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1

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

PubMed

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

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

2014-01-01

2

Determination of chlorobenzenes in water samples by solid-phase disk extraction and gas chromatography-electron capture detection.  

PubMed

A simple, rapid, sensitive and high throughput method is described, based on solid-phase disk extraction (SPDE) and gas chromatography-electron capture detection, for the determination of chlorobenzens (CBs) in water samples. The proposed SPDE sample pretreatment method was initially optimized and the optimum experimental conditions were found to be as follows: 500 mL water sample (pH 2.5) extracted and enriched by an Empore 3-stn C18 (octadecyl) SPE disk at flow rate of 5 to 50 mL/min, eluted by 5 mL of acetone and 3 × 5 mL of methylene dichloride. The linearity of the method ranged from 0.02 to 0.4 µg/L for dichlorobenzene isomers, 0.0022-0.044 µg/L for trichlorobenzene isomers, 0.005-0.01 µg/L for tetrachlorobenzene isomers and 0.00025 to 0.005 µg/L for pentachlorobenzenes and hexachlorobenzenes, with correlation coefficients ranging between 0.9991 and 0.9999. The limits of detection were in the low ng/L level, ranging between 0.05 and 4 ng/L. The recoveries of spiked CBs with the external calibration method at different concentration levels in deionized/distilled water, tap water and sea water samples were 99-115, 91-106% and 96-110%, respectively, and with relative standard deviations of 4.5-7.6, 4.2-6.8 and 3.6-6.6% (n = 5), respectively. It is concluded that this method can successfully be applied for the determination of CBs in deionized/distilled water, tap water and sea water samples. PMID:23645828

Hu, Hongmei; Guo, Yuanming; Sun, Xiumei; Chen, Xuechang; Zhang, Xiaoning; Liu, Qin; Xu, Chunxiu

2014-01-01

3

Gas chromatography–electron capture detection determination of Dacthal and its diacid metabolite in soil after ultrasound-assisted extraction and in situ focused microwave-assisted derivatization  

Microsoft Academic Search

A quantitative method for the determination of Dacthal and its di-acid metabolite in soil has been developed by coupling ultrasound-assisted\\u000a extraction and microwave-assisted derivatization of the analytes prior to gas chromatography–electron capture detection for\\u000a individual separation and measurement. The main factors affecting both extraction efficiency and derivatization were optimized\\u000a by experimental design methodology. The proposed approach allows extraction of these

A. Caballo-López; M. D. Luque de Castro

2006-01-01

4

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

2014-01-01

5

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

PubMed

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

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

2012-03-01

6

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

PubMed

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

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

2011-05-01

7

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

PubMed

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

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

2009-06-01

8

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

PubMed

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

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

2011-08-01

9

Dispersive liquid-liquid microextraction for the determination of organochlorine pesticides residues in honey by gas chromatography-electron capture and ion trap mass spectrometric detection.  

PubMed

A simple dispersive liquid-liquid microextraction (DLLME) protocol for the determination of 15 organochlorine pesticides residues in honey is proposed. The selected pesticides were separated using gas chromatography and detected by electron capture (ECD) or ion trap mass spectrometry (GC-IT/MS). Several parameters affecting the extraction efficiency namely type and volume of organic extraction solvent, type and volume of disperser solvent, sample pH, ionic strength, extraction time and centrifugation speed were systematically investigated. The final DLLME protocol involved the addition of 750 ?L acetonitrile (disperser) and 50 ?L chloroform (extraction solvent) into a 5 mL aqueous honey solution followed by centrifugation. The sedimented organic phase (chloroform) were analysed directly by GC-IT/MS or evaporated and reconstituted in acetonitrile prior to the GC-ECD analysis. The analytical performance of the GC-ECD and GC-IT/MS methods was compared and discussed. Under the selected experimental conditions, the enrichment factors varied between of 36 and 114. The limits of detection (LOD) were in the range of 0.02-0.15 ?g L(-1) (0.4-3 ng g(-1)) for GC-ECD and 0.01-0.2 ?g L(-1) (0.2-4 ng g(-1)) for GC-IT/MS which is adequate to verify compliance of products to legal tolerances. The proposed method was applied to the analysis of the selected organochlorine pesticides residues in various honey samples obtained from Greek region. Mean recoveries were ranged from 75% to 119% while the precision was better than 20% in both methodologies. PMID:25005997

Zacharis, Constantinos K; Rotsias, Ilias; Zachariadis, Petros G; Zotos, Anastasios

2012-10-01

10

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

11

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

12

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

PubMed

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

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

2015-03-01

13

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

PubMed

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

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

2014-12-01

14

Suitability of magnetic particle immunoassay for the analysis of PBDEs in Hawaiian freshwater fish and crabs in comparison with gas chromatography/electron capture detection-ion trap mass spectrometry  

Technology Transfer Automated Retrieval System (TEKTRAN)

A gas chromatograph/electron capture detector-ion trap mass spectrometer (GC/ECD-ITMS) was used for the determination of polybrominated diphenyl ethers (PBDEs) in freshwater fish and crabs. The samples were also analyzed with an enzyme-linked immunosorbent assay (ELISA). GC/ECD-ITMS results showed...

15

Comparison and analysis of organochlorine pesticides and hexabromobiphenyls in environmental samples by gas chromatography-electron capture detector and gas chromatography-mass spectrometry.  

PubMed

Two analytical methods, gas chromatography-electron capture detector (GC-ECD) and gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS), were evaluated and compared for the measurement of persistent organic pollutants, specifically for 26 organochlorine pesticides and two hexabromobiphenyls, in atmospheric particulate matter and soil samples. The hypothesis tested was that the coelution of non-target compounds may lead to false positives when analyzed by GC-ECD, and that the overestimation associated with these false positives can be eliminated using GC-NCI-MS. The study showed that both methods had satisfactory linearity and reproducibility for the target compounds. Although the sensitivities of GC-ECD for most of the compounds investigated were higher than those observed with the GC-NCI-MS method, the matrices interference was obvious with GC-ECD. There was indeed an apparently high false-positive rate or overestimate when GC-ECD was used for environmental samples, implying that the GC-ECD method has been used with care and that GC-NCI-MS is generally superior for the analysis of trace amounts of these compounds in environmental samples. Based on these results, the sample extraction and cleanup procedures of the GC-NCI-MS method were optimized for achieving acceptable recoveries and less matrices interference. PMID:24872522

Liu, Yu; Fu, Xiaofang; Tao, Shu; Liu, Liang; Li, Wei; Meng, Bingjun

2015-02-01

16

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 79Br- (or 81Br-) 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

17

Optimized cleanup method for the determination of short chain polychlorinated n-alkanes in sediments by high resolution gas chromatography/electron capture negative ion-low resolution mass spectrometry.  

PubMed

The performances of three adsorbents, i.e. silica gel, neutral and basic alumina, in the separation of short chain polychlorinated n-alkanes (sPCAs) from potential interfering substances such as polychlorinated biphenyls (PCBs) and organochlorine pesticides were evaluated. To increase the cleanup efficiency, a two-step cleanup method using silica gel column and subsequent basic alumina column was developed. All the PCB and organochlorine pesticides could be removed by this cleanup method. The very satisfying cleanup efficiency of sPCAs has been achieved and the recovery in the cleanup method reached 92.7%. The method detection limit (MDL) for sPCAs in sediments was determined to be 14 ng g(-1). Relative standard deviation (R.S.D.) of 5.3% was obtained for the mass fraction of sPCAs by analyzing four replicates of a spiked sediment sample. High resolution gas chromatography/electron capture negative ion-low resolution mass spectrometry (HRGC/ECNI-LRMS) was used for sPCAs quantification by monitoring [M-HCl](-) ions. When applied to the sediment samples from the mouth of the Daliao River, the optimized cleanup method in conjunction with HRGC/ECNI-LRMS allowed for highly selective identifications for sPCAs. The sPCAs levels in sediment samples are reported to range from 53.6 ng g(-1) to 289.3 ng g(-1). C(10)- and C(11)-PCAs are the dominant residue in most of investigated sediment samples. PMID:21889633

Gao, Yuan; Zhang, Haijun; Chen, Jiping; Zhang, Qing; Tian, Yuzeng; Qi, Peipei; Yu, Zhengkun

2011-10-10

18

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

PubMed

In this study, a new method was developed for analyzing malathion, cypermethrin and lambda-cyhalothrin from soil samples by using homogeneous liquid-liquid extraction (HLLE) and gas chromatography with electron capture detector (GC-ECD). Acetone was used as extraction solvent for the extraction of target pesticides from soil samples. When the extraction process was finished, the target analytes in the extraction solvent were rapidly transferred from the acetone extract to carbon tetrachloride, using HLLE. Under the optimum conditions, linearity was obtained in the range of 0.05-40 microg kg(-1) for malathion, 0.04-10 microg kg(-1) for lambda-cyhalothrin and 0.05-50 microg kg(-1) for cypermethrin, respectively. Coefficients of correlation (r(2)) ranged from 0.9993 to 0.9998. The repeatability was carried out by spiking soil samples at concentration levels of 2.5 microg kg(-1) for lambda-cyhalothrin, and 10 microg kg(-1) for malathion and cypermethrin, respectively. The relative standard deviations (RSDs) varied between 2.3 and 9.6% (n=3). The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, varied between 0.01 and 0.04 microg kg(-1). The relative recoveries of three pesticides from soil A1, A2 and A3 at spiking levels of 2.5, 5 and 10 microg kg(-1) were in the range of 82.20-91.60%, 88.90-110.5% and 77.10-98.50%, respectively. In conclusion, the proposed method can be successfully applied for the determination of target pesticide residues in real soil samples. PMID:18558137

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

2008-07-14

19

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

Microsoft Academic Search

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

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

2008-01-01

20

The determination of PCBs in Rocky Flats Type IV waste sludge by gas chromatography/electron capture detection. Part 2  

SciTech Connect

Before disposal, radioactive sludge (Type IV) from Rocky Flats Plant (RFP) must be evaluated for polychlorinated biphenyl (PCB) content. The Type IV sludge consists of organic solvents, degreasers, cutting oils, and transuranic (TRU) waste mixed with calcium silicate (MicroCel E{reg_sign} and Oil Dri{reg_sign} to form a grease or paste-like material. For laboratory testing, a nonradioactive simulated Type 17V RFP sludge was prepared at Argonne National Laboratory-East (ANL-E). This sludge has a composition similar to that expected from field samples. In an earlier effort, a simplified method was developed for extraction, cleanup of extract, and determination of PCBs in samples of simulated sludge spiked with Aroclors 1254 and 1260. The simplified method has now been used to determine the presence and quantities of other Aroclors in the simulated sludge, namely, Aroclors 10 1 6, 1221, 1232, 1242, and 1248. The accuracy and precision of the data for these Aroclors were found to be similar to the data for sludges spiked with Aroclors 1254 and 1260. Since actual sludges may vary in composition, the method was also verified by analyzing another source of Type IV simulated sludge, prepared by Argonne National Laboratory-West (ANL-W).

Parish, K.J.; Applegate, D.V.; Postlethwait, P.D.; Boparai, A.S.; Reedy, G.T.

1994-12-01

21

Validated semiquantitative\\/quantitative screening of 51 drugs in whole blood as silylated derivatives by gas chromatography-selected ion monitoring mass spectrometry and gas chromatography electron capture detection  

Microsoft Academic Search

A comprehensively validated procedure is presented for simultaneous semiquantitative\\/quantitative screening of 51 drugs of abuse or drugs potentially hazardous for traffic safety in serum, plasma or whole blood. Benzodiazepines (12), cannabinoids (3), opioids (8), cocaine, antidepressants (13), antipsychotics (5) and antiepileptics (2) as well as zolpidem, zaleplon, zopiclone, meprobamate, carisoprodol, tizanidine and orphenadrine and internal standard flurazepam, were isolated by

Teemu Gunnar; Sirpa Mykkänen; Kari Ariniemi; Pirjo Lillsunde

2004-01-01

22

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

Microsoft Academic Search

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

C Gonçalves; M. F Alpendurada

2002-01-01

23

Assessment of matrix effects in gas chromatography electron capture pesticide-residue analysis  

Microsoft Academic Search

Summary  The analysis of pesticide residues in vegetable samples leads in most cases to different results when solvent or matrix-matched\\u000a calibration is used for quantitation. Matrix effects in GC-ECD analysis of pesticides in vegetable samples have been assessed\\u000a by comparing calibration curves prepared in solvent and in blank matrix extracts. Eight different vegetables have been considered\\u000a among the most common commodities

M. E. Hernández Torres; F. J. Egea González; L. Cuadros-Rodríguez; E. Almansa López; J. L. Martínez Vidal

2003-01-01

24

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

25

Simultaneous determination of insecticide fipronil and its metabolites in maize and soil by gas chromatography with electron capture detection.  

PubMed

An integrated method for the simultaneous determination of insecticide fipronil and its three metabolites, desulfinyl, sulfide, and sulfone, in maize grain, maize stem, and soil was developed. This three-step method uses liquid-solid extraction with ultrasound or mechanical grinding, followed by liquid-liquid partitioning and florisil solid-phase extraction (SPE) for cleanup. The quantification was conducted by gas chromatography-electron capture detection in triplicate for each sample. The method was validated with five replicates at three fortification concentrations, 0.002, 0.01, and 0.1 mg kg(-1), in each matrix and gave mean recoveries from 83 to 106 % with relative standard deviation ? 8.9 %. The limits of quantification (LOQ) were 0.002 mg kg(-1) for the compounds in all matrixes. In the field study in Beijing and Shandong 2012, fipronil-coated maize seeds were planted and the proposed method was applied for checking the possible existence of four compounds in maize and soil samples, but none of them contained residues higher than the LOQs in both application rates. Moreover, the dissipation of fipronil in soil fits first-order kinetics with half-lives 9.90 and 10.34 days in Beijing and Shandong, respectively. Combined with an adequate sample treatment, this technique offers good sensitivity and selectivity in the three complex matrixes. The results could provide guidance for the further research on pesticide distribution and safe use of fipronil as seed coat in cereals. PMID:24338055

Wang, Tielong; Hu, Jiye; Liu, Chaolun

2014-05-01

26

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

PubMed

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

Mallette, Jennifer R; Casale, John F

2014-10-17

27

Detection of gas leakage  

DOEpatents

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

28

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

29

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

30

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

31

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

32

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 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...

2010-10-01

33

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

34

46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 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...

2014-10-01

35

Gas leakage detection system using Kalman filter  

Microsoft Academic Search

This paper is concerned with gas leakage fault detection of a pneumatic pipe system using Kalman filter. In modern plants, the ability to detect and identify gas leakage faults is becoming increasingly important. The main difficulty to detect gas leakage faults by sound signals lies in that the background noise is usually very strong in the practical plants. In this

Zhang Sheng; A. Toshiyuki; H. Shoji

2004-01-01

36

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

37

LC/ESI-MS/MS detection of FAs by charge reversal derivatization with more than four orders of magnitude improvement in sensitivity[S  

PubMed Central

Quantitative analysis of fatty acids (FAs) is an important area of analytical biochemistry. Ultra high sensitivity FA analysis usually is done with gas chromatography of pentafluorobenzyl esters coupled to an electron-capture detector. With the popularity of electrospray ionization (ESI) mass spectrometers coupled to liquid chromatography, it would be convenient to develop a method for ultra high sensitivity FA detection using this equipment. Although FAs can be analyzed by ESI in negative ion mode, this method is not very sensitive. In this study, we demonstrate a new method of FA analysis based on conversion of the carboxylic acid to an amide bearing a permanent positive charge, N-(4-aminomethylphenyl)pyridinium (AMPP) combined with analysis on a reverse-phase liquid chromatography column coupled to an ESI mass spectrometer operating in positive ion mode. This leads to an ?60,000-fold increase in sensitivity compared with the same method carried out with underivatized FAs. The new method is about 10-fold more sensitive than the existing method of gas chromatography/electron-capture mass spectrometry of FA pentafluorobenzyl esters. Furthermore, significant fragmentation of the precursor ions in the nontag portion improves analytical specificity. We show that a large number of FA molecular species can be analyzed with this method in complex biological samples such as mouse serum. PMID:23945566

Bollinger, James G.; Rohan, Gajendra; Sadilek, Martin; Gelb, Michael H.

2013-01-01

38

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. PMID:22122759

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

2012-01-01

39

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

40

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

41

46 CFR 154.1350 - Flammable gas detection system.  

Code of Federal Regulations, 2010 CFR

...Electrical equipment for each flammable gas detection system that is in a gas-dangerous space or area must meet §§ 154.1000 through 154.1015. (k) Each flammable gas detection system must have enough flame...

2010-10-01

42

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

43

Permanent gas analysis using gas chromatography with vacuum ultraviolet detection.  

PubMed

The analysis of complex mixtures of permanent gases consisting of low molecular weight hydrocarbons, inert gases, and toxic species plays an increasingly important role in today's economy. A new gas chromatography detector based on vacuum ultraviolet (VUV) spectroscopy (GC-VUV), which simultaneously collects full scan (115-240nm) VUV and UV absorption of eluting analytes, was applied to analyze mixtures of permanent gases. Sample mixtures ranged from off-gassing of decomposing Li-ion and Li-metal batteries to natural gas samples and water samples taken from private wells in close proximity to unconventional natural gas extraction. Gas chromatography separations were performed with a porous layer open tubular column. Components such as C1-C5 linear and branched hydrocarbons, water, oxygen, and nitrogen were separated and detected in natural gas and the headspace of natural gas-contaminated water samples. Of interest for the transport of lithium batteries were the detection of flammable and toxic gases, such as methane, ethylene, chloromethane, dimethyl ether, 1,3-butadiene, CS2, and methylproprionate, among others. Featured is the capability for deconvolution of co-eluting signals from different analytes. PMID:25724098

Bai, Ling; Smuts, Jonathan; Walsh, Phillip; Fan, Hui; Hildenbrand, Zacariah; Wong, Derek; Wetz, David; Schug, Kevin A

2015-04-01

44

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

45

Gas sensitive materials for gas detection and methods of making  

DOEpatents

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

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

2014-07-15

46

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

47

46 CFR 154.1350 - Flammable gas detection system.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

48

46 CFR 154.1350 - Flammable gas detection system.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

49

46 CFR 154.1350 - Flammable gas detection system.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 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...

2014-10-01

50

46 CFR 154.1350 - Flammable gas detection system.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 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...

2013-10-01

51

49 CFR 192.736 - Compressor stations: Gas detection.  

Code of Federal Regulations, 2010 CFR

...736 Compressor stations: Gas detection. (a) Not later...compressor station must have a fixed gas detection and alarm system, unless...50 percent of its upright side area is permanently open; or ...c) of this section, each gas detection and alarm system...

2010-10-01

52

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

53

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...

54

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...

55

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

EPA Science Inventory

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

56

Towards aerial natural gas leak detection system based on TDLAS  

NASA Astrophysics Data System (ADS)

Pipeline leakage is a complex scenario for sensing system due to the traditional high cost, low efficient and labor intensive detection scheme. TDLAS has been widely accepted as industrial trace gas detection method and, thanks to its high accuracy and reasonable size, it has the potential to meet pipeline gas leakage detection requirements if it combines with the aerial platform. Based on literature study, this paper discussed the possibility of applying aerial TDLAS principle in pipeline gas leak detection and the key technical foundation of implementing it. Such system is able to result in a high efficiency and accuracy measurement which will provide sufficient data in time for the pipeline leakage detection.

Liu, Shuyang; Zhou, Tao; Jia, Xiaodong

2014-11-01

57

DETECTION AND ESTIMATION OF OIL-GAS PIPELINE CORROSION DEFECTS  

Microsoft Academic Search

The paper presents a new approach for detection of oil-gas pipeline corrosion defects in which pipeline magnetic flux leakage (MFL) detection system is adopted. To test the new approach, some artificial defects are fabricated on the surface of oil-gas pipes to simulate different defects happening in practice. The interference eliminating method is introduced for compensation of defected MFL field and

Qi Jiang; Qingmei Sui; Nan Lu; Paschalis Zachariades; Jihong Wang

58

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

59

33 CFR 127.1203 - Gas detection.  

Code of Federal Regulations, 2010 CFR

...detectors, or a fixed gas detector, in the marine transfer area for LHG. Each detector...detectors, or a fixed gas detector, available in the area. The detectors must...workers' exposure to toxic gases in the area. [CGD...

2010-07-01

60

Optically selective, acoustically resonant gas detecting transducer  

NASA Technical Reports Server (NTRS)

A gas analyzer is disclosed which responds to the resonant absorption or emission spectrum of a specific gas by producing an acoustic resonance in a chamber containing a sample of that gas, and which measures the amount of that emission or absorption by measuring the strength of that acoustic resonance, e.g., the maximum periodic pressure, velocity or density achieved. In the preferred embodiment, a light beam is modulated periodically at the acoustical resonance frequency of a closed chamber which contains an optically dense sample of the gas of interest. Periodic heating of the absorbing gas by the light beam causes a cyclic expansion, movement, and pressure within the gas. An amplitude is reached where the increased losses were the cyclic radiation energy received. A transducing system is inclined for converting the pressure variations of the resonant gas into electronic readout signals.

Dimeff, J. (inventor)

1977-01-01

61

Flammable Gas Detection for the D-Zero Gas System  

SciTech Connect

The use of flammable gas and high voltage in detector systems is common in many experiments at Fermilab. To mitigate the hazards associated with these systems, Fermilab Engineering Standard SD-45B (Ref. 1) was adopted. Since this note is meant to be a guide and not a mandatory standard, each experiment is reviewed for compliance with SD-45B by the flammable gas safety subcommittee. Currently, there are only two types of flammable gas in use, ethane (Appendix A) and methane (Appendix B). The worst flammable-gas case is C2H6 (ethane), which has an estimated flow rate that is 73% of the CH4 (methane) flow but a heat of combustion (in kcal/g-mole) that is 173% of that of methane. In the worst case, if ethane were to spew through its restricting orifice into its gas line at 0 psig and then through a catastrophic leak into Room 215 (TRD) or Room 511 (CDC/FDCNTX), the time that would be required to build up a greater than Class 1 inventory (0.4kg H2 equivalent) would be 5.2 hours (Ref. 2). Therefore a worst-case flammable gas leak would have to go undetected for over 5 hours in order to transform a either mixing room to an environment with a Risk Class greater than Class 1. The mixing systems, gas lines, and detectors themselves will be thoroughly leak checked prior to active service. All vessels that are part of the mixing systems will be protected from overpressure by safety valves vented outside the building. Both the input and output of all detector volumes are protected from overpressure in the same way. The volume immediately outside the central tracking detectors is continuously purged by nitrogen from boiloff from the main nitrogen dewar at the site. However, if flammable gas were to build up in the mixing rooms or particular detector areas, no matter how unlikely, flammable gas detectors that are part of the interlock chain of each gas mixing system will shut down the appropriate system. This includes shutting off the output of flammable gas manifolds within the gas shed. Similarly, if a fire were to break out anywhere in the D-ZERO Hall, fire sensors would stop the output of all flammable gas manifolds within the gas shed, by unpowering electrically controlled solenoid valves that are normally closed in the event of a power failure. Fire sensor contacts have not yet been installed.

Spires, L.D.; Foglesong, J.; /Fermilab

1991-02-11

62

Detecting mustard gas using high Q-value SAW resonator gas sensors  

Microsoft Academic Search

Surface acoustic wave (SAW) resonator gas sensors have been applied in many fields for the advantages of high Q-value and low insertion loss, but seldom used in chemical warfare agents detection. In this paper, a novel SAW gas sensor with high Q-value for mustard gas (HD, a blister agent) detection was developed. The sensor was a two-port SAW resonator device

Chuan-zhi Chen; Bo-li Zuo; Jin-yi Ma; Hong-min Jiang

2008-01-01

63

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

64

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

65

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

2011-10-01

66

Naturally fractured tight gas reservoir detection optimization  

SciTech Connect

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

NONE

1998-11-30

67

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

68

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

69

Diagnostic Technique of Gas Insulated Substation by Partial Discharge Detection  

Microsoft Academic Search

To make more reliable operations of Gas Insulated Substation (GIS), the detecting methods of internal irregularities from outside of enclosure before major insulation failures occure are required. Internal irregularity may cause a partial discharge, then the methods to detect the partial discharge chemically, mechanically, electrically and optically, are developed and those methods are applied to GIS model simulating the intemal

S. Kusumoto; S. Itoh; Y. Tsuchiya; H. Mukae; S. Matsuda; K. Takahashi

1980-01-01

70

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

2011-12-01

71

Fire detection using smoke and gas sensors  

Microsoft Academic Search

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

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

2007-01-01

72

Gas Transport and Detection Following Underground Nuclear Explosions  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

73

Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection  

PubMed Central

Various applications, such as pollution monitoring, toxic-gas detection, non invasive medical diagnostics and industrial process control, require sensitive and selective detection of gas traces with concentrations in the parts in 109 (ppb) and sub-ppb range. The recent development of quantum-cascade lasers (QCLs) has given a new aspect to infrared laser-based trace gas sensors. In particular, single mode distributed feedback QCLs are attractive spectroscopic sources because of their excellent properties in terms of narrow linewidth, average power and room temperature operation. In combination with these laser sources, photoacoustic spectroscopy offers the advantage of high sensitivity and selectivity, compact sensor platform, fast time-response and user friendly operation. This paper reports recent developments on quantum cascade laser-based photoacoustic spectroscopy for trace gas detection. In particular, different applications of a photoacoustic trace gas sensor employing a longitudinal resonant cell with a detection limit on the order of hundred ppb of ozone and ammonia are discussed. We also report two QC laser-based photoacoustic sensors for the detection of nitric oxide, for environmental pollution monitoring and medical diagnostics, and hexamethyldisilazane, for applications in semiconductor manufacturing process.

Elia, Angela; Di Franco, Cinzia; Lugarà, Pietro Mario; Scamarcio, Gaetano

2006-01-01

74

Detect, troubleshoot gas-turbine blade failures  

SciTech Connect

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

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

1995-12-01

75

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

76

Naturally fractured tight gas reservoir detection optimization  

SciTech Connect

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

NONE

1998-11-30

77

Wide-band gas leak imaging detection system using UFPA  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

78

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

79

Compressive hyperspectral sensor for LWIR gas detection  

NASA Astrophysics Data System (ADS)

Focal plane arrays with associated electronics and cooling are a substantial portion of the cost, complexity, size, weight, and power requirements of Long-Wave IR (LWIR) imagers. Hyperspectral LWIR imagers add significant data volume burden as they collect a high-resolution spectrum at each pixel. We report here on a LWIR Hyperspectral Sensor that applies Compressive Sensing (CS) in order to achieve benefits in these areas. The sensor applies single-pixel detection technology demonstrated by Rice University. The single-pixel approach uses a Digital Micro-mirror Device (DMD) to reflect and multiplex the light from a random assortment of pixels onto the detector. This is repeated for a number of measurements much less than the total number of scene pixels. We have extended this architecture to hyperspectral LWIR sensing by inserting a Fabry-Perot spectrometer in the optical path. This compressive hyperspectral imager collects all three dimensions on a single detection element, greatly reducing the size, weight and power requirements of the system relative to traditional approaches, while also reducing data volume. The CS architecture also supports innovative adaptive approaches to sensing, as the DMD device allows control over the selection of spatial scene pixels to be multiplexed on the detector. We are applying this advantage to the detection of plume gases, by adaptively locating and concentrating target energy. A key challenge in this system is the diffraction loss produce by the DMD in the LWIR. We report the results of testing DMD operation in the LWIR, as well as system spatial and spectral performance.

Russell, Thomas A.; McMackin, Lenore; Bridge, Bob; Baraniuk, Richard

2012-06-01

80

Predicting detection probabilities for gas mixtures over HSI backgrounds  

SciTech Connect

Detecting and identifying weak gaseous plumes using thermal image data acquired by airborne detectors is an area of ongoing research. This contribution investigates the relative detectability of gas mixtures over different backgrounds and a range of plume temperatures that are warmer and cooler than the ground. The focus of this analysis to support mission planning. When the mission is intended to collect evidence of particular chemicals, the analysis presented is this report can be used to determine conditions under which useful data can be acquired. Initial analyses can be used to determine whether LWIR is useful for the anticipated gas, temperature, and background combination.

Tardiff, Mark F.; Walsh, Stephen J.; Anderson, Kevin K.; Chilton, Lawrence

2009-12-29

81

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

82

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

83

Position sensitive radioactivity detection for gas and liquid chromatography  

DOEpatents

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

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

2001-01-01

84

An ALMA detection of circumnuclear molecular gas in M87  

NASA Astrophysics Data System (ADS)

We present the detection of circumnuclear molecular gas in M87 using the Atacama Large Millimeter/submillimeter Array (ALMA).M87 (3C 274) is an archetypal giant elliptical galaxy at the centre of the Virgo cluster and is a unique object in which to study the origin and properties of the interstellar medium (ISM) in a radio galaxy located in a dense environment. While a very well-known object across most of the electromagnetic spectrum, M87 has long lacked a detailed study in the (sub)millimeter range, requiring the advance in both sensitivity and angular resolution only now made possible by ALMA.Molecular gas in the inner part of M87 has previously been detected in single-dish observations, suggesting that the molecular gas likely resides in a circumnuclear disk-like structure. However, the unique ALMA capabilities now allow us to make the first detailed, interferometric, investigation of the properties of the ISM around the galaxy's supermassive black hole.Here, we present results of ALMA band 3 and 7 data which we have used to map the CO J=1-0 and CO J=3-2 lines, respectively. With this data we are able to trace the bulk of the molecular gas, the warmer denser gas, and the continuum emission, at an angular resolution of 1 arcsecond (~80 pc), providing the deepest and highest spatial resolution image yet of the molecular gas content of this giant elliptical galaxy.

Vlahakis, Catherine E.; Leon, Stephane; Martin, Sergio

2015-01-01

85

Pattern Recognition for Selective Odor Detection with Gas Sensor Arrays  

PubMed Central

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

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

2012-01-01

86

Multidimensional detection of nitroorganic explosives by gas chromatography-pyrolysis-ultraviolet detection.  

PubMed

We describe a new methodology for the trace detection of organic explosives containing nitro functionalities. Conventional gas chromatography separates the components of an explosive mixture. Effluent from the gas chromatograph is pyrolyzed by passage over a heated Nichrome wire. Nitric oxide produced on pyrolysis of a nitroorganic compound is then detected by ultraviolet absorption spectroscopy between 180 and 240 nm, using a deuterium lamp as the light source. Nitric oxide exhibits a sharply banded, characteristic spectrum in this region, enabling detection of nitroorganics. The system is tested using the explosive simulants nitrobenzene and 2,4-dinitrotoluene, and with the nitramine explosive tetryl. Detection limits are 25 ng for nitrobenzene and 50 ng for 2,4-dinitrotoluene. Tetryl is detected with a detection limit of 50 ng. The system is both easy to implement and could be built as a compact, low-power device. PMID:15924395

Hodyss, Robert; Beauchamp, J L

2005-06-01

87

Remote laser detection of natural gas leakages from pipelines  

SciTech Connect

A differential absorption lidar based on a tunable TEA CO{sub 2} laser emitting at 42 lines of the 'hot' 01{sup 1}1 - 11{sup 1}0 band in the range from 10.9 to 11.4 {mu}m is developed for detecting natural gas leakages from oil pipelines by measuring the ethane content in the atmosphere. The ethane detection sensitivity is 0.9 ppm km. The presence of methane does not distort the measurement results. The developed lidar can detect the natural gas leakage from kilometre heights at the flying velocities up to 200 km h{sup -1} and a probe pulse repetition rate of 5 Hz. (laser applications and other topics in quantum electronics)

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

2010-02-28

88

Low-Cost Resonant Cavity Raman Gas Probe for Multi-Gas Detection  

NASA Astrophysics Data System (ADS)

Raman based gas sensing can be attractive in several industrial applications, due to its multi-gas sensing capabilities and its ability to detect O_2 and N_2. In this article, we have built a Raman gas probe, based on low-cost components, which has shown an estimated detection limit of 0.5 % for 30 second measurements of N_2 and O_2. While this detection limit is higher than that of commercially available equipment, our estimated component cost is approximately one tenth of the price of commercially available equipment. The use of a resonant Fabry-Pérot cavity increases the scattered signal, and hence the sensitivity, by a factor of 50. The cavity is kept in resonance using a piezo-actuated mirror and a photodiode in a feedback loop. The system described in this article was made with minimum-cost components to demonstrate the low-cost principle. However, it is possible to decrease the detection limit using a higher-powered (but still low-cost) laser and improving the collection optics. By applying these improvements, the detection limit and estimated measurement precision will be sufficient for e.g. the monitoring of input gases in combustion processes, such as e.g. (bio-)gas power plants. In these processes, knowledge about gas compositions with 0.1 % (absolute) precision can help regulate and optimize process conditions. The system has the potential to provide a low-cost, industrial Raman sensor that is optimized for specific gas-detection applications.

Thorstensen, J.; Haugholt, K. H.; Ferber, A.; Bakke, K. A. H.; Tschudi, J.

2014-12-01

89

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

90

Detection of circumstellar gas associated with GG Tauri  

NASA Technical Reports Server (NTRS)

Double-peaked (C-12)O (1-0) emission centered on the young T Tauri star GG Tau possesses a line profile which may be modeled on the assumption that CO emission arises in an extended circumstellar disk. While bounds on the observed gas mass can be estimated on this basis, it is suggested that a large amount of mass could lie within a small and optically thick region, escaping detection due to beam-dilution effects. In addition, CO may no longer accurately trace the gas mass due to its dissociation, or freezing into grains, or due to the locking-up of carbon into more complex molecules.

Skrutskie, M. F.; Snell, R. L.; Strom, K. M.; Strom, S. E.; Edwards, S.; Fukui, Y.; Mizuno, A.; Hayashi, M.; Ohashi, N.

1993-01-01

91

Tunable fiber ring laser absorption spectroscopic sensors for gas detection  

NASA Astrophysics Data System (ADS)

Fiber-optic gas sensing techniques are commonly based on the recognition of a wide range of chemical species from characteristic absorption, fluorescence or Raman-scattering spectra signatures. By tuning over the vibrational lines of species in the path of laser beam, tunable diode laser gas sensors measure signal spectroscopic intensity, gas concentration, and other properties. However, they have limitations of bulk architecture, small change of signal on top of large background, and low sensitivity of direct absorption. Here we report the fabrication and optical measurements of tunable Er-doped fiber ring laser absorption spectroscopic sensor featuring a gas cell that is a segment of photonic crystal fiber (PCF) with a long-period grating (LPG) inscribed. The tunable laser beam is coupled into the cladding of the PCF by the LPG where the gas in air holes absorbs light. The light travels along the PCF cladding and reflects at the end of the fiber where a silver film is coated as a mirror at one end facet. The light propagates back within cladding and passes through the gas one more time thus increasing the interaction length. This light is finally recoupled into the fiber core for intensity measurement. The proposed fiber gas sensors have been experimentally used for ammonia (NH3) concentration detection. They show excellent sensitivity and selectivity, and are minimally affected by temperature and/or humidity changes. The sensors using PCF-LPG gas cell are simple to fabricate, cost-effective, and are deployed for a variety of applications not possible using conventional optical fibers.

Zheng, Shijie; Zhu, Yinian; Krishnaswamy, Sridhar

2013-04-01

92

Improved sensitivity gas detection by spontaneous Raman scattering  

SciTech Connect

Accurate, real-time measurement of the dilute constituents of a gaseous mixture poses a significant challenge usually relegated to mass spectrometry. Here, spontaneous Raman backscattering is used to detect low pressure molecular gases. Rapid detection of gases in the ?100 parts in 106 ðppmÞ range is described. Improved sensitivity is brought about by use of a hollow-core, photonic bandgap fiber gas cell in the backscattering configuration to increase collection efficiency and an image-plane aperture to greatly reduce silica-Raman background noise. Spatial and spectral properties of the silica noise were examined with a two-dimensional CCD detector array

Michael P. Buric; Kevin P. Chen; Joel Falk; Steven D. Woodruff1

2009-08-01

93

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

94

Capacitive micromachined ultrasonic resonator for ultra sensitive trace gas detection  

NASA Astrophysics Data System (ADS)

The ultra-sensitive trace gas detection has become increasingly important due to the demand for environment and sci-tech progress. In recent years a capacitive micromachined ultrasonic transducer (CMUT) with circular diaphragms used for imaging has been successfully used to detect chemical gases, and shows promising results. However, its behavior is the same as that of CMUTs for ranging, imaging and therapy applications, where the acoustic radiation with a certain power, produced by the vibration of circular diaphragms operating at the first bending mode, is required but is undesirable for gas sensing since it disturbs inevitably the environment to be measured. This paper, therefore, presents to optimize its behavior after an ideal capacitive micromachined ultrasonic resonator (CMUR) and then to utilize second-order and high-order bending modes of the circular diaphragm to minimize its acoustic radiation and obtain higher resonance frequency also. Since the resonance frequencies of high-order modes much higher than the fundamental frequency, an ultra-high operating frequency of GHz can be reached so that raising greatly the sensitivity of the CMUR and being able to realize the ultra-sensitive trace gas detections.

Ge, Li-Feng

2013-01-01

95

Overview of micromachined platforms for thermal sensing and gas detection  

NASA Astrophysics Data System (ADS)

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

Manginell, Ronald P.; Smith, James H.; Ricco, Antonio J.

1997-06-01

96

Gas Leakage Fault Detection of Pneumatic Pipe System Using Neural Networks  

Microsoft Academic Search

This paper is concerned with gas leakage fault detection of a pneumatic pipe system using a neural network filter. In modern plants, the ability to detect and identify gas leakage faults is becoming increasingly important. The main difficulty to detect gas leakage faults by sound signals lies in that the practical plants are usually very noisy. In this research, neural

Sheng Zhang; Toshiyuki Asakura; Shoji Hayashi

2004-01-01

97

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

98

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

99

Dual-gas tracers for subsurface characterization and NAPL detection  

SciTech Connect

Effective design of in situ remediation technologies often requires an understanding of the mass transfer limitations that control the removal of contaminants from the soil. In addition, the presence of nonaqueous phase liquids (NAPLs) in soils will affect the ultimate success or failure of remediation processes. Knowing the location of NAPLs within the subsurface is critical to designing the most effective remediation approach. This work focuses on demonstrating that gas tracers can detect the location of the NAPLs in the subsurface and elucidating the mass transfer limitations associated with the removal of contaminants from soils.

Gauglitz, P.A.; Peurrung, L.M.; Mendoza, D.P.; Pillay, G.

1994-11-01

100

Wireless gas detection with a smartphone via rf communication.  

PubMed

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

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

2014-12-23

101

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

102

Quantum-cascade laser photoacoustic detection of methane emitted from natural gas powered engines  

NASA Astrophysics Data System (ADS)

In this work we present a laser photoacoustic arrangement for the detection of the important greenhouse gas methane. A quantum-cascade laser and a differential photoacoustic cell were employed. A detection limit of 45 ppbv in nitrogen was achieved as well as a great selectivity. The same methodology was also tested in the detection of methane issued from natural gas powered vehicles (VNG) in Brazil, which demonstrates the excellent potential of this arrangement for greenhouse gas detection emitted from real sources.

Rocha, M. V.; Sthel, M. S.; Silva, M. G.; Paiva, L. B.; Pinheiro, F. W.; Miklòs, A.; Vargas, H.

2012-03-01

103

Plasma emission spectral detection for pyrolysis-gas chromatography  

NASA Astrophysics Data System (ADS)

Specific element gas chromatographic detection by plasma emission spectroscopy has been evaluated for the characterization of volatile pyrolyzates from a number of polymers containing hetero-atoms. Directly interfaced rapid-temperature rise time pyrolysis with high resolution open tubular column gas chromatography was employed. The atmospheric pressure microwave induced and sustained plasma utilizing a "Beenakker" type TM 010 cavity was applied for specific detection of phosphorus and carbon in polyphosphazene pyrolysis and for boron in carborane-silicone pyrolysis. An interfaced d.c. argon atmospheric pressure plasma was found more advantageous for the specific determination of silicon in the pyrolysis products of novel linear silarylene-siloxanes. In phosphazene pyrolysis notable differences were seen in the phosphorus content of volatiles formed on pyrolysis between polymers fluoroalkoxy and chlorophenoxy substituents. For carborane-silicones sequential volatilization followed by pyrolysis allowed the identification of residual boron containing monomers as well as pyrolyzates. Pyrolysis of the silarylene-siloxanes showed markedly differing levels of silicon content in polymers with differing aromatic backbones and different levels of vinyl substitution.

Riska, Gregory D.; Estes, Scott A.; Beyer, John O.; Uden, Peter C.

104

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

105

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

106

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

107

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

108

Silicon Carbide-Based Hydrogen and Hydrocarbon Gas Detection  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

109

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

110

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 PMID:4959077

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

1966-01-01

111

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

112

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

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Cargo boil-off as fuel: Gas detection equipment. 154.709 Section...SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment...154.709 Cargo boil-off as fuel: Gas detection equipment. (a) The...

2010-10-01

113

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

114

Numerical investigation of coal seam gas detection using airborne electromagnetics  

NASA Astrophysics Data System (ADS)

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

Abdulla, Mohamed

115

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

NASA Astrophysics Data System (ADS)

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

Xia, Hua

2012-06-01

116

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

Microsoft Academic Search

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

Ok Chan Jeong; Satoshi Konishi

2007-01-01

117

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

PubMed

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

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

2014-10-01

118

Leakage detection of Marcellus Shale natural gas at an Upper Devonian gas monitoring well: a 3-d numerical modeling approach.  

PubMed

Potential natural gas leakage into shallow, overlying formations and aquifers from Marcellus Shale gas drilling operations is a public concern. However, before natural gas could reach underground sources of drinking water (USDW), it must pass through several geologic formations. Tracer and pressure monitoring in formations overlying the Marcellus could help detect natural gas leakage at hydraulic fracturing sites before it reaches USDW. In this study, a numerical simulation code (TOUGH 2) was used to investigate the potential for detecting leaking natural gas in such an overlying geologic formation. The modeled zone was based on a gas field in Greene County, Pennsylvania, undergoing production activities. The model assumed, hypothetically, that methane (CH4), the primary component of natural gas, with some tracer, was leaking around an existing well between the Marcellus Shale and the shallower and lower-pressure Bradford Formation. The leaky well was located 170 m away from a monitoring well, in the Bradford Formation. A simulation study was performed to determine how quickly the tracer monitoring could detect a leak of a known size. Using some typical parameters for the Bradford Formation, model results showed that a detectable tracer volume fraction of 2.0 × 10(-15) would be noted at the monitoring well in 9.8 years. The most rapid detection of tracer for the leak rates simulated was 81 days, but this scenario required that the leakage release point was at the same depth as the perforation zone of the monitoring well and the zones above and below the perforation zone had low permeability, which created a preferred tracer migration pathway along the perforation zone. Sensitivity analysis indicated that the time needed to detect CH4 leakage at the monitoring well was very sensitive to changes in the thickness of the high-permeability zone, CH4 leaking rate, and production rate of the monitoring well. PMID:25144442

Zhang, Liwei; Anderson, Nicole; Dilmore, Robert; Soeder, Daniel J; Bromhal, Grant

2014-09-16

119

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

120

Methane leaks from oil and gas fields detected from space  

NASA Astrophysics Data System (ADS)

A few years ago, while poring over satellite images of the Earth at night, scientists spotted the bright glow of natural gas flares burning in the oil and gas fields that have fueled America's recent energy boom. Now they have spotted something else from space: large plumes of fugitive methane gas liberated from these formations by unconventional extraction methods like horizontal drilling and hydraulic fracturing.

Rosen, Julia

2014-11-01

121

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

122

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...

123

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

124

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

125

Revised on: 2014-04-10 Curriculum Vitae  

E-print Network

Layer Dynamics Analytical Skills: Absorption Spectroscopy, Gas/Ion/Liquid Chromatography, Mass measurements of organic nitrates, gas chromatography/electron capture detector, micrometeorological measurements of ozone from aircraft, liquid/ion chromatography of agricultural inorganic trace gases, Climate

Thompson, Anne

126

Tin dioxide based sensors for the detection of liquified petroleum gas  

Microsoft Academic Search

Several methods are available for the detection and measurement of various gas species. Semiconductor sensors usually based on tin(IV) oxide (SnO2) are among the best known types of sensors for the detection of dangerous and harmful gases [1, 2]. As reported, a degree of sensitivity of these sensors for a particular gas can be obtained by careful control of the

G. S. Trivikrama Rao; S. S. Madhavendra

1995-01-01

127

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

Microsoft Academic Search

A novel method called Generalized Average of Signals (GAS) was developed and tested during the last two years (Málek et al., in press). This method is designed for processing of seismograms from dense seismic arrays and is convenient mainly for denoising and weak phase detection. The main idea of the GAS method is based on non-linear stacking of seismograms in

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

2007-01-01

128

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

Microsoft Academic Search

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

Qiang Wang; Xiaowei Wang

2010-01-01

129

Supporting Information First detection of methylgermylene in the gas-phase and time resolved study of  

E-print Network

1 Supporting Information First detection of methylgermylene in the gas-phase and time resolved anhydrous magnesium sulphate, filtered, and the solvent removed by distillation. Vacuum distillation as reference. Low resolution mass spectra were determined by GC/MS, using a Hewlett-Packard 5890II gas

Leigh, William J.

130

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

E-print Network

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

131

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

132

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. PMID:22115357

2011-01-01

133

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

134

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

135

Ultrasound detection in the Gulf menhaden requires gas-filled bullae and an intact lateral line.  

PubMed

Clupeiform fish species, including the Gulf menhaden (Brevoortia patronus) that belong to the subfamily Alosinae, can detect ultrasound. Clupeiform fishes are unique in that they have specialized gas-filled bullae in the head associated with the ear via the bulla membrane and with the lateral line via the lateral recess membrane. It has been hypothesized that the utricle of the inner ear is responsible for ultrasound detection through a specialized connection to the gas-filled bullae complex. Here, we show that the lateral line and its connection to the gas-filled bullae complex via the lateral recess are involved in ultrasound detection in Gulf menhaden. Removal of a small portion of the lateral line overlying the lateral recess membrane eliminates the ability of Gulf menhaden to detect ultrasound. We further show that the gas-filled bullae vibrates in response to ultrasound, that the gas-filled bullae are necessary for detecting ultrasound, and that the bullae connections to the lateral line via the lateral recess membrane play an important role in ultrasound detection. These results add a new dimension to the role of the lateral line and bullae as part of the ultrasonic detection system in Gulf menhaden. PMID:19837883

Wilson, Maria; Montie, Eric W; Mann, Kenneth A; Mann, David A

2009-11-01

136

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...

137

Temperature and pressure measurement based on tunable diode laser absorption spectroscopy with gas absorption linewidth detection  

NASA Astrophysics Data System (ADS)

A gas temperature and pressure measurement method based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) detecting linewidth of gas absorption line was proposed in this paper. Combined with Lambert-Beer Law and ideal gas law, the relationship between temperature, pressure and gas linewidth with Lorentzian line shape was investigated in theory. Taking carbon monoxide (CO) at 1567.32 nm for example, the linewidths of gas absorption line in different temperatures and pressures were obtained by simulation. The relationship between the linewidth of second harmonic and temperature, pressure with the coefficient 0.025 pm/K and 0.0645 pm/kPa respectively. According to the relationship of simulation results and detected linewidth, the undefined temperature and pressure of CO gas were measured. The gas temperature and pressure measurement based on linewidth detection, avoiding the influence of laser intensity, is an effective temperature and pressure measurement method. This method also has the ability to detect temperature and pressure of other gases with Lorentzian line shape.

Meng, Yunxia; Liu, Tiegen; Liu, Kun; Jiang, Junfeng; Wang, Tao; Wang, Ranran

2014-11-01

138

Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection  

PubMed Central

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

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

2009-01-01

139

Detection of gas hydrates by the measurement of instantaneous temperature  

E-print Network

methods used to measure sediment temperature were studied. A new method to detect hydrates was developed based on sediment temperature and its effectiveness was tested. This method involves the measurement of instantaneous temperature as a probe is pushed...

Dinakaran, Srikanth

1994-01-01

140

Model of detection for a modulated conductivity sensor: application for a NOx gas sensor  

Microsoft Academic Search

The performance of a chemical gas sensor based on polycristallyne tin oxide films is strongly related to their structure, thickness and doping. In previous works we have studied the influence of the thickness on the detection by impedance spectroscopy analysis [1,2]. In the present work we have focused our attention in designing and modelizing a sensor for detection of NOx

J. Gutierrez; L. Ares; J. I. Robla; I. Sayago; M. C. Horrillo; J. A. Agapito

1993-01-01

141

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

SciTech Connect

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

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

1995-08-01

142

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

143

Detection of unknown gas-phase chemical plumes in hyperspectral imagery  

NASA Astrophysics Data System (ADS)

Gas-phase chemical plumes exhibit, particularly in the infrared, distinctive emission signatures as a function of wavelength. Hyperspectral imagery can exploit this distinctiveness to detect specific chemicals, even at low concentrations, using matched filters that are tailored both the the specific structure of the chemical signature and to the statistics of the background clutter. But what if the chemical species is unknown? One can apply matched filters to a long list of candidate chemicals (or chemical mixtures), or one can treat the problem as one of anomaly detection. In this case, however, the anomalous signals of interest are not completely unknown. Gas spectra are generically sparse (absorbing or emitting at only a few wavelengths), and this property can be exploited to enhance the sensitivity of anomaly detection algorithms. This paper investigates the utility of sparse signal anomaly detection for the problem of finding plumes of gas with unknown chemistry in hyperspectral imagery.

Theiler, James; Wohlberg, Brendt

2013-05-01

144

False-alarm characterization in hyperspectral gas-detection applications  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

145

Recent developments in remote gas detection using molecular dispersion sensing  

NASA Astrophysics Data System (ADS)

In this paper we study signal amplitude in Chirp-modulated Chirped Laser Dispersion Spectroscopy (CM-CLaDS). CLaDS is a laser-based spectroscopic technique for molecular sensing that uses heterodyne detection to measure optical dispersion caused by molecular transitions. With baseline-free nature and high-immunity to optical power fluctuations CLaDS is well suited to long distance remote, open-path monitoring and stand-off chemical detection. In this work we analyze CM-CLaDS performance. We show that for certain conditions using proper modulation waveform can provide increase in the signal amplitude with respect to previously presented configurations.

Nikodem, Michal

2014-12-01

146

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

147

Selective CO Gas Detection of Zn 2 SnO 4 Gas Sensor  

Microsoft Academic Search

The ability of semiconductor gas sensors to differentiate between gases is essential but difficult to obtain. In this study, Zn2SnO4 was made to be CO selective and the possible mechanism for the selectivity was studied.

Ji Haeng Yu; Gyeong Man Choi

2002-01-01

148

Study on the MEMS-type gas sensor for detecting a nitrogen oxide gas  

Microsoft Academic Search

In this study, MEMS-based micro gas sensors were prepared by adopting MEMS technology and using sol–gel process. These sensors can be used for application of the air quality system monitoring the automobile indoor atmosphere. An array of MEMS-based gas sensors was designed to achieve low power consumption and high efficiency; this was done by adjusting the heater pattern and line

Jin-Ho Yoon; Jung-Sik Kim

2011-01-01

149

Detection of energetic particles and gamma rays Gas detectors  

E-print Network

· ionisation chamber ­ all electrons from direct ionisation collected ­ mostly used in current mode · ionisation · proportional · Geiger #12;3 Principle · radiation causes (either directly of via secondary radiation) ­ excitation (decay light can be the basis of radiation detection) ­ ionisation (electron

Peletier, Reynier

150

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

PubMed

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

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

2013-12-01

151

Gas Scintillation Chamber for Superheavy Elements Detection at GANIL  

NASA Astrophysics Data System (ADS)

In the paper we present scintillation-ionization detector (SID) -- a new device for support of the superheavy elements (SHE) identification in the standard, complete fusion methods. We highlight problems with background effects in SHE production and their minimization by introducing SID to the detection set-up at GANIL. We also point possible application of this detector in alternative approach for superheavy elements production.

Sosin, Z.; Wieloch, A.; Péter, J.; Drouart, A.; Dayras, R.; ?ojek, K.; Stodel, C.; Adamczyk, M.; Gonciarz, A.; Ba?ka, P.; Lasko, P.; Zosiak, L.; Alamanos, N.; Amar, N.; Anne, R.; Angélique, J. C.; Auger, G.; Fontbonne, J. M.; Gillibert, A.; Grévy, S.; Hanappe, F.; Hannachi, F.; Hue, R.; Khouaja, A.; Legou, T.; Lopez-Martens, A.; Liénard, E.; Manduci, L.; de Oliveira Santos, F.; Politi, G.; Saint-Laurent, M. G.; Stuttgé, L.; Tillier, J.; de Tourreil, R.; Villari, A. C. C.; Wieleczko, J. P.

2009-03-01

152

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

153

Chemoresistive Gas Sensors for the Detection of Colorectal Cancer Biomarkers  

PubMed Central

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

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

2014-01-01

154

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

155

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

156

System for detecting and estimating concentrations of gas or liquid analytes  

NASA Technical Reports Server (NTRS)

A sensor system for detecting and estimating concentrations of various gas or liquid analytes. In an embodiment, the resistances of a set of sensors are measured to provide a set of responses over time where the resistances are indicative of gas or liquid sorption, depending upon the sensors. A concentration vector for the analytes is estimated by satisfying a criterion of goodness using the set of responses. Other embodiments are described and claimed.

Homer, Margie L. (Inventor); Jan, Darrell L. (Inventor); Jewell, April D. (Inventor); Kisor, Adam (Inventor); Manatt, Kenneth S. (Inventor); Manfreda, Allison M. (Inventor); Ryan, Margaret A. (Inventor); Shevade, Abhijit V. (Inventor); Taylor, Charles (Inventor); Tran, Tuan A. (Inventor)

2011-01-01

157

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

NASA Astrophysics Data System (ADS)

Extensive methane release as a free gas phase from cold vents is well known from deep (>2000m) and shallow (10s of meters) water depths. Supposedly, much more methane is transported into the water column by free gas than by dissolved gas, which is oxidized by anaerobic and aerobic processes and partly precipitated as carbonate. Rising gas bubbles are not affected by this 'filter' mechanisms. Because of the strength of the backscattered signal from gas bubbles in the water column, bubbles can be detected by single-beam or multi-beam echosounder systems. Thus, hydroacoustic systems with different frequencies can be used to 1) detect free gas in the water column, 2) map the distribution of active vent sites which release free gas, 3) monitor a possible periodicity in the release of bubbles induced by e.g. tides or currents, 4) quantify the gas volume and gas flux that is released in a local area or larger region. In the German research project LOTUS we use ship- mounted single-beam echosounders to map gas plumes (flares) and investigate their periodicity (Flare Imaging). Using specialized single-beam echosounder systems makes it possible to measure the bubble sizes and their distribution. In combination with the volume of the backscattering strength these measurements can be used to estimate the gas volume in a defined part of the water body. Though gas bubbles rise in the water column, they are - particularly methane - rapidly dissolved and thus become smaller. Their rising speed as well as their diminishing size can be determined, which helps to understand the dissolution behaviour of methane bubbles; they form a hydrate skin at distinct pressure and temperature conditions. For a detailed, long-term observation of active bubble-expulsing areas we developed a lander based 180 kHz multi beam system that 'looks' horizontally (GasQuant). The system records backscatter data from a 75° swath that covers an area of about 5300m2. Via calibration we can quantify the methane flux of every single bubble-vent and calculate the methane flux of a bubble vent area. Both hydroacoustic techniques were used during several cruises in 2002 to investigate bubble vents at Hydrate Ridge (HR), offshore Oregon. Several bubble-vent areas were detected at the northern summit of HR. They are related to carbonate chemoherms and morphological heights but were also found in areas which do not show any of these features. The GasQuant system was successfully deployed at the northern and southern summit. The data processing is currently in progress.

Greinert, J.; Artemov, Y.; Gimpel, P.

2003-04-01

158

Detection of SF6 decomposition products generated by DC corona discharge using a carbon nanotube gas sensor  

Microsoft Academic Search

This paper describes application of carbon nanotube (CNT) gas sensor to detection of SF6 decomposition products generated by positive or negative DC corona discharge. The present authors have demonstrated CNT gas sensor-based partial discharge (PD) detection, aiming to develop a new diagnosis method of gas-insulated switchgear (GIS) filled with high pressure SF6 gas. In our previous studies, PD was generated

Yul Martin; Zhenyu Li; Takuya Tsutsumi; Ryuta Shou; Michihiko Nakano; Junya Suehiro; Shinya Ohtsuka

2012-01-01

159

Detection of individual atoms in helium buffer gas and observation of their real-time motion  

NASA Technical Reports Server (NTRS)

Single atoms are detected and their motion measured for the first time to our knowledge by the fluorescence photon-burst method in the presence of large quantities of buffer gas. A single-clipped digital correlator records the photon burst in real time and displays the atom's transit time across the laser beam. A comparison is made of the special requirements for single-atom detection in vacuum and in a buffer gas. Finally, the probability distribution of the bursts from many atoms is measured. It further proves that the bursts observed on resonance are due to single atoms and not simply to noise fluctuations.

Pan, C. L.; Prodan, J. V.; Fairbank, W. M., Jr.; She, C. Y.

1980-01-01

160

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

SciTech Connect

This report describes progress in the following five projects: (1) Geologic assessment of the Piceance Basin; (2) Regional stratigraphic studies, Upper Cretaceous Mesaverde Group, southern Piceance Basin, Colorado; (3) Structurally controlled and aligned tight gas reservoir compartmentalization in the San Juan and Piceance Basins--Foundation for a new approach to exploration and resource assessments of continuous type deposits; (4) Delineation of Piceance Basin basement structures using multiple source data--Implications for fractured reservoir exploration; and (5) Gas and water-saturated conditions in the Piceance Basin, western Colorado--Implications for fractured reservoir detection in a gas-centered coal basin.

NONE

1995-05-01

161

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

E-print Network

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 136 Xe. Conversely, a small admixture of xenon to CF 4 can reduce attachment in the latter. This gas mixture would be suitable for dark matter searches and the study of solar and reactor neutrinos. Various configurations of the Micromegas plane were investigated and are described.

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

2008-12-29

162

Combined raman and IR fiber-based sensor for gas detection  

DOEpatents

A double-pass fiber-optic based spectroscopic gas sensor delivers Raman excitation light and infrared light to a hollow structure, such as a hollow fiber waveguide, that contains a gas sample of interest. A retro-reflector is placed at the end of this hollow structure to send the light back through the waveguide where the light is detected at the same end as the light source. This double pass retro reflector design increases the interaction path length of the light and the gas sample, and also reduces the form factor of the hollow structure.

Carter, Jerry C; Chan, James W; Trebes, James E; Angel, Stanley M; Mizaikoff, Boris

2014-06-24

163

[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

164

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

E-print Network

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

Yutaka Fujita; Masahiro Nagashima; Naoteru Gouda

2000-05-15

165

Nanostructure Engineered Chemical Sensors for Hazardous Gas and Vapor Detection  

NASA Technical Reports Server (NTRS)

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

Li, Jing; Lu, Yijiang

2005-01-01

166

A Hazardous Gas Detection System for Aerospace and Commercial Applications  

NASA Technical Reports Server (NTRS)

The detection of explosive conditions in aerospace propulsion applications is important for safety and economic reasons. Microfabricated hydrogen, oxygen, and hydrocarbon sensors as well as the accompanying hardware and software are being, developed for a range of aerospace safety applications. The development of these sensors is being done using MEMS (Micro ElectroMechanical Systems) based technology and SiC-based semiconductor technology. The hardware and software allows control and interrocation of each sensor head and reduces accompanying cabling through multiplexing. These systems are being, applied on the X-33 and on an upcoming STS-95 Shuttle mission. A number of commercial applications are also being pursued. It is concluded that this MEMS-based technology has significant potential to reduce costs and increase safety in a variety of aerospace applications.

Hunter, G. W.; Neudeck, P. G.; Chen, L.-Y.; Makel, D. B.; Liu, C. C.; Wu, Q. H.; Knight, D.

1998-01-01

167

A Hazardous Gas Detection System for Aerospace and Commercial Applications  

NASA Technical Reports Server (NTRS)

The detection of explosive conditions in aerospace propulsion applications is important for safety and economic reasons. Microfabricated hydrogen, oxygen, and hydrocarbon sensors as well as the accompanying hardware and software are being developed for a range of aerospace safety applications. The development of these sensors is being done using MEMS (Micro ElectroMechanical Systems) based technology and SiC-based semiconductor technology. The hardware and software allows control and interrogation of each sensor head and reduces accompanying cabling through multiplexing. These systems are being applied on the X-33 and on an upcoming STS-95 Shuttle mission. A number of commercial applications are also being pursued. It is concluded that this MEMS-based technology has significant potential to reduce costs and increase safety in a variety of aerospace applications.

Hunter, G. W.; Neudeck, P. G.; Chen, L. - Y.; Makel, D. B.; Liu, C. C.; Wu, Q. H.; Knight, D.

1998-01-01

168

IV-VI semiconductor lasers for gas phase biomarker detection  

NASA Astrophysics Data System (ADS)

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

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

2007-09-01

169

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

170

[Carbon monoxide gas detection system based on mid-infrared spectral absorption technique].  

PubMed

Based on infrared spectral absorption technique, a carbon monoxide (CO) detection system was developed using the fundamental absorption band at the wavelength of 4.6 ?m of CO molecule and adopting pulse-modulated wideband incandescence and dual-channel detector. The detection system consists of pulse-modulated wideband incandescence, open ellipsoid light-collec- tor gas-cell, dual-channel detector, main-control and signal-processing module. By optimizing open ellipsoid light-collector gas- cell, the optical path of the gas absorption reaches 40 cm, and the amplitude of the electrical signal from the detector is 2 to 3 times larger than the original signal. Therefore, by using the ellipsoidal condenser, the signal-to-noise ratio of the system will be to some extent increased to improve performance of the system. With the prepared standard CO gas sample, sensing characteris- tics on CO gas were investigated. Experimental results reveal that, the limit of detection (LOD) is about 10 ppm; the relative er- ror at the LOD point is less than 14%, and that is less than 7. 8% within the low concentration range of 20~180 ppm; the maxi- mum absolute error of 50 min long-term measurement concentration on the 0 ppm gas sample is about 3 ppm, and the standard deviation is as small as 0. 18 ppm. Compared with the CO detection systems utilizing quantum cascaded lasers (QCLs) and dis- tributed feedback lasers (DFBLs), the proposed sensor shows potential applications in CO detection under the circumstances of coal-mine and environmental protection, by virtue of high performance-cost ratio, simple optical-path structure, etc. PMID:25739235

Li, Guo-Lin; Dong, Ming; Song, Nan; Song, Fang; Zheng, Chuan-Tao; Wang, Yi-Ding

2014-10-01

171

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

SciTech Connect

This report summarizes work performed by Physical Sciences Inc. (PSI) to advance the state-of-the-art of surveying for leaks of natural gas from transmission and distribution pipelines. The principal project goal was to develop means of deploying on an automotive platform an improved version of the handheld laser-based standoff natural gas leak detector previously developed by PSI and known as the Remote Methane Leak Detector or RMLD. A laser beam which interrogates the air for methane is projected from a spinning turret mounted upon a van. As the van travels forward, the laser beam scans an arc to the front and sides of the van so as to survey across streets and to building walls from a moving vehicle. When excess methane is detected within the arc, an alarm is activated. In this project, we built and tested a prototype Mobile RMLD (MRMLD) intended to provide lateral coverage of 10 m and one lateral scan for every meter of forward motion at forward speeds up to 10 m/s. Using advanced detection algorithms developed as part of this project, the early prototype MRMLD, installed on the back of a truck, readily detected simulated gas leaks of 50 liters per hour. As a supplement to the originally planned project, PSI also participated in a DoE demonstration of several gas leak detection systems at the Rocky Mountain Oilfield Testing Center (RMOTC) during September 2004. Using a handheld RMLD upgraded with the advanced detection algorithms developed in this project, from within a moving vehicle we readily detected leaks created along the 7.4 mile route of a virtual gas transmission pipeline.

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

2005-05-01

172

The Detection of Carbon Monoxide Gas Emission in (2060) Chiron  

NASA Astrophysics Data System (ADS)

2060 Chiron is among the small population of large, outer Solar System objects called Centaurs. Chiron's unusual, 51-year orbit ranges in distance from 8.5 to just over 19 AU, and exhibits an inclination to the ecliptic plane of 8.5 deg. Recent dynamical studies (Levison and Duncan, 1994; Dones et al., 1996) show this orbit is unstable to giant-planet perturbations on timescales of < 106 years, indicating that it is a recent addition to the planetary region. This, along with its low-inclination orbit, and its size similarity to the newly-discovered population of 100-400-km-diameter Kuiper Disk objects (Campins et al., 1994; Jewitt and Luu, 1995), provides strong circumstantial evidence that Chiron is an escaped object from the Kuiper Disk. Chiron's present orbit subjects it to much more intense insolation than objects in the Kuiper Disk experience. That insolation generates surface activity, as revealed by a highly variable coma (Hartmann et al., 1989; Meech and Belton, 1990; Bus etal., 1993). The source of Chiron's activity has been speculated on for many years (Stern, 1989) but never observationally identified. We report here the detection of CO molecules in Chiron's coma, which are probably the sublimation agent generating Chiron's activity.

Womack, Maria; Stern, S. Alan

173

Gas Detection with a Micro FTIR Spectrometer in the MIR Region  

Microsoft Academic Search

We report on the application of a silicon micromachined lamellar grating interferometer in a Fourier Transform Infrared (FTIR) spectrometer for the detection of gases in the mid-infrared (MIR) region. The FTIR spectrometer was equipped with MIR optical fibers for light coupling. Gas measurements in the MIR region were focused on specific gases (CO2, CH4) in order to determine the limit

T. Scharf; D. Briand; S. Bühler; O. Manzardo; H. P. Herzig; N. F. de Rooij

2009-01-01

174

Tin dioxide-based gas sensors for detection of hydrogen fluoride in air  

Microsoft Academic Search

This research concentrates on the sensitivity of semiconductor tin dioxide-based gas sensors to hydrogen fluoride in air. After evaluating the characteristic detection temperature, the sensor's signals were studied for different HF concentrations. Despite the corrosive effects of hydrogen fluoride, a reproducibility of the signal was found. Likewise, we did not observe any long-term degradation to the sensor. For the experiment,

J.-B. Sanchez; F. Berger; M. Fromm; M.-H. Nadal; V. Eyraud

2003-01-01

175

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

PubMed

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

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

2014-10-21

176

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

Microsoft Academic Search

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

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

2008-01-01

177

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

178

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

SciTech Connect

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

NONE

1996-12-31

179

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

SciTech Connect

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

NONE

1995-08-01

180

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

E-print Network

. Chemical vapor deposition recently has been reported to pro- duce large-area graphene films,8 process that is not suitable for large- scale production. Epitaxial growth of graphene layers re- quiresGas detection using low-temperature reduced graphene oxide sheets Ganhua Lu,1 Leonidas E. Ocola,2

Chen, Junhong

181

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

E-print Network

two-spool turbofan aircraft engine model for detection and isolation of incipient faults. Keywords both model-based and sensor-based analyses. A linear model-based method, called gas path analysis (GPA), was introduced in 1967 by Urban [5] and subsequently different modifications of this method were proposed

Ray, Asok

182

Toward coherent neutrino detection using low-background micropattern gas detectors  

Microsoft Academic Search

The detection of low energy neutrinos (1 kg) are not sensitive to sub keV nuclear recoils like those expected from this channel. The advent of micropattern gas detectors (MPGDs), new technologies originally intended for use in high energy physics, may soon put an end to this impasse. We present first tests of MPGDs fabricated with radioclean materials and discuss the

P. S. Barbeau; J. I. Collar; J. Miyamoto; I. Shipsey

2003-01-01

183

Self-heated silicon nanowires for high performance hydrogen gas detection.  

PubMed

Self-heated silicon nanowire sensors for high-performance, ultralow-power hydrogen detection have been developed. A top-down nanofabrication method based on well-established semiconductor manufacturing technology was utilized to fabricate silicon nanowires in wafer scale with high reproducibility and excellent compatibility with electronic readout circuits. Decoration of palladium nanoparticles onto the silicon nanowires enables sensitive and selective detection of hydrogen gas at room temperature. Self-heating of silicon nanowire sensors allows us to enhance response and recovery performances to hydrogen gas, and to reduce the influence of interfering gases such as water vapor and carbon monoxide. A short-pulsed heating during recovery was found to be effective for additional reduction of operation power as well as recovery characteristics. This self-heated silicon nanowire gas sensor will be suitable for ultralow-power applications such as mobile telecommunication devices and wireless sensing nodes. PMID:25670503

Ahn, Jae-Hyuk; Yun, Jeonghoon; Moon, Dong-Il; Choi, Yang-Kyu; Park, Inkyu

2015-03-01

184

Self-heated silicon nanowires for high performance hydrogen gas detection  

NASA Astrophysics Data System (ADS)

Self-heated silicon nanowire sensors for high-performance, ultralow-power hydrogen detection have been developed. A top-down nanofabrication method based on well-established semiconductor manufacturing technology was utilized to fabricate silicon nanowires in wafer scale with high reproducibility and excellent compatibility with electronic readout circuits. Decoration of palladium nanoparticles onto the silicon nanowires enables sensitive and selective detection of hydrogen gas at room temperature. Self-heating of silicon nanowire sensors allows us to enhance response and recovery performances to hydrogen gas, and to reduce the influence of interfering gases such as water vapor and carbon monoxide. A short-pulsed heating during recovery was found to be effective for additional reduction of operation power as well as recovery characteristics. This self-heated silicon nanowire gas sensor will be suitable for ultralow-power applications such as mobile telecommunication devices and wireless sensing nodes.

Ahn, Jae-Hyuk; Yun, Jeonghoon; Moon, Dong-Il; Choi, Yang-Kyu; Park, Inkyu

2015-03-01

185

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

186

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

187

Effect of Background Emissivity on Gas Detection in Thermal Hyperspectral Imagery  

SciTech Connect

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

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

2008-10-02

188

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

PubMed

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

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

2010-09-01

189

Selective CO gas detection of SnO 2–Zn 2SnO 4 composite gas sensor  

Microsoft Academic Search

For the selective detection of CO against H2 gas, SnO2–Zn2SnO4 composite-type sensors were fabricated. The surface of the pellet-type composite sensors was coated by CuO after sintering at 1000°C for 3h. The electrical conductivity and the sensitivity of the sensors to reducing gases (200ppm CO and 200ppm H2) were examined by measuring the current–voltage (I–V) characteristics of the composite sensors

Won Jae Moon; Ji Haeng Yu; Gyeong Man Choi

2001-01-01

190

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

191

Demonstration of neutron detection utilizing open cell foam and noble gas scintillation  

NASA Astrophysics Data System (ADS)

We present results demonstrating neutron detection via a closely spaced converter structure coupled to low pressure noble gas scintillation instrumented by a single photo-multiplier tube (PMT). The converter is dispersed throughout the gas volume using a reticulated vitreous carbon foam coated with boron carbide (B4C). A calibrated cold neutron beam is used to measure the neutron detection properties, using a thin film of enriched 10B as a reference standard. Monte Carlo computations of the ion energy deposition are discussed, including treatment of the foam random network. Results from this study indicate that the foam shadows a significant portion of the scintillation light from the PMT. The high scintillation yield of Xe appears to overcome the light loss, facilitating neutron detection and presenting interesting opportunities for neutron detector design.

Lavelle, C. M.; Coplan, M.; Miller, E. C.; Thompson, Alan K.; Kowler, A. L.; Vest, Robert E.; Yue, A. T.; Koeth, T.; Al-Sheikhly, M.; Clark, Charles W.

2015-03-01

192

Novel top-contact monolayer pentacene-based thin-film transistor for ammonia gas detection.  

PubMed

We report on the fabrication of an organic field-effect transistor (OFET) of a monolayer pentacene thin film with top-contact electrodes for the aim of ammonia (NH3) gas detection by monitoring changes in its drain current. A top-contact configuration, in which source and drain electrodes on a flexible stamp [poly(dimethylsiloxane)] were directly contacted with the monolayer pentacene film, was applied to maintain pentacene arrangement ordering and enhance the monolayer OFET detection performance. After exposure to NH3 gas, the carrier mobility at the monolayer OFET channel decreased down to one-third of its original value, leading to a several orders of magnitude decrease in the drain current, which tremendously enhanced the gas detection sensitivity. This sensitivity enhancement to a limit of the 10 ppm level was attributed to an increase of charge trapping in the carrier channel, and the amount of trapped states was experimentally evaluated by the threshold voltage shift induced by the absorbed NH3 molecular analyte. In contrast, a conventional device with a 50-nm-thick pentacene layer displayed much higher mobility but lower response to NH3 gas, arising from the impediment of analyte penetrating into the conductive channel, owing to the thick pentacene film. PMID:24684368

Mirza, Misbah; Wang, Jiawei; Li, Dexing; Arabi, S Atika; Jiang, Chao

2014-04-23

193

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

194

Tunnel-field-effect-transistor based gas-sensor: Introducing gas detection with a quantum-mechanical transducer  

NASA Astrophysics Data System (ADS)

A gas-sensor based on tunnel-field-effect-transistor (TFET) is proposed that leverages the unique current injection mechanism in the form of quantum-mechanical band-to-band tunneling to achieve substantially improved performance compared to conventional metal-oxide-semiconductor field-effect-transistors (MOSFETs) for detection of gas species under ambient conditions. While nonlocal phonon-assisted tunneling model is used for detailed device simulations, in order to provide better physical insights, analytical formula for sensitivity is derived for both metal as well as organic conducting polymer based sensing elements. Analytical derivations are also presented for capturing the effects of temperature on sensor performance. Combining the developed analytical and numerical models, intricate properties of the sensor such as gate bias dependence of sensitivity, relationship between the required work-function modulation and subthreshold swing, counter-intuitive increase in threshold voltage for MOSFETs and reduction in tunneling probability for TFETs with temperature are explained. It is shown that TFET gas-sensors can not only lead to more than 10 000× increase in sensitivity but also provide design flexibility and immunity against screening of work-function modulation through non-specific gases as well as ensure stable operation under temperature variations.

Sarkar, Deblina; Gossner, Harald; Hansch, Walter; Banerjee, Kaustav

2013-01-01

195

Gas chromatographic sensing on an optical fiber by mode-filtered light detection.  

PubMed

A chemical sensor for gas phase measurements is reported which combines the principles of chemical separation and fiber optic detection. The analyzer incorporates an annular column Chromatographic sensor, constructed by inserting a polymer-clad optical fiber into a silica capillary. Light from a helium-neon laser is launched down the fiber, producing a steady intensity distribution within the fiber, but a low background of scattered light. When sample vapor is introduced to the sensor, and an analyte-rich volume interacts with the polymer cladding, Chromatographic retention is observed simultaneously with a change in the local refractive index of the cladding. An increase in cladding refractive index (RI) causes light to be coupled out of the fiber, with detection at a right-angle to the annular column length to provide optimum S/N ratio. This detection mechanism is called mode-filtered light detection. We report a gas Chromatographic separation on a 3.1 m annular column (320 microm i.d. silica tube, 228 microm o.d. fiber with a 12 microm fluorinated silicone clad) of methane, benzene, butanone and chlorobenzene in 6 min. The annular column length was reduced to 22 cm to function as a sensor, with selected organic vapors exhibiting unique retention times and detection selectivity. The detection selectivity is determined by the analyte RI and the partition coefficient into the cladding. The calculated limit of detection (LOD) for benzene vapor is 0.03% by volume in nitrogen, and several chlorinated species had LOD values less than 1%. For binary mixtures of organic vapors, the detected response appears to be the linear combination of the two organic standards, suggesting that the annular column may be useful as a general approach for designing chemical sensors that incorporate separation and optical detection principles simultaneously. PMID:18966560

Bruckner, C A; Synovec, R E

1996-06-01

196

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

197

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

PubMed

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

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

2014-08-01

198

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

199

Detection of [N II] 5755 Emission from Low Density Ionized Interstellar Gas  

E-print Network

The extremely faint, temperature sensitive ``auroral'' emission line [N II] 5755 has been detected from the low density ionized gas along the sight line toward l = 130.0, b = -7.5 using the Wisconsin H-Alpha Mapper (WHAM). The intensity of this emission line, relative to the red nebular line [N II] 6584, is found to be twice that observed in bright, classical H II regions surrounding O stars. This implies that the electron temperature of the ionized gas along this sight line is about 2000 K higher than the H II regions, and that the enhanced [N II] 6584/H-Alpha and [S II] 6716/H-Alpha intensity ratios in this low density gas are due at least in part to an elevated temperature.

R. J. Reynolds; N. C. Sterling; L. M. Haffner; S. L. Tufte

2001-01-26

200

One-dimensional nanostructure field-effect sensors for gas detection.  

PubMed

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

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

2014-01-01

201

One-Dimensional Nanostructure Field-Effect Sensors for Gas Detection  

PubMed Central

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

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

2014-01-01

202

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

203

Detection of gas pipe wall thickness based on electromagnetic flux leakage  

Microsoft Academic Search

Based on electromagnetic flux leakage (EMFL), a nondestructive testing (NDT) technique for the detection of gas pipe wall\\u000a thickness is presented, and its principle and feasibility is evaluated by means of equivalent magnetic circuit analysis and\\u000a finite element analysis. An online NDT device adopting this technique is developed, and its structure and working principle\\u000a are introduced in detail. This device

Yunwei Zhang; Guozheng Yan

2007-01-01

204

Detection of leak acoustic signal in buried gas pipe based on the time–frequency analysis  

Microsoft Academic Search

A time–frequency technique for locating leaks in buried gas distribution pipes involves the use of the cross-correlation on two measured acoustic signals on either side of a leak. This technique can be problematic for locating leaks in steel pipes, as the acoustic signals in these pipes are generally narrow-band and low frequency. The effectiveness of the time–frequency technique for detecting

Min-Soo Kim; Sang-Kwon Lee

2009-01-01

205

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

206

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

207

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

PubMed

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

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

2014-02-01

208

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

209

Study on Oil-Gas Reservoir Detecting Methods Using Hyperspectral Remote Sensing  

NASA Astrophysics Data System (ADS)

Oil-gas reservoir exploration using hyperspectral remote sensing, which based on the theory of hydrocarbon microseepage information and fine spectral response of target, is a new direction for the application of remote sensing technology. In this paper, Qaidam Basin and Liaodong Bay in China were selected as the study areas. Based on the hydrocarbon microseepage theory, the analysis of crude oil in soil in Qaidam Basin and spectral experiment of crude oil in sea water in Liaodong Bay, Hyperion hyperspectral remote sensing images were used to develop the method of oil-gas exploration. The results indicated that the area of oil-gas reservoir in Qaidam Basin could be delimited in two ways: the oil-gas reservoir can be obtained directly by the absorption bands near 1730nm in Hyperion image; and Linear Spectral Unmixing (LSU) and Spectral Angle Matching (SAM) of alteration mineral (e.g. kaolinite, illite) could be used to indirectly detect the target area in Qaidam Basin. In addition, combined with the optimal bands in the region of visible/near-infrared, SAM was used to extract the thin oil slick of microseepage in Liaodong Bay. Then the target area of oil-gas reservoir in Liaodong Bay can be delineated.

Tian, Q.

2012-07-01

210

An overview of micromachined platforms for thermal sensing and gas detection  

SciTech Connect

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

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

1997-03-01

211

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

212

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

213

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

214

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

NASA Astrophysics Data System (ADS)

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

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

1999-03-01

215

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

SciTech Connect

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

Carrigan, C R; Sun, Y

2011-01-21

216

Numerical study on leakage detection and location in a simple gas pipeline branch using an array of pressure sensors  

Microsoft Academic Search

Pressure signals measured in gas pipelines provide useful information for monitoring the status of pipeline network operations.\\u000a This study numerically investigates leakage detection and location in a simple gas pipeline branch using transient signals\\u000a from an array of pressure sensors. A pipeline network simulation model was developed and used to predict one-dimensional compressible\\u000a flow in gas pipelines. Two monitoring methods

Sung Pill Jang; Chan Young Cho; Jin Hyun Nam; Si-Hyung Lim; Donghoon Shin; Tae-Yong Chung

2010-01-01

217

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

Microsoft Academic Search

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

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

2011-01-01

218

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

219

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

220

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

SciTech Connect

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

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

1999-09-30

221

Determination of acenocoumarol in human plasma by capillary gas chromatography with mass-selective detection.  

PubMed

A method for the determination of acenocoumarol in human plasma by capillary gas chromatography-mass-selective detection is described. After addition of a structurally related analogue as the internal standard, the compounds are extracted from plasma at acidic pH into toluene, back-extracted with a basic solution and re-extracted from hydrochloric acid solution with toluene, which is then evaporated to dryness. The compounds are converted into their methyl derivatives, which are determined by gas chromatography using a mass-selective detector at m/z 324 for acenocoumarol and m/z 338 for the internal standard. The reproducibility and accuracy of the method were found to be suitable over the acenocoumarol concentrations range 2.2-74 nmol/l. The method could be considered as selective for acenocoumarol in the presence of its major metabolites in plasma. PMID:8004241

Pommier, F; Ackermann, R; Sioufi, A; Godbillon, J

1994-03-18

222

Fission signal detection using helium-4 gas fast neutron scintillation detectors  

SciTech Connect

We demonstrate the unambiguous detection of the fission neutron signal produced in natural uranium during active neutron interrogation using a deuterium-deuterium fusion neutron generator and a high pressure {sup 4}He gas fast neutron scintillation detector. The energy deposition by individual neutrons is quantified, and energy discrimination is used to differentiate the induced fission neutrons from the mono-energetic interrogation neutrons. The detector can discriminate between different incident neutron energies using pulse height discrimination of the slow scintillation component of the elastic scattering interaction between a neutron and the {sup 4}He atom. Energy histograms resulting from this data show the buildup of a detected fission neutron signal at higher energies. The detector is shown here to detect a unique fission neutron signal from a natural uranium sample during active interrogation with a (d, d) neutron generator. This signal path has a direct application to the detection of shielded nuclear material in cargo and air containers. It allows for continuous interrogation and detection while greatly minimizing the potential for false alarms.

Lewis, J. M., E-mail: lewisj@ufl.edu; Kelley, R. P.; Jordan, K. A. [Nuclear Engineering Program, University of Florida, Gainesville, Florida 32611 (United States); Murer, D. [Arktis Radiation Detectors Ltd., 8045 Zurich (Switzerland)

2014-07-07

223

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

224

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

NASA Astrophysics Data System (ADS)

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

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

225

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

226

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

227

Determination of fluoxetine and norfluoxetine in plasma by gas chromatography with electron-capture detection  

SciTech Connect

This gas-chromatographic method for assay of fluoxetine and norfluoxetine in human plasma involves extraction of the drugs and use of a /sup 63/Ni electron-capture detector. The linear range of detection is 25 to 800 micrograms/L for each drug. Overall precision (CV) in the concentration range of 10 to 100 micrograms/L for both drugs was approximately 10%. Accuracy (relative error) in the same concentration range was approximately +10%. None of the commonly prescribed antidepressants or tranquilizers that we tested interfere with the assay.

Nash, J.F.; Bopp, R.J.; Carmichael, R.H.; Farid, K.Z.; Lemberger, L.

1982-10-01

228

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

229

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

230

Leakage detection and location in gas pipelines through an LPV identification approach  

NASA Astrophysics Data System (ADS)

A new approach to gas leakage detection in high pressure distribution networks is proposed, where two leakage detectors are modelled as a linear parameter varying (LPV) system whose scheduling signals are, respectively, intake and offtake pressures. Running the two detectors simultaneously allows for leakage location. First, the pipeline is identified from operational data, supplied by REN-Gasodutos and using an LPV systems identification algorithm proposed in [1]. Each leakage detector uses two Kalman filters where the fault is viewed as an augmented state. The first filter estimates the flow using a calculated scheduling signal, assuming that there is no leakage. Therefore it works as a reference. The second one uses a measured scheduling signal and the augmented state is compared with the reference value. Whenever there is a significant difference, a leakage is detected. The effectiveness of this method is illustrated with an example where a mixture of real and simulated data is used.

Lopes dos Santos, P.; Azevedo-Perdicoúlis, T.-P.; Jank, G.; Ramos, J. A.; Martins de Carvalho, J. L.

2011-12-01

231

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. PMID:23439655

Yilmaz, B; Kadioglu, Y.

2012-01-01

232

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

PubMed

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

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

2011-12-01

233

Determination of clemastine in human plasma by gas chromatography with nitrogen-phosphorus detection.  

PubMed

A method for the quantitative determination of clemastine in human plasma has been developed and validated. The assay uses gas chromatography with nitrogen-phosphorus detection and a HP-1 capillary column (25 mx0.22 mm, film thickness 0.33 mm) coated with dimethylpolysiloxane. Clemastine (with orphenadrine as internal standard) was isolated from human plasma using liquid-liquid extraction. A linear relationship was observed between 0.1 and 12.8 ng/ml using the peak area ratio of clemastine to orphenadrine with a correlation coefficient greater than 0.99 (the detection limit for clemastine was 0.06 ng/ml). The intra- and inter-day coefficients of variation were less than 11%. The developed method was used for the analysis of plasma samples from healthy volunteers (n = 19) to examine the pharmacokinetics of the antihistamine clemastine after single and multiple oral doses of clemastine fumarate. PMID:10985579

Davydova, N N; Yasuda, S U; Woosley, R L; Wainer, I W

2000-07-01

234

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

Microsoft Academic Search

The innovative NDE inspection system Acoustic Thermography is developed with Sonic Infrared (Sonic IR) technology. Since the probability of detection is sensitive to the flaw characteristics, the fabricated flaws could not simulated the nature flaws with accuracy. The study is focus on gas turbine blades with service induced fatigue cracks. The detection capability of this innovative NDE inspection system is

Y. Guo; F. R. Ruhge

2009-01-01

235

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

Microsoft Academic Search

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

S Sarkar; S Gupta; K Mukherjee; A Ray

2008-01-01

236

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

PubMed Central

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

2013-01-01

237

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

238

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

239

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

PubMed Central

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

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

2010-01-01

240

Rapid and sensitive gas chromatographic method for detection of barbital and pentobarbital in blood using flash-heater methylation and nitrogen-specific detection  

Microsoft Academic Search

Summary  A sensitive and simplified method is described for the determination of barbital (B) and pentobarbital (PB) in blood using\\u000a gas chromatography with a nitrogen-specific flame ionization detector. After a simple one-step extraction, B and PB were reconstituted\\u000a in trimethylanilinium hydroxide and introduced directly into the gas chromatograph. Lower limits of detection was 0.14 ?g\\/ml\\u000a for B and PB in either

C. Kim; R. Berg; J. M. Khanna

1987-01-01

241

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

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

242

Rapid detection of bacteria with miniaturized pyrolysis-gas chromatographic analysis  

NASA Astrophysics Data System (ADS)

Rapid detection and identification of bacteria and other pathogens is important for many civilian and military applications. The profiles of biological markers such as fatty acids can be used to characterize biological samples or to distinguish bacteria at the gram-type, genera, and even species level. Common methods for whole cell bacterial analysis are neither portable nor rapid, requiring lengthy, labor intensive sample preparation and bench-scale instrumentation. These methods chemically derivatize fatty acids to produce more volatile fatty acid methyl esters (FAMEs) that can be separated and analyzed by a gas chromatograph (GC)/mass spectrometer. More recent publications demonstrate decreased sample preparation time with in situ derivatization of whole bacterial samples using pyrolysis/derivatization. Ongoing development of miniaturized pyrolysis/GC instrumentation by this department capitalizes on Sandia advances in the field of microfabricated chemical analysis systems ((mu) ChemLab). Microdevices include rapidly heated stages capable of pyrolysis or sample concentration, gas chromatography columns, and surface acoustic wave (SAW) sensor arrays. We will present results demonstrating the capabilities of these devices toward fulfilling the goal of portable, rapid detection and early warning of the presence of pathogens in air or water.

Mowry, Curtis; Morgan, Catherine H.; Baca, Quentin; Manginell, Ronald P.; Kottenstette, Richard J.; Lewis, Patrick; Frye-Mason, Gregory C.

2002-02-01

243

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

PubMed Central

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

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

2013-01-01

244

Detection and tracking of gas plumes in LWIR hyperspectral video sequence data  

NASA Astrophysics Data System (ADS)

Automated detection of chemical plumes presents a segmentation challenge. The segmentation problem for gas plumes is difficult due to the diffusive nature of the cloud. The advantage of considering hyperspectral images in the gas plume detection problem over the conventional RGB imagery is the presence of non-visual data, allowing for a richer representation of information. In this paper we present an effective method of visualizing hyperspectral video sequences containing chemical plumes and investigate the effectiveness of segmentation techniques on these post-processed videos. Our approach uses a combination of dimension reduction and histogram equalization to prepare the hyperspectral videos for segmentation. First, Principal Components Analysis (PCA) is used to reduce the dimension of the entire video sequence. This is done by projecting each pixel onto the first few Principal Components resulting in a type of spectral filter. Next, a Midway method for histogram equalization is used. These methods redistribute the intensity values in order to reduce icker between frames. This properly prepares these high-dimensional video sequences for more traditional segmentation techniques. We compare the ability of various clustering techniques to properly segment the chemical plume. These include K-means, spectral clustering, and the Ginzburg-Landau functional.

Gerhart, Torin; Sunu, Justin; Lieu, Lauren; Merkurjev, Ekaterina; Chang, Jen-Mei; Gilles, Jérôme; Bertozzi, Andrea L.

2013-05-01

245

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

PubMed

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 mum, 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 air at atmospheric pressure with 1 ppb precision (parts in 10(9), by mole fraction) and 0.6% accuracy for a signal averaging time of 10 s. It employed a compact multipass absorption cell with a 18-m path length and a thermoelectrically cooled HgCdTe detector. Precision was limited by residual interference fringes arising from scattering in the multipass cell. This is the first demonstration of a portable high-precision gas sensor based on diode-pumped DFG at room temperature. The use of an external-cavity diode laser can provide a tuning range of 700 cm(-1) and allow the detection of several trace gases, including N(2) O, CO(2), SO(2), H(2) CO, and CH(4). PMID:18264334

Töpfer, T; Petrov, K P; Mine, Y; Jundt, D; Curl, R F; Tittel, F K

1997-10-20

246

Xenon Additives Detection in Helium Micro-Plasma Gas Analytical Sensor  

NASA Astrophysics Data System (ADS)

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

Tsyganov, Alexander; Kudryavtsev, Anatoliy; Mustafaev, Alexander

2012-10-01

247

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

248

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.

2007-05-01

249

Solidphase microextraction method for gas chromatography with mass spectrometric and pulsed flame photometric detection: studies of organoarsenical speciation  

Microsoft Academic Search

The development, optimization, and application of a novel method for arsenic speciation based on capillary gas–liquid chromatography with simultaneous quadrupole ion-trap mass spectrometric (MS) detection and pulsed flame photometric detection (PFPD) is described. The method couples the sensitive arsenic-selectivity of PFPD with the structure elucidation capability of molecular MS detection for the determination of trace levels of unknown organoarsenicals in

Daniel R. Killelea; Joseph H. Aldstadt

2001-01-01

250

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

251

Chandra detection of diffuse hot gas in and around the M31 bulge  

E-print Network

We report the detection of diffuse hot gas in M31, using archival Chandra observations which allow us to map out a 30' by 30' field (covering a galactocentric radius up to 4.5 kpc) and to detect sources in the galaxy down to a 0.5-8 keV luminosity limit of ~10^35 ergs/s. We estimate the remaining stellar contribution from fainter X-ray sources (primarily cataclysmic variables and coronally active binaries), assuming that they spatially follow the stellar distribution. Indeed, the near-IR K-band light of the galaxy closely traces the 2-8 keV unresolved X-rays, indicating a collective stellar X-ray emissivity consistent with those determined for the Galactic ridge and M32, whereas the amount of the 0.5-2 keV unresolved emission is significantly greater than the expected stellar contribution, especially within a galactocentric radius of ~2 kpc. Morphologically, this soft X-ray excess appears substantially rounder than the bulge as seen in K-band and is elongated approximately along the minor-axis at large radii. The excess thus most likely represents the emission of diffuse hot gas in and around the galactic bulge. Furthermore, the near side of the M31 disk casts an apparent shadow against the soft X-ray excess, indicating that the hot gas extends to at least 2.5 kpc from the galactic plane. We briefly discuss the implications of these results on the energy balance in the M31 bulge and on understanding the large-scale soft X-ray enhancement observed toward the inner region of our own Galaxy.

Z. Li; Q. D. Wang

2007-08-22

252

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

253

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

SciTech Connect

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

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

2006-08-30

254

Detection of hazardous gas using multidemensional porous iron oxide nanorods-decorated carbon nanoparticles.  

PubMed

Multidimensional porous iron oxide (Fe2O3) nanorods-decorated carbon nanoparticles (MPFCNPs) were fabricated using a dual-nozzle electrospray, thermal stirring, and heat treatment. Polypyrrole (PPy) NPs with FeOOH nanorods were synthesized by electrospraying Fe(3+) ions, which were adsorbed on the PPy NP surface; the adsorbed Fe(3+) ions reacted with NaOH to create FeOOH nuclei, and then followed thermal stirring grow nanorods without aggregation. MPFCNPs were fabricated through heat treatment, with the porous structure created in the Fe2O3 nanorods by hydroxyl group decomposition. The size of the MPFCNPs and the length of the porous Fe2O3 nanorods were controlled by the PPy NP template and concentration of initiator solution, respectively. The MPFCNPs were then utilized as a chemical sensor transducer for NO2 gas detection at room temperature. The response of the MFPCNP sensor was highly sensitive, displaying a minimum detectable level of 1 ppm; this detection level is lower than that of organic-inorganic hybrid sensors. Moreover, sensitivity also improved with decreasing the diameter of MPFCNPs and increasing Fe2O3 nanorod length. The enhanced sensitivity was attributed to the larger surface area presented by the particle size and the porous structure. PMID:25569462

Shin, Dong Hoon; Lee, Jun Seop; Jun, Jaemoon; Kim, Sung Gun; Jang, Jyongsik

2015-01-28

255

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

PubMed Central

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

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

2012-01-01

256

Novelty detection by multivariate kernel density estimation and growing neural gas algorithm  

NASA Astrophysics Data System (ADS)

One of the underlying assumptions when using data-based methods for pattern recognition in diagnostics or prognostics is that the selected data sample used to train and test the algorithm is representative of the entire dataset and covers all combinations of parameters and conditions, and resulting system states. However in practice, operating and environmental conditions may change, unexpected and previously unanticipated events may occur and corresponding new anomalous patterns develop. Therefore for practical applications, techniques are required to detect novelties in patterns and give confidence to the user on the validity of the performed diagnosis and predictions. In this paper, the application of two types of novelty detection approaches is compared: a statistical approach based on multivariate kernel density estimation and an approach based on a type of unsupervised artificial neural network, called the growing neural gas (GNG). The comparison is performed on a case study in the field of railway turnout systems. Both approaches demonstrate their suitability for detecting novel patterns. Furthermore, GNG proves to be more flexible, especially with respect to dimensionality of the input data and suitability for online learning.

Fink, Olga; Zio, Enrico; Weidmann, Ulrich

2015-01-01

257

Optimizing detection of noble gas emission at a former UNE site: sample strategy, collection, and analysis  

NASA Astrophysics Data System (ADS)

Underground nuclear tests may be first detected by seismic or air samplers operated by the CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization). After initial detection of a suspicious event, member nations may call for an On-Site Inspection (OSI) that in part, will sample for localized releases of radioactive noble gases and particles. Although much of the commercially available equipment and methods used for surface and subsurface environmental sampling of gases can be used for an OSI scenario, on-site sampling conditions, required sampling volumes and establishment of background concentrations of noble gases require development of specialized methodologies. To facilitate development of sampling equipment and methodologies that address OSI sampling volume and detection objectives, and to collect information required for model development, a field test site was created at a former underground nuclear explosion site located in welded volcanic tuff. A mixture of SF-6, Xe127 and Ar37 was metered into 4400 m3 of air as it was injected into the top region of the UNE cavity. These tracers were expected to move towards the surface primarily in response to barometric pumping or through delayed cavity pressurization (accelerated transport to minimize source decay time). Sampling approaches compared during the field exercise included sampling at the soil surface, inside surface fractures, and at soil vapor extraction points at depths down to 2 m. Effectiveness of various sampling approaches and the results of tracer gas measurements will be presented.

Kirkham, R.; Olsen, K.; Hayes, J. C.; Emer, D. F.

2013-12-01

258

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

SciTech Connect

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

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

2014-02-18

259

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

SciTech Connect

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

Lewicki, Jennifer L.; Oldenburg, Curtis M.

2004-12-15

260

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

261

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

262

A COST EFFECTIVE MULTI-SPECTRAL SCANNER FOR NATURAL GAS DETECTION  

SciTech Connect

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

Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan

2004-04-01

263

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

264

Detection of ritalinic acid in urine by thin-layer chromatography and gas chromatography.  

PubMed

A new method for the analysis of ritalinic acid, the major metabolite of methylphenidate in urine, is described. The procedure involves solid-phase extraction of ritalinic acid from urine using C-18 reverse phase columns. The ritalinic acid is methylated to form methylphenidate which, together with an internal standard, is then extracted into chloroform and analyzed by gas chromatography using a flame ionization detector. This procedure gives essentially quantitative recovery of ritalinic acid from 10 mL urine and is linear in the range of 0 to 10 micrograms/mL. A positive analysis for ritalinic acid is confirmed by thin-layer chromatography. Detection sensitivities of greater than or equal to 1 micrograms/mL urine were observed for both procedures. PMID:6716975

Allen, H W; Sedgwick, B

1984-01-01

265

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

266

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

267

Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments.  

PubMed

A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ?400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ?400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds. PMID:25430303

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

2014-11-01

268

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

PubMed Central

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

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

2014-01-01

269

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

270

Highly selective probe detects Cu2+ 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 Cu2+ and also shows FRET induced fluorescence turn-on exclusively with Cu2+. FI selectively detects Cu2+ 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 Cu2+, while other metals did not influence the FI fluorescence. In addition, the fluorescence of FI-Cu2+ was efficiently quenched by NO generated in macrophages through LPS stimulation. FI demonstrates characteristic "turn-on" behavior in the presence of Cu2+ via spirolactom ring-opening, while other metals such as Na+, K+, Ca2+, Cr3+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, and Ag+ did not influence FI fluorescence even at very high concentration. Further, the FI-Cu2+ complex fluorescence was not quenched with any anions or amino acids but totally quenched by NO and the paramagnetic nature of Cu2+ ion converted into the diamagnetic nature when reduced to Cu1+. FI and the FI-Cu2+ 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

271

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

272

Detection of exhaled hydrogen sulphide gas in rats exposed to intravenous sodium sulphide  

PubMed Central

Background and purpose: Sodium sulphide (Na2S) disassociates to sodium (Na+) hydrosulphide, anion (HS?) and hydrogen sulphide (H2S) in aqueous solutions. Here we have established and characterized a method to detect H2S gas in the exhaled breath of rats. Experimental approach: Male rats were anaesthetized with ketamine and xylazine, instrumented with intravenous (i.v.) jugular vein catheters, and a tube inserted into the trachea was connected to a pneumotach connected to a H2S gas detector. Sodium sulphide, cysteine or the natural polysulphide compound diallyl disulphide were infused intravenously while the airway was monitored for exhaled H2S real time. Key results: Exhaled sulphide concentration was calculated to be in the range of 0.4–11 ppm in response to i.v. infusion rates ranging between 0.3 and 1.1 mg·kg?1·min?1. When nitric oxide synthesis was inhibited with N?-nitro-L-arginine methyl ester the amount of H2S exhaled during i.v. infusions of sodium sulphide was significantly increased compared with that obtained with the vehicle control. An increase in circulating nitric oxide using DETA NONOate [3,3-bis(aminoethyl)-1-hydroxy-2-oxo-1-triazene] did not alter the levels of exhaled H2S during an i.v. infusion of sodium sulphide. An i.v. bolus of L-cysteine, 1 g·kg?1, and an i.v. infusion of the garlic derived natural compound diallyl disulphide, 1.8 mg·kg?1·min?1, also caused exhalation of H2S gas. Conclusions and implications: This method has shown that significant amounts of H2S are exhaled in rats during sodium sulphide infusions, and the amount exhaled can be modulated by various pharmacological interventions. PMID:19422378

Insko, Michael A; Deckwerth, Thomas L; Hill, Paul; Toombs, Christopher F; Szabo, Csaba

2009-01-01

273

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

274

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

275

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

276

Determination of levamisole in plasma and animal tissues by gas chromatography with thermionic specific detection.  

PubMed

A rapid and sensitive method has been developed for the determination of the anthelmintic levamisole in plasma and tissues from man and animals. The procedure involves the extraction of the drug and its internal standard from the biological material at alkaline pH, back-extraction into sulphuric acid and re-extraction into the organic phase (heptane-isoamyl alcohol). Several extraction steps can be omitted, however, whenever the gas chromatographic background permits and some operations can be simplified using Clin ElutTM extraction tubes. The analyses were carried out by gas chromatography using a nitrogen-selective thermionic specific detector. The detection limit was 5 ng, contained in 1 ml of plasma or in 1 g of the various tissues, and recoveries were sufficiently high (79-86%). The method was applied to human plasma samples in a comprehensive bioavailability study of levamisole in healthy volunteers, and to plasma and tissues in a residue trial in cattle. The effect of the blood collection technique on the plasma levels was also studied and pointed to decreased plasma concentrations when Vacutainer tubes were used. PMID:7263817

Woestenborghs, R; Michielsen, L; Heykants, J

1981-06-12

277

Portable gas chromatograph with tunable retention and sensor array detection for determination of complex vapor mixtures.  

PubMed

A prototype portable gas chromatograph that combines a multiadsorbent preconcentrator/focuser, a tandem-column separation stage with individual column temperature control and junction point pressure modulation, and a detector consisting of an integrated array of polymer-coated surface acoustic wave microsensors is described. Using scheduled first-column stop-flow intervals and independent temperature programming of the two columns, it is possible to adjust the retention of eluting analyte vapors to maximize vapor recognition with the microsensor array and minimize the time of analysis. A retention window approach is combined with Monte Carlo simulations to guide retention tuning requirements and facilitate pattern recognition analyses. The determination of a 30-vapor mixture of common indoor air contaminants in < 10 min is demonstrated using ambient air as the carrier gas. Detection limits of < 10 ppb are achieved for the majority of compounds from a 1-L air sample on the basis of the most sensitive sensor in the array. Performance is assessed in the context of near-real-time indoor air quality monitoring applications. PMID:12659202

Lu, Chia-Jung; Whiting, Joshua; Sacks, Richard D; Zellers, Edward T

2003-03-15

278

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

279

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

PubMed Central

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

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

2014-01-01

280

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

281

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

E-print Network

and submarine landslides. Information on the distribution of gas hydrates and free gas and an estimate of their concentra- tions in the sediments would allow a more quantitative assess- ment of gas hydrate influence on slope failure in the Storegga Slide...- ence of both hydrates and gas apparently does not affect the S-wave velocity within sediments of the northern Storegga sidewall. Distribution and concentration of gas hydrates and free gas Three different rock-physical models have been pro- posed...

Murad, Idris

2011-08-08

282

Photoacoustic spectroscopy for trace gas detection with cryogenic and room-temperature continuous-wave quantum cascade lasers  

NASA Astrophysics Data System (ADS)

The main characteristics that a sensor must possess for trace gas detection and pollution monitoring are high sensitivity, high selectivity and the capability to perform in situ measurements. The photacoustic Helmholtz sensor developed in Reims, used in conjunction with powerful Quantum Cascade Lasers (QCLs), fulfils all these requirements. The best cell response is # 1200 V W-1 cm and the corresponding ultimate sensitivity is j 3.3 × 10-10 W cm-11 Hz-11/2. This efficient sensor is used with mid-infrared QCLs from Alpes Lasers to reach the strong fundamental absorption bands of some atmospheric gases. A first cryogenic QCL emitting at 7.9 ?m demonstrates the detection of methane in air with a detection limit of 3 ppb. A detection limit of 20 ppb of NO in air is demonstrated using another cryogenic QCL emitting in the 5.4 ?m region. Real in-situ measurements can be achieved only with room-temperature QCLs. A room-temperature QCL emitting in the 7.9 ?m region demonstrates the simultaneous detection of methane and nitrous oxide in air (17 and 7 ppb detection limit, respectively). All these reliable measurements allow the estimated detection limit for various atmospheric gases using quantum cascade lasers to be obtained. Each gas absorbing in the infrared may be detected at a detection limit in the ppb or low-ppb range.

Zeninari, Virginie; Grossel, Agnès; Joly, Lilian; Decarpenterie, Thomas; Grouiez, Bruno; Bonno, Bernard; Parvitte, Bertrand

2010-04-01

283

Trace detection of dissolved hydrogen gas in oil using a palladium nanowire array.  

PubMed

The electrical resistance, R, of an array of 30 palladium nanowires is used to detect the concentration of dissolved hydrogen gas (H(2)) in transformer oil over the temperature range from 21 to 70 °C. The palladium nanowire array (PdNWA), consisting of Pd nanowires ?100 nm (width), ?20 nm (height), and 100 ?m (length), was prepared using the lithographically patterned nanowire electrodeposition (LPNE) method. The R of the PdNWA increased by up to 8% upon exposure to dissolved H(2) at concentrations above 1.0 ppm and up to 2940 ppm at 21 °C. The measured limit-of-detection for dissolved H(2) was 1.0 ppm at 21 °C and 1.6 ppm at 70 °C. The increase in resistance induced by exposure to H(2) was linear with [H(2)](oil)(1/2) across this concentration range. A PdNWA sensor operating in flowing transformer oil has functioned continuously for 150 days. PMID:22017676

Yang, Fan; Jung, Dongoh; Penner, Reginald M

2011-12-15

284

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

PubMed Central

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

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

2007-01-01

285

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

PubMed

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

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

2015-01-01

286

Algorithms for near real-time detection of gas leaks from buried pipelines using hyperspectral imagery  

NASA Astrophysics Data System (ADS)

Gas leaks from buried pipelines can directly impact the health of overlying vegetation. The leak can produce patches of highly stressed or dead vegetation. Plant health can be assessed remotely by measuring the depth of the chlorophyll absorption, which is located between 550 nm and 700 nm in reflectance imagery. Chlorophyll absorption is readily recognizable in multispectral and hyperspectral imagery as a strong absorption band centered on red light (typically 680 nm wavelength). We have examined several methods of measuring chlorophyll absorption with the goal of automating vegetation stress detection above underground pipelines in order to facilitate same-day detection of potential pipeline leak locations. One method, in which we measure vegetation stress as the ratio of the measured reflectance at peak absorption to the spectral continuum, was particularly successful. We compare the results of this measurement with a manual analysis of 0.18 m resolution imagery of several controlled CO2 leaks, finding the automatic analysis to be robust. High spatial resolution is shown to greatly increase the quality of the results, however, we show that this method works in even 3 m resolution imagery of an underground pipeline methane leak. This algorithm runs very quickly for large images. We are developing the image analysis algorithm to operate in real-time while flying buried pipeline right of way with hyperspectral sensors.

Hoffmann, G. D.; Silver, E. A.; Pickles, W.; Male, E.

2009-12-01

287

Gas chromatographic method for trapping and detection of volatile organic compounds from human mouth air.  

PubMed

The present investigation describes a convenient method for collection and analysis of volatile organic compounds from 25 ml mouth air samples. Tenax-GC trapping devices coated with Teflon are used to adsorb and concentrate volatile organic compounds in mouth air at -20 degrees C, which are then thermally desorbed at 140 degrees C. Gas chromatography (GC) analyses are performed using an aluminum column coated with Teflon and packed with 2% poly-MPE on 80/100 mesh Tenax-GC, and employing a flame ionization detector. This procedure allows for amplification of peak heights and detection of compounds that may otherwise escape direct analysis. Of the six prominent peaks detected, identification based on retention times indicates the presence of methanol, acetaldehyde, ethanol and acetone. Volatiles collected using this procedure can be maintained at -20 degrees C for up to 48 hours before analysis. The compact sample tubes allow the system to be easily portable, particularly suitable for sampling breath of persons with localized oral or systemic diseases at locations away from the laboratory. The superiority of this method is that relatively small samples are required for analysis, unlike previously published methods which are based on collection of large volumes of expired air in plastic bags. PMID:1930701

Tonzetich, J; Coil, J M; Ng, W

1991-01-01

288

Increasing the selectivity and sensitivity of gas sensors for the detection of explosives  

NASA Astrophysics Data System (ADS)

Over the past decade, the use of improvised explosive devices (IEDs) has increased, domestically and internationally, highlighting a growing need for a method to quickly and reliably detect explosive devices in both military and civilian environments before the explosive can cause damage. Conventional techniques have been successful in explosive detection, however they typically suffer from enormous costs in capital equipment and maintenance, costs in energy consumption, sampling, operational related expenses, and lack of continuous and real-time monitoring. The goal was thus to produce an inexpensive, portable sensor that continuously monitors the environment, quickly detects the presence of explosive compounds and alerts the user. In 2012, here at URI, a sensor design was proposed for the detection of triacetone triperoxide (TATP). The design entailed a thermodynamic gas sensor that measures the heat of decomposition between trace TATP vapor and a metal oxide catalyst film. The sensor was able to detect TATP vapor at the part per million level (ppm) and showed great promise for eventual commercial use, however, the sensor lacked selectivity. Thus, the specific objective of this work was to take the original sensor design proposed in 2012 and to make several key improvements to advance the sensor towards commercialization. It was demonstrated that a sensor can be engineered to detect TATP and ignore the effects of interferent H2O2 molecules by doping SnO2 films with varying amounts of Pd. Compared with a pure SnO2 catalyst, a SnO2, film doped with 8 wt. % Pd had the highest selectivity between TATP and H2O2. Also, at 12 wt. % Pd, the response to TATP and H2O2 was enhanced, indicating that sensitivity, not only selectivity, can be increased by modifying the composition of the catalyst. An orthogonal detection system was demonstrated. The platform consists of two independent sensing mechanisms, one thermodynamic and one conductometric, which take measurements from the same catalyst simultaneously and provide a redundancy in response for positive explosive identification. TATP, 2,6-DNT and ammonium nitrate were reliably detected. Each analyte displayed a unique conductometric signature and the results indicated a detection limit at the ppb level. A preconcentrator was designed to enhance the sensitivity of the sensor and was successfully demonstrated. The magnitude of the sensor response increased from by 50% and the preconcentrator could be operated semi-continuously, maintaining one of the most attractive features of this sensor platform: the capability to operate in real time. A method to filter out extraneous heat signals from sensor response using a dynamic control was also successfully demonstrated and will likely be a fixture in all sensor experimentation and design moving forward. Finally, two MEMS based sensor platforms were designed and fabricated. It was theoretically demonstrated that the newest iteration of the MEMS sensor consumes considerably less power due to thinner membranes, a smaller active surface area and an overall smaller thermal mass, allowing for the possibility of creating networks of sensor arrays, even in a portable device.

Mallin, Daniel

289

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

290

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

NASA Astrophysics Data System (ADS)

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

Guo, Y.; Ruhge, F. R.

2009-03-01

291

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

292

Imaging Molecular Gas in the Luminous Merger NGC 3256 : Detection of High-Velocity Gas and Twin Gas Peaks in the Double Nucleus  

E-print Network

Molecular gas in the merging starburst galaxy NGC 3256 has been imaged with the Submillimeter Array at a resolution of 1'' x 2'' (170 x 340 pc at 35 Mpc). This is the first interferometric imaging of molecular gas in the most luminous galaxy within z=0.01. There is a large disk of molecular gas (r > 3 kpc) in the center of the merger with a strong gas concentration toward the double nucleus. The gas disk having a mass of ~3*10^9 Msun in the central 3 kpc rotates around a point between the two nuclei that are 850 pc apart on the sky. The molecular gas is warm and turbulent and shows spatial variation of the intensity ratio between CO isotopomers. High-velocity molecular gas is discovered at the galactic center. Its velocity in our line of sight is up to 420 km/s offset from the systemic velocity of the galaxy; the terminal velocity is twice as large as that due to the rotation of the main gas disk. The high-velocity gas is most likely due to a molecular outflow from the gas disk, entrained by the starburst-driven superwind in the galaxy. The molecular outflow is estimated to have a rate of ~10 Msun/yr and to play a significant role in the dispersal or depletion of molecular gas from the galactic center. A compact gas concentration and steep velocity gradient are also found around each of the twin nuclei. They are suggestive of a small gas disk rotating around each nucleus. If these are indeed mini-disks, their dynamical masses are ~10^9 Msun within a radius of 170 pc.

Kazushi Sakamoto; Paul T. P. Ho; Alison B. Peck

2006-03-03

293

Detection of Water in the Shocked Gas Associated with IC 443: Constraints on Shock Models  

NASA Astrophysics Data System (ADS)

We have used the Submillimeter Wave Astronomy Satellite (SWAS) to observe the ground-state 110-->101 transition of ortho-H2O at 557 GHz in three of the shocked molecular clumps associated with the supernova remnant IC 443. We also observed simultaneously the 487 GHz line (3,1-->3,2) of O2, the 492 GHz line (3P1-->3P0) of C I, and the 550 GHz line (J=5-->4) of 13CO. We detected the H2O, C I, and 13CO lines toward the shocked clumps B, C, and G. In addition, ground-based observations of the J=1-->0 transitions of CO and HCO+ were obtained. Assuming that the shocked gas has a temperature of 100 K and a density of 5×105 cm-3, we derive SWAS beam-averaged ortho-H2O column densities of 3.2×1013, 1.8×1013, and 3.9×1013 cm-2 in clumps B, C, and G, respectively. Combining the SWAS results with our ground-based observations, we derive a relative abundance of ortho-H2O to CO in the postshock gas of between 2×10-4 and 3×10-3. On the basis of our results for H2O, published results of numerous atomic and molecular shock tracers, and archival Infrared Space Observatory (ISO) observations, we conclude that no single shock type can explain these observations. However, a combination of fast J-type shocks (~100 km s-1) and slow C-type shocks (~12 km s-1) or, more likely, slow J-type shocks (~12-25 km s-1) can most naturally explain the postshock velocities and the emission seen in various atomic and molecular tracers. Such a superposition of shocks might be expected as the supernova remnant overtakes a clumpy interstellar medium. The fast J-type shocks provide a strong source of ultraviolet radiation, which photodissociates the H2O in the cooling (T<=300 K) gas behind the slow shocks and strongly affects the slow C-type shock structure by enhancing the fractional ionization. At these high ionization fractions, C-type shocks break down at speeds ~10-12 km s-1, while faster flows will produce J-type shocks. Our model favors a preshock gas-phase abundance of oxygen not in CO that is depleted by a least a factor of 2, presumably as water ice on grain surfaces. Both freezeout of H2O and photodissociation of H2O in the postshock gas must be significant to explain the weak H2O emission seen by SWAS and ISO from the shocked and postshock gas.

Snell, R. L.; Hollenbach, D.; Howe, J. E.; Neufeld, D. A.; Kaufman, M. J.; Melnick, G. J.; Bergin, E. A.; Wang, Z.

2005-02-01

294

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

E-print Network

of fault detection and isolation (FDI) in aircraft gas turbine engines. The FDI algorithms are built upon. The FDI methodology is based on the analysis of time series data of available sensors and/or analytically the algorithms of FDI, formulated inthefirstpart

Ray, Asok

295

Determination of organic sulphur compounds in sediments of the river Elbe using gas chromatography with flame photometric detection  

Microsoft Academic Search

Sediment samples from different reference sites representing typical situations on the river Elbe were analyzed for organo-sulphur compounds (OSC). Gas chromatography with sulphur specific flame-photometric detection was used for the identification and quantification of individual OSC. Chromatographic retention data for 42 standard heterocycles were determined and compared with the composition of sediment extracts. An extraction scheme used for the OSC

P. Heininger; E. Claus

1995-01-01

296

Fabrication of Polyaniline-Based Gas Sensors Using Piezoelectric Inkjet and Screen Printing for the Detection of Hydrogen Sulfide  

Microsoft Academic Search

This work describes a fully printable polyaniline-copper (II) chloride sensor for the detection of hydrogen sulfide gas. The sensing device is composed of screen printed silver interdigitated electrode (IDE) on a flexible PET substrate with inkjet printed layers of polyaniline and copper (II) chloride. The sensor is employed as a chemiresistor with changes in measured current being correlated with concentration.

Karl Crowley; Aoife Morrin; Roderick L. Shepherd; Marc in het Panhuis; Gordon G. Wallace; Malcolm R. Smyth; Anthony J. Killard

2010-01-01

297

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...

298

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

299

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

Microsoft Academic Search

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

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

2005-01-01

300

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

SciTech Connect

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

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

2012-09-30

301

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

302

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.; Miller, Michael A.

2007-03-13

303

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

DOEpatents

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

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

2010-08-24

304

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

SciTech Connect

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

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

2000-12-07

305

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

306

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

307

Rapid determination of total sulfur in fuels using gas chromatography with atomic emission detection.  

PubMed

The purpose of this study is to determine whether gas chromatography (GC)-atomic emission detection (AED) can be used in a low-resolution mode for rapid, accurate determinations of total sulfur in fuels at trace levels to complement other popular methods of total sulfur analysis. A method for the rapid determination of total sulfur in fuels (called "fast GC-AED") is developed. The method is tested on gasoline, jet fuel, kerosene, and diesel fuel with sulfur concentrations ranging from 125 mg/L down to 2.5 mg/L. Fast GC-AED shows better performance than traditional GC-AED for total sulfur determinations, especially for complex mixtures containing many different sulfur-containing compounds at trace levels. This method also shows that GC-AED can be used for both rapid determinations of total sulfur and traditional determinations of speciated sulfur without requiring equipment changes. Fast GC-AED is competitive with other popular methods for sulfur analysis. The 5-min program that is developed for fast GC-AED is comparable with the time scale of other methods, such as wavelength dispersive X-ray fluorescence and UV-fluorescence (2 to 5 min). Fast GC-AED also compares favorably with UV-fluorescence for trace sulfur determinations, demonstrating accuracy down to 2.5-mg/L sulfur. PMID:12433111

Link, Dirk D; Baltrus, John P; Rothenberger, Kurt S; Zandhuis, Paul; Minus, Donald; Striebich, Richard C

2002-10-01

308

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

PubMed

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

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

2012-09-28

309

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

SciTech Connect

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

NONE

1994-10-01

310

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

311

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. PMID:22355681

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

2011-01-01

312

Enhanced field ionization/desorption on branched silicon nanowires: applications in gas ionization detection  

NASA Astrophysics Data System (ADS)

We demonstrate anomalous gaseous field ionization and field desorption on branching intrinsic silicon nanowires grown by a two-step VLS technique. Field ionization and desorption I-V curves of argon, nitrogen, helium, and ammonia, were recorded individually within a wide pressure range (10-7 to 10 Torr). Field ionization initiated at sub volt was followed by field desorption at about 7 - 38 V (applied field of ~ 7×102 to 3.8×103 V/cm). Such voltages are three orders of magnitude smaller than the applied voltages required to generate field ionization on sharp metallic tips having the same tip curvature. The measured I-V curves were pressure dependent. Low voltage filed ionization and desorption phenomena were attributed to the combination effects of geometrical field enhancement on the apex of nanoscale silicon branches, field penetration, increased tunneling critical distance, band gap widening due to quantum confinement, and the surface states formed by the catalyst. The results presented herein suggest that gold terminated branching silicon nanowires could be strong candidates in building low power gas ionization sensors useful in highly selective detection of gases with low adsorption energies.

Banan-Sadeghian, R.; Islam, M. Saif

2010-04-01

313

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

314

Detection of non-milk fat in milk fat by gas chromatography and linear discriminant analysis.  

PubMed

Gas chromatography was utilized to determine triacylglycerol profiles in milk and non-milk fat. The values of triacylglycerol were subjected to linear discriminant analysis to detect and quantify non-milk fat in milk fat. Two groups of milk fat were analyzed: A) raw milk fat from the central region of Mexico (n = 216) and B) ultrapasteurized milk fat from 3 industries (n = 36), as well as pork lard (n = 2), bovine tallow (n = 2), fish oil (n = 2), peanut (n = 2), corn (n = 2), olive (n = 2), and soy (n = 2). The samples of raw milk fat were adulterated with non-milk fats in proportions of 0, 5, 10, 15, and 20% to form 5 groups. The first function obtained from the linear discriminant analysis allowed the correct classification of 94.4% of the samples with levels <10% of adulteration. The triacylglycerol values of the ultrapasteurized milk fats were evaluated with the discriminant function, demonstrating that one industry added non-milk fat to its product in 80% of the samples analyzed. PMID:19389942

Gutiérrez, R; Vega, S; Díaz, G; Sánchez, J; Coronado, M; Ramírez, A; Pérez, J; González, M; Schettino, B

2009-05-01

315

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

316

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

PubMed

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

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

2013-04-21

317

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

Microsoft Academic Search

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

1989-01-01

318

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

319

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

320

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

PubMed Central

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

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

2013-01-01

321

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

PubMed

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

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

2013-01-01

322

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

323

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

SciTech Connect

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

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

2008-12-15

324

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

PubMed

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

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

2012-05-01

325

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

326

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

NASA Astrophysics Data System (ADS)

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

Weiner, Aaron

327

Validated assay for the quantification of anastrozole in human plasma by capillary gas chromatography- 63Ni electron capture detection  

Microsoft Academic Search

An assay was developed for the quantification of anastrozole [2,2?-[5-(1H-1,2,4-triazol-1-ymethyl)-1,3-phenylene]bis(2-methylpropiononitrile)] in human plasma using liquid-liquid extraction. Anastrozole and an internal standard were chromatographed and detected by gas chromatography with electron capture detection, using a combination temperature-pressure program. The range of the assay is 3 to 100 ng\\/ml. Anastrozole was quantified by comparing its peak area to that of an internal

Mary J. H. Bock; Ilene Bara; Norman LeDonne; Angela Martz; Martin Dyroff

1997-01-01

328

Validated assay for the quantification of anastrozole in human plasma by capillary gas chromatography-63Ni electron capture detection.  

PubMed

An assay was developed for the quantification of anastrozole [2,2'-[5-(1H-1,2,4-triazol-1-ymethyl)-1,3-phenylene]bis(2-++ +methylpropiononitrile)] in human plasma using liquid-liquid extraction. Anastrozole and an internal standard were chromatographed and detected by gas chromatography with electron capture detection, using a combination temperature-pressure program. The range of the assay is 3 to 100 ng/ml. Anastrozole was quantified by comparing its peak area to that of an internal standard. A cross-validation of this assay was also successfully performed between several laboratories. PMID:9390722

Bock, M J; Bara, I; LeDonne, N; Martz, A; Dyroff, M

1997-10-24

329

Reduced and Oxidized Sulfur Compounds Detected by Evolved Gas Analyses of Materials from Yellowknife Bay, Gale Crater, Mars  

NASA Technical Reports Server (NTRS)

Sulfate minerals have been directly detected or strongly inferred from several Mars datasets and indicate that aqueous alteration of martian surface materials has occurred. Indications of reduced sulfur phases (e.g., sulfides) from orbital and in situ investigations of martian materials have been fewer in number, but these phases are observed in martian meteorites and are likely because they are common minor phases in basaltic rocks. Here we discuss potential sources for the S-bearing compounds detected by the Mars Science Laboratory (MSL) Sample Analysis at Mars (SAM) instrument’s evolved gas analysis (EGA) experiments.

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

2014-01-01

330

Detection of biomarkers in the organic matter of rocks from the Romashkinskoe oil field using gas chromatography-mass spectrometry  

Microsoft Academic Search

Polycyclic hydrocarbons (biomarkers) were detected in the organic matter of Paleozoic and pre-Paleozoic rocks from the Romashkinskoe\\u000a oil field in the Volga-Ural region using gas chromatography-mass spectrometry. Coefficients were calculated from the ratio\\u000a between tetra- and pentacyclic hydrocarbons, and the facial genetic types, possible generation sources, and evolution transformation\\u000a conditions of the initial organic matter were determined from the array

N. S. Sharipova; G. K. Budnikov; B. V. Uspenskii; G. P. Kayukova

2010-01-01

331

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

Microsoft Academic Search

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

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

2004-01-01

332

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

PubMed

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 gas chromatograph is an expensive apparatus and needs trained personnel. The less specific Halimeter is the most used apparatus in halitosis research. In this study a newly developed portable gas chromatograph, the OralChroma™ (Abilit Corporation, Japan), was evaluated for use in the field of halitosis. The results show that the OralChroma is a very sensitive apparatus for measuring VSCs. Just like standard gas chromatography, it can perfectly differentiate between intra-oral and extra-oral blood-borne halitosis, while the Halimeter can only detect intra-oral halitosis. The hardware of the OralChroma meets all the needs for becoming the apparatus of choice in the field of halitosis. However, the software needs a major revision. Sometimes, the concentrations given for the different VSCs are completely incorrect due to a wrong assignment of the place of the VSCs in the chromatogram. PMID:21386154

Tangerman, A; Winkel, E G

2008-03-01

333

Comprehensive trace level determination of organotin compounds in environmental samples using high-resolution gas chromatography with flame photometric detection  

SciTech Connect

A comprehensive method for trace analysis of mono-, di-, tri-, and some tetrasubstituted organotin compounds is presented. The ionic compounds are extracted from diluted aqueous solutions as chlorides by using a Tropolon-C/sub 18/ silica cartridge and from sediment and sewage sludge by using an ethereal tropolon solution. The extracted organotin compounds are ethylated by a Grignard reagent and analyzed by using high-resolution gas chromatography with flame photometric detection (HRGC/FPD). Gas chromatography/mass spectrometry (GC/MS) was used for confirmation. The extraction behavior, gas chromatographic retention, and photometric response of a series of organotin compounds are described, and the identification via electron impact (EI) and chemical ionization (CI) mass spectrometry is discussed. The main organotin compounds detected in various samples are butyltins; cyclohexyl- and phenyltins were identified in some of the sediment and sewage sludge samples. Methylbutyltins and tetrabutyltin were not detected. Concentrations were found to range from low ng/L (part per trillion) in surface water to low mg/kg (parts per million) in sewage sludge.

Mueller, M.D.

1987-02-15

334

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

NASA Astrophysics Data System (ADS)

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

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

335

Determination of organic compounds leached from municipal incinerator fly ash by water at different pH levels  

SciTech Connect

This study concerns the possibility of organic compounds entering the environment through the leaching of municipal incinerator fly ash with water. A Soxhlet extraction of fly ash with water, followed by a benzene/water solvent extraction was used to isolate organic compounds. The pH of the extracting liquid was varied (pH 4, 7, 10) and both the type and amount of compounds extracted differed. Many organic compounds including polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polycyclic aromatic compounds, phenols, and hydrocarbons were found in the water extracts. Gas chromatography/flame ionization detection, gas chromatography/electron capture detection, and gas chromatography/mass spectrometry using electron impact, positive and negative ion chemical ionization techniques were used for compound identification and quantitation.

Karasek, F.W.; Charbonneau, G.M.; Reuel, G.J.; Tong, H.Y.

1987-04-01

336

Calculating the detection limits of chamber-based greenhouse gas flux measurements  

Technology Transfer Automated Retrieval System (TEKTRAN)

Chamber-based measurement of greenhouse gas emissions from soil is a common technique. However, when changes in chamber headspace gas concentrations are small over time, determination of the flux can be problematic. Several factors contribute to the reliability of measured fluxes, including: samplin...

337

A Microcantilever-based Gas Flow Sensor for Flow Rate and Direction Detection  

Microsoft Academic Search

The purpose of this paper is to apply characteristics of residual stress that causes cantilever beams to bend for manufacturing a micro-structured gas flow sensor. This study uses a silicon wafer deposited silicon nitride layers, reassembled the gas flow sensor with four cantilever beams that perpendicular to each other and manufactured piezoresistive structure on each micro-cantilever by MEMS technologies, respectively.

Yu-hsiang Wang; Tzu-Han Hsueh; Rong-Hua Ma; Chia-Yen Lee; Lung-Ming Fu; Po-cheng Chou; Chien-Hsiung Tsai

2008-01-01

338

Detection and quantification of fugitive emissions from Colorado oil and gas production operations using remote monitoring  

EPA Science Inventory

Western states contain vast amounts of oil and gas production. For example, Weld County Colorado contains approximately 25,000 active oil and gas well sites with associated production operations. There is little information on the air pollutant emission potential from this source...

339

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

SciTech Connect

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{sub 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{sub 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{sub 2} particles (<5 {mu}m 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{sub 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.

Dansby-Sparks, Royce N. [University of Tennessee, Knoxville (UTK); Jin, Jun [University of Tennessee, Knoxville (UTK); Mechery, Shelly J [ORNL; Sampathkumaran, Uma [InnoSense Incorporates; Owens, Thomas W [ORNL; Yu, Bi Dan [InnoSense Incorporates; Goswami, Kisholoy [InnoSense Incorporates; Hong, Kunlun [ORNL; Grant, Joseph [NASA Stennis Space Center; Xue, Ziling {nmn} [ORNL

2009-01-01

340

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

E-print Network

in the detection of thin resistive layers and randomly dispersed resistive nodules. The laboratory test results indicated that the four-electrode configuration may be more appropriate for the detection of both thin resistive layers and random resistive nodules...

McClelland, Martha Ann

1994-01-01

341

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

PubMed Central

Ultrasonic measurement techniques for velocity estimation are currently widely used in fluid flow studies and applications. An accurate determination of interfacial position in gas-liquid two-phase flows is still an open problem. The quality of this information directly reflects on the accuracy of void fraction measurement, and it provides a means of discriminating velocity information of both phases. The algorithm known as Velocity Matched Spectrum (VM Spectrum) is a velocity estimator that stands out from other methods by returning a spectrum of velocities for each interrogated volume sample. Interface detection of free-rising bubbles in quiescent liquid presents some difficulties for interface detection due to abrupt changes in interface inclination. In this work a method based on velocity spectrum curve shape is used to generate a spatial-temporal mapping, which, after spatial filtering, yields an accurate contour of the air-water interface. It is shown that the proposed technique yields a RMS error between 1.71 and 3.39 and a probability of detection failure and false detection between 0.89% and 11.9% in determining the spatial-temporal gas-liquid interface position in the flow of free rising bubbles in stagnant liquid. This result is valid for both free path and with transducer emitting through a metallic plate or a Plexiglas pipe. PMID:24858961

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

2014-01-01

342

Realization of rapid debugging for detection circuit of optical fiber gas sensor: Using an analog signal source  

NASA Astrophysics Data System (ADS)

An optical fiber gas sensor mainly consists of two parts: optical part and detection circuit. In the debugging for the detection circuit, the optical part usually serves as a signal source. However, in the debugging condition, the optical part can be easily influenced by many factors, such as the fluctuation of ambient temperature or driving current resulting in instability of the wavelength and intensity for the laser; for dual-beam sensor, the different bends and stresses of the optical fiber will lead to the fluctuation of the intensity and phase; the intensity noise from the collimator, coupler, and other optical devices in the system will also result in the impurity of the optical part based signal source. In order to dramatically improve the debugging efficiency of the detection circuit and shorten the period of research and development, this paper describes an analog signal source, consisting of a single chip microcomputer (SCM), an amplifier circuit, and a voltage-to-current conversion circuit. It can be used to realize the rapid debugging detection circuit of the optical fiber gas sensor instead of optical part based signal source. This analog signal source performs well with many other advantages, such as the simple operation, small size, and light weight.

Tian, Changbin; Chang, Jun; Wang, Qiang; Wei, Wei; Zhu, Cunguang

2015-03-01

343

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

344

Final design review report for the RMCS Flammable Gas Detection Interlock  

SciTech Connect

This report document the completion of the formal design review for the RMCS (Rotary Mode Core Sampling) flammable gas detector interlock. This hydrogen/flammable gas interlock, a proposed addition to the RMCS system portable exhauster, in intended to support core sampling operations in waste tanks requiring flammable gas controls. The objective of this review was to approve new drawings at the 100% design completion state. The conclusion reached by the review committee was that the design was acceptable and efforts should continue toward fabrication and delivery.

Corbett, J.E., Westinghouse Hanford

1996-08-20

345

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

346

The Gas Exchange Experiment for life detection - The Viking Mars Lander.  

NASA Technical Reports Server (NTRS)

The Gas Exchange Experiment of the Viking mission accepts a sample of Martian soil, incubates this soil with nutrient medium, and periodically samples the enclosed atmosphere over this soil for the gases H2, N2, O2, Kr, and CO2. These gases are analyzed by an automated gas chromatograph, and the data are transmitted to earth. The design of the experiment and the qualitative and quantitative changes, if any, of gas composition should allow conclusions to be made on the presence of life on Mars. Data and theory substantiating this approach are presented.

Oyama, V. I.

1972-01-01

347

A-2005 Site environmental report appenDiX a: GloSSarY  

E-print Network

and beta GC/eCD gas chromatography/electron capture detector GC/mS gas chromatography/mass spectrometry GDS GroundwaterDischargeStandard GEL GeneralEngineeringLaboratory,LLC Gev giga (billion) electron volts gge gas agreement iC ion chromatography iCp/mS inductively coupled plasma/mass spectrometry iSmS

348

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

E-print Network

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

Fitzgerald, Kevin Francis

1984-01-01

349

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

E-print Network

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

Swager, Timothy Manning

350

Criteria for evaluating gas and bitumen anomalies detected by geochemical prospecting  

SciTech Connect

Anomalous and normal hydrocarbon-gas concentration patterns are considered for the upper levels of the sedimentary section in relation to the lithology and organic matter. Various parameters are identified that indicate disturbances in the gas system arising from influx of hydrocarbon gases from gas pools. Calculations are presented on a genetic criterion for evaluating the hydrocarbon-gas anomalies, which employ information on the type and extent of alteration of the organic matter in a reference horizon. The Tunguska and North Ustyurt sedimentary basins are considered to define bitumenological and physical criteria for the syngenetic and epigenetic bituminous material. Particular attention is given to the structural features of the chloroform benzene extract and the distribution of the n-alkanes.

Starobinets, I.S.; Bartashevich, O.V.; Yemets, T.P.; Lopatin, N.V.

1983-01-01

351

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

352

Post-dive ultrasound detection of gas in the liver of rats and scuba divers  

Microsoft Academic Search

In a previous study, we obtained histologic documentation of liver gas embolism in the rat model of rapid decompression. The\\u000a aim of the study was to assess in the same model occurrence and time course of liver embolism using 2-D ultrasound imaging,\\u000a and to explore by this means putative liver gas embolism in recreational scuba divers. Following 42 min compression at

Antonio L’Abbate; Claudio Marabotti; Claudia Kusmic; Antonino Pagliazzo; Alessandro Navari; Vincenzo Positano; Mario Palermo; Antonio Benassi; Remo Bedini

353

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

SciTech Connect

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

NONE

1995-10-01

354

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

PubMed

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

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

2010-06-15

355

A marine electromagnetic survey to detect gas hydrate at Hydrate Ridge, Oregon  

NASA Astrophysics Data System (ADS)

Gas hydrates are a potential energy resource and hazard for drilling and infrastructure, yet estimates of global volume vary by over three orders of magnitude. Hydrates are electrically resistive compared to water saturated sediment and so electromagnetic methods provide an additional tool to seismic surveys and drilling for determining hydrate saturations. A marine electromagnetic survey was carried out at Hydrate Ridge, Oregon, USA, with the aim of testing the use of controlled source electromagnetic (CSEM) and magnetotelluric (MT) methods to map gas hydrate and free gas below the gas hydrate stability zone. A 2-D CSEM inversion supports the scenario deduced from previous seismic and drilling results, which indicate two mechanisms of hydrate emplacement: a transport-dominated and reaction-dominated regime. A prominent resistive region of 2.5-4 ?m at a depth of about 130 mbsf, near the seismic bottom simulating reflector (BSR), suggests that 27 to 46 per cent of the bulk volume is filled with hydrate, depending on whether Archie's Law or the Hashin-Strikman bounds are used. This is representative of a reaction-dominated regime for hydrate emplacement, and where a significant low velocity zone exists based on a seismic tomography inversion, suggests large quantities of free gas below the BSR. Electrical resistivity logging while drilling (LWD) data show general agreement with the CSEM inversion model except for a CSEM-derived resistive region at seismic horizon A, known to transport free gas into the gas hydrate stability zone. Inversion of MT data collected simultaneously during the CSEM survey provides a complimentary low-resolution image of the shallow sediments and shows folding in the accretionary complex sediments similar to that imaged by a tomographic seismic velocity model.

Weitemeyer, K. A.; Constable, S.; Tréhu, A. M.

2011-10-01

356

A University of Texas Arlington group has developed a passive RFID tag and reader for wirelessly detecting the presence of stomach acid, gas and water in the esophagus.  

E-print Network

detecting the presence of stomach acid, gas and water in the esophagus. By Claire Swedberg April 10, 2007, as well as working with simulated stomach acid in a test tube. It is now preparing to conduct testing in the esophagus. The sensor is designed to measure the presence of stomach acid, gas and water in the esophagus

Chiao, Jung-Chih

357

Evaluation of Xenon Gas Detection as a Means for Identifying Buried Transuranic Waste at the Radioactive Waste Management Complex, Idaho National Environmental and Engineering Laboratory  

Microsoft Academic Search

Xenon is produced as a fission product in nuclear reactors and through spontaneous fission of some transuranic (TRU) isotopes. Xenon gas is nearly inert and will be released from buried TRU waste. This document describes and evaluates the potential for analyzing xenon isotopes in soil gas to detect TRU waste in the subsurface at the Idaho National Environmental and Engineering

P Evan Dresel; Scott R. Waichler

2004-01-01

358

Detection of extraction artifacts in the analysis of honey volatiles using comprehensive two-dimensional gas chromatography.  

PubMed

Extraction using headspace solid phase microextraction (HS-SPME) coupled to comprehensive two-dimensional gas chromatography with flame ionisation detection (GC×GC-FID) was employed to evaluate the effect of SPME fractionation conditions (heating time and temperature) on the generation of artifacts. The occurrence of artifacts was more pronounced at higher fractionation temperatures and times which caused significant changes in the chromatographic profiles. The identification of the volatile fraction of the honey blend was performed through a two-dimensional gas chromatograph coupled to a mass spectrometer with time of flight analyser (GC×GC-ToFMS) by comparing the first dimension linear temperature programmed retention index ((1)D-LTPRI) with the peak's identities provided by the mass spectral similarity search. Several artifacts were found and identified - such as hydroxymethylfurfural, methyl-furone and furfural - and some of them were not previously detected as such in honey samples. These compounds were either the result of hydrolysis or thermal decomposition of components already present in the honey samples. This occurrence was attributed to the increased detectability provided by GC×GC compared to conventional GC. The possible emergence of previously unknown extraction artifacts as a general tendency related use of GC×GC instead of conventional GC is discussed as a result of these observations. PMID:23870897

Rivellino, Sandra Regina; Hantao, Leandro Wang; Risticevic, Sanja; Carasek, Eduardo; Pawliszyn, Janusz; Augusto, Fabio

2013-12-01

359

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

PubMed Central

An indium nitride (InN) gas sensor of 10 nm in thickness has achieved detection limit of 0.4 ppm acetone. The sensor has a size of 1 mm by 2.5 mm, while its sensing area is 0.25 mm by 2 mm. Detection of such a low acetone concentration in exhaled breath could enable early diagnosis of diabetes for portable physiological applications. The ultrathin InN epilayer extensively enhances sensing sensitivity due to its strong electron accumulation on roughly 5–10 nm deep layers from the surface. Platinum as catalyst can increase output current signals by 2.5-fold (94 vs. 37.5 ?A) as well as reduce response time by 8.4-fold (150 vs. 1,260 s) in comparison with bare InN. More, the effect of 3% oxygen consumption due to breath inhalation and exhalation on 2.4 ppm acetone gas detection was investigated, indicating that such an acetone concentration can be analyzed in air. PMID:22969342

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

2012-01-01

360

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

NASA Astrophysics Data System (ADS)

The development of a technically sound approach to detecting the subsurface release of noble gas radionuclides is a critical component of the on-site inspection (OSI) protocol under the Comprehensive Nuclear Test Ban Treaty. In this context, we are investigating a variety of technical challenges that have a significant bearing on policy development and technical guidance regarding the detection of noble gases and the creation of a technically justifiable OSI concept of operation. The work focuses on optimizing the ability to capture radioactive noble gases subject to the constraints of possible OSI scenarios. This focus results from recognizing the difficulty of detecting gas releases in geologic environments—a lesson we learned previously from the non-proliferation experiment (NPE). Most of our evaluations of a sampling or transport issue necessarily involve computer simulations. This is partly due to the lack of OSI-relevant field data, such as that provided by the NPE, and partly a result of the ability of computer-based models to test a range of geologic and atmospheric scenarios far beyond what could ever be studied by field experiments, making this approach very highly cost effective. We review some highlights of the transport and sampling issues we have investigated and complete the discussion of these issues with a description of a preliminary design for subsurface sampling that addresses some of the sampling challenges discussed here.

Carrigan, Charles R.; Sun, Yunwei

2014-03-01

361

Determination of Trichlorfon Pesticide Residues in Milk via Gas Chromatography with ?-Electron Capture Detection and GC-MS  

PubMed Central

The pesticide trichlorfon is readily degraded under experimental conditions to dichlorvos. A method has therefore been developed by which residues of trichlorfon in milk are determined as dichlorvos, using gas chromatography with ?-electron capture detection. The identification of dichlorvos was confirmed by mass spectrometry. Milk was extracted with acetonitrile followed by centrifugation, freezing lipid filtration, and partitioning into dichloromethane. The residue after partitioning of dichloromethane was dissolved in ethyl acetate for gas chromatography. Recovery concentration was determined at 0.5, 1.0, and 2.0 of times the maximum permitted residue limits (MRLs) for trichlorfon in milk. The average recoveries (n = 6) ranged from 92.4 to 103.6%. The repeatability of the measurements was expressed as relative standard deviations (RSDs) ranging from 3.6%, to 6.7%. Limit of detection (LOD) and limit of quantification (LOQ) were 3.7 and 11.1 ?g/l, respectively. The accuracy and precision (expressed as RSD) were estimated at concentrations from 25 to 250 ?g/l. The intra- and inter-day accuracy (n = 6) ranged from 89.2%to 91% and 91.3% to 96.3%, respectively. The intra- and inter-day precisions were lower than 8%. The developed method was applied to determine trichlorfon in real samples collected from the seven major cities in the Republic of Korea. No residual trichlorfon was detected in any samples. PMID:24278518

Hem, Lina; Khay, Sathya; Choi, Jeong-Heui; Morgan, E.D.; El-Aty, A.M. Abd

2010-01-01

362

Dielectrophoresis-assembled zeolitic imidazolate framework nanoparticle-coupled resonators for highly sensitive and selective gas detection.  

PubMed

This work reports on zeolitic imidazolate framework (ZIF)-coupled microscale resonators for highly sensitive and selective gas detection. The combination of microscale resonators and nanoscale materials simultaneously permits the benefit of larger capture area for adsorption from the resonator and enhanced surface adsorption capacity from the nanoscale ZIF structure. Dielectrophoresis (DEP) was demonstrated as a novel method for directly assembling concentrated ZIF nanoparticles on targeted regions of silicon resonant sensors. As part of the dielectrophoretic assembly process, the first ever measurements of the Clausius-Mossotti factor for ZIFs were conducted to determine optimal conditions for DEP assembly. The first ever real-time adsorption measurements of ZIFs were also performed to investigate the possibility of inherent gas selectivity. The ZIF-coupled resonators demonstrated sensitivity improvement up to 150 times over a bare silicon resonator with identical dimensions, and real-time adsorption measurements of ZIFs revealed different adsorption time constants for IPA and CO2. PMID:24099583

Hwang, Yongha; Sohn, Hyunmin; Phan, Anh; Yaghi, Omar M; Candler, Rob N

2013-11-13

363

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

NASA Technical Reports Server (NTRS)

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

Gregory, G. L.

1976-01-01

364

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

SciTech Connect

Pore structure and connectivity determine how microstructured materials perform in applications such as catalysis, fluid storage and transport, filtering, or as reactors. We report a model study on silica aerogel using a recently introduced time-of-flight (TOF) magnetic resonance imaging technique to characterize the flow field and elucidate the effects of heterogeneities in the pore structure on gas flow and dispersion with Xe-129 as the gas-phase sensor. The observed chemical shift allows the separate visualization of unrestricted xenon and xenon confined in the pores of the aerogel. The asymmetrical nature of the dispersion pattern alludes to the existence of a stationary and a flow regime in the aerogel. An exchange time constant is determined to characterize the gas transfer between them. As a general methodology, this technique provides new insights into the dynamics of flow in porous media where multiple phases or chemical species may be present.

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

2005-10-03

365

Laboratory Studies Of Titan Haze: Simultaneous In Situ Detection Of Gas And Particle Species  

NASA Astrophysics Data System (ADS)

Analyses of data obtained by multiple instruments carried by Cassini and Huygens have increased our knowledge of the composition of Titan’s atmosphere. While a wealth of new information about the aerosols in Titan’s atmosphere was obtained, their composition is still not well constrained. Laboratory experiments will therefore play a key role in furthering our understanding of the chemical processes resulting in the formation of haze in Titan’s atmosphere and its possible composition. We have obtained simultaneous in situ measurements of the gas- and particle-phase compositions produced by our Titan atmosphere simulation experiments (see e.g. [1]). The gas phase composition was measured using a Proton-Transfer Ion-Trap Mass Spectrometer (PIT-MS) and the aerosol composition was measured using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). This complementary set of measurements will allow us to address the partitioning of gas- and aerosol-phase species. Knowledge of the gas phase composition in which the particles in our experiments form allows both for better comparison to the chemistry that is occurring in Titan’s atmosphere and for enabling more accurate determination of the possible pathways involved in the transition from gas phase to aerosol. We will compare the results from experiments that used two different initial gas mixtures (98% N2/2% CH4 and 98%N2/2%CH4/50 ppm CO) and two different energy sources to initiate the chemical reactions that result in particle formation (spark discharge using a Tesla coil or FUV irradiation from a deuterium lamp (115-400 nm)). [1] Trainer, M.G., et al. (2012) Astrobiology, 12, 315-326. SMH is supported by NSF Astronomy and Astrophysics Postdoctoral Fellowship AST-1102827.

Horst, Sarah; Li, R.; Yoon, H.; Hicks, R.; de Gouw, J.; Tolbert, M.

2012-10-01

366

Detection and tracking of gas clouds in an urban area by imaging infrared spectroscopy  

NASA Astrophysics Data System (ADS)

The release of toxic industrial compounds in urban areas is a threat for the population and the environment. In order to supply emergency response forces with information about the released compounds after accidents or terrorist attacks, monitoring systems such as the scanning imaging spectrometer SIGIS 2 or the hyperspectral imager HI 90 were developed. Both systems are based on the method of infrared spectroscopy. The systems were deployed to monitor gas clouds released in the harbor area of Hamburg. The gas clouds were identified, visualized and quantified from a distance in real time. Using data of two systems it was possible to identify contaminated areas and to determine the source location.

Sabbah, Samer; Rusch, Peter; Gerhard, Jörn-Hinnrich; Harig, Roland

2013-05-01

367

Use of gas chromatography-ion trap tandem mass spectrometry for the detection and characterization of microorganisms in complex samples  

Microsoft Academic Search

Gas chromatography-mass spectrometry (GC-MS) can be applied to detect and characterize microorganisms in clinical and environmental\\u000a samples, and microbial contaminants in biotechnological production cultures. With this approach, unique microbial monomeric\\u000a compounds, known as chemical markers, are used as analytes. In the present article, two GC-MS-based techniques, viz. GC-ion\\u000a trap tandem MS (GC-MS-MS) and conventional quadrupole GC-MS used in the selected

Lennart Larsson; Anita Saraf

1997-01-01

368

Determination of primary and secondary amines in foodstuffs using gas chromatography and chemiluminescence detection with a modified thermal energy analyser.  

PubMed

A simple method is described for the determination of primary and secondary amines in foodstuffs by gas chromatography with a modified thermal energy analyser, operated in the nitrogen mode. Food samples were subjected to mineral oil vacuum distillation and the isolated amines were derivatized with benzenesulphonyl chloride to form the corresponding sulphonamides, which were fractionated to yield primary and secondary amine derivatives using a modified Hinsberg procedure. The detection limit for individual amines using a 10-g food sample was 10 micrograms/kg (ppb) and recoveries were in excess of 80%. PMID:2013610

Pfundstein, B; Tricker, A R; Preussmann, R

1991-02-01

369

Determination of a cyclooxygenase II inhibitor in human plasma by capillary gas chromatography with mass spectrometric detection  

Microsoft Academic Search

Sensitive methods based on capillary gas chromatography (GC) with mass spectrometric (MS) detection in a selected-ion monitoring mode (SIM) for the determination of a cyclooxygenase II (COX-II) inhibitor (3-isopropoxy-4-(4-methanesulfonylphenyl)-5,5?-dimethyl-5H-furan-2-one, I) in human plasma, in two concentration ranges of 0.1–20 and 5–1000ng\\/ml, are described. Following liquid–liquid extraction, the residue, after evaporation of the organic phase to dryness, was reconstituted in acetonitrile

J. D.-Y. Dru; C. M. Chavez-Eng; M. L. Constanzer; B. K. Matuszewski

2004-01-01

370

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

SciTech Connect

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

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

1993-07-09

371

DETECTION OF OUTFLOWING AND EXTRAPLANAR GAS IN DISKS IN AN ASSEMBLING GALAXY CLUSTER AT z = 0.37  

SciTech Connect

We detect ionized gas characteristics indicative of winds in three disk-dominated galaxies that are members of a super-group at z = 0.37 that will merge to form a Coma-mass cluster. All three galaxies are IR luminous (L{sub IR} > 4 Multiplication-Sign 10{sup 10} L{sub Sun }, SFR > 8 M{sub Sun} yr{sup -1}) and lie outside the X-ray cores of the galaxy groups. We find that the most IR-luminous galaxy has strong blueshifted and redshifted emission lines with velocities of {approx} {+-} 200 km s{sup -1} and a third, blueshifted ({approx}900 km s{sup -1}) component. This galaxy's line widths (H{beta}, [O III]{lambda}5007, [N II], H{alpha}) correspond to velocities of 100-1000 km s{sup -1}. We detect extraplanar gas in two of the three galaxies with SFR >8 M{sub Sun} yr{sup -1} whose orientations are approximately edge-on and which have integral field unit (IFU) spaxels off the stellar disk. IFU maps reveal that the extraplanar gas extends to r{sub h} {approx} 10 kpc; [N II] and H{alpha} line widths correspond to velocities of {approx}200-400 km s{sup -1} in the disk and decrease to {approx}50-150 km s{sup -1} above the disk. Multi-wavelength observations indicate that the emission is dominated by star formation. Including the most IR-luminous galaxy we find that 18% of supergroup members with SFR >8 M{sub Sun} yr{sup -1} show ionized gas characteristics indicative of outflows. This is a lower limit as showing that gas is outflowing in the remaining, moderately inclined, galaxies requires a non-trivial decoupling of contributions to the emission lines from rotational and turbulent motion. Ionized gas mass loss in these winds is {approx}0.1 M{sub Sun} yr{sup -1} for each galaxy, although the winds are likely to entrain significantly larger amounts of mass in neutral and molecular gases.

Freeland, Emily; Tran, Kim-Vy H.; Irwin, Trevor [George P. and Cynthia W. Mitchell Institute, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Giordano, Lea [Institute for Theoretical Physics, University of Zuerich, CH-8057 Zuerich (Switzerland); Saintonge, Amelie [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Zaritsky, Dennis; Just, Dennis, E-mail: freeland@physics.tamu.edu [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

2011-12-15

372

A micromachined calorimetric gas sensor: an application of electrodeposited nanostructured palladium for the detection of combustible gases.  

PubMed

Palladium films with regular nanoarchitectures were electrochemically deposited from the hexagonal (H1) lyotropic liquid crystalline phase of the nonionic surfactant octaethyleneglycol monohexadecyl ether (C16EO8) onto micromachined silicon hotplate structures. The H1-e Pd films were shown to have high surface areas (approximately 28 m2 g(-1)) and to act as effective and stable catalysts for the detection of methane in air on heating to 500 degrees C. The response of the H1-e Pd-coated planar pellistors was found to be linearly proportional to the concentration of methane between 0 and 2.5% in air with a detection limit below 0.125%. Our results show that the electrochemical deposition of nanostructured metal films offers a promising approach to the fabrication of micromachined calorimetric gas sensors for combustible gases. PMID:12530828

Bartlett, Philip N; Guerin, Samuel

2003-01-01

373

Water determination in active pharmaceutical ingredients using ionic liquid headspace gas chromatography and two different detection protocols.  

PubMed

A rapid, accurate, precise and versatile analytical method was developed for the detection and quantification of water in solid active pharmaceutical ingredients (APIs). The headspace gas chromatography (HSGC) method utilized an ionic liquid (IL) based open tubular capillary GC column to increase sensitivity and ruggedness of this method. ILs are also utilized as the headspace solvent because of their low vapor pressure, unique physiochemical properties and high thermal stability. This method is not affected by side reactions and solubility problems which are common with Karl Fischer Titration (KFT) methods. Nor is it as limited as weight loss on drying approaches. The ability to use either/both modern thermal conductivity or barrier ion discharge GC detection provides flexibility, different dynamic ranges and sensitivity. The developed method also was shown to be broadly applicable. PMID:24561336

Frink, Lillian A; Weatherly, Choyce A; Armstrong, Daniel W

2014-06-01

374

Local Frequency Based Estimators for Anomaly Detection in Oil and Gas Applications  

E-print Network

in the bore well which is typical in oil production. The short time Fourier transform and dynamical systems industrial applications such as the smart grid and oil and gas are continuously monitored. The massive of sensors to measure the flow rates, as well as the physical and chemical characteristics that affect

Slatton, Clint

375

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

NASA Technical Reports Server (NTRS)

A miniature gas chromatography (GC) system was designed and fabricated using silicon micromachining and integrated circuit (IC) processing techniques. The silicon micromachined gas chromatography system (SMGCS) is composed of a miniature sample injector that incorporates a 10 microliter sample loop; a 0.9 meter long, rectangular shaped (300 micrometer width and 10 micrometer height) capillary column coated with a 0.2 micrometer thick copper phthalocyanine (CuPc) stationary phase; and a dual detector scheme based upon a CuPc-coated chemiresistor and a commercially available 125 micrometer diameter thermal conductivity detector (TCD) bead. Silicon micromachining was employed to fabricate the interface between the sample injector and the GC column, the column itself, and the dual detector cavity. A novel IC thin-film processing technique was developed to sublime the CuPc stationary phase coating on the column walls that were micromachined in the host silicon wafer substrate and Pyrex (r) cover plate, which were then electrostatically bonded together. The SMGCS can separate binary gas mixtures composed of parts-per-million (ppm) concentrations of ammonia (NH3) and nitrogen dioxide (NO2) when isothermally operated (55-80 degrees C). With a helium carrier gas and nitrogen diluent, a 10 microliter sample volume containing ammonia and nitrogen dioxide injected at 40 psi ((2.8 x 10(exp 5)Pa)) can be separated in less than 30 minutes.

Kolesar, Edward S.; Reston, Rocky R.

1995-01-01

376

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

NASA Astrophysics Data System (ADS)

This chapter reviews the development of optical gas sensors, starting with an initial emphasis on optical-fibre remoted techniques and finishing with a particular focus on our own group's work on highly selective methods using correlation spectroscopy. This latter section includes extensive theoretical modelling of a correlation spectroscopy method, and compares theory with practice for a CO2 sensor.

Dakin, John P.; Chambers, Paul

377

A marine electromagnetic survey to detect gas hydrate at Hydrate Ridge, Oregon  

Microsoft Academic Search

Gas hydrates are a potential energy resource and hazard for drilling and infrastructure, yet estimates of global volume vary by over three orders of magnitude. Hydrates are electrically resistive compared to water saturated sediment and so electromagnetic methods provide an additional tool to seismic surveys and drilling for determining hydrate saturations. A marine electromagnetic survey was carried out at Hydrate

K. A. Weitemeyer; S. Constable; A. M. Tréhu

2011-01-01

378

ZnO nanowires-C microfiber hybrid nanosensor for liquefied petroleum gas detection.  

PubMed

Zinc oxide nanowires are integrated onto carbon microfibers using a two-step approach which includes electrochemical deposition of zinc and its thermal oxidation. Such nano-on-micro hybrid architecture is then used as resistive gas sensor. Some properties like mechanical flexibility, low cost and large-area fabrication make this design appealing for different applications. The huge surface-to-volume ratio of such structure comes from being structured at both microscale and nanoscale (ZnO nanowires and C microfiber) and leads to a strong and rapid response/recovery times when it is used as a gas sensor. The fabrication process of the ZnO-microC device is very simple and doesn't involve any expensive lithographic step. The sensors show excellent liquefied petroleum gas sensing properties, with very fast response on gas exposure (about 3 s) and very good reversibility (less than 2%). In addition, the carbon microfiber substrate allows the use of the ZnO-microC sensor also in applications where flexibility is required (for example integrated in fabric). PMID:24757984

Le, D T T; Iannotta, S; Hieu, N V; Corradi, C; Huy, T Q; Pola, M; Tonezzer, M

2014-07-01

379

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

SciTech Connect

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

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

2009-02-27

380

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

PubMed

Gas turbines are considered as one kind of the most important devices in power engineering and have been widely used in power generation, airplanes, and naval ships and also in oil drilling platforms. However, they are monitored without man on duty in the most cases. It is highly desirable to develop techniques and systems to remotely monitor their conditions and analyze their faults. In this work, we introduce a remote system for online condition monitoring and fault diagnosis of gas turbine on offshore oil well drilling platforms based on a kernelized information entropy model. Shannon information entropy is generalized for measuring the uniformity of exhaust temperatures, which reflect the overall states of the gas paths of gas turbine. In addition, we also extend the entropy to compute the information quantity of features in kernel spaces, which help to select the informative features for a certain recognition task. Finally, we introduce the information entropy based decision tree algorithm to extract rules from fault samples. The experiments on some real-world data show the effectiveness of the proposed algorithms. PMID:25258726

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

2014-01-01

381

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

PubMed Central

Gas turbines are considered as one kind of the most important devices in power engineering and have been widely used in power generation, airplanes, and naval ships and also in oil drilling platforms. However, they are monitored without man on duty in the most cases. It is highly desirable to develop techniques and systems to remotely monitor their conditions and analyze their faults. In this work, we introduce a remote system for online condition monitoring and fault diagnosis of gas turbine on offshore oil well drilling platforms based on a kernelized information entropy model. Shannon information entropy is generalized for measuring the uniformity of exhaust temperatures, which reflect the overall states of the gas paths of gas turbine. In addition, we also extend the entropy to compute the information quantity of features in kernel spaces, which help to select the informative features for a certain recognition task. Finally, we introduce the information entropy based decision tree algorithm to extract rules from fault samples. The experiments on some real-world data show the effectiveness of the proposed algorithms. PMID:25258726

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

2014-01-01

382

Calculating the detection limits of chamber-based soil greenhouse gas flux measurements  

Technology Transfer Automated Retrieval System (TEKTRAN)

Renewed interest in quantifying greenhouse gas emissions from soil has lead to an increase in the application of chamber-based flux measurement techniques. Despite the apparent conceptual simplicity of chamber-based methods, nuances in chamber design, deployment, and data analyses can have marked ef...

383

Natural gas  

NSDL National Science Digital Library

Natural gas is used as a means of power in households. Natural gas has no natural odor, so an odor is added to the gas. This is useful because gas leaks can be detected better and it also reduces the risk of accidents in homes.

N/A N/A (None; )

2003-07-27

384

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

E-print Network

With the recent development of temperature measurement systems, continuous wellbore temperature profiles can be obtained with high precision. Small temperature changes can be detected by modern temperature-measuring instruments, such as fiber optic...

Yoshioka, Keita

2007-09-17

385

Detection of gaseous compounds by needle trap sampling and direct thermal-desorption photoionization mass spectrometry: concept and demonstrative application to breath gas analysis.  

PubMed

A fast detection method to analyze gaseous organic compounds in complex gas mixtures was developed, using a needle trap device (NTD) in conjunction with thermal-desorption photoionization time-of-flight mass spectrometry (TD-PI-TOFMS). The mass spectrometer was coupled via a deactivated fused silica capillary to an injector of a gas chromatograph. In the hot injector, the analytes collected on the NTD were thermally desorbed and directly transferred to the PI-TOFMS ion source. The molecules are softly ionized either by single photon ionization (SPI, 118 nm) or by resonance enhanced multiphoton ionization (REMPI, 266 nm), and the molecular ion signals are detected in the TOF mass analyzer. Analyte desorption and the subsequent PI-TOFMS detection step only lasts ten seconds. The specific selectivity of REMPI (i.e., aromatic compounds) and universal ionization characteristics render PI-MS as a promising detection system. As a first demonstrative application, the alveolar phase breath gas of healthy, nonsmoking subjects was sampled on NTDs. While smaller organic compounds such as acetone, acetaldehyde, isoprene, or cysteamine can be detected in the breath gas with SPI, REMPI depicts the aromatic substances phenol and indole at 266 nm. In the breath gas of a healthy, smoking male subject, several xenobiotic substances such as benzene, toluene, styrene, and ethylbenzene can be found as well. Furthermore, the NTD-REMPI-TOFMS setup was tested for breath gas taken from a mechanically ventilated pig under continuous intravenous propofol (2,6-diisopropylphenol, narcotic drug) infusion. PMID:25517186

Kleeblatt, Juliane; Schubert, Jochen K; Zimmermann, Ralf

2015-02-01

386

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

PubMed Central

Soft rot is a commonly occurring potato tuber disease that each year causes substantial losses to the food industry. Here, we explore the possibility of early detection of the disease via gas/vapor analysis, in a laboratory environment, using a recent technology known as FAIMS (Field Asymmetric Ion Mobility Spectrometry). In this work, tubers were inoculated with a bacterium causing the infection, Pectobacterium carotovorum, and stored within set environmental conditions in order to manage disease progression. They were compared with controls stored in the same conditions. Three different inoculation time courses were employed in order to obtain diseased potatoes showing clear signs of advanced infection (for standard detection) and diseased potatoes with no apparent evidence of infection (for early detection). A total of 156 samples were processed by PCA (Principal Component Analysis) and k-means clustering. Results show a clear discrimination between controls and diseased potatoes for all experiments with no difference among observations from standard and early detection. Further analysis was carried out by means of a statistical model based on LDA (Linear Discriminant Analysis) that showed a high classification accuracy of 92.1% on the test set, obtained via a LOOCV (leave-one out cross-validation). PMID:25171118

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

2014-01-01

387

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

PubMed

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

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

2014-01-01

388

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

389

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

SciTech Connect

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

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

1994-07-01

390

A method for detecting breakthrough of organic solvent vapors in a charcoal tube using semiconductor gas sensors  

SciTech Connect

This study developed a method for detecting organic vapors that break through charcoal tubes, using semiconductor gas sensors as a breakthrough detector of vapors. A glass column equipped with two sensors was inserted in Teflon tubing, and air containing organic vapor was introduced at a constant flow rate. After the output signal of the sensors became stable, a charcoal tube was inserted into the tubing at the upstream of the sensors. The resistance of the sensors was collected temporally in an integrated circuit (IC) card. The vapor concentration of the air near the sensors was measured with a gas chromatograph (GC) equipped with a flame ionization detector (FID) at intervals of 5 minutes to obtain the breakthrough curve. When the relative humidity was zero, the output signals of the sensors began to change before the breakthrough point (1% breakthrough time). This tendency was almost the same for methyl acetate, ethyl acetate, isopropyl alcohol (IPA), toluene, and chloroform. For dichloromethane and 1,1,1-trichloroethane, the time when the sensor output signals began to rise was almost the same as the breakthrough point. When the relative humidity was 80 percent, the sensors could also detect many vapors before the breakthrough point, but they could not perceive dichloromethane and chloroform vapors. A personal sampling system with a breakthrough detector was developed and its availability is discussed.

Hori, Hajime; Noritake, Yuji; Murobushi, Hisako; Higashi, Toshiaki; Tanaka, Isamu

1999-08-01

391

Detection of interstellar NH sub 3 in the far-warm and dense gas in Orion-KL  

NASA Technical Reports Server (NTRS)

The detection of the (J,K) = a(4,3) yields s(3,3) rotation inversion transition of ammonia at 124.6 microns toward the center of the Orion-KL region is reported. The line is in emission and has a FWHM or = to 30 km s 0.15. The far IR ammonia line emission probably comes mainly from the 'hot core', a compact region of warm, very dense gas previously identified by the radio inversion lines of NH3. The a(4,3) yields s(3,3) line is very optically thick, and since it is seen in emission, radiative excitation of the (4,3) NH3 level by far IR emission from dust within the source can be ruled out. Radiative excitation via the 10 microns of vibrational transitions of NH3 also seems unlikely. Hence, the (4,3) level is probably collisionally excited and the gas in the hot core region is warmer than the dust. Since the far IR line emission is highly trapped, densities of approximately 10 to the 7th power cu cm are high enough to explain the observations. Shock heating by the mass outflow from IRc2 may account for the high gas temperatures in the hot core region.

Townes, C. H.; Gentzel, R.; Watson, D. M.; Storey, J. W. V.

1982-01-01

392

Multi-scale Detection of Organic and Inorganic Signatures Provides Insights into Gas Shale Properties and Evolution  

SciTech Connect

Organic geochemical analyses, including solvent extraction or pyrolysis, followed by gas chromatography and mass spectrometry, are generally conducted on bulk gas shale samples to evaluate their source and reservoir properties. While organic petrology has been directed at unravelling the matrix composition and textures of these economically important unconventional resources, their spatial variability in chemistry and structure is still poorly documented at the sub-micrometre scale. Here, a combination of techniques including transmission electron microscopy and a synchrotron-based microscopy tool, scanning transmission X-ray microscopy, have been used to characterize at a multiple length scale an overmature organic-rich calcareous mudstone from northern Germany. We document multi-scale chemical and mineralogical heterogeneities within the sample, from the millimetre down to the nanometre-scale. From the detection of different types of bitumen and authigenic minerals associated with the organic matter, we show that the multi-scale approach used in this study may provide new insights into gaseous hydrocarbon generation/retention processes occurring within gas shales and may shed new light on their thermal history.

Bernard, S.; Horsfield, B; Schultz, H; Schreiber, A; Wirth, R; Thi AnhVu, T; Perssen, F; Konitzer, S; Volk, H; et. al.

2010-01-01

393

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

DOEpatents

A method and apparatus are described for the quantitative analysis of vaporizable compounds, and in particular of polycyclic aromatic hydrocarbons which may be induced to fluoresce. The sample to be analyzed is injected into a gas chromatography column and is eluted through a narrow orifice into a vacuum chamber. The free expansion of the eluted sample into the vacuum chamber creates a supersonic molecular beam in which the sample molecules are cooled to the extent that the excited vibrational and rotational levels are substantially depopulated. The cooled molecules, when induced to fluoresce by laser excitation, give greatly simplified spectra suitable for analytical purposes. The laser induced fluorimetry provides great selectivity, and the gas chromatograph provides quantitative transfer of the sample to the molecular beam. 3 figures, 2 tables.

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

1982-04-26

394

Selective filter for SnO 2-based gas sensor: application to hydrogen trace detection  

Microsoft Academic Search

The main drawback of the SnO2-based gas sensors is their low selectivity. In this study, we present a highly selective hydrogen sensor with minimum cross sensitivity to ethanol, methane, carbon monoxide and hydrogen sulfide. Thick film SnO2 sensors are treated by hexamethyldisiloxane (HMDS) at high temperature (500–600°C). After this treatment, the electrical properties of sensors are greatly modified: the sensitivity

G. Tournier; C. Pijolat

2005-01-01

395

Carbon14 based biomass fraction detection in power plant flue gas CO2: validation and results  

Microsoft Academic Search

Replacing non-renewable fossil fuels by renewable fuels like biomass-based ones is one of the tools to combat increasing atmospheric CO2 concentrations. In order to promote biofuel-based electricity generation, a tool must be available to reliably quantify the bio-based CO2 fraction in the flue gas of a power plant. For traditional power plants, such as coal-fired ones to which wood is

S. W. L. Palstra; H. A. J. Meijer

2009-01-01

396

[Gas chromatographic study of broth cultures of microorganisms as a method of detecting extraterrestrial life].  

PubMed

The method of pyrolysis--gas chromatography was used to study the composition of cultural liquids obtained upon the incubation of desert soil samples in a rich growth medium. The composition of pyrolysis products was found to depend on the time of incubation. Cultural liquids differed in their composition from the original growth medium. This method is a dynamical one, and can be employed to control the activity of microorganisms. PMID:152380

Imshenetskii, A A; Murzakov, B G

1978-01-01

397

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

398

Detection of accreting circumstellar gas around weak emission-line Herbig Ae/Be stars  

NASA Technical Reports Server (NTRS)

Archival and recent International Ultraviolet Explorer (IUE) high dispersion spectra of late B stars which reveal the presence of accreting gas with velocities as high as 350 km/s, collisional ionization of the accreting gas to temperatures above the stellar T(sub eff), and column densities intermediate between those observed toward classical Herbig Ae/Be stars and the nearby proto-planetary system beta Pictoris are presented. One of the stars HD 176386, while lacking obvious optical signatures of youth, is a member of the R CrA star formation region, and with an inferred age of 2.8 Myr has not yet arrived on the zero-age main sequence (ZAMS). The other object, an isolated, field B star with pronounced IR excess due to warm, circumstellar dust, 51 Oph, exhibits only modest H(alpha) emission. The combination of high velocity, accreting gas in systems with IR excesses due to circumstellar dust suggests that not only are these objects candidate proto-planetary systems, but that they may represent an extension to higher stellar masses of the weak-emission pre-main sequence (PMS) stars.

Grady, C. A.; Perez, M. R.; The, P. S.

1993-01-01

399

Detection of accreting circumstellar gas around weak emission-line Herbig Ae/Be stars  

NASA Technical Reports Server (NTRS)

We present archival and recent IUE high dispersion spectra of late B stars which reveal the presence of accreting gas with velocities as high as 350 km/s, collisional ionization of the accreting gas to temperatures above the stellar T(sub eff), and column densities intermediate between those observed toward classical Herbig Ae/Be stars and the nearby proto-planetary system beta Pictoris. One of the stars, HD 176386, while lacking obvious optical signatures of youth, is a member of the R CrA star formation region, and with an inferred age of 2.8 Myr has not yet arrived on the zero-age main sequence (ZAMS). The other object, an isolated, field B star with pronounced IR excess due to warm, circumstellar dust, 51 Oph, exhibits only modest H(alpha) emission. The combination of high velocity, accreting gas in systems with IR excesses due to circumstellar dust suggests that not only are these objects candidate proto-planetary systems, but that they may represent an extension to higher stellar masses of the weak-emission pre-main sequence (PMS) stars.

Grady, C. A.; Perez, M. R.; The, P. S.

1994-01-01

400

Development of Gas Proportional Scintillation Counter for Light Heavy-Ion Detection  

SciTech Connect

In recent years, nuclear data have been needed in the medical field. Nuclear data induced by light heavy ions are especially needed at high precision for cancer treatment, although there are not enough usable data at present.We have a plan to measure light heavy-ion nuclear data with a dE-E detector. Low density is needed for the dE detector. We have two options for the dE detector: a semiconductor detector (SSD) and a Gas Counter. On one hand, SSD has good energy resolution, but on the other hand, it is expensive and its decay time is on the 100-microsecond order. A Gas Counter is inexpensive, and a Gas Proportional Scintillation Counter (GPSC) has fast decay time. Then, we developed a GPSC for the dE detector, and its evaluation experiment was carried out at the Heavy Ion Medical Accelerator in Chiba (HIMAC).We will report the results of the experiment with the performance of the GPSC.

Hohara, Sin-ya; Imamura, Minoru; Kin, Tadahiro; Yamashita, Yusuke; Maki, Daiske; Saiho, Fuminobu; Ikeda, Katsuhiko; Uozumi, Yusuke; Matoba, Masaru [Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 812-8581 (Japan)

2005-05-24

401

The detection of molecular gas in the ring galaxy Arp 143  

NASA Technical Reports Server (NTRS)

We have used the NRAO 12 m telescope to map the inner 10 kpc of NGC 2445, the ring galaxy in Arp 143, in CO-12(J = 1-0). Emission is peaked near the ring galaxy nucleus, but we find evidence for an additional asymmetric and extended CO component. This extended CO distribution is consistent with an approximately 8 kpc diameter crescent-shaped ring of molecular gas, similar to the one seen in H I, accounting for approximately half of the total CO flux. Assuming this distribution, we derive a total H2 mass for NGC 2445 of 0.4-2.4 x 10(exp 10) solar mass, depending on whether a Galactic or low-metallicity Large Magellanic Cloud (LMC) conversion factor is used, and an H2/H I mass ratio between 0.9 and 5. The ring is experiencing low rates of massive star formation despite very high gas column densities. We find that the gas surface density exceeds the critical threshold for star formation throughout the ring, even without a possible contribution from a significant molecular component. The absence of vigorous star formation is most simply understood in terms of its youth (approximately 30 Myr): massive stars have not had time to form in large numbers. Our results support the interpretation that NGC 2445 is a nascent ring galaxy, seen prior to its ring starburst phase.

Higdon, James L.; Smith, Beverly J.; Lord, Steven D.; Rand, Richard J.

1995-01-01

402

Gold nanoparticles-peptide based gas sensor arrays for the detection of food aromas.  

PubMed

A gas sensor array based on peptide modified gold nanoparticles deposited onto 20MHz quartz crystal microbalances has been realized. Glutathione and its constituting aminoacids and dipeptides have been used as ligands. A great increase in sensitivity (2 orders of magnitude) was achieved using gold nanoparticles versus monolayer modified QCMs. The sensors have been characterised in terms of sensitivity for hexane, water, trimethylammine and ethanol. Highest sensitivity was found for water. The ability to discriminate typical food aromas as cis-3-hexenol, isopentylacetate, ethylacetate, and terpinen-4-ol dissolved in different solvents was studied using a gas sensor array constituted by gold nanoparticles modified with the glutathione peptides, thioglycolic acid and an heptapeptide. The array was found able to discriminate the food aromas, the response being dependent on the polarity of the solvent used. Tests on real olive oil samples gave a satisfactory separation among samples having defects versus non defected samples demonstrating that this approach has high potential for the development of gas sensor arrays to be used in real samples. PMID:23261699

Compagnone, D; Fusella, G C; Del Carlo, M; Pittia, P; Martinelli, E; Tortora, L; Paolesse, R; Di Natale, C

2013-04-15

403

Molecularly imprinted polymer sensors for detection in the gas, liquid, and vapor phase.  

PubMed

Fast, reliable, and inexpensive analytical techniques for detection of airborne chemical warfare agents are desperately needed. Recent advances in the field of molecularly imprinted polymers have created synthetic nanomaterials that can sensitively and selectively detect these materials in aqueous environments, but thus far, they have not been demonstrated to work for detection of vapors. The imprinted polymers function by mimicking the function of biological receptors. They can provide high sensitivity and selectivity but, unlike their biological counterparts, maintain excellent thermal and mechanical stability. The traditional imprinted polymer approach is further enhanced in this work by the addition of a luminescent europium that has been introduced into the polymers to provide enhanced chemical affinity as well as a method for signal transduction to indicate the binding event. The europium in these polymers is so sensitive to the bound target; it can distinguish between species differing by a single methyl group. The imprinted polymer technology is fiber optic-based making it inexpensive and easily integratable with commercially available miniature fiber optic spectrometer technologies to provide a shoebox size device. In this work, we will describe efforts to apply these sensors for detection of airborne materials and vapors. Successful application of this technology will provide accurate low level vapor detection of chemical agents or pesticides with little to no false positives. PMID:22641530

Jenkins, Amanda L; Ellzy, Michael W; Buettner, Leonard C

2012-06-01

404

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

NASA Astrophysics Data System (ADS)

A population of intermediate-mass black holes (BHs) is predicted to be freely floating in the Milky Way (MW) halo, due to gravitational wave recoil, ejection from triple BH systems, or tidal stripping in the dwarf galaxies that merged to make the MW. As these BHs traverse the gaseous MW disk, a bow shock forms, producing detectable radio and mm/sub-mm synchrotron emission from accelerated electrons. We calculate the synchrotron flux to be $\\sim \\rm 0.01-10\\, mJy$ at GHz frequency, detectable by Jansky Very Large Array, and $\\sim 10-100\\,\\mu\\rm Jy$ at $\\sim10^{10}-10^{12} \\,\\rm Hz$ frequencies, detectable by Atacama Large Millimeter/sub-millimter Array. The discovery of the floating BH population will provide insights on the formation and merger history of the MW as well as on the evolution of massive BHs in the early Universe.

Wang, Xiawei; Loeb, Abraham

2014-12-01

405

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

E-print Network

A population of intermediate-mass black holes (BHs) is predicted to be freely floating in the Milky Way (MW) halo, due to gravitational wave recoil, ejection from triple BH systems, or tidal stripping in the dwarf galaxies that merged to make the MW. As these BHs traverse the gaseous MW disk, a bow shock forms, producing detectable radio synchrotron emission from accelerated electrons. We calculate the synchrotron flux to be $\\sim \\rm 0.01-10\\, mJy$ at GHz frequency, detectable by JVLA, and $\\sim0.1-1\\,\\mu\\rm Jy$ in the infrared, detectable by HST and JWST. The discovery of the floating BH population will provide insights on the formation and merger history of the MW as well as on the evolution of massive BHs in the early Universe.

Wang, Xiawei

2014-01-01

406

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

NASA Astrophysics Data System (ADS)

A population of intermediate-mass black holes (BHs) is predicted to be freely floating in the Milky Way (MW) halo, due to gravitational wave recoil, ejection from triple BH systems, or tidal stripping in the dwarf galaxies that merged to make the MW. As these BHs traverse the gaseous MW disc, a bow shock forms, producing detectable radio synchrotron emission from accelerated electrons. We calculate the synchrotron flux to be ˜0.01-10 mJy at GHz frequency, detectable by Jansky Very Large Array, and ˜ 0.1-1 ?Jy in the infrared, detectable by Hubble Space Telescope and James Webb Space Telescope. The discovery of the floating BH population will provide insights on the formation and merger history of the MW as well as on the evolution of massive BHs in the early Universe.

Wang, Xiawei; Loeb, Abraham

2014-06-01

407

Persistence behaviour of deltamethrin on tea and its transfer from processed tea to infusion.  

PubMed

The dynamics and residues of deltamethrin in a tea grown in an open field ecosystem were investigated. The quantification was performed using gas chromatography-electron capture detection (GC-ECD) and confirmed by gas chromatograph-mass spectrometry (GC-MS) in selective ion monitoring (SIM) mode. The method was validated using blank samples spiked at three levels and the results showed that recoveries ranged from 87% to 101% with relative standard deviations (RSD) ranging of 0.7-7.1%. The residues of deltamethrin were found to dissipate following first order kinetics with half-life ranging between 3.04 and 3.54d for two different rates of foliar application. The deltamethrin residues are present in the processed tea are not transferred into the tea infusion during the infusion process, since their water solubility is extremely low. These results can be utilized in formulating the spray schedule and safety evaluation on deltamethrin tea crop. PMID:24997931

Paramasivam, M; Chandrasekaran, S

2014-09-01

408

Determination of ten pyrethroids in various fruit juices: comparison of dispersive liquid-liquid microextraction sample preparation and QuEChERS method combined with dispersive liquid-liquid microextraction.  

PubMed

Dispersive liquid-liquid microextraction (DLLME) sample preparation and the quick, easy, cheap, effective, rugged and safe (QuEChERS) method combined with DLLME were developed and compared for the analysis of ten pyrethroids in various fruit juices using gas chromatography-electron capture detection (GC-ECD). QuEChERS-DLLME method has found its widespread applications to all the fruit juices including those samples with more complex matrices (orange, lemon, kiwi and mango) while DLLME was confined to the fruit juices with simpler matrices (apple, pear, grape and peach). The two methods provided acceptable recoveries and repeatability. In addition, the applicabilities of two methods were demonstrated with the real samples and further confirmed by gas chromatography-mass spectrometry (GC-MS). PMID:24767068

Zhang, Yaohai; Zhang, Xuelian; Jiao, Bining

2014-09-15

409

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

NASA Technical Reports Server (NTRS)

A method for detecting a target fluid in a fluid sample comprising a first fluid and the target fluid using photoacoustic spectroscopy (PAS), comprises a) providing a light source configured to introduce an optical signal having at least one wavelength into the fluid sample; b) modulating the optical signal at a desired modulation frequency such that the optical signal generates an acoustic signal in the fluid sample; c) measuring the acoustic signal in a resonant acoustic detector; and d) using the phase of the acoustic signal to detect the presence of the target fluid.

Kosterev, Anatoliy (Inventor)

2010-01-01

410

Development and validation of a gas chromatography-flame ionization detection method for quantifying sucrose in equine serum.  

PubMed

A simple and accurate method for quantifying sucrose in equine serum that can be applied to sucrose permeability testing in the horse was developed and validated using gas chromatography with flame ionization detection. The assay provided an acceptable degree of linearity, accuracy, and precision at concentrations of sucrose as low as 2.34 ?mol/l and as high as 20.45 ?mol/l. Percentage recovery of sucrose from serum ranged from 89% to 102%; repeatability and intermediate precision (relative standard deviation) ranged from 3.6% to 6.7% and 4.1% to 9.3%, respectively. The limit of detection was 0.73 ?mol/l. No interfering peaks were observed except lactose, which gave 2 peaks, one of which overlapped partially with sucrose. To evaluate the suitability of the method for quantifying sucrose in serum samples from horses with naturally occurring gastric ulceration, 10 horses with and without naturally occurring gastric ulceration were subjected to sucrose permeability testing. All horses demonstrated an increase in serum sucrose concentration over time following oral administration of sucrose; however, the increase from baseline was significant for horses with gastric ulceration at 45 min (P = 0.0082) and 90 min (P = 0.0082) when compared with healthy horses. It was concluded that gas chromatography with flame ionization detection is a valid method for quantifying sucrose in equine serum and can be applied directly to the analysis of sucrose in equine serum as part of a larger validation study aimed at developing a blood test for the diagnosis of gastric ulcers in horses. PMID:24518277

Hewetson, Michael; Aaltonen, Kaisa; Tulamo, Riitta-Mari; Sankari, Satu

2014-03-01

411

Early detection method of corrosion on buried steel gas pipeline using wireless sensor network  

Microsoft Academic Search

Early detection on any abnormality on the pipeline such as leakage is essential for efficient management. As to date, wireless sensors have been widely used to gather information in monitoring reliability of the pipeline. The commonly used sensors are temperature and pressure sensors. One of the issues that relate to pipeline monitoring is the reactive rather than proactive maintenance approach

Mohd Saiful Abdul Rahman; Halabi Hasbullah

2010-01-01

412

Gas chromatography for detection of citrus infestation by fruit fly larvae (Diptera: Tephritidae)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tephritid fruit flies are serious economic pests worldwide. As larvae, they feed and develop within the pulp of host fruits, making infestation difficult to detect by visual inspection. At U.S. ports of entry, incoming produce shipments are checked for infestation by manually cutting open a small ...

413

Sinking cities in Indonesia: ALOS PALSAR detects rapid subsidence due to groundwater and gas extraction  

E-print Network

to re- solve land subsidence in western Indonesia with high spatial and temporal resolution. The data/year. Land subsidence is detected near Lhokseumawe, in Medan, Jakarta, Bandung, Blanakan, Pekalongan and land use. Despite the fact that subsidence is taking place in compressible deposits there is no clear

Amelung, Falk

414

Detecting Greenhouse-Gas-Induced Climate Change with an Optimal Fingerprint Method  

Microsoft Academic Search

A strategy using statistically optimal fingerprints to detect anthropogenic climate change is outlined and applied to near-surface temperature trends. The components of this strategy include observations, information about natural climate variability, and a `guess pattern' representing the expected time-space pattern of anthropogenic climate change. The expected anthropogenic climate change is identified through projection of the observations onto an appropriate optimal

Gabriele C. Hegerl; Hans von Storch; Klaus Hasselmann; Benjamin D. Santer; Ulrich Cubasch; Philip D. Jones

1996-01-01

415

Figure 1. Principle of wireless detection of gas centration with a chipless sensor.  

E-print Network

presents a fully inkjet printed wireless chipless sensor for carbon dioxide detection. It is composed or a hazardous level of radiation. In this special case, chipless sensors [3]-[4] are more robust, and can still been studied for their sensing properties are CNTs [3], graphene [5] and silicon nanowires [4

Tentzeris, Manos

416

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

417

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

PubMed

A new multi-dimensional analytical method using gas chromatography-nitrogen phosphorus detection (GC-NPD) and gas chromatography-mass spectrometry (GC-MS) was developed for qualitative and quantitative measurement of lincomycin and spectinomycin residues in food animal tissues. This method is based on a new extraction procedure using accelerated solvent extraction (ASE). The analytes were extracted by phosphate buffer with trichloroacetic acid deproteinization and clean-up by C?? solid-phase extraction (SPE) adding dodecanesulfonic acid sodium salt as an ion-pair reagent. The eluted fraction was evaporated and derivatised with N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) for GC-NPD analysis and GC-MS confirmation. Parameters for extraction pressure, temperature and cycle of ASE, clean-up, derivatisation and analysis procedure were optimised. The method was validated in muscle, kidney and liver of swine, bovine with a low concentration (limit of quantification) of 16.4 and 21.4 µg kg?¹ for these two analytes using GC-NPD. For GC-MS, the limits of quantification were 4.1 and 5.6 µg kg?¹, respectively. Spiked recoveries from levels of 20 to 200 µg kg?¹ were found to be between 73% and 99% with a relative standard deviation (RSD) of less than 17% in GC-NPD. For GC-MS, levels from 5 to 20 µg kg?¹ had between 70% and 93% with an RSD of less than 21%. This rapid and reliable method can be used for the characterisation and quantification of residues of lincomycin and spectinomycin in animal tissues. PMID:21240824

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

2011-02-01

418

Tunable fiber laser based photoacoustic gas sensor for early fire detection  

NASA Astrophysics Data System (ADS)

A photoacoustic gas sensor using a near-infrared tunable fiber laser and based on wavelength modulation spectroscopy technique is developed. This sensor is capable of quasi-simultaneous quantification of water vapour, acetylene, carbon dioxide, and carbon monoxide (H2O, C2H2, CO and CO2) concentrations in the fire emulator. The feasibility of using this sensor as an early fire detector was demonstrated. The fire warning gases from smoldering paper were measured. The peak concentrations of gases from smoldering paper were 20,300 ppm H2O, 2.1 ppm C2H2, 756 ppm CO, and 1612 ppm CO2 after 400 s.

Wang, Jianwei; Wang, Huili

2014-07-01

419

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

PubMed Central

Palladium (Pd) has received attention as an ideal hydrogen sensor material due to its properties such as high sensitivity and selectivity to hydrogen gas, fast response, and operability at room temperature. Interestingly, various Pd nanostructures that have been realized by recent developments in nanotechnologies are known to show better performance than bulk Pd. This review highlights the characteristic properties, issues, and their possible solutions of hydrogen sensors based on the low-dimensional Pd nanostructures with more emphasis on Pd thin films and Pd nanowires. The finite size effects, relative strengths and weaknesses of the respective Pd nanostructures are discussed in terms of performance, manufacturability, and practical applicability. PMID:22346605

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

2011-01-01

420

Detection of Shock-Heated Gas Using the Sz Effect in Rxj 1347-1145  

NASA Technical Reports Server (NTRS)

Using the MUSTANG 3.3 mm bolometer array on the GBT we have measured the Sunyaev-Zel'dovich Effect (SZE) in the most x-ray luminous cluster known, RXJ 1 347-1145 (z=0.45) at a resolution of 10" (fwhm). This is the highest resolution image of the SZE to date and confirms previous indications of a localized departure from pressure equilibrium in the form of a small, very hot (>0 keV) parcel of gas, presumably resulting from a merger shock. We discuss the measurements, their interpretation, and future work.

Mason, Brian S.; Dicker, S.; Korngut, P.; Devlin, M.; Cotton, W.; Koch, P.; Molnar, S.; Aguirre, J.; Benford, D.; Staguhn, J.; Moseley, H.; Irwin, K.; Sievers, J.; Ade, P.

2010-01-01

421

Qualitative and quantitative analysis of pyrolysis oil by gas chromatography with flame ionization detection and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry.  

PubMed

Pyrolysis oils have attracted a lot of interest, as they are liquid energy carriers and general sources of chemicals. In this work, gas chromatography with flame ionization detector (GC-FID) and two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) techniques were used to provide both qualitative and quantitative results of the analysis of three different pyrolysis oils. The chromatographic methods and parameters were optimized and solvent choice and separation restrictions are discussed. Pyrolysis oil samples were diluted in suitable organic solvent and were analyzed by GC×GC-TOFMS. An average of 300 compounds were detected and identified in all three samples using the ChromaToF (Leco) software. The deconvoluted spectra were compared with the NIST software library for correct matching. Group type classification was performed by use of the ChromaToF software. The quantification of 11 selected compounds was performed by means of a multiple-point external calibration curve. Afterwards, the pyrolysis oils were extracted with water, and the aqueous phase was analyzed both by GC-FID and, after proper change of solvent, by GC×GC-TOFMS. As previously, the selected compounds were quantified by both techniques, by means of multiple point external calibration curves. The parameters of the calibration curves were calculated by weighted linear regression analysis. The limit of detection, limit of quantitation and linearity range for each standard compound with each method are presented. The potency of GC×GC-TOFMS for an efficient mapping of the pyrolysis oil is undisputable, and the possibility of using it for quantification as well has been demonstrated. On the other hand, the GC-FID analysis provides reliable results that allow for a rapid screening of the pyrolysis oil. To the best of our knowledge, very few papers have been reported with quantification attempts on pyrolysis oil samples using GC×GC-TOFMS most of which make use of the internal standard method. This work provides the ground for further analysis of pyrolysis oils of diverse sources for a rational design of both their production and utilization process. PMID:21036362

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

2011-05-27

422

Derivatization of organophosphorus nerve agent degradation products for gas chromatography with ICPMS and TOF-MS detection.  

PubMed

Separation and detection of seven V-type (venomous) and G-type (German) organophosphorus nerve agent degradation products by gas chromatography with inductively coupled plasma mass spectrometry (GC-ICPMS) is described. The nonvolatile alkyl phosphonic acid degradation products of interest included ethyl methylphosphonic acid (EMPA, VX acid), isopropyl methylphosphonic acid (IMPA, GB acid), ethyl hydrogen dimethylamidophosphate sodium salt (EDPA, GA acid), isobutyl hydrogen methylphosphonate (IBMPA, RVX acid), as well as pinacolyl methylphosphonic acid (PMPA), methylphosphonic acid (MPA), and cyclohexyl methylphosphonic acid (CMPA, GF acid). N-(tert-Butyldimethylsilyl)-N-methyltrifluroacetamide with 1% TBDMSCl was utilized to form the volatile TBDMS derivatives of the nerve agent degradation products for separation by GC. Exact mass confirmation of the formation of six of the TBDMS derivatives was obtained by GC-time of flight mass spectrometry (TOF-MS). The method developed here allowed for the separation and detection of all seven TBDMS derivatives as well as phosphate in less than ten minutes. Detection limits for the developed method were less than 5 pg with retention times and peak area precisions of less than 0.01 and 6%, respectively. This method was successfully applied to river water and soil matrices. To date this is the first work describing the analysis of chemical warfare agent (CWA) degradation products by GC-ICPMS. PMID:17356819

Richardson, Douglas D; Caruso, Joseph A

2007-06-01