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1

Study of the fragmentation pattern of ketamine-heptafluorobutyramide by gas chromatography/electron ionization mass spectrometry.  

PubMed

Ketamine is an anaesthetic compound used in human and veterinary medicine with hallucinogen properties that have resulted in its increased illicit use by teenagers at rave parties. Although several gas chromatography/mass spectrometry (GC/MS) methods have been reported for the quantification of the drug both in urine and in hair, its electron ionization (EI) fragmentation after derivatization with different reagents has been not yet fully investigated. The present work reports the study of the fragmentation of ketamine, derivatized with heptafluorobutyric anhydride (HFBA-Ket), using gas chromatography/electron ionization mass spectrometry (GC/EI-MS). The complete characterization of the fragmentation pattern represented an intriguing exercise and required tandem mass spectrometry (MS(n)) experiments, high-resolution accurate mass measurements and the use of deuterated d(4)-ketamine to corroborate the proposed structures and to characterize the fragment ions carrying the unchanged aromatic moiety. Extensive fragmentation was observed, mainly located at the cyclohexanone ring followed by rearrangement of the fragment ions, as confirmed by the mass spectra obtained from the deuterated molecule. The GC/EI-MS analysis of HFBA-Ket will represent a useful tool in forensic science since high-throughput analyses are enabled, preserving both the GC stationary phase and the cleanliness of the mass spectrometer ion optics. PMID:19957293

Pieri, Maria; Castiglia, Loredana; Miraglia, Nadia; Guadagni, Rossella; Malorni, Livia; Sannolo, Nicola; Acampora, Antonio; Della Casa, Elvira

2010-01-01

2

Gas chromatography electron ionization mass spectrometric analysis of O-alkyl methylphosphinates for verification of Chemical Weapons Convention.  

PubMed

We describe the gas chromatography/mass spectrometric (GC/MS) analysis of O-alkyl methylphosphinates (AMPs), which are included in schedule 2B4 chemicals in the Chemical Weapons Convention (CWC). GC/MS analysis of variety of AMPs and their deuterated analogues revealed that their fragmentations were determined by alpha-cleavages, McLafferty +1 and hydrogen rearrangements. Based on the obtained electron ionization mass spectra of AMPs the fragmentation routes were rationalized, which were substantiated by the GC/MS analysis of deuterated analogues. PMID:19679938

Pardasani, Deepak; Kanaujia, Pankaj K; Tak, Vijay; Garg, Prabhat; Mazumder, Avik; Dubey, Devendra K

2009-01-01

3

Improving quantitative gas chromatography-electron ionization mass spectrometry results using a modified ion source: demonstration for a pharmaceutical application.  

PubMed

Gas chromatography-mass spectrometry is a well established analytical technique. However, mass spectrometers with electron ionization sources may suffer from signal drifts, hereby negatively influencing quantitative performance. To demonstrate this phenomenon for a real application, a static headspace-gas chromatography method in combination with electron ionization-quadrupole mass spectrometry was optimized for the determination of residual dichloromethane in coronary stent coatings. Validating the method, the quantitative performance of an original stainless steel ion source was compared to that of a modified ion source. Ion source modification included the application of a gold coating on the repeller and exit plate. Several validation aspects such as limit of detection, limit of quantification, linearity and precision were evaluated using both ion sources. It was found that, as expected, the stainless steel ion source suffered from signal drift. As a consequence, non-linearity and high RSD values for repeated analyses were obtained. An additional experiment was performed to check whether an internal standard compound would lead to better results. It was found that the signal drift patterns of the analyte and internal standard were different, consequently leading to high RSD values for the response factor. With the modified ion source however, a more stable signal was observed resulting in acceptable linearity and precision. Moreover, it was also found that sensitivity improved compared to the stainless steel ion source. Finally, the optimized method with the modified ion source was applied to determine residual dichloromethane in the coating of coronary stents. The solvent was detected but found to be below the limit of quantification. PMID:21620408

D'Autry, Ward; Wolfs, Kris; Hoogmartens, Jos; Adams, Erwin; Van Schepdael, Ann

2011-05-14

4

Analysis of 5-methoxytryptamine at the femtomole level in the rat and quail brain by gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry.  

PubMed

A sensitive method for the measurement of endogenous 5-methoxytryptamine in brain tissue has been developed using capillary column gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry. 5-Methoxytryptamine was first converted to N-[2H3]acetyl-5-methoxytryptamine by reaction with hexa-deuterated acetic anhydride, followed by reaction with pentafluoropropionic anhydride to yield the highly electron-capturing 3,3'-spirocyclic pentafluoro-propionyl indolenine derivative. Quantitative analysis was carried out by selected-ion monitoring of the [M-HF].- and [M-HF-DF].- ion intensity of the 3.3'-spirocyclic pentafluoropropionyl indolenine derivative, using 5-methoxy-[alpha, alpha, beta, beta-2H4]tryptamine as the internal standard. The presence of 5-methoxytryptamine in the brain tissue was demonstrated. In the absence of a monoamine oxidase inhibitor, the mean +/- S.D. levels of 5-methoxytryptamine in the rat and quail whole brain were found to be 30 +/- 6 and 347 +/- 52 pg/g, respectively. The possible physiological functions of 5-methoxytryptamine as a neuromodulator and/or neurotransmitter have to be considered. PMID:8844409

Tsang, C W; Chan, C L; Li, P; Pang, S F

1996-07-12

5

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

PubMed Central

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

Bowden, John A.; Ford, David A.

2010-01-01

6

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

PubMed

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

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

2013-08-30

7

Microsynthesis and gas chromatography/electron ionization mass spectrometric and tandem mass spectrometric analysis of cyclic alkylphosphonates for verification of the Chemical Weapons Convention.  

PubMed

We describe the microsynthesis and gas chromatography/mass spectrometric (GC/MS) analysis of cyclic alkylphosphonates (CAPs), which are included in schedule 2B4 chemicals in the Chemical Weapons Convention (CWC). The reported microsynthesis is efficient in comparison with traditional synthesis. GC/MS and GC/tandem mass spectrometric (MS/MS) analysis of a variety of CAPs revealed that their fragmentations were dominated by alpha-cleavages, alkene eliminations and hydrogen rearrangements. Based on the obtained mass spectra and precursor and product ion analysis of five-, six- and seven-membered cyclic alkylphosphonates, the proposed fragmentation routes rationalize most of the characteristic ions. PMID:18636421

Dubey, Devendra K; Pardasani, Deepak; Kanaujia, Pankaj K; Tak, Vijay; Gupta, Hemendra K

2008-08-01

8

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

EPA Science Inventory

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

9

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

PubMed

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

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

2010-12-25

10

Systematic characterisation of long-chain aliphatic esters of wool wax by gas chromatography–electron impact ionisation mass spectrometry  

Microsoft Academic Search

A detailed structural characterisation of the aliphatic high-molecular-mass esters extracted from raw wool based on high-temperature gas chromatography–electron impact ionisation mass spectrometry is described. The raw wool esters extracted are in the range of C37 to C54 (i.e., molecular mass 550–788). The selected ion chromatogram exhibited four isomers for the esters with an odd number of carbon atoms (i:a, i:n,

Zaharie Moldovan; Eric Jover; José Maria Bayona

2002-01-01

11

Extraction and Gas Chromatography\\/Electron Capture Analysis of Polychlorinated Biphenyls in Railcar Paint Scrapings  

Microsoft Academic Search

Polychlorinated biphenyls (PCBs) in dried paints may present an occupational exposure hazard to maintenance workers and welders who are unaware of their past use in specialized metal coatings. Prior to their restriction to closed systems in 1970, PCBs were routinely added to these paints to impart properties of heat resistance, plasticity, and antifouling. Gas chromatography with electron capture detection was

Michael S. Welsh

1995-01-01

12

Simultaneous quantification of tramadol and O-desmethyltramadol in hair samples by gas chromatography-electron impact/mass spectrometry.  

PubMed

Over recent years, hair has become the ideal matrix for retrospective investigation of chronic abuse, including for tramadol. However, in order to exclude the possibility of external contamination, it is also important to quantify simultaneously its main metabolite, O-desmethyltramadol (M1), which presence in hair reflects systemic exposure. In the present study a methodology aimed at the simultaneous quantification of tramadol and M1 in human hair was developed and validated for the first time. After decontamination of hair samples (60 mg), tramadol and M1 were extracted with methanol in an ultrasonic bath (~5 h). Purification was performed by solid-phase extraction using mixed-mode extraction cartridges. Subsequently to derivatization, analysis was performed by gas chromatography-electron impact/mass spectrometry (GC-EI/MS). The method proved to be selective. The regression analysis for both analytes was shown to be linear in the range of 0.1-20.0 ng/mg with correlation coefficients of 0.9995 and 0.9997 for tramadol and M1, respectively. The coefficients of variation oscillated between 3.85 and 13.24%. The limits of detection were 0.03 and 0.02 ng/mg, and the lower limits of quantification were 0.08 and 0.06 ng/mg for tramadol and M1, respectively. The proof of applicability was performed in hair samples from six patients undergoing tramadol therapy. All samples were positive for tramadol and M1. PMID:23519701

Pinho, Sandra; Oliveira, Ana; Costa, Isabel; Gouveia, Carla Alexandra; Carvalho, Félix; Moreira, Roxana Falcão; Dinis-Oliveira, Ricardo Jorge

2013-03-21

13

Application of pentafluorophenyldimethylsilyl derivatization for gas chromatography–electron-capture detection of supercritically extracted sterols  

Microsoft Academic Search

We report a convenient method of extracting and detecting sterols in environmental water samples. Particle-associated sterols were extracted onto glass-fibre filters then the filters were supercritical fluid extracted (at 33 MPa, 80°C for 30 min) followed by pentafluorophenyldimethylsilyl (flophemesyl) derivatization for gas chromatographic–electron-capture detection (GC–ECD). Optimal derivatization of epicoprostanol, coprostanol, cholesterol, dihydrocholesterol, stigmasterol, ?-sitosterol and stigmastanol with neat flophemesyl chloride

Leonard Y Jayasinghe; Philip J Marriott; Peter D Carpenter; Peter D Nichols

1998-01-01

14

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

Microsoft Academic Search

Whole grain cereals are an important source of bioavailable lignans, the group of compounds with potential anti-cancerogenic, antioxidant, anti-proliferative, pro-apoptotic, and antiangiogenic properties. The aim of this work was to develop a sensitive method for determination of wheat bran lignans. The analysis of lignans secoisolariciresinol, hydroxymatairesinol, lariciresinol, matairesinol, pinoresinol, syringaresinol is based on derivatization with pentafluoropropionic anhydride (PFPA) and gas

Nikolina ?ukelj; Ivone Jakasa; Hrvoje Sarajlija; Dubravka Novotni; Duška ?uri?

2011-01-01

15

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

PubMed

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

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

2013-09-06

16

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

17

Ionization of Infalling Gas  

NASA Astrophysics Data System (ADS)

H? emission from neutral halo clouds probes the radiation and hydrodynamic conditions in the halo. Armed with such measurements, we can explore how radiation escapes from the Galactic plane and how infalling gas can survive a trip through the halo. The Wisconsin H-Alpha Mapper (WHAM) is one of the most sensitive instruments for detecting and mapping optical emission from the ISM. Here, we present recent results exploring the ionization of two infallling high-velocity complexes. First, we report on our progress mapping H? emission covering the full extent of Complex A. Intensities are faint (100 mR; EM 0.2pccm-6) but correlate on the sky and in velocity with 21-cm emission. Second, we explore the ionized component of some Anti-Center Complex clouds studied by Peek et al. (2007) that show dynamic shaping from interaction with the Galactic halo.

Haffner, L. M.; Duncan, A. K.; Hoffman, S. M.; Madsen, G. J.; Hill, A. S.; Reynolds, R. J.

2012-09-01

18

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

Microsoft Academic Search

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

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

2007-01-01

19

Gas amplified ionization detector for gas chromatography  

DOEpatents

A gas-amplified ionization detector for gas chromatography which possesses increased sensitivity and a very fast response time is described. 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. 4 figs.

Huston, G.C.

1989-11-27

20

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

21

Flame ionization gas analyzers  

Microsoft Academic Search

The paper deals with gas analyzers in which the measured change in conductivity of a standard flame due to the insertion of another gas is used to detect the gas. The application of gas analyzers of this type to the detection of atmospheric pollutants is examined, and some existing gas analyzer designs are discussed.

A. N. Belugin; A. Ia. Bonn; G. V. Verbovskaia; A. M. Drobiz; Iu. G. Khachaturov

1979-01-01

22

Determination of melatonin in pharmaceutical formulations and human plasma by gas chromatography-electron impact mass spectrometry.  

PubMed

A simple and reliable method for gas chromatography-mass spectrometry (GC-MS) has been developed for the determination of melatonin in commercially available tablet formulations and human plasma. The dissolution of the tablets in ethyl acetate was simply obtained by sonication. The filtrate of the resultant solution, after concentration, was derivatized with pentafluoropropionic anhydride (PFPA) and analysed by GC-MS using splitless injection. The linear response range for melatonin was 5-250 ng on column. The same method can be used, with minor modifications, for the determination of melatonin in spiked human plasma in the range 50-1000 pg/mL plasma. PMID:10477902

Covaci, A; Doneanu, C; Aboul-Enein, H Y; Schepens, P

1999-10-01

23

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

2012-11-19

24

Ionization coefficients in gas mixtures  

NASA Astrophysics Data System (ADS)

We have tested the application of the common E/N (E—electric field, N—gas number density) or Wieland approximation [Van Brunt, R.J., 1987. Common parametrizations of electron transport, collision cross section, and dielectric strength data for binary gas mixtures. J. Appl. Phys. 61 (5), 1773 1787.] and the common mean energy (CME) combination of the data for pure gases to obtain ionization coefficients for mixtures. Test calculations were made for Ar CH4, Ar N2, He Xe and CH4 N2 mixtures. Standard combination procedure gives poor results in general, due to the fact that the electron energy distribution is considerably different in mixtures and in individual gases at the same values of E/N. The CME method may be used for mixtures of gases with ionization coefficients that do not differ by more than two orders of magnitude which is better than any other technique that was proposed [Mari?, D., Radmilovi?-Ra?enovi?, M., Petrovi?, Z.Lj., 2005. On parametrization and mixture laws for electron ionization coefficients. Eur. Phys. J. D 35, 313 321.].

Mari?, D.; Šaši?, O.; Jovanovi?, J.; Radmilovi?-Ra?enovi?, M.; Petrovi?, Z. Lj.

2007-03-01

25

Electrical Conductivity of a Partially Ionized Gas  

Microsoft Academic Search

Electron velocity distribution functions for a partially ionized gas in a weak, steady electric field are obtained by solving the Boltzmann-Fokker-Planck equation numerically. As in the case of a fully ionized gas, the electron-electron interactions in a partially ionized gas affect the velocity distribution function and, consequently, the electrical conductivity. Electrical conductivities are calculated for a variety of assumed electron-molecule

L. C. Johnson

1967-01-01

26

Analysis of epoxyeicosatrienoic acids by chiral liquid chromatography/electron capture atmospheric pressure chemical ionization mass spectrometry using [13C]-analog internal standards  

PubMed Central

The metabolism of arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) is thought to be mediated primarily by the cytochromes P450 (P450s) from the 2 family (2C9, 2C19, 2D6, and 2J2). In contrast, P450s of the 4 family are primarily involved in omega oxidation of AA (4A11 and 4A22). The ability to determine enantioselective formation of the regioisomeric EETs is important in order to establish their potential biological activities and to asses which P450 isoforms are involved in their formation. It has been extremely difficult to analyze individual EET enantiomers in biological fluids because they are present in only trace amounts and they are extremely difficult to separate from each other. In addition, the deuterium-labeled internal standards that are commonly used for stable isotope dilution liquid chromatography/mass spectrometry (LC/MS) analyses have different LC retention times when compared with the corresponding protium forms. Therefore, quantification by LC/MS-based methodology can be compromised by differential suppression of ionization of the closely eluting isomers. We report the preparation of [13C20]-EET analog internal standards and the use of a validated high-sensitivity chiral LC/electron capture atmospheric pressure chemical ionization (ECAPCI)-MS method for the trace analysis of endogenous EETs as their pentafluorobenzyl (PFB) ester derivatives. The assay was then used to show the exquisite enantioselectivity of P4502C19-, P4502D6-, P4501A1-, and P4501B1-mediated conversion of AA into EETs and to quantify the enantioselective formation of EETs produced by AA metabolism in a mouse epithelial hepatoma (Hepa) cell line.

Mesaros, Clementina; Lee, Seon Hwa; Blair, Ian A.

2012-01-01

27

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

PubMed

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

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

2012-12-13

28

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

2010-04-29

29

Miniaturized gas ionization sensors using carbon nanotubes  

NASA Astrophysics Data System (ADS)

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

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

2003-07-01

30

Miniaturized gas ionization sensors using carbon nanotubes.  

PubMed

Gas sensors operate by a variety of fundamentally different mechanisms. Ionization sensors work by fingerprinting the ionization characteristics of distinct gases, but they are limited by their huge, bulky architecture, high power consumption and risky high-voltage operation. Here we report the fabrication and successful testing of ionization microsensors featuring the electrical breakdown of a range of gases and gas mixtures at carbon nanotube tips. The sharp tips of nanotubes generate very high electric fields at relatively low voltages, lowering breakdown voltages several-fold in comparison to traditional electrodes, and thereby enabling compact, battery-powered and safe operation of such sensors. The sensors show good sensitivity and selectivity, and are unaffected by extraneous factors such as temperature, humidity, and gas flow. As such, the devices offer several practical advantages over previously reported nanotube sensor systems. The simple, low-cost, sensors described here could be deployed for a variety of applications, such as environmental monitoring, sensing in chemical processing plants, and gas detection for counter-terrorism. PMID:12853951

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

2003-07-10

31

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

PubMed

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

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

2011-08-03

32

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

33

Dust and Ionized Gas in Elliptical Galaxies  

NASA Astrophysics Data System (ADS)

The thesis presents results of a study of the optical and far-infrared properties of dust and ionized gas in a complete, blue magnitude-limited (B_T^0 < 12) sample of 56 luminous elliptical (E) galaxies. The main aim is to investigate the origin and fate of this interstellar material and possible implications for scenarios of galaxy formation and evolution. To ensure consistency in the assignment of morphological types, the galaxy sample was drawn exclusively from the Revised Shapley-Ames Catalog of Bright Galaxies. A deep, systematic optical survey has been performed, including CCD imaging through both broad-band filters and narrow-band filters. For each galaxy we have constructed colour index (B-V, B-I) images and images of the H-alpha+ [N II]-emitting gas to derive the distributions of dust features and ionized gas. Long-slit spectra have also been obtained in two resolutions. Low-resolution spectra (covering the whole optical region) are used to study the properties of the underlying stellar populations (e.g., metallicity gradients), and to study the excitation mechanism of the ionized gas. Additional medium-resolution (~2A) spectra in the wavelength region around H-alpha have been obtained for all sample elliptical galaxies containing ionized gas to study the kinematics of the gas, and derive pure H-alpha luminosities. In this thesis, analysis of the extensive imaging data and of the medium-resolution spectra is reported. In Chapter 1 we report an early result of our survey: The galaxy IC 1459 is found to exhibit a large (15 Kpc diameter) H-alpha+[N II] emission-line region, showing spiral structure. Patchy dust absorption is also found in the inner part of the emission-line region. This galaxy was already shown to contain a massive stellar core which counter-rotates rapidly with respect to the stellar body of the galaxy. Interestingly, the sense of rotation of the spiral "arms" of the ionized gas distribution is the same as that of the rapidly rotating stellar component in the centre (assuming trailing spiral arms). These findings are clear signatures of an acquisition of a companion galaxy. The radial emission-line intensity profile peaks much more strongly towards the centre than the stellar light profile does, suggesting a powerful nuclear ionization source. In Chapter 2 we present deep surface photometry of NGC 1275, the central dominant galaxy of the Perseus cluster. This peculiar galaxy features two distinct filamentary systems, 3000 km s^-1 apart in velocity space. The "host"-galaxy NGC 1275 is associated with the low-velocity system, whereas the nature of the high-velocity system is still controversial. We find that prominent dust absorption features of NGC 1275 have the same distribution on the sky as the high-velocity system of ionized gas. Hence, the dust patches are most probably associated with the high-velocity system. However, our analysis of the extinction properties of the dust patches shows that the dust is well within NGC 1275, implying that the high-velocity system has moved approximately halfway through NGC 1275. We have also found many blue star clusters in our images of NGC 1275, for which we discuss the origin and nature by comparing colour-magnitude diagrams with theoretical population models. We suggest that the blue star clusters have been formed in a cooling flow in the central part of the X-ray-emitting gas of the Perseus cluster of galaxies. Chapter 3 presents the CCD broad-band photometry of the sample ellipticals. Radial profiles of the surface brightness, colours, and characteristics of the detailed isophotal shape are derived. In addition, we show that fitting power-laws to the outer radial intensity profiles of elliptical galaxies is an excellent tool for determining the sky background for CCD photometry. Chapter 4 presents colour-index images and narrow-band images of the H-alpha+[N II]-emitting gas to derive the distribution and amount of dust and ionized gas for the sample ellipticals. The detection rate of dust and ionized gas are found to be about 40%

Goudfrooij, Paul

1995-05-01

34

Molecular and Ionized Gas in Galaxies  

NASA Astrophysics Data System (ADS)

The thesis consists of three parts. The first is a study of distribution of molecular and ionized gas in our Galaxy. We collect data of Galactic HII regions, giant molecular clouds (GMCs) and 6.7 GHz methanol masers from literature, which are used as tracers to outline the spiral structure (Hou et al. 2009a; Hou & Han 2013). In the second part, we work on the galaxies with a lot of gas, which appear as ultraluminous infrared galaxies (ULIRGs). We find 308 ULIRGs from SDSS-DR6, and study the relationship between black hole masses (MBH) and the velocity dispersion ? of the Type I ULIRGs (Hou et al. 2009b), and then analyse the gas content and stellar populations of diverse ULIRGs (Hou et al. 2011). In the third part, we review the research on radio spectral lines at low frequencies (<9 GHz), and present our observation results of CH lines for a few nearby galaxies.

Hou, L. G.

2013-05-01

35

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

PubMed

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

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

2012-10-02

36

IONIZED GAS IN THE SMITH CLOUD  

SciTech Connect

We present Wisconsin Halpha Mapper observations of ionized gas in the Smith Cloud, a high-velocity cloud which Lockman et al. have recently suggested is interacting with the Galactic disk. Our Halpha map shows the brightest Halpha emission, 0.43 +- 0.04 R, coincident with the brightest H I, while slightly fainter Halpha emission (0.25 +- 0.02 R) is observed in a region with H I intensities <0.1 times as bright as the brightest H I. We derive an ionized mass of approx>3 x 10{sup 6} M {sub sun}, comparable to the H I mass, with the H{sup +} mass spread over a considerably larger area than that of H I. An estimated Galactic extinction correction could adjust these values upward by 40%. Halpha and [S II] line widths toward the region of brightest emission constrain the electron temperature of the gas to be between 8000 K and 23,000 K. A detection of [N II] lambda6583 in the same direction with a line ratio [N II]/Halpha = 0.32 +- 0.05 constrains the metallicity of the cloud: for typical photoionization temperatures of 8000-12,000 K, the nitrogen abundance is 0.15-0.44 times solar. These results lend further support to the claim that the Smith Cloud is new material accreting onto the Galaxy.

Hill, Alex S.; Haffner, L. Matthew; Reynolds, Ronald J., E-mail: hill@astro.wisc.ed, E-mail: haffner@astro.wisc.ed, E-mail: reynolds@astro.wisc.ed [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States)

2009-10-01

37

Dust and ionized gas in NGC 3607  

NASA Astrophysics Data System (ADS)

We report the detection of a broad dust ring in the X-ray-bright elliptical galaxy NGC 3607, the dominant member of a nearby group of galaxies. The inner radius of the ring is approximately 1.3 kpc from the nucleus and has a width of approximately 0.75 kpc. The maximum extinction corresponds to E(B-V) = 0.12 +/- 0.023. We also confirm the existence of bright H-alpha nebulosity around the nuclear region of the galaxy, just inside the dust ring. The luminosity in H-alpha is approximately 1.5 x 1040 ergs/s. The estimated amount of neutral hydrogen in the galaxy is approximately 4 x 107 solar masses and ionized hydrogen approximately 1.1 x 105 solar masses. We rule out H-alpha emission due to cooling flow, heat conduction from hot gas to the cold gas, photoionization by post-Asymptotic Giant Branch (AGB) stars or an active nucleus, and suggest that photoionization by young stars is the most plausible cause. We also suggest that the dust and associated gas are acquired from an interacting neighbor NGC 3608. The results are based on CCD surface photometry of the galaxy carried out using the broad-band filters V and R and a narrow-band filter appropriate for the red-shifted H-alpha + (N II) emission.

Singh, K. P.; Prabhu, T. P.; Kembhavi, A. K.; Bhat, P. N.

1994-04-01

38

Infrared observations of the ionized gas in the Galactic center  

SciTech Connect

Observations of ionic emission lines from the Galactic center are discussed. These observations provide information regarding the abundances of heavy elements, the spectrum of ionizing radiation, the distribution of ionized gas, and the gravitational potential in which the gas moves. There is evidence from the gas cloud velocities that a massive central black hole is present, but other considerations do not support this conclusion. The most plausible scenario involves a dense central star cluster in which stellar collisions disrupt stars, and recently formed OB stars provide the radiation which ionizes the gas.

Lacy, J.H.

1982-05-01

39

Enhanced stability of electrohydrodynamic jets through gas ionization.  

PubMed

Theoretical predictions of the nonaxisymmetric instability growth rate of an electrohydrodynamic jet based on the measured total current overestimate experimental values. We show that this apparent discrepancy is the result of gas ionization in the surrounding gas and its effect on the surface charge density of the jet. As a result of gas ionization, a sudden drop in the instability growth rate occurs below a critical electrode separation, yielding highly stable jets that can be used for nano- to microscale printing. PMID:18232986

Korkut, Sibel; Saville, Dudley A; Aksay, Ilhan A

2008-01-25

40

Simultaneous resonant enhanced multiphoton ionization and electron avalanche ionization in gas mixtures  

SciTech Connect

Resonant enhanced multiphoton ionization (REMPI) and electron avalanche ionization (EAI) are measured simultaneously in Ar:Xe mixtures at different partial pressures of mixture components. A simple theory for combined REMPI+EAI in gas mixture is developed. It is shown that the REMPI electrons seed the avalanche process, and thus the avalanche process amplifies the REMPI signal. Possible applications are discussed.

Shneider, Mikhail N.; Zhang Zhili; Miles, Richard B. [Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

2008-07-15

41

A New Gas Ionization Chamber For HELIOS  

NASA Astrophysics Data System (ADS)

The HELIcal Orbit Spectrometer (HELIOS) has become an important tool in studying reactions using radioactive ion beams, and its special design has successfully alleviated problems that arise from studying reactions in inverse kinematics, such as kinematic compression. Here we introduce a new gas ionization chamber, which will significantly improve heavy recoil detection in HELIOS. On one hand, it will help eliminate background by detecting the heavy secondary recoils in coincidence with the light reaction products detected in the silicon detector array; on the other hand, our chamber can tolerate count rates of at least 100 kHz. As a result, a high detection efficiency will be achieved. This design, which functions well with beam rates above 10^5 pps, and obtains a ?Z/Z resolution better than 2%, will be presented. In addition, we will also show the first test results from this detector, which illustrate the detector's performance. In the future, this detector will be used for radioactive ion beam experiments of interest for nuclear structure and nuclear astrophysics, such as those important for X-ray burst nucleosynthesis.

Lai, Jianping

2012-10-01

42

GAS CHROMATOGRAPHY-ELECTRON IONIZATION MASS SPECTROMETRY AND LIQUID CHROMATOGRAPHY-ELECTROSPRAY TANDEM MASS SPECTROMETRY FOR DETERMINATION OF IMPURITIES IN THE ANTI-CANCER DRUG ISOPHOSPHORAMIDE MUSTARD  

Technology Transfer Automated Retrieval System (TEKTRAN)

Isophosphoramide mustard (IPM) is known to have substantial anti-cancer activities in various animal models. Liquid chromatography-electrospray mass spectrometry (LC-ES-MS) methods have been developed and applied to the analysis of synthesized preparations of IPM. Possible impurities can be formed...

43

Gas chromatography electron ionization mass spectrometric analysis of trimethylsilyl derivatives of bis(2-hydroxyethylthio)alkanes and bis(2-hydroxyethylsulfonyl) alkanes.  

PubMed

This communication describes GC-MS analysis of bis(trimethylsilyl) (bis-TMS) derivatives of bis(2-hydroxyethylthio)alkanes (BHETAs) and bis(2-hydroxyethylsulfonyl) alkanes (BHESAs) which are important markers of sulfur mustard class of chemical warfare agents. The study was undertaken with a view to develop spectral database of these compounds for verification analysis of Chemical Weapons Convention (CWC). Based on the obtained mass spectra of bis-TMS derivatives of BHETAs and BHESAs, the fragmentation routes are proposed, which explain most of the characteristic ions. PMID:17057283

Kanaujia, Pankaj K; Tak, Vijay; Pardasani, Deepak; Gupta, A K; Jain, Rajiv; Dubey, D K

2006-01-01

44

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

Microsoft Academic Search

We use the first data release from the SINGG Halpha 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

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

2007-01-01

45

Warm ionized gas in the local interstellar medium  

NASA Astrophysics Data System (ADS)

The properties of widespread ionized gas in the disk and halo of the Milky Way have been explored through the detection of faint optical emission lines from hydrogen, helium, and trace atoms and ions within the gas. Observations reveal extensive regions of warm ( T?10 4 K), low density ( ne˜10 -1 cm -3) ionized hydrogen spread throughout the interstellar medium, with enormous loops and filaments stretching across the sky and arching far above the midplane of the Milky Way. These observations have provided new clues about the role of massive stars and supernova explosions in shaping the large scale properties of the interstellar medium as well as the possible relationship between this wide spread gas and the small interstellar cloud surrounding the sun. Observed differences between this local cloud and the more extensive regions of ionization appear to be due primarily to differences in the strength and spectrum of the ionizing radiation field.

Reynolds, R. J.

2004-01-01

46

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

47

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

Microsoft Academic Search

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

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

2007-01-01

48

Surface Ionization Gas Detection at SnO2 Surfaces  

NASA Astrophysics Data System (ADS)

In surface ionization (SI) gas detection adsorbed analyte molecules are converted into ionic species at a heated solid surface and extracted into free space by an oppositely biased counter electrode. In the present work we consider the formation of positive and negative analyte gas ions at SnO2 surfaces. We find that SI leads to positive ion formation only, with the SI efficiency scaling with the ionization energy of the analyte gas molecules. Aromatic and aliphatic hydrocarbons with amine functional groups exhibit particularly high SI efficiencies.

Krenkow, A.; Oberhüttinger, C.; Habauzit, A.; Kessler, M.; Göbel, J.; Müller, G.

2009-05-01

49

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

50

Physical Conditions in the Ionized Gas of 30 Doradus  

NASA Astrophysics Data System (ADS)

We present a mid-infrared spectroscopic data cube of the central part of 30 Doradus, observed with Spitzer's Infrared Spectrograph and Multiband Imaging Photometer for Spitzer/spectral energy distribution mode. Aromatic dust emission features and emission lines from molecular and atomic hydrogen are detected but they are not particularly strong. The dominant spectral features are emission lines from moderately ionized species of argon, neon, and sulfur, which are used to determine the physical conditions in the ionized gas. The ionized gas excitation shows strong variations on parsec scales, some of which can plausibly be associated with individual hot stars. We fit the ionic line strengths with photoionization and shock models, and find that photoionization dominates in the region. The ionization parameter U traces the rim of the central bubble, as well as highlighting isolated sources of ionization, and at least one quiescent clump. The hardness of the ionizing radiation field T rad reveals several "hot spots" that are either the result of individual very hot stars or trace the propagation of the diffuse ionizing field through the surrounding neutral cloud. Consistent with other measurements of giant H II regions, log(U) ranges between -3 and -0.75, and T rad between 30,000 and 85,000 K.

Indebetouw, R.; de Messières, G. E.; Madden, S.; Engelbracht, C.; Smith, J. D.; Meixner, M.; Brandl, B.; Smith, L. J.; Boulanger, F.; Galliano, F.; Gordon, K.; Hora, J. L.; Sewilo, M.; Tielens, A. G. G. M.; Werner, M.; Wolfire, M. G.

2009-03-01

51

Axisymmetric model of the ionized gas in the Orion Nebula  

SciTech Connect

New ionization and thermal equilibrium models for the ionized gas in the Orion Nebula with an axisymmetric two-dimensional 'blister' geometry/density distribution are presented. The HII region is represented more realistically than in previous models, while the physical detail of the microphysics and radiative transfer of the earlier spherical modeling is maintained. The predicted surface brightnesses are compared with observations for a large set of lines at different positions to determine the best-fitting physical parameters. The model explains the strong singly ionized line emission along the lines of sight near the Trapezium. 105 refs.

Rubin, R.H.; Simpson, J.P.; Haas, M.R.; Erickson, E.F. (NASA, Ames Research Center, Moffett Field, CA (USA))

1991-06-01

52

IUE absorption line studies of highly ionized interstellar gas  

NASA Astrophysics Data System (ADS)

IUE high dispersion echelle spectra of galactic and extragalactic sources have generally revealed the presence of absorption by interstellar Si IV and C IV. Occasionally N V has been detected. The observational results relating to these species will be reviewed for H II regions, supernova remnants, galactic disk gas, galactic halo gas, and extragalactic gas. For the various regions, the likely origin of the ionization is considered.

Savage, B. D.

1984-12-01

53

IONIZED GAS IN THE GALACTIC CENTER: NEW OBSERVATIONS AND INTERPRETATION  

SciTech Connect

We present new observations of the [Ne II] emission from the ionized gas in Sgr A West with improved resolution and sensitivity. About half of the emission comes from gas with kinematics indicating it is orbiting in a plane tipped about 25 Degree-Sign from the Galactic plane. This plane is consistent with that derived previously for the circumnuclear molecular disk and the northern arm and western arc ionized features. However, unlike most previous studies, we conclude that the ionized gas is not moving along the ionized features, but on more nearly circular paths. The observed speeds are close to, but probably somewhat less than expected for orbital motions in the potential of the central black hole and stars and have a small inward component. The spatial distribution of the emission is well fitted by a spiral pattern. We discuss possible physical explanations for the spatial distribution and kinematics of the ionized gas, and conclude that both may be best explained by a one-armed spiral density wave, which also accounts for both the observed low velocities and the inward velocity component. We suggest that a density wave may result from the precession of elliptical orbits in the potential of the black hole and stellar mass distribution.

Irons, Wesley T.; Lacy, John H. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Richter, Matthew J., E-mail: lacy@astro.as.utexas.edu [Department of Physics, University of California, Davis, CA 95616 (United States)

2012-08-20

54

Ionized Gas in the Galactic Center: New Observations and Interpretation  

NASA Astrophysics Data System (ADS)

We present new observations of the [Ne II] emission from the ionized gas in Sgr A West with improved resolution and sensitivity. About half of the emission comes from gas with kinematics indicating it is orbiting in a plane tipped about 25° from the Galactic plane. This plane is consistent with that derived previously for the circumnuclear molecular disk and the northern arm and western arc ionized features. However, unlike most previous studies, we conclude that the ionized gas is not moving along the ionized features, but on more nearly circular paths. The observed speeds are close to, but probably somewhat less than expected for orbital motions in the potential of the central black hole and stars and have a small inward component. The spatial distribution of the emission is well fitted by a spiral pattern. We discuss possible physical explanations for the spatial distribution and kinematics of the ionized gas, and conclude that both may be best explained by a one-armed spiral density wave, which also accounts for both the observed low velocities and the inward velocity component. We suggest that a density wave may result from the precession of elliptical orbits in the potential of the black hole and stellar mass distribution.

Irons, Wesley T.; Lacy, John H.; Richter, Matthew J.

2012-08-01

55

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

56

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

Code of Federal Regulations, 2013 CFR

...chromatograph with a flame ionization detector. 1065.267 Section 1065.267...chromatograph with a flame ionization detector. (a) Application. You may use a gas chromatograph with a flame ionization detector (GC-FID) to measure CH4...

2013-07-01

57

Fabrication of a miniaturized ionization gas sensor with polyimide spacer  

NASA Astrophysics Data System (ADS)

Gas sensing can be achieved by fingerprinting the ionization characteristics of distinct species. In this study, the fabrication of a miniaturized gas ionization sensor using polyimide as sacrificial layer is reported. The sensor consists of two planar metallic electrodes with a gap spacing obtained by the polyimide under-etching. This known sacrificial layer has the advantage besides a high planarization factor, to be CMOS compatible. Furthermore, its chemical resistance up to high temperatures, high resistance to radiation from both electrons and neutrons, and low outgassing are of primary importance to avoid interferences with the ionization gas sensing. A suspended micro-bridge with dimensions 20 ?m width and 220 ?m length has been developed and released by using etching holes in the membrane. The ionization characteristics of air at controlled temperature, humidity and pressure (21°C, 40% humidity and 1 atm) have been obtained during non-destructive electrical characterizations, with a breakdown voltage of 350 V for a 6 ?m gap. The growth of metallic nanowires templated in ion track-etched polyimide on the electrode is envisioned in order to enhance the ionization field and to reduce the required measurement power of the sensor.

Walewyns, T.; Scheen, G.; Tooten, E.; El Fissi, L.; Dupuis, P.; Francis, L. A.

2011-05-01

58

Stability of Ionized Molecular Gas Flows.  

National Technical Information Service (NTIS)

A theoretical investigation of the factors influencing the stability of molecular gas discharges typical of those utilized in high power laser systems has been carried out. These studies have revealed the mechanisms by which basic electronic, ionic, and n...

W. L. Nighan W. J. Wiegand R. H. Bullis

1973-01-01

59

Ionization from Fe Atoms Incident on Various Gas Targets  

Microsoft Academic Search

The ionization ratio beta, which is defined here as the ratio of the number of ion-electron pairs NI formed in a thick gas target to the number of atoms NA injected into the gas at a given velocity, has been determined for Fe atoms impinging on target gases of He, Ne, Ar, Kr, N2, O2, CO2, and air. The Fe

J. F. Friichtenicht; J. C. Slattery; D. O. Hansen

1967-01-01

60

Flow of nonequilibrium ionized radiating gas around blunt bodies  

Microsoft Academic Search

The hypersonic flow of a nonequilibrium ionized, monatomic, nonviscous, radiating gas around a spherically blunted object has been discussed taking into account the precursor radiation. In order to calculate the flow parameters, a system of gasdynamic equations along with the equations of radiative transfer was solved. Over the range of parameters considered, resonance radiation has little effect on the location

N. V. Leont'eva; Yu. P. Lun'kin; A. A. Fursenko

1973-01-01

61

Ionized Gas Velocities for Edge-on HALOGAS Galaxies  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

62

The Properties and Ionization Source of Diffuse Ionized Gas in Galactic Disks  

NASA Astrophysics Data System (ADS)

Diffuse ionized gas (DIG) is the dominant form of ionized gas and an important component of the ISM in spiral galaxies. We present a study of the properties of the DIG in face-on and edge-on galaxies, and show that a significant fraction of the DIG is ionized by OB stars outside of HII regions. We used deep H? images of 5 edge-on galaxies to examine the properties of extraplanar DIG. The H? halo of NGC 891 can be traced at least 5 kpc from the plane, and UGC 9242 has a halo which extends almost as far, but at much fainter surface brightness. We set upper limits on the emission from faint DIG in the outer disk, which in turn limits the strength of the metagalactic radiation field at low redshift. Using far-ultraviolet (FUV) images from the Ultraviolet Imaging Telescope, FUV and optical images from HST, and groundbased H? images of M33, we test whether DIG is ionized by OB stars outside of HII regions. The H? /FUV ratio in the DIG is consistent with ionization by field OB stars. FUV and optical photometry of stars was used to determine their spectral types and ionizing luminosity. Comparing the total ionizing luminosity from stars in the DIG with the H? emission, we find that field stars can account for at least 40% of the DIG ionization. This surprising result shows that field stars are important ionization sources, and reduces the amount of leakage necessary from HII regions. We used optical spectroscopy to probe the physical state of the DIG. A search for the HeI line in M33 allows us to set limits on the contribution of O7 and hotter stars to the ionization of the DIG, closing the loop on the FUV analysis. In M51 we discuss the spectral properties of the DIG and a possible outflow cone in NGC 5195. In NGC 4631 we examine the behavior of the DIG spectrum with distance from the plane. This project is supported by the NSF through grant AST96-17014, by NASA through grant AR-07546.01-96A from the STScI and grant NAG5-2426, and by a Cottrell Scholar Award from Research Corporation.

Hoopes, Charles G.

1999-12-01

63

Ionization front in a high-current gas discharge  

SciTech Connect

Spectroscopic measurements of ion/neutral density ratio profiles are made inside the high-current, low-pressure discharge of a coaxial magnetoplasmadynamic thruster and show the existence of a thin ionization front, upstream in the discharge, that effectively ionizes the incoming gas to ionization levels above 50%. The measurements allow an estimate of the width of this ionization front to be on the order of a few millimeters. Due to the known existence of microturbulence in the plasma, which can produce suprathermal electrons, an explanation of the measurements based on the existence of a suprathermal tail in the electron energy distribution function is sought. A theoretical model for the width of the ionization front is combined with a multilevel excitation model for argon and shows that a Maxwellian electron distribution function cannot account for the small length scale of the ionization front, and that the latter is more consistent with an electron distribution function having a suprathermal population, the magnitude of which is estimated by comparing the model to the experiments.

Choueiri, Edgar Y.; Randolph, Thomas M. [Electric Propulsion and Plasma Dynamics Laboratory, Princeton University, Princeton, New Jersey 08544 (United States); NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)

2007-03-15

64

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

65

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

PubMed

A comprehensively validated procedure is presented for simultaneous semiquantitative/quantitative screening of 51 drugs of abuse or drugs potentially hazardous for traffic safety in serum, plasma or whole blood. Benzodiazepines (12), cannabinoids (3), opioids (8), cocaine, antidepressants (13), antipsychotics (5) and antiepileptics (2) as well as zolpidem, zaleplon, zopiclone, meprobamate, carisoprodol, tizanidine and orphenadrine and internal standard flurazepam, were isolated by high-yield liquid-liquid extraction (LLE). The dried extracts were derivatized by two-step silylation and analyzed by the combination of two different gas chromatographic (GC) separations with both electron capture detection (ECD) and mass spectrometry (MS) operating in a selected ion-monitoring (SIM) mode. Quantitative or semiquantitative results were obtained for each substance based on four-point calibration. In the validation tests, accuracy, reproducibility, linearity, limit of detection (LOD) and limit of quantitation (LOQ), selectivity, as well as extraction efficiency and stability of standard stock solutions were tested, and derivatization was optimized in detail. Intra- and inter-day precisions were within 2.5-21.8 and 6.0-22.5%, and square of correlation coefficients of linearity ranged from 0.9896 to 0.9999. The limit of quantitation (LOQ) varied from 2 to 2000 ng/ml due to a variety of the relevant concentrations of the analyzed substances in blood. The method is feasible for highly sensitive, reliable and possibly routinely performed clinical and forensic toxicological analyses. PMID:15171931

Gunnar, Teemu; Mykkänen, Sirpa; Ariniemi, Kari; Lillsunde, Pirjo

2004-07-01

66

Surface Ionization Gas Detection on Platinum and Metal Oxide Surfaces  

Microsoft Academic Search

Surface ionization (SI) gas detection experiments have been performed on platinum (Pt) and metal oxide (MOX) films. The probability of surface ion emission varies with temperature in an Arrhenius-type manner. Among all hydrocarbons studied so far those with amine functional groups exhibited the lowest activation energies allowing detection in the ppm concentration range at emitter operation temperatures of about 400degC.

A. Hackner; A. Habauzit; G. Muller; E. Comini; G. Faglia; G. Sberveglieri

2009-01-01

67

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

68

Equation of state for a partially ionized gas. II  

NASA Astrophysics Data System (ADS)

The derivation of equations of state for fluid phases of a partially ionized gas or plasma is addressed from a fundamental point of view. A spherical cellular model is deduced for the hot curve limit (or ideal Fermi gas). Next the Coulomb interactions are added to the spherical cellular model for general ionic charge Z. Then an independent electron model within a Z electron cell plus several many-body effects are employed. Numerical examples of the theory for several elements (H, Li, N, Na, K, Ni, Rb, Pd, Cs, and Er) are reported. These results reduce in various limits of temperature and density to the expected behavior. They display electron, localization-delocalization phase transitions of liquid-gas character. In the higher Z elements, a second possible critical point has been found. The critical pressure, electron density and temperature for the lower-density critical points seem to obey power laws as a function of Z.

Baker, George A.

2003-11-01

69

Kinematics of the Diffuse Ionized Gas Disk of Andromeda  

NASA Astrophysics Data System (ADS)

This research focuses on the flattened rotating diffuse ionized gas (DIG) disk of the Andromeda Galaxy (M31). For this we use spectra from 25 multislit masks obtained by the SPLASH collaboration using the DEIMOS spectrograph on the Keck-II 10-meter telescope. Each mask contains 200 slits covering the region around M32 (S of the center of M31), the major axis of M31, and the SE minor axis. DIG emission was serendipitously detected in the background sky of these slits. By creating a normalized "sky spectrum” to remove various other sources of emission (such as night sky lines) in the background of these slits, we have examined the rotation of the DIG disk using individual line-of-sight velocity measurements of H?, [NII] and [SII] emission. his emission is probably the result of newly formed stars ionizing the gas in the disk. The measured IG rotation will be compared to the rotation of M31's stellar disk and HI gas disk, as well as models of an infinitely thin rotating disk, to better understand the relationship between the components of the galactic disk and its differential rotation. We wish to acknowledge the NSF for funding on this project.

Thelen, Alexander; Howley, K.; Guhathakurta, P.; Dorman, C.; SPLASH Collaboration

2012-01-01

70

A Novel Gas Sensor Based on Tunneling-Field-Ionization on Whisker-Covered Gold Nanowires  

Microsoft Academic Search

Typical gas ionization sensors (GISs) work by fingerprinting the ionization breakdown voltages of the gases to be identified. In this work, we developed a GIS that operates by field-ionizing the unknown gas at exceptionally low voltages. The resultant field-ion current-voltage (I-V) characteristic was then used to identify the gas. Freestanding gold nanowires (AuNW), terminated with nanoscale whisker-like features, were employed

Ramin Banan Sadeghian; Mojtaba Kahrizi

2008-01-01

71

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

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

72

Photoionized Mixing Layer Models of the Diffuse Ionized Gas  

NASA Astrophysics Data System (ADS)

It is generally believed that O stars, confined near the galactic midplane, are somehow able to photoionize a significant fraction of what is termed the "diffuse ionized gas" (DIG) of spiral galaxies, which can extend up to 1-2 kpc above the galactic midplane. The heating of the DIG remains poorly understood, however, as simple photoionization models do not reproduce the observed line ratio correlations well or the DIG temperature. We present turbulent mixing layer (TML) models in which warm photoionized condensations are immersed in a hot supersonic wind. Turbulent dissipation and mixing generate an intermediate region where the gas is accelerated, heated, and mixed. The emission spectrum of such layers is compared with observations of Rand of the DIG in the edge-on spiral NGC 891. We generate two sequence of models that fit the line ratio correlations between [S II]/H?, [O I]/H?, [N II]/[S II], and [O III]/H? reasonably well. In one sequence of models, the hot wind velocity increases, while in the other, the ionization parameter and layer opacity increase. Despite the success of the mixing layer models, the overall efficiency in reprocessing the stellar UV is much too low, much less than 1%, which compels us to reject the TML model in its present form.

Binette, Luc; Flores-Fajardo, Nahiely; Raga, Alejandro C.; Drissen, Laurent; Morisset, Christophe

2009-04-01

73

Molecular and ionized gas in the peculiar galaxy NGC 2146  

SciTech Connect

New observations probing the molecular and ionized gas content of the ultrahigh surface brightness, peculiar spiral galaxy NGC 2146 are presented. The dynamical center of the galaxy lies toward a dense dust lane. The molecular mass of the galaxy in the central 15 kpc is 10 to the 10th solar. Strong emission from the central 5 kpc, as well as a string of H II regions extending along an arc 8 arcmin long are observed. Evidence is found for a high mass concentration within the central 100 pc, highly noncircular motions along the major axis, and a significant discrepancy between the velocities of the H II regions in the arc and those in the disk. The high-mass star formation efficiency is elevated by more than two orders of magnitude in the center of the galaxy relative to that in the outer disk. 25 references.

Young, J.S.; Claussen, M.J.; Kleinmann, S.G.; Rubin, V.C.; Scoville, N.

1988-08-01

74

Parallel plate ionization chamber in low pressure helium gas  

NASA Astrophysics Data System (ADS)

A parallel plate ionization chamber was constructed for beam intensity monitoring. The chamber is placed in a gas-filled volume 1.5m upstream from the gas-filled separator SASSYER. Its output current will be used to determine absolute reaction cross sections. In a dedicated test experiment with a 100 MeV ^32S beam and an applied potential of 300V, the signal current had an average standard deviation of 0.4%, and demonstrated a linear relationship (R^2 = 0.9894) with the beam intensity. Also, at an intensity of 6 particle nanoamperes, the current exhibited a linear dependence (R^2 = 0.9813) on voltage, indicating that the chamber was operating in the proportional counter region. Our results agreed well with predictions made using extrapolated Townsend coefficients, though we observed a constant systematic and constant deviation between these estimates and our output current. This work was supported under US DOE grant number DE-FG0291ER-40609 and the Yale College Dean's Fellowship for Research in the Sciences.

Frank, D.; Heinz, A.; Winkler, R.; Qian, J.; Casperson, R. J.; Terry, J. R.

2007-10-01

75

Cross-phase modulation between lasers in a tunnel ionizing gas  

SciTech Connect

The phase modulation of a low power long pulse probe laser beam in a rapidly tunnel ionizing gas (helium) under a relativistic short pulse laser is investigated. The relativistic pulse creates a fast increasing plasma density at its front, far ahead of the intensity peak. The probe pulse sees these changes as modulation in its phase and undergoes large frequency upshift. The spectral content of the blueshifted potion of the probe pulse is large when its intensity peak commoves with the ionization front. There are two ionization front created by first and second ionizations, and the separation between the two increases as laser propagates through the gas. The rate of density variation by first and second ionizations, however, is fairly the same and varies little as the spot size of the laser beam increases up to three times its initial value. The ionization front velocity, as well as the upshift in probe pulse frequency, is bigger for sharper laser pulse.

Liu, C. S. [Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States); Pathak, Vishwa Bandhu; Tripathi, V. K. [Department of Physics, IIT Delhi, New Delhi 110016 (India)

2009-05-15

76

Analysis of the diffuse ionized gas database: DIGEDA  

NASA Astrophysics Data System (ADS)

Studies of the Diffuse Ionized Gas (DIG) have progressed without providing so far any strict criterion to distinguish DIGs from H II regions. In this work, we compile the emission line measurements of 29 galaxies that are available in the scientific literature, thereby setting up the first DIG database (DIGEDA). Making use of this database, we proceed to analyze the global properties of the DIG using the [NII]?6583/H?, [O I]?6300/H?, [O III]?5007/H? and [SII]?6716/H? lines ratios, including the H ? emission measure. This analysis leads us to conclude that the [N II]/H? ratio provides an objective criterion for distinguishing whether an emission region is a DIG or an H II region, while the EM(H?) is a useful quantity only when the galaxies are considered individually. Finally, we find that the emission regions of Irr galaxies classified as DIG in the literature appear in fact to be much more similar to H II regions than to the DIGs of spiral galaxies.

Flores-Fajardo, N.; Morisset, C.; Binette, L.

2009-10-01

77

The chemical composition of ionized gas in galaxies  

NASA Astrophysics Data System (ADS)

Active star formation in galaxies takes place in HII regions harbouring young massive stars within an extended ionized gaseous component. Their relative structural simplicity andcharacteristic emission line spectrum make them ideal laboratories to study the physical properties and chemical composition of gas and stars in galaxies. Chemical abundancescan be derived for Galactic and relatively nearby extragalactic HII regions, as well as for distant galaxies, applying different techniques. In this talk an overview of the derivation of chemical abundances for HII regions in galaxies is presented, with an emphasis on the different domains of spatial resolution covered by the data, from spatially resolved integral field spectra of HII regions in the Milky Way and nearby galaxies to integrated spectra of more distant galaxies.With the upcome of the new integral field spectrographs a wide coverage at good spatial sampling of galaxies and HII complexes is now possible. This new 2D spectroscopy provides us more realistic information and useful constrains to study the chemical enrichment process of the interstellar medium and some of the fundamental relations governing galaxy evolution.

Vilchez, J. M.

2011-11-01

78

Aerodynamic Effects in Weakly Ionized Gas: Phenomenology and Applications  

NASA Astrophysics Data System (ADS)

Successful application of gas discharges in aerodynamics requires their efficient generation, sustaining and control at supersonic or hypersonic flow conditions. Wall-free plasma formations that meet the requirements may then act as time-controlled and space-localized actuators to modify the flow. Potential candidates for this challenging task are plasmas contained in open or linear-cavity microwave field structures. We present and discuss direct observations of aerodynamic effects activated or modified by wall-free discharges. Further, we compare two generic types of wall-free discharges. First group, applicable for inlet-type structures, consists of a periodic series of microwave-induced plasmoids generated in a linear cavity, using the outgoing wave from a microwave antenna and the reflected wave from a nearby on-axis concave reflector. The plasmoids are spaced at half-wavelength separations according to the standing-wave pattern. The plasmoids are enhanced by an ``effective focusing'' in the near field of the antenna (Fresnel region) as a result of diffraction effects and mode structure. Second group, applicable to supersonic and hypersonic boundary layers, are the surface microwave discharges enhanced by a structure of Hertz dipoles. Standard microwave discharge phenomenology, such as microwave breakdown, mode structure and plasma parameters, is revisited to present a quantitative interpretation of the observed effects. Special attention is given to complex phenomena specific to flow-plasma interaction (double electric layers, ionization waves, instabilities), which provide the physical basis for localized heating in the aerodynamic flow.

Popovic, Svetozar

2006-10-01

79

Simultaneous multidetermination of residues of pesticides and polycyclic aromatic hydrocarbons in olive and olive-pomace oils by gas chromatography\\/tandem mass spectrometry  

Microsoft Academic Search

A multiresidue method for determining major pesticides and polycyclic aromatic hydrocarbons (PAHs) in olive oils in a single injection by use of gas chromatography\\/tandem mass spectrometry (GC–MS\\/MS) is proposed. Samples are previously extracted with an acetonitrile\\/n-hexane mixture and cleaned up by gel permeation chromatography. Electron ionization and chemical ionization allow pesticides and PAHs to be determined in a single analysis.

E. Ballesteros; A. García Sánchez; N. Ramos Martos

2006-01-01

80

Ionization cross sections for electron scattering from metastable rare-gas atoms (Ne* and Ar*)  

NASA Astrophysics Data System (ADS)

The optical-model approach has been used to investigate the electron-impact ionization of metastable rare-gas atoms. A complex equivalent-local polarization potential is obtained to describe the ionization continuum channels. We have calculated the cross sections for collisional ionization of the metastable atoms Ne* and Ar* by electrons in the energy range from threshold to 200 eV. The present results are in agreement with the available experimental measurements and other theoretical calculations.

Zhang, Yong-Zhi; Zhou, Ya-Jun

2013-07-01

81

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

82

Diffuse Ionized Gas in Edge-on Spiral Galaxies: Extraplanar and Outer Disk Halpha Emission  

Microsoft Academic Search

We present Halpha images of five edge-on galaxies: NGC 891, NGC 4631, NGC 4244, NGC 3003, and UGC 9242. We also analyze [S II] lambdalambda6717, 6731 and [O III] lambda5007 images of NGC 4631. For several of these galaxies, these images are the most sensitive to date. We analyze the ionized gas content, with particular attention to the diffuse ionized

Charles G. Hoopes; René A. M. Walterbos; Richard J. Rand

1999-01-01

83

Evaluation of Gas-filled Ionization Chamber Method for Radon Measurement at Two Reference Facilities  

SciTech Connect

For quality assurance, gas-filled ionization chamber method was tested at two reference facilities for radon calibration: EML (USA) and PTB (Germany). Consequently, the radon concentrations estimated by the ionization chamber method were in good agreement with the reference radon concentrations provided by EML as well as PTB.

Ishikawa, Tetsuo; Tokonami, Shinji; Kobayashi, Yosuke; Sorimachi, Atsuyuki; Yatabe, Yoshinori; Miyahara, Nobuyuki [National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555 (Japan)

2008-08-07

84

Localized magnetic reconnection as a cause of extraplanar diffuse ionized gas in the Galactic halo  

NASA Astrophysics Data System (ADS)

Many observations indicate the occurrence of ionized gas in the distant haloes of galaxies (including our own). Since photoionization by stars (mainly O stars, young stars or evolved low-mass stars depending on the kind of galaxy) does not seem to be exclusively responsible for the ionization of the hydrogen filaments that should otherwise cool fast and recombine quickly, the question arises which extra energy source can produce the quasi-stationary ionization. We show that stationary localized magnetic reconnection in current filaments may contribute to the ionization of the extraplanar halo gas. In these filaments magnetic energy is dissipated. Consequently, the ionized as well as the neutral component is heated and re-ionized on a time-scale significantly shorter than the recombination time-scale. The amount of energy required for efficient re-ionization can in principle easily be provided by the free magnetic energy. We present quasi-static models that are characterized by plasma temperatures and densities that agree well with the observed values for the diffuse ionized gas component of the interstellar medium. Plasma-neutral gas fluid simulations are made to show that the recombination-induced dynamical reconnection process indeed works in a self-regulatory way.

Birk, G. T.; Lesch, H.; Neukirch, T.

1998-05-01

85

IONIZED GAS TOWARD MOLECULAR CLUMPS: PHYSICAL PROPERTIES OF MASSIVE STAR-FORMING REGIONS  

SciTech Connect

We have conducted a search for ionized gas at 3.6 cm, using the Very Large Array, toward 31 Galactic intermediate- and high-mass clumps detected in previous millimeter continuum observations. In the 10 observed fields, 35 H II regions are identified, of which 20 are newly discovered. Many of the H II regions are multiply peaked indicating the presence of a cluster of massive stars. We find that the ionized gas tends to be associated toward the millimeter clumps; of the 31 millimeter clumps observed, nine of these appear to be physically related to ionized gas, and a further six have ionized gas emission within 1'. For clumps with associated ionized gas, the combined mass of the ionizing massive stars is compared to the clump masses to provide an estimate of the instantaneous star formation efficiency. These values range from a few percent to 25%, and have an average of 7% +- 8%. We also find a correlation between the clump mass and the mass of the ionizing massive stars within it, which is consistent with a power law. This result is comparable to the prediction of star formation by competitive accretion that a power-law relationship exists between the mass of the most massive star in a cluster and the total mass of the remaining stars.

Johnston, Katharine G.; Wood, Kenneth [SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS (United Kingdom); Shepherd, Debra S. [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Rd, Socorro, NM 87801 (United States); Aguirre, James E. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Dunham, Miranda K. [Department of Astronomy, University of Texas at Austin, 1 University Station, C1400, Austin, TX 78712-0259 (United States); Rosolowsky, Erik, E-mail: kgj1@st-andrews.ac.u [University of British Columbia at Okanagan, 3333 University Way, Kelowna BC V1V 1V7 (Canada)

2009-12-10

86

Ionized Gas and Sources of its Ionization in the Irr Galaxy IC 10  

NASA Astrophysics Data System (ADS)

We report the results of an analysis of the emission spectra of HII-regions in IC 10 ionized by star clusters and WR stars based on observations made with the 6-m telescope SAO RAS using MPFS field spectrograph and SCORPIO focal reducer operating in the slit spectrograph mode. We determine the masses and ages of ionizing star clusters in the violent star-forming region of the galaxy in terms of the new evolutionary models of emission-line spectra of HII-regions developed by Martin-Manjon et al. (2010). We estimate the amount of stars needed to ionize the brightest HII-region HL 111.

Egorov, O. V.; Arkhipova, V. P.; Lozinskaya, T. A.; Moiseev, A. V.

2011-07-01

87

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

88

Infrared spectroscopy of ionized corannulene in the gas phase  

NASA Astrophysics Data System (ADS)

The gas-phase infrared spectra of radical cationic and protonated corannulene were recorded by infrared multiple-photon dissociation (IRMPD) spectroscopy using the IR free electron laser for infrared experiments. Electrospray ionization was used to generate protonated corannulene and an IRMPD spectrum was recorded in a Fourier-transform ion cyclotron resonance mass spectrometer monitoring H-loss as a function of IR frequency. The radical cation was produced by 193-nm UV photoionization of the vapor of corannulene in a 3D quadrupole trap and IR irradiation produces H, H2, and C2Hx losses. Summing the spectral response of the three fragmentation channels yields the IRMPD spectrum of the radical cation. The spectra were analyzed with the aid of quantum-chemical calculations carried out at various levels of theory. The good agreement of theoretical and experimental spectra for protonated corannulene indicates that protonation occurs on one of the peripheral C-atoms, forming an sp3 hybridized carbon. The spectrum of the radical cation was examined taking into account distortions of the C5v geometry induced by the Jahn-Teller effect as a consequence of the degenerate 2E1 ground electronic state. As indicated by the calculations, the five equivalent Cs minima are separated by marginal barriers, giving rise to a dynamically distorted system. Although in general the character of the various computed vibrational bands appears to be in order, only a qualitative match to the experimental spectrum is found. Along with a general redshift of the calculated frequencies, the IR intensities of modes in the 1000-1250 cm-1 region show the largest discrepancy with the harmonic predictions. In addition to CH ``in-plane'' bending vibrations, these modes also exhibit substantial deformation of the pentagonal inner ring, which may relate directly to the vibronic interaction in the radical cation.

Galué, Héctor Alvaro; Rice, Corey A.; Steill, Jeffrey D.; Oomens, Jos

2011-02-01

89

Physics of a Partially Ionized Gas Relevant to Galaxy Formation Simulations—The Ionization Potential Energy Reservoir  

NASA Astrophysics Data System (ADS)

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.; Jachowicz, N.

2013-07-01

90

In situ transmission electron microscopy observation of silver oxidation in ionized/atomic gas.  

SciTech Connect

The interaction between silver and ionized and atomic gas was observed directly by in situ transmission electron microscopy with an environmental cell for the first time. The electron beam provides dual functions as the source of both gas ionization and imaging. The concentration of ionized gas was tuned via adjusting the current density of the electron beam. Oxidation of the silver is observed in situ, indicating the presence of ionized and/or atomic oxygen. The evolution of microstructure and phase constituents was characterized. Then the oxidation rate was measured, and the relationships among grain size, mass transport rate, and electron flux were characterized. The role of the electron beam is discussed, and the results are rationalized with respect to ex situ results from the literature.

Sun, L.; Noh, K. W.; Wen, J-G.; Dillon, S. J. (Materials Science Division); (Massachusetts Inst. Tech.); (Univ. Illinois - Urbana)

2011-10-17

91

A novel gas ionization sensor using Pd nanoparticle-capped ZnO  

PubMed Central

A novel gas ionization sensor using Pd nanoparticle-capped ZnO (Pd/ZnO) nanorods as the anode is proposed. The Pd/ZnO nanorod-based sensors, compared with the bare ZnO nanorod, show lower breakdown voltage for the detected gases with good sensitivity and selectivity. Moreover, the sensors exhibit stable performance after more than 200 tests for both inert and active gases. The simple, low-cost, Pd/ZnO nanorod-based field-ionization gas sensors presented in this study have potential applications in the field of gas sensor devices.

2011-01-01

92

The solitary ionization waves in the gas discharge positive column  

Microsoft Academic Search

The strata problem in positive-column plasma considered as a result of non-linear ionization and recombination processes is treated on the basis of the derived non-linear diffusion equation. Soliton solutions are obtained in analytical form. The theory has remarkable coincidence with the experimental results.

N. N. Christov; Kh. I. Pushkarov

1993-01-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

94

Self-sustained plasma waveguide structures produced by ionizing laser radiation in a dense gas  

Microsoft Academic Search

The propagation of high-power laser radiation producing rapid ionization in a dense gas is analyzed by using a nonlinear electrodynamical model. It is shown that the interplay between the Kerr-type and the defocusing ionization nonlinearities may lead to the formation of self-sustained plasma waveguide filaments. Quasi-steady-state laser-plasma structures supported by various electromagnetic field configurations are considered.

D. Anderson; A. V. Kim; M. Lisak; V. A. Mironov; A. M. Sergeev; L. Stenflo

1995-01-01

95

Ionization of rare-gas targets by collisions of fast highly charged projectiles  

Microsoft Academic Search

We have determined the net ionization cross section for total slow-ion or slow-electron charge production in rare-gas targets by passage of a fast projectile both experimentally and theoretically. We have experimentally studied ionization in these targets by C, Fe, Nb, and Pb projectiles with energies ranging from 310 keV\\/amu to 4.75 MeV\\/amu and for charge states in the range of

A. S. Schlachter; K. H. Berkner; W. G. Graham; R. V. Pyle; P. J. Schneider; K. R. Stalder; J. W. Stearns; J. A. Tanis; R. E. Olson

1981-01-01

96

Carbon14 labelling of biomolecules induced by 14 CO ionized gas  

Microsoft Academic Search

Ionized14CO gas provides a rapid method for producing14C-labelled biomolecules. The apparatus consists of a high vacuum system in which a small amount of14CO is ionized by electron impact. The resulting species drift towards a target where they interact with the molecule of interest\\u000a to produce14C-labelled compounds. Since the reaction time is only 2 minutes, the method is particularly promising for

J. E. van Lier; L. Sanche

1979-01-01

97

IONIZATION-DRIVEN FRAGMENTATION OF GAS OUTFLOWS RESPONSIBLE FOR FeLoBALs IN QUASARS  

SciTech Connect

We show that time variations in the UV ionizing continuum of quasars, on scales of {approx}1 yr, affect the dynamic structure of the plasmas responsible for low-ionization broad absorption lines. Variations of the ionizing continuum produce non-equilibrium photoionization conditions over a significant fraction of the absorbing clouds and supersonically moving ionization fronts. When the flux drops, the contraction of the ionized region drives a supersonic cooling front toward the radiation source and a rarefaction wave in the opposite direction. The pressure imbalance is compensated by an increased speed of the cool gas relative to the front. When the flux recovers, the cool gas is re-ionized and re-heated by a supersonic ionization front traveling away from the radiation source and a forward shock is created. The re-heated clouds equilibrate to a temperature of {approx}10{sup 4} K and are observed to have different radial velocities than the main cloud. Such fragmentation seems consistent with the multicomponent structure of troughs seen in some objects. The velocity differences measured among various components in the quasars QSO 2359-1241 and SDSS J0318-0600 can be reproduced by our model if strong magnetic fields ({approx}10 mG) are present within the clouds.

Bautista, Manuel A. [Department of Physics, Western Michigan University, Kalamazoo, MI 49008-5252 (United States); Dunn, Jay P. [Department of Physics, Virginia Polytechnic and State University, Blacksburg, VA 24061 (United States)

2010-07-10

98

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

SciTech Connect

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

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

2009-01-15

99

The Massive Stellar Population in the Diffuse Ionized Gas of M33  

NASA Astrophysics Data System (ADS)

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

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

1995-01-01

100

Ionized gas characteristics in the cavities of the gas and dust disc of the spiral galaxy NGC 6946  

NASA Astrophysics Data System (ADS)

The parameters of the ionized gas in NGC 6946 (in the [NII] ??6548, 6583, H ? and [SII] ??6717, 6731 lines) are investigated with the SAO RAS BTA telescope along three positions of the long slit of the SCORPIO focal reducer, passing through a number of large and small cavities of the gaseous disc of the galaxy. These cavities correspond exactly to the cavities in warm dust, visible at 5 - 8µm. We found that everywhere in the direction of NGC 6946 the lines of ionized gas are decomposed into two Gaussians, one of which shows almost constant [SII]/H ? and [NII]/H ? ratios, as well as an almost constant radial velocity within the measurement errors (about -35… - 50 km/s). This component is in fact the foreground radiation from the diffuse ionized gas of our Galaxy, which is not surprising, given the low (12°) latitude of NGC 6946; a similar component is also present in the emission of neutral hydrogen. The analysis of the component of ionized gas, occurring inNGC 6946, has revealed that it shows signs of shock excitation in the cavities of the gaseous disc of the galaxy. This shock excitation is as well typical for the extraplanar diffuse ionized gas (EDIG), observed in a number of spiral galaxies at their high Z-coordinates. This can most likely be explained by low density of the gas in the NGC 6946 disc (with the usual photoionization) inside the cavities, due to what we see the spectral features of the EDIG gas of NGC 6946, projected onto them, and located outside the plane of the galaxy. In the absence of separation of ionized gas into two components by radial velocities, there is an increasing contribution to the integral line parameters by the EDIG of our Galaxy when the gas density in NGC 6946 decreases, which explains some strange results, obtained in the previous studies. Themorphology of warmdust, visible in the infrared range and HI is almost the same (except for the peripheral parts of the galaxy, where there are no sources of dust heating).Moreover, the shock excitation of the ionized gas is detected in the smallest holes, distinguishable only in the IR images.

Efremov, Yu. N.; Afanasiev, V. L.; Egorov, O. V.

2011-07-01

101

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

102

Wavelength Scaling of Terahertz Generation by Gas Ionization  

NASA Astrophysics Data System (ADS)

Low-frequency currents induced by ultrashort laser-driven ionization can emit extremely broadband, single-cycle terahertz pulses. We present a model that predicts a strong wavelength dependence of the THz emission in good agreement with our experimental study. This reveals that the combined effects of plasma currents rising proportionally to the square of the pump wavelength and wavelength-dependent focusing conditions lead to 30 times higher THz emission at 1800 nm compared to an 800 nm wavelength. Unrivaled single-cycle electric field strengths of 4.4MV/cm are achieved with this compact table-top setup.

Clerici, Matteo; Peccianti, Marco; Schmidt, Bruno E.; Caspani, Lucia; Shalaby, Mostafa; Giguère, Mathieu; Lotti, Antonio; Couairon, Arnaud; Légaré, François; Ozaki, Tsuneyuki; Faccio, Daniele; Morandotti, Roberto

2013-06-01

103

Analysis of pesticides by gas chromatography/multiphoton ionization/mass spectrometry using a femtosecond laser.  

PubMed

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOFMS) was utilized for analysis of a standard mixture sample containing 49 pesticides and 4 real samples using the third-harmonic emission (267 nm) of a femtosecond Ti:sapphire laser (100 fs) as the ionization source. A sample of a standard mixture of n-alkane was also measured for calibration of the retention time indices of the pesticides. Two photons are required for the excitation of n-alkane due to an absorption band located in the far ultraviolet region (140 nm). The n-alkane molecule in the excited state was subsequently ionized either directly or by absorbing another photon because of a high ionization potential. Due to a large excess of energy, the molecular ion was decomposed and formed many fragment ions. Compared to n-alkanes, most of the pesticides were softly ionized by the femtosecond laser; one photon was used for excitation and another was used for the subsequent ionization. The pesticides with no conjugated double bond had a lower ionization efficiency. The present analytical instrument was applied to several samples prepared from a variety of vegetables and a single fruit after pretreatment with solid-phase extraction. Three pesticides were found in these samples, although some of them were not detected by conventional GC/EI/MS-MS due to insufficient sensitivity and selectivity. PMID:21763808

Li, Adan; Imasaka, Tomoko; Uchimura, Tomohiro; Imasaka, Totaro

2011-06-13

104

Observations and modeling of diffuse ionized gas in edge-on galaxies  

NASA Astrophysics Data System (ADS)

The present PhD theses deals with observations of diffuse ionized gas (DIG) in edge-on galaxies and their corresponding modeling. A still unexplained issue concerns possible ionization mechanisms of the DIG. Based upon energy estimations photoionization by young O stars appears to be the most likely ionizing source. Within the scope of this work, spectroscopic line ratios have been obtained which are compared to predictions of common photoionization models. As these codes cannot explain the observational data consistently, a new photoionization model code has been developed which is based on Monte Carlo techniques and assumes a more realistic geometry. First model iterations of the ionization structure of the DIG reveal encouraging results. In order to simulate individual galaxies in detail, a comprehensive investigation of the free parameter space is required.

Tuellmann, Ralph

2002-04-01

105

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

106

3D Modeling of Laser Propagation in Ionizing Gas and Plasma  

NASA Astrophysics Data System (ADS)

The interaction of a high intensity laser with ionizing gas and plasmas is of current interest for both Laser Wakefield Accelerators and x-ray generation. We have developed a 3D fluid simulation code based on the same quasistatic approximation used in the 2D code WAKE [1]. The object oriented structure of the code also allows it to couple to the quickPIC particle code [2]. We will present 3D studies of the ionization scattering instability [3], which occurs when a laser pulse propagates in an ionizing gas. [1] P. Mora and T. Antonsen, Jr., Phys. Plasmas 4(1), January 1997 [2] J. Cooley, T. Antonsen, Jr., C. Huang, etal., Proceedings, Advanced Accelerator Concepts, 2002 [3] Z. Bian and T. Antonsen, Jr., Phys. Plasmas 8(7), July 2001 * work supported by NSF and DOE

Cooley, J.; Antonsen, T., Jr.; Huang, C.; Mori, W.

2003-10-01

107

Gas chromatography positive chemical ionization and tandem mass spectrometry for the analysis of organic high explosives  

Microsoft Academic Search

The characteristic ions or the parent ion resulting from ionization can be isolated in an ion trap and subjected to further fragmentation during a gas chromatography–tandem mass spectrometry (GC\\/MS\\/MS) experiment. This approach can improve the selectivity and sensitivity of explosive compounds over gas chromatography–mass spectrometry (GC\\/MS) by improving the differentiation of the target compounds from interfering and co-eluting compounds and

Jeannette M. Perr; Kenneth G. Furton; José R. Almirall

2005-01-01

108

Isotopically selective counting of noble gas atoms, using resonance ionization spectroscopy  

SciTech Connect

The technique of Resonance Ionization Spectroscopy (RIS) is being extended to develop a means for counting individual atoms of a selected isotope of a noble gas. In this method, lasers are used for RIS to obtain atomic species (Z) selectivity and a small quadrupole mass spectrometer provides isotopic (A) selectivity. A progress report on the objective of counting each atom of a particular isotope of a noble gas is given. 10 references, 4 figures.

Chen, C.H.

1984-04-01

109

On the ionization conditions in the interarm gas of M 33  

Microsoft Academic Search

Deep spectroscopic observations of the galaxy Messier 33 in the spectral region 4300–6700 Å show the presence of the 5007 Å emission line of [O III] in the interarm region. We derive for the log I(5OO7)\\/I(Hß) a preliminary value of .12, which indicates moderate ionization conditions in the interarm gas.

P. Benvenuti; S. D'Odorico

1975-01-01

110

Kinematics of the ionized gas in the Local Group irregular galaxy IC 1613  

NASA Astrophysics Data System (ADS)

We present H? and [S Ii] observations for the Local Group irregular galaxy IC 1613 using the PUMA scanning Fabry-Perot interferometer. Our goal is to analyze the kinematics of the ionized gas in the complex sample of superbubbles located in the whole extension of our field (10\\arcmin ), which includes most of the optical emission of this galaxy, and to study the inter-relationship between young stellar associations and nebulae based on a previous study that we have made on the stellar associations of the central region of this galaxy. The ionized gas in this galaxy is distributed in classical H Ii regions and in a series of superbubbles (also called giant shells) covering a large fraction of the optical extent of the galaxy. We present a catalog of kinematical properties of both the H Ii regions of this galaxy and the superbubbles. We have also compared the kinematics of the ionized gas in H Ii regions to search for possible dynamic differences between neutral and ionized gas.

Valdez-Gutiérrez, M.; Rosado, M.; Georgiev, L.; Borissova, J.; Kurtev, R.

2001-01-01

111

Comparison of the Ionized Gas and Stellar Kinematics in the Circumnuclear Regions of Seyfert Galaxies  

Microsoft Academic Search

Integral-field spectroscopy techniques are ideal to study objects of complex morphology and kinematics such as the circumnuclear region of AGN. We have obtained the stellar and ionized gas kinematics of four Seyfert galaxies by using integral field spectroscopy with optical fibers. For each galaxy, the kinematics of the stellar component can be well explained as rotation in a disk. The

B. García-Lorenzo; J. A. Acosta-Pulido; A. M. Pérez-García; E. Mediavilla; S. Arribas

2001-01-01

112

The influence of neutral gas temperature on the parameters of ionization waves in neon  

Microsoft Academic Search

In the present paper, the influence of cooling down the neutral gas to a temperature of 77°K on the parameters of ionization waves excited in the positive column of a d. c. glow discharge in neon is studied. After the cooling, the group velocity, phase velocity, frequency and relaxation time of the waves of varietyp decreased and they increased in

K. Masek; V. Pe?ina

1968-01-01

113

Monte Carlo simulation of charged particle diffusion through an ionized gas: contributions of simultaneous multiple collisions  

Microsoft Academic Search

When a charged particle moves through fully or partially ionized plasmas, energy loss and momentum transfer occur through various kinds of elastic and inelastic collisions.In ordinary gases, composed primarily of neutral particles, the interactions are mainly close binary collisions, being the impact parameter well shorter than the mean free path. In a gas composed of charged particles, neglecting simultaneous multiple

V. Molinari; F. Teodori

2004-01-01

114

Stability of an ionized layer in a gas /the atmosphere/  

NASA Astrophysics Data System (ADS)

The layer in question is produced in the atmosphere and maintained by periodic pulsed breakdown in intersecting beams of radio waves (Borisov and Gurevich, 1980; Gurevich, 1980). It is assumed that the breakdown occurs in the field of two beams of radio waves of frequency tau that meet at some angle theta. It is further assumed that both waves have a horizontal polarization and that the length of the pulses maintaining the ionization is small. The repetition period is chosen in such a way that the plasma density changes only negligibly between pulses. It is also noted that the layer is inhomogeneous. Because of this inhomogeneity, a dependence on a corresponding dimensionless parameter (the ratio of the layer thickness to the wavelength) appears in the results. Consideration is given not only to attachment but also to recombination as a mechanism by which electrons are lost.

Borisov, N. D.

1982-07-01

115

Ionized Gas in the First 10 kpc of the Interstellar Galactic Halo: Metal Ion Fractions  

NASA Astrophysics Data System (ADS)

We present direct measures of the ionization fractions of several sulfur ions in the Galactic warm ionized medium (WIM). We obtained high-resolution ultraviolet absorption-line spectroscopy of post-asymptotic giant branch stars in the globular clusters Messier 3 [(l, b) = (42fdg2, +78fdg7), d = 10.2 kpc, and z = 10.0 kpc] and Messier 5 [(l, b) = (3fdg9, +46fdg8), d = 7.5 kpc, and z = +5.3 kpc] with the Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer to measure, or place limits on, the column densities of S I, S II, S III, S IV, S VI, and H I. These clusters also house millisecond pulsars, whose dispersion measures give an electron column density from which we infer the H II column in these directions. We find fractions of S+2 in the WIM for the M 3 and M 5 sight lines x(S+2) ? N(S+2)/N(S) = 0.33 ± 0.07 and 0.47 ± 0.09, respectively, with variations perhaps related to location. With negligible quantities of the higher ionization states, we conclude that S+ and S+2 account for all of the S in the WIM. We extend the methodology to study the ion fractions in the warm and hot ionized gas of the Milky Way, including the high ions Si+3, C+3, N+4, and O+5. The vast majority of the Galactic ionized gas is warm (T ~ 104 K) and photoionized (the WIM) or very hot (T > 4 × 105 K) and collisionally ionized. The common tracer of ionized gas beyond the Milky Way, O+5, traces <1% of the total ionized gas mass of the Milky Way. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA Contract NAS5-26555. These observations are associated with programs GO9150 and GO9410. Also based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE was operated for NASA by the Johns Hopkins University under NASA Contract NAS5-32985.

Howk, J. Christopher; Consiglio, S. Michelle

2012-11-01

116

Aerodynamic Effects in Weakly Ionized Gas: Phenomenology and Applications  

Microsoft Academic Search

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

Svetozar Popovic

2006-01-01

117

Kinetic temperature and charge of a dust grain in weakly ionized gas-discharge plasmas  

SciTech Connect

Analytical relations are given for estimating the energy of the stochastic motion of an individual dust grain heated by electrostatic ion oscillations in a weakly ionized gas-discharge plasma. Dust grain charging processes are analyzed, and an empirical approximation is obtained for the ion current to the grain surface. The processes are simulated under conditions similar to those of laboratory experiments on dusty plasmas. It is found that the kinetic temperature of a dust grain heated by electrostatic ion oscillations in a gas-discharge plasma can exceed the background gas temperature.

Vaulina, O. S., E-mail: vaul@ihed.ras.ru; Repin, A. Yu.; Petrov, O. F.; Adamovich, K. G. [Russian Academy of Sciences, Institute for High Energy Densities, Joint Institute for High Temperatures (Russian Federation)

2006-06-15

118

A Search for Very Extended Ionized Gas in Nearby Starburst and Active Galaxies  

NASA Astrophysics Data System (ADS)

We report the results from a pilot study of 10 nearby starburst and active galaxies conducted with the Taurus Tunable Filter (TTF) on the Anglo-Australian and William Herschel telescopes. The main purpose of this imaging survey is to search for warm emission-line gas on the outskirts (galactocentric distances R>~10 kpc) of galaxies to provide direct constraints on the size and geometry of the ``zone of influence'' of these galaxies on their environment. Gaseous complexes or filaments larger than ~20 kpc are discovered or confirmed in six of the galaxies in the sample (NGC 1068, 1482, 4388, 6240 and 7213, and MR 2251-178). Slightly smaller structures are seen for the first time in the ionization cones and galactic winds of NGC 1365, NGC 1705, the Circinus galaxy, and ESO 484-G036. The TTF data are combined with new optical long-slit spectra, as well as published and archived radio and X-ray maps, to constrain the origin and source of ionization of these filaments. A broad range of phenomena is observed, including large-scale ionization cones and galactic winds, tidal interaction, and ram-pressure stripping by an intracluster medium. The source of ionization in this gas ranges from shock ionization to photoionization by the central AGN or in situ hot young stars. The sample is too small to draw statistically meaningful conclusions about the extent and properties of the warm ionized medium on a large scale and its relevance to galaxy formation and evolution. The next generation of tunable filters on large telescopes promises to improve the sensitivity to faint emission-line fluxes at least tenfold and allow systematic surveys of a large sample of emission-line galaxies.

Veilleux, S.; Shopbell, P. L.; Rupke, D. S.; Bland-Hawthorn, J.; Cecil, G.

2003-11-01

119

Qualitative Gas Chromatography-Mass Spectrometry Analyses Using Amines as Chemical Ionization Reagent Gases  

NASA Astrophysics Data System (ADS)

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.

Little, James L.; Howard, Adam S.

2013-10-01

120

Quantitative analysis of plasma acylcarnitines using gas chromatography chemical ionization mass f rag mentog rap hy  

Microsoft Academic Search

A stable isotope dilution gas chromatography chemical ionization mass spectrometry (GC-CI-MS) method was developed for the quantitative profiling of plasma acylcar- nitines. The clean-up procedure was comprised of a solid- phase cation exchange extraction using PRScolumns from which the acylcarnitines were eluted with a barium chloride solution. Isolated acylcarnitines were transformed into acylox- ylactones and analyzed by positive GC-CI-MS using

C. G. Costa; E. A. Stnays; A. Bootsma; H. J. ten Brink; L. Dorland; I. Tavares de Almeida; M. Duran; C. Jakobs

121

Gas chromatography/mass spectrometric analysis of N,N-dialkylaminoethyl-2-chlorides and trimethylsilyl derivatives of N,N-dialkylaminoethan-2-ols for verification of the Chemical Weapons Convention.  

PubMed

Gas chromatography/electron ionization mass spectrometry (GC/EI-MS) of N,N-dialkylaminoethyl-2-chlorides (DAAECls) and trimethylsilyl (TMS) derivatives of N,N-dialkylaminoethan-2-ols (DAAEAs) has been carried out. GC/EI-MS data of these compounds are of importance for verification of the Chemical Weapons Convention (CWC). Based on these EI mass spectra, generalized fragmentation routes are proposed that rationalize most of the characteristic ions. PMID:16773673

Gupta, Arvinda K; Pardasani, Deepak; Kanaujia, Pankaj K; Tak, Vijay; Dubey, Devendra K

2006-01-01

122

Activation energies for gas-phase dissociations of multiply charged ions from electrospay ionization mass spectrometry  

SciTech Connect

The reactions of multiply protonated melittin molecular ions of various charge states produced from an electrospray ionization source have been studied. The flow of ions entrained in gas through a heated metal capillary inlet serves as a reaction vessel for gas-phase measurements of molecular ion reaction rates using mass spectrometry. Activation energies for the unimolecular dissociation reactions are calculated from the temperature dependence of the reaction kinetics. The differences in activation energies for the reactions of the different charge states are attributed to the destabilizing effect of Coulombic repulsion for high charged ions. 18 refs., 3 figs., 1 tab.

Busman, M.; Rockwood, A.L.; Smith, R.D. [Pacific Northwest Lab., Richland, WA (United States)

1992-03-19

123

The identification of bile acid methyl esters by gas chromatography methane chemical ionization mass spectrometry.  

PubMed

Methane chemical ionization mass spectrometric data and gas chromatography retention parameters are reported for 31 bile acid methyl esters. The group includes both saturated and unsaturated compounds with up to three keto or hydroxyl groups. Major ions include the quasimolecular ions and fragments resulting from the loss of neutral species such as methanol, water and methane. The combination of gas-liquid chromatography retention and mass spectral data is sufficient for an unequivocal distinction among all the bile acids studied. Application of this data to the identification of bile acid metabolites is cited. PMID:476290

Muschik, G M; Wright, L H; Schroer, J A

1979-06-01

124

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...

125

The ionized gas in the CALIFA early-type galaxies. I. Mapping two representative cases: NGC 6762 and NGC 5966  

NASA Astrophysics Data System (ADS)

As part of the ongoing CALIFA survey, we have conducted a thorough bidimensional analysis of the ionized gas in two E/S0 galaxies, NGC 6762 and NGC 5966, aiming to shed light on the nature of their warm ionized ISM. Specifically, we present optical (3745-7300 Å) integral field spectroscopy obtained with the PMAS/PPAK integral field spectrophotometer. Its wide field-of-view (1' × 1') covers the entire optical extent of each galaxy down to faint continuum surface brightnesses. To recover the nebular lines, we modeled and subtracted the underlying stellar continuum from the observed spectra using the STARLIGHT spectral synthesis code. The pure emission-line spectra were used to investigate the gas properties and determine the possible sources of ionization. We show the advantages of IFU data in interpreting the complex nature of the ionized gas in NGC 6762 and NGC 5966. In NGC 6762, the ionized gas and stellar emission display similar morphologies, while the emission line morphology is elongated in NGC 5966, spanning ~6 kpc, and is oriented roughly orthogonal to the major axis of the stellar continuum ellipsoid. Whereas gas and stars are kinematically aligned in NGC 6762, the gas is kinematically decoupled from the stars in NGC 5966. A decoupled rotating disk or an "ionization cone" are two possible interpretations of the elongated ionized gas structure in NGC 5966. The latter would be the first "ionization cone" of such a dimension detected within a weak emission-line galaxy. Both galaxies have weak emission-lines relative to the continuum[EW(H?) ? 3 Å] and have very low excitation, log([Oiii]?5007/H?) ? 0.5. Based on optical diagnostic ratios ([Oiii]?5007/H?, [Nii]?6584/H?, [Sii]?6717, 6731/H?, [Oi]?6300/H?), both objects contain a LINER nucleus and an extended LINER-like gas emission. The emission line ratios do not vary significantly with radius or aperture, which indicates that the nebular properties are spatially homogeneous. The gas emission in NGC 6762 can be best explained by photoionization by pAGB stars without the need of invoking any other excitation mechanism. In the case of NGC 5966, the presence of a nuclear ionizing source seems to be required to shape the elongated gas emission feature in the "ionization cone" scenario, although ionization by pAGB stars cannot be ruled out. Further study of this object is needed to clarify the nature of its elongated gas structure. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).

Kehrig, C.; Monreal-Ibero, A.; Papaderos, P.; Vílchez, J. M.; Gomes, J. M.; Masegosa, J.; Sánchez, S. F.; Lehnert, M. D.; Cid Fernandes, R.; Bland-Hawthorn, J.; Bomans, D. J.; Marquez, I.; Mast, D.; Aguerri, J. A. L.; López-Sánchez, Á. R.; Marino, R. A.; Pasquali, A.; Perez, I.; Roth, M. M.; Sánchez-Blázquez, P.; Ziegler, B.

2012-04-01

126

On the Origin of the High-Ionization Intermediate-Velocity Gas toward HD 14434  

NASA Astrophysics Data System (ADS)

We present Far-Ultraviolet Spectroscopic Explorer and Space Telescope Imaging Spectrograph observations of high-ionization interstellar absorption toward HD 14434 (l=135.1d, b=-3.8d d~2.3 kpc), an O5.5 V star in the Perseus OB1 association. Intermediate-velocity interstellar Si IV and C IV absorption is present at VLSR=-67 km s-1, while low-ionization gas associated with the Perseus arm is detected at about -50 km s-1. Neither N V nor O VI is detected at VLSR=-67 km s-1, although Al III and Fe III, tracers of warm ionized gas, are seen. The high-ion column densities in the -67 km s-1 component are log[N(CIV)]=13.92+/-0.02 cm-2, log[N(SiIV)]=13.34+/-0.02 cm-2, log[N(NV)]<=12.65 cm-2, and log[N(OVI)]<=13.73 cm-2 (3 ? limits). The observed C IV/Si IV ratio of 3.8+/-0.3 in this intermediate-velocity cloud (IVC) is similar to the Galactic average (4.3+/-1.9). Our analysis of the Si IV and C IV line widths yields a temperature of T~10,450+/-3400 K for this component. At this low temperature, neither Si IV nor C IV can be produced via collisions. We investigate several photoionization models to explain the intermediate-velocity Si IV and C IV absorption toward HD 14434. Photoionization models employing cooling of a hot (T~106 K) diffuse plasma as the source of ionizing radiation reproduce the observed properties of the IVC toward HD 14434 quite well. The hot plasma responsible for the ionizing radiation in these models may be attributed to hot gas contained in a supershell in or near the Perseus arm or from a more generally distributed hot ionized medium. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under the NASA contract NAS 5-26555.

Knauth, David C.; Howk, J. Christopher; Sembach, Kenneth R.; Lauroesch, James T.; Meyer, David M.

2003-08-01

127

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

SciTech Connect

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

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

2012-10-15

128

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

129

Observations of feedback from radio-quiet quasars - I. Extents and morphologies of ionized gas nebulae  

NASA Astrophysics Data System (ADS)

Black hole feedback - the strong interaction between the energy output of supermassive black holes and their surrounding environments - is routinely invoked to explain the absence of overly luminous galaxies, the black hole versus bulge correlations and the similarity of black hole accretion and star formation histories. Yet direct probes of this process in action are scarce and limited to small samples of active nuclei. In this paper, we present Gemini Integral Field Unit observations of the distribution of ionized gas around luminous, obscured, radio-quiet quasars at z ˜ 0.5. We detect extended ionized gas nebulae via [O III] ?5007 Å emission in every case, with a mean diameter of 28 kpc. These nebulae are nearly perfectly round, with H? surface brightness declining ?R-3.5 ± 1.0. The regular morphologies of nebulae around radio-quiet quasars are in striking contrast with lumpy or elongated [O III] nebulae seen around radio galaxies at low and high redshifts. We present the uniformly measured size-luminosity relationship of [O III] nebulae around Seyfert 2 galaxies and type 2 quasars spanning six orders of magnitude in luminosity and confirm the flat slope of the correlation (R_{[O III]}? L_{[O III]}^{0.25± 0.02}). We propose a model of clumpy nebulae in which clouds that produce line emission transition from being ionization-bounded at small distances from the quasar to being matter-bounded in the outer parts of the nebula. The model - which has a declining pressure profile - qualitatively explains line ratio profiles and surface brightness profiles seen in our sample. It is striking that we see such smooth and round large-scale gas nebulosities in this sample, which are inconsistent with illuminated merger debris and which we suggest may be the signature of accretion energy from the nucleus reaching gas at large scales.

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

2013-04-01

130

Multiple ionization of rare gas dimers by slow highly charged ions: screening effect during a collision  

NASA Astrophysics Data System (ADS)

Multiple ionization dynamics of rare gas dimers by slow highly charged ions has been investigated using the three-center Coulombic over-barrier model. The outermost electrons at two atomic sites in the dimer are sequentially removed by forming a quasi-molecule with a projectile, where partial screening is taken into account in the non-active site ionized during a collision. It is found that the fragment ion pair (Q,Q?) distribution is remarkably sensitive to the screening effect, which enhances the population of highly charge-asymmetric pairs such as (2,0) and (3,1). Recent measurement of the ion pair distribution in Ar9+ + Ar2 collisions is best reproduced with the present model by taking a screening parameter of s = 0.4.

Ohyama-Yamaguchi, Tomoko; Ichimura, Atsushi

2013-09-01

131

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

Microsoft Academic Search

Ion mobility spectrometry (IMS) featuring different ionization techniques was used to analyze isomeric ortho-, meta- and para-dihalogenated benzenes in order to assess how structural features affect ion formation and drift behavior. The structure of the product ions formed was investigated by atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) and IMS-MS coupling. Photoionization provided [M]+ ions for chlorinated and fluorinated

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

2004-01-01

132

Diffuse Ionized Gas in Edge-on Spiral Galaxies: Extraplanar and Outer Disk H? Emission  

NASA Astrophysics Data System (ADS)

We present H? images of five edge-on galaxies: NGC 891, NGC 4631, NGC 4244, NGC 3003, and UGC 9242. We also analyze [S II] lambdalambda6717, 6731 and [O III] lambda5007 images of NGC 4631. For several of these galaxies, these images are the most sensitive to date. We analyze the ionized gas content, with particular attention to the diffuse ionized gas (DIG). The DIG layer in NGC 891 is traced out to at least 5 kpc from the midplane, confirming an earlier spectroscopic detection. The DIG in four of these galaxies contributes 40%-50% of the total H? luminosity, similar to the contribution in face-on galaxies, but in NGC 891 the DIG contributes 80%-90%. This is likely due to the higher dust content in the disk of NGC 891, which obscures the H II regions but may also reflect the extraordinary prominence of the DIG layer in that galaxy. Our very deep image of UGC 9242 shows very low surface brightness emission, as low as 0.3 pc cm^-6, reaching 4-5 kpc above the midplane. This galaxy also exhibits filaments near the bright H? nucleus, an indication of a starburst superwind. In NGC 4631 we see a very large shell of emission extending 3.5 kpc into the halo. The [S II]/H? and [O III]/H? ratios in NGC 4631 are consistent with the ratios seen in other galaxies, and with photoionization models. There is a region on the southeast side of disk where the [O III]/(H?+[N II]) ratio reaches over 1.0 in the DIG, which coincides with an H I supershell. We use our very deep images of NGC 3003 and UGC 9242 to search for ionized gas in the outer disks as a test of the strength of the metagalactic ionizing radiation field. We find no outer disk emission down to our 1 sigma limit of 0.13 pc cm^-6 on scales of 1.5 kpc in NGC 3003. Based on this limit we rule out a metagalactic ionizing radiation field stronger than 11x10^-23 ergs cm^-2 s^-1 Hz^-1 sr^-1. There is an indication of extended disk emission in UGC 9242, which would imply a stronger radiation field, but various concerns, most importantly flat-fielding uncertainties due to foreground stars in the image, lead us to question whether this feature is real.

Hoopes, Charles G.; Walterbos, René A. M.; Rand, Richard J.

1999-09-01

133

Non-equilibirum ionization and cooling of metal-enriched gas in the presence of a photoionization background  

NASA Astrophysics Data System (ADS)

Simulations of the formation of galaxies, as well as ionization models used to interpret observations of quasar absorption lines, generally either assume ionization equilibrium or ignore the presence of the extragalactic background (EGB) radiation. We introduce a method to compute the non-equilibrium ionization and cooling of diffuse gas exposed to the EGB. Our method iterates the ionization states of the 11 elements that dominate the cooling (H, He, C, N, O, Ne, Si, Mg, S, Ca and Fe) and uses tabulated ion-by-ion cooling and photo-heating efficiencies to update the temperature of the gas. Our reaction network includes radiative and di-electric recombination, collisional ionization, photoionization, Auger ionization and charge transfer. We verify that our method reproduces published results for collisional equilibrium, collisional non-equilibrium and photoionized equilibrium. Non-equilibrium effects can become very important in cooling gas, particularly below 106 K. Photoionization and non-equilibrium effects both tend to boost the degree of ionization and to reduce cooling efficiencies. The effect of the EGB is larger for lower densities (i.e. higher ionization parameters). Hence, photoionization affects (equilibrium and non-equilibrium) cooling more under isochoric than under isobaric conditions. Non-equilibrium effects are smaller in the presence of the EGB and are thus overestimated when using collisional-only processes. The inclusion of the EGB alters the observational diagnostics of diffuse, metal-enriched gas (e.g. metal absorption lines probed in quasar sight lines) even more significantly than the cooling efficiencies. We argue that the cooling efficiency should be considered if ionization models are used to infer physical conditions from observed line ratios, as the a priori probability of observing gas is lower if its cooling time is shorter. We provide online tables of ionization fractions and cooling efficiencies, as well as other data, for equilibrium and non-equilibrium scenarios, and both with and without an EGB. Cooling efficiencies and diagnostics of the physical state of diffuse gas can become highly inaccurate if ionization equilibrium is assumed or if the existence of the ionizing background is ignored.

Oppenheimer, Benjamin D.; Schaye, Joop

2013-09-01

134

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

135

Can the Lyman Continuum Leaked Out of H II Regions Explain Diffuse Ionized Gas?  

NASA Astrophysics Data System (ADS)

We present an attempt to explain the diffuse H? 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 H? 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 H? emission with the scenario is found to be of the order of ~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 ?0 ? 0.4-0.8 kpc-1 at the galactic plane, or, equivalently, an effective cross section as low as ?eff ~ 10-5 of the photoionization cross section at 912 Å 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 H? emissions around H II regions, and can account for only lsim26% of the H? luminosity of the DIG. This result places a strong constraint on the ionizing source of the DIG. We also report that the H? intensity distribution functions not only of the DIG, but also of H II regions in M 51, appear to be lognormal.

Seon, Kwang-Il

2009-09-01

136

Determination of daminozide in apples by gas chromatography/chemical ionization mass spectrometry.  

PubMed

A method using gas chromatography/chemical ionization mass spectrometry (GC/CIMS) for the determination of daminozide residues in apples has been developed. Daminozide was separated from the sample matrix by water extraction and cation exchange, converted to the methyl ester by treatment with HCl-methanol, and determined by GC/CIMS using succinonitrile as an internal standard. The detection level was 0.05 ppm. Recoveries were 92-104% from apples spiked at the 0.05-0.5 ppm levels. Of the 25 apple samples analyzed, only 2 were positive for daminozide (1.04 and 0.32 ppm). PMID:2592322

Liu, C H; Mattern, G C; Singer, G M; Rosen, J D

137

Selective fragmentation and ionization of organic compounds using an energy-tunable rare-gas metastable beam source  

Microsoft Academic Search

The initial use of an energy-tunable rare-gas metastable beam source generated by a corona discharge as an ionization source for mass spectrometry is reported. The metastable atom beam is produced external to theion source and its excitation energy is controlled by the rare gas which is employed. The metastable beam source can be used routinely and provides sensitivities of the

D. Faubert; G. J. C. Paul; J. Giroux; M. J. Bertrand

1993-01-01

138

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

EPA Science Inventory

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

139

The Effect of Pre-Ionization Inhomogeneities on the Dynamics of a Subnanosecond Pulsed Electrical Breakdown in Gas Gaps1  

Microsoft Academic Search

The initiation and the development of a breakdown of highly overvoltaged gas gaps by voltage pulses having the rise time of 1 ns or shorter are studied experimentally and in theoreti- cal terms. The study revealed that ionization proc- esses leading to the breakdown start in the gas vol- ume and not from the surface of the electrodes. The gap

S. N. Ivanov; V. V. Lisenkov; V. G. Shpak

140

Collection of airborne fluorinated organics and analysis by gas chromatography/chemical ionization mass spectrometry.  

PubMed

The ubiquitous detection of perfluorooctane sulfonate (PFOS) in humans and animals has produced a need for sensitive and compound-specific analytical methods to determine the environmental distribution of fluorinated organic contaminants. A suite of potential PFOS precursors (sulfonamides) and fluorotelomer alcohols (FTOHs) were separated by gas chromatography and detected by chemical ionization mass spectrometry (GC/CI-MS). Full-scan spectra were collected in both positive and negative chemical ionization (PCI and NCI, respectively) mode to determine retention time windows and fragmentation patterns. In selected ion monitoring (SIM) mode, instrumental detection limits ranged from 0.2 to 20 pg for individual analytes, depending on ionization mode. PCI mode was preferred for routine analysis because of the simple mass spectra produced, typified by the presence of a major molecular ion [M + H]+. High-volume air samplers collected gaseous and particle-bound fluoroorganics on composite media consisting of XAD-2, polyurethane foam (PUF), and quartz-fiber filters. The combined collection efficiency for individual analytes was 87 to 136% in breakthrough experiments. Application of the method to the analysis of ambient air from urban and rural sites confirmed the presence of six novel fluorinated atmospheric contaminants at picogram per meter3 concentrations. Low concentrations of fluoroorganics were consistently detected in blanks (<4 pg m(-3)); however, this did not prevent confirmation or quantification of environmental concentrations. PMID:11842814

Martin, Jonathan W; Muir, Derek C G; Moody, Cheryl A; Ellis, David A; Kwan, Wai Chi; Solomon, Keith R; Mabury, Scott A

2002-02-01

141

Electron energy distribution function and dense-gas ionization in the presence of a strong field  

NASA Astrophysics Data System (ADS)

The mechanism for dense-gas ionization is analyzed in the case when the deceleration of electrons by gas can be neglected in the equation of motion of a single electron. An expression for the electron energy distribution function in the presence of a strong field is derived. The characteristic width of the distribution corresponds to the energy acquired by the electron at a length determined by the inverse Townsend coefficient. The electron energy distributions are calculated for various distances form the cathode. It is demonstrated that the distribution becomes independent of the coordinate at a distance from the cathode that is significantly greater than the inverse Townsend coefficient. In this case, the distribution coincides with the distribution obtained with analytical calculations. The absence of the coordinate dependence is realized even in the presence of an extremely strong field when, in accordance with the commonly accepted point of view, the majority of electrons are runaway electrons.

Tkachev, A. N.; Yakovlenko, S. I.

2006-09-01

142

Numerical models for the diffuse ionized gas in galaxies. I. Synthetic spectra of thermally excited gas with turbulent magnetic reconnection as energy source  

NASA Astrophysics Data System (ADS)

Aims: The aim of this work is to verify whether turbulent magnetic reconnection can provide the additional energy input required to explain the up to now only poorly understood ionization mechanism of the diffuse ionized gas (DIG) in galaxies and its observed emission line spectra. Methods: We use a detailed non-LTE radiative transfer code that does not make use of the usual restrictive gaseous nebula approximations to compute synthetic spectra for gas at low densities. Excitation of the gas is via an additional heating term in the energy balance as well as by photoionization. Numerical values for this heating term are derived from three-dimensional resistive magnetohydrodynamic two-fluid plasma-neutral-gas simulations to compute energy dissipation rates for the DIG under typical conditions. Results: Our simulations show that magnetic reconnection can liberate enough energy to by itself fully or partially ionize the gas. However, synthetic spectra from purely thermally excited gas are incompatible with the observed spectra; a photoionization source must additionally be present to establish the correct (observed) ionization balance in the gas.

Hoffmann, T. L.; Lieb, S.; Pauldrach, A. W. A.; Lesch, H.; Hultzsch, P. J. N.; Birk, G. T.

2012-08-01

143

Unresolved emission and ionized gas in the bulge of M31  

NASA Astrophysics Data System (ADS)

We study origin of unresolved X-ray emission from the bulge of M31 based on archival Chandra and XMM-Newton observations. We demonstrate that three different components are present: (i) Broad-band emission from large number of faint sources - mainly accreting white dwarfs and active binaries, associated with the old stellar population, similar to the Galactic Ridge X-ray emission of the Milky Way. (ii) Soft emission from ionized gas with temperature of about ˜ 300 keV and mass of ˜ 4 · 106 M . The gas distribution is significantly elongated in the minor axis direction suggesting that it may be outflowing in the direction perpendicular to the galactic disk. The shadows cast on the gas by spiral arms and the 10-kpc star-forming ring confirm large off-plane extent of the gas. (iii) Hard unresolved emission from spiral arms, most likely associated with protostars and young stellar objects located in the star-forming regions. Its luminosity corresponds to about ˜ 1/3 of the HMXBs contribution, determined earlier from Chandra observations of other nearby galaxies.

Gilfanov, Marat

144

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

145

Violent Interaction among Molecular Gas, Supernova Remnants, and Ionized Gas in the Galactic Center Region  

NASA Astrophysics Data System (ADS)

We present results of a high-resolution wide-field mapping observation of Central Molecular Zone (CMZ) in SiO v=0, J=2-1 and H13CO+ J=1-0 emission lines using the Nobeyama Radio Observatory 45-m telescope and the 25-beam receiver of 100 GHz band in order to explore molecular gas affected by shock in the regions and depict the molecular gas mass distribution. The mapping area covers an 1.5°×0.5° area involving several named molecular clouds, for example the Sgr A molecular cloud complex, the Sgr B2 molecular cloud, and so on. The SiO emission line is known as a privileged tracer of shocked molecular gas. We find many molecular clouds remarkable only in SiO emission line. The molecular clouds have large velocity width up to 60 km s-1. The brightness temperature ratio is high up to TB(SiO)/TB(H13CO+) ? 8. The features are dominated by shock SiO-emphasized gas. In such clouds, the ratio of fractional abundance of SiO and H13CO+ molecules is increased to X (SiO)/X(H13CO+) ? 30. Meanwhile, the H13CO+ emission line is a famous tracer of molecular gas mass. H13CO+ emission line presents clumpy distribution of molecular cloud. The averaged fractional abundance in the region is X(SiO)/X(h13CO+) ? 30. The total molecular mass of the CMZ is MLTE = 17 ± 8 × 106M?.

Tsuboi, M.; Tadaki, K.; Sato, M. T.; Miyazaki, A.; Handa, T.

2011-05-01

146

Spatially resolved observations of warm ionized gas and feedback in local ULIRGs  

NASA Astrophysics Data System (ADS)

We present Very Large Telescope (VLT)/VIsible MultiObject Spectrograph integral field unit (VIMOS-IFU) emission-line spectroscopy of a volume-limited sample of 18 southern ultraluminous infrared galaxies (ULIRGs) selected with z < 0.09 and ? < 10. By covering a wide range of ULIRG types, including many systems that have received very little previous attention, this data set provides an important set of templates for comparison with high-redshift galaxies. We employed an automated Gaussian line-fitting programme to decompose the emission-line profiles of H?, [N II], [S II] and [O I] into individual components, and chart the H? kinematics, and the ionized gas excitations and densities. 11 out of 18 of our galaxies show evidence for outflowing warm ionized gas with speeds between 500 and a few 1000 km s-1, with the fastest outflows associated with systems that contain an active galactic nucleus. Our spatially resolved spectroscopy has allowed us to map the outflows, and in some cases determine for the first time to which nucleus the wind is associated. In three of our targets we find line components with widths >2000 km s-1 over spatially extended regions in both the recombination and forbidden lines; in two of these three, they are associated with a known Sy2 nucleus. Eight galaxies have clear rotating gaseous discs, and for these we measure rotation velocities, virial masses, and calculate Toomre Q parameters. We find radial gradients in the emission-line ratios in a significant number of systems in our study. We attribute these gradients to changes in ionizing radiation field strength, most likely due to an increasing contribution of shocks with radius. We conclude with a detailed discussion of the results for each individual system, with reference to the existing literature. Our observations demonstrate that the complexity of the kinematics and gas properties in ULIRGs can only be disentangled with high sensitivity, spatially resolved IFU observations. Many of our targets are ideal candidates for future high spatial resolution follow-up observations. Based on observations collected at the European Organisation for Astronomical Research in the Southern hemisphere, Chile, under programmes 080.B-0085 and 383.B-0372.

Westmoquette, M. S.; Clements, D. L.; Bendo, G. J.; Khan, S. A.

2012-07-01

147

Extraction of neutral gas parameters from ionization gauge measurements in the lower thermosphere using DSMC calculations  

NASA Astrophysics Data System (ADS)

The extraction of neutral gas parameters (temperature, density, and three-dimensional winds) from ionization gauge measurements in the lower thermosphere using the direct simulation Monte Carlo (DSMC) method is described and discussed. Measurements from a multiple-sensor ionization gauge flown on a sounding rocket at low latitudes in the lower thermosphere are used to constrain DSMC models of the flow around the sounding rocket payload in the altitude range 95-113 km. Several aspects of the modeling are discussed, including creation of a large unstructured computational grid, the computational resources needed, the effects of transition flow, and the development of a hydrodynamic shock around the payload. Reliable, reproducible modeling of the pressures measured in the gauges is shown to be possible at the 0.5% level. This degree of precision is shown to allow good determination of the winds in this transition flow regime. Profiles of the modeled ambient temperature, density and three-dimensional winds are presented and discussed.

Clemmons, James; Burt, Jonathan M.; Boyd, Iain D.; Bishop, Rebecca L.; Pfaff, Robert; Rowland, Douglas

148

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

SciTech Connect

The interaction of intense extreme ultraviolet (XUV) laser pulses ({lambda}=32 nm, I=10{sup 11}-10{sup 14} W/cm{sup 2}) with small rare-gas clusters (Ar{sub 147}) is studied by quasiclassical molecular dynamics simulations. Our analysis supports a very general picture of the charging and heating dynamics in finite samples under short-wavelength radiation that is of relevance for several applications of free-electron lasers. First, up to a certain photon flux, ionization proceeds as a series of direct photoemission events producing a jellium-like cluster potential and a characteristic plateau in the photoelectron spectrum as observed in Bostedt et al. [Phys. Rev. Lett. 100, 133401 (2008)]. Second, beyond the onset of photoelectron trapping, nanoplasma formation leads to evaporative electron emission with a characteristic thermal tail in the electron spectrum. A detailed analysis of this transition is presented. Third, in contrast to the behavior in the infrared or low vacuum ultraviolet range, the nanoplasma energy capture proceeds via ionization heating, i.e., inner photoionization of localized electrons, whereas collisional heating of conduction electrons is negligible up to high laser intensities. A direct consequence of the latter is a surprising evolution of the mean energy of emitted electrons as function of laser intensity.

Arbeiter, Mathias; Fennel, Thomas [Institute of Physics, University of Rostock, D-18051 Rostock (Germany)

2010-07-15

149

Measurement of photon flux with a miniature gas ionization chamber in a Material Testing Reactor  

NASA Astrophysics Data System (ADS)

Nuclear heating measurements in Material Testing Reactors (MTR) are crucial for the design of the experimental devices and the prediction of the temperature of the hosted samples. Nuclear heating in MTR materials (except fuel) is mainly due to the energy deposition by the photon flux. Therefore, the photon flux is a key input parameter for the computer codes which simulate nuclear heating and temperature reached by samples/devices under irradiation. In the Jules Horowitz MTR under construction at the CEA Cadarache, the maximal expected nuclear heating levels will be about 15 to 18 W g?1 and it will be necessary to assess this parameter with the best accuracy. An experiment was performed at the OSIRIS reactor to combine neutron flux, photon flux and nuclear heating measurements to improve the knowledge of the nuclear heating in MTR. There are few appropriate sensors for selective measurement of the photon flux in MTR even if studies and developments are ongoing. An experiment, called CARMEN-1, was conducted at the OSIRIS MTR and we used in particular a gas ionization chamber based on miniature fission chamber design to measure the photon flux. In this paper, we detail Monte-Carlo simulations to analyze the photon fluxes with ionization chamber measurements and we compare the photon flux calculations to the nuclear heating measurements. These results show a good accordance between photon flux measurements and nuclear heating measurement and allow improving the knowledge of these parameters.

Fourmentel, D.; Filliatre, P.; Villard, J. F.; Lyoussi, A.; Reynard-Carette, C.; Carcreff, H.

2013-10-01

150

A Study of the Ionization of Deuterium Gas by Pyroelectric Crystals  

NASA Astrophysics Data System (ADS)

Pyroelectric crystals produce a stream of electrons or positive ions when heated or cooled in a near-vacuum environment. We studied the behavior of these crystals in deuterium gas. We look at what portion of the positive ion beam consists of D2^+ and what portion is D^+. Since D2^+ contains only half the energy of D^+ per deuterium atom after traversing a given potential difference, it has a notably lower cross-section for fusing than D^+ does, which lowers neutron yield. Looking at the equivalent dissociation question for H2 gas, we find that <0.1% is ionized as H^+ based on magnetic deflection of the ions. Analogous results are assumed for D2. Furthermore, we present a new phenomenon in which groups of positive ions arrive at the detector at the same time similar to multiple peaks present in electron spectra reported by Brownridge and Shafroth.ootnotetextJ. D. Brownridge, S. M. Shafroth, D. Trott, B. Stoner, and W. Hooke, Appl. Phys. Lett. 78, 1158 (2001) We provide a new theory on the workings of pyroelectric crystals based on the expulsion of gas trapped inside the crystal to explain these findings and other results. Funding provided by grant DOE DE-FG52-09NA29465.

Taylor, Bryce; Shafroth, Stephen; Tornow, Werner

2011-10-01

151

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

PubMed

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

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

2013-09-04

152

Determination of dexamethasone in urine by gas chromatography with negative chemical ionization mass spectrometry.  

PubMed

Dexamethasone, as some other synthetic corticosteroids, is licensed for therapy in veterinary practice, but its misuse as a growth promotor, often in combination with beta-agonists, is forbidden. In this report an analytical method is described for the detection and confirmation of very low concentrations of dexamethasone in urine. The influence of enzymatic hydrolysis time of samples with glucuronidase was studied. The proposed method consisted of the enzymatic hydrolysis of urine samples, which were then extracted and concentrated using solid-phase cartridges with mixed reversed-phase materials (OASIS). No further clean-up step was found to be necessary. Eluates were derivatized following a previously described method [Analyst 119 (1994) 2557]. Detection, identification and quantification of residues of this compound was carried out by gas chromatography with mass spectrometry in the negative chemical ionization mode. The proposed procedure permits the determination of dexamethasone in urine at levels as low as 0.2 ng ml(-1) PMID:12668079

Huetos Hidalgo, Olga; Jiménez López, Manuel; Ajenjo Carazo, Elisa; San Andrés Larrea, Manuel; Reuvers, Thea B A

2003-05-01

153

Warp of the ionized gas layer in the outer Galaxy, traced by recombination line observations  

NASA Astrophysics Data System (ADS)

We report results of H166? recombination line observations from the outer Galaxy in both the Northern and Southern Galactic Plane. The Southern observations were made with the 30 m antenna of the Instituto Argentino de Radioastronomía in Villa Elisa, Buenos Aires, Argentina, and the Northern ones ( more sensitive, high quality observations, performed with an ``state of the art'' receiver) with the 43 m antenna of the National Radio Astronomy Observatory, in Green Bank, West Virginia, USA. >From the two sets of observations we obtain evidence of the warp of the low-density ionized gas layer, traced by the H166? emission in the outer Milky Way, towards positive galactic latitudes in the Northern and towards negative latitudes in the Southern Galaxy. The warp of this tracer qualitatively agrees with that of the HI.

Azcárate, I. N.; Cersosimo, J. C.

154

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

PubMed Central

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

Yilmaz, B; Kadioglu, Y.

2012-01-01

155

Constraining Stellar Feedback: Shock-ionized Gas in Nearby Starburst Galaxies  

NASA Astrophysics Data System (ADS)

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 shockvpropSFR0.62, (2) L shockvprop?SFR, HL 0.92, and (3) L shock/L totvprop(LH /L ?, H )–0.65, where L shock is the H? luminosity from shock-ionized gas, ?SFR, HL the star formation rate (SFR) per unit half-light area, L tot the total H? luminosity, and LH /L ?, 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; Gallagher, John S., III; Martin, Crystal L.; Conselice, Christopher J.; Pellerin, Anne

2013-11-01

156

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

157

A Reservoir of Ionized Gas in the Galactic Halo to Sustain Star Formation in the Milky Way  

NASA Astrophysics Data System (ADS)

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

Lehner, Nicolas; Howk, J. Christopher

2011-11-01

158

Development of a portable greenhouse gas analyzer based on Penning ionization electron spectroscopy (PIES) in a pulsed glow discharge plasma  

Microsoft Academic Search

A greenhouse gas (GHG) analyzer currently under development at Lenterra, Inc. is described which utilizes Penning ionization electron spectroscopy (PIES) in a glow discharge plasma. A population of helium metastable atoms (2^3S, 19.8 eV) is produced in a pulsed (50 mus duration, 5 kHz rep rate) glow discharge in helium\\/analyte gas mixtures. In the afterglow electrons are produced due to

C. Mark Denning; Vadim Stepaniuk; Valery Sheverev

2009-01-01

159

Determination of nitrated polycyclic aromatic hydrocarbons by fused silica capillary gas chromatography\\/negative ion chemical ionization mass spectrometry  

Microsoft Academic Search

Gas chromotography\\/electron capture negative ion chemical ionization mass spectrometry is shown to be a very sensitive and selective determination method for nitrated polycyclic aromatic hydrocarbons (PAH). The detection limit was 1 pg injected to the GC column using single ion monitoring. The mass spectra are characterized by an intense molecular ion, the base peak in all spectra. The second most

Thomas. Ramdahl; Kjell. Urdal

1982-01-01

160

On-line derivatization gas chromatography with furan chemical ionization tandem mass spectrometry for screening of amphetamines in urine  

Microsoft Academic Search

A simple alternative method with minimal sample pretreatment is investigated for screening of amphetamines in small volume (using only 20?L) of urine sample. The method is sensitive and selective. The method uses gas chromatography (GC) direct sample introduction (DSI) for on-line derivatization (acylation) of amphetamines to improve sensitivity. Furan as chemical ionization (CI) reagent in conjunction with tandem mass spectrometry

Shin-Hwa Tzing; Anil Ghule; Jen-Yu Liu; Yong-Chien Ling

2006-01-01

161

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

NASA Astrophysics Data System (ADS)

We present Hubble Space Telescope Imaging Spectrograph (HST/STIS) and Far Ultraviolet Spectroscopic Explorer (FUSE) observations of high ion interstellar ultraviolet 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=304.9d, b=-16.1d. The sight line passes underneath the Sagittarius-Carina and the Norma-Centaurus spiral arms. The STIS E140H grating observations provide high-resolution (FWHM~2.7kms-1) spectra of the resonance doublets of Si IV, C IV, and N V. These data are complemented by medium-resolution (FWHM~20kms-1) FUSE spectra of O VI. The integrated logarithmic column densities are logN(Si IV)=13.60+/-0.02, logN(C IV)=14.08+/-0.03, logN(N V)=13.34+0.05-0.06, and logN(O VI)=14.28+/-0.01. 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-1 . 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. The temperature of the gas in these narrow components, as implied by their b-values, suggests that the gas is photoionized. The ratio of C IV to Si IV in these narrow components is low compared to the Galactic average. Second, we detect an intermediate-width component in C IV and Si IV, at 17 km s-1, 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-1, an amount large enough to suggest that the two ions may not coexist in the same physical location. If these two ions do exist together, then the ratio N(C IV)/N(O VI) is too low to be consistent with turbulent mixing layer models, but could be explained by radiative cooling or conductive heating models. Combining our results with high resolution observations of four other sight lines from the literature, we find an average C IV component frequency of 1.0+/-0.25kpc-1.

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

2003-01-01

162

A study of micro-strip gas chambers for the measurement of ionizing radiation  

NASA Astrophysics Data System (ADS)

This dissertation presents some empirical and theoretical studies of micro-strip gas chambers (MSGC) with emphasis on their gain and energy resolution characteristics. The analysis was extended to the micro-gap chamber (MGC), which is a new and enhanced type of MSGC. MSGCs and MGCs are newly developed detectors of ionizing radiation closely related to the well-established multi-wire proportional counter. In MSGCs, the wires are replaced by alternating narrow anode strips and wider cathode strips deposited on an insulator by the photolithography technique. In MGCs, a continuous cathode plane is used instead of strips and a thin and narrow insulator separates the anode strip and the cathode. Because of the reduced distance between the anode and the cathode compared with that of wire chambers, it is possible to create an extremely intense local electric field near the anode surface. Thus, MSGCs and MGCs can be operated with fairly low applied voltages to achieve practical gas gain. MSGCs and MGCs also have excellent rate capabilities and position resolutions. In addition, MSGCs and MGCs have demonstrated slightly better energy resolution than wire chambers. The present study has emphasized gas gain measurements with different detector geometries, electrostatic field calculations, and the statistical behavior of the gas amplification process. Results from gain measurements were consistent with predictions from the electrostatic models for different MSGC structures. A new type of configuration involving germanium extended cathodes was evaluated experimentally to address the problem of sparking at high anode voltage. It was possible to obtain a relatively high gas gain with the new structure. Short-term drift of the gas gain was also minimized. In the study of the avalanche statistics, it was demonstrated by modeling the electric field configurations that MSGCs and MGCs are expected to show lower variances of the gas amplification compared with the conventional wire chamber. This reduced variance is due to the larger electric field gradients inherent in these configurations, and is likely to be a contributing factor to the better energy resolution reported from MSGCs and MGCs.

Miyamoto, Jun

1997-08-01

163

Unresolved emission and ionized gas in the bulge of M31  

NASA Astrophysics Data System (ADS)

We study the origin of unresolved X-ray emission from the bulge of M31 based on archival Chandra and XMM-Newton observations. We demonstrate that three different components are present. (i) Broad-band emission from a large number of faint sources - mainly accreting white dwarfs and active binaries, associated with the old stellar population, similar to the Galactic ridge X-ray emission of the Milky Way. The X-ray to K-band luminosity ratios are compatible with those for the Milky Way and for M32; in the 2-10keV band, the ratio is (3.6 +/- 0.2) × 1027ergs-1L-1solar. (ii) Soft emission from ionized gas with a temperature of about ~300eV and a mass of ~2 × 106Msolar. The gas distribution is significantly extended along the minor axis of the galaxy, suggesting that it may be outflowing in the direction perpendicular to the galactic disc. The mass and energy supply from evolved stars and Type Ia supernovae is sufficient to sustain the outflow. We also detect a shadow cast on the gas emission by spiral arms and the 10-kpc star-forming ring, confirming significant extent of the gas in the `vertical' direction. (iii) Hard extended emission from spiral arms, most likely associated with young stellar objects and young stars located in the star-forming regions. The LX/SFR (star formation rate) ratio equals ~9 × 1038(ergs-1)(Msolaryr-1)-1, which is about ~1/3 of the high-mass X-ray binary contribution, determined earlier from Chandra observations of other nearby galaxies.

Bogdán, Á.; Gilfanov, M.

2008-07-01

164

Highly Ionized High-Velocity Gas in the Vicinity of the Galaxy  

NASA Astrophysics Data System (ADS)

We report the results of a FUSE study of high-velocity O VI absorption along complete sight lines through the Galactic halo in directions toward 100 extragalactic objects and two halo stars. The high-velocity O VI traces a variety of phenomena, including tidal interactions with the Magellanic Clouds, accretion of gas, outflowing material from the Galactic disk, warm/hot gas interactions in a highly extended Galactic corona, and intergalactic gas in the Local Group. We identify 84 high-velocity O VI features at >=3 ? confidence at velocities of -500=13.95+/-0.34 with a median value of 13.97. Values of b greater than the 17.6 km s-1 thermal width expected for O VI at T~3×105 K indicate that additional nonthermal broadening mechanisms are common. The O VI ?1031.926 absorption is detected at >=3 ? confidence along 59 of the 102 sight lines surveyed. The high-velocity O VI detections indicate that ~60% of the sky (and perhaps as much as ~85%, depending on data quality considerations) is covered by high-velocity H+ associated with the O VI. We find that N(H+)>~1018 cm-2 if the high-velocity hot gas has a metallicity similar to that of the Magellanic Stream; this detection rate is considerably higher than that of high-velocity warm H I traced through its 21 cm emission at a comparable column density level. Some of the high-velocity O VI is associated with known H I structures (the Magellanic Stream, Complex A, Complex C, the Outer Spiral Arm, and several discrete H I HVCs). Some of the high-velocity O VI features have no counterpart in H I 21 cm emission, including discrete absorption features and positive velocity absorption wings extending from ~100 to ~300 km s-1 that blend with lower velocity absorption produced by the Galactic thick disk/halo. The discrete features may typify clouds located in the Local Group, while the O VI absorption wings may be tidal debris or material expelled from the Galactic disk. Most of the O VI features have velocities incompatible with those of the Galactic halo, even if the halo has decoupled from the underlying Galactic disk. The reduction in the dispersion about the mean of the high-velocity O VI centroids when the velocities are converted from the LSR to the GSR and LGSR reference frames is necessary (but not conclusive) evidence that some of the clouds are located outside the Galaxy. Most of the O VI cannot be produced by photoionization, even if the gas is irradiated by extragalactic ultraviolet background radiation. Several observational quantities indicate that collisions in hot gas are the primary ionization mechanism responsible for the production of the O VI. These include the ratios of O VI column densities to those of other highly ionized species (C IV, N V) and the strong correlation between N(O VI) and O VI line width. Consideration of the possible sources of collisional ionization favors production of some of the O VI at the boundaries between cool/warm clouds of gas and a highly extended (R>~70 kpc), hot (T>106 K), low-density (n<~10-4-10-5 cm-3) Galactic corona or Local Group medium. The existence of a hot, highly extended Galactic corona or Local Group medium and the prevalence of high-velocity O VI are consistent with predictions of current galaxy formation scenarios. Distinguishing between the various phenomena producing high-velocity O VI in and near the Galaxy will require continuing studies of the distances, kinematics, elemental abundances, and physical states of the different types of high-velocity O VI found in this study. Descriptions of galaxy evolution will need to account for the highly ionized gas, and future X-ray studies of hot gas in the Local Group will need to consider carefully the relationship of the X-ray absorption/emission to the complex high-velocity absor

Sembach, K. R.; Wakker, B. P.; Savage, B. D.; Richter, P.; Meade, M.; Shull, J. M.; Jenkins, E. B.; Sonneborn, G.; Moos, H. W.

2003-05-01

165

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

166

Polycyclic Aromatic Hydrocarbons, Ionized Gas, and Molecular Hydrogen in Brightest Cluster Galaxies of Cool-core Clusters of Galaxies  

NASA Astrophysics Data System (ADS)

We present measurements of 5-25 ?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 H2 rotational line emission than star-forming galaxies with similar total infrared luminosities, as well as somewhat higher ratios of 70 ?m/24 ?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; de Messières, Geneviève E.; O'Connell, Robert W.; Voit, G. Mark; Hoffer, Aaron; McNamara, Brian R.; Nulsen, Paul E. J.

2011-05-01

167

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

168

The ionized gas at the centre of IC 10: a possible localized chemical pollution by Wolf-Rayet stars  

NASA Astrophysics Data System (ADS)

We present results from integral field spectroscopy with the Potsdam Multi-Aperture Spectrograph at the 3.5-m telescope at Calar Alto Observatory of the intense star-forming region [HL90] 111 at the centre of the starburst galaxy IC 10. We have obtained maps with a spatial sampling of 1 × 1 arcsec2= 3.9× 3.9 pc2 of different emission lines and analysed the extinction, physical conditions, nature of the ionization and chemical abundances of the ionized gas, as well determined locally the age of the most recent star formation event. By defining several apertures, we study the main integrated properties of some regions within [HL90] 111. Two contiguous spaxels show an unambiguous detection of the broad He II?4686 emission line, this feature seems to be produced by a single late-type WN star. We also report a probable N and He enrichment in the precise spaxels where the Wolf-Rayet (WR) features are detected. The enrichment pattern is roughly consistent with that expected for the pollution of the ejecta of a single or a very small number of WR stars. Furthermore, this chemical pollution is very localized (˜2 arcsec ˜7.8 pc) and it should be difficult to detect in star-forming galaxies beyond the Local Volume. We also discuss the use of the most common empirical calibrations to estimate the oxygen abundances of the ionized gas in nearby galaxies from 2D spectroscopic data. The ionization degree of the gas plays an important role when applying these empirical methods, as they tend to give lower oxygen abundances with increasing ionization degree. Based on observations collected at the Centro Astrónomico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Plank Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).Visiting Astronomer at the Instituto de Astrofísica de Canarias.

López-Sánchez, Á. R.; Mesa-Delgado, A.; López-Martín, L.; Esteban, C.

2011-03-01

169

How to Create a Strongly Coupled, Ultracold Plasma by Ionizing or Exciting a Gas of Trapped Atoms  

NASA Astrophysics Data System (ADS)

Recent experiments demonstrated the creation of ultracold plasmas by laser ionization of trapped atoms with temperatures in the microK range [1]. The initial ion properties correspond to a very strongly coupled plasma. Unfortunately, the subsequent build up of correlations strongly heats the ions [2]. The ion temperature at late times is usually characterized by a state with an effective coupling strength around unity. One possibility to prevent or reduce the ion heating is to ionize a gas of highly degenerate, fermionic atoms [2]. Here, the repulsion due to exchange effects creates structural properties similar to those of a Coulomb system. We give estimates for the minimum final temperature of the system that can be achieved applying this approach. A different avenue to create strongly coupled plasmas is to excite a fraction of the atoms into Rydberg states and subsequently ionize this system. A similar situation can be triggered spontaneously at high densities of Rydberg atoms [3]. Again, structure is introduced into the atomic system and the build up of correlations in the ionized system is much smaller than for an uncorrelated atomic gas. Accordingly, the final temperature is much lower and a strongly coupled ion subsystem can be created. [1] T.C. Killian et al., Phys. Rev. Lett. 83, 4776 (1999). [2] M.S. Murillo, Phys. Rev. Lett. 87, 1150031 (2001). [3] M.P. Robinson et al., Phys. Rev. Lett. 85, 4466 (2000).

Gericke, Dirk O.; Murillo, Michael S.

2003-03-01

170

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

PubMed

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

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

1989-10-01

171

Micro-flame ionization detector with a novel structure for portable gas chromatograph.  

PubMed

A micro-flame ionization detector (micro-FID) for portable gas chromatograph (GC) based on conventional mechanical fabrication techniques was developed and evaluated. Structure was redesigned and dimensions were optimized for best performance. Air is introduced from upper part of the detector, flowing downwards into the burning chamber along a narrow round gap between the collection electrode and the inner wall of the detector body, forming a uniform flow field around the burning jet. The lowest detection limit of the mu-FID was 5x10(-13)g/s for n-decane, with a linear response range of five orders of magnitude. The consumption of gases is only 10 ml/min for hydrogen, and 120 ml/min for air, that is about 1/3 of the gases required for conventional FIDs. A comparative study between the micro-FID and commercial FID was also performed that proved the advantages of the micro-FID. The micro-FID is simple in structure, low heating power, and low consumption of gases that not only decrease the cost of running, but also increase the portability of GC for filed applications. PMID:20678662

Wang, Jianwei; Wang, Hua; Duan, Chunfeng; Guan, Yafeng

2010-06-11

172

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

173

Low-temperature nonequilibrium-ionization inert-gas plasma and MHD-generators  

Microsoft Academic Search

The main results of theoretical and experimental studies of low-temperature magnetized (beta>1) nonequilibrium-ionization plasma properties are reported. Such plasma is found to be more stable as compared to the equilibrium-ionization one. Development of ionization instability in such plasma results in the formation of striae oriented perpendicularly to the plasma velocity and not decreasing its effective electric conductivity. Thus, the possibility

R. V. Vasil'Eva; V. L. Goryachev

1992-01-01

174

Low-temperature nonequilibrium-ionization inert-gas plasma and MHD-generators  

Microsoft Academic Search

The main results of theoretical and experimental studies of low-temperature magnetized (ß>1) nonequilibrium-ionization plasma properties are reported. Such plasma is found to be more stable as compared to the equilibrium-ionization one. Development of ionization instability in such plasma results in the formation of striae oriented perpendicularly to the plasma velocity and not decreasing its effective electric conductivity. Thus, the possibility

R. V. Vasil'eva; V. L. Goryachev

1992-01-01

175

Dust and ionized gas association in E/S0 galaxies with dust lanes: clues to their origin  

NASA Astrophysics Data System (ADS)

We present results from an ongoing programme to study the dust and ionized gas in E/S0 galaxies with dust lanes. Our data, together with results from previous studies of E/S0 galaxies, are used to demonstrate the close relationship between these two components. This relationship is discussed in light of our current understanding of the nature and origin of the interstellar medium (ISM), and in particular in the context of the interplay between the different multi-temperature components. We show that focusing on dust obscured regions as tracers of the ISM, and on their properties, serves as independent evidence for the external origin of the dust and ionized gas.

Finkelman, Ido; Brosch, Noah; Funes, José G.; Barway, Sudhanshu; Kniazev, Alexei; Väisänen, Petri

2012-05-01

176

Electron ionization gas chromatography–mass spectrometric determination of residues of thirteen pyrethroid insecticides in whole blood  

Microsoft Academic Search

A new rapid and sensitive electron ionization gas chromatography–mass spectrometry method in selective ion monitoring mode (SIM) was developed for the determination of l3 synthetic pyrethroid insecticide molecules and their stereo isomers in whole blood. The pyrethroid insecticides investigated are allethrin, bifenthrin, cypermethrin, cyphonothrin, cyfluthrin, lambda-cyhalothrin, deltamethrin, fenvalerate, fenpropathrin, imiprothrin, permethrin, prallethrin and transfluthrin. The residues of pyrethroids are extracted

Atmakuru Ramesh; Perumal Elumalai Ravi

2004-01-01

177

Two-photon above-threshold-ionization cross sections of rare-gas atoms by xuv photons  

Microsoft Academic Search

We have calculated the two-photon above-threshold-ionization cross sections of rare-gas atoms by extreme ultraviolet (xuv) photons in the extended framework of multichannel quantum defect theory. Since free-free dipole moments do not converge in the length gauge, we have made the combined use of the length gauge for small r and the acceleration gauge for large r . The two-photon above-threshold

Takashi Nakajima; Shuntaro Watanabe

2004-01-01

178

Characterization of a novel diclofenac metabolite in human urine by capillary gas chromatography-negative chemical ionization mass spectrometry  

Microsoft Academic Search

A sensitive analytical method was developed to characterize diclofenac metabolites in small amounts of body fluids. Desalted and lyophilized urine samples were extracted with supercritical carbon dioxide directly or after acidic hydrolysis. The extracts were derivatized with N-tert.-butyldimethylsilyl-N-methyltrifluoroacetamide. The derivatives were separated by capillary gas chromatography and identified by negative chemical ionization mass spectrometry. Full mass spectra were obtained at

Wolfgang Blum; Johann W. Faigle; Ulrike Pfaar; Alfred Sallmann

1996-01-01

179

Experimental observations of the expansion of an optical-field-induced ionization channel in a gas jet target  

Microsoft Academic Search

The evolution of an optical-field-ionized channel created by a 3.5 ps KrF laser pulse in a low density nitrogen gas jet target (1017 ions cm-3) has been studied using Moiré deflectometry. This allowed the density profiles in the channel and its lateral expansion to be quantitatively measured for the first time. The results were reproduced well by hydrocode simulations and

M. Dunne; T. Afshar-Rad; J. Edwards; A. J. MacKinnon; S. M. Viana; O. Willi; G. Pert

1994-01-01

180

Headspace Liquid-Phase Microextraction of Short-Chain Fatty Acids in Plasma, and Gas Chromatography with Flame Ionization Detection  

Microsoft Academic Search

A novel method for analysis of short-chain fatty acids (SCFA) in blood plasma has been developed by combining headspace liquid-phase microextraction (HS-LPME) and gas chromatography with flame ionization detection. HS-LPME conditions, for example working solution volume, salt concentration, and extraction temperature and time, were optimized by means of an L9 (34) orthogonal array design. The effects on extraction efficiency of

L. Tan; X. P. Zhao; X. Q. Liu; H. X. Ju; J. S. Li

2005-01-01

181

Townsend discharge nitric oxide chemical ionization gas chromatography/mass spectrometry for hydrocarbon analysis of the middle distillates  

SciTech Connect

Hydrocarbon type analysis of petroleum distillates (350-860 {degrees}F fraction) was performed using Townsend discharge nitric acid chemical ionization gas chromatography/mass spectrometry (TDNOCI GC/MS). Both n and z in the chemical formula, C{sub n}H{sub 2n + z} can be determined. GC separation allows quantification of heteroatom compounds in the presence of aromatics of the same mass. Results are presented for the analysis of feedstocks and hydrotreated products.

Dzidic, I.; Petersen, H.A.; Wadsworth, P.A.; Hart, H.V. [Westhollow Research Center, Houston, TX (United States)

1992-10-01

182

Origins of the Highly Ionized Gas toward the X-ray Bright BL Lac Object Mrk 421  

Microsoft Academic Search

The X-ray bright BL Lac object Mrk 421 is one of the small number of extragalactic objects for which it is possible to study the highly ionized gas in the ISM and Local Group using the full diagnostic power of UV, far-UV and X-ray observatories. High quality far-UV observations of OVI and other ions have been obtained by FUSE, whereas

Blair Savage

2004-01-01

183

Characterization of phenolic and secoiridoid aglycons present in virgin olive oil by gas chromatography-chemical ionization mass spectrometry  

Microsoft Academic Search

Olive oil phenolic and secoiridoid compound derivatives were detected by mass spectrometry. Chemical ionization (CI) allowed us to obtain parent ions, that were not detectable in the electron impact mode. CI experiments were performed using either CH4 or NH3 as the reactant gas. Unlike CH4-CI, which fails to give molecular mass information, NH3-CI provided, in all the cases explored, an

Franca Angerosa; Nicola d'Alessandro; Federica Corana; Giorgio Mellerio

1996-01-01

184

Two-dimensional high-resolution schemes and their application in the modeling of ionizing waves in gas discharges  

Microsoft Academic Search

The method for constructing upwind high-resolution schemes is proposed in application to the modeling of ionizing waves in\\u000a gas discharges. The flux-limiting criterion for continuity equations is derived using the proposed partial monotony property\\u000a of a finite difference scheme. For two-dimensional extension, the cone transport upwind approach for constructing genuinely\\u000a two-dimensional difference schemes is used. It is shown that when

Yu. V. Yurgelenas

2010-01-01

185

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

SciTech Connect

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

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

2011-10-20

186

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

187

Gas chromatography negative ion chemical ionization mass spectrometry: application to the detection of alkyl nitrates and halocarbons in the atmosphere.  

PubMed

Alkyl nitrates and very short-lived halocarbon species are important atmospheric trace gas species that are present in the low to sub parts per trillion concentration range. This presents an analytical challenge for their detection and quantification that requires instrumentation with high sensitivity and selectivity. In this paper, we present a new in situ gas chromatograph negative ion chemical ionization mass spectrometer (GC/NICI-MS) coupled to a non-cryogen sample pre-concentration system. This instrument, with detection limits of <0.01 ppt, is capable of detecting and quantifying a large suite of alkyl nitrate and halocarbon species with high sensitivity and precision. The effects of ion source temperature and reagent gas pressure on the ionization efficiency of the NICI mode are investigated and the results are used to optimize the sensitivity. The NICI mode is compared to the more frequently used electron impact (EI) ionization and the enhancements in sensitivity are presented for all the calibrated compounds. PMID:18586255

Worton, David R; Mills, Graham P; Oram, David E; Sturges, William T

2008-06-18

188

Beams of isotopes produced at LISOL by laser ionization after thermalization of energetic ions in a gas cell  

NASA Astrophysics Data System (ADS)

The laser ion source (LIS) at the Leuven isotope separator on-line facility has been used to produce beams of exotic nuclei obtained in different types of nuclear reactions. The application of a gas cell filled by noble gas for thermalizing, storing and transporting trace radioactive ions and atoms, has been studied in off- and on-line conditions. Two-step laser resonance ionization has been used to produce ions of stable and radioactive isotopes inside the cell of the LIS. Results from proton-induced fission on 238U and light-/heavy-ion-induced fusion reactions are presented. The interactions of ions with impurity molecules, with noble gas atoms, with electrons and with electrical fields have been investigated in order to specify the requirements for the gas cell as a source of radioactive rare isotopes for the next generation radioactive ion beam facilities.

Kudryavtsev, Yu.; Facina, M.; Huyse, M.; Gentens, J.; van den Bergh, P.; van Duppen, P.

2003-05-01

189

Two-dimensional Kinematical and Ionization Structure of the Warm Gas in the Nuclear Regions of Arp 220  

NASA Astrophysics Data System (ADS)

Integral field optical spectroscopy using the INTEGRAL system has been used to characterize the kinematic and ionization properties of the warm gas within 2 kpc of the dust-enshrouded nucleus of Arp 220. Owing to the large internal extinction toward the nuclei, the brightest stellar and line-emitting regions observed at optical wavelengths do not coincide with the dust-enshrouded near-infrared and radio nuclei of Arp 220 but are located northwest of the nucleus at a distance of about 750 pc. Moreover, although the continuum and the line-emitting gas share similar distributions, their emission peaks are displaced, with the H? emission peak located at about 300 pc southwest of the optical stellar continuum emission peak. A line decomposition analysis has been performed in the complex and high spatially variable emission-line profiles. Three different kinematically distinct and extended gaseous components have been identified in the ionized gas. One narrow component (R) indicates rotation, while the other two components (O and B) are well interpreted by the presence of a biconical outflow. Specifically, the rotational component R traces quiescent gas located in a nuclear disk with the spin axis along the southeast-northwest direction (P.A. 135°). This component of ionized gas seems to be coupled with the 100 kpc disklike H I gas and the 1 kpc molecular disk detected in CO (Scoville et al.). The inclination-corrected rotational velocities imply a dynamical mass (Mdyn) of 2×1010 Msolar within a radius of 1.5 kpc. This relatively high value indicates a large mass concentration in the nuclear region of Arp 220, as Scoville et al. already inferred by the presence of 5×109 Msolar of molecular gas in a nuclear, 0.5 kpc disk. One of the outflow components, O, has peak-to-peak velocities of 1000 km s-1. The broad component B, with an average width of 815 km s-1, is detected at about 600 pc northwest of the dust-enshrouded nucleus and is blueshifted by 300 km s-1 with respect to the system velocity. The two-dimensional distribution and kinematics of the components are consistent with a bipolar cone geometry with an opening angle of about 90° and are perpendicular to the nuclear disk of gas, as expected in the starburst-driven galactic wind scenario proposed by Heckman, Armus, & Miley. In most of the observed regions, the ionization status of the different gas components is consistent with a shock-heated LINER-like or Seyfert 2 nebula as judged by the [N II]/H? and [S II]/H? emission-line ratios. Although the [O III] and H? lines are undetected in most of the regions, the brightest zone located northwest of the nucleus could be classified as a Seyfert 2 nebula based on the additional constraint given by the measured lower limit (>=5) for the [O III]/H? ratio. There is no evidence of excitation gradients along the symmetry axis of the outflow nor of a biconical ionization structure, which suggests that the ionizing field is homogeneous and less collimated than the gas outflow. However, there are four clearly identified extranuclear regions where the [N II]/H? ratio decreases by a factor of 5 and is close to the typical values of H II regions. None of these regions are in spatial agreement with the star clusters found in the infrared by Scoville et al., confirming that they must be relatively old globular clusters.

Arribas, Santiago; Colina, Luis; Clements, David

2001-10-01

190

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

191

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

192

Flame ionization control of a partially premixed gas burner with regulated secondary air  

Microsoft Academic Search

A gas burning furnace is described which consists of: a gas burner mounted in a combustion chamber, the combustion chamber having an exhaust outlet adapted to be connected to a flue, a gas inlet to the burner connected to a gas control adapted to receive gas from a gas source, a primary air inlet of the burner connected to an

Torborg

1986-01-01

193

Characterization of magnetron-sputtered partially ionized deposition as a function of metal and gas species  

SciTech Connect

Conventional magnetron sputter deposition with a rf inductively coupled plasma (ICP) has demonstrated that ionized metal fluxes can be effectively utilized to fill trenches and vias with high aspect ratios. The ICP is created with a seven turn (1/2 wavelength), water cooled coil located between the magnetron cathode and the substrate. A large fraction of the metal atoms sputtered from the magnetron cathode are ionized by the ICP. These ions are accelerated across the sheath toward the substrate and deposited at normal incidence, by placing a negative bias on the substrate. A gridded energy analyzer configured with a quartz crystal microbalance is located in the center of the substrate plane to determine the ion and neutral deposition rates. While keeping the magnetron power, rf coil, target to substrate distance, pressure and diagnostic location constant, the ionization fraction was measured for two metal targets: Cu and Ti using three different working gases: Kr, Ar and Ne. Variations in target materials and working gases are shown to have an effect on ionization and deposition rates. The ionization rate is a sensitive function of the metal's ionization potential. The electron energy distribution in the plasma is affected by the sputtered metal and the working gases' ionization potential. (c) 2000 American Vacuum Society.

Allain, Monica M. C. [University of Illinois, Urbana, Illinois 61801 (United States); Hayden, D. B. [University of Illinois, Urbana, Illinois 61801 (United States); Juliano, D. R. [University of Illinois, Urbana, Illinois 61801 (United States); Ruzic, D. N. [University of Illinois, Urbana, Illinois 61801 (United States)

2000-05-01

194

Nanostructured silicon formations as a result of ionized N2 gas reactions on silicon with native oxide layers  

NASA Astrophysics Data System (ADS)

Nanostructured silicon was formed by means of the ionized N2 gas reaction on SiO2/Si, and the electronic structure, surface morphology, and optical properties were investigated. The physicochemically modified thin layers were resolved to SiNy and SiOxNy through the observation of Si 2p, O 1s, and N 1s core-level spectra in x-ray photoelectron spectroscopy. The formations of SiOxNy and SiO2 nanostructures (3-4 nm in size), performed by the etching process followed by adsorption of ionized nitrogen, were confirmed by atomic force microscopy. The nanocrystalline Si (6 nm in size) distributed within the modified layer (approximately 10 nm thick) was observed after the in situ rapid thermal annealing processes, using high-resolution transmission electron microscopy. Photoluminescence with a wavelength peaking at around 400 nm was emitted from the nanocrystalline Si formed from the SiOxNy/SiO2/Si structures. This work suggests that the nanocrystalline-Si formation and the nanostructured surface modification method, using the controlled ionized gas, were simple and efficient methods requiring low energy and low temperatures.

Jung, Min-Cherl; Lee, Tae Gyoung; Park, Young Ju; Jun, Sung Ho; Lee, Joosang; Han, Moonsup; Jeong, Jong Seok; Lee, Jeong Yong

2003-05-01

195

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

SciTech Connect

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

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

2009-12-15

196

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

197

Galaxy-scale Clouds Of Ionized Gas Around Agn - History And Obscuration  

Microsoft Academic Search

Motivated by the discovery of Hanny's Voorwerp, a 45-kpc highly-ionized cloud near the spiral galaxy IC 2497, and accompanying evidence for strong variability of its AGN over 105 year scales, members of the Galaxy Zoo project have carried out surveys for similar (albeit smaller) ionized clouds around galaxies both with and without spectroscopic AGN. The color-composite SDSS images detect strong

Drew Chojnowski; W. C. Keel

2011-01-01

198

Ionization equilibrium and partition functions of high-temperature weakly non-ideal Flibe gas  

Microsoft Academic Search

A model for the ionization equilibrium of weakly non-ideal Flibe plasma is presented in terms of a set of coupled non-linear Saha equations supplemented by electro-neutrality and conservation of nuclei. Non-ideality effects have been taken into account in terms of lowering of the ionization potentials and truncated partition functions. A simple formulation and solution strategy of the Saha equations for

Mofreh R. Zaghloul; Mofreh R

2003-01-01

199

Ionization of Local Interstellar Gas Based on STIS and FUSE spectra of Nearby Stars  

NASA Astrophysics Data System (ADS)

The ultraviolet contains many resonance line transitions that are sensitive to a range of ionization stages of ions present in the local interstellar medium (LISM). We couple observations of high resolution ultraviolet spectrographs, STIS and GHRS on the Hubble Space Telescope (HST) and the Far-Ultraviolet Spectroscopic Explorer (FUSE) in order to make a comprehensive survey of the ionization structure of the local interstellar medium. In particular, we focus on the sight line toward G191-B2B, a nearby (69 pc) white dwarf. We present interstellar detections of highly ionized elements (e.g., SiIII, CIII, CIV, etc) and compare them directly to neutral or singly ionized LISM detections (e.g., SiII, CII, etc). The extensive observations of G191-B2B provides an opportunity for a broad study of ionization stages of several elements, while a survey of several sight lines provides a comprehensive look at the ionization structure of the LISM. We acknowledge support for this project through NASA FUSE Grant NNX06AD33G.

Redfield, Seth; Linsky, J. L.

2009-01-01

200

Ionization of pesticides using a far-ultraviolet femtosecond laser in gas chromatography/time-of-flight mass spectrometry.  

PubMed

The fourth harmonic emission (200 nm) of a femtosecond Ti:sapphire laser (35 fs) was generated and used in the multiphoton ionization of 49 pesticides in gas chromatography/time-of-flight mass spectrometry. The limit of detection was improved when the ionization source from the third harmonic emission (267 nm) was replaced with the fourth harmonic emission for several pesticide molecules that contained no conjugated double bonds since their absorption bands are located in the far-ultraviolet region. This analytical instrument was used in the analysis of a series of real samples including potatoes, carrots, and cabbage, and a signal suspected to arise from di-allate was observed for the potato sample. Figure ? PMID:23624954

Hashiguchi, Yuichi; Zaitsu, Shin-Ichi; Imasaka, Totaro

2013-04-28

201

A region of violent star formation in the Irr galaxy IC 10: Structure and kinematics of ionized and neutral gas  

NASA Astrophysics Data System (ADS)

We have used observations of the galaxy IC10 at the 6-m telescope of the Special Astrophysical Observatory with the SCORPIO focal reducer in the Fabry-Perot interferometer mode and with the MPFS spectrograph to study the structure and kinematics of ionized gas in the central region of current intense star formation. Archive VLA 21-cm observations are used to analyze the structure and kinematics of neutral gas in this region. High-velocity wings of the H ? and [SII] emission lines were revealed in the inner cavity of the nebula HL 111 and in other parts of the complex of violent star formation. We discovered local expanding neutral-gas shells around the nebulae HL 111 and HL 106.

Egorov, O. V.; Lozinskaya, T. A.; Moiseev, A. V.

2010-04-01

202

PRESENT-DAY GALACTIC EVOLUTION: LOW-METALLICITY, WARM, IONIZED GAS INFLOW ASSOCIATED WITH HIGH-VELOCITY CLOUD COMPLEX A  

SciTech Connect

The high-velocity cloud Complex A is a probe of the physical conditions in the Galactic halo. The kinematics, morphology, distance, and metallicity of Complex A indicate that it represents new material that is accreting onto the Galaxy. We present Wisconsin H{alpha} Mapper kinematically resolved observations of Complex A over the velocity range of -250 to -50 km s{sup -1} in the local standard of rest reference frame. These observations include the first full H{alpha} intensity map of Complex A across (l, b) = (124 Degree-Sign , 18 Degree-Sign ) to (171 Degree-Sign , 53 Degree-Sign ) and deep targeted observations in H{alpha}, [S II] {lambda}6716, [N II] {lambda}6584, and [O I] {lambda}6300 toward regions with high H I column densities, background quasars, and stars. The H{alpha} data imply that the masses of neutral and ionized material in the cloud are similar, both being greater than 10{sup 6} M{sub Sun }. We find that the Bland-Hawthorn and Maloney model for the intensity of the ionizing radiation near the Milky Way is consistent with the known distance of the high-latitude part of Complex A and an assumed cloud geometry that puts the lower-latitude parts of the cloud at a distance of 7-8 kpc. This compatibility implies a 5% ionizing photon escape fraction from the Galactic disk. We also provide the nitrogen and sulfur upper abundance solutions for a series of temperatures, metallicities, and cloud configurations for purely photoionized gas; these solutions are consistent with the sub-solar abundances found by previous studies, especially for temperatures above 10{sup 4} K or for gas with a high fraction of singly ionized nitrogen and sulfur.

Barger, K. A.; Haffner, L. M.; Wakker, B. P.; Hill, Alex S. [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States); Madsen, G. J. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Duncan, A. K., E-mail: kbarger@astro.wisc.edu, E-mail: haffner@astro.wisc.edu, E-mail: Alex.Hill@csiro.au, E-mail: wakker@astro.wisc.edu, E-mail: greg.madsen@sydney.edu.au [Rose-Hulman Institute of Technology, Terre Haute, IN 47803 (United States)

2012-12-20

203

Present-day Galactic Evolution: Low-metallicity, Warm, Ionized Gas Inflow Associated with High-velocity Cloud Complex A  

NASA Astrophysics Data System (ADS)

The high-velocity cloud Complex A is a probe of the physical conditions in the Galactic halo. The kinematics, morphology, distance, and metallicity of Complex A indicate that it represents new material that is accreting onto the Galaxy. We present Wisconsin H? Mapper kinematically resolved observations of Complex A over the velocity range of -250 to -50 km s-1 in the local standard of rest reference frame. These observations include the first full H? intensity map of Complex A across (\\mathit {l, b}) = (124{^\\circ }, 18{^\\circ }) to (171°, 53°) and deep targeted observations in H?, [S II] ?6716, [N II] ?6584, and [O I] ?6300 toward regions with high H I column densities, background quasars, and stars. The H? data imply that the masses of neutral and ionized material in the cloud are similar, both being greater than 106 M ?. We find that the Bland-Hawthorn & Maloney model for the intensity of the ionizing radiation near the Milky Way is consistent with the known distance of the high-latitude part of Complex A and an assumed cloud geometry that puts the lower-latitude parts of the cloud at a distance of 7-8 kpc. This compatibility implies a 5% ionizing photon escape fraction from the Galactic disk. We also provide the nitrogen and sulfur upper abundance solutions for a series of temperatures, metallicities, and cloud configurations for purely photoionized gas; these solutions are consistent with the sub-solar abundances found by previous studies, especially for temperatures above 104 K or for gas with a high fraction of singly ionized nitrogen and sulfur.

Barger, K. A.; Haffner, L. M.; Wakker, B. P.; Hill, Alex. S.; Madsen, G. J.; Duncan, A. K.

2012-12-01

204

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

205

Effect of sweep gas composition on ionization chamber response in the BEATRIX-II tritium recovery experiment  

SciTech Connect

The BEATRIX-II irradiation experiment was an in situ tritium recovery experiment to evaluate the tritium release characteristics of fusion ceramic breeder materials and to characterize their stability under fast neutron irradiation to extended burnups. This is an International Energy Agency (IEA) sponsored experiment which is being carried out in the Materials Open Test Assembly of Fast Flux Test Facility (FFTF). The participants are Japan, Canada and the US The in situ tritium recovery experiment consisted of two individual in-reactor experimental assemblies (Phase I and Phase II) that were irradiated for 300 and 200 EFPD, respectively. Each experimental phase included two specimens: a thin annular specimen capable of temperature changes and a larger temperature-gradient specimen. In Phase I both specimens were Li[sub 2]O while for Phase II the temperature-change specimen consisted of Li[sub 2]O and the temperature-gradient specimen was a Li[sub 2]ZrO[sub 3] spherebed. Real-time measurements of the tritium release from the specimens during changing conditions (neutronics, temperature and sweep gas composition) were made using ion chambers. In order to correctly interpret the response of the ionization chambers it is necessary to understand the effect of changing sweep gas composition on the operation of the chambers. The purpose of this paper is to describe activities carried out to determine the effect of hydrogen additions to a helium sweep gas on the operation of these ionization chambers.

Slagle, O.D.; Hollenberg, G.W. (Pacific Northwest Lab., Richland, WA (United States)); Baker, D.E. (Westinghouse Hanford Co., Richland, WA (United States))

1992-10-01

206

Effect of sweep gas composition on ionization chamber response in the BEATRIX-II tritium recovery experiment  

SciTech Connect

The BEATRIX-II irradiation experiment was an in situ tritium recovery experiment to evaluate the tritium release characteristics of fusion ceramic breeder materials and to characterize their stability under fast neutron irradiation to extended burnups. This is an International Energy Agency (IEA) sponsored experiment which is being carried out in the Materials Open Test Assembly of Fast Flux Test Facility (FFTF). The participants are Japan, Canada and the US The in situ tritium recovery experiment consisted of two individual in-reactor experimental assemblies (Phase I and Phase II) that were irradiated for 300 and 200 EFPD, respectively. Each experimental phase included two specimens: a thin annular specimen capable of temperature changes and a larger temperature-gradient specimen. In Phase I both specimens were Li{sub 2}O while for Phase II the temperature-change specimen consisted of Li{sub 2}O and the temperature-gradient specimen was a Li{sub 2}ZrO{sub 3} spherebed. Real-time measurements of the tritium release from the specimens during changing conditions (neutronics, temperature and sweep gas composition) were made using ion chambers. In order to correctly interpret the response of the ionization chambers it is necessary to understand the effect of changing sweep gas composition on the operation of the chambers. The purpose of this paper is to describe activities carried out to determine the effect of hydrogen additions to a helium sweep gas on the operation of these ionization chambers.

Slagle, O.D.; Hollenberg, G.W. [Pacific Northwest Lab., Richland, WA (United States); Baker, D.E. [Westinghouse Hanford Co., Richland, WA (United States)

1992-10-01

207

Experimental observations of the expansion of an optical-field-induced ionization channel in a gas jet target  

SciTech Connect

The evolution of an optical-field-ionized channel created by a 3.5 ps KrF laser pulse in a low density nitrogen gas jet target (10[sup 17] ions cm[sup [minus]3]) has been studied using Moire deflectometry. This allowed the density profiles in the channel and its lateral expansion to be quantitatively measured for the first time. The results were reproduced well by hydrocode simulations and analytical models. In addition, structured Raman backscatter signals indicated very low longitudinal electron velocities in the rising part of the pulse, as confirmed by 2D PIC code simulations.

Dunne, M.; Afshar-Rad, T.; Edwards, J.; MacKinnon, A.J.; Viana, S.M.; Willi, O. (Blackett Laboratory, Imperial College of Science, Technology and Medicine, London SW7 2BZ (United Kingdom)); Pert, G. (Department of Physics, University of York, York (United Kingdom))

1994-02-14

208

A simple and sensitive quantitation of N,N-dimethyltryptamine by gas chromatography with surface ionization detection.  

PubMed

A simple and sensitive method for determination of N,N-dimethyltryptamine (DMT) by gas chromatography (GC) with surface ionization detection (SID) is presented. Whole blood or urine, containing DMT and gramine (internal standard), was subjected to solid-phase extraction with a Sep-Pak C18 cartridge before analysis by GC-SID. The calibration curve was linear in the DMT range of 1.25-20 ng/mL blood or urine. The detection limit of DMT was about 0.5 ng/mL (10 pg on-column). The recovery of both DMT and gramine spiked in biological fluids was above 86%. PMID:9013290

Ishii, A; Seno, H; Suzuki, O; Hattori, H; Kumazawa, T

209

Fast gas chromatography and negative-ion chemical ionization tandem mass spectrometry for forensic analysis of cannabinoids in whole blood  

Microsoft Academic Search

The present work describes a fast gas chromatography\\/negative-ion chemical ionization tandem mass spectrometric assay (Fast GC\\/NICI-MS\\/MS) for analysis of tetrahydrocannabinol (THC), 11-hydroxy-tetrahydrocannabinol (THC-OH) and 11-nor-9-carboxy-tetrahydrocannabinol (THC-COOH) in whole blood. The cannabinoids were extracted from 500?L of whole blood by a simple liquid–liquid extraction (LLE) and then derivatized by using trifluoroacetic anhydride (TFAA) and hexafluoro-2-propanol (HFIP) as fluorinated agents. Mass spectrometric

Aurélien Thomas; Christèle Widmer; Gérard Hopfgartner; Christian Staub

2007-01-01

210

Ionization Equilibrium and Partition Functions of High-Temperature Weakly Nonideal Flibe Gas  

SciTech Connect

A model for the ionization equilibrium of weakly non-ideal Flibe plasma is presented in terms of a set of coupled nonlinear Saha equations supplemented by electro-neutrality and conservation of nuclei. Non-ideality effects have been taken into account in terms of lowering of the ionization potentials and truncated partition functions. A simple formulation and solution strategy of the Saha equations for the single element case has been extended to apply for the case of plasma mixtures and has been used to calculate the composition of partially ionized Flibe plasma over a wide range of temperatures and densities. A criterion for the validity of the assumption of local thermodynamic equilibrium is presented and applied to the result. Effects of non-ideality corrections and approximating the partition function to the statistical weight of the ground state have been quantified and presented.

Zaghloul, Mofreh R. [University of California in San Diego (United States)

2003-09-15

211

Comparison of Gas Chromatography-Mass Spectrometry and Gas Chromatography-Tandem Mass Spectrometry with Electron Ionization and Negative-Ion Chemical Ionization for Analyses of Pesticides at Trace Levels in Atmospheric Samples  

PubMed Central

A comparison of detection limits of gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) with gas chromatography-tandem mass spectrometry (GC-MS/MS) in selected reaction monitoring (SRM) mode with both electron ionization (EI) and negative-ion chemical ionization (NCI) are presented for over 50 pesticides ranging from organochlorines (OCs), organophosphorus pesticides (OPs) and pre-emergent herbicides used in the Canadian prairies (triallate, trifluralin, ethalfluralin). The developed GC-EI/SIM, GC-NCI/SIM, and GC-NCI/SRM are suitable for the determination of pesticides in air sample extracts at concentrations <100 pg ?L?1 (<100 pg m?3 in air). No one method could be used to analyze the range of pre-emergent herbicides, OPs, and OCs investigated. In general GC-NCI/SIM provided the lowest method detection limits (MDLs commonly 2.5–10 pg ?L?1) along with best confirmation (<25% RSD of ion ratio), while GC-NCI/SRM is recommended for use where added selectivity or confirmation is required (such as parathion-ethyl, tokuthion, carbofenothion). GC-EI/SRM at concentration <100 pg ?L?1 was not suitable for most pesticides. GC-EI/SIM was more prone to interference issues than NCI methods, but gave good sensitivity (MDLs 1–10 pg ?L?1) for pesticides with poor NCI response (OPs: sulfotep, phorate, aspon, ethion, and OCs: alachlor, aldrin, perthane, and DDE, DDD, DDT).

Raina, Renata; Hall, Patricia

2008-01-01

212

Comparison of gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry with electron ionization and negative-ion chemical ionization for analyses of pesticides at trace levels in atmospheric samples.  

PubMed

A comparison of detection limits of gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) with gas chromatography-tandem mass spectrometry (GC-MS/MS) in selected reaction monitoring (SRM) mode with both electron ionization (EI) and negative-ion chemical ionization (NCI) are presented for over 50 pesticides ranging from organochlorines (OCs), organophosphorus pesticides (OPs) and pre-emergent herbicides used in the Canadian prairies (triallate, trifluralin, ethalfluralin). The developed GC-EI/SIM, GC-NCI/SIM, and GC-NCI/SRM are suitable for the determination of pesticides in air sample extracts at concentrations <100 pg microL(-1) (<100 pg m(-3) in air). No one method could be used to analyze the range of pre-emergent herbicides, OPs, and OCs investigated. In general GC-NCI/SIM provided the lowest method detection limits (MDLs commonly 2.5-10 pg microL(-1)) along with best confirmation (<25% RSD of ion ratio), while GC-NCI/SRM is recommended for use where added selectivity or confirmation is required (such as parathion-ethyl, tokuthion, carbofenothion). GC-EI/SRM at concentration <100 pg microL(-1) was not suitable for most pesticides. GC-EI/SIM was more prone to interference issues than NCI methods, but gave good sensitivity (MDLs 1-10 pg microL(-1)) for pesticides with poor NCI response (OPs: sulfotep, phorate, aspon, ethion, and OCs: alachlor, aldrin, perthane, and DDE, DDD, DDT). PMID:19609395

Raina, Renata; Hall, Patricia

2008-09-09

213

Development of methane positive chemical ionization gas chromatography/mass spectrometry procedures to determine polychlorinated biphenyls  

SciTech Connect

Positive ion chemical ionization GC/MS was evaluated for the quantitation of polychlorobiphenyls (PCBs) using 10 or less selected PCB standards. Positive ion chemical ionization MS conditions were found that resulted in the best sensitivity and least fragmentation for the PCBs. The optimal conditions were a source temperature of 100 /sup 0/C and source pressure of 0.6 torr, using 200 eV of energy. Mass spectral and response factor (RF) information was gathered for 137 pure cogeners to evaluate methodology of grouping PCBs by level of chlorination or by clustering according to similar responses for quantitation using 10 or less standards. Positive methane chemical ionization was well-suited for their analysis, since the RF values only varied by a factor of 12 at extremes and the technique was 2-6 times more sensitive than electron impact ionization. It was determined that quantitation by using a standard from each level of chlorination showed an overall mean deviation of 21%. It proved more useful for analysis of environmental samples than the cluster scheme, which required isomer identification for proper classification of the PCB to a cluster. The analysis of a sediment extract spiked with PCB congeners resulted in a 14% +/- 5% deviation between actual concentrations and measured concentrations using PCB standards at each level of chlorination. 24 references, 6 figures, 6 tables.

Voyksner, R.D.; Bursey, J.T.; Pack, T.W.; Porch, R.L.

1986-03-01

214

Population Density Measurements in Freejet Expansion Flow of a Partially Ionized Gas.  

National Technical Information Service (NTIS)

Population densities of the 4p and 5p levels of argon atom were measured along the freejet centerline of a partially ionized argon in a low density plasma wind tunnel. The Boltzmann plot for these levels showed that the 4p and 5p levels were not in the Bo...

A. Kimura M. Nishida

1974-01-01

215

The Kinematics and Ionization of Nuclear Gas Clouds in Centaurus A  

NASA Astrophysics Data System (ADS)

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-?. 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 105 cm-3 and very low filling factors, suggesting that models of the gamma-ray emission should incorporate jet Lorentz factors <~ 5.

Bicknell, Geoffrey V.; Sutherland, Ralph S.; Neumayer, Nadine

2013-03-01

216

Fast gas heating in fast ionization wave discharge: Experiment and modelling  

Microsoft Academic Search

Summary form only given. The fast ionization wave (FIW) resulting from nanosecond pulsed discharge at very high overvoltage provides an excellent high reduced electric field (E\\/N) example discharge due to its spatial uniformity. A comprehensive model of FIW would provide insight into other high E\\/N discharges used for plasma ignition applications, such as DBD and streamer discharge. To that end

S. J. Pendleton; M. A. Gundersen; N. A. Popov; E. Mintoussov; S. Starikovskaia

2010-01-01

217

Gas-phase stability of G-quadruplex DNA determined by electrospray ionization tandem mass spectrometry and molecular dynamics simulations  

Microsoft Academic Search

The relative gas-phase stabilities of seven quadruplex DNA structures, [d(TG4T)]4, [d(T2G3T)]4, [d(G4T4G4)]2, [d(T2AG3)2]2, d(T2AG3)4, d(T2G4)4, and d(G2T4)4, were investigated using molecular dynamics simulations and electrospray ionization mass spectrometry (ESI-MS). MD simulations\\u000a revealed that the G-quadruplexes maintained their structures in the gas phase although the G-quartets were distorted to some\\u000a degree and ammonium ions, retained by [d(TG4T)]4 and [d(T2G3T)]4, played a

Carolyn L. Mazzitelli; Junmei Wang; Suncerae I. Smith; Jennifer S. Brodbelt

2007-01-01

218

Isomer-specific determination of hexachlorodibenzo-p-dioxins by oxygen negative chemical ionization mass spectrometry, gas chromatography, and high-pressure liquid chromatography  

Microsoft Academic Search

All ten hexachlorodibenzo-p-dioxin (HCDD) isomers, prepared by micropyrolysis of chlorophenates, were studied by using mass spectrometry, gas chromatography, and high-pressure liquid chromatography. Of several ionization modes studied, oxygen negative chemical ionization was the most suitable for isomer identification. This technique enabling isomer specific identification to be carried out was applied to hexachlorodioxin impurities in pentachlorophenol samples and detected small amounts

Walter F. Miles; Narine P. Gurprasad; Greg P. Malis

1985-01-01

219

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

220

Electron ionization gas chromatography-mass spectrometric determination of residues of thirteen pyrethroid insecticides in whole blood.  

PubMed

A new rapid and sensitive electron ionization gas chromatography-mass spectrometry method in selective ion monitoring mode (SIM) was developed for the determination of l3 synthetic pyrethroid insecticide molecules and their stereo isomers in whole blood. The pyrethroid insecticides investigated are allethrin, bifenthrin, cypermethrin, cyphonothrin, cyfluthrin, lambda-cyhalothrin, deltamethrin, fenvalerate, fenpropathrin, imiprothrin, permethrin, prallethrin and transfluthrin. The residues of pyrethroids are extracted from the whole blood using hexane and acetone mixture (80 + 20%) as solvent. All the pyrethroid residues were separated by using a gas chromatography-mass spectrometry operated in electron ionization mode and quantified in selective ion monitoring mode. The method can detect the residues of different pyrethroids down to the level 0.05-2 ng/ml. Recovery experiments conducted in whole blood samples at the fortification level 1-1000 ng/ml showed 91-103% recovery. The applications of the analytical method for the determination of pyrethroid residues in real samples were tested by analyzing 45 human blood samples collected from the population exposed continuously to different pyrethroid based formulations. The results are confirmed by spiking the known quantity of pyrethroids and subsequently their positive detection. PMID:15018801

Ramesh, Atmakuru; Ravi, Perumal Elumalai

2004-04-01

221

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

NASA Astrophysics Data System (ADS)

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 109 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.

1994-11-01

222

Long slit spectroscopy of emission line galaxies. II - Physical properties of the ionized gas and general characteristics  

Microsoft Academic Search

A physical interpretation is given to long-slit spectroscopic data for 16 extended ionized envelopes surrounding different types of AGN presented in a previous paper. Ionization mechanisms are discussed, comparing reddened emission line ratios to published hot-ionization and shock ionization models. High ionization emission lines can be accounted for by photoionization by a nonstellar UV continuum, while low-ionization emission lines are

F. Durret

1990-01-01

223

Fragmentation and gas phase aggregation processes in the laser desorption ionization of chlorodiaminotriazines.  

PubMed

Fragmentation and supramolecular aggregation induced during the laser desorption/ionization (LDI) of four chlorodiaminotriazines (simazine, atrazine, terbutylazine and propazine) have been investigated. The laser wavelength employed (266 nm) lies within the first absorption band of the four triazines. The main fragmentation channel observed involves the prompt cleavage of the Cl atom, followed by partial or total fragmentation of the side alkyl chains. Breakage of the triazinic ring becomes efficient at moderate laser powers; however, the deamination of the triazine is not observed to take place. In addition, the formation of both covalent and non-covalent triazinic aggregates in the desorption plume is found to be particularly efficient. Aggregates as large as heptamers are neatly detected, with the observation that those with the most intense signal involve the dechlorinated triazinic fragment. Both aggregation and fragmentation are largely suppressed upon dilution of the triazine under matrix-assisted laser desorption/ionization conditions. PMID:18192725

Hurtado, Paola; Hortal, Ana R; Cruz-Guzmán, Marta; Martínez-Haya, Bruno

2007-01-01

224

Detection of gas-phase methoxy radicals by resonance-enhanced multiphoton ionization spectroscopy  

Microsoft Academic Search

Resonance-enhanced multiphoton ionization spectra of CHâO and CDâO between 313 and 328 nm are reported. Methoxy radicals were generated by the reaction of F atoms with CHâOH, CHâOD, and CDâOD in a flow reactor. The most prominent band of these spectra resides at 320.6 nm in CHâO and 319.3 nm in CDâO. Mass spectra of both isotopic analogues showed that

George R. Long; Russell D. Johnson; Jeffrey W. Hudgens

1986-01-01

225

Photoionization\\/flame-ionization detection of atmospheric hydrocarbons after capillary gas chromatography  

Microsoft Academic Search

A ''gastight, low-volume'' photoionization detector (PID) has been constructed for the purpose of detecting trace hydrocarbons in atmospheric samples. This modified PID, in tandem with an FID (flame-ionization detector), was tested by use of a standard gaseous mixture of aromatics, alkenes, and alkanes. The average minimum detectable amounts for the PID were found to be 1.2 pg for aromatics, 2.0

Winai. Nutmagul; Dagmar R. Cronn; Herbert H. Hill

1983-01-01

226

Ionization equilibrium and partition functions of high-temperature weakly non-ideal Flibe gas  

NASA Astrophysics Data System (ADS)

A model for the ionization equilibrium of weakly non-ideal Flibe plasma is presented in terms of a set of coupled non-linear Saha equations supplemented by electro-neutrality and conservation of nuclei. Non-ideality effects have been taken into account in terms of lowering of the ionization potentials and truncated partition functions. A simple formulation and solution strategy of the Saha equations for the single element case has been extended for application to the case of plasma mixtures and has been used to calculate the composition of partially ionized Flibe plasma over a wide range of temperatures and densities. A criterion for the validity of the assumption of local thermodynamic equilibrium is presented and applied to the result. Effects of non-ideality corrections and approximating the partition function to the statistical weight of the ground state have been quantified and presented. Much of this work has been presented at the 15th ANS Topical Meeting on the Technology of Fusion Energy (TOFE) (Washington, DC, November 2002).

Zaghloul, Mofreh R.

2003-09-01

227

Compressed xenon gas near its critical point as an ionization medium  

SciTech Connect

As part of an effort to study Ov [beta][beta] decay of [sup 136]Xe, a compressed xenon drift chamber has been developed. In such a chamber, the ability to drift ionization over large distances without attenuation, stability with time, and excellent energy resolution are essential. Xenon is an attractive candidate for use as an ionization detection medium. Its low cost in large volumes gives it an advantage over solid-state detectors. Its large atomic number (Z = 54) and density (when compressed or condensed) give a high stopping power for [gamma]-radiation. The low average energy required to produce an electron-ion pair and small Fano factor allow good energy resolution. The expected intrinsic energy resolution is 2 and 4 keV FWHM at 1 MeV in liquid and gaseous xenon, respectively. Thus, high density xenon spectrometers have a detection efficiency similar to NaI(T1) crystals of the same size and an energy resolution comparable in theory to that in Ge(Li) detectors. However, the best energy resolution results in liquid xenon, 34 and 54 keV FWHM for the 570 and 1,064 keV photo-peaks of [sup 207]Bi, respectively, fall considerably short of the Fano factor predictions. It appears that the resolution is limited by some process other than Poisson fluctuations. In this report the authors describe results obtained from a dual gridded ionization chamber filled with highly purified gaseous xenon operating near its critical point where the density, [rho][sub c] = 1.09 g/cm[sup 3], approaches that of the liquid phase. This thermodynamic regime has not previously been studied in xenon.

Levin, C.; Markey, J. (Yale Univ., New Haven, CT (United States). A.W. Wright Nuclear Structure Lab.)

1993-08-01

228

Dipole-Dipole Excitation and Ionization in an Ultracold Gas of Rydberg Atoms  

SciTech Connect

In cold dense Rydberg atom samples, the dipole-dipole interaction strength is effectively resonant at the typical interatomic spacing in the sample, and the interaction has a 1/R{sup 3} dependence on interatomic spacing R. The dipole-dipole attraction leads to ionizing collisions of initially stationary atoms, which produces hot atoms and ions and initiates the evolution of initially cold samples of neutral Rydberg atoms into plasmas. More generally, the strong dipole-dipole forces lead to motion, which must be considered in proposed applications.

Li Wenhui; Tanner, Paul J.; Gallagher, T. F. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

2005-05-06

229

Post-compression of high-energy femtosecond pulses using gas ionization.  

PubMed

We present a new optical post-compression technique designed for high-energy ultrashort pulses. A large spectral broadening is achieved through rapid ionization of helium by an intense pulse (>10(15) W/cm(2)) propagating in a capillary filled with low-pressure helium. The blueshifted pulses are re-compressed with chirped mirrors and silica plates. From a terawatt Ti:sapphire laser chain providing pulses of 40 fs, 70 mJ, we demonstrate the compression of pulses down to 11.4 fs (FWHM) with a total output energy of 13.7 mJ. PMID:20081985

Dutin, C Fourcade; Dubrouil, A; Petit, S; Mével, E; Constant, E; Descamps, D

2010-01-15

230

FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Pulse Operation of Chemical Oxygen-Iodine Laser by Pulsed Gas Discharge with the Assistance of Spark Pre-ionization  

NASA Astrophysics Data System (ADS)

The continuous wavelength chemical oxygen-iodine laser can be turned into pulse operation mode in order to obtain high energy and high pulse power. We propose an approach to produce iodine atoms instantaneously by pulsed gas discharge with the assistance of spark pre-ionization to achieve the pulsed goal. The influence of spark pre-ionization on discharge homogeneity is discussed. Voltage-current characteristics are shown and discussed in existence of the pre-ionization capacitor and peaking capacitor. The spark pre-ionization and peaking capacitor are very helpful in obtaining a stable and homogeneous discharge. The lasing is achieved at the total pressure of 2.2-2.9kPa and single pulse energy is up to 180 mJ, the corresponding specific output energy is 1.0 J/L.

Li, Guo-Fu; Yu, Hai-Jun; Duo, Li-Ping; Jin, Yu-Qi; Wang, Jian; Sang, Feng-Ting; Fang, Ben-Jie; Wang, De-Zhen

2009-11-01

231

65 kpc of ionized gas trailing behind NGC 4848 during its first crossing of the Coma cluster  

NASA Astrophysics Data System (ADS)

In a five hour H? exposure of the northwest region of the Coma cluster with the 2.1 m telescope at San Pedro Martir (Mx), we discovered a 65 kpc cometary emission of ionized gas trailing behind the SBab galaxy NGC 4848. The tail points in the opposite direction of the cluster center, in the same direction where stripped HI had been detected in previous observations. The galaxy shows bright HII regions in an inner ring-like pattern, where the star formation takes place at the prodigious rate of ~8.9 M? yr-1. From the morphologies of the galaxy and the trailing material, we infer that the galaxy is suffering from ram pressure due to its high velocity motion through the intergalactic medium. We estimate that ~4 × 109 M? of gas is swept out from the galaxy forming the tail. Given the ambient conditions in the Coma cluster (?0 = 6.3 × 10-27 g cm-3; ?vel = 940 km s-1), simulations predict that the ram pressure mechanism is able to remove such an amount of gas in less than 200 Myr. This, combined with the geometry of the interaction, is indicative of radial infall into the cluster, leading to the conclusion that NGC 4848 has been caught during its first passage through the dense cluster environment. Observations taken at the observatory of San Pedro Martir (Baja California, Mexico), belonging to the Mexican Observatorio Astronómico Nacional.

Fossati, Matteo; Gavazzi, Giuseppe; Boselli, Alessandro; Fumagalli, Michele

2012-08-01

232

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

PubMed

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

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

1987-07-24

233

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

2013-02-01

234

Analysis of tryptamine at the femtomole level in tissue using negative ion chemical ionization gas chromatography-mass spectrometry.  

PubMed

An ultra sensitive method for the detection of tryptamine, an endogenous amine in mammalian neuronal systems, at the femtomole level has been developed using negative chemical ionization gas chromatography-mass spectrometry (NCI-GC-MS). The amine is converted into a perfluorinated spirocyclic derivative, e.g. 1-pentafluoro-2-methylenepyrrolidine-3-spiro-3'-(3H-indole) which is detected using selected-ion monitoring of the (M-2HF) ions of the endogenous and deuterated internal standard compounds. Two mass spectrometers were compared; they gave minimum detectable quantities from tissue samples of 40 pg (VG-7070F) and 0.9 pg (VG-70S) respectively. These detection levels are approximately 5-200 times lower than have been obtained by previous MS methods. PMID:3403664

Durden, D A; Boulton, A A

1988-05-25

235

Highly Ionized High-Velocity Gas in the Vicinity of the Galaxy  

Microsoft Academic Search

We report the results of a FUSE study of high-velocity O VI absorption along complete sight lines through the Galactic halo in directions toward 100 extragalactic objects and two halo stars. The high-velocity O VI traces a variety of phenomena, including tidal interactions with the Magellanic Clouds, accretion of gas, outflowing material from the Galactic disk, warm\\/hot gas interactions in

K. R. Sembach; B. P. Wakker; B. D. Savage; P. Richter; M. Meade; J. M. Shull; E. B. Jenkins; G. Sonneborn; H. W. Moos

2003-01-01

236

Three-dimensional modeling of ionized gas. I. Did very massive stars of different metallicities drive the second cosmic reionization?  

NASA Astrophysics Data System (ADS)

Context. The first generation of stars, which formed directly from the primordial gas, is believed to have played a crucial role in the early phase of the epoch of reionization of the universe. Theoretical studies indicate that the initial mass function (IMF) of this first stellar population differs significantly from the present IMF, being top-heavy and thus allowing for the presence of supermassive stars with masses up to several thousand solar masses. The first generation of population III stars was therefore not only very luminous, but due to its lack of metals its emission of UV radiation considerably exceeded that of present stars. Because of the short lifetimes of these stars the metals produced in their cores were quickly returned to the environment, from which early population II stars with a different IMF and different spectral energy distributions (SEDs) were formed, already much earlier than the time at which the universe became completely reionized (at a redshift of z ? 6). Aims: Using a state-of-the-art model atmosphere code we calculate realistic SEDs of very massive stars (VMSs) of different metallicities to serve as input for the 3-dimensional radiative transfer code we have developed to simulate the temporal evolution of the ionization of the inhomogeneous interstellar and intergalactic medium, using multiple stellar clusters as sources of ionizing radiation. The ultimate objective of these simulations is not only to quantify the processes which are believed to have lead to the reionized state of the universe, but also to determine possible observational diagnostics to constrain the nature of the ionizing sources. Methods: The multifrequency treatment in our combination of 3d radiative transfer - based on ray-tracing - and time-dependent simulation of the ionization structure of hydrogen and helium allows, in principle, to deduce information about the spectral characteristics of the first generations of stars and their interaction with the surrounding gas on various scales. Results: As our tool can handle distributions of numerous radiative sources characterized by high resolution synthetic SEDs, and also yields occupation numbers of the required energy levels of the most important elements which are treated in non-LTE and are calculated consistently with the 3d radiative transfer, the ionization state of an inhomogeneous gaseous density structure can be calculated accurately. We further demonstrate that the increasing metallicity of the radiative sources in the transition from population III stars to population II stars has a strong impact on the hardness of the emitted spectrum, and hence on the reionization history of helium. Conclusions: A top-heavy stellar mass distribution characterized by VMSs forming in chemically evolved clusters of high core mass density may not only provide the progenitors of intermediate-mass and supermassive black holes (SMBHs), but also play an important role for the reionization of He ii. The number of VMSs required to reionize He ii by a redshift of z ~ 2.5 is astonishingly close to the number of VMSs required to explain galactic SMBHs if one assumes that these have been formed by mergers of smaller black holes.

Weber, J. A.; Pauldrach, A. W. A.; Knogl, J. S.; Hoffmann, T. L.

2013-07-01

237

Influence of wavelength, irradiance, and the buffer gas pressure on high irradiance laser ablation and ionization source coupled with an orthogonal Time of Flight Mass Spectrometer  

Microsoft Academic Search

Influence of laser wavelength, laser irradiance and the buffer gas pressure were studied in high irradiance laser ablation and ionization source coupled with an orthogonal time-of-flight mass spectrometer. Collisional cooling effects of energetic plasma ions were proved to vary significantly with the elemental mass number. Effective dissociation of interferential polyatomic ions in the ion source, resulting from collision and from

Rongfu Huang; Quan Yu; Qingguo Tong; Wei Hang; Jian He; Benli Huang

2009-01-01

238

Determination of o-phthalic acid in snow and its photochemical degradation by capillary gas chromatography coupled with flame ionization and mass spectrometric detection  

Microsoft Academic Search

Phthalic acid and its photochemical degradation has been determined in snow and rainwater samples collected during winters (2003–2010) in the Southeast of Massachusetts using capillary gas chromatography (GC) with flame ionization and mass spectrometric detection. Water samples were dried using a rotary evaporator and derivatized with a 14% BF3\\/methanol reagent before GC analysis. The developed method proved simple and accurate.

Yuegang Zuo; Kai Zhang; Jinping Wu; Bin Men; Mengchang He

2011-01-01

239

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

Microsoft Academic Search

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

H. Belcher; T. M. Sugden

1950-01-01

240

Radiation Produced by Partial Ionization  

Microsoft Academic Search

Emission of light by gases; a partial ionization theory.-In certain cases light seems to be emitted at the instant of ionization of the gas atoms; in other cases it seems to be emitted at the instant of recombination of gas ions; and in still other cases, the light emission seems to be associated with neither ionization nor recombination. These cases

C. D. Child

1920-01-01

241

Noise characteristics of the gas ionization cascade used in low vacuum scanning electron microscopy  

SciTech Connect

The noise characteristics of gas cascade amplified electron signals in low vacuum scanning electron microscopy (LVSEM) are described and analyzed. We derive expressions for each component contributing to the total noise culminating in a predictive, quantitative model that can be used for optimization of LVSEM operating parameters. Signal and noise behavior is characterized experimentally and used to validate the model. Under most operating conditions, the noise is dominated by the excess noise generated in the gas amplification cascade. At high gains, the excess noise increases proportionally with gain such that the signal-to-noise ratio is constant. The effects of several instrument operating parameters, including working distance, gas pressure, beam current, and detector bias, are condensed and presented in the form of a master curve.

Tileli, Vasiliki; Thiel, Bradley L. [College of Nanoscale Science and Engineering, University at Albany-SUNY, 257 Fuller Road, Albany, New York 12203 (United States); Knowles, W. Ralph; Toth, Milos [FEI Company, 5350 NE Dawson Creek Drive, Hillsboro, Oregon 97124 (United States)

2009-07-01

242

Effects of Partial Ionization and Pressure on Hydromagnetic Ionizing Waves.  

National Technical Information Service (NTIS)

The transverse hydromagnetic ionizing wave is studied theoretically without the assumption of infinite conductivity behind the wave. Finite gas pressures are included, as well as a variable degree of ionization behind the wave. The electric field in front...

R. S. Kushwaha A. G. Rubin

1966-01-01

243

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

244

Transport of microparticles in weakly ionized gas-discharge plasmas under microgravity conditions.  

PubMed

Measurements of effective structural (pair correlation function) and transport (diffusion constant) characteristics of the system of microparticles in dc and rf gas-discharge plasmas under microgravity conditions are reported. The comparison between these measurements and numerical simulations is used for complex plasma diagnostics. PMID:12857198

Fortov, V E; Vaulina, O S; Petrov, O F; Molotkov, V I; Lipaev, A M; Torchinsky, V M; Thomas, H M; Morfill, G E; Khrapak, S A; Semenov, Yu P; Ivanov, A I; Krikalev, S K; Kalery, A Yu; Zaletin, S V; Gidzenko, Yu P

2003-06-19

245

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

SciTech Connect

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

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

2011-09-21

246

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

NASA Astrophysics Data System (ADS)

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

Greenfield, E. J.; Jokipii, J. R.; Giacalone, Joe

2011-09-01

247

Atmospheric pressure-ion drift chemical ionization mass spectrometry for detection of trace gas species.  

PubMed

This paper describes atmospheric pressure-ion drift chemical ionization mass spectrometry (AP-ID-CIMS) for monitoring of ambient trace species. Operation of the drift tube at atmospheric pressure allows a significantly longer ion-molecule reaction time and eliminates dilution of the ambient samples, while a well-defined electric field inside the drift tube provides the benefits to confine the flight path and velocity of reagent/product ions, to break down ion clusters, and to control the ion-molecule reaction time. The AP-ID-CIMS exhibits advantages over the conventional low pressure ID-CIMS and flow tube AP-CIMS, improving the detection sensitivity by 3 orders of magnitude and a factor of 3, respectively. We demonstrate that the AP-ID-CIMS allows quantification of sulfuric acid concentrations and is capable of detecting gaseous sulfuric acid with a detection limit of less than 10(5) molecules cm(-3), on the basis of 3sigma of the baseline noise and an integration time of 12 s. A field evaluation of the AP-ID-CIMS is presented for ambient H(2)SO(4) measurements. PMID:20695435

Zheng, Jun; Khalizov, Alexei; Wang, Lin; Zhang, Renyi

2010-09-01

248

The Effects of Ionized Gas Exposure on the Toughness and Fatigue Properties of Aluminum Alloys and Composites.  

NASA Astrophysics Data System (ADS)

The effects of an oxygen ionized gas from simulated space exposure on the toughness and fatigue properties of several aerospace aluminum alloys and aluminum composites have been analyzed. The test matrix consisted of four aluminum systems: the 6000 and 1100 series and two 8090 aluminum-lithium alloys. The test specimens were prepared as Charpy V-notched impact and disk-shaped compact fracture toughness specimens. A small specimen size is used for the compact tension specimens to facilitate exposure in a Radio Frequency (RF) Plasma Prep II unit. Radio frequency plasma, sometimes referred to as the "electrodeless plasma", is used in disassociative ionization of molecular oxygen to simulate high fluence, relatively low energy, low earth orbit (LEO) space atomic oxygen. The plasma reacts with the aluminum alloy systems and forms a thin scale of alumina a few microns thick. Monolayer sensitive Variable Angle Spectroscopic Ellipsometry (VASE) is used to determine the growth characteristics and effect on optical constants, the reflective index, n and absorption coefficient, k. Atomic Force Microscopy (AFM) was also employed to determine the effect of short exposure to the oxygen plasma environment. AFM indicates that sharp spikes of oxygen rich material are produced above the aluminum specimen surface resulting in stress concentrations with gradual roughing of the surface. After 10 years of simulated exposure, the increased roughness results in a 34% increase in the fatigue crack growth, da/dN, for the 6000 series; the crack growth rate of the aluminum-lithium material was increased about 28%. The results of instrumented Charpy V-notched impact specimens indicated that exposure reduced the energy for fracture initiation by 29%. Plane strain fracture toughness effects could not be established because the influence of oxygen was concentrated at the surface of the specimens.

Zaat, Stephen Vincent

249

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

250

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

2013-06-29

251

The simultaneous separation and determination of chloropropanols in soy sauce and other flavoring with gas chromatography-mass spectrometry in negative chemical and electron impact ionization modes  

Microsoft Academic Search

Both gas chromatography-mass spectrometry in electron ionization (GC-MS-EI) and negative chemical ionization (GC-MS-NCI) modes are reported in this paper for the simultaneous determination of 1,3-dichloropropan-2-ol (1,3-DCP), 2,3-dichloropropan-1-ol (2,3-DCP), 3-chloropropane-1,2-diol (3-MCPD) and 2-chloropropane-1,3-diol (2-MCPD) in soy sauce and other flavoring. D5-3-MCPD (for 3-MCPD and 2-MCPD) and d5-1,3-DCP (for 1,3-DCP and 2,3-DCP) were used as the deuterium isotopic labelled internal standards. The

Xiaomin Xu; Yiping Ren; Pinggu Wu; Jianlong Han; Xianghong Shen

2006-01-01

252

[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

253

[S IV] in the NGC 5253 Supernebula: Ionized Gas Kinematics at High Resolution  

NASA Astrophysics Data System (ADS)

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 ?m line of S +3 at 3.8 km s-1 spectral and 1farcs4 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-1 and another of similar strength and FWHM 94 km s-1 centered ~20 km s-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.; Lacy, John H.; Turner, Jean L.; Kruger, Andrew; Richter, Matt; Crosthwaite, Lucian P.

2012-08-01

254

Determination of MK-287, a new platelet-activating factor antagonist, in plasma and serum by gas chromatography chemical ionization mass spectrometry.  

PubMed

MK-287 is a novel platelet-activating factor antagonist. A sensitive and specific gas chromatographic/mass spectrometric assay has been developed for the determination of the drug in serum and plasma. The assay utilizes an extraction with methyl-t-butyl ether and subsequent trimethylsilylation of the hydroxyl function. The gas chromatographic/mass spectrometric determinations are carried out with temperature-programmed capillary gas chromatography and ammonia negative chemical ionization mass spectrometry. The method has sufficient sensitivity, precision, accuracy and selectivity for the analysis of drug concentrations in clinical samples. PMID:1932155

Fisher, A L; Morris, M J; Gilbert, J D

1991-07-01

255

Simultaneous multidetermination of residues of pesticides and polycyclic aromatic hydrocarbons in olive and olive-pomace oils by gas chromatography/tandem mass spectrometry.  

PubMed

A multiresidue method for determining major pesticides and polycyclic aromatic hydrocarbons (PAHs) in olive oils in a single injection by use of gas chromatography/tandem mass spectrometry (GC-MS/MS) is proposed. Samples are previously extracted with an acetonitrile/n-hexane mixture and cleaned up by gel permeation chromatography. Electron ionization and chemical ionization allow pesticides and PAHs to be determined in a single analysis. The precision obtained was quite satisfactory (relative standard deviations ranged from 3 to 7.8%), and so were recoveries (84-110%). The linear relation was observed from 1 to 500 microg/kg for pesticides and 0.3 to 200 microg/kg for PAHs; also, the determination coefficient, R(2), was better than 0.995 in all instances. The proposed method was applied to the routine analysis of PAH and pesticide residues in virgin and refined olive oil and olive-pomace oil samples. PMID:16480730

Ballesteros, E; García Sánchez, A; Ramos Martos, N

2006-02-09

256

Gas-Phase Oxidation of Cm+ and Cm2+ -- Thermodynamics of neutral and ionized CmO  

SciTech Connect

Fourier transform ion cyclotron resonance mass spectrometry was employed to study the products and kinetics of gas-phase reactions of Cm+ and Cm2+; parallel studies were carried out with La+/2+, Gd+/2+ and Lu+/2+. Reactions with oxygen-donor molecules provided estimates for the bond dissociation energies, D[M+-O](M = Cm, Gd, Lu). The first ionization energy, IE[CmO], was obtained from the reactivity of CmO+ with dienes, and the second ionization energies, IE[MO+](M = Cm, La, Gd, Lu), from the rates of electron-transfer reactions from neutrals to the MO2+ ions. The following thermodynamic quantities for curium oxide molecules were obtained: IE[CmO]= 6.4+-0.2 eV; IE[CmO+]= 15.8+-0.4 eV; D[Cm-O]= 710+-45 kJ mol-1; D[Cm+-O]= 670+-40 kJ mol-1; and D[Cm2+-O]= 342+-55 kJ mol-1. Estimates for the M2+-O bond energies for M = Cm, La, Gd and Lu are all intermediate between D[N2-O]and D[OC-O]--i.e., 167 kJ mol-1< D[M2+-O]< 532 kJ mol-1 -- such that the four MO2+ ions fulfill the thermodynamic requirement for catalytic O-atom transport from N2O to CO. It was demonstrated that the kinetics are also favorable and that the CmO2+, LaO2+, GdO2+ and LuO2+ dipositive ions each catalyze the gas-phase oxidation of CO to CO2 by N2O. The CmO2+ ion appeared during the reaction of Cm+ with O2 when the intermediate, CmO+, was not collisionally cooled -- although its formation is kinetically and/or thermodynamically unfavorable, CmO2+ is a stable species.

Gibson, John K; Haire, Richard G.; Santos, Marta; Pires de Matos, Antonio; Marcalo, Joaquim

2008-12-08

257

Gas-Phase Oxidation of Cm+ and Cm2+ - Thermodynamics of Neutral and Ionized CmO  

SciTech Connect

Fourier transform ion cyclotron resonance mass spectrometry was employed to study the products and kinetics of gas-phase reactions of Cm+ and Cm2+; parallel studies were carried out with La+/2+, Gd+/2+ and Lu+/2+. Reactions with oxygen-donor molecules provided estimates for the bond dissociation energies, D[M+-O] (M ) Cm, Gd, Lu). The first ionization energy, IE[CmO], was obtained from the reactivity of CmO+ with dienes, and the second ionization energies, IE[MO+] (M ) Cm, La, Gd, Lu), from the rates of electrontransfer reactions from neutrals to the MO2+ ions. The following thermodynamic quantities for curium oxide molecules were obtained: IE[CmO] ) 6.4 ( 0.2 eV; IE[CmO+] ) 15.8 ( 0.4 eV; D[Cm-O] ) 710 ( 45 kJ mol-1; D[Cm+-O] ) 670 ( 40 kJ mol-1; and D[Cm2+-O] ) 342 ( 55 kJ mol-1. Estimates for the M2+-O bond energies for M ) Cm, La, Gd, and Lu are all intermediate between D[N2-O] and D[OC-O] - that is, 167 kJ mol-1 < D[M2+-O] < 532 kJ mol-1 - such that the four MO2+ ions fulfill the thermodynamic requirement for catalytic oxygen-atom transport from N2O to CO. It was demonstrated that the kinetics are also favorable and that the CmO2+, LaO2+, GdO2+, and LuO2+ dipositive ions each catalyze the gas-phase oxidation of CO to CO2 by N2O. The CmO2 + ion appeared during the reaction of Cm+ with O2 when the intermediate, CmO+, was not collisionally cooled - although its formation is kinetically and/or thermodynamically unfavorable, CmO2 + is a stable species.

Gibson, John K [ORNL; Haire, Richard G. [Oak Ridge National Laboratory (ORNL); Santos, Marta [ORNL; Pires de Matos, Antonio [Instituto Tecnologico e Nuclear, Sacavem, Portugal; Marcalo, Joaquim [Instituto Tecnologico e Nuclear, Sacavem, Portugal

2008-01-01

258

Gas-phase oxidation of Cm+ and Cm2+ --thermodynamics of neutral and ionized CmO.  

PubMed

Fourier transform ion cyclotron resonance mass spectrometry was employed to study the products and kinetics of gas-phase reactions of Cm (+) and Cm (2+); parallel studies were carried out with La (+/2+), Gd (+/2+) and Lu (+/2+). Reactions with oxygen-donor molecules provided estimates for the bond dissociation energies, D[M (+)-O] (M = Cm, Gd, Lu). The first ionization energy, IE[CmO], was obtained from the reactivity of CmO (+) with dienes, and the second ionization energies, IE[MO (+)] (M = Cm, La, Gd, Lu), from the rates of electron-transfer reactions from neutrals to the MO (2+) ions. The following thermodynamic quantities for curium oxide molecules were obtained: IE[CmO] = 6.4 +/- 0.2 eV; IE[CmO (+)] = 15.8 +/- 0.4 eV; D[Cm-O] = 710 +/- 45 kJ mol (-1); D[Cm (+)-O] = 670 +/- 40 kJ mol (-1); and D[Cm (2+)-O] = 342 +/- 55 kJ mol (-1). Estimates for the M (2+)-O bond energies for M = Cm, La, Gd, and Lu are all intermediate between D[N 2-O] and D[OC-O] - that is, 167 kJ mol (-1) < D[M (2+)-O] < 532 kJ mol (-1) - such that the four MO (2+) ions fulfill the thermodynamic requirement for catalytic oxygen-atom transport from N2O to CO. It was demonstrated that the kinetics are also favorable and that the CmO (2+), LaO (2+), GdO (2+), and LuO (2+) dipositive ions each catalyze the gas-phase oxidation of CO to CO2 by N2O. The CmO 2 (+) ion appeared during the reaction of Cm (+) with O 2 when the intermediate, CmO (+), was not collisionally cooled - although its formation is kinetically and/or thermodynamically unfavorable, CmO 2 (+) is a stable species. PMID:18921989

Gibson, John K; Haire, Richard G; Santos, Marta; de Matos, António Pires; Marçalo, Joaquim

2008-10-16

259

Integral field spectroscopy of ionized and molecular gas in cool cluster cores: evidence for cold feedback?  

NASA Astrophysics Data System (ADS)

We present VLT-SINFONI K-band integral field spectroscopy of the central galaxies in the cool core clusters A1664, A2204 and PKS 0745-191, to probe the spatio-kinematic properties of the Pa? and ro-vibrational H2 line emission. In A1664, the two emission-line velocity systems seen in our previous H? spectroscopy appear in both Pa? and H2 emission, with notable morphological differences. The recession velocity of the red component of Pa? increases linearly with decreasing radius, particularly along an 8kpc filament aligned with the major axis of the underlying galaxy and the cluster X-ray emission. These kinematics are modelled as gravitational free-fall as gas cools rapidly out of the hot phase. In A2204, the gas shows three or four filaments reaching radii of 10kpc, three of which lie towards `ghost bubbles' seen in X-ray imaging by Sanders et al. For PKS 0745-191, we confirm the twin-arm morphology in the narrow-band images of Donahue et al.; the Pa? kinematics suggest rotational motion about an axis aligned with the kiloparsec-scale radio jet; on nucleus, we find an underlying broad Pa? component [full width at half-maximum (FWHM) 1700kms-1] and a secondary H2 velocity system redshifted by +500kms-1. The H2v = 1-0 S(3)/Pa? ratio is the highest in the most isolated and extended regions where it matches the levels in the NGC 1275 filaments as modelled by Ferland et al. Regions with much lower ratios highlight active star formation and are often kinematically quiescent (FWHM < 200kms-1). Our findings suggest that the three clusters may be captured in different stages of the `cold feedback' cycle of Pizzolato & Soker, with A1664 in a short-lived phase of extreme cooling and star formation prior to an active galactic nucleus (AGN) heating event; PKS 0745-191 in an outburst state with the AGN accreting from a cool gas disc, and A2204 in a later phase in which cool gas is dragged out of the galaxy by the buoyant rise of old radio bubbles. Based on observations performed at the European Southern Observatory, Chile [Programme ID: 77.A-0057(A)]. E-mail: rwilman@unimelb.edu.au

Wilman, R. J.; Edge, A. C.; Swinbank, A. M.

2009-05-01

260

Low-frequency radio continuum evidence for cool ionized gas in normal spiral galaxies  

SciTech Connect

A 57.5-MHz survey of a total of 133 (mostly late-type spiral) galaxies has resulted in the detection of 68. The ratio of observed intensities to intensities extrapolated from higher-frequency measurements is well correlated with the axial ratio of the observed galaxies, and is interpretable due to increasing free-free absorption of nonthermal emission in galaxy disks with increasing tilt. The implied free-free absorption is interpreted as due to the pervasive presence of a clumpy medium of well-mixed, nonthermally emitting, thermally absorbing gas with small filling factor. 57 refs.

Israel, F.P.; Mahoney, M.J. (Leiden, Rijksuniversiteit, Sterrewacht (Netherlands) Clark Lake Radio Observatory, College Park, MD (USA))

1990-03-01

261

A Huge Reservoir of Ionized Gas around the Milky Way: Accounting for the Missing Mass?  

NASA Astrophysics Data System (ADS)

Most of the baryons from galaxies have been "missing" and several studies have attempted to map the circumgalactic medium (CGM) of galaxies in their quest. We report on X-ray observations made with the Chandra X-Ray Observatory probing the warm-hot phase of the CGM of our Milky Way at about 106 K. We detect O VII and O VIII absorption lines at z = 0 in extragalactic sight lines and measure accurate column densities using both K? and K? lines of O VII. We then combine these measurements with the emission measure of the Galactic halo from literature to derive the density and the path length of the CGM. We show that the warm-hot phase of the CGM is massive, extending over a large region around the Milky Way, with a radius of over 100 kpc. The mass content of this phase is over 10 billion solar masses, many times more than that in cooler gas phases and comparable to the total baryonic mass in the disk of the Galaxy. The missing mass of the Galaxy appears to be in this warm-hot gas phase.

Gupta, A.; Mathur, S.; Krongold, Y.; Nicastro, F.; Galeazzi, M.

2012-09-01

262

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

263

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

NASA Astrophysics Data System (ADS)

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 tested, photoionization model sequences. As a first step to reach these goals, we have obtained simultaneous blue to far red long-slit spectra with the William Herschel Telescope (WHT) of three compact HII galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 2 (DR2) spectral catalogue using the INAOE Virtual Observatory superserver. Our spectra cover the range from 3200 to 10500Å, including the Balmer jump, the [OII]??3727, 29Å lines, the [SIII]??9069, 9532Å doublet as well as various weak auroral lines such as [OIII]?4363Å and [SIII]?6312Å. For the three objects, we have measured at least four line temperatures, T([OIII]), T([SIII]), T([OII]) and T([SII]), and the Balmer continuum temperature T(Bac). These measurements and a careful and realistic treatment of the observational errors yield total oxygen abundances with accuracies between 5 and 9 per cent. These accuracies are expected to improve as better calibrations based on more precise measurements, both on electron temperatures and densities, are produced. We have compared our obtained spectra with those downloaded from the SDSS DR3 finding a satisfactory agreement. The analysis of these spectra yields values of line temperatures and elemental ionic and total abundances which are in general agreement with those derived from the WHT spectra, although for most quantities they can only be taken as estimates since, due to the lack of direct measurements of the required lines, theoretical models had to be used whose uncertainties are impossible to quantify. The ionization structure found for the observed objects from the O+/O2+ and S+/S2+ ratios points to high values of the ionizing radiation, as traced by the values of the `softness parameter' ? which is less than 1 for the three objects. The use of line temperatures derived from T([OIII]) based on current photoionization models yields for the two highest excitation objects, much higher values of ? which would imply lower ionizing temperatures. This is, however, inconsistent with the ionization structure as probed by the measured emission-line intensities. Finally, we have measured the T(Bac) for the three observed objects and derived temperature fluctuations. Only for one of the objects, the temperature fluctuation is significant and could lead to higher oxygen abundances by about 0.20dex.

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

2006-10-01

264

Development of a portable mass spectrometer characterized by discontinuous sample gas introduction, a low-pressure dielectric barrier discharge ionization source, and a vacuumed headspace technique.  

PubMed

The present study has attempted to downscale a mass spectrometer in order to make it portable and enable onsite analysis with it. The development of a small mass spectrometer required the use of a compact pump whose displacement was small, decreasing the sensitivity of that spectrometer. To get high sensitivity with a small mass spectrometer, we have integrated novel techniques: a highly sensitive ionization source and efficient extraction of sample vapor. The low-pressure dielectric barrier discharge ionization (LP-DBDI) source made it possible to increase the conductance between the source and the mass analyzer, compared with ambient ionization sources, enhancing the efficiency of the ion transfer from the ionization source to the mass analyzer. We have also developed a vacuumed headspace method efficiently transporting the sample vapor to the ionization source. The sensitivity was further enhanced by also using a discontinuous sample gas introduction technique. A prototype portable mass spectrometer using those novel techniques was found to be sensitive enough to detect 0.1 ppm methamphetamine, 1 ppm amphetamine, 1 ppm 3,4-methylenedioxymethamphetamine, and 10 ppm cocaine in liquid. PMID:23577896

Kumano, Shun; Sugiyama, Masuyuki; Yamada, Masuyoshi; Nishimura, Kazushige; Hasegawa, Hideki; Morokuma, Hidetoshi; Inoue, Hiroyuki; Hashimoto, Yuichiro

2013-05-07

265

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

266

Gas-Phase Stability of G-quadruplex DNA Determined by Electrospray Ionization Tandem Mass Spectrometry and Molecular Dynamics Simulations  

PubMed Central

The relative gas-phase stabilities of seven quadruplex DNA structures, [d(TG4T)]4, [d(T2G3T)]4, [d(G4T4G4)]2, [d(T2AG3)2]2, d(T2AG3)4, d(T2G4)4, and d(G2T4)4, were investigated using molecular dynamics simulations and electrospray ionization mass spectrometry (ESI-MS). MD simulations revealed that the G-quadruplexes maintained their structures in the gas phase although the G-quartets were distorted to some degree and ammonium ions, retained by [d(TG4T)]4 and [d(T2G3T)]4, played a key role in stabilizing the tetrad structure. Energy-variable collisional activated dissociation was used to assess the relative stabilities of each quadruplex based on E1/2 values, and the resulting order of relative stabilities was found to be [d(TG4T)]4 ? d(T2AG3)4 ? d(T2G4)4 > [d(T2G3T)]4 > [d(T2AG3)2]2 ? d(G2T4)4 ? [d(G4T4G4)]2. The stabilities from the E1/2 values generally paralleled the RMSD and relative free energies of the quadruplexes based on the MD energy analysis. One exception to the general agreement is [d(G4T4G4)]2 which had the lowest E1/2 value, but was determined to be the most stable quadruplex according to the free energy analysis and ranked fourth based on the RMSD comparison. This discrepancy is attributed to differences in the fragmentation pathway of the quadruplex.

Mazzitelli, Carolyn L.; Wang, Junmei; Smith, Suncerae I.; Brodbelt, Jennifer S.

2007-01-01

267

Determination of (-)-threo-chlorocitric acid in human plasma by gas chromatography-positive chemical-ionization mass spectrometry.  

PubMed

A method is described for measuring (-)-threo-chlorocitric acid in human plasma. Plasma is acidified to pH 1 to minimize lactonization and a 13C analogue of (-)-threo-chlorocitric acid is added as internal standard. The acidified plasma is then extracted with ethyl acetate containing 10% methanol. The ethyl acetate-methanol extract is back-extracted with acetate buffer (pH 5). This extract, following adjustment to pH 1, is reextracted with ethyl acetate. The residue after removal of the ethyl acetate is treated with ethereal diazomethane. The wet residue is reconstituted in ethyl acetate and a portion of this solution is analyzed by gas chromatography-chemical ionization mass spectrometry. The mass spectrometer is set to monitor m/z 269 [MH+ of trimethylated (-)-threo-chlorocitric acid] and m/z 270 [MH+ of trimethylated (-)-threo-[13C]chlorocitric acid] in the gas chromatographic effluent. The m/z 269 to m/z 270 ion ratio in a sample containing an unknown amount of (-)-threo-chlorocitric acid is converted to an amount of compound using a calibration curve. The calibration curve is generated by analyzing control plasma spiked with various known amounts of (-)-threo-chlorocitric acid and a fixed amount of (-)-threo-[13C]chlorocitric acid. The limit of quantitation is 0.1-0.6 micrograms ml-1, depending on the characteristics of the calibration curve generated with each set of samples. The precision (relative standard deviation) at a concentration of 2 micrograms ml-1 is 3.3%. PMID:7161329

Rubio, F; De Grazia, F; Miwa, B J; Garland, W A

1982-12-10

268

Determination of butyltin species in water and sediment by solid-phase microextraction-gas chromatography-flame ionization detection.  

PubMed

A procedure for determination of tetraethyltin (TeET) and tetrabutyltin (TeBT) in water by solid-phase microextraction (SPME) using the headspace approach has been developed. The method has been adapted for the simultaneous determination of mono-, di- and tributyltin species (MBT, DBT and TBT) after derivatization with sodium tetraethylborate in water and sediment samples. The analytical procedures were optimized with respect to stirring conditions, extraction time and extraction temperature. The pH and the amount of derivatizing reagent were also considered in derivatization reaction procedures. The analysis was carried out using gas chromatography equipped with flame ionization detection. The detection limits obtained for TeET and TeBT, in equilibrium conditions (room temperature for TeET and 40 degrees C for TeBT) were 28 and 20 ng/l (as Sn), respectively. The detection limit for butyltin species in water, which was limited by signals which are non-specific for the tin compounds and the sensitivity of the FID system, was found ca. 1 microg/l (as Sn). The SPME method was validated for analysis of sediments by analyzing the certified reference material PACS-2 finding a good agreement with the certified values. PMID:10757285

Millán, E; Pawliszyn, J

2000-03-17

269

Determination of nitrated polycyclic aromatic hydrocarbons by fused silica capillary gas chromatography/negative ion chemical ionization mass spectrometry  

SciTech Connect

Gas chromotography/electron capture negative ion chemical ionization mass spectrometry is shown to be a very sensitive and selective determination method for nitrated polycyclic aromatic hydrocarbons (PAH). The detection limit was 1 pg injected to the GC column using single ion monitoring. The mass spectra are characterized by an intense molecular ion, the base peak in all spectra. The second most abundant ions were (M - 16)/sup -/ and (M - 30)/sup -/ for mono- and dinitro-PAH, respectively. The NO/sub 2//sup -/ ion (m/z 46) is observed in most spectra. There are few differences in the mass spectra of various isomeric compounds. The pressure and the temperature in the ion source had little influence on the mass spectra and sensitivity within the limits tested. The method is demonstrated on a synthetic mixture containing nitro-PAH, and on a toluene extract of a formerly commercial carbon black. The application to urban air particulate extracts is discussed. 4 figures, 4 tables.

Ramdahl, T.; Urdal, K.

1982-11-01

270

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

271

Determination of polychlorinated biphenyls in serum using gas chromatography-mass spectrometry with negative chemical ionization for exposure estimation.  

PubMed

A sensitive and selective method for the determination of 24 polychlorinated biphenyls (PCBs) by gas chromatography-mass spectrometry with negative chemical ionization (GC-MS-NCI) was applied for the recent needs of occupational exposure in waste incineration. The three most abundant ions were used in determining compounds with at least five chlorine atoms in the PCB molecule. Selecting ions Cl(35) and Cl(37) for di-, tri-, and tetrachlorinated PCBs resulted in reliable quantification of these compounds. The detection limits for the 24 individual compounds varied from 0.01 to 0.08 microg/l. The recovery of the method was 113+/-16%. Stability tests showed no degradation of the compounds studied during 6 weeks. The sum of 24 PCB compounds measured from the sera of workers in a disposal plant was 1.9-10.9 microg/l, and 0.3-3.0 microg/l for controls, respectively. The mean proportion of the low chlorinated PCB compounds (with four or less chlorine atoms) was 20% for workers in the disposal plant and 14% for the controls. PMID:12798172

Kontsas, Helena; Pekari, Kaija

2003-07-01

272

Simultaneous determination of cyanide and thiocyanate in plasma by chemical ionization gas chromatography mass-spectrometry (CI-GC-MS).  

PubMed

An analytical method utilizing chemical ionization gas chromatography-mass spectrometry was developed for the simultaneous determination of cyanide and thiocyanate in plasma. Sample preparation for this analysis required essentially one-step by combining the reaction of cyanide and thiocyanate with pentafluorobenzyl bromide and simultaneous extraction of the product into ethyl acetate facilitated by a phase-transfer catalyst, tetrabutylammonium sulfate. The limits of detection for cyanide and thiocyanate were 1 ?M and 50 nM, respectively. The linear dynamic range was from 10 ?M to 20 mM for cyanide and from 500 nM to 200 ?M for thiocyanate with correlation coefficients higher than 0.999 for both cyanide and thiocyanate. The precision, as measured by %RSD, was below 9 %, and the accuracy was within 15 % of the nominal concentration for all quality control standards analyzed. The gross recoveries of cyanide and thiocyanate from plasma were over 90 %. Using this method, the toxicokinetic behavior of cyanide and thiocyanate in swine plasma was assessed following cyanide exposure. PMID:22941221

Bhandari, Raj K; Oda, Robert P; Youso, Stephanie L; Petrikovics, Ilona; Bebarta, Vikhyat S; Rockwood, Gary A; Logue, Brian A

2012-09-04

273

FR II Quasars: Infrared Properties, Star Formation Rates, and Extended Ionized Gas  

NASA Astrophysics Data System (ADS)

We present Spitzer Infrared Spectrograph spectra and Multiband Imaging Photometer for Spitzer photometry of 12 radio-loud QSOs with FR II morphologies at z ~ 0.3. Six of the sources are surrounded by luminous extended emission-line regions (EELRs), while the other six do not have such extended nebulae. The two subsamples are indistinguishable in their mid-infrared (MIR) spectra and overall IR spectral energy distributions (SEDs). For both subsamples, the MIR aromatic features are undetected in either individual sources or their stacked spectra, and the SEDs are consistent with pure quasar emission without significant star formation. The upper limits to the star formation rate (SFR) are sufficiently low that starburst-driven superwinds can be ruled out as a mechanism for producing the EELRs, which are instead likely the result of the ejection of most of the gas from the system by blast waves accompanying the launching of the radio jets. The FR II quasars deviate systematically from the correlation between host galaxy SFR and black hole accretion rate apparently followed by radio-quiet QSOs, implying little or no bulge growth coeval with the current intensive black hole growth. We also present a new Spitzer estimate of the SFR for the starburst in the host galaxy of the compact steep-spectrum radio quasar 3C 48.

Fu, Hai; Stockton, Alan

2009-05-01

274

FR II QUASARS: INFRARED PROPERTIES, STAR FORMATION RATES, AND EXTENDED IONIZED GAS  

SciTech Connect

We present Spitzer Infrared Spectrograph spectra and Multiband Imaging Photometer for Spitzer photometry of 12 radio-loud QSOs with FR II morphologies at z {approx} 0.3. Six of the sources are surrounded by luminous extended emission-line regions (EELRs), while the other six do not have such extended nebulae. The two subsamples are indistinguishable in their mid-infrared (MIR) spectra and overall IR spectral energy distributions (SEDs). For both subsamples, the MIR aromatic features are undetected in either individual sources or their stacked spectra, and the SEDs are consistent with pure quasar emission without significant star formation. The upper limits to the star formation rate (SFR) are sufficiently low that starburst-driven superwinds can be ruled out as a mechanism for producing the EELRs, which are instead likely the result of the ejection of most of the gas from the system by blast waves accompanying the launching of the radio jets. The FR II quasars deviate systematically from the correlation between host galaxy SFR and black hole accretion rate apparently followed by radio-quiet QSOs, implying little or no bulge growth coeval with the current intensive black hole growth. We also present a new Spitzer estimate of the SFR for the starburst in the host galaxy of the compact steep-spectrum radio quasar 3C 48.

Fu Hai [Department of Astronomy, California Institute of Technology, MS 105-24, Pasadena, CA 91125 (United States); Stockton, Alan [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)], E-mail: fu@astro.caltech.edu, E-mail: stockton@ifa.hawaii.edu

2009-05-10

275

IONIZED GAS KINEMATICS AND MORPHOLOGY IN Sgr B2 Main ON 1000 AU SCALES  

SciTech Connect

We have imaged the Sgr B2 Main region with the Very Large Array in the BnA configuration ({theta}{sub beam} = 0.''13) in both the H52{alpha} (45.453 GHz) radio recombination line and 7 mm continuum emission. At a distance of 8500 pc, this spatial resolution corresponds to a physical scale of 0.005 pc ({approx}1100 AU). The current observations detect H52{alpha} emission in 12 individual ultracompact and hypercompact H II regions. Two of the sources with detected H52{alpha} emission have broad ({Delta}V{sub FWHM} {approx} 50 km s{sup -1}) recombination lines, and two of the sources show lines with peaks at more than one velocity. We use line parameters from the H52{alpha} lines and our previous H66{alpha} line observations to determine the relative contribution of thermal, pressure, and kinematic broadening, and electron density. These new observations suggest that pressure broadening can account for the broad lines in some of the sources, but that gas motions (e.g., turbulence, accretion, or outflow) contribute significantly to the broad lines in at least one of the sources (Sgr B2 F3).

De Pree, C. G. [Department of Physics and Astronomy, Agnes Scott College, Decatur, GA 30030 (United States); Wilner, D. J. [Harvard Center for Astrophysics, Cambridge, MA (United States); Goss, W. M., E-mail: cdepree@agnesscott.edu, E-mail: dwilner@cfa.harvard.edu, E-mail: mgoss@nrao.edu [National Radio Astronomy Observatory, Socorro, NM (United States)

2011-11-15

276

Ionized Gas Kinematics and Morphology in Sgr B2 Main on 1000 AU Scales  

NASA Astrophysics Data System (ADS)

We have imaged the Sgr B2 Main region with the Very Large Array in the BnA configuration (?beam = 0farcs13) in both the H52? (45.453 GHz) radio recombination line and 7 mm continuum emission. At a distance of 8500 pc, this spatial resolution corresponds to a physical scale of 0.005 pc (~1100 AU). The current observations detect H52? emission in 12 individual ultracompact and hypercompact H II regions. Two of the sources with detected H52? emission have broad (?V FWHM ~ 50 km s-1) recombination lines, and two of the sources show lines with peaks at more than one velocity. We use line parameters from the H52? lines and our previous H66? line observations to determine the relative contribution of thermal, pressure, and kinematic broadening, and electron density. These new observations suggest that pressure broadening can account for the broad lines in some of the sources, but that gas motions (e.g., turbulence, accretion, or outflow) contribute significantly to the broad lines in at least one of the sources (Sgr B2 F3).

De Pree, C. G.; Wilner, D. J.; Goss, W. M.

2011-11-01

277

Quantification of Neurosteroids in Rat Plasma and Brain Following Swim Stress and Allopregnanolone Administration Using Negative Chemical Ionization Gas Chromatography\\/Mass Spectrometry  

Microsoft Academic Search

A simplified method for the quantitative analysis of neurosteroids in rat plasma and brain is described. The method uses negative chemical ionization gas chromatography\\/mass spectrometry and involves the synthesis of pentafluorobenzyloxime\\/trimethylsilyl ether derivatives with excellent chromatographic and electron-capturing properties. Deuterium-labeled analogs of the steroids of interest were synthesized and used as internal standards. The steroids (allopregnanolone, epiallopregnanolone, pregnenolone, testosterone, and

Monique Vallée; Jeffery D. Rivera; George F. Koob; Robert H. Purdy; Robert L. Fitzgerald

2000-01-01

278

Analytical method development for the determination of synthetic pyrethroid insecticides in soil by gas chromatography-mass spectrometry operated in negative-ion chemical-ionization mode  

Microsoft Academic Search

An effective analytical method for the simultaneous determination of five synthetic pyrethroid insecticides in soil is developed and method performance data presented. The pyrethroid residues were extracted with hexane-dichloromethane in an ultrasonic bath. The extract was cleaned up on a Florisil column prior to determination by gas chromatography—negative-ion chemical ionization mass spectrometry (GC-NICI-MS) in selected-ion monitoring (SIM) mode. The highest

M. Yasin; P. J. Baugh; G. A. Bonwick; D. H. Davies; P. Hancock; M. Leinoudi

1996-01-01

279

Simultaneous quantification of jasmonic acid and salicylic acid in plants by vapor-phase extraction and gas chromatography-chemical ionization-mass spectrometry  

Microsoft Academic Search

Jasmonic acid and salicylic acid represent important signaling compounds in plant defensive responses against other organisms. Here, we present a new method for the easy, sensitive, and reproducible quantification of both compounds by vapor-phase extraction and gas chromatography-positive ion chemical ionization-mass spectrometry. The method is based on a one-step extraction, phase partitioning, methylation with HCl\\/methanol, and collection of methylated and,

Juergen Engelberth; Eric A Schmelz; Hans T Alborn; Yasmin J Cardoza; Juan Huang; James H Tumlinson

2003-01-01

280

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

Microsoft Academic Search

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

Shin-Hwa Tzing; Wang-Hsien Ding

2010-01-01

281

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

SciTech Connect

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

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

1995-04-01

282

Gas chromatography with flame ionization detection for determination of additives in an electrolytic Zn bath.  

PubMed

The monitoring of additives in electrolytic baths is a fundamental task for proper coatings. Among the additives used in zinc baths, benzylideneacetone (BDA), benzoic acid (BA) and polyethylene glycol 400 (PEG400) are easily found. This paper deals with the possibilities of handling the bath sample before it is taken to a gas chromatograph (GC) in order to follow the additives concentration along the bath life. The applied techniques include solid phase extraction (SPE), solvent extraction (SE), static headspace (SHS), direct injection (DI) and headspace solid phase microextraction (HS-SPME) recoveries up to 6:1, 14:1, 9:1, 1:1 and 80:1 respectively have been obtained. Internal standards have been found for every case. Advantages and disadvantages of the techniques are collected. In this paper DI and HS-SPME have finally been applied, though none of them is able for PEG400 determination. DI provides quantitative information for BA (limit of detection, LOD, 1.6 gL(-1)) and BDA (LOD, 0.09 gL(-1)); HS-SPME only provides quantitative information for BDA (LOD, 0.05 gL(-1)). Taking into account that PEG400 and BA do not practically change with the use of the bath, that DI is very quick and simple and that no significant differences with spectrophotometric results have been found, DI is recommended for the monitoring of BA and BDA along the zinc bath life. This should be considered a technique for process analysis for these additives. PMID:22885048

Barriola, Ainara; Ostra, Miren; Ubide, Carlos

2012-07-28

283

A 'universal' B3LYP-based method for gas-phase molecular properties: bond dissociation enthalpy, ionization potential, electron and proton affinity and gas-phase acidity  

NASA Astrophysics Data System (ADS)

The paper describes a density functional theory methodology using the B3LYP functional, with small correction terms introduced for open shell doublet states and closed-shell anions. The procedure is based on a B3LYP/6-31G(d) geometry optimization and frequency determination, followed by (RO)B3LYP/6-311 + G(2d,2p) single point energy calculations. Using a correction term of +8.368 kJ mol-1 for (doublet) radicals and + 4.184 kJ mol-1 for (closed shell) anions, close agreement is obtained with experiment (i.e. within 10 kJ mol-1) for a series of molecular properties. These include bond dissociation enthalpies for X-H, where X = functional groups containing C, N, O, F, S, and X-Y, where X and Y are binary combinations of the same five heavy atoms plus Si and Cl, ionization potentials, electron and proton affinities, and gas-phase acidities. Using locally dense basis sets the approach can be extended to bond dissociation enthalpy calculations of large molecules with only a small increase in error. Using the same approach and popular solvation models allows a good starting point for reaction properties in solution. The approach is termed 'niversal' because by applying these corrections there is no need to change functionals and/or basis sets to obtain accurate results for different molecular properties, unlike some of the work reported previously.

Wright, J. S.; Rowley, C. N.; Chepelev, L. L.

284

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

SciTech Connect

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

Freiser, B.S.

1993-09-01

285

A fast, low perturbation ionization beam profile monitor based on a gas-jet curtain for the ultra low energy storage ring  

NASA Astrophysics Data System (ADS)

An ionization beam profile monitor relying on a supersonic gas-jet shaped into an extended, thin curtain is proposed for operation in an ultra high vacuum environment for very low perturbation on the accelerated beam, as requested for the in-ring profile monitoring at the Ultra low energy Storage Ring (USR) at the Facility for Low-energy Antiproton and Ion Research (FLAIR), in Darmstadt. In this paper, we describe the working principle of the monitor, as well as providing an analysis of sensitivity and resolution dependence on geometrical design and gas curtain thickness.

Putignano, M.; Kühnel, K.-U.; Schröter, C.-D.; Welsch, C. P.

2009-11-01

286

Rezonansnaya lazernaya ionizatsiya v gazovoj strue. Ehlementno-selektivnyj ionnyj istochnik dlya mass-separatora. (Resonance laser ionization in a gas jet. A element-selective ion source for a mass separator).  

National Technical Information Service (NTIS)

The isotropic shifts and hyperfine structures of atomic lines can be measured for short-lived radioactive isotopes by using resonance ionization spectroscopy (RIS) and the gas-jet technique. Products from nuclear reactions are stopped, transported by the ...

G. V. Myshinskij

1990-01-01

287

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

288

Deciphering the Ionized Gas Content in the Massive Star-forming Complex G75.78+0.34  

NASA Astrophysics Data System (ADS)

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 H2O and CH3OH maser emission, and the Owens Valley Radio Observatory and Submillimeter Array to study the millimeter continuum and recombination lines (H40? and H30?). We found radio continuum emission at all wavelengths, coming from three components: (1) a cometary ultracompact (UC) H II region with an electron density ~3.7 × 104 cm-3, excited by a B0 type star, and with no associated dust emission; (2) an almost unresolved UCH II region (EAST), located ~6'' to the east of the cometary UCH II region, with an electron density ~1.3 × 105 cm-3, and associated with a compact dust clump detected at millimeter and mid-infrared wavelengths; and (3) a compact source (CORE), located ~2'' to the southwest of the cometary arc, with a flux density increasing with frequency, and embedded in a dust condensation of 30 M ?. 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 ?m and the detected dust emission, suggest that the CORE source is a massive protostar driving a jet/outflow.

Sánchez-Monge, Álvaro; Kurtz, Stan; Palau, Aina; Estalella, Robert; Shepherd, Debra; Lizano, Susana; Franco, José; Garay, Guido

2013-04-01

289

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

290

Analytical calculation of the charge spectrum generated by ionizing particles in Resistive Plate Chambers at low gas gain  

NASA Astrophysics Data System (ADS)

In this article it is shown analytically that the charge spectrum generated by ionizing particles in Resistive Plate Chambers under Townsend avalanche conditions, that is, for sufficiently small avalanches not affected by space-charge and considering single-electron ionization clusters follows closely the statistical gamma distribution. This distribution describes well comparable simulation data taken from the literature, but seems to describe as well experimental data measured beyond these assumptions, rising some interpretation issues.

Fonte, P.

2013-04-01

291

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

SciTech Connect

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

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

1985-01-01

292

Deposition profile of Ti film inside a trench and its correlation with gas-phase ionization in high-pressure magnetron sputtering  

SciTech Connect

This article reports the relationship between the degree of ionization of Ti in the gas phase and the thickness profile of Ti film inside a trench in magnetron sputtering deposition. A conventional magnetron sputtering plasma source was used for depositing Ti films inside trenches formed on rf-biased SiO{sub 2} substrates. It was found that a high bottom coverage was obtained when a high gas pressure and a long distance between the target and the substrate were employed for the deposition. On the other hand, at a short distance between the target and the substrate, the bottom coverage was small and was almost independent of the gas pressure. The deposition profile was compared with the spatial distributions of Ti and Ti{sup +} densities measured by laser-induced fluorescence (LIF) imaging spectroscopy. The LIF results revealed that the density ratio of Ti{sup +} to Ti in the downstream region increased with the gas pressure up to 0.3, while in the upstream region, it was small (<0.05) and was roughly constant with the gas pressure. In the case with the enhanced density ratio of 0.3, the flux ratio of Ti{sup +} to Ti was estimated to be 4.4. Hence, it was concluded that, with a high gas pressure and a long distance between the target and substrate, the deposition profile with a high bottom coverage was obtained by accelerating Ti{sup +} toward the bottom of the trench. The high-pressure magnetron sputtering discharge is useful for enhancing the degree of ionization and the bottom coverage.

Nafarizal, N.; Takada, N.; Nakamura, K.; Sago, Y.; Sasaki, K. [Department of Electrical Engineering and Computer Science, Nagoya University, Nagoya 464-8603 (Japan); Department of Electrical Engineering, Chubu University, Kasugai, Aichi 487-8501 (Japan); Canon ANELVA Corporation, Fuchu, Tokyo 183-8508 (Japan); Department of Electrical Engineering and Computer Science, Nagoya University, Nagoya 464-8603 (Japan)

2006-11-15

293

Determination of PCBs in Rocky Flats Type IV waste sludge by gas chromatography/electron capture detection  

SciTech Connect

Type IV Rocky Flats Plant (RFP) radioactive sludge samples must be evaluated for polychlorinated biphenyl (PCB) content before disposal. The Type IV sludge consists of organic solvents, degreasers, cutting oils, and transuranic (TRU) waste mixed with calcium silicate (MicroCel E{reg_sign}) and Oil Dri{reg_sign} to form a grease or paste-like material. For laboratory studies a nonradioactive simulated Type IV RFP sludge was prepared having a composition similar to that expected from field samples. A simplified method was developed for extraction, purification and analysis of PCBs using samples of simulated sludge spiked with Aroclors 1254 and 1260 (reports provided to Argonne indicated Aroclors 1254 and 1260 as the most likely PCB contaminants in RFP sludge samples). The developed method was compared to the Environmental Protection Agency (EPA) accepted SW-846 method for analysis of PCBs (Method 8081). The accuracy and precision data were found to be similar for the two methods. The developed method was also tested with samples of simulated sludge spiked with Pu (in solid and solution forms). Reduction of radioactivity in final extract versus in the spike sample ranged from a factor of 10{sup 5} to 10{sup 7}.

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

1993-12-01

294

Gas-phase fragmentation study of novel synthetic 1,5-benzodiazepine derivatives using electrospray ionization tandem mass spectrometry.  

PubMed

The fragmentation patterns of a series of three novel synthesized 3-hydroxy-4-phenyl-tetrahydro-1,5-benzodiazepin-2-ones (1-3), possessing the same backbone structure, were investigated using electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS) techniques. A simple methodology, based on the use of ESI (positive ion mode) and by increasing the declustering potential in the atmospheric pressure/vacuum interface, collision-induced dissociation (CID), was used to enhance the formation of the fragment ions. In general, the novel synthetic 1,5-benzodiazepine derivatives afforded, in the gas phase, both protonated and sodiated molecules. This led to the confirmation of the molecular masses and chemical structures of the studied compounds. Exact accurate masses were measured using a high-resolution ESI-quadrupole orthogonal time-of-flight (QqToF)-MS/MS hybrid mass spectrometer instrument. The breakdown routes of the protonated molecules were rationalized by conducting low-energy collision CID-MS/MS analyses (product ion- and precursor ion scans) using a conventional quadrupole-hexapole-quadrupole (QhQ) tandem mass spectrometer. All the observed major fragmentations for the 1,5-benzodiazepines occurred in the saturated seven-membered ring containing the nitrogen atoms. These formed a multitude of product ions by different breakdown routes. All the major fragmentations involved cleavages of the N-1-C-2 and C-3-C-4 bonds. These occurred with concomitant eliminations of glyoxal, benzene and ethyl formate, forming the product ion at m/z 119, which was observed in all the studied compounds. In addition, an unique simultaneous CID-MS/MS fragmentation was noticed for the 1,5-benzodiazepines 1 and 3, which occurred by a pathway dictated by the substituent located on the N-1-position. It was evident that the aromatic ring portion of the 1,5-benzodiazepines was resistant to CID-MS/MS fragmentation. Re-confirmation of the various geneses of the product ions was achieved by conducting a series of precursor ion scans. ESI-MS and CID-MS/MS analyses have thus proven to be a specific and very sensitive method for the structural identification of these novel 1,5-benzodiazepine derivatives. PMID:18561279

Rida, Mohamed; El Meslouhi, Hamza; Es-Safi, Nour-Eddine; Essassi, El Mokhtar; Banoub, Joseph

2008-07-01

295

Capillary column gas chromatography, resonance enhanced multiphoton ionization, time-of-flight mass spectrometry, laser-induced fluorescence, flame ionization detection system for the determination of polynuclear aromatic compounds in complex mixtures  

SciTech Connect

A method is reached to fully characterize the polynuclear aromatic hydrocarbons (PAC) that have been deemed to be highly mutagenic or carcinogenic. A multidimensional, laser-based analytical instrument has been developed that, when utilized to the full extent of its capabilities could be the solution to this complex analytical problem. The overall technique is termed Capillary Column Gas Chromatography, Resonance Enhanced Multiphoton Ionization, Time-of-Flight Mass Spectrometry, Laser-induced Fluorescence, with parallel Flame Ionization Detection (CC/GC-REMPI-TOF/MS-LIF-FID). This system combines the selectivity of two complementary laser-based methods, REMPI and LIF, with an extremely powerful and proven analytical tool, GC/MS. The GC effluent passes through the ion source of a TOF/MS, where it is interrogated by a tunable ultraviolet laser beam. Thus, PAC and other absorbing species may be selectively excited and/or ionized in the presence of nonabsorbing components. All laser-analyte interaction products (actions, electrons, and photons) are simultaneously monitored utilizing the TOF/MS, a total electron current detector (TECD), and a LIF detector. The main advantage of this technique is that all analytically useful data for each absorbing chromatographic eluent may be collected on-the-fly. The simultaneous availability of this information simplifies the characterization task. The present absolute detection limits for several PAC have been determined to be low picogram range. Also, a linear dynamic range of approximately four orders of magnitude has been established for the TECD, indicating that this technique is both sensitive and quantitative. Further, the use of deuterated analogs, of selected PAC, as internal reference standards greatly assists in quantitation.

Dobson, R.L.M.

1986-01-01

296

The ionized and hot gas in M17 SW. SOFIA/GREAT THz observations of [C II] and 12CO J = 13-12  

NASA Astrophysics Data System (ADS)

Aims: With new THz maps that cover an area of ~3.3 × 2.1 pc2 we probe the spatial distribution and association of the ionized, neutral and molecular gas components in the M17 SW nebula. Methods: We used the dual band receiver GREAT on board the SOFIA airborne telescope to obtain a 5.'7 × 3.'7 map of the 12CO J = 13-12 transition and the [C II] 158 ?m fine-structure line in M17 SW and compare the spectroscopically resolved maps with corresponding ground-based data for low- and mid-J CO and [C I] emission. Results: For the first time SOFIA/GREAT allow us to compare velocity-resolved [C II] emission maps with molecular tracers. We see a large part of the [C II] emission, both spatially and in velocity, that is completely non-associated with the other tracers of photon-dominated regions (PDR). Only particular narrow channel maps of the velocity-resolved [C II] spectra show a correlation between the different gas components, which is not seen at all in the integrated intensity maps. These show different morphology in all lines but give hardly any information on the origin of the emission. The [C II] 158 ?m emission extends for more than 2 pc into the M17 SW molecular cloud and its line profile covers a broader velocity range than the 12CO J = 13-12 and [C I] emissions, which we interpret as several clumps and layers of ionized carbon gas within the telescope beam. The high-J12CO emission emerges from a dense region between the ionized and neutral carbon emissions, indicating the presence of high-density clumps that allow the fast formation of hot CO in the irradiated complex structure of M17 SW. The [C II] observations in the southern PDR cannot be explained with stratified or clumpy PDR models.

Pérez-Beaupuits, J. P.; Wiesemeyer, H.; Ossenkopf, V.; Stutzki, J.; Güsten, R.; Simon, R.; Hübers, H.-W.; Ricken, O.

2012-06-01

297

Trace level detection of chlorinated paraffins in biological and environmental samples, using gas chromatography/mass spectrometry with negative-ion chemical ionization.  

PubMed

A method is described for detection of chlorinated paraffins (CPs) in biological and environmental samples. Sample preparation includes sulfuric acid treatment followed by adsorption chromatography on alumina, which yields the CPs in one fraction that is almost free of interfering material. Using gas chromatography/mass spectrometry with negative-ion chemical ionization, the limit of detection is 5 ng (corresponding to the lower ppb range). CP levels of 30 ppm, 200 ppb, and 5 ppb were found in sewage sludge, human fat, and sediment, respectively. PMID:4019363

Schmid, P P; Müller, M D

298

Measurements of gas-phase inorganic and organic acids from biomass fires by negative-ion proton-transfer chemical-ionization mass spectrometry  

Microsoft Academic Search

Emissions from 34 laboratory biomass fires were investigated at the combustion facility of the U.S. Department of Agriculture Fire Sciences Laboratory in Missoula, Montana. Gas-phase organic and inorganic acids were quantified using negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS), open-path Fourier transform infrared spectroscopy (OP-FTIR), and proton-transfer-reaction mass spectrometry (PTR-MS). NI-PT-CIMS is a novel technique that measures the mass-to-charge ratio (m\\/z)

Patrick Veres; James M. Roberts; Ian R. Burling; Carsten Warneke; Joost de Gouw; Robert J. Yokelson

2010-01-01

299

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

300

A new measurement technique of peroxyacetyl nitrate at parts per trillion by volume levels: Gas chromatography\\/negative ion chemical ionization mass spectrometry  

Microsoft Academic Search

A new technique for measuring peroxyacetyl nitrate (PAN) at parts per trillion by volume (pptv) levels has been developed using gas chromatography with negative ion chemical ionization mass spectrometry (GC\\/NICI MS). Four fragment ions, CH3C(O)O- (mass-to-charge ratios (m\\/z)=59), NO3-(m\\/z=62), CH3C(O)OO-(m\\/z=75), and NO2-(m\\/z=46), were identified by NICI mass spectra. NO3-(m\\/z=62) was used in selected ion monitoring (SIM) mode among these fragment

Hiroshi Tanimoto; Jun Hirokawa; Yoshizumi Kajii; Hajime Akimoto

1999-01-01

301

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

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

2013-10-15

302

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

2013-09-11

303

Correlation between the charge of proteins in solution and in the gas phase investigated by protein charge ladders, capillary electrophoresis, and electrospray ionization mass spectrometry  

SciTech Connect

Charge ladders of bovine carbonic anhydrase II, hen egg-white lysozyme, and bovine pancreatic trypsin inhibitor, prepared by partial acetylation of primary amino groups on the surface of the protein, have been analyzed by capillary electrophoresis (CE) and on-line electrospray ionization mass spectrometry (ESIMS) using solution conditions that maintain the native structure of the protein. CE was used to separate the proteins that constitute the charge ladder into individual rungs-protein derivatives that have the same number of acetylated amino groups and approximately the same net charge in solution. ESI was used to produce ions i the gas phase of the proteins that constitute each rung of the charge ladder; the mass spectra of these ions were obtained and analyzed. The distributions in charge states observed in the gas phase for the groups of proteins comprising each rung of the charge ladders were narrow, consistent with the retention of a compact structure of the proteins in the gas phase, and substantially independent of the number of acetylated amino groups. The ions observed in the gas phase had surface charge densities in a relatively narrow range of {approximately}0.9--1.5 units of charge per 10{sup 3}{angstrom}{sup 2} of surface area (as estimated from crystallographic structures). These results demonstrate that the distribution of charge states for proteins produced in the gas phase by ESI do not necessarily reflect the net charge of the protein in solution or the number of amino groups on the protein.

Carbeck, J.D.; Gao, J.; Smith, R.D.; Whitesides, G.M. [Harvard Univ., Cambridge, MA (United States). Dept. of Chemistry and Chemical Biology; Severs, J.C.; Wu, Q. [Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Science Lab.

1998-12-17

304

Modeling of Ionization Physics with the PIC Code OSIRIS.  

National Technical Information Service (NTIS)

When considering intense particle or laser beams propagating in dense plasma or gas, ionization plays an important role. Impact ionization and tunnel ionization may create new plasma electrons, altering the physics of wakefield accelerators, causing blue ...

S. Deng F. Tsung S. Lee W. Lu W. B. Mori

2002-01-01

305

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

Microsoft Academic Search

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

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

2011-01-01

306

Modification of nitrogen Townsend ionization coefficient in a N2 laser with a weak corona preionization and high gas pressure using laser output power measurements  

NASA Astrophysics Data System (ADS)

Based on the reported experimental measurements on the output power in a transversely excited nitrogen laser with a weak corona preionization and rate equations, a simulation study was made to describe the laser output power behavior. For the study, we first made a literature survey for the appropriate E/p functional dependences of nitrogen molecules on drift velocity vd, and the Townsend ionization coefficient ?, to be applied for the laser operational characteristics of high gas pressures up to 1 atmosphere, and 20 < E/p < 1000 V cm-1 Torr-1. For the study when the corona UV preionization is applied, it was realized that it is necessary to modify the Townsend ionization coefficient to include the effect of the preionization for the laser system. This realization revealed that the Townsend coefficient upon utilizing the corona effect, (?/p)corona, can be viewed as a perturbation to be added to the (?/p)main due to the main gas discharge, where the total (?/p)t = (?/p)main + (?/p)corona was used for the calculation. We also introduced a single ?/p relation with A* and B* coefficients to explain the gas discharge due to both the main and corona discharges. The results of the two approaches are introduced and have been compared with each other. The present study indicates that laser optical measurements, by themselves, constitute a reliable approach for understanding the physical quantities that are involved during plasma formation in a gas discharge. Details of the approach will be presented in this paper.

Sarikhani, S.; Hariri, A.

2013-05-01

307

The effect of H2SO4 - amine clustering on chemical ionization mass spectrometry (CIMS) measurements of gas-phase sulfuric acid  

NASA Astrophysics Data System (ADS)

The state-of-the art method for measuring atmospheric gas-phase sulfuric acid is chemical ionization mass spectrometry (CIMS) based on nitrate reagent ions. We have assessed the possible effect of the sulfuric acid molecules clustering with base molecules on CIMS measurements using computational chemistry. From the computational data, three conclusions can be drawn. First, a significant fraction of the gas-phase sulfuric acid molecules are very likely clustered with amines if the amine concentration is around or above a few ppt. Second, some fraction of these acid-amine clusters may not be charged by the CIMS instrument, though the most reliable computational methods employed predict this fraction to be small; on the order of ten percent or less. Third, the amine molecules will evaporate practically immediately after charging, thus evading detection. These effects may need to be taken into account in the interpretation of atmospheric measurement data obtained using chemical ionization methods. The purpose of this study is not to criticize the CIMS method, but to help understand the implications of the measured results.

Kurtén, T.; Petäjä, T.; Smith, J.; Ortega, I. K.; Sipilä, M.; Junninen, H.; Ehn, M.; Vehkamäki, H.; Mauldin, L.; Worsnop, D. R.; Kulmala, M.

2011-03-01

308

[Multiresidue determination of organophosphorus pesticide residues in vegetables and fruit by gas chromatography-negative ion chemical ionization-mass spectrometry].  

PubMed

An analytical method of gas chromatography coupled with negative ion chemical ionization-mass spectrometry for simultaneous determination of nine organophosphorus pesticide residues in vegetables and fruit has been developed, and the negative ions structure and partition mechanism of the nine organophosphorus pesticides were interpreted. Meanwhile, the matrix effect for sample analysis was discussed, and matrix-matched calibration for quantification was introduced to reduce the matrix effect in this method. Pesticides were extracted from sample with ethyl acetate in an ultrasonic bath, then determined by gas chromatography-mass spectrometry operated in negative chemical ionization mode and quantified in selective ion monitoring mode, and ethion was used as an internal standard. The detection limits of the method were 0.12-1.0 microg/kg for the nine organophosphorus pesticides, and the relative coefficients were higher than 0.9993. A blank sample (tomato) was spiked at 100, 400, 800 microg/kg for each pesticide, and the recoveries were determined to be from 78% to 126% with relative standard deviations from 0.58% to 14.7% for the pesticides. PMID:16929836

Lin, Zhuguang; Fan, Yulan; Ma, Yu; Jin, Zhen; Tan, Jun; Chen, Meiyu; Chen, Zhaobin; Tu, Fengzhang; Liu, Yong

2006-05-01

309

Chemical Ionization  

Microsoft Academic Search

\\u000a Mass spectrometrists have ever been searching for ionization methods softer than EI, because molecular weight determination\\u000a is key for structure elucidation. Chemical ionization (CI) is the first of the so-called soft ionization methods we are going to discuss (cf. Fig. 1.2).

Jürgen H. Gross; Mass Spectrometry

310

Reactions of Ionized Methyl Benzoate with Methyl Isocyanide in the Gas Phase: Nucleophilic Aromatic Substitutions vs Hydrogen Migrations  

NASA Astrophysics Data System (ADS)

The chemistry leading to the competitive eliminations of H, CH3, and OCOCH3 from adducts of ionized methyl benzoate and neutral methyl isocyanide has been explored using density functional theory molecular orbital calculations. The energies of the various reactants and transition structures were estimated at the B3LYP/6-31+G(d,p) level of theory. Nucleophilic aromatic substitution is proposed to account for the H and OCOCH3 eliminations. The corresponding ?-complex intermediates, B1ipso and B1ortho, are stable species lying in deep energy wells situated 70 and 120 kJ/mol, respectively, below the reactants, ionized methyl benzoate and methyl isocyanide. The latter complex, B1ortho, may be also at the origin of a multistep rearrangement involving hydrogen migrations and methyl elimination from the original methoxy group of the benzoate moiety.

Bouchoux, Guy; Flammang, Robert; Winter, Julien De; Gerbaux, Pascal

2009-09-01

311

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

312

Capillary column gas chromatography, resonance enhanced multiphoton ionization, time-of-flight mass spectrometry laser-induced fluorescence, flame ionization detection system for the determination of polynuclear aromatic compounds in complex mixtures  

SciTech Connect

Of the thousands of chemical compounds that have been deemed mutagenic or carcinogenic, it is generally agreed that the polynuclear aromatic hydrocarbons (PAC) are among the most potent. Because of the wide range of potency of PAC, even among geometric isomers and substitutional derivatives, it is important to fully characterize these samples. This task is a formidable one, usually requiring elaborate sample clean-up and fractionation prior to analysis. A multidimensional, laser-based analytical instrument has been developed that, when utilized to the full extent of its capabilities, could be the solution to this complex analytical problem. The overall technique is termed Capillary Column Gas Chromatography, Resonance Enhanced Multiphoton Ionization, Time-Of-Flight Mass Spectrometry, Laser-induced Fluorescence, with parallel Flame Ionization Detection (CC/GC-REMPI-TOF/MS-LIF-FID). This system combines the selectivity and sensitivity of two complementary laser-based methods, REMPI and LIF, with an extremely powerful and proven analytical tool, GC/MS. The GC effluent passes through the ion source of a TOF/MS, where it is interrogated by a tunable ultraviolet laser beam. All laser-analyte interaction products (cations, electrons, and photons) are simultaneously monitored utilizing the TOF/MS, a total electron current detector (TECD), and a LIF detector. The simultaneous availability of this information simplifies the characterization task. The present absolute detection limits for several PAC have been determined to be in the low picogram range. Also, a linear dynamic range of approximately four orders of magnitude has been established for the TECD, indicating that this technique is both sensitive and quantitative. Further, the use of deuterated analogs, of selected PAC, as internal reference standards greatly assists in quantitation. 219 refs., 37 figs., 13 tabs.

Dobson, R.L.M.

1986-06-01

313

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

314

Performance evaluation of gas chromatography-atmospheric pressure chemical ionization-time-of-flight mass spectrometry for metabolic fingerprinting and profiling.  

PubMed

Gas chromatography-atmospheric-pressure chemical ionization-time-of-flight mass spectrometry (GC-APCI-TOFMS) was compared to GC × GC-electron ionization (EI)-TOFMS, GC-EI-TOFMS, GC-chemical ionization (CI)-quadrupole mass spectrometry (qMS), and GC-EI-qMS in terms of reproducibility, dynamic range, limit of detection, and quantification using a mix of 43 metabolites and 12 stable isotope-labeled standards. Lower limits of quantification for GC-APCI-TOFMS ranged between 0.06 and 7.81 ?M, and relative standard deviations for calibration replicates were between 0.4% and 8.7%. For all compounds and techniques, except in four cases, R(2) values were above 0.99. Regarding limits of quantification, GC-APCI-TOFMS was inferior to only GC × GC-EI-TOFMS, but outperformed all other techniques tested. GC-APCI-TOFMS was further applied to the metabolic fingerprinting of two Escherichia coli strains. Of 45 features that differed significantly (false discovery rate < 0.05) between the strains, 25 metabolites were identified through highly accurate and reproducible (?m ± SD below 5 mDa over m/z 190-722) mass measurements. Starting from the quasimolecular ion, six additional metabolites were identified that had not been found in a previous study using GC × GC-EI-TOFMS and an EI mass spectral library for identification purposes. Silylation adducts formed in the APCI source assisted the identification of unknown compounds, as their formation is structure-dependent and is not observed for compounds lacking a carboxylic group. PMID:21859117

Wachsmuth, Christian J; Almstetter, Martin F; Waldhier, Magdalena C; Gruber, Michael A; Nürnberger, Nadine; Oefner, Peter J; Dettmer, Katja

2011-09-09

315

Quantitative measurement of delta 9-tetrahydrocannabinol and two major metabolites in physiological specimens using capillary column gas chromatography negative ion chemical ionization mass spectrometry.  

PubMed

delta 9-Tetrahydrocannabinol and two of its metabolites, 11-hydroxy-delta 9-tetrahydrocannabinol and 11-nor-9-carboxy-delta 9-tetrahydrocannabinol, can be measured in a single 1-ml sample of blood, plasma, or urine by a new assay which combines a relatively rapid extraction procedure with capillary column gas chromatography and negative ion chemical ionization mass spectrometry. Deuterium-labeled analogs of each cannabinoid are added to the physiological specimen as internal standards. Two extracts are obtained from each sample: a neutral fraction containing delta 9-tetrahydrocannabinol and 11-hydroxy-delta 9-tetrahydrocannabinol, and an acid fraction containing 11-nor-9-carboxy-delta 9-tetrahydrocannabinol. The neutral fraction is derivatized by treatment with trifluoroacetic anhydride; the acid fraction is first treated with BF3-methanol followed by reaction with trifluoroacetic anhydride. Under electron-capture chemical ionization conditions the derivatized delta 9-tetrahydrocannabinol and 11-nor-9-carboxy-delta 9-tetrahydrocannabinol give abundant molecular anions ideally suited for selected ion monitoring. The negative ion chemical ionization spectrum of the HO-THC-trifluoroacetate shows no molecular anion. Consequently, quantitation of the hydroxy metabolite is achieved by monitoring a fragment ion formed by loss of CF3CO2 from its molecular anion. The limits of reliable measurement are judged to be 0.1 ng ml-1 for 11-nor-9-carboxy-delta 9-tetrahydrocannabinol, 0.2 ng ml-1 for delta 9-tetrahydrocannabinol and 0.5 ng ml-1 for 11-hydroxy-delta 9-tetrahydrocannabinol. Four examples are given of the application of the assay to the analysis of specimens of medico-legal importance. PMID:6305440

Foltz, R L; McGinnis, K M; Chinn, D M

1983-05-01

316

Extraction of explosives from soil followed by gas chromatography-mass spectrometry analysis with negative chemical ionization.  

PubMed

A new, simple and accurate method for extraction of explosives from soil was developed and validated. The method includes one hour gentle extraction of compounds from soil in acetonitrile:dichloromethane 50:50 at 30°C. Further analysis was made with GC-MS using cool on-column injection and negative chemical ionization. The method increased the recovery of the more volatile products, generated higher accuracy and was extensively time-saving compared to the conventional EPA (US Environmental Protection Agency) 8330 method. Applications are demonstrated on commercial reference materials. PMID:22226557

Holmgren, Erik; Ek, Stefan; Colmsjö, Anders

2011-12-13

317

Quantitative reproducibility of mass spectra in matrix-assisted laser desorption ionization and unraveling of the mechanism for gas-phase peptide ion formation.  

PubMed

In a previous study on matrix-assisted laser desorption ionization (MALDI) of peptides using ?-cyano-4-hydroxycinnamic acid (CHCA) as a matrix, we found that the patterns of single-shot spectra obtained under different experimental conditions became similar upon temperature selection. In this paper, we report that absolute ion abundances are also similar in temperature-selected MALDI spectra, even when laser fluence is varied. The result that has been obtained using CHCA and 2,5-dihydroxybenzoic acid as matrices is in disagreement with the hypothesis of laser-induced ionization of matrix as the mechanism for primary ion formation in MALDI. We also report that the total number of ions in such a spectrum is unaffected by the identity, concentration and number of analytes, i.e. it is the same as that in the spectrum of pure matrix. We propose that the generation of gas-phase ions in MALDI can be explained in terms of two thermal reactions, i.e. the autoprotolysis of matrix molecules and the matrix-to-analyte proton transfer, both of which are in quasi-equilibrium in the early matrix plume. PMID:23494784

Ahn, Sung Hee; Park, Kyung Man; Bae, Yong Jin; Kim, Myung Soo

2013-03-01

318

The simultaneous separation and determination of chloropropanols in soy sauce and other flavoring with gas chromatography-mass spectrometry in negative chemical and electron impact ionization modes.  

PubMed

Both gas chromatography-mass spectrometry in electron ionization (GC-MS-EI) and negative chemical ionization (GC-MS-NCI) modes are reported in this paper for the simultaneous determination of 1,3-dichloropropan-2-ol (1,3-DCP), 2,3-dichloropropan-1-ol (2,3-DCP), 3-chloropropane-1,2-diol (3-MCPD) and 2-chloropropane-1,3-diol (2-MCPD) in soy sauce and other flavoring. D(5)-3-MCPD (for 3-MCPD and 2-MCPD) and d(5)-1,3-DCP (for 1,3-DCP and 2,3-DCP) were used as the deuterium isotopic labelled internal standards. The feasibility of using heptafluorobutyric anhydride modified with triethylamine (HFBA-Et(3)N) as a new derivatization reagent to replace heptafluorobutyrylimidazole (HFBI) is proposed. Liquid/liquid extraction with hexane was introduced for high lipid content samples. A small survey was carried out of soy sauces (103 samples) and instant noodles (45 samples) and the applicability of GC-MS-NCI and GC-MS-EI was assessed in these different matrices. PMID:16449052

Xu, Xiaomin; Ren, Yiping; Wu, Pinggu; Han, Jianlong; Shen, Xianghong

2006-02-01

319

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

2011-04-19

320

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

PubMed

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

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

1980-10-01

321

Perfluoroalkyl ketones: novel derivatization products for the sensitive determination of fatty acids by gas chromatography/mass spectrometry in electron impact and negative chemical ionization modes.  

PubMed

Analytically useful pentafluoro ketone derivatives of fatty acids are described. The gas chromatographic/mass spectrometric characteristics of these new derivatives are compared with those of methyl, trimethylsilyl and pentafluorobenzyl esters. Pentafluoro ketones exhibit excellent chromatographic properties and significantly shorter chromatographic retention times than these other esters. The electron impact mass spectra of these new compounds show informative acylium ions, whose intensity decreases with the degree of unsaturation of the parent fatty acid. The formation of strong and informative fragment ions in negative chemical ionization (CH(4)) mass spectra of pentafluoro ketone derivatives allows the detection and the characterization (length of the chain and number of double bonds) of fatty acids at trace levels (femtomole), even in the case of polyunsaturated compounds. The scope and limitations of this new derivatization technique are also discussed. PMID:10844732

Aubert, C; Rontani, J F

2000-01-01

322

Warp of the ionized gas layer in the outer Galaxy, traced by Recombination Line Observations in both the First and Fourth Quadrants  

NASA Astrophysics Data System (ADS)

Results of H166? recombination line observations from the Outer Galaxy in both the Northern and Southern Galactic Plane, are reported. The Southern observations were made with the 30m antenna of the Instituto Argentino de Radioastronomia in Villa Elisa, Buenos Aires, Argentina and the Northern ones ( more sensitive, high quality observations, performed with an "state of the art" receiver) with the 43m antenna of the National Radio Astronomy Observatory, in Green Bank, West Virginia, USA. From the two sets of observations, we obtain evidence of the warp of the low density ionized gas layer, traced by the H166? emission in the outer MIlky Way, towards positive galactic latitudes in the Northern and towards negative latitudes in the Southern Galaxy. The warp of this tracer qualitatively agrees with that of the HI.

Azcarate, I. N.; Cersosimo, J. C.

2000-05-01

323

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

PubMed

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

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

2000-01-01

324

A study of the interplay between ionized gas and star clusters in the central region of NGC 5253 with 2D spectroscopy  

NASA Astrophysics Data System (ADS)

Context. Starbursts are one of the main contributors to the chemical enrichment of the interstellar medium. However, mechanisms governing the interaction between the recent star formation and the surrounding gas are not fully understood. Because of their a priori simplicity, the subgroup of H II galaxies constitute an ideal sample to study these mechanisms. Aims: A detailed 2D study of the central region of NGC 5253 has been performed to characterize the stellar and ionized gas structure as well as the extinction distribution, physical properties and kinematics of the ionized gas in the central ~210 pc × 130 pc. Methods: We utilized optical integral field spectroscopy (IFS) data obtained with FLAMES. Results: A detailed extinction map for the ionized gas in NGC 5253 shows that the largest extinction is associated with the prominent Giant H II region. There is an offset of ~0.5 arcsec between the peak of the optical continuum and the extinction peak in agreement with findings in the infrared. We found that stars suffer less extinction than gas by a factor of ~0.33. The [S ii]?6717/[S ii]?6731 map shows an electron density (Ne) gradient declining from the peak of emission in H? (790 cm-3) outwards, while the argon line ratio traces areas with Ne ~ 4200-6200 cm-3. The area polluted with extra nitrogen, as deduced from the excess [N ii]?6584/H?, extends up to distances of 3.3 farcsec (~60 pc) from the maximum pollution, which is offset by ~1.5 arcsec from the peak of continuum emission. Wolf-Rayet features are distributed in an irregular pattern over a larger area (~100 pc × 100 pc) and associated with young stellar clusters. We measured He+ abundances over most of the field of view and values of He++/H+ ? 0.0005 in localized areas which do not coincide, in general, with the areas presenting W-R emission or extra nitrogen. The line profiles are complex. Up to three emission components were needed to reproduce them. One of them, associated with the giant H II region, presents supersonic widths and [N ii]?6584 and [S ii]??6717,6731 emission lines shifted up to 40 km s-1 with respect to H?. Similarly, one of the narrow components presents offsets in the [N ii]?6584 line of ?20 km s-1. This is the first time that maps with such velocity offsets for a starburst galaxy have been presented. The observables in the giant H II region fit with a scenario where the two super stellar clusters (SSCs) produce an outflow that encounters the previously quiescent gas. The south-west part of the FLAMES IFU field is consistent with a more evolved stage where the star clusters have already cleared out their local environment. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (ESO Programme 078.B-0043).

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

2010-07-01

325

Quantitative Determination of Epinephrine and Norepinephrine in the Picogram Range by Flame Ionization Gas-Liquid Chromatography.  

National Technical Information Service (NTIS)

A gas-liquid chromatographic method has been developed using the hydrogen flame detector for the determination of epinephrine and norepinephrine in blood plasma, red blood cells, serum and urine. The chromatographic method presents several advantages over...

H. G. Lovelady H. A. Schwertner L. L. Foster

1974-01-01

326

Gas chromatography/mass spectrometric analysis of N,N-dialkylaminoethyl-2-methoxyethyl ethers as the decontamination markers of N,N-dialkylaminoethyl-2-chlorides for verification of the Chemical Weapons Convention.  

PubMed

The detection and identification of markers of scheduled chemicals plays an important role in verification analysis of Chemical Weapons Convention (CWC). This paper describes the gas chromatography electron ionization mass spectrometric (GC/EI-MS) analysis of N,N-dialkylaminoethyl-2-methoxyethyl ethers (DAEMEs), which are identified as characteristic degradation markers of N,N-dialkylaminoethyl-2-chlorides. N,N-dialkylaminoethyl-2-chlorides produced DAEMEs on reacting with the universally used decontamination solution (DS-2). DAEMEs were prepared by condensation of N,N-dialkylaminoethyl-2-chlorides with 2-methoxy ethanol the active ingredient of DS-2. Based on the GC/EI-MS analysis of DAEMEs the generalized fragmentation routes are proposed which rationalize most of the characteristic ions in EI-MS. PMID:17057284

Gupta, Arvinda K; Pardasani, Deepak; Kanaujia, Pankaj K; Tak, Vijay; Dubey, Devendra K

2006-01-01

327

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  

Microsoft Academic Search

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

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

2009-01-01

328

Nonequilibrium Photodissociation Regions: Ionization-Dissociation Fronts  

Microsoft Academic Search

We discuss the theory of coupled ionization-dissociation fronts produced when molecular clouds are exposed to lambda < 1110 Å radiation from hot stars. A steady, composite structure is developed, which generally includes an ionized outflow away from the cloud, an ionization front, a layer of photodissociated gas, a photodissociation front, and a shock wave preceding the photodissociation front. We show

Frank Bertoldi; B. T. Draine

1996-01-01

329

Alkali metal ionization detector  

DOEpatents

Variations in the conventional filament and collector electrodes of an alkali metal ionization detector, including the substitution of helical electrode configurations for either the conventional wire filament or flat plate collector; or, the substitution of a plurality of discrete filament electrodes providing an in situ capability for transferring from an operationally defective filament electrode to a previously unused filament electrode without removing the alkali metal ionization detector from the monitored environment. In particular, the helical collector arrangement which is coaxially disposed about the filament electrode, i.e. the thermal ionizer, provides an improved collection of positive ions developed by the filament electrode. The helical filament design, on the other hand, provides the advantage of an increased surface area for ionization of alkali metal-bearing species in a monitored gas environment as well as providing a relatively strong electric field for collecting the ions at the collector electrode about which the helical filament electrode is coaxially positioned. Alternatively, both the filament and collector electrodes can be helical. Furthermore, the operation of the conventional alkali metal ionization detector as a leak detector can be simplified as to cost and complexity, by operating the detector at a reduced collector potential while maintaining the sensitivity of the alkali metal ionization detector adequate for the relatively low concentration of alkali vapor and aerosol typically encountered in leak detection applications.

Bauerle, James E. (Plum Borough, PA); Reed, William H. (Monroeville, PA); Berkey, Edgar (Murrysville, PA)

1978-01-01

330

Plasma Production via Field Ionization  

SciTech Connect

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.; Hogan, M.J.; Iverson, R.; Krejcik, P.; Siemann, R.; Walz, D.R.; /SLAC; Clayton, C.E.; Huang, C.; Johnson, D.K.; Joshi, C.; Lu, W.; Marsh, K.A.; Mori, W.; Zhou, M.; /UCLA; Deng, S.; Katsouleas, T.; Muggli, P.; Oz, E.; /Southern California U.

2007-01-02

331

Ionizing radiation  

Technology Transfer Automated Retrieval System (TEKTRAN)

This chapter gives a comprehensive review on ionizing irradiation of fresh fruits and vegetables. Topics include principles of ionizing radiation, its effects on pathogenic and spoilage microorganisms, shelf-life, sensory quality, nutritional and phytochemical composition, as well as physiologic and...

332

The extended ionized gas around the z = 2.44 radio galaxy MRC 0406-244: the nature of the superbubbles and the optical line brightness asymmetries  

NASA Astrophysics Data System (ADS)

In this Letter, we investigate the nature of the dramatic `superbubble' emission structures associated with the z = 2.44 radio galaxy MRC 0406-244, using rest-frame optical spectroscopy and an archival Hubble Space Telescope (HST) Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) image. Based on the optical line ratios and the HST morphology, we conclude that the gas in the superbubbles is photoionized by the obscured active nucleus. We suggest that this type of structure might be related to the spatially extended HI absorbers that are detected in front of many high-z radio galaxies. We also suggest that we may be witnessing the destruction of the extended emission-line region. In addition, we investigate the nature of the emission-line brightness asymmetry in MRC 0406-244: we conclude that this asymmetry is due to an asymmetry in the mass of ionized gas, confirming the scenario of McCarthy, van Breugel & Kapahi, and leading us to reject that of Gopal-Krishna & Wiita.

Humphrey, A.; Iwamuro, F.; Villar-Martín, M.; Binette, L.; Sung, E. C.

2009-10-01

333

Studies on steroids. CCXXXVIII. Determination of bile acids in liver tissue by gas chromatography-mass spectrometry with negative ion chemical ionization detection.  

PubMed

A method for the determination of bile acids in 2-10 mg of human liver tissue by gas chromatography (GC) in combination with negative ion chemical ionization (NICI) mass spectrometry is described. Unconjugated, glycine- and taurine-conjugated bile acids labelled with 18O and 2H were used as internal standards. The preparation of these compounds was attained by the exchange reaction of the carbonyl group with H218O, followed by metal hydride reduction. Bile acids in solubilized liver tissue were extracted with a Sep-Pak C18 cartridge, separated into the unconjugated, glycine- and taurine-conjugated fractions by ion-exchange chromatography on piperidinohydroxypropyl-Sephadex LH-20 and then derivatized to the pentafluorobenzyl ester-dimethylethylsilyl ethers. Subsequent resolution of each fraction into lithocholate, deoxycholate, chenodeoxycholate, ursodeoxycholate and cholate was attained by GC on a cross-linked 5% phenylmethyl silicone fused-silica capillary column where bile acids were monitored with a characteristic carboxylate anion [M - 181]-in the NICI mode using isobutane as a reagent gas. The newly developed method was applied to the quantitation of bile acids in liver tissue with satisfactory sensitivity and reliability. PMID:3243844

Goto, J; Miura, H; Inada, M; Nambara, T; Nagakura, T; Suzuki, H

1988-10-28

334

Gas-phase fragmentation study of biotin reagents using electrospray ionization tandem mass spectrometry on a quadrupole orthogonal time-of-flight hybrid instrument.  

PubMed

In this study, we evaluated, by electrospray ionization mass spectrometry (ESI-MS) and collision-induced dissociation tandem mass spectrometry (CID-MS/MS) using a quadrupole orthogonal time-of-flight (QqToF)-MS/MS hybrid instrument, the gas-phase fragmentations of some commercially available biotinyl reagents. The biotin reagents used were: psoralen-BPE 1, p-diazobenzoyl biocytin (DBB) 2, photoreactive biotin 3, biotinyl-hexaethyleneglycol dimer 4, and the sulfo-SBED 5. The results showed that, during ESI-MS and CID-MS/MS analyses, the biotin reagents followed a similar gas-phase fragmentation pattern and the cleavages usually occurred at either end of the spacer arm of the biotin reagents. In general we have observed that the CID-MS/MS fragmentation routes of the five precursor protonated molecules obtained from the biotin linkers 1-5 afforded a series of product ions formed essentially by similar routes. The genesis and the structural identities of all the product ions obtained from the biotin linkers 1-5 have been assigned. All the exact mass assignments of the protonated molecules and the product ions were verified by conducting separate CID-MS/MS analysis of the deuterium-labelled precursor ions. PMID:19496066

Sioud, Salim; Genestie, Benoit; Jahouh, Farid; Martin, Patrick; Banoub, Joseph

2009-07-01

335

Simultaneous Determination of Miconazole Nitrate and Metronidazole in Different Pharmaceutical Dosage Forms by Gas Chromatography and Flame Ionization Detector (GC-FID)  

PubMed Central

A simple, rapid and precise gas chromatographic method has been developed for the simultaneous determination of miconazole nitrate (MIZ) and metronidazole (MNZ) in tablets and ovules, using a capillary column AE.SE-54 (15 m × 0.53 mm, i.d.) and nitrogen as a carrier gas at a flow rate of 9 mL min?1. The oven temperature was programmed at 140°C for 3 min, with a rise of 40°C min?1 up to 180°C (held for 2 min) and then increased to a final temperature of 250°C. The injector and detector port temperatures were maintained at 260°C. Detection was carried out using flame ionization detector. Results of assay and recovery studies were statistically evaluated for its accuracy and precision. The retention times were about 3.50 and 12.90 min for MNZ and MIZ, respectively. Linearity ranges were 50.0–6030.0 and 62.5–2000.0 ?g mL?1 for MNZ and MIZ, with limit of detection values of 2.5 and 3.1 ?g mL?1, respectively. Correlation coefficients (R2) of the regression equations were greater than 0.999 in all cases. No interference from any components of pharmaceutical dosage forms or degradation products was observed. According to the validation results, the proposed method was found to be specific, accurate, precise and could be applied to the simultaneous quantitative analysis of MIZ and MNZ in tablets and ovules.

Ashour, Safwan; Kattan, Nuha

2010-01-01

336

Determination of misoprostol free acid in human breast milk and serum by gas chromatography/negative ion chemical ionization tandem mass spectrometry.  

PubMed

To study an expected transition of misoprostol from human blood into breast milk, a novel method for the determination of its active metabolite misoprostol acid (MPA) was developed. MPA was determined in serum and breast milk samples by an isotope dilution assay using gas chromatography/negative ion chemical ionization tandem mass spectrometry (GC/NICI-MS/MS). After addition of (15S)-15-methylprostaglandin E(2) (15-methyl-PGE(2)) as an internal standard, MPA was extracted from both matrices using a reversed-phase cartridge. The prostanoids were derivatized with O-2,3,4,5,6-pentafluorobenzylhydroxylamine hydrochloride (PFBHA) and 2,3,4,5,6-pentafluorobenzyl bromide (PFBB) to the pentafluorobenzyl oxime (PFBO)-pentafluorobenzyl ester (PFB) derivatives. The sample was subjected to thin-layer chromatography with ethyl acetate-hexane (1 : 1 (v/v)) as the developing solvent. The corresponding zone was extracted. After derivatization to the trimethylsilyl ether, MPA was determined by GC/NICI-MS/MS using the [molecule (M) - pentafluorobenzyl (PFB)](-) ([P](-)) ions as precursor in the negative ion chemical ionization mode. The product ions used for quantification were [P - 2TMSOH - C(6)F(5)CH(2)OH](-) (MPA) and [P - 2TMSOH - C(6)F(5)CH(2)OH - CO(2)](-)(15-methyl-PGE(2)), respectively. The limit of quantification for MPA was approximately 1 pg ml(-1) in breast milk and serum samples. The correlation coefficients of the calibration curves for MPA were r > 0.997 in the 0.5-2000 pg ml(-1) range for both tested matrices. PMID:12271435

Watzer, Bernhard; Seyberth, Hannsjörg W; Schweer, Horst

2002-09-01

337

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

PubMed

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

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

2013-01-28

338

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

339

Comprehensive 2-dimensional gas chromatography fast quadrupole mass spectrometry (GC × GC-qMS) for urinary steroid profiling: mass spectral characteristics with chemical ionization.  

PubMed

Comprehensive 2-dimensional gas chromatography (GC × GC), coupled to either a time of flight mass spectrometry (TOF-MS) or a fast scanning quadrupole MS (qMS) has greatly increased the peak capacity and separation space compared to conventional GC-MS. However, commercial GC × GC-TOFMS systems are not equipped with chemical ionization (CI) and do not provide dominant molecular ions or enable single ion monitoring for maximal sensitivity. A GC × GC-qMS in mass scanning mode was investigated with electron ionization (EI) and positive CI (PCI), using CH(4) and NH(3) as reagent gases. Compared to EI, PCI-NH(3) produced more abundant molecular ions and high mass, structure-specific ions for steroid acetates. Chromatography in two dimensions was optimized with a mixture of 12 endogenous and 3 standard acetylated steroids (SM15-AC) relevant to doping control. Eleven endogenous target steroid acetates were identified in normal urine based on their two retention times, and EI and PCI-NH(3) mass spectra; nine of these endogenous target steroid acetates were identified in congenital adrenal hyperplasia (CAH) patients. The difference between the urinary steroids profiles of normal individuals and those from CAH patients can easily be visually distinguished by their GC × GC-qMS chromatograms. We focus here on the comparison and interpretation of the various mass spectra of the targeted endogenous steroids. PCI-NH(3) mass spectra were most useful for unambiguous molecular weight determination and for establishing the number of -OH by the losses of one or more acetate groups. We conclude that PCI-NH(3) with GC × GC-qMS provides improved peak capacity and pseudomolecular ions with structural specificity. PMID:22147458

Zhang, Ying; Tobias, Herbert J; Auchus, Richard J; Brenna, J Thomas

2011-12-06

340

Warp or lag? The ionized and neutral hydrogen gas in the edge-on dwarf galaxy UGC 1281  

NASA Astrophysics Data System (ADS)

The properties of gas in the haloes of galaxies constrain global models of the interstellar medium. Kinematical information is of particular interest since it is a clue to the origin of the gas. Until now mostly massive galaxies have been investigated for their halo properties. Here we report on deep H I and H? observations of the edge-on dwarf galaxy UGC 1281 in order to determine the existence of extraplanar gas and the kinematics of this galaxy. This is the first time a dwarf galaxy is investigated for its gaseous halo characteristics. We have obtained H? integral field spectroscopy using PPAK at Calar Alto and deep H I observations with the Westerbork Synthesis Radio Telescope (WSRT) of this edge-on dwarf galaxy. These observations are compared to 3D models in order to determine the distribution of H I in the galaxy. We find that UGC 1281 has H? emission up to 25 arcsec (655 pc) in projection above the plane and in general a low H? flux. Compared to other dwarf galaxies UGC 1281 is a normal dwarf galaxy with a slowly rising rotation curve that flattens off at 60 km s-1 and a central depression in its H I distribution. Its H I extends 70 arcsec (1.8 kpc) in projection from the plane. This gas can be explained by either a warp partially in the line-of-sight or a purely edge-on warp with rotational velocities that decline with a vertical gradient of 10.6 ± 3.7 km s-1 kpc-1. The line-of-sight warp model is the preferred model as it is conceptually simpler. In either model the warp starts well within the optical radius.

Kamphuis, P.; Peletier, R. F.; van der Kruit, P. C.; Heald, G. H.

2011-07-01

341

The influence of cisplatin on the gas-phase dissociation of oligonucleotides studied by electrospray ionization tandem mass spectrometry  

Microsoft Academic Search

cis-Diamminedichloroplatinum(II) (cisplatin, DDP) is a cornerstone of anticancer therapy and has become one of the most widely\\u000a used drugs for the treatment of various epithelial malignancies. The cytotoxicity of cisplatin is mainly based upon its affinity\\u000a to adjacent guanines in nucleic acids, resulting in the formation of 1,2-intrastrand adducts. In this study the gas-phase\\u000a dissociation of DNA- and RNA-cisplatin adducts

Adrien Nyakas; Michael Eymann; Stefan Schürch

2009-01-01

342

Comparison of a gas chromatography-optical fibre (GC-OF) detector with a gas chromatography-flame ionization detector (GC-FID) for determination of alcoholic compounds in industrial atmospheres.  

PubMed

An analytical methodology based on an optical fibre detector coupled to gas chromatograph has been developed for the speciation of some volatile alcoholic compounds. This methodology combines the separation capability of gas chromatography with an optical fibre detector made of an optical fibre sensitized with a thin polymeric film of poly[methyl(3,3,3-trifluoropropyl)siloxane] (PMTFPS). The response of the detector has been characterized at 650 nm for nine different alcohols (allyl alcohol, n-propyl alcohol, sec-butyl alcohol, isobutyl alcohol, n-butyl alcohol, isoamyl alcohol, methyl isobutyl carbinol, cyclohexanol and diacetone alcohol). An alternative method based on gas chromatography-flame ionization detector (GC-FID) was also used in order to evaluated the performance and compare the analytical results with the proposed method. The time of analysis, the analytical error and the analytical performance were similar for both methods. However, the analytical apparatus based on the GC-OF detector is much less expensive than the GC-FID and show high accuracy and suitability for actual monitoring on indoor atmospheres. PMID:18585296

Silva, Lurdes I B; Rocha-Santos, Teresa A P; Duarte, A C

2008-03-21

343

Novel Analytical Methods for Flame Retardants and Plasticizers Based on Gas Chromatography, Comprehensive Two-Dimensional Gas Chromatography, and Direct Probe Coupled to Atmospheric Pressure Chemical Ionization-High Resolution Time-of-Flight-Mass Spectrometry.  

PubMed

In this study, we assess the applicability of different analytical techniques, namely, direct probe (DP), gas chromatography (GC), and comprehensive two-dimensional gas chromatography (GC × GC) coupled to atmospheric pressure chemical ionization (APCI) with a high resolution (HR)-time-of-flight (TOF)-mass spectrometry (MS) for the analysis of flame retardants and plasticizers in electronic waste and car interiors. APCI-HRTOFMS is a combination scarcely exploited yet with GC or with a direct probe for screening purposes and to the best of our knowledge, never with GC × GC to provide comprehensive information. Because of the increasing number of flame retardants and questions about their environmental fate, there is a need for the development of wider target and untargeted screening techniques to assess human exposure to these compounds. With the use of the APCI source, we took the advantage of using a soft ionization technique that provides mainly molecular ions, in addition to the accuracy of HRMS for identification. The direct probe provided a very easy and inexpensive method for the identification of flame retardants without any sample preparation. This technique seems extremely useful for the screening of solid materials such as electrical devices, electronics and other waste. GC-APCI-HRTOF-MS appeared to be more sensitive compared to liquid chromatography (LC)-APCI/atmospheric pressure photoionization (APPI)-HRTOF-MS for a wider range of flame retardants with absolute detection limits in the range of 0.5-25 pg. A variety of tri- to decabromodiphenyl ethers, phosphorus flame retardants and new flame retardants were found in the samples at levels from microgram per gram to milligram per gram levels. PMID:24016281

Ballesteros-Gómez, Ana; de Boer, Jacob; Leonards, Pim E G

2013-09-24

344

On possible structures of transverse ionizing shock waves  

Microsoft Academic Search

The possible structures of ionizing shock waves propagating in gases across the magnetic field are investigated taking account of both ionization kinetics and the non-isothermality of the plasma which is formed within the shock front. It is shown that a definite factor in shaping the structure of the transverse ionizing shock wave is photo-ionization of the neutral gas across the

M A Liberman; A L Velikovich

1978-01-01

345

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

346

Quantitation of the tetrachloroethylene metabolite N-acetyl-S-(trichlorovinyl)cysteine in rat urine via negative ion chemical ionization gas chromatography/tandem mass spectrometry.  

PubMed

A sensitive and selective negative ion chemical ionization gas chromatographic/tandem mass spectrometric (NICI GC/MS/MS) method was developed for the determination of the tetrachlorethylene metabolite, N-acetyl-S-(trichlorovinyl)cysteine (TCVC), in rat urine. Urine samples were fortified with a 13C,D2-analog of TCVC, acidified and extracted with ethyl acetate. The extract were derivatized with methanolic HCl, and the resulting methyl esters analyzed via NICI GC/MS/MS. Detection of the TCVC analogs was performed by monitoring the Cl- product ion of M-Cl2C2HS-. The limit of detection for TCVC by this method was estimated to be 0.1 ng ml-1 urine (3 x noise). The quantitation limit was determined to be 0.3 ng TCVC per milliliter of urine. The method was found to be linear for TCVC concentrations from 0.3 to 104 ng ml-1 urine. Relative recovery of TCVC from urine ranged from 95.4% to 108.5%. Additional data are given for GC/MS and GC/MS/MS analysis of the pentafluoro-benzyl ester derivative of TCVC. Data are also presented for the isolation and analysis of this compound obtained from dosed rats. PMID:7811758

Bartels, M J

1994-11-01

347

Environmental PAH analysis by gas chromatography-atmospheric pressure laser ionization-time-of-flight-mass spectrometry (GC-APLI-MS).  

PubMed

The application of polycyclic aromatic hydrocarbon (PAH) analysis by gas chromatography coupled with atmospheric pressure laser ionization and mass spectrometry (GC-APLI-MS) to environmental samples was investigated in the study. The limit of detection for 40 PAH in a standard mixture was 5-100 fg, demonstrating GC-APLI-MS to be a highly sensitive technique and more sensitive by a factor of 100-3,500 compared to GC-MS. Acenaphthylene and cyclopenta[cd]pyrene were not detectable <2,500 fg per injection. To make use of this very high PAH sensitivity, the technique was applied to samples of environmental interest with limited available sample amounts such as particulate matter (PM), soot and a sample from a bioaccumulation test with Lumbriculus variegatus. First, special sample preparation was necessary and ultrasonic extraction proved to be suitable, if a thorough clean-up was performed and plastic materials avoided. By GC-APLI-MS and GC-MS, 224 and 28 single PAH compounds were detected in PM, about 1,000 and 15 in birch soot, and 9 and 2 in worm tissue, respectively, revealing the enormous potential of the method. The selectivity of GC-APLI-MS was shown for a crude oil where >2,200 PAH were detected without any sample preparation. PMID:23852149

Stader, Christian; Beer, Fokko Tjark; Achten, Christine

2013-07-14

348

Dissociation of gas-phase dimeric complexes of lactic acid and transition-metal ions formed under electrospray ionization conditions; the role of reduction of the metal ion.  

PubMed

Dimeric complex ions of the type [M(A-H)A]+, where M=metal ion (Co, Ni, Cu, and Zn) and A=ligand (lactic acid, methyl lactate or ethyl lactate), were generated in the gas phase under electrospray ionization conditions. The collision-induced dissociation spectra of [M(A-H)A]+ ions were recorded to study the behaviour of ligand and metal ions in decomposition of these dimeric complex ions. Based on the fragmentation pathways observed for complex ions of lactic acid, it is found that both the carboxylic and hydroxyl groups of lactic acid are involved in the complex formation following displacement of a proton by the metal ion. The dimeric complex ions of Co, Ni, and Zn dissociated to yield similar types of ions, whereas that of Cu behaved differently. The dissociations of Co-, Ni-, and Zn-bound dimeric complexes involved losses of neutral molecules while keeping the oxidation state of the metal ion unchanged. However, elimination of radicals is found in the dissociation of dimeric complex ions of Cu, and the oxidation state of copper is reduced from Cu(II) to Cu(I) in the resulting fragment ions. The deprotonated ligand is involved in the fragmentation pathway of Cu complexes, whereas it is intact in other complexes. The oxidation state of the metal ion, nature of the ligand, and site of attachment to the metal ion are found to control the dissociation of these dimeric complex ions. PMID:15593065

Kumar, M Ravi; Prabhakar, S; Kumar, M Kiran; Reddy, T Jagadeshwar; Vairamani, M

2005-01-01

349

Determination of Mercury in Real Water Samples Using in situ Derivatization Followed by Sol-Gel-Solid-Phase Microextraction with Gas Chromatography-Flame Ionization Detection.  

PubMed

An in situ derivatization and solid-phase microextraction (SPME) method based on sol-gel technology coupled with gas chromatography-flame ionization detection was proposed for the determination of mercury [Hg(??)] at ultra-trace levels in water samples.The analytical procedure involves aqueous-phase derivatization of Hg(??) with phenylboronic acid in a sample vial and subsequent extraction with a sol-gel fiber coating. In this study, poly(ethylene glycol), modified with a coating fiber of multi-walled carbon nanotubes was used for the determination of mercury. The pH of the feed solution was kept at 5 with acetic acid-sodium acetate buffer solution. The optimized conditions are as follows: derivatization time, 10 min; extraction time, 60 min; extraction temperature, 40°C; stirring rate, 1,000 rpm; sample volume, 5 mL. Under the optimal conditions, a detection limit of the method [signal-to-noise ratio (S/N) = 3] were obtained at 0.001 ng/mL and a limit of quantification (S/N = 10) were obtained at 0.005 ng/mL. Also, the relative standard deviations were obtained for one fiber (repeatability) (n = 5) and between fibers or batch to batch (n = 3) (reproducibility). The developed method was successfully applied to real water samples. PMID:23277157

Sarafraz-Yazdi, Ali; Fatehyan, Elham; Amiri, Amirhassan

2012-12-30

350

Determination of free and glucuronide conjugated 20-hydroxyarachidonic acid (20-HETE) in urine by gas chromatography/negative ion chemical ionization mass spectrometry.  

PubMed

20-Hydroxy-arachidonic acid (20-HETE) was determined in urine by an isotope dilution assay using gas chromatography/mass spectrometry (GC/MS). After addition of 18O2-internal standard, 20-HETE was extracted from urine with hexane either directly or after treatment with glucuronidase. 20-HETE was derivatized to the pentafluorobenzylester and the sample was applied to thin layer chromatography with iso-octane/iso-propanol 9:1 (v/v) as the developing solvent. The corresponding zone was extracted and 20-HETE was hydrogenated. After derivatization to the trimethylsilylether, 20-HETE was determined by GC/MS using the [M-pentafluorobenzyl]- -ion in the negative ion chemical ionization mode. Excretion rates of free and glucuronide conjugated 20-HETE was determined in healthy children and in children with hyperprostaglandin-E-syndrome/antenatal Bartter syndrome (HPS/aBS) with or without indomethacin treatment. Compared to the controls, the HPS/aBS children showed higher excretion rates of 20-HETE, which were suppressed to normal values under indomethacin medication. Free and glucuronide conjugated 20-HETE do not correlate with PGE2 excluding any participation in HPS/aBS. PMID:10841040

Watzer, B; Reinalter, S; Seyberth, H W; Schweer, H

2000-03-01

351

Lactone enol cation-radicals: gas-phase generation, structure, energetics, and reactivity of the ionized enol of butane-4-lactone.  

PubMed

The cation-radical of 2-hydroxyoxol-2-ene (1(+*)) represents the first lactone enol ion whose structure and gas-phase ion chemistry have been studied by experiment and theory. Ion 1(+*) was generated by the McLafferty rearrangement in ionized 2-acetylbutane-4-lactone and characterized by accurate mass measurements, isotope labeling, metastable ion and collisionally activated dissociation (CAD) spectra. Metastable 1(+*) undergoes competitive losses of H-4 and CO that show interesting deuterium and (13)C isotope effects. The elimination of CO from metastable 1(+*) shows a bimodal distribution of kinetic energy release and produces (*)CH(2)CH(2)CHdbond;OH(+) (14(+*)) and CH(3)CHdbond;CHOH(+*) (15(+*)) in ratios which are subject to deuterium isotope effects. Ab initio calculations at the G2(MP2) level of theory show that 1(+*) is 105 kJ mol(-1) more stable than its oxo form, [butane-4-lactone](+*)(2(+*)). The elimination of CO from 1(+*) involves multiple isomerizations by hydrogen migrations and proceeds through ion-molecule complexes of CO with 14(+*) and 15(+*). In addition, CO is calculated to catalyze an exothermic isomerization 14(+*) --> 15(+*) in the ion-molecule complexes. Multiple consecutive hydrogen migrations in metastable 1(+*), as modeled by RRKM calculations on the G2(MP2) potential energy surface, explain the unusual deuterium kinetic isotope effects on the CO elimination. PMID:12203676

Turecek, Frantisek; Vivekananda, Shetty; Sadílek, Martin; Polásek, Miroslav

2002-08-01

352

Trace analysis of impurities in bulk gases by gas chromatography-pulsed discharge helium ionization detection with "heart-cutting" technique.  

PubMed

A method has been developed for the detection of low-nL/L-level impurities in bulk gases such as H(2), O(2), Ar, N(2), He, methane, ethylene and propylene, respectively. The solution presented here is based upon gas chromatography-pulsed discharge helium ionization detection (GC-PDHID) coupled with three two-position valves, one two-way solenoid valve and four packed columns. During the operation, the moisture and heavy compounds are first back-flushed via a pre-column. Then the trace impurities (except CO(2) which is diverted to a separate analytical column for separation and detection) together with the matrix enter onto a main column, followed by the heart-cut of the impurities onto a longer analytical column for complete separation. Finally the detection is performed by PDHID. This method has been applied to different bulk gases and the applicability of detecting impurities in H(2), Ar, and N(2) are herewith demonstrated. As an example, the resulting detection limit of 100 nL/L and a dynamic range of 100-1000 nL/L have been obtained using an Ar sample containing methane. PMID:17850804

Weijun, Yao

2007-08-26

353

Determination of amantadine in biological fluids using simultaneous derivatization and dispersive liquid-liquid microextraction followed by gas chromatography-flame ionization detection.  

PubMed

A one-step derivatization and microextraction technique for the determination of amantadine in the human plasma and urine samples is presented. An appropriate mixture of methanol (disperser solvent), 1,2-dibromoethane (extraction solvent), and butylchloroformate (derivatization agent) is rapidly injected into samples. After centrifuging, the sedimented phase is analyzed by gas chromatography-flame ionization detection (GC-FID). The kind of extraction and disperser solvents and their volumes, amount of derivatization agent and reaction/extraction time which are effective in derivatization/dispersive liquid-liquid microextraction (DLLME) procedure are optimized. Under the optimal conditions, the enrichment factor (EF) of the target analyte was obtained to be 408 and 420, and limit of detection (LOD) 4.2 and 2.7ngmL(-1), in plasma and urine respectively. The linear range is 14-5000 and 8.7-5000ng/mL for plasma and urine, respectively (squared correlation coefficient?0.990). The relative recoveries obtained for the spiked plasma and urine samples are between 72% and 93%. Moreover, the inter- and intra-day precisions are acceptable at all spiked concentrations (relative standard deviation <7%). Finally the method was successfully applied to determine amantadine in biological samples. PMID:24157523

Farajzadeh, Mir Ali; Nouri, Nina; Alizadeh Nabil, Ali Akbar

2013-10-03

354

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

2012-10-01

355

Ionization detection system for aerosols  

DOEpatents

This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system utilizes a measuring ionization chamber which is modified to minimize false alarms and reductions in sensitivity resulting from changes in ambient temperature. In the preferred form of the modification, an annular radiation shield is mounted about the usual radiation source provided to effect ionization in the measuring chamber. The shield is supported by a bimetallic strip which flexes in response to changes in ambient temperature, moving the shield relative to the source so as to vary the radiative area of the source in a manner offsetting temperature-induced variations in the sensitivity of the chamber.

Jacobs, Martin E. (Chillicothe, OH)

1977-01-01

356

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

PubMed

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 Ar(16+) ions, respectively, within a high density (10(20)?cm(-3) atomic density) Ar plasma. This plasma was produced by irradiating a 2 mm wide clustering Ar gas jet with an ultrahigh intensity (10(19)?W/cm(2), 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. PMID:21034054

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

2010-10-01

357

Mapping the ionization state of laser-irradiated Ar gas jets with multiwavelength 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_equal}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 ultrahigh intensity (10{sup 19} W/cm{sup 2}, 50 TW) 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 {mu}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 {mu}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{alpha} and He-{alpha} emission regions are separated by approximately 330 {mu}m along the laser axis.

Kugland, N. L.; Niemann, C. [Department of Physics, University of California, Los Angeles, Los Angeles, California 90095 (United States); Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Doeppner, T.; Kemp, A.; Glenzer, S. H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Schaeffer, D. [Department of Physics, University of California, Los Angeles, Los Angeles, California 90095 (United States)

2010-10-15

358

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

359

Resonance ionization for analytical spectroscopy  

DOEpatents

This invention relates to a method for the sensitive and selective analysis of an atomic or molecular component of a gas. According to this method, the desired neutral component is ionized by one or more resonance photon absorptions, and the resultant ions are measured in a sensitive counter. Numerous energy pathways are described for accomplishing the ionization including the use of one or two tunable pulsed dye lasers.

Hurst, George S. (Oak Ridge, TN); Payne, Marvin G. (Harriman, TN); Wagner, Edward B. (Burchfield Heights, TN)

1976-01-01

360

Characterization of plant materials by pyrolysis-field ionization mass spectrometry: high-resolution mass spectrometry, time-resolved high-resolution mass spectrometry, and Curie-point pyrolysis-gas chromatography\\/mass spectrometry of spruce needles  

Microsoft Academic Search

In the course of a forest damage research project spruce needles are analyzed, without pretreatment except drying and milling, by in-source pyrolysis-field ionization mass spectrometry. The mass signals are assigned by using high-resolution mass measurements and thermal degradation products identified by Curie-point pyrolysis-gas chromatography. It is demonstrated that the thermal degradation products characterize the main chemical constituents of spruce needs

Hans Rolf. Schulten; Norbert. Simmleit; Rolf. Mueller

1989-01-01

361

A Chemical Ionization High-Resolution Time-of-Flight Mass Spectrometer Coupled to a Micro Orifice Volatilization Impactor (MOVI-HRToF-CIMS) for Analysis of Gas and Particle-Phase Organic Species  

Microsoft Academic Search

We describe a new instrument, chemical ionization high-resolution time-of-flight mass spectrometer coupled to a micro-orifice volatilization impactor (MOVI-HRToF-CIMS). The MOVI-HRToF-CIMS instrument is unique in that, within a compact field-deployable package, it provides (1) quantifiable molecular-level information for both gas and particle phase organic species on timescales ranging from ?1 second for gases and 10 - 60 minutes for particle-phase compounds

Reddy L. N. Yatavelli; Felipe Lopez-Hilfiker; Julia D. Wargo; Joel R. Kimmel; Michael J. Cubison; Timothy H. Bertram; Jose L. Jimenez; Marc Gonin; Douglas R. Worsnop; Joel A. Thornton

2012-01-01

362

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

363

Ambient gas/particle partitioning. 3. Estimating partition coefficients of apolar, polar, and ionizable organic compounds by their molecular structure.  

PubMed

Equilibrium gas/particle partitioning coefficients of terrestrial aerosols, Kip, are dependent on various intermolecular interactions that can be quantified by experimentally determined compound-specific descriptors. For many compounds of environmental interest, such as emerging contaminants and atmospheric phototransformation products, these compound-specific descriptors are unknown or immeasurable. Often, only the molecular structure is known. Here we present the ability of two computer programs to predict equilibrium partitioning to terrestrial aerosols solely on the basis of molecular structure: COSMOtherm and SPARC. The greatest hurdle with designing such an approach is to identify suitable molecular surrogates to represent the dominating sorbing phases, which for ambient terrestrial aerosols are the water insoluble organic matter (WIOM) phase and the mixed-aqueous phase. For the WI0M phase, hypothetical urban secondary organic aerosol structural units from Kalberer et al. Science 2004, 303, 1659-1662 were investigated as input surrogates, and for the mixed-aqueous phase mildly acidic water was used as a surrogate. Using a validation data set of more than 1400 experimentally determined Kip values for polar, apolar, and ionic compounds ranging over 9 orders of magnitude (including semivolatile compounds such as PCDD/Fs, pesticides, and PBDEs), SPARC and COSMOtherm were generally able to predict Kip values well within an order of magnitude over an ambient range of temperature and relative humidity. This is remarkable as these two models were not fitted or calibrated to any experimental data. As these models can be used for potentially any organic molecule, they are particularly recommended for environmental screening purposes and for use when experimental compound descriptor data are not available. PMID:19368193

Arp, Hans Peter H; Gosses, Kai-Uwe

2009-03-15

364

Generation of gas-phase VO2+, VOOH+, and VO2+-nitrile complex ions by electrospray ionization and collision-induced dissociation.  

PubMed

Cationic metal species normally function as Lewis acids, accepting electron density from bound electron-donating ligands, but they can be induced to function as electron donors relative to dioxygen by careful control of the oxidation state and ligand field. In this study, cationic vanadium(IV) oxohydroxy complexes were induced to function as Lewis bases, as demonstrated by addition of O2 to an undercoordinated metal center. Gas-phase complex ions containing the vanadyl (VO2+), vanadyl hydroxide (VOOH+), or vanadium(V) dioxo (VO2+) cation and nitrile (acetonitrile, propionitrile, butyronitrile, or benzonitrile) ligands were generated by electrospray ionization (ESI) for study by multiple-stage tandem mass spectrometry. The principal species generated by ESI were complexes with the formula [VO(L)n]2+, where L represents the respective nitrile ligands and n=4 and 5. Collision-induced dissociation (CID) of [VO(L)5]2+ eliminated a single nitrile ligand to produce [VO(L)4]2+. Two distinct fragmentation pathways were observed for the subsequent dissociation of [VO(L)4]2+. The first involved the elimination of a second nitrile ligand to generate [VO(L)3]2+, which then added neutral H2O via an association reaction that occurred for all undercoordinated vanadium complexes. The second [UO(L)4]2+ fragmentation pathway led instead to the formation of [VOOH(L)2]+ through collisions with gas-phase H2O and concomitant losses of L and [L+H]+. CID of [VOOH(L)2]+ caused the elimination of a single nitrile ligand to generate [VOOH(L)]+, which rapidly added O2 (in addition to H2O) by a gas-phase association reaction. CID of [VONO3(L)2]+, generated from spray solutions created by mixing VOSO4 and Ba(NO3)2 (and precipitation of BaSO4), caused elimination of NO2 to produce [VO2(L)2]+. CID of [VO2(L)2]+ produced elimination of a single nitrile ligand to form [VO2(L)]+, a V(V) analogue to the O2-reactive V(IV) species [VOOH(L)]+; however, this V(V) complex was unreactive with O2, which indicates the requirement for an unpaired electron in the metal valence shell for O2 addition. In general, the [VO2(L)2]+ species required higher collisions energies to liberate the nitrile ligand, suggesting that they are more strongly bound than the [VOOH(L)2]+ counterparts. PMID:17034156

Parsons, Zack; Leavitt, Chris; Duong, Thanh; Groenewold, Gary S; Gresham, Garold L; Van Stipdonk, Michael J

2006-10-19

365

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

366

IONIZATION CHAMBER  

DOEpatents

This patent describes a novel ionization chamber which is well suited to measuring the radioactivity of the various portions of a wire as the wire is moved at a uniform speed, in order to produce the neutron flux traverse pattern of a reactor in which the wire was previously exposed to neutron radiation. The ionization chamber of the present invention is characterized by the construction wherein the wire is passed through a tubular, straight electrode and radiation shielding material is disposed along the wire except at an intermediate, narrow area where the second electrode of the chamber is located.

Redman, W.C.; Shonka, F.R.

1958-02-18

367

Analytical method validation for the determination of 2,3,3,3-tetrafluoropropene in air samples using gas chromatography with flame ionization detection.  

PubMed

A new low global warming refrigerant, 2,3,3,3-tetrafluoro propene, or HFO-1234yf, has been successfully evaluated for automotive air conditioning, and is also being evaluated for stationary refrigeration and air conditioning systems. Due to the advantageous environmental properties of HFO-1234yf versus HFC-134a, coupled with its similar physical properties and system performance, HFO-1234yf is also being evaluated to replace HFC-134a in refrigeration applications where neat HFC-134a is currently used. This study reports on the development and validation of a sampling and analytical method for the determination of HFO-1234yf in air. Different collection media were screened for desorption and simulated sampling efficiency with three-section (350/350/350 mg) Anasorb CSC showing the best results. Therefore, air samples were collected using two 3-section Anasorb CSC sorbent tubes in series at 0.02 L/min for up to 8 hr for sample volumes of up to 9.6 L. The sorbent tubes were extracted in methylene chloride, and analyzed by gas chromatography with flame ionization detection. The method was validated from 0.1× to 20× the target level of 0.5 ppm (2.3 mg/m(3)) for a 9.6 L air volume. Desorption efficiencies for HFO-1234yf were 88 to 109% for all replicates over the validation range with a mean overall recovery of 93%. Simulated sampling efficiencies ranged from 87 to 104% with a mean of 94%. No migration or breakthrough to the back tube was observed under the sampling conditions evaluated. HFO-1234yf samples showed acceptable storage stability on Anasorb CSC sorbent up to a period of 30 days when stored under ambient, refrigerated, or frozen temperature conditions. PMID:24116663

Mawn, Michael P; Kurtz, Kristine; Stahl, Deborah; Chalfant, Richard L; Koban, Mary E; Dawson, Barbara J

2013-11-01

368

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

PubMed

A simple procedure for the determination of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), ethyl butyl ether (EBE), tert-amyl methyl ether (TAME), benzene, toluene, ethylbenzene, and xylenes (BTEX) in water using headspace (HS) solid-phase microextraction (HS-SPME) was developed. The analysis was carried out by gas chromatography (GC) equipped with flame ionization detector (FID) and 100% dimethylpolysiloxane fused capillary column. A 2 Plackett-Burman design for screening and a central composite design (CCD) for optimizing the significant variables were applied. Fiber type, extraction temperature, sodium chloride concentration, and headspace volume were the significant variables. A 65 microm poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB) SPME fiber, 10 degrees C, 300 g/l, and 20 ml of headspace (in 40 ml vial) were respectively chosen for the best extraction response. An extraction time of 10 min was enough to extract the ethers and BTEX. The relative standard deviation (R.S.D.) for the procedure varied from 2.6 (benzene) to 8.5% (ethylbenzene). The method detection limits (MDLs) found were from 0.02 (toluene, ethylbenzene, and xylenes) to 1.1 microg/l (MTBE). The optimized method was applied to the analysis of the rivers, marinas and fishing harbors surface waters from Gipuzkoa (North Spain). Three sampling were done in 1 year from June 2002 to June 2003. Toluene was the most detected analyte (in 90% of the samples analyzed), with an average concentration of 0.56 microg/l. MTBE was the only dialkyl ether detected (in 15% of the samples) showing two high levels over 400 microg/l that were related to accidental fuel spill. PMID:15088739

Arambarri, Idoia; Lasa, Maitena; Garcia, Rosa; Millán, Esmeralda

2004-04-16

369

Large Picture of the Galactic Center Studied by H_3^+: High Ionization Rate, Prevailing Warm and Diffuse Gas, and Non-Rotating Expanding Molecular Ring  

NASA Astrophysics Data System (ADS)

Following our initial studies of the diffuse interstellar medium in the Central Molecular Zone (CMZ) of the Galactic center (GC) toward two remarkable sightlines--one 140 pc to the West of Sgr A* near Sgr E, and the other 85 pc to the East of Sgr A* near Sgr B --we are in the process of using newly identified bright stars with smooth continua suitable for H_3^+ spectroscopy to both fill the gap between these sightlines and expand coverage to wider regions of the CMZ. So far we have identified 43 qualified stars, of which 24 have been at least partially observed (i.e., in at least one spectral setting). The high ionization rate (on the order of ?˜3×10^{-15} s^{-1}) and the existence of warm (T˜250 K) and diffuse (n?100 cm^{-3}) gas previously reported in the GC have also been observed in some of the new sightlines, indicating these conditions fill a large portion of the CMZ. The velocity profiles observed in the diffuse clouds, some of which show absorption extending ˜ 140 km s^{-1}, allow us to draw a velocity-longitude diagram. The high-velocity fronts of such a diagram reveal the existence of an expanding molecular ring (EMR) with radius of ˜ 140 pc and velocity of ˜ 140 km s^{-1}. This ring is similar to those previously reported but is qualitatively different in that it is not rotating, suggesting an expulsion rather than the gravitational potential as causing the EMR. Possible relations between our observations and other high energy events will be discussed. T. R. Geballe and T. Oka, ApJ, 709, L70 (2010). T. Oka, T. R. Geballe, M. Goto, T. Usuda, and B. J. McCall ApJ, 632, 882 (2005). N. Kaifu, T. Kato, and T. Iguchi, Nature, 238, 105 (1972). N. Z. Scoville, ApJ, 175, L127 (1972). Y. Sofue, PASJ, 47, 551 (1995).

Oka, Takeshi; Geballe, Thomas R.; Indriolo, Nick

2013-06-01

370

Kinetic-Hydrodynamic Models of the Solar Wind Interaction with the Partially Ionized Supersonic Flow of the Local Interstellar Gas: Predictions and Interpretations of the Experimental Data  

NASA Astrophysics Data System (ADS)

At present there is no doubt that the local interstellar medium (LISM) is mainly partially ionized hydrogen gas moving with a supersonic flow relative to the solar system. The bulk velocity of this flow is approximately equal ˜26 km/s. Although the interaction of the solar wind with the charged component (below plasma component) of the LISM can be described in the framework of hydrodynamic approach, the interaction of H atoms with the plasma component can be correctly described only in the framework of kinetic theory because the mean free path of H atoms in the main process of the resonance charge exchange is comparable with a characteristic length of the problem considered. Results of self-consistent, kinetic-hydrodynamic models are considered in this review paper. First, such the model was constructed by Baranov and Malama (J. Geophys. Res. 98(A9):15,157-15,163, 1993). Up to now it is mainly developed by Moscow group taking into account new experimental data obtained onboard spacecraft studying outer regions of the solar system (Voyager 1 and 2, Pioneer 10 and 11, Hubble Space Telescope, Ulysses, SOHO and so on). Predictions and interpretations of experimental data obtained on the basis of these models are presented. Kinetic models for describing H atom motion were later suggested by Fahr et al. (Astron. Astrophys 298:587-600, 1995) and Lipatov et al. (J. Geophys. Res. 103(A9):20,631-20,642, 1998). However they were not self-consistent and did not incorporate sources to the plasma component. A self-consistent kinetic-hydrodynamic model suggested by Heerikhuisen et al. (J. Geophys. Res. 111:A06110, 2006, Astrophys. J. 655:L53-L56, 2007) was not tested on the results by Baranov and Malama (J. Geophys. Res. 111:A06110, 1993) although it was suggested much later. Besides authors did not describe in details their Monte Carlo method for a solution of the H atom Boltzmann equation and did not inform about an accuracy of this method. Therefore the results of Heerikhuisen et al. (J. Geophys. Res. 111:A06110, 2006) are in open to question and will not be considered in this review paper. That is why below we will mainly consider a progress of the Moscow group on heliospheric modelling endeavours in the kinetic-hydrodynamic approach. Criticism of the models that treat interstellar hydrogen in the heliosphere as several fluids is given. It is shown that the multi-fluid models give rise to unreal results especially for distributions of neutral component parameters. Magnetohydrodynamic (MHD) modelling of the solar wind interaction with the LISM gas is also reviewed.

Baranov, Vladimir B.

2009-02-01

371

Instability of an ionization-shock layer  

NASA Astrophysics Data System (ADS)

We study the effect of a shock wave on the development of instability of the post-shock subsonic ionization front over a wide range of separations between the fronts, temperatures of the shock-compressed gas layer, and Mach numbers in the ionized zone. A linear analysis reveals a flow instability which is attributable to the multiple reflections of perturbations generated by the ionization front inside the layer. The wavelengths of the most rapidly growing perturbations correspond to the spatial scales of bright rims and `elephant trunks' observed near the boundaries of HII regions. The time it takes for the instability to develop is considerably shorter than the age of typical HII regions. We consider the formation mechanism for the cellular structure of the ionization-shock layer during the decay of the critical supersonic ionization front into a two-front configuration. The appearance of this structure is accompanied by randomization of the gas motion near the ionization (I) fronts.

Sysoev, N. E.

1998-07-01

372

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. 3 figures.

Wuest, C.R.; Lowry, M.E.

1994-03-29

373

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

374

Fingerprinting and source identification of an oil spill in China Bohai Sea by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry coupled with multi-statistical analyses.  

PubMed

This paper describes a case study in which advanced chemical fingerprinting and data interpretation techniques were used to characterize the chemical composition and determine the source of an unknown spilled oil reported on the beach of China Bohai Sea in 2005. The spilled oil was suspected to be released from nearby platforms. In response to this specific site investigation need, a tiered analytical approach using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID) was applied. A variety of diagnostic ratios of "source-specific marker" compounds, in particular isomers of biomarkers, were determined and compared. Several statistical data correlation analysis methods were applied, including clustering analysis and Student's t-test method. The comparison of the two methods was conducted. The comprehensive analysis results reveal the following: (1) The oil fingerprinting of three spilled oil samples (S1, S2 and S3) positively match each other; (2) The three spilled oil samples have suffered different weathering, dominated by evaporation with decrease of the low-molecular-mass n-alkanes at different degrees; (3) The oil fingerprinting profiles of the three spilled oil samples are positive match with that of the suspected source oil samples C41, C42, C43, C44 and C45; (4) There are significant differences in the oil fingerprinting profiles between the three spilled oil samples and the suspected source oil samples A1, B1, B2, B3, B4, C1, C2, C3, C5 and C6. PMID:19118832

Sun, Peiyan; Bao, Mutai; Li, Guangmei; Wang, Xinping; Zhao, Yuhui; Zhou, Qing; Cao, Lixin

2008-12-10

375

Absolute cross sections for electron-impact ionization of the rare-gas atoms by the fast-neutral-beam method  

Microsoft Academic Search

A new apparatus has been constructed for the measurement of absolute partial electron-impact-ionization cross sections of neutral atoms, molecules, and free radicals. A fast neutral beam is prepared by charge-transfer neutralization of a mass-selected ion beam and is ionized as it crosses an electron beam. From careful analysis of the apparatus, the absolute accuracy of measured cross sections is calculated

Robert C. Wetzel; Frank A. Baiocchi; Todd R. Hayes; Robert S. Freund

1987-01-01

376

Structural determination of zinc dithiophosphates in lubricating oils by gas chromatography–mass spectrometry with electron impact and electron-capture negative ion chemical ionization  

Microsoft Academic Search

Pentafluorobenzyl ester derivatives were used to identify zinc dialkyldithiophosphates and diaryldithiophosphates anti-wear engine oil additives by GC–electron impact ionization (EI) MS and GC–electron-capture negative ion chemical ionization (ECNCI) MS analysis. GC–EI-MS of the dialkyldithiophosphate–pentafluorobenzyl derivatives afforded characteristic fragment ions corresponding to the cleavage of one and two alkyl radicals. In most cases, information was only obtained on one alkyl chain.

M Becchi; F Perret; B Carraze; J. F Beziau; J. P Michel

2001-01-01

377

Initial Results of Positron Ionization Mass Spectrometry.  

National Technical Information Service (NTIS)

The use of monoenergetic positrons for the ionization of organic molecules in the gas phase is described. The ionic products are analyzed with a time-of-flight mass spectrometer and detected to produce a mass spectrum. The ionization mechanisms which can ...

D. L. Donohue L. D. Hulett S. A. Mcluckey G. L. Glish B. A. Eckenrode

1990-01-01

378

Dispersion of ionization waves in positive columns  

Microsoft Academic Search

Dispersion relations for ionization, ion-acoustic, and electron plasma waves are calculated numerically from the continuity and momentum equations for electrons and ions, the energy-balance equation for electrons, and the Maxwell equations. Only ionization waves are detectable at a gas pressure of a few torr. It is confirmed that the values for the real part of the frequency agree well with

Kazuyuki Ohe; Susumu Takeda

1975-01-01

379

Reactive evaporation in ionized gases.  

PubMed

By conventional reactive evaporation techniques, films with a certain deviation from stochiometric composition and, therefore, increased absorptance and dielectric losses were obtained. By ionization of the residual gas a considerable increase of reactivity has been achieved. The construction of a discharge tube with a region of high current density for ionization is described. The tube was arranged inside a bell jar. The ionized gas emerged from a nozzle in the wall of the tube directly into the high vacuum region. Production parameters for SiO(2), SiO(x)N(y), and TiO(2) films were evaluated. On unheated substrates SiO(2) films, which are practically free of absorptance down to 190 nm, and TiO(2) films with refractive indices up to 2.3, were obtained. PMID:20111347

Heitmann, W

1971-11-01

380

Experimental Investigations of Normal Ionizing Shock Waves.  

National Technical Information Service (NTIS)

Experiments were conducted on normal ionizing shock waves produced in a coaxial electromagnetic shock tube. Steady shock velocities were measured as a function of initial gas pressure, drive current, and applied axial magnetic field. The speeds agreed wel...

L. S. Levine

1967-01-01

381

Photolytic clean-up of biological samples for gas chromatographic analysis of chlorinated paraffins  

Microsoft Academic Search

A method based on gas chromatography electron capture detection (GC-ECD) for the analysis of chlorinated paraffins (CPs) in biological samples has been investigated. The method includes photolytic destruction of halogenated aromatic compounds, such as PCBs, to eliminate some of the interferences in the analysis of CPs in environmental samples. Gel permeation chromatography was used to isolate CPs from the interfering

Ulrika Fridén; Bo Jansson; Harun Parlar

2004-01-01

382

Development and validation of an analytical method for determination of 3-chloropropane-1,2-diol in rat blood and urine by gas chromatography-mass spectrometry in negative chemical ionization mode  

Microsoft Academic Search

We have developed a highly selective and sensitive method using gas chromatography-mass spectrometry with negative chemical\\u000a ionization for measuring 3-chloropropane-1,2-diol (3-MCPD) in rat blood and urine. Samples were adsorbed on silica gel, extracted\\u000a with ethyl acetate, and derivatized by chemical derivatization with heptafluorobutyric acid anhydride. For quantification,\\u000a matrix-based calibration curves and 3-MCPD-d\\u000a 5, as an isotope-labeled internal standard, were used.

Edith Berger-Preiß; Susanne Gerling; Elisabeth Apel; Alfonso Lampen; Otto Creutzenberg

2010-01-01

383

Direct analysis of artemisinin from Artemisia annua L. using high-performance liquid chromatography with evaporative light scattering detector, and gas chromatography with flame ionization detector  

Microsoft Academic Search

Since the isolation of artemisinin 32 years ago, it has been analyzed by different chromatographic techniques. This work compared the analysis of artemisinin from crude plant samples by GC with flame ionization detection (GC–FID) and HPLC with evaporative light scattering detector (HPLC–ELSD). Data is also presented indicating that GC is suitable for the quantification of two of artemisinin precursors (arteannuin

Congyue A. Peng; Jorge F. S. Ferreira; Andrew J. Wood

2006-01-01

384

Formation of ionization clusters in nanometric structures of propane-based tissue-equivalent gas or liquid water by electrons and a-particles  

Microsoft Academic Search

Despite the importance of ionization yield formation in sub-cellular structures a few nanometres in size, with regard to radiation damage our present knowledge in this respect is almost exclusively based on Monte Carlo simulations which in turn are based on cross section sets for water vapour or liquid water. Experimental data, although urgently needed, are still missing because the direct

B. Grosswendt

2002-01-01

385

Cross sections for ionization of rare gas excimers by electron impact and atomic and molecular processes in excimer lasers. Final report 1 Apr 78-30 Sep 79  

SciTech Connect

Theoretical cross sections for ionization of metastable excimers - helium, neon, argon, krypton and xenon - and of metastable mercury are presented. Systematic trends in inelastic form factors and Born cross sections for collisional transitions between excited neighboring levels of atoms are discovered and discussed. Key cycles of atomic and molecular collision processes in excimer lasers are delineated and discussed.

Flannery, M.R.; McCann, K.J.

1980-03-01

386

Copper clean-up procedure for ultrasonic extraction and analysis of pyrethroid and phenylpyrazole pesticides in sediments by gas chromatography-electron capture detection.  

PubMed

A rapid ultrasonic extraction method coupled with a heated-copper clean-up procedure for removing interfering constituents was developed for analyzing pyrethroid and phenylpyrazole pesticides in sediments. Incubation of the 60 mL extract with 12 g copper granules at 60 °C for 2h was determined to be the optimal conditions for removing the interfering constituents. Eleven pyrethroid and phenylpyrazole pesticides were spiked into sediment samples to determine the effectiveness of the ultrasonic extraction method. The average recoveries of pyrethroids and phenylpyrazoles in sediment at 4 °C storage on day 0, 1, 7, 14, and 21 ranged from 98.6 to 120.0%, 79.2 to 116.0%, 85.0 to 119.7%, 93.6 to 118.7%, and 92.1 to 118.2%, respectively, with all percent relative standard deviations less than 10% (most <6%). This illustrated the stability of pyrethroids and phenylpyrazoles in sediment during sediment aging at 4 °C. Recoveries of the pesticides ranged from 98.6% to 120.0% for lowest fortification level (2-16 ?g kg?¹), from 97.8% to 117.9% for middle fortification level (10-80 ?g kg?¹), and from 94.3% to 118.1% for highest fortification level (20-160 ?g kg?¹). Relative standard deviations of pesticide recoveries were usually less than 7%. Method detection limits of target pesticides ranged from 0.22 ?g kg?¹ to 3.72 ?g kg?¹. Furthermore, field sediment samples collected from four residential lakes during a three-month monitoring period were analyzed to evaluate the effectiveness of this method. Bifenthrin was detected in all of sediment samples (highest concentration 260.33±41.71 ?g kg?¹, lowest concentration 5.68±0.38 ?g kg?¹, and fipronil sulfone was detected at least once in sediment samples collected from three sites with concentrations ranging from 1.73±0.53 to 7.53±0.01 ?g kg?¹. PMID:21684581

Wu, Jun; Lin, Youjian; Lu, Jian; Wilson, Chris

2011-08-15

387

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

388

Determination of isoprostaglandin F 2? type III in human urine by gas chromatography–electronic impact mass spectrometry. Comparison with enzyme immunoassay  

Microsoft Academic Search

F2-Isoprostanes are stable lipid peroxidation products of arachidonic acid, the quantification of which provides an index of oxidative stress in vivo. We describe a method for analysing isoprostaglandin F2? type III (15-F2t-IsoP) in biological fluids. The method involves solid-phase extraction on octadecyl endcapped and aminopropyl cartridges. After conversion to trimethylsilyl ester trimethylsilyl ether derivatives, isoprostaglandin F2? type III is analysed

Janine Bessard; Jean-Luc Cracowski; Françoise Stanke-Labesque; Germain Bessard

2001-01-01

389

Determination of organochlorine pesticides in propolis by gas chromatography–electron capture detection using double column series solid-phase extraction  

Microsoft Academic Search

A rapid and reliable method was developed and applied for the simultaneous determination of 17 organochlorine pesticides (OCPs)\\u000a in propolis. After extraction with hexane and acetone (1:1, v\\/v), four sorbents (florisil, silica, graphitized carbon, and\\u000a tandem graphitized carbon plus florisil) were assayed for the clean-up step. The elution solvents hexane and ethyl acetate\\u000a (1:1, v\\/v), hexane and dichloromethane (3:7, v\\/v),

Fang Chen; Lanzhen Chen; Qiang Wang; Jinhui Zhou; Xiaofeng Xue; Jing Zhao

2009-01-01

390

Two-Dimensional Gas Chromatography\\/ Electron-Impact Mass Spectrometry with Cryofocusing for Simultaneous Quantification of MDMA, MDA, HMMA, HMA, and MDEA in Human Plasma  

Microsoft Academic Search

BACKGROUND: 3,4-Methylenedioxymethamphetamine (MDMA, or Ecstasy) is a popular recreational drug. Analysis of MDMA and metabolites in human plasma, particularly in pharmacokinetic studies, requires low limits of quantification. Two-dimensional GC\\/MS with cryofocusing is a chromatographic technique rec- ognized for its increased selectivity and resolution. METHODS: This method simultaneously quantifies 3,4- methylenedioxyethylamphetamine (MDEA), MDMA, and its metabolites, 3,4-methylenedioxyamphetamine (MDA), 4-hydroxy-3-methoxymethamphetamine (HMMA), and

Erin A. Kolbrich; Ross H. Lowe; Marilyn A. Huestis

391

Modeling of beam-ionized sources for plasma accelerators  

Microsoft Academic Search

When considering intense particle or laser beams propagating in dense plasma or gas, ionization plays an important role. Impact ionization and tunnel ionization may create new plasma electrons, altering the physics of wakefield accelerators, creating and modifying instabilities, etc. Here we describe the addition of an ionization package into the 3-D object-oriented fully parallel PIC code OSIRIS [R.G Hemker, F.S.

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

2003-01-01

392

Application of laser induced electron impact ionization to the deposition chemistry in the hot-wire chemical vapor deposition process with SiH4-NH3 gas mixtures.  

PubMed

The application of a laser-induced electron impact (LIEI) ionization source in studying the gas-phase chemistry of the SiH(4)/NH(3) hot-wire chemical vapor deposition (HWCVD) system has been investigated. The LIEI source is achieved by directing an unfocused laser beam containing both 118 nm (10.5 eV) vacuum ultraviolet (VUV) and 355 nm UV radiations to the repeller plate in a time-of-flight mass spectrometer. Comparison of the LIEI source with the conventional 118 nm VUV single-photon ionization (SPI) method has demonstrated that the intensities of the chemical species with ionization potentials (IP) above 10.5 eV, e.g., H(2), N(2) and He, have been significantly enhanced with the incorporation of the LIEI source. It is found that the SPI source due to the 118 nm VUV light coexists in the LIEI source. This allows simultaneous observations of parent ions with enhanced intensity from VUV SPI and their "fingerprint" fragmentation ions from LIEI. It is, therefore, an effective tool to diagnose the gas-phase chemical species involved with both NH(3) and SiH(4) in the HWCVD reactor. In using the LIEI source to SiH(4), NH(3) and their mixtures, it has been shown that the NH(3) decomposition is suppressed with the addition of SiH(4) molecules. Examination of the NH(3) decomposition percentage and the time to reach the N(2) and H(2) steady-state intensities for various NH(3)/SiH(4) mixtures suggests that the extent of the suppression is enhanced with more SiH(4) content in the mixture. With increasing filament temperatures, the negative effect of SiH(4) becomes less important. PMID:17869128

Eustergerling, Brett; Hèden, Martin; Shi, Yujun

2007-08-24

393

Capillary column gas chromatography, resonance enhanced multiphoton ionization, time-of-flight mass spectrometry, laser-induced fluorescence, flame ionization detection system for the determination of polynuclear aromatic compounds in complex mixtures  

Microsoft Academic Search

A method is reached to fully characterize the polynuclear aromatic hydrocarbons (PAC) that have been deemed to be highly mutagenic or carcinogenic. A multidimensional, laser-based analytical instrument has been developed that, when utilized to the full extent of its capabilities could be the solution to this complex analytical problem. The overall technique is termed Capillary Column Gas Chromatography, Resonance Enhanced

Dobson

1986-01-01

394

Laser Induced Avalanche Ionization in Gases with REMPI or Femtosecond Pre-Ionization  

NASA Astrophysics Data System (ADS)

Results of a theoretical study regarding the minimal requirements for the first pre-ionizing pulse to initiate avalanche ionization and essential gas heating by the second pulse are presented. The problem of minimal gas component density for the REMPI (Resonanse Enhanced Multi-Photon Ionization) pre-ionization with subsequent avalanche ionization in a bulk gas is explored on the basis of the theoretical model developed for the Ar:Xe mixture, where during the initial portion of the pulse (3+1) REMPI of Ar atoms starts the ionization, which subsequently continues to grow with an avalanche in the buffer Xe gas [1]. Note, that this method of plasma generation at intensities much lower than required for breakdown is very close to one considered in ref. [2] with femtosecond pre-ionizing laser pulse. Scaling parameters for gas mixtures, laser pulse shape, focusing and frequency are studied. Possible applications for improving of the detection sensitivity of Radar REMPI diagnostic technique and laser initiated ignition are discussed. [4pt] 1. M.N. Shneider, Z.Zhang, R.B. Miles, J.Appl.Phys. 104, 023302 (2008); 2. Z. Henis, G. Milikh, K. Papadopoulos, A. Zigler, J.Appl.Phys. 103, 103111 (2008)

Shneider, Mikhail; Miles, Richard

2009-10-01

395

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

396

Structural determination of zinc dithiophosphates in lubricating oils by gas chromatography-mass spectrometry with electron impact and electron-capture negative ion chemical ionization.  

PubMed

Pentafluorobenzyl ester derivatives were used to identify zinc dialkyldithiophosphates and diaryldithiophosphates antiwear engine oil additives by GC-electron impact ionization (EI) MS and GC-electron-capture negative ion chemical ionization (ECNCI) MS analysis. GC-EI-MS of the dialkyldithiophosphate-pentafluorobenzyl derivatives afforded characteristic fragment ions corresponding to the cleavage of one and two alkyl radicals. In most cases, information was only obtained on one alkyl chain. Additional and complete information was obtained with retention time indices using synthetic derivatives and with GC-ECNCI-MS analysis. ECNCI afforded characteristic dithiophosphate anions which allowed the determination of the total number of carbon atoms in the alkyl radicals. The diastereoisomer mixtures of 2-hydroxy-sec.-alkyl radicals were completely separated on GC analysis. PMID:11206788

Becchi, M; Perret, F; Carraze, B; Beziau, J F; Michel, J P

2001-01-01

397

Identification and quantification of polar naphthalene derivatives in contaminated groundwater of a former gas plant site by liquid chromatography–electrospray ionization tandem mass spectrometry  

Microsoft Academic Search

A liquid chromatography (LC) method followed by electrospray ionization (ESI) and tandem mass spectrometry (MS–MS) was developed for the quantification of acidic naphthalene derivatives in the concentration range 0.1 to 100 ?g\\/l without excessive sample preparation. For optimal sensitivity the LC–MS–MS measurements were performed recording mass fragmentation by collision induced dissociation in the multiple reaction mode. The collision energy was

Gerd Ohlenbusch; Christian Zwiener; Rainer U. Meckenstock; Fritz H. Frimmel

2002-01-01

398

Ionization potentials of seaborgium  

Microsoft Academic Search

Multiconfiguration relativistic Dirac-Fock values were calculated for the first six ionization potentials of seaborgium and of the other group 6 elements. No experimental ionization potentials are available for seaborgium. Accurate experimental values are not available for all of the other ionization potentials. Ionic radii for the 4+ through 6+ ions of seaborgium are also presented. The ionization potentials and ionic

E. Johnson; V. Pershina; B. Fricke

1999-01-01

399

Ionization and Electron Attachment in Methane  

Microsoft Academic Search

There has been a number of swarm experiments dealing with ionization in methane, but only one of them has dealt with electron attachment in this gas [1]. We have observed and interpreted direct, well diferentiated ionic avalanches in methane gas obtained from the pulsed Townsend method. The E\\/N range covered was 130 -- 950 Td, at pressures from 80 to

J. de Urquijo; C. A. Arriaga; I. Domínguez; C. Cisneros; I. Alvarez

1996-01-01

400

Effects of thermal ionization on atomic-ionization detection limits for gases  

SciTech Connect

Any atomizing gas has a certain matrix component, not necessarily the most readily ionized, for which the noise is maximal. The rate constants for the ionization of the atoms or molecules in that matrix will be equal to the ratio of the speed of the gas to the sum of the heights of the collector and recording electrodes. The calculations show that laser atomic ionization spectroscopy can be used under the best conditions for atomization and signal recording and with high efficiency in laser ionization even if there is a high interference from thermal and unselective matrix atom and molecule ionization, and one can attain limits of detection at the level of 10/sup -12/%.

Matveev, O.I.

1988-01-20

401

Matrix assisted ionization vacuum (MAIV), a new ionization method for biological materials analysis using mass spectrometry.  

PubMed

The introduction of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) for the mass spectrometric analysis of peptides and proteins had a dramatic impact on biological science. We now report that a wide variety of compounds, including peptides, proteins, and protein complexes, are transported directly from a solid-state small molecule matrix to gas-phase ions when placed into the vacuum of a mass spectrometer without the use of high voltage, a laser, or added heat. This ionization process produces ions having charge states similar to ESI, making the method applicable for high performance mass spectrometers designed for atmospheric pressure ionization. We demonstrate highly sensitive ionization using intermediate pressure MALDI and modified ESI sources. This matrix and vacuum assisted soft ionization method is suitable for the direct surface analysis of biological materials, including tissue, via mass spectrometry. PMID:23242551

Inutan, Ellen D; Trimpin, Sarah

2012-12-13

402

Atmospheric and ionospheric response to trace gas perturbations through the ice age to the next century in the middle atmosphere. Part II-ionization  

NASA Astrophysics Data System (ADS)

A global two-dimensional meridional ion composition model of the middle atmosphere is used to examine the effect of changing concentrations of several greenhouse gases on the overall distribution of ionization for this region, along with a steady state calculation for the upper heights. Changes in the neutral parameters for this study are taken from the companion article (Beig and Mitra, 1997). It has been predicted that there are several sensitive signals of man-made perturbations in the middle atmospheric ionization. In the mesospheric region, for a doubled CO2 scenario, we find that the total ionization density does not change appreciably and the maximum variation is found to be around 15% at about 70 km. However, the distribution of individual ions shows a considerable variation (up to about 100%) throughout the middle atmosphere. The fall-off height of the fractional abundance of water cluster ions is higher for 2050 A.D., suggesting domination of these ions up to greater heights. The concentration of water cluster ions increases below about 85 km; above this height it starts to decrease sharply with height. When a scenario with doubled CO2, with CH4 and business-as-usual (BAU) (for CFCs and N2O) is considered in the stratospheric region, it is found that only one family of negative ions, called NO3-core ions, is dominant instead of two in the normal case. Simulations are also made through the ages since the last ice age. Results indicate a reverse trend as compared to the above.

Beig, G.; Mitra, A. P.

1997-07-01

403

Electrospray ionization of uranyl-citrate complexes  

Microsoft Academic Search

Results presented here demonstrate the usefulness of electrospray ionization and gas-phase ion-molecule reactions to predict structural and electronic differences in complex inorganic ions. Electrospray ionization of uranyl citrate solutions generates positively and negatively charged ions that participate in further ion-molecule reactions in 3D ion trap and FT-ICR mass analyzers. Most ions observed are derived from the major solution uranyl-citrate complexes

Árpád Somogyi; Sofie P. Pasilis; Jeanne E. Pemberton

2007-01-01

404

Determination of elemental sulfur in gasoline by gas chromatography with on-column injection and flame ionization detection following derivatization with triphenylphosphine.  

PubMed

Several years ago, the presence of elemental sulfur in gasoline became a significant issue for the automotive and fuel industries. In several incidents, elemental sulfur at trace levels led to the corrosion of silver alloy fuel sensing elements in automobile gasoline tanks. This report describes a derivatization method that allows the determination of trace levels of elemental sulfur using flame ionization detection. The sample is derivatized with triphenylphosphine to form triphenylphosphine sulfide. This component is readily detected with a flame ionization detector. In most analyses, on-column injection was employed to allow detection of trace levels of elemental sulfur. However some analyses with splitless injection were also performed. For some gasolines, detection limits on the order of less than 1 microg/g elemental sulfur were possible with this approach. However, the detection limit can vary depending upon the concentration of trace higher boiling components. The precision of the analysis, as measured by the relative standard deviation of triplicate injections, for gasolines containing 1 to 10 microg/g of elemental sulfur was in the 1 to 3% range. The recovery of a gasoline spiked with approximately 4 microg/g elemental sulfur was 102%. The presence of ethanol did not appear to affect results. PMID:20412650