Sample records for h2 partial pressures

  1. Arterial oxygen partial pressures reduce the insulin-dependent induction of the perivenously located glucokinase in rat hepatocyte cultures: mimicry of arterial oxygen pressures by H2O2.

    PubMed

    Kietzmann, T; Roth, U; Freimann, S; Jungermann, K

    1997-01-01

    Liver glucokinase (GK) is localized predominantly in the perivenous zone. GK mRNA was induced by insulin maximally under venous O2 partial pressure (pO2) and only half-maximally under arterial pO2. CoCl2 and desferrioxamine mimicked venous pO2 and enhanced the insulin-dependent induction of GK mRNA under arterial pO2. H2O2 mimicked arterial pO2 and reduced insulin-induced GK mRNA under venous pO2 to the lower arterial levels. Thus the zonal O2 gradient in liver seems to have a key role in the heterogenous expression of the GK gene. PMID:9003396

  2. Melting of albite and dehydration of brucite in H 2 ONaCl fluids to 9 kbars and 700900C: implications for partial melting and water activities during high pressure metamorphism

    Microsoft Academic Search

    Kirill I. Shmulovich; Colin M. Graham

    1996-01-01

    The melting reaction: albite(solid)+ H2O(fluid) =albite-H2O(melt) has been determined in the presence of H2ONaCl fluids at 5 and 9.2?kbar, and results compared with those obtained in presence of H2OCO2 fluids. To a good approximation, albite melts congruently at 9?kbar, indicating that the melting temperature at constant\\u000a pressure is principally determined by water activity. At 5?kbar, the temperature (T)- mole fraction

  3. Association reactions at low pressure. III - The C2H2(+)/C2H2 system

    NASA Technical Reports Server (NTRS)

    Anicich, Vincent G.; Sen, Atish D.; Huntress, Wesley T., Jr.; Mcewan, Murray J.

    1990-01-01

    An ion cyclotron resonance mass spectrometer is used to examine the association reactions, C4H2(+) + C2H2 and C4H3(+) + C2H2, at pressures in the range of 8 x 10 to the -8 to 1 x 10 to the -4 Torr at 298 K. The association of C4H2(+) and C4H3(+) with C2H2 was found to exhibit classical behavior in the pressure range of 5 x 10 to the -8 Torr to 0.4 Torr. It is found that an efficient route via radiative association exists for unsaturated hydrocarbon cations to convert to aromatic structures in the presence of acetylene.

  4. Pressure-induced metallization of dense (H2S)2H2 with high-Tc superconductivity

    NASA Astrophysics Data System (ADS)

    Duan, Defang; Liu, Yunxian; Tian, Fubo; Li, Da; Huang, Xiaoli; Zhao, Zhonglong; Yu, Hongyu; Liu, Bingbing; Tian, Wenjing; Cui, Tian

    2014-11-01

    The high pressure structures, metallization, and superconductivity of recently synthesized H2-containing compounds (H2S)2H2 are elucidated by ab initio calculations. The ordered crystal structure with P1 symmetry is determined, supported by the good agreement between theoretical and experimental X-ray diffraction data, equation of states, and Raman spectra. The Cccm structure is favorable with partial hydrogen bond symmetrization above 37 GPa. Upon further compression, H2 molecules disappear and two intriguing metallic structures with R3m and Im-3m symmetries are reconstructive above 111 and 180 GPa, respectively. The predicted metallization pressure is 111 GPa, which is approximately one-third of the currently suggested metallization pressure of bulk molecular hydrogen. Application of the Allen-Dynes-modified McMillan equation for the Im-3m structure yields high Tc values of 191 K to 204 K at 200 GPa, which is among the highest values reported for H2-rich van der Waals compounds and MH3 type hydride thus far.

  5. High Tc phase of (H2S)2H2 at high pressures

    NASA Astrophysics Data System (ADS)

    Cui, Tian

    2015-03-01

    Hydrogen was predicted to metalize at high pressures and believed to be a room-temperature superconductor. However, metallization of hydrogen is still under debates. As an alternative, hydrogen dominated materials were extensively explored because of their lower metallization pressure. Here I present the high-pressure studies on structures, metallization, and superconductivity of (H2S)2H2 from ab initio calculations. At lower pressures, two phases containing H2 units are stable with P1 (<37 GPa) and Cccm (37-111 GPa) symmetries, which are still insulators. Upon further compression, H2 units disappear and two intriguing metallic structures with R3m and Im-3 m symmetries are reconstructive above 111 GPa and 180 GPa, respectively. Remarkably, the estimated Tc of Im-3 m phase at 200 GPa achieves a very high value of 191 ~ 204 K. Moreover, Tc decreases with pressure at an approximate rate (dTc/dP) of -0.12 K/GPa. Our predicted high Tc and its pressure dependence in Im-3 m phase are subsequently verified by recent experiments. Our findings support the conjecture that hydrogen-rich materials are a way to achieve a metallic phase with high Tc at accessibly experimental pressures and represent a significant step toward the understanding of high-pressure behavior of metallic hydrogen.

  6. The H2O (I) - H2O (III) - H2O (L) Triple Point of Water as a Fixed Pressure Point

    Microsoft Academic Search

    N. Bignell; V. E. Bean

    1988-01-01

    An apparatus to utilize the H2O (I) - H2O (III) - H2O (L) triple point as a pressure fixed point is described. A technique to establish the three phases simultaneously in the cell is described. The value of the pressure was measured with a piston gage and was found to be (208.829 +\\/- 0.025) MPa at the 99.7 percent confidence

  7. The solubility of fluorite in H2O and H2ONaCl at high pressure and temperature

    E-print Network

    Manning, Craig

    The solubility of fluorite in H2O and H2ONaCl at high pressure and temperature Peter Tropper a 12 March 2007; accepted 29 March 2007 Editor: D. Rickard Abstract The solubility of fluorite in H2O. Fluorite solubility was also measured in H2ONaCl fluids at 800 C and 1.0 GPa. Results indicate a strong

  8. H2O-rich magmas or silicate-rich H2O fluids? A perspective from high pressure and temperature experiments

    NASA Astrophysics Data System (ADS)

    Kawamoto, T.; Matsukage, K.; Mibe, K.; Isshiki, M.; Nishimura, K.; Ishimatsu, N.; Ono, S.

    2003-04-01

    Crystalline phases coexisting with H2O fluids in a Bassett type externally heated diamond anvil cell are identified at 800 - 1000 C and 0.5 - 5.2 GPa using synchrotron X-ray diffraction at SPring-8. Up to 3.3 GPa, forsterite (Mg2SiO4) crystallizes in enstatite (MgSiO3) - H2O system. In contrast, enstatite dissolve into the H2O fluids congruently at higher pressure conditions. This observation suggests that Mg/Si ratios of the H2O fluids become more than unity at 3.3 GPa corresponding to about 100 km depth. Chemical compositions of silicate dissolved into H2O fluids have been characterized by SiO2-rich feature at 1 - 3 GPa (Nakamura and Kushiro, 1974, Cargenie Year Book Ryabchikov et al., 1982, Contrib. Mineral. Petrol., Zhang and Frantz, 2000, Am. Mineral.). In contrast, recent quench experiments at higher pressure conditions suggested that H2O fluids coexisting with enstatite and forsterite become higher Mg/Si ratios as pressure increases from 3 to 10 GPa (Stalder et al., 2001, Contrib. Mineral. Petrol., Mibe et al., 2002, Geochim. Cosmochim. Acta). Our in-situ experimental data are consistent with the previous quench experimental studies. Partial melts of H2O-saturated peridotite up to 10 GPa (Kawamoto and Holloway, 1997, Science) show similar Mg/Si ratios to the H2O fluids compositions in the quench data by Stalder et al. (2001) and Mibe et al. (2002). It is, therefore, likely to suggest that there is no distinction between silicate-rich H2O fluids and H2O-rich silicate melts somewhere in the Earth's upper mantle.

  9. Partial pressure analysis of plasmas

    SciTech Connect

    Dylla, H.F.

    1984-11-01

    The application of partial pressure analysis for plasma diagnostic measurements is reviewed. A comparison is made between the techniques of plasma flux analysis and partial pressure analysis for mass spectrometry of plasmas. Emphasis is given to the application of quadrupole mass spectrometers (QMS). The interface problems associated with the coupling of a QMS to a plasma device are discussed including: differential-pumping requirements, electromagnetic interferences from the plasma environment, the detection of surface-active species, ion source interactions, and calibration procedures. Example measurements are presented from process monitoring of glow discharge plasmas which are useful for cleaning and conditioning vacuum vessels.

  10. New Equations for the Sublimation Pressure and Melting Pressure of H2O Ice Ih

    NASA Astrophysics Data System (ADS)

    Wagner, Wolfgang; Riethmann, Thomas; Feistel, Rainer; Harvey, Allan H.

    2011-12-01

    New reference equations, adopted by the International Association for the Properties of Water and Steam (IAPWS), are presented for the sublimation pressure and melting pressure of ice Ih as a function of temperature. These equations are based on input values derived from the phase-equilibrium condition between the IAPWS-95 scientific standard for thermodynamic properties of fluid H2O and the equation of state of H2O ice Ih adopted by IAPWS in 2006, making them thermodynamically consistent with the bulk-phase properties. Compared to the previous IAPWS formulations, which were empirical fits to experimental data, the new equations have significantly less uncertainty. The sublimation-pressure equation covers the temperature range from 50 K to the vapor-liquid-solid triple point at 273.16 K. The ice Ih melting-pressure equation describes the entire melting curve from 273.16 K to the ice Ih-ice III-liquid triple point at 251.165 K. For completeness, we also give the IAPWS melting-pressure equation for ice III, which is slightly adjusted to agree with the ice Ih melting-pressure equation at the corresponding triple point, and the unchanged IAPWS melting-pressure equations for ice V, ice VI, and ice VII.

  11. Partial phase diagram for the system NH3-H2O - The water-rich region

    NASA Technical Reports Server (NTRS)

    Johnson, M. L.; Schwake, A.; Nicol, M.

    1984-01-01

    Phase boundaries of the H2O-NH3 system for (NH3)/x/(H2O)/1-x/ have been determined with diamond-anvil cells for mixtures in two composition ranges: (1) for x in the range from 0 to 0.3, at pressures up to 4 GPa at 21 C, and (2) for x in the range from 0.46 to 0.50, at pressures up to 5 GPa from 150 to 400 K. Phases were identified visually with a microscope and polarized optics. The NH3.2(H2O) phase is strongly anisotropic with a much smaller refractive index than that of ice VII and cracks in two nonperpendicular networks. NH3.H2O has a refractive index closer to that of Ice VII and does not appear to form cracks. Both phases are colorless. Phase boundaries were determined on both increasing and decreasing pressures, and compositions of the ammonia ices were determined by estimating relative amounts of water and ammonia ices at known overall compositions. For low-ammonia compositions (x equal to or less than 0.15), the following assemblages succedd one another as pressure increases: liquid; liquid and Ice VI (at 1.0 + GPa); liquid and Ice VII (at 2.1 GPa); Ice VII and NH3.H2O (at 3.5 GPa). For x in the range from 0.15 to 0.30, the water ice and liquid fields are replaced by the NH3.2(H2O) and liquid field at pressures down to 1.0 GPa and lower.

  12. Gamma-H2AX-Based Dose Estimation for Whole and Partial Body Radiation Exposure

    PubMed Central

    Horn, Simon; Barnard, Stephen; Rothkamm, Kai

    2011-01-01

    Most human exposures to ionising radiation are partial body exposures. However, to date only limited tools are available for rapid and accurate estimation of the dose distribution and the extent of the body spared from the exposure. These parameters are of great importance for emergency triage and clinical management of exposed individuals. Here, measurements of ?-H2AX immunofluorescence by microscopy and flow cytometry were compared as rapid biodosimetric tools for whole and partial body exposures. Ex vivo uniformly X-irradiated blood lymphocytes from one donor were used to generate a universal biexponential calibration function for ?-H2AX foci/intensity yields per unit dose for time points up to 96 hours post exposure. Foci but not intensity levels remained significantly above background for 96 hours for doses of 0.5 Gy or more. Foci-based dose estimates for ex vivo X-irradiated blood samples from 13 volunteers were in excellent agreement with the actual dose delivered to the targeted samples. Flow cytometric dose estimates for X-irradiated blood samples from 8 volunteers were in excellent agreement with the actual dose delivered at 1 hour post exposure but less so at 24 hours post exposure. In partial body exposures, simulated by mixing ex vivo irradiated and unirradiated lymphocytes, foci/intensity distributions were significantly over-dispersed compared to uniformly irradiated lymphocytes. For both methods and in all cases the estimated fraction of irradiated lymphocytes and dose to that fraction, calculated using the zero contaminated Poisson test and ?-H2AX calibration function, were in good agreement with the actual mixing ratios and doses delivered to the samples. In conclusion, ?-H2AX analysis of irradiated lymphocytes enables rapid and accurate assessment of whole body doses while dispersion analysis of foci or intensity distributions helps determine partial body doses and the irradiated fraction size in cases of partial body exposures. PMID:21966430

  13. Pressure induced phase transitions in TiH2

    NASA Astrophysics Data System (ADS)

    Gao, Guoying; Bergara, Aitor; Liu, Guangtao; Ma, Yanming

    2013-03-01

    Recent room temperature experiments on TiH2 [Kalita et al., J. Appl. Phys. 108, 043511 (2010)], an important compound in hydrogen storage research, revealed a cubic (fcc, Fm-3m) to tetragonal (bct, I4/mmm) phase transition at around 0.6 GPa, which was suggested to remain stable up to at least 90 GPa. However, the simulated X-ray diffraction (XRD) pattern of the I4/mmm structure cannot explain all the diffraction peaks observed at 90 GPa. In this article, we apply the recently developed particle swarm optimization algorithm for crystal structure prediction to propose that at 63 GPa TiH2 presents a further phase transition from I4/mmm to P4/nmm, which we have also confirmed is dynamically and enthalpically stable up to 294 GPa. Moreover, the XRD patterns and calculated lattice parameters of the P4/nmm structure are in good agreement with the experimental available data. Above 294 GPa, we predict a monoclinic P21/m structure to be stable.

  14. Solubility of H2O in rhyolitic melts at low pressures and a new empirical model for mixed H2OCO2 solubility in rhyolitic melts

    E-print Network

    Zhang, Youxue

    Solubility of H2O in rhyolitic melts at low pressures and a new empirical model for mixed H2OCO2 solubility in rhyolitic melts Yang Liua,T, Youxue Zhanga , Harald Behrensb a Department of Geological Experiments of H2O solubility in synthetic haplogranitic and natural rhyolitic melts were conducted at 700

  15. Molecular motion in solid H2 at high pressures

    NASA Astrophysics Data System (ADS)

    Lee, Sam-Hyeon; Conradi, Mark S.; Norberg, R. E.

    1989-12-01

    Solid molecular hydrogen has been studied with proton nuclear magnetic resonance in a diamond anvil cell. Pressures from 18 to 68 kbar were used, resulting in melting temperatures from 160 to 350 K and relative densities ?/?0 as high as 3. At temperatures above 0.7Tmelt, translational self-diffusion narrows the resonance line. The pressure variation of the activation enthalpy ?H yields an activation volume of 5.7+/-0.6 cm3/mol or 63% of the molar volume, a reasonable value for a vacancy diffusion mechanism. The smooth variation of ?H/kTmelt with density also suggests that the diffusion mechanism remains the same for ?/?0 between 1 and 3. The spin-lattice relaxation is controlled primarily by molecular reorientation. The observed density dependence T1~?5/3 indicates that molecular electric quadrupole-quadrupole interactions cause reorientation, even at the high temperatures and densities of this work.

  16. Similitude and Anode Material Effects in H2 and D2 Discharges Below the Critical Pressure

    Microsoft Academic Search

    GORDON W. MCCLURE

    1959-01-01

    The breakdown potentials of H2 and. D2 gases were determined below the critical pressure in two discharge tubes of similar shape but of different size in order to ascertain whether or not the initial breakdown conditions conform to Paschen's similarity law. With stainless steel anodes and cathodes, both gases conform extremely well to Paschen's law over a range of pressures

  17. H2O-rich magmas or silicate-rich H2O fluids? A perspective from high pressure and temperature experiments

    Microsoft Academic Search

    T. Kawamoto; K. Matsukage; K. Mibe; M. Isshiki; K. Nishimura; N. Ishimatsu; S. Ono

    2003-01-01

    Crystalline phases coexisting with H2O fluids in a Bassett type externally heated diamond anvil cell are identified at 800 - 1000 C and 0.5 - 5.2 GPa using synchrotron X-ray diffraction at SPring-8. Up to 3.3 GPa, forsterite (Mg2SiO4) crystallizes in enstatite (MgSiO3) - H2O system. In contrast, enstatite dissolve into the H2O fluids congruently at higher pressure conditions. This

  18. Heat Treatment with High-Pressure H2O Vapor of Pulsed Laser Crystallized Silicon Films

    Microsoft Academic Search

    Katsumi Asada; Keiji Sakamoto; Tadashi Watanabe; Toshiyuki Sameshima; Seiichiro Higashi

    2000-01-01

    Improvement of electrical properties for 7.4 1017 cm-3 phosphorus-doped pulsed laser crystallized silicon films of 50 nm thickness formed on quartz glass substrates was achieved by heat treatment with high-pressure H2O vapor. The electrical conductivity was increased from 1.3 10-5 S\\/cm (as-crystallized) to 2 S\\/cm by annealing at 270^\\\\circC@ for 3 h with 1.3 106 Pa H2O

  19. A System for Incubations at High Gas Partial Pressure

    PubMed Central

    Sauer, Patrick; Glombitza, Clemens; Kallmeyer, Jens

    2012-01-01

    High-pressure is a key feature of deep subsurface environments. High partial pressure of dissolved gasses plays an important role in microbial metabolism, because thermodynamic feasibility of many reactions depends on the concentration of reactants. For gases, this is controlled by their partial pressure, which can exceed 1?MPa at in situ conditions. Therefore, high hydrostatic pressure alone is not sufficient to recreate true deep subsurface in situ conditions, but the partial pressure of dissolved gasses has to be controlled as well. We developed an incubation system that allows for incubations at hydrostatic pressure up to 60?MPa, temperatures up to 120C, and at high gas partial pressure. The composition and partial pressure of gasses can be manipulated during the experiment. To keep costs low, the system is mainly made from off-the-shelf components with only very few custom-made parts. A flexible and inert PVDF (polyvinylidene fluoride) incubator sleeve, which is almost impermeable for gases, holds the sample and separates it from the pressure fluid. The flexibility of the incubator sleeve allows for sub-sampling of the medium without loss of pressure. Experiments can be run in both static and flow-through mode. The incubation system described here is usable for versatile purposes, not only the incubation of microorganisms and determination of growth rates, but also for chemical degradation or extraction experiments under high gas saturation, e.g., fluidgasrock-interactions in relation to carbon dioxide sequestration. As an application of the system we extracted organic compounds from sub-bituminous coal using H2O as well as a H2OCO2 mixture at elevated temperature (90C) and pressure (5?MPa). Subsamples were taken at different time points during the incubation and analyzed by ion chromatography. Furthermore we demonstrated the applicability of the system for studies of microbial activity, using samples from the Isis mud volcano. We could detect an increase in sulfate reduction rate upon the addition of methane to the sample. PMID:22347218

  20. Metallization and superconductivity of BeH2 under high pressure.

    PubMed

    Wang, Ziwei; Yao, Yansun; Zhu, Li; Liu, Hanyu; Iitaka, Toshiaki; Wang, Hui; Ma, Yanming

    2014-03-28

    Pressure-induced metallization and potential superconductivity of BeH2 has been a topic of interest. In the present study, we extensively explored the crystal structures of BeH2 in a wide pressure range of 0-300 GPa using an unbiased structure searching method coupled with first-principles density functional calculations. A series of pressure-induced structural transformations are predicted for BeH2, as Ibam (? phase) ? P-3m1 (phase II) ? R-3m (phase III) ? Cmcm (phase IV). Calculated pressures of phase transition are 25, 140, and 202 GPa, respectively. The phase II is isostructural to the well-known 1T structure of transition metal dichalcogenides, which is composed of covalent bonded BeH2 slabs stacked along the perpendicular direction by van der Waals forces. The phase III is constructed by the same BeH2 slabs, but differs from the phase II in the stacking sequence. The ? phase, phase II, and phase III all have insulating electronic states while their band gaps decrease as pressure increases. We predicted that BeH2 reaches a metallic state by a III ? IV phase transition, instead of a direct band gap closure in phase III. The phase IV has a three-dimensional extended Be-H network formed by edge-sharing BeH8 polyhedrons with delocalized electrons. Electron-phonon coupling calculations implemented using linear response theory on the metallic BeH2 predict a large electron-phonon coupling parameter of 0.63, leading to an estimation of superconducting transition temperature (Tc) of ?38 K at 250 GPa. PMID:24697470

  1. H2O diffusion models in rhyolitic melt with new high pressure data Huaiwei Ni, Youxue Zhang

    E-print Network

    Zhang, Youxue

    H2O diffusion models in rhyolitic melt with new high pressure data Huaiwei Ni, Youxue Zhang in silicate melts, especially rhyolitic melt. However, the pressure dependence of H2O diffusion is not constrained satisfactorily. We investigated H2O diffusion in rhyolitic melt at 0.951.9 GPa and 4071629 C

  2. High pressure Raman spectroscopy of H2O-CH3OH mixtures

    NASA Astrophysics Data System (ADS)

    Hsieh, Wen-Pin; Chien, Yu-Hsiang

    2015-03-01

    Complex intra-molecular interactions and the hydrogen-bonding network in H2O-volatile mixtures play critical roles in many dynamics processes in physical chemistry, biology, and Earth and planetary sciences. We used high pressure Raman spectroscopy to study the pressure evolution of vibrational frequencies and bonding behavior in H2O-CH3OH mixtures. We found that the presence of low CH3OH content in H2O increases the transition pressure where water crystallizes to ice VI, but does not significantly change the pressure where ice VI transforms to ice VII. Furthermore, the stiffening rates of C-H stretching frequencies d? / dP in CH3OH significantly decrease upon the crystallization of water, and the softening rates of the O-H stretching frequencies of ice VII are suppressed over a narrow pressure range, after which the frequencies of these modes shift with pressure in ways similar to pure CH3OH and ice VII, respectively. Such complex pressure evolution of Raman frequencies along with pronounced variations in Raman intensities of CH3OH within the sample, and the hysteresis of the water-ice VI phase transition suggest pressure-induced segregation of low content CH3OH from ice VII.

  3. Crystal-field phenomena in hcp H2 and D2 at high pressures

    NASA Astrophysics Data System (ADS)

    Freiman, Yu. A.; Tretyak, S. M.; Grechnev, Alexei; Goncharov, Alexander F.; Hemley, Russell J.

    2014-07-01

    Crystal-field effects in hexagonal closed-packed molecular H2 and D2 are examined over a broad range of pressures. The lattice distortion parameter (the deviation of the c /a ratio from the ideal value 1.633), orientational order parameter, and crystal-field parameter in hexagonal close-packed (hcp) structures of p-H2,o-D2, and n-H2 are calculated using the semiempirical lattice-dynamic approach. It is shown that the lattice distortion in the J-even species is two order of magnitude smaller compared with that found in n-H2 and n-D2. The difference is due to splitting of the J-odd rotational levels in the J-even/J-odd mixtures.

  4. The search for shock-excited H2 in Virgo spirals experiencing ram pressure stripping

    E-print Network

    Wong, O Ivy; Murphy, Eric J; Helou, George

    2014-01-01

    We investigate the presence of shock-excited H2 in four Virgo cluster galaxies that show clear evidence of ongoing ram pressure stripping. Mid-infrared (MIR) spectral mapping of the rotational H2 emission lines were performed using the Infrared Spectrograph (IRS) on board the Spitzer space telescope. We target four regions along the leading side of galaxies where the intracluster medium (ICM) appears to be pushing back the individual galaxy's interstellar medium (ISM). For comparison purposes, we also study two regions on the trailing side of these galaxies, a region within an edge-on disk and an extraplanar star-forming region. We find a factor of 2.6 excess of warm H2/PAH in our sample relative to the observed fractions in other nearby galaxies. We attribute the H2/PAH excess to contributions of shock-excited H2 which is likely to have been triggered by ongoing ram pressure interaction in our sample galaxies. Ram pressure driven shocks may also be responsible for the elevated fractions of FeII/NeII found in...

  5. Gibbs free energy of reactions involving SiC, Si3N4, H2, and H2O as a function of temperature and pressure

    NASA Technical Reports Server (NTRS)

    Isham, M. A.

    1992-01-01

    Silicon carbide and silicon nitride are considered for application as structural materials and coating in advanced propulsion systems including nuclear thermal. Three-dimensional Gibbs free energy were constructed for reactions involving these materials in H2 and H2/H2O. Free energy plots are functions of temperature and pressure. Calculations used the definition of Gibbs free energy where the spontaneity of reactions is calculated as a function of temperature and pressure. Silicon carbide decomposes to Si and CH4 in pure H2 and forms a SiO2 scale in a wet atmosphere. Silicon nitride remains stable under all conditions. There was no apparent difference in reaction thermodynamics between ideal and Van der Waals treatment of gaseous species.

  6. Interleukin-1 Induction of NF B Is Partially Regulated by H2O2-mediated Activation of NF B-inducing Kinase*

    E-print Network

    Engelhardt, John F.

    Interleukin-1 Induction of NF B Is Partially Regulated by H2O2-mediated Activation of NF B B is partially regulated by H2O2-mediated activation of NIK and subsequent NIK-mediated phosphorylation of IKK . IL-1 induced H2O2 production in MCF-7 cells and clearance of this ROS through

  7. Solid-state phase transition induced by pressure in LiOH x H2O.

    PubMed

    Di Pietro, Elisa; Pagliai, Marco; Cardini, Gianni; Schettino, Vincenzo

    2006-07-13

    When the free energy surface of the lithium hydroxide monohydrate crystal was explored, the high-pressure solid-state phase transition was determined. The high-pressure phase has been obtained through ab initio Car-Parrinello molecular dynamics simulation in the isothermic-isobaric ensemble. The recent metadynamics method has been applied to overcome the high activation energy barriers typical of rare events, like solid-state phase transition at high pressures. In the LiOH x H2O system, there are two kinds of H bonds: water-water and hydroxyl-water. The effect of the pressure has been investigated, to give further insight into the high-pressure phase. The strengthening of the H bonds of the system produces modifications in the water and the hydroxyl ion dipole electronic environment. The infrared spectra of both phases have been calculated and compared with experiments, and the assignment of the external modes has been discussed. PMID:16821880

  8. EFFECTS ON CHP PLANT EFFICIENCY OF H2 PRODUCTION THROUGH PARTIAL OXYDATION OF NATURAL GAS OVER TWO GROUP VIII METAL

    E-print Network

    Paris-Sud XI, Universit de

    EFFECTS ON CHP PLANT EFFICIENCY OF H2 PRODUCTION THROUGH PARTIAL OXYDATION OF NATURAL GAS OVER TWO with natural gas in spark ignition engines can increase for electric efficiency. In-situ H23 production for spark ignition engines fuelled by natural gas has therefore been investigated recently, and4 reformed

  9. Traces of H2O in Ultrahigh-Pressure Metamorphic Rocks

    NASA Astrophysics Data System (ADS)

    Dobrzhinetskaya, L. F.

    2007-05-01

    Ultrahigh-pressure (UHP) metamorphic rocks accommodate a significant amount of H2O at high pressures and temperatures during their deep subduction. Fluid-driven processes are responsible for mineral reactions; they may trigger phase transformations and provide a decisive weakening effect on the rheological behavior of the rocks during deep subduction, or they may lead to brittle failure and earthquakes. Dehydration reactions, producing fluid (i.e., H2O, CO2) during regional metamorphism at low-to-mid crustal levels (P ~ 0.1 - 1 GPa), are reasonably pressure insensitive. At these levels, the maximum dehydration occurs at the greatest temperatures experienced by buried rocks. In the deep subduction zone (> 120 - 150 km), where both high pressures and temperatures operate, the situation is different. There, on the one hand, the water becomes chemically bonded and incorporated into the structure of both nominally hydrous and anhydrous minerals. On the other hand, the aqueous fluid (a supercritical fluid) dissolves a considerable amount of mineral components at high pressures and temperatures, and a solute concentration increases as pressure is increased. Microstructural observations on ultrahigh-pressure minerals from eclogites and metasediments provide convincing evidence of fluid involvement as deep as the upper mantle and possibly, the mantle transition zone. Diamond is one of the minerals of great importance because it unambiguously records the high pressure (minimum 4 GPa and possibly > 4GPa) at which the host rocks were recrystallized. We present here the results of studies of nano-inclusions associated with dislocations of growth and/or with interstitial defects of carbon in diamond structure obtained with transmission electron microscopy, microRaman, and microInfrared synchrotron assisted spectroscopy. A diverse composition of multicomponent fluid and crystalline inclusions and characteristic of nitrogen aggregations, provide evidence that the diamonds were crystallized from a supercritical C-O-H fluid during a UHP metamorphism related to continental collision. These observations are also consistent with diamonds synthesized at high pressure and high temperature from graphite, amorphous carbon, and coal in the presence of H2O. The crustal signature of carbon isotopes (? 13C) in the diamonds, together with their multiphase fluid- solid inclusions, provides evidence of a pathway by which organic carbon and H2O were subducted to the mantle depths and returned back to the Earth's surface. Microstructural patterns such as healed cracks, microfabrics, etc., observed in other minerals co-existing with diamonds, can therefore be recognized and attributed to UPH metamorphism events and may cast a light on the deformation and rheology of UHP metamorphic rocks.

  10. Erratum to "The solubility of corundum in H2O at high pressure and temperature and its implications for

    E-print Network

    Manning, Craig

    Erratum Erratum to "The solubility of corundum in H2O at high pressure and temperature and its: log mAl 1:131 3827=T 2:277 7336=T logqH2O 1 where mAl is molality of Al in equilibrium with corundum, H2O is the density of H2O in g/cm3 , and T is temperature in Kelvins. Available online at www

  11. Evidence for H 2 at high pressure in the silicon nanocavities after dipping in HF solution

    NASA Astrophysics Data System (ADS)

    Romano, E.; Cerofolini, G. F.; Narducci, D.; Corni, F.; Frabboni, S.; Ottaviani, G.; Tonini, R.

    2009-07-01

    The immersion in HF solutions of silicon containing nanocavities (produced by the annealing at high temperature, 950 C, of silicon implanted with helium at high fluence, 2 10 16 cm -2) results in the injection of hydrogen in an infrared-mute state (most likely H 2) into the nanocavities. The pressure achieved in the cavities is sufficiently high to stabilize the hydrogen coverage of the inner surfaces at temperatures exceeding by 200 C the one of complete desorption from the outer surface.

  12. Direct synthesis of MgH 2 nanofibers at different hydrogen pressures

    Microsoft Academic Search

    Chunyu Zhu; Haruya Hayashi; Itoko Saita; Tomohiro Akiyama

    2009-01-01

    This paper describes the direct synthesis of magnesium hydride (MgH2) nanofibers by hydriding chemical vapor deposition (HCVD), in which the effect of hydrogen pressure on the production rate, the composition and the shape of products obtained were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and BrunauerEmmettTeller (BET). The XRD patterns showed that the main product in each

  13. Author's personal copy CO2/CH4, CH4/H2 and CO2/CH4/H2 separations at high pressures using Mg2(dobdc)

    E-print Network

    improvements will lead to global energy savings [1]. Additionally, carbon capture and storage is an excitingorganic framework Carbon capture Mg2(dobdc) Hydrogen purification Natural gas purification a b s t r a c t High-pressure separations of binary and ternary mixtures of CO2, CH4, and H2 are relevant to carbon diox- ide capture

  14. The sulfidation of dilute Co-Cr alloys at low sulfur partial pressures

    Microsoft Academic Search

    S. K. Verma; D. P. Whittle; J. Stringer

    1972-01-01

    The sulfidation of pure chromium and Co-Cr alloys containing 1, 5, 10, 17, and 25 wt. % Cr in H2-1%H2S at 1000C has been studied in detail by thermogravimetric methods, metallography, and electron probe microanalysis. In this gas mixture, which has an effective sulfur partial pressure of 510?4 Torr, only CrS is formed, on all the alloys containing greater than

  15. The effects of small amounts of H2O on partial melting of model spinel lherzolite in the system CMAS

    NASA Astrophysics Data System (ADS)

    Liu, X.; St. C. Oneill, H.

    2003-04-01

    Water (H_2O) is so effective at lowering the solidus temperatures of silicate systems that even small amounts of H_2O are suspected to be important in the genesis of basaltic magmas. The realization that petrologically significant amounts of H_2O can be stored in nominally anhydrous mantle minerals (olivine and pyroxenes) has fundamental implications for the understanding of partial melting in the mantle, for it implies that the role that H_2O plays in mantle melting may not be appropriately described by models in which the melting is controlled by hydrous phases such as amphibole. Although the effect of water in suppressing the liquidus during crystallization is quite well understood, such observations do not provide direct quantitative information on the solidus. This is because liquidus crystallization occurs at constant major-element composition of the system, but at unbuffered component activities (high thermodynamic variance). By contrast, for partial melting at the solidus the major-element component activities are buffered by the coexisting crystalline phases (low variance), but the major-element composition of the melt can change as a function of added H_2O. Accordingly we have determined both the solidus temperature and the melt composition in the system CMAS with small additions of H_2O, to 4 wt%, in equilibrium with the four-phase lherzolite assemblage of fo+opx+cpx+sp. Experiments were conducted at 1.1 GPa and temperatures from 1473 K to the dry solidus at 1593 K in a piston-cylinder apparatus. Starting materials were pre-synthesised assemblage of fo+opx+cpx+sp, plus an oxide/hydroxide mix of approximately the anticipated melt composition. H_2O was added as either Mg(OH)_2 or Al(OH)_3. The crystalline assemblage and melt starting mix were added as separate layers inside sealed Pt capsules, to ensure large volumes of crystal-free melt. After the run doubly polished sections were prepared in order to analyse the quenched melt by FTIR spectroscopy, to quantify the amounts of H_2O. This is necessary, as Pt capsules are to some extent open to H_2 diffusion. All melts were found to contain CO_2 (<0.7 wt%), which appears to come mainly from the hydroxide starting materials but also by C diffusion through the Pt capsule. Since CO_2 is experimentally correlated with H_2O, its presence significantly effects the interpretation of the results. Ignoring this complication, we find that 1 wt% H_2O decreases the solidus by 40 K; melt compositions do not change greatly, the main effect being a small decrease in MgO.

  16. Melting phase relations in the system H2O - NH3 at high pressure

    NASA Astrophysics Data System (ADS)

    Sugimura, E.; Hirose, K.; Komabayashi, T.; Ohishi, Y.; Hirao, N.; Dubrovinsky, L. S.

    2012-12-01

    The density models of Uranus and Neptune constrained by their gravitational moments from Voyager mission suggest that mantles of these planets may be predominantly comprised of water (H2O), methane (CH4), and ammonia (NH3). The impurities in pure water would greatly influence the phase relations in the water-rich system expected in the icy mantle, which must be known to construct a plausible planetary model. One of important effects of the impurity is on the liquidus temperature (Tliq), since it decides the actual presence of solid phase within the icy mantle. In order to determine Tliq in H2O-rich region of the H2O - CH4 - NH3 ternary system, the melting phase relations in the H2O - CH4 and H2O - NH3 systems must be accurately known. However, previous melting experiments on each binary system were limited to several gigapascals, thus need to be explored to higher P-T conditions for application in interiors of Uranus and Neptune. We have investigated high-pressure (P) and -temperature (T) melting phase relations in the H2O - NH3 system based on a combination of visual observation and angle-dispersive x-ray diffraction (XRD) measurements at BL10XU, SPring-8. High-P-T conditions were generated in an externally-resistive heated diamond anvil cell (DAC). Starting material was 20wt% NH3 aqueous solution whose composition was checked via Tliq of the solution measured in a DAC at near atmospheric pressure. The aqueous solution was loaded into a gold-lined hole in a preindented rhenium gasket in order to insulate the sample from rhenium. Pressure was determined from the unit-cell volume of gold liner. Melting and freezing of the sample were detected by monitoring disappearance/appearance of diffraction peaks of solid and diffuse scattering of liquids, as well as observing melting/crystallization of crystal grains under microscope. Up to 20 GPa at room temperature, in addition to ice VII, diffraction peaks of bcc-like phase, which is most likely to be the reported phase VI of ammonia monohydrate (AMH VI), were observed, although the diffraction peaks were either too broad or too few to specify its structure. When temperature was raised until diffuse scattering appeared, the diffraction peaks of AMH VI disappeared, indicating ice VII is the liquidus phase. Newly obtained Tliq were higher than all the exiting melting curves of pure H2O determined in externally-heated DAC by 50 K at 15 GPa at minimum. This contradicts the previous reports that the H2O - NH3 system is eutectic, i.e. Tliq of our sample should be lower than the melting temperature of the H2O end member. We will discuss possible sources for this discrepancy. We also propose a new phase diagram of the system H2O - NH3 and possible implications for the structure of the icy planets.

  17. Pressure optimization of high harmonic generation in a differentially pumped Ar or H2 gas jet

    NASA Astrophysics Data System (ADS)

    Sayrac, M.; Kolomenskii, A. A.; Anumula, S.; Boran, Y.; Hart, N. A.; Kaya, N.; Strohaber, J.; Schuessler, H. A.

    2015-04-01

    We experimentally studied the dependence of high harmonic generation in argon and molecular hydrogen on pressure changes in a gas jet that cause variations of the phase matching conditions and absorption. The study was performed at a peak laser intensity of 1.5 1014 W/cm2. To enable measurements over a wide range of pressures, we employed differential pumping with an additional cell (20 cm3 volume) enclosing the gas jet. By increasing the pressure in the gas jet up to a maximum of 1.5 bars with argon or 0.5 bars with hydrogen, we observed an increase in the high harmonic (HH) yield until an optimum pressure of 0.2 bars was reached for Ar, beyond which the output began decreasing. For H2, we observed an increase of the HH output up to the maximum pressure of 0.5 bars. This pressure-dependence study allowed us to achieve a tenfold enhancement in the high harmonic yield at the optimum pressure.

  18. Partial melting in the mantle wedge the role of H 2O in the genesis of mantle-derived 'arc-related' magmas

    NASA Astrophysics Data System (ADS)

    Ulmer, Peter

    2001-12-01

    The fundamental role of H 2O in the generation of supra-subduction arc-related mantle derived magmas has long been recognized (e.g. Yoder and Tilley, 1962). This review of available experimental data attempts to highlight some principal factors controlling magma generation and magma chemistry that can be attributed to the presence of a hydrous component during partial melting in the mantle wedge. Arc-related igneous rocks display a typical trace element abundance spectrum, the so-called 'arc-signature', characterized by the enrichment of highly mobile large ion lithophile elements (LILE) relative to high field strength elements (HFSE). This signature can be explained by a two-component mantle source consisting of variably depleted asthenospheric mantle and a hydrous fluid (or H 2O-saturated low percentage melt) that originates from the breakdown of hydrous phases transported in the cold part of the partly hydrated oceanic lithosphere. The principal effect of H 2O on the partial melting is a reduction of the melting temperature by 100-150C for moderate to substantial amounts of partial melting (10-25 wt.%) compared to anhydrous melting of a lherzolite source. Such a reduction of the melting temperature requires the presence of 0.1-0.5 wt.% H 2O in the source and results in 1-7 wt.% H 2O in the basaltic to picritic primary liquid. The majority of primitive arc magmas are basaltic and do not represent near-solidus H 2O-saturated liquids that are highly alkalic and mostly nepheline-normative. The decrease of the melting temperature on the order of 100-150C compared to anhydrous peridotite melting requires high melting temperatures of 1250-1300C at 1.5 GPa (45 km depth) and 1350-1400C at 2.5 GPa (70 km depth) that are close to the average current mantle adiabat (ACMA). Therefore, partial melting in the mantle wedge is confined to the hottest region where temperatures approach undisturbed asthenospheric conditions. At a given pressure (depth) hydrous melts are less magnesian and more silica-rich than melts produced under anhydrous conditions. Arc magmas (and their mantle sources) are more oxidized than MORB or OIB melts (and their respective mantle sources). It is still controversial whether or not the oxidation state and the more silica-rich nature of hydrous arc-melts are indeed the principal factors controlling their predominantly calc-alkaline nature as opposed to the predominantly tholeiitic character of MORB and OIB basalts.

  19. H2 Equilibrium Pressure with a Neg-Coated Vacuum Chamber as a Function of Temperature and H2 Concentration

    Microsoft Academic Search

    Adriana Rossi

    2006-01-01

    Non Evaporable Getter (NEG) coating is used in the Large Hadron Collider (LHC) room-temperature sections to ensure a low residual gas pressure for its properties of distributed pumping, low outgassing and desorption under particle bombardment; and to limit or cure electron cloud build-up due to its low secondary electron emission. In certain regions of the LHC, and in particular close

  20. H2 adsorption on multiwalled carbon nanotubes at low temperatures and low pressures

    NASA Astrophysics Data System (ADS)

    Xu, F.; Barberio, M.; Vasta, R.; Barone, P.; Bonanno, A.; Pirronello, V.

    2008-11-01

    We present an experimental study on H2 adsorption on multiwalled carbon nanotubes (MWCNTs) at low temperatures (12-30 K) and low pressures (210-5Torr) using the temperature programmed desorption technique. Our results show that the molecular hydrogen uptake increases nearly exponentially from 610-9wt.% at 24.5 K to 210-7wt.% at 12.5 K and that the desorption kinetics is of the first order. Comparative measurements indicate that MWCNTs have an adsorption capacity about two orders higher than that of activated carbon (charcoal) making them a possible candidate as hydrogen cryosorber for eventual applications in accelerators and synchrotrons.

  1. Biomass hydrolysis inhibition at high hydrogen partial pressure in solid-state anaerobic digestion.

    PubMed

    Cazier, E A; Trably, E; Steyer, J P; Escudie, R

    2015-08-01

    In solid-state anaerobic digestion, so-called ss-AD, biogas production is inhibited at high total solids contents. Such inhibition is likely caused by a slow diffusion of dissolved reaction intermediates that locally accumulate. In this study, we investigated the effect of H2 and CO2 partial pressure on ss-AD. Partial pressure of H2 and/or CO2 was artificially fixed, from 0 to 1 557mbars for H2 and from 0 to 427mbars for CO2. High partial pressure of H2 showed a significant effect on methanogenesis, while CO2 had no impact. At high [Formula: see text] , the overall substrate degradation decreased with no accumulation of metabolites from acidogenic bacteria, indicating that the hydrolytic activity was specifically impacted. Interestingly, such inhibition did not occur when CO2 was added with H2. This result suggests that CO2 gas transfer is probably a key factor in ss-AD from biomass. PMID:25935390

  2. Hybrid Global Model Simulations of He/N2 and He/H2O Atmospheric Pressure Capacitive Discharges

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.; Kawamura, E.; Ke, Ding; Lichtenberg, A. J.; Chabert, P.; Lazzaroni, C.

    2014-10-01

    We used 1D particle-in-cell (PIC) simulations of an atmospheric He/0.1%N2 discharge with simplified chemistry to guide the development of a hybrid analytical/numerical global model that includes electron multiplication and two classes of electrons: ``hot'' electrons associated with the sheaths, and ``warm'' electrons associated with the bulk. The model and PIC results show reasonable agreement and indicate a transition from a low power ?-mode with a relatively high bulk electron temperature Te to a high power ?-mode with a low Te. The transition is accompanied by an increase in density and a decrease in sheath widths. Water is a trace gas of bio-medical interest since it may arise from contact with skin. We use the hybrid global model to simulate a chemically complex, bounded He/H2O atmospheric pressure discharge, including 148 volume reactions among 43 species, and including clusters up to H19O9+.For a planar discharge with a 1 cm electrode radius and a 0.5 mm gap driven at 13.56 MHz, we determine the depletion and diffusion effects and the ? to ? transition for secondary emission ?se = 0.25 over a range of rf currents and external H2O concentrations. Each simulation takes about 2 minutes on a moderate laptop. This work was partially supported by the Department of Energy Office of Fusion Energy Science Contract DE-SC000193 and by the Natural Science Foundation of China Contract 11375042.

  3. Influence of excited state spatial distributions on plasma diagnostics: Atmospheric pressure laser-induced He-H2 plasma

    NASA Astrophysics Data System (ADS)

    Monfared, Shabnam K.; Hwel, Lutz

    2012-10-01

    Atmospheric pressure plasmas in helium-hydrogen mixtures with H2 molar concentrations ranging from 0.13% to 19.7% were investigated at times from 1 to 25 ?s after formation by a Q-switched Nd:YAG laser. Spatially integrated electron density values are obtained using time resolved optical emission spectroscopic techniques. Depending on mixture concentration and delay time, electron densities vary from almost 1017 cm-3 to about 1014 cm-3. Helium based results agree reasonably well with each other, as do values extracted from the H? and H? emission lines. However, in particular for delays up to about 7 ?s and in mixtures with less than 1% hydrogen, large discrepancies are observed between results obtained from the two species. Differences decrease with increasing hydrogen partial pressure and/or increasing delay time. In mixtures with molecular hydrogen fraction of 7% or more, all methods yield electron densities that are in good agreement. These findings seemingly contradict the well-established idea that addition of small amounts of hydrogen for diagnostic purposes does not perturb the plasma. Using Abel inversion analysis of the experimental data and a semi-empirical numerical model, we demonstrate that the major part of the detected discrepancies can be traced to differences in the spatial distributions of excited helium and hydrogen neutrals. The model yields spatially resolved emission intensities and electron density profiles that are in qualitative agreement with experiment. For the test case of a 1% H2 mixture at 5 ?s delay, our model suggests that high electron temperatures cause an elevated degree of ionization and thus a reduction of excited hydrogen concentration relative to that of helium near the plasma center. As a result, spatially integrated analysis of hydrogen emission lines leads to oversampling of the plasma perimeter and thus to lower electron density values compared to those obtained from helium lines.

  4. Partial pressure measurements with an active spectrometer

    SciTech Connect

    Brooks, N.H.; Jensen, T.H. [General Atomics, San Diego, CA (United States); Colchin, R.J.; Maingi, R.; Wade, M.R. [Oak Ridge National Lab., TN (United States); Finkenthal, D.F. [Palomar Coll. (United States); Naumenko, N. [Inst. for Atomic and Molecular Physics (Japan); Tugarinov, S. [TRINITI (United States)

    1998-07-01

    Partial pressure neutral ga measurements have been made using a commercial Penning gauge in conjunction with an active spectrometer. In prior work utilizing bandpass filters and conventional spectrometers, trace concentrations of the hydrogen isotopes H, D, T and of the noble gases He, Ne and Ar were determined from characteristic spectral lines in the light emitted by the neutral species of these elements. For all the elements mentioned, the sensitivity was limited by spectral contamination from a pervasive background of molecular hydrogen radiation. The active spectrometer overcomes this limitations by means of a digital lock-in method and correlation with reference spectra. Preliminary measurements of an admixture containing a trace amount of neon in deuterium show better than a factor of 20 improvement in sensitivity over conventional techniques. This can be further improved by correlating the relative intensities of multiple lines to sets of reference spectra.

  5. Elevated atmospheric partial pressure of CO2 and plant growth

    Microsoft Academic Search

    Suan-Chin Wong

    1990-01-01

    Cotton plants were grown in late spring under full sunlight in glasshouses containing normal ambient partial pressure of CO2 (322Pa) and enriched partial pressure of CO2 (641.5Pa) and at four levels of nitrogen nutrition. Thirty-five days after planting, the total dry weights of high CO2-grown plants were 2- to 3.5-fold greater than plants grown in normal ambient CO2 partial pressure.

  6. Quantitative Analysis of Spectral Interference of Spontaneous Raman Scattering in High-Pressure Fuel-Rich H2-Air Combustion

    NASA Technical Reports Server (NTRS)

    Kojima, Jun; Nguyen, Quang-Viet

    2004-01-01

    We present a theoretical study of the spectral interferences in the spontaneous Raman scattering spectra of major combustion products in 30-atm fuel-rich hydrogen-air flames. An effective methodology is introduced to choose an appropriate line-shape model for simulating Raman spectra in high-pressure combustion environments. The Voigt profile with the additive approximation assumption was found to provide a reasonable model of the spectral line shape for the present analysis. The rotational/vibrational Raman spectra of H2, N2, and H2O were calculated using an anharmonic-oscillator model using the latest collisional broadening coefficients. The calculated spectra were validated with data obtained in a 10-atm fuel-rich H2-air flame and showed excellent agreement. Our quantitative spectral analysis for equivalence ratios ranging from 1.5 to 5.0 revealed substantial amounts of spectral cross-talk between the rotational H2 lines and the N2 O-/Q-branch; and between the vibrational H2O(0,3) line and the vibrational H2O spectrum. We also address the temperature dependence of the spectral cross-talk and extend our analysis to include a cross-talk compensation technique that removes the nterference arising from the H2 Raman spectra onto the N2, or H2O spectra.

  7. Sensor for headspace pressure and H2O concentration measurements in closed vials by tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Cai, Tingdong; Wang, Guishi; Cao, Zhensong; Zhang, Weijun; Gao, Xiaoming

    2014-07-01

    The concentration of H2O and the pressure in the headspace of vials are simultaneously measured by a tunable diode laser sensor based on absorption spectroscopy techniques. The 7168.437 cm-1 spectral line of H2O is chosen as the sensing transition for its strong absorption strength and being reasonably far away from its neighboring molecular transitions. In order to prevent interference absorption by ambient water vapor in the room air, a difference between the measured signal and the referenced signal is used to calculate the pressure and H2O concentration in the headspace of vials, eliminating the need for inert gas purges and calibration with known gas. The validation of the sensor is conducted in a static vial, yielding an accuracy of 1.23% for pressure and 3.81% for H2O concentration. The sensitivity of the sensor is estimated to be about 2.5 Torr for pressure and 400 ppm for H2O concentration over a 3 cm absorption path length respectively. Accurate measurements for commercial freeze-dried products demonstrate the in-line applications of the sensor for the pharmaceutical industry.

  8. Reaction pathways for bio-active species in a He/H2O atmospheric pressure capacitive discharge

    NASA Astrophysics Data System (ADS)

    Ding, Ke; Lieberman, M. A.

    2015-01-01

    Helium/trace gas atmospheric pressure radio-frequency (rf) capacitive discharges have increasing biomedical applications. We have performed a principal pathway analysis for a chemically complex, bounded He/H2O atmospheric pressure, planar capacitive discharge, with a discharge gap of 0.5 mm and a power of 0.85 W cm?2 at 13.56 MHz (ne ? 1.6 1017 m?3). The discharge is embedded in a larger volume in which the H2O fraction is controlled to be 0.001. The generation and loss pathways for eleven species of interest for discharge maintenance and biomedical applications have been determined. The production and consumption pathways of He*, H2O, {{\\text{H}}11}\\text{O}5+ and electrons are found to be tightly coupled. The metastable He* generated by electron impact excitation of He is mostly consumed by Penning reactions with H2O, followed by subsequent three-body association reactions with H2O, to form the dominant positive ion, {{\\text{H}}11}\\text{O}5+ . The main loss pathways for {{\\text{H}}11}\\text{O}5+ are ion cluster fragmentations at the wall, which are important generation pathways for H2O. The generation and loss pathways for electrons are almost the same as for {{\\text{H}}11}\\text{O}5+ . OH and H2O2 generation and loss are strongly coupled, and they are important intermediate species in the generation pathways for the purely O-containing bio-active species: O2(a), O, O3 and O*. The generation and loss pathways for the latter four species were found to be strongly coupled by volume and surface processes, with O2 as an important precursor. The generation of O2 from H2O involves H2O2 as a key long-lived intermediate.

  9. [Synthesis and combined H1-/H2 antagonist activity of mepyramine, pheniramine and cyclizine derivatives with cyanoguanidine, urea and nitroethenediamine partial structures].

    PubMed

    Schulze, F R; Alisch, R A; Buschauer, A; Schunack, W

    1994-07-01

    Compounds with combined histamine H1- and H2-receptor antagonist activity were synthesized by connecting H1- and H2-receptor substructures via cyanoguanidine, urea, or nitroethenediamine moieties. Loss of the strongly basic side-chain nitrogen results in a decrease of H1-receptor activity compared to single reference compounds. At the guinea-pig right atrium (H2-receptor model) compounds with mepyramine or cyclizine structure are also less active than the single references tiotidine, ranitidine, or lamtidine. Nevertheless substances with a pheniramine like partial structure proved to be potent histamine H2-receptor antagonists at the atrium model (about 27 times more active than cimetidine). PMID:7915515

  10. Pressure dependence of the absolute rate constant for the reaction Cl + C2H2 from 210-361 K

    NASA Technical Reports Server (NTRS)

    Brunning, J.; Stief, L. J.

    1985-01-01

    In recent years, considerable attention has been given to the role of chlorine compounds in the catalytic destruction of stratospheric ozone. However, while some reactions have been studied extensively, the kinetic data for the reaction of Cl with C2H2 is sparse with only three known determinations of the rate constant k3. The reactions involved are Cl + C2H2 yields reversibly ClC2H2(asterisk) (3a) and ClC2H2(asterisk) + M yields ClC2H2 + M (3b). In the present study, flash photolysis coupled with chlorine atomic resonance fluorescence have been employed to determine the pressure and temperature dependence of k3 with the third body M = Ar. Room temperature values are also reported for M = N2. The pressure dependence observed in the experiments confirms the expectation that the reaction involves addition of Cl to the unsaturated C2H2 molecule followed by collisional stabilization of the resulting adduct radical.

  11. A fiber optic probe for oxygen partial pressure sensing

    E-print Network

    Schlain, Leslie Ariel

    1986-01-01

    A FIBER OPTIC PROBE FOR OXYGEN PARTIAL PRESSURE SENSING A Thesis by LESLIE ARIEL SCHLAIN Submitted to the Graduate Col lege of Texas A & M University in partial fullfilment of the requirements for the degree of MASTER OF SCIENCE December...~ Aerl Jon F. Hunter (Hembel ) (Heed of Department) December 19S6 111 ABSTRACT A Fiber Optic Probe for Oxygen Partial Pressure Sensing (December, 1986) Leslie Ariel Schlain B. S. , Texas A & M University Chair of Advisory Committee: Dr. William...

  12. A fiber optic probe for oxygen partial pressure sensing

    E-print Network

    Schlain, Leslie Ariel

    1986-01-01

    A FIBER OPTIC PROBE FOR OXYGEN PARTIAL PRESSURE SENSING A Thesis by LESLIE ARIEL SCHLAIN Submitted to the Graduate Col lege of Texas A & M University in partial fullfilment of the requirements for the degree of MASTER OF SCIENCE December...~ Aerl Jon F. Hunter (Hembel ) (Heed of Department) December 19S6 111 ABSTRACT A Fiber Optic Probe for Oxygen Partial Pressure Sensing (December, 1986) Leslie Ariel Schlain B. S. , Texas A & M University Chair of Advisory Committee: Dr. William...

  13. H2S Protects Against Pressure Overload Induced Heart Failure via Upregulation of Endothelial Nitric Oxide Synthase (eNOS)

    PubMed Central

    Kondo, Kazuhisa; Bhushan, Shashi; King, Adrienne L.; Prabhu, Sumanth D.; Hamid, Tariq; Koenig, Steven; Murohara, Toyoaki; Predmore, Benjamin L.; Gojon, Gabriel; Gojon, Gabriel; Wang, Rui; Karusula, Naveena; Nicholson, Chad K.; Calvert, John W.; Lefer, David J.

    2013-01-01

    Introduction Cystathionine gamma-lyase (CSE) produces H2S via enzymatic conversion of L-cysteine and plays a critical role in cardiovascular homeostasis. We investigated the effects of genetic modulation of CSE and exogenous H2S therapy in the setting of pressure overload-induced heart failure. Methods and Results Transverse aortic constriction (TAC) was performed in wild-type (WT), CSE knockout (KO), and cardiac specific CSE transgenic (CS-CSE Tg) mice. In addition, C57BL/6J or CSE KO mice received a novelH2S donor (SG-1002). Mice were followed for 12 weeks using echocardiography. We observed a >60% reduction in myocardial and circulating H2S levels following TAC. CSE KO mice exhibited cardiac dilatation and dysfunction significantly greater than WT mice following TAC and CS-CSE Tg mice maintained cardiac structure and function following TAC. H2S therapy with SG-1002 resulted in cardioprotection during TAC via upregulation of the VEGF-Akt-eNOS-nitric oxide-cGMP pathway with preserved mitochondrial function, attenuated oxidative stress, and increased myocardial vascular density. Conclusions Our results demonstrate that H2S levels are decreased in mice in the setting of heart failure. Moreover, CSE plays a critical role in the preservation of cardiac function in heart failure and oral H2S therapy prevents the transition from compensated to decompensated heart failure in part via upregulation of endothelial nitric oxide synthase (eNOS) and increased NO bioavailability. PMID:23393010

  14. Melting behavior of H2O at high pressures and temperatures Jung-Fu Lin,1

    E-print Network

    Lin, Jung-Fu "Afu"

    in the melting curve of H2O is observed at approximately 35 GPa and 1040 K, indicating a triple point on the melting line. The melting curve of H2O increases significantly above the triple point and may intersect; revised 30 March 2005; accepted 5 May 2005; published 10 June 2005. [1] Water plays an important role

  15. Water-Steel Canister Interaction and H2 Gas Pressure Buildup in aNuclear Waste Repository

    SciTech Connect

    Xu, Tianfu; Senger, Rainer; Finstele, Stefan

    2007-01-02

    Corrosion of steel canisters, stored in a repository forspent fuel and high-level waste, leads to hydrogen gas generation in thebackfilled emplacement tunnels, which may significantly affect long-termrepository safety. Previous modeling studies used a constant H2generation rate. However, iron corrosion and H2 generation rates varywith time, depending on factors such as water chemistry, wateravailability, and water contact area. To account for these factors andfeedback mechanisms, we developed a chemistry model related to ironcorrosion, coupled with two-phase (liquid and gas) flow phenomena thatare driven by gas pressure buildup and water consumption. Resultsindicate that if H2 generation rates are dynamically calculated based ona chemistry model, the degree and extent of gas pressure buildup are muchsmaller compared to a simulation in which the coupling between flow andreactive transport mechansism is neglected.

  16. Sublimation pressure and sublimation enthalpy of H 2O ice Ih between 0 and 273.16 K

    Microsoft Academic Search

    Rainer Feistel; Wolfgang Wagner

    2007-01-01

    The sublimation of water in the region of extremely low pressures and temperatures meets increasing interest for the exploration of icy cosmic bodies. At temperatures below 130K, the shape of the sublimation curve of H2O is not known; neither experimental data nor theoretical treatments exist for this region. Based upon theoretical upper and lower bounds for the heat capacity of

  17. Rutile solubility in albite-H2O and Na2Si3O7-H2O at high temperatures and pressures by in-situ synchrotron radiation micro-XRF

    E-print Network

    Manning, Craig

    Rutile solubility in albite-H2O and Na2Si3O7-H2O at high temperatures and pressures by in online 12 June 2008 Editor: R.W. Carlson Keywords: rutile solubility high- eld-strength elements ti mobility uid ow Rutile is an important mineral host for high- eld strength elements, so its solubility

  18. Direct Measurements of the Pressure Coefficient, Partial

    NASA Astrophysics Data System (ADS)

    del Cueto, Joseph Antonio

    1984-06-01

    The pressure coefficient of liquid ('3)He-('4)He mixtures was coupled to directly, with a strain gauge capacitative cell. The cell was filled, pressurized and isolated with a mixture, of ('3)He mole fraction x between 0.50-0.80. The elastic properties of the cell effected a capacitance change in an LC tank circuit driven to oscillation by a Tunnel Diode. The frequency of the circuit, as well as the balance point of an AC Wheatstone circuit sensing a cryo-resistor mounted on the cell, were sampled by a data acquisition(DAS) system, to obtain pressure vs. temperature increments data. The DAS was enabled to perform temperature ramps and cycles with amplitudes of (TURN) (+OR-) 50-100 mK, while concurrently sampling pressure vs. temperature data. It is found that (PAR-DIFF)P/(PAR-DIFF)T)(,v,x) is a piecewise smooth function in the temperature T. For x < x(,t)(P), the data indicate a cusp discontinuity at the lambda temperature of the mixture T(,(lamda))(x,v(p(,(lamda)))), and a simple discontinuity at the onset of phase separation temperature T(,S)(x,v(p(,S))). For x > x(,t)(P), only the phase separation breaks the monotonic behaviour of the pressure coefficient. Where x(,t)(P) is the tricritical concentration at pressure P, referred to in the above. The data for the pressure coefficients are parametrized by smooth functions in appendix 5. This parametrization allows for further thermodynamic analysis, as that of appendix 6, the change in chemical potential difference upon compression. The thermodynamic implications of the measured step in (PAR -DIFF)P/(PAR-DIFF)T)(,v,x), across the onset separation temperature, are explored in appendix 4. The 'volume' minima at the pressures the isochores cross at their pressure minima in temperature, are plotted and analysed to imply that for some concentrations x, the entropy of the mixture is a double valued function of absolute pressure.

  19. The system NaCl?CaCl 2?H 2O: I. The ice liquidus at 1 atm total pressure

    NASA Astrophysics Data System (ADS)

    Oakes, Charles S.; Bodnar, Robert J.; Simonson, John M.

    1990-03-01

    Phase relations in the ice-stable field of the system NaCl?CaCl 2?H 2O have been determined under 1 atm total pressure along the NaCl?H 2O and CaCl 2?H 2O binaries and along five pseudobinaries with constant NaCl/( NaC1+ CaCl2) weight ratios. The results are in excellent agreement with published data along the NaCl?H 2O binary but show large discrepancies when compared to previous determinations of the ice liquidus along the CaCl 2?H 2O binary and in the NaCl?CaCl 2?H 2O ternary. Eutectic temperatures and compositions are -21.20C (0.01 ) and 23.2 wt% for the NaCl?H 2O binary and -49.95C (0.15) and 30.33 wt% for the CaCl 2?H 2O binary. The minimum temperature reached during our experiments in the ternary system was -34C; therefore, we do not report isotherms below -35C or the ternary eutectic temperature. At moderate to high salinities, isotherms cross the ice sub-field at lower total salt concentrations than previously reported. Fluid inclusion salinities determined from previously published freezing-point data may be in error by as much as 2 wt% total salt. In addition, NaCl/( NaCl+ CaCl2) weight ratios estimated from hydrohalite- and ice-melting temperatures may be in error by as much as 0.15.

  20. A study of the H2O absorption line shifts in the visible spectrum region due to air pressure

    NASA Technical Reports Server (NTRS)

    Grossmann, B. E.; Browell, E. V.; Bykov, A. D.; Kapitanov, V. A.; Korotchenko, E. A.

    1990-01-01

    Results of measured and calculated shift coefficients are presented for 170 absorption lines of H2O in five vibrational-rotational bands. The measurements have been carried out using highly sensitive laser spectrometers with a resolution of at least 0.01/cm; the calculations are based on the Anderson-Tsao-Curnutte-Frost method. Good agreement is obtained between the theoretical and experimental values of the shift coefficients of H2O lines due to N2, O2, and air pressure.

  1. Elevated atmospheric partial pressure of CO 2 and plant growth

    Microsoft Academic Search

    S. C. Wong

    1979-01-01

    Cotton and maize plants were grown under full sunlight in glass houses containing normal ambient partial pressure of CO2 (33020 bar) and enriched partial pressure of CO2 (640 15 bar) with four levels of nitrogen nutrient. In 40 day old cotton plants grown in high CO2, there was a 2-fold increase in day weight and a 1.6-fold increase in leaf

  2. Influence of under pressure dissolved oxygen on trichloroethylene degradation by the H2O2/TiO2 process

    PubMed Central

    2013-01-01

    Background The widespread use of trichloroethylene (TCE) and its frequent release into the environment has caused many environmental and health problems. In this study the degradation of TCE at different micromolar concentrations was investigated in a stainless steel reactor with various concentrations of H2O2 and TiO2 at different oxygen pressures and three different pHs. Methods To examine the synergistic effect of under pressure oxygen on TCE degradation, the concentrations of H2O2 and TiO2 as well as pH were first optimized, and then the experiments were performed under optimal conditions. Gas chromatography with a flame ionization detector (FID) was used to measure TCE concentrations. Results Results showed that the percentage of TCE degradation without pressurized oxygen was low and it increased with increasing pressure of oxygen at all initial concentrations of TCE. The degradation percentages without oxygen pressure were 48.27%, 51.22%, 58.13% and 64.33% for TCE concentrations of 3000, 1500, 300 and 150?g/L respectively. At an oxygen pressure of 2.5 atmospheres (atm) the percent degradation of TCE reached 84.85%, 89.14%, 93.13% and 94.99% respectively for the aforementioned TCE concentrations. Conclusions The results of this study show that the application of dissolved oxygen under pressure increases the efficiency of the H2O2/TiO2 process on the degradation of TCE and can be used along with other oxidants as an effective method for the removal of this compound from aqueous solutions. PMID:24359702

  3. Measurement and simulation of spontaneous Raman scattering in high-pressure fuel-rich H2 air flames

    NASA Astrophysics Data System (ADS)

    Kojima, Jun; Nguyen, Quang-Viet

    2004-03-01

    Rotational and vibrational spontaneous Raman scattering (SRS) spectra of H2, N2 and H2O have been measured in H2-air flames at pressures up to 30.4 bar as a first step towards establishing a comprehensive Raman spectral database for temperatures and species in high-pressure combustion. We have obtained an initial set of measurements that indicate the spectra are of sufficient quality in terms of spectral resolution, wavelength coverage and signal-to-noise ratio for use in the development of transferable standards for the cross-talk calibration matrix. The fully resolved Stokes and anti-Stokes shifted spectra were collected in the visible wavelength range (400-700 nm) using pulse-stretched 532 nm excitation and a spectrograph fitted with a non-intensified CCD detector and a high-speed shutter. Temperatures were determined via the intensity distribution of rotational H2 lines at stoichiometric and fuel-rich conditions. A discussion of the temperature measurement accuracy in terms of the number of laser shots, including a single-shot measurement, is presented. Theoretical Raman spectra of hydrogen were calculated using a semi-classical anharmonic-oscillator model with recent pressure broadening data and were compared with experimental data. The data and simulation showed good agreement at different equivalence ratios and pressures and indicate that high-J rotational lines of H2 may interfere with the N2 vibrational Q-branch lines, which could lead to errors in N2-Raman thermometry based on the line-fitting method. In addition, the relative intensities of the O- and S-branches to the Q-branch were determined theoretically and the result indicates that further studies of spectral interferences including contributions from O- and S-branches should be pursued. Finally, from a comparison of N2 Q-branch spectra in lean H2-air flames at nearly atmospheric (1.2 bar) and high pressure (30.4 bar), we found no significant line-narrowing or -broadening effects at a spectral resolution of 0.04 nm.

  4. Solubility of H 2O in rhyolitic melts at low pressures and a new empirical model for mixed H 2O-CO 2 solubility in rhyolitic melts

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Zhang, Youxue; Behrens, Harald

    2005-05-01

    Experiments of H 2O solubility in synthetic haplogranitic and natural rhyolitic melts were conducted at 700-1200 C and 0.098-25 MPa. Attainment of equilibrium was proven by reversals using starting materials with different initial H 2O contents. Dissolved H 2O contents were determined using Fourier transform infrared spectroscopy. When temperature decreases from 1000 to 700 C, the solubility of H 2O increases from 0.100 to 0.124 wt.% at 0.098 MPa, from 0.99 to 1.36 wt.% at 11 MPa, and from 1.46 to 2.17 wt.% at 25 MPa. At 6 MPa, the solubility of H 2O increases from 0.63 to 0.77 wt.% from 1200 to 850 C. Combining our data with those from the literature on pure H 2O and pure CO 2 solubility, mixed H 2O-CO 2 solubility, and H 2O solubility for H 2O-H 2 gas mixture (240 measurements for H 2O and 59 points for CO 2), we develop a single empirical model for solubility of pure H 2O vapor, that of pure CO 2 vapor, as well as that of mixed H 2O-CO 2 vapor in metaluminous high-silica rhyolitic melt. This model applies to the conditions of 700-1200 C and 0-500 MPa, and consists of two equations: HO=(354.94Pw0.5+9.623P-1.5223Pw1.5)/T+0.0012439Pw1.5+P(-1.08410Pw0.5-1.36210P) CO=P(5668-55.99P)/T+P(0.4133Pw0.5+2.04110Pw1.5) where H 2O t is total dissolved H 2O content in wt.%, CO 2 content is in ppm by mass, and T is temperature in Kelvin, Pw= XwfP and PCO 2= XCO 2fP (in MPa), where Xwf and XCO 2f are the mole fraction of water and CO 2 in the fluid. The 2 ? relative uncertainty is 15% for the H 2O equation, and 20% for the CO 2 equation. The above H 2O equation also applies to H 2O solubility in mixed H 2O-H 2 fluid for XH 2f<0.54 at 100 MPa, for XH 2f<0.49 at 200 MPa, and XH 2f?0.44 at 300 MPa (that is, the presence of H 2 in the fluid insignificantly affects H 2O solubility). This empirical model is recommended for the modeling of explosive volcanic eruptions and magma chamber dynamics.

  5. First-principles study on the structural and electronic properties of metallic HfH2 under pressure.

    PubMed

    Liu, Yunxian; Huang, Xiaoli; Duan, Defang; Tian, Fubo; Liu, Hanyu; Li, Da; Zhao, Zhonglong; Sha, Xiaojing; Yu, Hongyu; Zhang, Huadi; Liu, Bingbing; Cui, Tian

    2015-01-01

    The crystal structures and properties of hafnium hydride under pressure are explored using the first-principles calculations based on density function theory. The material undergoes pressure-induced structural phase transition I4/mmm?Cmma?P21/m at 180 and 250?GPa, respectively, and all of these structures are metallic. The superconducting critical temperature Tc values of I4/mmm, Cmma, and P21/m are 47-193?mK, 5.99-8.16?K and 10.62-12.8?K at 1?atm, 180 and 260?GPa, respectively. Furthermore, the bonding nature of HfH2 is investigated with the help of the electron localization function, the difference charge density and Bader charge analyses, which show that HfH2 is classified as a ionic crystal with the charges transferring from Hf atom to H. PMID:26096298

  6. First-principles study on the structural and electronic properties of metallic HfH2 under pressure

    PubMed Central

    Liu, Yunxian; Huang, Xiaoli; Duan, Defang; Tian, Fubo; Liu, Hanyu; Li, Da; Zhao, Zhonglong; Sha, Xiaojing; Yu, Hongyu; Zhang, Huadi; Liu, Bingbing; Cui, Tian

    2015-01-01

    The crystal structures and properties of hafnium hydride under pressure are explored using the first-principles calculations based on density function theory. The material undergoes pressure-induced structural phase transition I4/mmm?Cmma?P21/m at 180 and 250?GPa, respectively, and all of these structures are metallic. The superconducting critical temperature Tc values of I4/mmm, Cmma, and P21/m are 47193?mK, 5.998.16?K and 10.6212.8?K at 1?atm, 180 and 260?GPa, respectively. Furthermore, the bonding nature of HfH2 is investigated with the help of the electron localization function, the difference charge density and Bader charge analyses, which show that HfH2 is classified as a ionic crystal with the charges transferring from Hf atom to H. PMID:26096298

  7. 21 CFR 868.1150 - Indwelling blood carbon dioxide partial pressure (PCO2) analyzer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 false Indwelling blood carbon dioxide partial pressure (PCO2) analyzer...Devices 868.1150 Indwelling blood carbon dioxide partial pressure (PCO2 ) analyzer...Identification. An indwelling blood carbon dioxide partial pressure PCO2...

  8. 21 CFR 868.1150 - Indwelling blood carbon dioxide partial pressure (PCO2) analyzer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Indwelling blood carbon dioxide partial pressure (PCO2...Diagnostic Devices 868.1150 Indwelling blood carbon dioxide partial pressure (PCO2... (a) Identification. An indwelling blood carbon dioxide partial pressure...

  9. 21 CFR 868.1150 - Indwelling blood carbon dioxide partial pressure (PCO2) analyzer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false Indwelling blood carbon dioxide partial pressure (PCO2...Diagnostic Devices 868.1150 Indwelling blood carbon dioxide partial pressure (PCO2... (a) Identification. An indwelling blood carbon dioxide partial pressure...

  10. 21 CFR 868.1150 - Indwelling blood carbon dioxide partial pressure (PCO2) analyzer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false Indwelling blood carbon dioxide partial pressure (PCO2...Diagnostic Devices 868.1150 Indwelling blood carbon dioxide partial pressure (PCO2... (a) Identification. An indwelling blood carbon dioxide partial pressure...

  11. 21 CFR 868.1150 - Indwelling blood carbon dioxide partial pressure (PCO2) analyzer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Indwelling blood carbon dioxide partial pressure (PCO2...Diagnostic Devices 868.1150 Indwelling blood carbon dioxide partial pressure (PCO2... (a) Identification. An indwelling blood carbon dioxide partial pressure...

  12. P8The new French\\/German test facility for H 2 O 2 high pressure rocket engine combustion research

    Microsoft Academic Search

    Wolfgang W. Koschel; Oskar J. Haidn

    1998-01-01

    Having agreed in principle on a cooperation in the field of H2O2 high pressure combustion research, the partners CNES (Centre National d'Etudes Spatial, Evry, France), DASA (Daimler Benz Aerospace, Ottobrunn, Germany), DLR and SEP (Socit Europenne de Propulsion, Vernon, France) have decided by signing a Memorandum of Understanding (MoU) in December 1992 to erect, operate and utilize in a joint

  13. Pressure broadening data as a test of a recently proposed Ar-H2O interaction potential

    NASA Technical Reports Server (NTRS)

    Green, Sheldon

    1991-01-01

    An interaction potential for H2O-Ar that was recently determined from spectra of the van der Waals complex by Cohen and Saykally (1990) is used with accurate molecular scattering calculations to predict line broadening parameters for the 183 and 380 GHz transitions of water vapor. Theoretical values are about 15 percent higher than experiment. A comparison of experimental and theoretical pressure broadening cross sections for water in argon is presented.

  14. DOE H2 Program Annual Review, 5-20-2003 Insulated Pressure Vessels for

    E-print Network

    A. Low cost, due to lower need for fiber. B. Low volume. C. Efficient, due to the dual mode range. J. We are generating tank performance data. K. Testing BOP components. L. Low venting losses gasoline, equivalent energy liquid hydrogen insulated pressure vessel pressure vessel, 0.5 Minch pressure

  15. H 2 O activity in concentrated KCl and KCl-NaCl solutions at high temperatures and pressures measured by the brucite-periclase equilibrium

    Microsoft Academic Search

    L. Y. Aranovich; R. C. Newton

    1997-01-01

    H2O activities in supercritical fluids in the system KCl-H2O-(MgO) were measured at pressures of 1, 2, 4, 7, 10 and 15? kbar by numerous reversals of vapor compositions in equilibrium\\u000a with brucite and periclase. Measurements spanned the range 550900?C. A change of state of solute KCl occurs as pressures\\u000a increase above 2?kbar, by which H2O activity becomes very low and,

  16. OH density measurements in nanosecond pulsed discharges in atmospheric pressure N2-H2O mixtures

    NASA Astrophysics Data System (ADS)

    Verreycken, T.; Bruggeman, P. J.

    2014-02-01

    Time and spatially resolved OH densities are determined in a nanosecond pulsed filamentary discharge in N2-H2O for varying water concentration using laser-induced fluorescence (LIF). The OH densities are absolutely calibrated using Rayleigh scattering. A dip in the LIF signal is found at the centre of the filament. In the case of 2.6% H2O a remarkable increase in OH density is found in the far afterglow and is discussed in analogy with the pink splash or pink afterglow. It is believed that the large amount of energy released in the recombination of atomic nitrogen plays an important role in the production of OH in the far afterglow.

  17. Atmospheric pressure plasma jet utilizing Ar and Ar/H2O mixtures and its applications to bacteria inactivation

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng; Shen, Jie; Xiao, De-Zhi; Xie, Hong-Bing; Lan, Yan; Fang, Shi-Dong; Meng, Yue-Dong; Chu, Paul K.

    2014-07-01

    An atmospheric pressure plasma jet generated with Ar with H2O vapor is characterized and applied to inactivation of Bacillus subtilis spores. The emission spectra obtained from Ar/H2O plasma shows a higher intensity of OH radicals compared to pure argon at a specified H2O concentration. The gas temperature is estimated by comparing the simulated spectra of the OH band with experimental spectra. The excitation electron temperature is determined from the Boltzmann's plots and Stark broadening of the hydrogen Balmer H? line is applied to measure the electron density. The gas temperature, excitation electron temperature, and electron density of the plasma jet decrease with the increase of water vapor concentration at a fixed input voltage. The bacteria inactivation rate increases with the increase of OH generation reaching a maximum reduction at 2.6% (v/v) water vapor. Our results also show that the OH radicals generated by the Ar/H2O plasma jet only makes a limited contribution to spore inactivation and the shape change of the spores before and after plasma irradiation is discussed.

  18. Deactivation of lipopolysaccharide by Ar and H2 inductively coupled low-pressure plasma

    NASA Astrophysics Data System (ADS)

    Bartis, E. A. J.; Barrett, C.; Chung, T.-Y.; Ning, N.; Chu, J.-W.; Graves, D. B.; Seog, J.; Oehrlein, G. S.

    2014-01-01

    Using an inductively coupled plasma system, we study the effects of direct plasma, plasma-generated high-energy photons in the ultraviolet and vacuum ultraviolet (UV/VUV), and radical treatments on lipopolysaccharide (LPS). LPS is a biomolecule found in the outer membrane of Gram-negative bacteria and a potent stimulator of the immune system composed of polysaccharide and lipid A, which contains six aliphatic chains. LPS film thickness spun on silicon was monitored by ellipsometry while the surface chemistry was characterized before and after treatments by x-ray photoelectron spectroscopy (XPS). Additionally, biological activity was measured using an enzyme-linked immunosorbent assay under (a) a sensitive regime (sub-M concentrations of LPS) and (b) a bulk regime (above M concentrations of LPS) after plasma treatments. Direct plasma treatment causes rapid etching and deactivation of LPS in both Ar and H2 feed gases. To examine the effect of UV/VUV photons, a long-pass filter with a cut-off wavelength of 112 nm was placed over the sample. H2 UV/VUV treatment causes material removal and deactivation due to atomic and molecular UV/VUV emission while Ar UV/VUV treatment shows minimal effects as Ar plasma does not emit UV/VUV photons in the transmitted wavelength range explored. Interestingly, radical treatments remove negligible material but cause deactivation. Based on the amphiphilic structure of LPS, we expect a lipid A rich surface layer to form at the air-water interface during sample preparation with polysaccharide layers underneath. XPS shows that H2 plasma treatment under direct and UV/VUV conditions causes oxygen depletion through removal of C-O and O-C = O bonds in the films, which does not occur in Ar treatments. Damage to these groups can remove aliphatic chains that contribute to the pyrogenicity of LPS. Radical treatments from both Ar and H2 plasmas remove aliphatic carbon from the near-surface, demonstrating the important role of neutral species.

  19. Measurement of partial pressures in vacuum technology and vacuum physics

    NASA Technical Reports Server (NTRS)

    Huber, W. K.

    1986-01-01

    It is pointed out that the measurement of gaseous pressures of less than 0.0001 torr is based on the ionization of gas atoms and molecules due to collisions with electrons. The particle density is determined in place of the pressure. The ionization cross sections for molecules of various gases are discussed. It is found that the true pressure in a vacuum system cannot be determined with certainty if it is unknown which gas is present. Effects of partial pressure determination on the condition of the vacuum system are discussed together with ion sources, systems of separation, and ion detection.

  20. Report on ISS Oxygen Production, Resupply, and Partial Pressure Management

    NASA Technical Reports Server (NTRS)

    Schaezler, Ryan; Ghariani, Ahmed; Leonard, Daniel; Lehman, Daniel

    2011-01-01

    The majority of oxygen used on International Space Station (ISS) is for metabolic support and denitrogenation procedures prior to Extra-Vehicular Activities. Oxygen is supplied by various visiting vehicles such as the Progress and Shuttle in addition to oxygen production capability on both the United States On-Orbit Segment (USOS) and Russian Segment (RS). To maintain a habitable atmosphere the oxygen partial pressure is controlled between upper and lower bounds. The full range of the allowable oxygen partial pressure along with the increased ISS cabin volume is utilized as a buffer allowing days to pass between oxygen production or direct addition of oxygen to the atmosphere from reserves. This paper summarizes amount of oxygen supplied and produced from all of the sources and describes past experience of managing oxygen partial pressure along with the range of management options available to the ISS.

  1. Laser-fluorescence measurements of nitric oxide in low-pressure H2/O2/NO flames

    NASA Technical Reports Server (NTRS)

    Cattolica, R. J.; Mataga, T. G.; Cavolowsky, J. A.

    1989-01-01

    The concentration profiles of NO in low-pressure (76 Torr) H2/O2/Ar flames to which nitric oxide is added are measured by pulsed laser-induced fluorescence. Temporally resolved fluorescence measurements are used to determine the collisional deexcitation rates needed to convert time-integrated fluorescence signal into oxide concentration. Five flames are studied with H2/O2 equivalence ratios of 0.88, 0.98, 1.22, 1.37, and 1.50. In these flames the collisional deexcitation rate decreases rapidly above the burner surface as the density decreases with increasing temperature. A 20 percent decrease is observed for the lean flames, and a 30 percent decrease for the rich flames. Within the precision of the measurement technique (+ or - 10 percent), no significant removal of nitric oxide is observed in these flames.

  2. CO2, H2 and He Line Broadening Coefficients and Pressure Shifts for the HITRAN Database

    NASA Astrophysics Data System (ADS)

    Wilzewski, J. S.; Gordon, I. E.; Rothman, L. S.

    2015-04-01

    In order to aid studies of the Venusian atmosphere the spectral lines of selected molecules in the HITRAN database were supplemented with broadening coefficients (and their temperature exponents) and line shifts due to the pressure of CO2.

  3. H2O activity in concentrated KCl and KCl-NaCl solutions at high temperatures and pressures measured by the brucite-periclase equilibrium

    NASA Astrophysics Data System (ADS)

    Aranovich, L. Y.; Newton, R. C.

    H2O activities in supercritical fluids in the system KCl-H2O-(MgO) were measured at pressures of 1, 2, 4, 7, 10 and 15 kbar by numerous reversals of vapor compositions in equilibrium with brucite and periclase. Measurements spanned the range 550-900C. A change of state of solute KCl occurs as pressures increase above 2kbar, by which H2O activity becomes very low and, at pressures of 4kbar and above, nearly coincident with the square of the mole fraction (xH2O). The effect undoubtedly results primarily from ionic dissociation as H2O density (?H2O) approaches 1gm/cm3, and is more pronounced than in the NaCl-H2O system at the same P-T-X conditions. Six values of solute KCl activity were yielded by terminal points of the isobaric brucite-periclase T-xH2O curves where sylvite saturation occurs. The H2O mole fraction of the isobaric invariant assemblage brucite-periclase-sylvite-fluid is near 0.52 at all pressures, and the corresponding temperatures span only 100C between 1 and 15kbar. This remarkable convergence of the isobaric equilibrium curves reflects the great influence of pressure on lowering of both KCl and H2O activities. The H2O and KCl activities can be expressed by the formulas: aH2O=?H2O[xH2O+(1+(1+?)xKCl)], and aKCL=?KCl[(1+?)xKCl/(xH2O+(1+?)xKCl)](1+?), where ? is a degree of dissociation parameter which increases from zero at the lowest pressures to near one at high pressures and the ?'s are activity coefficients based on an empirical regular solution parameter W: ln ?i=(1-xi)2W. Least squares fitting of our H2O and KCl activity data evaluates the parameters: ?=exp(4.166 -2.709/?H2O) - 212.1P/T, and W=(-589.6-23.10P) /T, with ?H2O in gm/cm3, P in kbar and T in K. The standard deviation from the measured activities is only +/-0.014. The equations define isobaric liquidus curves, which are in perfect agreement with previous DTA liquidus measurements at 0.5-2kbar, but which depart progressively from their extrapolation to higher pressures because of the pressure-induced dissociation effect. The great similarity of the NaCl-H2O and KCl-H2O systems suggests that H2O activities in the ternary NaCl-KCl-H2O system can be described with reasonable accuracy by assuming proportionality between the binary systems. This assumption was verified by a few reconnaissance measurements at 10kbar of the brucite-periclase equilibrium with a Na/(Na+K) ratio of 0.5 and of the saturation temperature for Na/(Na+K) of 0.35 and 0.50. At that pressure the brucite-periclase curves reach a lowest xH2O of 0.45 and a temperature of 587C before salt saturation occurs, values considerably lower than in either binary. This double-salt eutectic effect may have a significant application to natural polyionic hypersaline solutions in the deep crust and upper mantle in that higher solute concentrations and very low H2O activities may be realized in complex solutions before salt saturation occurs. Concentrated salt solutions seem, from this standpoint, and also because of high mechanical mobility and alkali-exchanging potential, feasible as metasomatic fluids for a variety of deep-crust and upper mantle processes.

  4. Pressurized H_{2} rf Cavities in Ionizing Beams and Magnetic Fields

    SciTech Connect

    Chung, M.; et al.

    2013-10-01

    A major technological challenge in building a muon cooling channel is operating RF cavities in multi-tesla external magnetic fields. We report the first experimental characterization of a high pressure gas-filled 805 MHz RF cavity for use with intense ionizing beams and strong external magnetic fields. RF power consumption by beam-induced plasma was investigated with hydrogen and deuterium gases with pressures between 20 and 100 atm and peak RF gradients between 5 and 50 MV/m. The energy absorption per ion pair-RF cycle ranges from 10?18 to 10?16 J. The low pressure case agrees well with an analytical model based on electron and ion mobilities. Varying concentrations of oxygen gas were investigated to remove free electrons from the cavity and reduce the RF power consumption. Measurements of the electron attachment time to oxygen and rate of ion-ion recombination were also made. Additionally, we demonstrate the operation of the gas-filled RF cavity in a solenoidal field of up to 3 T, finding no major magnetic field dependence. These results indicate that a high pressure gas-filled cavity is potentially a viable technology for muon ionization cooling.

  5. A unified equation for calculating methane vapor pressures in the CH4-H2O system with measured Raman shifts

    USGS Publications Warehouse

    Lu, W.; Chou, I.-Ming; Burruss, R.C.; Song, Y.

    2007-01-01

    A unified equation has been derived by using all available data for calculating methane vapor pressures with measured Raman shifts of C-H symmetric stretching band (??1) in the vapor phase of sample fluids near room temperature. This equation eliminates discrepancies among the existing data sets and can be applied at any Raman laboratory. Raman shifts of C-H symmetric stretching band of methane in the vapor phase of CH4-H2O mixtures prepared in a high-pressure optical cell were also measured at temperatures between room temperature and 200 ??C, and pressures up to 37 MPa. The results show that the CH4 ??1 band position shifts to higher wavenumber as temperature increases. We also demonstrated that this Raman band shift is a simple function of methane vapor density, and, therefore, when combined with equation of state of methane, methane vapor pressures in the sample fluids at elevated temperatures can be calculated from measured Raman peak positions. This method can be applied to determine the pressure of CH4-bearing systems, such as methane-rich fluid inclusions from sedimentary basins or experimental fluids in hydrothermal diamond-anvil cell or other types of optical cell. ?? 2007 Elsevier Ltd. All rights reserved.

  6. Pressure Induced Local Structure Distortions in Cu(pyz)F2(H2O)2

    SciTech Connect

    Musfeldt, J.L.; Carr, G.; Liu, Z.; Li, S.; Kang, C.L., Jena, P.; Manson, J.L.; Schlueter, J.A. Whangbo, M.H.

    2011-06-06

    We employed infrared spectroscopy along with complementary lattice dynamics and spin density calculations to investigate pressure-driven local structure distortions in the copper coordination polymer Cu(pyz)F{sub 2}(H{sub 2}O){sub 2}. Here, pyz is pyrazine. Our study reveals rich and fully reversible local lattice distortions that buckle the pyrazine ring, disrupt the bc-plane O-H {hor_ellipsis} F hydrogen-bonding network, and reinforce magnetic property switching. The resiliency of the soft organic ring is a major factor in the stability of this material. Interestingly, the collective character of the lattice vibrations masks direct information on the Cu-N and Cu-O linkages through the series of pressure-induced Jahn-Teller axis switching transitions, although Cu-F bond softening is clearly identified above 3 GPa. These findings illustrate the importance of combined bulk and local probe techniques for microscopic structure determination in complex materials.

  7. Pressure-Induced Local Structure Distortions in Cu(pyz)F(2)(H(2)O)(2)

    SciTech Connect

    J Musfeldt; Z Liu; S Li; J Kang; C Lee; P Jena; J Manson; J Schlueter; G Carr; M Whangbo

    2011-12-31

    We employed infrared spectroscopy along with complementary lattice dynamics and spin density calculations to investigate pressure-driven local structure distortions in the copper coordination polymer Cu(pyz)F{sub 2}(H{sub 2}O){sub 2}. Here, pyz is pyrazine. Our study reveals rich and fully reversible local lattice distortions that buckle the pyrazine ring, disrupt the bc-plane O-H {hor_ellipsis} F hydrogen-bonding network, and reinforce magnetic property switching. The resiliency of the soft organic ring is a major factor in the stability of this material. Interestingly, the collective character of the lattice vibrations masks direct information on the Cu-N and Cu-O linkages through the series of pressure-induced Jahn-Teller axis switching transitions, although Cu-F bond softening is clearly identified above 3 GPa. These findings illustrate the importance of combined bulk and local probe techniques for microscopic structure determination in complex materials.

  8. Cross sections and transport of O- in H2O vapour at low pressures

    NASA Astrophysics Data System (ADS)

    Stojanovi?, Vladimir; Raspopovi?, Zoran; Mari?, Dragana; Petrovi?, Zoran Lj.

    2015-03-01

    The transport properties of O- ions in water vapour drifting in DC fields were obtained by using the Monte Carlo simulation technique with the scattering cross section sets assessed on the basis of Denpoh and Nanbu's technique and available experimental data. A swarm method is applied to determine recommended cross section set. For the first time in this work we present the transport parameters for the conditions of low to moderate reduced electric fields E/ N ( N is gas density) accounting for the effect of non-conservative collisions. The data are applicable in the limit of low pressures where cluster formation does not affect the transport or may be applied at higher pressures together with a model of cluster formation kinetics.

  9. The Sulfidation of Inconel 738 in H 2 \\/H 2 S\\/Ar Gas Mixture at 500900C

    Microsoft Academic Search

    W. Kai; Y. T. Lin; C. C. Yu; P. C. Chen; C.-H. Wu

    2004-01-01

    The sulfidation behavior of the cast nickel-base superalloy Inconel 738 (IN-738) was studied over the temperature range 500900C in three various ratios of H2\\/H2S\\/Ar atmospheres having sulfur partial pressures in the range 10-4102 Pa. The sulfidation kinetics followed the parabolic rate law in all cases, and the sulfidation rates increased with increasing temperature and sulfur partial pressure. In general, the

  10. Reduced atmospheric pressure in Radish: Alteration of NCER and transpiration at decreased oxygen partial pressures

    NASA Astrophysics Data System (ADS)

    Wehkamp, Cara Ann; Stasiak, Michael; Wheeler, Raymond; Dixon, Mike

    Fundamental to the future of space exploration is the development of advanced life support systems capable of maintaining crews for significant periods without re-supply from Earth. Significant research is focused on the development of bioregenerative life support systems to be used in conjunction with the current physico-chemical methods. These bioregenerative life support systems harness natural ecosystem processes and employ plant photosynthesis and transpiration to produce food, oxygen and regenerate water while consuming carbon dioxide. The forthcoming exploration of the Moon and Mars has prompted interest into the effects of hypobaria on plant development. Reduced atmospheric pressures will lessen the pressure gradient between the structure and the local environment thereby decreasing gas leakage and possibly the structural mass of the plant growth facility. In order to establish the optimal specifications for reduced pressure plant growth structures it is essential to determine the atmospheric pressure limits required for conventional plant development and growth. Due to its physiological importance, oxygen will compose a significant portion of these minimal environments. The objective of this study was to test the hypothesis that reduced atmospheric pressure and decreased oxygen partial pressures had no effect on radish productivity. Radishes (Raphanus sativa L. cv. Cherry Bomb II) were grown from seed in the University of Guelph's Hypobaric Plant Growth Chambers for a period of 21 days. Treatments included total pressures of 10, 33, 66 and 96 kPa and oxygen partial pressures of 2, 7, 14 and 20 kPa. Experiments demonstrated that reduced partial pressures of oxygen had a greater effect on radish growth than hypobaria. Results showed a reduction in net carbon exchange rate and transpiration with decreasing oxygen partial pressures leading to diminished productivity. Keywords: hypobaric, radish, oxygen partial pressure, variable pressure chamber, bioregenerative life support

  11. Effects of H2O on the phase behaviour of the forsterite-enstatite system at high pressures and temperatures and implications for the Earth

    Microsoft Academic Search

    Lin-Gun Liu

    1987-01-01

    In addition to many of the naturally occurring hydrous minerals known in the system MgO-SiO2-H2O, various dense hydrous magnesium silicates (10 -phase, phases A, B, C and D) have been synthesized by high-pressure and high-temperature experiments in the past two decades. In conjunction with these high-pressure hydrous phases, the effects of H2O on the observed phase transformations in the forsterite

  12. High Temperature and Pressure Steam-H2 Interaction with Candidate Advanced LWR Fuel Claddings

    SciTech Connect

    Pint, Bruce A [ORNL

    2012-08-01

    This report summarizes the work completed to evaluate cladding materials that could serve as improvements to Zircaloy in terms of accident tolerance. This testing involved oxidation resistance to steam or H{sub 2}-50% steam environments at 800-1350 C at 1-20 bar for short times. A selection of conventional alloys, SiC-based ceramics and model alloys were used to explore a wide range of materials options and provide guidance for future materials development work. Typically, the SiC-based ceramic materials, alumina-forming alloys and Fe-Cr alloys with {ge}25% Cr showed the best potential for oxidation resistance at {ge}1200 C. At 1350 C, FeCrAl alloys and SiC remained oxidation resistant in steam. Conventional austenitic steels do not have sufficient oxidation resistance with only {approx}18Cr-10Ni. Higher alloyed type 310 stainless steel is protective but Ni is not a desirable alloy addition for this application and high Cr contents raise concern about {alpha}{prime} formation. Higher pressures (up to 20.7 bar) and H{sub 2} additions appeared to have a limited effect on the oxidation behavior of the most oxidation resistant alloys but higher pressures accelerated the maximum metal loss for less oxidation resistant steels and less metal loss was observed in a H{sub 2}-50%H{sub 2}O environment at 10.3 bar. As some of the results regarding low-alloyed FeCrAl and Fe-Cr alloys were unexpected, further work is needed to fundamentally understand the minimum Cr and Al alloy contents needed for protective behavior in these environments in order to assist in alloy selection and guide alloy development.

  13. Interaction in NbVCo-H 2 and NbVFe-H 2 Systems under Hydrogen Pressure up to 2000 ATM

    Microsoft Academic Search

    S. A. Lushnikov; V. N. Verbetsky

    Interaction IMC (intermetallic compounds) NbVCo and NbVFe with hydrogen in wide temperatures and pressures intervals have\\u000a been investigated with PCT (pressure-composition) method. X-ray analyses has been shown that hydrogen introduction in lattice\\u000a was accompanied with volume increasing without rearrangement of metallic atoms.

  14. An experimental determination of the thermodynamic properties of H 2O-CO 2-NaCl fluids at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Joyce, David B.; Holloway, John R.

    1993-02-01

    Understanding the role of fluids in geological processes requires a knowledge of the mixing properties of common geological fluids. A technique for experimentally determining activity coefficients for H 2O in fluid mixtures at pressures and temperatures accessible to the internally heated pressure vessel (10 kbar, 1100C) is presented which uses a new fH2O buffer. The fH2O buffer involves the simultaneous control of fO2 (with Ni/NiO) and fH2 (with a hydrogen membrane), thereby buffering fH2O (or equivalently, aH2O through the reaction H 2 + 1/2O 2 = H 2O . After quenching the run, the sample is analyzed to determine the XH2O and, thus, the activity-composition relation for H 2O ( aH2O- XH2O). Reversals are obtained by simultaneously running capsules loaded with low and high XH2O, thereby allowing the equilibrium XH2O to be approached from both directions. Several experimental problems encountered during this study and their implications for the precise control of fH2 in hydrothermal experiments are discussed. Data were collected primarily in the H 2O-CO 2 system at 2 kbars, 550-850C, and at 4 kbars, 650C. At those conditions, the H 2O-CO 2 system generally shows small positive deviations from ideality. These results are in good agreement with the predictions of the MRK equation of state of HOLLWAY (1977) at low T ( T = 550 C) and are in good agreement with the predictions of the MRK equation of state of KERRICK And JACOBS (1981) at higher temperatures. At two conditions (2 kbar, 750C; 4 kbar, 650C), negative deviations from ideality are indicated at high XH2O. Some data were also collected in the H 2O-NaCl and H 2O-CO 2-NaCl systems. In the former, H 2O shows small positive deviations from ideality at 2 kbars, 850C, which increase with decreasing XH2O. In the H 2O-CO 2-NaCl system, isofugacity lines for H 2O were measured. In the two-phase region, these lines represent tie lines and, thus can be used to constrain the phase relations in the system.

  15. Study on the growth of heteroepitaxial cubic silicon carbide layers in atmospheric-pressure H2-based plasma.

    PubMed

    Kakiuchi, Hiroaki; Ohmi, Hiromasa; Yasutake, Kiyoshi

    2011-04-01

    The heteroepitaxial growths of cubic silicon carbide (3C-SiC) layers on Si(001) substrates are studied at a temperature of 800 degrees C in atmospheric-pressure (AP) plasma excited by a 150 MHz, very high-frequency (VHF) power using a porous carbon electrode. The effect of a very large C/Si ratio (-400) of the source molecules on the improvement of crystallinity of the resultant SiC layer is mainly investigated. For this purpose, we utilize the chemical transport of Si induced by AP H2/CH4 plasma instead of using SiH4 as the Si source. The layer crystallinity is characterized using reflection high-energy electron diffraction, transmission electron microscopy and infrared absorption spectroscopy. The results show that the SiC layer exhibits the (001) 3C-SiC growth aligned to the Si matrix epitaxially. Although the SiC layer contains a high density of defects originating presumably from anti-phase boundaries and twin boundaries, the layer crystallinity has been considerably improved in comparison with that of the layer grown with C/Si = 10. It is also demonstrated that the moderate dilution of H2 with He leads to a further improvement of the layer crystallinity. PMID:21776651

  16. Surface loss probability of atomic hydrogen for different electrode cover materials investigated in H2-Ar low-pressure plasmas

    NASA Astrophysics Data System (ADS)

    Sode, M.; Schwarz-Selinger, T.; Jacob, W.; Kersten, H.

    2014-07-01

    In an inductively coupled H2-Ar plasma at a total pressure of 1.5 Pa, the influence of the electrode cover material on selected line intensities of H, H2, and Ar are determined by optical emission spectroscopy and actinometry for the electrode cover materials stainless steel, copper, tungsten, Macor, and aluminum. Hydrogen dissociation degrees for the considered conditions are determined experimentally from the measured emission intensity ratios. The surface loss probability ?H of atomic hydrogen is correlated with the measured line intensities, and ?H values are determined for the considered materials. Without the knowledge of the atomic hydrogen temperature, ?H cannot be determined exactly. However, ratios of ?H values for different surface materials are in first order approximation independent of the atomic hydrogen temperature. Our results show that ?H of copper is equal to the value of stainless steel, ?H of Macor and tungsten is about 2 times smaller and ?H of aluminum about 5 times smaller compared with stainless steel. The latter ratio is in reasonable agreement with literature. The influence of the atomic hydrogen temperature TH on the absolute value is thoroughly discussed. For our assumption of TH = 600 K, we determine a ?H for stainless steel of 0.39 0.13.

  17. Study of thermodynamic properties of SiH4(H2)2 superconductor under high pressure

    NASA Astrophysics Data System (ADS)

    Durajski, A. P.

    2013-02-01

    The thermodynamic parameters of the superconducting state for SiH4(H2)2 compound under the pressure at 250 GPa have been investigated. The calculations have been made in the framework of the Eliashberg formalism. In particular, the free energy difference (?F) between the superconducting (S) and normal (N) state, the specific heat (C), as well as, the thermodynamic critical field (HC) have been determined. It has been shown that the considered thermodynamic functions are beyond the BCS predictions; the ratio CS(TC-CNTC)/CNTC decreases from 2.43 to 2.34 with increase of the Coulomb pseudopotential (???0.1,0.3), and the parameter TCCNTC/HC20 increases from 0.140 to 0.145. The numerical results have been supplemented with the interpolation approach.

  18. Differences between pressure-induced densification of LiCl-H2O glass and polyamorphic transition of H2O

    NASA Astrophysics Data System (ADS)

    Suzuki, Yoshiharu; Mishima, Osamu

    2009-04-01

    We perform volumetric measurements of LiCl aqueous solution up to 1.00 GPa in the 100-170 K range, examine the pressure-induced vitrification and densification, and draw the pressure-temperature-volume surface. The pressure-induced vitrification of the solution corresponds to the cooling-induced vitrification of the liquid. We found that the volumetric decrease of glassy solution during the densification is continuous and this behavior depends on the glassy state before the compression. Raman profiles of the glassy solutions before and after the densification are similar. In contrast, the polyamorphic transition from low-density amorphous ice (LDA) to high-density amorphous ice (HDA) is discontinuous and their Raman profile before and after the transition is distinct. These results suggest that the densification relates to the structural relaxation and differs intrinsically from the polyamorphic transition. Furthermore, the densification of HDA is observed under high pressure, suggesting that very high-density amorphous ice (VHDA) may be the densified HDA. In order to recognize a polyamorphic transition under a non-equilibrium condition correctly, evidence of not only large volume change but also some distinct structural changes in glassy state is necessary.

  19. Rheologies of H2O ices Ih, II, and III at high pressures - A progress report. [of relevance to Jovian and Saturn satellites

    NASA Technical Reports Server (NTRS)

    Kirby, S. H.; Durham, W. B.; Heard, H. C.

    1985-01-01

    Ordinary hexagonal ice (ice Ih) represents the stable crystalline form of H2O on the earth's surface. It is known that ice exists elsewhere in the solar system. Thus, several of the moons of Saturn and Jupiter are composed predominately of H2O and their surface temperatures are about 75 and 100 K. The pressures in the interior of some of the larger of the moons may be as high as 3 GPa. The involved pressures and temperatures extend far beyond the conditions over which the rheological laws for ice Ih can be confidently extrapolated. It is, therefore, necessary to obtain information regarding the rheologies of H2O ices in pressure and temperature ranges which had not yet been previously considered. Since 1981, over 100 triaxial compression tests have been conducted over a wide range of temperatures (77 to 258 K) and pressures (0.1 to 350 MPa). The present paper provides a progress report of these experiments.

  20. Partial discharge detection and analysis in low pressure environments

    NASA Astrophysics Data System (ADS)

    Liu, Xin

    Typical aerospace vehicles (aircraft and spacecraft) experience a wide range of operating pressures during ascending and returning to earth. Compared to the sea-level atmospheric pressure (760 Torr), the pressure at about 60 km altitude is 2 Torr. The performance of the electric power system components of the aerospace vehicles must remain reliable even under such sub-atmospheric operating conditions. It is well known that the dielectric strength of gaseous insulators, while the electrode arrangement remains unchanged, is pressure dependent. Therefore, characterization of the performance and behavior of the electrical insulation in flight vehicles in low-pressure environments is extremely important. Partial discharge testing is one of the practical methods for evaluating the integrity of electrical insulation in aerospace vehicles. This dissertation describes partial discharge (PD) measurements performed mainly with 60 Hz ac energization in air, argon and helium, for pressures between 2 and 760 Torr. Two main electrode arrangements were used. One was a needle-plane electrode arrangement with a Teflon insulating barrier. The other one was a twisted pair of insulated conductors taken from a standard aircraft wiring harness. The measurement results are presented in terms of typical PD current pulse waveforms and waveform analysis for both main electrode arrangements. The evaluation criteria are the waveform polarity, magnitude, shape, rise time, and phase angle (temporal location) relative to the source voltage. Two-variable histograms and statistical averages of the PD parameters are presented. The PD physical mechanisms are analyzed. For PD pattern recognition, both statistical methods (such as discharge parameter dot pattern representation, discharge parameter phase distribution, statistical operator calculations, and PD fingerprint development) and wavelet transform applications are investigated. The main conclusions of the dissertation include: (1) The PD current pulse waveforms are dependent on the pressure. (2) The rise time of the waveform is another effective PD current pulse characteristic indicator. (3) PD fingerprint patterns that are already available for atmospheric pressure (760 Torr) conditions are inadequate for the evaluation of PD pulses at low pressures. (4) Various wavelet transform techniques can be used effectively for PD pulse signal denoising purposes, and for PD pulse waveform transient feature recognition.

  1. Influence of temperature gradients on partial pressures in a low-pressure chemical-vapor-deposition reactor

    NASA Astrophysics Data System (ADS)

    Oosterlaken, T. G. M.; Leusink, G. J.; Janssen, G. C. A. M.; Radelaar, S.; Kuijlaars, K. J.; Kleijn, C. R.; van den Akker, H. E. A.

    1994-09-01

    Measurements and calculations of the influence of temperature gradients on the partial pressures of the gas species in a cold-wall chemical-vapor-deposition reactor are presented. The experiments were performed at low pressures (300-500 Pa total pressure) and gas mixtures consisting of hydrogen, nitrogen, and tetrafluoromethane. The partial pressures were determined by Raman spectroscopy. The Soret effect (or thermal diffusion) has a large influence on the partial pressures of heavy gases in the vicinity of the heated wafer. In some cases a decrease in partial pressure of 20% compared to the inlet partial pressures was observed. Numerical calculations were performed to predict the behavior of the gas mixture. For mixtures under investigation the gas temperatures as well as the changes in partial pressures due to the Soret effect were predicted correctly.

  2. Pressure-Swing Adsorption Separation of H2S from CO2 with Molecular Sieves 4A, 5A, and 13X

    Microsoft Academic Search

    Manolis M. Tomadakis; Howell H. Heck; Marwan E. Jubran; Khalid Al-Harthi

    2011-01-01

    The separation of bulk quantities of H2S from CO2 was investigated through a series of pressure-swing adsorption experiments utilizing 4A, 5A, and 13X molecular sieves. High selectivity of H2S over CO2 was encountered for all sieves, particularly for the 13X and 5A. Practically pure CO2 was produced in the adsorption stage with fresh 5A and 13X sieves, at high product

  3. Decomposition reaction of H 2O 2 over Pd\\/C catalyst in an aqueous medium at high pressure: Detailed kinetic study and modelling

    Microsoft Academic Search

    Teresa Moreno; Juan Garca-Serna; Mara Jos Cocero

    2011-01-01

    Decomposition of H2O2 is an undesired side reaction that occurs during the direct synthesis of H2O2 over Pd\\/C catalysts. Experiments have been carried out to understand the influence of pressure (0.27.5MPag), temperature (2350C), pH, halide concentration, catalyst and inert gas in decomposition. A model considering these effects is proposed, achieving average deviations lower than 5%. It has been found that

  4. 21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Indwelling blood oxygen partial pressure (PO2) analyzer...Diagnostic Devices 868.1200 Indwelling blood oxygen partial pressure (PO2 ) analyzer. (a) Identification. An indwelling blood oxygen partial pressure (PO2 )...

  5. 21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false Indwelling blood oxygen partial pressure (PO2) analyzer...Diagnostic Devices 868.1200 Indwelling blood oxygen partial pressure (PO2 ) analyzer. (a) Identification. An indwelling blood oxygen partial pressure (PO2 )...

  6. 21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false Indwelling blood oxygen partial pressure (PO2) analyzer...Diagnostic Devices 868.1200 Indwelling blood oxygen partial pressure (PO2 ) analyzer. (a) Identification. An indwelling blood oxygen partial pressure (PO2 )...

  7. 21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false Indwelling blood oxygen partial pressure (PO2) analyzer...Diagnostic Devices 868.1200 Indwelling blood oxygen partial pressure (PO2 ) analyzer. (a) Identification. An indwelling blood oxygen partial pressure (PO2 )...

  8. 21 CFR 868.1200 - Indwelling blood oxygen partial pressure (PO2) analyzer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Indwelling blood oxygen partial pressure (PO2) analyzer...Diagnostic Devices 868.1200 Indwelling blood oxygen partial pressure (PO2 ) analyzer. (a) Identification. An indwelling blood oxygen partial pressure (PO2 )...

  9. RAMAN SPECTROSCOPY OF THE CO2-H2O SYSTEM Presented in Partial Fulfillment of the Requirements for

    E-print Network

    . In addition, a solubility study is presented and determined the Henry's law constants to over a temperature range of 27 to 80 o C and a pressure range of 5 to 13 atm. At 27 o C, Henry's law constant was determined to be 3.42 x 10-2 M/atm. With increasing temperature, Henry's law constant decreased

  10. First experimental determination of the absolute gas-phase rate coefficient for the reaction of OH with 4-hydroxy-2-butanone (4H2B) at 294 K by vapor pressure measurements of 4H2B.

    PubMed

    El Dib, Gisle; Sleiman, Chantal; Canosa, Andr; Travers, Daniel; Courbe, Jonathan; Sawaya, Terufat; Mokbel, Ilham; Chakir, Abdelkhaleq

    2013-01-10

    The reaction of the OH radicals with 4-hydroxy-2-butanone was investigated in the gas phase using an absolute rate method at room temperature and over the pressure range 10-330 Torr in He and air as diluent gases. The rate coefficients were measured using pulsed laser photolysis (PLP) of H(2)O(2) to produce OH and laser induced fluorescence (LIF) to measure the OH temporal profile. An average value of (4.8 1.2) 10(-12) cm(3) molecule(-1) s(-1) was obtained. The OH quantum yield following the 266 nm pulsed laser photolysis of 4-hydroxy-2-butanone was measured for the first time and found to be about 0.3%. The investigated kinetic study required accurate measurements of the vapor pressure of 4-hydroxy-2-butanone, which was measured using a static apparatus. The vapor pressure was found to range from 0.056 to 7.11 Torr between 254 and 323 K. This work provides the first absolute rate coefficients for the reaction of 4-hydroxy-2-butanone with OH and the first experimental saturated vapor pressures of the studied compound below 311 K. The obtained results are compared to those of the literature and the effects of the experimental conditions on the reactivity are examined. The calculated tropospheric lifetime obtained in this work suggests that once emitted into the atmosphere, 4H2B may contribute to the photochemical pollution in a local or regional scale. PMID:23210721

  11. Influence of H2S Content on CO2 Corrosion Behaviors of N80 Tubing Steel

    Microsoft Academic Search

    D. Jingen; Y. Wei; L. Xiaorong; D. Xiaoqin

    2011-01-01

    The corrosion behaviors of N80 steel in pure CO2 and at different partial pressure ratios of CO2\\/H2S were tested by high-temperature and high-pressure autoclave. At 90C, with the additional H2S to pure CO2, the surface corrosion condition improved greatly and the corrosion rates were lower than in pure CO2 condition. With the increase of partial pressure ratio, the corrosion rate

  12. Assessment of kinetic modeling for lean H2/CH4/O2/diluent flames at high pressures

    E-print Network

    Ju, Yiguang

    CO, CO2, H2O, CH4 and other small hydrocarbons (synthetic gas or "syngas") from coal or biomass: Hydrogen; Methane; Syngas; Flame speed; Chemical mechanism 1. Introduction The H2/O2 reaction system gasification [2]. Typical syngas mixtures can contain significant amounts of small molecular weight

  13. H2O activity in concentrated NaCl solutions at high pressures and temperatures measured by the brucite-periclase equilibrium

    Microsoft Academic Search

    L. Y. Aranovich; R. C. Newton

    1996-01-01

    H2O activities in concentrated NaCl solutions were measured in the ranges 600 900 C and 2 15 kbar and at NaCl concentrations up to halite saturation by depression of the brucite (Mg(OH)2) periclase (MgO) dehydration equilibrium. Experiments were made in internally heated Ar pressure apparatus at 2 and 4.2 kbar and in 1.91-cm-diameter piston-cylinder apparatus with NaCl pressure medium at

  14. Constructing and testing the thermodynamic limits of synthetic NAD(P)H:H2 pathways.

    PubMed

    Veit, Andrea; Akhtar, M Kalim; Mizutani, Taeko; Jones, Patrik R

    2008-09-01

    NAD(P)H:H(2) pathways are theoretically predicted to reach equilibrium at very low partial headspace H(2) pressure. An evaluation of the directionality of such near-equilibrium pathways in vivo, using a defined experimental system, is therefore important in order to determine its potential for application. Many anaerobic microorganisms have evolved NAD(P)H:H(2) pathways; however, they are either not genetically tractable, and/or contain multiple H(2) synthesis/consumption pathways linked with other more thermodynamically favourable substrates, such as pyruvate. We therefore constructed a synthetic ferredoxin-dependent NAD(P)H:H(2) pathway model system in Escherichia coli BL21(DE3) and experimentally evaluated the thermodynamic limitations of nucleotide pyridine-dependent H(2) synthesis under closed batch conditions. NADPH-dependent H(2) accumulation was observed with a maximum partial H(2) pressure equivalent to a biochemically effective intracellular NADPH/NADP(+) ratio of 13:1. The molar yield of the NADPH:H(2) pathway was restricted by thermodynamic limitations as it was strongly dependent on the headspace:liquid ratio of the culture vessels. When the substrate specificity was extended to NADH, only the reverse pathway directionality, H(2) consumption, was observed above a partial H(2) pressure of 40 Pa. Substitution of NADH with NADPH or other intermediates, as the main electron acceptor/donor of glucose catabolism and precursor of H(2), is more likely to be applicable for H(2) production. PMID:21261858

  15. Wavelength-modulation spectroscopy near 1.4 m for measurements of H2O and temperature in high-pressure and -temperature gases

    NASA Astrophysics Data System (ADS)

    Goldenstein, C. S.; Spearrin, R. M.; Schultz, I. A.; Jeffries, J. B.; Hanson, R. K.

    2014-05-01

    The development, validation and demonstration of a two-color tunable diode laser (TDL) absorption sensor for measurements of temperature and H2O in high-pressure and high-temperature gases are presented. This sensor uses first-harmonic-normalized wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f/1f) to account for non-absorbing transmission losses and emission encountered in harsh, high-pressure environments. Two telecommunications-grade TDLs were used to probe H2O absorption transitions near 1391.7 and 1469.3 nm. The lasers were frequency-multiplexed and modulated at 160 and 200 kHz to enable a measurement bandwidth up to 30 kHz along a single line-of-sight. In addition, accurate measurements are enabled at extreme conditions via an experimentally derived spectroscopic database. This sensor was validated under low-absorbance (<0.05) conditions in shock-heated H2O-N2 mixtures at temperatures and pressures from 700 to 2400 K and 2 to 25 atm. There, this sensor recovered the known temperature and H2O mole fraction with a nominal accuracy of 2.8% and 4.7% RMS, respectively. Lastly, this sensor resolved expected transients with high bandwidth and high precision in a reactive shock tube experiment and a pulse detonation combustor.

  16. The role of dissociative attachment from Rydberg states in enhancing H - concentration in moderate- and low-pressure H 2 plasma sources

    NASA Astrophysics Data System (ADS)

    Hassouni, K.; Gicquel, A.; Capitelli, M.

    1998-07-01

    A numerical code, recently developed for describing the kinetics of H 2 microwave discharges obtained in diamond deposition plasma reactors, was used to estimate the importance of dissociative attachment from H 2 Rydberg states in enhancing the production of H - in this kind of discharge. It was also used to investigate H - production in multicusp low-pressure magnetic plasmas. Results show that the dissociative attachment from Rydberg states can be as important as the mechanism involving vibrationally excited molecules in both types of plasmas.

  17. Partial Pressures in Equilibrium with Group IV Tellurides. III. Germanium Telluride

    Microsoft Academic Search

    Robert F. Brebrick

    1964-01-01

    The partial pressures of Te2(g) and GeTe(g) over Ge&sngbnd;Te condensed phases between 1 and 52 at. % Te have been determined between 525 and 940C by measuring the optical density of the vapor. Partial optical densities due to each species are calculated and converted to partial pressures by assuming Beer's law and published vapor pressures.Over Te-saturated GeTe(c), pTe2 reaches a

  18. Direct measurement of oxygen partial pressure in a flying bumblebee.

    PubMed

    Komai, Y

    2001-09-01

    The gas transport system of a bumblebee was investigated by measuring the oxygen partial pressure P(O(2)) in the wing muscle. In the resting bee, P(O(2)) showed a regular pattern of fluctuation with a typical period of 70-120s. Fluctuations in muscular P(O(2)) were associated with intermittent abdominal pumping. Ventilation by abdominal movements may not be necessary during rest because P(O(2)) is high (8.5-9.2kPa) in the anaesthetised bee. Thermal effects on muscular P(O(2)) were examined by cooling the bee, causing the amplitude of P(O(2)) fluctuations to increase. In most flight experiments, the bee started to fly after elevating muscle P(O(2)) by abdominal pumping; muscle P(O(2)) then decreased at the onset of flight. However, when a flight began without pre-flight ventilation, P(O(2)) increased monotonically. During flight, muscle P(O(2)) reached a mean level (6.36+/-1.83kPa) that was much higher than the lowest value recorded during discontinuous ventilation during rest. The bumblebee effectively uses abdominal movements to assist in convective gas transport not only during flight but also at rest. PMID:11551988

  19. The rate constant of the reaction NCN + H2 and its role in NCN and NO modeling in low pressure CH4/O2/N2-flames.

    PubMed

    Faheber, Nancy; Lamoureux, Nathalie; Friedrichs, Gernot

    2015-06-28

    Bimolecular reactions of the NCN radical play a key role in modeling prompt-NO formation in hydrocarbon flames. The rate constant of the so-far neglected reaction NCN + H2 has been experimentally determined behind shock waves under pseudo-first order conditions with H2 as the excess component. NCN3 thermal decomposition has been used as a quantitative high temperature source of NCN radicals, which have been sensitively detected by difference UV laser absorption spectroscopy at [small nu, Greek, tilde] = 30383.11 cm(-1). The experiments were performed at two different total densities of ?? 4.1 10(-6) mol cm(-3) and ?? 7.4 10(-6) mol cm(-3) (corresponding to pressures between p = 324 mbar and p = 1665 mbar) and revealed a pressure independent reaction. In the temperature range 1057 K < T < 2475 K, the overall rate constant can be represented by the Arrhenius expression k/(cm(3) mol(-1) s(-1)) = 4.1 10(13) exp(-101 kJ mol(-1)/RT) (?log?k = 0.11). The pressure independent reaction as well as the measured activation energy is consistent with a dominating H abstracting reaction channel yielding the products HNCN + H. The reaction NCN + H2 has been implemented together with a set of reactions for subsequent HNCN and HNC chemistry into the detailed GDFkin3.0_NCN mechanism for NOx flame modeling. Two fuel-rich low-pressure CH4/O2/N2-flames served as examples to quantify the impact of the additional chemical pathways. Although the overall NCN consumption by H2 remains small, significant differences have been observed for NO yields with the updated mechanism. A detailed flux analysis revealed that HNC, mainly arising from HCN/HNC isomerization, plays a decisive role and enhances NO formation through a new HNC ? HNCO ? NH2? NH ? NO pathway. PMID:26017854

  20. Molecular dynamics computer simulations of the of the ternary H2O-CO2NaCl fluid under high temperatures and pressures

    Microsoft Academic Search

    A. G. Kalinichev; R. J. Kirkpatrick; T. V. Gerya

    2002-01-01

    Water and carbon dioxide are the most abundant volatile species in the Earth's outer parts. They represent the common solvents in which varying amounts of other volatiles and salts are dissolved under high-temperature, high-pressure thermodynamic conditions to form complex hydrothermal and metamorphic fluids. Thus, aqueous mixtures in the system H2O-CO2-NaCl can serve as a good approximation for most crustal and

  1. EFFECTS OF H2O AND CO2 DILUTION ON THE CATALYTIC AND GAS-PHASE COMBUSTION OF METHANE OVER PLATINUM AT ELEVATED PRESSURES

    Microsoft Academic Search

    MICHAEL REINKE; JOHN MANTZARAS; ROLF BOMBACH; SABINE SCHENKER; NICLAS TYLLI; KONSTANTINOS BOULOUCHOS

    2007-01-01

    The impact of large exhaust gas dilution (up to 59.5% H2O and 30.3% CO2 per vol.) on the heterogeneous (catalytic) and homogeneous (gas-phase) steady combustion of fuel-lean CH4\\/O2\\/N2 mixtures over platinum has been investigated experimentally and numerically at pressures of 5 to 14 bar. In situ, one-dimensional Raman measurements of major gas-phase species concentrations and planar laser induced fluorescence (LIF)

  2. H 2 O activity in concentrated NaCl solutions at high pressures and temperatures measured by the brucite-periclase equilibrium

    Microsoft Academic Search

    L. Y. Aranovich; R. C. Newton

    1996-01-01

    H2O activities in concentrated NaCl solutions were measured in the ranges 600900?C and 215 kbar and at NaCl concentrations\\u000a up to halite saturation by depression of the brucite (Mg(OH)2) periclase (MgO) dehydration equilibrium. Experiments were made in internally heated Ar pressure apparatus at 2 and 4.2\\u000a kbar and in 1.91-cm-diameter piston-cylinder apparatus with NaCl pressure medium at 4.2, 7,

  3. Pressure dependence of the absolute rate constant for the reaction OH + C2H2 from 228 to 413 K

    NASA Technical Reports Server (NTRS)

    Michael, J. V.; Nava, D. F.; Payne, W. A.; Stief, L. J.; Borkowski, R. P.

    1980-01-01

    The pressure dependence of the absolute rate constant for the reaction of the hydroxyl radical with acetylene, important in both atmospheric and combustion chemistry, is determined for temperatures between 228 and 413 K. The flash photolysis-resonance fluorescence technique was employed at five temperatures over wide ranges of pressure and acetylene concentrations, with the OH produced by water photolysis and hydroxyl resonance fluorescent photons measured by multiscaling techniques. Results indicate that, except at the lowest temperature, the bimolecular rate constant for the reaction depends strongly on total pressure, with the pressure effect becoming more pronounced with increasing temperature. At limiting high pressures, the rate constant is found to be equal to 6.83 + or - 1.19 x 10 to the -12th exp (-646 + or - 47/T) cu cm/molecule per sec, where T is the temperature. Results thus demonstrate the importance of environmental conditions in theoretical studies of atmospheric and combustion product compositions

  4. Partial discharge detection and analysis in low pressure environments

    Microsoft Academic Search

    Xin Liu

    2006-01-01

    Typical aerospace vehicles (aircraft and spacecraft) experience a wide range of operating pressures during ascending and returning to earth. Compared to the sea-level atmospheric pressure (760 Torr), the pressure at about 60 km altitude is 2 Torr. The performance of the electric power system components of the aerospace vehicles must remain reliable even under such sub-atmospheric operating conditions. It is

  5. Kinetics of CH2OO reactions with SO2, NO2, NO, H2O and CH3CHO as a function of pressure.

    PubMed

    Stone, Daniel; Blitz, Mark; Daubney, Laura; Howes, Neil U M; Seakins, Paul

    2014-01-21

    Kinetics of CH2OO Criegee intermediate reactions with SO2, NO2, NO, H2O and CH3CHO and CH2I radical reactions with NO2 are reported as a function of pressure at 295 K. Measurements were made under pseudo-first-order conditions using flash photolysis of CH2I2-O2-N2 gas mixtures in the presence of excess co-reagent combined with monitoring of HCHO reaction products by laser-induced fluorescence (LIF) spectroscopy and, for the reaction with SO2, direct detection of CH2OO by photoionisation mass spectrometry (PIMS). Rate coefficients for CH2OO + SO2 and CH2OO + NO2 are independent of pressure in the ranges studied and are (3.42 0.42) 10(-11) cm(3) s(-1) (measured between 1.5 and 450 Torr) and (1.5 0.5) 10(-12) cm(3) s(-1) (measured between 25 and 300 Torr), respectively. The rate coefficient for CH2OO + CH3CHO is pressure dependent, with the yield of HCHO decreasing with increasing pressure. Upper limits of 2 10(-13) cm(3) s(-1) and 9 10(-17) cm(3) s(-1) are placed on the rate coefficients for CH2OO + NO and CH2OO + H2O, respectively. The upper limit for the rate coefficient for CH2OO + H2O is significantly lower than has been reported previously, with consequences for modelling of atmospheric impacts of CH2OO chemistry. PMID:24287566

  6. Quantum scattering calculations for H2S-He between 1-600 K in comparison with pressure broadening, shift, and time resolved double resonance experiments

    NASA Astrophysics Data System (ADS)

    Ball, Christopher D.; Mengel, Markus; De Lucia, Frank C.; Woon, David E.

    1999-11-01

    We have performed quantum scattering calculations to predict pressure broadening, pressure shift, and inelastic depopulation cross-sections for the rotational transitions 11,0?10,1 and 22,0?21,1 of the H2S molecule in collision with helium atoms over a temperature range from 1 to 600 K. The calculated cross-sections are compared with experimental values obtained by millimeter wave spectroscopic techniques and the collisional cooling method. We observe good agreement between theory and experiment over the temperature region from 20 to 600 K, but increasing differences below 20 K. Possible reasons for the deviations at lower temperatures are discussed. The calculations also illustrate the contribution of elastic collisions to the pressure broadening cross-sections.

  7. Co-gasification of different rank coals with biomass and petroleum coke in a high-pressure reactor for H(2)-rich gas production.

    PubMed

    Fermoso, J; Arias, B; Gil, M V; Plaza, M G; Pevida, C; Pis, J J; Rubiera, F

    2010-05-01

    Four coals of different rank were gasified, using a steam/oxygen mixture as gasifying agent, at atmospheric and elevated pressure in a fixed bed reactor fitted with a solids feeding system in continuous mode. Independently of coal rank, an increase in gasification pressure led to a decrease in H(2) + CO production and carbon conversion. Gasification of the different rank coals revealed that the higher the carbon content and reactivity, the greater the hydrogen production. Co-gasification experiments of binary (coal-biomass) and ternary blends (coal-petcoke-biomass) were conducted at high pressure to study possible synergetic effects. Interactions between the blend components were found to modify the gas production. An improvement in hydrogen production and cold gas efficiency was achieved when the coal was gasified with biomass. PMID:20061144

  8. High-Temperature Phase Transitions in CsH2PO4 Under Ambient and High-Pressure Conditions: A Synchrotron X-ray Diffraction Study

    SciTech Connect

    Botez,C.; Hermosillo, J.; Zhang, J.; Qian, J.; Zhao, Y.; Majzlan, J.; Chianelli, R.; Pantea, C.

    2007-01-01

    To clarify the microscopic origin of the temperature-induced three-order-of-magnitude jump in the proton conductivity of CsH2PO4 (superprotonic behavior), we have investigated its crystal structure modifications within the 25-300 C temperature range under both ambient- and high-pressure conditions using synchrotron x-ray diffraction. Our high-pressure data show no indication of the thermal decomposition/polymerization at the crystal surface recently proposed as the origin of the enhanced proton conductivity. Instead, we found direct evidence that the superprotonic behavior of the title material is associated with a polymorphic structural transition to a high-temperature cubic phase. Our results are in excellent agreement with previous high-pressure ac impedance measurements.

  9. Potential hydrogen and oxygen partial pressures in legacy plutonium oxide packages at Oak Ridge

    SciTech Connect

    Veirs, Douglas K. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-07-07

    An approach to estimate the maximum hydrogen and oxygen partial pressures within sealed containers is described and applied to a set of packages containing high-purity plutonium dioxide. The approach uses experimentally determined maximum hydrogen and oxygen partial pressures and scales the experimentally determined pressures to the relevant packaged material properties. The important material properties are the specific wattage and specific surface area (SSA). Important results from the experimental determination of maximum partial pressures are (1) the ratio of hydrogen to oxygen is stoichiometric, and (2) the maximum pressures increase with increasing initial rates of production. The material properties that influence the rates are the material specific wattage and the SSA. The unusual properties of these materials, high specific wattage and high SSA, result in higher predicted maximum pressures than typical plutonium dioxide in storage. The pressures are well within the deflagration range for mixtures of hydrogen and oxygen.

  10. A "uniform" heterogeneous photocatalyst: integrated p-n type CuInS2/NaInS2 nanosheets by partial ion exchange reaction for efficient H2 evolution.

    PubMed

    Hu, Peng; Ngaw, Chee Keong; Tay, Yee Yan; Cao, Shaowen; Barber, James; Tan, Timothy Thatt Yang; Loo, Say Chye Joachim

    2015-05-21

    Single-crystalline-like P-N type CuInS2/NaInS2 heterogeneous nanosheets were synthesized by partial cation exchange reaction and show highly improved photocatalytic H2 evolution activity attributed to the increased efficiency of interfacial charge transfer. PMID:25959829

  11. Feature Article Negative pressure dependence of mass burning rates of H2/CO/O2/diluent flames

    E-print Network

    Ju, Yiguang

    for efficient, low-emission power generation with increased potential for carbon capture and storage (CCS but is demonstrated here to significantly impact predictions of lean high pressure flames using rates within its

  12. Effects of hydrogen partial pressure on the structure and properties of sputtered silicon layers

    Microsoft Academic Search

    A. Achiq; R Rizk; F Gourbilleau; P Voivenel

    1999-01-01

    Hydrogenated silicon films were deposited by RF sputtering with various hydrogen partial pressures. The samples were examined by infrared absorption spectroscopy, transmission electron microscopy and optical absorption techniques, in addition to dark conductivity measurements. For low hydrogen pressure ratios (? 20%), the deposited hydrogenated films were completely amorphous, but they increasingly crystallize for increasingly higher ratio of hydrogen pressure. Beside

  13. Method and apparatus for monitoring oxygen partial pressure in air masks

    NASA Technical Reports Server (NTRS)

    Kelly, Mark E. (Inventor); Pettit, Donald R. (Inventor)

    2006-01-01

    Method and apparatus are disclosed for monitoring an oxygen partial pressure in an air mask and providing a tactile warning to the user. The oxygen partial pressure in the air mask is detected using an electrochemical sensor, the output signal from which is provided to a comparator. The comparator compares the output signal with a preset reference value or range of values representing acceptable oxygen partial pressures. If the output signal is different than the reference value or outside the range of values, the air mask is vibrated by a vibrating motor to alert the user to a potentially hypoxic condition.

  14. Conductive and ferromagnetic contributions of H in ZnCoO using H2 hot isostatic pressure

    NASA Astrophysics Data System (ADS)

    Chan Cho, Yong; Lee, Seunghun; Hyun Nahm, Ho; Jae Kim, Su; Hong Park, Chul; Yeon Lee, Su; Kim, Sung-Kyu; Ryong Cho, Chae; Koinuma, Hideomi; Jeong, Se-Young

    2012-03-01

    For highly H injected ZnCoO achieved by simultaneous high pressure (1000 bar) and annealing using a hot isostatic pressure (HIP), we report electrical and magnetic properties with first-principles calculation results. The HIP process increased the carrier concentration by 103 times and restored the conductivity up to that of H injected ZnO. Interestingly, with maintaining high conductivity, the extended HIP processing time significantly enhanced the short-ranged spin orderings of Co-H-Co complexes. Based on the experimental and theoretical results, we proposed the explanation for the relation magnetic characteristics and the behavior of hydrogen triggering spin ordering for spintronic applications.

  15. Hybrid model of neutral diffusion, sheaths, and the ? to ? transition in an atmospheric pressure He/H2O bounded rf discharge

    NASA Astrophysics Data System (ADS)

    Ding, Ke; Lieberman, M. A.; Lichtenberg, A. J.

    2014-07-01

    Water is a trace gas of interest for plasma-based medical applications. We use a two-temperature hybrid global model to simulate a chemically complex, bounded, He/H2O atmospheric pressure discharge, including 43 species with clusters up to {H_{19}O_9^+} . The discharge is embedded in a larger volume, in which the trace gas fraction is controlled, leading to depletion of water within the discharge and diffusive flows of reaction products to the walls. For a planar discharge with a 1 cm electrode radius and a 0.5 mm gap, driven at 13.56 MHz, we determine the depletion and diffusion effects and the ? to ? transition, over a range of rf currents (100-1600 A m-2) and external H2O concentrations (500-10?000 ppm). The transition from the low power ?-mode to the high power ?-mode is accompanied by a collapse of the bulk electron temperature, an increase in the density and a decrease in the sheath width. At the highest external H2O concentration studied, there are no low current (?-mode) solutions because the sheath widths fill the device. The ?-mode is recovered at larger gaps (e.g., 1 mm) or higher frequencies (e.g., 27.12 MHz). The higher mass cluster densities decrease rapidly with increasing gas temperature. Each simulation takes about two minutes on a medium size laptop computer, allowing exploration of a large input parameter space.

  16. MEASUREMENT OF PARTIAL VAPOR PRESSURE OF AMMONIA OVER ACID AMMONIUM SULFATE SOLUTIONS BY AN INTEGRAL METHOD

    EPA Science Inventory

    We present a simple, integral, passive method for measuring partial vapor pressure. ntegral methods are useful tools when dealing with very low concentrations because collection over extended periods increases the analytical sensitivity. assive methods have the advantage of not i...

  17. Pressure-Induced Magnetic Crossover Driven by Hydrogen Bonding in CuF2(H2O)2(3-chloropyridine)

    NASA Astrophysics Data System (ADS)

    O'Neal, Kenneth R.; Brinzari, Tatiana V.; Wright, Joshua B.; Ma, Chunli; Giri, Santanab; Schlueter, John A.; Wang, Qian; Jena, Puru; Liu, Zhenxian; Musfeldt, Janice L.

    2014-08-01

    Hydrogen bonding plays a foundational role in the life, earth, and chemical sciences, with its richness and strength depending on the situation. In molecular materials, these interactions determine assembly mechanisms, control superconductivity, and even permit magnetic exchange. In spite of its long-standing importance, exquisite control of hydrogen bonding in molecule-based magnets has only been realized in limited form and remains as one of the major challenges. Here, we report the discovery that pressure can tune the dimensionality of hydrogen bonding networks in CuF2(H2O)2(3-chloropyridine) to induce magnetic switching. Specifically, we reveal how the development of exchange pathways under compression combined with an enhanced ab-plane hydrogen bonding network yields a three dimensional superexchange web between copper centers that triggers a reversible magnetic crossover. Similar pressure- and strain-driven crossover mechanisms involving coordinated motion of hydrogen bond networks may play out in other quantum magnets.

  18. The quenching effect of hydrogen on the nitrogen in metastable state in atmospheric-pressure N2-H2 microwave plasma torch

    NASA Astrophysics Data System (ADS)

    Li, Shou-Zhe; Zhang, Xin; Chen, Chuan-Jie; Zhang, Jialiang; Wang, Yong-Xing; Xia, Guang-Qing

    2014-07-01

    The atmospheric-pressure microwave N2-H2 plasma torch is generated and diagnosed by optical emission spectroscopy. It is found that a large amount of N atoms and NH radicals are generated in the plasma torch and the emission intensity of N2+ first negative band is the strongest over the spectra. The mixture of hydrogen in nitrogen plasma torch causes the morphology of the plasma discharge to change with appearance that the afterglow shrinks greatly and the emission intensity of N2+ first negative band decreases with more hydrogen mixed into nitrogen plasma. In atmospheric-pressure microwave-induced plasma torch, the hydrogen imposes a great influence on the characteristics of nitrogen plasma through the quenching effect of the hydrogen on the metastable state of N2.

  19. Pressure-Induced Magnetic Crossover Driven by Hydrogen Bonding in CuF2(H2O)2(3-chloropyridine)

    PubMed Central

    O'Neal, Kenneth R.; Brinzari, Tatiana V.; Wright, Joshua B.; Ma, Chunli; Giri, Santanab; Schlueter, John A.; Wang, Qian; Jena, Puru; Liu, Zhenxian; Musfeldt, Janice L.

    2014-01-01

    Hydrogen bonding plays a foundational role in the life, earth, and chemical sciences, with its richness and strength depending on the situation. In molecular materials, these interactions determine assembly mechanisms, control superconductivity, and even permit magnetic exchange. In spite of its long-standing importance, exquisite control of hydrogen bonding in molecule-based magnets has only been realized in limited form and remains as one of the major challenges. Here, we report the discovery that pressure can tune the dimensionality of hydrogen bonding networks in CuF2(H2O)2(3-chloropyridine) to induce magnetic switching. Specifically, we reveal how the development of exchange pathways under compression combined with an enhanced ab-plane hydrogen bonding network yields a three dimensional superexchange web between copper centers that triggers a reversible magnetic crossover. Similar pressure- and strain-driven crossover mechanisms involving coordinated motion of hydrogen bond networks may play out in other quantum magnets. PMID:25116701

  20. Viscosity of coal slags as a function of composition, temperature, and oxygen partial pressure

    Microsoft Academic Search

    J. Chen; S. Greenberg; R. B. Poeppel

    1984-01-01

    The viscosities of 22 synthetic and three natural coal slags were measured as a function of temperature under oxygen partial pressures typical of slagging coal gasifier conditions (approx. 10⁻⁸ to approx. 10⁻⁹ atm) and, in some cases, under an ambient air environment. The viscosity of any given slag composition is a single-valued function of temperature and oxygen partial pressure and

  1. Viscosity of synthetic coal slags as a function of composition, temperature and oxygen partial pressure

    Microsoft Academic Search

    K. S. Vorres; S. Greenberg; R. B. Poeppel

    1984-01-01

    The viscosities of 21 synthetic coal slags (30 to 50 wt % SiO) were measured as a function of temperature under oxygen partial pressures (about 10⁻⁸ to 10⁻⁹ atm) and, in some cases, under an ambient air environment. The viscosity of any given slag composition is a single-valued function of the temperature and oxygen partial pressure and does not exhibit

  2. Effects of operating pressure on flame oscillation and emission characteristics in a partially premixed swirl combustor

    SciTech Connect

    Kim, Jong-Ryul [Graduate School, Department of Mechanical Engineering, Pusan National University (Korea, Republic of); Choi, Gyung-Min; Kim, Duck-Jool [School of Mechanical Engineering, Pusan National University (Korea, Republic of)

    2011-01-15

    The influence of varying combustor pressure on flame oscillation and emission characteristics in the partially premixed turbulent flame were investigated. In order to investigate combustion characteristics in the partially premixed turbulent flame, the combustor pressure was controlled in the range of -30 to 30 kPa for each equivalence ratio ({phi} = 0.8-1.2). The r.m.s. of the pressure fluctuations increased with decreasing combustor pressure for the lean condition. The combustor pressure had a sizeable influence on combustion oscillation, whose dominant frequency varied with the combustor pressure. Combustion instabilities could be controlled by increasing the turbulent intensity of the unburned mixture under the lean condition. An unstable flame was caused by incomplete combustion; hence, EICO greatly increased. Furthermore, EINO{sub x} simply reduced with decreasing combustor pressure at a rate of 0.035 g/10 kPa. The possibility of combustion control on the combusting mode and exhaust gas emission was demonstrated. (author)

  3. Antigorite: High-pressure stability in the system MgO?SiO 2?H 2O (MSH)

    NASA Astrophysics Data System (ADS)

    Wunder, Bernd; Schreyer, Werner

    1997-08-01

    The breakdown reactions of antigorite: (1) forming talc + forsterite + water at low pressures and (2) forming forsterite + clinoenstatite + water at high pressures were determined in reversed equilibrium experiments. Results on reaction (1) were found to be in good agreement with former experimental determinations by both Johannes [Johannes, W., 1975. Zur Synthese und thermischen Stabilitt von Antigorit. Fortschr. Mineral. Beih. 53, 36.] and Evans et al. [Evans, B.W., Johannes, W., Oterdoom, H., Trommsdorff, V., 1976. Stability of crysotile and antigorite in the serpentinite multisystem. Schweiz. Mineral. Petrogr. Mitt. 56, 79-93.]. From our experiments the invariant point ( I1), interconnecting the two reactions, can be located at about 15 kbar/650C. This is consistent with the thermodynamic calculations using the dataset of Berman [Berman, R.G., 1988. Internally consistent thermodynamic data for minerals in the system J. Petrol. 29, 445-522.]; however, it is in contrast to recent experimental studies of Ulmer and Trommsdorff [Ulmer, P., Trommsdorff, V., 1995a. Serpentine stability to mantle depths and subduction-related magmatism. Science 268, 858-861.] who determined I1 at 21 kbar/730C. Our PT-conditions for I1 could be confirmed by equilibrium experiments on reaction (10) talc + forsterite ? clinoenstatite + water, which is generated at I1 as well. Up to about 25 kbar the breakdown reaction (2) is nearly pressure-independent. Towards still higher pressures the d P/d T-slope of reaction (2) bends and becomes negative. Schreinemakers analysis as well as thermodynamic calculations of the upper pressure-stability of antigorite show that the possible antigorite breakdown reaction (3) antigorite ? clinoenstatite + brucite + water and reaction (4) brucite + clinoenstatite ? forsterite + water could originate at a new invariant point I2, provided that the reactions (2) and (11) brucite + antigorite ? forsterite + water intersect. Bracketing equilibrium (4) and combining these results with those on reaction (2), I2 was located at only about 51 kbar/490C, compared to 77 kbar/680C according to Berman's data. However, when taking into account the dense hydrous magnesium silicate (= DHMS)-phase A, Mg 7Si 2O 8(OH) 6, the phase relations of antigorite are changed resulting (i) in the metastability of I2 and reaction (3) and (ii) in a new invariant point I7 at about 44 kbar and 580C generating the new antigorite breakdown-reaction (16) antigorite ? phase A + clinoenstatite + water. On the basis of these new data on the stability of antigorite, earlier conclusions about dehydration depths in subducted serpentine-bearing oceanic lithosphere have to be reconsidered. The maximum pressure stability of antigorite according to reaction (16) extends between 44 and 55 kbar, that is between about 130 and 160 km depths, as opposed to about 75 kbar (220 km) following Ulmer and Trommsdorff (see above). Because many different thermal regimes are possible in subduction zones, no specific dehydration depth can be expected but rather more continuous dehydration fronts in space and time.

  4. Determining noble gas partitioning within a CO2-H2O system at elevated temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Warr, Oliver; Rochelle, Christopher A.; Masters, Andrew; Ballentine, Christopher J.

    2015-06-01

    Quantifying the distribution of noble gases between phases is essential for using these inert trace gases to track the processes controlling multi-phase subsurface systems. Here we present experimental data that defines noble gas partitioning for two phase CO2-water systems. These are at the pressure and temperature range relevant for engineered systems used for anthropogenic carbon capture and geological storage (CCS) technologies, and CO2-rich natural gas reservoirs (CO2 density range 169-656 kg/m3 at 323-377 K and 89-134 bar). The new partitioning data are compared to predictions of noble gas partitioning determined in low-pressure, pure noble gas-water systems for all noble gases except neon and radon. At low CO2 density there was no difference between measured noble gas partitioning and that predicted in pure noble gas-water systems. At high CO2 density, however, partition coefficients express significant deviation from pure noble gas-water systems. At 656 kg/m3, these deviations are -35%, 74%, 113% and 319% for helium, argon, krypton and xenon, respectively. A second order polynomial fit to the data for each noble gas describes the deviation from the pure noble gas-water system as a function of CO2 density. We argue that the difference between pure noble gas-water systems and the high density CO2-water system is due to an enhanced degree of molecular interactions occurring within the dense CO2 phase due to the combined effect of inductive and dispersive forces acting on the noble gases. As the magnitude of these forces are related to the size and polarisability of each noble gas, xenon followed by krypton and argon become significantly more soluble within dense CO2. In the case of helium repulsive forces dominate and so it becomes less soluble as a function of CO2 density.

  5. Microwave measurements of water vapor partial pressure at temperatures up to 350{degree}C

    SciTech Connect

    Latorre, V.

    1989-09-01

    This paper describes the theory of operation, design, construction, calibration and installation of a microwave coaxial resonator system for measuring the partial pressure of water vapor in air at temperatures up to 350{degree}C. This is a relevant measurement for characterizing the unsaturated zone because the partial pressure of water vapor in the air in equilibrium with a rock mass is related to the capillary pressure of the rock. Microwave resonators can operate at high temperatures and, therefore, are the subject of this discussion. 7 refs., 8 figs.

  6. Fabricating TiO2 Photocatalysts by rf Reactive Magnetron Sputtering at Varied Oxygen Partial Pressures

    NASA Astrophysics Data System (ADS)

    Lin, W. S.; Kao, L. M.; Li, W. P.; Hsu, C. Y.; Hou, K. H.

    2011-08-01

    Titanium dioxide (TiO2) thin films were fabricated onto non-alkali glass substrates by rf reactive magnetron sputtering at room temperature using Ti-metal target at varied oxygen partial pressure [O2/(Ar + O2)]. The sputtering deposition was performed under an rf power of 200 W. The target to substrate distance was kept at 80 mm, and the total gas pressure was 10 mTorr after 2 h of deposition. It was found that the crystalline structure, surface morphology, and photocatalytic activities of the TiO2 thin films were affected by the oxygen partial pressure during deposition. The XRD patterns exhibited a broad-hump shape indicating the amorphous structure of TiO2 thin films. The thin films deposited at a relatively high value of oxygen partial pressure (70%) had a good photo-induced decomposition of methylene blue (MB), photo-induced hydrophilicity, and had a small grain size.

  7. Sulfidation properties of TiAl2 at.% X (X=V, Fe, Co, Cu, Nb, Mo, Ag and W) alloys at 1173 K and 1.3 Pa sulfur pressure in an H 2SH 2 gas mixture

    Microsoft Academic Search

    Takeshi Izumi; Takayuki Yoshioka; Shigenari Hayashi; Toshio Narita

    2000-01-01

    TiAl2 at. % X (X=V, Fe, Co, Cu, Nb, Mo, Ag and W) alloys were sulfidized at 1173 K for 86.4 ks at a 1.3 Pa sulfur pressure in an H2H2S gas mixture. The structure, phases, and compositions of the external sulfide scale and alloy surface layer were measured using EPMA and X-RD. The TiAl2Ag and 2Cu alloys sulfidized faster

  8. Experimental deformation of polycrystalline H2O ice at high pressure and low temperature - Preliminary results. [implications for Ganymede and Callisto

    NASA Technical Reports Server (NTRS)

    Durham, W. B.; Heard, H. C.; Kirby, S. H.

    1983-01-01

    A preliminary study is carried out of involving 70 constant strain deformation tests on pure polycrystalline H2O ice under conditions covering most of the stability field of ice I sub h. Brittle failure of I sub h is found to be promoted by lower P, lower T, and higher strain rates. Ductile flow is found to be promoted by higher P, higher T, and lower strain rates. The brittle failure of ice I sub h is found to be most unusual. The fracture strength is a positive function of P only below 50 MPa. At pressures greater than this, the fracture strength is independent of P, and the fracture plane lies approximately 45 deg from the load axis. It is believed that existing extrapolation based on existing experimental data to Ganymede and Callisto may be badly in error.

  9. Burn rates of TiH2/KClO4/Viton and output testing of NASA SKD26100098-301 pressure cartridges

    NASA Technical Reports Server (NTRS)

    Holy, John A.

    1993-01-01

    The burn rates of the pyrotechnic TiH2/KClO4/Viton with a mass ratio of 30/65/5 have been measured as a function of pressure in nitrogen up to 312 MPa(45 Kpsi). The burn rates were fit to R = a pn, with a = 2.055 cm/sec/MPan and n = 0.472 between 0.15 MPa (22 psi) and 21.6 MPa (3.13 Kpsi) and a = 4.38 cm/sec/MPan and n = 0.266 between 70 MPa (10.15 Kpsi) and 312 MPa (45.25 Kpsi). The decrease in slope at the higher pressures is attributed to a diffusion limited reaction. No acoustically driven flame instabilities or large conductive-to-convective burn transitions were observed. Solid reaction products were analyzed by x-ray diffraction and scanning electron microscopy (SEM). X-ray diffraction detected only TiO2 and KC1. SEM showed that the particle size of the reaction products increased as the nitrogen pressure increased. There were no anomalous characteristics of the burn of this pyrotechnic that could be interpreted as a cause of the o-ring blow-by problem in the forward shear bolt assembly. Three NASA SKD26100098-301 pressure cartridges were fired into a fixed volume vessel that was sealed with an O-ring. A maximum pressure of 181.7 MPa(26,350 psi) was reached in around 100 ,mu sec for two shots fired into a volume of 16.3 cm3(0.996 in3). A maximum pressure of 33,460 psi was reached for one shot fired into a volume of 9.55 cm3(0.583 in3). The O-ring burned through on one shot in the larger volume and leaked on the other two thereby simulating the effects of an O-ring leak. The results imply that the piston in the shear bolt assembly would receive a large impulse even if there was a leak in an O-ring seal.

  10. Steam catalysis in CaO carbonation under low steam partial pressure

    SciTech Connect

    Yang, S.J.; Xiao, Y.H. [Chinese Academy of Science, Beijing (China)

    2008-06-15

    CaO was widely used to capture CO{sub 2} in direct hydrogen production process, where steam always existed simultaneously. The effect of steam on CaO carbonation performance under low steam partial pressure was investigated using a pressurized thermogravimetric apparatus. The experimental results revealed that steam improved CaO carbonation performance significantly no matter whether Ca(OH){sub 2} was produced or not. At 823 K and 0.5 MPa of steam partial pressure, effect of steam on CaO carbonation performance could not be attributed mainly to production of Ca(OH){sub 2} because the hydration rate of CaO was very slow. The main reason was steam catalysis in CaO carbonation. Enhancement of steam on CaO carbonation performance without Ca(OH){sub 2} production could not be attributed to improvement of steam on the physical property, but to catalytic effect of steam. Effects of CaO precursors, CO{sub 2} partial pressure, steam partial pressure, and temperature with steam addition on CaO carbonation performance were also investigated.

  11. Solubility of corundum + kyanite in H2O at 700C and 10 kbar: evidence for Al-Si complexing at high pressure and

    E-print Network

    Manning, Craig

    Solubility of corundum + kyanite in H2O at 700C and 10 kbar: evidence for Al-Si complexing at high, Los Angeles, CA, USA ABSTRACT The solubility of the assemblage corundum + kyanite in H2O that of corundum solubility in pure H2O. This difference is interpreted to arise from complexing between Si and Al

  12. High-pressure partial melting and melt loss in felsic granulites in the Kutn Hora complex, Bohemian Massif (Czech Republic)

    NASA Astrophysics Data System (ADS)

    Nahodilov, Radmila; Faryad, Shah Wali; Dolej, David; Tropper, Peter; Konzett, Jrgen

    2011-07-01

    Felsic granulites from the Kutn Hora complex in the Moldanubian zone of central Europe preserve mineral assemblage that records transition from early eclogite to granulite facies conditions, and exhibits leucocratic banding, which is interpreted as an evidence for melt loss during the decompression path. The granulites are layered and consist of variable proportions of quartz, ternary feldspar, garnet, biotite, kyanite, and rutile. In the mesocratic layers, garnet grains show relatively high Ca contents corresponding to 28-41 mol% grossular end member. They have remarkably flat compositional profiles in their cores but their rims exhibit an increase in pyrope and a decrease in grossular and almandine components. In contrast, garnets from the leucocratic layers have relatively low Ca contents (15-26 mol% grossular) that further decrease towards the rims. In addition to modeling of pressure-temperature pseudosections, compositions of garnet core composition, garnet rim-ternary feldspar-kyanite-quartz equilibrium, ternary feldspar composition, and the garnet-biotite equilibrium provide five constraints that were used to reconstruct the pressure-temperature path from eclogite through the granulite and amphibolite facies. In both layers, garnet cores grew during omphacite breakdown and phengite dehydration melting at 940 C and 2.6 GPa. Subsequent decompression heating to 1020 C and 2.1 GPa produced Ca- and Fe-poor garnet rims due to the formation of Ca-bearing ternary feldspar and partial melt. In both the mesocratic and leucocratic layer, the maximum melt productivity was 26 and 18 vol.%, respectively, at peak temperature constrained by the maximum whole-rock H2O budget, ~ 1.05-0.75 wt.%, prior to the melting. The preservation of prograde garnet-rich assemblages required nearly complete melt loss (15-25 vol.%), interpreted to have occurred at 1000-1020 C and 2.2-2.4 GPa by garnet mode isopleths, followed by crystallization of small amounts of residual melt at 760 C and 1.0 GPa. Phase formation and melt productivity were independently determined by experiments in the piston-cylinder apparatus at 850-1100 C and 1.7-2.1 GPa. Both the thermodynamic calculations and phase equilibrium experiments suggest that the partial melt was produced by the dehydration melting: muscovite + quartz = melt + K-feldspar + kyanite. The presence of partial melt facilitated attainment of mineral equilibria at peak temperature thus eliminating any potential relics of early high-pressure phases such as phengite or omphacite. By contrast, adjacent mafic granulites and eclogites, which apparently share the same metamorphic path but have not undergone partial melting commonly preserve relics or inclusions of eclogite-facies mineral assemblages.

  13. Report on ISS O2 Production, Gas Supply and Partial Pressure Management

    NASA Technical Reports Server (NTRS)

    Schaezler, Ryan N.; Cook, Anthony J.

    2015-01-01

    Oxygen is used on International Space Station (ISS) for metabolic support and denitrogenation procedures prior to Extra-Vehicular Activities. Nitrogen is used to maintain total pressure and account for losses associated with leakage and operational losses. Oxygen and nitrogen have been supplied by various visiting vehicles such as the Progress and Shuttle in addition to the on-orbit oxygen production capability. Starting in 2014, new high pressure oxygen/nitrogen tanks are available to launch on commercial cargo vehicles and will replace the high pressure gas source that Shuttle used to provide. To maintain a habitable atmosphere the oxygen and nitrogen partial pressures are controlled between upper and lower bounds. The full range of the allowable partial pressures along with the increased ISS cabin volume are utilized as a buffer allowing days to pass between oxygen production or direct addition of oxygen and nitrogen to the atmosphere from reserves. This paper summarizes the amount of gas supplied and produced from all of the sources and describes past experience of managing partial pressures along with the range of management options available to the ISS.

  14. ORNL/CDIAC-152 GLOBAL OCEAN SURFACE WATER PARTIAL PRESSURE OF CO2 DATABASE

    E-print Network

    ORNL/CDIAC-152 NDP-088r GLOBAL OCEAN SURFACE WATER PARTIAL PRESSURE OF CO2 DATABASE: MEASUREMENTS.......................................................................................................3 5. QUALITY CONTROL .....................................................................................................................................9 #12;#12;v LIST OF FIGURES 1 Location of LDEO master database of sea surface pCO2 observations

  15. ORNL/CDIAC-152 GLOBAL OCEAN SURFACE WATER PARTIAL PRESSURE OF CO2 DATABASE

    E-print Network

    ORNL/CDIAC-152 NDP-088 GLOBAL OCEAN SURFACE WATER PARTIAL PRESSURE OF CO2 DATABASE: MEASUREMENTS.......................................................................................................2 4. QUALITY CONTROL .....................................................................................................................................9 #12;#12;v LIST OF FIGURES 1 Location of LDEO master database of sea surface pCO2 observations

  16. ORNL/CDIAC-152 GLOBAL OCEAN SURFACE WATER PARTIAL PRESSURE OF CO2 DATABASE

    E-print Network

    ORNL/CDIAC-152 NDP-088a GLOBAL OCEAN SURFACE WATER PARTIAL PRESSURE OF CO2 DATABASE: MEASUREMENTS.......................................................................................................2 4. QUALITY CONTROL .....................................................................................................................................9 #12;#12;v LIST OF FIGURES 1 Location of LDEO master database of sea surface pCO2 observations

  17. Crystalline structure of ceria particles controlled by the oxygen partial pressure and STI CMP performances

    Microsoft Academic Search

    Ye-Hwan Kim; Sang-Kyun Kim; Namsoo Kim; Jea-Gun Park; Ungyu Paik

    2008-01-01

    The effect of the crystalline structures of nano-sized ceria particles on shallow trench isolation (STI) chemical mechanical planarization (CMP) performance was investigated. The ceria particles were synthesized via a solid-state displacement reaction method, and their crystalline structure was controlled by regulating the oxygen partial pressure at the reaction site on the precursor. The crystalline structures of ceria particles were analyzed

  18. Response of the Endophytic Diazotroph Gluconacetobacter diazotrophicus on Solid Media to Changes in Atmospheric Partial O2 Pressure

    PubMed Central

    Pan, Bo; Vessey, J. Kevin

    2001-01-01

    Gluconacetobacter diazotrophicus is an N2-fixing endophyte isolated from sugarcane. G. diazotrophicus was grown on solid medium at atmospheric partial O2 pressures (pO2) of 10, 20, and 30 kPa for 5 to 6 days. Using a flowthrough gas exchange system, nitrogenase activity and respiration rate were then measured at a range of atmospheric pO2 (5 to 60 kPa). Nitrogenase activity was measured by H2 evolution in N2-O2 and in Ar-O2, and respiration rate was measured by CO2 evolution in N2-O2. To validate the use of H2 production as an assay for nitrogenase activity, a non-N2-fixing (Nif?) mutant of G. diazotrophicus was tested and found to have a low rate of uptake hydrogenase (Hup+) activity (0.016?? 0.009 ?mol of H2 1010 cells?1 h?1) when incubated in an atmosphere enriched in H2. However, Hup+ activity was not detectable under the normal assay conditions used in our experiments. G. diazotrophicus fixed nitrogen at all atmospheric pO2 tested. However, when the assay atmospheric pO2 was below the level at which the colonies had been grown, nitrogenase activity was decreased. Optimal atmospheric pO2 for nitrogenase activity was 0 to 20 kPa above the pO2 at which the bacteria had been grown. As atmospheric pO2 was increased in 10-kPa steps to the highest levels (40 to 60 kPa), nitrogenase activity decreased in a stepwise manner. Despite the decrease in nitrogenase activity as atmospheric pO2 was increased, respiration rate increased marginally. A large single-step increase in atmospheric pO2 from 20 to 60 kPa caused a rapid 84% decrease in nitrogenase activity. However, upon returning to 20 kPa of O2, 80% of nitrogenase activity was recovered within 10 min, indicating a switch-off/switch-on O2 protection mechanism of nitrogenase activity. Our study demonstrates that colonies of G. diazotrophicus can fix N2 at a wide range of atmospheric pO2 and can adapt to maintain nitrogenase activity in response to both long-term and short-term changes in atmospheric pO2. PMID:11571174

  19. Response of the endophytic diazotroph Gluconacetobacter diazotrophicus on solid media to changes in atmospheric partial O(2) pressure.

    PubMed

    Pan, B; Vessey, J K

    2001-10-01

    Gluconacetobacter diazotrophicus is an N(2)-fixing endophyte isolated from sugarcane. G. diazotrophicus was grown on solid medium at atmospheric partial O(2) pressures (pO(2)) of 10, 20, and 30 kPa for 5 to 6 days. Using a flowthrough gas exchange system, nitrogenase activity and respiration rate were then measured at a range of atmospheric pO(2) (5 to 60 kPa). Nitrogenase activity was measured by H(2) evolution in N(2)-O(2) and in Ar-O(2), and respiration rate was measured by CO(2) evolution in N(2)-O(2). To validate the use of H(2) production as an assay for nitrogenase activity, a non-N(2)-fixing (Nif(-)) mutant of G. diazotrophicus was tested and found to have a low rate of uptake hydrogenase (Hup(+)) activity (0.016 +/- 0.009 micromol of H(2) 10(10) cells(-1) h(-1)) when incubated in an atmosphere enriched in H(2). However, Hup(+) activity was not detectable under the normal assay conditions used in our experiments. G. diazotrophicus fixed nitrogen at all atmospheric pO(2) tested. However, when the assay atmospheric pO(2) was below the level at which the colonies had been grown, nitrogenase activity was decreased. Optimal atmospheric pO(2) for nitrogenase activity was 0 to 20 kPa above the pO(2) at which the bacteria had been grown. As atmospheric pO(2) was increased in 10-kPa steps to the highest levels (40 to 60 kPa), nitrogenase activity decreased in a stepwise manner. Despite the decrease in nitrogenase activity as atmospheric pO(2) was increased, respiration rate increased marginally. A large single-step increase in atmospheric pO(2) from 20 to 60 kPa caused a rapid 84% decrease in nitrogenase activity. However, upon returning to 20 kPa of O(2), 80% of nitrogenase activity was recovered within 10 min, indicating a "switch-off/switch-on" O(2) protection mechanism of nitrogenase activity. Our study demonstrates that colonies of G. diazotrophicus can fix N(2) at a wide range of atmospheric pO(2) and can adapt to maintain nitrogenase activity in response to both long-term and short-term changes in atmospheric pO(2). PMID:11571174

  20. Vapour pressures of H 2 16O and H 2 18O, and saturated aqueous solutions of KCl from T=298 K to T=318 K by the isoteniscopic method

    Microsoft Academic Search

    Alexander Apelblat

    1998-01-01

    Vapour pressures of normal water, water enriched by the heavy isotope of oxygen H218O, and saturated aqueous solutions of KCl were determined in the temperature range (298 to 318)K by the isoteniscopic method and compared with the literature data. Water activities, osmotic coefficients, vapour pressure lowerings, boiling point elevations, and molar enthalpies of vaporization at the saturation point of potassium

  1. Postoperative Pharyngolaryngeal Adverse Events with Laryngeal Mask Airway (LMA Supreme) in Laparoscopic Surgical Procedures with Cuff Pressure Limiting 25?cmH2O: Prospective, Blind, and Randomised Study

    PubMed Central

    Kang, Joo-Eun; Choi, Jae Won; Son, Il Soon

    2014-01-01

    To reduce the incidence of postoperative pharyngolaryngeal adverse events, laryngeal mask airway (LMA) manufacturers recommend maximum cuff pressures not exceeding 60?cmH2O. We performed a prospective randomised study, comparing efficacy and adverse events among patients undergoing laparoscopic surgical procedures who were allocated randomly into low (limiting 25?cmH2O, L group) and high (at 60?cmH2O, H group) LMA cuff pressure groups with LMA Supreme. Postoperative pharyngolaryngeal adverse events were evaluated at discharge from postanaesthetic care unit (PACU) (postoperative day 1, POD 1) and 24 hours after discharge from PACU (postoperative day 2, POD 2). All patients were well tolerated with LMA without ventilation failure. Before pneumoperitoneum, cuff volume and pressure and oropharyngeal leak pressure (OLP) showed significant differences. Postoperative sore throat at POD 2 (3 versus 12 patients) and postoperative dysphagia at POD 1 and POD 2 (0 versus 4 patients at POD 1; 0 versus 4 patients at POD 2) were significantly lower in L group, compared with H group. In conclusion, LMA with cuff pressure limiting 25?cmH2O allowed both efficacy of airway management and lower incidence of postoperative adverse events in laparoscopic surgical procedures. This clinical trial is registered with KCT0000334. PMID:24778598

  2. Experimental investigation of the H2O-CO2 system between 250-330 K and 0-1.7 GPa and modeling of the sI clathrate hydrate of CO2 and CH4 at high pressures

    NASA Astrophysics Data System (ADS)

    Bollengier, O.; Choukroun, M.; Grasset, O.; Le Menn, E.; Bellino, G.; Morizet, Y.; Bezacier, L.; Oancea, A.; Taffin, C.; Tobie, G.

    2013-12-01

    Despite the importance of carbon dioxide for the understanding of water-rich outer solar system bodies, few studies have been devoted so far to the H2O-CO2 system at pressures and temperatures relevant to the interior of the icy moons of the giant planets. We report here new sapphire and diamond anvil cell experiments recently conducted in this binary system to constrain the stability of the CO2 hydrates and H2O ice VI at CO2 saturation in the 250 - 330 K and 0 - 1.7 GPa temperature and pressure ranges. Using Raman spectroscopy and optical monitoring, (1) we constrained the equilibrium between the CO2 sI clathrate hydrate and the H2O-rich liquid over the entire pressure range of stability of the hydrate, up to 0.8 GPa, with results in agreement with previous studies at lower pressures, (2) we confirmed the transition from the CO2 sI clathrate hydrate to a new CO2 high-pressure hydrate reported recently, and (3) we determined for the first time the melting curve of the H2O ice VI at CO2 saturation between 0.8 and 1.7 GPa. Using these third set of data and a chemical potential model for H2O, we propose a first assessment of the solubility of CO2 in water at these P-T conditions. With all these new results and available data in the literature, we propose a P-T-X description of the H2O-CO2 system over the explored pressure and temperature ranges. In addition, the dissociation curve of the CO2 sI clathrate hydrate has been modeled using the approach of van der Waals and Platteeuw. The model adequately reproduces the stability domain of the hydrate up to the highest pressures constrained experimentally. Results of the modeling of the sI clathrate hydrate structure currently being implemented for the H2O-CH4 binary and H2O-CO2-CH4 ternary systems will also be presented.

  3. Phase relations in the system NaCl-KCl-H2O: IV. Differential thermal analysis of the sylvite liquidus in the KCl-H2O binary, the liquidus in the NaCl-KCl-H2O ternary, and the solidus in the NaCl-KCl binary to 2 kb pressure, and a summary of experimental data for thermodynamic-PTX analysis of solid-liquid equilibria at elevated P-T conditions

    USGS Publications Warehouse

    Chou, I.-Ming; Sterner, S.M.; Pitzer, Kenneth S.

    1992-01-01

    The sylvite liquidus in the binary system KCl-H2O and the liquidus in the ternary system NaCl-KCl-H2O were determined by using isobaric differential thermal analysis (DTA) cooling scans at pressures up to 2 kbars. Sylvite solubilities along the three-phase curve in the binary system KCl-H2O were obtained by the intersection of sylvite-liquidus isopleths with the three-phase curve in a P-T plot. These solubility data can be represented by the equation Wt.% KCl (??0.2) = 12.19 + 0.1557T - 5.4071 ?? 10-5 T2, where 400 ??? T ??? 770??C. These data are consistent with previous experimental observations. The solidus in the binary system NaCl-KCl was determined by using isobaric DTA heating scans at pressures up to 2 kbars. Using these liquidus and solidus data and other published information, a thermodynamic-PTX analysis of solid-liquid equilibria at high pressures and temperatures for the ternary system has been performed and is presented in an accompanying paper (Part V of this series). However, all experimental liquidus, solidus, and solvus data used in this analysis are summarized in this report (Part IV) and they are compared with the calculated values based on the analysis. ?? 1992.

  4. Partial Molar Volumes of Some of ?-Amino Acids in Binary Aqueous Solutions of MgSO 4 7H 2 O at 298.15 K

    Microsoft Academic Search

    Bairagi C. Mallick; Nand Kishore

    2006-01-01

    The apparent molar volume, V\\u000a o\\u000a ?, 2, of glycine, alanine, ?-amino-n-butyric acid, valine and leucine have been determined in aqueous solutions of 0.25, 0.5 and 1.0 mol?dm?3 magnesium sulfate, and the partial specific volume from density measurements at 298.15 K. These data have been used to calculate the infinite dilution apparent molar volume, V\\u000a o\\u000a 2,m\\u000a , group contribution

  5. Physical properties of copper oxide thin films prepared by dc reactive magnetron sputtering under different oxygen partial pressures

    Microsoft Academic Search

    Chun-Lung Chu; Hsin-Chun Lu; Chen-Yang Lo; Chi-You Lai; Yu-Hsiang Wang

    2009-01-01

    Nano-structured copper oxide thin films were deposited on glass substrates by dc reactive magnetron sputtering. The structural, morphological, electrical, and optical properties of the deposited copper oxide thin films were found to change with oxygen partial pressure. Changes in oxygen partial pressure during sputter deposition led to variations in Cu, Cu+ and Cu+2 concentrations, which resulted in corresponding changes in

  6. Serial blood pressure measurements and exogenous creatinine clearance rates in partially nephrectomized dogs: the effect of dietary sodium intake

    E-print Network

    Greco, Deborah Susan

    1987-01-01

    SERIAL BIOOD PRESSURE MEASUREMENTS AND EXOGENOUS CREATININE CLEARANCE RATES IN PARTIALLY NEPHRECTOM IZED DOGS: THE EFFECT OF DIETARY SODIUM INTAKE A Thesis DEBORAH SUSAN GRECO Submitted to the Graduate College of Texas A&M University... in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1987 Major Subject: Veterinary Medicine and Surgery SERIAL BLOOD PRESSURE MEASUREMENTS AND EXOGENOUS CREATININE CLEARANCE RATES IN PARTIALLY NEPHRECIOMIZED DOGS...

  7. Flight test evaluation of an RAF high altitude partial pressure protective assembly

    NASA Technical Reports Server (NTRS)

    Ashworth, G. R.; Putnam, T. W.; Dana, W. J.; Enevoldson, E. K.; Winter, W. R.

    1979-01-01

    A partial pressure suit was evaluated during tests in an F-104 and F-15 as a protective garment for emergency descents. The garment is an pressure jerkin and modified anti-g suit combined with an oronasal mask. The garment can be donned and doffed at the aircraft to minimize thermal buildup. The oronasal mask was favored by the pilots due to its immobility on the face during high g-loading. The garment was chosen to provide optimum dexterity for the pilot, which is not available in a full pressure suit, while protecting the pilot at altitudes up to 18,288 meters, during a cabin decompression, and subsequent aircraft descent. During cabin decompressions in the F-104 and F-15, cabin pressure altitude was measured at various aircraft angles of attack, Mach numbers, and altitudes to determine the effect of the aerodynamic slipstream on the cabin altitude.

  8. The model of nano-scale copper particles removal from silicon surface in high pressure CO2+H2O and CO2+H2O+IPA cleaning solutions

    Microsoft Academic Search

    Xin Tan; Jiajue Chai; Xiaogang Zhang; Jiawei Chen

    2010-01-01

    This study focuses on the description of static forces in a system with a fluid phase entrapped between nano-scale particles and a surface. Equilibrium separation distance (EDS) and net adhesion force (NAF) of a particle adhering on substrate can be used as the guideline for evaluating extend of the particle cleaning. Calculations demonstrate that pressure can significantly alter the static

  9. H2O Adsorption Kinetics on Smectites

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Howard, J.; Quinn, R. C.

    2000-01-01

    The adsorptive equilibration of H2O with montomorillonite has been measured. At low temperatures and pressures equilibration can require many hours, effectively preventing smectites at the martian surface from responding to diurnal pressure and temperature variations.

  10. Effects of reduced oxygen partial pressure on cognitive performance in confined spaces.

    PubMed

    Linde, L; Gustafsson, C; Ornhagen, H

    1997-01-01

    The reduction of oxygen levels is a technique used both for fire fighting and fire protection in confined spaces. The purpose of this study was to find out if and how reduced oxygen levels affect cognitive performance in a small group of persons living in a confined space such as a submarine. In 3 separate experiments lasting for 11 to 14 days, a total of 22 men were exposed to normoxic and different levels of hypoxic normobaric atmospheres (15, 14, and 13 kPa O2). Each participant completed a cognitive test battery twice every 24-hr period in the first 2 experiments, but only once a day in the 3rd experiment. Performance in almost all tests improved with the number of test sessions performed, despite reductions of the oxygen partial pressure. Under the conditions tested, cognitive performance decrements could not be observed if inspiratory oxygen partial pressure was kept above 13 kPa. PMID:11540405

  11. Melting of Bi-2212 under controlled oxygen partial pressures with silver

    NASA Astrophysics Data System (ADS)

    Lang, Th.; Buhl, D.; Gauckler, L. J.

    1997-02-01

    The solidus temperature Tsolidus of Bi 2Sr 2CaCu 2O x (Bi-2212) is decreased from 893C to 880C and further down to 834C when the oxygen partial pressure of the atmosphere is changed from pO 2 = 1 atm to 0.21 atm and further to 0.001 atm. Silver additions to the superconductor exceeding 2 wt% lower Tsolidus by up to 25 K in a pure oxygen atmosphere. The weight loss during melting, which is related to oxygen release, is highest at low oxygen partial pressures and can be reduced by silver additions due to increased oxygen solubility of the Bi-2212 melt in presence of dissolved silver. The experimental results are compared with thermodynamic data of the Bi?Sr?Ca?Cu?O system.

  12. Experimental equilibrium and modeling for the absorption of acid gases in diethanolamine solutions at low and high partial pressures

    SciTech Connect

    Elizondo-Villarreal, E.M.

    1989-01-01

    This study was undertaken to develop an experimental apparatus that would allow direct measurements of gas equilibrium solubility in aqueous alkanolamine solutions at low gas partial pressures. Carbon dioxide and hydrogen sulfide solubility in 20, 35 and 50% by weight diethanolamine aqueous solutions was measured. The measurements were made at acid gas partial pressures between 0.003 and 10.9 psia and temperatures of 80, 150 and 240{degree}F. The experimental data at low partial pressure were used in a procedure to correlate them with literature data at high partial pressures and establish a model for carbon dioxide-hydrogen sulfide-aqueous diethanolamine systems. An experimental apparatus was developed to measure the equilibrium solubility of acid gas in diethanolamine solutions at low acid gas partial pressures. The experimental procedure does not require that vapor liquid samples be withdrawn for analysis, so equilibrium in the experimental apparatus is never disturbed. A consistency test for evaluation of experimental acid gas-ethanolamine equilibrium data was developed. The test was shown to apply in the full range of partial pressures where chemical reactions dominate. Predictions of acid gas partial pressures were substantially improved and application to model an integrated high pressure natural gas plant gave good results. The experimental apparatus and the consistency test should be used for other amines of industrial interest to improve the modeling.

  13. Melting relations of the hydrous primitive mantle in the CMASH 2O system at high pressures and temperatures, and implications for generation of komatiites

    Microsoft Academic Search

    Yuki Asahara; Eiji Ohtani

    2001-01-01

    The hydrous phase relations of primitive mantle compositions in the CaOMgOAl2O3SiO2H2O system with 1, 2, and 5wt.% H2O have been investigated at 4, 6.5, and 8GPa. The stability field of orthopyroxene in the residue expands with increasing H2O content at 48GPa. Dissolution temperature of garnet decreases more rapidly than that of the other phases at 4 and 6.5GPa. The dissolution

  14. Introduction to total- and partial-pressure measurements in vacuum systems

    NASA Technical Reports Server (NTRS)

    Outlaw, R. A.; Kern, F. A.

    1989-01-01

    An introduction to the fundamentals of total and partial pressure measurement in the vacuum regime (760 x 10 to the -16th power Torr) is presented. The instrument most often used in scientific fields requiring vacuum measurement are discussed with special emphasis on ionization type gauges and quadrupole mass spectrometers. Some attention is also given to potential errors in measurement as well as calibration techniques.

  15. Role of determination of partial pressure of ammonia in cirrhotic patients with and without hepatic encephalopathy

    Microsoft Academic Search

    Francesca Nicolao; Cesare Efrati; Andrea Masini; Manuela Merli; Adolfo Francesco Attili; Oliviero Riggio

    2003-01-01

    Background\\/Aims: To compare venous, arterial and partial pressure of ammonia (pNH3) in 27 consecutive cirrhotics with hepatic encephalopathy, 15 cirrhotics without hepatic encephalopathy and nine controls; to reevaluate all parameters after the improvement of encephalopathy.Methods: Patients were studied by clinical examination and psychometric testing. pNH3 was calculated from arterial ammonia and pH.Results: In patients with encephalopathy, each form of ammonia

  16. Effect of partial pressure of hydrogen on IGSCC of alloy 600 in PWR primary water

    SciTech Connect

    Rebak, R.B.; Szklarska-Smialowska, Z. (Ohio State Univ., Columbus, OH (United States))

    1991-10-01

    The frequently reported effect of the partial pressures of hydrogen on the alloy 600 susceptibility to intergranular stress corrosion cracking (IGSCC) in high temperature water is explained in this paper. On the basis of thermodynamic calculations, it was demonstrated that the susceptibility of NiO in this environment. The lower the free energy of formation of NiO, the higher the susceptibility of alloy 600 to IGSCC.

  17. Effect of Partial H2O-D2O Replacement on the Anisotropy of Transverse Proton Spin Relaxation in Bovine Articular Cartilage

    PubMed Central

    Tadimalla, Sirisha; Momot, Konstantin I.

    2014-01-01

    Anisotropy of transverse proton spin relaxation in collagen-rich tissues like cartilage and tendon is a well-known phenomenon that manifests itself as the magic-angle effect in magnetic resonance images of these tissues. It is usually attributed to the non-zero averaging of intra-molecular dipolar interactions in water molecules bound to oriented collagen fibers. One way to manipulate the contributions of these interactions to spin relaxation is by partially replacing the water in the cartilage sample with deuterium oxide. It is known that dipolar interactions in deuterated solutions are weaker, resulting in a decrease in proton relaxation rates. In this work, we investigate the effects of deuteration on the longitudinal and the isotropic and anisotropic contributions to transverse relaxation of water protons in bovine articular cartilage. We demonstrate that the anisotropy of transverse proton spin relaxation in articular cartilage is independent of the degree of deuteration, bringing into question some of the assumptions currently held over the origins of relaxation anisotropy in oriented tissues. PMID:25545955

  18. Equilibrium solubility of acid gases in diethanolamine and monoethanolamine solutions at low partial pressures

    SciTech Connect

    Lal, D.; Isaacs, E.E.; Mather, A.E.; Otto, F.D.

    1980-01-01

    Aqueous monoethanolamine (MEA) and diethanolamine (DEA) solutions are used extensively for the removal of H/sub 2/S and CO/sub 2/ from gas streams. Advantages of the use of these particular chemical solvents include high reactivity, low cost, ease of reclamation, low absorption of hydrocarbons, and relatively high capacity at low acid gas partial pressures. The rational design and operation of MEA and DEA treating processes requires data for the equilibrium solubility of H/sub 2/S and CO/sub 2/ in the treating solutions over the wide range of acid gas partial pressures encountered in operating units. There has been a lack of data for low acid gas loadings. Low partial pressure data determined for the equilibrium solubility of H/sub 2/S, CO/sub 2/, and their mixtures in 2.0 kmol M/sup -3/ (20.5% by wt) DEA and 2.5 kmol M/sup -3/ (15.3% by wt) MEA solutions are presented. 20 references.

  19. A theoretical study on the reactivity and spectra of H2CO and HCOH. A dimeric model for nonzero pressure formaldehyde photochemistry

    Microsoft Academic Search

    M. J. H. Kemper; C. H. Hoeks; H. M. Buck

    1981-01-01

    The reactivity and spectra of formaldehyde isomers and dimeric complexes between them are studied with abinitio methods. A large number of complexes between H2CO, trans-HCOH, cis-HCOH is calculated. Infrared and Raman spectra of (H2CO)2 are calculated with relatively simple methods using spectroscopic masses and scaled force constants. In this way, the structure of dimers in matrices can be deduced. Hydroxycarbene

  20. Pressures of Partial Crystallization of Magmas from the Juan de Fuca Ridge: Implications for Crustal Accretion

    NASA Astrophysics Data System (ADS)

    Scott, J. L.; Barton, M.

    2010-12-01

    Plate spreading at the mid-ocean ridges is accompanied by intrusion of dikes and eruption of lava along the ridge axis. It has been suggested that the depth of magma chambers that feed the flows and dikes is related to the rate of spreading. As part of a larger effort to examine this hypothesis, we determined the depths of magma chambers beneath the intermediate spreading Juan de Fuca Ridge (JdF) which extends from the Blanco fracture zone at about 44.5 degrees North to the Triple junction of the JdF, Nootka Fault, and the Socanco fracture zone at 48.7 degrees North. Pressures of partial crystallization were determined by comparing the compositions of natural liquids (glasses) with those of experimental liquids in equilibrium with olivine, plagioclase, and clinopyroxene at different pressures and temperatures using the method described by Kelley and Barton (2008). Chemical analyses mid-ocean ridge basalts glasses sampled from along the JdF were used as liquid compositions. Samples with anomalous chemical compositions and samples that yielded pressures associated with unrealistically large uncertainties were filtered out of the database. The calculated pressures for the remaining 533 samples were used to calculate the depths of partial crystallization and to identify the likely location of magma chambers. Preliminary results indicate that the pressure of partial crystallization decreases from 2 to 10.5 kbars from the Blanco fracture zone to the north along the Cleft segment of the ridge. Calculated pressures remain approximately constant at 0.870.53 kbars along ridge segments to the north of the Cleft. These low pressures for the remaining segments of the ridge are interpreted to indicate magma chambers at depths of 1.3-4.9 km and agree reasonably well with the depths of seismically imaged tops of axial magma chambers (2-3 km) (Canales et al 2009). The higher pressures obtained for lavas erupted along the Cleft segment of the JdF agree very well with recent seismic imaging of chambers beneath the Cleft segment. Pressures calculated for samples from single lava flows along the cleft segment described by Stakes et al (2006) allow identification of two magma chambers at depths of 5.01.1 km and 5.60.8 km which is to the depth of 5 to 6 km for the seismically imaged sill (Canales et al 2009). The higher depths inferred for chambers beneath the Cleft segment are consistent with cooling and/or thickening of crust along ridges toward fracture zones. While calculated pressures provide evidence for crystallization in axial magma chambers, results obtained for some samples from virtually every locality also suggest partial crystallization in the crust beneath these chambers, and therefore support the many sill or crystal mush models for accretion of oceanic crust. This conclusion is strengthened by comparing the results with those calculated using Herzbergs (2004) method. The average difference between pressures calculated with both methods is 0.7 kbars ( 2.5 km) which is within the uncertainty in the calculation. .The Herzberg method returns slightly lower pressures for most samples

  1. Experimental study of local dehydration and partial melting of biotite-amphibole gneiss with participation of the H2O-CO2-(K, Na)Cl fluids at the middle-crustal conditions

    NASA Astrophysics Data System (ADS)

    Safonov, O.; Kozhukhantseva, S.

    2012-04-01

    Activity of aqueous chloride-rich brines coexisting with CO2-rich fluids is identified in many amphibolite and granulite terrains suggesting that this type of fluid is an important agent of high-grade metamorphism in the lower to middle crust (see reviews in Touret, 2009; Newton, Manning, 2010). Although thermodynamic and transport properties of these fluids is well constrained both theoretically and experimentally, their affect on complex natural assemblages is poorly understood and demands systematic experimental study. We report here results of the experiments on interaction of the biotite-amphibole gneiss from the Sand River formation (Limpopo Complex, South Africa) with the fluids H2O-CO2-(K, Na)Cl at 5.5 kbar, 750 and 800 C, the chloride/(H2O+CO2) varying from 0 0.1, and molar CO2/(CO2+H2O) = 0.5. No any reaction textures were identified in the sample interacted with the chloride-free CO2-H2O fluid at 750 C. At this temperature, addition of KCl into the fluid resulted in formation of spectacular reaction textures around biotite (Bt), amphibole (Amp), plagioclase (Pl) and quartz (Qtz) in the starting gneiss. These textures are intergrowths of low-Al clinopyroxene (Cpx) and K-feldspar (Kfs) (sporadically accompanied by ilmenite, sphene and Ti-bearing low-Al mica) corresponding to a progress of the following reactions: Phl + 3An + 18Qtz + 3(K2O in fluid) = 3Di + 7Kfs + (H2O in fluid) and Prg + Ed + 7(K2O in fluid) + 37Qtz + 5An = 9Di + 14Kfs + (2H2O + Na2O in fluid). Local partial melting of the gneiss interacted with KCl-bearing fluids at 750OC was observed only in the run at KCl/(CO2+H2O) = 1/30 and could be caused by local variation of water activity in the sample. Nevertheless, at 800 OC, granitic (>70 wt. % of SiO2) K2O-rich and Cl-bearing melt appears along the grain boundaries in all run samples. This melt produces K-feldspar and clinopyroxene, which are found as euhedral crystals in the glass. Melt films are usually accompanied by K-feldspar microveins and Cpx similar to those in the runs at 750 C. At KCl/(CO2+H2O) = 1/10, strongly "K-feldspartized" portions of the samples along cracks contain minute kalsilite, Ca-garnet, and calcite. In contrast, all NaCl-bearing (including mixed KCl-NaCl-bearing) runs both at 750 and 800 C show evidence for melting, whose intensity clearly increases with increasing NaCl/(CO2+H2O) ratio in the fluid. Na-granitic (> 70 wt. % of SiO2) melt forms at relatively low degrees of melting. Depending on NaCl concentration in the fluid, this melt coexists with Cpx, Opx and Na-rich (richteritic) Amp. Formation of Na-amphibole proceeds via peritectic reactions of biotite and pargasite-edenite amphibole with plagioclase and sodium-rich fluid, for example 5/3Phl + An + 12Qtz + 2Na2O = Richteritic Amp + [5/3Kfs + 2Ab] + 2/3H2O and 5/4Prg + 23/4Qtz + 1/4Na2O = Richteritic Amp + 1/4H2O + 3/2An + [1/4Ab], where Kfs and Ab are the basis of the silicate melt. Euhedral albite was observed crystallizing from the melt in the runs, where NaCl was the only chloride species in the fluid. Euhedral plagioclase crystals were found in glass in the runs with the mixed KCl-NaCl-bearing fluid, while melt films and pockets in the samples are accompanied by K-feldspar microveins. Na-rich "phonolitic" (55-56 wt. % of SiO2) melt containing up to 1.8 wt. % of Cl forms at almost complete melting of the gneiss in presence of NaCl-rich fluids. This melt coexists with pargasite-richterite amphibole and clinopyroxene, as well as with residual accessory phases. It should be noted that solubility of chlorine in the melts forming in equilibrium with the NaCl-rich fluids is by 0.3-0.5 wt. % higher than in the melts equilibrated with the KCl-rich fluids. Thus, the results of the experiments demonstrate that interaction of biotite-amphibole gneiss with H2O-CO2-(K, Na)Cl fluids is able to produce a wide spectrum of mineral assemblages and melts depending on temperature, bulk chloride concentration, and K/Na ratio in the fluid. These assemblages vary from syenitic Cpx+Kfs in presence of KCl-rich flu

  2. Assessment of metabolic flux distribution in the thermophilic hydrogen producer Caloramator celer as affected by external pH and hydrogen partial pressure

    PubMed Central

    2014-01-01

    Background Caloramator celer is a strict anaerobic, alkalitolerant, thermophilic bacterium capable of converting glucose to hydrogen (H2), carbon dioxide, acetate, ethanol and formate by a mixed acid fermentation. Depending on the growth conditions C. celer can produce H2 at high yields. For a biotechnological exploitation of this bacterium for H2 production it is crucial to understand the factors that regulate carbon and electron fluxes and therefore the final distribution of metabolites to channel the metabolic flux towards the desired product. Results Combining experimental results from batch fermentations with genome analysis, reconstruction of central carbon metabolism and metabolic flux analysis (MFA), this study shed light on glucose catabolism of the thermophilic alkalitolerant bacterium C. celer. Two innate factors pertaining to culture conditions have been identified to significantly affect the metabolic flux distribution: culture pH and partial pressures of H2 (PH2). Overall, at alkaline to neutral pH the rate of biomass synthesis was maximized, whereas at acidic pH the lower growth rate and the less efficient biomass formation are accompanied with more efficient energy recovery from the substrate indicating high cell maintenance possibly to sustain intracellular pH homeostasis. Higher H2 yields were associated with fermentation at acidic pH as a consequence of the lower synthesis of other reduced by-products such as formate and ethanol. In contrast, PH2 did not affect the growth of C. celer on glucose. At high PH2 the cellular redox state was balanced by rerouting the flow of carbon and electrons to ethanol and formate production allowing unaltered glycolytic flux and growth rate, but resulting in a decreased H2 synthesis. Conclusion C. celer possesses a flexible fermentative metabolism that allows redistribution of fluxes at key metabolic nodes to simultaneously control redox state and efficiently harvest energy from substrate even under unfavorable conditions (i.e. low pH and high PH2). With the H2 production in mind, acidic pH and low PH2 should be preferred for a high yield-oriented process, while a high productivity-oriented process can be achieved at alkaline pH and high PH2. PMID:24678972

  3. Pressure effect investigated with first-order reversal-curve method on the spin-transition compounds [FexZn1-x(btr)2(NCS)2] H2O (x=0.6,1)

    NASA Astrophysics Data System (ADS)

    Rotaru, Aurelian; Linares, Jorge; Varret, Franois; Codjovi, Epiphane; Slimani, Ahmed; Tanasa, Radu; Enachescu, Cristian; Stancu, Alexandru; Haasnoot, Jaap

    2011-06-01

    In this work we present results obtained by the first-order reversal-curve (FORC) method for finding the effect of pressure on a spin transition. The FORC data were recorded by diffuse reflectivity measurements for the spin-transition compounds [Fe(btr)2(NCS)2]H2O and [Fe0.6Zn0.4(btr)2(NCS)2]H2O (btr = 4,4'-bis-1,2,4-triazole) under constant pressure in the range 1-1600 bars. The joint distributions in coercivity-bias coordinates, obtained by the FORC method, were expressed in energy gap ? and interaction parameter J coordinates for a complete discussion of the pressure effect in terms of physical parameters, including their average values, distribution widths, and ?-J correlation parameter. Pressure increases both ? and J, as expected. Pressure has a negligible effect on the distribution widths but sizably decreases the correlation parameter value of the diluted system, an unexpected feature which suggests that the diluted system has multiple-domain behavior with pressure-dependent domain size. This deduction is supported by inspection of the samples using optical microscopy at room temperature. Simulations of the metal distribution in a two-dimensional lattice are performed in order to estimate the pressure-induced change in domain size.

  4. Payload specialist Umberto Guidioni, wearing the partial pressure launch and entry garment, prepares

    NASA Technical Reports Server (NTRS)

    1996-01-01

    STS-75 ONBOARD VIEW --- Payload specialist Umberto Guidioni, wearing the partial pressure launch and entry garment, prepares for the de-orbit phase of the 16-day flight. Guidioni represents the Italian Space Agency (ASI). The seven member crew was launched aboard the Space Shuttle Columbia on February 22, 1996, and landed on March 9, 1996. Crew members were Andrew M. Allen, mission commander; Scott J. Horowitz, pilot; Franklin R. Chang-Diaz, payload commander; and Maurizio Cheli, European Space Agency (ESA); Jeffrey A. Hoffman and Claude Nicollier, (ESA), all mission specialists; along with Guidioni.

  5. The formation of infinite-layer cuprates and correlation with temperature and partial pressure of oxygen

    Microsoft Academic Search

    C.-J. Liu; S. Koriyama; H. Yamauchi

    1993-01-01

    Various combinations of calcination temperature and oxygen partial pressures have been investigated to stabilize the infinite-layer structure in Ca1-xSrxCuO2 and (Ca1-x-yYy)SrxCuO2 systems using a solid-state reaction method. It is found that the stability of infinite-layer structure for different compositions strongly depends on the calcination conditions. The infinite-layer structure is stable in the range of 0.12 <= x <= 0.16 for

  6. Pressure Distribution Over a Rectangular Airfoil with a Partial-Span Split Flap

    NASA Technical Reports Server (NTRS)

    Wenzinger, Carl J; Harris, Thomas A

    1937-01-01

    This report presents the results of pressure-distribution tests of a Clark y wing model with a partial-span split flap made to determine the distribution of air loads over both the wing and the flap. The model was used in conjunction with a reflection plane in the NACA 7 by 10 foot wind tunnel. The 20-percent-chord split flap extended over the inboard 60 percent of the semispan. The tests were made at various flap deflections up to 45 degrees and covered a range of angles of attack from zero lift to approximately maximum lift for each deflection.

  7. Toxicity of elevated partial pressures of carbon dioxide to invasive New Zealand mudsnails

    USGS Publications Warehouse

    Nielson, R. Jordan; Moffitt, Christine M.; Watten, Barnaby J.

    2012-01-01

    The authors tested the efficacy of elevated partial pressures of CO2 to kill invasive New Zealand mudsnails. The New Zealand mudsnails were exposed to 100 kPa at three water temperatures, and the survival was modeled versus dose as cumulative C-h. We estimated an LD50 of 59.4C-h for adult and juvenile New Zealand mudsnails. The results suggest that CO2 may be an effective and inexpensive lethal tool to treat substrates, tanks, or materials infested with New Zealand mudsnails.

  8. Property variations of direct-current reactive magnetron sputtered copper oxide thin films deposited at different oxygen partial pressures

    Microsoft Academic Search

    Hsin-Chun Lu; Chun-Lung Chu; Chi-You Lai; Yu-Hsiang Wang

    2009-01-01

    Cuprous oxide (Cu2O) and cupric oxide (CuO) thin films were deposited on glass substrates at different oxygen partial pressures by direct-current reactive magnetron sputtering of pure copper target in a mixture of argon and oxygen gases. Oxygen partial pressure was found to be a crucial parameter in controlling the phases and, thus, the physical properties of the deposited copper oxide

  9. Oxidizer partial pressure window for YBa2Cu3O(7-x) thin film formation by metalorganic chemical vapor deposition

    Microsoft Academic Search

    C. S. Chern; J. Zhao; P. E. Norris; S. M. Garrison; K. Yau; Y. Q. Li; B. M. Gallois; B. H. Kear

    1992-01-01

    We conducted a systematic study of oxidizer partial pressure effects on both the superconducting transport properties and structural properties of YBa2Cu3O(7-x) (YBCO) films grown by conventional metalorganic chemical vapor deposition (MOCVD). Superconducting YBCO thin films were grown in partial N2O pressures ranging from 0.4 to 45 Torr and at substrate temperatures of 500 and 700 C. We observed a window

  10. Does the threshold of transcutaneous partial pressure of carbon dioxide represent the respiratory compensation point or anaerobic threshold?

    Microsoft Academic Search

    Yuefei Liu; Jrgen M. Steinacker; Martin Stanch

    1995-01-01

    On reaching the respiratory compensation point (RCP) during rapidly increasing incremental exercise, the ratio of minute ventilation (VE) to CO2 output (VCO2) rises, which coincides with changes of arterial partial pressure of carbon dioxide (P\\u000aaCO2). Since P\\u000aaCO2 changes can be monitored by transcutaneous partial pressure of carbon dioxide (PCO2,tc) RCP may be estimated by PCO2,tc measurement. Few available

  11. Novel cooperative interactions and structural ordering in H2S-H2

    SciTech Connect

    Kent, Paul R [ORNL

    2011-01-01

    Hydrogen sulfide (H2S) and hydrogen (H2) crystallize into a 'guest-host' structure at 3.5 GPa and, at the initial formation pressure, the rotationally disordered component molecules exhibit weak van der Waals type interactions. With increasing pressure, hydrogen bonding develops and strengthens between neighboring H2S molecules, reflected in a pronounced drop in S-H vibrational stretching frequency and also observed in first-principles calculations. At 17 GPa, an ordering process occurs where H2S molecules orient themselves to maximize hydrogen bonding and H2 molecules simultaneously occupy a chemically distinct lattice site. Intermolecular forces in the H2S+H2 system may be tuned with pressure from the weak hydrogen-bonding limit to the ordered hydrogen-bonding regime, resulting in a novel clathrate structure stabilized by cooperative interactions.

  12. Effect of the nonlinearity of the carbonate system on partial pressure of carbon dioxide in the oceans

    NASA Technical Reports Server (NTRS)

    Trela, Piotr; Sathyendranath, Shubha; Moore, Robert M.; Kelley, Dan E.

    1995-01-01

    Partial pressure of CO2 is a nonlinear function of several seawater properties. Due to the nonlinearity in this relationship, the partial pressure of a uniform ocean would be different from that of a nonuniform ocean with the same bulk seawater properties. Assuming uniformity of seawater properties at some temporal and spatial scales in carbon models leads to systematic errors in partial pressure of CO2. In this paper we evaluate the magnitude of these errors. We partition the Geochemical Ocean Sections Study and Transient Tracers in the Oceans data according to the horizontal structure of several box models from the literature. Our results suggest that assumption of uniformity at large scales leads to understanding of underestimation of global surface ocean partial pressure of CO2 by at least 3 - 12 microatm. Nonlinear effects also introduce systematic errors in the buffer factor estimated from bulk seawater properties. We find the standard deviation of partial pressure of CO2 to be an indicator of the magnitude of the nonlinear effects. We discuss the implications of these errors for some conclusions drawn from carbon models. Biogeochemical processes, such as mixing, gas exchange, or biological activity, influence the distribution of the seawater properties. A shift in spatial or temporal patterns of these processes can modify the nonuniformity of the seawater properties and thus alter the partial pressure of the surface waters, even if the mean intensities of the processes remain constant.

  13. H2S concentrations in the arterial blood during H2S administration in relation to its toxicity and effects on breathing.

    PubMed

    Klingerman, Candice M; Trushin, Neil; Prokopczyk, Bogdan; Haouzi, Philippe

    2013-09-15

    Our aim was to establish in spontaneously breathing urethane-anesthetized rats, the relationship between the concentrations of H2S transported in the blood and the corresponding clinical manifestations, i.e., breathing stimulation and inhibition, during and following infusion of NaHS at increasing rates. The gaseous concentration of H2S (CgH2S, one-third of the total soluble form) was computed from the continuous determination of H2S partial pressure in the alveolar gas, while H2S, both dissolved and combined to hemoglobin, was measured at specific time points by sulfide complexation with monobromobimane (CMBBH2S). We found that using a potent reducing agent in vitro, H2S added to the whole blood had little interaction with the plasma proteins, as sulfide appeared to be primarily combined and then oxidized by hemoglobin. In vivo, H2S was undetectable in the blood in its soluble form in baseline conditions, while CMBBH2S averaged 0.7 0.5 ?M. During NaHS infusion, H2S was primarily present in nonsoluble form in the arterial blood: CMBBH2S was about 50 times higher than CgH2S at the lowest levels of exposure and 5 or 6 times at the levels wherein fatal apnea occurred. CgH2S averaged only 1.1 0.7 ?M when breathing increased, corresponding to a CMBBH2S of 11.1 5.4 ?M. Apnea occurred at CgH2S above 5.1 ?M and CMBBH2S above 25.4 ?M. At the cessation of exposure, CMBBH2S remained elevated, at about 3 times above baseline for at least 15 min. These data provide a frame of reference for studying the putative effects of endogenous H2S and for testing antidotes against its deadly effects. PMID:23904109

  14. HCl Vapour Pressures and Reaction Probabilities for ClONO2 + HCl on Liquid H2SO4-HNO3-HCl-H20 Solutions

    NASA Technical Reports Server (NTRS)

    Elrod, M. J.; Koch, R. E.; Kim, J. E.; Molina, M. J.

    1995-01-01

    Henry's Law solubility constants for HCl have been measured for liquid H2SO4-HNO3-HCl-H2O solutions; the results are in good agreement with predictions from published semiempirical models. The ClONO2 + HCl reaction on the surfaces of such solutions with compositions simulating those of stratospheric aerosols has been investigated; as the composition changes following the temperature drop characteristic of the high-latitude stratosphere the reaction probability gamma increases rapidly. Furthermore, the gamma values remain essentially unchanged when HN03 uptake is neglected; the controlling factor appears to be the solubility of HCl. These results corroborate our earlier suggestion that supercooled liquid sulfate aerosols promote chlorine activation at low temperatures as efficiently as solid polar stratospheric cloud particles.

  15. Partial Melting in the Iron-Sulfur System at High1 Pressure: A Synchrotron X-ray Diffraction Study2

    E-print Network

    Campbell, Andrew

    bound was established at 80 GPa. The28 accuracy of the melting point measured in these studies52 melting point depression at the pressure of the inner core / outer core boundary (13653 GPa1 Partial Melting in the Iron-Sulfur System at High1 Pressure: A Synchrotron X-ray Diffraction

  16. Kinetics of the Ar-Hg Plasma of Fluorescent Lamp Discharges. II. Ar Partial Pressure and Discharge Current Variation

    Microsoft Academic Search

    R. Winkler; J. Wilhelm

    1983-01-01

    In continuation of recent kinetic investigations of the main macroscopic quantities of the Ar-Hg plasma which include realistic electron kinetics at various Hg partial pressures, this paper deals with the study of the macroscopic plasma behaviour at varying discharge current and buffer gas pressure respectively in a wide range of practical interest. By simultaneously solving the particle balances for the

  17. Effect of steam partial pressure on gasification rate and gas composition of product gas from catalytic steam gasification of HyperCoal

    SciTech Connect

    Atul Sharma; Ikuo Saito; Toshimasa Takanohashi [National Institute of Advanced Industrial Science and Technology, Ibaraki (Japan). Advanced Fuel Group

    2009-09-15

    HyperCoal was produced from coal by a solvent extraction method. The effect of the partial pressure of steam on the gasification rate and gas composition at temperatures of 600, 650, 700, and 750{sup o}C was examined. The gasification rate decreased with decreasing steam partial pressure. The reaction order with respect to steam partial pressure was between 0.2 and 0.5. The activation energy for the K{sub 2}CO{sub 3}-catalyzed HyperCoal gasification was independent of the steam partial pressure and was about 108 kJ/mol. The gas composition changed with steam partial pressure and H{sub 2} and CO{sub 2} decreased and CO increased with decreasing steam partial pressure. By changing the partial pressure of the steam, the H{sub 2}/CO ratio of the synthesis gas can be controlled. 18 refs., 7 figs., 2 tabs.

  18. Deformation mechanisms in granodiorite at effective pressures to 100 MPa and temperatures to partial melting

    SciTech Connect

    Friedman, M.; Handin, J.; Bauer, S.J.

    1981-01-01

    Deformation mechanisms in room-dry and water-saturated specimens of Charcoal Granodiorite, shortened at 10/sup -4/s/sup -1/, at effective pressures (Pe) to 100 MPa and temperatures to partial melting (less than or equal to 1050/sup 0/C) are documented with a view toward providing criteria to recognize and characterize the deformation for geological and engienering applications. Above 800/sup 0/C strength decreases dramatically at effective pressures greater than or equal to 50 MPa and water-weakening reduces strength an additional 30 to 40% at Pe = 100 MPa. Strains at failure are only 0.1 to 2.2% with macroscopic ductility (within this range) increasing as the effective pressures are increased and in wet versus dry tests. Shattering (multiple faulting) gives way to faulting along a single zone to failure without macroscopic faulting as ductility increases. Microscopically, cataclasis (extension microfracturing and thermal cracking with rigid-body motions) predominates at all conditions. Dislocation gliding contributes little to the strain. Precursive extension microfractures coalesce to produce the throughgoing faults with gouge zones exhibiting possible Riedel shears. Incipient melting, particularly in wet tests, produces a distinctive texture along feldspar grain boundaries that suggests a grain-boundary-softening effect contributes to the weakening. In addition, it is demonstrated that the presence of water does not lead to more microfractures, but to a reduction in the stresses required to initiate and propagate them.

  19. The high-pressure phase diagram of synthetic epsomite (MgSO47H2O and MgSO47D2O) from ultrasonic and neutron powder diffraction measurements

    NASA Astrophysics Data System (ADS)

    Gromnitskaya, E. L.; Yagafarov, O. F.; Lyapin, A. G.; Brazhkin, V. V.; Wood, I. G.; Tucker, M. G.; Fortes, A. D.

    2013-03-01

    We present an ultrasonic and neutron powder diffraction study of crystalline MgSO47H2O (synthetic epsomite) and MgSO47D2O under pressure up to ~3 GPa near room temperature and up to ~2 GPa at lower temperatures. Both methods provide complementary data on the phase transitions and elasticity of magnesium sulphate heptahydrate, where protonated and deuterated counterparts exhibit very similar behaviour and properties. Under compression in the declared pressure intervals, we observed three different sequences of phase transitions: between 280 and 295 K, phase transitions occurred at approximately 1.4, 1.6, and 2.5 GPa; between 240 and 280 K, only a single phase transition occurred; below 240 K, there were no phase transformations. Overall, we have identified four new phase fields at high pressure, in addition to that of the room-pressure orthorhombic structure. Of these, we present neutron powder diffraction data obtained in situ in the three phase fields observed near room temperature. We present evidence that these high-pressure phase fields correspond to regions where MgSO47H2O decomposes to a lower hydrate by exsolving water. Upon cooling to liquid nitrogen temperatures, the ratio of shear modulus G to bulk modulus B increases and we observe elastic softening of both moduli with pressure, which may be a precursor to pressure-induced amorphization. These observations may have important consequences for modelling the interiors of icy planetary bodies in which hydrated sulphates are important rock-forming minerals, such as the large icy moons of Jupiter, influencing their internal structure, dynamics, and potential for supporting life.

  20. Qualitative determination of H2S crossover rates in nation membranes using ion-probe techniques

    SciTech Connect

    Brosha, Eric L [Los Alamos National Laboratory; Rockward, Tommy [Los Alamos National Laboratory; Uribe, Francisco A [Los Alamos National Laboratory; Garzon, Fernando H [Los Alamos National Laboratory

    2008-01-01

    Polymer electrolyte membrane fuel cells are sensitive to impurities that may be present in either the oxidizer or fuel. H2S, even at the ppb level, will have a dramatic and adverse affect on fuel cell performance. The H2S permeability through dry and humidified Nafion PEMFC membranes was studied using ion probe techniques. A sulfide anti-oxidant buffer solution was used to trap and concentrate trace quantities of H2S that permeated through 50 cm2samples of Nafion 117 and 212 membranes using a partial pressure difference up to I030ppm at room temperature. Experiments were conducted for up to 24 hours in order to achieve sulfide ion concentrations high enough to be precisely determined by subsequent titration with Pb(N03)2. The rate of H2S crossover for dry 117 and 212 were identical at 1.2e-7 g/min. Humidification increased the crossover rate to 5.ge-7 glmin and 1.8e-6 glmin for 117 and 212 respectively. Although the data collected in this work show that the rate of H2S crossover increases with water content and reduced membrane thickness, an accurate determination of permeation constants from this work was not possible because the H2S partial pressure was not constant throughout the experiment.

  1. Decompression and H2O exsolution driven crystallization and fractionation: development of a new model for low-pressure fractional crystallization in calc-alkaline magmatic systems

    NASA Astrophysics Data System (ADS)

    Brophy, James Gerald

    2009-06-01

    Magma ascent, decompression-induced H2O exsolution and crystallization is now recognized as an important process in hydrous subduction zone magmas. During the course of such a process calculations suggest that the ascent rate of a degassing and crystallizing mafic magma will be greater than crystal settling velocities. Thus, any crystals formed as a consequence of volatile exsolution will remain suspended in the magma. If the magma erupts before the percentage of suspended crystals reaches the critical crystallinity value for mafic magma (~55 vol.%) it will produce the commonly observed crystal rich island arc basalt lava. If the magma reaches its critical crystallinity before it erupts then it will stall within the crust. Extension of compaction experiments on a 55 vol.% sand-Karo syrup suspension at different temperatures (and liquid viscosities) to the likely viscosities of interstitial andesitic to dacitic liquid within such a stalled magma suggest that small amounts (up to ~10%) can be expelled on a time scale of 1-10 years. The expelled liquid can create a new intermediate to silicic body of magma that is related to the original mafic magma via fractional crystallization. The short time scale for liquid expulsion indicate that decompression-induced H2O exsolution and crystallization can be an important mechanism for fractional crystallization. Based on this assumption a general model of decompression-induced crystallization and fractionation is proposed that explains many of the compositional, mineralogical and textural features of Aleutian (and other andesites).

  2. Effect of H2O on the density of silicate melts at high pressures: Static experiments and the application of a modified hard-sphere model of equation of state

    NASA Astrophysics Data System (ADS)

    Jing, Zhicheng; Karato, Shun-ichiro

    2012-05-01

    Density of ultramafic silicate melts was determined using the sink/float technique at high pressures. Seven melt compositions were studied, among which three were dry compositions with different Mg#'s (molar MgO/(MgO + FeO) 100) and the other four were hydrous compositions synthesized by adding 2-7 wt.% H2O to the anhydrous ones. Experimental conditions range from 9 to 15 GPa and from 2173 to 2473 K. The sinking and floatation of density markers were observed for all melt compositions. Melt density data were analyzed by applying the Birch-Murnaghan equation of state and a newly developed equation of state for silicate melts based on the model of hard sphere mixtures. The presence of water can significantly reduce the density of melts due to its small molecular mass. On the other hand, water makes hydrous silicate melts more compressible than anhydrous melts and therefore the effect of H2O on melt density is less significant at high pressures. The density of hydrous melts was then calculated as a function of H2O content at the conditions of the bottom of the upper mantle, and was compared with the density of the dominant upper mantle minerals. Results show that the conditions for a negatively buoyant melt that coexists with a pyrolite mantle atop the 410 km discontinuity are marginally satisfied if H2O is the only volatile component to facilitate melting, but such conditions will be satisfied by a broader range of conditions when other heavier volatile elements (C, K, etc.) are also present.

  3. Partial Pressures for Several In-Se Compositions from Optical Absorbance of the Vapor

    NASA Technical Reports Server (NTRS)

    Brebrick, R. F.; Su, Ching-Hua

    2001-01-01

    The optical absorbance of the vapor phase over various In-Se compositions between 33.3-60.99 at.% Se and 673-1418 K was measured and used to obtain the partial pressures of Se2(g) and In2Se(g). The results are in agreement with silica Bourdon gauge measurements for compositions between 50-61 at.%, but significantly higher than those from Knudsen cell and simultaneous Knudsen-torsion cell measurements. It is found that 60.99 at.% Se lies outside the sesquiselenide homogeneity range and 59.98 at.% Se lies inside and is the congruently melting composition. The Gibbs energy of formation of the liquid from its pure liquid elements between 1000-1300 K is essentially independent of temperature and falls between -36 to -38 kJ per g atomic weight for 50 and 56% Se at 1200 and 1300 K.

  4. Organic Tank Safety Project: Effect of water partial pressure on the equilibrium water content of waste samples from Hanford Tank 241-U-105

    SciTech Connect

    Scheele, R.D.; Bredt, P.R.; Sell, R.L.

    1997-09-01

    Water content plays a crucial role in the strategy developed by Webb et al. to prevent propagating or sustainable chemical reactions in the organic-bearing wastes stored in the 20 Organic Tank Watch List tanks at the U.S. Department of Energy`s Hanford Site. Because of water`s importance in ensuring that the organic-bearing wastes continue to be stored safely, Duke Engineering and Services Hanford commissioned the Pacific Northwest National Laboratory to investigate the effect of water partial pressure (P{sub H2O}) on the water content of organic-bearing or representative wastes. Of the various interrelated controlling factors affecting the water content in wastes, P{sub H2O} is the most susceptible to being controlled by the and Hanford Site`s environmental conditions and, if necessary, could be managed to maintain the water content at an acceptable level or could be used to adjust the water content back to an acceptable level. Of the various waste types resulting from weapons production and waste-management operations at the Hanford Site, determined that saltcake wastes are the most likely to require active management to maintain the wastes in a Conditionally Safe condition. Webb et al. identified Tank U-105 as a Conditionally Safe saltcake tank. A Conditionally Safe waste is one that is currently safe based on waste classification criteria but could, if dried, be classified as {open_quotes}Unsafe.{close_quotes} To provide information on the behavior of organic-bearing wastes, the Westinghouse Hanford Company provided us with four waste samples taken from Tank 241-U-105 (U-105) to determine the effect of P{sub H2O} on their equilibrium water content.

  5. Thickness and oxygen partial pressure dependence on optical band gap of indium oxide by reactive evaporation method

    NASA Astrophysics Data System (ADS)

    Muhammed Ali, A. V.; Kekuda, Dhananjaya

    2015-02-01

    Indium oxide film is deposited by reactive evaporation of indium in the presence of oxygen gas onto an unheated glass substrate. It was found that thickness of the film and partial oxygen pressure during the deposition affects the optical properties of the indium oxide thin film. We studied the optical band gap for different thickness and partial pressure keeping a constant annealing temperature. It was found that the band gap varies from 3.5 to 3.8eV, as thickness of the film increased. The band gap energy had also shows the similar trend and it was also studied as a function of annealing temperature. A systematic investigation of the optical band gap as a function of thickness and oxygen partial pressure at different annealing temperature was carried out.

  6. Prediction of the local pressure gradient during partially developed subcooled boiling in research reactors of high power density

    Microsoft Academic Search

    J. L. McDuffee; A. E. Ruggles

    1997-01-01

    A model is presented for predicting the pressure gradient in partially developed subcooled boiling of water for velocities from 15 to 30 m\\/s and inlet peaked, nonuniform axial flux profiles with channel average flux values of 6 MW\\/m². The partially and fully developed boiling regions are considered separately, however, the same general modeling technique is used for both. several correlations

  7. H2O Adsorption on Smectites: Application to the Diurnal Variation of H2O in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Howard, J.; Quinn, R. C.

    2000-01-01

    Observations of the Martian planetary boundary layer lead to interpretations that are baffling and contradictory. In this paper, we specifically address the question of whether or not water vapor finds a substantial diurnal reservoir in the Martian regolith. To address this issue, we have measured H2O adsorption kinetics on SWy-1, a Na-rich montmorillonite from Wyoming. The highest-temperature (273 K) data equilibrates rapidly. Data gathered at realistic H2O partial pressures and temperatures appropriate to early morning show two phenomena that preclude a significant role for smectites in diurnally exchanging a large column abundance. First, the equilibration timescale is longer than a sol. Second, the equilibrium abundances are a small fraction of that predicted by earlier adsorption isotherms. The explanation for this phenomenon is that smectite clay actually increases its surface area as a function of adsorptive coverage. At Mars-like conditions, we show that the interlayer sites of smectites are likely to be unavailable.

  8. Stratospheric H2O

    NASA Technical Reports Server (NTRS)

    Ellsaesser, H. W.; Harries, J. E.; Kley, D.; Penndorf, R.

    1980-01-01

    The present state of our knowledge and understanding of H2O in the stratosphere is reviewed. This reveals continuing discrepancies between observations and expectations following from the Brewer-Dobson hypothesis of stratospheric circulation. In particular, available observations indicate unexplained upward and poleward directed H2O gradients immediately downstream from the tropical tropopause and variable vertical gradients above 20 km which generally disagree with those expected from oxidation of CH4.

  9. Prediction of the local pressure gradient during partially developed subcooled boiling in research reactors of high power density

    SciTech Connect

    McDuffee, J.L. [JBF Associates, Knoxville, TN (United States); Ruggles, A.E. [Univ. of Tennessee, Knoxville, TN (United States)

    1997-02-01

    A model is presented for predicting the pressure gradient in partially developed subcooled boiling of water for velocities from 15 to 30 m/s and inlet peaked, nonuniform axial flux profiles with channel average flux values of 6 MW/m{sup 2}. The partially and fully developed boiling regions are considered separately, however, the same general modeling technique is used for both. several correlations for the void fraction at onset of significant void are considered, and their effect on the channel pressure drop is evaluated. The effect of nonuniform axial heat flux on the channel pressure drop is also evaluated. The model is compared with pressure drop data from the thermal-hydraulic test loop at Oak Ridge National Laboratory and is found to agree with the data within 24%.

  10. Spectroscopic studies on nanocrystalline silicon thin films prepared from H2-diluted SiH4-plasma in inductively coupled low pressure RF PECVD

    NASA Astrophysics Data System (ADS)

    Chakraborty, Mahua; Banerjee, Amit; Das, Debajyoti

    2014-07-01

    A comprehensive analysis on the evolution of the microstructure as well as optical constants and dielectric functions of intrinsic hydrogenated nano-crystalline silicon thin films prepared by highly H2 diluted SiH4 plasma in a planar inductively coupled RF plasma chemical vapor deposition (ICP-CVD) reactor has been performed by spectroscopic ellipsometry. Films are assumed to have a three-layer structure, with a thin incubation layer at substrate/bulk interface, the bulk layer and a thin growth zone and surface roughness layer. Individual composition and the thickness of each layer have been estimated from the simulation of the ellipsometry data using Bruggeman effective medium approximation (BEMA). The ellipsometry results are correlated with atomic force microscopy and micro-Raman data of these films. The effect of the flow rate of SiH4 and the key role of hydrogen dilution on growth dynamics, optical constants and dielectric functions of highly crystalline nanosilicon films is discussed elaborately. The bulk crystalline volume fraction of the deposited films varies considerably (~67-84%) with the change in flow rate of SiH4. With increasing SiH4 flow rate the overall bulk crystallinity reduces; however the ultra-nanocrystalline component (Xunc) enhances substantially that helps reducing the porosity and surface roughness.

  11. High Oxygen Partial Pressure Decreases Anemia-Induced Heart Rate Increase Equivalent to Transfusion

    PubMed Central

    Feiner, John R.; Finlay-Morreale, Heather E.; Toy, Pearl; Lieberman, Jeremy A.; Viele, Maurene K.; Hopf, Harriet W.; Weiskopf, Richard B.

    2011-01-01

    Background Anemia is associated with morbidity and mortality and frequently leads to transfusion of erythrocytes. We sought to compare directly the effect of high inspired oxygen fraction vs. transfusion of erythrocytes on the anemia-induced increased heart rate (HR) in humans undergoing experimental acute isovolemic anemia. Methods We combined HR data from healthy subjects undergoing experimental isovolemic anemia in seven studies performed by our group. We examined HR changes associated with breathing 100% oxygen by non-rebreathing face mask vs. transfusion of erythrocytes at their nadir hemoglobin (Hb) concentration of 5 g/dL. Data were analyzed using a mixed-effects model. Results HR had an inverse linear relationship to hemoglobin concentration with a mean increase of 3.9 beats per minute per gram of Hb (beats/min/g Hb) decrease (95% confidence interval [CI], 3.7 4.1 beats/min/g Hb), P < 0.0001. Return of autologous erythrocytes significantly decreased HR by 5.3 beats/min/g Hb (95% CI, 3.8 6.8 beats/min/g Hb) increase, P < 0.0001. HR at nadir Hb of 5.6 g/dL (95% CI, 5.5 5.7 g/dL) when breathing air (91.4 beats/min; 95% CI, 87.6 95.2 beats/min) was reduced by breathing 100% oxygen (83.0 beats/min; 95% CI, 79.0 -87.0 beats/min), P < 0.0001. The HR at hemoglobin 5.6 g/dL when breathing oxygen was equivalent to the HR at Hb 8.9 g/dL when breathing air. Conclusions High arterial oxygen partial pressure reverses the heart rate response to anemia, probably owing to its usability, rather than its effect on total oxygen content. The benefit of high arterial oxygen partial pressure has significant potential clinical implications for the acute treatment of anemia and results of transfusion trials. PMID:21768873

  12. H2O Adsorption Kinetics on Smectites

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Quinn, Richard C.; Howard, Jeanie; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The adsorptive equilibration of H2O a with montomorillonite, a smectite clay has been measured. At low temperatures and pressures, equilibration can require many hours, effectively preventing smectites at the martian surface from responding rapidly to diurnal pressure and temperature variations.

  13. Pressure and partial wetting effects on superhydrophobic friction reduction in microchannel flow

    NASA Astrophysics Data System (ADS)

    Kim, Tae Jin; Hidrovo, Carlos

    2012-11-01

    Friction reduction in microchannel flows can help alleviate the inherently taxing pumping power requirements associated with the dimensions involved. One possible way of achieving friction reduction is through the introduction of surface microtexturing that can lead to a superhydrophobic Cassie-Baxter state. The Cassie-Baxter state is characterized by the presence of air pockets within the surface microtexturing believed to act as an effective "shear free" (or at least shear reduced) layer, decreasing the overall friction characteristics of the surface. Most work in this area has concentrated on optimizing the surface microtexturing geometry to maximize the friction reduction effects and overall stability of the Cassie-Baxter state. However, less attention has been paid to the effects of partially wetted conditions induced by pressure and the correlation between the liquid-gas interface location within the surface microtexturing and the microchannel flow characteristics. This is mainly attributed to the difficulty in tracking the interface shape and location within the microtexturing in the typical top-down view arrangements used in most studies. In this paper, a rectangular microchannel with regular microtexturing on the sidewalls is used to visualize and track the location of the air-water interface within the roughness elements. While visually tracking the wetting conditions in the microtextures, pressure drops versus flow rates for each microchannel are measured and analyzed in terms of the non-dimensional friction coefficient. The frictional behavior of the Poiseuille flow suggests that (1) the air-water interface more closely resembles a no-slip boundary rather than a shear-free one, (2) the friction is rather insensitive to the degree of microtexturing wetting, and (3) the fully wetted (Wenzel state) microtexturing provides lower friction than the non-wetted one (Cassie state), in corroboration with observations (1) and (2).

  14. Value of measuring end tidal partial pressure of carbon dioxide as an adjunct to treadmill exercise testing

    Microsoft Academic Search

    John B Chambers; Peter J Kiff; William N Gardner; Graham Jackson; Christopher Bass

    1988-01-01

    The end tidal partial pressure of carbon dioxide (Pco2) was measured during treadmill exercise in 30 normal controls and 113 patients referred for assessment of chest pain. Among the 92 patients without significant ST depression hypocapnia occurred more often in those reporting typical than atypical chest pain (17 of 22 patients compared with 29 of 70; p<001). Hypocapnia was uncommon

  15. Near-infrared spectra of H2O under high pressure and high temperature: Implications for a transition from proton tunneling to hopping states

    NASA Astrophysics Data System (ADS)

    Noguchi, Naoki; Komatsu, Kazuki; Shinozaki, Ayako; Shinoda, Keiji; Kagi, Hiroyuki

    2014-12-01

    The nature of protons in ice VII up to 368 C and 16 GPa was investigated with synchrotron near-infrared spectroscopy. The absorption band of the first OH stretching overtone mode divided into doublet peaks above 5 GPa at room temperature, suggesting that proton tunneling occurs at the overtone level. As the temperature increased, the doublet peaks gradually reduced to a singlet. This result implies that thermally activated protons hop between the two potential minima along the oxygen-oxygen axis. A pressure-temperature diagram for the proton state was constructed from the changing band shape of the overtone mode.

  16. Silicate Carbonation in Supercritical CO2 Containing Dissolved H2O: An in situ High Pressure X-Ray Diffraction Study

    SciTech Connect

    Schaef, Herbert T.; Miller, Quin RS; Thompson, Christopher J.; Loring, John S.; Bowden, Mark E.; Arey, Bruce W.; McGrail, B. Peter; Rosso, Kevin M.

    2013-01-01

    Technological advances have been significant in recent years for managing environmentally harmful emissions (mostly CO2) resulting from combustion of fossil fuels. Deep underground geologic formations are emerging as reasonable options for long term storage of CO2 but mechanisms controlling rock and mineral stability in contact with injected supercritical fluids containing water are relatively unknown. In this paper, we discuss mineral transformation reactions occurring between supercritical CO2 containing water and the silicate minerals forsterite (Mg2SiO4), wollastonite (CaSiO3), and enstatite (MgSiO3). This study utilizes newly developed in situ high pressure x-ray diffraction (HXRD) and in situ infra red (IR) to examine mineral transformation reactions. Forsterite and enstatite were selected as they are important minerals present in igneous and mafic rocks and have been the subject of a large number of aqueous dissolution studies that can be compared with non-aqueous fluid tests in this study. Wollastonite, classified as a pyroxenoid (similar to a pyroxene), was chosen as a suitably fast reacting proxy for examining silicate carbonation processes associated with a wet scCO2 fluid as related to geologic carbon sequestration. The experiments were conducted under modest pressures (90 to 160 bar), temperatures between 35 to 70 C, and varying concentrations of dissolved water. Under these conditions scCO2 contains up to 3,500 ppm dissolved water.

  17. Crystalline structure of ceria particles controlled by the oxygen partial pressure and STI CMP performances.

    PubMed

    Kim, Ye-Hwan; Kim, Sang-Kyun; Kim, Namsoo; Park, Jea-Gun; Paik, Ungyu

    2008-09-01

    The effect of the crystalline structures of nano-sized ceria particles on shallow trench isolation (STI) chemical mechanical planarization (CMP) performance was investigated. The ceria particles were synthesized via a solid-state displacement reaction method, and their crystalline structure was controlled by regulating the oxygen partial pressure at the reaction site on the precursor. The crystalline structures of ceria particles were analyzed by the high-resolution TEM nano-beam diffraction pattern. In a calcination process with a high oxygen concentration, the synthesized ceria particles had a cubic fluorite structure (CeO(2)), because of the decarbonation of the cerium precursor. However, a low oxygen concentration results in a hexagonal phase cerium oxide (Ce(2)O(3)) rather than the cubic phase due to the insufficient oxidation of Ce(3+) to Ce(4+). In the STI CMP evaluation, the ceria slurry prepared with the cubic CeO(2) shows enhanced performances of the oxide-to-nitride removal selectivity. PMID:18562111

  18. Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

    SciTech Connect

    Singh, J.P.; Joo, J.; Guttschow, R.; Poeppel, R.B.

    1992-02-01

    Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {mu}m) and hence a high strength of 191 {plus_minus} 7 MPa. Addition of Ag as a second phase further improved the strength of YBCO. Composites of YBCO with 10 to 15 vol % Ag has a strength of 225 {plus_minus} 6 MPa and a fracture toughness of 3.3 {plus_minus} 0.2 MPa{radical}m. These improvements are believed to be due to compressive stresses in the YBCO matrix as a result of thermal mismatch between the YBCO and Ag phases. Furthermore, the Ag particles may provide increased resistance to crack propagation by pinning the crack. On the other hand, addition of Ag as a dopant to substitute for Cu sites in YBCO has a profound but nonmonotonic effect on grain microstructure and the resulting critical current density.

  19. Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

    SciTech Connect

    Singh, J.P.; Joo, J.; Guttschow, R.; Poeppel, R.B.

    1992-02-01

    Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {mu}m) and hence a high strength of 191 {plus minus} 7 MPa. Addition of Ag as a second phase further improved the strength of YBCO. Composites of YBCO with 10 to 15 vol % Ag has a strength of 225 {plus minus} 6 MPa and a fracture toughness of 3.3 {plus minus} 0.2 MPa{radical}m. These improvements are believed to be due to compressive stresses in the YBCO matrix as a result of thermal mismatch between the YBCO and Ag phases. Furthermore, the Ag particles may provide increased resistance to crack propagation by pinning the crack. On the other hand, addition of Ag as a dopant to substitute for Cu sites in YBCO has a profound but nonmonotonic effect on grain microstructure and the resulting critical current density.

  20. Re-oxidation Kinetics of Flash-Reduced Iron Particles in H2-H2O(g) Atmosphere Relevant to a Novel Flash Ironmaking Process

    NASA Astrophysics Data System (ADS)

    Yuan, Zhixue; Sohn, Hong Yong; Olivas-Martinez, Miguel

    2013-12-01

    A novel flash ironmaking process based on hydrogen-containing reduction gases is under development at the University of Utah. The goal of this work was to study the possibility of the re-oxidation of iron particles in a H2-H2O gas mixture in the lower part of the flash reactor from the kinetic point of view. The last stage of hydrogen reduction of iron oxide, i.e., the reduction of wustite, is limited by equilibrium. As the reaction mixture cools down, the re-oxidation of iron could take place because of the decreasing equilibrium constant and the high reactivity of the freshly reduced fine iron particles. The effects of temperature and H2O partial pressure on the re-oxidation rate were examined in the temperature range of 823 K to 973 K (550 C to 700 C) and H2O contents of 40 to 100 pct. The nucleation and growth kinetics model was shown to best describe the re-oxidation kinetics. The partial pressure dependence with respect to water vapor was determined to be of first order, and the activation energy of re-oxidation reaction was 146 kJ/mol. A complete rate equation that adequately represents the experimental data was developed.

  1. Pressures of Partial Crystallization along the East Pacific Rise: Preliminary Results and Evidence for Deep Crustal Chambers?

    NASA Astrophysics Data System (ADS)

    Zerda, C.; Scott, J. L.; Barton, M.

    2013-12-01

    The fast spreading East Pacific Rise (EPR) between 8N and 14N is characterized by ~20 ridge axis discontinuities. Previous work has suggested that magmas erupted at some of these discontinuities, specifically at transform faults, partially crystallize at higher pressures than magmas erupted along 'normal' ridge segments. In order to evaluate the factors that control the plumbing systems of MORB, we have determined the pressures (P) of partial crystallization of magmas beneath the EPR from 8N to 14N using 2,837 published chemical analyses of basalt glasses. Pressures were calculated using the two different methods described by Herzberg, 2004 (H) and Kelley and Barton, 2008 (KB). These two methods are expected to yield minimum and maximum values for calculated pressures. However, for the samples used in this work both methods yield virtually identical pressures for the entire data set (average pressures: H=182.3143.6 MPa and KB=200.9153.3 MPa) and we elected to use results obtained with the KB method for detailed analysis of the results. Based on sample frequency, the EPR was divided into 10 sections that include 'normal' segments lacking axial discontinuities and segments that include discontinuities such as a transform fault, an overlapping spreading center (OSC), or a deviation from axial linearity, or one or more of these features. The average pressure of partial crystallization for 'normal' segments is 145.659.9 MPa, and is essentially constant along the whole length of the ridge studied. These results are consistent with crystallization at depths of ~ 5km near the base of the crust and, as with results obtained for the Juan da Fuca and Reykjanes ridge, provide no evidence for crystallization in the upper mantle along 'normal' ridge segments. The pressures of partial crystallization of magmas at or near axial discontinuities show a wider range than those for magmas erupted along normal ridge segments. The maximum pressures for samples from the Clipperton and Siqueiros fracture zones, for example, exceed 300 Mpa and range up to ~600 MPa. This confirms the findings of previous workers and appears to indicate partial crystallization in the upper mantle at depths of 10-20 km. It has been suggested that the greater depths of partial crystallization of magmas at transform faults and other ridge discontinuities reflects the presence of cooler mantle beneath these features. However, many of the samples that yield high pressures have anomalous chemical compositions (shown primarily in the concentrations of CaO and Al2O3) compared with magmas erupted along 'normal' ridge segments. We interpret these chemical anomalies to result from magma-crust interaction, and when samples with anomalous compositions are filtered out of the data base, we obtain pressures of partial crystallization for magmas erupted near ridge discontinuities that are similar to those obtained for magmas erupted along normal ridge segments. Work is underway to refine the results reported here, and it is possible this refinement will lead to a decrease in calculated pressures of partial crystallization.

  2. A New Equation of State for H2O Ice Ih

    Microsoft Academic Search

    Rainer Feistel; Wolfgang Wagner

    2006-01-01

    Various thermodynamic equilibrium properties of naturally abundant, hexagonal ice (ice Ih) of water (H2O) have been used to develop a Gibbs energy function g(T,p) of temperature and pressure, covering the ranges 0273.16 K and 0 Pa210 MPa, expressed in the temperature scale ITS-90. It serves as a fundamental equation from which additional properties are obtained as partial derivatives by thermodynamic

  3. Revealing sub-?m and ?m-scale textures in H2O ice at megabar pressures by time-domain Brillouin scattering.

    PubMed

    Nikitin, Sergey M; Chigarev, Nikolay; Tournat, Vincent; Bulou, Alain; Gasteau, Damien; Castagnede, Bernard; Zerr, Andreas; Gusev, Vitalyi E

    2015-01-01

    The time-domain Brillouin scattering technique, also known as picosecond ultrasonic interferometry, allows monitoring of the propagation of coherent acoustic pulses, having lengths ranging from nanometres to fractions of a micrometre, in samples with dimension of less than a micrometre to tens of micrometres. In this study, we applied this technique to depth-profiling of a polycrystalline aggregate of ice compressed in a diamond anvil cell to megabar pressures. The method allowed examination of the characteristic dimensions of ice texturing in the direction normal to the diamond anvil surfaces with sub-micrometre spatial resolution via time-resolved measurements of the propagation velocity of the acoustic pulses travelling in the compressed sample. The achieved imaging of ice in depth and in one of the lateral directions indicates the feasibility of three-dimensional imaging and quantitative characterisation of the acoustical, optical and acousto-optical properties of transparent polycrystalline aggregates in a diamond anvil cell with tens of nanometres in-depth resolution and a lateral spatial resolution controlled by pump laser pulses focusing, which could approach hundreds of nanometres. PMID:25790808

  4. Revealing sub-?m and ?m-scale textures in H2O ice at megabar pressures by time-domain Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Nikitin, Sergey M.; Chigarev, Nikolay; Tournat, Vincent; Bulou, Alain; Gasteau, Damien; Castagnede, Bernard; Zerr, Andreas; Gusev, Vitalyi E.

    2015-03-01

    The time-domain Brillouin scattering technique, also known as picosecond ultrasonic interferometry, allows monitoring of the propagation of coherent acoustic pulses, having lengths ranging from nanometres to fractions of a micrometre, in samples with dimension of less than a micrometre to tens of micrometres. In this study, we applied this technique to depth-profiling of a polycrystalline aggregate of ice compressed in a diamond anvil cell to megabar pressures. The method allowed examination of the characteristic dimensions of ice texturing in the direction normal to the diamond anvil surfaces with sub-micrometre spatial resolution via time-resolved measurements of the propagation velocity of the acoustic pulses travelling in the compressed sample. The achieved imaging of ice in depth and in one of the lateral directions indicates the feasibility of three-dimensional imaging and quantitative characterisation of the acoustical, optical and acousto-optical properties of transparent polycrystalline aggregates in a diamond anvil cell with tens of nanometres in-depth resolution and a lateral spatial resolution controlled by pump laser pulses focusing, which could approach hundreds of nanometres.

  5. Organic tank safety project: Effect of water partial pressure on the equilibrium water contents of waste samples from Hanford Tank 241-BY-108

    SciTech Connect

    Scheele, R.D.; Bredt, P.R.; Sell, R.L.

    1997-02-01

    Water content plays a crucial role in the strategy developed by Webb et al. to prevent propagating or sustainable chemical reactions in the organic-bearing wastes stored in the 20 Organic Tank Watch List tanks at the US Department of Energy`s Hanford Site. Because of water`s importance in ensuring that the organic-bearing wastes continue to be stored safely, Duke Engineering and Services Hanford commissioned the Pacific Northwest National Laboratory (PNNL) to investigate the effect of water partial pressure (P{sub H2O}) on the water content of organic-bearing or representative wastes. Of the various interrelated controlling factors affecting the water content in wastes, P{sub H2O} is the most susceptible to being controlled by the and Hanford Site`s environmental conditions and, if necessary, could be managed to maintain the water content at an acceptable level or could be used to adjust the water content back to an acceptable level. Of the various waste types resulting from weapons production and waste-management operations at the Hanford Site, Webb et al. determined that saltcake wastes are the most likely to require active management to maintain the wastes in a Conditionally Safe condition. A Conditionally Safe waste is one that satisfies the waste classification criteria based on water content alone or a combination of water content and either total organic carbon (TOC) content or waste energetics. To provide information on the behavior of saltcake wastes, two waste samples taken from Tank 241-BY-108 (BY-108) were selected for study, even though BY-108 is not on the Organic Tanks Watch List because of their ready availability and their similarity to some of the organic-bearing saltcakes.

  6. CdTe I: Solidus curve and composition-temperature-tellurium partial pressure data for Te-rich CdTe(s) from optical density measurements

    Microsoft Academic Search

    Rei Fang; R. F. Brebrick

    1996-01-01

    Known weights of Cd and Te in a silica optical cell of known volume were reacted and the partial pressure of Te2 determined by measuring the optical density of the vapor in the visible. The composition of the condensed phase or phases was calculated from the original weights and the amount of material in the vapor phase. The partial pressure

  7. Abstract Atmospheric CO2 partial pressure (pCO2) was as low as 18 Pa during the Pleistocene and is projected to

    E-print Network

    Antonovics, Janis

    Abstract Atmospheric CO2 partial pressure (pCO2) was as low as 18 Pa during the Pleistocene Reproduction Selection Introduction That the high atmospheric CO2 partial pressure (pCO2) projected is important for predicting the degree to which plants may sequester atmospheric CO2 in the fu- ture

  8. Oxygen partial pressure influence on the character of InGaZnO thin films grown by PLD

    NASA Astrophysics Data System (ADS)

    Lu, Yi; Wang, Li

    2012-11-01

    The amorphous oxide semiconductors (AOSs) are promising for emerging large-area optoelectronic applications because of capability of large-area, uniform deposition at low temperatures such as room temperature (RT). Indium-gallium-zinc oxide (InGaZnO) thin film is a promising amorphous semiconductors material in thin film transistors (TFT) for its excellent electrical properties. In our work, the InGaZnO thin films are fabricated on the SiO2 glass using pulsed laser deposition (PLD) in the oxygen partial pressure altered from 1 to 10 Pa at RT. The targets were prepared by mixing Ga2O3, In2O3, and ZnO powder at a mol ratio of 1: 7: 2 before the solid-state reactions in a tube furnace at the atmospheric pressure. The targets were irradiated by an Nd:YAG laser(355nm). Finally, we have three films of 270nm, 230nm, 190nm thick for 1Pa, 5Pa, 10Pa oxygen partial pressure. The product thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), Hall-effect investigation. The comparative study demonstrated the character changes of the structure and electronic transport properties, which is probably occurred as a fact of the different oxygen partial pressure used in the PLD.

  9. Effects of elevated oxygen and carbon dioxide partial pressures on respiratory function and cognitive performance.

    PubMed

    Gill, Matthew; Natoli, Michael J; Vacchiano, Charles; MacLeod, David B; Ikeda, Keita; Qin, Michael; Pollock, Neal W; Moon, Richard E; Pieper, Carl; Vann, Richard D

    2014-08-15

    Hyperoxia during diving has been suggested to exacerbate hypercapnic narcosis and promote unconsciousness. We tested this hypothesis in male volunteers (12 at rest, 10 at 75 W cycle ergometer exercise) breathing each of four gases in a hyperbaric chamber. Inspired Po2 (PiO2 ) was 0.21 and 1.3 atmospheres (atm) without or with an individual subject's maximum tolerable inspired CO2 (PiO2 = 0.055-0.085 atm). Measurements included end-tidal CO2 partial pressure (PetCO2 ), rating of perceived discomfort (RPD), expired minute ventilation (V?e), and cognitive function assessed by auditory n-back test. The most prominent finding was, irrespective of PetCO2 , that minute ventilation was 8-9 l/min greater for rest or exercise with a PiO2 of 1.3 atm compared with 0.21 atm (P < 0.0001). For hyperoxic gases, PetCO2 was consistently less than for normoxic gases (P < 0.01). For hyperoxic hypercapnic gases, n-back scores were higher than for normoxic gases (P < 0.01), and RPD was lower for exercise but not rest (P < 0.02). Subjects completed 66 hyperoxic hypercapnic trials without incident, but five stopped prematurely because of serious symptoms (tunnel vision, vision loss, dizziness, panic, exhaustion, or near syncope) during 69 normoxic hypercapnic trials (P = 0.0582). Serious symptoms during hypercapnic trials occurred only during normoxia. We conclude serious symptoms with hyperoxic hypercapnia were absent because of decreased PetCO2 consequent to increased ventilation. PMID:24947022

  10. Resting and Post Bronchial Challenge Testing Carbon Dioxide Partial Pressure in Individuals with and without Asthma

    PubMed Central

    Miedinger, David; Jochmann, Anja; Schoenenberger, Lucia; Chhajed, Prashant N.; Leuppi, Jrg D.

    2012-01-01

    Objective There is conflicting evidence about resting carbon dioxide levels in asthmatic individuals. We wanted to determine if transcutaneously measured carbon dioxide levels prior and during bronchial provocation testing differ according to asthma status reflecting dysfunctional breathing. Methods We investigated active firefighters and policemen by means of a validated questionnaire on respiratory symptoms, spirometry, bronchial challenge testing with methacholine (MCT) and measurement of transcutaneous blood carbon dioxide partial pressure (PtcCO2) at rest prior performing spirometry, one minute and five minutes after termination of MCT. A respiratory physician blinded to the PtcCO2 results assigned a diagnosis of asthma after reviewing the available study data and the files of the workers medical screening program. Results The study sample consisted of 128 male and 10 female individuals. Fifteen individuals (11%) had physician-diagnosed asthma. There was no clinically important difference in median PtcCO2 at rest, one and five minutes after recovery from MCT in asthmatics compared to non-asthmatics (35.6 vs 35.7 mmHg, p?=?0.466; 34.7 vs 33.4 mmHg, p?=?0.245 and 37.4 vs 36.4 mmHg, p?=?0.732). The median drop in PtcCO2 during MCT and the increase after MCT was lower in asthmatics compared to non-asthmatics (0.1 vs 3.2 mmHg, p?=?0.014 and 1.9 vs 2.9 mmHg, p?=?0.025). Conclusions PtcCO2 levels at rest prior and during recovery after MCT do not differ in individuals with or without physician diagnosed asthma. The fall and subsequent increase in PtcCO2 levels are higher in non-asthmatics than in asthmatics and seems to be related with increased number of respiratory maneuvers during MCT. PMID:22412876

  11. Why is the partial oxygen pressure of human tissues a crucial parameter? Small molecules and hypoxia

    PubMed Central

    Carreau, Aude; Hafny-Rahbi, Bouchra El; Matejuk, Agata; Grillon, Catherine; Kieda, Claudine

    2011-01-01

    Abstract Oxygen supply and diffusion into tissues are necessary for survival. The oxygen partial pressure (pO2), which is a key component of the physiological state of an organ, results from the balance between oxygen delivery and its consumption. In mammals, oxygen is transported by red blood cells circulating in a well-organized vasculature. Oxygen delivery is dependent on the metabolic requirements and functional status of each organ. Consequently, in a physiological condition, organ and tissue are characterized by their own unique tissue normoxia or physioxia status. Tissue oxygenation is severely disturbed during pathological conditions such as cancer, diabetes, coronary heart disease, stroke, etc., which are associated with decrease in pO2, i.e. hypoxia. In this review, we present an array of methods currently used for assessing tissue oxygenation. We show that hypoxia is marked during tumour development and has strong consequences for oxygenation and its influence upon chemotherapy efficiency. Then we compare this to physiological pO2 values of human organs. Finally we evaluate consequences of physioxia on cell activity and its molecular modulations. More importantly we emphasize the discrepancy between in vivo and in vitro tissue and cells oxygen status which can have detrimental effects on experimental outcome. It appears that the values corresponding to the physioxia are ranging between 11% and 1% O2 whereas current in vitro experimentations are usually performed in 19.95% O2, an artificial context as far as oxygen balance is concerned. It is important to realize that most of the experiments performed in so-called normoxia might be dangerously misleading. PMID:21251211

  12. Global Autocorrelation Scales of the Partial Pressure of Oceanic CO2

    NASA Technical Reports Server (NTRS)

    Li, Zhen; Adamec, David; Takahashi, Taro; Sutherland, Stewart C.

    2004-01-01

    A global database of approximately 1.7 million observations of the partial pressure of carbon dioxide in surface ocean waters (pCO2) collected between 1970 and 2003 is used to estimate its spatial autocorrelation structure. The patterns of the lag distance where the autocorrelation exceeds 0.8 is similar to patterns in the spatial distribution of the first baroclinic Rossby radius of deformation indicating that ocean circulation processes play a significant role in determining the spatial variability of pCO2. For example, the global maximum of the distance at which autocorrelations exceed 0.8 averages about 140 km in the equatorial Pacific. Also, the lag distance at which the autocorrelation exceed 0.8 is greater in the vicinity of the Gulf Stream than it is near the Kuroshio, approximately 50 km near the Gulf Stream as opposed to 20 km near the Kuroshio. Separate calculations for times when the sun is north and south of the equator revealed no obvious seasonal dependence of the spatial autocorrelation scales. The pCO2 measurements at Ocean Weather Station (OWS) 'P', in the eastern subarctic Pacific (50 N, 145 W) is the only fixed location where an uninterrupted time series of sufficient length exists to calculate a meaningful temporal autocorrelation function for lags greater than a few days. The estimated temporal autocorrelation function at OWS 'P', is highly variable. A spectral analysis of the longest four pCO2 time series indicates a high level of variability occurring over periods from the atmospheric synoptic to the maximum length of the time series, in this case 42 days. It is likely that a relative peak in variability with a period of 3-6 days is related to atmospheric synoptic period variability and ocean mixing events due to wind stirring. However, the short length of available time series makes identifying temporal relationships between pCO2 and atmospheric or ocean processes problematic.

  13. Structural and optical properties of ZnO:Mg thin films grown under different oxygen partial pressures

    NASA Astrophysics Data System (ADS)

    Chen, Haixia; Ding, Jijun; Ma, Shuyi

    2010-03-01

    Pure and Mg-doped zinc oxide (ZnO:Mg) films were deposited using RF reactive magnetron sputtering at different oxygen partial pressures. The microstructures and optical properties in doped ZnO films were systematically investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and fluorescence spectrophotometer. The results indicated that ZnO grain orientation behavior was significantly affected by Mg-doping. And the ZnO:Mg film prepared at 15:10 had the best crystal quality among all ZnO:Mg films. The photoluminescence (PL) measurements at room temperature revealed a violet, two blue and a green emission. The origin of these emissions was discussed. It was also demonstrated that the optical band edge shifted to a shorter wavelength first as Mg was incorporated, and then to a longer wavelength with the increasing of oxygen partial pressures.

  14. A comparative study of the centrifugal and vacuum-pressure techniques of casting removable partial denture frameworks.

    PubMed

    Shanley, J J; Ancowitz, S J; Fenster, R K; Pelleu, G B

    1981-01-01

    A study was undertaken to evaluate two techniques for casting accuracy on removable partial denture frameworks: centrifugal casting and vacuum-pressure casting. A standard metal die with predetermined reference points in a horizontal plane was duplicated in refractory investment. The casts were waxed, and castings of nickel-chrome alloy were fabricated by the two techniques. Both the casts and the castings were measured between the reference points with a measuring microscope. With both casting methods, the differences between the casts and the castings were significant, but no significant differences were found between castings produced by the two techniques. Vertical measurements at three designated points also showed no significant differences between the castings. Our findings indicate that dental laboratories should be able to use the vacuum-pressure method of casting removable partial denture frameworks and achieve accuracy similar to that obtained by the centrifugal method of casting. PMID:7007622

  15. Two Phase Flow Modeling: Summary of Flow Regimes and Pressure Drop Correlations in Reduced and Partial Gravity

    NASA Technical Reports Server (NTRS)

    Balasubramaniam, R.; Rame, E.; Kizito, J.; Kassemi, M.

    2006-01-01

    The purpose of this report is to provide a summary of state-of-the-art predictions for two-phase flows relevant to Advanced Life Support. We strive to pick out the most used and accepted models for pressure drop and flow regime predictions. The main focus is to identify gaps in predictive capabilities in partial gravity for Lunar and Martian applications. Following a summary of flow regimes and pressure drop correlations for terrestrial and zero gravity, we analyze the fully developed annular gas-liquid flow in a straight cylindrical tube. This flow is amenable to analytical closed form solutions for the flow field and heat transfer. These solutions, valid for partial gravity as well, may be used as baselines and guides to compare experimental measurements. The flow regimes likely to be encountered in the water recovery equipment currently under consideration for space applications are provided in an appendix.

  16. Structural characteristics of Sr1?xLaxTi3+? as a function of oxygen partial pressure at 1400 C

    Microsoft Academic Search

    S. A. Howard; J. K. Yau; H. U. Anderson

    1989-01-01

    The structural characteristics of Sr1?x Lax TiO3+? (0?x?0.4) at 1400 C have been investigated as a function of ambient oxygen partial pressure. A modified Rietveld pattern-fitting structure-refinement program [H. M. Rietveld, J. Appl. Crystallogr. 2, 65 (1969)] was used to determine the nature of the distortions of the fundamental perovskite unit cell, the degree of lattice perfection, and the cation

  17. System identification and closed-loop control of end-tidal CO2 partial pressure in mechanically ventilated patients

    Microsoft Academic Search

    Jin-Oh Hahn; Guy A. Dumont; J. Mark Ansermino

    2011-01-01

    This paper presents a systematic approach to system identification and closed-loop control of end-tidal carbon dioxide partial pressure (PETCO2) in mechanically ventilated patients. An empirical model consisting of a linear dynamic system followed by an affine transform is proposed to derive a low-order and high-fidelity representation that can reproduce the positive and inversely proportional dynamic input-output relationship between PETCO2 and

  18. Equilibrium partial pressures and mean activity and osmotic coefficients of 0-100% nitric acid as a function of temperature

    Microsoft Academic Search

    Simon L. Clegg; Peter. Brimblecombe

    1990-01-01

    Rational activity and osmotic coefficients and Henry's law constants K{sub Hx} (for the reaction HNO{sub 3(g)} = H{sup +}{sub (aq)} + NO⁻{sub (aq)}), given as functions of temperature, enable p(HO) and p(HNO) to be calculated from -60 to 120°C, 0-100% HNO. Apparent molal enthalpies, heat capacities, and activity coefficients (derived from electromotive force (emf), freezing point, and partial pressure data)

  19. Index of refraction versus oxygen partial pressure for tantalum oxide and silicon dioxide films produced by ion beam deposition

    SciTech Connect

    Goward, W.D.; Petersen, H.E.; Dijaili, S.P.; Walker, J.D.

    1998-04-30

    Tantalum oxide and silicon oxide films were made using an ion beam sputtering system. It was found that even though these films were deposited from oxide targets, additions of oxygen were necessary to achieve stoichiometry and hence index of refraction. It was observed that the tantalum oxide target changed color from white to gray, indicating that the oxygen was being depleted from the target. The addition of oxygen to the chamber during deposition replenished the target and improved film stoichiometry. The deposition rate decreased with increasing oxygen partial pressure. It was experimentally determined that by varying the oxygen partial pressure and keeping all other variables fixed, the index of refraction of the film changed in a predictable manner. That is, as the oxygen partial pressure was increased, the index decreased rapidly initially and then reached a saturation point where it stayed fixed with oxygen content. With this data a coating process can be set up using the minimum amount of oxygen (thus increasing filament lifetime) to produce a fully stoichiometric film that has a fixed index. This paper will present the details of these observations and results.

  20. Method for sensing and measuring a concentration or partial pressure of a reactant used in a redox reaction

    DOEpatents

    Findl, E.

    1984-12-21

    A method for sensing or measuring the partial pressure or concentration of an electroactive species used in conjunction with an electrolyte, the method being characterized by providing a constant current between an anode and a cathode of an electrolyte-containing cell, while measuring changes in voltage that occur between either the anode and cathode or between a reference electrode and one of the main electrodes of the cell, thereby to determine the concentration or partial pressure of the electro-active species as a function of said measured voltage changes. The method of the invention can be practiced using either a cell having only an anode and a cathode, or using a cell having an anode and a cathode in combination with a reference electrode. Accurate measurements of small concentrations or partial pressures of electro-active species are obtainable with the method of the invention, by using constant currents of only a few microamperes between the anode and cathode of the cell, while the concentration-determining voltage is measured.

  1. Spatial and temporal dynamics of CO2 partial pressure in the Yellow River, China

    NASA Astrophysics Data System (ADS)

    Ran, L.; Lu, X. X.; Richey, J. E.; Sun, H.; Han, J.; Yu, R.; Liao, S.; Yi, Q.

    2014-10-01

    Carbon transport in river systems is an important component of the global carbon cycle. Most rivers of the world act as atmospheric CO2 sources due to high riverine CO2 partial pressure (pCO2). We investigated the pCO2 dynamics in the Yellow River watershed by using historical water chemistry records (1950s-1984) and recent sampling along the mainstem (2011-2012). Except the headwater region where the pCO2 was lower than the atmospheric equilibrium (i.e., 380 ?atm), river waters in the remaining watershed were supersaturated with CO2. The average pCO2 for the watershed was estimated at 2810 1985 ?atm, which is 7-fold the atmospheric equilibrium. This indicates a strong CO2 outgassing across the water-air interface. As a result of severe soil erosion and dry climate, waters from the Loess Plateau in the middle reaches had higher pCO2 than that from the upper and lower reaches. From a seasonal perspective, the pCO2 varied from about 200 ?atm to >30 000 ?atm with higher pCO2 usually occurring in the dry season and low pCO2 in the wet season (at 73% of the sampling sites), suggesting the dilution effect of water. While the pCO2 responded positively to total suspended solids (TSS) transport when the TSS was less than 100 kg m-3, it slightly decreased and remained stable when the TSS exceeded 100 kg m-3. This stable pCO2 is largely due to gully erosion that mobilizes subsoils characterized by low organic matter for decomposition. In addition, human activities have changed the pCO2 dynamics. Particularly, flow regulation by dams can diversely affect the temporal changes of pCO2, depending on the physiochemical properties of the regulated waters and adopted operation scheme. Given the high pCO2 in the Yellow River waters, the resultant CO2 outgassing is expected to be substantial and warrants further investigation.

  2. H2FC: Materials

    NSDL National Science Digital Library

    The Hydrogen and Fuel Cell Investor, an online resource covering fuel cell technologies and companies, hosts these pages on technology and materials of hydrogen fuel cells. The Materials page is a metapage with links to information about Hydrogen, H2 Storage Materials, Hydrogen Rich Fuels, Fuel Cell Components, and Metals. Examples of links found at the Materials page include Handling Hydrogen Safely (from the National Hydrogen Association), Hydride Information Center (Sandia National Laboratories), "Synthesis, Properties and Applications of Graphite Nanofibers" (research paper from Northeastern University), The American Methanol Institute, and a solubility graph for selected metals (from REB Research Services).

  3. Autothermal Cyclic Reforming Based H2 Generating & Dispensing System

    E-print Network

    or Biogas or Biomass Pyrolysis Oil ACR offers lower capital cost & inherent CO2 separationACR offers lower Pressure Reforming Comp- ressor 100 psig 100 psig Reformer H2 PSA SyngasNatural Gas Low Pressure Reforming CMP Syngas 5 psig5 psig Reformer CMP 100 psig H2 PSA Natural Gas Syngas CMP HX CMP HX Thermal

  4. Application of time-division-multiplexed lasers for measurements of gas temperature and CH4 and H2O concentrations at 30 kHz in a high-pressure combustor.

    PubMed

    Caswell, Andrew W; Kraetschmer, Thilo; Rein, Keith; Sanders, Scott T; Roy, Sukesh; Shouse, Dale T; Gord, James R

    2010-09-10

    Two time-division-multiplexed (TDM) sources based on fiber Bragg gratings were applied to monitor gas temperature, H(2)O mole fraction, and CH(4) mole fraction using line-of-sight absorption spectroscopy in a practical high-pressure gas turbine combustor test article. Collectively, the two sources cycle through 14 wavelengths in the 1329-1667 nm range every 33 ?s. Although it is based on absorption spectroscopy, this sensing technology is fundamentally different from typical diode-laser-based absorption sensors and has many advantages. Specifically, the TDM lasers allow efficient, flexible acquisition of discrete-wavelength information over a wide spectral range at very high speeds (typically 30 kHz) and thereby provide a multiplicity of precise data at high speeds. For the present gas turbine application, the TDM source wavelengths were chosen using simulated temperature-difference spectra. This approach is used to select TDM wavelengths that are near the optimum values for precise temperature and species-concentration measurements. The application of TDM lasers for other measurements in high-pressure, turbulent reacting flows and for two-dimensional tomographic reconstruction of the temperature and species-concentration fields is also forecast. PMID:20830185

  5. The H2O content of granite embryos

    NASA Astrophysics Data System (ADS)

    Bartoli, Omar; Cesare, Bernardo; Remusat, Laurent; Acosta-Vigil, Antonio; Poli, Stefano

    2015-04-01

    Quantification of H2O contents of natural granites has been an on-going challenge owing to the extremely fugitive character of H2O during cooling and ascent of melts and magmas. Here we approach this problem by studying granites in their source region (i.e. the partially melted continental crust) and we present the first NanoSIMS analyses of anatectic melt inclusions (MI) hosted in peritectic phases of migmatites and granulites. These MI which totally crystallized upon slow cooling represent the embryos of the upper-crustal granites [1, 2, 3]. The approach based on the combination of MI and NanoSIMS has been here tested on amphibolite-facies migmatites at Ronda (S Spain) that underwent fluid-present to fluid-absent melting at ~700 C and ~5 kbar. Small (? 5 m) crystallized MI trapped in garnet have been remelted using a piston-cylinder apparatus and they show leucogranitic compositions. We measure high and variable H2O contents (mean of 6.51.4 wt%) in these low-temperature, low-pressure granitic melts. We demonstrate that, when the entire population from the same host is considered, MI reveal the H2O content of melt in the specific volume of rock where the host garnet grew. Mean H2O values for the MI in different host crystals range from 5.4 to 9.1 wt%. This range is in rather good agreement with experimental models for granitic melts at the inferred P-T conditions. Our study documents for the first time the occurrence of H2O heterogeneities in natural granitic melts at the source region [3]. These heterogeneities are interpreted to reflect the birth of granitic melts under conditions of "mosaic" equilibrium, where the distinct fractions of melt experience different buffering assemblages at the micro-scale, with concomitant differences in melt H2O content. These results confirm the need for small-scale geochemical studies on natural samples to improve our quantitative understanding of crustal melting and granite formation. The same approach adopted here can be applied to MI hosted in higher-temperature, granulite-facies rocks that represent the parents of many upper-crustal granites. This will result in a better understanding of formation and evolution of granitic magmas. [1] Cesare et al. (2009) Geology, 37, 627-630. [2] Bartoli et al. (2013) Geology, 41, 115-118. [3] Bartoli et al. (2014) EPSL, 395, 281-290.

  6. The H2O Content of Granite Embryos

    NASA Astrophysics Data System (ADS)

    Bartoli, O.; Cesare, B.; Remusat, L.; Acosta-Vigil, A.; Poli, S.

    2014-12-01

    Quantification of H2O contents of natural granites has been an on-going challenge owing to the extremely fugitive character of H2O during cooling and ascent of melts and magmas. Here we approach this problem by studying granites in their source region (i.e. the partially melted continental crust) and we present the first NanoSIMS analyses of anatectic melt inclusions (MI) hosted in peritectic phases of migmatites and granulites. These MI which totally crystallized upon slow cooling represent the embryos of the upper-crustal granites. The approach based on the combination of MI and NanoSIMS has been here tested on amphibolite-facies migmatites at Ronda (S Spain) that underwent fluid-present to fluid-absent melting at ~700 C and ~5 kbar. Small (? 5 m) crystallized MI trapped in garnet have been remelted using a piston-cylinder apparatus and they show leucogranitic compositions. We measure high and variable H2O contents (mean of 6.51.4 wt%) in these low-temperature, low-pressure granitic melts. We demonstrate that, when the entire population from the same host is considered, MI reveal the H2O content of melt in the specific volume of rock where the host garnet grew. Mean H2O values for the MI in different host crystals range from 5.4 to 9.1 wt%. This range is in rather good agreement with experimental models for granitic melts at the inferred P-T conditions. Our study documents for the first time the occurrence of H2O heterogeneities in natural granitic melts at the source region. These heterogeneities are interpreted to reflect the birth of granitic melts under conditions of "mosaic" equilibrium, where the distinct fractions of melt experience different buffering assemblages at the micro-scale, with concomitant differences in melt H2O content. These results confirm the need for small-scale geochemical studies on natural samples to improve our quantitative understanding of crustal melting and granite formation. The same approach adopted here can be applied to MI hosted in higher-temperature, granulite-facies rocks that represent the parents of many upper-crustal granites. This will result in a better understanding of formation and evolution of granitic magmas.

  7. Direct H 2O 2 synthesis over Pd membranes at elevated temperatures

    Microsoft Academic Search

    Lei Shi; Andreas Goldbach; Gaofeng Zeng; Hengyong Xu

    2010-01-01

    H2O2 was directly synthesized from the elements over supported Pd membranes in O2-saturated, aqueous H2SO4 (0.03mol\\/l) between 303 and 348K while feeding H2 through the membrane. The H2O2 yield increased with temperature despite H2O2 selectivity declining simultaneously due to faster H2O2 decomposition. Both H2O2 yield and selectivity improved with H2 feed pressure, however. Comparison of H2 consumption during H2O2 synthesis

  8. Partial substitution of carbohydrate intake with protein intake from lean red meat lowers blood pressure in hypertensive persons1-3

    Microsoft Academic Search

    Jonathan M Hodgson; Valerie Burke; Lawrence J Beilin; Ian B Puddey

    Background:Comparedwithcarbohydrateintake,dietaryintakeof plant protein can lower blood pressure in humans, but the effects of animal protein intake on blood pressure have yet to be investigated. Objective: We aimed to determine whether partial substitution of carbohydrate intake with animal protein intake from lean red meat changes blood pressure and other markers of cardiovascular disease risk in hypertensive persons. Design: Hypertensive persons (n

  9. Positive End-Expiratory Pressure Improves Gas Exchange and Pulmonary Mechanics during Partial Liquid Ventilation

    Microsoft Academic Search

    MAX KIRMSE; YUJI FUJINO; DEAN HESS; ROBERT M. KACMAREK

    1998-01-01

    Partial liquid ventilation (PLV) with perflubron (PFB) has been proposed as an adjunct to the current therapies for the acute respiratory distress syndrome (ARDS). Because PFB has been also referred to as \\

  10. Seed storage at elevated partial pressure of oxygen, a fast method for analysing seed ageing under dry conditions

    PubMed Central

    Groot, S. P. C.; Surki, A. A.; de Vos, R. C. H.; Kodde, J.

    2012-01-01

    Background and Aims Despite differences in physiology between dry and relative moist seeds, seed ageing tests most often use a temperature and seed moisture level that are higher than during dry storage used in commercial practice and gene banks. This study aimed to test whether seed ageing under dry conditions can be accelerated by storing under high-pressure oxygen. Methods Dry barley (Hordeum vulgare), cabbage (Brassica oleracea), lettuce (Lactuca sativa) and soybean (Glycine max) seeds were stored between 2 and 7 weeks in steel tanks under 18 MPa partial pressure of oxygen. Storage under high-pressure nitrogen gas or under ambient air pressure served as controls. The method was compared with storage at 45 C after equilibration at 85 % relative humidity and long-term storage at the laboratory bench. Germination behaviour, seedling morphology and tocopherol levels were assessed. Key Results The ageing of the dry seeds was indeed accelerated by storing under high-pressure oxygen. The morphological ageing symptoms of the stored seeds resembled those observed after ageing under long-term dry storage conditions. Barley appeared more tolerant of this storage treatment compared with lettuce and soybean. Less-mature harvested cabbage seeds were more sensitive, as was the case for primed compared with non-primed lettuce seeds. Under high-pressure oxygen storage the tocopherol levels of dry seeds decreased, in a linear way with the decline in seed germination, but remained unchanged in seeds deteriorated during storage at 45 C after equilibration at 85 % RH. Conclusions Seed storage under high-pressure oxygen offers a novel and relatively fast method to study the physiology and biochemistry of seed ageing at different seed moisture levels and temperatures, including those that are representative of the dry storage conditions as used in gene banks and commercial practice. PMID:22967856

  11. Time-resolved absolute OH density of a nanosecond pulsed discharge in atmospheric pressure HeH2O: absolute calibration, collisional quenching and the importance of charged species in OH production

    NASA Astrophysics Data System (ADS)

    Verreycken, T.; Sadeghi, N.; Bruggeman, P. J.

    2014-08-01

    The time-resolved OH density in a nanosecond pulsed filamentary discharge in an atmospheric pressure He–H2O(0.05%) mixture is measured using laser induced fluorescence. The lifetime of the excited OH(A) state is found to be strongly time dependent during the plasma pulse, with the shortest decay time occurring at the moment the plasma is switched off. The measured LIF intensity is corrected for this time-resolved quenching and calibrated using Rayleigh scattering. Time-resolved electron density (n_e\\max=(7.6 +/- 0.8) 1021 m-3) , He (3S1) metastable density (He_m\\max=(1.6 +/- 0.3) 1020 m-3) , gas temperature (T_g\\max=(350 +/- 60) K) and optical emission are presented and used in the interpretation of the observed time dependence of the OH density. Based on these experimental data, it is shown that for the present discharge conditions, OH is mainly produced by charge transfer reactions to water followed by dissociative recombination of the water ion. In addition, two often encountered issues with the calibration of OH LIF are highlighted with an example.

  12. High magnetic-refrigeration performance of plate-shaped La0.5Pr0.5Fe11.4Si1.6 hydrides sintered in high-pressure H2 atmosphere

    NASA Astrophysics Data System (ADS)

    Sun, N. K.; Guo, J.; Zhao, X. G.; Si, P. Z.; Huang, J. H.; Zhang, Z. D.

    2015-03-01

    La(Fe, Si)13 hydride is regarded as one of the most promising room-temperature refrigerants. However, to use the alloys in an active magnetic regenerator machine, it is vital to prepare thin refrigerants. In this work, a high H2 gas pressure of 50 MPa was employed to suppress the desorption of hydrogen atoms during the sintering process of plate-shaped La0.5Pr0.5Fe11.4Si1.6 hydrides. At 330 K, a high-density sintered thin plate shows a large magnetic-entropy change ?Sm of 15.5 J/kg K (106 mJ/cm3 K) for a field change of 2 T. The volumetric ?Sm is almost twice as large as that of bonded La(Fe,Si)13 hydrides. Favorably, hysteresis is almost absent due to the existence of micropores with a porosity of 0.69% which has been analyzed with high-resolution X-ray microtomography.

  13. The metastable HCl 6H2O phase - IR spectroscopy, phase transitions and kinetic/thermodynamic properties in the range 170-205 K

    NASA Astrophysics Data System (ADS)

    Chiesa, S.; Rossi, M. J.

    2013-07-01

    In this laboratory study, 1 to 2 ?m thick polycrystalline ice films have been grown under stirred flow reactor (SFR) conditions and subsequently doped with metered amounts of HCl under static conditions. A multidiagnostic approach including FTIR absorption spectroscopy in transmission, residual gas mass spectrometry (MS) and total pressure measurement was employed. Depending on the growth protocol controlling both temperature and partial pressure of HCl (PHCl), either amorphous HCl/H2O or crystalline HCl hexahydrate (HCl 6H2O) have been obtained. After controlled doping with HCl and evaporation of excess H2O from the ice film, transmission FTIR of pure HCl 6H2O films and use of calibrated residual gas MS enabled the measurement of differential (peak) IR cross sections at several mid-IR frequencies (? = (6.5 1.9) 10-19 cm2 molec-1 at 1635 cm-1 as an example). Two types of kinetic experiments on pure HCl 6H2O have been performed under SFR conditions: (a) evaporation of HCl 6H2O under H2O-poor conditions over a narrow T range, and (b) observation of the phase transition from crystalline HCl 6H2O to amorphous HCl/H2O under H2O-rich conditions at increasing T. The temperature dependence of the zero-order evaporation flux of HCl in pure HCl 6H2O monitored at 3426 cm-1 led to log(Jev) molec cm-2s-1= (36.34 3.20) - (80 810 5800)/2.303RT with R=8.312 JK-1 mol-1. HCl 6H2O has a significant intrinsic kinetic barrier to HCl evaporation of 15.1 kJ mol-1 in excess of the HCl sublimation enthalpy of 65.8 kJ mol-1 at 200 K but is kinetically unstable (metastable) at typical UT/LS conditions of HCl partial pressure (P(HCl)) and temperature. Water-rich HCl 6H2O undergoes a facile phase transition from crystalline to the amorphous/ supercooled/disordered state easily observable at T? 195 K under both static and SFR conditions. This corresponds to low P(HCl) in the neighborhood of 10-7 Torr that also prevails at the Upper Troposphere/Lower Stratosphere (UT/LS). The atmospheric importance of HCl 6H2O is questioned in view of its nucleation barrier and its dependence on temperature and P(HCl) compared to the amorphous HCl/H2O phase.

  14. Partial melting in the iron?sulfur system at high pressure: A synchrotron X-ray diffraction study

    SciTech Connect

    Campbell, A.J.; Seagle, C.T.; Heinz, D.L.; Shen, G.; Prakapenka, V. (Maryland); (CIW); (UC)

    2008-09-18

    Partial melting in the Fe-S system was investigated at high pressures because of its importance to understanding the formation, composition, and thermal structure of the Earth's core. Earlier studies at very high pressure (>25 GPa) took place before the discovery of Fe{sub 3}, which compromised the interpretation of those results. Furthermore, they relied on textural criteria for melting that are difficult to apply at high pressure. In this study synchrotron X-ray diffraction was used to monitor coexisting metal and sulfide at high pressures and temperatures, during laser heating in a diamond anvil cell. The criterion for melting was the disappearance of one of the two coexisting phases, and reappearance upon quench. Temperatures of eutectic melting between Fe and Fe{sub 3}S were bracketed in this way up to 60 GPa, and a lower bound was established at 80 GPa. The accuracy of the melting point measured in these studies was improved through modelling of the axial temperature distribution through the thickness of the sample; this indicated an {approx}6% correction to the spectroradiometrically determined temperature. The Fe-Fe{sub 3}S eutectic composition remains close to 15 wt% S up to 60 GPa.

  15. Electrostrictive laser-induced gratings for time-resolved observation of translational-rotational energy transfer in H 2

    Microsoft Academic Search

    W. Hubschmid; R. Bombach

    2011-01-01

    Electrostrictive laser-induced gratings (LIG) have been formed in H2 of various pressures (0.55 bar) and with frequencies of the Brillouin modes (sound waves) of about 14 MHz. Under these conditions,\\u000a the rotational degrees of freedom can only partially follow the temperature variation from the acoustic oscillation. A model\\u000a is given, which completes the linearized fluid dynamical equations with equations for

  16. Kinetics and mechanism of the desulfurization of liquid blast furnace slags by Ar-H 2 O gas mixtures

    Microsoft Academic Search

    B. Agrawal; G. J. Yurek; J. F. Elliott

    1983-01-01

    The rate of evolution of sulfur-bearing gases from liquid silicate slags at 1400 C when exposed to Ar-H2O gas mixtures has been studied. The rate was first order with respect both to the concentration of sulfur ions adsorbed on\\u000a the surface of the slag and to the partial pressure of water vapor when PH\\u000a 2O was greater than 0.15 atm.

  17. Growth of MoO3 nanostructured thin films as a function of O2-partial pressure

    NASA Astrophysics Data System (ADS)

    Sharma, Rabindar Kumar; Kumar, Prabhat; Reddy, G. B.

    2015-06-01

    In this report, we synthesized molybdenum trioxide (?-MoO3) nanostructured thin films (NSTs) with nanoflakes (NFs) on the Ni-coated glass substrates employing plasma assisted sublimation process (PASP) as a function of oxygen partial pressure (PO2). The effect of oxygen partial pressure on structural, morphological, and vibrational properties have been investigated systematically. The structural analysis divulged that all films deposited at different PO2 have pure orthorhombic phase, no impurity phase is detected under the limit of resolution. The morphological studies of samples is carried out by SEM, revealed that features as well as alignment of MoO3 NSTs can be monitored by PO2 and the sample having best features is obtained at 7.510-2 Torr. In addition, the more insight information is accomplished by TEM/HRTEM on the best featured sample, which confirmed the single crystalline nature of nanoflakes. The vibrational study of all samples are performed by FTIR, and strongly supports the XRD observations. All the results are in consonance with each other.

  18. Vapor pressures in the ternary system water-nitric acid-sulfuric acid at low temperature: A reexamination

    Microsoft Academic Search

    Djamel-Eddine Taleb; Jean-Luc Ponche; Philippe Mirabel

    1996-01-01

    The equilibrium partial vapor pressures over the binary solutions H2O\\/HNO3, H2SO4\\/H2O, HNO3\\/H2SO4 and the ternary mixture H2SO4\\/HNO3\\/H2O have been re-determined for temperatures below 25C. The model presented here is valid over the entire range of concentrations, for temperatures in the range 190-298 K. The predictions of this model are compared with the existing measurements and other predictions, both at room

  19. Correlation between the Carbon Isotope Discrimination in Leaf Starch and Sugars of C3 Plants and the Ratio of Intercellular and Atmospheric Partial Pressures of Carbon Dioxide

    PubMed Central

    Brugnoli, Enrico; Hubick, Kerry T.; von Caemmerer, Susanne; Wong, Suan Chin; Farquhar, Graham D.

    1988-01-01

    Carbon isotope discrimination (?) was analyzed in leaf starch and soluble sugars, which represent most of the recently fixed carbon. Plants of three C3 species (Populus nigra L. P. deltoides Marsh., Gossypium hirsutum L. and Phaseolus vulgaris L.) were kept in the dark for 24 hours to decrease contents of starch and sugar in leaves. Then gas exchange measurements were made with constant conditions for 8 hours, and subsequently starch and soluble sugars were extracted for analysis of carbon isotope composition. The ratio of intercellular, pi, and atmospheric, pa, partial pressures of CO2, was calculated from gas exchange measurements, integrated over time and weighted by assimilation rate, for comparison with the carbon isotope ratios in soluble sugars and starch. Carbon isotope discrimination in soluble sugars correlated strongly (r = 0.93) with pi/pa in all species, as did ? in leaf starch (r = 0.84). Starch was found to contain significantly more 13C than soluble sugar, and possible explanations are discussed. The strong correlation found between ? and pi/pa suggests that carbon isotope analysis in leaf starch and soluble sugars may be used for monitoring, indirectly, the average of pi/pa weighted by CO2 assimilation rate, over a day. Because pi/pa has a negative correlation with transpiration efficiency (mol CO2/mol H2O) of isolated plants, ? in starch and sugars may be used to predict differences in this efficiency. This new method may be useful in ecophysiological studies and in selection for improved transpiration efficiency in breeding programs for C3 species. PMID:16666476

  20. Experimental Validation of the Methodology for Partial Defect Verification of the Pressurized Water Reactor Spent Fuel Assemblies

    SciTech Connect

    Ham, Y S; Sitaraman, S; Shin, H; Eom, S; Kim, H

    2009-06-01

    A set of controlled experiments and Monte Carlo simulation studies with actual commercial pressurized water reactor (PWR) spent fuel assemblies were performed in order to validate an earlier proposal for partial defect testing of the PWR spent fuel assemblies. The proposed methodology involved insertion of tiny neutron and gamma detectors into the guide tubes of PWR assemblies, measurements and data evaluation. One of the key features of the data evaluation method was the concept of the base signature obtained by normalizing the ratio of gamma to neutron signals at each measurement position. As the base signature is relatively invariant to the characteristic variations of spent fuel assemblies such as initial fuel enrichment, cooling time, and burn-up, the methodology could be a powerful verification method which does not require operator declared information on the spent fuel. The benchmarking experiments indeed demonstrated that the methodology can be used for partial defect verification of the PWR spent fuel assemblies without operator declared data. The results from the experiments were compared with the simulations and the agreement between the two was well within ten percent. Thus, based on the simulation studies and benchmarking measurements, the methodology developed promises to be a powerful and practical way to detect partial defects that constitute 10% or more of the total active fuel pins. This far exceeds the detection threshold of 50% missing pins from a spent fuel assembly, a threshold defined by the IAEA Safeguards Criteria.

  1. Hematocrit and Oxygenation Dependence of Blood 1H2O T1 At 7 Tesla

    PubMed Central

    Grgac, Ksenija; van Zijl, Peter C.M.; Qin, Qin

    2012-01-01

    Knowledge of blood 1H2O T1 is critical for perfusion-based quantification experiments such as arterial spin labeling (ASL) and CBV-weighted MRI using vascular space occupancy (VASO). The dependence of blood 1H2O T1 on hematocrit fraction (Hct) and oxygen saturation fraction (Y) was determined at 7 Tesla using in vitro bovine blood in a circulating system under physiological conditions. Blood 1H2O R1 values for different conditions could be readily fitted using a two-compartment (erythrocyte and plasma) model which are described by a monoexponential longitudinal relaxation rate constant dependence. It was found that T1 = 217139 ms for Y = 1 (arterial blood) and 201041 ms for Y = 0.6 (venous blood), for a typical Hct of 0.42. The blood 1H2O T1 values in the normal physiological range (Hct from 0.35 to 0.45, and Y from 0.6 to 1.0) were determined to range from 1900 ms to 2300 ms. The influence of oxygen partial pressure (pO2) and the effect of plasma osmolality for different anticoagulants were also investigated. It is discussed why blood 1H2O T1 values measured in vivo for human blood may be about 10-20% larger than found in vitro for bovine blood at the same field strength. PMID:23169066

  2. Hematocrit and oxygenation dependence of blood (1)H(2)O T(1) at 7 Tesla.

    PubMed

    Grgac, Ksenija; van Zijl, Peter C M; Qin, Qin

    2013-10-01

    Knowledge of blood (1)H2O T1 is critical for perfusion-based quantification experiments such as arterial spin labeling and cerebral blood volume-weighted MRI using vascular space occupancy. The dependence of blood (1)H2O T1 on hematocrit fraction (Hct) and oxygen saturation fraction (Y) was determined at 7 T using in vitro bovine blood in a circulating system under physiological conditions. Blood (1)H2O R1 values for different conditions could be readily fitted using a two-compartment (erythrocyte and plasma) model, which are described by a monoexponential longitudinal relaxation rate constant dependence. It was found that T1 = 2171 39 ms for Y = 1 (arterial blood) and 2010 41 ms for Y = 0.6 (venous blood), for a typical Hct of 0.42. The blood (1)H2O T1 values in the normal physiological range (Hct from 0.35 to 0.45, and Y from 0.6 to 1.0) were determined to range from 1900 to 2300 ms. The influence of oxygen partial pressure (pO2) and the effect of plasma osmolality for different anticoagulants were also investigated. It is discussed why blood (1)H2O T1 values measured in vivo for human blood may be about 10-20% larger than found in vitro for bovine blood at the same field strength. PMID:23169066

  3. Effects of pressure and partial water saturation on gas permeability in tight sands: experimental results

    SciTech Connect

    Walls, J.D.; Nur, A.M.; Bourbie, T.

    1980-01-01

    Effective permeability to gas with varying degrees of brine saturation has been measured in the laboratory on several tight sandstones from the Spirit River formation of Alberta, Canada. Gas permeability as low as 2 x 10/sup -8/ darcy was successfully measured using a pulse decay permeameter with nitrogen as the mobile fluid. Results show a very strong dependence of gas permeability on degree of saturation with 40% saturation causing an order of magnitude decrease in permeability relative to the dry rock. Accurate knowledge of in situ saturations is crucial before estimates of natural gas production rates can be made in these formations. The experiments also show that confining pressure causes significant permeability reduction in these sandstones. It also was found that as brine saturation was increased the sensitivity of the rock's permeability to small changes in confining pressure was increased.

  4. ?H2AX and cancer

    PubMed Central

    Bonner, William M.; Redon, Christophe E.; Dickey, Jennifer S.; Nakamura, Asako J.; Sedelnikova, Olga A.; Solier, Stphanie; Pommier, Yves

    2011-01-01

    Histone H2AX phosphorylation on a serine four residues from the carboxyl terminus (producing ?H2AX) is a sensitive marker for DNA double-strand breaks (DSBs). DSBs may lead to cancer but, paradoxically, are also used to kill cancer cells. Using ?H2AX detection to determine the extent of DSB induction may help to detect precancerous cells, to stage cancers, to monitor the effectiveness of cancer therapies and to develop novel anticancer drugs. PMID:19005492

  5. ?H2AX and cancer

    Microsoft Academic Search

    Christophe E. Redon; Jennifer S. Dickey; Asako J. Nakamura; Olga A. Sedelnikova; Stphanie Solier; Yves Pommier; William M. Bonner

    2008-01-01

    Histone H2AX phosphorylation on a serine four residues from the carboxyl terminus (producing ?H2AX) is a sensitive marker for DNA double-strand breaks (DSBs). DSBs may lead to cancer but, paradoxically, are also used to kill cancer cells. Using ?H2AX detection to determine the extent of DSB induction may help to detect precancerous cells, to stage cancers, to monitor the effectiveness

  6. H2A Delivery H2A Hydrogen Delivery

    E-print Network

    -life development of hydrogen storage and delivery infrastructure in a demand market #12;H2A Delivery Consistent depreciation period Includes standard MACRS table Color-coded to facilitate user input Information Optional Input User Input Required Calculated Cells #12;H2A Delivery Component Model Hierarchy Component Design

  7. Structural, mechanical, electrical and wetting properties of ZrNx films deposited by Ar/N2 vacuum arc discharge: Effect of nitrogen partial pressure

    NASA Astrophysics Data System (ADS)

    Abdallah, B.; Naddaf, M.; A-Kharroub, M.

    2013-03-01

    Non-stiochiometric zirconium nitride (ZrNx) thin films have been deposited on silicon substrates by vacuum arc discharge of (N2 + Ar) gas mixtures at different N2 partial pressure ratio. The microstructure, mechanical, electrical and wetting properties of these films are studied by means of X-ray diffraction (XRD), micro-Raman spectroscopy, Rutherford back scattering (RBS) technique, conventional micro-hardness testing, electrical resistivity, atomic force microscopy (AFM) and contact angle (CA) measurements. RBS results and analysis show that the (N/Zr) ratio in the film increases with increasing the N2 partial pressure. A ZrNx film with (Zr/N) ratio in the vicinity of stoichiometric ZrN is obtained at N2 partial pressure of 10%. XRD and Raman results indicate that all deposited films have strained cubic crystal phase of ZrN, regardless of the N2 partial pressure. On increasing the N2 partial pressure, the relative intensity of (1 1 1) orientation with respect to (2 0 0) orientation is seen to decrease. The effect of N2 partial pressure on micro-hardness and the resistivity of the deposited film is revealed and correlated to the alteration of grain size, crystallographic texture, stoichiometry and residual stress developed in the film. In particular, it is found that residual stress and nitrogen incorporation in the film play crucial role in the alteration of micro-hardness and resistivity respectively. In addition, CA and AFM results demonstrate that as N2 partial pressure increases, both the surface hydrophobicity and roughness of the deposited film increase, leading to a significant decrease in the film surface free energy (SFE).

  8. Reactions of H+ (pyridine)m(H2O)n and H+

    E-print Network

    Meskhidze, Nicholas

    Reactions of H+ (pyridine)m(H2O)n and H+ (NH3)1(pyridine)m(H2O)n with NH3: experiments and kinetic of the inbound H+ (H2O)15 clusters (> 90%) remains un-reacted because of the low NH3 pressure in the collision cell. H+ (H2O)15 + NH3 H+ (NH3)1(H2O)14 + 1H2O -1 u relative PI (RA) H+ (NH3)1(H2O)13 + 2H2O -19 u

  9. Radiation pressure on a submerged absorptive partial reflector deduced from the Doppler shift

    E-print Network

    Mansuripur, Masud

    2012-01-01

    When a light pulse is reflected from a mirror, energy and momentum are exchanged between the electromagnetic field and the material medium. The resulting change in the energy of the reflected photons is directly related to their Doppler shift arising from the change in the state of motion of the mirror. Similarly, the Doppler shift of photons that enter an absorber is intimately tied to the kinetic energy and momentum acquired by the absorber in its interaction with the incident light. The argument from the Doppler shift yields expressions for the exchanged energy and momentum that are identical with those obtained from Maxwell's equations and the Lorentz law of force, despite the fact that the physical bases of the two methods are fundamentally different. Here we apply the Doppler shift argument to a submerged partial reflector (one that absorbs a fraction of the incident light), deducing in the process the magnitude of the photon momentum within the submerging medium. We also discuss the case of the submerg...

  10. Modeling of axial vibrational control technique for CdTe VGF crystal growth under controlled cadmium partial pressure

    NASA Astrophysics Data System (ADS)

    Avetissov, I.; Kostikov, V.; Meshkov, V.; Sukhanova, E.; Grishechkin, M.; Belov, S.; Sadovskiy, A.

    2014-01-01

    A VGF growth setup assisted by axial vibrations of baffle submerged into CdTe melt with controlled Cd partial pressure was designed. An influence of baffle shape on flow velocity map, temperature distribution in CdTe melt and interface shape of growing crystal was analyzed by numerical simulation and physical modeling. To produce the desirable shape of crystal melt interface we slant under different angles vertical generatrix in a cylindrical disk and made chasing on faceplates of a disk. It was ascertained that a disk with conical generatrix formed more intensive convective flows from a faceplate with larger diameter. It was shown that at CdTe VGF crystal growth rate about 10 mm/h application of AVC technique made it possible to produce convex interface for 2 in. crystal diameter.

  11. Growth of GaAs from a free surface melt under controlled arsenic pressure in a partially confined configuration

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.; Lagowski, J.; Wu, Y.

    1988-01-01

    A partially confined configuration for the growth of GaAs from melt in space was developed, consisting of a triangular prism containing the seed crystal and source material in the form of a rod. It is suggested that the configuration overcomes two obstacles in the growth of GaAs in space: total confinement in a quartz crucible and lack of arsenic pressure control. Ground tests of the configuration show that it is capable of crystal growth in space and is useful for studying the growth of GaAs from a free-surface melt on earth. The resulting chemical composition, electrical property variations, and phenomenological models to account for the results are presented.

  12. Production of H - from heated SrH 2 powder and from H 2 introduced onto the powder

    NASA Astrophysics Data System (ADS)

    Kawano, Hiroyuki; Iseki, Takashi

    2002-06-01

    The currents ( J- and I-) of thermal electron (e -) and ion (H -) desorbed from heated powdery SrH 2 were simultaneously measured by mass spectrometry as a function of the sample temperature, introduced H 2 gas pressure or time elapsing after increasing temperature, introducing H 2 or stopping the introduction. Analysis of the data thus obtained yields the notable results as follows. (1) Above 800 K, those active spots (Sr) with low work function ( ?) is created by such a thermal decomposition as SrH 2?Sr+H 2. (2) From the spots, not only e - but also H - is desorbed even without introducing H 2. (3) By introducing H 2 up to 510 -4 Torr, ? is increased by up to 0.3 eV according to a deactivation reaction (Sr+H 2?SrH 2). (4) By this increase, J- is decreased to less than 1/10 but I- is increased up to 2.4 times. In conclusion, H - is thermally produced not only from the H constituent of powdery SrH 2 kept above 800 K but also from the H 2 introduced onto the hydride, in spite of low electron affinity of hydrogen.

  13. VUV photoionization cross sections of HO2, H2O2, and H2CO.

    PubMed

    Dodson, Leah G; Shen, Linhan; Savee, John D; Eddingsaas, Nathan C; Welz, Oliver; Taatjes, Craig A; Osborn, David L; Sander, Stanley P; Okumura, Mitchio

    2015-02-26

    The absolute vacuum ultraviolet (VUV) photoionization spectra of the hydroperoxyl radical (HO2), hydrogen peroxide (H2O2), and formaldehyde (H2CO) have been measured from their first ionization thresholds to 12.008 eV. HO2, H2O2, and H2CO were generated from the oxidation of methanol initiated by pulsed-laser-photolysis of Cl2 in a low-pressure slow flow reactor. Reactants, intermediates, and products were detected by time-resolved multiplexed synchrotron photoionization mass spectrometry. Absolute concentrations were obtained from the time-dependent photoion signals by modeling the kinetics of the methanol oxidation chemistry. Photoionization cross sections were determined at several photon energies relative to the cross section of methanol, which was in turn determined relative to that of propene. These measurements were used to place relative photoionization spectra of HO2, H2O2, and H2CO on an absolute scale, resulting in absolute photoionization spectra. PMID:25621533

  14. Equilibrium partial pressures and mean activity and osmotic coefficients of 0-100% nitric acid as a function of temperature

    SciTech Connect

    Clegg, S.L. (Plymouth Marine Laboratory (England)); Brimblecombe, P. (Univ. of East Anglia, Norwich (England))

    1990-06-28

    Rational activity and osmotic coefficients and Henry's law constants K{sub Hx} (for the reaction HNO{sub 3(g)} = H{sup +}{sub (aq)} + NO{sub 3}{sup {minus}}{sub (aq)}), given as functions of temperature, enable p(H{sub 2}O) and p(HNO{sub 3}) to be calculated from {minus}60 to 120{degree}C, 0-100% HNO{sub 3}. Apparent molal enthalpies, heat capacities, and activity coefficients (derived from electromotive force (emf), freezing point, and partial pressure data) are represented with the use of the species-interaction models of Pitzer. Equations for the partial molal functions are given. The Henry's law constant is evaluated from p(HNO{sub 3}) data at 298.15 K, tabulated heats of formation, and heat capacities. Calculated p(H{sub 2}O) and p(HNO{sub 3}) over the entire concentration range agree with available data over 5 orders of magnitude of p(H{sub 2}O) and 7 orders of magnitude of p(HNO{sub 3}).

  15. H2A Delivery: H2A Delivery

    E-print Network

    H2A Delivery: H2A Delivery: GH2 and LH2 Forecourt GH2 and LH2 Forecourt Land Areas Land Areas significant impact on overall land area requirements at the forecourt 5/8/2007 4 #12;Example of Model Structure /day 300 500 1000 1500 180 270 l in 16 16 16 16 i in 2 2 2 2 ls 6 6 6 6 3 3 3 3 in 20 20 20 20 1

  16. Photochemistry of CO and H2O - Analysis of laboratory experiments and applications to the prebiotic earth's atmosphere

    NASA Astrophysics Data System (ADS)

    Wen, Jun-Shan; Pinto, Joseph P.; Yung, Yuk L.

    1989-10-01

    The role photochemical reactions in the early earth's atmosphere played in the prebiotic synthesis of simple organic molecules was examined, extending an earlier calculation of formaldehyde production rates to more reduced carbon species, such as methanol, methane, and acetaldehyde. The experimental results of Bar-Nun and Chang (1983) are simulated as an aid in the construction of the photochemical scheme and as a way of validating the model. The results indicate that some fraction of CO2 and H2 present in the primitive atmosphere could have been converted to simple organic molecules. The exact amount is dependent on the partial pressure of CO2 and H2 in the atmosphere and on what assumptions are made concerning the shape of the absorption spectra of CO2 and H2O.

  17. Electrostrictive laser-induced gratings for time-resolved observation of translational-rotational energy transfer in H2

    NASA Astrophysics Data System (ADS)

    Hubschmid, W.; Bombach, R.

    2011-06-01

    Electrostrictive laser-induced gratings (LIG) have been formed in H2 of various pressures (0.55 bar) and with frequencies of the Brillouin modes (sound waves) of about 14 MHz. Under these conditions, the rotational degrees of freedom can only partially follow the temperature variation from the acoustic oscillation. A model is given, which completes the linearized fluid dynamical equations with equations for the rotational state relaxation, separately for the average relaxation of the states for Ortho-H2 and Para-H2. Using such a model, the dispersion of sound frequency is reproduced with an accuracy of a few percent. However, the total dissipation of sound and the observed strong alternation in peak heights in the temporal evolution of the LIG intensity is only approximately predicted by the model.

  18. Photochemistry of CO and H2O - Analysis of laboratory experiments and applications to the prebiotic earth's atmosphere

    NASA Technical Reports Server (NTRS)

    Wen, Jun-Shan; Pinto, Joseph P.; Yung, Yuk L.

    1989-01-01

    The role photochemical reactions in the early earth's atmosphere played in the prebiotic synthesis of simple organic molecules was examined, extending an earlier calculation of formaldehyde production rates to more reduced carbon species, such as methanol, methane, and acetaldehyde. The experimental results of Bar-Nun and Chang (1983) are simulated as an aid in the construction of the photochemical scheme and as a way of validating the model. The results indicate that some fraction of CO2 and H2 present in the primitive atmosphere could have been converted to simple organic molecules. The exact amount is dependent on the partial pressure of CO2 and H2 in the atmosphere and on what assumptions are made concerning the shape of the absorption spectra of CO2 and H2O.

  19. Simutaneous adsorption of CO2 and H2O under Mars-like conditions and application to the evolution of the Martian climate

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Quinn, Richard C.

    1995-01-01

    The Martian regolith is the most substantial volatile reservoir on the planet; estimates of its adsorbed inventory have been based on simple measurements of the adsorption of either water or CO2 in isolation. Under some conditions, H2O can poison adsorbate surfaces, such that CO2 uptake is greatly reduced. We have made the first measurements of the simultaneous adsorption of CO2 and H2O under conditions appropriate to the Martian regolith and have found that at H2O monolayer coverage above about 0.5, CO2 begins to be displaced into the gas phase. We have developed an empirical expression that describes our co-adsorption data and have applied it to standard models of the Martian regolith. We find that currently, H2O does not substantially displace CO2, implying that the adsorbate inventories previously derived may be accurate, not more than 3-4 kPa (30-40 mbar). No substantial increase in atmospheric pressure is predicted at higher obliquities because high-latitude ground ice buffers the partial pressure of H2O in the pores, preventing high monolayer coverages of H2O from displacing CO2. The peak atmospheric pressure at high obliquity does increase as the total inventory of exchangeable CO2 increases.

  20. Simultaneous adsorption of CO2 and H2O under Mars-like conditions and application to the evolution of the Martian climate

    NASA Technical Reports Server (NTRS)

    Zent, Aaron, P.; Quinn, Richard C.

    1995-01-01

    The Martian regolith is the most substantial volatile reservoir on the planet; estimates of its adsorbed inventory have been based on simple measurements of the adsorption of either water or CO2 in isolation. Under some conditions, H2O can poison adsorbate surfaces, such that CO2 uptake is greatly reduced. We have made the first measurements of the simultaneous adsorption of CO2 and H2O under conditions appropriate to the Martian regolith and have found that at H2O monolayer coverage above about 0.5, CO2 begins to be displaced into the gas phase. We have developed an empirical expression that describes our co-adsorption data and have applied it to standard models of the Martian regolith. We find that currently, H2O does not substantially displace CO, implying that the adsorbate inventories previously derived may be accurate, not more than 3-4 kPa (30-40 mbar). No substantial increase in atmospheric pressure is predicted at higher obliquities because high-latitude ground ice buffers the partial pressure of H2O in the pores, preventing high monolayer coverages of H2O from displacing CO2. The peak atmospheric pressure at high obliquity does increase as the total inventory of exchangeable CO2 increases.

  1. Kinetics of silicon-germanium deposition by atmospheric-pressure chemical vapor deposition

    Microsoft Academic Search

    T. I. Kamins; D. J. Meyer

    1991-01-01

    The deposition of Si1?xGex alloy layers in an atmospheric-pressure, chemical vapor deposition reactor has been studied by separately examining the silicon and the germanium components of the deposition rate. The overall deposition rate increases approximately linearly with GeH4 partial pressure, but is relatively independent of SiH2Cl2 partial pressure. The silicon component of the deposition rate increases rapidly with increasing temperature

  2. Stability of SiC/SiC composites in environments containing O 2 and H 2

    NASA Astrophysics Data System (ADS)

    Springer, G. D.; Windisch, C. F.; Jones, R. H.

    1996-10-01

    Silicon carbide composites with carbon interfaces have been analyzed by thermal gravimetric analysis (TGA) in O 2 and H 2 environments to predict their performance as structural materials in fusion applications. Conditions for testing included temperatures between 800 and 1200C, O 2 concentrations ranging from 100 to 1500 ppm, and H 2 concentrations of 0.1 and 1%. Weight losses observed by TGA were determined to be primarily due to the oxidation of the carbon interface. Linearparabolic kinetics governed the interfacial oxidation for all of the conditions in O 2. By focusing on the linear region, a simple model estimated the linear rate dependency on O 2 partial pressure to be on the order of 0.911. Weight loss data in H 2 environments yielded activation energies of 18 and 34 kcal/mol for 0.1 and 1%, respectively. The weight loss rates in H 2 were 6 to 26 times slower than rates in O 2, when approximations were made assuming linear kinetics.

  3. Effect of presulfidation on the oxidation behavior of Co-based alloys. Part I. Presulfidation at sulfur partial pressures above the dissociation pressure of cobalt sulfide

    Microsoft Academic Search

    M. E. El-Dahshan; D. P. Whittle; J. Stringer

    1974-01-01

    The effects of presulfidation in H2-H2S atmospheres of sulfur activity sufficient to form cobalt and chromium sulfides on the oxidation rates of Co-Cr binary alloys containing 025 wt.% Cr and Co-25 wt.% Cr alloys containing 02 wt.% C have been investigated. Presulfidation increases the oxidation rate, but the effect is not very dramatic. Carbon additions to the Co-25 wt.% Cr

  4. Kinetics of the Ar-Hg Plasma of Fluorescent Lamp Discharges. II. Ar Partial Pressure and Discharge Current Variation

    NASA Astrophysics Data System (ADS)

    Winkler, R. B.; Wilhelm, J.; Winkler, R.

    In continuation of recent kinetic investigations of the main macroscopic quantities of the Ar-Hg plasma which include realistic electron kinetics at various Hg partial pressures, this paper deals with the study of the macroscopic plasma behaviour at varying discharge current and buffer gas pressure respectively in a wide range of practical interest. By simultaneously solving the particle balances for the various kinds of excited Hg atoms, the current balance as well as the electron Boltzmann equation for such a mixture plasma, the densities of the electrons and excited Hg atoms, the electron energy distribution function, the energy budget of the electrons and the ultraviolet resonance radiation outputs could be determined, analysed and in part compared with experimental data available in the literature. In particular, a good agreement between theoretical and experimental results for the densities of the excited Hg atoms as well as for both resonance radiation outputs was found for a wide range of both considered parameters.Translated AbstractKinetik des Ar-Hg-Plasmas von Leuchtstofflampen-Entladungen II. Ar-Partialdruck- und EntladungsstromvariationIn Weiterfhrung vorausgehender kinetischer Untersuchungen der wesentlichen makroskopischen Gren des Ar-Hg-Plasmas unter Bercksichtigung der realistischen Elektronenkinetik bei Variation des Hg-Partialdruckes behandelt die vorliegende Arbeit das makroskopische Plasmaverhalten bei Vernderung des Entladungsstromes bzw. des Puffergasdruckes in umfangreichen, praktisch interessierenden Bereichen. Mittels simultaner Lsung der Teilchenzahlbilanzen fr die verschiedenen Arten von angeregten Hg-Atomen, der Strombilanz sowie der Elektronen-Boltzmann-Gleichung fr ein solches Mischplasma konnten die Dichten der Elektronen und angeregten Hg-Atome, die Elektronenenergieverteilungsfunktion, der Energiehaushalt der Elektronen und die Ausbeuten an ultravioletter Strahlung bestimmt, analysiert und teilweise mit in der Literatur verfgbaren experimentellen Daten verglichen werden. Insbesondere wurde eine gute bereinstimmung zwischen theoretischen und experimentellen Ergebnissen sowohl fr die Dichten der angeregten Hg-Atome als auch fr beide Resonanzstrahlungsausbeuten bei ausgedehnter Variation beider betrachteter Parameter gefunden.

  5. The interrelated effects of body size and choroid rete development on the ocular O 2 partial pressure of Atlantic ( Gadus morhua ) and Greenland cod ( Gadus ogac )

    Microsoft Academic Search

    Neill A. Herbert; John F. Steffensen; Anders D. Jordan

    2004-01-01

    The interrelated effects of body size and choroid rete development on the ocular partial pressure of oxygen (PO 2) of the mainly temperate Atlantic cod, Gadus morhua, and the exclusively polar Greenland cod, G. ogac, were investigated using micro-optode O 2 sensors. Due to a difference in geographical distribution, it is hypothesized that G. ogac will possess features favouring visual-metabolic

  6. Effects of ambient and acute partial pressures of ozone on leaf net CO sub 2 assimilation of field-grown Vitis vinifera L

    SciTech Connect

    Roper, T.R.; Williams, L.E. (Univ. of California, Davis (USA) Kearney Agricultural Center, Parlier, CA (USA))

    1989-12-01

    Mature, field-grown Vitis vinifera L. grapevines grown in open-top chambers were exposed to either charcoal-filtered air or ambient ozone partial pressures throughout the growing season. Individual leaves also were exposed to ozone partial pressures of 0.2, 0.4, or 0.6 micropascals per pascal for 5 hours. No visual ozone damage was found on leaves exposed to any of the treatments. Chronic exposure to ambient O{sub 3} partial pressures reduced net CO{sub 2} assimilation rate (A) between 5 and 13% at various times throughout the season when compared to the filtered treatment. Exposure of leaves to 0.2 micropascals per pascal O{sub 3} for 5 hours had no significant effect on A; however, A was reduced 84% for leaves exposed to 0.6 micropascals per pascal O{sub 3} when compared to the controls after 5 hours. Intercellular CO{sub 2} partial pressure (c{sub i}) was lower for leaves exposed to 0.2 micropascals per pascal O{sub 3} when compared to the controls, while c{sub i} of the leaves treated with 0.6 micropascals per pascal of O{sub 3} increased during the fumigation. The long-term effects of ambient O{sub 3} and short-term exposure to acute levels of O{sub 3} reduced grape leaf photosynthesis due to a reduction in both stomatal and mesophyll conductances.

  7. Effects of Ambient and Acute Partial Pressures of Ozone on Leaf Net CO2 Assimilation of Field-Grown Vitis vinifera L. 1

    PubMed Central

    Roper, Teryl R.; Williams, Larry E.

    1989-01-01

    Mature, field-grown Vitis vinifera L. grapevines grown in open-top chambers were exposed to either charcoal-filtered air or ambient ozone partial pressures throughout the growing season. Individual leaves also were exposed to ozone partial pressures of 0.2, 0.4, or 0.6 micropascals per pascal for 5 hours. No visual ozone damage was found on leaves exposed to any of the treatments. Chronic exposure to ambient O3 partial pressures reduced net CO2 assimilation rate (A) between 5 and 13% at various times throughout the season when compared to the filtered treatment. Exposure of leaves to 0.2 micropascals per pascal O3 for 5 hours had no significant effect on A; however, A was reduced 84% for leaves exposed to 0.6 micropascals per pascal O3 when compared to the controls after 5 hours. Intercellular CO2 partial pressure (ci) was lower for leaves exposed to 0.2 micropascals per pascal O3 when compared to the controls, while ci of the leaves treated with 0.6 micropascals per pascal of 03 increased during the fumigation. The long-term effects of ambient O3 and short-term exposure to acute levels of O3 reduced grape leaf photosynthesis due to a reduction in both stomatal and mesophyll conductances. PMID:16667208

  8. Modelling of temporal temperature and pressure change due to partial discharge events within a spherical cavity in a solid dielectric material using finite element analysis

    Microsoft Academic Search

    Hazlee A. Illias; George Chen; Paul L. Lewin

    2010-01-01

    Partial discharge (PD) events within a closed-volume cavity in a dielectric material can cause a temperature change in the cavity. This may influence the occurrence of following PDs because the pressure in the cavity is affected, which changes the inception voltage level for the next PD. In this paper, a two-dimensional axial symmetric model geometry consisting of a spherical cavity

  9. Rare earth elements in hydrothermal systems: Estimates of standard partial molal thermodynamic properties of aqueous complexes of the rare earth elements at high pressures and temperatures

    Microsoft Academic Search

    Johnson R. Haas; Everett L. Shock; David C. Sassani

    1995-01-01

    Standard partial molal thermodynamic properties including association constants for 246 inorganic aqueous rare earth element (REE) complexes with chloride, fluoride, hydroxide, carbonate, sulfate, bicarbonate, nitrate, and orthophosphate can be calculated at pressures from 1 to 5000 bars and temperatures from 0 to 1000C, using experimental data from the literature and correlation algorithms. Predicted association constants for REE complexes are used

  10. CO partial pressure dependence of the kinetics of melting of HbS aggregates studied in high concentration phosphate buffer

    NASA Astrophysics Data System (ADS)

    Aroutiounian, Svetlana

    2002-10-01

    Deoxygenated sickle cell hemoglobin (HbS) monomers enter the polymer phase either by incorporation into a critical nucleus, through heterogeneous nucleation and or through linear growth of the polymers when the concentration of monomers exceeds the solubility. CO-bound, R-state HbS monomers do not polymerize. Thus, polymer melting is enhanced by binding of carbon monoxide (CO) to HbS polymerized monomers. In our study, the melting of HbS aggregates mediated by dilution and CO binding to polymerized monomers is observed with time-resolved extinction spectroscopy. The CO partial pressure (pCO) dependence of the kinetics of melting is studied for pCO = 0, 0.25, 0.5, 0.75, 1 atm with difference progress curves. A phenomenological description with slow and fast relaxation modes reveals a variable relaxation time near the pCO=0.5 due to competition of kinetic mechanisms. The slow component increases with increasing pCO. It has a positive intercept due to the combined action of dilution of the sample and CO-ligation. The pCO dependence is near linear due to non-cooperative CO binding. Significant slowing down of aged samples, most likely due to gelation, is observed. As possible mechanism for variable relaxation time near pCO=0.5atm the fractional percolation threshold is discussed. This work was supported by NIH grant HL58091 (awarded to Daniel. B. Kim-Shapiro).

  11. Impedance analysis for oxygen reduction in a lithium carbonate melt: Effects of partial pressure of carbon dioxide and temperature

    SciTech Connect

    Dave, B.B.; White, R.E. (Texas A and M Univ., College Station, TX (United States). Dept. of Chemical Engineering); Srinivasan, S.; Appleby, A.J. (Texas A and M Univ., College Station, TX (United States))

    1993-08-01

    The oxygen reduction reaction in molten alkali carbonate electrolytes has been studied for the past quarter century because of its vital role in the performance of the molten carbonate fuel cell. Effects of partial pressure of carbon dioxide and temperature on oxygen reduction kinetics on a gold electrode in a lithium carbonate melt were examined using electrochemical impedance spectroscopic (EIS) and linear sweep voltammetric techniques. The impedance spectra were analyzed by a complex nonlinear least squares method, using the Randles-Ershler equivalent circuit model, to determine the electrode-kinetic and mass-transfer parameters such as the charge-transfer resistance and Warburg coefficient. The cyclic voltammetric measurements indicated that the oxygen reduction process in lithium carbonate melt is reversible up to 200 mV/s. The product D[sub 0][sup 1/2]C[sub 0] determined by cyclic voltammetry agreed well with those estimated by the EIS method. The reaction order with respect to carbon dioxide and the activation energy for the exchange current density were determined to be [minus]0.52 and 132 kJ/mol, respectively. Also, the reaction order with respect to carbon dioxide and the activation energy for D[sub 0][sup 1/2]C[sub 0] were calculated to be [minus]0.8 and 185 kJ/mol, respectively.

  12. Two-photon high-resolution measurement of partial pressure of oxygen in cerebral vasculature and tissue

    PubMed Central

    Sakadi?, Sava; Roussakis, Emmanuel; Yaseen, Mohammad A.; Mandeville, Emiri T.; Srinivasan, Vivek J.; Arai, Ken; Ruvinskaya, Svetlana; Devor, Anna; Lo, Eng H.; Vinogradov, Sergei A.; Boas, David A.

    2010-01-01

    The ability to measure oxygen partial pressure (pO2) with high temporal and spatial resolution in three dimensions is crucial for understanding oxygen delivery and consumption in normal and diseased brain. Among existing pO2 measurement methods, phosphorescence quenching is optimally suited for the task. However, previous attempts to couple phosphorescence with two-photon laser scanning microscopy have faced substantial difficulties because of extremely low two-photon absorption cross-sections of conventional phosphorescent probes. Here, we report the first practical in vivo two-photon high-resolution pO2 measurements in small rodents cortical microvasculature and tissue, made possible by combining an optimized imaging system with a two-photon-enhanced phosphorescent nanoprobe. The method features a measurement depth of up to 250 m, sub-second temporal resolution and requires low probe concentration. Most importantly, the properties of the probe allowed for the first direct high-resolution measurement of cortical extravascular (tissue) pO2, opening numerous possibilities for functional metabolic brain studies. PMID:20693997

  13. Pilot plant studies of CO/sub 2/ absorption by DEA at high CO/sub 2/ partial pressures

    SciTech Connect

    Ly, Y.-C.; Radovich, J.M.

    1985-01-01

    The removal of carbon dioxide from natural gas is a frequently encountered gas conditioning process. Absorption of CO/sub 2/ by an aqueous amine solution is one of the most common methods for CO/sub 2/ removal. In the past total acid gas (CO/sub 2/ + H/sub 2/S) usually accounted for less than 30% of the gas from the producing well. With the use of CO/sub 2/ miscible flooding for enhanced oil recovery and gas from ultra deep wells, the acid gas contant may easily exceed 80%. There is a lack of operating data in the literature for such high CO/sub 2/ concentrations. The goal was to determine the effects of CO/sub 2/ partial pressure (% CO/sub 2/ in the feed gas) on the rich DEA loading and on the overall mass transfer coefficient. The authors chose DEA because of its less corrosive nature; its resistance to degradation by COS and CS/sub 2/; its lower vaporization losses, and its low solubility for liquid hydrocarbons. The availability of this operating data can hopefully be used to develop correlations which can be used to design new adsorption plants or more accurately predict the performance of existing units.

  14. Kinetics and mechanism of the desulfurization of liquid blast furnace slags by Ar-H2O gas mixtures

    NASA Astrophysics Data System (ADS)

    Agrawal, B.; Yurek, G. J.; Elliott, J. F.

    1983-06-01

    The rate of evolution of sulfur-bearing gases from liquid silicate slags at 1400 C when exposed to Ar-H2O gas mixtures has been studied. The rate was first order with respect both to the concentration of sulfur ions adsorbed on the surface of the slag and to the partial pressure of water vapor when PH 2O was greater than 0.15 atm. When the partial pressure of water vapor was less than 0.15 atm, the rate was second order with respect to the concentration of sulfur ions adsorbed on the surface early in the reaction. At longer times in the latter case, the rate was independent of the partial pressure of water vapor, but first order with respect to the concentration of sulfur ions adsorbed on the surface. It was concluded, based on the kinetics of desulfurization, that the sulfur-bearing species evolved from the surface of the slag was S2 when the rate was second order with respect to the concentration of adsorbed sulfur ions, but SO2 was evolved when the rate was first order with respect to the concentration of adsorbed sulfur ions. Under the conditions employed in the experiments, H2S never evolved from the surface of the slag, although it did form, in some instances, in the gas phase.

  15. Electron transport coefficients in the mixtures of H2O with N2, O2, CO2 and dry air for the optimization of non-thermal atmospheric pressure plasmas

    Microsoft Academic Search

    G. Ruz-Vargas; M. Yousfi; J. de Urquijo

    2010-01-01

    This paper presents the simultaneous measurement and calculation of the electron drift velocity in binary and ternary mixtures of N2, O2, CO2 with H2O. The main aim of this study has been the generation of a self-consistent set of validated collision cross sections that explain thoroughly the dependence of the electron drift velocity in the above pure gases and their

  16. Biogeochemistry of dihydrogen (H2).

    PubMed

    Hoehler, Tori M

    2005-01-01

    Hydrogen has had an important and evolving role in Earth's geo- and biogeochemistry, from prebiotic to modern times. On the earliest Earth, abiotic sources of H2 were likely stronger than in the present. Volcanic out-gassing and hydrothermal circulation probably occurred at several times the modern rate, due to presumably higher heat flux. The H2 component of volcanic emissions was likely buffered close to the modern value by an approximately constant mantle oxidation state since 3.9 billion years ago, and may have been higher before that, if the early mantle was more reducing. The predominantly ultramafic character of the early, undifferentiated crust could have led to increased serpentinization and release of H2 by hydrothermal circulation, as in modern ultramafic-hosted vents. At the same time, the reactive atmospheric sink for H2 was likely weaker. Collectively, these factors suggest that steady state levels of H2 in the prebiotic atmosphere were 3-4 orders of magnitude higher than at present, and possibly higher still during transient periods following the delivery of Fe and Ni by large impact events. These elevated levels had direct or indirect impacts on the redox state of the atmosphere, the radiation budget, the production of aerosol hazes, and the genesis of biochemical precursor compounds. The early abiotic cycling of H2 helped to establish the environmental and chemical context for the origins of life on Earth. The potential for H2 to serve as a source of energy and reducing power, and to afford a means of energy storage by the establishment of proton gradients, could have afforded it a highly utilitarian role in the earliest metabolic chemistry. Some origin of life theories suggest the involvement of H2 in the first energy-generating metabolism, and the widespread and deeply-branching nature of H2-utilization in the modern tree of life suggests that it was at least a very early biochemical innovation. The abiotic production of H2 via several mechanisms of water-rock interaction could have supported an early chemosynthetic biosphere. Such processes offer the continued potential for a deep, rock-hosted biosphere on Earth or other bodies in the solar system. The continued evolution of metabolic and community-level versatility among microbes led to an expanded ability to completely exploit the energy available in complex organic matter. Under the anoxic conditions that prevailed on the early Earth, this was accomplished through the linked and sequential action of several metabolic classes of organisms. By transporting electrons between cells, H2 provides a means of linking the activities of these organisms into a highly functional and interactive network. At the same time, H2 concentrations exert a powerful thermodynamic control on many aspects of metabolism and biogeochemical function in these systems. Anaerobic communities based on the consumption of organic matter continue to play an important role in global biogeochemistry even into the present day. As the principal arbiters of chemistry in most aquatic sediments and animal digestive systems, these microbes affect the redox and trace-gas chemistry of our oceans and atmosphere, and constitute the ultimate biological filter on material passing into the rock record. It is in such communities that the significance of H2 in mediating biogeochemical function is most strongly expressed. The advent of phototrophic metabolism added another layer of complexity to microbial communities, and to the role of H2 therein. Anoxygenic and oxygenic phototrophs retained and expanded on the utilization of H2 in metabolic processes. Both groups produce and consume H2 through a variety of mechanisms. In the natural world, phototrophic organisms are often closely juxtaposed with a variety of other metabolic types, through the formation of biofilms and microbial mats. In the few examples studied, phototrophs contribute an often swamping term to the H2 economy of these communities, with important implications for their overall function-including regulation of the redox state of gaseo

  17. Extragalactic H2O Masers

    E-print Network

    L. J. Greenhill

    2001-09-24

    Study of extragalactic H2O masers has progressed significantly in the 25 years since their discovery. Existing in star forming regions and in the accretion disks supermassive black holes, they are familiar and unfamiliar at the same time. A review of how our understanding has grown, up to the present day, is followed by comments on future prospects.

  18. Quasi-unary homogeneous nucleation of H2SO4-H2O Fangqun Yua

    E-print Network

    Yu, Fangqun

    Quasi-unary homogeneous nucleation of H2SO4-H2O Fangqun Yua Atmospheric Sciences Research Center BHN of H2SO4-H2O can be treated as quasi-unary nucleation of H2SO4 in equilibrium with H2O vapor. A scheme to calculate the evaporation coefficient of H2SO4 molecules from H2SO4-H2O clusters is presented

  19. Phase diagram and thermodynamic properties of H2.

    PubMed

    Osman, S M; Ali, I; Singh, R N

    2013-01-01

    A statistical mechanical-based theory is used to develop the equation of state for the molecular fluid of H(2). We incorporate in this equation the long-range correlations through the double Yukawa potential, dimerization of the H(2) molecule by treating the fluid as a hard convex body fluid, and first-order quantum correction which is important at low temperatures. We use this to calculate the liquid-vapor equilibrium of H(2), including the temperature and pressure dependence of compressibility factor, entropy, specific heat, compressibility, and sound velocity. PMID:23410298

  20. Observed increase in springtime surface partial pressure of CO2 in the east equatorial Indian Ocean during 1962-2012

    NASA Astrophysics Data System (ADS)

    Xue, L.; Yu, W.; Wang, H.; Feng, L.; Wei, Q.; Ning, C.

    2014-01-01

    Rapidly rising atmospheric CO2 and global warming may have been impacting the ocean, and, in contrast, the response of surface CO2 partial pressure (pCO2) in the equatorial Indian Ocean is poorly understood. In this study, we attempted to evaluate the variation of springtime sea surface pCO2 in the east equatorial Indian Ocean (5 N to 5 S along 90 E and 95 E, EIO), which is relatively better occupied, using data collected in May 2012, together with the historical data since 1962 (LDEO_Database_V2012). Results showed that sea surface pCO2 in the investigation area increased from ~308 ?atm in April 1963, through ~373 ?atm in May 1999, to ~387?atm in May 2012, with a mean increase rate of ~1.7?atm yr-1. Given that the EIO during the study period was almost always a CO2 source to the atmosphere, it was obvious that the observed increase of sea surface pCO2 with time in this region was not due to the local uptake of CO2 via air-sea exchange, although quickly increasing atmospheric CO2 had the potential to increase seawater pCO2. Further, we checked the effects of variations in sea surface temperature, salinity, mixed layer depth and chlorophyll a (as a proxy of biological production) on surface pCO2. We found surface ocean warming partially contributed to sea surface pCO2 increase, whereas the effects of salinity, mixed layer depth, and biological activity were not significant. The pCO2 increase in the equatorial waters (CO2 source to the atmosphere) was probably due to the transport of carbon accumulated in the CO2 sink region (to the atmosphere) towards the CO2 source region on a basin scale via ocean circulation. Additionally, our study showed that more and more release of CO2 from the ocean to the atmosphere and big pH reduction (0.07 pH units) in the past 50 yr (from 1963 to 2012) may have occurred in the EIO. It also demonstrated that ocean acidification may have taken place in the global ocean, not just limited to the CO2 sink region.

  1. Hydrothermal phase equilibria in Ln 2O 3-H 2O-CO 2 systems . I. The lighter lanthanides

    NASA Astrophysics Data System (ADS)

    Tareen, J. A. K.; Kutty, T. R. N.

    1980-10-01

    Phase diagrams for Nd 2O 3-H 2O-CO 2 and Gd 2O 3-H 2O-CO 2 systems at 1500 atm are given along with the results of selected runs in La, Sm and Eu systems. The stable phases in systems of La and Nd, are Ln(OH)CO 3-B, Ln 2O 2CO 3-II and LnOOH, in addition to the Ln(OH) 3 phase at extremely low partial pressures of CO 2 in the system. The systems become more and more complex with decreasing ionic radi and the number of stable carbonate phases increases. Ln 2(CO 3) 3 3H 2O orthorhombic (tengerate-like phase) is stable from Sm to Gd in addition to the other phases. The Gd(OH)CO 3-A (ancylite-like phase) is hydrothermally stable at XCO 2 ? 0.5 while its hexagonal polymorph, Gd(OH)CO 3-B is stable at low partial pressures of CO 2 in the system.

  2. Kinetics of the Ar-Hg Plasma of Fluorescent Lamp Discharges. I. Model - Basic Equations - Hg Partial Pressure Variation

    NASA Astrophysics Data System (ADS)

    Winkler, R. B.; Wilhelm, J.; Winkler, R.

    A kinetic description of the dc Hg-Ar mixture plasma of fluorescent lamp discharges is given on the basis of the main microphysical processes and corresponding atomic data. The investigation comprises particle balances for the excited Hg atoms of the triplet 63P0,1,2 and singulet 61P1 state, the balance of the discharge current and an adequate form of the electron Boltzmann equation for such a mixture plasma, the latter including also the various binary collision processes with excited Hg atoms and the Coulomb interaction between the electrons. By simultaneously solving the balances together with the kinetic equation the densities of electrons and excited Hg atoms, the electron energy distribution, the resulting mean energy, mobility and various energy transfer rates of the electrons and the ultraviolet radiation output were determined and in part compared with measured data from the literature. This paper presents and analyses the macroscopic plasma properties mentioned for a wide range of the wall temperature or the corresponding Hg partial pressure variation, where a good agreement of calculated results with experimental data is obtained. In a second paper the change of the macroscopic plasma behaviour due to variation of buffer gas pressure and discharge current will be dealt with.Translated AbstractKinetik des Ar-Hg-Plasmas von Leuchtstofflampenentladungen I. Modell - Grundgleichungen - Hg-PartialdruckvariationDie Arbeit befat sich auf der Grundlage der wesentlichen mikrophysikalischen Prozesse und der entsprechenden atomaren Daten mit der kinetischen Beschreibung des de Hg-Ar-Mischplasmas von Leuchtstofflampenentladungen. Die Untersuchung verwendet die Teilchenbilanzen fr die angeregten Hg-Atome des Tripletts 63P0,1,2 und des Singuletts 61P1, die Bilanz fr den Entladungsstrom und eine adquate Form der Elektronen-Boltzmann-Gleichung fr ein solches Mischplasma, wobei in letzterer auch die verschiedenen Zweierstoprozesse mit angeregten Hg-Atomen und die Coulomb-Wechselwirkung zwischen den Elektronen bercksichtigt wird. Mittels simultaner Lsung der Bilanzgleichungen zusammen mit der kinetischen Gleichung wurden sowohl die Dichten der Elektronen und angeregten Hg-Atome, die Elektronenenergieverteilung, die sich ergebende mittlere Energie, Beweglichkeit und die verschiedenen Energiebertragungsraten der Elektronen als auch die Ausbeute an ultravioletter Strahlung bestimmt und teilweise mit in der Literatur verfgbaren Medaten verglichen. In dieser Arbeit werden die genannten makroskopischen Plasmaeigenschaften fr einen weiten Variationsbereich der Wandtemperatur und damit des Hg-Partialdruckes dargestellt und analysiert, wobei gute bereinstimmung von berechneten und experimentellen Ergebnissen erhalten wird. In einer weiteren Arbeit wird das makroskopische Plasmaverhalten bei Variation des Puffergasdruckes und des Entladungsstromes dargestellt und diskutiert.

  3. Intracellular carbonic anhydrase activity sensitizes cancer cell pH signaling to dynamic changes in CO2 partial pressure.

    PubMed

    Hulikova, Alzbeta; Aveyard, Nicholas; Harris, Adrian L; Vaughan-Jones, Richard D; Swietach, Pawel

    2014-09-12

    Carbonic anhydrase (CA) enzymes catalyze the chemical equilibration among CO2, HCO3(-) and H(+). Intracellular CA (CAi) isoforms are present in certain types of cancer, and growing evidence suggests that low levels correlate with disease severity. However, their physiological role remains unclear. Cancer cell CAi activity, measured as cytoplasmic CO2 hydration rate (kf), ranged from high in colorectal HCT116 (?2 s(-1)), bladder RT112 and colorectal HT29, moderate in fibrosarcoma HT1080 to negligible (i.e. spontaneous kf = 0.18 s(-1)) in cervical HeLa and breast MDA-MB-468 cells. CAi activity in cells correlated with CAII immunoreactivity and enzymatic activity in membrane-free lysates, suggesting that soluble CAII is an important intracellular isoform. CAi catalysis was not obligatory for supporting acid extrusion by H(+) efflux or HCO3(-) influx, nor for maintaining intracellular pH (pHi) uniformity. However, in the absence of CAi activity, acid loading from a highly alkaline pHi was rate-limited by HCO3(-) supply from spontaneous CO2 hydration. In solid tumors, time-dependence of blood flow can result in fluctuations of CO2 partial pressure (pCO2) that disturb cytoplasmic CO2-HCO3(-)-H(+) equilibrium. In cancer cells with high CAi activity, extracellular pCO2 fluctuations evoked faster and larger pHi oscillations. Functionally, these resulted in larger pH-dependent intracellular [Ca(2+)] oscillations and stronger inhibition of the mTORC1 pathway reported by S6 kinase phosphorylation. In contrast, the pHi of cells with low CAi activity was less responsive to pCO2 fluctuations. Such low pass filtering would "buffer" cancer cell pHi from non-steady-state extracellular pCO2. Thus, CAi activity determines the coupling between pCO2 (a function of tumor perfusion) and pHi (a potent modulator of cancer cell physiology). PMID:25059669

  4. Carbon dioxide partial pressure and 13C content of north temperate and boreal lakes at spring ice melt

    USGS Publications Warehouse

    Striegl, R.G.; Kortelainen, P.; Chanton, J.P.; Wickland, K.P.; Bugna, G.C.; Rantakari, M.

    2001-01-01

    Carbon dioxide (CO2) accumulates under lake ice in winter and degasses to the atmosphere after ice melt. This large springtime CO2 pulse is not typically considered in surface-atmosphere flux estimates, because most field studies have not sampled through ice during late winter. Measured CO2 partial pressure (pCO2) of lake surface water ranged from 8.6 to 4,290 Pa (85-4,230 ??atm) in 234 north temperate and boreal lakes prior to ice melt during 1998 and 1999. Only four lakes had surface pCO2 less than or equal to atmospheric pCO2, whereas 75% had pCO2 >5 times atmospheric. The ??13CDIC (DIC = ??CO2) of 142 of the lakes ranged from -26.28??? to +0.95.???. Lakes with the greatest pCO2 also had the lightest ??13CDIC, which indicates respiration as their primary CO2 source. Finnish lakes that received large amounts of dissolved organic carbon from surrounding peatlands had the greatest pCO2. Lakes set in noncarbonate till and bedrock in Minnesota and Wisconsin had the smallest pCO2 and the heaviest ??13CDIC, which indicates atmospheric and/or mineral sources of C for those lakes. Potential emissions for the period after ice melt were 2.36 ?? 1.44 mol CO2 m-2 for lakes with average pCO2 values and were as large as 13.7 ?? 8.4 mol CO2 m-2 for lakes with high pCO2 values.

  5. Mineralization of Basalts in the CO2-H2O-H2S System

    SciTech Connect

    Schaef, Herbert T.; McGrail, B. Peter; Owen, Antionette T.; Arey, Bruce W.

    2013-08-01

    Basalt samples representing five different formations were immersed in water equilibrated with supercritical carbon dioxide containing 1% hydrogen sulfide (H2S) at reservoir conditions (100 bar, 90C) for up to 3.5 years. Surface coatings in the form of pyrite and metal cation substituted carbonates were identified as reaction products associated with all five basalts. In some cases, high pressure tests contained excess H2S, which produced the most corroded basalts and largest amount of secondary products. In comparison, tests containing limited amounts of H2S appeared least reacted with significantly less concentrations of reaction products. In all cases, pyrite appeared to precede carbonation, and in some instances, was observed in the absence of carbonation such as in cracks, fractures, and within the porous glassy mesostasis. Armoring reactions from pyrite surface coatings observed in earlier shorter duration tests were found to be temporary with carbonate mineralization observed with all the basalts tested in these long duration experiments. Geochemical simulations conducted with the geochemical code EQ3/6 accurately predicted early pyrite precipitation followed by formation of carbonates. Reactivity with H2S was correlated with measured Fe(II)/Fe(III) ratios in the basalts with more facile pyrite formation occurring with basalts containing more Fe(III) phases. These experimental and modeling results confirm potential for long term sequestration of acid gas mixtures in continental flood basalt formations.

  6. Oxygen partial pressure dependence of magnetic, optical and magneto-optical properties of epitaxial cobalt-substituted SrTiO3 films.

    PubMed

    Onba?l?, Mehmet C; Goto, Taichi; Tang, Astera; Pan, Annia; Battal, Enes; Okyay, Ali K; Dionne, Gerald F; Ross, C A

    2015-05-18

    Cobalt-substituted SrTiO3 films (SrTi0.70Co0.30O3-?) were grown on SrTiO3 substrates using pulsed laser deposition under oxygen pressures ranging from 1 ?Torr to 20 mTorr. The effect of oxygen pressure on structural, magnetic, optical, and magneto-optical properties of the films was investigated. The film grown at 3 ?Torr has the highest Faraday rotation (FR) and magnetic saturation moment (Ms). Increasing oxygen pressure during growth reduced Ms, FR and optical absorption in the near-infrared. This trend is attributed to decreasing Co2+ ion concentration and oxygen vacancy concentration with higher oxygen partial pressure during growth. PMID:26074589

  7. 1 setting H 2 setting

    E-print Network

    Wu, Dapeng Oliver

    Outb: outside bright Outd: outside dark N: night 2 Inb ind outb outd n Canon + Sony + Iphone 1 h 2 0-50300-360 3 51-299 Iphone: 0 50 100 150 200 250 300 350 0 50 100 150 200 250 300 350 inb Nokia: 0 50 100 150 200 250 300 350 0 50 100 150 200 250 300 350 inb canonh nokiah inb inb nokia=iphone

  8. Prediction of the critical reduced electric field strength for carbon dioxide and its mixtures with 50% O2 and 50% H2 from Boltzmann analysis for gas temperatures up to 3500 K at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Zhao, Hu; Li, Xingwen; Jia, Shenli; Murphy, Anthony B.

    2014-08-01

    This paper provides theoretical calculations that predict the dielectric breakdown properties of carbon dioxide (CO2) and its mixtures with 50% O2 and 50% H2 for a gas temperature range of 300-3500 K at 0.1 MPa. CO2 is one of the most likely candidates for an environment-friendly arc-quenching medium to replace SF6 in high-voltage circuit breakers. Initially, the electron energy distribution function (EEDF) is derived by solving the Boltzmann equation under the zero-dimensional two-term spherical harmonic approximation. Then the reduced ionization and attachment coefficients are obtained, based on the calculated EEDF. Finally, the critical reduced electric field strength (E/N)cr, which is defined as the value for which total ionization reactions are equal to total attachment reactions, is obtained and analysed. The results demonstrate the superior breakdown properties of a 50% CO2-50% O2 mixture to those of both pure CO2 and 50% CO2-50% H2. Nearly no deviation in (E/N)cr is found in a 50% CO2-50% O2 mixture for gas temperatures up to 2500 K, and although there is clear reduction as the gas temperature is increased further to 3500 K, the value remains higher than that of pure CO2.

  9. Structural polymorphism in the L1 loop regions of human H2A.Z.1 and H2A.Z.2.

    PubMed

    Horikoshi, Naoki; Sato, Koichi; Shimada, Keisuke; Arimura, Yasuhiro; Osakabe, Akihisa; Tachiwana, Hiroaki; Hayashi-Takanaka, Yoko; Iwasaki, Wakana; Kagawa, Wataru; Harata, Masahiko; Kimura, Hiroshi; Kurumizaka, Hitoshi

    2013-12-01

    The histone H2A.Z variant is widely conserved among eukaryotes. Two isoforms, H2A.Z.1 and H2A.Z.2, have been identified in vertebrates and may have distinct functions in cell growth and gene expression. However, no structural differences between H2A.Z.1 and H2A.Z.2 have been reported. In the present study, the crystal structures of nucleosomes containing human H2A.Z.1 and H2A.Z.2 were determined. The structures of the L1 loop regions were found to clearly differ between H2A.Z.1 and H2A.Z.2, although their amino-acid sequences in this region are identical. This structural polymorphism may have been induced by a substitution that evolutionally occurred at the position of amino acid 38 and by the flexible nature of the L1 loops of H2A.Z.1 and H2A.Z.2. It was also found that in living cells nucleosomal H2A.Z.1 exchanges more rapidly than H2A.Z.2. A mutational analysis revealed that the amino-acid difference at position 38 is at least partially responsible for the distinctive dynamics of H2A.Z.1 and H2A.Z.2. These findings provide important new information for understanding the differences in the regulation and functions of H2A.Z.1 and H2A.Z.2 in cells. PMID:24311584

  10. Hydrogen storage property of MgH 2 synthesized by hydriding chemical vapor deposition

    Microsoft Academic Search

    I. Saita; T. Toshima; S. Tanda; T. Akiyama

    2007-01-01

    As reported previously, MgH2 synthesized by hydriding chemical vapor deposition (HCVD) was made of single crystals with nano-fibrous figures. Therefore, the hydrogen storage property of the HCVDed MgH2 is expected to reflect its structural character. In this study, we examined the hydrogen storage property of MgH2 synthesized by HCVD. Results of pressure-composition-isotherm (PCT) measurement showed that the HCVDed MgH2 reversibly

  11. Nitriding of titanium and its alloys by N2, NH3 or mixtures of N2 + H2 in a dc arc plasma at low pressures ( or = to torr)

    NASA Technical Reports Server (NTRS)

    Avni, R.

    1984-01-01

    The dc glow discharges in different gas mixtures of Ar + N2, Ar + NH3 or Ar + N2 + H2 result in the surface nitriding of Ti metal and its alloy (Ti6Al4V). Various gas mixtures were used in order to establish the main active species governing the nitriding process, i.e., N, N2, NH, or NH2 as excited or ionized particles. The dc discharge was sampled and analyzed by quadruple mass spectrometry (QPMS) and optical emission spectroscopy (OES), and the nitrided samples were analyzed by scanning electron microscopy (SEM) with an EDAX attachment, microhardness, and Fourier transform infrared reflectance spectrometry (FTIR). It was found that the excited and ionized nitrogen and hydrogen atoms are the main species responsible for the nitriding process in a dc glow discharge.

  12. Composition-Temperature-Partial Pressures Data for Cd(sub 0.8)Zn(sub 0.2)Te by Optical Absorption Measurements

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua

    2005-01-01

    Known weights of Cd, Zn and Te were reacted in silica optical cells of known volume and the partial pressure of Te2 and Zn between 485 and 1160 C were determined by measuring the optical density of the vapor in the ultra-violet to visible range. The composition of the condensed phase or phases was calculated from the original weights and the amount of material in the vapor phase. The corresponding composition - temperature - partial pressures, x(sub Te)-T-P(sub Te2), data, including five Te-rich solidus points, were established. The solubility range for the Te-rich Cd(sub 0.8)Zn(sub 0.2)Te(s) is similar to that of CdTe(s) with x(sub Te) = 0.50005 at 809 C and an estimated maximum solubility of x(sub Te) = 0.50012 at about 1000 C. The partial pressure of Cd and Te(sub 2) measured over the Cd(sub 0.8)Zn(sub 0.2)Te melt at 1140 C were about 1.55 and 0.02 atm, respectively, and the corresponding P(Sub Zn) was estimated to be 0.05 atm. It was recommended that a Cd reservoir maintaining at 800 to 820 C should be used during directional solidification of Cd(sub o.8)Zn(sub 0.2)Te to prevent the preferential loss of Cd to the vapor phase.

  13. Vacuum ultra-violet emission of plasma discharges with high Xe partial pressure using a cathode protective layer with high secondary electron emission

    NASA Astrophysics Data System (ADS)

    Zhu, Di; Song, Le; Zhang, Xiong; Kajiyama, Hiroshi

    2014-02-01

    In this work, the mechanism of the vacuum ultra-violet (VUV) emission of plasma discharges, with high Xe partial pressure and high ion-induced secondary electrons emission protective layer, is studied by measuring the VUV light emission directly and comparing it with two-dimensional simulations. From the panel measurement, we find that the high intensity of excimer VUV mainly contributes to the high luminous efficacy of SrCaO-plasma display panels (PDP) at a low sustain voltage. The unchanged Xe excitation efficiency indicates that the electron temperature is not decreased by the high secondary electrons emission protective layer, even though the sustain voltage is much lower. From the two-dimensional simulations, we can find that the ratio of excimer VUV to resonant VUV, which is determined by the collision rate in the discharge, is only significantly affected by the Xe partial pressure, while it is independent of the sustain voltage and the secondary-electrons-emission capability of protective layer. The unchanged average electron energy at the moment when the electric field becomes maximum confirms that the improvement of the VUV production efficiency mainly is attributed to the increase in electron heating efficiency of a PDP with high ion-induced secondary electrons emission protective layer. Combining the experimental and the simulation results, we conclude about the mechanism by which the VUV production is improved for the plasma display panel with a high Xe partial pressure and a cold cathode with high ion-induced secondary electrons emission.

  14. Long-term spatial and temporal variation of CO2 partial pressure in the Yellow River, China

    NASA Astrophysics Data System (ADS)

    Ran, L.; Lu, X. X.; Richey, J. E.; Sun, H.; Han, J.; Yu, R.; Liao, S.; Yi, Q.

    2015-02-01

    Carbon transport in river systems is an important component of the global carbon cycle. Most rivers of the world act as atmospheric CO2 sources due to high riverine CO2 partial pressure (pCO2). By determining the pCO2 from alkalinity and pH, we investigated its spatial and temporal variation in the Yellow River watershed using historical water chemistry records (1950s-1984) and recent sampling along the mainstem (2011-2012). Except the headwater region where the pCO2 was lower than the atmospheric equilibrium (i.e. 380 ?atm), river waters in the remaining watershed were supersaturated with CO2. The average pCO2 for the watershed was estimated at 2810 1985 ?atm, which is 7-fold the atmospheric equilibrium. As a result of severe soil erosion and dry climate, waters from the Loess Plateau in the middle reaches had higher pCO2 than that from the upper and lower reaches. From a seasonal perspective, the pCO2 varied from about 200 ?atm to > 30 000 ?atm with higher pCO2 usually occurring in the dry season and lower pCO2 in the wet season (at 73% of the sampling sites), suggesting the dilution effect of water. While the pCO2 responded exponentially to total suspended solids (TSS) export when the TSS concentration was less than 100 kg m-3, it decreased slightly and remained stable if the TSS concentration exceeded 100 kg m-3. This stable pCO2 is largely due to gully erosion that mobilizes subsoils characterized by low organic carbon for decomposition. In addition, human activities have changed the pCO2 dynamics. Particularly, flow regulation by dams can diversely affect the temporal changes of pCO2, depending on the physiochemical properties of the regulated waters and adopted operation scheme. Given the high pCO2 in the Yellow River waters, large potential for CO2 evasion is expected and warrants further investigation.

  15. GLOBAL OCEAN SURFACE WATER PARTIAL PRESSURE OF CO2 DATABASE: MEASUREMENTS PERFORMED DURING 19682007 (Version 2007)

    SciTech Connect

    none,

    2008-09-30

    More than 4.1 million measurements of surface water partial pressure of CO2 obtained over the global oceans during 19682007 are listed in the Lamont-Doherty Earth Observatory (LDEO) database, which includes open ocean and coastal water measurements. The data assembled include only those measured by equilibrator-CO2 analyzer systems and have been quality-controlled based on the stability of the system performance, the reliability of calibrations for CO2 analysis, and the internal consistency of data. To allow re-examination of the data in the future, a number of measured parameters relevant to pCO2 measurements are listed. The overall uncertainty for the pCO2 values listed is estimated to be 2.5 atm on the average. For simplicity and for ease of reference, this version is referred to as 2007, meaning that data collected through 31 December 2007 has been included. It is our intention to update this database annually. There are 37 new cruise/ship files in this update. In addition, some editing has been performed on existing files so this should be considered a "V2007" file. Also we have added a column reporting the partial pressure of CO2 in seawater in units of Pascals. The data presented in this database include the analyses of partial pressure of CO2 (pCO2), sea surface temperature (SST), sea surface salinity (SSS), pressure of the equilibration, and barometric pressure in the outside air from the ships observation system. The global pCO2 data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center (CDIAC). The NDP consists of the oceanographic data files and this printed documentation, which describes the procedures and methods used to obtain the data.

  16. Syn-collisional channel flow and exhumation of paleoproterozoic High Pressure rocks in the Trans-North China Orogen: the critical role of partial-melting and orogenic bending.

    E-print Network

    Paris-Sud XI, Universit de

    1 Syn-collisional channel flow and exhumation of paleoproterozoic High Pressure rocks in the Trans of the partially molten rocks that compose the HPB according to changes in melt fraction. A compilation of the P-slip component that accommodated the final uprise of the high-pressure rocks. Keywords: High-pressure rocks

  17. High-pressure partial melting of garnet pyroxenite: possible mafic lithologies in the source of ocean island basalts

    Microsoft Academic Search

    Tetsu Kogiso; Marc M. Hirschmann; Daniel J Frost

    2003-01-01

    Many ocean island basalts (OIB) that have isotopic ratios indicative of recycled crustal components in their source are silica-undersaturated and unlike silicic liquids produced from partial melting of recycled mid-ocean ridge basalt (MORB). However, experiments on a silica-deficient garnet pyroxenite, MIX1G, at 2.02.5 GPa show that some pyroxenite partial melts are strongly silica-undersaturated [M.M. Hirschmann et al., Geology 31 (2003)

  18. Role of partial miscibility on pressure buildup due to constant rate injection of CO2 into closed and open brine aquifers

    NASA Astrophysics Data System (ADS)

    Mathias, Simon A.; Gluyas, Jon G.; GonzLez MartNez de Miguel, Gerardo J.; Hosseini, Seyyed A.

    2011-12-01

    This work extends an existing analytical solution for pressure buildup because of CO2 injection in brine aquifers by incorporating effects associated with partial miscibility. These include evaporation of water into the CO2 rich phase and dissolution of CO2 into brine and salt precipitation. The resulting equations are closed-form, including the locations of the associated leading and trailing shock fronts. Derivation of the analytical solution involves making a number of simplifying assumptions including: vertical pressure equilibrium, negligible capillary pressure, and constant fluid properties. The analytical solution is compared to results from TOUGH2 and found to accurately approximate the extent of the dry-out zone around the well, the resulting permeability enhancement due to residual brine evaporation, the volumetric saturation of precipitated salt, and the vertically averaged pressure distribution in both space and time for the four scenarios studied. While brine evaporation is found to have a considerable effect on pressure, the effect of CO2 dissolution is found to be small. The resulting equations remain simple to evaluate in spreadsheet software and represent a significant improvement on current methods for estimating pressure-limited CO2 storage capacity.

  19. Multi Frequency Phase Fluorimetry (MFPF) for Oxygen Partial Pressure Measurement: Ex Vivo Validation by Polarographic Clark-Type Electrode

    PubMed Central

    Boehme, Stefan; Duenges, Bastian; Klein, Klaus U.; Hartwich, Volker; Mayr, Beate; Consiglio, Jolanda; Baumgardner, James E.; Markstaller, Klaus; Basciani, Reto; Vogt, Andreas

    2013-01-01

    Background Measurement of partial pressure of oxygen (PO2) at high temporal resolution remains a technological challenge. This study introduces a novel PO2 sensing technology based on Multi-Frequency Phase Fluorimetry (MFPF). The aim was to validate MFPF against polarographic Clark-type electrode (CTE) PO2 measurements. Methodology/Principal Findings MFPF technology was first investigated in N?=?8 anaesthetised pigs at FIO2 of 0.21, 0.4, 0.6, 0.8 and 1.0. At each FIO2 level, blood samples were withdrawn and PO2 was measured in vitro with MFPF using two FOXY-AL300 probes immediately followed by CTE measurement. Secondly, MFPF-PO2 readings were compared to CTE in an artificial circulatory setup (human packed red blood cells, haematocrit of 30%). The impacts of temperature (20, 30, 40C) and blood flow (0.8, 1.6, 2.4, 3.2, 4.0 L min?1) on MFPF-PO2 measurements were assessed. MFPF response time in the gas- and blood-phase was determined. Porcine MFPF-PO2 ranged from 63 to 749 mmHg; the corresponding CTE samples from 43 to 712 mmHg. Linear regression: CTE?=?15.59+1.18*MFPF (R2?=?0.93; P<0.0001). Bland Altman analysis: meandiff 69.2 mmHg, rangediff -50.1/215.6 mmHg, 1.96-SD limits -56.3/194.8 mmHg. In artificial circulatory setup, MFPF-PO2 ranged from 20 to 567 mmHg and CTE samples from 11 to 575 mmHg. Linear regression: CTE?=??8.73+1.05*MFPF (R2?=?0.99; P<0.0001). Bland-Altman analysis: meandiff 6.6 mmHg, rangediff -9.7/20.5 mmHg, 1.96-SD limits -12.7/25.8 mmHg. Differences between MFPF and CTE-PO2 due to variations of temperature were less than 6 mmHg (range 0140 mmHg) and less than 35 mmHg (range 140750 mmHg); differences due to variations in blood flow were less than 15 mmHg (all P-values>0.05). MFPF response-time (monoexponential) was 1.480.26 s for the gas-phase and 1.510.20 s for the blood-phase. Conclusions/Significance MFPF-derived PO2 readings were reproducible and showed excellent correlation and good agreement with Clark-type electrode-based PO2 measurements. There was no relevant impact of temperature and blood flow upon MFPF-PO2 measurements. The response time of the MFPF FOXY-AL300 probe was adequate for real-time sensing in the blood phase. PMID:23565259

  20. THE PARTIAL OXIDATION OF CH4 TO CH3OH AT HIGH PRESSURE IN A PACKED REACTOR

    Microsoft Academic Search

    Lawrence A. Morton; Hyman D. Cesser; Norman R. Hunter

    1991-01-01

    In a considered effort to improve turbulence and heat transfer while reducing reactant\\/product residence time (enhancing primary product preservation) in the partial oxidation of methane lo methanol, a glass lined reactor was packed successively with a scries of metal (beads), glass (beads) and carbon (solid foam). The metal surfaces included, nickel, copper, silver, line, tin and stainless steel.The surfaces were

  1. The partial oxidation of CH sub 4 to CH sub 3 OH at high pressure in a packed reactor

    Microsoft Academic Search

    L. A. Morton; H. D. Gesser; N. R. Hunter

    1991-01-01

    This paper reports on a considered effort to improve turbulence and heat transfer while reducing reactant\\/product residence time (enhancing primary product preservation) in the partial oxidation of methane to methanol, a glass lined reactor packed successively with a series of metal (beads), glass (beads) and carbon (solid foam). The metal surfaces included, nickel, copper, silver, zinc, tin and stainless steel.

  2. 20 CFR 655.132 - H-2A labor contractor (H-2ALC) filing requirements.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...labor contractor (H-2ALC) filing requirements. 655.132 Section 655.132 Employees' Benefits EMPLOYMENT AND TRAINING...Temporary Employment Certification Filing Procedures 655.132 H-2A labor contractor (H-2ALC)...

  3. 20 CFR 655.132 - H-2A labor contractor (H-2ALC) filing requirements.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...labor contractor (H-2ALC) filing requirements. 655.132 Section 655.132 Employees' Benefits EMPLOYMENT AND TRAINING...Temporary Employment Certification Filing Procedures 655.132 H-2A labor contractor (H-2ALC)...

  4. Availability of O(2) and H(2)O(2) on pre-photosynthetic Earth.

    PubMed

    Haqq-Misra, Jacob; Kasting, James F; Lee, Sukyoung

    2011-05-01

    Old arguments that free O(2) must have been available at Earth's surface prior to the origin of photosynthesis have been revived by a new study that shows that aerobic respiration can occur at dissolved oxygen concentrations much lower than had previously been thought, perhaps as low as 0.05?nM, which corresponds to a partial pressure for O(2) of about 4??10(-8) bar. We used numerical models to study whether such O(2) concentrations might have been provided by atmospheric photochemistry. Results show that disproportionation of H(2)O(2) near the surface might have yielded enough O(2) to satisfy this constraint. Alternatively, poleward transport of O(2) from the equatorial stratosphere into the polar night region, followed by downward transport in the polar vortex, may have brought O(2) directly to the surface. Thus, our calculations indicate that this "early respiration" hypothesis might be physically reasonable. PMID:21545266

  5. Impact of the hydrogen partial pressure on lactate degradation in a coculture of Desulfovibrio sp. G11 and Methanobrevibacter arboriphilus DH1.

    PubMed

    Junicke, H; Feldman, H; van Loosdrecht, M C M; Kleerebezem, R

    2015-04-01

    In this study, the impact of the hydrogen partial pressure on lactate degradation was investigated in a coculture of Desulfovibrio sp. G11 and Methanobrevibacter arboriphilus DH1. To impose a change of the hydrogen partial pressure, formate was added to the reactor. Hydrogen results from the bioconversion of formate besides lactate in the liquid phase. In the presence of a hydrogen-consuming methanogen, this approach allows for a better estimation of low dissolved hydrogen concentrations than under conditions where hydrogen is supplied externally from the gas phase, resulting in a more accurate determination of kinetic parameters. A change of the hydrogen partial pressure from 1,200 to 250 ppm resulted in a threefold increase of the biomass-specific lactate consumption rate. The 50 % inhibition constant of hydrogen on lactate degradation was determined as 0.692??0.064 ?M dissolved hydrogen (831??77 ppm hydrogen in the gas phase). Moreover, for the first time, the maximum biomass-specific lactate consumption rate of Desulfovibrio sp. G11 (0.083??0.006 mol-Lac/mol-XG11/h) and the affinity constant for hydrogen uptake of Methanobrevibacter arboriphilus DH1 (0.601??0.022 ?M dissolved hydrogen) were determined. Contrary to the widely established view that the biomass-specific growth rate of a methanogenic coculture is determined by the hydrogen-utilizing partner; here, it was found that the hydrogen-producing bacterium determined the biomass-specific growth rate of the coculture grown on lactate and formate. PMID:25472436

  6. Revealing sub-{\\mu}m inhomogeneities and {\\mu}m-scale texture in H2O ice at Megabar pressures via sound velocity measurements by time-domain Brillouin scattering

    E-print Network

    Nikitin, Sergey M; Tournat, Vincent; Bulou, Alain; Gasteau, Damien; Castagnede, Bernard; Zerr, Andreas; Gusev, Vitalyi E

    2014-01-01

    Time-domain Brillouin scattering technique, also known as picosecond ultrasonic interferometry, which provides opportunity to monitor propagation of nanometers to sub-micrometers length coherent acoustic pulses in the samples of sub-micrometers to tens of micrometers dimensions, was applied to depth-profiling of polycrystalline aggregate of ice compressed in a diamond anvil cell to Megabar pressures. The technique allowed examination of characteristic dimensions of elastic inhomogeneities and texturing of polycrystalline ice in the direction normal to the diamond anvil surfaces with sub-micrometer spatial resolution via time-resolved measurements of variations in the propagation velocity of the acoustic pulse traveling in the compressed sample. The achieved two-dimensional imaging of the polycrystalline ice aggregate in-depth and in one of the lateral directions indicates the feasibility of three-dimensional imaging and quantitative characterization of acoustical, optical and acousto-optical properties of tra...

  7. Oxygen partial pressure dependence of the structural properties of CdO thin films deposited by a modified reactive vacuum evaporation process

    Microsoft Academic Search

    F. C. Eze

    2005-01-01

    Thin films of cadmium oxide were thermally deposited on glass substrates at partial pressures of oxygen, pO2 in the range 1.3310?2 to 0.133Pa at a substrate temperature of 160C. Energy dispersive analysis of X-ray fluorescence (EDAX) revealed that the CdO films deposited at pO2 value of 4.0010?2Pa were nearly stoichiometric. X-ray diffractometry (XRD) confirmed the polycrystalline nature of the film

  8. Plant and environment interactions: Growth and yield response of commercial bearing-age {open_quote}Casselman{close_quote} plum trees to various ozone partial pressures

    SciTech Connect

    Retzlaff, W.A.; Williams, L.E. [Univ. of California, Parlier, CA (United States); DeJong, T.M. [Univ. of California, Davis, CA (United States)

    1997-05-01

    Nursery stock of plum (Prunus salicina Lindel., cv. Casselman) was planted 1 Apr. 1988 in an experimental orchard at the Univ. of California Kearney Agricultural Center near Fresno, CA. Trees in this study were enclosed in open-top fumigation chambers on 1 May 1989, and exposed to three atmospheric ozone partial pressures (charcoal filtered air, ambient air, and ambient air + ozone) during the 1989 through 1992 growing seasons (typically 1 Apr. - 1 Nov.). A nonchamber treatment plot was used to assess chamber effects on tree performance. This study details the results of the exposures during the initial commercial bearing period (1991 through 1993) in this orchard. The mean 12-h (0800-2000 h Pacific Daylight Time [PDT]) ozone partial pressures during the experimental periods in the charcoal filtered, ambient, ambient + ozone, and nonchamber treatments averaged 0.031, 0.048, 0.091, and 0.056 {mu}Pa Pa{sup {minus}1} in 1991 and 1992, respectively. Fruit number per tree decreased as atmospheric ozone partial pressure increased from the charcoal filtered to ambient + ozone treatment, significantly affecting yield. Yield of plum trees averaged 23.6, 19.8, 13.7, and 17.9 kg tree{sup {minus}1} in 1991 and 1992 in the charcoal filtered, ambient, ambient + ozone, and nonchamber treatments, respectively. Only one out of the five original treatment plots was exposed to ozone treatments during the 1993 growing season. Yield of plum trees in this single replicate in 1993 was reduced by increased atmospheric ozone partial pressure. Yield of plum trees in the four remaining unexposed treatment plots in 1993 was 16.7, 17.9, and 16.0 kg tree{sup {minus}1} in the previous charcoal filtered, ambient, and ambient + ozone treatments respectively. The similarity in yield of the post-chamber treatments indicates that a change in air quality in the current growing season can affect yield of Casselman plum trees. 26 refs., 6 figs., 4 tabs.

  9. Advanced H2/O2 space engine parametrics

    NASA Technical Reports Server (NTRS)

    Schneider, J. A.

    1989-01-01

    Engine cycle analyses conducted on a 3000-lbf component testing model of an H2/O2-fueled advanced orbit-transfer vehicle engine employing a dual-expander cycle have yielded pressure and temperature trend predictions. On the basis of the results obtained, the dual-expander cycle is projected to be scalable to thrust levels of as much as 50,000 lbf, with chamber pressures of 2000 psi. The high chamber pressure, in conjunction with the use of a gas-gas injector element, facilitates 10:1-range continuously variable throttling. The preferred thrust level for supporting mission studies would be of the order of 20,000 lbf.

  10. Fine-tuning control on CNT diameter distribution, length and density using thermal CVD growth at atmospheric pressure: an in-depth analysis on the role of flow rate and flow duration of acetylene (C2H2) gas

    NASA Astrophysics Data System (ADS)

    Tripathi, Nishant; Mishra, Prabhash; Harsh, Harsh; Islam, S. S.

    2015-01-01

    An optimization control has been demonstrated to obtain carbon nanotubes having specific diameter distribution, length, homogeneity, and yield during its growth by thermal chemical vapor deposition technique under atmospheric pressure. Carbon nanotubes (CNTs) were grown on silicon wafer where a predeposition of iron catalyst of 2 nm thickness was made by sputtering. The growth was conducted under two variable parameters, i.e., flow rate and flow duration. Argon and hydrogen mixture was used for pretreatment of catalyst and as etching gas, and acetylene as a carbon precursor. In-depth analysis shows that increase in flow rate from 10 to 50 sccm resulted in increase in the concentration of amorphous carbon, CNTs diameter range and decrease in length, we found best result at 20 sccm flow rate of acetylene gas. On the other hand, as we varied flow duration from 6 to 14 min, with keeping flow rate of acetylene 20 sccm constant, dense homogeneous growth of horizontal CNTs network plus an increase in length and diameter range were observed. An optimization of flow rate and flow duration is presented here to obtain a selective diameter distribution and length as expected by this growth technique. Atomic force microscopy, field emission scanning electron microscopy and Raman spectroscopy were used to investigate the samples' morphologies in support of the observations made.

  11. High-Resolution Numerical Simulation and Analysis of Mach Reflection Structures in Detonation Waves in Low-Pressure H2O2Ar Mixtures: A Summary of Results Obtained with the Adaptive Mesh Refinement Framework AMROC

    DOE PAGESBeta

    Deiterding, Ralf

    2011-01-01

    Numerical simulation can be key to the understanding of the multidimensional nature of transient detonation waves. However, the accurate approximation of realistic detonations is demanding as a wide range of scales needs to be resolved. This paper describes a successful solution strategy that utilizes logically rectangular dynamically adaptive meshes. The hydrodynamic transport scheme and the treatment of the nonequilibrium reaction terms are sketched. A ghost fluid approach is integrated into the method to allow for embedded geometrically complex boundaries. Large-scale parallel simulations of unstable detonation structures of Chapman-Jouguet detonations in low-pressure hydrogen-oxygen-argon mixtures demonstrate the efficiency of the described techniquesmorein practice. In particular, computations of regular cellular structures in two and three space dimensions and their development under transient conditions, that is, under diffraction and for propagation through bends are presented. Some of the observed patterns are classified by shock polar analysis, and a diagram of the transition boundaries between possible Mach reflection structures is constructed.less

  12. Partial discharges and breakdown in SF6 in the pressure range 25-150 kPa in non-uniform background fields

    NASA Astrophysics Data System (ADS)

    Seeger, M.; Clemen, M.

    2014-01-01

    The partial discharge (PD) and electric breakdown mechanisms in SF6 at a plug contact in the pressure range 25-150 kPa were investigated at ambient temperature in a plug-plate arrangement. This parameter range has similar particle number densities as in the previous investigation of the dielectric recovery in a high-voltage circuit breaker (Seeger et al 2012 J. Phys. D: Appl. Phys. 45 395204), where optical access was limited and the relevant parameters of pressure and temperature could only be determined indirectly by computational fluid dynamic simulations. The present investigation did not have these limitations, since the pressure and temperature were well defined. Optical observation by an image intensified high speed camera in combination with a photo multiplier tube allowed an understanding of the various mechanisms for the PDs and breakdown to be gained. The breakdown fields and PD parameters could be well described by a simple leader model in the pressure range 75-150 kPa for negative polarity and above 25 kPa for positive polarity. Discrepancies with the model are observed below 75 kPa for negative polarity and at 25 kPa for positive polarity. This could be explained by a slow, repetitive heating mechanism which has not been reported so far.

  13. Analysis of the Pressure Rise in a Partially Filled Liquid Tank in Microgravity with Low Wall Heat Flux and Simultaneous Boiling and Condensation

    NASA Technical Reports Server (NTRS)

    Hasan, Mohammad M.; Balasubramaniam, R.

    2012-01-01

    Experiments performed with Freon 113 in the space shuttle have shown that in a pro- cess of very slow heating, high liquid superheats can be sustained for a long period in microgravity. In a closed system explosive vaporization of superheated liquid resulted in pressure spikes of varying magnitudes. In this paper, we analyze the pressure rise in a partially lled closed tank in which a large vapor bubble (i.e., ullage) is initially present, and the liquid is subjected to a low wall heat ux. The liquid layer adjacent to the wall becomes superheated until the temperature for nucleation of the bubbles (or the incipience of boiling) is achieved. In the absence of the gravity-induced convection large quantities of superheated liquid can accumulate over time near the heated surface. Once the incipience temperature is attained, explosive boiling occurs and the vapor bubbles that are produced on the heater surface tend to quickly raise the tank pressure. The liquid-vapor saturation temperature increases as well. These two e ects tend to induce condensation of the large ullage bubble that is initially present, and tends to mitigate the tank pressure rise. As a result, the tank pressure is predicted to rise sharply, attain a maximum, and subsequently decay slowly. The predicted pressure rise is compared with experimental results obtained in the microgravity environments of the space shuttle for Freon 113. The analysis is appli- cable, in general to heating of liquid in closed containers in microgravity and to cryogenic fuel tanks, in particular where small heat leaks into the tank are unavoidable.

  14. Effects of Pleistocene, pre-industrial, current, and future CO[sub 2] partial pressures on C[sub 3] and C[sub 4] plant growth

    SciTech Connect

    Dippery, J.K.; Strain, B.R. (Duke Univ., Durham, NC (United States))

    1993-06-01

    To study plant growth in atmospheric CO[sub 2] concentrations ranging from Pleistocene through predicted future levels, Amaranthus retroflexus (C[sub 4]) and Abutilon theophrasti (C[sub 3]) were grown in growth chambers at four CO[sub 2] levels (15 Pa, Pleistocene minimum; 27 Pa, pre-industrial; 35 Pa, current; 70 Pa, future). Thirty-five days after emergence, shoot dry weight, root dry weight and leaf area did not differ between any CO[sub 2] levels for the C[sub 4] species. The C[sub 3] species showed increased root and shoot dry weights and leaf areas when grown in CO[sub 2] partial pressures of 15 Pa, 27 Pa and 35 Pa. This evidence indicates that plant growth in C[sub 4] species is unaffected by atmospheric CO[sub 2] levels ranging from the Pleistocene minimum through the future; whereas, C[sub 3] species show growth increases as CO[sub 2] partial pressures rise above the Pleistocene minimum.

  15. Pilot-scale UV/H2O2 advanced oxidation process for surface water treatment and downstream biological treatment: effects on natural organic matter characteristics and DBP formation potential.

    PubMed

    Sarathya, Siva R; Stefan, Mihaela I; Royce, Alan; Mohseni, M

    2011-12-01

    The effects of the advanced oxidation process (AOP) of ultraviolet radiation in combination with hydrogen peroxide (UV/H2O2) on the structure and biodegradability of dissolved natural organic matter (NOM) and on the formation of disinfection by-products (DBPs) through the post-UV/H2O2 chlorination were investigated using UV reactors equipped with either low-pressure amalgam lamps or medium-pressure mercury vapour lamps. With electrical energy doses and H2O2 concentrations typically applied in full-scale UV systems for water remediation, the UV/H2O2 AOP partially oxidized NOM, reducing its degree of aromaticity and leading to an increase in the level of biodegradable species. Also, when combined with a downstream biological activated carbon (BAC) filter, UV/H2O2 AOP reduced the formation of DBPs by up to 60% for trihalomethanes and 75% for haloacetic acids. Biological activated carbon was also shown to effectively remove biodegradable by-products and residual H2O2. PMID:22439556

  16. Cluster virial expansion of the equation of state for hydrogen plasma with e -H2 contributions

    NASA Astrophysics Data System (ADS)

    Omarbakiyeva, Y. A.; Reinholz, H.; Rpke, G.

    2015-04-01

    The equation of state of partially ionized hydrogen plasma is considered with special focus on the contribution of the e -H2 interaction. Traditional semiempirical concepts such as the excluded volume are improved using microscopic approaches to treat the e -H2 problem. Within a cluster virial expansion, the Beth-Uhlenbeck formula is applied to infer the contribution of bound and scattering states to the temperature-dependent second virial coefficient. The scattering states are calculated using the phase expansion method for the polarization interaction that incorporates experimental data for the e -H2 scattering cross section. We present results for the scattering phase shifts, differential scattering cross sections, and the second virial coefficient due to the e -H2 interaction. The influence of this interaction on the composition of the partially ionized hydrogen plasma is confined to the parameter range where both the H2 and the free-electron components are abundant.

  17. Predicting possible effects of H2S impurity on CO2 transportation and geological storage.

    PubMed

    Ji, Xiaoyan; Zhu, Chen

    2013-01-01

    For CO(2) geological storage, permitting impurities, such as H(2)S, in CO(2) streams can lead to a great potential for capital and energy savings for CO(2) capture and separation, but it also increases costs and risk management for transportation and storage. To evaluate the cost-benefits, using a recently developed model (Ji, X.; Zhu, C. Geochim. Cosmochim. Acta 2012, 91, 40-59), this study predicts phase equilibria and thermodynamic properties of the system H(2)S-CO(2)-H(2)O-NaCl under transportation and storage conditions and discusses potential effects of H(2)S on transportation and storage. The prediction shows that inclusion of H(2)S in CO(2) streams may lead to two-phase flow. For H(2)S-CO(2) mixtures, at a given temperature, the bubble and dew pressures decrease with increasing H(2)S content, while the mass density increases at low pressures and decreases at high pressures. For the CO(2)-H(2)S-H(2)O system, the total gas solubility increases while the mass density of the aqueous solution with dissolved gas decreases. For the CO(2)-H(2)S-H(2)O-NaCl system, at a given temperature, pressure and NaCl concentration, the solubility of the gas mixture in aqueous phase increases with increasing H(2)S content and then decreases, while the mass density of aqueous solution decreases and may be lower than the mass density of the solution without gas dissolution. PMID:22823266

  18. On the likelihood of decompression sickness during H2 biochemical decompression in pigs

    E-print Network

    Fahlman, Andreas

    - ness (DCS) outcome in pigs during exposures to hyperbaric H2 to quantify the effects of H2 biochemical dt, where Pamb is ambient pressure and is a time constant. The probability of DCS [P(DCS)] was predicted from the risk function: P(DCS) 1 e r , where r (PtisH2 PtisHe Thr Pamb) Pamb 1 dt, and Thr

  19. Observations of long-lived H-2 and D-2 ions from non-thermal plasmas

    Microsoft Academic Search

    Wei-Guo Wang; Yong Xu; Ai-Min Zhu; Zhong-Wei Liu; Xin Liu; Xue-Feng Yang

    2007-01-01

    Strong mass signals of H-2 and D-2 ions have been observed from low-pressure dielectric barrier discharge hydrogen and deuterium plasmas via molecular beam mass spectrometry. The observed H-2\\/H- and D-2\\/D- ratios (~0.35-0.4) are over five orders of magnitude higher than those observed by other techniques. The kinetic energy of H-2 and D-2 ions sampled from the plasmas was determined to

  20. Pressure

    NSDL National Science Digital Library

    Wolfgang Christian

    This page contains three Physlets that are able to share data using a connection made by a common superclass, SApplet. The ensemble walls keep track of the change in momentum, i.e., the pressure, during each time step, dt, and provides this data to the DataGraph Physlet and the DataTable Physlet.

  1. Effect of Partial Closure of the Channel on the Pressure Pulse in a Shock Wave Emerging from a Duct

    Microsoft Academic Search

    T. V. Bazhenova; V. V. Golub; A. L. Kotel'nikov; A. S. Chizhikov; S. B. Shcherbak

    2003-01-01

    The temporal-spatial development of the flow pattern behind a shock wave emerging from open-ended and half-closed ducts at M0=1.15 to 3.0 Mach number is investigated both experimentally and numerically and the action of the diffracted wave on a barrier placed at different distances from the duct exit is studied. Flow toeplerograms are obtained and the pressure on the barrier is

  2. Experimental Measurements of the H3+ + H2 ? H3+ + H2 Reaction in a Hollow Cathode

    NASA Astrophysics Data System (ADS)

    Kauffman, Carrie A.; Crabtree, Kyle N.; Tom, Brian A.; Beka, Eftalda; McCall, Benjamin, J.

    2010-11-01

    Hydrogen is the most abundant element in the universe and as a result, molecular hydrogen and the H3+ ion play a pivotal role in interstellar chemistry. Like H2, H3+ exists in two nuclear spin configurations, ortho (I = 3/2) and para (I = 1/2), which are unique molecules that can only interconvert through a chemical reaction. The reaction between these species, H3+ + H2 ? H3+ + H2, is the dominant means by which the nuclear spin of H3+ can be changed. It is also the most commonly occuring bimolecular reaction in the universe, and therefore it is important to understand how this reaction influences the ortho/para ratio of H3+ . We have studied the nuclear spin dependence of the H3+ + H2 proton-scrambling reaction by probing ?2 fundamental band of H3+ using multipass direct absorption spectroscopy. We have monitored the ortho/para ratio of H3+ in a variety of hydrogenic plasmas consisting of different ortho/para-H2 ratios. To deduce the temperature dependence of this reaction, we have performed these experiements in an uncooled hollow cathode and, for the first time at low temperature, in a liquid nitrogen cooled hollow cathode. Finally, we have also studied the pressure dependence of the chemistry in order to elucidate any three-body processes that may be occuring in our plasmas.

  3. H2 production from simulated coal syngas containing H2S in multi-tubular Pd and 80 wt% Pd-20 wt% Cu membrane reactors

    SciTech Connect

    Iyoha, O.; Enick, R.M.; Killmeyer, R.P.; Howard, B.H.; Ciocco, M.V.; Morreale, B.

    2007-12-01

    99.7% conversion of CO in a simulated syngas feed containing 53% CO, 35% H2 and 12% CO2 was achieved via the watergas shift (WGS) reaction in a counter-current Pd multi-tube membrane reactor (MR) at 1173 K and 2 s residence time. This conversion is significantly greater than the 32% equilibrium conversion associated with a conventional (non-membrane) reactor primarily due to the high rate of H2 extraction from the reaction zone through the Pd membranes at elevated temperatures. Furthermore, nearly complete H2 recovery was attained in the permeate, resulting in the simultaneous production of a high-pressure CO2 (>99%) retentate stream after condensation of the steam. When Pd80 wt%Cu tubes were used in the reactor, a significantly lower CO conversion of 68% was attained at comparable residence times, probably due to the lower H2 permeance of the alloy. When H2S was added to the syngas feed and the H2S-to-H2 ratio was maintained below the threshold required for thermodynamically stable sulfides to form, the Pd and Pd80 wt%Cu MRs retained their mechanical integrity and H2 selectivity, but a precipitous drop in CO conversion was observed due to deactivation of the catalytic surface. The Pd and Pd80 wt%Cu MRs were observed to fail within minutes after increasing the H2S-to-H2 ratio to levels above that expected for thermodynamically stable sulfides to form, as evidenced by rupturing of the membrane tubes. SEMEDS analyses of the membranes suggested that at high H2S-to-H2 ratios, the H2S compromised the mechanical integrity of the MRs by preferentially attacking the grain boundary region.

  4. Study of flow profile distortions and efficiency in counter pressure moderated partial filling micellar electrokinetic chromatography in relation to the relative buffer zone lengths.

    PubMed

    Michalke, Daniela; Welsch, Thomas

    2002-06-25

    The influence of the relative buffer zone lengths on the efficiency was investigated in partial filling micellar electrokinetic chromatography using sodium dodecyl sulfate as separation additive. Varying relative zone lengths were obtained by applying identical initial separation zone lengths but different total lengths of the capillaries. Plate numbers of a homologous series of omega-phenylalcohols were measured to indicate the effect of both a changing relative zone length during the run and a counter pressure applied on the cathodic buffer reservoir. The magnitude and the course of these plate numbers are discussed on the basis of models for flow profile superposition and flow profile deformation which are caused by an intersegmental pressure arising at the boundary between the two buffer zones with different electroosmotic flow velocities. Calculation of the intersegmental pressure and of the resulting laminar flow components in the buffer zones on the basis of some equations for electroosmotic and hydrodynamic flow supported the interpretation that a long background buffer zone should be avoided PMID:12150559

  5. Photolysis of H2O-H2O2 mixtures: The destruction of H2O2

    NASA Astrophysics Data System (ADS)

    Loeffler, M. J.; Fama, M.; Baragiola, R. A.; Carlson, R. W.

    2013-09-01

    We present laboratory results on the loss of H2O2 in solid H2O + H2O2 mixtures at temperatures between 21 and 145 K initiated by UV photolysis (193 nm). Using infrared spectroscopy and microbalance gravimetry, we measured the decrease of the 3.5 ?m infrared absorption band during UV irradiation and obtained a photodestruction cross section that varies with temperature, being lowest at 70 K. We use our results, along with our previously measured H2O2 production rates via ionizing radiation and ion energy fluxes from the spacecraft to compare H2O2 creation and destruction at icy satellites by ions from their planetary magnetosphere and from solar UV photons. We conclude that, in many cases, H2O2 is not observed on icy satellite surfaces because the H2O2 photodestruction rate is much higher than the production rate via energetic particles, effectively keeping the H2O2 infrared signature at or below the noise level.

  6. Histone H2A (H2A.X and H2A.Z) Variants in Molluscs: Molecular Characterization and Potential Implications

    E-print Network

    Eirin Lopez, Jose Maria

    Histone H2A (H2A.X and H2A.Z) Variants in Molluscs: Molecular Characterization and Potential in most organisms, specially protostome animals. Molluscs (which represent sentinel organisms. (2012) Histone H2A (H2A.X and H2A.Z) Variants in Molluscs: Molecular Characterization and Potential

  7. A SAFT equation of state for the quaternary H2S-CO2-H2O-NaCl system

    NASA Astrophysics Data System (ADS)

    Ji, Xiaoyan; Zhu, Chen

    2012-08-01

    Phase equilibria and thermodynamic properties of the quaternary H2S-CO2-H2O-NaCl system were studied using a statistical associating fluid theory (SAFT)-based equation of state (EOS) at temperatures from 0 to 200 C (373.15-473.15 K), pressures up to 600 bar (60 MPa) and concentrations of NaCl up to 6 mol/kgH2O. The understanding of the physical-chemical properties of this system is critical for predicting the consequences of co-injection of CO2 and H2S into geological formations (geological carbon sequestration) as an option for mitigating the global warming trend. Equation of state parameters were generated from regression of available and reliable experimental data and incorporation of existing parameters for some subsystems. Densities were predicted and compared with available experimental results. Using the EOS developed in this study, we predicted equilibrium compositions in both liquid and vapor phases, fugacity coefficients of components, the equilibrium pressures at a given composition of the H2O-rich phase in electrolyte solutions with NaCl varying from 0 to 4 mol/kgH2O, and the aqueous solution densities. These predicted values are tabulated and available as supplementary data in the electronic version online. These predictions provide information and guidance for future experiments regarding the thermodynamic properties and phase behaviors in the H2S-CO2-H2O-NaCl system.

  8. The reactions of HO2 with CO and NO and the reaction of O(1D) with H2O

    NASA Technical Reports Server (NTRS)

    Simonaitis, R.; Heicklen, J.

    1973-01-01

    HO2 radicals were generated by the photolysis of N2O at 2139 A in the presence of excess H2O or H2 and smaller amounts of CO and O2. The O(1D) atoms produced from the photolysis of N2O to give HO radicals or H2 to give HO + H. With H2O two HO radicals are produced for each O(1D) removed low pressures (i.e. approximately 20 torr H2O), but the HO yield drops as the pressure is raised. This drop is attributed to the insertion reaction: O(1D) + H2O + M yields H2O2 +M. The HO radicals generated can react with either CO or H2 to produce H atoms which then add to O2 to produce HO2. Two reactions are given for the reactions of the HO radicals, in the absence of NO.

  9. Photodegradation of the antibiotic sulphamethoxazole in water with UV\\/H2O2 advanced oxidation process

    Microsoft Academic Search

    Y. Lester; D. Avisar; H. Mamane

    2010-01-01

    Photodegradation of the antibiotic sulphamethoxazole (SMX) in water using a medium?pressure UV lamp combined with H2O2 (UV\\/H2O2) was used to generate the advanced oxidation process (AOP). The photodegradation process was steadily improved with addition of H2O2 at relatively low to moderate concentrations (5 to 50 mg L). However, the addition of H2O2 to the photolysis process at higher concentrations (50

  10. Ternary nucleation of H2SO4, NH3, and H2O in the atmosphere

    Microsoft Academic Search

    P. Korhonen; M. Kulmala; A. Laaksonen; Y. Viisanen; R. McGraw; J. H. Seinfeld

    1999-01-01

    Classical theory of binary homogeneous nucleation is extended to the ternary system H2SO4-NH3-H2O. For NH3 mixing ratios exceeding about 1 ppt, the presence of NH3 enhances the binary H2SO4-H2O nucleation rate by several orders of magnitude. The Gibbs free energies of formation of the critical H2SO4-NH3-H2O cluster, as calculated by two independent approaches, are in substantial agreement. The finding that

  11. Development of a Turnkey H2 Fueling

    E-print Network

    Feedstocks Storage NG Compression PSAPSARef.Ref. PTI, CATA, Penn State H2 Generator #12;5 Air ProductsDevelopment of a Turnkey H2 Fueling Station David E. Guro Air Products and Chemicals, Inc. Allentown, PA U.S. D.O.E. - Hydrogen Program Annual Review May 2003 #12;2 Air Products & Chemicals, Inc

  12. Discontinuous phase formation and selective attack of SiC materials exposed to low oxygen partial pressure environments

    SciTech Connect

    Butt, D.P. [Los Alamos National Lab., NM (United States); Tressler, R.E.; Spear, K.E. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

    1993-09-01

    Three SiC materials were exposed to gas mixtures containing N{sub 2}, H{sub 2}, and CO at 1000-1300C, 1-740 torr for a few to 1000 h. Kinetic and thermodynamic studies indicate that CO is the predominant oxidizing species. A variety of corrosion processes were observed, including surface and internal pit formation, needle growth, grain boundary attack, and attack of impurities and surrounding material. In the case of a siliconized SiC, impurities such as Ca, Al, and Fe diffused rapidly through the Si matrix forming complex calcium aluminosilicates on the surface, leaving behind internal voids. Evaluation of the mechanical properties, including fractography, revealed a variety of degradative phenomena. Efforts to identify causes of pit formation suggested that the overall process was complex. Pits formed during attack of grain boundaries and regions containing transition metal impurities. Studies of single crystals showed preferential attack near impurities and crystalline defects, indicating that damaged crystals or certain crystal orientations in the polycrystalline materials are susceptible to attack. In addition, under some conditions where pit formation was observed, the strength of certain materials increased apparently due to flaw healing. It is suggested that flaws can heal in the absence of mechanical stress due to their high surface energy. However, second phases observed within partially healed surface cracks suggest impurities also contribute to the flaw healing processes.

  13. Cantilever stress measurements for pulsed laser deposition of perovskite oxides at 1000 K in an oxygen partial pressure of 10(-4) millibars.

    PubMed

    Premper, J; Sander, D; Kirschner, J

    2015-03-01

    An in situ stress measurement setup using an optical 2-beam curvature technique is described which is compatible with the stringent growth conditions of pulsed laser deposition (PLD) of perovskite oxides, which involves high substrate temperatures of 1000 K and oxygen partial pressures of up to 1 10(-4) millibars. The stress measurements are complemented by medium energy electron diffraction (MEED), Auger electron spectroscopy, and additional growth rate monitoring by a quartz microbalance. A shielded filament is used to allow for simultaneous stress and MEED measurements at high substrate temperatures. A computer-controlled mirror scans an excimer laser beam over a stationary PLD target. This avoids mechanical noise originating from rotating PLD targets, and the setup does not suffer from limited lifetime issues of ultra high vacuum (UHV) rotary feedthroughs. PMID:25832240

  14. Effects of oxygen partial pressure on the crystallization of amorphous Bi-Sr-Ca-Cu-O and Bi-Sr-Ca-Cu-O + Ag

    NASA Astrophysics Data System (ADS)

    Kramer, M. J.; Margulies, L.; Arrasmith, S. R.; Dennis, K. W.; Lang, J. C.; McCallum, R. W.; Gallagher, P. K.

    1994-07-01

    The temperatures and pathways of crystallization for amorphous Bi-Sr-Ca-Cu-O are strongly dependent on oxygen partial pressure (P(sub O(2))), the oxidation state of the glass, and the presence of Ag. Reducing the P(sub O(2)) from 1 to 0 bar lowers the onset of melting 100 deg C, but does not change the onset of crystallization. Decreasing P(sub O(2)) does inhibit the formation of (CaSr)CuO3 (011). Although Ag appears to be immiscible in Bi-Sr-Ca-Cu-O, finely distributed Ag lowers the onset of melting by 20 to 35 C, depending on P(sub O(2)). In oxygen-deficient glass, two exotherms are observed upon heating.

  15. Laboratory flow reactor measurements of the reaction SO3 + H2O + M yields H2SO4 + M: Implications for gaseous H2SO4 and aerosol formation in the plumes of jet aircraft

    Microsoft Academic Search

    Th. Reiner; F. Arnold

    1993-01-01

    The reaction SO3 + H2O + M has been investigated with a tubular flow reactor at a pressure of 85 Torr. Sulfuric acid has been identified as the most probable product of the reaction. Both, reactant SO3 as well as the product H2SO4 have been measured quantitatively using chemical ionization mass spectrometry. An upper limit for the reaction rate coefficient

  16. Effects of temperature and partial pressure of CO 2/O 2 on corrosion behaviour of stainless-steel in molten Li/Na carbonate salt

    NASA Astrophysics Data System (ADS)

    Lim, Tae-Hoon; Hwang, Eung Rim; Ha, Heung Yong; Nam, Suk Woo; Oh, In-Hwan; Hong, Seong-Ahn

    The corrosion tests with AISI-type 316L and 310S stainless steels are carried out to understand the abnormal corrosion behaviour observed in a molten 52 m/o Li 2CO 3-48 m/o Na 2CO 3 salt in the temperature range of 520C to 580C, particularly in the presence of CO 2 and O 2. Two experimental methods, namely, an out-of-cell test and an electrochemical method, were employed to analyze the corrosion behaviour with varying gas composition as well as temperature. The samples tested in the temperature range of 520C to 580C suffer more corrosion attack than those tested in the temperature range of 600C to 650C. Optical microscope analysis of samples from out-of-cell tests for 100 h show that the surfaces of the samples, regardless of the type of stainless-steel, were corroded severely by pitting when the temperature is below 580C. Samples tested above 600C, however, do not suffer significant corrosion attack. This is also confirmed by potentiodynamic results. The polarization curves of 316L stainless-steel samples measured above 600C exhibit the typical active-passive behaviour, but the passive region disappears when the temperature is below 580C. This is attributed to the formation of a porous LiFe 5O 8 passive film. By contrast, the formation of a LiFeO 2 passive film, dense enough to provide protection, is observed with increasing temperature over 600C. It is also found that the partial pressure of CO 2 affects markedly the corrosion rate, but the partial pressure of O 2 does not.

  17. In-source fragmentation of partially oxidized mono- and polycyclic aromatic hydrocarbons in atmospheric pressure chemical ionization mass spectrometry coupled to liquid chromatography

    PubMed

    Letzel; Poschl; Rosenberg; Grasserbauer; Niessner

    1999-01-01

    Partially oxidized derivatives of polycyclic aromatic hydrocarbons (PAHs) are known to be important environmental pollutants. For the identification of these substances in complex mixtures, e.g. atmospheric aerosol samples, liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization (LC/APCI-MS) has been found to be a suitable analytical technique. In this study 31 derivatives of mono- and polycyclic aromatic hydrocarbons with up to five condensed aromatic rings carrying different functional groups (carboxyl, dicarboxylic anhydride, lactone, hydroxyl, and carbonyl) were characterized by LC/APCI-MS. Each substance was measured in positive and negative ion detection mode at four different fragmentor voltages (90 to 190 V). For the first time, the results show that characteristic and well-interpretable fragmentation patterns can be obtained for these classes of compounds by in-source collision-induced dissociation in a single quadrupole LC/APCI-MS system. For each class of compounds typical spectral features and optimum measurement conditions are reported, and fragmentation pathways are proposed. The study demonstrates the applicability of LC/APCI-MS for the determination of most of the investigated compounds at trace levels, and it provides a database for the identification of unknown partially oxidized aromatic hydrocarbons. Copyright 1999 John Wiley & Sons, Ltd. PMID:10589094

  18. The solubility of H2O and CO2 under predicted magma genesis conditions and some petrological and geophysical implications

    Microsoft Academic Search

    Bjrn O. Mysen

    1977-01-01

    Available data on the solubility of H2O and CO2 in silicate melts at high pressures and temperatures reveal that (1) the solubility of H2O is several times greater than that of CO2 and (2) the solubility of H2O depends strongly on pressure and, compared to that of CO2, depends only to a small extent on temperature. It has been suggested

  19. Aerobic oxidation of starch catalyzed by isopolyoxovanadate Na4Co(H2O)6V10O28.

    PubMed

    Chen, Xiaoli; Yan, Siqi; Wang, Hang; Hu, Zhiyun; Wang, Xiaohong; Huo, Mingxin

    2015-03-01

    The partial oxidation of starch was achieved in the presence of oxygen with Na4Co(H2O)6V10O2818H2O (abbreviated as CoV10) as catalyst. The oxidation degree of starch was determined by FT-IR, XRD and SEM measurements, which indicated that the aerobic oxidation of starch was promoted by oxidative catalyst CoV10. The application of CoV10 could give a high oxidation degree (DO) of 1.35 COOH/100 GU and 2.07 CO/100 GU with 86 wt.% yield of solid starch under mild reaction conditions (pH=6; reaction time, 8 h; temperature, 50 C; catalyst amount, 8 mg, when 1.5 g starch was used as substrate; atmospheric pressure). Among some vanadium compounds, CoV10 exhibited 4-fold activity higher than orthovanadate due to its coordination effect of cobalt and V10O28. Meanwhile, CoV10 could be recycled for six times with only a slight decrease in activity. Thus, CoV10/O2 is one of the most efficient systems for partial oxidation of starch reported so far. PMID:25498687

  20. An ab initio study of the (H2O)20H+ and (H2O)21H+ water clusters

    NASA Astrophysics Data System (ADS)

    Ku?, Tomasz; Lotrich, Victor F.; Perera, Ajith; Bartlett, Rodney J.

    2009-09-01

    The study of the minimum Born-Oppenheimer structures of the protonated water clusters, (H2O)nH+, is performed for n =20 and 21. The structures belonging to four basic morphologies are optimized at the Hartree-Fock, second-order many-body perturbation theory and coupled cluster level, with the 6-31G, 6-31G?, and 6-311G?? basis sets, using the parallel ACES III program. The lowest energy structure for each n is found to be the cagelike form filled with H2O, with the proton located on the surface. The cage is the distorted dodecahedron for the 21-mer case, and partially rearranged dodecahedral structure for the 20-mer. The results confirm that the lowest energy structure of the magic number n =21 clusters corresponds to a more stable form than that of the 20-mer clusters.

  1. Laboratory Measurements and Tentative Astronomical Identification of H2NCO+

    NASA Astrophysics Data System (ADS)

    Gupta, H.; Gottlieb, C. A.; Lattanzi, V.; Pearson, J. C.; McCarthy, M. C.

    2013-11-01

    The rotational spectrum of H2NCO+, the ground-state isomer of protonated HNCO, has been measured in a molecular beam in the centimeter band with a Fourier transform microwave spectrometer and in a low-pressure laboratory discharge in absorption in the millimeter band. Spectroscopic constants, including the nitrogen-14 hyperfine coupling constant, derived from 30 a-type transitions between 20 and 367 GHz with J <= 18 and Ka <= 3 allow the principal rotational transitions to be calculated to 1 km s-1 or better in equivalent radial velocity well into the far IR. Two low-lying rotational transitions of H2NCO+ in the centimeter band (00, 0-10, 1 and 11, 0-21, 1) were tentatively identified in absorption in the PRIMOS spectral line survey of Sgr B2(N) with the Green Bank Telescope. The lines of H2NCO+ arise in a region of the Sgr B2(N) halo whose density is low (n < 1 104 cm-3). The derived column density of (6-14) 1011 cm-2 implies that the fractional abundance is ~10-12. Owing to the ubiquity of HNCO in galactic molecular clouds, H2NCO+ is a good candidate for detection in sources spanning a wide range of physical conditions.

  2. Temperatures and H 2 O contents of low-MgO high-alumina basalts

    Microsoft Academic Search

    T. W. Sisson; T. L. Grove

    1993-01-01

    Experimental evidence is used to estimate H2O contents in low-MgO high-alumina basalts (HABs) (2O-saturated melting experiments on HABs at moderate pressure (12 kb). Low-MgO HABs and BAs therefore could have existed as H2O-rich multiply-saturated liquids within the crust. Results are presented for melting experiments on two HABs and an andesite at 1 kb pressure, H2O-saturated, with fO2 at the NNO

  3. Self-consistent particle modeling of radio frequency discharge in Ar/O{sub 2} mixtures: Effects of crossed electric and magnetic fields and partial pressure

    SciTech Connect

    Benyoucef, Djilali [University of Toulouse, UMR CNRS 5213, Laplace, Toulouse (France); Laboratoire Genie Electrique et Energie Renouvelables, Chlef University (Algeria); Yousfi, Mohammed [University of Toulouse, UMR CNRS 5213, Laplace, Toulouse (France); Belmadani, Bachir [Laboratoire Genie Electrique et Energie Renouvelables, Chlef University (Algeria)

    2011-04-15

    A particle-in-cell/Monte Carlo model is developed to study and analyze the electrical characteristics of the nonequilibrium plasma created by radio frequency (RF) discharge in Ar/O{sub 2} mixtures in the presence of crossed electric and magnetic fields. The method of collision treatment is based on an optimized estimation of the free time flight. The needed basic data--more specifically, the ion-neutral cross sections--are determined first. The simulation conditions are 50 mTorr for the total gas pressure and 200 V for the peak of the RF voltage at a frequency of 13.56 MHz. The magnetic field is varied from 0 to 50 G. The effect of the partial pressure ratio of O{sub 2} in the mixture and the effect of the magnitude of the magnetic field are discussed. In particular, the results show an increase of the plasma density that is ten times higher in the presence of a magnetic field.

  4. Hydrogen dissociation in a H2-N2 pulsed dc glow discharge

    PubMed

    Williamson; Ganguly

    2000-05-01

    The absolute concentration of hydrogen atoms is measured in the positve column of a pulsed dc discharge by two-photon absorption laser-induced fluorescence in H2 and H2-N2 gas mixtures at constant pressure and current. The discharge pulse duration is varied from 10 microseconds to 1 msec. For shorter pulse durations of 10 and 100 microseconds, the H-atom signal decreased monotonically with H2 concentration; for longer pulse durations of > or = 500 microseconds, the fractional dissociation of the H2 is enhanced with increasing N2 concentration. The change in H-atom production from direct electron impact dissociation of H2 at short times compared to that from multiquantum vibrational energy transfer induced dissociation of H2 at long times is determined from temporally resolved H-atom concentration measurements. PMID:11031633

  5. TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OL)

    Atmospheric Science Data Center

    2015-02-06

    TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OL) News: TES News ... Level: L2 Platform: TES/Aura L2 Water Vapor Spatial Coverage: 27 x 23 km Limb ... Access: OPeNDAP Parameters: H2O Water Volume Mixing Radio Precision Vertical Resolution Order ...

  6. TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OLS)

    Atmospheric Science Data Center

    2015-01-30

    TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OLS) News: TES News ... Level: L2 Platform: TES/Aura L2 Water Vapor Spatial Coverage: 27 x 23 km Limb ... Access: OPeNDAP Parameters: H2O Water Volume Mixing Radio Precision Vertical Resolution Order ...

  7. H2 MAGIE: H2 as a Major Agent to Galaxy Interaction and Evolution

    Microsoft Academic Search

    Pierre Guillard

    2010-01-01

    Spitzer space telescope spectroscopy reveal a new class of H2-luminous galaxies with enhanced H2 line emission, but where star formation is strongly suppressed. This is in sharp contrast with what is observed in standard star forming galaxies. These sources are all in active phases of galaxy evolution (galaxy interactions, AGN feedback, gas accretion in galaxy clusters, etc.). Why is H2

  8. Investigation of Surface Structure and Dynamics of H_2, p-H_2, HD and D2 Molecules Absorbed on in situ Cleaved MgO(001) by Helium Atom Scattering

    NASA Astrophysics Data System (ADS)

    Skofronick, J. G.; Toennies, J. P.; Traeger, F.; Weiss, H.

    2001-03-01

    Helium atom scattering has been used to probe the surface structure and dynamical character of H_2, p-H_2, HD and D2 molecules grown by isothermal adsorption at partial pressures in the 10-7 - 10-5 mbar range onto an in situ cleaved MgO(100) substrate held at temperatures between 7-12 K. The background pressure was in the mid 10-11 mbar range. A first and second adsorbed layer of hydrogen were observed. In the first, the sequence c(2x2), c(4x2) and c(6x2), as mentioned in the literature, was measured while in the second layer, the structure was not so clear. The surface dynamics for the c(4x2) showed a single mode at 9-10 meV in the [100] direction, but in the [110] direction two Einstein modes at about 10.5 and 8.5 meV were observed and a third mode (with dispersion) which ranged from 2 to 6 meV was also measured. The c(6x2) surface dynamics was similar to c(4x2). The second layer had a single Einstein surface mode very near 5 meV. The dispersive mode is believed associated with parallel oscillations along the long edge of the cell and the dispersionless modes from parallel and perpendicular oscillations along the short length of the elementary cell.

  9. SBA15 as a support for palladium in the direct synthesis of H 2O 2 from H 2 and O 2

    Microsoft Academic Search

    S. Abate; P. Lanzafame; S. Perathoner; G. Centi

    2011-01-01

    The behavior of a catalyst prepared by deposition of Pd nanoparticles over a mesoporous SBA-15 support is compared with that of Pd supported over commercial silica in the direct synthesis of H2O2 from H2 and O2. The activity was studied in a batch and semi-batch autoclave operating at r.t. and at pressures of 6.5bar using methanol as the solvent in

  10. Thermal modeling of NiH2 batteries

    NASA Technical Reports Server (NTRS)

    Ponthus, Agnes-Marie; Alexandre, Alain

    1994-01-01

    The following are discussed: NiH2 battery mission and environment; NiH2 cell heat dissipation; Nodal software; model development general philosophy; NiH2 battery model development; and NiH2 experimental developments.

  11. Infrared spectroscopy of Cu+(H2O)(n) and Ag+(H2O)(n): coordination and solvation of noble-metal ions.

    PubMed

    Iino, Takuro; Ohashi, Kazuhiko; Inoue, Kazuya; Judai, Ken; Nishi, Nobuyuki; Sekiya, Hiroshi

    2007-05-21

    M(+)(H(2)O)(n) and M(+)(H(2)O)(n)Ar ions (M=Cu and Ag) are studied for exploring coordination and solvation structures of noble-metal ions. These species are produced in a laser-vaporization cluster source and probed with infrared (IR) photodissociation spectroscopy in the OH-stretch region using a triple quadrupole mass spectrometer. Density functional theory calculations are also carried out for analyzing the experimental IR spectra. Partially resolved rotational structure observed in the spectrum of Ag(+)(H(2)O)(1) x Ar indicates that the complex is quasilinear in an Ar-Ag(+)-O configuration with the H atoms symmetrically displaced off axis. The spectra of the Ar-tagged M(+)(H(2)O)(2) are consistent with twofold coordination with a linear O-M(+)-O arrangement for these ions, which is stabilized by the s-d hybridization in M(+). Hydrogen bonding between H(2)O molecules is absent in Ag(+)(H(2)O)(3) x Ar but detected in Cu(+)(H(2)O)(3) x Ar through characteristic changes in the position and intensity of the OH-stretch transitions. The third H(2)O attaches directly to Ag(+) in a tricoordinated form, while it occupies a hydrogen-bonding site in the second shell of the dicoordinated Cu(+). The preference of the tricoordination is attributable to the inefficient 5s-4d hybridization in Ag(+), in contrast to the extensive 4s-3d hybridization in Cu(+) which retains the dicoordination. This is most likely because the s-d energy gap of Ag(+) is much larger than that of Cu(+). The fourth H(2)O occupies the second shells of the tricoordinated Ag(+) and the dicoordinated Cu(+), as extensive hydrogen bonding is observed in M(+)(H(2)O)(4) x Ar. Interestingly, the Ag(+)(H(2)O)(4) x Ar ions adopt not only the tricoordinated form but also the dicoordinated forms, which are absent in Ag(+)(H(2)O)(3) x Ar but revived at n=4. Size dependent variations in the spectra of Cu(+)(H(2)O)(n) for n=5-7 provide evidence for the completion of the second shell at n=6, where the dicoordinated Cu(+)(H(2)O)(2) subunit is surrounded by four H(2)O molecules. The gas-phase coordination number of Cu(+) is 2 and the resulting linearly coordinated structure acts as the core of further solvation processes. PMID:17523799

  12. Impact of fluctuations in gaseous H2S concentrations on sulfide uptake by sewer concrete: The effect of high H2S loads.

    PubMed

    Sun, Xiaoyan; Jiang, Guangming; Bond, Philip L; Keller, Jurg

    2015-09-15

    The acid production from the oxidation of hydrogen sulfide (H2S) in sewer air results in serious corrosion of exposed concrete surfaces in sewers. Large fluctuations of gaseous H2S concentrations occur in sewers due to the diurnal profiles of sewage flow and retention times and the necessity of intermittent pumping of sewage from pressure pipes into gravity pipes. How the high concentrations of H2S due to these events may affect H2S uptake and subsequent corrosion by concrete sewers is largely unknown. This study determined the effect of short- and long-term increases in H2S levels on the sulfide uptake rate (SUR) of concrete surfaces with an active corrosion layer. The results showed that during the high load situation the SUR increased significantly but then decreased (compared to the baseline SUR) by about 7-14% and 41-50% immediately after short- and long-term H2S high-load periods, respectively. For both exposure conditions, the SUR gradually (over several hours) recovered to approximately 90% of the baseline SUR. Further tests suggest multiple factors may contribute to the observed decrease of SUR directly after the high H2S load. This includes the temporary storage of elemental sulfur in the corrosion layer and inhibition of sulfide oxidizing bacteria (SOB) due to high H2S level and temporary acid surge. Additionally, the delay of the corrosion layer to fully recover the SUR after the high H2S load suggests that there is a longer-term inhibitive effect of the high H2S levels on the activity of the SOB in the corrosion layer. Due to the observed activity reductions, concrete exposed to occasional short-term high H2S load periods had an overall lower H2S uptake compared to concrete exposed to constant H2S levels at the same average concentration. To accurately predict H2S uptake by sewer concrete and hence the likely maximum corrosion rates, a correction factor should be adopted for the H2S fluctuations when average H2S levels are used in the prediction. PMID:26043374

  13. Interstellar clouds containing optically thin H2

    NASA Technical Reports Server (NTRS)

    Jura, M.

    1975-01-01

    The theory of Black and Delgarno that the relative populations of the excited rotational levels of H2 can be understood in terms of cascading following absorption in the Lyman and Werner bands is employed to infer the gas densities and radiation fields within diffuse interstellar clouds containing H2 that is optically thin in those bands. The procedure is described for computing the populations of the different rotation levels, the relative distribution among the different rotation levels of newly formed H2 is determined on the basis of five simplified models, and the rate of H2 formation is estimated. The results are applied to delta Ori, two components of iota Ori, the second components of rho Leo and zeta Ori, tau Sco, gamma Vel, and zeta Pup. The inferred parameters are summarized for each cloud.

  14. Partial Eval Partial Eval

    E-print Network

    Sumii, Eijiro

    Efficient Onl ine Partial E al ati n Eijiro Sumii o i o i i r i o o o umii o i u o o j #12; Partial/dynamic portions of p(s??,d) ¯ spec a e program p s?? (d) s p(s??,d) = = = = p s?? (d) or a am c pu d ope u e r . . . . -- -- -- . . #12; A Naive Onl ine Partial val at r E (expression) ::= x | l l l lx.E | E@E #12; A Naive Onl ine

  15. Dissociative photodetachment studies of O ,,H2O...2 , OH

    E-print Network

    Continetti, Robert E.

    Dissociative photodetachment studies of O ,,H2O...2 , OH ,,H2O...2 , and the deuterated photodetachment of the doubly hydrated clusters of oxide and hydroxide, M H2O 2M 2H2O e M O, OH are presented and compared to data for O H2O) and OH H2O). Unlike the singly hydrated species, no evidence

  16. Global Flux Balance in the Terrestrial H2O Cycle: Reconsidering the Post-Arc Subducted H2O Flux

    NASA Astrophysics Data System (ADS)

    Parai, R.; Mukhopadhyay, S.

    2010-12-01

    Quantitative estimates of H2O fluxes between the mantle and the exosphere (i.e., the atmosphere, oceans and crust) are critical to our understanding of the chemistry and dynamics of the solid Earth: the abundance and distribution of water in the mantle has dramatic impacts upon mantle melting, degassing history, structure and style of convection. Water is outgassed from the mantle is association with volcanism at mid-ocean ridges, ocean islands and convergent margins. H2O is removed from the exosphere at subduction zones, and some fraction of the subducted flux may be recycled past the arc into the Earths deep interior. Estimates of the post-arc subducted H2O flux are primarily based on the stability of hydrous phases at subduction zone pressures and temperatures (e.g. Schmidt and Poli, 1998; Rpke et al., 2004; Hacker, 2008). However, the post-arc H2O flux remains poorly quantified, in part due to large uncertainties in the water content of the subducting slab. Here we evaluate estimated post-arc subducted fluxes in the context of mantle-exosphere water cycling, using a Monte Carlo simulation of the global H2O cycle. Literature estimates of primary magmatic H2O abundances and magmatic production rates at different tectonic settings are used with estimates of the total subducted H2O flux to establish the parameter space under consideration. Random sampling of the allowed parameter space affords insight into which input and output fluxes satisfy basic constraints on global flux balance, such as a limit on sea-level change over time. The net flux of H2O between mantle and exosphere is determined by the total mantle output flux (via ridges and ocean islands, with a small contribution from mantle-derived arc output) and the input flux subducted beyond the arc. Arc and back-arc output is derived mainly from the slab, and therefore cancels out a fraction of the trench intake in an H2O subcycle. Limits on sea-level change since the end of the Archaean place constraints on the magnitude of the post-arc subducted H2O flux that can be accommodated by the global water cycle. Estimates of the post-arc subducted flux are up to an order of magnitude larger than the estimated mantle output flux. If the marked imbalance in the estimated global water cycle is accurate, then it must be a recent phenomenon: if propagated back in time, modeled net inward fluxes would consume half a present-day ocean volume of water in as little as 500 Myr (corresponding to ~1200 meters of sea level change given present-day hypsometry). Such changes are inconsistent with the limited sea level changed inferred from the geologic record since the end of the Archaean. The literature post-arc flux estimates reflect water carried to depth via a layer of serpentinized lithospheric mantle within the slab; however, the extent to which oceanic lithosphere may be serpentinized remains poorly constrained. A smaller post-arc subducted H2O flux of 2.3 x108 Tg/Ma would perfectly balance our mean modeled total mantle output. Such a post-arc flux corresponds to ~2% serpentinization of a 10 km thick layer of lithospheric mantle (i.e., a mean water content of ~0.25 wt% H2O).

  17. Effect of nuclear spin symmetry in cold and ultracold reactions: D + para/ortho-H2

    NASA Astrophysics Data System (ADS)

    Simbotin, Ionel; Ct, Robin

    2015-06-01

    We report results for reaction and vibrational quenching of the collision D with para-H2(v,j=0) and ortho-H2(v,j=1) at cold and ultracold temperatures. We investigate the effect of nuclear spin symmetry for barrier dominated processes (0?slant v?slant 4) and for one barrierless case (v = 5). We find resonant structures for energies in the range corresponding to 0.0110 K, which depend on the nuclear spin of H2, arising from contributions of specific partial waves. We discuss the implications on the results in this benchmark system for ultracold chemistry.

  18. Misconception of reductive elimination of H2, in the context of the mechanism of nitrogenase.

    PubMed

    Dance, Ian

    2015-05-21

    The elimination of H2 from an M(H)2 component of a coordination complex is often described as reductive elimination, in which the H atoms are regarded as hydride ions, and the product complex after elimination is regarded as reduced by two electrons. The concept is M(n+2)(H(-))2 ? M(n) + H2 (with oxidative addition as its reverse). This interpretation contravenes Pauling's electroneutrality principle, and a number of researchers of metal-hydrogen systems have warned against literal acceptance of the formalism. A mechanism suggested by others for the chemical catalysis occurring at the Fe7MoS9C active site cluster of nitrogenase has invoked reductive elimination of H2 from Fe as a central premise. I report here calculations of atom partial charges for the relevant nitrogenase steps, as well as atom partial charges for some well-studied Fe complexes that model the nitrogenase chemistry. Fe-coordinated H atoms are <20% hydridic, and during the H2 elimination process the charge on Fe is essentially invariant. The argument for literal reductive elimination of H2 as part of the mechanism of nitrogenase is not sustained. PMID:25891439

  19. Improved quasi-unary nucleation model for binary H2SO4H2O homogeneous nucleation

    E-print Network

    Yu, Fangqun

    Improved quasi-unary nucleation model for binary H2SO4H2O homogeneous nucleation Fangqun Yua implications. Binary homogeneous nucleation BHN of H2SO4 and H2O is the foundation of recently proposed dominate atmospheric nucleation under certain conditions. We have shown in previous work that H2SO4H2O BHN

  20. Atmospheric Environment 40 (2006) 75797588 Role of the binary H2SO4H2O homogeneous nucleation in the

    E-print Network

    Yu, Fangqun

    2006-01-01

    Atmospheric Environment 40 (2006) 75797588 Role of the binary H2SO4H2O homogeneous nucleation of the nucleation mechanisms of these particles remains to be achieved. We investigate the role of H2SO4H2O binary developed kinetic H2SO4H2O BHN model suitable for studying the nucleation process in rapidly diluting

  1. Reconstruction of pH and partial pressure of carbon dioxide during the Mesozoic era period using boron and oxygen isotopic compositions of fresh ammonoids & nautiloids

    NASA Astrophysics Data System (ADS)

    Kawahata, Hodaka; Fukushima, Ayaka; Moriya, Kazuyori; Ishikawa, Tsuyoshi; Suzuki, Atsushi; Tanabe, Kazushige

    2013-04-01

    The increase of partial pressure of carbon dioxide (pCO2) in the atmosphere induces global warming and ocean acidification at the modern condition. The reconstruction of pCO2 during the geological time is required together with proxy calibration by laboratory experiments to predict the future environments. Boron isotopic ratio is an excellent proxy for pH and the relevant partial pressure of carbon dioxide in the seawater (PCO2). This study is the first to quantify pH dependence of delta 11B of the ammonoids and nautiloids mainly in the Cretaceous and in Jurassic (70-162 Ma), which are expected to be much warmer due to higher PCO2. However, no reliable reconstruction data using foraminiferal delta 11B before Cenozoic era has been reported. We used the very fresh aragonite shells of ammonoids and nautiloids by big advantages. Since aragonite changes into secondary calcite by diagenesis, it is easy and effective to identify the degree of alteration at each sample by measuring calcite/aragonite ratio. Also we carefully conducted the assessment of secondary alteration from three perspectives: 1) Determination of calcite/aragonite ratio by X-ray diffraction (XRD), 2) Observation of microstructures of the nacreous layers by scanning electron microscope (SEM), and 3) Measurement of trace element contents and stable isotope ratios. We conducted high precision boron isotope analysis of biogenic carbonates with +/- 0.1 per mil reproducibility by adopting positive thermal ionization mass spectrometry (P-TIMS) methods. Also we analyzed delta 18O to estimate paleo-temperature, at which biogenic aragonite was formed. Combination of delta 11B and delta 18O of biogenic aragonite in 80 Ma and 86 Ma revealed that deeper dwellers showed lower delta 11B values, which corresponded to lower pH. This feature is consistent with those observed in the modern vertical water column. The respective shallow water temperature was 19.7 and 19.1 centigrade. Based on these results, the reconstructed maximum PCO2 levels at late Cretaceous (80 Ma and 86 Ma) were estimated to be 1750 and 1540 ppm, respectively. This coincides with the suggestion by Breecker et al. (2010) that pCO2 for the last 400 millions was usually at below 2000 ppm by reassessing the delta 13C proxy in soils.

  2. Partial molar volumes of NiO and CoO liquids: implications for the pressure dependence of metal-silicate partitioning

    NASA Astrophysics Data System (ADS)

    Courtial, Philippe; Gottsmann, Joachim; Holzheid, Astrid; Dingwell, Donald B.

    1999-08-01

    Volumetric measurements have been conducted on 7 Ni- and Co-containing sodium disilicate liquids within a compositional range varying from 0 to 9 mol% of NiO and from 0 to 23 mol% of CoO and over a large temperature interval (i.e., above their respective glass transition temperature and up to at least 1473 K). Their molar volumes and thermal expansivities have been determined by combining high-temperature measurements using the Pt-based double-bob Archimedean method and low-temperature measurements using the method described by Webb et al. [S.L. Webb, R. Knoche, D.B. Dingwell, Determination of silicate liquid thermal expansivity using dilatometry and calorimetry, Eur. J. Mineral. 4 (1992) 95-104] based on an assumed equivalence of the relaxation of volume and enthalpy at the glass transition. The molar volume of the present liquids decreases with increasing NiO and CoO contents and the Co-containing liquids exhibit a greater molar volume than the Ni-containing liquids at equivalent molar concentrations. The present results were analysed using a regression equation from which the partial molar volume of NiO and CoO liquids was obtained by the least squares method. This procedure yields partial molar volumes valid over the entire temperature range of 11.506 0.687 and 14.884 0.149 cm 3/mol and temperature derivatives of 2.684 1.6 10 -3 and 1.441 0.4 10 -3 cm 3/mol K, respectively for NiO and CoO at 800 K. The behavior of M-Fe metal-silicate exchange partition coefficient (M = Ni, Co), based on present molar volume determinations, has been estimated as a function of pressure over a wide temperature range. The metal-silicate exchange partition coefficients of both Ni and Co decrease with increasing pressure within the entire temperature range considered in this study (i.e., 800-3000 K).

  3. Thermochemical Kinetics of H2O and HNO3 on crystalline Nitric Acid Hydrates (alpha-, beta-NAT, NAD) in the range 175-200 K

    NASA Astrophysics Data System (ADS)

    Rossi, Michel J.; Iannarelli, Riccardo

    2015-04-01

    The growth of NAT (Nitric Acid Trihydrate, HNO3x3H2O) and NAD (Nitric Acid Dihydrate, HNO3x2H2O) on an ice substrate, the evaporative lifetime of NAT and NAD as well as the interconversion of alpha- and beta-NAT competing with evaporation and growth under UT/LS conditions depends on the interfacial kinetics of H2O and HNO3 vapor on the condensed phase. Despite the existence of some literature results we have embarked on a systematic investigation of the kinetics using a multidiagnostic experimental approach enabled by the simultaneous observation of both the gas (residual gas mass spectrometry) as well as the condensed phase (FTIR absorption in transmission). We report on thermochemically consistent mass accommodation coefficients alpha and absolute evaporation rates Rev/molecule s-1cm-3 as a function of temperature which yields the corresponding vapor pressures of both H2O and HNO3 in equilibrium with the crystalline phases, hence the term thermochemical kinetics. These results have been obtained using a stirred flow reactor (SFR) using a macroscopic pure ice film of 1 micron or so thickness as a starting substrate mimicking atmospheric ice particles and are reported in a phase diagram specifically addressing UT (Upper Troposphere)/LS (Lower Stratosphere) conditions as far as temperature and partial pressures are concerned. The experiments have been performed either at steady-state flow conditions or in transient supersaturation using a pulsed solenoid valve in order to generate gas pulses whose decay were subsequently monitored in real time. Special attention has been given to the effect of the stainless-steel vessel walls in that Langmuir adsorption isotherms for H2O and HNO3 have been used to correct for wall-adsorption of both probe gases. Typically, the accommodation coefficients of H2O and HNO3 are similar throughout the temperature range whereas the rates of evaporation Rev of H2O are significantly larger than for HNO3 thus leading to the difference in vapor pressure revealed in the phase diagram. A noteworthy effect seems to be that the accommodation coefficients obtained in pulsed gas admission experiments (transient supersaturation) lead to significantly lower values owing to surface saturation, especially in the case of the thermodynamically stable beta-NAT substrate.

  4. H2CO in the Horsehead nebula

    NASA Astrophysics Data System (ADS)

    Guzman, Viviana

    2011-07-01

    Photodissociation region (PDR) models are used to understand the evolution of the far-UV illuminated matter both in our Galaxy and in external galaxies. The spectacular instrumental improvements, which happens in radioastronomy with the advent of Herschel, ALMA and NOEMA, call for matching progresses in PDR modeling. While it is now confirmed that some interstellar species are mostly formed in the gas phase (CO for instance) and others on grains (CH3OH, Garrod et al. 2007), the chemical routes for other species, like H2CO, are still debated because it is likely that solid and gas phase processes are both needed. The availability of well defined observations is essential here to discriminate between chemical assumptions about the important grain surface processes: adsorption, desorption and reactivity. Due to its closeness (~400 pc) and simple geometry, the Horsehead PDR is particularly well suited to investigate the grain surface chemistry. We present observations of 7 transitions of formaldehyde (H2CO) toward two positions: the edge of the nebula exposed to the UV-field (PDR), and a colder region (cold core) shielded from the UV radiation. A non-LTE Montecarlo radiative transfer code is used to determine the H2CO abundance from the observed intensities and line profiles. We find that the H2CO abundance is very similar in the warm PDR and in the cold dense core. The inferred abundances are compared with PDR models, including both gas-phase and grain surface reactions, in order to study the dominant formation routes of H2CO. Pure gas-phase chemistry models fail to reproduce the observed H2CO abundance by a factor ~10 in the PDR, while surface grain chemistry increases the H2CO abundance up to 3 orders of magnitude in the PDR.

  5. A comparative study of the Au + H2, Au+ + H2, and Au- + H2 systems: Potential energy surfaces and dynamics of reactive collisions

    NASA Astrophysics Data System (ADS)

    Dorta-Urra, Anas; Zanchet, Alexandre; Roncero, Octavio; Aguado, Alfredo

    2015-04-01

    In order to study the Au- + H2 collision, a new global potential energy surface (PES) describing the ground electronic state of AuH 2- system is developed and compared with the PESs of the neutral [Zanchet et al., J. Chem. Phys. 132, 034301 (2010)] and cationic systems [Anas et al., J. Chem. Phys. 135, 091102 (2011)]. We found that Au- - H2 presents a H-Au-H insertion minimum attributed to the stabilization of the LUMO 3b2 orbital, which can be considered as the preamble of the chemisorption well appearing in larger gold clusters. While the LUMO orbital is stabilized, the HOMO 6a1 is destabilized, creating a barrier at the geometry where the energy orbitals' curves are crossing. In the anion, this HOMO is doubly occupied, while in the neutral system is half-filled and completely empty in the cation, explaining the gradual disappearance of the well and the barrier as the number of electrons decreases. The cation presents a well in the entrance channel partially explained by electrostatic interactions. The three systems' reactions are highly endothermic, by 1.66, 2.79, and 3.23 eV for AuH, AuH+, and AuH- products, respectively. The reaction dynamics is studied using quasi-classical trajectory method for the three systems. The one corresponding to the anionic system is new in this work. Collision energies between 1.00 and 8.00 eV, measured for the cation, are in good agreement with the simulated cross section for the AuH+. It was also found that the total fragmentation, in three atoms, competes becoming dominant at sufficiently high energy. Here, we study the competition between the two different reaction pathways for the anionic, cationic, and neutral species, explaining the differences using a simple model based on the topology of the potential energy surfaces.

  6. Simultaneous adsorption of CO2 and H2O under Mars-like conditions and application to the evolution of the Martian climate

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Quinn, Richard

    1994-01-01

    The Martian regolith is the most substantial volatile reservoir on the planet; it holds CO2 as adsorbate, and can exchange that CO2 with the atmosphere-cap system over timescales of 10(exp 5) to 10(exp 6) years. The climatic response to insolation changes caused by obliquity and eccentricity variations depends in part on the total reservoir of adsorbed CO2. Previous estimates of the adsorbate inventory have been made by measuring the adsorptive behavior of one or more Mars-analyog materials, and deriving an empirical equation that described that adsorption as a function of the partial pressure of CO2 and the temperature of the regolith. The current CO2 inventory is that which satisfies adsorptive equilibrium, observed atmospheric pressure, and no permanent CO2 caps. There is laboratory evidence that H2O poisons the CO2 adsorptive capacity of most materials. No consideration of CO2 - H2O co-adsorption was given in previous estimates of the Martian CO2 inventory, although H2O is present in the vapor phase, and so as adsorbate, throughout the regolith.

  7. Interstellar H2 toward HD 147888

    NASA Astrophysics Data System (ADS)

    Gnaci?ski, P.

    2013-01-01

    The ultraviolet and far-ultraviolet spectra of HD 147888 allows the H2 vibrational level ? = 0 to be accessed along with higher vibrational levels of the ground H2 electronic level. The large number of H2 absorption lines in the HST spectra allows column densities to be determined even from a noisy spectra. We have determined column densities of the H2 molecule on vibrational levels ? = 0-5 and rotational levels J = 0-6 using the profile fitting method. No variations in the column densities of H2 on vibrationally excited levels were observed from 2000 through 2009. The ortho to para H2 ratio (O/P)* for the excited vibrational states ? = 1-4 equals to 1.13. For the lowest vibrational state ? = 0 and rotational level J = 1 the ortho to para H2 ratio is only 0.15. The temperature of ortho-para thermodynamical equilibrium is TOP = 42 3 K. The measurements of H2 column densities on excited vibrational levels (from the HST spectra) leads to constraints on the radiation field in photon-dominated region (PDR) models of the interstellar cloud towards HD 147888. The Meudon PDR model locates the cloud 0.62 pc from the star. The modeled hydrogen cloud density (89-336 cm-3) agrees with independent density estimations based on the C2 molecule and the chemical model. The observed (O/P)J = 1 and (O/P)* H2 ratios cannot be explained by a simple model. Based on observations made with the NASA/ESA Hubble Space Telescope and with NASA/Johns Hopkins University Far Ultraviolet Spectroscopic Explorer, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. Support for FUSE data is provided by the NASA Office of Space Science via grant NAG5-7584 and by other grants and contracts.

  8. The Effect of Elevated Partial Pressures of CO2 on the Relationship between Photosynthetic Capacity and N Content in Rice Leaves.

    PubMed Central

    Nakano, H.; Makino, A.; Mae, T.

    1997-01-01

    The effects of growth CO2 levels on the photosynthetic rates; the amounts of ribulose-1,5-bisphosphate carboxylase (Rubisco), chlorophyll (Chl), and cytochrome f; sucrose phosphate synthase activity; and total N content were examined in young, fully expanded leaves of rice (Oryza sativa L.). The plants were grown hydroponically under two CO2 partial pressures of 36 and 100 Pa at three N concentrations. The light-saturated photosynthesis at 36 Pa CO2 was lower in the plants grown in 100 Pa CO2 than those grown in 36 Pa CO2. Similarly, the amounts of Rubisco, Chl, and total N were decreased in the leaves of the plants grown in 100 Pa CO2. However, regression analysis showed no differences between the two CO2 treatments in the relationship between photosynthesis and total N or in the relationship between Rubisco and Chl and total N. Although a relative decrease in Rubisco to cytochrome f or sucrose phosphate synthase was found in the plants grown in 100 Pa CO2, this was the result of a decrease in total N content by CO2 enrichment. The activation state of Rubisco was also unaffected by growth CO2 levels. Thus, decreases in the photosynthetic capacity of the plants grown in 100 Pa CO2 could be simply accounted for by a decrease in the absolute amount of leaf N. PMID:12223799

  9. Phenyl-modified reversed-phase liquid chromatography coupled to atmospheric pressure chemical ionization mass spectrometry: a universal method for the analysis of partially oxidized aromatic hydrocarbons.

    PubMed

    Letzel, T; Pschl, U; Wissiack, R; Rosenberg, E; Grasserbauer, M; Niessner, R

    2001-04-01

    A new liquid chromatographic method for the efficient separation of aromatic compounds having a wide range of sizes, molecular structures, and polarities has been developed. Based on a phenyl-modified silica reversed stationary phase and a methanol-water solvent gradient, it allows the separation of mono- and polycyclic aromatic hydrocarbons (PAHs) having up to five condensed aromatic rings and partially oxidized derivatives within a single chromatographic run of 40-min duration. The applicability of the method is demonstrated using 81 reference substances (PAHs, phenols, quinones, acids, lactones, esters, etc.) and real samples of environmental, medical, and technical relevance (ozonized PAHs, lake water, human urine, diesel exhaust condensates). The retention times of the investigated aromatics exhibit a regular increase with molecular mass and a systematic decrease with increasing number and polarity of functional groups. In case of intramolecular hydrogen bonding, a positive shift of retention time provides additional structural information. The combination of chromatographic retention time with the molecular mass and structural information from mass spectrometric detection allows the tentative identification of unknown aromatic analytes at trace levels, even without specific reference substances. With atmospheric pressure chemical ionization (APCI), low detection limits and highly informative fragmentation patterns can be obtained by in-source collision-induced fragmentation in a single-quadrupole LC-APCI-MS system as applied in this study, and multidimensional MS experiments are expected to further enhance the potential of the presented method. PMID:11321321

  10. Conductivity of porous Sm2O3-doped CeO2 as a function of temperature and oxygen partial pressure

    NASA Astrophysics Data System (ADS)

    Wright, James; Virkar, Anil V.

    2011-08-01

    Porous samples of Sm2O3-doped CeO2 (samaria-doped ceria, SDC) of composition Sm0.15Ce0.85O2-? were made by conventional ceramic processing and sintering in air at 1400 C. Crystal structure and microstructure of the samples were characterized, respectively, by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrical conductivity was measured using a four probe DC method over a temperature range from 200 C to 800 C, and over a wide range of oxygen partial pressures corresponding to testing in oxygen and in nearly dry hydrogen. Conductivity rapidly stabilized at any given temperature consistent with the attainment of thermodynamic equilibrium corresponding to the imposed conditions. At and below 300 C, the conduction was predominantly due to oxygen ion transport. At and above 400 C, however, significant electronic conduction occurred in reducing atmospheres. The ionic transference number of SDC at 400 C in hydrogen is only ?0.4. This result shows that the electrolytic domain of SDC at and above 400 C is rather narrow. These results also suggest that SDC (and possibly other rare earth oxide-doped CeO2) is not a suitable electrolyte without a thin electron blocking layer such as yttria-stabilized zirconia (YSZ).

  11. Direct Synthesis of H 2 O 2 by a H 2 \\/O 2 Fuel Cell

    Microsoft Academic Search

    Ichiro Yamanaka

    2008-01-01

    Direct synthesis of H2O2 solutions by a fuel cell method was reviewed. The fuel cell reactor of [O2, gas-diffusion cathode \\u000a $$ | $$ electrolyte solutions $$ | $$ Nafion membrane $$ | $$ electrolyte solutions $$ | $$ gas-diffusion anode, H2] is very effective for formation of H2O2. The three-phase boundary (O2(g)electrode(s)electrolyte(l)) in the gas-diffusion cathode is essential for efficient

  12. Water Speciation and properties of hydrous model basalt melt at high pressure

    NASA Astrophysics Data System (ADS)

    Bajgain, S. K.; Karki, B. B.

    2013-12-01

    Silicate melts in the Earth's interior are known/expected to be hydrous. Water can make major impact on physical properties including the structure, density, and mobility of melts. The behavior of relevant hydrous melts over most of the mantle pressure regime is poorly constrained. Water solubility increases rapidly with increasing pressure at low pressure [1] and a complete miscibility of liquid MgSiO3 and H2O has been suggested based on high-pressure simulations [2]. We have recently performed first principle molecular dynamics simulations of hydrous model basalt melt at high pressure. Our results show that with increasing pressure, the partial molar volume of water in the melt asymptotically approaches to that of pure water, and both the volumes become identical after certain point. Water is predicted to dissolve in the form of hydroxyls and water molecules at low pressure and as more extended structures at high pressure. The simulated basalt-H2O system commences to behave ideally at pressures above 10 GPa. In contrast, the simulated SiO2-H2O and MgSiO3-H2O systems approach to an ideal limit at much higher pressures of 50 GPa or above. These results imply an unlimited solubility of water in in silicate melts and the water solubility rather appears to be insensitive of composition at high pressure. Existence of water-rich silicate melts over most of the mantle in early history could have made substantial contribution to the origin of hydrosphere [3]. [1] Shen, A. H., and H. Keppler (1997), Direct observation of complete miscibility in the Albite-H2O system, Nature, 385, 710-712. [2] Mookherjee, M., L. Stixrude, and B. Karki (2008), Hydrous silicate melt at high pressure, Nature, 452, 983-986. [3] Matsui, T., and Y. Abe (1986), Evolution of an impact-induced atmosphere and magma ocean on the accreting Earth, Nature, 319, 303-305.

  13. Search for H2COH+ and H2(13)CO in dense interstellar molecular clouds

    NASA Technical Reports Server (NTRS)

    Minh, Y. C.; Irvine, W. M.; McGonagle, D.

    1993-01-01

    We have searched for the 2 mm transitions of H2COH+ (2(02) - 1(01)) and H2(13)CO (2(02) - 1(01), 2(12) - 1(11), and 2(11) - 1(10)) toward the dense interstellar molecular clouds Orion A, TMC-1 and L134N using the FCRAO 14m telescope. None of the transitions have been detected except the H2(13)CO transitions toward Orion-KL. We set upper limits for the abundances of the protonated formaldehyde ion (H2COH+), which are close to the abundances expected from ion-molecule chemistry.

  14. Desulfurization of Fuel by Leaching Using H2O2 and H2SO4

    Microsoft Academic Search

    Hseyin Karaca; Zehra Y?ld?z

    2005-01-01

    In this research, different concentrations of H2O2 and H2SO4 solutions were used in order to remove the sulfur from high sulfur contented No. 6 fuel oil. In desulphurization experiments, reaction temperature, reaction time, and the concentration of H2O2 and H2SO4 were varied in a range of 2050C, 30150min, 535%, and 0.052.00 N, respectively. The ratio of reagent\\/fuel oil was taken

  15. Removing textile mill effluent recalcitrant COD and toxicity using the H2O2/UV system.

    PubMed

    Mounteer, A H; Leite, T A; Lopes, A C; Medeiros, R C

    2009-01-01

    The potential of the H2O2/UV process for improving quality of an industrial textile effluent before biological treatment was evaluated in the laboratory using a multivariate experimental design to determine the effects of pH, H2O2 dose and reaction time on colour, COD and toxicity removal efficiencies. Increasing reaction time (from 10 to 120 min) and H2O2 dose (from 0 to 5 mmol L(-1)) significantly improved removal efficiencies, while increasing pH (from 4 to 10) had a negative effect on colour and toxicity removals. Laboratory H2O2/UV treatment of the mill effluent under optimum conditions (pH 7, 5 mmol L(-1) H2O2, 120 min) resulted in decreases in colour (70%), COD (21%) and toxicity (67%), without lowering BOD. H2O2 was consumed within the first 30-60 min, while the effluent average oxidation state stabilized after 60 min. Decreasing reaction time to 60 min resulted in similar colour (63%) and COD (20%) removals but lower toxicity removal (44%). Spectrophotometric monitoring of the optimized reaction indicated partial destruction of residual aromatic azo dyes. H2O2 and residual peroxide and average oxidation state of the effluent Effluent biodegradability (BOD/COD) increased by 28% after the H2O2/UV treatment. Improvements observed in effluent quality are expected to enhance combined AOP-biological treatment efficiency of the mill effluent. PMID:19809153

  16. H_2CO in the Horsehead nebula

    NASA Astrophysics Data System (ADS)

    Guzman, V.; Pety, J.; Goicoechea, J. R.; Gerin, M.; Roueff, E.

    2011-05-01

    Photodissociation region (PDR) models are used to understand the evolution of the far-UV illuminated matter both in our Galaxy and in external galaxies. The spectacular instrumental improvements, which happens in radioastronomy with the advent of Herschel, ALMA and NOEMA, call for matching progresses in PDR modeling. While it is now confirmed that some interstellar species are mostly formed in the gas phase (CO for instance) and others on grains (CH_3OH), the chemical routes for other species, like H_2CO, are still debated because it is likely that solid and gas phase processes are both needed. The availability of well defined observations is essential here to discriminate between chemical assumptions about the important grain surface processes: adsorption, desorption and reactivity. Due to its closeness (~400 pc) and simple geometry, the Horsehead PDR is particularly well suited to investigate the grain surface chemistry. We present observations of 7 transitions of formaldehyde (H_2CO) toward two positions: the edge of the nebula exposed to the UV-field (PDR), and a colder region (cold core) shielded from the UV radiation. A non-LTE Montecarlo radiative transfer code is used to determine the H2CO abundance from the observed intensities and line profiles. We find that the H_2CO abundance is very similar in the warm PDR and in the cold dense core. The inferred abundances are compared with PDR models, including both gas-phase and grain surface reactions, in order to study the dominant formation routes of H_2CO. Pure gas-phase chemistry models fail to reproduce the observed H2CO abundance by a factor ~10 in the PDR, while surface grain chemistry successfully reproduces the observed abundance.

  17. Adsorption isotherms of H$_{2}$ and mixtures of H$_{2}$, CH$_{4}$, CO and CO$_{2}$ on copper plated stainless steel at 4.2 K

    E-print Network

    Walln, E

    1996-01-01

    Adsorption isotherms in the pressure range 10$^{-11}$ to 10$^{-6} Torr have been measured for H$_2$ and mixtures of H$_2$ and CH$_4$, CO and CO$_2$ on copper plated stainless steel at 4.2 K. The measurements have been focused on the behaviour of the isotherms at low surface coverage, up to a few monolayers of adsorbed gas on the cold surface. The isotherms were measured in a static situation with a small amount of gas injected for each point on the isotherm. Co-adsorption measurements of H$_2$ with CH$_4$, CO and CO$_2$ as well as adsorption of H$_2$ on condensates of CH$_4$, CO and CO$_2$ have been made. A cryotrapping effect of H$_2$ is seen when co-adsorbing the gas mixtures, especially strong for the mixture of H$_2$ and CO$_2$. The measurements show that CO$_2$ condensed at 4.2 K may have a porous structure that H$_2$ can penetrate, while CO and CH$_4$ have rather dense structures when adsorbed at 4.2K. The measurements have been done within the framework of the Large Hadron Collider (LHC) project at CER...

  18. The 2.5 to 5.0 micrometer spectral of Io: Evidence for H2S and H2O frozen in SO2

    NASA Technical Reports Server (NTRS)

    Salama, F.; Allamandola, L. J.; Witteborn, F. C.; Cruikshank, D. P.; Sandford, S. A.; Bregman, J. D.

    1990-01-01

    Analysis of the 2.5 to 5.0 micrometer spectra of Io using detailed laboratory studies of plausible surface ices is described. The results show that Io's surface most likely contains H2S and H2O mixed with SO2. The 3.85 and 3.91 micrometer bands in the Io spectra can be assigned to the v sub 1 fundamental mode in H2S clusters and isolated molecules in SO2 ice. The 2.97 and 3.15 micrometer bands coincide with the v sub 3 and v sub 1 vibrations of clusters of H2O molecules complexed with SO2. The observations are well matched by the spectra of SO2 ices containing 3 percent H2S and 0.1 percent H2O which has been formed by condensation onto a 100 K surface. The shifts and splitting of the absorption bands seen in the Io spectrum and the fact that solid H2S is observed in the surface material of Io at temperature and pressure conditions above its sublimation point can only be explained by the mixed molecular ices model.

  19. Ab initio study of the structures and hydrogen storage capacity of (H2)nCH4 compound

    NASA Astrophysics Data System (ADS)

    Wang, Minghui; Cheng, Xinlu; Ren, Dahua; Zhang, Hong; Tang, Yongjian

    2015-05-01

    The hydrogen-rich compound (H2)nCH4 (for n = 1, 2, 3, 4) or for short (H2)nM is one of the most promising hydrogen storage materials. The (H2)4M molecule is the best hydrogen-rich compound among the (H2)nM structures and it can reach the hydrogen storage capacity of 50.2 wt.%. However, the (H2)nM always requires a certain pressure to remain stable. In this work, we first investigated the binding energy of the different structures in (H2)nM and energy barrier of H2 rotation under different pressures at ambient temperature, applying ab initio methods based on van der Waals density functional (vdW-DF). It was found that at 0 GPa, the (H2)nM is not stable, while at 5.8 GPa, the stability of (H2)nM strongly depends on its structure. We further investigate the Raman spectra of (H2)nM structures at 5.8 GPa and found the results were consistent with experiments. Excitingly, we found that boron nitride nanotubes (BNNTs) and graphite and hexagonal boron nitride (h-BN) can be used to store (H2)4M, which give insights into hydrogen storage practical applications.

  20. Adsorption equilibria and kinetics of H 2 at nearly ideal (2 1)Si(100) inner surfaces

    NASA Astrophysics Data System (ADS)

    Cerofolini, G. F.; Romano, E.; Narducci, D.; Corni, F.; Frabboni, S.; Ottaviani, G.; Tonini, R.

    2010-07-01

    Silicon nanocavities can be terminated with hydrogen by wet chemical etching. Their infrared spectra can to a large extent be interpreted in terms of silicon monohydrides on H(7 7)Si(111), H(1 1)Si(111) and H(2 1)Si(100), and of silicon dihydrides on H(1 1)Si(100). The time evolution under isothermal conditions (600 C) of the (1 0 0) faces admits a description in terms of transformation from H(1 1)Si(100) into (2 1)Si(100) with simultaneous H 2 adsorption onto (2 1)Si(100) neat dimers. In so doing the inner H 2 pressure decreases by about one order of magnitude from the initial value of 3 10 3 Torr. The unique properties of nanocavities allow their use as nanoreactors; this has led to the determination of the sticking coefficient for H 2 adsorption in conditions of pressure, temperature and adventitious contamination otherwise not achievable.

  1. Constraining the ortho-to-para ratio of H2 with anomalous H_2CO absorption

    NASA Astrophysics Data System (ADS)

    Troscompt, N.; Faure, A.; Maret, S.; Ceccarelli, C.; Hily-Blant, P.; Wiesenfeld, L.

    2009-11-01

    Context: The ortho-to-para ratio (OPR) of molecular hydrogen is a fundamental parameter in understanding the physics and chemistry of molecular clouds. In dark and cold regions, however, H2 is not directly observable and the OPR of H2 in these sources has so far remained elusive. Aims: We show that the 6 cm absorption line of ortho-formaldehyde (H2CO) can be employed to constrain both the density and the OPR of H2 in dark clouds. Methods: Green Bank Telescope (GBT) observations of ortho-H2CO toward the molecular cloud Barnard 68 (B68) are reported. Non-LTE radiative transfer calculations combined with the well-constrained structure of B68 are then employed to derive the physical conditions in the absorption region. Results: We provide the first firm confirmation of the Townes & Cheung mechanism: propensity rules for the collisions of H2CO with H2 molecules are responsible for the sub-2.7 K cooling of the 6 cm doublet. Non-LTE calculations show that in the absorption region of B68, the kinetic temperature is 10 K, the ortho-H2CO column density amounts to 2.2 1013 cm-2, the H2 density is in the range 1.4{-}2.4 10 4 cm-3, and the OPR of H2 is close to zero. Our observations thus provide fresh evidence that H2 is mostly in its para form in the cold gas, as expected from theoretical considerations. Our results also suggest that formaldehyde absorption originates in the edge of B68, at visual extinctions A_V? 0.5 mag. This work has been inspired by our colleague and friend Pierre Valiron, who passed away in August 2008. This paper is dedicated to his memory.

  2. Effect of reaction temperature on Cu(InGa)(SeS)2 formation by a sequential H2Se\\/H2S precursor reaction process

    Microsoft Academic Search

    Gregory M. Hanket; Rui Kamada; Woo Kyoung Kim; William N. Shafarman

    2008-01-01

    The effect of sulfization temperature on Ga through-film uniformity in a 2-reaction H2Se\\/H2S precursor process for Cu(InGa)(SeS)2 was studied. Cu0.8Ga0.2\\/In bi-layer precursors were prepared by sputter deposition. The precursors were then partially selenized at 450 C, followed by sulfization at temperatures ranging from 450 to 550 C. The observed threshold temperature for Ga homogenization during sulfization was ?500 C. It

  3. Reactive Ion Etching of Indium Nitride Using CH4 and H2 Gases

    Microsoft Academic Search

    Qixin Guo; Motoatsu Matsuse; Mitsuhiro Nishio; Hiroshi Ogawa

    2000-01-01

    We have studied the characteristics of reactive ion etching of indium nitride layers using CH4 and H2 gases. The effects of CH4\\/H2 gas composition, total gas pressure, and plasma power on the etching rates were investigated. It was found that variation of the CH4 concentration in gas mixtures leads to changes in both the etching rate and the surface morphology.

  4. Partitioning of F between H 2 O and CO 2 fluids and topaz rhyolite melt

    Microsoft Academic Search

    James D. Webster

    1990-01-01

    Fluid\\/melt distribution coefficients for F have been determined in experiments conducted with peraluminous topaz rhyolite melts and fluids consisting of H2O and H2O+CO2 at pressures of 0.5 to 5 kbar, temperatures of 7751000C, and concentrations of F in the melt ranging from 0.5 to 6.9 wt%. The major element, F, and Cl concentrations of the starting material and run product

  5. Character of the pair interaction in solid and gaseous H2

    NASA Technical Reports Server (NTRS)

    England, W.; Etters, R.; Raich, J.; Danilowicz, R.

    1974-01-01

    Existing theoretical H2 pair potentials are investigated. We develop a spherically symmetric potential applicable to solid H2. It yields a ground-state energy of -98.7 K (experimental values range from -93.5 to -101 K). Pressure-volume data are also in excellent agreement with experiment between 0 and 25 kbar. Second virial coefficients using this potential are consistently too low. When an anisotropic pair potential is used, agreement becomes very good.

  6. A Unified Fundamental Equation for the Thermodynamic Properties of H2O

    Microsoft Academic Search

    Philip G. Hill

    1990-01-01

    A new unified equation of state for H2O is presented, which includes the revised and extended scaling equation of Levelt Sengers, KamgarParsi, Balfour and Sengers, is continuous over all single phase states of H2O from triple point pressure and temperature to 1000 MPa (or the melting line) and 1000 C and provides accurate representation of existing thermodynamic data in that

  7. EPA H2O Software Tool

    EPA Science Inventory

    EPA H2O allows user to: Understand the significance of EGS in Tampa Bay watershed; visually analyze spatial distribution of the EGS in Tampa Bay watershed; obtain map and summary statistics of EGS values in Tampa Bay watershed; analyze and compare potential impacts of development...

  8. Cluster virial expansion of the equation of state for hydrogen plasma with e-H_{2} contributions.

    PubMed

    Omarbakiyeva, Y A; Reinholz, H; Rpke, G

    2015-04-01

    The equation of state of partially ionized hydrogen plasma is considered with special focus on the contribution of the e-H_{2} interaction. Traditional semiempirical concepts such as the excluded volume are improved using microscopic approaches to treat the e-H_{2} problem. Within a cluster virial expansion, the Beth-Uhlenbeck formula is applied to infer the contribution of bound and scattering states to the temperature-dependent second virial coefficient. The scattering states are calculated using the phase expansion method for the polarization interaction that incorporates experimental data for the e-H_{2} scattering cross section. We present results for the scattering phase shifts, differential scattering cross sections, and the second virial coefficient due to the e-H_{2} interaction. The influence of this interaction on the composition of the partially ionized hydrogen plasma is confined to the parameter range where both the H_{2} and the free-electron components are abundant. PMID:25974598

  9. Fugacity of H2O from 0 to 350C at the liquid-vapor equilibrium and at 1 atmosphere

    USGS Publications Warehouse

    Hass, John L., Jr.

    1970-01-01

    The fugacity and fugacity coefficient of H2O at the liquid-vapor equilibrium, the fugacity and the Gibbs free energy of formation of H2O at 1 atm (1.01325 bars) total pressure have been calculated from published data on the physical and thermodynamic properties of H2O and are presented at ten-degree intervals from 0 to 350C.

  10. 26 CFR 31.3406(h)-2 - Special rules.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 false Special rules. 31.3406(h)-2 Section 31.3406(h)-2 Internal Revenue INTERNAL REVENUE SERVICE... Collection of Income Tax at Source 31.3406(h)-2 Special rules. (a) Joint accounts...

  11. 26 CFR 31.3406(h)-2 - Special rules.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 false Special rules. 31.3406(h)-2 Section 31.3406(h)-2 Internal Revenue INTERNAL REVENUE SERVICE... Collection of Income Tax at Source 31.3406(h)-2 Special rules. (a) Joint accounts...

  12. 26 CFR 31.3406(h)-2 - Special rules.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 false Special rules. 31.3406(h)-2 Section 31.3406(h)-2 Internal Revenue INTERNAL REVENUE SERVICE... Collection of Income Tax at Source 31.3406(h)-2 Special rules. (a) Joint accounts...

  13. [The tissue oxygen partial pressure in organs of hens in the second half of embryogenesis and in the first days after hatching].

    PubMed

    Belichenko, V M; Turganbaeva, A S; Khodyrev, E V; Kisliakova, L P; Kisliakov, Iu Ia; Shoshenko, K A

    2014-01-01

    The aim of the study was measure the development chick tissue partial pressure of oxygen (pO2) in the brain cerebral hemispheres, liver, M. pectoralis, M. gastrocnemius, and to estimate the correlation of this index with our previously measured values (laser-Doppler flowmetry) volume blood flow (BF) in these organs. We studied 10-, 15-, and 19-day embryos and 4-day chickens thatwere anesthetized with urethane. pO2 measurements were made in thesurface layers of organs by the membrane amperometric Clark-type O2-electrode with a diameter of about 50 microm of the cathode placed in the center of the sensor with an outer diameter of 3.4 mm. Disclosed noticeable distinction of both the organ tissue pO2 values, and the dynamics of their changes duringthe study period. The most important of them: (1) the lowest pO2 (and BF) is observed in the brain and particularly in the liver of 10-day embryos; (2) in the subsequent period of embryogenesis pO2 in the brain increases 1.9 times (rising and BF) in M. pectoralis it falls by 1.7 times and in the liver.and in M. gastrocnemius changes little wherein the BF in both liver and muscles is not changed, (3) after hatching pO2 in the liver and M. petoralis fold increased (also increasing and BF), and in the brain and M. gastrocnemius, despite the increase BF (greater in the niuscle) did not significant change. In the analysis ofthedata are considered two possible mechanisms of change of tissue pO2 in the developing organs of chickens, one is due to the peculiarities of intracardiac blood flows; and the other is related to thesingularity of the oxyhemoglobin dissociation in the blood capillary bed of organ, determined by the specifics of its oxidative metabolism. PMID:25752150

  14. Design of H2-O2 space shuttle APU. Volume 1: APU design

    NASA Technical Reports Server (NTRS)

    Harris, E.

    1974-01-01

    The H2-O2 space shuttle auxiliary power unit (APU) program is a NASA-Lewis effort aimed at hardware demonstration of the technology required for potential use on the space shuttle. It has been shown that a hydrogen-oxygen power unit (APU) system is an attractive alternate to the space shuttle baseline hydrazine APU system for minimum weight. It has the capability for meeting many of the heat sink requirements for the space shuttle vehicle, thereby reducing the amount of expendable evaporants required for cooling in the baseline APU. Volume 1 of this report covers preliminary design and analysis of the current reference system and detail design of the test version of this reference system. Combustor test results are also included. Volume 2 contains the results of the analysis of an initial version of the reference system and the computer printouts of system performance. The APU consists of subsystems for propellant feed and conditioning, turbopower, and control. Propellant feed and conditioning contains all heat exchangers, valves, and the combustor. The turbopower subsystem contains a two-stage partial-admission pressure-modulated, 400-hp, 63,000-rpm turbine, a 0-to 4-g lubrication system, and a gearbox with output pads for two hydraulic pumps and an alternator (alternator not included on test unit). The electronic control functions include regulation of speed and system temperatures; and start-and-stop sequences, overspeed (rpm) and temperature limits, failsafe provisions, and automatic shutdown provisions.

  15. State-to-state rotational transitions in H$_2$+H$_2$ collisions at low temperatures

    E-print Network

    Teck-Ghee Lee; N. Balakrishnan; R. C. Forrey; P. C. Stancil; D. R. Schultz; Gary J. Ferland

    2006-07-18

    We present quantum mechanical close-coupling calculations of collisions between two hydrogen molecules over a wide range of energies, extending from the ultracold limit to the super-thermal region. The two most recently published potential energy surfaces for the H$_2$-H$_2$ complex, the so-called DJ (Diep and Johnson, 2000) and BMKP (Boothroyd et al., 2002) surfaces, are quantitatively evaluated and compared through the investigation of rotational transitions in H$_2$+H$_2$ collisions within rigid rotor approximation. The BMKP surface is expected to be an improvement, approaching chemical accuracy, over all conformations of the potential energy surface compared to previous calculations of H$_2$-H$_2$ interaction. We found significant differences in rotational excitation/de-excitation cross sections computed on the two surfaces in collisions between two para-H$_2$ molecules. The discrepancy persists over a large range of energies from the ultracold regime to thermal energies and occurs for several low-lying initial rotational levels. Good agreement is found with experiment (Mat\\'e et al., 2005) for the lowest rotational excitation process, but only with the use of the DJ potential. Rate coefficients computed with the BMKP potential are an order of magnitude smaller.

  16. Lowest-energy structures of water clusters (H2O)(11) and (H2O)(13)

    SciTech Connect

    Bulusu, Satya; Yoo, Soohaeng; Apra, Edoardo; Xantheas, Sotiris S.; Zeng, Xiao Cheng

    2006-10-26

    We employed a four-step searching/screening approach to determine best candidates for the global minima of (H2O)11 and (H2O)13. This approach can be useful when there exist a large number of low-lying and near-isoenergetic isomers, many of which have the same oxygen-skeleton structure. On the two new candidates for the global minimum of (H2O)11, one isomer can be viewed as placing the 11th molecule onto the side of the global minimum of (H2O)10 while the other can be viewed as removing the 12th molecule from the middle layer of the global minimum of (H2O)12. The three leading lowest-energy clusters of (H2O)13 can all be built upon the global minimum of (H2O)12, with the difference in the location of the 13th water molecule. This research was performed in part using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by DOEs Office of Biological and Environmental Research.

  17. Observations of cumulene carbenes, H2CCCC and H2CCC, in TMC-1

    NASA Technical Reports Server (NTRS)

    Kawaguchi, Kentarou; Kaifu, Norio; Ohishi, Masatoshi; Ishikawa, Shin-Ichi; Hirahara, Yasuhiro; Yamamoto, Satoshi; Saito, Shuji; Takano, Shuro; Murakami, Akinori; Vrtilek, J. M.

    1991-01-01

    Attention is given to the carbon chain molecule H2CCCC, detected in the dark cloud TMC-1 for the first time in the course of a molecular line survey using the Nobeyama 45-m telescope. From nine transitions observed in the frequency region of 17-45 GHz, the total column density of H2CCCC in TMC-1 is derived to be 7.5(+/-2.0) x 10 exp 12/sq cm, which is about half of the value reported in IRC + 10216. Five transitions of a related carbon chain molecule, H2CCC, were also detected in TMC-1. The column density of H2CCC obtained in TMC-1, 2.8(+/-0.9) x 10 exp 12/sq cm, is a factor of three smaller than that of H2CCCC. The ortho-to-para abundance ratios of H2CCCC and H2CCC were found to be 4.2 +/-1.5 and 5.9 +/-2.0, respectively. The chemical reactions of these carbon-chain molecules in dark clouds are discussed.

  18. Tyrosine nitration in prostaglandin H(2) synthase

    Microsoft Academic Search

    Ruba S. Deeb; Matthew J. Resnick; Dev Mittar; Timothy McCaffrey; David P. Hajjar; Rita K. Upmacis

    2002-01-01

    In this study, we investigated the effects of various nitrogen oxide (NO(x)) species on the extent of prostaglandin H(2) synthase-1 (PGHS-1) nitration in purified protein and in vascular smooth muscle cells. We also examined PGHS-1 activity under these conditions and found the degree of nitration to correlate inversely with enzyme activity. In addition, since NO(x) species are thought to invoke

  19. Ice Has Structure: H2O

    NSDL National Science Digital Library

    This is a lesson about water and water-ice. Learners will explore the molecular geometry and mechanics of ice. They will create a model of H2O, investigate its molecular structure and its consistent shape. Faraday's experiment is used as background. Activities include small group miming, speaking, drawing, and/or writing. This is lesson 2 of 12 in the unit, Exploring Ice in the Solar System.

  20. Stable H2-optimal controller synthesis

    Microsoft Academic Search

    J. R. Corrado; R. Scott Erwin; Dennis S. Bernstein; W. M. Haddad

    1997-01-01

    This paper considers fixed-structure stable H2-optimal controller synthesis using a multiobjective optimization technique. The problem is presented in a decentralized static output feedback framework developed for fixed-structure dynamic controller synthesis. A quasi-Newton\\/continuation algorithm is used to compute solutions to the necessary conditions. To demonstrate the approach, a numerical example is considered, which consists of a second-order spring-mass-damper system pulled from

  1. H2O Masers and Supersonic Turbulence

    E-print Network

    V. Strelnitski; J. Alexander; S. Gezari; B. P. Holder; J. M. Moran; M. J. Reid

    2002-10-15

    We use unpublished and published VLBI results to investigate the geometry and the statistical properties of the velocity field traced by H2O masers in five galactic regions of star formation -- Sgr B2(M), W49N, W51(MAIN), W51N, and W3(OH). In all sources the angular distribution of the H2O hot spots demonstrates approximate self-similarity (fractality) over almost four orders of magnitude in scale, with the calculated fractal dimension d between (approximately) 0.2 and 1.0. In all sources, the lower order structure functions for the line-of-sight component of the velocity field are satisfactorily approximated by power laws, with the exponents near their classic Kolmogorov values for the high-Reynolds-number incompressible turbulence. These two facts, as well as the observed significant excess of large deviations of the two-point velocity increments from their mean values, strongly suggest that the H2O masers in regions of star formation trace turbulence. We propose a new conceptual model of these masers in which maser hot spots originate at the sites of ultimate dissipation of highly supersonic turbulence produced in the ambient gas by the intensive gas outflow from a newly-born star. Due to the high brightness and small angular sizes of masing hot spots and the possibility of measuring their positions and velocities with high precision, they become a unique probe of supersonic turbulence.

  2. Petrological mapping of a Low Velocity Zone (LVZ) induced by CO2-H2O-bearing incipient melts

    NASA Astrophysics Data System (ADS)

    Massuyeau, M.; Gards, E.; Morizet, Y.; Le Trong, E.; Gaillard, F.

    2014-12-01

    The link between volatiles and mantle melting has so far been illuminated by experiments, revealing that ppm concentration levels of carbon and other volatiles in the Earth's mantle induce partial melting. Pressure-temperature conditions of incipient melting for CO2-H2O-peridotite [1] match fairly well with the upper part of the LVZ, as the redox melting [2] with the lower part. Recent experimental studies about the Earth mantle conductivity have shown the importance of small amounts of hydrated CO2-rich melts in the geophysical signature of the LVZ [3]. Although such melts are stable under the P-T-fO2 conditions of the LVZ [1-2, 4-6], the variability of these parameters complicates the definition of their chemical composition. Using Margules' formalisms, we established a multi-component model describing the Gibbs free energy of melt produced by mantle melting in presence of CO2-H2O, that are carbonatite-carbonated melt-nephilinite-basanite and basalt with increasing degree of partial melting. This parameterization is calibrated on crystal-liquid, redox, fluid-liquid and liquid-liquid equilibria obtained by experimental studies in the P-T range 1-10 GPa and 900-1800C. We propose a calculation of the composition of melts produced in the oceanic LVZ as a function of ages (temperature) and chemical heterogeneities (water, alkalis). At about 80 km depth, we show that the composition of the melts is > 30 wt% SiO2 for ages < 30 Ma, and comes closer to the carbonatitic terms for older lithosphere. Besides lateral chemical variations, our model calculates the melt composition along an oceanic ridge adiabat, predicting an abrupt compositional transition between a H2O-rich carbonatitic melt and a carbonated silicate melt, between 130 km and 100 km. We propose a chemical mapping of the melt composition (and of the degree of partial melting) as a function of the distance to the ridge and of the depth. Our model represents an innovating attempt to connect the chemical variations between carbonated and silicated melts with the geophysical observations. [1] Wallace & Green, 1988, Nature 335, 343-346 [2] Stagno et al., 2013, Nature 493, 84-88 [3] Sifr et al., 2014, Nature 509, 81-85 [4] Presnall & Gudfinnsson, 2005, SPGSA 388, 207-216 [5] Hirschmann et al., 2009, PEPI 176, 54-68 [6] Dasgupta et al., 2013, Nature 493, 211-215

  3. Oxidation of Si during the growth of SiO{sub x} by ion-beam sputter deposition: In situ x-ray photoelectron spectroscopy as a function of oxygen partial pressure and deposition temperature

    SciTech Connect

    Kim, Kyung Joong; Kim, Jeong Won; Yang, Moon-Seung; Shin, Jung Hoon [Nano Surface Group, Korea Research Institute of Standards and Science (KRISS), P.O. Box 102, Yusong, Taejon 305-600 (Korea, Republic of); Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Kusung-dong, Yusong-gu, Taejon (Korea, Republic of)

    2006-10-15

    Oxidation of silicon during the growth of silicon oxide by ion beam sputter deposition was studied by in situ x-ray photoelectron spectroscopy as a function of oxygen partial pressure at various deposition temperatures below 600 deg. C. At low temperatures, the variation of incorporated oxygen content is similar to a dissociative adsorption isotherm of O{sub 2} on Si indicating that the surface-confined reaction of the deposited Si atoms with the adsorbed oxygen atoms is the main process. However, it shows a three-step variation with the oxygen partial pressure at high temperatures. The evolution of SiO species confirmed by the XPS indicates that an adsorption-induced surface reaction and a diffusion-induced internal reaction are the main pathways for the Si oxidation.

  4. Interaction of sulfur-bearing silicate melts with H2O and H2 bearing fluids (Invited)

    NASA Astrophysics Data System (ADS)

    Behrens, H.; Stelling, J.; Wilke, M.; Backnaes, L.; Deubener, J.

    2009-12-01

    Reactions between fluids and melts, which are not in redox-equilibrium, may potentially change the oxidation state of species in both phases. Diffusion of hydrogen and water in the melt is expected to be a controlling parameter for the adjustment of the redox state of multivalent elements in the melt, at least over short distances. In the present paper we have investigated experimentally the interaction of sulfur-bearing silicate melts with either oxidizing or reducing fluid components. Two scenarios were studied: (i) Diffusion of water into an initial dry melt containing sulfide and (ii) diffusion of hydrogen into a water-poor melt containing sulfate. The experiments were performed in an internally heated gas pressure vessel at 100 or 200 MPa confining pressure and temperatures between 1000 and 1200C using as model systems soda-lime-silicate and sodiumtrisilicate melts containing ca. 1000 ppm sulfur. Type (i) experiments were carried out either at water-undersaturated conditions (max. 3 wt% H2O) using the diffusion couple technique or at water-saturated conditions by adding 10 wt% of H2O to the glass melt. Run time was always short (4 - 20 min), resulting in H2O diffusion profiles up 3 mm and S diffusion profiles up to 400 m in length. In the diffusion couple experiments new IR absorption bands at 3400 and 5020 cm-1 were observed while the characteristic combination band of molecular H2O at 5225 cm-1 strongly decreases in intensity. X-ray Absorption Near Edge Structure (XANES) spectroscopy demonstrate the appearance of a new S K pre-edge excitation at 2466.5 eV and a relative decrease in the intensity of the sulfide peak at 2474.0 eV, but no signal of sulfate at 2482.5 eV was detected. The intensity of the XANES pre-edge peak correlates directly with the intensities of the IR bands at 3400 and 5020 cm-1. On the basis of the spectroscopic results we infer the formation of a stable complex of S2- with probably 2 H2O molecules in the glasses. The lack of oxidation of sulfide can be explained by local redox buffering of the melt with hydrogen due to the low hydrogen solubility in the melt or by a relatively low oxygen fugacity. Oxidation of sulfide to sulfate was observed only in experiments with a free H2O fluid which may act as a sink for hydrogen. In all type (ii) experiments reaction rims were formed in the sulfate bearing part of the sample where sulfide was generated by in-diffusion of hydrogen from the pressure vessel. For instance after 8 h at 1100C, 100 MPa the reduced layer had a thickness of ca. 200 m. Neither in the reduction nor in the oxidation experiments a sulfite peak was observed in XANES spectra. Hence, we conclude that sulfite is not a stable (major) sulfur species in the melt or it is not quenchable, consistent with findings of Wilke et al. (2008). Ref.: M. Wilke, P.J. Jugo, J. Susini, R. Botcharnikov, S.C. Kohn, M. Janousch (2008). The origin of S4+ detected in silicate glasses by XANES. Am. Mineral. 93, 235-240.

  5. Partial liquid ventilation ventilates better than gas ventilation.

    PubMed

    Fujino, Y; Goddon, S; Chiche, J D; Hromi, J; Kacmarek, R M

    2000-08-01

    Partial liquid ventilation (PLV) improves oxygenation in several models of lung injury. However, PLV has only been compared with conventional gas ventilation (GV) with low PEEP. Both PLV and GV can markedly improve oxygenation when PEEP is set above the lower corner pressure (Plc) on the inspiratory pressure-volume (P-V) curve of the total respiratory system. We questioned if the use of PEEP set above the Plc during PLV and GV would result in similar gas exchange. Lung injury was induced in 12 sheep by saline lavage before randomization to PLV (n = 6) or GV (n = 6). Animals in the PLV group were filled with perflubron (22 ml/kg) until a meniscus at the teeth was observed. Both groups were then ventilated with pressure control (FI(O(2)), 1.0; rate, 20/min; I:E, 1:1) and PEEP (1 cm H(2)O above the Plc on the inspiratory P-V curve). Peak inspiratory pressure (PIP) was limited to 35 cm H(2)O. Animals were ventilated for 5 h and then killed for histologic examinations. All 12 animals survived the 5-h ventilation period. After increasing PEEP above Plc, Pa(O(2)) increased significantly (p < 0.01) in both the GV and the PLV groups, but it did not differ significantly between groups (p = 0.86) at any time during the experiment. Pa(CO(2)) and VD/VT in GV increased markedly throughout the experiment after increasing PEEP (p < 0.001), but there was no significant change in Pa(CO(2)) in PLV (p = 0.13). Mean arterial blood pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, and central venous pressure, increased and SVR decreased in GV (p < 0.05). The extent and the severity of lung injury in the dependent regions was greater in the GV group (p < 0.05). Both PLV and GV improved oxygenation, but PLV resulted in better ventilation than GV while preserving lung structure when PEEP was set 1 cm H(2)O above the Plc and PIP limited to 35 cm H(2)O. PMID:10934101

  6. CALCULATION OF THE BEHAVIOR UNDER PARTIAL LOADING OF A NUCLEAR POWER PLANT COOLED WITH GAS AT LOW PRESSURE AND WITH A SINGLE VAPOR CYCLE

    Microsoft Academic Search

    Spitalnik

    1961-01-01

    The behavior of a gas-cooled reactor under partial load was calculated ; for various load regimes according to the different control programs chosen. In ; the appendix the method used for the calculation of the heat exchange surfaces ; under full load and the variation of the parameters under partial charge are ; given. (J.S.R.);

  7. Intercellular adhesiveness of H-2 identical and H-2 disparate cells.

    PubMed

    Zelen, V; Matousek, V; Lengerov, A

    1978-02-01

    Using a 2 X 2 design, the collection rates of cells from radioactively labelled single-cell suspensions on cell-coated collecting surfaces were tested for a possible H-2 effect on intracellular adhesiveness. By a statistical procedure, the undesirable variability in the suspension and/or in the collecting surface could be eliminated, and the H-2 specific net effect estimated. In this way it was possible to detect (even on the background of a large non-specific variability) significant reductions of the allogeneic collection rates (i.e. between cells which differed only in their H-2 haplotypes) as compared to the syngeneic standards. It is concluded that cells of a given H-2 haplotype have preferential adhesiveness to syngeneic cells. PMID:641358

  8. Vapor-liquid phase equilibria of potassium chloride-water mixtures: Equation-of-state representation for KCl-H2O and NaCl-H2O

    USGS Publications Warehouse

    Hovey, J.K.; Pitzer, Kenneth S.; Tanger, J.C., IV; Bischoff, J.L.; Rosenbauer, R.J.

    1990-01-01

    Measurements of isothermal vapor-liquid compositions for KCl-H2O as a function of pressure are reported. An equation of state, which was originally proposed by Pitzer and was improved and used by Tanger and Pitzer to fit the vapor-liquid coexistence surface for NaCl-H2O, has been used for representation of the KCl-H2O system from 300 to 410??C. Improved parameters are also reported for NaCl-H2O from 300 to 500??C. ?? 1990 American Chemical Society.

  9. Contrail formation: Homogeneous nucleation of H2SO4\\/H2O droplets

    Microsoft Academic Search

    B. Kaercher; Th. Peter; R. Ottmann

    1995-01-01

    Homogeneous nucleation of sub-nanometer H2SO4\\/H2O germs, their growth and freezing probability in the cooling wake of a subsonic jet aircraft at tropopause altitude are investigated. Heteromolecular condensation, water uptake, and coagulation cause a small subset of the germs to grow into nm-sized solution droplets which overcome the Kelvin barrier. These droplets efficiently take up water vapor from the gas phase,

  10. Collisional energy transfer in H2(vab,jab)+H2(vcd,jcd)

    Microsoft Academic Search

    M. E. Mandy; P. G. Martin; W. J. Keogh

    1998-01-01

    Quasiclassical trajectory studies were carried out on the H2(vab,jab) + H2(vcd,jcd) system to survey the effects of initial vibrational, rotational, and translational energy on the collisional energy transfer behavior at total energies of 0.1 and 0.25 Eh. When the internal energy of the collider is low, repulsive interactions dominate and the energy transfer in the target molecule resembles the behavior

  11. Investigation of potential energy landscapes of (H2O)7- and (H2O)8- clusters

    NASA Astrophysics Data System (ADS)

    Shin, Byong-kyu; Choi, Tae Hoon

    2015-04-01

    The potential energy surfaces of (H2O)7- and (H2O)8- clusters, as described by a one-electron model Hamiltonian, are thoroughly explored. The local minima and first-order saddle points are located and then used to construct disconnectivity graphs. The minimum energy pathways connecting the transition states and local minima are identified and discussed in the context of existing experimental observations reported in the literature.

  12. Volatile composition of the phonolitic Laacher See magma (12,900 yr BP): implications for syn-eruptive degassing of S, F, Cl and H2O

    NASA Astrophysics Data System (ADS)

    Harms, E.; Schmincke, H.-U.

    A volatile-rich and chemically zoned phonolitic magma reservoir was tapped successively during the eruption of Laacher See volcano ca. 12,900years BP and produced a tephra sequence consisting of phenocryst-poor, highly evolved phonolite at the base and phenocryst-rich, more mafic phonolite at the top. The stratospheric volatile loading was estimated by comparing pre- and post-eruptive S, F, Cl and H2O contents of undegassed glass inclusions and partially degassed matrix glasses. Glass inclusions (150-1490ppm S) and host matrix glasses (150-820ppm S) both document a strong S decrease during progressive magmatic differentiation, which is interpreted to be partially caused by crystallization of hauyne. The S6+/Stotal ratio of the pre-eruptive melt increased with differentiation from 8 to 71%, as indicated by S k? wavelength shift measurements in glass inclusions. Sulfate-rich, highly evolved phonolitic magma was erupted during Plinian and sulfide-rich, more mafic phonolitic magma during late phreatomagmatic phases. F and Cl became enriched during late stages of differentiation (glass inclusions: 690-4060ppm F, 1770-4400ppm Cl; matrix glasses: 680-3660ppm F, 2130-4330ppm Cl). The most differentiated melts (maximum 13wt% Na2O) occur only as matrix glass and are extremely F enriched (5080-8780ppm) but Cl depleted (460-2820ppm), suggesting that F was retained in the melt, whereas some Cl was lost during pre- and/or syn-eruptive degassing. The H2O contents of glass inclusions increase irregularly with differentiation (2.5-5.7wt%). Matrix glasses are H2O depleted (0.2-2.8wt%) compared to most glass inclusions, showing that most H2O was released to the atmosphere by explosive degassing. A mass balance calculation yields a syn-eruptive volatile release of 1.9 Tg Stotal, 6.6 Tg Cl and 403 Tg H2O from the melt. This is a minimum estimate, since S and Cl could have accumulated in a separate fluid phase as indicated by fluid inclusions in hauyne and pre-eruption H2O contents close to saturation level at the likely pressure-temperature conditions in the Laacher See magma reservoir. We estimate that at least ca. 20 Tg SO2 were injected into the stratosphere causing a significant negative climate forcing as reflected by several paleoclimate proxies and as shown by recent modeling.

  13. Refinements in an Mg/MgH2/H2O-Based Hydrogen Generator

    NASA Technical Reports Server (NTRS)

    Kindler, Andrew; Huang, Yuhong

    2010-01-01

    Some refinements have been conceived for a proposed apparatus that would generate hydrogen (for use in a fuel cell) by means of chemical reactions among magnesium, magnesium hydride, and steam. The refinements lie in tailoring spatial and temporal distributions of steam and liquid water so as to obtain greater overall energy-storage or energy-generation efficiency than would otherwise be possible. A description of the prior art is prerequisite to a meaningful description of the present refinements. The hydrogen-generating apparatus in question is one of two versions of what was called the "advanced hydrogen generator" in "Fuel-Cell Power Systems Incorporating Mg-Based H2 Generators" (NPO-43554), NASA Tech Briefs, Vol. 33, No. 1 (January 2009), page 52. To recapitulate: The apparatus would include a reactor vessel that would be initially charged with magnesium hydride. The apparatus would exploit two reactions: The endothermic decomposition reaction MgH2-->Mg + H2, which occurs at a temperature greater than or equal to 300 C, and The exothermic oxidation reaction MgH2 + H2O MgO + 2H2, which occurs at a temperature greater than or equal to 330 C.

  14. Spontaneous H2 loss through the interaction of squaric acid derivatives and BeH2.

    PubMed

    Montero-Campillo, M Merced; Yez, Manuel; Lamsabhi, Al Mokhtar; M, Otilia

    2014-04-25

    The most stable complexes between squaric acid and its sulfur- and selenium-containing analogues (C4X4H2 ; X = O, S, Se) with BeY2 (Y = H, F) were studied by means of the Gaussian?04 (G4) composite ab initio theory. Squaric acid derivatives are predicted to be very strong acids in the gas phase; their acidity increases with the size of the chalcogen, with C4Se4H2 being the strongest acid of the series and stronger than sulfuric acid. The relative stability of the C4X4H2?BeY2 (X = O, S, Se; Y = H, F) complexes changes with the nature of the chalcogen atom; but more importantly, the formation of the C4X4H2?BeF2 complexes results in a substantial acidity enhancement of the squaric moiety owing to the dramatic electron-density redistribution undergone by the system when the beryllium bond is formed. The most significant consequence of this acidity enhancement is that when BeF2 is replaced by BeH2, a spontaneous exergonic loss of H2 is observed regardless of the nature of the chalcogen atom. This is another clear piece of evidence of the important role that closed-shell interactions play in the modulation of physicochemical properties of the Lewis acid and/or the Lewis base. PMID:24665080

  15. Activity and Activity Coefficient of Iron Oxides in the Liquid FeO-Fe2O3-CaO-SiO2 Slag Systems at Intermediate Oxygen Partial Pressures

    NASA Astrophysics Data System (ADS)

    Henao, Hector M.; Itagaki, Kimio

    2007-10-01

    At present, there is a scarcity of data on the activities of iron oxides in the FeO-Fe2O3-CaO-SiO2 slag system at intermediate oxygen partial pressures and temperatures relevant to sulfide smelting and nonferrous metallurgy. The present study provides relevant data at temperatures between 1573 and 1673 K and partial pressures of oxygen between 10-9 and 10-4 atm. The experiments were carried out by equilibrating the slag in a CO-CO2 gas mixture in a platinum crucible, after which the phases of all the experimental samples, including the platinum foil, were analyzed by electron probe microanalysis (EPMA). Where only liquid phase or liquid phase and tridymite (SiO2) were observed, wet chemical analysis was used to determine the ratio of (mass pct Fe2+)/(mass pct Fe3+). Activity and activity coefficients for FeO (liquid) and FeO1.33 (solid) were calculated. Tendencies of the effect of the (CaO/SiO2) ratio, temperature, and oxygen partial pressure on these thermochemical quantities are discussed in this article.

  16. Vanadate-induced cell death is dissociated from H2O2 generation.

    PubMed

    Capella, M A M; Capella, L S; Valente, R C; Gef, M; Lopes, A G

    2007-11-01

    Vanadium is an environmentally toxic metal with peculiar and sometimes contradictory cellular effects. It is insulin-mimetic, it can either stimulate cell growth or induce cell death, and it has both mutagenic and antineoplastic properties. However, the mechanisms involved in those effects are poorly understood. Several studies suggest that H(2)O(2) is involved in vanadate-induced cell death, but it is not known whether cellular sensitivity to vanadate is indeed related to H(2)O(2) generation. In the present study, the sensitivity of four cell lines from different origins (K562, K562-Lucena 1, MDCK, and Ma104) to vanadate and H(2)O(2) was evaluated and the production of H(2)O(2) by vanadate was analyzed by flow cytometry. We show that cell lines very resistant to H(2)O(2) (K562, K562-Lucena 1, and Ma104 cells) are much more sensitive to vanadate than MDCK, a cell line relatively susceptible to H(2)O(2), suggesting that vanadate-induced cytotoxicity is not directly related to H(2)O(2) responsiveness. In accordance, vanadate concentrations that reduced cellular viability to approximately 60-70% of the control (10 mumol/L) did not induce H(2)O(2) formation. A second hypothesis, that peroxovanadium (PV) compounds, produced once vanadate enters into the cells, are responsible for the cytotoxicity, was only partially confirmed because MDCK cells were resistant to both vanadate and PV compounds (10 micromol/L each). Therefore, our results suggest that vanadate toxicity occurs by two distinct pathways, one dependent on and one independent of H(2)O(2) production. PMID:17457679

  17. Simultaneous laboratory measurements of CO2 and H2O adsorption on palagonite: Implications for the Martian climate and volatile reservoir

    NASA Technical Reports Server (NTRS)

    Zent, A. P.; Quinn, R.

    1993-01-01

    We are measuring the simultaneous adsorption of H2O and CO2 on palagonite materials in order to improve the formulation of climate models for Mars. We report on the initial co-adsorption data. Models of the Martian climate and volatile inventory indicate that the regolith serves as one of the primary reservoirs of outgassed volatiles and that it exchanges H2O and CO2 with the atmosphere in response to changes in insolation associated with astronomical cycles. Physical adsorbate must exist on the surfaces of the cold particulates that constitute the regolith, and the size of that reservoir can be assessed through laboratory measurements of adsorption on terrestrial analogs. Many studies of the independent adsorption of H2O and CO2 on Mars analog were made and appear in the literature. Empirical expressions that relate the adsorptive coverage of each gas to the temperature of the soil and partial pressure have been derived based on the laboratory data. Numerical models incorporate these adsorption isotherms into climatic models, which predict how the adsorptive coverage of the regolith and hence, the pressure of each gas in the atmosphere will vary as the planet moves through its orbit. These models suggest that the regolith holds several tens to hundreds of millibars of CO2 and that during periods of high obliquity warming of the high-latitude regolith will result in desorption of the CO2, and a consequent increase in atmospheric pressure. At lower obliquities, the caps cool and the equator warms forcing the desorption of several tens of millibars of CO2, which is trapped into quasipermanent CO2 caps.

  18. One-dimensional Coordination Polymer {[Tm2(ttha)(H2O)6Tm2(ttha)(H2O)4]21H2O}n

    E-print Network

    Gao, Song

    -temperature magnetic susceptibility data indicates the presence of an overall antiferromagnetic behaviour with intra- dation of Peking University. Techniques used: FTIR, thermogravimetry, magnetic susceptibility, singleOne-dimensional Coordination Polymer {[Tm2(ttha)(H2O)6Tm2(ttha)(H2O)4]21H2O}n: Synthesis, Crystal

  19. NaBH4/H2O2 Fuel Cells for Lunar and Mars Exploration

    NASA Astrophysics Data System (ADS)

    Luo, Nie; Miley, George H.; Mather, Joseph; Burton, Rodney; Hawkins, Glenn; Gimlin, Richard; Rusek, John; Valdez, Tom I.; Narayanan, Sekharipuram R.

    2006-01-01

    The properties of direct hydrogen peroxide (H2O2) fuel cells are studied in this research. Different catalysts and diffusion electrodes are tested to optimize the cell performance. Initial results indicate: 1) conversion efficiency over 60% at a practical current density of 250mA/cm2; 2) power density over 0.6 W/cm2, at room temperature and ambient pressure, better than that of any traditional fuel cell. Further, the unique combination of NaBH4 and H2O2, both of which are in an aqueous form, paves the way for a convenient unitized regeneration, which is inherently compact compared to other cells that use gas phase reactants, such as the conventional H2 and O2. These excellent properties make the NaBH4/H2O2 fuel cell a very promising candidate for future space power systems. A conceptual design to power Lunar and Mars missions is discussed.

  20. Wave Driven Ar--N2--H2 Plasma

    NASA Astrophysics Data System (ADS)

    Henriques, J.; Dias, F. M.; Tatarova, E.; Ferreira, C. M.

    2009-10-01

    An experimental investigation of the spatial structure of an Ar--N2--H2 plasma torch is presented. A surface wave induced microwave (2.45 GHz) plasma torch is created using a conventional, surfaguide based set-up. A cylindrical, fused quartz discharge tube (with internal and external radii R1=7.5 mm and R2=9.0 mm, respectively) is filled by an Ar(78%)--N2(20%)--H2(2%) gas mixture at atmospheric pressure. A spectroscopic imaging system able to couple the plasma-emitted radiation into a SPEX 1250M spectrometer, equipped with a nitrogen cooled CCD camera, was used to measure 2D(r,z) profiles of emission intensities and line profiles. Abel inversion has been applied to derive the radial profiles from the side-on measurements. The H? line profiles have been measured to determine the corresponding Doppler temperature and the electron density. The measurements are well fitted by Voigt profiles, whose Gaussian and Lorenzian components have been deconvoluted. In this way, hyperthermal hydrogen atoms have been detected. The measured Doppler temperatures (5,000--8,000 K) are higher than the rotational temperature by a factor of about 2. The 2D map of the electron density (5x10^12--5x10^13 cm-3) was also obtained. Acknowledgement- This work was supported by the Fundaco para a Cincia e a Tecnologia, Minist'erio da Cincia, Tecnologia e Ensino Superior, Portugal

  1. H 2O diffusion in rhyolitic melts and glasses

    Microsoft Academic Search

    Youxue Zhang; Harald Behrens

    2000-01-01

    H2O diffusion plays a major role in bubble growth and volcanic eruption. We report a comprehensive study of H2O diffusion in rhyolitic melts and glasses. This new study and previous investigations together cover a wide range of conditions: 4001200C, 0.1810 MPa, and 0.17.7 wt.% total H2O content (H2Ot). In order to constrain how the diffusivity depends on H2Ot, both the

  2. V olatileC alc: a silicate meltH 2OCO 2 solution model written in Visual Basic for excel

    Microsoft Academic Search

    Sally Newman; Jacob B. Lowenstern

    2002-01-01

    We present solution models for the rhyoliteH2OCO2 and basaltH2OCO2 systems at magmatic temperatures and pressures below ?5000bar. The models are coded as macros written in Visual Basic for Applications, for use within Microsoft Excel (Office98 and 2000). The series of macros, entitled VolatileCalc, can calculate the following: (1) Saturation pressures for silicate melt of known dissolved H2O and CO2 concentrations

  3. Metalorganic complexes in geochemical processes: Estimation of standard partial molal thermodynamic properties of aqueous complexes between metal cations and monovalent organic acid ligands at high pressures and temperatures

    Microsoft Academic Search

    Everetr L. Shock; Carla M. Koretsky

    1995-01-01

    Regression of standard state equilibrium constants with the revised Helgeson-Kirkham-Flowers (HKF) equation of state allows evaluation of standard partial molal entropies (So) of aqueous metal-organic complexes involving monovalent organic acid ligands. These values of So provide the basis for correlations that can be used, together with correlation algorithms among standard partial molal properties of aqueous complexes and equation-of-state parameters, to

  4. Adsorption of H2O2 at the surface of Ih ice, as seen from grand canonical Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Picaud, Sylvain; Jedlovszky, Pl

    2014-04-01

    Adsorption of H2O2 at the (0 0 0 1) surface of Ih ice is investigated by GCMC simulations under tropospheric conditions. The results are in qualitative agreement with experimental data and reveal that the main driving force of the adsorption is the formation of new H2O2-H2O2 rather than H2O2-water H-bonds. The isotherm belongs to class III and not even its low pressure part can be described by the Langmuir formalism. At low coverages H2O2 prefers perpendicular alignment to the surface, in which they can form three H-bonds with surface waters. At higher coverages parallel alignment, stabilized by H-bonds between neighbouring H2O2 molecules, becomes increasingly preferred.

  5. Influence of 3d transition metals on the stability and electronic structure of MgH2

    NASA Astrophysics Data System (ADS)

    Zeng, X. Q.; Cheng, L. F.; Zou, J. X.; Ding, W. J.; Tian, H. Y.; Buckley, C.

    2012-05-01

    The effect of minor addition of 3d transition metals on the formation enthalpy (?H) and electronic structure of MgH2 have been studied using first-principle calculations, and considering the phonon-calculated zero point energy. The results indicate that the partial substitution of Mg atoms by 3d transition metal atoms increases the formation enthalpy of MgH2. Both formation enthalpy and Mulliken population analysis showed that the ability to destabilize MgH2 generally increases with the atomic number, except Mn and Zn, which have half-filled and completely filled 3d orbital states. The destabilization of MgH2 by partially alloying 3d elements was due to relatively stronger covalent bonds between 3d elements and the H atom, and a weaker ionic bond between Mg and H in the alloyed material with respect to pure MgH2. Based on electronic structure analyses, MgH2 and MgH2 alloyed with Ti, Fe, and Zn show no spin magnetism, while MgH2 alloyed with Sc, V, Cr, Mn, Co, Ni, and Cu show spin magnetism. In the MgH2-3d metal system except Zn, the bonding peak near the Fermi energy is mainly contributed by 3d electrons of transition metals and weak H (s) states. The bonding nature of MgH2 is ionic, and the bonding nature of MgH2-3d metal systems is mainly ionic with covalent bonds between 3d metal atoms and their neighbor H atoms.

  6. Analysis of ?2 of H 2Se

    NASA Astrophysics Data System (ADS)

    Lane, Wm. C.; Edwards, T. H.; Gillis, James R.; Bonomo, Francis S.; Murcray, Frank J.

    1984-10-01

    The infrared absorption spectrum of ?2 of H 2Se in the region from 885 to 1347 cm -1 was obtained with a resolution limit of 0.025 cm -1 on the University of Denver 50-cm FTIR spectrometer system. We have assigned 1604 lines for the six isotopomers of H 2Se, including 25 lines for the H 274Se isotopomer, and have analyzed them using Watson's A-reduced Hamiltonian in the Ir rotational representation. Ground state constants for each of the five most abundant isotopomers were obtained from fits of microwave transitions combined with weighted averaged ground state combination differences formed from the infrared bands (010), (020), (100), and (001). Upper state constants for each of the five most abundant isotopomers were obtained from least-squares fits of the spectral lines of ?2, keeping the ground state constants fixed to the values determined from our ground state fits. An alternate set of ground state constants together with isotopic mass adjustment constants for all six isotopomers was determined by simultaneously fitting all available microwave transitions and infrared ground state combination differences. Keeping this set of ground state constants fixed, a single set of upper state constants and isotopic mass adjustment constants for the ?2 band was determined by a simultaneous fit of infrared spectral lines from all six isotopomers.

  7. The effect of vibrational excitation of H2 and of OH on the rate of the reaction H2+OH --> H2O+H

    NASA Astrophysics Data System (ADS)

    Glass, G. P.; Chaturvedi, B. K.

    1981-09-01

    The reaction between the hydroxyl radical and H2 has been studied at room temperature using a discharge flow apparatus equipped for EPR detection of small, free radicals. Vibrationally excited H2 was generated using electric discharge techniques. The rate of the reaction H2+OH?H2O+H was shown to be enhanced by a factor of 155 when H2 was excited into its first vibrational state. Earlier work had shown that the rate of this reaction was increased by less than 50% when OH was excited to either its first or second vibrational state.

  8. Application of Symmetry-Broken H2-H2 Potential Energy Surface to Low Energy o-/p-H2+HD Collisions of Astrophysical Interest

    NASA Astrophysics Data System (ADS)

    Sultanov, R. A.; Guster, D.; Adhukari, S. K.

    2011-05-01

    A possibility of correct description of non-symmetrical HD+H2 collision at low temperatures (T?300 K) is considered by applying symmetrical H2-H2 potential energy surface (PES) [Diep, P. & Johnson, K. 2000, J. Chem. Phys. 113, 3480 (DJ PES)]. With the use of a special mathematical transformation technique, which was applied to this surface, and a quantum dynamical method we obtained a quite satisfactory agreement with previous results when another H2-H2 PES was used [Boothroyd, A.I. et al. 2002, J. Chem. Phys. 116, 666 (BMKP PES)].

  9. Quasiclassical trajectory study of formaldehyde unimolecular dissociation: H2CO?H2+CO, H +HCO

    NASA Astrophysics Data System (ADS)

    Zhang, Xiubin; Rheinecker, Jaime L.; Bowman, Joel M.

    2005-03-01

    We report quasiclassical trajectory calculations of the dynamics of the two reaction channels of formaldehyde dissociation on a global ab initio potential energy surface: the molecular channel H2CO?H2+CO and the radical H2CO?H+HCO. For the molecular channel, it is confirmed that above the threshold of the radical channel a second, intramolecular hydrogen abstraction pathway is opened to produce CO with low rotation and vibrationally hot H2. The low-jCO and high-?H2 products from the second pathway increase with the total energy. The competition between the molecular and radical pathways is also studied. It shows that the branching ratio of the molecular products decreases with increasing energy, while the branching ratio of the radical products increases. The results agree well with very recent velocity-map imaging experiments of Suits and co-workers and solves a mystery first posed by Moore and co-workers. For the radical channel, we present the translational energy distributions and HCO rotation distributions at various energies. There is mixed agreement with the experiments of Wittig and co-workers, and this provides an indirect confirmation of their speculation that the triplet surface plays a role in the formation of the radical products.

  10. Direct synthesis of H 2O 2 from H 2 and O 2 and decomposition\\/hydrogenation of H 2O 2 in an aqueous acidic medium over halide-modified Pd\\/Al 2O 3 catalysts

    Microsoft Academic Search

    Chanchal Samanta; Vasant R. Choudhary

    2007-01-01

    Direct synthesis of H2O2 from its elements was carried out in an acidic aqueous reaction medium over halide-modified oxidized and reduced Pd\\/Al2O3 catalysts under very mild conditions (at 27C and atmospheric pressure). The halide ions were introduced into the catalyst by incorporating halide ions into supported Pd\\/?-Al2O3 catalyst or via depositing halide ions on the support (?-Al2O3) prior to Pd

  11. Evaporation of forsterite in H 2 gas

    Microsoft Academic Search

    Hiroko Nagahara; Kazuhito Ozawa

    1996-01-01

    Kinetics of evaporation of forsterite in hydrogen gas was investigated by high temperature vacuum experiments in the pressure range plausible for the solar nebula. The evaporation rate at total pressure (Ptot) below 10?6 bar is nearly constant and is similar to that in vacuum, whereas the rate at 10?6 to 10?3 bar is dependent on Ptot. The evaporation rate, JexpFo,

  12. Collisional energy transfer in H2(vab,jab)+H2(vcd,jcd)

    NASA Astrophysics Data System (ADS)

    Mandy, M. E.; Martin, P. G.; Keogh, W. J.

    1998-01-01

    Quasiclassical trajectory studies were carried out on the H2(vab,jab) + H2(vcd,jcd) system to survey the effects of initial vibrational, rotational, and translational energy on the collisional energy transfer behavior at total energies of 0.1 and 0.25 Eh. When the internal energy of the collider is low, repulsive interactions dominate and the energy transfer in the target molecule resembles the behavior observed for the He+H2 system, in which interconversion of vibrational and rotational energy is strongly correlated. By contrast, an internally excited collider can yield energy transfer behavior with more randomly distributed vibrational and rotational changes, similar to that observed when a H atom is the collider. Implications for master equation calculations are discussed.

  13. Kinetic Energy Distribution of H(2p) Atoms from Dissociative Excitation of H2

    NASA Technical Reports Server (NTRS)

    Ajello, Joseph M.; Ahmed, Syed M.; Kanik, Isik; Multari, Rosalie

    1995-01-01

    The kinetic energy distribution of H(2p) atoms resulting from electron impact dissociation of H2 has been measured for the first time with uv spectroscopy. A high resolution uv spectrometer was used for the measurement of the H Lyman-alpha emission line profiles at 20 and 100 eV electron impact energies. Analysis of the deconvolved 100 eV line profile reveals the existence of a narrow line peak and a broad pedestal base. Slow H(2p) atoms with peak energy near 80 meV produce the peak profile, which is nearly independent of impact energy. The wings of H Lyman-alpha arise from dissociative excitation of a series of doubly excited Q(sub 1) and Q(sub 2) states, which define the core orbitals. The fast atom energy distribution peaks at 4 eV.

  14. H2O Emission Rate of Volcanic Plume During the 2000-2002 Miyakejima Volcanic Activity

    Microsoft Academic Search

    N. Matsushima; H. Shinohara

    2003-01-01

    After the onset of the 2000 eruption, Miyakejima has effused a large amount of volcanic gases from its summit crater. We have observed the volcanic plume and estimated H2O emission rate from the summit crater, using infrared thermal images of the plume and meteorological data, such as air-temperature, humidity and atmospheric pressure (Matsushima and Nishi, 2001). The infrared thermal images

  15. Absorption cross sections of surface-adsorbed H2O in the 295-370 nm region and heterogeneous nucleation of H2O on fused silica surfaces.

    PubMed

    Du, Juan; Huang, Li; Zhu, Lei

    2013-09-12

    We have determined absorption cross sections of a monolayer of H2O adsorbed on the fused silica surfaces in the 295-370 nm region at 293 1 K by using Brewster angle cavity ring-down spectroscopy. Absorption cross sections of surface-adsorbed H2O vary between (4.66 0.83) 10(-20) and (1.73 0.52) 10(-21) cm(2)/molecule over this wavelength range, where errors quoted represent experimental scatter (1?). Our experimental study provides direct evidence that surface-adsorbed H2O is an absorber of the near UV solar radiation. We also varied the H2O pressure in the surface study cell over the 0.01-17 Torr range and obtained probe laser absorptions at 295, 340, and 350 nm by multilayer of adsorbed H2O molecules until the heterogeneous nucleation of water occurred on fused silica surfaces. The average absorption cross sections of multilayer adsorbed H2O are (2.17 0.53) 10(-20), (2.48 0.67) 10(-21), and (2.34 0.59) 10(-21) cm(2)/molecule at 295, 340, and 350 nm. The average absorption cross sections of transitional H2O layer are (6.06 2.73) 10(-20), (6.48 3.85) 10(-21), and (8.04 4.92) 10(-21) cm(2)/molecule at 295, 340, and 350 nm. The average thin water film absorption cross sections are (2.39 0.50) 10(-19), (3.21 0.81) 10(-20), and (3.37 0.94) 10(-20) cm(2)/molecule at 295 nm, 340 nm, and 350 nm. Atmospheric implications of the results are discussed. PMID:23947798

  16. Vibrational-rotational energy transfer in H2-H2 collisions. I. Semiclassical decoupling approximation

    NASA Astrophysics Data System (ADS)

    Zenevich, Vladimir A.; Billing, Gert D.

    1999-08-01

    A new semiclassical decoupling procedure for rotational projection states in rovibrationally inelastic atom-diatom and diatom-diatom collisions is developed. Computed vibrational self-relaxation rate constants for para-H2 and ortho-H2 are in good quantitative agreement (within a factor of 1.5, except for the lowest temperatures) with experimental data over the investigated temperature range 50-2000 K. This allows us to hope that also more detailed (nonmeasured) rate constants for rovibrational state-to-state transitions in molecular hydrogen, calculated by our new model, are sufficiently accurate for astrophysical applications.

  17. Hydrogen permeance of palladiumcopper alloy membranes over a wide range of temperatures and pressures

    Microsoft Academic Search

    B. H. Howard; R. P. Killmeyer; K. S. Rothenberger; A. V. Cugini; B. D. Morreale; R. M. Enick; F. Bustamante

    2004-01-01

    The permeance of PdCu alloys containing 40, 53, 60, and 80wt.% Pd has been determined over the 6231173K temperature range for H2 partial pressure differences as great as 2.6MPa. Pure palladium and copper membranes were also evaluated. The PdCu alloys exhibited predictable permeances that reflected the crystalline phase structures as shown in the binary phase diagram. Under conditions of face-centered-cubic

  18. Ultrahigh pressures

    NASA Astrophysics Data System (ADS)

    Jayaraman, A.

    1986-06-01

    This article reviews mainly the use of the diamond anvil cell (DAC) for ultrahigh-pressure generation (a few hundred GPa) and the various techniques employed in studying the high-pressure behavior of solids. A brief historical introduction to devices used in the prediamond-anvil era is presented in Sec. I. The basic principles of the modern DAC, ultrahigh-pressure generation, and pressure calibration are presented. Among the techniques used, x-ray diffraction, optical spectroscopy including Raman and Brillouin spectroscopy, microscopy, electrical resistance,and Mssbauer measurements, and positron annihilation studies with the DAC are reviewed. High-temperature-high-pressure (HT-HP) and low-temperature-high-pressure (LT-HP) generation in the DAC, and the problems associated with pressure calibration under these conditions are discussed. A brief section is devoted to the sintered diamond-tipped anvil apparatus, for it offers a very convenient way of studying resistance changes and superconductivity to 50-GPa pressure at normal and at liquid-He temperatures. In Sec. IV, Raman studies on solid H2 and solid N2 to about 150 GPa, p-v studies on Xe, CsI to 50 GPa, the metallization of CsI, and superconductivity of Si high-pressure polymorphs are presented. Present trends and future possibilities for ultrahigh-pressure research are briefly set out in Sec. V.

  19. Shocking H2O Ice: The Role of Phase Changes during Impact Crater Formation

    NASA Astrophysics Data System (ADS)

    Stewart, S. T.; Senft, L. E.; Seifter, A.; Obst, A. W.

    2008-12-01

    New experimental data and cratering calculations illustrate the complex response of H2O ice to shock compression. We present peak and post-shock temperature measurements from shocked H2O ice. In experiments with shock pressures between 8 and 14 GPa, initially ~150 K ice is compressed to a supercritical state. In the time frame of the experiment, the supercritical H2O releases to the saturation vapor curve and does not achieve full decompression. Further decompression requires a significant volume expansion. In general, the time scale of expansion will depend on the internal energy and the surrounding conditions (e.g., confined or unconfined). The temperature data validate a new 5-Phase hydrocode equation of state model for H2O, which includes ice Ih, VI, VII, liquid, and vapor. Using the 5-Phase EOS, we model impact cratering onto icy satellites. After passage of the impact-generated shock wave, material beneath the growing transient crater has a layered composition: vapor, liquid, high- pressure phases (ices VII and VI), and ice Ih. The high pressure phases cannot fully decompress without a large volume increase. Thus, these phases initially unload to the pressure along the phase boundary; this pressurized region affects the excavation flow field. The changes in crater excavation lead to differences in crater size and amount of ejecta compared to excavation in a homogeneous target. The differences are significant for large craters (e.g., complex craters on Ganymede and Callisto). The modified excavation flow field also concentrates highly shocked material in the crater floor. In cases where a large, hot plug is buried during crater collapse, explosions occur as the material cools by transforming to vapor, producing features similar to central pits observed on Ganymede, Callisto, and Mars. The behavior of shocked H2O ice during decompression should lead to a variety of features that depend on the ambient conditions specific to each icy planetary body.

  20. Phase equilibria in the H2O-CO2 system between 250-330 K and 0-1.7 GPa: Stability of the CO2 hydrates and H2O-ice VI at CO2 saturation

    NASA Astrophysics Data System (ADS)

    Bollengier, Olivier; Choukroun, Mathieu; Grasset, Olivier; Le Menn, Erwan; Bellino, Guillaume; Morizet, Yann; Bezacier, Lucile; Oancea, Adriana; Taffin, Ccile; Tobie, Gabriel

    2013-10-01

    Although carbon dioxide is of interest in planetary science, few studies have been devoted so far to the H2O-CO2 system at pressures and temperatures relevant to planetary interiors, especially of the icy moons of the giant planets. In this study, new sapphire and diamond anvil cell experiments were conducted in this binary system to constrain the stability of the CO2 hydrates and H2O-ice VI at CO2 saturation in the 250-330 K and 0-1.7 GPa temperature and pressure ranges. Phases and equilibria were characterized by in situ Raman spectroscopy and optical monitoring. The equilibrium between the CO2 sI clathrate hydrate and the H2O-rich liquid phase was constrained over the entire pressure range of stability of the hydrate, up to 0.7-0.8 GPa, with results in agreement with previous studies at lower pressures. Above this pressure and below 1 GPa, our experiments confirmed the existence of the new CO2 high-pressure hydrate reported recently. Finally, the melting curve of the H2O-ice VI at CO2 saturation in the absence of CO2 hydrates was determined between 0.8 and 1.7 GPa. Using an available chemical potential model for H2O, a first assessment of the solubility of CO2 along the H2O-ice VI melting curve is given. Consistent with these new results and previous studies of the H2O-CO2 system, a P-T-X description of the binary system is proposed. The evolution with pressure of the Raman signatures of the two CO2 hydrates is detailed, and their stability is discussed in light of other clathrate hydrate-forming systems.

  1. Developmental Sculpting of Intracortical Circuits by MHC Class I H2-Db and H2-Kb.

    PubMed

    Adelson, Jaimie D; Sapp, Richard W; Brott, Barbara K; Lee, Hanmi; Miyamichi, Kazunari; Luo, Liqun; Cheng, Sarah; Djurisic, Maja; Shatz, Carla J

    2014-10-14

    Synapse pruning is an activity-regulated process needed for proper circuit sculpting in the developing brain. Major histocompatibility class I (MHCI) molecules are regulated by activity, but little is known about their role in the development of connectivity in cortex. Here we show that protein for 2 MHCI molecules H2-Kb and H2-Db is associated with synapses in the visual cortex. Pyramidal neurons in mice lacking H2-Kb and H2-Db (KbDb KO) have more extensive cortical connectivity than normal. Modified rabies virus tracing was used to monitor the extent of pyramidal cell connectivity: Horizontal connectivity is greater in the visual cortex of KbDb KO mice. Basal dendrites of L2/3 pyramids, where many horizontal connections terminate, are more highly branched and have elevated spine density in the KO. Furthermore, the density of axonal boutons is elevated within L2/3 of mutant mice. These increases are accompanied by elevated miniature excitatory postsynaptic current frequency, consistent with an increase in functional synapses. This functional and anatomical increase in intracortical connectivity is also associated with enhanced ocular dominance plasticity that persists into adulthood. Thus, these MHCI proteins regulate sculpting of local cortical circuits and in their absence, the excess connectivity can function as a substrate for cortical plasticity throughout life. PMID:25316337

  2. The every partial denture

    Microsoft Academic Search

    Andrew Ganly

    1954-01-01

    HE Every denture may be described as a precision plastic partial upper denture, so designed that it is free of the immediate supporting tissues of the remaining teeth. It has no clasps or occlusal rests. Retention is obtained primarily by atmospheric pressure as in a ~ull denture, but through a modified peripheral seal. Secondarily, retention is obtained by the accuracy

  3. Density-functional calculation of CeO2 surfaces and prediction of effects of oxygen partial pressure and temperature on stabilities

    E-print Network

    Adams, James B

    Density-functional calculation of CeO2 surfaces and prediction of effects of oxygen partial 111 , 110 , 210 , 211 , 100 , and 310 surfaces of ceria CeO2 . Compared with previous interatomic cycles.1 Ceria CeO2 has been recognized as an excellent oxygen buffer since the mid- 1980s, due to its

  4. H2o Quantitative Analysis of Transition Zone Minerals Wadsleyite and Ringwoodite By Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Novella, D.; Bolfan-Casanova, N.; Bureau, H.; Raepsaet, C.; Montagnac, G.

    2014-12-01

    Liquid H2O covers approximately 70% of the Earth's surface but it can also be incorporated as OH- groups in nominally anhydrous minerals (NAMs) that constitute the Earth's mantle, as observed in peridotitic xenoliths. The presence of even trace amounts (ppm wt) of hydrogen in mantle minerals strongly affect the physical, chemical and rheological properties of the mantle. The Earth's transition zone (410 to 660 km depth) is particularly important in this regard since it can store large amounts of H2O (wt%) as shown by experiments and recently by a natural sample. Addressing the behavior of H2O at high depths and its potential concentration in mantle NAMs is therefore fundamental to fully comprehend global-scale processes such as plate tectonics and magmatism. We developed an innovative technique to measure the H2O content of main transition zone NAMs wadsleyite and ringwoodite by Raman spectroscopy. This technique allows to use a beam of 1-3 m size to measure small samples that are typical for high pressure natural and synthetic specimens. High pressure polyphasic samples are indeed very challenging to be measured in terms of H2O content by the routinely used Fourier transform infra-red (FTIR) spectroscopy and ion probe mass spectroscopy analyses, making the Raman approach a valid alternative. High quality crystals of wadsleyite and ringwoodite were synthesized at high pressure and temperature in a multi-anvil press and analyzed by Raman and FTIR spectroscopy as well as elastic recoil detection analyses (ERDA) which is an absolute, standard-free technique. We will present experimental data that allow to apply Raman spectroscopy to the determination of H2O content of the most abundant minerals in the transition zone. The data gathered in this study will also permit to investigate the absorption coefficients of wadsleyite and ringwoodite that are employed in FTIR quantitative analyses.

  5. On the deuteration of C3H2 in dense interstellar clouds via the reaction C3H3+ + HD -> C3H2D+ + H2

    Microsoft Academic Search

    D. Talbi; E. Herbst

    2001-01-01

    Although deuterium isotope fractionation in cold, dark interstellar clouds is reasonably well understood via gas-phase chemistry, there are some discrepancies between observation and theory. For example, the observed abundance ratio between the deuterated species C3HD and the cyclic molecule C3H2 is significantly higher than most theoretical values unless the exchange reaction C3H3+ + HD -> C3H2D+ + H2 is efficient.

  6. Heterogeneous interaction of H2O2 with Arizona Test Dust.

    PubMed

    El Zein, Atallah; Romanias, Manolis N; Bedjanian, Yuri

    2014-01-16

    The heterogeneous interaction of H2O2 with solid films of Arizona Test Dust (ATD) was investigated under dark conditions and in presence of UV light using a low pressure flow tube reactor coupled with a quadrupole mass spectrometer. The uptake coefficients were measured as a function of the initial concentration of gaseous H2O2 ([H2O2]0 = (0.18 - 5.1) 10(12) molecules cm(-3)), irradiance intensity (JNO2 = 0.002 - 0.012 s(-1)), relative humidity (RH = 0.002 - 69%), and temperature (T = 268 - 320 K). The initial uptake coefficient was found to be independent of the concentration of H2O2 and UV irradiation intensity and to decrease with increasing RH and temperature according to the following expressions: ?0 = 4.8 10(-4)/(1+ RH(0.66)) at T = 275 K and ?0 = 3.2 10(-4)/(1 + 2.5 10(10)exp(-7360/T)) at RH = 0.35% (calculated using BET surface area, estimated conservative uncertainty of 30%). By contrast, the steady state uptake coefficient was found to be independent of temperature, to increase upon UV irradiation of the surface, and to be inversely (?SS ? [H2O2](-0.6)) dependent on the concentration of H2O2. The RH independent steady state uptake coefficient was measured under dark and UV irradiation conditions: ?SS(dark) = (0.95 0.30) 10(-5) and ?SS(UV) = (1.85 0.55) 10(-5), for RH = (2 - 69)% and [H2O2]0 ? 1.0 10(12) molecules cm(-3). The present experimental data support current considerations that uptake of H2O2 on mineral aerosol is potentially an important atmospheric process. PMID:24354511

  7. 8, 1048110530, 2008 Atmospheric H2O2

    E-print Network

    Paris-Sud XI, Universit de

    ACPD 8, 1048110530, 2008 Atmospheric H2O2 and organic hydroperoxides in PRD W. Hua et al. Title, Mito, Ibaraki, 310-8512, Japan 10481 #12;ACPD 8, 1048110530, 2008 Atmospheric H2O2 and organic Atmospheric H2O2 and organic hydroperoxides in PRD W. Hua et al. Title Page Abstract Introduction Conclusions

  8. The Role of H2O in Subduction Zone Magmatism

    E-print Network

    Skemer, Philip

    The Role of H2O in Subduction Zone Magmatism Timothy L. Grove,1 Christy B. Till,1,2 and Michael J, subducted slab, chlorite, H2O-saturated, hydrous magma, arc magmas Abstract Water is a key ingredient that occurs when magmas cool and crystallize in Earth's continental crust. The source of H2O for arc magma

  9. Water, Melting, and the Deep Earth H2O Cycle

    E-print Network

    Jellinek, Mark

    Water, Melting, and the Deep Earth H2O Cycle Marc M. Hirschmann Department of Geology anhydrous silicates Abstract Hydrous melting driven by changes in H2O storage capacity may occur and below the transition zone. The 50200 ppm H2O in the upper mantle likely derives from a blend of sources

  10. H2O Clouds: Issues, Challenges and Solutions Shahram Ghandeharizadeh

    E-print Network

    Ghandeharizadeh, Shahram

    H2O Clouds: Issues, Challenges and Solutions Shahram Ghandeharizadeh Computer Science Department University of Southern California Los Angeles, CA 90089, USA Abstract Home-to-Home Online (H2O) devices use to per- sonal libraries uploaded by each household. This paper describes the H2O framework and challenges

  11. Rhodium dihydride (RhH2) with high volumetric hydrogen density

    PubMed Central

    Li, Bing; Ding, Yang; Kim, Duck Young; Ahuja, Rajeev; Zou, Guangtian; Mao, Ho-Kwang

    2011-01-01

    Materials with very high hydrogen density have attracted considerable interest due to a range of motivations, including the search for chemically precompressed metallic hydrogen and hydrogen storage applications. Using high-pressure synchrotron X-ray diffraction technique and theoretical calculations, we have discovered a new rhodium dihydride (RhH2) with high volumetric hydrogen density (163.7g/L). Compressing rhodium in fluid hydrogen at ambient temperature, the fcc rhodium metal absorbs hydrogen and expands unit-cell volume by two discrete steps to form NaCl-typed fcc rhodium monohydride at 4GPa and fluorite-typed fcc RhH2 at 8GPa. RhH2 is the first dihydride discovered in the platinum group metals under high pressure. Our low-temperature experiments show that RhH2 is recoverable after releasing pressure cryogenically to 1bar and is capable of retaining hydrogen up to 150K for minutes and 77K for an indefinite length of time. PMID:22039219

  12. Estimation of negative ions in VHF SiH4/H2 plasma

    NASA Astrophysics Data System (ADS)

    Yamane, Tsukasa; Nakano, Shinya; Nakao, Sachiko; Takeuchi, Yoshiaki; Ichiki, Ryuta; Muta, Hiroshi; Uchino, Kiichiro; Kawai, Yoshinobu

    2014-11-01

    The characteristics of a VHF SiH4/H2 plasma (frequency: 60 MHz) at high pressures were examined as a function of silane concentration with a heated Langmuir probe. Anomalous reductions in electron saturation current were observed, suggesting the existence of many negative ions. An estimation of the concentration of negative ions was attempted using the sheath theory including negative ions. It was found that there exist H? and SiH3? ions as dominant negative ions in the VHF SiH4/H2 plasma. In addition, the measured floating potential agreed with the theoretical value.

  13. Assignment of the vibrational spectra of lithium hydroxide monohydrate, LiOH.H2O

    NASA Astrophysics Data System (ADS)

    Parker, Stewart F.; Refson, Keith; Bewley, Robert I.; Dent, Geoffrey

    2011-02-01

    The assignment of the vibrational spectra of lithium hydroxide monohydrate, LiOH.H2O, has been controversial for more than half-a-century. Here we show that only the combination of all three forms of vibrational spectroscopy: infrared, Raman and inelastic neutron scattering spectroscopies coupled with periodic-density functional theory calculations is able to satisfactorily assign the spectra. All previous work based on empirical criteria is, at least partially, incorrect. The librational modes of water do not follow the expected rock > wag > twist order and the calculations indicate that complete or partial deuterium substitution would not be useful in assigning the modes.

  14. Assignment of the vibrational spectra of lithium hydroxide monohydrate, LiOHH2O.

    PubMed

    Parker, Stewart F; Refson, Keith; Bewley, Robert I; Dent, Geoffrey

    2011-02-28

    The assignment of the vibrational spectra of lithium hydroxide monohydrate, LiOHH(2)O, has been controversial for more than half-a-century. Here we show that only the combination of all three forms of vibrational spectroscopy: infrared, Raman and inelastic neutron scattering spectroscopies coupled with periodic-density functional theory calculations is able to satisfactorily assign the spectra. All previous work based on empirical criteria is, at least partially, incorrect. The librational modes of water do not follow the expected rock > wag > twist order and the calculations indicate that complete or partial deuterium substitution would not be useful in assigning the modes. PMID:21361547

  15. Influence of H2O Rich Fluid Inclusions on Quartz Deformation

    NASA Astrophysics Data System (ADS)

    Thust, Anja; Heilbronner, Rene.; Stnitz, Holger; Tarantola, Alexandre; Behrens, Harald

    2010-05-01

    The effect of H2O on the strength of quartz is well known and has been discussed many times in the literature (e.g. Griggs & Blacic 1965, Kronenberg 1994). In this project we study the H2O interactions between natural dry quartz and H2O rich fluid inclusions during deformation in the solid medium Griggs apparatus. High pressure and temperature experiments were carried out using a quartz single crystal containing a large number of H2O-rich fluid inclusions. Adjacent to the fluid inclusions the crystal is essentially dry (< 100 H/106Si, as determined by FTIR). Two sample orientations where used: (1) ?{m} orientation: normal to one of the prism planes, (2) O+ orientation: 45 to and 45 to [c]. Confining pressures were 700 MPa, 1000 MPa and 1500 MPa, with a constant displacement rate of 10-6 s-1 and a constant temperature of 900 C. Additionally, experiments where carried out at lower temperatures (800 C, 700 C) and faster strain rate ( 10-5 s-1). During increasing pressure and temperature we remained close to the fluid inclusion isochore and exceeded the ? - ? transition as late as possible. The strengths of the majority of the samples are between 150 and 250 MPa (the weakest is 84 MPa, the strongest 414 MPa). Low strength can be explained by dynamic recrystallization and deformation by dislocation creep, higher strength correlates with a lower H2O content and absence of dislocation creep. In the undeformed material, the H2O rich fluid inclusions contain different chlorides like antarticite (CaCl26H2O) and hydrohalite (NaCl2H2O), as measured with micro thermometry. They show a large range in size from 50 ?m to 700 ?m and their spatial distribution is extremely heterogeneous. After deformation the inclusions are more homogeneously distributed throughout the sample and dramatically reduced in size (< 0.1?m). Regions with a high density of very small fluid inclusions are the regions with the highest concentration of deformation and yield an H2O content up to 3000 H/106Si. There is also a difference in fluid homogenization for the two different orientations. In crystals with orientation ?{m}, the fluid distribution is more homogeneous and to a finer scale than in crystals of O+ orientation. After deformation the salinity of the fluid inclusions is increased, from 10.6 wt.% equivalent NaCl up to 12 wt.% equivalent NaCl. FTIR spectra (point measurements, 100*100 ?m) also show a change in H2O content. Before deformation, the absorption spectra show no evidence for H2O in the quartz, H2O is only detected in the fluid inclusions (broad absorption band indicating molecular water). After deformation, the absorption spectra display a discrete peak, indicating OH- bonding in the quartz lattice. The release of H2O from fluid inclusions is an important process for crystal plastic deformation. Fluid inclusion rupture, micro cracking and the fast crack healing at these temperatures promote the distribution of H2O through the quartz and influences the strength of the material. Reference: Griggs, D.T. & Blacic, J.D., 1965: Quartz: Anomalous weakness of synthetic crystals. Science 174, 293-295. Kronenberg A.K., (1994): Hydrogen specifications and chemical weakening of quartz, Rev. Mineral. Ser. 29 (1994), pp. 123-176.

  16. H2O2 space shuttle APU

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A cryogenic H2-O2 auxiliary power unit (APU) was developed and successfully demonstrated. It has potential application as a minimum weight alternate to the space shuttle baseline APU because of its (1) low specific propellant consumption and (2) heat sink capabilities that reduce the amount of expendable evaporants. A reference system was designed with the necessary heat exchangers, combustor, turbine-gearbox, valves, and electronic controls to provide 400 shp to two aircraft hydraulic pumps. Development testing was carried out first on the combustor and control valves. This was followed by development of the control subsystem including the controller, the hydrogen and oxygen control valves, the combustor, and a turbine simulator. The complete APU system was hot tested for 10 hr with ambient and cryogenic propellants. Demonstrated at 95 percent of design power was 2.25 lb/hp-hr. At 10 percent design power, specific propellant consumption was 4 lb/hp-hr with space simulated exhaust and 5.2 lb/hp-hr with ambient exhaust. A 10 percent specific propellant consumption improvement is possible with some seal modifications. It was demonstrated that APU power levels could be changed by several hundred horsepower in less than 100 msec without exceeding allowable turbine inlet temperatures or turbine speed.

  17. H2 arcjet performance mapping program

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Work performed during the period of Mar. 1991 to Jan. 1992 is reviewed. High power H2 arcjets are being considered for electric powered orbit transfer vehicles (EOTV). Mission analyses indicate that the overall arcjet thrust efficiency is very important since increasing the efficiency increases the thrust, and thereby reduces the total trip time for the same power. For example, increasing the thrust efficiency at the same specific impulse from 30 to 40 percent will reduce the trip time by 25 percent. For a 200 day mission, this equates to 50 days, which results in lower ground costs and less time during which the payload is dormant. Arcjet performance levels of 1200 seconds specific impulse (lsp) at 35 to 40 percent efficiency with lifetimes over 1000 hours are needed to support EOTV missions. Because of the potential very high efficiency levels, the objective of this program was to evaluate the ability of a scaled Giannini-style thruster to achieve the performance levels while operating at a reduced nominal power of 10 kW. To meet this objective, a review of past literature was conducted; scaling relationships were developed and applied to establish critical dimensions; a development thruster was designed with the aid of the plasma analysis model KARNAC and finite element thermal modeling; test hardware was fabricated; and a series of performance tests were conducted in RRC's Cell 11 vacuum chamber with its null-balance thrust stand.

  18. Changes in glycosaminoglycan concentration and synovial permeability at raised intra-articular pressure in rabbit knees.

    PubMed Central

    Price, F M; Levick, J R; Mason, R M

    1996-01-01

    1. When intra-articular pressure is raised to pathological values (> 9 cmH2O) by saline, the hydraulic conductance of the synovial lining increases manyfold. The increase at 25 cmH2O is only partially accounted for by stretching of the tissue and has been ascribed to washout and/or dilution of interstitial matrix biopolymers. This suggestion was tested in this study by sampling synovium from control joints (rabbit knees) and from joints perfused with saline to 25 cmH2O, and analysing them quantitatively for collagen, chondroitin sulphate, heparan sulphate and hyaluronan. 2. Pressure and trans-synovial flow measurements showed that in samples taken at 25 cmH2O the conductance of the synovial lining had increased by a factor of 5.23 +/- 1.5 (mean +/- S.E.M.) over the conductance at low pressures (just above atmospheric pressure). 3. The tissue concentrations of collagen and the sulphated glycosaminoglycans (GAGs) were reduced by similar amounts after perfusion to 25 cmH2O, namely to 62.8-70.4% of control. The hyaluronan concentration by contrast was not significantly reduced (106% of control). 4. The reduction in collagen concentration (fixed material) indicated increased interstitial hydration. The closely similar reduction in sulphated GAGs indicated that dilution rather than washout of these components was occurring. The hyaluronan results could be explained by synthesis in vivo at a rate of > or = 91 micrograms h-1 (ml synovium)-1 (possibly a non-basal rate under the conditions of the experiment, i.e. raised pressure and a stretched hydrated membrane). 5. Because interstitial hydraulic drag is related to biopolymer concentration by a power function, the overall matrix dilution observed here was more than sufficient to explain the rise in synovial lining hydraulic conductance at 25 cmH2O when taken in conjunction with stretching of the synovial lining (increased area, reduced thickness). PMID:8887785

  19. H2O and CO2 in magmas from the Mariana arc and back arc systems

    NASA Astrophysics Data System (ADS)

    Newman, Sally; Stolper, Edward; Stern, Robert

    2000-05-01

    We examined the H2O and CO2 contents of glasses from lavas and xenoliths from the Mariana arc system, an intraoceanic convergent margin in the western Pacific, which contains an active volcanic arc, an actively spreading back arc basin, and active behind-the-arc cross-chain volcanoes. Samples include (1) glass rims from Mariana arc, Mariana trough, and cross-chain submarine lavas; (2) glass inclusions in arc and trough phenocrysts; and (3) glass inclusions from a gabbro + anorthosite xenolith from Agrigan (Mariana arc). Glass rims of submarine arc lavas contain 0.3-1.9 wt % H2O, and CO2 is below detection limits. Where they could be compared, glass inclusions in arc phenocrysts contain more H2O than their host glasses; most arc glasses and phenocryst inclusions contain no detectable CO2, with the exception of those from a North Hiyoshi shoshonite, which contains 400-600 ppm. The glass inclusions from the Agrigan xenolith contain 4-6% H2O, and CO2 is below the detection limit. Glasses from the cross-chain lavas are similar to those from the arc: H2O contents are 1.4-1.7 wt %, and CO2 is below detection limits. Volatile contents in Mariana trough lava glass rims are variable: 0.2-2.8 wt % H2O and 0-300 ppm CO2. Glass inclusions from trough phenocrysts have water contents similar to the host glass, but they can contain up to 875 ppm CO2. Volatile contents of melt inclusions from trough and arc lavas and from the xenolith imply minimum depths of crystallization of ~1-8 km. H2O and CO2 contents of Mariana trough glasses are negatively correlated, indicating saturation of the erupting magma with a CO2-H2O vapor at the pressure of eruption (~400 bars for these samples), with the vapor ranging from nearly pure CO2 at the CO2-rich end of the glass array to nearly pure H2O at the H2O-rich end. Degassing of these magmas on ascent and eruption leads to significant loss of CO2 (thereby masking preeruptive CO2 contents) but minimal disturbance of preeruptive H2O contents. For submarine Mariana arc magmas, depths were low enough that degassing on ascent and eruption led to loss of both H2O and CO2; as a result, H2O contents are positively correlated with water depth for these samples. The H2O contents of primitive Mariana trough magmas richest in the slab-derived component (i.e., the most ``arc-like'' magmas) are ~2 wt %. Although evolved glasses with up to 4-6 wt % H2O are present among Mariana arc samples, we interpret the glass inclusion data as indicating that primitive Mariana arc liquids contain 1-3 wt % H2O. The preeruptive H2O contents of primitive cross-chain seamount liquids are >1-2 wt %.

  20. Competitive sorption of CO2 and H2O in 2:1 layer phyllosilicates

    NASA Astrophysics Data System (ADS)

    Schaef, Herbert T.; Loring, John S.; Glezakou, Vassiliki-Alexandra; Miller, Quin R. S.; Chen, Jeffrey; Owen, Antoinette T.; Lee, Mal-Soon; Ilton, Eugene S.; Felmy, Andrew R.; McGrail, B. Pete; Thompson, Christopher J.

    2015-07-01

    Expandable clays such as montmorillonite have interlayer exchange sites whose hydration state can be systematically varied from near anhydrous to almost bulk-like water conditions. This phenomenon has new significance with the simultaneous implementation of geological sequestration and secondary utilization of CO2 to both mitigate climate warming and enhance extraction of methane from hydrated clay-rich formations. In this study, the partitioning of CO2 and H2O between Na-, Ca-, and Mg-exchanged montmorillonite and variably hydrated supercritical CO2 (scCO2) was investigated using in situ X-ray diffraction (HXRD), infrared (IR) spectroscopic titrations, and quartz crystal microbalance (QCM) measurements. Density functional theory calculations provided mechanistic insights. Structural volumetric changes were correlated to quantified changes in sorbed H2O and CO2 concentrations as a function of percent H2O saturation in scCO2. Intercalation of CO2 is inhibited when the clay is fully collapsed (dehydrated interlayer), peaks sharply with the introduction of some H2O and partial expansion of the interlayer region, and then decreases systematically with further hydration of the clay. This behavior is discussed in the context of recent theoretical calculations of the montmorillonite H2O-CO2 system.

  1. Rotational spectra and internal dynamics of Ne-H2S

    NASA Astrophysics Data System (ADS)

    Liu, Yaqian; Jger, Wolfgang

    Rotational spectra of 15 isotopomers of the Ne-H2S van der Waals complex were measured in the frequency range 4-22 GHz using a pulsed molecular beam Fourier transform spectrometer. Two K = 0 progressions were observed for each of the symmetric isotopomers (with H2S or D2S). This doubling is attributed to an internal rotation motion of the H2S subunit within the complex. These two states can be correlated with the 000and 101 rotational states of free H2S and D2S. By contrast, symmetry constraints no longer apply to isotopomers with DHS. The excited internal rotor state is no longer metastable, and only one K = 0 progression could be observed. The rotational constants obtained were compared with those of Ar-H2S and Ar-H2O. The ground state rotational constant remained almost constant upon substitution of H with D, showing an unusual isotope effect, similarly to a previous observation in Ar-H2S (GUTOWSKY, H. S., EMILSSON, T., and ARUNAN, E., 1997, J. chem. Phys., 106, 5309). This behaviour is in agreement with the ab initio study by OLIVEIRA, G. D., and DYKSTRA, C. E., 1999, J. chem. Phys., 110, 289. An approximate substitution analysis was carried out to deduce structural information from the ground state rotational constants. Nuclear quadrupole hyperfine structures were observed and resolved or partially resolved for isotopomers containing 33S and D, respectively, and the corresponding nuclear quadrupole coupling constants were determined. These were used to derive information about the internal dynamics of the dimer. Different sensitivities of the quadrupole coupling constants of D and 33S to the extent of out-of-plane motion were revealed.

  2. H2S regulation of nitric oxide metabolism

    PubMed Central

    Kolluru, Gopi K.; Yuan, Shuai; Shen, Xinggui; Kevil, Christopher G.

    2015-01-01

    Nitric oxide (NO) and hydrogen sulfide (H2S) are two major gaseous signaling molecules that regulate diverse physiological functions. Recent publications indicate the regulatory role of H2S on NO metabolism. In this chapter, we discuss the latest findings on H2S-NO interactions through formation of novel chemical derivatives, and experimental approaches to study these adducts. This chapter also addresses potential H2S interference on various NO detection techniques, along with precautions for analyzing biological samples from various sources. This information will facilitate critical evaluation and clearer insight into H2S regulation of NO signaling and its influence on various physiological functions. PMID:25725527

  3. Observations of the H2S toward OMC-1

    NASA Technical Reports Server (NTRS)

    Minh, Y. C.; Irvine, W. M.; Mcgonagle, D.; Ziurys, L. M.

    1990-01-01

    Observations of the 1(10) - 1(01) transition of interstellar H2S and its isotopes toward OMC-1 are reported. The fractional abundance of H2S in the quiescent regions of OMC-1 seems difficult to explain by currently known ion-molecular reactions. The fractional abundance of H2S relative to H2 is enhanced by a factor of 1000 in the hot core and the plateau relative to the quiescent clouds. The (HDS)/(H2S) abundance ratio in the hot core is estimated at 0.02 or less.

  4. Producing and quantifying enriched para-H2

    NASA Astrophysics Data System (ADS)

    Tom, Brian A.; Bhasker, Siddhartha; Miyamoto, Yuki; Momose, Takamasa; McCall, Benjamin J.

    2009-01-01

    The production of enriched para-H2 is useful for many scientific applications, but the technology for producing and measuring para-H2 is not yet widespread. In this note and in the accompanying auxiliary material, we describe the design, construction, and use of a versatile standalone converter that is capable of producing para-H2 enrichments of up to ?99.99% at continuous flow rates of up to 0.4 SLM. We also discuss para-H2 storage and back conversion rates, and improvements to three techniques (thermal conductance, NMR, and solid hydrogen impurity spectroscopy) used to quantify the para-H2 enrichment.

  5. A Reversible Structural Interconversion Involving [M(H2pdc)2(H2O)2] 2H2O (M Mn, Fe, Co, Ni, Zn, H3pdc 3,5-pyrazoledicarboxylic acid) and the Role

    E-print Network

    Li, Jing

    A Reversible Structural Interconversion Involving [M(H2pdc)2(H2O)2] 2H2O (M Mn, Fe, Co, Ni, Zn(H2O)2] 2H2O [M Mn (1), Fe (2), Co (3), Ni (4), Zn (5); H3pdc 3,5-pyrazoledicar- boxylic acid hydra- tion-dehydration: [M(H2pdc)2(H2O)2] 2H2O A B 4 H2O 4 H2O [M(H2pdc)2]. The process

  6. Spectroscopic Measurements of the Reaction H_3^+ + H_2 ? H_2 + H_3^+

    NASA Astrophysics Data System (ADS)

    Crabtree, Kyle N.; Kauffman, Carrie A.; Tom, Brian A.; Beka, Eftalda; McGuire, Brett A.; McCall, Benjamin J.

    2011-06-01

    The fundamental reaction involving H_3^+ and H_2 has not been well-studied in the laboratory. Typical approaches to studying kinetics using mass spectrometry are ineffective because the products have identical masses to the reactants. Isotopic labeling fundamentally alters the exchange symmetry of this system, and therefore cannot be employed. However, because the two nuclear spin configurations of H_3^+ (ortho, I=3/2, and para, I=1/2) and H_2 (ortho, I=1, and para, I=0) are linked to specific rotational states by symmetry, spectroscopy is a useful tool for studying this reaction. We have employed infrared multipass direct absorption spectroscopy to measure transitions in the ?b{2} fundamental band of H_3^+ using a difference frequency generation laser. Hydrogenic plasmas were produced in a hollow cathode discharge cell, which could be cooled as low as 130 K using liquid nitrogen. To measure the nuclear spin dependence of the H_3^+ + H_2 reaction, we prepared hydrogen gas enriched up to 99.9% para-H_2 using a para-hydrogen converter, and determined the ortho:para ratio of H_3^+ formed in the hollow cathode plasma at steady state as a function of both para-hydrogen enrichment and temperature. By utilizing steady state chemical models, we have determined that the ratio of the rates of the proton hop and hydrogen exchange pathways (? ? k^H/k^E) decreases from 1.60.1 at 350 K to 0.50.1 at 135 K. These results suggest that at lower temperatures, the intermediate (H_5^+)^* complex lifetime increases, leading to more statistical proton scrambling.

  7. Condensin II Regulates Interphase Chromatin Organization Through the Mrg-Binding Motif of Cap-H2

    PubMed Central

    Wallace, Heather A.; Klebba, Joseph E.; Kusch, Thomas; Rogers, Gregory C.; Bosco, Giovanni

    2015-01-01

    The spatial organization of the genome within the eukaryotic nucleus is a dynamic process that plays a central role in cellular processes such as gene expression, DNA replication, and chromosome segregation. Condensins are conserved multi-subunit protein complexes that contribute to chromosome organization by regulating chromosome compaction and homolog pairing. Previous work in our laboratory has shown that the Cap-H2 subunit of condensin II physically and genetically interacts with the Drosophila homolog of human MORF4-related gene on chromosome 15 (MRG15). Like Cap-H2, Mrg15 is required for interphase chromosome compaction and homolog pairing. However, the mechanism by which Mrg15 and Cap-H2 cooperate to maintain interphase chromatin organization remains unclear. Here, we show that Cap-H2 localizes to interband regions on polytene chromosomes and co-localizes with Mrg15 at regions of active transcription across the genome. We show that co-localization of Cap-H2 on polytene chromosomes is partially dependent on Mrg15. We have identified a binding motif within Cap-H2 that is essential for its interaction with Mrg15, and have found that mutation of this motif results in loss of localization of Cap-H2 on polytene chromosomes and results in partial suppression of Cap-H2-mediated compaction and homolog unpairing. Our data are consistent with a model in which Mrg15 acts as a loading factor to facilitate Cap-H2 binding to chromatin and mediate changes in chromatin organization. PMID:25758823

  8. Sensitivity analysis for airborne and spaceborne DIAL measurements of H2O profiles

    NASA Technical Reports Server (NTRS)

    Ismail, Syed; Browell, Edward V.

    1987-01-01

    Random and systematic error sourses are presently analyzed for atmospheric H2O detection in the vicinity of the 720 nm absorption bands with Differential Absorption Lidar (DIAL). Attention is given to the random errors due to undertainties in the measurement of the lidar signal and noise that are associated with the background and detector dark currents. Systematic errors are related to Doppler broadening due to backscattering from air molecules, the pressure shift of H2O lines, laser line distortions, spectral impurities, and laser tuning errors. Global measurements of H2O profiles from spaceborne DIAL systems are achievable with 200 m vertical x 10 km horizontal during nighttime, and 250 m vertical x 20 km horizontal during daytime.

  9. Endothelial nitric oxide synthase activation leads to dilatory H2O2 production in mouse cerebral arteries

    Microsoft Academic Search

    Annick Drouin; Nathalie Thorin-Trescases; Edith Hamel; John R. Falck; Eric Thorin

    2007-01-01

    Objective: Hydrogenperoxide(H2O2)producedbythevascularendotheliumisasignalingmoleculeregulatingvasculartone.Wehypothesized that H2O2 derived from eNOS activity could play a physiological role in endothelium-dependent dilation of mouse cerebral arteries. Methods: Simultaneous endothelium-dependent dilation and fluorescence-associated free radical (DCF-DA) or NO (DAF-2) production were recorded in isolated and pressurized (60 mm Hg) cerebral artery of C57Bl\\/6 male mice. Results: Without synergism, N-nitro-L-arginine (L-NNA) or the H2O2 scavengers catalase, PEG-catalase and

  10. Experimental measurements of vapor-liquid equilibria of the H2O + CO2 + CH4 ternary system

    USGS Publications Warehouse

    Qin, J.; Rosenbauer, R.J.; Duan, Zhenhao

    2008-01-01

    Reported are the experimental measurements on vapor-liquid equilibria in the H2O + CO2 + CH4 ternary system at temperatures from (324 to 375) K and pressures from (10 to 50) MPa. The results indicate that the CH4 solubility in the ternary mixture is about 10 % to 40 % more than that calculated by interpolation from the Henry's law constants of the binary system, H2O + CH4, and the solubility of CO2 is 6 % to 20 % more than what is calculated by the interpolation from the Henry's law constants of the binary mixture, H 2O + CO2. ?? 2008 American Chemical Society.

  11. High temperature and pressure electrochemical test station

    NASA Astrophysics Data System (ADS)

    Chatzichristodoulou, C.; Allebrod, F.; Mogensen, M.

    2013-05-01

    An electrochemical test station capable of operating at pressures up to 100 bars and temperatures up to 400 C has been established. It enables control of the partial pressures and mass flow of O2, N2, H2, CO2, and H2O in a single or dual environment arrangement, measurements with highly corrosive media, as well as localized sampling of gas evolved at the electrodes for gas analysis. A number of safety and engineering design challenges have been addressed. Furthermore, we present a series of electrochemical cell holders that have been constructed in order to accommodate different types of cells and facilitate different types of electrochemical measurements. Selected examples of materials and electrochemical cells examined in the test station are provided, ranging from the evaluation of the ionic conductivity of liquid electrolytic solutions immobilized in mesoporous ceramic structures, to the electrochemical characterization of high temperature and pressure alkaline electrolysis cells and the use of pseudo-reference electrodes for the separation of each electrode contribution. A future perspective of various electrochemical processes and devices that can be developed with the use of the established test station is provided.

  12. FLYING-WATER Renewables-H2-H2O TERRAFORMING: PERMANENT Drought(s)Elimination FOREVER!!!

    Microsoft Academic Search

    M. Lyons; E. Siegel

    2010-01-01

    ``Water water everywhere; ne'er a drop to drink''[Coleridg(1798)]; now:``Hydrogen hydrogen everywhere;STILL ne'er a drop to drink'': ONLY H2 can be ``FLYING-WATER''\\/``chemical-rain-in-pipelines''\\/ ``Hindenberg-effect (H2-UP;H2O-DOWN): atomic-weights ratio: O\\/H2O=[16]\\/[18]90%; O already in air uphill; NO H2O pumping need! In water-starved glacial-melting world, rescue ONLY by Siegel[3rd Intl.Conf.Alt.Energy,Hemisphere\\/Springer(1980)- vol.5\\/ p.459]Renewables-H2-H2O purposely flexible versatile agile customizable scaleable retrofitable integrated operating- system. Rosenfeld[Sci.315,1396(3\\/9\\/2007)]-Biello[Sci.Am.(3\\/9\\/ 2007)]crucial geomorphology which

  13. Melting experiments on the Udachnaya kimberlite at 6.3-7.5 GPa: Implications for the role of H2O in magma generation and formation of hydrous olivine

    NASA Astrophysics Data System (ADS)

    Sokol, Alexander G.; Kupriyanov, Igor N.; Palyanov, Yury N.; Kruk, Alexey N.; Sobolev, Nikolay V.

    2013-01-01

    Melting experiments on kimberlite from the Udachnaya pipe have been performed at 6.3-7.5 GPa and 1300-1600 C using a split-sphere multianvil apparatus. The water content in kimberlite varied from 2.5 to 11.6 wt.% and the CO2/(CO2 + H2O) molar ratio was from 0.61 to 0.23. The samples were placed in a graphite container inside a Pt capsule. The oxygen fugacity (fO2) during the experiment was controlled by the equilibrium between graphite and water-bearing carbonate-silicate melt. At relatively low temperatures, fO2 was close to the EMOG/D equilibrium, at higher temperatures, it shifted for approximately 1 log unit to more reduced conditions. An olivine + garnet + clinopyroxene assemblage was present at ?100 C below the liquidus of the Udachnaya kimberlite, with 6-8 wt.% H2O at the pressure 6.3 GPa and 6-10 wt.% H2O at 7.5 GPa. At 2.5 wt.% H2O the same assemblage appeared at ?150 C below liquidus, both at 6.3 and 7.5 GPa. Orthopyroxene did not form at any temperature and pressure of the experiments. The presence of clinopyroxene near the liquidus was due to the calcic nature and a high degree of silica undersaturation in the Udachnaya kimberlite. At the supra-solidus conditions, garnet and clinopyroxene compositionally distinct from minerals of the megacryst/macrocryst suite crystallized in equilibrium with low-H2O carbonated melt. Near the liquidus of high-H2O kimberlite, the stable olivine composition was from Fo91 to Fo98. The garnet composition (CaO 8 wt.%, TiO2 <1 wt.% and Cr2O3 up to 2.2 wt.%) approached that of Ti-bearing garnet typical of Cr-poor garnet megacrysts while the clinopyroxene was an analog of clinopyroxene megacrysts in kimberlite. Infrared absorption measurements showed that crystallized olivines contained water in the form of Ti-clinohumite-like and OH-clinohumite-like defects. The H2O content of olivine was found to depend mainly on water content in kimberlite melt and pressure. Olivine with 120-170 ppm H2O crystallized at 6 GPa in equilibrium with the melt compositionally close to the archetypical kimberlite rather than a carbonate one, and water as high as 6 wt.%. Olivine with 270-300 ppm H2O crystallized near kimberlite liquidus only at 7.5 GPa and 9.5-10.1 wt.% H2O. The experimental results imply that hydrous olivine, which is typical to kimberlites, including the Udachnaya pipe, very unlikely can crystallize from anhydrous carbonated magma. Judging by the conditions for multiphase saturation of the Udachnaya kimberlite melt, its generation was possible by partial melting of carbonated garnet wehrlite at pressures from 6 to 7.5 GPa and temperatures within 1450-1600 C in the presence of aqueous fluids. Thus, water must have been a trigger for generation of the primary kimberlite magma.

  14. Fourier transform-infrared studies of thin H2SO4/H2O films: Formation, water uptake, and solid-liquid phase changes

    NASA Technical Reports Server (NTRS)

    Middlebrook, Ann M.; Iraci, Laura T.; Mcneill, Laurie S.; Koehler, Birgit G.; Wilson, Margaret A.; Saastad, Ole W.; Tolbert, Margaret A.; Hanson, David R.

    1993-01-01

    Fourier transform-infrared (FTIR) spectroscopy was used to examine films representative of stratospheric sulfuric acid aerosols. Thin films of sulfuric acid were formed in situ by the condensed phase reaction of SO3 with H2O. FTIR spectra show that the sulfuric acid films absorb water while cooling in the presence of water vapor. Using stratospheric water pressures, the most dilute solutions observed were greater than 40 wt % before simultaneous ice formation and sulfuric acid freezing occurred. FTIR spectra also revealed that the sulfuric acid films crystallized mainly as sulfuric acid tetrahydrate (SAT). Crystallization occurred either when the composition was about 60 wt% H2SO4 or after ice formed on the films at temperatures 1-4 K below the ice frost point. Finally, we determined that the melting point for SAT depended on the background water pressure and was 216-219 K in the presence of 4 x 10(exp -4) Torr H2O. Our results suggest that once frozen, sulfuric acid aerosols in the stratosphere are likely to melt at these temperatures, 30 K colder than previously thought.

  15. H(2)S signaling in redox regulation of cellular functions.

    PubMed

    Ju, Youngjun; Zhang, Weihua; Pei, Yanxi; Yang, Guangdong

    2013-01-01

    Hydrogen sulfide (H(2)S) is traditionally recognized as a toxic gas with a rotten-egg smell. In just the last few decades, H(2)S has been found to be one of a family of gasotransmitters, together with nitric oxide and carbon monoxide, and various physiologic effects of H(2)S have been reported. Among the most acknowledged molecular mechanisms for the cellular effects of H(2)S is the regulation of intracellular redox homeostasis and post-translational modification of proteins through S-sulfhydration. On the one side, H(2)S can promote an antioxidant effect and is cytoprotective; on the other side, H(2)S stimulates oxidative stress and is cytotoxic. This review summarizes our current knowledge of the antioxidant versus pro-oxidant effects of H(2)S in mammalian cells and describes the Janus-faced properties of this novel gasotransmitter. The redox regulation for the cellular effects of H(2)S through S-sulfhydration and the role of H(2)S in glutathione generation is also recapitulated. A better understanding of H(2)S-regualted redox homeostasis will pave the way for future design of novel pharmacological and therapeutic interventions for various diseases. PMID:23368534

  16. Decrease of H2O2 plasma membrane permeability during adaptation to H2O2 in Saccharomyces cerevisiae.

    PubMed

    Branco, Miguel R; Marinho, H Susana; Cyrne, Luisa; Antunes, Fernando

    2004-02-20

    Contrary to what is widely believed, recent published results show that H2O2 does not freely diffuse across biomembranes. The fast removal of H2O2 by antioxidant enzymes is able to generate a gradient if H2O2 is produced in a different compartment from that containing the enzymes (Antunes, F., and Cadenas, E. (2000) FEBS Lett. 475, 121-126). In this work, we extended these studies and tested whether an active regulation of biomembranes permeability characteristics is part of the cell response to oxidative stress. Using Saccharomyces cerevisiae as a model, we showed that: (a) H2O2 gradients across the plasma membrane are formed upon exposure to external H2O2; (b) there is a correlation between the magnitude of the gradients and the resistance to H2O2; (c) there is not a correlation between the intracellular capacity to remove H2O2 and the resistance to H2O2; (d) the plasma membrane permeability to H2O2 decreases by a factor of two upon acquisition of resistance to this agent by pre-exposing cells either to nonlethal doses of H2O2 or to cycloheximide, an inhibitor of protein synthesis; and (e) erg3Delta and erg6Delta mutants, which have impaired ergosterol biosynthesis pathways, show higher plasma membrane permeability to H2O2 and are more sensitive to H2O2. Altogether, the regulation of the plasma membrane permeability to H2O2 emerged as a new mechanism by which cells respond and adapt to H2O2. The consequences of the results to cellular redox compartmentalization and to the origin and evolution of the eukaryotic cell are discussed. PMID:14645222

  17. A New Potential Energy Surface for H_2--N_2O and PIMC Simulation Probing Superfluidity and Vibrational Frequency Shifts in Doped para-H_2 Clusters

    NASA Astrophysics Data System (ADS)

    Wang, Lecheng; Le Roy, Robert J.; Roy, Pierre-Nicholas; Xie, Daiqian

    2013-06-01

    The existence of superfluidity of para-hydrogen clusters doped by the linear molecules such as CO, CO_2 and OCS stimulated our theoretical study of (para-H_2)_N-N_2O clusters. A new 6D ab initio PES for the H_2-N_2O dimer which explicitly included the symmetric and asymmetric vibrational coordinates Q_1 and Q_3 of N_2O was constructed. Four-dimensional global intermolecular PESs were then obtained by fitting the vibrational averaged interactions energies for ?_3(N_2O)=0 and 1 to the Morse/Long Range(MLR) analytical form with theoretically fixed long-range parameters. Using the adiabatic hindered-rotor approximation, effective two-dimensional PESs for the para-H_2-N_2O dimer were then generated. Predictions of the infrared spectra of para-H_2-N_2O based on these PESs have been in good agreement with the experimental observations. Based on these surfaces, predictions of structural properties, vibrational band origin shifts, rotational dynamics and superfluidity of (para-H_2)_N-N_2O clusters have been generated using bosonic PIMC simulation methods. The evolution of the calculated shifts agreed reasonably with that for the experimental observations. Reduction of the effective moment of inertia is predicted to occur when the dopant is partially surrounded by the para-H_2 solvent, which marked the onset of molecular superfluidity in para-H_2. Results obtained using our surfaces and PIMC algorithm will be presented. H. Li, R. J. Le Roy, P.-N. Roy and A.R.W. McKellar, Phys. Rev. Lett. {105}, 133401 (2010). S. Grebenev, B. G. Sartakov, J. P. Toennies and A. F. Vilesov, J. Chem. Phys. {132}, 064501 (2010). P. L. Raston, W. Jager, H. Li, R. J. Le Roy, and P.-N. Roy , Phys. Rev. Lett. {108}, 253402 (2012). J. Tang and A.R.W. McKellar, J. Chem. Phys. {117}, 8308 (2002). J. Tang and A.R.W. McKellar, J. Chem. Phys. {123}, 114314 (2005).

  18. The elusive HI-> H2 transition in high-z damped Lyman-alpha systems

    E-print Network

    Noterdaeme, P; Srianand, R

    2015-01-01

    We study the H2 molecular content in high redshift damped Lyman-alpha systems (DLAs) as a function of the HI column density. We find a significant increase of the H2 molecular content around log N(HI) (cm^-2)~21.5-22, a regime unprobed until now in intervening DLAs, beyond which the majority of systems have log N(H2) > 17. This is in contrast with lines of sight towards nearby stars, where such H2 column densities are always detected as soon as log N(HI)>20.7. This can qualitatively be explained by the lower average metallicity and possibly higher surrounding UV radiation in DLAs. However, unlike in the Milky Way, the overall molecular fractions remain modest, showing that even at a large N(HI) only a small fraction of overall HI is actually associated with the self-shielded H2 gas. Damped Lyman-alpha systems with very high-N(HI) probably arise along quasar lines of sight passing closer to the centre of the host galaxy where the gas pressure is higher. We show that the colour changes induced on the background...

  19. Modeling the Influence of Nuclear Spin in the Reaction of H_3^+ with H_2

    NASA Astrophysics Data System (ADS)

    Crabtree, Kyle N.; Tom, Brian A.; McCall, Benjamin J.

    2011-06-01

    The reaction H_3^+ + H_2 ? H_2 + H_3^+ is among the simplest of bimolecular chemical reactions, and may play an important role in determining the ortho:para ratios of H_3^+ and H_2 in interstellar environments. Despite its apparent simplicity, the kinetics of this reaction is not well understood, particularly the branching fractions of the proton hop and hydrogen exchange reaction pathways. In this contribution, we present a series of steady state chemical models that show how this reaction can be studied in the laboratory with spectroscopy. Our first model is based entirely on nuclear spin statistics, appropriate for high temperature, low pressure plasmas. This model is then extended to account for the possibility of a small number of three-body collisions which could influence the interpretation of spectroscopic measurements of the H_3^+ + H_2 binary reaction. Our final model employs rate coefficients calculated using a microcanonical statistical approach which takes into account energetic restrictions on certain reaction pathways, which may become important at lower temperatures. These models are directly aimed at extracting kinetic information about the H_3^+ + H_2 reaction from laboratory spectra of hydrogenic plasmas.

  20. Experimental study of the NaClH 2O system up to 28 GPa: Implications for ice-rich planetary bodies

    Microsoft Academic Search

    Mark R. Frank; Claire E. Runge; Henry P. Scott; Steven J. Maglio; Jessica Olson; Vitali B. Prakapenka; Guoyin Shen

    2006-01-01

    Recent studies have hypothesized that high-pressure H2O polymorphs, specifically Ice VI and Ice VII, make up a significant portion of the interiors of select outer planets and their moons; most notably the Galilean satellites, Saturn's Titan and possibly Neptune's moon Triton as well as potential H2O-rich extra-solar bodies. Several of these bodies have been conjectured to contain subsurface salty H2O