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1

Gas chromatography-electron ionization-mass spectrometry quantitation of valproic acid and gabapentin, using dried plasma spots, for therapeutic drug monitoring in in-home medical care.  

PubMed

A simple and sensitive gas chromatography-electron ionization-mass spectrometry (GC-EI-MS) method using dried plasma spot testing cards was developed for determination of valproic acid and gabapentin concentrations in human plasma from patients receiving in-home medical care. We have proposed that a simple, easy and dry sampling method is suitable for in-home medical patients for therapeutic drug monitoring. Therefore, in the present study, we used recently developed commercially available easy handling cards: Whatman FTA DMPK-A and Bond Elut DMS. In-home medical care patients can collect plasma using these simple kits. The spots of plasma on the cards were extracted into methanol and then evaporated to dryness. The residues were trimethylsilylated using N-methyl-N-trimethylsilyltrifluoroacetamide. For GC-EI-MS analysis, the calibration curves on both cards were linear from 10 to 200?µg/mL for valproic acid, and from 0.5 to 10?µg/mL for gabapentin. Intra- and interday precisions in plasma were both ?13.0% (coefficient of variation), and the accuracy was between 87.9 and 112% for both cards within the calibration curves. The limits of quantification were 10?µg/mL for valproic acid and 0.5?µg/mL for gabapentin on both cards. We believe that the present method will be useful for in-home medical care. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24889681

Ikeda, Kayo; Ikawa, Kazuro; Yokoshige, Satoko; Yoshikawa, Satoshi; Morikawa, Norifumi

2014-12-01

2

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

Microsoft Academic Search

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

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

2008-01-01

3

Determination of thiazolidine-4-carboxylates in urine by chloroformate derivatization and gas chromatography-electron impact mass spectrometry.  

PubMed

The derivatization method of thiazolidine-4-carboxylic acid (TZCA) and methyl-thiazolidine-4-carboxylic acid (Me-TZCA) in urine with alcohol/chloroformate was achieved. TZCA and Me-TZCA were derivatized in one step in urine with ethyl chloroformate in 1 min at room temperature. The derivatives of TZCA and Me-TZCA had very good chromatographic properties and offered very sensitive response for gas chromatography-electron impact ionization-mass spectrometry (GC-EI-MS). On the basis of derivatization, the method for simultaneous determination of TZCA and Me-TZCA in human urine was developed. Deuterated Me-TZCA (Me-TZCA-d(4)) was synthesized as the internal standard (IS) for the analysis of urine samples. TZCA and Me-TZCA were derivatized and extracted from urine at pH 9.5 with toluene, and then the dried extract was dissolved with 100 microl ethyl acetate and injected in GC/MS system. The recoveries of TZCA and Me-TZCA were about 102 and 103%, respectively, at the concentration of 0.05 mg/l. The method detection limits (MDL) were 1.0 and 0.5 microg/l, respectively, for TZCA and Me-TZCA in 1 ml human urine. The coefficients of variation of TZCA and Me-TZCA were less than 6% at the concentrations of 0.05 and 0.2 mg/l, respectively. To assess the formation of TZCA during inhalation with formaldehyde (FA) (about 3.1 and 38.1 ppm FA in air), urine samples from rats were taken during 3 days after initiation of treatment. The mean amount of TZCA determined was 0.07 mg/l in control group and 0.18 mg/l during treatment with 3.1 ppm. The TZCA levels increased up to about 1.01 mg/l during treatment with 38.1 ppm. It is planned to study whether urinary TZCA can be used as an indicator in the biological monitoring of exposure to FA. PMID:17610311

Shin, Ho-Sang; Ahn, Hye-Sil; Lee, Byung-Hoon

2007-09-01

4

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

5

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

Microsoft Academic Search

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

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

2007-01-01

6

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

7

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

PubMed

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

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

2007-04-30

8

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

PubMed

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

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

2012-03-01

9

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

PubMed

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

Liu, Dan; Min, Shungeng

2012-04-27

10

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

PubMed

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

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

2002-11-01

11

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

Microsoft Academic Search

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

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

2000-01-01

12

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

PubMed

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

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

2012-10-15

13

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

PubMed

A robust method for routine quality control of corky off-flavour compounds in wine and cork soak matrices has been established. Based on an automated headspace solid phase microextraction (HS-SPME), the method needs only marginal sample preparation and achieves low (sub-ng L(-1)) trace level detection limits (LODs) for the most relevant off-flavour compounds, such as 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA) and 2,4,6-tribromoanisole (TBA). Particularly for wine matrix, reliable trace level quantification had only been achieved after applying heart-cutting multidimensional gas chromatography (MDGC). Using a halogen-sensitive electron capture detector (ECD) and quantification with a stable isotope dilution assay (SIDA), LODs of 0.1ng L(-1) for TCA, TeCA and TBA could be obtained. Since a SIDA based quantification method is used with a non-mass spectrometric detector, the necessary chromatographic resolution of internal standard and target analyte peaks resulted from the use of highly deuterated [(2)H(5)]-isotopologues. PMID:23219330

Slabizki, Petra; Schmarr, Hans-Georg

2013-01-01

14

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

15

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

Microsoft Academic Search

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

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

2001-01-01

16

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

17

Simultaneous determination of amitraz and its metabolite residue in food animal tissues by gas chromatography-electron capture detector and gas chromatography-mass spectrometry with accelerated solvent extraction.  

PubMed

A new method has been developed for determination and confirmation of amitraz and its main metabolite, 2,4-dimethylaniline, in food animal tissues using gas chromatography-electron capture detector (GC-ECD) and gas chromatography-mass spectrometry detector (GC-MS). This method is based on a new extraction procedure using accelerated solvent extraction (ASE). It consists of an n-hexane/methanol extraction step, a cleaning-up step by BakerBond octadecyl C(18) silica bonded cartridge, hydrolysis and derivatization to 2,4-dimethyl-7-F-butyramide for GC-ECD analysis. For confirmation using GC-MS, hydrolysis and derivatization were not needed. Parameters for extraction pressure, temperature and cycle of ASE, clean-up, derivatization and analysis procedure have been optimized. Spike recoveries from 50 to 300 microg/kg levels were found to be between 72.4 and 101.3% with relative standard deviation less than 11.5% in GC-ECD, from 5 to 20 microg/kg levels were found to be between 77.4 and 107.1% with relative standard deviation less than 11.6% in GC-MS. The LOD and LOQ are 5 and 10 microg/kg, respectively, for these two analytes using GC-ECD. For GC-MS, LOD and LOQ were 2 and 5 microg/kg, respectively. The rapid and reliable method can be used for characterization and quantification of residues of amitraz and its main metabolite, 2,4-dimethylaniline, in liver and kidney samples of swine, sheep and bovine. PMID:20554255

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

2010-07-01

18

Diffuse ionized gas toward beta Canis Majoris  

NASA Astrophysics Data System (ADS)

This paper presents the study of the interstellar medium toward beta CMa, a disk sight-line known for its low neutral gas density. This study uses high and medium resolution HST-GHRS spectra including lines from the following species: H i, D i, N i, O i, S ii, S iii, Si ii, Si iii, Si iv, Al ii, Al iii, Fe ii, Mg i, Mg ii, Mn ii, C ii and C iv. The line of sight to beta CMa (153 pc) is dominated by two ionized regions with a velocity difference of 10 km s(-1) . The ionized regions account for most of the total hydrogen column density, around 2 10(19) cm(-2) , and the neutral gas represents only 10% of the total gas. The two ionized clouds display characteristics of the warm diffuse gas detected in the disk and the halo. Their gas-phase abundances indicate that their depletion is low, especially for the more ionized of the two clouds. Special models of photoionization by the two EUV-excess stars beta CMa and epsilon CMa would be needed for a detailed discussion of the ionizing mechanisms of the clouds ; their ionization ratios are nevertheless roughly compatible with collisional ionization at temperatures around 20 000 K, substantially higher than the kinetic temperatures derived from the line widths. Their characteristics suggest that the clouds may be in the process of cooling down and recombining after having been shocked and ionized by some violent events, possibly related to the Local Bubble formation. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Dupin, Olivier; Gry, Cecile

1998-07-01

19

Ionization in MHD-Gas interactions  

NASA Astrophysics Data System (ADS)

The study of partially ionized plasmas is important in a number of astrophysical situations and is vital for the study of laboratory plasmas. The interactions between a neutral gas and a plasma define a hybrid medium that has aspects of each, but does not only sustain the pure modes of the individual species. Previously we have shown that momentum coupling between the gas and the magnetized plasma alters the behaviour of both; as an extension of that simulation, we present results for the extension to the coupling in which the relative motion between the species provides enough kinetic energy in the flow to allow a measure of species exchange Alfvén ionization (AI) (also known as critical velocity ionization), allowing the ionization fraction to evolve as the dynamics evolve.

Wilson, A.; Diver, D. A.

2013-09-01

20

Laboratory simulation of cometary neutral gas ionization  

NASA Technical Reports Server (NTRS)

The laboratory simulation of the interaction of the solar wind with a comet is used to study the cometary neural gas ionization. The experiment is carried out in the UCR T-1 facility with an ice ball as the comet model. Photographs and data are taken with a variety of values of the solar wind velocity, interplanetary magnetic field (IMF), and comet configurations. The results show that the cometary neutral gas ionization depends on both the velocity of the solar wind and the interplanetary magnetic field. The plasma cloud surrounding the comet is visible only when the solar wind velocity and IMF are both above certain minimum values. This velocity dependent phenomena is explained by Alfven's critical ionization velocity effect. The critical magnetic field may be explained by assuming two stream lower hybrid instability as a triggering mechanism for the ionization of the neutral gas by plasma flow. Critical upper and lower limits for the magnetic field, required by anomalous ionization, are also derived that satisfy the experimental observations.

Chang, Tsuey-Fen; Rahman, H. U.; White, R. S.

1989-01-01

21

Laboratory simulation of cometary neutral gas ionization  

SciTech Connect

The laboratory simulation of the interaction of the solar wind with a comet is used to study the cometary neutral gas ionization. The experiment is carried out in the UCR T-1 facility with an ice ball as the comet model. Photographs and data are taken with a variety of values of the solar wind velocity, interplanetary magnetic field (IMF), and comet configurations. The results show that the cometary neutral gas ionization depends on both the velocity of the solar wind and the interplanetary magnetic field. The plasma cloud surrounding the comet is visible only when the solar wind velocity and IMF are both above certain minimum values. This velocity dependent phenomena is explained by Alfven's critical ionization velocity effect. The critical magnetic field may be explained by assuming two stream lower hybrid instability as a triggering mechanism for the ionization of the neutral gas by plasma flow. Critical upper and lower limits for the magnetic field, required by anomalous ionization, are also derived that satisfy the experimental observations.

Chang, Tsuey-Fen; Rahman, H.U.; White, R.S. (Univ. of California, Riverside (USA))

1989-05-01

22

Ionized gas in active molecular cloud cores  

NASA Astrophysics Data System (ADS)

The star-forming regions NGC 2071, CRL 961, S106 IR, and S87, contain compact continuum radio sources. It is hypothesized that powerful stellar winds generate the radio emission in S106 IR and CRL 961, in view of their miniscule 5-GHz angular size, strong 4.05 micron Br-alpha H-recombination line, and proximity to the centers of expanding molecular or ionized gas. All of the objects studied are sufficiently hot and active to produce ionizing radiation and/or powerful stellar winds. The disruption of the star-forming molecular cloud is in progress. The direct observation of high velocity molecular and ionized gas shows that energetic mass outflow is a major process associated with the birth and early life of the stars studied.

Bally, J.; Predmore, R.

1983-02-01

23

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

24

SELF-CONSISTENT MEAN FIELD THEORY IN WEAKLY IONIZED GAS  

E-print Network

of the dynamo in 3D and tur- bulent diffusion in 2D in weakly ionized gas. We find that in 3D, the backreac to the fully ionized gas. Furthermore, we show that in 2D, the turbulent diffusion is suppressed by backSELF-CONSISTENT MEAN FIELD THEORY IN WEAKLY IONIZED GAS Nicolas Leprovost Groupe Instabilit´e et

Paris-Sud XI, Université de

25

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

PubMed

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

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

2002-11-15

26

The Molecular Torus and Ionized Gas in the Circinus Galaxy  

Microsoft Academic Search

In the current AGN paradigm, distributions of ionized gas in so-called `ionization cones' are believed to be produced by shadowing of the central source of ionizing radiation by a molecular torus. If this is indeed the case, there should be an excellent correspondence between the locations of the inner edge of the torus and the edge of the inner apex

Andrew Wilson

1997-01-01

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

The Survey for Ionization in Neutral Gas Galaxies. III. Diffuse, Warm Ionized Medium and Escape of Ionizing Radiation  

NASA Astrophysics Data System (ADS)

We use the first data release from the SINGG H? survey of H I-selected galaxies to study the quantitative behavior of the diffuse, warm ionized medium (WIM) across the range of properties represented by these 109 galaxies. The mean fraction fWIM of diffuse ionized gas in this sample is 0.59+/-0.19, slightly higher than found in previous samples. Since lower surface brightness galaxies tend to have higher fWIM, we believe that most of this difference is due to selection effects favoring large, optically bright, nearby galaxies with high star formation rates. As found in previous studies, there is no appreciable correlation with Hubble type or total star formation rate. However, we find that starburst galaxies, defined here by an H? surface brightness >2.5×1039 erg s-1 kpc-2 within the H? half-light radius, do show much lower fractions of diffuse H? emission. The cause apparently is not dominated by a lower fraction of field OB stars. However, it is qualitatively consistent with an expected escape of ionizing radiation above a threshold star formation rate, predicted from our model in which the ISM is shredded by pressure-driven supernova feedback. The H I gas fractions in the starburst galaxies are also lower, suggesting that the starbursts are consuming and ionizing all the gas, and thus promoting regions of density-bounded ionization. If true, these effects imply that some amount of Lyman continuum radiation is escaping from most starburst galaxies, and that WIM properties and outflows from mechanical feedback are likely to be pressure-driven. However, in view of previous studies showing that the escape fraction of ionizing radiation is generally low, it is likely that other factors also drive the low fractions of diffuse ionized gas in starbursts.

Oey, M. S.; Meurer, G. R.; Yelda, S.; Furst, E. J.; Caballero-Nieves, S. M.; Hanish, D. J.; Levesque, E. M.; Thilker, D. A.; Walth, G. L.; Bland-Hawthorn, J.; Dopita, M. A.; Ferguson, H. C.; Heckman, T. M.; Doyle, M. T.; Drinkwater, M. J.; Freeman, K. C.; Kennicutt, R. C., Jr.; Kilborn, V. A.; Knezek, P. M.; Koribalski, B.; Meyer, M.; Putman, M. E.; Ryan-Weber, E. V.; Smith, R. C.; Staveley-Smith, L.; Webster, R. L.; Werk, J.; Zwaan, M. A.

2007-06-01

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

The kinematics of the diffuse ionized gas in NGC 4666  

NASA Astrophysics Data System (ADS)

Context. The global properties of the interstellar medium with processes such as infall and outflow of gas and a large scale circulation of matter and its consequences for star formation and chemical enrichment are important for the understanding of galaxy evolution. Aims: In this paper we studied the kinematics and morphology of the diffuse ionized gas (DIG) in the disk and in the halo of the star forming spiral galaxy NGC 4666 to derive information about its kinematical properties. Especially, we searched for infalling and outflowing ionized gas. Methods: We determined surface brightness, radial velocity, and velocity dispersion of the warm ionized gas via high spectral resolution (R ? 9000) Fabry-Pérot interferometry. This allows the determination of the global velocity field and the detection of local deviations from this velocity field. We calculated models of the DIG distribution and its kinematics for comparison with the measured data. In this way we determined fundamental parameters such as the inclination and the scale height of NGC 4666, and established the need for an additional gas component to fit our observed data. Results: We found individual areas, especially along the minor axis, with gas components reaching into the halo which we interpret as an outflowing component of the DIG. As the main result of our study, we were able to determine that the vertical structure of the DIG distribution in NGC 4666 is best modeled with two components of ionized gas, a thick and a thin disk with 0.8 kpc and 0.2 kpc scale height, respectively. Therefore, the enhanced star formation in NGC 4666 drives an outflow and also maintains a thick ionized gas layer reminiscent of the Reynold's layer in the Milky Way.

Voigtländer, P.; Kamphuis, P.; Marcelin, M.; Bomans, D. J.; Dettmar, R.-J.

2013-06-01

31

Studies on a Helium Ionization Detector for Gas Chromatography  

Microsoft Academic Search

A new type of helium direct current plasma ionization detector (HeDCPID) for gas chromatography has been developed. The detector is simple in construction and can function with helium as the carrier gas without the need to subject the helium to excessive purification procedures. The noise level of the HeDCPID was below 1.2 × 10?13 A when a stable plasma was

X. D. Tian; W. J. Yang; A. M. Yu; Q. H. Jin

1995-01-01

32

Stellar and Ionized Gas Kinematics of Peculiar Virgo Cluster Galaxies  

NASA Astrophysics Data System (ADS)

We present the results of the stellar and ionized gas kinematics of 13 bright peculiar Virgo cluster galaxies. The stellar velocity field are mostly consistent with a rotation pattern, but some of them shows interesting features such as; Sshaped stellar isovelocity contours in NGC 4064, and signatures of kinematical distinct components in NGC 4429, and NGC 4698.

Cortés, J. R.; Kenney, J. D. P.; Hardy, E.

33

Electron and Ion Runaway in a Fully Ionized Gas. I  

Microsoft Academic Search

Hydrodynamic equations are used to describe the flow of the electrons and ions of a fully ionized gas under the action of an electric field, E, of arbitrary magnitude. The dynamical friction force exerted by the electrons and ions upon each other through the agency of two-body Coulomb encounters is evaluated. In this connection the electrons and ions have been

H. Dreicer

1959-01-01

34

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

35

Pulsed extraction of ionization from helium buffer gas  

E-print Network

The migration of intense ionization created in helium buffer gas under the influence of applied electric fields is considered. First the chemical evolution of the ionization created by fast heavy-ion beams is described. Straight forward estimates of the lifetimes for charge exchange indicate a clear suppression of charge exchange during ion migration in low pressure helium. Then self-consistent calculations of the migration of the ions in the electric field of a gas-filled cell at the National Superconducting Cyclotron Laboratory (NSCL) using a Particle-In-Cell computer code are presented. The results of the calculations are compared to measurements of the extracted ion current caused by beam pulses injected into the NSCL gas cell.

D. J. Morrissey; G. Bollen; M. Facina; S. Schwarz

2008-08-13

36

The Distribution of Warm Ionized Gas in NGC 891: Erratum  

NASA Astrophysics Data System (ADS)

In the Letter "The Distribution of Warm Ionized Gas in NGC 891" by Richard J. Rand, Shrinivas R. Kulkarni, and J. Jeff Hester (Ap. J. [Letters], 352, L1 [1990]), there is an error in the equation for the form of the ionized gas emission components used in our modeling of the gas distribution. The scale heights z_0_ and R_0_ shown in the equation and in Table 1 refer to the electron density distributions, not the emission distributions. Therefore, the equation for the emission components, instead of reading e^-|z|/z_0_^e^- R/R_0_^, should read e^-2|z|/z_0_^e^-2R/R_0_^. None of the calculated quantities, results, or conclusions of the Letter are affected by this error.

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

1990-10-01

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

Enhanced ionization in small rare-gas clusters  

SciTech Connect

A detailed theoretical investigation of rare-gas atom clusters under intense short laser pulses reveals that the mechanism of energy absorption is akin to enhanced ionization first discovered for diatomic molecules. The phenomenon is robust under changes of the atomic element (neon, argon, krypton, xenon), the number of atoms in the cluster (16-30 atoms have been studied), and the fluence of the laser pulse. In contrast to molecules it does not disappear for circular polarization. We develop an analytical model relating the pulse length for maximum ionization to characteristic parameters of the cluster.

Siedschlag, Christian; Rost, Jan M. [Max-Planck-Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, D-01187 Dresden (Germany)

2003-01-01

39

Plasma wakefield acceleration in self-ionized gas or plasmas.  

PubMed

Tunnel ionizing neutral gas with the self-field of a charged particle beam is explored as a possible way of creating plasma sources for a plasma wakefield accelerator [Bruhwiler et al., Phys. Plasmas (to be published)]. The optimal gas density for maximizing the plasma wakefield without preionized plasma is studied using the PIC simulation code OSIRIS [R. Hemker et al., in Proceeding of the Fifth IEEE Particle Accelerator Conference (IEEE, 1999), pp. 3672-3674]. To obtain wakefields comparable to the optimal preionized case, the gas density needs to be seven times higher than the plasma density in a typical preionized case. A physical explanation is given. PMID:14683089

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

2003-10-01

40

40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section...1065.267 Gas chromatograph with a flame ionization detector. (a) Application. You may use a gas chromatograph with a flame ionization detector (GC-FID) to...

2012-07-01

41

40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section...1065.267 Gas chromatograph with a flame ionization detector. (a) Application. You may use a gas chromatograph with a flame ionization detector (GC-FID) to...

2013-07-01

42

Ionization and absorption effects in high-order harmonic generation in gas-filled hollow fibers  

E-print Network

Ionization and absorption effects in high-order harmonic generation in gas-filled hollow fibers A and ionization on high-order harmonic generation in a gas-filled hollow fiber is analyzed within the framework-order harmonic generation in hollow fibers filled with different rare gases. Ionization of the gas filling

von der Linde, D.

43

Monte Carlo Photoionization Simulations of Diffuse Ionized Gas  

E-print Network

We demonstrate that the observed increase of some nebular line ratios with height above the midplane in the diffuse ionized gas (DIG) in the Milky Way and other galaxies is a natural consequence of the progressive hardening of the radiation field far from the midplane ionizing sources. To obtain increasing temperatures and line ratios away from the midplane, our photoionization simulations of a multi-component interstellar medium do not require as much additional heating (over and above that from photoionization) as previous studies that employed one dimensional, spherically averaged models. Radiation leaking into the DIG from density bounded H II regions is generally harder in the H-ionizing continuum and has its He-ionizing photons suppressed compared to the ionizing source of the H II region. In line with other recent investigations, we find that such leaky H II region models can provide elevated temperatures and line ratios, and a lower He+ fraction in the DIG. For a composite model representing the relative spectral types of O stars in the solar neighbourhood, we find that additional heating less than 1.0E-26 n_e ergs/s/cm^3 can reproduce the observed elevated line ratios in the DIG. This additional heating is considerably less than previous estimates due to the natural hardening of the radiation field reaching large heights in our simulations.

Kenneth Wood; John S. Mathis

2004-02-17

44

Neutron spectrometry using a 3He gas ionization chamber  

Microsoft Academic Search

To deduce an accurate neutron spectrum with high energy resolution from the pulse height data of a 3He gas ionization chamber, the detector response functions are evaluated in the neutron energy range between 0.5 MeV and 6.0 MeV by adjusting the results of Monte Carlo calculation to the measured data with monoenergetic neutron sources. A spectral unfolding code suitable for

T. Iguchi; N. Nakayamada; H. Takahashi; M. Nakazawa

1994-01-01

45

Self-Consistent Mean Field Theory in Weakly Ionized Gas  

Microsoft Academic Search

We present a self-consistent mean field theory of the dynamo in 3D and turbulent diffusion in 2D in weakly ionized gas. We find that in 3D, the backreaction does not alter the beta effect while it suppresses the alpha effect when the strength of a mean magnetic field exceeds the critical value Bc ˜&surd;nu_in taun \\/R_m. Here, nu_in, tau_n, and

Nicolas Leprovost; Eun-Jin Kim

2003-01-01

46

Field emission model of carbon nanotubes to simulate gas breakdown in ionization gas sensor  

NASA Astrophysics Data System (ADS)

A new field emission model of carbon nanotubes (CNTs) to simulate gas detection mechanism in CNT based ionization gas sensor has been developed. The new model consists of three modules which are combined together and embedded in the standard particle-in-cell/Monte Carlo collision codes. The functionality of the enhanced model is checked by varying the gas pressure and gap spacing in the simulations. From the results, around one order of magnitude decrease in the breakdown voltages and two orders of magnitude faster response time is observed. The lowest breakdown voltages are observed when intertube spacing is equal to height of the nanotube. The field enhancement factor ? is calculated from our model and compared with the ? of the well established model. The closeness among the values of ? validates the performance of our field emission model. Furthermore, the ? of our model is compared with the ? of the existing ionization gas sensors. It was found that the ? of our sensor is around 3 times better than the ? of the gold nanowire based ionization gas sensor and 28 times better than the ? of the other CNT based ionization gas sensor. These results suggest that by properly controlling the growth of CNT structures, an optimized CNT based ionization gas sensor can be realized.

Mahmood, Salman; Arif Burhanudin, Zainal; Salman, Aysha

2013-01-01

47

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

48

Aerodynamic Effects in Weakly Ionized Gas: Phenomenology and Applications  

SciTech Connect

Aerodynamic effects in ionized gases, often neglected phenomena, have been subject of a renewed interest in recent years. After a brief historical account, we discuss a selected number of effects and unresolved problems that appear to be relevant in both aeronautic and propulsion applications in subsonic, supersonic, and hypersonic flow. Interaction between acoustic shock waves and weakly ionized gas is manifested either as plasma-induced shock wave dispersion and acceleration or as shock-wave induced double electric layer in the plasma, followed by the localized increase of the average electron energy and density, as well as enhancement of optical emission. We describe the phenomenology of these effects and discuss several experiments that still do not have an adequate interpretation. Critical for application of aerodynamic effects is the energy deposition into the flow. We classify and discuss some proposed wall-free generation schemes with respect to the efficiency of energy deposition and overall generation of the aerodynamic body force.

Popovic, S.; Vuskovic, L. [Department of Physics, Old Dominion University, Norfolk, Virginia (United States)

2006-12-01

49

Development of a portable gas-filled ionization chamber  

NASA Astrophysics Data System (ADS)

A new portable gas-filled ionization chamber has been designed and constructed at the Physics Department of Sung Kyun Kwan University. To overcome the maximum count rate of ˜105 particles per second of a conventional ionization chamber, which utilizes a Frisch grid, and to enhance the portability of a detector, we adopted the design of multiple electrodes and modified it from the original designs by Kimura et al. and Chae et al. The new design utilizes a stack of multiple electrodes installed perpendicular to the optical beam axis. This configuration provides a fast response time for the detector, which is essential for high-rate counting. The device has been tested with a 241Am ( t 1/2 = 432.2 years) radioactive ? source, which mainly emits 5.486-MeV (branching ratio of 85%) and 5.443-MeV (branching ratio of 13%) ? particles. An energy resolution of 6.3% was achieved.

Chae, K. Y.; Cha, S. M.; Gwak, M. S.

2014-02-01

50

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

51

Ionization Gas Sensor using Aligned Multiwalled Carbon Nanotubes Array  

SciTech Connect

The challenge with current conventional gas sensors which are operating using semiconducting oxides is their size. After the introduction of nanotechnology and in order to reduce the dimension and consequently the power consumption and cost, new materials such as carbon nanotubes (CNTs) are being introduced. From previous works and characterization results, it was proven that the CNTs based gas sensor has better sensitivity, selectivity and faster response time in compared with semiconducting oxides based gas sensors. As in this work, a fabrication and successful testing of an ionization-based gas sensor using aligned Multiwalled CNTs (MWCNTs) as sensing element is discussed, in which MWCNTs array and Al film are used as anode and cathode plates respectively with electrode separation ranging from 80 {mu}m to 140 {mu}m. Aligned MWCNTs array was incorporated into a sensor configuration in the gas chamber for testing of gases such as argon, air, and mixed gas of 2%H{sub 2} in air. Obtained results show that among the three gases, argon has the lowest breakdown voltage whilst air has the highest value and the breakdown voltage was found to decrease as the electrode spacing was reduced from 140 {mu}m to 80 {mu}m for all three gases.

Kermany, A. R. [Electrical and Electronics Engineering, 31750 Bandar Seri Iskandar, Tronoh, Perak (Malaysia); Mohamed, N. M.; Singh, B. S. M. [Fundamental and Applied Sciences Department Universiti Teknologi PETRONAS (UTP) 31750 Bandar Seri Iskandar, Tronoh, Perak (Malaysia)

2011-05-25

52

Selective determination of 2,4-xylenol by gas chromatography/supersonic jet/resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry.  

PubMed

Gas chromatography/supersonic jet/resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry (GC/SSJ/REMPI/TOF-MS) was employed for isomer-selective determination of 2,4-xylenol in river and seawater samples. The sample containing 2,4-xylenol was measured using argon, rather than helium, as the GC carrier gas to cool the analyte molecule sufficiently. The instrumental detection limit (IDL) achieved at a flow rate of 1 mLmin(-1) was 14 pg. Although this value was comparable to the value (ca. 10 pg) obtained by gas chromatography/electron impact/quadrupole mass spectrometry (GC/EI/QMS). When the flow rate was increased to 8 mLmin(-1), interference from the 2,5-xylenol isomer was completely suppressed. The IDL was degraded to 83 or 160 pg at a flow rate of 5 or 8 mLmin(-1), respectively. The recovery of 2,4-xylenol from the river and the seawater samples was 85 and 93%, respectively. The time for analysis was only 10 min per one sample in GC/SSJ/REMPI/TOF-MS. These results suggest that GC/SSJ/REMPI/TOF-MS is useful for the selective measurement of 2,4-xylenol, which has been designated a Class I chemical substance in the Pollutant Release and Transfer Register (PRTR). PMID:21056717

Tsukatani, Hiroko; Okudaira, Hiroki; Shitamichi, Osamu; Uchimura, Tomohiro; Imasaka, Totaro

2010-12-01

53

Electrical design considerations for a 40MHz gas ionization chamber  

SciTech Connect

The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high luminosity insertions of the Large Hadron Collider (LHC) each absorb approximately 1.8 TeV of forward collision products on average per pp interaction ({approx}235W at design luminosity 1034cm-2s-1). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. A novel segmented, multi-gap, pressurized gas ionization chambers is being developed for sampling the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The ionization chamber must be capable of resolving individual bunch crossings at 40MHz. The ionization chamber is segmented into quadrants; each quadrant consists of sixty (40x40)mm2 Cu plates 1.0mm thick, with 0.5mm gaps. The 0.5mm gap width has been chosen so that the time for the ionization electrons to drift across the gap, is short enough to produce at the output of the shaping amplifier, a signal that returns to the base line is less than the 25ns bunch spacing of the LHC. From noise considerations in the presence of a cable the stack of plates are connected electrically 10 in parallel, 6 in series to achieve an equivalent detector capacitance Cd{approx}50pF. This type connection forms an electrode inductive Le and electrode capacitive Ce network that must be optimized to transfer charge from the chamber to the sensing amplifier. This paper describes the design of the collection electrodes optimized for 40 MHz operation.

Datte, P.; Manfredi, P.F.; Millaud, J.E.; Turner, W.C.; Placidi, M.; Ratti, L.; Speziali, V.; Traversi, G.

2001-06-01

54

Dielectrophoresis of ionized gas microbubbles: Dipole reversal due to diffusive double-layer polarization  

E-print Network

Dielectrophoresis of ionized gas microbubbles: Dipole reversal due to diffusive double-layer ionized gas in the gas-phase double layer are shown to render the bubble insulating at low ac field for bubbles larger than a critical size of 40 m. A double-layer theory accurately captures the two crossover

Chang, Hsueh-Chia

55

Pressure of a partially ionized hydrogen gas: numerical results from exact low temperature expansions  

E-print Network

Pressure of a partially ionized hydrogen gas: numerical results from exact low temperature expansions A. Alastuey , V. Ballenegger Abstract We consider a partially ionized hydrogen gas at low interest for hydrogen described as a gas of quantum protons and electrons interacting via the Coulomb

Paris-Sud XI, Université de

56

Optical Spectroscopy of Diffuse Ionized Gas in M31  

E-print Network

We have obtained sensitive long-slit spectra of Diffuse Ionized Gas (DIG) in the Andromeda Galaxy, M31, covering the wavelength range of 3550-6850 Angs. By co-adding extracted DIG spectra, we reached a 1 sigma uncertainty of 9.3E-19 ergs/s/cm^{2}/arcsec^{2} corresponding to .46 pc/cm^{6} in Emission Measure. We present average spectra of DIG at four brightness levels with Emission Measures ranging from 9 to 59 pc/cm^{6}. We present the first measurements of [OII]\\lambda3727 and [OIII]\\lambda5007 of the truly diffuse ionized medium in the disk of an external spiral galaxy. We find that I_[OII]/I_H\\alpha=.9-1.4. The [OIII] line is weak (I_[OIII]/I_H\\beta = .5), but stronger than in the Galactic DIG. Measurements of [NII]\\lambda6583 and [SII](\\lambda6717+\\lambda6731) are also presented. The [SII] lines are clearly stronger than typical HII regions (I_[SII]/I_H\\alpha = .5 compared to .2). Overall, the line ratios are in agreement with predictions of photoionization models for diffuse gas exposed to a dilute stellar radiation field, but the line ratios of the DIG in M31 are somewhat different than observed for Galactic DIG. The differences indicate a less diluted radiation field in the DIG of M31's spiral arms compared to DIG in the Solar Neighborhood of the Milky Way. We have also detected HeI\\lambda5876 emission from the brightest DIG in M31. The HeI line appears to be stronger than in the Galactic DIG, possibly indicating that most of the Helium in the bright DIG in M31 is fully ionized. However, this result is somewhat tentative.

B. Greenawalt; R. A. M. Walterbos; R. Braun

1996-12-17

57

Highly Ionized Gas Surrounding High-Velocity Cloud Complex C  

NASA Astrophysics Data System (ADS)

We present Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope observations of high-, intermediate-, and low-ion absorption in high-velocity cloud (HVC) Complex C along the lines of sight toward five active galaxies. Our purpose is to investigate the idea that Complex C is surrounded by an envelope of highly ionized material, arising from the interaction between the cloud and a hot surrounding medium. We measure column densities of high-velocity high-ion absorption and compare the kinematics of low-, intermediate-, and high-ionization gas along the five sight lines. We find that in all five cases, the H I and O VI high-velocity components are centered within 20 km s-1 of one another, with an average displacement of OVI-vHI>=3+/-12 km s-1. In those directions where the H I emission extends to more negative velocities (the so-called high-velocity ridge), so does the O VI absorption. The kinematics of Si II is also similar to that of O VI, with OVI-vSiII>=0+/-15 km s-1. We compare our high-ion column density ratios to the predictions of various models, adjusted to account for both recent updates to the solar elemental abundances and relative elemental abundance ratios in Complex C. Along the PG 1259+593 sight line, we measure N(SiIV)/N(OVI)=0.10+/-0.02, N(CIV)/N(OVI)=0.35+0.05-0.06, and N(NV)/N(OVI)<0.07 (3 ?). These ratios are inconsistent with collisional ionization equilibrium at one kinetic temperature. Photoionization by the extragalactic background is ruled out as the source of the high ions since the path lengths required would make HVCs unreasonably large; photoionization by radiation from the disk of the Galaxy also appears unlikely since the emerging photons are not energetic enough to produce O VI. By themselves, ionic ratios are insufficient to discriminate between various ionization models, but by considering the absorption kinematics as well, we consider the most likely origin for the highly ionized high-velocity gas to be at the conductive or turbulent interfaces between the neutral/warm ionized components of Complex C and a surrounding hot medium. The presence of interfaces on the surface of HVCs provides indirect evidence for the existence of a hot medium in which the HVCs are immersed. This medium could be a hot (T>~106 K) extended Galactic corona or hot gas in the Local Group. Based on observations from the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer mission, operated by Johns Hopkins University, supported by NASA contract NAS 5-32985, and from 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, Inc., under NASA contract NAS 5-26555.

Fox, Andrew J.; Savage, Blair D.; Wakker, Bart P.; Richter, Philipp; Sembach, Kenneth R.; Tripp, Todd M.

2004-02-01

58

Intermediate- and High-Velocity Ionized Gas toward ? Orionis  

NASA Astrophysics Data System (ADS)

We combine near-UV spectra obtained with the Hubble Space Telescope GHRS echelle with far-UV spectra obtained with the Interstellar Medium Absorption Profile Spectrograph and Copernicus to study the abundances and physical conditions in the predominantly ionized gas seen at high velocity (-105 km s-1<~vsolar<~-65 km s-1) and at intermediate velocity (-60 km s-1<~vsolar<~-10 km s-1) along the line of sight to the star ? Ori. We have high-resolution (FWHM~3.3-4.5 km s-1) and/or high signal-to-noise ratio spectra for at least two significant ions of C, N, Al, Si, S, and Fe-enabling accurate estimates for both the total N(H II) and the elemental depletions. C, N, and S have essentially solar relative abundances; Al, Si, and Fe appear to be depleted by about 0.8, 0.3-0.4, and 0.95 dex, respectively, relative to C, N, and S. While various ion ratios would be consistent with collisional ionization equilibrium (CIE) at temperatures of 25,000-80,000 K, the widths of individual high-velocity absorption components indicate that T~9000+/-2000 K-so the gas is not in CIE. Analysis of the C II fine-structure excitation equilibrium, at that temperature, yields estimates for the densities (ne~nH~0.1-0.2 cm-3), thermal pressures (2nHT~2000-4000 cm-3 K), and thicknesses (0.5-2.7 pc) characterizing the individual clouds. We compare the abundances and physical properties derived for these clouds with those found for gas at similar velocities toward 23 Ori and ? CMa and also with several different models for shocked gas. While the shock models can reproduce some features of the observed line profiles and some of the observed ion ratios, there are also significant differences between the models and the data. The measured depletions suggest that roughly 10% of the Al, Si, and Fe originally locked in dust in the preshock medium may have been returned to the gas phase, consistent with recent predictions for the destruction of silicate dust in a 100 km s-1 shock. The observed near-solar gas-phase abundance of carbon, however, appears to be inconsistent with the predicted longer timescales for the destruction of graphite grains. Based in part 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, Inc., under NASA contract NAS 5-26555.

Welty, Daniel E.; Jenkins, Edward B.; Raymond, John C.; Mallouris, Christoforos; York, Donald G.

2002-11-01

59

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

60

Large-scale shock-ionized and photo-ionized gas in M83: the impact of star formation  

E-print Network

We investigate the ionization structure of the nebular gas in M83 using the line diagnostic diagram, [O III](5007 \\degA)/H{\\beta} vs. [S II](6716 \\deg A+6731 \\deg 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. For the photo-ionized 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 photo-ionized from the shock-ionized component of the gas. We find that the shock-ionized H{\\alpha} emission ranges from ~2% to about 15-33% of the total, depending on the separation criteria used. An interesting feature in the diagnostic diagram is an horizontal distribution aro...

Hong, Sungryong; Dopita, Michael A; Blair, William P; Whitmore, Bradley C; Balick, Bruce; Bond, Howard E; Carollo, Marcella; Disney, Michael J; Frogel, Jay A; Hall, Donald; Holtzman, Jon A; Kimble, Randy A; McCarthy, Patrick J; O'Connell, Robert W; Paresce, Francesco; Saha, Abhijit; Silk, Joseph I; Trauger, John T; Walker, Alistair R; Windhorst, Rogier A; Young, Erick T; Mutchler, Max

2011-01-01

61

THE KINEMATICS AND PHYSICAL CONDITIONS OF WARM IONIZED GAS IN SPIRAL DISKS  

E-print Network

THE KINEMATICS AND PHYSICAL CONDITIONS OF WARM IONIZED GAS IN SPIRAL DISKS Matthew A. Bershady1 integral-field echelle observations of the warm, ionized phase of the interstellar medium (ISM) of many Way and high-z galaxies. 1. Introduction What drives gas velocity dispersions in star-forming galaxies

Bershady, Matthew A.

62

Magnetic Field Effects on Ionization Inhomogeneities Advected by Motions of the Neutral Gas  

Microsoft Academic Search

Abstract. A theory is developed for the ambipolar diffusion, drift, distortion, and production of ionization irregularities within weakly ionized plasma in the presence of the geomagnetic field and motions of the neutral gas. The formulation takes into consideration turbulent, wave, or uniform motion of the neutral gas, as well as the effects of uniform electric and gravitational fields. Equations are

R. J. Hill

1979-01-01

63

Gas-phase recombination, grain neutralization and cosmic-ray ionization in diffuse gas  

E-print Network

Atomic ions are mostly neutralized by small grains (or PAH molecules) in current theories of heating and cooling in cool diffuse clouds; in the main they do not recombine with free electrons. This alters the ionization balance by depressing n(H+) and n(He+) while carbon generally remains nearly fully once-ionized: charge exchange with atomic oxygen and formation of H2 and OH also depress n(H+) in partly molecular gas. Seemingly restrictive empirical limits on the cosmic ray ionization rate of hydrogen ($\\zeta_H$) are relaxed and faster rates are favored in a wide range of circumstances, when grain neutralization is recognized. Maintenance of the proton density at levels needed to reproduce observations of HD requires $\\zeta_H$ at least 2x10^{-16} s^{-1}, but such models naturally explain the presence of both HD and H3^+ in relatively tenuous H I clouds. In dense gas, a higher ionization rate can account for high observed fractions of atomic hydrogen, and recognition of the effects of grain neutralization can resolve a major paradox in the formation of sulfur-bearing compounds.

H. Liszt

2002-11-15

64

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

65

Ionized gas rotation curves in nearby dwarf galaxies  

E-print Network

We present the results of study of the ionized gas velocity fields in 28 nearby (systemic velocity below 1000 km/s) dwarf galaxies. The observations were made at the 6-m BTA telescope of the SAO RAS with the scanning Fabry-Perot interferometer in the H-alpha emission line. We were able to measure regular circular rotation parameters in 25 galaxies. As a rule, rotation velocities measured in HII are in a good agreement with the data on the HI kinematics at the same radii. Three galaxies reveal position angles of the kinematic axis in the HII velocity fields that strongly (tens of degrees) differ from the measurements in neutral hydrogen at large distances from the center or from the orientation of the major axis of optical isophotes. The planes of the gaseous and stellar disks in these galaxies most likely do not coincide. Namely, in DDO 99 the gaseous disk is warped beyond the optical radius, and in UGC 3672 and UGC 8508 the inclination of orbits of gas clouds varies in the inner regions of galaxies. It is po...

Moiseev, A V

2014-01-01

66

The dynamic ionized gas halos of spiral galaxies  

NASA Astrophysics Data System (ADS)

A key element in understanding how galaxies evolve over time lies in understanding the evolution of the interstellar medium (ISM) and star-formation driven gaseous halos. In particular, studies of diffuse ionized gas (DIG) are crucial in tracing the disk-halo connection in normal spirals. This work examines the origin, excitation, and kinematics of these layers. In an effort to add observational evidence to the notion of a dynamic halo, H? images of a sample of edge-on galaxies are presented. These data are compared with existing HI and radio continuum maps with a specific goal of attempting to find correlations consistent with a ``chimney'' model of the ISM. 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 in particular, shows correlations between H? filaments, H I shells, and radio continuum spurs that are consistent with a chimney model. In order to explore how DIG layers are energized, we have assembled deep long-slit spectra for a sample of edge-on galaxies. In each case, photoionization models fail to explain both the observed runs with height off the galactic midplane of [S II]/[N II] and [O III ]/H?. Composite photoionization/shock models are generally more successful than photoionization models alone in explaining the observed line ratios. We also consider whether the data can be explained by a pure photoionization model with an increasing gas temperature with z. The runs of most of the line ratios in each of the galaxies are consistent with such an increase. However, in most cases, the unusually high ionization fractions of O++ implied by the data cannot be reconciled with predictions of a pure photoionization model. Finally, to better understand halo kinematics and rotation, a model has been developed which assumes clouds ejected from the disk cycle ballistically through the halo. From this model, synthetic velocity profiles in z have been generated for the purpose of comparing to velocity centroid data from the previously mentioned spectra. In each case, DIG kinematics cannot be explained by a purely ballistic model.

Collins, Joseph Andrew

2001-11-01

67

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

68

Galaxy-Scale Clouds of Ionized Gas around AGN  

NASA Astrophysics Data System (ADS)

The serendipitous 2007 discovery of the object now known (even by NED) as "Hanny's Voorwerp" (Lintott et al. 2009) set into motion a search for more examples of galaxy-scale clouds of highly-ionized gas in the vicinity of active galactic nuclei (AGN). Using a sample assembled primarily by 'citizen scientists' via a dedicated thread in the Galaxy Zoo Forum, we carried out the first part of a larger long- slit spectroscopic survey of such objects with the 2.1m telescope at Kitt Peak National Observatory (KPNO). Of the 30 objects targeted during seven nights (multiple exposures for several), extended emission clouds were observed in 15 objects, with [OIII]?5007 emission occasionally extending >30 kpc from galaxy cores. A strong majority (11/15) of the extended emission clouds coincide with merging or otherwise violently disrupted systems, but more relevant to our search were the handful of clouds coinciding with isolated, symmetric galaxies lacking an obvious excitation mechanism. We present the results of part one in the hunt for Voorwerp analogues, much of which served to weed-out the more interesting objects to be targeted for future, multi-wavelength studies.

Chojnowski, S. Drew; Keel, William C.

2012-02-01

69

Multiphoton Ionization of Hydrogen and Rare-Gas Atoms  

Microsoft Academic Search

A perturbation theory of the ionization of atoms by simultaneous absorption of several photons, each of whose energy is less than the ionization potential, is developed from the evolution-operator formalism. A precise computation is made for the hydrogen atom, giving transition rates as a function of photon energy for two- through twelve-photon photoionization. The eighth-order ionization rate (in cgs units)

H. Barry Bebb; Albert Gold

1966-01-01

70

Gas ionization induced by a high speed plasma injection in space  

NASA Technical Reports Server (NTRS)

Gas ionization induced by a fast plasma injection has been observed with the Space Experiments with Particle Accelerators (SEPAC) Experiment on Spacelab-1. When an impulsive high-density plasma was injected from the orbiter, waves near the lower-hybrid frequency were enhanced, and the surrounding gas drifting with the orbiter was ionized for several tens of milliseconds after the plasma injection. The long-duration gas ionization was observed only when the plasma flux incoming to the orbiter cargo bay and the orbital velocity perpendicular to the magnetic field were relatively large. This effect has been explained by the concept of critical velocity ionization (CVI) for the gas drifting with the orbiter, although the gas velocity perpendicular to the magnetic field was less than the Alfven critical velocity.

Sasaki, S.; Kawashima, N.; Kuriki, K.; Yanagisawa, M.; Obayashi, T.; Roberts, W. T.; Reasoner, D. L.; Taylor, W. W. L.

1986-01-01

71

CNT-Based MEMS\\/NEMS Gas Ionizers for Portable Mass Spectrometry Applications  

Microsoft Academic Search

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 low-voltage ionization using sparse forests of plasma-enhanced chemical-vapor-deposited CNTs as field emitters and a proximal extractor grid with apertures aligned to the CNT forests to facilitate electron transmission. The extractor gate

Luis Fernando Velasquez-Garcia; Blaise Laurent Patrick Gassend; Akintunde Ibitayo Akinwande

2010-01-01

72

Ionized Gas in Damped Lyman-alpha Systems and Its Effects on Elemental Abundance Studies  

E-print Network

Recent high-resolution observations of metal absorption lines in high-redshift damped Ly-alpha systems have shown that Al III, a tracer of moderately-ionized gas, very often has a velocity structure indistinguishable from that of low-ionization gas. Regions of ionized and neutral hydrogen in these systems are likely cospatial. The higher-ionization Si IV and C IV absorption shows a much weaker or non-existent correlation with the low ionization material, implying that the regions traced by Al III are photoionized by a soft (stellar) spectrum, by a hard (power law) spectrum with a very low ionization parameter, or a combination of both. We discuss the ionization of the damped Ly-alpha systems and use photoionization equilibrium models to make quantitative estimates of its effects on abundance studies in these systems. We show that ionization effects may be large enough to account for the observed dispersion in absolute metal abundances in damped Ly-alpha systems, causing systematically higher abundances in lower column density systems. The observed Si^+/Fe^+ and Zn^+/Cr^+ ratios may systematically overestimate the intrinsic Si/Fe and Zn/Cr ratios, respectively, if ionized gas is present in these systems, thereby mimicking the effects of alpha-element enrichment or dust depletion.

J. Christopher Howk; Kenneth R. Sembach

1999-07-29

73

Application of gas chromatography–surface ionization organic mass spectrometry to forensic toxicology  

Microsoft Academic Search

Surface ionization (SI), which consists in the formation of positive and negative ions along the course of thermal desorption of particles from a solid surface, was first applied as a detector for gas chromatography (GC), GC-surface ionization detection (SID); we developed many new sensitive methods for the determination of abused and other drugs by GC-SID. Recently, Fujii has devised a

Akira Ishii; Kanako Watanabe-Suzuki; Hiroshi Seno; Osamu Suzuki; Yoshinao Katsumata

2002-01-01

74

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

75

Analysis of polyaromatic hydrocarbon mixtures with laser ionization gas chromatography/mass spectrometry  

SciTech Connect

Excimer laser induced multiphoton ionization has been utilized for ion generation in capillary gas chromatography/mass spectrometry and the technique applied to the separation and detection of polyaromatic hydrocarbons. Detection limits as low as 200 fg and linearity over a range of 5 x 10/sup +4/ were obtained for the polyaromatic hydrocarbons examined. Multiphoton ionization mass spectra were dominated by parent ions. Selective ionization based upon small differences in ionization potentials has been demonstrated for coeluting chrysene and triphenylene. Instrumental parameters have been investigated to assess improvements in sensitivity.

Rhodes, G.; Opsal, R.B.; Meek, J.T.; Reilly, J.P.

1983-02-01

76

The ionization state in a gas with a non-Maxwellian electron distribution  

NASA Technical Reports Server (NTRS)

The inferred degree of ionization of a gas is often used in astrophysics as a diagnostic of the gas temperature. In the solar transition region and corona, in the outer atmospheres of cool stars, and in some portions of the interstellar medium), photoionization can be neglected, and the ionization state is fixed by the balance between ion-electron collisional ionization and dielectronic and/or radiative recombination. Under these conditions, higher degrees of ionization result from higher energy ion-electron collisions which are common in a high temperature gas. Actually, ionization occurs through collisions with electrons that have kinetic energies greater than the ionization potential of the given ion, and so the ionization rate depends on to the number of such high-energy electrons in the tail of the electron velocity distribution. High-velocity electrons move across large distances between effective coulomb collisions, and, in a strong temperature or density gradient, the tail can be overpopulated relative to Maxwell-Boltzmann distribution of equivalent energy density. Thus, the ionization rate can also be greatly increased. These effects for a parameterized form of the electron distribution function with an enhanced high-velocity tail, namely the kappa distribution are illustrated.

Owocki, S. P.; Scudder, J. D.

1981-01-01

77

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

78

Mass spectrometric behavior of anabolic androgenic steroids using gas chromatography coupled to atmospheric pressure chemical ionization source. Part I: ionization.  

PubMed

The detection of anabolic androgenic steroids (AAS) is one of the most important topics in doping control analysis. Gas chromatography coupled to (tandem) mass spectrometry (GC-MS(/MS)) with electron ionization and liquid chromatography coupled to tandem mass spectrometry have been traditionally applied for this purpose. However, both approaches still have important limitations, and, therefore, detection of all AAS is currently afforded by the combination of these strategies. Alternative ionization techniques can minimize these drawbacks and help in the implementation of a single method for the detection of AAS. In the present work, a new atmospheric pressure chemical ionization (APCI) source commercialized for gas chromatography coupled to a quadrupole time-of-flight analyzer has been tested to evaluate the ionization of 60 model AAS. Underivatized and trimethylsylil (TMS)-derivatized compounds have been investigated. The use of GC-APCI-MS allowed for the ionization of all AAS assayed irrespective of their structure. The presence of water in the source as modifier promoted the formation of protonated molecules ([M+H](+)), becoming the base peak of the spectrum for the majority of studied compounds. Under these conditions, [M+H](+), [M+H-H2O](+) and [M+H-2·H2O](+) for underivatized AAS and [M+H](+), [M+H-TMSOH](+) and [M+H-2·TMSOH](+) for TMS-derivatized AAS were observed as main ions in the spectra. The formed ions preserve the intact steroid skeleton, and, therefore, they might be used as specific precursors in MS/MS-based methods. Additionally, a relationship between the relative abundance of these ions and the AAS structure has been established. This relationship might be useful in the structural elucidation of unknown metabolites. PMID:24913403

Raro, M; Portolés, T; Sancho, J V; Pitarch, E; Hernández, F; Marcos, J; Ventura, R; Gómez, C; Segura, J; Pozo, O J

2014-06-01

79

Ionization and scintillation response of high-pressure xenon gas to alpha particles  

E-print Network

High-pressure xenon gas is an attractive detection medium for a variety of applications in fundamental and applied physics. In this paper we study the ionization and scintillation detection properties of xenon gas at 10 bar pressure. For this purpose, we use a source of alpha particles in the NEXT-DEMO time projection chamber, the large scale prototype of the NEXT-100 neutrinoless double beta decay experiment, in three different drift electric field configurations. We measure the ionization electron drift velocity and longitudinal diffusion, and compare our results to expectations based on available electron scattering cross sections on pure xenon. In addition, two types of measurements addressing the connection between the ionization and scintillation yields are performed. On the one hand we observe, for the first time in xenon gas, large event-by-event correlated fluctuations between the ionization and scintillation signals, similar to that already observed in liquid xenon. On the other hand, we study the field dependence of the average scintillation and ionization yields. Both types of measurements may shed light on the mechanism of electron-ion recombination in xenon gas for highly-ionizing particles. Finally, by comparing the response of alpha particles and electrons in NEXT-DEMO, we find no evidence for quenching of the primary scintillation light produced by alpha particles in the xenon gas.

NEXT Collaboration; V. Álvarez; F. I. G. M. Borges; S. Cárcel; S. Cebrián; A. Cervera; C. A. N. Conde; T. Dafni; J. Díaz; M. Egorov; R. Esteve; P. Evtoukhovitch; L. M. P. Fernandes; P. Ferrario; A. L. Ferreira; E. D. C. Freitas; V. M. Gehman; A. Gil; A. Goldschmidt; H. Gómez; J. J. Gómez-Cadenas; D. González-Díaz; R. M. Gutiérrez; J. Hauptman; J. A. Hernando Morata; D. C. Herrera; I. G. Irastorza; M. A. Jinete; L. Labarga; A. Laing; I. Liubarsky; J. A. M. Lopes; D. Lorca; M. Losada; G. Luzón; A. Marí; J. Martín-Albo; T. Miller; A. Moiseenko; F. Monrabal; C. M. B. Monteiro; F. J. Mora; L. M. Moutinho; J. Muñoz Vidal; H. Natal da Luz; G. Navarro; M. Nebot-Guinot; D. Nygren; C. A. B. Oliveira; R. Palma; J. Pérez; J. L. Pérez Aparicio; J. Renner; L. Ripoll; A. Rodríguez; J. Rodríguez; F. P. Santos; J. M. F. dos Santos; L. Segui; L. Serra; D. Shuman; A. Simón; C. Sofka; M. Sorel; J. F. Toledo; A. Tomás; J. Torrent; Z. Tsamalaidze; D. Vázquez; J. F. C. A. Veloso; R. Webb; J. T White; N. Yahlali

2012-11-19

80

DETECTION OF HIGHLY IONIZED C IV GAS WITHIN THE LOCAL CAVITY  

SciTech Connect

We present high resolution (R = 114,000) ultraviolet measurements of the interstellar absorption line profiles of the C IV (1550 A) high ionization doublet recorded toward the nearby B2Ve star HD 158427 (d {approx} 74 pc). These data, which were recorded with the recently re-furbished Space Telescope Imaging Spectrograph instrument on the Hubble Space Telescope, represent the most convincing detection yet of highly ionized C IV absorption that can be associated with interstellar gas located within the boundary of the Local Cavity (LC). Two highly ionized gas clouds at V {sub 1} = -24.3 km s{sup -1} and V {sub 2} = -41.3 km s{sup -1} are revealed in both C IV absorption lines, with the V {sub 1} component almost certainly being due to absorption by the Local Interstellar Cloud (d < 5 pc). Although the observed column densities for both cloud components can be explained by the predictions of current theoretical models of the local interstellar medium, the narrow Doppler width of the V {sub 2} line profile (b = 6.8 km s{sup -1}) indicates an unusually low gas temperature of {<=}34,000 K for this highly ionized component. It is conjectured that the V {sub 2} cloud may be due to an outflow of highly ionized and hot gas from the nearby Loop I superbubble. These new data also indicate that absorption due to highly ionized gas in the LC can be best described as being 'patchy' in nature.

Welsh, Barry Y.; Wheatley, Jonathan; Siegmund, Oswald H. W. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720 (United States); Lallement, Rosine [IPSL/LATMOS, Versailles (France)

2010-04-01

81

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

82

Simulations of prompt many-body ionization in a frozen Rydberg gas  

NASA Astrophysics Data System (ADS)

The results of a theoretical investigation of prompt many-body ionization are reported. Our calculations address an experiment that reported ionization in Rydberg gases for densities two orders of magnitude less than expected from ionization between pairs of atoms. The authors argued that the results were due to the simultaneous interaction between many atoms. We performed classical calculations for many interacting Rydberg atoms with the ions fixed in space and have found that the many-atom interaction does allow ionization at lower densities than estimates from two-atom interactions. However, we found that the density fluctuations in a gas play a larger role. These two effects are an order of magnitude too small to account for the experimental results suggesting at least one other mechanism strongly affects ionization.

Robicheaux, F.; Goforth, M. M.; Phillips, M. A.

2014-08-01

83

The structure of radiative shock waves. III. The model grid for partially ionized hydrogen gas  

E-print Network

The grid of the models of radiative shock waves propagating through partially ionized hydrogen gas with temperature 3000K gas is compressed mostly due to radiative cooling in the hydrogen recombination zone and final compression ratios are within 1 gas temperature affects the shock wave structure due to the equilibrium ionization of the unperturbed hydrogen gas, since the rates of postshock relaxation processes are very sensitive to the number density of hydrogen ions ahead the discontinuous jump. Both the increase of the preshock gas temperature and the decrease of the preshock gas density lead to lower postshock compression ratios. The width of the shock wave decreases with increasing upstream velocity while the postshock gas is still partially ionized and increases as soon as the hydrogen is fully ionized. All shock wave models exhibit stronger upstream radiation flux emerging from the preshock outer boundary in comparison with downstream radiation flux emerging in the opposite direction from the postshock outer boundary. The difference between these fluxes depends on the shock velocity and ranges from 1% to 16% for 20 km/s hydrogen lines significantly exceeds the flux of the background continuum and all shock wave models demonstrate the hydrogen lines in emission.

Yu. A. Fadeyev; D. Gillet

2001-01-10

84

Ionized Gas in the First 10 kpc of the Interstellar Galactic Halo  

E-print Network

We present FUSE observations of the post-asymptotic giant branch star von Zeipel 1128 (l=42.5, b=+78.7; z=10.0 kpc), located in the globular cluster Messier 3. The FUSE observations cover the wavelength range 905-1187 Ang at ~20 km/s (FWHM) resolution. These data exhibit many photospheric and interstellar absorption lines, including absorption from ions associated with the warm neutral, warm ionized, and highly-ionized phases of the interstellar medium along this sight line. Ionized hydrogen represents >12%, most likely ~45%, of the total hydrogen column along this sight line, most of it associated with the warm ionized phase. The warm ionized and neutral media toward von Zeipel 1128 have very similar gas-phase abundances and kinematics: the neutral and ionized gases in this region of the thick disk are closely related. Strong O VI absorption is seen with the same central velocity as the warm ionized gas, though the O VI velocity dispersion is much higher (sigma=32 km/s). Virtually all of the O VI is found at velocities where lower-ionization gas is seen, suggesting the O VI and WNM/WIM probes are tracing different portions of the same structures (e.g., the O VI may reside in interfaces surrounding the WNM/WIM clouds). We see no evidence for interstellar absorption associated with the globular cluster Messier 3 itself nor with the circumstellar environment of von Zeipel 1128. Neither high velocity cloud absorption (with v(LSR)>125 km/s) nor high velocity-dispersion gas (with sigma~60 km/s) is seen toward von Zeipel 1128. [Abridged

J. Christopher Howk; Kenneth R. Sembach; Blair D. Savage

2002-11-20

85

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

86

Polycyclic aromatic hydrocarbon ionization as a tracer of gas flows through protoplanetary disk gaps  

NASA Astrophysics Data System (ADS)

Context. Planet-forming disks of gas and dust around young stars contain polycyclic aromatic hydrocarbons (PAHs). Aims: We aim to characterize how the charge state of PAHs can be used as a probe of flows of gas through protoplanetary gaps. In this context, our goal is to understand the PAH spectra of four transitional disks. In addition, we want to explain the observed correlation between PAH ionization (traced by the I6.2/I11.3 feature ratio) and the disk mass (traced by the 1.3 mm luminosity). Methods: We implement a model to calculate the charge state of PAHs in the Monte Carlo radiative transfer code MCMax. The emission spectra and ionization balance are calculated in the parameter space set by the properties of the star and the disk. Results: A benchmark modeling grid is presented that shows how PAH ionization and luminosity behave as a function of star and disk properties. The PAH ionization is most sensitive to ultraviolet (UV) radiation and the electron density. In optically thick disks, where the UV field is low and the electron density is high, PAHs are predominantly neutral. Ionized PAHs trace low-density optically thin disk regions where the UV field is high and the electron density is low. Such regions are characteristic of gas flows through the gaps of transitional disks. We demonstrate that fitting the PAH spectra of four transitional disks requires a contribution of ionized PAHs in "gas flows" through the gap. Conclusions: The PAH spectra of transitional disks can be understood as superpositions of neutral and ionized PAHs. For HD 97048, neutral PAHs in the optically thick disk dominate the spectrum. In the cases of HD 169142, HD 135344 B and Oph IRS 48, small amounts of ionized PAHs located in the "gas flows" through the gap are strong contributors to the total PAH luminosity. The observed trend in the sample of Herbig stars between the disk mass and PAH ionization may imply that lower-mass disks have larger gaps. Ionized PAHs in gas flows through these gaps contribute strongly to their spectra.

Maaskant, K. M.; Min, M.; Waters, L. B. F. M.; Tielens, A. G. G. M.

2014-03-01

87

A spiral-like disk of ionized gas in IC 1459: Signature of a merging collision  

NASA Technical Reports Server (NTRS)

The authors report the discovery of a large (15 kpc diameter) H alpha + (NII) emission-line disk in the elliptical galaxy IC 1459, showing weak spiral structure. The line flux peaks strongly at the nucleus and is more concentrated than the stellar continuum. The major axis of the disk of ionized gas coincides with that of the stellar body of the galaxy. The mass of the ionized gas is estimated to be approx. 1 times 10 (exp 5) solar mass, less than 1 percent of the total mass of gas present in IC 1459. The total gas mass of 4 times 10(exp 7) solar mass has been estimated from the dust mass derived from a broad-band color index image and the Infrared Astronomy Satellite (IRAS) data. The authors speculate that the presence of dust and gas in IC 1459 is a signature of a merger event.

Goudfrooij, Paul; Norgaard-Nielsen, H. U.; Jorgensen, H. E.; Hansen, L.; Dejong, T.

1990-01-01

88

A spiral-like disk of ionized gas in IC 1459: Signature of a merging collision  

NASA Astrophysics Data System (ADS)

The authors report the discovery of a large (15 kpc diameter) H alpha + (NII) emission-line disk in the elliptical galaxy IC 1459, showing weak spiral structure. The line flux peaks strongly at the nucleus and is more concentrated than the stellar continuum. The major axis of the disk of ionized gas coincides with that of the stellar body of the galaxy. The mass of the ionized gas is estimated to be approx. 1 times 10 5 solar mass, less than 1 percent of the total mass of gas present in IC 1459. The total gas mass of 4 times 107 solar mass has been estimated from the dust mass derived from a broad-band color index image and the Infrared Astronomy Satellite (IRAS) data. The authors speculate that the presence of dust and gas in IC 1459 is a signature of a merger event.

Goudfrooij, Paul; Norgaard-Nielsen, H. U.; Jorgensen, H. E.; Hansen, L.; de Jong, T.

1990-11-01

89

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

PubMed

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

Mallette, Jennifer R; Casale, John F

2014-10-17

90

Study of the surface ionization detector for gas chromatography.  

PubMed

The structure of the surface ionization detector (SID) and the operation parameters of GC-SID were investigated to reduce peak tailing and to enhance sensitivity. The performances of the GC-SID, including its repeatability, linearity, sensitivity, selectivity, and tolerance towards water vapor, were evaluated systematically. Compared with nitrogen-phosphorus detector (NPD), the SID was able to detect fg level triethylamine, and selectively respond to alkylamines, some anilines, and some nitrogen heterocyclic compounds. Among alkylamines, the SID sensitivity to diisobutylamine was rather small. Even so, it was also still 10 times higher than that on NPD. The SID selectivity, defined as the sensitivity ratio between triethylamine and various tested non-nitrogen compounds, was higher than 10(6). It was found that the SID is highly tolerant towards water vapor, allowing direct injection of water sample. Finally, the GC-SID was applied to directly measure trace amines in headspace gases of rotted meat and trace simazine in tap water. The SID sensitivity to simazine was proven to be 5 times higher than that on flame ionization detector (FID). This study suggests that the SID is a promising GC detector. PMID:21839459

Li, Weiwei; Wu, Dapeng; Chen, Shiheng; Peng, Hong; Guan, Yafeng

2011-09-23

91

Ablation from High Velocity Clouds: A Source for Low Velocity Ionized Gas  

NASA Astrophysics Data System (ADS)

High velocity clouds shed material as they move through the Galaxy. This material mixes with the Galactic interstellar medium, resulting in plasma whose temperature and ionization levels are intermediate between those of the cloud and those of the Galaxy. As time passes, the mixed material slows to the velocity of the ambient gas. This raises the possibility that initially warm (T 10^3 K), poorly ionized clouds moving through hot (T 10^6 K), very highly ionized ambient gas could lead to mixed gas that harbors significant numbers of high ions (O+5, N+4, and C+3) and thus helps to explain the large numbers of low-velocity high ions seen on high latitude lines of sight through the Galactic halo. We have used a series of detailed FLASH simulations in order to track the hydrodynamics of warm clouds embedded in hot Galactic halo gas. These simulations tracked the ablated material as it mixed and slowed to low velocities. By following the ionization levels of the gas in a time-dependent fashion, we determined that the mixed material is rich in O+5, N+4, and C+3 ions and continues to contain these ions for some time after slowing to low velocities. Combining our simulational results with estimates of the high velocity cloud infall rate leads to the finding that the mixed gas can account for 1/3 of the normal-velocity O+5 column density found on high latitude lines of sight. It accounts for lesser fractions of the N+4 and C+3 column densities. We will discuss our high velocity cloud results as part of a composite halo model that also includes cooling Galactic fountain gas, isolated supernova remnants, and ionizing photons.

Shelton, Robin L.; Henley, D. B.; Kwak, K.

2012-05-01

92

Measuring Black Hole Masses Using Ionized Gas Kinematics  

E-print Network

We describe techniques for measuring the central masses of galaxies using emission-line kinematics observed with the Hubble Space Telescope. For accurate results, it is necessary to model various instrumental effects, particularly the blurring due to the telescope PSF and the width of the spectroscopic aperture. Observations of nuclear gas disks often reveal substantial internal velocity dispersions in the gas, suggesting that the disks may be partially pressure-supported. We also describe a technique for fitting 2-dimensional spectroscopic data directly in pixel space. This method may be useful for objects such as M84 that show highly complex and asymmetric line profiles.

Aaron J. Barth; Marc Sarzi; Luis C. Ho; Hans-Walter Rix; Joseph C. Shields; Alexei V. Filippenko; Greg Rudnick; Wallace L. W. Sargent

2001-10-30

93

Warm Ionized Gas on the Outskirts of Active and Star-Forming Galaxies  

E-print Network

The preliminary results from a deep emission-line search for warm ionized material in the halos of nearby active and star-forming galaxies are presented. The origin of this gas is discussed in the context of galaxy formation and evolution.

S. Veilleux

2001-08-10

94

Nonlinear focusing by residual-gas ionization in long-pulse electron linacs  

Microsoft Academic Search

For short electron bunches in accelerators, the radial ion density due to residual-gas ionization faithfully reproduces the radial electron bunch distribution for time scales similar to the electron bunch length. If the electron bunch length is sufficiently long, however, the ions focus and, even for radially uniform electron beams, tend to form a very nonuniform equilibrium distribution. This ion distribution,

Bruce E. Carlsten

2001-01-01

95

Diffuse Ionized Gas and the Disk-Halo Interaction in Spiral Galaxies  

Microsoft Academic Search

Observational evidence for the presence of diffuse ionized gas (DIG) in the halos of star forming disk galaxies is discussed in the context of a disk-halo connection of the interstellar medium driven by multiple and clustered supernovae. New results from a survey for H+ halos of edge-on galaxies support this picture and allow us to establish a minimum energy release

R.-J. Dettmar

2004-01-01

96

A study of the response of a gas ionization chamber to different sources of ionizing radiation  

E-print Network

pulses . C. Effects due to the material of the cathode pad D. Gas mixture eff'ect E. Shielding effect F. Monte Carlo simulation . 23 . 23 . 25 . 25 . 25 . 30 . 30 IV CONCLUSION TABLE OF CONTENTS (Continued) REFERENCES VITA Page . 42 . 44... conductor and insulated from it so a potential difference can be applied between the electrodes. If a and b are 11 the radii of the anode and cathode, respectively, the electric field and potential, at a distance r from the axis, become E(r) = ? ?, CVp...

Zamble?-Die?guez, Filiberto Edmundo

2012-06-07

97

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

E-print Network

We study the kinematic properties of the ambient ionized ISM and ionized gas outflows in a large and representative sample of local luminous and ultraluminous infrared galaxies (U/LIRGs) (58 systems, 75 galaxies), on the basis of integral field spectroscopy (IFS)-based high S/N integrated spectra at galactic and sub-galactic, i.e. star forming (SF) clumps, scales. Ambient ionized gas. The velocity dispersion of the ionized ISM in U/LIRGs ( ~ 70 kms-1) is larger than in lower luminosity local star forming galaxies ( ~ 25 kms-1). While for isolated disc LIRGs star formation appears to sustain turbulence, gravitational energy release associated to interactions and mergers plays an important role driving sigma in the U/LIRG range. We also find that the impact of an AGN in ULIRGs is strong, increasing sigma by a factor 1.5 on average. The observed weak dependency of sigma on SFR surface density for local U/LIRGs is in very good agreement with that measured in some high-z sources. Ionized outflows. The presence of ...

Arribas, Santiago; Bellocchi, Enrica; Maiolino, Roberto; Villar-Martin, Montserrat

2014-01-01

98

Development of a new electron ionization/field ionization ion source for gas chromatography/time-of-flight mass spectrometry.  

PubMed

We have developed a combined EI/FI source for gas chromatography/orthogonal acceleration time-of-flight mass spectrometry (GC/oaTOFMS). In general, EI (electron ionization) and FI (field ionization) mass spectra are complementary: the EI mass spectrum contains information about fragment ions, while the FI mass spectrum contains information about molecular ions. Thus, the comparative study of EI and FI mass spectra is useful for GC/MS analyses. Unlike the conventional ion sources for FI and EI measurements, the newly developed source can be used for both measurements without breaking the ion source vacuum or changing the ion source. Therefore, the combined EI/FI source is more preferable than the conventional EI or FI ion source from the viewpoint of the reliability of measurements and facility of operation. Using the combined EI/FI source, the complementarity between EI and FI mass spectra is demonstrated experimentally with n-hexadecane (100 pg): characteristic fragment ions for the n-alkane such as m/z 43, 57, 71, and 85 are obtained in the EI mass spectrum, while only the parent peak of m/z 226 (M+) without any fragment ions is observed in the FI mass spectrum. Moreover, the field desorption (FD) measurement is also demonstrated with poly(ethylene glycol)s M600 (10 ng) and M1000 (15 ng). Signals of [M+H]+, [M+Na]+ and [M+K]+ are clearly detected in the FD mass spectra. PMID:19764073

Miyamoto, Kenji; Fujimaki, Susumu; Ueda, Yoshihisa

2009-10-30

99

Dissociation and ionization of molecular gas in the spiral arms of M51  

NASA Technical Reports Server (NTRS)

Researchers derive the star formation rate and efficiency in the arm and interarm regions of M51 from observations of the molecular (Lo et al. 1987) and ionized (van der Hulst et al. 1988) phases of the interstellar medium, and show that the HI observations of Tilanus and Allen (1989) are consistent with dissociation of molecular gas by these young, massive stars if n sub H greater than or equal to 200 cm (-2). However, these stars are not able to dissociate or ionize all the gas, and at least 60 percent must remain molecular in the interarm regions. The efficiency of star formation in M51 seems to be similar to that in the Galaxy, and does not appear to be enhanced in the spiral arms. Therefore, the effect of the strong density wave may be only to concentrate the gas, and hence the young stars, to the arm regions.

Lees, J. F.; Lo, K. Y.

1990-01-01

100

The sensitivity and dynamic response of field ionization gas sensor based on ZnO nanorods  

Microsoft Academic Search

Field ionization gas sensors based on ZnO nanorods (50–300 nm in diameter, and 3–8 ?m in length) with and without a buffer\\u000a layer were fabricated, and the influence of the orientation of nano-ZnO on the ionization response of devices was discussed,\\u000a including the sensitivity and dynamic response of the ZnO nanorods with preferential orientation. The results indicated that\\u000a ZnO nanorods as sensor

Jiahua Min; Xiaoyan Liang; Bin Wang; Linjun Wang; Yue Zhao; Weimin Shi; Yiben Xia

101

A 3D Monte Carlo Photoionization Code for Modeling Diffuse Ionized Gas  

E-print Network

We have developed a three dimensional Monte Carlo photoionization code tailored for the study of Galactic H II regions and the percolation of ionizing photons in diffuse ionized gas. We describe the code, our calculation of photoionization, heating & cooling, and the approximations we have employed for the low density H II regions we wish to study. Our code gives results in agreement with the Lexington H II region benchmarks. We show an example of a 2D shadowed region and point out the very significant effect that diffuse radiation produced by recombinations of helium has on the temperature within the shadow.

K. Wood; J. Mathis; B. Ercolano

2003-11-26

102

A 3D Monte Carlo Photoionization Code for Modeling Diffuse Ionized Gas  

E-print Network

We have developed a three dimensional Monte Carlo photoionization code tailored for the study of Galactic H II regions and the percolation of ionizing photons in diffuse ionized gas. We describe the code, our calculation of photoionization, heating & cooling, and the approximations we have employed for the low density H II regions we wish to study. Our code gives results in agreement with the Lexington H II region benchmarks. We show an example of a 2D shadowed region and point out the very significant effect that diffuse radiation produced by recombinations of helium has on the temperature within the shadow.

Wood, K; Ercolano, B

2004-01-01

103

Ionized gas velocity dispersion and multiple supernova explosions  

E-print Network

Using 3D numerical simulations we study the evolution of the H$\\alpha$ intensity and velocity dispersion for single and multiple supenova (SN) explosions. We find that the $I_{\\rm H\\alpha}-\\sigma$ diagram obtained for simulated gas flows is similar in shape to that observed in dwarf galaxies. We conclude that colliding SN shells with significant difference in age are resposible for high velocity dispersion that reaches values high as $\\simgt 100$kms$^{-1}$. Such a high velocity dispersion could be hardly got for a single SN remnant. Peaks of velocity dispersion on the $I_{\\rm H\\alpha}-\\sigma$ diagram may correspond to several stand-alone or merged SN remnants with moderately different ages. The procedure of the spatial resolution degrading in the H$\\alpha$ intensity and velocity dispersion maps makes the simulated $I_{\\rm H\\alpha}-\\sigma$ diagrams close to those observed in dwarf galaxies not only in shape, but also quantitatively.

Vasiliev, Evgenii O; Shchekinov, Yuri A

2014-01-01

104

Influence of fuel quality on level of ionization of combustion products in gas turbine engines  

SciTech Connect

As the requirements imposed on gas turbine engines for economy, completeness of fuel, combustion, and smoke level and toxicity of exhaust have become severe, research methods are being developed and GTE combustion chambers are being designed on the basis of the known phenomenon of chemical ionization of a flame. In this paper the dependence of the ionization level on the contents of sodium, vanadium, sulfur, aromatics, and unsaturates in the fuel is investigated. Results indicate that fuel quality indexes of the contents of the above factors do have substantial effects on the level of ionization of the combustion chamber. Design of combustion chambers must therefore be carried out with fuel standards for which these quality indexes are restricted to sufficiently narrow limits.

Seregin, E.P.; Ozerov, E.A.; Petrov, V.I.; Samoilov, I.B.; Stotland, S.I.

1983-11-01

105

Qualitative gas chromatography-mass spectrometry analyses using amines as chemical ionization reagent gases.  

PubMed

Ammonia is a very useful chemical ionization (CI) reagent gas for the qualitative analyses of compounds by positive ion gas chromatography-mass spectrometry (GCMS). The gas is readily available, inexpensive, and leaves no carbon contamination in the MS source. Compounds of interest to our laboratory typically yield abundant protonated or ammoniated species, which are indicative of a compound's molecular weight. Nevertheless, some labile compounds fragment extensively by substitution and elimination reactions and yield no molecular weight information. In these cases, a CI reagent gas mixture of methylamine in methane prepared dynamically was found to be very useful in obtaining molecular weight data. Likewise, deuterated ammonia and deuterated methylamine are useful CI reagent gases for determining the exchangeable protons in organic compounds. Deuterated methylamine CI reagent gas is conveniently prepared by dynamically mixing small amounts of methylamine with excess deuterated ammonia. PMID:24114260

Little, James L; Howard, Adam S

2013-12-01

106

Studies of Flow in Ionized Gas: Historical Perspective, Contemporary Experiments, and Applications  

SciTech Connect

Since the first observations that a very small ionized fraction (order of 1 ppm) could strongly affect the gas flow, numerous experiments with partially or fully wall-free discharges have demonstrated the dispersion of shock waves, the enhancement of lateral forces in the flow, the prospects of levitation, and other aerodynamic effects with vast potential of application. A review of physical effects and observations are given along with current status of their interpretation. Special attention will be given to the physical problems of energy efficiency in generating wall-free discharges and the phenomenology of filamentary discharges. Comments and case examples are given on the current status of availability of necessary data for modelling and simulation of the aerodynamic phenomena in weakly ionized gas.

Popovic, S.; Vuskovic, L. [Department of Physics, Old Dominion University, Norfolk, Virginia 23529 (United States)

2007-04-23

107

Diffuse Ionized Gas and the Disk-Halo Interaction in Spiral Galaxies  

Microsoft Academic Search

Observational evidence for the presence of diffuse ionized gas (DIG) in the halos of star forming disk galaxies is discussed\\u000a in the context of a disk-halo connection of the interstellar medium driven by multiple and clustered supernovae. New results\\u000a from a survey for H+ halos of edge-on galaxies support this picture and allow us to establish a minimum energy release

R.-J. Dettmar

108

Kinematics and ionization of extended gas in active galaxies. VI - The Seyfert 2 galaxy NGC 1386  

NASA Technical Reports Server (NTRS)

Results are presented of direct imaging with a CCD detector and long-slit medium- and low-dispersion spectroscopy of the spatially extended narrow-line-emitting gas in the nearby Seyfert 2 galaxy NGC 1386. The distribution, kinematics, and ionization structure of the excited gas were examined in the regions surrounding the nucleus out to a distance of about 1.0. Results present evidence for a spiral structure in this galaxy and for the presence of H II regions in the disk (supporting the classification of NGC 1386 as a Sa galaxy).

Weaver, K. A.; Wilson, A. S.; Baldwin, J. A.

1991-01-01

109

Outflows of Very Ionized Gas in the Centers of Seyfert Galaxies: Kinematics and Physical Conditions  

NASA Astrophysics Data System (ADS)

Mid-resolution spectra are used to deduce the size and kinematics of the coronal region in a sample of Seyfert galaxies by means of observations of the [Fe XI], [Fe X], [Fe VII], [Si VI], and [Si VII] lines. These coronal lines (CLs) extend from the unresolved nucleus up to a few tens to a few hundreds of parsecs. The region of the highest ionized ions studied, [Fe XI] and [Fe X], is the least spatially extended and concentrates at the center; intermediate-ionization lines extend from the nucleus up to a few tens to a few hundred parsecs; lower [O III]-like ions are known to extend to the kpc range. All together indicate a stratification in the ionized gas, usually interpreted in terms of nuclear photoionization as the driving ionization mechanism. However, CL profiles show various peculiarities: they are broader by a factor of 2 than lower ionization lines, the broadening being in terms of asymmetric blue wings, and their centroid position at the nucleus is blueshifted by a few hundred km s-1. Moreover, in NGC 1386 and NGC 1068, a double-peaked [Fe VII] line is detected in the nuclear and extended coronal region, this being the first report of this type of profile in CLs in active galactic nuclei. If interpreted as outflow signatures, the total broadening of the lines at zero-intensity levels implies gas velocities up to 2000 km s-1. Although the stratification of ions across the coronal region means that photoionization is the main power mechanism, the high velocities deduced from the profiles, the relatively large spatial extension of the emission, and the results from photoionization models indicate that an additional mechanism is at work. We suggest that shocks generated by the outflow could provide the additional required power for line formation. Based on observations made with ESO Telescopes at the Paranal Observatory under program 68.B-0627.

Rodríguez-Ardila, Alberto; Prieto, M. Almudena; Viegas, Sueli; Gruenwald, Ruth

2006-12-01

110

H-alpha LEGUS: Unveiling the Interplay Between Stars, Star Clusters, and Ionized Gas  

NASA Astrophysics Data System (ADS)

We propose to obtain narrow-band, H-alpha observations for a significant subset of the star-forming, nearby galaxies recently targeted by the LEGUS treasury program (GO-13364). LEGUS is observing these galaxies in five broad-band filters: NUV, U, B, V, and I. The new H-alpha observations will reveal thousands of previously undetected HII regions, including those ionized by stellar clusters and single massive stars, allow us to measure their luminosities and sizes, and to separate discrete sources from diffuse ionized gas. We will use our narrow-band imaging survey to: (1) establish the connection between star and cluster formation, and determine the prevelance with which isolated massive stars form in different galaxies; (2) determine whether the initial cluster mass function is universal; (3) investigate the size evolution of ionized gas bubbles, and how this depends on cluster age and mass, as well as on local galactic conditions; and (4) place stringent limits on the leakage of ionizing photons from HII regions, and better understand how the interplay between properties of the ionizing source and the morphology of the HII region impacts leakage. The broad goal of this study is to better understand how feedback from massive stars affects the surrounding medium. Ultimately, the interplay between feedback and the ISM on these scales will enable a better understanding of galaxy-scale outflows in the early universe, a process critical to galaxy evolution. This program naturally lends itself to an improvement of the scientific output by involving the general public via an already established Citizen Science program.

Chandar, Rupali

2014-10-01

111

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...

112

GAS ACCRETION IS DOMINATED BY WARM IONIZED GAS IN MILKY WAY MASS GALAXIES AT z {approx} 0  

SciTech Connect

We perform high-resolution hydrodynamic simulations of a Milky Way mass galaxy in a fully cosmological setting using the adaptive mesh refinement code, Enzo, and study the kinematics of gas in the simulated galactic halo. We find that the gas inflow occurs mostly along filamentary structures in the halo. The warm-hot (10{sup 5} K 10{sup 6} K) ionized gases are found to dominate the overall mass accretion in the system (with M-dot = 3-5 M {sub Sun} yr{sup -1}) over a large range of distances, extending from the virial radius to the vicinity of the disk. Most of the inflowing gas (by mass) does not cool, and the small fraction that manages to cool does so primarily close to the galaxy (R {approx}< 100 kpc, with more pronounced cooling at smaller R), perhaps comprising the neutral gas that may be detectable as, e.g., high-velocity clouds. The neutral clouds are embedded within larger, accreting filamentary flows, and represent only a small fraction of the total mass inflow rate. The inflowing gas has relatively low metallicity (Z/Z {sub Sun} < 0.2). The outer layers of the filamentary inflows are heated due to compression as they approach the disk. In addition to the inflow, we find high-velocity, metal-enriched outflows of hot gas driven by supernova feedback. Our results are consistent with observations of halo gas at low z.

Joung, M. Ryan; Putman, Mary E.; Bryan, Greg L.; Fernandez, Ximena; Peek, J. E. G., E-mail: moo@astro.columbia.edu [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States)

2012-11-10

113

Fabrication of gas ionization sensor based on titanium oxide nanotube arrays  

NASA Astrophysics Data System (ADS)

Gas sensors have been fabricated based on field ionization from titanium oxide nanotubes grown on titanium foil. Ordered nanaotube arrays of titanium oxides were grown by the anodization method. We measured breakdown voltages and discharge currents of the device for various gases. Our gas ionization sensors (GIS) presented good sensitivity, selectivity, and short response time. The GISs based on TiO2 nanotube arrays showed lower breakdown voltage, higher discharge current, and good selectivity. An excellent response observed for Ar compared to other gases. Besides, by introducing 2 % CO and 4 % H2 to N2 flow gas, the amount of breakdown voltage shifts about 20 and 70 volts to the lower values, respectively. The GIS works at room temperature and has the ability of detect inert gases with high stability and good linearity. Besides, short response time of about 1 second for the GISs based on TiO2 nanotube arrays makes them excellent for gas sensing applications. Sharp edges of the nanotubes, through enhancing the applied electric field, reduce operating voltage to the reasonable values and power consumption.

Nikfarjam, Alireza; Mohammadpour, Raheleh; Iraji zad, Azam

2014-06-01

114

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

115

Ionized Plasma and Neutral Gas Coupling in the Sun's Chromosphere and Earth's Ionosphere/Thermosphere  

NASA Astrophysics Data System (ADS)

We review physical processes of ionized plasma and neutral gas coupling in the weakly ionized, stratified, electromagnetically-permeated regions of the Sun's chromosphere and Earth's ionosphere/thermosphere. Using representative models for each environment we derive fundamental descriptions of the coupling of the constituent parts to each other and to the electric and magnetic fields, and we examine the variation in magnetization of the components. Using these descriptions we compare related phenomena in the two environments, and discuss electric currents, energy transfer and dissipation. We present examples of physical processes that occur in both atmospheres, the descriptions of which have previously been conducted in contrasting paradigms, that serve as examples of how the chromospheric and ionospheric communities can further collaborate. We also suggest future collaborative studies that will help improve our understanding of these two different atmospheres, which while sharing many similarities, also exhibit large disparities in key quantities.

Leake, J. E.; DeVore, C. R.; Thayer, J. P.; Burns, A. G.; Crowley, G.; Gilbert, H. R.; Huba, J. D.; Krall, J.; Linton, M. G.; Lukin, V. S.; Wang, W.

2014-11-01

116

A Very Deep Spectrum of the Diffuse Ionized Gas in NGC 891  

NASA Astrophysics Data System (ADS)

A deep long-slit spectrum of the diffuse ionized gas (DIG) in the edge-on spiral galaxy NGC 891 has been obtained. The slit crosses the plane at a galactocentric radius of 5 kpc and covers DIG on both the east and west sides of the galaxy. The primary motivation was to attempt to detect the recombination line He I ?5876, the strength of which relative to H? provides a direct constraint on the hardness of the ionizing spectrum. In the DIG of the Milky Way, this line ratio has turned out to be surprisingly low (Reynolds & Tufte; Heiles et al.), implying an ionizing spectrum much softer than had been inferred from the more readily observable forbidden lines, such as [N II] ?6583 and [S II] ?6717. The He I line has been detected in NGC 891 to a height of about 1.5 kpc from the plane--well into the diffuse gas layer. In the DIG, He I/H? ~ 0.034, implying that helium is about 70% ionized and that the ionizing spectrum is significantly harder than in the Reynolds layer. The spectrum also allows very detailed mapping of the [N II] ?6583/H? ratio as a function of height off the plane. This ratio reaches peak values of about 1.4 at heights of z = 2 kpc on the east side of the plane and z = 4 kpc on the west side. Beyond this height on the east side, the ratio clearly declines again, falling to about 1.0 at z = 4 kpc. Previous modeling indicates that such high values of [N II] ?6583/H? require an ionizing spectrum significantly harder than that indicated by the He I/H? ratio. Hence, despite the higher values of He I/H?, the same dilemma exists as in the Reynolds layer case. These results suggest that we do not understand the heating and ionization of the diffuse gas well enough. A determination of the gas temperature would help, but the nondetection of the line [N II] ?5755 allows only upper limits to be set: 13,000 K on the east side and 10,000 K on the west side. Both the [N II] and H? lines are detected beyond z = 5 kpc; thus, the DIG layer extends much further than indicated by previous narrowband images. A model of the electron density distribution consisting of two components with scale heights of about 1 kpc and 5-6 kpc provides a good fit to the H? emission profile. The very extended component was also seen in the image of Rand, Kulkarni, & Hester, but the inferred scale height is now larger. Apart from the known effects of dust absorption on the velocity centroids at low z, there is a smooth gradient in velocity centroids with increasing z above the dust lane in the sense that they become closer to the systemic velocity, changing by about 30 km s-1 from z = 1 kpc to z = 4.5 kpc. We postulate that the effect is due in part to a decreasing rotation speed and an outward radial migration of gas with z. An illustrative model suggests that the rotation speed at z = 4.5 kpc may be about 20 km s-1 slower than in the disk, although other effects could change this estimate. Such a change in rotation velocity is expected in galactic fountain models, but some simple experiments with stellar orbits show that the flow in a fountain may be more complicated than previously thought.

Rand, Richard J.

1997-01-01

117

WARM IONIZED GAS REVEALED IN THE MAGELLANIC BRIDGE TIDAL REMNANT: CONSTRAINING THE BARYON CONTENT AND THE ESCAPING IONIZING PHOTONS AROUND DWARF GALAXIES  

SciTech Connect

The Magellanic System includes some of the nearest examples of galaxies disturbed by galaxy interactions. These interactions have redistributed much of their gas into the halos of the Milky Way (MW) and the Magellanic Clouds. We present Wisconsin H{alpha} Mapper kinematically resolved observations of the warm ionized gas in the Magellanic Bridge over the velocity range of +100 to +300 km s{sup -1} in the local standard of rest reference frame. These observations include the first full H{alpha} intensity map and the corresponding intensity-weighted mean velocity map of the Magellanic Bridge across (l, b) = (281 Degree-Sign .5, -30 Degree-Sign .0) to (302. Degree-Sign 5, -46. Degree-Sign 7). Using the H{alpha} emission from the Small Magellanic Cloud (SMC)-Tail and the Bridge, we estimate that the mass of the ionized material is between (0.7-1.7) Multiplication-Sign 10{sup 8} M{sub Sun }, compared to 3.3 Multiplication-Sign 10{sup 8} M{sub Sun} for the neutral mass over the same region. The diffuse Bridge is significantly more ionized than the SMC-Tail, with an ionization fraction of 36%-52% compared to 5%-24% for the Tail. The H{alpha} emission has a complex multiple-component structure with a velocity distribution that could trace the sources of ionization or distinct ionized structures. We find that incident radiation from the extragalactic background and the MW alone are insufficient to produced the observed ionization in the Magellanic Bridge and present a model for the escape fraction of the ionizing photons from both the SMC and Large Magellanic Cloud (LMC). With this model, we place an upper limit of 4.0% for the average escape fraction of ionizing photons from the LMC and an upper limit of 5.5% for the SMC. These results, combined with the findings of a half a dozen other studies for dwarf galaxies in different environments, provide compelling evidence that only a small percentage of the ionizing photons escape from dwarf galaxies in the present epoch to influence their surroundings.

Barger, K. A.; Haffner, L. M. [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States); Bland-Hawthorn, J., E-mail: kbargers@nd.edu, E-mail: haffner@astro.wisc.edu, E-mail: jbh@physics.usyd.edu.au [Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006 (Australia)

2013-07-10

118

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

119

OI and OIII in Sgr A: neutral and ionized gas at the Galactic center  

SciTech Connect

We have mapped the /sup 3/P/sub 1/-/sup 3/P/sub 2/ fine structure line emission at 63 microns from neutral oxygen in the vicinity of the galactic center. The emission is extended over more than 4' and is centered on Sgr A West. We conclude that the bulk of the OI emission arises in a predominantly neutral region outside of the ionized central 3 pc of our galaxy. Assuming that the oxygen is collisionally excited by neutral hydrogen impact, we estimate that the gas temperatures in this region are >130K, that is, significantly higher than the dust temperature of 70K. The OI line center velocities change systematically along the galactic plane in a manner consistent with galactic rotation. However, the unusual velocity distribution and linewidths suggest that the motions have a large noncircular component and that there are large scale inhomogeneities in the OI-emitting gas. We also have detected the 88 micron /sup 3/P/sub 1/-/sup 3/P/sub 0/ fine structure line of OIII in a 45triangle-solid FWHM beam centered on Sgr A West. The ratio of this line intensity to that of 52 micron /sup 3/P/sub 2/-/sup 3/P/sub 1/ line indicates that most of the ionized gas in this region has electron density >10/sup 4/ cm/sup -3/.

Genzel, R.; Watson, D.; Townes, C.; Lester, D.; Dinerstein, H.; Werner, M.; Storey, J.

1982-05-01

120

DYNAMO II: Coupled Stellar and Ionized Gas Kinematics in Two Low Redshift Clumpy Disks  

E-print Network

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 analogs to high-redshift clumpy disks. They were observed using the GMOS instrument in integral field spectroscopy (IFS) mode at the Gemini Observatory with high spectral resolution (R=5400, equivalent to 24 km/s at the observed wavelengths) and 6 hour 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-beta emission) is morphologically irregular, forming multiple giant clumps while stellar continuum light is smooth and well described by an exponential profile. Clumpy gas mo...

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

2014-01-01

121

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

122

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

123

Origins of the Highly Ionized Gas along the Line of Sight towards HD 116852  

E-print Network

We present Hubble Space Telescope Imaging Spectrograph (HST/STIS) and Far Ultraviolet Spectroscopic Explorer (FUSE) observations of high ion interstellar absorption along the sight line to HD 116852. At a distance of 4.8 kpc, HD 116852 is an O9 III star lying in the low Galactic halo, -1.3 kpc from the plane of the Galaxy in the direction l = 304.9, b = -16.1. The STIS E140H grating observations provide high-resolution (FWHM = 2.7 km/s) spectra of the resonance doublets of Si IV, C IV, and N V. These data are complemented by medium-resolution (FWHM = 20 km/s) FUSE spectra of O VI. We find evidence for three distinct types of highly ionized gas present in the data. First, two narrow absorption components are resolved in the Si IV and C IV profiles, at approximate LSR velocities of -36 and -10 km/s. These narrow components appear to be produced in gas associated with the Norma and Sagittarius spiral arms, at approximate z-distances of -1.0 and -0.5 kpc, respectively. Second, we detect an intermediate-width component in C IV and Si IV, at 17 km/s, which we propose could arise at the conductive interface at the boundary between a low column density neutral or weakly ionized cloud and the surrounding hot medium. Finally, a broad collisionally ionized component of gas responsible for producing the smooth N V and O VI profiles is observed; such absorption is also present to a lesser degree in the profiles of Si IV and C IV. The broad O VI absorption is observed at a velocity displaced from the broad C IV component by almost 20 km/s, an amount large enough to suggest that the two ions may not co-exist in the same physical location.

Andrew J. Fox; Blair D. Savage; Kenneth R. Sembach; Dirk Fabian; Philipp Richter; David M. Meyer; James Lauroesch; J. Christopher Howk

2002-09-26

124

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

NASA Astrophysics Data System (ADS)

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 ?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 ?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

2012-09-01

125

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

126

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

127

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

128

Filling factors and scale heights of the diffuse ionized gas in the Milky Way  

NASA Astrophysics Data System (ADS)

The combination of dispersion measures of pulsars, distances from the model of Cordes & Lazio (\\cite{cordes+lazio02}) and emission measures from the WHAM survey enabled a statistical study of electron densities and filling factors of the diffuse ionized gas (DIG) in the Milky Way. The emission measures were corrected for absorption and contributions from beyond the pulsar distance. For a sample of 157 pulsars at |b|>5° and 60° < ? < 360°, located in mainly interarm regions within about 3 kpc from the Sun, we find that: (1) The average volume filling factor along the line of sight /line{f}v and the mean density in ionized clouds /line{n}c are inversely correlated: /line{f}v(/line{n}c ) = (0.0184± 0.0011) /line{n}c{ -1.07± 0.03} for the ranges 0.03 < /line{n}c < 2 {cm-3 and 0.8 > /line{f}v > 0.01. This relationship is very tight. The inverse correlation of /line{f}v and /line{n}c causes the well-known constancy of the average electron density along the line of sight. As /line{f}v(z) increases with distance from the Galactic plane |z|, the average size of the ionized clouds increases with |z|. (2) For |z| < 0.9 kpc the local density in clouds nc (z) and local filling factor f(z) are inversely correlated because the local electron density ne (z) = f(z) nc (z) is constant. We suggest that f(z) reaches a maximum value of >0.3 near |z| = 0.9 kpc, whereas nc (z) continues to decrease to higher |z|, thus causing the observed flattening in the distribution of dispersion measures perpendicular to the Galactic plane above this height. (3) For |z| < 0.9 kpc the local distributions nc (z), f(z) and ne2(z) have the same scale height which is in the range 250 < h ? 500 pc. (4) The average degree of ionization of the warm atomic gas /line{I}w (z) increases towards higher |z| similarly to /line{f}v (z). Towards |z| = 1 kpc, /line{f}v (z) = 0.24± 0.05 and /line{I}w (z) = 0.24± 0.02. Near |z| = 1 kpc most of the warm, atomic hydrogen is ionized.

Berkhuijsen, E. M.; Mitra, D.; Mueller, P.

2006-01-01

129

High-ionization Gas in Active Galactic Nuclei: Line Profiles and Physical Conditions  

NASA Astrophysics Data System (ADS)

SOAR/Goodman spectroscopy is employed to detect the coronal lines [Fe VII] 3759, 5159, and 6087 Å, [Ne V] 3423 Å and [Fe X] 6083 Å, the former three suitable to determine the temperature and density of the high-ionization gas. The spectra allow us to fully characterize the profiles of the most conspicuous lines (asymmetries, shifts from the centroid position and line width). The combined results allow us to detect signatures of outflows in the coronal gas and thus set up constrains on the origin of the CLs in AGNs. In addition, AO GEMINI/NIFS IFU spectroscopy is used to study the coronal gas morphology at spatial scales of a few parsecs in the Seyfert 2 galaxy NGC 1068. We found that the gas distribution is rather inhomogeneous and asymmetric. From the comparison of the CL [Mg VIII] with the VLA 6 cm radio emission we found evidence that the CL gas kinematics and morphology is strongly related to the radio jet morphology. All above results allow us to confirm the role that coronal lines have to trace outflows at the inner tens of parsecs of AGNs.

Rodíguez-Ardila, A.; Riffel, R.; Mazzalay, X.; Portilla, J. G.

2012-08-01

130

Nonlinear focusing by residual-gas ionization in long-pulse electron linacs  

NASA Astrophysics Data System (ADS)

For short electron bunches in accelerators, the radial ion density due to residual-gas ionization faithfully reproduces the radial electron bunch distribution for time scales similar to the electron bunch length. If the electron bunch length is sufficiently long, however, the ions focus and, even for radially uniform electron beams, tend to form a very nonuniform equilibrium distribution. This ion distribution, in turn, leads to nonlinear focusing forces on the electron bunch itself. In this paper, we find the equilibrium distribution when the electron distribution is uniform, and calculate the emittance growth for axial slices in the electron bunch later in time. A regime is found in which the emittance growth is quadratic with both residual gas pressure and electron bunch length.

Carlsten, Bruce E.

2001-10-01

131

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

132

Neutral gas plasma interactions and critical ionization velocity phenomena. Interim report  

SciTech Connect

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.

1983-11-11

133

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

134

Use of Penning ionization electron spectroscopy in plasma for measurements of environmental gas constituents.  

PubMed

A breadboard GC detector based on Penning ionization electron spectroscopy in plasma (PIES) was investigated. The PIES detector was set up in series with a gas chromatograph and a thermal conductivity detector. Two-dimensional PIES chromatograms were recorded for carbon monoxide, carbon dioxide, and methane. The analytes were identified independently of the GC retention time, and their concentrations were measured in a range between 1 and 100 ppm. PIES spectra for methane were observed for the first time and displayed two characteristic peaks with electron energies of 7.1 and 5.4 eV. Rate coefficients for Penning ionization due to collisions between 2(3)S helium metastable atoms and analyte molecules under study were found to be k*(CO) = (0.7 +/- 0.2) x 10(-10), k*(CO2) = (1.8 +/- 0.7) x 10(-10), k*(7.1 CH4) = (4.7 +/- 0.6) x 10(-10), and k*(5.4 CH4) = (8 +/- 2) x 10(-10) cm(3)/s. The work provides the basis for the development of a portable and robust analytical platform capable of in situ real-time monitoring of greenhouse gases, with a perspective toward laboratory-on-chip realization. PMID:19260645

Stepaniuk, Vadim P; Popov, Gotze H; Sheverev, Valery A

2009-04-01

135

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry using a femtosecond laser.  

PubMed

A laser can be used for the selective excitation and subsequent ionization of a molecule with an absorption band at the laser wavelength. This technique of multiphoton ionization (MPI), when combined with time-of-flight mass spectrometry (TOF-MS), permits the efficient detection of induced ions in mass analysis. This combination of MPI/TOF-MS can be coupled with gas chromatography (GC) to achieve even more enhanced selectivity. Thus, GC/MPI/TOF-MS can be employed for trace analysis of samples containing numerous chemical species. A variety of laser sources have been used for this purpose. Since molecules that are classified as environmental pollutants frequently contain chlorine and bromine atoms, the lifetime of the excited state can be decreased by energy transfer from the singlet to triplet levels by spin-orbit interaction. A high-power femtosecond laser with a pulse width shorter than the lifetime of the analyte molecule provides femtogram or even subfemtogram detection limits, which have not yet been achieved using the most sensitive high-resolution double-focus sector-type mass spectrometers. Numerous environmental pollutants such as dioxins in soils and pesticides in foods have been successfully quantified using GC/MPI/TOF-MS, and this technique has proven itself to be a useful and practical method for trace analysis. PMID:23612871

Imasaka, Totaro

2013-09-01

136

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

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

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

139

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

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

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

142

Kinematics of Ionized Gas at 0.01 AU of TW Hya  

NASA Astrophysics Data System (ADS)

We report two-dimensional spectroastrometry of Br? 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 (~0.01 AU). The centroid of Br? 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°, 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°). The line-of-sight motion of the Br? 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? 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?, 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. Based on data collected by SINFONI observations [79.C-0559(B)] at the VLT on Cerro Paranal (Chile), which is operated by the European Southern Observatory (ESO).

Goto, M.; Carmona, A.; Linz, H.; Stecklum, B.; Henning, Th.; Meeus, G.; Usuda, T.

2012-03-01

143

INVESTIGATION OF THE ATTENUATION OF SHOCK WAVES PROPAGATED THROUGH AN IONIZED GAS IN THE PRESENCE OF A TRANSVERSE MAGNETIC FIELD. Project Squid Technical Report  

Microsoft Academic Search

Attenuation measurements were made of shock waves propagated through ; ionized gas in the presence of a transversc magnetic field. Ionization was ; produced by maintaining a radio frequency discharge in the low pressure section ; of a shock tube. The electrical gas conductivity achieved by this means was less ; than 1 mho\\/m, a value much smaller than was

S. P. Carfagno; G. P. Wachtell

1961-01-01

144

Nuclear Instruments and Methods in Physics Research A 577 (2007) 93102 Effects of finite pulse length, magnetic field, and gas ionization  

E-print Network

length, magnetic field, and gas ionization on ion beam pulse neutralization by background plasma Igor D of the conservation of generalized fluid vorticity. The predictions of the analytical model agree very well of a solenoidal magnetic field, gas ionization and the transition regions during beam pulse entry and exit from

Kaganovich, Igor

145

The thin layer of Warm Ionized Gas: towards a 3-D reconstruction of the spatial distribution of HII regions  

E-print Network

HII regions are known to contribute to the so-called thin layer of the diffuse Warm Ionized Gas. In order to constrain this contribution, we reconstruct the 3-D distribution of the sources. A detailed spatial analysis of the largest up-to-date sample of HII regions is presented.

Roberta Paladini; Rod Davies; Gianfranco DeZotti

2002-12-15

146

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

E-print Network

of Scientific Research, Department of Defense, and DARPA for flow control and stability about an air vehicleDevelopment 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

Roy, Subrata

147

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

E-print Network

was determined using tunable vacuum ultraviolet synchrotron radiation coupled to an effusive thermal source of energy (X- rays, electrons, particles, vacuum ultraviolet (VUV) photons) with DNA has been studiedA VUV Photoionization and Ab Initio Determination of the Ionization Energy of a Gas-Phase Sugar

Krylov, Anna I.

148

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...

149

Spectrophotometry of HII Regions, Diffuse Ionized Gas and Supernova Remnants in M31: The Transition from Photo- to Shock-Ionization  

E-print Network

We present results of KPNO 4-m optical spectroscopy of discrete emission-line nebulae and regions of diffuse ionized gas (DIG) in M31. Long-slit spectra of 16 positions in the NE half of M31 were obtained over a 5-15 kpc range in radial distance from the center of the galaxy. The spectra have been used to confirm 16 supernova remnant candidates from the Braun & Walterbos (1993) catalog. The slits also covered 46 HII regions which show significant differences among the various morphological types (center-brightened, diffuse, rings). Radial gradients in emission-line ratios such as [OIII]/H$\\beta$ and [OII]/[OIII] are observed most prominently in the center-brightened HII regions. These line ratio trends are either much weaker or completely absent in the diffuse and ring nebulae. The line ratio gradients previously seen in M31 SNRs (Blair, Kirshner, & Chevalier 1981; 1982) are well reproduced by our new data. The spectra of center-brightened HII regions and SNRs confirm previous determinations of the radial abundance gradient in M31. We use diagnostic diagrams which separate photoionized gas from shock-ionized gas to compare the spectral properties of HII regions, SNRs and DIG. This analysis strengthens earlier claims (Greenawalt, Walterbos, & Braun 1997) that the DIG in the disk of M31 is photoionized by a dilute radiation field.

V. C. Galarza; R. A. M. Walterbos; R. Braun

1999-08-24

150

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

Microsoft Academic Search

Pyrolysis oils have attracted a lot of interest, as they are liquid energy carriers and general sources of chemicals. In this work, gas chromatography with flame ionization detector (GC-FID) and two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC–TOFMS) techniques were used to provide both qualitative and quantitative results of the analysis of three different pyrolysis oils. The chromatographic methods and

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

2011-01-01

151

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

152

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

153

POLYCYCLIC AROMATIC HYDROCARBONS, IONIZED GAS, AND MOLECULAR HYDROGEN IN BRIGHTEST CLUSTER GALAXIES OF COOL-CORE CLUSTERS OF GALAXIES  

SciTech Connect

We present measurements of 5-25 {mu}m emission features of brightest cluster galaxies (BCGs) with strong optical emission lines in a sample of nine cool-core clusters of galaxies observed with the Infrared Spectrograph on board the Spitzer Space Telescope. These systems provide a view of dusty molecular gas and star formation, surrounded by dense, X-ray-emitting intracluster gas. Past work has shown that BCGs in cool-core clusters may host powerful radio sources, luminous optical emission-line systems, and excess UV, while BCGs in other clusters never show this activity. In this sample, we detect polycyclic aromatic hydrocarbons (PAHs), extremely luminous, rotationally excited molecular hydrogen line emission, forbidden line emission from ionized gas ([Ne II] and [Ne III]), and infrared continuum emission from warm dust and cool stars. We show here that these BCGs exhibit more luminous forbidden neon and H{sub 2} rotational line emission than star-forming galaxies with similar total infrared luminosities, as well as somewhat higher ratios of 70 {mu}m/24 {mu}m luminosities. Our analysis suggests that while star formation processes dominate the heating of the dust and PAHs, a heating process consistent with suprathermal electron heating from the hot gas, distinct from star formation, is heating the molecular gas and contributing to the heating of the ionized gas in the galaxies. The survival of PAHs and dust suggests that dusty gas is somehow shielded from significant interaction with the X-ray gas.

Donahue, Megan; Mark Voit, G.; Hoffer, Aaron [Physics and Astronomy Department, Michigan State University, East Lansing, MI 48824 (United States); De Messieres, Genevieve E.; O'Connell, Robert W. [Astronomy Department, University of Virginia, Charlottesville, VA (United States); McNamara, Brian R. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Nulsen, Paul E. J., E-mail: donahue@pa.msu.edu, E-mail: voit@pa.msu.edu, E-mail: hofferaa@msu.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2011-05-01

154

The Significant Contribution of Photo-ionized Circumgalactic Gas to the Total Baryonic Budget of L* Galaxies  

NASA Astrophysics Data System (ADS)

If the baryonic content of galaxies consists primarily of stars, interstellar gas, and hot (107 K) x-ray halo gas, then galaxies are missing between 70 - 95% of their baryons relative to the cosmological fraction. When accounting for the baryon budget of galaxies, however, we must not overlook the cooler (104 K) photo-ionized gas phase that makes up the circumgalactic medium (CGM). Our collaboration, COS-Halos, has been working to characterize the elusive multiphase CGM that extends out to at least 300 kpc from stellar components of galaxies. Specifically, we have observed the halo gas of 50 galaxies drawn from the imaging dataset of the Sloan Digital Sky Survey (SDSS) whose angular offsets from quasar sight-lines and redshifts imply impact parameters (? < 150 kpc) well inside their virial radii. As we have shown in previous empirical studies, these data comprise a carefully-selected statistically-sampled map of the physical state and metallicity of the CGM for L ? L* galaxies. Of particular relevance to the halo missing baryon problem is the total baryonic mass contained in the multiphase CGM, as traced by absorption from hydrogen and metal lines in various ionization states (e.g. MgII, SiII, CII, SiIII, CIII, SiIV, OVI). In this talk, I will describe how I have modeled the photo-ionized gas of the CGM with a range of physical conditions, and rigorously determined the CGM gas ionization parameters and metallicities along 33 of the COS-Halos sight-lines that provide the best-determined measurements of HI and metal-line column densities. With the constraints imposed by the data and models, I am able to provide the most reliable mass estimate of the CGM to date, and show definitively that the CGM is an important reservoir of baryons on galactic scales.

Werk, Jessica; Prochaska, J. X.; Tumlinson, J.; Peeples, M. S.; Tripp, T. M.; Fox, A.; Lehner, N.; COS-Halos

2014-01-01

155

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

156

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

157

Ionization and heating of the gas in the Galactic center probed by H3+  

NASA Astrophysics Data System (ADS)

The 3.5-4.0 mum infrared spectrum of the molecular ion H _{3} (+) has emerged as a powerful probe to study the Central Molecular Zone (CMZ), a region with a radius of ˜150 pc at the center of our Milky Way Galaxy. Because of the ubiquity of cosmic rays, H _{3} (+) , produced by the reaction H _{2} + H _{2} (+) -> H _{3} (+) + H, exists wherever H _{2} abounds. Although H _{3} (+) is ˜ 10 (7) - 10 (8) times less abundant than H _{2}, its infrared spectrum is more readily observable than that of H _{2} because its dipole spectrum is ˜ 10 (9) times stronger than the quadrupole spectrum of H _{2}. In the CMZ H_{3}(+) is not only abundant (Geballe et al. 1999) but also pervasive. We have observed H_{3}(+) with column densities of ˜ 2×10(15) cm(-2) toward over 20 stars distributed from 140 pc West to 120 pc East of Sgr A* (Oka et al. 2005; Goto et al. 2008; Geballe & Oka 2010; Oka 2013). To date it has been detected toward every star in the Galactic center toward which it has been sought, suggesting that the surface-filling factor of H _{3}&^{+} in the CMZ is 100 %. Our observations and analyses exploiting the simple and fundamental natures of physics and chemistry of H _{3}$(+) have led us to the following three conclusions, each of which radically change the previous concept of the gas in the CMZ. The first two conclusions are firm. The third is less definitive but is likely. (1) A large volume of the CMZ is occupied by warm (˜ 250 K) and diffuse (< 100 cm (-3) ) molecular gas. Such gas replaces some or all of the ultra-hot (10 (7) - 10 (8) K) X-ray emitting plasma which some thought to dominate the region. The vast amount of diffuse molecular gas makes the term “Central Molecular Zone” even more fitting. (2) The ionization rate in the CMZ, zeta > 2 × 10 (-15) s (-1) , is higher than in dense clouds and diffuse clouds in the Galactic disk by more than 100 times and 10 times, respectively. The high value is ascribed to high cosmic ray fluxes due to high densities of SNR in the CMZ. The high ionization rate may help explain the low star formation rate and high initial mass functions of stars observed in the CMZ. (3) The longitude velocity diagram drawn from the velocity profiles of H _{3}(+) lines indicates the presence of an expanding molecular ring of large scale diffuse clouds at the outer edge of the CMZ. Unlike previous reports, the ring is not rotating, suggesting that expulsion dominates over gravitational effects. More studies are under way. Geballe, T. R., McCall, B. J., Hinkle, K. H., Oka, T. ApJ, 510, 251 (1999) Oka, T., Geballe, T. R., Goto, M., Usuda, T., McCall, B. J. ApJ, 632, 882 (2005) Goto, M. Usuda, T., Nagata, T., Geballe, T. R., McCall, B. J., et al. ApJ, 688, (2008) Geballe, T. R., Oka, T. ApJ, 709, L70, (2010) Oka, T. Chem. Rev. (Astrochemistry special issue) 113, 8738 (2013)

Oka, Takeshi

158

Integral Field Unit Observations of NGC 4302: Kinematics of the Diffuse Ionized Gas Halo  

E-print Network

We present moderate resolution spectroscopy of extraplanar diffuse ionized gas (EDIG) emission in the edge-on spiral galaxy NGC 4302. The spectra were obtained with the SparsePak integral field unit (IFU) at the WIYN Observatory. The spectra are used to construct position-velocity (PV) diagrams at several ranges of heights above the midplane. Azimuthal velocities are directly extracted from the PV diagrams using the envelope tracing method, and indicate an extremely steep dropoff in rotational velocity with increasing height, with magnitude ~30 km/s/kpc. We find evidence for a radial variation in the velocity gradient on the receding side. We have also performed artificial observations of galaxy models in an attempt to match the PV diagrams. The results of a statistical analysis also favor a gradient of ~30 km/s/kpc. We compare these results with an entirely ballistic model of disk-halo flow, and find a strong dichotomy between the observed kinematics and those predicted by the model. The disagreement is worse than we have found for other galaxies in previous studies. The conclusions of this paper are compared to results from two other galaxies, NGC 5775 and NGC 891. We find that the vertical gradient in rotation speed, per unit EDIG scale height, for all three galaxies is consistent with a constant magnitude (within the errors) of approximately 15-25 km/s/scaleheight, independent of radius. This relationship is also true within the galaxy NGC 4302. We also discuss how the gradient depends on the distribution and morphology of the EDIG and the star formation rates of the galaxies, and consequences for the origin of the gas.

George H. Heald; Richard J. Rand; Robert A. Benjamin; Matthew A. Bershady

2007-03-13

159

Kinematics of Ionized Gas at 0.01 AU of TW Hya  

E-print Network

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 (~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 degrees, which is nearly equal to the major axis of the protoplanetary disk projected on the sky, previously reported by CO sub millimeter spectroscopy (P.A.= -27 degrees) 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 emiss...

Goto, M; Linz, H; Stecklum, B; Henning, Th; Meeus, G; Usuda, T

2012-01-01

160

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

E-print Network

The interaction of intense extreme ultraviolet (XUV) laser pulses ($\\lambda=32\\rm\\,nm$, $I=10^{11-14}$\\,W/cm$^2$) with small rare-gas clusters (Ar$_{147}$) is studied by quasi-classical 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 {\\it et al.}, Phys. Rev. Lett. {\\bf 100}, 013401 (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 nanop...

Arbeiter, Mathias

2010-01-01

161

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

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

Optical\\/Infrared Imaging and Modeling of Dust and Ionized Gas in the Planetary Nebulae M 4-18  

Microsoft Academic Search

We present high spatial resolution ground-- and space--based (HST) images of ionized gas and dust in the young, low--excitation Planetary Nebula M 4--18. Images of M 4--18 have been obtained in the optical (with WFPC2\\/HST), the near--IR, and at mid--IR wavelengths. The optical--Halpha image shows a complex morphology: a central cavity around the central star is surrounded by a toroidal

A. Dayal; R. Sahai; J. Trauger; J. L. Hora; G. G. Fazio; W. F. Hoffmann; J. H. Bieging; L. K. Deutsch; W. B. Latter

1997-01-01

164

Stars and Ionized Gas in the S0 Galaxy NGC 7743: An Inclined Large-scale Gaseous Disk  

NASA Astrophysics Data System (ADS)

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° ± 9° or 77° ± 9°. 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. Based on the 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).

Katkov, Ivan Yu.; Moiseev, Alexei V.; Sil'chenko, Olga K.

2011-10-01

165

Diffuse ionized gas in spiral galaxies and the disk-halo interaction  

E-print Network

Thick layers of warm, low density ionized hydrogen (i.e., the warm ionized medium or WIM) in spiral galaxies provide direct evidence for an interaction between the disk and halo. The wide-spread ionization implies that a significant fraction of the Lyman continuum photons from O stars, produced primarily in isolated star forming regions near the midplane and often surrounded by opaque clouds of neutral hydrogen, is somehow able to propagate large distances through the disk and into the halo. Moreover, even though O stars are the source of the ionization, the temperature and ionization state of the WIM differ significantly from what is observed in the classical O star H II regions. Therefore, the existence of the WIM and observations of its properties provide information about the structure of the interstellar medium and the transport of energy away from the midplane as well as place significant constraints on models.

R. J. Reynolds; L. M. Haffner; G. J. Madsen; K. Wood; A. S. Hill

2008-12-22

166

Reduction of plasma electron density in a gas ionized by an electron beam - Use of a gaseous dielectric  

NASA Technical Reports Server (NTRS)

Propagation of an electron beam through a gas creates a secondary electron/ion plasma which can have subsequent deleterious effects on the propagation of the beam. In the case of pulsed electron beams with short micropulse durations, these effects can be greatly reduced through the use of a small doping fraction of an electron attachment gas. We present a model which allows the calculation of the reduction in unbound plasma electron density attainable with a gaseous dielectric dopant. Potential problems with a dopant, including increased ionization, increased scattering, altered refractive index, and dopant saturation and fragmentation, are discussed.

Reid, Max B.

1993-01-01

167

The ATLAS3D project - X. On the origin of the molecular and ionized gas in early-type galaxies  

NASA Astrophysics Data System (ADS)

We make use of interferometric CO and H I observations, and optical integral-field spectroscopy from the ATLAS3D survey, to probe the origin of the molecular and ionized interstellar medium (ISM) in local early-type galaxies. We find that 36 ± 5 per cent of our sample of fast-rotating early-type galaxies have their ionized gas kinematically misaligned with respect to the stars, setting a strong lower limit on the importance of externally acquired gas (e.g. from mergers and cold accretion). Slow rotators have a flat distribution of misalignments, indicating that the dominant source of gas is external. The molecular, ionized and atomic gas in all the detected galaxies are always kinematically aligned, even when they are misaligned from the stars, suggesting that all these three phases of the ISM share a common origin. In addition, we find that the origin of the cold and warm gas in fast-rotating early-type galaxies is strongly affected by environment, despite the molecular gas detection rate and mass fractions being fairly independent of group/cluster membership. Galaxies in dense groups and the Virgo cluster nearly always have their molecular gas kinematically aligned with the stellar kinematics, consistent with a purely internal origin (presumably stellar mass loss). In the field, however, kinematic misalignments between the stellar and gaseous components indicate that at least 42 ± 5 per cent of local fast-rotating early-type galaxies have their gas supplied from external sources. When one also considers evidence of accretion present in the galaxies' atomic gas distributions, ?46 per cent of fast-rotating field ETGs are likely to have acquired a detectable amount of ISM from accretion and mergers. We discuss several scenarios which could explain the environmental dichotomy, including preprocessing in galaxy groups/cluster outskirts and the morphological transformation of spiral galaxies, but we find it difficult to simultaneously explain the kinematic misalignment difference and the constant detection rate. Furthermore, our results suggest that galaxy mass may be an important independent factor associated with the origin of the gas, with the most massive fast-rotating galaxies in our sample (MK?-24 mag; stellar mass of ?8 × 1010 M?) always having kinematically aligned gas. This mass dependence appears to be independent of environment, suggesting it is caused by a separate physical mechanism.

Davis, Timothy A.; Alatalo, Katherine; Sarzi, Marc; Bureau, Martin; Young, Lisa M.; Blitz, Leo; Serra, Paolo; Crocker, Alison F.; Krajnovi?, Davor; McDermid, Richard M.; Bois, Maxime; Bournaud, Frédéric; Cappellari, Michele; Davies, Roger L.; Duc, Pierre-Alain; de Zeeuw, P. Tim; Emsellem, Eric; Khochfar, Sadegh; Kuntschner, Harald; Lablanche, Pierre-Yves; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Scott, Nicholas; Weijmans, Anne-Marie

2011-10-01

168

Electrospray ionization gas-phase electrophoresis under ambient conditions and it's potential or high-speed separations.  

PubMed

A moderately high resolution nanoelectrospray ionization gas-phase electrophoresis instrument was constructed and evaluated for simple high-speed separations of several groups of compounds. The insertion of a plate containing a 1.6 cm diameter exit orifice, 2.5 cm from the location of electrospray, allowed ions to be created and desolvated under ambient conditions with minimal solvent contamination to the drift tube. Ion separation selectivity is discussed and shown to be slightly altered by changing the drift gas flow rate. Issues of using gas-phase electrophoresis as a high-speed separation technique are discussed. Gas-phase electrophoresis-spectra of selected benzodiazepines, triazine herbicides, and simple combinatorial chemistry libraries are demonstrated. PMID:11293698

Collins, D C; Lee, M L

2001-02-01

169

SIGGMA: A Survey of Ionized Gas in the Galaxy, Made with the Arecibo Telescope  

NASA Astrophysics Data System (ADS)

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° <= l <= 75° and -2° <= b <= 2° 175° <= l <= 207° and -2° <= b <= 1°) observable with the telescope in radio recombination lines (RRLs). Processed data sets are being produced in the form of data cubes of 2° (along l) × 4° (along b) × 151 (number of channels), archived and made public. The 151 channels cover a velocity range of 600 km s-1 and the velocity resolution of the survey changes from 4.2 km s-1 to 5.1 km s-1 from the lowest frequency channel to the highest frequency channel. RRL maps with 3.'4 resolution and a line flux density sensitivity of ~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? 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? and Cn? lines with S/N > 10.

Liu, B.; McIntyre, T.; Terzian, Y.; Minchin, R.; Anderson, L.; Churchwell, E.; Lebron, M.; Anish Roshi, D.

2013-10-01

170

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

171

CNT-based gas ionizers with integrated MEMS gate for portable mass spectrometry applications  

E-print Network

We report the fabrication and experimental characterization of a novel low-cost carbon nanotube (CNT)-based electron impact ionizer (EII) with integrated gate for portable mass spectrometry applications. The device achieves ...

Velasquez-Garcia, Luis Fernando

172

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

173

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

174

A helium ionization detector with a thermionic electron emitter for gas chromatography  

Microsoft Academic Search

The principal circuit of a helium ionization detector with a thermionic electron emitter (He-IDTEE) is described. The detector\\u000a works at atmospheric pressure. The characteristics of the detector were studied. The difference between the voltammetric characteristics\\u000a of He-IDTEE and that of a helium ionization detector with a radioactive source was shown. The dependences of the analytical\\u000a signal, background signal, and noise

Yu. A. Saprykin; V. M. Tsmots’; M. V. Tsyuper; Yu. A. Pazderskii

2009-01-01

175

Determination of low specific activity iodine-129 off-gas concentrations by GC separation and negative ionization mass spectrometry  

SciTech Connect

This document is the final report of the laboratory development of a method for determining the specific activity of the /sup 129/I emitted from a nuclear fuel reprocessing plant. The technique includes cryogenic sample collection, chemical form separation, quantitation by gas chromatography, and specific activity measurement of each chemical species by negative ionization mass spectrometry. The major conclusions were that both organic and elemental iodine can be quantitatively collected without fractionation and that specific activity measurements as low as one atom of /sup 129/I per 10/sup 5/ atoms of /sup 127/I are possible.

Fernandez, S.J.; Rankin, R.A.; McManus, G.J.; Nielsen, R.A.; Delmore, J.E.; Hohorst, F.A.; Murphy, L.P.

1983-09-01

176

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

177

Near-UV Resonant Two-Photon Ionization Spectroscopy of Gas Phase Guanine: Evidence for the Observation of Three Rare Tautomers  

E-print Network

Near-UV Resonant Two-Photon Ionization Spectroscopy of Gas Phase Guanine: Evidence) experiments on gas phase guanine, which is supported by quantum chemistry calculations. Whereas He droplet to a higher energy form: 7H enol syn 5. Finally, the fourth tautomer D observed was assigned to the 9H enol

Boyer, Edmond

178

The ionization mechanism of the extended gas in high redshift radio galaxies:shocks or AGN photoionization?  

E-print Network

We have compared the UV line ratios of a sample of very high redshift radio galaxies with shock and AGN photoionization models, with the goal of determining the balance between jet-induced shocks and AGN illumination in the extended emission line regions. We find that the UV line ratios cannot be explained in terms of photoionization of solar abundance gas by the classical power law of index $\\alpha=$-1.5, which successfully reproduces the general trends defined by the optical line ratios of low redshift radio galaxies. Pure shock models also provide a poor fit to the data. However, photoionization by a power law of index -1.0 provides an excellent fit to the UV line ratios. This suggests that the ionizing continuum spectral shape may depend on radio luminosity and/or redshift, such that it becomes harder as the radio power and/or redshift increase. However, an alternative possibility is that we are seeing the first signs of chemical evolution in these objects, since a power-law of index -1.5 with low metallicity also provides a good fit to the data. We further show that the UV line ratios provide a sensitive test of the ionization mechanism for the lower ionization conditions prevalent in some low redshift jet-cloud interaction candidates.

M. Villar-Martin; C. N. Tadhunter; N. E. Clark

1997-01-06

179

MECRIS: A compact ECRIS for ionization of noble gas radioisotopes at ISOLDE  

NASA Astrophysics Data System (ADS)

A very compact Electron Cyclotron Resonance Ion Source (ECRIS) for singly charged radioactive gases has been developed at ISOLDE/CERN. The radioisotopes are produced by fission, spallation, and fragmentation reactions induced via high-energy protons impacting on a thick target. The often short-lived radioactive elements required for ISOLDE physics diffuse out of the target, effuse through a transfer tube, and eventually reach the ionizing volume. An efficient ionization process is mandatory in view of the very small production cross sections of radioactive elements far from stability and fast ionization is desired to minimize decay losses. The MECRIS (Mono ECR ISOLDE) is intended for light noble gases (He, Ne, Ar, and Kr), which have low ionization efficiency in ordinary plasma ion sources, but also for gaseous molecular compounds of C, N, and O isotopes. We will report on the design and construction of the device, including magnetic field calculations and rf simulations. Results of the first tests performed with stable ion beams are presented.

Wenander, F.; Lettry, J.

2004-05-01

180

Optical/Infrared Imaging and Modeling of Dust and Ionized Gas in the Planetary Nebulae M 4-18  

NASA Astrophysics Data System (ADS)

We present high spatial resolution ground-- and space--based (HST) images of ionized gas and dust in the young, low--excitation Planetary Nebula M 4--18. Images of M 4--18 have been obtained in the optical (with WFPC2/HST), the near--IR, and at mid--IR wavelengths. The optical--H? image shows a complex morphology: a central cavity around the central star is surrounded by a toroidal shell. The emission peaks in two clumps which are disposed symmetrically (N-S) about the central star, and lie outside the cavity. These clumps appear to delineate the limb--brightened walls of the torus. The mid-IR images of thermal emission from warm (T~200K) dust also show a two--lobed morphology, but the position angle of the lobes lies orthogonal to the equatorial axis, as defined by the H? toroid. The difference between the dust emission and the ionized gas suggests that, the mid-IR peaks trace regions of hotter dust grains, rather than define the higher density equatorial plane of the nebula. Alternatively, it is possible that gas and dust are spatially separated, i.e. regions of highest gas density do not coincide with regions of highest dust density. We have created a code that constructs 3-D spatial and kinematical models of PNe, and applied it to M 4--18 and MyCn 18 (the Hourglass Nebula). Our results illustrate that optically thin, axially symmetric models are able to reproduce the overall structure and kinematics of the two sources.

Dayal, A.; Sahai, R.; Trauger, J.; Hora, J. L.; Fazio, G. G.; Hoffmann, W. F.; Bieging, J. H.; Deutsch, L. K.; Latter, W. B.

1997-12-01

181

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

182

Highly ionized gas in the Gum nebula and elsewhere - A comparison of IUE and Copernicus satellite results  

NASA Technical Reports Server (NTRS)

The data from six high-dispersion IUE echelle spectra are averaged in order to obtain an interstellar absorption line spectrum with an S/N of about 30 and a resolution of about 25 km/s. The interstellar lines of C IV and Si IV are very strong and broad and N V is detected. The profiles for these species and Al III are compared to the Copernicus satellite profiles for O VI. The high ionization lines toward HD 64760 are much stronger and broader than those recorded toward Zeta Pup and Gamma super 2 Vel, the two exciting stars of the Gum nebula. The profiles for Al III and Si IV are similar and considerably narrower than the O VI profile. An origin in photoionized Gum nebula gas is suggested as the most likely explanation for Al III and Si IV. The C IV profile has a high positive velocity wing extending to approximately +80 km/s, which is similar in appearance to the positive velocity portion of the O VI profile. It is inferred that a substantial part of the observed C IV has an origin in the collisionally ionized gas most likely rsponsible for the O VI.

Edgar, Richard J.; Savage, Blair D.

1992-01-01

183

Wave Coupling Across a Shock Wave in a Fully Ionized Gas  

Microsoft Academic Search

This paper presents a theory of the coupling between electron-acoustic, ion-acoustic, and electromagnetic plane waves at an idealized shock front in a two-fluid, fully ionized, inviscid plasma. The equations of hydrodynamics and Maxwell's equations are used to derive the dispersion equation relating the frequency and propagation constant of possible modes of propagation in a plasma. Boundary conditions which must hold

Samuel H. Francis; David Kahn

1968-01-01

184

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

185

Analysis of tert-butyldimethylsilyl derivatives in heavy gas oil from Brazilian naphthenic acids by gas chromatography coupled to mass spectrometry with electron impact ionization.  

PubMed

Naphthenic acids, C(n)H(2n+Z)O(2), are a complex mixture of alkyl-substituted acyclic and cycle-aliphatic carboxylic acids. The content of naphthenic acids and their derivatives in crude oils is very small, which hinders their extraction from matrixes of wide and varied composition. In this work, liquid-liquid extraction, followed by solid phase extraction with an ion exchange resin (Amberlyst A-27) and ultrasound desorption were used to isolate the acid fraction from heavy gas oil of Marlim petroleum (Campos, Rio de Janeiro, Brazil). The analysis was accomplished through gas chromatography coupled to mass spectrometry with electron impact ionization, after derivatization with N-methyl-N-(tert-butyldimethylsilyl)trifluoracetamide (MTBDMSTFA). The results indicate the presence of carboxylic acids belonging to families of alicyclic and naphthenic compounds which contain up to four rings in the molecule. PMID:16439253

Vaz de Campos, Maria Cecília; Oliveira, Eniz Conceição; Filho, Pedro José Sanches; Piatnicki, Clarisse Maria Sartori; Caramão, Elina Bastos

2006-02-10

186

A 2D multiwavelength study of the ionized gas and stellar population in the giant H II region NGC 588  

NASA Astrophysics Data System (ADS)

Giant H II regions (GHIIRs) in nearby galaxies are a local sample in which we can study in detail processes in the interaction of gas, dust and newly formed stars which are analogous to those which occurred in episodes of higher intensity in which much of the current stellar population was born. Here, we present an analysis of NGC 588, a GHIIR in M33, based on optical Integral Field Spectroscopy data obtained with the Potsdam Multi-Aperture Spectrophotometer at the 3.5-m telescope of the Calar Alto Observatory, CAHA, together with Spitzer infrared images at 8 and 24 ?m. The extinction distribution measured in the optical shows complex structure, with three maxima which correlate in position with those of the emission at 24 and 8 ?m. Furthermore, the H? luminosity absorbed by the dust within the H II region reproduces the structure observed in the 24-?m image, supporting the use of the 24-?m band as a valid tracer of recent star formation. A velocity difference of ˜50 km s-1 was measured between the areas of high and low surface brightness, which would be expected if NGC 588 were an evolved GHIIR. We have carefully identified the areas which contribute most to the line ratios measured in the integrated spectrum. Those line ratios which are used in diagnostic diagrams proposed by Baldwin, Phillips & Terlevich (i.e. the BPT diagrams) show a larger range of variation in the low surface brightness areas. The ranges are ˜0.5-1.2 dex for [N II]?6584/H?, 0.7-1.7 dex for [S II]??6717,6731/H? and 0.3-0.5 dex for [O III]?5007/H?, with higher values of [N II]?6584/H? and [S II]??6717,6731/H?, and lower values of [O III]?5007/H? in the areas of lower surface brightness. Ratios corresponding to large ionization parameter (U) are found between the peak of the emission in H? and the main ionizing source decreasing radially outwards within the region. Differences between the integrated and local values of the U tracers can be as high as ˜0.8 dex, notably when using [O III]??4959,5007/[O II]??3726,3729 and in the high surface brightness spaxels. [O II]??3726,3729/H? and [O III]??4959,5007/[O II]??3726,3729 yield similar local values for the ionization parameter, which are consistent with those expected from the integrated spectrum of an H II region ionized by a single star. The ratio [S II]??6717,6731/H? departs significantly from the range predicted by this scenario, indicating the complex ionization structure in GHIIRs. There is a significant scatter in derivations of the metallicity using strong line tracers as a function of position, caused by variations in the degree of ionization. The scatter is smaller for N2O3 which points to this tracer as a better metallicity tracer than N2. One interesting result emerges from our comparison between integrated and local line ratio values: measurements of the line ratios of GHIIRs in galaxies at distances ?25 Mpc may be dominated by the ionization conditions in their low surface brightness areas.

Monreal-Ibero, A.; Relaño, M.; Kehrig, C.; Pérez-Montero, E.; Vílchez, J. M.; Kelz, A.; Roth, M. M.; Streicher, O.

2011-05-01

187

Application of gas chromatography-hybrid chemical ionization mass spectrometry to the analysis of diclofenac in wastewater samples.  

PubMed

Hybrid chemical ionization (HCI), a new and useful alternative to conventional chemical ionization mass spectrometry, has been applied to the analysis of the pharmaceutical diclofenac in wastewater samples. This technique takes advantage of the high versatility of ion trap (IT) spectrometers combined with external ionization sources. In hybrid configuration, reagent ions are generated in the external source through electron ionisation (EI) of a reagent gas. These reagent ions are then drawn into the ion trap and only those selected are allowed to react with analytes eluting from the GC column. These ion-molecule reactions create analyte ions which are held in the ion trap. In this study ion-molecule reactions between C(3)F(5)(+) cations, generated from perfluorotributylamine (FC43), and diclofenac molecules have been investigated. The observed reaction products were [M+C(3)F(5)-H(2)O](+) adduct ions, which result from the initial electrophilic addition of C(3)F(5)(+) cations to the diclofenac molecule followed by the rapid loss of H(2)O. Further fragmentation of these ions by MS/MS yielded enough daughter ions for a reliable identification of diclofenac in complex matrices. The GC-HCI-MS/MS method applied to wastewater samples provided highly enhanced selectivity and sensibility, with a detection limit in real samples of 3.0 ng/L, for a solid-phase extraction (SPE) pre-concentration factor of 400. Other performance characteristics of the method, such as linearity and precision were also satisfactory. Finally, the method was successfully applied to the analysis of wastewater samples taken from the effluent of an urban sewage treatment plant (STP). PMID:16956617

Agüera, A; Mezcua, M; Mocholí, F; Vargas-Berenguel, A; Fernández-Alba, A R

2006-11-10

188

Determination of nitrosamines in water by gas chromatography/chemical ionization/selective ion trapping mass spectrometry.  

PubMed

A gas chromatography/mass spectrometry (GC/MS) method for determination of nine N-nitrosamines (NAs) in water is described. Two ionization modes, electron impact (EI) and chemical ionization (CI) with methanol, as well as different ion analysis techniques, i.e. full scan, selected ion storage (SIS) and tandem mass spectrometry (MS/MS) were tested. Chemical ionization followed by SIS resulted the mass spectrometric method of choice, with detection limits in the range of 1-2ng/L. Solid Phase Extraction (SPE) with coconut charcoal cartridges was applied to extract NAs from real samples, according EPA Method 521. Drinking water samples were collected from seven surface- and two groundwater treatment plants. Three surface water treatment plants were sampled before and after addition of O(3)/ClO(2) to observe the effect of disinfection on NAs' formation. N-nitrosodiethylamine (NDEA), n-nitrosodipropylamine (NDPA), n-nitrosomorpholine (NMOR) and n-nitrosodibutylamine (NDBA) were found up to concentrations exceeding three times the risk level of 10ng/L set by the California Department of Public Health. Because dermal adsorption has been recently indicated as a new contamination route of exposure to NAs for people who practice swimming activity, water samples from five swimming pools in the Bologna (Italy) area were collected. N-nitrosopyrrolidine (NPYR) was detected in all samples at concentrations larger than 50ng/L, likely as a disinfection by-product from the amino acid precursor proline, a main constituent of skin collagen. PMID:21377686

Pozzi, Romina; Bocchini, Paola; Pinelli, Francesca; Galletti, Guido C

2011-04-01

189

Pulsed discharge helium ionization detector with multiple combined bias/collecting electrodes for gas chromatography.  

PubMed

A pulsed discharge ionization detector (PDHID) with multiple combined bias/collecting electrodes (MC-PDHID) has been developed. Unlike most ionization detector designs with only one collecting electrode, the MC-PDHID builds multiple electrodes inside the detector cell. Each electrode serves as both a bias and a collecting electrode, thus gathering more information from the detector cell and improving PDHIP performance. The advantages of the MC-PDHID are: (1) sensitivity is increased by a factor of 2-3 times as compared with a single collecting electrode PDHID; (2) peak symmetry is improved, especially for narrow peaks; (3) it is possible to use a lower helium flow rate without compromising peak tailing; (4) linear dynamic range is increased by an order of magnitude through the calibration of electron and ion response factors; (5) certain groups of compounds can be identified. For example, if a trace amount of water is used as a dopant, the detector can identify alcohols and compounds with a hydrogen bond, since these compounds interact with the water coated on the wall in the detector cell which makes them stay in the detector cell longer than other compounds. In this research, the detector is characterized with different detector temperatures, flow rates, bias electrical potential arrangements, and bias potential polarities. PMID:23484651

Cai, Huamin; Stearns, Stanley D

2013-04-01

190

Detection of [OI] 6300 and Other Diagnostic Emission Lines in the Diffuse Ionized Gas of M33 with Gemini-North  

E-print Network

We present spectroscopic observations of diffuse ionized gas (DIG) in M33 near the HII region NGC 604. We present the first detection of [OI] 6300 in the DIG of M33, one of the critical lines for distinguishing photo- from shock ionization models. We measure [OI]/Ha in the range of 0.04 to 0.10 and an increase in this ratio with decreasing emission measure. Our measurements of [SII]/Ha and [NII]/Ha also rise with decreasing emission measure, while our [OIII]/Hb measurements remain fairly constant. We have one tentative detection of He I in the region of brightest emission measure, with a ratio of He I/Ha = 0.033 +- 0.019, indicating that the helium is at least partially ionized. We compare our observed emission line ratios to photoionization models and find that field star ionization models do not fit our data well. Leaky HII region models are consistent with our data, without the need to invoke additional ionization mechanisms to fit our [OI] or [OIII] measurements. The closest large HII region is NGC 604 and is therefore a likely candidate for the source of the ionizing photons for the gas in this region.

E. S. Voges; R. A. M. Walterbos

2006-05-09

191

Age, size, and position of H ii regions in the Galaxy. Expansion of ionized gas in turbulent molecular clouds  

E-print Network

This work aims at improving the current understanding of the interaction between H ii regions and turbulent molecular clouds. We propose a new method to determine the age of a large sample of OB associations by investigating the development of their associated H ii regions in the surrounding turbulent medium. Using analytical solutions, one-dimensional (1D), and three-dimensional (3D) simulations, we constrained the expansion of the ionized bubble depending on the turbulent level of the parent molecular cloud. A grid of 1D simulations was then computed in order to build isochrone curves for H ii regions in a pressure-size diagram. This grid of models allowed to date large sample of OB associations and was used on the H ii Region Discovery Survey (HRDS). Analytical solutions and numerical simulations showed that the expansion of H ii regions is slowed down by the turbulence up to the point where the pressure of the ionized gas is in a quasi-equilibrium with the turbulent ram pressure. Based on this result, we ...

Tremblin, P; Didelon, P; Raga, A C; Minier, V; Ntormousi, E; Pettitt, A; Pinto, C; Samal, M; Schneider, N; Zavagno, A

2014-01-01

192

A VUV photoionization measurement and ab-initio calculation of the ionization energy of gas phase SiO2  

SciTech Connect

In this work we report on the detection and vacuum-ultraviolet (VUV) photoionization of gas phase SiO2 generated in situ via laser ablation of silicon in a CO2 molecular beam. The resulting species are investigated by single photon ionization with tunable VUV synchrotron radiation and mass analyzed using reflectron mass spectrometry. Photoionization efficiency (PIE) curves are recorded for SiO and SiO2 and ionization energy estimates are revealed from such measurements. A state-to-state ionizationenergy of 12.60 (+-0.05) eV is recorded by fitting two prominent peaks in the PIE curve for the following process: 1SUM O-Si-O --> 2PRODg [O-Si-O]+. Electronic structure calculations aid in the interpretation of the photoionization process and allow for identification of the symmetric stretch of 2PRODg [O-Si-O]+ which is observed in the PIE spectrum to be 0.11 eV (890 cm-1) above the ground state of the cation and agrees with the 892 cm-1 symmetric stretch frequency calculated at the CCSD(T)/aug-cc-pVTZ level.

Kostko, Oleg; Ahmed, Musahid; Metz, Ricardo B.

2008-12-05

193

Tidal dwarf candidates in a sample of interacting galaxies. II. Properties and kinematics of the ionized gas  

NASA Astrophysics Data System (ADS)

We present low-resolution spectroscopy of the ionized gas in a sample of optical knots located along the tidal features of 14 interacting galaxies previously selected as candidate Tidal Dwarf Galaxies (TDGs). From redshift measurements, we are able to confirm their physical association with the interacting system in almost all cases. For most knots, the oxygen abundance does not depend on the blue luminosity. The average, 12+log (O/H) =8.34+/-0.20, is typical of TDGs and is comparable to that measured in the outer stellar disk of spirals from which they were formed. A few knots showing low metallicities are probably pre-existing low-mass companions. The estimated H? luminosity of the TDG candidates is higher than that of typical individual H Ii regions in spiral disks and is comparable to the global H? luminosity of dwarf galaxies. We find several instances of velocity gradients with amplitudes apparently larger than 100 km s-1 in the ionized gas in the tidal knots and discuss various possible origins for the large velocity amplitudes. While we can exclude tidal streaming motions and outflows, we cannot rule out projection effects with the current resolution. The velocity gradients could be indicative of the internal kinematic characteristic of self-gravitating objects. Higher resolution spectra are required to confirm whether the tidal knots in our sample have already acquired their dynamical independence and are therefore genuine Tidal Dwarf Galaxies. Based on observations collected at the European Southern Observatory, La Silla, Chile (ESO No 64.N-0361).Figures \\ref{fig:chart:AM0529-565} to \\ref{fig:chart:AM1325-292}, Table \\ref{tab:newTDGcandPhot} and Appendices A and B are only available in electronic form at http://www.edpsciences.org

Weilbacher, P. M.; Duc, P.-A.; Fritze-v. Alvensleben, U.

2003-01-01

194

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

195

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

196

Accurate Realizations of the Ionized Gas in Galaxy Clusters: Calibrating Feedback  

E-print Network

Using the full, three-dimensional potential of galaxy cluster halos (drawn from an N-body simulation of the current, most favored cosmology), the distribution of the X-ray emitting gas is found by assuming a polytropic equation of state and hydrostatic equilibrium, with constraints from conservation of energy and pressure balance at the cluster boundary. The resulting properties of the gas for these simulated redshift zero clusters (the temperature distribution, mass-temperature and luminosity-temperature relations, and the gas fraction) are compared with observations in the X-ray of nearby clusters. The observed properties are reproduced only under the assumption that substantial energy injection from non-gravitational sources has occurred. Our model does not specify the source, but star formation and AGN may be capable of providing this energy, which amounts to 3 to 5 x10^{-5} of the rest mass in stars (assuming ten percent of the gas initially in the cluster forms stars). With the method described here it is possible to generate realistic X-ray and Sunyaev-Zel'dovich cluster maps and catalogs from N-body simulations, with the distributions of internal halo properties (and their trends with mass, location, and time) taken into account.

Paul Bode; Jeremiah P. Ostriker; Jochen Weller; Laurie Shaw

2006-12-21

197

Pulsed discharge helium ionization detector : a new sensitive space detector for gas chromatography ?  

Microsoft Academic Search

Gas chromatography (GC) is a powerful analytical technique which has been widely used in the exploration of other planetary atmospheres and surfaces. It was part of the scientific payloads devoted to in situ chemical analysis of the soil of Mars, the atmosphere of Venus, and it is currently present in the Huygens probe en route to explore Titan's atmosphere as

C. Szopa; M. Cabane; D. Coscia; P. Coll; J. Eugenie; J. F. Brun; G. Israel

2003-01-01

198

The extent and content of low-ionization gas in galaxies  

Microsoft Academic Search

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

Donna Suzanne Womble

1992-01-01

199

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

200

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

201

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

202

A theoretical study of the gas-phase chemi-ionization reaction between uranium and oxygen atoms  

Microsoft Academic Search

The U+O chemi-ionization reaction has been investigated by quantum chemical methods. Potential-energy curves have been calculated for several electronic states of UO and UO+. Comparison with the available spectroscopic and thermodynamic values for these species is reported and a mechanism for the chemi-ionization reaction U+O-->UO++e- is proposed. The U+O and Sm+O chemi-ionization reactions are the first two metal-plus-oxidant chemi-ionization reactions

Jozef Paulovic; Laura Gagliardi; John M. Dyke; Kimihiko Hirao

2005-01-01

203

[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

204

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

205

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

206

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

207

Use of electron ionization and atmospheric pressure chemical ionization in gas chromatography coupled to time-of-flight mass spectrometry for screening and identification of organic pollutants in waters.  

PubMed

A new approach has been developed for multiclass screening of organic contaminants in water based on the use of gas chromatography coupled to hybrid quadrupole high-resolution time-of-flight mass spectrometry with atmospheric pressure chemical ionization (GC-(APCI)QTOF MS). The soft ionization promoted by the APCI source allows effective and wide-scope screening based on the investigation of the molecular ion and/or protonated molecule. This is in contrast to electron ionization (EI) where ionization typically results in extensive fragmentation, and diagnostic ions and/or spectra need to be known a priori to facilitate detection of the analytes in the raw data. Around 170 organic contaminants from different chemical families were initially investigated by both approaches, i.e. GC-(EI)TOF and GC-(APCI)QTOF, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and a notable number of pesticides and relevant metabolites. The new GC-(APCI)QTOF MS approach easily allowed widening the number of compounds investigated (85 additional compounds), with more pesticides, personal care products (UV filters, musks), polychloronaphthalenes (PCNs), antimicrobials, insect repellents, etc., most of them considered as emerging contaminants. Both GC-(EI)TOF and GC-(APCI)QTOF methodologies have been applied, evaluating their potential for a wide-scope screening in the environmental field. PMID:24674644

Portolés, Tania; Mol, Johannes G J; Sancho, Juan V; Hernández, Félix

2014-04-25

208

Molecular and ionized gas in the tidal tail in Stephan's Quintet  

NASA Astrophysics Data System (ADS)

We have mapped with the IRAM interferometer at Plateau de Bure (PdBI) the 12CO emission towards intergalactic star forming regions located in the tidal tail stemming from NGC 7319, in the Stephan's Quintet compact group of galaxies. The 13CO emission of the same region was observed with the IRAM 30 m telescope and optical spectroscopy of several HII regions in the area were obtained with the Calar Alto 3.5 m telescope.We recovered with the interferometer about 50% of the 12CO(1-0) total emission that had been earlier measured with single dish observations (Lisenfeld 2002, A&A, 394, 823), indicating that about half of the molecular gas is distributed on spatial scales larger than about 10-15 arcsec (corresponding to 4-6 kpc) to which PdBI is not sensitive. We find two main areas of CO emission: (i) an elongated region towards the area known as SQ B where a Tidal Dwarf Galaxy could currently be forming and (ii) a barely resolved area at the tip of the optical tidal arm. Both regions follow dust lanes visible on HST images and their CO peak coincides spatially exactly with the maximum of the H? line emission. In SQ B, there is furthermore very good kinematical agreement between the CO, H? and HI components. We conclude from these coincidences that the gaseous matter found in quantities in the area is physically associated to the optical tidal tail and thus that the intergalactic atomic hydrogen there was expelled from NGC 7319. Its origin had previously been much debated. Furthermore, the relatively high oxygen abundances (about solar) estimated from the optical spectra of the HII regions imply that the gas feeding the star formation originated from the inner regions of the parent galaxy. In SQ B, we derive from different tracers a star formation rate, corrected for dust extinction - which is important in the area - of 0.5 M?/yr, i.e. one of the highest values so far measured outside galaxies. The inferred molecular gas consumption time of 0.5 Gyr lies in the range of values found for spiral and starburst galaxies. On the other hand, the ratio of 12CO/13CO > 25 is much higher than the values found in disks of spiral galaxies. A relatively low opacity for the 12CO gas is the most likely reason.

Lisenfeld, U.; Braine, J.; Duc, P.-A.; Brinks, E.; Charmandaris, V.; Leon, S.

2004-11-01

209

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

210

Two-dimensional metallicity distribution of the ionized gas in NGC 628 and NGC 6946  

NASA Astrophysics Data System (ADS)

Aims: We present here two H II region catalogues with azimuthal resolution for the two grand design galaxies NGC 628 and NGC 6946. With the help of these catalogues, we study several properties of the star-forming processes occurring in spiral galaxies. Methods: We obtained direct imaging in the narrow-band filters centred at H?, H?, [O II]?3727, and [O III]??4959, 5007 and their respective continua. After the calibration and correction of the data, we obtained for each H II region the de-reddened fluxes in the aforementioned lines, the size, the H? equivalent width, and, using two different empirical calibrations, the metallicity. Employing a method based on the Delaunay triangulation, a two-dimensional (2D) representation of the metallicity was obtained. Results: Data for 209 H II regions of NGC 628 and 226 H II regions of NGC 6946 are obtained. The radial behaviours of the H? equivalent width, the excitation, and the oxygen abundance are derived. Two-dimensional representations of the metallicity and the excitation are calculated for the galaxies in the study. The two empirical calibrations of the metallicity are compared. Conclusions: The behaviours of the extinction and the H? equivalent width are similar to those presented in the literature. The oxygen abundance gradients obtained in this study agree with previously published values. However, more regions were examined than in previous studies. We find a difference of about 0.6 dex between the two empirical calibrations employed. Finally, the 2D representations of the metallicity reveal high metallicity knots in NGC 628, and for NGC 6946 a high metallicity azimuthal structure is discovered. These high metallicity regions seem to be linked to the arms of the galaxies and are probably produced by an increase in the temperature of the ionizing clusters in the H II regions, which may be linked to variations in the initial mass functions of the galaxies between the arm and interarm regions. Full Tables 4-9 are available in electronic form at http://www.aanda.org

Cedrés, B.; Cepa, J.; Bongiovanni, Á.; Castañeda, H.; Sánchez-Portal, M.; Tomita, A.

2012-09-01

211

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

212

Observation of gas-phase molecular dications formed from neutral organics in solution via qemical electron-transfer reactions by using electrospray Ionization Mass Spectrometry.  

PubMed

The first observation of organic dications formed by multiple electron loss in electrospray mass spectra is reported. The dications of ?-carotene, canthaxanthine, cobalt(II) octaethylporphyrin, and nicke(II) octaethylporphyrin were created in solution via chemical electrontransfer reactions and detected in the gas phase by electrospray ionization mass spectrometry (ES-MS) using a flow-injection experiment. The analytes were injected into a flowing solvent-oxidant stream (10 ?L/min) composed of dried methylene chloride containing ? 0.1% by volume trifluoroacetic acid and 0.1% by volume antimony pentafluoride (SbF5). The dications created in this oxidizing solvent system were preserved for detection by rapidly transferring them from the reactive solvent-oxidant system to the gas phase, where, in the absence of the solvent system, they were "long-lived" and amenable to mass analysis. This work demonstrates means to produce ions novel to ES-MS and means to detect and study by ES-MS species that are short-lived in solution. In addition, this work shows that electrospray ionization can potentially be used to generate gas-phase dications for mass spectrometric study that are difficult to produce directly from gas-phase neutrals by other ionization techniques (e.g., M(2+) from ?-carotene). PMID:24221970

Van Berkel, G J; Asano, K G; McLuckey, S A

1994-07-01

213

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

214

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

215

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

216

Application of gas chromatography with a pulsed discharge helium ionization detector for measurements of molecular hydrogen in the atmosphere.  

PubMed

The Earth's troposphere contains approximately 160 Tg H2 with an average surface mixing ratio approximately 530 nmole mole(-1) (ppb) and lifetime of 2 years. Atmospheric H2 is typically measured using gas chromatography (GC) followed by hot mercuric oxide reduction detection (GC-HgO). Here we describe an alternate method using GC with a pulsed-discharge helium ionization detector (HePPD). HePPD is a universal detector; when applied to H2, the GC-HePDD provides a wide linear range (0.3% over a range of 2000 ppb), a detection limit of approximately 0.03 pg, high precision (0.12%) and a stable response (+/-1.6% over nearly one year). HePPD is compared to HgO reduction using a suite of gravimetrically prepared reference gases spanning remote to urban concentrations. The method is excellent for atmospheric measurements as it provides a wide linear range with high precision, stability and reproducibility. We suggest these characteristics will improve the ability to maintain reference gases and improve measurements of atmospheric H2, thus providing better constraints on potential future changes in its sources and sinks. PMID:19452897

Novelli, P C; Crotwell, A M; Hall, B D

2009-04-01

217

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

218

Ionized Gas Kinematics at High Resolution. II. Discovery of a Double Infrared Cluster in II Zw 40  

NASA Astrophysics Data System (ADS)

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 ?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 ?m [S IV] emission line with effective spectral resolutions, including thermal broadening, of ~25 and ~3 km s-1 and spatial resolution ~1''. The line profile shows two distinct, spatially coextensive, emission features. The stronger feature is at galactic velocity and has FWHM 47 km s-1. The second feature is ~44 km s-1 redward of the first and has FWHM 32 km s-1. We argue that these are two giant embedded clusters, and estimate their masses to be ?3 × 105 M ? and ?1.5 × 105 M ?. 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; Turner, Jean; Lacy, John; Greathouse, Thomas; Lahad, Ohr

2013-04-01

219

[Determination of naphthenic acids in distillates of crude oil by gas chromatography/chemical ionization-mass spectrometry].  

PubMed

The petroleum carboxylic acids in 200-420 degrees C distillate of crude oil were separated by the extraction with column chromatography on an anion exchange resin. The effect of the composition and structure of naphthenic acids on separation were studied by the infra-red (IR) spectroscopic techniques. Naphthenic acids and iso-butane reagent gas were introduced into the ion source for chemical ionization, in which the ions represented by [M + C4H9]+ were used to calculate the relative molecular mass for each acid. Based on the mass spectra of pure fatty and naphthenic acids, in combination with the z-series formula CnH(2n + z)O2, the naphthenic acids can be classified into fatty, mono-, bi- ... hexa-cyclic types. The results indicated that the relative molecular mass range of naphthenic acids in this distillates was 170-510, and the carbon number range was C10-C35. The contents of bi-cyclic and tri-cyclic naphthenic acids were higher than others. PMID:15712901

Lü, Zhenbo; Tian, Songbai; Zhai, Yuchun; Sun, Yanwei; Zhuang, Lihong

2004-05-01

220

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

221

A theoretical study of the gas-phase chemi-ionization reaction between uranium and oxygen atoms  

NASA Astrophysics Data System (ADS)

The U +O chemi-ionization reaction has been investigated by quantum chemical methods. Potential-energy curves have been calculated for several electronic states of UO and UO +. Comparison with the available spectroscopic and thermodynamic values for these species is reported and a mechanism for the chemi-ionization reaction U +O?UO++e- is proposed. The U +O and Sm +O chemi-ionization reactions are the first two metal-plus-oxidant chemi-ionization reactions to be studied theoretically in this way.

Paulovi?, Jozef; Gagliardi, Laura; Dyke, John M.; Hirao, Kimihiko

2005-04-01

222

A theoretical study of the gas-phase chemi-ionization reaction between uranium and oxygen atoms.  

PubMed

The U+O chemi-ionization reaction has been investigated by quantum chemical methods. Potential-energy curves have been calculated for several electronic states of UO and UO(+). Comparison with the available spectroscopic and thermodynamic values for these species is reported and a mechanism for the chemi-ionization reaction U+O-->UO(+)+e(-) is proposed. The U+O and Sm+O chemi-ionization reactions are the first two metal-plus-oxidant chemi-ionization reactions to be studied theoretically in this way. PMID:15847532

Paulovic, Jozef; Gagliardi, Laura; Dyke, John M; Hirao, Kimihiko

2005-04-01

223

CO/H$_2$, C/CO, OH/CO, and OH/O$_2$ in Dense Interstellar Gas: From High Ionization to Low Metallicity  

E-print Network

We present numerical computations and analytic scaling relations for cold-gas, ionization-driven interstellar ion-molecule chemistry, down to the very low metallicities (gas parcels, and solve the chemical rate equations for steady-state conditions for a wide range of ionization parameters, $\\zeta/n$, and metallicties, $Z'$. We find that the OH abundances are always maximal at the H-to-H$_2$ conversion points, and that large OH abundances persist at very low metallicities even when the hydrogen is predominantly atomic. We study the OH/O$_2$, C/CO and OH/CO abundance ratios, from large to small, as functions of $\\zeta/n$ and $Z'$. Cold dense star-forming clouds for the Pop-II generation may have been OH-dominated and atomic rather than CO-dominated and molecular.

Bialy, Shmuel

2014-01-01

224

The Ionized Gas and Nuclear Environment in NGC 3783. I. Time-averaged 900 Kilosecond Chandra Grating Spectroscopy  

NASA Astrophysics Data System (ADS)

We present results from a 900 ks exposure of NGC 3783 with the High-Energy Transmission Grating Spectrometer on board the Chandra X-Ray Observatory. The resulting X-ray spectrum, which covers the 0.5-10 keV energy range, has the best combination of signal-to-noise ratio and resolution ever obtained for an AGN. This spectrum reveals absorption lines from H-like and He-like ions of N, O, Ne, Mg, Al, Si, and S. There are also possible absorption lines from H-like and He-like Ar and Ca as well as H-like C. We also identify inner-shell absorption from lower ionization ions such as Si VII-Si XII and S XII-S XIV. The iron absorption spectrum is very rich; L-shell lines of Fe XVII-Fe XXIV are detected, as well as probable resonance lines from Fe XXV. A strong complex of M-shell lines from iron ions is also detected in the spectrum. The absorption lines are blueshifted relative to the systemic velocity by a mean velocity of -590+/-150 km s-1. We resolve many of the absorption lines, and their mean FWHM is 820+/-280 km s-1. We do not find correlations between the velocity shifts or the FWHMs with the ionization potentials of the ions. Most absorption lines show asymmetry, having more extended blue wings than red wings. In O VII we have resolved this asymmetry to be from an additional absorption system at approximately -1300 km s-1. The two X-ray absorption systems are consistent in velocity shift and FWHM with the ones identified in the UV lines of C IV, N V, and H I. Equivalent width measurements for all absorption and emission lines are given and column densities are calculated for several ions. We resolve the narrow Fe K? line at 6398.2+/-3.3 eV to have an FWHM of 1720+/-360 km s-1, which suggests that this narrow line may be emitted from the outer part of the broad-line region or the inner part of the torus. We also detect a ``Compton shoulder'' redward of the narrow Fe K? line, which indicates that it arises in cold, Compton-thick gas.

Kaspi, Shai; Brandt, W. N.; George, Ian M.; Netzer, Hagai; Crenshaw, D. Michael; Gabel, Jack R.; Hamann, Frederick W.; Kaiser, Mary Elizabeth; Koratkar, Anuradha; Kraemer, Steven B.; Kriss, Gerard A.; Mathur, Smita; Mushotzky, Richard F.; Nandra, Kirpal; Peterson, Bradley M.; Shields, Joseph C.; Turner, T. J.; Zheng, Wei

2002-08-01

225

The merging dwarf galaxy UM 448: chemodynamics of the ionized gas from VLT integral field spectroscopy  

NASA Astrophysics Data System (ADS)

Using Very Large Telescope/Fibre Large Array Multi Element Spectrograph optical integral field unit observations, we present a detailed study of UM 448, a nearby blue compact galaxy (BCG) previously reported to have an anomalously high N/O abundance ratio. New Technology Telescope/Superb-Seeing Imager images reveal a morphology suggestive of a merger of two systems of contrasting colour, whilst our H? emission maps resolve UM 448 into three separate regions that do not coincide with the stellar continuum peaks. UM 448 exhibits complex emission line profiles, with most lines consisting of a narrow [full width at half-maximum (FWHM) ? 100 km s-1], central component, an underlying broad component (FWHM ˜ 150-300 km s-1) and a third, narrow blueshifted component. Radial velocity maps of all three components show signs of solid body rotation across UM 448, with a projected rotation axis that correlates with the continuum morphology of the galaxy. A spatially resolved, chemodynamical analysis, based on the [O iii] ??4363, 4959, [N ii] ?6584, [S ii] ??6716, 6731 and [Ne iii] ?3868 line maps, is presented. Whilst the eastern tail of UM 448 has electron temperatures (Te) that are typical of BCGs, we find a region within the main body of the galaxy where the narrow and broad [O iii] ?4363 line components trace temperatures differing by 5000 K and oxygen abundances differing by 0.4 dex. We measure spatially resolved and integrated ionic and elemental abundances for O, N, S and Ne throughout UM 448, and find that they do not agree, possibly due the flux weighting of Te from the integrated spectrum. This has significant implications for abundances derived from long-slit and integrated spectra of star-forming galaxies in the nearby and distant universe. A region of enhanced N/O ratio is indeed found, extended over a ˜0.6 kpc2 region within the main body of the galaxy. Contrary to previous studies, however, we do not find evidence for a large Wolf-Rayet (WR) population, and conclude that WR stars alone cannot be responsible for producing the observed N/O excess. Instead, the location and disturbed morphology of the N-enriched region suggest that interaction-induced inflow of metal-poor gas may be responsible.

James, B. L.; Tsamis, Y. G.; Barlow, M. J.; Walsh, J. R.; Westmoquette, M. S.

2013-01-01

226

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

227

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

NASA Astrophysics Data System (ADS)

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 singly and multiply charged vanadium oxide cluster anions including VxOy n- and VxOyCln- ions (x = 1-14, y = 2-36, n = 1-3), protonated clusters, and ligand-bound polyoxovanadate anions. The 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 as well as their protonated analogs. Accurate mass measurement using a high-resolution LTQ/Orbitrap mass spectrometer (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 much less abundant 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 originating from solution and from in-source CID. 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 anions originating directly from solution produced comparatively complex CID spectra. These results are consistent with the formation of more stable structures of VxOyCl and VxOy anions through low-energy CID. Furthermore, our results demonstrate that solution-phase synthesis of one precursor cluster anion combined with gas-phase CID is an efficient approach for the top-down synthesis of a wide range of singly and multiply charged gas-phase metal oxide cluster anions for subsequent investigations of structure and reactivity using mass spectrometry and ion spectroscopy techniques.

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

2013-09-01

228

Development, validation and application of a method to analyze phenols in water samples by solid phase micro extraction-gas chromatography-flame ionization detector  

Microsoft Academic Search

In this work the development, validation and application of method using Solid Phase Microexctration (SPME) for the analyses of five pollutants (phenol, 2-nitrophenol, 2,4-dimethylphenol, 2,4-dichlorophenol and 4-chloro, 3-methyl phenol) in supplying water, using gas chromatography (GC) with flame ionization detector (FID) is described. The optimal conditions obtained for SPME were: fiber type: Poliacrylate (PA); extraction time: 40 minutes; extraction temperature:

Fernando M. Lanças; Igor R. B. Olivares; Priscila M. Alves

2007-01-01

229

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

230

Evaluation of biodegradation behavior of poly(?-caprolactone) with controlled terminal structure by pyrolysis-gas chromatography and matrix-assisted laser desorption\\/ionization mass spectrometry  

Microsoft Academic Search

The enzymatic degradation behavior of poly(?-caprolactone) (PCL) with an ?-benzyloxy terminal during an enzymatic degradation test using cholesterol esterase was evaluated complementarily by pyrolysis-gas chromatography (Py-GC) in the presence of tetramethylammonium hydroxide (TMAH) and matrix-assisted laser desorption\\/ionization-mass spectrometry (MALDI-MS). On the pyrograms of PCL samples, dimethyl derivative of ?-caprolactone and some related products originating from ?-caprolactone (?-CL) units were observed

Hiroaki Sato; Yusuke Kiyono; Hajime Ohtani; Shin Tsuge; Hiromi Aoi; Keigo Aoi

2003-01-01

231

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

232

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

233

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

Microsoft Academic Search

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

Jia-Lin Wang; Cheng-Hsiu Wu

2002-01-01

234

Hydride spectroscopy of the diffuse interstellar medium: new clues on the gas fraction in molecular form and cosmic ray ionization rate in relation to H3+.  

PubMed

The Herschel-guaranteed time key programme PRobing InterStellar Molecules with Absorption line Studies (PRISMAS)(1) is providing a survey of the interstellar hydrides containing the elements C, O, N, F and Cl. As the building blocks of interstellar molecules, hydrides provide key information on their formation pathways. They can also be used as tracers of important physical and chemical properties of the interstellar gas that are difficult to measure otherwise. This paper presents an analysis of two sight-lines investigated by the PRISMAS project, towards the star-forming regions W49N and W51. By combining the information extracted from the detected spectral lines, we present an analysis of the physical properties of the diffuse interstellar gas, including the electron abundance, the fraction of gas in molecular form, and constraints on the cosmic ray ionization rate and the gas density. PMID:23028164

Gerin, M; Levrier, F; Falgarone, E; Godard, B; Hennebelle, P; Le Petit, F; De Luca, M; Neufeld, D; Sonnentrucker, P; Goldsmith, P; Flagey, N; Lis, D C; Persson, C M; Black, J H; Goicoechea, J R; Menten, K M

2012-11-13

235

Determination of deltamethrin in rat plasma and brain using gas chromatography-negative chemical ionization mass spectrometry.  

PubMed

Quantification of the pyrethroid deltamethrin (DLM) in small (100 ?L) biological samples from rodents is essential for toxicokinetic studies of trace levels of the insecticide in foods. Such empirical kinetic data are necessary for construction of valid physiologically-based toxicokinetic models. There are no validated methods in the literature for determining deltamethrin in 100 ?L plasma and brain samples. Plasma and brain samples were stabilized using sodium fluoride as an esterase inhibitor, and the DLM was extracted by protein precipitation using acetonitrile and phosphoric acid. The samples were vortexed, centrifuged, evaporated to dryness, and reconstituted in toluene prior to injection into a gas chromatograph equipped with a quadrupole mass analyzer. Samples were ionized via electron capture in the negative ion mode using methane, and the molecular ion and fragment ions of DLM were monitored using Selected-Ion Monitoring (SIM) for quantitation and verification of the analyte. Cis-permethrin was used as the internal standard for the method, which was validated according to current US FDA guidelines. Linearity was determined between 0.3 and 1,000 ng/mL, with a limit of detection of 150 pg/mL. The intra- and inter-batch variation for precision (as % relative standard deviation, RSD) and accuracy (as % bias) of the method were better than 20% at the limit of quantitation and better than 15% across the remaining linear range (n=18), with recoveries of 113% and 68% for plasma and brain respectively. Benchtop stability, autosampler stability, and freeze/thaw stability studies of the method (over a 3-day freeze/thaw cycle) were found to be within the acceptance criteria of 20% RSD and bias. This optimized method was applied to the quantitation of DLM in plasma and brain homogenate samples obtained up to 12h after oral dosing of Sprague-Dawley rats with 1mg DLM/kg body weight. PMID:24814001

Gullick, Darren; Popovici, Andrew; Young, Holly C; Bruckner, James V; Cummings, Brian S; Li, Pei; Bartlett, Michael G

2014-06-01

236

[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

237

Method development for the characterization of biofuel intermediate products using gas chromatography with simultaneous mass spectrometric and flame ionization detections.  

PubMed

Accurate analytical methods are required to develop and evaluate the quality of new renewable transportation fuels and intermediate organic liquid products (OLPs). Unfortunately, existing methods developed for the detailed characterization of petroleum products, are not accurate for many of the OLPs generated from non-petroleum feedstocks. In this study, a method was developed and applied to the detailed characterization of complex OLPs formed during triacylglyceride (TG) pyrolysis which is the basis for generating one class of emerging biofuels. This method uses gas chromatography coupled simultaneously with flame ionization and mass spectrometry detectors (GC-FID/MS). The FID provided accurate quantification of carbonaceous species while MS enabled identification of unknown compounds. A programed temperature vaporizer using a 25 °C, 0.1 min, 720 °C min(-1), 350 °C, 5 min temperature program is employed which minimizes compound discrimination better than the more commonly utilized split/splitless injector, as verified with injections at 250 and 350 °C. Two standard mixtures featuring over 150 components are used for accurate identification and a designed calibration standard accounts for compound discrimination at the injector and differing FID responses of various classes of compounds. This new method was used to identify and quantify over 250 species in OLPs generated from canola oil, soybean oil, and canola methyl ester (CME). In addition to hydrocarbons, the method was used to quantify polar (upon derivatization) and unidentified species, plus the unresolved complex mixture that has not typically been determined in previous studies. Repeatability of the analytical method was below 5% RSD for all individual components. Using this method, the mass balance was closed for samples derived from canola and soybean oil but only ca. 77 wt% of the OLP generated from CME could be characterized. The ability to close the mass balance depended on sample origin, demonstrating the need for an accurate quantification method for biofuels at various stages of production. PMID:22245174

S?ávová, Jana; Stahl, Danese C; Seames, Wayne S; Kubátová, Alena

2012-02-10

238

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

239

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

240

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

241

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

242

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

243

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

244

Fabrication of low-pressure low-voltage field ionization gas sensor using pure and Al-doped ZnO nanowires  

NASA Astrophysics Data System (ADS)

Zinc oxide nanowires were synthesized by a simple chemical method using zinc acetate dihydrate, polyvinylpyrrolidone (PVP) and DI water as precursor, capping and solvent, respectively. Aluminum-doped ZnO nanowires were also synthesized by adding AlCl3 during the growth process. Both types of nanowires were used to fabricate a novel field ionization based gas sensor. The high sensitivity in low pressures, low working voltages, very low recovery time and good selectivity are the main advantages of these fabricated sensors. Electrical characteristics of the fabricated sensors were investigated while being exposed to several gases. Scanning electron microscopy (SEM) was used to analyze the nanowires structures.

Haghighi, N.; Abdi, Y.; Arzia, E.

2012-06-01

245

Pulsed large volume injection gas chromatography coupled with electron-capture negative ionization quadrupole mass spectrometry for simultaneous determination of typical halogenated persistent organic pollutants  

Microsoft Academic Search

A pulsed large-volume injection gas chromatography coupled with electron-capture negative ionization quadrupole mass spectrometry\\u000a (pLVI-GC\\/ECNI-qMS) was developed for the simultaneous determination of typical halogenated persistent organic pollutants (H-POPs).\\u000a By monitoring the characteristic ions of large mass-to-charge ratio (m\\/z) for each of the H-POPs rather than the chlorine and\\/or bromine ions, this method avoided the possible interferences arising\\u000a from the H-POPs

Yuli Zhao; Limin Yang; Qiuquan Wang

2007-01-01

246

Application of gas chromatography-(triple quadrupole) mass spectrometry with atmospheric pressure chemical ionization for the determination of multiclass pesticides in fruits and vegetables.  

PubMed

A multi-residue method for the determination of 142 pesticide residues in fruits and vegetables has been developed using a new atmospheric pressure chemical ionization (APCI) source for coupling gas chromatography (GC) to tandem mass spectrometry (MS). Selected reaction monitoring (SRM) mode has been applied, acquiring three transitions for each compound. In contrast to the extensive fragmentation typically obtained in classical electron ionization (EI), the soft APCI ionization allowed the selection of highly abundant protonated molecules ([M+H](+)) as precursor ions for most compounds. This was favorable for both sensitivity and selectivity. Validation of the method was performed in which both quantitative and qualitative parameters were assessed using orange, tomato and carrot samples spiked at two levels, 0.01 and 0.1mg/kg. The QuEChERS method was used for sample preparation, followed by a 10-fold dilution of the final acetonitrile extract with a mixture of hexane and acetone. Recovery and precision were satisfactory in the three matrices, at both concentration levels. Very low limits of detection (down 0.01?g/kg for the most sensitive compounds) were achieved. Ion ratios were consistent and identification according to EU criteria was possible in 80% (0.01mg/kg) to 96% (0.1mg/kg) of the pesticide/matrix combinations. The method was applied to the analysis of various fruits and vegetables from the Mediterranean region of Spain. PMID:24070626

Cherta, Laura; Portolés, Tania; Beltran, Joaquim; Pitarch, Elena; Mol, Johannes G J; Hernández, Félix

2013-11-01

247

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

248

Resonance Ionization spectroscopy  

NASA Astrophysics Data System (ADS)

The paper presents a retrospective view on the appearance and early development of Resonance Ionization Spectroscopy (RIS) and briefly reviews its basic principles and unique characteristics. Most of the paper concentrates on RIS applications that are most active at present time including on-line facilities with particle accelerators, counting noble gas atoms, ultrasensitive and highly selective techniques, analytical systems which use RIS in combination with thermal atomization (TARIS), laser atomization (LARIS), ion sputtering (SIRIS) and collisional ionization (LEI).

Bekov, G. I.

1995-04-01

249

Resonance Ionization spectroscopy  

SciTech Connect

The paper presents a retrospective view on the appearance and early development of Resonance Ionization Spectroscopy (RIS) and briefly reviews its basic principles and unique characteristics. Most of the paper concentrates on RIS applications that are most active at present time including on-line facilities with particle accelerators, counting noble gas atoms, ultrasensitive and highly selective techniques, analytical systems which use RIS in combination with thermal atomization (TARIS), laser atomization (LARIS), ion sputtering (SIRIS) and collisional ionization (LEI)

Bekov, G. I. [Atom Sciences, Inc., 114 Ridgeway Center, Oak Ridge, TN, 37830 (United States); Institute of Spectroscopy Russian Academy of Sciences, Troitsk, Moscow Region 142092 (Russian Federation)

1995-04-01

250

Application of specific response factors in the gas chromatographic analysis of methyl esters of fatty acids with flame ionization detectors  

Microsoft Academic Search

The relative responses for flame ionization detectors in the analysis of the longer chain fatty acid methyl esters are shown\\u000a to correlate with the theoretical responses based on weight percent content of “active” carbon. While particularly affecting\\u000a estimation of the shorter chain length saturated fatty acids, these corrections have a less marked effect on the estimation\\u000a of unsaturated fatty acids.

R. G. Ackman; J. C. Sipos

1964-01-01

251

The effective ionization coefficients and electron drift velocities in gas mixtures of CF3I with N2 and CO2 obtained from Boltzmann equation analysis  

NASA Astrophysics Data System (ADS)

The electron swarm parameters including the density-normalized effective ionization coefficients (?-?)/N and the electron drift velocities Ve are calculated for a gas mixture of CF3I with N2 and CO2 by solving the Boltzmann equation in the condition of a steady-state Townsend (SST) experiment. The overall density-reduced electric field strength is from 100 Td to 1000 Td (1 Td = 10-17 V·cm2), while the CF3I content k in the gas mixture can be varied over the range from 0% to 100%. From the variation of (?-?)/N with the CF3I mixture ratio k, the limiting field strength (E/N)lim for each CF3I concentration is derived. It is found that for the mixtures with 70% CF3I, the values of (E/N)lim are essentially the same as that for pure SF6. Additionally, the global warming potential (GWP) and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of application in the gas insulation of power equipment.

Deng, Yun-Kun; Xiao, Deng-Ming

2013-03-01

252

Alfvén ionization in exoplanetary atmospheres  

NASA Astrophysics Data System (ADS)

Observations of continuous radio and sporadic X-ray emission from low-mass objects suggest such objects harbour an atmospheric, localized plasma. For lowmass objects, the degree of thermal ionization is insufficient to qualify the ionized gas as a plasma, posing the question: what ionization processes can efficiently produce the required plasma? We propose Alfvén ionization as a simple mechanism for producing localized pockets of ionized gas in the atmosphere, having sufficiently large degrees of ionization (? 10^-7) that they constitute plasmas. We outline the criteria required for Alfvén ionization to occur and justify it's applicability in the atmospheres of low-mass objects such as giant gas planets, brown dwarfs and M-dwarfs for 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 ranging from 10^-6-1 can be obtained. Observable consequences include continuum Bremsstrahlung emission, superimposed with spectral lines from the plasma ion species (e.g. He, Mg, H2 or CO lines). Forbidden lines are also expected from the metastable population as a consequence of the Penning Effect. The presence of an atmospheric plasma opens the door to a multitude of plasma and chemical processes not yet considered in current atmospheric models.

Stark, C. R.; Helling, Ch.; Diver, D. A.; Rimmer, P. B.

2013-09-01

253

Effect of ionization on infrared and electronic absorption spectra of methyl and ethyl formate in the gas phase and in astrophysical H2O ice: a computational study.  

PubMed

This work reports infrared and electronic absorption spectra of trans and gauche conformers of neutral ethyl formate, trans and cis conformers of neutral methyl formate, their ions in the gas phase, and neutral ethyl and methyl formate in astrophysical H(2)O ice. The second-order Møller-Plesset perturbation (MP2) method with TZVP basis set has been used to obtain ground-state geometries. An influence of ice on vibrational frequencies of neutral ethyl and methyl formate was obtained using integral equation formalism polarizable continnum model (IEFPCM). Significant shift in vibrational frequencies for neutral methyl and ethyl formate when studied in H(2)O ice and upon ionization is observed. Rotational and distortion constants for neutral ethyl and methyl formate from this work are in excellent agreement with the available experimental values. Electronic absorption spectra of conformers of ethyl and methyl formate and their ions are obtained using time-dependent density functional method (TDDFT). The nature of electronic transitions is also identified. We suggested lines especially good to detect these molecules in interstellar medium. Using these lines, we can identify the conformers of ethyl and methyl formate in gas phase and H(2)O ice in interstellar medium. This comparative study should provide useful guidelines to detect conformers of ethyl and methyl formate and their ions in gas phase and neutral molecules in H(2)O ice in different astronomical environment. PMID:21504217

Naganathappa, Mahadevappa; Chaudhari, Ajay

2011-05-12

254

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

255

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

E-print Network

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 con?firming 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; 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

2013-01-01

256

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

E-print Network

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 con?firming 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.

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

2013-11-27

257

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

258

Trace analysis of residual methyl methanesulfonate, ethyl methanesulfonate and isopropyl methanesulfonate in pharmaceuticals by capillary gas chromatography with flame ionization detection.  

PubMed

A capillary gas chromatographic method using flame ionization detection was developed and validated for the trace analysis (ppm level) of methyl methanesulfonate, ethyl methanesulfonate, and isopropyl methanesulfonate in pharmaceutical drug substance. The method utilizes a megabore capillary column with bonded and crosslinked polyethylene glycol stationary phase. A dissolve-and-injection approach was adopted for sample introduction in a splitless mode. The investigated sample solvents include acetonitrile, ethyl acetate, methylene chloride, 1,2-dichloromethane, and toluene. Aqueous mixtures of acetonitrile and water can also be used as sample solvent. A limit of detection of about 1 microg/g (1 ppm) and limit of quantitation of 5 microg/g (5 ppm) were achieved for the mesylate esters in drug substance samples. The method optimization and validation are also discussed in this paper. PMID:15387202

Li, Weiyong

2004-08-13

259

Rapid analysis of six phthalate esters in wine by ultrasound-vortex-assisted dispersive liquid-liquid micro-extraction coupled with gas chromatography-flame ionization detector or gas chromatography-ion trap mass spectrometry.  

PubMed

An Ultrasound-Vortex-Assisted Dispersive Liquid-Liquid Micro-Extraction (USVADLLME) procedure coupled with Gas Chromatography-Flame Ionization Detector (GC-FID) or Gas Chromatography-Ion Trap Mass Spectrometry (GC-IT/MS) is proposed for rapid analysis of six phthalate esters in hydroalcoholic beverages (alcohol by volume, alc vol(-1), ?40%). Under optimal conditions, the enrichment factor of the six analytes ranges from 220- to 300-fold and the recovery from 85% to 100.5%. The limit of detection (LOD) and limit of quantification (LOQ) are ?0.022 ?g L(-1) and ?0.075 ?g L(-1), respectively. Intra-day and inter-day precisions expressed as relative standard deviation (RSD), are ?8.2% and ?7.0%, respectively. The whole proposed methodology has demonstrated to be simple, reproducible and sensible for the determination of trace phthalate esters in red and white wine samples. PMID:23498123

Cinelli, Giuseppe; Avino, Pasquale; Notardonato, Ivan; Centola, Angela; Russo, Mario Vincenzo

2013-03-26

260

Quantification in gas chromatography: prediction of flame ionization detector response factors from combustion enthalpies and molecular structures.  

PubMed

In a previous report, we validated the use of a database that compiled the relative response factors of flavor and fragrance compounds under standard GC conditions for a flame ionization detector. Here we investigate the prediction of unknown response factors from the molecular structure by using combustion enthalpies. In a first step, this enthalpy was well-predicted with either ab initio calculation or multiple linear regression based on the molecular formula. In a second step, good correlation was observed between these combustion enthalpies and experimental relative response factors, and so the response factors were predictable from only the molecular formula. With a database of 351 compounds, about 60% of them exhibited a difference of less than 5% between the predicted and experimental relative response factors and about 80% exhibited a difference of less than 10%. PMID:20700911

de Saint Laumer, Jean-Yves; Cicchetti, Esmeralda; Merle, Philippe; Egger, Jonathan; Chaintreau, Alain

2010-08-01

261

Quantification in Gas Chromatography: Prediction of Flame Ionization Detector Response Factors from Combustion Enthalpies and Molecular Structures.  

PubMed

In a previous report, we validated the use of a database that compiled the relative response factors of flavor and fragrance compounds under standard GC conditions for a flame ionization detector. Here we investigate the prediction of unknown response factors from the molecular structure by using combustion enthalpies. In a first step, this enthalpy was well-predicted with either ab initio calculation or multiple linear regression based on the molecular formula. In a second step, good correlation was observed between these combustion enthalpies and experimental relative response factors, and so the response factors were predictable from only the molecular formula. With a database of 351 compounds, about 60% of them exhibited a difference of less than 5% between the predicted and experimental relative response factors and about 80% exhibited a difference of less than 10%. PMID:20698579

de Saint Laumer, Jean-Yves; Cicchetti, Esmeralda; Merle, Philippe; Egger, Jonathan; Chaintreau, Alain

2010-08-01

262

?-Cyclodextrin-bonded silica particles as the solid-phase extraction medium for the determination of phenol compounds in water samples followed by gas chromatography with flame ionization and mass spectrometry detection  

Microsoft Academic Search

A new absorbent for solid-phase extraction (SPE) was prepared by a ?-cyclodextrin bonded silica stationary phase (CDS) has been applied to determine the concentrations of phenol compounds in water samples. SPE of selected phenolic compounds from aqueous samples were performed using 250mg CDS. The determination was subsequently carried out by gas chromatography–flame ionization detection (GC–FID) and gas chromatography–mass spectrometry (GC–MS).

Hakim Faraji

2005-01-01

263

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

Microsoft Academic Search

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 21st century technology. This methodology requires the production and calibration of empirical relations between the different line temperatures that should supersede currently used ones based on very simple, and poorly

Guillermo F. Hägele; Enrique Pérez-Montero; Ángeles I. Díaz; Elena Terlevich; Roberto Terlevich

2006-01-01

264

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

265

Formation of tungstate-containing cluster ions by polyoxotungstate anions under matrix-assisted laser desorption/ionization conditions in the gas phase.  

PubMed

The gas-phase studies of transition-metal oxides continue to attract interest as such oxides are being used as catalysts in various oxidation processes. In this paper, singly negatively charged heteropolyoxotungstate and isopolyoxotungstate ion clusters were produced from Keggin-type polyoxotungstates by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR MS). It was found that the ion series [(PO(3))(WO(3))(n)](-), [(WO(3))(n)](-) and [(OH)(WO(3))(n)](-) were the main fragment ions in the mass spectra and the matrix greatly influenced the resulting cluster ion abundances. [(PO(3))(WO(3))(3)](-), [(WO(3))(3)](-) and [(OH)(WO(3))(4)](-) were the most intense ions in each series when 2-(4-hydroxyphenylazo)benzoic acid was the matrix, whereas [(PO(3))(WO(3))(4)](-), [(WO(3))(6)](-) and [(OH)(WO(3))(4)](-) were the most intense when dithranol (DIT) was the matrix. In addition, a new kind of hybrid ion [W(2)C(14)H(7)O(8)](-) was produced through the reaction of DIT and [(OH)(WO(3))](-) in the plume of the gas phase. These results highlight the utility of the MALDI-FT method for obtaining novel ion clusters and also show the stability of these clusters. PMID:22095498

Bai, Yun-Peng; Liu, Shu; Song, Feng-Rui; Liu, Zhi-Qiang; Liu, Shu-Ying

2011-12-15

266

Plasma production via field ionization  

NASA Astrophysics Data System (ADS)

Plasma production via field ionization occurs when an incoming particle beam is sufficiently dense that the electric field associated with the beam ionizes a neutral vapor or gas. Experiments conducted at the Stanford Linear Accelerator Center explore the threshold conditions necessary to induce field ionization by an electron beam in a neutral lithium vapor. By independently varying the transverse beam size, number of electrons per bunch, or bunch length, the radial component of the electric field is controlled to be above or below the threshold for field ionization. Additional experiments ionized neutral xenon and neutral nitric oxide by varying the incoming beam’s bunch length. A self-ionized plasma is an essential step for the viability of plasma-based accelerators for future high-energy experiments.

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

2006-10-01

267

Resonance Ionization spectroscopy  

SciTech Connect

The paper presents a retrospective view on the appearance and early development of Resonance Ionization Spectroscopy (RIS) and briefly reviews its basic principles and unique characteristics. Most of the paper concentrates on RIS applications that are most active at present time including on-line facilities with particle accelerators, counting noble gas atoms, ultrasensitive and highly selective techniques, analytical systems which use RIS in combination with thermal atomization (TARIS), laser atomization (LARIS), ion sputtering (SIRIS) and collisional ionization (LEI). {copyright} 1995 {ital American} {ital Institute} {ital of} {ital Physics}

Bekov, G.I. [Atom Sciences, Inc., 114 Ridgeway Center, Oak Ridge, Tennessee, 37830 (United States)]|[Institute of Spectroscopy Russian Academy of Sciences, Troitsk, Moscow Region 142092 (Russian Federation)

1995-04-01

268

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

269

Ionizing radiation  

NASA Technical Reports Server (NTRS)

The penetrating ionizing space radiations are found to be extremely diverse in the energy range of both their particulate and their electromagnetic components. Radiation terms and measures and ionizing radiation classes and sources are presented. Whole body radiation effects are examined, including radiation intensity and rate effectiveness factors. Radiation effects on specific body systems, such as blood, skin, visual, and reproductive systems are also discussed.

Warren, S.; Grahn, D.

1973-01-01

270

Gas chromatography-atmospheric pressure chemical ionization-time of flight mass spectrometry for profiling of phenolic compounds in extra virgin olive oil.  

PubMed

A new analytical approach based on gas chromatography coupled to atmospheric pressure chemical ionization-time of flight mass spectrometry was evaluated for its applicability for the analysis of phenolic compounds from extra-virgin olive oil. Both chromatographic and MS parameters were optimized in order to improve the sensitivity and to maximize the number of phenolic compounds detected. We performed a complete analytical validation of the method with respect to its linearity, sensitivity, precision, accuracy and possible matrix effects. The LODs ranged from 0.13 to 1.05ppm for the different tested compounds depending on their properties. The RSDs for repeatability test did not exceed 6.07% and the accuracy ranged from 95.4% to 101.5%. To demonstrate the feasibility of our method for analysis of real samples, we analyzed the extracts of three different commercial extra-virgin olive oils. We have identified unequivocally a number of phenolic compounds and obtained quantitative information for 21 of them. In general, our results show that GC-APCI-TOF MS is a flexible platform which can be considered as an interesting tool for screening, structural assignment and quantitative determination of phenolic compounds from virgin olive oil. PMID:21241992

García-Villalba, Rocío; Pacchiarotta, Tiziana; Carrasco-Pancorbo, Alegría; Segura-Carretero, Antonio; Fernández-Gutiérrez, Alberto; Deelder, André M; Mayboroda, Oleg A

2011-02-18

271

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

272

The determination of cyclophosphamide and its metabolites in blood plasma as stable trifluoroacetyl derivatives by electron capture chemical ionization gas chromatography/mass spectrometry.  

PubMed

A method is described for the determination of the antitumour drug cyclophosphamide and six stable metabolites in plasma of cancer patients, namely dechloroethyl-cyclophosphamide, 4-keto-cyclophosphamide, carboxy-phosphamide, alcophosphamide, nor-nitrogen mustard and the N-chloroethyl-1,3-oxazolidine-2-one, as methyl and/or trifluoroacetyl derivatives by single ion monitoring gas chromatography/mass spectrometry, mostly in the electron capture chemical ionization mode. The isolation of most metabolites was performed by solid-phase C-18 extraction in weakly acidic medium. The phosphoramide mustard isolated under these conditions decomposes readily to the nor-nitrogen mustard during derivatization. The original nor-nitrogen mustard and the chloroethyl-1,3-oxazolidine-2-one were isolated by liquid extraction with ethyl acetate in alkaline medium. Recoveries of 75-99% were measured using spiked blank plasma samples. Quantitation of metabolites in patient plasma samples was performed using two sets of calibration curves for the concentration ranges of 1-100 ng and 0.1-10 micrograms of metabolite per millilitre of original plasma. PMID:8148406

Momerency, G; Van Cauwenberghe, K; Slee, P H; Van Oosterom, A T; De Bruijn, E A

1994-03-01

273

Analysis of the thin layer of Galactic warm ionized gas in the range 20 < l < 30 deg, -1.5 < b < +1.5 deg  

E-print Network

We present an analysis of the thin layer of Galactic warm ionized gas at an angular resolution ~ 10'. This is carried out using radio continuum data at 1.4 GHz, 2.7 GHz and 5 GHz in the coordinate region 20 < l < 30 deg, -1.5 < b < +1.5 deg. For this purpose, we evaluate the zero level of the 2.7 and 5 GHz surveys using auxiliary data at 2.3 GHz and 408 MHz. The derived zero level corrections are T_{zero}(2.7 GHz)=0.15 +/- 0.06 K and T_{zero}(5 GHz)=0.1 +/- 0.05 K. We separate the thermal (free-free) and non-thermal (synchrotron) component by means of a spectral analysis performed adopting an antenna temperature spectral index -2.1 for the free-free emission, a realistic spatial distribution of indices for the synchrotron radiation and by fitting, pixel-by-pixel, the Galactic spectral index. We find that at 5 GHz, for |b| = 0 deg, the fraction of thermal emission reaches a maximum value of 82%, while at 1.4 GHz, the corresponding value is 68%. In addition, for the thermal emission, the analysis indicates a dominant contribution of the diffuse component relative to the source component associated with discrete HII regions.

R. Paladini; G. De Zotti; R. D. Davies; M. Giard

2005-04-25

274

Fluorohydrogenate cluster ions in the gas phase: electrospray ionization mass spectrometry of the [1-ethyl-3-methylimidazolium(+)][F(HF)2.3(-)] ionic liquid.  

PubMed

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. PMID:24313327

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

2013-12-27

275

Optimization of comprehensive two dimensional gas chromatography-flame ionization detection-quadrupole mass spectrometry for the separation of octyl- and nonylphenol isomers.  

PubMed

In the present work, the separation of complex nonylphenol technical mixtures has been optimized using comprehensive two-dimensional gas chromatography coupled with a flame ionization detector and quadrupole mass spectrometer (GC×GC-qMS), using valve-based modulator. The optimization of GC×GC-qMS has been carried out using experimental designs and the optimal separation was obtained at the following conditions: 1st column flow: 1mL/min; 2nd column flow: 17.75 mL/min, oven temperature ramp: 1°C/min, modulation period: 1.5s and discharge time: 0.12s. These values have been used to determinate the previously synthesized 22OP, 33OP, 363NP and 22NP isomers in two different nonylphenol technical mixtures. Percentages obtained were as follows: 4.86% and 0.59% for 22OP, 4.91% and 2.82% for 33OP, 11.79% and 7.71% for 363NP and 2.28% and 1.98% for 22NP, in Fluka and Aldrich mixtures, respectively. The values obtained for NP isomers are in good agreement with the literature. PMID:21489544

Vallejo, A; Olivares, M; Fernández, L A; Etxebarria, N; Arrasate, S; Anakabe, E; Usobiaga, A; Zuloaga, O

2011-05-20

276

Detection and quantification of 1,N6-ethenoadenine in human urine by stable isotope dilution capillary gas chromatography/negative ion chemical ionization/mass spectrometry.  

PubMed

1,N(6)-Ethenoadenine (epsilonAde) is a promutagenic lesion detected in tissue DNA; it has been shown that epsilonAde can be repaired by human DNA glycosylases, and it is expected to be excreted in urine. In this paper, we present for the first time detection and accurate quantification of epsilonAde in human urine samples by a highly sensitive and specific stable isotope dilution gas chromatography/negative ion chemical ionization/mass spectrometric assay (GC/NICI/MS). Analysis by GC/NICI/MS includes adduct enrichment by a solid phase extraction column, followed by electrophore labeling and postderivatization cleanup. Using selective ion monitoring mode, the assay allows quantification of 0.5 pg of epsilonAde in as little as 0.1 mL of the urine sample, which is equivalent to corresponding concentration quantification limit of 31 pM. Using this assay, concentrations of epsilonAde in the 24 h urine samples of 23 healthy individuals were determined, which ranged from 0 to 124 pg/mL. After we adjusted for creatinine, a statistically significant correlation was found between epsilonAde excretion and cigarette smoking in males (p = 0.03). Thus, this stable isotope dilution GC/NICI/MS assay offers a sensitive and accurate quantification of urinary epsilonAde as a potential biomarker for oxidative damage of DNA and repair. PMID:12971797

Chen, Hauh-Jyun Candy; Chiu, Wei-Loong

2003-09-01

277

Screening of pesticides and polycyclic aromatic hydrocarbons in feeds and fish tissues by gas chromatography coupled to high-resolution mass spectrometry using atmospheric pressure chemical ionization.  

PubMed

This paper reports a wide-scope screening for detection and identification of pesticides and polycyclic aromatic hydrocarbons (PAHs) in feeds and fish tissues. QuEChERS sample treatment was applied, using freezing as an additional cleanup. Analysis was carried out by gas chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry with atmospheric pressure chemical ionization (GC-(APCI) QTOF MS). The qualitative validation was performed for over 133 representative pesticides and 24 PAHs at 0.01 and 0.05 mg/kg. Subsequent application of the screening method to aquaculture samples made it possible to detect several compounds from the target list, such as chlorpyrifos-methyl, pirimiphos-methyl, and ethoxyquin, among others. Light PAHs (?4 rings) were found in both animal and vegetable samples. The reliable identification of the compounds was supported by accurate mass measurements and the presence of at least two representative m/z ions in the spectrum together with the retention time of the peak, in agreement with the reference standard. Additionally, the search was widened to include other pesticides for which standards were not available, thanks to the expected presence of the protonated molecule and/or molecular ion in the APCI spectra. This could allow the detection and tentative identification of other pesticides different from those included in the validated target list. PMID:24559176

Nácher-Mestre, Jaime; Serrano, Roque; Portolés, Tania; Berntssen, Marc H G; Pérez-Sánchez, Jaume; Hernández, Félix

2014-03-12

278

Analysis of isopropyl para-toluenesulphonate in palm-based esters by gas chromatography with flame ionization detection and confirmed with mass spectrometry.  

PubMed

A simple and rapid gas chromatography (GC) method with flame ionization detector was developed for detection of isopropyl para-toluenesulphonate (IPTS) in palm-based isopropyl palmitate (IPP) and isopropyl myristate (IPM). The method involved spiking the IPP/IPM samples with IPTS and directly injecting the spiked samples into GC without undergoing clean-up steps. The calibration curves for IPTS showed good linearity with coefficient correlation of 0.9999 for six-point calibration from 0.5 to 50 ?g mL(-1) and 0.9996 for six-point calibration from 0.5 to 200 ?g mL(-1) . IPTS recoveries from IPP were 98.6-103.5% with relative standard deviation (RSD) of 0.40-2.80%, whereas recoveries from IPM were 97.0-107.2% with RSD of 0.42-4.21%. The identity of IPTS recovered from the isopropyl esters was confirmed by a GC-mass spectrometer detector. The method was successfully applied to the analyses of IPTS in commercial samples. It was found that there were IPTS in the range of 34.8-1303.0 ?g g(-1) in the palm-based esters for some of the samples analysed. PMID:22994145

Tay, B Y P

2013-02-01

279

Ionization Modeling Astrophysical Gaseous Structures. I. The Optically Thin Regime  

E-print Network

We present a code for modelling the ionization conditions of optically thin astrophysical gas structures. Given the gas hydrogen density, equilibrium temperature, elemental abundances, and the ionizing spectrum, the code solves the equilibrium ionization fractions and number densities for all ions from hydrogen to zinc. The included processes are photoionization, Auger ionization, direct collisional ionization, excitation auto-ionization, charge exchange ionization, two-body radiative recombination, dielectronic recombination, and charge exchange recombination. The ionizing spectrum can be generalized to include the ultraviolet background (UVB) and/or Starburst99 stellar populations of various masses, ages, metallicities, and distances. The ultimate goal with the code is to provide fast computation of the ionization conditions of gas in N-body + hydrodynamics cosmological simulations, in particular adaptive mesh refinement codes, in order to facilitate absorption line analysis of the simulated gas for compari...

Churchill, Christopher W; Medina, Amber; Vliet, Jacob R Vander

2014-01-01

280

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

281

Mapping the ionization state of laser-irradiated Ar gas jets with multiwavelength monochromatic x-ray imaginga)  

NASA Astrophysics Data System (ADS)

Two-dimensional monochromatic images of fast-electron stimulated Ar K? and He-? x-ray self-emission have recorded a time-integrated map of the extent of Ar?6+ and Ar16+ ions, respectively, within a high density (1020 cm-3 atomic density) Ar plasma. This plasma was produced by irradiating a 2 mm wide clustering Ar gas jet with an ultrahigh intensity (1019 W/cm2, 50 TW) Ti:sapphire laser operating at 800 nm. Spherically bent quartz crystals in the 200 (for K?) and 201 (for He-?) planes were used as near-normal incidence reflective x-ray optics. We see that a large (830 ?m long) region of plasma emits K? primarily along the laser axis, while the He-? emission is confined to smaller hot spot (230 ?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 indicate that the centroids of the K? and He-? emission regions are separated by approximately 330 ?m along the laser axis.

Kugland, N. L.; Döppner, T.; Kemp, A.; Schaeffer, D.; Glenzer, S. H.; Niemann, C.

2010-10-01

282

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

283

The Relationship between the Dense Neutral and Diffuse Ionized Gas in the Thick Disks of Two Edge-on Spiral Galaxies  

NASA Astrophysics Data System (ADS)

We present high-resolution, optical images (BVI + H?) 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 ~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? 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? 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. Based on observations obtained with the NASA/ESA Hubble Space Telescope operated at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Also, based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the US, Italy, and Germany. LBT Corporation partners are the University of Arizona, on behalf of the Arizona University System; Instituto Nazionale do Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute of Potsdam, and Heidelberg University; Ohio State University, and the Research Corporation, on behalf of the University of Notre Dame, the University of Minnesota, and the University of Virginia. Also, based on observations obtained by the WIYN Observatory which is a joint facility of the University of Wisconsin-Madison, Yale University, Indiana University, and the National Optical Astronomy Observatories.

Rueff, Katherine M.; Howk, J. Christopher; Pitterle, Marissa; Hirschauer, Alec S.; Fox, Andrew J.; Savage, Blair D.

2013-03-01

284

Development and validation of a gas chromatography–negative chemical ionization tandem mass spectrometry method for the determination of ethyl glucuronide in hair and its application to forensic toxicology  

Microsoft Academic Search

Ethyl glucuronide (EtG) is a minor and direct metabolite of ethanol. EtG is incorporated into the growing hair allowing retrospective investigation of chronic alcohol abuse. In this study, we report the development and the validation of a method using gas chromatography–negative chemical ionization tandem mass spectrometry (GC–NCI-MS\\/MS) for the quantification of EtG in hair. EtG was extracted from about 30mg

Hicham Kharbouche; Frank Sporkert; Stéphanie Troxler; Marc Augsburger; Patrice Mangin; Christian Staub

2009-01-01

285

Parts per quadrillion level ultra-trace determination of polar and nonpolar compounds via solvent-free capillary microextraction on surface-bonded sol–gel polytetrahydrofuran coating and gas chromatography–flame ionization detection  

Microsoft Academic Search

Sol–gel polytetrahydrofuran (poly-THF) coating was developed for high-sensitivity sample preconcentration by capillary microextraction (CME). Parts per quadrillion (ppq) level detection limits were achieved for both polar and nonpolar analytes through sample preconcentration on sol–gel poly-THF coated microextraction capillaries followed by gas chromatography (GC) analysis of the extracted compounds using a flame ionization detector (FID). The sol–gel coating was in situ

Abuzar Kabir; Christina Hamlet; Abdul Malik

2004-01-01

286

Development of simultaneous gas chromatography–mass spectrometric and liquid chromatography–electrospray ionization mass spectrometric determination method for the new designer drugs, N-benzylpiperazine (BZP), 1-(3-trifluoromethylphenyl)piperazine (TFMPP) and their main metabolites in urine  

Microsoft Academic Search

To prove the intake of recently controlled designer drugs, N-benzylpiperazine (BZP) and 1-(3-trifluoromethylphenyl)piperazine (TFMPP), a simple, sensitive and reliable method which allows us to simultaneously detect BZP, TFMPP and their major metabolite in human urine has been established by coupling gas chromatography–mass spectrometry (GC–MS) and high-performance liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS). GC–MS accompanied by trifluoroacetyl (TFA) derivatization and LC–MS

Hiroe Tsutsumi; Munehiro Katagi; Akihiro Miki; Noriaki Shima; Tooru Kamata; Mayumi Nishikawa; Kunio Nakajima; Hitoshi Tsuchihashi

2005-01-01

287

Ionizing radiation  

NASA Technical Reports Server (NTRS)

The biological effects of ionizing radiation encountered in space are considered. Biological experiments conducted in space and some experiences of astronauts during space flight are described. The effects of various levels of radiation exposure and the determination of permissible dosages are discussed.

Tobias, C. A.; Grigoryev, Y. G.

1975-01-01

288

Pulsed large volume injection gas chromatography coupled with electron-capture negative ionization quadrupole mass spectrometry for simultaneous determination of typical halogenated persistent organic pollutants.  

PubMed

A pulsed large-volume injection gas chromatography coupled with electron-capture negative ionization quadrupole mass spectrometry (pLVI-GC/ECNI-qMS) was developed for the simultaneous determination of typical halogenated persistent organic pollutants (H-POPs). By monitoring the characteristic ions of large mass-to-charge ratio (m/z) for each of the H-POPs rather than the chlorine and/or bromine ions, this method avoided the possible interferences arising from the H-POPs themselves and from complex matrices encountered frequently in current GC/qMS methods; and allowed, on the other hand, the use of (13)C-labeled and perdeuterated analogues as internal standards for reliable quantification. pLVI up to 120 microL improved the instrumental detection limits down to pg-fg mL(-1), comparable to or lower than those obtained by the recognized GC/high-resolution MS methods reported so far. The H-POPs including 12 polybrominated diphenyl ethers, 1 polybrominated biphenyl, 10 polychlorinated biphenyls (PCBs), 4 hexachlorocyclohexane isomers, and hexachlorobenzene were involved in this study. The method developed demonstrated good linearity (r(2) = 0.9904-0.9999) within 0.5 to 50,000 pg mL(-1) for PCBs and 0.05 to 5000 pg mL(-1) for other H-POPs, and was satisfactory in terms of both repeatability (0.07%-2.2%) and reproducibility (2.1%-8.4%). It was validated by analyzing a NIST standard reference material SRM-1946 of Lake Superior fish tissue with low 0.01 to 63 pg g(-1) method detection limits, and successfully applied to the determination of the H-POPs in five reference materials of different matrices. PMID:17533137

Zhao, Yuli; Yang, Limin; Wang, Qiuquan

2007-08-01

289

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

290

Optical ionization detector  

DOEpatents

An optical ionization detector wherein a beam of light is split so that one arm passes through a fiber optics and the other arm passes through a gas-filled region, and uses interferometry to detect density changes in a gas when charged particles pass through it. The gas-filled region of the detector is subjected to a high electric field and as a charged particle traverses this gas region electrons are freed from the cathode and accelerated so as to generate an electron avalanche which is collected on the anode. The gas density is effected by the electron avalanche formation and if the index or refraction is proportional to the gas density the index will change accordingly. The detector uses this index change by modulating the one arm of the split light beam passing through the gas, with respect to the other arm that is passed through the fiber optic. Upon recombining of the beams, interference fringe changes as a function of the index change indicates the passage of charged particles through the gaseous medium.

Wuest, Craig R. (Danville, CA); Lowry, Mark E. (Castro Valley, CA)

1994-01-01

291

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

PubMed

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

Schellin, Manuela; Popp, Peter

2006-01-27

292

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

Microsoft Academic Search

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

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

293

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

Microsoft Academic Search

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

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

1996-01-01

294

VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies. III. The atlas of the stellar and ionized gas distribution  

NASA Astrophysics Data System (ADS)

Context. Luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) are much more numerous at higher redshifts than locally, dominating the star-formation rate density at redshifts ~1-2. Therefore, they are important objects in order to understand how galaxies form and evolve through cosmic time. Local samples provide a unique opportunity to study these objects in detail. Aims: We aim to characterize the morphologies of the stellar continuum and the ionized gas (H?) emissions from local sources, and investigate how they relate with the dynamical status and IR-luminosity of the sources. Methods: We use optical (5250-7450 Å) integral field spectroscopic (IFS) data for a representative sample of 38 sources (31 LIRGs and 7 ULIRGs), taken with the VIMOS instrument on the VLT. Results: We present an atlas of IFS images of continuum emission, H? emission, and H? equivalent widths for the sample. The morphologies of the H? emission are substantially different from those of the stellar continuum. The H? images frequently reveal extended structures that are not visible in the continuum, such as HII regions in spiral arms, tidal tails, rings, bridges, of up to few kpc from the nuclear regions. The morphologies of the continuum and H? images are studied on the basis of the C2 kpc parameter, which measures the concentration of the emission within the central 2 kpc. The C2 kpc values found for the H? images are higher than those of the continuum for the majority (85%) of the objects in our sample. On the other hand, most of the objects in our sample (~62%) have more than half of their H? emission outside the central 2 kpc. No clear trends are found between the values of C2 kpc and the IR-luminosity of the sources. On the other hand, our results suggest that the star formation in advance mergers and early-stage interactions is more concentrated than in isolated objects. Finally, we compared the H? and infrared emissions as tracers of the star-formation activity. We find that the star-formation rates derived using the H? luminosities generally underpredict those derived using the IR luminosities, even after accounting for reddening effects.

Rodríguez-Zaurín, J.; Arribas, S.; Monreal-Ibero, A.; Colina, L.; Alonso-Herrero, A.; Alfonso-Garzón, J.

2011-03-01

295

K-shell ionization of O4+ and C2+ ions in fast collisions with H2 and He gas targets  

NASA Astrophysics Data System (ADS)

Cross sections for 1s ionization of the 1s22s2 and 1s22s2p3P (metastable) states of C2+ and O4+ ions in 0.5-1.8 MeV/u collisions with H2 and He targets were measured using projectile Auger electron spectroscopy at 0°. Calculations of the K-shell ionization cross section ?K were performed including contributions from projectile-electron-target-nucleus interactions (?enI) within a plane-wave Born approximation (PWBA), and contributions from projectile-electron-target-electron interactions (?eeI) within an impulse approximation (IA). The theoretical total cross section ?K=?enI+?eeI was found to be in overall agreement with the K-shell ionization measurements indicating a contribution of up to ~30% due to electron-electron interactions. Separate screening-antiscreening calculations of ?K were also performed and found to be in overall agreement with our data. Additionally, our PWBA-IA ionization calculation was also tested for H-like projectiles and found to be in agreement with recently published data. These results suggest that the IA calculation of ?eeI when combined with a PWBA calculation of ?enI is quite adequate for describing K-shell ionization.

Lee, D. H.; Zouros, T. J. M.; Sanders, J. M.; Richard, P.; Anthony, J. M.; Wang, Y. D.; McGuire, J. H.

1992-08-01

296

Pulsed discharge helium ionization detector  

Microsoft Academic Search

A pulsed discharge helium ionization detector (PDHID) (patent pending) for gas chromatography has been developed. This detector uses a non-radioactive pulsed high voltage discharge source for generation of electrons and pulsed collection of these electrons. We have evaluated this detector for the analysis of a wide range of chemical compounds. In this paper the analytes are passed through the discharge

W. E. Wentworth; S. V. Vasnin; S. D. Stearns; C. J. Meyer

1992-01-01

297

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

298

Molecular Hydrogen in the Ionized Region of Planetary Nebulae  

Microsoft Academic Search

This paper presents an analysis of the concentration of hydrogen molecules inside the ionized region of planetary nebulae (PNs). The equations corresponding to the ionization and chemical equilibria of H, H+, H-, H2, H+2, and H+3 are coupled with the equations of ionization and thermal balance for a photoionized atomic gas. A total of 40 different reactions related to the

Isabel Aleman; Ruth Gruenwald

2004-01-01

299

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

300

Sources of artefacts in the electrospray ionization mass spectra of saturated diacylglycerophosphocholines: From condensed phase hydrolysis reactions through to gas phase intercluster reactions  

Microsoft Academic Search

The mass spectra of diacylglycerophosphocholine phospholipids comprised of saturated fatty acids (1,2-dipentanoyl-sn-glycero-3-phosphocholine\\u000a (D5PC); 1,2-dihexanoyl-sn-glycero-3-phosphocholine (D6PC), and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (D14PC)) are sensitive\\u000a to the electrospray ionization (ESI) conditions. When fresh solutions of phospholipid in 10 mM ammonium acetate are subjected\\u000a to ESI, protonated oligomeric clusters, [DxPCn+H]+ (x=5, 6, and 14) are observed in the following different types of mass spectrometers: 3D-quadrupole ion

Patrick F. James; Matthew A. Perugini; Richard A. J. O’Hair

2006-01-01

301

Laserspray Ionization, a New Atmospheric Pressure MALDI Method for Producing Highly Charged Gas-phase Ions of Peptides and Proteins Directly from Solid Solutions*  

PubMed Central

The first example of a matrix-assisted laser desorption/ionization (MALDI) process producing multiply charged mass spectra nearly identical to those observed with electrospray ionization (ESI) is presented. MALDI is noted for its ability to produce singly charged ions, but in the experiments described here multiply charged ions are produced by laser ablation of analyte incorporated into a common MALDI matrix, 2,5-dihydroxybenzoic acid, using standard solvent-based sample preparation protocols. Laser ablation is known to produce matrix clusters in MALDI provided a threshold energy is achieved. We propose that these clusters (liquid droplets) are highly charged, and under conditions that produce sufficient matrix evaporation, ions are field-evaporated from the droplets similarly to ESI. Because of the multiple charging, advanced mass spectrometers with limited mass-to-charge range can be used for protein characterization. Thus, using an Orbitrap mass spectrometer, low femtomole quantities of proteins produce full-range mass spectra at 100,000 mass resolution with <5-ppm mass accuracy and with 1-s acquisition. Furthermore, the first example of protein fragmentation using electron transfer dissociation with MALDI is presented. PMID:19955086

Trimpin, Sarah; Inutan, Ellen D.; Herath, Thushani N.; McEwen, Charles N.

2010-01-01

302

Characterization of low-molecular weight iodine-terminated polyethylenes by gas chromatography/mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with the use of derivatization.  

PubMed

Gas chromatography/mass spectrometry (GC/MS) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry, in conjunction with various derivatization approaches, have been applied to structure determination of individual oligomers and molecular-mass distributions (MMD) in low-molecular mass polyethylene having an iodine terminus. Direct GC/MS analysis has shown that the samples under investigation composed of polyethyelene-iodides (major components) and n-alkanes. Exchange reaction with methanol in the presence of NaOH gave rise to methoxy-derivatives and n-alkenes. Electron ionization mass spectra have shown that the former contained terminal methoxy groups indicating the terminal position of the iodine atom in the initial oligomers. MMD parameters have been determined with the aid of MALDI mass spectrometry followed by preliminary derivatization-formation of covalently bonded charge through the reaction of iodides with triphenylphosphine, trialkylamines, pyridine or quinoline. The mass spectra revealed well-resolved peaks for cationic parts of derivatized oligomers allowing the determination of MMD. The latter values have been compared with those calculated from GC/MS data. PMID:24308197

Zaikin, Vladimir G; Borisov, Roman S; Polovkov, Nikolai Yu; Zhilyaev, Dmitry I; Vinogradov, Aleksei A; Ivanyuk, Aleksei V

2013-01-01

303

Ionized oxygen around starforming galaxies .  

NASA Astrophysics Data System (ADS)

We consider the evolution of metal-enriched gas exposed to a superposition of time-dependent radiation field of a nearby starburt galaxy and nearly invariant (on timescales 100 Myr) extragalactic ionization background. We study the evolution of ionic species depending on the galactic mass and star formation rate, and derive conditions for the highly ionized oxygen, OVI, to appear in extended galactic haloes in absorption or emission spectra. We have found that the maximum OVI fraction can reach ˜ 0.4-0.6 under the action of both ionizing radiation field, which is typical in haloes of starforming galaxies, and the extragalactic background, the fraction remains high in a wide temperature range. We study the dependence of the OVI ion fraction on gas density and found that for the typical density of the circumgalactic gas, n˜ (0.5-2)× 10-4 cm-3 the OVI fraction is higher than ˜ 0.1 at distances r˜ 50-120 kpc. We have shown that the OVI fraction is high enough that even for ˜ 0.1 Z_? metallicity we can explain large OVI column densities (log [N(OVI), {cm-2]} ˜ 14.5 - 15.3) observed in the haloes of staforming galaxies by Tumlinson et al. (2011). Thus, the requirements to the sources of oxygen supply into the extended haloes become reasonably conservative.

Vasiliev, E. O.; Ryabova, M. V.; Shchekinov, Yu. A.

304

New Automated and High-Throughput Quantitative Analysis of Urinary Ketones by Multifiber Exchange-Solid Phase Microextraction Coupled to Fast Gas Chromatography/Negative Chemical-Electron Ionization/Mass Spectrometry  

PubMed Central

The present research is focused on automation, miniaturization, and system interaction with high throughput for multiple and specific Direct Immersion-Solid Phase Microextraction/Fast Gas Chromatography analysis of the urinary ketones. The specific Mass Spectrometry instrumentation, capable of supporting such the automated changeover from Negative Chemical to Electron Ionization mode, as well as the automation of the preparation procedure by new device called MultiFiber Exchange, through change of the fibers, allowed a friendly use of mass spectrometry apparatus with a number of advantages including reduced analyst time and greater reproducibility (2.01–5.32%). The detection limits for the seven ketones were less than 0.004?mg/L. For an innovative powerful meaning in high-throughput routine, the generality of the structurally informative Mass Spectrometry fragmentation patterns together with the chromatographic separation and software automation are also investigated. PMID:20628512

Pacenti, Marco; Dugheri, Stefano; Traldi, Pietro; Degli Esposti, Filippo; Perchiazzi, Nicola; Franchi, Elena; Calamante, Massimo; Kikic, Ireneo; Alessi, Paolo; Bonacchi, Alice; Salvadori, Edoardo; Arcangeli, Giulio; Cupelli, Vincenzo

2010-01-01

305

The Flatness and Sudden Evolution of the Intergalactic Ionizing Background  

E-print Network

The ionizing background of cosmic hydrogen is an important probe of the sources and absorbers of ionizing radiation, their evolution and relationship, in the post-reionization universe. Previous studies show that the ionization rate should be very sensitive to changes in the source population: as the emissivity rises, absorbers shrink in size, increasing the ionizing mean free path and, hence, the ionizing background. By contrast, observations of the ionizing background find a very flat evolution from z~2-5, before falling precipitously at z~6. We resolve this discrepancy by pointing out that, at z~2-5, neutral absorbers are associated with the same collapsed halos that additionally host ionizing galactic sources. Thus, an increasing abundance of galaxies is compensated for by a corresponding increase in the absorber population, which moderates the instability in the ionizing background. However, by z~5-6, gas outside of halos dominates the absorption, the coupling between sources and absorbers is lost, and t...

Muñoz, Joseph A; Davies, Frederick B; Furlanetto, Steven R

2014-01-01

306

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...

307

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 for oxidation of SO2 to SO3 (sulfuric acid production, SO2 removal), selective reduction of NOx with NH3

Rocca, Jorge J.

308

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

309

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

310

Screening of beta-blockers in human serum by ion-pair chromatography and their identification as methyl or acetyl derivatives by gas chromatography-mass spectrometry.  

PubMed

A simultaneous screening method for atenolol, acebutolol, metoprolol, oxprenolol, alprenolol and propranolol by ion-pair chromatography with a column-switching technique was developed. The serum samples were purified using either liquid-liquid extraction or solid-phase extraction methods. The pretreatment of the samples consisted of hydrolysis and protein precipitation. The drug separation was on either octadecylsilica or polymer-based alkyl column material. Binary eluent mixtures containing methanol and a buffer solution with a quaternary ammonium salt as an ion-pair former were used. Detection of the compounds in liquid chromatographic analysis was based on ultraviolet spectra. The effects of methanol, two buffers and the ion-pair former on the retention of the compounds were studied. The determination limits ranged from nanograms to micrograms in the ion-pair chromatographic method, depending on the drug studied. Identification was based on the mass spectra or, if necessary, on selected-ion monitoring spectra of either the methylated or the acetylated compounds obtained by means of gas chromatography-electron impact or negative chemical ionization mass spectrometry. The detection limits for the identified compounds were in the picogram range. The matrix effect was strong, and this resulted in determination limits in the nanogram range with the scan method. PMID:8095938

Sirén, H; Saarinen, M; Hainari, S; Lukkari, P; Riekkola, M L

1993-02-19

311

High resolution UV resonance enhanced two-photon ionization spectroscopy with mass selection of biologically relevant molecules in the gas phase  

NASA Astrophysics Data System (ADS)

The high resolution Doppler-free resonance-enhanced two-photon ionization (R2PI) spectroscopy with mass selection of jet-cooled (2-12 K) molecular species is a powerful experimental method providing comprehensive information on both isolated molecules and molecular clusters. We have demonstrated for the first time that this technique can be applied to large molecules and provides detailed information on their conformational structure. It allows rotationally resolved (FWHM = 70 MHz) spectra of the vibronic bands of the S1<--S0 electronic transition of the studied molecular systems to be measured. A specially designed computer-assisted fitting routine based on genetic algorithms is used to determine their rotational constants in the ground and excited electronic states, respectively, and the transition moment ratio. To interpret the experimental information and to discriminate and unambiguously assign the observed approach to the study of the neurotransmitter molecule, ephedrine. The results elucidate the role of the intramolecular hydrogen bonds stabilizing the respective conformations and affecting their intrinsic properties.

Chervenkov, S.; Wang, P. Q.; Karaminkov, R.; Chakraborty, T.; Braun, Juergen E.; Neusser, Hans J.

2005-04-01

312

Ionization structure of the nebula NGC 6857  

NASA Astrophysics Data System (ADS)

We present the results of our spectroscopic studies of the nebula NGC 6857 located in a region of current star formation. Data on the surface brightness distribution in the central region of the nebula (˜60? × 60?) in the H ?, H ?, [OIII], 5007 Å, [N II], 6548, 6583 Å, [S II], 6717, 6731 Å, and He I, 6678 Å lines have been obtained with an angular resolution of ˜4.?5 × 4.?5. The zones of maximum surface brightness and the region of maximum gas ionization ratio are located 12? south of the central star, which may suggest the existence of a second gas ionization source.

Kondrat'eva, L. N.; Rspaev, F. K.; Aimuratov, E. K.

2014-11-01

313

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

314

Determination of trace levels of pyrethroid metabolites in human urine by capillary gas chromatography-high resolution mass spectrometry with negative chemical ionization  

Microsoft Academic Search

Summary  Applications of high-resolution gas chromatography and high-resolution mass spectrometry (GC-MS) for identification and quantitation\\u000a of trace amounts of pyrethroid metabolites in human urine samples are demonstrated. The method covers the pyrethroid metabolitescis- andtrans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane carboxylic acid (cis- andtrans-DCCA),cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DBCA), 4-fluoro-3-phenoxybenzoic acid (FPBA), and 3-phenoxybenzoic acid (3-PBA). After acid-induced hydrolysis of urine samples\\u000a and exhaustive solvent extraction, a carbodiimide-coupled esterification

G. Leng; K.-H. Kühn; A. Leng; W. Gries; J. Lewalter; H. Idel

1997-01-01

315

First successful ionization of Lr (Z = 103) by a surface-ionization technique  

NASA Astrophysics Data System (ADS)

We have developed a surface ionization ion-source as part of the JAEA-ISOL (Isotope Separator On-Line) setup, which is coupled to a He/CdI2 gas-jet transport system to determine the first ionization potential of the heaviest actinide lawrencium (Lr, Z = 103). The new ion-source is an improved version of the previous source that provided good ionization efficiencies for lanthanides. An additional filament was newly installed to give better control over its operation. We report, here, on the development of the new gas-jet coupled surface ion-source and on the first successful ionization and mass separation of 27-s 256Lr produced in the 249Cf + 11B reaction.

Sato, Tetsuya K.; Sato, Nozomi; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Ooe, Kazuhiro; Miyashita, Sunao; Schädel, Matthias; Kaneya, Yusuke; Nagame, Yuichiro; Osa, Akihiko; Ichikawa, Shin-ichi; Stora, Thierry; Kratz, Jens Volker

2013-02-01

316

First successful ionization of Lr (Z = 103) by a surface-ionization technique.  

PubMed

We have developed a surface ionization ion-source as part of the JAEA-ISOL (Isotope Separator On-Line) setup, which is coupled to a He/CdI2 gas-jet transport system to determine the first ionization potential of the heaviest actinide lawrencium (Lr, Z = 103). The new ion-source is an improved version of the previous source that provided good ionization efficiencies for lanthanides. An additional filament was newly installed to give better control over its operation. We report, here, on the development of the new gas-jet coupled surface ion-source and on the first successful ionization and mass separation of 27-s (256)Lr produced in the (249)Cf + (11)B reaction. PMID:23464201

Sato, Tetsuya K; Sato, Nozomi; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Ooe, Kazuhiro; Miyashita, Sunao; Schädel, Matthias; Kaneya, Yusuke; Nagame, Yuichiro; Osa, Akihiko; Ichikawa, Shin-ichi; Stora, Thierry; Kratz, Jens Volker

2013-02-01

317

Method and apparatus utilizing ionizing and microwave radiation for saturation determination of water, oil and a gas in a core sample  

SciTech Connect

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

318

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

319

Deconstructing Desorption Electrospray Ionization: Independent Optimization of Desorption and Ionization by Spray Desorption Collection  

NASA Astrophysics Data System (ADS)

Spray desorption collection (SDC) and reflective electrospray ionization (RESI) were used to independently study the desorption and ionization processes that together comprise desorption electrospray ionization (DESI). Both processes depend on several instrumental parameters, including the nebulizing gas flow rate, applied potential, and source geometries. Each of these parameters was optimized for desorption, as represented by the results obtained by SDC, and ionization, as represented by the results obtained by RESI. The optimized conditions were then compared to the optimization results for DESI. Our results confirm that optimal conditions for desorption and ionization are different and that in some cases the optimized DESI conditions are a compromise between both sets. The respective results for DESI, RESI, and SDC for each parameter were compared across the methods to draw conclusions about the contribution of each parameter to desorption and ionization separately and then combined within DESI. Our results indicate that desorption efficiency is (1) independent of the applied potential and (2) the impact zone to inlet distance, and that (3) gas pressure settings and (4) sprayer to impact zone distances above optimal for DESI are detrimental to desorption but beneficial for ionization. In addition, possible interpretations for the observed trends are presented.

Douglass, Kevin A.; Jain, Shashank; Brandt, William R.; Venter, Andre R.

2012-11-01

320

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

321

Characteristic negative response of the helium ionization detector  

Microsoft Academic Search

When ultrapure helium is used as a carrier gas, the helium ionization detector provides a characteristic response, either positive or negative to each gas. The detector response can be made positive for all gases except neon by the inclusion of a few ppM of gaseous additives to the helium carrier gas, but the inclusion of gaseous additives decreases the detector

Fikry F. Andrawes; Everett K. Gibson

1980-01-01

322

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

323

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

PubMed

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

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

2014-01-17

324

Simultaneous quantification of cannabinoids and metabolites in oral fluid by two-dimensional gas chromatography mass spectrometry  

PubMed Central

Development and validation of a method for simultaneous identification and quantification of ?9-tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), and metabolites 11-hydroxy-THC (11-OH-THC) and 11-nor-9-carboxy-THC (THCCOOH) in oral fluid. Simultaneous analysis was problematic due to different physicochemical characteristics and concentration ranges. Neutral analytes, such as THC and CBD, are present in ng/mL, rather than pg/mL concentrations, as observed for the acidic THCCOOH biomarker in oral fluid. THCCOOH is not present in cannabis smoke, definitively differentiating cannabis use from passive smoke exposure. THC, 11-OH-THC, THCCOOH, CBD, and CBN quantification was achieved in a single oral fluid specimen collected with the Quantisal™ device. One mL oral fluid/buffer solution (0.25mL oral fluid and 0.75mL buffer) was applied to conditioned CEREX® Polycrom™ THC solid phase extraction (SPE) columns. After washing, THC, 11-OH-THC, CBD, and CBN were eluted with hexane/acetone/ethyl acetate (60:30:20, v/v/v), derivatized with N, O-bis-(trimethylsilyl) trifluoroacetamide and quantified by two-dimensional gas chromatography electron ionization mass spectrometry (2D-GCMS) with cold trapping. Acidic THCCOOH was separately eluted with hexane/ethyl acetate/acetic acid (75:25:2.5, v/v/v), derivatized with trifluoroacetic anhydride and hexafluoroisopropanol, and quantified by the more sensitive 2D-GCMS–electron capture negative chemical ionization (NCI-MS). Linearity was 0.5-50ng/mL for THC, 11-OH-THC, CBD and 1-50ng/mL for CBN. The linear dynamic range for THCCOOH was 7.5–500pg/mL. Intra-and inter-assay imprecision as percent RSD at three concentrations across the linear dynamic range were 0.3%-6.6%. Analytical recovery was within 13.8% of target. This new SPE 2D-GCMS assay achieved efficient quantification of five cannabinoids in oral fluid, including pg/mL concentrations of THCCOOH by combining differential elution, 2D-GCMS with electron ionization and negative chemical ionization. This method will be applied to quantification of cannabinoids in oral fluid specimens from individuals participating in controlled cannabis and Sativex® (50% THC and 50% CBD) administration studies, and during cannabis withdrawal. PMID:20083251

Milman, Garry; Barnes, Allan J.; Lowe, Ross H.; Huestis, Marilyn A.

2010-01-01

325

Mixed-terminal-ligand oxo-centered carboxylate-bridged trinuclear complexes: gas phase generation by means of electrospray ionization FT-ICR MS, condensed phase synthesis, and X-ray structure of K +[Cr 3O(C 6H 5COO) 6(F) 2(H 2O)] ?·2(CH 3) 2CO  

Microsoft Academic Search

The current state of knowledge concerning mixed-terminal-ligand oxo-centered carboxylate-bridged trinuclear complexes is summarized and the application of mass spectrometric techniques to the study of trinuclear basic carboxylates is briefly reviewed. The exchange\\/substitution reactions of terminal ligands with other molecules in both liquid and gas phase have been investigated using electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry (ESI FT-ICR MS),

Sergiu P. Palii; David E. Richardson; Marianne L. Hansen; Bo B. Iversen; Finn K. Larsen; Grigore A. Timco; Nicolae V. Gerbeleu; Keith R. Jennings; John R. Eyler

2001-01-01

326

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.

2011-05-25

327

Sensitivity of hot-cathode ionization vacuum gages in several gases  

NASA Technical Reports Server (NTRS)

Four hot-cathode ionization vacuum gages were calibrated in 12 gases. The relative sensitivities of these gages were compared to several gas properties. Ionization cross section was the physical property which correlated best with gage sensitivity. The effects of gage accelerating voltage and ionization-cross-section energy level were analyzed. Recommendations for predicting gage sensitivity according to gage type were made.

Holanda, R.

1972-01-01

328

Measurement of Organic Acids Produced By The Gas-Phase Ozonolysis of Simple Olefins Using Chemical Ionization Mass Spectrometry (CIMS) as a Function of Temperature And Humidity  

NASA Astrophysics Data System (ADS)

Non-methane hydrocarbons (NMHCs) form an important trace component of the atmosphere and are of particular environmental interest because of their deleterious effects on air quality, their numerous (and potentially counteractive) effects on Earth’s climate system and their sophisticated semiochemical roles in the world’s ecosystems. NMHCs are also important precursors to the formation of secondary organic aerosol (SOA) (e.g. Pandis et al., 1991; Kavouras et al., 1999). The ozonolysis reactions of olefins result in complex menageries of products, of which the acids are ubiquitous. Although the gas phase acid concentrations are small, they are thought to be key species in SOA formation as a result of their low volatility (e.g., Ma et al., 2009). Despite this, the factors that control acid formation are not well understood, especially with regards to humidity and temperature. Acid yields will be measured using the newly commissioned EXTreme RAnge (EXTRA) chamber (Leather et al., 2009). EXTRA is a 125 L stainless steel chamber, which can be temperature controlled using a commercial chest freezer unit (for T ? -20 °C) or a purpose built oven for T > 25 °C. The EXTRA chamber can be operated at pressures from 10-3800 Torr and at temperatures from 180-473 K. The stainless steel chamber walls have been coated with PFA to minimize wall loss of radicals. Fans, located at both ends of the cylinder, promote rapid mixing of reactants. Six sample ports are located at either end of the chamber for connection to ADS-GC-ECD, CIMS and commercial sensors such as a Thermo Electron Corporation 49i Ozone Analyzer, an Edinburgh Instruments Gascard CO2 sensor and a Trace Analytical inc. RGA3 CO analyzer. Experiments will be performed as a function of atmospherically relevant temperatures (T= 180-300 K). The field CIMS has sub ppt(v) L.O.D.s with a sub 1 Hz time response so will enable products to be quantified at very low concentrations in real time. Acid products will be detected using both the acetate ion (Verez et al., 2008) and silicon pentafluoride ion (Huey et al., 1998) reaction schemes, both of which have been used previously in atmospheric measurements, with little interference from water vapour. References Kavouras, I.G., Mihalopoulos N., Stephanou, E.G., 1999, Environ. Sci. Technol. 33: 1028-1037. Huey, L. G., E. J. Dunlea, E. R. Lovejoy, D. R. Hanson, R.B. Norton, F.C. Fehsenfeld and C. J. Howard, 1998, J. Geophys. Res, 103(D3), 3355-3360. Leather, K.E., Mcgillen, M.R. and Percival, C.J., 2009, Submitted to PCCP. Ma, Y., Porter, R.A., Chappell, D., Russell, A.T., Marston, G., 2009,. PCCP, 21, 4184-4197. Pandis, S. N., Paulson, S.E., Seinfeld, J.H., Flagan, R.C. 1991, Atmos. Environ. A, 1991, 25, 997-1008. Veres, P., Roberts, J.M., Warneke, C., Welsh-Bon, D., Zahniser, M., Herndon, S., Fall,R., de Gouw, J., 2008, Int. J. Mass Spectrom., 274, 48-55.

Percival, C. J.; Bacak, A.; Leather, K. E.; McGillen, M. R.

2009-12-01

329

Two-color laser-ionization injection.  

PubMed

A method is proposed to generate femtosecond, ultralow emittance (?10-8??m?rad), electron beams in a laser-plasma accelerator using two lasers of different colors. A long-wavelength pump pulse, with a large ponderomotive force and small peak electric field, excites a wake without fully ionizing a high-Z gas. A short-wavelength injection pulse, with a small ponderomotive force and large peak electric field, copropagating and delayed with respect to the pump laser, ionizes a fraction of the remaining bound electrons at a trapping wake phase, generating an electron beam that is accelerated in the wake. PMID:24724654

Yu, L-L; Esarey, E; Schroeder, C B; Vay, J-L; Benedetti, C; Geddes, C G R; Chen, M; Leemans, W P

2014-03-28

330

Two-Color Laser-Ionization Injection  

NASA Astrophysics Data System (ADS)

A method is proposed to generate femtosecond, ultralow emittance (˜10-8 m rad), electron beams in a laser-plasma accelerator using two lasers of different colors. A long-wavelength pump pulse, with a large ponderomotive force and small peak electric field, excites a wake without fully ionizing a high-Z gas. A short-wavelength injection pulse, with a small ponderomotive force and large peak electric field, copropagating and delayed with respect to the pump laser, ionizes a fraction of the remaining bound electrons at a trapping wake phase, generating an electron beam that is accelerated in the wake.

Yu, L.-L.; Esarey, E.; Schroeder, C. B.; Vay, J.-L.; Benedetti, C.; Geddes, C. G. R.; Chen, M.; Leemans, W. P.

2014-03-01

331

[Preliminary exploration of energy transfer about sample ionization process in electrospray ionization source].  

PubMed

Electrospray ionization source (ESI) can be used not only for the detection of small molecules, but also for large molecules such as proteins and peptides. This article proposes energy transfer theory based on the lowest energy principle by systematically analyzing ionization processes. The transference of the analyte from liquid phase to gas phase can be influenced by multiple forces during the ionization and vaporization processes, such as electrostatics force and van der Waals' force. The ionization of samples is the result of the interactions among multiple forces. During different stages of the ionization process, different forces lead to different effects. There are competition between evaporation and formation of multi-charge ions for charges. For molecules with different structures, Gibbs free energy between two phases from the changes of molecule shape or conformation may lead to ion evaporation, multiply charged macromolecule and chain ejection, etc. The energy transfer theory can simplify the three existing theories, as well as explain the solvent effect and electrolyte ion effect during ionization process. The proposed theory provides foundation to optimize the detection condition for different samples and to understand the real process of ionization. PMID:25069329

Zhang, Weibing; Gao, Fangyuan; Guan, Yafeng; Zhang, Yukui

2014-04-01

332

Determination of volatile compounds in wine by gas chromatography-flame ionization detection: comparison between the U.S. Environmental Protection Agency 3sigma approach and Hubaux-Vos calculation of detection limits using ordinary and bivariate least squares.  

PubMed

A capillary GC-flame ionization detection (FID) method to determine volatile compounds (ethyl acetate, 1,1-diethoxyethane, methyl alcohol, 1-propanol, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 1-butanol, and 2-butanol) in wine was investigated in terms of calculation of detection limits and calibration method. The main objectives were: (1) calculation of regression coefficient parameters by ordinary least-squares (OLS) and bivariate least-squares (BLS) regression models, taking into account errors in both axes; (2) estimation of linear dynamic range (LDR) according to International Conference on Harmonization recommendations; (3) performance evaluation of a method by using three different internal standards (ISs) such as acetonitrile, acetone, and 1-pentanol; (4) evaluation of LODs according to the U.S. Environmental Protection Agency (EPA) 3sigma approach and the Hubaux-Vos (H-V) method; (5) application of H-V theory to a gas chromatographic analytical method and to a food matrix; and (6) accuracy assessment of the method relative to methyl alcohol content through a Unione Italiana Vini (UIV) interlaboratory proficiency test. Calibration curves calculated via BLS and OLS show similar slopes, while intercepts are closer to zero in the first case, independent of the chosen IS. The studied ISs show a substantially equivalent behavior, even though the IS closer to the analyte retention time seems to be more appropriate in terms of LDR and LOD. Results indicate an underestimation of LODs using the EPA 3sigma approach instead of the more realistic H-V method, both with OLS and BLS regression models. Methanol contents compared with UIV average values indicate recovery between 90 and 110%. PMID:22649934

Caruso, Rosario; Scordino, Monica; Traulo, Pasqualino; Gagliano, Giacomo

2012-01-01

333

Determination of phenolic endocrine disrupting chemicals and acidic pharmaceuticals in surface water of the Pearl Rivers in South China by gas chromatography-negative chemical ionization-mass spectrometry.  

PubMed

An analytical method for phenolic endocrine disrupting chemicals and acidic pharmaceuticals in river water was developed using gas chromatography mass spectrometry (GC-MS) coupled with negative chemical ionization (NCI) technique, and used for the determination of these compounds in the Pearl Rivers (Liuxi, Zhujiang and Shijing Rivers). Derivatization using pentafluorobenzoyl chloride (PFBOCl) and pentafluorobenzyl bromide (PFBBr) before GC-MS analysis were applied and optimized for phenolic compounds and acidic compounds, respectively. The target compounds were analyzed for river waters from the upstream to downstream of the Pearl Rivers. Phenolic compounds 4-tert-octylphenol (4-t-OP), 4-nonylphenol (4-NP), bisphenol-A (BPA), estrone (E1), estradiol (E2) and triclosan (TCS) were detected at trace or low levels in the water samples from Liuxi River and Zhujiang River. Diethylstilbestrol (DES) was not detected in the Pearl Rivers. The highest concentrations of the phenolic compounds were found in Shijing River, and they were 3150 ng/L for 4-t-OP, 11,300 ng/L for 4-NP, 1040 ng/L for BPA, 79 ng/L for E1, 7.7 ng/L for E2 and 355 ng/L for TCS, respectively. Only a few acidic pharmaceuticals were detected at low concentrations in water from Liuxi River and Zhujiang River, but the highest concentrations for the acidic pharmaceuticals were also found in Shijing River. The highest concentrations detected for clofibric acid, ibuprofen, gemfibrozil, naproxen, mefenamic acid and diclofenac were 17 ng/L, 685 ng/L, 19.8 ng/L, 125 ng/L, 24.6 ng/l and 150 ng/L, respectively. The results suggest Liuxi and Zhujiang Rivers are only slightly contaminated and can be used as drinking water sources, but Shijing River is heavily polluted by the wastewater from nearby towns. PMID:19004474

Zhao, Jian-Liang; Ying, Guang-Guo; Wang, Li; Yang, Ji-Feng; Yang, Xiao-Bing; Yang, Li-Hua; Li, Xu

2009-01-01

334

Parts per quadrillion level ultra-trace determination of polar and nonpolar compounds via solvent-free capillary microextraction on surface-bonded sol-gel polytetrahydrofuran coating and gas chromatography-flame ionization detection.  

PubMed

Sol-gel polytetrahydrofuran (poly-THF) coating was developed for high-sensitivity sample preconcentration by capillary microextraction (CME). Parts per quadrillion (ppq) level detection limits were achieved for both polar and nonpolar analytes through sample preconcentration on sol-gel poly-THF coated microextraction capillaries followed by gas chromatography (GC) analysis of the extracted compounds using a flame ionization detector (FID). The sol-gel coating was in situ created on the inner walls of a fused silica capillary using a sol solution containing poly-THF as an organic component, methyltrimethoxysilane (MTMOS) as a sol-gel precursor, trifluoroacetic acid (TFA, 5% water) as a sol-gel catalyst, and hexamethyldisilazane (HMDS) as a deactivating reagent. The sol solution was introduced into a hydrothermally-treated fused silica capillary and the sol-gel reactions were allowed to take place inside the capillary for 60 min. A wall-bonded coating was formed due to the condensation of silanol groups residing on the capillary inner surface with those on the sol-gel network fragments evolving in close vicinity of the capillary walls. Poly-THF is a medium polarity polymer, and was found to be effective in carrying out simultaneous extraction of both polar and nonpolar analytes. Efficient extraction of a wide range of trace analytes from aqueous samples was accomplished using sol-gel poly-THF coated fused silica capillaries for further analysis by GC. The test analytes included polycyclic aromatic hydrocarbons (PAHs), aldehydes, ketones, chlorophenols, and alcohols. To our knowledge, this is the first report on the use of a poly-THF based sol-gel material in analytical microextraction. Sol-gel poly-THF coated CME capillaries showed excellent solvent and thermal stability (>320 degrees C). PMID:15481455

Kabir, Abuzar; Hamlet, Christina; Malik, Abdul

2004-08-20

335

Development of simultaneous gas chromatography-mass spectrometric and liquid chromatography-electrospray ionization mass spectrometric determination method for the new designer drugs, N-benzylpiperazine (BZP), 1-(3-trifluoromethylphenyl)piperazine (TFMPP) and their main metabolites in urine.  

PubMed

To prove the intake of recently controlled designer drugs, N-benzylpiperazine (BZP) and 1-(3-trifluoromethylphenyl)piperazine (TFMPP), a simple, sensitive and reliable method which allows us to simultaneously detect BZP, TFMPP and their major metabolite in human urine has been established by coupling gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). GC-MS accompanied by trifluoroacetyl (TFA) derivatization and LC-MS analyses were performed after the enzymatic hydrolysis and the solid phase extraction with OASIS HLB, and BZP, TFMPP and their major metabolites, 4'-hydroxy-BZP (p-OH-BZP), 3'-hydroxy-BZP (m-OH-BZP) and 4'-hydroxy-TFMPP (p-OH-TFMPP), have found to be satisfactorily separated on a semi-micro SCX column with acetonitrile-40 mM ammonium acetate buffer (pH 4) (75:25, v/v) as the eluent. The detection limits produced by GC-MS were estimated to be from 50 ng/ml to 1 microg/ml in the scan mode, and from 200 to 500 ng/ml in the selected ion monitoring (SIM) mode. Upon applying the LC-ESI-MS technique, the linear calibration curves were obtained by using the SIM mode for all analytes in the concentration range from 10 ng/ml to 10 microg/ml. The detection limits ranged from 5 to 40 ng/ml in the scan mode, and from 0.2 to 1 ng/ml in the SIM mode. These results indicate the high reliability and sensitivity of the present procedure, and this procedure will be applicable for proof of intake of BZP and TFMPP in forensic toxicology. PMID:15833296

Tsutsumi, Hiroe; Katagi, Munehiro; Miki, Akihiro; Shima, Noriaki; Kamata, Tooru; Nishikawa, Mayumi; Nakajima, Kunio; Tsuchihashi, Hitoshi

2005-05-25

336

Analysis of volatile compounds in fresh healthy and diseased peppers (Capsicum annuum L.) using solvent free solid injection coupled with gas chromatography-flame ionization detector and confirmation with mass spectrometry.  

PubMed

The characteristic volatile flavor compounds in healthy peppers (Capsicum annuum L.) were evaluated using a solvent-free solid injector coupled with a-gas chromatography-flame ionization detector (SFSI-GC-FID) and the results of evaluation were confirmed using GC-mass spectrometry (GC-MS). These compounds were compared with those obtained from peppers that were naturally infected or artificially inoculated with Colletotrichum spp. Parameters influencing the vaporization efficiency, including the injector temperature, pre-heating time and holding time, were optimized to improve the analytical efficiency. A total of 96 compounds (excluding eight capillary compounds), 17 of which were identified in healthy peppers, 49 of which were found in naturally infected peppers, and 61 of which were identified in artificially inoculated peppers, were separated and identified under the optimal conditions of an injector temperature of 250 degrees C and 7-min preheating and holding times. Acetic acid and 2-furanmethanol were the major compounds detected in the volatiles of the healthy and diseased peppers. The major compound detected in both the healthy and naturally infected peppers was 3-hydroxypyridine, while hexadecanoic acid was the primary compound identified in the artificially inoculated peppers. Indole derivatives (1H-indole, 4-methylindole and 1-ethylindole) were suggested to be the key factors contributing to the pepper infection caused by Colletotrichum spp. We conclude that SFSI in combination with GC is a suitable approach for distinguishing between healthy and diseased peppers by the investigation of their volatile compounds. It does not require the use of solvents and complicated equipment. PMID:17766077

Kim, In-Kyung; Abd El-Aty, A M; Shin, Ho-Chul; Lee, Hyang Burm; Kim, In-Seon; Shim, Jae-Han

2007-11-01

337

Theoretical determinations of ionization potentials of dopamine  

NASA Astrophysics Data System (ADS)

Adiabatic and vertical ionization potentials (IPs) of nine conformers of dopamine in the gas phase are determined using density functional theory (DFT) B3LYP, B3P86, B3PW91 methods and high level ab initio HF method with 6-311++G** basis set, respectively. And the nine stable cationic states have been found in the ionization process of dopamine. Vertical ionization potentials of nine conformers of dopamine are calculated using the older outer-valence Green's function (OVGF) calculations at 6-311++G** basis set. Vibrational frequencies and infrared spectrum intensities of G1b and G1b+ at B3LYP/6-311++G** level are discussed.

Lu, J. F.; Yu, Z. Y.

2013-04-01

338

A surface ionization source  

E-print Network

The main part of the work described herein is the development and testing of a surface ionization source for use on a collinear fast beam laser spectroscopy apparatus. A description of the previously existing fast beam apparatus is given...

Buzatu, Daniel J.

2012-06-07

339

PULSED POSITIVE ION NEGATIVE ION CHEMICAL IONIZATION MASS SPECTROMETRIC APPLICATONS TO ENVIRONMENTAL AND HAZARDOUS WASTE ANALYSIS  

EPA Science Inventory

The simultaneous acquisition of both positive ion and negative ion data under chemical ionization mass spectrometric conditions can aid in the confirmation of assignments made by electron impact gas chromatography mass spectrometry or electron capture gas chromatography. Pulsed p...

340

Dynamic Hydrogen Ionization  

E-print Network

We investigate the ionization of hydrogen in a dynamic Solar atmosphere. We show that the time scale for ionization/recombination can be estimated from the eigenvalues of a modified rate matrix where the optically thick Lyman transitions that are in detailed balance have been excluded. We find that the time scale for ionization/recombination is dominated by the slow collisional leakage from the ground state to the first excited state. Throughout the chromosphere the time scale is long ($10^3$-$10^5$ s), except in shocks where the increased temperature and density shorten the time scale for ionization/recombination, especially in the upper chromosphere. Because the relaxation time scale is much longer than dynamic time scales, hydrogen ionization does not have time to reach its equilibrium value and its fluctuations are much smaller than the variation of its statistical equilibrium value appropriate for the instantaneous conditions. The ionization state tends to represent the higher temperature of the shocks, and the mean electron density is up to a factor of six higher than the electron density calculated in statistical equilibrium from the mean atmosphere. The simulations show that a static picture and a dynamic picture of the chromosphere are fundamentally different and that time variations are crucial for our understanding of the chromosphere itself and the spectral features formed there.

Mats Carlsson; Robert F. Stein

2002-02-16

341

Modeling process of the neutral beam re-ionization loss  

NASA Astrophysics Data System (ADS)

The basic process of re-ionization loss was studied. In the drift duct there are three processes leading to re-ionization loss: the collision of neutral beam particles with the molecules of background gas, similar collisions with released molecules from the inner wall of the drift duct and the ferret-collisions among particles with different energy of the neutral beam. Mathematical models have been developed and taking EAST-NBI parameters as an example, the re-ionization loss was obtained within these models. The result indicated that in the early stage of the neutral beam injector operation the released gas was quite abundant. The amount of re-ionization loss owing to the released gas can be as high as 60%. In the case of a long-time operation of the neutral beam injector, the total re-ionization loss decreases from 13.7% to 5.7%. Then the reionization loss originating mainly from the collisions between particles of the neutral beam and the background molecules is dominant, covering about 92% of the total re-ionization loss. The drift duct pressure was the decisive factor for neutral beam re-ionization loss.

Liang, Li-Zhen; Hu, Chun-Dong; Xie, Yuan-Lai; Xie, Ya-Hong; Nbi-team

2010-07-01

342

Variable pressure ionization detector for gas chromatography  

DOEpatents

Method and apparatus for differentiating organic compounds based on their electron affinity. An electron capture detector cell (ECD) is operated at pressures ranging from atmospheric to less than 1 torr. Through variation of the pressure within the ECD cell, the organic compounds are induced to either capture or emit electrons. Differentiation of isomeric compounds can be obtianed when, at a given pressure, one isomer is in the emission mode and the other is in the capture mode. Output of the ECD is recorded by chromatogram. The invention also includes a method for obtaining the zero-crossing pressure of a compound, defined as the pressure at which the competing emission and capture reactions are balanced and which may be correlated to the electron affinity of a compound.

Buchanan, Michelle V. (Knoxville, TN); Wise, Marcus B. (Oak Ridge, TN)

1988-01-01

343

Microliter-sized ionization device and method  

NASA Technical Reports Server (NTRS)

A microliter-sized metastable ionization device with a cavity, a sample gas inlet, a corona gas inlet and a gas outlet. A first electrode has a hollow and disposed in the cavity and is in fluid communication with the sample gas inlet. A second electrode is in fluid communication with the corona gas inlet and is disposed around the first electrode adjacent the hollow end thereof. A gap forming means forms a corona gap between the first and second electrodes. A first power supply is connected to the first electrode and the second power supply is connected to the second electrode for generating a corona discharge across the corona gap. A collector has a hollow end portion disposed in the cavity which is in fluid communications with the gas outlet for the outgassing and detection of ionized gases. The first electrode can be a tubular member aligned concentrically with a cylindrical second electrode. The gap forming means can be in annular disc projecting radially inwardly from the cylindrical second electrode. The collector can have a tubular opening aligned coaxially with the first electrode and has an end face spaced a short distance from an end face of the first electrode forming a small active volume therebetween for the generation and detection of small quantities of trace analytes.

Cohen, Martin J. (Inventor); Simac, Robert M. (Inventor); Wernlund, Roger F. (Inventor)

1999-01-01

344

Ionizing shock-wave propagation in a homogeneous magnetic field  

Microsoft Academic Search

It is well known [I0] that complete ionization of air occurs at Mach numbers equal to 14-20, i.e., at p2\\/pl ~ 200-500 (where px is the pressure of the neutral gas ahead of the shock wave front and P2 is the gas pressure behind the front). At a height of ~ 3\\

N. A. Kudryashov

1983-01-01

345

The ionization mechanisms in direct and dopant-assisted atmospheric pressure photoionization and atmospheric pressure laser ionization.  

PubMed

A novel, gas-tight API interface for gas chromatography-mass spectrometry was used to study the ionization mechanism in direct and dopant-assisted atmospheric pressure photoionization (APPI) and atmospheric pressure laser ionization (APLI). Eight analytes (ethylbenzene, bromobenzene, naphthalene, anthracene, benzaldehyde, pyridine, quinolone, and acridine) with varying ionization energies (IEs) and proton affinities (PAs), and four common APPI dopants (toluene, acetone, anisole, and chlorobenzene) were chosen. All the studied compounds were ionized by direct APPI, forming mainly molecular ions. Addition of dopants suppressed the signal of the analytes with IEs above the IE of the dopant. For compounds with suitable IEs or Pas, the dopants increased the ionization efficiency as the analytes could be ionized through dopant-mediated gas-phase reactions, such as charge exchange, proton transfer, and other rather unexpected reactions, such as formation of [M?+?77](+) in the presence of chlorobenzene. Experiments with deuterated toluene as the dopant verified that in case of proton transfer, the proton originated from the dopant instead of proton-bound solvent clusters, as in conventional open or non-tight APPI sources. In direct APLI using a 266 nm laser, a narrower range of compounds was ionized than in direct APPI, because of exceedingly high IEs or unfavorable two-photon absorption cross-sections. Introduction of dopants in the APLI system changed the ionization mechanism to similar dopant-mediated gas-phase reactions with the dopant as in APPI, which produced mainly ions of the same form as in APPI, and ionized a wider range of analytes than direct APLI. PMID:25248413

Kauppila, Tiina J; Kersten, Hendrik; Benter, Thorsten

2014-11-01

346

Closed-loop pulsed helium ionization detector  

DOEpatents

A helium ionization detector for gas chromatography is operated in a constant current, pulse-modulated mode by configuring the detector, electrometer and a high voltage pulser in a closed-loop control system. The detector current is maintained at a fixed level by varying the frequency of fixed-width, high-voltage bias pulses applied to the detector. An output signal proportional to the pulse frequency is produced which is indicative of the charge collected for a detected species.

Ramsey, Roswitha S. (Knoxville, TN); Todd, Richard A. (Knoxville, TN)

1987-01-01

347

An analytical investigation of 24 oxygenated-PAHs (OPAHs) using liquid and gas chromatography-mass spectrometry.  

PubMed

We developed two independent approaches for separation and quantitation of 24 oxygenated polycyclic aromatic hydrocarbons (OPAHs) using both liquid chromatography-atmospheric pressure chemical ionization/mass spectrometry (LC-APCI/MS) and gas chromatography-electron impact/mass spectrometry (GC-EI/MS). Building on previous OPAH research, we examined laboratory stability of OPAHs, improved existing method parameters, and compared quantification strategies using standard addition and an internal standard on an environmental sample. Of 24 OPAHs targeted in this research, 19 compounds are shared between methods, with 3 uniquely quantitated by GC-EI/MS and 2 by LC-APCI/MS. Using calibration standards, all GC-EI/MS OPAHs were within 15 % of the true value and had less than 15 % relative standard deviations (RSDs) for interday variability. Similarly, all LC-APCI/MS OPAHs were within 20 % of the true value and had less than 15 % RSDs for interday variability. Instrument limits of detection ranged from 0.18 to 36 ng mL(-1) on the GC-EI/MS and 2.6 to 26 ng mL(-1) on the LC-APCI/MS. Four standard reference materials were analyzed with each method, and we report some compounds not previously published in these materials, such as perinaphthenone and xanthone. Finally, an environmental passive sampling extract from Portland Harbor Superfund, OR was analyzed by each method using both internal standard and standard addition to compensate for potential matrix effects. Internal standard quantitation resulted in increased precision with similar accuracy to standard addition for most OPAHs using 2-fluoro-fluorenone-(13)C as an internal standard. Overall, this work improves upon OPAH analytical methods and provides some considerations and strategies for OPAHs as focus continues to expand on this emerging chemical class. PMID:24005604

O'Connell, Steven G; Haigh, Theodore; Wilson, Glenn; Anderson, Kim A

2013-11-01

348

A solid phase microextraction coating based on ionic liquid sol-gel technique for determination of benzene, toluene, ethylbenzene and o-xylene in water samples using gas chromatography flame ionization detector.  

PubMed

Ionic liquid mediated sol-gel sorbents for head-space solid phase microextraction (HS-SPME) were developed for the extraction of benzene, toluene, ethylbenzene and o-xylene (BTEX) compounds from water samples in ultra-trace levels. The analytes were subsequently analyzed with gas chromatography coupled to flame ionization detector (GC-FID). Three different coating fibers were prepared including: poly(dimethylsiloxane) (PDMS), coating prepared from poly(dimethylsiloxane) in the presence of ionic liquid as co-solvent and conditioned at a higher temperature than decomposition temperature of ionic liquid (PDMS-IL-HT) and coating prepared from poly(dimethylsiloxane) in the presence of ionic liquid as co-solvent and conditioned at a lower temperature than decomposition temperature of ionic liquid (PDMS-IL-LT). Prepared fibers demonstrate many advantages such as high thermal and chemical stabilities due to the chemical bonding of the coatings with the silanol groups on the fused-silica surface fiber. These fibers have shown long life time up to 180 extractions. The scanning electron micrographs of the fibers surfaces revealed that addition of ionic liquid into the sol solution during the sol-gel process increases the fiber coating thickness, affects the form of fiber structure and also leaves high pores in the fiber surface that cause high surface area and therefore increases sample capacity of the fibers. The important parameters that affect the extraction efficiency are desorption temperature and time, sample volume, extraction temperature, extraction time, stirring speed and salt effect. Therefore these factors were investigated and optimized. Under optimal conditions, the dynamic linear range with PDMS-IL-HT, PDMS and PDMS-IL-LT fibers were 0.3-200,000; 50-200,000 and 170-150,000pgmL(-1) and the detection limits (S/N=3) were 0.1-2 and 15-200 and 50-500pgmL(-1), and limit of quantifications (S/N=10) were 0.3-8 and 50-700 and 170-1800, respectively. The relative standard deviations (RSD) for one fiber (repeatability) (n=5), were obtained from 3.1 up to 5.4% and between fibers or batch to batch (reproducibility) (n=3) in the range of 3.8-8.5% for three fibers. The developed method was successfully applied to the real water samples while the relative recovery percentages obtained for the spiked water samples at 20pgmL(-1) were from 91.2 to 103.3%. PMID:23582769

Sarafraz-Yazdi, Ali; Vatani, Hossein

2013-07-26

349

Strong-field atomic ionization in elliptically polarized laser fields  

NASA Astrophysics Data System (ADS)

We experimentally investigate strong-field ionization of noble-gas atoms in elliptically polarized laser fields with the Keldysh parameter ? ˜1, which is typical for most current strong-field experiments. Our data show that the single-ionization yields exhibit a rapid decrease with increasing elipticity and, moreover, the decrease becomes more dramatic for lower laser intensity. The experimental results are compared with the simulations of the Ammosov-Delone-Krainov (ADK) theory based on the quasistatic tunneling ionization picture and the strong-field approximation (SFA) theory, which involves the nonadiabatic effect in the tunneling ionization process. Our results show that although both the ADK simulations and the SFA calculations can qualitatively reproduce the experimental results, the SFA calculations are in a better agreement with the experimental data than the ADK simulations, which implies a nonadiabatic effect during strong-field atomic ionization for elliptical polarization with ? ˜1.

Wang, ChuanLiang; Lai, XuanYang; Hu, ZiLong; Chen, YongJu; Quan, Wei; Kang, HuiPeng; Gong, Cheng; Liu, XiaoJun

2014-07-01

350

Multiple-ionization of xenon atoms by positron impact  

NASA Technical Reports Server (NTRS)

Previously the cross sections were measured for positronium formation and single ionization by positron impact for He and H2. With the same apparatus, slightly modified, the single and multiple ionization of xenon is now investigated. The principle of the method is the detection of ion and positron in time correlation which allows the discrimination of positronium formation (whereby the positron vanishes) and the destinction of single, double and triple impact ionization (which lead to different ion flight times from the gas target to the ion detector). By using secondary electrons from the positron moderator, similar measurements were performed on electron impact ionization. By comparing with literature values for electron multiple ionization cross sections, the detection-probability ratios were determined for the differently charged ions.

Kruse, Georg; Quermann, Andreas; Raith, Wilhelm; Sinapius, Guenther

1990-01-01

351

The EUVE and the Ionization in the Local Interstellar Cloud  

NASA Astrophysics Data System (ADS)

EUVE white swarfs spectra analyses have provided HI, HeI and HeII column-densities in the ISM between the Sun and the target stars, and as a result the mean ionization in the local gas in different directions. It is found that, while hydrogen seems to be increasingly ionized in the direction of the so-called Canis Major tunnel, helium does not follow any trend, and seems to be uniformly ionized at 40 ionization gradient is consistent with other determinations of the electron density in the Local Interstellar Cloud, including the circumsolar ISM electron density from both EUVE and SOHO observations. We discuss this gradient and the local ISM ionization state.

Lallement, R.; Quemerais, E.; Bertaux, J. L.; Wolff, B.; Koester, D.

2000-05-01

352

On the origin of the ionization in the Galactic center  

NASA Astrophysics Data System (ADS)

We investigate the anomalously high ionization rate of the molecular gas in the Galactic center (GC) and the diffuse neutral iron line emission from the central region of the Galaxy. There are two alternative sources of the ionization of hydrogen and iron in the GC: they are either sub-relativistic particles or hard X-Ray photons. It is generally accepted that X-Ray photons emitted in the past by Sgr A* are the most probable candidate for excitation of the iron line in the GC molecular clouds. We showed that the same flare may be responsible for the diffuse iron line emission. According to experimental data on the ionization of diffuse molecular hydrogen charged particles contribution to the ionization of neutral iron is very low. On the other hand, the X-Ray photons from SGR A* are unable to reproduce the almost uniform spatial distribution of the ionization rate within the 100 pc radius of the GC. We showed that the most probable candidates for hydrogen ionizations there are subrelativistic cosmic ray protons. We also estimated the expected iron line flux from the molecular clouds from the particles responsible for ionization of the diffuse gas. It turns out that the corresponding flux is low and can be detected in the future only under some special conditions.

Chernyshov, Dmitry; Tatischeff, Vincent; Terrier, Regis; Dogiel, V. A.; Cheng, K. S.

353

Ionization and scintillation of nuclear recoils in gaseous xenon  

E-print Network

Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope $\\alpha$-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

Renner, J; Goldschmidt, A; Matis, H S; Miller, T; Nakajima, Y; Nygren, D; Oliveira, C A B; Shuman, D; Álvarez, V; Borges, F I G; Cárcel, S; Castel, J; Cebrián, S; Cervera, A; Conde, C A N; Dafni, T; Dias, T H V T; Díaz, J; Esteve, R; Evtoukhovitch, P; Fernandes, L M P; Ferrario, P; Ferreira, A L; Freitas, E D C; Gil, A; Gómez, H; Gómez-Cadenas, J J; González-Díaz, D; Gutiérrez, R M; Hauptman, J; Morata, J A Hernando; Herrera, D C; Iguaz, F J; Irastorza, I G; Jinete, M A; Labarga, L; Laing, A; Liubarsky, I; Lopes, J A M; Lorca, D; Losada, M; Luzón, G; Marí, A; Martín-Albo, J; Martínez, A; Moiseenko, A; Monrabal, F; Monserrate, M; Monteiro, C M B; Mora, F J; Moutinho, L M; Vidal, J Muñoz; da Luz, H Natal; Navarro, G; Nebot-Guinot, M; Palma, R; Pérez, J; Aparicio, J L Pérez; Ripoll, L; Rodríguez, A; Rodríguez, J; Santos, F P; Santos, J M F dos; Seguí, L; Serra, L; Simón, A; Sofka, C; Sorel, M; Toledo, J F; Tomás, A; Torrent, J; Tsamalaidze, Z; Veloso, J F C A; Villar, J A; Webb, R C; White, J; Yahlali, N

2014-01-01

354

Ionization and scintillation of nuclear recoils in gaseous xenon  

E-print Network

Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope $\\alpha$-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

J. Renner; V. M. Gehman; A. Goldschmidt; H. S. Matis; T. Miller; Y. Nakajima; D. Nygren; C. A. B. Oliveira; D. Shuman; V. Álvarez; F. I. G. Borges; S. Cárcel; J. Castel; S. Cebrián; A. Cervera; C. A. N. Conde; T. Dafni; T. H. V. T. Dias; J. Díaz; R. Esteve; P. Evtoukhovitch; L. M. P. Fernandes; P. Ferrario; A. L. Ferreira; E. D. C. Freitas; A. Gil; H. Gómez; J. J. Gómez-Cadenas; D. González-Díaz; R. M. Gutiérrez; J. Hauptman; J. A. Hernando Morata; D. C. Herrera; F. J. Iguaz; I. G. Irastorza; M. A. Jinete; L. Labarga; A. Laing; I. Liubarsky; J. A. M. Lopes; D. Lorca; M. Losada; G. Luzón; A. Marí; J. Martín-Albo; A. Martínez; A. Moiseenko; F. Monrabal; M. Monserrate; C. M. B. Monteiro; F. J. Mora; L. M. Moutinho; J. Muñoz Vidal; H. Natal da Luz; G. Navarro; M. Nebot-Guinot; R. Palma; J. Pérez; J. L. Pérez Aparicio; L. Ripoll; A. Rodríguez; J. Rodríguez; F. P. Santos; J. M. F. dos Santos; L. Seguí; L. Serra; A. Simón; C. Sofka; M. Sorel; J. F. Toledo; A. Tomás; J. Torrent; Z. Tsamalaidze; J. F. C. A. Veloso; J. A. Villar; R. C. Webb; J. White; N. Yahlali

2014-09-09

355

Ionized absorbers in AGN: the role of resonant absorption.  

NASA Astrophysics Data System (ADS)

Most of the models which describe X-ray spectra transmitted through ionized absorbers include photoelectric absorption only, neglecting line absorption. The authors show that resonance absorption lines are instead detectable even with moderate resolution X-ray detectors. In particular they show that the complexity of many NL Sy1 spectra may be explained in terms of transmission of those spectra through ionized matter, provided that the gas is turbulent (as it is the case for the UV/X-ray ionized absorbers of several classical Seyfert 1).

Nicastro, F.; Fiore, F.; Matt, G.

356

Modulated voltage metastable ionization detector  

NASA Technical Reports Server (NTRS)

The output current from a metastable ionization detector (MID) is applied to a modulation voltage circuit. An adjustment is made to balance out the background current, and an output current, above background, is applied to an input of a strip chart recorder. For low level concentrations, i.e., low detected output current, the ionization potential will be at a maximum and the metastable ionization detector will operate at its most sensitive level. When the detected current from the metastable ionization detector increases above a predetermined threshold level, a voltage control circuit is activated which turns on a high voltage transistor which acts to reduce the ionization potential. The ionization potential applied to the metastable ionization detector is then varied so as to maintain the detected signal level constant. The variation in ionization potential is now related to the concentration of the constituent and a representative amplitude is applied to another input of said strip chart recorder.

Carle, G. C.; Kojiro, D. R.; Humphrey, D. E. (inventors)

1985-01-01

357

Self-consistent Mean Field theory in weakly ionized media  

E-print Network

We present a self-consistent mean field theory of the dynamo in 3D and turbulent diffusion in 2D in weakly ionized gas. We find that in 3D, the backreaction does not alter the beta effect while it suppresses the alpha effect when the strength of a mean magnetic field exceeds a critical value. These results suggest that a mean field dynamo operates much more efficiently in weakly ionized gas compared to the fully ionized gas. Furthermore, we show that in 2D, the turbulent diffusion is suppressed by back reaction when a mean magnetic field reaches the same critical strength, with the upper bound on turbulent diffusion given by its kinematic value. Astrophysical implications are discussed.

Nicolas Leprovost; Eun-Jin Kim

2007-10-10

358

Thermionic gas switch  

DOEpatents

A temperature responsive thermionic gas switch having folded electron emitting surfaces. An ionizable gas is located between the emitter and an interior surface of a collector, coaxial with the emitter. In response to the temperature exceeding a predetermined level, sufficient electrons are derived from the emitter to cause the gas in the gap between the emitter and collector to become ionized, whereby a very large increase in current in the gap occurs. Due to the folded emitter surface area of the switch, increasing the "on/off" current ratio and adjusting the "on" current capacity is accomplished.

Hatch, George L. (San Francisco, CA); Brummond, William A. (Livermore, CA); Barrus, Donald M. (San Jose, CA)

1986-01-01

359

Radiation pressure confinement - III. The origin of the broad ionization distribution in AGN outflows  

NASA Astrophysics Data System (ADS)

The winds of ionized gas driven by active galactic nuclei (AGN) can be studied through absorption lines in their X-ray spectra. A recurring feature of these outflows is their broad ionization distribution, including essentially all ionization levels (e.g., Fe0+ to Fe25+). This characteristic feature can be quantified with the absorption measure distribution (AMD), defined as the distribution of column density with ionization parameter |dN/d log ?|. Observed AMDs extend over 0.1 ? ? ? 104 (cgs), and are remarkably similar in different objects. Power-law fits (|dN/d log ?| ? N1?a) yield N1 = 3 × 1021 cm- 2 ± 0.4 dex and a = 0-0.4. What is the source of this broad ionization distribution, and what sets the small range of observed N1 and a? A common interpretation is a multiphase outflow, with a wide range of gas densities in a uniform gas pressure medium. However, the incident radiation pressure leads to a gas pressure gradient in the photoionized gas, and therefore to a broad range of ionization states within a single slab. We show that this compression of the gas by the radiation pressure leads to an AMD with |dN/d log ?| = 8 × 1021 ?0.03 cm-2, remarkably similar to that observed. The calculated values of N1 and a depend weakly on the gas metallicity, the ionizing spectral slope, the distance from the nucleus, the ambient density, and the total absorber column. Thus, radiation pressure compression (RPC) of the photoionized gas provides a natural explanation for the observed AMD. RPC predicts that the gas pressure increases with decreasing ionization, which can be used to test the validity of RPC in ionized AGN outflows.

Stern, Jonathan; Behar, Ehud; Laor, Ari; Baskin, Alexei; Holczer, Tomer

2014-12-01

360

Venturi easy ambient sonic-spray ionization.  

PubMed

The development and illustrative applications of an ambient ionization technique termed Venturi easy ambient sonic-spray ionization (V-EASI) is described. Its dual mode of operation with Venturi self-pumping makes V-EASI applicable to the direct mass spectrometric analysis of both liquid (V(L)-EASI) and solid (V(S)-EASI) samples. V-EASI is simple and easy to assemble, operating solely via the assistance of a sonic stream of nitrogen or air. The sonic gas stream causes two beneficial and integrated effects: (a) the self-pumping of solutions via the Venturi effect and (b) sonic-spray ionization (SSI) of analytes either in solution or resting on solid surfaces. In its liquid mode, V(L)-EASI is applicable to analytes in solution, forming negatively and/or positively charged intact molecular species in a soft fashion with little or no fragmentation. In its solid mode, V(S)-EASI relies on Venturi self-pumping of a proper SSI solvent solution in combination with SSI to form a stream of bipolar charged droplets that bombard the sample surface, causing desorption and ionization of the analyte molecules. As for its precursor technique (EASI), V-EASI generates bipolar droplets with considerably lower average charging, which increases selectivity for ionization with high signal-to-noise ratios and clean spectra dominated by single molecular species with minimal solvent ions. V-EASI also operates in a voltage-, heat-, and radiation-free fashion and is therefore free of thermal, electrical, or discharge interferences. PMID:21235233

Santos, Vanessa G; Regiani, Thaís; Dias, Fernanda F G; Romão, Wanderson; Jara, Jose Luis Paz; Klitzke, Clécio F; Coelho, Fernando; Eberlin, Marcos N

2011-02-15

361

THE ESCAPE FRACTION OF IONIZING RADIATION FROM GALAXIES  

SciTech Connect

The escape of ionizing radiation from galaxies plays a critical role in the evolution of gas in galaxies, and the heating and ionization history of the intergalactic medium. We present semi-analytic calculations of the escape fraction of ionizing radiation for both hydrogen and helium from galaxies ranging from primordial systems to disk-type galaxies that are not heavily dust-obscured. We consider variations in the galaxy density profile, source type, location, and spectrum, and gas overdensity/distribution factors. For sufficiently hard first-light sources, the helium ionization fronts closely track or advance beyond that of hydrogen. Key new results in this work include calculations of the escape fractions for He I and He II ionizing radiation, and the impact of partial ionization from X-rays from early active galactic nuclei or stellar clusters on the escape fractions from galaxy halos. When factoring in frequency-dependent effects, we find that X-rays play an important role in boosting the escape fractions for both hydrogen and helium, but especially for He II. We briefly discuss the implications of these results for recent observations of the He II reionization epoch at low redshifts, as well as the UV data and emission-line signatures from early galaxies anticipated from future satellite missions.

Benson, Andrew [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Venkatesan, Aparna [Department of Physics and Astronomy, University of San Francisco, San Francisco, CA 94117 (United States); Shull, J. Michael, E-mail: abenson@obs.carnegiescience.edu, E-mail: avenkatesan@usfca.edu, E-mail: michael.shull@colorado.edu [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)

2013-06-10

362

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

Microsoft Academic Search

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

C Gonçalves; M. F Alpendurada

2002-01-01

363

X-ray secondary heating and ionization in quasar emission-line clouds  

Microsoft Academic Search

Accurate Monte Carlo computations of the X-ray secondary electron heating, ionization, and excitation of H and He gas in interstellar space and in quasar emission-line clouds, are presented. The fraction of energy deposited in each form is sensitive to the background ionization fraction, x = n(H+)\\/n(Htot), and can affect the temperature, ionization state, and line emissivities at large depths in

J. M. Shull; M. E. van Steenberg

1985-01-01

364

Capillary atmospheric pressure electron capture ionization (cAPECI): a highly efficient ionization method for nitroaromatic compounds.  

PubMed

We report on a novel method for atmospheric pressure ionization of compounds with elevated electron affinity (e.g., nitroaromatic compounds) or gas phase acidity (e.g., phenols), respectively. The method is based on the generation of thermal electrons by the photo-electric effect, followed by electron capture of oxygen when air is the gas matrix yielding O2(-) or of the analyte directly with nitrogen as matrix. Charge transfer or proton abstraction by O2(-) leads to the ionization of the analytes. The interaction of UV-light with metals is a clean method for the generation of thermal electrons at atmospheric pressure. Furthermore, only negative ions are generated and neutral radical formation is minimized, in contrast to discharge- or dopant assisted methods. Ionization takes place inside the transfer capillary of the mass spectrometer leading to comparably short transfer times of ions to the high vacuum region of the mass spectrometer. This strongly reduces ion transformation processes, resulting in mass spectra that more closely relate to the neutral analyte distribution. cAPECI is thus a soft and selective ionization method with detection limits in the pptV range. In comparison to standard ionization methods (e.g., PTR), cAPECI is superior with respect to both selectivity and achievable detection limits. cAPECI demonstrates to be a promising ionization method for applications in relevant fields as, for example, explosives detection and atmospheric chemistry. PMID:24399666

Derpmann, Valerie; Mueller, David; Bejan, Iustinian; Sonderfeld, Hannah; Wilberscheid, Sonja; Koppmann, Ralf; Brockmann, Klaus J; Benter, Thorsten

2014-03-01

365

Hydrodynamic Instability of Ionization Fronts in HII Regions  

NASA Astrophysics Data System (ADS)

The complex dynamics of an ionization front which is a surface of radiatively driven molecular cloud is a common feature of HII regions. We carried out two-dimensional numerical hydrodynamic simulations with a realistic initial density profile for a neutral gas region, and with perturbations at the ionization front considering detailed physics so far. The energy deposition and release due to the absorption of strong UV radiation from O-stars the recombination effects in the ionized region are included. The radiation loss from shocked molecular gas is also included. We introduce magnetic field's effect into the equation of state to prevent too high density because of radiative collapse in the molecular gas^a. The results are compared with recent detailed observational data of the Eagle Nebula by the Hubble Space Telescope (HST) and Berkeley-Illinois-Maryland Array (BIMA)^b,c. We also discuss the growth of the perturbations at the ionization front and the appropriateness of hydrodynamic instabilities on the ionized front. a. Ryutov, D, & Remington, B., Plasma Phys. Control. Fusion (2002) 44, B407, b. Hester, J. J, et al., AJ (1996) 111, 2349, c. Pound, M. W., et al., ApJ (1998) 493, L113

Mizuta, Akira; Kane, Jave; Remington, Bruce; Ryutov, Dmitri; Takabe, Hideaki

2003-10-01

366

IONIZED OUTFLOWS FROM COMPACT STEEP SPECTRUM SOURCES  

SciTech Connect

Massive outflows are known to exist, in the form of extended emission-line regions (EELRs), around about one-third of powerful FR II radio sources. We investigate the origin of these EELRs by studying the emission-line regions around compact-steep-spectrum (CSS) radio galaxies that are younger (10{sup 3}-10{sup 5} yr old) versions of the FR II radio galaxies. We have searched for and analyzed the emission-line regions around 11 CSS sources by taking integral field spectra using Gemini Multi-Object Spectrograph on Gemini North. We fit the [O III] {lambda}5007 line and present the velocity maps for each detected emission-line region. We find, in most cases, that the emission-line regions have multi-component velocity structures with different velocity dispersions and/or flux distributions for each component. The velocity gradients of the emission-line gas are mostly well aligned with the radio axis, suggesting a direct causal link between the outflowing gas and the radio jets. The complex velocity structure may be a result of different driving mechanisms related to the onset of the radio jets. We also present the results from the line-ratio diagnostics we used to analyze the ionization mechanism of the extended gas, which supports the scenario where the emission-line regions are ionized by a combination of active galactic nucleus radiation and shock excitation.

Shih, Hsin-Yi; Stockton, Alan; Kewley, Lisa, E-mail: hsshih@ifa.hawaii.edu, E-mail: stockton@ifa.hawaii.edu, E-mail: lisa.kewley@anu.edu.au [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

2013-08-01

367

Effect of internal and external conditions on ionization processes in the FAPA ambient desorption/ionization source.  

PubMed

Ambient desorption/ionization (ADI) sources coupled to mass spectrometry (MS) offer outstanding analytical features: direct analysis of real samples without sample pretreatment, combined with the selectivity and sensitivity of MS. Since ADI sources typically work in the open atmosphere, ambient conditions can affect the desorption and ionization processes. Here, the effects of internal source parameters and ambient humidity on the ionization processes of the flowing atmospheric pressure afterglow (FAPA) source are investigated. The interaction of reagent ions with a range of analytes is studied in terms of sensitivity and based upon the processes that occur in the ionization reactions. The results show that internal parameters which lead to higher gas temperatures afforded higher sensitivities, although fragmentation is also affected. In the case of humidity, only extremely dry conditions led to higher sensitivities, while fragmentation remained unaffected. PMID:25178932

Orejas, Jaime; Pfeuffer, Kevin P; Ray, Steven J; Pisonero, Jorge; Sanz-Medel, Alfredo; Hieftje, Gary M

2014-11-01

368

Ionizable-Substance Detector  

NASA Technical Reports Server (NTRS)

Device that includes all conventional components of fuel cell and electrolyzer continuously monitors concentration of ionizable substance in stream of fluid without significantly disrupting flow or chemical composition. Among substances monitored are hydrogen, sodium, fluorine, chlorine, oxygen, and bromine. Useful in early detection of fluctuations, malfunctions, or hazards. Particularly useful for detecting hydrogen in stream of water in closed system containing oxygen, wherein concentration of hydrogen must not exceed given maximum, lest hydrogen react explosively with oxygen. Also used to monitor exhaust stream to comply with environmental-protection requirements.

Mcelroy, William; Smith, William

1991-01-01

369

Journal of Chromatography B, 800 (2004) 145153 Application of liquid chromatographyelectrospray ionization mass  

E-print Network

Journal of Chromatography B, 800 (2004) 145­153 Application of liquid chromatography A high-performance liquid chromatography­atmospheric pressure ionization­electrospray ionization mass by Makin et al. [1]. The most frequently exploited methods for steroid anal- ysis are gas chromatography

Miksik, Ivan

370

Programs for Laser-AO Assisted Integral-Field Spectrometers on Ionized Flows  

E-print Network

and even accelerations of individual gas clumps in the bow-shock and "jet" complexes. Many classical HHO to a shock front is thermalized ini- tially, gas emission depends strongly on the shock geometry hence energy across the flow to alter the excitation and ionization of the pre-shock gas. Increased preshock

Cecil, Gerald

371

Theory of field ionization  

NASA Astrophysics Data System (ADS)

We describe calculations of tunnelling rate constants for the field ion microscope (FIM) using various model potentials, and potentials obtained from self-consistent electronic structure calculations incorporating the full screening of an applied electric field. For our tunnelling calculations we have used the JWKB method of Haydock and Kingham. The expression for the tunnelling rate constant for a flat surface given by Haydock and Kingham is inaccurate and we have derived a new and reliable formula. We have also introduced a new tunnelling potential for the FIM which includes explicitly the effects of image potentials. None of the potentials for smooth surfaces give ionization zone widths which are narrow enough to account for experimental values. However, the width of the ionization zone is found to be a strongly decreasing function of the corrugation of the surface potential, and for large corrugations we can obtain results in plausible agreement with experimental values. For corrugated model surfaces we have found cross-surface variations in the tunnelling rate constant which may be sufficient to account for the atomic resolution of the FIM under normal operating conditions at liquid nitrogen temperatures.

Lam, S. C.; Needs, R. J.

1994-03-01

372

Redox transformations in desorption electrospray ionization  

NASA Astrophysics Data System (ADS)

Redox changes occur in some circumstances when organic compounds are analyzed by desorption electrospray ionization mass spectrometry (DESI-MS). However, these processes are limited in scope and the data presented here suggest that there are only limited analogies between the redox behavior in DESI and the well-known solution-phase electrochemical processes in standard electrospray ionization (ESI). Positive and negative ion modes were both investigated and there is a striking asymmetry between the incidence of oxidation and of reduction. Although in negative ion mode DESI experiments, some aromatic compounds were ionized as odd-electron anion radicals, examples of full reduction were not found. By contrast, oxidation in the form of oxygen atom addition (or multiple oxygen atom additions) was observed for several different analytes. These oxidation reactions point to chemically rather than electrochemically controlled processes. Data is presented which suggests that oxidation is predominantly caused by reaction with discharge-created gas-phase radicals. The fact that common reducing agents and known antioxidants such as ascorbic acid are not modified, while a saturated organic acid like stearic acid is oxidized in DESI, indicates that the usual electrochemical redox reactions are not significant but that redox chemistry can be induced under special experimental conditions.

Benassi, Mario; Wu, Chunping; Nefliu, Marcela; Ifa, Demian R.; Volný, Michael; Cooks, R. Graham

2009-02-01

373

NEGATIVE CHEMICAL IONIZATION STUDIES OF HUMAN AND FOOD CHAIN CONTAMINATION WITH XENOBIOTIC CHEMICALS  

EPA Science Inventory

Negative chemical ionization mass spectrometry with a mixture of isobutane, methylene chloride, and oxygen as the reagent gas has been used to explore contamination of environmental substrates with xenobiotic chemicals. The substrates in question, fish tissue, human seminal plasm...

374

Double-gated isolated vertically aligned carbon nanofiber field emission and field ionization arrays  

E-print Network

Electron impact ionization (ElI) is used extensively in mass spectrometry for gas-phase analytes. Due to the significant amount of fragmentation generated by ElI, the spectrum is usually very noisy. In addition, the ...

Chen, Liang-Yu, 1979-

2007-01-01

375

[Ionizing and non-ionizing radiation (comparative risk estimations)].  

PubMed

The population has widely used mobile communication for already more than 15 years. It is important to note that the use of mobile communication has sharply changed the conditions of daily exposure of the population to EME We expose our brain daily for the first time in the entire civilization. The mobile phone is an open and uncontrollable source of electromagnetic radiation. The comparative risk estimation for the population of ionizing and non-ionizing radiation was carried out taking into account the real conditions of influence. Comparison of risks for the population of ionizing and non-ionizing radiation leads us to a conclusion that EMF RF exposure in conditions of wide use of mobile communication is potentially more harmful than ionizing radiation influence. PMID:22690585

Grigor'ev, Iu G

2012-01-01

376

An ionization region model for high-power impulse magnetron sputtering discharges  

Microsoft Academic Search

A time-dependent plasma discharge model has been developed for the ionization region in a high-power impulse magnetron sputtering (HiPIMS) discharge. It provides a flexible modeling tool to explore, e.g., the temporal variations of the ionized fractions of the working gas and the sputtered vapor, the electron density and temperature, and the gas rarefaction and refill processes. A separation is made

M A Raadu; I Axnäs; J T Gudmundsson; C Huo; N Brenning

2011-01-01

377

Ionizing radiation detector  

DOEpatents

An ionizing radiation detector is provided which is based on the principle of analog electronic integration of radiation sensor currents in the sub-pico to nano ampere range between fixed voltage switching thresholds with automatic voltage reversal each time the appropriate threshold is reached. The thresholds are provided by a first NAND gate Schmitt trigger which is coupled with a second NAND gate Schmitt trigger operating in an alternate switching state from the first gate to turn either a visible or audible indicating device on and off in response to the gate switching rate which is indicative of the level of radiation being sensed. The detector can be configured as a small, personal radiation dosimeter which is simple to operate and responsive over a dynamic range of at least 0.01 to 1000 R/hr.

Thacker, Louis H. (Knoxville, TN)

1990-01-01

378

[Development of a membrane inlet-single photon ionization/chemical ionization-mass spectrometer for online analysis of VOCs in water].  

PubMed

A home-made membrane inlet- single photon ionization/chemical ionization- time-of-flight mass spectrometer has been described. A vacuum ultraviolet (VUV) lamp with photon energy of 10.6 eV was used as the light source for single photon ionization (SPI). Chemical ionization (CI) was achieved through ion-molecule reactions with O2- reactant ions generated by photoelectron ionization. The two ionization modes could be rapidly switched by adjusting electric field in the ionization region within 2 s. Membrane inlet system used for rapid enrichment of volatile organic compounds (VOCs) in water was constructed by using a polydimethylsiloxane (PDMS) membrane with a thickness of 50 microm. A purge gas was added to accelerate desorption of analytes from the membrane surface. The purge gas could also help to prevent the pump oil back-streaming into the ionization region from the analyzer chamber and improve the signal to noise ratio (S/N). Achieved detection limits were 2 microg x L(-1) for methyl tert-butyl ether (MTBE) in SPI mode and 1 microg x L(-1) for chloroform in SPI-CI mode within 10 s analysis time, respectively. The instrument has been successfully applied to the rapid analysis of MTBE in simulated underground water nearby petrol station and VOCs in disinfected drinking water. The results indicate that the instrument has a great application prospect for online analysis of VOCs in water. PMID:22468530

Hua, Lei; Wu, Qing-Hao; Hou, Ke-Yong; Cui, Hua-Peng; Chen, Ping; Zhao, Wu-Duo; Xie, Yuan-Yuan; Li, Hai-Yang

2011-12-01

379

Vortices in a gas-discharge plasma  

Microsoft Academic Search

Processes of vortex generation in a weakly ionized gas are reviewed in circumstances where a high-speed flow propagates along the gas discharge and acoustic waves interact with a positive column. Results on the effect of longitudinal gas flow in the positive-column properties are presented. It is shown that in certain conditions the gas flow in the positive column gives rise

A R Aramyan; G A Galechyan

2007-01-01

380

Gas mixtures for spark gap closing switches  

DOEpatents

Gas mixtures for use in spark gap closing switches comprised of fluorocarbons and low molecular weight, inert buffer gases. To this can be added a third gas having a low ionization potential relative to the buffer gas. The gas mixtures presented possess properties that optimized the efficiency spark gap closing switches. 6 figs.

Christophorou, L.G.; McCorkle, D.L.; Hunter, S.R.

1987-02-20

381

Aliphatic Hydrocarbon Spectra by Helium Ionization Mass Spectrometry (HIMS) on a Modified Atmospheric-Pressure Source Designed for Electrospray Ionization  

NASA Astrophysics Data System (ADS)

Chemical-ionization techniques that use metastable species to ionize analytes traditionally use a flat pin or a sharp solid needle onto which the high potential needed to generate the discharge plasma is applied. We report here that direct analysis of samples containing volatile and semivolatile compounds, including saturated and unsaturated aliphatic hydrocarbons, can be achieved on any electrospray-ionization mass spectrometer by passing helium though the sample delivery metal capillary held at a high potential. In the helium plasma ionization source (HPIS) described here, the typical helium flow required (about 20-30 mL/min), was significantly lower than that needed for other helium-ionization sources. By this procedure, positive ions were generated by nominal hydride ion removal from molecules emanating from heated saturated hydrocarbons as large as tetratetracontane (C44H90), at capillary voltages ranging from 2.0 to 4.0 kV. Unsaturated hydrocarbons, on the other hand, underwent facile protonation under much lower capillary voltages (0.9 to 2.0 kV). Although saturated and monounsaturated hydrocarbons bearing the same number of carbon atoms generate ions of the same m/z ratio, a gas-phase deuterium exchange method is described to ascertain the identity of these isomeric ions originating from either protonation or hydride abstraction mechanisms. Moreover, mass spectrometric results obtained by exposing unsaturated hydrocarbons to D2O vapor in an HPIS-MS instrument confirmed that the proton donor for ionization of unsaturated hydrocarbons is protonated water.

Yang, Zhihua; Attygalle, Athula B.

2011-08-01

382

Probing background ionization: Positive streamers with varying pulse repetition rate and with a radioactive admixture  

E-print Network

Positive streamers need a source of free electrons ahead of them to propagate. A streamer can supply these electrons by itself through photo-ionization, or the electrons can be present due to external background ionization. Here we investigate the effects of background ionization on streamer propagation and morphology by changing the gas composition and the repetition rate of the voltage pulses, and by adding a small amount of radioactive Krypton 85. We find that the general morphology of a positive streamer discharge in high purity nitrogen depends on background ionization: at lower background ionization levels the streamers branch more and have a more feather-like appearance. This is observed both when varying the repetition rate and when adding Krypton 85, though side branches are longer with the radioactive admixture. But velocities and minimal diameters of streamers are virtually independent of the background ionization level. In air, the inception cloud breaks up into streamers at a smaller radius when ...

Nijdam, S; van Veldhuizen, E M; Ebert, U

2011-01-01

383

COSMIC RAY HEATING OF THE WARM IONIZED MEDIUM  

SciTech Connect

Observations of line ratios in the Milky Way's warm ionized medium suggest that photoionization is not the only heating mechanism present. For the additional heating to explain the discrepancy, it would have to have a weaker dependence on the gas density than the cooling rate, {Lambda}n{sub e}{sup 2}. Reynolds et al. suggested turbulent dissipation or magnetic field reconnection as possible heating sources. We investigate here the viability of MHD-wave mediated cosmic ray heating as a supplemental heating source. This heating rate depends on the gas density only through its linear dependence on the Alfven speed, which goes as n{sub e}{sup -1/2}. We show that, scaled to appropriate values of cosmic ray energy density, cosmic ray heating can be significant. Furthermore, this heating is stable to perturbations. These results should also apply to warm ionized gas in other galaxies.

Wiener, Joshua; Peng Oh, S. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States)] [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Zweibel, Ellen G. [Departments of Astronomy and Physics, and Center for Magnetic Self-Organization, University of Wisconsin-Madison, Madison, WI 53706 (United States)] [Departments of Astronomy and Physics, and Center for Magnetic Self-Organization, University of Wisconsin-Madison, Madison, WI 53706 (United States)

2013-04-10

384

Ionization satellites of the ArHe dimer  

NASA Astrophysics Data System (ADS)

Ionization satellites are key ingredients in the control of post ionization processes such as molecular dissociation and interatomic Coulombic decay. Here, using the high-level ab initio method of multi-reference configuration interaction up to triple excitations, we study the potential energy curves (PECs) of the ionization satellites of the ArHe dimer. With this model system, we demonstrate that the simple model used in alkaline earth metal and rare gas complexes to describe the satellites as a Rydberg electron moving on top of a dicationic core does not fully hold for the rare gas clusters. The more complex valence structure in the rare gas atom leads to the mixing of different electronic configurations of the dimer. This prevents one from assigning a single dicationic parent state to some of the ionization satellites. We further analyze the structure of the different PECs, demonstrating how the density of the Rydberg electron is reflected in the structure of the PEC wherever the simple model is applicable.

Miteva, Tsveta; Klaiman, Shachar; Gromov, Evgeniy V.; Gokhberg, Kirill

2014-05-01

385

Ionization satellites of the ArHe dimer.  

PubMed

Ionization satellites are key ingredients in the control of post ionization processes such as molecular dissociation and interatomic Coulombic decay. Here, using the high-level ab initio method of multi-reference configuration interaction up to triple excitations, we study the potential energy curves (PECs) of the ionization satellites of the ArHe dimer. With this model system, we demonstrate that the simple model used in alkaline earth metal and rare gas complexes to describe the satellites as a Rydberg electron moving on top of a dicationic core does not fully hold for the rare gas clusters. The more complex valence structure in the rare gas atom leads to the mixing of different electronic configurations of the dimer. This prevents one from assigning a single dicationic parent state to some of the ionization satellites. We further analyze the structure of the different PECs, demonstrating how the density of the Rydberg electron is reflected in the structure of the PEC wherever the simple model is applicable. PMID:24880293

Miteva, Tsveta; Klaiman, Shachar; Gromov, Evgeniy V; Gokhberg, Kirill

2014-05-28

386

Theory of ionization-induced trapping in laser-plasma accelerators  

NASA Astrophysics Data System (ADS)

Ionization injection in a laser-plasma accelerator is studied analytically and by multi-dimensional particle-in-cell (PIC) simulations. To enable the production of low energy spread beams, we consider a short region containing a high atomic number gas (e.g., nitrogen) for ionization-induced trapping, followed by a longer region using a low atomic number gas (e.g., hydrogen), that is, free of additional trapping, for post acceleration. For a broad laser pulse, ionization injection requires a minimum normalized laser field of a0?1.7, assuming a resonant Gaussian laser pulse. Effects of gas mix parameters, including species, concentration, and length of the mixture region, on the final electron injection number and beam quality are studied. The minimum energy spread is determined by the spread in initial ionized phases of the electrons in the wakefield due to the tunneling ionization process within the laser pulse. Laser polarization and intensity effects on injection number and final electron emittance are examined. Two-dimensional PIC simulations are used to study the ionization injection process and the transverse beam structure. With proper laser-plasma parameters, mono-energetic electron beams with 10 pC charge, a central energy at GeV level, and energy spread less than 1% can be produced in a mixed gas with ionized electron density of 1018cm-3. Lower density can give a higher final accelerated beam energy and reduce the final relative energy spread even further.

Chen, M.; Esarey, E.; Schroeder, C. B.; Geddes, C. G. R.; Leemans, W. P.

2012-03-01

387

An Analysis of Ionization Correction Factors in Planetary Nebulae  

NASA Astrophysics Data System (ADS)

I will present here some of the results derived from our recent analysis of ionization correction factors (ICFs) in planetary nebulae (PNe). We compute an extensive grid of ~15000 photoionization models using the c10.00 version of Cloudy code (Ferland et al. 1998) that cover a wide range of effective temperatures, nebular radius, luminosities, and gas densities. We use both blackbodies and Rauch atmospheres as ionizing sources, and we calculate constant and non-constant density models as well as radiation-and matter-bounded models. We derive new ICFs for PNe and their associated uncertainties. I will discuss the differences with previous ICFs used in the literature.

Delgado-Inglada, G.

2014-04-01

388

Quantum statistical mechanics of dense partially ionized hydrogen  

NASA Technical Reports Server (NTRS)

The theory of dense hydrogen plasmas beginning with the two component quantum grand partition function is reviewed. It is shown that ionization equilibrium and molecular dissociation equilibrium can be treated in the same manner with proper consideration of all two-body states. A quantum perturbation expansion is used to give an accurate calculation of the equation of state of the gas for any degree of dissociation and ionization. The statistical mechanical calculation of the plasma equation of state is intended for stellar interiors. The general approach is extended to the calculation of the equation of state of the outer layers of large planets.

Dewitt, H. E.; Rogers, F. J.

1972-01-01

389

Review of the critical ionization velocity effect in space  

NASA Technical Reports Server (NTRS)

Laboratory experiments have shown under a variety of conditions that when a neutral gas passes through a magnetized plasma with a relative velocity perpendicular to the magnetic field that is greater than a critical velocity, anomalously high ionization of the neutrals occurs. The conditions under which the same effect is to be expected in space plasmas is still unclear. The experimental evidence for the occurrence of the critical ionization velocity effect in space is summarized, and various areas in which it has been proposed that the effect should be significant are discussed.

Newell, P. T.

1985-01-01

390

Pulsed helium ionization detection system  

DOEpatents

A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

Ramsey, Roswitha S. (Knoxville, TN); Todd, Richard A. (Knoxville, TN)

1987-01-01

391

Pulsed helium ionization detection system  

DOEpatents

A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

Ramsey, R.S.; Todd, R.A.

1985-04-09

392

Martian Meteor Ionization Layers  

NASA Technical Reports Server (NTRS)

Small interplanetary grains bombard Mars, like all the solar system planets, and, like all the planets with atmospheres, meteoric ion and atom layers form in the upper atmosphere. We have developed a comprehensive one-dimensional model of the Martian meteoric ionization layer including a full chemical scheme. A persistent layer of magnesium ions should exist around an altitude of 70 km. Unlike the terrestrial case, where the metallic ions are formed via charge-exchange with the ambient ions, Mg(+) in the Martian atmosphere is produced by photoionization. Nevertheless, the predicted metal layer peak densities for Earth and Mars are similar. Diffusion solutions, such as those presented here, should be a good approximation of the metallic ions in regions where the magnetic field is negligible and may provide a significant contribution to the nightside ionosphere. The low ultraviolet absorption of the Martian atmosphere may make Mars an excellent laboratory in which to study meteoric ablation. Resonance lines not seen in the spectra of terrestrial meteors may be visible to a surface observatory in the Martian highlands.

Grebowsky, J. M.; Pesnell, W. D.

1999-01-01

393

Low-Pressure, Field-Ionizing Mass Spectrometer  

NASA Technical Reports Server (NTRS)

A small mass spectrometer utilizing a miniature field ionization source is now undergoing development. It is designed for use in a variety of applications in which there are requirements for a lightweight, low-power-consumption instrument that can analyze the masses of a wide variety of molecules and ions. The device can operate without need for a high-vacuum, carrier-gas feed radioactive ionizing source, or thermal ionizer. This mass spectrometer can operate either in the natural vacuum of outer space or on Earth at any ambient pressure below 50 torr (below about 6.7 kPa) - a partial vacuum that can easily be reached by use of a small sampling pump. This mass spectrometer also has a large dynamic range - from singly charged small gas ions to deoxyribonucleic acid (DNA) fragments larger than 104 atomic mass units - with sensitivity adequate for detecting some molecules and ions at relative abundances of less than one part per billion. This instrument (see figure) includes a field ionizer integrated with a rotating-field mass spectrometer (RFMS). The field ionizer effects ionization of a type characterized as "soft" in the art because it does not fragment molecules or initiate avalanche arcing. What makes the "soft" ionization mode possible is that the distance between the ionizing electrodes is less than mean free path for ions at the maximum anticipated operating pressure, so that the ionizer always operates on the non-breakdown side of the applicable Paschen curve (a standard plot of breakdown potential on the ordinate and pressure electrode separation on the abscissa). The field ionizer in this instrument is fabricated by micromachining a submicron-thick membrane out of an electrically nonconductive substrate, coating the membrane on both sides to form electrodes, then micromachining small holes through the electrodes and membrane. Because of the submicron electrode separation, even a potential of only 1 V applied between the electrodes gives rise to an electric field with a strength of in excess of a megavolt per meter strong enough to ionize any gas molecules passing through the holes. An accelerator grid and an electrostatic deflector focus the ions from the field ionizer into the rotating-field cell of the RFMS. The potentials applied to the electrodes of the cell to generate the rotating electric field typically range from 1 to 13 V. The ions travel in well-defined helices within this cell, after which they are collected in a Faraday cup. The mass of most of the molecules reaching the Faraday cup decreases with increasing frequency of rotation of the electric field in the cell. Therefore, the frequency of rotation of the electric field is made to vary in order to scan through a desired range of ion masses: For example, lightweight gas molecules are scanned at frequencies in the megahertz range, while DNA and other large organic molecules are scanned at kilohertz frequencies.

Hartley, Frank; Smith, Steven

2009-01-01

394

Propagation of ultrashort laser pulses in optically ionized gases  

SciTech Connect

Propagation of 800 nm, 120 fs laser pulses with intensities of 4x10{sup 16} W/cm{sup 2} in supersonic gas jets of N{sub 2} and H{sub 2} is studied using a shear-type interferometer. The plasma density distribution resulting from photoionization is resolved in space and time with simultaneously measured initial neutral density distribution. A distinct difference in laser beam propagation distance is observed when comparing propagation in jets of H{sub 2} and N{sub 2}. This is interpreted in terms of ionization induced refraction, which is stronger when electrons are produced from states of higher ionization potential. Three dimensional particle-in-cell simulations, based on directly solving the Maxwell-Lorentz system of equations, show the roles played by the forward Raman and ionization scattering instabilities, which further affect the propagation distance.

Morozov, A.; Luo, Y.; Suckewer, S. [Princeton University, Princeton, New Jersey 08544 (United States); Gordon, D. F.; Sprangle, P. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

2010-02-15

395