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1

Evaluation of BDE-47 hydroxylation metabolic pathways based on a strong electron-withdrawing pentafluorobenzoyl derivatization gas chromatography/electron capture negative ionization quadrupole mass spectrometry.  

PubMed

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

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

2014-07-15

2

Evaluation of gas chromatography-atmospheric pressure chemical ionization-mass spectrometry as an alternative to gas chromatography-electron ionization-mass spectrometry: avocado fruit as example.  

PubMed

Although GC-APCI-MS was developed more than 40 years ago this coupling is still far from being a routine technique. One of the reasons explaining the limited use of GC-APCI so far is the lack of spectral database which facilitates the identification of the compounds under study. The first application of a very recently developed GC-APCI database to identify as many compounds as possible in a complex matrix such as avocado fruit is presented here. The results achieved by using this database has been checked against those obtained using traditional GC-EI-MS and a comparison of the MS signals observed in both ionization sources has been carried out. 100 compounds belonging to different chemical families were identified in the matrix under study. Considering the results of this study, the wide range of application (in terms of polarity and size of analytes) and the robustness of APCI as interface, the high quality of TOF spectra, and our library as a publicly available resource, GC-APCI-TOF MS is definitively a valuable addition to the "metabolomics toolbox". PMID:24054422

Hurtado-Fernández, Elena; Pacchiarotta, Tiziana; Longueira-Suárez, Enrique; Mayboroda, Oleg A; Fernández-Gutiérrez, Alberto; Carrasco-Pancorbo, Alegría

2013-10-25

3

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

PubMed

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

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

2015-02-01

4

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

Microsoft Academic Search

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

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

2006-01-01

5

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

PubMed

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

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

2014-01-01

6

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

PubMed

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

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

2014-01-01

7

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

PubMed

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

Zhao, Dongmei

2014-01-01

8

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

PubMed

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

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

2014-12-01

9

Gas amplified ionization detector for gas chromatography  

DOEpatents

A gas-amplified ionization detector for gas chromatrography which possesses increased sensitivity and a very fast response time. Solutes eluding from a gas chromatographic column are ionized by UV photoionization of matter eluting therefrom. The detector is capable of generating easily measured voltage signals by gas amplification/multiplication of electron products resulting from the UV photoionization of at least a portion of each solute passing through the detector.

Huston, Gregg C. (LaBelle, PA)

1992-01-01

10

Electron acceleration in ionizable gas  

SciTech Connect

A flat-panel gas discharge cathodoluminescent display includes a plurality of mutually parallel, electron-transmissive accelerator electrodes respectively connected to sources of high positive voltage levels to increase the acceleration voltage of the display without causing ionization of the gas.

Glaser, D.

1983-07-12

11

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

PubMed

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

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

2012-03-01

12

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

PubMed

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

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

2011-05-01

13

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

PubMed

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

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

2011-08-01

14

Weakly ionized cosmic gas: Ionization and characterization  

NASA Technical Reports Server (NTRS)

Since collective plasma behavior may determine important transport processes (e.g., plasma diffusion across a magnetic field) in certain cosmic environments, it is important to delineate the parameter space in which weakly ionized cosmic gases may be characterized as plasmas. In this short note, we do so. First, we use values for the ionization fraction given in the literature, wherein the ionization is generally assumed to be due primarily to ionization by cosmic rays. We also discuss an additional mechanism for ionization in such environments, namely, the photoelectric emission of electrons from cosmic dust grains in an interstellar Far Ultra Violet (FUV) radiation field. Simple estimates suggest that under certain conditions this mechanism may dominate cosmic ray ionization, and possibly also the photoionization of metal atoms by the interstellar FUV field, and thereby lead to an enhanced ionization level.

Rosenberg, M.; Mendis, D. A.; Chow, V. W.

1994-01-01

15

Liquid chromatography-electron ionization mass spectrometry: fields of application and evaluation of the performance of a Direct-EI interface.  

PubMed

A comprehensive evaluation and a thorough discussion of the fields of possible applications of the Direct-EI interface are described in this review. Direct-EI allows the direct introduction of the effluent from a capillary HPLC column into the electron ionization (EI) ion source of a mass spectrometer. Thanks to the reduced liquid intake and an in-source nebulizer, the interfacing process occurs smoothly and entirely into the ion source. No intermediate interfacing mechanisms of any sort are interposed between the column and the mass spectrometer, thus circumventing any undesired sample loss and minimizing the effort for instrument modification. Theoretically, any GC-MS system can be converted into an LC-MS for EI amenable compounds. Several parameters, crucial for a successful integration of liquid chromatography and mass spectrometry, have been considered in the evaluation of the functioning of such an interface: limit of detection, linearity of response, reproducibility, and chromatographic compatibility. Different mobile phases, also containing non-volatile buffers, were taken into account, demonstrating an outstanding separation flexibility. The entire set of experiments was carried out at different flow rates and temperatures of the ion source. The interface behavior was also tested in real world applications, with mixtures of pesticides, hormones, nitro-PAH, and endocrine-disrupting compounds, allowing picogram level detection and the possibility to record library-matchable, readily interpretable electron ionization mass spectra, for prompt compound characterization and confirmation. PMID:15900616

Cappiello, Achille; Famiglini, Giorgio; Palma, Pierangela; Siviero, Antonella

2005-01-01

16

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

PubMed

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

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

2011-10-10

17

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

Microsoft Academic Search

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

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

2008-01-01

18

Interlaboratory reproducibility of fast gas chromatography–electron impact–time of flight mass spectrometry (GC–EI–TOF\\/MS) based plant metabolomics  

Microsoft Academic Search

The application of gas chromatography–mass spectrometry (GC–MS) to the ‘global’ analysis of metabolites in complex samples\\u000a (i.e. metabolomics) has now become routine. The generation of these data-rich profiles demands new strategies in data mining\\u000a and standardisation of experimental and reporting aspects across laboratories. As part of the META-PHOR project’s (METAbolomics\\u000a for Plants Health and OutReach: http:\\/\\/www.meta-phor.eu\\/) priorities towards robust technology

J. William Allwood; Alexander Erban; Sjaak de Koning; Warwick B. Dunn; Alexander Luedemann; Arjen Lommen; Lorraine Kay; Ralf Löscher; Joachim Kopka; Royston Goodacre

2009-01-01

19

Miniaturized gas ionization sensors using carbon nanotubes  

NASA Astrophysics Data System (ADS)

Gas sensors operate by a variety of fundamentally different mechanisms. Ionization sensors work by fingerprinting the ionization characteristics of distinct gases, but they are limited by their huge, bulky architecture, high power consumption and risky high-voltage operation. Here we report the fabrication and successful testing of ionization microsensors featuring the electrical breakdown of a range of gases and gas mixtures at carbon nanotube tips. The sharp tips of nanotubes generate very high electric fields at relatively low voltages, lowering breakdown voltages several-fold in comparison to traditional electrodes, and thereby enabling compact, battery-powered and safe operation of such sensors. The sensors show good sensitivity and selectivity, and are unaffected by extraneous factors such as temperature, humidity, and gas flow. As such, the devices offer several practical advantages over previously reported nanotube sensor systems. The simple, low-cost, sensors described here could be deployed for a variety of applications, such as environmental monitoring, sensing in chemical processing plants, and gas detection for counter-terrorism.

Modi, Ashish; Koratkar, Nikhil; Lass, Eric; Wei, Bingqing; Ajayan, Pulickel M.

2003-07-01

20

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

PubMed

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

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

2015-03-01

21

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

PubMed

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

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

2008-08-01

22

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

PubMed

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

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

2012-10-01

23

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

PubMed

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

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

2008-07-14

24

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

PubMed

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

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

2011-07-15

25

Highly ionized atoms in cooling gas  

NASA Technical Reports Server (NTRS)

The ionization of low density gas cooling from a high temperature was calculated. The evolution during the cooling is assumed to be isochoric, isobaric, or a combination of these cases. The calculations are used to predict the column densities and ultraviolet line luminosities of highly ionized atoms in cooling gas. In a model for cooling of a hot galactic corona, it is shown that the observed value of N(N V) can be produced in the cooling gas, while the predicted value of N(Si IV) falls short of the observed value by a factor of about 5. The same model predicts fluxes of ultraviolet emission lines that are a factor of 10 lower than the claimed detections of Feldman, Brune, and Henry. Predictions are made for ultraviolet lines in cooling flows in early-type galaxies and clusters of galaxies. It is shown that the column densities of interest vary over a fairly narrow range, while the emission line luminosities are simply proportional to the mass inflow rate.

Edgar, R. J.; Chevalier, R. A.

1986-01-01

26

Gas chromatography-electron ionization mass spectrometry and liquid chromatography-electrospray tandem mass spectrometry for determination of impurities in the anti-cancer drug isophosphoramide mustard  

NASA Astrophysics Data System (ADS)

Isophosphoramide mustard (IPM) is known to have substantial anti-cancer activities in various animal models. Liquid chromatography-electrospray mass spectrometry (LC-ES-MS) and LC-ES-MS/MS methodologies have been developed and applied to the analysis of synthesized preparations of IPM. Our studies reveal that the principal impurity in IPM is N-(2-chloroethyl)-N'-ethylphosphorodiamidic acid (MC-IPM) formed by dehydrochlorination of IPM with subsequent hydrogenation during synthesis. This impurity is present at levels in the range of 2-5% depending upon synthesis conditions. In addition, a second IPM derivative has been characterized by LC-ES-MS/MS and has been shown to be the product of a reaction of IPM with the dilute perchloric acid mobile phase used for liquid chromatography separations. The LC-ES-MS/MS method has been successfully employed to detect IPM spiked into a blood plasma sample. This work establishes that LC-ES-MS/MS is a viable tool for the detailed characterization of IPM and related products.

Cole, Richard B.; Chou, Chau-Wen; Boué, Stephen M.; Leblanc, Blaise W.; Rodgers, Andrew H.; Struck, Robert F.; Morgan, Lee Roy

2004-02-01

27

The distribution of warm ionized gas in NGC 891  

NASA Technical Reports Server (NTRS)

Narrow-band imaging is presented of the edge-on spiral NGC 891 in the H-alpha and S II 6716, 6731 A forbidden lines. Emission from H II regions confined to the plane of the galaxy and from diffuse gas up to about 4 kpc off the plane is readily detected. The full radial extent of the diffuse emission in the plane is about 30 kpc. NGC 891 is found to have a surface density of diffuse ionized gas twice the Galactic value, a thicker ionized gas layer, and a larger surface density of ionized gas relative to neutral gas. These are interpreted as consequences of a relatively high level of star formation in this galaxy. Other star formation tracers indicate the same conclusion. Many vertical H-alpha filaments, or 'worms,' extending to over 2 kpc off the plane of the galaxy are seen. These worms are interpreted in terms of chimney models for the interstellar media of spirals.

Rand, Richard J.; Kulkarni, Shrinivas R.; Hester, J. Jeff

1990-01-01

28

Gas electron multiplier (GEM) enhanced ionization chamber for fluorescence detector  

Microsoft Academic Search

Detecting dilute elements in thin materials using extended X-ray absorption fluorescence spectroscopy (EXAFS) method requires a detector capable of high count rate and low noise. For detection of dilute elements, the fluorescence signal amplitude is often overcome by the presence of noise or background interference. In this paper we have used a gas ionization chamber enhanced by a gas electron

E. H. Shaban; D. P. Siddons; A. Kuczewski

2007-01-01

29

Transport Phenomena in a Completely Ionized Gas  

Microsoft Academic Search

The coefficients of electrical and thermal conductivity have been computed for completely ionized gases with a wide variety of mean ionic charges. The effect of mutual electron encounters is considered as a problem of diffusion in velocity space, taking into account a term which previously had been neglected. The appropriate integro-differential equations are then solved numerically. The resultant conductivities are

Lyman Spitzer; Richard Härm

1953-01-01

30

A validated gas chromatographic–electron impact ionization mass spectrometric method for methamphetamine, methylenedioxymethamphetamine (MDMA), and metabolites in mouse plasma and brain  

PubMed Central

A method was developed and fully validated for simultaneous quantification of methamphetamine (MAMP), amphetamine, hydroxy-methamphetamine, methylenedioxymethamphetamine (MDMA, ecstasy), methylenedioxyamphetamine, 3-hydroxy-4-methoxy-methamphetamine, and 3-hydroxy-4-methoxy-amphetamine in 100 ?L mouse plasma and 7.5 mg brain. Solid phase extraction and gas chromatography–electron impact ionization mass spectrometry in selected-ion monitoring mode achieved plasma linear ranges of 10–20 to 20,000 ng/mL and 0.1–0.2 to 200 ng/mg in brain. Recoveries were greater than 91%, bias 92.3–110.4%, and imprecision less than 5.3% coefficient of variation. This method was used for measuring MAMP and MDMA and metabolites in plasma and brain during mouse neurotoxicity studies. PMID:19026602

Scheidweiler, Karl B.; Barnes, Allan J.; Huestis, Marilyn A.

2008-01-01

31

Herschel Galactic plane survey of ionized gas traced by [NII  

NASA Astrophysics Data System (ADS)

Far infrared and sub-/millimeter atomic & ionic fine structure and molecular rotational lines are powerful tracers of star formation on both Galactic and extragalactic scales. Although CO lines trace cool to moderately warm molecular gas, ionized carbon [CII] produces the strongest lines, which arise from almost all reasonably warm (T>50 K) parts of the ISM. However, [CII] alone cannot distinguish highly ionized gas from weakly ionized gas. [NII] plays a significant role in star formation as it is produced only in ionized regions; in [HII] regions as well as diffuse ionized gas. The ionization potential of nitrogen (14.5 eV) is greater than that of hydrogen (13.6 eV), therefore the ionized nitrogen [NII] lines reflect the effects of massive stars, with possible enhancement from X-ray and shock heating from the surroundings. Two far-infrared 122 um and 205 um [NII] fine structure spectral lines are targeted via Photodetector Array Camera and Spectrometer (PACS) onboard Herschel Space Observatory. The sample consists of 149 line-of-sight (LOS) positions in the Galactic plane. These positions overlap with the [CII] 158 um observations obtained with the GOT C+ survey. With a reasonable assumption that the emission from both 122 um and 205 um lines originate in the same gas; [NII] 122/205 um line ratio indicates the a good measure of the electron density of each of the LOS positions. [NII] detections are mainly toward the Galactic center direction and the [NII] electron densities are found between 7-50 cm^-3, which is enhanced WIM (Warm Ionized Medium). WIM densities are expected to be much lower (~1 cm-3), therefore non-detections toward the opposite side of the Galactic Center shows abundant of this gas. The pixel to pixel variation of the emission within a single Herschel pointing is relatively small, which is interpreted as the [NII] emission comes from an extended gas. It is important to quantify what fraction of [CII] emission arises in the ionized gas. Thus, with the present work of [NII] observations, it will be possible to resolve the different parts of the ISM leading to determine the total mass of the ISM.

Yildiz, Umut; Goldsmith, Paul; Pineda, Jorge; Langer, William

2015-01-01

32

Ionized gas at the edge of the central molecular zone  

NASA Astrophysics Data System (ADS)

Context. The edge of the central molecular zone (CMZ) is the location where massive dense molecular clouds with large internal velocity dispersions transition to the surrounding more quiescent and lower CO emissivity region of the Galaxy. Little is known about the ionized gas surrounding the molecular clouds and in the transition region. Aims: We determine the properties of the ionized gas at the edge of the CMZ near Sgr E using observations of N+ and C+. Methods: We observed a small portion of the edge of the CMZ near Sgr E with spectrally resolved [C ii] 158 ?m and [N ii] 205 ?m fine structure lines at six positions with the GREAT instrument on SOFIA and in [C ii] using Herschel HIFI on-the-fly strip maps. We use the [N ii] spectra along with a radiative transfer model to calculate the electron density of the gas and the [C ii] maps to illuminate the morphology of the ionized gas and model the column density of CO-dark H2. Results: We detect two [C ii] and [N ii] velocity components, one along the line of sight to a CO molecular cloud at - 207 km s-1 associated with Sgr E and the other at -174 km s-1 outside the edge of another CO cloud. From the [N ii] emission we find that the average electron density is in the range of ~5 to 21 cm-3 for these features. This electron density is much higher than that of the disk's warm ionized medium, but is consistent with densities determined for bright diffuse H ii nebula. The column density of the CO-dark H2 layer in the -207 km s-1 cloud is ~1-2 × 1021 cm-2 in agreement with theoretical models. The CMZ extends further out in Galactic radius by ~7 to 14 pc in ionized gas than it does in molecular gas traced by CO. Conclusions: The edge of the CMZ likely contains dense hot ionized gas surrounding the neutral molecular material. The high fractional abundance of N+ and high electron density require an intense EUV field with a photon flux of order 106 to 107 photons cm-2 s-1, and/or efficient proton charge exchange with nitrogen, at temperatures of order 104 K, and/or a large flux of X-rays. Sgr E is a region of massive star formation as indicated by the presence of numerous compact H ii regions. The massive stars are potential sources of the EUV radiation that ionizes and heat the gas. In addition, X-ray sources and the diffuse X-ray emission in the CMZ are candidates for ionizing nitrogen.

Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.; Velusamy, T.; Requena-Torres, M. A.; Wiesemeyer, H.

2015-04-01

33

Ionized gas and stellar kinematics of seventeen nearby spiral galaxies  

E-print Network

Ionized gas and stellar kinematics have been measured along the major axes of seventeen nearby spiral galaxies of intermediate to late morphological type. We discuss the properties of each sample galaxy distinguishing between those characterized by regular or peculiar kinematics. In most of the observed galaxies ionized gas rotates more rapidly than stars and have a lower velocity dispersion, as is to be expected if the gas is confined in the disc and supported by rotation while the stars are mostly supported by dynamical pressure. In a few objects, gas and stars show almost the same rotational velocity and low velocity dispersion, suggesting that their motion is dominated by rotation. Incorporating the spiral galaxies studied by Bertola et al. (1996), Corsini et al. (1999, 2003) and Vega Beltran et al. (2001) we have compiled a sample of 50 S0/a-Scd galaxies, for which the major-axis kinematics of the ionized gas and stars have been obtained with the same spatial (~1'') and spectral (~50km/s) resolution, and measured with the same analysis techniques. This allowed us to address the frequency of counterrotation in spiral galaxies. It turns out that less than 12% and less than 8% (at the 95% confidence level) of the sample galaxies host a counterrotating gaseous and stellar disc, respectively. The comparison with S0 galaxies suggests that the retrograde acquisition of small amounts of external gas gives rise to counterrotating gaseous discs only in gas-poor S0s, while in gas-rich spirals the newly acquired gas is swept away by the pre-existing gas. Counterrotating gaseous and stellar discs in spirals are formed only from the retrograde acquisition of large amounts of gas exceeding that of pre-existing gas, and subsequent star formation, respectively.

A. Pizzella; E. M. Corsini; J. C. Vega-Beltran; F. Bertola

2004-04-28

34

Ionized Gas Velocities for Edge-on HALOGAS Galaxies  

NASA Astrophysics Data System (ADS)

Several galaxies show decreasing rotational velocities of neutral and ionized hydrogen gas with increasing height above the disk. This is likely due to a combination of outflow from galactic fountains and infall from the IGM or satellite accretion. The degree to which each component contributes affects the rotational velocity gradient of the gas and has implications for halo formation and evolution. We present results from optical observations and modeling of the ionized extra-planar gas in NGC 4244, NGC 891, and NGC 4565, three edge-on galaxies from the HALOGAS (Hydrogen Accretion in LOcal GAlaxieS) sample. HALOGAS is a WSRT deep HI survey studying cold gas accretion in the local universe. Our observations are from a multi-slit spectroscopic setup on the ARC 3.5m telescope, which allows us to measure velocities of Ha-emitting gas as a function of height above the disk in 11 radial distance bins in a single exposure. We compare our results to the HI velocity data and show that the neutral and ionized gas exhibit similar kinematic characteristics. RW acknowledges support from NSF grant AST-0908126 and from a grant from Research Corporation for the Advancement of Science.

Wu, Catharine J.; Walterbos, R.; Rand, R.; Heald, G.; HALOGAS Team

2012-01-01

35

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

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

36

The distribution of warm ionized gas in NGC 891  

SciTech Connect

Narrow-band imaging is presented of the edge-on spiral NGC 891 in the H-alpha and S II 6716, 6731 A forbidden lines. Emission from H II regions confined to the plane of the galaxy and from diffuse gas up to about 4 kpc off the plane is readily detected. The full radial extent of the diffuse emission in the plane is about 30 kpc. NGC 891 is found to have a surface density of diffuse ionized gas twice the Galactic value, a thicker ionized gas layer, and a larger surface density of ionized gas relative to neutral gas. These are interpreted as consequences of a relatively high level of star formation in this galaxy. Other star formation tracers indicate the same conclusion. Many vertical H-alpha filaments, or 'worms,' extending to over 2 kpc off the plane of the galaxy are seen. These worms are interpreted in terms of chimney models for the interstellar media of spirals. 19 refs.

Rand, R.J.; Kulkarni, S.R.; Hester, J.J. (California Institute of Technology, Pasadena (USA) Infrared Processing and Analysis Center, Pasadena, CA (USA))

1990-03-01

37

Viscosity Coefficient Curve Fits for Ionized Gas Species Grant Palmer  

NASA Technical Reports Server (NTRS)

Viscosity coefficient curve fits for neutral gas species are available from many sources. Many do a good job of reproducing experimental and computational chemistry data. The curve fits are usually expressed as a function of temperature only. This is consistent with the governing equations used to derive an expression for the neutral species viscosity coefficient. Ionized species pose a more complicated problem. They are subject to electrostatic as well as intermolecular forces. The electrostatic forces are affected by a shielding phenomenon where electrons shield the electrostatic forces of positively charged ions beyond a certain distance. The viscosity coefficient for an ionized gas species is a function of both temperature and local electron number density. Currently available curve fits for ionized gas species, such as those presented by Gupta/Yos, are a function of temperature only. What they did was to assume an electron number density. The problem is that the electron number density they assumed was unrealistically high. The purpose of this paper is two-fold. First, the proper expression for determining the viscosity coefficient of an ionized species as a function of both temperature and electron number density will be presented. Then curve fit coefficients will be developed using the more realistic assumption of an equilibrium electron number density. The results will be compared against previous curve fits and against highly accurate computational chemistry data.

Palmer, Grant; Arnold, James O. (Technical Monitor)

2001-01-01

38

Time-Dependent Ionization in Radiatively Cooling Gas  

E-print Network

We present new computations of the equilibrium and non-equilibrium cooling efficiencies and ionization states for low-density radiatively cooling gas containing cosmic abundances of the elements H, He, C, N, O, Ne, Mg, Si, S, and Fe. We present results for gas temperatures between 1e4 and 1e8 K, assuming dust-free and optically thin conditions, and no external radiation. For non-equilibrium cooling we solve the coupled time-dependent ionization and energy loss equations for a radiating gas cooling from an initially hot, >5e6K equilibrium state, down to 1e4K. We present results for heavy element compositions ranging from 1e-3 to 2 times the elemental abundances in the Sun. We consider gas cooling at constant density (isochoric) and at constant pressure (isobaric). We calculate the critical column densities and temperatures at which radiatively cooling clouds make the dynamical transition from isobaric to isochoric evolution. We construct ion ratio diagnostics for the temperature and metallicity in radiatively cooling gas. We provide numerical estimates for the maximal cloud column densities for which the gas remains optically thin to the cooling radiation. We present our computational results in convenient on-line figures and tables (see http://wise-obs.tau.ac.il/~orlyg/cooling/).

Orly Gnat; Amiel Sternberg

2006-08-08

39

Resonance ionization spectroscopy: counting noble-gas atoms  

SciTech Connect

New work on the counting of noble gas atoms, using lasers for the selective ionization and detectors for counting individual particles (electrons or positive ions) is reported. When positive ions are counted, various kinds of mass analyzers (magnetic, quadrupole, or time-of-flight) can be incorporated to provide A selectivity. It is shown that a variety of interesting and important applications can be made with atom-counting techniques which are both atomic number (Z) and mass number (A) selective.

Hurst, G.S.; Payne, M.G.; Chen, C.H.; Willis, R.D.; Lehmann, B.E.; Kramer, S.D.

1981-06-01

40

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...

41

Kinematics of Ionized Gas in Edge-on HALOGAS Galaxies  

NASA Astrophysics Data System (ADS)

Extra-planar gas generally shows a decrease in rotational velocity with increasing height above the disk. It can originate from disk-halo cycling driven by star formation in the disk or from infalling gas clouds. Studies at optical and radio wavelengths suggest that a combination of the two is the most likely scenario. Our goal is to measure velocity gradients of the ionized gas in a large number of halos, which can then be used as a constraint for models of the origin of halo gas. Because we are observing in optical, our measurements are likely not affected by warps which generally occur further out in radial distance. Our targets are drawn from a well-defined sample and are also a subset of the HALOGAS survey, which is investigating cold gas accretion in spiral galaxies with deep WSRT observations. We restrict our targets to edge-on galaxies, and our data provide an optical complement to HALOGAS data. We perform our observations using a multi-slit spectroscopic setup on the ARC 3.5m telescope. Arranging the slits parallel to the minor axis allows us to measure velocities of H-alpha emitting gas as a function of height above the plane in 11 radial distance bins in a single exposure. Our field of view is 3.75' x 4', and our total exposure time for a typical field is 6-8 hours. We present our ionized halo gas velocities for three nearby, edge-on galaxies and show a comparison with HI data.

Wu, Catharine J.; Walterbos, R.; Rand, R.; Benjamin, R.; Heald, G.; HALOGAS Team

2011-01-01

42

Residual-gas-ionization beam profile monitors in RHIC  

SciTech Connect

Four ionization profile monitors (IPMs) are in RHIC to measure vertical and horizontal beam profiles in the two rings. These work by measuring the distribution of electrons produced by beam ionization of residual gas. During the last two years both the collection accuracy and signal/noise ratio have been improved. An electron source is mounted across the beam pipe from the collector to monitor microchannel plate (MCP) aging and the signal electrons are gated to reduce MCP aging and to allow charge replenishment between single-turn measurements. Software changes permit simultaneous measurements of any number of individual bunches in the ring. This has been used to measure emittance growth rates on six bunches of varying intensities in a single store. Also the software supports FFT analysis of turn-by-turn profiles of a single bunch at injection to detect dipole and quadrupole oscillations.

Connolly, R.; Fite, J.; Jao, S.; Trabocchi, C.

2010-05-02

43

RESIDUAL-GAS-IONIZATION BEAM PROFILE MONITORS IN RHIC.  

SciTech Connect

Four ionization profile monitors (IPMs) in RHIC measure vertical and horizontal beam profiles in the two rings by measuring the distribution of electrons produced by beam ionization of residual gas. During the last three years both the collection accuracy and signal/noise ratio have been improved. An electron source is mounted across the beam pipe from the collector to monitor microchannel plate (MCP) aging and the signal electrons are gated to reduce MCP aging and to allow charge replenishment between single-turn measurements. Software changes permit simultaneous measurements of any number of individual bunches in the ring. This has been used to measure emittance growth rates on six bunches of varying intensities in a single store. Also the software supports FFT analysis of turn-by-turn profiles of a single bunch at injection to detect dipole and quadrupole oscillations.

CONNOLLY, R.; MICHNOFF, R.; TEPIKIAN, S.

2005-05-16

44

Two-step laser ionization schemes for in-gas laser ionization and spectroscopy of radioactive isotopes  

NASA Astrophysics Data System (ADS)

The in-gas laser ionization and spectroscopy technique has been developed at the Leuven isotope separator on-line facility for the production and in-source laser spectroscopy studies of short-lived radioactive isotopes. In this article, results from a study to identify efficient optical schemes for the two-step resonance laser ionization of 18 elements are presented.

Kudryavtsev, Yu.; Ferrer, R.; Huyse, M.; Van den Bergh, P.; Van Duppen, P.; Vermeeren, L.

2014-02-01

45

Probing The Kinematics Of Ionized Gas In The Galactic Center  

NASA Astrophysics Data System (ADS)

We have carried out radio recombination line (RRL) observations of the inner 2.0x0.5 (lxb) degrees of the Galactic center using the 100 m Green Bank Telescope. These measurements provided 0.9 km/s spectral resolution, 73" spatial resolution, and was sensitive to six RRLs (H86alpha - H91alpha) with the center transition at 9.17 GHz. An on-the-fly frequency-switched Nyquist sampled mapping scheme centered at l=359.95, b=-0.0473 was utilized. Here, we present preliminary results of this extensive survey of ionized gas with maps of the integrated intensity and details of various kinematical features. In particular, the kinematics of the diffuse Warm Ionized Medium as well as well-known massive star forming sites such as: Sgr A, Sgr B1 (G0.5-0.0), Sgr B2 (G0.7-0.0), Sgr C (G359.4-0.1), the sickle (G0.18-0.04), and the arched filaments of the radio arc near l 0.18 degrees are given. Highlights of this survey include the detection for the first time of various diffuse emission throughout the Galactic center. One such feature is an extensive large scale blueshifted structure from -80 to 0 km/s that appears to extend from Sgr C to the western ridge of the thermal arch at G0.07+0.04, a projected distance of 75 pc (30'). In addition, we find an extended broad ionized thermal component at 0 km/s near G0.15-0.18. This large-scale ridge of ionized gas runs between the linear nonthermal filaments and the Sgr A complex, mirroring the thermal arched filaments. The morphology of this structure appears to trace a wind-blown cavity roughly 13.5 pc in extent at G0.14-0.12.

Royster, Marc; Yusef-Zadeh, F.; Braatz, J.

2012-01-01

46

CNT-based MEMS/NEMS gas ionizers for portable mass spectrometry applications  

E-print Network

We report the fabrication and experimental characterization of a carbon nanotube (CNT)-based MEMS/NEMS electron impact gas ionizer with an integrated extractor gate for portable mass spectrometry. The ionizer achieves ...

Velasquez-Heller, Luis Fernand

47

Constraining stellar feedback: Ionized gas structures in local starburst galaxies  

NASA Astrophysics Data System (ADS)

Stellar feedback, i.e., the return of mechanical energy from supernova explosions, and massive star and AGN winds to the interstellar medium, is one of the fundamental processes that shape galaxy evolution. Yet, some of its fundamental parameters, such as the efficiency of feedback, have not been solidly constrained from an observational point of view. In this thesis, we aim at addressing this issue. First, we investigate the kinematics of Damped Ly-alpha Absorbers (DLAs) at z = 3 using high-resolution cosmological hydrodynamical simulations. Our simulations include a heuristic model for galactic outflows driven by stellar feedback to test how these components affect the kinematics of neutral gas in high redshift systems. We determine that, without outflows, our simulations fail to yield a sufficient number of DLAs with broad velocity dispersion ('wide DLAs'), as in previous studies. With outflows, our predicted DLA kinematics are in much better agreement with observations. In the second part of the thesis, I investigate stellar feedback within 8 nearby star-forming galaxies, selected to fill the 2-dimensional parameter space of host galaxy stellar mass and star formation rate density. Here, I employ forbidden-line diagnostic diagrams, [O III](5007A)/Hbeta versus [S II](6716A+6731A)/Halpha (or [N II](6584A)/Halpha) to separate shock--ionized from photo--ionized gas within and outside the central star forming regions in these galaxies. I find that the Halpha luminosity from the shock--ionized gas correlates with the SFR density, in the sense of more luminous shocks for higher SFR density. The ratio of Halpha luminosity from shocks to the total Ha luminosity is related to the galaxy's stellar mass; increasing ratios are observed for decreasing stellar mass. The accepted HST proposal (GO-12497; P.I.: Hong) will expand on the observed correlations by adding two more starbursts to our sample.

Hong, Sungryong

48

Proper Motions of Ionized Gas at the Galactic Center: Evidence for Unbound Orbiting Gas  

E-print Network

We present radio continuum observations of the spiral-shaped ionized feature (Sgr A West) within the inner pc of the Galactic center at three epochs spanning 1986 to 1995. The VLA A-configuration was used at $\\lambda$2cm (resolution of 0\\dasec1$\\times$0\\dasec2). We detect proper motions of a number of features in the Northern and Eastern Arms of Sgr A West including the ionized gas associated with IRS 13 with V(RA)= 113 \\pm 10, V(Dec)=150 \\pm15 km/s, IRS 2 with V(RA)= 122 \\pm 11, V(Dec)=24 \\pm 34 km/s and the Norther Arm V(RA)= 126 \\pm 30, V(Dec)=--207 \\pm 58 km/s. We also report the detection of features having transverse velocities > 1000 km/s including a head-tail radio structure, the ``Bullet'', $\\approx4''$ northwest of Sgr A$^*$ with V(RA)= 722 \\pm 156, V(Dec)=832 \\pm 203 km/s, exceeding the escape velocity at the Galactic center. The proper motion measurements when combined with previous H92$\\alpha$ radio recombination line data suggest an unambiguous direction of the flow of ionized gas orbiting the Galactic center. The measured velocity distribution suggests that the ionized gas in the Northern Arm is not bound to the Galactic center assuming a 2.5 million solar mass of dark matter residing at the Galactic center. This implies that the stellar and ionized gas systems are not dynamically coupled, thus, supporting a picture in which the gas features in the Northern Arm and its extensions are the result of an energetic phenomenon that has externally driven a cloud of gas cloud into the Galactic center.

F. Yusef-Zadeh; D. A. Roberts; J. Biretta

1998-03-19

49

Neutral gas plasma interactions and critical ionization velocity phenomena  

NASA Astrophysics Data System (ADS)

The interplay of collisional and collisionless phenomena in the interaction of a magnetoplasma streaming through neutral gas produces some of the most fascinating plasma physics phenomena. A key notion controlling such interactions is the existence of a critical velocity (U sub c) effect postulated in an ad hoc fashion by Alfven, in his model of the formation of the solar system. According to Alfven's postulate, whenever the relative velocity between a neutral gas and a streaming magnetoplasma exceeds a value U sub c identical with Square root of (2Esub i/M), where E sub i is the ionization energy and M the mass of the neutral atoms, rapid ionization and anomalous momentum coupling occurs. Guided by recent laboratory and space experiments and plasma physics theory we present the basic plasma physics underlying the interaction. This is followed by a discussion of its relevance to the formation of the solar system and cometary tails, its controlling effect on plasma centrifuges and homopolar generators, and the fascinating possibility that critical velocity phenomena are controlling the space shuttle environment, transforming it into an artificial comet.

Papadopoulos, K.

1983-11-01

50

Gas electron multiplier (GEM) enhanced ionization chamber for fluorescence detector  

NASA Astrophysics Data System (ADS)

Detecting dilute elements in thin materials using extended X-ray absorption fluorescence spectroscopy (EXAFS) method requires a detector capable of high count rate and low noise. For detection of dilute elements, the fluorescence signal amplitude is often overcome by the presence of noise or background interference. In this paper we have used a gas ionization chamber enhanced by a gas electron multiplier (GEM) to amplify the primary ionized electrons due to the X-ray fluorescence of a dilute element. The GEM provides an essentially noise free electron amplification of the signal primary photoelectrons. It provides a larger output current prior to the electronic amplification, allowing a lower gain amplifier with lower electronic circuit noise contribution and hence improved S/ N ratio. In addition, since the signal is produced only by electrons, and not from ion motion, the detector is capable of recording rapidly changing signals. Iron in an arbitrary tree leaf was used as a test sample. This sample was measured using our detector SUBRSAB, and also with Lytle and passivated implanted planar silicon (PIPS) detectors. An improvement in the signal amplitude by a factor of 20 and a factor of 2 are recorded for the proposed detector with respect to the Lytle and PIPS detectors, respectively. Although the gain in signal over the PIPS detector is small for this detector, its lack of sensitivity to light and its low and temperature-independent dark current are further advantages.

Shaban, E. H.; Siddons, D. P.; Kuczewski, A.

2007-11-01

51

The Ionization of the Warm Gas in Early-type Galaxies and Its UV Upturn  

NASA Astrophysics Data System (ADS)

It has long been known that the majority of early-type galaxies contain warm ionized gas producing optical emission lines. These warm ionized gas are spatially extended to kpc scales. Their line ratios satisify the criteria of Low-ionization Nuclear Emission-line Regions (LINERs) on all major line-ratio diagnostic diagrams. However, their ionization mechanism has been hotly debated. Multiple ionization mechanisms can produce the same kind of line ratios, including photoionization by a central AGN, photoionization by hot evolved stars (e.g. post-AGB stars), collisional ionization by fast shocks, photoionization by hot X-ray emitting gas, and conductive heating or turbulent mixing. Therefore, determining the ionization mechanism requires other information.

Yan, Renbin; Blanton, Michael R.

2015-03-01

52

Spontaneous avalanche ionization of a strongly blockaded Rydberg gas.  

PubMed

We report the sudden and spontaneous evolution of an initially correlated gas of repulsively interacting Rydberg atoms to an ultracold plasma. Under continuous laser coupling we create a Rydberg ensemble in the strong blockade regime, which at longer times undergoes an ionization avalanche. By combining optical imaging and ion detection, we access the full information on the dynamical evolution of the system, including the rapid increase in the number of ions and a sudden depletion of the Rydberg and ground state densities. Rydberg-Rydberg interactions are observed to strongly affect the dynamics of plasma formation. Using a coupled rate-equation model to describe our data, we extract the average energy of electrons trapped in the plasma, and an effective cross section for ionizing collisions between Rydberg atoms and atoms in low-lying states. Our results suggest that the initial correlations of the Rydberg ensemble should persist through the avalanche. This would provide the means to overcome disorder-induced heating, and offer a route to enter new strongly coupled regimes. PMID:25166173

Robert-de-Saint-Vincent, M; Hofmann, C S; Schempp, H; Günter, G; Whitlock, S; Weidemüller, M

2013-01-25

53

Turbulent Diffusion of Magnetic Fields in Weakly Ionized Gas  

E-print Network

The diffusion of uni-directional magnetic fields by two dimensional turbulent flows in a weakly ionized gas is studied. The fields here are orthogonal to the plane of fluid motion. This simple model arises in the context of the decay of the mean magnetic flux to mass ratio in the interstellar medium. When ions are strongly coupled to neutrals, the transport of a large--scale magnetic field is driven by both turbulent mixing and nonlinear, ambipolar drift. Using a standard homogeneous and Gaussian statistical model for turbulence, we show rigorously that a large-scale magnetic field can decay on at most turbulent mixing time scales when the field and neutral flow are strongly coupled. There is no enhancement of the decay rate by ambipolar diffusion. These results extend the Zeldovich theorem to encompass the regime of two dimensional flows and orthogonal magnetic fields, recently considered by Zweibel (2002). The limitation of the strong coupling approximation and its implications are discussed.

Eun-jin Kim; P. H. Diamond

2002-09-25

54

Title of Dissertation: MODELING LASER PULSE EVOLUTION IN IONIZING GAS AND PLASMA WITH  

E-print Network

ABSTRACT Title of Dissertation: MODELING LASER PULSE EVOLUTION IN IONIZING GAS AND PLASMA of laser pulse evolution and plasma response in simulations ranging from modeling laser wakefield energy distribution. #12;MODELING LASER PULSE EVOLUTION IN IONIZING GAS AND PLASMA WITH APPILCATION

Anlage, Steven

55

Restoration of Rl-beams from a projectile fragment separator by Laser Ionization gas  

E-print Network

Restoration of Rl-beams from a projectile fragment separator by Laser Ionization gas Catcher -PALIS of the fragment separator enables to collect dead isotopes in the slits. The design concept and expected performance are discussed. Keywords: Fragment separator, Gas catcher. Laser ion source, Resonance ionization

Schuessler, Hans

56

A Study of the Residual Ionization in a Gas with Reference to Temperature Effects  

Microsoft Academic Search

A Study of the Residual Ionization in a Gas with Reference to Temperature Effects.-A form of electrometer was constructed which used the principle of the Wulf electrometer in separating the conduction of charge across the insulation from the conduction in the gas due to ionization. The new features of this apparatus were that it was possible (1) to make a

C. H. Kunsman

1920-01-01

57

Background studies in gas ionizing x ray detectors  

NASA Technical Reports Server (NTRS)

The background response of a gas ionizing proportional x ray detector is estimated by solving the one dimensional photon transport equation for two regions using Monte Carlo techniques. The solution was effected using the SSL VAX 780 and the CRAY XMP computers at Marshall Space Flight Center. The isotropic photon energy spectrum encompassing the range from 1 to 1000 KeV incident onto the first region, the shield, is taken so as to represent the measured spectrum at an altitude of 3 mb over Palastine, Texas. The differential energy spectrum deposited in the gas region, xenon, over the range of 0 to 100 KeV is written to an output file. In addition, the photon flux emerging from the shield region, tin, over the range of 1 to 1000 KeV is also tabulated and written to a separate file. Published tabular cross sections for photoelectric, elastic and inelastic Compton scattering as well as the total absorption coefficient are used. Histories of each incident photon as well as secondary photons from Compton and photoelectric interactions are followed until the photon either is absorbed or exits from the regions under consideration. The effect of shielding thickness upon the energy spectrum deposited in the xenon region for this background spectrum incident upon the tin shield was studied.

Eldridge, Hudson B.

1989-01-01

58

Hydrogen radical abstraction by small ionized molecules, distonic ions and ionized carbenes in the gas phase  

NASA Astrophysics Data System (ADS)

In the gas phase and within ion-neutral complexes, H[radical sign] abstraction by the ion from the neutral moiety was studied by using FT-ICR experiments and molecular orbital calculations. Ionized methanol abstracts rapidly H[radical sign] from methane and other alkanes while its [alpha]-distonic counterpart, [radical sign]CH2OH2+, is completely unreactive. On the other hand, [beta]-distonic ions, such as [radical sign]CH2CH2XH+ (X=OCH3, NH2), are also unreactive towards methane but can abstract H[radical sign] from ketones and ethers. Finally, ionized carbenes, such as HO---C---NH2[radical sign]+, react with methane by a slow H[radical sign] abstraction. Ab initio molecular orbital calculations at the G3(MP2) level were performed in order to understand these behaviors. For ionized methanol and its [alpha]-distonic counterpart, the reacting structure that could lead to H[radical sign] abstraction is the highly stabilized complex between protonated methanol and a methyl radical, which yields the final state (CH3OH2++[radical sign]CH3) by simple cleavage. In the case of methanol the encounter complex with methane leads easily by rotation of the methane molecule to this reacting structure. In contrast, in the case of the [alpha]-distonic ion, the almost linear structure of the encounter complex [[radical sign]CH2OH2+...CH4] and the high energy required for its isomerization into the reacting structure prevent the reaction. Two factors are required to observe H[radical sign] abstraction in [beta]-distonic ions: the interaction energy of the encounter complex and the distance between the hydrogen to be transferred and the carbon radical. Reaction of the HO---C---NH2[radical sign]+ carbene with methane lies between these two extreme cases. The encounter complex is poorly stabilized (-8.7 kcal mol-1) and the transition state for H[radical sign] abstraction is very close to the reactants energy.

Nedev, Hristo; van der Rest, Guillaume; Mourgues, Philippe; Audier, Henri E.

2004-02-01

59

Electron-impact ionization and dissociative ionization of sulfur in the gas phase  

NASA Astrophysics Data System (ADS)

We describe the methods and the results of investigation of the yield of positive ions formed as a result of electron-impact ionization of sulfur. The ionization energy for the basic molecule and the energies corresponding to the emergence of fragment ions are obtained from the ionization efficiency curves. The dynamics of formation of molecular sulfur ions in the temperature range 320-700 K is investigated. The energy dependences of efficiency S n of the ion formation for n = 1-6 are analyzed, and their appearance energies are determined. The total cross section of sulfur ionization by a monochromatic electron beam is also investigated. Using the linear approximation method, we marked out features on the ionization function curve, which correspond to the ionization and excitation energies for multiply charged ions. The total cross section of the formation of negative sulfur ions is measured in the energy range 0-9 eV.

Zavilopulo, A. N.; Markush, P. P.; Shpenik, O. B.; Mykyta, M. I.

2014-07-01

60

Supernova remnants and diffuse ionized gas in M31  

NASA Technical Reports Server (NTRS)

Researchers have compiled an initial list of radio/optical supernova remnants (SNRs) in M31, by searching for radio identifications of emission-line sources with a high (SII)/H alpha ratio (greater than 0.60). The (SII) filter included both sulfur lines and the H alpha filter did not include (NII). This search revealed 11 SNRs, of which only two were known. In addition, researchers detected radio emission from 3 SNRs that were identified in previous optical surveys (D'Odorico et al., 1980), but that were outside the charge coupled device (CCD) fields. The 14 objects only include the most obvious candidates, but a full search is in progress and the researchers expect to find several more SNRs. Also not all optical SNRs show detectable radio emission and a pure optical list of SNR candidates based only on the ratio of (SII)/H alpha emission contains many more objects. Two conclusions are apparent. First, the radio properties of the SNRs in M31 are quite similar to those of Galactic SNRs as is illustrated. The brightnesses are not systematically lower as has been suggested in the past (Dickel and D'Odorico, 1984). Second, the slope of the relation is close to -2; this slope is expected from the intrinsic dependence between surface brightness and diameter. The radio luminosity of the SNRs does not seem to depend strongly on diameter, or age, contrary to model predictions. Selection effects, however, play an important role in these plots. The CCD images show widespread diffuse ionized gas with a ratio of (SII)/H alpha that is higher than that of discrete HII regions. Discrete HII regions typically show ratios between 0.2 to 0.3, while the diffuse gas in the arms consistently shows ratios of 0.5. Researchers can trace this gas across the spiral arms to emission measures below 5 pc cm (-6). Its properties seem to be similar to that of the diffuse gas in the solar neighborhood.

Walterbos, Rene; Braun, Robert

1990-01-01

61

Distribution of ionized gas density measured by differential VLBI Observations of pulsars  

NASA Astrophysics Data System (ADS)

Differential VLBI observations of pulsars in our Galaxy can derive trigonometric parallax of them. Distance to pulsars derived by the parallax are very important to estimate some mean density of ionized gas between pulsars and the earth using rotation measures of them. Some preliminary results of distribution of the ionized gas density in our galaxy by using previous VLBI results are shown. Possibility of VLBI observations of pulsars using VERA and the other VLBI antennas will be described.

Kameya, Osamu

2013-03-01

62

An efficient procedure for computing partial ionization of a gas in numerical fluid dynamics  

NASA Technical Reports Server (NTRS)

A numerical procedure is described that allows efficient solution for the three nonlinear and implicit equations of state relating the equilibrium properties of a partially (and singly) ionized neutral gas. In the computation, the values for the intensive variables, that is pressure, temperature and ionization coefficient, are iteratively obtained with a given accuracy starting from assigned values for energy and volume per unit mass. Iterative computation is performed only when the value for the ionization coefficient lies within the lower and the upper bounds fixed by the required number of significant digits; otherwise the two explicit equations of state for nonionized or for fully ionized gases are employed.

Garribba, S.; Quartapelle, L.

1976-01-01

63

PHYSICS OF A PARTIALLY IONIZED GAS RELEVANT TO GALAXY FORMATION SIMULATIONS-THE IONIZATION POTENTIAL ENERGY RESERVOIR  

SciTech Connect

Simulation codes for galaxy formation and evolution take on board as many physical processes as possible beyond the standard gravitational and hydrodynamical physics. Most of this extra physics takes place below the resolution level of the simulations and is added in a ''sub-grid'' fashion. However, these sub-grid processes affect the macroscopic hydrodynamical properties of the gas and thus couple to the ''on-grid'' physics that is explicitly integrated during the simulation. In this paper, we focus on the link between partial ionization and the hydrodynamical equations. We show that the energy stored in ions and free electrons constitutes a potential energy term which breaks the linear dependence of the internal energy on temperature. Correctly taking into account ionization hence requires modifying both the equation of state and the energy-temperature relation. We implemented these changes in the cosmological simulation code GADGET2. As an example of the effects of these changes, we study the propagation of Sedov-Taylor shock waves through an ionizing medium. This serves as a proxy for the absorption of supernova feedback energy by the interstellar medium. Depending on the density and temperature of the surrounding gas, we find that up to 50% of the feedback energy is spent ionizing the gas rather than heating it. Thus, it can be expected that properly taking into account ionization effects in galaxy evolution simulations will drastically reduce the effects of thermal feedback. To the best of our knowledge, this potential energy term is not used in current simulations of galaxy formation and evolution.

Vandenbroucke, B.; De Rijcke, S.; Schroyen, J. [Department of Physics and Astronomy, Ghent University, Krijgslaan 281, S9, B-9000 Gent (Belgium); Jachowicz, N. [Department of Physics and Astronomy, Ghent University, Proeftuinstraat 86, B-9000 Gent (Belgium)

2013-07-01

64

Selective determination of haloperidol in human serum: surface ionization mass spectrometry and gas chromatography with surface ionization detection.  

PubMed

Surface ionization organic mass spectrometry (SIOMS) has been performed on the clinically important drug haloperidol using quadrupole mass spectrometry in which the thermal ion source has a rhenium oxide emitter. The surface ionization (SI) mass spectrum is presented, interpreted in a purely empirical way by means of evidence from previous investigations, and then compared to results from conventional electron impact (EI) ionization. An approach to detection of this drug in serum by gas chromatography (GC) with a surface ionization detector (SID) and GC-SIOMS is described. This approach demonstrates that (a) haloperidol is efficiently surface-ionized, giving a unique SI mass spectrum, (b) experimental results rationalize the combined sensitivity and selectivity of the GC-SID for the examined drug, (c) the detection limit for haloperidol in serum is 1.1 ng/ml (S/N = 3) by GC-SID (the coefficients of variation of the assay are generally low, i.e., below 8.5%) and (d) the GC-SIOMS coupling can be used for sensitive and selective detection of haloperidol in serum. PMID:9017463

Fujii, T; Hatanaka, K; Sato, G; Yasui, Y; Arimoto, H; Mitsutsuka, Y

1996-12-13

65

Electron impact ionization of the gas-phase sorbitol  

NASA Astrophysics Data System (ADS)

Ionization and dissociative ionization of the sorbitol molecule by electron impact have been studied using two different experimental methods. In the mass range of m/z = 10-190, the mass spectra of sorbitol were recorded at the ionizing electron energies of 70 and 30 eV. The ion yield curves for the fragment ions have been analyzed and the appearance energies of these ions have been determined. The relative total ionization cross section of the sorbitol molecule was measured using monoenergetic electron beam. Possible fragmentation pathways for the sorbitol molecule were proposed. Contribution to the Topical Issue "Elementary Processes with Atoms and Molecules in Isolated and Aggregated States", edited by Friedrich Aumayr, Bratislav Marinkovic, Stefan Matejcik, John Tanis and Kurt H. Becker.

Chernyshova, Irina; Markush, Pavlo; Zavilopulo, Anatoly; Shpenik, Otto

2015-03-01

66

Shock Structure Analysis and Aerodynamics in a Weakly Ionized Gas Flow  

NASA Technical Reports Server (NTRS)

The structure of a shock wave propagating through a weakly ionized gas is analyzed using an electrofluid dynamics model composed of classical conservation laws and Gauss Law. A viscosity model is included to correctly model the spatial scale of the shock structure, and quasi-neutrality is not assumed. A detailed analysis of the structure of a shock wave propagating in a weakly ionized gas is presented, together with a discussion of the physics underlying the key features of the shock structure. A model for the flow behind a shock wave propagating through a weakly ionized gas is developed and used to analyze the effect of the ionization on the aerodynamics and performance of a two-dimensional hypersonic lifting body.

Saeks, R.; Popovic, S.; Chow, A. S.

2006-01-01

67

Ionized Gas Velocities from Multi-Slit Spectroscopy for Nearby, Edge-on Galaxies  

NASA Astrophysics Data System (ADS)

Several galaxies show decreasing rotational velocities of neutral and ionized hydrogen gas with increasing height above the disk. This is likely due to a combination of outflow from galactic fountains and infall from the IGM or satellite accretion. The degree to which each component contributes affects the rotational velocity gradient of the gas and has implications for halo formation and evolution. We present an overview of our H-alpha observations and modeling of the ionized extra-planar gas for our sample of 12 edge-on, spiral galaxies, several of which are HALOGAS (Hydrogen Accretion in LOcal GAlaxieS) targets. HALOGAS is a WSRT deep HI survey studying cold gas accretion in the local universe. Our observations are from a multi-slit spectroscopic setup on the ARC 3.5m telescope, which allows us to measure velocities of H-alpha emitting gas as a function of height above the disk in 11 radial distance bins in a single exposure. The goal of this project is to characterize the kinematics of extra-planar ionized gas, measure a vertical velocity gradient for targets that show a lagging component, and compare the characteristics of neutral and ionized extra-planar hydrogen gas. RW acknowledges support from NSF grant AST-0908126 and from a grant from Research Corporation for the Advancement of Science.

Wu, Catharine J.; Walterbos, R. A.; Rand, R. J.; Heald, G.; HALOGAS

2013-01-01

68

Ionized Gas Velocities from Multi-Slit Spectroscopy for Nearby, Edge-on Galaxies  

NASA Astrophysics Data System (ADS)

Several galaxies show decreasing rotational velocities of neutral and ionized hydrogen gas with increasing height above the disk. This is likely due to a combination of outflow from galactic fountains and infall from the IGM or satellite accretion. The degree to which each component contributes affects the rotational velocity gradient of the gas and has implications for halo formation and evolution. We present an overview of our H-alpha observations and modeling of the ionized extra-planar gas for our sample of 12 edge-on, spiral galaxies, several of which are HALOGAS (Hydrogen Accretion in LOcal GAlaxieS) targets. HALOGAS is a WSRT deep HI survey studying cold gas accretion in the local universe. Our observations are from a multi-slit spectroscopic setup on the ARC 3.5m telescope, which allows us to measure velocities of H-alpha emitting gas as a function of height above the disk in 11 radial distance bins in a single exposure. The goal of this project is to characterize the kinematics of extra-planar ionized gas, measure a vertical velocity gradient for targets that show a lagging component, and compare the characteristics of neutral and ionized extra-planar hydrogen gas.

Wu, Catharine J.; Walterbos, R.; Patterson, M.; Rand, R.; Heald, G.; HALOGAS Team

2012-05-01

69

Prediction of Shock Wave Structure in Weakly Ionized Gas Flow by Solving MGD Equation  

NASA Technical Reports Server (NTRS)

This paper reports the recent research results of shockwave structure predictions using a new developed code. The modified Rankine-Hugoniot relations across a standing normal shock wave are discussed and adopted to obtain jump conditions. Coupling a electrostatic body force to the Burnett equations, the weakly ionized flow field across the shock wave was solved. Results indicated that the Modified Rankine-Hugoniot equations for shock wave are valid for a wide range of ionization fraction. However, this model breaks down with small free stream Mach number and with large ionization fraction. The jump conditions also depend on the value of free stream pressure, temperature and density. The computed shock wave structure with ionization provides results, which indicated that shock wave strength may be reduced by existence of weakly ionized gas.

Deng, Z. T.; Oviedo-Rojas, Ruben; Chow, Alan; Litchford, Ron J.; Cook, Stephen (Technical Monitor)

2002-01-01

70

Effect of laser self-defocusing on third harmonic generation in a tunnel ionizing gas  

SciTech Connect

A paraxial theory of third harmonic generation by a finite spot size laser in a tunnel ionizing gas is developed. The laser, with intensity close to tunnel ionization threshold, creates plasma whose density rises in a stepwise manner in every half wave period, giving a strong second harmonic component in electron density. The density beats with the oscillatory velocity at the fundamental to produce a nonlinear current, driving the third harmonic. The region of harmonic generation is localized near the laser axis. Further, the strong radial nonuniformity, created in electron density by the ionization process, causes defocusing of the laser, limiting the efficiency of harmonic generation.

Verma, Updesh; Sharma, A. K. [Center for Energy Studies, Indian Institute of Technology Delhi, New Delhi-110016 (India)

2009-01-15

71

The Massive Stellar Population in the Diffuse Ionized Gas of M33  

NASA Technical Reports Server (NTRS)

We compare Far-UV, H alpha, and optical broadband images of the nearby spiral galaxy M33, to investigate the massive stars associated with the diffuse ionized gas. The H-alpha/FUV ratio is higher in HII regions than in the DIG, possibly indicating that an older population ionizes the DIG. The broad-band colors support this conclusion. The HII region population is consistent with a young burst, while the DIG colors resemble an older population with constant star formation. Our results indicate that there may be enough massive field stars to ionize the DIG, without the need for photon leakage from HII regions.

Hoopes, Charles G.; Walterbos, Rene A. M.

1995-01-01

72

Radiation pressure confinement - I. Ionized gas in the ISM of AGN hosts  

NASA Astrophysics Data System (ADS)

We analyse the hydrostatic effect of active galactic nucleus (AGN) radiation pressure on optically thick gas in the host galaxy. We show that in luminous AGN, the radiation pressure likely confines the ionized layer of the illuminated gas. Radiation pressure confinement (RPC) has two main implications. First, the gas density near the ionization front is 7× 10^4 L_{i, 45} r_{50}^{-2} cm^{-3}, where Li, 45 is the ionizing luminosity in units of 1045 erg s-1 and r50 is the distance of the gas from the nucleus in units of 50 pc. Secondly, as shown by Dopita et al., the solution of the ionization structure within each slab is unique, independent of the ambient pressure. We show that the RPC density versus distance relation is observed over a dynamical range of ˜104 in distance, from sub-pc to kpc from the nucleus, and a range of ˜108 in gas density, from 103 to 1011 cm-3. This relation implies that the radiative force of luminous AGN can compress giant molecular clouds in the host galaxy and possibly affect the star formation rate. The unique ionization structure in RPC includes a highly ionized X-ray-emitting surface, an intermediate layer which emits coronal lines and a lower ionization inner layer which emits optical lines. This structure can explain the observed overlap of the extended X-ray and optical narrow line emission in nearby AGN. We further support RPC by comparing the predicted ratios of the narrow line strength and narrow line widths with available observations. We suggest a new method, based on the narrow line widths, to estimate the black hole mass of low-luminosity AGN.

Stern, Jonathan; Laor, Ari; Baskin, Alexei

2014-02-01

73

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

PubMed

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

Mallette, Jennifer R; Casale, John F

2014-10-17

74

The in-gas-jet laser ion source: Resonance ionization spectroscopy of radioactive atoms in supersonic gas jets  

NASA Astrophysics Data System (ADS)

New approaches to perform efficient and selective step-wise resonance ionization spectroscopy (RIS) of radioactive atoms in different types of supersonic gas jets are proposed. This novel application results in a major expansion of the in-gas laser ionization and spectroscopy (IGLIS) method developed at KU Leuven. Implementation of resonance ionization in the supersonic gas jet allows to increase the spectral resolution by one order of magnitude in comparison with the currently performed in-gas-cell ionization spectroscopy. Properties of supersonic beams, obtained from the de Laval-, the spike-, and the free jet nozzles that are important for the reduction of the spectral line broadening mechanisms in cold and low density environments are discussed. Requirements for the laser radiation and for the vacuum pumping system are also examined. Finally, first results of high-resolution spectroscopy in the supersonic free jet are presented for the 327.4 nm 3d104s 2S1/2? 3d104p 2P1/2 transition in the stable 63Cu isotope using an amplified single mode laser radiation.

Kudryavtsev, Yu.; Ferrer, R.; Huyse, M.; Van den Bergh, P.; Van Duppen, P.

2013-02-01

75

Particle-in-Cell Simulations of Gas Ionization by Short Intense Laser Pulses  

NASA Astrophysics Data System (ADS)

Laser wakefield accelerators (LWFA) can generate accelerating gradients orders of magnitude larger than those obtained in conventional metal structures. In many LWFA experiments, the leading edge of the short, intense laser pulse completely ionizes a background neutral gas. An important question is the effect of laser ionization on the evolution of the laser pulse. Dispersive effects can modify the length and shape of the pulse as it propagates through the gas/plasma. Pulse steepening or break-up can affect the growth of the plasma wake. We will present particle-in-cell simulations using the ADK [M.V. Ammosov et al., Sov. Phys. JETP 64, p. 1191 (1986)] tunneling ionization model in the XOOPIC [J.P. Verboncoeur et al., J. Comp. Phys. 104, p. 321 (1993)] code. These simulations will be compared with experimental LWFA results from the l'OASIS laboratory of LBNL [W.P. Leemans et al., Phys. Plasmas 8, p. 2510 (2001)].

Dimitrov, Dimitre; Bruhwiler, David; Leemans, Wim; Esarey, Eric; Catravas, Palma; Toth, Csaba; Shadwick, Brad; Cary, John; Giacone, Rodolfo; Verboncoeur, John; Mardahl, Peter

2001-10-01

76

The Performance of a Dual Alkali Aerosol Flame Ionization Detector for Gas Chromatography  

Microsoft Academic Search

The described alkali flame ionization detector (AFID) differs from other designs by introducing the alkali salt into the detector in the form of an aerosol. The preheated, desolvated alkali aerosol salt is introduced into a dual hydrogen gas flame assembly. This detector shows no evidence of fatigue due to the constant delivery of salt into the detector, compared to the

E. D. Conte; E. F. Barry

1993-01-01

77

In Gas Laser Ionization and Spectroscopy experiments at the Superconducting Separator Spectrometer (S3  

E-print Network

, published in "16th International Conference on Electromagnetic Isotope Separators and Technique related 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 In Gas Laser Ionization and Spectroscopy experiments at the Superconducting Separator Spectrometer (S3 ): Conceptual

Paris-Sud XI, Université de

78

Intermediate and High-Velocity Ionized Gas towardOrionis11  

Microsoft Academic Search

We combine near-UV spectra obtained with the Hubble Space Telescope GHRS echelle with far-UV spectra obtained with IMAPS and Copernicus to study the abun- dances and physical conditions in the predominantly ionized gas seen at high velocity ( 105 km s?1 . v? . 65 km s?1) and at intermediate velocity ( 60 km s?1 . v? .

Daniel E. Welty; Edward B. Jenkins; John C. Raymond; Christoforos Mallouris

79

Field ionization kinetic and electron impact studies of gas phase transition states - The cyclic bromonium ion  

NASA Technical Reports Server (NTRS)

Cis- and trans-isomers of 4-t-butylcyclohexyl bromide were studied to determine the mechanism of cyclic bromonium ion formation. The field ionization kinetic and electron impact data indicate that the formation of the cyclic structure occurs simultaneously with loss of the neutral fragment. The data also show that little or no gas-phase cis-trans isomerization occurs.

Green, M. M.; Giguere, R. J.; Falick, A. M.; Aberth, W.; Burlingame, A. L.

1978-01-01

80

Properties of the highly ionized disk and halo gas toward two distant high-latitude stars  

NASA Technical Reports Server (NTRS)

Goddard High Resolution Spectrograph (GHRS) intermediate -resolution observations of S III, Si III, Al III, Si IV, C IV, and N V absorption along the sight lines to HD 18100 (l = 217.9 deg, b = -62.7, d = 3.1 kpc, z = -2.8 kpc) and HD 100340 (l = 258.9 deg, b = +61.2 deg, d = 5.3 kpc, z = 4.6 kpc) are presented. These small science aperture spectra have resolutions ranging from 11 to 20 km/s full width at half maximum (FWHM) and S/N from 30 to 65 per diode substep. Strong absorption by moderately and highly ionized gas is seen in each direction. The absorption in the direction of the south Galactic polar region (HD 18100) is kinematically simple, while the absorption in the direction of north Galactic polar region (HD 100304) is kinematically complex. In each case the absorption by the highly ionized gas lies within the velocity range of absorption by neutral and weakly ionized gas. Along each sight line, the velocity dispersion determined from the unsaturated absorption lines increases with the energy required to create each ion. The logarithmic column densities for Al III, Si IV, C IV, and N V are log N(atoms/sq cm = 12.71, 13.10, 13.58, and 12.75 toward HD 18100 and log N = 12.88, 13.31, 13.83, and 13.04 toward HD 100340. Average ionic ratios among these species are very similar along the two sight lines. Differences in profile shape between the absorption for AL II, Si IV, C IV, and N V provide additional support for the claim of Savage, Sembach, & Cardelli (1994) that there exists two types of highly ionized gas in the interstellar medium. One type of highly ionized gas is responsible for the structured Si IV absorption and part of the C IV absorption. In this gas N(C IV)/N(Si IV) approximately 3.0 and N(C IV)/N(N V) greater than 6. The absorption by this gas seems to be associated with some type of self-regulating interface or mixing layer between the warm and hot interstellar medium. The other type of highly ionized gas is responsible for most of the N V absorption, part of the C IV absorption, and has very little associated Si IV absorption. In this gas N(C IV)/N(N V) is approximately 1 to 3. This gas is hot (T greater than 2 x 10(exp 5) K) and may be tracing the cooling gas of supernova (SN) bubbles or a Galactic fountain. The relative mixture of these two types of highly ionized gas varies from one sight line to the next. The two sight lines in this study sample halo gas in the solar neighborhood and have a smaller percentage of the more highly ionized gas than inner Galaxy sight lines.

Savage, Blair D.; Sembach, K. R.

1994-01-01

81

Neutral Gas and Low-Redshift Starbursts: From Infall to Ionization  

NASA Astrophysics Data System (ADS)

The interplay of gas inflows, star formation, and feedback drives galaxy evolution, and starburst galaxies provide important laboratories for probing these processes at their most extreme. With two samples of low-redshift starburst galaxies, we examine the conversion of neutral gas into stars and the subsequent effects of stellar feedback on the neutral interstellar medium (ISM). The ALFALFA H? survey represents a complete, volume-limited sample of HI-selected galaxies with 21 cm spectra and H? and R-band imaging. By contrasting the starburst galaxies with the rest of the gas-rich galaxy population, we investigate the roles of galaxy morphology, HI kinematics, and the atomic gas supply in triggering extreme levels of star formation. Both an elevated HI gas supply and an external disturbance are necessary to drive the starbursts. While neutral gas may fuel a starburst, it may also increase starbursts' optical depths and hinder the transport of ionizing radiation. In contrast to the expectations for high-redshift star-forming galaxies, neutral gas appears to effectively bar the escape of ionizing radiation in most low-redshift starbursts. To evaluate the impact of radiative feedback in extreme starbursts, we analyze optical spectra of the Green Pea galaxies, a low-redshift sample selected by their intense [O III] ?5007 emission and compact sizes. We use nebular photoionization and stellar population models to constrain the Peas' burst ages, ionizing sources, and optical depths and find that the Peas are likely optically thin to Lyman continuum (LyC) radiation. These young starbursts still generate substantial ionizing radiation, while recent supernovae may have carved holes in the ISM that enhance LyC photon escape into the intergalactic medium. While the ALFALFA survey demonstrates the role of external processes in triggering starbursts, the Green Peas show that starbursts' radiation can escape to affect their external environment.

Jaskot, Anne; Oey, M. S.; Salzer, J. J.; Van Sistine, A.; Haynes, M. P.

2014-01-01

82

Aerodynamic Effects in Weakly Ionized Gas: Phenomenology and Applications  

Microsoft Academic Search

Successful application of gas discharges in aerodynamics requires their efficient generation, sustaining and control at supersonic or hypersonic flow conditions. Wall-free plasma formations that meet the requirements may then act as time-controlled and space-localized actuators to modify the flow. Potential candidates for this challenging task are plasmas contained in open or linear-cavity microwave field structures. We present and discuss direct

Svetozar Popovic

2006-01-01

83

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

E-print Network

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

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

2001-01-26

84

IONIZED GAS IN THE FIRST 10 kpc OF THE INTERSTELLAR GALACTIC HALO: METAL ION FRACTIONS  

SciTech Connect

We present direct measures of the ionization fractions of several sulfur ions in the Galactic warm ionized medium (WIM). We obtained high-resolution ultraviolet absorption-line spectroscopy of post-asymptotic giant branch stars in the globular clusters Messier 3 [(l, b) = (42.{sup 0}2, +78.{sup 0}7), d = 10.2 kpc, and z = 10.0 kpc] and Messier 5 [(l, b) = (3.{sup 0}9, +46.{sup 0}8), d = 7.5 kpc, and z = +5.3 kpc] with the Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer to measure, or place limits on, the column densities of S I, S II, S III, S IV, S VI, and H I. These clusters also house millisecond pulsars, whose dispersion measures give an electron column density from which we infer the H II column in these directions. We find fractions of S{sup +2} in the WIM for the M 3 and M 5 sight lines x(S{sup +2}) {identical_to} N(S{sup +2})/N(S) = 0.33 {+-} 0.07 and 0.47 {+-} 0.09, respectively, with variations perhaps related to location. With negligible quantities of the higher ionization states, we conclude that S{sup +} and S{sup +2} account for all of the S in the WIM. We extend the methodology to study the ion fractions in the warm and hot ionized gas of the Milky Way, including the high ions Si{sup +3}, C{sup +3}, N{sup +4}, and O{sup +5}. The vast majority of the Galactic ionized gas is warm (T {approx} 10{sup 4} K) and photoionized (the WIM) or very hot (T > 4 Multiplication-Sign 10{sup 5} K) and collisionally ionized. The common tracer of ionized gas beyond the Milky Way, O{sup +5}, traces <1% of the total ionized gas mass of the Milky Way.

Howk, J. Christopher [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Consiglio, S. Michelle, E-mail: jhowk@nd.edu, E-mail: smconsiglio@ucla.edu [Current address: Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, CA 90095 (United States)

2012-11-10

85

An Experimental Study of the Ionization of Low-Density Gas Flows by Induced Discharges  

NASA Technical Reports Server (NTRS)

Induced discharges are advantageous for ionizing low-density flows in that they introduce no electrode contamination into the flow and they provide a relatively high degree of ionization with good coupling of power into the gas. In this investigation a 40-megacycle oscillator was used to produce and maintain induced discharges in argon and mercury-vapor flows. Methods for preventing blowout of the discharge were determined, and power measurements were made with an in-line wattmeter. Some results with damped oscillations pulsed at 1,000 pulses per second are also presented.

Barger, R. L.; Brooks, J. D.; Beasley, W. D.

1960-01-01

86

Hose instability and wake generation by an intense electron beam in a self-ionized gas.  

PubMed

The propagation of an intense relativistic electron beam through a gas that is self-ionized by the beam's space charge and wakefields is examined analytically and with 3D particle-in-cell simulations. Instability arises from the coupling between a beam and the offset plasma channel it creates when it is perturbed. The traditional electron hose instability in a preformed plasma is replaced with this slower growth instability depending on the radius of the ionization channel compared to the electron blowout radius. A new regime for hose stable plasma wakefield acceleration is suggested. PMID:16486834

Deng, S; Barnes, C D; Clayton, C E; O'Connell, C; Decker, F J; Fonseca, R A; Huang, C; Hogan, M J; Iverson, R; Johnson, D K; Joshi, C; Katsouleas, T; Krejcik, P; Lu, W; Mori, W B; Muggli, P; Oz, E; Tsung, F; Walz, D; Zhou, M

2006-02-01

87

DYNAMO - II. Coupled stellar and ionized-gas kinematics in two low-redshift clumpy discs  

NASA Astrophysics Data System (ADS)

We study the spatially resolved stellar kinematics of two star-forming galaxies at z ˜ 0.1 from the larger DYnamics of Newly Assembled Massive Objects (DYNAMO) sample. These galaxies, which have been characterized by high levels of star formation and large ionized-gas velocity dispersions, are considered possible analogues to high-redshift clumpy discs. They were observed using the Gemini Multi-Object Spectrograph instrument in integral field spectroscopy (IFS) mode at the Gemini Observatory with high spectral resolution (R ? 5400, equivalent to ? ? 24 km s-1 at the observed wavelengths) and ˜6 h exposure times in order to measure the resolved stellar kinematics via absorption lines. We also obtain higher quality emission-line kinematics than previous observations. The spatial resolution (1.2 kpc) is sufficient to show that the ionized gas in these galaxies (as traced by H? emission) is morphologically irregular, forming multiple giant clumps while stellar continuum light is smooth and well described by an exponential profile. Clumpy gas morphologies observed in IFS data are confirmed by complementary narrow-band H? imaging from the Hubble Space Telescope. Morphological differences between the stars and ionized gas are not reflected dynamically as stellar kinematics are found to be closely coupled to the kinematics of the ionized gas: both components are smoothly rotating with large velocity dispersions (˜40 km s-1) suggesting that the high gas dispersions are not primarily driven by star formation feedback. In addition, the stellar population ages of these galaxies are estimated to be quite young (60-500 Myr). The large velocity dispersions measured for these young stars suggest that we are seeing the formation of thick discs and/or stellar bulges in support of recent models which produce these from clumpy galaxies at high redshift.

Bassett, Robert; Glazebrook, Karl; Fisher, David B.; Green, Andrew W.; Wisnioski, Emily; Obreschkow, Danail; Cooper, Erin Mentuch; Abraham, Roberto G.; Damjanov, Ivana; McGregor, Peter J.

2014-08-01

88

A surface ionization detector for gas chromatography:? use of a supersonic free jet.  

PubMed

A new design of a gas chromatographic surface ionization detector (SID) based on hyperthermal positive surface ionization is described. There are two requirements:? use of a supersonic free jet nozzle and the high-work-function surface of rhenium oxide. This detector, which is sensitive in response to all the organics, can be operated as an universal detector with much higher sensitivity toward some species having low ionization energy but with selectivity to a lesser degree than that of a conventional SID. The minimum detectable amount (at S/N = 3) of pyrene is around 4.4 × 10(-)(13) g/s, with linearity greater than 10(6), while that of toluene is around 10(-)(12) g/s. Other unique properties are (1) the ability to control the degree of selectivity through molecular kinetic energy, the surface, and its temperature and (2) a very short response time. PMID:21619351

Kishi, H; Fujii, T

1996-09-01

89

Multiwavelength WHAM Observations of Extra-planar Warm Ionized Gas in the Galaxy  

E-print Network

We report on observations of several optical emission lines toward a variety of newly revealed faint, large-scale H-alpha-emitting structures in the warm ionized medium (WIM) of the Galaxy. The lines include [N II] 6583, [N II] 5755, [S II] 6716, [O III] 5007, and He I 5876 and were obtained with the Wisconsin H-Alpha Mapper (WHAM) toward sightlines that probe both large filamentary features and the more diffuse WIM, from the outer Perseus spiral arm to the inner Galaxy. These emission lines allow us to explore the temperature and ionization conditions within the emitting gas and their variations between the different emission regions. We compare the relative intensities of the emission lines toward these faint H II structures to brighter, classical O star H II regions. We find that the line ratios of [N II]/H-alpha and [S II]/H-alpha are generally high, while [O III]/H-alpha and He I/H-alpha are generally low in the diffuse WIM and in the faint filamentary structures. This suggests that the gas is warmer, in a lower ionization state, and ionized by a softer spectrum than the gas in classical H II regions surrounding O stars, the presumed ionization source for the WIM. In addition, we find differences in the physical conditions between the large filamentary structures and the more diffuse WIM, suggesting that the filaments are regions of higher density, not geometrical projections of folds in large sheet-like or shell-like structures.

G. J. Madsen

2004-09-20

90

Inner polar ionized-gas disks and properties of their host galaxies  

NASA Astrophysics Data System (ADS)

I have analyzed line-of-sight velocity fields of the stellar and ionized-gas components for the volume-limited sample of nearby lenticular galaxies by using the raw data of the ATLAS-3D survey undertaken with the integral-field spectrograph SAURON. Among 200 nearby lenticular galaxies, I distinguish 20 cases of nearly orthogonal rotation of the inner ionized gas with respect to the central stellar components; so I estimate a frequency of the inner polar disks in nearby S0 galaxies as 10%. Properties of the central stellar populations - mean ages, metallicities, magnesium-to-iron ratios - are derived through the Lick indices. The typical stellar population properties of the polar-disk host galaxies are exactly the same as the stellar population properties of the complete sample.

Sil'chenko, Olga K.

2015-02-01

91

Hair analysis for nordiazepam and oxazepam by gas chromatography-negative-ion chemical ionization mass spectrometry  

Microsoft Academic Search

A procedure is presented for the identification of nordiazepam and its metabolite, oxazepam, in human hair. The method involves decontamination of hair with dichloromethane, incubation in phosphate buffer (pH 7.6) in the presence of deuterated internal standards, liquid-liquid extraction, derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide plus 1% trimethylchlorosilane and gas chromatography-mass spectrometry using negative-ion chemical ionization with methane. Among thirty samples obtained from

Pascal Kintz; Vincent Cirimele; François Vayssette; Patrice Mangin

1996-01-01

92

Effect of CO/sub 2/ gas on the thermal-nonequilibrium ionization of nitrogen  

SciTech Connect

Experimental measurements of electron density in a supersonic CO/sub 2/:N/sub 2/ gas mixture containing varying amounts of CO/sub 2/ are reported. A series of current-voltage curves are recorded for mixtures with different CO/sub 2/ contents at constant E/N = 3 x 10 to the -16th V sq cm. It is shown that adding CO/sub 2/ in amounts typical for gas lasers (5-15 percent) decreases the electron density in the jet by no more than 50 percent. If N/sub 2/ molecules excited to high vibrational states are involved in the ionization reaction, enough of them remain to support ionization even after energy exchange with CO/sub 2/. It is concluded that the vibrational degrees of freedom of the laser-active molecules in homogeneous CO/sub 2/ gasdynamic lasers can be pumped further by using a bulk discharge in a supersonic jet of nonequilibrium ionized gas. 12 references.

Krauklis, A.V.; Samtsov, P.P.; Soloukhin, R.I.; Fomin, N.A.

1986-10-01

93

Investigating the Diffuse Ionized Gas throughout the Magellanic Cloud System with WHAM  

NASA Astrophysics Data System (ADS)

We present early stages of an H-? survey of the Magellanic System using the Wisconsin H-? Mapper (WHAM). Our maps of the Small Magellanic Cloud, Large Magellanic Cloud, and Magellanic Bridge are the most sensitive kinematic maps of ionized gas throughout the System. With a velocity resolution of 12 km/s, WHAM observations can cleanly separate diffuse emission at Magellanic velocities from that of the Milky Way and terrestrial sources. These new maps of the SMC and LMC compliment observations of the Magellanic Bridge by Barger et al. (2013), who found H-alpha emission extending throughout and beyond the observed H I emission. Using WHAM's unprecedented sensitivity to the limit of atmospheric line confusion (~ 10s of mR), we find that ionized gas emission extends at least 5 degrees beyond the traditional boundary of the SMC when compared to recent deep-imaging surveys (e.g., MCELS; Smith et al. 2005). The diffuse ionized emission extent is similar to the neutral gas extent as traced by 21 cm. We present spectra comparing H I and H-alpha kinematic signatures throughout the emission region, which are dominated by galactic rotation. Multi-wavelength observations are also underway in [S II] and [N II] for the SMC and LMC. WHAM research and operations are supported through NSF Award AST-1108911.

Smart, Brianna; Haffner, L. Matthew; Barger, Kathleen; Madsen, Gregory J.; Hill, Alex S.

2015-01-01

94

Fluctuations in microwave background radiation due to secondary ionization of the intergalactic gas in the universe  

NASA Technical Reports Server (NTRS)

Secondary heating and ionization of the intergalactic gas at redshifts z approximately 10-30 could lead to the large optical depth of the Universe for Thomson scattering and could smooth the primordial fluctuations formed at z approximately 1500. It is shown that the gas motions connected with the large scale density perturbations at z approximately 10-15 must lead to the generation of secondary fluctuations of microwave background. The contribution of the rich clusters of galaxies and young galaxies to the fluctuations of microwave background is also estimated.

Sunyayev, R. A.

1979-01-01

95

Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor  

SciTech Connect

Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14??m. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7??m gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal, E-mail: zainabh@petronas.com.my [Centre of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

2014-03-24

96

A VUV Photoionization and Ab Initio Determination of the Ionization Energy of a Gas-Phase Sugar (Deoxyribose)  

E-print Network

A VUV Photoionization and Ab Initio Determination of the Ionization Energy of a Gas-Phase Sugar, Clusters, Excited States Sugars, together with phosphates, constitute the scaffold on which nucleic acids ionization energy for sugars such as deoxyribose stems from the difficulty to prepare intact molecules

Krylov, Anna I.

97

DETERMINATION OF PHTHALATES IN WATER AND SOIL BY TANDEM MASS SPECTROMETRY UNDER CHEMICAL IONIZATION CONDITIONS WITH ISOBUTANE AS REAGENT GAS  

EPA Science Inventory

Phthalate determination is important because phthalates often are major impurities in samples and can have significant health effects. Tandem mass spectrometry under chemical ionization mass spectrometry conditions with isobutane as the reagent gas was used to determine 11 phthal...

98

Integral-field Stellar and Ionized Gas Kinematics of Peculiar Virgo Cluster Spiral Galaxies  

NASA Astrophysics Data System (ADS)

We present the stellar and ionized gas kinematics of 13 bright peculiar Virgo cluster galaxies observed with the DensePak Integral Field Unit at the WIYN 3.5 m telescope in order to look for kinematic evidence that these galaxies have experienced gravitational interactions or gas stripping. Two-dimensional maps of the stellar velocity V, stellar velocity dispersion ?, and the ionized gas velocity (H? and/or [O III]) are presented for the galaxies in the sample. The stellar rotation curves and velocity dispersion profiles are determined for 13 galaxies, and the ionized gas rotation curves are determined for 6 galaxies. Misalignments between the optical and kinematical major axes are found in several galaxies. While in some cases this is due to a bar, in other cases it seems to be associated with gravitational interaction or ongoing ram pressure stripping. Non-circular gas motions are found in nine galaxies, with various causes including bars, nuclear outflows, or gravitational disturbances. Several galaxies have signatures of kinematically distinct stellar components, which are likely signatures of accretion or mergers. For all of our galaxies, we compute the angular momentum parameter ? R . An evaluation of the galaxies in the ? R ellipticity plane shows that all but two of the galaxies have significant support from random stellar motions, and have likely experienced gravitational interactions. This includes some galaxies with very small bulges and truncated/compact H? morphologies, indicating that such galaxies cannot be fully explained by simple ram pressure stripping, but must have had significant gravitational encounters. Most of the sample galaxies show evidence for ICM-ISM stripping as well as gravitational interactions, indicating that the evolution of a significant fraction of cluster galaxies is likely strongly impacted by both effects.

Cortés, Juan R.; Kenney, Jeffrey D. P.; Hardy, Eduardo

2015-01-01

99

A study of the ionized gas in Stephan's Quintet from integral field spectroscopy observations?  

NASA Astrophysics Data System (ADS)

Stephan's Quintet (SQ) is a famous interacting compact group of galaxies in an important stage of dynamical evolution, but surprisingly very few spectroscopic studies are found in the literature. We present optical integral field spectroscopy (IFS) observations of the SQ from the PPAK IFS Nearby Galaxies Survey, that provide a powerful way of studying with spatial resolution the physical characteristics of the ionized gas within the group. The nature of the gas emission is analysed using 2D maps of continuum-subtracted, pure emission-line intensities, stacked spectra, diagnostic diagrams, and photoionization model predictions. In the case of NGC 7319, we study the galaxy-wide high-velocity outflow emission by comparing the emission properties with theoretical shock and AGN models. We conclude that the excitation mechanism of the gas in this galaxy is a mixture of AGN photoionization and shocks with a photoionizing precursor. The emission spectra from the large-scale shock front in the interacting pair NGC 7318A/B is analysed, confirming the presence of several kinematic components. Comparison with predictions from theoretical shock models suggests that the gas emission is consistent with shocks without a photoionizing precursor, low pre-shock density, and velocities in the range of ˜200-400 km s-1. The gas oxygen abundance for NGC 7318B is determined using an updated O3N2 calibration. Although NGC 7317 shows no significant gas emission, an ionizing cluster is found southwest of this galaxy, probably the result of tidal interaction. As a by-product, we analyse the gas emission of the foreground galaxy NGC 7320.

Rodríguez-Baras, M.; Rosales-Ortega, F. F.; Díaz, A. I.; Sánchez, S. F.; Pasquali, A.

2014-07-01

100

UV absorption and emission lines from highly ionized gas in the Galactic halo  

NASA Technical Reports Server (NTRS)

The detection of highly ionized gas in the Galactic halo through UV absorption and emission lines is reported. In absorption the species under consideration include Si IV, C IV, and N V. The presence of N V absorption implies the existence of some gas with a temperature near 200,000 K. The highly ionized absorbing gas toward distant stars in direction b of less than -50 deg has simple and relatively narrow line profiles and small average LSR velocities while the gas in the direction b of greater than 50 deg reveals a complex pattern of motions with substantial inflow and outflow velocities. C IV emission brightens toward the Galactic poles and has a polar intensity of 5000 photons/sq cm s ster. In the nonequilibrium cooling of a Galactic fountain, a flow rate of 4 M sub O/yr to each side of the Galaxy is required to produce the amount of N V absorption found in the halo, while a flow rate five times larger is required to produce the observed level of C IV emission.

Savage, Blair D.

1991-01-01

101

Fabry-Perot observations of the ionized gas in NGC 3938  

E-print Network

The nearly face-on spiral galaxy NGC 3938 has been observed in the $H_\\alpha$ line with the TAURUS II Fabry-Perot interferometer at the William Herschel Telescope in order to study the kinematics of the ionized gas. We are able to construct intensity, velocity and velocity dispersion maps for this galaxy. The rotation curve of the galaxy is calculated up to 4.5 radial scale lengths from the galactic centre. The residual velocity field shows very small values with no systematic pattern. The mean velocity dispersion is approximately constant with radius at about 11 km/s as previously reported for the neutral and molecular gas. We have also studied the relation between intensity and velocity dispersion for the ionized gas. We have found that this distribution is compatible with a turbulent gas relaxing to a Kolmogorov type turbulence as the stationary regime. The average dispersion varies with intensity as $\\sigma \\propto I^{1/8}$ although it becomes much steeper at higher intensities, for which the dispersion is kept almost constant at a value of about 19 km/s.

J. Jimenez-Vicente; E. Battaner; M. Rozas; H. Castaneda; C. Porcel

1998-11-24

102

Ionization effects in the generation of wake-fields by ultra-high contrast femtosecond laser pulses in argon gas  

SciTech Connect

Difference in mechanisms of wake-field generation and electron self-injection by high contrast femtosecond laser pulses in an initially neutral Argon gas and in pre-ionized plasma without ionization is studied via 2D particle-in-cell simulations including optical ionization of the media. For shorter laser pulses, 40 fs, ionization results only in an increase of the charge of accelerated electrons by factor of {approx}3 with qualitatively the same energy distribution. For longer pulses, 80 fs, a more stable wake field structure is observed in the neutral gas with the maximal energy of the accelerated electrons exceeding that in the fixed density plasma. In higher density Argon, an ionizing laser pulse converts itself to a complex system of solitons at a self-induced, critical density ramp.

Makito, K.; Shin, J.-H. [Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita, Osaka (Japan); Zhidkov, A.; Hosokai, T.; Masuda, S. [Photon Pioneers Center, Osaka University, 2-8, Yamadaoka, Suita, Osaka (Japan); Japan Science and Technology Agency (JST), CREST, 2-8 Yamadaoka, Suita, Osaka (Japan); Kodama, R. [Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita, Osaka (Japan); Photon Pioneers Center, Osaka University, 2-8, Yamadaoka, Suita, Osaka (Japan); Japan Science and Technology Agency (JST), CREST, 2-8 Yamadaoka, Suita, Osaka (Japan)

2012-10-15

103

Ionization effects in the generation of wake-fields by ultra-high contrast femtosecond laser pulses in argon gas  

NASA Astrophysics Data System (ADS)

Difference in mechanisms of wake-field generation and electron self-injection by high contrast femtosecond laser pulses in an initially neutral Argon gas and in pre-ionized plasma without ionization is studied via 2D particle-in-cell simulations including optical ionization of the media. For shorter laser pulses, 40 fs, ionization results only in an increase of the charge of accelerated electrons by factor of ˜3 with qualitatively the same energy distribution. For longer pulses, 80 fs, a more stable wake field structure is observed in the neutral gas with the maximal energy of the accelerated electrons exceeding that in the fixed density plasma. In higher density Argon, an ionizing laser pulse converts itself to a complex system of solitons at a self-induced, critical density ramp.

Makito, K.; Zhidkov, A.; Hosokai, T.; Shin, J.-H.; Masuda, S.; Kodama, R.

2012-10-01

104

Atmospheric pressure ionization and gas phase ion mobility studies of isomeric dihalogenated benzenes using different ionization techniques  

NASA Astrophysics Data System (ADS)

Ion mobility spectrometry (IMS) featuring different ionization techniques was used to analyze isomeric ortho-, meta- and para-dihalogenated benzenes in order to assess how structural features affect ion formation and drift behavior. The structure of the product ions formed was investigated by atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) and IMS-MS coupling. Photoionization provided [M]+ ions for chlorinated and fluorinated compounds while bromine was cleaved from isomers of dibromobenzene and bromofluorobenzene. This ionization technique does not permit the different isomers to be distinguished. Comparable ions and additional clustered ions were obtained using 63Ni ionization. Depending on the chemical constitution, different clustered ions were observed in ion mobility spectra for the separate isomers of dichlorobenzene and dibromobenzene. Corona discharge ionization permits the most sensitive detection of dihalogenated compounds. Only clustered product ions were obtained. Corona discharge ionization enables the classification of different structural isomers of dichlorobenzene, dibromobenzene and bromofluorobenzene.

Borsdorf, H.; Nazarov, E. G.; Eiceman, G. A.

2004-03-01

105

Ionized Gas Velocities from Multi-slit Spectroscopy for Nearby, Edge-on Galaxies  

NASA Astrophysics Data System (ADS)

Extra-planar (EP) gas in several spiral galaxies shows a decrease in rotational velocity with increasing height above the disk. The majority of this EP gas likely originates from disk-halo cycling driven by star formation in the disk via galactic fountains, which predict a lagging EP component. However, observations for a handful of galaxies show a steeper gradient than predicted by galactic fountains alone. A possible remedy for this is EP gas originating from infalling material, such as accreted satellites or the IGM. Accreted material with lower initial angular momentum than the disk could contribute to a steeper rotational velocity gradient. Studying the kinematics of EP gas can therefore provide constraints for how widespread accretion may be. We present optical observations and modeling of the ionized EP gas in our sample of 10 nearby, edge-on galaxies. For a subset of our targets, we compare our results to those from the HALOGAS (Hydrogen Accretion in LOcal GAlaxieS) project. HALOGAS is WSRT deep HI survey studying cold gas accretion in the local universe. Our optical observations are from a multi-slit spectroscopic setup on the ARC 3.5m telescope, which allows us to measure velocities of Ha-emitting gas as a function of height above the disk in 11 radial distance bins in a single exposure. RW acknowledges support from NSF grant AST-0908126 and from a grant from Research Corporation for the Advancement of Science.

Wu, Catharine J.; Walterbos, R. A.; Rand, R. J.; Heald, G.; HALOGAS Team

2014-01-01

106

A study of the ionized gas in Stephan's Quintet from integral field spectroscopy observations  

E-print Network

The Stephan's Quintet (SQ) is a famous interacting compact group of galaxies in an important stage of dynamical evolution, but surprisingly very few spectroscopic studies are found in the literature. We present optical integral field spectroscopy (IFS) observations of the SQ from the PPAK IFS Nearby Galaxies Survey (PINGS), that provide a powerful way of studying with spatial resolution the physical characteristics of the ionized gas within the group. The nature of the gas emission is analysed using 2D maps of continuum-subtracted, pure emission-line intensities, stacked spectra, diagnostic diagrams, and photoionization model predictions. In the case of NGC 7319, we study the galaxy-wide high-velocity outflow emission by comparing the emission properties with theoretical shock and AGN models. We conclude that the excitation mechanism of the gas in this galaxy is a mixture of AGN photoionization and shocks with a photoionizing precursor. The emission spectra from the large scale shock front in the interacting ...

Rodríguez-Baras, M; Díaz, A I; Sánchez, S F; Pasquali, A

2014-01-01

107

Electron fluence perturbation by cylindrical gas-filled ionization chambers with axes parallel to the beam  

NASA Astrophysics Data System (ADS)

A systematic imperfection of charged particle beam dosimetry performed with cavity ionization chambers according to the Bragg-Gray principle is theoretically evaluated. Due to differences in multiple scattering of the particles in the gas-filled cavity and in the solid or liquid medium replaced by the gas, the particle fluence in the gas exceeds the undisturbed fluence existing in the absence of the cavity. For cylindrical cavities with their axes parallel to the beam, three separable mechanisms contributing to this disturbance are evaluated by application of multiple scattering theory. The range of validity of the calculations is extended over that of a previous study, and a revised "perturbation correction factor" is derived. The accuracy of the results is confirmed by comparison with Monte Carlo calculations for 10 MeV electrons in carbon.

Abou Mandour, Mohsen; Harder, Dietrich

1983-01-01

108

Miniature triaxial metastable ionization detector for gas chromatographic trace analysis of extraterrestrial volatiles.  

PubMed

Gas chromatography has found highly successful application in NASA's flight programs. Gas chromatographs have been flown to both Mars and Venus where detailed compositional measurements were made. These instruments were quite small and relatively sensitive when compared to commercially available instruments; however, they do not appear adequate for future missions currently being planned. The earlier flight GC's had incorporated thermistor bead thermal conductivity cells as the detector. This detector requires very precise temperature control and only provides about 1 ppm sensitivity. Temperature stabilization causes the detector to be quite heavy, i.e., about 200 g. Greater sensitivity will be required for measurements of trace components in extraterrestrial environments. Review of other detector types revealed the metastable ionization detector as a likely candidate because of its superior thermal stability and high sensitivity. The metastable detector, first described by Lovelock as an argon ionization detector, has been studied and somewhat modified by others. The commercial design by Hartmann and Dimick was used for comparison purposes in our work. In the past, three features of the metastable detector are prominent: it has part-per-billion sensitivity, contamination must be carefully controlled, and anomalous response is common. Since it is an ionization detector, however, temperature instabilities do not cause the major perturbations experienced by the thermal conductivity detectors. This paper describes a miniature metastable ionization detector featuring an unconventional electrode configuration, whose performance characteristics parallel those of traditional design, while its weight is quite small. The prototype has been used in our laboratories routinely for 2 years, and the concept will be incorporated into a flight GC for use in the Space Shuttle. PMID:11536577

Woeller, F H; Kojiro, D R; Carle, G C

1984-04-01

109

Gas amplification and ionization coefficients in isobutane and argon–isobutane mixtures at low gas pressures  

Microsoft Academic Search

Measurements of the mean gas amplification factor in isobutane and in argon–isobutane mixtures are performed at total gas pressures of 10, 20, 30, 60 and 90 kPa over a range of reduced electric field strength 5×104gas gain with applied high voltage are observed. The

Ines Krajcar Broni?; Bernd Grosswendt

1998-01-01

110

Selective determination of haloperidol in human serum: surface ionization mass spectrometry and gas chromatography with surface ionization detection  

Microsoft Academic Search

Surface ionization organic mass spectrometry (SIOMS) has been performed on the clinically important drug haloperidol using quadrupole mass spectrometry in which the thermal ion source has a rhenium oxide emitter. The surface ionization (SI) mass spectrum is presented, interpreted in a purely empirical way by means of evidence from previous investigations, and then compared to results from conventional electron impact

Toshihiro Fujii; Kazuhiro Hatanaka; Gen Sato; Yumi Yasui; Hiromi Arimoto; Yoshihiro Mitsutsuka

1996-01-01

111

Ionized gas outflow in the isolated S0 galaxy NGC 4460  

NASA Astrophysics Data System (ADS)

We used integral-field and long-slit spectroscopy to study a bright extended nebulosity recently discovered in the isolated lenticular galaxy NGC 4460 during an H? survey of nearby galaxies. An analysis of archival Sloan Digital Sky Survey, GALEX and Hubble Space Telescope images indicates that current star formation is entirely concentrated in the central kiloparsec of the galaxy disc. The observed ionized gas parameters (morphology, kinematics and ionization state) can be explained by a gas outflow above the plane of the galaxy, caused by star formation in the circumnuclear region. Galactic wind parameters in NGC 4460 (outflow velocity, total kinetic energy) are several times smaller, compared with the known galactic wind in NGC 253, which is explained by the substantially lower total star formation rate. We discuss the cause of the star formation processes in NGC 4460 and in two other known isolated lenticular (S0) and elliptical (E) galaxies of the Local Volume: NGC 404 and 855. We provide evidence suggesting that the feeding of isolated galaxies by intergalactic gas on a cosmological time-scale is a steady process without significant variations. Based on observations collected with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences, which is operated under the financial support of the Science Department of Russia (registration number 01-43). E-mail: moisav@gmail.com

Moiseev, Alexei; Karachentsev, Igor; Kaisin, Serafim

2010-04-01

112

Development of a resonant laser ionization gas cell for high-energy, short-lived nuclei  

NASA Astrophysics Data System (ADS)

A new laser ion source configuration based on resonant photoionization in a gas cell has been developed at RIBF RIKEN. This system is intended for the future PArasitic RI-beam production by Laser Ion-Source (PALIS) project which will be installed at RIKEN's fragment separator, BigRIPS. A novel implementation of differential pumping, in combination with a sextupole ion beam guide (SPIG), has been developed. A few small scroll pumps create a pressure difference from 1000 hPa-10-3 Pa within a geometry drastically miniaturized compared to conventional systems. This system can utilize a large exit hole for fast evacuation times, minimizing the decay loss for short-lived nuclei during extraction from a buffer gas cell, while sufficient gas cell pressure is maintained for stopping high energy RI-beams. In spite of the motion in a dense pressure gradient, the photo-ionized ions inside the gas cell are ejected with an assisting force gas jet and successfully transported to a high-vacuum region via SPIG followed by a quadrupole mass separator. Observed behaviors agree with the results of gas flow and Monte Carlo simulations.

Sonoda, T.; Wada, M.; Tomita, H.; Sakamoto, C.; Takatsuka, T.; Furukawa, T.; Iimura, H.; Ito, Y.; Kubo, T.; Matsuo, Y.; Mita, H.; Naimi, S.; Nakamura, S.; Noto, T.; Schury, P.; Shinozuka, T.; Wakui, T.; Miyatake, H.; Jeong, S.; Ishiyama, H.; Watanabe, Y. X.; Hirayama, Y.; Okada, K.; Takamine, A.

2013-01-01

113

Development of a resonant laser ionization gas cell for high-energy, short-lived nuclei  

E-print Network

A new laser ion source configuration based on resonant photoionization in a gas cell has been developed at RIBF RIKEN. This system is intended for the future PArasitic RI-beam production by Laser Ion-Source (PALIS) project which will be installed at RIKEN's fragment separator, BigRIPS. A novel implementation of differential pumping, in combination with a sextupole ion beam guide (SPIG), has been developed. A few small scroll pumps create a pressure difference from 1000 hPa - 10^-3 Pa within a geometry drastically miniaturized compared to conventional systems. This system can utilize a large exit hole for fast evacuation times, minimizing the decay loss for short-lived nuclei during extraction from a buffer gas cell, while sufficient gas cell pressure is maintained for stopping high energy RI-beams. In spite of the motion in a dense pressure gradient, the photo-ionized ions inside the gas cell are ejected with an assisting force gas jet and successfully transported to a high-vacuum region via SPIG followed by a quadrupole mass separator. Observed behaviors agree with the results of gas flow and Monte Carlo simulations.

T. Sonoda; M. Wada; H. Tomita; C. Sakamoto; T. Takatsuka; T. Furukawa; H. Iimura; Y. Ito; T. Kubo; Y. Matsuo; H. Mita; S. Naimi; S. Nakamura; T. Noto; P. Schury; T. Shinozuka; T. Wakui; H. Miyatake; S. Jeong; H. Ishiyama; Y. X. Watanabe; Y. Hirayama; K. Okada; A. Takamine

2012-10-24

114

Preparation of the spacer for narrow electrode gap configuration in ionization-based gas sensor  

SciTech Connect

Carbon nanotubes (CNTs) have started to be developed as the sensing element for ionization-based gas sensors due to the demand for improved sensitivity, selectivity, stability and other sensing properties beyond what can be offered by the conventional ones. Although these limitations have been overcome, the problems still remain with the conventional ionization-based gas sensors in that they are bulky and operating with large breakdown voltage and high temperature. Recent studies have shown that the breakdown voltage can be reduced by using nanostructured electrodes and narrow electrode gap. Nanostructured electrode in the form of aligned CNTs array with evenly distributed nanotips can enhance the linear electric field significantly. The later is attributed to the shorter conductivity path through narrow electrode gap. The paper presents the study on the design consideration in order to realize ionization based gas sensor using aligned carbon nanotubes array in an optimum sensor configuration with narrow electrode gap. Several deposition techniques were studied to deposit the spacer, the key component that can control the electrode gap. Plasma spray deposition, electron beam deposition and dry oxidation method were employed to obtain minimum film thickness around 32 {mu}m. For plasma spray method, sand blasting process is required in order to produce rough surface for strong bonding of the deposited film onto the surface. Film thickness, typically about 39 {mu}m can be obtained. For the electron beam deposition and dry oxidation, the film thickness is in the range of nanometers and thus unsuitable to produce the spacer. The deposited multilayer film consisting of copper, alumina and ferum on which CNTs array will be grown was found to be removed during the etching process. This is attributed to the high etching rate on the thin film which can be prevented by reducing the rate and having a thicker conductive copper film.

Saheed, Mohamed Shuaib Mohamed; Mohamed, Norani Muti; Burhanudin, Zainal Arif [Electrical and Electronic Engineering, Universiti Teknologi PETRONAS, Seri Iskandar, Tronoh, Perak. (Malaysia); Fundamental and Applied Science, Universiti Teknologi PETRONAS, Seri Iskandar, Tronoh, Perak. (Malaysia); Electrical and Electronic Engineering, Universiti Teknologi PETRONAS, Seri Iskandar, Tronoh, Perak. (Malaysia)

2012-09-26

115

CAN THE LYMAN CONTINUUM LEAKED OUT OF H II REGIONS EXPLAIN DIFFUSE IONIZED GAS?  

SciTech Connect

We present an attempt to explain the diffuse Halpha emission of a face-on galaxy M 51 with the 'standard' photoionization model, in which the Lyman continuum (Lyc) escaping from H II regions propagates large distances into the diffuse interstellar medium (ISM). The diffuse Halpha emission of M 51 is analyzed using thin slab models and exponential disk models in the context of the 'on-the-spot' approximation. The scale height of the ionized gas needed to explain the diffuse Halpha emission with the scenario is found to be of the order of {approx}1-2 kpc, consistent with those of our Galaxy and edge-on galaxies. The model also provides a vertical profile, when the galaxy is viewed edge-on, consisting of two-exponential components. However, it is found that an incredibly low absorption coefficient of kappa{sub 0} {approx} 0.4-0.8 kpc{sup -1} at the galactic plane, or, equivalently, an effective cross section as low as sigma{sub eff} {approx} 10{sup -5} of the photoionization cross section at 912 A is required to allow the stellar Lyc photons to travel through the H I disk. Such a low absorption coefficient is out of accord with the properties of the ISM. Furthermore, we found that even the model that has the diffuse ionized gas (DIG) phase only and no H I gas phase shows highly concentrated Halpha emissions around H II regions, and can account for only {approx}<26% of the Halpha luminosity of the DIG. This result places a strong constraint on the ionizing source of the DIG. We also report that the Halpha intensity distribution functions not only of the DIG, but also of H II regions in M 51, appear to be lognormal.

Seon, Kwang-Il, E-mail: kiseon@kasi.re.k [Korea Astronomy and Space Science Institute, Hwaam-dong, Yuseong-gu, Daejeon, 305-348 (Korea, Republic of)

2009-09-20

116

Ionized gas outflows and global kinematics of low-z luminous star-forming galaxies  

NASA Astrophysics Data System (ADS)

We study the kinematic properties of the ionised gas outflows and ambient interstellar medium (ISM) in a large and representative sample of local luminous and ultra-luminous infrared galaxies (U/LIRGs) (58 systems, 75 galaxies) at galactic and sub-galactic (i.e., star-forming clumps) scales, thanks to integral field spectroscopy (IFS)-based high signal-to-noise integrated spectra. The velocity dispersion of the ionized ISM in U/LIRGs (? ? ? ~ 70 km s-1) is larger than in lower luminosity local star-forming galaxies (? ? ? ~ 25 km s-1). While for isolated disc LIRGs star formation appears to sustain turbulence, gravitational energy release associated with interactions and mergers plays an important role in driving ? in the U/LIRG range. We find that ? has a dependency on the star formation rate density (?SFR), which is weaker than expected if it were driven by the energy released by the starburst. The relatively small role of star formation (SF) driving the ? in U/LIRGs is reinforced by the lack of an increase in ? associated with high luminosity SF clumps. We also find that the impact of an active galactic nucleus (AGN) in ULIRGs is strong, increasing on average ? by a factor 1.5. Low-z U/LIRGs cover a range of velocity dispersion (? ~ 30 to 100 km s-1) and star formation rate density (?SFR ~ 0.1 to 20 M? yr-1 kpc-2) similar to those of high-z SFGs. Moreover, the observed weak dependency of ? on ?SFR for local U/LIRGs (? ? ?SFR+0.06) is in very good agreement with that measured in some high-z samples. The presence of ionized gas outflows in U/LIRGs seems universal based on the detection of a broad, usually blueshifted, H? line. The observed dependency of the maximum velocity of the outflow (Vmax) on the star formation rate (SFR) is of the type Vmax(non - AGN) ? SFR(LIR)+ 0.24. We find that AGNs in U/LIRGs are able to generate faster (~×2) and more massive (~× 1.4) ionized gas outflows than pure starbursts. The derived ionized mass loading factors (?) are in general below 1, with only a few AGNs above this limit. The escaping gas fraction is low with only less massive (log(Mdyn/M?) < 10.4) U/LIRGs having outflowing terminal velocities higher than their escape velocities, and more massive galaxies retaining the gas, even if they host an AGN. The observed average outflow properties in U/LIRGs are similar to high-z galaxies of comparable SFR. However, while high-z galaxies seem to require ?SFR > 1 M? yr-1 kpc-2 for launching strong outflows, this threshold is not observed in low-z U/LIRGs even after correcting for the differential fraction of the gas content. In the bright SF clumps found in LIRGs, ionized gas outflows appear to be very common (detection rate over 80%). Their observed properties are less extreme than those associated with the entire galaxy. The clumps in LIRGs follow the general size-L-? scaling relations found for low- and high-z clumps, though they are in general smaller, less luminous, and are characterized by lower ? than at high-z. For a given observed (no internal extinction correction applied) star formation surface density, outflows in LIRG clumps would be about one to two orders of magnitude less energetic than the outflows launched by clumps in high-z SF galaxies. Tables 1, 2, and Appendices are available in electronic form at http://www.aanda.org

Arribas, S.; Colina, L.; Bellocchi, E.; Maiolino, R.; Villar-Martín, M.

2014-08-01

117

The Volume Fraction of Ionized Intergalactic Gas at Redshift z=6.5  

E-print Network

The observed number density of Lyman-alpha sources implies a minimum volume of the inter-galactic medium that must be ionized, in order to allow the Lyman-alpha photons to escape attenuation. We estimate this volume by assigning to each Lyman-alpha emitter the minimum Stromgren sphere that would allow half its Lyman-alpha photons to escape. This implies a lower limit to ionized gas volume fraction of 20-50% at redshift z=6.5. This is a lower limit in two ways: First, we conservatively assume that the Lyman-alpha sources seen (at a relatively bright flux limit) are the only ones present; and second, we assume the smallest Stromgren sphere volume that will allow the photons to escape. This limit is completely independent of what ionizing photon sources produced the bubbles. Deeper Lyman-alpha surveys are possible with present technology, and can strengthen these limits by detecting a higher density of Lyman-alpha galaxies.

Sangeeta Malhotra; James Rhoads

2005-11-07

118

Determination of nitrogen monoxide in high purity nitrogen gas with an atmospheric pressure ionization mass spectrometer  

NASA Technical Reports Server (NTRS)

An atmospheric pressure ionization mass spectrometric (API-MS) method was studied for the determination of residual NO in high purity N2 gas. The API-MS is very sensitive to NO, but the presence of O2 interferes with the NO measurement. Nitrogen gas in cylinders as sample gas was mixed with NO standard gas and/or O2 standard gas, and then introduced into the API-MS. The calibration curves of NO and O2 has linearity in the region of 0 - 2 ppm, but the slopes changed with every cylinder. The effect of O2 on NO+ peak was additive and proportional to O2 concentration in the range of 0 - 0.5 ppm. The increase in NO+ intensity due to O2 was (0.07 - 0.13)%/O2, 1 ppm. Determination of NO and O2 was carried out by the standard addition method to eliminate the influence of variation of slopes. The interference due to O2 was estimated from the product of the O2 concentration and the ratio of slope A to Slope B. Slope A is the change in the NO+ intensity with the O2 concentration. Slope B is the intensity with O2 concentration.

Kato, K.

1985-01-01

119

Development of a resonant laser ionization gas cell for high-energy, short-lived nuclei  

E-print Network

A new laser ion source configuration based on resonant photoionization in a gas cell has been developed at RIBF RIKEN. This system is intended for the future PArasitic RI-beam production by Laser Ion-Source (PALIS) project which will be installed at RIKEN's fragment separator, BigRIPS. A novel implementation of differential pumping, in combination with a sextupole ion beam guide (SPIG), has been developed. A few small scroll pumps create a pressure difference from 1000 hPa - 10^-3 Pa within a geometry drastically miniaturized compared to conventional systems. This system can utilize a large exit hole for fast evacuation times, minimizing the decay loss for short-lived nuclei during extraction from a buffer gas cell, while sufficient gas cell pressure is maintained for stopping high energy RI-beams. In spite of the motion in a dense pressure gradient, the photo-ionized ions inside the gas cell are ejected with an assisting force gas jet and successfully transported to a high-vacuum region via SPIG followed by ...

Sonoda, T; Tomita, H; Sakamoto, C; Takatsuka, T; Furukawa, T; Iimura, H; Ito, Y; Kubo, T; Matsuo, Y; Mita, H; Naimi, S; Nakamura, S; Noto, T; Schury, P; Shinozuka, T; Wakui, T; Miyatake, H; Jeong, S; Ishiyama, H; Watanabe, Y X; Hirayama, Y; Okada, K; Takamine, A

2012-01-01

120

Interrelated structures of the transport shock and collisional relaxation layer in a multitemperature, multilevel ionized gas  

NASA Technical Reports Server (NTRS)

The gas dynamic structures of the transport shock and the downstream collisional relaxation layer are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. Three electronic levels are accounted for in the microscopic model of the atom. Nonequilibrium processes with respect to population of levels and species plus temperature are considered. By using an asymptotic technique the shock morphology is found on a continuum flow basis. The asymptotic procedure gives two distinct layers in which the nonequilibrium effects to be considered are different. A transport shock appears as the inner solution to an outer collisional relaxation layer in which the gas reaches local equilibrium. A family of numerical examples is displayed for different flow regimes. Argon and helium models are used in these examples.

Vinolo, A. R.; Clarke, J. H.

1972-01-01

121

Observations of the motion and distribution of the ionized gas in the central parsec of the galaxy. II  

Microsoft Academic Search

Observations of infrared fine-structure line emission from compact clouds of ionized gas within Sgr A West are presented. These clouds have diameters of 0.1--0.5 pc, internal velocity dispersions approx.100 km s⁻¹ (FWHM), and line center velocities up to +- 260 km s⁻¹. Their masses are not accurately determined but are probably between 0.1 and 10 M\\/sub sun\\/. They are ionized

J. H. Lacy; C. H. Townes; T. R. Geballe; D. J. Hollenbach

1980-01-01

122

Dust and ionized gas in elliptical galaxies: Signatures of merging collisions  

NASA Technical Reports Server (NTRS)

Traditionally elliptical galaxies were thought to be essentially devoid of interstellar matter. However, recent advances in instrumental sensitivity have caused a renaissance of interest in dust and gas in - or associated with - elliptical galaxies. In particular, the technique of co-adding IRAS survey scans has led to the detection of more than half of all ellipticals with BT less than 11 mag. in the Revised Shapley-Ames catalog, indicating the presence of 10(exp 7) - 10(exp 8) solar mass of cold interstellar matter (Jura et al. 1987). In addition, CCD multi-color surface photometry shows dust patches in about 30 percent of the cases studied to date (e.g., Veron-Cetty & Veron 1988). Thorough study of the gas and dust in ellipticals is important to (1) determine its origin (mass-loss from late-type stars, merging collisions with other galaxies or accretion inflows from cooling X-ray gas), and (2) investigate the 3-D shape of ellipticals, as can be derived from the orientation of the dust lanes and the 2-D velocity field of the gas. An important result of our comprehensive CCD imaging program is that a relevant fraction (approximately 40 percent) of the sample objects exhibits dust patches within extended H-alpha+(NII) line-emitting filaments. This common occurrence can be easily accounted for if the dust and gas have an external origin, i.e., mergers or interactions with gas-rich galaxies. Evidence supporting this suggestion: (1) the ionized gas is usually dynamically decoupled from the stellar velocity field (see, e.g., Sharples et al. 1983, Bertola & Bettoni 1988); (2) it is shown in a companion paper (Goudfrooij et al. 1992) that internal stellar mass loss alone can not account for the dust content of elliptical galaxies.

Goudfrooij, Paul; Dejong, Teije

1993-01-01

123

Gas kinematics and ionization along the extended sight line to HD 116852  

NASA Technical Reports Server (NTRS)

We present Goddard High-Resolution Spectrograph intermediate observations of the interstellar medium toward HD 116852, a low halo star at a distance of 4.8 kpc (z = -1.3 kpc) in the direction l = 304. deg 9, b = 16.deg 1. The small science aperture observations have signal-to-noise ratios ranging from 30 to 90 and resolutions of 11 to 18 km/s (FWHM). We confirm the optical MK classification of this star through an analysis of its ultraviolet photosperic and stellar wind profiles. We detect interstellar lines of Al III, Si IV, C IV, and N V together with lines of C I, C I*, C I**, Si II, Ge II, P II, and Ni II. We convert the Mg II, P II, S II, Al III, Si IV, C IV, and N V profiles into measure of apparent column density as a function of LSR velocity. Gas scale height, velocity dispersion, and differential Galactic rotation effects govern the profile shapes. A simple computer model of the expected sight line column density profiles for the low and high ion species indicates that the gas velocity dispersions and scale heights increase as the ionization level of the gas increases. We find scale heigts H greater than or = 1 kpc for the high ions, which are comparable to the z-distance of the star, whereas we find H approximatley = 0.6 to 0.7 kpc for A1 III and H approximatley 0.1 kpc for P II and Ge II. An enhancement in the Al II profile near -15 km/s accounts for approximately 25% of the A1 III column along the sight line and probably arises within gas located approximately 500 pc below the Sagittarius-Carina spiral arm link. Portions of the broad underlying A1 III distribution are associated with the higher ionization lines, perhaps in conductive interfaces. The presence of N V and the column density ratios of Si IV, C IV, and N V favor the interpretation that much of the high ion absorption is produced by collisional ionization in gas with T = 1-3 x 10(exp 5) K. An enhancement near -35 km/s in both the Si IV and C IV profiles may be due to an outflow from the Norma spiral arm at a z-distance of about -1 kpc. The smooth decrease of the N(C IV)/N(Si IV) ratio at negative velocities may be due to an ISM ionization structure for hot gas that changes distance from the Galactic plane or to a two phase gas distribution in which the relative contribution from each phase changes with distance from the Galactic plane.

Sembach, Kenneth R.; Savage, Blair D.

1994-01-01

124

Spectrum Blueshifting of Ultrashort UV Laser Pulse Induced by Ionization of Supersonic He and Ar Gas Jets  

NASA Astrophysics Data System (ADS)

The predominant spectral blueshifting of a sub-picosecond UV laser pulse induced by ultrafast ionization of noble gases was investigated. Spectral measurements were made at various gas densities. Typical quasi-periodic structures in the blueshifted spectrum were obtained. The observations were in connection with the so-called self-phase modulation of laser pulses in the ultrafast ionization process which was simply simulated with an ADK (Ammosov-Delone-Krainov) ionization model. Some quantitative information can be deduced from the measurements and calculations.

Yan, Lixin; Zhang, Yongsheng; Liu, Jingru; Huang, Wenhui; Tang, Chuanxiang; Cheng, Jianping

2008-06-01

125

Galaxy stellar mass assembly: supernova feedback, photo-ionization and no-star-forming gas reservoir.  

NASA Astrophysics Data System (ADS)

Semi-analytical models are currently the best way to understand the formation of galaxies within the cosmic dark-matter structures. While they fairly well reproduce the local stellar mass functions, they fail to match observations at high redshift. The inconsistency indicates that the gas accretion in galaxies and the transformation of gas into stars, are not well followed. With a new SAM: eGalICS, we explore the impacts of classical mechanisms (supernova feedback, photo-ionization) onto the stellar mass assembly. Even with a strong efficiency, these two processes cannot explain the observed stellar mass function and star formation rate distribution. We introduce an ad-hoc modification of the standard paradigm, based on the presence of a no-star-forming gas component in galaxy discs. We introduce this reservoir to generate a delay between the accretion of the gas and the star formation process. The new stellar mass function and SFR distributions are in good agreement with observations.

Cousin, M.

2014-12-01

126

Highly ionized interstellar gas located in the Galactic disk and halo  

NASA Technical Reports Server (NTRS)

High-resolution IUE absorption line spectra have been obtained for 40 distant stars in order to study the distribution of interstellar H I, Si IV, C IV, and N V in the Galactic disk and lower halo. Respective midplane densities of 2 x 10 to the -9th, 7 x 10 to the -9th, and 3 x 10 to the -9th are found for Si IV, C IV, and Ni V. Both column density and velocity data indicate that the highly ionized gas (HIG) is considerably more extended in directions away from the Galactic plane than is H I or Si II. The absorption-line velocities for the halo HIG are consistent with the notion that halo gas in the inner Galaxy rotates more slowly than gas in the underlying disk. The derived column densities suggest an exponential scale height for the HIG of about 3 kpc; however, a simple exponential distribution is a poor representation of the distribution of the gas. It is concluded that a full explanation of the origin of the halo HIG will probably require a blending of ideas from the Galactic fountain and the photoionized halo models.

Savage, Blair D.; Massa, Derck

1987-01-01

127

Ionized and neutral gas in the XUV discs of nearby spiral galaxies  

NASA Astrophysics Data System (ADS)

We are conducting a multiwavelength study of XUV discs in nearby, gas-rich spiral galaxies combining the available UV (GALEX) observations with H i data obtained at the ATCA as part of the Local Volume HI Survey (LVHIS) project and multi-object fibre spectroscopy obtained using the 2dF/AAOmega instrument at the 3.9m AAT. Here we present the results of the multiwavelength analysis of the galaxy pair NGC 1512/1510. The H i distribution of NGC 1512 is very extended with two pronounced spiral/tidal arms. Hundreds of independent UV-bright regions are associated with dense H i clouds in the galaxy outskirts. We confirm the detection of ionized gas in the majority of them and characterize their physical properties, chemical abundances and kinematics. Both the gas distribution andthe distribution of the star-forming regions are affected by gravitational interactionwith the neighbouring blue compact dwarf galaxy NGC 1510. Our multiwavelength analysis provides new clues about local star-formation processes, the metal redistribution in the outer gaseous discs of spiral galaxies, the importance of galaxy interactions, the fate of the neutral gas and the chemical evolution in nearby galaxies.

López-Sánchez, A.; Koribalski, B. S.; Westmeier, T.; Esteban, C.

2015-02-01

128

Observations of feedback from radio-quiet quasars - II. Kinematics of ionized gas nebulae  

NASA Astrophysics Data System (ADS)

The prevalence and energetics of quasar feedback is a major unresolved problem in galaxy formation theory. In this paper, we present Gemini Integral Field Unit observations of ionized gas around 11 luminous, obscured, radio-quiet quasars at z ˜ 0.5 out to ˜15 kpc from the quasar; specifically, we measure the kinematics and morphology of [O III] ?5007 Å emission. The round morphologies of the nebulae and the large line-of-sight velocity widths (with velocities containing 80 per cent of the emission as high as 103 km s-1) combined with relatively small velocity difference across them (from 90 to 520 km s-1) point towards wide-angle quasi-spherical outflows. We use the observed velocity widths to estimate a median outflow velocity of 760 km s-1, similar to or above the escape velocities from the host galaxies. The line-of-sight velocity dispersion declines slightly towards outer parts of the nebulae (by 3 per cent kpc-1 on average). The majority of nebulae show blueshifted excesses in their line profiles across most of their extents, signifying gas outflows. For the median outflow velocity, we find dot{E}_kin between 4 × 1044 and 3 × 1045 erg s-1 and dot{M} between 2 × 103 and 2 × 104 M? yr-1. These values are large enough for the observed quasar winds to have a significant impact on their host galaxies. The median rate of converting bolometric luminosity to kinetic energy of ionized gas clouds is ˜2 per cent. We report four new candidates for `superbubbles' - outflows that may have broken out of the denser regions of the host galaxy.

Liu, Guilin; Zakamska, Nadia L.; Greene, Jenny E.; Nesvadba, Nicole P. H.; Liu, Xin

2013-12-01

129

Kinematics of diffuse ionized gas in the disk halo interface of NGC 891 from Fabry-Pérot observations  

E-print Network

The properties of the gas in halos of galaxies constrain global models of the interstellar medium. Kinematical information is of particular interest since it is a clue to the origin of the gas. Here we report observations of the kinematics of the thick layer of the diffuse ionized gas in NGC 891 in order to determine the rotation curve of the halo gas. We have obtained a Fabry-P\\'erot data cube in Halpha to measure the kinematics of the halo gas with angular resolution much higher than obtained from HI 21 cm observations. The data cube was obtained with the TAURUS II spectrograph at the WHT on La Palma. The velocity information of the diffuse ionized gas extracted from the data cube is compared to model distributions to constrain the distribution of the gas and in particular the halo rotation curve. The best fit model has a central attenuation tau_H-alpha=6, a dust scale length of 8.1 kpc, an ionized gas scale length of 5.0 kpc. Above the plane the rotation curve lags with a vertical gradient of -18.8 km/s/kpc. We find that the scale length of the H-alpha must be between 2.5 and 6.5 kpc. Furthermore we find evidence that the rotation curve above the plane rises less steeply than in the plane. This is all in agreement with the velocities measured in the HI.

P. Kamphuis; R. F. Peletier; R. -J. Dettmar; J. M. van der Hulst; P. C. van der Kruit; R. J. Allen

2007-03-14

130

Gas chromatography plasma-assisted reaction chemical ionization mass spectrometry for quantitative detection of bromine in organic compounds.  

PubMed

We have recently introduced plasma-assisted reaction chemical ionization mass spectrometry (PARCI-MS) for elemental analysis of halogens in organic compounds. Here, we utilize gas chromatography (GC) coupled to PARCI-MS to investigate the mechanism of Br(-) ion generation from organobromines and to evaluate analytical performance of PARCI for organobromine analysis. Bromine atoms in compounds eluting from GC are converted to HBr in a low-pressure microwave induced helium plasma with trace amounts of hydrogen added as a reaction gas. Ionization is achieved by introducing nitrogen into the afterglow region of the plasma, liberating electrons via penning ionization and leading to formation of negative ions. We demonstrate that N2 largely affects the ionization process, whereas H2 affects both the ionization process and in-plasma reactions. Our investigations also suggest that dissociative electron capture is the main ionization route for formation of Br(-) ions. Importantly, GC-PARCI-MS shows a uniform response factor for bromine across brominated compounds of drastically different chemical structures, confirming PARCI's ability to quantify organobromines in the absence of compound-specific standards. Over 3 orders of magnitude linear dynamic range is demonstrated for bromine quantification. We report a detection limit of 29 fg of bromine on-column, ~4-fold better than inductively coupled plasma-MS. PMID:25003497

Lin, Ninghang; Wang, Haopeng; Kahen, Kaveh; Badiei, Hamid; Jorabchi, Kaveh

2014-08-01

131

Auger neutralization and ionization processes for charge exchange between slow noble gas atoms and solid surfaces  

NASA Astrophysics Data System (ADS)

Electron and energy transfer processes between an atom or molecule and a surface are extremely important for many applications in physics and chemistry. Therefore a profound understanding of these processes is essential in order to analyze a large variety of physical systems. The microscopic description of the two-electron Auger processes, leading to neutralization/ionization of an ion/neutral atom in front of a solid surface, has been a long-standing problem. It can be dated back to the 1950s when H.D. Hagstrum proposed to use the information contained in the spectrum of the electrons emitted during the neutralization of slow noble gas ions as a surface analytical tool complementing photoelectron spectroscopy. However, only recently a comprehensive description of the Auger neutralization mechanism has been achieved by the combined efforts of theoretical and experimental methods. In this article we review the theoretical models for this problem, stressing how their outcome compare with experimental results. We also analyze the inverse problem of Auger ionization. We emphasize the understanding of the key quantities governing the processes and outline the challenges remaining. This opens new perspectives for future developments of theoretical and experimental work in this field.

Carmina Monreal, R.

2014-02-01

132

Ionization heating in rare-gas clusters under intense XUV laser pulses  

NASA Astrophysics Data System (ADS)

The interaction of intense extreme ultraviolet (XUV) laser pulses (?=32nm, I=1011-1014 W/cm2) with small rare-gas clusters (Ar147) is studied by quasiclassical molecular dynamics simulations. Our analysis supports a very general picture of the charging and heating dynamics in finite samples under short-wavelength radiation that is of relevance for several applications of free-electron lasers. First, up to a certain photon flux, ionization proceeds as a series of direct photoemission events producing a jellium-like cluster potential and a characteristic plateau in the photoelectron spectrum as observed in Bostedt [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.100.133401 100, 133401 (2008)]. Second, beyond the onset of photoelectron trapping, nanoplasma formation leads to evaporative electron emission with a characteristic thermal tail in the electron spectrum. A detailed analysis of this transition is presented. Third, in contrast to the behavior in the infrared or low vacuum ultraviolet range, the nanoplasma energy capture proceeds via ionization heating, i.e., inner photoionization of localized electrons, whereas collisional heating of conduction electrons is negligible up to high laser intensities. A direct consequence of the latter is a surprising evolution of the mean energy of emitted electrons as function of laser intensity.

Arbeiter, Mathias; Fennel, Thomas

2010-07-01

133

Ionized gas (plasma) delivery of reactive oxygen species (ROS) into artificial cells  

NASA Astrophysics Data System (ADS)

This study was designed to enhance our understanding of how reactive oxygen species (ROS), generated ex situ by ionized gas (plasma), can affect the regulation of signalling processes within cells. A model system, comprising of a suspension of phospholipid vesicles (cell mimics) encapsulating a ROS reporter, was developed to study the plasma delivery of ROS into cells. For the first time it was shown that plasma unequivocally delivers ROS into cells over a sustained period and without compromising cell membrane integrity. An important consideration in cell and biological assays is the presence of serum, which significantly reduced the transfer efficiency of ROS into the vesicles. These results are key to understanding how plasma treatments can be tailored for specific medical or biotechnology applications. Further, the phospholipid vesicle ROS reporter system may find use in other studies involving the application of free radicals in biology and medicine.

Hong, Sung-Ha; Szili, Endre J.; Jenkins, A. Toby A.; Short, Robert D.

2014-09-01

134

The Effect of the Argon Carrier Gas in the Multiphoton Dissociation-Ionization of Tetracene  

PubMed Central

The multiphoton dissociation-ionization of tetracene at 355 nm using 6.5 nanosecond laser pulses, with and without argon as a carrier gas (CG), has been studied and compared. Ion fragments were analyzed in a time-of-flight mass spectrometer and separated according to their mass-to-charge ratio (m/z). The results show that the dynamic of photodissociation at ?1010 W cm?2 intensities is strongly influenced by the CG. The suppression of fragmentation channels primarily those relating to the formation of the CHm+ (m = 2, 4), C2H4+ and C5H4+2 ions. CH5+ and CH6+ were observed which have not been reported before in photodissociation tetracene experiments. PMID:19325732

Poveda, Juan Carlos; Román, Alejandro San; Guerrero, Alfonso; Álvarez, Ignacio; Cisneros, Carmen

2008-01-01

135

Bar effects on ionized gas properties and dust content in galaxy centers  

NASA Astrophysics Data System (ADS)

Observations and simulations indicate that bars are important agents to transfer material towards galaxy centers. However, observational studies devoted to investigate the effects of bars in galaxy centers are not yet conclusive. We have used a sample (Coelho & Gadotti 2011) of nearby face-on galaxies with available spectra (SDSS database) to investigate the footprints of bars in galaxy centers by analysing the central ionized gas properties of barred and unbarred galaxies separately. We find statistically significant differences in the H? Balmer extinction, star formation rate per unit area, in the [S ii]?6717/[S ii]?6731 line ratio, and notably in the N2 parameter (N2 = log([N ii]?6583/H?)). A deeper analysis reflects that these differences are only relevant for the less massive bulges (<~1010M?). These results have important consequences for studies on bulge formation and galaxy evolution.

Zurita, A.; Florido, E.; Pérez, I.; Coelho, P.; Gadotti, D. A.

2015-02-01

136

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

PubMed Central

This article describes gas chromatography-flame ionization detection method for determination of 17 ?-estradiol in rabbit plasma. 17 ?-estradiol and internal standard progesterone were extracted from plasma using liquid–liquid extraction method. Linearity was found between 0.25 and 20 ?g/ml (r2=0.994) for plasma samples. Intra-day and inter-day precision, expressed as the relative standard deviation were less than 5.5%, and accuracy (relative error) was less than 3.5%. The mean recovery of 17 ?-estradiol samples was 94.4%. The limits of detection and quantification of method for plasma samples were 0.10 ?g/ml and 0.15 ?g/ml, respectively. Also, clinically used other 10 drugs were investigated to check for potential interferences and the method was successfully applied to the determination of 17 ?-estradiol in New Zealand white rabbits. PMID:23439655

Yilmaz, B; Kadioglu, Y.

2012-01-01

137

Measuring Feedback from Mass Outflows of Ionized Gas in Nearby AGN  

NASA Astrophysics Data System (ADS)

We present an investigation into the impact of feedback from outflows of ionized gas in nearby (z < 0.04) AGN. From our studies of outflowing UV a and X-ray absorbers, we found that most Seyfert 1 galaxies with moderate bolometric luminosities have mass outflow rates that are 10 - 1000 times the mass accretion rates needed to generate their observed luminosities, indicating that most of the mass outflow originates from outside the inner accretion disk. We also found that many of these AGN have kinetic luminosities in the range 0.5 to 5% bolometric, which is in the range often suggested by feedback models needed for efficient self-regulation of black-hole and galactic bulge growth. We investigate the possibility that mass outflows on larger scales (hundreds of parsecs) may provide similar or even larger mass outflow rates and kinetic luminosities in nearby, moderate luminosity AGN.

Crenshaw, D. M.; Kraemer, S. B.; Schmitt, H. R.; Turner, J.; Fischer, T. C.

2013-01-01

138

CONSTRAINING STELLAR FEEDBACK: SHOCK-IONIZED GAS IN NEARBY STARBURST GALAXIES  

SciTech Connect

We investigate the properties of feedback-driven shocks in eight nearby starburst galaxies using narrow-band imaging data from the Hubble Space Telescope. We identify the shock-ionized component via the line diagnostic diagram [O III] (?5007)/H? versus [S II] (??6716, 6731) (or [N II] (?6583))/H?, applied to resolved regions 3-15 pc in size. We divide our sample into three sub-samples: sub-solar, solar, and super-solar, for consistent shock measurements. For the sub-solar sub-sample, we derive three scaling relations: (1) L{sub shock}?SFR{sup 0.62}, (2) L{sub shock}??{sub SFR,{sub HL}} {sup 0.92}, and (3) L{sub shock}/L{sub tot}?(L{sub H} /L{sub ?,{sub H}}){sup –0.65}, where L{sub shock} is the H? luminosity from shock-ionized gas, ?{sub SFR,{sub HL}} the star formation rate (SFR) per unit half-light area, L{sub tot} the total H? luminosity, and L{sub H} /L{sub ?,{sub H}} the absolute H-band luminosity from the Two Micron All Sky Survey normalized to solar luminosity. The other two sub-samples do not have enough number statistics, but appear to follow the first scaling relation. The energy recovered indicates that the shocks from stellar feedback in our sample galaxies are fully radiative. If the scaling relations are applicable in general to stellar feedback, our results are similar to those by Hopkins et al. for galactic superwinds. This similarity should, however, be taken with caution at this point, as the underlying physics that enables the transition from radiative shocks to gas outflows in galaxies is still poorly understood.

Hong, Sungryong; Calzetti, Daniela [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Gallagher, John S. III [Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States); Martin, Crystal L. [Physics Department, University of California, Santa Barbara, CA 93106-9530 (United States); Conselice, Christopher J. [University of Nottingham, School of Physics and Astronomy, Nottingham NG7 2RD (United Kingdom); Pellerin, Anne [Department of Physics and Astronomy, Texas A and M University, 4242 TAMU, College Station, TX 77843-4242 (United States)

2013-11-01

139

Ionized Gas in Damped Lyman Alpha Protogalaxies: II. Comparison Between Models and the Kinematic Data  

E-print Network

We test semi-analytic models for galaxy formation with accurate kinematic data of damped Lyman alpha protogalaxies (DLAs) presented in the companion paper I. The models envisage centrifugally supported exponential disks at the centers of dark matter halos which are filled with ionized gas undergoing radial infall to the disks. The halo masses are drawn from cross-section weighted mass distributions predicted by CDM cosmogonies, or by the null hypothesis (TF model) that the dark matter mass distribution has not evolved since z ~ 3. In our models, C IV absorption lines detected in DLAs arise in infalling ionized clouds while the low-ion absorption lines arise from neutral gas in the disks. Using Monte Carlo methods we find: (a) The CDM models are incompatible with the low-ion statistics at more than 99% confidence whereas some TF models cannot be excluded at more than 88% confidence. (b) Both CDM and TF models agree with the observed distribution of C IV velocity widths. (c) The CDM models generate differences between the mean velocities of C IV and low ion profiles in agreement with the data, while the TF model produces differences in the means that are too large. (d) Both CDM and TF models produce ratios of C IV to low-ion velocity widths that are too large. (e) Both CDM and TF models generate C IV versus low-ion cross-correlation functions incompatible with the data. While it is possible to select model parameters resulting in consistency with the data, the disk-halo configuration assumed in both cosmogonies still does not produce significant overlap in velocity space between C IV low-ion velocity profiles. We conjecture that including angular momentum of the infalling clouds will increase the overlap between C IV and low-ion profiles.

Arthur M. Wolfe; Jason X. Prochaska

2000-09-07

140

KINEMATICS OF IONIZED GAS AT 0.01 AU OF TW Hya  

SciTech Connect

We report two-dimensional spectroastrometry of Br{gamma} emission of TW Hya to study the kinematics of the ionized gas in the star-disk interface region. The spectroastrometry with the integral field spectrograph SINFONI at the Very Large Telescope is sensitive to the positional offset of the line emission down to the physical scale of the stellar diameter ({approx}0.01 AU). The centroid of Br{gamma} emission is displaced to the north with respect to the central star at the blue side of the emission line, and to the south at the red side. The major axis of the centroid motion is P.A. = -20 Degree-Sign , which is nearly equal to the major axis of the protoplanetary disk projected on the sky, previously reported by CO submillimeter spectroscopy (P.A. = -27 Degree-Sign ). The line-of-sight motion of the Br{gamma} emission, in which the northern side of the disk is approaching toward us, is also consistent with the direction of the disk rotation known from the CO observation. The agreement implies that the kinematics of Br{gamma} emission is accounted for by the ionized gas in the inner edge of the disk. A simple modeling of the astrometry, however, indicates that the accretion inflow similarly well reproduces the centroid displacements of Br{gamma}, but only if the position angles of the centroid motion and the projected disk ellipse are a chance coincidence. No clear evidence of disk wind is found.

Goto, M.; Linz, H.; Henning, Th. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Carmona, A. [ISDC, Ch. d'Ecogia 16, CH-1290 Versoix (Switzerland); Stecklum, B. [Thueringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg (Germany); Meeus, G. [Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam (Germany); Usuda, T., E-mail: mgoto@mpia.de [Subaru Telescope, 650 North A'ohoku Place, Hilo, HI 96720 (United States)

2012-03-20

141

A reservoir of ionized gas in the galactic halo to sustain star formation in the Milky Way.  

PubMed

Without a source of new gas, our Galaxy would exhaust its supply of gas through the formation of stars. Ionized gas clouds observed at high velocity may be a reservoir of such gas, but their distances are key for placing them in the galactic halo and unraveling their role. We have used the Hubble Space Telescope to blindly search for ionized high-velocity clouds (iHVCs) in the foreground of galactic stars. We show that iHVCs with 90 ? |v(LSR)| ? 170 kilometers per second (where v(LSR) is the velocity in the local standard of rest frame) are within one galactic radius of the Sun and have enough mass to maintain star formation, whereas iHVCs with |v(LSR)| ? 170 kilometers per second are at larger distances. These may be the next wave of infalling material. PMID:21868626

Lehner, Nicolas; Howk, J Christopher

2011-11-18

142

Stellar and Ionized Gas Kinematics in the Circumnuclear Region of the Galaxy NGC 7331  

NASA Astrophysics Data System (ADS)

We present simultaneous two-dimensional spectroscopy of the circumnuclear region (12" × 9") of the galaxy NGC 7331, obtained with an optical fiber system coupled to the ISIS double spectrograph of the 4.2 m William Herschel Telescope. The system allows simultaneous observation of 125 regions of this galaxy in two spectral ranges: 4590-5400 Å at high resolution (1.5 Å) and 6400-9620 Å at low resolution (5 Å). These spectra are mainly used to study the stellar and gas kinematics in the innermost region of this galaxy. The stellar velocity fields inferred from the Mg I b and Ca II absorption lines are in good agreement. They show a solid-body rotational pattern with the line of nodes along the position angle of the apparent major axis of the galaxy. The relatively large local stellar velocity dispersion suggests that we are observing the bulge rather than the disk kinematics. The two-dimensional kinematic data agree with previous one-dimensional studies that found no evidence for a massive black hole in NGC 7331. The [O III] emission lines are split into three components. One is distributed around the systemic velocity, another is systematically blueshifted, and the last is systematically redshifted. We propose that these arise from two distinct gaseous systems: a warped disk of irregular rotational pattern with the kinematic axes shifted by about 30° with respect to those of the stars, and a shell of gas flowing radially. Although alternative interpretations in terms of inflow driven by a central bar or outflow produced by a galactic wind are possible, the latter seems preferable. In NGC 7331 the ionized gas and stars are kinematically decoupled, the velocity dispersion of the ionized gas being substantially lower than that of the stars. This last result differs from what is generally found in Seyfert galaxies. However, NGC 7331 and M31 show a large degree of similarity, and the type of LINERs that they harbor are probably produced by the same type of phenomenon.

Mediavilla, E.; Arribas, S.; García-Lorenzo, B.; del Burgo, C.

1997-10-01

143

Plasma ionization frequency, edge-to-axis density ratio, and density on axis of a cylindrical gas discharge  

SciTech Connect

A rigorous derivation of expressions, starting from the governing equations, for the ionization frequency, edge-to-axis ratio of plasma density, plasma density at the axis, and radially averaged plasma density in a cylindrical gas discharge has been obtained. The derived expressions are simple and involve the relevant parameters of the discharge: Cylinder radius, axial current, and neutral gas pressure. The found expressions account for ion inertia, ion temperature, and changes in plasma ion collisionality.

Palacio Mizrahi, J. H. [Physics Department, Technion, Haifa 32000 (Israel)

2014-06-15

144

The influence of core polarization on photo-ionization of alkali and metastable rare gas atoms near threshold  

Microsoft Academic Search

The effect of the polarization of the atomic core by the outer electron on near-threshold photo-ionization of alkali atoms (Na-Cs) and metastable rare gas atoms (Ne*-Xe*) is investigated. The variational principle is applied to compute the core polarization potential and thereby obtain dipole polarizabilities of the alkali and rare gas ions. The calculated potential is considerably deeper inside the atomic

I. D. Petrov; V. L. Sukhorukov; H. Hotop

1999-01-01

145

Fundamental Processes in A general definition of a plasma is: plasma is an ionized gas or other medium  

E-print Network

is an ionized gas or other medium in which charged particle interactions are predominantly collective. In contrast, in a plasma the charged particles interact simultaneously and hence collectively with many other by the collective but weak interactions between large numbers of nearby charged particles in it. Charged particles

Callen, James D.

146

Development of a Multiscale Ionized Gas (MIG) Flow Code for Plasma Applications Subrata Roy Datta V. Gaitonde  

E-print Network

Development of a Multiscale Ionized Gas (MIG) Flow Code for Plasma Applications Subrata Roy Datta V Engineering Aeronautical Sciences Division Kettering University Air Vehicles Directorate Flint, Michigan 48504 applications including space propulsion thrusters and high-speed air vehicles. These are of considerable

Roy, Subrata

147

Determination of BROMATE AT PARTS-PER-TRILLION LEVELS BY GAS CHROMATOGRAPHY-MASS SPECTROMETRY WITH NEGATIVE CHEMICAL IONIZATION  

EPA Science Inventory

The ozonation of bromide-containing source waters produces bromate as a class 2B carcinogenic disinfection by-product. The present work describes the determination of bromate by gas chromatography-negative chemical ionization mass spectrometry (GC-NCIMS) following a bromate react...

148

Diffuse Ionized Gas in the Magellanic System: Early Results from WHAM-South  

NASA Astrophysics Data System (ADS)

From its new vantage point at CTIO, the Wisconsin H? Mapper is poised to explore the full distribution and kinematics of diffuse plasma in extended gaseous structures near the Magellanic Clouds. Shaped by the interaction between the Clouds and the Milky Way, the Bridge, Stream, and Leading Arm gas complexes have been studied extensively in 21 cm emission and optical/UV absorption. With spectral resolution of 12 km/s, WHAM is able to separate optical emission from these structures and brighter local gas near vLSR 0 km/s. Combined with its unprecedented sensitivity to the limit of atmospheric line confusion ( 10s of mR), we are embarking on a survey of the ionized component of the Magellanic System with WHAM. With observations of the southern component of our all-sky survey nearly completed, we have begun to examine some emission features toward the Magellanic System. Here we present a sample of several regions observed recently with WHAM in H?. WHAM was built and continues to operate with ongoing support from NSF. The research presented here is currently funded by award AST-0607512 and an International Program Development Fund from the University of Sydney.

Haffner, L. Matthew; Madsen, G. J.

2011-01-01

149

The Properties and the Evolution of the Highly Ionized Gas in MR 2251-178  

NASA Technical Reports Server (NTRS)

We present the first XMM-Newton observations of the radio-quiet quasar MR 2251-178 obtained in 2000 and 2002. The EPIC-pn spectra show a power-law continuum with a slope of Gamma = 1.6 at high energies absorbed by at least two warm absorbers (WAs) intrinsic to the source. The underlying continuum in the earlier observation shows a soft excess at low X-ray energies which can be modeled as an additional power-law with Gamma = 2.9. The spectra also show a weak narrow iron K alpha emission line. The high-resolution grating spectrum obtained in 2002 shows emission lines from N VI, O VII, O VIII, Ne IX, and Ne X, as well as absorption lines from the low-ionization ions of O III, O IV, and O V, and other confirmed and suspected weaker absorption lines. The O III - O V lines are consistent with the properties of the emission line gas observed as extended optical (O III) emission in this source. The signal-to-noise of the 2000 grating data is too low to detect any lines. We suggest a model for the high-resolution spectrum which consist of two or three warm-absorber (WA) components. The two-components model has a high-ionization WA with a column density of 10(exp 21.5)-10 (exp 21.8) sq cm and a low-ionization absorber with a column density of 10(exp 20.3) sq cm. In the three-components model we add a lower ionization component that produces the observed iron M-shell absorption lines. We investigate the spectral variations in MR 2251-178 over a period of 8.5 years using data from ASCA, BeppoSAX, and XMM-Newton. All X-ray observations can be fitted with the above two power laws and the two absorbers. The observed luminosity variations seems to correlate with variations in the soft X-ray continuum. The 8.5 year history of the source suggests a changing X-ray absorber due to material that enters and disappears from the line-of-sight on timescales of several months. We also present, for the first time, the entire FUSE spectrum of MR 2251-178. We detect emission from N III, C III, and O VI and at least 4 absorption systems in C III, H I, and O VI, one at -580 km/s and at least 3 others which are blended together and form a wide trough covering the velocity range of 0 to -500 km/s. The general characteristics of the UV and X-ray absorbers are consistent with an origin in the same gas.

Kaspi, Shai; Netzer, hagai; Chelouche, Doron; George, Ian M.; Nandra, Kirpal; Turner, T. J.

2004-01-01

150

Very metal-poor galaxies: ionized gas kinematics in nine objects  

NASA Astrophysics Data System (ADS)

The study of ionized gas morphology and kinematics in nine extremely metal-deficient (XMD) galaxies with the scanning Fabry-Perot interferometer on the Special Astrophysical Observatory (SAO) 6-m telescope is presented. Some of these very rare objects (with currently known range of O/H of 7.12 < 12 + log(O/H) < 7.65, or ) are believed to be the best proxies of `young' low-mass galaxies in the high-redshift Universe. One of the main goals of this study is to look for possible evidence of star formation (SF) activity induced by external perturbations. Recent results from HI mapping of a small subsample of XMD star-forming galaxies provided confident evidence for the important role of interaction-induced SF. Our observations provide complementary or new information that the great majority of the studied XMD dwarfs have strongly disturbed gas morphology and kinematics or the presence of detached components. We approximate the observed velocity fields by simple models of a rotating tilted thin disc, which allows us the robust detection of non-circular gas motions. These data, in turn, indicate the important role of current/recent interactions and mergers in the observed enhanced SF. As a by-product of our observations, we obtained data for two Low Surface Brightness (LSB) dwarf galaxies: Anon J012544+075957 that is a companion of the merger system UGC 993, and SAO 0822+3545 which shows off-centre, asymmetric, low star formation rate star-forming regions, likely induced by the interaction with the companion XMD dwarf HS 0822+3542. Based on observations obtained with the Special Astrophysical Observatory RAS 6-m telescope. E-mail: moisav@gmail.com (AVM); sap@sao.ru (SAP); akniazev@saao.ac.za (AYK)

Moiseev, A. V.; Pustilnik, S. A.; Kniazev, A. Y.

2010-07-01

151

Particle velocity distributions and ionization processes in a gas-puff Z pinch  

Microsoft Academic Search

We have measured the time-dependent radial velocity distributions of singly to five times ionized ions in an imploding plasma shell by observing the spectral shapes and intensities of emission lines in various directions. An ionization wave propagating much faster than the local radial ion velocities is observed. The ionization front velocity is found to be consistent with estimates of electron

M. E. Foord; Y. Maron; G. Davara; L. Gregorian; A. Fisher

1994-01-01

152

Analysis of hydroxy fatty acids as pentafluorobenzyl ester, trimethylsilyl ether derivatives by electron ionization gas chromatography\\/mass spectrometry  

Microsoft Academic Search

Electron ionization (EI) gas chromatography\\/mass spectrometry (GC\\/MS) analysis of pentafluorobenzyl ester-trimethyl sllyl\\u000a ether (PFB-TMS) derivatives of hydroxy-subshtuted fatty acids provides structural information comparable to that obtained\\u000a in analysis of methyl ester-trimethyl silyl ether (Me-TMS) derivatives. Use of this derivative eliminates the need to prepare\\u000a two separate derivatives, the PFB-TMS derivative for molecular weight determination by electron capture ionization (negative\\u000a ions)

Pat Wheelan; Joseph A. Zirrolli; Robert C. Murphy

1995-01-01

153

Highly ionized gas in the Galactic disk: The l = 295 deg, b,= 0 deg interarm direction  

NASA Technical Reports Server (NTRS)

I present new high-resolution measurements of ultraviolet interstellar absorption lines toward three distant stars in the Galactic disk in the general direction l = 295 deg, b = 0 deg. The high ionization lines of Si IV and C IV toward HD 100276, HD 103779, and HD 104705 show substantial variations on angular scales of less than 1 deg, or about 50-100 pc at the distance of the stars. The Si IV and C IV midplane densities derived for HD 100276 and HD 103779 are N(sub o) (Si IV) approximately = 1.3 x 10(exp -9) cm(exp -3) and n(sub o)(C IV) approximately = 4.5 x 10(exp -9) cvm(exp -3), approximately a factor of 2-3 lower than the Galactic averages. Toward HD 104705, the Si IV midplane density is near the average value, but the C IV midplane density is a factor of 3 higher than average. The integrated C IV and Si IV ratios along the HD 100276 and HD 100379 sight lines are similar to the N(C IV)/N(Si IV) = 3.6 +/- 1.3 ratio for a sample of halo stars. For the HD 104705 sight line, N(C IV)/N(Si IV) = 11 and N(C IV)/N(N V) greater than 10. Turbulent mixing layers provide a possible source for the observed absorption along the three sight lines as does gas associated with cooling flows. If mixing layers are the primary source of the absorption along the disk sight lines, then the entrainment velocity of the hot gas is approximately 100 km/s and the post mixed gas temperature is approximately 2 x 10(exp 5) K; same differences may exist for these mixing layers compared to those inferred for gas toward the Galactic poles. Current models of cooling, hot gas in supernova remnants, and magnetized conduction fronts do not accurately describe the high ion properties toward the disk stars in this study.

Sembach, Kenneth R.

1994-01-01

154

The nature and origin of diffuse ionized gas in the halos of nearby edge-on galaxies  

NASA Astrophysics Data System (ADS)

In an effort to constrain the source of ionization and the nature of the extraplanar diffuse ionized gas (eDIG) in nearby edge-on disk galaxies, a number of innovative observational techniques are used to acquire deep narrow- band images and long-slit spectra of these objects down to unprecedented flux levels (few 10-18 erg s-1 cm 2 arcsec-2). 17 edge-on galaxies were imaged in narrowband H? and H? + [N II] in an effort to statistically analyze the morphology and general characteristics of the eDIG. Although the galaxies in the imaging sample cover a broad range in total H? luminosity, the eDIG H? emission represents a rather constant 10 15% of the total luminosity. A cross-correlation analysis of the intensity of the extraplanar emission with that of the disk emission confirms the existence of a connection between the disk and halo emission in several objects. The second portion of the thesis focuses on the analysis of deep long-slit spectra of 9 previously imaged edge-on galaxies with known eDIG line emission. H?, [N II]?6583, and [S II]?6716 are observed in all 9 galaxies up to |z| = few kpc, and many other lines (such as [O III]?5007, [O I]?6300, and He I ?5876) are observed to lower heights in a majority of them. We find that in 7 out of the 9 objects, a general increase in the [N II]/H? and [S II]/H? line ratios is observed with height, as has been detected previously in other galaxies. Comparing the measured line ratios with a number of ionization models suggests that photoionization by massive OB stars alone is generally inadequate to ionize the halo gas. The best fit to the data is obtained using a combined photoionization/turbulent mixing layer (TML) model. Strong correlations between halo emission and disk H II regions support the theory that OB star associations are the primary source of ionization of the extraplanar gas. TML and shock models suggest that supernovae events play a supporting role as well, in both the ionizing of the gas in the halo and the expulsion of gas into the halo. We measure an average ionized halo mass of around 2.2 × 107 M? (with values ranging from 0.46 × 107 M? to 3.9 × 107 M? among galaxies), and an energy flow rate of 6.3 35 × 10 38 erg s-1 required to expel the gas into the halo in order to maintain the observed ionized halo mass. This is roughly equal to the mechanical energy produced by SNe events. As a result of our analysis, the most likely scenario which explains the observed emission is that photoionized gas is ejected into the halos of galaxies, bypassing the H I layer through pathways cleared by expanding superbubbles (which create galactic chimneys and give the eDIG its filamentary structure). This gas ultimately falls back towards the disk (in an extended, more uniform distribution), along the way cooling and turbulently mixing with rising gas, creating turbulent mixing layers, a source of additional ionization. (Abstract shortened by UMI.)

Miller, Scott Timothy

155

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

Microsoft Academic Search

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

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

2003-01-01

156

IZI: Inferring the Gas Phase Metallicity (Z) and Ionization Parameter (q) of Ionized Nebulae Using Bayesian Statistics  

NASA Astrophysics Data System (ADS)

We present a new method for inferring the metallicity (Z) and ionization parameter (q) of H II regions and star-forming galaxies using strong nebular emission lines (SELs). We use Bayesian inference to derive the joint and marginalized posterior probability density functions for Z and q given a set of observed line fluxes and an input photoionization model. Our approach allows the use of arbitrary sets of SELs and the inclusion of flux upper limits. The method provides a self-consistent way of determining the physical conditions of ionized nebulae that is not tied to the arbitrary choice of a particular SEL diagnostic and uses all the available information. Unlike theoretically calibrated SEL diagnostics, the method is flexible and not tied to a particular photoionization model. We describe our algorithm, validate it against other methods, and present a tool that implements it called IZI. Using a sample of nearby extragalactic H II regions, we assess the performance of commonly used SEL abundance diagnostics. We also use a sample of 22 local H II regions having both direct and recombination line (RL) oxygen abundance measurements in the literature to study discrepancies in the abundance scale between different methods. We find that oxygen abundances derived through Bayesian inference using currently available photoionization models in the literature can be in good (~30%) agreement with RL abundances, although some models perform significantly better than others. We also confirm that abundances measured using the direct method are typically ~0.2 dex lower than both RL and photoionization-model-based abundances.

Blanc, Guillermo A.; Kewley, Lisa; Vogt, Frédéric P. A.; Dopita, Michael A.

2015-01-01

157

Observations of columnal recombination in the ionization tracks of energetic heavy nuclei in an argon-methane gas mixture  

NASA Technical Reports Server (NTRS)

Measurements of ionization signals resulting from the passage of energetic heavy nuclei through a gas mixture consisting of 95 mol percent Ar plus 5 mol percent CH4, at an absolute pressure of 3 atm are presented. The measurements take place under a uniform electric field perpendicular to the ionization track. The signals were compared to the calculated energy losses, with an assumption of proportionality between energy loss rate and ionization rate. Significant deviations from proportionality are found for energy loss rate grater than about 3000 MeV sq cm/g, while fractional deviations are found to be proportional to the energy loss rate (dE/dx) exp m, where m is equal to about two. These results are attributed to the columnal recombination.

Wiedenbeck, Mark E.

1990-01-01

158

Self-injection and acceleration of electrons during ionization of gas atoms by a short laser pulse  

SciTech Connect

Using a relativistic three-dimensional single-particle code, acceleration of electrons created during the ionization of nitrogen and oxygen gas atoms by a laser pulse has been studied. Barrier suppression ionization model has been used to calculate ionization time of the bound electrons. The energy gained by the electrons peaks for an optimum value of laser spot size. The electrons created near the tail do not gain sufficient energy for a long duration laser pulse. The electrons created at the tail of pulse escape before fully interacting with the trailing part of the pulse for a short duration laser pulse, which causes electrons to retain sufficient energy. If a suitable frequency chirp is introduced then energy of the electrons created at the tail of the pulse further increases.

Singh, K.P. [Computational Plasma Dynamics Laboratory, Kettering University, Flint, Michigan 48504 (United States)

2006-04-15

159

Mass spectrometric evaluation of the gas phase structure of noncovalent quadruplex DNA obtained by electrospray ionization  

SciTech Connect

A number of quanine-rich DNA sequences have been recognized which assemble into quadrupole-helical non-Watson/Crick hybridized structures. These sequences have been localized in a number of key regions in chromosomal DNA including telomers and transcriptional promoters. The preservation of this tetrameric association in the gas phase following electrospray ionization (ESI) has been reported in this laboratory. The authors have extended these studies by the preparation of four candidate quadruplex oligomers. Three of these (I, 5{prime}-dCGC GGG GCG-3{prime}; II, 5{prime}dCGC GGGG GCG-3{prime} and III, 5{prime}-dCGC GGGGG GCG-3{prime}) differ in the number of quanine residues available for G-quartet stacking in the quadruplex array and a fourth (HG, 5{prime}-dCGC AGGG GCG03{prime}) is a sequence prominent in human telomeric DNA. During their preparation, the authors observed remarkable stability of the multimeric species in the condensed phase including intact migration in HPLC under apparently {open_quotes}denaturing{close_quotes} conditions. Under standard conditions (aqueous solution of oligonucleotide samples and nozzle-skimmer interface) on a linear quadrupole mass spectrometer oligonucleotide samples showed the typical distribution of charge states for unassociated oligonucleotides. ESI from phosphate-EDTA buffered solutions with the utilization of a capillary/skimmer interface arrangement which provides mild conditions for transfer of ions through the atmosphere/vacuum interface afforded spectra which show prominent contributions from species with quadrupole stoichiometry together monomeric materials.

Edmonds, C.G.; Cheng, Xueheng; Bakhtiar, R.; Van Orden, S.; Smith, R.D. [Pacific Northwest Lab., Richland, WA (United States); Schlegel, C.; Camp, D.G. II [Eastern Oregon State College, LaGrande, OR (United States)

1994-12-31

160

H? and [SII] Emission from Warm Ionized Gas in the Scutum-Centaurus Arm  

NASA Astrophysics Data System (ADS)

We present Wisconsin H-Alpha Mapper [SII] ?6716 and H? spectroscopic maps of the warm ionized medium (WIM) in the Scutum-Centaurus Arm at Galactic longitudes 310° < l < 345°. Using extinction-corrected H? intensities (I_{{H} \\alpha }^c), we measure an exponential scale height of electron density squared in the arm of H_{n_e^2}= 0.30 \\, {kpc} (assuming a distance of 3.5 kpc), intermediate between that observed in the inner Galaxy and in the Perseus Arm. The [S II]/H? line ratio is enhanced at large |z| and in sightlines with faint I_{{H} \\alpha }^c. We find that the [S II]/H? line ratio has a power-law relationship with I_{{H} \\alpha }^c from a value of ?1.0 at I_{{H} \\alpha }^c< 0.2 \\, {R} (Rayleighs) to a value of ?0.08 at I_{{H} \\alpha }^c\\gtrsim 100 \\, {R}. The line ratio is better correlated with H? intensity than with height above the plane, indicating that the physical conditions within the WIM vary systematically with electron density. We argue that the variation of the line ratio with height is a consequence of the decrease of electron density with height. Our results reinforce the well-established picture in which the diffuse H? emission is due primarily to emission from in situ photoionized gas, with scattered light only a minor contributor.

Hill, Alex S.; Benjamin, Robert A.; Haffner, L. Matthew; Gostisha, Martin C.; Barger, Kathleen A.

2014-06-01

161

Negative ion chemical ionization gas chromatography/mass spectrometry of valproic acid metabolites.  

PubMed

A negative ion chemical ionization (NICI) gas chromatographic/mass spectrometric method is described for the identification of 15 valproic acid (VPA) metabolites as their pentafluorobenzyl derivatives. Samples analyzed were serum, urine and saliva taken from a volunteer on VPA at steady state and also given selected doses of (2H6)VPA. Metabolite peaks were identified by comparison to synthetic standards. All the metabolites, like the parent drug, produced abundant [M - 181]- ions, except 3-keto VPA, which gave an [M - 181 - CO2]- ion. Using the NICI method, two new VPA metabolites were identified. One of these metabolites was characterized as 4'-keto-2-ene VPA by synthesis, while the second one appeared to be a positional isomer of 4'-keto-2-ene VPA. The sensitivity of the method was also sufficient to detect metabolites of VPA in saliva. The ratio of the levels of (Z)-2-ene VPA to (E)-2-ene VPA was much greater in saliva than in serum, suggesting stereoselective plasma protein binding or transport of these two metabolites. The lower limit of detection for the quantification of VPA in serum or saliva was 2 ng ml-1. PMID:2508808

Kassahun, K; Burton, R; Abbott, F S

1989-10-01

162

LARGE-SCALE SHOCK-IONIZED AND PHOTOIONIZED GAS IN M83: THE IMPACT OF STAR FORMATION  

SciTech Connect

We investigate the ionization structure of the nebular gas in M83 using the line diagnostic diagram, [O III](5007 A)/H{beta} versus [S II](6716 A+6731 A)/H{alpha}, with the newly available narrowband images from the Wide Field Camera 3 (WFC3) of the Hubble Space Telescope (HST). We produce the diagnostic diagram on a pixel-by-pixel (0.''2 x 0.''2) basis and compare it with several photo- and shock-ionization models. We select four regions from the center to the outer spiral arm and compare them in the diagnostic diagram. For the photoionized gas, we observe a gradual increase of the log ([O III]/H{beta}) ratios from the center to the spiral arm, consistent with the metallicity gradient, as the H II regions go from super-solar abundance to roughly solar abundance from the center out. Using the diagnostic diagram, we separate the photoionized from the shock-ionized component of the gas. We find that the shock-ionized H{alpha} emission ranges from {approx}2% to about 15%-33% of the total, depending on the separation criteria used. An interesting feature in the diagnostic diagram is a horizontal distribution around log ([O III]/H{beta}) {approx} 0. This feature is well fit by a shock-ionization model with 2.0 Z{sub sun} metallicity and shock velocities in the range of 250-350 km s{sup -1}. A low-velocity shock component, <200 km s{sup -1}, is also detected and is spatially located at the boundary between the outer ring and the spiral arm. The low-velocity shock component can be due to (1) supernova remnants located nearby, (2) dynamical interaction between the outer ring and the spiral arm, and (3) abnormal line ratios from extreme local dust extinction. The current data do not enable us to distinguish among those three possible interpretations. Our main conclusion is that, even at the HST resolution, the shocked gas represents a small fraction of the total ionized gas emission at less than 33% of the total. However, it accounts for virtually all of the mechanical energy produced by the central starburst in M83.

Hong, Sungryong; Calzetti, Daniela [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Dopita, Michael A. [Research School of Astronomy and Astrophysics, Australian National University, ACT 2611 (Australia); Blair, William P. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Whitmore, Bradley C.; Bond, Howard E. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Balick, Bruce [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Carollo, Marcella [Department of Physics, ETH-Zurich, Zurich 8093 (Switzerland); Disney, Michael J. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Frogel, Jay A. [Association of Universities for Research in Astronomy, Washington, DC 20005 (United States); Hall, Donald [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Holtzman, Jon A. [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States); Kimble, Randy A. [NASA-Goddard Space Flight Center, Greenbelt, MD 20771 (United States); McCarthy, Patrick J. [Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101-1292 (United States); O'Connell, Robert W. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Paresce, Francesco [Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, Via Gobetti 101, 40129 Bologna (Italy); Saha, Abhijit [National Optical Astronomy Observatories, Tucson, AZ 85726-6732 (United States); Silk, Joseph I. [Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom); Trauger, John T. [NASA-Jet Propulsion Laboratory, Pasadena, CA 91109 (United States); Walker, Alistair R., E-mail: wpb@pha.jhu.edu [Cerro Tololo Inter-American Observatory, La Serena (Chile)

2011-04-10

163

Ionized Gas Kinematics at High Resolution. IV. Star Formation and a Rotating Core in the Medusa (NGC 4194)  

NASA Technical Reports Server (NTRS)

NGC 4194 is a post-merger starburst known as The Medusa for its striking tidal features.We present here a detailed study of the structure and kinematics of ionized gas in the central 0.65 kpc of the Medusa. The data include radio continuum maps with resolution up to 0".18 (35 pc) and a 12.8 micron [Ne II] data cube with spectral resolution approx. 4 km/s: the first high-resolution, extinction-free observations of this remarkable object. The ionized gas has the kinematic signature of a core in solid-body rotation. The starburst has formed a complex of bright compact H II regions, probably excited by deeply embedded super star clusters, but none of these sources is a convincing candidate for a Galactic nucleus. The nuclei of the merger partners that created the Medusa have not yet been identified.

Beck, Sara C.; Lacy, John; Neff, Susan Gale; Turner, Jean; Greathouse, Thomas; Neff, Susan

2014-01-01

164

Method for the separate determination of electron density and negative-ion density in a dense ionized gas  

Microsoft Academic Search

A method for the separate determination of electron density and negative-ion density in a dense gas ionized by alpha particles from a radioisotope is experimentally demonstrated. The method is based on the use of a high-frequency electronic filter which crosses at the anode the nonself-sustained Thomson discharge column. The HF filter consists of thin parallel wires between which an ac-field

M. A. Kanatenko

1981-01-01

165

Effect of hydrogen impurity on the electrical characteristics of neon-argon gas mixtures. I. Measurement of ionization coefficients  

Microsoft Academic Search

The effect of H2 on the breakdown potential and Townsend ionization coefficients for Ne-A mixtures were measured by the luminous-flux method. Both argon and hydrogen form Penning mixtures with neon. The breakdown potentials for Ne-A gas mixtures are determined by the Penning reaction, Nem+A?Ne+e+A+, between metastable neon (Nem) and ground state A atoms. At low H2 concentrations (<0.1%) the breakdown

A. K. Bhattacharya

1983-01-01

166

STARS AND IONIZED GAS IN THE S0 GALAXY NGC 7743: AN INCLINED LARGE-SCALE GASEOUS DISK  

SciTech Connect

We used deep, long-slit spectra and integral-field spectral data to study the stars, ionized gas kinematics, and stellar population properties in the lenticular barred galaxy NGC 7743. We show that ionized gas at distances larger than 1.5 kpc from the nucleus settles in the disk, which is significantly inclined toward the stellar disk of the galaxy. Making different assumptions about the geometry of the disks and including different sets of emission lines in the fitting, under the assumption of thin, flat-disk circular rotation, we obtain the full possible range of angles between the disks to be 34{sup 0} {+-} 9{sup 0} or 77{sup 0} {+-} 9{sup 0}. The most probable origin of the inclined disk is the external gas accretion from a satellite orbiting the host galaxy, with a corresponding angular momentum direction. The published data on the H I distribution around NGC 7743 suggest that the galaxy has a gas-rich environment. The emission-line ratio diagrams imply the domination of shock waves in the ionization state of the gaseous disk, whereas the contribution of photoionization from recent star formation seems to be negligible. In some parts of the disk, a difference between the velocities of the gas emitting from the forbidden lines and Balmer lines is detected. This may be caused by the mainly shock-excited inclined disk, whereas some fraction of the Balmer-line emission is produced by a small amount of gas excited by young stars in the main stellar disk of NGC 7743. In the circumnuclear region (R < 200 pc), some evidence of the active galactic nucleus jet's interaction with an ambient interstellar medium was found.

Katkov, Ivan Yu.; Sil'chenko, Olga K. [Sternberg Astronomical Institute, Moscow 119992 (Russian Federation); Moiseev, Alexei V., E-mail: katkov.ivan@gmail.com, E-mail: moisav@gmail.com, E-mail: olga@sai.msu.su [Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnii Arkhyz, Karachaevo-Cherkesskaya Republic 369167 (Russian Federation)

2011-10-20

167

Techniques for the measurement of ionization times in ECR ion sources using a fast sputter sample and fast gas valve  

NASA Astrophysics Data System (ADS)

Two techniques for the discrete injection of material into an Electron Cyclotron Resonance ion source (ECRIS) have been developed for the purpose of measuring the ionization and confinement times of ion species. Previously only solid materials in conjunction with a pulsed laser were used in these studies due to the discrete material introduction produced by this configuration. The first method replaces the pulsed laser with a fast high voltage pulse applied to a sputter sample. The high voltage pulse has a rise time of 100 ns, fall time of 80.0 ?s, and variable pulse duration. The second method utilizes a fast-pulsed gas valve capable of producing a gas pulse 160 ?s in width. These pulse widths are well below the ionization times of the lower charge states and thus allows for time measurements to be made of all charge states. Both of these techniques can be employed to study the effects of rf power, coil configuration, biased disk, and gas mixing on ionization and confinement times. Rise times for neon, argon, and gold will be presented.

Vondrasek, R. C.; Scott, R. H.; Pardo, R. C.; Edgell, D.

2002-02-01

168

Characteristics of A-150 plastic equivalent gas in A-150 plastic ionization chambers for p(66)Be(49) neutrons  

SciTech Connect

The average energy necessary to produce an electron-ion pair (anti W) of a gas mixture having an atomic composition very close to that of A-150 plastic has been studied through use in different size ionization chambers made of that plastic in a p(66)Be(49) neutron therapy beam. A tentative value for anti W(A-150-gas) of 27.3 +/ -0.5 J C/sup -1/ was derived. The anti W value of the A-150 equivalent gas mixture is compared to those of methane-based tissue-equivalent gas and of air for the p(66)Be(49) neutron beam as well as to corresponding values found in similar experiments using 14.8 MeV monoenergetic neutrons.

Awschalom, M.; Rosenberg, I.; Ten Haken, R.K.; Pearson, D.W.; DeLuca, P.M. Jr.; Attix, F.H.

1982-01-01

169

Ionization of the diffuse gas in galaxies: Hot low-mass evolved stars at work  

Microsoft Academic Search

The Diffuse Ionized Medium (DIG) is visible through its faint optical line emission outside classical HII regions (Reynolds 1971) and turns out to be a major component of the interstellar medium in galaxies. OB stars in galaxies likely represent the main source of ionizing photons for the DIG. However, an additional source is needed to explain the increase of [NII]\\/Halpha,

N. Flores-Fajardo; C. Morisset; G. Stasinska; L. Binette

2011-01-01

170

Anomalous laser-induced ionization rates of molecules and rare-gas atoms  

NASA Astrophysics Data System (ADS)

Electron tunnel ionization is considered as the mechanism for producing free electrons in gases under laser radiation. The Keldysh result and the Ammosov-Delone-Krainov (ADK) formulation are amended by considering the excess forces due to the interaction of the electric field of the laser with the electron cloud in a simple mass-on-a-spring approximation. The result of this excess force is a kinetic energy that is directed along the polarization vector of the laser field and an induced potential energy that are proposed as a determining factor in electron tunnel ionization. Relative ionization rates for various pairs of gases are calculated and compared with reported figures. Comparisons were made between several combinations of O2 , Xe, Ar, N2 , Cl2 , H2 , CO, Kr, NO, F2 , and D2 . Predicted ratios of ionization rates between pairs of gases are compared to ADK predictions. Apparently anomalous ionization rates of O2 , D2 , and H2 are explained. A simple expression is developed that reveals why the ionization rate of Xe is about an order of magnitude larger than that of O2 even though their ionization potentials are nearly identical; why CO is only about half that of Kr even though their ionization potentials are nearly the same; why the ratio of O2 to O is about ten times larger than predicted by ADK; and why the ratio of NO to Xe is about an order of magnitude less than predicted by ADK.

Bettis, Jerry Ray

2009-12-01

171

A mobile mass spectrometer for comprehensive on-line analysis of trace and bulk components of complex gas mixtures: parallel application of the laser-based ionization methods VUV single-photon ionization, resonant multiphoton ionization, and laser-induced electron impact ionization.  

PubMed

A newly developed compact and mobile time-of-flight mass spectrometer (TOFMS) for on-line analysis and monitoring of complex gas mixtures is presented. The instrument is designed for a (quasi-)simultaneous application of three ionization techniques that exhibit different ionization selectivities. The highly selective resonance-enhanced multiphoton ionization (REMPI) technique, using 266-nm UV laser pulses, is applied for selective and fragmentationless ionization of aromatic compounds at trace levels (parts-per-billion volume range). Mass spectra obtained using this technique show the chemical signature solely of monocyclic (benzene, phenols, etc.) and polycyclic (naphthalene, phenathrene, indol, etc.) aromatic species. Furthermore, the less selective but still fragmentationless single photon ionization (SPI) technique with 118-nm VUV laser pulses allows the ionization of compounds with an ionization potential below 10.5 eV. Mass spectra obtained using this technique show the profile of most organic compounds (aliphatic and aromatic species, like nonane, acetaldehyde, or pyrrol) and some inorganic compounds (e.g., ammonia, nitrogen monoxide). Finally, the nonselective ionization technique laser-induced electron-impact ionization (LEI) is applied. However, the sensitivity of the LEI technique is adjusted to be fairly low. Thus, the LEI signal in the mass spectra gives information on the inorganic bulk constituents of the sample (i.e., compounds such as water, oxygen, nitrogen, and carbon dioxide). Because the three ionization methods (REMPI, SPI, LEI) exhibit largely different ionization selectivities, the isolated application of each method alone solely provides specific mass spectrometric information about the sample composition. Special techniques have been developed and applied which allow the quasi-parallel use of all three ionization techniques for on-line monitoring purposes. Thus, a comprehensive characterization of complex samples is feasible jointly using the characteristic advantages of the three ionization techniques. Laboratory applications show results on rapid overview characterization of mineral oil-based fuels and coffee headspace. The first reported field applications include timely resolved on-line monitoring results on automobile exhausts and of waste incineration flue gas. PMID:11510823

Mühlberger, F; Zimmermann, R; Kettrup, A

2001-08-01

172

Internally heated membrane interfaced to a gas chromatography flame ionization detector.  

PubMed

Volatile Organic Compounds (VOCs) mixtures in aqueous solutions have been investigated using a simple and efficient all-in-one on-line sampling, isolation, enrichment and pre-concentration internally heated membrane connected to a gas chromatography flame ionization detector (GC-FID). In our previous study with the internally heated membrane, no GC column was used in the instrument. In this new study, we introduce a GC column in the instrument design and this makes it possible for mixtures to be investigated. This new experimental design enabled high resolution separation of analyte mixtures capable of being adsorbed, diffused, and desorbed from the device for detection with an FID. With the new design we present data from investigation of competitive adsorption effects on the membrane. The data showed that analyte adsorption and diffusion onto the membrane can be affected when mixtures of analytes are introduced. The application of multiple linear regressions approach to the data enabled us to correct for the problem of competitive adsorption. Analyte adsorption and diffusion was affected by the diffusion coefficients of the analytes; the higher the diffusion coefficient the better the extraction from the membrane. Increasing the sampling time from 1 to 4 min increases the response by 77%. The sampling time responses were linear up to 4 min sampling time. Above 4 min sampling time, the data deviate from linearity. The effect of adding salt to standards has no effect on analyte absorption onto the membrane. The detection limits for key VOCs studied with an internal standard calibration ranged from 0.2 to 194 ng cm(-3). PMID:23622547

Kanu, A Bakarr; Thomas, C L P

2013-07-15

173

Ionized Gas in Damped Lyman Alpha Protogalaxies: I. Model-Independent Inferences From Kinematic Data  

E-print Network

We investigate the kinematics of ionized and neutral gas in a sample of 35 damped Lyman alpha protogalaxies (DLAs) with HIRES on the Keck I 10 m telescope. Velocity profiles with resolution of ~ 8 km/s are obtained for high ions such as C IV and Si IV, and for intermediate ions such as Al III. Combining these profiles with accurate low-ion (e.g., Fe II) profiles, we investigate the kinematic state of DLAs in the redshift range 1.8 < z < 4.4 by comparisons between data for various ion pairs. We find the DLAs comprise distinct kinematic subsystems: a low ion subsystem in which the low ions are physically associated with intermediate ions, and a high subsystem containing neither low nor intermediate ions. The evidence for two subsystems stems from (a) differences between the widths of the velocity profiles, (b) misalignment in velocity space between the narrow components comprising the profiles in each subsystem, and (c) significant dissimilarities between the mean velocities of the high ion and low ion velocity profiles. In every case we find that test statistics such as velocity width and various asymmetry parameters distribute differently for low ions than for high ions. Despite misalignment in velocity space, the low and high ion kinematic subsystems are interrelated. This is indicated by detection of a statistically significant C IV versus low-ion cross correlation function, and by a systematic effect where the C IV velocity widths are greater than or equal to the low ion velocity widths in 29 out of 32 systems. These phenomena are consistent with the location of the two subsystems in the same potential well.

Arthur M. Wolfe; Jason X. Prochaska

2000-09-07

174

SIGGMA: A SURVEY OF IONIZED GAS IN THE GALAXY, MADE WITH THE ARECIBO TELESCOPE  

SciTech Connect

A Survey of Ionized Gas in the Galaxy, made with the Arecibo telescope (SIGGMA), uses the Arecibo L-band Feed Array (ALFA) to fully sample the Galactic plane (30 Degree-Sign {<=} l {<=} 75 Degree-Sign and -2 Degree-Sign {<=} b {<=} 2 Degree-Sign ; 175 Degree-Sign {<=} l {<=} 207 Degree-Sign and -2 Degree-Sign {<=} b {<=} 1 Degree-Sign ) observable with the telescope in radio recombination lines (RRLs). Processed data sets are being produced in the form of data cubes of 2 Degree-Sign (along l) Multiplication-Sign 4 Degree-Sign (along b) Multiplication-Sign 151 (number of channels), archived and made public. The 151 channels cover a velocity range of 600 km s{sup -1} and the velocity resolution of the survey changes from 4.2 km s{sup -1} to 5.1 km s{sup -1} from the lowest frequency channel to the highest frequency channel. RRL maps with 3.'4 resolution and a line flux density sensitivity of {approx}0.5 mJy will enable us to identify new H II regions, measure their electron temperatures, study the physics of photodissociation regions with carbon RRLs, and investigate the origin of the extended low-density medium. Twelve Hn{alpha} lines fall within the 300 MHz bandpass of ALFA; they are resampled to a common velocity resolution to improve the signal-to-noise ratio (S/N) by a factor of three or more and preserve the line width. SIGGMA will produce the most sensitive fully sampled RRL survey to date. Here, we discuss the observing and data reduction techniques in detail. A test observation toward the H II region complex S255/S257 has detected Hn{alpha} and Cn{alpha} lines with S/N > 10.

Liu, B. [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); McIntyre, T. [University of New Mexico, Albuquerque, NM 87131 (United States); Terzian, Y. [Cornell University, Ithaca, NY 14853 (United States); Minchin, R. [Arecibo Observatory, HC03 Box 53995, Arecibo 00612, PR (United States); Anderson, L. [West Virginia University, Morgantown, WV 26506 (United States); Churchwell, E. [University of Wisconsin-Madison, Madison, WI 53706 (United States); Lebron, M. [University of Puerto Rico, P.O. Box 23323, 00931-3323, San Juan (Puerto Rico); Roshi, D. Anish [National Radio Astronomy Observatory, Green Bank and Charlottesville, VA 22903 (United States)

2013-10-01

175

Discovery of Nine Extended Ionized Gas Clouds in a z = 0.4 Cluster  

NASA Astrophysics Data System (ADS)

From deep H? imaging data of Suprime-Cam/Subaru, we discovered nine extended ionized gas clouds (EIG) around galaxies in the Abell 851 cluster (A851) at z = 0.4. We surveyed a 30 × 25 arcmin region, and the EIGs were found only near the cluster center (\\lt 2.3 arcmin ˜ 750 kpc). The parent galaxies of the EIGs are star-forming or post-starburst galaxies, all of which are spectroscopically confirmed members of the cluster. Four out of the nine parent galaxies show distortion of stellar distribution in the disk, which can be a sign of recent interaction, and the interaction may have made the EIGs. On the other hand, six parent galaxies (one overlaps those exhibiting distortion) show H? emission without stars, which implies ram pressure stripping. The spectrum of the brightest parent galaxy shows a post-starburst signature and resembles the H? stripped galaxies found in the Coma cluster. Meanwhile, two brightest parent galaxies in A851 are more massive than the EIG parent galaxies in the Coma cluster. This is consistent with a “downsizing” of star-forming galaxies, though it is still within the statistical variance. We also analyzed Suprime-Cam data of another z=0.39 cluster, CL0024+17, but found no EIGs. The key difference between A851 and CL0024+17 would be the existence of a subcluster colliding with the main body of A851, in which six or seven out of the nine parent galaxies in A851 exist, and the fraction of EIGs in the subcluster is significantly higher than the main subcluster of A851 and CL0024+17.

Yagi, Masafumi; Gu, Liyi; Koyama, Yusei; Nakata, Fumiaki; Kodama, Tadayuki; Hattori, Takashi; Yoshida, Michitoshi

2015-02-01

176

TIME-VARYING FLAME IONIZATION SENSING APPLIED TO NATURAL GAS AND PROPANE BLENDS IN A PRESSURIZED LEAN PREMIXED (LPM) COMBUSTOR  

SciTech Connect

In-situ monitoring of combustion phenomena is a critical need for optimal operation and control of advanced gas turbine combustion systems. The concept described in this paper is based on naturally occurring flame ionization processes that accompany the combustion of hydrocarbon fuels. Previous work has shown that flame ionization techniques may be applied to detect flashback, lean blowout, and some aspects of thermo-acoustic combustion instabilities. Previous work has focused on application of DC electric fields. By application of time-varying electric fields, significant improvements to sensor capabilities have been observed. These data have been collected in a lean premixed combustion test rig operating at 0.51-0.76 MPa (5-7.5 atm) with air preheated to 588 K (600°F). Five percent of the total fuel flow is injected through the centerbody tip as a diffusion pilot. The fuel composition is varied independently by blending approximately 5% (volume) propane with the pipeline natural gas. The reference velocity through the premixing annulus is kept constant for all conditions at a nominal value of 70 m/s. The fuel-air equivalence ratio is varied independently from 0.46 – 0.58. Relative to the DC field version, the time-varying combustion control and diagnostic sensor (TV-CCADS) shows a significant improvement in the correlation between the measured flame ionization current and local fuel-air equivalence ratio. In testing with different fuel compositions, the triangle wave data show the most distinct change in flame ionization current in response to an increase in propane content. Continued development of this sensor technology will improve the capability to control advanced gas turbine combustion systems, and help address issues associated with variations in fuel supplies.

D. L. Straub; B. T. Chorpening; E. D. Huckaby; J. D. Thornton; W. L. Fincham

2008-06-13

177

HII region G46.5-0.2: the interplay between ionizing radiation, molecular gas and star formation  

E-print Network

HII regions are particularly interesting because they can generate dense layers of gas and dust, elongated columns or pillars of gas pointing towards the ionizing sources, and cometary globules of dense gas, where triggered star formation can occur. Understanding the interplay between the ionizing radiation and the dense surrounding gas is very important to explain the origin of these peculiar structures, and hence to characterize triggered star formation. G46.5-0.2 (G46), a poorly studied galactic HII region located at about 4 kpc, is an excellent target to perform this kind of studies. Using public molecular data extracted from the Galactic Ring Survey (13CO J=1-0) and from the James Clerk Maxwell Telescope data archive (12CO, 13CO, C18O J=3-2, HCO+ and HCN J=4-3), and infrared data from the GLIMPSE and MIPSGAL surveys, we perform a complete study of G46, its molecular environment and the young stellar objects placed around it. We found that G46, probably excited by an O7V star, is located close to the edge...

Paron, S; Dubner, G; Yuan, Jing-Hua; Petriella, A; Giacani, E; Li, Jin Zeng; Wu, Yuefang; Liu, Hongli; Huang, Ya Fang; Zhang, Si-Ju

2015-01-01

178

An Ultra-Trace Analysis Technique for SF6 Using Gas Chromatography with Negative Ion Chemical Ionization Mass Spectrometry.  

PubMed

Sulfur hexafluoride (SF6) is widely used as a tracer gas because of its detectability at low concentrations. This attribute of SF6 allows the quantification of both small-scale flows, such as leakage, and large-scale flows, such as atmospheric currents. SF6's high detection sensitivity also facilitates greater usage efficiency and lower operating cost for tracer deployments by reducing quantity requirements. The detectability of SF6 is produced by its high molecular electronegativity. This property provides a high potential for negative ion formation through electron capture thus naturally translating to selective detection using negative ion chemical ionization mass spectrometry (NCI-MS). This paper investigates the potential of using gas chromatography (GC) with NCI-MS for the detection of SF6. The experimental parameters for an ultra-trace SF6 detection method utilizing minimal customizations of the analytical instrument are detailed. A method for the detection of parts per trillion (ppt) level concentrations of SF6 for the purpose of underground ventilation tracer gas analysis was successfully developed in this study. The method utilized a Shimadzu gas chromatography with negative ion chemical ionization mass spectrometry system equipped with an Agilent J&W HP-porous layer open tubular column coated with an alumina oxide (Al2O3) S column. The method detection limit (MDL) analysis as defined by the Environmental Protection Agency of the tracer data showed the method MDL to be 5.2 ppt. PMID:25452581

Jong, Edmund C; Macek, Paul V; Perera, Inoka E; Luxbacher, Kray D; McNair, Harold M

2014-12-01

179

Resonant Absorption in the Active Galactic Nucleus Spectra Emerging from Photoionized Gas: Differences between Steep and Flat Ionizing Continua  

NASA Astrophysics Data System (ADS)

We present photoionization models accounting for both photoelectric and resonant absorption. Resonance absorption lines from C, O, Ne, Mg, Si, S, and Fe between 0.1 and 10 keV are treated. In particular we consider the complex of almost 60 strong Fe L absorption lines around 1 keV. We calculate profiles, intensities, and equivalent widths of each line, considering both Doppler and natural broadening mechanisms. Doppler broadening includes a term accounting for turbulence of the gas along the line of sight. We computed spectra transmitted by gas illuminated by drastically different ionizing continua and compared them to spectra observed in flat X-ray spectrum, broad optical emission-line type 1 active galactic nuclei (AGNs), and steep X-ray spectrum, narrow optical emission-line type 1 AGNs. We show that the ~1 keV absorption feature observed in moderate-resolution X-ray spectra of several narrow-line Seyfert 1 galaxies can be explained by photoionization models, taking into account resonance absorption, without requiring relativistic outflowing velocities of the gas, if the physical properties of these absorbers are close to those found in flat X-ray spectrum Seyfert 1 galaxies. We finally present simulations of the spectra emerging from gas illuminated by both steep and flat ionizing continua, as seen by the AXAF high-energy transmission gratings and the baseline Constellation-X calorimeter. We discuss briefly the relevant physics that can be investigated with these instruments.

Nicastro, Fabrizio; Fiore, Fabrizio; Matt, Giorgio

1999-05-01

180

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

PubMed

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

Colina; Arribas; Borne; Monreal

2000-04-10

181

Anomalous laser-induced ionization rates of molecules and rare-gas atoms  

SciTech Connect

Electron tunnel ionization is considered as the mechanism for producing free electrons in gases under laser radiation. The Keldysh result and the Ammosov-Delone-Krainov (ADK) formulation are amended by considering the excess forces due to the interaction of the electric field of the laser with the electron cloud in a simple mass-on-a-spring approximation. The result of this excess force is a kinetic energy that is directed along the polarization vector of the laser field and an induced potential energy that are proposed as a determining factor in electron tunnel ionization. Relative ionization rates for various pairs of gases are calculated and compared with reported figures. Comparisons were made between several combinations of O{sub 2}, Xe, Ar, N{sub 2}, Cl{sub 2}, H{sub 2}, CO, Kr, NO, F{sub 2}, and D{sub 2}. Predicted ratios of ionization rates between pairs of gases are compared to ADK predictions. Apparently anomalous ionization rates of O{sub 2}, D{sub 2}, and H{sub 2} are explained. A simple expression is developed that reveals why the ionization rate of Xe is about an order of magnitude larger than that of O{sub 2} even though their ionization potentials are nearly identical; why CO is only about half that of Kr even though their ionization potentials are nearly the same; why the ratio of O{sub 2} to O is about ten times larger than predicted by ADK; and why the ratio of NO to Xe is about an order of magnitude less than predicted by ADK.

Bettis, Jerry Ray [5701 Woodlake Drive, Stillwater, Oklahoma 74074 (United States)

2009-12-15

182

The 3.3MICRON Feature H\\/2 and Ionized Gas in the Orion Bar  

Microsoft Academic Search

The results of spectroscopy of the 3.3 micron feature, H2 emission, P-alpha, and Br-alpha, obtained along a line perpendicular to the Orion ionization front, are presented. The intensity of the 3.3 micron feature reaches a maximum between the ionization front and the H2 peak. The 3.33 micron spatial distribution appears to be due to destruction of the emitting material within

K. Sellgren; A. T. Tokunaga; Y. Nakada

1990-01-01

183

A novel method of measuring the delay between pre-ionizing and main discharges in TE gas lasers  

NASA Astrophysics Data System (ADS)

A simple and reliable method of measurement of the very short delay (tens of nanoseconds) between the pre-ionizing and main discharge currents in a TEA CO2 laser operated in the spiker sustainer configuration has been demonstrated. In this method light emitted from the pre-ionizing spark and the main discharge are first collected separately using optical fibres and then the delay between the onsets of their emission is measured with the help of simple opto-electronic circuits. This method is noise free, since it does not involve measurement of large pulse currents, and can be useful for the measurement of similar delays in the operation of other TE gas lasers.

Kumar, Aniruddha; Bhatt, R. B.; Biswas, D. J.; Banerjee, N. S.; Mokhriwale, A.; Nundy, U.

2001-10-01

184

Warm and Diffuse Gas and High Ionization Rate Near the Galactic Center  

NASA Astrophysics Data System (ADS)

Using 12 newly found bright dust-embedded stars distributed from 140 pc West to 120 pc East of Sgr A*, we have observed spectra of H_3^+ and CO in the Central Molecular Zone of the Galactic center. Sightlines toward the 12 stars have been observed at the Gemini South Observatory on Cerro Pachon, Chile, and those for 2 of the stars at the Subaru Telescope on Mauna Kea Hawaii. This has extended our previous longitudinal coverage by a factor of 7. Although complete coverage of various transitions have yet to be made for some stars, almost all sightlines showed high total column densities of H_3^+ and highly populated (J, K) = (3, 3) metastable level, demonstrating the prevalence of the warm and diffuse gas previously observed from the center to 30 pc East and high ionization rate in the environment. A few sightlines did not show strong H_3^+ absorptions. It remains to be seen whether this is due to the radial and transverse location of the stars or lack of H_3^+. While the velocity profiles of H_3^+ toward stars from the center to 30 pc East are similar apart from subtle variations, the velocity profiles of the wider regions vary greatly ^a. A remarkable similarity has been noted between the velocity profile of H_3^+ toward a star nicknamed Iota and those of H_2O^+ and 13CH^+ observed toward Sgr B2 by the HIFI instrument of the Herschel Space Observatory. Although all these ions exist in diffuse environment, this is surprising since H_3^+ favors environments with high H_2 fraction f(H_2) while H_2O^+ and CH^+ favors low f(H_2). Also the peak of Sgr B2 and Iota are separated by 17 pc. Possible interpretations of this will be discussed. T. R. Geballe and T. Oka, ApJ, 709, L70 (2010). M. Goto, T. Usuda, T. R. Geballe, N. Indriolo, B. J. McCall, Th. Henning, and T. Oka, PASJ (2011) in press. P. Schilke, et al., A&A, 521, L11 (2010). E. Falgarone, private communication

Oka, T.; Morong, C. P.; Geballe, T. R.; Indriolo, N.; McCall, B. J.; Goto, M.; Usuda, T.

2011-06-01

185

Ultraviolet interstellar absorption toward stars in the Small Magellanic Cloud. IV - Highly ionized gas associated with the Small Magellanic Cloud  

NASA Technical Reports Server (NTRS)

High-dispersion International Ultraviolet Explorer satellite spectra of seven stars in the Small Magellanic Cloud (SMC) are examined to study the properties of interstellar C IV and Si IV absorption in the SMC. Absorption by C IV or Si IV or both is found near 160 km/s for all the stars. The velocity and the relative C IV and Si IV strengths suggest UV-photoionized nebular gas as the origin of this absorption. In addition, the stars show absorption by C IV and, sometimes, Si IV in the velocity range 100-130 km/s. This velocity is 30-60 km/s more negative than that expected for normal nebular gas, and the relative C IV and Si IV strengths indicate an ionization source other than stellar UV photoionization by normal Population I stars. Possible global origins are considered for this absorption, including a hot phase of the SMC interstellar medium and a circum-SMC distribution of highly ionized gas. The only detection of interstellar N V toward a SMC star is for HD 5980. The line is broad, possibly complex, and spans the velocity range of the nebular absorption and the 100-130 km/s absorption.

Fitzpatrick, E. L.; Savage, B. D.

1985-01-01

186

The ionized gas in the central region of NGC 5253. 2D mapping of the physical and chemical properties  

NASA Astrophysics Data System (ADS)

Context. Blue compact dwarf (BCD) galaxies constitute the ideal laboratories to test the interplay between massive star formation and the surrounding gas. As one of the nearest BCD galaxies, NGC 5253 was previously studied with the aim to elucidate in detail the starburst interaction processes. Some open issues regarding the properties of its ionized gas still remain to be addressed. Aims: The 2D structure of the main physical and chemical properties of the ionized gas in the core of NGC 5253 has been studied. Methods: Optical integral field spectroscopy (IFS) data has been obtained with FLAMES Argus and lower resolution gratings of the Giraffe spectrograph. Results: We derived 2D maps for different tracers of electron density (ne), electron temperature (Te) and ionization degree. The maps for ne as traced by [O ii], [S ii], [Fe iii], and [Ar iv] line ratios are compatible with a 3D stratified view of the nebula with the highest ne in the innermost layers and a decrease of ne outwards. 2D maps of Te were measured from [O iii] and [S ii] line ratios; to our knowledge, this is the first time that a Te map based on [S ii] lines for an extragalactic object has been presented. The joint interpretation of the Te([S ii]) and Te([O iii]) maps is consistent with a Te structure in 3D with higher temperatures close to the main ionizing source surrounded by a colder and more diffuse component. The highest ionization degree is found at the peak of emission for the gas with relatively high ionization in the main Giant H ii Region and lower ionization degree delineating the more extended diffuse component. We derived abundances of oxygen, neon, argon, and nitrogen. Abundances for O, Ne and Ar are constant over the mapped area within ?0.1 dex. The mean 12 + log (O/H) is 8.26 ± 0.04 while the relative abundances of log (N/O), log (Ne/O) and log (Ar/O) were ~-1.32 ± 0.05, -0.65 ± 0.03 and -2.33 ± 0.06, respectively. There are two locations with enhanced N/O. The first (log (N/O) ~ -0.95) occupies an area of about 80 pc × 35 pc and is associated to two super star clusters. The second (log (N/O) ~ -1.17), reported here for the first time, is associated to two moderately massive (2-4 × 104 M?) and relatively old (~10 Myr) clusters. A comparison of the N/O map with those produced by strong line methods supports the use of N2O2 over N2S2 in the search for chemical inhomogeneities within a galaxy. The results on the localized nitrogen enhancement were used to compile and discuss the factors that affect the complex relationship between Wolf-Rayet stars and N/O excess. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (ESO Programme 078.B-0043 and 383.B-0043).

Monreal-Ibero, A.; Walsh, J. R.; Vílchez, J. M.

2012-08-01

187

The quantitation of triazolam in postmortem blood by gas chromatography/negative ion chemical ionization mass spectrometry.  

PubMed

A specific and sensitive assay has been developed to quantitate triazolam in postmortem blood using 2H6-triazolam as an internal standard. Triazolam is isolated from whole blood by adsorption on an Amberlite XAD-2 resin and subsequent elution with an organic solvent. The extract is analyzed by gas chromatography/mass spectometry using selected ion monitoring (GC/MS/SIM) in the negative chemical ionization mode (Cl-). The procedure is presently being used in case work and the results from 36 cases are presented. PMID:3807323

Koves, G; Wells, J

1986-01-01

188

Restoration of RI-beams from a projectile fragment separator by Laser Ionization gas Catcher-PALIS-  

SciTech Connect

A fragment separator at heavy ion accelerator facilities is a versatile instrument to provide wide variety of radioactive isotope (RI) beams. However, more than 99.99% of precious RI-ions are simply dumped in the slits or elsewhere in the fragment separator. A novel concept to restore such RI-ions for parasitic slow RI-beams is proposed. Installation of a laser ionization gas catcher in the vicinity of the first or second focal point of the fragment separator enables to collect dead isotopes in the slits. The design concept and expected performance are discussed.

Sonoda, T.; Takamine, A.; Schury, P.; Yamazaki, Y. [Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Wada, M. [Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Nishina Center for Accelerator Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitame 351-0198 (Japan); Okada, K. [Department of Physics, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo 102-8554 (Japan); Yoshida, A.; Kubo, T.; Matsuo, Y.; Furukawa, T. [Nishina Center for Accelerator Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitame 351-0198 (Japan); Wakui, T.; Shinozuka, T. [Cyclotron and Radioisotope Center, Tohoku University, Sendai 980-0191 (Japan); Iimura, H. [Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1184 (Japan); Katayama, I. [Institute of Particle and Nuclear Studies, KEK, Tsukuba, Ibaraki 305-0801 (Japan); Ohtani, S. [Institute for Laser Science, University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan); Wollnik, H. [II. Physikalisches Institute, Justus-Liebig-Universitaet Giessen, Giessen (Germany); Schuessler, H. A. [Department of Physics, Texas A and M Universirty, College Station, TX 77843 (United States); Kudryavtsev, Yu.; Van Duppen, P.; Huyse, M. [Instituut voor Kern-en Stralingsfysica, K.U. Leuven, Celestijnenlaan 200D, B-3001, Leuven (Belgium)

2009-03-17

189

Compact ultrafast orthogonal acceleration time-of-flight mass spectrometer for on-line gas analysis by electron impact ionization and soft single photon ionization using an electron beam pumped rare gas excimer lamp as VUV-light source.  

PubMed

Orthogonal acceleration time-of-flight mass spectrometers (oaTOFMS), which are exhibiting a pulsed orthogonal extraction of ion bunches into the TOF mass analyzer from a continuous primary ion beam, are well-suited for continuous ionization methods such as electron impact ionization (EI). Recently an electron beam pumped rare gas excimer lamp (EBEL) was introduced, which emits intensive vacuum UV (VUV) radiation at, e.g., 126 nm (argon excimer) and is well suited as the light source for soft single photon ionization (SPI) of organic molecules. In this paper, a new compact oaTOFMS system which allows switching between SPI, using VUV-light from an EBEL-light source, and conventional EI is described. With the oaTOFMS system, EBEL-SPI and EI mass spectral transients can be recorded at very high repetition rates (up to 100 kHz), enabling high duty cycles and therefore good detection efficiencies. By using a transient recorder card with the capability to perform on-board accumulation of the oaTOF transients, final mass spectra with a dynamic range of 106 can be saved to the hard disk at a rate of 10 Hz. As it is possible to change the ionization modes (EI and SPI) rapidly, a comprehensive monitoring of complex gases with highly dynamic compositions, such as cigarette smoke, is possible. In this context, the EI based mass spectra address the bulk composition (compounds such as water, oxygen, carbon dioxide, etc. in the up to percentage concentration range) as well as some inorganic trace gases such as argon, sulfur dioxide, etc. down to the low ppm level. The EBEL-SPI mass spectra on the other hand are revealing the organic composition down to the lower ppb concentration range. PMID:17900147

Mühlberger, F; Saraji-Bozorgzad, M; Gonin, M; Fuhrer, K; Zimmermann, R

2007-11-01

190

The Ionized Gas and Nuclear Environment in NGC 3783. IV; Variability and Modeling of the 900 ks CHANDRA Spectrum  

NASA Technical Reports Server (NTRS)

We present a detailed analysis of the 900 ks spectrum of NGC3783 obtained by Chandra in 2000-2001 (Kaspi et al. 2002). We split the data in various ways to look for time dependent and luminosity dependent spectral variations. This analysis, the measured equivalent widths of a large number of X-ray lines, and our photoionization calculations, lead us to the following conclusions: 1) NGC 3783 fluctuated in luminosity, by a factor N 1.5, during individual 170 ks observations. The fluctuations were not associated with significant spectral variations. 2) On a longer time scale, of 20-120 days, we discovered two very different spectral shapes that are noted the high state and the low state spectra. The observed changes between the two can be described as the appearance and disappearance of a soft continuum component. The spectral variations are not related, in a simple way, to the brightening or the fading of the short wavelength continuum, as observed in other objects. NGC3783 seems to be the first AGN to show this unusual behavior. 3) The appearance of the soft continuum component is consistent with beeing the only spectral variation and there is no need to invoke changes in the absorber s opacity. In particular, all absorption lines with reliable measurements show the same equivalent width, within the observational uncertainties, during high and low states. 4) Photoionization model calculations show that a combination of three ionization components, each split into two kinematic components, explain very well the intensity of almost all absorption lines and the bound-free absorption. The components span a large range of ionization and a total column of about 3 x 10(exp 22) per square centimeter Moreover, all components are thermally stable and are situated on the vertical branch of the stability curve.. This means that they are in pressure equilibrium and perhaps occupy the same volume of space. This is the first detection of such a multi-component equilibrium gas in AGN. 5) The only real discrepancy between the model and the observations is the wavelength of the iron M-shell UTA feature. This is most likely due to an underestimation of the dielectronic recombination O VI and discuss its possible origin. 6) The lower limit on the distance of the absorbing gas in NGC3783 is between 0.2 and 3.2 pc, depending of the specific ionization component. The constant pressure assumption imposes an upper limit of about 25 pc on the distance of the least ionized gas from the central sourec.

Netzer, Hagai; Kaspi, Shai; Behar, Ehud; Brandt, W. N.; Chelouche, Doron; George, Ian M.; Crenshaw, D. Michael; Gabel, Jack R.; Hamann, Frederick W.; George, Steven B.

2003-01-01

191

Narrowband HST images of M87: Evidence for a disk of ionized gas around a massive black hole  

NASA Technical Reports Server (NTRS)

We present Hubble Space Telescope Wide Field/Planetary Camera-2 (HST WFPC2) narrowband H-alpha + (N II) images of M87 which show a small disk of ionized gas with apparent spiral structure surrounding the nucleus of M87. The jet projects approximately 19.5 deg from the minor axis of the disk, which suggests that the jet is approximately normal to the disk. In a companion Letter, Harms et al. measure the radial velocities at r = +/- 0.25 sec along a line perpendicular to the jet, showing that one side of the disk is approaching at 500 +/- 50 km/s and the other side of the disk is receding at 500 +/- 50 km/s. Absorption associated with the disk and the sense of rotation imply that the apparent spiral arms trail the rotation. The observed radial velocites corrected for a 42 deg inclination of the disk imply rotation at +/- 750 km/s. Analysis of velocity measurements at four positions near the nucleus gives a total mass of approximately 2.4 +/- 0.7 x 10(exp 9) solar mass within 18 pc of the nucleus, and a mass-to-light ratio (M/L)(sub I) = 170. We conclude that there is a disk of ionized gas feeding a massive black hole in the center of M87.

Ford, Holland C.; Harms, Richard J.; Tsvetanov, Zlatan I.; Hartig, George F.; Dressel, Linda L.; Kriss, Gerard A.; Bohlin, Ralph C.; Davidsen, Arthur F.; Margon, Bruce; Kochhar, Ajay K.

1994-01-01

192

HST FOS spectroscopy of M87: Evidence for a disk of ionized gas around a massive black hole  

NASA Technical Reports Server (NTRS)

Using the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) to observe the central region of M87, we have obtained spectra covering approximately 4600-6800 A at a spectral dispersion approximately 4.4 A per resolution element through the .26 sec diameter entrance aperture. One spectrum was obtained centered on the nucleus of M87 and two centered 0.25 sec off the nucleus at position angles of 21 deg and 201 deg, thus sampling the anticipated major axis of the disklike structure (described in a companion Letter) expected to lie approximately perpendicular to the axis of the M87 jet. Pointing errors for these observations are estimated to be less than 0.02 sec. Radial velocities of the ionized gas in the two positions 0.25 sec on either side of the nucleus are measured to be approx. equals +/- 500 km/s relative to the M87 systemic velocity. These observations plus emission-line spectra obtained at two additional locations near the nucleus show the ionized gas to be in Keplerian rotation about a mass M = (2.4 +/- 0.7) x 10(exp 9) solar mass within the inner 0.25 sec of M87. Our results provide strong evidence for the presence of a supermassive nuclear black hole in M87.

Harms, Richard J.; Ford, Holland C.; Tsvetanov, Zlatan I.; Hartig, George F.; Dressel, Linda L.; Kriss, Gerard A.; Bohlin, Ralph; Davidsen, Arthur F.; Margon, Bruce; Kochhar, Ajay K.

1994-01-01

193

Anomalous Motion of Ionized Gas in the Sickle (G0.18--0.04) Near the Galactic Center  

E-print Network

We present VLA measurements of H92alpha radio recombination line emission from an unusual HII region G0.18--0.04, the ``Sickle'', with spatial and spectral resolutions of 27" times 24".9 and 14 km/s, respectively. These observations detected two new kinematic components of ionized gas whose velocities differ greatly from the +25 km/s molecular cloud surrounding the Sickle. One component is highly red-shifted with peak velocity of about +150 km/s and the other is a blue-shifted velocity feature peaking near -35 km/s. Neither of these high-velocity features have molecular counterparts. The blue-shifted feature is forbidden in the sense of Galactic rotation and coincides with the prominent nonthermal filaments crossing the Sickle, thus suggesting that they are physically associated with each other. The results presented here are interpreted in terms of ionized gas being accelerated away from the surface of the cloud associated with the Sickle region, either by the magnetic field associated with the nonthermal filaments or by the stellar winds from the hot helium stars near G0.18--0.04.

F. Yusef-Zadeh; D. A. Roberts; M. Wardle

1997-10-04

194

Stability of plasma gamma-hydroxybutyrate determined by gas chromatography-positive ion chemical ionization-mass spectrometry.  

PubMed

An effective method for the determination of gamma-hydroxybutyric acid (GHB) in human plasma is described that utilizes a simple liquid-liquid extraction procedure and gas chromatography-positive ion chemical ionization-mass spectrometry (GC-PCI-MS). The method has been used to study the stability of plasma GHB under several storage conditions. Following the extraction with acetonitrile, GHB and deuterated GHB (GHB-d(6)) were derivatized with N,O-bis[trimethylsilyl] trifluoroacetamide (BSFTA). After the separation on a capillary GC column, the derivatives were ionized with ammonia reagent gas and analyzed by MS. The lower limit of quantitation in 100 microL of plasma was 2.5 microg/mL, over a range from 2.5 to 250 microg/mL. The coefficients of variation did not exceed 3.9% and the mean measured concentrations did not deviate more than 8% from the target for both intra- and interassay precision and accuracy. Plasma GHB was found to be stable at -20 degrees C for up to 9 months, at room temperature for 48 h, and after 3 freeze/thaw cycles. It was also found to be stable in processed samples stored at room temperature for 5 days and for 15 days at -20 degrees C. PMID:14606997

Chen, Meng; Andrenyak, David M; Moody, David E; Foltz, Rodger L

2003-10-01

195

Application of A150 plastic-equivalent gas in A150 plastic ionization chambers for Co60 gamma rays and 14.8MeV neutrons  

Microsoft Academic Search

An ion-chamber gas mixture having an atomic composition similar to that of A150 plastic has been tested experimentally. This ''A150 gas'', air, and methane-based Te gas were each flowed through A150 plastic-walled ion chambers of various sizes, and irradiated with ⁶°CO ..gamma.. rays and 14.8-MeV neutrons, separately administered. Observed ionization was measured and corrected for recombination losses. Best values for

P. M. Deluca Jr.; F. H. Attix; D. W. Pearson; M. C. Schell; M. Awschalom

1982-01-01

196

Ionization coefficients and sparking voltages in argon-long-chain hydrocarbon gas mixtures  

Microsoft Academic Search

Townsend primary and secondary ionization coefficients and the sparking voltage have been measured in 0?003, 0?03, 0?3 and 3% of n-octane. cis.bntetio-2 and benzene mixed in argon for u total pressure in the range 0?5 to 500 torr and for a uniform field gap up to 1 cm. The increase in the Penning effect and in the effectiveness of quenching with

A. E. D. HEYLEN

1971-01-01

197

Resonantly enhanced vacuum-ultraviolet generation and multiphoton ionization in carbon monoxide gas  

SciTech Connect

Competition between three-photon resonantly enhanced vacuum ultraviolet third-harmonic generation and six-photon multiphoton ionization using the A state in gaseous carbon monoxide is observed. Excitation spectra of the third-harmonic emission exhibit increasing blue shifts and broadening with increasing pressure due to the phase matching requirements. Estimates for the efficiency and tunability show that third-harmonic generation in carbon monoxide molecules is a promising source for coherent vacuum ultraviolet light.

Glownia, J.H.; Sander, R.K.

1982-01-01

198

Ionization of the diffuse gas in galaxies: hot low-mass evolved stars at work  

Microsoft Academic Search

We revisit the question of the ionization of the diffuse medium in late-type galaxies, by studying NGC 891, the prototype of edge-on spiral galaxies. The most important challenge for the models considered so far was the observed increase of [O III]\\/Hbeta, [O II]\\/Hbeta and [N II]\\/Halpha with increasing distance to the galactic plane. We propose a scenario based on the

N. Flores-Fajardo; C. Morisset; G. Stasinska; L. Binette

2011-01-01

199

THE KINEMATICS AND IONIZATION OF NUCLEAR GAS CLOUDS IN CENTAURUS A  

SciTech Connect

Neumayer et al. established the existence of a blueshifted cloud in the core of Centaurus A, within a few parsecs of the nucleus and close to the radio jet. We propose that the cloud has been impacted by the jet, and that it is in the foreground of the jet, accounting for its blueshifted emission on the southern side of the nucleus. We consider both shock excitation and photoionization models for the excitation of the cloud. Shock models do not account for the [Si VI] and [Ca VIII] emission line fluxes. However, X-ray observations indicate a source of ionizing photons in the core of Centaurus A; photoionization by the inferred flux incident on the cloud can account for the fluxes in these lines relative to Brackett-{gamma}. The power-law slope of the ionizing continuum matches that inferred from synchrotron models of the X-rays. The logarithm of the ionization parameter is -1.9, typical of that in Seyfert galaxies and consistent with the value proposed for dusty ionized plasmas. The model cloud density depends upon the Lorentz factor of the blazar and the inclination of our line of sight to the jet axis. For acute inclinations, the inferred density is consistent with expected cloud densities. However, for moderate inclinations of the jet to the line of sight, high Lorentz factors imply cloud densities in excess of 10{sup 5} cm{sup -3} and very low filling factors, suggesting that models of the gamma-ray emission should incorporate jet Lorentz factors {approx}< 5.

Bicknell, Geoffrey V.; Sutherland, Ralph S. [Research School of Astronomy and Astrophysics, Australian National University, Mt. Stromlo Observatory, Cotter Rd., Weston, ACT 2611 (Australia)] [Research School of Astronomy and Astrophysics, Australian National University, Mt. Stromlo Observatory, Cotter Rd., Weston, ACT 2611 (Australia); Neumayer, Nadine, E-mail: Geoff.Bicknell@anu.edu.au, E-mail: Ralph.Sutherland@anu.edu.au, E-mail: nadine.neumayer@universe-cluster.de [European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching (Germany)] [European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching (Germany)

2013-03-20

200

Anomalous laser-induced ionization rates of molecules and rare-gas atoms  

Microsoft Academic Search

Electron tunnel ionization is considered as the mechanism for producing free electrons in gases under laser radiation. The Keldysh result and the Ammosov-Delone-Krainov (ADK) formulation are amended by considering the excess forces due to the interaction of the electric field of the laser with the electron cloud in a simple mass-on-a-spring approximation. The result of this excess force is a

Bettis; Jerry Ray

2009-01-01

201

Comprehensive on-line characterization of complex gas mixtures by quasi-simultaneous resonance-enhanced multiphoton ionization, vacuum-UV single-photon ionization, and electron impact ionization in a time-of-flight mass spectrometer: setup and instrument characterization.  

PubMed

This paper reports on a newly developed mobile mass spectrometer for comprehensive on-line analysis of complex gas mixtures such as ambient air or industrial process gases. Three ionization methods, namely, the resonance-enhanced multiphoton ionization (REMPI), vacuum-ultraviolet single-photon ionization (SPI), and electron impact ionization (EI) are implemented in this instrument and can be operated (quasi-) simultaneously. By means of this setup, a wide range of compounds can be analyzed due to the unique ionization selectivitiy and sensitivity profiles provided by the different ionization techniques. The mass spectrometer is designed for field application even under severe conditions. The REMPI technique is suitable for the selective and soft ionization (without fragmentation) of aromatic compounds at trace level (ppbv/pptv). The also soft but less selective SPI technique with 118-nm vacuum-ultraviolet laser pulses is used as a second laser-based ionization method. Mass spectra obtained by this technique show profiles of most organic compounds (aliphatic and aromatic species) and of some low IP inorganic substances (e.g., ammonia, nitrogen oxide) down to ppbv concentrations. In addition to the laser-based ionization techniques, EI ionization can be used for analysis of the bulk components such as water, oxygen, nitrogen, and carbon dioxide as well as for detection of inorganic minor components such as HCN or HCl from combustion flue gases at ppmv concentration levels. Each method yields specific mass spectrometric information of the sample composition. Special techniques have been developed to combine the three ionization methods in a single mass spectrometer and to allow the quasi-parallel application of all three ionization techniques. PMID:15538800

Mühlberger, F; Hafner, K; Kaesdorf, S; Ferge, T; Zimmermann, R

2004-11-15

202

A Desorbed Gas Molecular Ionization Mechanism for Arcing Onset in Solar Arrays Immersed in a Low-Density Plasma  

NASA Technical Reports Server (NTRS)

Previous experimental studies have hypothesized that the onset of Solar Array Arc (SAA) initiation in low-density space plasmas is caused by a desorbed gas molecular ionization mechanism. Indeed past investigations performed at the NASA Glenn Plasma Interaction Facility tend to not only support the desorbed gas molecular ionization mechanism, but have gone as far as identifying the crucial molecular species that must be present for molecular ion dominated process to occur. When electrical breakdown occurs at a triple junction site on a solar array panel, a quasi-neutral plasma cloud is ejected. Assuming the main component of the expelled plasma cloud by weight is due to water vapor, the fastest process available is due to HO molecules and OH(+) ions, or more succinctly, dissociative molecular-ion dominated recombination processes: H2O(+) + e(-) yields H* + OH*. Recently published spectroscopic observations of solar array arc spectra in ground tests have revealed the well-known molecular OH band (302 to 309nm), as well as the molecular SiH band (387nm peak), and the molecular CH band (432nm peak). Note that the OH band is observed in emission arcs where water vapor is present. Strong atomic lines were also observed for H(sub beta) at 486nm and H(sub alpha) at 656.3nm in prior ground testing. Independent supporting evidence of desorbed gas molecular ionization mechanisms also come from measurements of arc current pulse widths at different capacitances. We will revisit an earlier first order approximation demonstrating the dependence of arc current pulse widths on the square root of the capacitance. The simple arc current pulse width model will be then be used to estimate the temperature of the arc plasma (currently believed to be somewhere in the range of 3 to 5 eV). The current paper then seeks to extend the outlined work by including numerous vacuum chamber measurements obtained with a quadrupole mass spectrometer. A small solar array was mounted inside the vacuum chamber. A plasma source, also mounted inside the vacuum chamber, is used to simulate a low-density plasma environment. The solar array is then biased to a high negative potential and allowed to arc while a mass spectrometer is used to record the partial pressure of H2O and to track other significant changes in mass (1 to 150) AMU.

Galofaro, J.; Vayner, B.; Ferguson, D.; Degroot, W.

2002-01-01

203

Acceleration of electrons generated during ionization of a gas by a nearly flat profile laser pulse  

SciTech Connect

A scheme of acceleration of electrons generated during ionization of krypton by nearly flat radial and nearly flat temporal laser pulse profiles has been suggested. The energy spectrum of the electrons suggests that energy of the electrons is higher for a nearly flat temporal profile than that for a nearly flat radial profile. The suppression of scattering of the electrons is better for a nearly flat radial profile than that for a nearly flat temporal profile. The energy of the electrons increases, scattering decreases, and beam quality improves with an increase in flatness of radial and temporal profiles.

Singh, Kunwar Pal [Department of Physics, MSJ College, Bharatpur, Rajasthan 321201 (India)

2009-09-15

204

Confirmation of clorsulon residues in cattle kidney by capillary gas chromatography-negative-ion chemical-ionization mass spectrometry.  

PubMed

A confirmatory assay for residues of the anthelmintic agent clorsulon [4-amino-6-(trichloroethenyl)-1,3-benzenedisulfonamide] in cattle kidney tissue has been developed. The assay involves isolation of a drug-containing fraction by solvent extraction, methylation of the analyte, and fused-silica capillary column gas chromatography-negative-ion chemical-ionization mass spectrometry of the pentamethyl derivative of clorsulon. The intensities of four negative ions [m/z 406 and 408 (trichloro species) and m/z 413 and 415 (dichloro species)] are monitored. Confirmation of the presence of drug in an analyte requires that all four ions appear at the appropriate retention time with their intensity ratios within 10-15% of those arising from analysis of the reference standard, methylated clorsulon; the lower limit of detection is 3 ppb. Quantification of the drug is based on the intensity of the m/z 406 ion. Identification and quantification of residues by the gas chromatographic-mass spectrometric assay gave results in good agreement with those obtained with an electron-capture gas chromatographic assay. PMID:3654857

Wehner, T A; Wood, J S; Walker, R; Downing, G V; Vandenheuvel, W J

1987-07-24

205

Isotopologue analysis of sugar phosphates in yeast cell extracts by gas chromatography chemical ionization time-of-flight mass spectrometry.  

PubMed

Metabolic flux analysis is based on the measurement of isotopologue ratios. In this work, a new GC-MS-based method was introduced enabling accurate determination of isotopologue distributions of sugar phosphates in cell extracts. A GC-TOFMS procedure was developed involving a two-step online derivatization (ethoximation followed by trimethylsilylation) offering high mass resolution, high mass accuracy and the potential of retrospective data analysis typical for TOFMS. The information loss due to fragmentation intrinsic for isotopologue analysis by electron ionization could be overcome by chemical ionization with methane. A thorough optimization regarding pressure of the reaction gas, emission current, electron energy and temperature of the ion source was carried out. For a substantial panel of sugar phosphates both of the glycolysis and the pentose phosphate pathway, sensitive determination of the protonated intact molecular ions together with low abundance fragment ions was successfully achieved. The developed method was evaluated for analysis of Pichia pastoris cell extracts. The measured isotopologue ratios were in the range of 55:1-2:1. The comparison of the experimental isotopologue fractions with the theoretical fractions was excellent, revealing a maximum bias of 4.6 % and an average bias of 1.4 %. PMID:25673246

Chu, Dinh Binh; Troyer, Christina; Mairinger, Teresa; Ortmayr, Karin; Neubauer, Stefan; Koellensperger, Gunda; Hann, Stephan

2015-04-01

206

THE ORIGIN OF THE 6.4 keV LINE EMISSION AND H{sub 2} IONIZATION IN THE DIFFUSE MOLECULAR GAS OF THE GALACTIC CENTER REGION  

SciTech Connect

We investigate the origin of the diffuse 6.4 keV line emission recently detected by Suzaku and the source of H{sub 2} ionization in the diffuse molecular gas of the Galactic center (GC) region. We show that Fe atoms and H{sub 2} molecules in the diffuse interstellar medium of the GC are not ionized by the same particles. The Fe atoms are most likely ionized by X-ray photons emitted by Sgr A* during a previous period of flaring activity of the supermassive black hole. The measured longitudinal intensity distribution of the diffuse 6.4 keV line emission is best explained if the past activity of Sgr A* lasted at least several hundred years and released a mean 2-100 keV luminosity {approx}> 10{sup 38} erg s{sup -1}. The H{sub 2} molecules of the diffuse gas cannot be ionized by photons from Sgr A*, because soft photons are strongly absorbed in the interstellar gas around the central black hole. The molecular hydrogen in the GC region is most likely ionized by low-energy cosmic rays, probably protons rather than electrons, whose contribution into the diffuse 6.4 keV line emission is negligible.

Dogiel, V. A.; Chernyshov, D. O. [I. E. Tamm Theoretical Physics Division of P. N. Lebedev Institute of Physics, Leninskii pr. 53, 119991 Moscow (Russian Federation); Tatischeff, V. [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, IN2P3/CNRS and Univ Paris-Sud, F-91405 Orsay Campus (France); Cheng, K.-S. [Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong (Hong Kong); Terrier, R. [Astroparticule et Cosmologie, Universite Paris7/CNRS/CEA, Batiment Condorcet, F-75013 Paris (France)

2013-07-10

207

Unified first principles description from warm dense matter to ideal ionized gas plasma: electron-ion collisions induced friction.  

PubMed

Electron-ion interactions are central to numerous phenomena in the warm dense matter (WDM) regime and at higher temperature. The electron-ion collisions induced friction at high temperature is introduced in the procedure of ab initio molecular dynamics using the Langevin equation based on density functional theory. In this framework, as a test for Fe and H up to 1000 eV, the equation of state and the transition of electronic structures of the materials with very wide density and temperature can be described, which covers a full range of WDM up to high energy density physics. A unified first principles description from condensed matter to ideal ionized gas plasma is constructed. PMID:20867307

Dai, Jiayu; Hou, Yong; Yuan, Jianmin

2010-06-18

208

The integrated radio continuum spectrum of M33 - Evidence for free-free absorption by cool ionized gas  

NASA Technical Reports Server (NTRS)

We present measurements of the integrated radio continuum flux density of M33 at frequencies between 22 and 610 MHz and discuss the radio continuum spectrum of M33 between 22 MHz and 10 GHz. This spectrum has a turnover between 500 and 900 MHz, depending on the steepness of the high frequency radio spectrum of M33. Below 500 MHz the spectrum is relatively flat. We discuss possible mechanisms to explain this spectral shape and consider efficient free-free absorption of nonthermal emission by a cool (not greater than 1000 K) ionized gas to be a very likely possibility. The surface filling factor of both the nonthermal and the thermal material appears to be small (of order 0.001), which could be explained by magnetic field/density fluctuations in the M 33 interstellar medium. We briefly speculate on the possible presence of a nuclear radio source with a steep spectrum.

Israel, F. P.; Mahoney, M. J.; Howarth, N.

1992-01-01

209

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

PubMed

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

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

2014-03-01

210

Analysis of human breath samples using a modified thermal desorption: gas chromatography electrospray ionization interface.  

PubMed

A two-stage thermal desorption/secondary electrospray ionization/time-of-flight mass spectrometry for faster targeted breath profiling has been studied. A new secondary electrospray ionization (SESI) source was devised to constrain the thermal desorption plume and promote efficient mixing in the ionization region. Further, a chromatographic pre-separation stage was introduced to suppress interferences from siloxanes associated with thermal desorption profiles of exhaled breath samples.In vitro tests with 5-nonanone indicated an increased sensitivity and a lowered limit-of-detection, both by a factor of ~4, the latter to an on-trap mass of 14.3?ng, equivalent to a sampled breath concentration of 967?pptv. Analysis of the mass spectrometric responses from 20 breath samples acquired sequentially from a single participant indicated enhanced reproducibility (reduced relative standard deviations (RSD) for 5-nonanone, benzaldehyde and 2-butanone were 28 %, 16% and 14% respectively. The corresponding values for an open SESI source were that 5-nonanone was not detected, with %RSD of 39% for benzaldehyde and 31% for 2-butanone).The constrained source with chromatographic pre-separation resulted in an increase in the number of detectable volatile organic compounds (VOCs) from 260 mass spectral peaks with an open SESI source to 541 peaks with the constrained source with pre-separation. Most of the observed VOCs were present at trace levels, at less than 2.5% of the intensity of the base peak.Seventeen 2.5?dm(3) distal breath samples were collected from asthma patients and healthy controls respectively, and subjected to comparative high-throughput screening using thermal desorption/SESI/time-of-flight mass spectrometry (TD-SESI-ToFMS). Breath metabolites were detected by using a background siloxane ion (hexamethylcyclotrisiloxane m/z 223.0642) as an internal lockmass. Eleven breath metabolites were selected from the breath research literature and successfully targeted. These data reinforce the proposition that TD-SESI-MS has potential for development as a rapid screening method for disease stratification and targeted metabolism profiling. PMID:25190194

Reynolds, James C; Jimoh, Modupe A; Guallar-Hoyas, Cristina; Creaser, Colin S; Siddiqui, Salman; Paul Thomas, C L

2014-09-01

211

On the origins of the diffuse H? emission: ionized gas or dust-scattered H? halos?  

NASA Astrophysics Data System (ADS)

We find that the dust-scattering origin of the diffuse H? emission cannot be ruled out. As opposed to the previous contention, the expected dust-scattered H? halos surrounding H II regions are, in fact, in good agreement with the observed H? morphology. We calculate an extensive set of photoionization models by varying elemental abundances, ionizing stellar types, and clumpiness of the interstellar medium (ISM) and find that the observed line ratios of [S II]/H?, [N II]/H?, and He I ?5876/H? in the diffuse ISM accord well with the dust-scattered halos around H II regions, which are photoionized by late O- and/or early B-type stars. We also demonstrate that the H? absorption feature in the underlying continuum from the dust-scattered starlight (``diffuse galactic light'') and unresolved stars is able to substantially increase the [S II]/H? and [N II]/H? line ratios in the diffuse ISM.

Seon, Kwang-Il; Witt, Adolf N.

2015-03-01

212

Penning Ionization Electron Spectroscopy in Glow Discharge: A New Dimension for Gas Chromatography Detectors  

NASA Technical Reports Server (NTRS)

Admixtures to helium of 100 ppm and 5 ppm of nitrogen, and 100 ppm and 10 ppm of carbon monoxide were identified and measured in the helium discharge afterglow using an electrical probe placed into the plasma. For nitrogen and carbon monoxide gases, the measured electron energy spectra display distinct characteristic peaks (fingerprints). Location of the peaks on the energy scale is determined by the ionization energies of the analyte molecules. Nitrogen and carbon monoxide fingerprints were also observed in a binary mixture of these gases in helium, and the relative concentration analytes has been predicted. The technically simple and durable method is considered a good candidate for a number of analytical applications, and in particular, in GC and for analytical flight instrumentation.

Sheverev, V. A.; Khromov, N. A.; Kojiro, D. R.; Fonda, Mark (Technical Monitor)

2002-01-01

213

Studies on the Ionization Produced by Metallic Salts in Flames. I. The Determination of the Collision Frequency of Electrons in Coal-Gas\\/Air Flames  

Microsoft Academic Search

As an introduction to the study of reactions contingent on ionization in flames, an experimental measurement has been made of the collision frequency of electrons with molecules in coal-gas\\/air flames, containing added alkali metal salt. This quantity is an important parameter in the expression relating the electron content of a flame with the attenuation of centimetric radio waves by it.

H. Belcher; T. M. Sugden

1950-01-01

214

Studies on the Ionization Produced by Metallic Salts in Flames II. Reactions Governed by Ionic Equilibria in Coal-Gas\\/Air Flames Containing Alkali Metal Salts  

Microsoft Academic Search

The ionization produced by adding alkali metal salts to coal-gas\\/air flames has been studied by measuring the attenuation of 3 cm. waves, this attenuation arising from free electrons. In a previous paper (Belcher & Sugden 1950) the coefficient relating attenuation to electron population has been determined and is used in applying the present results to the problems of chemical equilibrium

H. Belcher; T. M. Sugden

1950-01-01

215

The Black Hole in IC 1459 from Hubble Space Telescope Observations of the Ionized Gas Disk  

NASA Astrophysics Data System (ADS)

The peculiar elliptical galaxy IC 1459 (MV=-21.19, D=16.5 h-1 Mpc) has a fast counterrotating stellar core, stellar shells and ripples, a blue nuclear point source, and strong radio core emission. We present results of a detailed Hubble Space Telescope study of IC 1459, and in particular its central gas disk, aimed at constraining the central mass distribution. We obtained WFPC2 narrowband imaging centered on the H?+[N II] emission lines to determine the flux distribution of the gas emission at small radii, and we obtained FOS spectra at six aperture positions along the major axis to sample the gas kinematics. We construct dynamical models for the H?+[N II] and H? kinematics that include a supermassive black hole and in which the stellar mass distribution is constrained by the observed surface brightness distribution and ground-based stellar kinematics. In one set of models we assume that the gas rotates on circular orbits in an infinitesimally thin disk. Such models adequately reproduce the observed gas fluxes and kinematics. The steepness of the observed rotation velocity gradient implies that a black hole must be present. There are some differences between the fluxes and kinematics for the various line species that we observe in the wavelength range 4569-6819 Å. Species with higher critical densities generally have a flux distribution that is more concentrated toward the nucleus, and have observed velocities that are higher. This can be attributed qualitatively to the presence of the black hole. There is some evidence that the gas in the central few arcsec has a certain amount of asymmetric drift, and we therefore construct alternative models in which the gas resides in collisionless cloudlets that move isotropically. All models are consistent with a black hole mass in the range M•=1-4×108 Msolar, and models without a black hole are always ruled out at high confidence. The implied ratio of black holes mass to galaxy mass is in the range 0.4-1.5×10-3, which is not inconsistent with results obtained for other galaxies. These results for the peculiar galaxy IC 1459 and its black hole add an interesting data point for studies on the nature of galactic nuclei. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

Verdoes Kleijn, Gijs A.; van der Marel, Roeland P.; Carollo, C. Marcella; de Zeeuw, P. Tim

2000-09-01

216

The supergiant shell with triggered star formation in the dwarf irregular galaxy IC 2574: neutral and ionized gas kinematics  

NASA Astrophysics Data System (ADS)

We analyse the ionized gas kinematics in the star formation regions of the supergiant shell (SGS) of the IC 2574 galaxy using observations made with the Fabry-Perot interferometer at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences; the data of the H I Nearby Galaxy Survey (THINGS) are used to analyse the neutral gas kinematics in the area. We perform the `derotation' of the H? and H I data cubes and show its efficiency in the kinematics analysis. We confirm the SGS expansion velocity of 25 km s-1 obtained previously and conclude that the SGS is located at the far side of the galactic disc plane. We determine the expansion velocities, kinematic ages and the required mechanical energy input rates for four star formation complexes in the walls of the SGS; for those remaining, we give the limiting values of the above parameters. A comparison with the age and energy input of the stellar population of the complexes shows that sufficient energy is fed to all H II regions except one. We discuss in detail the possible nature of this region and that of another region, which was believed to be a supernova remnant, according to radio observations. We have measured the expansion velocity of the latter and we can confirm its identification as an old supernova remnant. Our observations have allowed us to identify a faint diffuse H? emission inside the SGS, which was not been previously observed.

Egorov, O. V.; Lozinskaya, T. A.; Moiseev, A. V.; Smirnov-Pinchukov, G. V.

2014-10-01

217

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

PubMed

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

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

2014-01-01

218

Quantum coherence in the dynamical excitation, ionization, and decaying of neon gas induced by X-ray laser  

E-print Network

We develop a large scale quantum master equation approach to describe dynamical processes of practical open quantum systems driven by both coherent and stochastic interactions by including more than one thousand true states of the systems, motivated by the development of highly bright and fully coherent lasers in the X-ray wavelength regime. The method combines the processes of coherent dynamics induced by the X-ray laser and incoherent relaxations due to spontaneous emissions, Auger decays, and electronic collisions. As examples, theoretical investigation of {\\it real} coherent dynamics of inner-shell electrons of a neon gas, irradiated by a high-intensity X-ray laser with a full temporal coherence, is carried out with the approach. In contrast to the rate equation treatment, we find that coherence can suppress the multiphoton absorptions of a neon gas in the ultra-intense X-ray pulse, due to coherence-induced Rabi oscillations and power broadening effects. We study the influence of coherence on ionization p...

Li, Yongqiang; Dong, Wenpu; Zeng, Jiaolong; Yuan, Jianmin

2015-01-01

219

Effect of ammonium on liquid- and gas-phase protonation and deprotonation in electrospray ionization mass spectrometry.  

PubMed

The electrospray ionization (ESI) is a complex process and there has been a long debate regarding the gas-phase effect on ion generation in the process. In this paper we investigated the effect of liquid chromatographic mobile phase additives (formic acid, aqueous ammonia and their combination) on the ESI signal intensities for a wide variety of compounds. The addition of a trace amount of aqueous ammonia to the common formic acid-methanol mobile phase significantly enhances the ESI signals of protonated molecules and suppresses the formation of sodium adduct ions. This effect is well observed for the compounds containing the -N-C=O group but not for those without N or O atoms. The ESI signal intensity of deprotonated molecules increases with increase in pH of the mobile phase for neutral compounds, such as substituted urea, whereas this trend is not observed for acidic compounds such as phenoxy acids. The mechanistic analysis regarding liquid- and gas-phase protonation and deprotonation is discussed. PMID:23181258

Yang, X Jin; Qu, Yixin; Yuan, Qipeng; Wan, Pingyu; Du, Zhenxia; Chen, Dazhou; Wong, Choon

2013-01-21

220

The Physics of Partially Ionized Gas with Applications to Processes in the Interstellar Medium  

SciTech Connect

The dynamical equations for a partially ionized plasma are a matter of some recent controversy. Understanding this problem is important in understanding the interaction of the interstellar medium with the heliosphere and for understanding the spectrum of interstellar turbulence. If collision scales are much smaller than the internal interaction scales such as the ion gyroradius, the fluid approximation may be used. The analysis then must deal with at least three fluids (protons, electrons, and neutrals) which are coupled to each other by collisions and/or electromagnetic fields. Often, the proton and electron gyro-radii are much smaller than the collision length scales, so the electric and magnetic fields dominate the motions of the electrons and protons. In this case, the only important particle-particle collisions are those of the electrons and protons with the neutral atoms. Since the three species have, in general, different velocities, it is not immediately clear which fluid velocity to use. This ambiguity in the choice of fluid velocity has led to recent confusion regarding the physics of partially ionized plasmas. If the neutrals have a significant fraction of the mass, working in the center-of-mass coordinate frame can result in dynamical equations that differ greatly from those of ideal MHD. This is because the magnetic field is not frozen into the frame moving at the center-of-mass velocity, which leads to additional effects on the magnetic field that can be difficult to understand intuitively. To the extent that the electron mass is negligible, the magnetic field is actually found to be frozen into the frame moving with the electron bulk velocity. If we then take U to be the bulk velocity of the proton fluid the resulting dynamical equations closely resemble those of ideal MHD with the exception of the Hall term in the induction equation. Similarly, the frequently used Cowling conductivity also depends on the choice of coordinate frame. These conclusions address directly the recent controversy regarding the interaction of the interstellar medium with the heliosphere and also impact our understanding of interstellar turbulence.

Greenfield, E. J. [Department of Physics, University of Arizona, Tucson, AZ 85721 (United States); Jokipii, J. R.; Giacalone, Joe [Department of Planetary Science, University of Arizona, Tucson, AZ 85721 (United States)

2011-09-21

221

[S IV] IN THE NGC 5253 SUPERNEBULA: IONIZED GAS KINEMATICS AT HIGH RESOLUTION  

SciTech Connect

The nearby dwarf starburst galaxy NGC 5253 hosts a deeply embedded radio-infrared supernebula excited by thousands of O stars. We have observed this source in the 10.5 {mu}m line of S{sup +3} at 3.8 km s{sup -1} spectral and 1.''4 spatial resolution, using the high-resolution spectrometer TEXES on the IRTF. The line profile cannot be fit well by a single Gaussian. The best simple fit describes the gas with two Gaussians, one near the galactic velocity with FWHM 33.6 km s{sup -1} and another of similar strength and FWHM 94 km s{sup -1} centered {approx}20 km s{sup -1} to the blue. This suggests a model for the supernebula in which gas flows toward us out of the molecular cloud, as in a 'blister' or 'champagne flow' or in the H II regions modelled by Zhu.

Beck, Sara C. [Department of Physics and Astronomy, Tel Aviv University, Ramat Aviv (Israel); Lacy, John H. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Turner, Jean L. [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547 (United States); Kruger, Andrew; Richter, Matt [Department of Physics, University of California at Davis, Davis, CA 95616 (United States); Crosthwaite, Lucian P., E-mail: sara@wise.tau.ac.il [Northrop Grumman Aerospace Systems, San Diego, CA 92127 (United States)

2012-08-10

222

Infrared and optical measurements of the ionized gas in K3-50  

NASA Technical Reports Server (NTRS)

Results are reported for optical, near-IR, and mid-IR spectrophotometry of the compact H II region K3-50A. The emission-line observations imply an electron density of about 100,000 per cu cm; the consistency of density measurements in the optical, IR, and radio sources suggests that the optical counterpart of K3-50A is a reflection nebula. Previous measurements of the anomalous extinction law in K3-50A are confirmed, this law is extended out to B-alpha at 4 microns, and a 9-micron optical depth of about 2.5 is obtained. Elemental abundances are derived from measurements of emission lines of several dominant ions of the same element and found to be in close agreement (50%) with mean cosmic abundances. Individual ionic ratios are compared with model H II region calculations to determine the nature of the ionizing radiation. It is concluded that if nongray UV dust absorption does not modify the spectrum appreciably, the radiation temperature can be associated with a stellar surface temperature of about 37,000 K, corresponding to an O6 supergiant.

Lester, D. F.; Dinerstein, H. L.; Rank, D. M.

1979-01-01

223

Influence of Gas Heating and Vibrational Kinetics on the Ionization Dynamics of Preformed Air Plasma Channels  

NASA Astrophysics Data System (ADS)

An extensive self-consistent air-plasma model based upon the Boltzmann equation for the electron energy distribution function, coupled with a heavy particle kinetics was developed to study electric discharges in a preexisting air plasma column [1]. Incorporated in the model are the steady-state balance equations for various nitrogen and oxygen species in ground and excited states, as well as atomic and molecular ions. The influence of the gas temperature is accounted for by reduction of the neutral density, collisional processes such as recombination, dissociation, V-V and V-T reactions [2], and by reactions involving electronically excited states of O2. The model was applied to study the influence of the gas temperature and vibrational kinetics on the breakdown processes in a preformed air plasma channel. Numerical calculations predict that electrical breakdown occurs at relatively low electric field. The calculated self-consistent breakdown electric field is ˜10 kV/cm for gas temperature of 300 K, while at temperature of 600 K it drops to ˜5.7 kV/cm, in excellent agreement with the experimentally determined breakdown electric field [1]. * NRC-NRL Postdoc [1] Tz.B. Petrova, H.D. Ladouceur, and A.P. Baronavski, 58th Gaseous Electronics Conference, 2005; San Jose, California, FM.00062 [2] J. Loureiro and C.M. Ferreira, J. Phys. D: Appl. Phys 19 (1986) 17-35

Ladouceur, Harold; Baronavski, Andrew; Petrova, Tzvetelina

2006-03-01

224

Characterization of diacylglycerol isomers in edible oils using gas chromatography-ion trap electron ionization mass spectrometry.  

PubMed

Verifying the authenticity of edible oils is of international concern. A new quality control standard for olive oil has been proposed that relates the ratio of 1,2-diacylglycerol (DAG) to 1,3-DAG to sensory aspects of olive oil. DAGs and their isomers are difficult to quantitate and characterize by Flame Ionization Gas Chromatography (GC-FID) due to the lack of suitable standards. Mass detectors offer the advantage of providing structural detail to the eluding DAG(s), thus removing ambiguity to the identification of both resolved and unresolved DAGs in GC chromatograms. In this study, a GC Electron Ionization Mass Spectrometry (GC-EI-MS) method was developed to determine the fatty acid composition and molecular structure of trimethylsilyl (TMS) derivatized DAGs present in edible oils. Twenty-two species of DAG isomers were identified in refined coconut oil and unrefined olive oil utilizing signature fragment ions, [M-15](+), [M-89](+), [M-RCO2](+), [RCO2+58](+) and [M-RCO2CH2](+). The [M-RCO2CH2](+) ion is considered the key diagnostic ion to distinguish between DAG positional isomers. MS/MS spectra of [M-RCO2](+) and [M-15](+) ions obtained from commercial standards containing both 1,2- and 1,3-DAG isomers were used as a model system to confirm the identification of DAG isomers in natural products. Furthermore, a number of reaction mechanisms are proposed to explain the formation of the most abundant mass fragments of DAGs and their isomers. PMID:23880469

Zhu, Hanjiang; Clegg, Michael S; Shoemaker, Charles F; Wang, Selina C

2013-08-23

225

KINEMATICS AND EXCITATION OF THE RAM PRESSURE STRIPPED IONIZED GAS FILAMENTS IN THE COMA CLUSTER OF GALAXIES  

SciTech Connect

We present the results of deep imaging and spectroscopic observations of very extended ionized gas (EIG) around four member galaxies of the Coma Cluster of galaxies: RB 199, IC 4040, GMP 2923, and GMP 3071. The EIGs were serendipitously found in an H{alpha} narrowband imaging survey of the central region of the Coma Cluster. The relative radial velocities of the EIGs with respect to the systemic velocities of the parent galaxies from which they emanate increase almost monotonically with the distance from the nucleus of the respective galaxies, reaching {approx} - 400 to - 800 km s{sup -1} at around 40-80 kpc from the galaxies. The one-sided morphologies and the velocity fields of the EIGs are consistent with the predictions of numerical simulations of ram pressure stripping. We found a very low velocity filament (v{sub rel} {approx} -1300 km s{sup -1}) at the southeastern edge of the disk of IC 4040. Some bright compact knots in the EIGs of RB 199 and IC 4040 exhibit blue continuum and strong H{alpha} emission. The equivalent widths of the H{alpha} emission exceed 200 A and are greater than 1000 Angstrom-Sign for some knots. The emission-line intensity ratios of the knots are basically consistent with those of sub-solar abundance H II regions. These facts indicate that intensive star formation occurs in the knots. Some filaments, including the low-velocity filament of the IC 4040 EIG, exhibit shock-like emission-line spectra, suggesting that shock heating plays an important role in ionization and excitation of the EIGs.

Yoshida, Michitoshi [Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Yagi, Masafumi; Komiyama, Yutaka; Kashikawa, Nobunari [Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Furusawa, Hisanori [Astronomical Data Center, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Hattori, Takashi [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'Ohoku Place, Hilo, HI 96720 (United States); Okamura, Sadanori, E-mail: yoshidam@hiroshima-u.ac.jp [Department of Astronomy, University of Tokyo, Tokyo 113-0033 (Japan)

2012-04-10

226

Gas phase enantiomeric distinction of (R)- and (S)-aromatic hydroxy esters by negative ion chemical ionization mass spectrometry using a chiral reagent gas  

NASA Astrophysics Data System (ADS)

Negative ion chemical ionization (NICI) using a chiral reagent gas such as (2S,3S) butanediol (GSS) allows the differentiation of chiral [alpha] hydroxy esters (MR or MS). The distinction is significantly enhanced by using CID on the deprotonated hetero dimer [M + (GSS-H)]-. The contribution of a non covalent [M + (GSS-H)]- competitive form is very minor. In fact, a covalent form appears favored. To produce a covalent adduct ion, an enantioselectivity of the alkoxide attack on the electrophilic ester site to form a tetravalent adduct is suggested by the product ion abundances. This observed steric control is consistent with the one observed in solution (Cram-Felkin addition/reduction orientation). The dissociations under collision conditions of the product deprotonated diastereomeric compounds show a stereospecific effect in the elimination of alcohol from the tetravalent adduct ions rather than a regeneration of the deprotonated diol reagent as expected from non-covalent heterodimer. This study shows an orientation with a chiral compound that allows, from an analytical point of view, the distinction of enantiomers and the attribution of chirality in the gas phase under NICI conditions.

Mancel, Valérie; Sellier, Nicole; Lesage, Denis; Fournier, Françoise; Tabet, Jean-Claude

2004-10-01

227

Analytical formula for residual current density excited in the process of gas ionization by a few-cycle laser pulse in the low-intensity limit  

NASA Astrophysics Data System (ADS)

This work is devoted to analytical study of excitation of the residual current density (RCD) in the process of gas ionization by a few-cycle laser pulse. The RCD remains in the laser-produced plasma after the passage of the laser pulse and is as an initial push leading to excitation of the plasma oscillations which can radiate terahertz waves. We derive simple closed-form analytical formula for RCD for relatively small peak intensity of few-cycle laser pulse, which corresponds to small final degree of ionization. The dependences of the RCD on laser pulse parameters are discussed.

Silaev, A. A.; Vvedenskii, N. V.

2015-03-01

228

Temperature, Density, Ionization Rate, and Morphology of Diffuse Gas Near the Galactic Center Probed by H_3^+  

NASA Astrophysics Data System (ADS)

Since last year, infrared spectra of H_3^+ and CO have been obtained toward nine stars (designated by us ?+, ?, ?, ?-, ?, ?, ?, ?, and ?-) along the Galactic plane from 138 pc to the west of Sgr A* to 115 pc east, using IRCS of the Subaru Telescope and GNIRS of the Gemini North Observatory. All of the objects lie within the Central Molecular Zone (CMZ), a region of radius ˜150 pc at the center of the Galaxy. All sightlines except that toward ? (a red giant not suitable for H_3^+ spectroscopy) have high H_3^+ column densities on the order of a few times 1015 cm-2. The metastable R(3,3)^l absorption line was sought on seven sightlines (?+, ?, ?, ?-, ?, ?, ?), each of which showed significant signal except ? for which detection of this line was inconclusive. These results indicate that the long (at least several tens of parsecs) columns of warm (T ˜ 250 K) and diffuse (n ? 100 cm-3) gas in which a high ionization rate of ? of a few times 10-15 s-1 exists, found earlier by us on sightlines passing through the central 30 pc of the CMZ are present over nearly the entire CMZ. The velocity profiles of the H_3^+ absorption lines provide information on the morphology of the diffuse gas in the CMZ. The velocity profile toward star ?- (2MASS J17482472-2824313) observed by GNIRS is particularly noteworthy. The sightline toward this star, located 115 pc to the east of Sgr A*, shows the presence of warm diffuse gas near 0 radial velocity and complements an identical result at the west end (on sightlines toward ?+ and previously observed sources ? and ?). Stars nearer to the center of the CMZ show the warm diffuse gas at negative velocities only. Although many more stars need to be observed, the results to date suggest the existence of an expanding molecular ring of diffuse gas which is, unlike previously reported, not rotating but purely expanding. Oka, T., Geballe, T. R., Goto, M., Usuda, T., and McCall, B. J. 2005, ApJ, 632 882 Goto, M., Usuda, T., Nagata, T. et al. 2008, ApJ, 688 306 Oka, T. 2013, Chem. Rev. 113 8738

Oka, Takeshi; Geballe, Thomas R.; Goto, Miwa; Usuda, Tomonori

2014-06-01

229

DENSITY OF WARM IONIZED GAS NEAR THE GALACTIC CENTER: LOW RADIO FREQUENCY OBSERVATIONS  

SciTech Connect

We have observed the Galactic center (GC) region at 0.154 and 0.255 GHz with the Giant Metrewave Radio Telescope. A total of 62 compact likely extragalactic (EG) sources are detected. Their scattering sizes decrease linearly with increasing angular distance from the GC up to about 1 Degree-Sign . The apparent scattering sizes of the sources are more than an order of magnitude less than predicted earlier by the NE2001 model of Galactic electron distribution within 359. Degree-Sign 5 < l < 0. Degree-Sign 5 and -0. Degree-Sign 5 < b < 0. Degree-Sign 5 (Hyperstrong Scattering Region) of the Galaxy. High free-free optical depths ({tau}) are observed toward most of the extended non-thermal sources within 0. Degree-Sign 6 from the GC. Significant variation of {tau} indicates that the absorbing medium is patchy at an angular scale of {approx}10' and n{sub e} is {approx}10 cm{sup -3}, which matches the NE2001 model. This model predicts the EG sources to be resolved out from 1.4 GHz interferometric surveys. However, out of 10 EG sources expected in the region, 8 likely EG are present in the 1.4 GHz catalog. Ionized interfaces of dense molecular clouds to the ambient medium are most likely responsible for strong scattering and low radio frequency absorption. However, dense GC clouds traced by CS J = 1-0 emission are found to have a narrow distribution of {approx}0. Degree-Sign 2 across the Galactic plane. Angular distribution of most EG sources seen through the so-called Hyperstrong Scattering Region are random in b, and typically {approx}7 out of 10 sources will not be seen through the dense molecular clouds, which explains why most of them are not scatter broadened at 1.4 GHz.

Roy, Subhashis, E-mail: roy@ncra.tifr.res.in [NCRA-TIFR, Pune 411007 (India)

2013-08-10

230

STIS observations of the nuclear ionized gas in the elliptical galaxy M84  

NASA Astrophysics Data System (ADS)

We present optical long-slit spectroscopy of the nucleus of the nearby radio galaxy M84 (NGC 4374 = 3C 272.1) obtained with STIS aboard HST. The velocity curve has an S-shape with a peak amplitude of 400 km/s at 0".1 = 8 pc from the nucleus. To model the observed gas kinematics, Bower et al. fit a thin Keplerian disk model to these data, leading to the conclusion that a is approx. = 1.5 x 109 Solar mass dark compact mass (most likely a supermassive black hole) resides in the nucleus of M84.

Bower, G. A.; Green, R. F.; Lindler, D.

1997-01-01

231

The extent and content of low-ionization gas in galaxies  

NASA Astrophysics Data System (ADS)

This dissertation reports combined observations of QSO absorption and H I emission from galaxies which comprise proximate pairs of background and foreground objects. The fortuitous juxtaposition of these QSO-galaxy 'pairs' provides unique opportunities to probe the extent and content of gas in foreground galaxies through evaluation of the incidence and strength of absorption lines in the spectra of the background QSOs. When combined with direct observations of the neutral hydrogen emission from galaxies, the high quality QSO absorption spectra help to quantify the relative distributions of hydrogen and metal-enriched gas in galaxies. We present optical, spectroscopic observations of a new sample of nine close QSO-galaxy pairs. Based on the results from previous studies, these objects were selected with strict limitations on the QSO-galaxy impact parameters. For a select subset of these galaxies, we present synthesis images of the H I emission distributions. These observations are combined with deep optical images and far-infrared fluxes of the galaxies to assess and interpret morphological and environmental conditions which may influence the absorption status. These observations are combined with the existing measurements for all pairs with similar impact parameters to form a 'complete' sample. Using the database from this sample of 22 close pairs, we provide a compilation of results for the individual sources and we draw a number of global conclusions. Naive assumptions regarding a direct correspondence between the incidence and strength of Ca II absorption and the impact parameters are invalid for these data. There does not appear to be a sharp impact parameter limit beyond which Ca II absorption is never detected, nor is there a minimum separation below which absorption is always detected. Limits on the relative abundance of Ca II and H I indicate that the QSO-galaxy pair absorption systems have gas-phase abundances of calcium which are larger than in the majority of Galactic halo sightlines. We tentatively find that the absorbing galaxies may be more luminous in the optical and far-infrared than the non-absorbers. Combined with a qualitative assessment of the galaxy morphologies and environments, we find that these results are consistent with the absorbers being characteristically more active than the non-absorbed. Tidal interactions and active star-formation play important and perhaps crucial roles in the origin of the absorbing gas. We interpret these results in the context of calcium depletion, and we briefly compare the inferred properties with those seen in higher red shift QSO absorption systems.

Womble, Donna Suzanne

1992-01-01

232

Probing the extent and content of low ionization gas in galaxies: QSO absorption and HI emission  

NASA Technical Reports Server (NTRS)

The small projected separations of some QSO's and low-redshift galaxies provide unique opportunities to study the extent and content of gas in galaxies through observation of absorption in the QSO spectra. Observations of these systems provide valuable information on the connection between the absorbing gas and the galaxy, as well as detailed information on the morphology and environment of the galaxy itself. While there is direct evidence that galaxies can produce the intervening-type QSO absorption lines, over the past decade, the study of such 'QSO-galaxy pairs' (at low redshift) has been considered unsuccessful because new detections of absorption were seldom made. A fundamental problem concerning the relation between these low-redshift systems and those seen at moderate to high redshift remains unresolved. Direct and indirect measures of galaxy absorption cross sections at moderate to high redshifts (z is approximately greater than 20.5) are much larger than the optical and HI sizes of local galaxies. However, direct comparison of the low and moderate to high redshift systems is difficult since different ions are observed in different redshift regimes. Observations are presented for a new sample of QSO-galaxy pairs. Nine new QSO's which shine through nearby galaxies (on the sky-plane) were observed to search for CaII absorption in the QSO spectra at the foreground galaxy redshifts.

Womble, Donna S.

1993-01-01

233

Radio Recombination Lines from Inner Galaxy Diffuse Gas. II. The Extended Low-Density Warm Ionized Medium and the ``Worm-ionized Medium''  

NASA Astrophysics Data System (ADS)

We have searched for 1.4 GHz radio recombination lines (RRLs) at 583 positions, mostly toward the galactic interior, and achieved detections at 418 positions. These data characterize the extended low- density warm ionized medium (the ELDWIM). We derive an electron temperature of 7000 K from a comparison of RRL and radio continuum, and estimate that non-LTE effects increase the line intensities by a factor of 1.3. We examine the distribution of the ELDWIM with a velocity-longitude diagram and find some concentration into spiral arms. The ELDWIM is not particularly well correlated with strong H II regions. The azimuthally symmetric inner Galaxy ring component of Taylor & Cordes does not appear in RRL emission, and we propose a revised model in which its electrons are located farther out in spiral arms. We derive the ELDWIM filling factor ?WIM ˜0.01 and an electron density in the emitting regions of ˜5 cm-3. A fraction of the diffuse radio continuum and 100 ?m IR emission is characterized by vertical structures that correspond well to the worm and "chimney" models, in which clustered supernovae blow large cavities in the gaseous disk that, for chimneys, connect to the gaseous halo. We interpret the RRL emission from these structures in terms of the "worm-ionized medium" (W-IM), in which the thermal radio emission arises in the worm walls; the walls are ionized by photons from hot stars in the cluster whose supernovae originally produced the cavity. The nearest example of a worm is the Orion/Eridanus cavity. The previously best-studied example is the Stockert chimney, which we argue is part of a much larger structure. The worms that have well-defined distances are closely confined to spiral arms. We discuss ionization requirements for worms and their associated H II regions and define three classes that describe the ionization of worm walls. These classes depend on the state of star formation in the central molecular cloud, which eventually dissipates. The global ionization requirement for all worm walls is small (˜20%) compared to the total requirement for the Galactic ELDWIM. High-|z| CO may be associated with at least two worms.

Heiles, Carl; Reach, William T.; Koo, Bon-Chul

1996-07-01

234

A new method for total OH reactivity measurements using a fast Gas Chromatographic Photo-Ionization Detector (GC-PID)  

NASA Astrophysics Data System (ADS)

The primary and most important oxidant in the atmosphere is the hydroxyl radical (OH). Currently OH sinks, particularly gas phase reactions, are poorly constrained. One way to characterize the overall sink of OH is to measure directly the ambient loss rate of OH, the total OH reactivity. To date direct measurements of total OH reactivity have been either performed using a Laser Induced Fluorescence (LIF) system ("pump-and-probe" or "flow reactor") or the Comparative Reactivity Method (CRM) with a Proton Transfer Reaction Mass Spectrometer (PTR-MS). Both techniques require large, complex and expensive detection systems. This study presents a feasibility assessment for CRM total OH reactivity measurements using a new detector, a Gas Chromatographic Photo-Ionization Detector (GC-PID). Such a system is smaller, more portable, less power consuming and less expensive than other total OH reactivity measurement techniques. Total OH reactivity is measured by the CRM using a competitive reaction between a reagent (here pyrrole) with OH alone and in the presence of atmospheric reactive molecules. The new CRM method for total OH reactivity has been tested with parallel measurements of the GC-PID and the previously validated PTR-MS as detector for the reagent pyrrole during laboratory experiments, plant chamber and boreal field studies. Excellent agreement of both detectors was found when the GC-PID was operated under optimum conditions. Time resolution (60-70 s), sensitivity (LOD 3-6 s-1) and overall uncertainty (25% in optimum conditions) for total OH reactivity were equivalent to PTR-MS based total OH reactivity measurements. One drawback of the GC-PID system was the steady loss of sensitivity and accuracy during intensive measurements lasting several weeks, and a possible toluene interference. Generally, the GC-PID system has been shown to produce closely comparable results to the PTR-MS and thus in suitable environments (e.g. forests) it presents a viably economical alternative for groups interested in total OH reactivity observations.

Nölscher, A. C.; Sinha, V.; Bockisch, S.; Klüpfel, T.; Williams, J.

2012-05-01

235

COMPLETE IONIZATION OF THE NEUTRAL GAS: WHY THERE ARE SO FEW DETECTIONS OF 21 cm HYDROGEN IN HIGH-REDSHIFT RADIO GALAXIES AND QUASARS  

SciTech Connect

From the first published z {approx}> 3 survey of 21 cm absorption within the hosts of radio galaxies and quasars, Curran et al. found an apparent dearth of cool neutral gas at high redshift. From a detailed analysis of the photometry, each object is found to have a {lambda} = 1216 A continuum luminosity in excess of L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}, a critical value above which 21 cm has never been detected at any redshift. At these wavelengths, and below, hydrogen is excited above the ground state so that it cannot absorb in 21 cm. In order to apply the equation of photoionization equilibrium, we demonstrate that this critical value also applies to the ionizing ({lambda} {<=} 912 A) radiation. We use this to show, for a variety of gas density distributions, that upon placing a quasar within a galaxy of gas, there is always an ultraviolet luminosity above which all of the large-scale atomic gas is ionized. While in this state, the hydrogen cannot be detected or engage in star formation. Applying the mean ionizing photon rate of all of the sources searched, we find, using canonical values for the gas density and recombination rate coefficient, that the observed critical luminosity gives a scale length (3 kpc) similar that of the neutral hydrogen (H I) in the Milky Way, a large spiral galaxy. Thus, this simple yet physically motivated model can explain the critical luminosity (L {sub 912} {approx} L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}), above which neutral gas is not detected. This indicates that the non-detection of 21 cm absorption is not due to the sensitivity limits of current radio telescopes, but rather that the lines of sight to the quasars, and probably the bulk of the host galaxies, are devoid of neutral gas.

Curran, S. J. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Whiting, M. T., E-mail: sjc@physics.usyd.edu.au [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)

2012-11-10

236

Highly Ionized Iron Absorption Lines from Outflowing Gas in the X-Ray Spectrum of NGC 1365  

NASA Astrophysics Data System (ADS)

We present the discovery of four absorption lines in the X-ray spectrum of the Seyfert galaxy NGC 1365, at energies between 6.7 and 8.3 keV. The lines are detected with high statistical confidence (from >20 ? for the strongest to ~4 ? for the weakest) in two XMM-Newton observations 60 ks long. We also detect the same lines, with a lower signal-to-noise ratio (but still >2 ? for each line), in two previous shorter (~10 ks) XMM-Newton observations. The spectral analysis identifies these features as Fe XXV and Fe XXVI K? and K? lines, outflowing with velocities varying between ~1000 and ~5000 km s-1 among the observations. These are the highest quality detections of such lines so far. The high equivalent widths [EW(K?)~100 eV] and the K?/K? ratios imply that the lines are due to absorption of the AGN continuum by a highly ionized gas with column density NH~5×1023 cm-2 at a distance of ~(50-100)RS from the continuum source.

Risaliti, G.; Bianchi, S.; Matt, G.; Baldi, A.; Elvis, M.; Fabbiano, G.; Zezas, A.

2005-09-01

237

IONIZED GAS KINEMATICS AT HIGH RESOLUTION. II. DISCOVERY OF A DOUBLE INFRARED CLUSTER IN II Zw 40  

SciTech Connect

The nearby dwarf galaxy II Zw 40 hosts an intense starburst. At the center of the starburst is a bright compact radio and infrared source, thought to be a giant dense H II region containing Almost-Equal-To 14, 000 O stars. Radio continuum images suggest that the compact source is actually a collection of several smaller emission regions. We accordingly use the kinematics of the ionized gas to probe the structure of the radio-infrared emission region. With TEXES on the NASA-IRTF we measured the 10.5 {mu}m [S IV] emission line with effective spectral resolutions, including thermal broadening, of {approx}25 and {approx}3 km s{sup -1} and spatial resolution {approx}1''. The line profile shows two distinct, spatially coextensive, emission features. The stronger feature is at galactic velocity and has FWHM 47 km s{sup -1}. The second feature is {approx}44 km s{sup -1} redward of the first and has FWHM 32 km s{sup -1}. We argue that these are two giant embedded clusters, and estimate their masses to be Almost-Equal-To 3 Multiplication-Sign 10{sup 5} M{sub Sun} and Almost-Equal-To 1.5 Multiplication-Sign 10{sup 5} M{sub Sun }. The velocity shift is unexpectedly large for such a small spatial offset. We suggest that it may arise in a previously undetected kinematic feature remaining from the violent merger that formed the galaxy.

Beck, Sara; Lahad, Ohr [School of Physics and Astronomy, Tel Aviv University, Ramat Aviv 69978 (Israel)] [School of Physics and Astronomy, Tel Aviv University, Ramat Aviv 69978 (Israel); Turner, Jean [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547 (United States)] [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547 (United States); Lacy, John [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States)] [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Greathouse, Thomas [Southwest Research Institute, San Antonio, TX 78228-0510 (United States)] [Southwest Research Institute, San Antonio, TX 78228-0510 (United States)

2013-04-10

238

Exploring petroleum hydrocarbons in groundwater by double solid phase extraction coupled to gas chromatography-flame ionization detector.  

PubMed

This work proposes an analytical procedure for measuring aliphatic and aromatic hydrocarbons fractions present in groundwater. In this method, hydrocarbons are solid phase extracted (SPE) twice from the groundwater and the resulting fractions are analyzed by gas chromatography with flame ionization detection. The first SPE disposes the hydrocarbons present in groundwater in organic solvents and the second SPE divides them into aliphatic and aromatic hydrocarbons. The validation study is carried out and its uncertainties are discussed. Identifying the main sources of uncertainty is evaluated through applying the bottom-up approach. Limits of detection for hydrocarbons ranges are below 5 µg L(-1), precision is not above of 30%, and acceptable recoveries are reached for aliphatic and aromatic fractions studied. The uncertainty due to volume of the sample, factor of calibration and recovery are the highest contributions. The expanded uncertainty range from 13% to 26% for the aliphatic hydrocarbons ranges and from 14% to 23% for the aromatic hydrocarbons ranges. As application, the proposed method is satisfactorily applied to a set of groundwater samples collected in a polluted area where there is evidence to present a high degree of hydrocarbons. The results have shown the range of aliphatic hydrocarbons >C21-C35 is the most abundant, with values ranging from 215 µg L(-1) to 354 µg L(-1), which it is associated to a contamination due to diesel. PMID:25281108

Pindado Jiménez, Oscar; Pérez Pastor, Rosa Ma; Escolano Segovia, Olga; del Reino Querencia, Susana

2015-01-01

239

Negative surface ionization mass spectrometry for real-time monitoring of iodine molecules in process off-gas  

SciTech Connect

Negative surface ionization mass spectrometry is being developed for continuous measurement of iodine found in the atmospheric environment as a result of nuclear fuel reprocessing. Studies have been made on a series of low work function surface materials (CaCO[sub 3]-SrCO[sub 3]-CaCO[sub 3], BaCO[sub 3]-SrCO[sub 3], LaB[sub 6]) with the intent of developing improved methods for iodine analysis, particularly at the environmental level (ppb concentration range). The results demonstrate the feasibility of performing real-time measurements of the trace amount of iodine encountered in process off-gas by use of a CaCO[sub 3]-SrCO[sub 3]-CaCO[sub 3]-coated rhenium filament emitter. This emitter surface with thermoelectronic work function [phi] at 2.0 eV gives 37.5 times greater sensitivity than the established LaB[sub 6] emitter for iodine analysis. 22 refs., 6 figs., 1 tab.

Kishi, Hiroshi (Oyama National College of Technology (Japan)); Fujii, Toshihiro (National Inst. for Environmental Studies, Tsukuba (Japan))

1994-12-15

240

Time-of-flight ERD with a 200 mm2 Si3N4 window gas ionization chamber energy detector  

NASA Astrophysics Data System (ADS)

Low energy heavy ion elastic recoil detection work has been carried out in Jyväskylä since 2009 using home made timing detectors, a silicon energy detector and a timestamping data acquisition setup forming a time-of-flight-energy telescope. In order to improve the mass resolution of the setup a new energy detector was designed to replace the silicon solid state detector, which suffered from radiation damage and had poor resolution for heavy recoils. In this paper the construction and operation of an isobutane filled gas ionization chamber with a 14 × 14 mm2 100 nm thick silicon nitride window are described. In addition to greatly improved energy resolution for heavy ions, the detector is also able to detect hydrogen recoils simultaneously in the energy range of 100-1000 keV. Additionally the detector has position sensitivity by means of timing measurement, which can be performed without compromising the performance of the detector in any other way. The achieved position sensitivity improves the depth resolution near the surface.

Julin, Jaakko; Laitinen, Mikko; Sajavaara, Timo

2014-08-01

241

Determination of free amino compounds in betalainic fruits and vegetables by gas chromatography with flame ionization and mass spectrometric detection.  

PubMed

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

Kugler, Florian; Graneis, Stephan; Schreiter, Pat P-Y; Stintzing, Florian C; Carle, Reinhold

2006-06-14

242

[Determination of trifluralin residue in aquatic products and edible oils by gas chromatography-negative chemical ionization mass spectrometry].  

PubMed

A confirmatory method was established for the determination of trifluralin residue in aquatic products and edible oils with the technique of offline disperse solid phase extraction and gas chromatography-negative chemical ionization mass spectrometry (DSPE-GC-MS/NCI). Trifluralin was extracted from aquatic products and edible oils with acetonitrile, and liquid-liquid partitioning formed by adding anhydrous magnesium sulfate followed by a simple cleanup step known as dispersive solid-phase extraction. The aliquot was analyzed by GC-MS/NCI using isotope internal standard method. The method was reliable and stable. The recoveries of trifluralin were in the range from 80% to 100% at three spiked levels of 1.0, 2.0, and 3.0 microg/kg, and the RSDs were not more than 10.3%. The linearity of method was good from 1 to 40 microg/L, and the LOD was 0.02 microg/kg. This method can be used as a conclusive evidence method for the determination of trifluralin residue in aquatic products and edible oils. PMID:24984475

Wang, Li; Xia, Guanghui; Shen, Weijian; Wu, Bin; Zhang, Rui; Lu, Huiyuan; Shen, Chongyu; Zhao, Zengyun

2014-03-01

243

Flow-modulated comprehensive two-dimensional gas chromatography with simultaneous flame ionization and quadrupole mass spectrometric detection.  

PubMed

Flow-modulated comprehensive two-dimensional gas chromatography with simultaneous monitoring of the separation by flame ionization (GC × GC-FID) and quadrupole mass spectrometric (GC × GC-qMSD) detection was studied for the analysis of gasoline and kerosene samples. The acquisition frequency of the FID was 100 Hz and of the qMSD 18 Hz for the mass range m/z 40-300. The instrumental set-up is such that both one-dimensional (GC-FID and GC-qMSD) and two-dimensional separations using the same working conditions can be performed. Gasoline and kerosene samples were analyzed on the column combination HP-5MS ((1)D)+HP INNOWax ((2)D). Three modulated peaks were obtained for each hydrocarbon present above 0.1% with ca. 300 ms peak width at the base using 6 s modulation times. Modulated peaks in GC × GC-FID were thus characterized by ca. 30 points while those in GC × GC-qMSD method by 6-8 points only. The FID speed is sufficient for reliable quantitative analysis, while the qMSD scan speed is perfectly appropriate for identification purposes. Moreover, in the GC × GC-qMSD method considerably improved quality of uncorrected spectra was obtained, arising from the enhanced separation over one-dimensional GC-MSD analysis. Spectral match qualities of up to 98% were found. PMID:23395547

Krup?ík, Ján; Gorovenko, Roman; Spánik, Ivan; Sandra, Pat; Armstrong, Daniel W

2013-03-01

244

The temperature and ionization structure of the emitting gas in HII galaxies: Implications for the accuracy of abundance determinations  

E-print Network

We propose a methodology to perform a self-consistent analysis of the physical properties of the emitting gas of HII galaxies adequate to the data that can be obtained with the XXI century technology. This methodology requires the production and calibration of empirical relations between the different line temperatures that should superseed currently used ones based on very simple, and poorly tested, photo-ionization model sequences. As a first step to reach these goals we have obtained simultaneous blue to far red longslit spectra with the William Herschel Telescope (WHT) of three compact HII galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 2 (DR2) spectral catalog using the INAOE Virtual Observatory superserver. Our spectra cover the range from 3200 to 10500 \\AA, including the Balmer jump, the [OII]3727,29 \\AA lines, the [SIII]9069,9532 \\AA doublet as well as various weak auroral lines such as [OIII]4363 \\AA and [SIII]6312 \\AA. For the three objects we have measured at least four line temperatures: T([OIII]), T([SIII]), T([OII]) and T([SII]) and the Balmer continuum temperature T(Bac). These measurements and a careful and realistic treatment of the observational errors yield total oxygen abundances with accuracies between 5 and 9%. These accuracies are expected to improve as better calibrations based on more precise measurements, both on electron temperatures and densities, are produced. ...

Guillermo F. Haegele; Enrique Perez-Montero; Angeles I. Diaz; Elena Terlevich; Roberto Terlevich

2006-08-11

245

Confirmatory method for sulfonamide residues in animal tissues by gas chromatography and pulsed positive ion-negative ion-chemical ionization mass spectrometry.  

PubMed

A confirmatory method has been developed for determination of 13 sulfonamides in edible tissues. The assay involves extraction from a solution resulting from a screening procedure by liquid chromatography and subsequent derivatization. Sulfachloropyridazine (SCP), sulfadiazine (SDA), sulfadimethoxine (SDM), sulfamethazine (SMZ), sulfamerazine (SME), sulfamethoxazole (SMX), sulfamethoxypyridazine (SMP), sulfapyridine (SPR), sulfaquinoxaline (SQX), and sulfathiazole (STA) were detected as the N1-methyl-N4-trifluoroacetyl derivatives, sulfaguanidine (SGU) as the same derivative after cyclization by hexafluoroacetylacetone, and sulfacetamide (SAC) as the methyl derivative. These sulfonamides were detected by gas chromatography and pulsed positive ion-negative ion-chemical ionization mass spectrometry with methane as the reactant gas, whereas sulfanilamide (SAA) was determined as the methyl derivative by electron-impact ionization. PMID:8241826

Mooser, A E; Koch, H

1993-01-01

246

Gas-Phase Synthesis of Singly and Multiply Charged Polyoxovanadate Anions Employing Electrospray Ionization and Collision Induced Dissociation  

SciTech Connect

Electrospray ionization mass spectrometry (ESI-MS) combined with in-source fragmentation and tandem mass spectrometry (MS/MS) experiments were used to generate a wide range of multiply charged vanadium oxide cluster anions including VxOyn- and VxOyCln- ions (x = 1 ? 14, y= 2 ? 36, n = 1 ? 3), protonated clusters, and ligand-bound VxOyn- species. These cluster anions were produced by electrospraying a solution of tetradecavanadate, V14O36Cl(L)5 (L= Et4N+, tetraethylammonium), in acetonitrile. Under mild source conditions, ESI-MS generates a distribution of doubly and triply charged VxOyCln- and VxOyCl(L)(n-1)- clusters predominantly containing 14 vanadium atoms. Accurate mass measurement using high-resolution mass spectrometry (m/?m = 60,000 at m/z 410) enabled unambiguous assignment of the elemental composition of the majority of peaks in the ESI-MS spectrum. In addition, high-sensitivity mass spectrometry allowed the charge state of the cluster ions to be assigned based on the separation of the major from the minor isotope of vanadium. In-source fragmentation resulted in facile formation of smaller VxOyCl(1-2)- and VxOy(1-2)- anions. Collision-induced dissociation (CID) experiments enabled systematic study of the gas-phase fragmentation pathways of the cluster anions generated from solution. Surprisingly simple fragmentation patterns were obtained for all singly and doubly charged VxOyCl and VxOy species generated through multiple MS/MS experiments. In contrast, cluster ions originating directly from solution produced comparatively complex CID spectra. These results indicate that low-energy CID results in formation of stable cage-like structures of VxOyCl and VxOy anions. Furthermore, solution-phase synthesis of one precursor cluster combined with gas-phase CID is an efficient approach for the top-down synthesis of a wide range of multiply charged gas-phase metal oxide clusters for subsequent investigations of structure and reactivity.

Al Hasan, Naila M.; Johnson, Grant E.; Laskin, Julia

2013-09-01

247

Determination of picogram levels of midazolam, and 1- and 4-hydroxymidazolam in human plasma by gas chromatography–negative chemical ionization–mass spectrometry  

Microsoft Academic Search

Midazolam is a widely accepted probe for phenotyping cytochrome P4503A. A gas chromatography–mass spectrometry (GC–MS)–negative chemical ionization method is presented which allows measuring very low levels of midazolam (MID), 1-OH midazolam (1OHMID) and 4-OH midazolam (4OHMID), in plasma, after derivatization with the reagent N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide. The standard curves were linear over a working range of 20pg\\/ml to 5ng\\/ml for the three

C. B. Eap; G. Bouchoux; K. Powell Golay; P. Baumann

2004-01-01

248

Application of Headspace Liquid-Phase Microextraction Using Ionic Liquid as Extractant Combined with Gas Chromatography-Hydrogen Flame Ionization Detector to the Determination of BTEXs in Water  

Microsoft Academic Search

This paper presents a new headspace-liquid-phase microextraction (HS-LPME) strategy for extraction and preconcentration of benzene, toluene, ethyl- benzene, and o-, m- and p-xylenes (BTEXs) from aqueous samples. A typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6), was used as extractant, and the extract was subsequently determined by gas chromatography-hydrogen flame ionization detection (GC-FID). Parameters such as ionic liquid volume, sampling

Minghua Huang; Xiaoguo Ma

2009-01-01

249

Three-step laser induced ionization of Ir and Hg atoms in an air-acetylene flame and a gas cell  

SciTech Connect

The feasibility and the application of three-step excitation and ionization schemes with excimer-pumped, pulsed dye lasers have been studied in the case of Iridium atoms in an air acetylene flame and of Mercury atoms in a gas cell. The detection limits obtained were 0.2 ng/ml in the case of Ir and 10{sup 7} atoms per cubic centimeter of air.

Matveev, Oleg I.; Cavalli, Paolo; Omenetto, Nicolo' [EC, Joint Research Centre Environment Institute, Ispra (Varese) (Italy)

1995-04-01

250

Determination of melamine and cyanuric acid in powdered milk using injection-port derivatization and gas chromatography–tandem mass spectrometry with furan chemical ionization  

Microsoft Academic Search

A reliable, sensitive and eco-friendly injection-port trimethylsilylated (TMS) derivatization and gas chromatography–tandem mass spectrometry (GC–MS\\/MS) with furan chemical ionization (furan-CI) method was developed to determine melamine and cyanuric acid in powdered milk samples. The effects of several parameters related to the TMS-derivatization process (i.e., injection-port temperature, residence time and volume of silylating agent) and of various CI agents were investigated.

Shin-Hwa Tzing; Wang-Hsien Ding

2010-01-01

251

Quantification of low levels of organochlorine pesticides using small volumes (?100 ?l) of plasma of wild birds through gas chromatography negative chemical ionization mass spectrometry  

Microsoft Academic Search

A solid phase extraction and gas chromatography with negative chemical ionization mass spectrometry in scan mode (GC-NCI-MS) method was developed to identify and quantify for the first time low levels of organochlorine pesticides (OCs) in plasma samples of less than 100?l from wild birds. The method detection limits ranged from 0.012 to 0.102pg\\/?l and the method reporting limit from 0.036

Laura B. Rivera-Rodríguez; Ricardo Rodríguez-Estrella; James Jackson Ellington; John J. Evans

2007-01-01

252

Identification of nonprotein amino acids from cycad seeds as N-ethoxycarbonyl ethyl ester derivatives by positive chemical-ionization gas chromatography-mass spectrometry  

Microsoft Academic Search

Nonprotein amino acids from nine species of cycad seeds were analyzed as N-ethoxycarbonyl ethyl ester (ECEE) derivatives by positive chemical-ionization gas chromatography-mass spectrometry. Based on the retention times and mass spectrometry analyses, 12 nonprotein amino acids were identified in these seeds. In addition to the excitatory and putative neurotoxin ß-N-methylamino-l-alanine (BMAA), the known neurotoxin ß-N-oxalylamino-l-alanine (BOAA) was detected from the

Meide Pan; Tom J. Mabry; Ping Cao; Mehdi Moini

1997-01-01

253

Determination of fuel dialkyl ethers and BTEX in water using headspace solid-phase microextraction and gas chromatography–flame ionization detection  

Microsoft Academic Search

A simple procedure for the determination of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), ethyl butyl ether (EBE), tert-amyl methyl ether (TAME), benzene, toluene, ethylbenzene, and xylenes (BTEX) in water using headspace (HS) solid-phase microextraction (HS-SPME) was developed. The analysis was carried out by gas chromatography (GC) equipped with flame ionization detector (FID) and 100% dimethylpolysiloxane fused capillary column.

Idoia Arambarri; Maitena Lasa; Rosa Garcia; Esmeralda Millán

2004-01-01

254

Ionized gas in the halos of edge-on, starburst galaxies: Data and results  

NASA Technical Reports Server (NTRS)

We present narrowband H-alpha and broadband R images, as well as long-slit spectra oriented along the minor and major axes of a sample of about 50 edge-on (a/b greater than or equal to 2), infrared-warm (S(sub 60 microns)/S(sub 100 microns) greater than 0.04), infrared-bright S(sub 60 microns) greater than or equal to 5.4 Jy galaxies. The infrared luminosity of the sample ranges over 10(exp 10) - 10(exp 12) solar luminosity. The spatially resolved spectroscopy includes the measurement of velocity relative to the nuclear velocity, full width at half-maximum, total integrated flux in the profile (for those spectra taken under photometric conditions) for the lines (N II) lambda lambda 6548, 6583, (O I) lambda 6300, H-alpha, and (S II) lambda lambda 6716, 6713 and line ratios as a function of slit position along both the major and minor axes. The resolution of the spectra are between about 3 and 5 A. The spectroscopic data are presented for 5 bins along each axis -- a nuclear bin that is a sum of the CCD rows that cover the half-light diameter centered on the nucleus of the galaxy, two near-nuclear bins which are sums of the CCD rows that cover from one to two half-light radii on each side of the nucleus, and two off-nuclear bins which are sums of the rows at nuclear distances greater than two half-light radii on each side of the nucleus. Additionally, we present recession velocities, nuclear line asymmetries, rotation speeds, minor axis velocity shears, H-alpha luminosities, R-band absolute magnitudes, minor axis H-alpha `excess' and effective radii of the galaxies in h-alpha and the R continuum. We defer discussion of the properties of the emission-line gas and their correlation with the infrared properties of this sample of galaxies to a later paper and limit ourselves to a presentation of the data and analysis.

Lehnert, Matthew D.; Heckman, Timothy M.

1995-01-01

255

Reactions of metal ions and their clusters in the gas phase using laser ionization: Fourier transform mass spectrometry. Progress report, February 1, 1993--January 31, 1994  

SciTech Connect

This report focuses on progress in seven areas: (1) Gas-Phase Reactions of Fe(Benzyne){sup +} with Simple Alkyl Halides; (2) Photodissociation and Collision-Induced Dissociation of Molecular Ions From Methylphenol and Chloromethylphenol; (3) Isotopomer Differentiation Using Metal Ion Chemical Ionization Reagents; (4) Multiple Excitation Collisional Activation (MECA) in Fourier Transform Mass Spectrometry; (5) Chemistry of Fe{sup +}-Arene Ions with Halobenzenes; (6) Gas-Phase Photodissociaton Study of Ag(Benzene){sup +} and Ag(Toluene){sup +}; and (7) Reactivity of Ti{sup 2+} and V{sup 2+} with Small Alkanes.

Freiser, B.S.

1993-09-01

256

Carbon nanotube-based field ionization vacuum  

E-print Network

We report the development of a novel micropump architecture that uses arrays of isolated vertical carbon nanotubes (CNT) to field ionize gas particles. The ionized gas molecules are accelerated to and implanted into a ...

Jang, Daniel, M. Eng. Massachusetts Institute of Technology

2012-01-01

257

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

PubMed

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

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

2009-06-01

258

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

SciTech Connect

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

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

1994-12-01

259

Simulations of a surface glow discharge in a supersonic gas flow in the presence of external ionization  

SciTech Connect

Results of two-dimensional hydrodynamic simulations of a surface glow discharge operating at pressures of 0.2-0.5 Torr in a nitrogen flow propagating with a velocity of 1000 m/s in the presence of external ionization are presented. The effect of the external ionization rate on discharge operation is analyzed. The current-voltage characteristics of the discharge are calculated for different intensities of external ionization in both the presence and absence of secondary electron emission from the cathode. The discharge structure and plasma parameters in the vicinity of the loaded electrode are considered. It is shown that, when the discharge operates at the expense of secondary emission from the cathode, the discharge current and cathode sheath configuration are insensitive to external ionization. It is also demonstrated that, even at a high rate of external ionization, the discharge operates due to secondary emission from the cathode.

Aleksandrov, A. L. [Russian Academy of Sciences, Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch (Russian Federation)

2011-09-15

260

[Determination of four insecticide residues in honey and royal jelly by gas chromatography-negative chemical ionization mass spectrometry].  

PubMed

A method was developed for the determination of four insecticide residues in honey and royal jelly by gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The honey and royal jelly samples were treated with different preparation methods as the result of the different components. The honey sample was extracted with ethyl acetate and cleaned up with primary second amine, and the royal jelly sample was extracted with acetonitrile-water (1:1, v/v), and cleaned up with a C18 solid-phase extraction column. Finally, the extracts of the honey and royal jelly were analyzed by GC-NCI/MS in selected ion monitoring (SIM) mode separately. External standard calibration method was used for quantification. The linearities of calibration curves of the four insecticides were good with the correlation coefficients greater than 0.99 in the range of 50-500 microg/L. The limits of the detection (LODs) of the four insecticides were in the range of 0.12- 5.0 microg/kg, and the limits of the quantification (LOQs) were in the range of 0.40-16.5 microg/kg. The recoveries of the four insecticides spiked in honey and royal jelly at three spiked levels (10, 15 and 20 microg/kg) were in the range of 78.2 -110.0%, and the relative standard deviations (RSDs) were all below 14%. The sensitivity and selectivity of this method were good with no interfering peaks. The proposed method is simple quick and effective to analyze the four insecticide residues in honey and royal jelly. PMID:25255567

Xia, Guanghui; Shen, Weijian; Yu, Keyao; Wu, Bin; Zhang, Rui; Shen, Chongyu; Zhao, Zengyun; Bian, Xiaohong; Xu, Jiyang

2014-07-01

261

DECIPHERING THE IONIZED GAS CONTENT IN THE MASSIVE STAR-FORMING COMPLEX G75.78+0.34  

SciTech Connect

We present subarcsecond observations toward the massive star-forming region G75.78+0.34. We used the Very Large Array to study the centimeter continuum and H{sub 2}O and CH{sub 3}OH maser emission, and the Owens Valley Radio Observatory and Submillimeter Array to study the millimeter continuum and recombination lines (H40{alpha} and H30{alpha}). We found radio continuum emission at all wavelengths, coming from three components: (1) a cometary ultracompact (UC) H II region with an electron density {approx}3.7 Multiplication-Sign 10{sup 4} cm{sup -3}, excited by a B0 type star, and with no associated dust emission; (2) an almost unresolved UCH II region (EAST), located {approx}6'' to the east of the cometary UCH II region, with an electron density {approx}1.3 Multiplication-Sign 10{sup 5} cm{sup -3}, and associated with a compact dust clump detected at millimeter and mid-infrared wavelengths; and (3) a compact source (CORE), located {approx}2'' to the southwest of the cometary arc, with a flux density increasing with frequency, and embedded in a dust condensation of 30 M{sub Sun }. The CORE source is resolved into two compact and unresolved sources which can be well fit by two homogeneous hypercompact H II regions each one photoionized by a B0.5 zero-age main sequence star, or by free-free radiation from shock-ionized gas resulting from the interaction of a jet/outflow system with the surrounding environment. The spatial distribution and kinematics of water masers close to the CORE-N and S sources, together with excess emission at 4.5 {mu}m and the detected dust emission, suggest that the CORE source is a massive protostar driving a jet/outflow.

Sanchez-Monge, Alvaro [Osservatorio Astrofisico di Arcetri, INAF, Largo E. Fermi 5, I-50125 Firenze (Italy)] [Osservatorio Astrofisico di Arcetri, INAF, Largo E. Fermi 5, I-50125 Firenze (Italy); Kurtz, Stan; Lizano, Susana [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 3-72, 58090, Morelia, Michoacan (Mexico)] [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 3-72, 58090, Morelia, Michoacan (Mexico); Palau, Aina [Institut de Ciencies de l'Espai (CSIC-IEEC), Campus UAB-Facultat de Ciencies, Torre C5p 2, E-08193 Bellaterra, Catalunya (Spain)] [Institut de Ciencies de l'Espai (CSIC-IEEC), Campus UAB-Facultat de Ciencies, Torre C5p 2, E-08193 Bellaterra, Catalunya (Spain); Estalella, Robert [Dpt d'Astronomia i Meteorologia (IEEC-UB), Institut de Ciencies del Cosmos, Universitat de Barcelona, Marti i Franques, 1, E-08028 Barcelona (Spain)] [Dpt d'Astronomia i Meteorologia (IEEC-UB), Institut de Ciencies del Cosmos, Universitat de Barcelona, Marti i Franques, 1, E-08028 Barcelona (Spain); Shepherd, Debra [NRAO, P.O. Box O, Socorro, NM 87801-0387 (United States)] [NRAO, P.O. Box O, Socorro, NM 87801-0387 (United States); Franco, Jose [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-264, 04510 Mexico, D.F. (Mexico)] [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-264, 04510 Mexico, D.F. (Mexico); Garay, Guido, E-mail: asanchez@arcetri.astro.it [Departamento de Astronomia, Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago (Chile)] [Departamento de Astronomia, Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago (Chile)

2013-04-01

262

What happens to hydrophobic interactions during transfer from the solution to the gas phase? The case of electrospray-based soft ionization methods.  

PubMed

The disappearance of the hydrophobic effect in the gas phase due to the absence of an aqueous surrounding raises a long-standing question: can noncovalent complexes that are exclusively bound by hydrophobic interactions in solution be preserved in the gas phase? Some reports of successful detection by mass spectrometry of complexes largely stabilized by hydrophobic effect are questionable by the presence of electrostatic forces that hold them together in the gas phase. Here, we report on the MS-based analysis of model supramolecular complexes with a purely hydrophobic association in solution, ?-cyclodextrin, and synthetic adamantyl-containing ligands with several binding sites. The stability of these complexes in the gas phase is investigated by quantum chemical methods (DFT-M06). Compared with the free interaction partners, the inclusion complex between ?-cyclodextrin and adamantyl-containing ligand is shown to be stabilized in the gas phase by ?G = 9.6 kcal mol(-1). The host-guest association is mainly enthalpy-driven due to strong dispersion interactions caused by a large nonpolar interface and a high steric complementarity of the binding partners. Interference from other types of noncovalent binding forces is virtually absent. The complexes are successfully detected via electrospray ionization mass spectrometry, although a high dissociation yield is also observed. We attribute this pronounced dissociation of the complexes to the collisional activation of ions in the atmospheric interface of mass spectrometer. The comparison of several electrospray-based ionization methods reveals that cold spray ionization provides the softest ion generation conditions for these complexes. PMID:21953099

Barylyuk, Konstantin; Balabin, Roman M; Grünstein, Dan; Kikkeri, Raghavendra; Frankevich, Vladimir; Seeberger, Peter H; Zenobi, Renato

2011-07-01

263

What Happens to Hydrophobic Interactions during Transfer from the Solution to the Gas Phase? The Case of Electrospray-Based Soft Ionization Methods  

NASA Astrophysics Data System (ADS)

The disappearance of the hydrophobic effect in the gas phase due to the absence of an aqueous surrounding raises a long-standing question: can noncovalent complexes that are exclusively bound by hydrophobic interactions in solution be preserved in the gas phase? Some reports of successful detection by mass spectrometry of complexes largely stabilized by hydrophobic effect are questionable by the presence of electrostatic forces that hold them together in the gas phase. Here, we report on the MS-based analysis of model supramolecular complexes with a purely hydrophobic association in solution, ?-cyclodextrin, and synthetic adamantyl-containing ligands with several binding sites. The stability of these complexes in the gas phase is investigated by quantum chemical methods (DFT-M06). Compared with the free interaction partners, the inclusion complex between ?-cyclodextrin and adamantyl-containing ligand is shown to be stabilized in the gas phase by ? G = 9.6 kcal mol-1. The host-guest association is mainly enthalpy-driven due to strong dispersion interactions caused by a large nonpolar interface and a high steric complementarity of the binding partners. Interference from other types of noncovalent binding forces is virtually absent. The complexes are successfully detected via electrospray ionization mass spectrometry, although a high dissociation yield is also observed. We attribute this pronounced dissociation of the complexes to the collisional activation of ions in the atmospheric interface of mass spectrometer. The comparison of several electrospray-based ionization methods reveals that cold spray ionization provides the softest ion generation conditions for these complexes.

Barylyuk, Konstantin; Balabin, Roman M.; Grünstein, Dan; Kikkeri, Raghavendra; Frankevich, Vladimir; Seeberger, Peter H.; Zenobi, Renato

2011-07-01

264

Gas-phase chemistry of ionized and protonated GeF4: a joint experimental and theoretical study.  

PubMed

The gas-phase ion chemistry of GeF(4) and of its mixtures with water, ammonia and hydrocarbons was investigated by ion trap mass spectrometry (ITMS) and ab initio calculations. Under ITMS conditions, the only fragment detected from ionized GeF(4) is GeF(3)(+). This cation is a strong Lewis acid, able to react with H(2)O, NH(3) and the unsaturated C(2)H(2), C(2)H(4) and C(6)H(6) by addition-HF elimination reactions to form F(2)Ge(XH)(+), FGe(XH)(2)(+), Ge(XH)(3)(+) (X = OH or NH(2)), F(2)GeC(2)H(+), F(2)GeC(2)H(3)(+) and F(2)GeC(6)H(5)(+). The structure, stability and thermochemistry of these products and the mechanistic aspects of the exemplary reactions of GeF(3)(+) with H(2)O, NH(3) and C(6)H(6) were investigated by MP2 and coupled cluster calculations. The experimental proton affinity (PA) and gas basicity (GB) of GeF(4) were estimated as 121.5 ± 6.0 and 117.1 ± 6.0 kcal mol(-1), respectively, and GeF(4)H(+) was theoretically characterized as an ion-dipole complex between GeF(3)(+) and HF. Consistently, it reacts with simple inorganic and organic molecules to form GeF(3)(+)-L complexes (L = H(2)O, NH(3), C(2)H(2), C(2)H(4), C(6)H(6), CO(2), SO(2) and GeF(4)). The theoretical investigation of the stability of these ions with respect to GeF(3)(+) and L disclosed nearly linear correlations between their dissociation enthalpies and free energies and the PA and GB of L. Comparing the behavior of GeF(3)(+) with the previously investigated CF(3)(+) and SiF(3)(+) revealed a periodically reversed order of reactivity CF(3)(+) < GeF(3)(+) < SiF(3)(+). This parallels the order of the Lewis acidities of the three cations. PMID:21500305

Antoniotti, Paola; Bottizzo, Elena; Operti, Lorenza; Rabezzana, Roberto; Borocci, Stefano; Grandinetti, Felice

2011-05-01

265

HST/COS detection of a Ne VIII absorber towards PG 1407+265: an unambiguous tracer of collisionally ionized hot gas?  

NASA Astrophysics Data System (ADS)

We report the detection of Ne VIII in a zabs = 0.599 61 absorber towards the QSO PG1407+265 (zem= 0.94). Besides Ne VIII, absorption from H I Lyman series lines (H I ?1025-?915), several other low (C II, N II, O II and S II), intermediate (C III, N III, N IV, O III, S IV and S V) and high (S VI, O VI and Ne VIII) ionization metal lines are detected. Disparity in the absorption line kinematics between different ions implies that the absorbing gas comprises of multiple ionization phases. The low and the intermediate ions (except S V) trace a compact (˜410 pc), metal-rich (Z ˜ Z?) and overdense (log nH ˜ -2.6) photoionized region that sustained star formation for a prolonged period. The high ions, Ne VIII and O VI, can be explained as arising in a low density (-5.3 ? log nH ? -5.0), metal-rich (Z ? Z?) and diffuse (˜180 kpc) photoionized gas. The S V, S VI and C IV [detected in the Faint Object Spectrograph (FOS) spectrum] require an intermediate photoionization phase with -4.2 < log nH < -3.5. Alternatively, a pure collisional ionization model, as used to explain the previous known Ne VIII absorbers, with 5.65 < log T < 5.72, can reproduce the S VI, O VI and Ne VIII column densities simultaneously in a single phase. However, even such models require an intermediate phase to reproduce any observable S V and/or C IV. Therefore, we conclude that when multiple phases are present, the presence of Ne VIII is not necessarily an unambiguous indication of collisionally ionized hot gas.

Hussain, T.; Muzahid, S.; Narayanan, A.; Srianand, R.; Wakker, B. P.; Charlton, J. C.; Pathak, A.

2015-01-01

266

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

PubMed

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

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

2011-05-27

267

Optimization of Direct Ionization of CO2 by Controlling the Gas Flow Inside of a Beam-Target  

SciTech Connect

We designed and optimized a target that directs a CO{sub 2} pulse onto a Ti surface where a Cs{sup +} sputtering beam ionizes the CO{sub 2} to generate C{sup -}. These targets will be used for the direct ionization of CO{sub 2} pulses to enable the measurement of carbon isotope ratios in real time. The design was based on the results of Comsol{trademark} simulations of the target configurations.

Salazar Quintero, G A; Ognibene, T

2011-03-07

268

Kinematics of ionized gas associated with the radio nucleus and lobes in the active galaxy IRAS 04210+0400  

Microsoft Academic Search

We have used high resolution longslit spectroscopy to investigate the ionized\\u000agas in the active galaxy IRAS 04210+0400 and its association with the radio\\u000astructure.\\u000a We suggest that two of the ionized components are associated with the central\\u000adouble radio source and observe that the relative positions of these components\\u000avary for different emission lines. Both results are consistent with

A. J. Holloway; W. Steffen; A. Pedlar; D. J. Axon; J. E. Dyson; J. Meaburn; C. N. Tadhunter

1995-01-01

269

Ultrashort soft x-ray pulse-shape measurement using optical field ionization dynamics in noble gas  

Microsoft Academic Search

We propose a cross-correlation technique for measuring the shape of an ultrashort soft x-ray-pulse using the rapid change in the Kr+ population that occurs during optical field-induced ionization. By calculating the time evolution of the Kr charge states during ionization, we showed that the increase in the Kr+ population operates as 'switch', and the transient state of Kr+ during the

Katsuya Oguri; Hidetoshi Nakano; Tadashi Nishikawa; Naoshi Uesugi

2001-01-01

270

Dependence of charge collection distributions and dose on the gas type filling the ionization chamber for a p(66)Be(49) clinical neutron beam  

SciTech Connect

Measurements of central axis depth charge distributions (CADCD) in a p(66)Be(49) clinical neutron beam using A-150 TE plastic ionization chambers (IC) have shown that these distributions are dependent on the gas type filling the ICs. IC volumes from 0.1 to 8 cm/sup 3/ and nine different gases were investigated. Off axis ratios and build-up measurements do not seem to be as sensitive to gas type. The gas dosimetry constants given in the AAPM Protocol for Neutron Beam Dosimetry for air and methane based TE gases were tested for consistency in water and in TE solution filled phantoms at depths of 10 cm, when used in conjunction with an IC having 5 mm thick walls of A-150. 29 refs., 7 figs., 1 tab.

Awschalom, M.; Haken, R.K.T.

1985-01-01

271

Application of A150 plastic-equivalent gas in A150 plastic ionization chambers for Co-60. gamma. rays and 14. 8-MeV neutrons  

SciTech Connect

An ion-chamber gas mixture having an atomic composition similar to that of A150 plastic has been tested experimentally. This ''A150 gas'', air, and methane-based Te gas were each flowed through A150 plastic-walled ion chambers of various sizes, and irradiated with /sup 60/CO ..gamma.. rays and 14.8-MeV neutrons, separately administered. Observed ionization was measured and corrected for recombination losses. Best values for W-bar/sub a150/ , averaged over all chamber sizes, were 26.2 eV/ion pair for /sup 60/CO ..gamma.. rays and 28.2 eV/ion pair for 14.8-MeV neutrons.

Deluca, P.M. Jr.; Attix, F.H.; Pearson, D.W.; Schell, M.C.; Awschalom, M.

1982-05-01

272

CF3+ fragmentation by electron impact ionization of perfluoro-propyl-vinyl-ethers, C5F10O, in gas phase  

NASA Astrophysics Data System (ADS)

The gas phase fragmentations of perfluoro-propyl-vinyl ether (PPVE, C5F10O) are studied experimentally. Dominant fragmentations of PPVE are found to be the result of a dissociative ionization reaction, i.e., CF3+ via direct bond cleavage, and C2F3O? and C3F7O? via electron attachment. Regardless of the appearance energy of around 14.5 eV for the dissociative ionization of CF3+, the observed ion efficiency for the CF3+ ion was extremely large the order of 10?20 cm?2, compared with only 10?21 cm?2 for the other channels. PPVE characteristically generated CF3+ as the largest abundant ion are advantageous for use of feedstock gases in plasma etching processes.

Kondo, Yusuke; Ishikawa, Kenji; Hayashi, Toshio; Miyawaki, Yudai; Takeda, Keigo; Kondo, Hiroki; Sekine, Makoto; Hori, Masaru

2015-04-01

273

Simple pretreatment procedure combined with gas chromatography/multiphoton ionization/mass spectrometry for the analysis of dioxins in soil samples obtained after the T?hoku earthquake.  

PubMed

A simple pretreatment procedure was developed for the analysis of dioxins in soil samples using gas chromatography/multiphoton ionization/time-of-flight mass spectrometry. The sample was subjected to a pressurized liquid extraction procedure, followed by separation using a pair of Sulfoxide and Ag-ION columns for cleanup. Due to the high selectivity of laser ionization, the procedure was simplified and the time required for an analysis was decreased to 3 h. The sample collected after the earthquake and tsunami contained relatively high concentrations of PCBs and PCDD/Fs. This simple and rapid pretreatment procedure can be useful for monitoring the environment to prevent unexpected exposure of toxic dioxins for the workers who have to process more than 20 million tons of the wastes in a few years. PMID:23199015

Chang, Yu-Ching; Imasaka, Totaro

2013-01-01

274

Kinematics and ionization of extended ionized gas in active galaxies. I - The X-ray luminous galaxies NGC 2110, NGC 5506, and MCG -5-23-16  

NASA Technical Reports Server (NTRS)

Direct CCD imaging and long-slit Vidicon spectroscopy have been used to map the emission-line ratios, profiles, and velocity fields over the extended narrow-line regions in three nearby Seyfert galaxies, NGC 2110, NGC 5506, and MCG -5-23-16. The gas in the letter is spatially unresolved. Similarities between the other two nebulae include the excitation mechanism (photoionization by a central nonthermal source) and the overall profiles of the very broad emission lines close to the nucleus. The nebulae are, however, quite different in their global kinematic behavior. In NGC 2110, the gas appears to lie in a disk or flattened spheroid and to be in ordered rotation, with a classical rotation curve, about an axis parallel to the minor axis of the stellar isophotes. The velocity field of NGC 5506 is quite irregular, but a component of rotation in the plane of the galaxy seems to exist.

Wilson, A. S.; Baldwin, J. A.; Ulvestad, J. S.

1985-01-01

275

Field ionization from carbon nanofibers  

E-print Network

The Micro Gas Analyzer project aims to develop power-efficient, high resolution, high sensitivity, portable and real-time gas sensors. We developed a field ionizer array based on gated CNTs. Arrays of CNTs are used because ...

Adeoti, Bosun J

2008-01-01

276

Diffuse Ionized Gas in a Sample of Edge-on Galaxies and Comparisons with H I and Radio Continuum Emission  

NASA Astrophysics Data System (ADS)

We present H? images of four edge-on galaxies: NGC 5775, NGC 3044, NGC 4183, and NGC 3556. Our goals are twofold: first, to continue the study of the occurrence and physical properties of extraplanar diffuse ionized gas (DIG), and second, to compare extraplanar H?, H I, and radio continuum emission. The DIG of NGC 5775 is found to be concentrated in numerous bright filaments extending as high as 6 kpc off the midplane. NGC 3044, on the other hand, has a bright, smooth region of DIG above the central part of the disk with some faint filaments at higher galactocentric radius. Vertical profile fits to the extraplanar emission show that both NGC 5775 and NGC 3044 have DIG layers more extended than the Reynolds layer. In contrast, NGC 4183 shows very little extraplanar DIG. Profile fits suggest that it is very unlikely that the DIG layer of NGC 4183 is as extended as the Reynolds layer. The correlation between levels of star formation and prominence of DIG layers for these galaxies is consistent with previous observations. A prediction of the ``chimney model'' of the ISM is that extraplanar H? features should have H I and radio continuum counterparts. Comparisons among these three tracers have revealed, for the first time, correlations on the scale of individual extraplanar filaments in a galactic disk. NGC 5775 shows correlations between H? filaments, H I shells, and radio continuum spurs that are consistent with a chimney model. However, features identified as possible chimneys in NGC 5775 show radio spectral indices steeper than would be expected if cosmic rays were swept into the halo via galactic winds. Calculations of cosmic-ray propagation scale lengths within the DIG filaments demonstrate that diffusion may indeed be responsible for transporting cosmic rays through chimneys marked by DIG filaments. Correlated emission in these three tracers is also seen in NGC 3044, where extraplanar H I and radio continuum features appear to be associated with the galaxy's central region of extraplanar DIG, as well as filaments above the disk. Such correlations are not as prominent in NGC 3556, where extraplanar DIG detection is hampered by the galaxy's relatively low inclination.

Collins, Joseph A.; Rand, Richard J.; Duric, Nebojsa; Walterbos, René A. M.

2000-06-01

277

Dynamics of Ionized Gas at the Galactic Center: Very Large Array Observations of the Three-dimensional Velocity Field and Location of the Ionized Streams in Sagittarius A West  

NASA Astrophysics Data System (ADS)

We present new results based on high-resolution observations of Sgr A West at the Galactic center with the Very Large Array (VLA) at 1.3 cm. By combining recent observations with those made at earlier epochs with the VLA at wavelengths of 1.3 and 3.6 cm, we measured proper motions for 71 compact H II components in the central 80'' (3 pc, assuming D = 8 pc). Using VLA archival data for the H92? radio recombination line, we also investigated radial velocities in the LSR velocity range from +200 to -415 km s-1. Combining proper motion and radial velocity measurements, we have determined the three-dimensional velocity distribution in Sgr A West. We find that the three ionized streams (Northern Arm, Eastern Arm, and Western Arc) in the central 3 pc can be modeled with three bundles of Keplerian orbits around Sgr A*. Assuming that each of the observed streams of ionized gas follows a single orbit, we determined the five orbital parameters (a, e, ?, ?, i) for each of them using least-square fitting to the loci of the streams. The degeneracy in the orbital solutions for both the direction of flow and the two mirror images can be further resolved using the information obtained from the velocity measurements. Our results confirm earlier results on the streams in the Western Arc and the Northern Arm to be in Keplerian orbits, suggesting that the stream in the Eastern Arm is also consistent with an elliptical orbit. All three are confined within the central 3 pc. Both the Northern and Eastern Arm streams have high eccentricities (e = 0.83 ± 0.10 and 0.82 ± 0.05, respectively), while the Western Arc stream is nearly circular, with e = 0.2 ± 0.15. All three streams orbit around Sgr A* in a counterclockwise sense (viewed from the Earth) and have orbital periods in the range 4-8 × 104 yr. To verify the fit, the distributions of radial and transverse velocity vectors in Sgr A West were also computed using the Keplerian model and they show good agreement with both the proper motion and radial velocity data. In addition, the computed orbits suggest that the Northern and Eastern Arm streams may collide in the "Bar" region (a few arcsec south of Sgr A*) and that most of the orbiting ionized gas in the "Bar" region is located behind Sgr A*. We also report an ionized nebula associated with IRS 8, including a bow shock in radio continuum emission which shows excellent agreement with near infrared observations. From the H92? line data, we find evidence of substantial interaction between the IRS 8 nebula and the Northern Arm stream occurring in the bow-shock region. Other new morphological features revealed in our high-resolution image include (1) a helical structure in the Northern Arm, suggesting that MHD plays an important role in the motion of the ionized gas, in addition to the dynamics determined by the central gravitational field, and (2) a linear feature in the IRS 16 region, suggesting that the compressed edge of the Northern Arm may result from the collective winds and radiation pressure from the high mass stars in the IRS16 cluster.

Zhao, Jun-Hui; Morris, Mark R.; Goss, W. M.; An, Tao

2009-07-01

278

Triboelectric spray ionization.  

PubMed

Triboelectric spray ionization (TESI) is a variation of electrospray ionization (ESI) using common instrumental components, including gas flow, solvent flow rate and heat, the only difference being the use of a high-voltage power supply for ESI or a static charge for TESI. The ionization of solvent or analyte is due to the electrostatic potential difference formed between the spray electrode and counter electrode. The ion source contains a pneumatic spray operated over a range of flow rates (0.15-1.5 µl/min) and gas pressures (0-100). This new design contains a standalone spray assembly and an optional metal mesh in front of the spray. There are several parameters that affect the performance during ionization of molecules including the flow rate of solvent, gas pressure, temperature, solvent acidity, distance and potential difference between emitter and counter electrode. A variable electrostatic potential can be applied for higher ionization efficiency. The new ionization method was successfully applied to solutions of various proteins under different conditions. The same charge-state distributions compared to other ESI techniques are observed for all the protein samples. The unique feature of TESI is very efficient spraying by using a natural electrostatic potential even at the potential that a human body can produce. This provides very gentle ionization efficiency of peptides and proteins in different solvents. PMID:23378087

Özdemir, Abdil; Lin, Jung-Lee; Gillig, Kent J; Chen, Chung-Hsuan

2013-02-01

279

Hydrocarbon type analysis by thin-layer chromatography with flame-ionization detection: vacuum gas oils, heavy feeds, and hydroprocessed products.  

PubMed

Thin-layer chromatography with flame-ionization detection (TLC-FID) provides quantitative hydrocarbon type data as well as distribution of aromatics by ring number. This method has been applied to obtain amounts of saturates, aromatics, and polars in heavy oil distillates such as light vacuum gas oils and heavy vacuum gas oils derived from different crude sources. TLC-FID chromatograms and resultant quantitative hydrocarbon type data show that these distillates vary markedly in aromatic contents and aromatic ring types. Similar observations are made with several fluid catalytic cracking feeds. Effects of process parameters such as operating pressure and temperature on hydroconversion of aromatics and polars from a heavy oil are assessed by TLC-FID. It has been demonstrated that there is a preferential reduction of higher polycyclic aromatic hydrocarbons and polars with an increase of both hydrogen partial pressure and reactor temperature. PMID:15334919

Barman, Bhajendra N

2004-03-01

280

Gas-phase copper and silver complexes with phosphorothioate and phosphorodithioate pesticides investigated using electrospray ionization mass spectrometry.  

PubMed

Efforts to improve agricultural productivity have led to a growing dependency on organophosphorus pesticides. Phosphorothioate and phosphorodithioate pesticides are organophosphorus pesticide subclasses with widespread application for the control of insects feeding on vegetables and fruits. However, even low doses of these pesticides can cause neurological problems in humans; thus, their determination and monitoring in agricultural foodstuffs is important for human health. Phosphorothioate and phosphorodithioate pesticides may be poorly ionized during electrospray, adversely affecting limits of detection. These pesticides can form complexes with Cu(2+) and Ag(+) , however, potentially improving ionization. In the present work, we used electrospray ionization/mass spectrometry (ESI/MS) to study fenitrothion, parathion, diazinon, and malathion coordination complexes with silver and copper ions. Stable?1?:?1 and 1?:?2 metal/pesticide complexes were detected. Mass spectra acquired from pesticide solutions containing Ag(+) or Cu(2+) showed a significant increase in signal-to-background ratio over those acquired from solutions containing only the pesticides, with Ag(+) improving detection more effectively than Cu(2+). Addition of Ag(+) to a pesticide solution improved the limit of detection by ten times. The relative affinity of each pesticide for Ag(+) was related to complex stability, following the order diazinon?>?malathion?>?fenitrothion?>?parathion. The formation of Ag(+)-pesticide complexes can significantly improve the detection of phosphorothioate and phosphorodithioate pesticides using ESI/MS. The technique could potentially be used in reactive desorption electrospray ionization/mass spectrometry to detect phosphorothioate and phosphorodithioate pesticides on fruit and vegetable skins. PMID:25601686

Mustapha, Adetayo M; Pasilis, Sofie P

2015-01-01

281

Separation of aromatic solvents from oil refinery reformates by a newly designed ionic liquid using gas chromatography with flame ionization detection.  

PubMed

The aim of this study was to determine whether the new ionic liquid, N,N-dimethyl-2-oxopyrrolidonium iodide, synthesized in our laboratory is a suitable solvent for the separation of aromatic components benzene, toluene, ethylbenzene, and xylenes from petroleum mixtures (reformates) in liquid-liquid extraction. In pursuance of the above aim, a method to extract all components of a mixture, containing four aromatic components simultaneously, was developed. A new ionic liquid and a previously used liquid were compared for their extraction abilities. These ionic liquids were, respectively, N,N-dimethyl-2-oxopyrrolidinium iodide and 1-ethyl-3-methyl imidazolium ethyl sulfate. The concentrations of each benzene, toluene, ethylbenzene, and xylenes component in the extract and raffinate phases were measured by gas chromatography with flame ionization detection as volume percent to determine the extraction ability of the ionic liquids. The results obtained for both the reformate samples and model mixtures indicated that the new ionic liquid was effective as an extracting solvent for the recovery of aromatic components from reformates. Also the analysis results, using gas chromatography with flame ionization detection, for the reformate samples were as good as the results obtained by a local oil refinery. The extraction results also show that the developed method is very suitable for the separation and analysis of aromatic components in reformates. PMID:25620438

Bahadur, Indra; Mabaso, Mbongeni; Redhi, Gan; Singh, Prashant; Kumar, Sudharsan; Moodley, Kandasamy

2015-03-01

282

Characterization of fatty acid and triacylglycerol composition in animal fats using silver-ion and non-aqueous reversed-phase high-performance liquid chromatography\\/mass spectrometry and gas chromatography\\/flame ionization detection  

Microsoft Academic Search

Fatty acid (FA) and triacylglycerol (TG) composition of natural oils and fats intake in the diet has a strong influence on the human health and chronic diseases. In this work, non-aqueous reversed-phase (NARP) and silver-ion high-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry detection and gas chromatography with flame-ionization detection (GC\\/FID) and mass spectrometry detection are used for

Miroslav Lísa; Kate?ina Netušilová; LukᚠFran?k; Hana Dvo?áková; Vladimír Vrkoslav; Michal Hol?apek

2011-01-01

283

Characteristics of A-150 plastic-equivalent gas in A-150 plastic ionization chambers for p(66)Be(49) neutrons  

SciTech Connect

The evaluation of a gas mixture having an atomic composition similar to that of A-150 tissue-equivalent (TE) plastic has been extended to a high-energy neutron therapy beam. ''A-150'' gas, air, and methane-based TE gas were each flowed through A-150 plastic-walled ion chambers of different sizes and irradiated with p(66)Be(49) neutrons. A tentative value for W-bar(A-150) of 27.3 +- 0.5 JC/sup -1/ was derived for this beam. The W-bar value of the A-150 gas mixture is compared to those of methane-based TE gas and of air for the p(66)Be(49) neutron beam as well as to corresponding values found in similar experiments using 14.8-MeV monoenergetic neutrons. Key words: gas mixture, ion chamber, TE gas, W-bar, neutrons, dosimetry

Awschalom, M.; Rosenberg, I.; Ten Haken, R.K.; Pearson, D.W.; Attix, F.H.; DeLuca, P.M.

1982-11-01

284

Kelvin spray ionization.  

PubMed

A novel self-powered dual spray ionization source has been developed for applications in mass spectrometry. This new source does not use any power supply and produces both positive and negative ions simultaneously. The idea behind this ionization source comes from the Kelvin water dropper. The source employs one or two syringes, two pneumatic sprays operated over a range of flow rates (0.15-15 ?L min(-1)) and gas pressures (0-150 psi), and two double layered metal screens for ion formation. A variable electrostatic potential from 0 to 4 kV can be produced depending on solvent and gas flow rates that allow gentle ionization of compounds. There are several parameters that affect the performance during ionization of molecules including the flow rate of solvent, gas pressure, solvent acidity, position of spray and metal screens with respect to each other and distance between metal screens and the counter electrode. This ionization method has been successfully applied to solutions of peptides, proteins and non-covalent complexes. In comparison with ESI, the charge number of the most populated state is lower than that from ESI. It indicates that this is a softer ionization technique and it produces more protein ions with folded structures. The unique features of Kelvin spray ionization (KeSI) are that the method is self-powered and ionization occurs at very low potentials by providing very low internal energy to the ions. This advantage can be used for the ionization of very fragile molecules and investigation of non-covalent interactions. PMID:24080942

Özdemir, Abdil; Lin, Jung-Lee; Gillig, Kent J; Chen, Chung-Hsuan

2013-11-21

285

Characteristics of A-150 plastic-equivalent gas in A-150 plastic ionization chambers for p(66)Be(49) neutrons  

Microsoft Academic Search

The evaluation of a gas mixture having an atomic composition similar to that of A-150 tissue-equivalent (TE) plastic has been extended to a high-energy neutron therapy beam. ''A-150'' gas, air, and methane-based TE gas were each flowed through A-150 plastic-walled ion chambers of different sizes and irradiated with p(66)Be(49) neutrons. A tentative value for W-bar(A-150) of 27.3 +- 0.5 JC⁻¹

M. Awschalom; I. Rosenberg; R. K. Ten Haken; D. W. Pearson; F. H. Attix; P. M. Deluca

1982-01-01

286

Characteristics of A-150 plastic-equivalent gas in A-150 plastic ionization chambers for p(66)Be(49) neutrons  

Microsoft Academic Search

The evaluation of a gas mixture having an atomic composition similar to that of A-150 tissue-equivalent (TE) plastic has been extended to a high-energy neutron therapy beam. ''A-150'' gas, air, and methane-based TE gas were each flowed through A-150 plastic-walled ion chambers of different sizes and irradiated with p(66)Be(49) neutrons. A tentative value for W(A-150) of 27.3 +\\/- 0.5 JC-1

M. Awschalom; I. Rosenberg; R. K. Ten Haken; D. W. Pearson; F. H. Attix; P. M. DeLuca

2009-01-01

287

Artifact-free quantification of free 3-chlorotyrosine, 3-bromotyrosine, and 3-nitrotyrosine in human plasma by electron capture-negative chemical ionization gas chromatography mass spectrometry and liquid chromatography-electrospray ionization tandem mass spectrometry.  

PubMed

Halogenation and nitration of biomolecules have been proposed as key mechanisms of host defense against bacteria, fungi, and viruses. Reactive oxidants also have the potential to damage host tissue, and they have been implicated in disease. In the current studies, we describe specific, sensitive, and quantitative methods for detecting three stable markers of oxidative damage: 3-chlorotyrosine, 3-bromotyrosine, and 3-nitrotyrosine. Our results indicate that electron capture-negative chemical ionization-gas chromatography/mass spectrometry (EC-NCI GC/MS) is 100-fold more sensitive than liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-MS/MS) for analyzing authentic 3-chlorotyrosine, 3-bromotyrosine, and 3-nitrotyrosine. Using an isotopomer of tyrosine to evaluate artifactual production of the analytes during sample preparation and analysis, we found that artifact generation was negligible with either technique. However, LC-MS/MS proved cumbersome for analyzing multiple samples because it required 1.5 h of run and equilibration time per analysis. In contrast, EC-NCI GC/MS required only 5 min of run time per analysis. Using EC-NCI GC/MS, we were able to detect and quantify attomole levels of free 3-chlorotyrosine, 3-bromotyrosine, and 3-nitrotyrosine in human plasma. Our results indicate that EC-NCI GC/MS is a sensitive and specific method for quantifying free 3-chlorotyrosine, 3-bromotyrosine, and 3-nitrotyrosine in biological fluids in a single, rapid analysis and that it avoids generating any of the analytes ex vivo. PMID:11779118

Gaut, Joseph P; Byun, Jaeman; Tran, Hung D; Heinecke, Jay W

2002-01-15

288

Application of pyrolysis-mass spectrometry and pyrolysis-gas chromatography-mass spectrometry with electron-ionization or resonance-enhanced-multi-photon ionization for characterization of crude oils.  

PubMed

A novel analytical system for gas-chromatographic investigation of complex samples has been developed, that combines the advantages of several analytical principles to enhance the analytical information. Decomposition of high molecular weight structures is achieved by pyrolysis and a high separation capacity due to the chromatographic step provides both an universal as well as a selective and sensitive substance detection. The latter is achieved by simultaneously applying electron ionization quadrupole mass spectrometry (EI-QMS) for structural elucidation and [1+1]-resonance-enhanced-multi-photon ionization (REMPI) combined with time-of-flight mass spectrometry (ToFMS). The system has been evaluated and tested with polycyclic aromatic hydrocarbon (PAH) standards. It was applied to crude oil samples for the first time. In such highly complex samples several thousands of compounds are present and the identification especially of low concentrated chemical species such as PAH or their polycyclic aromatic sulfur containing heterocyclic (PASH) derivatives is often difficult. Detection of unalkylated and alkylated PAH together with PASH is considerably enhanced by REMPI-ToFMS, at times revealing aromatic structures which are not observable by EI-QMS due to their low abundance. On the other hand, the databased structure proposals of the EI-QMS analysis are needed to confirm structural information and isomers distinction. The technique allows a complex structure analysis as well as selective assessment of aromatic substances in one measurement. Information about the content of sulfur containing compounds plays a significant role for the increase of efficiency in the processing of petroleum. PMID:25542090

Otto, Stefan; Streibel, Thorsten; Erdmann, Sabrina; Sklorz, Martin; Schulz-Bull, Detlef; Zimmermann, Ralf

2015-01-15

289

Characteristics of A-150 plastic-equivalent gas in A-150 plastic ionization chambers for p(66)Be(49) neutrons  

SciTech Connect

The evaluation of a gas mixture having an atomic composition similar to that of A-150 TE-plastic has been extended to a high energy neutron therapy beam. A-150 gas, air and methane-based TE gas were each flowed through A-150 plastic-walled ion chambers of different sizes and irradiated with p(66)Be(49) neutrons. A tentative value for anti W(A-150) of 27.3 +- 0.5 J C/sup -1/ was derived for this beam. The anti W value of the A-150 gas mixture is compared to those of methane-based TE gas and of air for the p(66)Be(49) neutron beam as well as to corresponding values found in similar experiments using 14.8 MeV monoenergetic neutrons. 17 references, 3 figures, 3 tables.

Awschalom, M.; Rosenberg, I.; Ten Haken, R.K.; Pearson, D.W.; Attix, F.H.; DeLuca, P.M.

1982-07-08

290

The Kinematics and Physical Conditions of the Ionized Gas in NGC 4593 from Chandra High-Energy Grating Spectroscopy  

E-print Network

We observed the Seyfert 1 galaxy NGC 4593 with the Chandra high energy transmission gratings and present a detailed analysis of the soft X-ray spectrum. We measure strong absorption lines from He-like O, Ne, Mg, Si, H-like N, O, Ne, Mg, Si and highly ionized Fe XIX-XXV. Only the NLya, OLya and MgLya lines appear to be marginally resolved. We identify a spectral feature at $\\sim 0.707$ keV with a neutral Fe L edge, which might suggest that there is dust along the line-of-sight to \

B. McKernan; T. Yaqoob; I. M. George; T. J. Turner

2003-04-24

291

Optical-field-ionization effects on the propagation of an ultraintense laser pulse in high- Z gas jets.  

PubMed

Interaction of an ultraintense, a(0) >1, laser pulse with an underdense Ar plasma is analyzed via a two-dimensional particle-in-cell simulation which self-consistently includes optical-field ionization. In spite of rapid growth of ion charge Z and, hence, electron density at the laser front, relativistic self-focusing is shown to persist owing to a reduction of the expected plasma defocusing resulting from the weak radial dependence of the ion charge on laser intensity (even for Z/gamma>1 where gamma is the electron relativistic factor). PMID:15244746

Zhidkov, A; Koga, J; Esirkepov, T; Hosokai, T; Uesaka, M; Tajima, T

2004-06-01

292

THE RELATIONSHIP BETWEEN THE DENSE NEUTRAL AND DIFFUSE IONIZED GAS IN THE THICK DISKS OF TWO EDGE-ON SPIRAL GALAXIES  

SciTech Connect

We present high-resolution, optical images (BVI + H{alpha}) of the multiphase interstellar medium (ISM) in the thick disks of the edge-on spiral galaxies NGC 4013 and NGC 4302. Our images from the Hubble Space Telescope (HST), Large Binocular Telescope, and WIYN 3.5 m telescope reveal an extensive population of filamentary dust absorption seen to z {approx}2-2.5 kpc. Many of these dusty thick disk structures have characteristics reminiscent of molecular clouds found in the Milky Way disk. Our H{alpha} images show that the extraplanar diffuse ionized gas (DIG) in these galaxies is dominated by a smooth, diffuse component. The strongly filamentary morphologies of the dust absorption have no counterpart in the smoothly distributed H{alpha} emission. We argue that the thick disk DIG and dust-bearing filaments trace physically distinct phases of the thick disk ISM, the latter tracing a dense, warm or cold neutral medium. The dense, dusty matter in the thick disks of spiral galaxies is largely tracing matter ejected from the thin disk via energetic feedback from massive stars. The high densities of the gas may be a result of converging gas flows. This dense material fuels some thick disk star formation, as evidenced by the presence of thick disk H II regions.

Rueff, Katherine M.; Howk, J. Christopher; Pitterle, Marissa; Hirschauer, Alec S. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Fox, Andrew J. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Savage, Blair D., E-mail: krueff@nd.edu [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States)

2013-03-15

293

Potential of gas chromatography-atmospheric pressure chemical ionization-time-of-flight mass spectrometry for the determination of sterols in human plasma.  

PubMed

The application of Gas Chromatography (GC)-Atmospheric Pressure Chemical Ionization (APCI)-Time-of-Flight Mass Spectrometry (TOF-MS) is presented for sterol analysis in human plasma. A commercial APCI interface was modified to ensure a well-defined humidity which is essential for controlled ionization. In the first step, optimization regarding flow rates of auxiliary gases was performed by using a mixture of model analytes. Secondly, the qualitative and quantitative analysis of sterols including oxysterols, cholesterol precursors, and plant sterols as trimethylsilyl-derivatives was successfully carried out. The characteristics of APCI together with the very good mass accuracy of TOF-MS data enable the reliable identification of relevant sterols in complex matrices. Linear calibration lines and plausible results for healthy volunteers and patients could be obtained whereas all mass signals were extracted with an extraction width of 20 ppm from the full mass data set. One advantage of high mass accuracy can be seen in the fact that from one recorded run any search for m/z can be performed. PMID:24463103

Matysik, S; Schmitz, G; Bauer, S; Kiermaier, J; Matysik, F-M

2014-04-11

294

Nonlinear equilibrium spherical dust structures II: Dependence of equilibrium states on volume ionization, number of trapped dust grains, and neutral gas pressure  

SciTech Connect

A study is made of how equilibrium spherical dust structures depend on the volume ionization power, the neutral gas pressure, the number of trapped dust grains, and the ion-to-electron temperature ratio. It is shown that the structures are charged negatively and their charge is determined by the floating potential, which depends on the radius of the structure and on the ion temperature. The structures are charged mainly by absorbing a plasma flux. Conditions are determined under which the polarization fields and charges out-side the structures change sign, indicating the presence of overscreening effects, previously known only for individual dust grains. It is shown that overscreening outside the structures results exclusively from the plasma fluxes that are generated by the structure itself and are required to maintain it in equilibrium.

Tsytovich, V. N. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation)

2009-05-15

295

Fluorohydrogenate Cluster Ions in the Gas Phase: Electrospray Ionization Mass Spectrometry of the [1-Ethyl-3-methylimidazolium+][F(HF)2.3–] Ionic Liquid  

SciTech Connect

Electrospray ionization of the fluorohydrogenate ionic liquid [1-ethyl-3-methylimidazolium][F(HF)2.3] ionic liquid was conducted to understand the nature of the anionic species as they exist in the gas phase. Abundant fluorohydrogenate clusters were produced; however, the dominant anion in the clusters was [FHF-], and not the fluoride-bound HF dimers or trimers that are seen in solution. Density functional theory (DFT) calculations suggest that HF molecules are bound to the clusters by about 30 kcal/mol. The DFT-calculated structures of the [FHF-]-bearing clusters show that the favored interactions of the anions are with the methynic and acetylenic hydrogen atoms on the imidazolium cation, forming planar structures similar to those observed in the solid state. A second series of abundant negative ions was also formed that contained [SiF5-] together with the imidazolium cation and the fluorohydrogenate anions that originate from reaction of the spray solution with silicate surfaces.

Gary S. Groenewold; James E. Delmore; Michael T. Benson; Tetsuya Tsuda; Rika Hagiwara

2013-12-01

296

Quantitation of fourteen urinary alpha-amino acids using isobutane gas chromatography chemical ionization mass spectrometry with 13C amino acids as internal standards.  

PubMed

Isobutane chemical ionization gas chromatography mass spectometry of the N-trifluoroacetyl-carboxy-n-butyl ester derivatives of amino acids, using a commercial per-13C-amino acid mixture as internal standards, provided a sensitive and specific method for quantitative analysis of fourteen urinary alpha-amino acids. A computer controlled quadrupole mass spectrometer was used in a selected ion monitoring mode to record the ion current due to the protonated molecular ions of each alpha-amino acid/13C analogue pair. BASIC programmes located peak maxima, and using previously established standard curves, calculated the amino acid content on the bases of both peak height and peak area ratios. Duplicate amino acid analyses are possible on 5 microliter of urine. Instrumental analysis required 25 minutes, automated data processing 10 minutes, and sample preparation 2 hours. Detection limits approached 1 ng with a typical mean standard deviation of 2% for the instrumental analysis. PMID:6452181

Finlayson, P J; Christopher, R K; Duffield, A M

1980-10-01

297

In-gas-cell laser ionization spectroscopy in the vicinity of 100Sn: Magnetic moments and mean-square charge radii of N=50-54 Ag  

NASA Astrophysics Data System (ADS)

In-gas-cell laser ionization spectroscopy studies on the neutron deficient 97-101Ag isotopes have been performed with the LISOL setup. Magnetic dipole moments and mean-square charge radii have been determined for the first time with the exception of 101Ag, which was found in good agreement with previous experimental values. The reported results allow tentatively assigning the spin of 97,99Ag to 9/2 and confirming the presence of an isomeric state in these two isotopes, whose collapsed hyperfine structure suggests a spin of 1/2 >. The effect of the N=50 shell closure is not only manifested in the magnetic moments but also in the evolution of the mean-square charge radii of the isotopes investigated, in accordance with the spherical droplet model predictions.

Ferrer, R.; Bree, N.; Cocolios, T. E.; Darby, I. G.; De Witte, H.; Dexters, W.; Diriken, J.; Elseviers, J.; Franchoo, S.; Huyse, M.; Kesteloot, N.; Kudryavtsev, Yu.; Pauwels, D.; Radulov, D.; Roger, T.; Savajols, H.; Van Duppen, P.; Venhart, M.

2014-01-01

298

Identification of nonprotein amino acids from cycad seeds as N-ethoxycarbonyl ethyl ester derivatives by positive chemical-ionization gas chromatography-mass spectrometry.  

PubMed

Nonprotein amino acids from nine species of cycad seeds were analyzed as N-ethoxycarbonyl ethyl ester (ECEE) derivatives by positive chemical-ionization gas chromatography-mass spectrometry. Based on the retention times and mass spectrometry analyses, 12 nonprotein amino acids were identified in these seeds. In addition to the excitatory and putative neurotoxin beta-N-methylamino-L-alanine (BMAA), the known neurotoxin beta-N-oxalylamino-L-alanine (BOAA) was detected from the seeds of Macrozamia moorei and M. communis, and delta-N-oxalyl-ornithine was obtained from the Cycas revoluta seeds. A novel nonprotein amino acid named cycasindene, previously reported from C. revoluta, was also found in the seeds of members of the C. angulata and C. rumphii complex. Eight additional known nonprotein amino acids were also identified. This is the first report of the neurotoxin BOAA from cycad seeds. PMID:9409004

Pan, M; Mabry, T J; Cao, P; Moini, M

1997-11-01

299

Determination of gamma-hydroxybutyric acid (GHB) in plasma and urine by headspace solid-phase microextraction and gas chromatography/positive ion chemical ionization mass spectrometry.  

PubMed

A new method for the qualitative and quantitative analysis of gamma-hydroxybutyric acid (GHB) in plasma and urine samples is described. It involves the conversion of GHB to gamma-butyrolactone (GBL), its subsequent headspace solid-phase microextraction (SPME), and detection by gas chromatography/positive ion chemical ionization mass spectrometry (GC/PICI-MS), using D(6)-GBL as internal standard. The assay is linear over a plasma GHB range of 1-100 microg/mL (n = 5, r = 0.999) and a urine GHB range of 5-150 microg/mL (n = 5, r = 0. 998). Relative intra- and inter-assay standard deviations, determined for plasma and urine samples at 5 and 50 microg/mL, are all below 5%. The method is simple, specific and reasonably fast. It may be applied for clinical and forensic toxicology as well as for purposes of therapeutic drug monitoring. PMID:11114057

Frison, G; Tedeschi, L; Maietti, S; Ferrara, S D

2000-01-01

300

Pyrolysis-gas chromatography/multiphoton ionization/time-of-flight mass spectrometry for the rapid and selective analysis of polycyclic aromatic hydrocarbons in aerosol particulate matter.  

PubMed

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOFMS) coupled with a Curie-point pyrolyzer as a sample introduction technique was applied for the rapid and selective analysis of the polycyclic aromatic hydrocarbons (PAHs) that are a part of aerosol particulate matter. Increasing the operating temperature of the pyrolyzer also increased the number of observed peaks, but the peak areas of a few PAHs decreased due to thermal decomposition. In the present study, more than 100 peaks were confirmed using 0.3 mg of an aerosol particulate matter, and further sensitive detection would be achievable. The advantages of MPI/TOFMS, such as optical selectivity and simultaneous determination properties, allowed the trace analysis of highly complicated particulate matter-even in the absence of pretreatment. Therefore, this method would help elucidate the origin of particulate matter when sampling from different points for short periods of time. PMID:25213817

Sakurai, Shunsuke; Uchimura, Tomohiro

2014-01-01

301

Electrospray Ionization Mass Spectrometry  

SciTech Connect

Electrospray Ionization (ESI) is a process whereby gas phase ions are created from molecules in solution. As a solution exits a narrow tube in the presence of a strong electric field, an aerosol of charged droplets are is formed that produces gas phase ions as they it desolvates. ESI-MS comprises the creation of ions by ESI and the determination of their mass to charge ratio (m/z) by MS.

Kelly, Ryan T.; Marginean, Ioan; Tang, Keqi

2014-06-13

302

Mechanistic investigation of ionization suppression in electrospray ionization  

Microsoft Academic Search

We show results from experiments designed to determine the relative importance of gas phase processes and solution phase processes\\u000a into ionization suppression observed in biological sample extracts. The data indicate that gas phase reactions leading to\\u000a the loss of net charge on the analyte is not likely to be the most important process involved in ionization suppression. The\\u000a results point

Richard King; Ryan Bonfiglio; Carmen Fernandez-Metzler; Cynthia Miller-Stein; Timothy Olah

2000-01-01

303

An argon-nitrogen-hydrogen mixed-gas plasma as a robust ionization source for inductively coupled plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

Multivariate optimization of an argon-nitrogen-hydrogen mixed-gas plasma for minimum matrix effects, while maintaining analyte sensitivity as much as possible, was carried out in inductively coupled plasma mass spectrometry. In the presence of 0.1 M Na, the 33.9 ± 3.9% (n = 13 elements) analyte signal suppression on average observed in an all-argon plasma was alleviated with the optimized mixed-gas plasma, the average being - 4.0 ± 8.8%, with enhancement in several cases. An addition of 2.3% v/v N2 in the outer plasma gas, and 0.50% v/v H2 to the central channel, as a sheath around the nebulizer gas flow, was sufficient for this drastic increase in robustness. It also reduced the background from ArO+ and Ar2+ as well as oxide levels by over an order of magnitude. On the other hand, the background from NO+ and ArN+ increased by up to an order of magnitude while the levels of doubly-charged ions increased to 7% (versus 2.7% in an argon plasma optimized for sensitivity). Furthermore, detection limits were generally degraded by 5 to 15 fold when using the mixed-gas plasma versus the argon plasma for matrix-free solution (although they were better for several elements in 0.1 M Na). Nonetheless, the drastically increased robustness allowed the direct quantitative multielement analysis of certified ore reference materials, as well as the determination of Mo and Cd in seawater, without using any matrix-matching or internal standardization.

Makonnen, Yoseif; Beauchemin, Diane

2014-09-01

304

Highly sensitive and selective analysis of urinary steroids by comprehensive two-dimensional gas chromatography combined with positive chemical ionization quadrupole mass spectrometry  

PubMed Central

Comprehensive two dimensional gas chromatography (GC×GC) provides greater separation space than conventional GC. Because of fast peak elution, a time of flight mass spectrometer (TOFMS) is the usual structure-specific detector of choice. The quantitative capabilities of a novel GC×GC fast quadrupole MS were investigated with electron ionization (EI), and CH4 or NH3 positive chemical ionization (PCI) for analysis of endogenous urinary steroids targeted in anti-doping tests. Average precisions for steroid quantitative analysis from replicate urine extractions were 6% (RSD) for EI and 8% for PCI-NH3. The average limits of detection (LOD) calculated by quantification ions for 12 target steroids spiked into steroid-free urine matrix (SFUM) were 2.6 ng mL?1 for EI, 1.3 ng mL?1 for PCI-CH4, and 0.3 ng mL?1 for PCI-NH3, all in mass scanning mode. The measured limits of quantification (LOQ) with full mass scan GC×GC-qMS were comparable with the LOQ values measured by one-dimensional GC-MS in single ion monitoring (SIM) mode. PCI-NH3 yields fewer fragments and greater (pseudo)molecular ion abundances than EI or PCI-CH4. These data show a benchtop GC×GC-qMS system has the sensitivity, specificity, and resolution to analyze urinary steroids at normal urine concentrations, and that PCI-NH3, not currently available on most GC×GC-TOFMS instruments, is of particular value for generation of structure-specific ions. PMID:22606686

Zhang, Ying; Tobias, Herbert J.; Brenna, J. Thomas

2014-01-01

305

Multiscale approach combining nonadiabatic dynamics with long-time radiative and non-radiative decay: dissociative ionization of heavy rare-gas tetramers revisited.  

PubMed

A multiscale approach is proposed to address short-time nonadiabatic dynamics and long-time decay. We show the role of both radiative and non-radiative processes in cluster decay mechanisms on examples of rare-gas cluster fragmentation after electron impact ionization. Nonadiabatic molecular dynamics is used as an efficient tool for theoretical study on femto- and picosecond scales and a multiscale approach based on kinetic rates of radiative as well as non-radiative transitions, both considered as parallel reaction channels, is used for the analysis of the long-time system relaxation spanning times over microseconds to infinity. While the radiative processes are typically slow, the system relaxation through non-radiative electronic transitions connected with electron-nuclear interchange of energy may, on the other hand, significantly vary in kinetic rates according to kinetic couplings between relevant adiabatic states. While the predictions of picosecond molecular dynamics themselves fail, the results of the multiscale model for the electron-impact post-ionization fragmentation of krypton and xenon tetramers are in agreement with experiment, namely, in leading to the conclusion that charged monomers prevail. More specifically, on microsecond and longer scales, mainly slow radiative processes are substantial for krypton cluster decay, while for xenon the radiative and slow non-radiative processes compete. In general, the role of slow decay processes through non-radiative transitions is comparable with the role of radiative decay mechanism. The novel multiscale model substantially improves theoretical predictions for the xenon tetramer decay and also further improves the good agreement between theory and experiment we reached previously for krypton. PMID:23387580

Jane?ek, Ivan; Jan?a, Tomáš; Naar, Pavel; Kalus, René; Gadea, Florent Xavier

2013-01-28

306

Radio polarimetric imaging of the interstellar medium: magnetic field and diffuse ionized gas structure near the W3/W4/W5/HB3 complex  

E-print Network

We have used polarimetric imaging to study the magneto-ionic medium of the Galaxy, obtaining 1420 MHz images with an angular resolution of 1' over more than 40 square-degrees of sky around the W3/W4/W5/HB3 HII region/SNR complex in the Perseus Arm. Features detected in polarization angle are imposed on the linearly polarized Galactic synchrotron background emission by Faraday rotation arising in foreground ionized gas having an emission measure as low as 1 cm^{-6} pc. Several new remarkable phenomena have been identified, including: mottled polarization arising from random fluctuations in a magneto-ionic screen that we identify with a medium in the Perseus Arm, probably in the vicinity of the HII regions themselves; depolarization arising from very high rotation measures (several times 10^3 rad m^{-2}) and rotation measure gradients due to the dense, turbulent environs of the HII regions; highly ordered features spanning up to several degrees; and an extended influence of the HII regions beyond the boundaries defined by earlier observations. In particular, the effects of an extended, low-density ionized halo around the HII region W4 are evident, probably an example of the extended HII envelopes postulated as the origin of weak recombination-line emission detected from the Galactic ridge. Our polarization observations can be understood if the uniform magnetic field component in this envelope scales with the square-root of electron density and is 20 microG at the edge of the depolarized region around W4, although this is probably an over-estimate since the random field component will have a significant effect.

A. D. Gray; T. L. Landecker; P. E. Dewdney; A. R. Taylor; A. G. Willis; M. Normandeau

1998-12-08

307

ON THE ORIGINS OF THE DIFFUSE H{alpha} EMISSION: IONIZED GAS OR DUST-SCATTERED H{alpha} HALOS?  

SciTech Connect

It is known that the diffuse H{alpha} emission outside of bright H II regions not only are very extended, but also can occur in distinct patches or filaments far from H II regions, and the line ratios of [S II] {lambda}6716/H{alpha} and [N II] {lambda}6583/H{alpha} observed far from bright H II regions are generally higher than those in the H II regions. These observations have been regarded as evidence against the dust-scattering origin of the diffuse H{alpha} emission (including other optical lines), and the effect of dust scattering has been neglected in studies on the diffuse H{alpha} emission. In this paper, we reexamine the arguments against dust scattering and find that the dust-scattering origin of the diffuse H{alpha} emission cannot be ruled out. As opposed to the previous contention, the expected dust-scattered H{alpha} halos surrounding H II regions are, in fact, in good agreement with the observed H{alpha} morphology. We calculate an extensive set of photoionization models by varying elemental abundances, ionizing stellar types, and clumpiness of the interstellar medium (ISM) and find that the observed line ratios of [S II]/H{alpha}, [N II]/H{alpha}, and He I {lambda}5876/H{alpha} in the diffuse ISM accord well with the dust-scattered halos around H II regions, which are photoionized by late O- and/or early B-type stars. We also demonstrate that the H{alpha} absorption feature in the underlying continuum from the dust-scattered starlight ({sup d}iffuse galactic light{sup )} and unresolved stars is able to substantially increase the [S II]/H{alpha} and [N II]/H{alpha} line ratios in the diffuse ISM.

Seon, Kwang-Il [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Witt, Adolf N., E-mail: kiseon@kasi.re.kr [Ritter Astrophysical Research Center, University of Toledo, Toledo, OH 43606 (United States)

2012-10-20

308

Total OH reactivity measurements using a new fast Gas Chromatographic Photo-Ionization Detector (GC-PID)  

NASA Astrophysics Data System (ADS)

The primary and most important oxidant in the atmosphere is the hydroxyl radical (OH). Currently OH sinks, particularly gas phase reactions, are poorly constrained. One way to characterize the overall sink of OH is to measure directly the ambient loss rate of OH, the total OH reactivity. To date, direct measurements of total OH reactivity have been either performed using a Laser-Induced Fluorescence (LIF) system ("pump-and-probe" or "flow reactor") or the Comparative Reactivity Method (CRM) with a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS). Both techniques require large, complex and expensive detection systems. This study presents a feasibility assessment for CRM total OH reactivity measurements using a new detector, a Gas Chromatographic Photoionization Detector (GC-PID). Such a system is smaller, more portable, less power consuming and less expensive than other total OH reactivity measurement techniques. Total OH reactivity is measured by the CRM using a competitive reaction between a reagent (here pyrrole) with OH alone and in the presence of atmospheric reactive molecules. The new CRM method for total OH reactivity has been tested with parallel measurements of the GC-PID and the previously validated PTR-MS as detector for the reagent pyrrole during laboratory experiments, plant chamber and boreal field studies. Excellent agreement of both detectors was found when the GC-PID was operated under optimum conditions. Time resolution (60-70 s), sensitivity (LOD 3-6 s-1) and overall uncertainty (25% in optimum conditions) for total OH reactivity were similar to PTR-MS based total OH reactivity measurements. One drawback of the GC-PID system was the steady loss of sensitivity and accuracy during intensive measurements lasting several weeks, and a possible toluene interference. Generally, the GC-PID system has been shown to produce closely comparable results to the PTR-MS and thus in suitable environments (e.g. forests) it presents a viably economical alternative for groups interested in total OH reactivity observations.

Nölscher, A. C.; Sinha, V.; Bockisch, S.; Klüpfel, T.; Williams, J.

2012-12-01

309

Ionization of Trimethylgallium  

NASA Astrophysics Data System (ADS)

We report the cross sections for ionization of Trimethylgallium (GaC_3H_9) by electron impact and rates for gas-phase ion-molecule collisions, measured by Fourier transform mass spectrometry. Electron impact ionization of GaC_3H9 over the energy range of 10-70 eV produces the molecular ion and 7 fragment ions, with a total cross section of 1.1±0.1x10-15 cm^2 at 50 eV, and approximately constant to 70 eV. Absolute cross sections are determined by adding Ar to the gas sample for signal comparison with the known Ar ionization cross section. All of the observed ions contain Ga, and more than 97% of the ion population consists of GaC_2H_6^+, Ga^+ and GaCH_3^+ within the energy range studied. The results illustrate the preferential methyl abstractions. Gas-phase ion-molecule collisions in the 10-7 Torr\\cdots range produce GaC_2H_6^+ and Ga^+ at the expense of other ionic species. Ar^+ is found to react with GaC_3H9 also forming mainly GaC_2H_6^+ and Ga^+. No significant clustering reactions have been observed, implying that gas-phase ionic polymerization does not contribute to the Ga film formation.

Jiao Dejoseph, C. Q., Jr.; Garscadden, A.

1999-10-01

310

Determination of nitrated polycyclic aromatic hydrocarbons in diesel particulate-related standard reference materials by using gas chromatography/mass spectrometry with negative ion chemical ionization.  

PubMed

Gas chromatography/mass spectrometry (GC/MS) with negative ion chemical ionization (NICI) detection was utilized for quantitative determination of nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in diesel particulate-related standard reference materials (SRMs). Prior to GC/MS analysis, isolation of the nitro-PAHs from the complex diesel particulate extract was accomplished using solid phase extraction (SPE) and normal-phase liquid chromatographic (LC) fractionation using an amino/cyano stationary phase. Concentrations of eight to ten mononitro-PAHs and three dinitropyrenes were determined in three diesel particulate-related SRMs: SRM 1650a Diesel Particulate Matter, SRM 1975 Diesel Particulate Extract, and SRM 2975 Diesel Particulate Matter (Industrial Forklift). The results from GC/MS NICI using two different columns (5% phenyl methylpolysiloxane and 50% phenyl methylpolysiloxane) were compared to each other and to results from two other laboratories for selected nitro-PAHs. 1-Nitropyrene was the most abundant nitro-PAHs in each of the diesel particulate SRMs (19.8+/-1.1 micro g g(-1) particle in SRM 1650a and 33.1+/-0.6 micro g g(-1) particle in SRM 2975). Three dinitropyrene isomers were measured in SRM 1975 at 0.5-1.4 micro g g(-1) extract and in SRM 2975 at 1-3 micro g g(-1) particle. PMID:12589503

Bezabeh, Dawit Z; Bamford, Holly A; Schantz, Michele M; Wise, Stephen A

2003-02-01

311

[Determination of polybrominated diphenyl ethers in indoor dust using ultrasonic-assisted extraction and gas chromatography-negative chemical ionization mass spectrometry].  

PubMed

A method for the determination of eight polybrominated diphenyl ethers (PBDEs) in indoor dust was developed. A vacuum cleaner was used for gathering the house dust, and n-hexane was added and the extraction was performed in an ultrasonic bath. The supernatant was concentrated and then n-hexane was added to 0.1 mL. Gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS) has been investigated for the determination of the eight PBDE congeners in indoor dust. The eight PBDEs were separated within 20 min. The absolute recoveries were 53.2% - 107.6%. The relative standard deviations (RSDs) of intra-day were between 2.8% and 16.5%, while the RSDs of inter-day were between 6.4% and 22.6%. The limits of detection (LOD, S/N = 3) were in the range of 0.003 - 0.015 ng/g except the LOD of BDE-209 was 0.15 ng/g. The results indicated that the proposed method is sensitive, accurate, fast, simple, low solvent consumption and suitable for the determination of tri- to deca-BDEs in indoor dust. PMID:23593880

Zhang, Xiaoling; Wang, Bingling; Lu, Xiaomei; Zhang, Qi; Zhang, Zhengdong

2012-12-01

312

Hollow fiber liquid-phase microextraction coupled with gas chromatography-flame ionization detection for the profiling of fatty acids in vegetable oils.  

PubMed

The development of a two phase hollow fiber liquid-phase microextraction technique, followed by gas-chromatography-flame ionization detection (GC-FID) for the profiling of the fatty acids (FAs) (lauric, myristic, palmitic, stearic, palmitoleic, oleic, linoleic, linolenic and arachidic) in vegetable oils is described. Heptadecanoic acid methyl ester was used as the internal standard. The FAs were transesterified to their corresponding methyl esters prior to the extraction. Extraction parameters such as type of extracting solvent, temperature, extraction time, stirring speed and salt addition were studied and optimized. Recommended conditions were extraction solvent, n-tridecane; extraction time, 35 min; extraction temperature, ambient; without addition of salt. Enrichment factors varying from 37 to 115 were achieved. Calibration curves for the nine FAs were well correlated (r(2)>0.994) within the range of 10-5000 ?g L(-1). The limit of detection (signal:noise, 3) was 4.73-13.21 ng L(-1). The method was successfully applied to the profiling of the FAs in palm oils (crude, olein, kernel, and carotino cooking oil) and other vegetable oils (soybean, olive, coconut, rice bran and pumpkin). The encouraging enrichments achieved offer an interesting option for the profiling of the minor and major FAs in palm and other vegetable oils. PMID:21081239

Siang, Gan Hui; Makahleh, Ahmad; Saad, Bahruddin; Lim, Boey Peng

2010-12-24

313

Characterization of a commercial gas chromatography-flame ionization detection system for the in situ determination of C5-C10 hydrocarbons in ambient air.  

PubMed

A commercial automated gas chromatograph with preconcentration on solid adsorbents (AirmoVoc HC1010) was coupled with a mass spectrometer in parallel with the flame ionization detection (FID) system and characterized for its suitability for quasi continuous measurements of atmospheric hydrocarbons (HCs) with a time resolution of 20 min. Of the 50 identified HCs in the range C5-C10, 15 elute in isolated peaks and 20 in groups of two or more HCs. The remaining 15 HCs suffer from coelution by oxygenated and halogenated compounds. Procedures to minimize and quantify the blanks and the memory from the adsorbents are described. Calibration was based on a custom-made diffusion source. The accuracy of this calibration (+/-10%, 2sigma) was verified by analysis of a certified 70-component standard (average deviation: -4.3+/-2%). During a field experiment in Summer 1998, the HC1010 system was compared with a custom-made GC system with cryogenic preconcentration and much better separation properties but lower time resolution. In ambient air, good agreement (2sigma deviation <14% or 10 ppt) was found for HCs and groups of HCs that are free from coelution with oxygenated compounds, whereas large discrepancies (in some cases more than a factor of three) were found for those HCs that coelute with oxygenated compounds, as identified by MS. Analysis of the mass spectra from those peaks via specific target ions showed much better agreement with the FID system of the reference GC within 25%. PMID:10866068

Konrad, S; Volz-Thomas, A

2000-05-12

314

Silica-based ionogels: nanoconfined ionic liquid-rich fibers for headspace solid-phase microextraction coupled with gas chromatography-barrier discharge ionization detection.  

PubMed

In this work, hybrid silica-based materials with immobilized ionic liquids (ILs) were prepared by sol-gel technology and evaluated as solid-phase microextraction (SPME) fiber coatings. High loadings of the IL 1-methyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide ([C4MIM][TFSI]) were confined within the hybrid network. Coatings composition and morphology were evaluated using scanning electron microscopy and energy dispersive X-ray spectrometry. The obtained ionogel SPME fibers exhibited high extractability for aromatic volatile compounds, yielding good sensitivity and precision when combined with a gas chromatograph with barrier ionization discharge (GC-BID) detection. A central composite design was used for assessing the effect of experimental parameters on the extraction process. Under optimized conditions, the proposed ionogel SPME fiber coatings enabled the achievement of excellent enrichment factors (up to 7400). The limits of detection (LODs) were found in the range 0.03-1.27 ?g L(-1), whereas the repeatability and fiber-to-fiber reproducibility were 5.6% and 12.0% on average, respectively. Water samples were analyzed by the proposed methodology, showing recovery values in the range of 88.7-113.9%. The results obtained in this work suggest that ionogels can be promising coating materials for future applications of SPME and related sample preparation techniques. PMID:25371321

Pena-Pereira, Francisco; Marcinkowski, Lukasz; Kloskowski, Adam; Namie?nik, Jacek

2014-12-01

315

Measurements of gas-phase inorganic and organic acids from biomass fires by negative-ion proton-transfer chemical-ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

Emissions from 34 laboratory biomass fires were investigated at the combustion facility of the U.S. Department of Agriculture Fire Sciences Laboratory in Missoula, Montana. Gas-phase organic and inorganic acids were quantified using negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS), open-path Fourier transform infrared spectroscopy (OP-FTIR), and proton-transfer-reaction mass spectrometry (PTR-MS). NI-PT-CIMS is a novel technique that measures the mass-to-charge ratio (m/z) of ions generated from reactions of acetate (CH3C(O)O-) ions with inorganic and organic acids. The emission ratios for various important reactive acids with respect to CO were determined. Emission ratios for isocyanic acid (HNCO), 1,2 and 1,3-benzenediols (catechol, resorcinol), nitrous acid (HONO), acrylic acid, methacrylic acid, propionic acid, formic acid, pyruvic acid, and glycolic acid were measured from biomass burning. Our measurements show that there is a significant amount of HONO in fresh smoke. The NI-PT-CIMS measurements were validated by comparison with OP-FTIR measurements of HONO and formic acid (HCOOH) and with PTR-MS measurements of HCOOH.

Veres, Patrick; Roberts, James M.; Burling, Ian R.; Warneke, Carsten; de Gouw, Joost; Yokelson, Robert J.

2010-12-01

316

Determination of triazole pesticide residues in edible oils using air-assisted liquid-liquid microextraction followed by gas chromatography with flame ionization detection.  

PubMed

In the present study, a rapid, simple, and highly efficient sample preparation method based on air-assisted liquid-liquid microextraction followed by gas chromatography with flame ionization detection was developed for the extraction, preconcentration, and determination of five triazole pesticides (penconazole, hexaconazole, diniconazole, tebuconazole, and triticonazole) in edible oils. Initially, the oil samples were diluted with hexane and a few microliter of a less soluble organic solvent (extraction solvent) in hexane was added. To form fine and dispersed extraction solvent droplets, the mixture of oil sample solution and extraction solvent is repeatedly aspirated and dispersed with a syringe. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 2.2-6.1 and 7.3-20 ?g/L, respectively. Enrichment factors and extraction recoveries were in the ranges of 71-96 and 71-96%, respectively. The relative standard deviations for the extraction of 100 and 250 ?g/L of each pesticide were less than 5% for intraday (n = 6) and interday (n = 3) precisions. Finally edible oil samples were successfully analyzed using the proposed method, and hexaconazole was found in grape seed oil. PMID:25580590

Farajzadeh, Mir Ali; Feriduni, Behruz; Mogaddam, Mohammad Reza Afshar

2015-03-01

317

Simultaneous derivatization and dispersive liquid-liquid microextraction of anilines in different samples followed by gas chromatography-flame ionization detection.  

PubMed

A new method based on simultaneous derivatization and dispersive liquid-liquid microextraction in one step is developed for determination of five anilines in different aqueous samples. In this method, acetonitrile containing microlitre-level of butylchloroformate was rapidly injected into aqueous sample by a syringe. After centrifugation of the cloudy solution, the fine droplets of the butylchloroformate containing the derivatized analytes were sedimented in the bottom of the conical test tube. Then, 0.5 ?L of the settled phase was injected into gas chromatography-flame ionization detector. Under optimum conditions the enrichment factors, extraction recoveries and enhancement factors were high and ranged between 197 and 298, 47 and 69%, and 4.7 and 6.2, respectively. Linearity was observed in the range of 10-10,000 ?g L(-1) (except for 4-chloroaniline), and the relative standard deviations (RSD %) were lower than 5.2% (n=6). The limits of detection of the six anilines ranged from 1 to 3 ?g L(-1). Different aqueous samples including tap, river and well waters as well as wastewaters were successfully analyzed. In this method the extraction solvent and derivatization agent are the same and the derivatization reaction was carried out under mild conditions. This method has several advantages over other reported techniques, being very simple, rapid and less hazardous for the environment. PMID:22967655

Farajzadeh, Mir Ali; Nouri, Nina

2012-09-15

318

Trace analysis of impurities in bulk gases by gas chromatography-pulsed discharge helium ionization detection with "heart-cutting" technique.  

PubMed

A method has been developed for the detection of low-nL/L-level impurities in bulk gases such as H(2), O(2), Ar, N(2), He, methane, ethylene and propylene, respectively. The solution presented here is based upon gas chromatography-pulsed discharge helium ionization detection (GC-PDHID) coupled with three two-position valves, one two-way solenoid valve and four packed columns. During the operation, the moisture and heavy compounds are first back-flushed via a pre-column. Then the trace impurities (except CO(2) which is diverted to a separate analytical column for separation and detection) together with the matrix enter onto a main column, followed by the heart-cut of the impurities onto a longer analytical column for complete separation. Finally the detection is performed by PDHID. This method has been applied to different bulk gases and the applicability of detecting impurities in H(2), Ar, and N(2) are herewith demonstrated. As an example, the resulting detection limit of 100 nL/L and a dynamic range of 100-1000 nL/L have been obtained using an Ar sample containing methane. PMID:17850804

Weijun, Yao

2007-10-12

319

The determination of 5-hydroxytryptamine, related indolealkylamines and 5-hydroxyindoleacetic acid in the bovine eye by gas chromatography-negative ion chemical ionization mass spectrometry.  

PubMed

Methods were developed for the analysis of 5-hydroxytryptamine, related indolealkylamines (tryptamine, melatonin, 5-methoxytryptamine, N-acetyl-5-hydroxytryptamine and 6-hydroxymelatonin) and 5-hydroxyindole-3-acetic acid (5HIAA) in bovine retina, aqueous and vitreous humours. 5-Hydroxytryptamine and related indolealkylamines were extracted and derivatized to form their corresponding pentafluoropropionyl spirocyclic derivatives. 5HIAA was extracted and derivatized to the corresponding pentafluoropropionamide-trifluoroethyl derivative. Identification and quantitation by gas chromatography-negative ion chemical ionization mass spectrometry was made with reference to deuteriated internal standards. 5-Hydroxytryptamine was present in all (n = 34) retinal samples analysed (20.53 +/- 1.64 ng) while N-acetyl-5-hydroxytryptamine was detected in half of the samples of retina (0.06 +/- 0.02 ng). Melatonin (0.15 +/- 0.06 ng) and tryptamine (0.78 +/- 0.34 ng) were detected in only a small number of retinas. 5-Methoxytryptamine was not present in retina. 5-Hydroxytryptamine was also present in aqueous (0.76 +/- 0.17 ng ml-1 and vitreous (0.35 +/- 0.05 ng ml-1' humours from bovine eye. Tryptamine, melatonin, 5-methoxytryptamine and N-acetyl-5-hydroxytryptamine were not detected in bovine aqueous and vitreous humours. 5HIAA was found in both bovine aqueous (2.03 +/- 0.38 ng ml-1) and vitreous (0.65 +/- 0.06 ng ml-1) humours, but its consistent determination in retina was obviated by interference from spurious peaks. PMID:7689343

Best, S A; Midgley, J M; Huang, W; Watson, D G

1993-01-01

320

Quantification of low levels of organochlorine pesticides using small volumes (gas chromatography negative chemical ionization mass spectrometry.  

PubMed

A solid phase extraction and gas chromatography with negative chemical ionization mass spectrometry in scan mode (GC-NCI-MS) method was developed to identify and quantify for the first time low levels of organochlorine pesticides (OCs) in plasma samples of less than 100 microl from wild birds. The method detection limits ranged from 0.012 to 0.102 pg/microl and the method reporting limit from 0.036 to 0.307 pg/microl for alpha, gamma, beta and delta-hexachlorocyclohexane (HCH), heptachlor, aldrin, heptachlor epoxide, endosulfan I, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), dieldrin, endrin, endosulfan-II, endrin-aldehyde and endosulfan-sulfate. Pesticide levels in small serum samples from individual Falco sparverius, Sturnella neglecta, Mimus polyglottos and Columbina passerina were quantified. Concentrations ranged from not detected (n/d) to 204.9 pg/microl for some OC pesticides. All levels in the food web in and around cultivated areas showed the presence of pesticides notwithstanding the small areas for agriculture existing in the desert of Baja California peninsula. PMID:17240024

Rivera-Rodríguez, Laura B; Rodríguez-Estrella, Ricardo; Ellington, James Jackson; Evans, John J

2007-07-01

321

Mapping the Ionization State of Laser-Irradiated Ar Gas Jets With Multi-Wavelength Monochromatic X-Ray Imaging  

SciTech Connect

Two-dimensional monochromatic images of fast-electron stimulated Ar K{alpha} and He-{alpha} x-ray self-emission have recorded a time-integrated map of the extent of Ar{sup {approx}6+} and Ar{sup 16+} ions, respectively, within a high density (10{sup 20} cm{sup -3} atomic density) Ar plasma. This plasma was produced by irradiating a 2 mm wide clustering Ar gas jet with an ultra-high intensity (10{sup 19} W/cm{sup 2}, 200 fs) Ti:Sapphire laser operating at 800 nm. Spherically bent quartz crystals in the 200 (for K{alpha}) and 201 (for He-{alpha}) planes were used as near-normal incidence reflective x-ray optics. We see that a large (830 {micro}m long) region of plasma emits K{alpha} primarily along the laser axis, while the He-{alpha} emission is confined to smaller hot spot (230 {micro}m long) region that likely corresponds to the focal volume of the f/8 laser beam. X-ray spectra from a Bragg spectrometer operating in the von Hamos geometry, which images in one dimension, indicate that the centroids of the K{alpha} and He-{alpha} emission regions are separated by approximately 330 {micro}m along the laser axis.

Kugland, N L; Doppner, T; Kemp, A; Schaeffer, D; Glenzer, S H; Niemann, C

2010-04-08

322

Gridded electron reversal ionizer  

NASA Technical Reports Server (NTRS)

A gridded electron reversal ionizer forms a three dimensional cloud of zero or near-zero energy electrons in a cavity within a filament structure surrounding a central electrode having holes through which the sample gas, at reduced pressure, enters an elongated reversal volume. The resultant negative ion stream is applied to a mass analyzer. The reduced electron and ion space-charge limitations of this configuration enhances detection sensitivity for material to be detected by electron attachment, such as narcotic and explosive vapors. Positive ions may be generated by generating electrons having a higher energy, sufficient to ionize the target gas and pulsing the grid negative to stop the electron flow and pulsing the extraction aperture positive to draw out the positive ions.

Chutjian, Ara (Inventor)

1993-01-01

323

Determination of benzene, toluene, ethylbenzene and xylenes in indoor air at environmental levels using diffusive samplers in combination with headspace solid-phase microextraction and high-resolution gas chromatography–flame ionization detection  

Microsoft Academic Search

An improved analytical method for passive air sampling is presented based on a combination of commercially available diffusive samplers with headspace solid-phase microextraction and high-resolution gas chromatography with flame ionization detection (HRGC–FID). This procedure is targeted for short-term BTEX (benzene, toluene, ethylbenzene and o-, m- and p-xylenes) determinations at environmental concentrations and can be applied for sampling intervals between 30

K Elke; E Jermann; J Begerow; L Dunemann

1998-01-01

324

Analysis of ketamine and norketamine in urine by automatic solid-phase extraction (SPE) and positive ion chemical ionization–gas chromatography–mass spectrometry (PCI–GC–MS)  

Microsoft Academic Search

Ketamine (KT) is widely abused for hallucination and also misused as a “date-rape” drug in recent years. An analytical method using positive ion chemical ionization–gas chromatography–mass spectrometry (PCI–GC–MS) with an automatic solid-phase extraction (SPE) apparatus was studied for the determination of KT and its major metabolite, norketamine (NK), in urine. Six ketamine suspected urine samples were provided by the police.

Eun-mi Kim; Ju-seon Lee; Sang-kil Choi; Mi-ae Lim; Hee-sun Chung

2008-01-01

325

A novel reusable ionic liquid chemically bonded fused-silica fiber for headspace solid-phase microextraction\\/gas chromatography-flame ionization detection of methyl tert-butyl ether in a gasoline sample  

Microsoft Academic Search

A novel ionic liquid (IL) bonded fused-sil-ica fiber for headspace solid-phase microextraction (HS-SPME)\\/gas chromatography-flame ionization detection (GC-FID) of methyl tert-butyl ether (MTBE) in a gasoline sample was prepared and used. The new proposed chemically bonded fiber has better thermal stability and durability than its corresponding physically coated fiber. Another advantage is that no spacer was used for the purpose of

Ramin Amini; Ahmad Rouhollahi; Mina Adibi; Ali Mehdinia

2011-01-01

326

Hollow fiber supported liquid-phase microextraction using ionic liquid as extractant for preconcentration of benzene, toluene, ethylbenzene and xylenes from water sample with gas chromatography-hydrogen flame ionization detection  

Microsoft Academic Search

A novel method has been developed for the analysis of benzene, toluene, ethyl-benzene, and o-, m- and p-xylenes (BTEXs) in water using hollow fiber supported liquid-phase microextraction (HF-LPME) followed by gas chromatography-hydrogen flame ionization detection. Ionic liquid 1-butyl-3-methy-limidazolium hexafluorophosphate ([BMIM][PF6]) was acted as the extractant for extraction and preconcentration of BTEXs from aqueous samples, and a porous-walled polypropylene hollow fiber

Xiaoguo Ma; Minghua Huang; Zhihua Li; Jianmei Wu

2011-01-01

327

Utilization of a benzyl functionalized polymeric ionic liquid for the sensitive determination of polycyclic aromatic hydrocarbons; parabens and alkylphenols in waters using solid-phase microextraction coupled to gas chromatography–flame ionization detection  

Microsoft Academic Search

The functionalized polymeric ionic liquid poly(1-(4-vinylbenzyl)-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide (poly(VBHDIm+NTf2?)) has been used as successful coating in solid-phase microextraction (SPME) to determine a group of fourteen endocrine disrupting chemicals (ECDs), including polycyclic aromatic hydrocarbons (PAHs), alkylphenols, and parabens, in several water samples. The performance of the PIL fiber in direct immersion mode SPME followed by gas chromatography (GC) with flame-ionization detection (FID)

Jessica López-Darias; Verónica Pino; Yunjing Meng; Jared L. Anderson; Ana M. Afonso

2010-01-01

328

Oscillations in Ionized Gases  

Microsoft Academic Search

A simple theory of electronic and ionic oscillations in an ionized gas has been developed. The electronic oscillations are so rapid (ca. 109 cycles) that the heavier positive ions are unaffected. They have a natural frequency nue=(ne2pim)12 and, except for secondary factors, do not transmit energy. The ionic oscillations are so slow that the electron density has its equilibrium value

Lewi Tonks; Irving Langmuir

1929-01-01

329

Determination of picogram levels of midazolam, and 1- and 4-hydroxymidazolam in human plasma by gas chromatography-negative chemical ionization-mass spectrometry.  

PubMed

Midazolam is a widely accepted probe for phenotyping cytochrome P4503A. A gas chromatography-mass spectrometry (GC-MS)-negative chemical ionization method is presented which allows measuring very low levels of midazolam (MID), 1-OH midazolam (1OHMID) and 4-OH midazolam (4OHMID), in plasma, after derivatization with the reagent N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide. The standard curves were linear over a working range of 20 pg/ml to 5 ng/ml for the three compounds, with the mean coefficients of correlation of the calibration curves (n = 6) being 0.999 for MID and 1OHMID, and 1.0 for 4OHMID. The mean recoveries measured at 100 pg/ml, 500 pg/ml, and 2 ng/ml, ranged from 76 to 87% for MID, from 76 to 99% for 1OHMID, from 68 to 84% for 4OHMID, and from 82 to 109% for N-ethyloxazepam (internal standard). Intra- (n = 7) and inter-day (n = 8) coefficients of variation determined at three concentrations ranged from 1 to 8% for MID, from 2 to 13% for 1OHMID and from 1 to 14% for 4OHMID. The percent theoretical concentrations (accuracy) were within +/-8% for MID and 1OHMID, within +/-9% for 4OHMID at 500 pg/ml and 2 ng/ml, and within +/-28% for 4OHMID at 100 pg/ml. The limits of quantitation were found to be 10 pg/ml for the three compounds. This method can be used for phenotyping cytochrome P4503A in humans following the administration of a very low oral dose of midazolam (75 microg), without central nervous system side-effects. PMID:15018796

Eap, C B; Bouchoux, G; Powell Golay, K; Baumann, P

2004-04-01

330

Measurement of the incorporation and repair of exogenous 5-hydroxymethyl-2'-deoxyuridine in human cells in culture using gas chromatography-negative chemical ionization-mass spectrometry.  

PubMed

The DNA of all organisms is constantly damaged by oxidation. Among the array of damage products is 5-hydroxymethyluracil, derived from oxidation of the thymine methyl group. Previous studies have established that HmU can be a sensitive and valuable marker of DNA damage. More recently, the corresponding deoxynucleoside, 5-hydroxymethyl-2'-deoxyuridine (HmdU), has proven to be valuable for the introduction of controlled amounts of a single type of damage lesion into the DNA of replicating cells, which is subsequently repaired by the base excision repair pathway. Complicating the study of HmU formation and repair, however, is the known chemical reactivity of the hydroxymethyl group of HmU under conditions used to hydrolyze DNA. In the work reported here, this chemical property has been exploited by creating conditions that convert HmU to the corresponding methoxymethyluracil (MmU) derivative that can be further derivatized to the 3,5-bis-(trifluoromethyl)benzyl analogue. This derivatized compound can be detected by gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) with good sensitivity. Using isotopically enriched exogenous HmdU and human osteosarcoma cells (U2OS) in culture, we demonstrate that this method allows for the measurement of HmU in DNA formed from the incorporation of exogenous HmdU. We further demonstrate that the addition of isotopically enriched uridine to the culture medium allows for the simultaneous measurement of DNA replication and repair kinetics. This sensitive and facile method should prove valuable for studies on DNA oxidation damage and repair in living cells. PMID:17914883

Rogstad, Daniel K; Darwanto, Agus; Herring, Jason L; Rogstad, Katherine Noyes; Burdzy, Artur; Hadley, Scott R; Neidigh, Jonathan W; Sowers, Lawrence C

2007-12-01

331

Methane standards made in whole and synthetic air compared by cavity ring down spectroscopy and gas chromatography with flame ionization detection for atmospheric monitoring applications.  

PubMed

There is evidence that the use of whole air versus synthetic air can bias measurement results when analyzing atmospheric samples for methane (CH4) and carbon dioxide (CO2). Gas chromatography with flame ionization detection (GC-FID) and wavelength scanned-cavity ring down spectroscopy (WS-CRDS) were used to compare CH4 standards produced with whole air or synthetic air as the matrix over the mole fraction range of 1600-2100 nmol mol(-1). GC-FID measurements were performed by including ratios to a stable control cylinder, obtaining a typical relative standard measurement uncertainty of 0.025%. CRDS measurements were performed using the same protocol and also with no interruption for a limited time period without use of a control cylinder, obtaining relative standard uncertainties of 0.031% and 0.015%, respectively. This measurement procedure was subsequently used for an international comparison, in which three pairs of whole air standards were compared with five pairs of synthetic air standards (two each from eight different laboratories). The variation from the reference value for the whole air standards was determined to be 2.07 nmol mol(-1) (average standard deviation) and that of synthetic air standards was 1.37 nmol mol(-1) (average standard deviation). All but one standard agreed with the reference value within the stated uncertainty. No significant difference in performance was observed between standards made from synthetic air or whole air, and the accuracy of both types of standards was limited only by the ability to measure trace CH4 levels in the matrix gases used to produce the standards. PMID:25679264

Flores, Edgar; Rhoderick, George C; Viallon, Joële; Moussay, Philippe; Choteau, Tiphaine; Gameson, Lyn; Guenther, Franklin R; Wielgosz, Robert Ian

2015-03-17

332

Kinetic-Hydrodynamic Models of the Solar Wind Interaction with the Partially Ionized Supersonic Flow of the Local Interstellar Gas: Predictions and Interpretations of the Experimental Data  

NASA Astrophysics Data System (ADS)

At present there is no doubt that the local interstellar medium (LISM) is mainly partially ionized hydrogen gas moving with a supersonic flow relative to the solar system. The bulk velocity of this flow is approximately equal ˜26 km/s. Although the interaction of the solar wind with the charged component (below plasma component) of the LISM can be described in the framework of hydrodynamic approach, the interaction of H atoms with the plasma component can be correctly described only in the framework of kinetic theory because the mean free path of H atoms in the main process of the resonance charge exchange is comparable with a characteristic length of the problem considered. Results of self-consistent, kinetic-hydrodynamic models are considered in this review paper. First, such the model was constructed by Baranov and Malama (J. Geophys. Res. 98(A9):15,157-15,163, 1993). Up to now it is mainly developed by Moscow group taking into account new experimental data obtained onboard spacecraft studying outer regions of the solar system (Voyager 1 and 2, Pioneer 10 and 11, Hubble Space Telescope, Ulysses, SOHO and so on). Predictions and interpretations of experimental data obtained on the basis of these models are presented. Kinetic models for describing H atom motion were later suggested by Fahr et al. (Astron. Astrophys 298:587-600, 1995) and Lipatov et al. (J. Geophys. Res. 103(A9):20,631-20,642, 1998). However they were not self-consistent and did not incorporate sources to the plasma component. A self-consistent kinetic-hydrodynamic model suggested by Heerikhuisen et al. (J. Geophys. Res. 111:A06110, 2006, Astrophys. J. 655:L53-L56, 2007) was not tested on the results by Baranov and Malama (J. Geophys. Res. 111:A06110, 1993) although it was suggested much later. Besides authors did not describe in details their Monte Carlo method for a solution of the H atom Boltzmann equation and did not inform about an accuracy of this method. Therefore the results of Heerikhuisen et al. (J. Geophys. Res. 111:A06110, 2006) are in open to question and will not be considered in this review paper. That is why below we will mainly consider a progress of the Moscow group on heliospheric modelling endeavours in the kinetic-hydrodynamic approach. Criticism of the models that treat interstellar hydrogen in the heliosphere as several fluids is given. It is shown that the multi-fluid models give rise to unreal results especially for distributions of neutral component parameters. Magnetohydrodynamic (MHD) modelling of the solar wind interaction with the LISM gas is also reviewed.

Baranov, Vladimir B.

2009-02-01

333

Screening and quantification of pesticide residues in fruits and vegetables making use of gas chromatography-quadrupole time-of-flight mass spectrometry with atmospheric pressure chemical ionization.  

PubMed

An atmospheric pressure chemical ionization source has been used to enhance the potential of gas chromatography coupled with quadrupole time-of-flight (QTOF) mass spectrometry (MS) for screening and quantification purposes in pesticide residue analysis. A screening method developed in our laboratory for around 130 pesticides has been applied to fruit and vegetable samples, including strawberries, oranges, apples, carrots, lettuces, courgettes, red peppers, and tomatoes. Samples were analyzed together with quality control samples (at 0.05 mg/kg) for each matrix and for matrix-matched calibration standards. The screening strategy consisted in first rapid searching and detection, and then a refined identification step using the QTOF capabilities (MS(E) and accurate mass). Identification was based on the presence of one characteristic m/z ion (Q) obtained with the low collision energy function and at least one fragment ion (q) obtained with the high collision energy function, both with mass errors of less than 5 ppm, and an ion intensity ratio (q/Q) within the tolerances permitted. Following this strategy, 15 of 130 pesticides were identified in the samples. Afterwards, the quantitation capabilities were tested by performing a quantitative validation for those pesticides detected in the samples. To this aim, five matrices were selected (orange, apple, tomato, lettuce, and carrot) and spiked at two concentrations (0.01 and 0.1 mg/kg), and quantification was done using matrix-matched calibration standards (relative responses versus triphenyl phosphate used as an internal standard). Acceptable average recoveries and relative standard deviations were obtained for many but not all pesticide-matrix combinations. These figures allowed us to perform a retrospective quantification of positives found in the screening without the need for additional analysis. Taking advantage of the accurate-mass full-spectrum data provided by QTOF MS, we searched for a higher number of compounds (up to 416 pesticides) in a second stage by performing extra data processing without any new sample injection. Several more pesticides were detected, confirmed, and/or tentatively identified when the reference standard was unavailable, illustrating in this way the potential of gas chromatography-QTOF MS to detect pesticides in addition to the ones targeted in quantitative analysis of pesticides in food matrices. PMID:24828980

Cervera, M I; Portolés, T; López, F J; Beltrán, J; Hernández, F

2014-11-01

334

Systems and methods for cylindrical hall thrusters with independently controllable ionization and acceleration stages  

DOEpatents

Systems and methods may be provided for cylindrical Hall thrusters with independently controllable ionization and acceleration stages. The systems and methods may include a cylindrical channel having a center axial direction, a gas inlet for directing ionizable gas to an ionization section of the cylindrical channel, an ionization device that ionizes at least a portion of the ionizable gas within the ionization section to generate ionized gas, and an acceleration device distinct from the ionization device. The acceleration device may provide an axial electric field for an acceleration section of the cylindrical channel to accelerate the ionized gas through the acceleration section, where the axial electric field has an axial direction in relation to the center axial direction. The ionization section and the acceleration section of the cylindrical channel may be substantially non-overlapping.

Diamant, Kevin David; Raitses, Yevgeny; Fisch, Nathaniel Joseph

2014-05-13

335

Application of FIGAERO (Filter Inlet for Gases and AEROsol) coupled to a high resolution time of flight chemical ionization mass spectrometer to field and chamber organic aerosol: Implications for carboxylic acid formation and gas-particle partitioning from monoterpene oxidation  

NASA Astrophysics Data System (ADS)

We present measurements of a large suite of gas and particle phase carboxylic acid containing compounds made with a Filter Inlet for Gas and AEROsol (FIGAERO) coupled to a high resolution time of flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. A prototype operated with acetate negative ion proton transfer chemistry was deployed on the Julich Plant Atmosphere Chamber to study a-pinene oxidation, and a modified version was deployed at the SMEAR II forest station in Hyytiälä, Finland and SOAS, in Brent Alabama. We focus here on results from JPAC and Hyytiälä, where we utilized the same ionization method most selective towards carboxylic acids. In all locations, 100's of organic acid compounds were observed in the gas and particles and many of the same composition acids detected in the gas-phase were detected in the particles upon temperature programmed thermal desorption. Particulate organics detected by FIGAERO are highly correlated with organic aerosol mass measured by an AMS, providing additional volatility and molecular level information about collected aerosol. The fraction of a given compound measured in the particle phase follows expected trends with elemental composition, but many compounds would not be well described by an absorptive partitioning model assuming unity activity coefficients. Moreover the detailed structure in the thermal desorption signals reveals a contribution from thermal decomposition of large molecular weight organics and or oligomers with implications for partitioning measurements and model validation

Lopez-Hilfiker, F.; Mohr, C.; Ehn, M.; Rubach, F.; Mentel, T. F.; Kleist, E.; Wildt, J.; Thornton, J. A.

2013-12-01

336

Ionization detector  

Microsoft Academic Search

An ionization detecting fire alarm device is disclosed which comprises a double chamber structure, a source disposed in at least one of the chambers, and a vernier adjusting screw electrode protruding into one chamber. The chamber containing the adjustable electrode is more open to the atmosphere than the other chamber. Porting is provided between chambers and detection occurs by sensing

1978-01-01

337

Effective ionization coefficients and electron drift velocities in gas mixtures of SF6 with He, Xe, CO2 and N2 from Boltzmann analysis  

Microsoft Academic Search

The effective reduced electron ionization coefficients (alpha-eta)\\/N, with alpha and eta denoting the first Townsend ionization and attachment coefficients, respectively, and the drift velocities are calculated for different mixture compositions of SF6 with He, Xe, CO2 and N2, by solving the electron Boltzmann equation, under the two-term approximation, in a steady-state Townsend discharge. It is shown that a self-contained equation

M. J. Pinheiro; J. Loureiro

2002-01-01

338

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

PubMed

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

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

2013-09-13

339

Characterization and quantification of 4-methylsterols and 4,4-dimethylsterols from Iberian pig subcutaneous fat by gas chromatography-mass spectrometry and gas chromatography-flame ionization detector and their use to authenticate the fattening systems.  

PubMed

4-Methylsterols and 4,4-dimethylsterols of 47 samples of subcutaneous fat from Iberian pigs reared on two different fattening systems, "Extensive" and "Intensive", have been analyzed by GC-MS and GC-FID. The lipids were extracted by melting the subcutaneous fat in a microwave oven. The unsaponifiable matter was fractionated by thin layer chromatography. Then, the analysis was performed on a capillary SPB-5 column (30 m × 0.25 mm i.d., 0.15 ?m film thickness), with hydrogen as a carrier gas and using a flame ionization detector. n-eicosanol was used as internal standard for quantification of individual methylsterols. These compounds have been analyzed by GC-MS for their identification. The full scan of free and trimethyl silyl ethers was used as acquisition mode. Six compounds have been identified for the first time in this type of samples: (3?,4?,5?)-4-methyl-cholesta-7-en-3-ol, (3?,4?,5?)-4-methyl-cholesta-8(14)-en-3-ol, (3?,5?)-4,4-dimethyl-cholesta-8(14),24-dien-3-ol, (3?)-lanosta-8,24-dien-3-ol, (3?, 5?)-4,4-dimethyl-cholesta-8,14-dien-3-ol and (3?)-lanost-9(11),24-dien-3-ol. The samples were derivatized as trimethyl silyl ethers before their analysis by GC-FID. By using these compounds as chemical descriptors, pattern recognition techniques were applied to differentiate between extensive and intensive fattening systems of Iberian pig. Several pattern recognition techniques, such as principal component analysis, linear discriminant analysis, support vector machines, artificial neural networks, soft independent modeling of class analogy and k nearest neighbors, have been used in order to find out a suitable classification model. A multilayer perceptron artificial neural network based on the contents of the above mentioned compounds allowed the differentiation of the two fattening systems with an overall classification performance of 91.7%. PMID:23598090

Jurado, J M; Jiménez-Lirola, A; Narváez-Rivas, M; Gallardo, E; Pablos, F; León-Camacho, M

2013-03-15

340

A new disposable ionic liquid based coating for headspace solid-phase microextraction of methyl tert-butyl ether in a gasoline sample followed by gas chromatography–flame ionization detection  

Microsoft Academic Search

A new ionic liquid (IL) based solid-phase microextraction (SPME) fiber was investigated and used for headspace (HS) extraction of methyl tert-butyl ether (MTBE) in a gasoline sample. Using the new IL coated HS-SPME fiber with the combination of gas chromatography–flame ionization detection (GC–FID); sub-to-low ?gL?1 concentrations of MTBE were detected. Four different ILs including 1-butyl-3-methylimidazolium tetraflouroborate ([C4C1IM] [BF4]), 1-octyl-3-methylimidazolium tetraflouroborate

Ramin Amini; Ahmad Rouhollahi; Mina Adibi; Ali Mehdinia

2011-01-01

341

Sensitive, rapid and validated gas chromatography\\/negative ion chemical ionization-mass spectrometry assay including derivatisation with a novel chiral agent for the enantioselective quantification of amphetamine-type stimulants in hair  

Microsoft Academic Search

A novel chiral derivatisation agent, (2S,4R)-N-heptafluorobutyryl-4-heptafluorobutoyloxy-prolyl chloride, was used for the indirect resolution of amphetamine (AM), methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyethylamphetamine (MDEA) enantiomers using gas chromatography coupled to mass spectrometry operating in the negative-ion chemical ionization mode (GC\\/MS-NICI). This new chiral derivatisation reagent was readily obtained in optically pure form after a simple two-step synthesis. Optimal derivatisation

Liliane Ferreira Martins; Michel Yegles; Heesun Chung; Robert Wennig

2006-01-01

342

Three-dimensional modeling of ionized gas. II. Spectral energy distributions of massive and very massive stars in stationary and time-dependent modeling of the ionization of metals in HII regions  

E-print Network

HII regions play a crucial role in the measurement of the chemical composition of the interstellar medium and provide fundamental data about element abundances that constrain models of galactic chemical evolution. Discrepancies that still exist between observed emission line strengths and those predicted by nebular models can be partly attributed to the spectral energy distributions (SEDs) of the sources of ionizing radiation used in the models as well as simplifying assumptions made in nebular modeling. The influence of stellar metallicity on nebular line strength ratios, via its effect on the SEDs, is of similar importance as variations in the nebular metallicity. We have computed a grid of model atmosphere SEDs for massive and very massive O-type stars covering a range of metallicities from significantly subsolar (0.1 Zsun) to supersolar (2 Zsun). The SEDs have been computed using a state-of-the-art model atmosphere code that takes into account the attenuation of the ionizing flux by the spectral lines of ...

Weber, J A; Hoffmann, T L

2015-01-01

343

Initial results of positron ionization mass spectrometry  

NASA Technical Reports Server (NTRS)

The use of monoenergetic positrons for the ionization of organic molecules in the gas phase is described. The ionic products are analyzed with a time-of-flight mass spectrometer and detected to produce a mass spectrum. The ionization mechanisms which can be studied in this way include positron impact at energies above the ionization limit of the target molecules, positronium formation in the Ore gap energy range, and positron attachment at energies less than 1eV. The technique of positron ionization mass spectrometry (PIMS) may have analytical utility in that chemical selectivity is observed for one or more of these processes.

Donohue, D. L.; Hulett, L. D., Jr.; Mcluckey, S. A.; Glish, G. L.; Eckenrode, B. A.

1990-01-01

344

A multi-residue method for pesticides analysis in green coffee beans using gas chromatography-negative chemical ionization mass spectrometry in selective ion monitoring mode.  

PubMed

In this study, a new gas chromatography-mass spectrometry (GC-MS) method, using the very selective negative chemical ionization (NCI) mode, was developed and applied in combination with a modified acetonitrile-based extraction method (QuEChERS) for the analysis of a large number of pesticide residues (51 pesticides, including isomers and degradation products) in green coffee beans. A previously developed integrated sample homogenization and extraction method for both pesticides and mycotoxins analysis was used. An homogeneous slurry of green milled coffee beans and water (ratio 1:4, w/w) was prepared and extracted with acetonitrile/acetic acid (1%), followed by magnesium sulfate addition for phase separation. Aliquots from this extract could be used directly for LC-MS/MS analysis of mycotoxins and LC-amenable pesticides. For GC-MS analysis, a further clean-up was necessary. C18- and PSA-bonded silica were tested as dispersive solid-phase extraction (d-SPE) sorbents, separate and as a mixture, and the best results were obtained using C18-bonded silica. For the optimal sensitivity and selectivity, GC-MS detection in the NCI-selected ion monitoring (SIM) mode had to be used to allow the fast analysis of the difficult coffee bean matrix. The validation was performed by analyzing recovery samples at three different spike concentrations, 10, 20 and 50 ?g kg(-1), with 6 replicates (n=6) at each concentration. Linearity (r(2)) of calibration curves, estimated instrument and method limits of detection and limits of quantification (LOD(i), LOD(m), LOQ(i) and LOQ(m), respectively), accuracy (as recovery %), precision (as RSD%) and matrix effects (%) were determined for each individual pesticide. From the 51 analytes (42 parent pesticides, 4 isomers and 5 degradation products) determined by GC-MS (NCI-SIM), approximately 76% showed average recoveries between 70-120% and 75% and RSD ? 20% at the lowest spike concentration of 10 ?g kg(-1), the target method LOQ. For the spike concentrations of 20 and 50 ?g kg(-1), the recoveries and RSDs were even better. The validated LOQ(m) was 10, 20 and 50 ?g kg(-1) for respectively 33, 3 and 6 of the analytes studied. For five compounds, the European Union method performance requirements for the validation of a quantitative method (average recoveries between 70-120% and repeatability RSD ? 20%) were not achieved and 4 problematic pesticides (captan, captafol, folpet and dicofol) could not be detected as their parent compound, but only via their degradation products. Although the matrix effect (matrix-enhanced detector response) was high for all pesticides studied, the matrix interference was minimal, due to the high selectivity obtained with the GC-NCI-MS detection. Matrix-matched calibration for applying the method in routine analysis is recommended for reliable quantitative results. PMID:22771261

Pizzutti, Ionara R; de Kok, Andre; Dickow Cardoso, Carmem; Reichert, Bárbara; de Kroon, Marijke; Wind, Wouter; Weber Righi, Laís; Caiel da Silva, Rosselei

2012-08-17

345

On-Line Emission Analysis of Polycyclic Aromatic Hydrocarbons down to pptv Concentration Levels in the Flue Gas of an Incineration Pilot Plant with a Mobile Resonance-Enhanced Multiphoton Ionization Time-of-Flight Mass Spectrometer.  

PubMed

A newly developed, mobile laser mass spectrometer (resonance-enhanced multiphoton ionization - time-of-flight mass spectrometer, REMPI-TOFMS) was applied to on-line measurements at a waste incineration pilot plant. REMPI-TOFMS combines the optical selectivity of resonance-enhanced multiphoton ionization with a time-of-flight mass analysis to give a two-dimensional analytical method. Special care was taken to build up a sampling and inlet system suitable for on-line measurements of large, semivolatile polycyclic aromatic hydrocarbons (PAHs). An effusive molecular beam inlet in combination with a fixed frequency UV laser (Nd:YAG at 266 nm or KrF excimer at 248 nm) was used. Under these conditions, many different PAHs can be ionized selectively from the complex flue gas matrix. For example, the achieved detection limit for naphthalene is in the 10 parts-per-trillion by volume (pptv) concentration range. Calibration was performed by using external concentration standards supplied in low ppbv concentrations. The instrumentation is sufficiently robust to be operated under industrial conditions at incineration plants, for instance. The REMPI mass spectra can be acquired at 5-50 Hz. Time profiles of the concentrations of different PAHs in the flue gas were monitored with a time resolution of 200 ms. Significant variations in the concentration profile of several PAHs up to mass 276 amu (e.g., benzo[ghi]perylene) and methylated PAHs have been observed while combustion parameters were changing. In summary, it was demonstrated that laser mass spectrometry (REMPI-TOFMS) enables a real-time on-line trace analysis of combustion flue gases or industrial process gases. PMID:21662925

Heger, H J; Zimmermann, R; Dorfner, R; Beckmann, M; Griebel, H; Kettrup, A; Boesl, U

1999-01-01

346

Mechanism for the formation of gas-phase protonated alcohol-ether adducts by VUV laser ionization and density-functional calculations  

SciTech Connect

The neutral vapors above liquid alcohol/ether mixtures (diethyl ether/methanol, diethyl ether/ethanol, tetrahydrofuran/methanol, and tetrahydrofuran/ethanol) were co-expanded with He in a supersonic jet, ionized with a 118-nm vacuum ultraviolet laser, and detected in a time-of-flight mass spectrometer. In each case, features attributed to protonated alcohol-ether dimers and protonated ether monomers were observed, as well as those ions obtained by ionizing neat alcohol or ether samples alone. Theoretical calculations, carried out to establish the energetics of the various possible reactions leading to the formation of the observed binary adducts, indicate that the most thermodynamically favorable pathway corresponds to the addition of a protonated alcohol monomer to neutral ether.

Lam, Selay; Shi, Y.J.; Mosey, N.J.; Woo, T.K.; Lipson, R.H. [Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7 (Canada)

2004-11-22

347

Structural determination of zinc dithiophosphates in lubricating oils by gas chromatography-mass spectrometry with electron impact and electron-capture negative ion chemical ionization.  

PubMed

Pentafluorobenzyl ester derivatives were used to identify zinc dialkyldithiophosphates and diaryldithiophosphates antiwear engine oil additives by GC-electron impact ionization (EI) MS and GC-electron-capture negative ion chemical ionization (ECNCI) MS analysis. GC-EI-MS of the dialkyldithiophosphate-pentafluorobenzyl derivatives afforded characteristic fragment ions corresponding to the cleavage of one and two alkyl radicals. In most cases, information was only obtained on one alkyl chain. Additional and complete information was obtained with retention time indices using synthetic derivatives and with GC-ECNCI-MS analysis. ECNCI afforded characteristic dithiophosphate anions which allowed the determination of the total number of carbon atoms in the alkyl radicals. The diastereoisomer mixtures of 2-hydroxy-sec.-alkyl radicals were completely separated on GC analysis. PMID:11206788

Becchi, M; Perret, F; Carraze, B; Beziau, J F; Michel, J P

2001-01-01

348

Reactions of Sulfur Dioxide with Neutral Vanadium Oxide Clusters in the Gas Phase. II. Experimental Study Employing Single-Photon Ionization  

E-print Network

Reactions of Sulfur Dioxide with Neutral Vanadium Oxide Clusters in the Gas Phase. II. Experimental employed for the study of the reactions of neutral vanadium oxide clusters (VmOn) with sulfur dioxide (SO2) in the gas phase. VmOn clusters are generated by reaction of a laser-generated vanadium plasma with O2

Rocca, Jorge J.

349

Single photon ionization (SPI) via incoherent VUV-excimer light: robust and compact time-of-flight mass spectrometer for on-line, real-time process gas analysis.  

PubMed

Fast on-line detection of organic compounds from complex mixtures, such as industrial process gas streams, require selective and sensitive analytical methods. One feasible approach for this purpose is the use of mass spectrometry (MS) with a selective and soft (fragment-free) ionization technique, such as chemical ionization (CI) or photo ionization (PI). Single photon ionization (SPI) with vacuum ultraviolet (VUV) light is a particularly sof tionization technique, well-suited for detection of both aromatic and aliphatic species. Problematic, however, is the generation of the VUV light. In general, the vacuum ultraviolet (VUV) light sources for SPI-MS are based either on lasers (e.g., 118-nm radiation generated by frequency-tripling of the third harmonic of a Nd:YAG laser) or on conventional VUV lamps, such as deuterium lamps. Althoughthe laser-based techniques are very sophisticated and expensive, the conventional lamps have serious drawbacks regarding their optical parameters, such as low-output power, low spectral power density, and broad emission bands. In this work, a novel excimer VUV light source, in which an electron beam is used to form rare gas excimer species, is used. The excimer VUV light sourceproduces brilliant and intense VUV light. The novel VUV light source was coupled to a compact and mobile time-of-flight mass spectrometer (TOFMS). A special interface design, including optical (VUV optics) as well as electronic measures (e.g., pulsed ion extraction) was realized. The use of the excimer VUV lamp for SPI will allow the realization of very compact, rugged, and sensitive SPI-TOFMS devices, which preferably will be adapted for process analytical application or monitoring issues (e.g., chemical warfare detection). The excimer VUV-lamp technology delivers VUV light with a good beam quality and high-output power at low costs. Furthermore, it allows changing the emitted wavelength as well as the bandwidth of the excimer VUV lamp in t he 100-200-nm region by changing the gas filling. Consequently, SPI-TOFMS with an excimer light source is a fast detection technique that can be used for online monitoring, for example, in environmental studies or industrial manufacturing processes. In this paper, technology and characteristics of the new excimer light source, as well as the combination with the TOFMS, are presented. Furthermore, a first characterization of the SPI-TOFMS instrument, regarding analytical parameters such as detection limits and selectivity, is given. This includes a discussion of potential improvements that probably will be achievable within a future prototype genertation. Finally, first applications of the system for on-line measurement of organic trace species in a complex gas mixture (here, motorcycle exhaust gas) are presented. PMID:12175168

Mühlberger, F; Wieser, J; Ulrich, A; Zimmermann, R

2002-08-01

350

Special feature: Tutorial. Desorption ionization mass spectrometry  

Microsoft Academic Search

CH 5 ` NH 4 ` in proton transfer to M to form (M ) H)`. In each of these methods, the sample molecule is originally in the gas phase. The volatilization process must create these gas-phase sample molecules without sample decomposi- tion or reorganization. For non-volatile sample molecules, other ionization methods must be used and have been developed over

Kenneth L. Busch

1995-01-01

351

Positron impact ionization phenomena  

NASA Astrophysics Data System (ADS)

In the present work, a beam of positrons, obtained from a radioactive source (MNa) in conjunction with a W moderator and guided by a magnetic field, has been used to investigate low energy positron-impact ionization phenomena from atomic and molecular targets. For He below threshold, the investigation discovered vacuum contaminants in creased with gas load and hence concluded that the high 7-ray/ion signal observed by Szluinska and Laricchia (2004a) in Ne could not be safely attributed to annihila tion. A detailed measurement of the total ionization cross-section for He has been performed from below threshold for Ps formation to high energy. Combined with previously measured data and previously measured direct ionization cross-sections (Moxom et al 1996, Ashley et al 1996), a new determination of the positronium formation cross-section has been achieved and compared to other available experi mental measurements and theoretical calculations. Measurements of the excited state (n > 1) positronium formation cross-section for He and Ar have been performed and compared to available theoretical calcu lations. This work has been motivated both for a direct comparison with theory and to test the hypothesis that structure observed in the total (all n) positron ium formation cross-sections for the heavier noble gases, is due to excited state positronium formation (Laricchia et al 2002). The present study is unable to verify fully this hypothesis due to the experimental methods insensitivity to positronium formation in to the 2S or n > 2 states. However, the present results are close to the most sophisticated theoretical calculation of positronium formation into the 2P state (Campbell et al 1998).

Murtagh, Daniel James

352

METHOD FOR THE MEASUREMENT OF THE MEAN IONIZING CROSS-SECTION OF FAST PARTICLES  

E-print Network

) Résumé. 2014 Une méthode utilisant un microphone capacitif comme chambre d'ionisation rend possible l as an ionization chamber enables the ionizing collision of a fast particle with a gas atom to be observed paper [1] that a capacitive microphone can be used as an ionization chamber to investigate the ionizing

Paris-Sud XI, Université de

353

What Happens to Hydrophobic Interactions during Transfer from the Solution to the Gas Phase? The Case of Electrospray-Based Soft Ionization Methods  

Microsoft Academic Search

The disappearance of the hydrophobic effect in the gas phase due to the absence of an aqueous surrounding raises a long-standing\\u000a question: can noncovalent complexes that are exclusively bound by hydrophobic interactions in solution be preserved in the\\u000a gas phase? Some reports of successful detection by mass spectrometry of complexes largely stabilized by hydrophobic effect\\u000a are questionable by the presence

Konstantin Barylyuk; Roman M. Balabin; Dan Grünstein; Raghavendra Kikkeri; Vladimir Frankevich; Peter H. Seeberger; Renato Zenobi

2011-01-01

354

Synthesis and hydrolysis of gas-phase lanthanide and actinide oxide nitrate complexes: a correspondence to trivalent metal ion redox potentials and ionization energies.  

PubMed

Several lanthanide and actinide tetranitrate ions, M(III)(NO3)4(-), were produced by electrospray ionization and subjected to collision induced dissociation in quadrupole ion trap mass spectrometers. The nature of the MO(NO3)3(-) products that result from NO2 elimination was evaluated by measuring the relative hydrolysis rates under thermalized conditions. Based on the experimental results it is inferred that the hydrolysis rates relate to the intrinsic stability of the M(IV) oxidation states, which correlate with both the solution IV/III reduction potentials and the fourth ionization energies. Density functional theory computations of the energetics of hydrolysis and atoms-in-molecules bonding analysis of representative oxide and hydroxide nitrates substantiate the interpretations. The results allow differentiation between those MO(NO3)3(-) that comprise an O(2-) ligand with oxidation to M(IV) and those that comprise a radical O(-) ligand with retention of the M(III) oxidation state. In the particular cases of MO(NO3)3(-) for M = Pr, Nd and Tb it is proposed that the oxidation states are intermediate between M(iii) and M(iv). PMID:25783464

Lucena, Ana F; Lourenço, Célia; Michelini, Maria C; Rutkowski, Philip X; Carretas, José M; Zorz, Nicole; Berthon, Laurence; Dias, Ana; Conceição Oliveira, M; Gibson, John K; Marçalo, Joaquim

2015-04-01

355

GAS-PHASE SYNTHESIS OF PRECURSORS OF INTERSTELLAR GLYCINE: A COMPUTATIONAL STUDY OF THE REACTIONS OF ACETIC ACID WITH HYDROXYLAMINE AND ITS IONIZED AND PROTONATED DERIVATIVES  

SciTech Connect

A computational study of the reactions of hydroxylamine and its ionized and protonated derivatives with acetic acid is provided. The reaction of neutral hydroxylamine with acetic acid, despite being clearly exothermic, involves a very large energy barrier. The reaction of ionized hydroxylamine with acetic acid is also clearly exothermic, but again a significant energy barrier is found (around 24 kcal mol{sup -1} at the CCSD(T) level). The reaction of the most stable protonated isomer of hydroxylamine, NH{sub 3}OH{sup +}, with acetic acid also involves a high barrier (more than 27 kcal mol{sup -1} at the CCSD(T) level). Only the higher energy isomer, NH{sub 2}OH{sup +}{sub 2}, leads to a sensibly lower energy barrier (about 2.3 kcal mol{sup -1} at the CCSD(T) level). Nevertheless, an estimate of the reaction coefficient at low temperatures such as those reigning in the interstellar medium gives very low values. Therefore, it seems that precursors of interstellar glycine could not be efficiently produced from the reactions of hydroxylamine-derived ions with acetic acid.

Barrientos, Carmen; Redondo, Pilar; Largo, Laura; Rayon, Victor M.; Largo, Antonio, E-mail: alargo@qf.uva.es [Departamento de Quimica Fisica y Quimica Inorganica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid (Spain)

2012-04-01

356

Development and validation of an analytical method for determination of 3-chloropropane-1,2-diol in rat blood and urine by gas chromatography-mass spectrometry in negative chemical ionization mode.  

PubMed

We have developed a highly selective and sensitive method using gas chromatography-mass spectrometry with negative chemical ionization for measuring 3-chloropropane-1,2-diol (3-MCPD) in rat blood and urine. Samples were adsorbed on silica gel, extracted with ethyl acetate, and derivatized by chemical derivatization with heptafluorobutyric acid anhydride. For quantification, matrix-based calibration curves and 3-MCPD-d (5), as an isotope-labeled internal standard, were used. The relative recoveries of 3-MCPD were between 80 and 110% in most cases and the relative standard deviations were typically less than 10%, with some exceptions. The limit of quantification of the method was found to be about 2 ng/mL. In conclusion, a valuable, robust, and sensitive method for detection of 3-MCPD is now available for biokinetics studies. PMID:20640896

Berger-Preiss, Edith; Gerling, Susanne; Apel, Elisabeth; Lampen, Alfonso; Creutzenberg, Otto

2010-09-01

357

Characterization of plant materials by pyrolysis-field ionization mass spectrometry: high-resolution mass spectrometry, time-resolved high-resolution mass spectrometry, and Curie-point pyrolysis-gas chromatography/mass spectrometry of spruce needles  

SciTech Connect

In the course of a forest damage research project spruce needles are analyzed, without pretreatment except drying and milling, by in-source pyrolysis-field ionization mass spectrometry. The mass signals are assigned by using high-resolution mass measurements and thermal degradation products identified by Curie-point pyrolysis-gas chromatography. It is demonstrated that the thermal degradation products characterize the main chemical constituents of spruce needs such as polysaccharides and lignin. Furthermore, thermostable constituents such as lipids, steroids, and flavons are detected. The thermal degradation process is studied by temperature-programmed microfurnace pyrolysis in combination with time-resolved high-resolution mass spectrometry. The integrated interpretation of results achieved by the presented methods can be applied for the universal characterization of complex and in particular nonsoluble, polydisperse biological and geochemical materials.

Schulten, H.F.; Simmleit, N.; Mueller, R.

1989-02-01

358

Real-time air monitoring of mustard gas and Lewisite 1 by detecting their in-line reaction products by atmospheric pressure chemical ionization ion trap tandem mass spectrometry with counterflow ion introduction.  

PubMed

A new method enabling sensitive real-time air monitoring of highly reactive chemical warfare agents, namely, mustard gas (HD) and Lewisite 1 (L1), by detecting ions of their in-line reaction products instead of intact agents, is proposed. The method is based on corona discharge-initiated atmospheric pressure chemical ionization coupled with ion trap tandem mass spectrometry (MS(n)) via counterflow ion introduction. Therefore, it allows for highly sensitive and specific real-time detection of a broad range of airborne compounds. In-line chemical reactions, ionization reactions, and ion fragmentations of these agents were investigated. Mustard gas is oxygenated in small quantity by reactive oxygen species generated in the corona discharge. With increasing air humidity, the MS(2) signal intensity of protonated molecules of mono-oxygenated HD decreases but exceeds that of dominantly existing intact HD. This result can be explained in view of proton affinity. Lewisite 1 is hydrolyzed and oxidized. As the humidity increases from zero, the signal of the final product, namely, didechlorinated, dihydroxylated, and mono-oxygenated L1, quickly increases and reaches a plateau, giving the highest MS(2) and MS(3) signals among those of L1 and its reaction products. The addition of minimal moisture gives the highest signal intensity, even under low humidity. The method was demonstrated to provide sufficient analytical performance to meet the requirements concerning hygienic management and counter-terrorism. It will be the first practical method, in view of sensitivity and specificity, for real-time air monitoring of HD and L1 without sample pretreatment. PMID:25553788

Okumura, Akihiko; Takada, Yasuaki; Watanabe, Susumu; Hashimoto, Hiroaki; Ezawa, Naoya; Seto, Yasuo; Sekiguchi, Hiroshi; Maruko, Hisashi; Takayama, Yasuo; Sekioka, Ryoji; Yamaguchi, Shintaro; Kishi, Shintaro; Satoh, Takafumi; Kondo, Tomohide; Nagashima, Hisayuki; Nagoya, Tomoki

2015-01-20

359

Field ionization of argon using -phase W nanorods J. P. Singh,a)  

E-print Network

Field ionization of argon using -phase W nanorods J. P. Singh,a) T. Karabacak,b) T.-M. Lu, and G 11 August 2004) We report testing of -phase W nanorods as a gas ionizer for neutral argon atoms voltage 3­4 V applied to the W nanorods generates a high electric field, which ionizes gas-phase argon

Wang, Gwo-Ching

360

A bipolar outflow of ionized gas in K3-50A: H76 alpha radio recombination line and continuum observations of K3-50  

NASA Technical Reports Server (NTRS)

The H II regions near K3-50 (G70.3 + 1.6) have been imaged at high angular resolution (approximately 1 sec .3) in the continuum and the recombination lines H76(sub alpha and He76(sub alpha) using the Very Large Array (VLA). The helium line is detected in only the brightest component K3-50A while the hydrogen line is detected in three components (K3-50A, B and C1). K3-50A shows a pronounced velocity gradient of approximately 150 km/sec/pc along its major axis (P.A. = 160 deg); in addition a wide range of line widths are observed, from 20 to 65 km/sec. Kinematics from the line data and the morphology of the continuum emission suggest that the ionized material associated with K3-50A is undergoing a high-velocity bipolar outflow.

Depree, C. G.; Goss, W. M.; Palmer, Patrick; Rubin, Robert H.

1994-01-01

361

Identification of alkylated phosphates by gas chromatography-mass spectrometric investigations with different ionization principles of a thermally aged commercial lithium ion battery electrolyte.  

PubMed

The thermal aging process of a commercial LiPF6 based lithium ion battery electrolyte has been investigated in view of the formation of volatile phosphorus-containing degradation products. Aging products were analyzed by GC-MS. Structure determination of the products was performed by support of chemical ionization MS in positive and negative modes. A fraction of the discovered compounds belongs to the group of fluorophosphates (phosphorofluoridates) which are in suspect of potential toxicity. This is well known for relative derivatives, e.g. diisopropyl fluorophosphate. Another fraction of the identified compounds belongs to the group of trialkyl phosphates. These compounds may provide a positive impact on the thermal and electrochemical performance of Li-based batteries as repeatedly described in the literature. PMID:25846260

Weber, Waldemar; Kraft, Vadim; Grützke, Martin; Wagner, Ralf; Winter, Martin; Nowak, Sascha

2015-05-15

362

Field ionizing elements and applications thereof  

NASA Technical Reports Server (NTRS)

A field ionizing element formed of a membrane that houses electrodes therein that are located closer to one another than the mean free path of the gas being ionized. The membrane includes a supporting portion, and a non supporting portion where the ions are formed. The membrane may be used as the front end for a number of different applications including a mass spectrometer, a thruster, an ion mobility element, or an electrochemical device such as a fuel cell.

Hartley, Frank T. (Inventor)

2003-01-01

363

Highly resolved online organic-chemical speciation of evolved gases from thermal analysis devices by cryogenically modulated fast gas chromatography coupled to single photon ionization mass spectrometry.  

PubMed

Multi-dimensional analysis (MDA) in analytical chemistry is often applied to improve the selectivity of an analytical device and, therefore, to achieve a better overview of a sample composition. Recently, the hyphenation of thermogravimetry with single photo ionization mass spectrometry (TG-SPIMS) using an electron beam pumped excimer lamp (EBEL) for VUV radiation was applied. The concept of MDA has been realized by upgrading the TG-SPIMS system with a quasi comprehensive chromatographic separation step before the soft ionization (TG-GCxSPIMS). The system was characterized by the thermal analysis of diesel fuel, which has often been investigated by the GCxGC-community and is therefore a well-known sample material in MDA. Data from this measurement are used to explain the three-dimensional data structure and the advantages of the online TG-GCxSPIMS as compared to TG-SPIMS. Subsequently, the thermal decomposition behavior of a polymer, acrylonitrile-butadiene-styrene (ABS), is investigated. TG-GCxSPIMS provides a two-dimensional analysis of the evolved gaseous products. TG relevant data are obtained as well as an improved resolution power to separate isobaric molecular structures without losing any fraction of the samples, as is often the case in heart cutting approaches. Additionally, this solution is not associated with any extension of the measurement time. The assignment of the substance pattern to distinct species is improved as compared to solely using mass spectrometry without a preceding separation step. Furthermore, hitherto undetected compounds have been found in the evolved gases from the thermal degradation of ABS. Finally, a first estimation of the limit of detection has been carried out. This results in a significant decrease of the LOD in case of TG-GCxSPIMS (500 ppt for toluene) as compared to 30 ppb, which could be reached with TG-SPIMS. PMID:21043436

Saraji-Bozorgzad, Mohammad R; Eschner, Markus; Groeger, Thomas M; Streibel, Thorsten; Geissler, Robert; Kaisersberger, Erwin; Denner, Thomas; Zimmermann, Ralf

2010-12-01

364

Non-equilibrium ionized blast wave  

NASA Technical Reports Server (NTRS)

The structure of a cylindrical blast wave with ionization at non-LTE conditions was calculated using equations previously developed by Wu and Fu (1970). The degree of ionization was predicted by a modified Saha equation. Temperature profiles show that the temperature at non-LTE conditions is lower than at LTE near the shock front. This corresponds to a higher degree of ionization for the non-LTE limit, which indicates that the neutral gas absorption is much more efficient at non-LTE than at the LTE limit. The decaying velocity under non-LTE is approximately 15% less than under LTE.

Wu, S. T.

1974-01-01

365

Disposable ionic liquid coating for headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and xylenes in paints followed by gas chromatography–flame ionization detection  

Microsoft Academic Search

Solid-phase microextraction (SPME) with a disposable ionic liquid (IL) coating was developed for headspace extraction of benzene, toluene, ethylbenzene, and xylenes (BTEX) in paints. The SPME fiber was coated with IL prior to every extraction, then the analytes were extracted and desorbed on the injection port of gas chromatography, and finally the IL coating on the fiber was washed out

Jing-fu Liu; Ning Li; Gui-bin Jiang; Jie-min Liu; Jan Åke Jönsson; Mei-juan Wen

2005-01-01

366

CRYOGENIC PRECONCENTRATION-DIRECT FID (FLAME IONIZATION DETECTION) METHOD FOR MEASUREMENT OF AMBIENT NMOC (NONMETHANE ORGANIC COMPOUNDS): REFINEMENT AND COMPARISON WITH GC (GAS CHROMATOGRAPHIC) SPECIATION  

EPA Science Inventory

A method for measuring total nonmethane organic compounds (NMOC) in the atmosphere has been refined to reduce measurement variability and evaluated for possible use in connection with the control of hydrocarbon emissions. The method, a simplification of the conventional gas chrom...

367

SIMULTANEOUS QUANTIFICATION OF JASMONIC ACID AND SALICYLIC ACID IN PLANTS BY VAPOR PHASE EXTRACTION AND GAS CHROMATOGRAPHY-CHEMICAL IONIZATION-MASS SPECTROMETRY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Jasmonic acid and salicylic acid represent important signaling compounds in plant defensive responses against other organisms. Here, we present a new method for the easy, sensitive and reproducible quantification of both compounds by vapor phase extraction and gas chromatography-positive ion chemic...

368

Kinetic simulation of neutral/ionized gas and electrically charged dust in the coma of comet 67P/Churyumov-Gerasimenko  

SciTech Connect

The cometary coma is a unique phenomenon in the solar system being a planetary atmosphere influenced by little or no gravity. As a comet approaches the sun, the water vapor with some fraction of other gases sublimate, generating a cloud of gas, ice and other refractory materials (rocky and organic dust) ejected from the surface of the nucleus. Sublimating gas molecules undergo frequent collisions and photochemical processes in the near-nucleus region. Owing to its negligible gravity, comets produce a large and highly variable extensive dusty coma with a size much larger than the characteristic size of the cometary nucleus.The Rosetta spacecraft is en route to comet 67P/Churyumov-Gerasimenko for a rendezvous, landing, and extensive orbital phase beginning in 2014. Both, interpretation of measurements and safety consideration of the spacecraft require modeling of the comet's dusty gas environment.In this work we present results of a numerical study of multispecies gaseous and electrically charged dust environment of comet Chyuryumov-Gerasimenko. Both, gas and dust phases of the coma are simulated kinetically. Photolytic reactions are taken into account. Parameters of the ambient plasma as well as the distribution of electric/magnetic fields are obtained from an MHD simulation of the coma connected to the solar wind. Trajectories of ions and electrically charged dust grains are simulated by accounting for the Lorentz force and the nucleus gravity.

Tenishev, Valeriy; Rubin, Martin; Combi, Michael R. [University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109 (United States)

2011-05-20

369

Molecular ion fragmentation and its effects on mass isotopomer abundances of fatty acid methyl esters ionized by electron impact  

Microsoft Academic Search

We have analyzed the isotopomer abundance ratios of an equimolar mixture of nine fatty acid methyl esters (decanoate, undecanoate,\\u000a laurate, tridecanoate, myristate, pentadecanoate, palmitate, heptadecanoate, and stearate) by selected-ion monitoring gas\\u000a chromatography\\/electron impact\\/mass spectrometry (GC\\/EI\\/MS). The abundance of the second lowest m\\/z isotopomer ($${I_{{M_1}}}$$) increased disproportionately compared with the abundance of the lowest m\\/z isotopomer ($${I_{{M_0}}}$$) as a function of:

Clifton K. Fagerquist; Richard A. Neese; Marc K. Hellerstein

1999-01-01

370

Study of gas-phase O-H bond dissociation enthalpies and ionization potentials of substituted phenols - Applicability of ab initio and DFT/B3LYP methods  

NASA Astrophysics Data System (ADS)

In this paper, the study of phenol and 37 compounds representing various ortho-, para-, and meta-substituted phenols is presented. Molecules and their radical structures were studied using ab initio methods with inclusion of correlation energy and DFT in order to calculate the O-H bond dissociation enthalpies (BDEs) and vertical ionization potentials (IPs). Calculated BDEs and IPs were compared with available experimental values to ascertain the suitability of used methods, especially for the description of the substituent induced changes in BDE and IP. MP2, MP3, and MP4 methods do not give reliable results, since they significantly underestimate substituent induced changes in BDE and do not reflect distinct effect of substituents related to para and meta position correctly. DFT/B3LYP method reflects the effect of substituents on BDE satisfactorily, though ?BDEs are in narrower range than experimental values. BDE of phenol was calculated also using CCSD(T) method in various basis sets. Both, DFT and HF methods describe the effect of substituents on IP identically. However, DFT considerably underestimates individual values. HF method gives IPs in very good agreement with experimental data. Obtained results show that dependences of BDEs and IPs on Hammett constants of the substituents are linear. Linearity of DFT BDE vs. IP dependence is even better than the dependences on Hammett constants and obtained equations allow estimating of O-H BDEs of meta- and para-substituted phenols from calculated IPs.

Klein, Erik; Lukeš, Vladimír

2006-11-01

371

Electrospray ionization mass spectrometry of organic-inorganic materials: identification and gas-phase reactivity of functionalized octahedral rhenium(III) clusters.  

PubMed

Electrospray ionization mass spectrometry was used for the analysis of functionalized rhenium clusters such as [Re6Se8(o-Me2TTFPPh2)6]2+ (1), {Re6Se8[(o-Me2TTF)2PPh]6}2+ (2) and [Re6Se8(MePPh2)6]2+ (3). The high-resolution mass spectra of the intact clusters, performed in dichloromethane, confirm the identification of the compounds by comparison with the theoretical isotopic distributions. Low-resolution full-scan mass spectra recorded at increasing desolvation cone voltage values allow the study of the intrinsic reactivity of ionic species. The survival yield curves illustrating the bimolecular reactivity of 1 and 2 suggest that a bisdimethyltetrathiafulvalene(phenyl)phosphine ligand increases the stability of the functionalized ML6(2+) cluster 2. In the case of the 3, instead of loss of a neutral ligand, ligand exchange is observed either with traces of water present in dichloromethane or with acetonitrile used as solvent. PMID:15584011

Rondeau, David; Perruchas, Sandrine; Avarvari, Narcis; Batail, Patrick; Vékey, Karoly

2005-01-01

372

IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. V. ALFVÉN IONIZATION  

SciTech Connect

Observations of continuous radio and sporadic X-ray emission from low-mass objects suggest they harbor localized plasmas in their atmospheric environments. For low-mass objects, the degree of thermal ionization is insufficient to qualify the ionized component as a plasma, posing the question: what ionization processes can efficiently produce the required plasma that is the source of the radiation? We propose Alfvén ionization as a mechanism for producing localized pockets of ionized gas in the atmosphere, having sufficient degrees of ionization (?10{sup –7}) that they constitute plasmas. We outline the criteria required for Alfvén ionization and demonstrate its applicability in the atmospheres of low-mass objects such as giant gas planets, brown dwarfs, and M dwarfs with both solar and sub-solar metallicities. We find that Alfvén ionization is most efficient at mid to low atmospheric pressures where a seed plasma is easier to magnetize and the pressure gradients needed to drive the required neutral flows are the smallest. For the model atmospheres considered, our results show that degrees of ionization of 10{sup –6}-1 can be obtained as a result of Alfvén ionization. Observable consequences include continuum bremsstrahlung emission, superimposed with spectral lines from the plasma ion species (e.g., He, Mg, H{sub 2}, or CO lines). Forbidden lines are also expected from the metastable population. The presence of an atmospheric plasma opens the door to a multitude of plasma and chemical processes not yet considered in current atmospheric models. The occurrence of Alfvén ionization may also be applicable to other astrophysical environments such as protoplanetary disks.

Stark, C. R.; Helling, Ch.; Rimmer, P. B. [SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS (United Kingdom); Diver, D. A., E-mail: craig.stark@st-andrews.ac.uk [SUPA, School of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)

2013-10-10

373

Single photon ionization time-of-flight mass spectrometry with a pulsed electron beam pumped excimer VUV lamp for on-line gas analysis: setup and first results on cigarette smoke and human breath.  

PubMed

Single-photon ionization (SPI) using vacuum ultraviolet (VUV) light produced by an electron beam pumped rare gas excimer source has been coupled to a compact and mobile time-of-flight mass spectrometer (TOFMS). The novel device enables real-time on-line monitoring of organic trace substances in complex gaseous matrixes down to the ppb range. The pulsed VUV radiation of the light source is employed for SPI in the ion source of the TOFMS. Ion extraction is also carried out in a pulsed mode with a short time delay with respect to ionization. The experimental setup of the interface VUV light source/time-of-flight mass spectrometer is described, and the novel SPI-TOFMS system is characterized by means of standard calibration gases. Limits of detection down to 50 ppb for aliphatic and aromatic hydrocarbons were achieved. First on-line applications comprised real-time measurements of aromatic and aliphatic trace compounds in mainstream cigarette smoke, which represents a highly dynamic fluctuating gaseous matrix. Time resolution was sufficient to monitor the smoking process on a puff-by-puff resolved basis. Furthermore, human breath analysis has been carried out to detect differences in the breath of a smoker and a nonsmoker, respectively. Several well-known biomarkers for smoke could be identified in the smoker's breath. The possibility for even shorter measurement times while maintaining the achieved sensitivity makes this new device a promising tool for on-line analysis of organic trace compounds in process gases or biological systems. PMID:16285693

Mühlberger, F; Streibel, T; Wieser, J; Ulrich, A; Zimmermann, R

2005-11-15

374

S1 certification of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in a candidate certified reference material (organochlorine pesticides in tea) by isotope dilution gas chromatography-mass spectrometry.  

PubMed

This paper presents the certification of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in a candidate tea certified reference material (code: GLHK-11-03) according to the requirements of the ISO Guide 30 series. Certification of GLHK-11-03 was based on an analytical method purposely developed for the accurate measurement of the mass fraction of the target analytes in the material. An isotope dilution mass spectrometry (IDMS) method involving determination by (i) gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) and (ii) gas chromatography-electron ionization-high-resolution mass spectrometry (GC-EI-HRMS) techniques was employed. The performance of the described method was demonstrated through participation in the key comparison CCQM-K95 "Mid-Polarity Analytes in Food Matrix: Mid-Polarity Pesticides in Tea" organized by the Consultative Committee for Amount of Substance-Metrology in Chemistry in 2012, where the study material was the same as the certified reference material (CRM). The values reported by using the developed method were in good agreement with the key comparison reference value (KCRV) assigned for beta-endosulfan (727?±?14 ?g kg(-1)) and endosulfan sulfate (505?±?11 ?g kg(-1)), where the degree of equivalence (DoE) values were 0.41 and 0.40, respectively. The certified values of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in dry mass fraction in GLHK-11-03 were 350, 730, and 502 ?g kg(-1), respectively, and the respective expanded uncertainties, due to sample inhomogeneity, long-term and short-term stability, and variability in the characterization procedure, were 27 ?g kg(-1) (7.8 %), 48 ?g kg(-1) (6.6 %), and 33 ?g kg(-1) (6.6 %). PMID:25619984

Sin, Della Wai-Mei; Wong, Yee-Lok; Cheng, Eddie Chung-Chin; Lo, Man-Fung; Ho, Clare; Mok, Chuen-Shing; Wong, Siu-Kay

2015-04-01

375

IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. II. DUST-INDUCED COLLISIONAL IONIZATION  

SciTech Connect

Observations have shown that continuous radio emission and also sporadic H{alpha} and X-ray emission are prominent in singular, low-mass objects later than spectral class M. These activity signatures are interpreted as being caused by coupling of an ionized atmosphere to the stellar magnetic field. What remains a puzzle, however, is the mechanism by which such a cool atmosphere can produce the necessary level of ionization. At these low temperatures, thermal gas processes are insufficient, but the formation of clouds sets in. Cloud particles can act as seeds for electron avalanches in streamers that ionize the ambient gas, and can lead to lightning and indirectly to magnetic field coupling, a combination of processes also expected for protoplanetary disks. However, the precondition is that the cloud particles are charged. We use results from DRIFT-PHOENIX model atmospheres to investigate collisional processes that can lead to the ionization of dust grains inside clouds. We show that ionization by turbulence-induced dust-dust collisions is the most efficient kinetic process. The efficiency is highest in the inner cloud where particles grow quickly and, hence, the dust-to-gas ratio is high. Dust-dust collisions alone are not sufficient to improve the magnetic coupling of the atmosphere inside the cloud layers, but the charges supplied either on grains or within the gas phase as separated electrons can trigger secondary nonlinear processes. Cosmic rays are likely to increase the global level of ionization, but their influence decreases if a strong, large-scale magnetic field is present as on brown dwarfs. We suggest that although thermal gas ionization declines in objects across the fully convective boundary, dust charging by collisional processes can play an important role in the lowest mass objects. The onset of atmospheric dust may therefore correlate with the anomalous X-ray and radio emission in atmospheres that are cool, but charged more than expected by pure thermal ionization.

Helling, Ch.; Jardine, M. [SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS (United Kingdom); Mokler, F., E-mail: ch80@st-andrews.ac.uk [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr. 1, D-85748 Garching (Germany)

2011-08-10

376

Ionization Energies of Lanthanides  

ERIC Educational Resources Information Center

This article describes how data are used to analyze the pattern of ionization energies of the lanthanide elements. Different observed pathways of ionization between different ground states are discussed, and the effects of pairing, exchange, and orbital interactions on ionization energies of the lanthanides are evaluated. When all the above…

Lang, Peter F.; Smith, Barry C.

2010-01-01

377

Comprehensive Two Dimensional Gas Chromatography Fast Quadrupole Mass Spectrometry (GC×GC-qMS) for Urinary Steroid Profiling. Mass Spectral Characteristics with Chemical Ionization  

PubMed Central

Comprehensive two dimensional GC (GC×GC), coupled to either a time of flight MS (TOF-MS) or a fast scanning quadrupole MS (qMS) has greatly increased the peak capacity and separation space compared to conventional GC-MS. However, commercial GC×GC-TOFMS systems are not equipped with chemical ionization (CI) and do not provide dominant molecular ions or enable single ion monitoring for maximal sensitivity. A GC×GC-qMS in mass scanning mode was investigated with EI and positive CI (PCI), using CH4 and NH3 as reagent gases. Compared to EI, PCI-NH3 produced more abundant molecular ions and high mass structure specific ions for steroid acetates. Chromatography in two dimensions was optimized with a mixture of 12 endogenous and 3 standard acetylated steroids (SM15-AC) relevant to doping control. Eleven endogenous target steroid acetates were identified in normal urine based on their two retention times, and EI and PCI-NH3 mass spectra; nine of these endogenous target steroid acetates were identified in congenital adrenal hyperplasia (CAH) patients. The difference between the urinary steroids profiles of normal individuals and from a CAH patient can easily be visually distinguished by their GC×GC-qMS chromatograms. We focus here on the comparison and interpretation of the various mass spectra of the targeted endogenous steroids. PCI-NH3 mass spectra were most useful for unambiguous molecular weight determination and for establishing the number of -OH by the losses of 1 or more acetate groups. We conclude that PCI-NH3 with GC×GC-qMS provides improved peak capacity and pseudomolecular ions with structural specificity. PMID:22147458

Zhang, Ying; Tobias, Herbert J.; Auchus, Richard J.; Brenna, J. Thomas

2013-01-01

378

WARPED IONIZED HYDROGEN IN THE GALAXY  

SciTech Connect

We report observations of the H166{alpha} ({nu} = 1424.734 MHz) radio recombination line (RRL) emission from the Galactic plane in the longitude range l = 267 deg. - 302 deg. and latitude range b = -3.{sup 0}0 to +1.{sup 0}5. The line emission observed describes the Carina arm in the Galactic azimuth range from {theta} = 260 deg. to 190 deg. The structure is located at negative latitudes with respect to the formal Galactic plane. The observations are combined with RRL data from the first Galactic quadrant. Both quadrants show the signature of the warp for the ionized gas, but an asymmetry of the distribution is noted. In the fourth quadrant, the gas is located between Galactic radii R {approx} 7 and 10 kpc, and the amplitude of the warp is seen from the midplane to z {approx} -150 pc. In the first quadrant, the gas is found between R {approx} 8 and 13-16 kpc, and flares to z {approx} +350 pc. We confirm the warp of the ionized gas near the solar circle. The distribution of the ionized gas is compared with the maximum intensity H I emission (0.30 < n{sub HI} < 0.45 cm{sup -3}) at intervals of the Galactic ring. The ionized material is correlated with the H I maximum intensity in both quadrants, and both components show the same tilted behavior with respect to the mid-Galactic plane.

Cersosimo, J. C.; Figueroa, N. Santiago; Velez, S. Figueroa; Soto, C. Lozada [Department of Physics and Electronics, University of Puerto Rico at Humacao, Humacao, PR 00791 (Puerto Rico); Mader, S. [CSIRO Parkes Observatory, New South Wales (Australia); Azcarate, D. [Instituto Argentino de RadioastronomIa, CC No. 5, 1894 Villa Elisa. BsAs (Argentina)], E-mail: juan.cersosimo@upr.edu

2009-07-01

379

Method and apparatus utilizing ionizing and microwave radiation for saturation determination of water, oil and a gas in a core sample  

DOEpatents

A system for determining the relative permeabilities of gas, water and oil in a core sample has a microwave emitter/detector subsystem and an X-ray emitter/detector subsystem. A core holder positions the core sample between microwave absorbers which prevent diffracted microwaves from reaching a microwave detector where they would reduce the signal-to-noise ratio of the microwave measurements. The microwave emitter/detector subsystem and the X-ray emitter/detector subsystem each have linear calibration characteristics, allowing one subsystem to be calibrated with respect to the other subsystem. The dynamic range of microwave measurements is extended through the use of adjustable attenuators. This also facilitates the use of core samples with wide diameters. The stratification characteristics of the fluids may be observed with a windowed cell separator at the outlet of the core sample. The condensation of heavy hydrocarbon gas and the dynamic characteristics of the fluids are observed with a sight glass at the outlet of the core sample.

Maerefat, Nicida L. (Sugar Land, TX); Parmeswar, Ravi (Marlton, NJ); Brinkmeyer, Alan D. (Tulsa, OK); Honarpour, Mehdi (Bartlesville, OK)

1994-01-01

380

Method and apparatus utilizing ionizing and microwave radiation for saturation determination of water, oil and a gas in a core sample  

DOEpatents

A system is described for determining the relative permeabilities of gas, water and oil in a core sample has a microwave emitter/detector subsystem and an X-ray emitter/detector subsystem. A core holder positions the core sample between microwave absorbers which prevent diffracted microwaves from reaching a microwave detector where they would reduce the signal-to-noise ratio of the microwave measurements. The microwave emitter/detector subsystem and the X-ray emitter/detector subsystem each have linear calibration characteristics, allowing one subsystem to be calibrated with respect to the other subsystem. The dynamic range of microwave measurements is extended through the use of adjustable attenuators. This also facilitates the use of core samples with wide diameters. The stratification characteristics of the fluids may be observed with a windowed cell separator at the outlet of the core sample. The condensation of heavy hydrocarbon gas and the dynamic characteristics of the fluids are observed with a sight glass at the outlet of the core sample. 11 figs.

Maerefat, N.L.; Parmeswar, R.; Brinkmeyer, A.D.; Honarpour, M.

1994-08-23

381

Double ionization in gases driven by optical field ionization using ultrashort laser pulses  

SciTech Connect

Rapid optical field ionization (OFI) for atoms and ions is distinguished using ultra-short laser pulses focused to peak fields comparable to Coulomb binding values. This nonperturbative field description facilitates understanding of standard sequential ionization and distinguishes the double (or two-electron ejection) ionization process. Following our discovery of double optical field ionization in He{sup +2} at 614 nm we have extended experiments to include helium, neon and argon at an 800 nm wavelength with varying ellipticity. We compare double ionization data with predictions from the semi-classical model by Corkum. New experimental results at 800 nm use 130 femtosecond laser pulses focused to intensities of order 10{sup 16} W/cm in the extraction region of a 1 meter time-of-flight spectrometer. Gas pressures ranged from 10{sup {minus}8} to 10{sup {minus}5} torr.

Bolton, P.R.; Fittinghoff, D.N.

1994-06-01

382

[Fe IV] emission in ionized nebulae  

E-print Network

This paper presents an analysis of [Fe IV] emission based on new identifications and previous measurements of [Fe IV] lines in 30 Doradus, IC 4846, M42, SMC N88A, and SBS 0335-052. The Fe abundances obtained by adding the abundances of the relevant Fe ions (mainly Fe^{++} and Fe^{3+}) are found to be lower, by factors in the range 2.6-5.9, than the Fe abundances implied by [Fe III] emission and an ionization correction factor derived from ionization models. The most likely explanation of this discrepancy is that either the collision strengths for [Fe IV] or the Fe ionization fractions predicted by models are unreliable. The available data neither allow one to distinguish between these two possibilities nor to exclude another possible explanation: that the discrepancy implies the presence of a gradient in the Fe abundance within the ionized gas. Further measurements of [Fe IV] lines and checks on the Fe^{3+} atomic data and ionization models are needed to reach a definitive conclusion. The discrepancy introduces an uncertainty in the determination of Fe abundances in ionized nebulae. This uncertainty has implications for our understanding of both the evolution of dust in ionized nebulae and the chemical history of low metallicity galaxies.

Monica Rodriguez

2003-02-25

383

The A 2Sigma + state of rare gas-NO van der Waals molecules probed by 1+1 multiphoton ionization spectroscopy  

NASA Astrophysics Data System (ADS)

The previously unobserved bound-bound spectra of ArNO, KrNO, and XeNO have been observed slightly blue shifted from the (1,0) and (0,0) bands of the A 2?+?X 2?1/2 transition of uncomplexed nitric oxide. Although the structured but incomplete spectra cannot be assigned with certainty, limits to the ground and excited state bond dissociation energies, D`0 and D0, respectively, can be estimated. For ArNO these limits are D`0 ?89 and 54 cm-1?D0 ?101 cm-1. The observed fragmentation of the KrNO and XeNO molecules, coupled with earlier results for MPI via the C 2? state, suggests that superexcited, autoionizing states of the van der Waals molecules dissociate to yield excited rare gas atoms whenever energetically possible.

Miller, John C.

1989-04-01

384

Gas Chromatography  

NSDL National Science Digital Library

This site contains a brief introduction to the concepts of injection and detection in gas chromatography, focusing on the split/splitless injection port and flame ionization detectors. The treatment is similar to that in analytical chemistry textbooks, and includes detailed illustrations.

385

Fundamentals of Biomolecule Analysis by Electrospray Ionization Mass Spectrometry  

ERIC Educational Resources Information Center

Electrospray ionization (ESI) is a soft ionization technique that allows transfer of fragile biomolecules directly from solution into the gas phase. An instrumental analysis laboratory experiment is designed that would introduce the students to the ESI technique, major parameters of the ion trap mass spectrometers and some caveats in…

Weinecke, Andrea; Ryzhov, Victor

2005-01-01

386

Ionized interstellar froth in irregular galaxies  

NASA Technical Reports Server (NTRS)

The warm interstellar medium of galaxies is a complicated place. It is often full of holes, neutral and ionized loops and shells, and diffuse ionized gas. Deep H alpha images of Magellanic-type irregular galaxies also reveal complex spatial structures consisting of loops and filaments in the interstellar gas outside of the boundaries of traditional HII regions. Researchers refer to these ionized structures as froth. Such structures could mark paths over which newly produced heavy elements are dispersed in irregular galaxies, and they could be the signatures of a feedback process related to star formation. In order to investigate the physical nature of the froth, researchers obtained narrow-band images and high and low dispersion spectra from Kitt Peak National Observatory (KPNO) and deep blue-passband plates from the Canada-France-Hawaii Observatory (CFHO).

Hunter, Deidre A.; Gallagher, John S., III

1990-01-01

387

A switchable reagent ion high resolution time-of-flight chemical ionization mass spectrometer for real-time measurement of gas phase oxidized species: characterization from the 2013 Southern Oxidant and Aerosol Study  

NASA Astrophysics Data System (ADS)

A novel configuration of the Aerodyne high resolution time-of-flight chemical ionization mass spectrometer (HR-TOF-CIMS) as a switchable reagent ion (SRI) HR-TOF-CIMS is presented and described along with data collected at the Southern Oxidant and Aerosol Study (SOAS) during the summer of 2013. The calibration system and reduced pressure gas-phase inlet are characterized. The average limit of detection and limit of quantification for formic acid during SOAS are 82 and 863 ppt, respectively, corresponding to an average sensitivity of 13 ± 5 Hz ppt-1. Hourly background determinations and calibrations are shown to be essential for tracking instrument performance and accurately quantifying formic acid. Maximum daytime formic acid concentrations of 10 ppb are reported during SOAS, and a strong diel cycle is observed leading to night time concentrations below the limit of quantification. Other species presented exhibit diel behavior similar to formic acid. The concept of the mass defect enhancement plot and the use of signal-to-noise are described in detail as a method for investigating HR-TOF-CIMS spectra in an effort to reduce data complexity.

Brophy, P.; Farmer, D. K.

2015-03-01

388

Hollow fiber supported liquid-phase microextraction using ionic liquid as extractant for preconcentration of benzene, toluene, ethylbenzene and xylenes from water sample with gas chromatography-hydrogen flame ionization detection.  

PubMed

A novel method has been developed for the analysis of benzene, toluene, ethyl-benzene, and o-, m- and p-xylenes (BTEXs) in water using hollow fiber supported liquid-phase microextraction (HF-LPME) followed by gas chromatography-hydrogen flame ionization detection. Ionic liquid 1-butyl-3-methy-limidazolium hexafluorophosphate ([BMIM][PF(6)]) was acted as the extractant for extraction and preconcentration of BTEXs from aqueous samples, and a porous-walled polypropylene hollow fiber was utilized to stabilize and protect [BMIM][PF(6)] during the extraction process. Various parameters that affect extraction efficiency were investigated in detail, and the optimized experimental conditions were as follows: 8 ?L of [BMIM][PF(6)] as extraction solvent for the target analytes in 20 mL of sample solution, 30 min of extraction time, a stirring rate of 1400 rpm and 15% NaCl (w/v) in aqueous sample at 25°C (ambient temperature). The recovery was found to be 90.0-111.5% with RSD (n=5) of 1.3-5.4%, and the detection limits (S/N=3) were in the range of 2.7-4.0 ?g/L. The proposed method was simple, cheap, rapid, sensitive and environmentally benign, and could act as an alternative to techniques for BTEXs analysis with expensive instrumentations. PMID:21871732

Ma, Xiaoguo; Huang, Minghua; Li, Zhihua; Wu, Jianmei

2011-10-30

389

A new disposable ionic liquid based coating for headspace solid-phase microextraction of methyl tert-butyl ether in a gasoline sample followed by gas chromatography-flame ionization detection.  

PubMed

A new ionic liquid (IL) based solid-phase microextraction (SPME) fiber was investigated and used for headspace (HS) extraction of methyl tert-butyl ether (MTBE) in a gasoline sample. Using the new IL coated HS-SPME fiber with the combination of gas chromatography-flame ionization detection (GC-FID); sub-to-low ?g L(-1) concentrations of MTBE were detected. Four different ILs including 1-butyl-3-methylimidazolium tetraflouroborate ([C(4)C(1)IM] [BF(4)]), 1-octyl-3-methylimidazolium tetraflouroborate ([C(8)C(1)IM] [BF(4)]), 1-octyl-3-methylimidazolium hexaflourophosphate ([C(8)C(1)IM] [PF(6)]) and 1-ethyl-3-methylimidazolium ethylsulphate ([C(2)C(1)IM] [ETSO(4)]) were synthesized and examined for extraction, preconcentration and determination of MTBE. It was observed that [C(8)C(1)IM] [BF(4)] showed the highest extraction efficiency and possessed the best extractability for MTBE. The fiber coating takes up the compounds from the sample by absorption in the case of liquid coatings. The calibration graph was linear in a concentration range of 1-120 ?g L(-1) (R(2)>0.994) with the detection limit of 0.09 ?g L(-1) level. The new IL-coated fiber was applied successfully for the determination of MTBE in a gasoline sample with good recoveries between 90 and 95%. PMID:21315889

Amini, Ramin; Rouhollahi, Ahmad; Adibi, Mina; Mehdinia, Ali

2011-03-15

390

Homogeneous liquid-liquid extraction (HoLLE) via flotation combined with gas chromatography-flame ionization detection as a very simple, rapid and sensitive method for the determination of fenitrothion in water samples.  

PubMed

Homogeneous liquid-liquid extraction via flotation assistance (HoLLE-FA) and gas chromatography-flame ionization detection (GC-FID) was presented for the extraction and determination of fenitrothion in water samples. In this work, a rapid, simple and efficient HoLLE-FA method was developed based on applying low-density organic solvents without employing centrifugation. A special extraction cell was designed to facilitate the collection of low-density solvent extraction in the determination of fenitrothion in water samples. The water sample solution was added into an extraction cell that contained an appropriate mixture of extraction and homogeneous solvents. By using air flotation, the organic solvent was collected at the conical part of the designed cell. Under the optimum conditions, the method performance was studied in terms of the linear dynamic range (LDR from 1.0 up to 100 ?g L?¹), linearity (r² > 0.998), and precision (repeatability < 8.0%). Also, limit of detection (LOD) of 0.4 ?g L?¹ was obtained for fenitrothion. The applicability of the HoLLE-FA method was evaluated by the extraction and determination of fenitrothion in three different water samples. PMID:23934566

Mashayekhi, Hossein Ali

2013-01-01

391

Molecular characterization of phospholipids by high-performance liquid chromatography combined with an evaporative light scattering detector, high-performance liquid chromatography combined with mass spectrometry, and gas chromatography combined with a flame ionization detector in different oat varieties.  

PubMed

Oat (Avena sativa L.) is an important crop produced in various regions of Europe and North America. Oat lipids are a heterogeneous mixture of acyl lipids and unsaponifiable components. The neutral lipids are mainly triacylglycerols and account for 50-60% of total oat lipids. Oat oil is also rich in polar lipids, that is, phospholipids and glycolipids. Characterization of oat polar lipids has largely been performed by thin-layer chromatography (TLC), but the composition of phospholipid classes has been poorly studied. The aim of our work was the determination of different phospholipids in Romanian oat samples. For that purpose, one commercial sample (Comun) and four pure varieties (Jeremy, Lovrin 1, Lovrin 27-T, and Mures) were used. High-performance liquid chromatography combined with an evaporative light scattering detector results allowed us to establish that phosphatidylethanolamine was the most representative phospholipid in all of the oat samples. In addition, high-performance liquid chromatography combined with electrospray ionization mass spectrometry analysis showed that C16:0, C16:1, C18:0, C18:1, C18:2, C18:3, C20:0, and C20:1 were the fatty acids bound to the glycerol backbone. Using first-preparative TLC and later gas chromatography, it was demonstrated that linoleic acid (C18:2) was the main fatty acid of the phospholipid fraction in all of the samples. PMID:23061991

Montealegre, Cristina; Verardo, Vito; Gómez-Caravaca, Ana Maria; García-Ruiz, Carmen; Marina, María Luisa; Caboni, Maria Fiorenza

2012-11-01

392

Determination of 2-, 3-, 4-methylpentanoic and cyclohexanecarboxylic acids in wine: development of a selective method based on solid phase extraction and gas chromatography-negative chemical ionization mass spectrometry and its application to different wines and alcoholic beverages.  

PubMed

A method to analyse 2-methylpentanoic, 3-methylpentanoic and 4-methylpentanoic acids as well as cyclohexanecarboxylic acid has been developed and applied to wine and other alcoholic beverages. Selective isolation with solid phase extraction, derivatization with 2,3,4,5,6-pentafluorobenzyl bromide at room temperature for 30 minutes, and further analysis by gas chromatography-mass spectrometry in negative chemical ionization mode provides detection limits between 0.4 and 2.4 ng/L. Good linearity up to 3.6 ?g/L, satisfactory reproducibility (RSD<10%) and signal recovery of around 100% represent a robust method of analysis. Concentration data of these analytes in wine and other alcoholic beverages are reported for the first time. The levels found ranged from the method detection limits to 2630 ng/L, 2040 ng/L and 3810 ng/L for 2-, 3- and 4-methylpentanoic acids, respectively, and to 1780 ng/L for cyclohexanecarboxylic acid. There are significant differences depending on the type of wine or beverage. Distilled beverages, beer and aged wines have higher contents in methylpentanoic and cyclohexanecarboxylic acids. PMID:25601317

Gracia-Moreno, Elisa; Lopez, Ricardo; Ferreira, Vicente

2015-02-13

393

Characterization and quantitative amino acids analysis of analgesic peptides in cinobufacini injection by size exclusion chromatography, matrix-assisted laser desorption/ionization time of flight mass spectrometry and gas chromatography mass spectrometry.  

PubMed

Cinobufacini injection that comes from the water extract of Bufo bufo gargarizans Cantor skin is widely used for cancer treatment in China. Peptide is one of its major types of constituents, however the biological effects and content of this injection are little reported. In present study, the analgesic effect of peptides was determined and evaluated by in-vivo models. To characterize and quantitatively analyze these peptides, a reliable and efficient method combining size exclusion chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with amino acid analysis was developed. The peptides presented as a series of analogs with similar molecular weights mostly ranging from 2 to 8 kDa. The amino acid analysis by gas chromatography mass spectrometry (GC-MS) was developed to determine both free and combined amino acids (FAA and CAA) in cinobufacini injection. This method achieved good linearity (R(2) , 0.9909-0.9999) and low limit of detection and quantification. FAA and CAA samples were efficiently analyzed by modified Phenomenex EZ: faast procedure. For the sample analysis, the method showed good repeatability (relative standard deviation, RSD???10%). For most FAA and CAA the mean recoveries were >80% with RSD <10%. The GC-MS based method is useful for quality assurance of both FAA and CAA in cinobufacini injection. PMID:24924921

Wu, Xu; Si, Nan; Bo, Gao; Hu, Hao; Yang, Jian; Bian, Baolin; Zhao, Hai Yu; Wang, Hongjie

2015-01-01

394

Vacuum-ultraviolet mass-analyzed threshold ionization spectra of iodobutane isomers: Conformer-specific ionization and ion-core  

E-print Network

Vacuum-ultraviolet mass-analyzed threshold ionization spectra of iodobutane isomers: Conformer-analyzed threshold ionization MATI spectra using coherent vacuum ultraviolet radiation have been obtained for t-photon MATI spectroscopy using a vacuum-ultraviolet VUV laser source generated by four-wave mixing in Kr gas.8

Kim, Myung Soo

395

Determination of plant stanols and plant sterols in phytosterol enriched foods with a gas chromatographic-flame ionization detection method: NMKL collaborative study.  

PubMed

This collaborative study with nine participating laboratories was conducted to determine the total plant sterol and/or plant stanol contents in phytosterol fortified foods with a gas chromatographic method. Four practice and 12 test samples representing mainly commercially available foodstuffs were analyzed as known replicates. Twelve samples were enriched with phytosterols, whereas four samples contained only natural contents of phytosterols. The analytical procedure consisted of two alternative approaches: hot saponification method, and acid hydrolysis treatment prior to hot saponification. As a result, sterol/stanol compositions and contents in the samples were measured. The amounts of total plant sterols and total plant stanols varying from 0.005 to 8.04 g/100 g product were statistically evaluated after outliers were eliminated. The repeatability RSD (RSDr) varied from 1.34 to 17.13%. The reproducibility RSD (RSDR) ranged from 3.03 to 17.70%, with HorRat values ranging from 0.8 to 2.1. When only phytosterol enriched food test samples are considered, the RSDr ranged from 1.48 to 6.13%, the RSD, ranged from 3.03 to 7.74%, and HorRat values ranged from 0.8 to 2.1. Based on the results of this collaborative study, the study coordinator concludes the method is fit for its purpose. PMID:25145144

Laakso, Päivi H

2014-01-01

396

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

Microsoft Academic Search

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

Teemu Gunnar; Sirpa Mykkänen; Kari Ariniemi; Pirjo Lillsunde

2004-01-01

397

Earth’s Interaction Region: Plasma-Neutral Interactions in the Weakly Ionized gas of Earth’s High Latitude Upper Atmosphere  

NASA Astrophysics Data System (ADS)

The high-latitude regions of Earth’s upper atmosphere are strongly influenced by plasma-neutral interactions. These interactions couple electrodynamic processes of the ionosphere with hydrodynamic processes of the more abundant thermosphere neutral gas, consequently connecting the high-latitude upper atmosphere to distant regions of the geoplasma environment. This produces a complex spatial and temporal interplay of competing processes that results in a myriad of physical and chemical responses and a rich array of neutral and plasma morphologies that constitute the high-latitude thermosphere and ionosphere. The altitude extent from the lower thermosphere to the upper ionosphere (90km – 1000km) can be considered Earth’s space-atmosphere interaction region - likened to the solar chromosphere’s interaction region where radiative processes and hydrodynamic waves from the dense lower atmosphere produce a cold lower boundary that quickly transitions over a few 100 kilometers to neutral and plasma temperatures that are five times hotter. A thousand or more kilometers further in altitude, Earth's upper atmosphere becomes a hot, collisionless, geomagnetically controlled protonosphere whose neutral and plasma population originates from the thermosphere and ionosphere. A grand challenge in the study of Earth’s interaction region is how the collision-dominated thermosphere/ionosphere system exchanges energy, mass and momentum with the collisionless magnetosphere. This talk will focus primarily on collision-dominated processes of the high-latitude ionosphere and the electromagnetic energy transfer processes that lead to frictional heating of ions and neutrals, and plasma instability phenomenon that leads to extreme electron heating. Observations of the ionosphere response to these processes will be illustrated using incoherent scatter radar measurements. Relevance to the solar chromosphere will be identified where appropriate and outstanding issues in Earth’s interaction region will be discussed.

Thayer, Jeffrey; Hsu, Vicki

2015-04-01

398

Fast procedure for the analysis of poly(hydroxyalkanoates) in bacterial cells by off-line pyrolysis/gas-chromatography with flame ionization detector.  

PubMed

Poly(hydroxyalkanoates) (PHAs) are polyesters formed by saturated short chain hydroxyacids, among which 3-hydroxybutanoic (HB) and 3-hydroxypentanoic (3-hydroxyvalerate, HV) are the most common monomers of homopolymers (e.g. poly(3-hydroxybutyrate), PHB) and copolymers (e.g. poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), PHB-HC). The most widely used approach for their determination is the polymer methanolysis followed by gas chromatography-mass spectrometry (GC-MS) analysis of the methylated monomers; this procedure generally requires the use of additional reagents (e.g. sulfuric acid) and is performed with harmful chlorinated solvents, such as chloroform. The development of fast routine solventless methods for the quantitative determination of PHAs and their monomeric composition is highly desirable to reduce sample pretreatment, speed up the analysis and decrease overall costs. It has been reported that under thermal treatment (e.g. pyrolysis, Py), PHAs are degraded in high yield (>40%, w/wPHA) into the corresponding 2-alkenoic acid (e.g. crotonic acid from PHB). This work aimed at investigating this reaction for direct analysis of PHAs in bacterial cells. The sample was directly subjected to pyrolysis and trapped pyrolysis products were analyzed by GC-FID. Off-line Py/GC-FID was first optimized on pure polymers with different monomer composition (PHB, PHB-HV, PHB-HC) and then applied to bacterial samples deriving from both mixed microbial cultures or selected strains, containing various types and amounts of PHAs. The Py/GC-FID method provided RSD <15% range, limit of detection of 100?g (1% PHAs in biomass), and results comparable to that of methanolysis (R(2)=0.9855), but with minimal sample pretreatment. PMID:25069742

Torri, Cristian; Cordiani, Helena; Samorì, Chiara; Favaro, Lorenzo; Fabbri, Daniele

2014-09-12

399

Field ionization of argon using beta-phase W nanorods  

Microsoft Academic Search

We report testing of beta-phase W nanorods as a gas ionizer for neutral argon atoms. These W nanorods having square-base pyramidal apexes were grown on oxidized Si(100) substrate using glancing angle sputter deposition technique with substrate rotation. Only a few volts of positive anode voltage (3-4 V) applied to the W nanorods generates a high electric field, which ionizes gas-phase

J. P. Singh; T. Karabacak; T.-M. Lu; G.-C. Wang; N. Koratkar

2004-01-01

400

Field ionization of argon using ?-phase W nanorods  

Microsoft Academic Search

We report testing of ?-phase W nanorods as a gas ionizer for neutral argon atoms. These W nanorods having square-base pyramidal apexes were grown on oxidized Si(100) substrate using glancing angle sputter deposition technique with substrate rotation. Only a few volts of positive anode voltage (3–4 V) applied to the W nanorods generates a high electric field, which ionizes gas-phase

J. P. Singh; T. Karabacak; T.-M. Lu; G.-C. Wang; N. Koratkar

2004-01-01