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Sample records for capture negative ionization

  1. Detection of trace levels of triclopyr using capillary gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry.

    PubMed

    Begley, P; Foulger, B E

    1988-04-01

    Triclopyr, after esterification, is shown to be a suitable candidate for detection by gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry forming a characteristic carboxylate anion which offers a high detection sensitivity. A detection limit of 70 fg reaching the ionizer is indicated. Low backgrounds and an absence of chemical interferences are shown for vegetation extracts, using a simple method of extraction and derivatisation. A similar behaviour is demonstrated for 2,4-D and 2,4,5-T. PMID:3379116

  2. Gas chromatographic-mass spectrometric analysis of the tripeptide glutathione in the electron-capture negative-ion chemical ionization mode.

    PubMed

    Tsikas, Dimitrios; Hanff, Erik; Kayacelebi, Arslan Arinc; Böhmer, Anke

    2016-02-01

    The dicarboxylic tripeptide glutathione (GSH) is the most abundant intracellular thiol. GSH analysis by liquid chromatography is routine. Yet, GSH analysis by gas chromatography is challenged due to thermal instability and lacking volatility. We report a high-yield laboratory method for the preparation of (2)H-labeled GSH dimethyl ester ((d3Me)2-GSH) for use as internal standard (IS) which was characterized by LC-MS/MS. For GC-MS analysis, the dimethyl esters of GSH and the IS were derivatized with pentafluoropropionic (PFP) anhydride. Electron-capture negative-ion chemical ionization of the (Me)2-(PFP)3-GSH provided high sensitivity. We encourage increasing use of GC-MS in the analysis of amino acids as their Me-PFP derivatives in the ECNICI mode. PMID:26602568

  3. Comparative analysis of dioxins and furans by electron impact, high-resolution mass spectrometry and by electron capture, negative ionization, low-resolution mass spectrometry

    SciTech Connect

    Koester, C.J.; Harless, R.L.; Hites, R.A.

    1990-01-01

    Electron impact, high resolution mass spectrometry (HRMS) is currently the method of choice for the analysis of polychlorinated dibenso-p-dioxins and dibenzofurans (PCDD/F) because of its ability to detect PCDD/F in the presence of interfering compounds, such as polychlorinated biphenyls (PCB), which cannot be resolved by low resolution methods. The PDCC/F analyses may also be performed using electron capture, negative ionization (ECNI) low resolution mass spectrometry, providing extensive sample preparation is done to remove interferences. Before ECNI low resolution mass spectrometry (MS) can be accepted as a routine method for PCDD/F analysis, it is necessary to show that results generated by this method are comparable to those obtained by HRMS. Known mixtures and unknown air samples were analyzed by electron impact HRMS (Finnigan MAT 90 system) and by ECNI low resolution MS (Hewlett Packard 5985B). Both instruments were fitted with a gas chromatographic inlet. The PCDD/F concentrations determined by the two techniques compare favorably, typically within 20%. The major difference between these two methods is that the ECNI low resolution method shows poor sensitivity in detecting 2,3,7,8-tetrachlorodioxin. However, ECNI MS offers the advantage of lower detection limits (50-100 fg) than electron impact HRMS (0.1 to 0.5 pg). These results suggest that ECNI low resolution MS can be a simple, low cost alternative to the common high resolution methods used for PCDD/F analysis.

  4. Optimization of the determination of polybrominated diphenyl ethers in human serum using solid-phase extraction and gas chromatography-electron capture negative ionization mass spectrometry.

    PubMed

    Covaci, Adrian; Voorspoels, Stefan

    2005-12-01

    A simple, rapid, sensitive and reproducible method based on solid-phase extraction (SPE) and acidified silica clean-up was developed for the measurement of 12 polybrominated diphenyl ethers (PBDEs), including BDE 209, and 2,2',4,4',5,5'-hexabromobiphenyl (BB 153) in human serum. Several solid-phase sorbents (Empore C(18), Isolute Phenyl, Isolute ENV+ and OASIS HLB) were tested and it was found that OASIStrade mark HLB (500 mg) gives the highest absolute recoveries (between 64% and 95%, R.S.D.<17%, n=3) for all tested analytes and internal standards. Removal of co-extracted biogenic materials was performed using a 6 ml disposable cartridge containing (from bottom to top) silica impregnated with sulphuric acid, activated silica and anhydrous sodium sulphate. PBDEs and BB 153 were quantified using a gas chromatograph coupled with a mass spectrometer (MS) operated in electron-capture negative ionization mode. The method limits of quantification (LOQ) ranged between 0.2 and 25 pg/ml serum (0.1 and 4 ng/g lipid weight). LOQs were dependent on the analyte levels in procedural blanks which resulted in the highest LOQs for PBDE congeners found in higher concentrations in blanks (e.g. BDE 47, 99 and 209). The use of OASIS HLB SPE cartridge allowed a good method repeatability (within- and between-day precision<12% for all congeners, except for BDE 209<17%, n=3). The method was applied to serum samples from a random Belgian population. The obtained results were within the range of PBDE levels in other non-exposed population from Europe. PMID:16203180

  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

    Bowden, John A; Ford, David A

    2011-05-15

    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 by-products 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 were 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. PMID:21094100

  6. Above-threshold ionization of negative hydrogen

    NASA Astrophysics Data System (ADS)

    Nikolopoulos, L. A. A.; Lambropoulos, P.

    1997-10-01

    We present detailed calculations for two-and three-photon above-threshold ionization of the negative hydrogen ion. In addition to calculated values for partial wave amplitudes and phase shifts pertaining to recent experimental results [Xin Miao Zhao et al., Phys. Rev. Lett. 78, 1656 (1997)], we also address the question of the asymmetry of photoelectron angular distributions in ionization under elliptically polarized radiation, which has been studied experimentally in other negative ions [C. Blondel and C. Delsart, Laser Phys. 3, 3 (1993); Nucl. Instrum. Methods Phys. Res. B 79, 156 (1993); F. Dulieu, C. Blondel, and C. Delsart, J. Phys. B 28, 3861 (1995)].

  7. Mechanism of branching in negative ionization fronts.

    PubMed

    Arrayás, Manuel; Fontelos, Marco A; Trueba, José L

    2005-10-14

    When a strong electric field is applied to nonconducting matter, narrow channels of plasma called streamers may form. Branchlike patterns of streamers have been observed in anode directed discharges. We explain a mechanism for branching as the result of a balance between the destabilizing effect of impact ionization and the stabilizing effect of electron diffusion on ionization fronts. The dispersion relation for transversal perturbation of a planar negative front is obtained analytically when the ratio D between the electron diffusion coefficient and the intensity of the externally imposed electric field is small. We estimate the spacing lambda between streamers and deduce a scaling law lambda approximately D(1/3). PMID:16241810

  8. A Novel Method for Profiling and Quantifying Short- and Medium-Chain Chlorinated Paraffins in Environmental Samples Using Comprehensive Two-Dimensional Gas Chromatography-Electron Capture Negative Ionization High-Resolution Time-of-Flight Mass Spectrometry.

    PubMed

    Xia, Dan; Gao, Lirong; Zheng, Minghui; Tian, Qichang; Huang, Huiting; Qiao, Lin

    2016-07-19

    Chlorinated paraffins (CPs) are complex technical mixtures containing thousands of isomers. Analyzing CPs in environmental matrices is extremely challenging. CPs have broad, unresolved profiles when analyzed by one-dimensional gas chromatography (GC). Comprehensive two-dimensional GC (GC×GC) can separate CPs with a high degree of orthogonality. A novel method for simultaneously profiling and quantifying short- and medium-chain CPs, using GC×GC coupled with electron capture negative ionization high-resolution time-of-flight mass spectrometry, was developed. The method allowed 48 CP formula congener groups to be analyzed highly selectively in one injection through accurate mass measurements of the [M - Cl](-) ions in full scan mode. The correlation coefficients (R(2)) for the linear calibration curves for different chlorine contents were 0.982 for short-chain CPs and 0.945 for medium-chain CPs. The method was successfully used to determine CPs in sediment and fish samples. By using this method, with enhanced chromatographic separation and high mass resolution, interferences between CP congeners and other organohalogen compounds, such as toxaphene, are minimized. New compounds, with the formulas C9H14Cl6 and C9H13Cl7, were found in sediment and biological samples for the first time. The method was shown to be a powerful tool for the analysis of CPs in environmental samples. PMID:27183176

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

    EPA Science Inventory

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

  10. Ionization phenomena and sources of negative ions

    SciTech Connect

    Alton, G.D.

    1983-01-01

    Negative ion source technology has rapidly advanced during the past several years as a direct consequence of the discovery of Krohn that negative ion yields can be greatly enhanced by sputtering in the presence of Group IA elements. Today, most negative ion sources use this discovery directly or the principles implied to effect negative ion formation through surface ionization. As a consequence, the more traditional direct extraction plasma and charge exchange sources are being used less frequently. However, the charge exchange generation mechanism appears to be as universal, is very competitive in terms of efficiency and has the advantage in terms of metastable ion formation. In this review, an attempt has been made to briefly describe the principal processes involved in negative ion formation and sources which are representative of a particular principle. The reader is referred to the literature for specific details concerning the operational characteristics, emittances, brightnesses, species and intensity capabilities of particular sources. 100 references.

  11. Dissociation and ionization in capture of antiprotons by the hydrogen molecular ion

    NASA Astrophysics Data System (ADS)

    Cohen, James S.

    2005-05-01

    Antiprotonic atoms and anti-hydrogen are hot areas of current experimental research. Cross sections for antiproton capture will soon be measured directly for the first time by the ASACUSA collaboration at the CERN antiproton decelerator and trap. In the present work [1], cross sections and initial quantum number distributions are calculated for capture of the antiproton (p) and the negative muon (^-) by the hydrogen molecular ion H2^+ using the fermion molecular dynamics (FMD) method. The capture of p is found to be almost entirely adiabatic, occurring via target dissociation without ionization, but nonadiabatic effects are found to play a significant role in the capture of ^-, especially at the higher capture energies. Generally good agreement is obtained with the recent adiabatic classical-trajectory Monte Carlo (CTMC-a) calculation of Sakimoto [2]. The capture properties of H2^+ are shown to be completely different from those previously calculated for both the H atom and neutral H2 molecule. Proposed experiments [3] on p capture by H, H2 and H2^+, at the same relative collision energies, will provide a major test of our theoretical understanding [4].[1] J.S. Cohen, J. Phys. B (to be published).[2] K. Sakimoto, J. Phys. B 37, 2255 (2004).[3] Y. Yamazaki et al., Nucl. Instrum. Methods B 154, 174 (1999); 214, 196 (2004); Hyperfine Interact. 138, 141 (2001).[4] J.S. Cohen, Rep. Prog. Phys. 67, 1769 (2004).

  12. Ionization and capture in water: a multi-differential cross sections study

    NASA Astrophysics Data System (ADS)

    Champion, Christophe; Galassi, Mariel E.; Weck, Philippe F.; Fojón, Omar; Hanssen, Jocelyn; Rivarola, Roberto D.

    2012-11-01

    Two quantum mechanical models (CB1 and CDW-EIS) are here presented to provide accurate multiple differential and total cross sections for describing the two most important ionizing processes, namely, ionization and capture induced by heavy charged particles in water. A detailed study of the influence of the target description on the cross section calculations is also provided.

  13. Ionization of water by (20-150)-keV protons: Separation of direct-ionization and electron-capture processes

    SciTech Connect

    Gobet, F.; Eden, S.; Coupier, B.; Tabet, J.; Farizon, B.; Farizon, M.; Gaillard, M.J.; Carre, M.; Ouaskit, S.; Maerk, T. D.; Scheier, P.

    2004-12-01

    Mass analyzed product ions have been detected in coincidence with the projectile following the ionization of water by proton impact. Measurement of the projectile charge state postcollision enables the different ionization processes to be identified: direct ionization, single electron capture, and double electron capture. A complete set of partial and total absolute cross sections is reported for the direct ionization and electron capture processes initiated by proton collisions at 20-150 keV. The cross sections for the direct ionization of H{sub 2}O by proton impact are compared with previous electron impact results [Straub et al., J. Chem. Phys. 108, 109 (1998)].

  14. Ion-induced ionization and capture cross sections for DNA nucleobases impacted by light ions

    NASA Astrophysics Data System (ADS)

    Champion, Christophe; Galassi, Mariel E.; Weck, Philippe F.; Fojón, Omar; Hanssen, Jocelyn; Rivarola, Roberto D.

    2012-11-01

    Two quantum mechanical models (CB1 and CDW-EIS) are here presented for describing electron ionization and electron capture induced by heavy charged particles in DNA bases. Multiple differential and total cross sections are determined and compared with the scarce existing experimental data.

  15. A Benign, Low Z Electron Capture Agent for Negative Ion TPCs

    NASA Technical Reports Server (NTRS)

    Martoff, C. J.; Dion, M. P.; Hosack, M.; Barton, D.; Black, J. K.

    2008-01-01

    We have identified nitromethane (CH3NO2) as an effective electron capture agent for negative ion TPCs (NITPCs). We present drift velocity and longitudinal diffusion measurements for negative ion gas mixtures using nitromethane as the capture agent. Not only is nitromethane substantially more benign than the only other identified capture agent, CS2, but its low atomic number will enable the use of the NITPC as a photoelectric X-ray polarimeter in the 1-10 keV band.

  16. Radiative Negative Pion Proton Capture and the Low Energy Theorem.

    NASA Astrophysics Data System (ADS)

    Liu, Kailin

    Four-point angular distributions of the differential cross section for the radiative capture reaction pi^-ptogamma n have been measured at pion laboratory energies of 9.8, 14.6 and 19.8 MeV. An undegraded pion beam was used, along with a bubble-free liquid hydrogen target of 1 cm thickness. The use of a high resolution NaI(Tl) spectrometer allowed us to resolve the in-flight capture gamma rays from those due to stopped pion capture at all pion beam energies and gamma-ray angles investigated. The lineshape response of the gamma-ray detector to ~130 MeV gamma rays was continuously measured over a broad energy range during the data collection with a second independent trigger. This allowed an accurate extraction of the in-flight capture yields and provided a precise measurement of the detector efficiency. From the measured angular distributions of cross section the electric dipole amplitude for capture of s-wave pions, E_{0+}, has been determined at each energy in a model-independent analysis. These data have been extrapolated to threshold by assuming an energy dependence given by the Born diagrams calculated with pseudovector coupling. The extrapolated E _{0+} value at threshold has been determined to be -34.7+/- 1.1 (10^ {-3}/m_pi) which is 9.4 +/- 3.2 percent larger in magnitude than the low energy theorem, which determines the threshold E_{0+} amplitude based upon the requirements of PCAC and electromagnetic gauge invariance.

  17. Cross sections of electron capture and electron capture ionization versus the impact parameter in collisions of a proton with multielectron atoms

    NASA Astrophysics Data System (ADS)

    Afrosimov, V. V.; Basalaev, A. A.; Ogurtsov, G. N.; Panov, M. N.

    2014-05-01

    The absolute differential cross sections of scattering of hydrogen atoms resulting from an electron capture and an electron capture ionization are measured for collisions of 4.5- and 11-keV protons with argon and xenon atoms. The range of scattering angles is 0°-2°. From the scattering differential cross section found experimentally, the probabilities of single-electron capture and electron capture ionization as a function of the impact parameter are calculated. The dependences of the incident particle scattering angle on the impact parameter (deviation function) for interactions with Ar and Xe atoms are calculated in terms of classical mechanics using the Moliére—Yukawa potential to describe the interaction of atomic particles. Analysis is given to the probabilities of electron capture and electron capture ionization versus the impact parameter and to the distribution of the electron density on different electron shells in a target atom versus a distance to the core. It is concluded that only electrons from the outer shell of the target atom are involved in the process of electron capture ionization. The cross section of electron capture ionization is calculated in the proton energy range 5-20 keV.

  18. Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

    DOE PAGESBeta

    Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.; Van Berkel, Gary J.

    2015-06-27

    Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to comparemore » internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.« less

  19. Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

    SciTech Connect

    Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.; Van Berkel, Gary J.

    2015-06-27

    Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to compare internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.

  20. Atmospheric CO2 capture by algae: Negative carbon dioxide emission path.

    PubMed

    Moreira, Diana; Pires, José C M

    2016-09-01

    Carbon dioxide is one of the most important greenhouse gas, which concentration increase in the atmosphere is associated to climate change and global warming. Besides CO2 capture in large emission point sources, the capture of this pollutant from atmosphere may be required due to significant contribution of diffuse sources. The technologies that remove CO2 from atmosphere (creating a negative balance of CO2) are called negative emission technologies. Bioenergy with Carbon Capture and Storage may play an important role for CO2 mitigation. It represents the combination of bioenergy production and carbon capture and storage, keeping carbon dioxide in geological reservoirs. Algae have a high potential as the source of biomass, as they present high photosynthetic efficiencies and high biomass yields. Their biomass has a wide range of applications, which can improve the economic viability of the process. Thus, this paper aims to assess the atmospheric CO2 capture by algal cultures. PMID:27005790

  1. Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture/Electrospray Ionization

    NASA Astrophysics Data System (ADS)

    Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.; Van Berkel, Gary J.

    2015-09-01

    Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed noncontact liquid-vortex capture probe has been used to efficiently collect material ablated by a 355 nm UV laser in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appears to be classic electrospray ionization spectra; however, the `softness' of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. In this work, a series of benzylpyridinium salts were employed as thermometer ions to compare internal energy distributions between electrospray ionization and the UV laser ablation/liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. These data, along with results from the analysis the biological molecules bradykinin and angiotensin III indicated that the ions or their fragments formed directly by UV laser ablation that survive the liquid capture/electrospray ionization process were likely to be an extremely small component of the total ion signal observed. Instead, the preponderate neutral molecules, clusters, and particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream, then electrosprayed, were the principal source of the ion signal observed. Thus, the electrospray ionization process used controls the overall `softness' of this technique.

  2. Measurement of atomic capture probabilities of negative pions in metal hydrides

    NASA Astrophysics Data System (ADS)

    Saito, Tadashi; Miura, Taichi; Shinohara, Atsushi; Shintai, Junichiro; Taniguchi, Eugene; Furukawa, Michiaki; Takesako, Kazuhiro; Imanishi, Nobutsugu; Muramatsu, Hisakazu; Yoshimura, Yoshio; Baba, Hiroshi; Doe, Hidekazu

    1994-12-01

    Atomic capture probabilities of negative pions in some metal hydrides were measured. The capture by a hydrogen atom was detected by means of a pair of the annihilation γ rays of π0 which had been produced by the charge-exchange reaction of π- with the capturing hydrogen nucleus (proton). This method ensures a high sensitivity and reliability of the measurements. The probabilities obtained were in agreement with previous measurements except for palladium hydride, which showed a much smaller probability than that given in the literature. The atomic capture of π- is well described in the framework of the large mesic molecular model, in which the proportionality constant reflects the chemical states of the capturing atoms and also the neighboring ones.

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

    PubMed

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

    2015-07-01

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

  4. Fully Automated Laser Ablation Liquid Capture Sample Analysis using NanoElectrospray Ionization Mass Spectrometry

    SciTech Connect

    Lorenz, Matthias; Ovchinnikova, Olga S; Van Berkel, Gary J

    2014-01-01

    RATIONALE: Laser ablation provides for the possibility of sampling a large variety of surfaces with high spatial resolution. This type of sampling when employed in conjunction with liquid capture followed by nanoelectrospray ionization provides the opportunity for sensitive and prolonged interrogation of samples by mass spectrometry as well as the ability to analyze surfaces not amenable to direct liquid extraction. METHODS: A fully automated, reflection geometry, laser ablation liquid capture spot sampling system was achieved by incorporating appropriate laser fiber optics and a focusing lens into a commercially available, liquid extraction surface analysis (LESA ) ready Advion TriVersa NanoMate system. RESULTS: Under optimized conditions about 10% of laser ablated material could be captured in a droplet positioned vertically over the ablation region using the NanoMate robot controlled pipette. The sampling spot size area with this laser ablation liquid capture surface analysis (LA/LCSA) mode of operation (typically about 120 m x 160 m) was approximately 50 times smaller than that achievable by direct liquid extraction using LESA (ca. 1 mm diameter liquid extraction spot). The set-up was successfully applied for the analysis of ink on glass and paper as well as the endogenous components in Alstroemeria Yellow King flower petals. In a second mode of operation with a comparable sampling spot size, termed laser ablation/LESA , the laser system was used to drill through, penetrate, or otherwise expose material beneath a solvent resistant surface. Once drilled, LESA was effective in sampling soluble material exposed at that location on the surface. CONCLUSIONS: Incorporating the capability for different laser ablation liquid capture spot sampling modes of operation into a LESA ready Advion TriVersa NanoMate enhanced the spot sampling spatial resolution of this device and broadened the surface types amenable to analysis to include absorbent and solvent resistant

  5. USE OF NEGATIVE ARI IONIZATION FOR REDUCING BACTERIAL PATHOGENS AND SPORES ON STAINLESS STEEL SURFACES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of chemicals in food plant sanitation for removing and killing microorganisms could be reduced by the use of alternative non-chemical interventions. Negative air ionization is a new technology that has shown potential to effectively reduce airborne and surface microorganisms. Current studies...

  6. ELECTRON AFFINITIES OF POLYNUCLEAR AROMATIC HYDROCARBONS AND NEGATIVE ION CHEMICAL IONIZATION SENSITIVITIES

    EPA Science Inventory

    Negative-ion chemical-ionization mass spectrometry (NICI MS) has the potential to be a very useful technique in identifying various polycyclic aromatic hydrocarbons (PAHs) in soil and sediment samples. Some PAHs give much stronger signals under NICI MS conditions than others. On ...

  7. Capture of negative muons by hydrogen atoms at low collision energies

    SciTech Connect

    Sakimoto, Kazuhiro

    2010-01-15

    A rigorous quantum mechanical calculation is carried out for negative muon capture by atomic hydrogen (mu{sup -}+H->mu{sup -}p+e) by using the R-matrix method. The total and final-state selected capture cross sections are calculated at low collision energies ranging from 0.001 to 1 eV. The total capture cross section can, on average, be explained in terms of a previously obtained empirical formula [K. Sakimoto, Phys. Rev. A 66, 032506 (2002)]. However, the present result exhibits additional undulation and cusp structures, which stem from quantum phenomena. The muons are predominantly captured into the highest energetically possible state of mu{sup -}p in the present energy region. However, the mu{sup -}p products having high angular momenta cannot be formed unless the collision energy becomes high.

  8. [Morphology determination of ionization region in multi-needle-to-plate negative corona discharge].

    PubMed

    Su, Peng-Hao; Zhu, Yi-Min; Chen, Hai-Feng

    2007-11-01

    Based on the former work on the current-voltage characteristics of a multi-needle-to-plate negative corona discharge at atmospheric pressure, the present work uses the method of OES (optical emission spectrum) for measuring N2 emission spectrum, and the morphology determination of the ionization region has been investigated. According to the distribution of N2 second positive band's intensity I(SPB), the highest of all bands, the outline of the ionization region was drawn fairly accurately. The relationship between I(SPB) and discharge current I can be obtained through the volume integral of the I(SPB). The experimental results show that the size of the ionization region enhances with the rise of the applied voltage U, and the electron avalanche begins at about 1 mm off the tips of needle electrode and multiplies only in the range of several millimeters, indicating that, the range of the ionization region is at the magnitude of mm. The electron avalanche along the axis of the needle develops farther than that along the radial direction of needle, and the shape of the ionization region looks like a bullet. The integral of I(SPB) is second-order linear to I, with a very second order coefficient, meaning that the main excited substance is N2. Energetic electrons mainly exist in ionization region while ions are the main charged particles to form discharge current in the transfer region. PMID:18260386

  9. Feasibility study of nuclear transmutation by negative muon capture reaction using the PHITS code

    NASA Astrophysics Data System (ADS)

    Abe, Shin-ichiro; Sato, Tatsuhiko

    2016-06-01

    Feasibility of nuclear transmutation of fission products in high-level radioactive waste by negative muon capture reaction is investigated using the Particle and Heave Ion Transport code System (PHITS). It is found that about 80 % of stopped negative muons contribute to transmute target nuclide into stable or short-lived nuclide in the case of 135Cs, which is one of the most important nuclide in the transmutation. The simulation result also indicates that the position of transmutation is controllable by changing the energy of incident negative muon. Based on our simulation, it takes approximately 8.5 × 108years to transmute 500 g of 135Cs by negative muon beam with the highest intensity currently available.

  10. Rapid differentiation of refined fuels using negative electrospray ionization/mass spectrometry

    USGS Publications Warehouse

    Rostad, C.E.; Hostettler, F.D.

    2005-01-01

    Negative electrospray ionization/MS enabled rapid, specific, and selective screening for unique polar components at parts per million concentrations in commercial hydrocarbon products without extensive sample preparation, separation, chromatography, or quantitation. Commercial fuel types were analyzed with this method, including kerosene, jet fuel, white gas, charcoal lighter fluid, on-road and off-road diesel fuels, and various grades and brands of gasolines. The different types of fuels produced unique and relatively simple spectra. These analyses were then applied to hydrocarbon samples from a large, long-term fuel spill. Although the alkane, isoprenoid, and alkylcyclohexane portions began to biodegrade or weather, the polar components in these samples remained relatively unchanged. The type of fuel involved was readily identified by negative electrospray ionization/MS. This is an abstract of a paper presented at the 230th ACS National Meeting (Washington, DC 8/28/2005-9/1/2005).

  11. The influence of negative ionization of the air on motor activity in Syrian hamsters ( Masocricetus auratus Waterhouse) in light conditions

    NASA Astrophysics Data System (ADS)

    Lenkiewicz, Zofia; Dabrowska, Barbara; Schiffer, Zofia

    1989-12-01

    The motor activity of Syrian hamsters ( Mesocricetus auratus Waterhouse) under the influence of negative ionization of the atmosphere applied for 10, 20 or 30 min per day was investigated. An ionizer with output of 14000 light negative ions per 1 cm3 of air was used. Studies carried out in the light phase of a 12∶12 h light/dark regime revealed a relation between the reaction of the animal and the time of day at which ionization was applied. Ionization for 20 or 30 min in the light phase decreased motor activity, while 10 min of ionization increased it compared to control animals. Ionization in the dark phase gave a more distinct rise in activity than that applied in the light phase for all three durations of ionization.

  12. Distracted by pleasure: Effects of positive versus negative valence on emotional capture under load.

    PubMed

    Gupta, Rashmi; Hur, Young-Jin; Lavie, Nilli

    2016-04-01

    We report 3 experiments examining the effects of positive versus negative valence and perceptual load in determining attention capture by irrelevant emotional distractors. Participants performed a letter search task searching for 1 of 2 target letters (X or N) in conditions of either low perceptual load (circular nontarget letters) or high perceptual load (angular nontarget letters that are similar to the target letters). On 25% of the trials an irrelevant emotional distractor was presented at the display center and participants were instructed to ignore it. The distractor stimulus was either positive or negative and was selected from 3 different classes: IAPS pictures of erotica or mutilated bodies (Experiment 1), happy or angry faces (Experiment 2), and faces associated with gain or loss in a prior value-learning phase involving a betting game (Experiment 3). The results showed a consistent pattern of interaction of load and valence across the 3 experiments. Irrelevant emotional distractors produced interference effects on search reaction time (RT) in conditions of low load, with no difference between negative and positive valence. High perceptual load, however, consistently reduced interference from the negative-valence distractors, but had no effect on the positive-valence distractors. As these results were consistently found across 3 different categories of emotional distractors, they suggest the general conclusion that attentional capture by irrelevant emotional distractors depends on both their valence and the level of perceptual load in the task and highlight the special status of distractors associated with pleasure. PMID:26479771

  13. Microbial Electrolytic Carbon Capture for Carbon Negative and Energy Positive Wastewater Treatment.

    PubMed

    Lu, Lu; Huang, Zhe; Rau, Greg H; Ren, Zhiyong Jason

    2015-07-01

    Energy and carbon neutral wastewater management is a major goal for environmental sustainability, but current progress has only reduced emission rather than using wastewater for active CO2 capture and utilization. We present here a new microbial electrolytic carbon capture (MECC) approach to potentially transform wastewater treatment to a carbon negative and energy positive process. Wastewater was used as an electrolyte for microbially assisted electrolytic production of H2 and OH(-) at the cathode and protons at the anode. The acidity dissolved silicate and liberated metal ions that balanced OH(-), producing metal hydroxide, which transformed CO2 in situ into (bi)carbonate. Results using both artificial and industrial wastewater show 80-93% of the CO2 was recovered from both CO2 derived from organic oxidation and additional CO2 injected into the headspace, making the process carbon-negative. High rates and yields of H2 were produced with 91-95% recovery efficiency, resulting in a net energy gain of 57-62 kJ/mol-CO2 captured. The pH remained stable without buffer addition and no toxic chlorine-containing compounds were detected. The produced (bi)carbonate alkalinity is valuable for wastewater treatment and long-term carbon storage in the ocean. Preliminary evaluation shows promising economic and environmental benefits for different industries. PMID:26076212

  14. Electron capture by U(91+) and U(92+) and ionization of U(90+) and U(91+)

    NASA Technical Reports Server (NTRS)

    Gould, H.; Greiner, D.; Lindstrom, P.; Symons, T. J. M.; Crawford, H.

    1984-01-01

    U(92+)/U(91+) and U(91+)/U(90+) electron-capture and ionization cross sections and equilibrium charge-state distributions are measured experimentally in mylar, Cu and Ta of varying thickness. Relativistic U(68+) ions at 437 or 962 MeV/nucleon are produced by a heavy-ion linear accelerator and synchrotron in tandem and passed through the target material into a magnetic specrometer and position-sensitive proportional counter for evaluation of charge states. The results are presented graphically and discussed. At 962 MeV/nucleon, beams containing 85 percent bare U(92+) nuclei are obtained using 150-mg/sq cm Cu or 85-mg/sq cm Ta; at 437 MeV/nucleon, 50 percent bare U(92+) nuclei are obtained with 90-mg/sq cm Cu. The techniques decribed can be applied to produce beams of bare U nuclei for acceleration to ultrarelativistic speeds or beams of few-electron U for atomic-physics experiments on quantum electrodynamics.

  15. Mesic molecular effects in the capture of negative pions stopped in gaseous hydrogen isotopes

    NASA Astrophysics Data System (ADS)

    Aniol, K. A.; Measday, D. F.; Hasinoff, M. D.; Roser, H. W.; Bagheri, A.; Entezami, F.; Virtue, C.; Stadlbauer, J. M.; Horváth, D.; Salomon, M.; Robertson, B. C.

    1983-11-01

    The influence of molecular structure on the nuclear capture probability of stopped negative pions has been observed by comparing the π0 gamma-ray spectrum from π- mesons stopped in HD gas to that from a mixture of equal amounts of H2 plus D2. The fraction of stopped pions that are captured by a proton in the H2+D2 mixture is fH2D2=0.417+/-0.004, while for HD it is fHD=0.338+/-0.008, independent of the gas pressure between 6 and 90 atm. The ratio, fH2D2fHD, of the fractions is 1.23+/-0.03.

  16. Absolute cross sections for electron loss, electron capture, and multiple ionization in collisions of Li2+ with argon

    NASA Astrophysics Data System (ADS)

    Losqui, A. L. C.; Zappa, F.; Sigaud, G. M.; Wolff, W.; Sant'Anna, M. M.; Santos, A. C. F.; Luna, H.; Melo, W. S.

    2014-02-01

    Exclusive absolute cross sections for the electron loss and capture processes, accompanied by target multiple ionization and pure target multiple ionization, as well as total electron loss and capture cross sections, in collisions of Li2+ with Ar have been measured in the 0.5-3.5 MeV energy range. The experimental data of the total electron loss cross section are compared with theoretical results based on the plane-wave Born approximation and the free-collision model, and with the available experimental data. Some discrepancies are observed when comparing the experimental data with the theoretical models, which can be attributed to the competitive mechanisms that lead to electron loss. The dependences of the single-capture and transfer-ionization processes on the projectile charge state are similar to those observed for collisions between other low-charged light ions and noble-gas targets. The same behaviour is observed when one compares the present data for the single- and double-ionization cross sections with those for He2+ projectiles on Ar. These facts indicate that the dynamics of the collision does not seem to depend on the projectile species, so that few-electron projectiles may act as structureless point charges in the intermediate- to high-velocity regime.

  17. A Negative-Surface Ionization for Generation of Halogen Radioactive Ion Beams

    SciTech Connect

    Zaim, H.

    2001-04-16

    A simple and efficient negative surface ionization source has been designed, fabricated and initially tested for on-line generation of radioactive ion beams of the halogens (Cl, Br, I, and At) for use in the nuclear-structure and nuclear-astrophysics research programs at the Holifield Radioactive Ion Beam Facility. The source utilizes a solid, spherical geometry LaB{sub 6} surface ionizer for forming highly electronegative atoms and molecules. Despite its widely publicized propensity for being easily poisoned, no evidences of this effect were experienced during testing of the source. Nominal efficiencies of 15% for Br{sup {minus}} beam generation were obtained during off-line evaluation of the source with AlBr3 feed material when account is taken of the fractional dissociation of the molecule. Principles of operation, design features, operational parameter data, initial performance results, and beam quality data (emittance) are presented in this article.

  18. Auger Stimulated Ion Desorption of Negative Ions via K -Capture Radioactive Decay

    SciTech Connect

    Verkhoturov, S. V.; Schweikert, E. A.; Chechik, Victor; Sabapathy, Rajaram C.; Crooks, Richard M.; Parilis, E. S.

    2001-07-16

    We report on Auger stimulated ion desorption via Coulomb explosion from surface self-assembled alkylthiol and fluorocarbon molecular layers, triggered by K -capture decay of an imbedded radioactive {sup 55}Fe atom. The charge state of the ejecta is determined by charge exchange in binary atomic collisions in bulk and electron tunneling outside the solid, as well as by fragmentation of electronically excited molecules or molecular fragments. We describe the first nonbeam experiments documenting positive and abundant negative ion desorption due solely to core electron excitation after radioactive decay.

  19. Alternative Filament Loading Solution for Accurate Analysis of Boron Isotopes by Negative Thermal Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Dwyer, G. S.; Vengosh, A.

    2008-12-01

    The negative thermal ionization mass spectrometry technique has become the major tool for investigating boron isotopes in the environment. The high sensitivity of BO2- ionization enables measurements of ng levels of boron. However, B isotope measurement by this technique suffers from two fundamental problems (1) fractionation induced by selective ionization of B isotopes in the mass spectrometer; and (2) CNO- interference on mass 42 that is often present in some load solutions (such as B-free seawater processed through ion-exchange resin). Here we report a potentially improved methodology using an alternative filament loading solution with a recently-installed Thermo Scientific TRITON thermal ionization mass spectrometer. Our initial results suggest that this solution -- prepared by combining high-purity single- element standard solutions of Ca, Mg, Na, and K in proportions similar to those in seawater in a 5% HCl matrix -- may offer significant improvement over some other commonly used load solutions. Total loading blank is around 15pg as determined by isotope dilution (NIST952). Replicate analyses of NIST SRM951 and modern seawater thus far have yielded 11B/10B ratios of 4.0057 (±0.0008, n=14) and 4.1645 (±0.0017, n=7; δ11B=39.6 permil), respectively. Replicate analyses of samples and SRM951 yield an average standard deviation (1 σ) of approximately 0.001 (0.25 permil). Fractionation during analysis (60-90 minutes) has thus far typically been less than 0.002 (0.5 permil). The load solution delivers ionization efficiency similar to directly-loaded seawater and has negligible signal at mass 26 (CN-), a proxy for the common interfering molecular ion (CNO-) on mass 42. Standards and samples loaded with the solution behave fairly predictably during filament heating and analysis, thus allowing for the possibility of fully automated data collection.

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

    PubMed

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

    1987-07-24

    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

  1. PENTACHLOROPHENOL IN THE ENVIRONMENT: EVIDENCE FOR ITS ORIGIN FROM COMMERCIAL PENTACHLOROPHENOL BY NEGATIVE CHEMICAL IONIZATION MASS SPECTROMETRY

    EPA Science Inventory

    Commercial pentachlorophenol (PCP) contains significant quantities of tetrachlorophenol (TCP). The occurrence of TCP in environmental samples provides a chemical marker for PCP originating from commercial formulations. Negative chemical ionization mass spectrometry has been used ...

  2. PENTACHLOROPHENOL IN THE ENVIRONMENT. EVIDENCE FOR ITS ORIGIN FROM COMMERCIAL PENTACHLOROPHENOL BY NEGATIVE CHEMICAL IONIZATION MASS SPECTROMETRY

    EPA Science Inventory

    Commercial pentachlorophenol (PCP) contains significant quantities of tetrachlorophenol (TCP). The occurrence of TCP in environmental samples provides a chemical marker for PCP originating from commercial formulations. Negative chemical ionization mass spectrometry has been used ...

  3. Flame-retardants and other organohalogens detected in sewage sludge by electron capture negative ion mass spectrometry.

    PubMed

    La Guardia, Mark J; Hale, Robert C; Harvey, Ellen; Chen, Da

    2010-06-15

    Numerous halogenated organic compounds have been identified as pollutants of concern. Those with high persistence and hydrophobicity may concentrate in biota, sediments, and wastewater sludge. Nonetheless, the release to the environment of many remains largely unrecognized. Stabilized sewage sludge (biosolids) is increasingly being land-applied as a soil amendment. However, understanding the risks of land application has been hampered by the compositional complexity of biosolids. Compound specific analytical approaches may also underestimate environmental impact of land application by overlooking additional contaminants. However, utilizing an alternative analytical approach based on compound functional group (i.e., alkyl halides) enhanced the information content of the analysis. To illustrate, 49 organohalogens were observed by gas chromatography with electron capture negative ionization mass spectrometry in sewage sludge; 23 identified as flame-retardants: that is, PBDEs, hexabromocyclododecane, 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (TBB), 2-ethylhexyl tetrabromophthalate, decabromodiphenyl ethane, 1,2-bis (2,4,6-tribromophenoxy) ethane and Dechlorane Plus. Concentrations ranged from 25 to 1,600,000 ng g(-1) total organic carbon. An additional 16 compounds were tentatively identified as triclosan, chlorinated-methoxy triclosan, chlorinated pesticides, hexachlorobiphenyl, TBB degradation products, brominated furans and nonabromochlorodiphenyl ethers. Such an analytical approach may enhance evaluations of the risks associated with biosolids land-application and assist in prioritizing specific chemicals for future environmental fate and toxicology studies. PMID:20486701

  4. Rapid differentiation of refined fuels using negative electrospray ionization/mass spectrometry

    USGS Publications Warehouse

    Rostad, C.E.; Hostettler, F.D.

    2005-01-01

    An application of electrospray ionization/mass spectrometry for identification of various commercially refined fuels using the unique signature of polar components, was investigated. The samples were analyzed by mass spectrometry using negative electrospray on an Agilent Series 1100 liquid chromatograph/mass spectrometer. These analysis were applied to hydrocarbon samples from a large, long-term fuel spill which were taken from the subsurface and different extent of biodegradation or weathering. The technique provided rapid identification of hydrocarbons released into the environment because these polar compounds are unique in different fuels.

  5. Ionization Efficiency of Doubly Charged Ions Formed from Polyprotic Acids in Electrospray Negative Mode.

    PubMed

    Liigand, Piia; Kaupmees, Karl; Kruve, Anneli

    2016-07-01

    The ability of polyprotic acids to give doubly charged ions in negative mode electrospray was studied and related to physicochemical properties of the acids via linear discriminant analysis (LDA). It was discovered that the compound has to be strongly acidic (low pK a1 and pK a2) and to have high hydrophobicity (logP ow) to become multiply charged. Ability to give multiply charged ions in ESI/MS cannot be directly predicted from the solution phase acidities. Therefore, for the first time, a quantitative model to predict the charge state of the analyte in ESI/MS is proposed and validated for small anions. Also, a model to predict ionization efficiencies of these analytes was developed. Results indicate that acidity of the analyte, its octanol-water partition coefficient, and charge delocalization are important factors that influence ionization efficiencies as well as charge states of the analytes. The pH of the solvent was also found to be an important factor influencing the ionization efficiency of doubly charged ions. Graphical Abstract ᅟ. PMID:27044024

  6. Ionization Efficiency of Doubly Charged Ions Formed from Polyprotic Acids in Electrospray Negative Mode

    NASA Astrophysics Data System (ADS)

    Liigand, Piia; Kaupmees, Karl; Kruve, Anneli

    2016-07-01

    The ability of polyprotic acids to give doubly charged ions in negative mode electrospray was studied and related to physicochemical properties of the acids via linear discriminant analysis (LDA). It was discovered that the compound has to be strongly acidic (low p K a1 and p K a2) and to have high hydrophobicity (log P ow) to become multiply charged. Ability to give multiply charged ions in ESI/MS cannot be directly predicted from the solution phase acidities. Therefore, for the first time, a quantitative model to predict the charge state of the analyte in ESI/MS is proposed and validated for small anions. Also, a model to predict ionization efficiencies of these analytes was developed. Results indicate that acidity of the analyte, its octanol-water partition coefficient, and charge delocalization are important factors that influence ionization efficiencies as well as charge states of the analytes. The pH of the solvent was also found to be an important factor influencing the ionization efficiency of doubly charged ions.

  7. The Effect of Salts on Electrospray Ionization of Amino Acids in the Negative Mode

    NASA Technical Reports Server (NTRS)

    Kim, H. I.; Johnson, P. V.; Beegle, L. W.; Kanik, I.

    2004-01-01

    The continued search for organics on Mars will require the development of simplified procedures for handling and processing of soil or rock core samples prior to analysis by onboard instrumentation. Extraction of certain organic molecules such as amino acids from rock and soil samples using a liquid solvent (H2O) has been shown to be more efficient (by approximately an order of magnitude) than heat extraction methods. As such, liquid extraction (using H2O) of amino acid molecules from rock cores or regolith material is a prime candidate for the required processing. In this scenario, electrospray ionization (ESI) of the liquid extract would be a natural choice for ionization of the analyte prior to interrogation by one of a variety of potential analytical separation techniques (mass spectroscopy, ion mobility spectroscopy, etc.). Aside from the obvious compatibility of ESI and liquid samples, ESI offers simplicity and a soft ionization capability. In order to demonstrate that liquid extraction and ESI can work as part of an in situ instrument on Mars, we must better understand and quantify the effect salts have on the ESI process. In the current work, we have endeavored to investigate the feasibility and limitations of negative mode ESI of Martian surface samples in the context of sample salt content using ion mobility spectroscopy (IMS).

  8. Picturing electron capture to the continuum in the transfer ionization of intermediate-energy He2+ collisions with argon

    NASA Astrophysics Data System (ADS)

    Zhang, R. T.; Ma, X.; Zhang, S. F.; Zhu, X. L.; Akula, Susmitha; Madison, D. H.; Li, B.; Qian, D. B.; Feng, W. T.; Guo, D. L.; Liu, H. P.; Yan, S. C.; Zhang, P. J.; Xu, S.; Chen, X. M.

    2013-01-01

    Electron emission occurring in transfer ionization for He2+ collisions with argon has been investigated using cold target recoil ion momentum spectroscopy. The double differential cross sections for electron capture to the continuum of the projectile (cusp-shaped electrons) are presented for collision energies from 17.5 to 75 keV/u. For an energy of 30 keV/u, we find a maximum in the experimental ratio of the cusp-shaped electron yield to the total electron yield. This result is explained in terms of the velocity matching between the projectile ion and the electron initially bound to the target. One of the important issues for double electron transitions is the role of electron-electron correlation. If this correlation is weak, then the transfer-ionization process can be viewed as two separate sequential processes. If this correlation is strong, then the transfer-ionization process would happen simultaneously and not sequentially. Our experimental and theoretical results indicate that correlation is weak and that the first step is target ionization followed by charge capture.

  9. Matrix-assisted laser desorption/ionization matrices for negative mode metabolomics.

    PubMed

    Fagerer, Stephan R; Nielsen, Simone; Ibáñez, Alfredo; Zenobi, Renato

    2013-01-01

    Matrix-assisted laser desorption/ionization (MALDI) has been shown to be highly sensitive for analyzing low-mass compounds such as metabolites if the right matrix is used. 9-aminoacridine (9AA) is the most commonly employed matrix for negative mode MALDI-MS in metabolomics. However, matrix interferences and the strongly varying sensitivity for different metabolites make a search for alternative matrices desirable, in order to identify compounds with a different chemical background and/or favoring a different range of analytes. We tested the performance of a series of potential negative mode MALDI matrices with a mix of 29 metabolites containing amino acids, nucleotide phosphates and Krebs cycle intermediates. While ethacridine lactate was found to provide limits of detection (LODs) in the low femtomole range for nucleotide phosphates, amino acids and Krebs cycle intermediates in the low picomole range, 4-amino-2-methylquinoline showed LODs in the picomole range for most metabolites, but is capable of ionizing a broader range of analytes than both 9AA and ethacridine. PMID:23841224

  10. Boron neutron capture therapy of brain tumors: investigation of urinary metabolites and oxidation products of sodium borocaptate by electrospray ionization mass spectrometry.

    PubMed

    Gibson, C R; Staubus, A E; Barth, R F; Yang, W; Kleinholz, N M; Jones, R B; Green-Church, K; Tjarks, W; Soloway, A H

    2001-12-01

    Boron neutron capture therapy (BNCT) is based on a nuclear capture reaction that occurs when boron-10, a stable isotope, is irradiated with low energy neutrons to produce high-energy alpha particles and recoiling lithium-7 nuclei. The purpose of the present study was to determine what urinary metabolites, if any, could be detected in patients with brain tumors who were given sodium borocaptate (BSH), a drug that has been used clinically for BNCT. BSH was infused intravenously over a 1-h time period at doses of 26.5, 44.1, or 88.2 mg/kg of body weight to patients with high-grade brain tumors. Electrospray ionization mass spectrometry has been used to investigate possible urinary metabolites of BSH. Chemical and instrument conditions were established to detect BSH and its possible metabolites in both positive and negative electrospray ionization modes. Using this methodology, boronated ions were found in patients' urine samples that appeared to be consistent with the following chemical structures: BSH sulfenic acid (BSOH), BSH sulfinic acid (BSO(2)H), BSH disulfide (BSSB), BSH thiosulfinate (BSOSB), and a BSH-S-cysteine conjugate (BSH-CYS). Although BSH has been used clinically for BNCT since the late 1960s, this is the first report of specific biotransformation products following administration to patients. Further studies will be required to determine both the biological significance of these metabolites and whether any of these accumulate in significant amounts in brain tumors. PMID:11717178

  11. Tetramethylammonium hydroxide as a reagent for complex mixture analysis by negative ion electrospray ionization mass spectrometry.

    PubMed

    Lobodin, Vladislav V; Juyal, Priyanka; McKenna, Amy M; Rodgers, Ryan P; Marshall, Alan G

    2013-08-20

    Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) enables the direct characterization of complex mixtures without prior fractionation. High mass resolution can distinguish peaks separated by as little as 1.1 mDa), and high mass accuracy enables assignment of elemental compositions in mixtures that contain tens of thousands of individual components (crude oil). Negative electrospray ionization (ESI) is particularly useful for the speciation of the most acidic petroleum components that are implicated in oil production and processing problems. Here, we replace conventional ammonium hydroxide by tetramethylammonium hydroxide (TMAH, a much stronger base, with higher solubility in toluene) to more uniformly deprotonate acidic components of complex mixtures by negative ESI FTICR MS. The detailed compositional analysis of four crude oils (light to heavy, from different geographical locations) reveals that TMAH reagent accesses 1.5-6 times as many elemental compositions, spanning a much wider range of chemical classes than does NH4OH. For example, TMAH reagent produces abundant negative electrosprayed ions from less acidic and neutral species that are in low abundance or absent with NH4OH reagent. More importantly, the increased compositional coverage of TMAH-modified solvent systems maintains, or even surpasses, the compositional information for the most acidic species. The method is not limited to petroleum-derived materials and could be applied to the analysis of dissolved organic matter, coal, lipids, and other naturally occurring compositionally complex organic mixtures. PMID:23919350

  12. Fragmentation of peptide negative molecular ions induced by resonance electron capture

    PubMed Central

    Vasil’ev, Yury V.; Figard, Benjamin J.; Morré, Jeff; Deinzer, Max L.

    2009-01-01

    A simple robust method to study resonance gas-phase reactions between neutral peptides of low volatility and free electrons has been designed and implemented. Resonance electron capture (REC) experiments were performed by several neutral model peptides and two naturally occurring peptides. The assignment of negative ions (NIs) formed in these gas-phase reactions was based on high mass-resolving power experiments. From these accurate mass measurements, it was concluded that fragment NIs formed by low (1–2 eV) energy REC are of the same types as those observed in electron capture∕transfer dissociation, where the positive charge is a factor. The main feature resulting from these REC experiments by peptides is the occurrence of zn−1 ions, which are invariably of the highest abundances in the negative ion mass spectra of larger peptides. [M–H]− NIs presumably the carboxylate anion structure dominate the REC spectra of smaller peptides. There was no evidence for the occurrence of the complementary reaction, i.e., the formations of cn+1 ions. Instead, cn ions arose without hydrogen∕proton transfer albeit with lower abundances than that observed for zn−1 ions. Only the amide forms of small peptides showed more abundant ion peaks for the cn ions than for the zn−1 ions. The mechanisms for the N–Cα bond cleavage are discussed. PMID:19655877

  13. Differentiation of (Mixed) Halogenated Dibenzo-p-Dioxins by Negative Ion Atmospheric Pressure Chemical Ionization.

    PubMed

    Fernando, Sujan; Green, M Kirk; Organtini, Kari; Dorman, Frank; Jones, Rhys; Reiner, Eric J; Jobst, Karl J

    2016-05-17

    Brominated and mixed halogenated dibenzo-p-dioxins (PBDDs and PXDDs) may well be as toxic as 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2378-TCDD), a compound reputed as one of the most toxic chemicals known to exist. However, studies on the occurrence of PXDDs have been hampered by a lack of authentic standards as well as separation techniques capable of resolving the enormous number of potential isomers. Electron ionization (EI) mass spectrometry based methods are of limited value due to the lack of isomer specific fragmentation. Negative ion atmospheric pressure chemical ionization (APCI(-)) of 2378-TCDD was described in this journal over 30 years ago. Under these conditions, the reaction between O2(-•) and 2378-TCDD results in structure diagnostic cleavages of the C-O bonds, which can distinguish TCDD isomers on the basis of Cl distribution between the two aromatic rings. In the present study, the analogous ether cleavages of PBDDs and PXDDs were studied using a gas chromatograph-quadrupole time-of-flight (GC-QTOF) mass spectrometer coupled using APCI. The results indicate comparable detection limits for the radical cations [M(•+)] and negative pseudomolecular ions [M-Cl+O](-): approximately 5 fg and 10 fg, respectively, for 2378-TCDD and 5-10 fg and 10-30 fg, respectively, for the 2,3,7,8-substituted PXDDs. Detection limits obtained by monitoring the ether cleavage products were somewhat higher (between 100 and 600 fg) but still acceptable for trace analysis of PXDDs. Such reactions may resolve coeluting isomers, which is crucial for the identification of PXDDs. The technique is demonstrated by differentiating PXDD isomer classes in a sample obtained from a major industrial fire that would not be feasible using EI or positive ion APCI(+). PMID:27074061

  14. Negative Ion In-Source Decay Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry for Sequencing Acidic Peptides

    NASA Astrophysics Data System (ADS)

    McMillen, Chelsea L.; Wright, Patience M.; Cassady, Carolyn J.

    2016-05-01

    Matrix-assisted laser desorption/ionization (MALDI) in-source decay was studied in the negative ion mode on deprotonated peptides to determine its usefulness for obtaining extensive sequence information for acidic peptides. Eight biological acidic peptides, ranging in size from 11 to 33 residues, were studied by negative ion mode ISD (nISD). The matrices 2,5-dihydroxybenzoic acid, 2-aminobenzoic acid, 2-aminobenzamide, 1,5-diaminonaphthalene, 5-amino-1-naphthol, 3-aminoquinoline, and 9-aminoacridine were used with each peptide. Optimal fragmentation was produced with 1,5-diaminonphthalene (DAN), and extensive sequence informative fragmentation was observed for every peptide except hirudin(54-65). Cleavage at the N-Cα bond of the peptide backbone, producing c' and z' ions, was dominant for all peptides. Cleavage of the N-Cα bond N-terminal to proline residues was not observed. The formation of c and z ions is also found in electron transfer dissociation (ETD), electron capture dissociation (ECD), and positive ion mode ISD, which are considered to be radical-driven techniques. Oxidized insulin chain A, which has four highly acidic oxidized cysteine residues, had less extensive fragmentation. This peptide also exhibited the only charged localized fragmentation, with more pronounced product ion formation adjacent to the highly acidic residues. In addition, spectra were obtained by positive ion mode ISD for each protonated peptide; more sequence informative fragmentation was observed via nISD for all peptides. Three of the peptides studied had no product ion formation in ISD, but extensive sequence informative fragmentation was found in their nISD spectra. The results of this study indicate that nISD can be used to readily obtain sequence information for acidic peptides.

  15. Aptamer Conjugated Multifunctional Nanoflowers as a Platform for Targeting, Capture and Detection in Laser Desorption Ionization Mass Spectrometry

    PubMed Central

    Ocsoy, Ismail; Gulbakan, Basri; Shukoor, Mohammed Ibrahim; Xiong, Xiangling; Chen, Tao; Powell, David H.; Tan, Weihong

    2013-01-01

    Although many different nanomaterials have been tested as substrates for laser desorption and ionization mass spectrometry (LDI-MS), this emerging field still requires more efficient multifuncional nanomaterials for targeting, enrichment and detection. Here, we report the use of gold-manganese oxide (Au@MnO) hybrid nanoflowers as an efficient matrix for LDI–MS. The nanoflowers were also functionalized with two different aptamers to target cancer cells and capture adenosine triphosphate (ATP), respectively. These nanoflowers were successfully used for metabolite extraction from cancer cell lysates. Thus, in one system, our multifunctional nanoflowers can 1) act as an ionization substrate for mass spectrometry, 2) target cancer cells, and 3) detect and analyze metabolites from cancer cells. PMID:23211039

  16. Specific interaction between negative atmospheric ions and organic compounds in atmospheric pressure corona discharge ionization mass spectrometry.

    PubMed

    Sekimoto, Kanako; Sakai, Mami; Takayama, Mitsuo

    2012-06-01

    The interaction between negative atmospheric ions and various types of organic compounds were investigated using atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. Atmospheric negative ions such as O(2)(-), HCO(3)(-), COO(-)(COOH), NO(2)(-), NO(3)(-), and NO(3)(-)(HNO(3)) having different proton affinities served as the reactant ions for analyte ionization in APCDI in negative-ion mode. The individual atmospheric ions specifically ionized aliphatic and aromatic compounds with various functional groups as atmospheric ion adducts and deprotonated analytes. The formation of the atmospheric ion adducts under certain discharge conditions is most likely attributable to the affinity between the analyte and atmospheric ion and the concentration of the atmospheric ion produced under these conditions. The deprotonated analytes, in contrast, were generated from the adducts of the atmospheric ions with higher proton affinity attributable to efficient proton abstraction from the analyte by the atmospheric ion. PMID:22528201

  17. Capture, ionization, and pair-production processes in relativistic heavy-ion collisions in the 1-GeV/nucleon energy range

    NASA Astrophysics Data System (ADS)

    Belkacem, A.; Gould, Harvey; Feinberg, B.; Bossingham, R.; Meyerhof, W. E.

    1997-10-01

    The cross sections for capture, ionization, capture from pair production, and free pair production were measured for 0.96-GeV/nucleon U92+ and 0.405-, 0.96-, and 1.3-GeV/nucleon La57+ ions incident on Au, Ag, and Cu targets. The cross sections for capture from pair production, free pair production, ionization, and total capture (the sum of capture from pair production, radiative electron capture, and nonradiative capture) are analyzed as a function of collision energy, projectile, and target atomic numbers. We find that, when the collision energy is increased from 0.405 GeV/nucleon to 1.3 GeV/nucleon, the capture from pair production and the free pair production cross sections increase by almost a factor of 6, while the capture cross section decreases by two orders of magnitude. The ionization cross section is found to vary very weakly with the collision energy in the 1-GeV/nucleon energy range. We found a dependence of free pair production cross sections on the target and projectile atomic number to be close to Z2, characteristic of an ionizationlike process. We also found a dependence of the capture from pair production cross sections on the target atomic number to be usually steeper than Z2t, and on the projectile atomic number, somewhat steeper than the Z5p, characteristic of a capturelike process. Theory and experiment are in some disagreement for capture from pair production, and free pair production, cross sections, but are in general agreement for the other capture processes and for ionization.

  18. Negative electrospray ionization on porous supporting tips for mass spectrometric analysis: electrostatic charging effect on detection sensitivity and its application to explosive detection.

    PubMed

    Wong, Melody Yee-Man; Man, Sin-Heng; Che, Chi-Ming; Lau, Kai-Chung; Ng, Kwan-Ming

    2014-03-21

    The simplicity and easy manipulation of a porous substrate-based ESI-MS technique have been widely applied to the direct analysis of different types of samples in positive ion mode. However, the study and application of this technique in negative ion mode are sparse. A key challenge could be due to the ease of electrical discharge on supporting tips upon the application of negative voltage. The aim of this study is to investigate the effect of supporting materials, including polyester, polyethylene and wood, on the detection sensitivity of a porous substrate-based negative ESI-MS technique. By using nitrobenzene derivatives and nitrophenol derivatives as the target analytes, it was found that the hydrophobic materials (i.e., polyethylene and polyester) with a higher tendency to accumulate negative charge could enhance the detection sensitivity towards nitrobenzene derivatives via electron-capture ionization; whereas, compounds with electron affinities lower than the cut-off value (1.13 eV) were not detected. Nitrophenol derivatives with pKa smaller than 9.0 could be detected in the form of deprotonated ions; whereas polar materials (i.e., wood), which might undergo competitive deprotonation with the analytes, could suppress the detection sensitivity. With the investigation of the material effects on the detection sensitivity, the porous substrate-based negative ESI-MS method was developed and applied to the direct detection of two commonly encountered explosives in complex samples. PMID:24492411

  19. CHLORIDEDETERMINATION IN HIGH IONIC STRENGTH SOLUTION OF AMMONIUM ACETATE USING NEGATIVE ION ELECTRON SPRAY IONIZATION (HPLC/MS)

    EPA Science Inventory

    A precise ion chromatography method has been developed for the determination of chloride in high ionic strength ammonium acetate solutions (10-5 M-5 M) using sodium carbonate/sodium bicarbonate as eluent. Negative ion electrospray ionization (ESI) mass spectrometry was used for q...

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

    EPA Science Inventory

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

  1. [Determination of cyflufenamid residue in carrots by gas chromatography-negative chemical ionization mass spectrometry].

    PubMed

    Yang, Wenquan; Shen, Weijian; Zhao, Zengyun; Xu, Jinzhong; Shen, Chongyu; Wu, Bin

    2008-07-01

    A method was developed for the determination of cyflufenamid residue in carrots by solid phase extraction-gas chromatography-negative chemical ionization mass spectrometry (SPE-GC-NCI/MS). Cyflufenamid residue was extracted with ethyl acetate from carrots. The extract was cleaned-up by an active carbon SPE column connected to a neutral alumina SPE column. The analysis was carried out by the GC-NCI/MS with selected ion monitoring mode. The recoveries of cyflufenamid in carrot samples were in the range from 74.9% to 94.6% at four spiked levels, 0.005, 0.01, 0.02, 0.04 mg/kg, and the relative standard deviations (RSD) were less than 9.7% for inter-days. The linearity of the method was good in the range from 10 to 1000 ng/mL, and the limit of detection (LOD) was 0.001 mg/kg, and the limit of quantitation (LOQ) was 0.005 mg/kg. The method is selective without interference and is suitable for the determination and confirmation of cyflufenamid residue in carrots. PMID:18959256

  2. Electron capture of dopants in two-photonic ionization in a poly(methyl methacrylate) solid

    SciTech Connect

    Tsuchida, Akira; Sakai, Wataru; Nakano, Mitsuru; Yamamoto, Masahide

    1992-10-29

    Behavior of the electron produced by two-photonic excitation of an aromatic donor in a poly(methyl methacrylate) solid was studied by the addition of the electron scavengers to the system. According to the Perrin type analysis for the two-photonically ejected electron, the capture radii (R{sub c}) of the scavengers examined were estimated to be from 8 to 40 {Angstrom}. For the two-photonically ejected electrons, R{sub c} is a capture radius for thermalized electrons. In this case the parent electron donor is not necessarily within this radius. On the other hand, for the fluorescence quenching, the distance between the donor and acceptor is within the static quenching radius (R{sub q}) of the donor. 13 refs., 4 figs., 2 tabs.

  3. Double-electron capture by highly-ionized atoms isolated at very low energy

    NASA Astrophysics Data System (ADS)

    Fogwell Hoogerheide, Shannon; Dreiling, Joan M.; Sahiner, Arda; Tan, Joseph N.

    2016-05-01

    Charge exchange with background gases, also known as electron capture processes, is important in the study of comets, controlled fusion energy, anti-matter atoms, and proposed one-electron ions in Rydberg states. However, there are few experiments in the very low energy regime that could be useful for further theoretical development. At NIST, highly-charged ions extracted from an electron-beam ion trap can be isolated with energy < 10 eV in a compact Penning trap. By controlling the background gas pressure and composition, the charge exchange rates can be studied. Fully stripped neon or other ions are held in the trap for varying lengths of time and allowed to interact with different background gases at multiple pressures. The ions are then pulsed to a time-of-flight detector to count the population of each charge state. Analysis using a system of rate equations yields information about the ion cloud expansion and single-electron capture rates. A substantial amount of double-electron capture is also observed. We present the relative rates and discuss the error budget. SFH and JMD were funded by National Research Council Research Associateship Awards during some of this work.

  4. Evidence of Double-Electron Capture by Highly-ionized Atoms Isolated at Very Low Energy

    NASA Astrophysics Data System (ADS)

    Fogwell Hoogerheide, Shannon; Sahiner, Arda; Tan, Joseph N.

    2015-05-01

    Electron capture processes are important in the study of comets, controlled fusion energy, anti-matter atoms, and proposed one-electron ions in Rydberg states. There are few studies for low energy. At NIST, highly-charged ions extracted from an electron-beam ion trap can be isolated with <10 eV energy using a recently developed compact Penning trap. By controlling the background gas pressure and composition, the charge exchange rates can be studied. Fully stripped neon ions are held in the trap for varying lengths of time and allowed to interact with different background gases at multiple pressures. The ions are then pulsed to a time-of-flight detector, to count the population of each charge state. Analysis yields information about the trap loss and single-electron capture rates. Moreover, evidence of double-electron capture is observed at low background gas pressures. Related work involves the resonant charge exchange of fully-stripped neon ions with laser-excited rubidium atoms to produce highly-excited one-electron ions, enabling a new measurement of the Rydberg constant. SFH funded by a National Research Council Research Associateship Award

  5. Electron emission from single-electron capture with simultaneous single-ionization reactions in 30-keV/u He{sup 2+}-on-argon collisions

    SciTech Connect

    Ma, X.; Zhang, S. F.; Zhu, X. L.; Feng, W. T.; Li, B.; Liu, H. P.; Zhang, R. T.; Guo, D. L.; Yan, S. C.; Zhang, P. J.; Wang, Q.; Li, C. Y.; Wang, J. G.

    2011-05-15

    Electron emission from the single-electron capture with simultaneous single ionization in 30 keV/u He{sup 2+} on argon was investigated using a reaction microscope, providing the electron energy spectra and momentum distributions. Intensive peaks for electrons with near-zero kinetic energies have been observed. It is demonstrated that mechanisms contributing to the electron emission include direct transfer ionization (DTI), double-electron capture with autoionization (DECA), and single-electron capture with autoionization (SECA) of target. Comparison of resonance energies shows that Ar{sup +} ions in SECA decay mainly through the 3s3p{sup 5}3d states by emitting Auger electrons, and He** in DECA decay through the 2l2l' states. The dependence of electron emission on the transverse momentum exchange has been studied. In the transfer ionization channel studied here, the DTI process dominates the electron emission, and no saddle point electron mechanism has been found.

  6. Characterization of a Hybrid Optical Microscopy/Laser Ablation Liquid Vortex Capture/Electrospray Ionization System for Mass Spectrometry Imaging

    DOE PAGESBeta

    Cahill, John F.; Kertesz, Vilmos; Van Berkel, Gary J.

    2015-10-22

    Herein, a commercial optical microscope, laser microdissection instrument was coupled with an electrospray ionization mass spectrometer via a low profile liquid vortex capture probe to yield a hybrid optical microscopy/mass spectrometry imaging system. The instrument has bright-field and fluorescence microscopy capabilities in addition to a highly focused UV laser beam that is utilized for laser ablation of samples. With this system, material laser ablated from a sample using the microscope was caught by a liquid vortex capture probe and transported in solution for analysis by electrospray ionization mass spectrometry. Both lane scanning and spot sampling mass spectral imaging modes weremore » used. The smallest area the system was able to ablate was ~0.544 μm × ~0.544 μm, achieved by oversampling of the smallest laser ablation spot size that could be obtained (~1.9 μm). With use of a model photoresist surface, known features as small as ~1.5 μm were resolved. The capabilities of the system with real world samples were demonstrated first with a blended polymer thin film containing poly(2-vinylpyridine) and poly(N-vinylcarbazole). Using spot sampling imaging, sub-micrometer sized features (0.62, 0.86, and 0.98 μm) visible by optical microscopy were clearly distinguished in the mass spectral images. A second real world example showed the imaging of trace amounts of cocaine in mouse brain thin tissue sections. Lastly, with use of a lane scanning mode with ~6 μm × ~6 μm data pixels, features in the tissue as small as 15 μm in size could be distinguished in both the mass spectral and optical images.« less

  7. Characterization of a Hybrid Optical Microscopy/Laser Ablation Liquid Vortex Capture/Electrospray Ionization System for Mass Spectrometry Imaging

    SciTech Connect

    Cahill, John F.; Kertesz, Vilmos; Van Berkel, Gary J.

    2015-10-22

    Herein, a commercial optical microscope, laser microdissection instrument was coupled with an electrospray ionization mass spectrometer via a low profile liquid vortex capture probe to yield a hybrid optical microscopy/mass spectrometry imaging system. The instrument has bright-field and fluorescence microscopy capabilities in addition to a highly focused UV laser beam that is utilized for laser ablation of samples. With this system, material laser ablated from a sample using the microscope was caught by a liquid vortex capture probe and transported in solution for analysis by electrospray ionization mass spectrometry. Both lane scanning and spot sampling mass spectral imaging modes were used. The smallest area the system was able to ablate was ~0.544 μm × ~0.544 μm, achieved by oversampling of the smallest laser ablation spot size that could be obtained (~1.9 μm). With use of a model photoresist surface, known features as small as ~1.5 μm were resolved. The capabilities of the system with real world samples were demonstrated first with a blended polymer thin film containing poly(2-vinylpyridine) and poly(N-vinylcarbazole). Using spot sampling imaging, sub-micrometer sized features (0.62, 0.86, and 0.98 μm) visible by optical microscopy were clearly distinguished in the mass spectral images. A second real world example showed the imaging of trace amounts of cocaine in mouse brain thin tissue sections. Lastly, with use of a lane scanning mode with ~6 μm × ~6 μm data pixels, features in the tissue as small as 15 μm in size could be distinguished in both the mass spectral and optical images.

  8. Avolition and expressive deficits capture negative symptom phenomenology: Implications for DSM-5 and schizophrenia research

    PubMed Central

    Messinger, Julie W; Trémeau, Fabien; Antonius, Daniel; Mendelsohn, Erika; Prudent, Vasthie; Stanford, Arielle D; Malaspina, Dolores

    2010-01-01

    The DSM-5 formulation presents an opportunity to refine the negative symptom assessments that are crucial for a schizophrenia diagnosis. This review traces the history of negative symptom constructs in neuropsychiatry from their earliest conceptualizations in the 19th century. It presents the relevant literature for distinguishing between different types of negative symptoms. Although a National Institute of Mental Health consensus initiative proposed that there are five separate negative symptom domains, our review of the individual items demonstrates no more than three negative symptom domains. Indeed, numerous factor analyses of separate negative symptom scales routinely identify only two domains: 1) expressive deficits, which include affective, linguistic and paralinguistic expressions, and 2) avolition for daily-life and social activities. We propose that a focus on expressive deficits and avolition will be of optimum utility for diagnosis, treatment-considerations, and research purposes compared to other negative symptom constructs. We recommend that these two domains should be assessed as separate dimensions in the DSM-5 criteria. PMID:20889248

  9. Power laws and self-similar behaviour in negative ionization fronts

    NASA Astrophysics Data System (ADS)

    Arrayás, Manuel; Fontelos, Marco A.; Trueba, José L.

    2006-06-01

    We study anode-directed ionization fronts in curved geometries. An electric shielding factor determines the behaviour of the electric field and the charged particle densities. From a minimal streamer model, a Burgers type equation which governs the dynamics of the electric shielding factor is obtained when electron diffusion is neglected. A Lagrangian formulation is then derived to analyse the ionization fronts. Power laws for the velocity and the amplitude of streamer fronts are found numerically and calculated analytically by using the shielding factor formulation. The phenomenon of geometrical diffusion is explained and clarified, and a universal self-similar asymptotic behaviour is derived.

  10. Native electrospray ionization and electron-capture dissociation for comparison of protein structure in solution and the gas phase

    PubMed Central

    Zhang, Hao; Cui, Weidong

    2013-01-01

    The importance of protein and protein-complex structure motivates improvements in speed and sensitivity of structure determination in the gas phase and comparison with that in solution or solid state. An opportunity for the gas phase measurement is mass spectrometry (MS) combined with native electrospray ionization (ESI), which delivers large proteins and protein complexes in their near-native states to the gas phase. In this communication, we describe the combination of native ESI, electron-capture dissociation (ECD), and top-down MS for exploring the structures of ubiquitin and cytochrome c in the gas phase and their relation to those in the solid-state and solution. We probe structure by comparing the protein's flexible regions, as predicted by the B-factor in X-ray crystallography, with the ECD fragments. The underlying hypothesis is that maintenance of structure gives fragments that can be predicted from B-factors. This strategy may be applicable in general when X-ray structures are available and extendable to the study of intrinsically disordered proteins. PMID:24363606

  11. MoS2/Ag nanohybrid: A novel matrix with synergistic effect for small molecule drugs analysis by negative-ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Zhao, Yaju; Deng, Guoqing; Liu, Xiaohui; Sun, Liang; Li, Hui; Cheng, Quan; Xi, Kai; Xu, Danke

    2016-09-21

    This paper reports a facile synthesis of molybdenum disulfide nanosheets/silver nanoparticles (MoS2/Ag) hybrid and its use as an effective matrix in negative ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The nanohybrid exerts a strong synergistic effect, leading to high performance detection of small molecule analytes including amino acids, peptides, fatty acids and drugs. The enhancement of laser desorption/ionization (LDI) efficiency is largely attributed to the high surface roughness and large surface area for analyte adsorption, better dispersibility, increased thermal conductivity and enhanced UV energy absorption as compared to pure MoS2. Moreover, both Ag nanoparticles and the edge of the MoS2 layers function as deprotonation sites for proton capture, facilitating the charging process in negative ion mode and promoting formation of negative ions. As a result, the MoS2/Ag nanohybrid proves to be a highly attractive matrix in MALDI-TOF MS, with desired features such as high desorption/ionization efficiency, low fragmentation interference, high salt tolerance, and no sweet-spots for mass signal. These characteristic properties allowed for simultaneous analysis of eight different drugs and quantification of acetylsalicylic acid in the spiked human serum. This work demonstrates for the first time the fabrication and application of a novel MoS2/Ag hybrid, and provides a new platform for use in the rapid and high throughput analysis of small molecules by mass spectrometry. PMID:27590549

  12. Alternative Methodology for Boron Isotopic Analysis of CaCO3 by Negative Thermal Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Dwyer, G. S.; Vengosh, A.

    2012-12-01

    Negative thermal ionization mass spectrometry (NTIMS) has been a common tool for investigating boron isotopes in CaCO3 and other environmental samples, the high sensitivity of BO2- ionization enabling measurements of ng levels of boron. However, B isotope measurement by this technique suffers from a number of problems, including: (1) fractionation induced by selective ionization of B isotopes in the mass spectrometer; (2) CNO- interference on mass 42 ([10BO2]-) that may be present in some filament load solutions (such as B-free seawater processed through ion-exchange resin), and (3) potential matrix effects due to widely differing chemistry of samples and standards. Here we examine a potentially improved NTIMS methodology that incudes removal of sample-related calcium (and other cations) by ion exchange and uses an alternative filament loading solution prepared from high-purity single-element solutions of Ca, Mg, Na, and K. Initial results suggest that this new method may offer significant improvement over the more traditional NTIMS approach in which digested CaCO3 samples are directly loaded onto filaments in B-free seawater. Replicate analyses of standards and samples yield a typical standard deviation of approximately 0.3‰ δ11B and boron isotopic compositions comparable to reported or consensus values. Fractionation during analysis has thus far typically been less than 0.5‰ δ11B. The method delivers boron ionization efficiency similar to directly-loaded seawater, and negligible signal at mass 26 (CN-), a proxy for the possible interfering molecular CNO- ion. Standards and samples behave similarly and predictably during filament heating and analysis, thus allowing for fully automated data acquisition, which in turn may increase sample throughput and reduce potential analytical inconsistencies associated with operator-controlled heating and analysis.

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

    PubMed

    Thomas, Aurélien; Widmer, Christèle; Hopfgartner, Gérard; Staub, Christian

    2007-11-01

    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 microL 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 detection of the analytes was performed in the selected reaction-monitoring mode on a triple quadrupole instrument after negative-ion chemical ionization. The assay was found to be linear in the concentration range of 0.5-20 ng/mL for THC and THC-OH, and of 2.5-100 ng/mL for THC-COOH. Repeatability and intermediate precision were found less than 12% for all concentrations tested. Under standard chromatographic conditions, the run cycle time would have been 15 min. By using fast conditions of separation, the assay analysis time has been reduced to 5 min, without compromising the chromatographic resolution. Finally, a simple approach for estimating the uncertainty measurement is presented. PMID:17913432

  14. The effect of ionizing radiation on the blood-brain-barrier (BBB): Considerations for the application of Boron Neutron Capture Therapy (BNCT) of brain tumors

    SciTech Connect

    Dorn, R.V. III; Spickard, J.H.; Griebenow, M.L.

    1988-01-01

    All methods of Boron Neutron Capture Therapy (BNCT) in use or envisioned for treatment of brain tumors have an element of ionizing radiation (incident and induced). This paper reviews data on the effects of ionizing radiation on the blood-brain-barrier (BBB) and the blood-tumor-barrier (BTB) and the potential impact of the effects on the delivery techniques of BNCT. The objectives are: review the available technique for BNCT of brain tumors; review the literature on experimental and human studies regarding the effects of ionizing radiation on the BBB; discuss the impact of these effects on the fractionization question for BNCT; and draw conclusions from that information. 22 refs., 4 tabs.

  15. Differentiation of commercial fuels based on polar components using negative electrospray ionization/mass spectrometry

    USGS Publications Warehouse

    Rostad, C.E.

    2006-01-01

    Polar components in fuels may enable differentiation between fuel types or commercial fuel sources. A range of commercial fuels from numerous sources were analyzed by flow injection analysis/electrospray ionization/mass spectrometry without extensive sample preparation, separation, or chromatography. This technique enabled screening for unique polar components at parts per million levels in commercial hydrocarbon products, including a range of products from a variety of commercial sources and locations. Because these polar compounds are unique in different fuels, their presence may provide source information on hydrocarbons released into the environment. This analysis was then applied to mixtures of various products, as might be found in accidental releases into the environment. Copyright ?? Taylor & Francis Group, LLC.

  16. Energy and charge state dependences of transfer ionization to single capture ratio for fast multiply charged ions on helium

    NASA Astrophysics Data System (ADS)

    Unal, Ridvan

    The charge state and energy dependences of Transfer Ionization (TI) and Single Capture (SC) processes in collisions of multiply charged ions with He from intermediate to high velocities are investigated using coincident recoil ion momentum spectroscopy. The collision chamber is commissioned on the 15-degree port of a switching magnet, which allows the delivery of a beam with very little impurity. The target was provided from a supersonic He jet with a two-stage collimation. The two-stage, geometrically cooled, supersonic He jet has significantly reduced background contribution to the spectrum compared to a single stage He jet. In the case of a differentially pumped gas cell complex calculations based on assumptions for the correction due to the collisions with the contaminant beam led to corrections, which were up to 50%. The new setup allows one to make a direct separation of contaminant processes in the experimental data using the longitudinal momentum spectra. Furthermore, this correction is much smaller (about 8.8%) yielding better overall precision. The collision systems reported here are 1 MeV/u O(4--8)+ , 0.5--2.5 MeV/u F(4--9)+, 2.0 MeV/u Ti 15,17,18+, 1.6--1.75 MeV/u Cu18,20+ and 0.25--0.5 MeV/u I(15--25)+ ions interacting with helium. We have determined the sTIsSC ratio for high velocity highly charged ions on He at velocities in the range of 6 to 10 au and observed that the ratio is monotonically decreasing with velocity. Furthermore, we see a ratio that follows a q2 dependence up to approximately q = 9. Above q = 9 the experimental values exceed the q2 dependence prediction due to antiscreening. C. D. Lin and H. C. Tseng have performed coupled channel calculations for the energy dependence of TI and SC for F9+ + He and find values slightly higher than our measured values, but with approximately the same energy dependence. The new data, Si, Ti and Cu, go up only to q = 20 and show a smooth monotonically increasing TI/SC ratio. The TI/SC ratio for I (15

  17. Quantitative determination of terbutaline and orciprenaline in human plasma by gas chromatography/negative ion chemical ionization/mass spectrometry.

    PubMed

    Leis, H J; Gleispach, H; Nitsche, V; Malle, E

    1990-06-01

    A method for the determination of unconjugated terbutaline and orciprenaline in human plasma is described. The assay is based on stable isotope dilution gas chromatography/negative ion chemical ionization/mass spectrometry. An inexpensive and rapid method for preparation of stable isotope labelled analogues as well as their use in quantitative gas chromatography/mass spectrometry is shown. A highly efficient sample work-up procedure with product recoveries of more than 95% is presented. The method developed permits quantitative measurement of terbutaline and orciprenaline in human plasma down to 100 pg ml-1, using 1 ml of sample. Plasma levels of terbutaline after oral administration of 5 mg of terbutaline sulphate were estimated. PMID:2357489

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

    PubMed

    Blum, W; Faigle, J W; Pfaar, U; Sallmann, A

    1996-10-25

    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 a level of 1.10(-9) g/ml. With direct extraction, the metabolites could be analysed in one step as open-chained acids and as (cyclic) oxindoles. By acidic hydrolysis the conjugates were transformed to the oxindoles. With both methods, a new main metabolite, [2-[2,6-dichloro-4-hydroxy-3-methoxyphenyl)amino]phenyl]acetic acid, was identified The mechanism of its formation is discussed. PMID:8953166

  19. The background atmospheric concentrations of cyclic perfluorocarbon tracers determined by negative ion-chemical ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Simmonds, P. G.; Greally, B. R.; Olivier, S.; Nickless, G.; Cooke, K. M.; Dietz, R. N.

    The background atmospheric mixing ratios for a range of cyclic perfluorocarbons (cyclic-PFCs), widely used in atmospheric dispersion studies, have been measured by gas chromatography-mass spectrometry in negative ion-chemical ionization mode. Background concentrations range from <1 fl l -1 to >10 fl l -1, where femtolitre is expressed as parts in 10 15 (ppqv). Because of their very long atmospheric lifetimes (>3000 yr) the present day concentrations represent the accumulated emissions from all sources, although significant commercial production did not commence until the 1960s. Cyclic-PFCs are potent greenhouse gases; however, their atmospheric concentrations are currently so low as to make an insignificant contribution to global warming.

  20. Collision-induced dissociation analysis of negative atmospheric ion adducts in atmospheric pressure corona discharge ionization mass spectrometry.

    PubMed

    Sekimoto, Kanako; Takayama, Mitsuo

    2013-05-01

    Collision-induced dissociation (CID) experiments were performed on atmospheric ion adducts [M + R](-) formed between various types of organic compounds M and atmospheric negative ions R(-) [such as O2(-), HCO3(-), COO(-)(COOH), NO2(-), NO3(-), and NO3(-)(HNO3)] in negative-ion mode atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. All of the [M + R](-) adducts were fragmented to form deprotonated analytes [M - H](-) and/or atmospheric ions R(-), whose intensities in the CID spectra were dependent on the proton affinities of the [M - H](-) and R(-) fragments. Precursor ions [M + R](-) for which R(-) have higher proton affinities than [M - H](-) formed [M - H](-) as the dominant product. Furthermore, the CID of the adducts with HCO3(-) and NO3(-)(HNO3) led to other product ions such as [M + HO](-) and NO3(-), respectively. The fragmentation behavior of [M + R](-) for each R(-) observed was independent of analyte type (e.g., whether the analyte was aliphatic or aromatic, or possessed certain functional groups). PMID:23479312

  1. Typing of Blood-Group Antigens on Neutral Oligosaccharides by Negative-Ion Electrospray Ionization Tandem Mass Spectrometry

    PubMed Central

    Zhang, Hongtao; Zhang, Shuang; Tao, Guanjun; Zhang, Yibing; Mulloy, Barbara; Zhan, Xiaobei; Chai, Wengang

    2013-01-01

    Blood-group antigens, such as those containing fucose and bearing the ABO(H)- and Lewis-type determinants expressed on the carbohydrate chains of glycoproteins and glycolipids, and also on unconjugated free oligosaccharides in human milk and other secretions, are associated with various biological functions. We have previously shown the utility of negative-ion electrospay ionization tandem mass spectrometry with collision-induced dissociation (ESI-CID-MS/MS) for typing of Lewis (Le) determinants, e.g. Lea, Lex, Leb, and Ley on neutral and sialylated oligosaccharide chains. In the present report we extended the strategy to characterization of blood-group A-, B- and H-determinants on type 1 and type 2, and also on type 4 globoside chains to provide a high sensitivity method for typing of all the major blood-group antigens, including the A, B, H, Lea, Lex, Leb, and Ley determinants, present in oligosaccharides. Using the principles established we identified two minor unknown oligosaccharide components present in the products of enzymatic synthesis by bacterial fermentation. We also demonstrated that the unique fragmentations derived from the D- and 0,2A-type cleavages observed in ESI-CID-MS/MS, which are important for assigning blood-group and chain types, only occur under the negative-ion conditions for reducing sugars but not for reduced alditols or under positive-ion conditions. PMID:23692402

  2. Processes involving electron capture and multiple ionization in collisions of fast H+ and He2+ ions with lead atoms

    NASA Astrophysics Data System (ADS)

    McCartney, P. C. E.; Shah, M. B.; Geddes, J.; Gilbody, H. B.

    1999-12-01

    A crossed-beam technique incorporating time-of-flight analysis and coincidence counting of the collision products has been used to study Pbq+ formation with q up to 8 in collisions between ground-state Pb atoms and H+ and He2+ ions within the range 50-600 keV amu-1. The separate cross sections for simple charge transfer, transfer ionization, and pure ionization leading to the formation of Pbq+ ions have been obtained and the relative importance of these processes has been established. Accurate measurements and rigorous theoretical descriptions of these multielectron processes in such heavy atoms are difficult and data are still very limited. The present measurements have been designed to extend our previous studies of multiple ionization of a few selected heavy metal atoms and to provide a further check on the extent to which the main collision processes can be described quantitatively in terms of simple models based on an independent electron description. In our previous work with Fe, Cu, and Ga atoms using the same experimental approach, we were able to describe the formation of multiply charged ions through both transfer ionization and pure ionization with a high degree of success using an independent electron model. However, the present results for Pb show that the success of this simple approach is much more limited for these much heavier atoms.

  3. Negative ion spectrometry for detecting nitrated explosives

    NASA Technical Reports Server (NTRS)

    Boettger, H. G.; Yinon, J.

    1975-01-01

    Ionization procedure is modified to produce mainly negative ions by electron capture. Peaks of negative ions are monitored conventionally. Nitrated organic materials could be identified directly from sample sniff inlet stream by suitably modified mass spectrometer because of unique electronegativity which nitro group imparts to organic material.

  4. Fine structure and ionization energy of the 1s2s2p 4P state of the helium negative ion He-.

    PubMed

    Wang, Liming; Li, Chun; Yan, Zong-Chao; Drake, G W F

    2014-12-31

    The fine structure and ionization energy of the 1s2s2p (4)P state of the helium negative ion He(-) are calculated in Hylleraas coordinates, including relativistic and QED corrections up to O(α(4)mc(2)), O((μ/M)α(4)mc(2)), O(α(5)mc(2)), and O((μ/M)α(5)mc(2)). Higher order corrections are estimated for the ionization energy. A comparison is made with other calculations and experiments. We find that the present results for the fine structure splittings agree with experiment very well. However, the calculated ionization energy deviates from the experimental result by about 1 standard deviation. The estimated theoretical uncertainty in the ionization energy is much less than the experimental accuracy. PMID:25615325

  5. Charge Enhancement of Single-Stranded DNA in Negative Electrospray Ionization Using the Supercharging Reagent Meta-nitrobenzyl Alcohol

    NASA Astrophysics Data System (ADS)

    Brahim, Bessem; Alves, Sandra; Cole, Richard B.; Tabet, Jean-Claude

    2013-12-01

    Charge enhancement of single-stranded oligonucleotide ions in negative ESI mode is investigated. The employed reagent, meta-nitrobenzyl alcohol (m-NBA), was found to improve total signal intensity (Itot), increase the highest observed charge states (zhigh), and raise the average charge states (zavg) of all tested oligonucleotides analyzed in negative ESI. To quantify these increases, signal enhancement ratios (SER1%) and charge enhancement coefficients (CEC1%) were introduced. The SER1%, (defined as the quotient of total oligonucleotide ion abundances with 1 % m-NBA divided by total oligonucleotide abundance without m-NBA) was found to be greater than unity for every oligonucleotide tested. The CEC1% values (defined as the average charge state in the presence of 1 % m-NBA minus the average charge state in the absence of m-NBA) were found to be uniformly positive. Upon close inspection, the degree of charge enhancement for longer oligonucleotides was found to be dependent upon thymine density (i.e., the number and the location of phospho-thymidine units). A correlation between the charge enhancement induced by the presence of m-NBA and the apparent gas-phase acidity (largely determined by the sequence of thymine units but also by the presence of protons on other nucleobases) of multiply deprotonated oligonucleotide species, was thus established. Ammonium cations appeared to be directly involved in the m-NBA supercharging mechanism, and their role seems to be consistent with previously postulated ESI mechanisms describing desorption/ionization of single-stranded DNA into the gas phase.

  6. Ionization and electron-capture cross sections for single- and multiple-electron removal from H2O by Li3 + impact

    NASA Astrophysics Data System (ADS)

    Luna, H.; Wolff, W.; Montenegro, E. C.; Tavares, André C.; Lüdde, H. J.; Schenk, G.; Horbatsch, M.; Kirchner, T.

    2016-05-01

    In this work, we report experimental and theoretical ionization and electron-capture cross sections for single-, double- and triple-electron removal from H2O by Li3 + impact at energies ranging from 0.75 to 5.8 MeV. The experiment was carried out by selecting both the final charge state of the projectile and the ejected fragments in coincidence to obtain cross sections associated with ionization and electron-capture channels. The ionic fragments and the emitted electrons produced under single-collision conditions were collected by a time-of-flight spectrometer with single-hit (e.g., OH++H0 ) and double-hit events (e.g., OH++H+ ) properly discriminated. For the one- and two-electron removal cases, the calculations based on the basis generator method for orbital propagation agree well with the experiment for most of the collision channels studied. Auger-electron emission after vacancy production in the inner 2 a1 orbital of H2O is shown to have a substantial effect on the final charge-state distributions over the entire impact-energy interval.

  7. Simultaneous enantioselective determination of amphetamine and congeners in hair specimens by negative chemical ionization gas chromatography-mass spectrometry.

    PubMed

    Martins, Liliane; Yegles, Michel; Chung, Heesun; Wennig, Robert

    2005-10-15

    Enantioselective quantification of amphetamine (AM), methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyethylamphetamine (MDEA) enantiomers in hair using gas chromatography-mass spectrometry (GC-MS) is described. Hair specimens were digested with 1M sodium hydroxide at 100 degrees C for 30 min and extracted by a solid phase procedure using Cleanscreen ZSDAU020. Extracted analytes were derivatised with (S)-heptafluorobutyrylprolyl chloride and the resulting diastereoisomers were quantified by GC-MS operating in the negative chemical ionization mode. Extraction yields were between 73.0 and 97.9%. Limits of detection varied in the range of 2.1-45.9 pg/mg hair, whereas the lowest limits of quantification varied between 4.3 and 91.8 pg/mg hair. Intra- and inter-assay precision and respective accuracy were acceptable. The enantiomeric ratios (R versus S) of AM, MA, MDA, MDMA and MDEA were determined in hair from suspected amphetamine abusers. Only MA and AM enantiomers were detectable in this collective and the quantification data showed in most cases higher concentrations of (R)-MA and (R)-AM than those of the corresponding (S)-enantiomers. PMID:16154523

  8. [Determination of 16 polychlorinated biphenyls in fish oil by gas chromatography-negative ion chemical ionization-mass spectrometry].

    PubMed

    Wang, Li; Li, Shushu; Zhang, Zhan; Wang, Shoulin; Li, Lei

    2015-08-01

    An analytical method for the simultaneous determination of 16 polychlorinated biphenyls (PCBs) in fish oil was developed. PCBs were extracted from fish oil with n-hexane, purified by sulfuric acid and determined by using gas chromatography-negative ion chemical ionization-mass spectrometry (GC-NCI-MS) in selected ion-monitoring (SIM) mode. A good linear relationship (r > 0.99) was observed with the PCBs concentrations from 0.01 µg/L to 10 µg/L, and the limits of quantification (LOQ, S/N = 10) were between 3 pg/g and 67 pg/g for different kinds of PCBs. The average recoveries ranged from 62.3% to 121.8% with the relative standard deviations ( RSDs, n = 3) smaller than 12%. Compared with the traditional pre-treatment of multiple material solid phase extraction, this new method is simple, rapid and less organic solvent usage. Meanwhile the method has good selectivity and sensitivity, and it is suitable for the determination of multiple trace PCBs in fish oil. PMID:26749866

  9. Identification of nitroaromatics in diesel exhaust particulate using gas chromatography/negative ion chemical ionization mass spectrometry and other techniques

    SciTech Connect

    Newton, D.L.; Erickson, M.D.; Tomer, K.B.; Pellizzari, E.D.; Gentry, P.

    1982-04-01

    A series of nitroaromatic compounds were identified in diesel exhaust particulate extract. Isomers of nitroanthracene (and/or nitrophenanthrene) and nitropyrene (and/or nitrofluoranthene) were unequivocally identified. Alkyl homologues of nitroanthracene through C/sub 3/-alkyl-nitroanthracene were tentatively identified. In addition, a C/sub 18/H/sub 11/NO/sub 2/ isomer was tentatively identified. The nitro-substituted polynuclear aromatic hydrocarbons (PAHs) were found in two fractions of diesel exhaust particulate extract collected from a low-pressure liquid chromatography (LPLC) column. One of the two fractions containing nitroaromatic constitutents accounted for a large percentage of the mutagenicity of the crude particulate extract. Initial identification were made by using high-resolution gas chromatography/electron impact mass spectrometry/computer (GC/EIMS) and negative ion chemical ionization mass specrometry/computer (GC/NICIMS). These identifications were confirmed by direct probe high-resolution mass spectrometry (HRMS) and gas chromatography/Fourier transform infrared spectrometry (GC/FT IR). The relative merit of each analytical technique for the determination of nitroaromatics is discussed with emphasis on the usefulness of GC/NICIMS as a means of analyzing for nitro-substituted PAHs.

  10. Measurement of the beta+ and orbital electron-capture decay rates in fully ionized, hydrogenlike, and heliumlike 140Pr ions.

    PubMed

    Litvinov, Yu A; Bosch, F; Geissel, H; Kurcewicz, J; Patyk, Z; Winckler, N; Batist, L; Beckert, K; Boutin, D; Brandau, C; Chen, L; Dimopoulou, C; Fabian, B; Faestermann, T; Fragner, A; Grigorenko, L; Haettner, E; Hess, S; Kienle, P; Knöbel, R; Kozhuharov, C; Litvinov, S A; Maier, L; Mazzocco, M; Montes, F; Münzenberg, G; Musumarra, A; Nociforo, C; Nolden, F; Pfützner, M; Plass, W R; Prochazka, A; Reda, R; Reuschl, R; Scheidenberger, C; Steck, M; Stöhlker, T; Torilov, S; Trassinelli, M; Sun, B; Weick, H; Winkler, M

    2007-12-31

    We report on the first measurement of the beta+ and orbital electron-capture decay rates of 140Pr nuclei with the simplest electron configurations: bare nuclei, hydrogenlike, and heliumlike ions. The measured electron-capture decay constant of hydrogenlike 140Pr58+ ions is about 50% larger than that of heliumlike 140Pr57+ ions. Moreover, 140Pr ions with one bound electron decay faster than neutral 140Pr0+ atoms with 59 electrons. To explain this peculiar observation one has to take into account the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay. PMID:18233571

  11. Trace level determination of organochlorine, organophosphorus and pyrethroid pesticides in lanolin using gel permeation chromatography followed by dual gas chromatography and gas chromatography-negative chemical ionization mass spectrometric confirmation.

    PubMed

    Jover, Eric; Bayona, Josep Maria

    2002-03-15

    A methodology for multi-class pesticide determination at trace level in lanolin is presented. Gel permeation chromatography on a Bio-Beads SX-3 column followed by a dual GC chromatographic determination has been developed. The effluent of the analytical column (50% diphenyl-methyl- or 14% cyanopropyl-phenylpolysiloxane) was split into an electron-capture and a nitrogen-phosphorus detection system. The chromatographic system was optimised for 28 pesticides commonly used to control sheep pests and corresponding to organochlorine, organophosphorus and pyretroid classes. Identification has been carried out by gas chromatography coupled to negative chemical ionization mass spectrometry. Recoveries ranged from 72 to 94% and the detection limits from 20 to 97 ng/g depending on the pesticide class, the RSDs were below 10%. Finally, the developed analytical methodology has been successfully applied to the determination of pesticides in several lanolin samples. PMID:11990995

  12. Evaluation of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry for species identification of nonfermenting Gram-negative bacilli.

    PubMed

    Almuzara, Marisa; Barberis, Claudia; Traglia, Germán; Famiglietti, Angela; Ramirez, Maria Soledad; Vay, Carlos

    2015-05-01

    Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) to identify 396 Nonfermenting Gram-Negative Bacilli clinical isolates was evaluated in comparison with conventional phenotypic tests and/or molecular methods. MALDI-TOF MS identified to species level 256 isolates and to genus or complex level 112 isolates. It identified 29 genera including uncommon species. PMID:25765149

  13. Soft Ionization of Saturated Hydrocarbons, Alcohols and Nonpolar Compounds by Negative-Ion Direct Analysis in Real-Time Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Cody, Robert B.; Dane, A. John

    2013-03-01

    Large polarizable n-alkanes (approximately C18 and larger), alcohols, and other nonpolar compounds can be detected as negative ions when sample solutions are injected directly into the sampling orifice of the atmospheric pressure interface of the time-of-flight mass spectrometer with the direct analysis in real time (DART) ion source operating in negative-ion mode. The mass spectra are dominated by peaks corresponding to [M + O2]‾•. No fragmentation is observed, making this a very soft ionization technique for samples that are otherwise difficult to analyze by DART. Detection limits for cholesterol were determined to be in the low nanogram range.

  14. M-shell electron capture and direct ionization of gold by 25-MeV carbon and 32-MeV oxygen ions

    NASA Astrophysics Data System (ADS)

    Andrews, M. C.; McDaniel, F. D.; Duggan, J. L.; Miller, P. D.; Pepmiller, P. L.; Krause, H. F.; Rosseel, T. M.; Rayburn, L. A.; Mehta, R.; Lapicki, G.

    1985-05-01

    M-shell X-ray production cross sections have been measured for thin solid targets of Au for 25 MeV 126C q+ ( q = 4, 5, 6) and for 32 MeV 168O q+ ( q = 5, 7, 8). The microscopic cross sections were determined from measurements made with targets ranging in thickness from 0.5 to 100 μg/cm 2. For projectiles with one or two K-shell vacancies, the target M-shell X-ray production cross sections are found to be enhanced over those by projectiles without a K-shell vacancy. The sum of direct ionization to the continuum (DI) and electron capture (EC) to the L, M, N.. shells and EC to the K-shell of the projectile have been extracted from the data. The results are compared with the predictions of first Born theories, i.e. PWBA for DI and OBK of Nikolaev for EC and the ECPSSR approach that accounts for energy loss. Coulomb deflection and relativistic effects in the perturbed stationary state theory.

  15. Conversion of 3-nitrotyrosine to 3-aminotyrosine residues facilitates mapping of tyrosine nitration in proteins by electrospray ionization-tandem mass spectrometry using electron capture dissociation.

    PubMed

    Guo, Jia; Prokai, Laszlo

    2012-12-01

    Protein tyrosine nitration is associated with oxidative stress and various human diseases. Tandem mass spectrometry has been the method of choice for the identification and localization of this posttranslational modification to understand the underlying mechanisms and functional consequences. Due to the electron predator effect of the nitro group limiting fragmentation of the peptide backbone, electron-based dissociation has not been applicable, however, to nitrotyrosine-containing peptides. A straightforward conversion of the nitrotyrosine to the aminotyrosine residues is introduced to address this limitation. When tested with nitrated ubiquitin and human serum albumin as model proteins in top-down and bottom-up approaches, respectively, this chemical derivatization enhanced backbone fragmentation of the corresponding nitroproteins and nitropeptides by electron capture dissociation (ECD). Increased sequence coverage has been obtained by combining in the bottom-up strategy the conversion of nitrotyrosine to aminotyrosine and introducing, in addition to trypsin, a further digesting enzyme of complementary specificity, when protein nitration was mapped by liquid chromatography-electrospray ionization tandem mass spectrometry using both collision-induced dissociation (CID) and ECD. PMID:23280749

  16. 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

    Raina, Renata; Hall, Patricia

    2008-01-01

    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 μL−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 μL−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 μL−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 μL−1) for pesticides with poor NCI response (OPs: sulfotep, phorate, aspon, ethion, and OCs: alachlor, aldrin, perthane, and DDE, DDD, DDT). PMID:19609395

  17. Comparison of negative-ion proton-transfer with iodide ion chemical ionization mass spectrometry for quantification of isocyanic acid in ambient air

    NASA Astrophysics Data System (ADS)

    Woodward-Massey, Robert; Taha, Youssef M.; Moussa, Samar G.; Osthoff, Hans D.

    2014-12-01

    Isocyanic acid (HNCO) is a trace gas pollutant of potential importance to human health whose measurement has recently become possible through the development of negative-ion proton-transfer chemical ionization mass spectrometry (NI-PT-CIMS) with acetate reagent ion. In this manuscript, an alternative ionization and detection scheme, in which HNCO is quantified by iodide CIMS (iCIMS) as a cluster ion at m/z 170, is described. The sensitivity was inversely proportional to water vapor concentration but could be made independent of humidity changes in the sampled air by humidifying the ion-molecule reaction (IMR) region of the CIMS. The performance of the two ionization schemes was compared and contrasted using ambient air measurements of HNCO mixing ratios in Calgary, AB, Canada, by NI-PT-CIMS with acetate reagent ion from Dec 16 to 20, 2013, and by the same CIMS operated in iCIMS mode from Feb 3 to 7, 2014. The iCIMS exhibited a greater signal-to-noise ratio than the NI-PT-CIMS, not because of its sensitivity, which was lower (˜0.083 normalized counts per second (NCPS) per parts-per-trillion by volume (pptv) compared to ˜9.7 NCPS pptv-1), but because of a much lower and more stable background (3 ± 4 compared to a range of ˜2 × 103 to ˜6 × 103 NCPS). For the Feb 2014 data set, the HNCO mixing ratios in Calgary air ranged from <12 to 94 pptv (median 34 pptv), were marginally higher at night than during day, and correlated with nitrogen oxide (NOx = NO + NO2) mixing ratios and submicron particle volume. The ratios of HNCO to NOx observed are within the range of emission ratios reported for gasoline-powered motor vehicles.

  18. A sensitive and selective method for the determination of selected pesticides in fruit by gas chromatography/mass spectrometry with negative chemical ionization.

    PubMed

    Belmonte Valles, N; Retamal, M; Mezcua, M; Fernández-Alba, A R

    2012-11-16

    Multiresidue methods (MRMs) for pesticides residues determination in fruit and vegetables, based on GC-MS, are mainly performed in electron impact ionization mode. However an important group of them provide much better response working in negative chemical ionization mode due to the elimination of a high percentage of background signal. Considering that a selective and sensitive method has been developed for the determination of multiclass pesticide residues in different commodities by GC-MS with a triple stage quadrupole analyzer (GC-TSQ-MS); the pesticide signal has been optimized in MS-MS whilst working in negative chemical ionization mode using methane as the reagent gas. The proposed method was fully validated for 53 compounds in tomato, apple and orange matrices. The obtained limits of determination were lower than 0.1 μg/kg for more than 50% of the pesticides studied, and lower than 1 μg/kg for all pesticides studied, except for cypermethrin, boscalid, bifenthrin and deltamethrin. Linearity was studied in the 0.5-50 μg/kg range and a linear response was obtained for all pesticides in all matrices. Recoveries were evaluated at two different levels (1 and 50 μg/kg) and recoveries were ranged between 70 and 120% in tomato, apple and orange, except in the cases of chlorfenapyr, ofurace, chlozolinate, chlorothalonil, tolylfluanid and dichlofluanid with recovery values close to 60% at 1 μg/kg fortification levels. Repetitivity was evaluated and the relative standard deviation (RSD%) was lower than 10% in all cases. The developed method was employed in the analysis of real samples intended for baby food and the obtained results showed that 50% of the samples were positive for different pesticide residues. The concentration range detected was between 5 and 100 μg/kg. The positive detection of OCs was particularly noticeable; these included chlorothalonil, fenhexamide, clorpyrifos and lambda cyhalothrin, which are very persistent and toxic with low acute

  19. Non-aqueous capillary electrophoresis for the analysis of acidic compounds using negative electrospray ionization mass spectrometry.

    PubMed

    Bonvin, Grégoire; Schappler, Julie; Rudaz, Serge

    2014-01-01

    Non-aqueous capillary electrophoresis (NACE) is an attractive CE mode, in which water solvent of the background electrolyte (BGE) is replaced by organic solvent or by a mixture of organic solvents. This substitution alters several parameters, such as the pKa, permittivity, viscosity, zeta potential, and conductivity, resulting in a modification of CE separation performance (i.e., selectivity and/or efficiency). In addition, the use of NACE is particularly well adapted to ESI-MS due to the high volatility of solvents and the low currents that are generated. Organic solvents reduce the number of side electrochemical reactions at the ESI tip, thereby allowing the stabilization of the ESI current and a decrease in background noise. All these features make NACE an interesting alternative to the aqueous capillary zone electrophoresis (CZE) mode, especially in combination with mass spectrometry (MS) detection. The aim of this work was to evaluate the use of NACE coupled to negative ESI-MS for the analysis of acidic compounds with two available CE-MS interfaces (sheath liquid and sheathless). First, NACE was compared to aqueous CZE for the analysis of several pharmaceutical acidic compounds (non-steroidal anti-inflammatory drugs, NSAIDs). Then, the separation performance and the sensitivity achieved by both interfaces were evaluated, as were the impact of the BGE and the sample composition. Finally, analyses of glucuronides in urine samples subjected to a minimal sample pre-treatment ("dilute-and-shoot") were performed by NACE-ESI-MS, and the matrix effect was evaluated. A 20- to 100-fold improvement in sensitivity was achieved using the NACE mode in combination with the sheathless interface and no matrix effect was observed regardless of the interfaces. PMID:24315358

  20. Negative Ion Chemical Ionization Mass Spectrometry for the Analysis of 3,5,6-trichloro-2-pyridinol in Saliva of Rats Exposed to Chlorpyrifos

    SciTech Connect

    Campbell, James A.; Timchalk, Chuck; Kousba, Ahmed A.; Wu, Hong; Valenzuela, Blandina R.; Hoppe, Eric W.

    2005-05-01

    Organophosphorus (OP) insecticides (e.g. chlorpyrifos) are widely used in a variety of applications, and the potential exists for significant occupational and environmental exposures. They have been associated with more occupational poisoning cases than any other class of insecticides. One of the best approaches for accurately assessing human dosimetry and determining risk from both occupational and environmental exposure is biomonitoring. Biological matrices such as blood and urine have been routinely used for biomonitoring; however, other matrices such as saliva represent a simple and readily obtainable fluid. As a result, saliva has been suggested as an alternative biological matrix for the evaluation of a broad range of biomarkers such as environmental contaminants, drugs of abuse, hormones, chemotherapeutics, heavy metals, and pesticides. Chlorpyrifos (CPF), and its major metabolite, 3,5,6-trichloro-2-pyridinol (TCP), have been quantified in urine and blood as a biomarker for exposure to OP insecticides. The purpose of this study was to develop an analytical approach for detecting and quantitating the levels of TCP in saliva obtained from rats exposed to CPF and to evaluate the potential of saliva as a non-invasive biomonitoring matrix. Adult male rats were administered CPF, and blood and saliva were humanely collected for analysis of TCP and CPF. TCP was detected and quantitated in saliva using negative ion chemical ionization mass spectrometry with selected ion monitoring. Initial results indicate that saliva may be potentially utilized as a non-invasive biomonitoring matrix to determine exposure to organophosphate insecticides.

  1. Determination of betamethasone and betamethasone 17-monopropionate in human plasma by liquid chromatography-positive/negative electrospray ionization tandem mass spectrometry.

    PubMed

    Zou, Jian-Jun; Dai, Li; Ding, Li; Xiao, Da-Wei; Bin, Zhu-Yu; Fan, Hong-Wei; Liu, Li; Wang, Guang-Ji

    2008-10-01

    This study presents a high-performance liquid chromatography-positive/negative electrospray ionization tandem mass spectrometric (LC-ESI(+/-)-MS-MS) method for the determination of betamethasone (BOH) and betamethasone 17-monopropionate (B17P) in human plasma using beclomethasone dipropionate as the internal standard (I.S.). Both compounds were extracted from human plasma with ether-cyclohexane (4:1, v/v) and were separated by HPLC on a Hanbon Lichrospher C(18) column with a mobile phase of methanol-water (85:15, v/v) at a flow rate of 0.7ml/min. Calibration curves were linear over the range of 0.10-50ng/ml for BOH and 0.050-50ng/ml for B17P. The inter-run relative standard deviations were less than 14.4% for BOH and 12.3% for B17P. The intra-run relative standard deviations were less than 9.3% for BOH and 7.9% for B17P. The mean plasma extraction recovery for BOH and B17P were in the ranges of 82.7-85.9% and 83.6-85.3%, respectively. The method was successfully applied to study the pharmacokinetics of a new formulation of betamethasone phosphate/betamethasone dipropionate injection in healthy Chinese volunteers. PMID:18757252

  2. Bio-oil Analysis Using Negative Electrospray Ionization: Comparative Study of High-Resolution Mass Spectrometers and Phenolic versus Sugaric Components

    SciTech Connect

    Smith, Erica A.; Park, Soojin; Klein, Adam T.; Lee, Young Jin

    2012-05-16

    We have previously demonstrated that a petroleomic analysis could be performed for bio-oils and revealed the complex nature of bio-oils for the nonvolatile phenolic compounds (Smith, E.; Lee, Y. J. Energy Fuels 2010, 24, 5190−5198). As a subsequent study, we have adapted electrospray ionization in negative-ion mode to characterize a wide variety of bio-oil compounds. A comparative study of three common high-resolution mass spectrometers was performed to validate the methodology and to investigate the differences in mass discrimination and resolution. The mass spectrum is dominated by low mass compounds with m/z of 100–250, with some compounds being analyzable by gas chromatography–mass spectrometry (GC–MS). We could characterize over 800 chemical compositions, with only about 40 of them being previously known in GC–MS. This unveiled a much more complex nature of bio-oils than typically shown by GC–MS. The pyrolysis products of cellulose and hemicellulose, particularly polyhydroxy cyclic hydrocarbons (or what we call “sugaric” compounds), such as levoglucosan, could be effectively characterized with this approach. Phenolic compounds from lignin pyrolysis could be clearly distinguished in a contour map of double bond equivalent (DBE) versus the number of carbons from these sugaric compounds.

  3. Determination of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in poultry and porcine muscle and liver by gas chromatography-negative chemical ionization mass spectrometry.

    PubMed

    Shen, Jianzhong; Xia, Xi; Jiang, Haiyang; Li, Cun; Li, Jiancheng; Li, Xiaowei; Ding, Shuangyang

    2009-05-15

    A sensitive and reliable method using gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS) was developed for the simultaneous determination of chloramphenicol (CAP), thiamphenicol (TAP), florfenicol (FF), and florfenicol amine (FFA) at trace levels in muscle and liver. Before extraction with ethyl acetate, CAP-d(5) was added to tissue samples as internal standard. The organic extracts were frozen to remove lipid and further purified by liquid-liquid extraction (LLE) with hexane and solid-phase extraction (SPE) using Oasis HLB cartridges. The target compounds were derivatized with BSTFA+1% TMCS prior to GC-NCI/MS determination in selected ion monitoring mode (SIM). The recovery values ranged from 78.5 to 105.5%, with relative standard deviations (RSD) <17%. The limits of detections (LODs) of 0.1 microg/kg for CAP and 0.5 microg/kg for TAP, FF, and FFA were obtain. Incurred sample and samples from local market were successfully analyzed using this method. PMID:19395324

  4. Quantification of low levels of organochlorine pesticides using small volumes (negative chemical ionization mass spectrometry.

    PubMed

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

    2007-07-01

    A solid phase extraction and gas chromatography with negative chemical ionization mass spectrometry in scan mode (GC-NCI-MS) method was developed to identify and quantify for the first time low levels of organochlorine pesticides (OCs) in plasma samples of less than 100 microl from wild birds. The method detection limits ranged from 0.012 to 0.102 pg/microl and the method reporting limit from 0.036 to 0.307 pg/microl for alpha, gamma, beta and delta-hexachlorocyclohexane (HCH), heptachlor, aldrin, heptachlor epoxide, endosulfan I, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), dieldrin, endrin, endosulfan-II, endrin-aldehyde and endosulfan-sulfate. Pesticide levels in small serum samples from individual Falco sparverius, Sturnella neglecta, Mimus polyglottos and Columbina passerina were quantified. Concentrations ranged from not detected (n/d) to 204.9 pg/microl for some OC pesticides. All levels in the food web in and around cultivated areas showed the presence of pesticides notwithstanding the small areas for agriculture existing in the desert of Baja California peninsula. PMID:17240024

  5. Use of capillary gas chromatography with negative ion-chemical ionization mass spectrometry for the determination of perfluorocarbon tracers in the atmosphere.

    PubMed

    Cooke, K M; Simmonds TPG; Nickless, G; Makepeace, A P

    2001-09-01

    A sensitive and selective technique for the quantitative measurement of atmospheric perfluorocarbon trace species at the sub part per quadrillion (10(-15)) levels is presented. The method utilizes advances in adsorbent enrichment techniques coupled with benchtop capillary gas chromatography and negative ion-chemical ionization mass spectrometry. The development and enhancement of sampling technology for tracer experiments is described, and the results from background measurements and a preliminary field experiment are presented. The overall precision of the analytical method with respect to the preferred tracer for these atmospheric transport studies, perfluoromethylcyclohexane, was +/-1.7%. The background concentrations of perfluorodimethylcyclobutane, perfluoromethylcyclopentane, and perfluoromethylcyclohexane at a remote coastal location (Mace Head, Ireland, 53 degrees N, 10 degrees W) were found to be 2.5 (+/-0.4), 6.8 (+/-1.0), and 5.2 fL L(-1) (+/-1.3), respectively. Background concentrations within an urban conurbation (Bristol, U.K.) were slightly greater at 3.0 (+/-1.5), 8.1 (+/-1.8), and 6.3 fL L(-1) (+/-1.1), respectively. PMID:11569822

  6. Measurement of the {beta}{sup +} and Orbital Electron-Capture Decay Rates in Fully Ionized, Hydrogenlike, and Heliumlike {sup 140}Pr Ions

    SciTech Connect

    Litvinov, Yu. A.; Geissel, H.; Winckler, N.; Knoebel, R.; Litvinov, S. A.; Scheidenberger, C.; Bosch, F.; Beckert, K.; Brandau, C.; Dimopoulou, C.; Hess, S.; Kozhuharov, C.; Mazzocco, M.; Nociforo, C.; Nolden, F.; Prochazka, A.; Reuschl, R.; Steck, M.; Stoehlker, T.; Trassinelli, M.

    2007-12-31

    We report on the first measurement of the {beta}{sup +} and orbital electron-capture decay rates of {sup 140}Pr nuclei with the simplest electron configurations: bare nuclei, hydrogenlike, and heliumlike ions. The measured electron-capture decay constant of hydrogenlike {sup 140}Pr{sup 58+} ions is about 50% larger than that of heliumlike {sup 140}Pr{sup 57+} ions. Moreover, {sup 140}Pr ions with one bound electron decay faster than neutral {sup 140}Pr{sup 0+} atoms with 59 electrons. To explain this peculiar observation one has to take into account the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay.

  7. Identification of coagulase-negative staphylococci from bovine intramammary infection by matrix-assisted laser desorption ionization-time of flight mass spectrometry.

    PubMed

    Tomazi, Tiago; Gonçalves, Juliano Leonel; Barreiro, Juliana Regina; de Campos Braga, Patrícia Aparecida; Prada e Silva, Luis Felipe; Eberlin, Marcos Nogueira; dos Santos, Marcos Veiga

    2014-05-01

    Coagulase-negative staphylococci (CoNS) are among the main pathogens causing bovine intramammary infection (IMI) in many countries. However, one of the limitations related to the specific diagnosis of CoNS is the lack of an accurate, rapid, and convenient method that can differentiate the bacterial species comprising this group. The aim of this study was to evaluate the ability of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) to accurately identify CoNS species in dairy cow IMI. In addition, the study aimed to determine the frequency of CoNS species causing bovine IMI. A total of 108 bacterial isolates were diagnosed as CoNS by microbiological cultures from two milk samples collected from 21 dairy herds; the first sample was collected at the cow level (i.e., 1,242 composite samples from all quarters), while the second sample was collected at the mammary quarter level (i.e., 1,140 mammary samples collected from 285 cows). After CoNS isolation was confirmed by microbiological culture for both samples, all CoNS isolates (n=108) were genotypically differentiated by PCR restriction fragment length polymorphism (RFLP) analysis of a partial groEL gene sequence and subjected to the MALDI-TOF MS identification procedure. MALDI-TOF MS correctly identified 103 (95.4%) of the CoNS isolates identified by PCR-RFLP at the species level. Eleven CoNS species isolated from bovine IMI were identified by PCR-RFLP, and the most prevalent species was Staphylococcus chromogenes (n=80; 74.1%). In conclusion, MALDI-TOF MS may be a reliable alternative method for differentiating CoNS species causing bovine IMI. PMID:24622096

  8. The effects of ionizing radiation and dexamethasone on the blood-brain-barrier (BBB) and blood-tumor-barrier (BTB): Implications for boron neutron capture therapy (BNCT) of brain tumors

    SciTech Connect

    Dorn, R.V. III; Spickard, J.H.; Griebenow, M.L.

    1988-01-01

    Currently envisioned techniques for Boron Neutron Capture Therapy (BNCT) of brain tumors rely on the increased permeability of the blood-brain-barrier (BBB) (more specifically, the blood-tumor-barrier (BTB)) which occurs around the malignant tumor. As a result of this increased permeability, higher boron concentrations (Na/sub 2/B/sub 12/H/sub 11/SH) should be obtainable in the tumor than in the surrounding normal brain. The effects on the BBB and BTB by the ionizing component of this radiation and by the steroid dexamethasone (almost universally used in the clinical management of these patients) must be considered in the formulation of this treatment technique. 32 refs., 5 tabs.

  9. Determination of naltrexone and 6-beta-naltrexol in plasma by solid-phase extraction and gas chromatography-negative ion chemical ionization-mass spectrometry.

    PubMed

    Huang, W; Moody, D E; Foltz, R L; Walsh, S L

    1997-01-01

    Solid-phase extraction (SPE) and a one-step derivatization are combined with gas chromatography-negative ion chemical ionization-mass spectrometry to simplify a previously reported method for the determination of naltrexone and its metabolite, 6-beta-naltrexol, in human plasma. Deuterated isotopomers of naltrexone and 6-beta-naltrexol are used as internal standards. After SPE, the extracts are derivatized with pentafluoropropionic anhydride at room temperature to form predominantly the bispentafluoropropionyl derivative of naltrexone and the trispentafluoropropionyl derivative of 6-beta-naltrexol. The derivatized extracts are analyzed by monitoring ion currents at m/z 633 (naltrexone), m/z 636 (naltrexone-2H3), m/z 633 6-beta-naltrexol), and m/z 640 (6-beta-naltrexol-2H7). Control plasma samples containing 0.3, 3, or 30 ng/nl of each analyte were analyzed for precision and accuracy with the following results: intra-assay, the percentage of target concentrations were 107-113% for naltrexone and 107-120% for 6-beta-naltrexol, and the coefficients of variation (CVs) were 3.1-6.3% for naltrexone and 3.1-5.7% for 6-beta-naltrexol; interassay, the percentage of target concentrations were 103-110% for naltrexone and 110-113% for 6-beta-naltrexol, and the CVs were 6.1-9.1% for naltrexone and 5.9-9.1% for 6-beta-naltrexol. At the limit of quantitation (LOQ) of 0.1 ng/ml, both analytes quantified within 20% of the target concentration with CVs less than 17%. The extraction recoveries determined at 0.3 and 30 ng/ml were 79 and 80% for naltrexone and 76 and 75% for 6-beta-naltrexol. Bench-top stability tested with concentrations of 0.3 and 3.0 ng/ml did not decrease more than 10% from the zero-hour controls at 3, 6 and 24 h. Selectively was determined using plasma from six donors and none showed interfering peaks greater than 22% of the LOQ for naltrexone and 53% of the LOQ for 6-beta-naltrexol. Using this method, naltrexone and 6-beta-naltrexol were readily detected in plasma

  10. Kinetic-energy release in the dissociative capture-ionization of CO molecules by 97-MeV Ar14+ ions

    NASA Astrophysics Data System (ADS)

    Watson, R. L.; Sampoll, G.; Horvat, V.; Heber, O.

    1996-02-01

    The dissociation of COQ+ molecular ions (Q=4 to 9) produced in multiply ionizing collisions accompanied by the transfer of an electron to the projectile has been studied using time-of-flight techniques. Analysis of the coincident-ion-pair flight-time-difference distributions yielded average values of the kinetic-energy releases for the various dissociation reactions. These values were found to be as much as a factor of 2 greater than the kinetic-energy releases expected for dissociation along Coulombic potential curves. The average kinetic-energy release observed for a given ion pair with charges q1 and q2 are nearly equal to the point-charge Coulomb potential energies for an ion pair with charges q1+1 and q2+1, suggesting that the parent molecular ion is formed with two electrons, on average, in highly excited states that do not contribute to the screening of the nuclei.

  11. Theory of the capture of antiprotons by atoms and molecules

    NASA Astrophysics Data System (ADS)

    Cohen, James S.

    2002-04-01

    Antiprotonic (barp) atoms are formed in low-energy collisions between antiprotons and normal atoms or molecules. The fermion molecular dynamics (FMD) method has enabled us to go beyond the atomic hydrogen target and study electron-correlation effects with noble-gas targets (He, Ne, Ar, Kr, and Xe) and molecular effects with isotopic hydrogen targets (H_2, D_2, and HD). Multiple ionization and ro-vibrational excitation are found to greatly increase the maximum energy of capture, with the latter also leading to a significant dependence on the projectile mass and target isotope. The kinetic energies of the ionized electrons are found to increase somewhat with the target nuclear charge. Atomic capture of barp is mechanistically very similar to capture of the lighter negative particles μ^- and π^-. Recent calculations of π^- capture by molecular hydrogen clear up the long-standing anomaly of pion transfer from p to d being apparently very different in HD and in H_2/D2 mixtures. Calculations on the noble-gas atoms yield capture ratios in agreement with a number of experiments with muons and pions. They demonstrate the role of multiple electrons and suggest what features will be important in a future completely quantum-mechanical treatment. The agreement with experiments done with μ^- and π^- lends support to the theoretical results for barp capture, which will soon be observed experimentally for the first time.

  12. A multi-residue method for pesticides analysis in green coffee beans using gas chromatography-negative chemical ionization mass spectrometry in selective ion monitoring mode.

    PubMed

    Pizzutti, Ionara R; de Kok, Andre; Dickow Cardoso, Carmem; Reichert, Bárbara; de Kroon, Marijke; Wind, Wouter; Weber Righi, Laís; Caiel da Silva, Rosselei

    2012-08-17

    In this study, a new gas chromatography-mass spectrometry (GC-MS) method, using the very selective negative chemical ionization (NCI) mode, was developed and applied in combination with a modified acetonitrile-based extraction method (QuEChERS) for the analysis of a large number of pesticide residues (51 pesticides, including isomers and degradation products) in green coffee beans. A previously developed integrated sample homogenization and extraction method for both pesticides and mycotoxins analysis was used. An homogeneous slurry of green milled coffee beans and water (ratio 1:4, w/w) was prepared and extracted with acetonitrile/acetic acid (1%), followed by magnesium sulfate addition for phase separation. Aliquots from this extract could be used directly for LC-MS/MS analysis of mycotoxins and LC-amenable pesticides. For GC-MS analysis, a further clean-up was necessary. C18- and PSA-bonded silica were tested as dispersive solid-phase extraction (d-SPE) sorbents, separate and as a mixture, and the best results were obtained using C18-bonded silica. For the optimal sensitivity and selectivity, GC-MS detection in the NCI-selected ion monitoring (SIM) mode had to be used to allow the fast analysis of the difficult coffee bean matrix. The validation was performed by analyzing recovery samples at three different spike concentrations, 10, 20 and 50 μg kg(-1), with 6 replicates (n=6) at each concentration. Linearity (r(2)) of calibration curves, estimated instrument and method limits of detection and limits of quantification (LOD(i), LOD(m), LOQ(i) and LOQ(m), respectively), accuracy (as recovery %), precision (as RSD%) and matrix effects (%) were determined for each individual pesticide. From the 51 analytes (42 parent pesticides, 4 isomers and 5 degradation products) determined by GC-MS (NCI-SIM), approximately 76% showed average recoveries between 70-120% and 75% and RSD ≤ 20% at the lowest spike concentration of 10 μg kg(-1), the target method LOQ. For the

  13. Electron Capture and Loss Processes in the Interaction of Hydrogen, Oxygen, and Fluorine Atoms and Negative Ions with a MgO(100) Surface

    SciTech Connect

    Ustaze, S.; Verucchi, R.; Lacombe, S.; Guillemot, L.; Esaulov, V.A.

    1997-11-01

    A study of electron capture and loss processes during the scattering of H, O, and F atoms and anions on a MgO(100) surface is described. Large fractions of anions in the scattering of atoms are observed, indicating the existence of an efficient electron capture process. This is ascribed to a nonresonant, localized charge exchange mechanism between an atom and a MgO lattice oxygen anion. This charge transfer becomes possible because of anion level shifts in the Madelung field. The existence of an electron loss channel is demonstrated using incident anions and is ascribed to loss to the conduction band or Mg cations. {copyright} {ital 1997} {ital The American Physical Society}

  14. Inner-shell capture and ionization in collisions of H/sup +/, He/sup 2 +/, and Li/sup 3 +/ projectiles with neon and carbon

    SciTech Connect

    Ford, A.L.; Reading, J.F.; Becker, R.L.

    1981-02-01

    Theoretical methods used previously for H/sup +/, He/sup 2 +/, and C/sup 6 +/ collisions with neutral argon atoms have been applied to collisions of H/sup +/, He/sup 2 +/, and Li/sup 3 +/ projectiles with neon, and to collisions of H/sup +/ with carbon targets. The energy range covered by the calculations is 0.4 to 4.0 MeV/amu for the neon target, and 0.2 to 2.0 MeV/amu for carbon. We calculate single-electron amplitudes for target K-shell ionization and target K- and L-shell, to projectile K-shell, charge transfer. These single-electron amplitudes are used, in an independent-particle model that allows for multielectron processes, to compute K-shell vacancy production cross sections sigma/sup IPM//sub V/K, and cross sections sigma/sup IPM//sub C/,VK for producing a charge-transfer state of the projectile in the coincidence with a K-shell vacancy in the target. These cross sections are in reasonable agreement with the recent experiments of Rodbro et al. at Aarhus. In particular, the calculated, as well as the experimental, sigma/sub C/,VK scale with projectile nuclear charge Z/sub p/ less strongly than the Z/sup 5//sub p/ of the Oppenheimer-Brinkman-Kramers (OBK) approximation. For He/sup 2 +/ and Li/sup 3 +/ projectiles at collision energies below where experimental data are available, our calculated multielectron corrections to the single-electron approximation for sigma/sub C/,VK are large.

  15. CuFe2O4 magnetic nanocrystal clusters as a matrix for the analysis of small molecules by negative-ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Lin, Zian; Zheng, Jiangnan; Bian, Wei; Cai, Zongwei

    2015-08-01

    CuFe2O4 magnetic nanocrystal clusters (CuFe2O4 MNCs) were proposed as a new matrix for small molecule analysis by negative ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the first time. We demonstrated its advantages over conventional organic matrices in the detection of small molecules such as amino acids, peptides, nucleobases, fatty acids, and steroid hormones. A systematic comparison of CuFe2O4 MNCs with different ionization modes revealed that MS spectra obtained for the CuFe2O4 MNC matrix in the negative ion mode was only featured by deprotonated ion peaks with a free matrix background, which was different from the complicated alkali metal adducts produced in the positive ion mode. The developed method was found relatively tolerant to salt contamination and exhibited good reproducibility. A detection limit down to the subpicomolar level was achieved when testosterone was analyzed. In addition, by comparison of the MS spectra obtained from bare Fe3O4 and MFe2O4 MNC (M = Co, Ni, Cu, Zn) matrices, two main factors of MFe2O4 MNC matrices were revealed to play a vital role in assisting the negative ion desorption/ionization (D/I) process: doping transition metals into ferrite nanocrystals favoring laser absorption and energy transfer and a good match between the UV absorption of MFe2O4 MNCs and the excitation of nitrogen laser source facilitating LDI efficiency. This work creates a new branch of application for MFe2O4 MNCs and provides an alternative solution for small molecule analysis. PMID:26086699

  16. Comparison Of Quantum Mechanical And Classical Trajectory Calculations Of Cross Sections For Ion-Atom Impact Ionization of Negative - And Positive -Ions For Heavy Ion Fusion Applications

    SciTech Connect

    Igor D. Kaganovich; Edward A. Startsev; Ronald C. Davidson

    2003-05-15

    Stripping cross sections in nitrogen have been calculated using the classical trajectory approximation and the Born approximation of quantum mechanics for the outer shell electrons of 3.2GeV I{sup -} and Cs{sup +} ions. A large difference in cross section, up to a factor of six, calculated in quantum mechanics and classical mechanics, has been obtained. Because at such high velocities the Born approximation is well validated, the classical trajectory approach fails to correctly predict the stripping cross sections at high energies for electron orbitals with low ionization potential.

  17. Ionization-based detectors for gas chromatography.

    PubMed

    Poole, Colin F

    2015-11-20

    The gas phase ionization detectors are the most widely used detectors for gas chromatography. The column and makeup gases commonly used in gas chromatography are near perfect insulators. This facilitates the detection of a minute number of charge carriers facilitating the use of ionization mechanisms of low efficiency while providing high sensitivity. The main ionization mechanism discussed in this report are combustion in a hydrogen diffusion flame (flame ionization detector), surface ionization in a plasma (thermionic ionization detector), photon ionization (photoionization detector and pulsed discharge helium ionization detector), attachment of thermal electrons (electron-capture detector), and ionization by collision with metastable helium species (helium ionization detector). The design, response characteristics, response mechanism, and suitability for fast gas chromatography are the main features summarized in this report. Mass spectrometric detection and atomic emission detection, which could be considered as ionization detectors of a more sophisticated and complex design, are not discussed in this report. PMID:25757823

  18. Dependence of negative-mode electrospray ionization response factors on mobile phase composition and molecular structure for newly-authenticated neutral acylsucrose metabolites.

    PubMed

    Ghosh, Banibrata; Jones, A Daniel

    2015-10-01

    Authentic standards of known concentrations serve as references for accurate absolute quantification of plant metabolites using liquid chromatography/mass spectrometry (LC/MS). However, often such standards are not commercially available or not amenable for custom syntheses. Despite the widespread use of electrospray ionization for metabolite analyses, the fundamentals needed for reliable prediction of molecular response factors have yet to be explored in detail for analytes that lack ionized functional groups. In order to lay a foundation for quantifying unknown neutral plant metabolites in absence of authentic standards, sub-milligram quantities of purified homologous acylsucrose metabolites were authenticated by subjecting each to basic hydrolysis and quantifying the sucrose product using stable-isotope dilution ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with multiple reaction monitoring (MRM). Once authenticated, molar response factors of [M + formate](-) ions for the acylsucrose metabolites were determined at different mobile phase compositions ranging from 40%-80% acetonitrile, and demonstrated relationships of response factors with mobile phase composition and metabolite structural features including nonpolar surface areas, the length of the longest acyl chain, and the number of hydroxyl groups. This approach was employed to calculate predicted response factors for three authenticated acylsucroses based on mean values for all isomers with a common number of total acyl carbon atoms. Absolute UHPLC-MS quantification was performed on these three metabolites in an extract from leaves of the wild tomato Solanum habrochaites LA1777, yielding deviations of 26%, 6.7%, and 7.3% from values established using compound-specific response factors. PMID:26331907

  19. Method and apparatus to monitor a beam of ionizing radiation

    SciTech Connect

    Blackburn, Brandon W.; Chichester, David L.; Watson, Scott M.; Johnson, James T.; Kinlaw, Mathew T.

    2015-06-02

    Methods and apparatus to capture images of fluorescence generated by ionizing radiation and determine a position of a beam of ionizing radiation generating the fluorescence from the captured images. In one embodiment, the fluorescence is the result of ionization and recombination of nitrogen in air.

  20. EVALUATION OF N-METHYL-N-TERT-BUTYLDIMETHYLSILYLTRIFLUOROACETAMIDE FOR ENVIRONMENTAL ANALYSIS UNDER BOTH EIMS AND ELECTRON CAPTURE NICIMS CONDITIONS AND COMPARISON TO TRIMETHYLSILYL REAGENTS UNDER EIMS

    EPA Science Inventory

    Sewage effluent was analyzed for 3,5,6-trichloropyridinol (TCP) by extracting one liter of water using liquid-liquid extraction and determined by GC/MS operated in the negative ion chemical ionization (electron capture) mode, TCP is the major metabolite of the commonly used insec...

  1. High-performance liquid chromatography/high-resolution multiple stage tandem mass spectrometry using negative-ion-mode hydroxide-doped electrospray ionization for the characterization of lignin degradation products.

    PubMed

    Owen, Benjamin C; Haupert, Laura J; Jarrell, Tiffany M; Marcum, Christopher L; Parsell, Trenton H; Abu-Omar, Mahdi M; Bozell, Joseph J; Black, Stuart K; Kenttämaa, Hilkka I

    2012-07-17

    In the search for a replacement for fossil fuel and the valuable chemicals currently obtained from crude oil, lignocellulosic biomass has become a promising candidate as an alternative biorenewable source for crude oil. Hence, many research efforts focus on the extraction, degradation, and catalytic transformation of lignin, hemicellulose, and cellulose. Unfortunately, these processes result in the production of very complex mixtures. Further, while methods have been developed for the analysis of mixtures of oligosaccharides, this is not true for the complex mixtures generated upon degradation of lignin. For example, high-performance liquid chromatography/multiple stage tandem mass spectrometry (HPLC/MS(n)), a tool proven to be invaluable in the analysis of complex mixtures derived from many other biopolymers, such as proteins and DNA, has not been implemented for lignin degradation products. In this study, we have developed an HPLC separation method for lignin degradation products that is amenable to negative-ion-mode electrospray ionization (ESI doped with NaOH), the best method identified thus far for ionization of lignin-related model compounds without fragmentation. The separated and ionized compounds are then analyzed by MS(3) experiments to obtain detailed structural information while simultaneously performing high-resolution measurements to determine their elemental compositions in the two parts of a commercial linear quadrupole ion trap/Fourier-transform ion cyclotron resonance mass spectrometer. A lignin degradation product mixture was analyzed using this method, and molecular structures were proposed for some components. This methodology significantly improves the ability to analyze complex product mixtures that result from degraded lignin. PMID:22746183

  2. Calcium - ionized

    MedlinePlus

    ... at both ionized calcium and calcium attached to proteins. You may need to have a separate ionized calcium test if you have factors that increase or decrease total calcium levels. These may include abnormal blood levels ...

  3. Development and validation of an analytical method for determination of 3-chloropropane-1,2-diol in rat blood and urine by gas chromatography-mass spectrometry in negative chemical ionization mode.

    PubMed

    Berger-Preiss, Edith; Gerling, Susanne; Apel, Elisabeth; Lampen, Alfonso; Creutzenberg, Otto

    2010-09-01

    We have developed a highly selective and sensitive method using gas chromatography-mass spectrometry with negative chemical ionization for measuring 3-chloropropane-1,2-diol (3-MCPD) in rat blood and urine. Samples were adsorbed on silica gel, extracted with ethyl acetate, and derivatized by chemical derivatization with heptafluorobutyric acid anhydride. For quantification, matrix-based calibration curves and 3-MCPD-d (5), as an isotope-labeled internal standard, were used. The relative recoveries of 3-MCPD were between 80 and 110% in most cases and the relative standard deviations were typically less than 10%, with some exceptions. The limit of quantification of the method was found to be about 2 ng/mL. In conclusion, a valuable, robust, and sensitive method for detection of 3-MCPD is now available for biokinetics studies. PMID:20640896

  4. Identification of phosphorylated peptides from complex mixtures using negative-ion orifice-potential stepping and capillary liquid chromatography/electrospray ionization mass spectrometry.

    PubMed

    Ding, J; Burkhart, W; Kassel, D B

    1994-01-01

    A rapid method for identifying and characterizing sites of phosphorylation of peptides and proteins is described. High-performance capillary liquid chromatography (HPLC) coupled with electrospray ionization mass spectrometry (ESI-MS) is used to distinguish non-phosphorylated and phosphorylated peptides originating from mixtures as complex as enzyme digests. The method relies on the ability to produce a fragment ion characteristic and unique to phosphopeptides (m/z 79, PO3) by stepping the orifice potential of the mass spectrometer as a function of mass. At low m/z values, a high orifice potential is applied to induce extensive fragmentation of the peptide, leading to the formation of the m/z 79 phosphate-derived ion. This method is analogous to that described by Carr et al. for the identification of glycopeptides from enzymatic digestion of glycoproteins (S.A. Carr, M.J. Huddleston, M.F. Bean, Protein Science 2, 183 (1993)). The method was first evaluated and validated for a mixture of non-, mono- and di-phosphorylated synthetic peptides. Both mono- and di-phosphorylated peptides were found to generate fragment ions characteristic of PO3 whereas the non-phosphorylated peptide did not. Application of the method was extended to identifying phosphopeptides generated from an endoprotease Lys-C digestion of beta-casein. Both the expected mono- and tetra-phosphorylated Lys-C peptides were observed and identified rapidly in the LC/SEI-MS analysis. The procedure was used additionally to identify the site(s) of phosphorylation of the cytosolic non-receptor tyrosine kinase, pp60(c-src). PMID:8118063

  5. Resistance gene capture.

    PubMed

    Rowe-Magnus, D A; Mazel, D

    1999-10-01

    Integrons are the primary mechanism for antibiotic-resistance gene capture and dissemination among Gram-negative bacteria. The recent finding of super-integron structures in the genomes of several bacterial species has expanded their role in genome evolution and suggests that they are the source of mobile multi-resistant integrons. PMID:10508722

  6. Ionizing air affects influenza virus infectivity and prevents airborne-transmission.

    PubMed

    Hagbom, Marie; Nordgren, Johan; Nybom, Rolf; Hedlund, Kjell-Olof; Wigzell, Hans; Svensson, Lennart

    2015-01-01

    By the use of a modified ionizer device we describe effective prevention of airborne transmitted influenza A (strain Panama 99) virus infection between animals and inactivation of virus (>97%). Active ionizer prevented 100% (4/4) of guinea pigs from infection. Moreover, the device effectively captured airborne transmitted calicivirus, rotavirus and influenza virus, with recovery rates up to 21% after 40 min in a 19 m(3) room. The ionizer generates negative ions, rendering airborne particles/aerosol droplets negatively charged and electrostatically attracts them to a positively charged collector plate. Trapped viruses are then identified by reverse transcription quantitative real-time PCR. The device enables unique possibilities for rapid and simple removal of virus from air and offers possibilities to simultaneously identify and prevent airborne transmission of viruses. PMID:26101102

  7. Ionizing air affects influenza virus infectivity and prevents airborne-transmission

    PubMed Central

    Hagbom, Marie; Nordgren, Johan; Nybom, Rolf; Hedlund, Kjell-Olof; Wigzell, Hans; Svensson, Lennart

    2015-01-01

    By the use of a modified ionizer device we describe effective prevention of airborne transmitted influenza A (strain Panama 99) virus infection between animals and inactivation of virus (>97%). Active ionizer prevented 100% (4/4) of guinea pigs from infection. Moreover, the device effectively captured airborne transmitted calicivirus, rotavirus and influenza virus, with recovery rates up to 21% after 40 min in a 19 m3 room. The ionizer generates negative ions, rendering airborne particles/aerosol droplets negatively charged and electrostatically attracts them to a positively charged collector plate. Trapped viruses are then identified by reverse transcription quantitative real-time PCR. The device enables unique possibilities for rapid and simple removal of virus from air and offers possibilities to simultaneously identify and prevent airborne transmission of viruses. PMID:26101102

  8. Factors influencing the analytical performance of an atmospheric sampling glow discharge ionization source as revealed via ionization dynamics modeling.

    PubMed

    Goeringer, Douglas E

    2003-11-01

    A kinetic model is developed for the dynamic events occurring within an atmospheric sampling glow discharge that affect its performance as an ion source for analytical mass spectrometry. The differential equations incorporate secondary electron generation and thermalization, reagent and analyte ion formation via electron capture and ion-molecule reactions, ion loss via recombination processes, diffusion, and ion-molecule reactions with matrix components, and the sampling and pumping parameters of the source. Because the ion source has a flow-through configuration, the number densities of selected species can be estimated by applying the steady-state assumption. However, understanding of its operation is aided by knowledge of the dynamic behavior, so numerical methods are applied to examine the time dependence of those species as well. As in other plasma ionization sources, the ionization efficiency is essentially determined by the ratio of the relevant ion formation and recombination rates. Although thermal electron and positive reagent ion number densities are comparable, the electron capture/ion-molecule reaction rate coefficient ratio is normally quite large and the ion-electron recombination rate coefficient is about an order of magnitude greater than that for ion-ion recombination. Consequently, the efficiency for negative analyte ion formation via electron capture is generally superior to that for positive analyte ion generation via ion-molecule reaction. However, the efficiency for positive analyte ion formation should be equal to or better than that for negative analyte ions when both ionization processes occur via ion-molecule reaction processes (with comparable rate coefficients), since the negative reagent ion density is considerably less than that for positive reagent ions. Furthermore, the particularly high number densities of thermal electrons and reagent ions leads to a large dynamic range of linear response for the source. Simulation results also

  9. 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...

  10. Determination of chlorinated paraffins in sediments from the Firth of Clyde by gas chromatography with electron capture negative ionisation mass spectrometry and carbon skeleton analysis by gas chromatography with flame ionisation detection.

    PubMed

    Hussy, Ines; Webster, Lynda; Russell, Marie; Moffat, Colin

    2012-07-01

    Short chain chlorinated paraffins (SCCPs) are a group of persistent organic pollutants (POPs) of increasing concern, but are to date not widely investigated in the environment, largely due to the challenges involved in their quantification. Here, SCCPs were quantified in marine sediments from the Firth of Clyde, Scotland, by gas chromatography with electron capture negative ionisation mass spectrometry (GC-ECNIMS) and through carbon skeleton analysis by gas chromatography with flame ionisation detection (GC-FID), and the analytical challenges encountered are discussed. Concentrations in the sediments ranged from 0.4 to 69 μg kg(-1) when determined by GC-ECNIMS, and from 5.6 to 379 μg kg(-1) when determined by GC-FID. For 8 out of 11 samples, analysis by GC-FID gave higher results than analysis by GC-ECNIMS. Unexpected aspects of the analysis, such as the presence of high concentrations of longer chain chlorinated paraffins in the samples, are also presented. PMID:22417782

  11. An integrated strategy for rapid and accurate determination of free and cell-bound microcystins and related peptides in natural blooms by liquid chromatography-electrospray-high resolution mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry using both positive and negative ionization modes.

    PubMed

    Flores, Cintia; Caixach, Josep

    2015-08-14

    An integrated high resolution mass spectrometry (HRMS) strategy has been developed for rapid and accurate determination of free and cell-bound microcystins (MCs) and related peptides in water blooms. The natural samples (water and algae) were filtered for independent analysis of aqueous and sestonic fractions. These fractions were analyzed by MALDI-TOF/TOF-MS and ESI-Orbitrap-HCD-MS. MALDI, ESI and the study of fragmentation sequences have been provided crucial structural information. The potential of combined positive and negative ionization modes, full scan and fragmentation acquisition modes (TOF/TOF and HCD) by HRMS and high resolution and accurate mass was investigated in order to allow unequivocal determination of MCs. Besides, a reliable quantitation has been possible by HRMS. This composition helped to decrease the probability of false positives and negatives, as alternative to commonly used LC-ESI-MS/MS methods. The analysis was non-target, therefore covered the possibility to analyze all MC analogs concurrently without any pre-selection of target MC. Furthermore, archived data was subjected to retrospective "post-targeted" analysis and a screening of other potential toxins and related peptides as anabaenopeptins in the samples was done. Finally, the MS protocol and identification tools suggested were applied to the analysis of characteristic water blooms from Spanish reservoirs. PMID:26141269

  12. Molecular characterization of S- and N-containing organic constituents in ambient aerosols by negative ion mode high-resolution Nanospray Desorption Electrospray Ionization Mass Spectrometry: CalNex 2010 field study

    NASA Astrophysics Data System (ADS)

    O'Brien, Rachel E.; Laskin, Alexander; Laskin, Julia; Rubitschun, Caitlin L.; Surratt, Jason D.; Goldstein, Allen H.

    2014-11-01

    Samples of ambient aerosols from the 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field study were analyzed using negative ion mode Nanospray Desorption Electrospray Ionization High-Resolution Mass Spectrometry (nano-DESI/MS). Four samples per day (6 h each) were collected in Bakersfield, CA on 20-24 June. Four characteristic groups were identified: molecules composed of carbon, hydrogen, and oxygen only (CHO), sulfur- (CHOS), nitrogen- (CHON), and both nitrogen- and sulfur-containing organics (CHONS). The chemical formula and elemental ratios were consistent with the presence of organonitrates, organosulfate, and nitroxy organosulfates in the negative ion mode mass spectra. The number of observed CHO compounds increased in the afternoon samples, suggesting photochemical processing as a source. The average number of CHOS compounds had the smallest changes during the day, consistent with a more broadly distributed source. Both of the nitrogen-containing groups (CHONS and CHON) had greater numbers of compounds in the early morning (midnight to 6 A.M.) and night (6 P.M. to midnight) samples, respectively, consistent with nitrate radical chemistry as a likely source for those compounds. Most of the compounds were found in submicron particles. The size distribution of the number of CHON compounds was bimodal, potentially indicating two types of sources. We conclude that the majority of the compounds observed were secondary in nature with both biogenic and anthropogenic sources. These data are complementary to previous results from positive ion mode nano-DESI/MS analysis of a subset of the same samples providing a more complete view of aerosol chemical composition at Bakersfield.

  13. Competitive Deprotonation and Superoxide [O₂⁻•)] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions.

    PubMed

    Hassan, Isra; Pinto, Spencer; Weisbecker, Carl; Attygalle, Athula B

    2016-03-01

    Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the hydroperoxyl radical (HO-O(•)) preferentially form superoxide radical-anion (O2(-•)) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2(-•)) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2(-•) adducts of N-alkylacetamides either lose the neutral amide or the hydroperoxyl radical (HO-O(•)) to generate the superoxide radical-anion (m/z 32) or the deprotonated amide [m/z (M - H)(-)], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions. PMID:26545766

  14. Competitive Deprotonation and Superoxide [O2 -•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions

    NASA Astrophysics Data System (ADS)

    Hassan, Isra; Pinto, Spencer; Weisbecker, Carl; Attygalle, Athula B.

    2016-03-01

    Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the hydroperoxyl radical (HO-O•) preferentially form superoxide radical-anion (O2 -•) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2 -•) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2 -• adducts of N-alkylacetamides either lose the neutral amide or the hydroperoxyl radical (HO-O•) to generate the superoxide radical-anion ( m/z 32) or the deprotonated amide [ m/z (M - H)-], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions.

  15. Facile Synthesis of N-Doped Carbon Dots as a New Matrix for Detection of Hydroxy-Polycyclic Aromatic Hydrocarbons by Negative-Ion Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry.

    PubMed

    Lu, Wenjing; Li, Yong; Li, Ruijin; Shuang, Shaomin; Dong, Chuan; Cai, Zongwei

    2016-05-25

    N-doping carbon dots (N-CDs) were prepared by microwave-assisted pyrolysis of dl-malic acid and ethanolamine as precursors. The material served as an excellent matrix for the detection of the environmental pollutants hydroxy-polycyclic aromatic hydrocarbons (OH-PAHs) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in negative ion mode. The obtained N-CDs exhibited good UV absorption capacity and favorable solubility. The use of the N-CDs matrix exhibited low matrix background interference and was beneficial to improve the signal response due to the specific π-conjugated polyaromatic structure and the doping of nitrogen atoms. The developed method was found to have good reproducibility and sensitivity. The N-CDs as a new matrix also were employed for the detection of OH-PAHs in real PM2.5 samples. The mass concentrations of Σ-hydroxy-pyrene, Σ-dihydroxy-anthraquinone, and Σ-dihydroxy-benzo(a)pyrene on the collected PM2.5 samples ranged from 0.125 to 0.136 ng/m(3), 0.039 to 0.052 ng/m(3), and 0.053 to 0.072 ng/m(3), respectively. This work extends the application field of N-CDs and provides a good candidate of matrix for MALDI-TOF MS detection of environmental pollutants. PMID:27180617

  16. Capturing Movement

    ERIC Educational Resources Information Center

    Lord, Lynda

    2007-01-01

    The idea for the art lesson presented in this article grew out of watching the lively actions of fourth grade students. Since drawing is the author's first love, she is always looking for new ways to teach it. This time, instead of setting up a still life, she decided to teach students how to capture their actions on paper. (Contains 5 online…

  17. Laser capture.

    PubMed

    Potter, S Steven; Brunskill, Eric W

    2012-01-01

    This chapter describes detailed methods used for laser capture microdissection (LCM) of discrete subpopulations of cells. Topics covered include preparing tissue blocks, cryostat sectioning, processing slides, performing the LCM, and purification of RNA from LCM samples. Notes describe the fine points of each operation, which can often mean the difference between success and failure. PMID:22639264

  18. Negative ion source

    DOEpatents

    Leung, K.N.; Ehlers, K.W.

    1982-08-06

    An ionization vessel is divided into an ionizing zone and an extraction zone by a magnetic filter. The magnetic filter prevents high-energy electrons from crossing from the ionizing zone to the extraction zone. A small positive voltage impressed on a plasma grid, located adjacent an extraction grid, positively biases the plasma in the extraction zone to thereby prevent positive ions from migrating from the ionizing zone to the extraction zone. Low-energy electrons, which would ordinarily be dragged by the positive ions into the extraction zone, are thereby prevented from being present in the extraction zone and being extracted along with negative ions by the extraction grid. Additional electrons are suppressed from the output flux using ExB drift provided by permanent magnets and the extractor grid electrical field.

  19. Negative ion source

    DOEpatents

    Leung, K.N.; Ehlers, K.W.

    1984-12-04

    An ionization vessel is divided into an ionizing zone and an extraction zone by a magnetic filter. The magnetic filter prevents high-energy electrons from crossing from the ionizing zone to the extraction zone. A small positive voltage impressed on a plasma grid, located adjacent an extraction grid, positively biases the plasma in the extraction zone to thereby prevent positive ions from migrating from the ionizing zone to the extraction zone. Low-energy electrons, which would ordinarily be dragged by the positive ions into the extraction zone, are thereby prevented from being present in the extraction zone and being extracted along with negative ions by the extraction grid. Additional electrons are suppressed from the output flux using ExB drift provided by permanent magnets and the extractor grid electrical field. 14 figs.

  20. Negative ion source

    DOEpatents

    Leung, Ka-Ngo; Ehlers, Kenneth W.

    1984-01-01

    An ionization vessel is divided into an ionizing zone and an extraction zone by a magnetic filter. The magnetic filter prevents high-energy electrons from crossing from the ionizing zone to the extraction zone. A small positive voltage impressed on a plasma grid, located adjacent an extraction grid, positively biases the plasma in the extraction zone to thereby prevent positive ions from migrating from the ionizing zone to the extraction zone. Low-energy electrons, which would ordinarily be dragged by the positive ions into the extraction zone, are thereby prevented from being present in the extraction zone and being extracted along with negative ions by the extraction grid. Additional electrons are suppressed from the output flux using ExB drift provided by permanent magnets and the extractor grid electrical field.

  1. Gridded electron reversal ionizer

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor)

    1993-01-01

    A gridded electron reversal ionizer forms a three dimensional cloud of zero or near-zero energy electrons in a cavity within a filament structure surrounding a central electrode having holes through which the sample gas, at reduced pressure, enters an elongated reversal volume. The resultant negative ion stream is applied to a mass analyzer. The reduced electron and ion space-charge limitations of this configuration enhances detection sensitivity for material to be detected by electron attachment, such as narcotic and explosive vapors. Positive ions may be generated by generating electrons having a higher energy, sufficient to ionize the target gas and pulsing the grid negative to stop the electron flow and pulsing the extraction aperture positive to draw out the positive ions.

  2. Sensitivity improvement in hydrophilic interaction chromatography negative mode electrospray ionization mass spectrometry using 2-(2-methoxyethoxy)ethanol as a post-column modifier for non-targeted metabolomics.

    PubMed

    Koch, Wendelin; Forcisi, Sara; Lehmann, Rainer; Schmitt-Kopplin, Philippe

    2014-09-26

    The application of ammonia acetate buffered liquid chromatography (LC) eluents is known to concomitantly lead to ion suppression when electrospray ionization mass spectrometry (ESI-MS) detection is used. In negative ESI mode, post column infusion of 2-(2-methoxyethoxy)ethanol (2-MEE) was shown in the literature to help to compensate this adverse effect occurring in reversed phase liquid chromatography mass spectrometry (RP-LC-MS) analyses. Here a setup of direct infusion and hydrophilic interaction chromatography (HILIC) post-column infusion experiments was established in order to investigate systematically the beneficial effects of 2-MEE. We demonstrate that, 2-MEE can help to improve ESI-MS sensitivity in HILIC too and reveal analyte structure specific behaviors. Our study indicates that 2-MEE especially improves ESI response for small and polar molecules. The ESI response of stable isotope labeled amino acids spiked into biological matrices increases up to 50-fold (i.e. D5-l-glutamic acid) when post column infusion of 2-MEE is applied. A non-targeted analysis of a pooled urine sample via HILIC-ESI-QTOF-MS supports this hypothesis. In direct infusion, the combined application of an ammonia acetate buffered solution together with 2-MEE results in an improved ESI response compared to a non-buffered solution. We observed up to 60-fold increased ESI response of l-lysine. We propose this effect is putatively caused by the formation of smaller ESI droplets and stripping of positive charge from ESI droplets due to evaporation of acetic acid anions. In summary, post-column infusion of 2-MEE especially enhances ESI response of small and polar molecules. Therefore it can be regarded as a valuable add-on in targeted or non-targeted metabolomic HILIC-MS studies since this method sets a focus on this molecule category. PMID:25160955

  3. Rapid multi-residue method for the determination of azinphos methyl, bromopropylate, chlorpyrifos, dimethoate, parathion methyl and phosalone in apricots and peaches by using negative chemical ionization ion trap technology.

    PubMed

    Liapis, Konstantinos S; Aplada-Sarlis, Pipina; Kyriakidis, Nikolaos V

    2003-05-01

    A rapid, selective and sensitive multi-residue method for the determination of six common pesticides in stone fruit samples is described. The proposed method involves the extraction of the pesticides with the use of acetone solvent followed by liquid-liquid partition with a mixture of dichloromethane and light petroleum (40-60 degrees C) and subsequent determination by a gas chromatographic-mass spectrometry system using ion trap technology in negative ion chemical ionization mode. The average percent recoveries of bromopropylate and phosalone in the concentration range 0.2-2.0 mg/kg were 97.3 +/- 6.7 to 120 +/- 1.0%, while the recoveries of chlorpyrifos and parathion methyl examined in the concentration range 0.02-0.2 mg/kg were 95.5 +/- 7.5 to 145 +/- 3.6%, the recoveries of azinphos methyl in the range 0.05-0.5 mg/kg were 74.8 +/- 29.6 to 96.5 +/- 13% and those of dimethoate in the range 0.1-1.0 mg/kg were 73.1 +/- 5.7 to 92.8 +/- 2.8% for n = 3 for all the above pesticides. The high mean recovery (145%) for chlorpyrifos is attributed to a matrix enhancement effect. The limits of quantitation in apricots were 0.01 mg/kg for chlorpyrifos, 0.02 mg/kg for dimethoate and parathion methyl, 0.05 mg/kg for azinphos methyl and phosalone and 0.1 mg/kg for bromopropylate. The usefulness of tandem mass spectrometry for confirmation purposes was also examined. The method was applied successfully to the determination of the target pesticides in 32 samples of stone fruits (apricots and peaches). PMID:12830919

  4. High-Precision Tungsten Isotopic Analysis by Multicollection Negative Thermal Ionization Mass Spectrometry Based on Simultaneous Measurement of W and (18)O/(16)O Isotope Ratios for Accurate Fractionation Correction.

    PubMed

    Trinquier, Anne; Touboul, Mathieu; Walker, Richard J

    2016-02-01

    Determination of the (182)W/(184)W ratio to a precision of ± 5 ppm (2σ) is desirable for constraining the timing of core formation and other early planetary differentiation processes. However, WO3(-) analysis by negative thermal ionization mass spectrometry normally results in a residual correlation between the instrumental-mass-fractionation-corrected (182)W/(184)W and (183)W/(184)W ratios that is attributed to mass-dependent variability of O isotopes over the course of an analysis and between different analyses. A second-order correction using the (183)W/(184)W ratio relies on the assumption that this ratio is constant in nature. This may prove invalid, as has already been realized for other isotope systems. The present study utilizes simultaneous monitoring of the (18)O/(16)O and W isotope ratios to correct oxide interferences on a per-integration basis and thus avoid the need for a double normalization of W isotopes. After normalization of W isotope ratios to a pair of W isotopes, following the exponential law, no residual W-O isotope correlation is observed. However, there is a nonideal mass bias residual correlation between (182)W/(i)W and (183)W/(i)W with time. Without double normalization of W isotopes and on the basis of three or four duplicate analyses, the external reproducibility per session of (182)W/(184)W and (183)W/(184)W normalized to (186)W/(183)W is 5-6 ppm (2σ, 1-3 μg loads). The combined uncertainty per session is less than 4 ppm for (183)W/(184)W and less than 6 ppm for (182)W/(184)W (2σm) for loads between 3000 and 50 ng. PMID:26751903

  5. Ultrasound-assisted dispersive liquid-liquid microextraction combined with gas chromatography-mass spectrometry in negative chemical ionization mode for the determination of polybrominated diphenyl ethers in water.

    PubMed

    Zhang, Qian; Liang, Tao; Guan, Lili

    2013-04-01

    A simple and economical method for the determination of eight polybrominated diphenyl ethers (BDE-28, 47, 99, 100,153,154,183, and 209) in water was developed. This method involves the use of ultrasound-assisted dispersive liquid-liquid microextraction combined with GC-MS in negative chemical ionization mode. Various parameters affecting the extraction efficiency, including the type and volume of extraction and dispersive solvents, salt concentration, extraction time, and ultrasonic time, were investigated. A volume of 1.0 mL of acetone (dispersive solvent) containing 10 μL tetrachloroethylene (extraction solvent) was injected into 5.0 mL of water samples and then emulsified by ultrasound for 2.0 min to produce the cloudy solution. Under the optimal condition, the enrichment factors for the eight PBDEs were varied from 845- to 1050-folds. Good linearity was observed in the range of 1.0-200 ng L(-1) for BDE-28, 47, 99, and 100; 5.0-200 ng L(-1) for BDE-153, 154, and 183; and 5.0-500 ng L(-1) for BDE-209. The RSD values were in the range of 2.5-8.4% (n = 5) and the LODs ranged from 0.40 to 2.15 ng L(-1) (S/N = 3). The developed method was applied for the determination of eight BPDEs in the river and lake water samples, and the mean recoveries at spiking levels of 5.0 and 50.0 ng L(-1) were in the range of 70.6-105.1%. PMID:23483741

  6. Simultaneous determination of lovastatin and its metabolite lovastatin acid in rat plasma using UPLC-MS/MS with positive/negative ion-switching electrospray ionization: Application to a pharmacokinetic study of lovastatin nanosuspension.

    PubMed

    Guo, Mengran; Zhao, Longshan; Li, Mo; Fu, Qiang; Pu, Xiaohui; Liu, Bingyang; He, Zhonggui; Yang, Li

    2016-06-15

    Lovastatin (LOV) is an antihyperlipidemic agent which exhibits low bioavailability due to its poor solubility. Therefore, a nanosuspension (NS) was developed as an efficient strategy to improve its oral bioavailability. To evaluate the pharmacokinetics of LOV-NS, a novel, sensitive, and rapid UPLC-MS/MS method was developed and validated for the simultaneous determination of LOV and its metabolite lovastatin acid (LOVA) in rat plasma. Simvastatin (IS) was chosen as the internal standard, and a liquid-liquid extraction method was used to isolate LOV and LOVA from biological matrices. The analytes were analyzed on an Acquity UPLC BEH C18 column, and a gradient program was applied at a flow rate of 0.2mL/min. Then, a tandem quadrupole mass spectrometer coupled with a positive/negative ion-switching electrospray ionization interface was employed to detect the analytes. Quantitation of the analytes was performed in the multiple reaction monitoring mode to monitor the transitions of m/z 427.1→325.0 for LOV and m/z 441.1→325.0 for IS in the positive ion mode and m/z 421.0→101.0 for LOVA in the negative ion mode, respectively. The method was validated over the concentration range 0.25-500ng/mL (r(2)≥0.99) for both LOV and LOVA. The intra-day and inter-day precision (RSD%) of LOV and LOVA were less than 12.87% and the accuracy (RE%) was less than 5.22%. The average extraction recoveries were 90.1% and 91.9% for LOV and LOVA, and the matrix effects were found to be between 85% and 115%. The stability study showed that both analytes were stable during the experiment. Finally, this method has been successfully applied to a pharmacokinetic study in rats following a single oral dose of 10mg/kg LOV-NS. PMID:27200472

  7. Ionization chamber

    DOEpatents

    Walenta, Albert H.

    1981-01-01

    An ionization chamber has separate drift and detection regions electrically isolated from each other by a fine wire grid. A relatively weak electric field can be maintained in the drift region when the grid and another electrode in the chamber are connected to a high voltage source. A much stronger electric field can be provided in the detection region by connecting wire electrodes therein to another high voltage source. The detection region can thus be operated in a proportional mode when a suitable gas is contained in the chamber. High resolution output pulse waveforms are provided across a resistor connected to the detection region anode, after ionizing radiation enters the drift region and ionize the gas.

  8. Ionization chamber

    DOEpatents

    Walenta, A.H.

    An ionization chamber is described which has separate drift and detection regions electrically isolated from each other by a fine wire grid. A relatively weak electric field can be maintained in the drift region when the grid and another electrode in the chamber are connected to a high voltage source. A much stronger electric field can be provided in the detection region by connecting wire electrodes therein to another high voltage source. The detection region can thus be operated in a proportional mode when a suitable gas is contained in the chamber. High resolution output pulse waveforms are provided across a resistor connected to the detection region anode, after ionizing radiation enters the drift region and ionizes the gas.

  9. IONIZATION CHAMBER

    DOEpatents

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

    1958-02-18

    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.

  10. Microwave remote sensing of ionized air.

    SciTech Connect

    Liao, S.; Gopalsami, N.; Heifetz, A.; Elmer, T.; Fiflis, P.; Koehl, E. R.; Chien, H. T.; Raptis, A. C.

    2011-07-01

    We present observations of microwave scattering from ambient room air ionized with a negative ion generator. The frequency dependence of the radar cross section of ionized air was measured from 26.5 to 40 GHz (Ka-band) in a bistatic mode with an Agilent PNA-X series (model N5245A) vector network analyzer. A detailed calibration scheme is provided to minimize the effect of the stray background field and system frequency response on the target reflection. The feasibility of detecting the microwave reflection from ionized air portends many potential applications such as remote sensing of atmospheric ionization and remote detection of radioactive ionization of air.

  11. Correlation of ionizing irradiation-induced late pulmonary fibrosis with long-term bone marrow culture fibroblast progenitor cell biology in mice homozygous deletion recombinant negative for endothelial cell adhesion molecules.

    PubMed

    Epperly, Michael W; Guo, Hongliang; Shields, Donna; Zhang, Xichen; Greenberger, Joel S

    2004-01-01

    Ionizing irradiation damage to the lung is associated with an acute inflammatory reaction, followed by a latent period and then late effects including predominantly pulmonary fibrosis. The cells mediating fibrosis have recently been shown to derive from the bone marrow hematopoietic microenvironment. Initiation of late pulmonary irradiation lung damage has been correlated with up-regulation of VCAM-1 and ICAM-1 in pulmonary endothelial cells, followed by infiltration of macrophages and bone marrow-derived fibroblasts forming the fibrotic lesions of organizing alveolitis/fibrosis. To determine whether the absence of expression of VCAM-1, ICAM-1, or other adhesion molecules known to be relevant to inflammatory cell attachment to lung endothelial cells was associated with a decrease in irradiation-induced lung fibrosis, homozygous deletion recombinant knockout mice lacking each of several adhesion molecules were tested compared to littermates for survival and development of organizing alveolitis following 20 Gy irradiation to both lungs. Bone marrow culture longevity has been shown to be a parameter, which correlates with both hematopoietic stem cell reserve and the integrity of fibroblast progenitors of the supportive hematopoietic microenvironment; radiation lung survival data were correlated to longevity of hematopoiesis in long-term bone marrow cultures established from tibia and femur bone marrow of the same mice. Homozygous deletion recombinant negative mice including VCAM-1-/-, ICAM-1-/-, E-Selectin-/-, or L-Selectin-/- were irradiated to 20 Gy to both lungs and followed for survival and percent organizing alveolitis at time of death compared to each normal littermate. A significant increase in survival (median 190 days) was detected with L-Selectin-/- compared to littermate control mice (median 140 days) or other groups. Long-term bone marrow cultures from L-Selectin-/- mice showed no detectable difference in marrow fibroblasts or hematopoietic cell biology

  12. Three chamber negative ion source

    DOEpatents

    Leung, Ka-Ngo; Ehlers, Kenneth W.; Hiskes, John R.

    1985-01-01

    A negative ion vessel is divided into an excitation chamber, a negative ionization chamber and an extraction chamber by two magnetic filters. Input means introduces neutral molecules into a first chamber where a first electron discharge means vibrationally excites the molecules which migrate to a second chamber. In the second chamber a second electron discharge means ionizes the molecules, producing negative ions which are extracted into or by a third chamber. A first magnetic filter prevents high energy electrons from entering the negative ionization chamber from the excitation chamber. A second magnetic filter prevents high energy electrons from entering the extraction chamber from the negative ionizing chamber. An extraction grid at the end of the negative ion vessel attracts negative ions into the third chamber and accelerates them. Another grid, located adjacent to the extraction grid, carries a small positive voltage in order to inhibit positive ions from migrating into the extraction chamber and contour the plasma potential. Additional electrons can be suppressed from the output flux using ExB forces provided by magnetic field means and the extractor grid electric potential.

  13. Electron collisional detachment processes for a 250 keV D/sup -/ ion beam in a partially ionized hydrogen target

    SciTech Connect

    Savas, S.E.

    1980-09-01

    Neutral atom beams with energies above 200 keV may be required for various purposes in magnetic fusion devices following TFTR, JET and MFTF-B. These beams can be produced much more efficiently by electron detachment from negative ion beams than by electron capture by positive ions. We have investigated the efficiency with which such neutral atoms can be produced by electron detachment in partially ionized hydrogen plasma neutralizers.

  14. Capturing Callisto

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The New Horizons Long Range Reconnaissance Imager (LORRI) captured these two images of Jupiter's outermost large moon, Callisto, as the spacecraft flew past Jupiter in late February. New Horizons' closest approach distance to Jupiter was 2.3 million kilometers (1.4 million miles), not far outside Callisto's orbit, which has a radius of 1.9 million kilometers (1.2 million miles). However, Callisto happened to be on the opposite side of Jupiter during the spacecraft's pass through the Jupiter system, so these images, taken from 4.7 million kilometers (3.0 million miles) and 4.2 million kilometers (2.6 million miles) away, are the closest of Callisto that New Horizons obtained.

    Callisto's ancient, crater-scarred surface makes it very different from its three more active sibling satellites, Io, Europa and Ganymede. Callisto, 4,800 kilometers (3000 miles) in diameter, displays no large-scale geological features other than impact craters, and every bright spot in these images is a crater. The largest impact feature on Callisto, the huge basin Valhalla, is visible as a bright patch at the 10 o'clock position. The craters are bright because they have excavated material relatively rich in water ice from beneath the dark, dusty material that coats most of the surface.

    The two images show essentially the same side of Callisto -- the side that faces Jupiter -- under different illumination conditions. The images accompanied scans of Callisto's infrared spectrum with New Horizons' Linear Etalon Imaging Spectral Array (LEISA). The New Horizons science team designed these scans to study how the infrared spectrum of Callisto's water ice changes as lighting and viewing conditions change, and as the ice cools through Callisto's late afternoon. The infrared spectrum of water ice depends slightly on its temperature, and a goal of New Horizons when it reaches the Pluto system (in 2015) is to use the water ice features in the spectrum of Pluto's moon Charon, and

  15. 6D Muon Ionization Cooling with an Inverse Cyclotron

    SciTech Connect

    Summers, D. J.; Bracker, S. B.; Cremaldi, L. M.; Godang, R.; Palmer, R. B.

    2006-03-20

    A large admittance sector cyclotron filled with LiH wedges surrounded by helium or hydrogen gas is explored. Muons are cooled as they spiral adiabatically into a central swarm. As momentum approaches zero, the momentum spread also approaches zero. Long bunch trains coalesce. Energy loss is used to inject the muons into the outer rim of the cyclotron. The density of material in the cyclotron decreases adiabatically with radius. The sector cyclotron magnetic fields are transformed into an azimuthally symmetric magnetic bottle in the center. Helium gas is used to inhibit muonium formation by positive muons. Deuterium gas is used to allow captured negative muons to escape via the muon catalyzed fusion process. The presence of ionized gas in the center may automatically neutralize space charge. When a bunch train has coalesced into a central swarm, it is ejected axially with an electric kicker pulse.

  16. Negative mass

    NASA Astrophysics Data System (ADS)

    Hammond, Richard T.

    2015-03-01

    Some physical aspects of negative mass are examined. Several unusual properties, such as the ability of negative mass to penetrate any armor, are analysed. Other surprising effects include the bizarre system of negative mass chasing positive mass, naked singularities and the violation of cosmic censorship, wormholes, and quantum mechanical results as well. In addition, a brief look into the implications for strings is given.

  17. Weakly ionized cosmic gas: Ionization and characterization

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  18. Distinction between sequential and direct ionization in two-photon double ionization of helium

    NASA Astrophysics Data System (ADS)

    Selstø, Sølve; Raynaud, Xavier; Simonsen, Aleksander Skjerlie; Førre, Morten

    2014-11-01

    This paper aims to shed some light on the role of the direct, or nonsequential, ionization channel in the regime in which the sequential channel is open in two-photon double ionization (TPDI) of helium. In this regime the sequential channel dominates any direct contribution unless the laser pulse is of very short duration, in which case their distinction is hard to draw. Based on both a simple model and full solutions of the time-dependent Schrödinger equation, we aim to provide evidence of direct double ionization by identifying a term proportional to the pulse duration in the double ionization yield. Indeed, such a term is identified in the energy-differential yield. When it comes to the total double ionization probability, however, it turns out that the net first-order contribution is negative. The nature of the negative first-order contribution is discussed, and we argue that it is of correlated origin.

  19. Can radiative forcing be limited to 2.6 Wm-2 without negative emissions from bioenergy Aand CO2 capture and storage?

    SciTech Connect

    Edmonds, James; Luckow, Patrick; Calvin, Katherine; Wise, Marshall; Dooley, Jim; Kyle, Page; Kim, Son H.; Patel, Pralit; Clarke, Leon

    2013-01-18

    Combining bioenergy and carbon dioxide (CO2) capture and storage (CCS) technologies (BECCS) has the potential to remove CO2 from the atmosphere while producing useful energy. BECCS has played a central role in scenarios that reduce climate forcing to low levels such as 2.6Wm-2. In this paper we consider whether BECCS is essential to limiting radiative forcing (RF) to 2.6Wm-2 by 2100 using the Global Change Assessment Model, a closely coupled model of biogeophysical and human Earth systems. We show that BECCS can potentially reduce the cost of limiting RF to 2.6Wm-2 by 2100 but that a variety of technology combinations that do not include BECCS can also achieve this goal, under appropriate emissions mitigation policies. We note that with appropriate supporting land-use policies terrestrial sequestration could deliver carbon storage ranging from 200 to 700 PgCO2-equiavalent over the 21st century. We explore substantial delays in participation by some geopolitical regions. We find that the value of BECCS is substantially higher under delay and that delay results in higher transient RF and climate change. However, when major regions postponed mitigation indefinitely, it was impossible to return RF to 2.6Wm-2 by 2100. Neither finite land resources nor finite potential geologic storage capacity represented a meaningful technical limit on the ability of BECCS to contribute to emissions mitigation in the numerical experiments reported in this paper.

  20. Negative ions of polyatomic molecules.

    PubMed Central

    Christophorou, L G

    1980-01-01

    In this paper general concepts relating to, and recent advances in, the study of negative ions of polyatomic molecules area discussed with emphasis on halocarbons. The topics dealt with in the paper are as follows: basic electron attachment processes, modes of electron capture by molecules, short-lived transient negative ions, dissociative electron attachment to ground-state molecules and to "hot" molecules (effects of temperature on electron attachment), parent negative ions, effect of density, nature, and state of the medium on electron attachment, electron attachment to electronically excited molecules, the binding of attached electrons to molecules ("electron affinity"), and the basic and the applied significance of negative-ion studies. PMID:7428744

  1. Surface-enhanced laser desorption/ionization time of flight mass spectrometry protein profiling identifies ubiquitin and ferritin light chain as prognostic biomarkers in node-negative breast cancer tumors.

    PubMed

    Ricolleau, Gabriel; Charbonnel, Catherine; Lodé, Laurence; Loussouarn, Delphine; Joalland, Marie-Pierre; Bogumil, Ralf; Jourdain, Sabine; Minvielle, Stéphane; Campone, Mario; Déporte-Fety, Régine; Campion, Loïc; Jézéquel, Pascal

    2006-03-01

    Novel prognostic biomarkers are imperatively needed to help direct treatment decisions by typing subgroups of node-negative breast cancer patients. The current study has used a proteomic approach of SELDI-TOF-MS screening to identify differentially cytosolic expressed proteins with a prognostic impact in 30 node-negative breast cancer patients with no relapse versus 30 patients with metastatic relapse. The data analysis took into account 73 peaks, among which 2 proved, by means of univariate Cox regression, to have a good cumulative prognostic-informative power. Repeated random sampling (n = 500) was performed to ensure the reliability of the peaks. Optimized thresholds were then computed to use both peaks as risk factors and, adding them to the St. Gallen ones, improve the prognostic classification of node-negative breast cancer patients. Identification of ubiquitin and ferritin light chain (FLC), corresponding to the two peaks of interest, was obtained using ProteinChip LDI-Qq-TOF-MS. Differential expression of the two proteins was further confirmed by Western blotting analyses and immunohistochemistry. SELDI-TOF-MS protein profiling clearly showed that a high level of cytosolic ubiquitin and/or a low level of FLC were associated with a good prognosis in breast cancer. PMID:16470659

  2. Molecular Characterization of S- and N-containing Organic Constituents in Ambient Aerosols by negative ion mode High-Resolution Nanospray Desorption Electrospray Ionization Mass Spectrometry: CalNex 2010 field study

    SciTech Connect

    O'Brien, Rachel E.; Laskin, Alexander; Laskin, Julia; Rubitschun, Caitlin L.; Surratt, Jason D.; Goldstein, Allen H.

    2014-11-27

    Samples of ambient aerosols from the 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field study were analyzed using Nanospray Desorption Electrospray Ionization High Resolution Mass Spectrometry (nano-DESI/MS). Four samples per day were collected in Bakersfield, CA on June 20-24 with a collection time of 6 hours per sample. Four characteristic groups of organic constituents were identified in the samples: compounds containing carbon, hydrogen, and oxygen only (CHO), sulfur- (CHOS), nitrogen-(CHON), and both nitrogen- and sulfur-containing organics (CHONS). Within the groups, organonitrates, organosulfates, and nitroxy organosulfates were assigned based on accurate mass measurements and elemental ratio comparisons. Changes in the chemical composition of the aerosol samples were observed throughout the day. The number of observed CHO compounds increased in the afternoon samples, suggesting regional photochemical processing as a source. The average number of CHOS compounds had the smallest changes throughout the day, consistent with a more broadly distributed source. Both of the nitrogen-containing groups (CHON and CHONS) had greater numbers of compounds in the night and morning samples, indicating that nitrate radical chemistry was likely a source for those compounds. Most of the compounds were found in submicron particles. The size distribution of CHON compounds was bimodal. We conclude that the majority of the compounds observed were secondary in nature with both biogenic and anthropogenic sources.

  3. Video Screen Capture Basics

    ERIC Educational Resources Information Center

    Dunbar, Laura

    2014-01-01

    This article is an introduction to video screen capture. Basic information of two software programs, QuickTime for Mac and BlueBerry Flashback Express for PC, are also discussed. Practical applications for video screen capture are given.

  4. Boron-neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Haque, A. M.; Moschini, G.; Valkovic, Vlado; Zafiropoulos, D.

    1995-03-01

    The final goal of any radiotherapy project is to expose the tumor as the target to a lethal dose of ionizing radiation, sparing thereby the surrounding healthy tissues to a maximum extent. Precise treatment is nevertheless essential for cure, since the danger exists that the tumor might re-establish itself if every cancer cell is not destroyed. The conventional therapy treatments existing to date, e.g., surgery, radiation therapy, and chemotherapy, have been successful in curing some kinds of cancers, but still there are many exceptions. In the following, the progress of a promising therapy tool, called the boron neutron capture therapy (BNCT), which has made its dynamic evolution in recent years, is briefly described. The approach towards clinical trials with BNCT is described in detail.

  5. Ionization potentials of seaborgium

    SciTech Connect

    Johnson, E.; Pershina, V.; Fricke, B.

    1999-10-21

    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 radii obtained will be used to predict some physiochemical properties of seaborgium and its compounds.

  6. Ionization Energies of Lanthanides

    ERIC Educational Resources Information Center

    Lang, Peter F.; Smith, Barry C.

    2010-01-01

    This article describes how data are used to analyze the pattern of ionization energies of the lanthanide elements. Different observed pathways of ionization between different ground states are discussed, and the effects of pairing, exchange, and orbital interactions on ionization energies of the lanthanides are evaluated. When all the above…

  7. Capture Their Attention: Capturing Lessons Using Screen Capture Software

    ERIC Educational Resources Information Center

    Drumheller, Kristina; Lawler, Gregg

    2011-01-01

    When students miss classes for university activities such as athletic and academic events, they inevitably miss important class material. Students can get notes from their peers or visit professors to find out what they missed, but when students miss new and challenging material these steps are sometimes not enough. Screen capture and recording…

  8. Production of negative hydrogen ions on metal grids

    SciTech Connect

    Oohara, W.; Maetani, Y.; Takeda, Takashi; Takeda, Toshiaki; Yokoyama, H.; Kawata, K.

    2015-03-15

    Negative hydrogen ions are produced on a nickel grid with positive-ion irradiation. In order to investigate the production mechanism, a copper grid without the chemisorption of hydrogen atoms and positive helium ions without negative ionization are used for comparison. Positive hydrogen ions reflected on the metal surface obtain two electrons from the surface and become negatively ionized. It is found that the production yield of negative ions by desorption ionization of chemisorbed hydrogen atoms seems to be small, and the production is a minor mechanism.

  9. Cryogenic Carbon Capture

    SciTech Connect

    2010-07-15

    IMPACCT Project: SES is developing a process to capture CO2 from the exhaust gas of coal-fired power plants by desublimation - the conversion of a gas to a solid. Capturing CO2 as a solid and delivering it as a liquid avoids the large energy cost of CO2 gas compression. SES’ capture technology facilitates the prudent use of available energy resources. Coal is our most abundant energy resource and is an excellent fuel for baseline power production. SES capture technology can capture 99% of the CO2 emissions in addition to a wide range of other pollutants more efficiently and at lower costs than existing capture technologies. SES’ capture technology can be readily added to our existing energy infrastructure.

  10. Isotope separation by photoselective dissociative electron capture

    DOEpatents

    Stevens, Charles G. [Pleasanton, CA

    1978-08-29

    A method of separating isotopes based on photoselective electron capture dissociation of molecules having an electron capture cross section dependence on the vibrational state of the molecule. A molecular isotope source material is irradiated to selectively excite those molecules containing a desired isotope to a predetermined vibrational state having associated therewith an electron capture energy region substantially non-overlapping with the electron capture energy ranges associated with the lowest vibration states of the molecules. The isotope source is also subjected to electrons having an energy corresponding to the non-overlapping electron capture region whereby the selectively excited molecules preferentially capture electrons and dissociate into negative ions and neutrals. The desired isotope may be in the negative ion product or in the neutral product depending upon the mechanism of dissociation of the particular isotope source used. The dissociation product enriched in the desired isotope is then separated from the reaction system by conventional means. Specifically, .sup.235 UF.sub.6 is separated from a UF.sub.6 mixture by selective excitation followed by dissociative electron capture into .sup.235 UF.sub.5 - and F.

  11. Isotope separation by photoselective dissociative electron capture

    DOEpatents

    Stevens, C.G.

    1978-08-29

    Disclosed is a method of separating isotopes based on photoselective electron capture dissociation of molecules having an electron capture cross section dependence on the vibrational state of the molecule. A molecular isotope source material is irradiated to selectively excite those molecules containing a desired isotope to a predetermined vibrational state having associated therewith an electron capture energy region substantially non-overlapping with the electron capture energy ranges associated with the lowest vibration states of the molecules. The isotope source is also subjected to electrons having an energy corresponding to the non-overlapping electron capture region whereby the selectively excited molecules preferentially capture electrons and dissociate into negative ions and neutrals. The desired isotope may be in the negative ion product or in the neutral product depending upon the mechanism of dissociation of the particular isotope source used. The dissociation product enriched in the desired isotope is then separated from the reaction system by conventional means. Specifically, [sup 235]UF[sub 6] is separated from a UF[sub 6] mixture by selective excitation followed by dissociative electron capture into [sup 235]UF[sub 5]- and F. 2 figs.

  12. Iodine neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Ahmed, Kazi Fariduddin

    A new technique, Iodine Neutron Capture Therapy (INCT) is proposed to treat hyperthyroidism in people. Present thyroid therapies, surgical removal and 131I treatment, result in hypothyroidism and, for 131I, involve protracted treatment times and excessive whole-body radiation doses. The new technique involves using a low energy neutron beam to convert a fraction of the natural iodine stored in the thyroid to radioactive 128I, which has a 24-minute half-life and decays by emitting 2.12-MeV beta particles. The beta particles are absorbed in and damage some thyroid tissue cells and consequently reduce the production and release of thyroid hormones to the blood stream. Treatment times and whole-body radiation doses are thus reduced substantially. This dissertation addresses the first of the several steps needed to obtain medical profession acceptance and regulatory approval to implement this therapy. As with other such programs, initial feasibility is established by performing experiments on suitable small mammals. Laboratory rats were used and their thyroids were exposed to the beta particles coming from small encapsulated amounts of 128I. Masses of 89.0 mg reagent-grade elemental iodine crystals have been activated in the ISU AGN-201 reactor to provide 0.033 mBq of 128I. This activity delivers 0.2 Gy to the thyroid gland of 300-g male rats having fresh thyroid tissue masses of ˜20 mg. Larger iodine masses are used to provide greater doses. The activated iodine is encapsulated to form a thin (0.16 cm 2/mg) patch that is then applied directly to the surgically exposed thyroid of an anesthetized rat. Direct neutron irradiation of a rat's thyroid was not possible due to its small size. Direct in-vivo exposure of the thyroid of the rat to the emitted radiation from 128I is allowed to continue for 2.5 hours (6 half-lives). Pre- and post-exposure blood samples are taken to quantify thyroid hormone levels. The serum T4 concentration is measured by radioimmunoassay at

  13. Effective ionization rate in nitrogen-oxygen mixtures

    NASA Astrophysics Data System (ADS)

    Pancheshnyi, Sergey

    2013-04-01

    The effective Townsend ionization coefficient in nitrogen-oxygen mixtures at various pressures is determined. In addition to the commonly accepted difference of the ionization and the attachment coefficients, α and η, respectively, the electron detachment from the negative ions created by the avalanche itself is taken into account. This leads to non-zero effective ionization rate below the threshold field corresponding to α - η = 0.

  14. Ambient Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Huang, Min-Zong; Yuan, Cheng-Hui; Cheng, Sy-Chyi; Cho, Yi-Tzu; Shiea, Jentaie

    2010-07-01

    Mass spectrometric ionization methods that operate under ambient conditions and require minimal or no sample pretreatment have attracted much attention in such fields as biomedicine, food safety, antiterrorism, pharmaceuticals, and environmental pollution. These technologies usually involve separate ionization and sample-introduction events, allowing independent control over each set of conditions. Ionization is typically performed under ambient conditions through use of existing electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) techniques. Rapid analyses of gas, liquid, and solid samples are possible with the adoption of various sample-introduction methods. This review sorts different ambient ionization techniques into two main subcategories, primarily on the basis of the ionization processes, that are further differentiated in terms of the approach used for sampling.

  15. Physics of Partially Ionized Plasmas

    NASA Astrophysics Data System (ADS)

    Krishan, Vinod

    2016-05-01

    Figures; Preface; 1. Partially ionized plasmas here and everywhere; 2. Multifluid description of partially ionized plasmas; 3. Equilibrium of partially ionized plasmas; 4. Waves in partially ionized plasmas; 5. Advanced topics in partially ionized plasmas; 6. Research problems in partially ionized plasmas; Supplementary matter; Index.

  16. An atmospheric pressure chemical ionization study of the positive and negative ion chemistry of the hydrofluorocarbons 1,1-difluoroethane (HFC-152a) and 1,1,1,2-tetrafluoroethane (HFC-134a) and of perfluoro-n-hexane (FC-72) in air plasma at atmospheric pressure.

    PubMed

    Marotta, Ester; Paradisi, Cristina; Scorrano, Gianfranco

    2004-07-01

    A report is given on the ionization/dissociation behavior of the title compounds within air plasmas produced by electrical corona discharges at atmospheric pressure: both positive and negative ions were investigated at different temperatures using atmospheric pressure chemical ionization mass spectrometry (APCI-MS). CHF(2)CH(3) (HFC-152a) undergoes efficient ionic oxidation to C(2)H(5)O(+), in which the oxygen comes from water present in the plasma. In contrast, CF(3)CH(2)F (HFC-134a) does not produce any characteristic positive ion under APCI conditions, its presence within the plasma being revealed only as a neutral ligand in ion-molecule complexes with ions of the background (H(3)O(+) and NO(+)). Analogously, the perfluorocarbon FC-72 (n-C(6)F(14)) does not produce significant positive ions at 30 degrees C: at high temperature, however, it undergoes dissociative ionization to form many product ions including C(3)F(6)(+), C(2)F(4)(+), C(n)F(2n+1)(+) and a few families of oxygen containing cations (C(n)F(2n+1)OH(2)(+), C(n)F(2n)OH(+), C(n)F(2n-1)O(+), C(n)F(2n-1)O(2)H(2)(+), C(n)F(2n-2)O(2)H(+)) which are suggested to derive from C(n)F(2n+1)(+) in a cascade of steps initiated by condensation with water followed by steps of HF elimination and H(2)O addition. Negative ions formed from the fluoroethanes CHF(2)CH(3) and CF(3)CH(2)F (M) include complexes with ions of the background, O(2)(-)(M), O(3)(-)(M) and some higher complexes involving also water, and complexes of the fluoride ion, F(-)(H(2)O), F(-)(M) and higher complexes with both M and H(2)O also together. The interesting product O(2)(-)(HF) is also formed from 1,1-difluoroethane. In contrast to the HFCs, perfluoro-n-hexane gives stable molecular anions, M(-), which at low source temperature or in humidified air are also detected as hydrates, M(-)(H(2)O). In addition, in humidified air F(-)(H(2)O)(n) complexes are also formed. The reactions leading to all major positive and negative product ions are discussed

  17. Overriding auditory attentional capture.

    PubMed

    Dalton, Polly; Lavie, Nilli

    2007-02-01

    Attentional capture by color singletons during shape search can be eliminated when the target is not a feature singleton (Bacon & Egeth, 1994). This suggests that a "singleton detection" search strategy must be adopted for attentional capture to occur. Here we find similar effects on auditory attentional capture. Irrelevant high-intensity singletons interfered with an auditory search task when the target itself was also a feature singleton. However, singleton interference was eliminated when the target was not a singleton (i.e., when nontargets were made heterogeneous, or when more than one target sound was presented). These results suggest that auditory attentional capture depends on the observer's attentional set, as does visual attentional capture. The suggestion that hearing might act as an early warning system that would always be tuned to unexpected unique stimuli must therefore be modified to accommodate these strategy-dependent capture effects. PMID:17557587

  18. Testing the Capture Magnet

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image of a model capture magnet was taken after an experiment in a Mars simulation chamber at the University of Aarhus, Denmark. It has some dust on it, but not as much as that on the Mars Exploration Rover Spirit's capture magnet. The capture and filter magnets on both Mars Exploration Rovers were delivered by the magnetic properties team at the Center for Planetary Science, Copenhagen, Denmark.

  19. Negative-ion source applications.

    PubMed

    Ishikawa, J

    2008-02-01

    In this paper heavy negative-ion sources which we developed and their applications for materials science are reviewed. Heavy negative ions can be effectively produced by the ejection of a sputtered atom through the optimally cesiated surface of target with a low work function. Then, enough continuous negative-ion currents for materials-science applications can be obtained. We developed several kinds of sputter-type heavy negative-ion sources such as neutral- and ionized-alkaline metal bombardment-type heavy negative-ion source and rf-plasma sputter type. In the case where a negative ion is irradiated on a material surface, surface charging seldom takes place because incoming negative charge of the negative ion is well balanced with outgoing negative charge of the released secondary electron. In the negative-ion implantation into an insulator or insulated conductive material, high precision implantation processing with charge-up free properties can be achieved. Negative-ion implantation technique, therefore, can be applied to the following novel material processing systems: the surface modification of micrometer-sized powders, the nanoparticle formation in an insulator for the quantum devices, and the nerve cell growth manipulation by precise control of the biocompatibility of polymer surface. When a negative ion with low kinetic energy approaches the solid surface, the kinetic energy causes the interatomic bonding (kinetic bonding), and formation of a metastable material is promoted. Carbon films with high constituent of sp(3) bonding, therefore, can be formed by carbon negative-ion beam deposition. PMID:18315249

  20. Spatial capture-recapture

    USGS Publications Warehouse

    Royle, J. Andrew; Chandler, Richard B.; Sollmann, Rahel; Gardner, Beth

    2013-01-01

    Spatial Capture-Recapture provides a revolutionary extension of traditional capture-recapture methods for studying animal populations using data from live trapping, camera trapping, DNA sampling, acoustic sampling, and related field methods. This book is a conceptual and methodological synthesis of spatial capture-recapture modeling. As a comprehensive how-to manual, this reference contains detailed examples of a wide range of relevant spatial capture-recapture models for inference about population size and spatial and temporal variation in demographic parameters. Practicing field biologists studying animal populations will find this book to be a useful resource, as will graduate students and professionals in ecology, conservation biology, and fisheries and wildlife management.

  1. Intelsat VI Capture Attempt

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The first single crewmember EVA capture attempt of the Intelsat VI as seen from Endeavour's aft flight deck windows. EVA Mission Specialist Pierre Thuot standing on the Remote Manipulator System (RMS) end effector platform, with the satellite capture bar attempting to attach it to the free floating communications satellite.

  2. Demonstrating carbon capture

    SciTech Connect

    Qader, A.; Hooper, B.; Stevens, G.

    2009-11-15

    Australia is at the forefront of advancing CCS technology. The CO2CRC's H3 (Post-combustion) and Mulgrave (pre-combustion) capture projects are outlined. The capture technologies for these 2 demonstration projects are described. 1 map., 2 photos.

  3. Nucleon pairing in μ- capture by 40Ca

    NASA Astrophysics Data System (ADS)

    Martoff, C. J.; Cummings, W. J.; Poanić, D.; Hanna, S. S.; Ullrich, H.; Furić, M.; Petković, T.; Kozlowski, T.; Perroud, J. P.

    1991-03-01

    Spectra of energetic protons above 35 MeV have been measured following negative muon capture from rest in Ca. The spectrum extends to the kinematic limit near 93 MeV, with a branching ratio of (2.3+/-0.3)×10-4 per capture above 40 MeV. Nuclear cascade calculations of the proton and neutron spectra in this energy region are presented and are consistent with the measured proton spectrum when capture on correlated pp and np pairs in the nucleus is included. The ratio of capture on np to pp pairs is 6.7+/-1.6, which is consistent with results from pion capture.

  4. Analytical instruments, ionization sources, and ionization methods

    DOEpatents

    Atkinson, David A.; Mottishaw, Paul

    2006-04-11

    Methods and apparatus for simultaneous vaporization and ionization of a sample in a spectrometer prior to introducing the sample into the drift tube of the analyzer are disclosed. The apparatus includes a vaporization/ionization source having an electrically conductive conduit configured to receive sample particulate which is conveyed to a discharge end of the conduit. Positioned proximate to the discharge end of the conduit is an electrically conductive reference device. The conduit and the reference device act as electrodes and have an electrical potential maintained between them sufficient to cause a corona effect, which will cause at least partial simultaneous ionization and vaporization of the sample particulate. The electrical potential can be maintained to establish a continuous corona, or can be held slightly below the breakdown potential such that arrival of particulate at the point of proximity of the electrodes disrupts the potential, causing arcing and the corona effect. The electrical potential can also be varied to cause periodic arcing between the electrodes such that particulate passing through the arc is simultaneously vaporized and ionized. The invention further includes a spectrometer containing the source. The invention is particularly useful for ion mobility spectrometers and atmospheric pressure ionization mass spectrometers.

  5. Negative-ion formation in the explosives RDX, PETN, and TNT using the Reversal Electron Attachment Detection (READ) technique

    NASA Technical Reports Server (NTRS)

    Chutijian, Ara; Boumsellek, S.; Alajajian, S. H.

    1992-01-01

    In the search for high sensitivity and direct atmospheric sampling of trace species, techniques have been developed such as atmospheric-sampling, glow-discharge ionization (ASGDI), corona discharge, atmospheric pressure ionization (API), electron-capture detection (ECD), and negative-ion chemical ionization (NICI) that are capable of detecting parts-per-billion to parts-per-trillion concentrations of trace species. These techniques are based on positive- or negative-ion formation via charge-transfer to the target, or electron capture under multiple-collision conditions in a Maxwellian distribution of electron energies at the source temperature. One drawback of the high-pressure, corona- or glow-discharge devices is that they are susceptible to interferences either through indistinguishable product masses, or through undesired ion-molecule reactions. The ASGDI technique is relatively immune from such interferences, since at target concentrations of less than 1 ppm the majority of negative ions arises via electron capture rather than through ion-molecule chemistry. A drawback of the conventional ECD, and possibly of the ASGDI, is that they exhibit vanishingly small densities of electrons with energies in the range 0-10 millielectron volts (meV), as can be seen from a typical Maxwellian electron energy distribution function at T = 300 K. Slowing the electrons to these subthermal (less than 10 meV) energies is crucial, since the cross section for attachment of several large classes of molecules is known to increase to values larger than 10(exp -12) sq cm at near-zero electron energies. In the limit of zero energy these cross sections are predicted to diverge as epsilon(exp -1/2), where epsilon is the electron energy. In order to provide a better 'match' between the electron energy distribution function and attachment cross section, a new concept of attachment in an electrostatic mirror was developed. In this scheme, electrons are brought to a momentary halt by

  6. IMPACCT: Carbon Capture Technology

    SciTech Connect

    2012-01-01

    IMPACCT Project: IMPACCT’s 15 projects seek to develop technologies for existing coal-fired power plants that will lower the cost of carbon capture. Short for “Innovative Materials and Processes for Advanced Carbon Capture Technologies,” the IMPACCT Project is geared toward minimizing the cost of removing carbon dioxide (CO2) from coal-fired power plant exhaust by developing materials and processes that have never before been considered for this application. Retrofitting coal-fired power plants to capture the CO2 they produce would enable greenhouse gas reductions without forcing these plants to close, shifting away from the inexpensive and abundant U.S. coal supply.

  7. STRUCTURAL DETERMINATION AND QUANTITATIVE ANALYSIS OF BACTERIAL PHOSPHOLIPIDS USING LIQUID CHROMATOGRAPHY/ELECTROSPRAY IONIZATION/MASS SPECTROMETRY

    EPA Science Inventory

    This report presents a comprehensive spectral analysis of common bacterial phospholipids using electrospray/mass spectrometry (ESI/MS) under both negative and positive ionization conditions. Phospholipids under positive ionization yield sodium-adduct molecular ions which are mos...

  8. Laser ionization mass spectroscopy

    NASA Astrophysics Data System (ADS)

    Bernardez, Luis J., III; Siekhaus, W. J.

    1989-10-01

    Laser Ionization Mass Spectroscopy (LIMS) is a simple technique with several advantages and disadvantages over standard mass spectroscopy techniques. The LIMS technique uses a laser to vaporize a small portion of a sample. The vapor from the sample consists of a mixture of charged and neutral atoms or fragments. Using electrostatic grids, the ions (positive or negative) are given a known amount of kinetic energy and sent down a time-of-flight tube. The time it takes the ions to travel down the flight tube is recorded. Knowing the ions' energy, the length of the flight tube, and the time it takes the ions to travel that distance, the masses of the ions can be calculated. The instrument used is a LIMA 3 made by Cambridge Mass Spectrometry. It has a Quanta Ray DCR-11 Nd:YAG laser, which was frequency-quadrupled to 266 nm. The laser spot size is typically between 2 and 5 microns in diameter and the pulse width is between 5 and 10 nanoseconds. The energy of the laser is continually variable between 0.1 and 3.0 millijoules. The detector is a 17-stage venetian-blind multiplier made by Thorn EMI. The analysis is carried out under vacuum, usually between 10(exp -8) and 10(exp -9) Torr. The LIMA 3 has several useful features such as: a He-Ne pilot laser used to target the Nd:YAG laser; a microscope (which is used to view the sample through the laser optics); and a precision sample stage for accurate sample alignment.

  9. Laser ionization mass spectroscopy

    SciTech Connect

    Bernardez, L.J. III; Siekhaus, W.J. )

    1989-10-01

    Laser Ionization Mass Spectroscopy (LIMS) is a simple technique with several advantages and disadvantages over standard mass spectroscopy techniques. The LIMS technique uses a laser to vaporize a small portion of a sample. The vapor from the sample consists of a mixture of charged and neutral atoms or fragments. Using electrostatic grids, the ions (positive or negative) are given a known amount of kinetic energy and sent down a time-of-flight tube. The time it takes the ions to travel down the flight tube is recorded. Knowing the ions' energy, the length of the flight tube, and the time it takes the ions to travel that distance, the masses of the ions can be calculated. The instrument we use is a LIMA 3 made by Cambridge Mass Spectrometry. It has a Quanta Ray DCR-11 Nd:YAG laser, which we frequency-quadruple to 266 nm. The laser spot size is typically between 2 and 5 microns in diameter and the pulse width is between 5 and 10 nanoseconds. The energy of the laser is continually variable between 0.1 and 3.0 millijoules. The detector is a 17-stage venetian-blind multiplier made by Thorn EMI. The analysis is carried out under vacuum, usually between 10{sup {minus}8} and 10{sup {minus}9} Torr. The LIMA 3 has several useful features such as: a He-Ne pilot laser used to target the Nd:YAG laser; a microscope (which is used to view the sample through the laser optics); and a precision sample stage for accurate sample alignment. 6 figs., 1 tab.

  10. Physical applications of muon catalysis: Muon capture in hydrogen

    NASA Astrophysics Data System (ADS)

    Filchenkov, V. V.

    2016-07-01

    Results of theoretical and experimental research on capture of negative muons in hydrogen are reported with an emphasis on the accompanying phenomenon of muon catalysis in hydrogen and subtleties of the experimental method. A conclusion is drawn that precise determination of the capture rate is important for refining the standard model.

  11. Biological Effects of Ionizing Radiation

    DOE R&D Accomplishments Database

    Ingram, M.; Mason, W. B.; Whipple, G. H.; Howland, J. W.

    1952-04-07

    This report presents a review of present knowledge and concepts of the biological effects of ionizing radiations. Among the topics discussed are the physical and chemical effects of ionizing radiation on biological systems, morphological and physiological changes observed in biological systems subjected to ionizing radiations, physiological changes in the intact animal, latent changes following exposure of biological systems to ionizing radiations, factors influencing the biological response to ionizing radiation, relative effects of various ionizing radiations, and biological dosimetry.

  12. Radiative pion capture by C12.

    NASA Technical Reports Server (NTRS)

    Lam, W. C.; Gotow, K.; Macdonald, B.; Trower, W. P.; Anderson, D. K.

    1972-01-01

    The energy spectrum of neutrons from radiative pion capture by carbon is investigated. Radiative pion capture is identified by coincidence of a stop signal and a signal from one of six lead-glass gamma detectors when negative pions traverse a beam telescope and are stopped in a carbon target. The energy of the neutrons is measured using the time interval between a stop signal coincident with a gamma-counter signal and a signal from a liquid-oscillator neutron counter. Asymmetry in the neutron-photon angular correlation increases with neutron energy and is accounted for by direct neutron emission.

  13. Dielectric Barrier Discharge Ionization of Perfluorinated Compounds.

    PubMed

    Schütz, Alexander; Brandt, Sebastian; Liedtke, Sascha; Foest, Daniel; Marggraf, Ulrich; Franzke, Joachim

    2015-11-17

    The soft ionization ability based on plasma-jet protonation of molecules initiated by a dielectric barrier discharge ionization source (DBDI) is certainly an interesting application for analytical chemistry. Since the change of an applied sinusoidal voltage may lead to different discharge modes the applied discharge was powered by a square wave generator in order to get a homogeneous plasma. It is known that besides the protonation [M+H](+) of unpolar as well as some polar molecules the homogeneous DBDI can be used to ionize molecules directly [M](+). Here we prove that the DBDI can be applied to exchange fluorine by oxygen of perfluorinated compounds (PFC). PFC are organofluorine compounds with carbon-fluorine and carbon-carbon bonds only but no carbon-hydrogen bonds. While the position of the introduction into the plasma-jet is essential, PFC can be measured in the negative mass spectrometer (MS) mode. PMID:26496892

  14. Massive cluster impact ionization of saccharides

    SciTech Connect

    Dookeran, N.N.; Todd, P.J.

    1995-12-31

    The authors studied the utility of ionizing saccharides by massive cluster impact (MCI), a form of secondary ionization wherein the primary ions are high molecular weight clusters. For a number of compounds and classes, MCI yields copious secondary ions without prior derivitization or the need to find a suitable matrix. In fact, MCI can be used for in situ ionization of some analytes directly from biologic tissue. For the simple sugars and disaccharides that were studied, the authors found that persistent ( e.g. > 2 h) positive and negative secondary ion emission could almost always be detected from pure samples. The authors characterized the secondary anions from a variety of saccharides by tandem mass spectrometry (MS/MS), and found the behavior of the MS/MS spectra to be consistent, sensible, diagnostic and invariant with the dose suffered by the sample.

  15. Non-linear photoelectron effect contributes to the formation of negative matrix ions in UV-MALDI.

    PubMed

    Alonso, E; Zenobi, R

    2016-07-20

    The mechanism of negative ion formation in matrix-assisted laser desorption/ionization (MALDI) is less well understood than that of positive ions: electron capture, disproportionation, and liberation of negatively charged sample molecules or clusters have been proposed to produce the initial anions in MALDI. Here, we propose that the non-linear photoelectric effect can explain the emission of electrons from the metallic target material. Moreover, electrons with sufficient kinetic energy (0-10 eV) could be responsible for the formation of initial negative ions. Gas-phase electron capture by neutral 2,5-dihydroxy benzoic acid (DHB) to yield M(-) is investigated on the basis of a coupled physical and chemical dynamics (CPCD) theory from the literature. A three-layer energy mass balance model is utilized to calculate the surface temperature of the matrix, which is used to determine the translational temperature, the number of desorbed matrix molecules per unit area, and the ion velocity. Calculations of dissociative attachment and autoionization rates of DHB are presented. It was found that both processes contribute significantly to the formation of [M - H](-) and [M - H2](-), although the predicted yield in the fluence range of 5-100 mJ cm(-2) is low, certainly less than that for positive ions M(+). This work represents the first proposal for a comprehensive theoretical description of negative ion formation in UV-MALDI. PMID:27181273

  16. Target capture and target ghosts

    NASA Astrophysics Data System (ADS)

    Auerbach, Steven P.

    1996-05-01

    Optimal detection methods for small targets rely on whitened matched filters, which convolve the measured data with the signal model, and whiten the result with the noise covariance. In real-world implementations of such filters, the noise covariance must be estimated from the data, and the resulting covariance estimate may be corrupted by presence of the target. The resulting loss in SNR is called 'target capture'. Target capture is often thought to be a problem only for bright targets. This presentation shows that target capture also arises for dim targets, leading to an SNR loss which is independent of target strength and depends on the averaging method used to estimate the noise covariance. This loss is due to a 'coherent beat' between the true noise and that portion of the estimated noise covariance due to the target. This beat leads to 'ghost targets', which diminish the target SNR by producing a negative target ghost at the target's position. A quantitative estimate of this effect will be given, and shown to agree with numerical results. The effect of averaging on SNR is also discussed for data scenes with synthetic injected targets, in cases where the noise covariance is estimated using 'no target' data. For these cases, it is shown that the so-called 'optimal' filter, which uses the true noise covariance, is actually worse than a 'sub-optimal' filter which estimates the noise from scene. This apparent contradiction is resolved by showing that the optimal filter is best if the same filter is used for many scenes, but is outperformed by a filter adapted to a specific scene.

  17. Contingent Attentional Capture

    NASA Technical Reports Server (NTRS)

    Remington, Roger; Folk, Charles L.

    1994-01-01

    Four experiments address the degree of top-down selectivity in attention capture by feature singletons through manipulations of the spatial relationship and featural similarity of target and distractor singletons in a modified spatial cuing paradigm. Contrary to previous studies, all four experiments show that when searching for a singleton target, an irrelevant featural singleton captures attention only when defined by the same feature value as the target. Experiments 2, 3, and 4 provide a potential explanation for this empirical discrepancy by showing that irrelevant singletons can produce distraction effects that are independent of shifts of spatial attention. The results further support the notion that attentional capture is contingent on top-down attention control settings but indicates that such settings can be instantiated at the level of feature values.

  18. Spatial Knowledge Capture Library

    Energy Science and Technology Software Center (ESTSC)

    2005-05-16

    The Spatial Knowledge Capture Library is a set of algorithms to capture regularities in shapes and trajectories through space and time. We have applied Spatial Knowledge Capture to model the actions of human experts in spatial domains, such as an AWACS Weapons Director task simulation. The library constructs a model to predict the expert’s response to sets of changing cues, such as the movements and actions of adversaries on a battlefield, The library includes amore » highly configurable feature extraction functionality, which supports rapid experimentation to discover causative factors. We use k-medoid clustering to group similar episodes of behavior, and construct a Markov model of system state transitions induced by agents’ actions.« less

  19. AKM capture device

    NASA Technical Reports Server (NTRS)

    Harwell, William D.

    1987-01-01

    In an effort to recover the Westar and Palapa satellites and the considerable investment each represented, NASA and Hughes undertook the Satellite Retrieval Mission. The mechanism used to capture each of the errant satellites was the AKM (Apogee Kick Motor) Capture Device (ACD), also referred to as the Stinger. The ACD had three interface requirements: interface with the Manned Maneuvering Unit (MMU) for transportation to and stabilization of the spacecrafts; interface with each satellite for retrieval; and finally, interface with the Shuttle's Remote Manipulator System (RMS or robot arm) for satellite transport back to the Orbiter's payload bay. The majority of the design requirements were associated with the capture and release of the satellites. In addition to these unique requirements, the general EVA, RMS grapple, and RMS manipulation requirements applied. These requirements included thermal, glare, snag, RMS runaway and crewman safety considerations.

  20. Coincidence measurements of electron capture and loss in ion-atom collisions

    SciTech Connect

    DuBois, R.D.

    1990-09-01

    Collisions between fast, fully stripped projectiles and atomic targets predominantly result in target electrons being ejected to the continuum. For fast partially stripped projectiles which bring weakly bound electrons into the collision, projectile ionization can also contribute to the observed electron spectra. At lower impact velocities, electron capture by the projectile ion becomes important and higher order processes, often referred to as transfer ionization, can be a significant source of free electrons. In recent years, coincidence techniques have been used to evaluate the relative importance of electron capture and loss in free electron production, to separate the capture and loss contributions from those resulting from target ionization alone, and to provide more detailed information about electron capture and loss mechanisms than is available from total cross section measurements. A brief survey of these experiments will be presented. 23 refs., 9 figs.

  1. US Spacesuit Knowledge Capture

    NASA Technical Reports Server (NTRS)

    Chullen, Cinda; Thomas, Ken; McMann, Joe; Dolan, Kristi; Bitterly, Rose; Lewis, Cathleen

    2011-01-01

    The ability to learn from both the mistakes and successes of the past is vital to assuring success in the future. Due to the close physical interaction between spacesuit systems and human beings as users, spacesuit technology and usage lends itself rather uniquely to the benefits realized from the skillful organization of historical information; its dissemination; the collection and identification of artifacts; and the education of those in the field. The National Aeronautics and Space Administration (NASA), other organizations and individuals have been performing United States (U.S.) Spacesuit Knowledge Capture since the beginning of space exploration. Avenues used to capture the knowledge have included publication of reports; conference presentations; specialized seminars; and classes usually given by veterans in the field. More recently the effort has been more concentrated and formalized whereby a new avenue of spacesuit knowledge capture has been added to the archives in which videotaping occurs engaging both current and retired specialists in the field presenting technical scope specifically for education and preservation of knowledge. With video archiving, all these avenues of learning can now be brought to life with the real experts presenting their wealth of knowledge on screen for future learners to enjoy. Scope and topics of U.S. spacesuit knowledge capture have included lessons learned in spacesuit technology, experience from the Gemini, Apollo, Skylab and Shuttle programs, hardware certification, design, development and other program components, spacesuit evolution and experience, failure analysis and resolution, and aspects of program management. Concurrently, U.S. spacesuit knowledge capture activities have progressed to a level where NASA, the National Air and Space Museum (NASM), Hamilton Sundstrand (HS) and the spacesuit community are now working together to provide a comprehensive closed-looped spacesuit knowledge capture system which includes

  2. "Magic" Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Trimpin, Sarah

    2016-01-01

    The systematic study of the temperature and pressure dependence of matrix-assisted ionization (MAI) led us to the discovery of the seemingly impossible, initially explained by some reviewers as either sleight of hand or the misinterpretation by an overzealous young scientist of results reported many years before and having little utility. The "magic" that we were attempting to report was that with matrix assistance, molecules, at least as large as bovine serum albumin (66 kDa), are lifted into the gas phase as multiply charged ions simply by exposure of the matrix:analyte sample to the vacuum of a mass spectrometer. Applied heat, a laser, or voltages are not necessary to achieve charge states and ion abundances only previously observed with electrospray ionization (ESI). The fundamentals of how solid phase volatile or nonvolatile compounds are converted to gas-phase ions without added energy currently involves speculation providing a great opportunity to rethink mechanistic understanding of ionization processes used in mass spectrometry. Improved understanding of the mechanism(s) of these processes and their connection to ESI and matrix-assisted laser desorption/ionization may provide opportunities to further develop new ionization strategies for traditional and yet unforeseen applications of mass spectrometry. This Critical Insights article covers developments leading to the discovery of a seemingly magic ionization process that is simple to use, fast, sensitive, robust, and can be directly applied to surface characterization using portable or high performance mass spectrometers.

  3. "Magic" Ionization Mass Spectrometry.

    PubMed

    Trimpin, Sarah

    2016-01-01

    The systematic study of the temperature and pressure dependence of matrix-assisted ionization (MAI) led us to the discovery of the seemingly impossible, initially explained by some reviewers as either sleight of hand or the misinterpretation by an overzealous young scientist of results reported many years before and having little utility. The “magic” that we were attempting to report was that with matrix assistance, molecules, at least as large as bovine serum albumin (66 kDa), are lifted into the gas phase as multiply charged ions simply by exposure of the matrix:analyte sample to the vacuum of a mass spectrometer. Applied heat, a laser, or voltages are not necessary to achieve charge states and ion abundances only previously observed with electrospray ionization (ESI). The fundamentals of how solid phase volatile or nonvolatile compounds are converted to gas-phase ions without added energy currently involves speculation providing a great opportunity to rethink mechanistic understanding of ionization processes used in mass spectrometry. Improved understanding of the mechanism(s) of these processes and their connection to ESI and matrix-assisted laser desorption/ionization may provide opportunities to further develop new ionization strategies for traditional and yet unforeseen applications of mass spectrometry. This Critical Insights article covers developments leading to the discovery of a seemingly magic ionization process that is simple to use, fast, sensitive, robust, and can be directly applied to surface characterization using portable or high performance mass spectrometers. PMID:26486514

  4. Alkali metal ionization detector

    DOEpatents

    Bauerle, James E.; Reed, William H.; Berkey, Edgar

    1978-01-01

    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.

  5. Pharmacokinetics screening for multi-components absorbed in the rat plasma after oral administration of traditional Chinese medicine Flos Lonicerae Japonicae-Fructus Forsythiae herb couple by sequential negative and positive ionization ultra-high-performance liquid chromatography/tandem triple quadrupole mass spectrometric detection.

    PubMed

    Zhou, Wei; Tam, Kin Y; Meng, Minxin; Shan, Jinjun; Wang, Shouchuan; Ju, Wenzheng; Cai, Baochang; Di, Liuqing

    2015-01-01

    The current study aims to investigate the pharmacokinetics of multi-components (caffeic acid, quinic acid, genistein, luteolin, quercetin, neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, arctigenin, genistin, luteoloside, astragalin, hyperoside, isoquercitrin, 3,5-dicaffeoylquinic acid, 3,4-dicaffeoylquinic acid, rutin, loganin, pinoresinol-β-d-glucoside, phillyrin, isoforsythoside, forsythoside A and forsythoside B) following oral administration of Flos Lonicerae Japonicae-Fructus Forsythiae herb couple in rats. A rapid and sensitive UPLC-ESI-MS/MS with sequential positive and negative ionization modes was developed to determine the 23 absorbed ingredients using one sample preparation combined with three chromatographic conditions in rat plasma. After mixing with internal standard (IS) (tinidazole and chloramphenicol), samples were pretreated by liquid-liquid extraction (LLE) with n-butyl alcohol/ethyl acetate (1:1, v/v). The separations for pinoresinol-β-d-glucoside, phillyrin, isoforsythoside, forsythoside A and forsythoside B were performed on an ACQUITY UPLC BEH C18 column (100mm×2.1mm, 1.7μm) with acetonitrile/methanol (4:1, v/v)-water as mobile phase. For analyzing quinic acid, an ACQUITY UPLC HSS T3 column (100mm×2.1mm, 1.8μm) was applied with acetonitrile/methanol (4:1, v/v)-0.01% formic acid as mobile phase after dilution up to 25-fold. The same column was applied to the other components with acetonitrile/methanol (4:1, v/v)-0.4% formic acid as mobile phase. The method validation results demonstrated that the proposed method was sensitive, specific and reliable, which was successfully applied to the pharmacokinetic study of the multi-components after oral administration of Flos Lonicerae Japonicae-Fructus Forsythiae herb couple. PMID:25533397

  6. Neutron capture therapies

    SciTech Connect

    Yanch, J.C.; Shefer, R.E.; Klinkowstein, R.E.

    1999-11-02

    In one embodiment there is provided an application of the {sup 10}B(n,{alpha}){sup 7}Li nuclear reaction or other neutron capture reactions for the treatment of rheumatoid arthritis. This application, called Boron Neutron Capture Synovectomy (BNCS), requires substantially altered demands on neutron beam design than for instance treatment of deep seated tumors. Considerations for neutron beam design for the treatment of arthritic joints via BNCS are provided for, and comparisons with the design requirements for Boron Neutron Capture Therapy (BNCT) of tumors are made. In addition, exemplary moderator/reflector assemblies are provided which produce intense, high-quality neutron beams based on (p,n) accelerator-based reactions. In another embodiment there is provided the use of deuteron-based charged particle reactions to be used as sources for epithermal or thermal neutron beams for neutron capture therapies. Many d,n reactions (e.g. using deuterium, tritium or beryllium targets) are very prolific at relatively low deuteron energies.

  7. Neutron capture therapies

    SciTech Connect

    Yanch, Jacquelyn C.; Shefer, Ruth E.; Klinkowstein, Robert E.

    1999-01-01

    In one embodiment there is provided an application of the .sup.10 B(n,.alpha.).sup.7 Li nuclear reaction or other neutron capture reactions for the treatment of rheumatoid arthritis. This application, called Boron Neutron Capture Synovectomy (BNCS), requires substantially altered demands on neutron beam design than for instance treatment of deep seated tumors. Considerations for neutron beam design for the treatment of arthritic joints via BNCS are provided for, and comparisons with the design requirements for Boron Neutron Capture Therapy (BNCT) of tumors are made. In addition, exemplary moderator/reflector assemblies are provided which produce intense, high-quality neutron beams based on (p,n) accelerator-based reactions. In another embodiment there is provided the use of deuteron-based charged particle reactions to be used as sources for epithermal or thermal neutron beams for neutron capture therapies. Many d,n reactions (e.g. using deuterium, tritium or beryllium targets) are very prolific at relatively low deuteron energies.

  8. Attention Capture by Faces

    ERIC Educational Resources Information Center

    Langton, Stephen R. H.; Law, Anna S.; Burton, A. Mike; Schweinberger, Stefan R.

    2008-01-01

    We report three experiments that investigate whether faces are capable of capturing attention when in competition with other non-face objects. In Experiment 1a participants took longer to decide that an array of objects contained a butterfly target when a face appeared as one of the distracting items than when the face did not appear in the array.…

  9. Carbon Smackdown: Carbon Capture

    ScienceCinema

    Jeffrey Long

    2010-09-01

    In this July 9, 2010 Berkeley Lab summer lecture, Lab scientists Jeff Long of the Materials Sciences and Nancy Brown of the Environmental Energy Technologies Division discuss their efforts to fight climate change by capturing carbon from the flue gas of power plants, as well as directly from the air

  10. Capturing the Market

    ERIC Educational Resources Information Center

    Ramaswami, Rama

    2009-01-01

    Digital lecture capture and broadcast solutions have been around for only about 10 years, but are poised for healthy growth. Frost & Sullivan research analysts estimate that the market (which amounts to $25 million currently) will quadruple by 2013. It's still dominated by a few key players, however: Sonic Foundry holds a hefty 40 percent-plus…

  11. Carbon Smackdown: Carbon Capture

    SciTech Connect

    Jeffrey Long

    2010-07-12

    In this July 9, 2010 Berkeley Lab summer lecture, Lab scientists Jeff Long of the Materials Sciences and Nancy Brown of the Environmental Energy Technologies Division discuss their efforts to fight climate change by capturing carbon from the flue gas of power plants, as well as directly from the air

  12. Fuel cell with ionization membrane

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T. (Inventor)

    2007-01-01

    A fuel cell is disclosed comprising an ionization membrane having at least one area through which gas is passed, and which ionizes the gas passing therethrough, and a cathode for receiving the ions generated by the ionization membrane. The ionization membrane may include one or more openings in the membrane with electrodes that are located closer than a mean free path of molecules within the gas to be ionized. Methods of manufacture are also provided.

  13. Surface ionization of terpene hydrocarbons

    SciTech Connect

    Zandberg, E.Y.; Nezdyurov, A.L.; Paleev, V.I.; Ponomarev, D.A.

    1986-09-01

    By means of a surface ionization indicator for traces of materials in the atmosphere it has been established that many natural materials containing terpenes and their derivatives are ionized on the surface of heated molybdenum oxide at atmospheric air pressure. A mass-spectrometer method has been used to explain the mechanism of ionization of individual terpene hydrocarbons and to establish its principles. The ionization of ..cap alpha..-pinene, alloocimene, camphene, and also adamantane on oxidized tungsten under vacuum conditions has been investigated. The ..cap alpha..-pinene and alloocimene are ionized by surface ionization but camphene and adamantane are not ionized under vacuum conditions. The surface ionization mass spectra of ..cap alpha..-pinene and alloocimene are of low line brightness in comparison with electron ionization mass spectra and differ between themselves. The temperature relations for currents of the same compositions of ions during ionization of ..cap alpha..-pinene and alloocimene are also different, which leads to the possibility of surface ionization analysis of mixtures of terpenes being ionized. The ionization coefficients of alloocimene and ..cap alpha..-pinene on oxidized tungsten under temperatures optimum for ionization and the ionization potentials of alloocimene molecules and of radicals (M-H) of both compounds have been evaluated.

  14. Atmospheric Ionization Measurements

    NASA Astrophysics Data System (ADS)

    Slack, Thomas; Mayes, Riley

    2015-04-01

    The measurement of atmospheric ionization is a largely unexplored science that potentially holds the key to better understanding many different geophysical phenomena through this new and valuable source of data. Through the LaACES program, which is funded by NASA through the Louisiana Space Consortium, students at Loyola University New Orleans have pursued the goal of measuring high altitude ionization for nearly three years, and were the first to successfully collect ionization data at altitudes over 30,000 feet using a scientific weather balloon flown from the NASA Columbia Scientific Ballooning Facility in Palestine, TX. In order to measure atmospheric ionization, the science team uses a lightweight and highly customized sensor known as a Gerdien condenser. Among other branches of science the data is already being used for, such as the study of aerosol pollution levels in the atmosphere, the data may also be useful in meteorology and seismology. Ionization data might provide another variable with which to predict weather or seismic activity more accurately and further in advance. Thomas Slack and Riley Mayes have served as project managers for the experiment, and have extensive knowledge of the experiment from the ground up. LaSPACE Louisiana Space Consortium.

  15. Ionizing potential waves and high-voltage breakdown streamers.

    NASA Technical Reports Server (NTRS)

    Albright, N. W.; Tidman, D. A.

    1972-01-01

    The structure of ionizing potential waves driven by a strong electric field in a dense gas is discussed. Negative breakdown waves are found to propagate with a velocity proportional to the electric field normal to the wavefront. This causes a curved ionizing potential wavefront to focus down into a filamentary structure, and may provide the reason why breakdown in dense gases propagates in the form of a narrow leader streamer instead of a broad wavefront.

  16. Laser-induced electron capture mass spectrometry

    PubMed

    Wang; Giese

    2000-02-15

    Two techniques are reported for detection of electrophorederivatized compounds by laser-induced electron capture time-of-flight mass spectrometry (LI-EC-TOF-MS). In both cases, a nitrogen laser is used to induce the electron capture. The analyte is deposited in a matrix consisting of a compound with a low ionization potential such as benzo[ghi]perylene in the first technique, where the electron for electron capture apparently comes from this matrix. In the second technique, the analyte is deposited on a silver surface in the absence of matrix. It seems that "monoenergetic" ions instantly desorb from the target surface in the latter case, since the peak width in the continuous extraction mode essentially matches the pulse width of the laser (4 ns). Ten picomoles of 3-O-(pentafluorobenzyl)-alpha-estradiol were detected at a S/N > or = 50, where the spot size of the laser was approximately 0.25% of the sample spot. It is attractive that simple conditions can enable sensitive detection of electrophores on routine TOF-MS equipment. The technique can be anticipated to broaden the range of analytes in both polarity and size that can be detected by EC-MS relative to the range for GC/EC-MS. PMID:10701262

  17. Monte Carlo beam capture and charge breeding simulation

    SciTech Connect

    Kim, J.S.; Liu, C.; Edgell, D.H.; Pardo, R.

    2006-03-15

    A full six-dimensional (6D) phase space Monte Carlo beam capture charge-breeding simulation code examines the beam capture processes of singly charged ion beams injected to an electron cyclotron resonance (ECR) charge breeder from entry to exit. The code traces injected beam ions in an ECR ion source (ECRIS) plasma including Coulomb collisions, ionization, and charge exchange. The background ECRIS plasma is modeled within the current frame work of the generalized ECR ion source model. A simple sample case of an oxygen background plasma with an injected Ar +1 ion beam produces lower charge breeding efficiencies than experimentally obtained. Possible reasons for discrepancies are discussed.

  18. Muon capture for the front end of a muon collider

    SciTech Connect

    Neuffer, D.; Yoshikawa, C.; /MUONS Inc., Batavia

    2011-03-01

    We discuss the design of the muon capture front end for a {mu}{sup +}-{mu}{sup -} Collider. In the front end, a proton bunch on a target creates secondary pions that drift into a capture transport channel, decaying into muons. A sequence of rf cavities forms the resulting muon beams into strings of bunches of differing energies, aligns the bunches to (nearly) equal central energies, and initiates ionization cooling. The muons are then cooled and accelerated to high energy into a storage ring for high-energy high luminosity collisions. Our initial design is based on the somewhat similar front end of the International Design Study (IDS) neutrino factory.

  19. Advanced Telemetry Data Capturing

    SciTech Connect

    Paschke, G.A.

    2000-05-16

    This project developed a new generation or advanced data capturing process specifically designed for use in future telemetry test systems at the Kansas City Plant (KCP). Although similar data capturing processes are performed both commercially and at other DOE weapon facilities, the equipment used is not specifically designed to perform acceptance testing requirements unique to the KCP. Commercially available equipment, despite very high cost (up to $125,000), is deficient in reliability and long-term maintainability necessary in test systems at this facility. There are no commercial sources for some requirements, specifically Terminal Data Analyzer (TDA) data processing. Although other custom processes have been developed to satisfy these test requirements, these designs have become difficult to maintain and upgrade.

  20. Target activated frame capture

    NASA Astrophysics Data System (ADS)

    Roberts, G. Marlon; Fitzgerald, James; McCormack, Michael; Steadman, Robert

    2008-04-01

    Over the past decade, technological advances have enabled the use of increasingly intelligent systems for battlefield surveillance. These systems are triggered by a combination of external devices including acoustic and seismic sensors. Such products are mainly used to detect vehicles and personnel. These systems often use infra-red imagery to record environmental information, but Textron Defense Systems' Terrain Commander is one of a small number of systems which analyze these images for the presence of targets. The Terrain Commander combines acoustic, infrared, magnetic, seismic, and visible spectrum sensors to detect nearby targets in military scenarios. When targets are detected by these sensors, the cameras are triggered and images are captured in the infrared and visible spectrum. In this paper we discuss a method through which such systems can perform target tracking in order to record and transmit only the most pertinent surveillance images. This saves bandwidth which is crucial because these systems often use communication systems with throughputs below 2400bps. This method is expected to be executable on low-power processors at frame rates exceeding 10HZ. We accomplish this by applying target activated frame capture algorithms to infra-red video data. The target activated frame capture algorithms combine edge detection and motion detection to determine the best frames to be transmitted to the end user. This keeps power consumption and bandwidth requirements low. Finally, the results of the algorithm are analyzed.

  1. Ambient ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Lebedev, A. T.

    2015-07-01

    Ambient ionization mass spectrometry emerged as a new scientific discipline only about ten years ago. A considerable body of information has been reported since that time. Keeping the sensitivity, performance and informativity of classical mass spectrometry methods, the new approach made it possible to eliminate laborious sample preparation procedures and triggered the development of miniaturized instruments to work directly in the field. The review concerns the theoretical foundations and design of ambient ionization methods. Their advantages and drawbacks, as well as prospects for application in chemistry, biology, medicine, environmetal analysis, etc., are discussed. The bibliography includes 194 references.

  2. DNA lesion can facilitate base ionization: vertical ionization energies of aqueous 8-oxoguanine and its nucleoside and nucleotide.

    PubMed

    Palivec, Vladimír; Pluhařová, Eva; Unger, Isaak; Winter, Bernd; Jungwirth, Pavel

    2014-12-01

    8-Oxoguanine is one of the key products of indirect radiation damage to DNA by reactive oxygen species. Here, we describe ionization of this damaged nucleobase and the corresponding nucleoside and nucleotide in aqueous phase, modeled by the nonequilibrium polarizable continuum model, establishing their lowest vertical ionization energies of 6.8-7.0 eV. We thus confirm that 8-oxoguanine has even lower ionization energy than the parental guanine, which is the canonical nucleobase with the lowest ionization energy. Therefore, it can act as a trap for the cationic hole formed by ionizing radiation and thus protect DNA from further radiation damage. We also model using time-dependent density functional theory and measure by liquid jet photoelectron spectroscopy the valence photoelectron spectrum of 8-oxoguanine in water. We show that the calculated higher lying ionization states match well the experiment which, however, is not sensitive enough to capture the electron signal corresponding to the lowest ionization process due to the low solubility of 8-oxoguanine in water. PMID:25390766

  3. Prompt ionization in the CRIT II barium releases. [Critical Ionization Tests

    NASA Technical Reports Server (NTRS)

    Torbert, R. B.; Kletzing, C. A.; Liou, K.; Rau, D.

    1992-01-01

    Observations of electron and ion distributions inside a fast neutral barium jet in the ionosphere show significant fluxes within 4 km of release, presumably related to beam plasma instability processes involved in the Critical Ionization Velocity (CIV) effect. Electron fluxes exceeding 5 x 10 exp 12/sq cm-str-sec-keV were responsible for ionizing both the streaming barium and ambient oxygen. Resulting ion fluxes seem to be consistent with 1-2 percent ionization of the fast barium, as reported by optical observations, although the extended spatial distribution of the optically observed ions is difficult to reconcile with the in situ observations. When the perpendicular velocity of the neutrals falls below critical values, these processes shut off. Although these observations resemble the earlier Porcupine experimental results (Haerendel, 1982), theoretical understanding of the differences between these data and that of earlier negative experiments is still lacking.

  4. Alkali ionization detector

    DOEpatents

    Hrizo, John; Bauerle, James E.; Witkowski, Robert E.

    1982-01-01

    A calibration filament containing a sodium-bearing compound is included in combination with the sensing filament and ion collector plate of a sodium ionization detector to permit periodic generation of sodium atoms for the in-situ calibration of the detector.

  5. WARPED IONIZED HYDROGEN IN THE GALAXY

    SciTech Connect

    Cersosimo, J. C.; Figueroa, N. Santiago; Velez, S. Figueroa; Soto, C. Lozada; Mader, S.; Azcarate, D.

    2009-07-01

    We report observations of the H166{alpha} ({nu} = 1424.734 MHz) radio recombination line (RRL) emission from the Galactic plane in the longitude range l = 267 deg. - 302 deg. and latitude range b = -3.{sup 0}0 to +1.{sup 0}5. The line emission observed describes the Carina arm in the Galactic azimuth range from {theta} = 260 deg. to 190 deg. The structure is located at negative latitudes with respect to the formal Galactic plane. The observations are combined with RRL data from the first Galactic quadrant. Both quadrants show the signature of the warp for the ionized gas, but an asymmetry of the distribution is noted. In the fourth quadrant, the gas is located between Galactic radii R {approx} 7 and 10 kpc, and the amplitude of the warp is seen from the midplane to z {approx} -150 pc. In the first quadrant, the gas is found between R {approx} 8 and 13-16 kpc, and flares to z {approx} +350 pc. We confirm the warp of the ionized gas near the solar circle. The distribution of the ionized gas is compared with the maximum intensity H I emission (0.30 < n{sub HI} < 0.45 cm{sup -3}) at intervals of the Galactic ring. The ionized material is correlated with the H I maximum intensity in both quadrants, and both components show the same tilted behavior with respect to the mid-Galactic plane.

  6. Transfer ionization in collisions with a fast highly charged ion.

    PubMed

    Voitkiv, A B

    2013-07-26

    Transfer ionization in fast collisions between a bare ion and an atom, in which one of the atomic electrons is captured by the ion whereas another one is emitted, crucially depends on dynamic electron-electron correlations. We show that in collisions with a highly charged ion a strong field of the ion has a very profound effect on the correlated channels of transfer ionization. In particular, this field weakens (strongly suppresses) electron emission into the direction opposite (perpendicular) to the motion of the ion. Instead, electron emission is redirected into those parts of the momentum space which are very weakly populated in fast collisions with low charged ions. PMID:23931364

  7. Ionization induced damage in crystalline silicon

    NASA Technical Reports Server (NTRS)

    Meulenberg, A., Jr.

    1977-01-01

    Close examination of the interaction of the energetic knock-on atoms with the local lattice environment reveals a damage mechanism which does satisfy the experimental data on proton irradiation of silicon. A proton-atom interaction with high energy transfer is considered where the proton path is delineated by a trail of ionization, and the silicon ion path is characterized by much heavier ionization terminating in a dense displacement cluster. At collision, many of the silicon electrons are stripped off, and the resulting energetic ion subsequently loses energy rapidly by Coulomb interaction with bound electrons. The rate of energy loss depends on the charge state and velocity of the knock-on ion. For ion energies in excess of 1 MeV, the intensity of ionization is sufficient to permit lattice atoms, stripped of their binding electrons, to reorient randomly before having an opportunity to recombine with electrons and re-establish the lattice. The path of a knock-on ion thus becomes a thin cylinder of amorphous material within the crystal. Amorphous silicon has a Fermi level closer to mid-band than does single crystal silicon, and a strong field therefore, results around this damaged region. The field produces a large depletion region, representing a very large capture cross section for minority carriers.

  8. Capturing nature's diversity.

    PubMed

    Pascolutti, Mauro; Campitelli, Marc; Nguyen, Bao; Pham, Ngoc; Gorse, Alain-Dominique; Quinn, Ronald J

    2015-01-01

    Natural products are universally recognized to contribute valuable chemical diversity to the design of molecular screening libraries. The analysis undertaken in this work, provides a foundation for the generation of fragment screening libraries that capture the diverse range of molecular recognition building blocks embedded within natural products. Physicochemical properties were used to select fragment-sized natural products from a database of known natural products (Dictionary of Natural Products). PCA analysis was used to illustrate the positioning of the fragment subset within the property space of the non-fragment sized natural products in the dataset. Structural diversity was analysed by three distinct methods: atom function analysis, using pharmacophore fingerprints, atom type analysis, using radial fingerprints, and scaffold analysis. Small pharmacophore triplets, representing the range of chemical features present in natural products that are capable of engaging in molecular interactions with small, contiguous areas of protein binding surfaces, were analysed. We demonstrate that fragment-sized natural products capture more than half of the small pharmacophore triplet diversity observed in non fragment-sized natural product datasets. Atom type analysis using radial fingerprints was represented by a self-organizing map. We examined the structural diversity of non-flat fragment-sized natural product scaffolds, rich in sp3 configured centres. From these results we demonstrate that 2-ring fragment-sized natural products effectively balance the opposing characteristics of minimal complexity and broad structural diversity when compared to the larger, more complex fragment-like natural products. These naturally-derived fragments could be used as the starting point for the generation of a highly diverse library with the scope for further medicinal chemistry elaboration due to their minimal structural complexity. This study highlights the possibility to capture a

  9. Capturing Nature's Diversity

    PubMed Central

    Pascolutti, Mauro; Campitelli, Marc; Nguyen, Bao; Pham, Ngoc; Gorse, Alain-Dominique; Quinn, Ronald J.

    2015-01-01

    Natural products are universally recognized to contribute valuable chemical diversity to the design of molecular screening libraries. The analysis undertaken in this work, provides a foundation for the generation of fragment screening libraries that capture the diverse range of molecular recognition building blocks embedded within natural products. Physicochemical properties were used to select fragment-sized natural products from a database of known natural products (Dictionary of Natural Products). PCA analysis was used to illustrate the positioning of the fragment subset within the property space of the non-fragment sized natural products in the dataset. Structural diversity was analysed by three distinct methods: atom function analysis, using pharmacophore fingerprints, atom type analysis, using radial fingerprints, and scaffold analysis. Small pharmacophore triplets, representing the range of chemical features present in natural products that are capable of engaging in molecular interactions with small, contiguous areas of protein binding surfaces, were analysed. We demonstrate that fragment-sized natural products capture more than half of the small pharmacophore triplet diversity observed in non fragment-sized natural product datasets. Atom type analysis using radial fingerprints was represented by a self-organizing map. We examined the structural diversity of non-flat fragment-sized natural product scaffolds, rich in sp3 configured centres. From these results we demonstrate that 2-ring fragment-sized natural products effectively balance the opposing characteristics of minimal complexity and broad structural diversity when compared to the larger, more complex fragment-like natural products. These naturally-derived fragments could be used as the starting point for the generation of a highly diverse library with the scope for further medicinal chemistry elaboration due to their minimal structural complexity. This study highlights the possibility to capture a

  10. Modulated voltage metastable ionization detector

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  11. Capturing the Daylight Dividend

    SciTech Connect

    Peter Boyce; Claudia Hunter; Owen Howlett

    2006-04-30

    Capturing the Daylight Dividend conducted activities to build market demand for daylight as a means of improving indoor environmental quality, overcoming technological barriers to effective daylighting, and informing and assisting state and regional market transformation and resource acquisition program implementation efforts. The program clarified the benefits of daylight by examining whole building systems energy interactions between windows, lighting, heating, and air conditioning in daylit buildings, and daylighting's effect on the human circadian system and productivity. The project undertook work to advance photosensors, dimming systems, and ballasts, and provided technical training in specifying and operating daylighting controls in buildings. Future daylighting work is recommended in metric development, technology development, testing, training, education, and outreach.

  12. Capturing Darwin's dream.

    PubMed

    Glenn, Travis C; Faircloth, Brant C

    2016-09-01

    Evolutionary biologists from Darwin forward have dreamed of having data that would elucidate our understanding of evolutionary history and the diversity of life. Sequence capture is a relatively old DNA technology, but its use is growing rapidly due to advances in (i) massively parallel DNA sequencing approaches and instruments, (ii) massively parallel bait construction, (iii) methods to identify target regions and (iv) sample preparation. We give a little historical context to these developments, summarize some of the important advances reported in this special issue and point to further advances that can be made to help fulfill Darwin's dream. PMID:27454358

  13. Hydraulic effects in a radiative atmosphere with ionization

    NASA Astrophysics Data System (ADS)

    Bhat, P.; Brandenburg, A.

    2016-03-01

    Context. In his 1978 paper, Eugene Parker postulated the need for hydraulic downward motion to explain magnetic flux concentrations at the solar surface. A similar process has also recently been seen in simplified (e.g., isothermal) models of flux concentrations from the negative effective magnetic pressure instability (NEMPI). Aims: We study the effects of partial ionization near the radiative surface on the formation of these magnetic flux concentrations. Methods: We first obtain one-dimensional (1D) equilibrium solutions using either a Kramers-like opacity or the H- opacity. The resulting atmospheres are then used as initial conditions in two-dimensional (2D) models where flows are driven by an imposed gradient force that resembles a localized negative pressure in the form of a blob. To isolate the effects of partial ionization and radiation, we ignore turbulence and convection. Results: Because of partial ionization, an unstable stratification always forms near the surface. We show that the extrema in the specific entropy profiles correspond to the extrema in the degree of ionization. In the 2D models without partial ionization, strong flux concentrations form just above the height where the blob is placed. Interestingly, in models with partial ionization, such flux concentrations always form at the surface well above the blob. This is due to the corresponding negative gradient in specific entropy. Owing to the absence of turbulence, the downflows reach transonic speeds. Conclusions: We demonstrate that, together with density stratification, the imposed source of negative pressure drives the formation of flux concentrations. We find that the inclusion of partial ionization affects the entropy profile dramatically, causing strong flux concentrations to form closer to the surface. We speculate that turbulence effects are needed to limit the strength of flux concentrations and homogenize the specific entropy to a stratification that is close to marginal.

  14. Holographic capture of femtosecond pulse propagation

    SciTech Connect

    Centurion, Martin; Pu Ye; Psaltis, Demetri

    2006-09-15

    We have implemented a holographic system to study the propagation of femtosecond laser pulses with high temporal (150 fs) and spatial resolutions (4 {mu}m). The phase information in the holograms allows us to reconstruct both positive and negative index changes due to the Kerr nonlinearity (positive) and plasma formation (negative), and to reconstruct three-dimensional structure. Dramatic differences were observed in the interaction of focused femtosecond pulses with air, water, and carbon disulfide. The air becomes ionized in the focal region, while in water long plasma filaments appear before the light reaches a tight focus. In contrast, in carbon disulfide the optical beam breaks up into multiple filaments but no plasma is measured. We explain these different propagation regimes in terms of the different nonlinear material properties.

  15. Power systems: Carbon negative at the regional level

    NASA Astrophysics Data System (ADS)

    Bauer, Nico

    2015-03-01

    Modelling of the power system on the west coast of North America shows that including bioenergy with carbon capture and sequestration technologies could enable the region to be carbon negative by 2050.

  16. Ultrahigh vacuum measuring ionization gauge

    NASA Technical Reports Server (NTRS)

    Brock, F. J. (Inventor)

    1968-01-01

    The ionization gage described consists of separate ionization and collector regions connected at an exit area with a modulator electrode. In addition to the standard modulation function, the modulator in this location yields a suprising increase in collector current, apparently due to improved focussing and extraction of ions from the ionization region.

  17. Perceptual objects capture attention.

    PubMed

    Yeshurun, Yaffa; Kimchi, Ruth; Sha'shoua, Guy; Carmel, Tomer

    2009-06-01

    A recent study has demonstrated that the mere organization of some elements in the visual field into an object attracts attention automatically [Kimchi, R., Yeshurun, Y., & Cohen-Savransky, A. (2007). Automatic, stimulus-driven attentional capture by objecthood. Psychonomic Bulletin & Review, 14(1), 166-172]. We tested whether similar results will emerge when the target is not a part of the object and with simplified task demands. A matrix of 16 black L elements in various orientations preceded the presentation of a Vernier target. The target was either added to the matrix (Experiment 1), or appeared after its offset (Experiment 2). On some trials four elements formed a square-like object, and on some of these trials the target appeared in the center of the object. No featural uniqueness or abrupt onset was associated with the object and it did not predict the target location or the direction of the target's horizontal offset. Performance was better when the target appeared in the center of the object than in a different location than the object, even when the target appeared after the matrix offset. These findings support the hypothesis that a perceptual object captures attention (Kimchi et al., 2007), and demonstrate that this automatic deployment of attention to the object is robust and involves a spatial component. PMID:18299141

  18. Alfvén ionization in an MHD-gas interactions code

    NASA Astrophysics Data System (ADS)

    Wilson, A. D.; Diver, D. A.

    2016-07-01

    A numerical model of partially ionized plasmas is developed in order to capture their evolving ionization fractions as a result of Alfvén ionization (AI). The mechanism of, and the parameter regime necessary for, AI is discussed and an expression for the AI rate based on fluid parameters, from a gas-MHD model, is derived. This AI term is added to an existing MHD-gas interactions' code, and the result is a linear, 2D, two-fluid model that includes momentum transfer between charged and neutral species as well as an ionization rate that depends on the velocity fields of both fluids. The dynamics of waves propagating through such a partially ionized plasma are investigated, and it is found that AI has a significant influence on the fluid dynamics as well as both the local and global ionization fraction.

  19. Some options for the muon collider capture and decay solenoids

    NASA Astrophysics Data System (ADS)

    Green, Michael A.

    1996-05-01

    This report discusses some of the problems associated with using solenoid magnets to capture the secondary particles that are created when an intense beam of 8 to 10 GeV protons interacts with the target at the center of the capture region. Hybrid capture solenoids with inductions of 28 T and a 22 T are described. The first 14 to 15 T of the solenoid induction will be generated by a superconducting magnet. The remainder of the field will be generated by a Bitter type of water cooled solenoid. The capture solenoids include a transition section from the high field solenoid to a 7 T decay channel where pions and kaons that come off of the target decay into muons. A short 7 T solenoidal decay channel between the capture solenoid system and the phase rotation system is described. A concept for separation of negative and positive pions and kaons is briefly discussed.

  20. Negative ion source with hollow cathode discharge plasma

    DOEpatents

    Hershcovitch, Ady; Prelec, Krsto

    1983-01-01

    A negative ion source of the type where negative ions are formed by bombarding a low-work-function surface with positive ions and neutral particles from a plasma, wherein a highly ionized plasma is injected into an anode space containing the low-work-function surface. The plasma is formed by hollow cathode discharge and injected into the anode space along the magnetic field lines. Preferably, the negative ion source is of the magnetron type.

  1. Negative ion source with hollow cathode discharge plasma

    DOEpatents

    Hershcovitch, A.; Prelec, K.

    1980-12-12

    A negative ion source of the type where negative ions are formed by bombarding a low-work-function surface with positive ions and neutral particles from a plasma, wherein a highly ionized plasma is injected into an anode space containing the low-work-function surface is described. The plasma is formed by hollow cathode discharge and injected into the anode space along the magnetic field lines. Preferably, the negative ion source is of the magnetron type.

  2. Meningitis - gram-negative

    MedlinePlus

    Gram-negative meningitis ... Acute bacterial meningitis can be caused by Gram-negative bacteria. Meningococcal and H. influenzae meningitis are caused by Gram-negative bacteria and are covered in detail in other articles. This article ...

  3. Layered solid sorbents for carbon dioxide capture

    SciTech Connect

    Li, Bingyun; Jiang, Bingbing; Gray, McMahan L; Fauth, Daniel J; Pennline, Henry W; Richards, George A

    2014-11-18

    A solid sorbent for the capture and the transport of carbon dioxide gas is provided having at least one first layer of a positively charged material that is polyethylenimine or poly(allylamine hydrochloride), that captures at least a portion of the gas, and at least one second layer of a negatively charged material that is polystyrenesulfonate or poly(acryclic acid), that transports the gas, wherein the second layer of material is in juxtaposition to, attached to, or crosslinked with the first layer for forming at least one bilayer, and a solid substrate support having a porous surface, wherein one or more of the bilayers is/are deposited on the surface of and/or within the solid substrate. A method of preparing and using the solid sorbent is provided.

  4. Electrospray Ionization Mass Spectrometry

    SciTech Connect

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

    2014-06-13

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

  5. Negative thermal ion mass spectrometry of osmium, rhenium, and iridium

    NASA Technical Reports Server (NTRS)

    Creaser, R. A.; Papanastassiou, D. A.; Wasserburg, G. J.

    1991-01-01

    This paper describes a technique for obtaining, in a conventional surface ionization mass spectrometer, intense ion beams of negatively charged oxides of Os, Re, and Ir by thermal ionization. It is shown that the principal ion species of these ions are OsO3(-), ReO4(-), and IrO2(-), respectively. For Re-187/Os-187 studies, this technique offers the advantage of isotopic analyses without prior chemical separation of Re from Os.

  6. Transmission geometry laser desorption atmospheric pressure photochemical ionization mass spectrometry for analysis of complex organic mixtures.

    PubMed

    Nyadong, Leonard; Mapolelo, Mmilili M; Hendrickson, Christopher L; Rodgers, Ryan P; Marshall, Alan G

    2014-11-18

    We present laser desorption atmospheric pressure photochemical ionization mass spectrometry (LD/APPCI MS) for rapid throughput analysis of complex organic mixtures, without the need for matrix, electric discharge, secondary electrospray, or solvents/vaporizers. Analytes dried on a microscope slide are vaporized in transmission geometry by a laser beam aligned with the atmospheric pressure inlet of the mass spectrometer. The laser beam initiates a cascade of reactions in the region between the glass slide and MS inlet, leading to generation of reagent ions for chemical ionization of vaporized analyte. Positive analyte ions are generated predominantly by proton transfer, charge exchange, and hydride abstraction, whereas negative ions are generated by electron capture or proton transfer reactions, enabling simultaneous analysis of saturated, unsaturated, and heteroatom-containing hydrocarbons. The absence of matrix interference renders LD/APPCI MS particularly useful for analysis of small molecules (<2000 Da) such as those present in petroleum crude oil and petroleum deposits. [M + H](+) and M(+•) dominate the positive-ion mass spectra for olefins and polyaromatic hydrocarbons, whereas saturated hydrocarbons are observed mainly as [M - H](+) and/or M(+•). Heteroatom-containing hydrocarbons are observed predominantly as [M + H](+). [M - H](-) and M(-•) are the dominant negative ions observed for analytes of lower gas-phase basicity or higher electron affinity than O2. The source was coupled with a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer (FTICR MS) to resolve and identify thousands of peaks from Athabasca bitumen heavy vacuum gas oil distillates (400-425 and 500-538 °C), enabling simultaneous characterization of their polar and nonpolar composition. We also applied LD/APPCI FTICR MS for rapid analysis of sodium and calcium naphthenate deposits with little to no sample pretreatment to provide mass spectral fingerprints that enable

  7. Robust automated knowledge capture.

    SciTech Connect

    Stevens-Adams, Susan Marie; Abbott, Robert G.; Forsythe, James Chris; Trumbo, Michael Christopher Stefan; Haass, Michael Joseph; Hendrickson, Stacey M. Langfitt

    2011-10-01

    This report summarizes research conducted through the Sandia National Laboratories Robust Automated Knowledge Capture Laboratory Directed Research and Development project. The objective of this project was to advance scientific understanding of the influence of individual cognitive attributes on decision making. The project has developed a quantitative model known as RumRunner that has proven effective in predicting the propensity of an individual to shift strategies on the basis of task and experience related parameters. Three separate studies are described which have validated the basic RumRunner model. This work provides a basis for better understanding human decision making in high consequent national security applications, and in particular, the individual characteristics that underlie adaptive thinking.

  8. Capture-ejector satellites

    NASA Technical Reports Server (NTRS)

    Macconochie, I. O.; Eldred, C. H.; Martin, J. A.

    1983-01-01

    A satellite in the form of a large rotating rim which can be used to boost spacecraft from low-Earth orbit to higher orbits is described. The rim rotates in the plane of its orbit such that the lower portion of the rim is traveling at suborbital velocity, while the upper portion is travelling at greater than orbital velocity. Ascending spacecraft or payloads arrive at the lowest portion of the rim at suborbital velocities, where the payloads are released on a trajectory for higher orbits; descending payloads employ the reverse procedure. Electric thrusters placed on the rim maintain rim rotational speed and altitude. From the standpoint of currently known materials, the capture-ejector concept may be useful for relatively small velocity increments.

  9. Passive Ball Capture Joint

    NASA Technical Reports Server (NTRS)

    Cloyd, Richard A. (Inventor); Bryan, Thomas C. (Inventor)

    2003-01-01

    A passive ball capture joint has a sleeve with a plurality of bores distributed about a circumference thereof and formed therethrough at an acute angle relative to the sleeve's longitudinal axis. A spring-loaded retainer is slidingly fitted in each bore and is biased such that, if allowed, will extend at least partially into the sleeve to retain a ball therein. A ring, rotatably mounted about the bores, has an interior wall defining a plurality of shaped races that bear against the spring-loaded retainers. A mechanized rotational force producer is coupled to the ring. The ring can be rotated from a first position (that presses the retainers into the sleeve to lock the ball in place) to a second position (that allows the retainers to springback out of the sleeve to release the ball).

  10. Capturing the uncultivated majority

    SciTech Connect

    Green, Brian D.; Keller, Martin

    2007-04-02

    The metagenomic analysis of environmental microbialcommunities continues to be a rapidly developing area of study. DNAisolation, the first step in capturing the uncultivated majority, hasseen many advances in recent years. Protocols have been developed todistinguish DNA from live versus dead cells and to separate extracellularfrom intracellular DNA. Looking to increase our understanding of the rolethat members of a microbial community play in ecological processes,several techniques have been developed that are enabling greater indepthanalysis of environmental metagenomes. These include the development ofenvironmental gene tags and the serial analysis of 16S rRNA gene sequencetags. In addition, new screening methods have been designed to select forspecific functional genes within metagenomic libraries. Finally, newcultivation methods continue to be developed to improve our ability tocapture a greater diversity of microorganisms within theenvironment.

  11. Particle capture device

    DOEpatents

    Jayne, John T.; Worsnop, Douglas R.

    2016-02-23

    In example embodiments, particle collection efficiency in aerosol analyzers and other particle measuring instruments is improved by a particle capture device that employs multiple collisions to decrease momentum of particles until the particles are collected (e.g., vaporized or come to rest). The particle collection device includes an aperture through which a focused particle beam enters. A collection enclosure is coupled to the aperture and has one or more internal surfaces against which particles of the focused beam collide. One or more features are employed in the collection enclosure to promote particles to collide multiple times within the enclosure, and thereby be vaporized or come to rest, rather than escape through the aperture.

  12. Fragment capture device

    DOEpatents

    Payne, Lloyd R.; Cole, David L.

    2010-03-30

    A fragment capture device for use in explosive containment. The device comprises an assembly of at least two rows of bars positioned to eliminate line-of-sight trajectories between the generation point of fragments and a surrounding containment vessel or asset. The device comprises an array of at least two rows of bars, wherein each row is staggered with respect to the adjacent row, and wherein a lateral dimension of each bar and a relative position of each bar in combination provides blockage of a straight-line passage of a solid fragment through the adjacent rows of bars, wherein a generation point of the solid fragment is located within a cavity at least partially enclosed by the array of bars.

  13. ECC study in positron impact ionization in molecular hydrogen

    NASA Astrophysics Data System (ADS)

    Campeanu, R. I.; Zohouri Haghian, N.

    2012-12-01

    The electron capture to the continuum phenomenon in positron impact ionization of molecular hydrogen is studied with the distorted wave Born approximation. Our theoretical model produces results which are in better agreement with the experiment than the more elaborate models of [J. Fiol, V.D. Rodriguez, R.O. Barrachina, J. Phys. B: At. Mol. Opt. Phys. 34, 933 (2001)] and [A. Benedek, R.I. Campeanu, J. Phys. B: At. Mol. Opt. Phys. 40, 1589 (2007)] previously employed in this study.

  14. Anion formation in sputter ion sources by neutral resonant ionization.

    PubMed

    Vogel, J S

    2016-02-01

    Focused Cs(+) beams in sputter ion sources create mm-diameter pits supporting small plasmas that control anionization efficiencies. Sputtering produces overwhelmingly neutral products that the plasma can ionize as in a charge-change vapor. Electron capture between neutral atoms rises as the inverse square of the difference between the ionization potential of the Cs state and the electron affinity of the sputtered atom, allowing resonant ionization at very low energies. A plasma collision-radiation model followed electronic excitation up to Cs(7d). High modeled Cs(7d) in a 0.5 mm recess explains the 80 μA/mm(2) C(-) current density compared to the 20 μA/mm(2) from a 1 mm recess. PMID:26931912

  15. Anion formation in sputter ion sources by neutral resonant ionization

    NASA Astrophysics Data System (ADS)

    Vogel, J. S.

    2016-02-01

    Focused Cs+ beams in sputter ion sources create mm-diameter pits supporting small plasmas that control anionization efficiencies. Sputtering produces overwhelmingly neutral products that the plasma can ionize as in a charge-change vapor. Electron capture between neutral atoms rises as the inverse square of the difference between the ionization potential of the Cs state and the electron affinity of the sputtered atom, allowing resonant ionization at very low energies. A plasma collision-radiation model followed electronic excitation up to Cs(7d). High modeled Cs(7d) in a 0.5 mm recess explains the 80 μA/mm2 C- current density compared to the 20 μA/mm2 from a 1 mm recess.

  16. Materials design for electrocatalytic carbon capture

    NASA Astrophysics Data System (ADS)

    Tan, Xin; Tahini, Hassan A.; Smith, Sean C.

    2016-05-01

    We discuss our philosophy for implementation of the Materials Genome Initiative through an integrated materials design strategy, exemplified here in the context of electrocatalytic capture and separation of CO2 gas. We identify for a group of 1:1 X-N graphene analogue materials that electro-responsive switchable CO2 binding behavior correlates with a change in the preferred binding site from N to the adjacent X atom as negative charge is introduced into the system. A reconsideration of conductive N-doped graphene yields the discovery that the N-dopant is able to induce electrocatalytic binding of multiple CO2 molecules at the adjacent carbon sites.

  17. M-shell ionization of atoms by C, N, and O ions

    NASA Astrophysics Data System (ADS)

    Pajek, M.; Braziewicz, J.; Semaniak, J.; CzyŻewski, T.; Glowacka, L.; Jaskól, M.; Haller, M.; Karschnick, R.; Kretschmer, W.; Kobzev, A. P.; Trautmann, D.; Lapicki, G.

    1997-02-01

    M-shell ionization in selected heavy atoms (Au, Bi, Th and U) by energetic Cq+, Nq+ and Oq+, ions of different charge states (q=1-6) has been studied in the energy range 0.1-2 MeV/amu. The measurements were performed using target thicknesses allowing ion charge equilibration in the target. Derived equilibrium M-shell ionization cross sections are compared with the theoretical predictions based on the semiclassical (SCA) and the PWBA approximations for direct ionization and the OBK approximation for the electron capture, as well as the ECPSSR theory including the corrections for higher-order effects. Substantial contribution of the electron capture caused by the ion charge equilibration is observed for high energies. The influence of the multiple ionization in M-, N- and O-shells on measured cross sections is discussed.

  18. Desorption electrospray ionization mass spectrometry of intact bacteria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Desorption electrospray ionization (DESI) mass spectrometry (MS) was used to differentiate 7 bacterial species based on their measured DESI-mass spectral profile. Both Gram positive and Gram negative bacteria were tested and included Escherichia coli, Staphyloccocus aureus, Enterococcus sp., Bordete...

  19. Intact capture of hypervelocity projectiles.

    PubMed

    Tsou, P

    1990-01-01

    The ability to capture projectiles intact at hypervelocities opens new applications in science and technology that would either not be possible or would be very costly by other means. This capability has been demonstrated in the laboratory for aluminum projectiles of 1.6 mm diameter, captured at 6 km/s, in one unmelted piece, and retaining up to 95% of the original mass. Furthermore, capture was accomplished passively using microcellular underdense polymer foam. Another advantage of capturing projectiles in an underdense medium is the ability of such a medium to preserve a record of the projectile's original velocity components of speed and direction. A survey of these experimental results is described in terms of a dozen parameters which characterize the amount of capture and the effect on the projectile due to different capture media. PMID:11538362

  20. Lunar Sulfur Capture System

    NASA Technical Reports Server (NTRS)

    Berggren, Mark; Zubrin, Robert; Bostwick-White, Emily

    2013-01-01

    The Lunar Sulfur Capture System (LSCS) protects in situ resource utilization (ISRU) hardware from corrosion, and reduces contaminant levels in water condensed for electrolysis. The LSCS uses a lunar soil sorbent to trap over 98 percent of sulfur gases and about two-thirds of halide gases evolved during hydrogen reduction of lunar soils. LSCS soil sorbent is based on lunar minerals containing iron and calcium compounds that trap sulfur and halide gas contaminants in a fixed-bed reactor held at temperatures between 250 and 400 C, allowing moisture produced during reduction to pass through in vapor phase. Small amounts of Earth-based polishing sorbents consisting of zinc oxide and sodium aluminate are used to reduce contaminant concentrations to one ppm or less. The preferred LSCS configuration employs lunar soil beneficiation to boost concentrations of reactive sorbent minerals. Lunar soils contain sulfur in concentrations of about 0.1 percent, and halogen compounds including chlorine and fluorine in concentrations of about 0.01 percent. These contaminants are released as gases such as H2S, COS, CS2,HCl, and HF during thermal ISRU processing with hydrogen or other reducing gases. Removal of contaminant gases is required during ISRU processing to prevent hardware corrosion, electrolyzer damage, and catalyst poisoning. The use of Earth-supplied, single-use consumables to entirely remove contaminants at the levels existing in lunar soils would make many ISRU processes unattractive due to the large mass of consumables relative to the mass of oxygen produced. The LSCS concept of using a primary sorbent prepared from lunar soil was identified as a method by which the majority of contaminants could be removed from process gas streams, thereby substantially reducing the required mass of Earth-supplied consumables. The LSCS takes advantage of minerals containing iron and calcium compounds that are present in lunar soil to trap sulfur and halide gases in a fixedbed reactor

  1. The physics of intact capture

    NASA Technical Reports Server (NTRS)

    Tsou, Peter; Griffiths, D. J.; Albee, A. L.

    1994-01-01

    The ability to capture projectiles intact at hypervelocities in underdense media open a new area of study in physics. Underdense material behaves markedly different than solid, liquid, or gas upon hypervelocity impact. This new phenomenon enables applications in science that would either not be possible or would be very costly by other means. This phenomenon has been fully demonstrated in the laboratory and validated in space. Even more interesting is the fact that this hypervelocity intact capture was accomplished passively. A better understanding of the physics of intact capture will lead to improvements in intact capture. A collection of physical observations of this phenomenon is presented here.

  2. Resource capture by single leaves

    SciTech Connect

    Long, S.P.

    1992-05-01

    Leaves show a variety of strategies for maximizing CO{sub 2} and light capture. These are more meaningfully explained if they are considered in the context of maximizing capture relative to the utilization of water, nutrients and carbohydrates reserves. There is considerable variation between crops in their efficiency of CO{sub 2} and light capture at the leaf level. Understanding of these mechanisms indicate some ways in which efficiency of resource capture could be level cannot be meaningfully considered without simultaneous understanding of implications at the canopy level. 36 refs., 5 figs., 1 tab.

  3. Inland capture fisheries

    PubMed Central

    Welcomme, Robin L.; Cowx, Ian G.; Coates, David; Béné, Christophe; Funge-Smith, Simon; Halls, Ashley; Lorenzen, Kai

    2010-01-01

    The reported annual yield from inland capture fisheries in 2008 was over 10 million tonnes, although real catches are probably considerably higher than this. Inland fisheries are extremely complex, and in many cases poorly understood. The numerous water bodies and small rivers are inhabited by a wide range of species and several types of fisher community with diversified livelihood strategies for whom inland fisheries are extremely important. Many drivers affect the fisheries, including internal fisheries management practices. There are also many drivers from outside the fishery that influence the state and functioning of the environment as well as the social and economic framework within which the fishery is pursued. The drivers affecting the various types of inland water, rivers, lakes, reservoirs and wetlands may differ, particularly with regard to ecosystem function. Many of these depend on land-use practices and demand for water which conflict with the sustainability of the fishery. Climate change is also exacerbating many of these factors. The future of inland fisheries varies between continents. In Asia and Africa the resources are very intensely exploited and there is probably little room for expansion; it is here that resources are most at risk. Inland fisheries are less heavily exploited in South and Central America, and in the North and South temperate zones inland fisheries are mostly oriented to recreation rather than food production. PMID:20713391

  4. Captured by Aliens

    NASA Astrophysics Data System (ADS)

    Achenbach, Joel

    2000-03-01

    Captured by Aliens is a long and twisted voyage from science to the supernatural and back again. I hung out in Roswell, N.M., spent time with the Mars Society, met a guy who was figuring out the best way to build a spaceship to go to Alpha Centauri. I visited the set of the X-Files and talked to Mulder and Scully. One day over breakfast I was told by NASA administrator Dan Goldin, We live in a fog, man! He wants the big answers to the big questions. I spent a night in the base of a huge radio telescope in the boondocks of West Virginia, awaiting the signal from the aliens. I was hypnotized in a hotel room by someone who suspected that I'd been abducted by aliens and that this had triggered my interest in the topic. In the last months of his life, I talked to Carl Sagan, who believed that the galaxy riots with intelligent civilizations. He's my hero, for his steadfast adherence to the scientific method. What I found in all this is that the big question that needs immediate attention is not what's out THERE, but what's going on HERE, on Earth, and why we think the way we do, and how we came to be here in the first place.

  5. Capture-recapture methodology

    USGS Publications Warehouse

    Gould, William R.; Kendall, William L.

    2013-01-01

    Capture-recapture methods were initially developed to estimate human population abundance, but since that time have seen widespread use for fish and wildlife populations to estimate and model various parameters of population, metapopulation, and disease dynamics. Repeated sampling of marked animals provides information for estimating abundance and tracking the fate of individuals in the face of imperfect detection. Mark types have evolved from clipping or tagging to use of noninvasive methods such as photography of natural markings and DNA collection from feces. Survival estimation has been emphasized more recently as have transition probabilities between life history states and/or geographical locations, even where some states are unobservable or uncertain. Sophisticated software has been developed to handle highly parameterized models, including environmental and individual covariates, to conduct model selection, and to employ various estimation approaches such as maximum likelihood and Bayesian approaches. With these user-friendly tools, complex statistical models for studying population dynamics have been made available to ecologists. The future will include a continuing trend toward integrating data types, both for tagged and untagged individuals, to produce more precise and robust population models.

  6. Vehicle capture system

    NASA Astrophysics Data System (ADS)

    Tacke, Kenneth L.

    1998-12-01

    Primex Aerospace Company, under contract with the U.S. Army Armament Research Development & Engineering Center (ARDEC), has developed a portable vehicle capture system for use at vehicle checkpoints. Currently when a vehicle does not stop at a checkpoint, there are three possible reactions: let the vehicle go unchallenged, pursue the vehicle or stop the vehicle with lethal force. This system provides a non-lethal alternative that will stop and contain the vehicle. The system is completely portable with the heaviest component weighing less than 120 pounds. It can be installed with no external electrical power or permanent anchors required. In its standby mode, the system does not impede normal traffic, but on command erects a barrier in less than 1.5 seconds. System tests have been conducted using 5,100 and 8.400 pound vehicles, traveling at speeds up to 45 mph. The system is designed to minimize vehicle damage and occupant injury, typically resulting in deceleration forces of less than 2.5 gs on the vehicle. According to the drivers involved in tests at 45 mph, the stopping forces feel similar to a panic stop with the vehicle brakes locked. The system is completely reusable and be rapidly reset.

  7. Revisiting the Effect of Capture Heterogeneity on Survival Estimates in Capture-Mark-Recapture Studies: Does It Matter?

    PubMed Central

    Abadi, Fitsum; Botha, Andre; Altwegg, Res

    2013-01-01

    Recently developed capture-mark-recapture methods allow us to account for capture heterogeneity among individuals in the form of discrete mixtures and continuous individual random effects. In this article, we used simulations and two case studies to evaluate the effectiveness of continuously distributed individual random effects at removing potential bias due to capture heterogeneity, and to evaluate in what situation the added complexity of these models is justified. Simulations and case studies showed that ignoring individual capture heterogeneity generally led to a small negative bias in survival estimates and that individual random effects effectively removed this bias. As expected, accounting for capture heterogeneity also led to slightly less precise survival estimates. Our case studies also showed that accounting for capture heterogeneity increased in importance towards the end of study. Though ignoring capture heterogeneity led to a small bias in survival estimates, such bias may greatly impact management decisions. We advocate reducing potential heterogeneity at the sampling design stage. Where this is insufficient, we recommend modelling individual capture heterogeneity in situations such as when a large proportion of the individuals has a low detection probability (e.g. in the presence of floaters) and situations where the most recent survival estimates are of great interest (e.g. in applied conservation). PMID:23646131

  8. Ionization of polarized hydrogen atoms

    SciTech Connect

    Alessi, J.G.

    1983-01-01

    Methods are discussed for the production of polarized H/sup -/ ions from polarized atoms produced in ground state atomic beam sources. Present day sources use ionizers of two basic types - electron ionizers for H/sup +/ Vector production followed by double charge exchange in a vapor, or direct H/sup -/ Vector production by charge exchange of H/sup 0/ with Cs/sup 0/. Both methods have ionization efficiencies of less than 0.5%. Ionization efficiencies in excess of 10% may be obtained in the future by the use of a plasma ionizer plus charge exchange in Cs or Sr vapor, or ionization by resonant charge exchange with a self-extracted D/sup -/ beam from a ring magnetron or HCD source. 36 references, 4 figures.

  9. Plasma Production via Field Ionization

    SciTech Connect

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

    2007-01-02

    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.

  10. Atmospheric-pressure Penning ionization mass spectrometry.

    PubMed

    Hiraoka, Kenzo; Fujimaki, Susumu; Kambara, Shizuka; Furuya, Hiroko; Okazaki, Shigemitsu

    2004-01-01

    A preliminary study on the atmospheric-pressure Penning ionization (APP(e)I) of gaseous organic compounds with Ar* has been made. The metastable argon atoms (Ar*: 11.55 eV for (3)P(2) and 11.72 eV for (3)P(0)) were generated by the negative-mode corona discharge of atmospheric-pressure argon gas. By applying a high positive voltage (+500 to +1000 V) to the stainless steel capillary for the sample introduction (0.1 mm i.d., 0.3 mm o.d.), strong ion signals could be obtained. The ions formed were sampled through an orifice into the vacuum and mass-analyzed by an orthogonal time-of-flight mass spectrometer. The major ions formed by APP(e)I are found to be molecular-related ions for alkanes, aromatics, and oxygen-containing compounds. Because only the molecules with ionization energies less than the internal energy of Ar* are ionized, the present method will be a selective and highly sensitive interface for gas chromatography/mass spectrometry. PMID:15384154

  11. Continuous flow-extractive desorption electrospray ionization: analysis from "non-electrospray ionization-friendly" solvents and related mechanism.

    PubMed

    Li, Li; Yang, Samuel H; Lemr, Karel; Havlicek, Vladimir; Schug, Kevin A

    2013-03-26

    Due to their low polarities and dielectric constants, analytes in solvents such as hexane, chloroform, and ethyl acetate exhibit poor electrospray ionization (ESI) efficiency. These are deemed to be "non-ESI-friendly" solvents. Continuous flow extractive desorption electrospray ionization (CF-EDESI) is a novel ambient ionization technique that was recently developed in our group to manipulate protein charge distributions. Here we demonstrate its potential for ionizing analytes from non-ESI-friendly solvents. This feature makes CF-EDESI attractive to the general analytical community due to its apparent potential in lipidomics, normal phase separations, and hyphenation of mass spectrometry with HPLC-NMR systems. In this context, interest was subsequently initiated to discern mechanistic aspects of CF-EDESI. To achieve this, mechanistic experiments associated with a seemingly similar ambient ionization technique, extractive electrospray ionization (EESI), were emulated to compare CF-EDESI and EESI. Analysis of a series of fatty acids in multiple solvents in the negative ionization mode revealed differences between the two techniques. Whereas EESI has been previously shown to operate via extraction of analytes into the spray solvent, data presented here for CF-EDESI point toward a liquid-liquid mixing process to facilitate ionization. Further, a partial factorial design experiment was performed to evaluate the effects of different experimental variables on signal intensity. Sample flow rate was confirmed to be among the most significant factors to affect sensitivity. As a whole, the work presented provides greater insight into a new ambient ionization process, which exhibits expanded capabilities over conventional ESI; in this case, for direct analysis from non-ESI-friendly solvents. PMID:23498125

  12. Identification of Streptococcus intermedius Central Nervous System Infection by Use of PCR and Electrospray Ionization Mass Spectrometry

    PubMed Central

    Bhatia, Nisha S.; Sampath, Rangarajan; Ranken, Raymond; Rounds, Megan A.; Ecker, David J.; Bonomo, Robert A.

    2012-01-01

    We describe the utility of PCR and electrospray ionization with mass spectrometry (PCR/ESI-MS) of culture-negative cerebrospinal fluid (CSF) in order to identify Gram-positive cocci noted on a Gram stain of CSF from a previously healthy 26-year-old man with community-acquired pneumonia (CAP) and multiple brain abscesses. CSF samples were obtained 2 weeks apart, first by lumbar puncture and 2 weeks later from an external ventricular drain that was inserted into the right ventricle. Both CSF cultures were negative. A Gram stain of bronchoalveolar lavage (BAL) fluid was notable for many Gram-positive cocci (GPC), but cultures of BAL fluid and subcarinal lymph node biopsy tissue were negative. PCR/ESI-MS detected Streptococcus intermedius, a common cause of brain abscesses, in both CSF samples as well as in the fixed tissue from the biopsy. This unique case confirms S. intermedius pulmonary infection as the source of metastatic CNS infection and reveals the potential of PCR/ESI-MS to detect a streptococcal pathogen not captured by conventional cultures. PMID:23035188

  13. Nonsequential double ionization of molecules

    SciTech Connect

    Prauzner-Bechcicki, Jakub S.; Sacha, Krzysztof; Zakrzewski, Jakub; Eckhardt, Bruno

    2005-03-01

    Double ionization of diatomic molecules by short linearly polarized laser pulses is analyzed. We consider the final stage of the ionization process, that is the decay of a highly excited two electron molecule, which is formed after rescattering. The saddles of the effective adiabatic potential energy close to which simultaneous escape of electrons takes place are identified. Numerical simulations of the ionization of molecules show that the process can be dominated by either sequential or nonsequential events. In order to increase the ratio of nonsequential to sequential ionizations very short laser pulses should be applied.

  14. Intact capture of cosmic dust

    NASA Technical Reports Server (NTRS)

    Tsou, P.

    1991-01-01

    The focus of this development effort is to capture dust particles at hypervelocities intact and unmelted in order to preserve volatile organics. At the same time, the capture process must minimize any organic elemental or compound contamination to prevent any compromise of exobiological analyses. Inorganic silicate aerogel has been developed as a successful capture medium to satisfy both requirements of intact capture and minimal organic contamination. Up to 6 km/s, silicate projectiles from a few microns up to 100 microns have been captured intact without any melting and with minimal loss of mass. Carbon in silicate aerogel can be reduced to less than 1 part in 1000 and hydrogen 3 parts in 1000 when baked in air. Under controlled inert gas environments, additional hydrocarbon reduction can be achieved.

  15. Two-photon ionization of helium studied with the multiconfigurational time-dependent Hartree-Fock method

    SciTech Connect

    Hochstuhl, David; Bonitz, Michael

    2011-02-28

    The multiconfigurational time-dependent Hartree-Fock method (MCTDHF) is applied for simulations of the two-photon ionization of helium. We present results for the single and double ionizations from the ground state for photon energies in the nonsequential regime and compare them to direct solutions of the Schroedinger equation using the time-dependent (full) configuration interaction (TDCI) method. We find that the single ionization is accurately reproduced by MCTDHF, whereas the double ionization results correctly capture the main trends of TDCI.

  16. River Capture in Disequilibrium Landscapes

    NASA Astrophysics Data System (ADS)

    McCoy, S. W.; Perron, J.; Willett, S.; Goren, L.

    2013-12-01

    The process of river piracy or river capture has long drawn interest as a potential mechanism by which drainage basins large and small evolve towards an equilibrium state. River capture transfers both drainage area and drainage lines from one river basin to another, which can cause large, abrupt shifts in network topology, drainage divide positions, and river incision rates. Despite numerous case studies in which river capture has been proposed to have occurred, there is no general, mechanistic framework for understanding the controls on river capture, nor are there quantitative criteria for determining if capture has occurred. Here we use new metrics of landscape disequilibrium to first identify landscapes in which drainage reorganization is occurring. These metrics are based on a balance between an integral of the contributing drainage area and elevation. In an analysis of rivers in the Eastern United States we find that many rivers are in a state of disequilibrium and are experiencing recent or ongoing area exchange between basins. In these disequilibrium basins we find widespread evidence for network rearrangement via river capture at multiple scales. We then conduct numerical experiments with a 2-D landscape evolution model to explore the conditions in which area exchange among drainage basins is likely to occur as discrete capture events as opposed to continuous divide migration. These experiments indicate that: (1) capture activity increases with the degree of disequilibrium induced by persistent spatial gradients in tectonic forcing or by temporal changes in climate or tectonic forcing; (2) capture activity is strongly controlled by the initial planform drainage network geometry; and (3) capture activity scales with the fluvial incision rate constant in the river power erosion law.

  17. Betting on negative emissions

    NASA Astrophysics Data System (ADS)

    Fuss, Sabine; Canadell, Josep G.; Peters, Glen P.; Tavoni, Massimo; Andrew, Robbie M.; Ciais, Philippe; Jackson, Robert B.; Jones, Chris D.; Kraxner, Florian; Nakicenovic, Nebosja; Le Quéré, Corinne; Raupach, Michael R.; Sharifi, Ayyoob; Smith, Pete; Yamagata, Yoshiki

    2014-10-01

    Bioenergy with carbon capture and storage could be used to remove carbon dioxide from the atmosphere. However, its credibility as a climate change mitigation option is unproven and its widespread deployment in climate stabilization scenarios might become a dangerous distraction.

  18. Negative-ion states

    SciTech Connect

    Compton, R.N.

    1982-01-01

    In this brief review, we discuss some of the properties of atomic and molecular negative ions and their excited states. Experiments involving photon reactions with negative ions and polar dissociation are summarized. 116 references, 14 figures.

  19. Carbon Capture and Storage

    SciTech Connect

    Friedmann, S

    2007-10-03

    Carbon capture and sequestration (CCS) is the long-term isolation of carbon dioxide from the atmosphere through physical, chemical, biological, or engineered processes. This includes a range of approaches including soil carbon sequestration (e.g., through no-till farming), terrestrial biomass sequestration (e.g., through planting forests), direct ocean injection of CO{sub 2} either onto the deep seafloor or into the intermediate depths, injection into deep geological formations, or even direct conversion of CO{sub 2} to carbonate minerals. Some of these approaches are considered geoengineering (see the appropriate chapter herein). All are considered in the 2005 special report by the Intergovernmental Panel on Climate Change (IPCC 2005). Of the range of options available, geological carbon sequestration (GCS) appears to be the most actionable and economic option for major greenhouse gas reduction in the next 10-30 years. The basis for this interest includes several factors: (1) The potential capacities are large based on initial estimates. Formal estimates for global storage potential vary substantially, but are likely to be between 800 and 3300 Gt of C (3000 and 10,000 Gt of CO{sub 2}), with significant capacity located reasonably near large point sources of the CO{sub 2}. (2) GCS can begin operations with demonstrated technology. Carbon dioxide has been separated from large point sources for nearly 100 years, and has been injected underground for over 30 years (below). (3) Testing of GCS at intermediate scale is feasible. In the US, Canada, and many industrial countries, large CO{sub 2} sources like power plants and refineries lie near prospective storage sites. These plants could be retrofit today and injection begun (while bearing in mind scientific uncertainties and unknowns). Indeed, some have, and three projects described here provide a great deal of information on the operational needs and field implementation of CCS. Part of this interest comes from several

  20. Analysis of solvent dyes in refined petroleum products by electrospray ionization mass spectrometry

    USGS Publications Warehouse

    Rostad, C.E.

    2010-01-01

    Solvent dyes are used to color refined petroleum products to enable differentiation between gasoline, diesel, and jet fuels. Analysis for these dyes in the hydrocarbon product is difficult due to their very low concentrations in such a complex matrix. Flow injection analysis/electrospray ionization/mass spectrometry in both negative and positive mode was used to optimize ionization of ten typical solvent dyes. Samples of hydrocarbon product were analyzed under similar conditions. Positive electrospray ionization produced very complex spectra, which were not suitably specific for targeting only the dyes. Negative electrospray ionization produced simple spectra because aliphatic and aromatic moieties were not ionized. This enabled screening for a target dye in samples of hydrocarbon product from a spill.

  1. Negative ion generator

    DOEpatents

    Stinnett, R.W.

    1984-05-08

    A negative ion generator is formed from a magnetically insulated transmission line having a coating of graphite on the cathode for producing negative ions and a plurality of apertures on the opposed anode for the release of negative ions. Magnetic insulation keeps electrons from flowing from the cathode to the anode. A transverse magnetic field removes electrons which do escape through the apertures from the trajectory of the negative ions. 8 figs.

  2. Negative ion generator

    DOEpatents

    Stinnett, Regan W.

    1984-01-01

    A negative ion generator is formed from a magnetically insulated transmission line having a coating of graphite on the cathode for producing negative ions and a plurality of apertures on the opposed anode for the release of negative ions. Magnetic insulation keeps electrons from flowing from the cathode to the anode. A transverse magnetic field removes electrons which do escape through the apertures from the trajectory of the negative ions.

  3. [Negative symptoms: which antipsychotics?].

    PubMed

    Maurel, M; Belzeaux, R; Adida, M; Azorin, J-M

    2015-12-01

    Treating negative symptoms of schizophrenia is a major issue and a challenge for the functional and social prognosis of the disease, to which they are closely linked. First- and second-generation antipsychotics allow a reduction of all negative symptoms. The hope of acting directly on primary negative symptoms with any antipsychotic is not supported by the literature. However, the effectiveness of first- and second-generation antipsychotics is demonstrated on secondary negative symptoms. PMID:26776390

  4. Choosing between atmospheric pressure chemical ionization and electrospray ionization interfaces for the HPLC/MS analysis of pesticides

    USGS Publications Warehouse

    Thurman, E.M.; Ferrer, I.; Barcelo, D.

    2001-01-01

    An evaluation of over 75 pesticides by high-performance liquid chromatography/mass spectrometry (HPLC/MS) clearly shows that different classes of pesticides are more sensitive using either atmospheric pressure chemical ionization (APCI) or electrospray ionization (ESI). For example, neutral and basic pesticides (phenylureas, triazines) are more sensitive using APCI (especially positive ion). While cationic and anionic herbicides (bipyridylium ions, sulfonic acids) are more sensitive using ESI (especially negative ion). These data are expressed graphically in a figure called an ionization-continuum diagram, which shows that protonation in the gas phase (proton affinity) and polarity in solution, expressed as proton addition or subtraction (pKa), is useful in selecting APCI or ESI. Furthermore, sodium adduct formation commonly occurs using positive ion ESI but not using positive ion APCI, which reflects the different mechanisms of ionization and strengthens the usefulness of the ionization-continuum diagram. The data also show that the concept of "wrong-way around" ESI (the sensitivity of acidic pesticides in an acidic mobile phase) is a useful modification of simple pKa theory for mobile-phase selection. Finally, this finding is used to enhance the chromatographic separation of oxanilic and sulfonic acid herbicides while maintaining good sensitivity in LC/MS using ESI negative.

  5. Sentential Negation in English

    ERIC Educational Resources Information Center

    Mowarin, Macaulay

    2009-01-01

    This paper undertakes a detailed analysis of sentential negation in the English language with Chomsky's Government-Binding theory of Transformational Grammar as theoretical model. It distinguishes between constituent and sentential negation in English. The essay identifies the exact position of Negation phrase in an English clause structure. It…

  6. Ionizing radiation detector

    DOEpatents

    Thacker, Louis H.

    1990-01-01

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

  7. Ionized cluster beam deposition

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, A. R.

    1983-01-01

    Ionized Cluster Beam (ICB) deposition, a new technique originated by Takagi of Kyoto University in Japan, offers a number of unique capabilities for thin film metallization as well as for deposition of active semiconductor materials. ICB allows average energy per deposited atom to be controlled and involves impact kinetics which result in high diffusion energies of atoms on the growth surface. To a greater degree than in other techniques, ICB involves quantitative process parameters which can be utilized to strongly control the characteristics of films being deposited. In the ICB deposition process, material to be deposited is vaporized into a vacuum chamber from a confinement crucible at high temperature. Crucible nozzle configuration and operating temperature are such that emerging vapor undergoes supercondensation following adiabatic expansion through the nozzle.

  8. Multiphoton ionization of Uracil

    NASA Astrophysics Data System (ADS)

    Prieto, Eladio; Martinez, Denhi; Guerrero, Alfonso; Alvarez, Ignacio; Cisneros, Carmen

    2016-05-01

    Multiphoton ionization and dissociation of Uracil using a Reflectron time of flight spectrometer was performed along with radiation from the second harmonic of a Nd:YAG laser. Uracil is one of the four nitrogen bases that belong to RNA. The last years special interest has been concentrated on the study of the effects under UV radiation in nucleic acids1 and also in the role that this molecule could have played in the origin and development of life on our planet.2 The MPI mass spectra show that the presence and intensity of the resulting ions strongly depend on the density power. The identification of the ions in the mass spectra is presented. The results are compared with those obtained in other laboratories under different experimental conditions and some of them show partial agreement.3 The present work was supported by CONACYT-Mexico Grant 165410 and DGAPA UNAM Grant IN101215 and IN102613.

  9. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, R.A.; Mendez, V.P.; Kaplan, S.N.

    1988-11-15

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation. 15 figs.

  10. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, Robert A.; Mendez, Victor P.; Kaplan, Selig N.

    1988-01-01

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation.

  11. Analytic formulas for above threshold ionization or detachment plateau spectra

    NASA Astrophysics Data System (ADS)

    Frolov, M. V.; Manakov, N. L.; Starace, Anthony F.

    2009-11-01

    Closed form analytic formulas are derived in the tunneling limit for both above threshold detachment (ATD) of negative ions and above threshold ionization (ATI) of neutral atoms. These formulas provide a fully quantum justification of the well-known classical three-step scenario for strong field ionization and detachment spectra in the high energy region of the ATI or ATD plateau and also provide analytical insight into how the ATI/ATD rates may be controlled by varying the laser field parameters or by varying the atomic species.

  12. Surface Ionization Gas Detection at SnO2 Surfaces

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

    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.

  13. New effects of a long-lived negatively charged massive particle on big bang nucleosynthesis

    SciTech Connect

    Kusakabe, Motohiko; Kim, K. S.; Cheoun, Myung-Ki; Kajino, Toshitaka; Kino, Yasushi; Mathews, Grant J.

    2014-05-02

    Primordial {sup 7}Li abundance inferred from observations of metal-poor stars is a factor of about 3 lower than the theoretical value of standard big bang nucleosynthesis (BBN) model. One of the solutions to the Li problem is {sup 7}Be destruction during the BBN epoch caused by a long-lived negatively charged massive particle, X{sup −}. The particle can bind to nuclei, and X-bound nuclei (X-nuclei) can experience new reactions. The radiative X{sup −} capture by {sup 7}Be nuclei followed by proton capture of the bound state of {sup 7}Be and X{sup −} ({sup 7}Be{sub x}) is a possible {sup 7}Be destruction reaction. Since the primordial abundance of {sup 7}Li originates mainly from {sup 7}Li produced via the electron capture of {sup 7}Be after BBN, the {sup 7}Be destruction provides a solution to the {sup 7}Li problem. We suggest a new route of {sup 7}Be{sub x} formation, that is the {sup 7}Be charge exchange at the reaction of {sup 7}Be{sup 3+} ion and X{sup −}. The formation rate depends on the ionization fraction of {sup 7}Be{sup 3+} ion, the charge exchange cross section of {sup 7}Be{sup 3+}, and the probability that excited states {sup 7}Be{sub x}* produced at the charge exchange are converted to the ground state. We find that this reaction can be equally important as or more important than ordinary radiative recombination of {sup 7}Be and X{sup −}. The effect of this new route is shown in a nuclear reaction network calculation.

  14. Intact capture of hypervelocity particles

    NASA Technical Reports Server (NTRS)

    Tsou, P.; Brownlee, D. E.; Albee, A. L.

    1986-01-01

    Knowledge of the phase, structure, and crystallography of cosmic particles, as well as their elemental and isotopic compositions, would be very valuable information toward understanding the nature of our solar system. This information can be obtained from the intact capture of large mineral grains of cosmic particles from hypervelocity impacts. Hypervelocity experiments of intact capture in underdense media have indicated realistic potential in this endeaver. The recovery of the thermal blankets and louvers from the Solar Max spacecraft have independently verified this potential in the unintended capture of cosmic materials from hypervelocity impacts. Passive underdense media will permit relatively simple and inexpensive missions to capture cosmic particles intact, either by going to a planetary body or by waiting for the particles to come to the Shuttle or the Space Station. Experiments to explore the potential of using various underdense media for an intact comet sample capture up to 6.7 km/s were performed at NASA Ames Research Center Vertical Gun Range. Explorative hypervelocity experiments up to 7.9 km/s were also made at the Ernst Mach Institute. These experiments have proven that capturing intact particles at hypervelocity impacts is definitely possible. Further research is being conducted to achieve higher capture ratios at even higher hypervelocities for even smaller projectiles.

  15. Intact capture of hypervelocity particles

    NASA Astrophysics Data System (ADS)

    Tsou, P.; Brownlee, D. E.; Albee, A. L.

    Knowledge of the phase, structure, and crystallography of cosmic particles, as well as their elemental and isotopic compositions, would be very valuable information toward understanding the nature of our solar system. This information can be obtained from the intact capture of large mineral grains of cosmic particles from hypervelocity impacts. Hypervelocity experiments of intact capture in underdense media have indicated realistic potential in this endeaver. The recovery of the thermal blankets and louvers from the Solar Max spacecraft have independently verified this potential in the unintended capture of cosmic materials from hypervelocity impacts. Passive underdense media will permit relatively simple and inexpensive missions to capture cosmic particles intact, either by going to a planetary body or by waiting for the particles to come to the Shuttle or the Space Station. Experiments to explore the potential of using various underdense media for an intact comet sample capture up to 6.7 km/s were performed at NASA Ames Research Center Vertical Gun Range. Explorative hypervelocity experiments up to 7.9 km/s were also made at the Ernst Mach Institute. These experiments have proven that capturing intact particles at hypervelocity impacts is definitely possible. Further research is being conducted to achieve higher capture ratios at even higher hypervelocities for even smaller projectiles.

  16. Neutron capture reactions at DANCE

    SciTech Connect

    Bredeweg, T. A.

    2008-05-12

    The Detector for Advanced Neutron Capture Experiments (DANCE) is a 4{pi} BaF{sub 2} array consisting of 160 active detector elements. The primary purpose of the array is to perform neutron capture cross section measurements on small (> or approx.100 {mu}g) and/or radioactive (< or approx. 100 mCi) species. The measurements made possible with this array will be useful in answering outstanding questions in the areas of national security, threat reduction, nuclear astrophysics, advanced reactor design and accelerator transmutation of waste. Since the commissioning of DANCE we have performed neutron capture cross section measurements on a wide array of medium to heavy mass nuclides. Measurements to date include neutron capture cross sections on {sup 241,243}Am, neutron capture and neutron-induced fission cross sections and capture-to-fission ratio ({alpha} = {sigma}{sub {gamma}}/{sigma}{sub f}) for {sup 235}U using a new fission-tagging detector as well as neutron capture cross sections for several astrophysics branch-point nuclei. Results from several of these measurements will be presented along with a discussion of additional physics information that can be extracted from the DANCE data.

  17. Neutron capture reactions at DANCE

    NASA Astrophysics Data System (ADS)

    Bredeweg, T. A.

    2008-05-01

    The Detector for Advanced Neutron Capture Experiments (DANCE) is a 4π BaF2 array consisting of 160 active detector elements. The primary purpose of the array is to perform neutron capture cross section measurements on small (>~100 μg) and/or radioactive (<~100 mCi) species. The measurements made possible with this array will be useful in answering outstanding questions in the areas of national security, threat reduction, nuclear astrophysics, advanced reactor design and accelerator transmutation of waste. Since the commissioning of DANCE we have performed neutron capture cross section measurements on a wide array of medium to heavy mass nuclides. Measurements to date include neutron capture cross sections on 241,243Am, neutron capture and neutron-induced fission cross sections and capture-to-fission ratio (α = σγ/σf) for 235U using a new fission-tagging detector as well as neutron capture cross sections for several astrophysics branch-point nuclei. Results from several of these measurements will be presented along with a discussion of additional physics information that can be extracted from the DANCE data.

  18. Ionization detection system for aerosols

    DOEpatents

    Jacobs, Martin E.

    1977-01-01

    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.

  19. IEHI: Ionization Equilibrium for Heavy Ions

    NASA Astrophysics Data System (ADS)

    Cranmer, Steven R.

    2015-07-01

    IEHI, written in Fortran, outputs a simple "coronal" ionization equilibrium (i.e., collisional ionization and auto-ionization balanced by radiative and dielectronic recombination) for a plasma at a given electron temperature.

  20. COMPARATIVE ANALYSIS OF DIOXINS AND FURANS BY HIGH RESOLUTION AND ELECTRON CAPTURE MASS SPECTROMETRY

    EPA Science Inventory

    Known mixtures and unknown atmospheric sample extracts containing polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/P) were analyzed by both electron impact, high resolution, mass spectrometry (HRMS) and by electron capture, negative ion, low resolution ma...

  1. Electron capture and fragmentation in Ar11+ + CO collisions

    NASA Astrophysics Data System (ADS)

    Ben-Itzhak, I.; Wells, E.; Stöckli, M. P.; Tawara, H.; Carnes, K. D.

    1997-01-01

    Collisions between 32.2, 130.5 and 570.5 keV Ar11+ ions and CO molecules have been studied using the Macdonald Laboratory CRYEBIS. Coincidence time of flight was used to detect all recoil ions originating from each molecule and a position sensitive detector was used to determine final projectile charge states. Single-and double-electron capture cross-sections are much larger than those for ionization at these collision energies. The dominant recoil channel associated with the Ar10+ final charge state is the CO+ molecular ion. The main ion-pair channel is the C+ + O+ dissociation of CO2+ while the relative yields of higher charge states of the transient COq+ fall off rapidly. The dissociated ions corresponding to charge states up to CO4+ were detected in coincidence with Ar10+ (and Ar9+), indicating that multielectron capture followed by autoionization occurs.

  2. Effect of nickel grid parameters on production of negative hydrogen ions

    SciTech Connect

    Oohara, W.; Yokoyama, H.; Takeda, Toshiaki; Maetani, Y.; Takeda, Takashi; Kawata, K.

    2014-06-15

    Negative hydrogen ions are produced by plasma-assisted catalytic ionization using a nickel grid. When positive ions passing through the grid are decelerated by an electric field, the extraction current density of passing positive ions is sharply reduced by neutralization and negative ionization of the ions. This phenomenon is found to depend on the specific surface area of the grid and the current density.

  3. ISS Update: Capturing a Dragon

    NASA Video Gallery

    NASA Public Affairs Officer Josh Byerly talks with Melanie Miller, Robotics Officer, about the capture of the SpaceX Dragon commercial cargo craft by the Expedition 33 crew of the International Spa...

  4. Radiative capture reactions in astrophysics

    SciTech Connect

    Brune, Carl R.; Davids, Barry

    2015-08-07

    Here, the radiative capture reactions of greatest importance in nuclear astrophysics are identified and placed in their stellar contexts. Recent experimental efforts to estimate their thermally averaged rates are surveyed.

  5. ISS Update: Capturing a Dragon

    NASA Video Gallery

    NASA Public Affairs Officer Josh Byerly talks with space station training instructors Jeff Tuxhorn and Graeme Newman, who trained the space station crews on how to capture SpaceX’s Dragon spacecr...

  6. Toward transformational carbon capture systems

    SciTech Connect

    Miller, David C.; Litynski, John T.; Brickett, Lynn A.; Morreale, Bryan D.

    2015-10-28

    This paper will briefly review the history and current state of Carbon Capture and Storage (CCS) research and development and describe the technical barriers to carbon capture. it will argue forcefully for a new approach to R&D, which leverages both simulation and physical systems at the laboratory and pilot scales to more rapidly move the best technoogies forward, prune less advantageous approaches, and simultaneously develop materials and processes.

  7. Resonance capture at arbitrary inclination

    NASA Astrophysics Data System (ADS)

    Namouni, F.; Morais, M. H. M.

    2015-01-01

    Resonance capture is studied numerically in the three-body problem for arbitrary inclinations. Massless particles are set to drift from outside the 1:5 resonance with a Jupiter-mass planet thereby encountering the web of the planet's diverse mean motion resonances. Randomly constructed samples explore parameter space for inclinations from 0 to 180° with 5° increments totalling nearly 6 × 105 numerical simulations. 30 resonances internal and external to the planet's location are monitored. We find that retrograde resonances are unexpectedly more efficient at capture than prograde resonances and that resonance order is not necessarily a good indicator of capture efficiency at arbitrary inclination. Capture probability drops significantly at moderate sample eccentricity for initial inclinations in the range [10°,110°]. Orbit inversion is possible for initially circular orbits with inclinations in the range [60°,130°]. Capture in the 1:1 co-orbital resonance occurs with great likelihood at large retrograde inclinations. The planet's orbital eccentricity, if larger than 0.1, reduces the capture probabilities through the action of the eccentric Kozai-Lidov mechanism. A capture asymmetry appears between inner and outer resonances as prograde orbits are preferentially trapped in inner resonances. The relative capture efficiency of retrograde resonance suggests that the dynamical lifetimes of Damocloids and Centaurs on retrograde orbits must be significantly larger than those on prograde orbits implying that the recently identified asteroids in retrograde resonance, 2006 BZ8, 2008 SO218, 2009 QY6 and 1999 LE31 may be among the oldest small bodies that wander between the outer giant planets.

  8. Neutron densities from muon capture

    NASA Astrophysics Data System (ADS)

    Huan Ching, Chiang; Oset, Eulogio

    1991-10-01

    We show that, because of Pauli blocking and renormalization of the weak currents in nuclei, the muon capture rates are rather sensitive to the neutron distributions. We also show that, because of intrinsic theoretical uncertainties, neutron radia cannot be determined with precision but some reasonable limits can be given. However, the ratio of capture rates in different isotopes serves to determine the neutron radii of the isotopes provided the neutron density distribution for one of them is known.

  9. High pressure xenon ionization detector

    DOEpatents

    Markey, John K.

    1989-01-01

    A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0.degree. to 30.degree. C.

  10. High pressure xenon ionization detector

    DOEpatents

    Markey, J.K.

    1989-11-14

    A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0 to 30 C. 2 figs.

  11. Iron ionization and recombination rates and ionization equilibrium

    NASA Technical Reports Server (NTRS)

    Arnaud, M.; Raymond, J.

    1992-01-01

    In the past few years important progress has been made on the knowledge of ionization and recombination rates of iron, an astrophysically abundant heavy element and a major impurity in laboratory fusion devices. We make a critical review of the existing data on ionization and dielectronic recombination and present new computations of radiative recombination rate coefficients of Fe(+14) through Fe(+25) using the photoionization cross sections of Clark et al. (1986). We provide analytical fits to the recommended data (direct ionization and excitation-autoionization cross sections; radiative and dielectronic recombination rate coefficients). Finally we determine the iron ionic fractions at ionization equilibrium and compare them with previous computations as well as with observational data.

  12. Prompt ionization in the CRIT II barium releases

    NASA Astrophysics Data System (ADS)

    Torbert, R. B.; Kletzing, C. A.; Liou, K.; Rau, D.

    1992-05-01

    Observations of electron and ion distributions inside a fast neutral barium jet in the ionosphere show significant fluxes within 4 km of release, presumably related to beam plasma instability processes involved in the Critical Ionization Velocity (CIV) effect. Electron fluxes exceeding 5 x 10 exp 12/sq cm-str-sec-keV were responsible for ionizing both the streaming barium and ambient oxygen. Resulting ion fluxes seem to be consistent with 1-2 percent ionization of the fast barium, as reported by optical observations, although the extended spatial distribution of the optically observed ions is difficult to reconcile with the in situ observations. When the perpendicular velocity of the neutrals falls below critical values, these processes shut off. Although these observations resemble the earlier Porcupine experimental results (Haerendel, 1982), theoretical understanding of the differences between these data and that of earlier negative experiments is still lacking.

  13. Microwave reflectometer ionization sensor

    NASA Technical Reports Server (NTRS)

    Seals, Joseph; Fordham, Jeffrey A.; Pauley, Robert G.; Simonutti, Mario D.

    1993-01-01

    The development of the Microwave Reflectometer Ionization Sensor (MRIS) Instrument for use on the Aeroassist Flight Experiment (AFE) spacecraft is described. The instrument contract was terminated, due to cancellation of the AFE program, subsequent to testing of an engineering development model. The MRIS, a four-frequency reflectometer, was designed for the detection and location of critical electron density levels in spacecraft reentry plasmas. The instrument would sample the relative magnitude and phase of reflected signals at discrete frequency steps across 4 GHz bandwidths centered at four frequencies: 20, 44, 95, and 140 GHz. The sampled data would be stored for later processing to calculate the distance from the spacecraft surface to the critical electron densities versus time. Four stepped PM CW transmitter receivers were located behind the thermal protection system of the spacecraft with horn antennas radiating and receiving through an insulating tile. Techniques were developed to deal with interference, including multiple reflections and resonance effects, resulting from the antenna configuration and operating environment.

  14. Optical ionization detector

    DOEpatents

    Wuest, Craig R.; Lowry, Mark E.

    1994-01-01

    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.

  15. Optical ionization detector

    DOEpatents

    Wuest, C.R.; Lowry, M.E.

    1994-03-29

    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.

  16. Martian Meteor Ionization Layers

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  17. Pulsed helium ionization detection system

    DOEpatents

    Ramsey, Roswitha S.; Todd, Richard A.

    1987-01-01

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

  18. Pulsed helium ionization detection system

    DOEpatents

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

    1985-04-09

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

  19. Ionizing radiation promotes protozoan reproduction

    SciTech Connect

    Luckey, T.D.

    1986-11-01

    This experiment was performed to determine whether ionizing radiation is essential for maximum growth rate in a ciliated protozoan. When extraneous ionizing radiation was reduced to 0.15 mrad/day, the reproduction rate of Tetrahymena pyriformis was significantly less (P less than 0.01) than it was at near ambient levels, 0.5 or 1.8 mrad/day. Significantly higher growth rates (P less than 0.01) were obtained when chronic radiation was increased. The data suggest that ionizing radiation is essential for optimum reproduction rate in this organism.

  20. Capture of the gaze does not capture the mind.

    PubMed

    Lange, Elke B; Starzynski, Christian; Engbert, Ralf

    2012-08-01

    Sudden visual changes attract our gaze, and related eye movement control requires attentional resources. Attention is a limited resource that is also involved in working memory--for instance, memory encoding. As a consequence, theory suggests that gaze capture could impair the buildup of memory respresentations due to an attentional resource bottleneck. Here we developed an experimental design combining a serial memory task (verbal or spatial) and concurrent gaze capture by a distractor (of high or low similarity to the relevant item). The results cannot be explained by a general resource bottleneck. Specifically, we observed that capture by the low-similar distractor resulted in delayed and reduced saccade rates to relevant items in both memory tasks. However, while spatial memory performance decreased, verbal memory remained unaffected. In contrast, the high-similar distractor led to capture and memory loss for both tasks. Our results lend support to the view that gaze capture leads to activation of irrelevant representations in working memory that compete for selection at recall. Activation of irrelevant spatial representations distracts spatial recall, whereas activation of irrelevant verbal features impairs verbal memory performance. PMID:22648605

  1. Negative Ion Density Fronts

    SciTech Connect

    Igor Kaganovich

    2000-12-18

    Negative ions tend to stratify in electronegative plasmas with hot electrons (electron temperature Te much larger than ion temperature Ti, Te > Ti ). The boundary separating a plasma containing negative ions, and a plasma, without negative ions, is usually thin, so that the negative ion density falls rapidly to zero-forming a negative ion density front. We review theoretical, experimental and numerical results giving the spatio-temporal evolution of negative ion density fronts during plasma ignition, the steady state, and extinction (afterglow). During plasma ignition, negative ion fronts are the result of the break of smooth plasma density profiles during nonlinear convection. In a steady-state plasma, the fronts are boundary layers with steepening of ion density profiles due to nonlinear convection also. But during plasma extinction, the ion fronts are of a completely different nature. Negative ions diffuse freely in the plasma core (no convection), whereas the negative ion front propagates towards the chamber walls with a nearly constant velocity. The concept of fronts turns out to be very effective in analysis of plasma density profile evolution in strongly non-isothermal plasmas.

  2. Physiological ramifications for loggerhead turtles captured in pelagic longlines.

    PubMed

    Williard, Amanda; Parga, Mariluz; Sagarminaga, Ricardo; Swimmer, Yonat

    2015-10-01

    Bycatch of endangered loggerhead turtles in longline fisheries results in high rates of post-release mortality that may negatively impact populations. The factors contributing to post-release mortality have not been well studied, but traumatic injuries and physiological disturbances experienced as a result of capture are thought to play a role. The goal of our study was to gauge the physiological status of loggerhead turtles immediately upon removal from longline gear in order to refine our understanding of the impacts of capture and the potential for post-release mortality. We analysed blood samples collected from longline- and hand-captured loggerhead turtles, and discovered that capture in longline gear results in blood loss, induction of the systemic stress response, and a moderate increase in lactate. The method by which turtles are landed and released, particularly if released with the hook or line still attached, may exacerbate stress and lead to chronic injuries, sublethal effects or delayed mortality. Our study is the first, to the best of our knowledge, to document the physiological impacts of capture in longline gear, and our findings underscore the importance of best practices gear removal to promote post-release survival in longline-captured turtles. PMID:26490415

  3. The addiction to negativity.

    PubMed

    Lane, R C; Hull, J W; Foehrenbach, L M

    1991-01-01

    In this paper, we have described a type of resistance that has attracted increasing psychoanalytic attention in recent years. Patients exposed to intense negativity during early life may develop an addiction to negative experience as adolescents and adults, and this may constitute a central organizing feature of their personality. In almost all patients, however, some moments of negativity may be observed. We have traced the developmental origins of an attachment to negativity, drawing especially on psychoanalytic investigations of preoedipal pathology. Manifestations and derivatives of early negativity include anhedonia, attachment to physical pain, fear of success, masochism, deprivation of self and others, and negative voyeurism. In discussing the dynamic functions of negativity, we place particular emphasis on two motives: the patient's desires for revenge against early objects that have been a source of deprivation and frustration; and the defensive function of negativity in helping to express as well as ward off dangerous wishes to merge with the object. Deviant forms of autoerotism are likely to be used by these patients to deal with the reactivation of early experiences of neglect and rejection. When negativity is used as a defense or method of relating to others it can lead to a severe disruption of the psychotherapeutic relationship. We have reviewed suggestions for the management of extreme negativity in treatment. Resolution of the therapist's countertransference reactions, especially induced feelings of frustration, rage, and helplessness, is crucial. Emphasis also has been placed on the patient's desires for revenge against self and object, and the manner in which these may be understood and eventually resolved. Only when patient and therapist begin to investigate the adaptive functions of extreme negativity can this pathological symptom be resolved and the patient's awareness of self and sense of autonomy be enhanced. PMID:1763149

  4. Measuring Ionization at Extreme Densities

    NASA Astrophysics Data System (ADS)

    Kraus, Dominik; Doeppner, Tilo; Kritcher, Andrea; Bachmann, Benjamin; Fletcher, Luke; Falcone, Roger; Gericke, Dirk; Glenzer, Siegfried; Masters, Nathan; Nora, Ryan; Boehm, Kurt; Divol, Laurent; Landen, Otto; Yi, Austin; Kline, John; Redmer, Ronald; Neumayer, Paul

    2015-11-01

    A precise knowledge of ionization at given temperature and density is crucial in order to properly model compressibility and heat capacity of ICF ablator materials for efficient implosions producing energy gain. Here, we present a new experimental platform to perform spectrally resolved x-ray scattering measurements of ionization, density and temperature in imploding CH or beryllium capsules on the National Ignition Facility. Recording scattered x-rays at 9 keV from a zinc He-alpha plasma source at a scattering angle of 120 degrees, first experiments show strong sensitivity to k-shell ionization, while at the same time constraining density and temperature. This platform will allow for x-ray Thomson scattering studies of dense plasmas with free electron densities up to 1025 cm-3, giving the possibility to investigate effects of continuum lowering and Pauli blocking on the ablator ionization state right before stagnation of the implosion.

  5. Double ionization of atomic cadmium

    SciTech Connect

    Linusson, P.; Fritzsche, S.; Eland, J. H. D.; Hedin, L.; Karlsson, L.; Feifel, R.

    2011-02-15

    We have recorded the double photoionization spectrum of atomic Cd at four different photon energies in the range 40-200 eV. The main channel is single ionization and subsequent decay of excited Cd{sup +} states, some involving Coster-Kronig processes, whereas direct double ionization is found to be weak. The decay of the excited Cd{sup +} states shows a strong selectivity, related to the configuration of the final state. Double ionization leading to the Cd{sup 2+} ground state is investigated in some detail and is found to proceed mainly through ionization and decay of 4d correlation satellites. The most prominent autoionization peaks have been identified with the aid of quantum-mechanical calculations.

  6. Salts Are Mostly NOT Ionized.

    ERIC Educational Resources Information Center

    Hawkes, Stephen J.

    1996-01-01

    Discusses the misconception that salts are completely ionizing in solution, the presence of this error in textbooks, probable origins of the error, covalent bonding and ion pairs, and how to tell students the truth. (MKR)

  7. Calculation of multiphoton ionization processes

    NASA Technical Reports Server (NTRS)

    Chang, T. N.; Poe, R. T.

    1976-01-01

    We propose an accurate and efficient procedure in the calculation of multiphoton ionization processes. In addition to the calculational advantage, this procedure also enables us to study the relative contributions of the resonant and nonresonant intermediate states.

  8. Simulation Based on Ion Propulsion Rocket System with Using Negative ion - Negative Ion Pair Techniques

    NASA Astrophysics Data System (ADS)

    Sathiyavel, C.

    2016-07-01

    Ion propulsion rocket system is expected to become popular with the development of ion-ion pair techniques because of their stimulated of low propellant, Design of Thrust range is 1N with low electric power and high efficiency. A Negative ion-Negative ion pair of ion propulsion rocket system is proposed in this work .Negative Ion Based Rocket system consists of three parts 1.ionization chamber 2. Repulsion force and ion accelerator 3. Exhaust of Nozzle. The Negative ions from electro negatively gas are produced by attachment of the gas ,such as chlorine with electron emitted from a Electron gun ionization chamber. The formulate of large stable negative ion is achievable in chlorine gas with respect to electron affinity (∆E). The electron affinity is a measure of the energy change when an electron is added to a neutral atom to form a negative ion. When a neutral chlorine atom in the gaseous form picks up an electron to form a Cl- ion, it releases energy of 349 kJ/mol or 3.6 ev/atom. It is said to have an electron affinity of -349 kJ/mol ,the negative sign indicating that energy is released during this process .The mechanisms of attachment involve the formation of intermediate states. In that reason for , the highly repulsive force created between the same negative ions. The distance between same negative ions is important for the evaluate of the rocket thrust and is also determined by the exhaust velocity of the propellant. The mass flow rate of propellant is achieved by the ratio of total mass of the propellant (Kg) needed for operation to time period(s). Accelerate the Negative ions to a high velocity in the thrust vector direction with a significantly intense Magnetic field and the exhaust of negative ions through Nozzle. The simulation of the ion propulsion system has been carried out by MATLAB. By comparing the simulation results with the theoretical and previous results, we have found that the proposed method is achieved of thrust value with estimated

  9. Zero Volt Paper Spray Ionization and Its Mechanism.

    PubMed

    Wleklinski, Michael; Li, Yafeng; Bag, Soumabha; Sarkar, Depanjan; Narayanan, Rahul; Pradeep, T; Cooks, R Graham

    2015-07-01

    The analytical performance and a suggested mechanism for zero volt paper spray using chromatography paper are presented. A spray is generated by the action of the pneumatic force of the mass spectrometer (MS) vacuum at the inlet. Positive and negative ion signals are observed, and comparisons are made with standard kV paper spray (PS) ionization and nanoelectrospray ionization (nESI). While the range of analytes to which zero volt PS is applicable is very similar to kV PS and nESI, differences in the mass spectra of mixtures are interpreted in terms of the more significant effects of analyte surface activity in the gentler zero volt experiment than in the other methods due to the significantly lower charge. The signal intensity of zero volt PS is also lower than in the other methods. A Monte Carlo simulation based on statistical fluctuation of positive and negative ions in solution has been implemented to explain the production of ions from initially uncharged droplets. Uncharged droplets first break up due to aerodynamics forces until they are in the 2-4 μm size range and then undergo Coulombic fission. A model involving statistical charge fluctuations in both phases predicts detection limits similar to those observed experimentally and explains the effects of binary mixture components on relative ionization efficiencies. The proposed mechanism may also play a role in ionization by other voltage-free methods. PMID:26024306

  10. The Evolution of Negation.

    ERIC Educational Resources Information Center

    Croft, William

    1991-01-01

    Discusses a method for extrapolation of diachronic processes from synchronic states, the dynamicization of synchronic typologies, to propose a hitherto unobserved historical source for markers of verbal negation, namely irregular negative existential predicate forms. Explanations are proposed for the occurrence of the attested processes in this…

  11. Learning from Negative Morality.

    ERIC Educational Resources Information Center

    Oser, Fritz K.

    1996-01-01

    Identifies and discusses the elements and applications of learning from negative morality. Negative morality refers to the experience of learning from mistakes thereby creating a body of personal knowledge about "what not to do." This knowledge not only protects individuals but steers them to the right behavior. (MJP)

  12. Ionization oscillations in Hall accelerators

    NASA Astrophysics Data System (ADS)

    Barral, S.; Peradzyński, Z.

    2010-01-01

    The underlying mechanism of low-frequency oscillations in Hall accelerators is investigated theoretically. It is shown that relaxation oscillations arise from a competition between avalanche ionization and the advective transport of the working gas. The model derived recovers the slow progression and fast recession of the ionization front. Analytical approximations of the shape of current pulses and of the oscillation frequency are provided for the case of large amplitude oscillations.

  13. Resonance ionization for analytical spectroscopy

    DOEpatents

    Hurst, George S.; Payne, Marvin G.; Wagner, Edward B.

    1976-01-01

    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.

  14. Rare gene capture in predominantly androgenetic species

    PubMed Central

    Hedtke, Shannon M.; Glaubrecht, Matthias; Hillis, David M.

    2011-01-01

    The long-term persistence of completely asexual species is unexpected. Although asexuality has short-term evolutionary advantages, a lack of genetic recombination leads to the accumulation over time of deleterious mutations. The loss of individual fitness as a result of accumulated deleterious mutations is expected to lead to reduced population fitness and possible lineage extinction. Persistent lineages of asexual, all-female clones (parthenogenetic and gynogenetic species) avoid the negative effects of asexual reproduction through the production of rare males, or otherwise exhibit some degree of genetic recombination. Another form of asexuality, known as androgenesis, results in offspring that are clones of the male parent. Several species of the Asian clam genus Corbicula reproduce via androgenesis. We compared gene trees of mitochondrial and nuclear loci from multiple sexual and androgenetic species across the global distribution of Corbicula to test the hypothesis of long-term clonality of the androgenetic species. Our results indicate that low levels of genetic capture of maternal nuclear DNA from other species occur within otherwise androgenetic lineages of Corbicula. The rare capture of genetic material from other species may allow androgenetic lineages of Corbicula to mitigate the effects of deleterious mutation accumulation and increase potentially adaptive variation. Models comparing the relative advantages and disadvantages of sexual and asexual reproduction should consider the possibility of rare genetic recombination, because such events seem to be nearly ubiquitous among otherwise asexual species. PMID:21606355

  15. Capturing carbon and saving coal

    SciTech Connect

    Johnson, J.

    2007-10-15

    Electric utilities face a tangle of choices when figuring how to pull CO{sub 2} from coal-fired plants. The article explains the three basic approaches to capturing CO{sub 2} - post-combustion, oxyfuel combustion and pre-combustion. Researchers at US DOE labs and utilities are investigating new solvents that capture CO{sub 2} more efficiently than amines and take less energy. Ammonium carbonate has been identified by EPRI as one suitable solvent. Field research projects on this are underway in the USA. Oxyfuel combustion trials are also being planned. Pre-combustion, or gasification is a completely different way of pulling energy from coal and, for electricity generation, this means IGCC systems. AEP, Southern Cinergy and Xcel are considering IGCC plants but none will capture CO{sub 2}. Rio Tinto and BP are planning a 500 MW facility to gasify coke waste from petroleum refining and collect and sequester CO{sub 2}. However, TECO recently dropped a project to build a 789 MW IGCC coal fired plant even though it was to receive a tax credit to encourage advanced coal technologies. The plant would not have captured CO{sub 2}. The company said that 'with uncertainty of carbon capture and sequestration regulations being discussed at the federal and state levels, the timing was not right'. 4 figs.

  16. CHAOTIC CAPTURE OF NEPTUNE TROJANS

    SciTech Connect

    Nesvorny, David; Vokrouhlicky, David

    2009-06-15

    Neptune Trojans (NTs) are swarms of outer solar system objects that lead/trail planet Neptune during its revolutions around the Sun. Observations indicate that NTs form a thick cloud of objects with a population perhaps {approx}10 times more numerous than that of Jupiter Trojans and orbital inclinations reaching {approx}25 deg. The high inclinations of NTs are indicative of capture instead of in situ formation. Here we study a model in which NTs were captured by Neptune during planetary migration when secondary resonances associated with the mean-motion commensurabilities between Uranus and Neptune swept over Neptune's Lagrangian points. This process, known as chaotic capture, is similar to that previously proposed to explain the origin of Jupiter's Trojans. We show that chaotic capture of planetesimals from an {approx}35 Earth-mass planetesimal disk can produce a population of NTs that is at least comparable in number to that inferred from current observations. The large orbital inclinations of NTs are a natural outcome of chaotic capture. To obtain the {approx}4:1 ratio between high- and low-inclination populations suggested by observations, planetary migration into a dynamically excited planetesimal disk may be required. The required stirring could have been induced by Pluto-sized and larger objects that have formed in the disk.

  17. Nonlinear optical response of multiply ionized noble-gas atoms

    NASA Astrophysics Data System (ADS)

    Tarazkar(1, 3), Maryam; Romanov(2, 3), Dmitri; Levis(1, 3), Robert

    2016-05-01

    Calculation of dynamic polarizabilities and hyperpolarizabilities of ionized species using ab initio methods presents computational and conceptual difficulties, as these ionized species often have open-shell electronic system. We use multi-configurational self-consistent field (MCSCF) method with extended basis sets for calculating dynamic polarizability and second-order hyperpolarizabilities of atomic noble gases and their multiply charged cations in non-resonant regime. The calculations were performed at wavelengths ranging from about 100 nm to the red of the first multi-photon resonance all the way toward the static regime. The results were benchmarked to those of CCSD calculations for ions of even-number charge. The second-order hyperpolarizability coefficients were found to decrease when the electrons are progressively removed from the system. At higher ionization states, these coefficients become less dispersive as a function of wavelength. The values and even the signs of the γ (2) coefficients were found to depend on the spin of the ionic quantum state. Thus, for Ne+3 and Ne+4, in low-spin states (2 Pu, and 1 Sg, respectively) the sign of γ (2) is positive, whereas in high-spin states (4 Su, and 3 Pg) the sign is negative. The calculated hyperpolarizabilities of multiply ionized atoms relate to experiments on very bright high-order harmonic generation in multiply ionized plasmas.

  18. On Negative Mass

    NASA Astrophysics Data System (ADS)

    Belletête, Jonathan; Paranjape, M. B.

    2013-06-01

    The Schwarzschild solution to the matter free, spherically symmetric Einstein equations has one free parameter, the mass. But the mass can be of any sign. What is the meaning of the negative mass solutions? The answer to this question for the case of a pure Schwarzschild negative mass black solution is still elusive, however, in this essay, we will consider negative mass solutions within a Schwarzschild-de Sitter geometry. We show that there exist reasonable configurations of matter, bubbles of distributions of matter, that satisfy the dominant energy condition everywhere, that are nonsingular and well behaved everywhere, but correspond to the negative mass Schwarzschild-de Sitter geometry outside the matter distribution. These negative mass bubbles could occur as the end state of a quantum tunneling transition.

  19. Resonance ionization of holmium for ion implantation in microcalorimeters

    NASA Astrophysics Data System (ADS)

    Schneider, F.; Chrysalidis, K.; Dorrer, H.; Düllmann, Ch. E.; Eberhardt, K.; Haas, R.; Kieck, T.; Mokry, C.; Naubereit, P.; Schmidt, S.; Wendt, K.

    2016-06-01

    The determination of the electron neutrino mass by calorimetric measurement of the 163 Ho electron capture spectrum requires ultra-pure samples. Several collaborations, like ECHo or HOLMES, intend to employ microcalorimeters into which 163 Ho is implanted as an ion beam. This makes a selective and additionally very efficient ion source for holmium mandatory. For this purpose, laser resonance ionization of stable holmium 165 Ho was studied, using a three step excitation scheme driven by pulsed Ti:sapphire lasers. Five measurements with sample sizes of 1014 and 1015 atoms were performed for the efficiency investigation. In average, an excellent ionization efficiency of 32(5) % could be shown, demonstrating the suitability for ion beam implantation.

  20. Effects of diagnostic ionizing radiation on pregnancy via TEM

    NASA Astrophysics Data System (ADS)

    Mohammed, W. H.; Artoli, A. M.

    2008-08-01

    In Sudan, X-rays are routinely used at least once for measurements of pelvis during the gestation period, though this is highly prohibited worldwide, except for a few life threatening cases. To demonstrate the effect of diagnostic ionizing radiation on uterus, fetus and neighboring tissues to the ovaries, two independent experiments on pregnant rabbits were conducted. The first experiment was a proof of concept that diagnostic ionizing radiation is hazardous throughout the gestation period. The second experiment was done through Transmission Electron Microscopy (TEM) to elucidate the morphological changes in the ultra structure of samples taken from irradiated pregnant rabbits. This study uses TEM to test the effect of diagnostic radiation of less than 0.6 Gray on the cellular level. Morphological changes have been captured and the images were analyzed to quantify these effects.

  1. Novel analytical approach for brominated flame retardants based on the use of gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry with emphasis in highly brominated congeners.

    PubMed

    Portolés, Tania; Sales, Carlos; Gómara, Belén; Sancho, Juan Vicente; Beltrán, Joaquim; Herrero, Laura; González, María José; Hernández, Félix

    2015-10-01

    The analysis of brominated flame retardants (BFRs) commonly relies on the use of gas chromatography coupled to mass spectrometry (GC-MS) operating in electron ionization (EI) and electron capture negative ionization (ECNI) modes using quadrupole, triple quadrupole, ion trap, and magnetic sector analyzers. However, these brominated contaminants are examples of compounds for which a soft and robust ionization technique might be favorable since they show high fragmentation in EI and low specificity in ECNI. In addition, the low limits of quantification (0.01 ng/g) required by European Commission Recommendation 2014/118/EU on the monitoring of traces of BFRs in food put stress on the use of highly sensitive techniques/methods. In this work, a new approach for the extremely sensitive determination of BFRs taking profit of the potential of atmospheric pressure chemical ionization (APCI) combined with GC and triple quadrupole (QqQ) mass analyzer is proposed. The objective was to explore the potential of this approach for the BFRs determination in samples at pg/g levels, taking marine samples and a cream sample as a model. Ionization and fragmentation behavior of 14 PBDEs (congeners 28, 47, 66, 85, 99, 100, 153, 154, 183, 184, 191, 196, 197, and 209) and two novel BFRs, decabromodiphenyl ethane (DBDPE) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), in the GC-APCI-MS system has been investigated. The formation of highly abundant (quasi) molecular ion was the main advantage observed in relation to EI. Thus, a notable improvement in sensitivity and specificity was observed when using it as precursor ion in tandem MS. The improved detectability (LODs < 10 fg) achieved when using APCI compared to EI has been demonstrated, which is especially relevant for highly brominated congeners. Analysis of samples from an intercomparison exercise and samples from the marine field showed the potential of this approach for the reliable identification and quantification at very low

  2. Nest visits and capture events affect breeding success of Yellow-billed and Pacific loons

    USGS Publications Warehouse

    Uher-Koch, Brian D.; Schmutz, Joel A.; Wright, Kenneth G.

    2015-01-01

    Accurate estimates of breeding success are essential for understanding population dynamics and for managing populations. Unfortunately, research activities to collect these data can negatively impact the breeding success of the study species and bias estimates of breeding success. Despite the potential for negative impacts, few studies have documented the effect of capturing incubating adults on nest survival or compared nest survival following different capture methods. In this study we evaluate the impacts of investigator disturbance associated with captures and nest visits on nest survival of Yellow-billed Loons (Gavia adamsii) and Pacific Loons (Gavia pacifica) in the National Petroleum Reserve-Alaska (NPR-A), an area of conservation concern, in 2011–2013. In an effort to reduce capture-related nest failures, we developed a new suspended dive net technique to catch territorial aquatic birds while off their nests. We then compared nest survival following suspended dive net captures to bow-net trap captures of breeding adult loons. Daily nest survival following bow-net trap or suspended dive net capture was about 30% lower than when adults were not captured. The effect of captures on nest survival was similar between bow-net trap and suspended dive net capture methods. Nest visits without captures also negatively impacted nest survival, although less than captures. If not accounted for, nest visitation biased daily survival rates of nests downward 6%. Effects of investigator disturbance did not differ by species or between years. Our results suggest that any source of disturbance that displaces incubating adult loons could potentially reduce nest survival. To maximize breeding success, human disturbance factors should be limited near loon nests.

  3. Electrode activation in cesium-free negative ion sources

    SciTech Connect

    Dudnikov, Vadim; Johnson, Rolland P.

    2010-02-15

    Features of emission electrode activation leading to enhancement of negative ion emission in cesium-free discharges are discussed. In some ion sources with cesium-free discharges, the emission of negative ions has been increased significantly by emission electrode activation using strong heating of the negative biased electrode by discharge plasma. A simple explanation of this enhancement is that it is due to an accumulation on the emission surface of the plasma electrode of impurities with low ionization potential that decreases in surface work function and increases the secondary emission of negative ions similar to ''Cesiation.'' The negative biasing of emission surface is important for accumulation and trapping the impurities on the emission surface. To effectively control the activation process it is important to directly detect the evolution of the work function and the impurity concentration during electrode activation with enhancement of negative ion emission.

  4. Ionized Physical Vapor Deposition and Diagnostics

    NASA Astrophysics Data System (ADS)

    Ruzic, D. N.; Hayden, D. B.; Juliano, D. R.

    1997-11-01

    Magnetron sputtering is a typical method of physical vapor deposition (PVD) often used in depositing metal interconnects between layers of a semiconductor substrate. However, conventional PVD places an upper limit on the aspect ratio (depth:width) of features to be filled due to the isotropic velocity distribution of the sputtered neutrals. At higher aspect ratios the sputtered particles can coat the sides of a trench before filling it, thus pinching off the trench and leaving either an open circuit or a high resistivity connection. In our system an ICP coil is introduced between the magnetron target and substrate, creating a secondary plasma that can ionize a significant fraction of the sputtered neutral atoms. A negatively biased substrate will accelerate these ions normally, giving a directional flux that can fill the trench from the bottom up. The deposition rates and metal flux ionization fractions are measured with a quartz crystal microbalance and a multi-grid analyzer. Plasma conditions are measured with a time-resolved Langmuir probe system. Both diagnostics are employed for various pressures, magnetron and RF powers, and background gas types. The ability of the system to fill higher aspect ratio features is also discussed.

  5. Ground state of the hydrogen negative ion

    NASA Astrophysics Data System (ADS)

    Obreshkov, Boyan

    2009-03-01

    Based on recently developed variational many-body Schr"odinger equation for electrons with Coulomb interactions [1], we provide first numerical results for the ground state electron structure of the hydrogen negative ion. It is shown that Fermi-Teller promotion effect together with non-adiabatic screening effects due to the Pauli's exclusion principle are responsible for the weak binding of the anion. The calculated ionization potential J=-1/2 - 2 λ+ <1/r12> of the hydrogen negative ion is compared with the experiment, where λ is the mean binding energy per one electron in the ground state.[0pt] [1] B. D. Obreshkov , Phys. Rev. A 78, 032503 (2008).

  6. Adaptive capture of expert behavior

    SciTech Connect

    Jones, R.D.; Barrett, C.L.; Hand, U.; Gordon, R.C.

    1994-08-01

    The authors smoothed and captured a set of expert rules with adaptive networks. The motivation for doing this is discussed. (1) Smoothing leads to stabler control actions. (2) For some sets of rules, the evaluation of the rules can be sped up. This is important in large-scale simulations where many intelligent elements are present. (3) Variability of the intelligent elements can be achieved by adjusting the weights in an adaptive network. (4) After capture has occurred, the weights can be adjusted based on performance criteria. The authors thus have the capability of learning a new set of rules that lead to better performance. The set of rules the authors chose to capture were based on a set of threat determining rules for tank commanders. The approach in this paper: (1) They smoothed the rules. The rule set was converted into a simple set of arithmetic statements. Continuous, non-binary inputs, are now permitted. (2) An operational measure of capturability was developed. (3) They chose four candidate networks for the rule set capture: (a) multi-linear network, (b) adaptive partial least squares, (c) connectionist normalized local spline (CNLS) network, and (d) CNLS net with a PLS preprocessor. These networks were able to capture the rule set to within a few percent. For the simple tank rule set, the multi-linear network performed the best. When the rules were modified to include more nonlinear behavior, CNLS net performed better than the other three nets which made linear assumptions. (4) The networks were tested for robustness to input noise. Noise levels of plus or minus 10% had no real effect on the network performance. Noise levels in the plus or minus 30% range degraded performance by a factor of two. Some performance enhancement occurred when the networks were trained with noisy data. (5) The scaling of the evaluation time was calculated. (6) Human variation can be mimicked in all the networks by perturbing the weights.

  7. Ionizing gas breakdown waves in strong electric fields.

    NASA Technical Reports Server (NTRS)

    Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

    1972-01-01

    A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

  8. Negative hydrogen ion yields at plasma grid surface in a negative hydrogen ion source

    SciTech Connect

    Wada, M.; Kenmotsu, T.; Sasao, M.

    2015-04-08

    Negative hydrogen (H{sup −}) ion yield from the plasma grid due to incident hydrogen ions and neutrals has been evaluated with the surface collision cascade model, ACAT (Atomic Collision in Amorphous Target) coupled to a negative surface ionization models. Dependence of negative ion fractions upon the velocity component normal to the surface largely affect the calculation results of the final energy and angular distributions of the H{sup −} ions. The influence is particularly large for H{sup −} ions desorbed from the surface due to less than several eV hydrogen particle implact. The present calculation predicts that H{sup −} ion yield can be maximized by setting the incident angle of hydrogen ions and neutrals to be 65 degree. The Cs thickness on the plasma grid should also affect the yields and mean energies of surface produced H{sup −} ions by back scattering and ion induced desorption processes.

  9. Kriging without negative weights

    SciTech Connect

    Szidarovszky, F.; Baafi, E.Y.; Kim, Y.C.

    1987-08-01

    Under a constant drift, the linear kriging estimator is considered as a weighted average of n available sample values. Kriging weights are determined such that the estimator is unbiased and optimal. To meet these requirements, negative kriging weights are sometimes found. Use of negative weights can produce negative block grades, which makes no practical sense. In some applications, all kriging weights may be required to be nonnegative. In this paper, a derivation of a set of nonlinear equations with the nonnegative constraint is presented. A numerical algorithm also is developed for the solution of the new set of kriging equations.

  10. Negative birefringent polyimide films

    NASA Technical Reports Server (NTRS)

    Harris, Frank W. (Inventor); Cheng, Stephen Z. D. (Inventor)

    1994-01-01

    A negative birefringent film, useful in liquid crystal displays, and a method for controlling the negative birefringence of a polyimide film is disclosed which allows the matching of an application to a targeted amount of birefringence by controlling the degree of in-plane orientation of the polyimide by the selection of functional groups within both the diamine and dianhydride segments of the polyimide which affect the polyimide backbone chain rigidity, linearity, and symmetry. The higher the rigidity, linearity and symmetry of the polyimide backbone, the larger the value of the negative birefringence of the polyimide film.

  11. Modified calutron negative ion source operation and future plans

    SciTech Connect

    Dagenhart, W.K.; Stirling, W.L.; Haselton, H.H.; Kelley, G.G.; Kim, J.; Tsai, C.C.; Whealton, J.H.

    1980-01-01

    Negative ion generation has advanced rapidly by employing the concept of surface ionization. The modified calutron has proven to be a successful tool to explore these concepts and provide solutions to the many problems which must be evaluated. Many features of the SITEX (Surface Ionization with Transverse Extraction) ion source are ideally suited to this exploration. Some of these features are; a ribbon-like plasma, electron control by transverse magnetic fields and the ability to separate the Cs oven parameters from those which control the positive ion generation.

  12. Spectral Evidence for Ionization in Air-Filled Glow Discharge Tubes: Application to Sprites

    NASA Astrophysics Data System (ADS)

    Armstrong, R. A.; Williams, E. R.; Golka, R. K.; Williams, D. R.

    2001-12-01

    The question of ionization in sprites and the evidence for VLF backscatter from sprites has motivated a quantitative spectral analysis of the various (classical) regions of the glow discharge tube under DC excitation and at air densities appropriate for sprites in the mesosphere. A PR-650 colorimeter (Photo Research, Inc.) has enabled calibrated irradiance measurements for localized zones along the axis of the discharge tube--in the dominantly blue negative glow, in the Faraday dark space and in the red/pink positive column. Consistent with historical nomenclature, nitrogen first and second positive emission is dominant in the positive column (associated with neutral N2), and nitrogen first negative emission, with a prominent peak at 4278 A, is dominant in the blue negative glow (associated with ionized N2+). Whereas nitrogen first and second positive emission are also detected in the negative glow, no spectral evidence for ionization (no 4279, no 3914, no Meinel) is found in the red/pink positive column. This negative result is attributed not to an absence of ionization in the positive column, but rather to a sparse population of N2+ relative to neutral nitrogen in this region, and to the prominent emission in the blue part of the spectrum due to nitrogen second positive. A similar interpretation may be appropriate for the time-integrated spectra from the red body of sprites, also lacking direct evidence for ionization.

  13. Two-center approach to fully differential positron-impact ionization of hydrogen

    NASA Astrophysics Data System (ADS)

    Kadyrov, A. S.; Bailey, J. J.; Bray, I.; Stelbovics, A. T.

    2014-01-01

    The two-center approach to positron-impact ionization of atomic hydrogen is shown to follow from the exact post form of the breakup amplitude [Kadyrov, Bray, Mukhamedzhanov, and Stelbovics, Phys. Rev. Lett. 101, 230405 (2008), 10.1103/PhysRevLett.101.230405]. In such approaches distinct ionization amplitudes arise from each center for the same ionization process. The fully differential cross section for the positron-impact breakup of atomic hydrogen is calculated including direct ionization of the target and electron capture into the positronium continuum. We show that the coherent combination of the amplitudes leads to oscillations in the differential cross sections, whereas the incoherent combination does not. The latter has also the advantage of being consistent with the unitary close-coupling formalism.

  14. Capture of soft particles on electrostatically heterogeneous collectors: brushy particles.

    PubMed

    Wen, Yicun; Guo, Xuhong; Kalasin, Surachate; Santore, Maria M

    2014-03-01

    This work investigated how particle softness can influence the initial adhesive capture of submicrometer colloidal particles from flow onto collecting surfaces. The study focused on the case dominated by potential attractions at the particle periphery (rather than, for instance, steric stabilization, requiring entropically costly deformations to access shorter-range van der Waals attractions.) The particles, "spherical polyelectrolyte brushes" with diameters in the range of 150-200 nm depending on the ionic strength, consisted of a polystyrene core and a corona of grafted poly(acrylic acid) chains, producing a relatively thick (20-40 nm) negative brushy layer. The adhesion of these particles was studied on electrostatically heterogeneous collecting surfaces: negatively charged substrates carrying flat polycationic patches made by irreversibly adsorbing the poly-l-lysine (PLL) polyelectrolyte. Variation in the amount of adsorbed PLL changed the net collector charge from completely negatively charged (repulsive) to positively charged (attractive). Adjustments in ionic strength varied the range of the electrostatic interactions. Comparing capture kinetics of soft brushy particles to those of similarly sized and similarly charged silica particles revealed nearly identical particle capture kinetics over the full range of collecting surface compositions at high ionic strengths. Even though the brushy particles contained an average of 5 vol % PAA in the brushy shell, with the rest being water under these conditions, their capture was indistinguishable from that of similarly charged rigid spheres. The brushy particles were, however, considerably less adherent at low ionic strengths where the brush was more extended, suggesting an influence of particle deformability or reduced interfacial charge. These findings, that the short time adhesion of brushy particles can resemble that of rigid particles, suggest that for bacteria and cell capture, modeling the cells as rigid

  15. Apparatus for separating particles utilizing engineered acoustic contrast capture particles

    SciTech Connect

    Kaduchak, Gregory; Ward, Michael D

    2014-10-21

    An apparatus for separating particles from a medium includes a capillary defining a flow path therein that is in fluid communication with a medium source. The medium source includes engineered acoustic contrast capture particle having a predetermined acoustic contrast. The apparatus includes a vibration generator that is operable to produce at least one acoustic field within the flow path. The acoustic field produces a force potential minima for positive acoustic contrast particles and a force potential minima for negative acoustic contrast particles in the flow path and drives the engineered acoustic contrast capture particles to either the force potential minima for positive acoustic contrast particles or the force potential minima for negative acoustic contrast particles.

  16. Apparatus for separating particles utilizing engineered acoustic contrast capture particles

    DOEpatents

    Kaduchak, Gregory; Ward, Michael D.

    2011-12-27

    An apparatus for separating particles from a medium includes a capillary defining a flow path therein that is in fluid communication with a medium source. The medium source includes engineered acoustic contrast capture particle having a predetermined acoustic contrast. The apparatus includes a vibration generator that is operable to produce at least one acoustic field within the flow path. The acoustic field produces a force potential minima for positive acoustic contrast particles and a force potential minima for negative acoustic contrast particles in the flow path and drives the engineered acoustic contrast capture particles to either the force potential minima for positive acoustic contrast particles or the force potential minima for negative acoustic contrast particles.

  17. Apparatus for separating particles utilizing engineered acoustic contrast capture particles

    DOEpatents

    Kaduchak, Gregory; Ward, Michael D

    2016-05-17

    An apparatus for separating particles from a medium includes a capillary defining a flow path therein that is in fluid communication with a medium source. The medium source includes engineered acoustic contrast capture particle having a predetermined acoustic contrast. The apparatus includes a vibration generator that is operable to produce at least one acoustic field within the flow path. The acoustic field produces a force potential minima for positive acoustic contrast particles and a force potential minima for negative acoustic contrast particles in the flow path and drives the engineered acoustic contrast capture particles to either the force potential minima for positive acoustic contrast particles or the force potential minima for negative acoustic contrast particles.

  18. HUBBLE SNAPSHOT CAPTURES LIFE CYCLE OF STARS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In this stunning picture of the giant galactic nebula NGC 3603, the crisp resolution of NASA's Hubble Space Telescope captures various stages of the life cycle of stars in one single view. To the upper right of center is the evolved blue supergiant called Sher 25. The star has a unique circumstellar ring of glowing gas that is a galactic twin to the famous ring around the supernova 1987A. The grayish-bluish color of the ring and the bipolar outflows (blobs to the upper right and lower left of the star) indicates the presence of processed (chemically enriched) material. Near the center of the view is a so-called starburst cluster dominated by young, hot Wolf-Rayet stars and early O-type stars. A torrent of ionizing radiation and fast stellar winds from these massive stars has blown a large cavity around the cluster. The most spectacular evidence for the interaction of ionizing radiation with cold molecular-hydrogen cloud material are the giant gaseous pillars to the right and lower left of the cluster. These pillars are sculptured by the same physical processes as the famous pillars Hubble photographed in the M16 Eagle Nebula. Dark clouds at the upper right are so-called Bok globules, which are probably in an earlier stage of star formation. To the lower left of the cluster are two compact, tadpole-shaped emission nebulae. Similar structures were found by Hubble in Orion, and have been interpreted as gas and dust evaporation from possibly protoplanetary disks (proplyds). The 'proplyds' in NGC 3603 are 5 to 10 times larger in size and correspondingly also more massive. This single view nicely illustrates the entire stellar life cycle of stars, starting with the Bok globules and giant gaseous pillars, followed by circumstellar disks, and progressing to evolved massive stars in the young starburst cluster. The blue supergiant with its ring and bipolar outflow marks the end of the life cycle. The color difference between the supergiant's bipolar outflow and the diffuse

  19. Negative electrode composition

    DOEpatents

    Kaun, Thomas D.; Chilenskas, Albert A.

    1982-01-01

    A secondary electrochemical cell and a negative electrode composition for use therewith comprising a positive electrode containing an active material of a chalcogen or a transiton metal chalcogenide, a negative electrode containing a lithium-aluminum alloy and an amount of a ternary alloy sufficient to provide at least about 5 percent overcharge capacity relative to a negative electrode solely of the lithium-aluminum alloy, the ternary alloy comprising lithium, aluminum, and iron or cobalt, and an electrolyte containing lithium ions in contact with both of the positive and the negative electrodes. The ternary alloy is present in the electrode in the range of from about 5 percent to about 50 percent by weight of the electrode composition and may include lithium-aluminum-nickel alloy in combination with either the ternary iron or cobalt alloys. A plurality of series connected cells having overcharge capacity can be equalized on the discharge side without expensive electrical equipment.

  20. Logo and Negative Numbers.

    ERIC Educational Resources Information Center

    Strawn, Candace A.

    1998-01-01

    Describes LOGO's turtle graphics capabilities based on a sixth-grade classroom's activities with negative numbers and Logo programming. A sidebar explains LOGO and offers suggestions to teachers for using LOGO effectively. (LRW)

  1. Atomic negative ions

    SciTech Connect

    Brage, T.

    1991-01-01

    We review some of the recent progress in the studies of alkaline-earth, negative ions. Computations of autodetachment rates, electron affinities and transition wavelengths are discussed and some new and improved results are given.

  2. Atomic negative ions

    SciTech Connect

    Brage, T.

    1991-12-31

    We review some of the recent progress in the studies of alkaline-earth, negative ions. Computations of autodetachment rates, electron affinities and transition wavelengths are discussed and some new and improved results are given.

  3. Multiplexed electronically programmable multimode ionization detector for chromatography

    DOEpatents

    Wise, Marcus B.; Buchanan, Michelle V.

    1989-01-01

    Method and apparatus for detecting and differentiating organic compounds based on their electron affinity. An electron capture detector cell (ECD) is operated in a plurality of multiplexed electroncially programmable operating modes to alter the detector response during a single sampling cycle to acquire multiple simultaneous chromatograms corresponding to each of the different operating modes. The cell is held at a constant subatmospheric pressure while the electron collection bias voltage applied to the cell is modulated electronically to allow acquisition of multiple chromatograms for a single sample elution from a chromatograph representing three distinctly different response modes. A system is provided which automatically controls the programmed application of bias pulses at different intervals and/or amplitudes to switch the detector from an ionization mode to the electron capture mode and various degrees therebetween to provide an improved means of tuning an ECD for multimode detection and improved specificity.

  4. Multiplexed electronically programmable multimode ionization detector for chromatography

    DOEpatents

    Wise, M.B.; Buchanan, M.V.

    1988-05-19

    Method and apparatus for detecting and differentiating organic compounds based on their electron affinity. An electron capture detector cell (ECD) is operated in a plurality of multiplexed electronically programmable operating modes to alter the detector response during a single sampling cycle to acquire multiple simultaneous chromatograms corresponding to each of the different operating modes. The cell is held at a constant subatmospheric pressure while the electron collection bias voltage applied to the cell is modulated electronically to allow acquisition of multiple chromatograms for a single sample elution from a chromatograph representing three distinctly different response modes. A system is provided which automatically controls the programmed application of bias pulses at different intervals and/or amplitudes to switch the detector from an ionization mode to the electron capture mode and various degrees therebetween to provide an improved means of tuning an ECD for multimode detection and improved specificity. 6 figs.

  5. Capturing Attention When Attention "Blinks"

    ERIC Educational Resources Information Center

    Wee, Serena; Chua, Fook K.

    2004-01-01

    Four experiments addressed the question of whether attention may be captured when the visual system is in the midst of an attentional blink (AB). Participants identified 2 target letters embedded among distractor letters in a rapid serial visual presentation sequence. In some trials, a square frame was inserted between the targets; as the only…

  6. EDOS Data Capture for ALOS

    NASA Technical Reports Server (NTRS)

    McLemore, Bruce; Cordier, Guy R.; Wood, Terri; Gamst, Harek

    2012-01-01

    In 2008, NASA's Earth Sciences Missions Operations (ESMO) at Goddard Space Flight Center (GSFC) directed the Earth Observing System Data Operations System (EDOS) project to provide a prototype system to assess the feasibility of high rate data capture for the Japan Aerospace Exploration Agency's (JAXA) Advanced Land Observing Satellite (ALOS) spacecraft via NASA's Tracking and Data Relay Satellite System (TDRSS). The key objective of this collaborative effort between NASA and JAXA was to share science data collected over North and South America previously unavailable due to limitations in ALOS downlink capacity. EDOS provided a single system proof-of-concept in 4 months at White Sands TDRS Ground Terminal The system captured 6 ALOS events error-free at 277 Mbps and delivered the data to the Alaska Satellite Facility (ASF) within 3 hours (May/June '08). This paper describes the successful rapid prototyping approach which led to a successful demonstration and agreement between NASA and JAXA for operational support. The design of the operational system will be discussed with emphasis on concurrent high-rate data capture, Level-O processing, real-time display and high-rate delivery with stringent latency requirements. A similar solution was successfully deployed at Svalbard, Norway to support the Suomi NPP launch (October 2011) and capture all X-band data and provide a 30-day backup archive.

  7. Negative affixes in medical English.

    PubMed

    Dzuganova, B

    2006-01-01

    Many medical terms have negative meaning expressed by means of a negative prefix or suffix. The most frequently used negative prefixes are: a-, dis-, in-, non-, and un-. There is only one negative suffix -less (Ref. 15). PMID:17125069

  8. Electrospray Ionization-Induced Protein Unfolding

    NASA Astrophysics Data System (ADS)

    Lin, Hong; Kitova, Elena N.; Johnson, Margaret A.; Eugenio, Luiz; Ng, Kenneth K. S.; Klassen, John S.

    2012-12-01

    Electrospray ionization mass spectrometry (ESI-MS) measurements were performed under a variety of solution conditions on a highly acidic sub-fragment (B3C) of the C-terminal carbohydrate-binding repeat region of Clostridium difficile toxin B, and two mutants (B4A and B4B) containing fewer acidic residues. ESI-MS measurements performed in negative ion mode on aqueous ammonium acetate solutions of B3C at low ionic strength ( I < 80 mM) revealed evidence, based on the measured charge state distribution, of protein unfolding. In contrast, no evidence of unfolding was detected from ESI-MS measurements made in positive ion mode at low I or in either mode at higher I. The results of proton nuclear magnetic resonance and circular dichroism spectroscopy measurements and gel filtration chromatography performed on solutions of B3C under low and high I conditions suggest that the protein exists predominantly in a folded state in neutral aqueous solutions with I > 10 mM. The results of ESI-MS measurements performed on B3C in a series of solutions with high I at pH 5 to 9 rule out the possibility that the structural changes are related to ESI-induced changes in pH. It is proposed that unfolding of B3C, observed in negative mode for solutions with low I, occurs during the ESI process and arises due to Coulombic repulsion between the negatively charged residues and liquid/droplet surface charge. ESI-MS measurements performed in negative ion mode on B4A and B4B also reveal a shift to higher charge states at low I but the magnitude of the changes are smaller than observed for B3C.

  9. Orbital electron capture by the nucleus

    NASA Technical Reports Server (NTRS)

    Bambynek, W.; Behrens, H.; Chen, M. H.; Crasemann, B.; Fitzpatrick, M. L.; Ledingham, K. W. D.; Genz, H.; Mutterer, M.; Intemann, R. L.

    1976-01-01

    The theory of nuclear electron capture is reviewed in the light of current understanding of weak interactions. Experimental methods and results regarding capture probabilities, capture ratios, and EC/Beta(+) ratios are summarized. Radiative electron capture is discussed, including both theory and experiment. Atomic wave function overlap and electron exchange effects are covered, as are atomic transitions that accompany nuclear electron capture. Tables are provided to assist the reader in determining quantities of interest for specific cases.

  10. Dissociative ionization of sodium molecules via repulsive Rydberg states

    NASA Astrophysics Data System (ADS)

    Chen, Hong

    In this thesis, an investigation of two color resonance multiphoton ionization (REMPI) and fragmentation processes in Na2 has been performed in combination with Linear Time-of-Flight Mass Spectrometry technique. The ionization and dissociative ionizations channels in the energy range up to 2500cm -1 above the dissociative ionization threshold into Na(3s)+Na ++e have been studied. After a mild supersonic expansion from the beam source, neutral sodium dimers in the ground state have been produced. Two tunable, pulsed lasers excite Na2 molecules via the intermediate A1S+u state to a single ro-vibrational level of the second intermediate 21pig state. Following absorption of a third photon, the total energy is above the dissociation limit into Na(3s) + Na+ + e. Typically, a small portion of atomic ions is produced under our experimental conditions. By varying the total available energy below and through the doubly excited states correlating with the Na(3p)+Na(4s) atom pair, there is no evidence that the doubly excited states positioned in the ionic continuum get involved. By calculation of the expected transition probabilities for all possible channels which can decay directly and indirectly into atomic ions, I find that direct dissociative ionization via 12S+u is impossible. The transition probabilities for dissociative ionization via the repulsive Rydberg states with principal quantum numbers n from 5˜12 converging toward the 12S+u state are three to four orders of magnitude larger than those for direct ionization into the continuum of the X2S+g ground state. These repulsive Rydberg states are much more likely to play a role in the photo-ionization through the intermediate 21Pg state. A semi-classical model which was originally developed for negative ion dissociative attachment (O'MAL'67) describes how dissociative ionization occurs along the repulsive Rydberg states. Its prediction concerning the ratio of atomic to molecular ion production as a function of initial

  11. Negative-continuum dielectronic recombination for heavy ions

    SciTech Connect

    Artemyev, A.N.; Yerokhin, V.A.; Beier, T.; Kozhuharov, C.; Eichler, J.; Klasnikov, A.E.; Shabaev, V.M.; Stoehlker, T.

    2003-05-01

    The process of recombination of an electron with a bare heavy nucleus via the creation of a free-positron-bound-electron pair is considered. This process is denoted as 'negative-continuum dielectronic recombination' because it results in the capture of an incident electron into a bound state accompanied by a transition of a negative-continuum electron into a bound state. The calculations are performed for a wide range of incident electron energies for Z=82 and 92.

  12. Mycobacteriophage cell binding proteins for the capture of mycobacteria

    PubMed Central

    Arutyunov, Denis; Singh, Upasana; El-Hawiet, Amr; Seckler, Henrique dos Santos; Nikjah, Sanaz; Joe, Maju; Bai, Yu; Lowary, Todd L; Klassen, John S; Evoy, Stephane; Szymanski, Christine M

    2014-01-01

    Slow growing Mycobacterium avium subsp. paratuberculosis (MAP) causes a deadly condition in cattle known as Johne's disease where asymptomatic carriers are the major source of disease transmission. MAP was also shown to be associated with chronic Crohn's disease in humans. Mycobacterium smegmatis is a model mycobacterium that can cause opportunistic infections in a number of human tissues and, rarely, a respiratory disease. Currently, there are no rapid, culture-independent, reliable and inexpensive tests for the diagnostics of MAP or M. smegmatis infections. Bacteriophages are viruses producing a number of proteins that effectively and specifically recognize the cell envelopes of their bacterial hosts. We demonstrate that the mycobacterial phage L5 minor tail protein Gp6 and lysin Gp10 are useful tools for the rapid capture of mycobacteria. Immobilized Gp10 was able to bind both MAP and M. smegmatis cells whereas Gp6 was M. smegmatis specific. Neither of the 2 proteins was able to capture E. coli, salmonella, campylobacter or Mycobacterium marinum cells. Gp6 was detected previously as a component of the phage particle and shows no homology to proteins with known function. Therefore, electrospray ionization mass spectrometry was used to determine whether recombinant Gp6 could bind to a number of chemically synthesized fragments of mycobacterial surface glycans. These findings demonstrate that mycobacteriophage proteins could be used as a pathogen capturing platform that can potentially improve the effectiveness of existing diagnostic methods. PMID:26713219

  13. Does Electron Capture Dissociation Cleave Protein Disulfide Bonds?

    PubMed Central

    Ganisl, Barbara; Breuker, Kathrin

    2012-01-01

    Peptide and protein characterization by mass spectrometry (MS) relies on their dissociation in the gas phase into specific fragments whose mass values can be aligned as ‘mass ladders’ to provide sequence information and to localize possible posttranslational modifications. The most common dissociation method involves slow heating of even-electron (M+n H)n+ ions from electrospray ionization by energetic collisions with inert gas, and cleavage of amide backbone bonds. More recently, dissociation methods based on electron capture or transfer were found to provide far more extensive sequence coverage through unselective cleavage of backbone N–Cα bonds. As another important feature of electron capture dissociation (ECD) and electron transfer dissociation (ETD), their unique unimolecular radical ion chemistry generally preserves labile posttranslational modifications such as glycosylation and phosphorylation. Moreover, it was postulated that disulfide bond cleavage is preferred over backbone cleavage, and that capture of a single electron can break both a backbone and a disulfide bond, or even two disulfide bonds between two peptide chains. However, the proposal of preferential disulfide bond cleavage in ECD or ETD has recently been debated. The experimental data presented here reveal that the mechanism of protein disulfide bond cleavage is much more intricate than previously anticipated. PMID:24363980

  14. Advances in atomic data for neutron-capture elements

    NASA Astrophysics Data System (ADS)

    Sterling, Nicholas C.; Witthoeft, Michael C.; Esteves, David A.; Stancil, Phillip C.; Kilcoyne, A. L. David; Bilodeau, Rene C.; Aguilar, Alejandro

    2012-08-01

    Neutron(n)-capture elements (atomic number Z > 30), which can be produced in planetary nebula (PN) progenitor stars via s-process nucleosynthesis, have been detected in nearly 100 PNe. This demonstrates that nebular spectroscopy is a potentially powerful tool for studying the production and chemical evolution of trans-iron elements. However, significant challenges must be addressed before this goal can be achieved. One of the most substantial hurdles is the lack of atomic data for n-capture elements, particularly that needed to solve for their ionization equilibrium (and hence to convert ionic abundances to elemental abundances). To address this need, we have computed photoionization cross sections and radiative and dielectronic recombination rate coefficients for the first six ions of Se and Kr. The calculations were benchmarked against experimental photoionization cross section measurements. In addition, we computed charge transfer (CT) rate coefficients for ions of six n-capture elements. These efforts will enable the accurate determination of nebular Se and Kr abundances, allowing robust investigations of s-process enrichments in PNe.

  15. Microwave ionization of Rydberg atoms

    SciTech Connect

    Gallagher, T.F.

    1996-12-31

    An atom can be ionized by a static field if the field depresses the potential below the binding energy W, leading to the requirement E = W{sup 2}/4 in atomic units. The atomic units of field and energy are 5.14 {times} 10{sup 9} V/cm and 27.2 eV. The ionization field is often expressed in terms of the principal quantum number n of the state in question as E = 1/16n{sup 4}. In a microwave field with frequency far less than the separation {Delta}W = 1/n{sup 3} between adjacent n states, atoms other than H ionize at the much lower microwave field amplitude of E = 1/3n{sup 5}. This field corresponds to the Inglis-Teller limit, where it is impossible to resolve spectrally adjacent n states due to Stark broadening in a plasma. In H ionization occurs as it does in a static field. The difference exists because the finite sized ionic core of a non hydrogenic atom breaks one of the symmetries found in H. In non hydrogenic atoms the microwave field drives a series of transitions through successively higher n states culminating in ionization. These transitions can be understood in terms of a Landau-Zener picture based on the variation of the energies of the atoms produced by the time varying field or as the resonant multiphoton absorption of the microwave photons. In either case, the atoms make transitions through real intermediate states en route to ionization. With short, four cycle, microwave pulses complete ionization does not occur with fields of E = 1/3n{sup 5}, and population is left in intermediate states. The transition from ionization at fields near E = 1/3n{sup 5} to fields of E = 1/16n{sup 4} occurs when the frequency becomes low enough that the energies of the states vary adiabatically in the temporally varying field.

  16. Characteristics of low-temperature plasma ionization for ambient mass spectrometry compared to electrospray ionization and atmospheric pressure chemical ionization.

    PubMed

    Albert, Anastasia; Engelhard, Carsten

    2012-12-18

    Ambient desorption/ionization mass spectrometry (ADI-MS) is an attractive method for direct analysis with applications in homeland security, forensics, and human health. For example, low-temperature plasma probe (LTP) ionization was successfully used to detect, e.g., explosives, drugs, and pesticides directly on the target. Despite the fact that the field is gaining significant attention, few attempts have been made to classify ambient ionization techniques based on their ionization characteristics and performance compared to conventional ionization sources used in mass spectrometry. In the present study, relative ionization efficiencies (RIEs) for a large group of compound families were determined with LTP-Orbitrap-MS and compared to those obtained with electrospray ionization mass spectrometry (ESI-MS) and atmospheric pressure chemical ionization mass spectrometry (APCI-MS). RIEs were normalized against one reference compound used across all methods to ensure comparability of the results. Typically, LTP analyte ionization through protonation/deprotonation (e.g., 4-acetamidophenol) was observed; in some cases (e.g., acenaphthene) radicals were formed. Amines, amides, and aldehydes were ionized successfully with LTP. A benefit of LTP over conventional methods is the possibility to successfully ionize PAHs and imides. Here, the studied model compounds could be detected by neither APCI nor ESI. LTP is a relatively soft ionization method because little fragmentation of model compounds was observed. It is considered to be an attractive method for the ionization of low molecular weight compounds over a relatively wide polarity range. PMID:23134531

  17. The influence of the adsorption of metoclopramide on the surface ionization of fumed silica.

    PubMed

    Buyuktimkin, Tuba; Wurster, Dale Eric

    2015-01-15

    The effect of adsorbed metoclopramide on the surface ionization of fumed silica was studied using potentiometric titration. Adsorption isotherms of metoclopramide to unionized and negatively-charged silica surfaces were generated and compared to the titration data. The adsorption of metoclopramide caused the silica surface charge to become more negative with increasing pH that was independent of ionic strength which suggested that specific adsorbate-surface interactions were occurring. Adsorption studies showed that metoclopramide adsorbs to the unionized silica surface. Ionization caused drug adsorption to increase which was consistent with at least two distinct surface adsorption sites. The ratio of the additional amount of metoclopramide adsorbed to the surface ionized group density determined from the titration curves was approximately unity which showed conclusively that the negatively-charged silanols constitute one of the surface adsorption sites. Potentiometric titration has been shown to be a useful technique for determining the number and types of adsorption sites on the silica surface. PMID:25448578

  18. Speciation of arsenic oxides using laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Allen, T M; Bezabeh, D Z; Smith, C H; McCauley, E M; Jones, A D; Chang, D P; Kennedy, I M; Kelly, P B

    1996-11-15

    Positive and negative ion mass spectra of arsenic trioxide (As2O3) and arsenic pentaoxide (As2O5) have been obtained by single-step laser desorption/ionization time-of-flight mass spectrometry. Pulsed UV radiation at 266 nm was used for the simultaneous desorption and ionization of the solid sample. High-mass cluster ions that are unique to the oxidation state of each oxide sample appear in the negative ion mass spectra. The As2O3 produces As3O5-, while the As2O5 yields As3O8-. The formation of unique negative cluster ions presents the capability for arsenic oxidation state speciation by laser desorption/ionization mass spectrometry. The ability of time-of-flight mass spectrometry to examine the relative amounts of each arsenic oxide present in a series of mixtures is discussed. Application of our speciation technique to a model incinerator sample is demonstrated. PMID:8916457

  19. Electron Ionization Mass Spectrum of Tellurium Hexafluoride

    SciTech Connect

    Clark, Richard A.; McNamara, Bruce K.; Barinaga, Charles J.; Peterson, James M.; Govind, Niranjan; Andersen, Amity; Abrecht, David G.; Schwantes, Jon M.; Ballou, Nathan E.

    2015-05-18

    The first electron ionization mass spectrum of tellurium hexafluoride (TeF6) is reported. The starting material was produced by direct fluorination of Te metal or TeO2 with nitrogen trifluoride. Formation of TeF6 was confirmed through cryogenic capture of the tellurium fluorination product and analysis through Raman spectroscopy. The eight natural abundance isotopes were observed for each of the set of fragment ions: TeF5+, TeF4+ TeF3+, TeF2+, TeF1+, and Te+, Te2+. A trend in increasing abundance was observed for the even fluoride bearing ions: TeF1+ < TeF3+ < TeF5+, and a decreasing abundance was observed for the even fragment series: Te(0)+ > TeF2+ > TeF4+ > TeF6+, with the molecular ion TeF6+ not observed at all. Density functional theory based electronic structure calculations were used to calculate optimized ground state geometries of these gas phase species and their relative stabilities explain the trends in the data and the lack of observed signal for TeF6+.

  20. Natural materials for carbon capture.

    SciTech Connect

    Myshakin, Evgeniy M.; Romanov, Vyacheslav N.; Cygan, Randall Timothy

    2010-11-01

    Naturally occurring clay minerals provide a distinctive material for carbon capture and carbon dioxide sequestration. Swelling clay minerals, such as the smectite variety, possess an aluminosilicate structure that is controlled by low-charge layers that readily expand to accommodate water molecules and, potentially, carbon dioxide. Recent experimental studies have demonstrated the efficacy of intercalating carbon dioxide in the interlayer of layered clays but little is known about the molecular mechanisms of the process and the extent of carbon capture as a function of clay charge and structure. A series of molecular dynamics simulations and vibrational analyses have been completed to assess the molecular interactions associated with incorporation of CO2 in the interlayer of montmorillonite clay and to help validate the models with experimental observation.

  1. Internal energy distribution of carboxylate negative-ions of the herbicide diclofop acid in the gas-phase

    NASA Astrophysics Data System (ADS)

    Headley, J. V.; Peru, K. M.

    1997-11-01

    Unimolecular dissociations of diclofop acid and three of its esters were studied using electron capture negative-ion mass spectrometry, to determine to what extent the gas-phase chemistry correlated with transformation products reported for the herbicide in soils and microbial biofilms. Electron capture of the trimethylsilyl (TMS) and pentafluorobenzyl (PFB) esters along with H+ abstraction of diclofop acid were used to form the carboxylate ion at m / z 325. The degree of dissociation of this ion was strongly dependent on the relative distribution of internal energies, chemical nature and size of the ester group. For carboxylate ions formed with relatively low distribution of internal energies (PFB ester), elimination of HCl only was the preferred pathway. In contrast, m / z 325 from the TMS ester and diclofop acid, underwent loss of Cl, followed by loss of HCl to give m / z 254 with some direct loss of HCl for the TMS ester. For carboxylate ions formed with little or no internal energy under electrospray ionization, no unimolecular dissociations were observed. However, a wide range of product-ions were observed for the latter using collision-induced dissociations. For the methyl ester there was a preponderance for initial formation of a chlorodibenzofuran oxide ion (m / z 217) instead of electron attachment on the carbonyl function. The ion (m / z 217) was also prevalent for fragmentation of m / z 253 produced directly by electron capture of diclofop acid and the TMS ester. In general, the gas-phase ion chemistry correlated well with the distribution of some transformation products reported in the literature for the herbicide in soils and microbial biofilms.

  2. Negative pressure wound therapy.

    PubMed

    Thompson, James T; Marks, Malcolm W

    2007-10-01

    Negative pressure wound therapy has become an increasingly important part of wound management. Over the last decade, numerous uses for this method of wound management have been reported, ranging from acute and chronic wounds, to closure of open sternal and abdominal wounds, to assistance with skin grafts. The biophysics behind the success of this treatment largely have focused on increased wound blood flow, increased granulation tissue formation, decreased bacterial counts, and stimulation of wound healing pathways through shear stress mechanisms. The overall success of negative pressure wound therapy has led to a multitude of clinical applications, which are discussed in this article. PMID:17967622

  3. Elastomeric Capture Microparticles (ECmuPs) and Their use with Acoustophoresis to Perform Affinity Capture Assays

    NASA Astrophysics Data System (ADS)

    Cushing, Kevin Wallace

    This dissertation describes the development of elastomeric capture microparticles (ECmicroPs) and their use with acoustophoresis to perform affinity capture assays. ECμPs that function as negative acoustic contrast particles were developed by crosslinking emulsion-based droplets composed of commercially available silicone precursors followed by functionalization with avidin/biotin reagents. The size distribution of the ECμPs was very broad or narrow depending on the emulsion system that was used during the synthesis process. Elastomeric particles exhibited a very broad size distribution when a bulk-emulsion process was used; however, when microfluidic systems were utilized, their size distribution became comparatively narrow. The functionalization of elastomeric particles was accomplished by the non-specific adsorption of avidin protein followed by bovine serum albumin (BSA) blocking and bio-specific adsorption of a biotinylated-capture antibody. Polydisperse ECμPs were functionalized to bind prostate specific antigen (PSA) or IgG-phycoerythrin (PE) in aqueous media (buffer, plasma, blood); whereas monodisperse ECμPs were functionalized to bind a high density lipoprotein in the aqueous media. Polydisperse ECμPs functionalized to bind PSA in a physiological buffer (PBS pH 7.4) demonstrated nanomolar detection using flow cytometry analysis; whereas ECμPs functionalized to bind IgG-PE demonstrated picomolar detection in 10% porcine plasma. ECμPs have a specific density of ~1.03 and are more compressible than their surrounding aqueous media; which allowed the ECμPs to exhibit negative acoustic contrast properties under an ultrasonic acoustic standing wave field. The negative acoustic contrast property of ECμPs was advantageously utilized in an IgG-PE assay conducted in 0.1% whole porcine blood. The ligand-bound ECμPs suspended in the diluted blood sample were flowed through an acoustofluidic device where the application of an ultrasonic acoustic standing wave

  4. KINEMATICS IN PARTIALLY IONIZED MOLECULAR CLOUDS: IMPLICATIONS FOR THE TRANSITION TO COHERENCE

    SciTech Connect

    Bailey, Nicole D.; Caselli, Paola; Basu, Shantanu E-mail: caselli@mpe.mpg.de

    2015-01-10

    A previous paper by Bailey and Basu shows analysis of density and mass-to-flux ratio maps for simulations with either an ionization profile which takes into account photoionization (step-like profile) or a cosmic ray only ionization profile. We extend this study to analyze the effect of these ionization profiles on velocity structures, kinematics, and synthetic spectra. Clump regions are found to occur at the convergence of two flows with a low velocity region and velocity direction transition occurring at the junction. Models with evident substructure show that core formation occurs on the periphery of these velocity valleys. Analysis of synthetic spectra reveals the presence of large non-thermal components within low-density gas, especially for models with the step-like ionization profile. All cores show small, sub-thermal relative motions compared to background gas. Large deviations within this analysis are due to the line of sight intersecting low- and high-density regions across the velocity switch transition. Positive deviations correspond to a foreground core moving away from the observer while negative deviations correspond to a background core moving toward the observer. Comparison of velocities resulting from different ionization profiles suggest that high ionization fractions yield supersonic velocities, up to two times the sound speed, while regions with low ionization fractions tend to be subsonic or mildly supersonic. This suggests that the transition to coherence within cores could be a transition between high and low ionization fractions within the gas.

  5. A commercialization strategy for carbon-negative energy

    NASA Astrophysics Data System (ADS)

    Sanchez, Daniel L.; Kammen, Daniel M.

    2016-01-01

    Climate change mitigation requires gigatonne-scale CO2 removal technologies, yet few examples exist beyond niche markets. The flexibility of thermochemical conversion of biomass and fossil energy, coupled with carbon capture and storage, offers a route to commercializing carbon-negative energy.

  6. Spacecraft capture and docking system

    NASA Technical Reports Server (NTRS)

    Kong, Kinyuen (Inventor); Rafeek, Shaheed (Inventor); Myrick, Thomas (Inventor)

    2001-01-01

    A system for capturing and docking an active craft to a passive craft has a first docking assembly on the active craft with a first contact member and a spike projecting outwardly, a second docking assembly on the passive craft having a second contact member and a flexible net deployed over a target area with an open mesh for capturing the end of the spike of the active craft, and a motorized net drive for reeling in the net and active craft to mate with the passive craft's docking assembly. The spike has extendable tabs to allow it to become engaged with the net. The net's center is coupled to a net spool for reeling in. An alignment funnel has inclined walls to guide the net and captured spike towards the net spool. The passive craft's docking assembly includes circumferentially spaced preload wedges which are driven to lock the wedges against the contact member of the active craft. The active craft's docking assembly includes a rotary table and drive for rotating it to a predetermined angular alignment position, and mating connectors are then engaged with each other. The system may be used for docking spacecraft in zero or low-gravity environments, as well as for docking underwater vehicles, docking of ancillary craft to a mother craft in subsonic flight, in-flight refueling systems, etc.

  7. Chemical protection against ionizing radiation

    NASA Astrophysics Data System (ADS)

    Maisin, J. R.

    Some of the problems related to chemical protection against ionizing radiation are discussed with emphasis on : definition, classification, degree of protection, mechanisms of action and toxicity. Results on the biological response modifyers (BRMs) and on the combination of nontoxic (i.e. low) doses of sulphydryl radioprotectors and BRMs are presented.

  8. Ionization Potentials for Isoelectronic Series.

    ERIC Educational Resources Information Center

    Agmon, Noam

    1988-01-01

    Presents a quantitative treatment of ionization potentials of isoelectronic atoms. By looking at the single-electron view of calculating the total energy of an atom, trends in the screening and effective quantum number parameters are examined. Approaches the question of determining electron affinities. (CW)

  9. A compact high resolution electrospray ionization ion mobility spectrometer.

    PubMed

    Reinecke, T; Kirk, A T; Ahrens, A; Raddatz, C-R; Thoben, C; Zimmermann, S

    2016-04-01

    Electrospray is a commonly used ionization method for the analysis of liquids. An electrospray is a dispersed nebular of charged droplets produced under the influence of a strong electrical field. Subsequently, ions are produced in a complex process initiated by evaporation of neutral solvent molecules from these droplets. We coupled an electrospray ionization source to our previously described high resolution ion mobility spectrometer with 75mm drift tube length and a drift voltage of 5kV. When using a tritium source for chemical gas phase ionization, a resolving power of R=100 was reported for this setup. We replaced the tritium source and the field switching shutter by an electrospray needle, a desolvation region with variable length and a three-grid shutter for injecting ions into the drift region. Preliminary measurements with tetraalkylammonium halides show that the current configuration with the electrospray ionization source maintains the resolving power of R=100. In this work, we present the characterization of our setup. One major advantage of our setup is that the desolvation region can be heated separately from the drift region so that the temperature in the drift region stays at room temperature even up to desolvation region temperatures of 100°C. We perform parametric studies for the investigation of the influence of temperature on solvent evaporation with different ratios of water and methanol in the solvent for different analyte substances. Furthermore, the setup is operated in negative mode and spectra of bentazon with different solvents are presented. PMID:26838374

  10. The Negative Repetition Effect

    ERIC Educational Resources Information Center

    Mulligan, Neil W.; Peterson, Daniel J.

    2013-01-01

    A fundamental property of human memory is that repetition enhances memory. Peterson and Mulligan (2012) recently documented a surprising "negative repetition effect," in which participants who studied a list of cue-target pairs twice recalled fewer targets than a group who studied the pairs only once. Words within a pair rhymed, and…

  11. [Chemotherapies of negative schizophrenia].

    PubMed

    Petit, M; Dollfus, S

    1991-01-01

    Five years ago, Goldberg claimed that negative symptoms of schizophrenia do respond to neuroleptics. This apparent discovery is, in fact, a very common way of thinking for European schools of psychiatry, specially the French one guided by Delay and Deniker. Initially focused on reserpine and some alerting phenothiazines such as thioproperazine, this opinion has been extended to benzamides in the 1970s. The analysis of the publications devoted to this point indicates that several drugs are actually considered as potent disinhibitors (i.e. active on negative symptoms of schizophrenia): Phenothiazines: As shown in the controlled studies by Itil (1971), Poirier-Littré (1988), fluphenazine and pipotiazine improve the BPRS anergia factor and the SANS score. Butyrophenones: The first description of the "imipramine like" effect of trifluperidol by Janssen (1959) initiated the studies by Gallant (1960), Fox (1963). They compared trifluperidol at low doses versus haloperidol and chlorpromazine at medium and high doses, BPRS anergia factor improved only at low doses. Diphenylbutylpiperidines (DPBP): Meltzer's review (1986) concluded to the efficacy of such drugs on negative symptoms appearing as a specific biochemical relationship effect. A definite analysis about doses leads to a very different interpretation: DPBP low doses and only low doses improved negative symptoms as much as some low doses of phenothiazines. On the opposite, DPBP, phenothiazines and butyrophenones high doses are inefficient.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1683624

  12. Atomic electron excitation probabilities during orbital electron capture by the nucleus

    NASA Technical Reports Server (NTRS)

    Crasemann, B.; Chen, M. H.; Briand, J. P.; Chevallier, P.; Chetioui, A.; Tavernier, M.

    1979-01-01

    Approximate probabilities of electron excitation (shakeup/shakeoff) from various atomic states during nuclear ns electron capture have been calculated in the sudden approximation, using Hartree-Fock wave functions. Total excitation probabilities are much lower than during inner-shell ionization by photons or electrons, and ns states are more likely to be excited than np states. This latter result is borne out by K-alpha X-ray satellite spectra.

  13. Description of ionization in the molecular approach to atomic collisions

    SciTech Connect

    Harel, C.; Jouin, H.; Pons, B.; Errea, L.F.; Mendez, L.; Riera, A.

    1997-01-01

    Molecular treatments of atomic collisions have traditionally been restricted to low nuclear velocities because of their failure to reproduce the fall of the capture cross sections at higher velocities. The limitation has recently been seen to be due to their description of ionizing processes. This feature is shown here to be a general one for multicharged ion-atom collisions. Its origin and characteristics are described and illustrated for the prototypical Li{sup 3+}+H(1s) reaction. Ionization appears as a result of the inertia of the electron cloud to adiabatically follow the nuclear motion. This gives rise to nonadiabatic transitions, which represent an ionizing flux whenever the nuclear velocity is high enough that the energy of the traveling molecular orbitals involved is positive in both moving atomic reference frames. Two strongly connected mechanisms appear, corresponding to the relative translational and rotational nuclear motions. Because of the finiteness of the basis, these mechanisms terminate with unphysical trapping effects. While interesting {ital per se}, knowledge of these features is also useful with respect to improving molecular treatments of atomic collisions with the addition of pseudostates. {copyright} {ital 1996} {ital The American Physical Society}

  14. Asymmetric particle fluxes from drifting ionization zones in sputtering magnetrons

    NASA Astrophysics Data System (ADS)

    Panjan, Matjaž; Franz, Robert; Anders, André

    2014-04-01

    Electron and ion fluxes from direct current and high-power impulse magnetron sputtering (dcMS and HiPIMS) plasmas were measured in the plane of the target surface. Biased collector probes and a particle energy and mass analyzer showed asymmetric emission of electrons and of singly and doubly charged ions. For both HiPIMS and dcMS discharges, higher fluxes of all types of particles were observed in the direction of the electrons' E × B drift. These results are put in the context with ionization zones that drift over the magnetron's racetrack. The measured currents of time-resolving collector probes suggest that a large fraction of the ion flux originates from drifting ionization zones, while energy-resolving mass spectrometry indicates that a large fraction of the ion energy is due to acceleration by an electric field. This supports the recently proposed hypothesis that each ionization zone is associated with a negative-positive-negative space charge structure, thereby producing an electric field that accelerates ions from the location where they were formed.

  15. Intense laser ionization of transiently aligned CO

    SciTech Connect

    Pinkham, D.; Jones, R.R.

    2005-08-15

    We have measured the ionization rate for CO molecules exposed to intense 30 fsec 780 nm laser pulses as a function of the angle between the molecular and laser polarization axes. Nonionizing, 70 fsec laser pulses are used to coherently prepare the molecules, preferentially aligning them for the strong-field ionization experiments. We find a 2:1 ionization-rate ratio for molecules aligned parallel or perpendicular to the ionizing field.

  16. Five-photon double ionization of helium

    NASA Astrophysics Data System (ADS)

    Li, Y.; Pindzola, M. S.; Colgan, J.

    2016-03-01

    A time-dependent close-coupling method is used to calculate the five-photon double ionization of He. It is found that the generalized cross section used in the past for two-photon double ionization of He cannot be extended to five-photon double ionization of He. Therefore only five-photon double ionization probabilities that depend on specific radiation field pulses can be calculated.

  17. Calculation of doublet capture rate for muon capture in deuterium within chiral effective field theory

    NASA Astrophysics Data System (ADS)

    Adam, J.; Tater, M.; Truhlík, E.; Epelbaum, E.; Machleidt, R.; Ricci, P.

    2012-03-01

    The doublet capture rate Λ1 / 2 of the negative muon capture in deuterium is calculated employing the nuclear wave functions generated from accurate nucleon-nucleon (NN) potentials constructed at next-to-next-to-next-to-leading order of heavy-baryon chiral perturbation theory and the weak meson exchange current operator derived within the same formalism. All but one of the low-energy constants that enter the calculation were fixed from pion-nucleon and nucleon-nucleon scattering data. The low-energy constant dˆR (cD), which cannot be determined from the purely two-nucleon data, was extracted recently from the triton β-decay and the binding energies of the three-nucleon systems. The calculated values of Λ1 / 2 show a rather large spread for the used values of the dˆR. Precise measurement of Λ1 / 2 in the future will not only help to constrain the value of dˆR, but also provide a highly nontrivial test of the nuclear chiral EFT framework. Besides, the precise knowledge of the constant dˆR will allow for consistent calculations of other two-nucleon weak processes, such as proton-proton fusion and solar neutrino scattering on deuterons, which are important for astrophysics.

  18. Realistic costs of carbon capture

    SciTech Connect

    Al Juaied, Mohammed . Belfer Center for Science and International Affiaris); Whitmore, Adam )

    2009-07-01

    There is a growing interest in carbon capture and storage (CCS) as a means of reducing carbon dioxide (CO2) emissions. However there are substantial uncertainties about the costs of CCS. Costs for pre-combustion capture with compression (i.e. excluding costs of transport and storage and any revenue from EOR associated with storage) are examined in this discussion paper for First-of-a-Kind (FOAK) plant and for more mature technologies, or Nth-of-a-Kind plant (NOAK). For FOAK plant using solid fuels the levelised cost of electricity on a 2008 basis is approximately 10 cents/kWh higher with capture than for conventional plants (with a range of 8-12 cents/kWh). Costs of abatement are found typically to be approximately US$150/tCO2 avoided (with a range of US$120-180/tCO2 avoided). For NOAK plants the additional cost of electricity with capture is approximately 2-5 cents/kWh, with costs of the range of US$35-70/tCO2 avoided. Costs of abatement with carbon capture for other fuels and technologies are also estimated for NOAK plants. The costs of abatement are calculated with reference to conventional SCPC plant for both emissions and costs of electricity. Estimates for both FOAK and NOAK are mainly based on cost data from 2008, which was at the end of a period of sustained escalation in the costs of power generation plant and other large capital projects. There are now indications of costs falling from these levels. This may reduce the costs of abatement and costs presented here may be 'peak of the market' estimates. If general cost levels return, for example, to those prevailing in 2005 to 2006 (by which time significant cost escalation had already occurred from previous levels), then costs of capture and compression for FOAK plants are expected to be US$110/tCO2 avoided (with a range of US$90-135/tCO2 avoided). For NOAK plants costs are expected to be US$25-50/tCO2. Based on these considerations a likely representative range of costs of abatement from CCS excluding

  19. Algal Energy Conversion and Capture

    NASA Astrophysics Data System (ADS)

    Hazendonk, P.

    2015-12-01

    We address the potential for energy conversions and capture for: energy generation; reduction in energy use; reduction in greenhouse gas emissions; remediation of water and air pollution; protection and enhancement of soil fertility. These processes have the potential to sequester carbon at scales that may have global impact. Energy conversion and capture strategies evaluate energy use and production from agriculture, urban areas and industries, and apply existing and emerging technologies to reduce and recapture energy embedded in waste products. The basis of biocrude production from Micro-algal feedstocks: 1) The nutrients from the liquid fraction of waste streams are concentrated and fed into photo bioreactors (essentially large vessels in which microalgae are grown) along with CO2 from flue gasses from down stream processes. 2) The algae are processed to remove high value products such as proteins and beta-carotenes. The advantage of algae feedstocks is the high biomass productivity is 30-50 times that of land based crops and the remaining biomass contains minimal components that are difficult to convert to biocrude. 3) The remaining biomass undergoes hydrothermal liquefaction to produces biocrude and biochar. The flue gasses of this process can be used to produce electricity (fuel cell) and subsequently fed back into the photobioreactor. The thermal energy required for this process is small, hence readily obtained from solar-thermal sources, and furthermore no drying or preprocessing is required keeping the energy overhead extremely small. 4) The biocrude can be upgraded and refined as conventional crude oil, creating a range of liquid fuels. In principle this process can be applied on the farm scale to the municipal scale. Overall, our primary food production is too dependent on fossil fuels. Energy conversion and capture can make food production sustainable.

  20. Negative ion states of sulfur hexafluoride

    SciTech Connect

    Chen, E.C.M.; Shuie, L.; Desai D'sa, E.; Batten, C.F.; Wentworth, W.E.

    1988-04-15

    The reaction of SF/sub 6/ with thermal electrons has been studied in a Ni-63 atmospheric pressure ionization source for a quadrupole mass spectrometer (API/MS). The major ions that are observed are the parent negative ion (SF/sup -//sub 6/) and the parent minus a fluorine atom (SF/sup -//sub 5/). The ratio of (SF/sup -//sub 5/)/(SF/sup -//sub 6/) is highly temperature dependent above 500 K. The dissociation energy of the ground state negative ion into SF/sup -//sub 5/ and F has been determined to be 1.35 +- 0.1 eV. This gives values of 3.8 +- 0.15 eV for the electron affinity of SF/sub 5/ and 1.15 +- 0.15 eV for the electron affinity of SF/sub 6/. The negative ion states of sulfur hexafluoride have been described by ''pseudo-two-dimensional'' Morse potentials calculated using experimental data.

  1. Negative refraction and superconductivity

    NASA Astrophysics Data System (ADS)

    Amariti, Antonio; Forcella, Davide; Mariotti, Alberto; Siani, Massimo

    2011-10-01

    We discuss exotic properties of charged hydrodynamical systems, in the broken superconducting phase, probed by electromagnetic waves. Motivated by general arguments from hydrodynamics, we observe that negative refraction, namely the propagation in opposite directions of the phase velocities and of the energy flux, is expected for low enough frequencies. We corroborate this general idea by analyzing a holographic superconductor in the AdS/CFT correspondence, where the response functions can be explicitly computed. We study the dual gravitational theory both in the probe and in the backreacted case. We find that, while in the first case the refractive index is positive at every frequency, in the second case there is negative refraction at low enough frequencies. This is in agreement with hydrodynamic considerations.

  2. Think (Gram) negative!

    PubMed Central

    2010-01-01

    The increasing prevalence of multiresistant Gram-negative bacteria of the Enterobacteriaceae family in Europe is a worrisome phenomenon. Extended spectrum betalactamase-producing Escherichia coli strains are widespread in the community and are frequently imported into the hospital. Of even more concern is the spread of carbapenem-resistant strains of Klebsiella spp. from regions where they are already endemic. Antibiotic use is a main driver of antibiotic resistance, which again increases broad spectrum antibiotic use, resulting in a vicious circle that is difficult to interrupt. The present commentary highlights important findings of a surveillance study of antimicrobial use and resistance in German ICUs over 8 years with a focus on Gram-negative resistance. PMID:20587087

  3. Electron-Impact Ionization and Dissociative Ionization of Biomolecules

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Chaban, Galina M.; Dateo, Christopher E.

    2006-01-01

    It is well recognized that secondary electrons play an important role in radiation damage to humans. Particularly important is the damage of DNA by electrons, potentially leading to mutagenesis. Molecular-level study of electron interaction with DNA provides information on the damage pathways and dominant mechanisms. Our study of electron-impact ionization of DNA fragments uses the improved binary-encounter dipole model and covers DNA bases, sugar phosphate backbone, and nucleotides. An additivity principle is observed. For example, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3(sup prime)- and C5 (sup prime)-deoxyribose-phospate cross sections, differing by less than 5%. Investigation of tandem double lesion initiated by electron-impact dissociative ionization of guanine, followed by proton reaction with the cytosine in the Watson-Crick pair, is currently being studied to see if tandem double lesion can be initiated by electron impact. Up to now only OH-induced tandem double lesion has been studied.

  4. Enhanced image capture through fusion

    NASA Technical Reports Server (NTRS)

    Burt, Peter J.; Hanna, Keith; Kolczynski, Raymond J.

    1993-01-01

    Image fusion may be used to combine images from different sensors, such as IR and visible cameras, to obtain a single composite with extended information content. Fusion may also be used to combine multiple images from a given sensor to form a composite image in which information of interest is enhanced. We present a general method for performing image fusion and show that this method is effective for diverse fusion applications. We suggest that fusion may provide a powerful tool for enhanced image capture with broad utility in image processing and computer vision.

  5. Carbon Capture and Storage, 2008

    ScienceCinema

    None

    2010-01-08

    The U.S. Department of Energy is researching the safe implementation of a technology called carbon sequestration, also known as carbon capture and storage, or CCS. Based on an oilfield practice, this approach stores carbon dioxide, or CO2 generated from human activities for millennia as a means to mitigate global climate change. In 2003, the Department of Energys National Energy Technology Laboratory formed seven Regional Carbon Sequestration Partnerships to assess geologic formations suitable for storage and to determine the best approaches to implement carbon sequestration in each region. This video describes the work of these partnerships.

  6. Carbon Capture and Storage, 2008

    SciTech Connect

    2009-03-19

    The U.S. Department of Energy is researching the safe implementation of a technology called carbon sequestration, also known as carbon capture and storage, or CCS. Based on an oilfield practice, this approach stores carbon dioxide, or CO2 generated from human activities for millennia as a means to mitigate global climate change. In 2003, the Department of Energys National Energy Technology Laboratory formed seven Regional Carbon Sequestration Partnerships to assess geologic formations suitable for storage and to determine the best approaches to implement carbon sequestration in each region. This video describes the work of these partnerships.

  7. Negative Emissions Technology

    NASA Astrophysics Data System (ADS)

    Day, Danny

    2006-04-01

    Although `negative emissions' of carbon dioxide need not, in principle, involve use of biological processes to draw carbon out of the atmosphere, such `agricultural' sequestration' is the only known way to remove carbon from the atmosphere on time scales comparable to the time scale for anthropogenic increases in carbon emissions. In order to maintain the `negative emissions' the biomass must be used in such a way that the resulting carbon dioxide is separated and permanently sequestered. Two options for sequestration are in the topsoil and via geologic carbon sequestration. The former has multiple benefits, but the latter also is needed. Thus, although geologic carbon sequestration is viewed skeptically by some environmentalists as simply a way to keep using fossil fuels---it may be a key part of reversing accelerating climate forcing if rapid climate change is beginning to occur. I will first review the general approach of agricultural sequestration combined with use of resulting biofuels in a way that permits carbon separation and then geologic sequestration as a negative emissions technology. Then I discuss the process that is the focus of my company---the EPRIDA cycle. If deployed at a sufficiently large scale, it could reverse the increase in CO2 concentrations. I also estimate of benefits --carbon and other---of large scale deployment of negative emissions technologies. For example, using the EPRIDA cycle by planting and soil sequestering carbon in an area abut In 3X the size of Texas would remove the amount of carbon that is being accumulated worldwide each year. In addition to the atmospheric carbon removal, the EPRIDA approach also counters the depletion of carbon in the soil---increasing topsoil and its fertility; reduces the excess nitrogen in the water by eliminating the need for ammonium nitrate fertilizer and reduces fossil fuel reliance by providing biofuel and avoiding natural gas based fertilizer production.

  8. The negative repetition effect.

    PubMed

    Mulligan, Neil W; Peterson, Daniel J

    2013-09-01

    A fundamental property of human memory is that repetition enhances memory. Peterson and Mulligan (2012) recently documented a surprising negative repetition effect, in which participants who studied a list of cue-target pairs twice recalled fewer targets than a group who studied the pairs only once. Words within a pair rhymed, and across pairs, the target words were drawn from a small set of categories. In the repetition condition, the pairs were initially presented in a random order and then presented a 2nd time blocked by the category of the target words. In the single presentation condition, the pairs were presented only in the blocked order. Participants in the former condition recalled fewer target words on a free recall test despite having seen the word pairs twice (the negative repetition effect). This phenomenon is explored in a series of 5 experiments assessing 3 theoretical accounts of the effect. The experiments demonstrate that the negative repetition effect generalizes over multiple encoding conditions (reading and generative encoding), over different memory tests (free and cued recall), and over delay (5 min and 2 days). The results argue against a retrieval account and a levels-of-processing account but are consistent with the item-specific-relational account, the account upon which the effect was initially predicated. PMID:23421508

  9. Average local ionization energy generalized to correlated wavefunctions

    SciTech Connect

    Ryabinkin, Ilya G.; Staroverov, Viktor N.

    2014-08-28

    The average local ionization energy function introduced by Politzer and co-workers [Can. J. Chem. 68, 1440 (1990)] as a descriptor of chemical reactivity has a limited utility because it is defined only for one-determinantal self-consistent-field methods such as the Hartree–Fock theory and the Kohn–Sham density-functional scheme. We reinterpret the negative of the average local ionization energy as the average total energy of an electron at a given point and, by rewriting this quantity in terms of reduced density matrices, arrive at its natural generalization to correlated wavefunctions. The generalized average local electron energy turns out to be the diagonal part of the coordinate representation of the generalized Fock operator divided by the electron density; it reduces to the original definition in terms of canonical orbitals and their eigenvalues for one-determinantal wavefunctions. The discussion is illustrated with calculations on selected atoms and molecules at various levels of theory.

  10. 49 CFR 563.9 - Data capture.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 6 2010-10-01 2010-10-01 false Data capture. 563.9 Section 563.9 Transportation..., DEPARTMENT OF TRANSPORTATION EVENT DATA RECORDERS § 563.9 Data capture. The EDR must capture and record the data elements for events in accordance with the following conditions and circumstances: (a) In...

  11. 49 CFR 563.9 - Data capture.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 6 2011-10-01 2011-10-01 false Data capture. 563.9 Section 563.9 Transportation..., DEPARTMENT OF TRANSPORTATION EVENT DATA RECORDERS § 563.9 Data capture. Link to an amendment published at 76 FR 47489, Aug. 5, 2011. The EDR must capture and record the data elements for events in...

  12. 49 CFR 563.9 - Data capture.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 6 2012-10-01 2012-10-01 false Data capture. 563.9 Section 563.9 Transportation..., DEPARTMENT OF TRANSPORTATION EVENT DATA RECORDERS § 563.9 Data capture. The EDR must capture and record the data elements for events in accordance with the following conditions and circumstances: (a) In...

  13. 49 CFR 563.9 - Data capture.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 6 2013-10-01 2013-10-01 false Data capture. 563.9 Section 563.9 Transportation..., DEPARTMENT OF TRANSPORTATION EVENT DATA RECORDERS § 563.9 Data capture. The EDR must capture and record the data elements for events in accordance with the following conditions and circumstances: (a) In...

  14. 49 CFR 563.9 - Data capture.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 6 2014-10-01 2014-10-01 false Data capture. 563.9 Section 563.9 Transportation..., DEPARTMENT OF TRANSPORTATION EVENT DATA RECORDERS § 563.9 Data capture. The EDR must capture and record the data elements for events in accordance with the following conditions and circumstances: (a) In...

  15. The Effectiveness of Classroom Capture Technology

    ERIC Educational Resources Information Center

    Ford, Maire B.; Burns, Colleen E.; Mitch, Nathan; Gomez, Melissa M.

    2012-01-01

    The use of classroom capture systems (systems that capture audio and video footage of a lecture and attempt to replicate a classroom experience) is becoming increasingly popular at the university level. However, research on the effectiveness of classroom capture systems in the university classroom has been limited due to the recent development and…

  16. Rewarded visual items capture attention only in heterogeneous contexts.

    PubMed

    Feldmann-Wüstefeld, Tobias; Brandhofer, Ruben; Schubö, Anna

    2016-07-01

    Reward is known to affect visual search performance. Rewarding targets can increase search performance, whereas rewarding distractors can decrease search performance. We used subcomponents of the N2pc in the event-related EEG, the NT (target negativity) and ND /PD (distractor negativity/positivity), in a visual search task to disentangle target and distractor processing related to reward. The visual search task comprised homogeneous and heterogeneous contexts in which a target and a colored distractor were embedded. After each correct trial, participants were given a monetary reward that depended on the color of the distractor. We found longer response times for displays with high-reward distractors compared to displays with low-reward distractors, indicating reward-induced interference, however, only for heterogeneous contexts. The NT component, indicative of attention deployment to the target, showed that target selection was impaired by high-reward distractors, regardless of the context homogeneity. Processing of distractors was not affected by reward in homogeneous contexts. In heterogeneous contexts, however, high-reward distractors were more likely to capture attention (ND ) and required more effort to be suppressed (PD ) than low-reward distractors. In sum the results showed that, despite the fact that target selection is impaired by high-reward distractors in both homogeneous and heterogeneous background contexts, high-reward distractors capture attention only in scenarios that foster attentional capture. PMID:26997364

  17. Negative-ion source applications (invited)a)

    NASA Astrophysics Data System (ADS)

    Ishikawa, J.

    2008-02-01

    In this paper heavy negative-ion sources which we developed and their applications for materials science are reviewed. Heavy negative ions can be effectively produced by the ejection of a sputtered atom through the optimally cesiated surface of target with a low work function. Then, enough continuous negative-ion currents for materials-science applications can be obtained. We developed several kinds of sputter-type heavy negative-ion sources such as neutral- and ionized-alkaline metal bombardment-type heavy negative-ion source and rf-plasma sputter type. In the case where a negative ion is irradiated on a material surface, surface charging seldom takes place because incoming negative charge of the negative ion is well balanced with outgoing negative charge of the released secondary electron. In the negative-ion implantation into an insulator or insulated conductive material, high precision implantation processing with charge-up free properties can be achieved. Negative-ion implantation technique, therefore, can be applied to the following novel material processing systems: the surface modification of micrometer-sized powders, the nanoparticle formation in an insulator for the quantum devices, and the nerve cell growth manipulation by precise control of the biocompatibility of polymer surface. When a negative ion with low kinetic energy approaches the solid surface, the kinetic energy causes the interatomic bonding (kinetic bonding), and formation of a metastable material is promoted. Carbon films with high constituent of sp3 bonding, therefore, can be formed by carbon negative-ion beam deposition.

  18. Ambient aerodynamic ionization source for remote analyte sampling and mass spectrometric analysis.

    PubMed

    Dixon, R Brent; Sampson, Jason S; Hawkridge, Adam M; Muddiman, David C

    2008-07-01

    The use of aerodynamic devices in ambient ionization source development has become increasingly prevalent in the field of mass spectrometry. In this study, an air ejector has been constructed from inexpensive, commercially available components to incorporate an electrospray ionization emitter within the exhaust jet of the device. This novel aerodynamic device, herein termed remote analyte sampling, transport, and ionization relay (RASTIR) was used to remotely sample neutral species in the ambient and entrain them into an electrospray plume where they were subsequently ionized and detected using a linear ion trap Fourier transform mass spectrometer. Two sets of experiments were performed in the ambient environment to demonstrate the device's utility. The first involved the remote (approximately 1 ft) vacuum collection of pure sample particulates (i.e., dry powder) from a glass slide, entrainment and ionization at the ESI emitter, and mass spectrometric detection. The second experiment involved the capture (vacuum collection) of matrix-assisted laser desorbed proteins followed by entrainment in the ESI emitter plume, multiple charging, and mass spectrometric detection. This approach is in principle a RASTIR-assisted matrix-assisted laser desorption electrospray ionization source (Sampson, J. S.; Hawkridge, A. M.; Muddiman, D. C. J. Am. Soc. Mass Spectrom. 2006, 17, 1712-1716; Rapid Commun. Mass Spectrom. 2007, 21, 1150-1154.). A detailed description of the device construction, operational parameters, and preliminary small molecule and protein data are presented. PMID:18529018

  19. Adaptive capture of expert knowledge

    SciTech Connect

    Barrett, C.L.; Jones, R.D.; Hand, Un Kyong |

    1995-05-01

    A method is introduced that can directly acquire knowledge-engineered, rule-based logic in an adaptive network. This adaptive representation of the rule system can then replace the rule system in simulated intelligent agents and thereby permit further performance-based adaptation of the rule system. The approach described provides both weight-fitting network adaptation and potentially powerful rule mutation and selection mechanisms. Nonlinear terms are generated implicitly in the mutation process through the emergent interaction of multiple linear terms. By this method it is possible to acquire nonlinear relations that exist in the training data without addition of hidden layers or imposition of explicit nonlinear terms in the network. We smoothed and captured a set of expert rules with an adaptive network. The motivation for this was to (1) realize a speed advantage over traditional rule-based simulations; (2) have variability in the intelligent objects not possible by rule-based systems but provided by adaptive systems: and (3) maintain the understandability of rule-based simulations. A set of binary rules was smoothed and converted into a simple set of arithmetic statements, where continuous, non-binary rules are permitted. A neural network, called the expert network, was developed to capture this rule set, which it was able to do with zero error. The expert network is also capable of learning a nonmonotonic term without a hidden layer. The trained network in feedforward operation is fast running, compact, and traceable to the rule base.

  20. Negative Ions Enhance Survival of Membrane Protein Complexes

    NASA Astrophysics Data System (ADS)

    Liko, Idlir; Hopper, Jonathan T. S.; Allison, Timothy M.; Benesch, Justin L. P.; Robinson, Carol V.

    2016-06-01

    Membrane protein complexes are commonly introduced to the mass spectrometer solubilized in detergent micelles. The collisional activation used to remove the detergent, however, often causes protein unfolding and dissociation. As in the case for soluble proteins, electrospray in the positive ion mode is most commonly used for the study of membrane proteins. Here we show several distinct advantages of employing the negative ion mode. Negative polarity can yield lower average charge states for membrane proteins solubilized in saccharide detergents, with enhanced peak resolution and reduced adduct formation. Most importantly, we demonstrate that negative ion mode electrospray ionization (ESI) minimizes subunit dissociation in the gas phase, allowing access to biologically relevant oligomeric states. Together, these properties mean that intact membrane protein ions can be generated in a greater range of solubilizing detergents. The formation of negative ions, therefore, greatly expands the possibilities of using mass spectrometry on this intractable class of protein.

  1. Negative Ions Enhance Survival of Membrane Protein Complexes.

    PubMed

    Liko, Idlir; Hopper, Jonathan T S; Allison, Timothy M; Benesch, Justin L P; Robinson, Carol V

    2016-06-01

    Membrane protein complexes are commonly introduced to the mass spectrometer solubilized in detergent micelles. The collisional activation used to remove the detergent, however, often causes protein unfolding and dissociation. As in the case for soluble proteins, electrospray in the positive ion mode is most commonly used for the study of membrane proteins. Here we show several distinct advantages of employing the negative ion mode. Negative polarity can yield lower average charge states for membrane proteins solubilized in saccharide detergents, with enhanced peak resolution and reduced adduct formation. Most importantly, we demonstrate that negative ion mode electrospray ionization (ESI) minimizes subunit dissociation in the gas phase, allowing access to biologically relevant oligomeric states. Together, these properties mean that intact membrane protein ions can be generated in a greater range of solubilizing detergents. The formation of negative ions, therefore, greatly expands the possibilities of using mass spectrometry on this intractable class of protein. Graphical Abstract ᅟ. PMID:27106602

  2. Negative Ions Enhance Survival of Membrane Protein Complexes

    NASA Astrophysics Data System (ADS)

    Liko, Idlir; Hopper, Jonathan T. S.; Allison, Timothy M.; Benesch, Justin L. P.; Robinson, Carol V.

    2016-04-01

    Membrane protein complexes are commonly introduced to the mass spectrometer solubilized in detergent micelles. The collisional activation used to remove the detergent, however, often causes protein unfolding and dissociation. As in the case for soluble proteins, electrospray in the positive ion mode is most commonly used for the study of membrane proteins. Here we show several distinct advantages of employing the negative ion mode. Negative polarity can yield lower average charge states for membrane proteins solubilized in saccharide detergents, with enhanced peak resolution and reduced adduct formation. Most importantly, we demonstrate that negative ion mode electrospray ionization (ESI) minimizes subunit dissociation in the gas phase, allowing access to biologically relevant oligomeric states. Together, these properties mean that intact membrane protein ions can be generated in a greater range of solubilizing detergents. The formation of negative ions, therefore, greatly expands the possibilities of using mass spectrometry on this intractable class of protein.

  3. Ultraviolet femtosecond laser ionization mass spectrometry.

    PubMed

    Imasaka, Totaro

    2008-01-01

    For this study, multiphoton ionization/mass spectrometry using an ultraviolet (UV) femtosecond laser was employed for the trace analysis of organic compounds. Some of the molecules, such as dioxins, contain several chlorine atoms and have short excited-state lifetimes due to a "heavy atom" effect. A UV femtosecond laser is, then, useful for efficient resonance excitation and subsequent ionization. A technique of multiphoton ionization using an extremely short laser pulse (e.g., <10 fs), referred to as "impulsive ionization," may have a potential for use in fragmentation-free ionization, thus providing information on molecular weight in mass spectrometry. PMID:18302290

  4. Low-density ionization behavior

    SciTech Connect

    Baker, G.A. Jr.

    1995-04-01

    As part of a continuing study of the physics of matter under extreme conditions, I give some results on matter at extremely low density. In particular I compare a quantum mechanical calculation of the pressure for atomic hydrogen with the corresponding pressure given by Thomas-Fermi theory. (This calculation differs from the ``confined atom`` approximation in a physically significant way.) Since Thomas-Fermi theory in some sense, represents the case of infinite nuclear charge, these cases should represent extremes. Comparison is also made with Saha theory, which considers ionization from a chemical point of view, but is weak on excited-state effects. In this theory, the pressure undergoes rapid variation as electron ionization levels are passed. This effect is in contrast to the smooth behavior of the Thomas-Fermi fixed temperature, complete ionization occurs in the low density limit, I study the case where the temperature goes appropriately to zero with the density. Although considerable modification is required, Saha theory is closer to the actual results for this case than is Thomas-Fermi theory.

  5. Theory of dissociative tunneling ionization

    NASA Astrophysics Data System (ADS)

    Svensmark, Jens; Tolstikhin, Oleg I.; Madsen, Lars Bojer

    2016-05-01

    We present a theoretical study of the dissociative tunneling ionization process. Analytic expressions for the nuclear kinetic energy distribution of the ionization rates are derived. A particularly simple expression for the spectrum is found by using the Born-Oppenheimer (BO) approximation in conjunction with the reflection principle. These spectra are compared to exact non-BO ab initio spectra obtained through model calculations with a quantum mechanical treatment of both the electronic and nuclear degrees of freedom. In the regime where the BO approximation is applicable, imaging of the BO nuclear wave function is demonstrated to be possible through reverse use of the reflection principle, when accounting appropriately for the electronic ionization rate. A qualitative difference between the exact and BO wave functions in the asymptotic region of large electronic distances is shown. Additionally, the behavior of the wave function across the turning line is seen to be reminiscent of light refraction. For weak fields, where the BO approximation does not apply, the weak-field asymptotic theory describes the spectrum accurately.

  6. Ionization coefficients in gas mixtures

    NASA Astrophysics Data System (ADS)

    Marić, D.; Šašić, O.; Jovanović, J.; Radmilović-Rađenović, M.; Petrović, Z. Lj.

    2007-03-01

    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 [Marić, D., Radmilović-Rađenović, M., Petrović, Z.Lj., 2005. On parametrization and mixture laws for electron ionization coefficients. Eur. Phys. J. D 35, 313-321.].

  7. Nanotip Ambient Ionization Mass Spectrometry.

    PubMed

    Zhou, Zhenpeng; Lee, Jae Kyoo; Kim, Samuel C; Zare, Richard N

    2016-05-17

    A method called nanotip ambient ionization mass spectrometry (NAIMS) is described, which applies high voltage between a tungsten nanotip and a metal plate to generate a plasma in which ionized analytes on the surface of the metal plate are directed to the inlet and analyzed by a mass spectrometer. The dependence of signal intensity is investigated as a function of the tip-to-plate distance, the tip size, the voltage applied at the tip, and the current. These parameters are separately optimized to achieve sensitivity or high spatial resolution. A partially observable Markov decision process is used to achieve a stabilized plasma as well as high ionization efficiency. As a proof of concept, the NAIMS technique has been applied to phenanthrene and caffeine samples for which the limits of detection were determined to be 0.14 fmol for phenanthrene and 4 amol for caffeine and to a printed caffeine pattern for which a spatial resolution of 8 ± 2 μm, and the best resolution of 5 μm, was demonstrated. The limitations of NAIMS are also discussed. PMID:27087600

  8. The elements of design knowledge capture

    NASA Technical Reports Server (NTRS)

    Freeman, Michael S.

    1988-01-01

    This paper will present the basic constituents of a design knowledge capture effort. This will include a discussion of the types of knowledge to be captured in such an effort and the difference between design knowledge capture and more traditional knowledge base construction. These differences include both knowledge base structure and knowledge acquisition approach. The motivation for establishing a design knowledge capture effort as an integral part of major NASA programs will be outlined, along with the current NASA position on that subject. Finally the approach taken in design knowledge capture for Space Station will be contrasted with that used in the HSTDEK project.

  9. Neutron capture cross section of 136 Xe

    NASA Astrophysics Data System (ADS)

    Daugherty, Sean; Albert, Joshua; Johnson, Tessa; O'Conner, Thomasina; Kaufman, Lisa

    2015-04-01

    136 Xe is an important 0 νββ candidate, studied in experiments such as EXO-200 and, in the future, nEXO. These experiments require a precise study of neutron capture for their background models. The neutron capture cross section of 136 Xe has been measured at the Detector for Advanced Capture Experiments (DANCE) at the Los Alamos Neutron Science Center. A neutron beam ranging from thermal energy to 100 keV was incident on a gas cell filled with isotopically pure 136 Xe . We will discuss the measurement of partial neutron capture cross sections at thermal and first neutron resonance energies along with corresponding capture gamma cascades.

  10. Negative Enrichment of Target Cells by Microfluidic Affinity Chromatography

    PubMed Central

    Li, Peng; Gao, Yan; Pappas, Dimitri

    2011-01-01

    A three-dimensional microfluidic channel was developed for high purity cell separations. This system featured high capture affinity using multiple vertical inlets to an affinity surface. In cell separations, positive selection (capture of the target cell) is usually employed. Negative enrichment, the capture of non-target cells and elution of target cells, has distinct advantages over positive selection. In negative enrichment, target cells are not labeled, and are not subjected to strenuous elution conditions or dilution. As a result, negative enrichment systems are amenable to multi-step processes in microfluidic systems. In previous work, we reported cell capture enhancement effects at vertical inlets to the affinity surface. In this study, we designed a chip that has multiple vertical and horizontal channels, forming a three-dimensional separation system. Enrichment of target cells showed separation purities of 92-96%, compared with straight-channel systems (77% purity). A parallelized chip was also developed for increased sample throughput. A two-channel showed similar separation purity with twice the sample flow rate. This microfluidic system, featuring high separation purity, ease of fabrication and use, is suitable for cell separations when subsequent analysis of target cells is required. PMID:21939198

  11. Exertional myopathy in a grizzly bear (Ursus arctos) captured by leghold snare.

    PubMed

    Cattet, Marc; Stenhouse, Gordon; Bollinger, Trent

    2008-10-01

    We diagnosed exertional myopathy (EM) in a grizzly bear (Ursus arctos) that died approximately 10 days after capture by leghold snare in west-central Alberta, Canada, in June 2003. The diagnosis was based on history, post-capture movement data, gross necropsy, histopathology, and serum enzyme levels. We were unable to determine whether EM was the primary cause of death because autolysis precluded accurate evaluation of all tissues. Nevertheless, comparison of serum aspartate aminotransferase and creatine kinase concentrations and survival between the affected bear and other grizzly bears captured by leghold snare in the same research project suggests EM also occurred in other bears, but that it is not generally a cause of mortality. We propose, however, occurrence of nonfatal EM in grizzly bears after capture by leghold snare has potential implications for use of this capture method, including negative effects on wildlife welfare and research data. PMID:18957653

  12. Polarization phenomena in multiphoton ionization of atoms

    NASA Technical Reports Server (NTRS)

    Jacobs, V. L.

    1973-01-01

    The theory of multiphoton ionization for an atomic system of arbitrary complexity is developed using a density matrix formalism. An expression is obtained which determines the differential N-photon ionization cross section as a function of the polarization states of the target atom and the incident radiation. The parameters which characterize the photoelectron angular distribution are related to the general reduced matrix elements for the N-photon transition. Two-photon ionization of unpolarized atoms is treated as an illustration of the use of the theory. The dependence of the multiphoton ionization cross section on the polarization state of the incident radiation, which has been observed in two- and three-photon ionization of Cs, is accounted for by the theory. Finally, the photoelectron spin polarization produced by the multiphoton ionization of unpolarized atoms, like the analogous polarization resulting from single-photon ionization, is found to depend on the circular polarization of the incident radiation.

  13. Relativistic ionization fronts in gas jets

    NASA Astrophysics Data System (ADS)

    Lemos, Nuno; Dias, J. M.; Gallacher, J. G.; Issac, R. C.; Fonseca, R. A.; Lopes, N. C.; Silva, L. O.; Mendonça, J. T.; Jaroszynski, D. A.

    2006-10-01

    A high-power ultra-short laser pulse propagating through a gas jet, ionizes the gas by tunnelling ionization, creating a relativistic plasma-gas interface. The relativistic ionization front that is created can be used to frequency up-shift electromagnetic radiation either in co-propagation or in counter-propagation configurations. In the counter-propagation configuration, ionization fronts can act as relativistic mirrors for terahertz radiation, leading to relativistic double Doppler frequency up-shift to the visible range. In this work, we identified and explored, the parameters that optimize the key features of relativistic ionization fronts for terahertz radiation reflection. The relativistic ionization front generated by a high power laser (TOPS) propagating in a supersonic gas jet generated by a Laval nozzle has been fully characterized. We have also performed detailed two-dimensional relativistic particle-in-cell simulations with Osiris 2.0 to analyze the generation and propagation of the ionization fronts.

  14. The susceptibility of TaOx-based memristors to high dose rate ionizing radiation and total ionizing dose

    DOE PAGESBeta

    McLain, Michael Lee; Sheridan, Timothy J.; Hjalmarson, Harold Paul; Mickel, Patrick R.; Hanson, Donald J.; McDonald, Joseph K.; Hughart, David Russell; Marinella, Matthew J.

    2014-11-11

    This paper investigates the effects of high dose rate ionizing radiation and total ionizing dose (TID) on tantalum oxide (TaOx) memristors. Transient data were obtained during the pulsed exposures for dose rates ranging from approximately 5.0 ×107 rad(Si)/s to 4.7 ×108 rad(Si)/s and for pulse widths ranging from 50 ns to 50 μs. The cumulative dose in these tests did not appear to impact the observed dose rate response. Static dose rate upset tests were also performed at a dose rate of ~3.0 ×108 rad(Si)/s. This is the first dose rate study on any type of memristive memory technology. Inmore » addition to assessing the tolerance of TaOx memristors to high dose rate ionizing radiation, we also evaluated their susceptibility to TID. The data indicate that it is possible for the devices to switch from a high resistance off-state to a low resistance on-state in both dose rate and TID environments. The observed radiation-induced switching is dependent on the irradiation conditions and bias configuration. Furthermore, the dose rate or ionizing dose level at which a device switches resistance states varies from device to device; the enhanced susceptibility observed in some devices is still under investigation. As a result, numerical simulations are used to qualitatively capture the observed transient radiation response and provide insight into the physics of the induced current/voltages.« less

  15. Earth-Mars transfers with ballistic capture

    NASA Astrophysics Data System (ADS)

    Topputo, F.; Belbruno, E.

    2015-04-01

    We construct a new type of transfer from the Earth to Mars, which ends in ballistic capture. This results in substantial savings in capture from that of a classical Hohmann transfer under certain assumptions as well as an alternate way for spacecraft to transfer to Mars. This is accomplished by first becoming captured at Mars, very distant from the planet, and then from there, following a ballistic capture transfer to a desired altitude within a ballistic capture set. This is achieved by using stable sets, which are sets of initial conditions whose orbits satisfy a definition of orbital stability. This transfer type may be of interest for Mars missions because of low capture , flexibility of launch period from the Earth, moderate flight time, and the benign nature of the capture process.

  16. Capture of uncontrolled satellites - A flight demonstration

    NASA Technical Reports Server (NTRS)

    Lenox, H. M.

    1984-01-01

    NASA is presently exploring concepts, systems, and devices for capturing uncontrolled or non-operational satellites. Understanding of this type capture involves development of requirements and options, analyses of approaches, and extensive ground simulations. The verification of an approach is expected to require flight demonstrations of the concepts and hardware to assure confidence in application. This paper addresses a flight demonstration involving the Shuttle, an Orbital Maneuvering Vehicle (OMV), a capture mechanism, and a target vehicle capable of providing characteristic motion. A mission scenario is projected which demonstrates a capture concept, mission sequencing, capture vehicle potential, and overall capture possibilities with man-in-the-loop control. The proposed demonstration is considered a stepping stone to more demanding capture requirements. On-orbit activities are deliberately constrained to existing technology and projected systems and hardware capability for the year 1990.

  17. The solenoid muon capture system for the MELC experiment

    NASA Astrophysics Data System (ADS)

    Djilkibaev, Rashid M.; Lobashev, Vladimir M.

    1996-05-01

    A solenoid capture system for the MELC experiment in which the efficiency of soft muon generation from the primary proton (600 MeV) is 10-4 in comparison with 10-8 for ordinary schemes has been proposed. Both signs of muons with an intensity 1011 μ-/sec for negative and 2×1011 μ+/sec for positive component can be generated by a pulse proton beam with an average current up to ≂200 μA. A detail 3-D calculation of the magnetic field for the MELC setup are presented. Production of muon from pion decay in solenoid capture system is studied. The target life time and radiation condition of the superconducting coil are considered.

  18. Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture

    NASA Astrophysics Data System (ADS)

    Tan, Xin; Kou, Liangzhi; Tahini, Hassan A.; Smith, Sean C.

    2015-12-01

    Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 1013 cm-2 or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility.

  19. Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture

    PubMed Central

    Tan, Xin; Kou, Liangzhi; Tahini, Hassan A.; Smith, Sean C.

    2015-01-01

    Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 1013 cm−2 or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility. PMID:26621618

  20. Semantic and affective salience: the role of meaning and preference in attentional capture and disengagement.

    PubMed

    Biggs, Adam T; Kreager, Ryan D; Gibson, Bradley S; Villano, Michael; Crowell, Charles R

    2012-04-01

    Emotion appears to have a substantial impact on a wide variety of attentional functions. However, stimuli that elicit affective responses also tend to be meaningful. Here we attempted to disentangle the effects of meaning from the effects of affect on attentional capture by irrelevant distractors. Experiment 1 used a previously unfamiliar distractor stimulus, and manipulated the amount of knowledge provided to observers about the distractor. The results suggested that increases in meaning can reduce attentional capture. Experiments 2 and 3 used both familiar and unfamiliar symbols (baseball logos and flags, respectively) as distractors. Critically, of the two familiar symbols, one was rated as affective-positive and the other was rated as affective-negative. As in Experiment 1, the results showed that unfamiliar distractors can capture attention. In addition, the results also suggested that the two affective distractors captured attention (so long as they were sufficiently intense). This finding suggests that while increased knowledge can reduce capture, affect can restore an item's ability to capture attention. Finally, the results of Experiment 4 showed that observers were slower to disengage from a negative item than from a positive item. This evidence emphasizes the differential roles of semantic knowledge versus affect on attentional capture. PMID:22390289

  1. Small Particles Intact Capture Experiment (SPICE)

    NASA Astrophysics Data System (ADS)

    Nishioka, Ken-Ji; Carle, G. C.; Bunch, T. E.; Mendez, David J.; Ryder, J. T.

    The Small Particles Intact Capture Experiment (SPICE) will develop technologies and engineering techniques necessary to capture nearly intact, uncontaminated cosmic and interplanetary dust particles (IDP's). Successful capture of such particles will benefit the exobiology and planetary science communities by providing particulate samples that may have survived unaltered since the formation of the solar system. Characterization of these particles may contribute fundamental data to our knowledge of how these particles could have formed into our planet Earth and, perhaps, contributed to the beginnings of life. The term 'uncontaminated' means that captured cosmic and IDP particles are free of organic contamination from the capture process and the term 'nearly intact capture' means that their chemical and elemental components are not materially altered during capture. The key to capturing cosmic and IDP particles that are organic-contamination free and nearly intact is the capture medium. Initial screening of capture media included organic foams, multiple thin foil layers, and aerogel (a silica gel); but, with the exception of aerogel, the requirements of no contamination or nearly intact capture were not met. To ensure no contamination of particles in the capture process, high-purity aerogel was chosen. High-purity aerogel results in high clarity (visual clearness), a useful quality in detection and recovery of embedded captured particles from the aerogel. P. Tsou at the Jet Propulsion Laboratory (JPL) originally described the use of aerogel for this purpose and reported laboratory test results. He has flown aerogel as a 'GAS-can Lid' payload on STS-47 and is evaluating the results. The Timeband Capture Cell Experiment (TICCE), a Eureca 1 experiment, is also flying aerogel and is scheduled for recovery in late April.

  2. Small Particles Intact Capture Experiment (SPICE)

    NASA Technical Reports Server (NTRS)

    Nishioka, Ken-Ji; Carle, G. C.; Bunch, T. E.; Mendez, David J.; Ryder, J. T.

    1994-01-01

    The Small Particles Intact Capture Experiment (SPICE) will develop technologies and engineering techniques necessary to capture nearly intact, uncontaminated cosmic and interplanetary dust particles (IDP's). Successful capture of such particles will benefit the exobiology and planetary science communities by providing particulate samples that may have survived unaltered since the formation of the solar system. Characterization of these particles may contribute fundamental data to our knowledge of how these particles could have formed into our planet Earth and, perhaps, contributed to the beginnings of life. The term 'uncontaminated' means that captured cosmic and IDP particles are free of organic contamination from the capture process and the term 'nearly intact capture' means that their chemical and elemental components are not materially altered during capture. The key to capturing cosmic and IDP particles that are organic-contamination free and nearly intact is the capture medium. Initial screening of capture media included organic foams, multiple thin foil layers, and aerogel (a silica gel); but, with the exception of aerogel, the requirements of no contamination or nearly intact capture were not met. To ensure no contamination of particles in the capture process, high-purity aerogel was chosen. High-purity aerogel results in high clarity (visual clearness), a useful quality in detection and recovery of embedded captured particles from the aerogel. P. Tsou at the Jet Propulsion Laboratory (JPL) originally described the use of aerogel for this purpose and reported laboratory test results. He has flown aerogel as a 'GAS-can Lid' payload on STS-47 and is evaluating the results. The Timeband Capture Cell Experiment (TICCE), a Eureca 1 experiment, is also flying aerogel and is scheduled for recovery in late April.

  3. Polarized negative ions

    SciTech Connect

    Haeberli, W.

    1981-04-01

    This paper presents a survey of methods, commonly in use or under development, to produce beams of polarized negative ions for injection into accelerators. A short summary recalls how the hyperfine interaction is used to obtain nuclear polarization in beams of atoms. Atomic-beam sources for light ions are discussed. If the best presently known techniques are incorporated in all stages of the source, polarized H/sup -/ and D/sup -/ beams in excess of 10 ..mu..A can probably be achieved. Production of polarized ions from fast (keV) beams of polarized atoms is treated separately for atoms in the H(25) excited state (Lamb-Shift source) and atoms in the H(1S) ground state. The negative ion beam from Lamb-Shift sources has reached a plateau just above 1 ..mu..A, but this beam current is adequate for many applications and the somewhat lower beam current is compensated by other desirable characteristics. Sources using fast polarized ground state atoms are in a stage of intense development. The next sections summarize production of polarized heavy ions by the atomic beam method, which is well established, and by optical pumping, which has recently been demonstrated to yield very large nuclear polarization. A short discussion of proposed ion sources for polarized /sup 3/He/sup -/ ions is followed by some concluding remarks.

  4. Bad data packet capture device

    DOEpatents

    Chen, Dong; Gara, Alan; Heidelberger, Philip; Vranas, Pavlos

    2010-04-20

    An apparatus and method for capturing data packets for analysis on a network computing system includes a sending node and a receiving node connected by a bi-directional communication link. The sending node sends a data transmission to the receiving node on the bi-directional communication link, and the receiving node receives the data transmission and verifies the data transmission to determine valid data and invalid data and verify retransmissions of invalid data as corresponding valid data. A memory device communicates with the receiving node for storing the invalid data and the corresponding valid data. A computing node communicates with the memory device and receives and performs an analysis of the invalid data and the corresponding valid data received from the memory device.

  5. Subsurface capture of carbon dioxide

    SciTech Connect

    Blount, Gerald; Siddal, Alvin A.; Falta, Ronald W.

    2014-07-22

    A process and apparatus of separating CO.sub.2 gas from industrial off-gas source in which the CO.sub.2 containing off-gas is introduced deep within an injection well. The CO.sub.2 gases are dissolved in the, liquid within the injection well while non-CO.sub.2 gases, typically being insoluble in water or brine, are returned to the surface. Once the CO.sub.2 saturated liquid is present within the injection well, the injection well may be used for long-term geologic storage of CO.sub.2 or the CO.sub.2 saturated liquid can be returned to the surface for capturing a purified CO.sub.2 gas.

  6. Brownian motion using video capture

    NASA Astrophysics Data System (ADS)

    Salmon, Reese; Robbins, Candace; Forinash, Kyle

    2002-05-01

    Although other researchers had previously observed the random motion of pollen grains suspended in water through a microscope, Robert Brown's name is associated with this behaviour based on observations he made in 1828. It was not until Einstein's work in the early 1900s however, that the origin of this irregular motion was established to be the result of collisions with molecules which were so small as to be invisible in a light microscope (Einstein A 1965 Investigations on the Theory of the Brownian Movement ed R Furth (New York: Dover) (transl. Cowper A D) (5 papers)). Jean Perrin in 1908 (Perrin J 1923 Atoms (New York: Van Nostrand-Reinhold) (transl. Hammick D)) was able, through a series of painstaking experiments, to establish the validity of Einstein's equation. We describe here the details of a junior level undergraduate physics laboratory experiment where students used a microscope, a video camera and video capture software to verify Einstein's famous calculation of 1905.

  7. Neutron capture therapy for melanoma

    SciTech Connect

    Coderre, J.A.; Glass, J.D.; Micca, P.; Fairchild, R.G.

    1988-01-01

    The development of boron-containing compounds which localize selectively in tumor may require a tumor-by-tumor type of approach that exploits any metabolic pathways unique to the particular type of tumor. Melanin-producing melanomas actively transport and metabolize aromatic amino acids for use as precursors in the synthesis of the pigment melanin. It has been shown that the boron-containing amino acid analog p-borono-phenylalanine (BPA) is selectively accumulated in melanoma tissue, producing boron concentrations in tumor that are within the range estimated to be necessary for successful boron neutron capture therapy (BNCT). We report here the results of therapy experiments carried out at the Brookhaven Medical Research Reactor (BMRR). 21 refs., 5 figs., 3 tabs.

  8. Workshop on neutron capture therapy

    SciTech Connect

    Fairchild, R.G.; Bond, V.P.

    1986-01-01

    Potentially optimal conditions for Neutron Capture Therapy (NCT) may soon be in hand due to the anticipated development of band-pass filtered beams relatively free of fast neutron contaminations, and of broadly applicable biomolecules for boron transport such as porphyrins and monoclonal antibodies. Consequently, a number of groups in the US are now devoting their efforts to exploring NCT for clinical application. The purpose of this Workshop was to bring these groups together to exchange views on significant problems of mutual interest, and to assure a unified and effective approach to the solutions. Several areas of preclinical investigation were deemed to be necessary before it would be possible to initiate clinical studies. As neither the monomer nor the dimer of sulfhydryl boron hydride is unequivocally preferable at this time, studies on both compounds should be continued until one is proven superior.

  9. Shock tube study of ionization rates of NaCl-contaminated argon

    NASA Technical Reports Server (NTRS)

    Schneider, K.-P.; Park, C.

    1975-01-01

    Electron density, electron temperature, and concentration of excited sodium atoms are measured in the weakly ionized regime behind a shock wave in impure argon in a shock tube using microwave techniques and spectrally resolved radiometry. Evidence is presented to show that an apparent increase in the rate of ionization is due to electron detachment of negative chlorine ions produced from sodium chloride vapor contained as an impurity. To be consistent with this chemical model, rate coefficients are found in the temperature range between 5500 and 8600 K for the dissociation of NaCl into an ion pair, dissociation of NaCl into a neutral pair, and electron detachment of a negative chlorine ion. Electron temperature is lower than heavy-particle temperature by roughly 1000 K. The electron-argon impact-ionization rate coefficient is a weak function of electron temperature in contradiction to expectation.

  10. Electron Capture Dissociation of Trivalent Metal Ion-Peptide Complexes

    NASA Astrophysics Data System (ADS)

    Flick, Tawnya G.; Donald, William A.; Williams, Evan R.

    2013-02-01

    With electrospray ionization from aqueous solutions, trivalent metal ions readily adduct to small peptides resulting in formation of predominantly (peptide + MT - H)2+, where MT = La, Tm, Lu, Sm, Ho, Yb, Pm, Tb, or Eu, for peptides with molecular weights below ~1000 Da, and predominantly (peptide + MT)3+ for larger peptides. ECD of (peptide + MT - H)2+ results in extensive fragmentation from which nearly complete sequence information can be obtained, even for peptides for which only singly protonated ions are formed in the absence of the metal ions. ECD of these doubly charged complexes containing MT results in significantly higher electron capture efficiency and sequence coverage than peptide-divalent metal ion complexes that have the same net charge. Formation of salt-bridge structures in which the metal ion coordinates to a carboxylate group are favored even for (peptide + MT)3+. ECD of these latter complexes for large peptides results in electron capture by the protonation site located remotely from the metal ion and predominantly c/ z fragments for all metals, except Eu3+, which undergoes a one electron reduction and only loss of small neutral molecules and b/ y fragments are formed. These results indicate that solvation of the metal ion in these complexes is extensive, which results in the electrochemical properties of these metal ions being similar in both the peptide environment and in bulk water.

  11. Electron capture by bare ions on water molecules

    NASA Astrophysics Data System (ADS)

    Rivarola, Roberto; Montenegro, Pablo; Monti, Juan; Fojón, Omar

    2016-05-01

    Single electron capture from water molecules by impact of bare ions is theoretically investigated at intermediate and high collision energies. This reaction is of fundamental importance to determine the deposition of energy in biological matter irradiated with ion beams (hadrontherapy), dominating other ionizing processes of the target at low-intermediate impact velocities and giving principal contributions to the energetic region where electronic stopping power maximizes. The dynamics of the interaction between the aggregates is described within the one active-electron continuum distorted wave-eikonal initial state theory. The orbitals of the target in the ground state are represented using the approximate self-consistent complete neglect of differential orbitals (SC-CNDO) model. The contribution of different molecular orbitals on the partial cross sections to selected n-principal quantum number projectile states is discriminated as well as the collaboration of these n-states on total cross sections. The latter ones are dominated by capture to n=1 states at high enough energies decreasing their contribution as n increases.

  12. Femtosecond Laser Ionization of Organic Amines with Very Low Ionization Potential.

    NASA Astrophysics Data System (ADS)

    Yatsuhashi, Tomoyuki; Obayashi, Takashi; Tanaka, Michinori; Murakami, Masanao; Nakashima, Nobuaki

    2006-03-01

    The interaction between high intensity femtosecond laser and molecules is one of the most attractive areas in laser chemistry and ionization is the most fundamental subject. Theoretical consideration successfully reproduced the ionization behavior of rare gases. However, the understanding of ionization mechanisms of large molecules is difficult more than those of rare gases due to their complexity. Generally speaking, molecules are harder to ionize than rare gases even if they have the same ionization potential. The suppressed ionization phenomena are one of the important features of molecular ionization. Hankin et al. examined 23 organic molecules with ionization potentials between 8.25 and 11.52 eV. We have examined ionization and/ or fragmentation of many organic molecules, including aromatic compounds, halogenated compounds, methane derivatives etc. at various wavelengths below 10^16 Wcm-2. In order to investigate the nature of molecular ionization, it is interesting to examine a variety of molecule in a wide range of ionization potential. In this study, we examined several organic amines because we can explore the uninvestigated ionization potential range down to 5.95 eV. In addition to the significant suppression of the ionization rates, stepwise ionization behavior, which was not observed in rare gases, was observed.

  13. An experimental investigation of mesospheric ionization

    NASA Technical Reports Server (NTRS)

    Mitchell, J. D.

    1973-01-01

    Mesospheric ionization and its variability are examined. Data were obtained primarily by the parachute-borne blunt probe technique conducted in coordinated rocket experiments at White Sands Missile Range, New Mexico and Wallops Island, Virginia. Electrical conductivity measurements and deduced charge density values from ten rocket launches are presented and discussed. Positive ion conductivity and electron density were found to be relatively invariant with height between 45 and 60 km. Variations in positive conductivity of a factor of two and enhancements in negative conductivity by as much as a factor of four were measured by the blunt probe. A simple lumped parameter ion chemistry model is shown to satisfactorily explain the charge density values for the undisturbed lower D-region. Implications of the data in terms of this model are considered. The principal loss mechanism for positive ions in the 45 to 60 km. region is concluded to be dissociative recombination. Electron densities deduced from the conductivity data are explained by detachment involving a minor neutral constituent which is mixed between 65 and 45 km. and then cuts off sharply below 45 km. A correlation study involving blunt probe measurements shows relatively good agreement between variations in positive conductivity and temperature.

  14. Direct-Semidirect Thermal Neutron Capture Calculations

    SciTech Connect

    Arbanas, G; Dietrich, F S; Kerman, A K

    2005-12-20

    A method for computing direct-semidirect (DSD) neutron radiative capture is presented and applied to thermal neutron capture on {sup 19}F, {sup 27}Al, {sup 28,29.30}Si, {sup 35,37}Cl, {sup 39,41}K, {sup 56}Fe, and {sup 238}U, in support of data evaluation effort at the O.R.N.L. The DSD method includes both direct and semidirect capture; the latter is a core-polarization term in which the giant dipole resonance is formed. We study the effects of a commonly used ''density'' approximation to the EM operator and find it to be unsatisfactory for the nuclei considered here. We also study the magnitude of semidirect capture relative to the pure direct capture. Furthermore, we compare our results with those obtained from another direct capture code (Tedca [17]). We also compare our results with those obtained from analytical expression for external capture derived by Lane and Lynn [3], and its extension to include internal capture [7]. To estimate the effect of nuclear deformation on direct capture, we computed direct thermal capture on {sup 238}U with and without imposition of spherical symmetry. Direct capture for a spherically symmetric {sup 238}U was approximately 6 mb, while a quadrupole deformation of 0.215 on the shape of {sup 238}U lowers this cross section down to approximately 2 mb. This result suggests that effects of nuclear deformation on direct capture warrant a further study. We also find out that contribution to the direct capture on {sup 238}U from the nuclear interior significantly cancels that coming from the exterior region, and hence both contributions must be taken into account. We reproduced a well known discrepancy between the computed and observed branching ratios in {sup 56}Fe(n,{gamma}). This will lead us to revisit the concept of doorway states in the particle-hole model.

  15. Dielectrophoretic Capture and Genetic Analysis of Single Neuroblastoma Tumor Cells

    PubMed Central

    Carpenter, Erica L.; Rader, JulieAnn; Ruden, Jacob; Rappaport, Eric F.; Hunter, Kristen N.; Hallberg, Paul L.; Krytska, Kate; O’Dwyer, Peter J.; Mosse, Yael P.

    2014-01-01

    Our understanding of the diversity of cells that escape the primary tumor and seed micrometastases remains rudimentary, and approaches for studying circulating and disseminated tumor cells have been limited by low throughput and sensitivity, reliance on single parameter sorting, and a focus on enumeration rather than phenotypic and genetic characterization. Here, we utilize a highly sensitive microfluidic and dielectrophoretic approach for the isolation and genetic analysis of individual tumor cells. We employed fluorescence labeling to isolate 208 single cells from spiking experiments conducted with 11 cell lines, including 8 neuroblastoma cell lines, and achieved a capture sensitivity of 1 tumor cell per 106 white blood cells (WBCs). Sample fixation or freezing had no detectable effect on cell capture. Point mutations were accurately detected in the whole genome amplification product of captured single tumor cells but not in negative control WBCs. We applied this approach to capture 144 single tumor cells from 10 bone marrow samples of patients suffering from neuroblastoma. In this pediatric malignancy, high-risk patients often exhibit wide-spread hematogenous metastasis, but access to primary tumor can be difficult or impossible. Here, we used flow-based sorting to pre-enrich samples with tumor involvement below 0.02%. For all patients for whom a mutation in the Anaplastic Lymphoma Kinase gene had already been detected in their primary tumor, the same mutation was detected in single cells from their marrow. These findings demonstrate a novel, non-invasive, and adaptable method for the capture and genetic analysis of single tumor cells from cancer patients. PMID:25133137

  16. Negative Entropy of Life

    NASA Astrophysics Data System (ADS)

    Goradia, Shantilal

    2015-10-01

    We modify Newtonian gravity to probabilistic quantum mechanical gravity to derive strong coupling. If this approach is valid, we should be able to extend it to the physical body (life) as follows. Using Boltzmann equation, we get the entropy of the universe (137) as if its reciprocal, the fine structure constant (ALPHA), is the hidden candidate representing the negative entropy of the universe which is indicative of the binary information as its basis (http://www.arXiv.org/pdf/physics0210040v5). Since ALPHA relates to cosmology, it must relate to molecular biology too, with the binary system as the fundamental source of information for the nucleotides of the DNA as implicit in the book by the author: ``Quantum Consciousness - The Road to Reality.'' We debate claims of anthropic principle based on the negligible variation of ALPHA and throw light on thermodynamics. We question constancy of G in multiple ways.

  17. Negative Optical Torque

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Ng, Jack; Ding, Kun; Fung, Kin Hung; Lin, Zhifang; Chan, C. T.

    2014-09-01

    Light carries angular momentum, and as such it can exert torques on material objects. Applications of these opto-mechanical effects were limited initially due to their smallness in magnitude, but later becomes powerful and versatile after the invention of laser. Novel and practical approaches for harvesting light for particle rotation have since been demonstrated, where the structure is always subjected to a positive optical torque along a certain axis if the incident angular momentum has a positive projection on the same axis. We report here an interesting phenomenon of ``negative optical torque'', meaning that incoming photons carrying angular momentum rotate an object in the opposite sense. Surprisingly this can be realized quite straightforwardly in simple planar structures. Field retardation is a necessary condition and discrete rotational symmetry of material object plays an important role. The optimal conditions are explored and explained.

  18. Negative Optical Torque

    PubMed Central

    Chen, Jun; Ng, Jack; Ding, Kun; Fung, Kin Hung; Lin, Zhifang; Chan, C. T.

    2014-01-01

    Light carries angular momentum, and as such it can exert torques on material objects. Applications of these opto-mechanical effects were limited initially due to their smallness in magnitude, but later becomes powerful and versatile after the invention of laser. Novel and practical approaches for harvesting light for particle rotation have since been demonstrated, where the structure is always subjected to a positive optical torque along a certain axis if the incident angular momentum has a positive projection on the same axis. We report here an interesting phenomenon of “negative optical torque”, meaning that incoming photons carrying angular momentum rotate an object in the opposite sense. Surprisingly this can be realized quite straightforwardly in simple planar structures. Field retardation is a necessary condition and discrete rotational symmetry of material object plays an important role. The optimal conditions are explored and explained. PMID:25226863

  19. Do `negative' temperatures exist?

    NASA Astrophysics Data System (ADS)

    Lavenda, B. H.

    1999-06-01

    A modification of the second law is required for a system with a bounded density of states and not the introduction of a `negative' temperature scale. The ascending and descending branches of the entropy versus energy curve describe particle and hole states, having thermal equations of state that are given by the Fermi and logistic distributions, respectively. Conservation of energy requires isentropic states to be isothermal. The effect of adiabatically reversing the field is entirely mechanical because the only difference between the two states is their energies. The laws of large and small numbers, leading to the normal and Poisson approximations, characterize statistically the states of infinite and zero temperatures, respectively. Since the heat capacity also vanishes in the state of maximum disorder, the third law can be generalized in systems with a bounded density of states: the entropy tends to a constant as the temperature tends to either zero or infinity.

  20. Negative pion capture in atomic nuclei near the closed neutron shell at N = 82

    NASA Astrophysics Data System (ADS)

    Butsev, V. S.; Chultem, D.; Zhivotov, I. N.

    1982-07-01

    The results of studies of the excitation of high-spin states in stopped π - absorption in Nd, Pr, Ce, La and Ba nuclei are reported. States with spins 7 -, 8 - and {19}/{2}- have been identified. The isometric ratios for the isotopes 131Ba and 133Ba have been determined to be equal to σ m/σ g = 5.1±0.5 and 2.2±0.3, respectively. For the isomers 134mCs and 135mCs, the isotopic ratio is found to be σ m1/σ m2 = 8.9±2.3. The distinguishing features of the mechanisms of excitation of high-spin states by stopped π - and fast protons are discussed.

  1. The SWAN Captures Variance at the Negative and Positive Ends of the ADHD Symptom Dimension

    ERIC Educational Resources Information Center

    Arnett, Anne B.; Pennington, Bruce F.; Friend, Angela; Willcutt, Erik G.; Byrne, Brian; Samuelsson, Stefan; Olson, Richard K.

    2013-01-01

    Objective: The Strengths and Weaknesses of ADHD Symptoms and Normal Behavior (SWAN) Rating Scale differs from previous parent reports of ADHD in that it was designed to also measure variability at the positive end of the symptom spectrum. Method: The psychometric properties of the SWAN were tested and compared with an established measure of ADHD,…

  2. Novel CO{sub 2} capture. Final CRADA Report.

    SciTech Connect

    Snyder, S. W.; Energy Systems

    2009-11-30

    The goal of this work was to use electrochemically driven pH control to develop a second generation, enzyme-based contained liquid membrane (CLM) permeator to extract CO{sub 2} from a variety of coal-based flue gas streams more efficiently than does the CLM current design, while achieving performance coincident with DOE targets of less than 45% Cost of electricity (COE) in 2007 and less than 20% COE in 2012. Central to this goal the CLM would be alkaline (>pH 8) at the feed gas side and acid (capture and release using Argonne's resin-wafer electrode ionization (RW-EDI) system integrated with Carbozyme's carbonic anhydrase (CA) enzyme. Argonne developed RW-EDI for pH controlled desalination of process streams (e.g. Patents 7,452,920 & 7,306,934). In the current work, Argonne captured CO{sub 2} as HCO{sub 3}{sup -} and released it as CO{sub 2}. The goal is to both capture CO{sub 2} from a simulated flue gas stream and release it within the DOE targets for increase in COE. Initial performance results indicate that the 2012 COE targets are achievable with the developed technology. The design is subject to patent-hold. This task was funded in an exploratory phase, so no process optimization was attempted. Argonne believes that with optimization this performance could be significantly improved.

  3. Research in Boron Neutron Capture Therapy at MIT LABA

    SciTech Connect

    Yanch, J.C.; Shefer, R.E.; Klinkowstein, R.E.; Howard, W.B.; Song, H.; Blackburn, B.; Binello, E.

    1997-02-01

    A 4.1 MeV tandem electrostatic accelerator designed for research into Boron Neutron Capture Therapy (BNCT) has recently been installed in the MIT Laboratory for Accelerator Beam Applications (LABA). This accelerator uses a very high current switch mode high voltage power supply in conjunction with a multi-cusp negative ion source to supply the multimilliampere current required for clinical BNCT applications. A number of individual research projects aimed at evaluating the potential of this accelerator design as a hospital-based neutron source for radiation therapy of both tumors and rheumatoid arthritis are described here. {copyright} {ital 1997 American Institute of Physics.}

  4. Ionizing Radiation and Its Risks

    PubMed Central

    Goldman, Marvin

    1982-01-01

    Penetrating ionizing radiation fairly uniformly puts all exposed molecules and cells at approximately equal risk for deleterious consequences. Thus, the original deposition of radiation energy (that is, the dose) is unaltered by metabolic characteristics of cells and tissue, unlike the situation for chemical agents. Intensely ionizing radiations, such as neutrons and alpha particles, are up to ten times more damaging than sparsely ionizing sources such as x-rays or gamma rays for equivalent doses. Furthermore, repair in cells and tissues can ameliorate the consequences of radiation doses delivered at lower rates by up to a factor of ten compared with comparable doses acutely delivered, especially for somatic (carcinogenic) and genetic effects from x- and gamma-irradiation exposure. Studies on irradiated laboratory animals or on people following occupational, medical or accidental exposures point to an average lifetime fatal cancer risk of about 1 × 10-4 per rem of dose (100 per 106 person-rem). Leukemia and lung, breast and thyroid cancer seem more likely than other types of cancer to be produced by radiation. Radiation exposures from natural sources (cosmic rays and terrestrial radioactivity) of about 0.1 rem per year yield a lifetime cancer risk about 0.1 percent of the normally occurring 20 percent risk of cancer death. An increase of about 1 percent per rem in fatal cancer risk, or 200 rem to double the “background” risk rate, is compared with an estimate of about 100 rem to double the genetic risk. Newer data suggest that the risks for low-level radiation are lower than risks estimated from data from high exposures and that the present 5 rem per year limit for workers is adequate. PMID:6761969

  5. 19. Print from copy negative (original glass plate negative in ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    19. Print from copy negative (original glass plate negative in Tippecanoe County Historical Society.) Original photo dated May 7, 1893. View north, south side. - Big Four Depot, 10 South Second Street, Lafayette, Tippecanoe County, IN

  6. Cesium Delivery System for Negative Ion Source at IPR

    SciTech Connect

    Bansal, G.; Pandya, K.; Soni, J.; Gahlaut, A.; Parmar, K. G.; Bandyopadhyay, M.; Chakraborty, A.; Singh, M. J.

    2011-09-26

    The technique of surface production of negative ions using cesium, Cs, has been efficiently exploited over the years for producing negative ion beams with increased current densities from negative ion sources used on neutral beam lines. Deposition of Cs on the source walls and the plasma grid lowers the work function and therefore enables a higher yield of H{sup -}, when hydrogen particles (H and/or H{sub x}{sup +}) strike these surfaces.A single driver RF based (100 kW, 1 MHz) negative ion source test bed, ROBIN, is being set up at IPR under a technical collaboration between IPR and IPP, Germany. The optimization of the Cs oven design to be used on this facility as well as multidriver sources is underway. The characterization experiments of such a Cs delivery system with a 1 g Cs inventory have been carried out using surface ionization technique. The experiments have been carried by delivering Cs into a vacuum chamber without plasma. The linear motion of the surface ionization detector, SID, attached with a linear motion feedthrough allows measuring the angular distribution of the Cs coming out of the oven. Based on the experimental results, a Cs oven for ROBIN has been proposed. The Cs oven design and experimental results of the prototype Cs oven are reported and discussed in the paper.

  7. XUV ionization of aligned molecules

    SciTech Connect

    Kelkensberg, F.; Siu, W.; Gademann, G.; Rouzee, A.; Vrakking, M. J. J.; Johnsson, P.; Lucchini, M.; Lucchese, R. R.

    2011-11-15

    New extreme-ultraviolet (XUV) light sources such as high-order-harmonic generation (HHG) and free-electron lasers (FELs), combined with laser-induced alignment techniques, enable novel methods for making molecular movies based on measuring molecular frame photoelectron angular distributions. Experiments are presented where CO{sub 2} molecules were impulsively aligned using a near-infrared laser and ionized using femtosecond XUV pulses obtained by HHG. Measured electron angular distributions reveal contributions from four orbitals and the onset of the influence of the molecular structure.

  8. The Tevatron Ionization Profile Monitors

    SciTech Connect

    Jansson, A.; Fitzpatrick, T.; Bowie, K.; Kwarciany, R.; Lundberg, C.; Slimmer, D.; Valerio, L.; Zagel, J.; /Fermilab

    2006-05-01

    In designing an ionization profile monitor system for the Tevatron some novel approaches were taken, in particular for the readout electronics. This was motivated by the desire to resolve the individual bunches in both beams simultaneously. For this purpose, custom made electronics originally developed for Particle Physics experiments was used to provide a fast charge integration with very low noise. The various parts of the read-out electronics have been borrowed or adapted from the KTev, CMS, MINOS and BTev experiments. The detector itself also had to be modified to provide clean signals with sufficient bandwidth. The system design will be described along with the initial results.

  9. Advanced Thin Ionization Calorimeter (ATIC)

    NASA Technical Reports Server (NTRS)

    Wefel, John P.

    1998-01-01

    This is the final report for NASA grant NAGW-4577, "Advanced Thin Ionization Calorimeter (ATIC)". This grant covered a joint project between LSU and the University of Maryland for a Concept Study of a new type of fully active calorimeter to be used to measure the energy spectra of very high energy cosmic rays, particularly Hydrogen and Helium, to beyond 1014 eV. This very high energy region has been studied with emulsion chamber techniques, but never investigated with electronic calorimeters. Technology had advanced to the point that a fully active calorimeter based upon Bismuth Germanate (BGO) scintillating crystals appeared feasible for balloon flight (and eventually space) experiments.

  10. Optical Detection of Tunneling Ionization

    SciTech Connect

    Verhoef, Aart J.; Mitrofanov, Alexander V.; Kartashov, Daniil V.; Baltuska, Andrius

    2010-04-23

    We have experimentally detected optical harmonics that are generated due to a tunneling-ionization-induced modulation of the electron density. The optical signature of electron tunneling can be isolated from concomitant optical responses by using a noncollinear pump-probe setup. Whereas previously demonstrated tools for attosecond metrology of gases, plasmas, and surfaces rely on direct detection of charged particles, detection of the background-free time-resolved optical signal, which uniquely originates from electron tunneling, offers an interesting alternative that is especially suited for systems in which free electrons cannot be directly measured.

  11. Economic and energetic analysis of capturing CO2 from ambient air.

    PubMed

    House, Kurt Zenz; Baclig, Antonio C; Ranjan, Manya; van Nierop, Ernst A; Wilcox, Jennifer; Herzog, Howard J

    2011-12-20

    Capturing carbon dioxide from the atmosphere ("air capture") in an industrial process has been proposed as an option for stabilizing global CO(2) concentrations. Published analyses suggest these air capture systems may cost a few hundred dollars per tonne of CO(2), making it cost competitive with mainstream CO(2) mitigation options like renewable energy, nuclear power, and carbon dioxide capture and storage from large CO(2) emitting point sources. We investigate the thermodynamic efficiencies of commercial separation systems as well as trace gas removal systems to better understand and constrain the energy requirements and costs of these air capture systems. Our empirical analyses of operating commercial processes suggest that the energetic and financial costs of capturing CO(2) from the air are likely to have been underestimated. Specifically, our analysis of existing gas separation systems suggests that, unless air capture significantly outperforms these systems, it is likely to require more than 400 kJ of work per mole of CO(2), requiring it to be powered by CO(2)-neutral power sources in order to be CO(2) negative. We estimate that total system costs of an air capture system will be on the order of $1,000 per tonne of CO(2), based on experience with as-built large-scale trace gas removal systems. PMID:22143760

  12. Application of amine-tethered solid sorbents for direct CO2 capture from the ambient air.

    PubMed

    Choi, Sunho; Drese, Jeffrey H; Eisenberger, Peter M; Jones, Christopher W

    2011-03-15

    While current carbon capture and sequestration (CCS) technologies for large point sources can help address the impact of CO(2) buildup on global climate change, these technologies can at best slow the rate of increase of the atmospheric CO(2) concentration. In contrast, the direct CO(2) capture from ambient air offers the potential to be a truly carbon negative technology. We propose here that amine-based solid adsorbents have significant promise as key components of a hypothetical air capture process. Specifically, the CO(2) capture characteristics of hyperbranched aminosilica (HAS) materials are evaluated here using CO(2) mixtures that simulate ambient atmospheric concentrations (400 ppm CO(2) = "air capture") as well as more traditional conditions simulating flue gas (10% CO(2)). The air capture experiments demonstrate that the adsorption capacity of HAS adsorbents are only marginally influenced even with a significant dilution of the CO(2) concentration by a factor of 250, while capturing CO(2) reversibly without significant degradation of performance in multicyclic operation. These results suggest that solid amine-based air capture processes have the potential to be an effective approach to extracting CO(2) from the ambient air. PMID:21323309

  13. Risk factors associated with capture-related death in eastern wild turkey hens

    USGS Publications Warehouse

    Nicholson, D.S.; Lochmiller, R.L.; Stewart, M.D.; Masters, R.E.; Leslie, David M., Jr.

    2000-01-01

    Capture-related mortality has been a notable risk in the handling of eastern wild turkey (Meleagris gallopavo silvestris). Our objective was to evaluate how environmental factors influence risk and identify physiological correlates that could be used to identify susceptible birds. During winter (January-March) 1995-97, 130 eastern wild turkey hens were captured in southeastern Oklahoma and radiocollared. Of those, 20 hens died ??? 14 days of capture. Serum creatine kinase activity (CK; P < 0.01), body temperature (P < 0.01), processing time (P = 0.02), and ambient temperature (P < 0.01) showed a positive relationship with mortality that occurred within 14 days of capture. Plasma corticosterone concentration (P = 0.08) and relative humidity (P < 0.01) showed a negative relationship with mortalities that occurred within 14 days post-capture. Stepwise logistic regression selected CK activity, relative humidity, and ambient temperature as the best predictors of mortality within 14 days post-capture. Our data suggest that susceptible individuals may be identified from CK activity and that capture-related mortality may be minimized by establishing guidelines of when to curtail capture operations based on various weather conditions.

  14. Impaired Contingent Attentional Capture Predicts Reduced Working Memory Capacity in Schizophrenia

    PubMed Central

    Mayer, Jutta S.; Fukuda, Keisuke; Vogel, Edward K.; Park, Sohee

    2012-01-01

    Although impairments in working memory (WM) are well documented in schizophrenia, the specific factors that cause these deficits are poorly understood. In this study, we hypothesized that a heightened susceptibility to attentional capture at an early stage of visual processing would result in working memory encoding problems. 30 patients with schizophrenia and 28 demographically matched healthy participants were presented with a search array and asked to report the orientation of the target stimulus. In some of the trials, a flanker stimulus preceded the search array that either matched the color of the target (relevant-flanker capture) or appeared in a different color (irrelevant-flanker capture). Working memory capacity was determined in each individual using the visual change detection paradigm. Patients needed considerably more time to find the target in the no-flanker condition. After adjusting the individual exposure time, both groups showed equivalent capture costs in the irrelevant-flanker condition. However, in the relevant-flanker condition, capture costs were increased in patients compared to controls when the stimulus onset asynchrony between the flanker and the search array was high. Moreover, the increase in relevant capture costs correlated negatively with working memory capacity. This study demonstrates preserved stimulus-driven attentional capture but impaired contingent attentional capture associated with low working memory capacity in schizophrenia. These findings suggest a selective impairment of top-down attentional control in schizophrenia, which may impair working memory encoding. PMID:23152783

  15. Negative Ions for Emerging Interdisciplinary Applications

    SciTech Connect

    Guharay, Samar K.

    2011-09-26

    In many applications related to ion beam-materials interactions negative ions are particularly desirable due to its merit to yield a very low surface charge-up voltage, {approx} a few volts, for both electrically isolated surfaces and insulators. Some important applications pertaining to ion beam-material interactions include surface analysis by secondary ion mass spectrometry (SIMS), voltage-contrast microscopy for semiconductor device inspection, materials processing, and ion beam lithography. These applications primarily require vacuum environments. On the other hand, a distinct area of activities constitutes formation of ions and ion transport in ambient environmental conditions, i.e., at atmospheric pressures. In this context, ion mobility spectrometry (IMS) is an important analytical device that uses negative ions and operates at ambient conditions. IMS is widely used in both physical and biological sciences including monitoring environmental conditions, security screening and disease detection. This article highlights several critical issues related to the ionization sources and ion transport in IMS. Additionally, the critical issues related to ion sources, transport and focusing are discussed in the context of SIMS with sub-micrometer spatial resolution.

  16. Accelerators and Neutron Capture Therapy

    NASA Astrophysics Data System (ADS)

    Burlon, A. A.; Kreiner, A. J.; Valda, A.

    2002-08-01

    Within the frame of Accelerator Based Boron Neutron Capture Therapy (AB-BNCT), the 7Li (p,n) 7Be reaction, relatively near its energy threshold is one of the most promising, due to its high yield and low neutron energy. In this work a thick LiF target irradiated with a proton beam was studied as a neutron source. The 1.88-2.0 MeV proton beam was produced by the tandem accelerator TANDAR at CNEA's facilities in Buenos Aires. A water-filled phantom, containing a boron sample was irradiated with the resulting neutron flux. The 10B(n,αγ)7Li boron neutron capture reaction produces a 0.478 MeV gamma ray in 94% of the cases. The neutron yield was measured through the detection of this gamma ray using a hyperpure germanium detector with an anti-Compton shield. In addition, the thermal neutron flux was evaluated at different depths inside the phantom using bare and Cd-covered gold foils. A maximum neutron thermal flux of 1.4×108 cm-2s-1mA-1 was obtained at 4.2 cm from the phantom surface. In order to optimize the design of the neutron production target and the beam shaping assembly extensive Monte Carlo Neutron and Photon (MCNP) simulations have been performed. Neutron fields from a thick LiF and a Li metal target (with both a D2O-graphite and a Al/AlF3-graphite moderator/reflector assembly) were evaluated along the centerline of a head and a whole body phantom. Simulations were carried out for 1.89, 2.0 and 2.3 MeV proton beams. The results show that it is more advantageous to irradiate the target with 2.3 MeV near-resonance protons, instead of very near threshold, because of the higher neutron yield at this energy. On the other hand, the Al/AlF3-graphite exhibits a more efficient performance than D2O in terms of tumor to maximum healthy tissue dose ratio. Treatment times of less than 15 min and tumor control probabilities larger than 98% are obtained for a 50 mA, 2.3 MeV proton beam. The alternative neutron-producing reaction 13C(d,n) is also briefly reviewed. A

  17. Atmospheric sampling glow discharge ionization source

    DOEpatents

    McLuckey, Scott A.; Glish, Gary L.

    1989-01-01

    An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above.

  18. Fluid hydrogen at high density - Pressure ionization

    NASA Technical Reports Server (NTRS)

    Saumon, Didier; Chabrier, Gilles

    1992-01-01

    The Helmholtz-free-energy model for nonideal mixtures of hydrogen atoms and molecules by Saumon and Chabrier (1991) is extended to describe dissociation and ionization in similar mixtures in chemical equilibrium. A free-energy model is given that describes partial ionization in the pressure and temperature ionization region. The plasma-phase transition predicted by the model is described for hydrogen mixtures including such components as H2, H, H(+), and e(-). The plasma-phase transition has a critical point at Tc = 15,300 K and Pc = 0.614 Mbar, and thermodynamic instability is noted in the pressure-ionization regime. The pressure dissociation and ionization of fluid hydrogen are described well with the model yielding information on the nature of the plasma-phase transition. The model is shown to be valuable for studying dissociation and ionization in astrophysical objects and in high-pressure studies where pressure and temperature effects are significant.

  19. Atmospheric sampling glow discharge ionization source

    DOEpatents

    McLuckey, S.A.; Glish, G.L.

    1989-07-18

    An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above. 3 figs.

  20. Negative Expertise: Comparing Differently Tenured Elder Care Nurses' Negative Knowledge

    ERIC Educational Resources Information Center

    Gartmeier, Martin; Lehtinen, Erno; Gruber, Hans; Heid, Helmut

    2011-01-01

    Negative expertise is conceptualised as the professional's ability to avoid errors during practice due to certain cognitive agencies. In this study, negative knowledge (i.e. knowledge about what is wrong in a certain context and situation) is conceptualised as one such agency. This study compares and investigates the negative knowledge of elder…

  1. Silica Aerogel Captures Cosmic Dust Intact

    NASA Technical Reports Server (NTRS)

    Tsou, P.

    1994-01-01

    The mesostructure of silica aerogel resembles stings of grapes, ranging in size from 10 to 100 angstrom. This fine mesostructure transmits nearly 90 percent of incident light in the visible, while providing sufficiently gentle dissipation of the kinetric energy of hypervelocity cosmic dust particles to permit their intact capture. We introduced silica aerogel in 1987 as capture medium to take advantage of its low density, fine mesostruicture and most importantly, its transparency, allowing optical location of captured micron sized particles.

  2. Techniques for capturing bighorn sheep lambs

    USGS Publications Warehouse

    Smith, Joshua B.; Walsh, Daniel P.; Goldstein, Elise J.; Parsons, Zachary D.; Karsch, Rebekah C.; Stiver, Julie R.; Cain, James W.; Raedeke, Kenneth J.; Jenks, Jonathan A.

    2014-01-01

    Low lamb recruitment is a major challenge facing managers attempting to mitigate the decline of bighorn sheep (Ovis canadensis), and investigations into the underlying mechanisms are limited because of the inability to readily capture and monitor bighorn sheep lambs. We evaluated 4 capture techniques for bighorn sheep lambs: 1) hand-capture of lambs from radiocollared adult females fitted with vaginal implant transmitters (VITs), 2) hand-capture of lambs of intensively monitored radiocollared adult females, 3) helicopter net-gunning, and 4) hand-capture of lambs from helicopters. During 2010–2012, we successfully captured 90% of lambs from females that retained VITs to ≤1 day of parturition, although we noted differences in capture rates between an area of high road density in the Black Hills (92–100%) of South Dakota, USA, and less accessible areas of New Mexico (71%), USA. Retention of VITs was 78% with pre-partum expulsion the main cause of failure. We were less likely to capture lambs from females that expelled VITs ≥1 day of parturition (range = 80–83%) or females that were collared without VITs (range = 60–78%). We used helicopter net-gunning at several sites in 1999, 2001–2002, and 2011, and it proved a useful technique; however, at one site, attempts to capture lambs led to lamb predation by golden eagles (Aquila chrysaetos). We attempted helicopter hand-captures at one site in 1999, and they also were successful in certain circumstances and avoided risk of physical trauma from net-gunning; however, application was limited. In areas of low accessibility or if personnel lack the ability to monitor females and/or VITs for extended periods, helicopter capture may provide a viable option for lamb capture.

  3. TARGETED CAPTURE IN EVOLUTIONARY AND ECOLOGICAL GENOMICS

    PubMed Central

    Jones, Matthew R.; Good, Jeffrey M.

    2016-01-01

    The rapid expansion of next-generation sequencing has yielded a powerful array of tools to address fundamental biological questions at a scale that was inconceivable just a few years ago. Various genome partitioning strategies to sequence select subsets of the genome have emerged as powerful alternatives to whole genome sequencing in ecological and evolutionary genomic studies. High throughput targeted capture is one such strategy that involves the parallel enrichment of pre-selected genomic regions of interest. The growing use of targeted capture demonstrates its potential power to address a range of research questions, yet these approaches have yet to expand broadly across labs focused on evolutionary and ecological genomics. In part, the use of targeted capture has been hindered by the logistics of capture design and implementation in species without established reference genomes. Here we aim to 1) increase the accessibility of targeted capture to researchers working in non-model taxa by discussing capture methods that circumvent the need of a reference genome, 2) highlight the evolutionary and ecological applications where this approach is emerging as a powerful sequencing strategy, and 3) discuss the future of targeted capture and other genome partitioning approaches in light of the increasing accessibility of whole genome sequencing. Given the practical advantages and increasing feasibility of high-throughput targeted capture, we anticipate an ongoing expansion of capture-based approaches in evolutionary and ecological research, synergistic with an expansion of whole genome sequencing. PMID:26137993

  4. Opportunity Captures 'Lion King' Panorama

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Click on the image for Opportunity Captures 'Lion King' Panorama (QTVR)

    This approximate true-color panorama, dubbed 'Lion King,' shows 'Eagle Crater' and the surrounding plains of Meridiani Planum. It was obtained by the Mars Exploration Rover Opportunity's panoramic camera on sols 58 and 60 using infrared (750-nanometer), green (530-nanometer) and blue (430-nanometer) filters.

    This is the largest panorama obtained yet by either rover. It was taken in eight segments using six filters per segment, for a total of 558 images and more than 75 megabytes of data. Additional lower elevation tiers were added to ensure that the entire crater was covered in the mosaic.

    This panorama depicts a story of exploration including the rover's lander, a thorough examination of the outcrop, a study of the soils at the near-side of the lander, a successful exit from Eagle Crater and finally the rover's next desination, the large crater dubbed 'Endurance'.

  5. Light capture by human cones.

    PubMed Central

    Chen, B; Makous, W

    1989-01-01

    1. The variation in visual efficiency of light with varying pupillary entry (the Stiles-Crawford effect) was measured to determine the proportion of light incident on the cones that escapes them without recovery by other cones. 2. The variation in detectability of interference fringes with varying pupillary entry of the interfering beams was measured to determine the proportion of incident light that was recaptured by cones in the dark stripes after escaping cones in the bright stripes of the fringes. 3. By exclusion, these observations determine the variation, with varying pupillary entry, in the proportion of incident light that was captured and absorbed by the first cones it entered. 4. Some 70-90% of the light absorbed by the cones when it passes through the centre of the pupil, is entirely lost to the visual system if it passes instead through the margin of the (dilated) pupil. 5. Over half the light that cones absorb when the light enters the margin of the pupil is light that has previously passed through other cones. 6. If the spread of recaptured light is assumed to be Gaussian, its standard deviation is at most one minute of visual angle. 7. Such recaptured light makes a previously unknown contribution to the various Stiles-Crawford effects. PMID:2607444

  6. Electron impact ionization of glycolaldehyde

    NASA Astrophysics Data System (ADS)

    Ptasinska, Sylwia; Denifl, Stephan; Scheier, Paul; Märk, Tilmann D.

    2005-05-01

    Positive ion formation upon electron impact ionization of the monomeric and dimeric form of glycolaldehyde is studied with high electron energy resolution. In the effusive neutral beam of evaporated monomeric glycolaldehyde some ions with a mass larger than the monomer indicate the presence of weakly bound neutral dimers. The yield of all ions that originate from the electron impact ionization of these neutral dimers exhibit a strong temperature dependence that can be interpreted as being due to the formation of dimers via three body collisions and thermal decomposition of the dimeric form back into monomers at higher temperatures. Ion efficiency curves are measured and analyzed for the 10 most abundant product cations of monomeric glycolaldehyde. The appearance energies of the parent ion signals of the monomer and dimer of glycolaldehyde (10.2 and 9.51 eV, respectively) are lower than the appearance energy of the parent cation of the more complex sugar deoxyribose that was recently determined to be 10.51 eV.

  7. Ionizing radiation and orthopaedic prostheses

    NASA Astrophysics Data System (ADS)

    Rimnac, Clare M.; Kurtz, Steven M.

    2005-07-01

    Ultra high molecular weight polyethylene (UHMWPE) materials have been used successfully as one half of the bearing couple (against metallic alloys or ceramics) in total hip and total knee joint replacements for four decades. This review describes the impact of ionizing radiation (used for sterilization and for microstructural modification via crosslinking) on the performance of UHMWPE total joint replacement components. Gamma radiation sterilization in air leads to oxidative degradation of UHMWPE joint components that occurs during shelf-aging and also during in vivo use. Efforts to mitigate oxidative degradation of UHMWPE joint components include gamma radiation sterilization in inert barrier-packaging and processing treatments to reduce free radicals. Ionizing radiation (both gamma and electron-beam) has recently been used to form highly crosslinked UHMWPEs that have better adhesive and abrasive wear resistance than non-crosslinked UHMWPE, thereby potentially improving the long-term performance of total joint replacements. Along with increased wear resistance, however, there are deleterious changes to ductility and fracture resistance of UHMWPE, and an increased risk of fracture of these components remains a clinical concern.

  8. Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory.

    PubMed

    Sissay, Adonay; Abanador, Paul; Mauger, François; Gaarde, Mette; Schafer, Kenneth J; Lopata, Kenneth

    2016-09-01

    Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagating the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals. PMID:27608987

  9. Ultrafast isomerization initiated by X-ray core ionization

    NASA Astrophysics Data System (ADS)

    Liekhus-Schmaltz, Chelsea E.; Tenney, Ian; Osipov, Timur; Sanchez-Gonzalez, Alvaro; Berrah, Nora; Boll, Rebecca; Bomme, Cedric; Bostedt, Christoph; Bozek, John D.; Carron, Sebastian; Coffee, Ryan; Devin, Julien; Erk, Benjamin; Ferguson, Ken R.; Field, Robert W.; Foucar, Lutz; Frasinski, Leszek J.; Glownia, James M.; Gühr, Markus; Kamalov, Andrei; Krzywinski, Jacek; Li, Heng; Marangos, Jonathan P.; Martinez, Todd J.; McFarland, Brian K.; Miyabe, Shungo; Murphy, Brendan; Natan, Adi; Rolles, Daniel; Rudenko, Artem; Siano, Marco; Simpson, Emma R.; Spector, Limor; Swiggers, Michele; Walke, Daniel; Wang, Song; Weber, Thorsten; Bucksbaum, Philip H.; Petrovic, Vladimir S.

    2015-09-01

    Rapid proton migration is a key process in hydrocarbon photochemistry. Charge migration and subsequent proton motion can mitigate radiation damage when heavier atoms absorb X-rays. If rapid enough, this can improve the fidelity of diffract-before-destroy measurements of biomolecular structure at X-ray-free electron lasers. Here we study X-ray-initiated isomerization of acetylene, a model for proton dynamics in hydrocarbons. Our time-resolved measurements capture the transient motion of protons following X-ray ionization of carbon K-shell electrons. We Coulomb-explode the molecule with a second precisely delayed X-ray pulse and then record all the fragment momenta. These snapshots at different delays are combined into a `molecular movie' of the evolving molecule, which shows substantial proton redistribution within the first 12 fs. We conclude that significant proton motion occurs on a timescale comparable to the Auger relaxation that refills the K-shell vacancy.

  10. Tunneling Ionization Time Resolved by Backpropagation

    NASA Astrophysics Data System (ADS)

    Ni, Hongcheng; Saalmann, Ulf; Rost, Jan-Michael

    2016-07-01

    We determine the ionization time in tunneling ionization by an elliptically polarized light pulse relative to its maximum. This is achieved by a full quantum propagation of the electron wave function forward in time, followed by a classical backpropagation to identify tunneling parameters, in particular, the fraction of electrons that has tunneled out. We find that the ionization time is close to zero for single active electrons in helium and in hydrogen if the fraction of tunneled electrons is large. We expect our analysis to be essential to quantify ionization times for correlated electron motion.

  11. Tunneling Ionization Time Resolved by Backpropagation.

    PubMed

    Ni, Hongcheng; Saalmann, Ulf; Rost, Jan-Michael

    2016-07-01

    We determine the ionization time in tunneling ionization by an elliptically polarized light pulse relative to its maximum. This is achieved by a full quantum propagation of the electron wave function forward in time, followed by a classical backpropagation to identify tunneling parameters, in particular, the fraction of electrons that has tunneled out. We find that the ionization time is close to zero for single active electrons in helium and in hydrogen if the fraction of tunneled electrons is large. We expect our analysis to be essential to quantify ionization times for correlated electron motion. PMID:27447504

  12. Two-step single-ionization mechanisms

    SciTech Connect

    Boeyen, R. W. van; Doering, J. P.; Watanabe, N.; Cooper, J. W.; Coplan, M. A.; Moore, J. H.

    2006-03-15

    In a recent publication [Phys. Rev. Lett. 92, 233202 (2004)] two different electron impact double ionization (e,3e) mechanisms were identified and the way in which two-electron momentum distributions for atoms and molecules could be obtained by triple coincidence (e,3e) measurements was discussed. The apparatus used detected the two ejected electrons both in and out of the scattering plane at an angle of 45 deg. to the momentum transfer direction in triple coincidence with the scattered electron. Ejected electrons detected out of the scattering plane were shown to be a result of two-step double ionization processes. With the same apparatus we have made double coincidence (e,2e) measurements of electron impact single ionization cross sections for ionization of magnesium 3s (valence) and 2p and 2s (inner) shell electrons at incident energies from 400 to 3000 eV in order to obtain more information about two-step ionization. The experimental results were compared with distorted-wave and plane-wave Born approximations carried out to second order. For the experimental conditions, two-step ionization processes involving one ionizing collision and a second elastic collision with the atomic core are the dominant contribution to the measured cross sections. Calculations are in moderate agreement with the data. The angular distributions of the ionized electrons in these two-step ionizations reflect the initial momentum distributions of the target electrons, a result that is analogous with the earlier (e,3e) measurements.

  13. Ionization probes of molecular structure and chemistry

    SciTech Connect

    Johnson, P.M.

    1993-12-01

    Various photoionization processes provide very sensitive probes for the detection and understanding of the spectra of molecules relevant to combustion processes. The detection of ionization can be selective by using resonant multiphoton ionization or by exploiting the fact that different molecules have different sets of ionization potentials. Therefore, the structure and dynamics of individual molecules can be studied even in a mixed sample. The authors are continuing to develop methods for the selective spectroscopic detection of molecules by ionization, and to use these methods for the study of some molecules of combustion interest.

  14. On the ionization potential of molecular oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Gardner, J. L.

    1974-01-01

    The ionization potential of O2 was measured by the technique of high resolution photoelectron spectroscopy taking into account the influence of rotational structure on the shape of the vibrational bands. A value of 12.071 + or - .001 eV (1027.1 + or - 0.1 A) was found for the ionization potential. A lowering of the ionization potential caused by a branch-head when delta N = -2 gave an appearance potential for ionization of 12.068 + or - .001 eV (1027.4 + or - 0.1 A).

  15. Development of dielectric-barrier-discharge ionization.

    PubMed

    Guo, Cheng'an; Tang, Fei; Chen, Jin; Wang, Xiaohao; Zhang, Sichun; Zhang, Xinrong

    2015-03-01

    Dielectric-barrier-discharge ionization is an ambient-ionization technique. Since its first description in 2007, it has attracted much attention in such fields as biological analysis, food safety, mass-spectrometry imaging, forensic identification, and reaction monitoring for its advantages, e.g., low energy consumption, solvent-free method, and easy miniaturization. In this review a brief introduction to dielectric barrier discharge is provided, and then a detailed introduction to the dielectric-barrier-discharge-ionization technique is given, including instrumentation, applications, and mechanistic studies. Based on the summary of reported work, possible future uses of this type of ionization source are discussed at the end. PMID:25510973

  16. Tunneling ionization time-resolved by backpropagation

    NASA Astrophysics Data System (ADS)

    Ni, Hongcheng; Saalmann, Ulf; Rost, Jan M.; Max-Planck-Institut für Physik komplexer Systeme Team

    2016-05-01

    We determine the ionization time in tunneling ionization by an elliptically polarized light pulse relative to its maximum. This is achieved by a full quantum propagation of the electron wave function forward in time, followed by a classical backpropagation to identify tunneling parameters, in particular the fraction of electrons that has tunneled out. We find, that the ionization time is close to zero for single active electrons in helium and in hydrogen if the fraction of tunneled electrons is large. We expect our analysis to be essential to quantify ionization times for correlated electron motion. This work was supported by Alexander von Humboldt Foundation.

  17. Multiple ionization of xenon by proton impact

    SciTech Connect

    Manson, S.T.; DuBois, R.D.

    1987-12-01

    An experimental and theoretical study of multiple ionization of xenon for 0.2- to 2.0-MeV proton impact was made. Absolute cross sections for producing xenon ions with charges from +1 to +3 were measured, and calculations of subshell cross sections were performed. Experiment and theory are consistent and indicate that multiple ionization of xenon by fast protons occurs via inner-shell ionization. This is in contrast to the lighter noble gases where direct multiple outer shell ionization can be predominant.

  18. Reversal electron attachment ionizer for detection of trace species

    NASA Technical Reports Server (NTRS)

    Bernius, Mark T. (Inventor); Chutjian, Ara (Inventor)

    1990-01-01

    An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of said electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus.

  19. Coagulase-Negative Staphylococci

    PubMed Central

    Heilmann, Christine; Peters, Georg

    2014-01-01

    SUMMARY The definition of the heterogeneous group of coagulase-negative staphylococci (CoNS) is still based on diagnostic procedures that fulfill the clinical need to differentiate between Staphylococcus aureus and those staphylococci classified historically as being less or nonpathogenic. Due to patient- and procedure-related changes, CoNS now represent one of the major nosocomial pathogens, with S. epidermidis and S. haemolyticus being the most significant species. They account substantially for foreign body-related infections and infections in preterm newborns. While S. saprophyticus has been associated with acute urethritis, S. lugdunensis has a unique status, in some aspects resembling S. aureus in causing infectious endocarditis. In addition to CoNS found as food-associated saprophytes, many other CoNS species colonize the skin and mucous membranes of humans and animals and are less frequently involved in clinically manifested infections. This blurred gradation in terms of pathogenicity is reflected by species- and strain-specific virulence factors and the development of different host-defending strategies. Clearly, CoNS possess fewer virulence properties than S. aureus, with a respectively different disease spectrum. In this regard, host susceptibility is much more important. Therapeutically, CoNS are challenging due to the large proportion of methicillin-resistant strains and increasing numbers of isolates with less susceptibility to glycopeptides. PMID:25278577

  20. Improved negative ion source

    DOEpatents

    Delmore, J.E.

    1984-05-01

    A method and apparatus for providing a negative ion source accelerates electrons away from a hot filament electron emitter into a region of crossed electric and magnetic fields arranged in a magnetron configuration. During a portion of the resulting cycloidal path, the electron velocity is reduced below its initial value. The electron accelerates as it leaves the surface at a rate of only slightly less than if there were no magnetic field, thereby preventing a charge buildup at the surface of the emitter. As the electron traverses the cycloid, it is decelerated during the second, third, and fourth quadrants, then reaccelerated as it approaches the end of the fourth quadrant to regain its original velocity. The minimum velocity occurs during the fourth quadrant, and corresponds to an electron temperature of 200 to 500/sup 0/C for the electric and magnetic fields commonly encountered in the ion sources of magnetic sector mass spectrometers. An ion source using the above-described thermalized electrons is also disclosed.