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Sample records for ionized tetrahydrofuran studied

  1. An (e, 2e + ion) study of low-energy electron-impact ionization and fragmentation of tetrahydrofuran with high mass and energy resolutions.

    PubMed

    Ren, Xueguang; Pflüger, Thomas; Weyland, Marvin; Baek, Woon Yoon; Rabus, Hans; Ullrich, Joachim; Dorn, Alexander

    2014-10-01

    We study the low-energy (E0 = 26 eV) electron-impact induced ionization and fragmentation of tetrahydrofuran using a reaction microscope. All three final-state charged particles, i.e., two outgoing electrons and one fragment ion, are detected in triple coincidence such that the momentum vectors and, consequently, the kinetic energies for charged reaction products are determined. The ionic fragments are clearly identified in the experiment with a mass resolution of 1 amu. The fragmentation pathways of tetrahydrofuran are investigated by measuring the ion kinetic energy spectra and the binding energy spectra where an energy resolution of 1.5 eV has been achieved using the recently developed photoemission electron source. Here, we will discuss the fragmentation reactions for the cations C4H8O(+), C4H7O(+), C2H3O(+), C3H6(+), C3H5(+), C3H3(+), CH3O(+), CHO(+), and C2H3(+). PMID:25296813

  2. An (e, 2e + ion) study of low-energy electron-impact ionization and fragmentation of tetrahydrofuran with high mass and energy resolutions

    SciTech Connect

    Ren, Xueguang Pflüger, Thomas; Weyland, Marvin; Baek, Woon Yoon; Rabus, Hans; Ullrich, Joachim; Dorn, Alexander

    2014-10-07

    We study the low-energy (E{sub 0} = 26 eV) electron-impact induced ionization and fragmentation of tetrahydrofuran using a reaction microscope. All three final-state charged particles, i.e., two outgoing electrons and one fragment ion, are detected in triple coincidence such that the momentum vectors and, consequently, the kinetic energies for charged reaction products are determined. The ionic fragments are clearly identified in the experiment with a mass resolution of 1 amu. The fragmentation pathways of tetrahydrofuran are investigated by measuring the ion kinetic energy spectra and the binding energy spectra where an energy resolution of 1.5 eV has been achieved using the recently developed photoemission electron source. Here, we will discuss the fragmentation reactions for the cations C{sub 4}H{sub 8}O{sup +}, C{sub 4}H{sub 7}O{sup +}, C{sub 2}H{sub 3}O{sup +}, C{sub 3}H{sub 6}{sup +}, C{sub 3}H{sub 5}{sup +}, C{sub 3}H{sub 3}{sup +}, CH{sub 3}O{sup +}, CHO{sup +}, and C{sub 2}H{sub 3}{sup +}.

  3. Tetrahydrofuran

    Integrated Risk Information System (IRIS)

    Tetrahydrofuran ; CASRN 109 - 99 - 9 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic E

  4. Experimental and theoretical triple-differential cross sections for tetrahydrofuran ionized by low-energy 26-eV-electron impact

    NASA Astrophysics Data System (ADS)

    Ali, Esam; Ren, XueGuang; Dorn, Alexander; Ning, Chuangang; Colgan, James; Madison, Don

    2016-06-01

    We report an experimental and theoretical study of low-energy electron-impact ionization of tetrahydrofuran, which is a molecule of biological interest. The experiments were performed using an advanced reaction microscope specially built for electron-impact ionization studies. The theoretical calculations were performed within the molecular three-body distorted-wave model. Reasonably good agreement is found between experiment and theory.

  5. Cross sections for ionization of tetrahydrofuran by protons at energies between 300 and 3000 keV

    NASA Astrophysics Data System (ADS)

    Wang, Mingjie; Rudek, Benedikt; Bennett, Daniel; de Vera, Pablo; Bug, Marion; Buhr, Ticia; Baek, Woon Yong; Hilgers, Gerhard; Rabus, Hans

    2016-05-01

    Double-differential cross sections for ionization of tetrahydrofuran by protons with energies from 300 to 3000 keV were measured at the Physikalisch-Technische Bundesanstalt ion accelerator facility. The electrons emitted at angles between 15∘ and 150∘ relative to the ion-beam direction were detected with an electrostatic hemispherical electron spectrometer. Single-differential and total ionization cross sections have been derived by integration. The experimental results are compared to the semiempirical Hansen-Kocbach-Stolterfoht model as well as to the recently reported method based on the dielectric formalism. The comparison to the latter showed good agreement with experimental data in a broad range of emission angles and energies of secondary electrons. The scaling property of ionization cross sections for tetrahydrofuran was also investigated. Compared to molecules of different size, the ionization cross sections of tetrahydrofuran were found to scale with the number of valence electrons at large impact parameters.

  6. Theoretical and experimental quantification of doubly and singly differential cross sections for electron-induced ionization of isolated tetrahydrofuran molecules

    DOE PAGESBeta

    Champion, Christophe; Quinto, Michele A.; Bug, Marion U.; Baek, Woon Y.; Weck, Philippe F.

    2014-07-29

    Electron-induced ionization of the commonly used surrogate of the DNA sugar-phosphate backbone, namely, the tetrahydrofuran molecule, is here theoretically described within the 1st Born approximation by means of quantum-mechanical approach. Comparisons between theory and recent experiments are reported in terms of doubly and singly differential cross sections.

  7. Theoretical and experimental quantification of doubly and singly differential cross sections for electron-induced ionization of isolated tetrahydrofuran molecules

    SciTech Connect

    Champion, Christophe; Quinto, Michele A.; Bug, Marion U.; Baek, Woon Y.; Weck, Philippe F.

    2014-07-29

    Electron-induced ionization of the commonly used surrogate of the DNA sugar-phosphate backbone, namely, the tetrahydrofuran molecule, is here theoretically described within the 1st Born approximation by means of quantum-mechanical approach. Comparisons between theory and recent experiments are reported in terms of doubly and singly differential cross sections.

  8. Inhalation developmental toxicology studies: Teratology study of tetrahydrofuran in mice and rats: Final report

    SciTech Connect

    Mast, T.J.; Evanoff, J.J.; Stoney, K.H.; Westerberg, R.B.; Rommereim, R.L.; Weigel, R.J.

    1988-08-01

    Tetrahydrofuran (THF), a four-carbon cyclic ether, is widely used as an industrial solvent. Although it has been used in large quantities for many years, few long-term toxicology studies, and no reproductive or developmental studies, have been conducted on THF. This study addresses the potential for THF to cause developmental toxicity in rodents by exposing Sprague-Dawley rats and Swiss (CD-1) mice to 0, 600, 1800, or 5000 ppm tetrahydrofuran (THF) vapors, 6 h/day, 7 dy/wk. Each treatment group consisted of 10 virgin females (for comparison), and approx.33 positively mated rats or mice. Positively mated mice were exposed on days 6--17 of gestation (dg), and rats on 6--19 dg. The day of plug or sperm detection was designated as O dg. Body weights were obtained throughout the study period, and uterine and fetal body weights were obtained at sacrifice (rats, 20 dg; mice, 18 dg). Implants were enumerated and their status recorded and live fetuses were examined for gross, visceral, skeletal, and soft-tissue craniofacial defects. 27 refs., 6 figs., 23 tabs.

  9. NMR studies of the conformation and motion of tetrahydrofuran in graphite intercalation compounds

    SciTech Connect

    Caplan, D. F.

    1991-11-01

    The behavior of tetrahydrofuran (THF) molecules intercalated in graphite layers in compounds Cs(THF){sub 1.3}C{sub 24} and K(THF){sub 2.5}C{sub 24} was studied by proton NMR. The graphite layers in these compounds impose a uniform ordering on the THF molecules, giving rise to sharp NMR spectra. Experimental and simulated proton NMR spectra were used to investigate geometry, orientation and conformation of intercalated THF, and to determine whether pseudorotation, a large amplitude low-frequency vibration observed in gaseous THF, can also occur in the constrained environment provided by the graphite intercalation compounds. Deuterium and multiple quantum proton NMR spectra were also simulated in order to determine if these techniques could further refine the proton NMR results.

  10. Observations related to tetrahydrofuran and methane hydrates for laboratory studies of hydrate-bearing sediments

    USGS Publications Warehouse

    Lee, J.Y.; Yun, T.S.; Santamarina, J.C.; Ruppel, C.

    2007-01-01

    The interaction among water molecules, guest gas molecules, salts, and mineral particles determines the nucleation and growth behavior of gas hydrates in natural sediments. Hydrate of tetrahydrofuran (THF) has long been used for laboratory studies of gas hydrate-bearing sediments to provide close control on hydrate concentrations and to overcome the long formation history of methane hydrate from aqueous phase methane in sediments. Yet differences in the polarizability of THF (polar molecule) compared to methane (nonpolar molecule) raise questions about the suitability of THF as a proxy for methane in the study of hydrate-bearing sediments. From existing data and simple macroscale experiments, we show that despite its polar nature, THF's large molecular size results in low permittivity, prevents it from dissolving precipitated salts, and hinders the solvation of ions on dry mineral surfaces. In addition, the interfacial tension between water and THF hydrate is similar to that between water and methane hydrate. The processes that researchers choose for forming hydrate in sediments in laboratory settings (e.g., from gas, liquid, or ice) and the pore-scale distribution of the hydrate that is produced by each of these processes likely have a more pronounced effect on the measured macroscale properties of hydrate-bearing sediments than do differences between THF and methane hydrates themselves.

  11. Experimental study on the effect of ammonia on the phase behavior of tetrahydrofuran clathrates.

    PubMed

    Vu, Tuan Hoang; Gloesener, Elodie; Choukroun, Mathieu; Ibourichene, Anaïs; Hodyss, Robert

    2014-11-26

    Clathrate hydrates, ice-like crystalline compounds in which small guest molecules are enclosed inside cages formed by tetrahedrally hydrogen-bonded water molecules, are naturally abundant on Earth and are generally expected to exist on icy celestial bodies. A prototypical example is Saturn's moon Titan, where dissociation of methane clathrates, a major crustal component, could contribute significantly to the replenishment of atmospheric methane. Ammonia is an important clathrate inhibiting agent that may be present (potentially at high concentrations) in Titan's interior. In this study, low-temperature Raman experiments are conducted to examine the dissociation point of tetrahydrofuran clathrates, an ambient-pressure analogue of methane clathrates, over a wide range of ammonia concentrations from 0 to 25 wt %. A phase diagram for the H2O-THF-NH3 system is generated, showing two main results: (i) ammonia lowers the dissociation point of clathrate hydrates to a similar extent compared to the melting of water ice and (ii) THF clathrate exhibits a "liquidus-like" behavior in the presence of ammonia, with a eutectic temperature of about 203.6 K. As temperatures higher than this estimated eutectic are anticipated within Titan's icy crust, these results imply that partial dissociation of clathrates can occur readily and may contribute to outgassing from the interior. PMID:24940841

  12. Analytical validation applied to simultaneous determination of solvents dichloromethane (DCM), methyl isobutyl ketone (MIBK), tetrahydrofuran (THF) and toluene (TOL) in urine by headspace extraction and injection on chromatographic system with a flame ionization detector

    NASA Astrophysics Data System (ADS)

    Muna, E. D. M.; Pereira, R. P.

    2016-07-01

    The determination of the volatile organic solvents dichloromethane (DCM), methyl isobutyl ketone (MIBK), tetrahydrofuran (THF) and toluene (TOL) is applied on toxicological monitoring of employees in various industrial activities. The gas chromatography technique with flame ionization detector and headspace injection system has been applied. The analytical procedure developed allows the simultaneous determination of the above-mentioned solvents and the accuracy of the method was tested following the INMETRO guidelines through the DOQ-CGRE 008 Rev.04-July/2011.

  13. Photofragmentation of tetrahydrofuran molecules in the vacuum-ultraviolet region via superexcited states studied by fluorescence spectroscopy

    SciTech Connect

    Wasowicz, Tomasz J.; Dampc, Marcin; Zubek, Mariusz; Kivimaeki, Antti; Simone, Monica de; Coreno, Marcello

    2011-03-15

    Photofragmentation of tetrahydrofuran molecules in the vacuum-ultraviolet region, producing excited atomic and molecular fragments, has been studied over the energy range 14-68 eV using photon-induced fluorescence spectroscopy. Excited hydrogen atoms H(n), n = 3-11, have been detected by observation of the H{sub {alpha}} to H{sub i} lines of the Balmer series. The diatomic CH(A{sup 2}{Delta}), CH(B{sup 2}{Sigma}{sup -}) and C{sub 2}(d{sup 3}{Pi}{sub g}) fragments, which are excited to low vibrational and high rotational levels are identified by their A{sup 2}{Delta}{yields}X{sup 2}{Pi}{sub r}, B{sup 2}{Sigma}{sup -}{yields}X{sup 2}{Pi}{sub r} and d{sup 3}{Pi}{sub g}{yields}a{sup 3}{Pi}{sub u} emission bands, respectively. Dissociation efficiency curves for CH(A{sup 2}{Delta}) and H(n), n = 3-7, have been obtained in the photon energy ranges from their appearance thresholds up to 68 eV. The appearance energies for CH(A{sup 2}{Delta}) and H(n), n = 3-7, have been determined and are compared with estimated fragmentation energy limits in order to discuss the possible fragmentation processes. In the present studies, superexcited states of tetrahydrofuran are found, which dissociate into the above excited atomic and molecular fragments.

  14. Molecular dynamics study on the nucleation of methane + tetrahydrofuran mixed guest hydrate.

    PubMed

    Wu, Jyun-Yi; Chen, Li-Jen; Chen, Yan-Ping; Lin, Shiang-Tai

    2016-04-21

    The nucleation of methane (CH4), tetrahydrofuran (THF), and CH4 + THF hydrates are investigated by microsecond MD simulations. These three systems exhibit distinct structural developments in the aqueous phase quantified by the formation of cage structures of hydrogen bonded water molecules. The development of a cluster of cages in the CH4 system is limited by the scarce CH4 molecules in the solution, while in the THF system it is limited by the short lifetime of cages. In the CH4 + THF mixed guest system, a small cluster of caged CH4 molecules can be rapidly stabilized by abundant neighboring cages of THF molecules. Therefore, the induction time of the CH4 + THF mixed guest system is found to be significantly shorter than that of the pure CH4 and pure THF systems. Furthermore, the structure of cages found in the initially formed cage clusters are often different from the typical 5(12)6(n) (n = 0, 2, 3, 4) cages observed in clathrate hydrate systems. The cluster of cages may grow or transform into structure I or II clathrate hydrate in the later stages. PMID:26750660

  15. Acoustical studies of some derivatives of 1,5-benzodiazepines formamide and tetrahydrofuran solutions at 298.15 K

    NASA Astrophysics Data System (ADS)

    Baluja, S.; Movaliya, J.; Godvani, N.

    2009-12-01

    Some derivatives of 1,5-benzodiazepines have been synthesized and characterized by TLC, IR, NMR, and Mass Spectral data. The ultrasonic velocity, density and viscosity of these synthesized compounds have been measured in dimethyl formamide and tetrahydrofuran at 298.15 K. From these experimental data, various acoustical parameters such as isentropic compressibility, intermolecular free path length, molar compressibility, Rao’s molar sound function, relaxation strength, internal pressure, free volume etc., have been calculated which helps in understanding the molecular interactions occurring in these solutions.

  16. Synthetic studies towards 1α-hydroxysolasodine from diosgenin and the unexpected tetrahydrofuran ring opening in the Birch reduction process.

    PubMed

    Liu, Chao; Xie, Fei; Zhao, Guo-Dong; Wang, De-Feng; Lou, Hong-Xiang; Liu, Zhao-Peng

    2015-12-01

    The synthesis of 1α-hydroxysolasodine from diosgenin was attempted. The Pd/C catalyst mediated dehydrogenation of diosgenin generated the 1,4,6-trien-3-one (3), which was reacted with Ac2O in pyridine in the presence of a catalytic amount of POCl3 followed by hydrolysis to give the 22-hydroxyfurostan (4) in 65% yield. Conversion of the primary 26-OH group into the azide and simultaneously 22-OH dehydration were achieved in one step by Mitsunobu reaction. Treatment of the (25R)-26-azidofurosta-1,4,6,20(22)-tetraen-3-one (5) with chlorotrimethylsilane (TMSCl)/NaI/MeCN and cyclisation in situ provided the (22R,25R)-spirosola-1,4,6-trien-3-one (6) in good yield. Stereoselective and regioselective epoxidation of trienone (6) with 30% H2O2 and 5% NaOH in methanol gave the 1α,2α-epoxy-(22R,25R)-spirosola-4,6-dien-3-one (7). Birch reduction of the epoxide (7) with Li/NH3 in THF followed by the treatment with NH4Cl, however, failed to generate the expected 1α-hydroxysolasodine, but provided a tetrahydrofuran ring opening product, (22S,25R)-1α,16β-dihydroxy-22,26-epiminocholest-4-en-3-one (8). Compounds 3 and 5-8 as well as solasodine were evaluated for their cell growth inhibitory activities against human prostate cancer PC3, human cervical carcinoma Hela, and human hepatoma HepG2 cells. At the concentration of 10 μM, only epoxide 7 displayed moderate inhibitory rates towards these cells (40-54%). PMID:26476186

  17. Tetrahydrofuran lignans from Viburnum betulifolium.

    PubMed

    Hu, Jiang; Song, Yan; Mao, Xia; Li, Hui; Shi, Xiao-Dong

    2016-09-01

    A phytochemical investigation of the EtOH extract from the aerial parts of Viburnum betulifolium Batal. afforded four new tetrahydrofuran lignans, betulifolium A-D (1, 2, 4, and 5), together with two known compounds vibsanol-9'-al (3) and sarcomeginal (6). This paper deals with the isolation and structure elucidation of the new compounds on the basis of spectroscopic methods, including 1D NMR, 2D NMR analyses and HR-ESI-MS data. PMID:27140524

  18. Structure and component dynamics in binary mixtures of poly(2-(dimethylamino)ethyl methacrylate) with water and tetrahydrofuran: A diffraction, calorimetric, and dielectric spectroscopy study.

    PubMed

    Goracci, G; Arbe, A; Alegría, A; Su, Y; Gasser, U; Colmenero, J

    2016-04-21

    We have combined X-ray diffraction, neutron diffraction with polarization analysis, small angle neutron scattering,differential scanning calorimetry, and broad band dielectric spectroscopy to investigate the structure and dynamics of binary mixtures of poly(2-(dimethylamino)ethyl methacrylate) with either water or tetrahydrofuran (THF) at different concentrations. Aqueous mixtures are characterized by a highly heterogeneous structure where water clusters coexist with an underlying nano-segregation of main chains and side groups of the polymeric matrix. THF molecules are homogeneously distributed among the polymeric nano-domains for concentrations of one THF molecule/monomer or lower. A more heterogeneous situation is found for higher THF amounts, but without evidences for solvent clusters. In THF-mixtures, we observe a remarkable reduction of the glass-transition temperature which is enhanced with increasing amount of solvent but seems to reach saturation at high THF concentrations. Adding THF markedly reduces the activation energy of the polymer β-relaxation. The presence of THF molecules seemingly hinders a slow component of this process which is active in the dry state. The aqueous mixtures present a strikingly broad glass-transition feature, revealing a highly heterogeneous behavior in agreement with the structural study. Regarding the solvent dynamics, deep in the glassy state all data can be described by an Arrhenius temperature dependence with a rather similar activation energy. However, the values of the characteristic times are about three orders of magnitude smaller for THF than for water. Water dynamics display a crossover toward increasingly higher apparent activation energies in the region of the onset of the glass transition, supporting its interpretation as a consequence of the freezing of the structuralrelaxation of the surrounding matrix. The absence of such a crossover (at least in the wide dynamic window here accessed) in THF is attributed to

  19. Structure and component dynamics in binary mixtures of poly(2-(dimethylamino)ethyl methacrylate) with water and tetrahydrofuran: A diffraction, calorimetric, and dielectric spectroscopy study

    NASA Astrophysics Data System (ADS)

    Goracci, G.; Arbe, A.; Alegría, A.; Su, Y.; Gasser, U.; Colmenero, J.

    2016-04-01

    We have combined X-ray diffraction, neutron diffraction with polarization analysis, small angle neutron scattering, differential scanning calorimetry, and broad band dielectric spectroscopy to investigate the structure and dynamics of binary mixtures of poly(2-(dimethylamino)ethyl methacrylate) with either water or tetrahydrofuran (THF) at different concentrations. Aqueous mixtures are characterized by a highly heterogeneous structure where water clusters coexist with an underlying nano-segregation of main chains and side groups of the polymeric matrix. THF molecules are homogeneously distributed among the polymeric nano-domains for concentrations of one THF molecule/monomer or lower. A more heterogeneous situation is found for higher THF amounts, but without evidences for solvent clusters. In THF-mixtures, we observe a remarkable reduction of the glass-transition temperature which is enhanced with increasing amount of solvent but seems to reach saturation at high THF concentrations. Adding THF markedly reduces the activation energy of the polymer β-relaxation. The presence of THF molecules seemingly hinders a slow component of this process which is active in the dry state. The aqueous mixtures present a strikingly broad glass-transition feature, revealing a highly heterogeneous behavior in agreement with the structural study. Regarding the solvent dynamics, deep in the glassy state all data can be described by an Arrhenius temperature dependence with a rather similar activation energy. However, the values of the characteristic times are about three orders of magnitude smaller for THF than for water. Water dynamics display a crossover toward increasingly higher apparent activation energies in the region of the onset of the glass transition, supporting its interpretation as a consequence of the freezing of the structural relaxation of the surrounding matrix. The absence of such a crossover (at least in the wide dynamic window here accessed) in THF is attributed to

  20. Fundamental studies of molecular multiphoton ionization

    SciTech Connect

    Miller, J.C.; Compton, R.N.

    1984-04-01

    For several years the authors have performed fundamental studies of molecular multiphoton ionization (MPI). We will present a potpourri of techniques and results chosen to illustrate the interesting complexities of molecular MPI. Techniques used include time-of-flight mass spectroscopy, photoelectron spectroscopy, supersonic expansion cooling of molecular beams, harmonic generation, two-color laser MPI, and polarization spectroscopy. Whenever possible the relevance of these results to resonance ionization spectroscopy schemes will be delineated. 23 references, 10 figures.

  1. Low latitude middle atmosphere ionization studies

    NASA Technical Reports Server (NTRS)

    Bassi, J. P.

    1976-01-01

    Low latitude middle atmosphere ionization was studied with data obtained from three blunt conductivity probes and one Gerdien condenser. An investigation was conducted into the effects of various ionization sources in the 40 to 65 Km altitude range. An observed enhancement of positive ion conductivity taking place during the night can be explained by an atmsopheric effect, with cosmic rays being the only source of ionization only if the ion-ion recombination coefficient (alpha sub i) is small(10 to the -7 power cu cm/s) and varies greatly with altitude. More generally accepted values of alpha sub i ( approximately equal to 3x10 to the -7 power cu cm/s) require an additional source of ionization peaking at about 65 Km, and corresponding approximately to the integrated effect of an X-ray flux measured on a rocket flown in conjunction with the ionization measurements. The reasonable assumption of an alpha sub i which does not vary with altitude in the 50-70 Km range implies an even greater value alpha sub i and a more intense and harder X-ray spectrum.

  2. Reaction of chlorine radical with tetrahydrofuran: a theoretical investigation on mechanism and reactivity in gas phase.

    PubMed

    Begum, Samiyara; Subramanian, Ranga

    2014-06-01

    Reaction of chlorine (Cl) radical with heterocyclic saturated ether, tetrahydrofuran has been studied. The detailed reactivity and mechanism of this reaction is analyzed using hybrid density functional theory (DFT), B3LYP and BB1K methods, and aug-cc-pVTZ basis set. To explore the mechanism of the reaction of tetrahydrofuran with Cl radical, four possible sites of hydrogen atom (H) abstraction pathways in tetrahydrofuran were analyzed. The barrier height and rate constants are calculated for the four H-abstraction channels. The BB1K calculated rate constant for α-axial H-abstraction is comparable with the experimentally determined rate constant. It reflects that α-axial H-abstraction is the main degradation pathway of tetrahydrofuran with Cl radical. DFT-based reactivity descriptors are also calculated and these values describe α-axial H-abstraction as the main reaction channel. PMID:24867438

  3. Fundamental study of impact ionization plasma detector

    NASA Astrophysics Data System (ADS)

    Ohashi, H.; Muranaga, K.; Sasaki, S.; Nogami, K.; Shibata, H.

    Impact ionization plasma detectors are commonly used for cosmic dust research on board spacecraft. There seems to be no scientific background on their shape, area, and applied high voltage; they are determined empirically. To design a dust detector having large aperture and lightweight to collect dust effectively for the future mission, we are to study fundamental physics of dust impact ionization phenomena. To determine parameters of impact ionization, a simple detector is designed; metal target, two grids, with/without sidewall. Distance from target to grid, grid to grid, applied voltages are variable. Each electrode is connected to charge sensitive preamplifiers, signals are observed with a digital oscilloscope. Experiments using micro-particle accelerators are made at HIT, Univ. Tokyo in Japan, and at MPI-K in Germany. Time difference of two grid signals (plasma expansion velocity), and target signal rise time are determined from observed signals. Preliminary study shows, plasma expansion velocity is dependent on applied high voltage, not dependent on dust velocity. There is a clear correlation between dust particle velocity and target signal rise time. Sidewall effect is to be studied in the near future experiment.

  4. Theoretical studies of highly ionized species

    NASA Astrophysics Data System (ADS)

    Dalgarno, A.; Victor, G. A.

    1980-10-01

    The calculations of the charge transfer recombination and ionization rate coefficients for a wide range of ionic systems in collision with hydrogen and helium at thermal energies were completed. For the carbon ions in hydrogen, the calculations were extended to energies of 100 ev. The importance of the processes in ionized plasmas was demonstrated by studies of the solar corona and of shock waves. Preliminary results were obtained on cross sections for the excitation of fine structure transitions by proton impacts. The mechanisms leading to the photodissociation of alkali metal dimers were identified and quantitative predictions were made for Li2. Calculations using the model potential method of properties of the Cu and Zn sequences were brought to a conclusion. Applications of the relativistic random phase approximation were made to the calculation of photoionization cross sections of magnesium-like and zinc-like ions and of oscillator strengths of mercury.

  5. 21 CFR 178.3950 - Tetrahydrofuran.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... solvent in the casting of film from a solution of polymeric resins of vinyl chloride, vinyl acetate, or..., or it may be used as a solvent in the casting of film prepared from vinyl chloride copolymers complying with § 177.1980 of this chapter. (b) The residual amount of tetrahydrofuran in the film does...

  6. 21 CFR 178.3950 - Tetrahydrofuran.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... provisions of this section. (a) It is used as a solvent in the casting of film from a solution of polymeric... copolymerized with one another in any combination, or it may be used as a solvent in the casting of film... of tetrahydrofuran in the film does not exceed 1.5 percent by weight of film....

  7. 21 CFR 178.3950 - Tetrahydrofuran.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... provisions of this section. (a) It is used as a solvent in the casting of film from a solution of polymeric... copolymerized with one another in any combination, or it may be used as a solvent in the casting of film... of tetrahydrofuran in the film does not exceed 1.5 percent by weight of film....

  8. Structure and reactivity of lithium amides. /sup 6/Li, /sup 13/C, and /sup 15/N NMR spectroscopic studies and colligative measurements of lithium diphenylamide and lithium diphenylamide-lithium bromide complex solvated by tetrahydrofuran

    SciTech Connect

    DePue, J.S.; Collum, D.B.

    1988-08-03

    /sup 6/Li, /sup 13/C, and /sup 15/N NMR spectroscopic studies of lithium diphenylamide in THF/hydrocarbon solutions (THF = tetrahydrofuran) detected two different species. /sup 6/Li and /sup 15/N NMR spectroscopic studies of (/sup 6/Li, /sup 15/N)lithium diphenylamide showed the species observed at low THF concentrations to be a cyclic oligomer. Structural analogies provided strong support for a dimer while colligative measurements at 0/degrees/C indicated the dimer to be di- or trisolvated. On the basis of the observed mass action effects, the species appearing at intermediate THF concentrations is assigned as a contact or solvent-separated ion-paired monomer. Lithium diphenylamide forms a 1:1 adduct with lithium bromide at low THF concentrations. A combination of /sup 6/Li-/sup 15/N double labeling studies and colligative measurements supports a trisolvated cyclic mixed dimer structure. Although detailed spectroscopic studies at elevated THF concentrations were precluded by high fluctionality, the similarity of the /sup 13/C chemical shifts of lithium diphenylamide in the presence and absence of lithium bromide provide indirect evidence that the mixed dimer undergoes a THF concentration dependent dissociation to the monomeric amide and free lithium bromide. 24 references, 9 figures, 2 tables.

  9. Trehalose promotes Rhodococcus sp. strain YYL colonization in activated sludge under tetrahydrofuran (THF) stress

    PubMed Central

    He, Zhixing; Zhang, Kai; Wang, Haixia; Lv, Zhenmei

    2015-01-01

    Few studies have focused on the role of compatible solutes in changing the microbial community structure in bioaugmentation systems. In this study, we investigated the influence of trehalose as a biostimulant on the microbial community in tetrahydrofuran (THF)-treated wastewater bioaugmentation systems with Rhodococcus sp. YYL. Functional gene profile changes were used to study the variation in the microbial community. Soluble di-iron monooxygenases (SDIMO), particularly group-5 SDIMOs (i.e., tetrahydrofuran and propane monooxygenases), play a significant role in the initiation of the ring cleavage of tetrahydrofuran. Group-5 SDIMOs genes are enriched upon trehalose addition, and exogenous tetrahydrofuran monooxygenase (thmA) genes can successfully colonize bioaugmentation systems. Cytochrome P450 monooxygenases (P450s) have a significant role in catalyzing the region- and stereospecific oxidation of non-activated hydrocarbons, and THF was reported to inhibit P450s in the environment. The CYP153 family was chosen as a representative P450 to study the inhibitory effects of THF. The results demonstrated that CYP153 family genes exhibited significant changes upon THF treatment and that trehalose helped maintain a rich diversity and high abundance of CYP153 family genes. Biostimulation with trehalose could alleviate the negative effects of THF stress on microbial diversity in bioaugmentation systems. Our results indicated that trehalose as a compatible solute plays a significant role for environmental strains under extreme conditions. PMID:26029182

  10. Simulation study of the ionizing front in the critical ionization velocity phenomenon

    NASA Technical Reports Server (NTRS)

    Machida, S.; Goertz, C. K.; Lu, G.

    1988-01-01

    The simulation of the critical ionization velocity for a neutral gas cloud moving across the static magnetic field is presented. A low-beta plasma is studied, using a two and a half-dimensional electrostatic code linked with the Plasma and Neutral Interaction Code (Goertz and Machida, 1987). The physics of the ionizing front and the instabilities which occur there are discussed. Results are presented from four numerical runs designed so that the effects of the charge separation field can be distinguished from the wave heating.

  11. Micromechanical adhesion force measurements between tetrahydrofuran hydrate particles.

    PubMed

    Taylor, Craig J; Dieker, Laura E; Miller, Kelly T; Koh, Carolyn A; Sloan, E Dendy

    2007-02-15

    Adhesion forces between tetrahydrofuran (THF) hydrate particles in n-decane were measured using an improved micromechanical technique. The experiments were performed at atmospheric pressure over the temperature range 261-275 K. The observed forces and trends were explained by a capillary bridge between the particles. The adhesion force of hydrates was directly proportional to the contact force and contact time. A scoping study examined the effects of temperature, anti-agglomerants, and interfacial energy on the particle adhesion forces. The adhesion force of hydrates was found to be directly proportional to interfacial energy of the surrounding liquid, and to increase with temperature. Both sorbitan monolaurate (Span20) and poly-N-vinyl caprolactam (PVCap) decreased the adhesion force between the hydrate particles. PMID:17126359

  12. Fundamental studies and applications of strong field ionization

    NASA Astrophysics Data System (ADS)

    Yan, Lu

    In an intense laser field, atoms and molecules experience tunneling ionization directly to the continuum. We used this method to study several aspects and applications of strong field ionization (SFI) in atoms and molecules. One study used SFI to probe the photofragments produced by photodissociation using DC sliced imaging. The photodissociation mechanism of two polyatomic molecules (sulfur dioxide and nitromethane) were investigated. In a second study, we show the strong field ionization rate depends on the sign of the magnetic number distribution. We detect the signal of sequential double ionization of argon dications by a pump-probe method to investigate the ionization rate sensitivity to circularly polarized light. In a third study, we also found that the modest fragmentation that accompanies strong field ionization may be used to identify isomers and molecules in a complex mixture based on their mass spectral "finger print". The experiments were carried out in a DC sliced imaging apparatus. For the isomer selective detection experiment, the machine was used simply as a time-of-flight mass spectrometer. The mass spectrum of each isomer was used as "basis function" to characterize the complex mixtures quantitatively.

  13. Comparison Study of Atomic and Molecular Single Ionization in the Multiphoton Ionization Regime

    SciTech Connect

    Wu Jian; Zeng Heping; Guo Chunlei

    2006-06-23

    In this Letter, we report, for the first time in the multiphoton ionization regime, a comparison study of single-electron ionization of diatomic molecules versus rare gas atoms with virtually the same ionization potentials. In comparing N{sub 2}{sup +} to Ar{sup +}, a higher ion signal is seen in N{sub 2}{sup +} compared to Ar{sup +} for linear polarization but the difference vanishes in circularly polarized light. In comparing O{sub 2}{sup +} to Xe{sup +}, we observe a suppression in O{sub 2}{sup +} compared to Xe{sup +} for both linear and circular polarization but this suppression exhibits an intensity dependence; i.e., there is little suppression for O{sub 2}{sup +} at the lowest intensity range, but the suppression becomes increasingly stronger as the laser intensity increases. The multielectron screening model is used to discuss possible mechanisms of this intensity dependent suppression in O{sub 2}{sup +} in the multiphoton ionization regime.

  14. A dynamical (e,2e) investigation of the structurally related cyclic ethers tetrahydrofuran, tetrahydropyran, and 1,4-dioxane

    NASA Astrophysics Data System (ADS)

    Builth-Williams, J. D.; Bellm, S. M.; Chiari, L.; Thorn, P. A.; Jones, D. B.; Chaluvadi, H.; Madison, D. H.; Ning, C. G.; Lohmann, B.; da Silva, G. B.; Brunger, M. J.

    2013-07-01

    Triple differential cross section measurements for the electron-impact ionization of the highest occupied molecular orbitals of tetrahydropyran and 1,4-dioxane are presented. For each molecule, experimental measurements were performed using the (e,2e) technique in asymmetric coplanar kinematics with an incident electron energy of 250 eV and an ejected electron energy of 20 eV. With the scattered electrons being detected at -5°, the angular distributions of the ejected electrons in the binary and recoil regions were observed. These measurements are compared with calculations performed within the molecular 3-body distorted wave model. Here, reasonable agreement was observed between the theoretical model and the experimental measurements. These measurements are compared with results from a recent study on tetrahydrofuran [D. B. Jones, J. D. Builth-Williams, S. M. Bellm, L. Chiari, C. G. Ning, H. Chaluvadi, B. Lohmann, O. Ingolfsson, D. Madison, and M. J. Brunger, Chem. Phys. Lett. 572, 32 (2013)] in order to evaluate the influence of structure on the dynamics of the ionization process across this series of cyclic ethers.

  15. IRIS Toxicological Review of Tetrahydrofuran (Thf) (External Review Draft)

    EPA Science Inventory

    EPA is conducting a peer review and public comment of the scientific basis supporting the human health hazard and dose-response assessment of tetrahydrofuran (THF) that when finalized will appear on the Integrated Risk Information System (IRIS) database.

  16. Biodegradation kinetics of tetrahydrofuran, benzene, toluene, and ethylbenzene as multi-substrate by Pseudomonas oleovorans DT4.

    PubMed

    Chen, Dong-Zhi; Ding, Yun-Feng; Zhou, Yu-Yang; Ye, Jie-Xu; Chen, Jian-Meng

    2015-01-01

    The biodegradation kinetics of tetrahydrofuran, benzene (B), toluene (T), and ethylbenzene (E) were systematically investigated individually and as mixtures by a series of aerobic batch degradation experiments initiated by Pseudomonas oleovorans DT4. The Andrews model parameters, e.g., maximum specific growth rates (μmax), half saturation, and substrate inhibition constant, were obtained from single-substrate experiments. The interaction parameters in the sum kinetics model (SKIP) were obtained from the dual substrates. The μmax value of 1.01 for tetrahydrofuran indicated that cell growth using tetrahydrofuran as carbon source was faster than the growth on B (μmax, B = 0.39) or T (μmax, T = 0.39). The interactions in the dual-substrate experiments, including genhancement, inhibition, and co-metabolism, in the mixtures of tetrahydrofuran with B or T or E were identified. The degradation of the four compounds existing simultaneously could be predicted by the combination of SKIP and co-metabolism models. This study is the first to quantify the interactions between tetrahydrofuran and BTE. PMID:25561017

  17. Biodegradation Kinetics of Tetrahydrofuran, Benzene, Toluene, and Ethylbenzene as Multi-substrate by Pseudomonas oleovorans DT4

    PubMed Central

    Chen, Dong-Zhi; Ding, Yun-Feng; Zhou, Yu-Yang; Ye, Jie-Xu; Chen, Jian-Meng

    2014-01-01

    The biodegradation kinetics of tetrahydrofuran, benzene (B), toluene (T), and ethylbenzene (E) were systematically investigated individually and as mixtures by a series of aerobic batch degradation experiments initiated by Pseudomonas oleovorans DT4. The Andrews model parameters, e.g., maximum specific growth rates (μmax), half saturation, and substrate inhibition constant, were obtained from single-substrate experiments. The interaction parameters in the sum kinetics model (SKIP) were obtained from the dual substrates. The μmax value of 1.01 for tetrahydrofuran indicated that cell growth using tetrahydrofuran as carbon source was faster than the growth on B (μmax, B = 0.39) or T (μmax, T = 0.39). The interactions in the dual-substrate experiments, including genhancement, inhibition, and co-metabolism, in the mixtures of tetrahydrofuran with B or T or E were identified. The degradation of the four compounds existing simultaneously could be predicted by the combination of SKIP and co-metabolism models. This study is the first to quantify the interactions between tetrahydrofuran and BTE. PMID:25561017

  18. Experimental Resonance Enhanced Multiphoton Ionization (REMPI) studies of small molecules

    NASA Technical Reports Server (NTRS)

    Dehmer, J. L.; Dehmer, P. M.; Pratt, S. T.; Ohalloran, M. A.; Tomkins, F. S.

    1987-01-01

    Resonance enhanced multiphoton ionization (REMPI) utilizes tunable dye lasers to ionize an atom or molecule by first preparing an excited state by multiphoton absorption and then ionizing that state before it can decay. This process is highly selective with respect to both the initial and resonant intermediate states of the target, and it can be extremely sensitive. In addition, the products of the REMPI process can be detected as needed by analyzing the resulting electrons, ions, fluorescence, or by additional REMPI. This points to a number of exciting opportunities for both basic and applied science. On the applied side, REMPI has great potential as an ultrasensitive, highly selective detector for trace, reactive, or transient species. On the basic side, REMPI affords an unprecedented means of exploring excited state physics and chemistry at the quantum-state-specific level. An overview of current studies of excited molecular states is given to illustrate the principles and prospects of REMPI.

  19. Cleave and capture chemistry illustrated through bimetallic-induced fragmentation of tetrahydrofuran

    NASA Astrophysics Data System (ADS)

    Mulvey, Robert E.; Blair, Victoria L.; Clegg, William; Kennedy, Alan R.; Klett, Jan; Russo, Luca

    2010-07-01

    The cleavage of ethers is commonly encountered in organometallic chemistry, although rarely studied in the context of new, emerging bimetallic reagents. Recently, it was reported that a bimetallic sodium-zinc base can deprotonate cyclic tetrahydrofuran under mild conditions without opening its heterocyclic (OC4) ring. In marked contrast to this synergic sedation, herein we show that switching to the more reactive sodium-magnesium or sodium-manganese bases promotes cleavage of at least six bonds in tetrahydrofuran, but uniquely the ring fragments are captured in separate crystalline complexes. Oxide fragments occupy guest positions in bimetallic, inverse crown ethers and C4 fragments ultimately appear in bimetallated butadiene molecules. These results demonstrate the special synergic reactivity that can be executed by bimetallic reagents, which include the ability to capture and control, and thereby study, reactive fragments from sensitive substrates.

  20. Cleave and capture chemistry illustrated through bimetallic-induced fragmentation of tetrahydrofuran.

    PubMed

    Mulvey, Robert E; Blair, Victoria L; Clegg, William; Kennedy, Alan R; Klett, Jan; Russo, Luca

    2010-07-01

    The cleavage of ethers is commonly encountered in organometallic chemistry, although rarely studied in the context of new, emerging bimetallic reagents. Recently, it was reported that a bimetallic sodium-zinc base can deprotonate cyclic tetrahydrofuran under mild conditions without opening its heterocyclic (OC(4)) ring. In marked contrast to this synergic sedation, herein we show that switching to the more reactive sodium-magnesium or sodium-manganese bases promotes cleavage of at least six bonds in tetrahydrofuran, but uniquely the ring fragments are captured in separate crystalline complexes. Oxide fragments occupy guest positions in bimetallic, inverse crown ethers and C(4) fragments ultimately appear in bimetallated butadiene molecules. These results demonstrate the special synergic reactivity that can be executed by bimetallic reagents, which include the ability to capture and control, and thereby study, reactive fragments from sensitive substrates. PMID:20571579

  1. Ratios of photoelectron to EUV ionization rates for aeronomic studies

    SciTech Connect

    Richards, P.G.; Torr, D.G. )

    1988-05-01

    This study reveals that the ratios of the photoelectron to EUV ionization rates are not constant but depend on the degree of attenuation of the solar EUV flux and on the transport of photoelectrons. At high altitudes in the absence of photoelectron transport, the O{sup +} and N{sub 2}{sup +} ionization rate ratios are about 0.35, but they increase with increasing optical depth to such an extent that in the vicinity of the ionization peak, photoelectron impact ionization is as important as photoionization for O{sup +} and N{sub 2}{sup +}. The O{sub 2}{sup +} ratio is about half that of O{sup +} at high altitudes adn also increases with increasing optical depth but reaches a peak of about 0.4. The authors present simple formulae which mimic the attenuation behavior of the ionization ratios. Transport effects become important above about 250 km where the ratios vary by a factor of 2 depending on the presence or absence of photoelectrons from the conjugate ionosphere. In addition to the photoelectron to EUV ionization ratios, they present photodissociative branching ratios for O{sub 2} and N{sub 2}. These photodissociative ratios are also a function of the degree of attenuation of the EUV flux. In the region where attenuation is not important, the N{sup +} to N{sub 2}{sup +} ratio is 0.14, and the O{sup +} to O{sub 2}{sup +} ratio is 0.22. There is a factor of 2 uncertainty in our calculated ratios on account of uncertainties in the solar EUV flux spectrum and also uncertainties in the electron impact cross sections.

  2. Lithium and cesium acidities of some terminal acethylenes and aggregation of their salts in tetrahydrofuran

    SciTech Connect

    Gareyev, R.; Streitwieser, A.

    1995-12-01

    Ion-pair acidity equilibria have been determined for 4-ethynylbiphenyl (1), 1-ethynyladamantane (2) and 3,3,3-triphenylpropyne (3) with lithium and cesium as counterions in tetrahydrofuran. The pK values increase, 1 < 3 < 2, with lithium as the counterion. With the cesium gegenion the pK of compound 2 is also higher than that of 3. The cesium salt of 1 is insoluble in tetrahydrofuran. Comparison of lithium and cesium acidities shows a difference of 6 pK units for both 2 and 3, the lithium pK being lower. In some cases, the measured equilibrium acidities depend on the concentration of the acetylene salt, which indicates aggregation of ion pairs into higher ionic clusters. The average aggregation numbers were determined from the equilibrium studies.

  3. 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.

  4. Theoretical studies of photoexcitation and ionization in H2O

    NASA Technical Reports Server (NTRS)

    Diercksen, G. H. F.; Kraemer, W. P.; Rescigno, T. N.; Bender, C. F.; Mckoy, B. V.; Langhoff, S. R.; Langhoff, P. W.

    1982-01-01

    Theoretical studies using Franck-Condon and static-exchange approximations are reported for the complete dipole excitation and ionization spectrum in H2O, where (1) large Cartesian Gaussian basis sets are used to represent the required discrete and continuum electronic eigenfunctions at the ground state equilibrium geometry, and (2) previously devised moment-theory techniques are employed in constructing the continuum oscillator-strength densities from the calculated spectra. Comparisons are made of the calculated excitation and ionization profiles with recent experimental photoabsorption studies and corresponding spectral assignments, electron impact-excitation cross sections, and dipole and synchrotron-radiation studies of partial-channel photoionization cross sections. The calculated partial-channel cross sections are found to be atomic-like, and dominated by 2p-kd components. It is suggested that the latter transition couples with the underlying 1b(1)-kb(1) channel, accounting for a prominent feature in recent synchrotron-radiation measurements.

  5. Dynamic Metabolic and Transcriptional Profiling of Rhodococcus sp. Strain YYL during the Degradation of Tetrahydrofuran

    PubMed Central

    He, Zhixing; Yao, Yanlai

    2014-01-01

    Although tetrahydrofuran-degrading Rhodococcus sp. strain YYL possesses tetrahydrofuran (THF) degradation genes similar to those of other tetrahydrofuran-degrading bacteria, a much higher degradation efficiency has been observed in strain YYL. In this study, nuclear magnetic resonance (NMR)-based metabolomics analyses were performed to explore the metabolic profiling response of strain YYL to exposure to THF. Exposure to THF slightly influenced the metabolome of strain YYL when yeast extract was present in the medium. The metabolic profile of strain YYL over time was also investigated using THF as the sole carbon source to identify the metabolites associated with high-efficiency THF degradation. Lactate, alanine, glutarate, glutamate, glutamine, succinate, lysine, trehalose, trimethylamine-N-oxide (TMAO), NAD+, and CTP were significantly altered over time in strain YYL grown in 20 mM THF. Real-time quantitative PCR (RT-qPCR) revealed changes in the transcriptional expression levels of 15 genes involved in THF degradation, suggesting that strain YYL could accumulate several disturbances in osmoregulation (trehalose, glutamate, glutamine, etc.), with reduced glycolysis levels, an accelerated tricarboxylic acid cycle, and enhanced protein synthesis. The findings obtained through 1H NMR metabolomics analyses and the transcriptional expression of the corresponding genes are complementary for exploring the dynamic metabolic profile in organisms. PMID:24532074

  6. Thermodynamic Functions of Solvation of Hydrocarbons, Noble Gases, and Hard Spheres in Tetrahydrofuran-Water Mixtures.

    PubMed

    Sedov, I A; Magsumov, T I

    2015-07-16

    Thermodynamic solvation properties of mixtures of water with tetrahydrofuran at 298 K are studied. The Gibbs free energies and enthalpies of solvation of n-octane and toluene are determined experimentally. For molecular dynamics simulations of the binary solvent, we have modified a TraPPE-UA model for tetrahydrofuran and combined it with the SPC/E potential for water. The excess thermodynamic functions of neon, xenon, and hard spheres with two different radii are calculated using the particle insertion method. Simulated and real systems share the same characteristic trends for the thermodynamic functions. A maximum is present on dependencies of the enthalpy of solvation from the composition of solvent at 70-90 mol % water, making it higher than in both of the cosolvents. It is caused by a high enthalpy of cavity formation in the mixtures rich with water due to solvent reorganization around the cavity, which is shown by calculation of the enthalpy of solvation of hard spheres. Addition of relatively small amounts of tetrahydrofuran to water effectively suppresses the hydrophobic effect, leading to a quick increase of both the entropy and enthalpy of cavity formation and solvation of low polar molecules. PMID:26115405

  7. Debenzylative Cycloetherification: An Overlooked Key Strategy for Complex Tetrahydrofuran Synthesis.

    PubMed

    Tikad, Abdellatif; Delbrouck, Julien A; Vincent, Stéphane P

    2016-07-01

    Tetrahydrofuran (THF) is a major structural feature found in many synthetic and natural products displaying a variety of biological properties. This review summarizes the main synthetic approaches that have been developed to construct tetrahydrofuran moieties involving debenzylative cycloetherification reactions (DBCE). Interestingly, this reaction is regio- and stereoselective without the requirement of a selective protection/deprotection strategy. Many applications of this process have been reported, including carbafuranoside synthesis, regioselective deprotection of the benzyl group positioned γ to an alkene, and total synthesis of natural products. The stereochemical outcome and the mechanism of these interesting transformations are also discussed. PMID:27304427

  8. IRIS Toxicological Review of Tetrahydrofuran (THF) (Interagency Science Discussion Draft)

    EPA Science Inventory

    EPA is releasing the draft report, Toxicological Review of Tetrahydrofuran, that was distributed to Federal agencies and White House Offices for comment during the Science Discussion step of the IRIS Assessment Development Proc...

  9. Resonant enhanced multiphoton ionization studies of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Dixit, S. N.; Levin, D.; Mckoy, V.

    1987-01-01

    In resonant enhanced multiphoton ionization (REMPI), an atom absorbs several photons making a transition to a resonant intermediate state and subsequently ionizing out of it. With currently available tunable narrow-band lasers, the extreme sensitivity of REMPI to the specific arrangement of levels can be used to selectively probe minute amounts of a single species (atom) in a host of background material. Determination of the number density of atoms from the observed REMPI signal requires a knowledge of the multiphoton ionization cross sections. The REMPI of atomic oxygen was investigated through various excitation schemes that are feasible with available light sources. Using quantum defect theory (QDT) to estimate the various atomic parameters, the REMPI dynamics in atomic oxygen were studied incorporating the effects of saturation and a.c. Stark shifts. Results are presented for REMPI probabilities for excitation through various 2p(3) (4S sup o) np(3)P and 2p(3) (4S sup o) nf(3)F levels.

  10. Design of HIV-1 Protease Inhibitors with Amino-bis-tetrahydrofuran Derivatives as P2-Ligands to Enhance Backbone-Binding Interactions. Synthesis, Biological Evaluation, and Protein-Ligand X-ray Studies

    SciTech Connect

    Ghosh, Arun K.; Martyr, Cuthbert D.; Osswald, Heather L.; Sheri, Venkat Reddy; Kassekert, Luke A.; Chen, Shujing; Agniswamy, Johnson; Wang, Yuan-Fang; Hayashi, Hironori; Aoki, Manabu; Weber, Irene T.; Mitsuya, Hiroaki

    2015-10-30

    Structure-based design, synthesis, and biological evaluation of a series of very potent HIV-1 protease inhibitors are described. In an effort to improve backbone ligand–binding site interactions, we have incorporated basic-amines at the C4 position of the bis-tetrahydrofuran (bis-THF) ring. We speculated that these substituents would make hydrogen bonding interactions in the flap region of HIV-1 protease. Synthesis of these inhibitors was performed diastereoselectively. A number of inhibitors displayed very potent enzyme inhibitory and antiviral activity. Inhibitors 25f, 25i, and 25j were evaluated against a number of highly-PI-resistant HIV-1 strains, and they exhibited improved antiviral activity over darunavir. Two high resolution X-ray structures of 25f- and 25g-bound HIV-1 protease revealed unique hydrogen bonding interactions with the backbone carbonyl group of Gly48 as well as with the backbone NH of Gly48 in the flap region of the enzyme active site. These ligand–binding site interactions are possibly responsible for their potent activity.

  11. Laser ionization/MS study of smog formation

    SciTech Connect

    Hewitt, A.D.; Lee, C.M.; Quimpo, B.C.

    1995-12-01

    Resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry (REMPI/TOFMS) is a highly sensitive and selective technique which we are using to study atmospheric chemistry kinetics and reaction mechanisms. We are presently focusing our attention on toluene, the most abundant of the aromatic hydrocarbons in the troposphere, in order to understand the oxidation pathways which lead to smog formation. Our most recent results monitoring toluene and products of the OH + toluene reaction will be discussed, as well as our future plans to detect short-lived reaction intermediates, such as the methylhydroxycyclohexadienyl radical, formed by the addition of OH to the aromatic ring of toluene.

  12. Molecular Driving Forces behind the Tetrahydrofuran-Water Miscibility Gap.

    PubMed

    Smith, Micholas Dean; Mostofian, Barmak; Petridis, Loukas; Cheng, Xiaolin; Smith, Jeremy C

    2016-02-01

    The tetrahydrofuran-water binary system exhibits an unusual closed-loop miscibility gap (transitions from a miscible regime to an immiscible regime back to another miscible regime as the temperature increases). Here, using all-atom molecular dynamics simulations, we probe the structural and dynamical behavior of the binary system in the temperature regime of this gap at four different mass ratios, and we compare the behavior of bulk water and tetrahydrofuran. The changes in structure and dynamics observed in the simulations indicate that the temperature region associated with the miscibility gap is distinctive. Within the miscibility-gap temperature region, the self-diffusion of water is significantly altered and the second virial coefficients (pair-interaction strengths) show parabolic-like behavior. Overall, the results suggest that the gap is the result of differing trends with temperature of minor structural changes, which produces interaction virials with parabolic temperature dependence near the miscibility gap. PMID:26734991

  13. A Study of Muon Ionization Cooling at MICE

    SciTech Connect

    Sakamoto, Hideyuki; /Osaka U.

    2010-02-01

    A Neutrino Factory based on a high-energy muon storage-ring is proposed to study neutrino oscillation with high precision. An emittance reduction of muon beam by ionization cooling, which has never been demonstrated in practice, is one of the critical issues for Neutrino Factory. The international Muon Ionisation Cooling Experiment (MICE) is the first experiment to verify an effect of the ionization cooling with muons. MICE will measure a change in transverse emittance of approximately 10% with a precision of {+-}0.1%. In order to meet the requirements, muon trackers based on 350 {micro}m diameter scintillating fibers have been proposed. The construction of such trackers is a very challenging task and some innovative techniques are needed to realize, since there have been no trackers made with such a small diameter of scintillating fibers in the world. Upstream and downstream SciFi trackers have been successfully constructed with the international collaboration of UK, US and Japan by 2008. Both of the trackers have been tested with cosmic-rays at the RAL by 2009, at which high tracking efficiencies more than 90% are measured for both trackers. It is also confirmed that by collecting the misalignments found in both of the trackers, the requirements for the emittance measurement is met.

  14. Study of the surface ionization detector for gas chromatography.

    PubMed

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

    2011-09-23

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

  15. Microscopic Structure of Contact Ion Pairs in Concentrated LiCl- and LiClO4-Tetrahydrofuran Solutions Studied by Low-Frequency Isotropic Raman Scattering and Neutron Diffraction with (6)Li/(7)Li Isotopic Substitution Methods.

    PubMed

    Kameda, Yasuo; Ebina, Saki; Amo, Yuko; Usuki, Takeshi; Otomo, Toshiya

    2016-05-26

    Low-frequency isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for (6)Li/(7)Li and H/D isotopically substituted *LiCl- and *LiClO4-tetrahydrofuran (*THF) solutions in order to obtain microscopic insight into solvated Li(+), Li(+)···Cl(-) and Li(+)···ClO4(-) contact ion pairs formed in concentrated THF solutions. Symmetrical stretching vibrational mode of solvated Li(+) in LiCl and LiClO4 solutions was observed at ν = 181-184 and 140 cm(-1), respectively. The stretching vibrational mode of Li(+)···Cl(-) and Li(+)···ClO4(-) solvated contact ion pairs formed in 4 mol % (6)LiCl-THF-h8 and (7)LiCl-THF-h8 solutions was found at ν = 469 and 435 cm(-1), respectively. Detailed structural properties of solvated Li(+) and the contact ion pairs were derived from the least-squares fitting analyses of the first-order difference function, ΔLi(Q), obtained from neutron diffraction measurements on (6)Li/(7)Li isotopically substituted THF-d8 solutions. It has been revealed that Li(+) takes 4-fold coordination in the average local structure of Li(+)X(-)(THF)3, X = Cl and ClO4. The nearest neighbor Li(+)···O(THF) distance was determined to be 2.21 ± 0.01 Å and 2.07 ± 0.01 Å for 4 mol % *LiCl- and 10 mol % *LiClO4-THF-d8 solutions, respectively. The Li(+)···anion distances for Li(+)···Cl(-) and Li(+)···O(ClO4(-)) contact ion pairs were determined to be 2.4 ± 0.1 Å and 2.19 ± 0.01 Å, respectively. The nearest neighbor Li(+)···THF interaction is significantly modified by the anion in the first solvation shell. PMID:27157529

  16. Ionization of vitamin C in gas phase: Theoretical study.

    PubMed

    Abyar, Fatemeh; Farrokhpour, Hossein

    2016-07-01

    In this work, the gas phase ionization energies and photoelectron spectra of four important conformers of vitamin C were calculated. Symmetry adapted cluster/configuration interaction methodology employing the single and double excitation operators (SAC-CI SD-R) along with D95++(d,p) basis set were used for the calculations. Thermochemistry calculations were also performed on all possible conformers of vitamin C to find the relative stability of conformers in the gas phase. The calculated ionization bands of each conformer were assigned by calculating the contribution of natural bonding orbital (NBO) in the calculated canonical molecular orbitals involved in the ionization. SAC-CI calculations showed that the first ionization band of vitamin C is related to the π electrons of CC bond of the ring of molecule although, there is the lone electron pairs of oxygen atoms and π electrons of CO bond in the molecule. PMID:27092998

  17. Elastic Scattering of Low-Energy Electrons byTetrahydrofuran

    SciTech Connect

    Trevisan, Cynthia S.; Orel, Ann E.; Rescigno, Thomas N.

    2006-05-09

    We present the results of ab initio calculations for elasticelectron scattering by tetrahydrofuran (THF) using the complex Kohnvariational method. We carried out fixed-nuclei calculations at theequilibrium geometry of the target molecule for incident electronenergies up to 20 eV. The calculated momentum transfer cross sectionsclearly reveal the presence of broad shape resonance behavior in the 8-10eV energy range, in agreement with recent experiments. The calculateddifferential cross sections at 20 eV, which include the effects of thelong-range electron-dipole interaction, are alsofound to be in agreementwith the most recent experimental findings.

  18. Single- and multi-photon ionization studies of organosulfur species

    SciTech Connect

    Cheung, Y.S.

    1999-02-12

    Accurate ionization energies (IE`s) for molecular species are used for prediction of chemical reactivity and are of fundamental importance to chemists. The IE of a gaseous molecule can be determined routinely in a photoionization or a photoelectron experiment. IE determinations made in conventional photoionization and photoelectron studies have uncertainties in the range of 3--100 meV (25--250 cm{sup {minus}1}). In the past decade, the most exciting development in the field of photoionization and photoelectron spectroscopy has been the availability of high resolution, tunable ultraviolet (UV) and vacuum ultraviolet (VUV) laser sources. The laser pulsed field ionization photoelectron (PFI-PE) scheme is currently the state-of-the-art photoelectron spectroscopic technique and is capable of providing photoelectron energy resolution close to the optical resolution. The author has focused attention on the photoionization processes of some sulfur-containing species. The studies of the photoionization and photodissociation on sulfur-containing compounds [such as CS{sub 2}, CH{sub 3}SH, CH{sub 3}SSCH{sub 3}, CH{sub 3}CH{sub 2}SCH{sub 2}CH{sub 3}, HSCH{sub 2}CH{sub 2}SH and C{sub 4}H{sub 4}S (thiophene) and sulfur-containing radicals, such as HS, CS, CH{sub 3}S, CH{sub 3}CH{sub 2}S and CH{sub 3}SS], have been the major subjects in the group because sulfur is an important species contributing to air pollution in the atmosphere. The modeling of the combustion and oxidation of sulfur compounds represents important steps for the control of both the production and the elimination of sulfur-containing pollutants. Chapter 1 is a general introduction of the thesis. Chapters 2 and 6 contain five papers published in, or accepted for publication in, academic periodicals. In Chapter 7, the progress of the construction in the laboratory of a new vacuum ultraviolet laser system equipped with a reflectron mass spectrometer is presented. Chapters 2 through 7 have been removed for separate

  19. Cross-linked poly(tetrahydrofuran) as promising sorbent for organic solvent/oil spill.

    PubMed

    Yati, Ilker; Ozan Aydin, Gulsah; Bulbul Sonmez, Hayal

    2016-05-15

    In this study, a series of different molecular weights of poly(tetrahydrofuran) (PTHF), which is one of the most important commercial polymers around the world, was condensed with tris[3-(trimethoxysilyl)propyl]isocyanurate (ICS) to generate a cross-linked 3-dimensional network in order to obtain organic solvent/oil sorbents having high swelling capacity. The prepared sorbents show high and fast swelling capacity in oils such as dichloromethane (DCM), tetrahydrofuran (THF), acetone, t-butyl methyl ether (MTBE), gasoline, euro diesel, and crude oil. The recovery of the absorbed oils from contaminated surfaces, especially from water, and the regeneration of the sorbents after several applications are effective. The characterization and thermal properties of the sorbents are identified by Fourier transform infrared spectroscopy (FTIR), solid-state (13)C and (29)Si cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and thermal gravimetric analyses (TGA), respectively. The new usage area of PTHF is emerged by the preparation of PTHF-based network structure with high oil absorption capacity and having excellent reusability as an oil absorbent for the removal of organic liquids from the spill site. PMID:26894295

  20. Studying Simple Molecular Ionization using Radiation Emission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Proctor, Christopher; Lemmer, Kristina; Western Michigan University Aerospace LaboratoryPlasma Experiments Team

    2015-11-01

    This study focuses on radiation emission from the formation of simple molecular plasma using a DC glow discharge. The purpose is to measure the emission from argon and molecular nitrogen gas as a function of time with an optical emission spectroscopy system operating in kinetic mode as the gases go from their neutral state to ionized state. The end goal of the research is to develop a diagnostic tool that will be used to study the formation of plasma discharges from complex molecules. The kinetic mode of the CCD camera allows for fast data acquisition so that the species present and their relative concentrations as a function of time can be measured as the plasma is forming. The primary difficulty in the development of this diagnostic tool is designing a device and data analysis technique to allow for kinetic mode operation of the CCD camera. Experimental devices have been designed and built to enable the CCD to operate in kinetic mode, including a fiber optic adapter, camera mount, and twin razor blade system. The twin blades allow for the reduction of exposed pixels on the CCD camera and thereby allow the camera to store data on rows of pixels, rather than imaging the entire camera, allowing for faster data transfer. PhD in Aerospace Engineering.

  1. Background studies in gas ionizing x ray detectors

    NASA Technical Reports Server (NTRS)

    Eldridge, Hudson B.

    1989-01-01

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

  2. Enantioselective syntheses and sensory properties of 2-methyl-tetrahydrofuran-3-thiol acetates.

    PubMed

    Dai, Yifeng; Shao, Junqiang; Yang, Shaoxiang; Sun, Baoguo; Liu, Yongguo; Ning, Ting; Tian, Hongyu

    2015-01-21

    The enantioselective synthesis of four stereoisomers of 2-methyl-tetrahydrofuran-3-thiol acetate was achieved. The two enantiomers of the important intermediate cis-2-methyl-3-hydroxy-tetrahydrofuran were obtained by Sharpless asymmetric dihydroxylation (AD), whereas the two enantiomers of trans-2-methyl-3-hydroxy-tetrahydrofuran were derived from the corresponding optically active cis-isomers by Mitsunobu reaction. Each stereoisomer of 2-methyl-3-hydroxy-tetrahydrofuran went through mesylation and nucleophilic substitution to afford the corresponding product with specific configuration. (2R,3S)- and (2R,3R)-2-methyl-tetrahydrofuran-3-thiol acetate were obtained in 80% ee, whereas the (2S,3R)- and (2S,3S)-isomers were in 62% ee. The odor properties of the synthesized four stereoisomers were evaluated by gas chromatography-olfactometry (GC-O), which revealed perceptible differences among stereoisomers both in odor features and in intensities. PMID:25560460

  3. 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.

  4. Influence of Multiple Ionization on Studies of Nanoflare Heated Plasmas

    NASA Astrophysics Data System (ADS)

    Hahn, Michael; Savin, Daniel Wolf

    2015-04-01

    The spectrum emitted by a plasma depends on the charge state distribution (CSD) of the gas. This, in turn, is determined by the corresponding rates for electron-impact ionization and recombination. Current CSD calculations for solar physics do not account for electron-impact multiple ionization (EIMI), a process in which multiple electrons are ejected by a single electron-ion collision. We have estimated the EIMI cross sections for all charge states of iron using a combination of the available experimental data and semi-empirical formulae. We then modeled the CSD and observed the influence of EIMI compared to only including single ionization. One case of interest for solar physics is nanoflare heating. Recent work has attempted to predict the spectra of impulsively heated plasmas in order to identify diagnostics arising from non-equilibrium ionization that can constrain the nanoflare properties, but these calculations have ignored EIMI. Our findings suggest that EIMI can have a significant effect on the CSD of a nanoflare-heated plasma, changing the ion abundances by up to about 50%.

  5. Characterization of Reaction Pathways in Low Temperature Oxidation of Tetrahydrofuran with Multiplexed Photoionization Mass Spectrometry Technique

    NASA Astrophysics Data System (ADS)

    Antonov, Ivan; Sheps, Leonid

    2015-06-01

    Tetrahydrofuran (THF) is a prototype biofuel and a common intermediate in combustion of alkanes and alkenes. Photolytic Cl atom-initiated oxidation of THF was studied with multiplexed photoionization mass spectrometry (MPIMS) technique at temperatures 400-650 K and pressures 0.005-2 bar. Photoionization spectra and kinetic time traces were recorded simultaneously for all mass channels. Photoionization spectra, recorded with tunable VUV synchrotron radiation, were used to separate and identify isomers with the same nominal molecular formula, providing mechanistic insight into the the underlying kinetics. Our study suggests that formation of alkylperoxy radicals and their subsequent isomerization to hydroperoxyalkyl radicals plays an important role in low temperature oxidation of THF, while ring opening of THF-H radical (which dominates THF oxidation at T>800 K) is less important at our conditions.

  6. Developing a fast ionization chamber for transfer reaction studies

    NASA Astrophysics Data System (ADS)

    Chae, K. Y.; Bardayan, D. W.; Smith, M. S.; Schmitt, K. T.; Ahn, S. H.; Peters, W. A.; Strauss, S.

    2011-10-01

    Detection of beam and beam like recoils at far forward angles is often critical for radioactive beam measurements in inverse kinematics. Gas-filled ionization chambers are well suited for these applications, since they have moderately good energy resolution and can take prolonged exposure to beam compared to fragile semiconductor detectors. Conventional ion counters using a Frisch grid, however, have slow response times because the ionized electrons must travel long distances to the anodes. To reduce response times, a fast ion counter using a tilted window and tilted electrodes was developed and tested at ORNL's Holifield Radioactive Ion Beam Facility, modified from an original design by Kimura et al.. The maximum counting rate and energy resolution, along with future plans for using the new ion counter, will be presented. This work was sponsored by the Office of Nuclear Physics, U.S. Department of Energy.

  7. Theoretical study of ionization radiation effects on optical fiber parameters

    NASA Astrophysics Data System (ADS)

    Poret, Jay C.; Suter, Joseph J.

    1994-06-01

    The effect of ionizing radiation on various fiber parameters has been examined. It was demonstrated that when the real refractive index increases, the V number increases as does the numerical aperture. The percentage of power propagating in the cladding decreases with increasing real refractive index. Small changes in the refractive index will induce additional modes to form. The effect of radiation on fiber dispersion was reasoned to be negligible for short lengths of fibers (< 2 km).

  8. Numerical studies of ablation and ionization of railgun materials

    SciTech Connect

    Schnurr, N.M.; Kerrisk, J.F.

    1985-01-01

    The intense radiation from the arc in a railgun may cause vaporization and partial ionization of rail and insulator material. The mass of material added to the arc can have a significant adverse effect on projectile velocity. A numerical model has been developed to predict the change in mass of the arc as a function of several parameters. That model has been incorporated in the Los Alamos Railgun Estimator (LARGE) code and simulations have been run to assess the accuracy of the model. Analytical predictions were found to be in good agreement with experimental data for railgun tests run at Los Alamos. Ablation appears to have a significant effect on railgun performance.

  9. INSTRUMENTS AND METHODS OF INVESTIGATION: Surface-ionization field mass-spectrometry studies of nonequilibrium surface ionization

    NASA Astrophysics Data System (ADS)

    Blashenkov, Nikolai M.; Lavrent'ev, Gennadii Ya

    2007-01-01

    The ionization of polyatomic molecules on tungsten and tungsten oxide surfaces is considered for quasiequilibrium or essentially nonequilibrium conditions (in the latter case, the term nonequilibrium surface ionization is used for adsorbate ionization). Heterogeneous reactions are supposed to proceed through monomolecular decay of polyatomic molecules or fragments of multimolecular complexes. The nonequilibrium nature of these reactions is established. The dependences of the current density of disordered ions on the surface temperature, electric field strength, and ionized particle energy distribution are obtained in analytical form. Heterogeneous dissociation energies, the ionization potentials of radicals, and the magnitude of reaction departure from equilibrium are determined from experimental data, as are energy exchange times between reaction products and surfaces, the number of molecules in molecular complexes, and the number of effective degrees of freedom in molecules and complexes. In collecting the data a new technique relying on surface-ionization field mass-spectrometry was applied.

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

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

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

  11. Epoxygenase Eicosanoids: Synthesis of Tetrahydrofuran-Diol Metabolites and Their Vasoactivity

    PubMed Central

    Falck, J. R.; Reddy, L. Manmohan; Byun, Kihwan; Campbell, William B.; Yi, Xiu-Yu

    2007-01-01

    Eight members of a recently identified family of tetrahydrofuran-diols (THFDs), originating from epoxyeicosatrienoic acids (EETs), were prepared stereospecifically from D-(+)-glucose. The THFDs potently induced relaxation of pre-contracted bovine arteries. PMID:17293113

  12. [Characteristics of tetrahydrofuran degradation by Pseudomonas oleovorans DT4].

    PubMed

    Zhou, Yu-Yang; Chen, Dong-Zhi; Jin, Xiao-Jun; Chen, Jian-Meng; He, Jie

    2011-01-01

    A tetrahydrofuran (THF)-degrading strain Pseudomonas oleovorans DT4 was isolated from the activated sludge of a pharmaceutical plant. P. oleovorans DT4 was able to utilize THF as the sole carbon and energy source under aerobic condition. 5 mmol/L of THF could be completely degraded by 3.2 mg/L inoculums of P. oleovorans DT4 in 14 h at pH 7.2 and 30 degrees C, with the cells concentration increasing to 188.6 mg/L. After the complete consumption of THF, no TOC could be detected but IC reached the stable value of about 46 mg/L, with pH decreasing to 6.54, which indicated that the substance was totally mineralized by P. oleovorans DT4. The optimum conditions for THF biodegradation in shaking flasks were pH 7.5 and temperature 37 degrees C, respectively. Results from the oxygen control experiments revealed that the oxygen supply by shaking was the satisfactory growth condition. Additionally, as the important elements for DT4, Mg2+ and Ca2+ at concentrations of 0.80 mmol/L and 0.20 mmol/L, respectively, were suitable for THF degradation. All the results contribute to the efficient bioremediation for the THF contaminated. PMID:21404697

  13. VUV photo-processing of PAH cations: quantitative study on the ionization versus fragmentation processes

    PubMed Central

    Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M.

    2016-01-01

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7 – 20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ~13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies, all species behave similarly, the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ~18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section, but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them, all are in good agreement with theoretical ones confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models. PMID:27212712

  14. VUV Photo-processing of PAH Cations: Quantitative Study on the Ionization versus Fragmentation Processes

    NASA Astrophysics Data System (ADS)

    Zhen, Junfeng; Rodriguez Castillo, Sarah; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M.

    2016-05-01

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7–20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ∼13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies all species behave similarly; the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ∼18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them; all are in good agreement with theoretical ones, confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models.

  15. Biodegradation of tetrahydrofuran and 1,4-dioxane by soluble diiron monooxygenase in Pseudonocardia sp. strain ENV478.

    PubMed

    Masuda, Hisako; McClay, Kevin; Steffan, Robert J; Zylstra, Gerben J

    2012-01-01

    1,4-Dioxane is an important groundwater contaminant. Pseudonocardia sp. strain ENV478 degrades 1,4-dioxane via cometabolism after the growth on tetrahydrofuran (THF) and other carbon sources. Here, we have identified a THF monooxygenase (thm) in ENV478. The thm genes are transcribed constitutively and are induced to higher levels by THF. Decreased translation of the thmB gene encoding one of the monooxygenase subunits by antisense RNA resulted in the loss of its ability to degrade THF and 1,4-dioxane. This is the first study to link thm genes to THF degradation, as well as the cometabolic oxidation of 1,4-dioxane. PMID:23147387

  16. Fundamental sputtering studies: Nonresonant ionization of sputtered neutrals

    SciTech Connect

    Burnett, J.W.; Pellin, M.J.; Calaway, W.F.; Gruen, D.M. ); Yates, J.T. Jr. . Dept. of Chemistry)

    1989-01-04

    Because of the practical importance of sputtering, numerous theories and computer simulations are used for predicting many aspects of the sputtering process. Unfortunately, many of the calculated sputtering results are untested by experiment. Until recently, most sputtering experiments required either very high ion fluences or the detection of only minor constituents of the sputtered flux, i.e., ions. These techniques may miss the subtleties involved in the sputtering process. High-detection-efficiency mass spectrometry, coupled with the laser ionization of neutral atoms, allows the detection of the major sputtered species with very low incident ion fluences. The depth-of-origin of sputtered atoms is one example of an important but poorly understood aspect of the sputtering process. By following the sputtering yield of a substrate atom with various coverages of an adsorbed overlayer, the depth of origin of sputtered atoms has been determined. Our results indicate that two-thirds of the sputtered flux originates in the topmost atomic layer. The ion-dose dependence of sputtering yields has long been assumed to be quite minor for low- to-moderate primary ion fluences. We have observed a two-fold decrease in the sputtering yield of the Ru(0001) surface for very low primary ion fluences. Data analysis results in a cross section for damage of 2.7 {plus minus} 1.0 {times} 10{sup {minus}15}cm{sup 2}. 40 refs., 3 figs., 2 tabs.

  17. Numerical studies of wall-plasma interactions and ionization phenomena in an ablative pulsed plasma thruster

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Zeng, Guangshang; Tang, Haibin; Huang, Yuping; Liu, Xiangyang

    2016-07-01

    Wall-plasma interactions excited by ablation controlled arcs are very critical physical processes in pulsed plasma thrusters (PPTs). Their effects on the ionization processes of ablated vapor into discharge plasma directly determine PPT performances. To reveal the physics governing the ionization phenomena in PPT discharge, a modified model taking into account the pyrolysis effect of heated polytetrafluoroethylene propellant on the wall-plasma interactions was developed. The feasibility of the modified model was analyzed by creating a one-dimensional simulation of a rectangular ablative PPT. The wall-plasma interaction results based on this modified model were found to be more realistic than for the unmodified model; this reflects the dynamic changes of the inflow parameters during discharge in our model. Furthermore, the temporal and spatial variations of the different plasma species in the discharge chamber were numerically studied. The numerical studies showed that polytetrafluoroethylene plasma was mainly composed of monovalent ions; carbon and fluorine ions were concentrated in the upstream and downstream discharge chamber, respectively. The results based on this modified model were in good agreement with the experimental formation times of the various plasma species. A large number of short-lived and highly ionized carbon and fluorine species (divalent and trivalent ions) were created during initial discharge. These highly ionized species reached their peak density earlier than the singly ionized species.

  18. Surface ionization mass spectrometry of drugs in the thermal and hyperthermal energy range -- a comparative study

    NASA Astrophysics Data System (ADS)

    Dagan, Shai; Amirav, Aviv; Fujü, Toshihiro

    1995-12-01

    Thermal and hyperthermal surface ionization (SI) mass spectra of nicotine, caffeine and lidocaine were obtained using a rhenium oxide surface. Thermal surface ionization was studied on an oxidized surface positioned inside an electron impact ion source, while hyperthermal surface ionization (HSI) was obtained upon seeding the compounds into a hydrogen or helium supersonic molecular beam that scattered from the rhenium oxide surface. Both HSI and SI provide rich, informative and complementary mass spectral information. The results indicate that SI follows thermal dissociation processes on the surface prior to the desorption of the ion, while in HSI no thermal equilibrium is established and the ionization process is impulsive, followed by mostly unimolecular ion dissociation. HSI mass spectra are similar to electron impact mass spectra in the fragment ion masses, but the observed relative intensities are different. HSI is a softer ionization method compared to SI, and enables the degree of ion fragmentation to be tuned so that it can be minimized to a low level at low molecular kinetic energy. In SI, limited control over the degree of fragmentation is possible through the surface temperature. The analytical mass spectrometric applications of SI and HSI are briefly mentioned.

  19. Use of Medical Imaging Procedures With Ionizing Radiation in Children: A Population-Based Study

    PubMed Central

    Dorfman, Adam L.; Fazel, Reza; Einstein, Andrew J.; Applegate, Kimberly E.; Krumholz, Harlan M.; Wang, Yongfei; Christodoulou, Emmanuel; Chen, Jersey; Sanchez, Ramon; Nallamothu, Brahmajee K.

    2013-01-01

    Objective To determine population-based rates of use of diagnostic imaging procedures with ionizing radiation in children, stratified by age and gender. Design Retrospective cohort analysis. Setting All settings utilizing imaging procedures with ionizing radiation. Patients Individuals less than 18 years old, alive and continuously enrolled in Unitedhealthcare between January 1, 2005 and December 31, 2007 in 5 large U.S. healthcare markets. Main Outcome Measure Number and type of diagnostic imaging procedures utilizing ionizing radiation in children. Results 355,088 children were identified. A total of 436,711 imaging procedures using ionizing radiation were performed in 150,930 (42.5%) patients. The highest rates of use were in children greater than 10 years old, with frequent use in infants under 2 years old as well. Plain radiography accounted for nearly 85% of imaging procedures performed. Computed tomography (CT) scans – associated with substantially higher doses of radiation – were commonly used, accounting for 12% of all procedures during the study period. Overall, 7.9% of children received at least one CT and 3.5% received 2 or more, with CT of the head most frequent. Conclusions Exposure to ionizing radiation from medical diagnostic imaging procedures may occur frequently among children. Efforts to optimize and ensure appropriate use of these procedures in the pediatric population should be encouraged. PMID:21199972

  20. Hot-cavity studies for the Resonance Ionization Laser Ion Source

    NASA Astrophysics Data System (ADS)

    Henares, J. L.; Lecesne, N.; Hijazi, L.; Bastin, B.; Kron, T.; Lassen, J.; Le Blanc, F.; Leroy, R.; Osmond, B.; Raeder, S.; Schneider, F.; Wendt, K.

    2016-09-01

    The Resonance Ionization Laser Ion Source (RILIS) has emerged as an important technique in many Radioactive Ion Beam (RIB) facilities for its reliability, and ability to ionize target elements efficiently and element selectively. GISELE is an off-line RILIS test bench to study the implementation of an on-line laser ion source at the GANIL separator facility. The aim of this project is to determine the best technical solution which combines high selectivity and ionization efficiency with small ion beam emittance and stable long term operation. The ion source geometry was tested in several configurations in order to find a solution with optimal ionization efficiency and beam emittance. Furthermore, a low work function material was tested to reduce the contaminants and molecular sidebands generated inside the ion source. First results with ZrC ionizer tubes will be presented. Furthermore, a method to measure the energy distribution of the ion beam as a function of the time of flight will be discussed.

  1. Effects of ionization on stability of 1-methylcytosine - DFT and PCM studies.

    PubMed

    Raczyńska, Ewa D; Michalec, Piotr; Zalewski, Marcin; Sapuła, Mariusz

    2016-07-01

    Consequences of ionization were studied by quantum-chemical methods (DFT and PCM) for 1-methylcytosine (MC)-a model of the nucleobase cytosine (C) connected with sugar in DNA. For calculations, three prototropic tautomers (one amino and two imino forms) and two imino zwitterions were considered, including conformational or configurational isomerism of exo heterogroups. Ionization and interactions between neighboring groups affect intramolecular proton-transfers, geometric and thermodynamic parameters, and electron delocalization for individual isomers. We discovered that an imino isomer is present in the isomeric mixture in the highest amount for positively ionized MC. Its contribution in neutral and negatively ionized MC is considerably smaller. Acid-base parameters for selected radical ions were estimated in the gas phase and compared to those of neutral MC. Gas-phase acidity of radical cations is close to that of the conjugate acid of MC, and gas-phase basicity of radical anions is close to that of the conjugate base of MC. Various routes of amino-imino conversion between neutral and ionized isomers were considered. Energetic-barrier for intramolecular proton-transfer in MC is close to that in the parent system-formamidine. PMID:27259531

  2. Oxidative Cyclization of 1,5-Dienes with Hydrogen Peroxide Catalyzed by an Osmium(III) Complex: Synthesis of cis-Tetrahydrofurans.

    PubMed

    Sugimoto, Hideki; Kanetake, Takayuki; Maeda, Kazuki; Itoh, Shinobu

    2016-03-18

    Stereoselective oxidative cyclization of 1,5-dienes with hydrogen peroxide catalyzed by [Os(III)(OH)(H2O)(L-N4Me2)](PF6)2 (1: L-N4Me2 = N,N'-dimethyl-2,11-diaza-[3,3](2,6)pyridinophane) is explored. 1,5-Dienes involving geraniol derivatives are converted to the corresponding tetrahydrofurans in modest to high yields. The products exclusively have the cis-conformation with respect to the substituents at the 2- and 5-positions of the tetrahydrofuran ring. The products also have a syn-conformation with respect to the furan oxygen atom and the hydroxyl groups. Mechanistic studies including a direct reaction of the oxo-hydroxo-osmium(V) complex, 2, with a dihydroxylated geraniol derivative are performed. PMID:26950609

  3. Numerical quasi-linear study of the critical ionization velocity phenomenon

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Goertz, C. K.

    1993-01-01

    The critical ionization velocity (CIV) for a neutral barium (Ba) gas cloud moving across the static magnetic field is studied numerically using quasi-linear equations and a parameter range which is typical for the shaped-charge Ba gas release experiments in space. For consistency the charge exchange between the background oxygen ions and neutral atoms and its reverse process, as well as the excitation of the neutral Ba atoms, are included. The numerical results indicate that when the ionization rate due to CIV becomes comparable to the charge exchange rate the energy lost to the ionization and excitation collisions by the superthermal electrons exceeds the energy gain from the waves that are excited by the ion beam. This results in a CIV yield less than the yield by the charge exchange process.

  4. Numerical quasi-linear study of the critical ionization velocity phenomenon

    SciTech Connect

    Moghaddam-Taaheri, E.; Goertz, C.K. )

    1993-02-01

    The critical ionization velocity, (CIV) for a neutral barium (Ba) gas cloud moving across the static magnetic field is studied numerically using quasi-linear equations and a parameter range which is typical for the shaped-charge Ba gas release experiments in space. For consistency the charge exchange between the background oxygen ions and neutral atoms and its reverse process, as well as the excitation of the neutral Ba atoms, are included. The numerical results indicate that when the ionization rate due to CIV becomes comparable to the charge exchange rate the energy lost to the ionization and excitation collisions by the superthermal electrons exceeds the energy gain from the waves that are excited by the ion beam. This results in a CIV yield less than the yield by the charge exchange process. 75 refs., 18 figs., 3 tabs.

  5. The study of ionization by electron impact of a substance simulating spent nuclear fuel components

    NASA Astrophysics Data System (ADS)

    Antonov, N. N.; Bochkarev, E. I.; Gavrikov, A. V.; Samokhin, A. A.; Smirnov, V. P.

    2015-11-01

    Plasma sources of model substances are necessary to solve problems associated with development of the spent nuclear fuel (SNF) plasma separation method. Lead was chosen to simulate kinetic and dynamic properties of the heavy SNF components. In this paper we present the results of a study of a lead vapor discharge with a lead concentration of 1012-1013 cm-3. Ionization was carried out by an electron beam (with energy of up to 500 eV per electron) inside a centimeter gap between planar electrodes. The discharge was numerically modeled using the hydrodynamic and single-particle approximation. Current-voltage characteristics and single ionization efficiency were obtained as functions of the vapors concentration and thermoelectric current. An ion current of hundreds of microamperes at the ionization efficiency near tenths of a percent was experimentally obtained. These results are in good agreement with our model.

  6. Numerical Study on Blast Wave Propagation Driven by Unsteady Ionization Plasma

    SciTech Connect

    Ogino, Yousuke; Sawada, Keisuke; Ohnishi, Naofumi

    2008-04-28

    Understanding the dynamics of laser-produced plasma is essential for increasing the available thrust and energy conversion efficiency from a pulsed laser to a blast wave in a gas-driven laser-propulsion system. The performance of a gas-driven laser-propulsion system depends heavily on the laser-driven blast wave dynamics as well as on the ionizing and/or recombining plasma state that sustains the blast wave. In this study, we therefore develop a numerical simulation code for a laser-driven blast wave coupled with time-dependent rate equations to explore the formation of unsteady ionizing plasma produced by laser irradiation. We will also examine the various properties of blast waves and unsteady ionizing plasma for different laser input energies.

  7. A comparative study of Dissociative Ionization of N2 and CO

    NASA Astrophysics Data System (ADS)

    Pandey, Amrendra; Bapat, B.; Shamsundar, K. R.

    2014-04-01

    A comparative study on the properties of charge symmetric dissociation (CSD) and charge asymmetric dissociation (CAD) of doubly ionized N2 and CO is performed. Kinetic energy release (KER) distributions resulting from the dissociation of doubly charged molecular ions are explained on the basis of calculated potential energy curves.

  8. Comparison of the Reactivity of the Three Distonic Isomers of the Pyridine Radical Cation Toward Tetrahydrofuran in Solution and in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Widjaja, Fanny; Jin, Zhicheng; Nash, John J.; Kenttämaa, Hilkka I.

    2013-04-01

    The reactivity of the three distonic isomers of the pyridine radical cation toward tetrahydrofuran is compared in solution and in the gas phase. In solution, the distonic ions were generated by UV photolysis at 300 nm from iodo-precursors in acidic 50:50 tetrahydrofuran/water solutions. In the gas phase, the ions were generated by collisionally activated dissociation (CAD) of protonated iodo-precursors in an FT-ICR mass spectrometer, as described in the literature. The same major reaction, hydrogen atom abstraction, was observed in solution and in the gas phase. Attempts to cleave the iodine atom from the 2-iodopyridinium cation in the gas phase and in solution yielded the 2-pyridyl cation in addition to the desired 2-dehydropyridinium cation. In the gas phase, this ion was ejected prior to the examination of the desired ion's chemical properties. This was not possible in solution. This study suggests that solvation effects are not significant for radical reactions of charged radicals. On the other hand, the even-electron ion studied, the 2-pyridyl cation, shows substantial solvation effects. For example, in solution, the 2-pyridyl cation forms a stable adduct with tetrahydrofuran, whereas in the gas phase, only addition/elimination reactions were observed.

  9. Ionization of cytosine monomer and dimer studied by VUV photoionization and electronic structure calculations

    SciTech Connect

    Kostko, Oleg; Bravaya, Ksenia; Krylov, Anna; Ahmed, Musahid

    2009-12-14

    We report a combined theoretical and experimental study of ionization of cytosine monomers and dimers. Gas-phase molecules are generated by thermal vaporization of cytosine followed by expansion of the vapor in a continuous supersonic jet seeded in Ar. The resulting species are investigated by single photon ionization with tunable vacuum-ultraviolet (VUV) synchrotron radiation and mass analyzed using reflectron mass spectrometry. Energy onsets for the measured photoionization efficiency (PIE) spectra are 8.60+-0.05 eV and 7.6+-0.1 eV for the monomer and the dimer, respectively, and provide an estimate for the adiabatic ionization energies (AIE). The first AIE and the ten lowest vertical ionization energies (VIEs) for selected isomers of cytosine dimer computed using equation-of-motion coupled-cluster (EOM-IP-CCSD) method are reported. The comparison of the computed VIEs with the derivative of the PIE spectra, suggests that multiple isomers of the cytosine dimer are present in the molecular beam. The calculations reveal that the large red shift (0.7 eV) of the first IE of the lowest-energy cytosine dimer is due to strong inter-fragment electrostatic interactions, i.e., the hole localized on one of the fragments is stabilized by the dipole moment of the other. A sharp rise in the CH+ signal at 9.20+-0.05 eV is ascribed to the formation of protonated cytosine by dissociation of the ionized dimers. The dominant role of this channel is supported by the computed energy thresholds for the CH+ appearance and the barrierless or nearly barrierless ionization-induced proton transfer observed for five isomers of the dimer.

  10. Molecular-dynamics simulations of binary structure II hydrogen and tetrahydrofurane clathrates.

    PubMed

    Alavi, Saman; Ripmeester, J A; Klug, D D

    2006-01-01

    The binary structure II hydrogen and tetrahydrofurane (THF) clathrates are studied with molecular-dynamics simulations. Simulations are done at pressures of 120 and 1.013 bars for temperatures ranging from 100 to 273 K. For the small cages of the structure II unit cell, H2 guest molecule occupancies of 0, 16 (single occupancy), and 32 (double occupancy) are considered. THF occupancies of 0-8 in the large cages are studied. For cases in which THF does not occupy all large cages in a unit cell, the remaining large cages can be occupied with sets of four H2 guest molecules. The unit-cell volumes and configurational energies are compared in the different occupancy cases. Increasing the small cage occupancy leads to an increase in the unit-cell volume and thermal-expansion coefficient. Among simulations with the same small cage occupancy, those with the large cages containing 4H2 guests have the largest volumes. The THF guest molecules have a stabilizing effect on the clathrate and the configurational energy of the unit cell decreases linearly as the THF content increases. For binary THF + H2 clathrates, the substitution of the THF molecules in the large cages with sets of 4H2 molecules increases the configurational energy. For the binary clathrates, various combinations of THF and H2 occupancies have similar configurational energies. PMID:16409048

  11. Studies of nanosecond pulse surface ionization wave discharges over solid and liquid dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Petrishchev, Vitaly; Leonov, Sergey; Adamovich, Igor V.

    2014-12-01

    Surface ionization wave discharges generated by high-voltage nanosecond pulses, propagating over a planar quartz surface and over liquid surfaces (distilled water and 1-butanol) have been studied in a rectangular cross section test cell. The discharge was initiated using a custom-made, alternating polarity, high-voltage nanosecond pulse plasma generator, operated at a pulse repetition rate of 100-500 Hz, with a pulse peak voltage and current of 10-15 kV and 7-20 A, respectively, a pulse FWHM of ˜100 ns, and a coupled pulse energy of 2-9 mJ/pulse. Wave speed was measured using a capacitive probe. ICCD camera images demonstrated that the ionization wave propagated predominantly over the quartz wall or over the liquid surface adjacent to the grounded waveguide placed along the bottom wall of the test cell. Under all experimental conditions tested, the surface plasma ‘sheet’ was diffuse and fairly uniform, both for positive and negative polarities. The parameters of ionization wave discharge propagating over distilled water and 1-butanol surfaces were close to those of the discharge over a quartz wall. No perturbation of the liquid surface by the discharge was detected. In most cases, the positive polarity surface ionization wave propagated at a higher speed and over a longer distance compared to the negative polarity wave. For all three sets of experiments (surface ionization wave discharge over quartz, water and 1-butanol), wave speed and travel distance decreased with pressure. Diffuse, highly reproducible surface ionization wave discharge was also observed over the liquid butanol-saturated butanol vapor interface, as well as over the distilled water-saturated water vapor interface, without buffer gas flow. No significant difference was detected between surface ionization discharges sustained using single-polarity (positive or negative), or alternating polarity high-voltage pulses. Plasma emission images yielded preliminary evidence of charge removal from the

  12. Choosing populations to study the health effects of low-dose ionizing radiation.

    PubMed Central

    Dreyer, N A; Loughlin, J E; Friedlander, E R; Clapp, R W; Fahey, F H

    1981-01-01

    In January 1978, the United States Congress requested information about the utility of additional epidemiologic studies for quantifying the health effects of low-dose ionizing radiation. In our judgment, no single population can be recommended for study on purely scientific grounds, since the largest group offers only a small chance to obtain a definitive result. On the other hand, if social pressures and regulatory agencies mandate that such studies be attempted, we would recommend prospective cohort studies of occupational populations. We propose that a national worker registry be developed using ionizing radiation as the prototype for studying other occupational exposures. The problems related to studying low-level radiation are not unique, but apply equally to investigations dealing with a great variety of toxic agents. A national plan for collecting information on workers' exposure and health could provide a cost-efficient means to answer public health questions posed by the Congress, scientists and the public. PMID:7294269

  13. Study of gel formation by ionizing radiation in polypropylene

    NASA Astrophysics Data System (ADS)

    Oliani, W. L.; Parra, D. F.; Fermino, D. M.; Riella, H. G.; Lima, L. F. C. P.; Lugao, A. B.

    2013-03-01

    The objective of this work is to study the formation of microgel in pristine PP and modified PP. The modified PP in pellets was synthesized by gamma irradiation of pristine PP under a crosslinking atmosphere of acetylene in different doses of 5, 12.5 and 20 kGy, followed by thermal treatment for radical recombination and annihilation of the remaining radicals. The gel content of the modified polypropylenes was determined by extraction in boiling xylene for period of 12 h at 138 °C. The gel formed of pristine PP and modified (i.e., irradiated) was characterized using optical microscopy (OM), scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR) and X-ray diffraction (XDR). The PP morphological study indicated the microgel formation with increase of spherulitic concentration with dose.

  14. Studies of oxidative degradation of polymers induced by ionizing radiation

    SciTech Connect

    Clough, R.L.; Gillen, K.T.

    1989-01-01

    Radiation effects on polymers in the presence of air are characterized by complicated phenomena such as dose-rate effects and post-irradiation degradation. These time-dependent effects can be understood in these terms: (1) features of the free radical chain-reaction chemistry underlying the oxidation, and (2) oxygen diffusion effects. A profiling technique has been developed to study heterogeneous degradation resulting from oxygen diffusion, and kinetic schemes have been developed to allow long-term aging predictions from short-term high dose-rate experiments. Low molecular weight additives which act either as free-radical scavengers or else as energy-scavengers are effective as stabilizers in radiation-oxidation environments. Non-radical oxidation mechanisms, involving species such as ozone, can also be important in the radiation-oxidation of polymers. 18 refs., 15 figs.

  15. Ionization and excitation in collisions between antiprotons and H(1s) atoms studied with Sturmian bases

    SciTech Connect

    Winter, Thomas G.

    2011-02-15

    Coupled two-center as well as one-center Sturmian cross sections have been determined for ionization and excitation in p-bar-H(1s) collisions at p-bar energies from 1 to 16 000 keV, following the author's recent work for p-H(1s) collisions [Phys. Rev. A 80, 032701 (2009)]. Basis convergence is studied in detail. Results for ionization and excitation are compared to other coupled-state results and to numerical results, as well as limited experimental results for ionization only. Except for the large, two-center coupled-Gaussian-pseudostate calculation of Toshima for ionization only [Phys. Rev. A 64, 024701 (2001)], previous calculations employed one-center bases, including a one-center Sturmian calculation by Igarashi et al. [Phys. Rev. A 61, 062712 (2000)]. A strong contrast with p-H collisions is confirmed at intermediate energies, while at high energies the extent of agreement is revealed between coupled-state results for the two collisional systems, as well as with first Born results.

  16. Studying the Effect of Ionization Radiation of 60Co on the Spirulina

    NASA Astrophysics Data System (ADS)

    Ai, Weidang; Guo, Shuang-Sheng; Ai, Weidang; Dong, Wen-Ping; Qin, Li-Feng; Tang, Yong-Kang

    It studied the effect of ionization radiation on the Spirulina plastensis(No.6) by using the γ-rays of 60 Co. In the experiment, Spirulina were irradiated, and the dose of the ionization radiation covered 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0kGy. After irradiating, these Spirulina were cultured under the same conditions. During the course of the experiment, the growth rate, photosynthetic efficiency and nutrition quality of the Spirulina, were analyzed. From the results, low dose of γ-rays (less than 1.5kGy) could improve the content of phycobilin and protein of Spirulina. Only small changes in the morphology of algae filament were found at dose less than 1.0kGy. But with the increase of the dose of γ-rays (more than 1.5kGy), the filaments would break up or even disintegrate. Spirulina had stronger ionization radiation proof and self-rehabilitation capacity, but the growth of Spirulina was stagnated. The LD50 (i.e. the dose resulted in 50% death of the Spirulina) of the colony was 2.0kGy. Considering the capacity of being resistant to γ-rays irradiation, Spirulina can be considered as one of the key biological components in the Controlled Ecological Life Support System (CELSS) for future long-term space missions. Keywords: Controlled Ecological Life Support System (CELSS); Spirulina; ionization radiation; biological component

  17. Studies of the ionization states of solar and galactic cosmic ray heavy nuclei

    NASA Technical Reports Server (NTRS)

    Biswas, S.

    1982-01-01

    Enhancement of abundances of heavy nuclei (e.g., Mg, Si, and Fe) at low energies relative to solar photospheric abundances and anomalously high abundances of iron relative to oxygen nuclei at low energies were recently discovered in solar energetic particles studied at low energy. These phenomena are not understood at present. The proposed experiment is designed to study the recently discovered anomalous component of low energy galactic cosmic ray ions of C, N, O, Ne, and Ca to Fe of energy 5- to 10-million electron volts per atomic mass unit in regard to their ionization states, composition, and intensity, and to study the ionization states of heavy elements from oxygen to iron in energetic solar particles emitted during flare events. The same detector system will serve for both studies, with the second objective being given priority if there are any solar particle events during the mission.

  18. Infrared depletion spectroscopy of the doubly hydrogen-bonded aniline-(tetrahydrofuran) 2 complex produced in supersonic jet

    NASA Astrophysics Data System (ADS)

    Chowdhury, Pradyot K.

    2006-01-01

    The vibrational frequencies of the N-H stretching modes of aniline after forming a strong doubly H-bonded complex with tetrahydrofuran (THF) are measured with infrared depletion spectroscopy that uses cluster-size-selective resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry. Two strong infrared absorption features observed at 3355 and 3488 cm -1 are assigned to the symmetric and antisymmetric N-H stretching vibrations of the 1:2 aniline-THF complex, respectively. The red-shifts of the N-H stretching vibrations of aniline agree with the ab initio calculated (MP2/6-31G**) aniline-(THF) 2 structure in which both aniline N-H bonds interact with the oxygen atom of THF through two hydrogen bonds. The calculated binding energy is found to be 29.6 kJ mol -1 after corrections for basis set superposition error (BSSE) and zero-point energy. The calculated structure revealed that the angle between the N-H bonds in the NH 2 group increased to 112.5° in the aniline-(THF) 2 complex from that of 109.8° in the aniline. The electronic 0-0 band origin for the S1 ← S0 transition is observed at 32,900 cm -1 in the aniline-(THF) 2 complex, giving a red-shift of 1129 cm -1 from that of the aniline molecule.

  19. Benchmark theoretical study of the ionization threshold of benzene and oligoacenes

    NASA Astrophysics Data System (ADS)

    Deleuze, M. S.; Claes, L.; Kryachko, E. S.; François, J.-P.

    2003-08-01

    In straightforward continuation of Green's function studies of the ultraviolet photoelectron spectra of polycyclic aromatic compounds [Deleuze et al., J. Chem. Phys. 115, 5859 (2001); M. S. Deleuze, ibid. 116, 7012 (2002)], we present a benchmark theoretical determination of the ionization thresholds of benzene, naphthalene, anthracene, naphthacene (tetracene), pentacene, and hexacene, within chemical accuracy [0.02-0.07 eV]. The vertical ionization potentials of these compounds have been obtained from series of single-point calculations at the Hartree-Fock, second-, third-, and partial fourth-order Møller-Plesset (MP2, MP3, MP4SDQ) levels, and from coupled cluster calculations including single and double excitations (CCSD) as well as a perturbative estimate of connected triple excitations [CCSD(T)], using basis sets of improving quality, introducing up to 510, 790, 1070, 1350, 1630, and 1910 basis functions in the computations, respectively. A focal point analysis of the convergence of the calculated ionization potentials has been performed in order to extrapolate the CCSD(T) results to an asymptotically (cc-pV∞Z) complete basis set. The present results confirm the adequacy of the outer-valence Green's function scheme for strongly correlated systems. Adiabatic ionization energies have been further determined by incorporating Beck-three-parameter Lee-Yang-Parr functional corrections for zero-point vibrational energies and for geometrical relaxations. Extension of the analysis to the CCSD(T)/cc-pV∞Z level shows that the energy minimum form of the benzene radical cation is an obtuse structure related to the 2B2g state. Isotopic shifts of the adiabatic ionization potentials, due to deuterium substitution of hydrogens, have also been discussed.

  20. Alkene Dioxygenation with Malonoyl Peroxides: Synthesis of γ-Lactones, Isobenzofuranones, and Tetrahydrofurans.

    PubMed

    Alamillo-Ferrer, Carla; Karabourniotis-Sotti, Marianna; Kennedy, Alan R; Campbell, Matthew; Tomkinson, Nicholas C O

    2016-07-01

    Treatment of homoallylic alcohols or carboxylic acids with malonoyl peroxide 1 provides a stereoselective method for the preparation of tetrahydrofurans, γ-lactones, and isobenzofuranones in 44-82% yield and up to 27:1 trans selectivity. Application of this simple and effective heterocyclization in the synthesis of the antidepressant citalopram is also described. PMID:27314605

  1. Manipulation of a Schlenk Line: Preparation of Tetrahydrofuran Complexes of Transition-Metal Chlorides

    ERIC Educational Resources Information Center

    Davis, Craig M.; Curran, Kelly A.

    2007-01-01

    Before taking an inorganic laboratory course few students have experience handling air-sensitive materials using Schlenk techniques. This exercise introduces them to techniques they will employ in later syntheses. The procedure involves the formation of anhydrous tetrahydrofuran complexes of transition-metal chlorides from metal-chloride hydrates;…

  2. Synthesis of the gymnodimine tetrahydrofuran core through a Ueno-Stork radical cyclization.

    PubMed

    Toumieux, Sylvestre; Beniazza, Redouane; Desvergnes, Valérie; Aráoz, Rómulo; Molgó, Jordi; Landais, Yannick

    2011-05-21

    A straightforward access to the C10-C20 skeleton of gymnodimine, incorporating a tetrahydrofuran fragment, is described. The elaboration of the THF moiety is based on a stereocontrolled Ueno-Stork cyclization. A Lewis-acid mediated allylation of the resulting acetal at C13 and a Horner-Wadsworth-Emmons olefination on the ketone at C17 complete the synthesis. PMID:21472158

  3. Computer study of convection of weakly ionized plasma in a nonuniform magnetic field.

    NASA Technical Reports Server (NTRS)

    Shiau, J. N.

    1972-01-01

    A weakly ionized plasma in a strong and nonuniform magnetic field exhibits an instability analogous to the flute instability in a fully ionized plasma. The instability sets in at a critical magnetic field. To study the final state of the plasma after the onset of the instability, the plasma equations are integrated numerically assuming a certain initial spectrum of small disturbances. In the regime studied, numerical results indicate a final steadily oscillating state consisting of a single finite amplitude mode together with a time-independent modification of the original equilibrium. These results agree with the analytic results obtained by Simon in the slightly supercritical regime. As the magnetic field is increased further, the wavelength of the final oscillation becomes nonunique. There exists a subinterval in the unstable wave band. Final stable oscillation with a wavelength in this subinterval can be established if the initial disturbance has a sufficiently strong component at the particular wavelength.

  4. The study of ionizing radiation effects on polypropylene and rice husk ash composite

    NASA Astrophysics Data System (ADS)

    Alfaro, E. F.; Dias, D. B.; Silva, L. G. A.

    2013-03-01

    The aim of this work was to study the ionizing radiation effects on polypropylene/20% of rice husk ash composites. The composites were irradiated by electron beam at different doses and the mechanical and thermal properties were evaluated using tensile strength, Izod impact, hardness, softening temperature, differential scanning calorimetry (DSC) and thermogravimetry (TG). The results showed that the properties decreased by increasing irradiation dose due to chain scission.

  5. Spatially resolved study of the physical properties of the ionized gas in NGC 595

    NASA Astrophysics Data System (ADS)

    Relaño, M.; Monreal-Ibero, A.; Vílchez, J. M.; Kennicutt, R. C.

    2010-03-01

    We present Integral Field Spectroscopy (IFS) of NGC 595, one of the most luminous HII regions in M33. This type of observations allows us to study the variation of the principal emission-line ratios across the surface of the nebula. At each position of the field of view, we fit the main emission-line features of the spectrum within the spectral range of 3650-6990Å and create maps of the principal emission-line ratios for the total surface of the region. The extinction map derived from the Balmer decrement and the absorbed Hα luminosity show good spatial correlation with the 24μm emission from Spitzer. We also show here the capability of the IFS to study the existence of Wolf-Rayet (WR) stars, identifying the previously catalogued WR stars and detecting a new candidate towards the north of the region. The ionization structure of the region nicely follows the Hα shell morphology and is clearly related to the location of the central ionizing stars. The electron density distribution does not show strong variations within the HII region nor any trend with the Hα emission distribution. We study the behaviour within the HII region of several classical emission-line ratios proposed as metallicity calibrators: while [NII]/Hα and [NII]/[OIII] show important variations, the R23 index is substantially constant across the surface of the nebula, despite the strong variation of the ionization parameter as a function of the radial distance from the ionizing stars. These results show the reliability in using the R23 index to characterize the metallicity of HII regions even when only a fraction of the total area is covered by the observations.

  6. Absolute vibrational cross sections for 1-19 eV electron scattering from condensed tetrahydrofuran (THF)

    NASA Astrophysics Data System (ADS)

    Lemelin, V.; Bass, A. D.; Cloutier, P.; Sanche, L.

    2016-02-01

    Absolute cross sections (CSs) for vibrational excitation by 1-19 eV electrons impacting on condensed tetrahydrofuran (THF) were measured with a high-resolution electron energy loss spectrometer. Experiments were performed under ultra-high vacuum (3 × 10-11 Torr) at a temperature of about 20 K. The magnitudes of the vibrational CSs lie within the 10-17 cm2 range. Features observed near 4.5, 9.5, and 12.5 eV in the incident energy dependence of the CSs were compared to the results of theoretical calculations and other experiments on gas and solid-phase THF. These three resonances are attributed to the formation of shape or core-excited shape resonances. Another maximum observed around 2.5 eV is not found in the calculations but has been observed in gas-phase studies; it is attributed to the formation of a shape resonance.

  7. a Study of Biophysical Mechanisms of Damage by Ionizing Radiation to Mammalian Cells in Vitro.

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Zhang

    Available from UMI in association with The British Library. An extensive survey made of published survival data of damage by ionizing radiation to mammalian cells in vitro has led to the new conclusion that the damage is determined by the specific ionization or the mean free path between ionizing events along the charged particle tracks. The optimum damage is observed when the mean free path is equivalent to the DNA double strand spacing of 1.8 nm. Therefore, the biological mechanism of ionizing radiation to mammalian cells in vitro is intra track dominant. A 100 keV electron accelerator has been constructed and commissioned to produce a broad beam irradiation field of greater than 1 cm diameter. The fluence rate may be adjusted from 10^8cm^ {-2}sec^{-1} downwards to enable further development as a chronic irradiation facility. Another new feature of the accelerator is that it incorporates a differential vacuum system which permits irradiation of the monolayer cell cultures to be carried out in normal pressure. Experiments of irradiation to Chinese hamster cells, by ^{241}Am alpha particles at low fluence rate, have supplied satisfactory data for testing a new DNA-rupture model which is under development. For V79 cells irradiated at a low fluence rate of 10^5cm^{ -2}min^{-1}, when survival data were fitted into the model, new biophysical parameters were extracted and a proposal was made that the repair phenomenon of cellular survival at very low doses is determined by three time factors: the irradiation time, the damage fixation time and the repair time. The values obtained were 3-4 hours for the mean repair time, and more than 10 hours for the damage to be considered permanent. Details of the monolayer cell culture technique developed and used in the present experiments are described. Consideration has been given to the significance of the results obtained from the study in radiation protection and in radiotherapy. In future studies it is recommended that more

  8. Study of Electrochemical Reactions Using Nanospray Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Liu, Pengyuan; Lanekoff, Ingela T.; Laskin, Julia; Dewald, Howard D.; Chen, Hao

    2012-07-03

    The combination of electrochemistry (EC) and mass spectrometry (MS) is a powerful analytical tool for studying mechanisms of redox reactions, identification of products and intermediates, and online derivatization/recognition of analytes. This work reports a new coupling interface for EC/MS by employing nanospray desorption electrospray ionization (nano-DESI), a recently developed ambient ionization method. We demonstrate online coupling of nano-DESI-MS with a traditional electrochemical flow cell, in which the electrolyzed solution emanating from the cell is ionized by nano-DESI for MS analysis. Furthermore, we show first coupling of nano-DESI-MS with an interdigitated array (IDA) electrode enabling chemical analysis of electrolyzed samples directly from electrode surfaces. Because of its inherent sensitivity, nano-DESI enables chemical analysis of small volumes and concentrations of sample solution. Specifically, good-quality signal of dopamine and its oxidized form, dopamine ortho-quinone, was obtained using 10 μL of 1 μM solution of dopamine on the IDA. Oxidation of dopamine, reduction of benzodiazepines, and electrochemical derivatization of thiol groups were used to demonstrate the performance of the technique. Our results show the potential of nano-DESI as a novel interface for electrochemical mass spectrometry research.

  9. Differential study on molecular suppressed ionization in intense linearly and circularly polarized laser fields

    NASA Astrophysics Data System (ADS)

    Deng, Yongkai; Liu, Yunquan; Liu, Xianrong; Liu, Hong; Yang, Yudong; Wu, Chengyin; Gong, Qihuang

    2011-12-01

    We present a differential study on above-threshold ionization of the O2 (N2) molecule as well as the companion atom Xe (Ar) (with close ionization potential) produced by linearly and circularly polarized laser fields (25 fs, 795 nm). The photoelectron angular distributions of the companion target are similar at the same laser condition. In both linearly and circularly polarized fields, we observe that the photoelectron yields of O2 are suppressed in the entire energy spectral range as compared with Xe with fully differential measurements, but not for the N2-Ar pair. This is different from the prediction of photoelectron energy spectra by the model including the interference terms [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.85.2280 85, 2280 (2000)], from which the low-energy photoelectrons of O2 were expected to be strongly suppressed in both linearly and circularly polarized laser fields. Resorting to the basic strong-field ionization picture, we believe that the lower orbital-dependent multiphoton excitation or tunneling possibility of O2 as compared with Xe is responsible for this effect. High-resolution fully differential data pose a stringent test on the current strong-field calculations on molecules.

  10. An electron impact and chemical ionization study of some diethyl dicarboxylates

    NASA Astrophysics Data System (ADS)

    Harrison, Alex G.; Malat, Jan

    1997-11-01

    The electron ionization and Bronsted acid chemical ionization mass spectra of the diethyl esters of succinic acid, methylmalonic acid, glutaric acid, ethylmalonic acid and dimethylmalonic acid have been determined. The major primary fragmentation reaction of the molecular ion in the electron ionization mass spectra is by loss of OC2H5 while the MH+ ions fragment by loss of C2H5OH to form the same fragment ion. Using isotopic labelling (diethyl-d5 esters) and metastable ion studies, it is shown that the [M---OC2H5]+ ions formed from diethyl succinate and diethyl glutarate have ethyl-cationated cyclic anhydride structures which fragment further by elimination of C2H4 to form the protonated anhydride. For the remaining esters the [M---OC2H5]+ ions have an acylium ion structure and fragment primarily by elimination of CO to form, initially, substituted [alpha]-carboethoxy carbenium ions although there is significant rearrangement to protonated ethyl esters of olefinic acids prior to further fragmentation.

  11. In-gas-cell laser ionization studies of plutonium isotopes at IGISOL

    NASA Astrophysics Data System (ADS)

    Pohjalainen, I.; Moore, I. D.; Kron, T.; Raeder, S.; Sonnenschein, V.; Tomita, H.; Trautmann, N.; Voss, A.; Wendt, K.

    2016-06-01

    In-gas-cell resonance laser ionization has been performed on long-lived isotopes of Pu at the IGISOL facility, Jyväskylä. This initiates a new programme of research towards high-resolution optical spectroscopy of heavy actinide elements which can be produced in sufficient quantities at research reactors and transported to facilities elsewhere. In this work a new gas cell has been constructed for fast extraction of laser-ionized elements. Samples of 238-240,242Pu and 244Pu have been evaporated from Ta filaments, laser ionized, mass separated and delivered to the collinear laser spectroscopy station. Here we report on the performance of the gas cell through studies of the mass spectra obtained in helium and argon, before and after the radiofrequency quadrupole cooler-buncher. This provides valuable insight into the gas phase chemistry exhibited by Pu, which has been additionally supported by measurements of ion time profiles. The resulting monoatomic yields are sufficient for collinear laser spectroscopy. A gamma-ray spectroscopic analysis of the Pu samples shows a good agreement with the assay provided by the Mainz Nuclear Chemistry department.

  12. Embryos of the zebrafish Danio rerio in studies of non-targeted effects of ionizing radiation.

    PubMed

    Choi, V W Y; Yu, K N

    2015-01-01

    The use of embryos of the zebrafish Danio rerio as an in vivo tumor model for studying non-targeted effects of ionizing radiation was reviewed. The zebrafish embryo is an animal model, which enables convenient studies on non-targeted effects of both high-linear-energy-transfer (LET) and low-LET radiation by making use of both broad-beam and microbeam radiation. Zebrafish is also a convenient embryo model for studying radiobiological effects of ionizing radiation on tumors. The embryonic origin of tumors has been gaining ground in the past decades, and efforts to fight cancer from the perspective of developmental biology are underway. Evidence for the involvement of radiation-induced genomic instability (RIGI) and the radiation-induced bystander effect (RIBE) in zebrafish embryos were subsequently given. The results of RIGI were obtained for the irradiation of all two-cell stage cells, as well as 1.5 hpf zebrafish embryos by microbeam protons and broad-beam alpha particles, respectively. In contrast, the RIBE was observed through the radioadaptive response (RAR), which was developed against a subsequent challenging dose that was applied at 10 hpf when <0.2% and <0.3% of the cells of 5 hpf zebrafish embryos were exposed to a priming dose, which was provided by microbeam protons and broad-beam alpha particles, respectively. Finally, a perspective on the field, the need for future studies and the significance of such studies were discussed. PMID:24176822

  13. Stereodivergent Organocatalytic Intramolecular Michael Addition/Lactonization for the Asymmetric Synthesis of Substituted Dihydrobenzofurans and Tetrahydrofurans

    PubMed Central

    Belmessieri, Dorine; de la Houpliere, Alix; Calder, Ewen D D; Taylor, James E; Smith, Andrew D

    2014-01-01

    A stereodivergent asymmetric Lewis base catalyzed Michael addition/lactonization of enone acids into substituted dihydrobenzofuran and tetrahydrofuran derivatives is reported. Commercially available (S)-(−)-tetramisole hydrochloride gives products with high syn diastereoselectivity in excellent enantioselectivity (up to 99:1 d.r.syn/anti, 99 % eesyn), whereas using a cinchona alkaloid derived catalyst gives the corresponding anti-diastereoisomers as the major product (up to 10:90 d.r.syn/anti, 99 % eeanti). PMID:24989672

  14. Environmental analysis of the life cycle emissions of 2-methyl tetrahydrofuran solvent manufactured from renewable resources.

    PubMed

    Slater, C Stewart; Savelski, Mariano J; Hitchcock, David; Cavanagh, Eduardo J

    2016-01-01

    An environmental analysis has been conducted to determine the cradle to gate life cycle emissions to manufacture the green solvent, 2-methyl tetrahydrofuran. The solvent is considered a greener chemical since it can be manufactured from renewable resources with a lower life cycle footprint. Analyses have been performed using different methods to show greenness in both its production and industrial use. This solvent can potentially be substituted for other ether and chlorinated solvents commonly used in organometallic and biphasic reactions steps in pharmaceutical and fine chemical syntheses. The 2-methyl tetrahydrofuran made from renewable agricultural by-products is marketed by Penn A Kem under the name ecoMeTHF™. The starting material, 2-furfuraldehyde (furfural), is produced from corn cob waste by converting the available pentosans by acid hydrolysis. An evaluation of each step in the process was necessary to determine the overall life cycle and specific CO2 emissions for each raw material/intermediate produced. Allocation of credits for CO2 from the incineration of solvents made from renewable feedstocks significantly reduced the overall carbon footprint. Using this approach, the overall life cycle emissions for production of 1 kg of ecoMeTHF™ were determined to be 0.191 kg, including 0.150 kg of CO2. Life cycle emissions generated from raw material manufacture represents the majority of the overall environmental impact. Our evaluation shows that using 2-methyl tetrahydrofuran in an industrial scenario results in a 97% reduction in emissions, when compared to typically used solvents such as tetrahydrofuran, made through a conventional chemical route. PMID:26889729

  15. Copper-Catalyzed Oxidative C-H Amination of Tetrahydrofuran with Indole/Carbazole Derivatives.

    PubMed

    Yang, Qingjing; Choy, Pui Ying; Fu, Wai Chung; Fan, Baomin; Kwong, Fuk Yee

    2015-11-01

    A simple α-C-H amination of cyclic ether with indole/carbazole derivatives has been accomplished by employing copper(II) chloride/bipy as the catalyst system. In the presence of the di-tert-butyl peroxide oxidant, cyclic ethers such as tetrahydrofuran, 1,4-dioxane, and tetrahydropyran successfully undergo C-H/N-H cross dehydrogenative coupling (CDC) with various carbazole or indole derivatives in good-to-excellent yields. PMID:26485515

  16. Resonantly enhanced multiphoton ionization under XUV FEL radiation: a case study of the role of harmonics

    NASA Astrophysics Data System (ADS)

    Nikolopoulos, G. M.; Lambropoulos, P.

    2015-12-01

    We provide a detailed quantitative study of the possible role of a small admixture of harmonics on resonant two-photon ionization. The motivation comes from the occasional presence of 2nd and 3rd harmonics in FEL radiation. We obtain the dependence of ionic yields on the intensity of the fundamental, the percentage of 2nd harmonic and the detuning of the fundamental from resonance. Having examined the cases of one and two intermediate resonances, we arrive at results of general validity and global behaviour, showing that even a small amount of harmonic may seem deceptively innocuous.

  17. Influence of electron impact ionization on the termination shock: model case studies

    SciTech Connect

    Soloviev, V.Y.; Schwadron, N.A.; McComas, D.J.

    2004-09-15

    We include a latitudinally localized increase in ionization and subsequent mass loading in a 2.5-dimensional magneto-hydrodynamic case study to analyze its impact on the magnetic field, the flow field geometry, and the TS location. The localized additional mass loading leads to deflection of the flow and weakens the TS. We suggest the possibility that Voyager 1 may have been inside such a region during the recent {approx} 6 month period in 2002 when Voyager 1 observed energetic particle signatures consistent with a TS crossing, but only moderate changes in the magnetic field intensity and ACR spectrum.

  18. Study on the noncovalent complexes of ginsenoside and cytochrome c by electrospray ionization mass spectrometry.

    PubMed

    Zhang, Huarong; Ding, Lan; Qu, Chenling; Li, Dan; Zhang, Hanqi

    2007-10-01

    The noncovalent complexes of cytochrome c and ginsenoside were studied by electrospray ionization mass spectrometry (ESI-MS). Ginsenoside Rb2 and Re were bound to cytochrome c to form several complexes with different stoichiometric relation. The 1:1 and 1:2 complexes of cytochrome c to ginsenoside were considered and the dissociation constants were obtained according to the intensities of cytochrome c and complexes when the concentrations of cytochrome c and ginsenoside have been known. Competition experiment was performed to validate the result. The K(D) values obtained with different reactive systems were consistent with each other. PMID:17324614

  19. Pulsed-field-ionization spectroscopy for the study of molecular cations

    NASA Astrophysics Data System (ADS)

    Takazawa, Ken; Fujii, Masaaki; Ebata, Takayuki; Ito, Mitsuo

    1992-02-01

    It is shown that pulsed-field-ionization (PFI) spectroscopy using usual MPI apparatus without any magnetic shielding gives the spectra of molecular cations comparable to those obtained by ZEKE spectroscopy which requires a thorough magnetic shielding. The electrons detected by PFI spectroscopy were proved to come from very high Rydberg states of a neutral molecule near the convergence limit. The potential of PFI spectroscopy for the study of the vibrational structures of cations is demonstrated for the cations of DABCO, 1,2,4,5-tetrafluorobenzene and m-fluorotoluene.

  20. Fully differential study of wave packet scattering in ionization of helium by proton impact

    NASA Astrophysics Data System (ADS)

    Arthanayaka, T.; Lamichhane, B. R.; Hasan, A.; Gurung, S.; Remolina, J.; Borbély, S.; Járai-Szabó, F.; Nagy, L.; Schulz, M.

    2016-07-01

    We present a fully differential study of projectile coherence effects in ionization in p + He collisions. The experimental data are qualitatively reproduced by a non-perturbative ab initio time-dependent model, which treats the projectile coherence properties in terms of a wave packet. A comparison between first- and higher-order treatments shows that the observed interference structures are primarily due to a coherent superposition of different impact parameters leading to the same scattering angle. Higher-order contributions have a significant effect on the interference term.

  1. Ionization in inductively coupled argon plasmas studied by optical emission spectroscopy

    SciTech Connect

    Lee, Young-Kwang; Chung, Chin-Wook

    2011-01-01

    Contribution of stepwise ionization to total ionization was experimentally investigated in low-pressure inductively coupled argon plasmas. In the pressure range 3-50 mTorr, optical emission spectroscopy was employed to determine metastable fractions (metastable density relative to ground state density) by measuring the emission intensity of selected lines. The measured metastable fractions were in good agreement with the calculation, showing a dependence on the discharge pressure. The rate of stepwise ionization was estimated from the excited level densities (measurements and model predictions) and their ionization rate coefficients. It is observed that at relatively low discharge pressures (<10 mTorr) the ionization is mainly provided by the direct ionization, whereas at higher pressure the stepwise ionization is predominant with increasing absorbed power.

  2. A combined electron-ion spectrometer for studying complete kinematics of molecular dissociation upon shell selective ionization

    SciTech Connect

    Saha, K.; Banerjee, S. B.; Bapat, B.

    2013-07-15

    A combined electron-ion spectrometer has been built to study dissociation kinematics of molecular ions upon various electronic decay processes ensuing from ionization of neutral molecules. The apparatus can be used with various ionization agents. Ion time-of-flight (ToF) spectra arising from various electronic decay processes are acquired by triggering the ToF measurement in coincidence with energy analyzed electrons. The design and the performance of the spectrometer in a photoionization experiment is presented in detail. Electron spectra and ion time of flight spectra resulting from valence and 2p{sub 1/2} ionization of Argon and those from valence ionization of CO are presented to demonstrate the capability of the instrument. The fragment ion spectra show remarkable differences (both kinematic and cross sectional) dependent on the energy of the ejected electron, corresponding to various electron loss and decay mechanisms in dissociative photoionization of molecules.

  3. Ionizable Nitroxides for Studying Local Electrostatic Properties of Lipid Bilayers and Protein Systems by EPR.

    PubMed

    Voinov, Maxim A; Smirnov, Alex I

    2015-01-01

    Electrostatic interactions are known to play a major role in the myriad of biochemical and biophysical processes. Here, we describe biophysical methods to probe local electrostatic potentials of proteins and lipid bilayer systems that are based on an observation of reversible protonation of nitroxides by electron paramagnetic resonance (EPR). Two types of probes are described: (1) methanethiosulfonate derivatives of protonatable nitroxides for highly specific covalent modification of the cysteine's sulfhydryl groups and (2) spin-labeled phospholipids with a protonatable nitroxide tethered to the polar head group. The probes of both types report on their ionization state through changes in magnetic parameters and degree of rotational averaging, thus, allowing the electrostatic contribution to the interfacial pKa of the nitroxide, and, therefore, the local electrostatic potential to be determined. Due to their small molecular volume, these probes cause a minimal perturbation to the protein or lipid system. Covalent attachment secures the position of the reporter nitroxides. Experimental procedures to characterize and calibrate these probes by EPR, and also the methods to analyze the EPR spectra by simulations are outlined. The ionizable nitroxide labels and the nitroxide-labeled phospholipids described so far cover an exceptionally wide range of ca. 2.5-7.0 pH units, making them suitable to study a broad range of biophysical phenomena, especially at the negatively charged lipid bilayer surfaces. The rationale for selecting proper electrostatically neutral interface for probe calibration, and examples of lipid bilayer surface potential studies, are also described. PMID:26477252

  4. Potential human study populations for non-ionizing (radio frequency) radiation health effects

    SciTech Connect

    Novotney, L.C.; Gravitis, I.

    1982-12-01

    This research project was initiated to identify potential human populations for future epidemiological studies of the health effects of radio frequency radiation. Through a literature search and contacts with various groups and organizations, numerous occupations and applications of radio frequency radiation (RFR) were identified and evaluated for their suitability for further study. Many populations were eliminated early because their potential exposure to RFR was too limited or data necessary for epidemiological research were unavailable. Eight populations were evaluated in detail and appear to satisfy many of the criteria for epidemiological research and could be useful study groups in an investigation of the health effects of non-ionizing radiation. The eight potential study populations are: RF heat sealer operators, HF (high frequency) tube welder operators, medical diathermy operators in Veterans Administration hospitals, medical diathermy operators in rehabilitation facilities, school children located near broadcasting towers, state policemen, security guards, and radar technicians.

  5. Studies of ground-state dynamics in isolated species by ionization-detected stimulated Raman techniques

    SciTech Connect

    Felker, P.M.

    1993-12-01

    First, the author aims to develop methods of nonlinear Raman spectroscopy for application in studies of sparse samples. Second, the author wishes to apply such methods to structural and dynamical studies of species (molecules, complexes, and clusters) in supersonic molecular beams. In the past year, the author has made progress in several areas. The first pertains to the application of mass-selective ionization-detected stimulated Raman spectroscopies (IDSRS) to the size-specific vibrational spectroscopy of solute-solvent{sub n} clusters. The second involves the application of IDSRS methods to studies of jet-cooled benzene clusters. The third pertains to the use of IDSRS methods in the study of intermolecular vibrational transitions in van der Waals complexes.

  6. Epidemiologic Study of One Million American Workers and Military Veterans Exposed to Ionizing Radiation

    SciTech Connect

    Boice, John D.

    2015-02-27

    A pilot study was completed demonstrating the feasibility of conducting an epidemiologic study assessing cancer and other disease mortality among nearly one million US veterans and workers exposed to ionizing radiation, a population 10 times larger than atomic bomb survivor study with high statistical power to evaluate low dose rate effects. Among the groups enumerated and/or studied were: (1) 194,000 Department of Energy Uranium Workers; (2) 6,700 Rocketdyne Radiation Workers; (3) 7,000 Mound Radiation Workers; (4) 156,000 DOE Plutonium Workers; (5) 212,000 Nuclear Power Plant Workers; (6) 130,000 Industrial Radiography Workers; (7) 1.7 million Medical Workers and (8) 135,000 Atomic Veterans.

  7. Studying the Chemistry of Cationized Triacylglycerols Using Electrospray Ionization Mass Spectrometry and Density Functional Theory Computations

    NASA Astrophysics Data System (ADS)

    Grossert, J. Stuart; Herrera, Lisandra Cubero; Ramaley, Louis; Melanson, Jeremy E.

    2014-08-01

    Analysis of triacylglycerols (TAGs), found as complex mixtures in living organisms, is typically accomplished using liquid chromatography, often coupled to mass spectrometry. TAGs, weak bases not protonated using electrospray ionization, are usually ionized by adduct formation with a cation, including those present in the solvent (e.g., Na+). There are relatively few reports on the binding of TAGs with cations or on the mechanisms by which cationized TAGs fragment. This work examines binding efficiencies, determined by mass spectrometry and computations, for the complexation of TAGs to a range of cations (Na+, Li+, K+, Ag+, NH4 +). While most cations bind to oxygen, Ag+ binding to unsaturation in the acid side chains is significant. The importance of dimer formation, [2TAG + M]+ was demonstrated using several different types of mass spectrometers. From breakdown curves, it became apparent that two or three acid side chains must be attached to glycerol for strong cationization. Possible mechanisms for fragmentation of lithiated TAGs were modeled by computations on tripropionylglycerol. Viable pathways were found for losses of neutral acids and lithium salts of acids from different positions on the glycerol moiety. Novel lactone structures were proposed for the loss of a neutral acid from one position of the glycerol moiety. These were studied further using triple-stage mass spectrometry (MS3). These lactones can account for all the major product ions in the MS3 spectra in both this work and the literature, which should allow for new insights into the challenging analytical methods needed for naturally occurring TAGs.

  8. Distributions of deposited energy and ionization clusters around ion tracks studied with Geant4 toolkit

    NASA Astrophysics Data System (ADS)

    Burigo, Lucas; Pshenichnov, Igor; Mishustin, Igor; Hilgers, Gerhard; Bleicher, Marcus

    2016-05-01

    The Geant4-based Monte Carlo model for Heavy-Ion Therapy (MCHIT) was extended to study the patterns of energy deposition at sub-micrometer distance from individual ion tracks. Dose distributions for low-energy 1H, 4He, 12C and 16O ions measured in several experiments are well described by the model in a broad range of radial distances, from 0.5 to 3000 nm. Despite the fact that such distributions are characterized by long tails, a dominant fraction of deposited energy (∼80%) is confined within a radius of about 10 nm. The probability distributions of clustered ionization events in nanoscale volumes of water traversed by 1H, 2H, 4He, 6Li, 7Li, and 12C ions are also calculated. A good agreement of calculated ionization cluster-size distributions with the corresponding experimental data suggests that the extended MCHIT can be used to characterize stochastic processes of energy deposition to sensitive cellular structures.

  9. Valence ionized states of iron pentacarbonyl and eta5-cyclopentadienyl cobalt dicarbonyl studied by symmetry-adapted cluster-configuration interaction calculation and collision-energy resolved Penning ionization electron spectroscopy.

    PubMed

    Fukuda, Ryoichi; Ehara, Masahiro; Nakatsuji, Hiroshi; Kishimoto, Naoki; Ohno, Koichi

    2010-02-28

    Valence ionized states of iron pentacarbonyl Fe(CO)(5) and eta(5)-cyclopentadienyl cobalt dicarbonyl Co(eta(5)-C(5)H(5))(CO)(2) have been studied by ultraviolet photoelectron spectroscopy, two-dimensional Penning ionization electron spectroscopy (2D-PIES), and symmetry-adapted cluster-configuration interaction calculations. Theory provided reliable assignments for the complex ionization spectra of these molecules, which have metal-carbonyl bonds. Theoretical ionization energies agreed well with experimental observations and the calculated wave functions could explain the relative intensities of PIES spectra. The collision-energy dependence of partial ionization cross sections (CEDPICS) was obtained by 2D-PIES. To interpret these CEDPICS, the interaction potentials between the molecules and a Li atom were examined in several coordinates by calculations. The relation between the slope of the CEDPICS and the electronic structure of the ionized states, such as molecular symmetry and the spatial distribution of ionizing orbitals, was analyzed. In Fe(CO)(5), an attractive interaction was obtained for the equatorial CO, while the interaction for the axial CO direction was repulsive. For Co(eta(5)-C(5)H(5))(CO)(2), the interaction potential in the direction of both Co-C-O and Co-Cp ring was attractive. These anisotropic interactions and ionizing orbital distributions consistently explain the relative slopes of the CEDPICS. PMID:20192297

  10. Resonance ionization mass spectrometric study of the promethium/samarium isobaric pair

    SciTech Connect

    Shaw, R.W.; Young, J.P.; Smith, D.H.

    1988-01-01

    Samarium daughters are problematic in isotope ratio measurements of promethium because they are isobaric. Resonance ionization mass spectrometry was utilized to circumvent this problem. An ionization selectivity factor of at least 1000:1 has been measured for promethium over samarium at 584.6 nm. Resonance ionization spectra have been recorded for both elements over the 528-560 and 580-614 nm wavelength ranges.

  11. Theoretical study of γ-aminobutyric acid conformers: Intramolecular interactions and ionization energies

    NASA Astrophysics Data System (ADS)

    Wang, Ke-Dong; Wang, Mei-Ting; Meng, Ju

    2014-10-01

    Allowing for all combinations of internal single-bond rotamers, 1,296 unique trial structures of γ-Aminobutyric acid (GABA) are obtained. All of these structures are optimized at the M06-2X level of theory and a total of 68 local minimal conformers are found. The nine low-lying conformers are used for further studies. According to the calculated relative Gibbs free energies at M06-2X level of theory, we find that the dispersion is important for the relative energy of GABA. The intramolecular hydrogen bonds and hyperconjugative interaction and their effects on the conformational stability are studied. The results show that both of them have great influence on the conformers. The vertical ionization energies (VIE) are calculated and match the experimental data well. The results show that the neutral GABA in the gas phase is a multi-conformer system and at least four conformations exist.

  12. Study on the electromagnetic waves propagation characteristics in partially ionized plasma slabs

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Bin; Li, Bo-Wen; Nie, Qiu-Yue; Wang, Xiao-Gang; Kong, Fan-Rong

    2016-05-01

    Propagation characteristics of electromagnetic (EM) waves in partially ionized plasma slabs are studied in this paper. Such features are significant to applications in plasma antennas, blackout of re-entry flying vehicles, wave energy injection to plasmas, and etc. We in this paper developed a theoretical model of EM wave propagation perpendicular to a plasma slab with a one-dimensional density inhomogeneity along propagation direction to investigate essential characteristics of EM wave propagation in nonuniform plasmas. Particularly, the EM wave propagation in sub-wavelength plasma slabs, where the geometric optics approximation fails, is studied and in comparison with thicker slabs where the geometric optics approximation applies. The influences of both plasma and collisional frequencies, as well as the width of the plasma slab, on the EM wave propagation characteristics are discussed. The results can help the further understanding of propagation behaviours of EM waves in nonuniform plasma, and applications of the interactions between EM waves and plasmas.

  13. Study of multi-electron ionization and charge exchange in HIBF

    NASA Astrophysics Data System (ADS)

    Wu, Linchun

    Beam ion stripping on background gases or plasma in a Heavy Ion Beam Fusion (HIBF) chamber increases the charge state of the beam and the diameter of the focus, complicating the final focusing on the focusing target. To model beam transport in the chamber, it is necessary to know the beam charge-state evolution, including both ionization and charge exchange dynamics. The main objective of this research is to explore theoretical approaches including scaling law. Improved models are developed to calculate multi-electron loss, especially ion stripping and charge exchange cross sections, for both near-term experiments and future power plant scale HIBF research. First, a new space-charge neutralization approach that uses electron injection is proposed for the ion beam transport in HIBF chamber. An analytical study was performed to illustrate the plasma dynamics and final neutralization effects with this technique. The results examine the effect of different injected electron profiles. Next, to improve the accuracy of such simulations, methods to improve cross sections of ionization and charge exchange are studied. Both classical and quantum mechanical approaches are examined. Attention is focused on the interaction by low-charge-state heavy ions. Multi-electron processes for dressed ions, including screening and anti-screening effects, internuclear forces, are given special attention, This analysis is complex and requires a combining several different theoretical approaches. Finally, a Classic Trajectory Monte Carlo (CTMC) model based on an improvement of Olson's n-body CTMC method is presented. This model solves the n-body ion-atom ionization problem in a regime of intent to HIBF. In the paper, a new and complete computational module for these interactions has been developed. The cross section data for Xe, Cs, and Bi ions colliding with various background gases (Xe, N2, Ar and Flibe) is presented. After the calculation of the cross section data, the predicted energy

  14. 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 ...

  15. Study of bis(bibenzyls) in bryophytes using electron ionization time-of-flight and electrospray ionization triple-quadrupole mass spectrometry.

    PubMed

    Guo, Huaifang; Xing, Jie; Xie, Chunfeng; Qu, Jianbo; Gao, Yanhui; Lou, Hongxiang

    2007-01-01

    A detailed analysis of mass spectra generated from bis(bibenzyl) compounds in bryophytes under electron ionization time-of-flight (EI-TOF) and electrospray ionization triple-quadrupole (ESI-TQ) mass spectrometry conditions is reported. Proposed structures of the fragment ions were obtained by tracking the functional groups of 15 bis(bibenzyls), the structures of which are similar except for some alkoxyl substituents and linkage sites of biphenyl ether bonds. The elucidation was aided by the use of accurate mass measurements. Attempts have been made to provide rational pathways for the formation of these fragment ions, and a generalized fragmentation mechanism is proposed. The bis(bibenzyls) mentioned in this study include three types according to their structure characteristics, i.e. one biphenyl ether bond (A-type), two biphenyl ether bonds (B-type), one biphenyl ether and one biphenyl bond (C-type). The three types display different EI-MS and ESI-MS/MS product profiles, by which the bis(bibenzyl) type and the number of alkoxyl substituents can be identified. Isomers of bis(bibenzyls) can be differentiated to some extent, while the linkage sites of biphenyl ether bonds are difficult to identify. The structure-fragmentation relationships will facilitate the characterization of other bis(bibenzyls) and this will be of value for the high-throughput screening of novel bis(bibenzyls) in bryophytes. PMID:17348087

  16. Ionizable Nitroxides for Studying Local Electrostatic Properties of Lipid Bilayers and Protein Systems by EPR

    PubMed Central

    Voinov, Maxim A.; Smirnov, Alex I.

    2016-01-01

    Electrostatic interactions are known to play one of the major roles in the myriad of biochemical and biophysical processes. In this Chapter we describe biophysical methods to probe local electrostatic potentials of proteins and lipid bilayer systems that is based on an observation of reversible protonation of nitroxides by EPR. Two types of the electrostatic probes are discussed. The first one includes methanethiosulfonate derivatives of protonatable nitroxides that could be used for highly specific covalent modification of the cysteine’s sulfhydryl groups. Such spin labels are very similar in magnetic parameters and chemical properties to conventional MTSL making them suitable for studying local electrostatic properties of protein-lipid interfaces. The second type of EPR probes is designed as spin-labeled phospholipids having a protonatable nitroxide tethered to the polar head group. The probes of both types report on their ionization state through changes in magnetic parameters and a degree of rotational averaging, thus, allowing one to determine the electrostatic contribution to the interfacial pKa of the nitroxide, and, therefore, determining the local electrostatic potential. Due to their small molecular volume these probes cause a minimal perturbation to the protein or lipid system while covalent attachment secure the position of the reporter nitroxides. Experimental procedures to characterize and calibrate these probes by EPR and also the methods to analyze the EPR spectra by least-squares simulations are also outlined. The ionizable nitroxide labels and the nitroxide-labeled phospholipids described so far cover an exceptionally wide pH range from ca. 2.5 to 7.0 pH units making them suitable to study a broad range of biophysical phenomena especially at the negatively charged lipid bilayer surfaces. The rationale for selecting proper electrostatically neutral interface for calibrating such probes and example of studying surface potential of lipid bilayer is

  17. Study of ionizing radiation on the properties of polyamide 6 with fiberglass reinforcement

    NASA Astrophysics Data System (ADS)

    Pinto, Clovis; Silva, Leonardo G. Andrade e.

    2007-11-01

    The use of polymers reinforced with fiberglass is becoming more and more common in the switches for household industries. These compounds perform a good tension resistance to the impact and the humidity absorption being used at the present time and also are in the automobile industry in parts underneath the hood, especially in the radiator frames. The aim of this work is to study the effect of ionizing radiation on the properties of polyamide 6 with fiberglass reinforcement and undergone to different irradiation doses. Samples were prepared and irradiated on JOB 188 accelerator with an electron beam energy of 1.5 MeV in air with different doses and a dose rate of 27.99 kGy/h. Afterward, the properties of the non-irradiated and irradiated polyamide 6 with fiberglass reinforcement were evaluated.

  18. Experimental and theoretical study on nonsequential double ionization of carbon disulfide in strong near-IR laser fields

    NASA Astrophysics Data System (ADS)

    Zuo, Wanlong; Ben, Shuai; Lv, Hang; Zhao, Lei; Guo, Jing; Liu, Xue-Shen; Xu, Haifeng; Jin, Mingxing; Ding, Dajun

    2016-05-01

    Nonsequential double ionization (NSDI) of carbon disulfide CS2 in strong 800-nm laser fields is studied experimentally and theoretically. A knee structure is observed in the intensity-dependent double ionization (DI) yield in linearly polarized laser fields, which exhibits a strong dependence on the laser ellipticity. The electron momentum distributions and energy trajectories after DI in both linearly and circularly polarized laser fields are investigated by employing the two-dimensional classical ensemble method. The results clearly show the evidence of NSDI in the strong-field DI of CS2 molecules. It is demonstrated that, similar to that of atoms, NSDI of CS2 molecules is produced via laser-driven electron recollision with the ion core and presents electron-electron correlations in the process. Analysis indicates that both mechanisms in atomic strong-field NSDI, i.e., recollision impact ionization and recollision excitation with subsequent ionization, may also be contributed to NSDI of CS2 in strong laser fields. Further studies are no doubt necessary for a full understanding of the underlying physical mechanism of molecular strong-field NSDI, due to the multicenter character of the molecular structure and the complex molecular excited states that could be involved in the ionization.

  19. Mechanical properties of sand, silt, and clay containing tetrahydrofuran hydrate

    USGS Publications Warehouse

    Yun, T.S.; Santamarina, C.J.; Ruppel, C.

    2007-01-01

    The mechanical behavior of hydrate-bearing sediments subjected to large strains has relevance for the stability of the seafloor and submarine slopes, drilling and coring operations, and the analysis of certain small-strain properties of these sediments (for example, seismic velocities). This study reports on the results of comprehensive axial compression triaxial tests conducted at up to 1 MPa confining pressure on sand, crushed silt, precipitated silt, and clay specimens with closely controlled concentrations of synthetic hydrate. The results show that the stress-strain behavior of hydrate-bearing sediments is a complex function of particle size, confining pressure, and hydrate concentration. The mechanical properties of hydrate-bearing sediments at low hydrate concentration (probably 50% of pore space), the behavior becomes more independent of stress because the hydrates control both stiffness and strength and possibly the dilative tendency of sediments by effectively increasing interparticle coordination, cementing particles together, and filling the pore space. The cementation contribution to the shear strength of hydrate-bearing sediments decreases with increasing specific surface of soil minerals. The lower the effective confining stress, the greater the impact of hydrate formation on normalized strength.

  20. Differential cross sections for electron-impact vibrational-excitation of tetrahydrofuran at intermediate impact energies

    SciTech Connect

    Do, T. P. T.; Lopes, M. C. A.; Konovalov, D. A.; White, R. D.; Brunger, M. J. E-mail: darryl.jones@flinders.edu.au; Jones, D. B. E-mail: darryl.jones@flinders.edu.au

    2015-03-28

    We report differential cross sections (DCSs) for electron-impact vibrational-excitation of tetrahydrofuran, at intermediate incident electron energies (15-50 eV) and over the 10°-90° scattered electron angular range. These measurements extend the available DCS data for vibrational excitation for this species, which have previously been obtained at lower incident electron energies (≤20 eV). Where possible, our data are compared to the earlier measurements in the overlapping energy ranges. Here, quite good agreement was generally observed where the measurements overlapped.

  1. Tetrahydrofuran amino acid-containing gramicidin S analogues with improved biological profiles.

    PubMed

    Pal, Sudip; Singh, Gajendra; Singh, Shyam; Tripathi, Jitendra Kumar; Ghosh, Jimut Kanti; Sinha, Sudhir; Ampapathi, Ravi Sankar; Chakraborty, Tushar Kanti

    2015-06-28

    Gramicidin S (GS) is a cyclic cationic antimicrobial peptide (CAP) with a wide spectrum of antibiotic activities whose usage has been limited to topical applications owing to its cytotoxic side effects. We have synthesized tetrahydrofuran amino acid (Taa)-containing GS analogues, and we have carried out conformational analysis and explored their structure activity relationships by evaluating their antitubercular, antibacterial and cytotoxic properties. Two of these analogues showed impressive as well as selective activity against Mycobacterium tuberculosis (MTB) without toxicity towards mammalian Vero cells or human RBCs, and are promising as potential leads. PMID:26008215

  2. New MOF based on lithium tetrahydrofuran-2,3,4,5-tetracarboxylate: Its structure and conductivity behavior

    SciTech Connect

    Zima, Vitezslav; Patil, Deepak S.; Raja, Duraisamy Senthil; Chang, Ting-Guang; Lin, Chia-Her; Shimakawa, Koichi; Wagner, Tomas

    2014-09-15

    A novel metal–organic framework, [Li{sub 6}(HTFTA){sub 2}(H{sub 2}O){sub 3}]·3H{sub 2}O (LiTFTA, H{sub 4}TFTA is tetrahydrofuran-2,3,4,5-tetracarboxylic acid), has been synthesized under solvothermal conditions and its structure was determined by single-crystal X-ray diffraction studies. It has six different LiO{sub 4} tetrahedra which forms two kinds of tetranuclear clusters that are coordinated to the ligands and form an overall three-dimensional structure with channels running along the crystallographic a axis. Some of the carboxylate groups of the ligand moiety jut out into the channels and the channels are occupied by water molecules. The proton conductivity behavior of LiTFTA with respect to temperature and relative humidity was analyzed by our newly developed impedance data analysis method called a random-walk approach. The results were compared with the data obtained by an analysis using an equivalent electric circuit model. Based on the physical parameters obtained by the random-walk method and the known structure we suggested the mechanism of the proton conductivity in this material. The proton conduction proceeds most probably by a vehicle conduction mechanism which employs mainly water molecules of crystallization present in the channels of LiTFTA. The value of the diffusion coefficient increases with temperature whereas the number of charge carriers remains constant. On the other hand, both the number of charge carriers and diffusion coefficient increase with increasing relative humidity. - Graphical abstract: Structure of a new metal organic framework was determined and its ionic conductivity was evaluated using a random-walk approach. - Highlights: • Lithium tetrahydrofuran-2,3,4,5-tetracarboxylate is a MOF with water-filled pores. • The impedance spectra indicate that this material is ion conductive. • Conductivity was evaluated using a random walk approach. • The number of charge carriers and diffusion coefficient was determined.

  3. Ionization states, cellular toxicity and molecular modeling studies of midazolam complexed with trimethyl-β-cyclodextrin.

    PubMed

    Shityakov, Sergey; Sohajda, Tamás; Puskás, István; Roewer, Norbert; Förster, Carola; Broscheit, Jens-Albert

    2014-01-01

    We investigated the ionization profiles for open-ring (OR) and closed-ring (CR) forms of midazolam and drug-binding modes with heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (trimethyl-β-cyclodextrin; TRIMEB) using molecular modeling techniques and quantum mechanics methods. The results indicated that the total net charges for different molecular forms of midazolam tend to be cationic for OR and neutral for CR at physiological pH levels. The thermodynamic calculations demonstrated that CR is less water-soluble than OR, mainly due to the maximal solvation energy (ΔG(CR)(solv = -9.98 kcal·mol ⁻¹), which has a minimal ΔG(OR)(solv) of -67.01 kcal·mol⁻¹. A cell viability assay did not detect any signs of TRIMEB and OR/CR-TRIMEB complex toxicity on the cEND cells after 24 h of incubation in either Dulbecco's Modified Eagles Medium or in heat-inactivated human serum. The molecular docking studies identified the more flexible OR form of midazolam as being a better binder to TRIMEB with the fluorophenyl ring introduced inside the amphiphilic cavity of the host molecule. The OR binding affinity was confirmed by a minimal Gibbs free energy of binding (ΔG(bind)) value of -5.57 ± 0.02 kcal·mol⁻¹, an equilibrium binding constant (K(b)) of 79.89 ± 2.706 μM, and a ligand efficiency index (LE(lig)) of -0.21 ± 0.001. Our current data suggest that in order to improve the clinical applications of midazolam via its complexation with trimethyl-β-cyclodextrin to increase drug's overall aqueous solubility, it is important to concern the different forms and ionization states of this anesthetic. All mean values are indicated with their standard deviations. PMID:25338177

  4. Atmospheric pressure chemical ionization studies of non-polar isomeric hydrocarbons using ion mobility spectrometry and mass spectrometry with different ionization techniques

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    The ionization pathways were determined for sets of isomeric non-polar hydrocarbons (structural isomers, cis/trans isomers) using ion mobility spectrometry and mass spectrometry with different techniques of atmospheric pressure chemical ionization to assess the influence of structural features on ion formation. Depending on the structural features, different ions were observed using mass spectrometry. Unsaturated hydrocarbons formed mostly [M - 1]+ and [(M - 1)2H]+ ions while mainly [M - 3]+ and [(M - 3)H2O]+ ions were found for saturated cis/trans isomers using photoionization and 63Ni ionization. These ionization methods and corona discharge ionization were used for ion mobility measurements of these compounds. Different ions were detected for compounds with different structural features. 63Ni ionization and photoionization provide comparable ions for every set of isomers. The product ions formed can be clearly attributed to the structures identified. However, differences in relative abundance of product ions were found. Although corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra detected are complex and differ from those obtained with 63Ni ionization and photoionization. c. 2002 American Society for Mass Spectrometry.

  5. Is ionized calcium a reliable predictor of hypocalcemia after total thyroidectomy? A before and after study

    PubMed Central

    TARTAGLIA, F.; GIULIANI, A.; SGUEGLIA, M.; PATRIZI, G.; DI ROCCO, G.; BLASI, S.; RUSSO, G.; TORTORELLI, G.; GIANNOTTI, D.; REDLER, A.

    2014-01-01

    Summary Wanting to find a way of identifying patients suitable for early discharge after thyroidectomy, we set out to establish whether ionized calcium concentration is a better predictor of post-surgical hypocalcemia than total serum calcium. Data were analyzed to establish whether serum ionized calcium concentrations are correlated with total serum calcium levels and symptomatic hypocalcemia after thyroidectomy. Sixty-two patients undergoing total thyroidectomy at the Department of Surgical Sciences of the “Sapienza” University of Rome, Italy, in 2010. Ionized calcium was measured before (day 0) and after surgery (days 1, 2 and 60) in all the patients. These measurements were compared with preoperative (day 0) and postoperative total serum calcium levels (days 1, 2 and 60). The preoperative ionized calcium levels differed from the ionized calcium levels recorded on days 1 and 2; this pattern was not observed for the total calcium concentrations. Conversely, total calcium on days I and II correlated significantly with the various ionized calcium measurements. The presence of parathyroid glands in the surgical specimen did not seem to affect suitability for discharge. The statistical analysis showed that ionized calcium measurements are more reliable than total calcium measurements in the immediate and long-term follow-up of total thyroidectomy patients. Applying a 95% confidence interval we established reference values for both total serum calcium and ionized calcium, below which all patients develop postoperative symptomatic hypocalcemia. In conclusion, measurement of ionized calcium, as opposed to total calcium, should be strongly recommended in the immediate and long-term follow-up of total thyroidectomy patients. PMID:24690338

  6. Is ionized calcium a reliable predictor of hypocalcemia after total thyroidectomy? A before and after study.

    PubMed

    Tartaglia, F; Giuliani, A; Sgueglia, M; Patrizi, G; Di Rocco, G; Blasi, S; Russo, G; Tortorelli, G; Giannotti, D; Redler, A

    2014-01-01

    Wanting to find a way of identifying patients suitable for early discharge after thyroidectomy, we set out to establish whether ionized calcium concentration is a better predictor of post-surgical hypocalcemia than total serum calcium. Data were analyzed to establish whether serum ionized calcium concentrations are correlated with total serum calcium levels and symptomatic hypocalcemia after thyroidectomy. Sixty-two patients undergoing total thyroidectomy at the Department of Surgical Sciences of the "Sapienza" University of Rome, Italy, in 2010. Ionized calcium was measured before (day 0) and after surgery (days 1, 2 and 60) in all the patients. These measurements were compared with preoperative (day 0) and postoperative total serum calcium levels (days 1, 2 and 60). The preoperative ionized calcium levels differed from the ionized calcium levels recorded on days 1 and 2; this pattern was not observed for the total calcium concentrations. Conversely, total calcium on days I and II correlated significantly with the various ionized calcium measurements. The presence of parathyroid glands in the surgical specimen did not seem to affect suitability for discharge. The statistical analysis showed that ionized calcium measurements are more reliable than total calcium measurements in the immediate and long-term follow-up of total thyroidectomy patients. Applying a 95% confidence interval we established reference values for both total serum calcium and ionized calcium, below which all patients develop postoperative symptomatic hypocalcemia. In conclusion, measurement of ionized calcium, as opposed to total calcium, should be strongly recommended in the immediate and longterm follow-up of total thyroidectomy patients. PMID:24690338

  7. Protecting-Group-Free Total Synthesis of (-)-Jiadifenolide: Development of a [4 + 1] Annulation toward Multisubstituted Tetrahydrofurans.

    PubMed

    Shen, Yang; Li, Linbin; Pan, Zhisheng; Wang, Yinglu; Li, Jundong; Wang, Kuangyu; Wang, Xiance; Zhang, Youyu; Hu, Tianhui; Zhang, Yandong

    2015-11-01

    A concise, protecting-group-free total synthesis of (-)-jiadifenolide, a synthetically challenging seco-prezizaane sesquiterpene with potent neurotrophic activity, is reported. The convergent route features a SmI2/H2O-mediated stereoselective reductive cyclization, an unprecedented formal [4 + 1] annulative tetrahydrofuran-forming reaction and programmed redox manipulations. The newly developed annulation of β-hydroxy aldehydes or ketones with lithium trimethylsilyldiazomethane provides access to a diverse array of multisubstituted tetrahydrofurans. The synthetic jiadifenolide exhibited weak cytotoxicity against five human cancer cell lines. PMID:26509873

  8. Divergent Synthesis of Multisubstituted Tetrahydrofurans and Pyrrolidines via Intramolecular Aldol-type Trapping of Onium Ylide Intermediates.

    PubMed

    Jing, Changcheng; Xing, Dong; Gao, Lixin; Li, Jia; Hu, Wenhao

    2015-12-21

    This paper reports a divergent strategy for the synthesis of multisubstituted tetrahydrofurans and pyrrolidines, starting from easily accessible β-hydroxyketones or β-aminoketones to react with diazo compounds. Under Rh(II) catalysis, this transformation is proposed to proceed through a metal-carbene-induced oxonium ylide or ammonium ylide formation followed by an intramolecular aldol-type trapping of these active intermediates. A series of highly substituted tetrahydrofurans and pyrrolidines are synthesized in high yields with good to excellent diastereoselectivities. Preliminary biological evaluations revealed that both types of heterocycles show good PTP1B inhibitory activities. PMID:26592374

  9. Understanding the Phase Behavior of Tetrahydrofuran + Carbon Dioxide, + Methane, and + Water Binary Mixtures from the SAFT-VR Approach.

    PubMed

    Míguez, J M; Piñeiro, M M; Algaba, J; Mendiboure, B; Torré, J P; Blas, F J

    2015-11-01

    The high-pressure phase diagrams of the tetrahydrofuran(1) + carbon dioxide(2), + methane(2), and + water(2) mixtures are examined using the SAFT-VR approach. Carbon dioxide molecule is modeled as two spherical segments tangentially bonded, water is modeled as a spherical segment with four associating sites to represent the hydrogen bonding, methane is represented as an isolated sphere, and tetrahydrofuran is represented as a chain of m tangentially bonded spherical segments. Dispersive interactions are modeled using the square-well intermolecular potential. In addition, two different molecular model mixtures are developed to take into account the subtle balance between water-tetrahydrofuran hydrogen-bonding interactions. The polar and quadrupolar interactions present in water, tetrahydrofuran, and carbon dioxide are treated in an effective way via square-well potentials of variable range. The optimized intermolecular parameters are taken from the works of Giner et al. (Fluid Phase Equil. 2007, 255, 200), Galindo and Blas (J. Phys. Chem. B 2002, 106, 4503), Patel et al. (Ind. Eng. Chem. Res. 2003, 42, 3809), and Clark et al. (Mol. Phys. 2006, 104, 3561) for tetrahydrofuran, carbon dioxide, methane, and water, respectively. The phase diagrams of the binary mixtures exhibit different types of phase behavior according to the classification of van Konynenburg and Scott, ranging from types I, III, and VI phase behavior for the tetrahydrofuran(1) + carbon dioxide(2), + methane(2), and + water(2) binary mixtures, respectively. This last type is characterized by the presence of a Bancroft point, positive azeotropy, and the so-called closed-loop curves that represent regions of liquid-liquid immiscibility in the phase diagram. The system exhibits lower critical solution temperatures (LCSTs), which denote the lower limit of immiscibility together with upper critical solution temperatures (UCSTs). This behavior is explained in terms of competition between the incompatibility

  10. High-resolution pulsed-field ionization photoelectron study of O{sub 2}

    SciTech Connect

    Hsu, C.W.; Evans, M.; Stimson, S.

    1997-04-01

    There have been numerous photoionization studies of O{sub 2} over the past 10 years. Using the pulsed field ionization (PFI) photoelectron spectroscopy (PES) technique, the electronic ground state of O{sub 2}{sup +} (X{sup 2}{Pi}{sub g}{sup {minus}}) has been well studied on the rotationally resolved level by several groups. However, due to the difficulty of producing photon energies above 18 eV using the tunable lasers, the electronic excited states of O{sub 2}{sup +} have been mostly studied on the vibrationally resolved level using the threshold photoelectron spectroscopy (TPES) and the synchrotron radiation. Recently, the authors developed a new technique for performing the PFI-PE experiments using multi-bunch synchrotron radiation at the Chemical Dynamics Beamline of the Advanced Light Source (ALS). Using the high resolution VUV light from the ALS, they have obtained the PFI-PE spectra of O{sub 2} between 12 and 24 eV. In this abstract, the authors report for the first time the rotationally resolved spectra of O{sub 2}{sup +} (b{sup 4}{Sigma}{sub g}{sup {minus}}, v{sup +}=0).

  11. Background Ionizing Radiation and the Risk of Childhood Cancer: A Census-Based Nationwide Cohort Study

    PubMed Central

    Lupatsch, Judith E.; Zwahlen, Marcel; Röösli, Martin; Niggli, Felix; Grotzer, Michael A.; Rischewski, Johannes; Egger, Matthias; Kuehni, Claudia E.

    2015-01-01

    Background Exposure to medium or high doses of ionizing radiation is a known risk factor for cancer in children. The extent to which low-dose radiation from natural sources contributes to the risk of childhood cancer remains unclear. Objectives In a nationwide census-based cohort study, we investigated whether the incidence of childhood cancer was associated with background radiation from terrestrial gamma and cosmic rays. Methods Children < 16 years of age in the Swiss National Censuses in 1990 and 2000 were included. The follow-up period lasted until 2008, and incident cancer cases were identified from the Swiss Childhood Cancer Registry. A radiation model was used to predict dose rates from terrestrial and cosmic radiation at locations of residence. Cox regression models were used to assess associations between cancer risk and dose rates and cumulative dose since birth. Results Among 2,093,660 children included at census, 1,782 incident cases of cancer were identified including 530 with leukemia, 328 with lymphoma, and 423 with a tumor of the central nervous system (CNS). Hazard ratios for each millisievert increase in cumulative dose of external radiation were 1.03 (95% CI: 1.01, 1.05) for any cancer, 1.04 (95% CI: 1.00, 1.08) for leukemia, 1.01 (95% CI: 0.96, 1.05) for lymphoma, and 1.04 (95% CI: 1.00, 1.08) for CNS tumors. Adjustment for a range of potential confounders had little effect on the results. Conclusions Our study suggests that background radiation may contribute to the risk of cancer in children, including leukemia and CNS tumors. Citation Spycher BD, Lupatsch JE, Zwahlen M, Röösli M, Niggli F, Grotzer MA, Rischewski J, Egger M, Kuehni CE, for the Swiss Pediatric Oncology Group and the Swiss National Cohort. 2015. Background ionizing radiation and the risk of childhood cancer: a census-based nationwide cohort study. Environ Health Perspect 123:622–628; http://dx.doi.org/10.1289/ehp.1408548 PMID:25707026

  12. Oxidation of the Cyclic Ethers 1,4-Dioxane and Tetrahydrofuran by a Monooxygenase in Two Pseudonocardia Species

    PubMed Central

    Sales, Christopher M.; Grostern, Ariel; Parales, Juanito V.; Parales, Rebecca E.

    2013-01-01

    The bacterium Pseudonocardia dioxanivorans CB1190 grows on the cyclic ethers 1,4-dioxane (dioxane) and tetrahydrofuran (THF) as sole carbon and energy sources. Prior transcriptional studies indicated that an annotated THF monooxygenase (THF MO) gene cluster, thmADBC, located on a plasmid in CB1190 is upregulated during growth on dioxane. In this work, transcriptional analysis demonstrates that upregulation of thmADBC occurs during growth on the dioxane metabolite β-hydroxyethoxyacetic acid (HEAA) and on THF. Comparison of the transcriptomes of CB1190 grown on THF and succinate (an intermediate of THF degradation) permitted the identification of other genes involved in THF metabolism. Dioxane and THF oxidation activity of the THF MO was verified in Rhodococcus jostii RHA1 cells heterologously expressing the CB1190 thmADBC gene cluster. Interestingly, these thmADBC expression clones accumulated HEAA as a dead-end product of dioxane transformation, indicating that despite its genes being transcriptionally upregulated during growth on HEAA, the THF MO enzyme is not responsible for degradation of HEAA in CB1190. Similar activities were also observed in RHA1 cells heterologously expressing the thmADBC gene cluster from Pseudonocardia tetrahydrofuranoxydans K1. PMID:24096414

  13. Study on the Properties of Ionized Metal Plasma Methodology on Titanium

    SciTech Connect

    Leow, M. T.; Hassan, Z.; Lee, K. E.; Omar, G.; Lim, S. P.; Chan, C. F.; Siew, E. T.; Chuah, Z. M.

    2010-07-07

    Ionized Metal Plasma (IMP) deposition was used in depositing metal interconnection of titanium metal film. Inductively coupled plasma (ICP) was attached to chamber wall where it creates an electromagnetic field, thus, ionizing the sputtered metal atoms from target. The film morphology was observed by scanning electron microscope (SEM). Acoustic measurement of titanium film thickness showed that there was a comparable result with film resistance measured by 4-point probe. Results show that higher plasma density would cause tensile properties on the film stress.

  14. Ionizing radiation-induced mutagenesis: radiation studies in Neurospora predictive for results in mammalian cells

    NASA Technical Reports Server (NTRS)

    Evans, H. H.; DeMarini, D. M.

    1999-01-01

    Ionizing radiation was the first mutagen discovered and was used to develop the first mutagenicity assay. In the ensuing 70+ years, ionizing radiation became a fundamental tool in understanding mutagenesis and is still a subject of intensive research. Frederick de Serres et al. developed and used the Neurospora crassa ad-3 system initially to explore the mutagenic effects of ionizing radiation. Using this system, de Serres et al. demonstrated the dependence of the frequency and spectra of mutations induced by ionizing radiation on the dose, dose rate, radiation quality, repair capabilities of the cells, and the target gene employed. This work in Neurospora predicted the subsequent observations of the mutagenic effects of ionizing radiation in mammalian cells. Modeled originally on the mouse specific-locus system developed by William L. Russell, the N. crassa ad-3 system developed by de Serres has itself served as a model for interpreting the results in subsequent systems in mammalian cells. This review describes the primary findings on the nature of ionizing radiation-induced mutagenesis in the N. crassa ad-3 system and the parallel observations made years later in mammalian cells.

  15. Epidemiologic studies of ionizing radiation and cancer: past successes and future challenges.

    PubMed Central

    Samet, J M

    1997-01-01

    The health effects of radiation have been a focus for research since early in the 20th century. As the century ends, extensive experimental and epidemiologic evidence has been accumulated that addresses the adverse consequences of radiation exposure; epidemiologic studies of radiation-exposed groups from the general population and specific occupational groups provide quantitative estimates of the cancer risks associated with exposure. This report provides a perspective on the extensive epidemiologic evidence on the health effects of ionizing radiation and on likely needs for further epidemiologic research on radiation and health. Epidemiologic studies have proved informative on the quantitative risks of radiation-caused cancer but we now face the challenges of more precisely characterizing risks at lower levels of exposure and also of assessing modifiers of the risks, including dose rate, genetic susceptibility, and other environmental exposures. This report considers investigative approaches, such as pooled analysis of multiple data sets, that can be used to address these complex questions and the limitations of these approaches for addressing societal concerns about the risks of radiation exposure. PMID:9255575

  16. Distribution of terfenadine and its metabolites in locusts studied by desorption electrospray ionization mass spectrometry imaging.

    PubMed

    Olsen, Line Rørbæk; Hansen, Steen Honoré; Janfelt, Christian

    2015-03-01

    Desorption electrospray ionization (DESI) mass spectrometry (MS) imaging was used to image locusts dosed with the antihistamine drug terfenadine. The study was conducted in order to elucidate a relatively high elimination rate of terfenadine from the locust hemolymph. In this one of the few MS imaging studies on insects, a method for cryosectioning of whole locusts was developed, and the distributions of a number of endogenous compounds are reported, including betaine and a number of amino acids and phospholipids. Terfenadine was detected in the stomach region and the intestine walls, whereas three different metabolites-terfenadine acid (fexofenadine), terfenadine glucoside, and terfenadine phosphate-were detected in significantly smaller amounts and only in the unexcreted feces in the lower part of the intestine. The use of MS/MS imaging was necessary in order to detect the metabolites. With use of DESI-MS imaging, no colocalization of the drug and the metabolites was observed, suggesting a very rapid excretion of metabolites into the feces. Additional liquid chromatography-MS investigations were performed on hemolymph and feces and showed some abundance of terfenadine and the three metabolites, although at low levels, in both the hemolymph and the feces. PMID:25404166

  17. Deciphering the bipolar planetary nebula Abell 14 with 3D ionization and morphological studies

    NASA Astrophysics Data System (ADS)

    Akras, S.; Clyne, N.; Boumis, P.; Monteiro, H.; Gonçalves, D. R.; Redman, M. P.; Williams, S.

    2016-04-01

    Abell 14 is a poorly studied object despite being considered a born-again planetary nebula. We performed a detailed study of its 3D morphology and ionization structure using the SHAPE and MOCASSIN codes. We found that Abell 14 is a highly evolved, bipolar nebula with a kinematical age of ˜19 400 yr for a distance of 4 kpc. The high He abundance, and N/O ratio indicate a progenitor of 5 M⊙ that has experienced the third dredge-up and hot bottom burning phases. The stellar parameters of the central source reveal a star at a highly evolved stage near to the white dwarf cooling track, being inconsistent with the born-again scenario. The nebula shows unexpectedly strong [N I] λ5200 and [O I] λ6300 emission lines indicating possible shock interactions. Abell 14 appears to be a member of a small group of highly evolved, extreme type-I planetary nebulae (PNe). The members of this group lie at the lower-left corner of the PNe regime on the [N II]/Hα versus [S II]/Hα diagnostic diagram, where shock-excited regions/objects are also placed. The low luminosity of their central stars, in conjunction with the large physical size of the nebulae, result in a very low photoionization rate, which can make any contribution of shock interaction easily perceptible, even for small velocities.

  18. New Modeling Approaches to Study DNA Damage by the Direct and Indirect Effects of Ionizing Radiation

    NASA Technical Reports Server (NTRS)

    Plante, Ianik; Cucinotta, Francis A.

    2012-01-01

    DNA is damaged both by the direct and indirect effects of radiation. In the direct effect, the DNA itself is ionized, whereas the indirect effect involves the radiolysis of the water molecules surrounding the DNA and the subsequent reaction of the DNA with radical products. While this problem has been studied for many years, many unknowns still exist. To study this problem, we have developed the computer code RITRACKS [1], which simulates the radiation track structure for heavy ions and electrons, calculating all energy deposition events and the coordinates of all species produced by the water radiolysis. In this work, we plan to simulate DNA damage by using the crystal structure of a nucleosome and calculations performed by RITRACKS. The energy deposition events are used to calculate the dose deposited in nanovolumes [2] and therefore can be used to simulate the direct effect of the radiation. Using the positions of the radiolytic species with a radiation chemistry code [3] it will be possible to simulate DNA damage by indirect effect. The simulation results can be compared with results from previous calculations such as the frequencies of simple and complex strand breaks [4] and with newer experimental data using surrogate markers of DNA double ]strand breaks such as . ]H2AX foci [5].

  19. Amifostine, a radioprotectant agent, protects rat brain tissue lipids against ionizing radiation induced damage: An FTIR microspectroscopic imaging study

    SciTech Connect

    Cakmak G.; Miller L.; Zorlu, F.; Severcan, F.

    2012-03-03

    Amifostine is the only approved radioprotective agent by FDA for reducing the damaging effects of radiation on healthy tissues. In this study, the protective effect of amifostine against the damaging effects of ionizing radiation on the white matter (WM) and grey matter (GM) regions of the rat brain were investigated at molecular level. Sprague-Dawley rats, which were administered amifostine or not, were whole-body irradiated at a single dose of 800 cGy, decapitated after 24 h and the brain tissues of these rats were analyzed using Fourier transform infrared microspectroscopy (FTIRM). The results revealed that the total lipid content and CH{sub 2} groups of lipids decreased significantly and the carbonyl esters, olefinic=CH and CH{sub 3} groups of lipids increased significantly in the WM and GM after exposure to ionizing radiation, which could be interpreted as a result of lipid peroxidation. These changes were more prominent in the WM of the brain. The administration of amifostine before ionizing radiation inhibited the radiation-induced lipid peroxidation in the brain. In addition, this study indicated that FTIRM provides a novel approach for monitoring ionizing radiation induced-lipid peroxidation and obtaining different molecular ratio images can be used as biomarkers to detect lipid peroxidation in biological systems.

  20. Studies on laser-assisted Penning ionization by the optogalvanic effect in Ne/Eu hollow cathode discharge.

    PubMed

    Saini, V K; Kumar, P; Dixit, S K; Nakhe, S V

    2015-02-01

    Laser-assisted Penning ionization (LAPI) is detected in a Ne/Eu hollow cathode (HC) discharge lamp using the pulsed optogalvanic (OG) method. In the Ne/Eu discharge, doubly ionized europium excited energy levels Eu[4f(7)(P(7/2,5/2)6)] lie within the thermal limit (∼kT) from the laser-excited neon's energy level [2p(5)(P3/202)3p or 2p(8) (in Paschen notation)] lying at 149,848  cm(-1). Therefore, Penning ionization (PI) of europium atoms likely to occur into its highly excited ionic states is investigated. To probe the PI of europium, the temporal profiles of its counterpart neon OG signal are studied as a function of discharge current for the transitions (1s(4)→2p(8)) and (1s(2)→2p(2)), corresponding to 650.65 and 659.89 nm wavelengths, respectively. It is observed that PI of europium alters the overall discharge characteristics significantly and, hence, modifies the temporal profile of the OG signals accordingly. The quasi-resonant ionizing energy transfer collisions between laser-excited Ne 2p(8) atoms and electronically excited europium P(9/2)10 atoms are used to explain the LAPI mechanism. Such LAPI studies carried out in HC discharge could be useful for the discharge of a metal-vapor laser with appropriate Penning mixtures. PMID:25967764

  1. A MULTIWAVELENGTH STUDY ON THE FATE OF IONIZING RADIATION IN LOCAL STARBURSTS

    SciTech Connect

    Hanish, D. J.; Oey, M. S.; Rigby, J. R.; Lee, J. C.; De Mello, D. F.

    2010-12-20

    The fate of ionizing radiation is vital for understanding cosmic ionization, energy budgets in the interstellar and intergalactic medium, and star formation rate indicators. The low observed escape fractions of ionizing radiation have not been adequately explained, and there is evidence that some starbursts have high escape fractions. We examine the spectral energy distributions (SEDs) of a sample of local star-forming galaxies, containing 13 local starburst galaxies and 10 of their ordinary star-forming counterparts, to determine if there exist significant differences in the fate of ionizing radiation in these galaxies. We find that the galaxy-to-galaxy variations in the SEDs are much larger than any systematic differences between starbursts and non-starbursts. For example, we find no significant differences in the total absorption of ionizing radiation by dust, traced by the 24 {mu}m, 70 {mu}m, and 160 {mu}m MIPS bands of the Spitzer Space Telescope, although the dust in starburst galaxies appears to be hotter than that of non-starburst galaxies. We also observe no excess ultraviolet flux in the Galaxy Evolution Explorer bands that could indicate a high escape fraction of ionizing photons in starburst galaxies. The small H{alpha} fractions of the diffuse, warm ionized medium (WIM) in starburst galaxies are apparently due to temporarily boosted H{alpha} luminosity within the star-forming regions themselves, with an independent, constant WIM luminosity. This independence of the WIM and starburst luminosities contrasts with WIM behavior in non-starburst galaxies and underscores our poor understanding of radiation transfer in both ordinary and starburst galaxies.

  2. Study of Hydrophobic and Ionizable Hydrophilic Copolymers at Polymer/Solid and Polymer/Liquid Interfaces

    SciTech Connect

    Perahia, Dvora

    2011-11-01

    Joint experimental-computational efforts were set to characterize the interfacial effects on the structure and dynamics of polymers consisting of highly rigid hydrophilic-ionizable and hydrophobic sub-units within one polymeric chain casted into thin films of several molecular dimensions. Focusing on the ultra thin film region we separate out the interfacial effects from bulk characteristics. Specifically, the study sought to: identify the parameters that control the formation of a stable polymer-solid interface. The study consists of two components, experimental investigations and computational efforts. The experimental component was designed to derive empirical trends that can be used to correlate the set of coupled polymer molecular parameters with the interfacial characteristics of these polymers, and their response to presence of solvents. The computational study was designed to provide molecular insight into the ensemble averages provided by the experimental efforts on multiple length scales from molecular dimensions, to the nanometer lengths to a macroscopic understanding of solvent interactions with structured polymers. With the ultimate goal of correlating molecular parameters to structure, dynamics and properties of ionic polymers, the first stage of the research began with the study of two systems, one which allowed tailoring the flexibility of the backbone without the presence of ionic groups, but with a potential to sulfonate groups at a later stage, and a polymer whose backbone is rigid and the density of the ionic group can be varied. The combined experimental and computational studies significantly extended the understanding of polymers at interfaces from model systems to polydispersed copolymers with blocks of varying nature and complexity. This new insight directly affects the design of polymers for sustainable energy applications from batteries and fuel cells to solar energy.

  3. Off-line studies of the laser ionization of yttrium at the IGISOL facility

    NASA Astrophysics Data System (ADS)

    Kessler, T.; Moore, I. D.; Kudryavtsev, Y.; Peräjärvi, K.; Popov, A.; Ronkanen, P.; Sonoda, T.; Tordoff, B.; Wendt, K. D. A.; Äystö, J.

    2008-02-01

    A laser ion source is under development at the IGISOL facility, Jyväskylä, in order to address deficiencies in the ion guide technique. The key elements of interest are those of a refractory nature, whose isotopes and isomers are widely studied using both laser spectroscopic and high precision mass measurement techniques. Yttrium has been the first element of choice for the new laser ion source. In this work, we present a new coupled dye-Ti:Sapphire laser scheme and give a detailed discussion of the results obtained from laser ionization of yttrium atoms produced in an ion guide via resistive heating of a filament. The importance of not only gas purity, but indeed the baseline vacuum pressure in the environment outside the ion guide is discussed in light of the fast gas phase chemistry seen in the yttrium system. A single laser shot model is introduced and is compared to the experimental data in order to extract the level of impurities within the gas cell.

  4. Study of the Ionization Dynamics and Equation of State of a Strongly Coupled Plasma

    SciTech Connect

    Shepherd, R; Audebert, P; Geindre, J P; Iglesias, C; Foord, M; Rogers, F; Gauthier, J C; Springer, P

    2003-02-06

    Preliminary experiments to study the ionization dynamics and equation of state of a strongly coupled plasma have been performed at the LLNL COMET laser facility. In these experiment, a 1.0 J, 500 fs, 532 nm laser was used to create a uniform, warm dense plasma.The primary diagnostic, Fourier Domain Interferometry (FDI), was used to provide information about the position of the critical density of the target and thus the expansion hydrodynamics, laying the ground work for the plasma characterization. The plasmas were determined to be strongly coupled. In addition work was performed characterizing the back-lighter. A von Hamos spectrograph coupled to a 500 fs X-ray streak camera (TREX-VHS) developed at LLNL was used for these measurements. This diagnostic combines high collection efficiency ({approx} 10{sup -4} steradians) with fast temporal response ({approx} 500 fs), allowing resolution of extremely transient spectral variations. The TREX-VHS will be used to determine the time history, intensity, and spectral content of the back-lighter resulting in absorption measurements that provide insight into bound states in strongly coupled conditions.

  5. Theoretical study of energy deposition in ionization chambers for tritium measurements

    NASA Astrophysics Data System (ADS)

    Chen, Zhilin; Peng, Shuming; Meng, Dan; He, Yuehong; Wang, Heyi

    2013-10-01

    Energy deposition in ionization chambers has been theoretically studied for tritium measurements in gaseous form. A one-dimension model is introduced to establish the quantitative relationship between energy deposition rate and many factors, including carrier gas, gas pressure, wall material, chamber size, and gas temperature. Energy deposition rate has been calculated at pressure varying from 5 kPa to 500 kPa based on some approximations. It is found that energy deposition rate varies greatly for different parameters, especially at low gas pressure. For the same chamber, energy deposition rate in argon is much higher than in deuterium, as much as 70.7% higher at 5 kPa. Gold plated chamber gives highest energy deposition rate in the calculations while aluminum chamber results in the lowest. As chamber size gets smaller, β ray emitted by tritium will deposit less energy in the sensitive region of the chamber. For chambers flowing through with the same gas, energy deposition rate in a 10 L chamber is 23.9% higher than in a 0.05 L chamber at 5 kPa. Gas temperature also places slight influence on energy deposition rate, and 373 K will lead to 6.7% lower deposition rate than 233 K at 5 kPa. In addition, experiments have been performed to obtain energy deposition rate in a gold plated chamber, which show good accordance with theoretical calculations.

  6. Numerical studies of the behavior of ionized residual gas in an energy recovering linac

    NASA Astrophysics Data System (ADS)

    Pöplau, Gisela; van Rienen, Ursula; Meseck, Atoosa

    2015-04-01

    Next generation light sources such as energy recovering linacs (ERLs) are highly sensitive to instabilities due to ionized residual gas, which must be mitigated for successful operation. Vacuum pumps are insufficient for removal of the ions, as the ions are trapped by the beam's electrical potential. Two effective measures are (i) introducing clearing gaps in the bunch train, and (ii) installing clearing electrodes which pull out the trapped ions from the electrical potential of the beam. In this paper, we present numerical studies on the behavior of ion clouds that interact with bunch trains in an ERL taking into account the effects of the clearing gaps and clearing electrodes. We present simulations with different compositions of the residual gas. Simulations are done using the MOEVE PIC Tracking software package developed at Rostock University, which has been upgraded to include the behavior of ion clouds in the environment of additional electromagnetic fields, such as generated by clearing electrodes. The simulations use the parameters of the Berlin Energy Recovery Linac Project (bERLinPro) to allow for the deduction of appropriate measures for bERLinPro 's design and operation.

  7. Theoretical study of energy deposition in ionization chambers for tritium measurements

    SciTech Connect

    Chen, Zhilin; Peng, Shuming; Meng, Dan; He, Yuehong; Wang, Heyi

    2013-10-15

    Energy deposition in ionization chambers has been theoretically studied for tritium measurements in gaseous form. A one-dimension model is introduced to establish the quantitative relationship between energy deposition rate and many factors, including carrier gas, gas pressure, wall material, chamber size, and gas temperature. Energy deposition rate has been calculated at pressure varying from 5 kPa to 500 kPa based on some approximations. It is found that energy deposition rate varies greatly for different parameters, especially at low gas pressure. For the same chamber, energy deposition rate in argon is much higher than in deuterium, as much as 70.7% higher at 5 kPa. Gold plated chamber gives highest energy deposition rate in the calculations while aluminum chamber results in the lowest. As chamber size gets smaller, β ray emitted by tritium will deposit less energy in the sensitive region of the chamber. For chambers flowing through with the same gas, energy deposition rate in a 10 L chamber is 23.9% higher than in a 0.05 L chamber at 5 kPa. Gas temperature also places slight influence on energy deposition rate, and 373 K will lead to 6.7% lower deposition rate than 233 K at 5 kPa. In addition, experiments have been performed to obtain energy deposition rate in a gold plated chamber, which show good accordance with theoretical calculations.

  8. Review of certain low-level ionizing radiation studies in mice and guinea pigs

    SciTech Connect

    Congdon, C.C.

    1987-05-01

    Starting in the early 1940s, Egon Lorenz and collaborators at the National Cancer Institute began an extended study of chronic low-level ionizing radiation effects in what was then the tolerance range for man. Observations on life span, body weight and radiation carcinogenesis, among others, were made in mice, guinea pigs and rabbits. At the then-permissible exposure level, 0.1 R** per 8-h day until natural death, experimental mice and guinea pigs had a slightly greater mean life span compared to control animals. In addition, there was marked weight gain during the growth phase in both species. Increased tumor incidence was also observed at the 0.1-R level in mice. The primary hypothesis for increased median life span has been rebound regenerative hyperplasia during the early part of the exposure; in the presence of continuing injury, there is physiological enhancement of defense mechanisms against intercurrent infection. The body weight gain has not been explained. 32 references.

  9. A new dynamical atmospheric ionizing radiation (AIR) model for epidemiological studies

    NASA Technical Reports Server (NTRS)

    De Angelis, G.; Clem, J. M.; Goldhagen, P. E.; Wilson, J. W.

    2003-01-01

    A new Atmospheric Ionizing Radiation (AIR) model is currently being developed for use in radiation dose evaluation in epidemiological studies targeted to atmospheric flight personnel such as civilian airlines crewmembers. The model will allow computing values for biologically relevant parameters, e.g. dose equivalent and effective dose, for individual flights from 1945. Each flight is described by its actual three dimensional flight profile, i.e. geographic coordinates and altitudes varying with time. Solar modulated primary particles are filtered with a new analytical fully angular dependent geomagnetic cut off rigidity model, as a function of latitude, longitude, arrival direction, altitude and time. The particle transport results have been obtained with a technique based on the three-dimensional Monte Carlo transport code FLUKA, with a special procedure to deal with HZE particles. Particle fluxes are transformed into dose-related quantities and then integrated all along the flight path to obtain the overall flight dose. Preliminary validations of the particle transport technique using data from the AIR Project ER-2 flight campaign of measurements are encouraging. Future efforts will deal with modeling of the effects of the aircraft structure as well as inclusion of solar particle events. Published by Elsevier Ltd on behalf of COSPAR.

  10. 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...

  11. Physician exposure to ionizing radiation during trauma resuscitation: A prospective clinical study

    SciTech Connect

    Weiss, E.L.; Singer, C.M.; Benedict, S.H.; Baraff, L.J.

    1990-02-01

    A prospective study of emergency physician whole body and extremity exposure to ionizing radiation during trauma resuscitation over a three-month period was conducted. Radiation film badges and thermoluminescent dosimeter finger rings were permanently attached to leaded aprons worn by emergency medicine residents during all trauma resuscitations. One set of apron and finger ring dosimeters was designated for the resident who managed the airway and stabilized the neck, when necessary, during cervical spine radiography (A-CS resident). A separate set of dosimeters was designated for the resident supervising the resuscitation. During the study period, 150 major trauma patients requiring 481 radiographic studies were treated. The mean monthly cumulative whole body exposures were 136.7 +/- 85.0 and 103.3 +/- 60.3 mrem for A-CS and supervising residents, respectively. The mean weekly cumulative extremity exposures were 523.3 +/- 611.0 and 46.7 +/- 18.6 mrem for A-CS and supervising residents, respectively. Calculated whole body exposures per patient were 2.7 mrem for the A-CS resident and 2.1 mrem for the supervising resident. Calculated extremity exposures per patient were 41.9 +/- 48.9 and 3.7 +/- 1.5 mrem, respectively. To exceed the annual whole body exposure limit established by the National Council of Radiologic Protection, the A-CS resident, working 200 shifts per year, would have to treat 9.2 trauma patients per shift. To exceed the annual extremity exposure limit, the A-CS resident would have to treat 5.9 trauma patients per shift. Of note, European exposure limits are 10% of current US limits. We conclude that significant exposures may occur to physicians working in trauma centers and that the use of shielding devices is indicated.

  12. Muon Tracking Studies in a Skew Parametric Resonance Ionization Cooling Channel

    SciTech Connect

    Sy, Amy; Afanaciev, Andre; Derbenev, Yaroslav S.; Johnson, Rolland; Morozov, Vasiliy

    2015-09-01

    Skew Parametric-resonance Ionization Cooling (SPIC) is an extension of the Parametric-resonance Ionization Cooling (PIC) framework that has previously been explored as the final 6D cooling stage of a high-luminosity muon collider. The addition of skew quadrupoles to the PIC magnetic focusing channel induces coupled dynamic behavior of the beam that is radially periodic. The periodicity of the radial motion allows for the avoidance of unwanted resonances in the horizontal and vertical transverse planes, while still providing periodic locations at which ionization cooling components can be implemented. A first practical implementation of the magnetic field components required in the SPIC channel is modeled in MADX. Dynamic features of the coupled correlated optics with and without induced parametric resonance are presented and discussed.

  13. Cosmic ray studies with a gas Cherenkov counter in association with an ionization spectrometer

    NASA Technical Reports Server (NTRS)

    Balasubrahmanyan, V. K.; Ormes, J. F.; Arens, J. F.; Siohan, F.; Yodh, G. B.; Simon, M.; Spiegelhauer, H.

    1980-01-01

    The results from a balloon-borne gas Cherenkov counter (threshold 16.5 GeV/nucleon) and an ionization spectrometer are presented. The gas Cherenkov counter provides an absolute energy distribution for the response of the calorimeter for 5 or = Z 26 nuclei of cosmic rays. The contribution of scintillation to the gas Cherenkov pulse height was obtained by independently selecting particles below the gas Cherenkov threshold using the ionization spectrometer. Energy spectra were derived by minimizing the chi squared between Monte Carlo simulted data and flight data. Best fit power laws, dN/dE = AE-gamma, were determined for C, N, O, Ne, Mg, and Si. The power laws, all consistent with E (-2.7) are not good fits to the data. A better fit is obtained using the spectrum derived from the spectrometer. The data from the ionization calorimeter and the gas Cherenkov are thus completely self-consistent.

  14. 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.

  15. Theoretical study of Jesse effect in tritium measurements using ionization chambers

    NASA Astrophysics Data System (ADS)

    Chen, Zhilin; Peng, Shuming; Lu, Hanghang; Tan, Zhaoyi; Wang, Heyi; Long, Xingui; Masao, Matsuyama

    2016-01-01

    Jesse effect caused by impurities in helium might enhance the output signal significantly in tritium measurements with ionization chamber, which will lead to overestimation of tritium concentration in experiments. A theoretical method was proposed to evaluate Jesse effect quantitatively. Results indicate that besides Penning ionization, sub-excitation electrons also place very important influence on ionization enhancement by Jesse effect. An experiential expression about the relationship between enhancement factor and impurity concentration was established, in which second order of it fits experimental results very well. Theoretical calculation method in this paper is also applicable to evaluate Jesse effect in other kinds of mixtures besides hydrogen as impurities in helium. In addition, Jesse effects about tritium molecules as impurities have also been investigated.

  16. [Biodegradation of tetrahydrofuran by combined immobilized of Pseudomonas oleovorans DT4].

    PubMed

    Shao, Qian; Ye, Jie-Xu; Ouyang, Du-Juan; Chen, Jian-Meng; Chen, Dong-Zhi

    2013-08-01

    A new composite matrix, calcium alginate (CA) coupled with activated carbon fiber (ACF) was designed to immobilize the cells of Pseudomonas oleovorans DT4 for tetrahydrofuran (THF) degradation. The average removal rate of the CA-ACF immobilized cells reached 24.0 mg x (L x h)(-1) with an initial THF concentration of 360 mg x L(-1) when the concentration of CA and ACF was 3% and 1.5% respectively. The mechanical strength of the mobilized cells was also significantly improved with the addition of ACF. Compared to the free suspended cells, higher stable removal efficiency (more than 80%) of CA-ACF cells was detected under different conditions of temperature and pH. The feasibility of the newly designed matrix was also reflected by the repeated batch degradation which showed that the removal activity decreased insignificantly after 80 cycles with the modified reaction system (PNS). PMID:24191576

  17. The role of electron-impact vibrational excitation in electron transport through gaseous tetrahydrofuran

    SciTech Connect

    Duque, H. V.; Do, T. P. T.; Konovalov, D. A.; White, R. D.; Brunger, M. J. E-mail: darryl.jones@flinders.edu.au; Jones, D. B. E-mail: darryl.jones@flinders.edu.au

    2015-03-28

    In this paper, we report newly derived integral cross sections (ICSs) for electron impact vibrational excitation of tetrahydrofuran (THF) at intermediate impact energies. These cross sections extend the currently available data from 20 to 50 eV. Further, they indicate that the previously recommended THF ICS set [Garland et al., Phys. Rev. A 88, 062712 (2013)] underestimated the strength of the electron-impact vibrational excitation processes. Thus, that recommended vibrational cross section set is revised to address those deficiencies. Electron swarm transport properties were calculated with the amended vibrational cross section set, to quantify the role of electron-driven vibrational excitation in describing the macroscopic swarm phenomena. Here, significant differences of up to 17% in the transport coefficients were observed between the calculations performed using the original and revised cross section sets for vibrational excitation.

  18. False Results Caused by Solvent Impurity in Tetrahydrofuran for MALDI TOF MS Analysis of Amines

    NASA Astrophysics Data System (ADS)

    Lou, Xianwen; Leenders, Christianus M. A.; van Onzen, Arthur H. A. M.; Bovee, Ralf A. A.; van Dongen, Joost L. J.; Vekemans, Jef A. J. M.; Meijer, E. W.

    2013-11-01

    Tetrahydrofuran (THF) is one of the most frequently used solvents in the MALDI TOF MS analysis of synthetic compounds. However, it should be used with caution because a trace amount of 4-hydroxybutanal (HBA) might be generated and accumulated in THF during storage. Since only a tiny amount of analytes is required in MALDI MS measurements, a trace amount of HBA might have a significant effect on the MS results. It was found that HBA will quickly react with primary and secondary amino compounds, leading to false results about the sample composition with an extra series of ions with additional mass of 70 Da in between. The formation of HBA can be inhibited by butylated hydroxytoluene (BHT) antioxidant. Therefore, when THF is required as the solvent for sample preparation, it is strongly recommended to use a BHT-stabilized one, at least for the analysis of compounds with amino groups.

  19. Synthesis and characterization of polyurethanes made from copolymers of epoxidized natural oil and tetrahydrofuran.

    PubMed

    Hoong, Seng Soi; Yeong, Shoot Kian; Hassan, Hazimah Abu; Din, Ahmad Kushairi; Choo, Yuen May

    2015-01-01

    Polyols were synthesized from epoxidized natural oils and tetrahydrofuran through ring opening copolymerization catalyzed by Lewis acid. The properties of these polyols depend on the type of natural oils as well as the reaction conditions (monomer concentration, catalyst amount, reaction temperature and reaction time). These polyols were evaluated as a raw material for making polyurethane (PU) in order to understand the structure-property relationship between a natural oil and PU made from it. The tensile test analysis shows that the incorporation of natural oil moiety into the PU polymer network improves the elasticity of these PU samples when compared to a benchmark PU sample. In addition, the PU samples made from palm oil and soybean oil based polyols exhibit better tensile strength than benchmark PU. These polyols samples are suitable for making elastomeric PU, where high flexibility (high elongation at break) of PU is a common requirement. PMID:25492233

  20. X-ray laser studies using plasmas created by optical field ionization

    SciTech Connect

    Krushelnick, K.M.; Tighe, W.; Suckewer, S.

    1995-01-01

    X-ray laser experiments involving the creation of fast recombining plasmas by optical field ionization of preformed targets were conducted. A nonlinear increase in the intensity of the 13.5nm Lyman-{alpha} line in Li III with the length of the target plasma was observed but only for distances less than the laser confocal parameter and for low plasma electron temperatures. Multiphoton pumping of resonant atomic transitions was also examined and the process of multiphoton ionization of FIII was found to be more probable than multiphoton excitation.

  1. Electron impact ionization in plasma technologies; studies on atomic boron and BN molecule

    NASA Astrophysics Data System (ADS)

    Joshi, Foram M.; Joshipura, K. N.; Chaudhari, Asha S.

    2016-05-01

    Electron impact ionization plays important role in plasma technologies. Relevant cross sections on atomic boron are required to understand the erosion processes in fusion experiments. Boronization of plasma exposed surfaces of tokomaks has proved to be an effective way to produce very pure fusion plasmas. This paper reports comprehensive theoretical investigations on electron scattering with atomic Boron and Boron Nitride in solid phases. Presently we determine total ionization cross-section Qion and the summed-electronic excitation cross section ΣQexc in a standard quantum mechanical formalism called SCOP and CSP-ic methods. Our calculated cross sections are examined as functions of incident electron energy along with available comparisons.

  2. Shock tube study of ionization rates of NaCl-contaminated argon

    NASA Technical Reports Server (NTRS)

    Scheneider, C.-P.; Park, C.

    1975-01-01

    Spectrally resolved radiometry and a microwave technique were used to measure the electron density, electron temperature, and concentration, and the concentration of sodium atoms in the weakly ionized region behind a shock wave in an argon shock tube. It is shown that the observed increase in the ionization rate is due to electron detachment of negative chlorine ions produced from sodium chloride vapor contained as an impurity in the argon gas. The observed behavior of the electron temperature in time and the reactions controlled by the electron temperature are analyzed in the light of the impurity reaction scheme.

  3. A Comparative PCET Study of a Donor-Acceptor Pair Linked by Ionized and Non-ionized Asymmetric Hydrogen-Bonded Interfaces

    PubMed Central

    Young, Elizabeth R.; Rosenthal, Joel; Hodgkiss, Justin M.

    2012-01-01

    A Zn(II) porphyrin-amidinium is the excited state electron donor (D) to a naphthalene diimide acceptor (A) appended with either a carboxylate or sulfonate functionality. The two-point hydrogen bond (---[H+]---) formed between the amidinium and carboxylate or sulfonate establishes a proton-coupled electron transfer (PCET) pathway for charge transfer. The two D---[H+]---A assemblies differ only by the proton configuration within the hydrogen bonding interface. Specifically, the amidinium transfers a proton to the carboxylate to form a non-ionized amidine-carboxylic acid two-point hydrogen network whereas the amidinium maintains both protons when bound to the sulfonate functionality forming an ionized amidinium-sulfonate two-point hydrogen network. These two interface configurations within the dyads thus allow for a direct comparison of PCET kinetics for the same donor and acceptor juxtaposed by an ionized and non-ionized hydrogen-bonded interface. Analysis of PCET kinetics ascertained from transient absorption and transient emission spectroscopy reveal that the ionized interface is more strongly impacted by the local solvent environment, thus establishing that the initial static configuration of the proton interface is a critical determinant to the kinetics of PCET. PMID:19489645

  4. Sonic and resistivity measurements on Berea sandstone containing tetrahydrofuran hydrates: a possible analogue to natural-gas-hydrate deposits. [Tetrahydrofuran hydrates

    SciTech Connect

    Pearson, C.; Murphy, J.; Halleck, P.; Hermes, R.; Mathews, M.

    1983-01-01

    Deposits of natural gas hydrates exist in arctic sedimentary basins and in marine sediments on continental slopes and rises. However, the physical properties of such sediments are largely unknown. In this paper, we report laboratory sonic and resistivity measurements on Berea sandstone cores saturated with a stoichiometric mixture of tetrahydrofuran (THF) and water. We used THF as the guest species rather than methane or propane gas because THF can be mixed with water to form a solution containing proportions of the proper stoichiometric THF and water. Because neither methane nor propane is soluble in water, mixing the guest species with water sufficiently to form solid hydrate is difficult. Because THF solutions form hydrates readily at atmospheric pressure it is an excellent experimental analogue to natural gas hydrates. Hydrate formation increased the sonic P-wave velocities from a room temperature value of 2.5 km/s to 4.5 km/s at -5/sup 0/C when the pores were nearly filled with hydrates. Lowering the temperature below -5/sup 0/C did not appreciably change the velocity however. In contrast, the electrical resistivity increases nearly two orders of magnitude upon hydrate formation and continues to increase more slowly as the temperature is further decreased. In all cases the resistivities are nearly frequency independent to 30 kHz and the loss tangents are high, always greater than 5. The dielectric loss shows a linear decrease with frequency suggesting that ionic conduction through a brine phase dominates at all frequencies, even when the pores are nearly filled with hydrates. We find that the resistivities are strongly a function of the dissolved salt content of the pore water. Pore water salinity also influences the sonic velocity, but this effect is much smaller and only important near the hydrate formation temperature.

  5. Gas phase studies on terpenes by ion mobility spectrometry using different atmospheric pressure chemical ionization techniques

    NASA Astrophysics Data System (ADS)

    Borsdorf, H.; Stone, J. A.; Eiceman, G. A.

    2005-11-01

    The ionization pathways and drift behavior were determined for sets of constitutional isomeric and stereoisomeric non-polar hydrocarbons (unsaturated monocyclic terpenes, unsaturated and saturated bicyclic terpenes) using ion mobility spectrometry (IMS) with different techniques of atmospheric pressure chemical ionization (APCI) to assess how structural and stereochemical differences influence ion formation. Depending on the structural features, different ions were observed for constitutional isomers using ion mobility spectrometry with photoionization (PI) and corona discharge (CD) ionization. Photoionization provides ion mobility spectra containing one major peak for saturated compounds while at two peaks were observed for unsaturated compounds, which can be assigned to product ions related to monomer and dimer ions. However, differences in relative abundance of product ions were found depending on the position of the double bond. Although IMS using corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra are complex and differ from those obtained using photoionization. Additional cluster ions and fragment ions were detected. Only small differences in ion mobility spectra were observed for the diastereomers while the enantiomers provide identical spectra. The structure of the product ions formed was checked by investigations using the coupling of ion mobility spectrometry with mass spectrometry (IMS-MS).

  6. Semiclassical Study of the Wave Vector Dependence of the Interband Impact Ionization Rate in Bulk Silicon

    NASA Technical Reports Server (NTRS)

    Wang, Yang; Brennan, Kevin F.

    1994-01-01

    We present calculations of the interband impact ionization rate calculated using a wave vector dependent (k-dependent) semiclassical formulation of the transition rate. The transition rate is determined using Fermi's golden rule from a two-body screened Coulomb interaction assuming energy and momentum conservation. The transition rate is calculated for the first two conduction bands of silicon by numerically integrating over the full Brillouin zone. The overlap integrals in the expression for the transition rate are determined numerically using a 15 band k-p calculation. It is found that the transition rate depends strongly on the initiating electron wave vector (k vector) and that the transition rate is greatest for electrons originating within the second conduction band than the first conduction band. An ensemble Monte Carlo simulation, which includes the numerically determined ionization transition rate as well as the full details of the first two conduction bands, is used to calculate the total impact ionization rate in bulk silicon. Good agreement with the experimentally determined electron ionization rate data is obtained.

  7. Photoionization mass spectrometric study of HOCl: Photoionization efficiency spectrum and ionization energy

    SciTech Connect

    Thorn, R.P. Jr.; Stief, L.J.

    1999-02-18

    The photoionization efficiency (PIE) spectrum of HOCl was measured over the wavelength range {lambda} = 102--115 nm, using a discharge flow-photoionization mass spectrometer (DF-PIMS) apparatus coupled to a synchrotron radiation source. The PIE spectra displayed steplike behavior near threshold. This study represents the first determination of the HOCl photoionization efficiency spectrum and the photoionization threshold. A value of 11.12{sub 3} {+-} 0.01{sub 8} eV was obtained for the adiabatic ionization energy (IE) of HOCl from analysis of photoion thresholds, corresponding to the HOCl{sup +}(X{sup 2}A{double_prime}) {l_arrow} HOCl(X{sup 1}A{double_prime}) transition. The PIMS result is identical to the only previous experimental measurement and in good agreement with a recent ab initio calculation. From the result for IE(HOCl), a value of 999.4 {+-} 3.6 kJ mol{sup {minus}1} was calculated for {Delta}{sub f}H{degree}{sub 0}(HOCl{sup +}), and from the latter, the proton affinity of ClO at T = 0 K, PA{sub 0}(ClO), was determined to be 629.6 {+-} 3.6 kJ mol{sup {minus}1}. At 298 K, the computed values for {Delta}{sub f}H{degree}{sub 298}(HOCl{sup +}) and PA{sub 298}(ClO) are 996.5 {+-} 3.6 and 635.1 {+-} 3.6 kJ mol{sup {minus}1}, respectively.

  8. A study of inter-species ion suppression in electrospray ionization-mass spectrometry of some phospholipid classes.

    PubMed

    Khoury, Spiro; El Banna, Nadine; Tfaili, Sana; Chaminade, Pierre

    2016-02-01

    Phospholipid quantification in biological samples is crucial and is increasingly studied in lipidomics. Quantitative studies are often performed using commercially available standards of phospholipid classes in order to mimic the composition of biological samples. For this, studies are conducted by liquid chromatography coupled to electrospray ionization-mass spectrometry. In liquid chromatography coupled to mass spectrometry (LC-MS) analysis, the matrix components and the co-elution of several phospholipid species lead to the phenomenon of ion suppression. As a result, a decrease in the response of phospholipid species in mass spectrometry MS is observed. In fact, inter-species ion suppression affects the efficiency of phospholipid (PL) ionization and might also influence the quantitative results. The aim of this work is to study the PL inter-species ion suppression phenomenon in electrospray ionization (ESI)-mass spectrometry on a triple quadrupole TQ and an LTQ-Orbitrap in order to improve quantification in natural and biological samples. Thus, the phospholipid MS response was evaluated to study the effect of acyl chain length, the degree, and the position of unsaturation on acyl chain and the effect of the polar head group structure. A number of saturated and unsaturated phospholipid species and mixtures were analyzed in different ionization modes to a better understanding of inter-species ion suppression phenomenon. PL molecular species responded differently according to the length of fatty acid chains, the number of unsaturation, and the nature of the polar head group. Fatty acid chain length showed to have the most marked effect on MS response. PMID:26780707

  9. Annonacin, a mono-tetrahydrofuran acetogenin, arrests cancer cells at the G1 phase and causes cytotoxicity in a Bax- and caspase-3-related pathway.

    PubMed

    Yuan, Shyng-Shiou F; Chang, Hsueh-Ling; Chen, Hsiao-Wen; Yeh, Yao-Tsung; Kao, Ying-Hsien; Lin, Kuei-Hsiang; Wu, Yang-Chang; Su, Jinu-Huang

    2003-05-01

    Annonaceous acetogenins are a group of potential anti-neoplastic agents isolated from Annonaceae plants. In this study, we purified annonacin, a cytotoxic mono-tetrahydrofuran acetogenin, from the seeds of Annona reticulata and analyzed its biological effects. Herein, we have shown that annonacin caused significant cell death in various cancer cell lines. T24 bladder cancer cells at the S phase were more vulnerable to the cytotoxicity of annonacin. Furthermore, annonacin activated p21 in a p53-independent manner and arrested T24 cells at the G1 phase. It also induced Bax expression, enhanced caspase-3 activity, and caused apoptotic cell death in T24 cells. In summary, these results suggest that annonacin is potentially a promising anti-cancer compound. PMID:12697268

  10. Secondary electrospray ionization-mass spectrometry: breath study on a control group.

    PubMed

    Martínez-Lozano, P; Zingaro, L; Finiguerra, A; Cristoni, S

    2011-03-01

    A series of fatty acids among other compounds have recently been detected in breath in real time by secondary electrospray ionization mass spectrometry (SESI-MS) (Martínez-Lozano P and Fernández de la Mora J 2008 Anal. Chem. 80 8210). Our main aim in this work was to (1) quantify their abundance in breath calibrating the system with standard vapors and (2) extend the study to a control group for several days, both under fasting conditions and after sucrose intake. For the quantitative study, we fed our system with controlled amounts (∼140-1440 ppt) of fatty acid vapors (i.e. propanoic, butanoic, pentanoic and hexanoic acids). As a result, we found sensitivities ranging between 1 and 2.2 cps/ppt. Estimated concentrations of these particular acids in the breath of a fasting subject were in the order of 100 ppt. These values were in reasonable agreement with those expected from reported typical plasma concentrations and Henry constants. A second set of experiments on three fasting individuals before and after ingesting 15 g of sucrose showed that the concentration of propionic and butanoic acids increased rapidly in breath for two subjects. This response was attributed to bacterial activity in mouth and pharynx. In contrast, a third subject showed no response to the administration of sucrose. In addition, we performed a survey among six fasting subjects comparing nasal and mouth exhalations during 11 days, 4 months apart. The signal intensity was comparable for mouth and nose breath. This observation, in conjunction with the quantitative study, suggests that these compounds are mostly systemic when measured under fasting conditions. We finally used the NIST MS search algorithm to evaluate the possibility of recognizing a breathing subject based on his/her breath signature. The global recognition score was 63% (41 out of 65), while the probability by chance alone was 6 × 10(-17). This indicates that (i) there are statistically recognizable differences in

  11. A new in-gas-laser ionization and spectroscopy laboratory for off-line studies at KU Leuven

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, Yu.; Creemers, P.; Ferrer, R.; Granados, C.; Gaffney, L. P.; Huyse, M.; Mogilevskiy, E.; Raeder, S.; Sels, S.; Van den Bergh, P.; Van Duppen, P.; Zadvornaya, A.

    2016-06-01

    The in-gas laser ionization and spectroscopy (IGLIS) technique is used to produce and to investigate short-lived radioactive isotopes at on-line ion beam facilities. In this technique, the nuclear reaction products recoiling out of a thin target are thermalized and neutralized in a high-pressure noble gas, resonantly ionized by the laser beams in a two-step process, and then extracted from the ion source to be finally accelerated and mass separated. Resonant ionization of radioactive species in the supersonic gas jet ensures very high spectral resolution because of essential reduction of broadening mechanisms. To obtain the maximum efficiency and the best spectral resolution, properties of the supersonic jet and the laser beams must be optimized. To perform these studies a new off-line IGLIS laboratory, including a new high-repetition-rate laser system and a dedicated off-line mass separator, has been commissioned. In this article, the specifications of the different components necessary to achieve optimum conditions in laser-spectroscopy studies of radioactive beams using IGLIS are discussed and the results of simulations are presented.

  12. Cosmic ray studies with a gas Cerenkov counter in association with an ionization spectrometer

    NASA Technical Reports Server (NTRS)

    Balasubrahmanyan, V. K.; Ormes, J. F.; Arens, J. F.; Siohan, F.; Simon, M.; Spiegelhauer, H.; Yodh, G. B.

    1980-01-01

    The results from a balloon-borne gas Cerenkov counter (threshold 16.5 GeV/nuc) and an ionization spectrometer are presented. The gas Cerenkov counter provides an absolute energy calibration for the response of the calorimeter for the Z range of 5-26 nuclei of cosmic rays. The contribution of scintillation to the gas Cerenkov pulse height has been obtained by independently selecting particles below the gas Cerenkov threshold using the ionization spectrometer. Energy spectra were derived by minimizing the chi-squared between a Monte Carlo simulated data and flight data. Best fit power laws were determined for C, N, O, Ne, Mg, and Si. The power laws, all consistent with E exp-2.7, are not good fits to the data. A better fit is obtained using the spectrum derived from the spectrometer.

  13. Differential studies and projectile charge effects in ionization of molecular nitrogen by positron and electron impact

    NASA Astrophysics Data System (ADS)

    de Lucio, O. G.; DuBois, R. D.

    2016-03-01

    Singly, doubly, and triply differential information, obtained from coincidence measurements, are presented for 250-eV positron- and electron-impact ionization of molecular nitrogen. Comparisons of these data as functions of energy loss, scattering, and emission angles illustrate differences associated with the sign of the projectile charge. Via a deconvolution and normalization procedure, the triply differential data are converted to absolute cross sections. By fitting the triply differential cross sections for single ionization with simple functions, the intensities, directions, and peak to background intensities of the binary peaks plus the ratio of recoil to binary interactions are compared for positron and electron impact. Formulas for the binary and recoil intensities plus for the orientation of the binary peak as a function of momentum transfer are extracted from the data. Differences in the relative amount of fragmentation as a function of energy loss are also observed.

  14. Multielectron coincidence study of the double Auger decay of 3d-ionized krypton

    SciTech Connect

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

    2010-10-15

    Multielectron coincidence data for triple ionization of krypton have been recorded above the 3d ionization threshold at two photon energies (140 and 150 eV). Three principal transition pathways have been observed, two involving double Auger transitions from Kr{sup +}, and one involving single Auger transitions from Kr{sup 2+} created by direct single-photon double ionization. The decay of the 3d{sup 9} {sup 2}D{sub 5/2,3/2} states in Kr{sup +} has been analyzed in some detail and is found to be strongly dominated by cascade processes where two electrons with well-defined energies are emitted. The decay paths leading to the 4s{sup 2}4p{sup 3} {sup 4}S, {sup 2}D, and {sup 2}P states of Kr{sup 3+} are analyzed and energies of seven intermediate states in Kr{sup 2+} are given. A preliminary investigation of the decay paths from Kr{sup +} 3d{sup 9}4p{sup 5}nl shake-up states has also been carried out.

  15. The 30 Doradus Nebula: An Imaging Study of Molecular and Ionized Hydrogen

    NASA Astrophysics Data System (ADS)

    Yeh, Sherry; Seaquist, E. R.; Matzner, C. D.

    2013-01-01

    We present the very first, fully calibrated H2 1--0 S(1) image of the entire 30 Doradus nebula. The observations were carried out using the NOAO Extremely Wide Field Infrared Imager on the CTIO 4-meter telescope. Together with a Brγ image of 30 Dor taken by NEWFIRM, our images reveal the morphologies of the warm molecular gas and ionized gas in 30 Doradus. Based on the morphologies of H2 and Brγ, line ratio H2 to Brγ, and Cloudy models, we found that the H2 emission is formed inside the photodissociation regions of 30 Doradus, very close to the surface in association with the ionization front of the HII region. We also suggest that the bright H2-emitting area, which expands from the northeast to the southwest of R136, is a photodissociation region viewed face-on, while many clumps and elephant trunk features located at the outer shells of 30 Doradus are also photodissociation regions viewed edge-on. The characteristic radiation to gas pressure ratio is evaluated at selected regions in 30 Doradus, and we conclude that radiation pressure is not the dominating force at the current phase of 30 Doradus, while the pressurization of stellar winds and the injection of photoevaporative flows are likely the major feedback mechanisms acting to reduce the observed ionization parameter in 30 Doradus.

  16. Studies of the Twin Helix Parametric-resonance Ionization Cooling Channel with COSY INFINITY

    SciTech Connect

    J.A. Maloney, K.B. Beard, R.P. Johnson, A. Afanasev, S.A. Bogacz, Y.S. Derbenev, V.S. Morozov, B. Erdelyi

    2012-07-01

    A primary technical challenge to the design of a high luminosity muon collider is an effective beam cooling system. An epicyclic twin-helix channel utilizing parametric-resonance ionization cooling has been proposed for the final 6D cooling stage. A proposed design of this twin-helix channel is presented that utilizes correlated optics between the horizontal and vertical betatron periods to simultaneously focus transverse motion of the beam in both planes. Parametric resonance is induced in both planes via a system of helical quadrupole harmonics. Ionization cooling is achieved via periodically placed wedges of absorbing material, with intermittent rf cavities restoring longitudinal momentum necessary to maintain stable orbit of the beam. COSY INFINITY is utilized to simulate the theory at first order. The motion of particles around a hyperbolic fixed point is tracked. Comparison is made between the EPIC cooling channel and standard ionization cooling effects. Cooling effects are measured, after including stochastic effects, for both a single particle and a distribution of particles.

  17. Study of the replacement correction factors for ionization chamber dosimetry by Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Wang, Lilie

    In ionization chamber radiation dosimetry, the introduction of the ion chamber into medium will unavoidably distort the radiation field near the chamber because the chamber cavity material (air) is different from the medium. A replacement correction factor, Prepl was introduced in order to correct the chamber readings to give an accurate radiation dose in the medium without the presence of the chamber. Generally it is very hard to measure the values of Prepl since they are intertwined with the chamber wall effect. In addition, the P repl values always come together with the stopping-power ratio of the two media involved. This makes the problem of determining the P repl values even more complicated. Monte Carlo simulation is an ideal method to investigate the replacement correction factors. In this study, four different methods of calculating the values of Prepl by Monte Carlo simulation are discussed. Two of the methods are designated as 'direct' methods in the sense that the evaluation of the stopping-power ratio is not necessary. The systematic uncertainties of the two direct methods are estimated to be about 0.1-0.2% which comes from the ambiguous definition of the energy cutoff Delta used in the Spencer-Attix cavity theory. The two direct methods are used to calculate the values of P repl for both plane-parallel chambers and cylindrical thimble chambers in either electron beams or photon beams. The calculation results are compared to measurements. For electron beams, good agreements are obtained. For thimble chambers in photon beams, significant discrepancies are observed between calculations and measurements. The experiments are thus investigated and the procedures are simulated by the Monte Carlo method. It is found that the interpretation of the measured data as the replacement correction factors in dosimetry protocols are not correct. In applying the calculation to the BIPM graphite chamber in a 60Co beam, the calculated values of P repl differ from those

  18. Backbone Relaxation Coupled to the Ionization of Internal Groups in Proteins: A Self-Guided Langevin Dynamics Study

    PubMed Central

    Damjanović, Ana; Wu, Xiongwu; García-Moreno E., Bertrand; Brooks, Bernard R.

    2008-01-01

    Pathways of structural relaxation triggered by ionization of internal groups in staphylococcal nuclease (SNase) were studied through multiple self-guided Langevin dynamics (SGLD) simulations. Circular dichroism, steady-state Trp fluorescence, and nuclear magnetic resonance spectroscopy have shown previously that variants of SNase with internal Glu, Asp, and Lys at positions 66 or 92, and Arg at position 66, exhibit local reorganization or global unfolding when the internal ionizable group is charged. Except for Arg-66, these internal ionizable groups have unusual pKa values and are neutral at physiological pH. The structural trends observed in the simulations are in general agreement with experimental observations. The I92D variant, which unfolds globally upon ionization of Asp-92, in simulations often exhibits extensive hydration of the protein core, and sometimes also significant perturbations of the β-barrel. In the crystal structure of the V66R variant, the β1 strand from the β-barrel is domain-swapped; in the simulations, the β1 strand is sometimes partially released. The V66K variant, which in solutions shows reorganization of six residues at the C-terminus of helix α1 and perturbations in the β-barrel structure, exhibits fraying of three residues of helix α1 in one simulation, and perturbations and partial unfolding of three β-strands in a few other simulations. In sharp contrast, very small structural changes were observed in simulations of the wild-type protein. The simulations indicate that charging of internal groups frequently triggers penetration of water into the protein interior. The pKa values of Asp-92 and Arg-66 calculated with continuum methods on SGLD-relaxed structures reached the normal values in most simulations. Detailed analysis of accuracy and performance of SGLD demonstrates that SGLD outperforms LD in sampling of alternative protein conformations without loss of the accuracy and level of detail characteristic of regular LD. PMID

  19. Monte Carlo study of electron initiated impact ionization in bulk zincblende and wurtzite phase ZnS

    NASA Astrophysics Data System (ADS)

    Bellotti, E.; Brennan, K. F.; Wang, R.; Ruden, P. P.

    1998-05-01

    This paper presents a theoretical study of the high field electronic transport properties of the cubic and hexagonal phases of zinc sulfide (ZnS) using an ensemble Monte Carlo method. Essential features of the model are the inclusion of realistic energy band structures calculated from a local pseudopotential method and numerically calculated impact ionization transition rates. The polar optical phonon scattering rate has also been computed numerically from the band structure. The relevant transport quantities have been computed for field values between 100 kV/cm and 2 MV/cm. On the basis of these calculations it is predicted that the electron distribution is cooler and the average energy lower in the wurtzite phase than in the zincblende phase over the entire field range examined. The difference in average energy between the two phases becomes pronounced for field magnitudes above 1 MV/cm while it is smaller in the field range between 700 kV/cm and 1 MV/cm. As a result, the ionization coefficients are expected to be higher in the zincblende phase than in the wurtzite phase. This can be attributed to differences in the density of states between the two polytypes. The quantum yield has also been computed. It is found that even though the threshold for impact ionization is relatively hard in both polytypes, the threshold for the wurtzite phase is harder than the threshold for the zincblende phase.

  20. 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.

  1. 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.

  2. 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.

  3. Unexpected lateral-lithiation-induced alkylative ring opening of tetrahydrofurans in deep eutectic solvents: synthesis of functionalised primary alcohols.

    PubMed

    Sassone, Francesca C; Perna, Filippo M; Salomone, Antonio; Florio, Saverio; Capriati, Vito

    2015-06-11

    o-Tolyl-substituted tetrahydrofurans undergo highly regioselective ring opening with the concomitant formation of new C-C bonds as the result of a lateral lithiation reaction. This reaction provides a new method for the synthesis of functionalised primary alcohols and can be run directly in protic eutectic mixtures as benign reaction media at 0 °C and under air, competitively with protonolysis. PMID:25959580

  4. Study of Simvastatin Self-Association Using Electrospray-Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Vetrova, E. V.; Lekar, A. V.; Filonova, O. V.; Borisenko, S. N.; Maksimenko, E. V.; Borisenko, N. I.

    2015-07-01

    Self-association of simvastatin, which is widely used to treat coronary heart disease, was investigated using electrospray-ionization mass spectrometry. Formation of simvastatin self-associates in various solvents was demonstrated using mass spectrometry. Solvation effects were shown to play a special role in the formation of the self-associates. Self-associates containing from two to fi ve simvastatin molecules were detected in mass spectra of an aqueous MeOH (20%) solution of simvastatin. The formation of simvastatin self-associates could compete with the complexation of supramolecular structures during the synthesis of new generation drugs.

  5. Status of Studies of Achromat-based 6D Ionization Cooling Rings for Muons

    SciTech Connect

    Ding, X.; Kirk, H.; Cline, D.; Garren, A.A.; Berg, J.S.

    2011-09-04

    Six dimensional ionization cooling of muons is needed to achieve the necessary luminosity for a muon collider. If that cooling could occur over multiple turns in a closed ring, there would be significant cost savings over a single-pass cooling channel. We report on the status of a cooling ring with achromatic arcs. The achromatic design permits the design to easily switch between a closed ring and a snaking geometry on injection or extraction from the ring. The ring is designed with sufficient space in each superperiod for injection and extraction magnets. We describe the ring's lattice design, performance, and injection/extraction requirements.

  6. A DEEP CHANDRA ACIS STUDY OF NGC 4151. III. THE LINE EMISSION AND SPECTRAL ANALYSIS OF THE IONIZATION CONE

    SciTech Connect

    Wang, Junfeng; Fabbiano, Giuseppina; Elvis, Martin; Risaliti, Guido; Karovska, Margarita; Zezas, Andreas; Mundell, Carole G.; Dumas, Gaelle; Schinnerer, Eva

    2011-11-20

    This paper is the third in a series in which we present deep Chandra ACIS-S imaging spectroscopy of the Seyfert 1 galaxy NGC 4151, devoted to study its complex circumnuclear X-ray emission. Emission features in the soft X-ray spectrum of the bright extended emission (L{sub 0.3-2{sub keV}} {approx} 10{sup 40} erg s{sup -1}) at r > 130 pc (2'') are consistent with blended brighter O VII, O VIII, and Ne IX lines seen in the Chandra HETGS and XMM-Newton RGS spectra below 2 keV. We construct emission line images of these features and find good morphological correlations with the narrow-line region clouds mapped in [O III] {lambda}5007. Self-consistent photoionization models provide good descriptions of the spectra of the large-scale emission, as well as resolved structures, supporting the dominant role of nuclear photoionization, although displacement of optical and X-ray features implies a more complex medium. Collisionally ionized emission is estimated to be {approx}<12% of the extended emission. Presence of both low- and high-ionization spectral components and extended emission in the X-ray image perpendicular to the bicone indicates leakage of nuclear ionization, likely filtered through warm absorbers, instead of being blocked by a continuous obscuring torus. The ratios of [O III]/soft X-ray flux are approximately constant ({approx}15) for the 1.5 kpc radius spanned by these measurements, indicating similar relative contributions from the low- and high-ionization gas phases at different radial distances from the nucleus. If the [O III] and X-ray emission arise from a single photoionized medium, this further implies an outflow with a wind-like density profile. Using spatially resolved X-ray features, we estimate that the mass outflow rate in NGC 4151 is {approx}2 M{sub Sun} yr{sup -1} at 130 pc and the kinematic power of the ionized outflow is 1.7 Multiplication-Sign 10{sup 41} erg s{sup -1}, approximately 0.3% of the bolometric luminosity of the active nucleus in

  7. Time-dependent density-functional study of the ionization and fragmentation of C2H2 and H2 by strong circularly polarized laser pulses

    NASA Astrophysics Data System (ADS)

    Russakoff, Arthur; Varga, Kálmán

    2015-11-01

    The ionization and fragmentation dynamics of acetylene and the hydrogen molecule driven by strong short circularly polarized laser pulses are investigated within the framework of the time-dependent density-functional theory coupled with the Ehrenfest dynamics. The effects of alignment are considered and the dynamics is compared to that driven by linearly polarized pulses. It is found that the coupled ion-electron dynamics of both molecules driven by circularly polarized pulses follows the enhanced ionization mechanism, as was found in previous theoretical studies with linearly polarized pulses. A moderate localization asymmetry in the ionization dynamics of the hydrogen molecule was also found, in qualitative agreement with previous experimental investigations.

  8. An efficient and economical process for lignin depolymerization in biomass-derived solvent tetrahydrofuran.

    PubMed

    Long, Jinxing; Zhang, Qi; Wang, Tiejun; Zhang, Xinghua; Xu, Ying; Ma, Longlong

    2014-02-01

    The depolymerization of renewable lignin for phenolic monomer, a versatile biochemical and precursor for biofuel, has attracted increasing attention. Here, an efficient base-catalyzed depolymerization process for this natural aromatic polymer is presented with cheap industrial solid alkali MgO and biomass-derived solvent tetrahydrofuran (THF). Results showed that more than 13.2% of phenolic monomers were obtained under 250°C for 15 min, because of the excellent lignin dissolution of THF and its promotion effect on the catalytic activity of MgO. Furthermore, comparison characterization on the raw material, products and residual solid using elemental analysis, FT-IR, TG-DSC, Py-GC-MS and chemo-physical absorption and desorption demonstrated that this base-catalyzed process can inhibit char formation significantly. Whereas, the fact that thermal repolymerization of oligomer on the pore and surface of catalyst resulting in the declination of the catalytic performance is responsible for the residue formation. PMID:24370950

  9. Preparations, structures and properties of heterobimetallic complexes based on tetrahydrofuran-2,3,4,5-tetracarboxylate

    NASA Astrophysics Data System (ADS)

    Jia, Tian-Jing; Li, Shu-Mu; Cao, Wei; Li, Li-Cun; Zheng, Xiang-Jun; Yuan, Da-Qiang

    2013-05-01

    Transition heterobimetallic metal-organic frameworks based on tetrahydrofuran-2,3,4,5-tetracarboxylicate (FTA), namely [M(H2O)6][Cu2M(FTA)2(H2O)2]·4H2O [M=Mn (1), Co (2)], and [CuZn(FTA)(H2O)5]·H2O (3) have been synthesized and characterized. Single-crystal X-ray diffraction indicates that complexes 1 and 2 are isomorphic. In 1 and 2, FTA ligand links the metal ions to a 2-D wave-like negative-charged layer with a topology of {4;62}2{4;63;82}2{6}. They possess 1-D channels with [M(H2O)6]2+ and lattice water molecules enclathrated. While in the complex 3, Cu2+ and Zn2+ ions are bridged by FTA to a 2-D neutral layer structure with a {8}2{84;122} topology. Magnetic properties of 1-3 were analyzed in connection with their structures, which show that there exist weak antiferromagnetic interactions between metal ions.

  10. Characteristics of tetrahydrofuran-based electrolytes with magnesium alkoxide additives for rechargeable magnesium batteries

    NASA Astrophysics Data System (ADS)

    Kim, In-Tae; Yamabuki, Kazuhiro; Sumimoto, Michinori; Tsutsumi, Hiromori; Morita, Masayuki; Yoshimoto, Nobuko

    2016-08-01

    The electrochemical behavior of magnesium (Mg) metal was investigated in tetrahydrofuran (THF)-based solutions containing magnesium bromide (MgBr2) and/or magnesium ethoxide (Mg(OEt)2). THF solutions containing a single solute, MgBr2 or Mg(OEt)2, show no visible faradaic current based on Mg deposition and/or dissolution. However, the electrolyte system containing both solutes, MgBr2 + Mg(OEt)2/THF, gives a reversible current response of Mg deposition and dissolution. The ionic structure of the electrolyte system containing the binary solute was examined by infrared (IR) spectroscopy and density functional theory (DFT) calculations. It was confirmed that MgBr2 and Mg(OEt)2 are coordinated (solvated) with THF molecules to form an EtOsbnd Mgsbnd Br·4THF complex. The DFT calculations also suggest the possible formation of μ-complexes for the MgBr2/Mg(OEt)2 binary system in THF. The voltammetric responses at the Pt electrode indicate low overpotential and high coulombic efficiency for Mg deposition and dissolution in THF-based solutions containing suitable molar ratios of MgBr2 and Mg(OEt)2. The constant-current charge-discharge cycling of Mg in MgBr2 + Mg(OEt)2/THF electrolyte also shows low overpotential and good cyclability over 300 cycles.

  11. Diffusive hydrogen inter-cage migration in hydrogen and hydrogen-tetrahydrofuran clathrate hydrates.

    PubMed

    Cao, Huayu; English, Niall J; MacElroy, J M D

    2013-03-01

    Classical equilibrium molecular dynamics simulations have been performed to investigate the diffusive properties of inter-cage hydrogen migration in both pure hydrogen and mixed hydrogen-tetrahydrofuran sII hydrates at 0.05 kbar from 200 K and up to 250-260 K. For mixed H2-THF systems in which there is single H2 occupation of the small cage (labelled "1S1L"), we found that no H2 migration occurs. However, for more densely filled H2-THF and pure-H2 systems, in which there is more than single H2 occupation in the small cage, there is an onset of inter-cage H2 migration events from the small cages to neighbouring cavities at around 200 K. The mean square displacements of the hydrogen molecules were fitted to a mathematical model consisting of an anomalous term and a Fickian component, and nonlinear regression fitting was conducted to estimate long-time (inter-cage) diffusivities. An approximate Arrhenius temperature relationship for the diffusion coefficient was examined and an estimation of the hydrogen hopping energy barrier was calculated for each system. PMID:23485313

  12. "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

  13. "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.

  14. Study of ozone-initiated limonene reaction products by low temperature plasma ionization mass spectrometry.

    PubMed

    Nørgaard, Asger W; Vibenholt, Anni; Benassi, Mario; Clausen, Per Axel; Wolkoff, Peder

    2013-07-01

    Limonene and its ozone-initiated reaction products were investigated in situ by low temperature plasma (LTP) ionization quadrupole time-of-flight (QTOF) mass spectrometry. Helium was used as discharge gas and the protruding plasma generated ~850 ppb ozone in front of the glass tube by reaction with the ambient oxygen. Limonene applied to filter paper was placed in front of the LTP afterglow and the MS inlet. Instantly, a wide range of reaction products appeared, ranging from m/z 139 to ca. 1000 in the positive mode and m/z 115 to ca. 600 in the negative mode. Key monomeric oxidation products including levulinic acid, 4-acetyl-1-methylcyclohexene, limonene oxide, 3-isopropenyl-6-oxo-heptanal, and the secondary ozonide of limonene could be identified by collision-induced dissociation. Oligomeric products ranged from the nonoxidized dimer of limonene (C20H30) and up to the hexamer with 10 oxygen atoms (C60H90O10). The use of LTP for in situ ozonolysis and ionization represents a new and versatile approach for the assessment of ozone-initiated terpene chemistry. PMID:23666602

  15. Study of Ozone-Initiated Limonene Reaction Products by Low Temperature Plasma Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Nørgaard, Asger W.; Vibenholt, Anni; Benassi, Mario; Clausen, Per Axel; Wolkoff, Peder

    2013-07-01

    Limonene and its ozone-initiated reaction products were investigated in situ by low temperature plasma (LTP) ionization quadrupole time-of-flight (QTOF) mass spectrometry. Helium was used as discharge gas and the protruding plasma generated ~850 ppb ozone in front of the glass tube by reaction with the ambient oxygen. Limonene applied to filter paper was placed in front of the LTP afterglow and the MS inlet. Instantly, a wide range of reaction products appeared, ranging from m/ z 139 to ca. 1000 in the positive mode and m/ z 115 to ca. 600 in the negative mode. Key monomeric oxidation products including levulinic acid, 4-acetyl-1-methylcyclohexene, limonene oxide, 3-isopropenyl-6-oxo-heptanal, and the secondary ozonide of limonene could be identified by collision-induced dissociation. Oligomeric products ranged from the nonoxidized dimer of limonene (C20H30) and up to the hexamer with 10 oxygen atoms (C60H90O10). The use of LTP for in situ ozonolysis and ionization represents a new and versatile approach for the assessment of ozone-initiated terpene chemistry.

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

    Giant H II regions (GHIIRs) in nearby galaxies are a local sample in which we can study in detail processes in the interaction of gas, dust and newly formed stars which are analogous to those which occurred in episodes of higher intensity in which much of the current stellar population was born. Here, we present an analysis of NGC 588, a GHIIR in M33, based on optical Integral Field Spectroscopy data obtained with the Potsdam Multi-Aperture Spectrophotometer at the 3.5-m telescope of the Calar Alto Observatory, CAHA, together with Spitzer infrared images at 8 and 24 μm. The extinction distribution measured in the optical shows complex structure, with three maxima which correlate in position with those of the emission at 24 and 8 μm. Furthermore, the Hα luminosity absorbed by the dust within the H II region reproduces the structure observed in the 24-μm image, supporting the use of the 24-μm band as a valid tracer of recent star formation. A velocity difference of ˜50 km s-1 was measured between the areas of high and low surface brightness, which would be expected if NGC 588 were an evolved GHIIR. We have carefully identified the areas which contribute most to the line ratios measured in the integrated spectrum. Those line ratios which are used in diagnostic diagrams proposed by Baldwin, Phillips & Terlevich (i.e. the BPT diagrams) show a larger range of variation in the low surface brightness areas. The ranges are ˜0.5-1.2 dex for [N II]λ6584/Hα, 0.7-1.7 dex for [S II]λλ6717,6731/Hα and 0.3-0.5 dex for [O III]λ5007/Hβ, with higher values of [N II]λ6584/Hα and [S II]λλ6717,6731/Hα, and lower values of [O III]λ5007/Hβ in the areas of lower surface brightness. Ratios corresponding to large ionization parameter (U) are found between the peak of the emission in Hβ and the main ionizing source decreasing radially outwards within the region. Differences between the integrated and local values of the U tracers can be as high as ˜0.8 dex, notably when

  17. Time resolved studies of interfacial reactions of ozone with pulmonary phospholipid surfactants using field induced droplet ionization mass spectrometry.

    PubMed

    Kim, Hugh I; Kim, Hyungjun; Shin, Young Shik; Beegle, Luther W; Goddard, William A; Heath, James R; Kanik, Isik; Beauchamp, J L

    2010-07-29

    Field induced droplet ionization mass spectrometry (FIDI-MS) comprises a soft ionization method to sample ions from the surface of microliter droplets. A pulsed electric field stretches neutral droplets until they develop dual Taylor cones, emitting streams of positively and negatively charged submicrometer droplets in opposite directions, with the desired polarity being directed into a mass spectrometer for analysis. This methodology is employed to study the heterogeneous ozonolysis of 1-palmitoyl-2-oleoyl-sn-phosphatidylglycerol (POPG) at the air-liquid interface in negative ion mode using FIDI mass spectrometry. Our results demonstrate unique characteristics of the heterogeneous reactions at the air-liquid interface. We observe the hydroxyhydroperoxide and the secondary ozonide as major products of POPG ozonolysis in the FIDI-MS spectra. These products are metastable and difficult to observe in the bulk phase, using standard electrospray ionization (ESI) for mass spectrometric analysis. We also present studies of the heterogeneous ozonolysis of a mixture of saturated and unsaturated phospholipids at the air-liquid interface. A mixture of the saturated phospholipid 1,2-dipalmitoyl-sn-phosphatidylglycerol (DPPG) and unsaturated POPG is investigated in negative ion mode using FIDI-MS while a mixture of 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) and 1-stearoyl-2-oleoyl-sn-phosphatidylcholine (SOPC) surfactant is studied in positive ion mode. In both cases FIDI-MS shows the saturated and unsaturated pulmonary surfactants form a mixed interfacial layer. Only the unsaturated phospholipid reacts with ozone, forming products that are more hydrophilic than the saturated phospholipid. With extensive ozonolysis only the saturated phospholipid remains at the droplet surface. Combining these experimental observations with the results of computational analysis provides an improved understanding of the interfacial structure and chemistry of a surfactant layer system when

  18. Electron-correlation effects in enhanced ionization of molecules: A time-dependent generalized-active-space configuration-interaction study

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, S.; Bauch, S.; Madsen, L. B.

    2015-12-01

    We numerically study models of H2 and LiH molecules, aligned collinearly with the linear polarization of the external field, to elucidate the possible role of correlation in the enhanced-ionization (EI) phenomena. Correlation is considered at different levels of approximation with the time-dependent generalized-active-space configuration-interaction method. The results of our studies show that enhanced ionization occurs in multielectron molecules and that correlation is important, and they also demonstrate significant deviations between the results of the single-active-electron approximation and more accurate configuration-interaction methods. We further investigate the role of low-lying excited states in the EI phenomena. With the inclusion of correlation we show strong carrier-envelope-phase effects in the enhanced ionization of the asymmetric heteronuclear LiH -like molecule. The correlated calculation shows an intriguing feature of crossover in enhanced ionization with two carrier-envelope phases at critical internuclear separation.

  19. Time-dependent close-coupling studies of the electron-impact ionization of excited-state helium

    SciTech Connect

    Colgan, J.; Pindzola, M. S.

    2002-12-01

    The time-dependent close-coupling theory is applied to the study of the electron-impact ionization of helium from the excited (1s2s) configuration. Calculations are made in an effort to resolve the discrepancy between theoretical calculations and existing experimental measurements for this cross section. We find good agreement with the existing convergent close-coupling calculations of Bray and Fursa [J. Phys. B 28, L197 (1995)], but are in substantial disagreement with the experimental measurements of this quantity by Dixon et al. [J. Phys. B 9, 2617 (1976)].

  20. Micellar versus hydro-organic mobile phases for retention-hydrophobicity relationship studies with ionizable diuretics and an anionic surfactant.

    PubMed

    Ruiz-Angel, M J; Carda-Broch, S; García-Alvarez-Coque, M C; Berthod, A

    2004-03-19

    Logarithm of retention factors (log k) of a group of 14 ionizable diuretics were correlated with the molecular (log P o/w) and apparent (log P(app)) octanol-water partition coefficients. The compounds were chromatographed using aqueous-organic (reversed-phase liquid chromatography, RPLC) and micellar-organic mobile phases (micellar liquid chromatography, MLC) with the anionic surfactant sodium dodecyl sulfate (SDS), in the pH range 3-7, and a conventional octadecylsilane column. Acetonitrile was used as the organic modifier in both modes. The quality of the correlations obtained for log P(app) at varying ionization degree confirms that this correction is required in the aqueous-organic mixtures. The correlation is less improved with SDS micellar media because the acid-base equilibriums are shifted towards higher pH values for acidic compounds. In micellar chromatography, an electrostatic interaction with charged solutes is added to hydrophobic forces; consequently, different correlations should be established for neutral and acidic compounds, and for basic compounds. Correlations between log k and the isocratic descriptors log k(w), log k(wm) (extrapolated retention to pure water in the aqueous-organic and micellar-organic systems, respectively), and psi0 (extrapolated mobile phase composition giving a k = 1 retention factor or twice the dead time), and between these descriptors and log P(app) were also satisfactory, although poorer than those between log k and log P(app) due to the extrapolation. The study shows that, in the particular case of the ionizable diuretics studied, classical RPLC gives better results than MLC with SDS in the retention hydrophobicity correlations. PMID:15043280

  1. The Chandra X-Ray Observatory and its Role for the Study of Ionized Plasmas

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.

    2010-01-01

    NASA's Chandra X-Ray Observatory was launched in July of 1999. Featuring a 1000cm2-class X-ray telescope with sub-arcsecond angular resolution, the Observatory has observed targets from the solar system including the earth s moon, comets, and planets to the most distant galaxy clusters and active galactic nuclei. Capable of performing moderate energy resolution image-resolved spectroscopy using its CCD detectors, and high-resolution grating spectroscopy, the Observatory has produced, and continues to produce, valuable data and insights into the emission mechanisms of the ionized plasmas in which the X-rays originate. We present a brief overview of the Observatory to provide insight as to how to use it for your investigations. We also present an, admittedly brief and biased, overview of some of the results of investigations performed with Chandra that may be of interest to this audience.

  2. Theoretical study of the ionospheric plasma cave in the equatorial ionization anomaly region

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Tsung; Lin, C. H.; Chen, C. H.; Liu, J. Y.; Huba, J. D.; Chang, L. C.; Liu, H.-L.; Lin, J. T.; Rajesh, P. K.

    2014-12-01

    This paper investigates the physical mechanism of an unusual equatorial electron density structure, plasma cave, located underneath the equatorial ionization anomaly by using theoretical simulations. The simulation results provide important new understanding of the dynamics of the equatorial ionosphere. It has been suggested previously that unusual E>⇀×B>⇀ drifts might be responsible for the observed plasma cave structure, but model simulations in this paper suggest that the more likely cause is latitudinal meridional neutral wind variations. The neutral winds are featured by two divergent wind regions at off-equator latitudes and a convergent wind region around the magnetic equator, resulting in plasma divergences and convergence, respectively, to form the plasma caves structure. The tidal-decomposition analysis further suggests that the cave related meridional neutral winds and the intensity of plasma cave are highly associated with the migrating terdiurnal tidal component of the neutral winds.

  3. Ab initio Study on Ionization Energies of 3-Amino-1-propanol

    NASA Astrophysics Data System (ADS)

    Wang, Ke-dong; Jia, Ying-bin; Lai, Zhen-jiang; Liu, Yu-fang

    2011-06-01

    Fourteen conformers of 3-amino-1-propanol as the minima on the potential energy surface are examined at the MP2/6-311++G** level. Their relative energies calculated at B3LYP, MP3 and MP4 levels of theory indicated that two most stable conformers display the intramolecular OH···N hydrogen bonds. The vertical ionization energies of these conformers calculated with ab initio electron propagator theory in the P3/aug-cc-pVTZ approximation are in agreement with experimental data from photoelectron spectroscopy. Natural bond orbital analyses were used to explain the differences of IEs of the highest occupied molecular ortibal of conformers. Combined with statistical mechanics principles, conformational distributions at various temperatures are obtained and the temperature dependence of photoelectron spectra is interpreted.

  4. A (e,2e +ion) study of low-energy electron-impact ionization of THF

    NASA Astrophysics Data System (ADS)

    Ali, Esam; Ren, Xueguang; Ning, Chuangang; Dorn, Alexander; Madison, Don

    2015-09-01

    We have investigated the Fully Differential Cross Sections (FDCS) for electron impact induced ionization of THF (C4H8O) by low-energy (Eo = 26 eV) for three different orbital states of the highest, next highest, and next-next highest occupied molecular orbitals (HOMO, NHOMO, and Next NHOMO). Theoretical results are compared with experiment for in plane scattering with projectile scattering angles of 15°, 25°, 35°, and 50°. Different theoretical models are examined - the molecular 3 body distorted wave (M3DW), and the distorted wave Born approximation (DWBA), with the effects of the post collision interaction (PCI) treated either exactly or with the Ward-Macek approximations. This work is supported by the US National Science Foundation under Grant No. PHY-1068237 and XSEDE resources provided by the Texas Advanced Computing Center (Grant No. TG-MCA07S029).

  5. An ionization chamber with Frisch grids for studies of high-energy neutron-induced fission

    NASA Astrophysics Data System (ADS)

    Tutin, G. A.; Ryzhov, I. V.; Eismont, V. P.; Kireev, A. V.; Condé, H.; Elmgren, K.; Olsson, N.; Renberg, P.-U.

    2001-01-01

    A gridded ionization chamber for fission fragment detection is described. The chamber has been specially designed for use at the quasi-monoenergetic 7Li(p, n) neutron source at the The Svedberg Laboratory, Uppsala, Sweden. The detector permits measurements of fission fragment energy and emission angle for two targets with diameter of up to 10 cm. The time response of the chamber (⩽5 ns FWHM) is adequate to apply time-of-flight discrimination against background events induced by non-peak neutrons. Results of angular anisotropy measurements for the 232Th (n, f) and 238U(n, f) reactions in the 20-160 MeV energy range are given.

  6. Functional Proteomics Analysis to Study ATM Dependent Signaling in Response to Ionizing Radiation

    PubMed Central

    Timofeeva, Olga; Zhang, Lihua; Kirilyuk, Alexander; Zandkarimi, Fereshteh; Kaur, Prabhjit; Ressom, Habtom W.; Jung, Mira; Dritschilo, Anatoly

    2013-01-01

    Ataxia telangiectasia (AT) is a human genetic disease characterized by radiation sensitivity, impaired neuronal development and predisposition to cancer. Using a genetically defined model cell system consisting of cells expressing a kinase dead or a kinase proficient ATM gene product, we previously reported systemic alterations in major metabolic pathways that translate at the gene expression, protein and small molecule metabolite levels. Here, we report ionizing radiation induced stress response signaling arising from perturbations in the ATM gene, by employing a functional proteomics approach. Functional pathway analysis shows robust translational and post-translational responses under ATM proficient conditions, which include enrichment of proteins in the Ephrin receptor and axonal guidance signaling pathways. These molecular networks offer a hypothesis generating function for further investigations of cellular stress responses. PMID:23642045

  7. Spectroscopy of neutral and ionized PAHs. From laboratory studies to astronomical observations

    NASA Technical Reports Server (NTRS)

    Salama, Farid

    2005-01-01

    Polycyclic Aromatic Hydrocarbons (PAHs) are an important and ubiquitous component of carbon-bearing materials in space. PAHs are the best-known candidates to account for the IR emission bands (UIR bands) and PAH spectral features are now being used as new probes of the ISM. PAHs are also thought to be among the carriers of the diffuse interstellar absorption bands (DIBs). In the model dealing with the interstellar spectral features, PAHs are present as a mixture of radicals, ions and neutral species. PAH ionization states reflect the ionization balance of the medium while PAH size, composition, and structure reflect the energetic and chemical history of the medium. A major challenge for laboratory astrochemistry is to reproduce (in a realistic way) the physical conditions that are associated with the emission and absorption interstellar zones. An extensive laboratory program has been developed at NASA Ames to assess the physical and chemical properties of PAHs in such environments and to describe how they influence the radiation and energy balance in space and the interstellar chemistry. PAHs, neutrals and ions, are expanded through a pulsed discharge nozzle (PDN) and probed with high-sensitivity cavity ringdown spectroscopy (CRDS). These laboratory experiments provide unique information on the spectra of free, cold large carbon molecules and ions in the gas phase from the ultraviolet and visible range to the near-infrared range. Intrinsic band profiles and band positions of cold gas-phase PAHs can now be measured with high-sensitivity spectroscopy and directly compared to the astronomical data. Preliminary conclusions from the comparison of the laboratory data with astronomical observations of interstellar and circumstellar environments will also be discussed.

  8. Photochemistry of limonene secondary organic aerosol studied with chemical ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Pan, Xiang

    Limonene is one of the most abundant monoterpenes in the atmosphere. Limonene easily reacts with gas-phase oxidants in air such as NO3, ozone and OH. Secondary organic aerosol (SOA) is formed when low vapor pressure products condense into particles. Chemicals in SOA particles can undergo further reactions with oxidants and with solar radiation that significantly change SOA composition over the course of several days. The goal of this work was to characterize radiation induced reaction in SOA. To perform experiments, we have designed and constructed an Atmospheric Pressure Chemical Ionization Mass Spectrometer (APCIMS) coupled to a photochemical cell containing SOA samples. In APCIMS, (H2O)nH 3O+ clusters are generated in a 63Ni source and react with gaseous organic analytes. Most organic chemicals are not fragmented by the ionization process. We have focused our attention on limonene SOA prepared in two different ways. The first type of SOA is produced by oxidation of limonene by ozone; and the second type of SOA is formed by the NO3-induced oxidation of limonene. They model the SOA formed under daytime and nighttime conditions, respectively. Ozone initiated oxidation is the most important chemical sink for limonene both indoors, where it is used for cleaning purposes, and outdoors. Terpenes are primarily oxidized by reactions with NO3 at night time. We generated limonene SOA under different ozone and limonene concentrations. The resulting SOA samples were exposed to wavelength-tunable radiation in the UV-Visible range between 270 nm and 630 nm. The results show that the photodegradation rates strongly depend on radiation wavelengths. Gas phase photodegradation products such as acetone, formaldehyde, acetaldehyde, and acetic acid were shown to have different production rates for SOA formed in different concentration conditions. Even for SOA prepared under the lowest concentrations, the SOA photodegradation was efficient. The conclusion is that exposure of SOA to

  9. Photoelectron spectroscopic studies of polyatomic molecules: Degree of orientation and ionization of rotationally state selected, oriented molecules

    NASA Astrophysics Data System (ADS)

    Chandra, N.; Chakraborty, M.

    1991-11-01

    In this paper we report theoretical studies of angle-resolved photoelectron spectroscopy (ARPES) and of circular dichroism in photoelectron angular distribution (CDAD) for ionization in molecules oriented in a single ‖JKJMJ> rotational eigenstate. These processes have been investigated also as two of the possible alternatives to photodissociation to determine orientational distribution function of rotationally state selected, oriented molecules. Expressions are derived which can be used to calculate ARPES and CDAD for such molecular species from ab initio methods or to analyze these experimentally observed spectra for extracting information about the degree of orientation of the molecular framework. These formulas are put in their simplest possible forms using the transformation properties of the molecular point group to their full advantage. The ionization amplitude is thus shown to decompose into a sum of transitions each involving the final state wave function belonging to an irreducible representation of the point group of the target molecule. It is found that, similar to the case of photodissociation, one can determine the rotational quantum number J purely from experimental photoionization data. Expressions developed herein are used to study ARPES and CDAD for ionization in a1 orbital of those rotationally state selected and oriented spherical top molecules which transform according to the Td point symmetry group. In this case, the detection-integrated cross section, singly differential in molecular orientation, is found to be independent of the photoionization dynamics and directly gives the molecular orientational function. The other ARPES and CDAD formulas are shown to depend upon the dynamics through the integrated partial cross section σ¯, the angularly asymmetry parameter β¯, the phase shift of the continuum waves representing the photoelectron, and the phase of the dipole transition amplitudes. The formulation presented in this paper sets a

  10. Effect of fluoro substitution on the fragmentation of the K-shell excited/ionized pyridine studied by electron impact.

    PubMed

    Sakai, Masamichi; Okada, Kazumasa

    2011-07-01

    Fragmentation of the pyridine ring followed by K-shell excitation/ionization has been studied with 2-fluoropyridine (2FPy) by electron impact. Ab initio molecular orbital (MO) calculations were also carried out to investigate the electronic states correlating with specific fragment ions. The fragment ions are produced characteristically at the N 1s edge, while the spectra observed at the F 1s and C 1s edges exhibit a small difference from that at the valence ionization. The production of the C(4)H(2)(+), C(4)H(3)(+) and C(4)H(2)F(+) ions indicates that the cleavage of the N-C6 and C2-C3 bonds or the N-C2 and C5-C6 bonds is likely to occur after the N 1s excitation/ionization. Ab initio MO calculations indicate that the former fission is likely to proceed through the n(N)(1)π(2)(1)π(3)(2) and n(N)(0)π(2)(2)π(3)(2) excited states of the parent molecular dication. On the other hand, the breakage of the N-C2 and C4-C5 bonds, which specifically proceeds at the N 1s edge for 2-methylpyridine, does not occur for 2FPy. The present calculation reveals that the products of this channel are unstable by the electronegativity of fluorine and that the relative energy of the Auger-final states of 2FPy is lowered by the reorganization and electron correlation effects. PMID:21744416

  11. Thermodynamics of lanthanide and uranyl complexes with tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THFTCA).

    SciTech Connect

    Morss, L. R.; Nash, K. L.; Tennessee Technological Univ.

    2000-01-01

    We present the results of an investigation of the thermochemistry of the complexation of La{sup 3+} Nd{sup 3+}, Eu{sup 3+}, Dy{sup 3+}, Tm{sup 3+}, and UO{sub 2}{sup 2+} by tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THFTCA). This predisposed structural analog to oxydiacetic acid (ODA) has been previously shown both to exhibit greater sensitivity to lanthanide cation radius than complexes with the unconstrained ODA and to form anomalously weak complexes with UO{sub 2}{sup 2+}. Our purpose is to interpret these observations in terms of the balance between enthalpy and entropy contributions to the overall complexation thermodynamics. Enthalpies have been calculated from titration calorimetry experiments both for the protonation of the free ligand and for the formation of selected 1:1 and 1:2 complexes in pH 2-3 acidic media (I = 0.1 M). The complexation entropies for the lanthanide complexes have been calculated using the previously reported stability constants for the MH{sub 2}L{sup +}, MHL, and M(H{sub 2}L){sup 2-}. The stability constants for the uranyl complexes have been determined by potentiometric titration and these values used to calculate the thermodynamic parameters. Complexation enthalpies for the 1:1 lanthanide-THFTCA complexes (MH{sub 2}L{sup +} species) are nearly identical to those of the lanthanide ODA complexes. Therefore, the size-selectivity observed in the lanthanide-THFTCA complexes arises from the complexation entropy. The comparative weakness of the uranyl complexes with THFTCA also is accounted for thermodynamically in the entropy term. Calculations based on an electrostatic model for complexation entropy and molecular mechanics modeling are used to help interpret the experimental results.

  12. Activating tert-butyl hydroperoxide by chelated vanadates for stereoselectively preparing sidechain-functionalized tetrahydrofurans.

    PubMed

    Dönges, Maike; Amberg, Matthias; Niebergall, Mark; Hartung, Jens

    2015-06-01

    tert-Butyl hydroperoxide (TBHP) stereoselectively oxidizes substituted 4-pentenols, when activated by (ethyl)[cis-(piperidine-2,6-diyl)dimethyl] vanadates. The reaction affords (tetrahydrofuran-2-yl)methanols in up to 89% yield, and in stereoselectivity ranging between moderate (cis:trans=32:68) to excellent (>99:1). Correlating structures of 4-pentenols, differing by substitution at tetragonal and trigonal stereocenters, to configuration of products obtained from oxidative cyclization provides a reaction model explaining the origin of stereoselectivity by (i) intramolecular oxygen atom transfer to (ii) a chair-like folded alkenol, being (iii) hydrogen-bonded to one of the two aminodiolate oxygens of the chelated vanadate, having (iv) substituents in the chair-like transition structure preferentially aligned equatorially. Substituents at trigonal stereocenters improve 2,5-cis- and 2,4-trans-selectivity for oxidative 4-pentenol cyclization in case of (Z)-configuration. An (E)-substituent does not alter selectivity exerted by a terminal (Z)-substituent of similar steric size. Larger (E)-groups increase the fraction of 2,5-trans-cyclized products. The reaction model additionally implements results from vanadium-51 NMR spectroscopy and density functional theory. According to theory, the (dialkoxy)(oxo)vanadium substituent exerts in the preferred end-on conformation almost no effect on structure and bonding of the peroxide group in tert-butylperoxy vanadates. Changing conformation to a higher in energy side-on arrangement puts the vanadate-bound tert-butylperoxy group into a position to serve in a concerted reaction as combined electron acceptor and oxygen atom donor. PMID:25958253

  13. Preparations, structures and properties of heterobimetallic complexes based on tetrahydrofuran-2,3,4,5-tetracarboxylate

    SciTech Connect

    Jia, Tian-Jing; Li, Shu-Mu; Cao, Wei; Li, Li-Cun; Zheng, Xiang-Jun; Yuan, Da-Qiang

    2013-05-01

    Transition heterobimetallic metal-organic frameworks based on tetrahydrofuran-2,3,4,5-tetracarboxylicate (FTA), namely [M(H₂O)₆][Cu₂M(FTA)₂(H₂O)₂]·4H₂O [M=Mn (1), Co (2)], and [CuZn(FTA)(H₂O)₅]·H₂O (3) have been synthesized and characterized. Single-crystal X-ray diffraction indicates that complexes 1 and 2 are isomorphic. In 1 and 2, FTA ligand links the metal ions to a 2-D wave-like negative-charged layer with a topology of (4;6²)₂(4;6³;8²)₂(6). They possess 1-D channels with [M(H₂O)₆]²⁺ and lattice water molecules enclathrated. While in the complex 3, Cu²⁺ and Zn²⁺ ions are bridged by FTA to a 2-D neutral layer structure with a (8)₂(8⁴;12²) topology. Magnetic properties of 1–3 were analyzed in connection with their structures, which show that there exist weak antiferromagnetic interactions between metal ions. - Graphical abstract: Three heterobimetallic MOFs were constructed through the size-selectivity of TFA coordination sites for different transition metal ions based on the concept of “Hard and Soft Acids and Bases”. Highlights: • Complexes 1 and 3 contain 2-D wave-like negative-charged layers. • Complex 2 is a 2-D neutral layer structure with a (8)₂(8⁴;12²) topology. • Complexes 1–3 are the first example of heterobimetallic MOFs based on FTA. • The coordination sites of FTA show size-selectivity to metal ions.

  14. Laboratory ultrasonic and resistivity measurements on sedimentary rocks containing tetrahydrofuran hydrates

    SciTech Connect

    Pearson, C.F.; Murphy, J.R.; Hermes, R.E.; Halleck, P.M.

    1984-01-01

    In this paper, we report laboratory ultrasonic and resistivity measurements on Berea Sandstone and Austin Chalk samples saturated with a stoichiometric mixture of tetrahydrofuran (THF) and water. We used THF as the guest species rather than methane or propane gas because THF can be mixed with water to form a solution containing the proper stoichiometric proportions of the THF and water. Neither methane nor propane is soluble in water. Because THF solutions form hydrates readily at atmospheric pressure, it is an excellent experimental analogue to natural gas hydrates. Hydrate formation increased the ultrasonic P-wave velocities from a room temperature value of 2.5 km/s to 4.5 km/s at -5/sup 0/C when the pores were nearly filled with hydrates. However, lowering the temperature below -5/sup 0/C did not appreciably change the velocity. In contrast, the electrical resistivity increased nearly two orders of magnitude upon hydrate formation and continued to increase more slowly as the temperature was further decreased. In all cases the resistivities were nearly frequency independent to 30 kHz and the loss tangents were high, always greater than 5. The dielectric loss showed a linear decrease with frequency suggesting that ionic conduction through a brine phase dominates at all frequencies, even when the pores are nearly filled with hydrates. We find that the resistivities are strongly a function of the dissolved salt content of the pore water. Pore water salinity also influenced the sonic velocity, but this effect is much smaller and only important near the hydrate formation temperature. 11 references, 9 figures.

  15. Experimental and theoretical study of three-photon ionization of He(1s2p3Po)

    NASA Astrophysics Data System (ADS)

    Génévriez, Matthieu; Urbain, Xavier; Brouri, Mohand; O'Connor, Aodh P.; Dunseath, Kevin M.; Terao-Dunseath, Mariko

    2014-05-01

    A joint experimental and theoretical study of three-photon ionization of the 1s2p3Po(ML=0,±1) states of helium is presented. The ion yield is recorded in the 690-730 nm wavelength range for different laser pulse energies, using an excited helium beam produced by photodetachment of helium negative ions. Two series of asymmetric peaks due to two-photon resonances with 1snp and 1snf Rydberg states are observed. In one series, the peaks have tails towards higher frequencies, while in the other series the tails change direction for higher Rydberg states. An effective Hamiltonian is built in the dressed state picture, and a numerical model simulating the traversal of the helium atom across the laser pulse is developed. The simulated and observed ion yields are in good qualitative agreement. The observed behavior is shown to result from the contributions of two different resonantly enhanced multiphoton ionization processes, depending on the magnetic quantum number ML of the initial state. The asymmetry reversal is explained by the strong 1s2p-1s3s dynamic Stark mixing for ML=0.

  16. Phloroglucinol protects small intestines of mice from ionizing radiation by regulating apoptosis-related molecules: a comparative immunohistochemical study.

    PubMed

    Ha, Danbee; Bing, So Jin; Cho, Jinhee; Ahn, Ginnae; Kim, Dae Seung; Al-Amin, Mohammad; Park, Suk Jae; Jee, Youngheun

    2013-01-01

    Phloroglucinol (PG) is a phenolic compound isolated from Ecklonia cava, a brown algae abundant on Jeju island, Korea. Previous reports have suggested that PG exerts antioxidative and cytoprotective effects against oxidative stress. In this study, we confirmed that PG protected against small intestinal damage caused by ionizing radiation, and we investigated its protective mechanism in detail. Regeneration of intestinal crypts in the PG-treated irradiated group was significantly promoted compared with that in irradiated controls. The expression level of proapoptotic molecules such as p53, Bax, and Bak in the small intestine was downregulated and that of antiapoptotic molecules such as Bcl-2 and Bcl-X(S/L) was augmented in the PG-treated group. On histological observation of the small intestine, PG inhibited the immunoreactivity of p53, Bax, and Bak and increased that of Bcl-2 and Bcl-X(S/L). These results demonstrate the protective mechanisms of PG in mice against intestinal damage from ionizing radiation, providing the benefit of raising the apoptosis threshold of jejunal crypt cells. PMID:23117934

  17. Density functional theory study on the ionization potentials and electron affinities of thymine-formamide complexes

    NASA Astrophysics Data System (ADS)

    Sun, Haitao; Tang, Ke; Li, Yanmin; Su, Chunfang; Zhou, Zhengyu; Wang, Zhizhong

    The effect of hydrogen bond interactions on ionization potentials (IPs) and electron affinities (EAs) of thymine-formamide complexes (T-F) have been investigated employing the density functional theory B3LYP at 6-311++G(d, p) basis set level. All complexes experience a geometrical change on either electron detachment or attachment, and the change might be facilitated or hindered according to the strength of the hydrogen-bonding interaction involved. The strength of hydrogen bonds presents an opposite changing trend on the two processes. A more important role that H-bonding interaction plays in the process of electron attachment than in the process of electron detachment can be seen by a comparison of the IPs and EAs of complexes with that of isolated thymine. Futhermore, the EAs of isolated thymine are in good agreement with the experimental values (AEA is 0.79 eV, VEA is -0.29 eV [Wetmore et al., Chem Phys Lett 2000, 322, 129]). The calculated total NPA charge distributions reveal that nearly all the negative charges locate on thymine monomer in the anions and even in the cationic states, there are a few negative charges on thymine monomer. An analysis of dissociation energies predicts the processes T-F+→ T++ F and T-F- → T- + F to be the most energetically favorable for T-F+ and T-F-, respectively. Content:text/plain; charset="UTF-8"

  18. 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.

  19. Long-Term Effects of Exposure to Ionizing Irradiation on Periodontal Health Status - The Tinea capitis Cohort Study.

    PubMed

    Sadetzki, Siegal; Chetrit, Angela; Sgan-Cohen, Harold D; Mann, Jonathan; Amitai, Tova; Even-Nir, Hadas; Vered, Yuval

    2015-01-01

    Studies among long-term survivors of childhood cancer who had received high-dose irradiation therapy of 4-60 Gy, demonstrated acute and chronic dental effects, including periodontal diseases. However, the possible effects of low to moderate doses of radiation on dental health are sparse. The aim of this study is to investigate the association between childhood exposure to low-moderate doses of ionizing radiation and periodontal health following 50 years since exposure. The study population included 253 irradiated subjects (treated for Tinea capitis in the 1950s) and, 162 non-irradiated subjects. The estimated dose to the teeth was 0.2-0.4 Gy. Dental examination was performed according to the community periodontal index (CPI). Socioeconomic and health behavior variables were obtained through a personal questionnaire. Periodontal disease was operationally defined as "deep periodontal pockets." A multivariate logistic regression model was used for the association of irradiation status and other independent variables with periodontal status. The results showed that among the irradiated subjects, 23%, (95% CI 18-28%) demonstrated complete edentulousness or insufficient teeth for CPI scoring as compared to 13% (95% CI 8-19%) among the non-irradiated subjects (p = 0.01). Periodontal disease was detected among 54% of the irradiated subjects as compared to 40% of the non-irradiated (p = 0.008). Controlling for education and smoking, the ORs for the association between radiation and periodontal disease were 1.61 (95% CI 1.01-2.57) and 1.95 (95% CI 1.1-3.5) for ever never and per 1 Gy absorbed in the salivary gland, respectively. In line with other studies, a protective effect for periodontal diseases among those with high education and an increased risk for ever smokers were observed. In conclusion, childhood exposure to low-moderate doses of ionizing radiation might be associated with later outcomes of dental health. The results add valuable data on the long

  20. Long-Term Effects of Exposure to Ionizing Irradiation on Periodontal Health Status – The Tinea capitis Cohort Study

    PubMed Central

    Sadetzki, Siegal; Chetrit, Angela; Sgan-Cohen, Harold D.; Mann, Jonathan; Amitai, Tova; Even-Nir, Hadas; Vered, Yuval

    2015-01-01

    Studies among long-term survivors of childhood cancer who had received high-dose irradiation therapy of 4–60 Gy, demonstrated acute and chronic dental effects, including periodontal diseases. However, the possible effects of low to moderate doses of radiation on dental health are sparse. The aim of this study is to investigate the association between childhood exposure to low–moderate doses of ionizing radiation and periodontal health following 50 years since exposure. The study population included 253 irradiated subjects (treated for Tinea capitis in the 1950s) and, 162 non-irradiated subjects. The estimated dose to the teeth was 0.2–0.4 Gy. Dental examination was performed according to the community periodontal index (CPI). Socioeconomic and health behavior variables were obtained through a personal questionnaire. Periodontal disease was operationally defined as “deep periodontal pockets.” A multivariate logistic regression model was used for the association of irradiation status and other independent variables with periodontal status. The results showed that among the irradiated subjects, 23%, (95% CI 18–28%) demonstrated complete edentulousness or insufficient teeth for CPI scoring as compared to 13% (95% CI 8–19%) among the non-irradiated subjects (p = 0.01). Periodontal disease was detected among 54% of the irradiated subjects as compared to 40% of the non-irradiated (p = 0.008). Controlling for education and smoking, the ORs for the association between radiation and periodontal disease were 1.61 (95% CI 1.01–2.57) and 1.95 (95% CI 1.1–3.5) for ever never and per 1 Gy absorbed in the salivary gland, respectively. In line with other studies, a protective effect for periodontal diseases among those with high education and an increased risk for ever smokers were observed. In conclusion, childhood exposure to low-moderate doses of ionizing radiation might be associated with later outcomes of dental health. The results add

  1. 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.

  2. Studies of the mechanism of the cluster formation in a thermally sampling atmospheric pressure ionization mass spectrometer

    SciTech Connect

    Albrecht, Sascha Stroh, Fred; Klopotowski, Sebastian Derpmann, Valerie Klee, Sonja Brockmann, Klaus J. Benter, Thorsten

    2014-01-15

    In this study a thermally sampling atmospheric pressure ionization mass spectrometer is described and characterized. The ion transfer stage offers the capability to sample cluster ions at thermal equilibrium and during this transfer fundamental processes possibly affecting the cluster distribution are also readily identified. Additionally, the transfer stage combines optional collision-induced dissociation (CID) analysis of the cluster composition with thermal equilibrium sampling of clusters. The performance of the setup is demonstrated with regard to the proton-bound water cluster system. The benefit of the studied processes is that they can help to improve future transfer stages and to understand cluster ion reactions in ion mobility tubes and high-pressure ion sources. In addition, the instrument allows for the identification of fragmentation and protonation reactions caused by CID.

  3. Studies of the mechanism of the cluster formation in a thermally sampling atmospheric pressure ionization mass spectrometer.

    PubMed

    Albrecht, Sascha; Klopotowski, Sebastian; Derpmann, Valerie; Klee, Sonja; Brockmann, Klaus J; Stroh, Fred; Benter, Thorsten

    2014-01-01

    In this study a thermally sampling atmospheric pressure ionization mass spectrometer is described and characterized. The ion transfer stage offers the capability to sample cluster ions at thermal equilibrium and during this transfer fundamental processes possibly affecting the cluster distribution are also readily identified. Additionally, the transfer stage combines optional collision-induced dissociation (CID) analysis of the cluster composition with thermal equilibrium sampling of clusters. The performance of the setup is demonstrated with regard to the proton-bound water cluster system. The benefit of the studied processes is that they can help to improve future transfer stages and to understand cluster ion reactions in ion mobility tubes and high-pressure ion sources. In addition, the instrument allows for the identification of fragmentation and protonation reactions caused by CID. PMID:24517784

  4. H II Region Ionization of the Interstellar Medium: A Case Study of NGC 7538

    NASA Astrophysics Data System (ADS)

    Luisi, Matteo; Anderson, L. D.; Balser, Dana S.; Bania, T. M.; Wenger, Trey V.

    2016-06-01

    Using data from the Green Bank Telescope, we analyze the radio continuum (free–free) and radio recombination line (RRL) emission of the compact H ii region NGC 7538 (Sharpless 158). We detect extended radio continuum and hydrogen RRL emission beyond the photodissociation region (PDR) toward the north and east, but a sharp decrease in emission toward the south and west. This indicates that a non-uniform PDR morphology is affecting the amount of radiation “leaking” through the PDR. The strongest carbon RRL emission is found in the western PDR that appears to be dense. We compute a leaking fraction f R = 15 ± 5% of the radio continuum emission measured in the plane of the sky which represents a lower limit when accounting for the three-dimensional geometry of the region. We detect an average {}4{{{He}}}+/{{{H}}}+ abundance ratio by number of 0.088 ± 0.003 inside the H ii region and a decrease in this ratio with increasing distance from the region beyond the PDR. Using Herschel Space Observatory data, we show that small dust temperature enhancements to the north and east of NGC 7538 coincide with extended radio emission, but that the dust temperature enhancements are mostly contained within a second PDR to the east. Unlike the giant H ii region W43, the radiation leaking from NGC 7538 seems to only affect the local ambient medium. This suggests that giant H ii regions may have a large effect in maintaining the ionization of the interstellar medium.

  5. Electrospray Ionization Mechanisms for Large Polyethylene Glycol Chains Studied Through Tandem Ion Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Larriba, Carlos; de la Mora, Juan Fernandez; Clemmer, David E.

    2014-08-01

    Ion mobility mass spectrometry (IMS-MS) is used to investigate the abundance pattern, n z (m) of Poly-(ethyleneglycol) (PEG) electrosprayed from water/methanol as a function of mass and charge state. We examine n z (m) patterns from a diversity of solution cations, primarily dimethylammonium and triethylammonium. The ability of PEG chains to initially attach to various cations in the spraying chamber, and to retain them (or not) on entering the MS, provide valuable clues on the ionization mechanism. Single chains form in highly charged and extended shapes in most buffers. But the high initial charge they hold under atmospheric pressure is lost on transit to the vacuum system for large cations. In contrast, aggregates of two or more chains carry in all buffers at most the Rayleigh charge of a water drop of the same volume. This shows either that they form via Dole's charge residue mechanism, or that highly charged and extended aggregates are ripped apart by Coulombic repulsion. IMS-IMS experiments in He confirm these findings, and provide new mechanistic insights on the stability of aggregates. When collisionally activated, initially globular dimers are stable. However, slightly nonglobular dimers projecting out a linear appendix are segregated into two monomeric chains. The breakup of a charged dimer is therefore a multi-step process, similar to the Fenn-Consta polymer extrusion mechanism. The highest activation barrier is associated to the first step, where a short chain segment carrying a single charge escapes (ion-evaporates) from a charged drop, leading then to gradual field extrusion of the whole chain out of the drop.

  6. Determination of solubility products of complex compounds of certain lanthanide and actinide diiodies with 18-crown-6 in tetrahydrofuran

    SciTech Connect

    Mikheev, N.B.; Kamenskaya, A.N.; Kulyukhin, S.A.

    1988-09-01

    The existence of divalent americium in a tetrahydrofuran (THF) solution was proved for the first time. The values of the solubility products (SP) of the complex compounds with the composition of MeI{sub 2}{centered dot}18-crown-6 (Me = Sm, Eu, Yb, Am, Cf, Es, Fm) in the THF solutions were determined by the cocrystallization method. The SP values obtained are within (5.9-7.9){centered dot}10{sup {minus}12} and are close to the SP value for SrI{sub 2}{centered dot}10{sup {minus}12}, which indicates a similarity in the properties of these elements.

  7. Dynamical and energetic properties of hydrogen and hydrogen-tetrahydrofuran clathrate hydrates.

    PubMed

    Gorman, Paul D; English, Niall J; MacElroy, J M D

    2011-11-28

    Classical equilibrium molecular dynamics (MD) simulations have been performed to investigate the dynamical and energetic properties in hydrogen and mixed hydrogen-tetrahydrofuran sII hydrates at 30 and 200 K and 0.05 kbar, and also at intermediate temperatures, using SPC/E and TIP4P-2005 water models. The potential model is found to have a large impact on overall density, with the TIP4P-2005 systems being on average 1% more dense than their SPC/E counterparts, due to the greater guest-host interaction energy. For the lightly-filled mixed H(2)-THF system, in which there is single H(2) occupation of the small cage (1s1l), we find that the largest contribution to the interaction energy of both types of guest is the van der Waals component with the surrounding water molecules in the constituent cavities. For the more densely-filled mixed H(2)-THF system, in which there is double H(2) occupation in the small cage (2s1l), we find that there is no dominant component (i.e., van der Waals or Coulombic) in the H(2) interaction energy with the rest of the system, but for the THF molecules, the dominant contribution is again the van der Waals interaction with the surrounding cage-water molecules; again, the Coulombic component increases in importance with increasing temperature. The lightly-filled pure H(2) hydrate (1s4l) system exhibits a similar pattern vis-à-vis the H(2) interaction energy as for the lightly-filled mixed H(2)-THF system, and for the more densely-filled pure H(2) system (2s4l), there is no dominant component of interaction energy, due to the multiple occupancy of the cavities. By consideration of Kubic harmonics, there is some evidence of preferential alignment of the THF molecules, particularly at 200 K; this was found to arise at higher temperatures due to transient hydrogen bonding of the oxygen atom in THF molecules with the surrounding cage-water molecules. PMID:21968598

  8. On interfacial properties of tetrahydrofuran: Atomistic and coarse-grained models from molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Garrido, J. M.; Algaba, J.; Míguez, J. M.; Mendiboure, B.; Moreno-Ventas Bravo, A. I.; Piñeiro, M. M.; Blas, F. J.

    2016-04-01

    We have determined the interfacial properties of tetrahydrofuran (THF) from direct simulation of the vapor-liquid interface. The molecules are modeled using six different molecular models, three of them based on the united-atom approach and the other three based on a coarse-grained (CG) approach. In the first case, THF is modeled using the transferable parameters potential functions approach proposed by Chandrasekhar and Jorgensen [J. Chem. Phys. 77, 5073 (1982)] and a new parametrization of the TraPPE force fields for cyclic alkanes and ethers [S. J. Keasler et al., J. Phys. Chem. B 115, 11234 (2012)]. In both cases, dispersive and coulombic intermolecular interactions are explicitly taken into account. In the second case, THF is modeled as a single sphere, a diatomic molecule, and a ring formed from three Mie monomers according to the SAFT-γ Mie top-down approach [V. Papaioannou et al., J. Chem. Phys. 140, 054107 (2014)]. Simulations were performed in the molecular dynamics canonical ensemble and the vapor-liquid surface tension is evaluated from the normal and tangential components of the pressure tensor along the simulation box. In addition to the surface tension, we have also obtained density profiles, coexistence densities, critical temperature, density, and pressure, and interfacial thickness as functions of temperature, paying special attention to the comparison between the estimations obtained from different models and literature experimental data. The simulation results obtained from the three CG models as described by the SAFT-γ Mie approach are able to predict accurately the vapor-liquid phase envelope of THF, in excellent agreement with estimations obtained from TraPPE model and experimental data in the whole range of coexistence. However, Chandrasekhar and Jorgensen model presents significant deviations from experimental results. We also compare the predictions for surface tension as obtained from simulation results for all the models with

  9. On interfacial properties of tetrahydrofuran: Atomistic and coarse-grained models from molecular dynamics simulation.

    PubMed

    Garrido, J M; Algaba, J; Míguez, J M; Mendiboure, B; Moreno-Ventas Bravo, A I; Piñeiro, M M; Blas, F J

    2016-04-14

    We have determined the interfacial properties of tetrahydrofuran (THF) from direct simulation of the vapor-liquid interface. The molecules are modeled using six different molecular models, three of them based on the united-atom approach and the other three based on a coarse-grained (CG) approach. In the first case, THF is modeled using the transferable parameters potential functions approach proposed by Chandrasekhar and Jorgensen [J. Chem. Phys. 77, 5073 (1982)] and a new parametrization of the TraPPE force fields for cyclic alkanes and ethers [S. J. Keasler et al., J. Phys. Chem. B 115, 11234 (2012)]. In both cases, dispersive and coulombic intermolecular interactions are explicitly taken into account. In the second case, THF is modeled as a single sphere, a diatomic molecule, and a ring formed from three Mie monomers according to the SAFT-γ Mie top-down approach [V. Papaioannou et al., J. Chem. Phys. 140, 054107 (2014)]. Simulations were performed in the molecular dynamics canonical ensemble and the vapor-liquid surface tension is evaluated from the normal and tangential components of the pressure tensor along the simulation box. In addition to the surface tension, we have also obtained density profiles, coexistence densities, critical temperature, density, and pressure, and interfacial thickness as functions of temperature, paying special attention to the comparison between the estimations obtained from different models and literature experimental data. The simulation results obtained from the three CG models as described by the SAFT-γ Mie approach are able to predict accurately the vapor-liquid phase envelope of THF, in excellent agreement with estimations obtained from TraPPE model and experimental data in the whole range of coexistence. However, Chandrasekhar and Jorgensen model presents significant deviations from experimental results. We also compare the predictions for surface tension as obtained from simulation results for all the models with

  10. Fragmentation study and analysis of benzoylurea insecticides and their analogs by liquid chromatography-electrospray ionization-mass spectrometry.

    PubMed

    Yang, Xia; Xia, Yan; Liao, Xun; Zuo, Yumin; Liao, Yiping; Liu, Huwei

    2006-08-15

    Two insecticides, diflubenzuron and hexaflumuron, and their analogs have been separated by liquid chromatography (LC) and their fragmentation mechanisms were studied by electrospray ionization-ion trap mass spectrometry (ESI-MS(n)) in both positive- and negative-ion modes. Sequential product ion fragmentation experiments were performed in order to explain the degradation pathways and identify their predominant fragment ions. It was indicated that the characteristic fragmentations are the loss of neutral molecules such as HF, HNO(2), and HCl to form stable ring structure or the cleavage of the acyl amine to form conjugated structure. Furthermore, the separation and determination of two benzoylurea (BU) insecticides and their analogs in the water samples from Weiming Lake have been described by LC-ESI-MS in negative mode. By the use of deprotonated molecule for quantitative analysis at low capillary exit voltage, low detection limits, good linearity and reproducibility for standard solutions were presented. PMID:18970732