heating expels chemisorbed molecules from the foam's surface leading to fully-reversible and low-power operation.

Yavari, Fazel; Chen, Zongping; Thomas, Abhay V.; Ren, Wencai; Cheng, Hui-Ming; Koratkar, Nikhil

2011-01-01

391

Determination of volatile nitrosamines in grilled lamb and vegetables using comprehensive gas chromatography - nitrogen chemiluminescence detection.  

PubMed

The grilling of meat may generate dangerous levels of mutagenic and carcinogenic nitrosamines (NAs). Meat and vegetable samples underwent a two-step solid-phase extraction before analysis by comprehensive gas chromatography with a nitrogen chemiluminescence detection system (GCxGC-NCD). The GCxGC-NCD method showed high selectivity, sensitivity and equimolarity in its response to six specific NAs. NA contamination of charcoal-grilled lamb at various stages of cooking and with various fat contents and also charcoal-grilled vegetables were investigated. The grilling of lamb on unready charcoal resulted in the formation of considerable quantities of NAs. Grilling lamb on properly prepared, ready charcoal resulted in an increase in total concentrations of six NAs from 0 to 4.51 ?g kg(-1) over a period of 16 min. Increasing the fat content of the grilled lamb from 5% to 20% caused a modest increase in total concentrations of the six investigated NAs from 4.51 to 5.30 ?g kg(-1). PMID:22980793

Kocak, D; Ozel, M Z; Gogus, F; Hamilton, J F; Lewis, A C

2012-12-15

392

High sensitivity gas detection using a macroscopic three-dimensional graphene foam network.  

PubMed

Nanostructures are known to be exquisitely sensitive to the chemical environment and offer ultra-high sensitivity for gas-sensing. However, the fabrication and operation of devices that use individual nanostructures for sensing is complex, expensive and suffers from poor reliability due to contamination and large variability from sample-to-sample. By contrast, conventional solid-state and conducting-polymer sensors offer excellent reliability but suffer from reduced sensitivity at room-temperature. Here we report a macro graphene foam-like three-dimensional network which combines the best of both worlds. The walls of the foam are comprised of few-layer graphene sheets resulting in high sensitivity; we demonstrate parts-per-million level detection of NH(3) and NO(2) in air at room-temperature. Further, the foam is a mechanically robust and flexible macro-scale network that is easy to contact (without Lithography) and can rival the durability and affordability of traditional sensors. Moreover, Joule-heating expels chemisorbed molecules from the foam's surface leading to fully-reversible and low-power operation. PMID:22355681

Yavari, Fazel; Chen, Zongping; Thomas, Abhay V; Ren, Wencai; Cheng, Hui-Ming; Koratkar, Nikhil

2011-01-01

393

High Sensitivity Gas Detection Using a Macroscopic Three-Dimensional Graphene Foam Network  

NASA Astrophysics Data System (ADS)

Nanostructures are known to be exquisitely sensitive to the chemical environment and offer ultra-high sensitivity for gas-sensing. However, the fabrication and operation of devices that use individual nanostructures for sensing is complex, expensive and suffers from poor reliability due to contamination and large variability from sample-to-sample. By contrast, conventional solid-state and conducting-polymer sensors offer excellent reliability but suffer from reduced sensitivity at room-temperature. Here we report a macro graphene foam-like three-dimensional network which combines the best of both worlds. The walls of the foam are comprised of few-layer graphene sheets resulting in high sensitivity; we demonstrate parts-per-million level detection of NH3 and NO2 in air at room-temperature. Further, the foam is a mechanically robust and flexible macro-scale network that is easy to contact (without Lithography) and can rival the durability and affordability of traditional sensors. Moreover, Joule-heating expels chemisorbed molecules from the foam's surface leading to fully-reversible and low-power operation.

Yavari, Fazel; Chen, Zongping; Thomas, Abhay V.; Ren, Wencai; Cheng, Hui-Ming; Koratkar, Nikhil

2011-11-01

394

Rapid and sensitive assay for fluconazole which uses gas chromatography with electron capture detection.  

PubMed Central

Fluconazole, an orally active antifungal agent, has been shown to be clinically beneficial for maintenance therapy of cryptococcal meningitis. A sensitive gas-liquid chromatographic assay with electron capture detection, which required only a single extraction step and precluded any pretreatment of the chromatographic column, was developed for fluconazole. The assay was linear from 0.1 to 20 micrograms/ml, with a correlation coefficient of 0.999. The intraassay and interassay coefficients of variation were less than 9%. The measured values on average were within 8% of the target values. The extraction recoveries ranged from 87 to 106%. Steady-state plasma fluconazole levels (mean +/- standard deviation) in three AIDS patients with cryptococcal meningitis receiving 200 mg of fluconazole per day ranged from 8.95 +/- 1.32 to 11.41 +/- 0.63 micrograms/ml and were within the expected range for this dosing rate, on the basis of previous studies. The ratio of fluconazole concentration in cerebrospinal fluid to fluconazole concentration in plasma in one patient receiving 400 mg/day was 0.73 at steady state and was consistent with published reports.

Rege, A B; Walker-Cador, J Y; Clark, R A; Lertora, J J; Hyslop, N E; George, W J

1992-01-01

395

Respeciation of organic gas emissions and the detection of excess unburned gasoline in the atmosphere  

Microsoft Academic Search

The development of a set of organic gas composition profiles for key source categories is described. This information is used to recompute the organic gas emission inventory for the Los Angeles area. Comparisons are made between the revised emission inventory and ambient concentration measurements in southern California. Respeciation of the organic gas emissions results in large changes in the basinwide

Robert A. Harley; Michael P. Hannigan; Glen R. Cass

1992-01-01

396

In2O3-based micro gas sensor for detecting NO x gases  

NASA Astrophysics Data System (ADS)

In this study, NO x micro gas sensors for monitoring the indoor atmosphere of automobile were fabricated using MEMS (microelectromechanical system) technology and a sol-gel process. The sensing electrode and micro heater were designed to have a co-planar typed structure in a Pt thin film layer. The thermal characteristics of a micro heater array were analyzed using a finite element method (FEM). The chip size of the gas sensor was approximately 2 mm × 2 mm. Indium oxide as a sensing material for NO x gas was synthesized by a sol-gel process with indium isopropoxide as a precursor. Field emission Scanning electron microscopy and x-ray diffraction showed that particle size of the synthesized In2O3 was approximately 17-45 nm. The maximum gas sensitivity as the relative resistance ( R s = R gas / R air ) was observed at 275°C with a value of 8.0 at 1 ppm NO2 gas. The response (80% saturation) and recovery times were within 1 min. The sensing properties of NO2 gas exhibited linear behavior with increasing gas concentration. The sensing mechanism of the gas sensor was explained by the variations in the electron depletion layers and the adsorption of gas molecules on the In2O3 particle surface. These results suggest that in the future, MEMS-based gas sensors can be used as automotive-exhaust-gas sensors.

Kim, Bum-Joon; Song, In-Gyu; Kim, Jung-Sik

2014-03-01

397

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

398

Comparison of breath and in-mouth collection for the measurement of oral malodorous compounds by gas chromatography using sulfur chemiluminescence detection  

Microsoft Academic Search

Volatile sulfur compounds (VSCs), specifically hydrogen sulfide, methyl mercaptan and dimethyl sulfide, are generally considered to be the primary volatiles responsible for 'morning' malodors in breath. To date, the 'gold standard' for detecting VSC concentrations in breath is the use of gas chromatography coupled with sulfur chemiluminescence detection. Breath gas is often collected in a polypropylene syringe and then aliquots

Debbie J. Paetznick; G. A. Reineccius; T. L. Peppard; J. M. Herkert; P. Lenton

2010-01-01

399

Comparison of breath and in-mouth collection for the measurement of oral malodorous compounds by gas chromatography using sulfur chemiluminescence detection  

Microsoft Academic Search

Volatile sulfur compounds (VSCs), specifically hydrogen sulfide, methyl mercaptan and dimethyl sulfide, are generally considered to be the primary volatiles responsible for ‘morning’ malodors in breath. To date, the ‘gold standard’ for detecting VSC concentrations in breath is the use of gas chromatography coupled with sulfur chemiluminescence detection. Breath gas is often collected in a polypropylene syringe and then aliquots

Debbie J Paetznick; G A Reineccius; T L Peppard; J M Herkert; P Lenton

2010-01-01

400

The use of soil mercury and radon gas surveys to assist the detection of concealed faults in Fuzhou City, China  

NASA Astrophysics Data System (ADS)

Soil gas approaches have been proven useful for detecting buried faults in field survey. How about their applicability in urban area? A trial soil gas survey has been conducted in an attempt to evaluate this in Fuzhou City, Southeastern China. The detection was performed by measuring the adsorbed mercury, free mercury and radon gases in soil in the sites such as crop soil, refilled soil and those with shallow groundwater levels. The resulting distributions show that anomalous concentrations of soil gases over faults are generally two to four times as much as those in the surrounding areas. The locations of peak values of absorbed and free mercury could possibly be applied to assist to determine the trend of faults. The background values of free mercury seems to be more stable and the anomalous zones narrower than those of radon gas, therefore, the free mercury method seems to be good for detection at this area, especially in those sites with shallow groundwater levels. The false gas anomalies may occur in such a site as refilled with external soil, refilled pond and abandoned construction bases.

Wang, Guangcai; Liu, Chenglong; Wang, Jihua; Liu, Wuzhou; Zhang, Peiren

2006-10-01

401

[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

402

Assessment of technology for detection of stress corrosion cracking in gas pipelines. Final report, July 1993-March 1994  

SciTech Connect

The objective of the project was to assess the nondestructive evaluation (NDE) technology that may be applied to natural gas steel pipelines for the detection of stress corrosion cracking (SCC). In particular, the application of such technology would be from the inside of the pipe while the pipeline is in service, and inspection commonly called in-line inspection (ILI). The assessment focused on two basic NDE methods, ultrasonics and electromagnetics (including magnetic flux leakage). A third technology was data acquisition/analysis systems. Based on the experience of British Gas (BG) and others doing SCC inspections in different industries, crack discrimination is the important challenge for any such inspection system.

Crouch, A.E.; Teller, C.M.; Fisher, J.L.; Light, G.M.; Fortunko, C.M.

1994-04-01

403

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

404

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

PubMed

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

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

2014-07-15

405

Comparison of thermal neutron detection efficiency of 6Li scintillation glass and 3He gas proportional tube  

NASA Astrophysics Data System (ADS)

We report on a comparison study of the 3He gas proportional tube and the 6Li incorporated scintillation glasses on thermal neutron detection efficiency. Both 3He and 6Li are used commonly for thermal neutron detection because of their high neutron capture absorption coefficient. By using a neutron source 252Cf 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 has been modeled with GEANT4 to validate the results against the Monte Carlo simulation.

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

2013-10-01

406

Detection of potential chronic kidney disease markers in breath using gas chromatography with mass-spectral detection coupled with thermal desorption method.  

PubMed

The analytical potential of chromatographic breath analysis towards detection of compounds suggested as markers of chronic kidney disease (CKD) was tested. Until now, trimethylamine (TMA) considered as a potential marker of renal disorder was detected mainly in plasma. Detection of TMA in breath was rarely undertaken due to analytical difficulties associated with amines' properties. The results of our investigations confirmed that an application of thermal desorption (TD) and gas chromatography with mass-spectral detection (GC/MS) allows direct detection of TMA in breath. The preliminary studies allowed to determine the breath composition in case of patients suffering from CKD and to compare the obtained results to a control group. Breath samples were collected from 14 patients and 9 healthy volunteers. TMA was detected in all patients suffering from CKD in the range 1.76-38.02ppb, but not in the control group. Acetone and isoprene were present in the exhaled air of all examined persons. The concentration of acetone was in the range of 26.52-329.46ppb in the patient group and 73.11-437.14ppb in the control group. Isoprene was detected in the range 57.17-329.8ppb among CKD patients and 27.99-143.77ppb in healthy volunteers. Additionally aliphatic hydrocarbons and sulfur compounds were determined in breath as compounds which could be essential in case of diseases coexisting with CKD. Apart from TMA and pentane no statistically significant differences were found using our analytical technique. TMA was detected in the breath of all patients with CKD and in none of breath samples in control group. TMA seems to be a promising marker of CKD. PMID:23764192

Grabowska-Polanowska, Beata; Faber, Jacek; Skowron, Monika; Miarka, Przemys?aw; Pietrzycka, Agata; Sliwka, Ireneusz; Amann, Anton

2013-08-01

407

Polymer/Ordered mesoporous carbon nanocomposite platelets as superior sensing materials for gas detection with surface acoustic wave devices.  

PubMed

We have prepared nanocomposites of polymers and platelet CMK-5-like carbon and have demonstrated their superior performance for gravimetric gas detection. The zirconium-containing platelet SBA-15 was used as hard template to prepare CMK-5-like carbon, which was then applied as a lightweight and high-surface-area scaffold for the growth of polymers by radical polymerization. Mesoporous nanocomposites composed of four different polymers were used as sensing materials for surface acoustic wave devices to detect ppm-level ammonia gas. The sensors showed much better sensitivity and reversibility than those coated with dense polymer films, and the sensor array could still generate a characteristic pattern for the analyte with a concentration of 16 ppm. The results show that the nanocomposite sensing materials are promising for highly sensitive gravimetric-type electronic nose applications. PMID:22835071

Ku, Pei-Hsin; Hsiao, Chen-Yun; Chen, Mei-Jing; Lin, Tai-Hsuan; Li, Yi-Tian; Liu, Szu-Chieh; Tang, Kea-Tiong; Yao, Da-Jeng; Yang, Chia-Min

2012-08-01

408

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

409

Assessment of soil and soil-gas radon activity using active and passive detecting methods in Korea.  

PubMed

Radon ((222)Rn) is a carcinogenic gas produced by the radioactive decay of radium ((226)Ra). It has been reported that soil and soil-gas are primary factors that could cause indoor radon problems. Six sites were selected for this study--Sanbook, Gangcheon, Jikyeong, Choojung, Geumsung and Homyoung--each was classified according to bedrock type. In order to investigate soil-gas radon activities and radon emanating power, innovated active and passive detecting methods were developed and applied under both field and laboratory conditions. Statistical analysis of results confirmed that the radon activity values measured using either active or passive methods under field or laboratory conditions could be interchangeable with each other. PMID:17578670

Je, Hyun-Kuk; Kang, Chi-Gu; Choi, Jae-Young; Lee, Jin-Soo; Chon, Hyo-Taek

2007-08-01

410

Detecting internal corrosion of natural gas transmission pipelines: field tests of probes and systems for real-time corrosion measurement  

Microsoft Academic Search

A field study was conducted to evaluate the use of automated, multi-technique electrochemical corrosion-rate monitoring devices and probes for detecting corrosion in environments similar to those found in natural gas transmission pipelines. It involved measurement of real-time corrosion signals from operating pipelines. Results and interpretation were reported from four different field test locations. Standard flush-mount and custom flange probes were

Covino Bernard S. Jr; Sophie J. Bullard; Stephen D. Cramer; Gordon R. Holcomb; M. Ziomek-Moroz; R. D. Kane; B. Meidinger

2005-01-01

411

Structural studies on soil nitrogen by Curie-point pyrolysis — gas chromatography\\/mass spectrometry with nitrogen-selective detection  

Microsoft Academic Search

Curie-point pyrolysis-gas chromatography mass spectrometry with N-selective detection was used to characterize the structure of organic N compounds in four mineral soils. The technique was found suitable for the fast, sensitive, and highly specific identification of N-containing pyrolysis products from whole soils with total N contents between 0.08 and 0.46%. In order to optimize the methodology, one agricultural soil was

H.-R. Schulten; C. Sorge; M. Schnitzer

1995-01-01

412

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

Microsoft Academic Search

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

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

1995-01-01

413

Element-specific derivatization for enhanced detectability by the gas chromatograph-microwave emission detector (GC-MED)  

NASA Astrophysics Data System (ADS)

The applicability or using the gas chromatograph-microwave plasma emission detector (GC-MED) in combination with chemical derivatization based on unique elements for enhanced detectability of selected compounds in complex samples is discussed. A number of potential derivatization schemes are surveyed and results for two specific approaches are presented. In addition to high sensitivity and element selectivity, the possibility of determining empirical formulas by plasma emission will be an advantage unique to this approach.

Delaney, Michael F.; Warren, F. Vincent

414

Determination of oxadiazon and oxyfluorfen in thyme by gas chromatography with electron-capture detection and gas chromatography\\/mass spectrometry  

Microsoft Academic Search

The present paper reports on an analytical method for the routine analysis of oxadiazon (5-tert-butyl-3-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2(3H)-one) and oxyfluorfen (2-chloro-?,?,?-trifluoro-p-tolyl 3-ethoxy-4-nitrophenyl ether) residues in thyme (Thymus vulgaris L. and Thymus zygis subsp. gracilis). Samples were extracted by sonication with a water-acetonitrile mixture and the herbicides were partitioned into dichloromethane. Residue levels in thyme were determined by gas chromatography with electron-capture detection (ECD).

José Fenoll; Pilar Hellín; Pilar Flores; José A. Sotomayor; María I. Nicolás

2008-01-01

415

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...

416

Detection of greenhouse gases emitted by engines powered by natural gas  

Microsoft Academic Search

The greenhouse effect is a major environmental problem, and a cause of climatic changes. Gas species such as methane and carbon dioxide cause this effect. These substances are mainly produced by Vehicle Natural Gas (VNG, more than 85% methane)?powered engines, thermoelectric plants, etc. In this paper, we report work by an infrared analyser based on the photo?acoustic method (URAS) to

G. R. Lima; M. S. Sthel; D. U. Schramm; M. V. Rocha; J. R. Tavares; L. S. Campos; H. Vargas

2010-01-01

417

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

418

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

419

Fluorescent-dye-doped sol-gel sensor for highly sensitive carbon dioxide gas detection below atmospheric concentrations.  

PubMed

Optical fluorescence sol-gel sensors have been developed for the detection of carbon dioxide gas in the 0.03-30% range with a detection limit of 0.008% (or 80 ppm) and a quantitation limit of 0.02% (or 200 ppm) CO(2). Sol-gels were spin-coated on glass slides to create an organically modified silica-doped matrix with the 1-hydroxypyrene-3,6,8-trisulfonate (HPTS) fluorescent indicator. The luminescence intensity of the HPTS indicator (513 nm) is quenched by CO(2), which protonates the anionic form of HPTS. An ion pair technique was used to incorporate the lipophilic dye into the hydrophilic sol-gel matrix. TiO(2) particles (<5 microm diameter) were added to induce Mie scattering and increase the incident light interaction with the sensing film, thus increasing the signal-to-noise ratio. Moisture-proof overcoatings have been used to maintain a constant level of water inside the sensor films. The optical sensors are inexpensive to prepare and can be easily coupled to fiber optics for remote sensing capabilities. A fiber-optic bundle was used for the gas detection and shown to work as part of a multianalyte platform for simultaneous detection of multiple analytes. The studies reported here resulted in the development of sol-gel optical fluorescent sensors for CO(2) gas with sensitivity below that in the atmosphere (ca. 387 ppm). These sensors are a complementary approach to current FT-IR measurements for real-time carbon dioxide detection in environmental applications. PMID:20038093

Dansby-Sparks, Royce N; Jin, Jun; Mechery, Shelly J; Sampathkumaran, Uma; Owen, Thomas William; Yu, Bi Dan; Goswami, Kisholoy; Hong, Kunlun; Grant, Joseph; Xue, Zi-Ling

2010-01-15

420

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.

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

2014-01-01

421

A new method for ultrasound detection of interfacial position in gas-liquid two-phase flow.  

PubMed

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, Fábio Rizental; Ofuchi, César Yutaka; de Arruda, Lúcia Valéria Ramos; Neves, Flávio; Morales, Rigoberto E M

2014-01-01

422

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

423

Galactic Observations of Terahertz C+ (GOT C+): [CII] Detection of Warm "Dark Gas" in the ISM  

NASA Astrophysics Data System (ADS)

The Herschel HIFI Key Program, Galactic Observations of Terahertz C+ (GOT C+) is a survey of [CII] 1.9 THz emission throughout the Galaxy. Comparison of the first results of this survey with HI and CO isotopomer emission reveals excess [CII] emission beyond that expected from HI and CO layers alone, and is best explained as coming from a hidden layer of H2 gas, the so-called ISM "dark gas".

Langer, W. D.; Velusamy, T.; Pineda, J.; Goldsmith, P.; Li, D.; Yorke, H. W.

2011-11-01

424

Noble gas detection using resonance ionization spectroscopy and a quadrupole mass spectrometer  

SciTech Connect

The technique of Resonance Ionization Spectroscopy (RIS) is being extended to develop a means for counting individual atoms of a selected isotope of a noble gas. In this method, lasers are used for RIS to obtain atomic species (Z) selectivity and a small quadrupole mass spectrometer provides isotopic (A) selectivity. A progress report on the objective of counting each atom of a particular isotope of a noble gas is given. 11 references, 4 figures.

Chen, C.H.; Hurst, G.S.

1983-01-01

425

Detection of deep traps for gas molecules in the diffusion processes in low-molecular glasses  

NASA Astrophysics Data System (ADS)

The kinetics of the diffusion-controlled radical oxidation in galssy alcohol matrices of n-butanol- d10 and isopentanol has been studied at various concentrations of oxygen and nitrogen in the samples. The influences of matrix annealing and gas concentrations on the kinetics have been analyzed. A conclusion on the existence of deep traps for gas molecules in n-butanol- d10 and isoamyl alcohol is drawn.

Vasenkov, S. V.; Tolkatchev, V. A.; Bazhin, N. M.

1993-05-01

426

Method and apparatus for noble gas atom detection with isotopic selectivity  

DOEpatents

Apparatus and methods of operation are described for determining, with isotopic selectivity, the number of noble gas atoms in a sample. The analysis is conducted within an evacuated chamber which can be isolated by a valve from a vacuum pumping system capable of producing a pressure of 10.sup.-8 Torr. Provision is made to pass pulses of laser beams through the chamber, these pulses having wavelengths appropriate for the resonance ionization of atoms of the noble gas under analysis. A mass filter within the chamber selects ions of a specific isotope of the noble gas, and means are provided to accelerate these selected ions sufficiently for implantation into a target. Specific types of targets are discussed. An electron measuring device produces a signal relatable to the number of ions implanted into the target and thus to the number of atoms of the selected isotope of the noble gas removed from the gas sample. The measurement can be continued until a substantial fraction, or all, of the atoms in the sample have been counted. Furthermore, additional embodiments of the apparatus are described for bunching the atoms of a noble gas for more rapid analysis, and for changing the target for repetitive cycling of the gas in the chamber. The number of repetitions of the cyclic steps depend upon the concentration of the isotope of interest, the separative efficiency of the mass filter, etc. The cycles are continued until a desired selectivity is achieved. Also described are components and a method of operation for a pre-enrichment operation for use when an introduction of a total sample would elevate the pressure within the chamber to levels in excess of those for operation of the mass filter, specifically a quadrupole mass filter. Specific examples of three noble gas isotope analyses are described.

Hurst, G. Samuel (Oak Ridge, TN); Payne, Marvin G. (Harriman, TN); Chen, Chung-Hsuan (Knoxville, TN); Parks, James E. (Oak Ridge, TN)

1984-01-01

427

Detection Of Gas-Phase Polymerization in SiH4 And GeH4  

NASA Technical Reports Server (NTRS)

Inelastic scattering of laser light found to indicate onset of gas-phase polymerization in plasma-enhanced chemical-vapor deposition (PECVD) of photoconductive amorphous hydrogenated silicon/germanium alloy (a-SiGe:H) film. In PECVD process, film deposited from radio-frequency glow-discharge plasma of silane (SiH4) and germane (GeH4) diluted with hydrogen. Gas-phase polymerization undesirable because it causes formation of particulates and defective films.

Shing, Yuh-Han; Perry, Joseph W.; Allevato, Camillo E.

1990-01-01

428

Naturally fractured tight gas reservoir detection optimization. Quarterly report, April--June 1994  

SciTech Connect

Geologic assessment of the basin during the third quarter possessed several major objectives. The first task was to test the validity of the gas-centered basin model for the Piceance Basin. The second objective was to define the location and variability of gas-saturated zones within the Williams Fork and Iles Formation reservoir horizons. A third objective was to prepare an updated structure map of the Piceance Basin on the top of the Iles Formation (Rollins Sandstone) to take advantage of new data provided by ten years of drilling activity throughout the basin. The first two objectives formed the core of the ARI poster session presented at the AAPG annual meeting in Denver. The delineation of the gas and water-saturated zone geometries for the Williams Fork and Iles Formations in the basin was presented in the form of a poster session at the AAPG Annual meeting held in Denver in mid-June. The poster session outlined the nature of the gas-centered basin geometry and demonstrated the gas and water-saturated conditions for the Williams Fork, Cozzette and Corcoran reservoir horizons throughout the basin. Initial and cumulative production data indicate that these reservoir horizons are gas-saturated in most of the south-central and eastern basin. The attached report summarizes the data and conclusions of the poster session.

Not Available

1994-07-01