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Sample records for gas chromatography-electron-capture detection

  1. Identification and quantification of lignans in wheat bran by gas chromatography-electron capture detection.

    PubMed

    Cukelj, Nikolina; Jakasa, Ivone; Sarajlija, Hrvoje; Novotni, Dubravka; Curi?, Duška

    2011-03-15

    Whole grain cereals are an important source of bioavailable lignans, the group of compounds with potential anti-cancerogenic, antioxidant, anti-proliferative, pro-apoptotic, and antiangiogenic properties. The aim of this work was to develop a sensitive method for determination of wheat bran lignans. The analysis of lignans secoisolariciresinol, hydroxymatairesinol, lariciresinol, matairesinol, pinoresinol, syringaresinol is based on derivatization with pentafluoropropionic anhydride (PFPA) and gas chromatography-electron capture detection (GC-ECD), using styrene glycol as internal standard. To our knowledge, this is the first time that EC detection has been used for lignan analysis. The results show that the technique is reproducible and sensitive enough for detecting lignans in wheat at parts-per-billion (ppb) levels, except for hydroxymatairesinol. The method developed showed good recovery (85-105%) and precision (4-20%) for five types of lignans and thus represents a simpler and more affordable alternative to state-of-the-art wheat lignan liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. PMID:21315909

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

    PubMed

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

    2014-01-01

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

  3. Optimization of nonequilibrium liquid-phase microextraction for the determination of nitrobenzenes in aqueous samples by gas chromatography-electron capture detection.

    PubMed

    Zhao, Rusong; Chu, Shaogang; Xu, Xiaobai

    2004-04-01

    In the present work, a novel method for the determination of nitrobenzenes in water has been described. It is based on nonequilibrium liquid-phase microextraction and gas chromatography-electron capture detection (GC-ECD). Extraction conditions such as solvent selection, organic solvent dropsize, stirring rate, content of NaCl and extraction time were found to have significant influence on extraction efficiency. The optimized conditions were 1.5 microl toluene and 20 min extraction time at 400 rpm stirring rate without NaCl addition. The linear range was 0.1 - 50 microg l(-1) for most nitrobenzenes. The limits of detection (LODs) ranged from 0.02 microg l(-1) (for 2.6-DNT) to 0.4 microg l(-1) (for NB); and relative standard deviations (RSD) for most of the nitrobenzenes at the 10 microg l(-1) level, except for 2,6-DNT in 3 microg l(-1), were below 10%. Natural samples collected from Miyun Reservoir and tap water samples from a laboratory were successfully analyzed using the proposed method, but none of the analytes were detected. The relative recoveries of spiked water samples (at the 10 microg l(-1) level except for 2,6-DNT in 3 microg l(-1)) were from 82.6 to 118.7%. PMID:15116965

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

    PubMed

    Zhou, Qingxiang; Wu, Wei; Xie, Guohong

    2013-01-01

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

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

    PubMed

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

    2011-05-01

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

  6. Use of solid-phase microextraction/gas chromatography-electron capture detection for the determination of energetic chemicals in marine samples.

    PubMed

    Monteil-Rivera, Fanny; Beaulieu, Chantale; Hawari, Jalal

    2005-02-25

    Gas chromatography with electron capture detection (GC-ECD) is a highly explosive-sensitive analytical technique. However, its application to the analysis of sediment extracts is hampered by the presence of numerous endogenous interferences. In the present study, solid-phase microextraction (SPME) was used both as a purification technique for sediment extracts and as an extraction technique for water samples prior to analysis by GC-ECD. SPME/GC-ECD coupling was optimized and applied to the trace analysis of nine explosives including nitroaromatics and RDX in real seawater and marine sediment samples. Addition of a high concentration of salt (30%, w/v) in the aqueous medium and use of a carbowax/divinylbenzene (CW/DVB) coating led to optimal extraction efficiencies. Method detection limits (MDLs) ranged from 0.05 to 0.81 microg/L in water and from 1 to 9 microg/kg in dry sediment. Except for RDX, spike recoveries in seawater were satisfactory (89-147%) when samples were fortified at 2 microg/L of each analyte. Spike recoveries from dry sediment fortified at 10 microg/kg of each analyte gave lower recoveries but these could also be due to degradation in the matrix. With a smaller volume of aqueous sample required compared to solid-phase extraction (SPE), SPME is an attractive method for the analysis of limited volumes of sediment pore-water. Moreover, the use of SPME eliminated interferences present in sediment extracts thus allowing the detection of the target analytes that were otherwise difficult to detect by direct injection. PMID:15794569

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

    PubMed

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

    2012-11-30

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

  8. 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

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

    2011-07-15

    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

  9. Hollow fiber liquid-liquid-liquid microextraction followed by solid-phase microextraction and in situ derivatization for the determination of chlorophenols by gas chromatography-electron capture detection.

    PubMed

    Saraji, Mohammad; Ghani, Milad

    2015-10-30

    A method based on the combination of hollow fiber liquid-liquid-liquid microextraction and solid-phase microextraction (SPME) followed by gas chromatography-electron capture detection was developed for the determination of chlorophenols in water and wastewater samples. Silica microstructures fabricated on the surface of a stainless steel wire were coated by an organic solvent and used as a SPME fiber. The analytes were extracted through a hollow fiber membrane containing n-decane from sample solution to an alkaline aqueous acceptor phase. They were then extracted and in situ derivatized on the SPME fiber using acetic anhydride. Experimental parameters such as the type of extraction solvent, acceptor phase NaOH concentration, donor phase HCl concentration, the amount of derivatizing reagent, salt concentration, stirring rate and extraction time were investigated and optimized. The precision of the method for the analytes at 0.02-30?gL(-1) concentration level ranged from 7.1 to 10.2% (as intra-day relative standard deviation) and 6.4 to 9.8% (as inter-day relative standard deviation). The linear dynamic ranges were in the interval of 5-500?gL(-1), 0.05-5?gL(-1), 0.02-1?gL(-1) and 0.001-0.5?gL(-1) for 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol, respectively. The enrichment factors were between 432 and 785. The limits of detection were in the range of 0.0004-1.2?gL(-1). Tap water, well water and wastewater samples were also analyzed to evaluate the method capability for real sample analysis. PMID:26411480

  10. 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...

  11. Sample pretreatment optimization for the analysis of short chain chlorinated paraffins in soil with gas chromatography-electron capture negative ion-mass spectrometry.

    PubMed

    Chen, Laiguo; Huang, Yumei; Han, Shuang; Feng, Yongbin; Jiang, Guo; Tang, Caiming; Ye, Zhixiang; Zhan, Wei; Liu, Ming; Zhang, Sukun

    2013-01-25

    Accurately quantifying short chain chlorinated paraffins (SCCPs) in soil samples with gas chromatograph coupled with electron capture negative ionization mass spectrometry (GC-ECNI-MS) is difficult because many other polychlorinated pollutants are present in the sample matrices. These pollutants (e.g., polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and toxaphene) can cause serious interferences during SCCPs analysis with GC-MS. Four main columns packed with different adsorbents, including silica gel, Florisil and alumina, were investigated in this study to determine their performance for separating interfering pollutants from SCCPs. These experimental results suggest that the optimum cleanup procedure uses a silica gel column and a multilayer silica gel-Florisil composite column. This procedure completely separated 22 PCB congeners, 23 OCPs and three toxaphene congeners from SCCPs. However, p,p'-DDD, cis-nonachlor and o,p'-DDD were not completely removed and only 53% of the total toxaphene was removed. This optimized method was successfully and effectively applied for removing interfering pollutants from real soil samples. SCCPs in 17 soil samples from different land use areas within a suburban region were analyzed with the established method. The concentrations of SCCPs in these samples were between 7 and 541 ng g(-1) (mean: 84 ng g(-1)). Similar homologue SCCPs patterns were observed between the soil samples collected from different land use areas. In addition, lower chlorinated (Cl(6/7)) C(10)- and C(11)- SCCPs were the dominant congeners. PMID:23287694

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

    SciTech Connect

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

    1994-12-01

    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).

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

    PubMed

    Wang, Tielong; Hu, Jiye; Liu, Chaolun

    2014-05-01

    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

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

    PubMed

    Leong, Mei-I; Huang, Shang-Da

    2008-11-21

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

  15. Detection of gas leakage

    DOEpatents

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

    2012-06-19

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

  16. Detection of gas leakage

    DOEpatents

    Thornberg, Steven M; Brown, Jason

    2015-02-17

    A method of detecting leaks and measuring volumes as well as a device, the Power-free Pump Module (PPM), provides a self-contained leak test and volume measurement apparatus that requires no external sources of electrical power during leak testing or volume measurement. The PPM 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) using a venturi pump, 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.

  17. Gas Flow Detection System

    NASA Technical Reports Server (NTRS)

    Moss, Thomas; Ihlefeld, Curtis; Slack, Barry

    2010-01-01

    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.

  18. Fission gas detection system

    DOEpatents

    Colburn, Richard P. (Pasco, WA)

    1985-01-01

    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.

  19. Advances in gas leak detection

    SciTech Connect

    Hennigar, G.W.

    1985-11-01

    The use of laser instruments in leak detection is discussed. These instruments respond to and measure gases in the light beam. The use of sound for leak detection involves the insertion of a known sound wave into the gas in the main. Another method, leak sound correlation, is described as a computer-based detection system that applies computer sonic detection technology to pinpoint and evaluate difficult leaks in pipeline networks. Various types of internal leak detection devices are described which can be used for specific operations, associated mainly with transmission lines.

  20. Determination of Chlorophenols in Water Samples Using Solid-Phase Extraction Enrichment Procedure and Gas Chromatography Analysis.

    PubMed

    Ben Hassine, S; Hammami, B; Touil, S; Driss, M R

    2015-11-01

    Solid-phase extraction (SPE) procedure followed by derivatization and gas chromatography electron capture detection was evaluated for the determination of trace amounts of chlorophenols (CPs) in waters samples. Different parameters affecting extraction efficiency such as, volume of elution solvent, volume and pH of water sample, quantity of sorbent phase were studied and optimized. SPE was carried out on polystyrene-divinylbenzene (Bond Elut ENV) and high recoveries were obtained using 1000 mg of this cartridge for the treatment of 500 mL of acidified water sample. The described method was then tested on spiked tap, mineral, ground and surface water samples. The overall procedure provided limits of detection lower than 20 ng L(-1), recoveries of 70 %-106 % and an enrichment factor of 500 for the examined CPs in 500 mL water samples. Among the studied compounds, pentachlorophenol was detected in tap water at a concentration level of 0.06 µg L(-1). PMID:26067701

  1. Structure elucidation of an artifact discharging from rubber-based vial closures by means of gas chromatography/tandem mass spectrometry.

    PubMed

    Kapp, Thomas; Vetter, Walter

    2006-12-01

    The use of vial closures equipped with butyl rubber septa may lead to sample contamination by rubber additives discharging from the septum material. In this study, the structure elucidation of an artifact causing intense signals in gas chromatography/electron capture negative ion mass spectrometry (GC/ECNI-MS) and gas chromatographic analyses with electron capture detection is described. Tentative identification of the leached compound was achieved by employing tandem mass spectrometric techniques both in electron capture negative ion and in electron ionization modes. The artifact could thus be characterized as 2-benzothiazolyl-N,N-dimethyl dithiocarbamate, which is a known vulcanization accelerator for rubber. It is conceivable that the identified compound or related substances are also used in other applications. Therefore, two food-related matrixes were investigated for a possible migration of this compound into foods. During these analyses, the tentatively identified rubber additive was detected in an aqueous extract of a rubber seal ring for canning jars. GC/ECNI-MS provided better sensitivity and selectivity than GC/EI-MS for the determination of the rubber additive and other mercaptobenzothiazole-derived substances. PMID:17134153

  2. 33 CFR 127.1203 - Gas detection.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...2011-07-01 2011-07-01 false Gas detection. 127.1203 Section 127.1203...Gas Equipment § 127.1203 Gas detection. (a) Each waterfront facility...of this section must serve to detect leaks, check structures for gas...

  3. 33 CFR 127.1203 - Gas detection.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...2010-07-01 2010-07-01 false Gas detection. 127.1203 Section 127.1203...Gas Equipment § 127.1203 Gas detection. (a) Each waterfront facility...of this section must serve to detect leaks, check structures for gas...

  4. 33 CFR 127.1203 - Gas detection.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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

  5. 33 CFR 127.1203 - Gas detection.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

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

  6. 33 CFR 127.1203 - Gas detection.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

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

  7. Gas Phase Detection of Benzocyclopropenyl.

    PubMed

    Maity, Surajit; Steglich, Mathias; Maier, John P

    2015-11-01

    The gas phase detection of benzocyclopropenyl is reported. In this aromatic resonance stabilized radical, a large angular strain is present due to a three-membered ring annelated to a benzene. The resonant two-color two-photon ionization technique is used to record the D1((2)A2) ? D0((2)B1) electronic transition of this radical after the in situ synthesis in a discharge source. The spectrum features absorptions up to 3300 cm(-1) above the origin band at 19?305 cm(-1). Benzocyclopropenyl is possibly the major product of the bimolecular reaction of benzene and an atomic carbon at low temperatures. PMID:26463227

  8. Preparation of porous aromatic framework/ionic liquid hybrid composite coated solid-phase microextraction fibers and their application in the determination of organochlorine pesticides combined with GC-ECD detection.

    PubMed

    Wu, Mingxue; Chen, Gang; Liu, Ping; Zhou, Weihong; Jia, Qiong

    2016-01-01

    A novel hybrid material incorporating porous aromatic frameworks and an ionic liquid, 1-(triethoxy silyl)propyl-3-aminopropyl imidazole hexafluorophosphate, was prepared as solid-phase microextraction coating and employed for the extraction of organochlorine pesticides. Combining the advantages of porous aromatic frameworks and an ionic liquid, the fiber exhibited a high adsorption capacity for organochlorine pesticides. Under optimized experimental conditions, enhancement factors of 247-1696 were obtained with good linearity in the range of 1-500 ?g L(-1). The detection limits and quantification limits were determined to be in the range of 0.11-0.29 ?g L(-1) and 0.35-0.93 ?g L(-1). The relative standard deviations for six replicates of organochlorine pesticides were in the range of 4.4%-7.2% and 5.7%-10.1% for one fiber and fiber-to-fiber, respectively. By coupling with a gas chromatography-electron capture detector, the novel fiber was successfully used for the determination of organochlorine pesticides in juice and milk samples with recoveries of 76.1%-121.3%. PMID:26579991

  9. System and method for detecting gas

    DOEpatents

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

    2010-03-16

    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.

  10. 49 CFR 192.736 - Compressor stations: Gas detection.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Compressor stations: Gas detection. 192.736...Maintenance § 192.736 Compressor stations: Gas detection. (a) Not...compressor building in a compressor station must have a fixed gas detection and alarm...

  11. Method for detecting gas turbine engine flashback

    DOEpatents

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

    2012-09-04

    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.

  12. Microwave radar detection of gas pipeline leaks.

    SciTech Connect

    Gopalsami, N.; Kanareykin, D. B.; Asanov, V. D; Bakhtiari, S.; Raptis, A. C.

    2002-10-02

    We are developing a microwave radar sensing and imaging system to detect and locate gas leaks in natural gas pipelines. The underlying detection principle is radar backscattering from the index-of-refraction inhomogeneities introduced by the dispersion of methane in air. An essential first step in the development effort is modeling to estimate the radar cross section. This paper describes the modeling results and the experimental efforts underway to validate the model. For the case of leaks from small holes in a pressurized gas pipeline, we modeled the gas dynamics of the leak jet to determine the plume geometry and the variation of methane concentration in air as a function of distance from the leak source. From the static and dynamic changes in the index of refraction in the turbulent plume, the radar backscatter cross sections were calculated. The results show that the radar cross sections of the leak plumes should be detectable by special-purpose radars.

  13. Air Monitoring for Hazardous Gas Detection

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  14. Semiconducting polymers for gas detection

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  15. 49 CFR 192.736 - Compressor stations: Gas detection.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

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

  16. 49 CFR 192.736 - Compressor stations: Gas detection.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  17. 49 CFR 192.736 - Compressor stations: Gas detection.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

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

  18. 49 CFR 192.736 - Compressor stations: Gas detection.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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

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

    PubMed

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

    2010-02-01

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

  20. Automated Hydrogen Gas Leak Detection System

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The Gencorp Aerojet Automated Hydrogen Gas Leak Detection System was developed through the cooperation of industry, academia, and the Government. Although the original purpose of the system was to detect leaks in the main engine of the space shuttle while on the launch pad, it also has significant commercial potential in applications for which there are no existing commercial systems. With high sensitivity, the system can detect hydrogen leaks at low concentrations in inert environments. The sensors are integrated with hardware and software to form a complete system. Several of these systems have already been purchased for use on the Ford Motor Company assembly line for natural gas vehicles. This system to detect trace hydrogen gas leaks from pressurized systems consists of a microprocessor-based control unit that operates a network of sensors. The sensors can be deployed around pipes, connectors, flanges, and tanks of pressurized systems where leaks may occur. The control unit monitors the sensors and provides the operator with a visual representation of the magnitude and locations of the leak as a function of time. The system can be customized to fit the user's needs; for example, it can monitor and display the condition of the flanges and fittings associated with the tank of a natural gas vehicle.

  1. Permanent gas analysis using gas chromatography with vacuum ultraviolet detection.

    PubMed

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

    2015-04-01

    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 (115-240 nm) 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

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

    DOEpatents

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

    2014-07-15

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

  3. Gas sensitive materials for gas detection and method of making

    DOEpatents

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

    2012-12-25

    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.

  4. 46 CFR 154.1350 - Flammable gas detection system.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    .... (f) Each flammable gas detection system must have an audible and visual alarm for power failure and... flammable gas detection system must have at least one flow meter capable of measuring the flow to the gas... 46 Shipping 5 2010-10-01 2010-10-01 false Flammable gas detection system. 154.1350 Section...

  5. 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...

  6. 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...

  7. Air Monitoring for Hazardous Gas Detection

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  8. Sensor array for toxic gas detection

    DOEpatents

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

    1987-01-01

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

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

    PubMed

    Zhou, Ting; Xiao, Xiaohua; Li, Gongke

    2012-01-01

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

  10. 46 CFR 154.1350 - Flammable gas detection system.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Instrumentation § 154.1350 Flammable gas detection system. (a...vessel must have a fixed flammable gas detection system that has sampling...pump room; (2) Each cargo compressor room; (3) Each motor room...control station that is not gas-safe; (5) Each...

  11. Symbolic identification for fault detection in aircraft gas turbine engines

    E-print Network

    Ray, Asok

    Symbolic identification for fault detection in aircraft gas turbine engines S Chakraborty, S Sarkar and computationally inexpensive technique of component-level fault detection in aircraft gas-turbine engines the NASA C-MAPSS model of a generic commercial aircraft engine. Keywords: fault detection, model

  12. Time reversal technique for gas leakage detection.

    PubMed

    Maksimov, A O; Polovinka, Yu A

    2015-04-01

    The acoustic remote sensing of subsea gas leakage traditionally uses sonars as active acoustic sensors and hydrophones picking up the sound generated by a leak as passive sensors. When gas leaks occur underwater, bubbles are produced and emit sound at frequencies intimately related to their sizes. The experimental implementation of an acoustic time-reversal mirror (TRM) is now well established in underwater acoustics. In the basic TRM experiment, a probe source emits a pulse that is received on an array of sensors, time reversed, and re-emitted. After time reversal, the resulting field focuses back at the probe position. In this study, a method for enhancing operation of the passive receiving system has been proposed by using it in the regime of TRM. Two factors, the local character of the acoustic emission signal caused by the leakage and a resonant nature of the bubble radiation at their birth, make particularly effective scattering with the conjugate wave (CW). Analytical calculations are performed for the scattering of CW wave on a single bubble when CW is formed by bubble birthing wail received on an array, time reversed, and re-emitted. The quality of leakage detection depends on the spatio-temporal distribution of ambient noise. PMID:25920866

  13. ENVIRONMENTAL APPLICATION OF GAS CHROMATOGRAPHY/ATOMIC EMISSION DETECTION

    EPA Science Inventory

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

  14. Quartz crystals detect gas contaminants during vacuum chamber evacuation

    NASA Technical Reports Server (NTRS)

    Stephens, J. B.

    1967-01-01

    Piezoelectric quartz crystals detect condensable gas contaminants backstreaming into a vacuum chamber when a pump is evacuating the chamber. One crystal acts as a thermometer, the other detects mass change. They are energized by electronic equipment which records frequency changes.

  15. Towards aerial natural gas leak detection system based on TDLAS

    NASA Astrophysics Data System (ADS)

    Liu, Shuyang; Zhou, Tao; Jia, Xiaodong

    2014-11-01

    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.

  16. Flammable Gas Detection for the D-Zero Gas System

    SciTech Connect

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

    1991-02-11

    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.

  17. Detection of Greenhouse-Gas-Induced Climatic Change

    SciTech Connect

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

    1998-05-26

    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.

  18. Naturally fractured tight gas reservoir detection optimization

    SciTech Connect

    1999-06-01

    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.

  19. Naturally fractured tight gas reservoir detection optimization

    SciTech Connect

    1998-11-30

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

  20. 46 CFR 154.1345 - Gas detection.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... limit value listed in 29 CFR 1910.1000 for that cargo; and (2) Fixed gas sampling tubes in each hold... must be set at or below the threshold limit value listed in 29 CFR 1910.1000 for the cargo carried. ... detector; (iii) If the vessel carries cargo that is heavier than the atmosphere of the space, each...

  1. 46 CFR 154.1345 - Gas detection.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... limit value listed in 29 CFR 1910.1000 for that cargo; and (2) Fixed gas sampling tubes in each hold... must be set at or below the threshold limit value listed in 29 CFR 1910.1000 for the cargo carried. ... detector; (iii) If the vessel carries cargo that is heavier than the atmosphere of the space, each...

  2. 46 CFR 154.1345 - Gas detection.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... limit value listed in 29 CFR 1910.1000 for that cargo; and (2) Fixed gas sampling tubes in each hold... must be set at or below the threshold limit value listed in 29 CFR 1910.1000 for the cargo carried. ... detector; (iii) If the vessel carries cargo that is heavier than the atmosphere of the space, each...

  3. In-fiber modal interferometer for high sensitivity gas detection

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Jin, Wei

    2015-09-01

    We demonstrate a gas sensor based on mode interference in a hollow-core photonic bandgap fiber. Gas absorption of a pump laser beam induces phase modulation of a propagating probe beam, which is detected by use of an in-fiber modal interferometer. An estimated detection limit of ~2 ppm acetylene (~7x10-5 in terms of noise equivalent absorbance or NEA) is achieved with 30-cm-long HC-PBF operating at the near infrared wavelength. This NEA is ~22 times better than state-of-the-art HC-PBF gas sensors based on direct absorption spectroscopy.

  4. Naturally fractured tight gas reservoir detection optimization

    SciTech Connect

    1998-09-30

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

  5. Radon gas detection apparatus and method

    SciTech Connect

    Kovac, M.

    1987-10-13

    A radon sampling unit is described comprising a cylindrical body containing a measured amount of charcoal for collecting and holding radon gas, a fine mesh screen inside the body and resting on the charcoal, retaining ring means engageable with the inner sidewall of the cylindrical body for frictionally holding the charcoal in place, a lid screw threaded to the body and hermetically sealed thereto, a layer of desiccant spaced vertically above the measured amount of charcoal to absorb moisture and permit diffusion of radon gas and help integrate radon fluctuations by creating a diffusion barrier, and a cylindrical element removably mounted adjacent the inner wall of the cylindrical body to enable replacement thereof with a removable cylindrical element of different diameter to meet the desired L/D ratio.

  6. Naturally fractured tight gas reservoir detection optimization

    SciTech Connect

    Decker, D.

    1995-05-01

    Exploration strategies are needed to identify subtle basement features critical to locating fractured regions in advance of drilling in tight gas reservoirs. The Piceance Basin served as a demonstration site for an analysis utilizing aeromagnetic surveys, remote sensing, Landsat Thematic Mapper, and Side Looking Airborne Radar imagery for the basin and surrounding areas. Spatially detailed aeromagnetic maps were used to to interpret zones of basement structure.

  7. Multi-species gas detection with long-wavelength VCSEL

    NASA Astrophysics Data System (ADS)

    Lytkine, Alexandre; Jaeger, Wolfgang; Tulip, John

    2004-12-01

    A long-wavelength VCSEL has been used for the first time for multi-species gas detection and for trace gas sensing. The VCSEL with a buried tunnel junction (VERTILAS, Germany) was capable of covering a spectral range of 7 nm or 28 cm-1 (central wavelength at 1576.3 nm) with the laser temperature and injection current varied between 0-50 °C and 0.5-5 mA respectively. The pressure of CO:CO2=3:2 gas mixtures buffered with N2 (N2 content 0 - 90 %) was varied from 1 mBar up to 1 Bar. To avoid a non-linear dynamic tuning, the combination of a direct injection current with a saw-tooth waveform was used to sweep the laser frequency across absorption lines. A LabVIEW-based computer code was developed for multi-species gas analysis in time domain. Absorption spectra were averaged over 102-103 laser scans. It has been shown that a cross interference from all collisional partners should be taken into account for accurate multi-component gas detection. A concentration of 600 ppm of CO2 in atmospheric air (fractional absorption ~ 10-4) was detected with laser output power of 120 uW. Long-wavelength VCSELs can be used both for multi-species gas detection in a wide range of pressures and for trace gas monitoring.

  8. Naturally fractured tight gas reservoir detection optimization

    SciTech Connect

    1999-04-30

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

  9. Temperature detection in a gas turbine

    DOEpatents

    Lacy, Benjamin; Kraemer, Gilbert; Stevenson, Christian

    2012-12-18

    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.

  10. Bernoulli excitation and detection of gas bubbles.

    PubMed

    Telling, R H; Walton, A J

    2001-10-01

    A simple method is proposed for detecting and sizing bubbles in pipeline fluid flow. This is based on changing the pressure of the fluid, which in turn excites volume oscillations in the bubble. If the change in pressure is of sufficient brevity and magnitude, the transient distortion results in excitation of the bubble into radiative oscillation at its natural frequency. In a moving fluid, the Bernoulli equation predicts that such a pressure change can be achieved through a suitable gradient in the flow velocity. In the experiments described here, this is achieved by altering the cross-sectional area of the pipe in which the fluid is flowing. We demonstrate the efficacy of this excitation method and, by detecting the radiated sound using a nearby hydrophone, determine the size of individual bubbles from their characteristic oscillation frequency. PMID:11775661

  11. Gas Transport and Detection Following Underground Nuclear Explosions

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  12. Naturally fractured tight gas reservoir detection optimization

    SciTech Connect

    1998-11-30

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    NASA Astrophysics Data System (ADS)

    Naranjo, Edward; Baliga, Shankar

    2012-06-01

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

  15. Methods for gas detection using stationary hyperspectral imaging sensors

    DOEpatents

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

    2012-04-24

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

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

    PubMed

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

    2012-02-01

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

  17. Predicting detection probabilities for gas mixtures over HSI backgrounds

    SciTech Connect

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

    2009-12-29

    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.

  18. ACOUSTIC DETECTING AND LOCATING GAS PIPE LINE INFRINGEMENT

    SciTech Connect

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

    2004-10-31

    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.

  19. ACOUSTIC DETECTING AND LOCATING GAS PIPE LINE INFRINGEMENT

    SciTech Connect

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

    2004-12-01

    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.

  20. Position sensitive radioactivity detection for gas and liquid chromatography

    DOEpatents

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

    2001-01-01

    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.

  1. Remote laser detection of natural gas leakages from pipelines

    SciTech Connect

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

    2010-02-28

    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)

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  3. Improved sensitivity gas detection by spontaneous Raman scattering

    SciTech Connect

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

    2009-08-01

    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

  4. Detection and Appraisal of Gas Hydrates: Indian Scenario

    NASA Astrophysics Data System (ADS)

    Sain, K.

    2009-04-01

    Gas hydrates, found in shallow sediments of permafrost and outer continental margins, are crystalline form of methane and water. The carbon within global gas hydrates is estimated two times the carbon contained in world-wide fossil fuels. It is also predicted that 15% recovery of gas hydrates can meet the global energy requirement for the next 200 years. Several parameters like bathymetry, seafloor temperature, sediment thickness, rate of sedimentation and total organic carbon content indicate very good prospect of gas hydrates in the vast offshore regions of India. Methane stored in the form of gas hydrates within the Indian exclusive economic zone is estimated to be few hundred times the country's conventional gas reserve. India produces less than one-third of her oil requirement and gas hydrates provide great hopes as a viable source of energy in the 21st century. Thus identification and quantitative assessment of gas hydrates are very important. By scrutiny and reanalysis of available surface seismic data, signatures of gas hydrates have been found out in the Kerala-Konkan and Saurashtra basins in the western margin, and Krishna-Godavari, Mahanadi and Andaman regions in the eastern margin of India by mapping the bottom simulating reflector or BSR based on its characteristic features. In fact, the coring and drilling in 2006 by the Indian National Gas Hydrate Program have established the ground truth in the eastern margin. It has become all the more important now to identify further prospective regions with or without BSR; demarcate the lateral/areal extent of gas hydrate-bearing sediments and evaluate their resource potential in both margins of India. We have developed various approaches based on seismic traveltime tomography; waveform inversion; amplitude versus offset (AVO) modeling; AVO attributes; seismic attributes and rock physics modeling for the detection, delineation and quantification of gas-hydrates. The blanking, reflection strength, instantaneous frequency and attenuation (Q-1) attributes are found very useful for the identification of gas hydrates in areas where BSR is not clearly observed on seismic section. These attributes can also be used to ascertain whether a BSR is related to gas hydrates. Since seismic velocity of pure gas hydrates is much higher than that host sediments, hydrates-bearing sediments exhibit higher velocities than normal oceanic sediments, whereas underlying free-gas laden sediments have considerably low P-wave velocity. Thus traveltime tomography of large offset multi channel seismic (MCS) or ocean bottom seismic (OBS) data can delineate the extent of gas hydrates and free-gas bearing sediments. Estimating accurate velocities by full-waveform inversion or AVO modeling followed by rock physics modeling has been an efficient tool for appraisal of gas hydrates and free-gas. Examples of these approaches to the Indian data sets will be presented in this paper. Key words: BSR, Gas hydrates, delineation, appraisal, approaches

  5. Capacitive micromachined ultrasonic resonator for ultra sensitive trace gas detection

    NASA Astrophysics Data System (ADS)

    Ge, Li-Feng

    2013-01-01

    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.

  6. Tunable fiber ring laser absorption spectroscopic sensors for gas detection

    NASA Astrophysics Data System (ADS)

    Zheng, Shijie; Zhu, Yinian; Krishnaswamy, Sridhar

    2013-04-01

    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.

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

    SciTech Connect

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

    1982-01-01

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

  8. Graphene oxide for gas detection under standard humidity conditions

    NASA Astrophysics Data System (ADS)

    Donarelli, Maurizio; Prezioso, Stefano; Perrozzi, Francesco; Giancaterini, Luca; Cantalini, Carlo; Treossi, Emanuele; Palermo, Vincenzo; Santucci, Sandro; Ottaviano, Luca

    2015-09-01

    Graphene oxide (GO) synthesis is the easiest way to functionalize graphene, preserving the high graphene surface to volume ratio. Therefore, GO is a promising candidate for gas sensing applications. In this paper, an easy-to-fabricate and high sensitivity GO-based gas sensor is proposed. The device is fabricated by drop-casting a solution of GO flakes dispersed in water on a prepatterned Si3N4 substrate with 30 ?m spaced Pt electrodes. The sensing material has been studied using scanning electron microscopy and x-ray photoelectron spectroscopy. The large lateral dimensions of the flakes (tens of microns) allow single GO flake to bridge adjacent electrodes. The high quality of the synthesized flakes results in the gas sensor high sensitivity to and low detection limit (20 ppb) of NO2. The gas sensor response to NO2 has been studied in various relative humidity environments and it is demonstrated not to be affected by the presence of water vapor. Finally, the gas sensor responses to acetone, toluene, ethanol, and ammonia are reported.

  9. ULTRASENSITIVE HIGH-TEMPERATURE SELECTIVE GAS DETECTION USING PIEZOELECTRIC MICROCANTILEVERS

    SciTech Connect

    Wan Y. Shih; Tejas Patil; Qiang Zhao; Yi-Shi Chiu; Wei-Heng Shih

    2004-03-05

    We have obtained very promising results in the Phase I study. Specifically, for temperature effects, we have established that piezoelectric cantilever sensors could retain their resonance peak strength at high temperatures, i.e., the Q values of the resonance peaks remained above 10 even when the temperature was very close to the Curie temperature. This confirms that a piezoelectric cantilever sensor can be used as a sensor up to its Curie temperature. Furthermore, we have shown that the mass detection sensitivity remained unchanged at different temperatures. For selective gas detection, we have demonstrated selective NH{sub 3} detection using piezoelectric cantilever sensors coated with mesoporous SiO{sub 2}. For high-temperature sensor materials development, we have achieved highly oriented Sr-doped lead titanate thin films that possessed superior dielectric and ferroelectric properties. Such highly oriented films can be microfabricated into high-performance piezoelectric microcantilever sensors that can be used up to 490 C. We have accomplished the goal of Phase I study in exploring the various aspects of a high-temperature gas sensor. We propose to continue the study in Phase II to develop a sensor that is suitable for high-temperature applications using piezoelectrics with a high Curie temperature and by controlling the effects of temperature. The lead titanate based thin film developed in Phase I is good for applications up to 490 C. In phase II, we will develop lithium niobate thin film based cantilevers for applications up to 1000 C.

  10. ACOUSTIC DETECTING AND LOCATING GAS PIPE LINE INFRINGEMENT

    SciTech Connect

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

    2003-04-01

    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.

  11. Naturally fractured tight gas reservoir detection optimization. Final report

    SciTech Connect

    1997-11-19

    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.

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

    PubMed

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

    2014-12-23

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

  13. Wireless gas detection with a smartphone via rf communication

    PubMed Central

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

    2014-01-01

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

  14. Dual-gas tracers for subsurface characterization and NAPL detection

    SciTech Connect

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

    1994-11-01

    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.

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

    SciTech Connect

    Maxwell, J.M.; Ortoleva, P.; Payne, D.; Sibo, W.

    1996-11-15

    This document contains the status report for the Naturally Fractured Tight Gas-Gas Reservoir Detection Optimization project for the contract period 9/30/93 to 3/31/97. Data from seismic surveys are analyzed for structural imaging of reflector units. The data were stacked using the new, improved statics and normal moveout velocities. The 3-D basin modeling effort is continuing with code development. The main activities of this quarter were analysis of fluid pressure data, improved sedimentary history, lithologic unit geometry reconstruction algorithm and computer module, and further improvement, verification, and debugging of the basin stress and multi-phase reaction transport module.

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

    NASA Technical Reports Server (NTRS)

    O'Hara, Dean; Singh, Hanwant B.

    1988-01-01

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

  17. Flashback Detection Sensor for Hydrogen Augmented Natural Gas Combustion

    SciTech Connect

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

    2007-05-01

    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.

  18. Hydrocarbon gas detection with microelectromechanical Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  20. Silicon Carbide-Based Hydrogen and Hydrocarbon Gas Detection

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

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

    E-print Network

    Shaw, Joseph A.

    Low-cost multispectral vegetation imaging system for detecting leaking CO2 gas Justin A. Hogan,1 imaging system has been developed for indirect detection of gas leaks through observations detec- tion systems. Remote sensing techniques proposed for leak detection include ground

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

    E-print Network

    Ray, Asok

    307 Fault detection and isolation in aircraft gas turbine engines. Part 1: underlying concept methodology of degradation monitoring of aircraft gas tur- bine engines with emphasis on detection two-spool turbofan aircraft engine model for detection and isolation of incipient faults. Keywords

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

    E-print Network

    , and pipeline leak detection. Applications such as landfill emissions monitoring require measurements of gasRoom-temperature mid-infrared laser sensor for trace gas detection Thomas To¨ pfer, Konstantin P. The instrument was used for detection of CO in air at atmospheric pressure with 1 ppb precision parts in 109

  4. Interchangeability of gas detection tubes and hand pumps.

    PubMed

    Haag, W R

    2001-01-01

    Users of gas detection tubes occasionally seek the convenience of using a single hand pump with different brands of tubes, to avoid the need to carry more than one pump. Several professional organizations recommend against such interchange. However, these recommendations appear to be based on a single study of pump designs that mostly are no longer in use. The present study was undertaken to determine if current hand pumps are interchangeable. Both piston-type and bellows-type hand pumps were evaluated by comparing pump flow profiles and test gas measurements with a variety of tubes. The results demonstrate that three piston hand pumps in common use (Sensidyne/Gastec GV/100, RAE Systems LP-1200, and Matheson-Kitagawa 8104-400A) are fully interchangeable. Two bellows pumps (Draeger Accuro and MSA Kwik-Draw) also are interchangeable with each other. Mixing of bellows and piston systems is often possible, but there are enough exceptions to conclude that such practice should be discouraged because it can give inaccurate readings. It is recommended that technical standards be adopted, such as total volume and an initial pump vacuum or a pump flow curve, to assess hand pump interchangeability. When two manufacturers' pumps meet the same standard and routine leak tests are conducted, interchangeability is scientifically valid and poses no risk to the end user while offering greater convenience. PMID:11258870

  5. Detection of Smoldering Fire Using Tin Oxide Gas Sensors

    NASA Astrophysics Data System (ADS)

    Higashino, Tsubasa; Sawada, Ayako; Oyabu, Takashi; Takei, Yoshinori; Nanto, Hidehito; Toko, Kiyoshi

    Detecting technique of smoldering fire was examined using tin oxide gas sensors. Eight sensors were installed in a room. They were same type. Four kinds of materials were adopted as a fire-source material. The materials were cotton cloth, wallpaper, curtain cloth and woodchip, which were main smoldering fire-source materials in an indoor environment. The sensor outputs to gases evolved upon the smoldering fire of the materials were measured. The differential characteristic of the output was derived to analyze. As for the results, it became obvious that the sensor locating at higher position had a higher sensitivity and it could sense the fire instantaneously. It is thought that the generated gases rise up directly toward the ceiling and reflect downward. A small type of electric cooking stove was used as a fire-source. The surface temperature of the stove plate arrived at 340 °C. A bar was adopted to set the sensors freely. In this experiment, three bars were adopted and the heights of the sensor position were 50, 100, 150 and 200 cm from the floor. It is effective to locate the sensor at higher position in detecting a smoldering fire. The sensor characteristics were analyzed using principal component analysis (PCA). The system could discriminate source materials among wallpaper, woodchip and curtain for smoldering fire by utilizing the result of PCA. But, the smoldering fire of cotton cloth could not be distinguished from that of curtain by this system. Each fire could be identified in four minutes.

  6. Detection of atmospheric trace gas species by DOAS gas-analyzer

    NASA Astrophysics Data System (ADS)

    Geiko, Pavel P.; Smirnov, Sergey S.; Samokhvalov, Ignatii V.

    2014-11-01

    A differential optical absorption spectroscopy (DOAS) gas-analyzer was successfully tested. A high pressure 150-W Xe arc lamp was employed as a light source This system consisted of a coaxial telescope, a spectrometer, an analyzer and retroreflector. In order to record the spectra, a monochrometer with a grating and photodiode array was adopted. Gas analyzer spectral data bank includes more than 30 moleculas absorbed in UV spectral region. The measured absorption spectra were evaluated by using a least-squares fit to determine the average mixing ratio of each species in the atmosphere. A number of air pollutants concentrations: SO2, NO2, O3, etc were trace measured. Minimally detected concentration on pathlength 400 m is the unit of ppb at the time of accumulation of 2 min. The results of the field test measurements of pollutants in Tomsk are presented.

  7. a Mini Multi-Gas Detection System Based on Infrared Principle

    NASA Astrophysics Data System (ADS)

    Zhijian, Xie; Qiulin, Tan

    2006-12-01

    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.

  8. Method of detecting a fault of an exhaust gas recirculation system

    SciTech Connect

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

    1989-05-30

    This patent describes a method of detecting a fault of an exhaust gas recirculation system of an internal combustion engine, wherein a temperature relating to a temperature of the exhaust gas recirculating through the exhaust gas recirculation system is detected when the exhaust gas recirculation system is in a condition in which the system should be operated to return part of the exhaust gas of the engine to an intake passage, and it is detected that the exhaust gas recirculation system in defective, when the detected temperature is lower than a fault discriminating value. The method consists of: detecting a condition of air to be sucked into the engine, and setting the fault discriminating value in accordance with the detected condition of air.

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

    E-print Network

    Fan, Xudong "Sherman"

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

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

    E-print Network

    Tentzeris, Manos

    been studied for their sensing properties are CNTs [3], graphene [5] and silicon nanowires [4Figure 1. Principle of wireless detection of gas centration with a chipless sensor. A Novel Inkjet Printed Carbon Nanotube-Based Chipless RFID Sensor for Gas Detection Arnaud Vena#1 , Lauri Sydänheimo#2

  11. 46 CFR 154.709 - Cargo boil-off as fuel: Gas detection equipment.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Cargo boil-off as fuel: Gas detection equipment. 154.709 Section 154.709 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS... Equipment Cargo Pressure and Temperature Control § 154.709 Cargo boil-off as fuel: Gas detection...

  12. 46 CFR 154.709 - Cargo boil-off as fuel: Gas detection equipment.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Cargo boil-off as fuel: Gas detection equipment. 154.709 Section 154.709 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS... Equipment Cargo Pressure and Temperature Control § 154.709 Cargo boil-off as fuel: Gas detection...

  13. 46 CFR 154.709 - Cargo boil-off as fuel: Gas detection equipment.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Cargo boil-off as fuel: Gas detection equipment. 154.709 Section 154.709 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS... Equipment Cargo Pressure and Temperature Control § 154.709 Cargo boil-off as fuel: Gas detection...

  14. 46 CFR 154.709 - Cargo boil-off as fuel: Gas detection equipment.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Cargo boil-off as fuel: Gas detection equipment. 154.709 Section 154.709 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS... Equipment Cargo Pressure and Temperature Control § 154.709 Cargo boil-off as fuel: Gas detection...

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

    PubMed

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

    2014-12-15

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

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

    PubMed

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

    2014-10-01

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

  17. Evaluation of Gas Chromatography/Mini-IMS to Detect VOCs

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

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

    SciTech Connect

    1997-12-31

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

  19. Detection of gas hydrate sediments using prestack seismic AVA inversion

    NASA Astrophysics Data System (ADS)

    Zhang, Ru-Wei; Li, Hong-Qi; Zhang, Bao-Jin; Huang, Han-Dong; Wen, Peng-Fei

    2015-09-01

    Bottom-simulating reflectors (BSRs) in seismic profile always indicate the bottom of gas hydrate stability zone, but is difficult to determine the distribution and features of gas hydrate sediments (GHS). In this study, based on AVA forward modeling and angle-domain common-image gathers we use prestack AVA parameters consistency inversion in predicting gas hydrate sediments in the Shenhu area at northern slope of South China Sea, and obtain the vertical and lateral features and saturation of GHS.

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

    NASA Astrophysics Data System (ADS)

    Xia, Hua

    2012-06-01

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

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

    PubMed

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

    2014-09-16

    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

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

    DOEpatents

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

    1983-06-01

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

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

    SciTech Connect

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

    2013-05-07

    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.

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

    SciTech Connect

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

    1993-12-31

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

  5. Fiber-Optic Based Compact Gas Leak Detection System

    NASA Technical Reports Server (NTRS)

    deGroot, Wim A.

    1995-01-01

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

  6. Three-gas detection system with IR optical sensor based on NDIR technology

    NASA Astrophysics Data System (ADS)

    Tan, Qiulin; Tang, Licheng; Yang, Mingliang; Xue, Chenyang; Zhang, Wendong; Liu, Jun; Xiong, Jijun

    2015-11-01

    In this paper, a three-gas detection system with a environmental parameter compensation method is proposed based on Non-dispersive infra-red (NDIR) technique, which can be applied to detect multi-gas (methane, carbon dioxide and carbon monoxide). In this system, an IR source and four single-channel pyroelectric sensors are integrated in the miniature optical gas chamber successfully. Inner wall of the chamber coated with Au film is designed as paraboloids. The infrared light is reflected twice before reaching to detectors, thus increasing optical path. Besides, a compensation method is presented to overcome the influence in variation of environment (ambient temperature, humidity and pressure), thus leading to improve the accuracy in gas detection. Experimental results demonstrated that detection ranges are 0-50,000 ppm for CH4, 0-44,500 ppm for CO, 0-48,000 ppm for CO2 and the accuracy is ±0.05%.

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

    E-print Network

    Dinakaran, Srikanth

    1994-01-01

    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...

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

    PubMed Central

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

    2009-01-01

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

  9. Instrumental Analysis in Environmental Chemistry - Gas Phase Detection Systems

    ERIC Educational Resources Information Center

    Stedman, Donald H.; Meyers, Philip A.

    1974-01-01

    Discusses advances made in chemical analysis instrumentation used in environmental monitoring. This first of two articles is concerned with analytical instrumentation in which detection and dispersion depend ultimately on the properties of gaseous molecules. (JR)

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

    SciTech Connect

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

    1995-08-01

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

  11. Gas and flame detection and identification using uncooled MWIR imaging sensors

    NASA Astrophysics Data System (ADS)

    Linares, Rodrigo; Vergara, Germán.; Gutiérrez, Raúl; Fernández, Carlos; Villamayor, Víctor; Gómez, Luis; González-Camino, María.; Baldasano, Arturo

    2015-05-01

    Gas detectors are nowadays widely spread for safety purposes in industrial facilities. They are categorized by the type of gas they detect: combustible and/or toxic. Whereas electrochemical sensors have limited lifetime and maintenance issues, infrared sensors are reliable and free of maintenance devices used for detecting a wide variety of VOCs and inflammable gases such as hydrocarbon vapors. They usually work via a system of transmitters (light sources) which power is interfered when a gas is present in the optical path. A spectral analysis of this optical interference allows the gas detection and identification. Optical flame detectors are sensors intended to sight and respond to the presence of a flame, faster than a smoke detector or a heat detector would do. Many of these systems operate in the infrared band in order to detect the heat radiation, most of the times by comparison of three specific wavelength bands. Most of the present infrared gas and optical flame detectors traditionally make use of MWIR single point sensors rather than imaging sensors; this is mainly due to the lack of affordable imaging sensing technologies in this band of the infrared spectrum. However, the appearance of uncooled imaging MWIR sensors made of VPD PbSe, with spectral detection range from 1 to 5 microns, opens the possibility to incorporate these sensors into gas and flame detection systems to allow area monitoring.

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

    SciTech Connect

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

    1999-07-08

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

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

    E-print Network

    Titov, Anatoly

    Slow neutron detection without 3He: far ultraviolet noble-gas-excimer radiation induced by neutron radiation, Drain Gate Source 1 zero-energy neutron in ~ 1 atm noble gas 30,000 far ultraviolet photons out quantified an efficient (30%) mechanism for channelling nuclear reaction energy into far ultraviolet

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

    E-print Network

    Herr, Hugh

    such as methane from leaking natural gas pipelines or nitrogen oxides from failing electrical equipment requireTechNotes November 2014www.ll.mit.edu The detection and localization of gas releases of the laser (e.g., stability, power). WACS Technique The WACS system uses a spectrally self

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

    E-print Network

    Trace gas detection based on off-beam quartz enhanced photoacoustic spectroscopy: Optimization July 2010; published online 19 October 2010 A gas sensor based on off-beam quartz enhanced sensitivity. The impact of the distance between the quartz tuning fork and an acoustic microresonator

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  17. 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...

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

    EPA Science Inventory

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

  19. Detecting gas hydrate behavior in crude oil using NMR.

    PubMed

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

    2006-04-01

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

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

    NASA Technical Reports Server (NTRS)

    Johnston, P. A.

    1970-01-01

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

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

    DOEpatents

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

    2011-01-04

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

  2. Gas detection for alternate-fuel vehicle facilities.

    PubMed

    Ferree, Steve

    2003-05-01

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

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

    SciTech Connect

    Ross, G.A.

    1998-03-27

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

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

    E-print Network

    Ray, Asok

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

  5. Metal-oxide Nanowires for Toxic Gas Detection

    SciTech Connect

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

    2007-01-02

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2013-12-01

    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

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

    USGS Publications Warehouse

    Barker, C.E.

    2006-01-01

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

  9. A Hazardous Gas Detection System for Aerospace and Commercial Applications

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    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.

  10. A Hazardous Gas Detection System for Aerospace and Commercial Applications

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    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.

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

    SciTech Connect

    Sentell, J.C.

    1994-12-31

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

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

    SciTech Connect

    McCord, R.B.; Lysher, W.M.

    1993-12-01

    Encapsulation of a unique isotopic blend of krypton and xenon gas employs a special application of laser technology. The encapsulated gas is then used as the primary medium for detection and identification of failed nuclear fuel rods. The use of gas tagging as a means of detecting and identifying failed nuclear fuel rods has been successfully demonstrated and used by the Argonne National Laboratory, Experimental Breeder Reactor (EBR-2) Project, and the Westinghouse Hanford Company (WHC), Fast Flux Test Facility (FFTF) Fast Breeder Reactor Program. The Power Reactor and Nuclear Fuel Development Corporation (PNC) of Japan has selected this leak detection system for use in their MONJU Prototype Reactor fuel assemblies. The MONJU reactor is almost identical in design to the highly successful FFTF reactor, which is currently in standby status.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

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

    SciTech Connect

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

    2002-09-01

    The U.S. Department of Energy, National Energy Technology Laboratory funded a Natural Gas Infrastructure Reliability program directed at increasing and enhancing research and development activities in topics such as remote leak detection, pipe inspection, and repair technologies and materials. The Albany Research Center (ARC), U.S. Department of Energy was funded to study the use of electrochemical noise sensors for detection of localized and general corrosion of natural gas transmission pipelines. As part of this, ARC entered into a collaborative effort with the corrosion sensor industry to demonstrate the capabilities of commercially available remote corrosion sensors for use with the Nation's Gas Transmission Pipeline Infrastructure needs. The goal of the research was to develop an emerging corrosion sensor technology into a monitor for the type and degree of corrosion occurring at key locations in gas transmission pipelines.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  16. Nanostructure Engineered Chemical Sensors for Hazardous Gas and Vapor Detection

    NASA Technical Reports Server (NTRS)

    Li, Jing; Lu, Yijiang

    2005-01-01

    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.

  17. System for detecting and estimating concentrations of gas or liquid analytes

    NASA Technical Reports Server (NTRS)

    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

    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.

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

    SciTech Connect

    1998-12-31

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

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

    SciTech Connect

    1998-04-01

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

  20. Small-Size Resonant Photoacoustic Cell of Inclined Geometry for Gas Detection

    E-print Network

    Gorelik, A V; Nikonovich, F N; Zakharich, M P; Chebotar, A I; Firago, V A; Stetsik, V M; Kazak, N S; Starovoitov, V S

    2009-01-01

    A photoacoustic cell intended for laser detection of trace gases is represented. The cell is adapted so as to enhance the gas-detection performance and, simultaneously, to reduce the cell size. The cell design provides an efficient cancellation of the window background (a parasite response due to absorption of laser beam in the cell windows) and acoustic isolation from the environment for an acoustic resonance of the cell. The useful photoacoustic response from a detected gas, window background and noise are analyzed in demonstration experiments as functions of the modulation frequency for a prototype cell with the internal volume ~ 0.5 cm^3. The minimal detectable absorption for the prototype is estimated to be ~ 1.2 10^{-8} cm^{-1} W Hz^{-1/2}.

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

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

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

  2. Detection of Molecular Gas in Void Galaxies : Implications for Star Formation in Isolated Environments

    NASA Astrophysics Data System (ADS)

    Das, M.; Saito, T.; Iono, D.; Honey, M.; Ramya, S.

    2015-12-01

    We present the detection of molecular gas from galaxies located in nearby voids using the CO(1–0) line emission as a tracer. The observations were performed using the 45 m single dish radio telescope of the Nobeyama Radio Observatory. Void galaxies lie in the most underdense parts of our universe and a significant fraction of them are gas rich, late-type spiral galaxies. Although isolated, they have ongoing star formation but appear to be slowly evolving compared to galaxies in denser environments. Not much is known about their star formation properties or cold gas content. In this study, we searched for molecular gas in five void galaxies. The galaxies were selected based on their relatively high IRAS fluxes or H? line luminosities, both of which signify ongoing star formation. All five galaxies appear to be isolated and two lie within the Bootes void. We detected CO(1–0) emission from four of the five galaxies in our sample and their molecular gas masses lie between 108 and 109 M?. We conducted follow-up H? imaging observations of three detected galaxies using the Himalayan Chandra Telescope and determined their star formation rates (SFRs) from their H? fluxes. The SFR varies from 0.2 to 1 M? yr?1 which is similar to that observed in local galaxies. Our study indicates that although void galaxies reside in underdense regions, their disks contain molecular gas and have SFRs similar to galaxies in denser environments. We discuss the implications of our results.

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

    NASA Astrophysics Data System (ADS)

    Andio, Mark A.

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

  4. Combined raman and IR fiber-based sensor for gas detection

    DOEpatents

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

    2014-06-24

    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.

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

    SciTech Connect

    1995-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  7. Electrochemical corrosion rate sensors for detecting internal corrosion of natural gas transmission pipelines

    SciTech Connect

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

    2005-01-01

    This paper is a report on the evaluation of the use of electrochemical corrosion rate probes to detect internal corrosion in natural gas transmission pipeline environments. Flange and flush-mount probes were used in four different environments at three different sites that were selected to represent normal and upset conditions in a gas transmission pipeline. The environments consisted of humidified natural gas, organic/water mixtures removed from natural gas, and the environments at the 6 and 12 o'clock positions of a natural gas pipeline carrying multiphase gas/liquid flow. This paper will summarize and extend results presented previously and add additional data. A re-analysis of previously-reported data will be presented along with the results of physical examinations on the probes. New data on the measurement of corrosion in multiphase gas/liquid environments and for coupons used to determine corrosion rate and to detect the presence of microbiologically-influenced corrosion (MIC) will also be presented.

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

    SciTech Connect

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

    2005-05-01

    This report summarizes work performed by Physical Sciences Inc. (PSI) to advance the state-of-the-art of surveying for leaks of natural gas from transmission and distribution pipelines. The principal project goal was to develop means of deploying on an automotive platform an improved version of the handheld laser-based standoff natural gas leak detector previously developed by PSI and known as the 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.

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

    PubMed

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

    2009-03-01

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

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

    SciTech Connect

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

    2005-10-01

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

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

    PubMed

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

    2014-10-21

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

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

    E-print Network

    Constable, Steve

    First results from a marine controlled-source electromagnetic survey to detect gas hydrates electromagnetic surveys have the potential to provide an estimate of the total hydrate volume fraction more directly than by using seismic and well log data. We conducted a marine controlled-source electromagnetic

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

    SciTech Connect

    1995-08-01

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

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

    E-print Network

    Amelung, Falk

    Sinking cities in Indonesia: ALOS PALSAR detects rapid subsidence due to groundwater and gas and Atmospheric Science, University of Miami, USA b Institute of Technology, Bandung (ITB), Indonesia c Korea online xxxx Keywords: Subsidence Interferometric synthetic aperture radar SBAS time-series Indonesia We

  15. In situ refreshing enabled parts-per-quadrillion gas detection with pristine carbon nanotubes and graphene

    E-print Network

    Maruyama, Shigeo

    refreshing of the sensor surface with continuous ultraviolet light illumination during the course53 P7 P8 NT13 In situ refreshing enabled parts-per-quadrillion gas detection with pristine carbon Badar, Shigeo Maruyama* Department of Mechanical Engineering, The University of Tokyo, Japan (*maruyama

  16. 46 CFR 154.709 - Cargo boil-off as fuel: Gas detection equipment.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Cargo boil-off as fuel: Gas detection equipment. 154.709 Section 154.709 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment Cargo Pressure...

  17. Detectability of trace gases in the Martian atmosphere using gas correlation filter radiometry

    NASA Astrophysics Data System (ADS)

    Sinclair, J.; Irwin, P. G. J.; Wilson, E.; Calcutt, S.

    2015-10-01

    We present the results of radiative transfer simulations of a gas correlation filter radiometer (GCFR) in the detection of trace species in the Martian atmosphere. We investigated two scenarios: 1) nadir and/or limb sounding from a Mars orbiter in the thermal infrared, 2) solar occultation measurements in the near-infrared from the Martian surface. In both scenarios, a GCFR would allow detection of trace gases at a lower concentration than that detectable by a conventional filter radiometer. In nadir/limb sounding, we find that CH4, SO2, N2O, C2H2 and CH3OH are detectable at concentrations lower than previously-derived upper limits. From solar occultation measurements, we find that CH4, SO2, C2H2, C2H6 are detectable at concentrations lower than previously-derived upper limits but only in low dust conditions.

  18. On the detectability of trace chemical species in the martian atmosphere using gas correlation filter radiometry

    NASA Astrophysics Data System (ADS)

    Sinclair, J. A.; Irwin, P. G. J.; Calcutt, S. B.; Wilson, E. L.

    2015-11-01

    The martian atmosphere is host to many trace gases including water (H2O) and its isotopologues, methane (CH4) and potentially sulphur dioxide (SO2), nitrous oxide (N2O) and further organic compounds, which would serve as indirect tracers of geological, chemical and biological processes on Mars. With exception of the recent detection of CH4 by Curiosity, previous detections of these species have been unsuccessful or considered tentative due to the low concentrations of these species in the atmosphere (?10-9 partial pressures), limited spectral resolving power and/or signal-to-noise and the challenge of discriminating between telluric and martian features when observing from the Earth. In this study, we present radiative transfer simulations of an alternative method for detection of trace gas species - the gas correlation radiometry method. Two potential observing scenarios were explored where a gas correlation filter radiometer (GCFR) instrument: (1) performs nadir and/or limb sounding of the martian atmosphere in the thermal infrared (200-2000 cm-1 from an orbiting spacecraft or (2) performs solar occultation measurements in the near-infrared (2000-5000 cm-1) from a lander on the martian surface. In both scenarios, simulations of a narrowband filter radiometer (without gas correlation) were also generated to serve as a comparison. From a spacecraft, we find that a gas correlation filter radiometer, in comparison to a filter radiometer (FR), offers a greater discrimination between temperature and dust, a greater discrimination between H2O and HDO, and would allow detection of N2O and CH3OH at concentrations of ?10 ppbv and ?2 ppbv, respectively, which are lower than previously-derived upper limits. However, the lowest retrievable concentration of SO2 (approximately 2 ppbv) is comparable with previous upper limits and CH4 is only detectable at concentrations of approximately 10 ppbv, which is an order of magnitude higher than the concentration recently measured by Curiosity. From a lander in low dust conditions, both a filter radiometer and gas correlation filter radiometer would provide measurement of H2O and HDO, which allows the D/H ratio in H2O to be determined. Detection of N2O, CH4, SO2, C2H2, C2H6 at concentrations lower than previously-derived upper limits would be possible using a gas correlation filer radiometer in low dust conditions. However, either radiometer would be unable to detect these trace gases in high dust conditions, with the exception of H2O.

  19. Single ZnO Nanowire-Based Gas Sensors to Detect Low Concentrations of Hydrogen.

    PubMed

    Cardoza-Contreras, Marlene N; Romo-Herrera, José M; Ríos, Luis A; García-Gutiérrez, R; Zepeda, T A; Contreras, Oscar E

    2015-01-01

    Low concentrations of hazardous gases are difficult to detect with common gas sensors. Using semiconductor nanostructures as a sensor element is an alternative. Single ZnO nanowire gas sensor devices were fabricated by manipulation and connection of a single nanowire into a four-electrode aluminum probe in situ in a dual-beam scanning electron microscope-focused ion beam with a manipulator and a gas injection system in/column. The electrical response of the manufactured devices shows response times up to 29 s for a 121 ppm of H? pulse, with a variation in the nanowire resistance appreciable at room temperature and at 373.15 K of approximately 8% and 14% respectively, showing that ZnO nanowires are good candidates to detect low concentrations of H?. PMID:26690158

  20. A DETECTION OF MOLECULAR GAS EMISSION IN THE HOST GALAXY OF GRB 080517

    SciTech Connect

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

    2015-01-01

    We have observed the host galaxy of the low-redshift, low-luminosity Swift GRB 080517 at 105.8 GHz using the IRAM Plateau de Bure interferometer. We detect an emission line with integrated flux S?? = 0.39 ± 0.05 Jy km s{sup –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, M{sub H{sub 2}}?6.3×10{sup 8} M {sub ?}, 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

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

    PubMed

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

    2015-03-01

    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

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

    SciTech Connect

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

    2015-03-02

    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 (B{sub 4}C). A calibrated cold neutron beam is used to measure the neutron detection properties, using a thin film of enriched {sup 10}B 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.

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

    SciTech Connect

    Jerry Myers

    2005-04-15

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

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

    NASA Astrophysics Data System (ADS)

    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

    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.

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

    SciTech Connect

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

    2008-10-02

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

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

    PubMed Central

    Reiß, Sebastian; Hagen, Gunter; Moos, Ralf

    2008-01-01

    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.

  8. Interface engineering: broadband light and low temperature gas detection abilities using a nano-heterojunction device.

    PubMed

    Chang, Chien-Min; Hsu, Ching-Han; Liu, Yi-Wei; Chien, Tzu-Chiao; Sung, Chun-Han; Yeh, Ping-Hung

    2015-12-21

    Herein, we have designed a nano-heterojunction device using interface defects and band bending effects, which can have broadband light detection (from 365-940 nm) and low operating temperature (50 °C) gas detection abilities. The broadband light detection mechanism occurs because of the defects and band bending between the heterojunction interface. We have demonstrated this mechanism using CoSi2/SnO2, CoSi2/TiO2, Ge/SnO2 and Ge/TiO2 nano-heterojunction devices, and all these devices show broadband light detection ability. Furthermore, the nano-heterojunction of the nano-device has a local Joule-heating effect. For gas detection, the results show that the nano-heterojunction device presents a high detection ability. The reset time and sensitivity of the nano-heterojunction device are an order faster and larger than Schottky-contacted devices (previous works), which is due to the local Joule-heating effect between the interface of the nano-heterojunction. Based on the abovementioned idea, we can design diverse nano-devices for widespread use. PMID:26567487

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

    SciTech Connect

    Oudman, P. )

    1993-12-01

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

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

    SciTech Connect

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

    2007-12-18

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

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

    PubMed

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

    2007-12-01

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

  12. Real-time detection of chlorine gas using Ni/Si shell/core nanowires

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Jin; Heo, Kwang; Lee, Hyungwoo; Jin, Joon-Hyung; Chang, Hochan; Park, Minjun; Lee, Han-Bo-Ram; Kim, Hyungjun; Lee, Byung Yang

    2015-01-01

    We demonstrate the selective adsorption of Ni/Si shell/core nanowires (Ni-Si NWs) with a Ni outer shell and a Si inner core on molecularly patterned substrates and their application to sensors for the detection of chlorine gas, a toxic halogen gas. The molecularly patterned substrates consisted of polar SiO2 regions and nonpolar regions of self-assembled monolayers of octadecyltrichlorosilane (OTS). The NWs showed selective adsorption on the polar SiO2 regions, avoiding assembly on the nonpolar OTS regions. Utilizing these assembled Ni-Si NWs, we demonstrate a sensor for the detection of chlorine gas. The utilization of Ni-Si NWs resulted in a much larger sensor response of approximately 23% to 5 ppm of chlorine gas compared to bare Ni NWs, due to the increased surface-to-volume ratio of the Ni-Si shell/core structure. We expect that our sensor will be utilized in the future for the real-time detection of halogen gases including chlorine with high sensitivity and fast response.

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

    PubMed

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

    2011-09-01

    Nanowires of various materials and configurations have been shown to be highly effective in the detection of chemical and biological species. In this paper, we report a novel, nanosphere-enabled approach to fabricating highly sensitive gas sensors based on ordered arrays of vertically aligned silicon nanowires topped with a periodically porous top electrode. The vertical array configuration helps to greatly increase the sensitivity of the sensor while the pores in the top electrode layer significantly improve sensing response times by allowing analyte gases to pass through freely. Herein, we show highly sensitive detection to both nitrogen dioxide (NO(2)) and ammonia (NH(3)) in humidified air. NO(2) detection down to 10 parts per billion (ppb) is demonstrated and an order-of-magnitude improvement in sensor response time is shown in the detection of NH(3). PMID:21817785

  14. Use of nonlocal helium microplasma for gas impurities detection by the collisional electron spectroscopy method

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, Anatoly A.; Stefanova, Margarita S.; Pramatarov, Petko M.

    2015-10-01

    The collisional electron spectroscopy (CES) method, which lays the ground for a new field for analytical detection of gas impurities at high pressures, has been verified. The CES method enables the identification of gas impurities in the collisional mode of electron movement, where the advantages of nonlocal formation of the electron energy distribution function (EEDF) are fulfilled. Important features of dc negative glow microplasma and probe method for plasma diagnostics are applied. A new microplasma gas analyzer design is proposed. Admixtures of 0.2% Ar, 0.6% Kr, 0.1% N2, and 0.05% CO2 are used as examples of atomic and molecular impurities to prove the possibility for detecting and identifying their presence in high pressure He plasma (50-250 Torr). The identification of the particles under analysis is made from the measurements of the high energy part of the EEDF, where maxima appear, resulting from the characteristic electrons released in Penning reactions of He metastable atoms with impurity particles. Considerable progress in the development of a novel miniature gas analyzer for chemical sensing in gas phase environments has been made.

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

    SciTech Connect

    Gehue, H.L.; Sommer, P.

    1996-12-31

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

  16. Electrically detected magnetic resonance of neutral donors interacting with a two-dimensional electron gas.

    PubMed

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

    2011-05-20

    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 resonance signal increases by 2 orders of magnitude from X to W band, while the donor resonance signals are enhanced by over 1 order of magnitude. Bolometric effects and spin-dependent scattering are inconsistent with the observations. We propose that polarization transfer from the donor to the two-dimensional electron gas is the main mechanism giving rise to the spin resonance signals. PMID:21668263

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

    SciTech Connect

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

    2007-12-01

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

  18. Sensing Materials for the Detection of Chlorine Gas Using Embedded Piezoresistive Microcantilever Sensors

    SciTech Connect

    T. L. Porter, T. Vail, A. Wooley, R. J. Venedam

    2008-10-01

    Embedded piezoresistive microcantilever (EPM) sensors may be constructed for a variety of sensing applications. In each application, a custom sensing material is designed that will respond volumetrically to the desired analyte. Here, we have constructed EPM sensors for the detection of chlorine gas (Cl2). The sensing materials used consisted of polymer matrices combined with sodium iodide crystals. Sensors constructed from a silicone-based matrix exhibited the greatest response to Cl2, with detection limits in an outdoor exposure setting of approximately 20 parts per million.

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

    NASA Technical Reports Server (NTRS)

    Kantsios, A. G.

    1978-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  1. Optically multiplexed multi-gas detection using quantum cascade laser photoacoustic spectroscopy.

    PubMed

    Mukherjee, Anadi; Prasanna, Manu; Lane, Michael; Go, Rowel; Dunayevskiy, Ilya; Tsekoun, Alexei; Patel, C Kumar N

    2008-09-20

    We report high-throughput, nondispersive optical multiplexing of laser beams using a scanning galvanometer. We have utilized this technique for multispecies trace-gas detection using multiple quantum cascade laser photoacoustic spectroscopy. We demonstrate switching from one laser to another in less than 1 s, a performance level needed for a comprehensive multispecies sensor, and a high signal-to-noise ratio detection of five gaseous components, NH(3), NO(2), dimethyl methyl phosphonate (DMMP, a simulant for nerve agents), acetone, and ethylene glycol, in a room air gas mixture containing approximately 3 ppb of NH(3), approximately 8 ppb of NO(2), approximately 20 ppb of DMMP, approximately 30 ppb of acetone, and approximately 40 ppb of ethylene glycol. PMID:18806847

  2. Molecular Gas Sensing Below Parts Per Trillion: Radiocarbon-Dioxide Optical Detection

    NASA Astrophysics Data System (ADS)

    Galli, I.; Bartalini, S.; Borri, S.; Cancio, P.; Mazzotti, D.; de Natale, P.; Giusfredi, G.

    2011-12-01

    Radiocarbon (C14) concentrations at a 43 parts-per-quadrillion level are measured by using saturated-absorption cavity ringdown spectroscopy by exciting radiocarbon-dioxide (C14O216) molecules at the 4.5?m wavelength. The ultimate sensitivity limits of molecular trace gas sensing are pushed down to attobar pressures using a comb-assisted absorption spectroscopy setup. Such a result represents the lowest pressure ever detected for a gas of simple molecules. The unique sensitivity, the wide dynamic range, the compactness, and the relatively low cost of this table-top setup open new perspectives for C14-tracing applications, such as radiocarbon dating, biomedicine, or environmental and earth sciences. The detection of other very rare molecules can be pursued as well thanks to the wide and continuous mid-IR spectral coverage of the described setup.

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

    PubMed

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

    2014-08-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

    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].

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

    SciTech Connect

    Loui, A; McCall, S K

    2011-10-24

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

  6. One-Dimensional Nanostructure Field-Effect Sensors for Gas Detection

    PubMed Central

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

    2014-01-01

    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

  7. Neutron detection using far ultraviolet radiation from noble-gas excimers

    NASA Astrophysics Data System (ADS)

    Coplan, Michael A.; McComb, Jacob C.; Al-Sheikhly, Mohamad I.; Miller, Eric; Lavelle, Christopher M.; Thompson, Alan K.; Vest, Robert E.; Clark, Charles W.; Neutron Observatory Collaboration

    2015-03-01

    When triggered in a noble gas medium at around atmospheric pressure, low-energy neutron-absorption reactions such as 3He(n,tp) and 10B(n, ?)7Li can generate tens of thousands of far ultraviolet photons per neutron absorbed. In some cases, up to 30% of the ~ MeV nuclear reaction energy is channeled into far ultraviolet emission. The far ultraviolet photons are produced by noble-gas excimer radiation, to which the noble gas medium is transparent, facilitating efficient optical detection. We report progress in the development of the Neutron Observatory, http://j.mp/N3utr0n , an absolute neutron detector stationed at the fundamental physics beamline at the NIST Center for Neutron Research. Our reaction initiators consist of arrays of thin films of 10B and boron-coated vitreous carbon foams

  8. In situ gas sensing using a remotely detectable probe with replaceable insert.

    PubMed

    Lim, Sun Do; Ma, Kyungsik; Jeong, Ji Ho; Kim, Gilhwan; Lee, Kwanil; Jeong, Je-Myung; Lee, Sang Bae

    2012-01-16

    We demonstrate a spectroscopic gas sensor using an optical fiber probe with a replaceable insert. The probe consists of a hollow-core photonic bandgap fiber (HC-PBGF) with a core diameter of 10.9 ?m and a glass tube where a 2-?m hollow core fiber (HCF) with a gold coated end facet can be inserted. The HCF is designed to function as both a gate where gases can enter the HC-PBGF and a mirror reflecting the guided light back to the HC-PBGF. The opposite distal end of the probe is also designed to be able to regulate the gas pressure within the HC-PBGF for a high gas flow rate, while still transmitting the reflected light to the analysis instrument. The remote sensing probe, we believe, has much potential for detecting gases in hazardous environments. PMID:22274515

  9. Non-intrusive detection of methanol in gas phase using infrared degenerate four-wave mixing

    NASA Astrophysics Data System (ADS)

    Zhou, J.; Sahlberg, A. L.; Nilsson, H.; Lundgren, E.; Zetterberg, J.

    2015-11-01

    Sensitive and non-intrusive detection of gas-phase methanol with high spatial and temporal resolution has for the first time been reported using mid-infrared degenerate four-wave mixing (IR-DFWM). IR-DFWM spectra of methanol have been successfully recorded in nitrogen-diluted gas flows at room temperature and at 300 °C, by probing ro-vibrational transitions belonging to the fundamental C-H stretching modes, ? 2 and ? 9, and the O-H stretching mode, ? 1. The detection limit of methanol vapor at room temperature and atmospheric pressure is estimated to be 250 ppm with the present setup. Potential interference from CH4 and CO2 is discussed from recorded IR-DFWM spectra of CH4 and CO2, and it was found that detection of methanol free from CH4 and CO2 interference is possible. These results show the potential of the detection of methanol with IR-DFWM for applications in both combustion and catalytic environments, such as CO2 hydrogenation and CH4 oxidation.

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

    DOEpatents

    Bond, Tiziana; Cole, Garrett; Goddard, Lynford

    2012-11-13

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

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

    PubMed

    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

    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

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

    PubMed

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

    2014-02-12

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

  13. Highly sensitive trace gas detection of molecular species with dense, poorly resolved spectra

    NASA Astrophysics Data System (ADS)

    Karpf, Andreas B.

    The development and demonstration of two new techniques for highly sensitive trace gas detection of molecules with dense, poorly resolved spectra are presented. Unlike many other spectroscopic detection methods, these approaches may be used at atmospheric pressure and are of particular use for cases where resolving the individual spectral lines of the target molecules is not practical. The techniques described in this work are: 1) Frequency Modulated Off-Axis Cavity Ringdown Spectroscopy (FM OA-CRDS); and 2) Multiple Line Integrated Absorption Spectroscopy (MLIAS). FM OA-CRDS is a variation of cavity ring down spectroscopy in which the laser frequency is modulated and off-axis alignment is used to make it more suitable for deployment in vibration-prone such as in-situ studies of the chemical balance in the atmosphere. An additional advantage is that the experimental arrangement is simple and does not involve the elaborate adjustments necessary to lock to a cavity resonance. The technique is demonstrated to detect Nitrogen Dioxide (NO2) with a sensitivity of 1.5 ppb (parts-per-billion). MLIAS is a technique that enhances the sensitivity of a spectrometer for trace gas detection by integrating the absorption spectra of a species across multiple lines. When combined with the long pathlengths available using Integrated Cavity Output Spectroscopy (ICOS), MLIAS allows one to achieve extremely high levels of sensitivity. The technique is demonstrated using NO2, where we integrate over more than 100 transitions in the R-band, and record an effective sensitivity of detection of 10 ppt. To the best of our knowledge, this is the most sensitive level of detection of NO2 to date using room-temperature apparatus.

  14. Quantitation of dissolved gas content in emulsions and in blood using mass spectrometric detection

    PubMed Central

    Grimley, Everett; Turner, Nicole; Newell, Clayton; Simpkins, Cuthbert; Rodriguez, Juan

    2011-01-01

    Quantitation of dissolved gases in blood or in other biological media is essential for understanding the dynamics of metabolic processes. Current detection techniques, while enabling rapid and convenient assessment of dissolved gases, provide only direct information on the partial pressure of gases dissolved in the aqueous fraction of the fluid. The more relevant quantity known as gas content, which refers to the total amount of the gas in all fractions of the sample, can be inferred from those partial pressures, but only indirectly through mathematical modeling. Here we describe a simple mass spectrometric technique for rapid and direct quantitation of gas content for a wide range of gases. The technique is based on a mass spectrometer detector that continuously monitors gases that are rapidly extracted from samples injected into a purge vessel. The accuracy and sample processing speed of the system is demonstrated with experiments that reproduce within minutes literature values for the solubility of various gases in water. The capability of the technique is further demonstrated through accurate determination of O2 content in a lipid emulsion and in whole blood, using as little as 20 ?L of sample. The approach to gas content quantitation described here should greatly expand the range of animals and conditions that may be used in studies of metabolic gas exchange, and facilitate the development of artificial oxygen carriers and resuscitation fluids. PMID:21497566

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

    SciTech Connect

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

    1997-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Reshetyuk, Yuriy; Mårtensson, Stig-Göran

    2014-04-01

    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.

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

    SciTech Connect

    Carrigan, C R; Sun, Y

    2011-01-21

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

  18. FTIR gas analysis with improved sensitivity and selectivity for CWA and TIC detection

    NASA Astrophysics Data System (ADS)

    Phillips, Charles M.; Tan, Huwei

    2010-04-01

    This presentation describes the use of an FTIR (Fourier Transform Infrared)-based spectrometer designed to continuously monitor ambient air for the presence of chemical warfare agents (CWAs) and toxic industrial chemicals (TICs). The necessity of a reliable system capable of quickly and accurately detecting very low levels of CWAs and TICs while simultaneously retaining a negligible false alarm rate will be explored. Technological advancements in FTIR sensing have reduced noise while increasing selectivity and speed of detection. These novel analyzer design characteristics are discussed in detail and descriptions are provided which show how optical throughput, gas cell form factor, and detector response are optimized. The hardware and algorithms described here will explain why this FTIR system is very effective for the simultaneous detection and speciation of a wide variety of toxic compounds at ppb concentrations. Analytical test data will be reviewed demonstrating the system's sensitivity to and selectivity for specific CWAs and TICs; this will include recent data acquired as part of the DHS ARFCAM (Autonomous Rapid Facility Chemical Agent Monitor) project. These results include analyses of the data from live agent testing for the determination of CWA detection limits, immunity to interferences, detection times, residual noise analysis and false alarm rates. Sensing systems such as this are critical for effective chemical hazard identification which is directly relevant to the CBRNE community.

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

    SciTech Connect

    Lewis, J. M. Kelley, R. P.; Jordan, K. A.; Murer, D.

    2014-07-07

    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.

  20. Nanomolecular gas sensor architectures based on functionalized carbon nanotubes for vapor detection

    NASA Astrophysics Data System (ADS)

    Hines, Deon; Zhang, Henan; Rümmeli, Mark H.; Adebimpe, David; Akins, Daniel L.

    2015-05-01

    There is enormous interest in detection of simple & complex odors by mean of electronic instrumentation. Specifically, our work focuses on creating derivatized-nanotube-based "electronic noses" for the detection and identification of gases, and other materials. We have grafted single-walled carbon nanotubes (SWNTs) with an array of electron-donating and electron withdrawing moieties and have characterized some of the physicochemical properties of the modified nanotubes. Gas sensing elements have been fabricated by spin coating the functionalized nanotubes onto interdigitated electrodes (IDE's), creating an array of sensors. Each element in the sensor array can contain a different functionalized matrix. This facilitates the construction of chemical sensor arrays with high selectivity and sensitivity; a methodology that mimics the mammalian olfactory system. Exposure of these coated IDEs to organic vapors and the successful classification of the data obtained under DC monitoring, indicate that the system can function as gas sensors of high repeatability and selectivity for a wide range of common analytes. Since the detection of explosive materials is also of concern in this research, our next phase focuses on explosives such as, TNT, RDX, and Triacetone Triperoxide (TATP). Sensor data from individual detection are assessed on their own individual merits, after which they are amalgamated and reclassified to present each vapor as unique data point on a 2-dimensional map and with minimum loss of information. This approach can assist the nation's need for a technology to defeat IEDs through the use of methods that detect unique chemical signatures associated with explosive molecules and byproducts.

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

    SciTech Connect

    Hoekstra, P.; Lynn, H.

    1993-12-31

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    PubMed

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

    2013-05-01

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

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

    SciTech Connect

    Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan; Seonghyeon Park

    2005-12-07

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  6. Detection of the Elusive Triazane Molecule (N3 H5 ) in the Gas Phase.

    PubMed

    Förstel, Marko; Maksyutenko, Pavlo; Jones, Brant M; Sun, Bing-Jian; Chen, Shih-Hua; Chang, Agnes H-H; Kaiser, Ralf I

    2015-10-01

    We report the detection of triazane (N3 H5 ) in the gas phase. Triazane is a higher order nitrogen hydride of ammonia (NH3 ) and hydrazine (N2 H4 ) of fundamental importance for the understanding of the stability of single-bonded chains of nitrogen atoms and a potential key intermediate in hydrogen-nitrogen chemistry. The experimental results along with electronic-structure calculations reveal that triazane presents a stable molecule with a nitrogen-nitrogen bond length that is a few picometers shorter than that of hydrazine and has a lifetime exceeding 6±2??s at a sublimation temperature of 170?K. Triazane was synthesized through irradiation of ammonia ice with energetic electrons and was detected in the gas phase upon sublimation of the ice through soft vacuum ultraviolet (VUV) photoionization coupled with a reflectron-time-of-flight mass spectrometer. Isotopic substitution experiments exploiting [D3 ]-ammonia ice confirmed the identification through the detection of its fully deuterated counterpart [D5 ]-triazane (N3 D5 ). PMID:26331382

  7. Gas detection with microelectromechanical Fabry-Perot interferometer technology in cell phone

    NASA Astrophysics Data System (ADS)

    Mannila, Rami; Hyypiö, Risto; Korkalainen, Marko; Blomberg, Martti; Kattelus, Hannu; Rissanen, Anna

    2015-06-01

    VTT Technical Research Centre of Finland has developed a miniaturized optical sensor for gas detection in a cell phone. The sensor is based on a microelectromechanical (MEMS) Fabry-Perot interferometer, which is a structure with 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. VTT has designed and manufactured a MEMS FPI based carbon dioxide sensor demonstrator which is integrated to a cell phone shield cover. The demonstrator contains light source, gas cell, MEMS FPI, detector, control electronics and two coin cell batteries as a power source. It is connected to the cell phone by Bluetooth. By adjusting the wavelength range and customizing the MEMS FPI structure, it is possible to selectively sense multiple gases.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  9. Method for Detection of Trace Metal and Metalloid Contaminants in Coal-Generated Fuel Gas Using Gas Chromatography/Ion Trap Mass Spectrometry

    SciTech Connect

    Rupp, Erik C.; Granite, Evan J.; Stanko, Dennis C.

    2010-07-15

    There exists an increasing need to develop a reliable method to detect trace contaminants in fuel gas derived from coal gasification. While Hg is subject to current and future regulations, As, Se, and P emissions may eventually be regulated. Sorbents are the most promising technology for the removal of contaminants from coal-derived fuel gas, and it will be important to develop a rapid analytical detection method to ensure complete removal and determine the ideal time for sorbent replacement/regeneration in order to reduce costs. This technical note explores the use of a commercial gas chromatography/ion trap mass spectrometry system for the detection of four gaseous trace contaminants in a simulated fuel gas. Quantitative, repeatable detection with limits at ppbv to ppmv levels were obtained for arsine (AsH3), phosphine (PH3), and hydrogen selenide (H2Se), while qualitative detection was observed for mercury. Decreased accuracy and response caused by the primary components of fuel gas were observed.

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

    NASA Technical Reports Server (NTRS)

    Lo, Ching F.; Hoyt, W. Andes

    1989-01-01

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

  11. Detection of OH on photolysis of styrene oxide at 193 nm in gas phase

    NASA Astrophysics Data System (ADS)

    Kumar, Awadhesh; SenGupta, Sumana; Pushpa, K. K.; Naik, P. D.; Bajaj, P. N.

    2006-10-01

    Photodissociation of styrene oxide at 193 nm in gas phase generates OH, as detected by laser-induced fluorescence technique. Under similar conditions, OH was not observed from ethylene and propylene oxides, primarily because of their low absorption cross-sections at 193 nm. Mechanism of OH formation involves first opening of the three-membered ring from the ground electronic state via cleavage of either of two C sbnd O bonds, followed by isomerization to enolic forms of phenylacetaldehyde and acetophenone, and finally scission of the C sbnd OH bond of enols. Ab initio molecular orbital calculations support the proposed mechanism.

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

    NASA Astrophysics Data System (ADS)

    Vai?ikauskas, V.; Kau?ikas, M.; Švedas, V.; Kuprionis, Z.

    2007-02-01

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

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

    SciTech Connect

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

    2011-04-20

    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.

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

    PubMed

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

    2011-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    PubMed

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

    2000-07-01

    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

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

    SciTech Connect

    Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan

    2004-10-25

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

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

    SciTech Connect

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

    2010-08-20

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

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

    PubMed Central

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

    2010-01-01

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

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

    SciTech Connect

    Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan; Seonghyeon Park

    2005-12-07

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

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

    PubMed

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

    2010-01-01

    Atmospheric pollution is one of the worst threats to modern society. The consequences derived from different forms of atmospheric pollution vary from the local to the global scale, with deep impacts on climate, environment and human health. Several gaseous pollutants, even when present in trace concentrations, play a fundamental role in important processes that occur in atmosphere. Phenomena such as global warming, photochemical smog formation, acid rain and the depletion of the stratospheric ozone layer are strongly related to the increased concentration of certain gaseous species in the atmosphere. The transport sector significantly produces atmospheric pollution, mainly when diesel oil is used as fuel. Therefore, new methodologies based on selective and sensitive gas detection schemes must be developed in order to detect and monitor pollutant gases from this source. In this work, 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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Welsh, Barry Y.; Montgomery, Sharon

    2013-07-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Chu, Yun

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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2013-01-01

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

  8. Rapid detection of bacteria with miniaturized pyrolysis-gas chromatographic analysis

    NASA Astrophysics Data System (ADS)

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

    2002-02-01

    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.

  9. AIRBORNE, OPTICAL REMOTE SENSING OF METHANE AND ETHANE FOR NATURAL GAS PIPELINE LEAK DETECTION

    SciTech Connect

    Jerry Myers

    2003-05-13

    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.

  10. AIRBORNE, OPTICAL REMOTE SENSING OF METHANE AND ETHANE FOR NATURAL GAS PIPLINE LEAK DETECTION

    SciTech Connect

    Jerry Myers

    2004-05-12

    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.

  11. Direct Measurement of Trace Elemental Mercury in Hydrocarbon Matrices by Gas Chromatography with Ultraviolet Photometric Detection.

    PubMed

    Gras, Ronda; Luong, Jim; Shellie, Robert A

    2015-11-17

    We introduce a technique for the direct measurement of elemental mercury in light hydrocarbons such as natural gas. We determined elemental mercury at the parts-per-trillion level with high precision [<3% RSD (n = 20 manual injection)] using gas chromatography with ultraviolet photometric detection (GC-UV) at 254 nm. Our approach requires a small sample volume (1 mL) and does not rely on any form of sample preconcentration. The GC-UV separation employs an inert divinylbenzene porous layer open tubular column set to separate mercury from other components in the sample matrix. We incorporated a 10-port gas-sampling valve in the GC-UV system, which enables automated sampling, as well as back flushing capability to enhance system cleanliness and sample throughput. Total analysis time is <2 min, and the procedure is linear over a range of 2-83 ?g/m(3) [correlation coefficient of R(2) = 0.998] with a measured recovery of >98% over this range. PMID:26456880

  12. A micro gas preconcentrator with improved performance for pollution monitoring and explosives detection.

    PubMed

    Camara, E H M; Breuil, P; Briand, D; de Rooij, N F; Pijolat, C

    2011-03-01

    This paper presents the optimization of a micro gas preconcentrator based on a micro-channel in porous and non-porous silicon filled with an adequate adsorbent. This micro gas preconcentrator is both applicable in the fields of atmospheric pollution monitoring (Volatil organic compounds--VOCs) and explosives detection (nitroaromatic compounds). Different designs of micro-devices and adsorbent materials have been investigated since these two parameters are of importance in the performances of the micro-device. The optimization of the device and its operation were driven by its future application in outdoor environments. Parameters such as the preconcentration factor, cycle time and the influence of the humidity were considered along the optimization process. As a result of this study, a preconcentrator with a total cycle time of 10 min and the use of single wall carbon nanotubes (SWCNTs) as adsorbent exhibits a good preconcentration factor for VOCs with a limited influence of the humidity. The benefits of using porous silicon to modify the gas desorption kinetics are also investigated. PMID:21334483

  13. Xenon Additives Detection in Helium Micro-Plasma Gas Analytical Sensor

    NASA Astrophysics Data System (ADS)

    Tsyganov, Alexander; Kudryavtsev, Anatoliy; Mustafaev, Alexander

    2012-10-01

    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.

  14. THz quartz-enhanced photoacoustic sensor for H?S trace gas detection.

    PubMed

    Spagnolo, Vincenzo; Patimisco, Pietro; Pennetta, Riccardo; Sampaolo, Angelo; Scamarcio, Gaetano; Vitiello, Miriam S; Tittel, Frank K

    2015-03-23

    We report on a quartz-enhanced photoacoustic (QEPAS) gas sensing system for hydrogen sulphide (H?S) detection. The system architecture is based on a custom quartz tuning fork (QTF) optoacoustic transducer with a novel geometry and a quantum cascade laser (QCL) emitting 1.1 mW at a frequency of 2.913 THz. The QTF operated on the first flexion resonance frequency of 2871 Hz, with a quality factor Q = 17,900 at 20 Torr. The tuning range of the available QCL allowed the excitation of a H?S rotational absorption line with a line-strength as small as S = 1.13·10?²² cm/mol. The measured detection sensitivity is 30 ppm in 3 seconds and 13 ppm for a 30 seconds integration time, which corresponds to a minimum detectable absorption coefficient ?(min) = 2.3·10?? cm?¹ and a normalized noise-equivalent absorption NNEA = 4.4·10?¹? W·cm?¹·Hz(-1/2), several times lower than the values previously reported for near-IR and mid-IR H?S QEPAS sensors. PMID:25837095

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

    NASA Astrophysics Data System (ADS)

    Caron, James N.; Kunapareddy, Pratima

    2014-02-01

    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.

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

    SciTech Connect

    Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan; Seonghyeon Park

    2005-04-15

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

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

    SciTech Connect

    Caron, James N.; Kunapareddy, Pratima

    2014-02-18

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

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

    PubMed

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

    2012-01-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    SciTech Connect

    Lewicki, Jennifer L.; Oldenburg, Curtis M.

    2004-12-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

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

    DOEpatents

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

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

    2001-07-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  5. Research on ground-based LWIR hyperspectral imaging remote gas detection

    NASA Astrophysics Data System (ADS)

    Yang, Zhixiong; Yu, Chunchao; Zheng, Weijian; Lei, Zhenggang; Yan, Min; Yuan, Xiaochun; Zhang, Peizhong

    2015-10-01

    The new progress of ground-based long-wave infrared remote sensing is presented, which describes the windowing spatial and temporal modulation Fourier spectroscopy imaging in details. The prototype forms the interference fringes based on the corner-cube of spatial modulation of Michelson interferometer, using cooled long-wave infrared photovoltaic staring FPA (focal plane array) detector. The LWIR hyperspectral imaging is achieved by the process of collection, reorganization, correction, apodization, FFT etc. from data cube. Noise equivalent sensor response (NESR), which is the sensitivity index of CHIPED-1 LWIR hyperspectral imaging prototype, can reach 5.6×10-8W/(cm-1.sr.cm2) at single sampling. Hyperspectral imaging is used in the field of organic gas VOC infrared detection. Relative to wide band infrared imaging, it has some advantages. Such as, it has high sensitivity, the strong anti-interference ability, identify the variety, and so on.

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

    NASA Technical Reports Server (NTRS)

    Grant, W. B.

    1986-01-01

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

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

    SciTech Connect

    Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan

    2004-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

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

    PubMed Central

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

    2014-01-01

    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

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

    SciTech Connect

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

    2014-11-15

    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 C{sub 2}F{sub 6}, 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.

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

    PubMed

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

    2014-01-01

    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

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

    PubMed

    Ringer, Joachim M

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Mallin, Daniel

    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.

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

    PubMed Central

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

    2014-01-01

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

  15. Towards Coherent Neutrino Detection Using Low-Background Micropattern Gas Detectors

    E-print Network

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

    2002-12-14

    The detection of low energy neutrinos ($nuclear scattering remains a holy grail of sorts in neutrino physics. This uncontroversial mode of interaction is expected to profit from a sizeable increase in cross section proportional to neutron number squared in the target nucleus, an advantageous feature in view of the small probability of interaction via all other channels in this energy region. A coherent neutrino detector would open the door to many new applications, ranging from the study of fundamental neutrino properties to true "neutrino technology". Unfortunately, present-day radiation detectors of sufficiently large mass ($>$ 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 approach to assessing their sensitivity to these faint signals. Applications are reviewed, in particular their use as a safeguard against illegitimate operation of nuclear reactors. A first industrial mass production of Gas Electron Multipliers (GEMs) is succinctly described.

  16. AIRBORNE, OPTICAL REMOTE SENSING OF METHANE AND ETHANE FOR NATURAL GAS PIPELINE LEAK DETECTION

    SciTech Connect

    Jerry Myers

    2003-11-12

    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.

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

    PubMed

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

    2011-02-15

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

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

    PubMed

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

    2013-02-19

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

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

    PubMed

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

    2009-02-01

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

  20. A gas ionisation detector in the axial (Bragg) geometry used for the time-of-flight elastic recoil detection analysis.

    PubMed

    Siketi?, Zdravko; Skukan, Natko; Bogdanovi? Radovi?, Iva

    2015-08-01

    In this paper, time-of-flight elastic recoil detection analysis spectrometer with a newly constructed gas ionization detector for energy detection is presented. The detector is designed in the axial (Bragg) geometry with a 3 × 3 array of 50 nm thick Si3N4 membranes as an entrance window. 40 mbar isobutane gas was sufficient to stop a 30 MeV primary iodine beam as well as all recoils in the detector volume. Spectrometer and detector performances were determined showing significant improvement in the mass and energy resolution, respectively, comparing to the spectrometer with a standard silicon particle detector for an energy measurement. PMID:26329175

  1. A gas ionisation detector in the axial (Bragg) geometry used for the time-of-flight elastic recoil detection analysis

    NASA Astrophysics Data System (ADS)

    Siketi?, Zdravko; Skukan, Natko; Bogdanovi? Radovi?, Iva

    2015-08-01

    In this paper, time-of-flight elastic recoil detection analysis spectrometer with a newly constructed gas ionization detector for energy detection is presented. The detector is designed in the axial (Bragg) geometry with a 3 × 3 array of 50 nm thick Si3N4 membranes as an entrance window. 40 mbar isobutane gas was sufficient to stop a 30 MeV primary iodine beam as well as all recoils in the detector volume. Spectrometer and detector performances were determined showing significant improvement in the mass and energy resolution, respectively, comparing to the spectrometer with a standard silicon particle detector for an energy measurement.

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

    NASA Technical Reports Server (NTRS)

    Medelius, Pedro J.

    2006-01-01

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

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

    EPA Science Inventory

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

  4. Detection threshold energy of high energy cascade showers using thermoluminescence PTFE-sheet and hot-gas reader

    NASA Technical Reports Server (NTRS)

    Kino, S.; Nakanishi, A.; Miono, S.; Kitajima, T.; Yanagita, T.; Nakatsuka, T.; Ohmori, N.; Hazama, M.

    1985-01-01

    A new thermoluminescence (TL) sheet was developed as a detector for high energy components in air showers. For the investigation of detection threshold energy for a cascade showeer, TL sheets were exposed at Mt. Fuji with X ray films in emulsion chambers and were scanned by a hot-gas reader. It is concluded that if a gamma ray whose energy is more than 6 TeV enters vertically into lead chambers, the resulting cascade shower is readily detectable at maximum development.

  5. CO2 gas detection properties of a TIO2/Al2O3 heterostructure under UV light irradiation

    NASA Astrophysics Data System (ADS)

    Karaduman, Irmak; Demir, Mehmet; Y?ld?z, Dilber Esra; Acar, Selim

    2015-05-01

    Al/TiO2/p-Si and Al/T?O2/Al2O3/p-Si samples were prepared using the atomic layer deposition method (ALD) and their gas sensing properties were investigated. The electrical properties of the samples were studied using a two probe method in the temperature range 25-230 °C and at room temperature UV conditions. The TiO2/Al2O3 heterojunction sample exhibited an excellent gas sensing response to CO2 gas at room temperature and improved the effect of UV light irradiation. The results showed that heterostructures helped to improve the gas sensor properties, affected the sensing at room temperature and thus guided the design of photocatalysts. The TiO2/Al2O3 heterojunction prepared using this method can be used as a material for semiconductor gas sensors detecting poisonous gases like CO2 at room temperature with high sensitivity and selectivity.

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

    SciTech Connect

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

    2000-12-07

    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).

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

    DOEpatents

    Owen, Thomas E.; Miller, Michael A.

    2007-03-13

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

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

    DOEpatents

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

    2010-08-24

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

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

    EPA Science Inventory

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

  11. 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...

  12. Detecting the Influence of Gas Seepage on Vegetation, using Hyperspectral Remote Sensing

    E-print Network

    on vegetation reflectance, in which both natural gas seepage and gas pipeline leakage will be studied. Keywords: noomen@itc.nl ABSTRACT A high gas concentration in the soil - whether from natural hydrocarbon seepage or from leaking gas pipelines ­ affects the vegetation reflectance. However, the exact mechanism

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

    SciTech Connect

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

    2012-09-30

    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.

  14. Gas leak localization and detection method based on a multi-point ultrasonic sensor array with TDOA algorithm

    NASA Astrophysics Data System (ADS)

    Tao, Wang; Dongying, Wang; Yu, Pei; Wei, Fan

    2015-09-01

    To resolve the measured target position to determine and locate leak problems with current gas leak detection and localization systems based on ultrasonic technology, this paper presents an improved multi-array ultrasonic gas leak TDOA (time difference of arrival) localization and detection method. This method involves arranging ultrasonic transducers at equal intervals in a high-sensitivity detector array, using small differences in ultrasonic sound intensity to determine the scope of the leak and generate a rough localization, and then using an array TDOA localization algorithm to determine the precise leak location. This method is then implemented in an ultrasonic leak detection and localization system. Experimental results showed that the TDOA localization method, using auxiliary sound intensity factors to avoid dependence on a single sound intensity to determine the leak size and location, achieved a localization error of less than 2?mm. The validity and correctness of this approach were thus verified.

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

    NASA Technical Reports Server (NTRS)

    Haralambous, Michael G.

    2001-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Haralambous, Michael G.

    2002-01-01

    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.

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

    SciTech Connect

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

    2007-06-13

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

  18. Determination of methyltetrahydrophthalic anhydride in air using gas chromatography with electron-capture detection.

    PubMed

    Johyama, Y; Yokota, K; Fujiki, Y; Takeshita, T; Morimoto, K

    1999-10-01

    Methyltetrahydrophthalic anhydride (MTHPA) stimulates the production of specific IgE antibodies which can cause occupational allergy even at extremely low levels of exposure (15-22 micrograms/m3). Safe use in industry demands control of the levels of exposure causing allergic diseases. Thus, the air monitoring of MTHPA is very important, and sensitive methods are required to measure low air concentrations or short-time peak exposures. This paper outlines the use of silica-gel tubes for sampling airborne MTHPA vapour, followed by analysis using gas chromatography with electron-capture detection. No breakthrough was observed at 113, 217, 673 and 830 micrograms/m3 (sampling volume 30, 60, 60 and 20 l, respectively; relative humidity 40-55%). Concentrations > 1.0 microgram/m3 could be quantified at 20-min sampling with a sampling rate of 1 l/min. The present method can also be applied to measurements of exposure to hexahydrophthalic and methylhexahydrophthalic anhydride. The risk of MTHPA exposure in two condenser plants was also assessed by determining MTHPA levels in air of the workplace. In conclusion, our method was found to be reliable and sensitive, and can be applied to the evaluation of MTHPA exposure. PMID:10547951

  19. Determination of tobacco alkaloids by gas chromatography with nitrogen-phosphorus detection.

    PubMed

    Yang, S S; Smetena, I; Huang, C B

    2002-04-01

    An improved method, gas chromatography (GC) with nitrogen-phosphorus detection (NPD), has been used for determination of alkaloids in green and cured tobacco. Tobacco alkaloids of interest included nicotine, nornicotine, myosmine, anabasine, and anatabine. Tobacco samples were treated with a small quantity of aqueous ammonia solution to "loosen" tobacco tissue and to adjust pH, then extracted with solvent. The composition of the extraction solvent solution affected recoveries of the alkaloids, particularly nornicotine, and also contributed to other phenomena such as carry-over in the injection liner and "quenching" of the nitrogen-phosphorus detector. Use of a packed injection liner (e.g. with Carbowax-KOH on Chromosorb) to reduce carry-over was studied. Quenching of the nitrogen-phosphorus detector was eliminated by reducing the injection volume (i.e. increasing the split ratio), by use of a packed injection liner, and by reducing the amount of pretreatment with aqueous ammonia. A narrow bore capillary column (i.e. 0.18 mm id) was used to improve sensitivity and resolution and to increase the speed of GC analysis. An internal standard, 2,4'-dipyridyl, was used for quantitative measurement of these tobacco alkaloids. PMID:12194047

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

    SciTech Connect

    1994-10-01

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

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

    PubMed Central

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

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2012-05-01

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

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

    SciTech Connect

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

    2008-12-15

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

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

    USGS Publications Warehouse

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

    2004-01-01

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

  7. Improved method for rapid detection of phthalates in bottled water by gas chromatography-mass spectrometry.

    PubMed

    Otero, Paz; Saha, Sushanta Kumar; Moane, Siobhan; Barron, John; Clancy, Gerard; Murray, Patrick

    2015-08-01

    An improved gas chromatography-mass spectrometry (GC-MS) method for simple, rapid and precise quantification of phthalates in drinking water is presented. This method was validated for bis (2-n-butoxyethyl) phthalate (DBEP), bis (2-n-ethylhexyl) phthalate (DEHP), butyl benzyl phthalate (BBP), di-butyl phthalate (DBP), diethyl phthalate (DEP), dihexyl phthalate (DHP), dimethyl phthalate (DMP), di-n-octyl phthalate (DNOP) and dinonyl phthalate (DINP). Linearity of 0.9984>r(2)>0.9975 in the range of 0.075-4.8?g/mL for the selected phthalates was obtained. Accuracy values were in the range of 93-114% and RSD% for the analysis of 1.2?g/mL of each phthalate was below 2.3% (n=9). This new method design has significantly improved the detection in terms of rapidity, specificity, repeatability and accuracy compared to available methods. The procedure has been applied to the analyses of three different brands of commercially available bottled mineral water and the corresponding plastic bottles. Phthalates were extracted with dichloromethane and re-constituted in cyclohexane prior to GC-MS analysis. When the validated GC-MS method was applied to the quantification of the selected phthalates in the samples, only DBP (up to 0.0675±0.0018?g/mL) and DEHP (up to 1.6848±0.1631?g/mL) were found. Furthermore, we provide specific data about the concentration of DBP and DEHP in bottled water attributable to migration of phthalates from respective plastic bottles. PMID:26134297

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

    NASA Technical Reports Server (NTRS)

    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

    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.

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

    PubMed

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

    2012-08-01

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

  10. 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)

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

    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.

  11. 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

    Zhang, Yaohai; Zhang, Xuelian; Jiao, Bining

    2014-09-15

    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

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

    PubMed

    Belden, Jesse; Jandron, Michael

    2014-08-01

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

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

    PubMed

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

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    PubMed Central

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

    2014-01-01

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

  16. Detection and quantification of adulteration of sesame oils with vegetable oils using gas chromatography and multivariate data analysis.

    PubMed

    Peng, Dan; Bi, Yanlan; Ren, Xiaona; Yang, Guolong; Sun, Shangde; Wang, Xuede

    2015-12-01

    This study was performed to develop a hierarchical approach for detection and quantification of adulteration of sesame oil with vegetable oils using gas chromatography (GC). At first, a model was constructed to discriminate the difference between authentic sesame oils and adulterated sesame oils using support vector machine (SVM) algorithm. Then, another SVM-based model is developed to identify the type of adulterant in the mixed oil. At last, prediction models for sesame oil were built for each kind of oil using partial least square method. To validate this approach, 746 samples were prepared by mixing authentic sesame oils with five types of vegetable oil. The prediction results show that the detection limit for authentication is as low as 5% in mixing ratio and the root-mean-square errors for prediction range from 1.19% to 4.29%, meaning that this approach is a valuable tool to detect and quantify the adulteration of sesame oil. PMID:26041212

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

    NASA Technical Reports Server (NTRS)

    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

    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.

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

    EPA Science Inventory

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

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

    E-print Network

    Slatton, Clint

    to positively impact the bottom line. In the oil and gas industry, modern oil rigs are outfitted with thousands in the bore well which is typical in oil production. The short time Fourier transform and dynamical systems of oil and gas -from rock formations in the sea bed that contain deposits- to distribution systems

  20. 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...

  1. Fire Detections and Fire Radiative Power Intercomparison Using Multiple Sensor Products over a Predominantly Gas Flaring Region

    NASA Astrophysics Data System (ADS)

    Sharma, A.; Wang, J.

    2014-12-01

    Gas flaring is a global environmental hazard severely impacting climate, economy and public health. The associated emissions are frequently unreported and have large uncertainties. Prior studies have established a direct relationship between radiative energy released from fires and the biomass burned, making fire radiative power (FRP), i.e., the rate of radiative energy release, an important proxy to characterize emissions. In this study fire properties from four different satellite products were obtained over a 10? x 10? gas flaring region in Russia for all days of May 2013. The target area is part of Russia's biggest gas flaring region, Khanty-Mansiysk autonomous okrug. The objective of the study is to investigate the consistency of fire detections, FRP retrievals and effects of gridding FRP data from the region on a uniform grid. The four products used were: MODIS Terra level2 thermal anomalies (MOD14), MODIS Aqua level2 thermal anomalies (MYD14), VIIRS Active fire product and a recent NOAA Nightfire product. 1 km nominal resolution FRP from MOD14 AND MYD14, subpixel radiant heat (RH) from NOAA Nightfire product and fire detections from all four products were recorded on a 0.25? x 0.25? grid on a daily basis. Results revealed the Nightfire product had maximum detections, almost six times the number of detections by other products, mainly because of the use of M10 (1.6 µm) band as their primary detection band. The M10 band is highly efficient in identifying radiant emissions from hot sources during night-time. The correlation (after omitting outliers) between gridded NOAA Nightfire RH and corresponding MOD14 FRP and MYD14 FRP gave a moderate regression value, with MODIS FRP being mostly higher than RH. As an extension to this work, a comprehensive study for a larger temporal domain also incorporating viewing geometries and cloud cover would advance our understanding of flare detections and associated FRP retrievals not just for the target region but also gas flaring regions globally.

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

    NASA Technical Reports Server (NTRS)

    Gregory, G. L.

    1976-01-01

    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.

  3. Analytical accuracy of hydrogen measurement using gas chromatography with thermal conductivity detection.

    PubMed

    Weijun, Yao

    2015-08-01

    Gas chromatography employing a thermal conductivity detector with a nitrogen carrier gas and a molecular sieve 5 Å column is commonly used for the analysis of widely varying hydrogen concentrations. Flow variation of the column, caused by carrier gas adsorption, affects the peak shape and impacts the analytical accuracy. The mechanism and factors affecting the adsorption effect are explored, errors caused by the deviation from the linearity of the detector's response are considered, and practical advice is given for improving the analytical accuracy. PMID:26011605

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

    NASA Technical Reports Server (NTRS)

    Oyama, V. I.

    1972-01-01

    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.

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

    SciTech Connect

    Heasler, Patrick G.

    2008-09-30

    This report develops a random field model that describes gas plumes in LWIR remote sensing images. The random field model serves as a prior distribution that can be combined with LWIR data to produce a posterior that determines the probability that a gas plume exists in the scene and also maps the most probable location of any plume. The random field model is intended to work with a single pixel regression estimator--a regression model that estimates gas concentration on an individual pixel basis.

  6. GC/HRSIR as a Complementary Technique to GC/ECNIMS

    EPA Science Inventory

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

  7. Comprehensive two-dimensional gas chromatography - time-of-flight mass spectrometry and simultaneous electron capture detection/nitrogen phosphorous detection for incense analysis

    NASA Astrophysics Data System (ADS)

    Tran, Tin C.; Marriott, Philip J.

    This study reports comprehensive two-dimensional gas chromatography hyphenated to time-of-flight mass spectrometry detection (GC × GC/TOFMS) for characterisation and identification of components generated by four different types of powdered incense headspace (H/S) and incense smoke. GC × GC/TOFMS allowed simultaneous separation and identification of compounds emitted into the atmosphere as a result of combustion of incense powder. The smoke stream comprised compounds originating from the incense powder, and combustion products such as saturated and unsaturated hydrocarbons, essential oil type compounds, nitromusks, fatty acid methyl esters (FAMEs), polycyclic aromatic hydrocarbons (PAHs, which possibly include oxygenated and nitrated PAH), N-heterocyclics, pyrans and furans, which were detected and tentatively identified by GC × GC/TOFMS. GC × GC-electron capture detector/nitrogen phosphorous detector (ECD/NPD) potentially offers the prospect of providing selective chemical compositional information of incense powder and smoke, such as nitrogen-containing (N-containing) and halogenated compounds. Results of GC×GC-ECD/NPD showed that both incense powder and smoke generated emission of N-containing and halogenated compounds. A significant number of halogenated and N-containing compounds were emitted during the incomplete combustion of incense. However, one further objective of this paper is to demonstrate the capacity of comprehensive two-dimensional gas chromatography coupled to specific and/or selective detectors such as those used in this study (GC × GC-ECD/NPD) for the detection of particular classes of compounds such as N-containing and halogenated compounds at trace level concentrations in complex smoke samples.

  8. Microcomputer-based instrument for the detection and analysis of precession motion in a gas centrifuge machine. Revision 1

    SciTech Connect

    Paulus, S.S.

    1986-03-01

    The Centrifuge Procession Analyzer (CPA) is a microcomputer-based instrument which detects precession motion in a gas centrifuge machine and calculates the amplitude and frequency of precession. The CPA consists of a printed circuit board which contains signal-conditioning circuitry and a 24-bit counter and an INTEL iSBC 80/24 single/board computer. Pression motion is detected by monitoring a signal generated by a variable reluctance pick-up coil in the top of the centrifuge machine. This signal is called a Fidler signal. The initial Fidler signal triggers a counter which is clocked by a high-precision, 20.000000-MHz, temperature-controlled, crystal oscillator. The contents of the counter are read by the computer and the counter reset after every ten Fidler signals. The speed of the centrifuge machine and the amplitude and frequency of precession are calculated and the results are displayed on a liquid crystal display on the front panel of the CPA. The report contains results from data generated by a Fidler signal simulator and data taken when the centrifuge was operated under three test conditions: (1) nitrogen gas during drive-up, steady state, and drive-down; (2) xenon gas during slip test, steady state, and the addition of gas; and (3) no gas during steady state. The qualitative results were consistent with experience with centrifuge machines using UF/sub 6/ in that the amplitude of precession increased and the frequency of precession decreased during drive-up, drive-down and the slip check. The magnitude of the amplitude and frequency of precession were proportional to the molecular weight of the gases in steady state.

  9. Microcomputer-based instrument for the detection and analysis of precession motion in a gas centrifuge machine

    SciTech Connect

    Paulus, S.S.

    1986-03-01

    The Centrifuge Precession Analyzer (CPA) is a microcomputer-based instrument which detects precession motion in a gas centrifuge machine and calculates the amplitude and frequency of precession. The CPA consists of a printed circuit board which contains signal-conditioning circuitry and a 24-bit counter and an INTEL iSBC 80-/24 single-board computer. Precession motion is detected by monitoring a signal generated by a variable reluctance pick-up coil in the top of the centrifuge machine. This signal is called a Fidler signal. The initial Fidler signal triggers a counter which is clocked by a high-precision, 20.000000-MHz, temperature-controlled, crystal oscillator. The contents of the counter are read by the computer, and the counter reset after every ten Fidler signals. The speed of the centrifuge machine and the amplitude and frequency of precession are calculated, and the results are displayed on a liquid crystal display on the front panel of the CPA. The thesis contains results from data generated by a Fidler signal simulator and data taken when the centrifuge was operated under three test conditions: (1) nitrogen gas during drive-up, steady state, and drive-down, (2) xenon gas during slip test, steady state, and the addition of gas, and (3) no gas during steady state. The qualitative results were consistent with experience with centrifuge machines UF/sub 6/ in that the amplitude of precession increased and the frequency of precession decreased during drive-up, drive-down and the slip check. The magnitude of the amplitude and frequency of precession were proportional to the molecular weight of the gases in steady state.

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

    E-print Network

    Swager, Timothy Manning

    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 ...

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

    E-print Network

    Fitzgerald, Kevin Francis

    1984-01-01

    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 ...

  12. Ultrasound detection of foreign body and gas contamination of a penetrating wound

    PubMed Central

    Testa, A.; Giannuzzi, R.; Zirio, G.; La Greca, A.; Silveri, N. Gentiloni

    2009-01-01

    We report a case in which ultrasonography (US) examination was used in the Emergency Department to reveal and diagnose gas contamination of a penetrating wound. Air microbubbles are extremely small and their typical distribution and movement are like those of “sparkling-wine microbubbles”. US assessment of spontaneous disappearance of the air bubbles can distinguish a harmless traumatic nature of the wound from a life-threatening gas-producing bacterial infection. PMID:23397000

  13. Method and apparatus for noble gas atom detection with isotopic selectivity

    DOEpatents

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

    1984-01-01

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

  14. Infrared hollow waveguide sensors for simultaneous gas phase detection of benzene, toluene, and xylenes in field environments.

    PubMed

    Young, Christina R; Menegazzo, Nicola; Riley, Andrew E; Brons, Cornelius H; DiSanzo, Frank P; Givens, Jacquelyn L; Martin, John L; Disko, Mark M; Mizaikoff, Boris

    2011-08-15

    Simultaneous and molecularly selective parts-per-billion detection of benzene, toluene, and xylenes (BTX) using a thermal desorption (TD)-FTIR hollow waveguide (HWG) trace gas sensor is demonstrated here for the first time combining laboratory calibration with real-world sample analysis in field. A calibration range of 100-1000 ppb analyte/N(2) was developed and applied for predicting the concentration of blinded environmental air samples within the same concentration range, and demonstrate close agreement with the validation method used here, GC-FID. The analyte concentration prediction capability of the TD-FTIR-HWG trace gas sensor also compares well with the industrial standard and other experimental techniques including GC-PID, ultrafast GC-FID, and GC-DMS, which were simultaneously operated in the field. With the advent of a quantum cascade laser with emission frequencies specifically tailored to efficiently overlap benzene absorption as the most relevant analyte, the overall sensor footprint could be considerably reduced to ultimately yield hand-held trace gas sensors facilitating direct and real-time detection of BTX in air down to low ppb levels. PMID:21612210

  15. Gas sensitivity and sensing mechanism studies on Au-doped TiO? nanotube arrays for detecting SF? decomposed components.

    PubMed

    Zhang, Xiaoxing; Yu, Lei; Tie, Jing; Dong, Xingchen

    2014-01-01

    The analysis to SF6 decomposed component gases is an efficient diagnostic approach to detect the partial discharge in gas-insulated switchgear (GIS) for the purpose of accessing the operating state of power equipment. This paper applied the Au-doped TiO2 nanotube array sensor (Au-TiO2 NTAs) to detect SF6 decomposed components. The electrochemical constant potential method was adopted in the Au-TiO2 NTAs' fabrication, and a series of experiments were conducted to test the characteristic SF6 decomposed gases for a thorough investigation of sensing performances. The sensing characteristic curves of intrinsic and Au-doped TiO2 NTAs were compared to study the mechanism of the gas sensing response. The results indicated that the doped Au could change the TiO2 nanotube arrays' performances of gas sensing selectivity in SF6 decomposed components, as well as reducing the working temperature of TiO2 NTAs. PMID:25330053

  16. Improving the Detection Limit in a Capillary Raman System for In Situ Gas Analysis by Means of Fluorescence Reduction

    PubMed Central

    Rupp, Simone; Off, Andreas; Seitz-Moskaliuk, Hendrik; James, Timothy M.; Telle, Helmut H.

    2015-01-01

    Raman spectroscopy for low-pressure or trace gas analysis is rather challenging, in particular in process control applications requiring trace detection and real-time response; in general, enhancement techniques are required. One possible enhancement approach which enjoys increasing popularity makes use of an internally-reflective capillary as the gas cell. However, in the majority of cases, such capillary systems were often limited in their achievable sensitivity by a significant fluorescence background, which is generated as a consequence of interactions between the laser light and optical glass components in the setup. In order to understand and counteract these problems we have investigated a range of fluorescence-reducing measures, including the rearrangement of optical elements, and the replacement of glass components—including the capillary itself—by metal alternatives. These studies now have led to a capillary setup in which fluorescence is practically eliminated and substantial signal enhancement over standard Raman setups is achieved. With this improved (prototype) setup, detection limits of well below 1 mbar could be obtained in sub-second acquisition times, demonstrating the potential of capillary Raman spectroscopy for real-time, in situ gas sensing and process control applications, down to trace level concentrations. PMID:26378545

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

    SciTech Connect

    1995-10-01

    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.

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

    PubMed

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

    2010-06-15

    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

  19. Chemotaxonomic differentiation of legionellae by detection and characterization of aminodideoxyhexoses and other unique sugars using gas chromatography-mass spectrometry.

    PubMed

    Fox, A; Rogers, J C; Fox, K F; Schnitzer, G; Morgan, S L; Brown, A; Aono, R

    1990-03-01

    Legionellae have been differentiated previously by analyzing their carbohydrate contents by gas chromatography with flame ionization detection. In the present study, total ion mode gas chromatography-mass spectrometry (GC-MS) was used to detect a number of unusual sugars, including one that is structurally related to O-methyldideoxyheptoses. Increased sensitivity and selectivity for carbohydrate detection was achieved by selected ion-monitoring GC-MS. Two of the uncommon sugars previously discovered in the legionellae (X1 and X2) were identified as quinovosamine and fucosamine, respectively. Legionella pneumophila contained rhamnose and quinovosamine but not the quinovosamine isomer fucosamine. Tatlockia micdadei and Legionella maceachernii contained large amounts of rhamnose, fucose, and fucosamine but not quinovosamine. These two species were the only legionellae studied that contained another unusual sugar that is referred to as X3, pending determination of its structure. Fluoribacter dumoffi, Fluoribacter bozemanae, and Legionella anisa were varied in their carbohydrate contents, both within and between species, but could be distinguished from L. pneumophila and the T. micdadei and L. maceachernii group. Fluoribacter gormanii was unique among the legionellae in that it lacked both quinovosamine and fucosamine. Legionella jordanis contained other unusual carbohydrates in addition to quinovosamine. GC-MS may have wide application in the differentiation of bacterial species. PMID:2324276

  20. Remote Gas Detection Using Millimeter-Wave Spectroscopy for Counter Bio-Terrorism

    NASA Astrophysics Data System (ADS)

    Szlazak, Matthew; Yam, Seng Yiep; Majstorovic, Dejan; Hansen, Hedley J.; Abbott, Derek

    2002-11-01

    The mm-wave (10-110 GHz) frequency band contains the fundamental rotational resonance frequencies of many molecular gases composed of carbon, nitrogen, oxygen and sulfur. The high specificity of the rotational spectra to organic molecules affords mm-wave spectroscopy having potential use in remotely sensing atmospheric pollutants and the detection of airborne chemicals is gaining importance for arms control treaty verification, intelligence collection and environmental monitoring. This paper considers RF receiver systems for remote chemical detection measurements based on mm-wave spectral line emissions. It discusses the design, performance and operation of specific receiving systems for detecting the presence of ammonia in laboratory based transmit-and-receive experiments.

  1. The Determination of Pesticidal and Non-Pesticidal Organotin Compounds by in situ Ethylation and Capillary Gas Chromatography with Pulsed Flame Photometric Detection

    EPA Science Inventory

    The concurrent determination of pesticidal and non-pesticidal organotin compounds in several water matrices, using a simultaneous in situ ethylation and liquid-liquid extraction followed by splitless injection mode capillary gas chromatography with pulsed flame photometric detect...

  2. The Determination of Pesticidal and Non-Pesticidal Organotin Compounds in Water Matrices by in situ Ethylation and Gas Chromatography with Pulsed Flame Photometric Detection

    EPA Science Inventory

    The concurrent determination of pesticidal and non-pesticidal organotin compounds in several water matrices, using a simultaneous in situ ethylation and liquid-liquid extraction followed by splitless injection mode capillary gas chromatography with pulsed flame photometric detect...

  3. Effects of washing, peeling, storage, and fermentation on residue contents of carbaryl and mancozeb in cucumbers grown in greenhouses.

    PubMed

    Saravi, Ss Saeedi; Shokrzadeh, M

    2014-10-23

    Cucumbers grown in two different greenhouses were exposed to mancozeb and carbaryl at different times. The effects of 10-day preharvest period, water and detergent washing, peeling, predetermined storage period at 4°C (refrigeration), and fermentation on the reduction of residue levels in the plant tissues were investigated. Mancozeb and carbaryl residues in cucumbers were determined by gas chromatography-electron capture detection. Results showed that residue levels in samples, which were collected after 10 days following the pesticide application, were significantly lower than the samples collected after 2 h subsequent to the pesticide application. The culinary applications were effective in reducing the residue levels of the pesticides in cucumbers. As a result, non-fermentative pickling in sodium chloride and acetic acid was the most effective way to reduce the mancozeb and carbaryl residues of the cucumbers. PMID:25342670

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

    USGS Publications Warehouse

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

    2003-01-01

    Polychlorinated biphenyls (PCBs) were determined in fish tissue using an enzyme-linked immunosorbent assay (ELISA). Standard curves for Aroclor 1248, 1254, and 1260 in catfish tissue were developed with ranges from 0.05 to 0.5 ppm and 0.5 to 5.0 ppm. Wild fish were initially analyzed using gas chromatography/electron-capture detection (GC/ECD) and those having residues within the standard curve ranges were analyzed with ELISA. Results obtained using ELISA and GC/ECD were not significantly different (p < 0.05) from 0.05 to 0.5 ppm. From 0.5 to 5.0 ppm, the standard curve for Aroclor 1254 was the best predictor of total PCB in wild fish samples.

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

    NASA Astrophysics Data System (ADS)

    Ding, B.

    2010-12-01

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

  6. Evaluation of gas chromatography detection systems for total gaseous nonmethane organic compounds

    SciTech Connect

    Philipp, S.B.; Dayton, D.P.; Merrill, R.G.; Jackson, M.D.

    1994-12-31

    The development of an emissions monitoring prototype instrument to provide continuous or semi-continuous quantitative measurement of total gaseous nonmethane organic carbon (TGNMOC) emissions from stationary sources will allow for better characterization and control of compounds under the Clean Air Act Amendments of 1990, Title 3. To meet this development goal a search has been initiated to identify detection systems for TGNMOC that are both simple to use and accurate. The measurement of oxygenated compounds are of particular interest since many emission sources may have a large proportion of them. Detection system identification has been accomplished by conducting a search of detector manufacturers` literature, and talking with manufacturers` technical personnel. Several detector systems, marketed as appropriate for TGNMOC measurement, have been identified and evaluated in the laboratory. The detection systems evaluated include a Catalyzed Flame Ionization Detector and a Thermionic Ionization Detector, both produced by DETector and Engineering Technology, Inc., and an oxygen-Flame Ionization Detector and an Elemental Analyzer, both produced by Fisons Corporation. The primary performance goal for the detection systems required that those systems yield equal response for all organic compounds in a mixture, including oxygenated compounds, based on carbon number. None of the detection systems evaluated met the primary performance goal of uniformly measuring organic carbon, regardless of the chemical structure of compounds in the sample. While some success was realized for many classes of organic compounds, oxygenated compounds presented a challenge that none of the detection systems could master.

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

    SciTech Connect

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

    2005-10-03

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

  8. Determination of alkyllead salts in water and whole eggs by capillary column gas chromatography with electron capture detection

    SciTech Connect

    Forsyth, D.S.; Marshall, W.D.

    1983-11-01

    Alkyllead salts (R/sub 3/Pb/sup +/ and R/sub 2/Pb/sup 2 +/, R = Methyl or Ethyl) are recovered from water or whole eggs by complexometric extraction with dithizone. The dithizonates are phenylated and speciated by capillary column gas chromatography with electron capture detection. The method is sensitive to low parts per billion levels of lead salts in 2.5 g egg homogenate. At these levels methyllead salts (but not ethyllead salts) interact strongly with the sample matrix. Treatment of the matrix with lipases and proteases releases them. 4 figures, 3 tables.

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

    SciTech Connect

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

    1993-07-09

    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).

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    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.

  11. Trace-Gas Detection with Off-Beam Quartz Enhanced Photoacoustic Spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Kun; Wang, Lei; Tan, Tu; Zhang, Weijun; Chen, Weidong; Gao, Xiaoming

    2015-06-01

    Trace-gas sensors have a wide range of potential applications such as environmental monitoring, climate research, agriculture, workplace safety, medical diagnostics, and industrial process control. A recently introduced technique called quartz-enhanced photoacoustic spectroscopy (QEPAS) is described. QEPAS use a quartz tuning fork as an acoustic transducer for a photoacoustic signal induced in an absorbing gas by modulated optical radiation. Advantages of the QEPAS compared to conventional photoacoustic spectroscopy include immunity to environmental acoustic noise and ultra-small sample volume. Trace gases of , and were monitored with a novel off-beam QEPAS approach and are described in detail.

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

    E-print Network

    Chiao, Jung-Chih

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

  13. Determination of methyl mercury by aqueous phase Eehylation, followed by gas chromatographic separation with cold vapor atomic fluorescence detection

    USGS Publications Warehouse

    De Wild, John F.; Olsen, Mark L.; Olund, Shane D.

    2002-01-01

    A recent national sampling of streams in the United States revealed low methyl mercury concentrations in surface waters. The resulting median and mean concentrations, calculated from 104 samples, were 0.06 nanograms per liter (ng/L) and 0.15 ng/L, respectively. This level of methyl mercury in surface water in the United States has created a need for analytical techniques capable of detecting sub-nanogram per liter concentrations. In an attempt to create a U.S. Geological Survey approved method, the Wisconsin District Mercury Laboratory has adapted a distillation/ethylation/ gas-phase separation method with cold vapor atomic fluorescence spectroscopy detection for the determination of methyl mercury in filtered and unfiltered waters. This method is described in this report. Based on multiple analyses of surface water and ground-water samples, a method detection limit of 0.04 ng/L was established. Precision and accuracy were evaluated for the method using both spiked and unspiked ground-water and surface-water samples. The percent relative standard deviations ranged from 10.2 to 15.6 for all analyses at all concentrations. Average recoveries obtained for the spiked matrices ranged from 88.8 to 117 percent. The precision and accuracy ranges are within the acceptable method-performance limits. Considering the demonstrated detection limit, precision, and accuracy, the method is an effective means to quantify methyl mercury in waters at or below environmentally relevant concentrations

  14. Organophosphorus pesticide and ester analysis by using comprehensive two-dimensional gas chromatography with flame photometric detection.

    PubMed

    Liu, Xiangping; Li, Dengkun; Li, Jiequan; Rose, Gavin; Marriott, Philip J

    2013-12-15

    Thirty-seven phosphorus (P)-containing compounds comprising organophosphorus pesticides and organophosphate esters were analyzed by using comprehensive two-dimensional gas chromatography with flame photometric detection in P mode (GC × GC-FPD(P)), with a non-polar/moderately polar column set. A suitable modulation temperature and period was chosen based on experimental observation. A number of co-eluting peak pairs on the (1)D column were well separated in 2D space. Excellent FPD(P) detection selectivity, responding to compounds containing the P atom, produces clear 2D GC × GC plots with little interference from complex hydrocarbon matrices. Limits of detection (LOD) were within the range of 0.0021-0.048 ?mol L(-1), and linear calibration correlation coefficients (R(2)) for all 37 P-compounds were at least 0.998. The P-compounds were spiked in 2% diesel and good reproducibility for their response areas and retention times was obtained. Spiked recoveries were 88%-157% for 5 ?g L(-1) and 80%-138% for 10 ?g L(-1) spiked levels. Both (1)tR and (2)tR shifts were noted when the content of diesel was in excess of 5% in the matrix. Soil samples were analyzed by using the developed method; some P-compounds were positively detected. In general, this study shows that GC × GC-FPD(P) is an accurate, sensitive and simple method for P-compound analysis in complicated environmental samples. PMID:24238476

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

    PubMed Central

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

    2014-01-01

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

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

    SciTech Connect

    Freeland, Emily; Tran, Kim-Vy H.; Irwin, Trevor; Giordano, Lea; Saintonge, Amelie; Gonzalez, Anthony H.; Zaritsky, Dennis; Just, Dennis

    2011-12-15

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

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

    NASA Technical Reports Server (NTRS)

    Kolesar, Edward S.; Reston, Rocky R.

    1995-01-01

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

  18. 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...

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

    PubMed Central

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

    2014-01-01

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

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

    E-print Network

    McClelland, Martha Ann

    1994-01-01

    properties of ocean sediments, and (2) the effect that their dissociation has on the engineering properties of ocean sediments. The recovery of intact, in-situ samples of gas hydrates can be difficult due to their dependence on pressure and temperature...

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

    PubMed

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

    2014-01-01

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

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

    PubMed

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

    2014-07-01

    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

  3. Modeling panel detection frequencies by queuing system theory: an application in gas chromatography olfactometry.

    PubMed

    Bult, Johannes H F; van Putten, Bram; Schifferstein, Hendrik N J; Roozen, Jacques P; Voragen, Alphons G J; Kroeze, Jan H A

    2004-10-01

    In continuous vigilance tasks, the number of coincident panel responses to stimuli provides an index of stimulus detectability. To determine whether this number is due to chance, panel noise levels have been approximated by the maximum coincidence level obtained in stimulus-free conditions. This study proposes an alternative method by which to assess noise levels, derived from queuing system theory (QST). Instead of critical coincidence levels, QST modeling estimates the duration of coinciding responses in the absence of stimuli. The proposed method has the advantage over previous approaches that it yields more reliable noise estimates and allows for statistical testing. The method was applied in an olfactory detection experiment using 16 panelists in stimulus-present and stimulus-free conditions. We propose that QST may be used as an alternative to signal detection theory for analyzing data from continuous vigilance tasks. PMID:15751471

  4. Trace detection of oxygen--ionic liquids in gas sensor design.

    PubMed

    Baltes, N; Beyle, F; Freiner, S; Geier, F; Joos, M; Pinkwart, K; Rabenecker, P

    2013-11-15

    This paper presents a novel electrochemical membrane sensor on basis of ionic liquids for trace analysis of oxygen in gaseous atmospheres. The faradaic response currents for the reduction of oxygen which were obtained by multiple-potential-step-chronoamperometry could be used for real time detection of oxygen down to concentrations of 30 ppm. The theoretical limit of detection was 5 ppm. The simple, non-expensive sensors varied in electrolyte composition and demonstrated a high sensitivity, a rapid response time and an excellent reproducibility at room temperature. Some of them were continuously used for at least one week and first results promise good long term stability. Voltammetric, impedance and oxygen detection studies at temperatures up to 200 °C (in the presence and absence of humidity and CO2) revealed also the limitations of certain ionic liquids for some electrochemical high temperature applications. Application areas of the developed sensors are control and analysis processes of non oxidative and oxygen free atmospheres. PMID:24148432

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

    NASA Technical Reports Server (NTRS)

    Kosterev, Anatoliy (Inventor)

    2010-01-01

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

  6. 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 ...

  7. Gas chromatography for detection of citrus infestation by tephritid fruit flies

    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 ...

  8. Gas chromatography for detection of fruit fly infestation(Diptera:Tephritidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    ABSTRACT. Tephritid fruit flies are one of the most serious economic pests of fruit crops worldwide. Detection of infestation is difficult since the larval stages are concealed within host fruits. At U.S. ports of entry, quarantine inspectors currently check only ~2% of incoming shipments by man...

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

    DOEpatents

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

    2011-05-17

    A method may detect a flashback condition in a fuel nozzle of a combustor. The method may include obtaining a current acoustic pressure signal from the combustor, analyzing the current acoustic pressure signal to determine current operating frequency information for the combustor, and indicating that the flashback condition exists based at least in part on the current operating frequency information.

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

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

    SciTech Connect

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

    1999-08-01

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

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

    SciTech Connect

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

    1994-07-01

    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.

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

    PubMed

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

    2015-02-01

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

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

    DOEpatents

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

    1982-04-26

    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.

  15. Fiber Optic Sensing Technology for Detecting Gas Hydrate Formation and Decomposition

    SciTech Connect

    Rawn, Claudia J; Leeman, John R; Ulrich, Shannon M; Alford, Jonathan E; Phelps, Tommy Joe; Madden, Megan Elwood

    2011-01-01

    A fiber optic-based distributed sensing system (DSS) has been integrated with a large volume (72 L) pressure vessel providing high spatial resolution, time resolved, 3-D measurement of hybrid temperature-strain (TS) values within experimental sediment gas hydrate systems. Areas of gas hydrate formation (exothermic) and decomposition (endothermic) can be characterized through this proxy by time series analysis of discrete data points collected along the length of optical fibers placed within a sediment system. Data is visualized as a 'movie' of TS values along the length of each fiber over time. Experiments conducted in the Seafloor Processing Simulator (SPS) at Oak Ridge National Laboratory show clear indications of hydrate formation and dissociation events at expected P-T conditions given the thermodynamics of the CH4-H2O system. The high spatial resolution achieved with fiber optic technology makes the DSS a useful tool for visualizing time resolved formation and dissociation of gas hydrates in large-scale sediment experiments.

  16. Detection of hot gas in the filament connecting the clusters of galaxies Abell 222 and Abell 223

    E-print Network

    N. Werner; A. Finoguenov; J. S. Kaastra; A. Simionescu; J. P. Dietrich; J. Vink; H. Boehringer

    2008-03-17

    About half of the baryons in the local Universe are invisible and - according to simulations - their dominant fraction resides in filaments connecting clusters of galaxies in the form of low density gas with temperatures in the range of 10^5filaments by observing a filament connecting the massive clusters of galaxies A 222 and A 223 (z=0.21) which has a favorable orientation approximately along our line of sight. This filament has been previously detected using weak lensing data and as an over-density of colour selected galaxies. We analyse X-ray images and spectra obtained in a deep observation (144 ks) of A 222/223 with XMM-Newton. We present here observational evidence of the X-ray emission from the filament connecting the two clusters. We detect the filament in the wavelet decomposed soft band (0.5-2.0 keV) X-ray image with a 5 sigma significance. Following the emission down to 3 sigma significance, the observed filament is approximately 1.2 Mpc wide. The temperature of the gas associated with the filament determined from the spectra is kT=0.91\\pm0.25 keV and its emission measure corresponds to a baryon density of (3.4\\pm1.3)x10^-5 (l/15Mpc)^-1/2 cm^-3, where l is the length of the filament along the line of sight. This density corresponds to a baryon over-density of approximately 150. The properties of the gas in the filament are consistent with the results of simulations for the densest and hottest parts of the warm-hot intergalactic medium.

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

    SciTech Connect

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

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  19. Stereoisomeric Specificity and Soil Gas Disequilibria: Implications for Martian Life Detection

    PubMed Central

    Keeley, Lee M.; Meyer, Edward D.; Zumberge, John E.; Bandurski, Eric L.; Nagy, Bartholomew

    1975-01-01

    Variations in the atmospheric composition of soil samples were monitored by mass spectrometry after the addition of mixtures of D- and L-carbohydrates and/or amino acids. The changes in concentrations of CO2 in these experiments were found to be related to the stereoisomeric configurations of the compounds with which the soil samples were enriched. The potential of this relationship provides a comparatively simple approach for detecting life in extraterrestrial soils. PMID:1115497

  20. Derivation of new emission factors for quantification of mass emissions when using optical gas imaging for detecting leaks.

    PubMed

    Lev-On, Miriam; Epperson, David; Siegell, Jeffrey; Ritter, Karin

    2007-09-01

    This paper describes the development of new "leak/no-leak" emission factors that are suitable for estimating facilities' fugitive emissions when using an alternative work practice (AWP) that is based on optical gas imaging technology for detecting leaking piping system components. These emission factors were derived for valves, pumps, and connectors/flanges for instrument leak detection thresholds ranging from 3 to 60 g/hr using a combination of field data and Monte Carlo statistical simulation techniques. These newly derived leak/no-leak emission factors are designed to replace the U.S. Environment Protection Agency (EPA) 1995 Protocol factors, which were based on Method 21 monitoring of leaks at "uncontrolled" facilities. The emission factors published in the 1995 Protocol have not been updated since the 1970s. This derivation is based on results where the authors document the use of a Monte Carlo simulation technique to quantify the required leak detection thresholds that provide equal--or better--environmental benefits for an AWP. The use of these newly derived emission factors is demonstrated for different methods of computing fugitive emissions from a hypothetical model refinery. The resulting facility emissions calculated by using these new emission factors is compared with the existing emission estimation methods provided in the EPA 1995 Protocol. The results demonstrate that the new emission factors provide an emission estimate that is the closest to that obtained from the direct determination of total emissions by Monte Carlo simulations. PMID:17912925

  1. THE GEOMETRY EFFECTS OF AN EXPANDING UNIVERSE ON THE DETECTION OF COOL NEUTRAL GAS AT HIGH REDSHIFT

    SciTech Connect

    Curran, S. J.

    2012-03-20

    Recent high-redshift surveys for 21 cm absorption in damped Ly{alpha} absorption systems (DLAs) take the number of published searches at z{sub abs} > 2 to 25, the same number as at z{sub abs} < 2, although the detection rate at high redshift remains significantly lower (20% compared to 60%). Using the known properties of the DLAs to estimate the unknown profile widths of the 21 cm non-detections and including the limits via a survival analysis, we show that the mean spin temperature/covering factor degeneracy at high redshift is, on average, double that of the low-redshift sample. This value is significantly lower than the previous factor of eight for the spin temperatures and is about the same factor as in the angular diameter distance ratios between the low- and high-redshift samples. That is, without the need for the several pivotal assumptions, which lead to an evolution in the spin temperature, we show that the observed distribution of 21 cm detections in DLAs can be accounted for by the geometry effects of an expanding universe. That is, as yet there is no evidence of the spin temperature of gas-rich galaxies evolving with redshift.

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

    PubMed

    Richardson, Douglas D; Caruso, Joseph A

    2007-06-01

    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

  3. Nanoscale gas sensors and their detection mechanisms: Carbon nanotubes and beyond

    NASA Astrophysics Data System (ADS)

    Boyd, Anthony K.

    The research presented in this thesis focuses on the experimental investigation of nanoscale electronic devices for gas sensing applications. The majority of the experiments were conducted on carbon nanotube field-effect transistors (CNTFETs) made with variable density carbon nanotube networks. The carbon nanotube networks were grown using chemical vapor deposition on doped silicon wafers capped with silicon dioxide. Contact electrodes were attached to the networks with standard e-beam lithography and thin film deposition techniques. To better understand the sensing mechanism of CNTFETs, numerous samples were fabricated with varying densities of nanotubes and nanotube junctions. These samples were exposed to nitrogen dioxide and the change in conductance was recorded. Selected parts of the device were then passivated with a thick photoresist to determine whether they contribute to the sensing mechanism. Our previous work showed that for devices made with a single CNT, the response to nitrogen dioxide was mainly due to modifications at the contact interfaces rather than molecular adsorption on the nanotube sidewalls. However, here we show that when using CNT networks, both gas sensing mechanisms are involved. We will illustrate this through the comparison of the experimental response of high-density versus low-density CNT networks and show that the effect of adsorption is linked to the number of CNT junctions, or cross-over points, in the network. Adsorption plays a major role for high-density networks. Its effect is much weaker for low-density networks and not measureable in a single nanotube, where the response is mainly due to the electrodes. Experiments were also performed on field-effect transistor devices with molybedenum disulfide (MoS2) being substituted for the nanotubes. These devices were fabricated using the same substrates and metal deposition techniques used for carbon nanotube devices; however the MoS2 was mechanically exfoliated onto the wafers. Their gas sensing properties and majority carrier mobilities were explored. While testing these devices, we found that the choice of metals used for electrodes had a great impact on device behavior. In addition to their gas sensing properties, the potential use for optoelectronics was studied.

  4. Detection of fusion alphas from D2-T2 gas targets

    NASA Astrophysics Data System (ADS)

    Cilliers, W. A.; Brooks, F. D.; England, J. B. A.

    1993-03-01

    Detectors for recording alphas from fusions in D2 T2 gas targets require protection against diffusion of tritium into the detector medium. Tests have been carried out on surface barrier detectors to determine the feasibility of using thin coatings of oxide and metal for this purpose. The results show that a layer of 0.5 ?m aluminium oxide plus 0.2 ?m gold provides effective protection for at least 280 h, without impairing the transmission of 2 MeV alphas into the detector. Tests of an alternative detector, a phoswich of thin film plastic and lithium-glass scintillators, are also described.

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

    NASA Technical Reports Server (NTRS)

    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

    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.

  6. Tunable fiber laser based photoacoustic gas sensor for early fire detection

    NASA Astrophysics Data System (ADS)

    Wang, Jianwei; Wang, Huili

    2014-07-01

    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.

  7. A Detection of Gas Associated with the M31 Stellar Stream

    NASA Astrophysics Data System (ADS)

    Koch, Andreas; Danforth, Charles W.; Rich, R. Michael; Ibata, Rodrigo; Keeney, Brian A.

    2015-07-01

    Detailed studies of stellar populations in the halos of the Milky Way and the Andromeda (M31) galaxies have shown increasing numbers of tidal streams and dwarf galaxies, attesting to a complicated and on-going process of hierarchical structure formation. The most prominent feature in the halo of M31 is the Giant Stellar Stream, a structure ?4.°5 in extent along the sky, which is close to, but not coincident with the galaxy's minor axis. The stars that make up this stream are kinematically and chemically distinct from the other stars in the halo. Here, we present Hubble Space Telescope/Cosmic Origins Spectrograph high-resolution ultraviolet absorption spectra of three active galactic nuclei sight lines which probe the M31 halo, including one that samples gas in the main southwestern portion of the Giant Stream. We see two clear absorption components in many metal species at velocities typical of the M31 halo and a third, blueshifted component which arises in the stream. Photoionization modeling of the column density ratios in the different components shows gas in an ionization state typical of that seen in other galaxy halo environments and suggests solar to slightly super-solar metallicity, consistent with previous findings from stellar spectroscopy. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  8. Generation, detection and characterization of gas-phase transition metal aggregates and compounds

    SciTech Connect

    Steimle, T.C.

    1992-01-01

    The goal of our research is to employ spectroscopic techniques to characterize the bound portions of the potential energy surface (PES) for chemical systems involving diatomic and triatomic transition metal molecules. The approach incorporates the generation and isolation of new metal compounds via supersonic laser ablation molecular beam techniques. Detection and characterization is achieved using high resolution dye laser induced fluorescence spectroscopy. A major objective is to produce information which can be compared to theoretical predictions and thereby provide guidelines and insight into the development of reaction models.

  9. Gas chromatography/ion mobility spectrometry as a hyphenated technique for improved explosives detection and analysis

    NASA Technical Reports Server (NTRS)

    Mercado, AL; Marsden, Paul

    1995-01-01

    Ion Mobility Spectrometry (IMS) is currently being successfully applied to the problem of on-line trace detection of plastic and other explosives in airports and other facilities. The methods of sample retrieval primarily consist of batch sampling for particulate residue on a filter card for introduction into the IMS. The sample is desorbed into the IMS using air as the carrier and negative ions of the explosives are detected, some as an adduct with a reagent ion such as Cl(-). Based on studies and tests conducted by different airport authorities, this method seems to work well for low vapor pressure explosives such as RDX and PETN, as well as TNT that are highly adsorptive and can be found in nanogram quantities on contaminated surfaces. Recently, the changing terrorist threat and the adoption of new marking agents for plastic explosives has meant that the sample introduction and analysis capabilities of the IMS must be enhanced in order to keep up with other detector developments. The IMS has sufficient analytical resolution for a few threat compounds but the IMS Plasmogram becomes increasingly more difficult to interpret when the sample mixture gets more complex.

  10. Ultrasensitive gas detection of large-area boron-doped graphene.

    PubMed

    Lv, Ruitao; Chen, Gugang; Li, Qing; McCreary, Amber; Botello-Méndez, Andrés; Morozov, S V; Liang, Liangbo; Declerck, Xavier; Perea-López, Nestor; Cullen, David A; Feng, Simin; Elías, Ana Laura; Cruz-Silva, Rodolfo; Fujisawa, Kazunori; Endo, Morinobu; Kang, Feiyu; Charlier, Jean-Christophe; Meunier, Vincent; Pan, Minghu; Harutyunyan, Avetik R; Novoselov, Konstantin S; Terrones, Mauricio

    2015-11-24

    Heteroatom doping is an efficient way to modify the chemical and electronic properties of graphene. In particular, boron doping is expected to induce a p-type (boron)-conducting behavior to pristine (nondoped) graphene, which could lead to diverse applications. However, the experimental progress on atomic scale visualization and sensing properties of large-area boron-doped graphene (BG) sheets is still very scarce. This work describes the controlled growth of centimeter size, high-crystallinity BG sheets. Scanning tunneling microscopy and spectroscopy are used to visualize the atomic structure and the local density of states around boron dopants. It is confirmed that BG behaves as a p-type conductor and a unique croissant-like feature is frequently observed within the BG lattice, which is caused by the presence of boron-carbon trimers embedded within the hexagonal lattice. More interestingly, it is demonstrated for the first time that BG exhibits unique sensing capabilities when detecting toxic gases, such as NO2 and NH3, being able to detect extremely low concentrations (e.g., parts per trillion, parts per billion). This work envisions that other attractive applications could now be explored based on as-synthesized BG. PMID:26575621

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

    E-print Network

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

    2007-05-25

    We present a review of precursor observing programs for the SIM PlanetQuest Key project devoted to detecting Jupiter mass planets around young stars. In order to ensure that the stars in the sample are free of various sources of astrometric noise that might impede the detection of planets, we have initiated programs to collect photometry, high contrast images, interferometric data and radial velocities for stars in both the Northern and Southern hemispheres. We have completed a high contrast imaging survey of target stars in Taurus and the Pleiades and found no definitive common proper motion companions within one arcsecond (140 AU) of the SIM targets. Our radial velocity surveys have shown that many of the target stars in Sco-Cen are fast rotators and a few stars in Taurus and the Pleiades may have sub-stellar companions. Interferometric data of a few stars in Taurus show no signs of stellar or sub-stellar companions with separations of 0.1 mag) that would degrade the astrometric accuracy achievable for that star. While the precursor programs are still a work in progress, we provide a comprehensive list of all targets ranked according to their viability as a result of the observations taken to date. By far, the observable that moves the most targets from the SIM-YSO program is photometric variability.

  12. Ultrasensitive gas detection of large-area boron-doped graphene

    PubMed Central

    Lv, Ruitao; Chen, Gugang; Li, Qing; McCreary, Amber; Botello-Méndez, Andrés; Morozov, S. V.; Declerck, Xavier; Perea-López, Nestor; Cullen, David A.; Feng, Simin; Elías, Ana Laura; Cruz-Silva, Rodolfo; Fujisawa, Kazunori; Endo, Morinobu; Kang, Feiyu; Charlier, Jean-Christophe; Meunier, Vincent; Pan, Minghu; Harutyunyan, Avetik R.; Novoselov, Konstantin S.; Terrones, Mauricio

    2015-01-01

    Heteroatom doping is an efficient way to modify the chemical and electronic properties of graphene. In particular, boron doping is expected to induce a p-type (boron)-conducting behavior to pristine (nondoped) graphene, which could lead to diverse applications. However, the experimental progress on atomic scale visualization and sensing properties of large-area boron-doped graphene (BG) sheets is still very scarce. This work describes the controlled growth of centimeter size, high-crystallinity BG sheets. Scanning tunneling microscopy and spectroscopy are used to visualize the atomic structure and the local density of states around boron dopants. It is confirmed that BG behaves as a p-type conductor and a unique croissant-like feature is frequently observed within the BG lattice, which is caused by the presence of boron-carbon trimers embedded within the hexagonal lattice. More interestingly, it is demonstrated for the first time that BG exhibits unique sensing capabilities when detecting toxic gases, such as NO2 and NH3, being able to detect extremely low concentrations (e.g., parts per trillion, parts per billion). This work envisions that other attractive applications could now be explored based on as-synthesized BG. PMID:26575621

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    We present a review of precursor observing programs for the SIM PlanetQuest Key project devoted to detecting Jupiter mass planets around young stars. In order to ensure that the stars in the sample are free of various sources of astrometric noise that might impede the detection of planets, we have initiated programs to collect photometry, high contrast images, interferometric data and radial velocities for stars in both the Northern and Southern hemispheres. We have completed a high contrast imaging survey of target stars in Taurus and the Pleiades and found no definitive common proper motion companions within one arcsecond (140 AU) of the SIM targets. Our radial velocity surveys have shown that many of the target stars in Sco-Cen are fast rotators and a few stars in Taurus and the Pleiades may have sub-stellar companions. Interferometric data of a few stars in Taurus show no signs of stellar or sub-stellar companions with separations of <5 mas. The photometric survey suggests that approximately half of the stars initially selected for this program are variable to a degree (1(sigma) >0.1 mag) that would degrade the astrometric accuracy achievable for that star. While the precursor programs are still a work in progress, we provide a comprehensive list of all targets ranked according to their viability as a result of the observations taken to date. By far, the observable that removes the most targets from the SIM-YSO program is photometric variability.

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

    PubMed

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

    2011-02-01

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

  15. Detection of ergot (Claviceps purpurea) in a dairy feed component by gas chromatography and mass spectrometry.

    PubMed

    Mantle, P G

    1996-11-01

    A dairy feed that contained barley malt screenings caused hyperthermia in dairy cattle. The feed was suspected of containing ergot and was subsequently analyzed to determine the ricinoleate component, a special and prominent feature of oil-rich ergot tissue. Triglyceride oil was extracted by organic solvents from the dairy feed, and the oil was saponified to release fatty acids. Ricinoleate, as a methyl ester, was selectively resolved from other fatty acids by silica gel chromatography and was analyzed by capillary gas chromatography coupled with chemical ionization mass spectrometry, which demonstrated the presence of the methyl ricinoleate molecule and proved that the feed contained ergot. The methodology may be refined to monitor for ergot in powdered dairy feed more routinely. PMID:8961105

  16. Apparatus for sensor failure detection and correction in a gas turbine engine control system

    NASA Technical Reports Server (NTRS)

    Spang, H. A., III; Wanger, R. P. (inventors)

    1981-01-01

    A gas turbine engine control system maintains a selected level of engine performance despite the failure or abnormal operation of one or more engine parameter sensors. The control system employs a continuously updated engine model which simulates engine performance and generates signals representing real time estimates of the engine parameter sensor signals. The estimate signals are transmitted to a control computational unit which utilizes them in lieu of the actual engine parameter sensor signals to control the operation of the engine. The estimate signals are also compared with the corresponding actual engine parameter sensor signals and the resulting difference signals are utilized to update the engine model. If a particular difference signal exceeds specific tolerance limits, the difference signal is inhibited from updating the model and a sensor failure indication is provided to the engine operator.

  17. Laser system for natural gas detection. Phase 1: Laboratory feasibility studies

    NASA Technical Reports Server (NTRS)

    Grant, W. B.; Hinkley, E. D., Jr.

    1982-01-01

    This project demonstrated the feasibility of using laser remote sensing technology as a tool for leak survey work in natural gas distribution systems. A laboratory device was assembled using a pair of helium neon (HeNe) lasers to measure methane. One HeNe laser emits radiation at a wavelength of 3.3922 micrometers, which corresponds to a strong absorption feature of methane, while the other emits radiation at a wavelength of 3.3911 micrometers, which corresponds to a weak absorption by methane. As a particular area is scanned for leaks, the laser is pointed at convenient topographic targets within its operating range, about 25 m. A portion of the backscattered radiation is collected by a receiver and focused onto an indium antimonide (InSb) photodetector, cooled to 77K. Methane concentrations were determined from the differential absorption at the two wavelengths for the backscattered radiation.

  18. MHz few-body frequency shift detected in a cold {sup 85}Rb Rydberg gas

    SciTech Connect

    Han Jianing

    2011-11-15

    We have observed a density-dependent frequency shift of more than 4 MHz in a cold {sup 85}Rb Rydberg gas trapped in a magneto-optical trap. A one-dimensional linearly aligned four-body model is proposed to explain the experimental data, and the calculation matches the experimental data. The calculation also shows that if the energy detuning between the two coupled states, the nsnsns(n+1)s and nsnsnpnp states in this case, is small, the lowest level of the nsnsnpnp manifold has the maximum mixing probability, causing a frequency shift instead of line broadening. The results reported may be used for few-body blockade, Rydberg single-atom imaging, studying few-body to many-body transitions and interactions, and few-body ionization as well as quantum metrology.

  19. On the ability of the Viking gas chromatograph–mass spectrometer to detect organic matter

    PubMed Central

    Biemann, Klaus

    2007-01-01

    A recent paper by Navarro-Gonzalez et al. [Navarro-Gonzalez R, Navarro KF, de la Rosa J, Iniguez E, Molina P, Miranda LD, Morales P, Cienfuegos E, Coll P, Raulin F, et al. (2006) Proc Natl Acad Sci USA 103:16089–16094] claims to show that the Viking GCMS (gas chromatograph–mass spectrometer) experiment, which carried out a search for organic matter at the surface of Mars in 1976, “may have been blind to low levels of organics.” To rebut this assertion, the Viking experiment, test data, and results on Mars are reviewed, and the fallacies in the design, execution, and interpretation of the new experiments presented by Navarro-Gonzalez et al. are critically examined. PMID:17548829

  20. Detection of discoloration in diesel fuel based on gas chromatographic fingerprints.

    PubMed

    Krakowska, Barbara; Stanimirova, Ivana; Orzel, Joanna; Daszykowski, Michal; Grabowski, Ireneusz; Zaleszczyk, Grzegorz; Sznajder, Miroslaw

    2015-02-01

    In the countries of the European Community, diesel fuel samples are spiked with Solvent Yellow 124 and either Solvent Red 19 or Solvent Red 164. Their presence at a given concentration indicates the specific tax rate and determines the usage of fuel. The removal of these so-called excise duty components, which is known as fuel "laundering", is an illegal action that causes a substantial loss in a government's budget. The aim of our study was to prove that genuine diesel fuel samples and their counterfeit variants (obtained from a simulated sorption process) can be differentiated by using their gas chromatographic fingerprints that are registered with a flame ionization detector. To achieve this aim, a discriminant partial least squares analysis, PLS-DA, for the genuine and counterfeit oil fingerprints after a baseline correction and the alignment of peaks was constructed and validated. Uninformative variables elimination (UVE), variable importance in projection (VIP), and selectivity ratio (SR), which were coupled with a bootstrap procedure, were adapted in PLS-DA in order to limit the possibility of model overfitting. Several major chemical components within the regions that are relevant to the discriminant problem were suggested as being the most influential. We also found that the bootstrap variants of UVE-PLS-DA and SR-PLS-DA have excellent predictive abilities for a limited number of gas chromatographic features, 14 and 16, respectively. This conclusion was also supported by the unitary values that were obtained for the area under the receiver operating curve (AUC) independently for the model and test sets. PMID:25407430

  1. Solid-phase extraction and cleanup of organophosphorus pesticide residues in bovine muscle with gas chromatographic detection.

    PubMed

    Kuivinen, Jorma; Bengtsson, Staffan

    2002-08-01

    The purpose of this investigation is to develop a rapid and simple method for the assessment of organophosphorus pesticides in bovine muscle by using solid-phase extraction (SPE). After extraction with ethyl acetate (EtOAc) the homogenate is centrifuged and filtered through sodium sulfate. The fat is precipitated in methanol by cooling and the extract is diluted with water and passed through a SPE column (Isolute ENV+). After elution with EtOAc, evaporation, and redissolution, the sample is injected into a gas chromatographic (GC) capillary column DB-1701 and detected by a flame photometric detector. Recoveries from bovine muscle fortified with 12 pesticides between 4 and 65 microg/kg include three levels ranging between 59% and 109% for ten of them. The two most polar pesticides (metamidophos and acephate) are not successful. The relative standard deviations are between 1% and 10% for the ten pesticides. A simplex method is used to optimize the GC conditions. PMID:12201481

  2. Feasibility of an on-line fission-gas-leak detection system

    NASA Technical Reports Server (NTRS)

    Lustig, P. H.

    1973-01-01

    Calculations were made to determine if a cladding failure could be detected in a 100-kW zirconium hydride reactor primary system by monitoring the highly radioactive NaK coolant for the presence of I-131. The system is to be completely sealed. A leak of 0.01 percent from a single fuel pin was postulated. The 0.364-MeV gamma of I-131 could be monitored on an almost continuous basis, while its presence could be varified by using a longer counting time for the 0.638-MeV gamma. A lithium-drifted germanium detector would eliminate radioactive corrosion product interference that could occur with a sodium iodide scintillation detector.

  3. Mitigation of Memory Effects in Beta Scintillation Cells for Radioactive Gas Detection

    SciTech Connect

    Seifert, Carolyn E.; McIntyre, Justin I.; Antolick, Kathryn C.; Carman, April J.; Cooper, Matthew W.; Hayes, James C.; Heimbigner, Tom R.; Hubbard, C. W.; Litke, Kevin E.; Ripplinger, Mike D.; Suarez, Reynold

    2005-08-31

    The Automated Radioxenon Sampler/Analyzer (ARSA) developed at PNNL measures the relative concentrations of xenon isotopes using a ?-? coincidence system. Previous tests of the ARSA system have shown that latent radioactivity remains in the plastic cells after evacuation of the gases, leading to a “memory effect” in which the background count rate is dependent on the sample history. The increased background results in lower detection sensitivity. Two possible solutions to the memory effect are explored in this work: depositing a thin layer of metal on the plastic cell (“metallization”), and using an inorganic scintillating cell composed of yttrium aluminum perovskite (YAP). In both cases, the presence of inorganic material at the surface is intended to inhibit the diffusion of gases into the cell walls.

  4. Direct detection of Rydberg-Rydberg millimeter-wave transitions in a buffer gas cooled molecular beam

    NASA Astrophysics Data System (ADS)

    Zhou, Yan; Grimes, David D.; Barnum, Timothy J.; Patterson, David; Coy, Stephen L.; Klein, Ethan; Muenter, John S.; Field, Robert W.

    2015-11-01

    Millimeter-wave transitions between molecular Rydberg states (n ? 35) of barium monofluoride are directly detected via Free Induction Decay (FID). Two powerful technologies are used in combination: Chirped-Pulse millimeter-Wave (CPmmW) spectroscopy and a buffer gas cooled molecular beam photoablation source. Hundreds of Rydberg-Rydberg transitions are recorded in 1 h with >10:1 signal:noise ratio and ?150 kHz resolution. This high resolution, high spectral velocity experiment promises new strategies for rapid measurements of structural and dynamical information, such as the electric structure (multipole moments and polarizabilities) of the molecular ion-core and the strengths and mechanisms of resonances between Rydberg electron and ion-core motions. Direct measurements of Rydberg-Rydberg transitions with kilo-Debye dipole moments support efficient and definitive spectral analysis techniques, such as the Stark demolition and polarization diagnostics, which enable semi-automatic assignments of core-nonpenetrating Rydberg states. In addition, extremely strong radiation-mediated collective effects (superradiance) in a dense Rydberg gas of barium atoms are observed.

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

    PubMed

    Colina; Arribas; Borne; Monreal

    2000-04-10

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

  6. Enantioselective gas chromatographic assay with electron-capture detection for dl-fenfluramine and dl-norfenfluramine in plasma.

    PubMed

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

    1988-12-01

    An enantioselective gas chromatographic assay utilising electron-capture detection has been developed for the simultaneous quantitation of enantiomers of fenfluramine and nonfenfluramine in plasma. The assay involves the conversion of the enantiomers of both fenfluramine and norfenfluramine into their corresponding diastereomeric amide derivatives by an acylation reaction with n-heptafluorobutyryl-S-prolyl chloride under Schotten-Baumann conditions prior to gas chromatographic separation on an achiral polar OV-225 capillary column. Linear and reproducible standard curves were obtained over the concentration ranges 4.30-86.3 ng/ml per enantiomer and 1.25-42.25 ng/ml per enantiomer for the enantiomers of fenfluramine and norfenfluramine, respectively. The method was applied to a single-dose pharmacokinetic study in a healthy adult subject. Stereoselective differences were observed in the plasma concentration versus time profiles of the enantiomers of both fenfluramine and norfenfluramine. The area under the plasma concentration versus time curve values obtained for the l-isomers of fenfluramine or norfenfluramine were higher than the values of their corresponding d-antipodes. PMID:3235539

  7. A fast response & recovery H2S gas sensor based on ?-Fe2O3 nanoparticles with ppb level detection limit.

    PubMed

    Li, Zhijie; Huang, Yanwu; Zhang, Shouchao; Chen, Weimei; Kuang, Zhong; Ao, Dongyi; Liu, Wei; Fu, Yongqing

    2015-12-30

    H2S gas sensor based on ?-Fe2O3 nanoparticles was fabricated by post-thermal annealing of Fe3O4 precursor which was synthesized using a facile hydrothermal route. The characteristic techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were adopted to characterize the chemical composition and microstructure of the obtained samples. Gas-sensing performance of the sensor was investigated at different operation temperatures from 100°C to 400°C. Results showed that the sensor exhibited the best sensitivity, reproducibility and long-term stability for detecting H2S gas at an operating temperature of 300°C. The detection limit towards H2S gas was 0.05ppm, and the response time and recovery time was 30s and 5s, respectively. In addition, sensing mechanism of the sensor towards H2S was discussed. PMID:26177493

  8. Electrochemical Noise Sensors for Detection of Localized and General Corrosion of Natural Gas Transmission Pipelines. Final Report for the Period July 2001-October 2002

    SciTech Connect

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

    2002-12-01

    The U.S. Department of Energy, National Energy Technology Laboratory funded a Natural Gas Infrastructure Reliability program directed at increasing and enhancing research and development activities in topics such as remote leak detection, pipe inspection, and repair technologies and materials. The Albany Research Center (ARC), U.S. Department of Energy was funded to study the use of electrochemical noise sensors for detection of localized and general corrosion of natural gas transmission pipelines. As part of this, ARC entered into a collaborative effort with the corrosion sensor industry to demonstrate the capabilities of commercially available remote corrosion sensors for use with the Nation's Gas Transmission Pipeline Infrastructure needs. The goal of the research was to develop an emerging corrosion sensor technology into a monitor for the type and degree of corrosion occurring at key locations in gas transmission pipelines.

  9. III-nitride nanostructures for optical gas detection and pH sensing

    NASA Astrophysics Data System (ADS)

    Paul, Sumit; Maier, Konrad; Das, Aparna; Furtmayr, Florian; Helwig, Andreas; Teubert, Jörg; Monroy, Eva; Müller, Gerhard; Eickhoff, Martin

    2013-05-01

    The paper presents a novel concept for the realization of optochemical sensor systems which are capable of operating in harsh environments. Key components in such sensors are nanostructures formed from gallium nitride (GaN) and its alloys with aluminum (Al) and indium (In). Nanostructures of this kind emit an efficient, visible-light photoluminescence (PL) which can be excited with low-cost ultraviolet light sources and which extends up to temperatures in the order of 200°C. When exposed to various chemical environments, changes in the PL intensity occur which constitute valuable sensor signals. Due to the all-optical approach, the PL can be excited and its chemically induced changes be read out without requiring electrical wiring at the point of measurement. The present paper presents this innovative sensor concept, the nanostructures and optochemical transducer structures that form its material base, as well as several applications of such transducers in the fields of gas and fluid sensing. The applications addressed here range from the sensing of ppb concentrations of H2, NO2 and O3 in gaseous environments to the pH monitoring in aqueous solutions.

  10. Gas Phase Detection of the NH-P Hydrogen Bond and Importance of Secondary Interactions.

    PubMed

    Møller, Kristian H; Hansen, Anne S; Kjaergaard, Henrik G

    2015-11-01

    We have observed the NH···P hydrogen bond in a gas phase complex. The bond is identified in the dimethylamine-trimethylphosphine complex by a red shift of the fundamental NH-stretching frequency observed using Fourier transform infrared spectroscopy (FT-IR). On the basis of the measured NH-stretching frequency red shifts, we find that P is a hydrogen bond acceptor atom similar in strength to S. Both are stronger acceptors than O and significantly weaker acceptors than N. The hydrogen bond angle, ?NHP, is found to be very sensitive to the functional employed in density functional theory (DFT) optimizations of the complex and is a possible parameter to assess the quality of DFT functionals. Natural bonding orbital (NBO) energies and results from the topological methods atoms in molecules (AIM) and noncovalent interactions (NCI) indicate that the sensitivity is caused by the weakness of the hydrogen bond compared to secondary interactions. We find that B3LYP favors the hydrogen bond and M06-2X favors the secondary interactions leading to under- and overestimation, respectively, of the hydrogen bond angle relative to a DF-LCCSD(T)-F12a calculated angle. The remaining functionals tested, B3LYP-D3, B3LYP-D3BJ, CAM-B3LYP, and ?B97X-D, as well as MP2, show comparable contributions from the hydrogen bond and the secondary interactions and are close to DF-LCCSD(T)-F12a results. PMID:26451467

  11. Pt- and Pd-decorated MWCNTs for vapour and gas detection at room temperature

    PubMed Central

    Baccar, Hamdi; Clément, Pierrick; Abdelghani, Adnane

    2015-01-01

    Summary Here we report on the gas sensing properties of multiwalled carbon nanotubes decorated with sputtered Pt or Pd nanoparticles. Sputtering allows for an oxygen plasma treatment that removes amorphous carbon from the surface of the carbon nanotubes and creates oxygenated surface defects in which metal nanoparticles nucleate within a few minutes. The decoration with the 2 nm Pt or the 3 nm Pd nanoparticles is very homogeneous. This procedure is performed at the device level (i.e., for carbon nanotubes deposited onto sensor substrates) for many devices in one batch, which illustrates the scalability for the mass production of affordable nanosensors. The response to selected aromatic and non-aromatic volatile organic compounds, as well as pollutant gases has been studied. Pt- and Pd-decorated multiwalled carbon nanotubes show a fully reversible response to the non-aromatic volatile organic compounds tested when operated at room temperature. In contrast, these nanomaterials were not responsive to the aromatic compounds studied (measured at concentrations up to 50 ppm). Therefore, these sensors could be useful in a small, battery-operated alarm detector, for example, which is able to discriminate aromatic from non-aromatic volatile organic compounds in ambient. PMID:25977863

  12. Analysis of amplitude versus offset to detect gas/oil contacts in Arabian Gulf

    SciTech Connect

    Chiburis, E.F.

    1985-02-01

    The theoretical behavior of P-wave reflection amplitude as a function of incidence angle (offset) indicates that diagnostic changes should be spatially observable when crossing boundaries between different formation fluids. In particular, when free gas is present in porous sand, Poison's ratios are known to be abnormally low (usually < 0.1-0.2), whereas for oil and water the ratios are usually much greater than 0.3. If the overlying layer has an impedance and Poisson's ratio greater than the target layer, the reflection amplitudes will increase with offset, thereby producing bright spots in stacks. The problems in analyzing seismic amplitudes are well known. The distortions produced in the recorded amplitudes owing to the effects of sources and receivers, instrumentation, processing, attenuation and absorption, layer tuning, multiple interference, and noise can render the measurements meaningless unless corrected for, which would be difficult. However, by using relative instead of absolute amplitudes and by applying suitable analysis techniques, most of these effects can be virtually eliminated. The resulting amplitude behavior can then be properly interpreted in terms of changes in formation properties.

  13. A Detection of Gas Associated with the M 31 Stellar Stream

    E-print Network

    Koch, Andreas; Rich, R Michael; Ibata, Rodrigo; Keeney, Brian A

    2015-01-01

    Detailed studies of stellar populations in the halos of the Milky Way and the Andromeda (M 31) galaxies have shown increasing numbers of tidal streams and dwarf galaxies, attesting to a complicated and on-going process of hierarchical structure formation. The most prominent feature in the halo of M 31 is the Giant Stellar Stream, a structure ~4.5 degrees in extent along the sky, which is close to, but not coincident with the galaxy's minor axis. The stars that make up this stream are kinematically and chemically distinct from the other stars in the halo. Here, we present HST/COS high-resolution ultraviolet absorption spectra of three Active Galactic Nuclei sight lines which probe the M 31 halo, including one that samples gas in the main southwestern portion of the Giant Stream. We see two clear absorption components in many metal species at velocities typical of the M 31 halo and a third, blue-shifted component which arises in the stream. Photoionization modeling of the column density ratios in the different ...

  14. Detecting excitation and magnetization of individual dopants in a semiconductor two-dimensional electron gas

    NASA Astrophysics Data System (ADS)

    Wiebe, Jens

    2011-03-01

    Magnetic atoms doped into a semiconductor are the building blocks for bottom up spintronic and quantum logic devices. They also provide model systems for the investigation of fundamental effects. In order to correlate the dopant's atomic structure with its magnetism magnetically sensitive techniques with atomic resolution are a prerequisite. Here, I show electrical excitation and read-out [ 1 ] of single magnetic dopant associated spins in a two-dimensional electron gas (2DEG) confined to a semiconductor surface [ 2 ] using spin-resolved scanning tunneling spectroscopy [ 3 ] . I will review our real-space study of the quantum Hall transition in the 2DEG [ 2 ] and of the magnetic properties of the dopants [ 1 ] . Finally, I will demonstrate that the dopant serves as an atomic scale probe for local magnetometry of the 2DEG. This work was done in collaboration with A. A. Khajetoorians, B. Chillian, S. Schuwalow, F. Lechermann, K. Hashimoto, C. Sohrmann, T. Inaoka, F. Meier, Y. Hirayama, R. A. Römer, M. Morgenstern, and R. Wiesendanger. [ 1 ] A. A. Khajetoorians et al., Nature 467, 1084 (2010). [ 2 ] K. Hashimoto et al., Phys. Rev. Lett. 101, 256802 (2008). [ 3 ] J. Wiebe et al., Rev. Sci. Instrum. 75, 4871 (2004). We acknowledge financial support from ERC Advanced Grant ``FURORE'', by the DFG via SFB668 and GrK1286, and by the city of Hamburg via the cluster of excellence ``Nanospintronics''.

  15. Direct detection of Mycobacterium tuberculosis in sputum using combined solid phase extraction-gas chromatography-mass spectrometry.

    PubMed

    Dang, Ngoc A; Mourão, Marta; Kuijper, Sjoukje; Walters, Elisabetta; Janssen, Hans-Gerd; Kolk, Arend H J

    2015-04-01

    Recently, thermally-assisted hydrolysis and methylation followed by gas chromatography-mass spectrometry (THM-GC-MS) in combination with chemometrics has been used to develop a 20-compound model for fast differentiation of Mycobacterium tuberculosis (MTB) from Non-tuberculous mycobacteria (NTM) in bacterial cultures. This model provided better than 95% accuracy. In our current work a hexane/methanol/water extraction followed by a solid phase extraction (SPE) clean-up procedure was developed for use before THM-GC-MS, to make the test suitable for the identification of mycobacteria in sputum. The 20 biomarker model had to be adapted since many compounds were also found in the sputum of non-tuberculosis patients. An algorithm was established based on tuberculostearic acid, hexacosanoic acid and mycoserosates. The detection limit of the method was approximately 1×10(4) bacteria/mL sputum. Sputum specimens from 32 patients from South Africa who were suspected of having tuberculosis were blindly tested using the new method. Eight of the nine culture-positive sputum specimens were detected by the new SPE-THM-GC-MS method, resulting in a sensitivity of 89%. The specimen that was missed by the new method was also microscopy negative. The specificity of the test was 100%; all 23 microscopy- and culture-negative specimens were correctly identified as negative by SPE-THM-GC-MS. PMID:25728368

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

    PubMed Central

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

    2014-01-01

    We develop a novel peak detection algorithm for the analysis of comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOF MS) data using normal-exponential-Bernoulli (NEB) and mixture probability models. The algorithm first performs baseline correction and denoising simultaneously using the NEB model, which also defines peak regions. Peaks are then picked using a mixture of probability distribution to deal with the co-eluting peaks. Peak merging is further carried out based on the mass spectral similarities among the peaks within the same peak group. The algorithm is evaluated using experimental data to study the effect of different cut-offs of the conditional Bayes factors and the effect of different mixture models including Poisson, truncated Gaussian, Gaussian, Gamma, and exponentially modified Gaussian (EMG) distributions, and the optimal version is introduced using a trial-and-error approach. We then compare the new algorithm with two existing algorithms in terms of compound identification. Data analysis shows that the developed algorithm can detect the peaks with lower false discovery rates than the existing algorithms, and a less complicated peak picking model is a promising alternative to the more complicated and widely used EMG mixture models. PMID:25264474

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

    PubMed

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

    2014-06-01

    We develop a novel peak detection algorithm for the analysis of comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOF MS) data using normal-exponential-Bernoulli (NEB) and mixture probability models. The algorithm first performs baseline correction and denoising simultaneously using the NEB model, which also defines peak regions. Peaks are then picked using a mixture of probability distribution to deal with the co-eluting peaks. Peak merging is further carried out based on the mass spectral similarities among the peaks within the same peak group. The algorithm is evaluated using experimental data to study the effect of different cut-offs of the conditional Bayes factors and the effect of different mixture models including Poisson, truncated Gaussian, Gaussian, Gamma, and exponentially modified Gaussian (EMG) distributions, and the optimal version is introduced using a trial-and-error approach. We then compare the new algorithm with two existing algorithms in terms of compound identification. Data analysis shows that the developed algorithm can detect the peaks with lower false discovery rates than the existing algorithms, and a less complicated peak picking model is a promising alternative to the more complicated and widely used EMG mixture models. PMID:25264474

  18. Determination of free amino compounds in betalainic fruits and vegetables by gas chromatography with flame ionization and mass spectrometric detection.

    PubMed

    Kugler, Florian; Graneis, Stephan; Schreiter, Pat P-Y; Stintzing, Florian C; Carle, Reinhold

    2006-06-14

    Amino acids and amines are the precursors of betalains. Therefore, the profiles of free amino compounds in juices obtained from cactus pears [Opuntia ficus-indica (L.) Mill. cv. Bianca, cv. Gialla, and cv. Rossa], pitaya fruits [Selenicereus megalanthus (K. Schumann ex Vaupel) Moran, Hylocereus polyrhizus (Weber) Britton & Rose, and Hylocereus undatus (Haworth) Britton & Rose], and in extracts from differently colored Swiss chard [Beta vulgaris L. ssp. cicla (L.) Alef. cv. Bright Lights] petioles and red and yellow beets (B. vulgaris L. ssp. vulgaris var. conditiva Alef. cv. Burpee's Golden) were investigated for the first time. Amino compounds were derivatized with propyl chloroformate. While gas chromatography (GC) with mass spectrometry was used for peak assignment, GC flame ionization detection was applied for quantification of individual compounds. Whereas proline was the major free amino compound of cactus pear and pitaya fruit juices, glutamine dominated in Swiss chard stems and beets, respectively. Interestingly, extremely high concentrations of dopamine were detected in Swiss chard stems and beets. Furthermore, the cleavage of betaxanthins caused by derivatization in alkaline reaction solutions is demonstrated for the first time. Amino acids and amines thus released might increase the actual free amino compound contents of the respective sample. To evaluate the contribution of betaxanthin cleavage to total amino acid and amine concentration, isolated betaxanthins were derivatized according to the "EZ:faast" method prior to quantification of the respective amino compounds released. On a molar basis, betaxanthin contribution to overall amino compound contents was always below 6.4%. PMID:16756361

  19. Determination of ambient sulfuric acid aerosol by gas chromatography/photo-ionization detection after pre-concentration in a denuder

    NASA Astrophysics Data System (ADS)

    Lindqvist, F.

    A technique, adaptable to automation, has been applied to monitoring ambient sulfuric acid (H 2SO 4) aerosol concentrations. H 2SO 4 is preconcentrated and separated from sulfate species by sampling air through a coated diffusion tube (denuder) at an elevated temperature. The H 2SO 4 collected is released as SO x by thermal desorption while the coating is regenerated simultaneously. Then SO x, is reduced to H 2S and analysed selectively by gas chromatography/photoionization detection. The stoichiometry factor for the conversion H 2SO 4-H 2S being 0.96 (relative standard deviation 17%, n = 56), the analytical system can be calibrated with gaseous H 2S standards. The minimum detectable concentration (defined as 3 times the standard deviation of the denuder blank) varied with the denuder storage time. For a storage time of a few hours, 0.06 ?g m -3 (60-? sample) was a representative value and 0.45 ?g m -3 that for a storage time exceeding 24 h. Results for ambient air sampling with a minimum time resolution of 60 min are presented. The precision of the determinations of H 2SO 4 concentrations in ambient air, expressed as the relative standard deviation, is 15%. No decrease in collecting efficiency was observed for denuders that had passed 40 sampling runs in ambient air with a minimum sampling duration of 60 min.

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

    SciTech Connect

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

    1982-05-01

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

  1. Analysis of free and conjugated phytosterols in tobacco by an improved method using gas chromatography-flame ionization detection.

    PubMed

    Liu, Wen-Hui; Ding, Bin; Ruan, Xiao-Ming; Xu, Hai-Tao; Yang, Jun; Liu, Shao-Min

    2007-09-01

    An improved and simple method using capillary gas chromatography coupled with a flame ionization detection system (GC-FID) has been developed for quantitative analysis of free and conjugated phytosterols in tobacco. Direct acid and alkaline hydrolysis were first introduced into tobacco analysis to liberate free phytosterols from conjugates, followed by extraction with hexane, derivatization to trimethylsilyl ether derivatives and finally GC quantitative determination. The generality and applicability of this improved method for analyzing free and conjugated phytosterols in tobacco were validated after a series of optimization and comparison were done. Compared with traditional methods, this improved method not only simplified procedures, but also saved time and solvent. The limits of detection (LODs) of phytosterols varied from 0.35 to 0.10 microg mL(-1), the relative standard deviations (RSD) were from 2.3% to 3.3% and recovery ranged from 87% to 99%. The analysis results showed that total phytosterols' content in tobacco ranged from 1.0 to 2.5 mg g(-1), and most phytosterols existed as conjugates, only approximately 15-25% phytosterols existed in free-form. Ergosterol was only found in mildewy flued-cured tobacco and the level was approximately 0.2-0.25 mg g(-1). PMID:17624356

  2. Rapid, Real-time Methane Detection in Ground Water Using a New Gas-Water Equilibrator Design

    NASA Astrophysics Data System (ADS)

    Ruybal, C. J.; DiGiulio, D. C.; Wilkin, R. T.; Hargrove, K. D.; McCray, J. E.

    2014-12-01

    Recent increases in unconventional gas development have been accompanied by public concern for methane contamination in drinking water wells near production areas. Although not a regulated pollutant, methane may be a marker contaminant for others that are less mobile in groundwater and thus may be detected later, or at a location closer to the source. In addition, methane poses an explosion hazard if exsolved concentrations reach 5 - 15% volume in air. Methods for determining dissolved gases, such as methane, have evolved over 60 years. However, the response time of these methods is insufficient to monitor trends in methane concentration in real-time. To enable rapid, real-time monitoring of aqueous methane concentrations during ground water purging, a new gas-water equilibrator (GWE) was designed that increases gas-water mass exchange rates of methane for measurement. Monitoring of concentration trends allows a comparison of temporal trends between sampling events and comparison of baseline conditions with potential post-impact conditions. These trends may be a result of removal of stored casing water, pre-purge ambient borehole flow, formation physical and chemical heterogeneity, or flow outside of well casing due to inadequate seals. Real-time information in the field can help focus an investigation, aid in determining when to collect a sample, save money by limiting costs (e.g. analytical, sample transport and storage), and provide an immediate assessment of local methane concentrations. Four domestic water wells, one municipal water well, and one agricultural water well were sampled for traditional laboratory analysis and compared to the field GWE results. Aqueous concentrations measured on the GWE ranged from non-detect to 1,470 ?g/L methane. Some trends in aqueous methane concentrations measured on the GWE were observed during purging. Applying a paired t-test comparing the new GWE method and traditional laboratory analysis yielded a p-value 0.383, suggesting no significant difference between the two methods for the current study. Additional field and laboratory experimentation are necessary to justify use beyond screening. However, early GWE use suggests promising results and applications.

  3. Detection of hydrogen fluoride absorption in diffuse molecular clouds with Herschel/HIFI: an ubiquitous tracer of molecular gas

    NASA Astrophysics Data System (ADS)

    Sonnentrucker, P.; Neufeld, D. A.; Phillips, T. G.; Gerin, M.; Lis, D. C.; de Luca, M.; Goicoechea, J. R.; Black, J. H.; Bell, T. A.; Boulanger, F.; Cernicharo, J.; Coutens, A.; Dartois, E.; Ka?mierczak, M.; Encrenaz, P.; Falgarone, E.; Geballe, T. R.; Giesen, T.; Godard, B.; Goldsmith, P. F.; Gry, C.; Gupta, H.; Hennebelle, P.; Herbst, E.; Hily-Blant, P.; Joblin, C.; Ko?os, R.; Kre?owski, J.; Martín-Pintado, J.; Menten, K. M.; Monje, R.; Mookerjea, B.; Pearson, J.; Perault, M.; Persson, C. M.; Plume, R.; Salez, M.; Schlemmer, S.; Schmidt, M.; Stutzki, J.; Teyssier, D.; Vastel, C.; Yu, S.; Caux, E.; Güsten, R.; Hatch, W. A.; Klein, T.; Mehdi, I.; Morris, P.; Ward, J. S.

    2010-10-01

    We discuss the detection of absorption by interstellar hydrogen fluoride (HF) along the sight line to the submillimeter continuum sources W49N and W51. We have used Herschel's HIFI instrument in dual beam switch mode to observe the 1232.4762 GHz J = 1-0 HF transition in the upper sideband of the band 5a receiver. We detected foreground absorption by HF toward both sources over a wide range of velocities. Optically thin absorption components were detected on both sight lines, allowing us to measure - as opposed to obtain a lower limit on - the column density of HF for the first time. As in previous observations of HF toward the source G10.6-0.4, the derived HF column density is typically comparable to that of water vapor, even though the elemental abundance of oxygen is greater than that of fluorine by four orders of magnitude. We used the rather uncertain N(CH)-N(H2) relationship derived previously toward diffuse molecular clouds to infer the molecular hydrogen column density in the clouds exhibiting HF absorption. Within the uncertainties, we find that the abundance of HF with respect to H2 is consistent with the theoretical prediction that HF is the main reservoir of gas-phase fluorine for these clouds. Thus, hydrogen fluoride has the potential to become an excellent tracer of molecular hydrogen, and provides a sensitive probe of clouds of small H2 column density. Indeed, the observations of hydrogen fluoride reported here reveal the presence of a low column density diffuse molecular cloud along the W51 sight line, at an LSR velocity of ~24 km s-1, that had not been identified in molecular absorption line studies prior to the launch of Herschel. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  4. Kinematics of dwarf galaxies in gas-rich groups, and the survival and detectability of tidal dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Sweet, Sarah M.; Drinkwater, Michael J.; Meurer, Gerhardt; Kilborn, Virginia; Audcent-Ross, Fiona; Baumgardt, Holger; Bekki, Kenji

    2016-01-01

    We present DEIMOS multi-object spectroscopy (MOS) of 22 star-forming dwarf galaxies located in four gas-rich groups, including six newly discovered dwarfs. Two of the galaxies are strong tidal dwarf galaxy (TDG) candidates based on our luminosity-metallicity relation definition. We model the rotation curves of these galaxies. Our sample shows low mass-to-light ratios (M/L = 0.73 ± 0.39 M?/L?) as expected for young, star-forming dwarfs. One of the galaxies in our sample has an apparently strongly falling rotation curve, reaching zero rotational velocity outside the turnover radius of rturn = 1.2re. This may be (1) a polar ring galaxy, with a tilted bar within a face-on disc; (2) a kinematic warp. These scenarios are indistinguishable with our current data due to limitations of slit alignment inherent to MOS-mode observations. We consider whether TDGs can be detected based on their tidal radius, beyond which tidal stripping removes kinematic tracers such as H? emission. When the tidal radius is less than about twice the turnover radius, the expected falling rotation curve cannot be reliably measured. This is problematic for as much as half of our sample, and indeed more generally, galaxies in groups like these. Further to this, the H? light that remains must be sufficiently bright to be detected; this is only the case for three (14 per cent) galaxies in our sample. We conclude that the falling rotation curves expected of TDGs are intrinsically difficult to detect.

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

    PubMed

    Hawkins, Justin L

    2014-03-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    Tunable narrowband mid-infrared radiation from 3.25 to 4.4 micrometers is generated by a compact fiber-coupled, difference-frequency-based spectroscopic source. A 20-mW external cavity diode laser (with a tuning range from 814 to 870 nm) and a 50-mW distributed-Bragg-reflector diode-laser-seeded ytterbium-doped fiber amplifier operating at 1083 nm are difference-frequency mixed in a multi-grating, temperature-controlled periodically poled LiNbO3 crystal. A conversion efficiency of 0.44 mW/(W2cm) (corresponding to a power of approximately equal to 3 microW at 3.3 micrometers) represents the highest conversion efficiency reported for a portable device. Performance characteristics of such a sensor and its application to spectroscopic detection of CO2, N2O, H2CO, HCl, NO2, and CH4 will be reported in this work.

  7. QCM gas phase detection with ceramic materials--VOCs and oil vapors.

    PubMed

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

    2011-06-01

    Titanate sol-gel layers imprinted with carbonic acids were used as sensitive layers on quartz crystal microbalance. These functionalized ceramics enable us detection of volatile organic compounds such as ethanol, n-propanol, n-butanol, n-hexane, n-heptane, n-/iso-octane, and n-decane. Variation of the precursors (i.e., tetrabutoxy titanium, tetrapropoxy titanium, tetraethoxy titanium) allows us to tune the sensitivity of the material by a factor of 7. Sensitivity as a function of precursors leads to selective inclusion of n-butanol vapors down to 1 ppm. The selectivity of materials is optimized to differentiate between isomers, e.g., n- and iso-octane. The results can be rationalized by correlating the sensor effects of hydrocarbons with the Wiener index. A mass-sensitive sensor based on titanate layer was also developed for monitoring emanation of degraded engine oil. Heating the sensor by a meander avoids vapor condensation. Thus, a continuously working oil quality sensor was designed. PMID:21301823

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

    SciTech Connect

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

    1996-12-31

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

  9. Detection of nitro-aromatic compounds by optical gas sensors based on sensitive or photoluminescent polymers

    NASA Astrophysics Data System (ADS)

    Lamarque, T.; Le Barny, P.; Obert, E.; Chastaing, E.; Loiseaux, B.; Leray, I.

    2006-04-01

    In the first part of this paper, we use a specially developed sensitive polymer (PLG) which belongs to the polysiloxane family. Thin layers of this polymer are deposited onto the surface of the optical transducers. Results will be presented on the response of diffraction-based optical transducers such as gratings and also on interferometric transducers and especially integrated Mach-Zehnder (MZ) interferometers. In the first case, a relief grating is coated with the sensitive polymer. A small variation of the refractive index of this layer, due to the presence of pollutant, induces a variation of the intensity of the diffracted orders which can be measured. In the second case, one arm of the integrated MZ interferometers is coated with the polymer. The variation of the refractive index of the polymer causes a phase shift in the measuring arm which can be measured by the modification of the output intensity. Assessment of sensitivity for the detection of nitro-aromatic compounds using a PLG sensitive layer on both sensors are presented and are also compared to the response of a SAW-based sensor coated with the same polymer. In the second part of this paper, synthesis, spectroscopy and fluorescence quenching behaviour of a N-(2,5-ditertio-butylphenyl)-1,8-naphthalimide functionalised polystyrene (PST-NI) are reported. PST-NI was synthesized by free radical polymerisation of the corresponding monomer. The molecular weight (Mn) is 43 000 g.mol-1. Introduction of a bulky moiety on the naphthalimide chromophores avoids P-stacking of the polymer side chains as well as excimer formation and hence leads to very high fluorescence quantum yields in thin solid films (up to 60%). Upon 1 minute exposure to DNT vapour, it was shown that a 5.5 nm thick film of PST-NI exhibits a 45% drop in its fluorescence intensity, which makes this polymer very attractive for sensing applications.

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

    PubMed

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

    2014-01-01

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

  11. Specific detection of primary amines in the effluent of a gas-chromatographic column by on-line measurement of fluorescence.

    PubMed

    Chow, F; Karmen, A

    1980-09-01

    Compounds with primary amino groups react with o-phthalaldehyde in solution to yield highly fluorescent products. This reaction is now in wide use for detecting amino acids and amines in liquid-chromatography effluents. We report here a method for using o-phthalaldehyde to detect primary amines in the effluent of a gas-liquid-chromatographic column. The effluent gas, nominally 20 mL/min, is delivered to a scrubber consisting of a small-bore, simulated capillary chromatographic column that is simultaneously supplied with 1 mL/min of the reagent solution. The liquid effluent of the scrubber, separated from the gas, is drawn through the flow cell of a fluorometer. Short-chain amines and ammonia were quantitatively scrubbed. The response of the fluorometer was directly proportional to the number of nanomoles injected into the column. Less than a nanomole of amine was detectable. Comparison of results with those from a hydrogen flame-ionization detector showed minimal additional peak broadening or compromise of resolution. These results demonstrate the feasibility of using highly specific, as well as sensitive, liquid-chromatographic detection methods for gas-liquid chromatography. PMID:7408177

  12. Kinematics of dwarf galaxies in gas-rich groups, and the survival and detectability of tidal dwarf galaxies

    E-print Network

    Sweet, Sarah M; Meurer, Gerhardt; Kilborn, Virginia; Audcent-Ross, Fiona; Baumgardt, Holger; Bekki, Kenji

    2015-01-01

    We present DEIMOS multi-object spectroscopy (MOS) of 22 star-forming dwarf galaxies located in four gas-rich groups, including six newly-discovered dwarfs. Two of the galaxies are strong tidal dwarf galaxy (TDG) candidates based on our luminosity-metallicity relation definition. We model the rotation curves of these galaxies. Our sample shows low mass-to-light ratios (M/L=0.73$\\pm0.39M_\\odot/L_\\odot$) as expected for young, star-forming dwarfs. One of the galaxies in our sample has an apparently strongly-falling rotation curve, reaching zero rotational velocity outside the turnover radius of $r_{turn}=1.2r_e$. This may be 1) a polar ring galaxy, with a tilted bar within a face-on disk; 2) a kinematic warp. These scenarios are indistinguishable with our current data due to limitations of slit alignment inherent to MOS-mode observations. We consider whether TDGs can be detected based on their tidal radius, beyond which tidal stripping removes kinematic tracers such as H$\\alpha$ emission. When the tidal radius i...

  13. He Bulge Detection by MAVEN Neutral Gas and Ion Mass Spectrometer (NGIMS) in the Upper Atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Elrod, Meredith K.; Mahaffy, Paul R.; Yelle, Roger; Stone, Shane; Benna, Mehdi; Jakowski, Bruce

    2015-11-01

    Studies of the Venusian atmospheres have demonstrated enhanced He densities at high latitudes and on the night-side detections. To determine if Mars has a similar enhanced He ‘bulge’ in the same region, we compared several periapsis passes from night to dayside. The first six weeks of the MAVEN prime mission had periapsis at high latitudes on the night-side, followed by the next three months at mid latitudes on the dayside moving to low latitudes on the night-side. In addition to its normal orbit, which has a periapsis of approximately 150 km, MAVEN conducts a few deep dip orbits where the spacecraft has a periapsis closer to 125km. The first deep dip was at dusk at mid latitudes, the second at noon at the equator, with the third going from dawn to night in the southern hemisphere. Initial analysis of the Neutral Gas and Ion Mass Spectrometer (NGIMS) closed source data from all orbits with good pointing revealed an enhanced He density on the night-side orbits and a decreased He density on the dayside. This enhancement of He demonstrates a bulge at Mars that will continue to be explored over the course of the mission.

  14. Evaluation of musk contamination of freshwater fish in Italy by accelerated solvent extraction and gas chromatography with mass spectrometric detection.

    PubMed

    Draisci, R; Marchiafava, C; Ferretti, E; Palleschi, L; Catellani, G; Anastasio, A

    1998-07-24

    Musk compounds play an important role as perfuming agents for household chemicals, detergents and cosmetics. It has been demonstrated that the oral absorption of these compounds in humans is significant in the case of contaminated fish. In this study we developed a new extraction procedure, using an accelerated solvent extraction system and a gas chromatography-mass spectrometry detection method, for the determination of 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta [g]-2-benzopyran, 7-acetyl-1,1,3,4,4,6-hexamethyltetralin, 4-acetyl-1,1-dimethyl-6-tert.-butylindan, 6-acetyl 1,2,3,3,5-hexamethylindan and 5-acetyl-1,1,2,6-tetramethyl-3-isopropylindan in freshwater fish samples, collected from several Italian rivers and one lake. 6,7-Dihydro-1,1,2,3,3-pentamethyl-4-(5H)-indanon was used as internal standard. The method provides a rapid and highly extraction procedure, and is sensitive in determining these musk compounds in freshwater fish samples. This is the first report on the contamination from musk compounds in freshwater fish collected in Italy. PMID:9718694

  15. Intracavity CO laser photoacoustic trace gas detection: cyclic CH 4 , H 2 O and CO 2 emission by cockroaches and scarab beetles

    NASA Astrophysics Data System (ADS)

    Bijnen, F. G. C.; Harren, F. J. M.; Hackstein, J. H. P.; Reuss, J.

    1996-09-01

    A liquid-nitrogen-cooled CO laser and an intracavity resonant photoacoustic cell are employed to monitor trace gases. The setup was designed to monitor trace gas emissions of biological samples on line. The arrangement offers the possibility to measure gases at the 10 9 by volume (ppbv) level (e.g., CH 4 , H 2 O) and to detect rapid changes in trace gas emission. A detection limit of 1 ppbv for CH 4 in N 2 equivalent to a minimal detectable absorption of 3 10 9 cm 1 can be achieved. Because of the kinetic cooling effect we lowered the detection limit for CH 4 in air is decreased to 10 ppbv. We used the instrument in a first application to measure the CH 4 and H 2 O emission of individual cockroaches and scarab beetles. These emissions could be correlated with CO 2 emissions that were recorded simultaneously with an infrared gas analyzer. Characteristic breathing patterns of the insects could be observed; unexpectedly methane was also found to be released.

  16. Determination of total sulfur compounds and benzothiazole in asphalt fume samples by gas chromatography with sulfur chemiluminescence detection.

    PubMed

    Jaycox, L B; Olsen, L D

    2000-09-01

    As part of a collaborative project between the National Institute for Occupational Safety and Health and the Federal Highway Administration to evaluate asphalt pavers' exposures to asphalt fume and their potential health effects, a method was developed for the determination of total sulfur compounds and benzothiazole in asphalt fume samples. Asphalt fume samples were collected from asphalt mixtures with and without the addition of ground-up rubber tires. The asphalt fume samples were collected with sampling trains that consisted of a Teflon membrane filter and an XAD-2 adsorbent tube. Filter and sampling tube media were extracted with hexane and subsequently analyzed by gas chromatography with a sulfur chemiluminescence detector. Separation was achieved with a 100 percent dimethyl polysiloxane fused silica column. Typical calibration curves had linear correlation coefficients of 0.99 or better with a relative standard deviation (RSD) of 5 percent. Benzothiazole desorption efficiency (DE) determined using spiked sampling tubes ranged from 96.5 percent at 5.0 micrograms to 89.4 percent at 40 micrograms with RSD values from 0.9 to 4.0 percent. Benzothiazole storage recovery determined using sampling tubes spiked at 20 micrograms and refrigerated for 30 days at 4 degrees C was 89.8 percent when corrected for the DE with an RSD of 1.1 percent. The limit of detection for the method determined using spiked sampling tubes was 0.30 microgram. Quantitation for total sulfur compounds and benzothiazole was against benzothiazole standards in hexane. Because of detector selectivity, sample preparation consisted of a simple hexane extraction even when samples had a high background due to hydrocarbon overload. Detector sensitivity provided quantitation in the sub-microgram region. Because of the sample preparation step and because benzothiazole was determined during the same analysis run, this method is straightforward and analytically efficient. The method has been used to analyze asphalt fume samples collected at several asphalt paving and roof operations. PMID:10983404

  17. DETECTION OF WEAK CIRCUMSTELLAR GAS AROUND THE DAZ WHITE DWARF WD 1124-293: EVIDENCE FOR THE ACCRETION OF MULTIPLE ASTEROIDS

    SciTech Connect

    Debes, J. H.; Kilic, M.; Faedi, F.; Shkolnik, E. L.; Lopez-Morales, M.; Weinberger, A. J.; Slesnick, C.; West, R. G.

    2012-07-20

    Single metal-polluted white dwarfs with no dusty disks are believed to be actively accreting metals from a circumstellar disk of gas caused by the destruction of asteroids perturbed by planetary systems. We report, for the first time, the detection of circumstellar Ca II gas in absorption around the DAZ WD 1124-293, which lacks an infrared excess. We constrain the gas to >7 R{sub WD} and <32000 AU, and estimate it to be at {approx}54 R{sub WD}, well within WD 1124-293's tidal disruption radius. This detection is based on several epochs of spectroscopy around the Ca II H and K lines ({lambda} = 3968 A, 3933 A) with the MIKE spectrograph on the Magellan/Clay Telescope at Las Campanas Observatory. We confirm the circumstellar nature of the gas by observing nearby sightlines and finding no evidence for gas from the local interstellar medium. Through archival data we have measured the equivalent width of the two photospheric Ca lines over a period of 11 years. We see <5%-7% epoch-to-epoch variation in equivalent widths over this time period, and no evidence for long term trends. The presence of a circumstellar gas implies a near edge-on inclination to the system, thus we place limits to short period transiting planetary companions with R > R{sub Circled-Plus} using the Wide Angle Search for Planets survey. The presence of gas in orbit around WD 1124-293 implies that most DAZs could harbor planetary systems. Since 25%-30% of white dwarfs show metal line absorption, the dynamical process for perturbing small bodies must be robust.

  18. Optical sensing elements for nitrogen dioxide (NO.sub.2) gas detection, a sol-gel method for making the sensing elements and fiber optic sensors incorporating nitrogen dioxide gas optical sensing elements

    DOEpatents

    Mechery, Shelly John (Mississippi State, MS); Singh, Jagdish P. (Starkville, MS)

    2007-07-03

    A sensing element, a method of making a sensing element, and a fiber optic sensor incorporating the sensing element are described. The sensor can be used for the quantitative detection of NO.sub.2 in a mixture of gases. The sensing element can be made by incorporating a diazotizing reagent which reacts with nitrous ions to produce a diazo compound and a coupling reagent which couples with the diazo compound to produce an azo dye into a sol and allowing the sol to form an optically transparent gel. The sensing element changes color in the presence of NO.sub.2 gas. The temporal response of the absorption spectrum at various NO.sub.2 concentrations has also been recorded and analyzed. Sensors having different design configurations are described. The sensing element can detect NO.sub.2 gas at levels of parts per billion.

  19. Ram pressure stripping of hot coronal gas from group and cluster galaxies and the detectability of surviving X-ray coronae

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, Rukmani; Ricker, Paul M.

    2015-05-01

    Ram pressure stripping can remove hot and cold gas from galaxies in the intracluster medium, as shown by observations of X-ray and H I galaxy wakes in nearby clusters of galaxies. However, ram pressure stripping, including pre-processing in group environments, does not remove all the hot coronal gas from cluster galaxies. Recent high-resolution Chandra observations have shown that ˜1-4 kpc extended, hot galactic coronae are ubiquitous in group and cluster galaxies. To better understand this result, we simulate ram pressure stripping of a cosmologically motivated population of galaxies in isolated group and cluster environments. The galaxies and the host group and cluster are composed of collisionless dark matter and hot gas initially in hydrostatic equilibrium with the galaxy and host potentials. We show that the rate at which gas is lost depends on the galactic and host halo mass. Using synthetic X-ray observations, we evaluate the detectability of stripped galactic coronae in real observations by stacking images on the known galaxy centres. We find that coronal emission should be detected within ˜10 arcsec, or ˜5 kpc up to ˜2.3 Gyr in the lowest (0.1-1.2 keV) energy band. Thus, the presence of observed coronae in cluster galaxies significantly smaller than the hot X-ray haloes of field galaxies indicates that at least some gas removal occurs within cluster environments for recently accreted galaxies. Finally, we evaluate the possibility that existing and future X-ray cluster catalogues can be used in combination with optical galaxy positions to detect galactic coronal emission via stacking analysis. We briefly discuss the effects of additional physical processes on coronal survival, and will address them in detail in future papers in this series.

  20. The study of flow characteristic of gas-liquid two-phase flow based on the near-infrared detection device

    NASA Astrophysics Data System (ADS)

    Fang, Lide; Liang, Yujiao; Zhang, Yao; Zhang, Chen; Gao, Jingzhe

    2014-04-01

    With the importance of the two-phase flow, many scholars pay attention on it; and for the so many parameters in the gas-liquid two-phase flow, flow characteristic is the basis. For the four flow patterns in the vertical direction, slug flow, bubbly flow, annular flow, and milk foam-like flow, the paper used the laser diode of 980nm and the silicon photodiode to detect the flow status. The absorption coefficients of the infrared in the gas and the liquid are very different; at the meantime, the infrared is affected by the interface obviously. As a result, it can reflect the fluctuation of the gas-liquid two-phase flow with the detection by the infrared. By analyzing the experiment data, four characteristic parameters are extracted, such as the average value, the variance, the kurtosis, and the frequency center of gravity. They can not only reflect the change of the different flow patterns, but also can reflect the fluctuation in the same flow pattern. The feature vector constituted of the four characteristic parameters can identify the flow pattern correctly in this system. What's more, it can achieve an accurate measurement of the real-time online, providing a basis for the other parameters' analysis in the gas-liquid two-phase flow.

  1. Comparative study of comprehensive gas chromatography-nitrogen chemiluminescence detection and gas chromatography-ion trap-tandem mass spectrometry for determining nicotine and carcinogen organic nitrogen compounds in thirdhand tobacco smoke.

    PubMed

    Ramírez, Noelia; Vallecillos, Laura; Lewis, Alastair C; Borrull, Francesc; Marcé, Rosa M; Hamilton, Jacqueline F

    2015-12-24

    Thirdhand tobacco smoke (THS) constitutes a poorly understood pathway of exposure of non-smokers, especially toddlers, to tobacco-related carcinogens. However, to date most of the carcinogens present in tobacco smoke have not been detected in THS and, therefore, the significance of THS health risk is still unknown. In this study, we have compared the performance of two analytical methods - one based on gas chromatography coupled to ion trap mass spectrometry detection (GC-IT-MS) and the other on comprehensive two-dimensional gas chromatography coupled to a nitrogen chemiluminescence detector (GC×GC-NCD) - for simultaneously determining, in settled house dust, the presence of 16 organic nitrogen carcinogens already detected in tobacco smoke. The target compounds included four aromatic amines, two nitrocompounds, eight N-nitrosamines and two tobacco-specific nitrosamines, as well as nicotine as a tobacco marker. Dust samples were extracted using in-cell clean up pressurized liquid extraction with silica as clean up sorbent and ethyl acetate as the organic solvent, with average recovery of 89%. Although GC-IT-MS, using chemical ionization with methanol and tandem MS, performed well, the optimized GC×GC-NCD gave lower limits of detection (from 4 to 22ngg(-1)) and better repeatability and reproducibility a low concentration levels (%RSD<8%) and, therefore, was applicable for determining these different groups of carcinogens without the need for derivatization prior to the GC analysis. The performance of the optimized PLE/GC×GC-NCD method was tested by quantifying the target compounds in house dust samples from smokers' and non-smokers' homes. The median carcinogen compounds detected was 3.8?gg(-1) and 1.1?gg(-1) in smokers' and non-smokers' house dust, respectively. In this study, we have detected highly carcinogenic aromatic amines and nitro compounds for the first time in settled house dust complementing the state of knowledge of THS composition and providing fresh evidence about THS health risks. PMID:26684592

  2. Analytical Method for the Detection of Ozone Depleting Chemicals (ODC) in Commercial Products Using a Gas Chromatograph with an Electron Capture Detector (GC-ECD)

    SciTech Connect

    Lee, Richard N.; Dockendorff, Brian P.; Wright, Bob W.

    2008-08-01

    This document describes an analytical procedure that was developed for the trace level detection of residual ozone depleting chemicals (ODC) associated with the manufacture of selected commercial products. To ensure the United States meets it obligation under the Montreal Protocol, Congress enacted legislation in 1989 to impose an excise tax on electronic goods imported into the United States that were produced with banned chemicals. This procedure was developed to technically determine if residual ODC chemicals could be detected on electronic circuit boards. The analytical method utilizes a “purge and trap” technique followed by gas chromatography with electron capture detection to capture and analyze the volatile chemicals associated with the matrix. The method describes the procedure, the hardware, operating conditions, calibration, and quality control measures in sufficient detail to allow the capability to be replicated. This document corresponds to internal Standard Operating Procedure (SOP) EFL-130A, Rev 4.

  3. Use of an accelerometer and a microphone as gas detectors in the online quantitative detection of hydrogen released from ammonia borane by gas chromatography.

    PubMed

    He, Yi-San; Chen, Kuan-Fu; Lin, Chien-Hung; Lin, Min-Tsung; Chen, Chien-Chung; Lin, Cheng-Huang

    2013-03-19

    The use of an accelerometer as a gas detector in gas chromatography (GC) is described for the first time. A milli-whistle was connected to the outlet of the GC capillary. When the eluted and GC carrier gases pass through the capillary and milli-whistle, a sound is produced. After a fast Fourier transform (FFT), the sound wave generated from the milli-whistle is picked up by a microphone and the resulting vibration of the milli-whistle body can be recorded by an accelerometer. The release of hydrogen gas, as the result of thermal energy, from ammonia borane (NH3BH3), which has been suggested as a storage medium for hydrogen, was selected as the model sample. The findings show that the frequencies generated, either by sound or by the vibration from the whistle body, were identical. The concentration levels of the released hydrogen gas can be determined online, based on the frequency changes. Ammonia borane was placed in a brass reservoir, heated continually, and the released hydrogen gas was directly injected into the GC inlet at 0.5 min intervals, using a home-built electromagnetic pulse injector. The concentration of hydrogen for each injection can be calculated immediately. When the ammonia borane was encapsulated within a polycarbonate (PC) microtube array membrane, the temperature required for the release of hydrogen can be decreased, which would make such a material more convenient for use. The findings indicate that 1.0 mg of ammonia borane can produce hydrogen in the range of 1.0-1.25 mL, in the temperature range of 85-115 °C. PMID:23419032

  4. Detection of [SiLL] (34.8 micron) emission in Orion-KL: A measurement of the silicon abundance in dense interstellar gas

    NASA Technical Reports Server (NTRS)

    Haas, M. R.; Hollenbach, D. J.; Erickson, E. F.

    1985-01-01

    The first detection of the ground state fine structure transition of Si+ at a rest wavelength determined to be 34.815 + or - 0.004 micron are reported. These observations were obtained with the facility spectrometer on NASA's Kuiper Airborne Observatory. A 6' NW-SE strip scan across the Orion-KL region shows SiII emission from both the extended photodissociation region surrounding theta 1 Ori C and from the shocked gas NW of BN-KL. The inferred gas-phase silicon elemental abundance relative to hydrogen in the dense 10 to the 5/cc primarily neutral photodissociation region is approximately 2.6 x to the -6, a factor of 0.075 times the solar value and 3.4 times greater than the abundance in the moderate density approx. 10 to the 3/cc cloud toward zeta Oph. The silicon abundance in the shocked gas is approximately solar, indicating that any pre-existing grains have been destroyed in the shock wave or that the preshock gas carries a near solar abundance of gas phase silicon. The shock-excited SiII (34.8 micron) emission may arise from shocked wind material in the outflow around IRc2, with wind velocities approx. 100 km/s.

  5. Observing Cold Gas in Submillimeter Galaxies: Detection of CO(1-0) Emission in SMM J13120+4242 with the Green Bank Telescope

    E-print Network

    L. J. Hainline; A. W. Blain; T. R. Greve; S. C. Chapman; I. Smail; R. J. Ivison

    2006-07-05

    We report the first detection of CO(1-0) emission from a submillimeter-selected galaxy, using the Green Bank Telescope. We identify the line in the spectrum of SMM J13120+4242 as a broad emission feature at z=3.408, with Delta(V_FWHM)=1040 +/- 190 km/s. If the observed CO(1-0) line profile arises from a single object and not several merging objects, then the CO(4-3)/CO(1-0) brightness temperature ratio of ~0.26 suggests n(H_2) > 3-10 x 10^2 cm^-3 and the presence of sub-thermally excited gas. The integrated line flux implies a cold molecular gas mass M(H_2)=1.6 x 10^11 M_sun, comparable to the dynamical mass estimate and 4 times larger than the H_2 mass predicted from the CO(4-3) line assuming a brightness temperature ratio of 1.0. While our observations confirm that this submillimeter galaxy is massive and gas-rich, they also suggest that extrapolating gas masses from J_upper >= 3 transitions of CO leads to considerable uncertainties. We also report an upper limit to the mass of cold molecular gas in a second submillimeter galaxy, SMM J09431+4700, of M(H_2)< 4 x 10^10 M_sun.

  6. Comparison of enzyme-linked immunosorbent assay and gas chromatography procedures for the detection of cyanazine and metolachlor in surface water samples

    USGS Publications Warehouse

    Schraer, S.M.; Shaw, D.R.; Boyette, M.; Coupe, R.H.; Thurman, E.M.

    2000-01-01

    Enzyme-linked immunosorbent assay (ELISA) data from surface water reconnaissance were compared to data from samples analyzed by gas chromatography for the pesticide residues cyanazine (2-[[4-chloro-6-(ethylamino)-l,3,5-triazin-2-yl]amino]-2-methylpropanenitrile ) and metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide). When ELISA analyses were duplicated, cyanazine and metolachlor detection was found to have highly reproducible results; adjusted R2s were 0.97 and 0.94, respectively. When ELISA results for cyanazine were regressed against gas chromatography results, the models effectively predicted cyanazine concentrations from ELISA analyses (adjusted R2s ranging from 0.76 to 0.81). The intercepts and slopes for these models were not different from 0 and 1, respectively. This indicates that cyanazine analysis by ELISA is expected to give the same results as analysis by gas chromatography. However, regressing ELISA analyses for metolachlor against gas chromatography data provided more variable results (adjusted R2s ranged from 0.67 to 0.94). Regression models for metolachlor analyses had two of three intercepts that were not different from 0. Slopes for all metolachlor regression models were significantly different from 1. This indicates that as metolachlor concentrations increase, ELISA will over- or under-estimate metolachlor concentration, depending on the method of comparison. ELISA can be effectively used to detect cyanazine and metolachlor in surface water samples. However, when detections of metolachlor have significant consequences or implications it may be necessary to use other analytical methods.

  7. The limitations on organic detection in Mars-like soils by thermal volatilization-gas chromatography-MS and their implications for the Viking results.

    PubMed

    Navarro-González, Rafael; Navarro, Karina F; de la Rosa, José; Iñiguez, Enrique; Molina, Paola; Miranda, Luis D; Morales, Pedro; Cienfuegos, Edith; Coll, Patrice; Raulin, François; Amils, Ricardo; McKay, Christopher P

    2006-10-31

    The failure of Viking Lander thermal volatilization (TV) (without or with thermal degradation)-gas chromatography (GC)-MS experiments to detect organics suggests chemical rather than biological interpretations for the reactivity of the martian soil. Here, we report that TV-GC-MS may be blind to low levels of organics on Mars. A comparison between TV-GC-MS and total organics has been conducted for a variety of Mars analog soils. In the Antarctic Dry Valleys and the Atacama and Libyan Deserts we find 10-90 mug of refractory or graphitic carbon per gram of soil, which would have been undetectable by the Viking TV-GC-MS. In iron-containing soils (jarosites from Rio Tinto and Panoche Valley) and the Mars simulant (palogonite), oxidation of the organic material to carbon dioxide (CO(2)) by iron oxides and/or their salts drastically attenuates the detection of organics. The release of 50-700 ppm of CO(2) by TV-GC-MS in the Viking analysis may indicate that an oxidation of organic material took place. Therefore, the martian surface could have several orders of magnitude more organics than the stated Viking detection limit. Because of the simplicity of sample handling, TV-GC-MS is still considered the standard method for organic detection on future Mars missions. We suggest that the design of future organic instruments for Mars should include other methods to be able to detect extinct and/or extant life. PMID:17060639

  8. The limitations on organic detection in Mars-like soils by thermal volatilization–gas chromatography–MS and their implications for the Viking results

    PubMed Central

    Navarro-González, Rafael; Navarro, Karina F.; de la Rosa, José; Iñiguez, Enrique; Molina, Paola; Miranda, Luis D.; Morales, Pedro; Cienfuegos, Edith; Coll, Patrice; Raulin, François; Amils, Ricardo; McKay, Christopher P.

    2006-01-01

    The failure of Viking Lander thermal volatilization (TV) (without or with thermal degradation)–gas chromatography (GC)–MS experiments to detect organics suggests chemical rather than biological interpretations for the reactivity of the martian soil. Here, we report that TV–GC–MS may be blind to low levels of organics on Mars. A comparison between TV–GC–MS and total organics has been conducted for a variety of Mars analog soils. In the Antarctic Dry Valleys and the Atacama and Libyan Deserts we find 10–90 ?g of refractory or graphitic carbon per gram of soil, which would have been undetectable by the Viking TV–GC–MS. In iron-containing soils (jarosites from Rio Tinto and Panoche Valley) and the Mars simulant (palogonite), oxidation of the organic material to carbon dioxide (CO2) by iron oxides and/or their salts drastically attenuates the detection of organics. The release of 50–700 ppm of CO2 by TV–GC–MS in the Viking analysis may indicate that an oxidation of organic material took place. Therefore, the martian surface could have several orders of magnitude more organics than the stated Viking detection limit. Because of the simplicity of sample handling, TV–GC–MS is still considered the standard method for organic detection on future Mars missions. We suggest that the design of future organic instruments for Mars should include other methods to be able to detect extinct and/or extant life. PMID:17060639

  9. Detection and quantification of methane and VOC emissions from oil and gas production operations using remote measurements, Interim report

    EPA Science Inventory

    Improved understanding of air pollutant emissions from oil and gas production operations is needed. With a steadily increasing number of production sources, the impact of emitted volatile organic compounds (VOCs) on regional ozone is potentially significant. As the separation dis...

  10. Detection of hydrocarbon microseepage in a rain forest environment (Jurua Gas field, northern Brazil) using Landsat MSS data

    SciTech Connect

    Miranda, F.P.; Cunha, F.M.B. )

    1990-05-01

    The Jurua gas field is the first important hydrocarbon accumulation found in the jungle-covered Solimoes basin. The tectonic framework in this area is characterized by a right-lateral transpressional zone (Jurua structural trend). Hydrocarbon traps are anticlines developed along the upthrown block of a reverse fault. The prospective 2,200-m-thick Paleozoic section is unconformably covered by a 2,800-m-thick pile of Mesozoic and Cenozoic continental sediments. Anomalous concentrations of hydrocarbons (C{sub 2}-C{sub 4}) in soil samples are concordantly aligned with the trace of the reverse fault crossing the gas field, indicating that this feature acted as a conduit for hydrocarbon microseepage. Gas-producing wells are located over a tabular watershed which coincides with the northeast-southwest Jurua structural trend. An unsupervised classification of Landsat MSS data over the gas field area reveals that one spectral class of vegetation is aligned with the Jurua structural trend. Field checking shows that the vegetation near the gas-producing well 1-JR-1-AM is not as dense as the forest outside the limits of the Jurua gas field. Two geologic factors may account for the vegetation anomaly over the gas field. (1) The northeast-southwest tabular watershed corresponds to a Pleistocene erosional surface associated with weathering products such as bauxite and laterite. The resulting soil is impermeable and low in nutrients. (2) The spectral behavior of vegetation may represent the response of plants to long-term anaerobic soil conditions brought about by gas leakage from the Paleozoic reservoir.

  11. Portable sick house syndrome gas monitoring system based on novel colorimetric reagents for the highly selective and sensitive detection of formaldehyde.

    PubMed

    Suzuki, Yoshio; Nakano, Nobuo; Suzuki, Koji

    2003-12-15

    Formaldehyde (HCHO) emitted from the furniture and the walls in the rooms injures the eyes, nose, and respiratory organs and causes allergies, which is called sick house syndrome. We designed and synthesized novel colorimetric HCHO-sensing molecules (KD-XA01 and KD-XA02) which possess an enaminone structure and developed a hand-held instrument to monitor indoor HCHO gas with the use of KD-XA01. These sensing molecules produced speedy color changes from colorless to yellow under mild conditions, which was caused by the fact that the enaminone structure in the reagent reacts with HCHO to give a lutidine derivative. This reaction took place not only in the solution phase but also in the solid phase (surface of the cellulose paper). To take advantage of this phenomena, a handy and rapid monitoring system has been developed for detecting indoor HCHO gas using a highly sensitive and selective detection tablet constructed from the porous cellulose paper that contains silica gel as an adsorbent, KD-XA01, and phosphoric acid under optimum conditions. This instrument detected the surface color change of the tablet from white to yellow, which was monitored as a function of the intensity of the reflected light illuminated by an LED (475 nm). The response was proportional to the HCHO concentration at a constant sampling time and flow rate; 0.05 ppm HCHO, which is under the standard value set by the World Health Organization, was able to be detected in 5 min. The detection limit was 0.005 ppm. This monitoring system was not interfered by carbonyl compounds such as acetaldehyde and acetone, alcohols, hydrocarbons, and typical gases such as carbon monoxide, carbon dioxide, nitrogen dioxide, etc., which contributes to the measurement of correct HCHO concentrations. It was possible to monitor the HCHO gas in the room of a new apartment and school using this instrument; the response values were in good agreement with those obtained by the standard DNPH method. This highly sensitive, selective, and handy HCHO gas monitor is widely applicable and convenient for users who are not specialists in this field. PMID:14717182

  12. Optical detection of argon gas flow based on vibration-induced change in photoluminescence of a semiconducting single-walled carbon nanotube bundle.

    PubMed

    Kim, Hong-Seok; Kim, Woo-Jae; Strano, Michael S; Hanl, Jae-Hee

    2014-12-01

    In this work, we demonstrate that Ar gas flow can be optically detected using mechanical vibration of a semiconducting single-walled carbon nanotube (SWCNT) bundle as a platform. A change in the photoluminescence (PL) intensity was induced by out-of-focusing of the SWCNT bundle of interest due to vibration caused by the introduced gas stream, for which a gas flow control system was installed in an optical microscope. The PL intensity was found to change systemically with the Ar flow rates in a range of relatively large flow rate intervals [0.70 to 3.0 standard cubic liters per minute (SLM) with 0.1-0.5 SLM intervals] with a noticeable hysteresis. It was, however, difficult to obtain a detectable PL change in a range of very small flow rate intervals (0.67 to 0.70 SLM with a 0.01 SLM interval). The detailed results and underlying mechanism are discussed in detail. PMID:25971023

  13. Gas Sensitivity and Sensing Mechanism Studies on Au-Doped TiO2 Nanotube Arrays for Detecting SF6 Decomposed Components

    PubMed Central

    Zhang, Xiaoxing; Yu, Lei; Tie, Jing; Dong, Xingchen

    2014-01-01

    The analysis to SF6 decomposed component gases is an efficient diagnostic approach to detect the partial discharge in gas-insulated switchgear (GIS) for the purpose of accessing the operating state of power equipment. This paper applied the Au-doped TiO2 nanotube array sensor (Au-TiO2 NTAs) to detect SF6 decomposed components. The electrochemical constant potential method was adopted in the Au-TiO2 NTAs' fabrication, and a series of experiments were conducted to test the characteristic SF6 decomposed gases for a thorough investigation of sensing performances. The sensing characteristic curves of intrinsic and Au-doped TiO2 NTAs were compared to study the mechanism of the gas sensing response. The results indicated that the doped Au could change the TiO2 nanotube arrays' performances of gas sensing selectivity in SF6 decomposed components, as well as reducing the working temperature of TiO2 NTAs. PMID:25330053

  14. Single-QCL-based absorption sensor for simultaneous trace-gas detection of CH4 and N2O

    E-print Network

    concentrations of greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) now substantially pig farming. Cavity-enhanced absorption spectroscopy (CEAS) achieved a minimum detection limit of 10

  15. Empirical Methods for Detecting Regional Trends and Other Spatial Expressions in Antrim Shale Gas Productivity, with Implications for Improving Resource Projections Using Local Nonparametric Estimation Techniques

    USGS Publications Warehouse

    Coburn, T.C.; Freeman, P.A.; Attanasi, E.D.

    2012-01-01

    The primary objectives of this research were to (1) investigate empirical methods for establishing regional trends in unconventional gas resources as exhibited by historical production data and (2) determine whether or not incorporating additional knowledge of a regional trend in a suite of previously established local nonparametric resource prediction algorithms influences assessment results. Three different trend detection methods were applied to publicly available production data (well EUR aggregated to 80-acre cells) from the Devonian Antrim Shale gas play in the Michigan Basin. This effort led to the identification of a southeast-northwest trend in cell EUR values across the play that, in a very general sense, conforms to the primary fracture and structural orientations of the province. However, including this trend in the resource prediction algorithms did not lead to improved results. Further analysis indicated the existence of clustering among cell EUR values that likely dampens the contribution of the regional trend. The reason for the clustering, a somewhat unexpected result, is not completely understood, although the geological literature provides some possible explanations. With appropriate data, a better understanding of this clustering phenomenon may lead to important information about the factors and their interactions that control Antrim Shale gas production, which may, in turn, help establish a more general protocol for better estimating resources in this and other shale gas plays. ?? 2011 International Association for Mathematical Geology (outside the USA).

  16. A new gas detection technique utilizing amplified spontaneous emission light source from a ? co-doped silica fibre in the 2.0 ?m region

    NASA Astrophysics Data System (ADS)

    Oh, Kyunghwan; Morse, T. F.; Kilian, A.

    1998-09-01

    A new technique for the measurement of the concentration of gas species is presented. The method is based on absorption spectroscopy in the infrared region utilizing a high-power broad band amplified spontaneous emission source from an optical fibre. Vibrational bands of 0957-0233/9/9/007/img8 gas in the range 1.9-2.1 0957-0233/9/9/007/img9m were measured and the relative intensities of bands were calibrated in terms of concentration. The amplified spontaneous emission from a 0957-0233/9/9/007/img10 co-doped silica fibre pumped near 800 nm was used as a light source that consisted of the 0957-0233/9/9/007/img11 transition of the 0957-0233/9/9/007/img12 ion and the 0957-0233/9/9/007/img13 transition of the 0957-0233/9/9/007/img14 ion with a full width at half maximum of 225 nm and total output power over 1 mW. The technique has potential for the simultaneous detection of multiple gas species due to its high spectral energy density over a wide wavelength band in the infrared where the vibrational overtones of gas molecules are located.

  17. Determination of Low Concentrations of Acetochlor in Water by Automated Solid-Phase Extraction and Gas Chromatography with Mass-Selective Detection

    USGS Publications Warehouse

    Lindley, C.E.; Stewart, J.T.; Sandstrom, M.W.

    1996-01-01

    A sensitive and reliable gas chromatographic/mass spectrometric (GC/MS) method for determining acetochlor in environmental water samples was developed. The method involves automated extraction of the herbicide from a filtered 1 L water sample through a C18 solid-phase extraction column, elution from the column with hexane-isopropyl alcohol (3 + 1), and concentration of the extract with nitrogen gas. The herbicide is quantitated by capillary/column GC/MS with selected-ion monitoring of 3 characteristic ions. The single-operator method detection limit for reagent water samples is 0.0015 ??g/L. Mean recoveries ranged from about 92 to 115% for 3 water matrixes fortified at 0.05 and 0.5 ??g/L. Average single-operator precision, over the course of 1 week, was better than 5%.

  18. Collection and analysis of NASA clean room air samples

    NASA Technical Reports Server (NTRS)

    Sheldon, L. S.; Keever, J.

    1985-01-01

    The environment of the HALOE assembly clean room at NASA Langley Research Center is analyzed to determine the background levels of airborne organic compounds. Sampling is accomplished by pumping the clean room air through absorbing cartridges. For volatile organics, cartridges are thermally desorbed and then analyzed by gas chromatography and mass spectrometry, compounds are identified by searching the EPA/NIH data base using an interactive operator INCOS computer search algorithm. For semivolatile organics, cartridges are solvent entracted and concentrated extracts are analyzed by gas chromatography-electron capture detection, compound identification is made by matching gas chromatogram retention times with known standards. The detection limits for the semivolatile organics are; 0.89 ng cu m for dioctylphlhalate (DOP) and 1.6 ng cu m for polychlorinated biphenyls (PCB). The detection limit for volatile organics ranges from 1 to 50 parts per trillion. Only trace quantities of organics are detected, the DOP levels do not exceed 2.5 ng cu m and the PCB levels do not exceed 454 ng cu m.

  19. High power, widely tunable, mode-hop free, continuous wave external cavity quantum cascade laser for multi-species trace gas detection

    SciTech Connect

    Centeno, R.; Marchenko, D.; Mandon, J.; Cristescu, S. M.; Harren, F. J. M.; Wulterkens, G.

    2014-12-29

    We present a high power, widely tunable, continuous wave external cavity quantum cascade laser designed for infrared vibrational spectroscopy of molecules exhibiting broadband and single line absorption features. The laser source exhibits single mode operation with a tunability up to 303?cm{sup ?1} (?24% of the center wavelength) at 8??m, with a maximum optical output power of 200?mW. In combination with off-axis integrated output spectroscopy, trace-gas detection of broadband absorption gases such as acetone was performed and a noise equivalent absorption sensitivity of 3.7 × 10{sup ?8?}cm{sup ?1?}Hz{sup ?1/2} was obtained.

  20. Simultaneous determination of bromide and iodide as acetone derivatives by gas chromatography and electron capture detection in natural waters and biological fluids

    SciTech Connect

    Maros, L.; Kaldy, M.; Igaz, S.

    1989-04-01

    Oxidation of bromide and iodide ions in acidic solutions in the presence of acetone forms the corresponding acetone derivatives. Iodate was reduced with thiosulfate prior to the determination. After extraction with benzene the bromo- and iodoacetone were measured by gas chromatography using electron capture detection. The bromide and iodide contents of rainwater, drinking water, river water, seawater, oil brine, common salt, cow milk, and human blood serum were determined. The relative standard deviations for bromide at 10/sup /minus/7/ M and for iodide at 10/sup /minus/8/ M concentration were 1.9% and 3.0%, respectively, using 10-mL sample for the determination without preconcentration.

  1. Repeated detection of gas in the portal vein after liver transplantation: A sign of EBV-associated post-transplant lymphoproliferation?

    PubMed

    Wallot, Michael A; Klepper, Jörg; Clapuyt, Philippe; Dirsch, Olaf; Malagó, Max; Reding, Raymond; Otte, Jean Bernard; Sokal, Etienne M

    2002-08-01

    A 1-yr-old child presented with intractable right sided pleural effusion and progressive clinical deterioration 3 weeks after liver transplantation for Alagille Syndrome. He had been treated successfully for severe acute rejection before. Ultrasound and Doppler mode studies repeatedly demonstrated air in the portal vein. Intra-abdominal and intra-thoracic lymphoproliferation was detected, and EBV virus load and serology were suggestive of primary EBV infection. Liver biopsy revealed blast-like infiltrates of B-cells, considered diagnostic for post-transplant lymphoproliferative disease. The disease resolved upon reduction of immunosuppression. We suggest that the detection of portal vein gas in pediatric liver transplant recipients beyond the early post-operative period may be a sign of intra-abdominal post-transplant lymphoproliferative disease. PMID:12234275

  2. Three sources and three components of success in detection of ultra-rare alpha decays at the Dubna Gas-Filled Recoil separator

    E-print Network

    Y. S. Tsyganov

    2015-06-05

    General philosophy of procedure of detecting rare events in the recent experiments with 48Ca projectile at the Dubna Gas-Filled Recoil Separator(DGFRS) aimed to the synthesis of superheavy elements (SHE) has been reviewed. Specific instruments and methods are under consideration. Some historical sources of the successful experiments for Z=112-118 are considered too. Special attention is paid to application of method of active correlations in heavy-ion induced complete fusion nuclear reactions. Example of application in Z=115 experiment is presented. Brief description of the 243Am + 48Ca -> 291-x115+xn experiment is presented too. Some attention is paid to the role of chemical experiments in discoveries of SHEs. The DGFRS detection/monitoring system is presented in full firstly.

  3. Three sources and three components of success in detection of ultra-rare alpha decays at the Dubna Gas-Filled Recoil separator

    E-print Network

    Tsyganov, Y S

    2015-01-01

    General philosophy of procedure of detecting rare events in the recent experiments with 48Ca projectile at the Dubna Gas-Filled Recoil Separator(DGFRS) aimed to the synthesis of superheavy elements (SHE) has been reviewed. Specific instruments and methods are under consideration. Some historical sources of the successful experiments for Z=112-118 are considered too. Special attention is paid to application of method of active correlations in heavy-ion induced complete fusion nuclear reactions. Example of application in Z=115 experiment is presented. Brief description of the 243Am + 48Ca -> 291-x115+xn experiment is presented too. Some attention is paid to the role of chemical experiments in discoveries of SHEs. The DGFRS detection/monitoring system is presented in full firstly.

  4. Automatic on-line monitoring of atmospheric volatile organic compounds: gas chromatography-mass spectrometry and gas chromatography-flame ionization detection as complementary systems.

    PubMed

    de Blas, Maite; Navazo, Marino; Alonso, Lucio; Durana, Nieves; Iza, Jon

    2011-11-15

    Traditionally air quality networks have been carrying out the continuous, on-line measurement of volatile organic compounds (VOC) in ambient air with GC-FID. In this paper some identification and coelution problems observed while using this technique in long-term measurement campaigns are described. In order to solve these problems a GC-MS was set up and operated simultaneously with a GC-FID for C2-C11 VOCs measurement. There are few on-line, unattended, long term measurements of atmospheric VOCs performed with GC-MS. In this work such a system has been optimized for that purpose, achieving good repeatability, linearity, and detection limits of the order of the GC-FID ones, even smaller in some cases. VOC quantification has been made by using response factors, which is not frequent in on-line GC-MS. That way, the identification and coelution problems detected in the GC-FID, which may led to reporting erroneous data, could be corrected. The combination of GC-FID and GC-MS as complementary techniques for the measurement of speciated VOCs in ambient air at sub-ppbv levels is proposed. Some results of the measurements are presented, including concentration values for some compounds not found until now on public ambient air VOC databases, which were identified and quantified combining both techniques. Results may also help to correct previously published VOC data with wrongly identified compounds by reprocessing raw chromatographic data. PMID:21978614

  5. USE OF MAILBOX APPROACH, VIDEO SURVEILLANCE, AND SHORT-NOTICE RANDOM INSPECTIONS TO ENHANCE DETECTION OF UNDECLARED LEU PRODUCTION AT GAS CENTRIFUGE ENRICHMENT PLANTS.

    SciTech Connect

    BOYER, B.D.; GORDON, D.M.; JO, J.

    2006-07-16

    Current safeguards approaches used by the IAEA at gas centrifuge enrichment plants (GCEPs) need enhancement in order to detect undeclared LEU production with adequate detection probability. ''Mailbox'' declarations have been used in the last two decades to verify receipts, production, and shipments at some bulk-handling facilities (e.g., fuel-fabrication plants). The operator declares the status of his plant to the IAEA on a daily basis using a secure ''Mailbox'' system such as a secure tamper-resistant computer. The operator agrees to hold receipts and shipments for a specified period of time, along with a specified number of annual inspections, to enable inspector access to a statistically large enough population of UF{sub 6} cylinders and fuel assemblies to achieve the desired detection probability. The inspectors can access the ''Mailbox'' during randomly timed inspections and then verify the operator's declarations for that day. Previously, this type of inspection regime was considered mainly for verifying the material balance at fuel-fabrication, enrichment, and conversion plants. Brookhaven National Laboratory has expanded the ''Mailbox'' concept with short-notice random inspections (SNRIs), coupled with enhanced video surveillance, to include declaration and verification of UF{sub 6} cylinder operational data to detect activities associated with undeclared LEU production at GCEPs. Since the ''Mailbox'' declarations would also include data relevant to material-balance verification, these randomized inspections would replace the scheduled monthly interim inspections for material-balance purposes; in addition, the inspectors could simultaneously perform the required number of Limited-Frequency Unannounced Access (LFUA) inspections used for HEU detection. This approach would provide improved detection capabilities for a wider range of diversion activities with not much more inspection effort than at present.

  6. A Micro-Preconcentrator Combined Olfactory Sensing System with a Micromechanical Cantilever Sensor for Detecting 2,4-Dinitrotoluene Gas Vapor

    PubMed Central

    Chae, Myung-Sic; Kim, Jinsik; Yoo, Yong Kyoung; Kang, Ji Yoon; Lee, Jeong Hoon; Hwang, Kyo Seon

    2015-01-01

    Preventing unexpected explosive attacks and tracing explosion-related molecules require the development of highly sensitive gas-vapor detection systems. For that purpose, a micromechanical cantilever-based olfactory sensing system including a sample preconcentrator was developed to detect 2,4-dinitrotoluene (2,4-DNT), which is a well-known by-product of the explosive molecule trinitrotoluene (TNT) and exists in concentrations on the order of parts per billion in the atmosphere at room temperature. A peptide receptor (His-Pro-Asn-Phe-Ser-Lys-Tyr-Ile-Leu-His-Gln-Arg) that has high binding affinity for 2,4-DNT was immobilized on the surface of the cantilever sensors to detect 2,4-DNT vapor for highly selective detection. A micro-preconcentrator (µPC) was developed using Tenax-TA adsorbent to produce higher concentrations of 2,4-DNT molecules. The preconcentration was achieved via adsorption and thermal desorption phenomena occurring between target molecules and the adsorbent. The µPC directly integrated with a cantilever sensor and enhanced the sensitivity of the cantilever sensor as a pretreatment tool for the target vapor. The response was rapidly saturated within 5 min and sustained for more than 10 min when the concentrated vapor was introduced. By calculating preconcentration factor values, we verified that the cantilever sensor provides up to an eightfold improvement in sensing performance. PMID:26213944

  7. Detection of Stimulants and Narcotics by Liquid Chromatography-Tandem Mass Spectrometry and Gas Chromatography-Mass Spectrometry for Sports Doping Control.

    PubMed

    Ahrens, Brian D; Kucherova, Yulia; Butch, Anthony W

    2016-01-01

    Sports drug testing laboratories are required to detect several classes of compounds that are prohibited at all times, which include anabolic agents, peptide hormones, growth factors, beta-2 agonists, hormones and metabolic modulators, and diuretics/masking agents. Other classes of compounds such as stimulants, narcotics, cannabinoids, and glucocorticoids are also prohibited, but only when an athlete is in competition. A single class of compounds can contain a large number of prohibited substances and all of the compounds should be detected by the testing procedure. Since there are almost 70 stimulants on the prohibited list it can be a challenge to develop a single screening method that will optimally detect all the compounds. We describe a combined liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) testing method for detection of all the stimulants and narcotics on the World Anti-Doping Agency prohibited list. Urine for LC-MS/MS testing does not require sample pretreatment and is a direct dilute and shoot method. Urine samples for the GC-MS method require a liquid-liquid extraction followed by derivatization with trifluoroacetic anhydride. PMID:26660193

  8. DETECTION OF MERCURIC BROMIDE IN A GAS PHASE FLOW CELL BY LASER PHOTOFRAGMENT FLUORESCENCE SPECTROSCOPY. (R825380)

    EPA Science Inventory

    Photofragment fluorescence (PFF) spectroscopy offers real-time monitoring
    capability with high-analytical sensitivity and selectivity for volatile mercury
    compounds found in process gas streams, such as incinerator stacks. In this
    work, low concentrations (6 ppb to...

  9. Detection of Caribbean fruit fly [(Anastrepha suspensa Loew (Diptera: Tephritidae)]-infested grapefruit with portable gas chromatography

    Technology Transfer Automated Retrieval System (TEKTRAN)

    New technologies are being sought by plant protection officials to more quickly and efficiently identify concealed pests in imported commodities. The zNose portable gas chromatography unit was investigated as a tool for identifying organic volatile signatures indicative of Caribbean fruit fly infest...

  10. A poly(dimethylsiloxane) based prism for surface plasmon resonance imaging system and its application for gas detection

    NASA Astrophysics Data System (ADS)

    Zhang, L. L.; Chen, X.; Sun, J. H.; Cai, H. Y.; Li, H.; Chao, Y. P.; Cui, D. F.

    2013-03-01

    This paper presents a surface plasmon resonance (SPR) imaging system based on a low-cost, convenient poly(dimethylsiloxane) (PDMS) prism featured with a close contact with the gold film. Compared to conventional glass prism, both numerical simulations and experimental studies indicated a deeper but wider absorption peak with a higher coupling angle for the PDMS based prism. System repeatability was quantified by the cycled detection of helium and air, with the effect of the flow rate investigated. Furthermore, five types of gases (nitrogen, air, oxygen, hydrogen, and helium) were detected and differentiated by the SPR system, with a calculated sensitivity of 5 × 10-6 RIU.

  11. Application of a miniaturized photoacoustic cell for high-sensitivity laser detection of ammonia in gas media

    E-print Network

    Gorelik, A V

    2008-01-01

    We present a photoacoustic resonant cell, the internal volume of which is ~ 0.5 cm^3. The cavity shape of the cell is so adapted in order to minimize the background signal arising due to absorption of laser beam in the cell windows. An experimental setup, measurement procedure and design of the cell are described. Results of detection of ammonia in nitrogen flow with the help of a CO2-laser are represented. The minimal detectable absorption for the cell is estimated in the experiment to be ~ 5.1 cm^(-1) W Hz^(-1/2)

  12. DETECTING COLD GAS AT z = 3 WITH THE ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY AND THE SQUARE KILOMETER ARRAY

    SciTech Connect

    Obreschkow, D.; Heywood, I.; Rawlings, S.

    2011-12-10

    We forecast the abilities of the Atacama Large Millimeter/submillimeter Array (ALMA) and the Square Kilometer Array (SKA) to detect CO and H I emission lines in galaxies at redshift z = 3. A particular focus is set on Milky Way (MW) progenitors at z = 3 since their detection within 24 hr constitutes a key science goal of ALMA. The analysis relies on a semi-analytic model, which permits the construction of an MW progenitor sample by backtracking the cosmic history of all simulated present-day galaxies similar to the real MW. Results are as follows: (1) ALMA can best observe an MW at z = 3 by looking at CO(3-2) emission. The probability of detecting a random model MW at 3{sigma} in 24 hr using 75 km s{sup -1} channels is roughly 50%, and these odds can be increased by co-adding the CO(3-2) and CO(4-3) lines. These lines fall into ALMA band 3, which therefore represents the optimal choice toward MW detections at z = 3. (2) Higher CO transitions contained in the ALMA bands {>=}6 will be invisible, unless the considered MW progenitor coincidentally hosts a major starburst or an active black hole. (3) The high-frequency array of SKA, fitted with 28.8 GHz receivers, would be a powerful instrument for observing CO(1-0) at z = 3, able to detect nearly all simulated MWs in 24 hr. (4) H I detections in MWs at z = 3 using the low-frequency array of SKA will be impossible in any reasonable observing time. (5) SKA will nonetheless be a supreme H I survey instrument through its enormous instantaneous field of view (FoV). A one-year pointed H I survey with an assumed FoV of 410 deg{sup 2} would reveal at least 10{sup 5} galaxies at z = 2.95-3.05. (6) If the positions and redshifts of those galaxies are known from an optical/infrared spectroscopic survey, stacking allows the detection of H I at z = 3 in less than 24 hr.

  13. Detection of [O I] ?6300 and Other Diagnostic Emission Lines in the Diffuse Ionized Gas of M33 with Gemini-North

    NASA Astrophysics Data System (ADS)

    Voges, E. S.; Walterbos, R. A. M.

    2006-06-01

    We present spectroscopic observations of diffuse ionized gas (DIG) in M33 near the H II region NGC 604. We present the first detection of [O I] ?6300 in the DIG of M33, one of the critical lines for distinguishing photoionization from shock ionization models. We measure [O I]/H? in the range of 0.04-0.10 and an increase in this ratio with decreasing emission measure. Our measurements of [S II]/H? and [N II]/H? also rise with decreasing emission measure, while our [O III]/H? measurements remain fairly constant. We have one tentative detection of He I in the region of brightest emission measure, with a ratio of He I/H? = 0.033 +/- 0.019, indicating that the helium is at least partially ionized. We compare our observed emission-line ratios to photoionization models and find that field star ionization models do not fit our data well. Leaky H II region models are consistent with our data, without the need to invoke additional ionization mechanisms to fit our [O I] or [O III] measurements. The closest large H II region is NGC 604 and is therefore a likely candidate for the source of the ionizing photons for the gas in this region.

  14. Controllable manipulation and detection of local densities and bipartite entanglement in a quantum gas by a dissipative defect

    SciTech Connect

    Barmettler, Peter; Kollath, Corinna

    2011-10-15

    We study the complex dynamics of a one-dimensional Bose gas subjected to a dissipative local defect which induces one-body atom losses. In experiments these atom losses occur, for example, when a focused electron or light beam or a single trapped ion is brought into contact with a quantum gas. We discuss how within such setups one can measure or manipulate densities locally and specify the excitations that are induced by the defect. In certain situations the defect can be used to generate entanglement in a controlled way despite its dissipative nature. The careful examination of the interplay between hole excitations and the collapse of the wave function due to nondetection of loss is crucial for the understanding of the dynamics we observe.

  15. Metabolic Polymorphisms and Clinical Findings Related to Benzene Poisoning Detected in Exposed Brazilian Gas-Station Workers

    PubMed Central

    Mitri, Simone; Fonseca, Antônio Sérgio Almeida; Otero, Ubirani Barros; Tabalipa, Marianne Medeiros; Moreira, Josino Costa; Sarcinelli, Paula de Novaes

    2015-01-01

    Benzene is a ubiquitous environmental pollutant and an important industrial chemical present in both gasoline and motor vehicle emissions. Occupational human exposure to benzene occurs in the petrochemical and petroleum refining industries as well as in gas-station workers, where it can lead to benzene poisoning (BP), but the mechanisms of BP are not completely understood. In Brazil, a significant number of gas-station service workers are employed. The aim of the present study was to evaluate alterations related to BP and metabolic polymorphisms in gas-station service workers exposed to benzene in the city of Rio de Janeiro, Brazil. Occupational exposure was based on clinical findings related to BP, and metabolic polymorphisms in 114 Brazilian gas-station attendants. These workers were divided into No Clinical Findings (NCF) and Clinical Findings (CF) groups. Neutrophil and Mean Corpuscular Volume (MCV) showed a significant difference between the two study groups, and neutrophil has the greatest impact on the alterations suggestive of BP. The clinical findings revealed higher frequencies of symptoms in the CF group, although not all members presented statistical significance. The frequencies of alleles related to risk were higher in the CF group for GSTM1, GSTT1, CYP2E1 7632T > A, but lower for NQO1 and CYP2E1 1053C > T genotypes. Moreover, an association was found between GSTM1 null and alterations related to BP, but we did not observe any effects of other polymorphisms. Variations in benzene metabolizing genes may modify benzene toxicity and should be taken into consideration during risk assessment evaluations. PMID:26197327

  16. Metabolic Polymorphisms and Clinical Findings Related to Benzene Poisoning Detected in Exposed Brazilian Gas-Station Workers.

    PubMed

    Mitri, Simone; Fonseca, Antônio Sérgio Almeida; Otero, Ubirani Barros; Tabalipa, Marianne Medeiros; Moreira, Josino Costa; Sarcinelli, Paula de Novaes

    2015-07-01

    Benzene is a ubiquitous environmental pollutant and an important industrial chemical present in both gasoline and motor vehicle emissions. Occupational human exposure to benzene occurs in the petrochemical and petroleum refining industries as well as in gas-station workers, where it can lead to benzene poisoning (BP), but the mechanisms of BP are not completely understood. In Brazil, a significant number of gas-station service workers are employed. The aim of the present study was to evaluate alterations related to BP and metabolic polymorphisms in gas-station service workers exposed to benzene in the city of Rio de Janeiro, Brazil. Occupational exposure was based on clinical findings related to BP, and metabolic polymorphisms in 114 Brazilian gas-station attendants. These workers were divided into No Clinical Findings (NCF) and Clinical Findings (CF) groups. Neutrophil and Mean Corpuscular Volume (MCV) showed a significant difference between the two study groups, and neutrophil has the greatest impact on the alterations suggestive of BP. The clinical findings revealed higher frequencies of symptoms in the CF group, although not all members presented statistical significance. The frequencies of alleles related to risk were higher in the CF group for GSTM1, GSTT1, CYP2E1 7632T > A, but lower for NQO1 and CYP2E1 1053C > T genotypes. Moreover, an association was found between GSTM1 null and alterations related to BP, but we did not observe any effects of other polymorphisms. Variations in benzene metabolizing genes may modify benzene toxicity and should be taken into consideration during risk assessment evaluations. PMID:26197327

  17. On the effect of oxygen flooding on the detection of noble gas ions in a SIMS instrument

    NASA Astrophysics Data System (ADS)

    Williams, Peter; Franzreb, Klaus; Sobers, Richard C.; Lörin?ík, Jan

    2010-09-01

    We have investigated the report by Desgranges and Pasquet (2004) [1] that O 2 gas flooding in a secondary ion mass spectrometer could enhance by a factor of about ˜5 the Xe + ion yield for a Xe implant in UO 2 sputtered by O2+ primary ions. For a Xe implant in Si sputtered by O2+ primary ions and for Xe + sputtering of silicon in steady state, O 2 gas flooding reduced the Xe + ion signal by a factor of about 2, presumably due to loss of Xe + by resonant charge exchange with gas-phase oxygen molecules. The yield of a Kr co-implant in Si was unaffected by oxygen flooding. However, we demonstrate that for steady-state Ar + sputtering of uranium, the Ar + ion yield can be increased by a factor of ˜1.7 by oxygen flooding. This enhancement, predicted by a simple model to be a factor of ?3, is attributed to a lowering of the neutral Ar emission velocity and hence increased post-ionization efficiency, caused by the suppression of argon bubble formation in uranium by oxidation of the near-surface region, and re-emission of argon by thermal effusion rather than in supersonic expansions from bursting high-pressure gas bubbles. We show that bubble formation, evidenced by the observation of Xe2+ clusters, also occurs for Xe +-bombarded uranium when the surface is sufficiently sputter-cleaned, and that the bubbles are similarly suppressed by oxygen flooding producing a factor of ˜?3 enhancement in the Xe + signal.

  18. LABORATORY GAS-PHASE DETECTION OF THE CYCLOPROPENYL CATION (c-C{sub 3}H{sub 3} {sup +})

    SciTech Connect

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

    2014-08-20

    The cyclopropenyl cation (c-C{sub 3}H{sub 3} {sup +}) is the smallest aromatic hydrocarbon molecule and considered to be a pivotal intermediate in ion-molecule reactions in space. An astronomical identification has been prohibited so far, because of a lack of gas-phase data. Here we report the first high resolution infrared laboratory gas-phase spectrum of the ? {sub 4} (C-H asymmetric stretching) fundamental band of c-C{sub 3}H{sub 3} {sup +}. The c-C{sub 3}H{sub 3} {sup +} cations are generated in supersonically expanding planar plasma by discharging a propyne/helium gas pulse, yielding a rotational temperature of ?35 K. The absorption spectrum is recorded in the 3.19 ?m region using sensitive continuous-wave cavity ring-down spectroscopy. The analysis of about 130 ro-vibrational transitions results in precise spectroscopic parameters. These constants allow for an accurate comparison with high-level theoretical predictions, and provide the relevant information needed to search for this astrochemically relevant carbo-cation in space.

  19. A portable, high-speed, vacuum-outlet GC vapor analyzer employing air as carrier gas and surface acoustic wave detection.

    PubMed

    Whiting, J J; Lu, C J; Zellers, E T; Sacks, R D

    2001-10-01

    Vacuum-outlet GC with atmospheric-pressure air as the carrier gas is implemented at outlet pressures up to 0.8 atm using a low-dead-volume polymer-coated surface acoustic wave (SAW) detector. Increases in the system outlet pressure from 0.1 to 0.8 atm lead to proportional increases in detector sensitivity and significant increases in column efficiency. The latter effect arises from the fact that optimal carrier gas velocities are lower in air than in more conventional carrier gases such as helium or hydrogen due to the smaller binary diffusion coefficients of vapors in air. A 12-m-long, 0.25-mm-i.d. tandem column ensemble consisting of 4.5-m dimethyl polysiloxane and 7.5-m trifluoropropylmethyl polysiloxane operated at an outlet pressure of 0.5 atm provides up to 4 x 10(4) theoretical plates and a peak capacity of 65 (resolution, 1.5) for a 3-min isothermal analysis. At 30 degrees C, mixtures of vapors ranging in vapor pressure from 8.6 to 76 Torr are separated in this time frame. The SAW detector cell has an internal volume of < 2 microL, which allows the use of higher column outlet pressures with minimal dead time. The sensor response is linear with solute mass over at least 2-3 decades and provides detection limits of 20-50 ng for the vapors tested. The combination of atmospheric-pressure air as carrier gas, modest operating pressures, and SAW sensor detection is well-suited for field instrumentation since it eliminates the need for support gases, permits smaller, low-power pumps to be used, and provides sensitivity to a wide range of vapor analytes. PMID:11605845

  20. Room-temperature NH3 gas sensors based on Ag-doped ?-Fe2O3/SiO2 composite films with sub-ppm detection ability.

    PubMed

    Tang, Yongliang; Li, Zhijie; Zu, Xiaotao; Ma, Jinyi; Wang, Lu; Yang, Jing; Du, Bo; Yu, Qingkai

    2015-11-15

    In this report, NH3 gas sensors based on Ag-doped ?-Fe2O3/SiO2 composite films are investigated. The composite films were prepared with a sol-gel process, and the films' electrical resistance responded to the change of NH3 concentration in the environment. The SEM and AFM investigations showed that the films had a porous structure, and the XRD investigation indicated that the size of Ag particles changed with the modification of Ag loading content. Through a comparative gas sensing study among the Ag-doped composite films, undoped composite film, ?-Fe2O3 film, and SiO2 film, the Ag-doped composite films were found to be much more sensitive than the sensors based on the undoped composite film and ?-Fe2O3 film at room temperature, indicating the significant influences of the SiO2 and Ag on the sensing property. Moreover, the sensor based on Ag-doped (4%) ?-Fe2O3/SiO2 composite film was able to detect the NH3 gas at ppb level. Conversely, the responses of the sensor to other test gases (C2H5OH, CO, H2, CH4 and H2S) were all markedly low, suggesting excellent selectivity. PMID:26057440

  1. Palladium nanoparticle decorated silicon nanowire field-effect transistor with side-gates for hydrogen gas detection

    SciTech Connect

    Ahn, Jae-Hyuk; Yun, Jeonghoon; Park, Inkyu; KI for the NanoCentury, KAIST, Daejeon 305-701; Mobile Sensor and IT Convergence Center, KAIST, Daejeon 305-701 ; Choi, Yang-Kyu

    2014-01-06

    A silicon nanowire field-effect transistor (SiNW FET) with local side-gates and Pd surface decoration is demonstrated for hydrogen (H{sub 2}) detection. The SiNW FETs are fabricated by top-down method and functionalized with palladium nanoparticles (PdNPs) through electron beam evaporation for H{sub 2} detection. The drain current of the PdNP-decorated device reversibly responds to H{sub 2} at different concentrations. The local side-gates allow individual addressing of each sensor and enhance the sensitivity by adjusting the working region to the subthreshold regime. A control experiment using a non-functionalized device verifies that the hydrogen-sensitivity is originated from the PdNPs functionalized on the SiNW surface.

  2. Application of time array detection to capillary column gas chromatography/conventional time-of-flight mass spectrometry.

    PubMed

    Erickson, E D; Enke, C G; Holland, J F; Watson, J T

    1990-05-15

    The technique of time array detection (TAD) is designed to take advantage of the high spectral generation rate available in time-of-flight (TOF) mass spectrometry. In TAD, a number of successive TOF arrival time transient signals are summed to produce each recorded mass spectrum. The TOF/TAD technique offers significant improvements over conventional scanning mass spectrometers for the analysis of capillary GC effluents. Up to 20 mass spectra per second were generated to demonstrate the accurate reconstruction of the chromatographic profile and the lack of mass spectral distortion despite the rapidly changing analyte concentration. Varying the number of TOF transients per recorded spectrum allows the chromatography to be optimized for speed of analysis without sacrificing chromatographic resolution or detection limits. Components of charcoal lighter fluid were chromatographically separated in less than 4 min with quality mass spectra obtained for each eluent. PMID:2360715

  3. Fiber-Amplifier-Enhanced QEPAS Sensor for Simultaneous Trace Gas Detection of NH3 and H2S

    PubMed Central

    Wu, Hongpeng; Dong, Lei; Liu, Xiaoli; Zheng, Huadan; Yin, Xukun; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Jia, Suotang

    2015-01-01

    A selective and sensitive quartz enhanced photoacoustic spectroscopy (QEPAS) sensor, employing an erbium-doped fiber amplifier (EDFA), and a distributed feedback (DFB) laser operating at 1582 nm was demonstrated for simultaneous detection of ammonia (NH3) and hydrogen sulfide (H2S). Two interference-free absorption lines located at 6322.45 cm?1 and 6328.88 cm?1 for NH3 and H2S detection, respectively, were identified. The sensor was optimized in terms of current modulation depth for both of the two target gases. An electrical modulation cancellation unit was equipped to suppress the background noise caused by the stray light. An Allan-Werle variance analysis was performed to investigate the long-term performance of the fiber-amplifier-enhanced QEPAS sensor. Benefitting from the high power boosted by the EDFA, a detection sensitivity (1?) of 52 parts per billion by volume (ppbv) and 17 ppbv for NH3 and H2S, respectively, were achieved with a 132 s data acquisition time at atmospheric pressure and room temperature. PMID:26506351

  4. Fiber-Amplifier-Enhanced QEPAS Sensor for Simultaneous Trace Gas Detection of NH? and H?S.

    PubMed

    Wu, Hongpeng; Dong, Lei; Liu, Xiaoli; Zheng, Huadan; Yin, Xukun; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Jia, Suotang

    2015-01-01

    A selective and sensitive quartz enhanced photoacoustic spectroscopy (QEPAS) sensor, employing an erbium-doped fiber amplifier (EDFA), and a distributed feedback (DFB) laser operating at 1582 nm was demonstrated for simultaneous detection of ammonia (NH?) and hydrogen sulfide (H?S). Two interference-free absorption lines located at 6322.45 cm(-1) and 6328.88 cm(-1) for NH? and H?S detection, respectively, were identified. The sensor was optimized in terms of current modulation depth for both of the two target gases. An electrical modulation cancellation unit was equipped to suppress the background noise caused by the stray light. An Allan-Werle variance analysis was performed to investigate the long-term performance of the fiber-amplifier-enhanced QEPAS sensor. Benefitting from the high power boosted by the EDFA, a detection sensitivity (1?) of 52 parts per billion by volume (ppbv) and 17 ppbv for NH? and H?S, respectively, were achieved with a 132 s data acquisition time at atmospheric pressure and room temperature. PMID:26506351

  5. Determination of coumaphos, chlorpyrifos and ethion residues in propolis tinctures by matrix solid-phase dispersion and gas chromatography coupled to flame photometric and mass spectrometric detection.

    PubMed

    Pérez-Parada, Andrés; Colazzo, Marcos; Besil, Natalia; Geis-Asteggiante, Lucía; Rey, Federico; Heinzen, Horacio

    2011-08-26

    A new analytical method has been developed and successfully evaluated in routine application for the quantitative analysis of a selected group of organophosphate pesticides (coumaphos, chlorpyrifos and ethion) which can be found at trace levels in propolis tinctures (ethanolic propolis extracts); a valuable commodity used as raw material in the food and pharmaceutical industries for which there have been few attempts for pesticide residue analysis reported in the literature. The proposed methodology is based on matrix solid phase dispersion (MSPD) using aluminum sulfate anh. a novel dispersant material and subsequent column chromatography clean-up in silica gel prior to gas chromatography (GC) with both flame photometric detector (FPD) and mass spectrometry (MS) detection used for the routine quantification and identification of the residues, respectively. The limits of detection, for coumaphos, chlorpyrifos and ethion were below 26.0 ?g/kg in FPD and 1.43 ?g/kg for MS detection. Mean recoveries were in the range of 85-123% with RSD values below 13%, which suggests that the proposed method is fit for the purpose of analyzing pesticides in propolis tinctures containing high concentration of polyphenolics. The method has been successfully applied in our laboratory for the last 2 year in the analysis of real propolis tinctures samples. PMID:21782188

  6. Simple and sensitive determination of o-phenylphenol in citrus fruits using gas chromatography with atomic emission or mass spectrometric detection.

    PubMed

    Kolbe, Nina; Andersson, Jan T

    2006-08-01

    In this work, a simple and sensitive method for the analysis of the pesticide o-phenylphenol (OPP) on citrus fruits was developed. OPP is extracted with dichloromethane by ultrasonication and derivatized with ferrocenecarboxylic acid chloride. Using ferrocene as a label, residues of OPP are determined by gas chromatography with atomic emission detection in the iron selective mode or with mass spectrometric detection. Sample cleanup is simple and rapid and merely involves a removal of excess reagent on an alumina minicolumn. The method detection limit is 2 ng of OPP/g of fruit, and recoveries from lemon samples fortified at levels of 35 and 140 ng/g are 101 and 106%, respectively. The citrus fruits analyzed (oranges, grapefruits, lemons) contained between 60 ng/g and 0.37 microg/g OPP (RSD = 8-13%), and the results were in good agreement with results obtained when OPP was analyzed using an established HPLC-FLD method. Several alcohols could also be identified in the fruit peel. PMID:16881671

  7. Characterization of volatile compounds in chilled cod (Gadus morhua) fillets by gas chromatography and detection of quality indicators by an electronic nose.

    PubMed

    Olafsdottir, Gudrun; Jonsdottir, Rosa; Lauzon, Hélène L; Luten, Joop; Kristbergsson, Kristberg

    2005-12-28

    Volatile compounds in cod fillets packed in Styrofoam boxes were analyzed during chilled storage (0.5 degrees C) by gas chromatography (GC)-mass spectrometry and GC-olfactometry to screen potential quality indicators present in concentrations high enough for detection by an electronic nose. Photobacterium phosphoreum dominated the spoilage bacteria on day 12 when the fillets were rejected by sensory analysis. Ketones, mainly 3-hydroxy-2-butanone, were detected in the highest level (33%) at sensory rejection, followed by amines (TMA) (29%), alcohols (15%), acids (4%), aldehydes (3%), and a low level of esters (<1%). The electronic nose's CO sensor showed an increasing response with storage time coinciding with the production of ethanol and 2-methyl-1-propanol that were produced early in the storage, followed by the production of 3-methyl-1-butanol, 3-methyl-butanal, 2,3-butandiol, and ethyl acetate. Lipid-derived aldehydes, like hexanal and decanal, were detected in similar levels throughout the storage time and contributed to the overall sweet odors of cod fillets in combination with other carbonyls (3-hydroxy-2-butanone, acetaldehyde, 2-butanone, 3-pentanone, and 6-methyl-5-heptene-2-one). PMID:16366707

  8. Gas sensor

    SciTech Connect

    Bunner, T.A.

    1982-03-16

    A detection unit for detecting hydrocarbon gases includes a cylindrical housing having a pair of opposed rectangular slots formed in the wall of the housing near the lower end. A support is mounted within the housing adjacent the upper end. A pair of baffle plates are mounted within the housing from the walls thereof. A semiconductor hydrocarbon gas detector is mounted to the support and is connected by electrical leads to an analyzer and recorder. The detection unit is mounted at the mouth of an oil or gas drilling rig and receives drilling mud into the housing at the rectangular slots such that gases released from the drilling mud are analyzed by the gas detector to determine the hydrocarbon gas content therein.

  9. Nanoparticle cluster gas sensor: Pt activated SnO2 nanoparticles for NH3 detection with ultrahigh sensitivity.

    PubMed

    Liu, Xu; Chen, Nan; Han, Bingqian; Xiao, Xuechun; Chen, Gang; Djerdj, Igor; Wang, Yude

    2015-09-28

    Pt activated SnO2 nanoparticle clusters were synthesized by a simple solvothermal method. The structure, morphology, chemical state and specific surface area were analyzed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and N2-sorption studies, respectively. The SnO2 nanoparticle cluster matrix consists of tens of thousands of SnO2 nanoparticles with an ultra-small grain size estimated to be 3.0 nm. And there are abundant random-packed wormhole-like pores, caused by the inter-connection of the SnO2 nanoparticles, throughout each cluster. The platinum element is present in two forms including metal (Pt) and tetravalent metal oxide (PtO2) in the Pt activated SnO2 nanoparticle clusters. The as-synthesized pure and Pt activated SnO2 nanoparticle clusters were used to fabricate gas sensor devices. It was found that the gas response toward 500 ppm of ammonia was improved from 6.48 to 203.44 through the activation by Pt. And the results indicate that the sensor based on Pt activated SnO2 not only has ultrahigh sensitivity but also possesses good response-recovery properties, linear dependence, repeatability, selectivity and long-term stability, demonstrating the potential to use Pt activated SnO2 nanoparticle clusters as ammonia gas sensors. At the same time, the formation mechanisms of the unique nanoparticle clusters and highly enhanced sensitivity are also discussed. PMID:26289622

  10. Detection of Alpha Particles and Low Energy Gamma Rays by Thermo-Bonded Micromegas in Xenon Gas

    E-print Network

    Yuehuan Wei; Liang Guan; Zhiyong Zhang; Qing Lin; Xiaolian Wang; Kaixuan Ni; Tianchi Zhao

    2013-08-09

    Micromegas is a type of micro-pattern gaseous detector currently under R&D for applications in rare event search experiments. Here we report the performance of a Micromegas structure constructed with a micromesh thermo-bonded to a readout plane, motivated by its potential application in two-phase xenon detectors for dark matter and neutrinoless double beta decay experiments. The study is carried out in pure xenon at room temperature. Measurements with alpha particles from the Americium-241 source showed that gas gains larger than 200 can be obtained at xenon pressure up to 3 atm. Gamma rays down to 8 keV were observed with such a device.

  11. A High Sensitivity and Wide Dynamic Range Fiber-Optic Sensor for Low-Concentration VOC Gas Detection

    PubMed Central

    Khan, Md. Rajibur Rahaman; Kang, Shin-Won

    2014-01-01

    In this paper, we propose a volatile organic compound (VOC) gas sensing system with high sensitivity and a wide dynamic range that is based on the principle of the heterodyne frequency modulation method. According to this method, the time period of the sensing signal shift when Nile Red containing a VOC-sensitive membrane of a fiber-optic sensing element comes into contact with a VOC. This sensing membrane produces strong, fast and reversible signals when exposed to VOC gases. The response and recovery times of the proposed sensing system were less than 35 s, and good reproducibility and accuracy were obtained. PMID:25490592

  12. Development of a Low Power Gas Chromatograph-Mass Spectrometer for In-Situ Detection of Organics in Martian Soil

    NASA Technical Reports Server (NTRS)

    Pinnick, Veronica; Buch, Arnaud; VanAmerom, Friso H. W.; Danell, Ryan M.; Brinckerhoff, William; Mahaffy, Paul; Cotter, Robert J.

    2011-01-01

    The Mars Organic Molecule Analyzer (MOMA) is a joint venture by NASA and the European Space Agency (ESA) to develop a sensitive, light-weight, low-power mass spectrometer for chemical analysis on Mars. MOMA is a key analytical instrument aboard the 2018 ExoMars rover mission seeking signs of past or present life. The current prototype was built to demonstrate operation of gas chromatography (OC) and laser desorption (LD) mass spectrometry under martian ambient conditions (5-7 Torr of CO2-rich atmosphere). Recent reports have discussed the MO MA concept, design and performance. Here, we update the current prototype performance, focusing specifically on the GCMS mode.

  13. Detection of Alpha Particles and Low Energy Gamma Rays by Thermo-Bonded Micromegas in Xenon Gas

    E-print Network

    Wei, Yuehuan; Zhang, Zhiyong; Lin, Qing; Wang, Xiaolian; Ni, Kaixuan; Zhao, Tianchi

    2013-01-01

    Micromegas is a type of micro-pattern gaseous detector currently under R&D for applications in rare event search experiments. Here we report the performance of a Micromegas structure constructed with a micromesh thermo-bonded to a readout plane, motivated by its potential application in two-phase xenon detectors for dark matter and neutrinoless double beta decay experiments. The study is carried out in pure xenon at room temperature. Measurements with alpha particles from the Americium-241 source showed that gas gains larger than 200 can be obtained at xenon pressure up to 3 atm. Gamma rays down to 8 keV were observed with such a device.

  14. Experimental Detection of Neutron Gas Pressure on the Control Rods of a Nuclear Reactor under the Microgravity Conditions

    NASA Astrophysics Data System (ADS)

    Zrodnikov, Anatoly V.; Poupko, Victor Ya.; Gryaznov, George M.

    1994-07-01

    In typical reactor conditions, where the neutron density is not very great, the neutron gas behaves as a statistical ensemble of neutral particles. As a result of impulse exchanges between moving neutrons and the nuclei of substance of the reactor construction, the latter will experience the pressure effects similar to that created by usual gases. However, these efforts are so negligible that it always remains unnoticed in the terrestrial conditions of reactor operation. Another matter is the reactor operation in the state of non-gravity at Earth orbit, when the unique conditions exist for the showing of effects even for very low-power mechanical forces, in particular, because of the moving neutrons braking in solid bodies. Use of the thermoelectric NPS in space in the USSR since October 1970 (Poupko et al. 1992) gave the possibility, for the first time in the world, to identify and to measure by indirect method the mentioned effects of neutron gas pressure. These results are discussed below.

  15. Research on the trace detection of carbon dioxide gas and modulation parameter optimization based on the TDLAS technology

    NASA Astrophysics Data System (ADS)

    Zhao, Peng; Tao, Jun; Yu, Chang-rui; Li, Ye

    2014-02-01

    Based on the technology of tunable diode laser absorption spectroscopy, modulation of the center wavelength of 2004 nm distributed feedback laser diode at a room-temperature, the second harmonic amplitude of CO2 at 2004nm can be obtained. The CO2 concentration can be calculated via the Beer-Lambert law. Sinusoidal modulation parameter is an important factor that affects the sensitivity and accuracy of the system, through the research on the relationship between sinusoidal modulation signal frequency, amplitude and Second harmonic linetype, we finally achieve the detection limit of 10ppm under 12 m optical path.

  16. Generation, detection and characterization of gas-phase transition metal aggregates and compounds. Progress report, year one

    SciTech Connect

    Steimle, T.C.

    1992-08-01

    The goal of our research is to employ spectroscopic techniques to characterize the bound portions of the potential energy surface (PES) for chemical systems involving diatomic and triatomic transition metal molecules. The approach incorporates the generation and isolation of new metal compounds via supersonic laser ablation molecular beam techniques. Detection and characterization is achieved using high resolution dye laser induced fluorescence spectroscopy. A major objective is to produce information which can be compared to theoretical predictions and thereby provide guidelines and insight into the development of reaction models.

  17. The detection of CN and HNC mm-wave absorption lines in spiral-arm gas clouds

    NASA Astrophysics Data System (ADS)

    Nyman, L.-A.; Millar, T. J.

    1989-09-01

    Radio absorption lines have been detected from the J = 1-0 transition of HNC and the N = 1-0 transition of CN toward a few Galactic continuum sources. Column densities and abundance ratios are derived, and it is argued that the results can be best explained if the absorption lines arise in the outer envelopes of molecular clouds along the line of sight. These clouds provide a shadowing effect so that the radiation field along the line of sight is much reduced from that estimated from the visual extinction.

  18. Aerobic synthetic approach and characterisation of some acetylide-thiourea derivatives for the detection of carbon monoxide (CO) gas

    NASA Astrophysics Data System (ADS)

    Daud, Adibah Izzati; Khairul, Wan M.; Mohamed Zuki, Hafiza; Kubulat, K.

    2015-08-01

    Novel acetylide-thiourea systems (PAT, EBT, and ETT), that possess both withdrawing and donating system properties were successfully synthesised with good yield (64-72%) and were characterised via several spectroscopic and analytical techniques. In turn, all synthesised derivatives were deposited onto glass substrates by dip-coating, and then their responses towards CO exposure were evaluated via UV-visible spectroscopy to identify their thin-film sensitivity towards CO. Theoretical studies using Gaussian 09 analysis were used to determine the relationship between the experimental and theoretical analyses of the molecules. The data revealed that acetylide-thiourea derivatives exhibit great potential for the detection of CO.

  19. Identification of aroma-active volatiles in banana Terra spirit using multidimensional gas chromatography with simultaneous mass spectrometry and olfactometry detection.

    PubMed

    Capobiango, Michely; Mastello, Raíssa Bittar; Chin, Sung-Tong; Oliveira, Evelyn de Souza; Cardeal, Zenilda de Lourdes; Marriott, Philip John

    2015-04-01

    Fruit spirits have been produced and consumed throughout the world for centuries. However, the aroma composition of banana spirits is still poorly characterised. We have investigated the aroma-impact compounds of the banana Terra spirit for the first time, using multidimensional gas chromatography (MDGC and GC × GC) in a multi-hyphenated system - i.e., coupled to flame ionisation detection (FID), mass spectrometry (MS), and olfactometry (O). Solid-phase microextraction (SPME) was used to isolate the headspace aroma compounds of the banana spirit. The detection frequency (DF) technique was applied and aroma regions, detected in the first column separation at >60% Nasal Impact Frequency (NIF), were screened as target potent odour regions in the sample. Using a polar/non-polar phase column set, the potent odour regions were further subjected to MDGC separation with simultaneous O and MS detection for correlation of the aroma perception with MS data for individual resolved aroma-impact compounds. GC-O analysis enabled 18 aroma-impact regions to be located as providing volatiles of interest for further study; for example, those comprising perceptions of flower, whisky, green, amongst others. Compounds were tentatively identified through MS data matching and retention indices in both first and second dimensions. The principal volatile compounds identified in this work, which are responsible for the characteristic aroma of the banana spirit, are 3-methylbutan-1-ol, 3-methylbutan-1-ol acetate, 2-phenylethyl acetate and phenylethyl alcohol. This is the first such study to reveal the major aroma compounds that contribute to banana spirit aroma. PMID:25728661

  20. Multiwalled carbon nanotubes coated fibers for solid-phase microextraction of polybrominated diphenyl ethers in water and milk samples before gas chromatography with electron-capture detection.

    PubMed

    Wang, Jun-Xia; Jiang, Dong-Qing; Gu, Zhi-Yuan; Yan, Xiu-Ping

    2006-12-22

    Determination of polybrominated diphenyl ethers (PBDEs) in environmental samples has raised great concerns due to the widespread use of PBDEs and their potential risk to humans. Solid-phase microextraction (SPME) is a fast, simple, cost-effective, and green sample preparation technique and is widely used for environmental analysis, but reports on the application of SPME for determination of PBDEs are very limited, and only a few publications dealing with commercial SPME fibers are available for extraction of PBDEs. Herein, we report a novel SPME method using multiwalled carbon nanotubes (MWCNTs) as the SPME fiber coating for gas chromatography with electron-capture detection (GC-ECD) of PBDEs in environmental samples. The MWCNTs coating gave much higher enhancement factors (616-1756) than poly (5% dibenzene-95% dimethylsiloxane) coating (139-384) and activated carbon coating (193-423). Thirty-minute extraction of 10 mL of sample solution using the MWCNTs coated fiber for GC-ECD determination yielded the limits of detection of 3.6-8.6 ng L(-1) and exhibited good linearity of the calibration functions (r(2)>0.995). The precision (RSD%, n=4) for peak area and retention time at the 500 ng L(-1) level was 6.9-8.8% and 0.6-0.9%, respectively. The developed method was successfully applied for the analysis of real samples including local river water, wastewater, and milk samples. The recovery of the PBDEs at 500 ng L(-1) spiked in these samples ranged from 90 to 119%. No PBDEs were detected in the river water and skimmed milk samples, whereas in the wastewater sample, 134-215 ng L(-1) of PBDEs were found. The PBDEs were detected in all whole fat milk samples, ranging from 13 to 484 ng L(-1). In a semiskimmed milk sample, only BDE-47 was found at 21 ng L(-1). PMID:17055524